REINFORCED PRODUCT COMPRISING A SELF-ADHESIVE COMPOSITE REINFORCEMENT CONTAINING A BLOCK COPOLYMER

Abstract

A reinforced product, which can be used in particular for the reinforcing of a finished rubber article, comprises one or more textile or metallic reinforcing threads, the said thread or threads being covered individually or collectively with a sheath comprising a sheathing composition comprising one or more block copolymers comprising at least one polyamide block and at least one polyolefin block, the sheathed thread or threads being themselves embedded in a rubber composition.

Claims

1.-15. (canceled)

16. A reinforced product comprising one or more reinforcing threads, wherein the thread or threads are covered individually or collectively with a sheath comprising a sheathing composition comprising one or more block copolymers comprising at least one polyamide block and at least one polyolefin block, and wherein the sheathed thread or threads are embedded in a rubber composition.

17. The reinforced product according to claim 16, wherein the polyolefin block or blocks each exhibit a viscosity of less than 60,000 cPs, the viscosity being measured at 25 C. with a Brookfield device and according to the Brookfield method.

18. The reinforced product according to claim 17, wherein the polyolefin block or blocks each exhibit a viscosity of less than 40,000 cPs.

19. The reinforced product according to claim 18, wherein the polyolefin block or blocks each exhibit a viscosity of and preferably of less than 20,000 cPs.

20. The reinforced product according to claim 19, wherein the polyolefin block or blocks each exhibit a viscosity of between 1000 and 20,000 cPs.

21. The reinforced product according to claim 17, wherein the polyolefin block or blocks are a polybutadiene block or blocks.

22. The reinforced product according to claim 16, wherein the polyamide block or blocks comprise at least one unit selected from the group consisting of PA 6, PA 11, PA 12, PA 6.10, PA 6.6, PA 6.12, PA 10.10, PA 10.12, PA 11/10.T, PA 11/6.T, 12/10.T, 6.10/10.T, 6.12/10.T, 10.10/10.T, 10.12/10.T, 11/6.T/10.T, 12.12/10.T, 12/6.10/10.T, 12/6.12/10.T, 12/10.10/10.T, 12/10.12/10.T and 12/12.12/10.T.

23. The reinforced product according to claim 16, wherein the polyamide block or blocks each exhibit a number-average molecular weight, measured by potentiometry, of between 600 and 20,000 g/mol.

24. The reinforced product according to claim 23, wherein the polyamide block or blocks each exhibit a number-average molecular weight, measured by potentiometry, of between 4,000 and 10,000 g/mol.

25. The reinforced product according to claim 16, wherein the block copolymer comprises a content of polyolefin block between 2% and 98% by weight with respect to a total weight of the block copolymer.

26. The reinforced product according to claim 25, wherein the block copolymer comprises a content of polyolefin block between 5% and 70% by weight with respect to a total weight of the block copolymer.

27. The reinforced product according to claim 26, wherein the block copolymer comprises a content of polyolefin block between 6% and 50% by weight with respect to a total weight of the block copolymer.

28. The reinforced product according to claim 27, wherein the block copolymer comprises a content of polyolefin block between 8% and 30% by weight with respect to a total weight of the block copolymer.

29. The reinforced product according to claim 28, wherein the block copolymer comprises a content of polyolefin block between 9% and 25% by weight with respect to a total weight of the block copolymer.

30. The reinforced product according to claim 16, wherein the block copolymer or copolymers comprise at least one chain-extending block.

31. The reinforced product according to claim 16, wherein the block copolymer or copolymers comprise at least one alkylene block.

32. The reinforced product according to claim 31, wherein the at least one alkylene block is a fatty acid dimer.

33. The reinforced product according to claim 32, wherein the fatty acid dimer is a C2-C36 fatty acid dimer.

34. The reinforced product according to claim 33, wherein the fatty acid dimer is a C8-C36 fatty acid dimer.

35. The reinforced product according to claim 31, wherein the block copolymer or copolymers comprise: at least one polybutadiene block as polyolefin block, and at least one C2-C36 diacid alkylene block.

36. The reinforced product according to claim 35, wherein the block copolymer or copolymers comprise: at least one polybutadiene block as polyolefin block, and at least one C8-C36 diacid alkylene block.

37. A reinforced product according to claim 31, wherein the block copolymer or copolymers have the following formula:
PA-(R-Pol)n-R-Pol-R-PA wherein n is between 0 and 100, PA denotes the polyamide block, R denotes the alkylene block, and Pol denotes the polyolefin block.

38. The reinforced product according to claim 16, wherein the rubber composition comprises a reinforcing filler.

39. The reinforced product according to claim 16, wherein the rubber composition comprises a crosslinking system.

40. The reinforced product according to claim 39, wherein the reinforcing thread or threads are metallic.

41. A tire comprising a reinforced product according to claim 16.

Description

EXAMPLES

I. Synthesis of the Block Copolymers

[0349] Synthesis of the Copolymer: PA 1 According to the Invention

[0350] The mixing of polybutadiene and of fatty acid dimer in a molar ratio of (polybutadiene/fatty acid dimer) is carried out.

[0351] The mixture obtained is then mixed with the polyamide as described below.

[0352] Manufacture of PA 11 Diamine with a Number-Average Molecular Weight of 5000 g/Mol:

[0353] 5000 g of 11-aminoundecanoic acid, 116.2 g of hexamethylenediamine and 750 g of deionized water are introduced into a 12 l autoclave equipped with a stirrer of anchor type. The medium is rendered inert with nitrogen and then heated up to a material temperature of 210 C. with stirring. The pressure is then 20 bar. The medium is then heated to a material temperature of 230 C. while maintaining a pressure of 20 bar. When this temperature is reached, the pressure is brought back to atmospheric pressure by reducing in pressure and flushing under nitrogen is applied for 90 minutes.

[0354] The product obtained is thus emptied into liquid nitrogen and recovered in the form of blocks.

[0355] The chain ends are quantitatively determined by potentiometry:

[0356] NH.sub.2=0.399 meq/g

[0357] The molecular weight is indeed 5000 g/mol.

[0358] Manufacture of a Pentablock:

[0359] 761.9 g of Krasol LBH-P 2000 (viscosity 13 000 cP, Mn=2100, 0.36 mol), 438.1 g of Pripol 1013 (M=575 g/mol, 0.76 mol), 1.2 g of Irganox 1098 and 1.2 g of phosphoric acid are introduced into a 12 l autoclave equipped with a stirrer of anchor type. The medium is stirred and is brought to a temperature of 235 C. under vacuum for 3 h. The medium is brought back to atmospheric pressure. 3800 g (0.76 mol) of the polyamide prepared above are added and the reaction takes place under vacuum at 235 C. for 90 min.

[0360] The product is subsequently emptied into water and granulated.

[0361] Potentiometric titration of the chain ends is:

[0362] NH.sub.2=0.18 meq/g

[0363] Potentiometric Titration of the Amine Chain Ends:

[0364] 500 mg of polymer are dissolved in 80 g of m-cresol at 130 C. for 1 h.

[0365] 0.02N perchloric acid (in acetic acid) is added until the amine chain ends have been neutralized. This neutralization is accompanied by a modification of potential, monitored using electrodes.

II. Preparation of the Extruded Part

[0366] A reinforcing thread with a diameter of approximately 0.35 mm, for example a metal cord composed simply of three individual monofilaments with a diameter of 0.18 mm twisted together, is covered with a first layer of a block copolymer with a maximum thickness equal to approximately 0.25 mm at the diameter, in order to obtain a sheathed reinforcing thread having a total diameter of approximately 0.6 mm, on an extrusion/sheathing line comprising two dies, a first die (counter-die or upstream die) with a diameter equal to approximately 0.41 mm and a second die (or downstream die) with a diameter equal to approximately 0.53 mm, both dies being positioned in an extrusion head brought to approximately 210 C.

[0367] The block copolymer, molten at a temperature of 210 C. to 230 C. according to the heating zones of the extrusion die (Z1=210 C., Z2=220 C., Z3=230 C., Collar=220 C.) in the extruder, thus covers the reinforcing thread, via the sheathing head, at a rate of forward progression of the thread typically equal to several tens of m/min, for an extrusion pump throughput typically of several tens of cm.sup.3/min. On exiting from this sheathing operation, the thread can be immersed in a cooling tank filled with cold water, in order to solidify and set the polyamide in its amorphous state, and then dried, for example by passing the take-up reel into the oven.

III. Tests and Results

Description of the Adhesion Test:

[0368] The quality of the bond between the rubber and the sheathed reinforcing elements manufactured above is subsequently assessed by a test in which the force needed to extract the sheathed reinforcing elements from a vulcanized rubber composition, also known as vulcanizate, is measured. This rubber composition is a conventional composition used for the calendering of pneumatic tyre belt metal plies, based on natural rubber, carbon black and standard additives.

Rubber Composition Used:

[0369] The rubber composition comprises 100 phr of natural rubber, 70 phr of series 300 carbon black, 1.5 phr of N-(1,3-dimethylbutyl)-N-phenyl-para-phenylenediamine, 1 phr of a cobalt salt, 0.9 phr of stearic acid, 6 phr of insoluble molecular sulfur, 0.8 phr of N-(tert-butyl)-2-benzothiazolesulfamide and 7.5 phr of ZnO.

[0370] The vulcanizate is a rubber block composed of two sheets having dimensions of 200 mm by 4.5 mm and having a thickness of 3.5 mm, applied against each other before curing (the thickness of the resulting block is then 7 mm). It is during the production of this block that the sheathed reinforcing elements (15 strands in total) are trapped between the two rubber sheets in the raw state, an equal distance apart and while leaving to protrude, on either side of these sheets, a sheathed reinforcing element end having a length sufficient for the subsequent tensile test. The block comprising the reinforcing elements is then placed in a suitable mould and then cured under pressure. The curing of the block is carried out at 160 C. for 15 min, under a pressure of 16 bar.

[0371] On conclusion of the curing, the test specimen, thus consisting of the vulcanized block and the 15 reinforcers, is placed between the jaws of a suitable tensile testing machine in order to make it possible to pull each sheathed reinforcing element individually out of the rubber, at a given rate and a given temperature: at 50 mm/min and 20 C.

[0372] The adhesion levels are characterized by measuring the pull-out force (denoted Fmax) for pulling the reinforcing elements out of the test specimen (average over 15 tensile tests).

[0373] The block copolymer is compared with a homopolyamide of PA 6.6 structure, obtained by polycondensation of a hexanediamine and adipic acid.

[0374] 1/ Tensile Test at 23 C.

TABLE-US-00001 TABLE 1 Faver (N/mm.sup.2) Fmax (N/mm.sup.2) PA 66 (comporative) 1.1 2.1 Block PA 1 according to the invention 14.2 15.6

[0375] 2/ Tensile Test at 100 C.

TABLE-US-00002 TABLE 2 Faver (N/mm.sup.2) Fmax (N/mm.sup.2) Block PA 1 according to the invention 5.8 6.6

[0376] 3/ Tensile Test at 120 C.

TABLE-US-00003 TABLE 3 Faver (N/mm.sup.2) Fmax (N/mm.sup.2) PA 66 0.3 0.5

IV. Conclusion

[0377] These results show that the reinforced product including the block copolymer of use according to the invention makes it possible to obtain an adhesion, whether at ambient temperature or at higher temperature, which is improved with respect to the reinforced product including a homopolyamide of PA 66 structure. The adhesion obtained is more than 10 times greater than that obtained with the PA 66 conventionally used.