JP5617253B2 - Method for producing modified crushed vulcanized rubber - Google Patents

Description

  The present invention relates to a method for producing a modified ground vulcanized rubber. More specifically, the present invention relates to a method for producing a pulverized vulcanized rubber having higher strength and reinforcement than conventional waste tire recycled powder rubber.

  From the viewpoint of reducing environmental impact, the effective use of waste tires is one of the important issues in the tire manufacturing industry. In order to recycle vulcanized rubber (reuse tire rubber pieces or rubber powder as it is), it is necessary to plasticize vulcanized rubber. Plasticization methods include hydrocarbon decomposition and sulfur crosslinking. Decomposition.

  Examples of hydrocarbon decomposition include acceleration of auto-oxidation by peroxide / redox system, and examples of sulfur bridge decomposition include oxidation, heat, shear, use of nucleophile, rearrangement, promotion mechanism by substitution reaction, etc. Is generally known. However, only by plasticization by such a method, when it is added to a new rubber, the strength and reinforcement of the rubber are insufficient.

Japanese Patent No. 4046734 Japanese Patent No. 4101242 Japanese Patent No. 4243320 JP 2008-297559 A

  An object of the present invention is to provide a method for producing a pulverized vulcanized rubber having higher strength and reinforcement than conventional waste tire recycled powder rubber.

The object of the present invention is to mix a pulverized vulcanized rubber, a compound having a nitroxide free radical, and a radical initiator at a temperature of 160 to 180 ° C. using a heating mixer and react them to produce a modified pulverized vulcanized rubber. This is achieved by the manufacturing method. If necessary, an alkoxysilyl group or aryloxysilyl group-containing radical polymerizable monomer may be further added to the modified pulverized vulcanized rubber and mixed at a temperature of 160 to 180 ° C. for reaction. Here, the (meth) acryloxy group means an acryloxy group or a methacryloxy group.

  The modified pulverized vulcanized rubber produced by the method of the present invention has a higher hardness and reinforcement than conventional waste tire recycled powder by imparting to the pulverized vulcanized rubber a functional group that improves the affinity with the filler. It is possible to provide a pulverized vulcanized rubber having This modified pulverized vulcanized rubber is used as one component of a diene rubber composition.

If necessary, when an alkoxysilyl group- or aryloxysilyl group-containing radical polymerizable monomer is added to the modified pulverized vulcanized rubber and reacted, the pulverized vulcanized rubber, a compound having a nitroxide free radical, and a radical initiator are added. After mixing and reacting at a temperature of 160 to 180 ° C. using a heating mixer, further adding an alkoxysilyl group or aryloxysilyl group-containing radical polymerizable monomer, mixing at a temperature of 160 to 180 ° C., React to form a modified ground vulcanized rubber. The silane-modified ground vulcanized rubber thus obtained is used as one component of a silica-containing diene rubber composition.

  As the pulverized vulcanized rubber, waste tire recycled powder is generally used. Waste tire recycling powder is, for example, crushing (rough crushing → crushing) waste tires, removing things other than rubber components such as fiber, steel, wire, etc., then regenerating agent (organic disulfide, ester acid, etc.) and oil ( Aromatech oil or the like) is mixed, heated, and rolled into a sheet to obtain a product, which may be a commercial product.

  The raw materials are mainly waste tires, and other unvulcanized scraps produced during tire production, spew pieces produced during tire vulcanization, etc., so diene such as natural rubber, synthetic isoprene rubber, SBR, butadiene rubber, etc. This is a vulcanized product of rubber and contains various compounding agents including fillers such as carbon black. The average particle diameter is about 500 μm or less, preferably about 200 μm or less, and the appearance and feel are close to those of flour.

またはその誘導体が用いられる。 The compounds having a nitroxide free radical (—NO ·) are described in detail in Patent Documents 1 to 4, and preferably 2,2,6,6-tetramethylpiperidine-1-oxyl [TEMPO].

Alternatively, derivatives thereof are used.

  As derivatives of TEMPO, derivatives substituted in the 4-position, such as oxo, methyl, ethyl, methoxy, ethoxy, chloro, amino, hydroxy, carboxyl, isocyanate, glycidyl ether, thioglycidyl ether, phenyl, phenoxy, methylcarbonyl, ethyl Examples include carbonyl, benzoyl, benzoyloxy, acetoxy, ethoxycarbonyl, N-methylcarbamoyloxy, N-ethylcarbamoyloxy, N-phenylcarbamoyloxy and the like, and methyl (4-TEMPO) sulfate, ethyl (4-TEMPO) Examples thereof include sulfate and phenyl (4-TEMPO) sulfate.

  The present applicant has made various proposals regarding modified polymers obtained by modifying a polymer having an isomonoolefin unit in a structural unit or a diene rubber with a compound having a nitroxide free radical (see, for example, Patent Documents 1 to 4). ).

  In Patent Document 1, (A) a polymer having an isomonoolefin unit, (B) a compound having a specific nitroxide free radical, and (C) an organic peroxide radical initiator are mixed and reacted in a kneader, and then ( D) A method for modifying a polymer by grafting an acrylic monomer or an aromatic vinyl monomer is described.

  Patent Document 2 discloses that (A) a polymer having an isomonoolefin unit, (B) a compound having a nitroxide free radical, and (C) an organic peroxide radical initiator have a (B) / (C) molar ratio of 1 A method for modifying a polymer is described in which an organic group derived from a compound having a nitroxide free radical is introduced into the polymer (A) by being used at a large ratio and modified while suppressing a decrease in the molecular weight of the polymer (A). Yes.

  In the above Patent Documents 1 and 2, butyl rubber, brominated butyl rubber, isobutylene-p-methylstyrene copolymer, brominated isobutylene-p-methylstyrene copolymer are used as the polymer having an isomonoolefin unit of component (A). , Polyisobutylene, polybutene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-propylene-butene terpolymer, polystyrene-based thermoplastic elastomer (SEBS, SEPS), polyolefin-based thermoplastic elastomer, polypropylene, Examples include propylene copolymer, fluororubber, hydrogenated acrylonitrile-butadiene copolymer rubber, and the like.

  Patent Document 3 discloses (A) a specific diene rubber, (B) a compound having a nitroxide free radical in the molecule, (C) a radical initiator, and (D) a radical having an alkoxysilyl group in the molecule. Silica is added to the rubber component containing 5% by weight or more of a modified diene rubber obtained by adding a polymerizable monomer (acrylate or methacrylate having an alkoxysilyl group, vinyltrialkoxysilane, etc.) and causing a graft reaction. A rubber composition containing% reinforcing filler is described.

  In the rubber composition described in Patent Document 3, a modified diene rubber not containing silica is described in Patent Document 4.

  In patent documents 3 to 4, natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene copolymer rubber, chloroprene rubber are used as the diene rubber of component (A). Is used.

  However, these modified polymers described in Patent Documents 1 to 4 are directed to modification with a compound having an isomonoolefin unit in a structural unit or a compound having a nitroxide free radical of a new rubber which is a diene rubber. Not related to ground vulcanized rubber.

  As the radical initiator used in the modification reaction of the present invention, an organic peroxide is generally used. For example, benzoyl peroxide, tertiary butyl peroxybenzoate, dicumyl peroxide, tertiary butyl cumyl peroxide, di tertiary Butyl peroxide, 2,5-dimethyl-2,5-ditertiarybutylperoxyhexane, 2,5-dimethyl-2,5-ditertiarybutylhexyne-3, 2,4-dichlorobenzoyl peroxide, ditertiary 3-butylperoxydiisopropylbenzene, 1,1-bis (tertiary butylperoxy) -3,3,5-trimethylcyclohexane, n-butyl-4,4-bis (tertiary butylperoxy) valerate, 2,2 -Bis (tertiary butyl peroxy) butane and the like.

  These radical initiators can generate carbon radicals in the polymer when added to a reaction system with a compound having a nitroxide radical.

  Each of the above components is composed of 2 parts by weight or more, preferably 5 to 20 parts by weight of a compound having a nitroxide radical, and 0.1 to 15 parts by weight of a radical initiator, preferably 100 parts by weight of pulverized vulcanized rubber. Is used in a proportion of 0.2 to 10 parts by weight, and a molar ratio of the compound having a nitroxide radical to the radical initiator is 1 or more, preferably 1.5 or more, more preferably 1.7 to 2.0.

  If the proportion of the compound having a nitroxide radical is less than this, the desired pulverized vulcanized rubber cannot be modified. On the other hand, if it is used in a proportion larger than this, the compound having an unreacted nitroxide radical is not contained in the system. Therefore, the physical properties of the blend may be lowered. If the proportion of the radical initiator used is less than this, the desired modification of the pulverized vulcanized rubber cannot be achieved. On the other hand, if it is used in a proportion higher than this, decomposition or deterioration of the powder rubber is promoted. , Causing a decrease in the physical properties of the blend. On the other hand, if the molar ratio of the compound having a nitroxide radical to the radical initiator is less than this, decomposition or deterioration of the polymer chain of the pulverized vulcanized rubber to be modified cannot be suppressed, and the molecular weight may be lowered.

The above components used in such a proportion are mixed and reacted at a temperature of 160 to 180 ° C. using a heating mixer to modify the pulverized vulcanized rubber. As the heating mixer, a kneader, a Banbury mixer, a biaxial kneader, a Henschel mixer or the like generally used as a rubber heating mixer is used.

Heat mixing using these heating mixers, pulverized vulcanized rubber, a compound having a nitroxide free radical and a radical initiator are charged into the heating mixer, and after stirring at room temperature to about 100 ° C. for about 5 minutes, In order to facilitate plasticization by heating and mixing, aroma oil or the like is added, and after stirring for about 1 to 5 minutes at this temperature, the temperature of the mixture is increased to 160 to 180 ° C, preferably 170 to 180 ° C. Once reached, the reaction is carried out at that temperature for about 5 to 20 minutes to modify the crushed vulcanized rubber.

  The degree of modification of the crushed vulcanized rubber is an index when the bulk specific gravity is measured in accordance with JIS K6316 and the bulk specific gravity of the unmodified crushed vulcanized rubber in which only the aroma oil is mixed with the pulverized vulcanized rubber is 100. When the compound is modified with a compound having a nitroxide free radical, the number is about 105 to 108, and the bulk specific gravity was not increased in the modified pulverized vulcanized rubber when the mixing and reaction temperature was 150 ° C.

The resulting modified crushed vulcanized rubber can be further modified by adding an alkoxysilyl group or aryloxysilyl group-containing radical polymerizable monomer and reacting at a temperature of 160 to 180 ° C. for about 5 to 20 minutes. it can.

The alkoxysilyl group- or aryloxysilyl group-containing radical polymerizable monomer has the general formula
Si (OR ¹ ) _4-n (RA) _n
(Where R is a hydrocarbon group or a direct bonding group to Si, R ¹ is a hydrocarbon group and may have an ether bond, A is a radically polymerizable group, and n is an integer of 1 to 3, when n is 2 or 3, R each other, R ¹ and between a together are a compound represented by each may be a different group).

Specific examples of the hydrocarbon group of the hydrocarbon group R include, for example, alkyl groups such as methyl, ethyl, propyl, hexyl, dodecyl, and octadecyl, cycloalkyl groups such as cyclopropyl and cyclohexyl, and aryls such as phenyl and benzyl. Examples include groups. R is also a direct bond group with Si. In this case, the alkoxysilyl group- or aryloxysilyl group-containing radical polymerizable monomer is represented by the general formula Si (OR ¹ ) _4-n (A) _n .

Specific examples of R ¹ which is a hydrocarbon group that can have an ether bond include, for example, alkyl groups such as methyl, ethyl, propyl, hexyl, dodecyl, and octadecyl, cycloalkyl groups such as cyclopropyl and cyclohexyl, phenyl And aryl groups such as benzyl, and polyoxyalkylene groups such as polyethylene glycol and polypropylene glycol.

  Examples of the radical polymerizable group A include a vinyl group, an allyl group, a styryl group, a (meth) acryloxy group, a (meth) acrylamide group, a vinyl halide group, an acrylonitrile group, and among them, an electron withdrawing group ( Those containing a carbonyl group, halogen, cyano group and the like are preferred. Further, among them, those having a (meth) acryloxy group are particularly preferable. Here, the (meth) acryloxy group refers to an acryloxy group or a methacryloxy group, and the (meth) acrylamide group refers to an acrylamide group or a methacrylamide group.

  The alkoxysilyl group-containing radical polymerizable monomer that can be used in the present invention is not particularly limited, but preferred examples include vinylmethoxysilane, vinyltrimethoxysilane, vinylethoxysilane, vinyltriethoxysilane, γ- Methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyldimethylmethoxysilane, γ-acryloxypropylmethyldiethoxysilane, γ-acryloxypropyldimethylethoxysilane, γ-acryloxypropyltri Examples thereof include ethoxysilane, N- (propyltriethoxysilane) maleimide and the like.

  The aryloxysilyl group-containing radical polymerizable monomer that can be used in the present invention is not particularly limited, but preferred examples include vinylphenoxysilane, vinyltriphenoxysilane, γ-methacryloxypropyltriphenoxysilane, γ -Methacryloxypropylmethyldiphenoxysilane, γ-methacryloxypropyldimethylphenoxysilane, γ-acryloxypropylmethyldiphenoxysilane, γ-acryloxypropyldimethylphenoxysilane, γ-acryloxypropyltriphenoxysilane, N- (propyl And triphenoxysilane) maleimide.

  In addition, a hydrolyzed condensation of the above alkoxysilyl group or aryloxysilyl group-containing radical polymerizable monomer may be used, and a silicone oil type cup having two or more repeating units of a siloxane bond and having an alkoxysilyl group. An oligomer having a radical polymerizable group as a ring agent may be used.

  The alkoxysilyl group- or aryloxysilyl group-containing radical polymerizable monomer is effective when used in an addition ratio of 0.1 part by weight or more, preferably 0.5 to 7 parts by weight with respect to 100 parts by weight of the pulverized vulcanized rubber. The second-stage denaturation reaction using the same is carried out using a heating mixer as in the first-stage denaturation reaction.

  Furthermore, the bulk specific gravity of the crushed vulcanized rubber modified with an alkoxysilyl group or aryloxysilyl group-containing radical polymerizable monomer is increased to about 110 when the mixing and reaction temperature is set to 100 when the reaction temperature is 150 ° C. Can be made.

  These modified pulverized vulcanized rubbers are used by blending with new rubbers such as natural rubber, isoprene rubber, butadiene rubber and SBR. The pulverized vulcanized rubber modified with a compound having a nitroxide free radical was used as a recycled rubber component of a carbon black compounded rubber composition, and was further modified with an alkoxysilyl group or aryloxysilyl group-containing radical polymerizable monomer. The pulverized vulcanized rubber is used as a recycled rubber component of the silane compounded rubber composition.

  Next, the present invention will be described with reference to examples.

Example 1
Commercially crushed vulcanized rubber (LEHIGH TECHNOLOGY product GF-80 REPROCESSED GROUND RUBBER; average particle size 180 μm) 450 g, organic peroxide (AKZO NOBEL product Kayahexa AD) 1.87 g and 4-hydroxy-2,6,6-tetra Methylpiperidine-1-oxyl [OH-TEMPO] (Asahi Denka Kogyo Co., Ltd.) 9.0 g was added to a Henschel mixer, stirred at 70 ° C for 5 minutes, and then an aroma oil (Showa Shell Petroleum Product Extract No. 4 S) 50 g was added and heated and stirred for 3 minutes. When the temperature of the mixture was raised to 180 ° C., the mixture was reacted at that temperature for 15 minutes to obtain 508 g of a modified ground vulcanized rubber A.

  For the crushed vulcanized rubber A after modification, the bulk specific gravity was measured according to JIS K6316, and the bulk specific gravity of the unmodified crushed vulcanized rubber in which only 50 g of the aroma oil was mixed with 450 g of the crushed vulcanized rubber was set to 100. When expressed as an index of time, the value was 108. The larger this value, the more denaturation with the modifying agent OH-TEMPO is performed.

Example 2
In Example 1, the reaction temperature was changed to 160 ° C., and modified crushed vulcanized rubber B was obtained. The bulk specific gravity of the modified ground vulcanized rubber B was 105.

Comparative Example 1
In Example 1, the reaction temperature was changed to 150 ° C., and modified crushed vulcanized rubber C was obtained. The bulk specific gravity of the modified ground vulcanized rubber C was 100.

Example 3
After adding 4.0 g of γ-methacryloxypropyltrialkoxysilane (Shin-Etsu Chemical KBM-503) to 100 g of the modified crushed vulcanized rubber A obtained in Example 1, the mixture is reacted at 180 ° C. for 15 minutes, and modified crushed vulcanized. Rubber D was obtained. The bulk specific gravity of the modified ground vulcanized rubber D was 110.

Comparative Example 2
After adding 4.0 g of γ-methacryloxypropyltrialkoxysilane (KBM-503) to the modified crushed vulcanized rubber C obtained in Comparative Example 1, the mixture was reacted at 150 ° C. for 15 minutes to obtain a modified crushed vulcanized rubber E. It was. This modified crushed vulcanized rubber E had a bulk specific gravity of 100.

Reference example 1
100 parts by weight of natural rubber (RSS # 3)
GPF carbon black (Tokai carbon product seast V) 40 〃
Stearic acid (Japanese fat beads stearic acid YR) 2 〃
Zinc Hana (Zinc Oxide Product Zinc Oxide 3 types) 2 〃
Anti-aging agent (SANTOFLEX 6PPD, product of Flexis) 1 〃
Paraffin wax (Onouchi Emerging Chemical Industries Sannock) 1 〃
Sulfur (Tsurumi Chemical Co., Ltd., Jinhua Indian Oil Fine Sulfur)
Vulcanization accelerator (Ouchi Emerging Chemical Industry Noxeller CZ-G) 1.4 〃
Among the above components, each component excluding sulfur and vulcanization accelerator is kneaded with a 1.7 L Banbury mixer for 5 minutes, sulfur and vulcanization accelerator are added to the resulting mixture, and 8-inch test kneading is performed. A rubber composition was prepared by kneading for 4 minutes in a roll machine. This rubber composition was heated and vulcanized at 150 ° C. for 30 minutes to prepare a target test piece, and the physical properties of the following items were measured.
Hardness: JIS K6253 compliant (20 ° C)
100% modulus, breaking strength: JIS K6301 compliant

Reference example 2
In Reference Example 1, 20 parts by weight of unmodified ground vulcanized rubber was further used.

Reference example 3
In Reference Example 1, 20 parts by weight of modified crushed vulcanized rubber C was further used.

Reference example 4
In Reference Example 1, 20 parts by weight of modified crushed vulcanized rubber A was further used.

The measurement results obtained in the above Reference Examples 1 to 4 are shown in the following Table 1 together with the blending amounts (parts by weight) of carbon black and various modified pulverized vulcanized rubbers in the rubber composition. In addition, a measurement result is shown by the index | exponent which sets the reference example 1 used as a standard example to 100.
Table 1
Reference example
1 2 3 4
(Rubber composition)
Carbon black (part) 40 40 40 40
Unmodified ground vulcanized rubber (part) − 20 − −
Modified ground vulcanized rubber C (part) − − 20 −
Modified ground vulcanized rubber A (part) − − − 20
〔Measurement result〕
Hardness 100 101 101 101
100% modulus 100 101 101 102
Breaking strength 100 95 97 103

Reference Examples 5-8
In Reference Examples 1 to 4, the amount of GPF carbon black was changed to 30 parts by weight, 10 parts by weight of silica (Tosoh / Silica product nip seal / AQ) and 0.8 parts by weight of silane coupling agent (Degussa product Si69) were used. It was.

The measurement results obtained in the above Reference Examples 5 to 8 are shown in the following Table 2 together with blending amounts (parts by weight) of carbon black, silica, silane coupling agent, and various modified pulverized vulcanized rubbers in the rubber composition. Indicated. In addition, a measurement result is shown by the index | exponent which sets the reference example 5 used as a standard example to 100.
Table 2
Reference example
5 6 7 8
(Rubber composition)
Carbon black (part) 30 30 30 30
Silica (part) 10 10 10 10
Silane coupling agent (parts) 0.8 0.8 0.8 0.8
Unmodified ground vulcanized rubber (part) − 20 − −
Modified ground vulcanized rubber E (Part) − − 20 −
Modified ground vulcanized rubber D (Part) − − − 20
〔Measurement result〕
Hardness 100 101 101 101
100% modulus 100 101 100 101
Breaking strength 100 95 97 102

Claims (9)

A method for producing a modified pulverized vulcanized rubber, characterized by mixing and reacting a pulverized vulcanized rubber, a compound having a nitroxide free radical and a radical initiator at a temperature of 160 to 180 ° C. using a heating mixer.   The method for producing a modified crushed vulcanized rubber according to claim 1, wherein a recycled tire waste powder is used as the crushed vulcanized rubber.   The process for producing a modified ground vulcanized rubber according to claim 1, wherein 2,2,6,6-tetramethylpiperidine-1-oxyl or a derivative thereof is used as the compound having a nitroxide free radical.   The method for producing a modified crushed vulcanized rubber according to claim 1 or 3, wherein a compound having a nitroxide free radical is used in a proportion of 2% by weight or more with respect to the crushed vulcanized rubber.   The process for producing a modified crushed vulcanized rubber according to claim 1, wherein an organic peroxide is used as the radical initiator. Milling vulcanized rubber, a compound having a nitroxide free radical and a radical initiator, and mixed at 160 to 180 ° C. using a heating mixer and allowed to react further alkoxysilyl group or an aryloxy silyl group-containing radical polymerization A method for producing a modified pulverized vulcanized rubber, comprising adding a functional monomer, mixing at 160 to 180 ° C., and reacting.   The method for producing a modified pulverized vulcanized rubber according to claim 6, wherein the alkoxysilyl group- or aryloxysilyl group-containing radical polymerizable monomer is γ- (meth) acryloxypropyltrialkoxysilane.   The method for producing a modified crushed vulcanized rubber according to claim 6 or 7, wherein the radically polymerizable monomer containing an alkoxysilyl group or aryloxysilyl group is used at a ratio of 0.1 part by weight or more with respect to 100 parts by weight of the crushed vulcanized rubber.   A modified ground vulcanized rubber produced by the method according to claim 1 or 6.