JP6461613B2 - Isobutylene copolymer, rubber composition comprising the same, and crosslinked rubber composition thereof - Google Patents

Description

  The present invention relates to an isobutylene copolymer obtained by hydrosilylating a part of an unsaturated bond portion derived from β-pinene of an isobutylene copolymer containing β-pinene as a comonomer, and the isobutylene copolymer, silica And a rubber composition comprising an unsaturated rubber, and a crosslinked rubber composition thereof.

  An isobutylene copolymer having isobutylene as a main monomer and a compound having two carbon-carbon unsaturated groups as a comonomer is a styrene butadiene copolymer rubber (hereinafter referred to as “SBR”). It is known that a co-crosslinking reaction is started from an unsaturated group (carbon-carbon double bond) that is kneaded with a saturated rubber and then present in the side chain by a subsequent crosslinking treatment. The present applicant has found that an isobutylene copolymer obtained from a vinyl monomer having isobutylene and a cyclic olefin causes a good co-crosslinking reaction with an unsaturated rubber such as a styrene butadiene rubber copolymer (SBR) to deteriorate mechanical properties. In addition, it has been found that the grip characteristics of the tread portion of a tire made of an SBR rubber composition are improved (Patent Documents 1 and 2).

  The present inventors believe that the above effect is because the viscoelastic properties of the polyisobutylene main chain improve the grip properties of the tread portion of the tire and do not deteriorate the mechanical properties due to co-crosslinking of unsaturated groups. Therefore, in the isobutylene copolymer, selection of a comonomer having an unsaturated group in the side chain as a starting point of copolymerization with an unsaturated rubber and development of a method for producing a copolymer containing the comonomer are expected. .

International Publication No. WO2010 / 137655 International Publication WO2011 / 021437

  Based on the fact that β-pinene is excellent in copolymerizability with isobutylene, the present inventors have hydrosilylated a part of β-pinene-derived unsaturated groups of an isobutylene copolymer containing β-pinene as a comonomer. The obtained isobutylene copolymer is found to be excellent in crosslinkability with an unsaturated rubber represented by SBR containing silica (particles) (with a glass transition temperature of 25 ° C. or lower) and in improving viscoelastic properties by crosslinking. The present invention has been completed.

  The first of the present invention relates to an isobutylene copolymer having a structural unit represented by the following formula (1), a structural unit represented by the following formula (2) and / or the following formula (3).

Ｒ１が炭素数１〜５のアルキル基、Ｒ２、Ｒ３は、それぞれ独立に、水素原子または炭素数１〜５のアルキル基、アルコシル基、あるいはフェニル基である。

R1 is an alkyl group having 1 to 5 carbon atoms, and R2 and R3 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an arcosyl group, or a phenyl group.

  The second of the present invention relates to a rubber composition comprising an unsaturated rubber, the isobutylene copolymer according to the first of the present invention, and silica.

  3rd of this invention is related with the crosslinked rubber composition formed by bridge | crosslinking the rubber composition described in 2nd of this invention.

  A fourth aspect of the present invention is a rubber composition comprising 100 parts by mass of styrene-butadiene rubber (SBR), 1 to 100 parts by mass of the isobutylene copolymer according to the first aspect of the present invention, and 1 to 150 parts by mass of silica particles. It is related with the 2nd crosslinked rubber composition of this invention formed by bridge | crosslinking a thing.

  5th of this invention is related with the pneumatic tire containing the crosslinked rubber composition as described in 4th of this invention.

  The isobutylene copolymer according to the present invention is kneaded with an unsaturated rubber typified by SBR (with a glass transition point of 25 ° C. or lower) to form a rubber composition, which is subjected to a crosslinking treatment and disposed in the side chain. Interaction of viscoelastic behavior in the composition is dramatically improved by co-crosslinking with unsaturated rubber starting from saturated groups and formation of chemical bonds between alkoxysilyl groups and silanol groups on the silica (particle) surface. It is possible to obtain a rubber composition that is reinforced. By strengthening the interaction, the SBR rubber composition used in the tread portion of the tire exhibits improved grip characteristics, and has great industrial utility.

2 is a 1H-NMR chart of “precursor”. 1 is a 1H-NMR chart of a hydrosilylated isobutylene copolymer according to the present invention.

Isobutylene and β-pinene represented by the chemical formula (4) are cationically copolymerized to form a copolymer comprising the structural unit represented by the above formula (1) and the structural unit represented by the above chemical formula (2). give. Hereinafter, this polymer is referred to as “precursor”.
As β-pinene, “β-pinene” extracted from citrus fruit peel is well known and may mean various isomers, and β-pinene according to the present invention includes all of these. Chemical formula (4) represents these without distinction. Hereinafter, unless otherwise specified, β-pinene in the present specification includes various isomers represented by the chemical formula (4).

  Β-Pinene represented by the chemical formula (4) according to the present invention can be obtained from the supplier's market by Nippon Terpene Chemical, Yashara Chemical, Tokyo Chemical Industry, and the like.

In the “precursor”, the total of the structural units represented by the formula (2) is preferably 1 mol% or more and 60 mol% or less, more preferably 1 mol% or more and 40 mol% or less. More preferably, it is at least 20 mol%.
If the temperature deviates from these ranges, the glass transition point becomes room temperature or higher, and it is not rubbery at room temperature, and vitrification may occur, resulting in poor mixing with the unsaturated rubber. It may become.

The copolymer form of chemical formula (1), which is a structural unit derived from isobutylene, and chemical formula (2), which is a structural unit derived from β-pinene, may be either block copolymerization or random copolymerization. A random copolymer is preferable from the viewpoint of easy progress of the co-crosslinking reaction with the unsaturated rubber, and a block copolymer is preferable from the viewpoint of improving characteristics resulting from the reaction with the silica surface described later. The copolymerization ratio here is an average value of the copolymerization ratio per molecule, and by measuring and comparing the intensity of the resonance signal of hydrogen attributed to each structure by the 1H-NMR (600 MHz) method. Can be sought.
Below, the manufacturing method of the "precursor" concerning this invention is demonstrated.

  In the copolymerization reaction according to the present invention, a Lewis acid is used as a polymerization catalyst. As a Lewis acid, it can use widely from well-known things which can be used for cationic polymerization. For example, boron halide compounds such as boron trichloride and boron trifluoride; titanium halide compounds such as titanium tetrachloride; tin halide compounds such as tin tetrachloride; aluminum halide compounds such as aluminum trichloride; antimony pentachloride Antimony halide compounds such as antimony pentafluoride; tungsten halide compounds such as tungsten pentachloride; molybdenum halide compounds such as molybdenum pentachloride; tantalum halide compounds such as tantalum pentachloride; It is not limited. Of these Lewis acids, boron trifluoride, aluminum trichloride, ethyldichloroaluminum, tin tetrachloride, titanium tetrachloride and the like are preferable. Of these Lewis acids, boron trifluoride and ethyldichloroaluminum, which can easily control the molecular weight by changing the reaction temperature, are preferred.

  The Lewis acid can be used in an amount of 0.01 to 1000 mmol equivalent, preferably 0.05 to 500 mmol equivalent, per 1 mol of the raw material monomer. The above Lewis acid can also be used as a complex in which a polar compound such as alcohol is coordinated (hereinafter referred to as “Lewis acid complex”). A compound that coordinates to a Lewis acid to form a complex is also referred to as a complexing agent. The Lewis acid complex is preferably a boron trifluoride complex or ethyldichloroaluminum obtained by coordinating a complexing agent of a polar compound such as the above alcohol with boron trifluoride. As for the boron trifluoride complex, an alcohol complex of boron trifluoride is more preferable. According to such a Lewis acid complex, the molecular weight can be easily controlled by changing the reaction temperature.

  In order to modify the unsaturated rubber, the “precursor” according to the present invention preferably has a lower viscosity than the unsaturated rubber. This is because it is easily dispersed in the modified rubber to form a fine dispersed state (dispersed phase). On the other hand, if the molecular weight is too small, the length of the polyisobutylene chain may be insufficient even when co-crosslinked with the unsaturated rubber, and the viscoelastic behavior may not be exhibited. In this respect, the preferred range of weight molecular weight is 500 to 500,000 (GPC measurement in terms of polystyrene; the same applies hereinafter), and more preferably 10,000 to 500,000.

  Further, a reaction solvent can be used in the copolymerization reaction related to the “precursor” synthesis. Examples of the reaction solvent include a single solvent selected from the group consisting of halogenated hydrocarbons, aliphatic hydrocarbons, and aromatic hydrocarbons, or a mixed solvent thereof.

  In the embodiment of the present invention, when a reaction solvent is used for the synthesis of the “precursor”, the polymer concentration is 0.1 in consideration of the solubility of the resulting polymer, the viscosity of the solution, and the ease of heat removal. It is preferable to use a solvent having solubility in the range of ˜80% by weight, and more preferably 1 to 50% by weight from the viewpoint of production efficiency and operability. Further, the monomer concentration at the time of polymerization is preferably about 0.1 to 8 mol / liter, more preferably about 0.5 to 5 mol / liter. In addition, the amount of the organic solvent used in the polymerization is preferably 0.5 to 100 times the amount of the monomer used from the viewpoint of controlling appropriate viscosity and heat generation.

  Since the polymerization temperature affects the average molecular weight of the obtained “precursor”, the polymerization temperature to be employed may be appropriately selected according to the target average molecular weight, but the polymerization temperature is about −80 ° C. to 20 ° C. The polymerization time is usually about 0.5 to 180 minutes, preferably about 20 to 150 minutes.

In the present invention, the unsaturated bond portion in the chemical formula (2) in the structural unit derived from β-pinene in the “precursor” is hydrosilylated. A preferred proportion of hydrosilylation is in the range of 30% to 80% of the unsaturated groups. If it is less than this range, the effect expression derived from the silica surface and the alkoxysilyl group is insufficient, and if it exceeds this range, the effect expression derived from co-crosslinking with the unsaturated rubber may be insufficient .

  As a compound used for hydrosilylation according to the present invention, the following formula (5) is used. These may be synthesized by a known reaction or obtained from the market. A known addition reaction can be used for the hydrosilylation reaction.

Ｒ１は、炭素数１〜５のアルキル基、Ｒ２、Ｒ３は、それぞれ独立に、水素原子または炭素数１〜５のアルキル基、アルコシル基、あるいはフェニル基である。

R1 is an alkyl group having 1 to 5 carbon atoms, and R2 and R3 are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, an arcosyl group, or a phenyl group.

When the number of carbon atoms in R1, R2, and R3 in chemical formula (5) exceeds 5, the hydrosilylation reaction does not proceed easily. Further, when both R2 and R3 in the compound (5) are hydrogen atoms, handling may be difficult due to the volatility of the compound (5). When both R2 and R3 are alkyl groups, Chemical reactivity (dealcoholization reaction) with silanol groups on the surface of silica (particles) may not proceed easily. Preferable chemical formula (5) is a compound in which either R2 or R3 is an alkoxy group, particularly preferably R1 is a methyl group or an ethyl group, and R2 and R3 are a methoxy group or an ethoxy group. In particular, in the case of an ethoxy group, the generated alcohol is ethanol, which is preferable for safety management.

  The isobutylene polymer according to the present invention obtained by the hydrosilylation reaction between the compound represented by the chemical formula (5) and the “precursor” is a silica surface in a rubber composition in addition to co-crosslinking with an unsaturated rubber. It is possible to form a chemical bond with the silanol, uniformly disperse the silica, and / or enhance the reinforcing property of the silica. The present inventors consider that the viscoelastic property enhancement of the present invention is due to the manifestation of this effect.

  In the hydrosilylation reaction, even if a predetermined amount of the compound of the chemical formula (5) and the “precursor” are reacted together, the predetermined amount of the compound of the chemical formula (5) is dropped into the “precursor” in the organic solvent. For example, the reaction may be performed sequentially.

  The hydrosilylation reaction is preferably performed in an organic solvent. The solvent used for the hydrosilylation reaction is not particularly limited as long as it does not inhibit the progress of the reaction. Among organic solvents, aromatic hydrocarbon solvents are preferable, and toluene is most preferable among them.

  The hydrosilylation reaction may be performed at room temperature or may be heated to accelerate the reaction. You may carry out under the recirculation | reflux of an organic solvent.

  By adding a hydrosilylation catalyst, the polymerization can proceed more easily. As the hydrosilylation catalyst, a Karstedt catalyst, a Speyer catalyst, hexachloroplatinic acid, a platinum-based catalyst (for example, a platinum chloride-based catalyst) and the like can be preferably used.

  The rubber capable of obtaining a large modification effect by co-crosslinking with the isobutylene copolymer according to the present invention is a “unsaturated rubber having a carbon-carbon unsaturated bond in the main chain and a glass transition point of −25 ° C. or lower. Specifically, styrene butadiene rubber (SBR), natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), hydrogenated acrylonitrile-butadiene rubber (HNBR) Acrylonitrile-butadiene rubber (NBR), isobutene-isoprene rubber (IIR), ethylene-propylene-diene monomer rubber (EPDM), and the like. These may use only 1 type and can also use 2 or more types together. As a specific example of the modification effect, a modification effect such as grip property in a tire mainly composed of SBR can be cited as in the case of a known isobutylene copolymer.

  In the co-crosslinking reaction of the isobutylene copolymer and the “unsaturated rubber” according to the present invention, a known cross-linking agent (system) related to the unsaturated rubber can be used as it is. It is known to be effective in the same manner as the co-crosslinking conditions of the coalescence and unsaturated rubber and the co-crosslinking conditions of EPDM and unsaturated rubber. Also, the blending method for making a rubber composition is usually a rubber blending method in which raw rubbers are first blended and then a cross-linking agent is added. The masterbatch method of mixing these may be used.

  The crosslinking agent used for crosslinking of the isobutylene copolymer according to the present invention and co-crosslinking with the unsaturated rubber is not particularly limited as long as it is a crosslinking agent that can be used for the unsaturated rubber. Among these, so-called sulfur crosslinking is preferable. This is because there is no risk of main chain scission of the isobutylene copolymer according to the present invention in organic peroxide crosslinking. In particular, since a sulfur-based crosslinking agent is generally used in the manufacture of tires, sulfur crosslinking is extremely effectively used in the modification effect by copolymerization of the isobutylene-based copolymer according to the present invention.

  There is no restriction | limiting in particular in the silica which chemically reacts with the alkoxylane group in the isobutylene-type copolymer based on this invention. Any material having a silanol group on its surface may be used. The dealcoholization reaction between the alkoxy group in the isobutylene copolymer according to the present invention and the silanol group on the silica (particle) surface proceeds without requiring a special catalyst when the co-crosslinking reaction proceeds. The amine compound is recognized to have a reaction-promoting effect, and is preferably added as necessary.

  The addition amount of the isobutylene copolymer for expressing the modification effect is determined depending on the desired degree of modification. The addition amount in a range not impairing the properties of the unsaturated rubber is usually 1 to 100 parts by mass, preferably 3 to 50 parts by mass with respect to 100 parts by mass of the unsaturated rubber. When the wet grip property is improved in the application field of the crosslinked rubber composition for tires comprising SBR 100 parts by mass and silica 20 to 100 parts by mass, it is 3 to 30 parts by mass, preferably 5 to 15 parts by mass. .

  In the cross-linking of the isobutylene copolymer according to the present invention and the co-crosslinking with the unsaturated rubber, in addition to the cross-linking agent, additives such as a softener / plasticizer, an antioxidant, an ultraviolet absorber, an anti-aging agent, etc. It is possible to add chemicals used in normal rubber processing, such as reinforcing materials such as carbon black and silica, and coupling agents.

  As an anti-aging agent, primary amines such as p, p′-diaminodiphenylmethane; secondary amines such as phenyl-α-naphthylamine and N, N′-diphenyl-p-phenylenediamine; 2,6-di Alkylphenols such as -tert-butyl-p-cresol, 2,5-di-tert-butyl-hydroquinone, hydroquinone monobenzyl ether; and imidazoles such as 2-mercaptobenzimidazole. The blending amount is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

Examples of the vulcanization accelerator include thiuram accelerators such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetraethylthiuram disulfide; thiazole accelerators such as 2-mercaptobenzothiazole and dibenzothiazyl disulfide; N-cyclohexyl Sulfenamide accelerators such as 2-benzothiazylsulfenamide and N-oxydiethylene-2-benzothiazolylsulfenamide; guanidine accelerators such as diphenylguanidine and diortolylguanidine; n-butyraldehyde -Aldehyde-amine accelerators such as aniline condensates and butyraldehyde-monobutylamine condensates; aldehyde-ammonia accelerators such as hexamethylenetetramine; thiourea accelerators such as thiocarbanilide Agents, and the like. When blending these vulcanization accelerators, one type may be used alone, or two or more types may be used in combination. The content of the vulcanization accelerator is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

Vulcanization aids include metal oxides such as zinc oxide (zinc white) and magnesium oxide; metal hydroxides such as calcium hydroxide; metal carbonates such as zinc carbonate and basic zinc carbonate; stearic acid and oleic acid Aliphatic acid salts such as zinc stearate and magnesium stearate; amines such as di-n-butylamine and dicyclohexylamine; ethylene dimethacrylate, diallyl phthalate, N, Nm-phenylene dimaleimide, triallyl isocyanurate And trimethylolpropane trimethacrylate. When blending these vulcanization aids, one type may be used alone, or two or more types may be used in combination. The content of the vulcanization aid is 0.1 with respect to 100 parts by mass of the rubber component.
It is preferable that it is -10 mass parts.

  Examples of the reinforcing agent include carbon black and silica.

  Carbon black is suitably used as a reinforcing agent from the viewpoints of improving wear resistance, improving rolling resistance characteristics, preventing cracks and cracks caused by ultraviolet rays (preventing ultraviolet degradation), and the like. The type of carbon black is not particularly limited, and conventionally known carbon blacks such as furnace black, acetylene black, thermal black, channel black, and graphite can be used. Further, the physical characteristics such as particle size, pore volume and specific surface area of carbon black are not particularly limited, and various carbon blacks conventionally used in the rubber industry, for example, SAF, ISAF, HAF, FEF, GPF, SRF (all are abbreviations of carbon black classified according to the US ASTM standard D-1765-82a) and the like can be used as appropriate. In the case of using carbon black, the blending amount is preferably 5 to 80 parts by mass, more preferably 10 to 60 parts by mass with respect to 100 parts by mass of the rubber component. Moreover, it can also be set as 30-80 mass parts, and can also be set as 40-60 mass parts. In such a blending amount, the effect as a reinforcing agent can be favorably obtained in the rubber composition and the crosslinked rubber composition according to the present embodiment.

  As silica, those conventionally used as rubber reinforcing agents can be used without particular limitation, such as dry method white carbon, wet method white carbon, synthetic silicate white carbon, colloidal silica, precipitated silica and the like. It is done. The specific surface area of silica is not particularly limited, but a silica having a surface area of 40 to 600 m2 / g, preferably 70 to 300 m2 / g, and a primary particle diameter of 10 to 1000 nm can be used. . These may be used alone or in combination of two or more. The amount of silica used is preferably 0.1 to 150 parts by mass, more preferably 10 to 100 parts by mass, and even more preferably 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. .

  Moreover, you may mix | blend a silane coupling agent with a rubber composition in order to mix | blend a silica. Examples of the silane coupling agent include vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxy-ethoxy) silane, β- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, and 3-chloropropyltrimethoxy. Silane, 3-chloropropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, bis (3- (triethoxysilyl) propyl) tetrasulfide, bis (3- (triethoxysilyl) propyl ) Disulfide and the like. These may be used alone or in combination of two or more. The addition amount of the silane coupling agent can be appropriately changed depending on the desired amount of silica, but is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the rubber component.

  As fillers, mineral powders such as clay and talc, carbonates such as magnesium carbonate and calcium carbonate, and alumina hydrates such as aluminum hydroxide are mainly used to improve strength, workability and economic efficiency. be able to.

  As softeners and plasticizers, plant oil softeners such as tall oil, mainly linoleic acid, oleic acid, and abithienic acid, pineapple, rapeseed oil, cottonseed oil, peanut oil, castor oil, palm oil, fuacitis, paraffinic oil, Examples thereof include naphthenic oils, aromatic oils, and phthalic acid derivatives such as dibutyl phthalate. It is preferable that the compounding quantity of a softening agent is 0-50 mass parts with respect to 100 mass parts of rubber components.

  As the ultraviolet absorber, benzotriazole, triazine, benzophenone, benzoate, hindered amine light stabilizers (low molecular weight type and high molecular weight type) and the like are used. Usually, it is 0.1-0.5 mass part with respect to 100 mass parts of rubber components.

  Antioxidants include hindered phenol, monophenol, bisphenol, polyphenol, amine-ketone, aromatic secondary amine, benzimidazole, phosphorus, phosphorous acid, dithiocarbamic acid, thiourea A system, an organic thioic acid system, etc. are used, and 0.5-3 mass parts is normally added with respect to 100 mass parts of rubber components.

  The rubber composition according to the present embodiment can be produced by applying a method generally used as a method for producing a rubber composition. For example, the above-described components can be produced by mixing using a kneader such as a Brabender, Banbury mixer, roll mixer, or the like.

  The present invention will be described more specifically with reference to the following examples and comparative examples. However, the present invention is not limited to the following examples.

<Synthesis of precursor and isobutylene copolymer>
(Structural analysis (i) 1H-NMR measurement)
The measurement object was dissolved in deuterated chloroform and measured with INOVA-600 manufactured by Varian (currently Agilent). The presence of hydrogen peaks attributed to the chemical formulas (1) to (3) was confirmed, and it was confirmed that both were random copolymers. In addition, the molar ratio in the copolymer was calculated from the hydrogen peak attributed to each structural unit.

(Structural analysis (ii) GPC measurement)
The measurement object was dissolved in tetrahydrofuran, TSK-GEL SuperH1000, SuperH2000, SuperH3000, and SuperH4000 were connected in series with an 8020 GPC system manufactured by Tosoh Corporation, and GPC measurement was performed using tetrahydrofuran as an eluent to obtain a weight average molecular weight. Polystyrene standards were used for molecular weight calibration.

(Sulfur crosslinkability test)
In DAR-50 apparatus manufactured by REOLOGICA INSTRUMENTS AB, 100 parts by mass of precursor or isobutylene copolymer, 4 parts by mass of sulfur (manufactured by Kokusan Kagaku), Noxeller CZ (manufactured by Ouchi Shinsei Chemical Industry: vulcanization accelerator) ) A rubber composition obtained by kneading 1 part by mass, 3 parts by mass of zinc oxide (manufactured by Kanto Chemical Co., Ltd .: vulcanization accelerator), and 2 parts by mass of stearic acid (manufactured by Kokusan Kagaku) was installed, and 100 ° C to 160 ° C. The temperature was raised at a rate of 2 ° C./minute until reaching 160 ° C., and the shear viscosity behavior at each temperature was followed while maintaining for 30 minutes. The shear viscosity was applied under conditions of a frequency of 1 Hz and a strain of 10%. Crosslinkability was confirmed by the presence of a viscosity increase starting temperature at 160 ° C.

[Example 1]
(Synthesis of “precursors”)
[Production Example 1]
A 300 mL three-necked flask is fitted with a ball stopper, a three-way cock with a vacuum line, a thermometer, a stirrer bar is inserted, and the system is degassed and replaced with nitrogen 10 times while heating with a dryer using the vacuum line. And under a normal pressure nitrogen atmosphere. Into the flask, 15.7 g of hexane solvent dried with molecular sieves was injected using a syringe. Next, 5.2 g (0.038 mol) of β-pinene was injected using a syringe. The flask was immersed in a low temperature bath at -70 ° C., and after confirming that the liquid temperature in the system reached a predetermined temperature, 18.0 g (0.32 mmol) of isobutylene was transferred from the cylinder to the reactor through a hose.
When the liquid temperature in the system reached −70 ° C., 2.16 g of 10.3% ethylaluminum dichloride (EADC) / n-hexane solution (1.75 mmol as ethylaluminum dichloride) was weighed with a syringe. Was injected into the reactor.
One hour after the injection of the catalyst solution, methanol was injected to stop the reaction, and the flask was taken out of the low temperature bath and left to room temperature. The reaction mixture was washed with water (twice) and then reprecipitated using methanol. The precipitate was dried in a vacuum dryer at 1 mmHg for 12 hours at 60 ° C., and 11.6 g (yield: 51.6%) of the desired “precursor” (copolymer of isobutylene and β-pinene). Got. From the 1H-NMR measurement, the β-pinene introduction rate was 11.3 mol%, Mw = 40,000, and Mw / Mn = 3.6.
Further, the obtained “precursor” exhibited sulfur crosslinkability.

A 300 mL two-necked flask was equipped with a ball stopper and a reflux tube connected to a vacuum line, a stirrer bar was added, and the system was degassed and replaced with nitrogen 10 times while heating with a dryer using a vacuum line. A nitrogen atmosphere was used. Into the flask, 47.7 g of the “precursor” obtained above (0.737 mol as the amount of olefin) was placed, and then 67 g of toluene solvent dried by molecular sieves was injected using a syringe. Then, it was stirred and dissolved using a stirrer. Next, 19.75 g (0.120 mmol) of triethoxysilane was injected as a compound (5) using a syringe.
Finally, 0.1 g (0.019 mmol) of 10% ethanol solution of chloroplatinic acid was injected, the flask was immersed in an oil bath, the bath temperature was gradually raised to 130 ° C., and toluene was refluxed. 34 hours after the start of reflux, the flask was removed from the oil bath and allowed to stand at room temperature. Next, reprecipitation was performed using methanol.
The precipitate was dried in a vacuum dryer at 1 mmHg for 12 hours at 60 ° C. to obtain 46.5 g of the desired isobutylene copolymer. According to 1H-NMR measurement (FIG. 2), the introduction rate of triethoxysilane into the “precursor” was 3.95 mol%, and the addition rate to the olefin in the “precursor” was 35%.
Further, the obtained “precursor” exhibited sulfur crosslinkability.

<Rubber composition and production of the crosslinked rubber composition>
Measuring method <JIS-A hardness>
The measurement was performed according to JIS K6253.
<Measurement of dynamic viscoelasticity>
The test was carried out in accordance with JIS K-7244-4 (Plastic-Test method for dynamic mechanical properties-Part 4: Tensile vibration - Non-resonant method). Specifically, from the sheets of Examples 1 and 2 and Comparative Example 1, a test piece having a thickness of 1 mm, a width of 5 mm, and a length of 20 mm was cut out and used under the conditions of a frequency of 10 Hz and a strain of 0.1%. The temperature was measured in the tensile mode while raising the temperature in the range of −50 to 100 ° C. at 2 ° C./min. The apparatus used is a dynamic viscoelasticity measuring apparatus RSA-3 (manufactured by TA INSTRUMENTS). The measurement results are shown in Table 1. At this time, the frequency is 10 Hz. This is because the wet grip property correlates with the tan δ value at 10 Hz-0 ° C. using the viscoelastic time-temperature conversion rule. It is known that the wet grip property is good. Similarly, the rolling resistance correlates with the tan δ value at 10 Hz-60 ° C., and it is known that the smaller the value, the better the rolling resistance.

(Production of cross-linked isobutylene copolymer and measurement of properties)
[Example 1]
To the styrene-butadiene copolymer rubber (JSR SL563, manufactured by JSR Corporation, referred to as S-SBR in Table 1), the isobutylene copolymer obtained in Production Example 1, a filler, a plasticizer, a vulcanization aid, and Antiaging agents were blended in predetermined amounts shown in Table 1 and kneaded with a kneader under the predetermined conditions shown in Table 1. Next, kneading with a vulcanizing agent and a vulcanization accelerator was carried out on a roll machine (6 inches φ × 16 inches) under the conditions of a rotation speed of 30 rpm and a front-rear roll rotation ratio of 1: 1.22. The rubber composition obtained by this kneading was compression molded under a vulcanization condition of 160 ° C. × 20 minutes to produce a sheet. The moldability at this time was extremely good. Subsequently, using this production sheet, the characteristic measurement was performed. The results are shown in Table 1.
Silica AQ (manufactured by Tosoh Silica Co., Ltd.) as the filler, T-DAE oil (manufactured by JX Nippon Oil & Energy Corporation) as the plasticizer, and sulfur (manufactured by Kawagoe Chemical Co., Ltd.) as the vulcanizing agent, Zinc oxide No. 3 (manufactured by Hakusuitec Co., Ltd.) and stearic acid (manufactured by Nippon Seika Co., Ltd.) are used as vulcanization aids. Thiaxylsulfenamide (manufactured by Ouchi Shinsei Chemical Co., Ltd.) and guanidine accelerator Noxeller D (1,3-diphenylguanidine, manufactured by Ouchi Shinsei Chemical Co., Ltd.) are used as anti-aging agents. Shinsei Chemical Co., Ltd.) were used.

(Production and measurement of commercial isobutylene polymer “precursor”)
[Comparative Example 1]
Using “Tetrax 3T” (manufactured by JX Nippon Mining & Energy Co., Ltd., catalog molecular weight 49,000) as an isobutylene polymer (polymer containing only isobutene), a sheet was prepared according to Example 1. Characteristic measurement was performed.

(Crosslinked “precursor” production and property measurement)
[Example 2]
A sheet was prepared according to Example 1 except that the silane-modified product obtained by carrying out the above-mentioned silane modification reaction using the “precursor” synthesized in Production Example 1 was used instead of the isobutylene-pinene copolymer. Characteristic measurements were made.

  The rubber compositions of Examples 1 and 2 have substantially the same hardness as Comparative Example 1. Regarding the tensile strength, it can be seen that the tensile strength and elongation are low, but the modulus is high and the reinforcement is high. Further, tan δ at 0 ° C. was high, and wet grip properties were improved. In addition, tan δ at 60 ° C. was almost the same, indicating that the rolling resistance characteristics were not impaired. It can be seen that the ratio between 0 ° C. tan δ and 60 ° C. tan δ is greatly improved.

  The isobutylene copolymer of the present invention uses β-pinene as a comonomer, an alkoxysilyl group is introduced into a part thereof, and a rubber composition containing the isobutylene copolymer, silica (particles), and unsaturated rubber In the product and its crosslinked rubber composition, a rubber composition having vastly improved viscoelastic behavior is obtained, which can be applied to the tread portion of a tire, and the grip characteristics are remarkably improved.

Claims (5)

A structural unit represented by the following formula (1):
A structural unit represented by the following formula (2), and
Structural units represented by the following formula (3), isobutylene copolymers composed of.

R1 is an alkyl group having 1 to 5 carbon atoms, and R2 and R3 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an arcosyl group, or a phenyl group.   A rubber composition comprising an unsaturated rubber, the isobutylene copolymer according to claim 1, and silica.   A crosslinked rubber composition obtained by crosslinking the rubber composition according to claim 2. Styrene - butadiene rubber (SBR) 100 parts by weight, isobutylene styrene copolymer 1-100 parts by weight of claim 1, comprising silica particles 1-150 parts by mass, the rubber composition according to claim 2 A crosslinked rubber composition obtained by crosslinking.   A pneumatic tire containing the crosslinked rubber composition according to claim 4.

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