JP2007106919A - Rubber material, rubber composition using the same, and crosslinked rubber - Google Patents

Abstract

The present invention provides a novel rubber material having excellent silica dispersibility of a rubber composition containing silica. Furthermore, the present invention provides a rubber composition having an excellent balance of rubber characteristics that can fully exhibit the characteristics of silica compounding using the rubber material.
The rubber material is made of a high molecular compound having a phenyl sulfide group in the molecule and having a number average molecular weight of 2,000 to 500,000, and a crosslinked rubber can be decrosslinked. The crosslinked rubber is a sulfur-crosslinked diene rubber, and the content of the phenyl sulfide group in the polymer compound is 1 to 25% by weight. The rubber composition of the present invention contains the rubber material as a rubber component and contains 5 to 120 parts by weight of silica with respect to 100 parts by weight of the rubber component.
[Selection figure] None

Description

  The present invention relates to a rubber material and a rubber composition, and more specifically, a rubber material capable of improving silica dispersibility in a rubber composition containing silica, and a rubber composition having an excellent balance of rubber properties using the rubber material It is about.

  For rubber products such as pneumatic tires, anti-vibration rubbers, belts, etc., natural rubber and various synthetic rubbers are used as rubber bases according to the required characteristics, and reinforcing agents such as carbon black and silica, oils, waxes, anti-aging agents Rubber compositions containing various compounding agents such as vulcanizing agents and vulcanization accelerators are used.

  For example, rubber compositions used in tire treads are strongly demanded to reduce rolling resistance due to market needs for low fuel consumption, and braking performance and handling stability (hereinafter referred to as wet performance) on wet roads from the standpoint of safety. In addition, there is a need for excellent wear resistance in terms of durability and economy, and these low rolling resistance, wet performance, and wear resistance, which exhibit a contradiction tendency as rubber properties, are at a high level. It is desired to improve in a balanced manner.

  In response to these requirements, instead of carbon black conventionally used as a rubber reinforcing agent, a rubber composition containing silica that can easily achieve a balance between the rolling resistance and the wet performance is used for a tire tread. It is like that.

  However, silica is hydrophilic and has a strong self-aggregation property because the surface is covered with silanol groups, and when mixed into rubber, it is not easy to disperse in rubber and the rubber kneading time is increased. However, there are drawbacks in that temperature control is required and workability in a subsequent process due to poor dispersion is reduced.

  Conventionally, silane coupling agents have been used to improve the dispersibility of silica by increasing the affinity between silica and rubber, and to increase the binding force between the two, further improving the dispersibility of silica. Therefore, many improvements of these silane coupling agents have been proposed (for example, Patent Documents 1 to 3). In addition, a surface-treated silica that improves the kneading operation and characteristics such as rolling resistance at the same time (for example, Patent Document 4), and further by preblending and using low molecular weight butadiene rubber (BR) and high molecular weight BR Many studies have been made to improve the above-mentioned drawbacks of silica compounding, such as improving the dispersibility and processability of the silica (for example, Patent Document 5).

However, although the effect of the above technical improvement is recognized, there is still room for improvement in improving the dispersibility of silica, and there has not yet been a sufficient solution in terms of workability and scorch problems, or improvement in properties such as strength and modulus. This is the actual situation, and there is a social demand for satisfying higher demands.
Japanese Patent No. 3021516 JP 2000-336209 A JP 2005-2065 A Japanese Patent Laid-Open No. 11-124474 JP 2004-51797 A

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a novel rubber material capable of solving the above-mentioned problems of silica with excellent dispersibility of silica, and further to the rubber An object of the present invention is to provide a rubber composition that fully exhibits the characteristics of silica compounding using materials and has an excellent balance of rubber properties such as strength, modulus, wear resistance, and low heat build-up.

  As a result of intensive studies to solve the above problems, the present inventors have found that a polymer compound containing a phenyl sulfide group in the molecule remarkably improves the dispersibility of silica in a rubber component. Has reached

  That is, the invention according to claim 1 is a rubber material comprising a polymer compound having a number average molecular weight of 2,000 to 500,000 containing a phenyl sulfide group in the molecule.

  The invention according to claim 2 is the rubber material according to claim 1, which is obtained by decrosslinking the crosslinked rubber.

  The invention according to claim 3 is the rubber material according to claim 2, wherein the crosslinked rubber is a sulfur-crosslinked diene rubber.

  The invention according to claim 4 is the rubber material according to any one of claims 1 to 3, wherein the content of the phenyl sulfide group in the polymer compound is 1 to 25% by weight. .

  The invention according to claim 5 is characterized in that the polymer compound is obtained by subjecting the crosslinked rubber to a decrosslinking reaction using diphenyl disulfide as a decrosslinking agent. The rubber material described.

  The invention according to claim 6 is the rubber material according to claim 5, wherein the decrosslinking reaction of the crosslinked rubber is obtained by heat treatment in a solvent of carbon dioxide.

  The invention according to claim 7 is the rubber material according to claim 6, wherein the carbon dioxide is in a supercritical state.

  The invention described in claim 8 includes the rubber material according to any one of claims 1 to 7 as a rubber component, and includes 5 to 120 parts by weight of silica with respect to 100 parts by weight of the rubber component. It is a rubber composition.

  The invention according to claim 9 is characterized in that diene rubber is a main rubber component and the rubber material is contained in an amount of 0.5 to 30 parts by weight in 100 parts by weight of the rubber component. It is a rubber composition.

  Invention of Claim 10 is a rubber composition of Claim 8 or 9 characterized by including a silane coupling agent.

  The invention according to claim 11 is a crosslinked rubber obtained by crosslinking the rubber composition according to any one of claims 8 to 10 using a crosslinking agent.

  According to the rubber material of the present invention, by containing a phenyl sulfide group, it exhibits an excellent affinity for both hydrophilic silica and hydrophobic rubber, and has an excellent action as a silica dispersant. It can significantly improve the dispersibility of silica in the rubber component, improve the processability such as mixing and processability of unvulcanized rubber, and unvulcanized rubber properties, and fully demonstrate the features of silica compounding. It is possible to obtain a cross-linked rubber that can be used, and to provide rubber products for various uses that are excellent in balance of rubber properties such as strength, modulus, wear resistance, and low heat build-up.

  Hereinafter, embodiments of the present invention will be described.

  The rubber material of the present invention comprises a polymer compound having a phenyl sulfide group in the molecule and a number average molecular weight of 2,000 to 500,000.

  The rubber material can be obtained by decrosslinking a crosslinked rubber, and can also be obtained by a so-called vulcanized rubber regeneration treatment.

  The crosslinked rubber is preferably composed of a sulfur-crosslinked diene rubber, and the raw rubber for the crosslinked rubber is natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR). ), Chloroprene rubber (CR), nitrile rubber (NBR), diene rubber such as ethylene / propylene / diene copolymer (EPDM), or a mixture of two or more thereof, preferably NR, IR, SBR and BR.

  The rubber material of the present invention contains a phenyl sulfide group in the molecule, and the content thereof is 1 to 25% by weight in the polymer compound, preferably 1 to 15% by weight, more preferably 1 to 10%. % By weight, more preferably 1 to 6% by weight. When the content of the phenyl sulfide group is less than 1% by weight, the polarity of the rubber material cannot be obtained so much, the effect of improving the affinity with silica is small, and the dispersibility is insufficiently improved. On the other hand, if it exceeds 25% by weight, the molecular weight tends to decrease and mechanical properties such as strength and modulus tend to decrease.

  Moreover, the number average molecular weight (Mn) of this rubber material is 2,000-500,000, Preferably it is 5,000 or more, More preferably, it is 10,000 or more. If Mn is less than 2,000, affinity with a rubber component having a large molecular weight cannot be obtained, that is, Mn is preferably as large as possible, and even if the amount of the rubber material of the present invention is small, silica dispersion of the rubber composition The effect of can be produced. Further, a rubber material having Mn of 500,000 or more is an upper limit of Mn of the diene-based crosslinked rubber and is difficult to be obtained practically.

  Further, the rubber material can be obtained from sulfur-crosslinked crosslinked rubber, and in the decrosslinking step for regenerating the crosslinked rubber, the network structure is collapsed, and the rubber material is easily plasticized by depolymerization of the rubber molecules.

  In the rubber material of the present invention, diphenyl disulfide can be used as a decrosslinking agent (a regenerative agent for crosslinked rubber), and the crosslinked rubber can be decrosslinked. In this decrosslinking reaction, the S—S bond of diphenyl disulfide is cleaved to generate a radical, and the sulfur bond is cleaved by reacting with the sulfur bond (— (S) n—) between the molecular chains of the crosslinked rubber. This is because phenyl sulfide is added to the sulfur atom to regenerate the crosslinked rubber.

  The decrosslinking reaction of the crosslinked rubber is obtained by pressurization and heat treatment under an organic solvent such as carbon dioxide, toluene, and acetone as a solvent. The treatment is preferably carried out in a carbon dioxide solvent, particularly in a carbon dioxide atmosphere. When treated under critical conditions (for example, pressure 5 MPa, temperature 100 ° C. or higher), the reactivity of the decrosslinking agent, the heat treatment can be made effective, and the crosslinked rubber can be efficiently regenerated, resulting in silica dispersibility. It is preferable in that the rubber characteristics can be improved.

  The decrosslinking treatment of the crosslinked rubber in the carbon dioxide solvent can be performed, for example, by the method described in JP 2000-95895 A.

  The rubber composition of the present invention comprises the above rubber material as a rubber component and comprises 5 to 120 parts by weight of silica with respect to 100 parts by weight of the rubber component. The content of the rubber material in the rubber component is not particularly limited and can be used in any amount depending on the use of the rubber product.

  In addition, for applications such as tires and anti-vibration rubber, which require durability when used under severe conditions such as mechanical properties, fatigue resistance, and wear resistance, new rubber made of diene rubber is the main rubber component. The rubber material is preferably contained in an amount of 0.5 to 30 parts by weight in 100 parts by weight of the rubber component.

  As the diene rubber component which is the new rubber, NR and diene synthetic rubber can be used, and examples of the diene synthetic rubber include IR, SBR, BR, NBR, CR, EPDM and the like. The diene-based synthetic rubber is not limited by its polymerization method, molecular weight, microstructure, etc., and these diene-based rubbers may be used alone or in combination of two or more, and the blend ratio is arbitrary. . Depending on the application, non-diene rubbers such as butyl rubber (IIR) and chlorobutyl rubber (CIIR) may be included.

  Examples of the silica used in the present invention include wet silica, dry silica, sol-gel method silica, etc. Among them, wet silica having a good balance between the improvement effect of mechanical properties and low rolling resistance and wet performance is preferable. In addition, surface-treated silica whose surface is modified with various treating agents such as amines and organic polymers can also be used.

As the wet and dry silica, those having a nitrogen adsorption specific surface area (BET) of 100 to 300 m ² / g and a DBP oil absorption of 150 to 300 ml / 100 g are preferable, and if the BET is less than 100 m ² / g, When the reinforcing effect is difficult to obtain, and it exceeds 300 m ² / g, the dispersibility of silica is remarkably lowered, and the processability (mixing, extrudability, etc.) tends to deteriorate. Moreover, dispersibility can be more favorably maintained by setting the DBP oil absorption to 150 to 300 ml / 100 g. The BET of silica is measured according to the BET method described in ISO 5794, and the DBP oil absorption is measured according to the method described in JIS K6221.

  The compounding amount of the silica is 20 to 120 parts by weight, preferably 20 to 100 parts by weight, and more preferably 20 to 80 parts by weight with respect to 100 parts by weight of the rubber component. If the blending amount of silica is less than 20 parts by weight, rubber properties such as reinforcement and low heat build-up due to the blending of silica cannot be obtained, and if exceeding 120 parts by weight, even if the dispersibility is improved by using the rubber material according to the present invention, the rubber This increases the Mooney viscosity, deteriorates the problem of temperature rise during mixing and deteriorates workability, and decreases the strength and wear resistance.

  Moreover, it is preferable to mix | blend a silane coupling agent with the rubber composition of this invention. As the silane coupling agent, any conventionally known silane coupling agent such as sulfide type, mercapto type, amino type, vinyl type and the like can be arbitrarily selected and used, and silica and rubber molecules are physically bonded. Not only can it be chemically bonded firmly.

  Specific examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, and bis (2- Trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3- Chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamo Tetratetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3 -Triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, bis (3-triethoxysilylpropyl) tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide and the like are preferable.

  The amount of the silane coupling agent is preferably 5 to 25% by weight, more preferably 5 to 20% by weight, based on the total weight of the silica. If the blending amount is less than 5% by weight with respect to the amount of silica, the coupling effect between silica and rubber molecules is insufficient and the reinforcing property cannot be obtained, and the properties such as strength and modulus of the rubber composition cannot be secured. Also, the dispersibility of silica is adversely affected. Moreover, even if it exceeds 25 weight%, the effect corresponding to it is not acquired and it may become economically disadvantageous.

  In the rubber composition of the present invention, in addition to the rubber material, diene rubber (new rubber component), silica, and optionally a silane coupling agent, various conventional rubber materials such as carbon black, crosslinking agent ( Radical generators such as sulfur, sulfur chloride compounds, organic sulfur compounds, organic peroxides, azo compounds, oxime compounds, nitroso compounds, polyamine compounds, etc.), vulcanization accelerators (guanidine, aldehyde-amine, aldehyde- Ammonia, thiazole, sulfenamide, thiourea, thiuram, dithiocarbamate, zanddate, etc.), vulcanization accelerator, oil (paraffinic process oil, naphthenic process oil, aromatic) Process oil), zinc white, stearic acid, softener, resins, anti-aging agent (diphenylamine, p Amine derivatives such as phenylenediamines, quinoline derivatives, hydroquinone derivatives, monophenols, diphenols, thiobisphenols, hindered phenols, phosphites, etc.), clay, calcium carbonate, colorants, firing agents, etc. These various compounding agents can be appropriately blended, and the blending amount thereof can be used within a range not impairing the effects of the present invention.

  The method for producing the rubber composition of the present invention is not particularly limited, and the rubber composition can be produced according to a conventional method using various kneaders such as a Banbury mixer, a roll, and a kneader by blending the above-described blending components.

  The crosslinked rubber of the present invention is obtained by crosslinking the above rubber composition with a crosslinking agent. As the crosslinking agent, radical generation of sulfur, sulfur chloride compound, organic sulfur compound, organic peroxide, azo compound, etc. Agents, oxime compounds, nitroso compounds, polyamine compounds and the like.

  Among them, it is preferable to use a sulfur-based or organic peroxide, and it is used for tire treads, tires such as sidewalls and bead parts, and rubber products for various uses such as vibration-proof rubbers and belts. be able to.

  The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

  The rubber compositions of Examples and Comparative Examples according to the formulation shown in Table 2 were mixed and prepared according to a conventional method using a 20 L capacity closed Banbury mixer. The compounding materials and “rubber materials” used are as follows.

・ Natural rubber (NR): RSS # 3
・ Silica: Nippon Silica Co., Ltd. VN3
Silane coupling agent: Si69 manufactured by Degussa
・ Zinc flower: Zinc flower No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. ・ Stearic acid: Lunac S-20 manufactured by Kao Corporation
・ Sulfur: Powdered sulfur for rubber and vulcanization accelerator manufactured by Hosoi Chemical Co., Ltd .; Noxeller CZ manufactured by Ouchi Shinsei Chemical Co., Ltd.

・ Rubber materials (Table 1)
NR (RSS # 3) 100 parts by weight, carbon black (Showa Cabot Co., Ltd., Show Black N330) 50 parts by weight, zinc white (same as above) 3 parts by weight, stearic acid (same as above) 2 parts by weight, sulfur (same as above) 2 parts by weight and 1 part by weight of a vulcanization accelerator (same as above) were kneaded by a roll and vulcanized at 160 ° C. for 20 minutes to produce a crosslinked rubber.

  To the autoclave, 5 g of the crosslinked rubber and 20 parts by weight of diphenyl disulfide were added, a treatment solvent was introduced at a pressure of 7 MPa, and heat treatment was performed at 180 ° C. Thereafter, the processing solvent was brought into contact with the heat-treated rubber while maintaining the autoclave at 180 ° C. and 10 MPa, and the processing solvent containing diphenyl disulfide in the rubber was extracted and removed to prepare a reclaimed rubber to obtain a rubber material. The processing solvent was no solvent, carbon dioxide, toluene, and acetone. Mn of the obtained rubber material was determined in terms of polystyrene by GPC (gel permeation chromatography) method.

  For each rubber composition, a tensile test sample was prepared under vulcanization conditions at 160 ° C. for 20 minutes, and 100% modulus (M100), tensile strength (TB), and elongation were tensile according to JIS K6251 (using dumbbell No. 3). Tested and measured. Next, silica dispersibility and tire rolling resistance were evaluated according to the following methods. The results are shown in Table 2.

[Silica dispersibility]
With respect to the vulcanized rubber obtained under vulcanization conditions at 160 ° C. for 20 minutes, the rubber cross section was observed with an optical microscope (300 times), and the silica dispersion was evaluated according to a limit sample ranked in 10 stages. The results of the evaluation of three people were averaged, and the result was shown as an index with Comparative Example 1 being 100. The greater the value, the better the dispersibility.

[Rolling resistance]
When manufacturing a radial tire of size 215 / 60R16 in which each rubber composition is applied to the tread portion according to a conventional method, and running on a drum at an internal pressure of 200 kPa, a load load of 400 kg, and a speed of 80 km / h using a single-axis drum tester The rolling resistance index was measured, the rolling resistance index of each test tire was calculated according to the following formula, and the index was shown with the tire of Comparative Example 1 as 100. The larger the value, the smaller the rolling resistance and the better the fuel economy.
Rolling resistance (index) = (Rolling resistance of tire in Comparative Example 1) × 100 / (Rolling resistance of each tire)

  From the results of Table 2, the rubber composition using the rubber material-A according to the present invention can improve silica dispersibility, improve the rubber properties of modulus, strength, and elongation, and reduce the rolling resistance of the tire. can do. However, when the amount of the rubber material-A is increased (Examples 5 and 6), the dispersibility and rolling resistance are improved, but the rubber characteristics tend to be reduced, and mechanical characteristics such as tires and wear resistance are required. In use, the amount of the rubber material according to the present invention is preferably about 15 parts by weight. On the other hand, in rubber materials (Examples 7 and 8) using toluene and acetone as processing solvents, the dispersibility of silica is improved as compared with Comparative Example 1, but it is not as good as that due to carbon dioxide.

  The rubber composition obtained by the present invention can be used for various rubber products such as tires, anti-vibration rubbers, belts, packings, floor materials, sheet materials and the like. For example, by balancing low rolling resistance with wet performance and wear resistance, it is suitable as a tread rubber for pneumatic tires with excellent fuel efficiency, safety and durability, and a low dynamic magnification can be achieved. Therefore, it is useful as a rubber composition for vibration-proof rubber.

Claims (11)

A rubber material comprising a polymer compound having a phenyl sulfide group in the molecule and having a number average molecular weight of 2,000 to 500,000. The rubber material according to claim 1, wherein the rubber material is obtained by decrosslinking the crosslinked rubber. The rubber material according to claim 2, wherein the crosslinked rubber is a sulfur-crosslinked diene rubber. Content of the said phenyl sulfide group in the said high molecular compound is 1-25 weight%. The rubber material in any one of Claims 1-3 characterized by the above-mentioned. The rubber material according to any one of claims 2 to 4, wherein the polymer compound is obtained by subjecting the crosslinked rubber to a decrosslinking reaction using diphenyl disulfide as a decrosslinking agent. The rubber material according to claim 5, wherein the decrosslinking reaction of the crosslinked rubber is obtained by heat treatment in a solvent of carbon dioxide. The rubber material according to claim 6, wherein the carbon dioxide is in a supercritical state. A rubber composition comprising the rubber material according to claim 1 as a rubber component, and comprising 5 to 120 parts by weight of silica with respect to 100 parts by weight of the rubber component. The rubber composition according to claim 8, wherein diene rubber is a main rubber component and 0.5 to 30 parts by weight of the rubber material is contained in 100 parts by weight of the rubber component. The rubber composition according to claim 8 or 9, comprising a silane coupling agent. A crosslinked rubber obtained by crosslinking the rubber composition according to any one of claims 8 to 10 using a crosslinking agent.