JP2000044730A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition having excellent processability during molding and giving a product being excellent in properties such as tensile strength and abrasion resistance and having a low loss tangent by incorporating an elastomer having organic salt structures as side chains with a solid rubber. SOLUTION: It is desirable that the starting material for the elastomer is a liquid rubber having a weight-average molecular weight of 1,000-80,000, the organic salt structure is an onium salt structure and is a linear alkyl, and the weight ratio of the elastomer to the solid rubber, (the starting material for the elastomer)/(solid rubber), is 2/98 to 60/40. A cation which forms the organic salt structure is exemplified by ammonium, and an anion is exemplified by a halide ion. An onium salt structure, especially, a combination of ammonium with a carboxylate anion is desirable. An example of a combination of the elastomer-forming material with a compound is a carboxyl-modified liquid isoprene rubber with stearylamine. This composition can be desirably used for e.g. automobile tire treads.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition obtained by crosslinking a mixture of an elastomer having an organic salt structure in a side chain and a solid rubber, and more particularly to processability and tensile strength during molding, and abrasion resistance. The present invention relates to a rubber composition having excellent properties and other physical properties and having a small loss tangent (tan δ).

[0002]

2. Description of the Related Art Conventionally, rubber compositions for tires have been
There is known a method of blending a liquid polyisoprene rubber with a diene rubber to reduce the viscosity and improve the workability during molding (Japanese Patent No. 2727228).
On the other hand, Japanese Patent No. 2710263 discloses a method for improving grip properties of a tire by blending a liquid polyisoprene rubber having a hydroxyl group and / or a liquid polybutadiene rubber having a hydroxyl group with the rubber. Further, Japanese Patent No. 2710264 discloses a method of improving loss tangent (tan δ) and improving driving stability of an automobile by blending liquid polyisoprene with rubber. However, when a liquid polyisoprene rubber or the like is blended with the tire rubber as described above, the tensile strength and abrasion resistance are reduced, the loss tangent (tan δ) becomes too large, and the tire generates heat due to friction. However, there is a problem that the size becomes large.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a rubber composition which is excellent in processability and tensile strength during molding, has excellent wear resistance and other physical properties, and has a small loss tangent (tan δ). It is an object of the present invention to provide a tire suitably used for a tire or the like.

[0004]

That is, the present invention provides a rubber composition containing an elastomer having an organic salt structure in a side chain and a solid rubber.

[0005] The elastomer is an elastomer having an organic salt structure in a side chain.

In a preferred embodiment, the raw material of the elastomer is a liquid rubber.

It is preferable that the weight average molecular weight of the raw material of the elastomer is from 1,000 to 80,000.

Preferably, the organic salt structure is an onium salt structure.

It is preferable that the organic salt structure is an organic salt structure having a chain alkyl group.

The weight ratio of the elastomer to the solid rubber is (the raw material of the elastomer in the elastomer) /
(Solid rubber) = 2/98 to 60/40 is preferable.

[0011] The present invention also provides a rubber composition for tires containing the rubber composition.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The present invention is a rubber composition containing an elastomer having an organic salt structure in a side chain and a solid rubber. If necessary, the rubber composition of the present invention can be used as a crosslinked and cured rubber composition. In the present invention, the organic salt structure is a structure having an ion-binding portion (moiety) in which a functional group-modified product of a polymer constituting an elastomer and a functional group of a compound are bonded via an ionic bond. It refers to those without metal ions. Ionic bonds refer to bonds formed by electrostatic attraction between cations and anions. In the present invention, the organic salt structure is formed by cations and anions other than metal ions.

The elastomer having an organic salt structure in the side chain used in the present invention is obtained by modifying the raw material of this elastomer with a compound having a reactive site capable of generating a cation or a reactive site capable of generating an anion. The mixture is reacted with a compound capable of generating ions to form an organic salt structure on a side chain.

The raw material of the elastomer preferably has a weight average molecular weight of 1,000 to 80,000. This is because when the content is in the above range, the workability and physical properties at the time of molding are well balanced.

It is a preferred embodiment that the raw material of the elastomer is liquid rubber. This is because the rubber composition of the present invention is easily mixed during synthesis of an elastomer having an organic salt structure in a side chain and has excellent workability, and the rubber composition of the present invention has low viscosity and excellent processability during molding.

Cations forming the organic salt structure include:
There is no particular limitation as long as it is other than a metal ion.
Nium ions are preferred. Onium ions are non-shared
Proton or cation type reagent
Generated by coordination, for example, ammonium
([R_ThreeNR ']⁺, R is a proton or other cation
(The same applies hereinafter)), phosphonium ([R_ThreePR ']⁺),
Arsonium ([R_ThreeAsR ']⁺), Stibonium
([R_ThreeSbR ']⁺), Oxonium ([R_TwoOR
´]⁺), Sulfonium ([R_TwoSR ']⁺), Seleno
([R_TwoSeR '] ⁺), Stanonium ([R_Two
SnR ']⁺), Iodonium ([RIR ']⁺)
I can do it.

The anions forming the organic salt structure include:
Although not particularly limited, examples include a halide ion, a carboxylate anion, an alcoholate anion, a phenolate anion, a thiocarboxylate anion, and a sulfonate anion.

In the present invention, the organic salt structure is not particularly limited, and can be appropriately selected from the above-mentioned cations and anions in combination. As described above, the structure in which the cation is the above-mentioned onium ion, , An onium salt structure is preferred, and an organic salt structure comprising a combination of ammonium and a carboxylate anion is particularly preferred.

The elastomer having an organic salt structure in the side chain used in the present invention is formed from an elastomer material having a reaction site capable of forming an ionic bond in the side chain and an ionic bond with the reaction site of the elastomer material. And a compound having a reactive site through an ionic bond.
That is, the elastomer used in the present invention comprises a raw material of an elastomer having a reactive site capable of generating one of a cation and an anion in a side chain, and a compound having a reactive site capable of generating the other. The reactive site capable of generating a cation is not particularly limited, and examples thereof include a site containing an atom having an unshared electron pair such as an amino group and an imino group. The reaction site that can generate an anion is not particularly limited. For example, halides (fluoride, chloride, bromide, iodide, astatine), carboxyl groups,
Hydroxyl group, phenoxy group, thiocarboxyl group,
Sulfonyl groups and substituents thereof are mentioned.

As a raw material of the elastomer having a reaction site capable of forming an ionic bond in the side chain, a modified or synthesized elastomer having a reaction site capable of generating a cation or a reaction site capable of generating an anion is used. Can be used. Elastomers to be modified include ordinary rubber (including liquid rubber), thermoplastic elastomer,
Thermoset elastomers are included. Specifically, diene rubbers and hydrogenated products thereof (for example, natural rubber, epoxidized natural rubber, isoprene rubber, styrene-butadiene rubber, hydrogenated styrene-butadiene rubber, butadiene rubber (high cis-butadiene rubber, low cis-butadiene rubber) Rubber), acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber), olefin rubber (for example, ethylene-propylene rubber, ethylene-propylene-diene rubber, maleic acid-modified ethylene-propylene rubber, butyl rubber, isobutylene and aromatic vinyl or diene) Copolymer with acrylic monomer, acrylic rubber, ionomer), halogen-containing rubber (for example, brominated butyl rubber, chlorinated butyl rubber, bromide of isobutylene-paramethylstyrene copolymer, chloroprene rubber, hydroringo) , Chlorosulfonated polyethylene, chlorinated polyethylene, maleic acid-modified chlorinated polyethylene), silicone rubber (e.g., methylvinyl silicone rubber, methylphenyl vinyl silicone rubber), sulfur-containing rubbers (for example,
Polysulfide rubber), fluorine rubber (for example, vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, fluorine-containing phosphazene rubber), urethane rubber, liquid polyisoprene, liquid polybutadiene, liquid 1,2-
Polybutadiene, liquid styrene-butadiene rubber, liquid polychloroprene, liquid silicone rubber, liquid fluororubber, thermoplastic elastomer (for example, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylenebutylene-styrene block copolymer) Styrene-based elastomers, olefin-based elastomers, ester-based elastomers, urethane-based elastomers, polyamide-based elastomers, polyvinyl chloride-based elastomers), and thermosetting elastomers (for example, urethane-based elastomers and silicone-based elastomers).

Examples of the elastomer modified so as to have a reaction site capable of generating an anion include a low-modified carboxyl liquid isoprene rubber, a high-modified carboxyl liquid isoprene rubber, a carboxyl-terminated butadiene rubber, a carboxyl-terminated nitrile rubber, a carboxyl-modified polybutane, and a carboxyl-modified polybutane Highly reactive polybutene, ethylene-acrylic acid copolymer and the like can be mentioned. Among them, highly modified carboxyl liquid isoprene rubber is preferred. As a method for synthesizing the above-mentioned carboxyl group-containing elastomer, for example, a toluene solution containing a diene rubber such as butadiene rubber and mercaptoacetic acid at room temperature under a nitrogen atmosphere,
The mixture is stirred for 1 hour, the reaction mixture is precipitated in methanol, and dried under reduced pressure, whereby a diene rubber having a carboxyl group can be obtained.

As the compound having a reactive site capable of forming an ionic bond, the above-described compound having a reactive site capable of generating a cation or a reactive site capable of generating an anion can be used.

In the present invention, the organic salt structure is preferably an organic salt structure having a chain alkyl group. That is,
The compound having a reactive site capable of forming an ionic bond preferably has a linear alkyl group at the reactive site capable of generating a cation or an anion. Among them, a chain alkyl group having 6 or more carbon atoms is preferable. This is because, at room temperature, chain alkyl chains are regularly arranged at room temperature to form a pseudo-crosslinked structure by ion-bonding with a raw material of the elastomer, so that the rubber tends to be formed. As the compound having a reactive site capable of generating a cation, a primary amine is preferable, and methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine having a chain alkyl group,
Heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, cetylamine, stearylamine and the like can be suitably used.

Suitable specific examples of the combination of the raw material and the compound of the elastomer include a carboxyl-modified liquid isoprene rubber and stearylamine.

The ratio of the raw material of the elastomer to the compound in the elastomer having an organic salt structure in the side chain used in the present invention is such that the amount of the ionic compound in the compound per one equivalent of a reactive site capable of forming an ionic bond in the raw material of the elastomer is used. Preferably, the number of reactive sites capable of forming a bond is 0.1 to 5 equivalents,
More preferably, the amount is 0.5 to 1.5 equivalents. If it exceeds 5 equivalents, or if it is less than 0.1 equivalent, the number of reaction sites not involved in ionic bonding increases, and the crosslinking efficiency deteriorates.

In the elastomer having an organic salt structure in the side chain used in the present invention, other additives such as various stabilizers, a flame retardant, an antistatic agent, and a coloring agent are provided as long as the object of the present invention is not impaired. , Fillers and the like can be added during or after production.

The method for producing the elastomer having an organic salt structure in the side chain used in the present invention is not particularly limited.
For example, a method in which melt kneading is performed under heating to about 120 ° C. using a twin-screw extruder, a Banbury mixer, a kneader, or the like and a raw material, a compound of the elastomer, and other additives as necessary, can be used.

In the present invention, the solid rubber mixed with the elastomer having an organic salt structure in the side chain is not particularly limited, and examples thereof include diene rubbers and hydrogenated products thereof (for example, natural rubber, epoxidized natural rubber, Isoprene rubber,
Styrene-butadiene rubber, hydrogenated styrene-butadiene rubber, butadiene rubber (high cis-butadiene rubber, low cis-butadiene rubber), acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber), olefin rubber (for example, ethylene-propylene rubber, Ethylene-propylene-diene rubber, maleic acid-modified ethylene-propylene rubber, butyl rubber, copolymer of isobutylene with aromatic vinyl or diene monomer, acrylic rubber, ionomer), halogen-containing rubber (for example,
Brominated butyl rubber, chlorinated butyl rubber, isobutylene
Bromide of paramethylstyrene copolymer, chloroprene rubber, hydrin rubber, chlorosulfonated polyethylene,
Chlorinated polyethylene, maleic acid-modified chlorinated polyethylene), silicone rubber (for example, methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber), sulfur-containing rubber (for example, polysulfide rubber), fluorine rubber (for example, vinylidene fluoride-based rubber, Fluorine vinyl ether rubber, fluorine-containing phosphazene rubber), urethane rubber, thermoplastic elastomer (for example, styrene-
Butadiene-styrene block copolymer, styrene-
Isoprene-styrene block copolymer, styrene-
Styrene-based elastomer such as ethylene-butylene-styrene block copolymer, olefin-based elastomer, ester-based elastomer, urethane-based elastomer, polyamide-based elastomer, polyvinyl chloride-based elastomer), thermosetting elastomer (for example, urethane-based elastomer, silicone-based elastomer) Is mentioned.

The combination of the elastomer having an organic salt structure in the side chain and the solid rubber is not particularly limited, but is preferably a combination of those having similar polarities in terms of affinity. A combination in which the raw material of the elastomer and the solid rubber are the same is more preferable.

The weight ratio of the elastomer having an organic salt structure in the side chain to the solid rubber is preferably such that (the raw material in the elastomer) / (solid rubber) = 2/98 to 60/40. When the amount of the elastomer having an organic salt structure in the side chain is less than the above range, the effect of improving workability and abrasion resistance at the time of molding is small, and when the amount is large, the tensile strength is small and the loss tangent (tan δ) is large. There is. In particular, it is preferable that the weight ratio is (raw material in the elastomer) / (solid rubber) = 10/90 to 30/70.

In the rubber composition of the present invention, a cured product is obtained by crosslinking an elastomer having an organic salt structure in a side chain with a solid rubber. Crosslinking is performed by sulfur, organic sulfur-containing compounds such as tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), dipentamethylenethiuram disulfide (DPTD), organic peroxides such as dicumyl peroxide, zinc white, magnesia, etc. May be performed by a method using a crosslinking agent such as a metal oxide or quinone dioxime, or by a method not using a crosslinking agent such as thermal crosslinking. In the cured product of the rubber composition of the present invention, so-called co-crosslinking has occurred, and between the molecules of the elastomer and the solid rubber having an organic salt structure in the side chain and between the molecules of both are crosslinked. . In addition, between the molecules of the elastomer having an organic salt structure in the side chain, a pseudo-crosslinked structure is formed by a portion having the organic salt structure, for example, a chain alkyl group, in addition to the above-described crosslinking. Due to this pseudo-crosslinked structure, tensile strength, abrasion resistance and other physical properties are excellent, and the loss tangent (ta)
nδ) becomes smaller.

The method for producing the rubber composition of the present invention is not particularly limited. An elastomer having an organic salt structure in a side chain,
A method of kneading the solid rubber and, if necessary, other additives with a twin-screw extruder, a Banbury mixer, a kneader or the like can be used. It is preferable to perform the kneading under heating because the viscosity decreases and the dispersion becomes more uniform. Further, in the above method, in place of the elastomer having an organic salt structure in a side chain, a raw material of the elastomer,
That is, the rubber composition of the present invention can be obtained by using a raw material of an elastomer having a reactive site capable of generating one of a cation or an anion in a side chain and a compound having a reactive site capable of generating the other. That is, an elastomer having a reactive site capable of generating one of a cation or an anion in a side chain,
By kneading a compound having a reaction site capable of generating the other, solid rubber and other additives as necessary, using a twin-screw extruder, a Banbury mixer, a kneader, or the like,
The rubber composition of the present invention can be obtained.

The rubber composition of the present invention is excellent in tensile strength, abrasion resistance and other physical properties, and has a small loss tangent (tan δ), so that it can be suitably used for tire treads for automobiles and the like.

[0034]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. <Preparation of Rubber Composition> Using the following raw materials, various rubber compositions shown in Table 1 were prepared at the ratios shown in Table 1. Crosslinking was performed at 160 ° C. for 20 minutes. (1) Elastomer Isoprene: Nipol IR-2200, manufactured by Zeon Corporation Carboxylic acid-modified liquid polyisoprene: Claprene LI
R-410, manufactured by Kuraray Co., Ltd., weight average molecular weight 2500
0, carboxylic acid content 10 / molecule, Tg-59
C. Elastomer 1: To 36.52 g of carboxylic acid-modified liquid isoprene rubber 1 (Claprene LIR-410), 5.07 g (18.8 mmol) of stearylamine was added,
After heating and stirring at 100 ° C. for 2 hours to confirm that a homogeneous solution was obtained, the elastomer obtained by being allowed to stand overnight was found to have an onium salt structure introduced into its side chain by measurement of ¹ H NMR spectrum and IR spectrum. Liquid polyisoprene containing 14 parts by weight of stearylamine with respect to 100 parts by weight of the carboxylic acid-modified liquid isoprene rubber 1: liquid polyisoprene: Claprene LIR-30, manufactured by Kuraray Co., Ltd., weight average molecular weight 29000, Tg -63 ° C (2) Compounding agent Carbon black: Show black N339HAF, manufactured by Showa Cabot Co., Ltd. Zinc flower: Zinc flower, manufactured by Toho Zinc Co., Ltd. Stearic acid: Beads stearic acid, manufactured by NOF Corporation Antioxidant: Santoflex 13, Nippon Monsanto Stearylamine Sulfur Crosslinking accelerator: Noxeller CZ-G Ouchi Shinko Chemical Co., Ltd.

The following tests were performed on the mixture before crosslinking and the obtained various rubber compositions. <Mooney viscosity test> The Mooney viscosity of the mixture before crosslinking was measured using a Mooney viscometer in accordance with JIS K6300. The measurement was performed using an L-shaped rotor under the conditions of a residual heat time of 1 minute, a rotor rotation time of 4 minutes and a temperature of 100 ° C. <Tensile test> JIS for various rubber compositions obtained
According to K6251, tensile strength, elongation and 10
0% elongation and at 300% elongation at a tensile stress (M ₁₀₀ and M ₃₀₀₎ was measured. <Measurement of loss tangent (tan δ)> The obtained various rubber compositions were cut into strip-shaped test pieces having a width of 5 mm, a length of 40 mm, and a thickness of 2 mm, and were subjected to a mechanical impedance method (JIS H70).
No. 02) was measured for the loss tangent (tan δ). Measurements at 20 Hz, ± 2% amplitude, 0 ° C, 20 ° C,
Performed at 40 ° C. and 60 °. <Wear test> The obtained rubber compositions were tested according to JIS.
A Lambourn abrasion test was performed according to K6264. The test was carried out under a load of 1.5 kg and a slip ratio of 50%. The results are shown as relative values with the value of the wear resistance index of Comparative Example 1 being 100. <Immersion Test> With respect to the obtained various rubber compositions, the mass ratio of the extract (toluene extraction amount) [%] was determined by a Soxhlet extraction test using toluene as a solvent.

The results are shown in Table 1.

[Table 1]

The rubber composition of the present invention (Examples 1 to 3)
The case where the elastomer 1 is not blended with the solid rubber (Comparative Example 1) and the case where the same amount of the carboxylic acid-modified liquid polyisoprene or liquid isoprene as the amount of the elastomer raw material of the elastomer 1 is blended with the solid rubber (Comparative Examples 2 to 4) In comparison, it can be seen that the Mooney viscosity before cross-linking is small and the workability is excellent. Similarly, it can be seen that the rubber composition of the present invention is excellent in tensile strength, elongation and modulus, and has a small loss tangent (tan δ) at each temperature. In addition, when the blending amount of the elastomer 1 is relatively small (Examples 1 and 2), it is understood that the abrasion resistance is excellent, and the extraction amount of toluene is small, so that the solvent resistance is also excellent. These are, in the rubber composition of the present invention, cross-linked between the respective molecules of the elastomer and the solid rubber having an organic salt structure in the side chain and between the two molecules by co-crosslinking, and furthermore, in the side chain. This is presumed to be due to the formation of a pseudo-crosslinked structure between molecules of the elastomer having an organic salt structure (FIGS. 1 and 2).

[0038]

The rubber composition of the present invention is excellent in processability and tensile strength at the time of molding, abrasion resistance and other physical properties, and
Since the loss tangent (tan δ) is small, it is useful in a wide range of applications such as for automobile tires.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state in which an elastomer having an organic salt structure in a side chain is co-crosslinked with a solid rubber, and a pseudo-crosslinking is performed between molecules of the elastomer having an organic salt structure in a side chain. .

FIG. 2 shows an elastomer having an organic salt structure in a side chain,
It is a figure which shows the pseudo crosslinked structure when it consists of carboxylic acid modified liquid isoprene rubber and stearylamine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Rubber composition 2 Pseudo-crosslinked structure formed by elastomer having organic salt structure in side chain

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4J002 AC01W AC01X AC03W AC03X AC06W AC06X AC08W AC08X AC09W AC09X BB15W BB15X BB18W BB18X BB21W BB21X BB24W BB24X BB27W BB27X BD14W 0414 BG27X BB27X CP03X CQ01W CQ01X FD140 GN01

Claims (8)

[Claims] 1. A rubber composition comprising an elastomer having an organic salt structure in a side chain and a solid rubber. 2. The rubber composition according to claim 1, wherein the elastomer is an elastomer having an organic salt structure in a side chain. 3. The rubber composition according to claim 2, wherein the raw material of the elastomer is a liquid rubber. 4. The rubber composition according to claim 2, wherein the raw material of the elastomer has a weight average molecular weight of 1,000 to 80,000. 5. The rubber composition according to claim 1, wherein the organic salt structure is an onium salt structure. 6. The rubber composition according to claim 1, wherein the organic salt structure is an organic salt structure having a chain alkyl group. 7. The weight ratio of said elastomer to said solid rubber is (the raw material of said elastomer in said elastomer) /
(Solid rubber) = 2 / 98-60 / 40.
7. The rubber composition according to any one of 6. 8. A rubber composition for a tire, comprising the rubber composition according to claim 1.