ADHESIVE COMPOSITION COMPRISING A PHOSPHATE SALT AND A THERMOSETTING RESIN

Abstract

The present invention relates to an adhesive composition comprising: at least one phosphate salt chosen from sodium phosphate, potassium phosphate and mixtures of these phosphates; and at least one resin based on: at least one compound A1, compound A1 being chosen from a compound A11 comprising at least two functions, one of these functions being a hydroxymethyl function and the other being an aldehyde function or a hydroxymethyl function, or a compound A12 comprising at least one aldehyde function, or a mixture of a compound A11 and of a compound A12; and at least one phenol A21.

Claims

1.-15. (canceled)

16. An adhesive composition comprising: a phosphate salt selected from the group consisting of sodium phosphate, potassium phosphate and mixtures thereof; and at least one resin based on: at least one compound A1 selected from the group consisting of: a compound A11 comprising at least two functions, one function being a hydroxymethyl function and one function being an aldehyde function or a hydroxymethyl function, a compound A12 comprising at least one aldehyde function, and a mixture of a compound A11 and of a compound A12, and at least one phenol A21.

17. The adhesive composition according to claim 16, wherein a water content of the adhesive composition is between 70% and 95% by weight.

18. The adhesive composition according to claim 16, wherein the phosphate salt is sodium phosphate.

19. The adhesive composition according to claim 16, wherein a pH of the adhesive composition is strictly greater than 7.

20. The adhesive composition according to claim 16, wherein compound A12 comprises at least one aromatic nucleus bearing at least one aldehyde function.

21. The adhesive composition according to claim 20, wherein the at least one aromatic nucleus of compound A12 bears two aldehyde functions.

22. The adhesive composition according to claim 20, wherein compound A12 is selected from the group consisting of 1,2-benzenedicarboxaldehyde, 1,3-benzenedicarboxaldehyde, 1,4-benzenedicarboxaldehyde, 2-hydroxybenzene-1,3,5-tricarbaldehyde and mixtures thereof.

23. The adhesive composition according to claim 16, wherein compound A11 is an aromatic compound comprising at least one aromatic nucleus bearing at least two functions, one function being a hydroxymethyl function and one function being an aldehyde function or a hydroxymethyl function.

24. The adhesive composition according to claim 23, wherein compound A11 corresponds to general formula (IIa1) or (IIa2): ##STR00032##

25. The adhesive composition according to claim 16, wherein the phenol A21 is selected from the group consisting of: an aromatic polyphenol A2 comprising at least one aromatic nucleus bearing at least two hydroxyl functions in the meta position relative to each other, the two positions ortho to at least one of the hydroxyl functions being unsubstituted, an aromatic monophenol A2 comprising at least one 6-membered aromatic nucleus bearing a single hydroxyl function, the two positions ortho to the single hydroxyl function being unsubstituted or at least one ortho position and the position para to the single hydroxyl function being unsubstituted, and a mixture of A2 and A2.

26. The adhesive composition according to claim 16 further comprising a latex of at least one elastomer.

27. A coated conductive element, wherein the coated conductive element is coated with an adhesive layer based on the adhesive composition according to claim 16.

28. A tire comprising a coated conductive element according to claim 27.

29. A belt comprising a coated conductive element according to claim 27.

Description

[0394] The invention will be better understood on reading the following description, given solely by way of non-limiting example and with reference to the drawings, in which:

[0395] FIG. 1 is a diagram of a tyre according to the invention; and

[0396] FIG. 2 is a diagram of a belt according to the invention;

[0397] The appended FIG. 1 is a highly diagrammatic representation (without being to a specific scale) of a radial cross section of a tyre in accordance with the invention for a vehicle of the passenger vehicle type.

[0398] This tyre 1 includes a crown 2 reinforced by a crown reinforcement or belt 6, two sidewalls 3 and two beads 4, each of these beads 4 being reinforced with a bead wire 5. The crown 2 is surmounted by a tread, not represented in this schematic figure. A carcass reinforcement 7 is wound around the two bead wires 5 in each bead 4, the turn-up 8 of this reinforcement 7 being, for example, positioned towards the outside of the tyre 1, which is represented here fitted onto its wheel rim 9. The carcass reinforcement 7 is, in a manner known per se, formed of at least one ply reinforced with radial cords, for example made of textile, that is to say that these cords are positioned virtually parallel to each other and extend from one bead to the other so as to form an angle of between 80 and 90 with the median circumferential plane (plane perpendicular to the axis of rotation of the tyre which is located midway between the two beads 4 and passes through the middle of the crown reinforcement 6).

[0399] This tyre 1 of the invention has, for example, the essential feature that at least a crown reinforcement 6 includes a conductive element, in this instance a coated metal wire element or an elastomeric composite according to the invention. According to another possible exemplary embodiment of the invention, it is, for example, the bead wires which might be entirely or partially composed of a conductive element, in this instance a coated metal wire element.

[0400] FIG. 2 depicts 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 coated metallic 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 each other. The ribs 24 extend over the entire length of the belt P. These ribs 24 are intended to be engaged in recesses or grooves of complementary shape, for example borne by pulleys on which the belt is intended to be mounted.

[0401] The elastomeric body 20 is formed on the one hand by a first elastomeric layer 26 made from a first elastomeric matrix and on the other hand by a second elastomeric layer 28 made from a second elastomeric matrix. The mechanical drive layer 22 is formed by a third layer made from a third elastomeric matrix.

[0402] Each first and second elastomeric matrix is based, respectively, on a first and second elastomeric composition, each comprising a reinforcing filler, in this instance carbon black (10 to 100 phr), an , -unsaturated organic acid metal salt, in this instance 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).

[0403] At least one of the first and second elastomeric compositions, and thus the elastomeric body 20, also comprises at least one elastomer chosen from the group consisting of an elastomer of -olefin ethylene type, a polychloroprene (CR) elastomer and mixtures of these elastomers. In the present case, each first and second elastomeric composition 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.

[0404] The third elastomeric material based on a third elastomeric composition comprising at least one elastomer chosen from the group consisting of an ethylene/-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 of these elastomers. In the present case, the elastomer of the elastomeric composition of the third elastomeric matrix is chosen from the group consisting of an ethylene/-olefin type elastomer, a polychloroprene elastomer (CR), a polybutadiene (BR), a natural rubber (NR), a butadiene-styrene copolymer (SBR) and mixtures of these elastomers. In this instance, the elastomer of the elastomeric composition of the third elastomeric matrix is an ethylene/-olefin type elastomer, for example an ethylene-propylene copolymer (EPM), an ethylene-propylene-diene copolymer (EPDM) or a mixture of these copolymers. The belt P according to the invention has, for example, the essential of including several coated conductive elements, in this instance metal wire elements, R and an elastomeric composite 20 according to the invention.

[0405] Needless to say, the invention relates to the objects described previously, namely the elastomeric composite and the tyre or belt comprising it, both in the uncured state (before crosslinking) and in the cured state (after crosslinking).

[0406] Comparative Tests

[0407] Adhesion Test

[0408] Each conductive wire element comprises a single elementary metallic monofilament comprising a steel core which has been coated with a metallic layer of brass. More preferentially, the or each elementary metallic monofilament comprises a steel core. The steel comprises for example from 0.2% to 1.2%, preferably from 0.3% to 1% and more preferentially from 0.3% to 0.7% of carbon by mass. The steel may also comprise specific alloying elements such as Cr, Ni, Co, V, or various other known elements (see, for example, Research Disclosure 34984Micro-alloyed steel cord constructions for tyresMay 1993; Research Disclosure 34054High tensile strength steel cord constructions for tyresAugust 1992). In the present instance, a conventional steel containing 0.7% of carbon is used.

[0409] Each metal wire element was coated with the test adhesive composition according to a conventional dipping process or an electroplating process according to the invention. Each coated conductive wire element was dried in a drying oven at 180 C. for 30 seconds. The adhesive composition was then crosslinked by passing the coated steel reinforcing elements through a treatment furnace at 240 C. for 30 seconds. Next, each steel reinforcing element thus coated was embedded in an elastomeric matrix and the composite thus formed was vulcanized by means of a thermal vulcanization treatment.

[0410] In the present case, the elastomeric matrix is based on an elastomeric composition comprising 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, and a crosslinking system comprising 0.9 phr of stearic acid, 2.2 phr of insoluble molecular sulfur, 0.8 phr of N-tert-butyl-2-benzothiazole sulfamide and 7.5 phr of ZnO.

[0411] More precisely, the vulcanized elastomeric matrix is a block of rubber consisting of two plates with dimensions of 200 mm12.5 mm and a thickness of 7 mm, applied one on the other before curing (the thickness of the resulting block is then 14 mm). It is during the manufacture of this block that the coated conductive wire elements (15 lengths in total) are trapped between the two rubber plates in the uncured state, at an equal distance and allowing one end of the conductive wire element to protrude on either side of these plates by a length sufficient for subsequent pulling. The block including the conductive wire elements is then placed in a suitable mould and then cured under pressure. The curing time and temperature are adapted to the targeted test conditions and left to the initiative of the person skilled in the art; by way of example, in the present case, the curing of the block is performed at 160 C. for 20 minutes.

[0412] Composite T0 is a control composite comprising brass-plated steel monofilaments free of adhesive layer.

[0413] Composite T1 is a composite comprising brass-plated steel monofilaments coated with an adhesive layer comprising an adhesive composition comprising a resin based on phloroglucinol and 1,4-benzenedicarboxaldehyde.

[0414] Composite C1 is a composite comprising brass-plated steel monofilaments coated with an adhesive layer comprising an adhesive composition comprising Na.sub.3PO.sub.4 and a resin based on phloroglucinol and 1,4-benzenedicarboxaldehyde.

[0415] The levels of adhesion are characterized by measuring the tear force to separate the coated steel reinforcing elements of each composite just after cooling after curing (denoted Fmax0) and the tear force to separate the coated steel reinforcing elements of each composite after thermal ageing at 55 C. under 90% humidity for 14 days (noted Fmax14). For the two tear forces (Fmax0 and Fmax14), an acceptable adhesion value was set at 100, this acceptable value corresponding to the minimum acceptable force for ensuring sufficient adhesion both initially and after thermal ageing.

[0416] A value of greater than 100 indicates an improved result, i.e. a tear force greater than the minimum acceptable force. A value of less than 100 indicates a degraded result, i.e. a tear force less than the minimum acceptable force.

[0417] The adhesive compositions of the various composites described above are collated in Table 1 below, along with the corresponding results.

TABLE-US-00001 TABLE 1 Adhesive compositions T0 T1 C1 Compound A1 1,4-Benzenedicarboxaldehyde (1) 0.89 0.71 Compound A21/A22 Phloroglucinol (2) 1.67 1.33 Sodium hydroxide (3) 0.76 Elastomeric latex: NR (4) 6.43 6.43 SBR (5) 3.24 3.24 VP-SBR (6) 6.48 6.48 Aqueous ammonia (7) 0.55 0.55 Sodium phosphate (8) 0.75 Total solids content of 19.5 19.5 the adhesive composition Weight of water 80.5 80.5 Adhesion tests on composite F.sub.max0 at 20 C. after cooling after curing 69 119 110 F.sub.max14 at 20 C. after 14 days NM 88 113 (1) 1,4-Benzenedicarboxaldehyde (from the company ABCR; 98% purity); (2) Phloroglucinol (from the company Alfa Aesar; 99% purity); (3) Sodium hydroxide (from the company Aldrich; diluted to 30%); (4) NR Latex (Trang Latex from the company Bee tex; diluted to 61% by weight); (5) SBR Latex (Encord-201 from the company Jubilant; diluted to 41% by weight); (6) Vinylpyridine-styrene-butadiene latex (VP 106S from the Eliokem; diluted to 41%); (7) Aqueous ammonia (from the company Aldrich; diluted to 21%); (8) Na.sub.3PO.sub.4 sodium phosphate (from the company Aldrich; 99% purity).

[0418] The comment NM (meaning not measured) indicates that the value was not measured or is meaningless.

[0419] The control composite T0 has insufficient initial adhesion on account of the relatively low sulfur content of the elastomeric matrix and of the low adhesion by the copper and zinc sulfide dendrites.

[0420] It is noted that composite C1 according to the invention has an initial adhesion F.sub.max0 which is greater than that of the control composite T0 and which is greater than the acceptable adhesion value.

[0421] After thermal and wet ageing, it is observed that the tear force F.sub.max14 of composite T1 decreases greatly whereas, unexpectedly, it does not undergo any reduction for composite C1 of the invention.

[0422] These tests confirm that the adhesion to an elastomeric matrix with an adhesive composition free of phosphate salt, of coated steel wire elements is deteriorated over time, whereas the adhesive composition comprising a phosphate salt makes it possible, surprisingly, to obtain a high initial adhesion, which is long-lasting.

[0423] The invention is not limited to the embodiments described previously.

[0424] It may also be envisaged to coat several elementary metallic monofilaments each comprising a steel core. In one embodiment, the elementary metallic monofilaments are assembled together and the elementary metallic monofilaments are then collectively coated with the adhesive composition. In another embodiment, each elementary metallic monofilament is individually coated with the adhesive composition and the elementary metallic monofilaments are then assembled together.

[0425] Elementary metallic monofilaments coated with a nonmetallic intermediate adhesive layer directly coating the steel core of the elementary metallic monofilaments or the metal coating layer may also be envisaged, the layer of the adhesive composition then directly coating this nonmetallic intermediate adhesive layer or the metal coating layer.

[0426] In another embodiment not in accordance with the invention, the reinforcing element is coated with an adhesive layer based on an aqueous adhesive composition, comprising: [0427] at least one unsaturated elastomeric latex comprising a butadiene copolymer, a vinylpyridine-styrene-butadiene terpolymer and a natural rubber, [0428] at least one resin based on resorcinol and formaldehyde, and [0429] at least one zinc phosphate such that the zinc phosphate is at a mass content ranging from 0.15% to 0.90% of the aqueous adhesive composition.

[0430] In this embodiment not in accordance with the invention, the zinc phosphate is at a mass content ranging from 0.20% to 0.75% of the aqueous adhesive composition, which avoids the need to use a dispersant.

[0431] Notably, in contrast with the invention, zinc phosphate is not water-soluble under standard temperature and pressure conditions. Although not making it possible to render the adhesion long-lasting, the zinc phosphate nevertheless makes it possible, while at the same time keeping the composite stable, to give the coated reinforcing element improved corrosion resistance relative to the same reinforcing element coated with an analogous aqueous adhesive composition free of zinc phosphate.