JP2003082167A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition which excels in processability and dispersibility and, simultaneously, has good mechanical properties, particularly a high modulus of elasticity. SOLUTION: This rubber composition comprises (A) a nonpolar rubber, (B) a polar resin, and (C) a block copolymer composed of a conjugated diene polymer block P and an acrylic polymer block Q.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition,
More specifically, the present invention relates to a rubber composition having excellent processability and dispersibility and a high elastic modulus as compared with a rubber composition obtained by blending a nonpolar rubber and a polar resin.

[0002]

2. Description of the Related Art It has been well known that the impact resistance of a synthetic resin is improved by mixing a diene rubber polymer with a synthetic resin such as a styrene resin. On the other hand, contrary to this, there have been few attempts to improve the strength of the rubber by mixing a synthetic resin with a diene rubber,
For example, only a lightweight rubber composition in which a crystalline polyolefin resin is finely dispersed in EPDM crosslinked rubber and which is excellent in mechanical strength has been proposed (JP-A-9-286882, JP-A-9-309986). reference). However, since these rubber compositions are composed only of non-polar components, there is a problem that the oil resistance, the adhesion to polar components, etc. are not sufficient. For the above problems, even if a diene rubber and a polar resin having a large difference in solubility parameter are blended, sufficient workability cannot be obtained due to poor processability and dispersibility, and thus far good. The reality is that a rubber composition having excellent mechanical properties has not been obtained.

[0003]

Therefore, the present invention is excellent in processability and dispersibility and has good mechanical strength, especially in a blend of a nonpolar rubber and a polar resin having a large difference in solubility parameter. An object is to provide a rubber composition having a high elastic modulus.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a non-polar rubber (A) and a polar resin (B) having a large difference in solubility parameter are
Furthermore, they have found that the above problem can be solved by adding a block copolymer (C) composed of a conjugated diene polymer block P and an acrylic polymer block Q, and have completed the present invention. That is, according to the present invention, the above-mentioned objects are non-polar rubber (A), polar resin (B) and conjugated diene-based polymer block P and acrylic-based polymer block Q.
It can be achieved by a rubber composition containing a block copolymer (C).

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The nonpolar rubber (A) used in the present invention does not have a polar group or a polar bond (for example, a carboxyl group, a nitrile group, a halogen atom, etc.) in the molecule, and the rubber has no polarity. Specific examples of the non-polar rubber (A) used in the present invention include natural rubber, polyisoprene rubber, styrene-butadiene rubber, butadiene rubber, butyl rubber, ethylene-α olefin copolymer rubber, ethylene-α olefin-diene copolymer. Examples thereof include polymerized rubber and oil-extended products thereof. Among them, natural rubber, ethylene-α-olefin-diene copolymer rubber, oil-extended ethylene-
An α-olefin-diene copolymer rubber is preferably used. These non-polar rubbers can be used alone or in combination of two or more.

The polar resin (B) used in the rubber composition of the present invention has a polar group or a polar bond (for example, an ester group, a carboxyl group, a nitrile group, a halogen atom, etc.) in the molecule, whereby a resin is obtained. It has a polarity. In the present invention, any of the polar resins can be used, of which the solubility parameter value is 17,2.
00-24,000 (J / m ³ ) ^1/2 (8.6-12)
A resin in the range of (cal / cm ³ ) ^1/2 ) is preferably used.

Specific examples of the polar resin (B) used in the present invention include poly (meth) acrylic acid ester resins, polycarbonate resins, polyamide resins, polyester resins, polyphenylene ether resins, styrene resins, poly resins. Examples thereof include vinyl chloride-based resin, polyvinyl acetate-based resin, poly (meth) acrylamide-based resin, polysulfone-based resin, fluorine-based resin, polyimide-based resin, and thermoplastic polyurethane-based resin. These polar resins may be used alone or in combination of two or more. Among these resins, in the present invention, the polar resin (B) is preferably a poly (meth) acrylic acid ester resin or a polycarbonate resin, and particularly preferably a methacrylic resin.

In the rubber composition of the present invention, the content ratio of the non-polar rubber (A) and the polar resin (B) can be adjusted according to the application and usage of the rubber composition. ) Phase matrix forming properties and polar resin (B)
From the viewpoint of the reinforcing effect of the components, the content ratio (A / B) of the non-polar rubber (A) and the polar resin (B) is 3/97 to 97.
/ 3 (mass ratio) is preferable, and 40/60 to 9
6/4 is more preferable, and 50/50 to 95 /
More preferably, it is 5.

The block copolymer (C) used in the present invention
Is a block copolymer having a conjugated diene polymer block P (hereinafter sometimes simply referred to as “block P”) and an acrylic polymer block Q (hereinafter sometimes simply referred to as “block Q”). The block copolymer (C) used in the present invention is characterized in that the block P and the block Q having a large difference in solubility parameter are bonded.

The conjugated diene polymer block P in the block copolymer (C) is a polymer block mainly composed of a structural unit derived from a conjugated diene. Block P
May be composed of only structural units derived from a conjugated diene or may have structural units derived from a monomer other than the conjugated diene. When the block P has a structural unit derived from a monomer other than the conjugated diene, the structural unit is derived from a nonpolar monomer such as olefins and aromatic vinyl compounds. Is preferred. The conjugated diene constituting the block P may be either a conjugated diene having a chain structure or a conjugated diene having a cyclic structure, but it is preferably a conjugated diene having no polarity. Specific examples of the conjugated diene constituting the block P include 1,3-butadiene,
Examples thereof include isoprene, myrcene, 2-methyl-1,3-pentadiene, cyclohexadiene and the like.
Among these, the block P is preferably a structural unit derived from butadiene and / or isoprene, and more preferably a structural unit derived from isoprene, from the viewpoint of compatibility with a nonpolar rubber. More preferable.

The acrylic polymer block Q in the block copolymer (C) is a polymer block mainly composed of structural units derived from an acrylic monomer.
The block Q may consist only of structural units derived from an acrylic monomer, or may have structural units derived from a monomer other than an acrylic monomer. When the block Q has a structural unit derived from a monomer other than the acrylic monomer, the structural unit is derived from a monomer having a polar group and / or a single unit having no polar group. It may be derived from a monomer. As the acrylic monomer constituting the block Q, at least one kind of monomer selected from alkyl acrylate and alkyl methacrylic acid (hereinafter referred to as “(meth) acrylic acid alkyl ester and methacrylic acid alkyl ester”). It may be collectively referred to as "acrylic acid alkyl ester").

The (meth) acrylic acid alkyl ester constituting the block Q is preferably a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms. Specific examples of such (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate,
N-Butyl (meth) acrylate, t (meth) acrylic acid
ert-butyl, isobutyl (meth) acrylate, isooctyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, dodecyl (meth) acrylate, Examples thereof include lauryl (meth) acrylate. The block Q is preferably formed of one or more of these (meth) acrylic acid alkyl esters. Among these, the block Q is methyl (meth) acrylate, ethyl (meth) acrylate,
Propyl (meth) acrylate, n- (meth) acrylic acid
It is preferably formed of one or more of butyl, tert-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, and more preferably formed of methyl methacrylate.

The block copolymer (C) contains at least 1
As long as it is a copolymer in which one block P and at least one block Q are bonded in a block shape, the number of bonds in each block, the number of bonded blocks, the bonding form, etc. are not particularly limited. Examples of the block copolymer (C) include the block copolymers represented by the following general formulas (1) to (5).

[0014]

(PQ) x (1) (PQ) x-P (2) (QP) x-Q (3) {(PQ) y} r-Z (4) {(QP) y} r-Z (5) (In the formula, P is block P, Q is block Q, Z is a compound residue having a valence of 2 or more, x is an integer of 1 or more, y is an integer of 1 or more, and r is a compound residue Z. The same integers of 2 or more are respectively shown.)

Block copolymer (C) having at least one block P and at least one block Q
As long as it is, there is no particular difference in any bonding mode from the viewpoint of compatibilization performance, but from the viewpoint of ease of production of the block copolymer (C), one block P
Diblock copolymer PQ in which one block Q is bonded to
And / or a triblock copolymer PQP in which one block P is bonded to each end of one block Q is preferably used, and a diblock copolymer PQ is more preferably used.

The composition ratio of the block P and the block Q constituting the block copolymer (C) is not particularly limited,
The content ratio of block P and block Q is 97/3 to 3 /
It is preferably 97 (mass ratio). When the proportion of the block P composed of the conjugated diene-based polymer is 3% by mass or more, the dispersibility of the block copolymer (B) in the non-polar rubber (A) becomes good, while the proportion of the block Q is 3%. mass%
It is preferable for it to be above because the elastic modulus will be good.

Although the molecular weights of the conjugated diene polymer block P and the acrylic polymer block Q constituting the block copolymer (C) are not particularly limited, generally, the number average molecular weight of the block P and the block Q is 3,000. ~ 1,
It is preferably in the range of, 000,000 and 5,0
More preferably, it is in the range of 00 to 500,000. The number average molecular weight of the entire block copolymer (C) is preferably 6,000 to 1,500,000, more preferably 10,000 to 1,000,000. The number average molecular weight in the present specification is
The number average molecular weight in terms of polyethylene by gel permeation chromatography (GPC).

The method for producing the block copolymer (C) is not particularly limited, and it can be produced by solution polymerization, suspension polymerization or the like. For example, in polymerizing a conjugated diene, n-
Using an organic alkali metal compound such as butyllithium or sec-butyllithium as a polymerization initiator, and when polymerizing an acrylic monomer, it is composed of an organic alkali metal compound and a compound such as an organic aluminum compound or an organic zinc compound. Produced by using one of the initiator systems described above, depending on the bonding form (bonding order) of the block P and the block Q in the block copolymer (C), and then in the presence of the polymer. It can be produced by binding and polymerizing the other monomer component.

The content ratios of the component (A), the component (B) and the component (C) in the rubber composition of the present invention can be appropriately adjusted according to the application and usage form of the rubber composition, but a high phase From the viewpoint of solubility and development of high elastic modulus, the total amount of the nonpolar rubber (A) and the polar resin (B) is 100.
The block copolymer (C) is added in an amount of 0.1 to 5 parts by weight.
The content is preferably 0 part by mass, and 0.5 to 3
It is more preferable that the content is 0 part by mass.

In addition to the above-mentioned essential components (A), (B) and component (C), various additives commonly used in rubber applications are added to the rubber composition of the present invention as required. be able to. As these additives, vulcanizing agents, vulcanization accelerators, vulcanization accelerating aids, antioxidants, reinforcing agents, fillers,
Examples include softening agents and plasticizers.

Examples of the vulcanizing agent include sulfur and organic peroxides, and examples of the organic peroxides include benzoyl peroxide and dicumyl peroxide.

As the vulcanization accelerator, thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide and tetramethylthiuram monosulfide; zinc dibutyldithiocarbamate, zinc diethyldithiocarbamate, sodium dimethyldithiocarbamate, etc. Dithiocarbamic acids; thiazoles such as 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfenamide; organic accelerators such as thioureas such as trimethylthiourea and N, N'-diethylthiourea; and slaked lime;
Inorganic accelerators such as magnesium oxide, titanium oxide and litharge (PbO) can be mentioned.

Examples of the vulcanization accelerator include metal oxides such as zinc white and fatty acids such as stearic acid, oleic acid and cottonseed fatty acid. Examples of the antiaging agent include imidazoles such as 2-mercaptobenzimidazole; phenyl-α-naphthylamine, N, N ′.
-Amines such as -di-β-naphthyl-p-phenylenediamine and N-phenyl-N'-isopropyl-p-phenylenediamine;2,2'-methylenebis (4-methyl-)
6-t-butylphenol), di-t-butyl-p-cresol, styrenated phenol, and other phenols.

Carbon black is mainly used as a reinforcing agent, and inorganic reinforcing agents such as silica, zinc white, surface-treated precipitated calcium carbonate, magnesium carbonate, and clay are also used.
Alternatively, organic reinforcing agents such as coumarone indene resin, phenol resin and high styrene resin can be used. Examples of the softening agent include various vegetable oil-based, mineral oil-based and synthetic softening agents such as fatty acids (stearic acid, lauric acid, etc.), cottonseed oil, tall oil, asphalt substances, paraffin wax and the like. Examples of the plasticizer include dibutyl phthalate, dioctyl phthalate, tricresyl phosphate and the like.

The method for producing the rubber composition of the present invention is not particularly limited, and a known method can be adopted. For example, non-polar rubber component (A), polar resin (B),
A method of adding and mixing the block copolymer (C) and, if necessary, an additive to a kneading machine is adopted, in which case a commonly used rubber kneading machine such as Labo Plastomill, open roll, Banbury mixer or Brabender is used. be able to. Furthermore, a vulcanized product (vulcanized molded article or the like) can be produced by vulcanizing the above rubber composition in the same manner as is usually adopted in the rubber industry. For vulcanization, for example, a vulcanization press molding machine is used, and generally 8
It is carried out by heating at 0 ° C to 250 ° C for about 3 minutes to 60 minutes. In the rubber composition of the present invention obtained by the above-mentioned production method, the polar resin (B) is finely dispersed in the nonpolar rubber (A), and the average dispersed particle diameter of the polar resin (B) is usually 3 μm or less,
It is preferably 1 μm or less.

[0026]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

<Synthesis of Block Copolymer: Synthesis Example 1>
Add 9 toluene to a 1.5 liter autoclave container.
25 ml was charged and a nitrogen purge was performed for 20 minutes. To this, 8.5 ml of a 1.3 M sec-butyllithium cyclohexane solution and 220 ml of isoprene were added,
The block P was polymerized under stirring at 25 ° C. for 5 hours.
When a part of the obtained reaction mixture was sampled and analyzed by gas chromatography (hereinafter referred to as GC), it was found that the reaction rate of isoprene was 99% or more. In addition, as a result of analysis by GPC (polystyrene conversion), the number average molecular weight (Mn) of the polyisoprene of the obtained block P was 21,430, and its weight average molecular weight / number average molecular weight ratio (Mw / Mn). Was 1.02.

The above reaction mixture was then cooled to 0 ° C. and
5 mmol of isobutylbis (2,6-di-tert-
79 ml of a toluene solution containing butyl-4-methylphenoxy) aluminum and 11.5 ml of 1,2-dimethoxyethane were added, and the mixture was stirred for 10 minutes. Next, while vigorously stirring the obtained solution, 54 ml of methyl methacrylate was added thereto, polymerization was carried out at 0 ° C. for 3 hours under stirring, and then about 1 ml of methanol was added.
The polymerization was stopped. The reaction mixture obtained is 8,000 m
Block copolymer I was obtained by reprecipitation in 1 of methanol. The yield of the obtained polymer is almost 100.
%Met. As a result of GPC measurement (polystyrene conversion),
The polymer had a number average molecular weight of 26,390 and Mw / Mn of 1.03, and the results of NMR measurement showed that
The methyl methacrylate content was 25% by mass.

<Synthesis of Block Copolymer: Synthesis Example 2>
Add 9 toluene to a 1.5 liter autoclave container.
25 ml was charged and a nitrogen purge was performed for 20 minutes. To this, 4.0 ml of a 1.3 M sec-butyllithium cyclohexane solution and 200 ml of isoprene were added,
The block P was polymerized under stirring at 25 ° C. for 5 hours.
When a part of the obtained reaction mixture was sampled and analyzed by GC, it was found that the reaction rate of isoprene was 99% or more. Further, as a result of analysis by GPC (polystyrene conversion), the number average molecular weight (Mn) of the polyisoprene of the obtained block P was 41,300, and its weight average molecular weight / number average molecular weight ratio (Mw / Mn) Is 1.0
It was 2.

The above reaction mixture was then cooled to 0 ° C. and
6 mmol of isobutylbis (2,6-di-tert-
37 ml of a toluene solution containing butyl-4-methylphenoxy) aluminum and 11.3 ml of 1,2-dimethoxyethane were added, and the mixture was stirred for 10 minutes. Next, while vigorously stirring the obtained solution, 16 ml of methyl methacrylate was added thereto, polymerization was carried out at 0 ° C. for 3 hours with stirring, and then about 1 ml of methanol was added to stop the polymerization. It was 8,000 ml of the obtained reaction mixture
Block copolymer II was obtained by reprecipitation in methanol. The yield of the obtained polymer is almost 100.
%Met. As a result of GPC measurement (polystyrene conversion),
The polymer had a number average molecular weight of 44,700 and its Mw / Mn of 1.03, and the results of NMR measurement showed that
The methyl methacrylate content was 10% by mass.

Examples 1 and 2, Comparative Examples 1 and 2 Natural rubber (NR: RSS #) in the proportions (parts by mass) shown in Table 1
1), methacrylic resin (Kuraray Co., Ltd .: LW500), block copolymer and antiaging agent (Ouchi Shinko Chemical Co., Ltd .: Nocrac NS-6) were subjected to primary kneading at 160 ° C. for 5 minutes with a Labo Plastomill. Then, the obtained rubber composition, a cross-linking agent, a vulcanization accelerator, a vulcanization acceleration aid, and a processing aid were subjected to secondary kneading with a 4-inch roll at the following compounding ratio, and then at 5 MPa. A vulcanization press was performed under pressure at 145 ° C. for 25 minutes to prepare a 1 mm-thick test piece. (Blending ratio) Rubber composition: 100 parts by mass vulcanizing agent (sulfur): 2 parts by mass vulcanization accelerator (Ouchi Shinko Chemical Co., Ltd .: Nocceller CZ): 1
Parts by mass Vulcanization acceleration aid (zinc oxide): 5 parts by mass Processing aid (stearic acid): 3 parts by mass

The change in morphology of the rubber composition obtained above before and after vulcanization was evaluated by observing with a scanning electron microscope after the rubber composition was freeze-cut and stained with osmium tetroxide. The obtained test piece was evaluated according to JIS K-6301 except that the thickness of the test piece was 1 mm, and 100% modulus, 200% modulus and JIS-A hardness were measured and obtained. The results are shown in Table 1.

[0033]

[Table 1]

From the results of Comparative Example 1, if the block copolymer was not added, the kneading could not be sufficiently carried out in the primary kneading by the plastomill, macrophase separation would occur, and roll kneading and vulcanization press could be carried out. Moreover, the mechanical properties could not be evaluated. On the other hand, from the results of Example 1 and Example 2, the composition of the present invention can be uniformly kneaded in the plastomill, and the dispersed particle size before vulcanization is both 0.12.
It can be seen that the particle size is μm and can be finely dispersed, and the dispersed particle size after vulcanization does not change significantly. Further, from the results of Example 1 and Example 2 and Comparative Example 2, by adding the polar resin component and the block copolymer component,
It can be seen that a rubber composition having a high elastic modulus and hardness can be obtained.

[0035]

EFFECT OF THE INVENTION Nonpolar rubber (A) and polar resin (B)
In the rubber composition of the present invention containing the block copolymer (C) together, the non-polar rubber (A) and the polar resin (B) are compatibilized with each other to form a morphology in which both are uniformly and finely mixed and dispersed. ing. Therefore, the rubber composition of the present invention is excellent in workability because the rubber composition does not adhere to a kneading device such as a roll during kneading. Moreover, the rubber composition of the present invention, when vulcanized or crosslinked, provides a rubber composition having mechanical properties, particularly a high elastic modulus, and therefore, for example, gaskets, hoses, tubes, rubber plates, conveyor belts. It can be suitably used in a wide range of applications such as, packing, O-rings, bearing seals, oil seals, rubber rolls, blades, and vehicle tires.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshiko Hamashima             41 Miyukigaoka, Tsukuba City, Ibaraki Prefecture Co., Ltd.             Kuraray F-term (reference) 4J002 AC01W AC03W AC06W AC08W                       BB04W BB15W BB18W BC02X                       BD03X BD12X BF02X BG04X                       BG05X BG13X BL01W BP033                       CF00X CG00X CH07X CK02X                       CL00X CM04X CN03X FD010                       FD020 FD140 FD150 GC00                       GJ00 GN01

Claims (3)

[Claims] 1. A rubber containing a non-polar rubber (A), a polar resin (B) and a block copolymer (C) comprising a conjugated diene polymer block P and an acrylic polymer block Q. Composition. 2. The rubber composition according to claim 1, wherein the polar resin (B) dispersed in the non-polar rubber (A) has an average dispersed particle size of 3 μm or less. 3. The rubber composition according to claim 1, wherein the polar resin (B) is a methacrylic resin.