JPH09279043A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition improved in both modulus at low elongation and fatigue resistance. SOLUTION: This composition is obtained by blending at least one kind of organic or inorganic short fibers with a base rubber comprising at least one rubber and a composition wherein fine short fibers of a thermoplastic polymer amide groups on the main chain are dispersed in a matrix comprising a rubber and/or a polyolefin and in such a manner that the fibers are bonded to the matrix.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition having improved modulus at low elongation and fatigue resistance (flexing fatigue resistance).

[0002]

2. Description of the Related Art Generally, a tire member, for example, a bead filler, is made of a rubber composition having a high modulus (tensile stress) and a high elastic modulus at a low elongation, thereby exercising the tire's dynamic performance (driving stability, high-speed durability, etc.). It is well known to make improvements. Various methods have been studied for increasing the modulus and elastic modulus of rubber. As one of them, compounding various short fibers into the rubber is a well-known method. However, although this method can obtain a rubber with a very high modulus, simply blending short fibers does not sufficiently adhere to the rubber, so that fracture easily progresses along the short fiber interface and the fatigue life is short. have.

In order to improve this drawback, various improvements have been proposed in which short fibers and rubber are adhered to each other (JP-A-59-59).
43041, Japanese Patent Publication 1-17494, Japanese Patent Publication 4-33300
Gazette, JP-A-7-278360, etc.). However, the polyamide-based short fibers described therein do not have such a large reinforcing effect (especially in the low elongation region), so that the compounding amount must be increased in order to obtain a desired modulus and elastic modulus. However, there is a problem that the fatigue life of the rubber composition is eventually deteriorated.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rubber composition having improved modulus and fatigue resistance at low elongation.

[0005]

Means for Solving the Problems The rubber composition of the present invention comprises:
A thermoplastic rubber having an amide group in the main chain is dispersed as fine short fibers (b) in a base rubber (A) composed of one or more rubbers and a matrix composed of rubber and / or polyolefin, Further, the composition (B) in which the short fibers (b) are bonded to the matrix is blended with one or more kinds of organic or inorganic short fibers (C).

As described above, since the composition (B) in which the short fibers (b) are bound to the matrix and the organic or inorganic short fibers (C) are used for the base rubber (A), low elongation It is possible to achieve both modulus and fatigue resistance.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Base rubber (A) Consists of one or more kinds of rubber. The rubber is not particularly limited, but examples thereof include diene rubber and hydrogenated products thereof (for example, natural rubber (NR), polyisoprene rubber (IR), epoxidized natural rubber, styrene-butadiene copolymer rubber (SBR)). ), Polybutadiene rubber (high cis BR and low cis B
R), NBR, hydrogenated NBR, hydrogenated SBR), various elastomers such as olefin rubbers (eg ethylene propylene rubber (EPRM, EPM), maleic acid modified ethylene propylene rubber (M-EPM), butyl rubber (IIR) , Isobutylene and aromatic vinyl or diene monomer copolymer), halogen-containing rubber (for example, brominated butyl rubber,
Chlorinated butyl rubber, bromide of isobutylene paramethylstyrene copolymer (Br-IPMS), chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid modified chlorinated polyethylene (M-CM)), thermoplastic Examples thereof include elastomers (for example, styrene-based elastomer, olefin-based elastomer, ester-based elastomer) and the like. A composition in which a thermoplastic polymer having a main chain amide group is dispersed as fine short fibers (b) in a matrix composed of rubber and / or polyolefin, and the short fibers (b) are bonded to the matrix. Material (B) Examples of this composition (B) include the following (i), (ii),
(iii) can be mentioned. Short fiber (b) is 0.0
It is preferable to have an average diameter of 5 to 5.0 μm. (I) Fine short fiber 1 of thermoplastic polymer having amide group in polymer molecule in 100 parts by weight of vulcanizable rubber 1
To 100 parts by weight are embedded, and the polymer and the vulcanizable rubber are grafted at the interface of the fiber through an initial condensation product of a novolac type phenol formaldehyde resin (specifically, Kaisho 59-43
041 publication). The initial condensate of novolac type phenol formaldehyde resin is, for example, sulfuric acid, hydrochloric acid,
Using acids such as phosphoric acid and oxalic acid as catalysts, phenol,
It is a soluble and fusible resin obtained by subjecting phenols such as bisphenols and formaldehyde (may be paraformaldehyde) to a condensation reaction, and a modification (modified product) thereof. (ii) A fiber-reinforced thermoplastic composition in which thermoplastic polyamide is finely dispersed in a matrix composed of a polyolefin and an elastomer, and the fine fibers are bonded to the matrix through a silane coupling agent (special (See Kaihei 7-278360).

Specific examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrioxysilane such as vinyltriethoxy (β-methoxyethoxy) silane, vinyltriacetylsilane, and γ-methacryloxypropyltrisilane. Methoxysilane,
γ- [N- (β-methacryloxyethyl) -N, N-dimethylammonium (chloride)] propylmethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, and styryldiaminosilane, γ-
Ureidopropyltriethoxysilane and the like. (Iii) An average diameter of 0.05 to 100 parts by weight of vulcanizable rubber.
1 to 70 parts by weight of 0.8 μm nylon fine fibers are embedded, and nylon and vulcanizable rubber are graft-bonded at the interface of the fibers through an initial condensation product of a resole-type alkylphenol formaldehyde resin. Reinforced rubber composition (see JP-A-58-79037).

The initial condensate of a resol type alkylphenol formaldehyde resin is, for example, a resol type initial condensate obtained by reacting an alkylphenol such as cresol with formaldehyde or atcealdehyde in the presence of an alkali catalyst and a modified product thereof. Can be mentioned. In particular, as the alkylphenol formaldehyde resin, one having two or more methylol groups in the molecule can be preferably used. (iv) Vulcanizable rubber according to the above (i) and (iii),
The elastomer in (ii) above is the same as the rubber constituting the base rubber (A). Examples of the thermoplastic polymer having an amide group in (i) above and the thermoplastic polyamide in (ii) above include thermoplastic polyamide and urea resin. Among these, those having a melting point of 135 ° C to 350 ° C are preferable, and those having a melting point of 150 ° C are particularly preferable.
An example is a thermoplastic polyamide at 300 ° C.

As the thermoplastic polyamide, nylon 6, nylon 66, nylon 6-nylon 66 copolymer, nylon 610, nylon 612, nylon 46,
Nylon 11, Nylon 12, Nylon MXD6, Polycondensate of xylylenediamine and adipic acid, Polycondensate of xylylenediamine and pimelic acid, Polycondensate of xylylenediamine and speric acid, Xylylenediamine and azelaine Polycondensate with acid, xylylenediamine with sebacic acid, tetramethylenediamine with terephthalic acid, hexamethylenediamine with terephthalic acid, octamethylenediamine with terephthalic acid , Polycondensate of trimethylhexamethylenediamine and terephthalic acid, polycondensate of decamethylenediamine and terephthalic acid, polycondensate of undecamethylenediamine and terephthalic acid, polycondensate of dodecamethylenediamine and terephthalic acid, tetramethylenediamine And polyphthalic acid Polycondensate of diamine and isophthalic acid, Polycondensate of octamethylenediamine and isophthalic acid, Polycondensate of trimethylhexamethylenediamine and isophthalic acid, Polycondensate of decamethylenediamine and isophthalic acid, Undecamethylenediamine and isophthalic acid Examples thereof include polycondensates of acids and polycondensates of dodecamethylenediamine and isophthalic acid.

Among these thermoplastic polyamides, a particularly preferable one is a thermoplastic polyamide having a melting point of 160 to 265 ° C., specifically nylon 6 and nylon 6
6, nylon 6-nylon 66 copolymer, nylon 61
0, nylon 612, nylon 46, nylon 11, nylon 12 and the like. The polyolefin in (ii) above has a melting point of 80 to 250 ° C. Further, those having a softening point of 50 ° C. or higher, particularly those having a softening point of 50 to 200 ° C. are preferably used. Examples of such polyolefins include homopolymers and copolymers of olefins of C ₂ -C _8, and, olefin and styrene and chlorostyrene of C ₂ -C _8, such as α- methylstyrene and an aromatic vinyl compound copolymers, copolymers of olefin and vinyl acetate C ₂ -C _8, a copolymer of an olefin with acrylic acid or its esters of _{C 2 ~C 8, C 2 ~C} 8
Or the olefin and methacrylic acid olefin copolymers and their esters, and copolymers of an olefin and a vinyl silane compound of C ₂ -C ₈ can be mentioned as preferable for use. Specifically, for example, high-density polyethylene, low-density polyethylene, polypropylene, ethylene / propylene block copolymer, ethylene-propylene random copolymer, linear low-density polyethylene, poly-4-methylpentene-1, polybutene-1, Polyhexene-1, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene /
Propyl acrylate copolymer, ethylene / butyl acrylate copolymer, ethylene / 2-ethylhexyl acrylate copolymer, ethylene / hydroxyethyl acrylate copolymer, ethylene / vinyltrimethoxysilane copolymer, ethylene vinyltri Examples include ethoxysilane copolymer, ethylene / vinylsilane copolymer, ethylene / styrene copolymer, and propylene / styrene copolymer.
Further, halogenated polyolefins such as chlorinated polyethylene, brominated polyethylene, chlorosulfonated polyethylene are also preferably used. These polyolefins are 1
You may use only 1 type and may combine 2 or more types. Organic or Inorganic Short Fibers (C) Organic fibers are, for example, polyester fibers, polyvinyl alcohol fibers (vinylon fibers) nylon fibers, cotton fibers, silk fibers, hemp fibers, wool fibers, cellulose fibers, Syn-
1,2-polybutadiene fine crystals, aromatic polyamide fibers (aramid fibers), rayon fibers, wholly aromatic polyester fibers (polyarylate fibers), heterocycle-containing aromatic fibers (eg polyparaphenylene benzbisoxazole fibers, polyparaphenylene) Benzbisthiazole fiber)
And the like.

Examples of the inorganic fibers include metal fibers (chopped wires, etc.), titanium dioxide, alkali metal titanate crystals, glass fibers, boron, carbon fibers, silicon carbide whiskers and the like. Moreover, as the short fibers (C), it is preferable to use short fibers that are fibrillated in rubber. Examples of the fibrillated short fiber include polyvinyl alcohol fiber (vinylon fiber), cotton fiber, hemp fiber, cellulose fiber, aromatic polyamide fiber (aramid fiber), wholly aromatic polyester fiber (polyarylate fiber), and heterocyclic ring. Aromatic fibers (for example, polyparaphenylenebenzbisoxazole fiber, polyparaphenylenebenzbisthiazole fiber) and the like can be mentioned.

Among these fibrillated fibers, polyvinyl alcohol fibers are more preferable in terms of cost and affinity with rubber. The total amount of the short fibers (b) and the short fibers (C) is preferably 1 to 50 parts by weight based on 100 parts by weight of the total rubber component. If the amount of short fibers is less than 1 part by weight, the reinforcing effect cannot be exerted, and if it is more than 50 parts by weight, the viscosity of the rubber remarkably increases, workability deteriorates, and processing becomes difficult, which is not preferable. Also, the weight composition ratio of (b) and (C) (b) /
(C) is preferably 9/1 to 1/9. The rubber composition of the present invention, if necessary, carbon black, zinc white,
A compounding agent such as oil can be appropriately mixed.

FIG. 1 shows stress (modulus) -elongation curves of rubber compositions having various compositions. In FIG. 1, “x” indicates a rubber composition containing no short fibers, and “◯” indicates a case where the composition (B) is added to the rubber composition (short fibers (b) per 100 parts by weight of all rubber components). 5 parts by weight), "△" indicates the case where short fibers to be fibrillated are mixed in this rubber composition (5 parts by weight of short fibers to 100 parts by weight of all rubber components), and "●" indicates this rubber composition. In the case of a hybrid composition in which both the composition (B) and short fibers to be fibrillated are mixed (2.5 parts by weight of short fibers (b) and 2.5 parts by weight of fibrillated short fibers to 100 parts by weight of all rubber components). Part), respectively.

As can be seen from FIG. 1, in the case of "x", the whole modulus including low expansion is low, in the case of "○", the modulus at low expansion is not so high, and in the case of "△". The modulus at low elongation increases, but the yield point occurs, and the modulus in the subsequent expansion region drops sharply. On the other hand, in the case of the hybrid composition such as the rubber composition of the present invention, the defects in the cases of “◯” and “Δ” can be compensated, as can be seen from “●”.

[0016]

[Example] A masterbatch was prepared by mixing a vulcanization accelerator and raw materials other than sulfur among the components (parts by weight) shown in Tables 1 to 3 in a closed mixer. The mixing time was 3.5 minutes and the discharge temperature was 160 ° C. The remaining compounding ingredients were added to this masterbatch with an open roll to prepare an unvulcanized rubber composition. The obtained unvulcanized rubber composition was heated under pressure in a mold at 160 ° C. for 20 minutes to prepare vulcanized rubber test pieces (Examples 1 to 7 and Comparative Examples 1 to 8).

With respect to this test piece, 10% modulus, 100% modulus, dynamic elastic modulus E ', and flex fatigue resistance were measured as follows. The results are shown in Tables 1-3.
In Tables 1 to 3, NR represents natural rubber, Ny represents nylon, and PE represents polyethylene. 10% modulus, 100% modulus : Tensile tests were carried out at room temperature according to JIS K6251 (using dumbbell No. 3) using the obtained test pieces to obtain 10% and 100% deformation modulus. Dynamic elastic modulus E ′ : Rheograph solid manufactured by Toyo Seiki Co., Ltd., pre-stretching 5%, dynamic strain of ± 1% at 20 Hz, 60 ° C.
A viscoelasticity test was carried out to determine the dynamic elastic modulus E '. Bending fatigue resistance : A bending crack growth test was performed according to JIS K6260. A scratch having a length of 2 mm was preliminarily attached to the center of the test sample, a displacement amount of 26% was applied, and bending was performed 300 times per minute, and the number of bendings until the scratch reached a certain length was measured. The index in the table is expressed by the logarithmic ratio of the number of flexing times, and the larger the value is, the better the flexing fatigue resistance is.

[0018]

[Table 1] In Table 1, Comparative Example 1 is a case where the short fibers are not blended (standard). Comparative Examples 2 and 3 are cases where only the short fiber reinforcing composition was blended, and the 100% modulus was large but the 10% modulus was small.

Comparative Example 4 is a case where only the cellulose short fibers are blended, and the 10% modulus is large, but the 100% modulus is small because the yield point is shown. Examples 1, 2
Is a case where a short fiber reinforcing composition and a short cellulose fiber are blended, and the balance of modulus and E ′ is improved,
In addition, the fatigue resistance is better than that of the plain mixture containing the same amount.

[0020]

[Table 2] In Table 2, Comparative Examples 5 and 6 are plain blends of short fiber reinforcing compositions containing a polyolefin in the matrix, and also have a large 100% modulus but a small 10% modulus.

Comparative Example 7 is a case where the vinylon short fiber alone is blended, and although the 10% modulus is large, the 100% modulus is small because the yield point is exhibited. Examples 3 to 5 are cases where the short fiber reinforcing composition and vinylon short fibers are blended, the balance of modulus and E ′ is improved, and the fatigue resistance is better than that of the plain mixture of the same amount.

[0022]

[Table 3] In Table 3, Comparative Example 8 is a case of aramid short fiber alone blending, and although the 10% modulus is large, the 100% modulus is small because it shows a yield point. In Examples 6 and 7,
This is a case in which a short fiber reinforcing composition and an aramid short fiber are blended, the balance of modulus and E ′ is improved, and the fatigue resistance is better than that of the plain mixture of the same amount.

[0023]

As described above, the rubber composition of the present invention comprises the base rubber (A) composed of one or more kinds of rubber and the matrix composed of rubber and / or polyolefin,
The composition (B) in which the thermoplastic polymer having an amide group in the main chain is dispersed as fine short fibers (b), and the short fibers (b) are bound to the matrix is an organic or inorganic composition. Since one or more kinds of short fibers (C) are blended, both modulus and fatigue resistance at low elongation can be improved. Therefore, this rubber composition can be suitably used for tire members such as bead filler, belt layer coat rubber, sidewalls, and undertread.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing stress (modulus) -elongation curves in the case of various formulations.

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Claims (6)

[Claims] 1. A base rubber (A) comprising one or more rubbers.
A thermoplastic polymer having an amide group in the main chain is dispersed as fine short fibers (b) in a matrix composed of rubber and / or polyolefin, and the short fibers (b) are bonded to the matrix. Composition (B)
A rubber composition comprising at least one organic or inorganic short fiber (C). 2. The short fiber (b) in the composition (B) is at least one selected from a silane coupling agent, an initial condensate of a resol type phenol formaldehyde resin and an initial condensate of a novolac type phenol formaldehyde resin. The rubber composition according to claim 1, which is bonded to the matrix through a kind. 3. The short fibers (b) in the composition (B) have an average diameter of 0.05 to 5.0 μm.
The rubber composition as described in the above. 4. The total amount of the short fibers (b) and the short fibers (C) is 1 to 50 with respect to 100 parts by weight of the total rubber component.
And the weight composition ratio of (b) and (C) (b)
The rubber composition according to any one of claims 1 to 3, wherein / (C) is 9/1 to 1/9. 5. The rubber composition according to any one of claims 1 to 4, wherein the polyolefin in the composition (B) has a softening point of 50 ° C or higher or a melting point in the range of 80 to 250 ° C. 6. The short fibers (C) are short fibers that are fibrillated in rubber and have an average length of 1.0 to 5000 μm.
m, and the average diameter after fibrillation is 0.05 to 50 μm.
The rubber composition according to claim 1, wherein the rubber composition is m.