Title of Invention

A FORMULATION USEFUL AS CONTACT ADHESIVE FOR LEATHER, RUBBER AND PVC SURFACES

Abstract

This invention relates to a formulation useful as Contact Adhesive for leather, rubber and PVC surfaces. The formulation is of high quality polychloroprene (also known as Neoprene) based contact adhesive useful for shoe, automobile, upholstry and in construction applications. A formulation comprises: polychloroprene 10-12 wt.%, tackifying resins 5 to 9wt.%; halogenated rubber such as chlorinated rubber having viscosity in the range of 20 to 40 CPS 1.5-2.0wt.%; antioxidant such as butylhydroxy toluene and butylhydroxy anisole 0.2 to 0.3 wt.%, Stabilizer 0.2 - 0.3 wt.% in a combination of organic solvents 75 to 85 wt.% consisting 60 to 65 wt.% aromatic hydrocarbon solvents; 15 to 20 wt.% aliphatic hydrocarbon solvents.

Full Text

This invention relates to a formulation useful as Contact Adhesive for leather, rubber and PVC surfaces. Particularly this invention relates to a formulation of high quality polychloroprene (also known as Neoprene) based contact adhesive useful for shoe, automobile, upholstry and in construction applications. Polychloroprene has a formula – (Formula Removed) Polychoroprene is the basis for one of the largest and most important group of rubber adhesives in the world. The rapid development of bond strength of films from solution, combined with tack or auto - adhesion, resistance of the cured glue line to heat oxidation, water, solvents, oils, acids and alkalies have led to the extensive use of this adhesive in various industrial applications. These adhesives are applied on the substrates, dried and mated under only enough pressure to result in good contact. The bond is immediate and sufficiently strong to hold the surfaces together. These adhesives are prepared by either milling or slurring followed by churning. The most widely used method involves milling the polychloroprene rubber and compounding it with tackifying resins, fillers, metal oxides, antioxidants dissolved in combination of aromatic and aliphatic hydrocarbon solvents. Though there are several varieties of contact adhesives based on nitrile rubber and SBR rubbers, they do not bond all varieties of leather to leather, carpet to floor, PVC to floor and other applications. Most of the nitrile rubber adhesives are heat cured. This is a draw back when compared with neoprene contact adhesive. SBR adhesives have not become commercially successful due to their slow development of bond strength and also their high cost structure. These adhesives are known since four decades and few patents and reports are already available and these are : A.F. Thomson (3M Co)., U.S.Patent. 2,610,910 (1952) W.W.Reynolds and H.J.Gebhart Jr. Off.Digest 29,1174(1957) J.Smith: Adhesive Age Dec 1970 H.Burrell, J.Paint Technol. 40 (520), 197(1968) Dupont Elastomers Bulletin (1964) (1968) However, most of these formulations described in the above literature vary in their consistency and do not bond to the required bond strength between various surfaces. The main object of the present invention is to provide a formulation useful as contact adhesives which obviates the draw back of such adhesives. Another object is to provide a contact adhesive which will give constant viscosities, give high bond strength between various surfaces such as leather, rubber and PVC and reduced the time required to crystallize the adhesive in ord> r to get immediate bond strength The adhesive thus developed contain polychloroprene rubber. Tackifying resins such as phenolics, coumarone - indene, rosin derivatives and hydrocarbons, antioxidants and hydrocarbon solvents. Yet another object of the present invention is to develop such a type of contact adhesive which can be sued in broad spectrum of applications. Accordingly the present invention provides a formulation useful as contact adhesive for leather, rubber and poly vinyl chloride surfaces which comprises: polychloroprene 10-12 wt.%, tackifying resins 5 to 9wt.%; halogenated rubber such as chlorinated rubber having viscosity in the range of 20 to 40 Centipoise 1.5-2.0wt.%; antioxidant such as butylhydroxy toluene and butylhydroxy anisole 0.2 to 0.3 wt.%, stabilizer 0.2 - 0.3 wt.% in a combination of organic solvents 75 to 85 wt.% consisting 60 to 65 wt.% aromatic hydrocarbon solvents; 15 to 20 wt.% aliphatic hydrocarbon solvents. In an embodiment of the present invention the tackifying resins used may be such as phenolic resins, aliphatic substituted hydrocarbons and aromatic hydrocarbons. In an another embodiment the halogenated rubber used may be such as chlorinated rubber. In yet another embodiment of the invention the antioxidants used may be such as butyl hydroxy toluene, butyl hydroxy anisole. Still another embodiment of the invention, the stabilizer used may be such as magnesium and zinc oxides, ionol, bis phenols, zinc dimethyl dithiocarbonate, phenyl beta naphtyl anisole. In another embodiment the organic solvents used may be 15 to 20wt.% aliphatic hydrocarbons such as hexane, heptane; 60 to 65wt.% aromatic hydrocarbons such as benzene, toluene, xylene and mixtures thereof. In the process of the present invention, the polychloroprene AC/DC grades having specific gravity 1.23, rate of crystallization 2 1/2 hours and having mooney viscosity 75-105 is used as such or after milling. This rubber is dissolved in a vertical churner at slow speed which enables the neoprene rubber to go into the solution faster without settling at the bottom. With a slow churner, it is often necessary to dissolve all the tackifying resins and antioxidants etc., in appropriate hydrocarbon solvents and then adding the solution to the polychloroprene rubber solution. This technique is called slurry method and is most economical as it does not necessitate expensive milling equipments and added labour. Milling the polychloroprene results in films which crystallize more readily giving shorter tack times and faster development of cohesive strength. Unmilled polychloroprene has higher initial cohesive strength at elevated temperatures. Accordingly, the present invention provides a formulation for the preparation of polychloroprene based contact adhesive which has very broad spectrum of applications such as bonding leather to leather, rexin to wood, carpet to floor, PVC to floor etc. All the raw materials used may be of commercial grade. The process of the invention is described hereunder. The polychoroprene adhesive grade was milled in a double roll mill. The rubber sheets were cut into small pieces and were added in a stainless steel vertical reactor. The solvent like aromatic hydrocarbons e.g.,benzene,toulene,xylene was added. To effect better solubility of the rubber, some quantity of aliphatic hydrocarbon solvent such as hexane, heptane was added. The contents were mixed at a stirrer speed 60-80RPM.The material gets dissolved over a period of 3-4 hours. In a separate vessel, tackifying resins such as tertiary butyl phenolic resins, aromatic hydrocarbons resins,rosin esters were taken in solvents and dissolved. This solution was then added to the main rubber solution. Chlorinatd rubber was also dissolved separately in a hydrocarbon solvent and it was also added to the rubber solution to effect better bond strength between the marble floor and fibres of a carpet.Polychloroprene releases hydrochloric acid on storage and therefore, it is also necessary to add magnesium oxide or any zinc and calcium oxides in the formulation so that the product would be stable. Apart from this, this adhesive can also undergo oxidation due to the presence of unsaturation in the polymer. Therefore, it is also necessary to add antioxidants into the adhesive before it is packed in metal containers. The formulations prepared are not a mere admixture of ingredients but it is a synergistic mixture in which the properties of the formulation is different from the mere aggregated properties of individual ingredients. The adhesive formulation prepared by the process described above has the following composition: a) Polychloroprene rubber : 10-12% b) Aromatic hydrocaron solvents such as Benzene/Toluene : 60-65% c) Aliphatic hydrocarbon solvents such as Hexane/Heptane : 15-20% d) Tertiary butyl phenolic resin : 5-9% e) Stabilizers Magnesium oxide/Zinc oxide : 0.2 - 0.3% f) Halogenated rubber : 1.5-2.0% $) Antioxidants : 0.2-0.3% The following examples are given by way of illustrations and therefore, should not be construed to limit the scope of the present invention: EXAMPLE - 1 In a vertical reaction kettle (also called churner) toluene (750ml) and hexane(400ml) were added. To this polychloroprene (neoprene) rubber AC (200g), phenolic resin (6411) (80g) was dissolved in toluene (250ml) and to this, magnesium oxide (8g) was added. On keeping it for about one hour, magnesium oxide forms a complex with phenolic resin and a clear solution is obtained. This clear solution was then added to the reaction kettle. Separately, capolite phenolic resin (15g) chlorinated rubber (30g) were dissolved in toluene (70ml). This solution was then later added to the rubber solution and stirred till a clear solution was obtained. An antioxidant such as phenyl beta napthyl amine (0.1% on the weight of the total adhesive) was added. Now the adhesive is ready for discharge. The kettle was then washed with 100ml of extra toluene to remove the adhesive sticking to the walls of the reactor vessel. This extra toluene is then drained off into the container. This adhesie has a percent solid 20, viscosity 2625cps. colour dark tan and its density o9g per ml This adhesive has open time of 2-3 minutes It has peel strength of 8kg per linear inch between the casvas cloth . strips. It has a covering capacity -of 5-6 sqml It. EXAMPLE - 2 In a vertical churner. neoprene (DC) (140g) rubber was dissolved in toluene (600ml) and to this separately dissolved phenolic resin 260 (65g) in toluene (130ml) was added. To this stabilizer 0.3g lonol was added and finally additional quantity of toluene 100ml was added to maintain the viscosity 2000cps and solid content at 24%. This adhesive gave a peel strength (kg linear inch) of between rubber to rubber 6.4Kg, rubber to rexin 4.6kg, rubber to metal 1.3kg, rubber to wood 2kg. EXAMPLE - 3 Neoprene rubber (120g) was dissolved in a mixture of Heptane (320ml) and benzene (480ml) in a vertical churner at 30°C over a period of 4 hours. Phenolic resin 260 (60g) and penta estergum (20g) were powdered together and dissolved in 118ml of benzene. This solution was then added to neoprene rubber solution and then the adhesive completed by adding zinc dimethyl dithiocarbonate (2g) taken in benzene (160ml). After getting the clear solution, the adhesive was drawn out and packed. This adhesive gave a viscosity 2000cps, solid content 22% and its open tack of 1-2 minutes, the peel strength 8-10kg/linear inch on canvass pieces. EXAMPLE - 4 Neoprene rubber (90g) was dissolved in toluene (600ml) in a vertical churner at 35°C over a period of 4 hours. Separately yellow phenolic resin (45g) chlorinated rubber (55g) were dissolved together in toluene (160ml). Antioxidant phenyl beta naphthyl amine (2g) was added. To this zinc oxide (3g) was added to fix liberated hydrochloric acid from the neoprene rubber on storage. This adhesive was yellow in colour and had viscosity of 600 cps. It has excellent bond strength between marble stone - PVC and marble stone - woolen carpet. The peel strength kg/linear inch are of the order of 5kg and 6kg respectively. The main advantages of this process are: 1) The utilisation of mixture of solvents i.e., aromatic and aliphatic hydrocarbons to dissolve the neoprene rubber. This will enable us to get a low viscosity product with high solid content. 2) The utilisation of chlorinated rubber which helps in bonding cellulosics such as canvass, cloth etc. to various surfaces. 3) Use of magnesium,calcium or zinc oxide in the formulation which makes the adhesive more stable by fixing the liberated hydrochloric acid from neoprene rubber. 4) This adhesive formulation is capable of bonding leather, canvas, rubber, PVC to various rigid surfaces. We Claim: 1. A formulation useful as contact adhesive for leather, rubber and polyvinyl chloride surfaces which comprises: polychloroprene 10-12 wt.%, tackifying resins 5 to 9wt.%; halogenated rubber such as chlorinated rubber having viscosity in the range of 20 to 40 Centipoise 1.5-2.0wt.%; antioxidant such as butylhydroxy toluene and butylhydroxy anisole 0.2 to 0.3 wt.%, stabilizer 0.2 - 0.3 wt.% in a combination of organic solvents 75 to 85 wt.% consisting 60 to 65 wt.% aromatic hydrocarbon solvents; 15 to 20 wt.% aliphatic hydrocarbon solvents. 2. A formulation as claimed in claim 1 wherein the tackifying resins used is selected from phenolic resins and and aromatic hydrocarbon resins but preferably phenolic resins. 3. A formulation as claimed in claim 1 to 2 wherein the aromatic hydrocarbon solvents used is selected from benzene, toluene, xylene. 4. A formulation as claimed in claim 1 to 3 wherein the stabilizer used is selected from magnesium oxide, zinc oxide, calcium oxide, ionol, bis phenols, zinc dimethyldithio carbonate, phenyl beta naphthyl anisole. 5. A formulation as claimed in claims 1 to 4 wherein the aliphatic hydrocarbon solvents used is hexane or heptane. 6. A formulation useful as contact adhesive for leather, rubber and Polyvinyl chloride surfaces substantially as herein described with reference to the examples.

Documents:

1401-del-1999-abstract.pdf

1401-del-1999-claims.pdf

1401-del-1999-correspondence-others.pdf

1401-del-1999-correspondence-po.pdf

1401-del-1999-description (complete).pdf

1401-del-1999-form-1.pdf

1401-del-1999-form-19.pdf

1401-del-1999-form-2.pdf