COMPOSITE AND POWER TRANSMISSION BELT

Abstract

A composite comprises: at least one reinforcing element (10), an adhesive layer (14) made from an adhesive composition and coating the reinforcing element (10), an elastomeric bonding layer (16) made from an elastomeric bonding composition and directly coating the adhesive layer (14), and an elastomeric body made from an elastomeric matrix and embedded in which is the reinforcing element (10) coated with the adhesive layer (14) and with the elastomeric bonding layer (16). The adhesive composition comprises a phenol-aldehyde resin based: on an aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted; and on an aromatic aldehyde bearing an aldehyde function, comprising at least one aromatic ring.

Claims

1.-49. (canceled)

50. A composite comprising: at least one reinforcing element; an adhesive layer made from an adhesive composition and coating the reinforcing element; an elastomeric bonding layer made from an elastomeric bonding composition and directly coating the adhesive layer; and an elastomeric body made from an elastomeric matrix, wherein the at least one reinforcing element coated with the adhesive layer and with the elastomeric bonding layer is embedded in the elastomeric body, and wherein the adhesive composition comprises at least one phenol-aldehyde resin based on: at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted, and at least one aromatic aldehyde bearing at least one aldehyde function, comprising at least one aromatic ring.

51. The composite according to claim 50, wherein the aromatic ring of the aromatic polyphenol bears three hydroxyl functions in the meta position relative to one another.

52. The composite according to claim 50, wherein the aromatic polyphenol is selected from the group consisting of resorcinol, phloroglucinol, 2,2,4,4-tetrahydroxydiphenyl sulfide, 2,2,4,4-tetrahydroxybenzophenone, resins pre-condensed from at least one of these aromatic polyphenols, and mixtures thereof.

53. The composite according to claim 50, wherein the aromatic aldehyde is selected from the group consisting of 1,2-benzenedicarboxaldehyde, 1,3-benzenedicarboxaldehyde, 1,4-benzenedicarboxaldehyde, furfuraldehyde, 2,5-furandicarboxaldehyde and the mixtures of these compounds, preferably the aromatic aldehyde is selected from 1,3-benzenedicarboxaldehyde, 1,4-benzenedicarboxaldehyde, furfuraldehyde, 2,5-furandicarboxaldehyde, and mixtures thereof.

54. The composite according to claim 50, wherein the adhesive composition comprises at least one unsaturated elastomer latex.

55. The composite according to claim 50, wherein the unsaturated elastomer of the latex is a diene elastomer selected from the group consisting of polybutadienes, butadiene copolymers, polyisoprenes, isoprene copolymers, vinylpyridine-styrene-butadiene terpolymers, ethylene/alpha-olefin type elastomers, polychloroprene elastomers (CR), and mixtures thereof.

56. The composite according to claim 55, wherein the ethylene/alpha-olefin type elastomer is selected from the group consisting of ethylene-propylene copolymers (EPM), ethylene-propylene-diene copolymers (EPDM), and mixtures thereof.

57. The composite according to claim 50, wherein the elastomeric matrix comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer, a hydrogenated nitrile elastomer (HNBR), a nitrile elastomer (NBR), a chlorosulfonated polyethylene with alkyl groups (ACSM), a polychloroprene elastomer (CR), a polybutadiene (BR), a natural rubber (NR), a synthetic polyisoprene (IR), a butadiene-styrene copolymer (SBR), an isoprene-butadiene copolymer (BIR), an isoprene-styrene copolymer (SIR), a butadiene-styrene-isoprene copolymer (SBIR), and mixtures thereof.

58. The composite according to claim 57, wherein the elastomeric matrix comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer, a hydrogenated nitrile elastomer (HNBR), a polychloroprene elastomer (CR), a polybutadiene (BR), a natural rubber (NR), a butadiene-styrene copolymer (SBR), and mixtures thereof.

59. The composite according to claim 58, wherein the ethylene/alpha-olefin type elastomer is selected from the group consisting of ethylene-propylene copolymers (EPM), ethylene-propylene-diene copolymers (EPDM), and mixtures thereof.

60. The composite according to claim 50, wherein the reinforcing element is nonmetallic.

61. The composite according to claim 60, wherein the nonmetallic reinforcing element comprises at least one multifilament ply of elementary monofilaments.

62. The composite according to claim 60, wherein the nonmetallic reinforcing element is made from a material selected from the group consisting of textile materials, mineral materials and combinations thereof.

63. The composite according to claim 62, wherein the nonmetallic reinforcing element is made from a textile material selected from the group consisting of polyesters, polyamides, polyketones, polyvinyl alcohols, celluloses and combinations thereof.

64. The composite according to claim 50, wherein the elastomeric bonding composition comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer, a hydrogenated nitrile elastomer (HNBR), a nitrile elastomer (NBR), a chlorosulfonated polyethylene with alkyl groups (ACSM), a polychloroprene elastomer (CR), a polybutadiene (BR), a natural rubber (NR), a synthetic polyisoprene (IR), a butadiene-styrene copolymer (SBR), an isoprene-butadiene copolymer (BIR), an isoprene-styrene copolymer (SIR), a butadiene-styrene-isoprene copolymer (SBIR), and mixtures thereof.

65. The composite according to claim 64, wherein the at least one elastomer of the elastomeric bonding composition is selected from the group consisting of an ethylene/alpha-olefin type elastomer, a polychloroprene elastomer (CR), a natural rubber (NR), and mixtures thereof.

66. The composite according to claim 64, wherein the ethylene/alpha-olefin type elastomer is selected from the group consisting of ethylene-propylene copolymers (EPM), ethylene-propylene-diene copolymers (EPDM), and mixtures thereof.

67. A power transmission belt comprising the composite according to claim 50.

68. A process for manufacturing a composite, the process comprising the following steps: (1) arranging, in the uncured state, a stack comprising, in this order: a first elastomeric layer made from a first elastomeric material, at least one reinforcing element coated with an adhesive layer made from an adhesive composition, the adhesive layer being directly coated with an elastomeric bonding layer made from an elastomeric bonding composition, the adhesive composition comprising at least one phenol-aldehyde resin based on: at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted, and at least one aromatic aldehyde bearing at least one aldehyde function, comprising at least one aromatic ring, and a second elastomeric layer made from a second elastomeric material; and (2) molding and crosslinking the stack.

69. A process for manufacturing a power transmission belt, the process comprising the following steps: (1) arranging, in the uncured state, a stack comprising, in this order: a first elastomeric layer made from a first elastomeric material, at least one reinforcing element coated with an adhesive layer made from an adhesive composition, the adhesive layer being directly coated with an elastomeric bonding layer made from an elastomeric bonding composition, the adhesive composition comprising at least one phenol-aldehyde resin based on: at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted, and at least one aromatic aldehyde bearing at least one aldehyde function, comprising at least one aromatic ring, a second elastomeric layer made from a second elastomeric material, and a third elastomeric mechanical drive layer arranged in contact with the second elastomeric layer and made from a third elastomeric material; and (2) molding and crosslinking the stack.

Description

EXEMPLARY EMBODIMENTS OF THE INVENTION AND COMPARATIVE TESTS

[0233] Represented in FIG. 1 is a composite according to the invention that forms a power transmission belt P. The power transmission belt P is intended for driving any member in rotation. The power transmission belt P comprises an elastomeric body 20 made from an elastomeric matrix and in which the coated reinforcing elements R are embedded. The power transmission belt P also comprises a mechanical drive layer 22 arranged in contact with the elastomeric body 20. The mechanical drive layer 22 is provided with several ribs 24 that each extend along a general direction Y substantially perpendicular to a longitudinal direction X of the belt P. Each rib 24 has a trapezoidal shape in cross section. The general directions of the ribs 24 are substantially parallel to one another. The ribs 24 extend over the entire length of the belt P. These ribs 24 are intended to be engaged in the recesses or grooves of complementary shape, for example borne by pulleys on which the belt is intended to be mounted.

[0234] The elastomer body 20 is formed on the one hand by a first elastomeric layer 26 made from a first elastomeric material and on the other hand by a second elastomeric layer 28 made from a second elastomeric material. The mechanical drive layer 22 is formed by a third layer made from a third elastomeric material.

[0235] Each first and second elastomeric material comprises a reinforcing filler, here carbon black (10 to 100 phr), an , -unsaturated organic acid metal salt, here zinc monomethacrylate (2 to 50 phr), an agent for dispersing the reinforcing filler (1 to 10 phr), an antioxidant (0.5 to 8 phr), an organic peroxide (0.5 to 8 phr), a co-crosslinking agent (0.5 to 5 phr by weight) and a plasticizer (1 to 20 phr by weight).

[0236] Each first and second elastomeric material also comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer, a hydrogenated nitrile elastomer (HNBR), a nitrile elastomer (NBR), a chlorosulfonated polyethylene with alkyl groups (ACSM), a polychloroprene elastomer (CR), a polybutadiene (BR), a natural rubber (NR), a synthetic polyisoprene (IR), a butadiene-styrene copolymer (SBR), an isoprene-butadiene copolymer (BIR), an isoprene-styrene copolymer (SIR), a butadiene-styrene-isoprene copolymer (SBIR) and the mixtures of these elastomers. In this case, each first and second elastomeric material comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer, a hydrogenated nitrile elastomer (HNBR), a polychloroprene elastomer (CR), a polybutadiene (BR), a natural rubber (NR), a butadiene-styrene copolymer (SBR) and the mixtures of these elastomers. More preferentially, each first and second elastomeric material comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer, a mixture of natural rubber (NR) and of an ethylene/alpha-olefin type elastomer, a polychloroprene elastomer (CR) and a mixture of a polybutadiene (BR) and of a hydrogenated nitrile elastomer (HNBR). More preferentially still, each first and second elastomeric material comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer and a polychloroprene elastomer (CR). Here, each first and second elastomeric material comprises a mixture of natural rubber (NR) and of an ethylene-propylene-diene copolymer (EPDM), the proportion of natural rubber being less than 30 phr.

[0237] The third elastomeric material is made from an elastomeric composition comprising at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer, a hydrogenated nitrile elastomer (HNBR), a nitrile elastomer (NBR), a chlorosulfonated polyethylene with alkyl groups (ACSM), a polychloroprene elastomer (CR), a polybutadiene (BR), a natural rubber (NR), a synthetic polyisoprene (IR), a butadiene-styrene copolymer (SBR), an isoprene-butadiene copolymer (BIR), an isoprene-styrene copolymer (SIR), a butadiene-styrene-isoprene copolymer (SBIR) and the mixtures of these elastomers. In this case, the elastomer of the elastomeric composition of the third elastomeric material is selected from the group consisting of an ethylene/alpha-olefin type elastomer, a polychloroprene elastomer (CR), a polybutadiene (BR), a natural rubber (NR), a butadiene-styrene copolymer (SBR) and the mixtures of these elastomers. Here, the elastomer of the elastomeric composition of the third elastomeric material is an ethylene/alpha-olefin type elastomer, for example an ethylene-propylene copolymer (EPM), an ethylene-propylene-diene copolymer (EPDM) or a mixture of these copolymers.

[0238] Represented in FIGS. 2A and 2B are two variants of coated reinforcing elements R in accordance with the invention. Represented in FIG. 2A is a reinforcing element R comprising a reinforcing element 10 impregnated with a cohesion composition 12 described below, directly coated with an adhesive layer 14 made from an adhesive composition C1 described below. The reinforcing element 10 comprises several multifilament plies of elementary monofilaments 18, here monofilaments made of polyamide, in this case nylon 4-6. Unlike the reinforcing element R from FIG. 1A, the reinforcing element from FIG. 1B is devoid of cohesion composition 12. The coated reinforcing elements R from FIGS. 2A and 2B comprise an elastomeric bonding layer 16 directly coating the adhesive layer 14. The elastomeric body 20 directly coats the elastomeric bonding layer 16.

[0239] The elastomeric bonding composition comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer, a hydrogenated nitrile elastomer (HNBR), a nitrile elastomer (NBR), a chlorosulfonated polyethylene with alkyl groups (ACSM), a polychloroprene elastomer (CR), a polybutadiene (BR), a natural rubber (NR), a synthetic polyisoprene (IR), a butadiene-styrene copolymer (SBR), an isoprene-butadiene copolymer (BIR), an isoprene-styrene copolymer (SIR), a butadiene-styrene-isoprene copolymer (SBIR) and the mixtures of these elastomers. In this case, the elastomer of the elastomeric bonding composition is selected from the group consisting of an ethylene/alpha-olefin type elastomer, a polychloroprene elastomer (CR), a natural rubber (NR) and the mixtures of these elastomers. More preferentially, the elastomeric bonding composition comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer, a mixture of natural rubber (NR) and of an ethylene/alpha-olefin type elastomer and a polychloroprene elastomer (CR). More preferentially still, the elastomeric bonding composition comprises at least one elastomer selected from the group consisting of an ethylene/alpha-olefin type elastomer and a polychloroprene elastomer (CR). Here, each first and second elastomeric material comprises a mixture of natural rubber (NR) and of an ethylene-propylene-diene copolymer (EPDM), the proportion of natural rubber being less than 30 phr.

[0240] A process will now be described for manufacturing the belt P from the variants from FIGS. 2A, 2B of the coated reinforcing elements R.

[0241] Firstly, for the coated reinforcing element R from FIG. 2A, the process comprises a step of impregnating each reinforcing element 10 with the cohesion composition 12. In order to do this, the reinforcing element 10 is run through a bath generally based on isocyanate in a solvent, for example based on toluene.

[0242] Next, the process comprises a step of coating the reinforcing element with the adhesive composition C1. In order to do this, the reinforcing elements are run through the adhesive composition C0 or C1, then the reinforcing elements thus coated are dried in a drying oven at 140 C. for 30 s. Next the adhesive composition is crosslinked by passing the coated reinforcing elements through a treatment oven at 240 C. for 30 s.

[0243] Then, during a subsequent step, the process comprises a step of coating the adhesive layer directly with an elastomeric bonding composition. In this case, the adhesive layer C1 is directly coated with the elastomeric bonding composition by extruding a sheath of the elastomeric bonding composition around the reinforcing element coated with the adhesive layer layer. Reinforcing elements coated with the adhesive layer made from the adhesive composition, the adhesive layer being directly coated with the elastomeric bonding layer made from the elastomeric bonding composition, are then obtained. The elastomeric bonding layer then forms a sheath around the reinforcing element.

[0244] Next, in the uncured state, i.e. in the non-crosslinked state, a stack is arranged comprising in this order: [0245] the first elastomeric layer 26 made from the first elastomeric material, [0246] several reinforcing elements R as described above, [0247] the second elastomeric layer 28 made from the second elastomeric material, [0248] the third elastomeric layer 22 in contact with the second elastomeric layer 28 and made from the third elastomeric material.

[0249] Then, after this arranging step, the stack in the uncured state is manipulated and placed in a mould. The stack obtained previously is moulded and crosslinked. The belt P from FIG. 1 is then obtained.

[0250] Endurance Test

[0251] Five power transmission belts P1 to P5 were manufactured in a manner similar to the process described above in order to evaluate the endurance performance provided by the adhesive composition according to the invention (belts P1 and P2 according to the invention) relative to an adhesive composition of RFL type (control belts P3, P4 and P5).

[0252] For this, two aqueous adhesive compositions were prepared, one in accordance with the invention (hereinafter denoted C1) and one not in accordance with the invention (control composition, hereinafter denoted C0). Their formulations (expressed as percentage by weight) are presented in the appended Table 1. The amounts listed in this table are those of the constituents in the dry state, with respect to a total of 100 parts by weight of aqueous adhesive composition (that is to say, the constituents plus the water).

[0253] The control composition C0 is a conventional RFL adhesive.

[0254] The composition C1 comprises at least one phenol-aldehyde resin based on at least: [0255] on at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted, and [0256] on at least one aromatic aldehyde bearing at least one aldehyde function, comprising at least one aromatic ring.

[0257] Regarding the aromatic polyphenol, the aromatic ring of the aromatic polyphenol bears three hydroxyl functions in the meta position relative to one another. The two positions ortho to each hydroxyl function are unsubstituted. The remainder of the aromatic ring of the aromatic polyphenol is unsubstituted. Here, the polyphenol comprises a single aromatic ring and this aromatic ring is a benzene ring. The polyphenol is selected from the group consisting of resorcinol, phloroglucinol, 2,2,4,4-tetrahydroxydiphenyl sulfide, 2,2,4,4-tetrahydroxybenzophenone, resins pre-condensed from at least one of these aromatic polyphenols and the mixtures of these compounds. Here, this is phloroglucinol.

[0258] Regarding the aldehyde, the aromatic ring bears the aldehyde function. The aromatic aldehyde is selected from the group consisting of 1,2-benzenedicarboxaldehyde, 1,3-benzenedicarboxaldehyde, 1,4-benzenedicarboxaldehyde, furfuraldehyde, 2,5-furandicarboxaldehyde and the mixtures of these compounds, preferably the aromatic aldehyde is selected from 1,3-benzenedicarboxaldehyde, 1,4-benzenedicarboxaldehyde, furfuraldehyde, 2,5-furandicarboxaldehyde and the mixtures of these compounds. The aromatic aldehyde is an aromatic polyaldehyde in which the aromatic ring bears at least two aldehyde functions, here exactly two aldehyde functions. The aromatic ring of the aromatic aldehyde is a benzene ring. More preferentially here, the aromatic aldehyde is 1,4-benzenedicarboxaldehyde.

[0259] The adhesive composition also comprises an unsaturated elastomer latex comprising one or more elastomers. In this case, the unsaturated elastomers of the latex are diene elastomers, preferably selected from the group consisting of polybutadienes, butadiene copolymers, polyisoprenes, isoprene copolymers, vinylpyridine-styrene-butadiene terpolymers, ethylene/alpha-olefin type elastomers, polychloroprene elastomers and the mixtures of these elastomers. Here, this is an NR/SBRNP-SBR mixture.

TABLE-US-00001 TABLE 1 Adhesive compositions C0 C1 Aldehyde: Formaldehyde (1) 0.9 1,4-Benzenedicarboxaldehyde (2) 0.9 Polyphenol: Resorcinol (3) 1.7 Phloroglucinol (4) 1.7 Sodium hydroxide (5) 0.2 0.2 Elastomer latex: NR (6) 6.4 6.4 SBR (7) 3.2 3.2 VP-SBR (8) 6.4 6.4 Aqueous ammonia (9) 0.5 0.5 Total weight of solids of adhesive composition 19.3 19.3 Weight of water 80.7 80.7 Adhesion tests F.sub.max at 20 C. 100 120 F.sub.max at 120 C. 100 116 (1) Formaldehyde (from Caldic; diluted to 36%); (2) 1,4-Benzenedicarboxaldehyde (from ABCR; purity of 98%); (3) Resorcinol (from Sumitomo; purity of 99.5%); (4) Phloroglucinol (from Alfa Aesar; purity of 99%); (5) Sodium hydroxide (from Aldrich; diluted to 30%); (6) NR Latex (Trang Latex from Bee tex; diluted to 61% by weight); (7) SBR Latex (Encord-201 from Jubilant; diluted to 41% by weight); (8) Vinylpyridine-styrene-butadiene latex (VP 106S from Eliokem; diluted to 41%); (9) Aqueous ammonia (from Aldrich; diluted to 21%).

[0260] Using these two adhesive compositions, several coated reinforcing elements R01, R02, R11 and R12 were prepared, the features of which are collated in Table 2 below.

[0261] Each reinforcing element is a nonmetallic reinforcing element comprising three multifilament plies of elementary monofilaments having a count of 2350 tex assembled together with a twist of 125 turns.Math.m.sup.1. Each reinforcing element is made from a textile material, here an aliphatic polyamide, in this case nylon 4-6.

[0262] As indicated in Table 2, the reinforcing elements R01 and R11 are impregnated with a cohesion composition which is subsequently itself directly coated with the layer of adhesive composition, respectively C0 and C1. In this case, the cohesion composition is based on a reaction product of at least one isocyanate, here this reaction product is an isocyanurate. As indicated in Table 2, the reinforcing elements R02 and R12 are devoid of the cohesion composition.

[0263] Each reinforcing element R01, R02, R11 and R12 is coated with an adhesive layer C0 or C1 made from an adhesive composition and either directly coating the reinforcing element directly for the reinforcing elements R02 and R12, or directly coating the cohesion composition impregnating the reinforcing element for the reinforcing elements R01 and R11.

TABLE-US-00002 TABLE 2 R01 R02 R11 R12 Cohesion composition Yes No Yes No Adhesive composition C0 C0 C1 C1

[0264] Then, for some of them (reinforcing elements used in the belts P1 to P4), the adhesive layer C0 or C1 was directly coated with the elastomeric bonding composition by extruding a sheath of the elastomeric bonding composition around the reinforcing element coated with the adhesive layer in accordance with the process described above.

[0265] Each power transmission belt P1 to P5 is then obtained, the features of which are collated in Table 3 below. Next, an endurance test was carried out during which ten samples were tested for each belt P1 to P5. Each sample was subjected to displacement cycles at a temperature between 100 C. and 150 C., at a frequency between 5 and 20 Hz under a preload of between 20 and 100 N.

TABLE-US-00003 TABLE 3 P1 P2 P3 P4 P5 Cohesion No Yes No Yes Yes composition Adhesive C1 C1 C0 C0 C0 composition Reinforcing R12 R11 R02 R01 R01 element Bonding Yes Yes Yes Yes No layer Mean no. No. = No. > 10.sup.8 No. = No. = No. < 10.sup.6 of cycles 3 10.sup.6 3 10.sup.6 5 10.sup.6 at failure

[0266] These results demonstrate that the belts according to the invention P1 and P2 have an endurance that is comparable to or even greater than belts that use conventional adhesive compositions of RFL type. The endurance is in particular markedly improved when the reinforcing element of the belt is impregnated with a cohesion composition (belt P2) which demonstrates a synergistic effect between the cohesion composition, the adhesive composition and the bonding layer.

[0267] Moreover, these results demonstrate that the presence of a bonding layer makes it possible to significantly improve the endurance of the belts. A posteriori, the inventors behind the invention explain this by the green tack that the bonding layer confers and which ensures a good cohesion between the adhesive composition and the elastomeric matrix. In the absence of this bonding layer, as is the case in the belt five, the cohesion created during the arrangement of the stack between the adhesive composition and the elastomeric matrix is insufficient and results in a reduced endurance.

[0268] The invention is not limited to the embodiments described above.

[0269] It could also be envisaged to use a composite in which the reinforcing element is metallic. Thus, the metallic reinforcing element would comprise one or more elementary metallic monofilaments each comprising a steel core. In one embodiment, the adhesive layer directly coats the steel core of the or each elementary metallic monofilament. In another embodiment, the adhesive layer directly coats a layer of a metallic coating directly coating the steel core of the or each elementary metallic monofilament. The metal of the layer of the metallic coating directly coating the steel core of the or each elementary metallic monofilament is selected from zinc, copper, tin and the alloys of these metals. Advantageously, the adhesive layer directly coats a nonmetallic intermediate adhesive layer coating the steel core of the or each elementary metallic monofilament.