JP2012051969A - Method for producing modified diene-based rubber polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dispersibility of fillers, such as carbon black and silica.SOLUTION: An unvulcanized diene-based rubber polymer is irradiated with electron beams. Then, a compound having a carbon-carbon double bond and an amino group in the molecule is added to the electron beam-irradiated diene-based rubber polymer. Thus, a modified diene-based rubber polymer is obtained by the reaction of the compound with the diene-based rubber polymer. Also, a rubber composition is obtained by blending and mixing the fillers, such as carbon black and silica, with the modified diene-based rubber polymer.

Description

  The present invention relates to a modified diene rubber polymer and a method for producing the same, and also relates to a rubber composition using the modified diene rubber polymer and a method for producing the same.

  Conventionally, in a diene rubber such as styrene-butadiene rubber, it is known that a terminal-modified polymer is prepared by adding a modifying group at the time of polymer production. Such a modified polymer, for example, when mixed with a filler such as silica to prepare a rubber composition, can improve the dispersion of the filler by improving the affinity with the filler. As compared with the case of using the diene rubber polymer, the hysteresis loss of the rubber composition can be reduced, that is, the loss coefficient (tan δ) can be kept low. Therefore, for example, the rolling resistance of a pneumatic tire can be reduced, contributing to a reduction in fuel consumption of an automobile. However, the above conventional methods generally have a problem that they can be carried out only under anionic polymerization.

Japanese Patent Laid-Open No. 04-045114 Japanese Patent Application Laid-Open No. 10-025358

  The present inventor has intensively studied to improve the dispersion of the filler, and has considered adding a compound having a specific functional group to the diene rubber polymer by electron beam irradiation.

  As a technique for imparting a compound to a rubber polymer using electron beam irradiation, the above-mentioned Patent Document 1 discloses that a crosslinked silicone rubber is impregnated with a radical polymerizable monomer and then the monomer is polymerized by electron beam irradiation. Is disclosed. Further, Patent Document 2 discloses that a monomer is applied to a natural rubber latex film and a polymer film is formed by electron beam irradiation. However, Patent Document 1 aims to increase the hardness of silicone rubber, and Patent Document 2 aims to improve the adhesiveness of rubber products, both of which improve the dispersion of fillers. is not. In addition, in any case, a crosslinked (vulcanized) rubber product is irradiated with an electron beam and is not intended for an unvulcanized diene rubber polymer.

  An object of this invention is to provide the manufacturing method of the modified | denatured diene type rubber polymer which can improve dispersion | distribution of a filler.

  The method for producing a modified diene rubber polymer according to the present invention includes a step of irradiating an unvulcanized diene rubber polymer with an electron beam, and a compound having a carbon-carbon double bond and an amino group in the molecule. And a step of imparting to the rubber polymer.

  The method for producing a rubber composition according to the present invention is characterized in that a filler is blended in the modified diene rubber polymer obtained above and mixed.

  The modified diene rubber polymer according to the present invention reacts a compound having a carbon-carbon double bond and an amino group in the molecule with the diene rubber polymer by electron beam irradiation on the unvulcanized diene rubber polymer. It is a thing. The rubber composition according to the present invention contains the modified diene rubber polymer and a filler.

  According to the present invention, an amino group having high reactivity or affinity for a functional group such as a hydroxyl group or a carboxyl group present on the surface of a filler such as silica or carbon black is converted into a diene rubber polymer by electron beam irradiation. By adding, when dispersed in the rubber composition, the dispersion of the filler can be improved.

  Embodiments of the present invention will be described below.

  In the embodiment of the present invention, examples of the unvulcanized diene rubber polymer to be treated include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), Examples thereof include various diene rubber polymers such as styrene-isoprene copolymer rubber, butadiene-isoprene copolymer, and styrene-isoprene-butadiene copolymer rubber. Of these, styrene-butadiene rubber, butadiene rubber, and natural rubber are preferably used.

  Such a diene rubber polymer is commercially available as a solid or latex, and these can be used. You may use the oil-extended rubber marketed in the state which added oil. Of course, a polymer obtained by a known method using a diene monomer (a vinyl monomer may be included as a copolymerization component) can also be used.

  In this embodiment, an electron beam is irradiated to an unvulcanized diene rubber polymer. Radiation can be generated at the carbon-carbon double bond (C═C) portion or C—H bond portion of the diene rubber polymer by irradiation with an electron beam. The unvulcanized one is used because the diene rubber polymer modified according to the present embodiment is used as a raw rubber blended in the rubber composition, that is, a matrix in which a filler such as carbon black or silica is dispersed. The rubber component is modified in advance to improve the dispersion of the filler.

  When the diene rubber polymer is a solid substance upon electron beam irradiation, radicals are generated mainly on the surface layer of the solid substance, and it is difficult to modify the solid part. Therefore, in the case of a solid material, in order to modify it as uniformly as possible, it is preferable to use, for example, a sheet-like material cut or sheeted to a thickness of 2 cm or less, more preferably about 1 cm or less. That is, it is preferable to irradiate the surface of the sheet-like material made of an unvulcanized diene rubber polymer with an electron beam. Even when latex of styrene-butadiene rubber or natural rubber is used, it is preferable to irradiate the surface of the water with an electron beam at a water depth of 2 cm or less, more preferably 1 cm or less, in order to modify as uniformly as possible.

  The electron beam irradiation conditions are not particularly limited, but the acceleration voltage is preferably 1 to 5 MV, and the irradiation dose is preferably 10 to 400 kGy, more preferably 50 to 250 kGy. The reason why the acceleration voltage is set to be high in this way is to allow the electron beam to penetrate into the solid as much as possible.

  Thus, the monomer as a modifier is imparted to the diene rubber polymer irradiated with the electron beam at the stage where the generated radical is present (that is, before the radical disappears). Here, the monomer refers to a low molecular compound having a carbon-carbon double bond and an amino group in the molecule.

More specifically, the monomer includes an unsaturated group (for example, vinyl group) represented by H ₂ C═CR— (wherein R is a hydrogen atom or a methyl group) as a radically polymerizable carbon-carbon double bond. (H ₂ C═CH—), isopropenyl group (H ₂ C═C (CH ₃ ) —), allyl group (H ₂ C═CH—CH ₂ —)) and at least one carbon black or silica It is preferable to use those having at least one amino group having high reactivity or affinity for the functional group (for example, hydroxyl group or carboxyl group) on the surface of the filler. The amino group may be a primary amino group, a secondary amino group, or a tertiary amino group, or may be a nitrogen-containing heterocyclic ring such as a pyridyl group.

  Examples of the monomer that is such a radical polymerizable amine compound include amines represented by the following general formula (1) such as allylamine, 4-aminostyrene, N, N-dimethylallylamine, and 4-vinylbenzylamine. Compound, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminomethyl methacrylate, dimethylaminomethyl acrylate, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylate, dimethylaminobutyl methacrylate, dimethylaminobutyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, Diethylaminopropyl methacrylate, diethylaminopropyl acrylate, diethylaminobutyl methacrylate DOO, aminoalkyl (meth) acrylate compound represented by the following general formula, such as diethylaminoethyl acrylate (2), 2-vinylpyridine, 3-vinylpyridine, and vinyl pyridine, such as 4-vinyl pyridine. Any of these may be used alone or in combination of two or more.

In the formula, R represents a hydrogen atom or a methyl group. A represents a C1-C10 bivalent hydrocarbon group (for example, an alkylene group, an arylene group, an aralkyl group, etc.) which may contain an aromatic ring. n represents 0 or 1. R ¹ and R ² each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. p represents an integer of 1 to 4.

  The method for applying the monomer to the diene rubber polymer is not particularly limited. For example, when the monomer is liquid, it is diluted as it is or with a solvent such as water, or when the monomer is solid, the monomer is added to a solvent such as water. Dissolve to prepare a monomer liquid (a liquid containing monomer) and immerse the diene rubber polymer in the monomer liquid, or apply the monomer liquid to the surface of the diene rubber polymer by brushing or spraying. May be. When the monomer is a gas, the monomer can also be imparted by placing a diene rubber polymer in an atmosphere filled with the monomer. When the diene rubber polymer is latex, the monomer can be added by mixing the latex and the monomer liquid by dropping the monomer liquid into the latex or conversely dropping the latex into the monomer liquid. .

  After adding the monomer, it is allowed to stand for a predetermined time. In addition, when letting it stand, you may put in an oven etc. and heat (for example, 30-80 degreeC). Then, it wash | cleans with warm water etc. and removes the unreacted monomer and the homopolymer formed by polymerizing monomers.

  Thereby, an unvulcanized modified diene rubber polymer obtained by adding the monomer is obtained. More specifically, in the monomer, the carbon-carbon double bond portion in the molecule reacts with the diene rubber polymer by radical polymerization reaction. That is, when the carbon-carbon double bond of the monomer reacts with the radical of the diene rubber polymer generated by electron beam irradiation, the monomer is bonded to the diene rubber polymer, and thus the amino group is diene-based. Introduced into rubber polymer. In addition, a graft polymer having a diene rubber polymer as a trunk and a polymer portion formed by linking the monomers as side chains may be formed by sequentially linking the monomers by radical polymerization reaction. .

  Although the addition amount (namely, reaction amount) of the said monomer is not specifically limited, It is preferable that it is 0.01-100 mass parts with respect to 100 mass parts of diene rubber polymers before a process.

  In the said embodiment, although the monomer was provided after irradiating an electron beam, you may irradiate an electron beam after providing a monomer. That is, in the present invention, the unvulcanized diene rubber polymer may be irradiated with an electron beam and then the monomer may be added to the electron beam irradiated diene rubber polymer. Alternatively, the unvulcanized diene may be added. After the above monomer is added to the rubber-based rubber polymer, the diene rubber polymer may be irradiated with an electron beam, and further, the irradiation of the electron beam and the monomer may be performed simultaneously. Can be reacted with a diene rubber polymer.

  The modified diene rubber polymer obtained as described above can be used to produce a rubber composition by blending and mixing a filler. The modified diene rubber polymer has an amino group having a high reactivity or affinity for a functional group such as a hydroxyl group or a carboxyl group present on the surface of a filler such as carbon black or silica. The dispersion of the filler in the product can be improved, and therefore the tan δ of the rubber composition can be kept low, and the fuel efficiency can be improved. In particular, unlike a terminal-modified polymer carried out under conventional anionic polymerization, a monomer having the amino group can be added to the main chain of the polymer, so that the effect of improving the dispersibility of the filler can be improved. It is advantageous.

  As the rubber component to be blended in the rubber composition, the above-mentioned modified diene rubber polymer may be used alone, or an unmodified rubber polymer may be blended together with the modified diene rubber polymer. The unmodified rubber polymer is not particularly limited, and natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber. Various rubber polymers such as butadiene-isoprene copolymer, styrene-isoprene-butadiene copolymer rubber, butyl rubber, and halogenated butyl rubber can be used. Preferably, a diene rubber polymer is used, and styrene-butadiene rubber, butadiene rubber, and natural rubber are particularly preferably used. The blending ratio of the modified diene rubber polymer contained in the rubber component is not particularly limited, but it is preferably 20% by mass or more, more preferably, in order to more effectively exhibit the effect of improving the dispersibility of the filler. It is 50 mass% or more.

  Carbon black and / or silica are preferably used as the filler to be blended in the rubber composition. In particular, the present invention is highly practical and beneficial in that tan δ can be lowered not only for silica blends but also for carbon black blends. Although the compounding quantity of this filler is not specifically limited, It is preferable that it is 10-200 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 40-120 mass parts. The carbon black is not particularly limited, but those of SAF class (N100 series), ISAF class (N200 series), HAF class (N300 series), and FEF (N500 series) (both are ASTM grade) are preferably used. . Examples of the silica include wet silica, dry silica, colloidal silica, and precipitated silica. It is particularly preferable to use wet silica containing hydrous silicic acid as a main component. In addition, when mix | blending a silica as a filler, it is preferable to use together silane coupling agents, such as sulfide silane and mercaptosilane, and a silane coupling agent is 2-25 mass parts normally with respect to 100 mass parts of silica. Can be used.

  In addition to the rubber composition, various additives generally used in the rubber composition such as oil, zinc white, stearic acid, anti-aging agent, wax, vulcanizing agent, vulcanization accelerator, and the like are appropriately blended. Can do. Examples of the vulcanizing agent include sulfur and sulfur-containing compounds, and are not particularly limited. However, the blending amount is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. More 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 rubber components, More preferably, it is 0.5-5 mass parts.

  The rubber composition is prepared by kneading according to a conventional method using a rubber kneader such as a normal Banbury mixer or kneader. The use of the rubber composition thus obtained is not particularly limited, and can be used for various rubber compositions such as tires such as treads and sidewalls, conveyor belts, and vibration-proof rubbers.

  Preferably, it is used as a rubber composition for tires. Particularly, it is suitably used for a tread rubber, and a pneumatic tire 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)
As an unvulcanized diene rubber polymer, styrene-butadiene rubber “Nipol 1739” (Tg = −35 ° C., 37.5 parts by mass oil-extended rubber) manufactured by Nippon Zeon Co., Ltd. was used. The polymer was cut into a sheet having a thickness of about 1 cm. The surface of the obtained sheet-like diene rubber polymer was irradiated with an electron beam using an electron beam irradiation apparatus under the conditions of temperature: room temperature, acceleration voltage: 3 MV, and irradiation dose: 200 kGy. Immediately after the irradiation, the diene rubber polymer is immersed in a treatment liquid using allylamine as the monomer A (50% by mass aqueous solution of allylamine) and left at room temperature for 4 hours. To react. Thereafter, the diene rubber polymer is taken out from the above treatment solution and washed twice with warm water at 80 ° C. to remove the unreacted monomer A adhering to the surface of the diene rubber polymer and the homopolymer of the monomer A. did. Thereby, modified SBR1 modified with monomer A was obtained.

  In the modified SBR1, the addition amount of the monomer A was 1.2 parts by mass (that is, the graft ratio = 1.2% by mass) with respect to 100 parts by mass of the diene rubber polymer (excluding the oil fraction). Here, the graft ratio is a value obtained by dividing the sample mass change before and after graft polymerization by the mass of the sample before graft polymerization and multiplying by 100.

  A modified SBR2 modified with the monomer B was obtained in the same manner as the modified SBR1, except that dimethylaminoethyl methacrylate was used as the monomer B instead of the monomer A and a 50% by mass aqueous solution thereof was used as the treatment liquid. In the modified SBR2, the graft ratio of the monomer B was 1.0% by mass.

  A modified SBR3 modified with the monomer C was obtained in the same manner as the modified SBR1, except that 2-vinylpyridine was used as the monomer C instead of the monomer A and a 100% solution was used as the treatment liquid. In the modified SBR3, the graft ratio of the monomer C was 1.0% by mass.

  In the production method of the modified SBR1, a modified SBR4 (comparative example) was obtained in the same manner as the modified SBR1, except that the modified SBR1 was immersed in the treatment solution of the monomer A without being irradiated with an electron beam. Moreover, although it irradiated with the electron beam, it did not immerse in the process liquid of the monomer A, and others modified | denatured SBR5 (comparative example) was obtained like modified | denatured SBR1. In these modified SBR4 and 5, the graft ratio of the monomer A was 0% by mass.

  Using the modified SBR1 to 5 and unmodified SBR (“Nipol 1739” manufactured by Nippon Zeon Co., Ltd.), Examples 1-1 to 3 and Comparative Examples 1-1 to 6 in accordance with a conventional method using a Banbury mixer A rubber composition was prepared. The rubber component of each rubber composition is as shown in Table 1 below. In addition, the mass part of the rubber component in Table 1 is a mass part as a polymer component excluding oil blended in the oil fraction. BR is butadiene rubber “UBEPOL BR150” manufactured by Ube Industries, Ltd.

  In each rubber composition, 75 parts by mass of silica ("Ultrasil VN3" manufactured by Evonik), 6 parts by mass of a silane coupling agent ("Si69" manufactured by Evonik), aroma, per 100 parts by mass of the rubber component 31 parts by mass of oil ("Extract 4 S" manufactured by Showa Shell Sekiyu KK) (however, the total amount including the oil component of the rubber component), anti-aging agent (N-phenyl-N '-(1, 3-dimethylbutyl) -p-phenylenediamine) 2 parts by mass, stearic acid (industrial stearic acid) 2 parts by mass, zinc oxide (No. 1 zinc white) 3 parts by mass, wax (manufactured by Nippon Seiwa Co., Ltd.) Wax ") 2 parts by mass, vulcanization accelerator (N-tert-butyl-2-benzothiazolesulfenamide) 1.5 parts by mass, and sulfur (5% oil-treated powder sulfur) 2 parts by mass were blended. In Comparative Examples 1-4 to 6, monomers A to C were added at the time of rubber mixing.

  About each obtained rubber composition, tan-delta was measured as a parameter | index of low fuel consumption. The measuring method is as follows.

Tan δ: For a test piece vulcanized at 160 ° C. × 30 minutes, according to JIS K6394, using a viscoelasticity tester manufactured by Toyo Seiki, temperature 70 ° C., frequency 10 Hz, initial strain 10%, dynamic strain 2% The loss coefficient tan δ was measured under the conditions, and the result was displayed as an index with the value of Comparative Example 1-1 as 100. The smaller the index, the smaller the tan δ, and the less the heat generation, that is, the better the fuel efficiency.

  The results are as shown in Table 1, and in Examples 1-1 to 3 using modified SBR into which an amino group having high reactivity with the hydroxyl group on the silica surface was introduced, comparison of the control using unmodified SBR Compared to Example 1-1, tan δ was low due to improved dispersibility of silica, and the fuel efficiency was excellent. On the other hand, in Comparative Example 1-2 in which the electron beam irradiation was not performed and in Comparative Example 1-3 in which the monomer having an amino group was applied, although the electron beam irradiation was performed, the effect of improving tan δ was seen. There wasn't. From this, it is clear that in the modified SBR1 to 3 used in the examples, modification by amino groups, that is, amino groups are introduced into the diene rubber polymer. In Comparative Examples 1-4 to 6 in which the monomers A to C were added at the time of rubber kneading, no effect of improving tan δ was observed.

(Second embodiment)
Natural rubber (RSS # 3) was used as the unvulcanized diene rubber polymer, and the solid diene rubber polymer was cut into a sheet having a thickness of about 1 cm. The surface of the cut diene rubber polymer was irradiated with an electron beam using an electron beam irradiation apparatus under the conditions of temperature: room temperature, acceleration voltage: 3 MV, and irradiation dose: 200 kGy. Immediately after the irradiation, the diene rubber polymer is immersed in a treatment liquid using allylamine as the monomer A (50% by mass aqueous solution of allylamine) and left at room temperature for 4 hours. To react. Thereafter, the diene rubber polymer is taken out from the above treatment solution and washed twice with warm water at 80 ° C. to remove the unreacted monomer A adhering to the surface of the diene rubber polymer and the homopolymer of the monomer A. did. As a result, modified NR1 modified with monomer A was obtained. In the modified NR1, the graft ratio of the monomer A was 1.2% by mass.

  A modified NR2 modified with the monomer B was obtained in the same manner as the modified NR1 except that the monomer A was replaced with dimethylaminoethyl methacrylate as the monomer B and a 50% by mass aqueous solution thereof was used as the treatment liquid. In the modified NR2, the graft ratio of the monomer B was 1.0% by mass.

  A modified NR3 modified with the monomer C was obtained in the same manner as the modified NR1, except that 2-vinylpyridine was used as the monomer C instead of the monomer A and a 100% solution was used as the treatment liquid. In the modified NR3, the graft ratio of the monomer C was 1.1% by mass.

  In the modified NR1 production method, a modified NR4 (comparative example) was obtained in the same manner as the modified NR1 except that the modified NR1 was immersed in the treatment solution of the monomer A without being irradiated with an electron beam. Moreover, although it irradiated with the electron beam, it did not immerse in the process liquid of the monomer A, and modified | denatured NR5 (comparative example) was obtained like modification | denaturation NR1 others. In these modified NR4 and 5, the graft ratio of the monomer A was 0% by mass.

  Using the modified NR1 to 5 and unmodified NR (RSS # 3), rubber compositions of Examples 2-1 to Comparative Examples 2-1 to 6 were prepared according to a conventional method using a Banbury mixer. The rubber component of each rubber composition is as shown in Table 2 below.

  In each rubber composition, carbon black HAF (“Seast 3” manufactured by Tokai Carbon Co., Ltd.) 50 parts by mass and aroma oil (“Extra” manufactured by Showa Shell Sekiyu Co., Ltd.) per 100 parts by mass of the rubber component are commonly used. Kuct 4 S ") 3 parts by mass, anti-aging agent (N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine) 1 part by mass, stearic acid (industrial stearic acid) 2 parts by mass , 3 parts by mass of zinc oxide (No. 1 zinc white), 1.0 part by mass of vulcanization accelerator (N-tert-butyl-2-benzothiazolesulfenamide), 2 parts by mass of sulfur (5% oil-treated powder sulfur) Was formulated. In Comparative Examples 1-4 to 6, monomers A to C were added at the time of rubber mixing.

  About each obtained rubber composition, tan-delta was measured as a parameter | index of low fuel consumption (The measuring method is as above-mentioned, but it displayed with the index | exponent which set the value of Comparative Example 2-1 to 100).

  The results are as shown in Table 2, and in Examples 2-1 to 3 using modified NR introduced with a functional group highly reactive with the carboxyl group on the surface of carbon black, control using unmodified NR As compared with Comparative Example 2-1, the tan δ was low due to the improved dispersibility of carbon black, and the fuel efficiency was excellent. On the other hand, in Comparative Example 2-2 in which the electron beam irradiation was not performed and in Comparative Example 2-3 in which the monomer having an amino group was applied although the electron beam irradiation was performed, the effect of improving tan δ was seen. There wasn't. From this, it is clear that in the modified NR1 to 3 used in the examples, the modification by the amino group, that is, the amino group is introduced into the diene rubber polymer. In Comparative Examples 2-4 to 6 in which the monomers A to C were added at the time of rubber kneading, the effect of improving tan δ was not observed.

Claims (6)

Irradiating an uncured diene rubber polymer with an electron beam;
Providing the diene rubber polymer with a compound having a carbon-carbon double bond and an amino group in the molecule;
A process for producing a modified diene rubber polymer. The carbon - carbon double bond is H _{2 C} = CR- (where, R represents a hydrogen atom or a methyl group) The method of manufacturing according to claim 1 modified diene rubber polymers wherein a group represented by .   A method for producing a rubber composition, comprising blending and mixing a filler with the modified diene rubber polymer obtained by the method according to claim 1 or 2.   4. The method for producing a rubber composition according to claim 3, wherein the filler is carbon black and / or silica.   A modified diene rubber polymer, wherein a compound having a carbon-carbon double bond and an amino group in the molecule is reacted with the diene rubber polymer by electron beam irradiation on an unvulcanized diene rubber polymer. .   A rubber composition comprising the modified diene rubber polymer according to claim 5 and a filler.