JP2012136584A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition capable of achieving higher elasticity and lower heat generation while suppressing substantial lowering of tensile elongation.SOLUTION: The rubber composition is prepared by compounding 100 pts.mass of a diene-based rubber with 10-150 pts.mass of carbon black and 1-50 pts.mass of a thermoplastic polyester resin containing in the molecule 20-50 mass% of a rubber block comprising a polymer of isoprene and/or 1,3-butadiene, and dispersing the thermoplastic polyester resin in the diene-based rubber.

Description

  The present invention relates to a rubber composition obtained by dispersing a polyester resin in a diene rubber.

  In general, characteristics required for rubbers used under high loads and high speeds such as tires and vibration-proof rubbers include high elasticity, high breaking elongation, and fatigue resistance. In order to meet such demands, techniques for increasing the elasticity of the rubber composition include techniques such as increasing the amount of the crosslinking agent and increasing the reinforcing filler, but these techniques cause a decrease in tensile elongation (breaking elongation). There is a problem.

  As another method for achieving high elasticity, there is a method of adding a thermosetting phenolic resin to a rubber composition as described in Patent Document 1 below. However, reactive phenolic resins are inferior in processability because resin crosslinking starts at the processing temperature and becomes high viscosity.

  Patent Document 2 below proposes adding a liquid diene rubber capable of co-crosslinking to butyl rubber in order to improve physical properties such as elastic modulus and breaking strength while ensuring processability. However, this document is mainly intended to improve workability, and it is considered that high elasticity in a low strain region is insufficient.

  On the other hand, in Patent Document 3 below, in order to exert the characteristics of both rubber and resin, in a composite dispersion in which a vulcanized rubber phase is a matrix phase and a resin phase is a dispersed phase, a resin having an active atom or a crosslink It has been proposed to firmly bond a rubber phase and a resin phase using a resin having reactivity with a vulcanizing agent such as a resin having a functional group. However, in this document, the resin is pulverized in advance by a freeze pulverization method or the like, and is mixed with a rubber component in a molten state to obtain the composite dispersion. Moreover, although the point which mix | blends carbon black is disclosed, what is actually used is only 1 mass part with respect to 100 mass parts of rubber components. Therefore, in this document, the point that the resin is melted and finely dispersed at the time of mixing with the rubber component, and that the dispersibility of the resin is improved by adding more than a predetermined amount of carbon black at that time. Is not disclosed at all.

  Further, Patent Document 4 below discloses that the strength of the rubber composition is improved by adding a thermoplastic resin, and that a polyphenylene thermoplastic resin is used as the thermoplastic resin. . However, polyphenylene ether resins are actually used as polyphenylene resins, and since these resins have a high glass transition temperature, they can be pulverized in advance by a freezing and pulverization method, or an aromatic solvent and a rubber component. It is dissolved and mixed into a master batch, and no features of the present invention are disclosed.

Japanese Patent Laid-Open No. 05-051487 JP 61-243843 A JP 2003-049023 A JP 2004-238547 A

  An object of this invention is to provide the rubber composition which can aim at high elasticity, suppressing the significant fall of tensile elongation in view of the said problem.

  While the inventors are diligently considering in view of the above points, by blending and dispersing a specific polyester resin that is a thermoplastic resin while blending a predetermined amount of carbon black in the rubber composition, It has been found that high elasticity can be achieved in a low strain region while suppressing a significant decrease in tensile elongation, and the present invention has been completed.

  That is, the rubber composition according to the present invention contains 10 to 150 parts by mass of carbon black in 100 parts by mass of a diene rubber, and contains a rubber block made of a polymer of isoprene and / or 1,3-butadiene in the molecule. 1 to 50 parts by mass of a thermoplastic polyester resin having 20 to 50% by mass is mixed and dispersed in the diene rubber.

  According to the present invention, high elasticity can be achieved while suppressing a decrease in tensile elongation as much as possible by mixing and dispersing a specific polyester resin together with carbon black in diene rubber. Moreover, since the polyester resin to be added is a thermoplastic resin, problems such as burns during mixing can be avoided, and there are few restrictions on the mixing method and temperature range during mixing. In addition, since the polyester resin is rubber-modified, it is flexible against deformation, and low heat build-up can be improved as compared with a polyester resin not modified with rubber.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  In the rubber composition according to the present invention, a diene rubber is used as a rubber component. The diene rubber is not particularly limited. For example, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber, butadiene-isoprene rubber, Styrene-butadiene-isoprene rubber, ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) and the like can be mentioned, and these can be used alone or in combination of two or more.

  The rubber composition according to the present invention is blended with a rubber-modified thermoplastic polyester resin. The polyester resin has a rubber block composed of a polymer of isoprene and / or 1,3-butadiene in the molecule in an amount of 20 to 50% by mass (hereinafter sometimes referred to as a rubber-modified polyester resin).

  The rubber block may be a polyisoprene block made of a homopolymer of isoprene, a polybutadiene block made of a homopolymer of 1,3-butadiene, or a copolymer of isoprene and 1,3-butadiene. Isoprene butadiene copolymer block may be used.

The rubber block is contained in the polyester resin molecule in an amount of 20 to 50% by mass. When the content is less than 20% by mass, the effect of improving the low heat build-up due to rubber modification becomes insufficient. On the other hand, when the content exceeds 50% by mass, the reinforcing property becomes insufficient. Here, the composition ratio of the rubber block is determined by assigning each constituent component from the chemical shift obtained by ¹ H-NMR measurement, and the ratio of the signal strength of the chemical shift of the rubber block and the signal strength of the chemical shift of other components. Can be obtained from

  As the rubber-modified polyester resin, one having a glass transition temperature (Tg) of 130 ° C. or less is preferably used. When the glass transition temperature exceeds 130 ° C., the rubber-modified polyester resin is insufficiently melted when mixed with the diene rubber, which may cause poor dispersion. The glass transition temperature is more preferably 110 ° C. or lower. The lower limit of the glass transition temperature is not particularly limited, but is preferably higher than the use temperature (use temperature in rubber products), for example, preferably 5 ° C. or more, and more preferably 25 ° C. or more.

  As for the glass transition temperature, 5 mg of resin was sampled, sealed in an aluminum sample pan, and heated from -20 ° C. to 200 ° C. using a differential scanning calorimeter DSC-220 manufactured by Seiko Instruments Inc. The measurement was performed at 20 ° C./min, and the temperature was determined at the temperature of the intersection of the base line extension below the glass transition temperature and the tangent indicating the maximum slope at the transition.

As the rubber-modified polyester resin, one having a melt viscosity of 5000 Pa · s or less at a shear rate of 100 s ⁻¹ at 140 ° C. is preferably used. The temperature range of the mixing condition of the rubber composition is usually around 140 ° C., and the lower the melt viscosity in such a temperature range, the more the fine dispersion in the diene rubber that is the matrix phase is promoted, High elasticity can be achieved. In particular, a rubber-modified polyester resin has a low melt viscosity, so that processability can be improved. The melt viscosity is more preferably 3000 Pa · s or less, and still more preferably 2000 Pa · s or less. Although the minimum of this melt viscosity is not specifically limited, Usually, it is 10 mPa * s or more.

  In the following examples, the melt viscosity was measured using an AR550 type rheometer manufactured by TA Instruments Japan Co., Ltd.

  The rubber-modified polyester resin as described above is obtained by reacting at least one diol component selected from the group consisting of polybutadiene diol, polyisoprene diol and isoprene butadiene copolymer diol with a dibasic acid component. Preferably used. More specifically, polyisoprene diol, polybutadiene diol, and isoprene butadiene copolymer diol having molecular weight of several thousand are melt-polymerized as a copolymer component together with a dibasic acid component and other glycol components to be incorporated into a copolymer polyester resin skeleton. Can be used.

  The diol component is polyisoprene, polybutadiene, or isoprenebutadiene copolymer having a hydroxyl group at the molecular end, and the molecular weight is not particularly limited, but the number average molecular weight is preferably 1000 to 10,000.

  Here, the number average molecular weight was measured using a gel permeation chromatograph (GPC) 150C manufactured by Waters Co., with tetrahydrofuran as a carrier solvent at a flow rate of 1 ml / min. The detector used RI detector, three Shodex KF-802, KF-804, and KF-806 by Showa Denko KK were connected as a column, and column temperature was set to 30 degreeC. A polystyrene standard was used as the molecular weight standard sample.

  Examples of the dibasic acid component include aliphatic dibasic acids (aliphatic dicarboxylic acids) such as oxalic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid, 1,2-cyclohexanedicarboxylic acid, 1,3 -Alicyclic dibasic acids (cycloaliphatic dicarboxylic acid) such as cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, and aromatic dibasic acids (aromatic such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid) Group dicarboxylic acid), or dialkyl ester compounds of these aliphatic, alicyclic and aromatic dibasic acid compounds. Any of these may be used alone or in combination of two or more. Among these, aromatic dibasic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and naphthalenedicarboxylic acid are preferable from the viewpoint of the physical properties of the resulting rubber-modified polyester resin.

Examples of the other glycol components include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl- Aliphatic glycols such as 1,3-propanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, Aromatic glycols such as ethylene oxide or propylene oxide adducts of bisphenol A, 1,3-bis (hydroxymethyl) cyclohexane, 1,4-bis (hydroxymethyl) cyclohexane, 3 (4), 8 (9) -tricyclo [5.2.1.0 ^{2, 6]} decane alicyclic glycols include these such as methanol These may be used alone or in combination of two or more either. Among these, since it is easy to increase the copolymerization mass ratio of the rubber component in the rubber-modified polyester resin and the surface of copolymerization reactivity, a liquid, low molecular weight compound ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, and 2-methyl-1,3-propanediol are preferred.

  As a reaction procedure of the diol component, a copolymerization component other than the diol component, that is, the dibasic acid component and the other glycol component are first esterified or transesterified, and then the diol component is polymerized. It is preferable to put into the system. Thereby, the thermal history of the diol component can be kept low, and adverse effects due to thermal decomposition, such as a decrease in copolymerization efficiency and abnormal coloring of the produced resin can be avoided. It is also effective to add an additive such as a hindered phenol antioxidant to the polymerization reaction system in advance.

  The compounding amount of the rubber-modified polyester resin is 1 to 50 parts by mass with respect to 100 parts by mass of the diene rubber, and the effect of improving the elastic modulus can be obtained by blending 1 part by mass or more. On the other hand, if the amount of the rubber-modified polyester resin is too large, the tensile strength is greatly reduced, and it becomes difficult to ensure a practical level of tensile strength. The amount of the rubber-modified polyester resin is more preferably 5 to 30 parts by mass.

Carbon black is blended in the rubber composition according to the present invention as a reinforcing filler. The carbon black is not particularly limited, and is, for example, ASTM grade, SAF class (N100 series), ISAF class (N200 series), HAF class (N300 series), FEF (N500 series), GPF (N600 series), SRF. (N700 series) can be mentioned, and these can be used alone or in combination of two or more. Among these, those having a nitrogen adsorption specific surface area (N ₂ SA) of 40 to 150 m ² / g are particularly preferably used. Here, the nitrogen adsorption specific surface area (N ₂ SA) is a value measured according to JIS K6217-2.

  The compounding amount of carbon black is 10 to 150 parts by mass with respect to 100 parts by mass of the diene rubber. When the blending amount of carbon black is less than 10 parts by mass, the effect of finely dispersing the rubber-modified polyester resin becomes insufficient, and a significant improvement effect of the elastic modulus is not recognized. That is, by setting the blending amount of carbon black to 10 parts by mass or more, the resin is finely dispersed, and the effect of adding the rubber-modified polyester resin can be exhibited. As the amount of carbon black is increased, fine dispersion by crushing the rubber-modified polyester resin during mixing is promoted, and the particle size of the rubber-modified polyester resin as a dispersed phase can be reduced, leading to an improvement in elastic modulus. . On the other hand, when the blending amount exceeds 150 parts by mass, it becomes difficult to ensure a practical level of tensile elongation. The compounding amount of carbon black is more preferably 20 to 120 parts by mass.

  The rubber composition according to the present invention includes various fillers such as silica, other fillers such as silica, zinc white, stearic acid, oil, wax, anti-aging agent, vulcanizing agent, and vulcanization accelerator. Chemicals, additives, etc. can be added as necessary. Examples of the vulcanizing agent include sulfur and sulfur-containing compounds, and are not particularly limited. However, the amount of the vulcanizing agent is 0.1 to 10 parts by mass with respect to 100 parts by mass of the diene rubber. Preferably, it is 0.5-5 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of said diene rubbers, More preferably, it is 0.5-5 mass parts.

  As a manufacturing method (mixing method) of the rubber composition, a normal dry mixing method can be applied. That is, a rubber composition can be obtained by mixing (kneading) at 180 ° C. or lower, for example, with various mixers such as a commonly used batch mixer such as a Banbury mixer or a continuous kneader. The mixing temperature can be selected from the temperatures at which the rubber composition softens and the rubber-modified polyester resin melts, and is preferably 90 to 180 ° C, more preferably 120 to 160 ° C.

  In the rubber composition thus prepared, the rubber-modified polyester resin is melted by heat at the time of mixing, and is kneaded with the diene rubber in the presence of a predetermined amount of carbon black, thereby comprising the diene rubber. A rubber composition is obtained in which the rubber phase is the matrix phase and the rubber-modified polyester resin phase is the dispersed phase. That is, the rubber-modified polyester resin can be finely dispersed in the rubber compound. In the obtained rubber composition, a rubber-modified polyester resin dispersion having a physical bond that is strong and flexible with respect to deformation is present in the rubber matrix phase. Can be made highly elastic. Further, since the polyester resin is rubber-modified, the resin dispersion is more flexible with respect to deformation, and thus can improve the low heat buildup (that is, the hysteresis loss is reduced to make it difficult to generate heat, For example, it contributes to low fuel consumption when used in tires).

  The particle diameter of the rubber-modified polyester resin particles in the rubber matrix phase is not particularly limited, but it is preferable to form a dispersed phase having an average particle diameter of 1 μm or less. By dispersing in such fine particles, the effects of the present invention can be further enhanced. Since the average particle size is preferably as small as possible, the lower limit is not particularly limited, but may be, for example, 0.01 μm or more.

  The average particle size of the dispersed phase was magnified with a transmission electron microscope (TEM) at a magnification of 5000 to 10,000 times, and the diameter of 10 randomly extracted particles (average value of the maximum diameter portion and the minimum diameter portion). Is obtained as an arithmetic average thereof.

  The use of the rubber composition according to the present invention is not particularly limited, and can be used for various rubber compositions such as tires such as treads and sidewalls, anti-vibration rubbers, rubber belts, and the like. Of these, the rubber composition for tires is particularly preferably used. When the rubber composition is used for a tire, rubber portions (tread rubber, sidewall rubber, etc.) of various pneumatic tires can be formed by vulcanization molding at, for example, 140 to 180 ° C. according to a conventional method.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[First embodiment]
Using a Banbury mixer, a rubber composition was prepared according to the formulation shown in Table 1 below. Specifically, in the first mixing stage, components other than sulfur and a vulcanization accelerator are added to the diene rubber and kneaded to obtain a first mixture (discharge temperature: 150 ° C.). In the second mixing stage, a vulcanization accelerator and sulfur were added to the first mixture and kneaded to obtain a rubber composition (discharge temperature: 100 ° C.). The details of each component in Table 1 are as follows.

IR: “IR2200” manufactured by JSR Corporation
・ SBR: "SBR1502" manufactured by JSR Corporation
・ NBR: “N230SV” manufactured by JSR Corporation
Carbon black HAF: “Dia Black N339” manufactured by Mitsubishi Chemical Corporation (N ₂ SA = 96 m ² / g)
Carbon black SAF: “Seast 9” manufactured by Tokai Carbon Co., Ltd. (N ₂ SA = 142 m ² / g)
Carbon black FEF: “Seast SO” (N ₂ SA = 42 m ² / g) manufactured by Tokai Carbon Co., Ltd.

-Rubber-modified polyester resin A: 2L glass 4-neck flask equipped with a stir bar, thermometer, Liebig condenser, 244 parts by mass of 2,6-dimethylnaphthalate, ethylene oxide adduct of bisphenol A (Sanyo Chemical Industries ( Co., Ltd. BPE-20F) 225 parts by mass, 102 parts by mass of ethylene glycol, and 0.1 part by mass of butyl titanate monomer as a reaction catalyst were charged at a temperature of 190 ° C, 210 ° C and 230 ° C for 1 hour. The generated methanol was distilled off. Next, the reaction temperature was lowered to 180 ° C., 170 parts by mass of polyisoprene diol (poly-ip manufactured by Idemitsu Kosan Co., Ltd., number average molecular weight: 2500), and antioxidant (Irganox 1330 manufactured by Ciba Specialty Chemicals) Was added, and the temperature was raised again. When the reaction temperature reached 250 ° C., pressure reduction of the system was started and the temperature was raised so that the reaction temperature reached 260 ° C. after 10 minutes while removing the distillate. did. After continuing the polymerization reaction at the same temperature for 30 minutes, the reaction was terminated and the product was taken out on a Teflon sheet. The obtained polyester resin was a polyester resin having a polyisoprene block of 30% by mass in the molecule, and had a melt viscosity (measuring temperature 140 ° C., shear rate 100 s ⁻¹ ) = 1610 Pa · s, Tg = 91 ° C.

・ Phenolic resin: "Sumikanol T620" manufactured by Sumitomo Chemical Co., Ltd.
HMMM: Hexamethoxymethylmelamine, “CYRETS 963L” manufactured by Nippon Cytec Industries, Ltd.
Polystyrene: “Styrene (polymer)” manufactured by Nacalai Tesque Co., Ltd. (melt viscosity (measuring temperature 140 ° C., shear rate 100 s ⁻¹ ) = 1450 Pa · s, Tg = 85 ° C.)
PMMA: polymethyl methacrylate, “Methyl methacrylate (polymer)” manufactured by Nacalai Tesque Co., Ltd. (melt viscosity (measuring temperature 140 ° C., shear rate 100 s ⁻¹ ) = 23000 Pa · s, Tg = 125 ° C.)
TPU: Thermoplastic polyurethane, “E380” manufactured by Nippon Milactolan Co., Ltd. (melt viscosity (measuring temperature 140 ° C., shear rate 100 s ⁻¹ ) = 4800 Pa · s, Tg = −61 ° C., softening point = 90 ° C.)
・ Zinc flower: “Zinc oxide 3 types” manufactured by Sakai Chemical Industry Co., Ltd.
・ Stearic acid: “Stearic acid” manufactured by NOF Corporation
・ Sulfur: "Sulfur powder 150 mesh" manufactured by Hosoi Chemical Co., Ltd.
・ Vulcanization accelerator: Sanshin Chemical Industry Co., Ltd. “Sunseller CM-G”

  About each obtained rubber composition, while measuring the Mooney viscosity at the time of unvulcanized | curing, it vulcanizes | cures at 160 degreeC x 20 minutes, and produces the test piece of a predetermined shape, and using the obtained test piece, tension | pulling Elongation and dynamic modulus were measured. Each evaluation method is as follows.

Mooney viscosity: Mooney viscosity ML (1 + 4) at 125 ° C. is measured according to JIS K6300-1.

・ Tensile elongation: A tensile test (dumbbell No. 3, type, ambient temperature 23 ° C.) was performed according to JIS K6251.

-Dynamic elastic modulus: Using a viscoelastic spectrometer "VR7110" manufactured by Ueshima Seisakusho Co., Ltd., the dynamic elastic modulus was measured under the conditions of a temperature of 25 ° C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 5%.

  The results are as shown in Table 1, and the rubber compositions of Comparative Examples 2 and 3 in which the compounding amount of carbon black and the compounding amount of sulfur are increased with respect to the rubber composition of Comparative Example 1 as a control are increased in elasticity. However, the tensile elongation was significantly reduced. In Comparative Example 4 in which a phenol resin, which is a thermosetting resin, was blended, the elasticity increased compared to Comparative Example 1, but the Mooney viscosity significantly increased and the workability was inferior, and the decrease in tensile elongation was large. It was. Comparative Examples 5 to 7 were blended with a thermoplastic resin other than the polyester resin, and these thermoplastic resins had a small increase in elastic modulus.

In contrast, the rubber composition of Example 1 blended with a rubber-modified polyester resin has a large increase in elastic modulus without a significant decrease in tensile elongation, and has a low Mooney viscosity and processability. It was excellent. Moreover, as is clear when Examples 2 to 5 and Comparative Examples 8 to 11 are compared, by adding a rubber-modified polyester resin, the tensile elongation is greatly increased regardless of the type of carbon black and diene rubber. The elastic modulus increased greatly without decreasing.

[Second Embodiment]
According to the formulation shown in Table 2 below, a rubber composition was prepared by the same mixing method as in the first example. The details of each component in Table 2 are the same as in the first example except for the following.

・ Rubber-modified polyester resin B: 97 parts by mass of dimethyl terephthalate, 97 parts by mass of dimethyl isophthalate, 81 parts by mass of ethylene glycol, neopentyl glycol, in a 2 L glass four-necked flask equipped with a stir bar, thermometer and Liebig condenser 73 parts by mass and 0.1 part by mass of butyl titanate monomer as a reaction catalyst were charged, and a transesterification reaction was performed at 190 ° C., 210 ° C., and 230 ° C. for 1 hour, and the generated methanol was distilled off. Subsequently, the reaction temperature was lowered to 180 ° C., 70 parts by mass of polybutadiene diol (KRASOL manufactured by Idemitsu Kosan Co., Ltd., number average molecular weight: 5000), and 0.1 parts of antioxidant (Irganox 1330 manufactured by Ciba Specialty Chemicals). 5 parts by mass was added, the temperature was raised again, and when the reaction temperature reached 250 ° C., the pressure reduction of the system was started, and the temperature was raised so that the reaction temperature became 260 ° C. after 10 minutes while removing the distillate. After continuing the polymerization reaction at the same temperature for 30 minutes, the reaction was terminated and the product was taken out on a Teflon sheet. The obtained polyester resin was a polyester resin having a polybutadiene block in the molecule of 23% by mass, and had a melt viscosity (measuring temperature 140 ° C., shear rate 100 s ⁻¹ ) = 1490 Pa · s, Tg = 58 ° C.

Polyester resin C: In a 3 L four-neck glass flask equipped with a stirrer, a Liebig condenser, and a thermometer, 349 parts by mass of dimethyl terephthalate ester, 341 parts by mass of dimethyl isophthalate ester, 250 parts by mass of neopentyl glycol, 347 parts by mass of ethylene glycol and 0.4 parts by mass of tetrabutyl titanate as a catalyst were charged, the temperature was gradually raised from 190 ° C. to 230 ° C., and the transesterification reaction was completed in 3 hours while distilling off the generated methanol. The temperature of the reaction was cooled to 180 ° C. Subsequently, 64 parts by mass of adipic acid was added, and while the generated water was distilled off, the reaction temperature was gradually raised and reached 250 ° C. after 1 hour. The reaction system was further heated under reduced pressure, and after polymerization at 260 ° C. for 30 minutes, the polymerization reaction was terminated. The produced polymer was taken out into a Teflon sheet. The obtained resin was a polyester resin not modified with rubber, and had a melt viscosity (measuring temperature 140 ° C., shear rate 100 s ⁻¹ ) = 740 Pa · s, Tg = 45 ° C.

Polyester resin D: In a 3 L four-neck glass flask equipped with a stirrer, a Liebig condenser, and a thermometer, 388 parts by mass of dimethyl terephthalate ester, 388 parts by mass of dimethyl isophthalate ester, 250 parts by mass of neopentyl glycol, 347 parts by mass of ethylene glycol and 0.4 parts by mass of tetrabutyl titanate as a catalyst were charged, the temperature was gradually raised from 190 ° C. to 230 ° C., and the transesterification reaction was completed in 3 hours while distilling off the generated methanol. The reaction temperature was gradually raised and reached 250 ° C. after 1 hour. The reaction system was further heated under reduced pressure, and after polymerization at 260 ° C. for 60 minutes, the polymerization reaction was terminated. The produced polymer was taken out into a Teflon sheet. The obtained resin was a polyester resin that was not rubber-modified, and had a melt viscosity (measuring temperature 140 ° C., shear rate 100 s ⁻¹ ) = 3350 Pa · s, Tg = 66 ° C.

Polyester resin E: 97 parts by mass of dimethyl terephthalate, 366 parts by mass of 2,6-dimethyl naphthalate, 3 (4), 8 (9) in a 2 L glass four-necked flask equipped with a stirring bar, a thermometer, and a Liebig condenser ) -Tricyclo [5.2.1.0 ^2,6 ] decandimethanol (TCD-DM glycol manufactured by Mitsubishi Chemical Corporation), 157 parts by mass of ethylene oxide adduct of bisphenol A (BPE manufactured by Sanyo Chemical Industries, Ltd.) -20F) 258 parts by mass, 149 parts by mass of ethylene glycol, and 0.2 parts by mass of butyl titanate monomer as a reaction catalyst were generated by performing an ester exchange reaction at 190 ° C, 210 ° C, and 230 ° C for 1 hour, respectively. The methanol was distilled off. Next, the reaction temperature was raised, and when the temperature reached 250 ° C., pressure reduction of the system was started, and the temperature was raised so that the reaction temperature became 260 ° C. after 10 minutes while removing the distillate. After continuing the polymerization reaction at the same temperature for 30 minutes, the reaction was terminated and the product was taken out on a Teflon sheet. The obtained polyester resin was a polyester resin not modified with rubber, and had a melt viscosity (measuring temperature: 140 ° C., shear rate: 100 s ⁻¹ ) = 5150 Pa · s, Tg = 102 ° C.

  Each rubber composition obtained was vulcanized at 160 ° C. for 20 minutes in the same manner as in the first example to prepare a test piece of a predetermined shape, and using the obtained test piece, tensile elongation and dynamics were obtained. The elastic modulus was measured. Further, the loss tangent tan δ as an index of low heat generation was measured by the following method.

Tan δ: tan δ was measured under the conditions of a temperature of 25 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 5% using a viscoelastic spectrometer “VR7110” manufactured by Ueshima Seisakusho. The smaller tan δ, the less heat is generated and the lower the heat build-up property.

The results are as shown in Table 2, and in Examples 1 and 6 to 8 in which a rubber-modified polyester resin was blended, compared to Comparative Examples 12 to 16 in which a polyester resin that was not rubber-modified was blended, low exothermic properties. It was excellent. This is because the melt viscosity of the resin itself decreases due to rubber modification, the processability (mixability) improves, and the rubber block in the molecule makes it flexible against deformation. is there. In Comparative Example 12 in which the polyester resin E having a melt viscosity exceeding 5000 Pa · s was added, the degree of high elasticity was small while maintaining the tensile elongation because the dispersibility of the polyester resin was not sufficient. It was.

[Third embodiment]
In order to examine the influence of the blending amount of carbon black, a rubber composition was prepared according to the blending shown in Table 3 below by the same mixing method as in the first example. Details of each component in Table 3 are the same as in the first example. Each rubber composition obtained was vulcanized at 160 ° C. for 20 minutes to produce a test piece of a predetermined shape, and using the obtained test piece, tensile elongation and dynamics were obtained in the same manner as in the first example. The elastic modulus was measured.

  The results are as shown in Table 3, and it is clear that Comparative Example 17 and Comparative Example 18 to which no carbon black was added were compared with Comparative Example 19 and Comparative Example 20 in which the amount of carbon black was 5 parts by mass. In addition, when the amount of carbon black is small, the effect of adding the rubber-modified polyester resin is small, and the effect of improving the elastic modulus is hardly obtained. On the other hand, as is clear from the comparison between Comparative Example 21 and Example 9, by adding 10 parts by mass of carbon black, the effect of adding the rubber-modified polyester resin is exhibited and the effect of increasing elasticity is achieved. It was played clearly.

  Further, for each rubber composition of Comparative Example 18, Comparative Example 20 and Example 9, the average particle diameter of the rubber-modified polyester resin phase was measured by an electric micrograph. In Comparative Example 20 in which the amount of carbon black was 5 parts by mass, the average particle size was 3.1 μm, whereas in Example 9 in which the amount of carbon black was 10 parts by mass, the average particle size was Was 0.95 μm. From this, as the compounding amount of carbon black increased, the rubber-modified polyester resin was finely dispersed, and the effect of increasing the elasticity by the fine dispersion was supported.

As shown in Examples 1 and 9 to 12, the blending amount of carbon black greatly improved as the blending amount increased at 10 parts by mass or more, but in Comparative Example 22 exceeding 150 parts by mass, The drop in elongation was so great that it did not reach the practical level.

[Fourth embodiment]
In order to examine the influence of the blending amount of the rubber-modified polyester resin, a rubber composition was prepared by the same mixing method as in the first example according to the blending shown in Table 4 below. The details of each component in Table 4 are the same as in the first example. Each rubber composition obtained was vulcanized at 160 ° C. for 20 minutes to produce a test piece of a predetermined shape, and using the obtained test piece, tensile elongation and dynamics were obtained in the same manner as in the first example. The elastic modulus was measured and the tensile strength was also measured. The measuring method of tensile strength is as follows.

-Tensile strength: A tensile test (dumbbell No. 3, type, ambient temperature 23 ° C.) is performed according to JIS K6251.

A result is as showing in Table 4, and the elasticity modulus improved by the addition of 1 mass part or more of the rubber-modified polyester resin, and the elasticity modulus improved as the blending amount increased. However, the compounding amount of the rubber-modified polyester resin was 60 parts by mass, and in Comparative Example 23, which was too much, the tensile strength was significantly reduced and the practical level was not reached.

Claims (5)

  Thermoplastic polyester having 10 to 150 parts by mass of carbon black in 100 parts by mass of diene rubber and 20 to 50% by mass of a rubber block made of a polymer of isoprene and / or 1,3-butadiene in the molecule. A rubber composition comprising 1 to 50 parts by mass of a resin and dispersed in the diene rubber.   The rubber composition according to claim 1, wherein the polyester resin has a glass transition temperature of 130 ° C. or lower.   The rubber composition according to claim 1 or 2, wherein the polyester resin forms a dispersed phase having an average particle diameter of 1 µm or less. The rubber composition according to any one of claims 1 to 3, wherein the polyester resin has a melt viscosity of 5000 Pa · s or less at a shear rate of 100 s ^-1 at 140 ° C.   The polyester resin is obtained by reacting at least one diol component selected from the group consisting of polyisoprene diol, polybutadiene diol and isoprene butadiene copolymer diol with a dibasic acid component. The rubber composition according to any one of the above.