JP3369301B2 - Rubber composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition having high anisotropy, fatigue resistance and low heat buildup.

[0002]

2. Description of the Related Art In recent years, various kinds of rubber products such as automobile tires, conveyor belts, hoses, etc. are required to have higher performance, and fatigue properties and low heat generation properties are required to be compatible with each other. .

Conventionally, in order to obtain a rubber composition having excellent processability and excellent strength and modulus of a vulcanized product, it has been known to mix short fibers such as nylon, polyester and vinylon into a vulcanizable rubber. Has been. For example, JP-A-59-43041 discloses a reinforced rubber composition in which rubber and nylon fibers embedded therein are graft-bonded through an initial condensation product of a novolac type phenol formaldehyde resin. . However, in this rubber composition, a kneaded product of rubber and nylon fibers is mixed with a resin curing agent and cured in the rubber, so that it is difficult to control the graft bond between the nylon fibers and the rubber, and the usable rubber is also Only rubber compositions having a limited and low nylon fiber content could be obtained.

To solve this problem, Japanese Patent Publication No. 3-499
No. 32 discloses a rubber composition in which short fibers and a resin are reinforced by kneading aromatic polyamide pulp short fibers and a phenol resin into a rubber, and thereby a high elastic modulus can be obtained. However, in this rubber composition, since rubber molecules and aromatic polyamide pulp short fibers are not directly bonded, the reinforcing efficiency is low, and the short fibers themselves act as fracture nuclei in the rubber, resulting in fatigue durability of the rubber. And has the drawback of significantly lowering the creep property, and because pulp-like fibers are dispersed in rubber using a kneading machine such as a Banbury mixer, the dispersion level is extremely low. The reinforcing effect with respect to the amount decreases, and when the amount is further increased, there is a drawback that kneading and extrusion become extremely difficult.

Further, in order to obtain a desired elastic modulus, it is conceivable to add carbon black and a novolac type phenol resin to a rubber containing short fibers, but by adding carbon black or a novolac type phenol resin,
The viscosity of the rubber increases significantly, and in each process such as kneading, sheeting, heating, and extrusion, not only the work becomes extremely difficult, but it becomes difficult to arrange the short fibers in the desired direction. It had a drawback that the effect of blending was significantly reduced.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, the present invention solves these problems, and provides a rubber composition having high anisotropy, fatigue resistance and low heat buildup. The purpose is to do.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor
By blending a specific resin with a diene rubber component, the rubber composition for the above purpose, which could not be achieved by fiber reinforcement alone, was successfully obtained, and the present invention was completed. That is, the rubber composition of the present invention comprises 1 to 100 parts by weight of polyamide fiber and 1 part by weight of olefin resin based on 100 parts by weight of at least one rubber component selected from the group consisting of natural rubber and diene-based synthetic rubber. ~ 100
Reinforced rubber reinforced with polyamide fiber and olefin resin, which are parts by weight and have a blending ratio of the polyamide fiber and the olefin resin of 3/7 to 7/3 and contain no vulcanization accelerator or vulcanizing agent. The final kneading temperature in the kneading stage of the masterbatch is 3 ° C. or more higher than the melting point of the olefin resin. It is preferable that the polyamide fiber is made of nylon 6 and the olefin resin is made of polypropylene. The average diameter D of the polyamide fiber is 0.1 to 1.0 μm,
The ratio (L / D) of the average length L and the average diameter D is preferably 8 or more. The melting point of the olefin resin is 130-
It is preferably 200 ° C. Further, the vulcanization temperature is preferably a temperature higher than the melting point of the olefin resin by 3 ° C. or more.

[0008]

The rubber composition of the present invention contains 100 parts by weight of at least one rubber component selected from the group consisting of natural rubber and diene-based synthetic rubber, and a specific amount of polyamide fiber and olefin resin. The final kneading temperature in the kneading stage of the reinforcing rubber masterbatch compounded and containing no vulcanization accelerator or polyamide fiber and reinforced with the olefin resin is treated at a temperature higher than the melting point of the olefin resin by 3 ° C or more. The polyamide fiber and the olefin resin synergistically interact with each other to obtain a rubber composition having high anisotropy and excellent fatigue resistance and low heat buildup. However, the object of the present invention is not achieved even if the respective conditions are partially satisfied (in this respect, Detailed in further examples and the like).

The contents of the present invention will be described below. Examples of rubber components that can be preferably used in the present invention include natural rubber (NR), synthetic polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butyl rubber (IIR), chloroprene. Examples thereof include rubber (CR), chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (Br-IIR) and ethylene-propylene rubber (EPDM), and these rubbers can be used alone or in combination of two or more kinds.

Examples of the material of the polyamide fiber used in the present invention include nylon 6, nylon 11, nylon 12, nylon 610, nylon 611, nylon 612 and nylon 6/66 copolymer containing polyamide,
And mixed polyamides of two or more of these. The molecular weight of the polyamide used is preferably 8,000 or more, and the melting point thereof is preferably in the range of 170 to 240 ° C. in consideration of the temperature of kneading when preparing a masterbatch. The blending amount of the polyamide fiber can be appropriately adjusted by, for example, further kneading the diene rubber with the reinforcing rubber of the polyamide fiber as the masterbatch and the olefin resin described later. Further, in the rubber composition of the present invention, the polyamide fibers are contained in the form of short fibers, and from the viewpoint of physical properties and processed surface, it is necessary to consider the amount of polyamide as short fibers, and the amount thereof is the above-mentioned diene. 1 to 100 parts by weight of the rubber component
100 parts by weight, preferably 2.5 to 50 parts by weight, more preferably 5 to 30 parts by weight. If the content of polyamide fiber is less than 1 part by weight, the effect of the present invention cannot be exhibited, and if it exceeds 100 parts by weight, workability is significantly reduced and workability becomes difficult, which is not preferable.

The polyamide in the rubber composition of the present invention may be in any bonding state with rubber molecules, but is preferably chemically bonded such as graft bonding. This polyamide has a circular cross section or a shape similar thereto, and has an average diameter D of 0.1 to 1.0 μm, preferably 0.1 to 0.8 μm, and more preferably 90% by weight or more. Is 1.0 μm or less, the average fiber length L is 10 μm or more, and 90% by weight thereof.
The above is preferably 1000 μm or less. If the average diameter D exceeds 1.0 μm, the stress concentration at the fiber ends causes the fatigue durability to decrease. Further, the larger the ratio (L / D) of the average length L and the average diameter D of the polyamide, the easier the orientation and the effect of increasing the anisotropy. Therefore, the ideal characteristics of polyamide are small diameter,
It can be said that it is preferable to increase L / D. Therefore,
L / D is required to be 8 or more, preferably 50 to
It is 5000. When L / D is less than 8, anisotropy cannot be increased, which is not preferable. Since the polyamide used in the present invention is melt-stretched in rubber, it is an extremely microfiber, and can significantly improve fatigue durability.

Examples of the olefin resin used in the present invention include low density polyethylene (L-PE), high density polyethylene (H-PE), polypropylene (P
P) and the like. The melting point of olefin resin is 13
It is 0 to 200 ° C, preferably 150 to 170 ° C. If the melting point is less than 130 ° C, the exothermic property, which is a physical property of rubber after vulcanization, cannot be lowered, and the melting point is 200 ° C.
If it exceeds, the workability will deteriorate and it will not dissolve when kneading rubber,
Not preferable.

The blending amount of the olefin resin can be appropriately adjusted by further kneading the olefin resin as the masterbatch and the reinforcing rubber of the above polyamide with the diene rubber, and 100 parts by weight of the above diene rubber component. 1 to 100 parts by weight, preferably 2.5 to 5 parts by weight
The amount is 0 parts by weight, more preferably 5 to 30 parts by weight. If the blending amount of the olefin resin is less than 1 part by weight, the effect of the present invention cannot be exhibited, and if it exceeds 100 parts by weight, the workability is remarkably lowered and the workability becomes difficult, which is not preferable. Furthermore, the compounding ratio of the polyamide and the olefin resin is 3/7 to 7/3, preferably 4 /
When it is 6 to 6/4 and the compounding ratio is less than 3/7,
Anisotropy and fatigue resistance are reduced, which is not preferable, and when the compounding ratio exceeds 7/3, heat generation is increased, which is not preferable.

Next, an example of the method for producing the rubber composition according to the present invention will be described. The materials and their amounts used here are as described above. First, a diene rubber and an amine anti-aging agent are kneaded for about 1 to 3 minutes, and then a polyamide and an olefin resin are added and kneaded to raise the temperature to a temperature equal to or higher than the melting points of the polyamide and the olefin resin and melt them. . Then, if necessary, a coupling agent such as a phenol resin oligomer is added and further kneaded to obtain a masterbatch. Then, this masterbatch is extruded by an extruder and stretched to obtain a rubber composition reinforced with a polyamide fiber / olefin resin.

Further, to the obtained masterbatch (the diene rubber is reinforced with polyamide and olefin resin by graft bonding), the diene rubber is added to adjust the amount of polyamide and olefin resin in the blend to a desired amount. Add rubber as appropriate, carbon black normally used in the rubber industry, sulfur, vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids,
Besides the antiaging agent and carbon black, for example, a filler such as silica, a novolac type phenol resin, a process oil and the like are appropriately added and kneaded with a Banbury mixer, a kneader or the like to obtain the intended rubber composition.
This kneading is carried out for 30 seconds to 10 minutes in a kneading stage containing no vulcanization accelerator or vulcanizing agent so that the final kneading temperature is 3 ° C. or more higher than the melting point of the olefin resin. The final kneading temperature after the above kneading is set to a temperature higher than the melting point of the olefin resin by 3 ° C. or more in order to completely melt the olefin resin and promote good dispersion of the olefin resin and fusion with the polyamide. Is.
The vulcanization temperature is preferably set higher than the melting point of the olefin resin by 3 ° C. or more. This is because if the temperature is raised to 3 ° C. or higher, the olefin resin is easily dispersed and fused to the polyamide.

In the rubber composition of the present invention, the diene rubber and the polyamide are chemically bonded, and the olefin resin is fused to the polyamide. By combining the improvement of the fatigue property and the improvement of the anisotropy, which is a characteristic of the olefin resin, the anisotropy is high, and the fatigue property and the low heat generation property are excellent. Therefore, by appropriately adjusting the compounding amounts of polyamide, olefin resin, carbon black, sulfur, vulcanization accelerator, etc. to the desired physical properties, belts, carcasses, tire internal members such as beads, treads, sidewalls, etc. It can be suitably used as a tire external member or in various rubber products such as conveyor belts and hoses.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples and the like.

The polyamide fibers [nylon 6 (Ny-6)] and olefin resin [polypropylene (PP)] used in this example are various types shown in Tables 1 and 2 below. The melting point was measured by the following method. (Measurement of melting point) Suggested thermal analyzer DS by Seiko Instruments Inc.
Using C200, the temperature rise rate is 10 ° C / min.
The temperature was raised in the temperature range up to 50 ° C., and the melting point temperature was measured from the obtained endothermic peak.

[0019]

[Table 1]

[0020]

[Table 2]

Examples 1 to 5 and Comparative Examples 1 to 12 100 parts by weight of natural rubber and N- (3-methacryloyloxy-)
2-hydroxypropyl) -N'-phenyl-P-phenylenediamine [trade name "Nocrac G-1", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.] 1.0 part by weight was kneaded, and then the molecular weight was 300,000 and the melting point was 220. 6-Nylon resin 50 ℃
50 parts by weight of polypropylene resin having a melting point of 160 ° C. and kneading for 7 minutes, and the kneading temperature becomes 232 ° C.,
6-nylon was melted, then 2 parts by weight of novolak type phenol formaldehyde initial condensate was added, and 0.2 part by weight of hexamethylenetetramine was further added to obtain a masterbatch. Then, the master batch was stretched by an extruder to obtain a short fiber polyamide / olefin resin reinforced rubber master batch. In this masterbatch, the compounding amounts of polyamide (6-nylon) and olefin resin (polypropylene) can be appropriately adjusted by further kneading with a diene rubber in a Banbury mixer. Further, by changing the average particle size of the polyamide powder used, the average diameter (D) and length (L) of the polyamide (6-nylon) in the masterbatch were obtained as shown in Table 1. In addition, olefin resins having different melting points shown in Table 2 were used.

Next, the reinforced rubber masterbatch was blended with the compounding agents shown in Tables 3 and 4 below in a Banbury mixer to prepare various rubber compositions, which were vulcanized to have an orientation direction 50% modulus (M _50p). ), 50% modulus in the vertical direction of orientation (M _50V ), anisotropy (M _50p / M _50V ), exothermicity (Tanδ), cyclic fatigue resistance (dynamic creep), fracture limit Tb (p), Tb (v) Was evaluated. The results are shown in Tables 3 and 4 below.

The above 50% modulus (M _50p , M _50V ),
The following methods were used to measure exothermicity (Tan δ), cyclic fatigue (dynamic creep), fracture limit Tb (p), and Tb (v). The fiber blending direction is indicated as p, and the direction perpendicular to the fiber blending direction is denoted as v. (1) 50% modulus (M _50p , M _50V ) According to JIS K 6301, dumbbell No. 3 was used as a sample for measurement. (2) Exothermicity (Tanδ) Exothermicity was evaluated by tanδ. tan δ is 25 ° C under the conditions of dynamic strain of 1.0% and frequency (vibration) of 52 Hz using a mechanical spectrometer manufactured by Rheometrics.
Was measured.

(3) Repeated Fatigue (Dynamic Creep) Initial load 5 kgf / c according to JIS K6301
It was measured at m ² and a dynamic load of 50 kgf / cm ² . (4) Breaking limit Tb (p), Tb (v) Breaking strength was measured according to JIS K 6301.

[0025]

[Table 3]

[0026]

[Table 4]

[Discussion of Tables 3 and 4] Generally, Examples 1 to 5, which are within the scope of the present invention, have anisotropy as compared with Comparative Examples 1 to 12, which are outside the scope of the present invention. (M _50p /
Excellent M _{50 V),} pyrogenic (Tan?) Is low, excellent repeated fatigue resistance (dynamic creep), moreover, breaking limit Tb
It was found that (p) and Tb (v) were large.

When examined individually, Examples 1 and 2
Is the same as the physical properties of the polyamide and the olefin resin and the composition thereof, but when the kneading temperature (final) is 3 ° C. or more higher than the melting point of the olefin resin, that is,
Example 1 is 10 ° C., and Example 2 is 5 ° C. higher. It can be seen that Example 1 having a higher difference from the melting point has higher anisotropy and a larger fracture limit. On the other hand, Comparative Examples 1 to 3
The composition is the same as in Examples 1 and 2, but Comparative Example 1
When the kneading temperature (final) is 5 ° C. lower than the melting point of the olefin resin, and the olefin resin is not sufficiently melted, anisotropy, repeated fatigue resistance, and fracture limit are lowered, which is not preferable. Physical properties (L / D is 7.
8) is low, in particular, the anisotropy is significantly reduced,
In Comparative Example 3, the physical properties of polyamide (average fiber diameter D is 1.
1) was large, and it was found that the repeated fatigue properties were significantly reduced due to the stress concentration generated at the fiber ends.

Example 3 has the same composition as in Examples 1 and 2, but the melting point of the olefin resin is 140 ° C., and the effect of the present invention can be exhibited even at this melting point temperature. found. On the other hand, Comparative Examples 4 to 6
Has the same composition as in Example 3, but Comparative Example 4 has a melting point of the olefin resin lower than 140 ° C. and 120 ° C.
In this case, the exothermicity becomes high, which is not preferable, and Comparative Example 5 is a case where the melting point of the olefin resin is further increased from 140 ° C. to 202 ° C., the exothermicity becomes high, and the repeated fatigue resistance is high. It was not preferable because it was significantly decreased, and Comparative Example 6 was a case where only polyamide was used (no olefin-based resin was blended), and in this case, it was found that the anisotropy was significantly decreased. Further, Comparative Example 7 is a case where only the olefin resin is used (no polyamide is blended), and in particular, it was found that the anisotropy and the repeated fatigue property are significantly reduced.

In Example 4, compared to Examples 1 and 2, the composition of the polyamide and the olefin resin was both 5 parts by weight (from 10 parts by weight). Even with this composition, the effect of the present invention was obtained. It turned out to be able to exert.
On the other hand, Comparative Example 8 was a case where only polyamide was used (the olefin resin was not compounded), and it was found that the repeated fatigue resistance was significantly reduced, and Comparative Example 9 had a polyamide compounding composition of 5%. It was found that the amount was changed from 10 parts by weight to 10 parts by weight, and the olefin resin was not mixed, and in this case, it was found that especially the exothermic property was significantly increased.

Compared to Examples 1 and 2, Example 5 is a case of a high elastic modulus rubber compounding in which the compounding composition of the polyamide and the olefin resin is both 60 parts by weight (from 10 parts by weight). However, it has been found that the effects of the present invention can be exhibited, and in particular, repeated fatigue resistance can be significantly improved. On the other hand, in Comparative Example 10, M _50v is set to be the _{same as} that of Example 5, and since only polyamide (no olefin resin is mixed) is used, the amount of carbon black needs to be increased accordingly (15% by weight). It was found that the heat generation property was increased, the anisotropy was small, and the repeated fatigue property was significantly reduced. In addition, Comparative Examples 11 and 12
Is the case where the compounding ratios of the polyamide and the olefin resin are 10/30 (= 1/3) and 60/20 (= 3), respectively. In Comparative Example 11, it was found that the amount of olefin resin was extremely increased as compared with Example 1, so that the anisotropy and discard limit were small, and the repeated fatigue property was also reduced. In Comparative Example 12, it was found that the amount of polyamide was extremely increased as compared with Example 5, so that the anisotropy was reduced, the heat buildup was increased, and the repeated fatigue property was also lowered.

[0032]

According to the present invention, the diene rubber and the fiber made of the thermoplastic elastomer having an amide group are chemically bonded to each other and the olefin resin is fused to the polyamide. Since the properties of the polyamide fiber, such as break resistance and fatigue properties, and the anisotropy, which is a property of the olefin resin, are improved, the anisotropy is high, and the fatigue property and the low heat buildup property are high. Therefore, it can be suitably used for a tire as an inner member of a tire such as a belt, a carcass, and a bead, a tire as an outer member of a tire such as a tread, a sidewall, or various rubber products such as a conveyor belt and a hose. A rubber composition capable of

Claims (5)

(57) [Claims] 1. A polyamide fiber in an amount of 1 to 100 parts by weight and an olefin resin in an amount of 1 to 100 parts by weight, based on 100 parts by weight of at least one rubber component selected from the group consisting of natural rubber and diene-based synthetic rubber. A reinforcing rubber masterbatch in which the mixing ratio of the polyamide fiber to the olefin resin is 3/7 to 7/3, and the polyamide fiber and the olefin resin do not contain a vulcanization accelerator or a vulcanizing agent and are reinforced. A rubber composition, which is obtained by treating at a final kneading temperature in the kneading stage at a temperature higher than the melting point of the olefin resin by 3 ° C. or more. 2. The rubber composition according to claim 1, wherein the polyamide fiber is nylon 6 and the olefin resin is polypropylene. 3. A polyamide fiber having an average diameter D of 0.1 to 0.1.
1.0 μm, the ratio of the average length L and the average diameter D (L /
The rubber composition according to claim 1, wherein D) is 8 or more. 4. The melting point of the olefin resin is 130 to 20.
The rubber composition according to claim 1, which has a temperature of 0 ° C. 5. The rubber composition according to claim 1, wherein the rubber composition is treated at a vulcanization temperature higher than the melting point of the olefin resin by 3 ° C. or more.