Title of Invention	A PROCESS FOR THE PREPARATION OF NYLON 6 DISCRETE FIBERS FOR SECONDARY REINFORCEMENT IN CONCRETE AND PLASTER APPLICATIONS
Abstract	The present invention provides a process for preparing discrete grade Nylon 6 fibres as secondary reinforcement for cementitious composites to enhance concrete/plaster properties. The discrete Nylon 6 fiber has fineness of 2 denier, 6 mm to 18 mm length and trilobal cross section. In another aspect of the present invention there is provided reinforced cementitious concrete composites comprising a cementious material and Nylon 6 discrete fibres , wherein Nylon 6 discrete fibres is in the range of 0.02 to 0.04 % by weight of the cementitious material.

Title of Invention

A PROCESS FOR THE PREPARATION OF NYLON 6 DISCRETE FIBERS FOR SECONDARY REINFORCEMENT IN CONCRETE AND PLASTER APPLICATIONS

Abstract

The present invention provides a process for preparing discrete grade Nylon 6 fibres as secondary reinforcement for cementitious composites to enhance concrete/plaster properties. The discrete Nylon 6 fiber has fineness of 2 denier, 6 mm to 18 mm length and trilobal cross section. In another aspect of the present invention there is provided reinforced cementitious concrete composites comprising a cementious material and Nylon 6 discrete fibres , wherein Nylon 6 discrete fibres is in the range of 0.02 to 0.04 % by weight of the cementitious material.

Full Text	FORM - 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2006 Complete Specification (See Section 10 and Rule 13) A process for the preparation of Nylon 6 Discrete Fibers for Secondary Reinforcement in Concrete and Plaster applications GUJARAT STATE FERTILIZERS & CHEMICALS LIMITED an Indian Company P.O FERTILIZER NAGAR-391750 DISTRICT VADODARA GUJARAT, INDIA The Following Specification Particularly Describes the Invention and the manner in which it is to be performed. Field of the invention The present invention relates to Nylon 6 fibers as a secondary reinforcement in a cementitious composite. The present invention envisages process for the preparation of discrete grade Nylon 6 fibers as a secondary reinforcement in a cementitious composite with enhanced concrete/plaster properties. Background and Prior art It is common knowledge that concrete or mix of cementitious composites are prone to self induced cracking which makes them further weak and brittle. These self induced cracks propagate through concrete / plaster under relatively low stresses into bigger cracks under tension. It is, therefore, required to minimize the presence of micro cracks to improve the durability of structures. When a mix of concrete, or any other mix of a cementitious composite, is placed (e.g., poured, molded, layered, sprayed, etc.), the solids, e.g. aggregates, fines and cement therein begin to settle downward due to gravity. As the solids sink, water is displaced and forced to the surface as bleed water. Plastic shrinkage cracking of the concrete or mix of cementitious composite occurs when the rate of water evaporation exceeds the rate of water displacement. Shrinkage stresses associated with early volume change account for the majority of all non-structural cracks in concrete or mix of a cementitious composite. As mentioned above, these cracks, which are formed while the concrete or mix of a cementitious composite settles, affect the strength and durability of the structure during its service. Therefore, in the common practice, concrete or cementitious composite mix products / structures are watered and cooled while hardening. However, as watering of these products / structures while hardening does not completely eliminate micro cracks formation and subsequent bigger cracks, it calls for special attention and need to search and incorporate fiber additives which act as secondary reinforcement and reduce / eliminate micro cracks formation in products / structures. The concept of using fibers as reinforcement is not new. Fibers have been used as reinforcement since ancient times. Historically, horsehair was used in mortar and straw in mud bricks for imparting reinforcement in structures. In the early 1900s asbestos fibers were used in concrete, and in the 1950s the concept of composite materials came in to being and fiber reinforced concrete / cementitious composite mix emerged as one of the areas of keen interest. There was a need to find a replacement of asbestos used as reinforcement in concrete / cementitious composite mix and other building materials once the health risks associated with the substance were discovered. By the 1960s, steel, glass, and synthetic fibers such as Polypropylene made their ways for use as reinforcement in concrete / cementitious composite mix products / structures. Fibers are usually used in concrete / cementitious composite mix to control plastic shrinkage cracking and drying shrinkage cracking. They also lower the permeability of water in concrete / cementitious composite mix and thus improves the life and reduces the repairing / repainting requirements of structures in long run. Fiber reinforced concrete (FRC) or Fiber Reinforced Plaster (FRP) is a cementitious composite mix containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly dispersed and layered within composite mix. Such fibers include steel, glass, synthetic and natural fibers. Nylon (majority being nylon 6 and nylon 66 fibers), Polyester and Polypropylene fibers can be used for fiber reinforced concrete and plaster reinforcements. Fiber Reinforced Concrete and Plaster utilizes discrete synthetic fibers, typically 15-25 mm and 4-8 mm in length to provide improvements in concrete and plaster properties such as: • Reduction in shrinkage cracks / micro cracks • Rise in compression, flexural and impact strength • Reduction in water permeability • Improvement in homogeneity of concrete by reducing segregation of aggregates • Improvement in ductility of concrete under cyclic loading • Rise in freeze / thaw resistance • Improvement in durability of concrete • Higher abrasion resistance The type of fiber, its inherent polymer properties, fineness, cross section, length, density etc. are critical parameters which determine its performance as secondary reinforcement in improving various structural properties in concrete and plaster applications. Type of fiber cross section and fineness determine the available fiber surface area for interaction and bonding with concrete mix and resultant improvement in FRC or FRP properties and performance. Fiber fineness i.e. fiber diameter and cross section type play critical role in reducing plastic shrinkage cracking within concrete or cementitious composite mix. Therefore, there is felt a need to develop Nylon 6 discrete fibers with the characteristic properties for enhancing concrete/plaster properties. Object of the Invention The object of the invention is to provide Nylon 6 discrete fibers with specific attributes and superior FRC and FRP properties. Another object of the invention is to provide Nylon 6 discrete fibers to reduce the plastic shrinking cracking and water permeability of reinforced cementitious concrete and mortar mix. Another object of the invention is to provide Nylon 6 discrete fibers to reduce water permeability of reinforced cementitious concrete and mortar mix. A further object of the invention is to provide reinforced cementitious concrete composites of Nylon 6 discrete fibers with superior compression, flexural, impact strength and enhanced life of concrete. Summary of the Invention. In accordance with the present invention there is provided a process for the preparation of Nylon 6 discrete fibers comprising the following steps; i) extruding molten Nylon 6 fibers through fine orifices of a spinneret to obtain a plurality of filaments of non-circular cross section; ii) quenching the extruded filaments in air, preferably cold air; iii) combining the quenched filaments to form a bundle; iv) applying spin finish oil to the bundle ; v) winding the bundled filaments on tubes at winding speed of 600 to 1000 meter per minute to obtain low oriented Nylon 6 filament yarn (LOY) product; vi) conditioning the LOY at 75-80% relative humidity; vii) drawing the conditioned LOY, twisting it to form Nylon 6 multifilament flat yarns of filament fineness 2.0 to 4.5 denier and yarn denier 20.0 to about 111.0, tenacity 4-5 grams/denier, % uster 1.5 to 2.0 and breaking elongation of 40-50% and winding the yarns on cop package; viii) combining the yarn ends from the package to form a tow; ix) impregnating the tow sequentially with water at 20°C to 35°C temperature and an aqueous stabilizer at 80°C to 100°C temperature to yield stabilized tow; x) squeezing the stabilized tow at a pressure of about 1 to 10 KN pressure and draw ratio of 1.01 to 1.1 ; and xi) cutting the squeezed tow to obtain staple length Nylon discrete fibers. Typically, Nylon 6 fiber is textile Nylon 6 fiber with relative viscosity of 2.6 to 2.66, caprolactum content less than 0.7% and moisture less than 0.08%. The non-circular cross section of extruded Nylon 6 filament yarn is trilobal. The aqueous stabilizer comprises 8-10% by weight of Benzene Phosphonic Acid. The Benzene Phosphonic Acid is applied to the tow at the rate of 400 -1000 ppm/kg of fibre . Typically, the discrete Nylon 6 fiber has 2 denier fineness and length from 6 mm to 18 mm. In another aspect of the present invention there is provided a reinforced cementitious concrete composites comprising a cementious material and Nylon 6 discrete fibres , said Nylon 6 discrete fibres being in the range of 0.02 to 0.04 % by weight of the cementitious material. The reinforced cementitious concrete composites further comprises sulfonated melamine formaldehyde in the range of 0.08 to 0.1 % by volume of the cementitious material. Brief Description of the Invention Nylon 6 fiber, which is a man made synthetic fiber, is hydrophilic by nature and absorbs typically 4-5% moisture. When this fiber is incorporated in to concrete/mortar mix, it absorbs moisture from the free water available in the mix and acts as reservoir of water within the concrete plaster mix. It would be highly advantageous to make use of textile grade of Nylon 6 fiber and impart required properties to make it perform as secondary reinforcement in concrete or cementitious composite mix. The present invention is related to the cementitious composites mix which include suitable grade of textile Nylon 6 fibers, cut into staples, which are used for reinforcing its cementitios - matrix. The cementitious matrix is formed by activating a common cementitious material such as cement in presence of water. However, the scope of the invention is not limited to cement and other cementitious material like silicates, clay, and gypsum. Further the invention is also not limited to water activated setting process. The cementitious composites may further include additional ingredients like aggregates and fines used traditionally to acquire specific characteristics such as strength, durability, workability, insulation etc. The present investigation is directed towards the development of unique fiber characteristic in Nylon 6 fiber with optimized attributes to be as secondary reinforcement for cementitious composites such as concrete and mortar. Fibre Reinforced Concrete and Plaster results from the addition of short Nylon 6 discrete fibers as secondary reinforcement to the cement based matrix. The behavioral efficiency of these composite structures is far more superior compared to plain concrete and plaster and many other construction materials of equal cost. An extensive R&D investigations have been carried out i) to develop different grades of Nylon 6 fiber, ii) to evaluate these grades for Fiber Reinforced Concrete / Plaster application properties, hi) to evolve a non round cross section i.e. trilobal and low diameter textile fiber with superior FRC and FRP properties. In accordance with the present invention the process for the preparation of Nylon 6 discrete fibers is carried out as follows a) Nylon 6 fibres are melted in an extruder and molten fibres are extruded through fine orifices of a spinneret of non circular cross sections such as circular, triangular or trilobal, to obtain a plurality of filaments, b) The filaments are quenched in cold air and then combined to form a bundle; c) Spin finish oil is applied to the bundle and the lubricated filaments are wound on the tubes at winding speed of 600 to 1000 meter per minute to obtain low oriented Nylon 6 filament yarn (LOY) product. Spin finish oil made up of lubricant, binding agent and antistatic agent is encapsulated on yarn surface as processing additive during melt spinning of Nylon 6 yarn. 0.8 - 1.0 % Spin finish oil per weight of yarn is applied on Nylon 6 fibre. Spin finish oil acts as lubricant and binding and antistatic agent during Nylon 6 yarn melt spinning process and also facilitates unwinding of yarn from package for subsequent processing. d) The LOY is conditioned at 75-80% relative humidity. In order to impart necessary morphological changes in yarn structure, the Nylon 6 Low Oriented Yarn (LOY) is kept at 75 - 80 % relative Humidity for definite time interval This is called conditioning of LOY. e) After conditioning the Nylon 6 LOY is further drawn and twisted in Draw - Twisting process to form Nylon 6 multifilament flat yarns of filament fineness 2.0 to 4.5 denier and yarn denier 20.0 to about 111.0, tenacity 4-5 grams/denier, % uster 1.5 to 2.0 and breaking elongation of 40-50% ; f) Large no of cop packages ranging from 500-1000, each containing 0.7 to 2.0 kg Nylon 6 multifilament flat yarn are mounted in a suitably designed creel. Yarn ends from all cops are pulled and combined in tow form. The tow is fed through tensioning device, guiding mechanism and pair of feed rollers to an impregnation bath. In case of finer yarn deniers, alternately, 30 to 40 yarns are parallel wound on a package in parallel winding unit to make 2500-3000 final denier of each package. 50-100 such packages are mounted in a suitably designed creel and yarn ends are pulled and combined in tow form, g) The tow is impregnated sequentially with water at 20 C to 35 C temperature and an aqueous stabilizer at 80°C to 100 C temperature. The impregnation bath includes i) pair of motorized feed rollers, ii) big trough divided in two compartments - first for water impregnation and second for solution / boiling water impregnation with electric heaters for controlled heating of solution / water and both compartments with internal guiding rollers, and iii) pair of motorized draws off cum squeeze rollers having pneumatics pressure controller. The tow, at ambient temperature, is impregnated in water in first compartment. The process spin finish oil is removed from the bundle of filaments in this compartment. In second compartment stabilizer viz. benzene phosphonic acid (4-10% solution) is applied (@ 400 -lOOOppm) to the tow for imparting stabilization against hydrolytic degradation. h) The impregnated tow is drawn off through squeeze roller (8-10 KN pressure). The tow is maintained under constant tension during impregnation through differential speed of draw off rollers (190-210 meters/minute) and feed rollers (180-200 meters/minute), applying positive draw of 1.05 -1.10 between two pairs of rollers. i) The drawn tow is further fed to radial cutter and cut in to different staple lengths viz. 6 mm , 12 mm and 18 mm Nylon 6 discrete fibers. The fibres prepared accordingly have filament finenessof 2.0 to 4.5 denier, thickness of 16-18 micron, 4.00 - 4.50 gm/denier tenacity, and 40 - 50% elongation. In accordance with another aspect of the present invention there is provided reinforced cementitious concrete composites comprising a cementious material and Nylon 6 discrete fibres , said Nylon 6 discrete fibres is in the range of 0.02 to 0.04 % by weight of the cementitious material. Different cross section, fineness and staple length fibers as prepared in accordance with the present invention are. incorporated in M25 & Ml5 grade RCC and Mortar (1: 3) at different volume fractions with/without sulfonated melamine formaldehyde plasticizer. The process of incorporating nylon discrete fibres in the cementitous composite is carried out as follows. Nylon 6 discrete fibres prepared in accordance with the present invention are dispersed in water. The cement concrete mix / mortar is charged into the mixer drum and dry mixed. To this dry mix, dispersed fibre mixture is added and stirred till the entire material is dispersed. Sulfonated melamine formaldehyde may be added to the entire material. The SMF mixed concrete must be utilized within 15 minute from the time of SMF addition. The ratio of Nylon 6 fiber in mortar / concrete mix is 50 to 100 gm / 50 kg cement bag and the ratio of SMF (optional) in mortar / concrete mix (Part III process) is 300 ml / 50 kg cement bag. The reinforced cementitious concrete composites comprising trilobal Nylon 6 , 2 denier discrete fibres prepared in accordance with the invention is found to have superior FRC properties namely, compression, flexural strength as compared to concrete structure reinforced with circular cross section Nylon 6 fibre. Trilobal Nylon 6, 2 denier discrete fibre reinforcement in mortar mix significantly reduces the water permeability as compared to without fiber mortar mix which increase the life of the structures prepared with fibre reinforced mortar mix. Trilobal Nylon 6, 2 denier discrete fibre reinforcement in RCC and plaster reduces the plastic shrinkage cracking of the structures which increases the durability of the structures. Use of sulfonated melamine formaldehyde plasticizer along with Nylon 6, 2 denier, trilobal cross section fiber in reinforcement of RCC yields significant rise in compression, flexural and impact strength of concrete. Use of both fibre and plasticizer in RCC confer higher strength and toughness to the structures resulting in enhanced performance and life of concrete. The invention will now be described with respect to the following examples which do not limit the invention in any way and only exemplify the invention. Examples: Step 1 Preparation of Nylon 6 multifilament yarn of required quality viz. tensile strength, elongation, uniformity, fineness and cross section. Raw material fiber grade Nylon 6 chips having R.V. 2.6 - 2.66, % extractable Different flat yarn products with filament fineness 2.0 to 4.5 denier, yarn denier 20.0 to 111.0 and circular & trilobal cross sections are prepared accordingly. Step 2: Preparation of Nylon 6 staple fibers from Nylon 6 flat yarn products produced in step 1 For each Nylon 6 multifilament yarn product, nylon 6 staple fibers, in different cut length, are prepared on radial cutter as per following. Large no of cop packages ranging from 200-1000, each containing 0.7 to 2.0 kg Nylon 6 multifilament flat yarn are mounted in a suitably designed creel. Yarn ends from all cops are pulled and combined in tow form. The tow is fed through tensioning device, guiding mechanism and pair of feed rollers to an impregnation bath. In case of finer yarn deniers, alternately, 30 to 40 yarns are parallel wound on a package in parallel winding unit to make 500-1500 final denier of each package. 50-100 such packages are mounted in a suitably designed creel and yarn ends are pulled and combined in tow form. The tow is fed through tensioning device, guiding mechanism and pair of feed rollers to an impregnation bath. The tow is guided through feed rollers in impregnation bath and drawn off through squeeze roller (1-10 KN pressure). The tow is maintained under constant tension during impregnation through differential speed of draw off rollers (50-550 meters/minute) and feed rollers (50-500 meters/minute) applying positive draw of 1.01 -1.1 between two pairs of rollers. The dried tow is further fed to radial cutter where in it is cut in to different staple lengths viz. 6 mm, 12 mm and 18 mm Nylon 6 discrete fibers. Step 3 : Preparation of Composite Different cross section, fineness and staple length fibers prepared at step 2 are incorporated in M25 & Ml5 grade RCC and Mortar (1: 3) at different volume fractions with/without sulfonated melamine formaldehyde plasticizer. Detailed evaluation of various concrete properties viz compressive strength, flexural strength, impact strength, water permeability and plastic shrinkage cracking are carried out of Fiber Reinforced Concrete and without fibre concrete specimens. Nylon 6 discrete fibres prepared in accordance with the present invention are dispersed in water. The cement concrete mix / mortar is charged into the mixer drum and dry mixed. To this dry mix, dispersed fibre mixture is added and stirred till the entire material is dispersed. Sulfonated melamine formaldehyde may be added to the entire material. The SMF mixed concrete must be utilized within 15 minute from the time of SMF addition. The ratio of Nylon 6 fiber in mortar / concrete mix is 50 to 100 gm / 50 kg cement bag and the ratio of SMF (optional) in mortar / concrete mix (Part III process) is 300 ml / 50 kg cement bag. All Mix design and evaluations are carried out as per IS: 10262-1982, IS: 456-2000, IS:516-1959, IS: 3085-1965 & IS: 2645-2003 test standards. Incorporation of Nylon 6 discrete fibers having i) fineness of 2 denier, ii) trilobal cross section and iii) 18 mm length as a secondary reinforcement in concrete or cementitious composite mix results in, • Reduction in shrinkage cracks / micro cracks, • Rise in compression, flexural and impact strength, • Reduction in water permeability, • Improvement in homogeneity of concrete by reducing segregation of aggregates, • Improvement in ductility of concrete under cyclic loading, • Rise in freeze thaw resistance, • Improvement in durability of concrete , • Higher abrasion resistance. While considerable emphasis has been placed herein on the specific steps of the preferred process, it will be highly appreciated that many steps can be made and that many changes can be made in the preferred steps without departing from the principles of the invention. These and other changes in the preferred steps of the invention will be apparent to those skilled in the art from the disclosures herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. We Claim: 1. A process for the preparation of Nylon 6 discrete fibers comprising the following steps; i) extruding molten Nylon 6 fibers through fine orifices of a spinneret to obtain a plurality of filaments of non-circular cross section; ii) quenching the extruded filaments in air, preferably cold air; iii) combining the quenched filamentsto form a bundle; iv) applying spin finish oil to the bundle ; v) winding the bundled filaments on tubes at winding speed of 600 to 1000 meter per minute to obtain low oriented Nylon 6 filament yarn (LOY) product; vi) conditioning the LOY at 75-80% relative humidity; vii) drawing the conditioned LOY, twisting it to form Nylon 6 multifilament flat yarns of filament fineness 2.0 to 4.5 denier and yarn denier 20.0 to about 111.0, tenacity 4-5 grams/denier, % uster 1.5 to 2.0 and breaking elongation of 40-50% and winding the yarn on cop package ; viii) combining the yarn ends from the package to form a tow; ix) impregnating the tow sequentially with water at 20 C to 35 C temperature and an aqueous stabilizer at 80°C to 100 C temperature to yield stabilized tow; x) squeezing the dried tow at a pressure of about 1 to 10 KN pressure and draw ratio of 1.01 to 1.1 ; and xi) cutting the drawn tow to obtain staple length Nylon discrete fibers. 2. The process as claimed in claim 1,wherein Nylon 6 fiber is textile Nylon 6 fiber with relative viscosity of 2.6 to 2.66, caprolactum content less than 0.7% and moisture less than 0.08%. 3. The process as claimed in claim 1, wherein the non-circular cross section of extruded Nylon 6 filament yarn is trilobal. 4. The process as claimed in claim 1, wherein the aqueous stabilizer comprises 8-10% by weight of Benzene Phosphonic Acid. 5. The process as claimed in claim 4, wherein the Benzene Phosphonic Acid is applied to the tow at the rate of 400 - 1000 ppm/kg of the fibre . 6. The process as claimed in claim 1, wherein the discrete Nylon 6 fiber has fineness of 2 denier, 6 mm to 18 mm length and trilobal cross section. 7. A reinforced cementitious concrete composites comprising a cementious material and Nylon 6 discrete fibres as claimed in claim 1. 8. The reinforced cementitious concrete composites as claimed in claim 7 wherein the Nylon 6 discrete fibres is in the range of 0.02 to 0.04% by weight of the cementitious material. 9. The reinforced cementitious concrete composites as claimed in claim 7 further comprises sulfonated melamine formaldehyde in the range of 0.08 to 0.1 % by volume of the cementitious material.

Full Text

FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2006
Complete
Specification
(See Section 10 and Rule 13)
A process for the preparation of Nylon 6 Discrete Fibers for Secondary Reinforcement in Concrete and Plaster applications
GUJARAT STATE FERTILIZERS & CHEMICALS LIMITED
an Indian Company P.O FERTILIZER NAGAR-391750 DISTRICT VADODARA GUJARAT, INDIA
The Following Specification Particularly Describes the Invention and the manner in which it is to be performed.

Field of the invention
The present invention relates to Nylon 6 fibers as a secondary reinforcement in a cementitious composite.
The present invention envisages process for the preparation of discrete grade Nylon 6 fibers as a secondary reinforcement in a cementitious composite with enhanced concrete/plaster properties.
Background and Prior art
It is common knowledge that concrete or mix of cementitious composites are prone to self induced cracking which makes them further weak and brittle. These self induced cracks propagate through concrete / plaster under relatively low stresses into bigger cracks under tension. It is, therefore, required to minimize the presence of micro cracks to improve the durability of structures.
When a mix of concrete, or any other mix of a cementitious composite, is placed (e.g., poured, molded, layered, sprayed, etc.), the solids, e.g. aggregates, fines and cement therein begin to settle downward due to gravity. As the solids sink, water is displaced and forced to the surface as bleed water. Plastic shrinkage cracking of the concrete or mix of cementitious composite occurs when the rate of water evaporation exceeds the rate of water displacement. Shrinkage stresses associated with early volume change account for the majority of all non-structural cracks in

concrete or mix of a cementitious composite. As mentioned above, these cracks, which are formed while the concrete or mix of a cementitious composite settles, affect the strength and durability of the structure during its service. Therefore, in the common practice, concrete or cementitious composite mix products / structures are watered and cooled while hardening. However, as watering of these products / structures while hardening does not completely eliminate micro cracks formation and subsequent bigger cracks, it calls for special attention and need to search and incorporate fiber additives which act as secondary reinforcement and reduce / eliminate micro cracks formation in products / structures.
The concept of using fibers as reinforcement is not new. Fibers have been used as reinforcement since ancient times. Historically, horsehair was used in mortar and straw in mud bricks for imparting reinforcement in structures. In the early 1900s asbestos fibers were used in concrete, and in the 1950s the concept of composite materials came in to being and fiber reinforced concrete / cementitious composite mix emerged as one of the areas of keen interest. There was a need to find a replacement of asbestos used as reinforcement in concrete / cementitious composite mix and other building materials once the health risks associated with the substance were discovered. By the 1960s, steel, glass, and synthetic fibers such as Polypropylene made their ways for use as reinforcement in concrete / cementitious composite mix products / structures.
Fibers are usually used in concrete / cementitious composite mix to control plastic shrinkage cracking and drying shrinkage cracking. They also lower the permeability of water in concrete / cementitious composite mix and thus

improves the life and reduces the repairing / repainting requirements of structures in long run.
Fiber reinforced concrete (FRC) or Fiber Reinforced Plaster (FRP) is a cementitious composite mix containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly dispersed and layered within composite mix. Such fibers include steel, glass, synthetic and natural fibers. Nylon (majority being nylon 6 and nylon 66 fibers), Polyester and Polypropylene fibers can be used for fiber reinforced concrete and plaster reinforcements.
Fiber Reinforced Concrete and Plaster utilizes discrete synthetic fibers, typically 15-25 mm and 4-8 mm in length to provide improvements in concrete and plaster properties such as:
• Reduction in shrinkage cracks / micro cracks
• Rise in compression, flexural and impact strength
• Reduction in water permeability
• Improvement in homogeneity of concrete by reducing segregation of aggregates
• Improvement in ductility of concrete under cyclic loading
• Rise in freeze / thaw resistance
• Improvement in durability of concrete
• Higher abrasion resistance

The type of fiber, its inherent polymer properties, fineness, cross section, length, density etc. are critical parameters which determine its performance as secondary reinforcement in improving various structural properties in concrete and plaster applications.
Type of fiber cross section and fineness determine the available fiber surface area for interaction and bonding with concrete mix and resultant improvement in FRC or FRP properties and performance. Fiber fineness i.e. fiber diameter and cross section type play critical role in reducing plastic shrinkage cracking within concrete or cementitious composite mix.
Therefore, there is felt a need to develop Nylon 6 discrete fibers with the characteristic properties for enhancing concrete/plaster properties.
Object of the Invention
The object of the invention is to provide Nylon 6 discrete fibers with specific attributes and superior FRC and FRP properties.
Another object of the invention is to provide Nylon 6 discrete fibers to reduce the plastic shrinking cracking and water permeability of reinforced cementitious concrete and mortar mix.
Another object of the invention is to provide Nylon 6 discrete fibers to reduce water permeability of reinforced cementitious concrete and mortar mix.

A further object of the invention is to provide reinforced cementitious concrete composites of Nylon 6 discrete fibers with superior compression, flexural, impact strength and enhanced life of concrete.
Summary of the Invention.
In accordance with the present invention there is provided a process for the preparation of Nylon 6 discrete fibers comprising the following steps;
i) extruding molten Nylon 6 fibers through fine orifices of a spinneret to obtain a plurality of filaments of non-circular cross section;
ii) quenching the extruded filaments in air, preferably cold air;
iii) combining the quenched filaments to form a bundle;
iv) applying spin finish oil to the bundle ;
v) winding the bundled filaments on tubes at winding speed of 600 to 1000 meter per minute to obtain low oriented Nylon 6 filament yarn (LOY) product;
vi) conditioning the LOY at 75-80% relative humidity;
vii) drawing the conditioned LOY, twisting it to form Nylon 6 multifilament flat yarns of filament fineness 2.0 to 4.5 denier and yarn denier 20.0 to about 111.0, tenacity 4-5 grams/denier, % uster 1.5 to 2.0 and breaking elongation of 40-50% and winding the yarns on cop package;
viii) combining the yarn ends from the package to form a tow;
ix) impregnating the tow sequentially with water at 20°C to 35°C temperature and an aqueous stabilizer at 80°C to 100°C temperature to yield
stabilized tow;

x) squeezing the stabilized tow at a pressure of about 1 to 10 KN pressure and draw ratio of 1.01 to 1.1 ; and
xi) cutting the squeezed tow to obtain staple length Nylon discrete fibers.
Typically, Nylon 6 fiber is textile Nylon 6 fiber with relative viscosity of 2.6 to 2.66, caprolactum content less than 0.7% and moisture less than 0.08%.
The non-circular cross section of extruded Nylon 6 filament yarn is trilobal.
The aqueous stabilizer comprises 8-10% by weight of Benzene Phosphonic Acid. The Benzene Phosphonic Acid is applied to the tow at the rate of 400 -1000 ppm/kg of fibre .
Typically, the discrete Nylon 6 fiber has 2 denier fineness and length from 6 mm to 18 mm.
In another aspect of the present invention there is provided a reinforced cementitious concrete composites comprising a cementious material and Nylon 6 discrete fibres , said Nylon 6 discrete fibres being in the range of 0.02 to 0.04 % by weight of the cementitious material.
The reinforced cementitious concrete composites further comprises sulfonated melamine formaldehyde in the range of 0.08 to 0.1 % by volume of the cementitious material.

Brief Description of the Invention
Nylon 6 fiber, which is a man made synthetic fiber, is hydrophilic by nature and absorbs typically 4-5% moisture. When this fiber is incorporated in to concrete/mortar mix, it absorbs moisture from the free water available in the mix and acts as reservoir of water within the concrete plaster mix.
It would be highly advantageous to make use of textile grade of Nylon 6 fiber and impart required properties to make it perform as secondary reinforcement in concrete or cementitious composite mix.
The present invention is related to the cementitious composites mix which include suitable grade of textile Nylon 6 fibers, cut into staples, which are used for reinforcing its cementitios - matrix. The cementitious matrix is formed by activating a common cementitious material such as cement in presence of water. However, the scope of the invention is not limited to cement and other cementitious material like silicates, clay, and gypsum. Further the invention is also not limited to water activated setting process. The cementitious composites may further include additional ingredients like aggregates and fines used traditionally to acquire specific characteristics such as strength, durability, workability, insulation etc. The present investigation is directed towards the development of unique fiber characteristic in Nylon 6 fiber with optimized attributes to be as secondary reinforcement for cementitious composites such as concrete and mortar.

Fibre Reinforced Concrete and Plaster results from the addition of short Nylon 6 discrete fibers as secondary reinforcement to the cement based matrix. The behavioral efficiency of these composite structures is far more superior compared to plain concrete and plaster and many other construction materials of equal cost.
An extensive R&D investigations have been carried out i) to develop different grades of Nylon 6 fiber, ii) to evaluate these grades for Fiber Reinforced Concrete / Plaster application properties, hi) to evolve a non round cross section i.e. trilobal and low diameter textile fiber with superior FRC and FRP properties.
In accordance with the present invention the process for the preparation of Nylon 6 discrete fibers is carried out as follows
a) Nylon 6 fibres are melted in an extruder and molten fibres are extruded
through fine orifices of a spinneret of non circular cross sections such as
circular, triangular or trilobal, to obtain a plurality of filaments,
b) The filaments are quenched in cold air and then combined to form a
bundle;
c) Spin finish oil is applied to the bundle and the lubricated filaments are wound on the tubes at winding speed of 600 to 1000 meter per minute to obtain low oriented Nylon 6 filament yarn (LOY) product. Spin finish oil made up of lubricant, binding agent and antistatic agent is encapsulated on yarn surface as processing additive during melt spinning of Nylon 6 yarn. 0.8 - 1.0 % Spin finish oil per weight of yarn is applied on Nylon 6 fibre. Spin finish oil acts as lubricant and binding and antistatic agent during

Nylon 6 yarn melt spinning process and also facilitates unwinding of yarn from package for subsequent processing.
d) The LOY is conditioned at 75-80% relative humidity. In order to impart necessary morphological changes in yarn structure, the Nylon 6 Low Oriented Yarn (LOY) is kept at 75 - 80 % relative Humidity for definite time interval This is called conditioning of LOY.
e) After conditioning the Nylon 6 LOY is further drawn and twisted in Draw - Twisting process to form Nylon 6 multifilament flat yarns of filament fineness 2.0 to 4.5 denier and yarn denier 20.0 to about 111.0, tenacity 4-5 grams/denier, % uster 1.5 to 2.0 and breaking elongation of 40-50% ;
f) Large no of cop packages ranging from 500-1000, each containing 0.7 to 2.0 kg Nylon 6 multifilament flat yarn are mounted in a suitably designed creel. Yarn ends from all cops are pulled and combined in tow form. The tow is fed through tensioning device, guiding mechanism and pair of feed rollers to an impregnation bath.
In case of finer yarn deniers, alternately, 30 to 40 yarns are parallel wound on a package in parallel winding unit to make 2500-3000 final denier of each package. 50-100 such packages are mounted in a suitably designed creel and yarn ends are pulled and combined in tow form,
g) The tow is impregnated sequentially with water at 20 C to 35 C
temperature and an aqueous stabilizer at 80°C to 100 C temperature.
The impregnation bath includes i) pair of motorized feed rollers, ii) big trough divided in two compartments - first for water impregnation and second for solution / boiling water impregnation with electric heaters for controlled heating of solution / water and both compartments with internal

guiding rollers, and iii) pair of motorized draws off cum squeeze rollers having pneumatics pressure controller.
The tow, at ambient temperature, is impregnated in water in first compartment. The process spin finish oil is removed from the bundle of filaments in this compartment. In second compartment stabilizer viz. benzene phosphonic acid (4-10% solution) is applied (@ 400 -lOOOppm) to the tow for imparting stabilization against hydrolytic degradation. h) The impregnated tow is drawn off through squeeze roller (8-10 KN pressure). The tow is maintained under constant tension during impregnation through differential speed of draw off rollers (190-210 meters/minute) and feed rollers (180-200 meters/minute), applying positive draw of 1.05 -1.10 between two pairs of rollers.
i) The drawn tow is further fed to radial cutter and cut in to different staple lengths viz. 6 mm , 12 mm and 18 mm Nylon 6 discrete fibers. The fibres prepared accordingly have filament finenessof 2.0 to 4.5 denier, thickness of 16-18 micron, 4.00 - 4.50 gm/denier tenacity, and 40 - 50% elongation.
In accordance with another aspect of the present invention there is provided reinforced cementitious concrete composites comprising a cementious material and Nylon 6 discrete fibres , said Nylon 6 discrete fibres is in the range of 0.02 to 0.04 % by weight of the cementitious material.
Different cross section, fineness and staple length fibers as prepared in accordance with the present invention are. incorporated in M25 & Ml5 grade RCC and Mortar (1: 3) at different volume fractions with/without sulfonated melamine formaldehyde plasticizer.

The process of incorporating nylon discrete fibres in the cementitous composite is carried out as follows.
Nylon 6 discrete fibres prepared in accordance with the present invention are dispersed in water. The cement concrete mix / mortar is charged into the mixer drum and dry mixed. To this dry mix, dispersed fibre mixture is added and stirred till the entire material is dispersed. Sulfonated melamine formaldehyde may be added to the entire material. The SMF mixed concrete must be utilized within 15 minute from the time of SMF addition.
The ratio of Nylon 6 fiber in mortar / concrete mix is 50 to 100 gm / 50 kg cement bag and the ratio of SMF (optional) in mortar / concrete mix (Part III process) is 300 ml / 50 kg cement bag.
The reinforced cementitious concrete composites comprising trilobal Nylon 6 , 2 denier discrete fibres prepared in accordance with the invention is found to have superior FRC properties namely, compression, flexural strength as compared to concrete structure reinforced with circular cross section Nylon 6 fibre.
Trilobal Nylon 6, 2 denier discrete fibre reinforcement in mortar mix significantly reduces the water permeability as compared to without fiber mortar mix which increase the life of the structures prepared with fibre reinforced mortar mix.
Trilobal Nylon 6, 2 denier discrete fibre reinforcement in RCC and plaster reduces the plastic shrinkage cracking of the structures which increases the durability of the structures.

Use of sulfonated melamine formaldehyde plasticizer along with Nylon 6, 2 denier, trilobal cross section fiber in reinforcement of RCC yields significant rise in compression, flexural and impact strength of concrete. Use of both fibre and plasticizer in RCC confer higher strength and toughness to the structures resulting in enhanced performance and life of concrete.
The invention will now be described with respect to the following examples which do not limit the invention in any way and only exemplify the invention.
Examples:
Step 1
Preparation of Nylon 6 multifilament yarn of required quality viz. tensile strength, elongation, uniformity, fineness and cross section. Raw material fiber grade Nylon 6 chips having R.V. 2.6 - 2.66, % extractable
Different flat yarn products with filament fineness 2.0 to 4.5 denier, yarn denier 20.0 to 111.0 and circular & trilobal cross sections are prepared accordingly.
Step 2: Preparation of Nylon 6 staple fibers from Nylon 6 flat yarn products produced in step 1
For each Nylon 6 multifilament yarn product, nylon 6 staple fibers, in different cut length, are prepared on radial cutter as per following. Large no of cop packages ranging from 200-1000, each containing 0.7 to 2.0 kg Nylon 6 multifilament flat yarn are mounted in a suitably designed creel. Yarn ends from all cops are pulled and combined in tow form. The tow is fed through tensioning device, guiding mechanism and pair of feed rollers to an impregnation bath.
In case of finer yarn deniers, alternately, 30 to 40 yarns are parallel wound on a package in parallel winding unit to make 500-1500 final denier of each package. 50-100 such packages are mounted in a suitably designed creel and yarn ends are pulled and combined in tow form. The tow is fed through tensioning device, guiding mechanism and pair of feed rollers to an impregnation bath.
The tow is guided through feed rollers in impregnation bath and drawn off through squeeze roller (1-10 KN pressure). The tow is maintained under constant tension during impregnation through differential speed of draw off

rollers (50-550 meters/minute) and feed rollers (50-500 meters/minute) applying positive draw of 1.01 -1.1 between two pairs of rollers.
The dried tow is further fed to radial cutter where in it is cut in to different staple lengths viz. 6 mm, 12 mm and 18 mm Nylon 6 discrete fibers.
Step 3 : Preparation of Composite
Different cross section, fineness and staple length fibers prepared at step 2 are incorporated in M25 & Ml5 grade RCC and Mortar (1: 3) at different volume fractions with/without sulfonated melamine formaldehyde plasticizer. Detailed evaluation of various concrete properties viz compressive strength, flexural strength, impact strength, water permeability and plastic shrinkage cracking are carried out of Fiber Reinforced Concrete and without fibre concrete specimens.
Nylon 6 discrete fibres prepared in accordance with the present invention are dispersed in water. The cement concrete mix / mortar is charged into the mixer drum and dry mixed. To this dry mix, dispersed fibre mixture is added and stirred till the entire material is dispersed. Sulfonated melamine formaldehyde may be added to the entire material. The SMF mixed concrete must be utilized within 15 minute from the time of SMF addition.
The ratio of Nylon 6 fiber in mortar / concrete mix is 50 to 100 gm / 50 kg cement bag and the ratio of SMF (optional) in mortar / concrete mix (Part III process) is 300 ml / 50 kg cement bag.
All Mix design and evaluations are carried out as per IS: 10262-1982, IS: 456-2000, IS:516-1959, IS: 3085-1965 & IS: 2645-2003 test standards.

Incorporation of Nylon 6 discrete fibers having i) fineness of 2 denier, ii) trilobal cross section and iii) 18 mm length as a secondary reinforcement in concrete or cementitious composite mix results in,
• Reduction in shrinkage cracks / micro cracks,
• Rise in compression, flexural and impact strength,
• Reduction in water permeability,
• Improvement in homogeneity of concrete by reducing segregation of aggregates,

• Improvement in ductility of concrete under cyclic loading,
• Rise in freeze thaw resistance,
• Improvement in durability of concrete ,
• Higher abrasion resistance.
While considerable emphasis has been placed herein on the specific steps of the preferred process, it will be highly appreciated that many steps can be made and that many changes can be made in the preferred steps without departing from the principles of the invention. These and other changes in the preferred steps of the invention will be apparent to those skilled in the art from the disclosures herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We Claim:
1. A process for the preparation of Nylon 6 discrete fibers comprising the following steps;
i) extruding molten Nylon 6 fibers through fine orifices of a spinneret to obtain a plurality of filaments of non-circular cross section; ii) quenching the extruded filaments in air, preferably cold air; iii) combining the quenched filamentsto form a bundle; iv) applying spin finish oil to the bundle ;
v) winding the bundled filaments on tubes at winding speed of 600 to 1000 meter per minute to obtain low oriented Nylon 6 filament yarn (LOY) product;
vi) conditioning the LOY at 75-80% relative humidity; vii) drawing the conditioned LOY, twisting it to form Nylon 6 multifilament flat yarns of filament fineness 2.0 to 4.5 denier and yarn denier 20.0 to about 111.0, tenacity 4-5 grams/denier, % uster 1.5 to 2.0 and breaking elongation of 40-50% and winding the yarn on cop package ; viii) combining the yarn ends from the package to form a tow; ix) impregnating the tow sequentially with water at 20 C to 35 C temperature and an aqueous stabilizer at 80°C to 100 C temperature to yield stabilized tow;
x) squeezing the dried tow at a pressure of about 1 to 10 KN pressure and draw ratio of 1.01 to 1.1 ; and xi) cutting the drawn tow to obtain staple length Nylon discrete fibers.

2. The process as claimed in claim 1,wherein Nylon 6 fiber is textile Nylon 6
fiber with relative viscosity of 2.6 to 2.66, caprolactum content less than
0.7% and moisture less than 0.08%.
3. The process as claimed in claim 1, wherein the non-circular
cross section of extruded Nylon 6 filament yarn is trilobal.
4. The process as claimed in claim 1, wherein the aqueous stabilizer
comprises 8-10% by weight of Benzene Phosphonic Acid.
5. The process as claimed in claim 4, wherein the Benzene Phosphonic Acid is applied to the tow at the rate of 400 - 1000 ppm/kg of the fibre .
6. The process as claimed in claim 1, wherein the discrete Nylon 6 fiber has fineness of 2 denier, 6 mm to 18 mm length and trilobal cross section.
7. A reinforced cementitious concrete composites comprising a cementious material and Nylon 6 discrete fibres as claimed in claim 1.
8. The reinforced cementitious concrete composites as claimed in claim 7 wherein the Nylon 6 discrete fibres is in the range of 0.02 to 0.04% by weight of the cementitious material.

9. The reinforced cementitious concrete composites as claimed in claim 7 further comprises sulfonated melamine formaldehyde in the range of 0.08 to 0.1 % by volume of the cementitious material.

Documents:

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Patent Number

269550

Indian Patent Application Number

1230/MUM/2010

PG Journal Number

44/2015

Publication Date

30-Oct-2015

Grant Date

27-Oct-2015

Date of Filing

13-Apr-2010

Name of Patentee

GUJARAT STATE FERTILIZERS & CHEMICALS LIMITED

Applicant Address

P.O. FERTILIZER NAGAR 391750 DISTRICT VADODARA GUJARAT, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	KOTAK, PRASHANT	P.O. FERTILIZER NAGAR 391750, DISTRICT VADODARA, GUJARAT, INDIA
2	SINGH, YASHPAL	P.O. FERTILIZER NAGAR 391750, DISTRICT VADODARA, GUJARAT, INDIA
3	PANDY, HARSHADRAI	P.O. FERTILIZER NAGAR 391750, DISTRICT VADODARA, GUJARAT, INDIA
4	PATEL, HARIBHAI	P.O. FERTILIZER NAGAR 391750, DISTRICT VADODARA, GUJARAT, INDIA

PCT International Classification Number

C08G69/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA