Title of Invention	ELECTRICALLY CONDUCTIVE SIZED GLASS STRANDS
Abstract	The present invention relates to glass strands coated with a sizing composition capable of conducting an electric current, which comprises at least one film- forming agent, at least one compound chosen from plasticizers, surfactants and dispersants, at least one coupling agent for coupling to the glass, and electrically conductive particles. The glass strands according to the invention are more particularly intended for the production of electrically conductive parts by compression molding, said glass strands being employed in SMC or BMC form.

Title of Invention

ELECTRICALLY CONDUCTIVE SIZED GLASS STRANDS

Abstract

The present invention relates to glass strands coated with a sizing composition capable of conducting an electric current, which comprises at least one film- forming agent, at least one compound chosen from plasticizers, surfactants and dispersants, at least one coupling agent for coupling to the glass, and electrically conductive particles. The glass strands according to the invention are more particularly intended for the production of electrically conductive parts by compression molding, said glass strands being employed in SMC or BMC form.

Full Text	- 1 - ELECTRICALLY CONDUCTIVE SIZED GLASS STRANDS The present invention relates to glass strands coated with a size capable of conducting an electric current, 5 said strands being intended to reinforce organic materials of the polymer type, so as to obtain composites. The invention also relates to the sizing composition 10 used to coat said strands, to the method for producing the composites from these strands, and to the resulting composites. Conventionally, glass reinforcing strands are produced 15 by mechanically attenuating molten glass streams flowing out from numerous orifices in a bushing filled with molten glass, under gravity, through the effect of the hydrostatic pressure due to the height of the liquid, in order to form filaments that are assembled 20 into base strands, said strands then being collected on a suitable support. During the attenuation, and before they are assembled into strands, the glass filaments are coated with a 25 sizing composition, generally an aqueous composition, by passing them over a sizing member. The size is essential on several counts. 30 During manufacture of the strands, it protects the filaments from the abrasion that results from them rubbing, at high speed, on the members for attenuating and winding the strand by acting as a lubricant. The size also provides the strand with cohesion, by 35 ensuring that the filaments are linked together. Finally, it makes the strand sufficiently integral to withstand the rewinding operations necessary for forming, in particular, "assembled" rovings from several base strands, and it also makes it possible for - 2 - the electrostatic charges generated during these operations to be eliminated. During use for the purpose of producing composites, the 5 size improves the impregnation of the strand by the matrix to be reinforced and it promotes adhesion between the glass and said matrix, thus resulting in composites with improved mechanical properties. Furthermore, the size protects the strands from 10 chemical and environmental attack, thereby helping to increase their durability. In applications requiring the strand to be chopped, the size prevents the filaments from splaying out and separating, and, together with the oversize, it contributes to 15 dispersing the electrostatic charges generated during chopping. The glass strands in their various forms (continuous, chopped or ground strands, mats, meshes, wovens, knits, 20 etc.) are commonly used for the effective reinforcement of matrices of various types, for example thermoplastic or thermosetting organic materials and inorganic materials, for example cement. 25 The invention is applicable here to reinforcing strands that are incorporated into polymer matrices of the thermosetting type in order to manufacture either impregnated mats or SMCs (Sheet Molding Compounds), which may be formed directly by molding in a hot 30 compression mold, or pastes intended to be molded using the BMC (Bulk Molding Compound) technique. An SMC is a semifinished product in which a glass strand mat is combined with a paste of a thermosetting 35 resin, in particular one chosen from polyesters. In the SMC, the glass acts as reinforcement and provides the mechanical properties and dimensional stability of the molded parts. It generally represents - 3 - 25 to 60% of the weight of the SMC. Usually, the glass is in the form of chopped strands, even though continuous strands may be used for some applications. The paste comprises the thermosetting resin and 5 fillers, and optionally additives, such as initiators, viscosity regulators and mold release agents. As is known, an SMC is manufactured by depositing a first paste layer on a film supported by a conveyor 10 belt, by chopping strands unwound from rovings by means of a rotary chopper to a length of 12 to 50 millimeters on top of the resin, the strands being randomly (isotropically) distributed, and by depositing a second paste layer supported by a film, the resin face being 15 turned toward the glass. The combination of the various layers then passes through the nip of one or more calendering devices so as to impregnate glass strands with the resin and to remove the trapped air. 20 An SMC must also undergo a maturation treatment, for the purpose of increasing the viscosity of the resin, up to an imposed value of 40-100 Pa.s so as to allow it to be properly molded. 25 Molding with SMCs allows the production of individual parts, in medium or long runs, which are less expensive in particular owing to the fact that the SMC is deposited directly in the mold without it being required to cut it precisely to the dimensions thereof. 30 What distinguishes a BMC from an SMC is the form, which here is a paste intended to be injected into a compression mold. 35 The parts produced by these molding techniques are used in particular in the automotive field as a replacement for body parts or impact protection parts, which are currently made of metal, especially steel. - 4 - However, automobile manufacturers are constantly preoccupied with reducing the weight of vehicles as much as possible, so as to reduce the fuel consumption. To do this, it has been envisioned to substitute 5 certain metal parts of the body with lighter parts made of composites. The problem that arises with parts made of composites is that of painting. 10 The operation of painting metal parts is carried out on an industrial scale by cataphoresis. This consists in electrostatically depositing one or more primer coats in order to "smooth" the surface, and one or more paint 15 coats. Composite parts cannot be used as such as the polymer material is an electrical insulator. It is therefore necessary to make them conductive in order to be able 20 to use them on conventional cataphoretic painting lines. Solutions aiming to make composites electrically conductive have been disclosed. 25 US 6 648 593 proposes, prior to application of the paint, to deposit a first coat of a conductive paint comprising a resin and conductive particles (in the form of whiskers), and a second metal coat applied 30 without intervention of the electric current. This solution requires the addition of other steps that are difficult to implement in the current process, and consequently it generates an additional cost. 35 WO-A-03/0 511 992 and US-A-2003/0 042 468 propose a composition intended to be used in molding processes, which comprises a crosslinkable prepolymer, at least one unsaturated monomer copolymerizable with the - 5 - prepolymer, a copolymerization initiator and electrically conductive fillers, for example graphite, metal-coated particles or metal particles. 5 The processing of the composition is made difficult by the high conductive filler content needed to obtain a high level of conduction. Thus, the conductive fillers are incorporated directly into the matrix. This greatly increases the viscosity - impregnation of the glass 10 strand is made more difficult and the pressure to be applied for molding has to be increased. The solution consisting in increasing the amount of solvent in order to reduce the viscosity has other drawbacks - it reduces the mechanical properties of the composite and 15 generates microbubbles that impair the quality of the surface finish of the final parts. The object of the present invention is to provide reinforcing strands that are particularly suitable for 20 SMC production and are capable of conducting an electric current so as to obtain molded parts made of composites that can be cataphoretically treated. One subject of the invention is glass strands coated 25 with an aqueous sizing composition which comprises at least one film-forming agent, at least one compound, chosen from plasticizers, surfactants and dispersants, at least one coupling agent for coupling to the glass and electrically conductive particles. 30 In the present invention, the expression "glass strands coated with a sizing composition that comprises ..." is understood to mean not only glass strands coated with the composition in question, such as those obtained 35 immediately on leaving the sizing member(s), but also the same strands that have undergone one or more other subsequent treatments. Examples that may be mentioned include the drying treatment, for the purpose of removing water, and the treatments that lead to the - 6 - polymerization/crosslinking of certain constituents of the sizing composition. Again within the context of the invention, the term 5 "strands" should be understood to mean the base strands resulting from the twist-free assembly of a multitude of filaments, and the products derived from these strands, especially assemblies of these base strands in the form of rovings. Such assemblies may be obtained by 10 simultaneously paying out base strands from several packages and then assembling said strands into tows that are wound onto a rotating support. They may also be "direct" rovings with a titer (or linear density) equivalent to that of assembled rovings obtained by 15 gathering the filaments directly beneath the bushing and winding onto a rotating support. Also according to the invention, the expression "aqueous sizing composition" is understood to mean a 20 composition that can be deposited on the filaments during attenuation, which composition is in the form of a suspension or dispersion comprising at least 70%, preferably 75%, by weight of water and possibly containing, where appropriate, less than 10%, 25 preferably less than 5%, by weight of one or more essentially organic solvents helping to dissolve certain constituents of the sizing composition. In the majority of cases, the composition contains no organic solvent, especially so as to limit the emission of 30 volatile organic compounds (VOCs) into the atmosphere. The film-forming agent according to the invention acts in several ways: it gives the coating mechanical cohesion, by making the conductive particles adhere to 35 the glass filaments and ensuring that these particles are linked together, where appropriate with the material to be reinforced; it helps to bind the filaments together; finally, it protects the strands from any mechanical damage and from chemical and - 7 – environmental attack. The film-forming agent is a polymer chosen from polyvinyl acetates (homopolymers or copolymers, for 5 example vinyl acetate/ethylene copolymers), polyesters, epoxies, polyacrylics (homopolymers or copolymers), polyurethanes, polyamides (homopolymers or copolymers, for example polyamide/polystyrene or polyamide/polyoxyethylene block copolymers), cellulose 10 polymers and blends of these compounds. Polyvinyl acetates, epoxies and polyurethanes are preferred. The plasticizer lowers the glass transition temperature of the film-forming agent, giving the size flexibility 15 and limiting shrinking after drying. The surfactant improves the suspension and dispersion of the conductive particles and promotes compatibility between the other constituents and water. It may be 20 chosen from cationic, anionic or nonionic compounds. To avoid stability and ununiform particle dispersion problems in the sizing composition, it is preferred to use cationic or nonionic surfactants. 25 The dispersant helps to disperse the conductive particles in the water and to reduce their sedimentation. 30 The plasticizers, surfactants and dispersants may possess one or more functions specific to each of the abovementioned categories. The choice of these agents and the amount to be used depend on the film-forming agent and on the conductive particles. 35 These agents may especially be chosen from: > organic compounds, in particular: - optionally halogenated, aliphatic or aromatic, polyalkoxylated compounds, such as - 8 - ethoxylated/propoxylated alkylphenols, preferably containing 1 to 30 ethylene oxide groups and 0 to 15 propylene oxide groups, ethoxylated/propoxylated bisphenols, preferably containing 1 to 40 ethylene 5 oxide groups and 0 to 20 propylene oxide groups, ethoxylated/propoxylated fatty alcohols, preferably the alkyl chain of which comprises 8 to 20 carbon atoms, and containing 2 to 50 ethylene oxide groups and up to 20 propylene oxide groups. These 10 polyalkoxylated compounds may be block copolymers or random copolymers, - polyalkoxylated fatty acid esters, for example polyethyleneglycol, the alkyl chain of which preferably comprises 8 to 20 carbon atoms, 15 and containing 2 to 50 ethylene oxide groups and up to 20 propylene oxide groups and - amine compounds, for example optionally alkoxylated amines, a*nine oxides, alkylamides, sodium, potassium or ammonium succinates and 20 taurates, sugar derivatives, especially sorbitan, and sodium, potassium or ammonium alkyl sulfates and alkyl phosphates; and > inorganic compounds, for example silica derivatives, these compounds possibly being used by 25 themselves or as a mixture with the aforementioned organic compounds. The electrically conductive particles confer electrical conductivity on the glass strands and the level of 30 performance depends on the amount of particles present on the strands. According to the invention, these are carbon-based particles, especially graphite and/or carbon black particles. 35 The origin of the graphite - natural or synthetic - has no appreciable impact on the electrical conductivity. It therefore does not matter whether one or other type of graphite, by itself or as a blend, is used. - 9 - The particles may have any shape - for example they may be spheres, flakes or needles. However, it has been found that the electrical conductivity of a blend of particles of different shapes is improved compared with 5 the same amount of particles but of the same shape. Blends combining two shapes (binary blend) or three shapes (ternary blend) of particles prove to be advantageous. 10 Preferably, 30 to 60% of the conductive particles have a high aspect ratio (defined by the ratio of the longest dimension to the shortest), this ratio preferably varying from 5 to 20, especially around 10, and advantageously at least 15% of the particles are in 15 the form of flakes or needles. Like the shape, the size of the particles is an important parameter as regards electrical conductivity. As a general rule, the size of the particles taken 20 along their longest dimension does not exceed 250 urn, preferably 100 urn. It is advantageous to combine the aforementioned particles, generally made of graphite, with a carbon 25 black powder that conducts electric current, with a particle size not exceeding 1 μm, preferably having a mean size of less than 100 nm. The carbon black particles, owing to their small size, create points of contact between the graphite particles, thereby further 30 improving the electrical conductivity. The coupling agent ensures that the size is attached to the surface of the glass. 35 The coupling agent is chosen from hydrolyzable compounds, especially in acid medium containing, for example, citric acid or acetic acid, these compounds belonging to the group consisting of silanes, such as γ-glycidoxypropyltrimethoxysilane, γ-acryloxypropyl- - 10 - trimethoxysilane, γ-methacryloxypropyltrimethoxysilane, poly(oxyethylene/oxypropylene) trimethoxysilane, γ- aminopropyltriethoxysilane, vinyltrimethoxysilane, phenylaminopropyltrimethoxysilane or styrylaminoethyl- 5 aminopropyltrimethoxysilane, siloxanes, titanates, zirconates and blends of these compounds. Preferably, silanes are chosen. In addition to the aforementioned constituents that 10 essentially contribute to the structure of the size, one or more other constituents may be present. Thus, a viscosity regulator may be introduced, so as to adjust the viscosity of the composition to the 15 conditions of applying the size to the filaments, in general this viscosity being between 5 and 80 mPa.s and preferably at least 7 mPa.s. This regulator also helps to stabilize the dispersion of particles so that they do not form a sedimented deposit too rapidly and do not 20 migrate to the outside and lie on the surface of the package when winding the strand. The viscosity regulator is chosen from highly hydrophilic compounds, that is to say those that are 25 able to capture a large amount of water, such as carboxymethyl celluloses, guar or xanthan gums, carrageenans, alginates, polyacrylics, polyamides, polyethylene glycols, especially those with a molecular weight of greater than 100 000, and blends of these 30 compounds. The size may also include the usual additives for glass strands, namely lubricants, such as mineral oils, fatty esters, for example isopropyl palmitate or butyl 35 stearate, alkylamines, complexing agents, such as EDTA and gallic acid derivatives, and antifoams, such as silicones, polyols and vegetable oils. All of the abovementioned compounds contribute to the - 11 - production of glass strands that can be easily manufactured, are able to be used as reinforcements, and which are incorporated without any problem into the resin during manufacture of the composites and also 5 possess electrical conduction properties. As a general rule, the amount of size represents 2 to 7%, preferably 3.5 to 6%, of the weight of the final strand. 10 The conductive strand according to the invention may be made of glass of any kind, for example E-glass, C- glass, R-glass or AR-glass, and glass with a low boron content (less than 6%). E-glass and AR-glass are 15 preferred. The diameter of the glass filaments constituting the strands may vary widely, for example from 5 to 30 urn. Likewise, wide variations may occur in the linear 20 density of the strand used, such as an assembled roving, for which the linear density ranges from 68 to 4800 tex depending on the intended applications, this roving possibly being formed from base strands whose linear density varies from 17 to 320 tex. 25 Another subject of the invention is the sizing composition itself, before it has been deposited on the glass filaments. It comprises the aforementioned constituents and water. 30 The sizing composition comprises (in % by weight): - 2 to 10%, preferably 3 to 8.5%, of at least one film-forming agent; - 0.2 to 8%, preferably 0.25 to 6%, of at least 35 one compound chosen from plasticizers, surfactants and dispersants; - 4 to 25%, preferably 6 to 20%, of electrically conductive particles; - 0.1 to 4%, preferably 0.15 to 2%, of at least - 12 - one coupling agent; - 0 to 4%, preferably 0 to 1.8%, of at least one viscosity regulator; and - 0 to 6%, preferably 0 to 3%, of additives. 5 The amount of water to be used is determined so as to obtain a solids content that varies from 8 to 35%, preferably 12 to 25%. 10 The preparation of the sizing composition is carried out as follows: a) producing a dispersion D of the conductive particles in water containing the dispersant; b) introducing the other components of the size, 15 namely the film-forming agents, the plasticizers, the surfactants, the coupling agents, in hydrolyzed form, and, where appropriate, the viscosity regulators and the additives, in water in order to form an emulsion E; and 20 c) blending the dispersion D with the emulsion E. Advantageously, steps a) and c) are carried out with sufficient stirring to prevent the risk of 25 sedimentation of the conductive particles. When a viscosity regulator is used, it is introduced at step b) firstly in the form of an aqueous solution, where necessary heated to about 80°C so that it 30 dissolves more easily. In general, the dispersion D is stable under the usual storage conditions at a temperature of 20 to 25°C. In particular, it may be used without major drawback over 35 a period of about six months, where necessary stirring it before use if the particles have sedimented. However, the sizing composition should be used almost immediately after it has been prepared, preferably - 13 - within a period of time not exceeding about four days under the aforementioned storage conditions. As previously, the particles that have sedimented may be redispersed without the properties of the composition 5 being affected thereby. As mentioned previously, the aqueous solution is deposited on the filaments before they are assembled into base strand (s) . The water is usually removed by 10 drying the strands after collection. Yet another subject of the invention is a composite, in particular an SMC or a BMC, in which at least one thermosetting polymer material is combined with 15 reinforcing strands, said strands consisting partly or completely of glass strands coated with the sizing composition described above. The glass content in the composite is generally between 5 and 60% by weight. 20 According to a first embodiment, the composite is in the form of an SMC having a glass content of between 10 to 60%, preferably of 20 to 45%, by weight. According to a second embodiment, the composite is in 25 the form of a BMC having a glass content of between 5 to 20% by weight. Preferably, the thermosetting polymer material is a phenolic resin. 30 A further subject of the invention is the use of the sized glass strands according to the invention for producing electrically conductive molded parts using the technique of compression molding, said strands 35 being used in particular in SMC. or BMC form. As already mentioned, the molded parts can be painted on standard lines for applying paint cataphoretically, especially for the production of automobile parts. - 14 - Hitherto, it was considered that a part molded from an SMC or BMC could be coated with paint under the aforementioned conditions when it has in particular a 5 surface resistivity of between 0.5 and 1.5 MΩ/D. The inventors have discovered that a part having an "internal" resistivity, that is to say a volume resistivity as may be conferred by a layer of 10 conductive fibers within the matrix, for example of the order of 0.01 to 1000 MΩ.m, could also be treated under the same conditions. As a result, the size with which the glass strands are 15 coated does not necessarily have to possess a high solubility in the matrix to be reinforced, so that the conductive particles are dispersed throughout the part in order that it can undergo the cataphoretic painting treatment. A size that is only slightly soluble in the 20 matrix, for example containing one or more polyurethanes as film-forming agent, or even one that is insoluble, may consequently be suitable for applying paint to such molded parts. 25 The use of the conductive glass strand according to the invention is not limited to the SMC or BMC molding technique. More generally, the glass strands can be used in any technique for manufacturing composites involving a reinforcement in the form of glass strands 30 that advantageously requires electrical conduction. In particular, the glass strands may be in the form of a mat or veil, especially one that can be used as an SMC surface coating or reinforcing element, said strands possibly being combined with other reinforcing strands, 35 especially glass strands. The strands according to the invention may thus be used in all fields in which it is desired to achieve thermal conduction and heat dispersion properties, for example - 15 - in the domestic electrical appliance and automotive fields. These strands may also be used for electromagnetic shielding applications, especially in the transport field, in particular in automobiles, in 5 the building field and in fields requiring protection of electronic components, especially those relating to magnetic media for storing data. The examples given below illustrate the invention 10 without however limiting it. In these examples, the following methods were used: - On the glass strand: → the loss on ignition of the sized glass strand 15 was measured under the conditions in the ISO 1887 standard. This loss on ignition is given in %; → the flock was measured by making the tows, paid out from two rovings, pass simultaneously over a turn roll at a speed of 200 m/min. The flock is defined by 20 the amount of fibrils obtained after a 3 kg mass of strand has unwound, and it is expressed in mg/100 g of strand; → the tenacity of the strand was determined by measuring the tensile breaking force under the 25 conditions in the ISO 3341 standard. The tenacity is expressed in N/tex; → the linear resistivity, in MΩ/cm, was obtained by calculating it from the equation: ρ = R/l 30 in which ρ is the resistivity in MΩ/cm R is the resistance in MΩ and 1 is the length of the fiber in cm, the resistance R being measured using an ohmmeter and the distance between the two electrodes being 20 cm. 35 - On the molded part: → the surface resistivity, in MΩ/D, was measured according to the NF EN 1149-1 standard; → the "internal" resistivity, in MΩ.m, was measured on a plaque, obtained according to the - 16 - aforementioned NF EN 1149-1 standard, drilled with two holes 20 cm apart. A metal rivet (diameter: 4 mm) serving as connector was inserted into each hole, said connectors being connected to the electrodes of an 5 ohmmeter. The internal resistivity was calculated from the equation: ρ' = R'S/d in which ρ' is the internal resistivity, in MΩ.m R' is the resistance, in MΩ 10 S is the area of the plaque, in m2 and d is the distance between the connectors; → the flexural strength and the flexural modulus, in MPa, and the deflection, in mm, were measured under 15 the conditions in the ISO 14125-1 standard; and → the Charpy impact strength, in kJ/m2, was measured under the conditions in the ISO 179-1 eU93 standard. 20 EXAMPLE 1 A sizing composition was prepared that comprised (in % by weight): - film-forming agents: 25 ■ polyvinyl acetate(1) 6.92 ■ polyvinyl acetate(2) of 50000 molecular weight 3.46 ■ epoxy resin(3) 2.40 - plasticizer: a blend of dipropylene glycol dibenzoate and diethylene glycol dibenzoate(4) 0.25 30 - cationic dispersant(5) 2.22 - antifoam(6) 0.28 - conductive particles: ■ carbon black powder(7) 2.37 ■ carbon black powder(8) 35 (mean particle size: 50 nm) 0.97 ■ synthetic graphite powder(9) (particle size: 1-10 μm) 7.77 - coupling agents: ■ γ-methacryloxypropyltriethoxysilane(10) 0.29 - 17 - ■ γ-aminopropyltriethoxysilane(11) 0.19 - lubricant: polyethyleneimine salt(12) 0.59 The composition was prepared by adding the constituents 5 to a vessel containing water at 80°C, it was kept vigorously stirred, the conductive particles being added last. The composition had a viscosity of 7 mPa.s at 20°C and 10 a solids content of 19.2%. The sizing composition was deposited on E-glass filaments 11 urn in diameter, before they were assembled into a single strand, which was wound into a cake. 15 The properties of this strand were the following: - linear density: 202 tex; - loss on ignition: 4.49%; - fuzz: 0.92 mg/100 g of strand; 20 - tenacity: 0.659 N/tex; and - linear resistivity: 0.040 M Ω/cm (standard deviation: 0.015). EXAMPLE 2 25 This example was produced under the conditions of Example 1, but modified in that the sizing composition that was prepared comprised (in % by weight): - film-forming agents: 30 ■ polyvinyl acetate(1) 3.48 ■ polyvinyl acetate(2) of 50000 molecular weight 1.73 ■ epoxy resin(3) 1.20 - plasticizer: a blend of dipropylene glycol dibenzoate and diethylene glycol dibenzoate(4) 0.12 35 - cationic dispersant(5) 2.96 - antifoam(6) 0.28 - conductive particles: ■ carbon black powder(8) (mean particle size: 50 nm) 4.44 - 18 - ■ synthetic graphite powder(9) (particle size: 1-10 μm) 10.36 - coupling agents: ■ γ-methacryloxypropyltriethoxysilane(10) 0.15 5 ■ γ-aminopropyltriethoxysilane(11) 0.10 - lubricant: polyethyleneimine salt(12) 0.30 The composition had a viscosity of 15 mPa.s at 20°C and a solids content of 19.5%. 10 The properties of this strand were the following: - linear density: 200 tex; - loss on ignition: 5.80%; - fuzz: 0.53 mg/100 g of strand; 15 - tenacity: 0.580 N/tex; and - linear resistivity: 0.015 M Ω/cm (standard deviation: 0.010) . EXAMPLE 3 20 A sizing composition was prepared, under the conditions of Example 1, which comprised (in % by weight): - film-forming agents: ■ polyvinyl acetate(1) 5.15 25 ■ polyvinyl acetate(2) of 50000 molecular weight 2.57 ■ epoxy resin(3) 1.73 - plasticizer: a blend of dipropylene glycol dibenzoate and diethylene glycol dibenzoate(4) 0.18 - cationic dispersant(5) 2.60 30 - antifoam(6) 0.18 - conductive particles: ■ carbon black powder(8) (mean particle size: 50 nm) 3.90 ■ expanded synthetic graphite powder(13) 35 in the form of flakes (particle size: 10-50 μm) 2.60 ■ synthetic graphite powder(9) (particle size: 1-10 μm) 6.50 - coupling agents: ■ γ-methacryloxypropyltriethoxysilane(10) 0.22 - 19 - ■ γ-aminopropyltriethoxysilane(11) 0.14 - lubricant: polyethyleneimine salt(12) 0.42 The composition had a viscosity of 12 mPa.s at 20°C and 5 a solids content of 20.2%. The composition was applied to E-glass filaments 16 urn in diameter, which were assembled as four 100 tex strands that were wound directly beneath the bushing in 10 the form of cakes comprising the four separate strands. After the cakes were dried, the strands extracted from the latter were rewound in the form of a 2400 tex assembled roving (six 4x100 tex cakes). 15 The properties of this strand were the following: - linear density: 100 tex; - loss on ignition: 4.40%; - fuzz: 0.125 mg/100 g of strand; - linear resistivity: 0.017 M Ω/cm (standard 20 deviation: 0.009). EXAMPLE 4 This example was prepared under the conditions of 25 Example 3, but modified in that the sizing composition comprised (in % by weight): - film-forming agents: ■ polyvinyl acetate(1) 7.21 ■ polyvinyl acetate(2) of 50000 molecular weight 3.60 30 ■ epoxy resin(3) 1.73 - plasticizer: a blend of dipropylene glycol dibenzoate and diethylene glycol dibenzoate(4) 0.18 - cationic dispersant(5) 2.70 - antifoam(6) 0.18 35 - conductive particles: ■ carbon black powder(8) (mean particle size: 50 nm) 3.90 ■ expanded synthetic graphite powder(13) in the form of flakes (particle size: 10-50 μm) 2.60 - 20 - ■ synthetic graphite powder(9) (particle size: 1-10 μm) 6.50 - coupling agents: ■ γ-methacryloxypropyltriethoxysilane(10) 0.22 5 ■ γ-aminopropyltriethoxysilane(11) 0.14 - lubricant: polyethyleneimine salt(12) 0.42 The composition had a viscosity of 14 mPa.s at 20°C and a solids content of 21.6%. 10 The properties of this strand were the following: - linear density: 100 tex; - loss on ignition: 4.0%; - fuzz: 0.625 mg/100 g of strand; 15 - linear resistivity: 0.034 M Ω/cm (standard deviation: 0.013). An SMC was produced from this strand in the following manner. Deposited in succession on a polyethylene film 20 were: a first layer of unsaturated polyester resin paste; chopped glass strands (length: 25 mm) ; a second layer of the aforementioned paste; and a second polyethylene film, identical to the first. 25 The paste had the following composition (in parts by weight): - polyester resin (M 0494 from Cray Valley) 52 - filler: calcium carbonate 200 - polymerization catalysts: 30 • Trigonox® 117 peroxide from Akzo 1.1 • Trigonox® 141 peroxide from Akzo 0.1 - polyvinyl acetate (Fast Cure® 9005 from Dow Chemicals) 48 - inhibitor: p-benzoquinone 0.06 35 - wetting agent/viscosity reducer (Byk® 996 from Byk Chemie) 1.3 - viscosity reducer (VR3 from Dow Chemicals) 2.0 - mold release agent: zinc stearate 2.0 - thickener: magnesium oxide 2.4 - 21 - The glass strands represented 30% by weight of the SMC composite. 5 The SMC was cut to a size slightly smaller than that of the mold and deposited in the latter after the polyethylene films had been removed. The molding operation was carried out at a temperature of 145°C at a pressure of 70 bar, and a loading factor of 25%. 10 The molded part had the electrical and mechanical properties indicated in the following table. For comparison, this table also shows the properties of a part molded under the same conditions from an SMC 15 composite comprising glass strands coated with a conventional, nonconductive, size (control specimen). Ex. 4 Control Surface resistivity 3-point bending: Strength (MPa) Modulus (MPa) Deflection (mm) Charpy impact strength (kJ/m2) 500 kΩ/‭ - 100 MΩ/‭130 - 140 7000 - 9000 3.00 - 3.8040 - 65 not measurable130 - 150 7000 - 9000 3.25 - 4.0060 - 80 The molded part obtained from the strands according to 20 the invention had a substantially better surface resistivity than the control, within the range of values required for electrostatic painting applications. It had mechanical properties in three- point bending that were equivalent to those of the 25 control. EXAMPLE 5 A sizing composition was prepared, under the conditions 30 of Example 3, which comprised (in % by weight): - 22 - - film-forming agents: ■ polyurethane(14) 16.80 - dispersant: polyetherphosphate(15) 6.68 - antifoam(6) 0.80 5 - conductive particles: ■ carbon black powder(8) (mean particle size: 50 nm) 3.90 ■ expanded synthetic graphite powder(13) in the form of flakes (particle size: 10-50 μm) 2.60 10 ■ synthetic graphite powder(9) (particle size: 1-10 μm) 6.50 - coupling agents: ■ γ-methacryloxypropyltriethoxysilane(10) 0.30 ■ γ-aminopropyltriethoxysilane(11) 0.40 15 The composition had a viscosity of 35 mPa.s at 20°C and a solids content of 22.4%. The strand had a linear density of 91 tex and a loss on 20 ignition of 4.7%. A 1456 tex assembled roving (four 4x91 tex cakes) was produced from the strands extracted from the cakes. 25 The assembled rovings were used under the conditions of Example 4 to form an SMC. The molded part had a surface resistivity of lxlO6 MΩ/‭ and an internal resistivity of 1 MΩ.m. 30 EXAMPLE 6 This example was prepared under the conditions of Example 5, but modified in that the sizing composition 35 comprised (in % by weight): - film-forming agents: ■ polyurethane(14) 16.80 - dispersant: polyetherphosphate(15) 6.68 - antifoam(6) 0.18 - 23 – - - conductive particles: ■ carbon black powder(8) (mean particle size: 50 nm) 5.20 ■ expanded synthetic graphite powder(13) 5 in the form of flakes (particle size: 10-50 μm) 5.20 ■ synthetic graphite powder(9) (particle size: 1-10 μm) 2.60 - coupling agents: ■ γ-methacryloxypropyltriethoxysilahe(10) 0.30 10 ■ γ-aminopropyltriethoxysilane(11) 0.40 The composition had a viscosity of 15 mPa.s at 20°C and a solids content of 22.4%. 15 The strand had a linear density of 96 tex and a loss on ignition of 4.5%. An SMC was produced from this strand under the same conditions as for Example 4. 20 The molded part had a surface resistivity of lx105 MΩ/‭ and an internal resistivity of 0.1 MΩ.m. The molded parts of Examples 4 to 6 have lower surface 25 resistivity values than the control based on a conventional, non electrically conductive, SMC. The parts of Examples 5 and 6 also have a markedly lower internal resistivity than the control (internal 30 resistivity greater than 106 MΩ.m). The inventors attribute this effect to the fact that the film-forming agent present in the glass strand size is relatively insoluble in the matrix. Thus, the conductive particles remain on the strands, or in their immediate 35 environment, and do not migrate to the surface of the part. The conducting network formed by the glass strands within the part gives an internal resistivity sufficient to permit it to be cataphoretically painted. - 24 - (1) Sold under the reference VINAMUL® 8828 by Vinamul (solids content: 52% by weight); 5 (2) Sold under the reference VINAMUL® 8852 by Vinamul (solids content: 55% by weight); (3) Sold under the reference FILCO® 310 by COIM (solids content: 52% by weight); (4) Sold under the reference K-FLEX® 500 by Noveon (solids 10 content: 100% by weight); (5) Sold under the reference SOLSPERSE® 2700 by Lubrizol Additives (solids content: 100% by weight); (6) Sold under the reference TEGO® Foafex 830 by Tego (solids content: 100% by weight); 15 (7) Sold under the reference VULCAN® XC 72 by Cabot; (8) Sold under the reference VULCAN® XC 72 R by Cabot; (9) Sold under the reference SPF 17 by Ucar; (10) Sold under the reference SILQUEST® A-174 by GE Silicones (solids content: 100% by weight); 20 (11) Sold under the reference SILQUEST® A-1100 by GE Silicones (solids content: 100% by' weight) ; (12) Sold under the reference EMERY® 6760 by Cognis (solids content: 17% by weight); (13) Sold under the reference GRAFPOWDER® TG 407 by Ucar; 25 (14) Sold under the reference BAYBOND® PU 401 by Bayer (solids content: 40% by weight); and (15) Sold under the reference TEGO Dispers® 651 by Tego Chemie (solids content: 100% by weight). - 25 – CLAIMS 1. A glass strand coated with an electrically conductive sizing composition which comprises at 5 least one film-forming agent, at least one compound, chosen from plasticizers, surfactants and dispersants, at least one coupling agent for coupling to the glass and electrically conductive particles. 10 2. The glass strand as claimed in claim 1, characterized in that the film-forming agent is a polymer chosen from polyvinyl acetates (homopolymers or copolymers) , polyesters, epoxies, 15 polyacrylics (homopolymers or copolymers), polyurethanes, polyamides, cellulose polymers and blends of these compounds. 3. The glass strand as claimed in claim 2, 20 characterized in that the film-forming agent is polyvinyl acetate, an epoxy or a polyurethane. 4. The glass strand as claimed in one of claims 1 to 3, characterized in that the plasticizer, 25 surfactant and dispersant is chosen from organic compounds, such as optionally halogenated, aliphatic or aromatic, polyalkoxylated compounds, polyalkoxylated fatty acid esters and amine compounds, and from inorganic compounds. 30 5. The glass strand as claimed in one of claims 1 to 4, characterized in that the coupling agent is chosen from hydrolyzable compounds belonging to the group consisting of silanes, siloxanes, 35 titanates, zirconates and blends of these compounds. 6. The glass strand as claimed in one of claims 1 to 5, characterized in that the electrically - 26 - conductive particles are particles based on graphite and/or carbon black. 7. The glass strand as claimed in claim 6, 5 characterized in that the particles are in the form of a blend of particles having different shapes, preferably two or three shapes. 8. The glass strand as claimed in claim 6 or 7, 10 characterized in that 30 to 60% of the particles have an aspect ratio varying from 5 to 20. 9. The glass strand as claimed in one of claims 6 to 8, characterized in that the size of the particles 15 taken along their largest dimension does not exceed 250 urn, preferably 100 μm. 10. The glass strand as claimed in one of claim 1 to 9, characterized in that the particles consist of 20 a blend of graphite particles and , a carbon black powder with a particle size not exceeding 1 μm. 11. The glass strand as claimed in one of claims 1 to 10, characterized in that the dispersant is chosen 25 from cationic, anionic and nonionic compounds. 12. The glass strand as claimed in one of claims 1 to 11, characterized in that the composition further includes a viscosity regulator chosen from 30 carboxymethyl celluloses, guar or xanthan gums, carrageenans, alginates, polyacrylics, polyamides, polyethylene glycols and blends of these compounds. 35 13. The glass strand as claimed in one of claims 1 to 12, characterized in that the composition further includes, as additives, lubricants, complexing agents and antifoams. - 27 - 14. The glass strand as claimed in one of claims 1 to 13, characterized in that the amount of size represents 3.5 to 6% by weight of the strand. 5 15. A sizing composition intended to coat the glass strands as claimed in one of claims 1 to 14, characterized in that it comprises (in % by weight): - 2 to 10%, preferably 3 to 8.5%, of at 10 least one film-forming agent; - 0.2 to 8%, preferably 0.25 to 6%, of at least one compound chosen from plasticizers, surfactants and dispersants; - 4 to 25%, preferably 6 to 20%, of 15 electrically conductive particles; - 0.1 to 4%, preferably 0.15 to 2%, of at least one coupling agent; - 0 to 4%, preferably 0 to 1.8%, of at least one viscosity regulator; and 20 - 0 to 6%, preferably 0 to 3%, of additives. 16 The composition as claimed in claim 15, characterized in that it has a solids content 25 varying from 8 to 35%, preferably 12 to 25%. 17. A method of preparing the composition as claimed in either of claims 15 and 16, which comprises the steps consisting in: 30 a) producing a dispersion D of the conductive particles in water containing the dispersant; b) introducing the other components of the size, namely the film-forming agents, the 35 plasticizers, the surfactants, the coupling agents, in hydrolyzed form, and, where appropriate, the viscosity regulators and the additives, in water in order to form an emulsion E; and - 28 - c) blending the dispersion D with the emulsion E. 18. The method as claimed in claim 17, characterized 5 in that steps a) and c) are carried out with sufficient stirring to prevent sedimentation of the conductive particles. 19. A composite in which at least one thermosetting 10 polymer material is combined with reinforcing strands, characterized in that said strands consist partly or completely of glass strands as claimed in one of claims 1 to 14. 15 20. The composite as claimed in claim 19, characterized in that the glass content in the composite is between 5 and 60%. 21. The composite as claimed in either of claims 19 20 and 20, characterized in that it is in the form of an SMC and in that the glass content is between 10 and 60%, preferably 20 to 45%. 22. The composite as claimed in either of claims 19 25 and 20, characterized in that it is in the form of a BMC and in that the glass content is between 5 and 20%. 23. The use of the glass strands as claimed in one of 30 claims 1 to 14 for producing electrically conductive molded parts using the technique of compression molding, said strands being used in SMC or BMC form. 35 24. A glass strand mat, characterized in that said strands consist partly or completely of glass strands as claimed in one of claims 1 to 14. 25. A glass strand veil, characterized in that said - 29 - strands consist partly or completely of glass strands as claimed in one of claims 1 to 14. Dated this 20th day of APRIL 2007 The present invention relates to glass strands coated with a sizing composition capable of conducting an electric current, which comprises at least one film- forming agent, at least one compound chosen from plasticizers, surfactants and dispersants, at least one coupling agent for coupling to the glass, and electrically conductive particles. The glass strands according to the invention are more particularly intended for the production of electrically conductive parts by compression molding, said glass strands being employed in SMC or BMC form.

Full Text

- 1 -
ELECTRICALLY CONDUCTIVE SIZED GLASS STRANDS
The present invention relates to glass strands coated
with a size capable of conducting an electric current,
5 said strands being intended to reinforce organic
materials of the polymer type, so as to obtain
composites.
The invention also relates to the sizing composition
10 used to coat said strands, to the method for producing
the composites from these strands, and to the resulting
composites.
Conventionally, glass reinforcing strands are produced
15 by mechanically attenuating molten glass streams
flowing out from numerous orifices in a bushing filled
with molten glass, under gravity, through the effect of
the hydrostatic pressure due to the height of the
liquid, in order to form filaments that are assembled
20 into base strands, said strands then being collected on
a suitable support.
During the attenuation, and before they are assembled
into strands, the glass filaments are coated with a
25 sizing composition, generally an aqueous composition,
by passing them over a sizing member.
The size is essential on several counts.
30 During manufacture of the strands, it protects the
filaments from the abrasion that results from them
rubbing, at high speed, on the members for attenuating
and winding the strand by acting as a lubricant. The
size also provides the strand with cohesion, by
35 ensuring that the filaments are linked together.
Finally, it makes the strand sufficiently integral to
withstand the rewinding operations necessary for
forming, in particular, "assembled" rovings from
several base strands, and it also makes it possible for

- 2 -
the electrostatic charges generated during these
operations to be eliminated.
During use for the purpose of producing composites, the
5 size improves the impregnation of the strand by the
matrix to be reinforced and it promotes adhesion
between the glass and said matrix, thus resulting in
composites with improved mechanical properties.
Furthermore, the size protects the strands from
10 chemical and environmental attack, thereby helping to
increase their durability. In applications requiring
the strand to be chopped, the size prevents the
filaments from splaying out and separating, and,
together with the oversize, it contributes to
15 dispersing the electrostatic charges generated during
chopping.
The glass strands in their various forms (continuous,
chopped or ground strands, mats, meshes, wovens, knits,
20 etc.) are commonly used for the effective reinforcement
of matrices of various types, for example thermoplastic
or thermosetting organic materials and inorganic
materials, for example cement.
25 The invention is applicable here to reinforcing strands
that are incorporated into polymer matrices of the
thermosetting type in order to manufacture either
impregnated mats or SMCs (Sheet Molding Compounds),
which may be formed directly by molding in a hot
30 compression mold, or pastes intended to be molded using
the BMC (Bulk Molding Compound) technique.
An SMC is a semifinished product in which a glass
strand mat is combined with a paste of a thermosetting
35 resin, in particular one chosen from polyesters.
In the SMC, the glass acts as reinforcement and
provides the mechanical properties and dimensional
stability of the molded parts. It generally represents

- 3 -
25 to 60% of the weight of the SMC. Usually, the glass
is in the form of chopped strands, even though
continuous strands may be used for some applications.
The paste comprises the thermosetting resin and
5 fillers, and optionally additives, such as initiators,
viscosity regulators and mold release agents.
As is known, an SMC is manufactured by depositing a
first paste layer on a film supported by a conveyor
10 belt, by chopping strands unwound from rovings by means
of a rotary chopper to a length of 12 to 50 millimeters
on top of the resin, the strands being randomly
(isotropically) distributed, and by depositing a second
paste layer supported by a film, the resin face being
15 turned toward the glass. The combination of the various
layers then passes through the nip of one or more
calendering devices so as to impregnate glass strands
with the resin and to remove the trapped air.
20 An SMC must also undergo a maturation treatment, for
the purpose of increasing the viscosity of the resin,
up to an imposed value of 40-100 Pa.s so as to allow it
to be properly molded.
25 Molding with SMCs allows the production of individual
parts, in medium or long runs, which are less expensive
in particular owing to the fact that the SMC is
deposited directly in the mold without it being
required to cut it precisely to the dimensions thereof.
30
What distinguishes a BMC from an SMC is the form, which
here is a paste intended to be injected into a
compression mold.
35 The parts produced by these molding techniques are used
in particular in the automotive field as a replacement
for body parts or impact protection parts, which are
currently made of metal, especially steel.

- 4 -
However, automobile manufacturers are constantly
preoccupied with reducing the weight of vehicles as
much as possible, so as to reduce the fuel consumption.
To do this, it has been envisioned to substitute
5 certain metal parts of the body with lighter parts made
of composites.
The problem that arises with parts made of composites
is that of painting.
10
The operation of painting metal parts is carried out on
an industrial scale by cataphoresis. This consists in
electrostatically depositing one or more primer coats
in order to "smooth" the surface, and one or more paint
15 coats.
Composite parts cannot be used as such as the polymer
material is an electrical insulator. It is therefore
necessary to make them conductive in order to be able
20 to use them on conventional cataphoretic painting
lines.
Solutions aiming to make composites electrically
conductive have been disclosed.
25
US 6 648 593 proposes, prior to application of the
paint, to deposit a first coat of a conductive paint
comprising a resin and conductive particles (in the
form of whiskers), and a second metal coat applied
30 without intervention of the electric current.
This solution requires the addition of other steps that
are difficult to implement in the current process, and
consequently it generates an additional cost.
35
WO-A-03/0 511 992 and US-A-2003/0 042 468 propose a
composition intended to be used in molding processes,
which comprises a crosslinkable prepolymer, at least
one unsaturated monomer copolymerizable with the

- 5 -
prepolymer, a copolymerization initiator and
electrically conductive fillers, for example graphite,
metal-coated particles or metal particles.
5 The processing of the composition is made difficult by
the high conductive filler content needed to obtain a
high level of conduction. Thus, the conductive fillers
are incorporated directly into the matrix. This greatly
increases the viscosity - impregnation of the glass
10 strand is made more difficult and the pressure to be
applied for molding has to be increased. The solution
consisting in increasing the amount of solvent in order
to reduce the viscosity has other drawbacks - it
reduces the mechanical properties of the composite and
15 generates microbubbles that impair the quality of the
surface finish of the final parts.
The object of the present invention is to provide
reinforcing strands that are particularly suitable for
20 SMC production and are capable of conducting an
electric current so as to obtain molded parts made of
composites that can be cataphoretically treated.
One subject of the invention is glass strands coated
25 with an aqueous sizing composition which comprises at
least one film-forming agent, at least one compound,
chosen from plasticizers, surfactants and dispersants,
at least one coupling agent for coupling to the glass
and electrically conductive particles.
30
In the present invention, the expression "glass strands
coated with a sizing composition that comprises ..." is
understood to mean not only glass strands coated with
the composition in question, such as those obtained
35 immediately on leaving the sizing member(s), but also
the same strands that have undergone one or more other
subsequent treatments. Examples that may be mentioned
include the drying treatment, for the purpose of
removing water, and the treatments that lead to the

- 6 -
polymerization/crosslinking of certain constituents of
the sizing composition.
Again within the context of the invention, the term
5 "strands" should be understood to mean the base strands
resulting from the twist-free assembly of a multitude
of filaments, and the products derived from these
strands, especially assemblies of these base strands in
the form of rovings. Such assemblies may be obtained by
10 simultaneously paying out base strands from several
packages and then assembling said strands into tows
that are wound onto a rotating support. They may also
be "direct" rovings with a titer (or linear density)
equivalent to that of assembled rovings obtained by
15 gathering the filaments directly beneath the bushing
and winding onto a rotating support.
Also according to the invention, the expression
"aqueous sizing composition" is understood to mean a
20 composition that can be deposited on the filaments
during attenuation, which composition is in the form of
a suspension or dispersion comprising at least 70%,
preferably 75%, by weight of water and possibly
containing, where appropriate, less than 10%,
25 preferably less than 5%, by weight of one or more
essentially organic solvents helping to dissolve
certain constituents of the sizing composition. In the
majority of cases, the composition contains no organic
solvent, especially so as to limit the emission of
30 volatile organic compounds (VOCs) into the atmosphere.
The film-forming agent according to the invention acts
in several ways: it gives the coating mechanical
cohesion, by making the conductive particles adhere to
35 the glass filaments and ensuring that these particles
are linked together, where appropriate with the
material to be reinforced; it helps to bind the
filaments together; finally, it protects the strands
from any mechanical damage and from chemical and

- 7 –
environmental attack.
The film-forming agent is a polymer chosen from
polyvinyl acetates (homopolymers or copolymers, for
5 example vinyl acetate/ethylene copolymers), polyesters,
epoxies, polyacrylics (homopolymers or copolymers),
polyurethanes, polyamides (homopolymers or copolymers,
for example polyamide/polystyrene or
polyamide/polyoxyethylene block copolymers), cellulose
10 polymers and blends of these compounds. Polyvinyl
acetates, epoxies and polyurethanes are preferred.
The plasticizer lowers the glass transition temperature
of the film-forming agent, giving the size flexibility
15 and limiting shrinking after drying.
The surfactant improves the suspension and dispersion
of the conductive particles and promotes compatibility
between the other constituents and water. It may be
20 chosen from cationic, anionic or nonionic compounds.
To avoid stability and ununiform particle dispersion
problems in the sizing composition, it is preferred to
use cationic or nonionic surfactants.
25
The dispersant helps to disperse the conductive
particles in the water and to reduce their
sedimentation.
30 The plasticizers, surfactants and dispersants may
possess one or more functions specific to each of the
abovementioned categories. The choice of these agents
and the amount to be used depend on the film-forming
agent and on the conductive particles.
35
These agents may especially be chosen from:
> organic compounds, in particular:
- optionally halogenated, aliphatic or
aromatic, polyalkoxylated compounds, such as

- 8 -
ethoxylated/propoxylated alkylphenols, preferably
containing 1 to 30 ethylene oxide groups and 0 to
15 propylene oxide groups, ethoxylated/propoxylated
bisphenols, preferably containing 1 to 40 ethylene
5 oxide groups and 0 to 20 propylene oxide groups,
ethoxylated/propoxylated fatty alcohols, preferably
the alkyl chain of which comprises 8 to 20 carbon
atoms, and containing 2 to 50 ethylene oxide groups
and up to 20 propylene oxide groups. These
10 polyalkoxylated compounds may be block copolymers
or random copolymers,
- polyalkoxylated fatty acid esters, for
example polyethyleneglycol, the alkyl chain of
which preferably comprises 8 to 20 carbon atoms,
15 and containing 2 to 50 ethylene oxide groups and up
to 20 propylene oxide groups and
- amine compounds, for example optionally
alkoxylated amines, a*nine oxides, alkylamides,
sodium, potassium or ammonium succinates and
20 taurates, sugar derivatives, especially sorbitan,
and sodium, potassium or ammonium alkyl sulfates
and alkyl phosphates; and
> inorganic compounds, for example silica
derivatives, these compounds possibly being used by
25 themselves or as a mixture with the aforementioned
organic compounds.
The electrically conductive particles confer electrical
conductivity on the glass strands and the level of
30 performance depends on the amount of particles present
on the strands. According to the invention, these are
carbon-based particles, especially graphite and/or
carbon black particles.
35 The origin of the graphite - natural or synthetic - has
no appreciable impact on the electrical conductivity.
It therefore does not matter whether one or other type
of graphite, by itself or as a blend, is used.

- 9 -
The particles may have any shape - for example they may
be spheres, flakes or needles. However, it has been
found that the electrical conductivity of a blend of
particles of different shapes is improved compared with
5 the same amount of particles but of the same shape.
Blends combining two shapes (binary blend) or three
shapes (ternary blend) of particles prove to be
advantageous.
10 Preferably, 30 to 60% of the conductive particles have
a high aspect ratio (defined by the ratio of the
longest dimension to the shortest), this ratio
preferably varying from 5 to 20, especially around 10,
and advantageously at least 15% of the particles are in
15 the form of flakes or needles.
Like the shape, the size of the particles is an
important parameter as regards electrical conductivity.
As a general rule, the size of the particles taken
20 along their longest dimension does not exceed 250 urn,
preferably 100 urn.
It is advantageous to combine the aforementioned
particles, generally made of graphite, with a carbon
25 black powder that conducts electric current, with a
particle size not exceeding 1 μm, preferably having a
mean size of less than 100 nm. The carbon black
particles, owing to their small size, create points of
contact between the graphite particles, thereby further
30 improving the electrical conductivity.
The coupling agent ensures that the size is attached to
the surface of the glass.
35 The coupling agent is chosen from hydrolyzable
compounds, especially in acid medium containing, for
example, citric acid or acetic acid, these compounds
belonging to the group consisting of silanes, such as
γ-glycidoxypropyltrimethoxysilane, γ-acryloxypropyl-

- 10 -
trimethoxysilane, γ-methacryloxypropyltrimethoxysilane,
poly(oxyethylene/oxypropylene) trimethoxysilane, γ-
aminopropyltriethoxysilane, vinyltrimethoxysilane,
phenylaminopropyltrimethoxysilane or styrylaminoethyl-
5 aminopropyltrimethoxysilane, siloxanes, titanates,
zirconates and blends of these compounds. Preferably,
silanes are chosen.
In addition to the aforementioned constituents that
10 essentially contribute to the structure of the size,
one or more other constituents may be present.
Thus, a viscosity regulator may be introduced, so as to
adjust the viscosity of the composition to the
15 conditions of applying the size to the filaments, in
general this viscosity being between 5 and 80 mPa.s and
preferably at least 7 mPa.s. This regulator also helps
to stabilize the dispersion of particles so that they
do not form a sedimented deposit too rapidly and do not
20 migrate to the outside and lie on the surface of the
package when winding the strand.
The viscosity regulator is chosen from highly
hydrophilic compounds, that is to say those that are
25 able to capture a large amount of water, such as
carboxymethyl celluloses, guar or xanthan gums,
carrageenans, alginates, polyacrylics, polyamides,
polyethylene glycols, especially those with a molecular
weight of greater than 100 000, and blends of these
30 compounds.
The size may also include the usual additives for glass
strands, namely lubricants, such as mineral oils, fatty
esters, for example isopropyl palmitate or butyl
35 stearate, alkylamines, complexing agents, such as EDTA
and gallic acid derivatives, and antifoams, such as
silicones, polyols and vegetable oils.
All of the abovementioned compounds contribute to the

- 11 -
production of glass strands that can be easily
manufactured, are able to be used as reinforcements,
and which are incorporated without any problem into the
resin during manufacture of the composites and also
5 possess electrical conduction properties.
As a general rule, the amount of size represents 2 to
7%, preferably 3.5 to 6%, of the weight of the final
strand.
10
The conductive strand according to the invention may be
made of glass of any kind, for example E-glass, C-
glass, R-glass or AR-glass, and glass with a low boron
content (less than 6%). E-glass and AR-glass are
15 preferred.
The diameter of the glass filaments constituting the
strands may vary widely, for example from 5 to 30 urn.
Likewise, wide variations may occur in the linear
20 density of the strand used, such as an assembled
roving, for which the linear density ranges from 68 to
4800 tex depending on the intended applications, this
roving possibly being formed from base strands whose
linear density varies from 17 to 320 tex.
25
Another subject of the invention is the sizing
composition itself, before it has been deposited on the
glass filaments. It comprises the aforementioned
constituents and water.
30
The sizing composition comprises (in % by weight):
- 2 to 10%, preferably 3 to 8.5%, of at least
one film-forming agent;
- 0.2 to 8%, preferably 0.25 to 6%, of at least
35 one compound chosen from plasticizers, surfactants and
dispersants;
- 4 to 25%, preferably 6 to 20%, of
electrically conductive particles;
- 0.1 to 4%, preferably 0.15 to 2%, of at least

- 12 -
one coupling agent;
- 0 to 4%, preferably 0 to 1.8%, of at least
one viscosity regulator; and
- 0 to 6%, preferably 0 to 3%, of additives.
5
The amount of water to be used is determined so as to
obtain a solids content that varies from 8 to 35%,
preferably 12 to 25%.
10 The preparation of the sizing composition is carried
out as follows:
a) producing a dispersion D of the conductive
particles in water containing the dispersant;
b) introducing the other components of the size,
15 namely the film-forming agents, the plasticizers, the
surfactants, the coupling agents, in hydrolyzed form,
and, where appropriate, the viscosity regulators and
the additives, in water in order to form an emulsion E;
and
20 c) blending the dispersion D with the emulsion
E.
Advantageously, steps a) and c) are carried out with
sufficient stirring to prevent the risk of
25 sedimentation of the conductive particles.
When a viscosity regulator is used, it is introduced at
step b) firstly in the form of an aqueous solution,
where necessary heated to about 80°C so that it
30 dissolves more easily.
In general, the dispersion D is stable under the usual
storage conditions at a temperature of 20 to 25°C. In
particular, it may be used without major drawback over
35 a period of about six months, where necessary stirring
it before use if the particles have sedimented.
However, the sizing composition should be used almost
immediately after it has been prepared, preferably

- 13 -
within a period of time not exceeding about four days
under the aforementioned storage conditions. As
previously, the particles that have sedimented may be
redispersed without the properties of the composition
5 being affected thereby.
As mentioned previously, the aqueous solution is
deposited on the filaments before they are assembled
into base strand (s) . The water is usually removed by
10 drying the strands after collection.
Yet another subject of the invention is a composite, in
particular an SMC or a BMC, in which at least one
thermosetting polymer material is combined with
15 reinforcing strands, said strands consisting partly or
completely of glass strands coated with the sizing
composition described above. The glass content in the
composite is generally between 5 and 60% by weight.
20 According to a first embodiment, the composite is in
the form of an SMC having a glass content of between 10
to 60%, preferably of 20 to 45%, by weight.
According to a second embodiment, the composite is in
25 the form of a BMC having a glass content of between 5
to 20% by weight.
Preferably, the thermosetting polymer material is a
phenolic resin.
30
A further subject of the invention is the use of the
sized glass strands according to the invention for
producing electrically conductive molded parts using
the technique of compression molding, said strands
35 being used in particular in SMC. or BMC form.
As already mentioned, the molded parts can be painted
on standard lines for applying paint cataphoretically,
especially for the production of automobile parts.

- 14 -
Hitherto, it was considered that a part molded from an
SMC or BMC could be coated with paint under the
aforementioned conditions when it has in particular a
5 surface resistivity of between 0.5 and 1.5 MΩ/D.
The inventors have discovered that a part having an
"internal" resistivity, that is to say a volume
resistivity as may be conferred by a layer of
10 conductive fibers within the matrix, for example of the
order of 0.01 to 1000 MΩ.m, could also be treated under
the same conditions.
As a result, the size with which the glass strands are
15 coated does not necessarily have to possess a high
solubility in the matrix to be reinforced, so that the
conductive particles are dispersed throughout the part
in order that it can undergo the cataphoretic painting
treatment. A size that is only slightly soluble in the
20 matrix, for example containing one or more
polyurethanes as film-forming agent, or even one that
is insoluble, may consequently be suitable for applying
paint to such molded parts.
25 The use of the conductive glass strand according to the
invention is not limited to the SMC or BMC molding
technique. More generally, the glass strands can be
used in any technique for manufacturing composites
involving a reinforcement in the form of glass strands
30 that advantageously requires electrical conduction. In
particular, the glass strands may be in the form of a
mat or veil, especially one that can be used as an SMC
surface coating or reinforcing element, said strands
possibly being combined with other reinforcing strands,
35 especially glass strands.
The strands according to the invention may thus be used
in all fields in which it is desired to achieve thermal
conduction and heat dispersion properties, for example

- 15 -
in the domestic electrical appliance and automotive
fields. These strands may also be used for
electromagnetic shielding applications, especially in
the transport field, in particular in automobiles, in
5 the building field and in fields requiring protection
of electronic components, especially those relating to
magnetic media for storing data.
The examples given below illustrate the invention
10 without however limiting it.
In these examples, the following methods were used:
- On the glass strand:
→ the loss on ignition of the sized glass strand
15 was measured under the conditions in the ISO 1887
standard. This loss on ignition is given in %;
→ the flock was measured by making the tows, paid
out from two rovings, pass simultaneously over a turn
roll at a speed of 200 m/min. The flock is defined by
20 the amount of fibrils obtained after a 3 kg mass of
strand has unwound, and it is expressed in mg/100 g of
strand;
→ the tenacity of the strand was determined by
measuring the tensile breaking force under the
25 conditions in the ISO 3341 standard. The tenacity is
expressed in N/tex;
→ the linear resistivity, in MΩ/cm, was obtained
by calculating it from the equation:
ρ = R/l
30 in which ρ is the resistivity in MΩ/cm
R is the resistance in MΩ and
1 is the length of the fiber in cm,
the resistance R being measured using an ohmmeter and
the distance between the two electrodes being 20 cm.
35 - On the molded part:
→ the surface resistivity, in MΩ/D, was measured
according to the NF EN 1149-1 standard;
→ the "internal" resistivity, in MΩ.m, was
measured on a plaque, obtained according to the

- 16 -
aforementioned NF EN 1149-1 standard, drilled with two
holes 20 cm apart. A metal rivet (diameter: 4 mm)
serving as connector was inserted into each hole, said
connectors being connected to the electrodes of an
5 ohmmeter. The internal resistivity was calculated from
the equation:
ρ' = R'S/d
in which ρ' is the internal resistivity, in MΩ.m
R' is the resistance, in MΩ
10 S is the area of the plaque, in m2 and
d is the distance between the
connectors;
→ the flexural strength and the flexural modulus,
in MPa, and the deflection, in mm, were measured under
15 the conditions in the ISO 14125-1 standard; and
→ the Charpy impact strength, in kJ/m2, was
measured under the conditions in the ISO 179-1 eU93
standard.
20 EXAMPLE 1
A sizing composition was prepared that comprised (in %
by weight):
- film-forming agents:
25 ■ polyvinyl acetate(1) 6.92
■ polyvinyl acetate(2) of 50000 molecular weight 3.46
■ epoxy resin(3) 2.40
- plasticizer: a blend of dipropylene glycol
dibenzoate and diethylene glycol dibenzoate(4) 0.25
30 - cationic dispersant(5) 2.22
- antifoam(6) 0.28
- conductive particles:
■ carbon black powder(7) 2.37
■ carbon black powder(8)
35 (mean particle size: 50 nm) 0.97
■ synthetic graphite powder(9)
(particle size: 1-10 μm) 7.77
- coupling agents:
■ γ-methacryloxypropyltriethoxysilane(10) 0.29

- 17 -
■ γ-aminopropyltriethoxysilane(11) 0.19
- lubricant: polyethyleneimine salt(12) 0.59
The composition was prepared by adding the constituents
5 to a vessel containing water at 80°C, it was kept
vigorously stirred, the conductive particles being
added last.
The composition had a viscosity of 7 mPa.s at 20°C and
10 a solids content of 19.2%.
The sizing composition was deposited on E-glass
filaments 11 urn in diameter, before they were assembled
into a single strand, which was wound into a cake.
15
The properties of this strand were the following:
- linear density: 202 tex;
- loss on ignition: 4.49%;
- fuzz: 0.92 mg/100 g of strand;
20 - tenacity: 0.659 N/tex; and
- linear resistivity: 0.040 M Ω/cm (standard
deviation: 0.015).
EXAMPLE 2
25
This example was produced under the conditions of
Example 1, but modified in that the sizing composition
that was prepared comprised (in % by weight):
- film-forming agents:
30 ■ polyvinyl acetate(1) 3.48
■ polyvinyl acetate(2) of 50000 molecular weight 1.73
■ epoxy resin(3) 1.20
- plasticizer: a blend of dipropylene glycol
dibenzoate and diethylene glycol dibenzoate(4) 0.12
35 - cationic dispersant(5) 2.96
- antifoam(6) 0.28
- conductive particles:
■ carbon black powder(8)
(mean particle size: 50 nm) 4.44

- 18 -
■ synthetic graphite powder(9)
(particle size: 1-10 μm) 10.36
- coupling agents:
■ γ-methacryloxypropyltriethoxysilane(10) 0.15
5 ■ γ-aminopropyltriethoxysilane(11) 0.10
- lubricant: polyethyleneimine salt(12) 0.30
The composition had a viscosity of 15 mPa.s at 20°C and
a solids content of 19.5%.
10
The properties of this strand were the following:
- linear density: 200 tex;
- loss on ignition: 5.80%;
- fuzz: 0.53 mg/100 g of strand;
15 - tenacity: 0.580 N/tex; and
- linear resistivity: 0.015 M Ω/cm (standard
deviation: 0.010) .
EXAMPLE 3
20
A sizing composition was prepared, under the conditions
of Example 1, which comprised (in % by weight):
- film-forming agents:
■ polyvinyl acetate(1) 5.15
25 ■ polyvinyl acetate(2) of 50000 molecular weight 2.57
■ epoxy resin(3) 1.73
- plasticizer: a blend of dipropylene glycol
dibenzoate and diethylene glycol dibenzoate(4) 0.18
- cationic dispersant(5) 2.60
30 - antifoam(6) 0.18
- conductive particles:
■ carbon black powder(8)
(mean particle size: 50 nm) 3.90
■ expanded synthetic graphite powder(13)
35 in the form of flakes (particle size: 10-50 μm) 2.60
■ synthetic graphite powder(9)
(particle size: 1-10 μm) 6.50
- coupling agents:
■ γ-methacryloxypropyltriethoxysilane(10) 0.22

- 19 -
■ γ-aminopropyltriethoxysilane(11) 0.14
- lubricant: polyethyleneimine salt(12) 0.42
The composition had a viscosity of 12 mPa.s at 20°C and
5 a solids content of 20.2%.
The composition was applied to E-glass filaments 16 urn
in diameter, which were assembled as four 100 tex
strands that were wound directly beneath the bushing in
10 the form of cakes comprising the four separate strands.
After the cakes were dried, the strands extracted from
the latter were rewound in the form of a 2400 tex
assembled roving (six 4x100 tex cakes).
15 The properties of this strand were the following:
- linear density: 100 tex;
- loss on ignition: 4.40%;
- fuzz: 0.125 mg/100 g of strand;
- linear resistivity: 0.017 M Ω/cm (standard
20 deviation: 0.009).
EXAMPLE 4
This example was prepared under the conditions of
25 Example 3, but modified in that the sizing composition
comprised (in % by weight):
- film-forming agents:
■ polyvinyl acetate(1) 7.21
■ polyvinyl acetate(2) of 50000 molecular weight 3.60
30 ■ epoxy resin(3) 1.73
- plasticizer: a blend of dipropylene glycol
dibenzoate and diethylene glycol dibenzoate(4) 0.18
- cationic dispersant(5) 2.70
- antifoam(6) 0.18
35 - conductive particles:
■ carbon black powder(8)
(mean particle size: 50 nm) 3.90
■ expanded synthetic graphite powder(13)
in the form of flakes (particle size: 10-50 μm) 2.60

- 20 -
■ synthetic graphite powder(9)
(particle size: 1-10 μm) 6.50
- coupling agents:
■ γ-methacryloxypropyltriethoxysilane(10) 0.22
5 ■ γ-aminopropyltriethoxysilane(11) 0.14
- lubricant: polyethyleneimine salt(12) 0.42
The composition had a viscosity of 14 mPa.s at 20°C and
a solids content of 21.6%.
10
The properties of this strand were the following:
- linear density: 100 tex;
- loss on ignition: 4.0%;
- fuzz: 0.625 mg/100 g of strand;
15 - linear resistivity: 0.034 M Ω/cm (standard
deviation: 0.013).
An SMC was produced from this strand in the following
manner. Deposited in succession on a polyethylene film
20 were: a first layer of unsaturated polyester resin
paste; chopped glass strands (length: 25 mm) ; a second
layer of the aforementioned paste; and a second
polyethylene film, identical to the first.
25 The paste had the following composition (in parts by
weight):
- polyester resin (M 0494 from Cray Valley) 52
- filler: calcium carbonate 200
- polymerization catalysts:
30 • Trigonox® 117 peroxide from Akzo 1.1
• Trigonox® 141 peroxide from Akzo 0.1
- polyvinyl acetate (Fast Cure® 9005 from
Dow Chemicals) 48
- inhibitor: p-benzoquinone 0.06
35 - wetting agent/viscosity reducer (Byk® 996 from
Byk Chemie) 1.3
- viscosity reducer (VR3 from Dow Chemicals) 2.0
- mold release agent: zinc stearate 2.0
- thickener: magnesium oxide 2.4

- 21 -
The glass strands represented 30% by weight of the SMC
composite.
5 The SMC was cut to a size slightly smaller than that of
the mold and deposited in the latter after the
polyethylene films had been removed. The molding
operation was carried out at a temperature of 145°C at
a pressure of 70 bar, and a loading factor of 25%.
10
The molded part had the electrical and mechanical
properties indicated in the following table. For
comparison, this table also shows the properties of a
part molded under the same conditions from an SMC
15 composite comprising glass strands coated with a
conventional, nonconductive, size (control specimen).
Ex. 4 Control
Surface resistivity 3-point bending: Strength (MPa) Modulus (MPa) Deflection (mm) Charpy impact strength (kJ/m2) 500 kΩ/‭ - 100 MΩ/‭130 - 140 7000 - 9000 3.00 - 3.8040 - 65 not measurable130 - 150 7000 - 9000 3.25 - 4.0060 - 80
The molded part obtained from the strands according to
20 the invention had a substantially better surface
resistivity than the control, within the range of
values required for electrostatic painting
applications. It had mechanical properties in three-
point bending that were equivalent to those of the
25 control.
EXAMPLE 5
A sizing composition was prepared, under the conditions
30 of Example 3, which comprised (in % by weight):

- 22 -
- film-forming agents:
■ polyurethane(14) 16.80
- dispersant: polyetherphosphate(15) 6.68
- antifoam(6) 0.80
5 - conductive particles:
■ carbon black powder(8)
(mean particle size: 50 nm) 3.90
■ expanded synthetic graphite powder(13)
in the form of flakes (particle size: 10-50 μm) 2.60
10 ■ synthetic graphite powder(9)
(particle size: 1-10 μm) 6.50
- coupling agents:
■ γ-methacryloxypropyltriethoxysilane(10) 0.30
■ γ-aminopropyltriethoxysilane(11) 0.40
15
The composition had a viscosity of 35 mPa.s at 20°C and
a solids content of 22.4%.
The strand had a linear density of 91 tex and a loss on
20 ignition of 4.7%.
A 1456 tex assembled roving (four 4x91 tex cakes) was
produced from the strands extracted from the cakes.
25 The assembled rovings were used under the conditions of
Example 4 to form an SMC.
The molded part had a surface resistivity of lxlO6 MΩ/‭
and an internal resistivity of 1 MΩ.m.
30
EXAMPLE 6
This example was prepared under the conditions of
Example 5, but modified in that the sizing composition
35 comprised (in % by weight):
- film-forming agents:
■ polyurethane(14) 16.80
- dispersant: polyetherphosphate(15) 6.68
- antifoam(6) 0.18

- 23 –
- - conductive particles:
■ carbon black powder(8)
(mean particle size: 50 nm) 5.20
■ expanded synthetic graphite powder(13)
5 in the form of flakes (particle size: 10-50 μm) 5.20
■ synthetic graphite powder(9)
(particle size: 1-10 μm) 2.60
- coupling agents:
■ γ-methacryloxypropyltriethoxysilahe(10) 0.30
10 ■ γ-aminopropyltriethoxysilane(11) 0.40
The composition had a viscosity of 15 mPa.s at 20°C and
a solids content of 22.4%.
15 The strand had a linear density of 96 tex and a loss on
ignition of 4.5%.
An SMC was produced from this strand under the same
conditions as for Example 4.
20
The molded part had a surface resistivity of lx105 MΩ/‭
and an internal resistivity of 0.1 MΩ.m.
The molded parts of Examples 4 to 6 have lower surface
25 resistivity values than the control based on a
conventional, non electrically conductive, SMC.
The parts of Examples 5 and 6 also have a markedly
lower internal resistivity than the control (internal
30 resistivity greater than 106 MΩ.m). The inventors
attribute this effect to the fact that the film-forming
agent present in the glass strand size is relatively
insoluble in the matrix. Thus, the conductive particles
remain on the strands, or in their immediate
35 environment, and do not migrate to the surface of the
part. The conducting network formed by the glass
strands within the part gives an internal resistivity
sufficient to permit it to be cataphoretically painted.

- 24 -

(1) Sold under the reference VINAMUL® 8828 by Vinamul (solids
content: 52% by weight);
5 (2) Sold under the reference VINAMUL® 8852 by Vinamul (solids
content: 55% by weight);
(3) Sold under the reference FILCO® 310 by COIM (solids content:
52% by weight);
(4) Sold under the reference K-FLEX® 500 by Noveon (solids
10 content: 100% by weight);
(5) Sold under the reference SOLSPERSE® 2700 by Lubrizol Additives
(solids content: 100% by weight);
(6) Sold under the reference TEGO® Foafex 830 by Tego (solids
content: 100% by weight);
15 (7) Sold under the reference VULCAN® XC 72 by Cabot;
(8) Sold under the reference VULCAN® XC 72 R by Cabot;
(9) Sold under the reference SPF 17 by Ucar;
(10) Sold under the reference SILQUEST® A-174 by GE Silicones
(solids content: 100% by weight);
20 (11) Sold under the reference SILQUEST® A-1100 by GE Silicones
(solids content: 100% by' weight) ;
(12) Sold under the reference EMERY® 6760 by Cognis (solids
content: 17% by weight);
(13) Sold under the reference GRAFPOWDER® TG 407 by Ucar;
25 (14) Sold under the reference BAYBOND® PU 401 by Bayer (solids
content: 40% by weight); and
(15) Sold under the reference TEGO Dispers® 651 by Tego Chemie
(solids content: 100% by weight).

- 25 –
CLAIMS
1. A glass strand coated with an electrically
conductive sizing composition which comprises at
5 least one film-forming agent, at least one
compound, chosen from plasticizers, surfactants
and dispersants, at least one coupling agent for
coupling to the glass and electrically conductive
particles.
10
2. The glass strand as claimed in claim 1,
characterized in that the film-forming agent is a
polymer chosen from polyvinyl acetates
(homopolymers or copolymers) , polyesters, epoxies,
15 polyacrylics (homopolymers or copolymers),
polyurethanes, polyamides, cellulose polymers and
blends of these compounds.
3. The glass strand as claimed in claim 2,
20 characterized in that the film-forming agent is
polyvinyl acetate, an epoxy or a polyurethane.
4. The glass strand as claimed in one of claims 1 to
3, characterized in that the plasticizer,
25 surfactant and dispersant is chosen from organic
compounds, such as optionally halogenated,
aliphatic or aromatic, polyalkoxylated compounds,
polyalkoxylated fatty acid esters and amine
compounds, and from inorganic compounds.
30
5. The glass strand as claimed in one of claims 1 to
4, characterized in that the coupling agent is
chosen from hydrolyzable compounds belonging to
the group consisting of silanes, siloxanes,
35 titanates, zirconates and blends of these
compounds.
6. The glass strand as claimed in one of claims 1 to
5, characterized in that the electrically

- 26 -
conductive particles are particles based on
graphite and/or carbon black.
7. The glass strand as claimed in claim 6,
5 characterized in that the particles are in the
form of a blend of particles having different
shapes, preferably two or three shapes.
8. The glass strand as claimed in claim 6 or 7,
10 characterized in that 30 to 60% of the particles
have an aspect ratio varying from 5 to 20.
9. The glass strand as claimed in one of claims 6 to
8, characterized in that the size of the particles
15 taken along their largest dimension does not
exceed 250 urn, preferably 100 μm.
10. The glass strand as claimed in one of claim 1 to
9, characterized in that the particles consist of
20 a blend of graphite particles and , a carbon black
powder with a particle size not exceeding 1 μm.
11. The glass strand as claimed in one of claims 1 to
10, characterized in that the dispersant is chosen
25 from cationic, anionic and nonionic compounds.
12. The glass strand as claimed in one of claims 1 to
11, characterized in that the composition further
includes a viscosity regulator chosen from
30 carboxymethyl celluloses, guar or xanthan gums,
carrageenans, alginates, polyacrylics, polyamides,
polyethylene glycols and blends of these
compounds.
35 13. The glass strand as claimed in one of claims 1 to
12, characterized in that the composition further
includes, as additives, lubricants, complexing
agents and antifoams.

- 27 -
14. The glass strand as claimed in one of claims 1 to
13, characterized in that the amount of size
represents 3.5 to 6% by weight of the strand.
5 15. A sizing composition intended to coat the glass
strands as claimed in one of claims 1 to 14,
characterized in that it comprises (in % by
weight):
- 2 to 10%, preferably 3 to 8.5%, of at
10 least one film-forming agent;
- 0.2 to 8%, preferably 0.25 to 6%, of at
least one compound chosen from plasticizers,
surfactants and dispersants;
- 4 to 25%, preferably 6 to 20%, of
15 electrically conductive particles;
- 0.1 to 4%, preferably 0.15 to 2%, of at
least one coupling agent;
- 0 to 4%, preferably 0 to 1.8%, of at
least one viscosity regulator; and
20 - 0 to 6%, preferably 0 to 3%, of
additives.
16 The composition as claimed in claim 15,
characterized in that it has a solids content
25 varying from 8 to 35%, preferably 12 to 25%.
17. A method of preparing the composition as claimed
in either of claims 15 and 16, which comprises the
steps consisting in:
30 a) producing a dispersion D of the
conductive particles in water containing the
dispersant;
b) introducing the other components of the
size, namely the film-forming agents, the
35 plasticizers, the surfactants, the coupling
agents, in hydrolyzed form, and, where
appropriate, the viscosity regulators and the
additives, in water in order to form an emulsion
E; and

- 28 -
c) blending the dispersion D with the
emulsion E.
18. The method as claimed in claim 17, characterized
5 in that steps a) and c) are carried out with
sufficient stirring to prevent sedimentation of
the conductive particles.
19. A composite in which at least one thermosetting
10 polymer material is combined with reinforcing
strands, characterized in that said strands
consist partly or completely of glass strands as
claimed in one of claims 1 to 14.
15 20. The composite as claimed in claim 19,
characterized in that the glass content in the
composite is between 5 and 60%.
21. The composite as claimed in either of claims 19
20 and 20, characterized in that it is in the form of
an SMC and in that the glass content is between 10
and 60%, preferably 20 to 45%.
22. The composite as claimed in either of claims 19
25 and 20, characterized in that it is in the form of
a BMC and in that the glass content is between 5
and 20%.
23. The use of the glass strands as claimed in one of
30 claims 1 to 14 for producing electrically
conductive molded parts using the technique of
compression molding, said strands being used in
SMC or BMC form.
35 24. A glass strand mat, characterized in that said
strands consist partly or completely of glass
strands as claimed in one of claims 1 to 14.
25. A glass strand veil, characterized in that said

- 29 -
strands consist partly or completely of glass
strands as claimed in one of claims 1 to 14.
Dated this 20th day of APRIL 2007

The present invention relates to glass strands coated
with a sizing composition capable of conducting an
electric current, which comprises at least one film-
forming agent, at least one compound chosen from
plasticizers, surfactants and dispersants, at least one
coupling agent for coupling to the glass, and
electrically conductive particles.
The glass strands according to the invention are more
particularly intended for the production of
electrically conductive parts by compression molding,
said glass strands being employed in SMC or BMC form.

Documents:

01401-kolnp-2007-abstract.pdf

01401-kolnp-2007-claims.pdf

01401-kolnp-2007-correspondence others 1.1.pdf

01401-kolnp-2007-correspondence others 1.2.pdf

01401-kolnp-2007-correspondence others.pdf

01401-kolnp-2007-description complete.pdf

01401-kolnp-2007-form 1.pdf

01401-kolnp-2007-form 2.pdf

01401-kolnp-2007-form 3.pdf

01401-kolnp-2007-form 5.pdf

01401-kolnp-2007-gpa.pdf

01401-kolnp-2007-international publication.pdf

01401-kolnp-2007-international search report.pdf

01401-kolnp-2007-pct request.pdf

01401-kolnp-2007-priority document 1.1.pdf

01401-kolnp-2007-priority document.pdf

1401-KOLNP-2007-(06-05-2014)-ABSTRACT.pdf

1401-KOLNP-2007-(06-05-2014)-ANNEXURE TO FORM 3.pdf

1401-KOLNP-2007-(06-05-2014)-CLAIMS.pdf

1401-KOLNP-2007-(06-05-2014)-CORRESPONDENCE-1.pdf

1401-KOLNP-2007-(06-05-2014)-CORRESPONDENCE.pdf

1401-KOLNP-2007-(06-05-2014)-FORM-1.pdf

1401-KOLNP-2007-(06-05-2014)-FORM-2.pdf

1401-KOLNP-2007-(06-05-2014)-FORM-5.pdf

1401-KOLNP-2007-(06-05-2014)-PETITION UNDER RULE 137.pdf

1401-KOLNP-2007-CORRESPONDENCE 1.1.pdf

1401-kolnp-2007-form 18.pdf

« Previous Patent

Next Patent »

Patent Number

264096

Indian Patent Application Number

1401/KOLNP/2007

PG Journal Number

50/2014

Publication Date

12-Dec-2014

Grant Date

05-Dec-2014

Date of Filing

20-Apr-2007

Name of Patentee

SAINT-GOBAIN VETROTEX FRANCE, S.A.

Applicant Address

130 AVENUE DES FOLLAZ F-73000 CHAMBERY

Inventors:

#	Inventor's Name	Inventor's Address
1	MOIREAU, PATRICK	LIEU-DIT VERNAY 73190 CURIENNE
2	METRA, CLAIRE	CLOS PARC TRIVIER 73190 CHALLES LES EAUX
3	CEUGNIET, CLAIRE	BASSA 73410 SAINT OURS

PCT International Classification Number

C03C 25/10

PCT International Application Number

PCT/FR2005/050885

PCT International Filing date

2005-10-21

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0452398	2004-10-21	France