High-Performance Toothed Belt Made of EPDM

Abstract

The present invention relates to elastomer toothed belts comprising a fabric spanning the teeth of the toothed belt, wherein the elastomer mixture forming the teeth contains a crosslinked ethylene-propylene rubber (EPM) and/or a crosslinked ethylene-propylene terpolymer rubber (EPDM) accounting for at least 70% by weight of the elastomer mixture based on the polymer proportion and wherein an interlayer is arranged between the fabric and the elastomer mixture forming the teeth which contains at least 70% by weight of hydrogenated acrylonitrile-butadiene rubber (HNBR) based on the polymer proportion of the interlayer. Such elastomer toothed belts are halogen-free and feature improved durability and good low-temperature stability properties. The present invention further relates to processes for producing such elastomer toothed belts and to the use of a layer of hydrogenated acrylonitrile-butadiene rubber (HNBR) in such toothed belts to increase service life, to improve low-temperature stability and to improve the adhesion between the teeth and the fabric.

Claims

1.-15. (canceled)

16. An elastomer toothed belt comprising: a body having a length and sides arranged at a lateral distance to one another also having an inside, an outside and a plurality of teeth spaced apart from one another in a longitudinal direction on the inside and/or the outside; a fabric that spans the plurality of teeth; and an elastomer mixture that forms the teeth can contains a crosslinked ethylene-propylene rubber (EPM) and/or a crosslinked ethylene-propylene terpolymer rubber (EPDM) which accounts for at least 70% by weight of the elastomer mixture based on the polymer proportion and wherein an interlayer containing at least 70% by weight of hydrogenated acrylonitrile-butadiene rubber (HNBR) based on the polymer proportion of the interlayer is arranged between the fabric and the elastomer mixture forming the teeth.

17. The belt of claim 16, wherein the teeth contain the crosslinked ethylene-propylene rubber (EPM) and/or an ethylene-propylene terpolymer rubber (EPDM) in a proportion of at least 80% by weight based on the polymer proportion of the elastomer mixture forming the teeth.

18. The belt of claim 16, wherein the body is formed from crosslinked ethylene-propylene rubber (EPM) and/or ethylene-propylene-terpolymer rubber (EPDM) as the elastomer.

19. The belt of claim 16, wherein the crosslinked elastomer in the elastomer mixture from which the teeth are formed is a sulfur-crosslinked or peroxidically crosslinked elastomer and preferably a peroxidically crosslinked elastomer.

20. The belt of claim 16, wherein the interlayer contains at least 80% by weight and preferably at least 90% by weight of hydrogenated acrylonitrile-butadiene rubber (HNBR) based on the polymer proportion of the interlayer.

21. The belt of claim 16, wherein the hydrogenated acrylonitrile-butadiene rubber has a degree of hydrogenation in the range from 70% to 99% and preferably 95% to 98% and/or an acrylonitrile content of 18% to 47% by mass and preferably 30% to 37% by mass.

22. The belt of claim 16, wherein the interlayer has a thickness of at least about 10 m, preferably in the range from about 10 to 500 m and particularly preferably in the range from about 50 to 200 m and/or a Shore A hardness of less than 90.

23. The belt of claim 16, wherein the interlayer contains an additive for imparting electrical conductivity, preferably in the form of carbon black.

24. The belt of claim 16, wherein the interlayer contains a proportion of 20 to 70 parts and preferably 30 to 60 parts of the additive based on 100 parts of polymer in the interlayer and/or wherein the elastomer toothed belt has an electrical resistance determined according to ISO 9563:2015 of less than 50 M and preferably less than 5 M.

25. The belt of claim 16, wherein the fabric is formed to an extent of more than 70% from polyamide and preferably from linear aliphatic amide.

26. The belt of claim 16, wherein the fabric has a coating with a resorcinol/formaldehyde/latex, wherein the latex of the resorcinol/formaldehyde/latex preferably has a vinylpyridine content of more than 50% by weight.

27. A method for producing an elastomer toothed belt, the method comprising: (i) providing a fabric; (ii) applying a coating to the fabric, wherein the coating composition contains at least 70% by weight of hydrogenated acrylonitrile-butadiene rubber (HNBR) based on the polymer proportion in the coating composition, and (iii) securing the fabric to an elastomer toothed belt body whose teeth are formed from an elastomer mixture containing at least 70% by weight, based on the polymer proportion of the elastomer mixture forming the teeth, a crosslinked ethylene-propylene rubber (EPM) and/or a crosslinked ethylene-propylene terpolymer rubber (EPDM) in such a way that the coating from step (ii) is arranged between the teeth and the fabric.

28. The method of claim 27, wherein the coating in step (ii) is carried out by applying a solution of the hydrogenated acrylonitrile-butadiene rubber to the fabric and subsequently evaporating the solvent or by calendering a film containing the hydrogenated acrylonitrile-butadiene rubber onto the fabric.

29. The method of claim 27, wherein the process additionally comprises a step of applying an adhesion-promoting layer of resorcinol/formaldehyde/latex to the fabric prior to step (i).

30. The method of claim 27, further comprising incorporating a layer of hydrogenated acrylonitrile-butadiene rubber (HNBR) arranged between ethylene-propylene rubber (EPM) and/or ethylene-propylene-terpolymer rubber (EPDM) teeth of the toothed belt and incorporating a fabric spanning the teeth for increasing the service life of the toothed belt and/or for improving the adhesion between the teeth and the fabric in a toothed belt and/or improving the low-temperature stability of the toothed belt.

Description

[0053] FIG. 1 shows a three-dimensional representation of a toothed belt provided with a coating;

[0054] FIG. 2 shows a longitudinal section through a toothed belt having a coating.

[0055] FIG. 1 shows a toothed belt having an outer ply 2 as the belt backing, an embedded strength member 3 and a substructure 4. The strength member consists of a plurality of tensile strands which in a parallel arrangement form a strength member ply shown as a single-ply embodiment in FIG. 1. The tensile strand, especially in the form of cords, may be made of polyamide (PA), aramid, polyester, glass (for example E- or K-glass), carbon, polyetheretherketone (PEEK) or polyethylene 2,6-naphthalate (PEN) or of combinations of the cited materials.

[0056] The outer ply (2) and the substructure (4) as a whole form the elastic main body which in the context of the present invention is composed of a vulcanizate based on EPM, EPDM or an EPM/EPDM mixture for example.

[0057] The substructure 4 is provided with a tooth-shaped profile comprising teeth 5 and tooth-connecting webs 6 and forms the force-transmission zone 7 which is particularly susceptible to wear. For this reason the force-transmission zone is provided with an abrasion-resistant coating 8 in the form of a textile cover ply. The textile cover ply is made of a woven or knitted fabric which is preferably composed of polyamide (PA) and/or polyester and/or cotton and/or aramid and/or polyetheretherketone (PEEK). A layer composed of HNBR is arranged between the textile cover ply and the elastomer forming the teeth and tooth-connecting webs of the toothed belt. According to the invention an interlayer composed of HNBR (not shown) is arranged between the textile cover ply and the elastomer forming the teeth and tooth-connecting webs.

[0058] The toothed belt according to FIG. 2 comprises an outer ply 11 as the belt backing, an embedded strength member 12 in the form of tensile strands and a substructure 13 having a tooth-shaped force-transmission zone 14. In this working example both the cover ply 11 and the force-transmission zone are provided with a coating 15/16. The two coatings each comprise a textile cover ply, especially in the form of a fabric, which are coated with an elastomer mixture 18 or 19 for bonding of the fabric to the EPDM of the substructure.

[0059] The present invention is hereinbelow illustrated with reference to a number of examples which should not in any way be regarded as restricting the scope of protection of the application.

EXAMPLE

[0060] Various toothed belts having the geometry STD 1280 8M-15 were produced with the following construction:

TABLE-US-00001 TABLE 1 Comparative Comparative Inventive Comparative 1 2 1 3 Mixture Chloroprene EPDM EPDM EPDM 40 phr FEF 40 phr FEF 40 phr FEF 40 phr FEF carbon black carbon black carbon black carbon black ZnO Peroxide Peroxide Peroxide crosslinked crosslinked crosslinked crosslinked Reinforcement Glass cord Glass cord Glass cord Glass cord Fabric coating Chloroprene* Chloroprene* HNBR 35 phr FEF 35 phr FEF 32 phr SRF carbon black carbon black carbon black ZnO ZnO Sulfur crosslinked crosslinked crosslinked RFL coating Vinylpyridine Vinylpyridine Vinylpyridine Vinylpyridine latex basis: latex basis: latex basis: latex basis: RFL content RFL content RFL content RFL content 14% 14% 14% 14% Fabric type Polyamide Polyamide Polyamide Polyamide *Chloroprene rubber; phr = parts per 100 parts of rubber (parts per hundred rubber).

[0061] The toothed belts thus produced were subjected to customary tests. The values of properties thus determined are reported in the following table 2:

TABLE-US-00002 TABLE 2 Compar- Compar- Inventive Compar- ative 1 ative 2 1 ative 3 Belt Tests Breaking strength on 2 1.3 1.23 1.28 1.24 runs [kN/mm/2 run] Breaking elongation [%] 3.2 2.8 3.01 3.01 EA secant stiffness of 18 20.5 20.2 18.2 one run up to 1% [kN/mm/1 run] Shore hardness of belt 84 84 82 83 [shore A] Fabric separation 13.9 3.2 4.5 5.5 strength [N/mm] Connecting web 2.35 1.32 1.99 0.59 adhesion [N/mm] Tooth shear strength 111 95 100 88 [N/mm] Material tests ISO 9563 resistance 0.03 3400 1.12 402.83 [M] Skipping torque 6.3 6.8 6.80 6.86 [Nm/tooth] Tensile strand adhesion 1304 1266 1248 110 of individual cords [N] Test bench investigations 8M service life 5 STD 292 87 352 276 pulleys [h] Low-temperature + ++ ++ stability Absence of chlorine + + It is apparent from table 2 that relative to the comparative toothed belts 1 to 3 the toothed belt inventive 1 had the best durability (352 h), compared to which the toothed belts made of chloroprene rubber (comparative 1) and EPDM without an interlayer (comparative 3) show a marked decline. The toothed belt made of EPDM having a chloroprene rubber interlayer (comparative 2) shows an inadequate service life of only 87 h.

[0062] The toothed belts inventive 1 and comparative 3 contained no chlorine. The toothed belts comparative 1 and inventive 1 had a relatively low resistance, which allows electrical charges to be discharged via the belt. It is accordingly apparent that the toothed belt inventive 1 has the best profile of properties.

[0063] Compared to a toothed belt made entirely of HNBR as the elastomer material (not shown), the toothed belt inventive 1 also has a markedly improved low-temperature stability.