JP2002105789A - Rubber-reinforcing cord and fiber-reinforced rubber material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber-reinforcing cord excellent in adhesion to a rubber, and suitably used with various rubber materials such as a tire, belt, hose, etc. SOLUTION: This rubber-reinforcing cord is obtained by impregnating a carbon fiber bundle with a resin composition containing a resorcinol- formaldehyde initial condensate of novolak type and rubber latex.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber reinforcing cord and a fiber reinforced rubber material, and more particularly to a rubber reinforcing cord and a fiber reinforced rubber material which can be suitably used for industrial materials such as tires, belts, hoses and the like. It is about.

[0002]

2. Description of the Related Art Fiber-reinforced rubber materials in which rubber is reinforced by reinforcing fibers are widely used as industrial materials such as tires, belts and hoses. In general, these rubber materials are obtained by reinforcing a base material containing rubber with a cord material obtained by applying an adhesive to a surface layer portion of a twisted reinforcing fiber bundle.

The properties required of such cord materials include tensile strength, tensile elasticity, heat resistance, water resistance, and adhesion to rubber, among others. From the viewpoint of preventing the problem, the adhesion at the interface between the reinforcing cord and the base material mainly composed of rubber is important. The rubber reinforcing cord made of carbon fiber is excellent in tensile strength, tensile elastic modulus, heat resistance, and water resistance, but is inferior in adhesion to rubber, and has an interface between the rubber reinforcing cord and a base material mainly composed of rubber. Has a drawback that peeling easily occurs.

As an attempt to solve such a problem, JP-A-61-203139 discloses a method of adhering an epoxy resin to a carbon fiber bundle, and JP-A-62-141179 discloses a method of applying a urethane-modified epoxy resin. JP-A-11-158780 discloses a method for attaching a resin composition containing urea to a carbon fiber bundle.

[0005] However, even with these techniques, in various applications of fiber reinforced rubber materials, the required adhesiveness is insufficient, and rubber reinforcing cords using carbon fiber bundles include tires, belts, hoses and the like. At present, a material having sufficient adhesiveness that can be applied to industrial uses without any practical problems has not yet been obtained.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rubber reinforcing cord having excellent adhesion at an interface between a rubber reinforcing cord and a base material mainly composed of rubber, and the use of the rubber reinforcing cord. An object of the present invention is to provide a fiber-reinforced rubber material that can be suitably used for industrial materials such as tires, belts, hoses, and the like.

[0007]

In order to solve the above problems, the present invention has the following arrangement. That is, in the carbon fiber bundle,
A rubber reinforcing cord impregnated with a resin composition containing a novolak resorcinol-formaldehyde precondensate and a rubber latex.

Further, in order to solve the above problems, the present invention has the following configuration. That is, it is a fiber reinforced rubber material in which a base material containing rubber is reinforced by the rubber reinforcing cord.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have prepared a rubber reinforcing cord by impregnating a carbon fiber bundle with a resin composition containing a novolak type resorcinol-formaldehyde precondensate and a rubber latex. Surprisingly, it has been surprisingly found that the rubber reinforcing cord has extremely excellent adhesion to rubber and solves the above-mentioned problems at once.

A resorcinol-formaldehyde initial condensate (hereinafter simply referred to as an RF condensate) is a resorcinol having a methylol group obtained by condensing resorcinol and formaldehyde in a basic aqueous solution, and resorcinol-formaldehyde in an acidic aqueous solution. And a novolak type having no methylol group, which is obtained by condensation of

In the present invention, the novolak-type RF condensate has an adhesive property at an interface between a rubber reinforcing cord (hereinafter abbreviated as a cord) and a base material containing a rubber (hereinafter abbreviated as a rubber base material). It is more preferably used than a resol-type RF condensate from the viewpoint of improving adhesiveness (abbreviation) and preventing delamination.

In the present invention, the novolak type RF condensate is 5 to 20% by weight, preferably 8 to 17% by weight, more preferably 10 to 10% by weight, based on 100% by weight of the resin composition.
It is better to contain 15% by weight. If it is less than 5% by weight,
Adhesion may be insufficient, and if it exceeds 20% by weight,
In some cases, the rigidity of the rubber reinforcing cord becomes excessive, and the fatigue resistance of the obtained fiber reinforced rubber material is reduced.

Specific examples of the rubber latex used in the present invention include acrylic rubber latex, acrylonitrile-butadiene rubber latex, isoprene rubber latex, urethane rubber latex, ethylene-propylene rubber latex, chloroprene rubber latex, silicone rubber latex, and styrene rubber latex. Butadiene rubber latex, natural rubber latex, vinylpyridine-styrene-
Butadiene rubber latex, butadiene rubber latex, and the like. Among them, vinylpyridine-styrene-
Butadiene rubber latex is preferably used because it significantly improves the adhesiveness.

In the present invention, the rubber latex is used in an amount of 55 to 95% by weight, preferably 60 to 90% by weight, more preferably 65 to 85% by weight, based on 100% by weight of the resin composition. If the amount is less than 55% by weight, the adhesiveness may be insufficient. If the amount exceeds 95% by weight, the tackiness of the cord becomes excessive, and the handleability when producing a fiber reinforced rubber material may be reduced. .

The epoxy resin is classified into an aromatic epoxy resin represented by a bisphenol type epoxy resin and a phenol novolak type epoxy resin, and an aliphatic epoxy resin having no aromatic ring.
Aliphatic epoxy resins are preferably used from the viewpoint of improving adhesion and preventing peeling destruction.

Specific examples of the aliphatic epoxy resin used in the present invention include glycerol polyglycidyl ether, sorbitol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol polyglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol poly. Glycidyl ether and the like. Among them, glycerol polyglycidyl ether and sorbitol polyglycidyl ether, since they significantly improve the adhesiveness,
It is preferably used.

The resin composition used in the present invention is prepared, for example, by adding a novolak-type RF condensate obtained by a reaction in an acidic aqueous solution to a basic aqueous solution, and then adding a rubber latex and formaldehyde. can do. Here, formaldehyde is a novolak type R
It has a role of reacting with the F condensate to form three-dimensional crosslinks.

Since each component constituting the resin composition of the present invention is dissolved or dispersed in water, it is impregnated into a carbon fiber bundle, and then the moisture remaining in the cord is removed by heating and drying. Is preferred. If the removal of water is insufficient, voids are likely to be generated in the cord during molding of the fiber reinforced rubber material, which is not preferable.

In the present invention, the resin composition is impregnated with 10 to 40% by weight, preferably 15 to 35% by weight, more preferably 20 to 30% by weight, based on 100% by weight of the carbon fiber bundle. . If the amount is less than 10% by weight, the fatigue resistance of the cord may be reduced due to the rubbing of the single fibers in the fiber bundle. If the amount exceeds 40% by weight, the heat resistance and water resistance of the cord may be insufficient. There is.

The carbon fiber bundle used in the present invention has a breaking elongation of 1.7% or more, preferably 1.8% or more, and more preferably 1.9% or more. If it is less than 1.7%, the cord may break when subjected to stress deformation, and may not be practically used for applications such as tires.

In the carbon fiber bundle, it is preferable that the cross-sectional shape of the single fiber constituting the fiber bundle is substantially a perfect circle. The cross-sectional shape of the single fiber is not substantially a perfect circle, but other shapes, for example, an elliptical shape, a bean shape, a three-leaf shape,
The cord may be broken due to abrasion between the single fibers, and may not be practically used for a tire or the like.

Here, the “substantially perfect circle” means a cross section defined by a ratio (= R / r) of a radius R of a circumscribed circle and a radius r of an inscribed circle of a cross section of a single fiber by a method described later. Deformation degree is 1
1.1.

The carbon fiber bundle used in the present invention has a twist number of 20 turns / m or less, preferably 10 turns / m or less, more preferably 5 turns / m or less. If it exceeds 20 times / m, an unimpregnated portion of the resin composition is generated at the center of the cord, and the cord may be broken due to abrasion between the single fibers.

The fiber-reinforced rubber material according to the present invention is obtained by reinforcing a rubber-containing base material with the rubber reinforcing cord.

Specific examples of the rubber used in the present invention include acrylic rubber, acrylonitrile-butadiene rubber, isoprene rubber, urethane rubber, ethylene-propylene rubber, chloroprene rubber, silicone rubber, hydrogenated nitrile rubber, styrene-butadiene rubber, and polystyrene. Sulfurized rubber, natural rubber, butadiene rubber, butyl rubber, fluorine rubber, and the like are included.

In addition to the rubber which is a main component, an inorganic filler such as carbon black and silica, an organic filler such as a coumarone resin and a phenol resin, and a naphthenic oil and the like may be used as necessary. You may mix a softener.

The rubber reinforcing cord according to the present invention can be manufactured, for example, by the following method. That is, the method is such that the carbon fiber bundle is passed through a treatment liquid tank containing the resin composition, impregnated with the resin composition, and then further passed through a heating and drying oven to remove moisture contained in the cord.

The fiber reinforced rubber material according to the present invention can be produced, for example, by the following method. That is, a method in which a rubber reinforcing cord aligned in the same direction is sandwiched between base materials containing rubber from both sides, and the obtained cord / rubber composite is heated and pressed in a press machine to form it.

In the present invention, various physical properties of the carbon fiber bundle and the rubber reinforcing cord were evaluated by the following methods. <Elongation at break and tensile strength of carbon fiber bundle> JIS R760
1 Determined according to “Resin-impregnated strand test method”. Here, the resin impregnated strand of the carbon fiber to be measured is 3, 4
-Ethoxycyclohexylmethyl-3,4-ethoxy-cyclohexane-carboxylate (100 parts by weight) / boron trifluoride monoethylamine
A carbon fiber was impregnated with (BF3.MEA) (3 parts by weight) / acetone (4 parts by weight) and cured at 130 ° C. for 35 minutes. In addition, the number of measurement was set to 6, and the average value of each measurement result was defined as the elongation at break and tensile strength of the carbon fiber. <Cross Section Shape of Single Fiber of Carbon Fiber Bundle> The carbon fiber was cut by a razor perpendicular to the fiber direction, and the cross section was photographed with a scanning electron microscope at a magnification of 10,000 times and an acceleration voltage of 15 kV. Draw a circle circumscribed and a circle inscribed in the photograph of the cross-section, measure the radius R of the circumscribed circle and the length of the inscribed circle, determine the ratio (= R / r), and use it as the degree of cross-sectional deformation of the single fiber . In addition, the number of measurement was five, and the average value of each measurement result was defined as the degree of cross-sectional deformation of the single fiber of the carbon fiber bundle. <Evaluation of adhesion of rubber reinforcing cord> ASTM D213
8 Measured in accordance with “Characteristics of rubber: Adhesion to cord (H test)”. Here, the pull-out test piece to be measured is a natural rubber (100 parts by weight) / sulfur (2 parts by weight) / zinc oxide (5 parts by weight) / stearic acid (2 parts by weight) / silver thiocyanyl sulfite (1 part by weight). / Carbon black (50 parts by weight) with a cord interposed therebetween. In addition, the number of measurement was set to 10, and the average value of each measurement result was defined as the pull-out strength.

[0030]

The present invention will be described more specifically below. In the present Example and Comparative Example, the following raw materials were used for producing a rubber reinforcing cord and a fiber reinforced rubber material. still,
Tables 1 to 4 collectively show the resin composition impregnated in the carbon fiber bundle and the adhesiveness evaluation results of the rubber reinforcing cord. <Carbon fiber bundle>"T700S-12K-50C" (model number, manufactured by Toray Industries, Inc.): elongation at break 2.1%, tensile strength 4900 MPa, cross-sectional deformation of single fiber 1.05 ・ "T800H-12K-" 40B "(model number, manufactured by Toray Industries, Inc.): elongation at break 1.9%, tensile strength 5500 MPa, cross-sectional deformation degree of single fiber 1.37 <Rubber latex>-vinylpyridine-styrene-butadiene copolymer: J
SR0652 (manufactured by JSR Corporation), solid content concentration 40%-Styrene-butadiene copolymer: JSR2108 (J
SR Inc.), solid content concentration 40% <aliphatic epoxy resin>-Glycerol polyglycidyl ether: "Denacol" EX-313 (registered trademark, manufactured by Nagase Kasei Kogyo Co., Ltd.)-Sorbitol polyglycidyl ether: "Denacol "EX-614 (registered trademark, manufactured by Nagase Kasei Kogyo Co., Ltd.) (Examples and Comparative Examples) A carbon fiber bundle is conveyed at a speed of 10 m / min, and a treatment liquid tank containing an epoxy resin and a rubber latex, RF condensation After passing continuously through the treatment liquid tank containing the product and the rubber latex, the mixture was passed through a heating and drying furnace at 150 ° C. to remove the moisture contained in the treatment liquid and dried to obtain a rubber reinforcing cord. Here, the composition of the resin composition of the cord after drying was as shown in Tables 1 and 2, and the adhesion amount was 25% by weight with respect to 100% by weight of the carbon fiber bundle.

Next, after embedding this rubber reinforcing cord in an unvulcanized rubber composition so that one end thereof has a length of 8 mm, the temperature is set to 150 ° C. and the pressure is set to 9.8 MPa in a press machine.
Under the conditions of 30 minutes, the rubber was vulcanized to obtain a test piece.

Next, the rubber base portion of the test piece was firmly fixed by sandwiching it with a jig, and the cord portion was pulled out in the axial direction at a speed of 5 mm / s by a pull-out tester at 25 ° C. . At this time, the external force (N / code) required for drawing was used as an index of the adhesiveness at the cord / rubber interface.

Here, Instron 4208 (manufactured by Instron Japan) was used as a pull-out tester.

As shown in Tables 3 and 4, the rubber reinforcing cord of the present invention has very excellent adhesion to rubber.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

The rubber reinforcing cord according to the present invention is obtained by impregnating a carbon fiber bundle with a resin composition containing a novolak-type resorcinol-formaldehyde precondensate and a rubber latex, so that it is bonded to rubber. It has excellent properties and exhibits characteristics that are practically acceptable as industrial materials such as tires, belts and hoses.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D06M 15/55 D06M 15/55 15/693 15/693 // B60C 9/00 B60C 9/00 H C08L 9 : 08 C08L 9:08 D06M 101: 40 D06M 101: 40 F term (reference) 4F072 AA01 AA07 AA08 AB10 AB22 AD02 AK03 AK20 AL18 AL19 4J002 AC082 CC041 CD013 GM01 GN01 4L033 AA09 AC11 CA34 CA04 MA24 PA24

Claims (8)

[Claims] 1. A rubber reinforcing cord obtained by impregnating a carbon fiber bundle with a resin composition containing a novolak-type resorcinol-formaldehyde precondensate and a rubber latex. 2. The resin composition according to claim 1, wherein the resorcinol-formaldehyde precondensate is 5% by weight based on 100% by weight of the resin composition.
2. The rubber reinforcing cord according to claim 1, wherein the amount is from 20 to 20% by weight. 3. The rubber latex according to claim 2, wherein the vinyl latex is
The rubber reinforcing cord according to claim 1 or 2, comprising a styrene-butadiene rubber latex. 4. The rubber reinforcing cord according to claim 1, wherein the resin composition contains an aliphatic epoxy resin. 5. The method according to claim 1, wherein the resin composition comprises the carbon fiber bundle 100.
The amount is 10 to 40% by weight based on the weight%.
The rubber reinforcing cord according to any one of the above. 6. The rubber reinforcing cord according to claim 1, wherein the carbon fiber bundle has a breaking elongation of 1.7% or more. 7. The rubber reinforcing cord according to claim 1, wherein the cross-sectional shape of the single fiber constituting the carbon fiber bundle is substantially a perfect circle. 8. A fiber-reinforced rubber material in which a rubber-containing base material is reinforced by the rubber reinforcing cord according to claim 1.