JP2000143875A - Staple fiber-reinforced rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a staple fiber-reinforced rubber composition good in workability in an industrial large-scale production and excellent in durability and anisotropy. SOLUTION: The title staple fiber-reinforced rubber composition is obtained by kneading (A) a staple fiber-reinforced rubber composition comprising (a) a first diene-based elastomer, (b) a polyolefin having a melting point of 100-150 deg.C and (c) a thermoplastic polymer bearing an amide group in its main chain and constituting a matrix comprising 100 pts.wt. of a continuous phase of the component (a) and less than 100 pts.wt. of the component (b) dispersed therein, the component (c) being dispersed as fine fibers in the matrix, with (B) a second diene-based elastomer. In this case, the component (c) is contained in an amount of 5-30 pts.wt. based on 100 pts.wt. of the total of (a) the first diene-based elastomer and (B) the second diene-based elastomer and is dispersed finely and uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short fiber reinforced rubber composition having improved workability on a large industrial scale, excellent durability and anisotropy, and relates to a tire member, in particular, a tire material. The present invention relates to a short fiber reinforced rubber composition that can be suitably used for reinforcing a side member.

[0002]

2. Description of the Related Art Conventionally, various short fiber reinforced rubber compositions in which short fibers are dispersed in a diene rubber such as natural rubber to improve the modulus, strength and the like have been known. It has been manufactured by blending short organic fibers such as vinylon and vulcanizing as necessary.

Further, for the purpose of improving the strength and elongation of such a short fiber reinforced rubber composition, for example, a fiber reinforced elastic body in which the average fiber diameter of short fibers such as nylon has been reduced and reinforced with fine fibers has been proposed. . In this production, for example, vulcanizable rubber, nylon and a binder are melt-kneaded at a temperature equal to or higher than the melting point of nylon, and the obtained kneaded material is extruded at a temperature equal to or higher than the melting point of nylon, and further stretched or rolled. A method of blending an additional vulcanizable rubber and a vulcanizing agent into the fiber reinforced rubber obtained as described above and vulcanizing the mixture (Japanese Patent Application Laid-Open Nos. 58-79037 and 59-43041; JP-A-61-225858). Although the tensile strength and modulus were certainly improved by such a method, the fiber-reinforced rubber had a structure in which fine fibers such as nylon were dispersed in a vulcanizable rubber, so that pelletization was extremely difficult. There was a problem that it was difficult. In addition, if a large amount of nylon is blended, it becomes extremely hard, so it is necessary to extend the kneading time or blend a vulcanizable rubber etc. after heating and softening the fiber reinforced rubber. Even so, there was a problem with productivity.

As a means for solving such a problem, a fiber reinforced composition obtained by kneading an additional diene elastomer into a thermoplastic composition in which fine fibers of a thermoplastic polyamide are dispersed in a matrix comprising a polyolefin and a diene elastomer. An elastic body has been proposed (JP-A-7-27).
No. 8360).

[0005]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 7-278 is disclosed.
The fiber-reinforced elastic body disclosed in Japanese Patent Publication No. 360 has improvements in productivity on a laboratory scale, modulus and fatigue resistance as compared with the previous fiber-reinforced elastic bodies, but is industrially large. It was found that the workability at the capacity scale was inferior. Further, since such a fiber-reinforced elastic body has a small difference between the orientation direction of the fiber and a direction perpendicular thereto, when a higher reinforcing effect is required in a specific direction such as reinforcement of a side member of a tire, it is not necessarily sufficient. I couldn't say it.

Accordingly, an object of the present invention is to provide a short fiber reinforced rubber composition which has good workability on a large industrial scale, and has excellent durability and anisotropy.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor has focused on the material constituting the matrix of the master batch at the time of kneading, and as a result, the matrix was formed with a continuous layer of a diene elastomer. It has been found that the above objects can be achieved by controlling the amounts and procedures of the various additives so that the present invention has been completed.

That is, the short fiber reinforced rubber composition of the present invention comprises (a) a first diene elastomer and (b) 10
A polyolefin having a melting point of 0 to 150 ° C., and (c) a thermoplastic polymer having an amide group in a main chain,
A matrix in which less than 100 parts by weight of the component (b) is dispersed in 100 parts by weight of the continuous phase of the component (a), and the component (c) is dispersed as fine fibers in the matrix (A). A short fiber reinforced rubber composition obtained by kneading a short fiber reinforced rubber composition with (B) a second diene elastomer, wherein (a) a first diene elastomer and (B) a second diene elastomer. The component (c) is 5 to 30 parts by weight and the component (c) is finely and uniformly dispersed with respect to 100 parts by weight in total with the system elastomer.

In the short fiber reinforced rubber composition of the present invention, the component (c) is chemically bonded to both the components (a) and (b).

The component (c) in the matrix composed of the components (a) and (b) has an average diameter (D) of 0.05 to 1.0 μm and an average length (L). It preferably exists in a fine fiber state having a ratio (L / D) to the average diameter (D) of 10 to 2000.

Further, the amount of the component (b) in 100 parts by weight of the continuous phase of the component (a) in the rubber composition (A) is preferably less than 85 parts by weight, more preferably 65 parts by weight. And even more preferably less than 45 parts by weight.

Further, the amount of the component (c) occupying in 100 parts by weight of the continuous phase of the component (a) in the rubber composition (A) is preferably 50 parts by weight or more and 110 parts by weight or more.
It is less than 50 parts by weight, more preferably less than 100 parts by weight.

The operation of the present invention will be described below with reference to Japanese Patent Application Laid-Open No. 7-278.
This will be described in detail below in comparison with the fiber-reinforced elastic body disclosed in JP-A-360. In the (A) short fiber reinforced rubber composition according to the present invention, a masterbatch of a diene-based elastomer continuous phase is obtained, that is, (a) the first diene-based elastomer contains (b) 100 to 150 ° C. Since a polyolefin having a melting point and (c) a thermoplastic polymer having an amide group in the main chain are present, chemically kneading (A) blending with the master batch (B) The affinity with the diene elastomer of No. 2 is greatly increased. Also, mechanically, the viscosity of the master batch (A) itself is lower than that of a polyolefin phase described below as a continuous phase. This chemical and mechanical effect contributes significantly to:

First, in the kneading for preparing the short fiber reinforced rubber composition of the present invention using (A) a master batch, (B) a second diene-based elastomer, and an appropriately selected compounding agent, Since the rotor slip is small from the beginning (start of kneading) and the shear is efficiently applied, an ideal temperature rise curve can be obtained. By such an appropriate temperature rise, the temperature of the kneaded rubber reaches the melting point of the polyolefin (b) early, and the polyolefin phase is melted. As a result, (c) the thermoplastic polymer fiber having an amide group in the main chain is extremely microscopically dispersed.

On the other hand, as disclosed in JP-A-7-278360, when (A) the masterbatch has a continuous polyolefin phase, (a) a diene-based elastomer phase and (c) ) The thermoplastic polymer fiber having an amide group in the main chain is present, so that it has a low affinity for the (B) second diene-based elastomer chemically, and is mechanically very rigid and deformable. The melting point of the polyolefin (usually 100 to 14
(0 ° C.). As a result, when the (A) masterbatch is kneaded with the (B) second diene-based elastomer, the affinity is low and the mixture is rigid.
Area), a state in which the two do not adapt to each other continues.

A component of the temperature rise in the usual rubber kneading is that each material has high affinity and viscosity. When the elements are satisfied by kneading, the share continues to be efficiently applied, and the temperature rise is achieved by the self-heating of the compounded material. Therefore, if the state in which the materials do not fit together continues as described above, rotor slip is induced in an important region that controls the temperature rise at the initial stage of kneading, and it is difficult to apply shear. The rise cannot be expected. That is, only after the temperature starts to rise slowly after a long rotor slip and the kneading temperature reaches (b) the melting point of the polyolefin, (c) the thermoplastic polymer fiber having an amide group in the main chain changes from a rigid form. It is sometimes loosened and begins to disperse.

In a laboratory-level mixer with a small capacity (50-5000 cc), the rotor clearance is extremely small, so that it is easy to apply a shear. In addition, since the capacity is small, temperature control is easy and the temperature distribution can be made uniform. Therefore, even when the master batch (A) is a polyolefin continuous phase, a composition having a uniform dispersion level can be obtained. However, in the case of an industrial large-capacity mixer (50 to 500 liters), the manner in which the shear is applied becomes non-uniform, and the temperature control is coarse, so that the temperature distribution in the kneaded rubber becomes extremely non-uniform. Therefore, in the masterbatch of the continuous phase of the polyolefin (b), the region where the melting point of the polyolefin (b) is reached is melted by the polyolefin (b), and the thermoplastic polymer fibers (c) having an amide group in the main chain are formed. In the region where the temperature rise was insufficient, the three components (a) / (b) / (c) remained in their respective forms because the polyolefin (b) was insufficiently melted. It was found that the composition became extremely uneven. This non-dispersed material becomes a large fracture nucleus, and is a main factor that significantly reduces the durability of the vulcanized rubber composition.

As described above, in the present invention, by using a master batch of a diene elastomer continuous phase instead of a master batch of a polyolefin continuous phase, rotor slip is not induced even in an industrial large-scale system. The workability is good, and the obtained short fiber reinforced rubber composition also has good dispersibility, and exhibits excellent effects in durability and anisotropy.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION As the (a) first diene elastomer and (B) the second diene elastomer component which can be suitably used in the short fiber reinforced rubber composition of the present invention, for example, natural rubber ( NR), synthetic polyisoprene rubber (IR), styrene-butadiene copolymer rubber (S
BR), polybutadiene rubber (BR), butyl rubber (I
IR), chloroprene rubber (CR), chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (Br-II)
R), ethylene-propylene rubber (EPDM) and the like, and these rubbers can be used alone or in combination of two or more.

Examples of the thermoplastic polymer (c) having an amide group in its main chain (hereinafter referred to as "polyamide") include nylon 6, nylon 66 and nylon 4
6, nylon 11, nylon 12, nylon 610, nylon 611, nylon 612, polyamide containing a copolymer of nylon 6/66, and a mixed polyamide of two or more of these. The molecular weight of the polyamide to be used is preferably 8000 or more, and the melting point is preferably in the range of 170 to 240 ° C. in consideration of the kneading temperature at the time of producing a master batch.

(C) The amount of polyamide is as follows:
5 to 30 parts by weight based on 100 parts by weight of the total amount of the diene elastomer and (B) the second elastomer.
If the amount is less than 5 parts by weight, the effects of the present invention cannot be exerted. If the amount is more than 30 parts by weight, workability is significantly reduced and processing becomes difficult. Further, the amount of the component (c) occupied in 100 parts by weight of the component (a) continuous phase in the short fiber reinforced rubber composition (A) is preferably 50 parts by weight or more and less than 110 parts by weight, more preferably 50 parts by weight. Parts or more and less than 100 parts by weight. If the amount is less than 50 parts by weight, it becomes difficult to exert the effects of the present invention, while if it is more than 110 parts by weight, the workability of the master batch (A) decreases, and processing becomes difficult.

With the amount of the polyamide (c),
The component (c) is dispersed as fine fibers in a matrix in which the component (b) is dispersed in the continuous phase of the component (a), and the component (c) is chemically good with both the components (a) and (b). It is possible to maintain the combined state.

The fine (c) polyamide short fiber has a circular or similar cross-section and an average diameter (D).
Is preferably 0.05 to 1.0 μm, more preferably 0.1 to 0.8 μm, and further preferably 9
0% by weight or more is 1.0 μm or less. If the average diameter (D) is less than 0.05 μm, cutting during kneading tends to occur. On the other hand, if it exceeds 1.0 μm, the stress concentration generated at the end of the fiber causes a decrease in fatigue durability. Become. The average length L is preferably 10 μm or more, and 90% by weight or more of the average length L is 1000 μm or less. This means that if the length (L) is less than 10 μm, (L /
This is because the ratio of D) is small, so that the orientation decreases.

(C) The ratio (L / D) of the average length (L) to the average diameter (D) of the polyamide is preferably from 10 to 2,000.
It is. The higher the ratio, the easier the orientation and the effect of increasing the anisotropy. However, if the ratio exceeds 2,000, it becomes difficult to secure the dispersibility in the rubber. On the other hand, if it is less than 10, good anisotropy cannot be obtained. (C) As ideal characteristics of the polyamide, it is preferable to reduce the diameter and increase the ratio (L / D). In addition, since the polyamide (c) used in the present invention is melt-drawn in rubber, it becomes a very microfiber, and a great improvement in fatigue durability can be realized.

The polyamide (c) in such a form is represented by (A)
In the short fiber reinforced rubber composition, it is chemically bonded to both components (a) and (b). This bond is desirably a chemical bond such as a primary bond or a graft bond by a coupling agent.

Next, as the polyolefin having a melting point of 100 to 150 ° C. (b) which can be suitably used in the short fiber reinforced rubber composition of the present invention, low density polyethylene (LP)
E), high density polyethylene (H-PE), polypropylene (PP) and the like. Preferably, polyethylene having a melting point of 100 to 140 ° C is used.

The melting point of the polyolefin (b) is 100
When the melting point is less than 100 ° C., the fusion property of the polyamide (c) to short fibers is reduced. On the other hand, when the melting point exceeds 150 ° C., the processing is performed. This is because the property deteriorates and it becomes impossible to melt the rubber during kneading. Preferably it is 100-140 degreeC.

In order to sufficiently disperse (b) the polyolefin, the temperature at the time of kneading the (b) polyolefin, that is, the final kneading temperature in the kneading stage containing no vulcanizing agent or vulcanization accelerator, must be adjusted. , (B) preferably at least 3 ° C. higher than the melting point of the polyolefin.

(B) The blending amount of the polyolefin is (a)
Less than 100 parts by weight, preferably less than 85 parts by weight, in 100 parts by weight of the continuous phase of the first diene-based elastomer component,
More preferably less than 65 parts by weight, even more preferably less than 45 parts by weight. The masterbatch of the diene-based elastomer continuous phase can be obtained by making the blending amount of the (b) polyolefin always smaller than that of the (a) first diene-based elastomer component. When the amount is equal to or larger than (a) the first diene-based elastomer component, the masterbatch has a polyolefin phase as a continuous phase, and the durability is greatly reduced.

When the short fiber reinforced rubber composition of the present invention is prepared, a masterbatch prepared in advance based on (a) the first diene-based elastomer and (b) polyolefin and (c) polyamide fibers is prepared. Then, it is further kneaded with (B) the second diene-based elastomer. Hereinafter, a production example will be described. The amount is as described above.

(1) (a) The first diene-based elastomer component and the amine-based antioxidant are kneaded for about 1 to 3 minutes. (2) To this, (c) polyamide and (b) polyolefin are charged and kneaded, and (c) polyamide and (b)
The temperature is raised to above the melting point of the polyolefin and both are melted. (3) If necessary, a coupling agent such as a phenol resin oligomer, a silane coupling agent, and the like are added, and the mixture is further kneaded to obtain the master batch (A). (4) The master batch is extruded with an extruder and stretched to obtain a rubber composition reinforced with (c) polyamide fibers and (b) polyolefin. That is, the rubber component (diene-based elastomer) is reinforced with the polyamide (c) and the polyolefin (b) by the graft bond or the primary bond by the coupling agent.

(5) To the obtained master batch (A), (B) a second diene-based elastomer is appropriately added, and the polyamide (c) and the polyolefin (b) in the blend are mixed in a desired manner. To the amount (proportion), and, except for the vulcanizing agent, vulcanization accelerator and vulcanization accelerator,
Compounding materials commonly used in the rubber industry are compounded and kneaded with a Banbury mixer, kneader or the like. Such compounding materials include organic unsaturated fatty acids (if necessary),
Examples include fillers such as carbon black and silica, zinc white, an antioxidant, stearic acid, and process oil. In this step, kneading is performed for 30 seconds to 10 minutes so that the “final kneading temperature” is a temperature higher than the melting point of the polyolefin (b) by 3 ° C. or more. This is to ensure dispersion of the fusion mixture of (b) polyolefin and (c) polyamide. (6) Finally, a vulcanizing agent, a vulcanization accelerator and a vulcanization accelerator are added and kneaded until each rubber chemical is sufficiently dispersed.
Obtain the desired rubber composition.

Preferred examples of the organic unsaturated fatty acids include dehydrated castor oil fatty acids. This dehydrated castor oil fatty acid is obtained by a dehydration reaction of castor oil. In the case of this dehydrated castor oil fatty acid, as the conjugated diene acid,
The main component is 9,11-octadecadienoic acid, and other organic unsaturated fatty acids mainly include non-conjugated octadecadienoic acid. Other non-conjugated unsaturated fatty acids also include linoleic acid, linoleic acid, and the like.

Since the organic unsaturated fatty acid has the effect of greatly improving processability and anisotropy, it is preferable to add 0.5 to 10 parts by weight to 100 parts by weight of the rubber component. Further, in the rubber composition of the present invention, it is more effective to use a conventionally used fatty acid represented by stearic acid in addition to the organic unsaturated fatty acid.

In the rubber composition of the present invention, (a) a diene rubber and (c) a polyamide are chemically bonded, and (b) a polyolefin is fused to the (c) polyamide. Anisotropy can be greatly improved by compounding (c) the improvement of rupture resistance and fatigue resistance which are the characteristics of polyamide and (b) the improvement of anisotropy which is the characteristic of polyolefin. When an organic unsaturated fatty acid is also incorporated, the anisotropy can be further increased as described above.

A more specific production example of the master batch shown in the above production example is shown below. Such a masterbatch comprises (1) (a) a rubber component, (c) a polyamide,
(B) preparing a matrix consisting of component (a) and component (b) in the three components of polyolefin;
(2) a step of reacting the component (c) with a binder, (3) a step of melting and kneading the matrix and the component (c) reacted with the binder, and (4) a step of mixing the obtained kneaded material with: (C)
It can be produced by extruding at a temperature equal to or higher than the melting point of the component, and then stretching and / or rolling at a temperature lower than the melting point of the component (c). These steps (1) to (4) will be described below. explain.

First, the step of preparing a matrix comprising the components (a) and (b) in the step (1) will be described. In order to prepare a matrix composed of the component (a) and the component (b), for example, the component (b) is first melt-kneaded with a binder and reacted, and then this and the component (a) are melted and kneaded. . Further, the component (a) and the component (b) may be melted and kneaded together with a binder. Melting and kneading can be performed by an apparatus usually used for kneading resin or rubber. Examples of such an apparatus include a Banbury mixer, a kneader, a kneader extruder, an open roll, a single-screw kneader, and a twin-screw kneader.

The amount of the binder is preferably in the range of 0.1 to 2.0 parts by weight, particularly preferably 0.2 to 1.0 part by weight, per 100 parts by weight of component (b). When the amount of the binder is less than 0.1 part by weight, a composition having high strength cannot be obtained, and when the amount is more than 2.0 parts by weight, a composition having excellent modulus cannot be obtained.

As the binder, a silane coupling agent,
Titanate coupling agent, novolak type alkylphenol formaldehyde precondensate, resol type alkylphenol formaldehyde precondensate, novolak type phenol formaldehyde precondensate, resol type phenol formaldehyde precondensate, unsaturated carboxylic acid and its derivative, organic peroxide, etc. Alternatively, those commonly used as a polymer coupling agent can be used. Among these binders, a silane coupling agent is preferable because the component (a) and the component (b) are less likely to gel, and a strong bond can be formed at the interface between these components. Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, vinyltriacetylsilane, γ-methacryloxypropyltrimethoxysilane, γ- [N- (β-methacryloxy ethyl)
-N, N-dimethylammonium (chloride)] propylmethoxysilane and styryldiaminosilane;
A silane coupling agent having a group, such as a vinyl group and an alkoxy group, which easily desorbs a hydrogen atom from another and / or a polar group is preferably used.

When a silane coupling agent is used as a binder, an organic peroxide can be used in combination. As the organic peroxide, those having a one-minute half-life temperature in the range of the same temperature as the higher of the melting point of the component (b) or the melting point of the component (a) or a temperature about 30 ° C. higher than this temperature are used. It is preferably used. Specifically, those having a one-minute half-life temperature of about 110 to 200 ° C. are preferably used. Such organic peroxides include 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane,
1,1-di-t-butylperoxycyclohexane,
2,2-di-t-butylperoxybutane, 4,4-di-t-butylperoxyvaleryl acid n-butyl ester, 2,2-bis (4,4-di-t-butylperoxycyclohexane ) Propyl, 2,2,4-trimethylpentyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyacetate, t-butyl peroxylaurate, t-butyl peroxybenzoate, t-peroxyisophthalate -Butyl and the like.

The amount of the organic peroxide to be used is as follows:
The range of 0.01 to 1.0 part by weight relative to 0 part by weight is preferable.

However, when the component (a) and the component (b) are melted and kneaded together with a silane coupling agent to modify the silane, the natural rubber, polyisoprene or isoprene copolymer is added to the component (a). When used, an organic peroxide may not be used. This is because rubber having an isoprene structure undergoes a main chain scission due to a mechanochemical reaction during kneading, and a type of peroxide having a -COO. Group at the end of the main chain is generated. This is because it is considered that they perform almost the same operation.

Next, the step of kneading the component (c) with the above matrix will be described. The component (c) may be melt-kneaded with the binder in advance and then melt-kneaded with the matrix, or may be melt-kneaded with the matrix in the presence of the binder. Melt kneading can be performed by a device usually used for kneading a resin or rubber, for example, a Banbury mixer, a kneader, a kneader extruder, an open roll, a single-screw kneader, a twin-screw kneader, or the like. Same as in the preparation.

The ratio of the binder to the component (c) is as follows:
When the total amount of the component (c) and the binder is 100% by weight, the range is preferably 0.1 to 5.5% by weight, and 0.2 to 5.5% by weight.
A range of 5.5% by weight is particularly preferred, and 0.2 to 3% by weight.
Is most preferable.

As the binder, a silane coupling agent,
Titanate coupling agent, novolak type alkylphenol formaldehyde precondensate, resol type alkylphenol formaldehyde precondensate, novolak type phenol formaldehyde precondensate, resol type phenol formaldehyde precondensate, unsaturated carboxylic acid and its derivative, organic peroxide, etc. Alternatively, those commonly used as a polymer coupling agent can be used. Among these binders, a silane coupling agent is most preferred because it hardly causes the component (c) to gel and can form a strong bond at the interface with the matrix. Examples of the silane coupling agent include those having a group capable of forming a bond with a nitrogen atom of an —NHCO— bond of the component (c) by a dehydration reaction, a dealcoholation reaction, or the like, such as an alkoxy group and a vinyl group. As such a silane coupling agent, specifically, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β
-Methoxyethoxy) silane, vinyltriacetylsilane, γ-methacryloxypropyltrimethoxysilane,
γ- [N- (β-methacryloxyethyl) -N, N-dimethylammonium (chloride)] propylmethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, and styryldiaminosilane, γ-
Ureidopropyltriethoxysilane and the like.

In this step, the matrix and (c)
The temperature at which the components are melted and kneaded must be equal to or higher than the melting point of component (c). Even if melting and kneading are performed at a temperature lower than the melting point of the component (c), the kneaded material does not have a structure in which the fine particles of the component (c) are dispersed in the matrix. This is because the component (c) cannot be made into fine fibers even when drawn. The kneading temperature is preferably a temperature higher than the melting point or Vicat softening point of the polyolefin of the component (b).

The kneaded product obtained in the above step is extruded from a spinneret, an inflation die or a T die, and then stretched or rolled.

In this step, the fine particles of the component (c) in the kneaded material are transformed into fibers by spinning or extrusion.
This fiber is drawn by subsequent drawing or rolling, and becomes a stronger fiber. Therefore, spinning and extrusion must be performed at a temperature equal to or higher than the melting point of the component (c), and stretching and rolling must be performed at a temperature lower than the melting point of the component (c).

The spinning or extrusion and the subsequent stretching or rolling are carried out, for example, by extruding the kneaded material from a spinneret, spinning it into a string or a thread, and winding it around a bobbin while drafting it. it can. Here, "drafting" means that the winding speed is higher than the spinning speed. Winding speed / spinning speed ratio (draft ratio) is 1.5
The range is preferably from 100 to 100, and particularly preferably from 2 to 50. The most preferred range of the draft ratio is 3-30.

This step can also be carried out by continuously rolling the spun kneaded material with a rolling roll or the like. Further, it can be carried out by extruding the kneaded material from an inflation die or a T-die and winding it around a roll while drafting. Also, instead of rolling up the roll while drafting, it may be rolled by a rolling roll or the like.

It is preferable that the master batch after stretching or rolling is pelletized. This is because the pellets can be uniformly kneaded with the additional (B) diene rubber.

[0052]

The present invention will be specifically described below with reference to examples and comparative examples. First, preparation of a master batch of a fiber reinforcing member layer used for the pneumatic tires of the examples and comparative examples will be described. [Preparation of master batches 1 to 4] Using natural rubber (NR, SMR-L) as component (a) and high density polyethylene (PE) as component (b)
(Mitsubishi Chemical Co., Ltd. Mitsubishi Polyethylene HJ560, melting point 13
5 ° C.) and nylon 6 (PA) as the component (c).
(Ube Nylon 1030B, melting point: 215 to 220 ° C, molecular weight: 30,000, manufactured by Ube Industries, Ltd.) was used.
The component (b) is added in an amount of 0.1 to 100 parts by weight of the component (b).
5 parts by weight of γ-methacryloxypropyltrimethoxysilane and 0.1 part by weight of n-butyl 4,4-di-t-butylperoxyvalerate were melt-kneaded for modification. The component (c) was modified by melt-kneading 1.0 part by weight of N-β (aminoethyl) γ-aminopropyltrimethoxysilane with respect to 100 parts by weight of the component (c).

The modified components (b) and (c) and the component (a) were processed in the following order to obtain a master batch. First, the component (b) modified as described above was kneaded with the component (a) in a mixing ratio shown in Table 1 below using a Banbury-type mixer to prepare a matrix, which was dumped at 170 ° C. and pelletized. Then, this matrix and (c)
The components were kneaded in a biaxial kneader heated to 240 ° C. at the mixing ratio shown in Table 1 below, and the kneaded product was pelletized. The obtained kneaded material was extruded in a string shape with a single screw extruder set at 245 ° C., and pelletized with a pelletizer while being drawn at a draft ratio of 10. In the obtained masterbatches 1 to 3, natural rubber constituted a continuous layer, whereas in masterbatch 4, high-density polyethylene was a continuous layer. The obtained pellets were refluxed in a mixed solvent of o-dichlorobenzene and xylene to remove polyolefin and NR, and the shape and diameter of the remaining fibers were observed with an electron microscope. The average fibers shown in Table 1 below were obtained. The diameter was confirmed.

[0054]

[Table 1]

Next, using the various masterbatches,
Further, with respect to the various fiber-reinforced rubber compositions prepared by using a 240-liter mass-produced Banbury mixer with the contents shown in Tables 2 and 3, the 50% tensile stress (Mod 50%) at room temperature and 100 ° C. was JIS. K630
According to No. 1, the dumbbell-shaped No. 3 test piece was measured in the short fiber orientation direction and in two directions perpendicular thereto.

Further, a fatigue test was performed on the obtained short fiber reinforced rubber composition as follows. JIS K6
A flex fatigue test based on No. 301 was performed. The orientation direction of the short fibers was taken as the longitudinal direction of the sample, and the number of bending times required for the crack length to reach 5 mm was measured (the number of bending times was 300.
Times / min). In the evaluation, the number of times until the crack length reached 5 mm was indicated by an index in direct comparison with each comparative example corresponding to 100 in each example. The higher the value, the better the result.

Further, the kneading time at a dump temperature of 150 ° C. was represented by an index by taking the reciprocal of the same direct comparison. The higher the value, the better the result. further,
The dispersion level of the fine fibers in the unvulcanized rubber sheet was also evaluated. The evaluation method is as follows. Unvulcanized rubber
It was cooled in liquid nitrogen to about 100 ° C., and a shock was applied in a solidified state to obtain a fractured surface, and the fractured surface was observed with an optical microscope (175 times magnification). 1mm x 1mm
The number of the lump having a size of 100 μm or more existing in the observation area was counted. The number of observations was 1 cm ² (100
Coma), and the results are shown as the number of lumps present per 1 cm ² . The obtained results are shown in Tables 2 and 3 below.
It is described together.

[0058]

[Table 2]

[0059]

[Table 3] * N-tert-butyl-2-benzothiazolylsulfenamide

[0060]

As described above, the short fiber reinforced rubber composition of the present invention has excellent industrial large-scale workability, and also has excellent durability and anisotropy. Play.

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Claims (8)

[Claims] (A) a first diene elastomer,
(B) a polyolefin having a melting point of 100 to 150 ° C., and (c) a thermoplastic polymer having an amide group in the main chain.
(A) a short fiber reinforced rubber composition comprising a matrix in which the component (b) of less than 00 parts by weight is dispersed and the component (c) is dispersed as fine fibers in the matrix;
(B) a short fiber reinforced rubber composition kneaded with a second diene elastomer, wherein the total amount of (a) the first diene elastomer and (B) the second diene elastomer is 100 wt. Component (c) is 5 to 30 parts by weight, and component (c) is finely and uniformly dispersed with respect to parts, and the short fiber reinforced rubber composition is characterized in that: 2. The short fiber reinforcement according to claim 1, wherein the component (c) is a short fiber reinforced rubber composition (A) chemically bonded to both the components (a) and (b). Rubber composition. 3. The component (c) in the matrix comprising the component (a) and the component (b) has an average diameter (D) of 0.0
5 to 1.0 μm, average length (L) and average diameter (D)
The short fiber-reinforced rubber composition according to claim 1 or 2, which exists in a fine fiber state having a ratio (L / D) of 10 to 2,000. 4. The method according to claim 1, wherein the component (b) accounts for less than 85 parts by weight based on 100 parts by weight of the component (a) continuous phase in the rubber composition (A). 9. The short fiber reinforced rubber composition according to claim 1. 5. The method according to claim 1, wherein the component (b) accounts for less than 65 parts by weight based on 100 parts by weight of the component (a) continuous phase in the rubber composition (A). 9. The short fiber reinforced rubber composition according to claim 1. 6. The method according to claim 1, wherein the amount of the component (b) occupied by 100 parts by weight of the continuous phase of the component (a) in the rubber composition (A) is less than 45 parts by weight. 9. The short fiber reinforced rubber composition according to claim 1. 7. An amount of the component (c) occupying in 100 parts by weight of the continuous phase (a) in the short fiber reinforced rubber composition (A) is not less than 50 parts by weight and less than 110 parts by weight.
The staple fiber reinforced rubber composition according to any one of claims 6 to 6. 8. The amount of the component (c) occupying in 100 parts by weight of the continuous phase of the component (a) in the short fiber reinforced rubber composition (A) is 50 parts by weight or more and less than 100 parts by weight.
The staple fiber reinforced rubber composition according to any one of claims 6 to 6.