CA1045264A

CA1045264A - Rubber composition

Info

Publication number: CA1045264A
Application number: CA246,760A
Authority: CA
Inventors: Kunihiro Kaneda; Masashi Kida; Akihiko Nakayama; Atsushi Kanazawa; Hiroyuki Kaido; Yasuhiro Mizumoto; Tsuneo Koyama
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 1975-10-04
Filing date: 1976-02-27
Publication date: 1978-12-26
Also published as: NL7601909A; FR2326444B1; FR2326444A1; DE2608113A1; JPS5335824B2; DE2608113C2; JPS5243851A; NL181278C; NL181278B

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides a rubber composition containing more than 0.5 wt. part of a cobalt salt of an organic acid and more than 0.5 wt. part of a monohydroxybenzoic acid component per 100 wt. parts of a rubber. The composition may also contain more than 0.5 wt. part of at least one of an alkylphenol type resin and a cresol-formaldehyde type resin per 100 wt. parts of a rubber. The composition has excellent moisture resistant properties with reinforcing material particularly metallic tire cords.

Description

; ~045Z64 .,.
~ The present invention is related to a rubber composition .
which has excellent adhesive properties with a reinforcing material. The present invention also provides for the prepara-tion of a composite vulcanized product of the rubber and the :
reinforcing material.
:. -Heretofore, for adhesion between a rubber and a metallic :
material such as a steel cord or between a rubber and a fibrousmaterial such as nylon cord, the metallic material has been plated with a zinc or a copper alloy such as brass and bronze and to ~ 10 treat the fibrous material such as nylon cord with a resorcinol- ; ;~
- formaldehyde latex. Further to improve adhesive properties of the rubber, certain additives such as a cobalt salt of organic acid such as cobalt naphthenate, cobalt stearate, and cobalt octylate have been incorporated in the rubber. However, the adhesive . ,, ~
l J system has the disadvantages that the adhesive properties greatly .
decrease with excess time or temperature of heat treatment in a vulcanization and the moisture resistance of adhesion is low.
`~ To improve adhesion, it has also been proposed to add an alkyl-~, phenol resin to allow for the decrease of adhesive property caused -s 20 by the vulcanization. However in such case an improvement of ~ -~;` moisture resistance is not to be expected and the vulcanization is disadvantageously slow.
~ .
The present invention provides a rubber composition which has high adhesive properties with a reinforcing material and high moisture resistance of adhesive properties and has . .. .

sufficient vulcanization characteristics.

The object of the invention can be attained by providing .~
-~ a rubber composition which comprises more than 0.5 wt. part of ,~ a cobalt salt of organic acid, more than 0.5 wt. part of mono-~ 30 hydroxybenzoic acid component and 100 wt. parts of a ~ubber.

-~ Typical rubbers used in the composition of the present invention include natural rubber and synthetic rubbers such as ::
.. , -- 1 --, ~- ~045Z64 styrene-butadiene rubber, polybutadiene rubber, polyisoprene rubber, chloroprene rubber and nitrile rubber. Natural rubber is mainly used for the manufacture of tires. Typical cobalt salts of organic acids include cobalt salts of organic acids having carbon atoms of 6 - 30 such as cobalt naphthenate, cobalt î stearate, cobalt octylate, cobalt-octoate, cobalt-oleate, cobalt-resinate, cobalt-linoleate, and cobalt-tallate.
The monohydroxybenzoic acid component may be provided by monohydroxybenzoic acid and derivatives thereof which form monohydroxybenzoic acid or a salt thereof in the rubber composition.
Typical derivatives include alkyl monohydroxybenzoates. It is preferable to use paramonohydroxybenoic acid. However, a desirable effect cannot be obtained by using small amount of ;~ orthomonohydroxybenzoic acid. It is desirable to combine 0.5 -10 wt. parts, preferably 1 - 6 wt. parts, of a cobalt salt of ~,!, organic acid and 0.5 - 10 wt. parts, preferably 1 - 6 wt. parts ;~ of monohydroxybenzoic acid with 100 wt. parts of a rubber. When the content of the cobalt salt of organic acid and the content of the monohydroxybenzoic acid are less than the lower limit, they are not effective whereas when they are more than the upper limit the physical properties of the rubber composition are adversely affected although the increase of the content does , not effectively affect the characteristic advantages of the t invention. With the combination of the cobalt salt of the organic acid and the monohydroxybenzoic acid with the rubber, it is possi-ble to provide a rubber composition which has excellent adhesive i properties with a metallic material by a vulcanization wherein a cure rate (a vulcanization speed) of unvulcanized rubber composi-tion is not delayed and the adhesive properties are maintained even with excess vulcanization.
It is possible to improve the adhesive properties with a fibrous material and the moisture resistance of the adhesion , . . ~-. .

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before or after the vulcani~ation by further combining more than 0.5 wt. part, preferably 0.5 - 10 wt. parts based on 100 parts of the rubber of at least one of an alkylphenol type resin and cresol-formaldehyde type resin, with the above-mention-ed rubber composition (I). The resulting rubber composition will be referred as the rubber composition (II). When a content of the alkylphenol type resin or cresol-formaldehyde type resin r; is less than the lower limit, the aforesaid effect is not achieved - whereas when it is more than the upper limit, physical properties of the rubber composition (II) are adversely affected though the increase of the content does not effectively affected to the above-mentioned characteristic advantages. The alkyphenol type resins include t-butylphenol-formaldehyde resin, p-octyl-;~ phenol-formaldehyde resin, and modified phenol resins such as .
cashew oil modified phenol resin, dicyclopentadiene modifed phenol resin. The cresol-formaldehyde type resins include o-` cresol-formaldehyde resin and p-cresol-formaldehyde resin.
, The rubber c~mposition of the present invention can be ' prepared by blending said components to the rubber by the conven-s 20 tional blending method. It is usual to add a suitable vulcani-;~ zing agent, a filler, a reinforcing material or other additives together with said additives or separately before the vulcaniza-tion, as described in the prior art. The conditions of the present invention can be considered to be in accordance with ~' the prior art such as Encyclopedia of Polymer Science and Tech-nology Vol. 12 Pages 161-353 on rubbers; ibid Vol. 14 Pages 42 -64 on tires and tire cord; ibid Vol. 8 Pages 184 - 185 on tire cord dip; ibid Vol. 14 Pages 740 - 756 on Vulcanization; and Rubber Chemistry and Technology 46 (4) Pages 981 - 998 on rubber-to-textile and rubber-to-steel cord adhesion.
The present invention will be further illustrated by way of the following Examples.

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lV45Z64 Examples l - 7, Standard Example l; and Comparative Example 1:
The compositions in Table l were blended as follows.
The test results of the rubber compositions of Examples 1 - 7;
Standard Example l; and Comparative Example l are stated in : Table 2.
. .
: Preparation and Vulcanization of Rubber composition:
., ~ _ . .... _ The components of each master batch was blended by a Blambury's mixer and a vulcanizing agent was blended to the .-: master batch by a roller mill to prepare each rubber composition.
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The vulcanization of the rubber composition was ~; carried out at 145C for 45 minutes.
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; The compositions stated in Table 3 were blended as :
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The test results of the rubber compositions of Examples 8-14:
: Standard ~ Example 2 and Comparative Example 2 are stated in Table 4.
Preparation and Vulcanization of Rubber composition:
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i , . . , : ' *4: RFL treatment: resorcino-formaldehyde latex treatment *5: Kevlar(Aramid fiber) cord: a trademark of duPont Co.
*6: The test piece being similar to that of adhesion test waspreparedinunvulcanized condition by pressing in ` a mold as follows.
Rubber composition was filled in a mold of ASTM D 2229 wherein brass-plated steel cords were disposed in parallel with each gap of 12.5 cm and were embedded for 1 inch. The rubber composition was molded by a I 10 press at the room temperature.
The test piece was kept in 100% of relative humidity for 10 days and then it was vulcanized at 145C for 45 min , i The pull-out test was carried out.
*7: The rubber composition was filled in a mold of ASTM D
' 2229 wherein brass-plated steel cords were disposed ~ in parallel with each gap of 12.5 cm and were embedded ;, for 1 inch. The rubber composition was molded by a ,. ~ .
press at the room temperature. It was vulcanized at ~, 20 145C for 45 min. and then the test piece was kept `^'q in 100% of relative humidity for 10 days. The pull-, out test was carried out.
.
The tests of adhesive strength Mooneyscorch time (t5) - Rheometer vulcanization degree T95 were carried out as follows.
Adhesive strength test 1) Adhesive strength to metal material Steel cords plated with brass or zinc were arranged , 30 in parallel with each gap of 12.5 mm. ~ach rubber composition , was coated from both side of the steel cords to form each fabrica-ted product in which each cord was embedded for 1 inch and the ' :~ - 10 -1~ 5264 ~ fabricated product was vulcanized under condition of 145C - 45 mm.;
.
160C-20 min.; or 160C - 60 min..

- The pull-out test was carried out in accordance with , ASTM D 2229.

`~ 2) Adhesive strength to fibrous material .
- The adhesive strength to nylon cord or Kevlar (a trademark)(or Aramid, (atrademark) fiber) cord was measured in accordance with H test of ASTM D 2138. (under a vulcanization at ., ; 148C for 30 min.) ~ . .
Mooney scorch time: (t ) - In accordance with Japanese Industrial Standard K 6301, it was measured at 125C.
, . :
Rheometer vulcanization degree T95:
-~ In order to measure suitable vulcanizing time by a Rheometer manufactured by Monsanto Co., Ltd., the time for reaching to 95% torque of the maximum torque was shown as T95.
As will be seen from the results shown in Table 2, the rubber compositions (I) of the invention have cure rates (vulcani-. . i .
' zation speeds) faster than that of the Standard Example, superior ' 20 adhesive strength under appropriate vulcanization at 145C for :.
45 min., to those of Standard Example 1 and Comparative Example 1 and remarkably superior adhesive strength under excess vulcaniza-tion at 160C for 60 min. to those of Standard Example 1 and Comparative Example 1. The fact was clearly found from the result of rubber adhesion on the surface of steel cord pulled out (rubber coverage).
The other characteristics of the rubber compositions of the invention are superior to those of the Standard Examples and the Comparative Examples. Moreover, in processability, the rubber compositions of the invention are easily mixed without excessive stickness on the surface of a mill roll comparing with those of the Comparative Examples. From the results of Table 4, it will ~........................................................................ .

lV~5~64 be seen that the rubber compositions (II) which contain the alkylphenol type resin or the cresol-formaldehyde type resin have remarkably superior adhesive properties comparing with those of Standard Example 2 and Comparative Example 2 through the physi-cal properties of the vulcanized products are similar. Thus, the rubber compositions (II) of the present invention have excellent adhesive property to nylon cord and Kevlar (a trademark) cord which are treated with resorcinol-formaldehyde latex and steel cord plated with zinc. In particular, the rubber compositions (II) of the present invention have excellent moisture resistance in the adhesion to the brass plated steel cord even though the unvulcan-` ized or vulcanized rubber samples are exposed under high humidity comparing with those of the Standard Example and the Comparative . Example. These characteristics are very important in the case of preparation of rubber-wire composites under high humidity, and can be attained by the rubber composition of the present invention. As stated above, the rubber compositions (I) of the present invention have excellent adhesive properties to a wire material in both cases of appropriate vulcanization and excess vulcanization without delaying the vulcanization, and they can be used as an adhesive rubber composition. The rubber composi- - `
~ tions (II) of the present invention have excellent adhesive -~ properties to the nylon cord, Kevlar (a trademark) cord and the zinc plated or brass plated steel cord with high heat resistance in excess vulcanization and without a delay of vulcanization.
With regard to the adhesion to the brass plated steel ` cord, the rubber compositions (II) have excellent moisture resistance so that they can be used, for composites or rubber-fibrous material or metallic material such as in the belt and carcass of tires and in the cores of belt conveyors as adhesive rubber compositions.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A rubber composition containing more than 0.5 wt.
part of a cobalt salt of an organic acid and more than 0.5 wt.
part of a monohydroxybenzoic acid component per 100 wt. parts of a rubber.

2. A composition as claimed in claim 1 which contains more than 0.5 wt. part of a cobalt salt of an organic acid, more than 0.5 wt. part of a monohydroxybenzoic acid component and more than 0.5 wt. part of at least one of an alkylphenol type resin and a cresol-formaldehyde type resin per 100 wt. parts of a rubber.

3. The composition according to claim 1 or 2 wherein the organic acid has 6 to 30 carbon atoms.

4. A composition as claimed in claim 1 or 2 in which the organic acid is selected from naphthenic, stearic, octylic, octeric, oleic, resinic, linoleic and tallic acid.

5. The composition according to claim 1 or 2 wherein the monohydroxybenzoic acid component is monohydroxybenzoic acid, or an alkyl ester thereof.

6. The composition according to claim 1 or 2 wherein said monohydroxybenzoic acid is para-mono-hydroxybenzoic acid.

7. The composition according to claim 1 or 2 wherein said rubber is natural rubber, styrene-butadiene rubber, polybuta-diene rubber or polyisoprene rubber.

8. The rubber composition according to claim 2, wherein said alkylphenol type resins and cresol-formaldehyde type resins are o-cresol-formaldehyde resin, p-cresol-formaldehyde resins, t-butylphenol-formaldehyde resins, p-octylphenol-formaldehyde-resins and modified phenol resins.

9. A vulcanized rubber product reinforced with tire cords which comprises a rubber composition containing more than 0.5 wt. part of a cobalt salt of an organic acid, more than 0.5 wt.

part of a monohydroxybenzoic acid component per 100 wt. parts of a rubber.

10. A product according to claim 9, wherein the tire cords are steel cords.

11. A product according to claim 9, wherein the tire cords are a copper alloy coated steel tire cords.

12. A product as claimed in claim 9, 10 or 11 in which the composition contains more than 0.5 wt. part of at least one of an alkylphenol type resin and a cresol-formaldehyde type resin per 100 wt. parts of a rubber.