JP4779354B2 - Modified butyl rubber-containing thermoplastic elastomer composition - Google Patents

Description

  The present invention relates to a modified butyl rubber-containing thermoplastic elastomer composition, and more particularly to a butyl rubber-containing thermoplastic elastomer composition containing less halogen and a pneumatic tire friendly to the global environment using the same for an air permeation preventive layer.

  Halogenated butyl rubber is known as, for example, a rubber for an inner liner of a pneumatic tire, and dehalogenation of halogenated butyl rubber is also known as described in, for example, Patent Documents 1 to 4. Further, Patent Document 5 proposes a method for producing anhydrous maleated butyl rubber by adding hindered amine or hindered phenol. Further, a modified butyl rubber (80 to 5 parts by weight) obtained by reacting an unsaturated compound having a functional group such as a carboxyl group, an acid anhydride group, a hydroxyl group, an amino group, or an epoxy group and a thermoplastic resin (20 to A thermoplastic resin composition containing 95 parts by weight is also described in, for example, Patent Documents 6 and 7. Although these materials are low gas permeability materials, they are at the same level as conventional butyl halides as they are, and since the dispersed particle size of rubber in the thermoplastic resin composition is large and inferior in durability, air It was impossible to apply it to the inner liner of a tire.

JP 59-84901 A JP 53-42289 A JP-A-48-90385 U.S. Pat. No. 3,965,213 JP 2004-91766 A Japanese Patent Laid-Open No. 2-84453 Japanese Patent Laid-Open No. 3-131634

  Accordingly, an object of the present invention is to provide a modified butyl rubber-containing thermoplastic elastomer composition which is excellent in the air permeation preventing effect by improving the modified butyl rubber and is friendly to the global environment, and a pneumatic tire using the same in an air permeation preventive layer. is there.

According to the present invention, 30 to 80 parts by weight of a modified butyl rubber having a modification rate of 0.01 to 2.0 mol% and a number average molecular weight of 200,000 to 500,000 and 70 to 20 parts by weight of a thermoplastic resin (total of both components) comprises 100 parts by weight), preventing air permeation of the average particle diameter of 3.0 microns or less modified butyl rubber-containing thermoplastic elastomer composition dynamically vulcanized discontinuous dispersed allowed the modified butyl rubber in the thermoplastic resin A pneumatic tire used for the layer is provided.

  A pneumatic tire using the modified butyl rubber-containing thermoplastic elastomer composition according to the present invention as an air permeation preventive layer has less air leakage as a tire, so that maintenance of air replenishment is reduced. Since the content is very small, it is possible to obtain a pneumatic tire that is friendly to the global environment.

As a result of researches on a thermoplastic elastomer discontinuously dispersed in a thermoplastic resin, the present inventors have found that ordinary butyl rubber (IIR) or halogenated IIR (for example, brominated butyl rubber, chlorinated butyl rubber) is thermoplastic. When used as an elastomer, the dispersed particle size becomes very large, and it has been found that the durability of the pneumatic tire is not sufficiently satisfactory for use as, for example, an air permeation preventive layer (inner liner). As a means for solving such a problem, the present inventors disperse a halogenated butyl rubber dynamic vulcanizate modified with maleic anhydride and having a low halogen group in a thermoplastic resin discontinuously. The thermoplastic elastomer composition was found to have good durability and high gas retention, and a desired pneumatic tire could be obtained.

The modified butyl rubber according to the present invention can be produced as follows.
A butyl rubber having a conjugated diene unit is obtained by dehydrohalogenating a halogenated butyl rubber by applying a dehydrohalogenating agent such as a carboxylate metal salt (for example, zinc naphthenate, 2-ethylhexane zinc, zinc stearate). Various modified butyl rubbers can be produced by reacting with a parent diene compound such as maleic anhydride. Such techniques are disclosed in, for example, JP-A-48-90385 and US Pat. No. 3,965,213. Has been. Acid acceptors that can accept hydrogen halides, specifically metal oxides, metal hydroxides, metal carbonates (magnesium oxide, lead oxide, calcium oxide, zinc oxide, magnesium hydroxide, calcium hydroxide, carbonate Calcium, barium carbonate) and the like, and monofunctional hindered amines (for example, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, p, p'-dioctyldiphenylamine, p, p'-dicumyldiphenylamine) N-phenyl-1-naphthylamine, p- (p-thruenesulfonylamido) diphenylamine, alkylated diphenylamine, octylated diphenylamine, etc.) or monofunctional hindered phenols (eg 2,6-di-t-butyl) -4-methylphenol, 3- (3,5-di-tert-butyl-4- (Roxy-phenyl) propionic acid stearate, (α-methylbenzyl) phenol, 2,6-di-t-4-ethylphenol) anti-aging agent was added, and maleic anhydride was converted to brominated butyl rubber by the same mechanism. Japanese Patent Application Laid-Open No. 2004-91766 discloses a method for introducing a modified butyl rubber having good processability. These methods can be applied to brominated butyl rubber and chlorinated butyl rubber. Not only can functional groups such as acid anhydride groups, carboxylic acid groups, hydroxyl groups, and epoxy groups be introduced into halogenated butyl rubber, but they can be removed. Halogenation on the polymer can be reduced by hydrogen halide. A modified butyl rubber containing less halogen by using a method in which a halogen-free butyl rubber is reacted with an unsaturated carboxylic acid derivative such as maleic anhydride at a high temperature of 180 ° C. or higher, or in the presence of a radical initiator. However, these modification methods are not preferable because molecular modification of butyl rubber is severely generated, and only low molecular weight modified butyl rubber is obtained.

  The modified butyl rubber used in the present invention has a modification rate (that is, a ratio of acid anhydride to modified butyl rubber) of 0.01 to 2.0 mol%, preferably 0.01 to 1.5 mol%, and a number average molecular weight. It must be 200,000 to 500,000, preferably 200,000 to 400,000. If the modification rate is too low, the dispersed particle size becomes large, which is not preferable. Conversely, if the modification rate is too high, gelation occurs during mixing.

  The thermoplastic elastomer composition according to the present invention comprises 30 to 80 parts by weight of the modified butyl rubber, preferably 35 to 80 parts by weight, 20 to 70 parts by weight of a thermoplastic resin, preferably 20 to 65 parts by weight (of both components). Total amount 100 parts by weight). At this time, it is preferable to form a so-called sea-island structure in which the thermoplastic resin forms a sea phase and the rubber forms an island phase. If the amount of the modified butyl rubber in the thermoplastic elastomer composition is too small (and therefore the amount of the thermoplastic resin is too large), it is not preferable because the rigidity at low temperature increases and the durability at low temperature decreases. If the amount is too large (and therefore if the amount of the thermoplastic resin is too small), the sea phase becomes rubber and gas permeability decreases, which is not preferable.

  Examples of the thermoplastic resin that can be used in the present invention include polyamide resins (for example, nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11), nylon 12 (N12), Nylon 610 (N610), Nylon 612 (N612), Nylon 6/66 copolymer (N6 / 66), Nylon 6/66/610 copolymer (N6 / 66/610), Nylon MXD6 (MXD6), Nylon 6T Nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer) and N-alkoxyalkylated products thereof, for example, methoxymethylated product of 6-nylon, methoxylated 6-610-nylon Methylated products, 612-nylon methoxymethylated products, polyester resins (eg Polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET / PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, polyoxyalkylene diimidic acid / Aromatic polyester such as polybutylene terephthalate copolymer), polynitrile resins (for example, polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), (meth) acrylonitrile / styrene copolymer, (Meth) acrylonitrile / styrene / butadiene copolymer), polymethacrylate resin (for example, polymethyl methacrylate (PMMA). Polyethyl methacrylate). Polyvinyl resins (for example, vinyl acetate, polyvinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PDVC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / Methyl acrylate copolymer, vinylidene chloride / acrylonitrile copolymer), cellulose resin (for example, cellulose acetate, cellulose acetate butyrate), fluorine resin (for example, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polyvinyl chloride) Fluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer), imide resins (for example, aromatic polyimide (PI)), and the like can be used, and these can be used alone or as an arbitrary mixture. A preferred thermoplastic resin is a polyamide-based resin.

The modified butyl-containing thermoplastic elastomer composition according to the present invention has a structure in which the modified butyl rubber dynamic vulcanizate is discontinuously dispersed in a thermoplastic resin. The thermoplastic elastomer is as follows. Can be manufactured. That is, a thermoplastic resin component and an elastomer component (unvulcanized in the case of rubber) are previously melt-kneaded with a twin-screw kneading extruder or the like, and the elastomer component is dispersed in the thermoplastic resin that forms a continuous phase. . When the elastomer component is vulcanized, a vulcanizing agent is added under kneading to dynamically vulcanize the elastomer component. Further, various compounding agents (excluding the vulcanizing agent) to the thermoplastic resin or the elastomer component may be added during the kneading, but are preferably mixed in advance before kneading. The kneading machine used for kneading the thermoplastic resin and the elastomer component is not particularly limited, and examples thereof include a screw extruder, a kneader, a Banbury mixer, and a biaxial kneading extruder. Among these, it is preferable to use a twin-screw kneading extruder for kneading the thermoplastic resin and the elastomer component and for dynamic vulcanization of the elastomer component. Further, two or more types of kneaders may be used and kneaded sequentially. As conditions for melt kneading, the temperature may be higher than the temperature at which the thermoplastic resin melts. The shear rate during kneading is preferably 1000 to 7500 sec ⁻¹ . The entire kneading time is from 30 seconds to 10 minutes, and when a vulcanizing agent is added, the vulcanization time after addition is preferably from 15 seconds to 5 minutes. The polymer composition produced by the above method is then formed into a film by extrusion molding or calendering. The film forming method may be a method of forming a normal thermoplastic resin or thermoplastic elastomer into a film.

  The pneumatic tire according to the present invention can be manufactured, for example, by the following method. That is, a film made of the thermoplastic elastomer composition is wound around a tire molding drum, and tire members such as carcass, side, belt, and tread are laminated thereon and inflated to obtain a green tire, which is a vulcanizer. A tire is produced by vulcanization with.

  The composition of the present invention can also be used as a laminate by laminating with other rubber compositions. In this case, the rubber in the rubber composition is not particularly limited, and any rubber material that has been conventionally used as a rubber material for tires or the like can be used. Examples of such rubbers include diene rubbers such as NR, IR, BR, and SBR, halogenated butyl rubbers, ethylene-propylene copolymer rubbers, and styrene elastomers. These include carbon black, process oil, vulcanizing agents, and the like. A rubber composition can be obtained by adding the above compounding agent.

When used in the air permeation preventive layer of a pneumatic tire according to the present invention, the air permeation coefficient is preferably 1.0 to 200 × 10 ⁻¹² cm ³ · cm ² / sec ² · cmHg. The thickness of the laminate is preferably from 0.505 to 7.0 mm, and the thermoplastic elastomer composition layer is preferably from 0.05 to 4.0 mm.

  In addition to the essential components described above, the thermoplastic elastomer composition according to the present invention includes other reinforcing agents (fillers) such as carbon black and silica, vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, Various additives that are generally blended for tires such as anti-aging agents and plasticizers and other general rubbers can be blended, and these additives are kneaded and vulcanized by a general method to form a composition. And can be used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Examples 1-6 and Comparative Examples 1-6
Production of thermoplastic elastomers In accordance with the formulation shown in Table I, a predetermined elastomer component and a vulcanization system are put into a Banbury mixer, kneaded for about 2 minutes, and discharged at 120 ° C. to adjust the elastomer component containing the vulcanization system, and rubber Pelletized with a pelletizer. Thereafter, the elastomer component and the resin were dry blended in a predetermined composition, charged into a twin-screw kneader, and dynamically vulcanized to prepare a thermoplastic elastomer composition. The kneading conditions at this time were 230 ° C. (270 ° C. in Comparative Example 4) and a shear rate of 1000 s ⁻¹ . For Example 6, after the elastomer component and the resin were melted and decomposed, the vulcanization system was added. The thermoplastic elastomer composition produced by biaxial kneading was cooled with water, pelletized, and then passed through a T-die with a single screw extruder to form a film having a width of 350 mm and a thickness of 100 μm.

Table I Footnote IIR: Bayer Co., Ltd. Butyl 301
BrIIR: Bromobutyl 2222 manufactured by Exxon Chemical Co., Ltd.
Tack roll: Taki roll 250-1 manufactured by Taoka Chemical Co., Ltd.
Zno: Zinc Hana 3 manufactured by Shodo Chemical Co., Ltd. St-Acid: Bead stearic acid manufactured by Nippon Oil & Fats Co., Ltd. St-Zn: Zinc stearate manufactured by Shodo Chemical Co., Ltd. 5033B: Copolymer manufactured by Ube Industries, Ltd. Nylon BM-4: n-butyl benzene sulfonamide manufactured by Daihachi Chemical Co., Ltd. BESNO: nylon 11 manufactured by Atofina Co., Ltd.

Physical property evaluation test method About various thermoplastic elastomer compositions obtained, in accordance with JIS K6301
1) Normal temperature physical properties (20 ° C.): Hardness, tensile strength (T _B ), elongation (E _B ), stress at 50% elongation (M50)

  Dispersion state: After the ultrathin section was prepared using a microtome etc. for the film prepared by the above tensile strength and elongation test, it was stained with osmium tetroxide etc. and directly using a transmission electron microscope (Hitachi H-800 type). Observations were made.

Tire durability test 1) Molding of tire Applying rubber cement to a 350mm wide thermoplastic elastomer film, winding it on a tire molding drum, and laminating carcass, side, belt and tread tire members on it, Inflated to give a green tire. The green tire was vulcanized with a vulcanizer at 180 ° C. for 10 minutes to finish a tire having a tire size of 165SR13.
2) Tire endurance test method A 165SR13 steel radial tire (rim 13 × 41 / 2-J) is used, a load of 5.5 kN is applied at an air pressure of 140 kPa, and the vehicle runs on an actual road for 10,000 km. After running, remove the tire from the rim, visually observe the liner layer on the inner surface of the tire, and if the liner layer has cracks, cracks, visible wrinkles, peeling of the liner layer, lifting, it is rejected (x), and what is not is passed (○) is determined.

Production of modified butyl rubber (Mah-IIR-1 to 6) Brominated butyl rubber 120.0 g (2.08 mol; butyl unit), maleic anhydride 12.0 g (0.123 mol), xylene 18.0 g (0.123 mol), 1.43 g (0.0354 mol) of magnesium oxide and 1,2 g (1.0 phr) of p, p′-dicumyldiphenylamine were placed in a pressure kneader set at 90 ° C. and mixed for 20 minutes. The obtained mixture was kneaded in a pressure kneader set at a temperature of 210 ° C. A part of the obtained polymer was dissolved in toluene, and the polymer was isolated and purified by reprecipitation operation. By conducting IR analysis and ¹ H-NMR analysis using the purified product, introduction of an acid anhydride group into the polymer was confirmed, and the introduction rate was 2.1 mol%.
The results are shown in Table II.

  As described above, when the modified butyl rubber-containing thermoplastic elastomer composition according to the present invention is used as an air permeation preventive layer, there is little air leakage and the organic halogen content is very low. Useful as.

Claims (1)

30 to 80 parts by weight of modified butyl rubber having a modification rate of 0.01 to 2.0 mol% and a number average molecular weight of 200,000 to 500,000 and 70 to 20 parts by weight of a thermoplastic resin (100 parts by weight in total of both components) A pneumatic tire using, as an air permeation preventive layer, a thermoplastic elastomer composition in which the dynamic vulcanizate of the modified butyl rubber having an average particle size of 3.0 microns or less is dispersed discontinuously in the thermoplastic resin.