GB1577942A

GB1577942A - Method of bonding

Info

Publication number: GB1577942A
Application number: GB21221/76A
Authority: GB
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1976-05-21
Filing date: 1976-05-21
Publication date: 1980-10-29
Also published as: JPS52142786A; ZA772305B; FR2352099B2; AU2427677A; AU507402B2; FR2352099A2; DE2722679A1; CA1087823A

Description

(54) METHOD OF BONDING (71) We, DUNLOP LIMITED, a British Company of Dunlop House, Ryder Street, St. James's, London S.W.I, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method of bonding an aromatic polyamide filamentary material to a rubber composition and is a modification of the method described in U.K. Patent Specification No. 1,465,063 in that the present invention involves one less step in the bonding process.

According to the present invention a method of bonding an aromatic polyamide filamentary material to a rubber composition comprises applying an aqueous solution or dispersion of an epoxy resin to the filamentary material, drying the coated filamentary material and assembling the coated filamentary material with a rubber composition containing aldehyde resin precursors as hereinafter defined and subjecting the assembly to conditions which will vulcanize the rubber composition and cause the aldehyde resin precursors to react.

The aromatic polyamide filamentary material may be of the formula

wherein Arl and Ar2 are aromatic radicals and n is an integer, for example poly-1,4benzamide

and poly(l,4-phenylene terephthalamide)

which are available in fibre form from DuPont as Fibre B or Keviar, and poly( 13- phenylene isophthalamide)

which is available in fibre form from DuPont as Nomex (registered Trade Mark).

Epoxy resins that may be used are those resins that may be formed into an aqueous solution or dispersion. Typical epoxy compounds include those based on the reaction product of 2,2-bis(p-hydroxyphenyl)propane (Bisphenol A) with epichlorohydrin; the reaction product of an aliphatic diol or triol with epichlorohydrin; epoxidised polybutadiene and triglycidyl isocyanurate.

A typical example of a water soluble epoxy resin is "NER 010" which is commercially available from Nogasi and is based on the diglycidyl ether of glycerol.

The aqueous solution or dispersion of an epoxy resin may also contain swelling agents for the resin e.g. 2-pyrrolidone, wetting agents e.g. dioctyl sodium sulphosuccinate (e.g. the compound which is commercially available as "Aerosol OT" from American Cynamid) or any other compound that will assist in the formation of the solution or dispersion, or the coating of the filamentary material with the solution or dispersion.

The rubber composition containing resin precursors is preferably vulcanized using sulphur as the vulcanising agent. The rubber employed in the composition may be natural rubber, styrene-butadiene rubber, cis-l,4-polyisoprene rubber, polybutadiene rubber or a blend of any of these rubbers. Silica may be included in the rubber composition.

By "aldehyde resin precursors" is meant at least two components, the reaction product of which is a thermosetting aldehyde condensation resin. Particularly suitable compounds are an aromatic hydroxy compound and a compound which on heating becomes a methylene donor. Alternatively one of the resin precursors may itself be a resin capable of further reaction e.g. a novolac phenol-formaldehyde resin deficient in methylol groups in combination with a compound which on heating becomes a methylene donor.

The compound which becomes a methylene donor is preferably stable up to a temperature of at least 1000C. These compounds include those which generate formaldehyde on heating or may be a compound such as hexamethylene-tetramine.

Other suitable compounds include hexamethoxymethyl melamine, lauryloxymethyl pyridinium chloride, cetyloxymethyl pyridinium chloride, ethyloxymethyl pyridinium chloride, formaldehyde, polymers of formaldehyde and polymers of formaldehyde having stabilising groups or residues of substances such as pentaerythritol at the ends of the molecules.

The amount of compound employed which liberates methylene groups may be from 0.1 to 10 parts by weight, preferably from 0.5 to 3 parts by weight, per 100 parts by weight of rubber in the composition.

The aromatic hydroxy compound which may be employed may be a monohydroxy compound, but it is preferably one containing two hydroxy groups and it is especially preferred that the hydroxy groups be meta to each other.

Examples of suitable aromatic hydroxy compounds are resorcinol and 1,3dihydroxy naphthalene. If desired, melamine or urea or a compound which generates either of these two compounds on heating may be employed in place of the aromatic hydroxy compound.

The amount of aromatic hydroxy compound or other compound employed to react with the compound which liberates methylene groups may be from 0.1 to 10 parts by weight, preferably from 1.0 to 4.0 parts by weight, per 100 parts by weight of rubber in the composition.

The aqueous solution or dispersion of an epoxy resin may be applied to the filamentary material by passing the material into the aqueous solution or dispersion at room temperature, but if desired higher temperatures may be used.

After the application of the epoxy resin coating the material is dried. The drying process may comprise drying at room temperature followed by drying at a higher temperature. The rubber composition containing resin precursors is then applied to the coated filamentary material and the assembly is then suitably subjected to heat and pressure to vulcanise the composition and form the resin precursors into a resin, thereby producing a bond between the coated filamentary material and the rubber composition.

The method of the present invention may be used to bond aromatic polyamide filamentary materials in the form of reinforcing cords to rubber compositions, in the manufacture of e.g. tyres, driving belts, conveyor belts and hose.

The method according to the present invention is illustrated by the following Example in which all parts are by weight: EXAMPLE Reinforcing cords based on the fibres produced from poly(l,4-phenylene terephthalamide) as Fibre B available from DuPont were coated on a laboratory scale with an epoxy resin solution of the formulation given below, and were subsequently dried.

Parts Water 84.0 Sodium hydroxide (10 /" solution) 1.0 Epoxy resin 3.0 2-pyrrolidone 10.0 Wetting agent2 2.0 I=Diglycidyl ether of glycerol (commercially available as "Epon 812" from Shell).

2=Dioctyl sodium sulphosuccinate (commercially available as "Aerosol OT" from American Cynamide).

Untreated cords and cords treated with the epoxy resin solution were embedded in rubber compositions A to C (Table I). The compositions were then vulcanised for 25 minutes at 148"C.

The adhesion between the reinforcing cords and the rubber composition in each case was then measured using a standard I cm pull-through test (similar to J.

O. Wood trans I R I, Vol. 32, No. 1, February 1956). The average adhesion values determined over 10 measurements are recorded in Table II.

TABLE I A B C Natural rubber 100.00 100.00 100.00 Stearic acid 2.75 1.90 1.05 Retarder (50% active cyclo- 0.60 0.60 0.60 hexylthiophthalimide) Antioxidant (diphenylamine/ 1.00 1.00 1.00 acetone reaction product) Process oil (aromatic process 7.00 7.00 7.00 oil available as Dutrex RT from Shell) Zinc oxide 7.50 7.50 7.50 Carbon black (A furnace black 43.00 43.00 43.00 available as Regal 300) Sulphur 2.60 2.60 2.60 Accelerator (2,4 morphiolinyl 1.20 1.20 1.20 mercaptobenzthiazole Hexamethylene tetramine 0.80 1.60 Resorcinol/stearic acid 2.10 4.20 (60/40 melt) 165.65 167.70 169.75 TABLE II Adhesion (Newtons/cm) Rubber Treated Untreated Composition Cords Cords A 50 34 B 140 65 C 138 96 "Kevlar", "Aerosol", "Epon" and "Dutrex" are registered Trade Marks.

Claims

WHAT WE CLAIM IS:

1. A method of bonding an aromatic polyamide filamentary material to a rubber composition which comprises applying an aqueous solution or dispersion of an epoxy resin to the filamentary material, drying the coated filamentary material and assembling the coated filamentary material with a rubber composition containing aldehyde resin precursors as hereinbefore defined and subjecting the assembly to conditions which will vulcanise the rubber composition and cause the resin precursors to react.

2. A method according to claim 1 wherein the aromatic polyamide filamentary material comprises a polymer of the formula

where Ar1 and Ar2 are aromatic radicals and n is an integer.

3. A method according to claim 2 wherein the aromatic polyamide filamentary material comprises poly(l,4-benzamide).

4. A method according to claim 2 wherein the aromatic polyamide filamentary material comprises poly(l,3-phenylene isophthalamide).

5. A method according to claim 2 wherein the aromatic polyamide filamentary material comprises poly(l,4-phenylene terephthalamide).

6. A method according to any of the preceding claims wherein the epoxy resin is based on the reaction product of 2,2-bis(p-hydroxyphenyl)-propane with epichlorohydrin.

7. A method according to any of the preceding claims wherein the rubber composition comprises sulphur as the vulcanising agent.

8. A method according to any of the preceding claims wherein the rubber employed in the composition comprises natural rubber, cis-l,4-polyisoprene rubber, styrene-butadiene rubber, polybutadiene rubber or a mixture of two or more of these rubbers.

9. A method according to any of the preceding claims wherein the resin precursors comprise an aldehyde condensation resin and a compound which on heating becomes a methylene donor.

10. A method according to any of claims 1 to 8 wherein the resin precursors comprise an aromatic hydroxy compound and a compound which becomes a methylene donor on heating.

11. A method according to claim 9 or 10 wherein the methylene donating compound comprises hexamethylenetetramine, hexamethoxymethylmelamine, lauryloxymethyl pyridinium chloride, cetyloxymethyl pyridinium chloride, formaldehyde, a formaldehyde polymer or a formaldehyde polymer having stabilising groups or residues of substances such as pentaerythritol at the ends of the molecules.

12. A method according to claim 9, 10 or 11 wherein the methylene donating compound is used in an amount of 0.1 to 10 parts by weight per 100 parts by weight of rubber in the composition.

13. A method according to claim 10 wherein the aromatic hydroxy compound has two hydroxy groups arranged meta to each other.

14. A method according to claim 13 wherein the aromatic hydroxy compound comprises resorcinol or 1,3-dihydroxy naphthalene.

15. A method according to claim 10, 13 or 14 wherein the aromatic hydroxy compound is used in an amount of 0.1 to 10 parts by weight per 100 parts by weight of rubber in the composition.

16. A method according to any of the preceding claims wherein the rubber composition contains silica.

17. A method according to claim 1 substantially as described herein.

18. A method according to claim 1 substantially as hereinbefore described with reference to compositions B and C of the Example.

19. A rubber bonded aromatic polyamide filamentary material whenever prepared by a method according to any of the preceding claims.

20. A pneumatic tyre comprising a rubber bonded aromatic polyamide filamentary material according to claim 19.

21. A conveyor belt comprising a rubber bonded aromatic polyamide filamentary material according to claim 19.

22. A hose comprising a rubber bonded aromatic polyamide filamentary material according to claim 19.