CA1238441A - Belt comprising rubber and fibers - Google Patents

Abstract

Abstract of the Disclosure A belt comprising a copolymer rubber and fibers and having strong adhesion strength even after heat-aging in air or oil and repeated deformation. The copolymer rubber has in its polymer chain (1) 10 to 60 % by weight of units derived from all unsaturated nitrile, (2) 0 to 30 % by weight of units derived from a conjugated diene and (3) 10 to 90 % by weight of units derived from an ethylenically unsaturated monomer other than unsaturated nitriles and/or units formed by hydrogenating units derived from a conjugated diene.

Description

This invention relates to a belt composed ox a rubber and gibers which retain strong adhesion between the components even after it has been heat aged in air or oil or repeatedly deformed.
Because of its superior oil resistance, an acrylonitrile/butadiene copolymer rubber It be sometimes referred to as NOR hereinafter) has been exten~iYely used as automotive rubber materials such as belts Rubber products such as a belt composed ox NOR and gibers, however, tend to undergo separation at the adhering surface between NOR and gibers when sub~ecked to repeated stretching and contraction or to the ejects of heat and oils during use Ply separation shortens the service life ox such rubber products.
various proposals have been made for improving the adhesion ~krength ox a composite of a rubber and fibers aster deterioration. Most of them, however ? retake to a method or treating the gibers. Such a method certainly improves the initial adhesion strength between the rubber and gibers, but no satisfactory improvement in adhesion strength aster repeated deformation and heat aging in a r or oil can be achieved. It has been desired wherefore Jo develop a novel composite having improved adhesion strength after deterioration.
It is an object of this invention to provide a belt comprising a rubber and fiber which can meet such a desire.
According to this invention, the above object is achieved by a belt comprising a eopolymer rubber an fibers, said copolymer rubber having if its polymer chain I units derived from an unsaturated nitrite,

(2) units derived from a conjugated dine and (3) units derived from an ethylenically unsaturated monomer other than unsaturated nitrites and/or units formed by hydrogenating units derived prom conjugated dine.
The copolymer rubber should contain 10 to 60 %
by weight of units derived from an unsaturated nitrite in its polymer chain. It the amount of these units is less than 10 % by wow, the copolymer rubber has interior oil resistance, and it it exceeds 60 % by weight, the copolymer rubber has reduced cold resistance. The pro-furred amount of these units is 20 to 50 % by weight.
The copolymer rubber contains 0 to 30 % by weight of units derived from a conjugated dine in its polymer chain. If the amount or these units exceeds 30 %
by weight, the adhesion durability of the copolymer rubber becomes inferior. The preferred amount of these units is 0 to 20 % by weight particularly 0 to 10 % by weight The copolymer rubber should further contain in its polymer chain units derived from an ethylenically unsaturated monomer other than unsaturated nitrites and/or units formed by hydrogenating units derived from a conjugated dine. If the amount of these units is less than 10 % by weight, the adhesion durability of the copolymer rubber becomes inferior. The preferred .

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amount of these units is 35 to 90 % by weight, portico laxly 40 to 90 by weight.
The copolymer rubber used in this invention thus includes a copolymer rubber obtained by partially or completely hydrogenating the conjugated dine units of an unsaturated nitrlle/conjugated dine copolymer rubber;
a copolymer rubber obtained by partially or completely hydrogenating the conjugated dine units of an unsaturated nitrile/conjugated diene/ethylenically unsaturated monomer copolymer rubber; an unsaturated nitrile/conjugated diene/ethylenically unsaturated monomer copolymen rubber;
and an unsaturated nitrile/ethylenically unsaturated monomer copolymer rubber.
Monomers used or the production of the co-polymer rubbers used in this invention include, for example, unsaturated nitrites such as acrylonitrile and methacrylonitrile; conjugated dines such as butadiene, isoprene and 1,3-pentadiene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid and malefic acid; alkyd esters ox unsaturated carboxylic acids such as methyl acrylate, 2-ethylhexyl acrylate and octal acrylate; alkoxyalkyl acrylates such as methoxyethyl acrylate, ethoxyethyl acrylate and methoxyethoxyethyl acrylate; and other ethylenically unsaturated monomers such a ally glycidyl ether, vinyl chloroacetate, ethylene, buttonhole and isobutylene. In the production of an unsaturated nitrile/ethylenically unsaturated monomer copolymer rubber, a part of the unsaturated monomer may be replaced by a non-conjugated dine such as vinyl norbornene, dicyclopentadiene and 1,4-hexadiene.
Specific examples of the copolymer rubbers in the present invention are copolymer rubbers obtained by partially or completely hydrogenating a butadiene/
acrylonitrlle copolymer rubber, an isoprene/acrylonitrile copolymer rubber or a butadiene/isoprene/acrylonitrile copolymer rubber; a butadiene/methyl acrylate/acrylo-nitrite copolymer rubber; a butadiene/acrylic acid/
acrylonitrile coupler rubber, a copolymer rubber obtained by partially or completely hydrogenating a butadiene/acrylic acid/acrylonitrile copolymer rubber;
a bottle acrylate/ethoxyethyl acrylate/vinyl chloroacetate/
acrylonitrile copolymer rubber, and a bottle acrylateJ
ethoxyethyl acrylate~vinyl norbornene~acrylonitrile copolymer rubber.
The fibers used in this invention include natural fibers such as cotton, regenerated fibers such as rayon, synthetic fibers such as nylon, polyester, polyp vinyl alcohol and aromatic polyamide fibers, steel fiberglass fibers, and carbon fibers. These fibers may be used singly or in combination with each other. The fibers are embedded in the copolymer rubber as a tensile member in the form of, for example, a staple, filament, cord rope, non-woven ~abrlc or woven fabric. The type and form of the fibers can be properly chosen depending upon the type and end use of the belt.
Desirably, the fibers are subjected to a bonding treatment by usual methods prior to their comb-nation with the rubber.
For example, cotton, rayon or nylon fibers are usually subjected to dip in a mixture (Jo be referred to as RFL) of an aqueous solution of an initial condensate of resorcinol and formaldehyde (to be referred to as RF) and a rubber latex. The rubber latex is not particularly limited, but is preferably an acrylonitrile/butadiene copolymer latex an acrylonitrile~butadiene/methacrylic acid copolymer latex, an acrylonitrile/butadiene~acrylic acid copolymer latex, or an acnylonitrile~butadiene~
v~nylpyridine copolymer latex.
Polyester or aromatic polyamide fibers have interior adhesion to rubbers because Or their molecular structures, and cannot attain sufficient adhesion strength by the above pretreatment with RFL. Hence, these fibers are first treated with a dip containing at least one of isocyanates, ethylenethioureas an epoxies and heat-treated, and then subjected to the aforesaid RFL
treatment.
Generally 9 it is effective to treat glass fibers with a Solon compound such as epoxysilane and aminosillane before they are subjected Jo the RFL treat-mint. A Sloane coupling agent such as aminopropyltri-ethoxysilane is an especially preferred pretreating agent The belt of this invention is produced mixing the copolymer rubber (which may further contain another ~23~

rubber in amounts which do not adversely affect the scope of this invention) with ordinary rubber compounding agents such as fillers, reinforcing agents, vulcanizing agents, plasticizers and antioxidant by ordinary mixers, combing in the resulting rubber composition with the pretreated fibers in accordance with a usual method of belt product lion, molding the composite into a shape conforming to the purpose for which the final belt product is to be used, and thereafter vulcanizing the molded product.
Thor is no particular restriction on the structure and type (use) ox the belt of this invention but it is particularly suitable or applications which require oil resistance, heat resistance and ozone no-distance as well as durability. Examples of such a belt are power transmission belts such as timing belts used in internal combustion engines or machine tools, conveyor belts for transporting oil shale or oil sand, and other belts which are used in an atmosphere in which they undergo repeated bending and deformation in air or oil at high temperatures.
The following examples specifically illustrate the present invention. All part in these examples are by weight.
ration Example 1 __ _ one hundred parts of each of the rubbers India acted in Table 1 was mixed with 5 parts of zinc oxide, 1 part of starlike acid, 40 parts of FEZ carbon black, 0.5 part of sulfur, 2 parts of tetramethyl~hiuram disulfide, 0.5 part of mercaptobenzothiazole, 1 part of octylated diphenylamine, and 1 part of N-phenyl_N'_ isopropyl p-phenylenediamine to obtain a rubber compost-lion. The composition was molded into a sheet having a thickness Or about 3 mm by means of a 6-inch roll.
Rectangular test samples, 155 mm long and 25 mm wide, were punched out Prom the sheet.
Table 1 summarizes the copolymer rubbers used.

Table 1 _ _ _ _ _ . . .
\ Copolymer rubber Acryloni~ril~/butadien~/ ~cryloni~ile/
\ hydrogenated Bedouin b~adiene/butyl \ copolymer rubber a slate copolymer Composition A E C D E (~) F G
_ _. __ _ I_ Ac~ylonitrile units 37 37 45 37 33 35 35 wow Butadiene us en 18.9 6.3 5.5 34.6 67 5 30 hydrogenated butadiene 44.1 56.749.5 28.4 = _ _ units (wits) Bottle acrylate units _ _ _ _ _ 60 35 (we .%) Jo _ Jo _ __ _ (*) Nope 1042; a paddock of Nippon Zion Co., lid.) Sample Preparation Example 2 Nylon cord (6-nylon; structure 1260D/2), rayon cord (3-Super; structure 1650D/2) and polyester cord (polyethylene terephthalate; structure 1500D/3) were each dipped in an RF/RFL mixture, and heat treated at 200 C
for 1 minute to prepare cords for tensile members).

Cut D I my I

Sample Preparation Example _ I Armed fibers (I or, a trade name of E. I. duo Pont de Numerous & Co.; structure 1500D/2, 127T/m) were immersed in a dip having the composition shown in Table 2, then immersed in RFL, and heat-treated at 230 C for 1 minute to form a cord for a tensile member.
Glass fiber cord (structure HOG 150 3/10 20S) was immersed in a 5 % aqueous dispersion of ~-aminopropyl_ triethoxysilane, heat treated at 150 C for 3 minutes, and further heat-treated at 200 C for 1 minute to obtain a cord for a tensile member.

Table 2 _ Diglycidyl ether of glycerol 2.22 parts 10% Aqueous solution of Noah 0.28 5% "AEROSOL" OX (75% solids) (~) 0.56 "

Water 96.94 Total lQO.OO
__ (#* ): A product of Nippon Aerosol Co., Ltd.

Each of the cords prepared in Sample Preparation Examples 2 and 3 was interposed between two test samples prepared in Sample Preparation Example 1 in such a manner that the lengthwise direction of the cord agreed with the lengthwise direction of the samples) to form a three-layer assembly. The assembly was press-cured at 160 C
for 20 minutes to prepare a belt sample having a width of 25.0 mm, a length of 155 mm and a thickness of 6.35 mm.

my - g To examine the adhesion of the cords to the rubber of each heft sample after heat-aging, it was subjected to an aging test in heated air at 125 C for 14 days, and then its adhesion strength was measured in accordance with JIG K-6301. The results are shown in Table 3.

Table 3: Adhesion strength (Kgf) t Adhesion strength before eat-aglng Run No. Invention Comparison . _ , F biers 1 2 3 4 5 6 7 twill byway, _ _ .
member \ A F B C E D G
_._ _ . ___ _ 16.5 18.5 17.0 18.0 8.0 5-5 9-0 Rayon 20.5 19.5 19.0 19.0 by . .__ . _.
18.0 16.518~5 18.0 I 5.0 6.0 Nylon 19.5 20. big . 5 18.5 __ ___ __ . Jo . . __ Polyester 16 5 16 0 17 5 17.5 405 2 0 3 0 __~ __ 5_ _ __ _ _ __ . . 20 20 23 21.5 8.5 8.0 5~0 Armload fibers ~0~.5 20.0 2-3.0 _ . _ lass fibers 16 5 17 5 18.015.0 6.5 5 5 It I

_ 10 --Example ?
Belt test samples prepared in the same way as in Example 1 were subjected to repeated flexing by De Mattia Flexing Machine at room temperature through 10,000 cycles in accordance with JIG K-6301, and then the adhesion strengths of the samples were measured.
The results are shown in Table 4.

Table 4: Adhesion strength (Kgf) Adhesion strength after the_bendin~_test adhesion strung before the bending test]
I
Run No. Invention Comparison __ _ __ , Fibers \ 1 2 3 4 5 6 7 f or \~'4bf~ _ _ tensile eye member \ A F B C E D G
_ _ I, _ _ ___ _ _ __ 19.5 18.019.0 18.5 9-5 13.5 11.0 Rayon 20.5 19.519.0 19.0 ~2.5 . . _ __ __ __ Nylon 19.5 17.019.0 OWE 10 5 13 0 9 5 _ _ _........... __ _ Polyester 16.515 0 13 5 14.5 19.5 19.0 _ _ ,_ _ _ __ __ _ Armed fibers 17 5 19 0 20 0 21 0 10 0 8 0 _ Glass fibers 17.5 19.0 17.5 16 0 12.5 6 0 15.5 Jo , . .

I

Example 3 Belt test samples prepared in the same way as in Example 1 were subjected to an immersion text in accordance with JIG K-6301. Specifically, they were each immersed in JIG No. 3 oil at 130 C for 14 days, and when their adhesion strengths were measured. The results are shown in Table 5.

Table 5: Adhesion strength (Kgf) Adhesion strength after immersion in JIG No. 3 oil _ Adhesion strength before immersion n JIG No. 3 oil _ - - , Run No. Invention Comparison Fiber = 2 3 4 5 6 7 member A F B C E D G
. . _ _ __ _ _ Rayon 13 5 14 0 15 5 19~0 6 53 5 21.5 _ __ .___ . __ __ Nylon 13 5 14 0 15 5 17.0 6 5 6 0 _ _ _ _ _ _ _ __ Polyester 11 5 It 5 16 5 17 0 19.5 lB.5 19.0 Jo __ .___ , _ I _ Armed fibers 11 5 I- JO 16 5 17 5 4 5 6 5 __ __ _ _ Glass fibers 19.5 16 0 It 5 17.0~7~ 6 0 15.5 - 12 _ The results obtained in the above Examples demonstrate that the belts ox this invention have much higher adhesion strength between the rubbers and the fibers after mechanical fatigue, heat deterioration and immersion in oil than conventional belts based on NOR.

Claims (4)

What is claimed is:

1. A belt comprising a copolymer rubber and fibers, said copolymer rubber having in its polymer chain (1) 10 to 60 % by weight of units derived from an unsatu-rated nitrile, (2) 0 to 30 % by weight of units derived from a conjugated diene, and (3) 10 to 90 % by weight of units derived from an ethylenically unsaturated monomer other than unsaturated nitriles and/or units formed by hydrogenating units derived from a conjugated diene.

2. The belt of claim 1 wherein the copolymer rubber has 20 to 50 % by weight of the units (1), 0 to 20 % by weight of the units (2) and 35 to 90 % by weight of the units (3) in its polymer chain.

3. The belt of claim 1 wherein the fibers are natural fibers, regenerated fibers, synthetic fibers, steel fibers, glass fibers or carbon fibers.

4. The belt of claim 1 wherein the fibers are in the form of a staple, filament, cord, rope, nonwoven fabric or woven fabric composed of natural fibers, regenerated fibers, synthetic fibers, steel fibers, glass fibers or carbon fibers.