JPH06299004A - Reticulated-fiber-reinforced rubber composition and production thereof - Google Patents

Abstract

PURPOSE:To provide a rubber composition which can be used suitably for rubber products that demand high mechanical properties such as high elastic modulus, high breaking strength and fatigue resistance, and a process for producing the same. CONSTITUTION:100 pts.wt. cross-linkable rubber and 0.5-130 pts.wt. liquid crystalline polymer are kneaded at a temperature above the heat deformation temperature of the polymer to obtain a high-temperature kneaded product, which is then kneaded at a temperature below the heat distortion temperature of the polymer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a reticulated fiber reinforced rubber composition and a method for producing the same. More specifically, rubber products such as power transmission belts, conveyor belts, anti-vibration rubber, damping materials, tires, lining materials, and flooring materials that require high mechanical properties such as high elastic modulus, high breaking strength, and fatigue resistance. The present invention relates to a reticulated fiber reinforced rubber composition that can be preferably used in the above and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, fiber reinforced rubber compositions have been used for rubber products such as transmission belts and conveyor belts which are required to have high mechanical properties.

As the fiber reinforced rubber composition, a short fiber reinforced rubber composition in which short fibers such as nylon, polyester and cotton are mixed in a crosslinkable rubber, vulcanizable rubber and fine nylon short fibers are grafted. Known reinforced rubber compositions (Japanese Patent Publication No. 17494/1989), aramid fiber reinforced rubber compositions in which aramid is fibrillated and grafted by mixing rubber and short aramid fibers with high shear energy are known. There is.

However, all of the above-mentioned fiber-reinforced rubber compositions certainly impart some mechanical properties to rubber products, but the fibers are present as a dispersed phase in the rubber which is a continuous phase, When such a rubber composition is strained, the rubber undergoes a strain amplification effect,
There is a drawback that there is a limit to the improvement of mechanical properties of a rubber product made of the rubber composition.

Therefore, in recent years, a rubber composition which is required to have higher mechanical properties and which can be suitably used for rubber products such as power transmission belts, vibration damping materials, tires and floor materials, which are particularly subjected to dynamic stimulation, has been obtained. Development is awaited.

[0006]

The inventors of the present invention have conducted extensive studies in view of the above-mentioned prior art, and as a result, kneaded the crosslinkable rubber and the liquid crystalline polymer at a specific blending ratio at a specific high temperature. After that, it was finally found that a rubber product comprising a rubber composition obtained by kneading at a specific low temperature has excellent mechanical properties such as high elastic modulus and high breaking strength, and to complete the present invention. Only

[0007]

That is, according to the present invention, 100 parts by weight of a crosslinkable rubber is used to add 0.5 to 0.5 parts of a liquid crystalline polymer.
130 parts by weight are kneaded at a temperature not lower than the heat distortion temperature of the liquid crystalline polymer to obtain a high temperature kneaded material, and then the high temperature kneaded material is kneaded at a temperature lower than the heat distortion temperature of the liquid crystalline polymer. To a reticulated fiber reinforced rubber composition, and a reticulated fiber reinforced rubber composition obtained by the method.

[0008]

FUNCTION AND EXAMPLES As described above, the reticulated fiber reinforced rubber composition of the present invention contains 0.5 to 130 parts of the liquid crystalline polymer per 100 parts of the crosslinkable rubber (parts by weight, the same hereinafter). This is obtained by kneading at a temperature not lower than the heat distortion temperature of the polymer to obtain a high temperature kneaded material, and then kneading the high temperature kneaded material at a temperature lower than the heat distortion temperature of the liquid crystalline polymer.

The reason why the rubber composition obtained by the production method of the present invention exhibits an excellent reinforcing effect is considered as follows.

First, when the crosslinkable rubber and the liquid crystalline polymer are kneaded at a temperature not lower than the heat deformation temperature of the liquid crystalline polymer, the viscosity of the liquid crystalline polymer becomes smaller than the viscosity of the rubber, so that the shearing force causes the liquid crystalline property. When the polymer is in the orientation-extended state and the kneading amount of the liquid crystalline polymer is increased, the liquid crystalline polymer forms a complete liquid crystal continuous phase, and the rubber forms a dispersed phase.

Next, when this is kneaded at a temperature lower than the heat distortion temperature of the liquid crystalline polymer, the rubber flows to form a rubber continuous phase, but the liquid crystal continuous phase is difficult to deform, so that fibrils are formed. It will be destroyed in a shape, the reversal of the phase will occur,
The rubber composition has a structure in which the fibrillated liquid crystalline polymer is present in the continuous rubber phase in a network form. Since this reticulated liquid crystalline polymer can be deformed to follow the deformation of rubber, the obtained rubber composition exhibits an excellent reinforcing effect.

In the method for producing the reticulated fiber reinforced rubber composition of the present invention, as described above, first, the crosslinkable rubber and the liquid crystalline polymer are kneaded at a temperature not lower than the heat distortion temperature of the liquid crystalline polymer to obtain a high temperature. This is a kneaded product (hereinafter referred to as the first-stage kneading).

In the present invention, the first-stage kneading is carried out in order to uniformly knead both the crosslinkable rubber and the liquid crystalline polymer. Therefore, the kneading temperature at this time is the heat distortion temperature of the liquid crystalline polymer. The above temperature is adopted.

Examples of the crosslinkable rubber include natural rubber; diene rubbers such as butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber and chloroprene rubber, and hydrogenated products thereof, ethylene-
Propylene rubber, ethylene-propylene rubber such as ethylene-propylene-diene rubber, ethylene rubber such as chlorosulfonated polyethylene rubber, chlorinated polyethylene rubber, acrylic rubber, fluorine compound rubber, synthetic rubber such as silicone rubber. , And these can be used alone or in combination of two or more. Among them, the double bond in the main chain is preferable from the viewpoint of being less likely to deteriorate at a temperature higher than the heat distortion temperature of the liquid crystalline polymer. Hydrogenated products of acrylonitrile-butadiene rubber having a small number, chlorosulfonated polyethylene rubber, ethylene-propylene rubber, and the like are preferable.

Examples of the liquid crystal polymer include p
-Hydroxybenzoic acid (hereinafter referred to as PHB) -biphenol-terephthalic acid-based polymer (type I), PHB-6-hydroxy-2-naphthalenecarboxylic acid-terephthalic acid-based polymer (type) II), PHB-polyethylene terephthalate, a polymer composed of PHB such as a polymer (type III) having a basic backbone, and the like. In the present invention,
From the point that the first-stage kneading is easy and that the crosslinkable rubber is easily dispersed in the process, the heat distortion temperature is about 60 to 300 ° C, especially 60 to 25 ° C.
Those having a temperature of about 0 ° C. are preferably used.

The mixing ratio of the crosslinkable rubber and the liquid crystalline polymer is 0.5 to 130 parts, preferably 1 to 120 parts, more preferably 5 to 50 parts of the liquid crystalline polymer to 100 parts of the crosslinkable rubber. is there. When the compounding ratio is less than the above range, the reinforcing effect of the obtained rubber composition will not be sufficiently exhibited, and when it exceeds the above range, the elasticity of the rubber composition is lost. Like

If the kneading temperature in the first step of kneading is too high, the crosslinkable rubber may be deteriorated and the physical properties of the obtained rubber composition may be deteriorated. Cannot be unconditionally determined because it depends on the type of crosslinkable rubber used, but it is preferably about 300 ° C. or less, especially about 250 ° C. or less for ordinary crosslinkable rubber.

The kneading time of the first stage is not particularly limited, and when an internal mixer is used, for example, a kneading time of about 2 to 20 minutes is sufficient.

Next, the obtained high temperature kneaded product is kneaded at a temperature lower than the heat distortion temperature of the liquid crystalline polymer (hereinafter referred to as the second stage kneading) to form a fibrillated reticulated liquid crystalline polymer. A reticulated fiber reinforced rubber composition having a structure reinforced with the fibrillated reticulated liquid crystalline polymer is obtained.

In the present invention, the second-stage kneading is carried out in order to allow only the crosslinkable rubber to flow without thermally deforming the liquid crystalline polymer in the high-temperature kneaded product. As the temperature, a temperature lower than the heat distortion temperature of the liquid crystalline polymer is adopted.

The kneading time in the second stage is not particularly limited and may be any time as long as the liquid crystalline polymer is sufficiently dispersed in the rubber continuous phase. For example, when using an internal mixer or the like. It is preferably about 5 to 20 minutes.

In the present invention, the kneaded product obtained by the second kneading may be further kneaded uniformly by using, for example, a roll.

The reticulated fiber reinforced rubber composition of the present invention can be obtained by kneading a crosslinkable rubber and a liquid crystalline polymer as described above, but it further improves the reinforcing effect in the rubber composition, and particularly the breaking strength. In order to obtain an excellent rubber product, the rubber composition is blended with, for example, resorcin-formalin initial condensate or resorcin-alkylphenol-formalin co-initial condensate and methylolated melamine. can do.

A cured product of the resorcin-formalin precondensate or the resorcinol-alkylphenol-formalin co-precondensate with a methylolated melamine brings about a bond at the interface between the crosslinkable rubber and the liquid crystalline polymer to further enhance the reinforcing effect. To improve.

The resorcin-formalin precondensate or resorcin-alkylphenol-formalin co-condensate uses a methylene acceptor component of a so-called HRH direct adhesion system, requires a relatively high temperature for softening and dispersing, and has a crosslinking property. From the point that it must exist near the interface between rubber and liquid crystalline polymer,
It is preferable to add it at the time of kneading at the first stage. Further, if the blending amount is too small, the adhesive effect tends to be insufficient, and if it is too large, the heat aging resistance of the obtained rubber composition is lowered and it will be described later. Since the crosslinking efficiency due to peroxide tends to decrease, it is usually 1 to 10 parts, preferably 2 to 8 parts per 100 parts of the crosslinkable rubber.

Examples of the methylolated melamine include hexamethoxymethylol melamine and the like, and these use the methylene donor component of the HRH direct adhesion system. In addition, in the present invention, in addition to the methylolated melamine, hexamethylenetetramine and the like can be similarly used.

The above-mentioned methylolated melamine is preferably blended at the time of the second and subsequent kneadings from the viewpoint of easy thermal decomposition or volatilization. Moreover, the compounding amount is usually
It is preferable to appropriately adjust the amount by the combination with the methylene acceptor component so that the amount is suitable for adhesion.

In order to exert an excellent reinforcing effect, the rubber composition of the present invention contains the above-mentioned resorcin-formalin precondensate or resorcin-alkylphenol-formalin co-precondensate and methylolated melamine in addition to carvone. Acid metal salt vinyl monomers can be included.

The carboxylic acid metal salt vinyl monomer is
By radical reaction, it is graft-bonded to the crosslinkable rubber and the liquid crystalline polymer and polymerized, and as a result, a bond is brought to the interface between the crosslinkable rubber and the liquid crystalline polymer, and the reinforcing effect is improved.

Examples of the carboxylic acid metal salt vinyl monomer include metal salts of vinyl monomers having a carboxyl group such as (meth) acrylic acid such as magnesium, zinc, aluminum and lead, and these may be used alone or in combination of two kinds. The above can be mixed and used.

The carboxylic acid metal salt vinyl monomer may be blended either during the first stage kneading or during the second stage kneading, and is not particularly limited. Further, if the compounding amount is too small, the bonding effect at the interface tends not to be sufficiently exhibited, and if it is too large, the elastic modulus of the obtained rubber composition becomes too high. Since there is a tendency, it is usually 2 to 50 parts, preferably 5 to 20 parts per 100 parts of the crosslinkable rubber.

When the vinyl carboxylate metal salt monomer is compounded in the rubber composition, a peroxide is used as an initiator of the radical reaction of the vinyl carboxylate metal salt monomer with the crosslinkable rubber and the liquid crystalline polymer. What is necessary is just to mix them.

As the above-mentioned peroxide, those generally used as a crosslinking agent for rubber are used, for example, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane. , 1,3-bis (t
Examples thereof include organic peroxides such as -butylperoxy-i-propyl) benzene.

The above-mentioned peroxide is preferably blended during the second and subsequent kneadings in order to sufficiently suppress the decomposition during mixing. Further, since such a peroxide acts not only as an initiator of a radical reaction but also as a cross-linking agent, the content thereof should be appropriately adjusted depending on the cross-linking efficiency of the cross-linkable rubber and the amount of active oxygen of the peroxide. Is preferred.

In the rubber composition of the present invention, in addition to the above components, for example, an antioxidant (deterioration) inhibitor, a vulcanization aid,
Processing aids, vulcanization accelerators, crosslinking agents, co-crosslinking agents, rubber adhesives, reinforcing agents, fillers, softening agents, plasticizers, tackifiers, activators, etc. It can be blended by appropriately selecting it according to its use and adjusting the blending amount.

Among the components usually used in the rubber composition, the antioxidant can be blended in the kneading of the first stage, and the other components can be blended in the kneading of the second and subsequent stages. Can be blended with.

Since the reticulated fiber reinforced rubber composition of the present invention thus obtained exhibits an excellent reinforcing effect, the rubber product obtained from such a rubber composition has mechanical properties such as elastic modulus, breaking strength and fatigue resistance. It has excellent physical properties.

Next, the reticulated fiber reinforced rubber composition of the present invention and the method for producing the same will be described in more detail based on the following examples, but the present invention is not limited to these examples.

Examples 1 to 9 and Comparative Examples 1 to 3 Of the compounding components shown in Table 1, components other than peroxide were kneaded in the first stage at a temperature shown in Table 1 using a Labo Plastomill. After 10 minutes, a high temperature kneaded product was obtained. For this high-temperature kneaded product, 1st kneading at the temperature shown in Table 1
The mixture was run for 0 minutes to obtain a kneaded product. A peroxide was added to the obtained kneaded product and the mixture was kneaded using a roll at about 60 ° C. to obtain a rubber composition.

The kneaded product obtained by the second-stage kneading is softer than the high-temperature kneaded product obtained by the first-stage kneading because the liquid crystalline polymer phase is loosened in a fibril shape. there were.

The obtained rubber composition was extruded with a roll,
A sheet having a thickness of 1 mm was prepared. This sheet was subjected to pressure crosslinking for 30 minutes using a press at 160 ° C. to obtain a crosslinked sheet.

As the physical properties of the obtained crosslinked sheet, the mechanical properties in the grain direction (direction parallel to the sheet feeding direction) and the opposite grain direction (direction perpendicular to the sheet feeding direction) were examined according to the following methods. . The results are shown in Table 1.

(Mechanical properties) Elastic modulus (hereinafter referred to as E ') (MPa), 50% in accordance with JIS K-6301
Tensile stress (hereinafter referred to as M50) (MPa), breaking strength (hereinafter referred to as TB) (MPa) and elongation at break (hereinafter referred to as EB) (%) were measured.

[0044]

[Table 1]

The blending components in Table 1 are as follows.

(Crosslinkable rubber) R-1: Hydrogenated nitrile rubber (Zetpol 202
0, trade name, manufactured by Nippon Zeon Co., Ltd. R-2: ethylene-propylene rubber (EP11, trade name, manufactured by Japan Synthetic Rubber Co., Ltd.) (liquid crystalline polymer) P-1: Novacurate E310 (trade name, Mitsubishi Kasei Co., Ltd., heat distortion temperature 70 ° C., type III) P-2: Rod Run LC-5000 (trade name, manufactured by Unitika Ltd., heat distortion temperature 170 ° C., type III) P-3: Vectra A950 ( Product name, manufactured by Polyplastics Co., Ltd., heat distortion temperature 180 ° C, type II) (antioxidant) 2,6-di-t-butyl-4-methylphenol (Nocrac 200, product name, Ouchi Shinko Kagaku) (Co., Ltd.) (Peroxide) 1,3-bis (t-butylperoxy-i-propyl)
Benzene (Peroximon F40, trade name, manufactured by NOF CORPORATION) In Comparative Examples 1 and 3, each component was added at about 60 ° C.
Kneading was performed using a roll of No. 1 to obtain a rubber composition.

From the results shown in Table 1, the crosslinked sheets obtained in Examples 1 to 9 were compared with the crosslinked sheets obtained in Comparative Examples 1 and 3 in which the liquid crystalline polymer was not blended. It has excellent elastic modulus and tensile stress, especially breaking strength, while maintaining high elongation at break, and has a particularly high elastic modulus as compared with the crosslinked sheet obtained in Comparative Example 2 in which the compounding amount of the liquid crystalline polymer is too large. It is also found that the material has excellent elongation at break.

Examples 10 to 14 and Comparative Example 4 The components (A) shown in Tables 2 and 3 were kneaded at the first stage for 5 minutes at 180 ° C. using a Labo Plastomill, and then ( The component (B) was added and the second stage kneading was carried out at 60 ° C. for 10 minutes to obtain a kneaded product. The component (C) was added to the obtained kneaded product and kneaded using a roll at about 60 ° C. to obtain a rubber composition. From the rubber composition obtained,
Crosslinked sheets were obtained in the same manner as in Examples 1-9.

The physical properties of the obtained crosslinked sheet were evaluated in Examples 1-9.
I examined it in the same way. The results are shown in Tables 2 and 3.

[0050]

[Table 2]

[0051]

[Table 3]

The crosslinkable rubbers, liquid crystalline polymers, antioxidants and peroxides shown in Tables 2 and 3 were the same as those in Example 1.
Same as that used in ~ 9. The rubber adhesive and the vulcanization accelerator are as follows.

(Rubber Adhesive) S-1: Sumikanol 620 (trade name, manufactured by Sumitomo Chemical Co., Ltd.) S-2: Sumikanol 508 (trade name, manufactured by Sumitomo Chemical Co., Ltd.) (vulcanization accelerator) ) TT: Tetramethyl thiuram disulfide CZ: N-cyclohexyl-2-benzothiazolylsulfenamide From the results shown in Tables 2 and 3, Examples 10 to 14
All of the crosslinked sheets obtained in Comparative Example 4 were excellent in elastic modulus, tensile stress and rupture strength while maintaining high elongation at break, as compared with the crosslinked sheet obtained by not adding the liquid crystalline polymer obtained in Comparative Example 4. It turns out to be a thing. Further, Example 1 in which a resorcin-formalin initial condensate and a methylolated melamine were blended as an adhesive for rubber
0, the crosslinked sheet obtained in Example 11 containing a vinyl carboxylate metal salt monomer, and the crosslinked sheets obtained in Examples 12 to 14 containing a condensate and a metal salt vinyl monomer. Shows that the elastic modulus, the tensile stress and the breaking strength are further improved as compared with the crosslinked sheet obtained in Example 4, and that the breaking strength in the anti-parallel direction is particularly improved.

[0054]

The reticulated fiber reinforced rubber composition obtained by the production method of the present invention has a structure in which the fibrillated reinforcing phase is formed like a net in the rubber and the elastic three-dimensional net is reinforced by being embedded in the rubber. Rubber products that exhibit high reinforcing properties and require high mechanical properties such as high elastic modulus, high breaking strength, and fatigue resistance, such as transmission belts, conveyor belts, and anti-vibration rubber that receive dynamic stimulation. There is an effect that it can be suitably used.

Claims (5)

[Claims] 1. A high temperature kneaded product is obtained by kneading 0.5 to 130 parts by weight of a liquid crystalline polymer with 100 parts by weight of a crosslinkable rubber at a temperature not lower than the heat distortion temperature of the liquid crystalline polymer.
A method for producing a reticulated fiber reinforced rubber composition, which comprises kneading the high-temperature kneaded material at a temperature lower than the heat distortion temperature of the liquid crystalline polymer. 2. When a high-temperature kneaded product is blended with a resorcin-formalin precondensate or a resorcin-alkylphenol-formalin co-precondensate, the high-temperature kneaded product is kneaded at a temperature lower than the heat distortion temperature of the liquid crystalline polymer. The method according to claim 1, wherein the methylolated melamine is added to the composition. 3. The method according to claim 1, wherein the high temperature kneaded product is blended with a vinyl carboxylate metal salt monomer. 4. The method according to claim 1, 2 or 3, wherein a carboxylic acid metal salt vinyl monomer is added when the high temperature kneaded material is kneaded at a temperature lower than the heat distortion temperature of the liquid crystalline polymer. 5. A reticulated fiber reinforced rubber composition obtained by the method according to claim 1, 2, 3 or 4.