Copolymer, rubber composition, tire, method for producing copolymer, and method for decomposing copolymer

Abstract

The present invention addresses the problem of providing a polymer that is easily decomposed and can improve the characteristics of a rubber product. The means for solving the problem is a copolymer having a hard segment (A), a soft segment (B), and an enol ether segment (C), the copolymer being characterized in that the hard segment (A) has a cyclic structure, the soft segment (B) is linear or branched, and the proportion of the enol ether segment (C) in the copolymer is 0.1-40 mass%.

Description

Copolymer, rubber composition, tire, method for producing copolymer, and method for decomposing copolymer

[0001] This invention relates to copolymers, rubber compositions, tires, methods for producing copolymers, and methods for decomposing copolymers.

[0002] Traditionally, rubber products have been difficult to recycle, and after their lifespan, they are often reused as fuel, particularly in cement factories. However, with the growing concern for the environment, there is growing interest in reusing materials obtained by decomposing used rubber products, rather than burning them as fuel. For example, methods for decomposing vulcanized rubber include desulfurization with solvents (see Patent Document 1). Furthermore, copolymers with a biodegradable structure have been proposed as reusable polymers (see Patent Document 2).

[0003] Japanese Patent Publication No. 2000-128901, International Publication No. 2024 / 090034

[0004] As described in Patent Document 1 and others, vulcanized rubber can be decomposed by desulfurization with a solvent, but the decomposition conditions are inevitably strict. Furthermore, as described in Patent Document 2 and others, easily decomposable polymers have been proposed, but further investigation is needed to improve the properties of rubber products containing these polymers.

[0005] Therefore, the present invention aims to solve the problems of the above-mentioned prior art and provide a polymer that is easily decomposed and can improve the properties of rubber products. Furthermore, the present invention aims to provide an easily decomposable rubber composition and tire containing such polymer, as well as a method for producing such polymer and a method for decomposing it.

[0006] The gist of the copolymer, rubber composition, tire, method for producing the copolymer, and method for decomposing the copolymer according to the present invention, which solves the above problems, is as follows.

[0007] [1] A copolymer comprising a hard segment (A), a soft segment (B), and an enol ether segment (C), wherein the hard segment (A) has a cyclic structure, the soft segment (B) is linear or branched, and the proportion of the enol ether segment (C) in the copolymer is 0.1 to 40% by mass.

[0008] [2] The copolymer according to [1], wherein the proportion of the enol ether segment (C) in the copolymer is 0.1 to 10% by mass.

[0009] [3] The copolymer according to [1] or [2], wherein the hard segment (A) has a cycloalkylene structure having 1 to 30 carbon atoms.

[0010] [4] The copolymer according to any one of [1] to [3], wherein the soft segment (B) has a linear alkylene structure having 1 to 30 carbon atoms or a branched alkylene structure.

[0011] [5] The copolymer according to any one of [1] to [4], wherein the mass ratio of the hard segment (A) to the soft segment (B) [(A):(B)] is 5:95 to 95:5.

[0012] [6] The copolymer according to any one of [1] to [5], wherein the mass ratio of the hard segment (A) to the soft segment (B) [(A):(B)] is 30:70 to 30:70.

[0013] [7] A copolymer according to any one of [1] to [6], wherein the number average molecular weight is 100,000 or more.

[0014] [8] A copolymer according to any one of [1] to [7] that is biodegradable.

[0015] [9] A rubber composition characterized by containing a copolymer according to any one of [1] to [8].

[0016] A tire characterized by comprising the rubber composition described in

[10] [9].

[0017]

[11] A method for producing a copolymer according to any one of [1] to [8], characterized by ring-opening polymerization of a compound having a norbornene skeleton (A'), a monocyclic unsaturated compound (B'), and an unsaturated heterocyclic compound (C').

[0018]

[12] A method for decomposing a copolymer, characterized by decomposing the copolymer described in any one of [1] to [8] in the presence of an acid.

[0019] According to the present invention, it is possible to provide a polymer that is easily decomposed and can improve the properties of rubber products. Furthermore, according to the present invention, it is possible to provide an easily decomposable rubber composition and tire containing such polymer, as well as a method for producing such polymer and a method for decomposing it.

[0020] The copolymer, rubber composition, tire, method for producing the copolymer, and method for decomposing the copolymer of the present invention will be described in detail below, based on embodiments thereof.

[0021] <Definitions> The compounds described herein may be derived in part or in whole from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires. They may also be derived from a mixture of two or more of fossil resources, biological resources, or recycled resources.

[0022] <Copolymer> The copolymer of this embodiment comprises a hard segment (A), a soft segment (B), and an enol ether segment (C). In the copolymer of this embodiment, the hard segment (A) has a cyclic structure, and the soft segment (B) is linear or branched. Furthermore, the proportion of the enol ether segment (C) in the copolymer of this embodiment is 0.1 to 40% by mass.

[0023] The copolymer of this embodiment has a hard segment (A) having a cyclic structure, and the hard segment (A) improves the physical properties of the copolymer itself and improves the strength of the rubber composition and rubber products containing the copolymer. Furthermore, the copolymer of this embodiment has a linear or branched soft segment (B), and the soft segment (B) improves the flexibility of the copolymer itself and the rubber composition and rubber products containing the copolymer. In addition, the copolymer of this embodiment has an enol ether segment (C), and the enol ether segment (C) acts as a decomposition site, improving the decomposability of the copolymer itself and the rubber composition and rubber products containing the copolymer. Furthermore, in the copolymer of this embodiment, if the proportion of the enol ether segment (C) is 0.1% by mass or more, the decomposability of the copolymer itself and the rubber composition and rubber products containing the copolymer is further improved. Moreover, in the copolymer of this embodiment, if the proportion of the enol ether segment (C) is 40% by mass or less, the physical properties of the copolymer itself are further improved, and the strength of the rubber composition and rubber products containing the copolymer is further improved.Therefore, the copolymer of this embodiment is easily decomposed and can improve the properties of rubber products.

[0024] The copolymer of this embodiment only needs to have a hard segment (A), a soft segment (B), and an enol ether segment (C), and may be a random copolymer or a block copolymer. Furthermore, as described above, the copolymer of this embodiment is biodegradable. Because the copolymer of this embodiment is biodegradable, the degradation products obtained after degradation can be reused.

[0025] "Hard Segment (A)" The copolymer of this embodiment has a hard segment (A). Examples of the hard segment (A) include a segment having a rigid group such as a cyclic structure in the main chain skeleton, or a segment that enables intermolecular packing by intermolecular hydrogen bonding. More preferably, the hard segment (A) is a segment having a cyclic structure, and may consist only of a cyclic structure, or it may have a linear structure or a branched structure in addition to the cyclic structure. Various substituents may be attached to the cyclic structure, linear structure and branched structure as side chains. Examples of substituents include halogen groups, alkyl groups and alkylidene groups. Furthermore, the substituents as side chains may include heteroatoms such as oxygen, sulfur and nitrogen.

[0026] The hard segment (A) preferably has a cycloalkylene structure having 1 to 30 carbon atoms. A copolymer having a cycloalkylene structure having 1 to 30 carbon atoms as the hard segment (A) has high physical properties of the copolymer itself, and can further improve the strength of rubber compositions and rubber products containing the copolymer. Examples of cycloalkylene structures having 1 to 30 carbon atoms include cyclopropylene groups, cyclobutylene groups, cyclopentylene groups, cyclohexylene groups, cycloheptylene groups, and cyclooctylene groups.

[0027] The hard segment (A) can be a segment (monomer unit) derived from various monomers. In one embodiment, the hard segment (A) is preferably a segment (monomer unit) derived from a compound (A') having a norbornene skeleton. The compound (A') having a norbornene skeleton is the following general formula (1): [In the formula, R １ These are, independently, a halogen, an alkyl group, and an alkenyl group, and two R groups bonded to adjacent carbon atoms. １ These may bond to each other to form a ring, and two R atoms bonded to the same carbon atom. １may together form an alkylidene group, and n1 is an integer from 0 to 10. Examples of the norbornene compound represented by [ ] include those where the halogen includes fluorine, chlorine, bromine, etc. Also, as the alkyl group, an alkyl group having 1 to 5 carbon atoms is preferred, and examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, etc. Further, as the alkenyl group, an alkenyl group having 2 to 5 carbon atoms is preferred, and examples include a vinyl group, an allyl group, etc. Also, when two Rs bonded to adjacent carbon atoms １ １ are bonded to form a ring, examples of the divalent group formed by the bonding of the two Rs include an alkylene group, an alkenylene group, etc. Here, examples of the alkylene group include an ethylene group, a trimethylene group, a tetramethylene group, etc., and examples of the alkenylene group include a vinylene group, a propenylene group, a butenylene group, etc. Specific examples of the formed ring structure include a cyclopentane ring, a cyclopentene ring, a cyclohexane ring, a cyclohexene ring, etc. Also, examples of the alkylidene group formed by the combination of two Rs bonded to the same carbon atom １ ２ ３ include a methylidene group (=CH ), an ethylidene group (=CH-CH ). In the general formula (1), R １ １ is a substituent of the norbornene ring and may substitute any hydrogen atom bonded to the norbornene ring, and n1 is the number of the substituent R １ . １ When two Rs bonded to adjacent carbon atoms １ １ are bonded to form a ring, １ examples of the divalent group formed by the bonding of the two Rs include an alkylene group, an alkenylene group, etc. Here, examples of the alkylene group include an ethylene group, a trimethylene group, a tetramethylene group, etc., and examples of the alkenylene group include a vinylene group, a propenylene group, a butenylene group, etc. Also, specific examples of the formed ring structure include a cyclopentane ring, a cyclopentene ring, a cyclohexane ring, a cyclohexene ring, etc. Also, when two Rs bonded to the same carbon atom １ ２ ３ are bonded to form a ring, １ examples of the divalent group formed by the bonding of the two Rs include an alkylene group, an alkenylene group, etc. Here, examples of the alkylene group include an ethylene group, a trimethylene group, a tetramethylene group, etc., and examples of the alkenylene group include a vinylene group, a propenylene group, a butenylene group, etc. Also, specific examples of the formed ring structure include a cyclopentane ring, a cyclopentene ring, a cyclohexane ring, a cyclohexene ring, etc. Also, examples of the alkylidene group formed by the combination of two Rs bonded to the same carbon atom １ ２ ３ include a methylidene group (=CH ), an ethylidene group (=CH-CH ). In the general formula (1), R １ １ is a substituent of the norbornene ring and may substitute any hydrogen atom bonded to the norbornene ring, and n1 is the number of the substituent R １ . ２ )), an ethylidene group (=CH-CH ３ )), etc. In the general formula (1), R １ １ is a substituent of the norbornene ring and may substitute any hydrogen atom bonded to the norbornene ring, and n1 is the number of the substituent R １ . １ is a substituent of the norbornene ring and may substitute any hydrogen atom bonded to the norbornene ring, and n1 is the number of the substituent R １ １ １ １ １ is the number of.

[0028] As the norbornene compound of the general formula (1), commercially available ones may be used, or those synthesized according to known methods may be used. From the viewpoint of easy availability, etc., when n1 is 0 or n1 is an integer from 1 to 10, R １ １ １ is a compound where R is a halogen atom, a methyl group or an ethyl group, or a compound where two Rs bonded to adjacent carbon atoms are bonded to each other to form a ring, or a compound where two Rs bonded to the same carbon atom １ １ １ １ is a compound where R is a halogen atom, a methyl group or an ethyl group, or a compound where two Rs bonded to adjacent carbon atoms are bonded to each other to form a ring, or a compound where two Rs bonded to the same carbon atom １ １ １ １ are bonded to each other to form a ring, or a compound where two Rs bonded to the same carbon atom １ １ １ １Compounds in which these groups combine to form an ethylidene group are preferred. Examples of norbornene compounds of general formula (1) include 2-norbornene, 5-methyl-2-norbornene, 5-vinyl-2-norbornene, dicyclopentadiene, and 5-ethylidene-2-norbornene.

[0029] The compound (A') having the norbornene skeleton can be incorporated into the copolymer by ring-opening polymerization (preferably by ring-opening metathesis polymerization) to form the hard segment (A).

[0030] In this embodiment, the proportion of the hard segment (A) in the copolymer is preferably in the range of 5 to 95% by mass, and more preferably in the range of 30 to 70% by mass. When the proportion of the hard segment (A) in the copolymer is 5% by mass or more, the physical properties of the copolymer itself are further improved, and the strength of the rubber composition and rubber product containing the copolymer can be further improved. Furthermore, when the proportion of the hard segment (A) in the copolymer is 30% by mass or more, the physical properties of the copolymer itself are further improved, and the strength of the rubber composition and rubber product containing the copolymer can be further improved.

[0031] "Soft Segment (B)" The copolymer of this embodiment has a soft segment (B). The soft segment (B) is a linear or branched segment and does not have a cyclic structure. Examples of the soft segment (B) include a segment having a linear or branched group (e.g., a linear alkylene group) in the main chain skeleton, having a high degree of freedom of molecular rotation and a flexible structure. The soft segment (B) may have substituents on the side chain. Examples of substituents that can be attached to the side chain include alkyl groups and halogen groups. Furthermore, the substituents as side chains may include heteroatoms such as oxygen, sulfur, and nitrogen.

[0032] The soft segment (B) preferably has a linear alkylene structure or a branched alkylene structure having 1 to 30 carbon atoms. As the soft segment (B), a copolymer having a linear alkylene structure or a branched alkylene structure having 1 to 30 carbon atoms has high flexibility of the copolymer itself, and the flexibility of a rubber composition or a rubber product containing the copolymer can be further improved. Examples of the linear alkylene structure having 1 to 30 carbon atoms include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group and the like. Examples of the branched alkylene structure having 1 to 30 carbon atoms include a 2-methyltrimethylene group, a 2-methyltetramethylene group, a 2-methylpentamethylene group, a 3-methylpentamethylene group, a 2-methylhexamethylene group, a 3-methylhexamethylene group, a 2-methylheptamethylene group, a 3-methylheptamethylene group, a 4-methylheptamethylene group, a 2-methyloctamethylene group, a 3-methyloctamethylene group, a 4-methyloctamethylene group and the like.

[0033] The soft segment (B) can be a segment (monomer unit) derived from various monomers, and the monomer may be a linear monomer, a branched-chain monomer or a cyclic monomer. When the soft segment (B) is derived from a cyclic monomer, the cyclic monomer is incorporated into the copolymer by ring-opening polymerization.

[0034] In one embodiment, the soft segment (B) is preferably a segment (monomer unit) derived from a monocyclic unsaturated compound (B'). Further, as the monocyclic unsaturated compound (B'), from the viewpoint of availability and the like, a monocyclic compound having one carbon-carbon double bond is preferable. Examples of such a monocyclic unsaturated compound (B') include cycloalkene compounds. Here, the cycloalkene compound includes a cycloalkene and a compound in which a hydrogen atom in the cycloalkene is substituted with a substituent. Examples of the substituent include a halogen, an alkyl group, an alkenyl group, etc. Examples of the halogen include fluorine, chlorine, bromine, etc. Further, as the alkyl group, an alkyl group having 1 to 5 carbon atoms is preferable, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, etc.

[0035] As the monocyclic unsaturated compound (B'), the following general formula (2): [In the formula, R ２ are each independently hydrogen or a substituent, n21 is an integer of 1 to 10, and n22 is an integer of 1 to 3.] A cycloalkene compound represented by is preferable. Here, examples of the substituent include a halogen, an alkyl group, etc. Examples of the halogen include fluorine, chlorine, bromine, etc. Further, as the alkyl group, an alkyl group having 1 to 5 carbon atoms is preferable, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, etc. Further, the substituent may contain heteroatoms such as oxygen, sulfur, nitrogen, etc.

[0036] As the cycloalkene compound of the general formula (2), a commercially available one may be used, or one synthesized according to a known method may be used. From the viewpoint of availability and the like, a compound in which n22 is 1 is preferable. Examples of the cycloalkene compound of the general formula (2) include cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, etc.

[0037] The monocyclic unsaturated compound (B') can form the soft segment (B) by being incorporated into a copolymer by ring-opening polymerization (preferably by ring-opening metathesis polymerization).

[0038] In this embodiment, the proportion of the soft segment (B) in the copolymer is preferably in the range of 5 to 95% by mass, and more preferably in the range of 30 to 70% by mass. When the proportion of the soft segment (B) in the copolymer is 5% by mass or more, the flexibility of the copolymer itself and the rubber composition and rubber products containing the copolymer are further improved. Furthermore, when the proportion of the soft segment (B) in the copolymer is 30% by mass or more, the flexibility of the copolymer itself and the rubber composition and rubber products containing the copolymer are further improved.

[0039] The mass ratio [(A):(B)] of the hard segment (A) to the soft segment (B) is preferably in the range of 5:95 to 95:5, and more preferably in the range of 30:70 to 70:30. If the proportion of hard segment (A) in the total amount of hard segment (A) to soft segment (B) is 5% by mass or more, the physical properties of the copolymer itself are further improved, and the strength of the rubber composition and rubber product containing the copolymer can be further improved. Furthermore, if the proportion of hard segment (A) in the total amount of hard segment (A) to soft segment (B) is 30% by mass or more, the physical properties of the copolymer itself are further improved, and the strength of the rubber composition and rubber product containing the copolymer can be further improved. Furthermore, if the proportion of soft segment (B) in the total amount of hard segment (A) to soft segment (B) is 5% by mass or more, the flexibility of the copolymer itself and the rubber composition and rubber product containing the copolymer are further improved. Furthermore, when the proportion of soft segments (B) in the total amount of hard segments (A) is 30% by mass or more, the flexibility of the copolymer itself and the rubber composition and rubber products containing the copolymer are further improved. Therefore, a copolymer in which the mass ratio of hard segments (A) to soft segments (B) [(A):(B)] is 5:95 to 95:5 can be applied to rubber compositions and rubber products to further improve the strength and flexibility of the rubber composition and rubber products. Also, a copolymer in which the mass ratio of hard segments (A) to soft segments (B) [(A):(B)] is 30:70 to 70:30 can be applied to rubber compositions and rubber products to further improve the strength and flexibility of the rubber composition and rubber products.

[0040] "Eno-ether segment (C)" The copolymer of this embodiment has an enol-ether segment (C). The enol-ether segment (C) is a segment having an enol-ether moiety (-C=C-O-) in the main chain. The enol-ether moiety is easily hydrolyzed by acids, etc., and the presence of an enol-ether moiety in the main chain of the copolymer makes the main chain of the copolymer more easily cleaved and decomposed.

[0041] The enol ether segment (C) can be a segment (monomer unit) derived from various monomers, which may be a chain monomer or a cyclic monomer.

[0042] In one embodiment, the enol ether segment (C) is preferably a segment (monomer unit) derived from an unsaturated heterocyclic compound (C') as a monomer, and more preferably a segment (monomer unit) derived from an unsaturated heterocyclic compound (C'') having oxygen in the main chain of the ring and having one or two carbon-carbon double bonds. Here, "having oxygen in the main chain of the ring" means that one or more of the constituent atoms (members) of the ring are oxygen. The following general formula (3) is an example of such an unsaturated heterocyclic compound (C'): [In the formula, R ３ Each of the elements is independently a halogen atom or an alkyl group, and n3 is an integer from 0 to 6. Examples include dihydrofuran compounds (cyclic enol ether compounds) represented by [ ]. Here, examples of halogen atoms include fluorine, chlorine, bromine, etc. As the alkyl group, alkyl groups having 1 to 5 carbon atoms are preferred, for example, methyl group, ethyl group, n-propyl group, isopropyl group, etc. In general formula (3), R ３ n3 is a substituent on the dihydrofuran ring, and may substitute any hydrogen atom bonded to the dihydrofuran ring, and n3 is substituent R ３ It is a number.

[0043] As the dihydrofuran compound of general formula (3), a commercially available one may be used, or one synthesized according to a known method may be used. From the viewpoint of availability, etc., if n3 is 0 or an integer from 1 to 6, R ３ However, compounds comprising a halogen atom, a methyl group, or an ethyl group are preferred, and compounds comprising a methyl group are more preferred. Examples of dihydrofuran compounds of general formula (3) include 2,3-dihydrofuran and 5-methyl-2,3-dihydrofuran.

[0044] The unsaturated cyclic heterocyclic compound (C') is not particularly limited as long as it is an unsaturated heterocyclic compound that contains oxygen in the main chain of the ring and has one or two carbon-carbon double bonds. In addition to the dihydrofuran compound of general formula (3), a dihydropyran compound can also be used. From the viewpoint of polymerization reactions, etc., it is preferable to use a dihydrofuran compound.

[0045] The unsaturated heterocyclic compound (C') can be incorporated into the copolymer by ring-opening polymerization (preferably by ring-opening metathesis polymerization) to form the enol ether segment (C).

[0046] In this embodiment, the proportion of the enol ether segment (C) in the copolymer is 0.1 to 40% by mass, preferably 0.1 to 10% by mass. If the proportion of the enol ether segment (C) in the copolymer is 0.1% by mass or more, the copolymer itself and the rubber composition or rubber product containing the copolymer become more easily decomposed. Furthermore, if the proportion of the enol ether segment (C) in the copolymer is 40% by mass or less, the physical properties of the copolymer itself are improved, and the strength of the rubber composition or rubber product containing the copolymer is improved. Furthermore, if the proportion of the enol ether segment (C) in the copolymer is 10% by mass or less, the physical properties of the copolymer itself are further improved, and the strength of the rubber composition or rubber product containing the copolymer is further improved. Therefore, copolymers in which the proportion of the enol ether segment (C) is 0.1 to 10% by mass are easily decomposed, and by applying them to rubber compositions or rubber products, the strength of the rubber composition or rubber product can be further improved.

[0047] -Other Segments (D)- The copolymer of this embodiment may further have other segments (D). When the copolymer of this embodiment has other segments (D), the proportion of other segments (D) in the copolymer is preferably in the range of 0.005 to 40% by mass, more preferably in the range of 0.005 to 10% by mass, even more preferably in the range of 0.005 to 5% by mass, and particularly preferably in the range of 0.005 to 3% by mass.

[0048] The proportions of the hard segment (A), the soft segment (B), the enol ether segment (C), and the other segment (D) in the copolymer of this embodiment are as follows: (1) １ (2) The integral ratio of each peak in the H-NMR spectrum and the amount of each monomer used in the production of the copolymer and the amount of each unreacted monomer can be used to calculate the mass ratio of each content.

[0049] "Molecular Weight" The copolymer of this embodiment preferably has a number average molecular weight of 100,000 or more. Copolymers with a number average molecular weight (Mn) of 100,000 or more can be suitably used in various rubber products such as tires, rubber tracks, and seismic isolation rubber. Furthermore, the copolymer of this embodiment preferably has a number average molecular weight (Mn) of 2,000,000 or less, and more preferably 1,000,000 or less. Copolymers with a number average molecular weight (Mn) of 2,000,000 or less are easily kneaded together with various compounding agents for rubber products. Furthermore, the copolymer of this embodiment preferably has a weight average molecular weight (Mw) of 200,000 or more. Copolymers with a weight average molecular weight (Mw) of 200,000 or more can be suitably used in various rubber products such as tires, rubber tracks, and seismic isolation rubber. Furthermore, the copolymer of this embodiment preferably has a weight-average molecular weight (Mw) of 4,000,000 or less, and more preferably 2,000,000 or less. Copolymers with a weight-average molecular weight (Mw) of 4,000,000 or less are easily kneaded with various compounding agents for rubber products. In this specification, the number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the copolymer are determined by gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0050] "Glass Transition Temperature" The copolymer of this embodiment preferably has a glass transition temperature (Tg) of -20°C to -10°C. If the glass transition temperature (Tg) of the copolymer is -20°C or higher, the physical properties of the copolymer itself are further improved, and the strength of the rubber composition and rubber products containing the copolymer can be further improved. If the glass transition temperature (Tg) of the copolymer is -10°C or lower, the flexibility of the copolymer itself and the rubber composition and rubber products containing the copolymer are further improved. In this specification, the glass transition temperature of the copolymer is a value measured using a differential scanning calorimeter in accordance with JIS K 7121-1987.

[0051] "Applications of the Copolymer" The copolymer of this embodiment can be used in various rubber products. Examples of rubber products include tires, rubber tracks, seismic isolation rubber, and various hoses.

[0052] <Rubber Composition> The rubber composition of this embodiment is characterized by containing the copolymer described above. As described above, the copolymer of this embodiment is easily decomposed and has sufficient strength and flexibility, so the rubber composition of this embodiment is also easily decomposed and has sufficient strength and flexibility, and its properties are improved. Furthermore, rubber products made from such a rubber composition are easy to decompose and reuse after use.

[0053] The rubber composition of this embodiment contains the above-mentioned copolymer as a rubber component, and may further contain other rubber components. Examples of such other rubber components include natural rubber (NR), synthetic diene rubber, and non-diene rubber. Examples of synthetic diene rubber include synthetic isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene rubber (SIR), chloroprene rubber (CR), ethylene-butadiene copolymer, and ethylene-styrene-butadiene copolymer. Examples of non-diene rubber include silicone rubber, fluororubber, and urethane rubber.

[0054] The rubber composition of this embodiment may contain various compounding agents in addition to the rubber components described above. Examples of such compounding agents include fillers (carbon black, silica, etc.), softeners, waxes, stearic acid, antioxidants, silane coupling agents, zinc oxide, and vulcanization accelerators.

[0055] As described above, the copolymer of this embodiment is easily decomposed, and therefore, the rubber composition containing the copolymer of this embodiment is also easily decomposed. Furthermore, rubber products made from such a rubber composition are easily decomposed and reused after use.

[0056] <Tire> The tire of this embodiment is characterized by containing the rubber composition described above. As described above, the rubber composition of this embodiment is easily decomposed and has improved properties, so the tire of this embodiment is also easily decomposed and has improved properties. Furthermore, the tire of this embodiment is easy to disassemble and reuse after use.

[0057] The tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire to be applied, or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process, and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and as the gas to fill the pneumatic tire, in addition to ordinary air or air with adjusted oxygen partial pressure, an inert gas such as nitrogen, argon, or helium can be used.

[0058] <Method for Producing Copolymers> The method for producing copolymers in this embodiment is the same as the method for producing copolymers described above. That is, the copolymer obtained by the method for producing copolymers in this embodiment has a hard segment (A), a soft segment (B), and an enol ether segment (C). The method for producing copolymers in this embodiment is characterized by ring-opening polymerization of a compound having a norbornene skeleton (A'), a monocyclic unsaturated compound (B'), and an unsaturated heterocyclic compound (C').

[0059] As described above, the copolymer obtained by the copolymer manufacturing method of this embodiment is easily decomposed and can improve the properties of rubber products. Furthermore, according to the copolymer manufacturing method of this embodiment, the presence of a compound having a norbornene skeleton (A'), a monocyclic unsaturated compound (B'), and an unsaturated heterocyclic compound (C') in the reaction system allows for rapid ring-opening polymerization. Therefore, according to the copolymer manufacturing method of this embodiment, a copolymer that is easily decomposed and can improve the properties of rubber products can be efficiently obtained. In one embodiment, the copolymer obtained by ring-opening polymerization according to the copolymer manufacturing method of this embodiment has a hard segment (A), a soft segment (B), and an enol ether segment (C) linked by carbon-carbon double bonds.

[0060] "A compound having a norbornene skeleton (A'), a monocyclic unsaturated compound (B'), and an unsaturated heterocyclic compound (C')" In the method for producing the copolymer of this embodiment, the compounds having a norbornene skeleton (A'), a monocyclic unsaturated compound (B'), and an unsaturated heterocyclic compound (C') used as raw materials are as described above.

[0061] The amount of compound (A') having the norbornene skeleton used is preferably in the range of 5 to 95% by mass of the total amount of monomers used, and more preferably in the range of 40 to 60% by mass. If the amount of compound (A') having the norbornene skeleton used is 5% by mass or more of the total amount of monomers used, the physical properties of the resulting copolymer itself are further improved, and the strength of the rubber composition or rubber product containing the copolymer can be further improved. Furthermore, if the amount of compound (A') having the norbornene skeleton used is 40% by mass or more of the total amount of monomers used, the physical properties of the resulting copolymer itself are further improved, and the strength of the rubber composition or rubber product containing the copolymer can be further improved.

[0062] The amount of monocyclic unsaturated compound (B') used is preferably in the range of 5 to 95% by mass of the total amount of monomers used, and more preferably in the range of 40 to 60% by mass. When the amount of monocyclic unsaturated compound (B') used is 5% by mass or more of the total amount of monomers used, the flexibility of the resulting copolymer itself and the rubber composition and rubber products containing the copolymer are further improved. Furthermore, when the amount of monocyclic unsaturated compound (B') used is 40% by mass or more of the total amount of monomers used, the flexibility of the resulting copolymer itself and the rubber composition and rubber products containing the copolymer are further improved.

[0063] The amount of the unsaturated heterocyclic compound (C') used is preferably in the range of 0.1 to 40% by mass of the total amount of monomers used, and more preferably in the range of 0.1 to 10% by mass. If the amount of the unsaturated heterocyclic compound (C') used is 0.1% by mass or more of the total amount of monomers used, the resulting copolymer itself and the rubber composition or rubber product containing the copolymer become more easily decomposed. Furthermore, if the amount of the unsaturated heterocyclic compound (C') used is 40% by mass or less of the total amount of monomers used, the physical properties of the resulting copolymer itself are improved, and the strength of the rubber composition or rubber product containing the copolymer is improved.

[0064] "Other monomers (D')" In the copolymer manufacturing method of this embodiment, other monomers (D') may also be used. When other monomers (D') are used in the copolymer manufacturing method of this embodiment, the amount of other monomers (D) used is preferably in the range of 0.005 to 40% by mass of the total amount of monomers used, more preferably in the range of 0.005 to 10% by mass, even more preferably in the range of 0.005 to 5% by mass, and particularly preferably in the range of 0.005 to 3% by mass.

[0065] "Ring-opening polymerization" The method for producing the copolymer of this embodiment involves ring-opening polymerization of the monomers described above, preferably by ring-opening metathesis polymerization. For example, it is preferable to perform ring-opening metathesis polymerization of the norbornene compound represented by the above general formula (1), the cycloalkene compound represented by the above general formula (2), and the dihydrofuran compound represented by the above general formula (3). As an example, the reaction scheme for ring-opening metathesis polymerization when 2-norbornene is used as the compound represented by general formula (1), cyclopentene is used as the compound represented by general formula (2), and 2,3-dihydrofuran is used as the compound represented by general formula (3) is shown below.

[0066] In the ring-opening polymerization described above, known catalysts can be used. Similarly, in the ring-opening metathesis polymerization described above, known catalysts can be used, including transition metal complexes such as titanium complexes, zirconium complexes, molybdenum complexes, ruthenium complexes, tantalum complexes, tungsten complexes, and rhenium complexes. Among these, transition metal-carbene complexes, such as Grubbs first-generation catalysts, Grubbs second-generation catalysts, and Hoveyda-Grubbs catalysts, are preferred. The structural formula of the Grubbs first-generation catalyst is as follows: It is expressed as and commercially available products can be used. The amount of catalyst used is preferably 0.00001 to 0.1 mol, more preferably 0.0001 to 0.01 mol, and particularly preferably 0.0001 to 0.001 mol per 1 mol of monomer of the raw material.

[0067] In the ring-opening polymerization described above, the reaction temperature is preferably -50°C to 200°C, and more preferably 0 to 200°C. The reaction time is preferably 1 to 24 hours, and more preferably 1 to 6 hours. The reaction pressure can be pressurized, depressurized, or atmospheric pressure, but atmospheric pressure is preferred. The reaction atmosphere is preferably an inert gas atmosphere such as nitrogen or argon. The ring-opening polymerization may be carried out in a batch process or a flow process.

[0068] The ring-opening polymerization may be carried out in a solvent, and preferred solvents are those that are inert to the reaction, such as aliphatic halogen solvents such as dichloromethane, chloroform, and 1,2-dichloroethane; ether solvents such as diethyl ether, tetrahydrofuran, and dioxane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, and mesitylene; aromatic halogen solvents such as monochlorobenzene and dichlorobenzene; and aliphatic hydrocarbon solvents such as hexane, heptane, octane, and cyclohexane.

[0069] <Method for Decomposing Copolymer> The method for decomposing copolymer according to this embodiment is characterized by decomposing the copolymer in the presence of an acid. The copolymer according to this embodiment is easily decomposed, and in particular, is easily hydrolyzed in the presence of an acid. Therefore, according to the method for decomposing copolymer according to this embodiment, the copolymer can be easily decomposed.

[0070] The material obtained by the copolymer decomposition method of this embodiment can be reused for various purposes, for example, it can be used as a raw material for the manufacture of copolymers, or as a raw material for the synthesis of other chemical substances.

[0071] The acid may be an inorganic acid or an organic acid. Examples of inorganic acids include hydrochloric acid, sulfuric acid, and nitric acid. Examples of organic acids include formic acid, acetic acid, and propionic acid. Among these, hydrochloric acid is preferred as the acid. When hydrochloric acid is used as the acid, the copolymer is further decomposed more easily, and the waste liquid is also easier to treat.

[0072] The decomposition temperature in the presence of the acid is not particularly limited, but is preferably in the range of 0°C to 100°C, and may also be at a temperature near room temperature of 15°C to 30°C. The decomposition time in the presence of the acid is not particularly limited and can be appropriately selected depending on the decomposition temperature and the properties of the copolymer, but is preferably 1 to 24 hours, and more preferably 1 to 6 hours. The reaction pressure during decomposition may be pressurized, depressurized, or atmospheric pressure, but atmospheric pressure is preferred. The reaction atmosphere is not particularly limited and may be in air, or in an inert gas atmosphere such as nitrogen or argon.

[0073] The decomposition in the presence of the acid is preferably carried out in a solvent. The solvent used should be one that readily dissolves the acid, such as water or alcohol. Among these, water is preferred as the solvent. Water has excellent acid solubility and also facilitates the treatment of waste liquid after use.

[0074] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0075] <Methods for analyzing polymers> (1) Method for analyzing the proportion of each segment in the polymer The proportions of the 2-norbornene-derived segment, the cyclopentene-derived segment, and the 2,3-dihydrofuran-derived segment in the polymer are as follows: １ H-NMR (room temperature, CDCl ３ The integral ratio of each peak in the solvent spectrum was used to determine this.

[0076] (2) Method for analyzing the molecular weight of polymers. Using gel permeation chromatography [GPC: HLC-8321GPC / HT manufactured by Tosoh Corporation, column: HT-806M x 2 manufactured by Showa Denko Corporation, detector: differential refractometer (RI)], the number-average molecular weight (Mn), weight-average molecular weight (Mw), peak-top molecular weight (Mp), and molecular weight distribution (Mw / Mn) of the polymer were determined using monodisperse polystyrene as the reference. The measurement temperature was 40°C.

[0077] (3) Glass transition temperature (Tg) The glass transition temperature (Tg) of the copolymer was measured using a differential scanning calorimeter (DSC, manufactured by T.A. Instruments Japan, "DSCQ2000") in accordance with JIS K 7121-1987.

[0078] <Method for Synthesis of Copolymer> (Example 1) 17.36 g (184 mmol) of 2-norbornene, 16 g (235 mmol) of cyclopentene, and 0.0927 g (1.23 mmol) of 2,3-dihydrofuran were added to a nitrogen-purged glass container. The container was closed and purged with nitrogen for 5 minutes, after which 75.0 g of anhydrous toluene was added. Next, 0.2 mL of a toluene solution of 0.014 M Ru catalyst (Grubbs first-generation catalyst) was added to the container. The polymerization reaction was carried out at 25°C for 4 hours. Next, excess ethyl vinyl ether was added to the container and the mixture was stirred for 30 minutes to quench the reaction. After that, the contents of the container were poured into a large isopropanol solution containing BHT (2,6-di-tert-butyl-4-methylphenol) to precipitate the polymer, which was filtered and dried under reduced pressure at 60°C for 12 hours to obtain 22.5 g of polymer.

[0079] (Examples 2, 3, Comparative Example 1) Polymers were obtained in the same manner as in Example 1, with the amounts of 2-norbornene, cyclopentene, 2,3-dihydrofuran used, the molar concentration of Ru catalyst in the Ru catalyst toluene solution, the amount of Ru catalyst toluene solution used, and the polymerization time as shown in Table 1.

[0080] (Example 4) Using dicyclopentadiene instead of 2-norbornene, the polymer was obtained in the same manner as in Example 1, with the amount of dicyclopentadiene used, the amount of cyclopentene used, the amount of 2,3-dihydrofuran used, the molar concentration of Ru catalyst in the Ru catalyst toluene solution, the amount of Ru catalyst toluene solution used, and the polymerization time as shown in Table 1.

[0081] <Method for Decomposition of Copolymer> 30 mg of polymer was dissolved in 15 mL of anhydrous tetrahydrofuran (THF) to obtain a solution. 0.2 mL of 0.1 M HCl solution was added to this solution, and the decomposition reaction was carried out at room temperature for the reaction time shown in Table 1. The molecular weight before and after the decomposition reaction was analyzed by GPC to confirm the degree of molecular weight reduction. The results are shown in Table 1.

[0082]

[0083] Table 1 shows that the copolymers of the examples according to the present invention decompose in the presence of acid, resulting in a significant decrease in molecular weight.

[0084] The copolymer of the present invention and rubber compositions containing the same can be used in various rubber products such as tires, rubber tracks, and seismic isolation rubber.

Claims

1. A copolymer comprising a hard segment (A), a soft segment (B), and an enol ether segment (C), wherein the hard segment (A) has a cyclic structure, the soft segment (B) is linear or branched, and the proportion of the enol ether segment (C) in the copolymer is 0.1 to 40% by mass.

2. The copolymer according to claim 1, wherein the proportion of the enol ether segment (C) in the copolymer is 0.1 to 10% by mass.

3. The copolymer according to claim 1, wherein the hard segment (A) has a cycloalkylene structure having 1 to 30 carbon atoms.

4. The copolymer according to claim 1, wherein the soft segment (B) has a linear alkylene structure having 1 to 30 carbon atoms or a branched alkylene structure.

5. The copolymer according to claim 1, wherein the mass ratio of the hard segment (A) to the soft segment (B) [(A):(B)] is 5:95 to 95:

5.

6. The copolymer according to claim 1, wherein the mass ratio of the hard segment (A) to the soft segment (B) [(A):(B)] is 30:70 to 70:

30.

7. The copolymer according to claim 1, wherein the number average molecular weight is 100,000 or more.

8. The copolymer according to claim 1, which is biodegradable.

9. A rubber composition characterized by comprising the copolymer described in any one of claims 1 to 8.

10. A tire characterized by comprising the rubber composition described in claim 9.

11. A method for producing a copolymer according to any one of claims 1 to 8, characterized by ring-opening polymerization of a compound having a norbornene skeleton (A'), a monocyclic unsaturated compound (B'), and an unsaturated heterocyclic compound (C').

12. A method for decomposing a copolymer, characterized by decomposing the copolymer according to any one of claims 1 to 8 in the presence of an acid.

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