JP4659303B2 - Diene rubber composition - Google Patents

Description

【００３５】
表１に示される結果から、本発明のゴム組成物は混練時のトルク変化が小さくなり、加工性及びシリカの分散状態が向上することがわかる。
また、実施例１及び実施低２と比較例２との比較から、タイヤのグリップ性能と相関ある０℃でのｔａｎδは、未変性ポリイソプレンを添加した場合に比べても、本発明のゴム組成物の場合には向上していることがわかる。
【００３６】
【発明の効果】
以上説明したように、本発明のジエン系ゴム組成物は、加工性に優れかつシリカ粉末の分散性にも優れており、その特性を生かす各種用途、例えばトレッド、カーカス、サイドウォール、ビード部などのタイヤ各部位、あるいはホース、窓枠、ベルト、靴底、防振ゴム、自動車部品などのゴム製品への利用が好適である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diene rubber composition, and more specifically, a diene rubber excellent in processability and dispersibility of an inorganic filler obtained by blending a specific block copolymer and a silicon inorganic filler in a diene rubber. The present invention relates to a rubber composition.
[0002]
[Prior art]
Conventionally, silica is also called white carbon and has excellent reinforcing properties, so it has been used for rubber products that require white or light color. Further, in recent years, a rubber composition in which silica is blended in place of carbon black as a reinforcing agent in a diene rubber has been proposed in order to achieve both high grip performance and low rolling resistance of the tire as a rubber material for tires. . However, since silica is designed to have a very small particle size in order to develop a high degree of physical properties, the filling specific gravity is small and bulky, and poor dispersion tends to occur when blended with rubber, and grip performance, and There has been a problem that characteristics such as rolling resistance of the tire are not sufficiently improved.
[0003]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a diene rubber composition having not only excellent processability but also excellent dispersibility of a silicon-based inorganic filler.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have determined that a specific amount of block copolymer and silica powder comprising a conjugated diene polymer block P and an acrylic polymer block Q is added to the diene rubber. By blending, it was found that the above object was achieved, and the present invention was completed.
That is, according to the present invention, the object is 100 parts by mass of a diene rubber, 1 to 50 parts by mass of a block copolymer composed of a conjugated diene polymer block P and an acrylic polymer block Q, and a silicon inorganic filler. This can be achieved by a diene rubber composition composed of 4 to 100 parts by mass.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The diene rubber used in the present invention is not particularly limited as long as it is a diene rubber used in ordinary rubber products, and is a solid rubber mainly composed of a diene monomer such as butadiene and isoprene. Specific examples thereof include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, styrene-isoprene rubber, nitrile-conjugated diene copolymer rubber, chloroprene rubber, and butyl rubber. These diene rubbers can be used alone or in combination of two or more.
[0006]
The block copolymer used in the present invention comprises 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”). It is a block copolymer having. The block copolymer 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 to each other, whereby an acrylic polymer block which is a polar part and silicon such as silica powder. It seems that the affinity with inorganic inorganic fillers is improved.
[0007]
The conjugated diene polymer block P in the block copolymer is a polymer block mainly composed of structural units derived from conjugated diene. The block P may be composed of only a structural unit derived from a conjugated diene or may have a structural unit 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 monomer having no polarity such as an olefin or an aromatic vinyl compound. It is preferable that
The conjugated diene constituting the block P may be a conjugated diene having a chain structure or a conjugated diene having a cyclic structure, but is preferably a conjugated diene having no polarity. Specific examples of the conjugated diene constituting the block P include 1,3-butadiene, isoprene, myrcene, 2-methyl-1,3-pentadiene, cyclohexadiene and the like. Among these, from the viewpoint of compatibility with nonpolar rubber, the block P is preferably composed of a structural unit derived from butadiene and / or isoprene, and is preferably composed of a structural unit derived from isoprene. More preferred.
[0008]
The acrylic polymer block Q in the block copolymer is a polymer block mainly composed of structural units derived from an acrylic monomer. The block Q may be composed of only a structural unit derived from an acrylic monomer, or may have a structural unit derived from a monomer other than the acrylic monomer. When the block Q has a structural unit derived from a monomer other than an 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 monomer selected from an alkyl acrylate ester and an alkyl methacrylate ester (hereinafter referred to as “(meth) acrylate alkyl ester and methacrylate alkyl ester”). May be collectively referred to as “alkyl acrylate ester”).
[0009]
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 esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. Tert-butyl acid, isobutyl (meth) acrylate, isooctyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, dodecyl (meth) acrylate And lauryl (meth) acrylate. The block Q is preferably formed from one or more of these (meth) acrylic acid alkyl esters.
Among these, the block Q is composed of methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, (meta ) It is preferably formed from one or more of 2-ethylhexyl acrylate, and more preferably formed from methyl methacrylate.
[0010]
As long as the block copolymer is a copolymer in which at least one block P and at least one block Q are bonded in a block shape, the number of bonds, the number of blocks connected, and the form of bonding are not particularly limited. .
As an example of a block copolymer, the block copolymer shown by the following general formula (1)-(5) can be mentioned.
[0011]
[Chemical 1]
(PQ) x (1)
(PQ) x-P (2)
(QP) xQ (3)
{(PQ) y} r-Z (4)
{(QP) y} r-Z (5)
(Wherein 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 the same as compound residue Z 2 Each of the above integers is shown.)
[0012]
As long as the block copolymer has at least one block P and at least one block Q, there is no particular difference in any bonding mode from the viewpoint of compatibilization performance. From the viewpoint of ease of production, a diblock copolymer PQ in which one block P and one block Q are combined and / or one block P is bonded to each end of one block Q. Triblock copolymer PQP is preferably used, and diblock copolymer PQ is more preferably used.
[0013]
The composition ratio of the block P and the block Q constituting the block copolymer is not particularly limited, but the content ratio of the block P and the block Q is preferably 97/3 to 3/97 (mass ratio). When the proportion of the block P made of the conjugated diene polymer is 3% by mass or more, the dispersibility of the block copolymer in the diene rubber becomes good, while the proportion of the block Q is 3% by mass or more. This is preferable because the elastic modulus is good.
[0014]
The molecular weights of the conjugated diene polymer block P and the acrylic polymer block Q constituting the block copolymer are not particularly limited, but generally the number average molecular weight of the block P and block Q is 5,000 to 1,000,000. It is preferable to be within the range of 7,000, more preferably within the range of 7,000 to 500,000. The number average molecular weight of the entire block copolymer (B) is preferably 10,000 to 1,500,000, and more preferably 14,000 to 1,000,000.
In addition, the number average molecular weight in this specification means the number average molecular weight in polyethylene conversion by gel permeation chromatography (GPC).
[0015]
The production method of the block copolymer is not particularly limited, and can be produced by solution polymerization, suspension polymerization or the like.
For example, in the polymerization of conjugated dienes, an organic alkali metal compound such as n-butyllithium or sec-butyllithium is used as a polymerization initiator, and in the polymerization of an acrylic monomer, an organic alkali metal compound and organic aluminum are used. Using an initiator system composed of a compound such as a compound or an organic zinc compound, one of the polymers was produced according to the bonding form (bonding order) of the block P and the block Q in the block copolymer. Then, it can manufacture by couple | bonding and polymerizing another monomer component in presence of this polymer.
[0016]
The blending ratio of the block copolymer is in the range of 1 to 50 parts by mass, preferably in the range of 2 to 40 parts by mass with respect to 100 parts by mass of the diene rubber. When the blending amount of the block copolymer is less than 1 part by mass, the affinity with the silicon-based inorganic filler is insufficient and the dispersion improving effect cannot be obtained, which is not preferable. On the other hand, when the blending amount exceeds 50 parts by mass, the mechanical properties of the rubber composition are undesirably lowered.
[0017]
The silicon-based inorganic filler used in the present invention can be used without particular limitation as long as it is an inorganic material mainly composed of a silicon component such as silicic acid, silicate, silicon dioxide, etc. A silica powder is mentioned. The silica powder is mainly composed of silicic acid and / or silicate, and any silica powder produced by a wet method or a dry method can be used.
[0018]
The blending ratio of the silicon-based inorganic filler is in the range of 4 to 100 parts by mass, preferably in the range of 10 to 90 parts by mass with respect to 100 parts by mass of the diene rubber. When the amount of the silicon-based inorganic filler is less than 4 parts by mass, the reinforcing property is inferior.
[0019]
In the diene rubber composition of the present invention, various additives commonly used in the rubber industry are used as necessary in addition to the diene rubber, the block copolymer and the silicon inorganic filler which are essential components. Examples of these additives include vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids, anti-aging agents, reinforcing agents, other fillers, softeners, and plasticizers.
[0020]
Examples of the vulcanizing agent include sulfur and organic peroxides, and examples of the organic peroxide include benzoyl peroxide and dicumyl peroxide.
The vulcanization accelerators include thiuram vulcanization accelerators such as tetramethylthiuram disulfide and tetramethylthiuram monosulfide; zinc dibutyldithiocarbamate, zinc diethyldithiocarbamate, sodium dimethyldithiocarbamate and the like. Dithiocarbamic acids; thiazoles such as 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfenamide; organic accelerators such as thioureas such as trimethylthiourea and N, N′-diethylthiourea, slaked lime, oxidation Examples thereof include inorganic promoters such as magnesium, titanium oxide, and resurge (PbO).
[0021]
Examples of the vulcanization acceleration aid include metal oxides such as zinc white, or fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid.
Examples of the antioxidant include imidazoles such as 2-mercaptobenzimidazole; phenyl-α-naphthylamine, N, N′-di-β-naphthyl-p-phenylenediamine, N-phenyl-N′-isopropyl-p- Examples include amines such as phenylenediamine; phenols such as 2,2′-methylenebis (4-methyl-6-tert-butylphenol), di-tert-butyl-p-cresol, and styrenated phenol.
[0022]
Examples of reinforcing agents and other fillers include inorganic materials such as carbon black, zinc white, surface-treated precipitated calcium carbonate, magnesium carbonate, and clay, coumarone indene resin, and phenol as long as the object of the present invention is not impaired. Organic materials such as resins and high styrene resins can be used.
[0023]
Examples of the softener include vegetable oil-based, mineral oil-based, and synthetic softeners such as fatty acids (stearic acid, lauric acid, etc.), cottonseed oil, tall oil, asphalt substances, and paraffin wax.
Examples of the plasticizer include various plasticizers such as dibutyl phthalate, dioctyl phthalate, and tricresyl phosphate.
[0024]
The method for producing the diene rubber composition of the present invention is not particularly limited, and a conventionally known method can be adopted. More specifically, a lab plast mill, an open roll, a Banbury mixer, a Brabender, etc. It is prepared by mixing and kneading using a normal rubber kneader. For example, a compounding agent excluding a vulcanizing agent and a vulcanization accelerator and silicon-based inorganic fillers such as diene rubber, block copolymer and silica powder, which are essential components, are mixed in a kneader such as Laboplast Mill, Banbury or the like. Next, the mixture, vulcanizing agent and vulcanization accelerator are secondarily kneaded in a kneader such as an open roll, and the resulting mixture is press vulcanized to obtain the diene rubber composition of the present invention. You can get things.
[0025]
In this case, the temperature during the primary kneading is generally in the range of 80 to 200 ° C. If this temperature is lower than 80 ° C., the improvement in wear resistance may be reduced, and conversely if it exceeds 200 ° C., the diene rubber component may be burnt. The kneading time is generally 30 seconds to 30 minutes.
Subsequently, after cooling the obtained mixture to 100 degrees C or less normally, Preferably it is room temperature-80 degreeC, a vulcanizing agent and a vulcanization accelerator are added, and secondary kneading is performed. The temperature is generally room temperature to 80 ° C. Thereafter, the diene rubber composition of the present invention is obtained by press vulcanization at 80 ° C. to 200 ° C. for about 2 minutes to 60 minutes using a press vulcanization molding machine or the like.
[0026]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.
[0027]
<Synthesis of Block Copolymer: Synthesis Example 1>
920 ml of toluene was charged into a 1.5 liter autoclave container and purged with nitrogen for 20 minutes. To this was added 4.9 ml of a cyclohexane solution of 1.3 M sec-butyllithium and 287 ml of isoprene, and polymerization of block P was carried out with 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), the reaction rate of isoprene was 99% or more. As a result of analysis by GPC (polystyrene conversion), the number average molecular weight (Mn) of the polyisoprene of the obtained block P is 48,460, and the ratio of the weight average molecular weight / number average molecular weight (Mw / Mn). Was 1.03.
[0028]
The reaction mixture was then cooled to −30 ° C., 89 ml of a toluene solution containing 62 mmol of isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum and 9,2-dimethoxyethane. 2 ml was added and stirred for 10 minutes.
Next, while vigorously stirring the resulting solution, 6.3 ml of n-butyl acrylate was added thereto, and polymerization was performed with stirring at −30 ° C. for 1 hour, and then about 1 ml of methanol was added. The polymerization was stopped.
The obtained reaction mixture was reprecipitated in 8,000 ml of methanol to obtain block copolymer I. The yield of the obtained polymer was almost 100%. As a result of GPC measurement (polystyrene conversion), the polymer has a number average molecular weight of 51,390 and an Mw / Mn of 1.02, and as a result of NMR measurement, the n-butyl acrylate content is 2.6 mass. %Met.
[0029]
<Synthesis of block copolymer: Synthesis example 2>
920 ml of toluene was charged into a 1.5 liter autoclave container and purged with nitrogen for 20 minutes. To this, 7.1 ml of a 1.3M sec-butyllithium cyclohexane solution and 287 ml of isoprene were added, and polymerization of block P was conducted with stirring at 25 ° C. for 5 hours.
When a part of the obtained reaction mixture was sampled and analyzed by GC, the reaction rate of isoprene was 99% or more. As a result of analysis by GPC (polystyrene conversion), the number average molecular weight (Mn) of the polyisoprene of the obtained block P is 33,000, and the ratio of the weight average molecular weight / number average molecular weight (Mw / Mn). Was 1.03.
[0030]
Then, the reaction mixture was cooled to −30 ° C., 129 ml of a toluene solution containing 91 mmol of isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum and 1,2-dimethoxyethane. 2 ml was added and stirred for 10 minutes.
Next, while vigorously stirring the resulting solution, 6.3 ml of n-butyl acrylate was added thereto, and polymerization was performed with stirring at −30 ° C. for 1 hour, and then about 1 ml of methanol was added. The polymerization was stopped.
The obtained reaction mixture was reprecipitated in 8000 ml of methanol to obtain block copolymer II. The yield of the obtained polymer was almost 100%. As a result of GPC measurement (polystyrene conversion), the polymer has a number average molecular weight of 35,000 and an Mw / Mn of 1.02, and as a result of NMR measurement, the n-butyl acrylate content is 2.6 weight. %Met.
[0031]
Examples 1-2 and Comparative Examples 1-2
Natural rubber (RSS # 1), block copolymer, unmodified polyisoprene (manufactured by Kuraray Co., Ltd .: LIR50), silica powder (manufactured by Nippon Silica Kogyo Co., Ltd .: nip seal VN3), and anti-aging ratio shown in Table 1 (parts by mass) Agent (manufactured by Ouchi Shinsei Chemical Co., Ltd .: Nocrack NS-6) and stearic acid were mixed, and this was subjected to primary kneading at 130 ° C. for 5 minutes, and the resulting mixture, crosslinking agent, and vulcanization acceleration After the secondary kneading using a 4-inch roll at a compounding ratio shown below, the vulcanization accelerator, vulcanization accelerator, and amine compound were pressed at 145 ° C. under a pressure of 5 MPa and pressed for an optimal vulcanization time of 1 mm thickness. A test piece was prepared.
(Mixing ratio)
Rubber composition: 100 parts by mass vulcanizing agent (sulfur): 2 parts by mass vulcanizing accelerator (manufactured by Ouchi Shinsei Chemical Co., Ltd .: Noxeller CZ): 1.3 parts by mass vulcanizing accelerator (zinc oxide): 5 parts by mass Part dicyclohexylamine: 3 parts by mass
The following evaluation tests were performed using the obtained test pieces, and the obtained results are shown in Table 1.
(Evaluation test method)
(1) Workability: Torque change during primary kneading by a plast mill was measured, and the degree of change was indicated by a symbol from the least change.
○: Almost no change in torque is confirmed.
Δ: A slight increase in torque is confirmed.
X: Torque increase enough to generate heat is confirmed.
[0033]
(2) Dispersibility of silica powder: The obtained rubber composition was freeze-cut and stained with osmium tetroxide, and then evaluated by observation with a scanning electron microscope.
(3) tan δ: Measured at 11 Hz using a DVE-V4 FT Rheospectr manufactured by Rheology.
(4) Mechanical performance: Except that the thickness of the test piece is 1 mm, the tensile strength, tension, 100% modulus and JIS-A hardness of the vulcanized rubber composition are determined in accordance with JIS K-6301. Each was measured.
[0034]
[Table 1]

[0035]
From the results shown in Table 1, it can be seen that the rubber composition of the present invention has a small torque change during kneading, and the processability and the dispersion state of silica are improved.
Further, from comparison between Example 1 and Example 2 and Comparative Example 2, tan δ at 0 ° C., which correlates with the grip performance of the tire, is a rubber composition of the present invention even when compared with the case where unmodified polyisoprene is added. In the case of a thing, it turns out that it is improving.
[0036]
【The invention's effect】
As described above, the diene rubber composition of the present invention has excellent processability and excellent dispersibility of silica powder, and various uses that make use of the characteristics, such as treads, carcass, sidewalls, bead parts, etc. It is suitable for use in rubber parts such as tire parts, hoses, window frames, belts, shoe soles, anti-vibration rubbers and automobile parts.

Claims (2)

Diene rubber composition comprising 100 parts by mass of diene rubber, 1 to 50 parts by mass of block copolymer comprising conjugated diene polymer block P and acrylic polymer block Q, and 4 to 100 parts by mass of silicon inorganic filler object. The diene rubber composition according to claim 1, wherein the silicon-based inorganic filler is silica powder.