Complex polymer, rubber composition, method for producing rubber composition, and rubber product

Abstract

The problem to be solved by the present invention is to provide a polymer with performance as good as that of new products. The solution to this problem is a complex polymer comprising a polymer backbone comprising conjugated diene units and / or olefin units, and functional groups bonded to the polymer backbone, wherein the functional groups comprise nitrogen atoms and / or phosphorus atoms and are complexed with metal ions of elements from Groups 7 to 10 of the periodic table. The complex polymer is characterized in that the bond dissociation energy between the metal ions and the functional groups is greater than 200 kJ / mol.

Description

Technical Field

[0001] The present invention relates to a complex polymer, a rubber composition, a method for producing the rubber composition, and a rubber product. Background Art

[0002] In the past, most used vulcanized rubber products, such as old tires, were treated as waste rather than recycled. However, from the perspectives of addressing environmental issues and promoting resource conservation, recycling vulcanized rubber waste, such as old tires, is a top priority.

[0003] As a method for regenerating vulcanized rubber, for example, there is a conventionally known method of regenerating the vulcanized rubber by applying heat and shearing force to the vulcanized rubber using a twin-screw extruder.

[0004] Further, PTL 1 proposes a technology of devulcanizing vulcanized rubber and regenerating the rubber into unvulcanized rubber.

[0005] Reference List

[0006] Patent Literature

[0007] PTL 1: JP2005-023225 A Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, in the prior art, cross-linked products of polymers, such as vulcanized rubber, inevitably deteriorate due to regeneration because the cross-linked products are regenerated by treatment under harsh conditions. For example, compared to rubber products that do not use regenerated rubber, rubber products using regenerated rubber have the problem of poor performance in physical properties such as breaking strength. Therefore, there is still room for improvement in recycling cross-linked products of polymers, such as vulcanized rubber, and further research is needed.

[0010] In view of this, an object of the present invention is to provide a recyclable polymer (such as rubber) whose performance is as good as that of new products, thereby solving the above-mentioned problems of the prior art.

[0011] Furthermore, another object of the present invention is to provide a rubber composition comprising the polymer, a method for producing the rubber composition, and a rubber product comprising the rubber composition.

[0012] Solutions for solving problems

[0013] The inventors of the present invention have discovered, as a result of intensive research to solve the above-mentioned problems, that a specific complex polymer is recyclable and, after regeneration, has the same performance as new products, thereby completing the present invention. Specifically, the main features of the present invention for achieving the above-mentioned objects are as follows.

[0014] The complex polymer of the present invention comprises: a polymer main chain comprising conjugated diene units and / or olefin units; and a functional group bonded to the polymer main chain, wherein: the functional group contains nitrogen atoms and / or phosphorus atoms therein and is complexed with a metal ion of an element from Groups 7 to 10 in the periodic table; and the bond dissociation energy of dissociation between the metal ion and the functional group is greater than 200 kJ / mol.

[0015] A rubber composition according to one embodiment of the present invention is a rubber composition including the above-mentioned complex polymer, wherein the content of sulfur in the rubber composition is 0.3 parts by mass or less relative to 100 parts by mass of the rubber component.

[0016] Further, a rubber composition according to another embodiment of the present invention is a rubber composition including the complex polymer, wherein the content of the peroxide in the rubber composition is 0.3 parts by mass or less relative to 100 parts by mass of the rubber component.

[0017] A method for producing a rubber composition according to one embodiment of the present invention is a method for producing a rubber composition containing the complex polymer, the method comprising: in a first stage of kneading, kneading a compound containing a polymer main chain and a compound containing a functional group to form a functionalized polymer, wherein the functional group is bonded to the polymer main chain; and, in a second stage of kneading or thereafter, adding a metal salt to the functionalized polymer, kneading the functionalized polymer and the metal salt to complex the functionalized polymer with the metal, thereby forming a complex polymer.

[0018] Furthermore, a method for producing a rubber composition according to another embodiment of the present invention is a method for producing a rubber composition containing the complex polymer, the method comprising: preparing the complex polymer in advance; and blending the complex polymer thus prepared in advance with other components of the rubber composition, and kneading the mixture.

[0019] The rubber product of the present invention is characterized by comprising the above-mentioned rubber composition.

[0020] Effects of the Invention

[0021] According to the present invention, a polymer can be provided which can be recycled and has properties as good as new products.

[0022] Furthermore, the present invention can provide a rubber composition comprising the polymer, a method for producing the rubber composition, and a rubber product comprising the rubber composition. DETAILED DESCRIPTION

[0023] Hereinafter, the complex polymer, the rubber composition, the method for producing the rubber composition, and the rubber product of the present invention will be described in detail based on the embodiments of the present invention.

[0024] <Complex Polymer>

[0025] The complex polymer of the present invention comprises: a polymer main chain comprising conjugated diene units and / or olefin units; and a functional group bonded to the polymer main chain, wherein: the functional group contains a nitrogen atom and / or a phosphorus atom and is complexed with a metal ion of an element from Groups 7 to 10 in the periodic table; and the bond dissociation energy of dissociation between the metal ion and the functional group is 200 kJ / mol or more.

[0026] The complex polymer of the present invention has a polymer main chain and functional groups, wherein the functional groups are complexed with metal ions of elements from Groups 7 to 10 in the periodic table, so that the bond dissociation energy of the metal ions and the functional groups is greater than 200 kJ / mol. The complex polymer has high durability due to the highly strong crosslinking of the polymer main chain.

[0027] On the other hand, the bond between the metal ion and the functional group (which is not a sulfur cross-linked bond as is common in vulcanized rubber) can be easily broken, for example, by heating, thereby allowing the rubber to flow for reshaping. Since the bond between the metal ion and the functional group can be easily broken, the complex polymer does not need to be exposed to the harsh conditions for bond rupture. The functionalized polymer comprising the polymer backbone and the functional group (re)generated due to the dissociation of the metal ion and the functional group maintains the original properties of the polymer backbone unchanged, because the complex polymer does not need to be exposed to the harsh conditions for bond rupture, as described above. Therefore, the performance of the complex polymer regenerated by complexing the functionalized polymer recovered with the metal ion can continue to perform as well as a new complex polymer.

[0028] Therefore, the complex polymer of the present invention is recyclable and has the same good performance as new complex polymer after regeneration.Further, according to the present invention, a novel polymer having a new cross-linking structure instead of sulfur cross-linking can be provided.

[0029] (Polymer backbone)

[0030] The complex polymer of the present invention includes a polymer backbone comprising conjugated diene units and / or olefin units. That is, the polymer backbone comprises conjugated diene units or olefin units, or comprises both conjugated diene units and olefin units simultaneously. The complex polymer has at least one polymer backbone. Where the complex polymer has one polymer backbone, the complex polymer forms a cross-linked structure by the metal ions within its molecule. Where the complex polymer has two or more polymer backbones, the complex polymer forms a cross-linked structure by the metal ions within its molecule and between its two or more polymer backbones. The complex polymer has multiple functional groups therein for forming a cross-linked structure. In this regard, multiple functional groups can be bonded to a single polymer backbone or multiple polymer backbones, respectively. Multiple functional groups can be of the same species or different species.

[0031] The conjugated diene unit represents a monomer unit derived from a conjugated diene compound. The conjugated diene compound as a monomer preferably has 4 to 8 carbon atoms. Specific examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. From the perspective of satisfactory elastomer properties, the conjugated diene compound as a monomer preferably includes 1,3-butadiene and / or isoprene.

[0032] The content of the conjugated diene unit in the polymer backbone is not particularly limited and may be 0 mol%, preferably ≥ 0.1 mol%, more preferably ≥ 1 mol%, and may be 100 mol%. When the above content is ≥ 1 mol%, a complex polymer having excellent elastomeric properties may be obtained.

[0033] The olefin unit refers to a monomer unit derived from an olefin compound. The olefin compound as a monomer preferably has 2 to 10 carbon atoms. Specific examples of the olefin compound include: α-olefins such as ethylene, propylene, 1-pentene, 1-hexene, 1-heptene, and 1-octene; heteroatom-substituted olefin compounds such as vinyl pivalate, 1-phenylthioethylene, and N-vinylpyrrolidone; and the like.

[0034] The content of the olefin unit in the polymer main chain is not particularly limited, and may be 0 mol%, preferably ≥ 1 mol%, and may be 100 mol%.

[0035] The polymer backbone may further include units derived from other monomers copolymerizable with the conjugated diene compound and / or olefin compound. Examples of units derived from other monomers include aromatic vinyl units and the like. The content of units derived from other monomers in the polymer backbone is not particularly limited and may be 0 mol %, and in one embodiment, is preferably ≥1 mol % and ≤50 mol %.

[0036] The aromatic vinyl unit refers to a monomer unit derived from an aromatic vinyl compound. An aromatic vinyl compound refers to an aromatic compound substituted with at least one vinyl group. The aromatic vinyl compound as a monomer preferably has 8 to 10 carbon atoms. Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2-ethylstyrene, 3-ethylstyrene, and 4-ethylstyrene.

[0037] (Functional Group)

[0038] The complex polymer of the present invention includes a functional group bonded to the polymer backbone. The functional group contains a nitrogen atom and / or a phosphorus atom therein and is complexed with a metal ion of an element from Groups 7 to 10 in the periodic table. Since the functional group contains a nitrogen atom and / or a phosphorus atom therein and is complexed with a metal ion of an element from Groups 7 to 10 in the periodic table, the functional group and the metal ion are strongly bonded, thereby successfully forming a crosslink as strong as a sulfur crosslink. Preferred examples of nitrogen-containing functional groups include groups having nitrogen-containing heterocycles such as a 4,5-dihydropyridazine ring, a pyridine ring, a pyrimidine ring, a triazine ring, or a tetrazine ring. Examples of phosphorus-containing functional groups include groups obtained by replacing each nitrogen atom of the nitrogen-containing heterocycle of the above-mentioned nitrogen-containing functional groups with a phosphorus atom.

[0039] In the present invention, it is preferred that the functional group does not contain a sulfur atom. In the case where the functional group does not contain a sulfur atom, crosslinking between polymer main chains due to the sulfur atom can be prevented, and thus the recyclability of the product can be improved.

[0040] In the complex polymer of the present invention, the bond dissociation energy for the dissociation of the metal ion and the functional group is ≥200 kJ / mol, and preferably ≥250 kJ / mol and ≤500 kJ / mol. When the bond dissociation energy is ≥200 kJ / mol, a cross-linked structure having a high strength comparable to that of sulfur crosslinks can be formed, thereby ensuring satisfactory high durability of the complex polymer. When the bond dissociation energy is ≥250 kJ / mol, the durability of the complex polymer is further improved. When the bond dissociation energy is ≤500 kJ / mol, the bond between the metal ion and the functional group can be more easily broken, and thus the complex polymer can be more easily recycled than otherwise.

[0041] In the present invention, the bond dissociation energy of the dissociation of a metal ion and a functional group represents the value measured in a vacuum at the structural optimization level of M06 / 6-31G(d,p) / / B3PW91-D3 / 6-31G(d,p) or M06 / 6-31G(d,p). It is assumed that the metal ion and the functional group form an ionic aggregate. Gaussian09 or GRRM14 can be used for the calculation of the bond dissociation energy.

[0042] In the complex polymer of the present invention, the metal ion and the functional group are preferably bonded to each other via a coordinate bond. When the metal ion and the functional group are bonded via a coordinate bond, their bond is satisfactorily reversible or breakable. Further, in the case where the metal ion and the functional group are bonded to each other via a coordinate bond in the complex polymer, the metal ion and the functional group can easily form a satisfactory strong bond, and the complex polymer can be easily made to flow by heating, thereby making it easier to reshape, and thus the recyclability of the complex polymer is further improved than in other cases.

[0043] In the complex polymer of the present invention, the functional groups are preferably derived from compounds containing triazine rings or tetrazine rings. Compounds containing triazine rings or tetrazine rings that react with the polymer backbone easily form functionalized polymers due to their reactivity with the polymer backbone. Furthermore, the nitrogen-containing functional groups derived from compounds containing triazine rings or tetrazine rings readily complex with metal ions of elements from Groups 7 to 10 of the periodic table, successfully forming crosslinked structures with strength comparable to sulfur crosslinks.

[0044] In the present invention, in the case where the functional group is derived from a compound containing a triazine ring or a tetrazine ring, it is preferred that the pyridyl or pyrimidyl group is bonded to the triazine or tetrazine ring of the compound. In this regard, it is more preferred that two pyridyl or pyrimidyl groups are bonded to the triazine or tetrazine ring. In the case where the pyridyl or pyrimidyl group is bonded to the triazine or tetrazine ring, the functional group is more likely to be complexed with a metal ion of an element of Groups 7 to 10 in the periodic table, whereby the associated bond dissociation energy is likely to be high, and thus a cross-linked structure having a strength higher than that of other cases can be formed. Further, in the case where two pyridyl or pyrimidyl groups are bonded to the triazine or tetrazine ring, the functional group is even more likely to be complexed with a metal ion of an element of Groups 7 to 10 in the periodic table, whereby the associated bond dissociation energy is likely to be high, and thus a cross-linked structure having an even higher strength than that of other cases can be formed.

[0045] The pyridyl group may be any one of 2-pyridyl, 3-pyridyl and 4-pyridyl, preferably 2-pyridyl. The pyrimidinyl group may be any one of 2-pyrimidinyl, 4-pyrimidinyl and 5-pyrimidinyl.

[0046] The functional group is preferably derived from a compound represented by the following general formula (1).

[0047]

[0048] In the general formula (1), X 1 and X 2 Each independently represents a pyridyl group or a pyrimidinyl group, and Y 1 and Y 2Each independently represents a single bond or a divalent hydrocarbon group.

[0049] The compound represented by the general formula (1) easily undergoes a Diels-Alder reaction with a polymer backbone containing a conjugated diene unit and / or an olefin unit, thereby easily forming a functionalized polymer. Further, in the case where the functional group is derived from the compound represented by the general formula (1), the functional group is particularly likely to be complexed with a metal ion of an element from Groups 7 to 10 in the periodic table, whereby the associated bond dissociation energy is even more likely to be high, and thus a cross-linked structure having particularly high strength can be formed.

[0050] In the general formula (1), X 1 and X 2 Each independently represents a pyridyl group or a pyrimidinyl group. From the viewpoint of ease of synthesis, X 1 and X 2 Each is preferably a pyridyl group. The pyridyl group may be any one of 2-pyridyl, 3-pyridyl and 4-pyridyl, preferably 2-pyridyl. The pyrimidinyl group may be any one of 2-pyrimidinyl, 4-pyrimidinyl and 5-pyrimidinyl.

[0051] In the general formula (1), Y 1 and Y 2 Each independently represents a single bond or a divalent hydrocarbon group. Examples of divalent hydrocarbon groups include alkylene, alkenylene, and arylene groups. Specifically, examples of alkylene groups include methylene, ethylene, trimethylene, and tetramethylene groups. Examples of alkenylene groups include vinylene, propenylene, and butenylene groups. Examples of arylene groups include phenylene, tolylene, and naphthylene groups. From the perspective of ease of synthesis, Y 1 and Y 2 Each is preferably a single bond (ie, preferably, X 1 and X 2 each directly bonded to a triazine ring).

[0052] In the present invention, in the general formula (1), preferably, X 1 and X 2 Each is a pyridyl group, and Y 1 and Y 2 Each is a single bond. In this case, the compound of general formula (1) is not only easily available, but the functional group is also particularly easy to complex with metal ions of elements of Groups 7 to 10 in the periodic table, whereby the relevant bond dissociation energy is even more likely to be high, and thus a cross-linked structure with particularly high strength can be formed.

[0053] Examples of the compound represented by the general formula (1) include 3,6-di(2-pyridyl)-1,2,4,5-tetrazine, 3,6-di(3-pyridyl)-1,2,4,5-tetrazine, 3,6-di(4-pyridyl)-1,2,4,5-tetrazine, 3,6-di(2-pyridylmethyl)-1,2,4,5-tetrazine, 3,6-di(2-pyridylethyl)-1,2,4,5-tetrazine, 3-(2-pyridylmethyl)-6-(2-pyridylethyl)-1,2,4,5-tetrazine, 3,6-di(2-pyrimidinyl)-1,2,4,5-tetrazine, 3,6-di(4-pyrimidinyl)-1,2,4,5-tetrazine, and 3,6-di(5-pyrimidinyl)-1,2,4,5-tetrazine. Among these examples, 3,6-di(2-pyridyl)-1,2,4,5-tetrazine is preferred.

[0054] In the complex polymer of the present invention, the functional groups are bonded to the polymer backbone in an amount preferably in the range of 0.1 to 10 mol%, more preferably in the range of 0.3 to 8 mol%, even more preferably in the range of 0.4 to 5 mol%, and particularly preferably in the range of 0.5 to 3 mol%, relative to the monomer units of the polymer backbone. In the case where the functional groups are bonded to the polymer backbone in an amount of ≥0.1 mol% relative to the monomer units of the polymer backbone, a cross-linked structure having a high strength comparable to sulfur cross-linking can be formed, thereby obtaining a complex polymer having satisfactorily high durability. In the case where the functional groups are bonded to the polymer backbone in an amount of ≤10 mol% relative to the monomer units of the polymer backbone, a complex polymer having satisfactory elastomeric properties can be easily obtained.

[0055] (metal ions)

[0056] In the complex polymer of the present invention, the metal ion complexed with the functional group is a metal ion of an element from Groups 7 to 10 in the periodic table, and preferably a metal ion of an element from Group 8 in the periodic table.

[0057] Specifically, examples of the Group 7 element include manganese, rhenium, and the like.

[0058] Examples of Group 8 elements include iron, ruthenium, osmium, and the like.

[0059] Examples of Group 9 elements include cobalt, rhodium, iridium, and the like.

[0060] Examples of the Group 10 element include nickel, palladium, platinum, and the like.

[0061] Metal ions of elements from Groups 7 to 10 in the periodic table easily form strong bonds with functional groups. Furthermore, in the case where the metal ions are metal ions of elements from Group 8 in the periodic table, the bonds between the metal ions and the functional groups tend to be stronger than in other cases, thereby ensuring the formation of a cross-linked structure having a high strength comparable to that of sulfur cross-links.

[0062] The valence of the metal ion of the element of Groups 7 to 10 in the periodic table is not particularly limited and can be set to any valence that the element can take.

[0063] Iron ions are particularly preferred as the metal ions. Iron ions easily form particularly strong bonds with functional groups containing nitrogen atoms and / or phosphorus atoms, thereby allowing the formation of a cross-linked structure having a higher strength than otherwise possible. The valence of the iron ion is preferably divalent (Fe 2+ ) or trivalent (Fe 3+ ).

[0064] In the complex polymer of the present invention, it is preferred that the metal ion be complexed with the functional group by adding the relevant metal salt to the polymer backbone having the functional group bonded thereto. In this case, the complex polymer can be easily obtained, and thus a cross-linked structure having a high strength comparable to that of sulfur cross-linking can be easily formed. The form of the added metal salt is not particularly limited, and for example, it can be a metal salt hydrate. The amount of the metal salt added is preferably in the range of 1 to 30 parts by mass, more preferably in the range of 1 to 15 parts by mass, even more preferably in the range of 1 to 10 parts by mass, and particularly preferably in the range of 1 to 5 parts by mass, relative to 100 parts by mass of the polymer backbone.

[0065] Examples of metal salts include metal halides, metal sulfates, and metal nitrates. Among these examples, metal halides are preferred. Metal halides are easy to handle and are more likely to form a cross-linked structure having a high strength comparable to sulfur cross-linking than other cases.

[0066] Examples of metal halides include metal fluorides, metal chlorides, metal bromides, and metal iodides. Among these examples, metal chlorides are preferred. Metal chlorides are easy to handle and can even more easily form a cross-linked structure having a high strength comparable to that of sulfur cross-links.

[0067] Specific examples of the metal salt include FeCl 2 , FeCl 2 ·4H 2 O, FeCl 3 , and FeCl 3 ·6H 2 O, etc. One of these examples alone or a combination of two or more thereof may be used as the metal salt.

[0068] (Method for producing complex polymer)

[0069] The complex polymer of the present invention can be synthesized by, for example, reacting a compound having a nitrogen and / or phosphorus functional group with a polymer chain to form a functionalized polymer, wherein the nitrogen and / or phosphorus functional group is bonded to the polymer chain; and complexing the functionalized polymer with a metal ion of an element from Groups 7 to 10 of the periodic table. In the present invention, as the compound having a nitrogen-containing functional group, a compound containing a triazine ring or a tetrazine ring as described above is preferred, and a compound represented by the general formula (1) is more preferred. In the reaction between the polymer chain and the compound having a nitrogen and / or phosphorus functional group, it is preferred that the reaction conditions such as temperature, pressure, and reaction time are appropriately selected according to the type and reactivity of the polymer chain and / or the compound having a nitrogen and / or phosphorus functional group used for the reaction. Furthermore, in the reaction of complexing the functionalized polymer with a metal ion, it is preferred that the reaction conditions such as temperature, pressure, and reaction time are appropriately selected according to the type and reactivity of the functionalized polymer and the metal ion used for the reaction.

[0070] As an example of a method for producing a complex polymer, when 3,6-di(2-pyridyl)-1,2,4,5-tetrazine is used as a compound having a nitrogen-containing functional group and ferrous chloride (FeCl2) is used as a raw material for metal ions, a reaction scheme for functionalizing the polymer backbone and complexing the resulting functionalized polymer with the metal ions is shown below.

[0071]

[0072] As shown in the upper half of the reaction scheme, one embodiment of the present invention causes a Diels-Alder reaction between a compound having a nitrogen-containing functional group and a polymer backbone comprising conjugated diene units and / or olefin units to produce a functionalized polymer. Although nitrogen is released in the Diels-Alder reaction in this embodiment, any other optional reaction can be used to functionalize the polymer backbone.

[0073] Furthermore, as shown in the lower half of the reaction scheme, one embodiment of the present invention complexes the functionalized polymer with ferrous chloride to form a complex polymer. Although the reaction scheme shows a reaction in which the nitrogen atom in the tetrazine residue and the nitrogen atom in the pyridyl group bonded to the tetrazine residue are complexed with iron ions, the complex polymer of the present invention can adopt any of a variety of complex forms.

[0074] The complex polymer may further include other functional groups that do not complex with metal ions of Groups 7 to 10 of the periodic table. The types of such other functional groups as described above are not particularly limited and can be appropriately selected according to the desired physical properties of the complex polymer.

[0075] The complex polymer of the present invention can be prepared in advance by pre-synthesis as described above. Alternatively, the complex polymer can be synthesized in situ during the manufacture of the rubber composition, as disclosed in the method of making the rubber composition discussed below.

[0076] <Rubber Composition>

[0077] The rubber composition of the present invention includes the above-mentioned complex polymer. The rubber composition of the present invention is recyclable (for example, can be remolded by hot pressing) and has the same good performance as new products after recycling because it includes the above-mentioned complex polymer, which is recyclable and has the same good performance as new products after recycling.

[0078] The rubber composition of one embodiment of the present invention comprises above-mentioned complex polymer as rubber component.Rubber composition of the present invention can further comprise the rubber component except above-mentioned complex polymer, and the example of this other rubber component comprises natural rubber (NR), synthetic diene rubber and non-(conjugated) diene rubber etc.The example of synthetic diene rubber comprises 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 etc.The example of non-diene rubber comprises silicone rubber, fluororubber and polyurethane rubber etc.

[0079] The content of the complex polymer in the rubber component of the rubber composition is preferably ≥ 10% by mass and may be 100% by mass.

[0080] When the polymer backbone of complex polymer comprises olefin unit therein and does not contain diene unit, this complex polymer is considered as resin component.In this case, any rubber can be used as the rubber component of rubber combination, and the example of rubber component that can be used comprises above-mentioned natural rubber (NR), synthetic diene rubber and non-(conjugated) diene rubber etc. Further, when adopting complex polymer as resin combination therein, thermoplastic resin etc. can be used as other resin components.The example of thermoplastic resin comprises polyolefin resin, polyamide resin and polyester resin (such as PET) etc.

[0081] In addition to the above-mentioned complex polymer and rubber component, the compounding agent commonly used in the rubber industry such as filler (carbon black, silicon dioxide etc.), softening agent, stearic acid, antioxidant and silane coupling agent etc. can be suitably selected and added into the rubber composition of the present invention, unless its addition adversely affects the purpose of the present invention. Commercially available product can be suitably used as these compounding agents. Preferably, the rubber composition of the present invention only comprises a small amount of or does not comprise sulphur / peroxide therein. However, in the present invention, even when only comprising a small amount of or not comprising sulphur in the rubber composition wherein, the rubber composition of the present invention also can comprise or preferably comprise vulcanization accelerator. Sulfonamide-based vulcanization accelerator is preferably as the vulcanization accelerator comprised in the rubber composition.

[0082] In one embodiment of the rubber composition of the present invention, the content of sulfur in the rubber composition is preferably 0.3 parts by mass or less relative to 100 parts by mass of the rubber component and may be 0 parts by mass. Such a rubber composition having a low sulfur content as described above includes very few sulfur-derived crosslinking structures such as SS bonds and CS bonds (once a sulfur-derived crosslinking structure is formed, it is rarely broken), and is therefore easily recyclable.

[0083] In another embodiment of the rubber composition of the present invention, the content of peroxide in the rubber composition is preferably 0.3 parts by mass or less relative to 100 parts by mass of the rubber component and may be 0 parts by mass. Such a rubber composition having a low peroxide content as described above includes very few peroxide-derived crosslinking structures such as C-C bonds therein (once a peroxide-derived crosslinking structure is formed, it is hardly broken), and is therefore easily recyclable.

[0084] In another embodiment of the rubber composition of the present invention, the content of sulfur in the rubber composition is preferably 0.3 parts by mass or less relative to 100 parts by mass of the rubber component, and the content of peroxide in the rubber composition is preferably 0.3 parts by mass or less relative to 100 parts by mass of the rubber component. Such a rubber composition having a low sulfur content and a low peroxide content as described above includes very few crosslinking structures derived from sulfur and / or crosslinking structures derived from peroxides such as SS bonds, CS bonds, and CC bonds, and is therefore easily recyclable.

[0085] <Method for producing rubber composition>

[0086] The method for producing a rubber composition of the present invention is a method for producing a rubber composition comprising the above-mentioned complex polymer. It should be noted that the complex polymer can be generated in situ during the production process of the rubber composition.

[0087] In the manufacturing method of the rubber composition according to one embodiment of the present invention, the first stage of its mixing process includes: mixing a compound containing a polymer backbone and a compound containing a functional group, thereby forming a functionalized polymer as a polymer backbone having a functional group bonded thereto. Further, in the manufacturing method of the rubber composition according to one embodiment of the present invention, the second stage of its mixing process or a stage after the second stage includes: adding a metal salt to the functionalized polymer, and mixing the metal salt and the functionalized polymer, thereby complexing the functionalized polymer with the metal ion, and thus forming a complex polymer. The manufacturing method of the above-mentioned rubber composition allows the preparation of the complex polymer during the manufacturing (mixing) process of the rubber composition, which is advantageous in terms of productivity.

[0088] The functionalized polymer can be complexed with the metal ion by adding a metal salt to the functionalized polymer in the second stage of the kneading process or at any stage after the second stage. Any optional compounding agent as described above can be blended simultaneously in the first / second stage of the kneading process or at a stage after the second stage. As the compound containing a functional group, a compound having a triazine ring or a tetrazine ring as described above is preferred, and a compound represented by the general formula (1) is more preferred.

[0089] The method for manufacturing the rubber composition of the present invention is not limited to the above method. For example, the method for manufacturing the rubber composition according to another embodiment of the present invention includes pre-forming a complex polymer and adding the pre-formed complex polymer to other components during the mixing process. The method for manufacturing the rubber composition of the another embodiment also allows for simplification of the manufacture of the rubber composition containing the above complex polymer and is advantageous in terms of productivity.

[0090] Furthermore, a method for producing a rubber composition according to another embodiment of the present invention includes: pre-preparing a functionalized polymer in which a functional group is bonded to a polymer backbone; mixing the functionalized polymer and an optional compounding agent in the first stage of the mixing process; and adding a metal salt thereto in the second stage of the mixing process / a stage after the second stage, and mixing the mixture to complex the functionalized polymer with the metal ion, thereby forming a complex polymer. The method for producing a rubber composition according to another embodiment of the present invention also allows for simplified production of the rubber composition containing the complex polymer and is advantageous in terms of productivity.

[0091] <Rubber products>

[0092] The rubber product of the present invention is characterized in that it comprises the above-mentioned rubber composition. The rubber product of the present invention comprises the rubber composition comprising the above-mentioned recyclable complex polymer, is recyclable, and has the same good performance as new products after recycling.

[0093] The rubber product of the present invention is preferably a tire. Even after the tire is worn, it generally maintains satisfactory durability at its rubber portion. Therefore, by regenerating the rubber portion of the tire, the tire can be fully recycled.

[0094] Examples of tire portions to which the rubber composition may be applied include, but are not limited to, treads, sidewalls, sidewall reinforcing rubber, and bead fillers.

[0095] A tire can be manufactured by, for example, sequentially stacking components commonly used for tire manufacturing, such as a carcass layer, a belt layer, and a tread layer made of a rubber composition, on a tire-building drum; removing the drum to obtain a green tire; and heating the green tire as needed.

[0096] The rubber composition of the present invention is suitable not only for tires but also for, for example, anti-vibration rubber, shock-isolating rubber, belts (conveyor belts), rubber crawlers, and various hoses.

[0097] Example

[0098] The present invention will be described in further detail below by way of examples, but the present invention is not limited in any way by these examples.

[0099] <Method for producing functionalized polymer A>

[0100] A functionalized polymer sample (Functionalized Polymer A) was prepared by:

[0101] In a glass bottle, 50 g of "TUFDENE TM 2000R” (styrene-butadiene rubber (SBR) as the polymer backbone containing conjugated diene units) was dissolved in 600 mL of THF;

[0102] 2.4 g (10 mmol) of 3,6-di(2-pyridyl)-1,2,4,5-tetrazine manufactured by Tokyo Chemical Industry Co., Ltd. was added to a glass bottle, and the reaction mixture was heated under reflux for 3 hours; and

[0103] The resulting solution was vacuum-dried at 60° C. for 7 hours, thereby obtaining 50 g of a functionalized polymer A.

[0104] In the functionalized polymer A thus obtained, the content of the functional group capable of complexing with metal ions was 1.2 mol% relative to the monomer units of the polymer main chain.

[0105] <Method for producing functionalized polymer B>

[0106] The functionalized polymer sample (Functionalized Polymer B) was prepared as follows:

[0107] In a glass bottle, 50 g of "TUFDENE TM 2000R" (styrene-butadiene rubber (SBR) as the polymer main chain containing conjugated diene units) was dissolved in 600 mL of THF;

[0108] 1.8 g (7.5 mmol) of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine manufactured by Tokyo Chemical Industry Co., Ltd. and 0.44 g (0.25 mmol) of 4-phenyl-1,2,4-triazoline-3,5-dione were added to the glass bottle, and the reaction mixture was heated under reflux for 3 hours; and

[0109] The resulting solution was dried under vacuum at 60 °C for 7 hours to obtain 50 g of Functionalized Polymer B.

[0110] In the Functionalized Polymer B thus obtained, the content of the functional groups capable of complexing with metal ions was 0.9 mol% relative to the monomer units of the polymer main chain.

[0111] <Manufacture of Rubber Composition>

[0112] According to the blending formula shown in Table 1, rubber composition samples were prepared using a conventional Banbury mixer. The first and second stages of the mixing process were carried out in this order. In each example, ferrous chloride tetrahydrate was added to the mixture in the second stage of the mixing process to form a complex polymer. The first stage of the mixing process was carried out at 140 °C for 3 minutes, and the second stage of the mixing process was carried out at 80 °C for 1 minute. For each of the rubber composition samples thus obtained, the tensile strength (Tb) and elongation at break (Eb) were measured by the following methods, respectively.

[0113] In the rubber composition samples prepared in Examples 1 to 4, the bond dissociation energy of the dissociation of iron ions and nitrogen-containing functional groups in each complex polymer was 249.7 kJ / mol.

[0114] <Measurement of Tb and Eb>

[0115] No. 7 dumbbell-shaped test pieces were prepared from the rubber composition samples, and the tensile strength (Tb (MPa)) and elongation at break (Eb (%)) of each rubber composition sample were measured by performing a tensile test on the test pieces at room temperature (23 °C) and high temperature (100 °C) in accordance with JIS-K6251.

[0116] <Recycling of Rubber Composition>

[0117] Each rubber composition sample was placed in a mold and heated at 160° C. for 30 minutes, thereby remolding it. Tb and Eb of the rubber composition sample thus remolded were measured by the above-mentioned respective methods.

[0118] The remolding process was performed three times in total, and the recyclability of the rubber composition samples was evaluated. The results are shown in Table 1. In Table 1, "failed" means that the rubber composition sample was never successfully remolded in three remolding attempts, and "three or more" means that the rubber composition sample was successfully remolded in each of the three remolding attempts.

[0119] Table 1

[0120]

[0121] *1Polymer: "TUFDENE" manufactured by Asahi Kasei Corporation TM 2000R" (Styrene-butadiene rubber (SBR))

[0122] *2 Functionalized polymer A: synthesized by the above method

[0123] *3 Functionalized polymer B: synthesized by the above method

[0124] *4Silicon dioxide: "Nipsil AQ" manufactured by Toso Silica Corporation

[0125] *5 Carbon black: "N234" manufactured by TOKAI CARBON CO., LTD.

[0126] *6 Oil: "JOMO PROCESS NC300BN" manufactured by JX Nippon Oil & Energy Corporation

[0127] *7 Wax: "SUNTIGHT A" manufactured by Seiko Chemical Co., Ltd.

[0128] *8 Antioxidant: "Nocrac 6C" manufactured by Ouchi-Shinko Chemical Industrial Co., Ltd.

[0129] *9 Silane coupling agent: Bis(triethoxysilylpropyl)polysulfide

[0130] *10 Vulcanization accelerator A: bis(2-benzothiazolyl) persulfide

[0131] *11 Vulcanization accelerator B: N-tert-butyl-2-benzothiazolylsulfenamide

[0132] *12 Vulcanization accelerator C: diphenylguanidine

[0133] As can be understood from Table 1, the rubber compositions according to the examples of the present invention have physical properties (tensile properties) comparable to those of the rubber compositions of the comparative examples cross-linked using sulfur. In particular, the rubber compositions according to the examples of the present invention have physical properties (tensile properties) comparable to those of the rubber compositions of the comparative examples cross-linked using sulfur at high temperatures (100° C.).

[0134] Further, it can be understood from Table 1 that the rubber composition according to the Examples of the present invention can be reshaped, that is, recycled, and the physical properties after reshaping (recycling) are as good as those of new products.

[0135] Industrial applicability

[0136] The complex polymer and rubber composition of the present invention are suitable for various rubber products such as tires.

Claims

1. A complex polymer comprising: a polymer backbone comprising conjugated diene units and / or olefin units; and functional groups bonded to the polymer backbone, wherein: The functional group is derived from a compound containing a triazine ring or a tetrazine ring and is complexed with a metal ion of an element from Groups 7 to 10 of the periodic table; The bond dissociation energy of the metal ion and the functional group is greater than 200 kJ / mol, The functional group does not contain a sulfur atom, and The polymer backbone further comprises aromatic vinyl units. 2 . The complex polymer according to claim 1 , wherein the metal ion and the functional group are bonded to each other through a coordinate bond. The complex polymer according to claim 1 , wherein a pyridyl group or a pyrimidyl group is bonded to the triazine ring or the tetrazine ring. The complex polymer according to claim 3 , wherein two pyridyl groups or pyrimidyl groups are bonded to the triazine ring or the tetrazine ring.

5. The complex polymer according to claim 1, wherein the functional group is derived from a compound represented by the following general formula (1): In the general formula (1), X 1 and X 2 Each independently represents a pyridyl group or a pyrimidinyl group, and Y 1 and Y 2 Each independently represents a single bond or a divalent hydrocarbon group.

6. The complex polymer according to claim 5, wherein in the general formula (1), X 1 and X 2 Each is a pyridyl group, and Y 1 and Y 2 Each is a single bond. The complex polymer according to claim 1 , wherein the metal ion is a metal ion of an element of Group 8 of the periodic table. The complex polymer according to claim 7 , wherein the metal ion is an iron ion.

9. The complex polymer of claim 1, wherein the metal ion is complexed with the polymer backbone having the functional group bonded thereto by adding a metal salt to the polymer backbone.

10. The complex polymer according to claim 9, wherein the metal salt is a metal halide. The complex polymer according to claim 10 , wherein the metal salt is a metal chloride. 12 . The complex polymer according to claim 1 , wherein the functional group is bonded to the polymer main chain in an amount ranging from 0.1 to 10 mol % relative to the monomer units of the polymer main chain. 13 . A rubber composition comprising the complex polymer according to claim 1 , wherein the content of sulfur in the rubber composition is 0.3 parts by mass or less relative to 100 parts by mass of the rubber component. 14 . A rubber composition comprising the complex polymer according to claim 1 , wherein the content of the peroxide in the rubber composition is 0.3 parts by mass or less relative to 100 parts by mass of the rubber component.

15. A method for producing a rubber composition comprising the complex polymer according to any one of claims 1 to 12, the method comprising: In a first stage of mixing, a compound comprising a polymer backbone and a compound comprising a functional group are mixed to form a functionalized polymer, wherein the functional group is bonded to the polymer backbone; and In the second stage of kneading or thereafter, a metal salt is added to the functionalized polymer, and the functionalized polymer and the metal salt are kneaded to form a complex polymer by complexing the functionalized polymer with the metal.

16. A method for producing a rubber composition comprising the complex polymer according to any one of claims 1 to 12, the method comprising: Preparing the complex polymer in advance; and The complex polymer thus prepared in advance is blended with the other components of the rubber composition, and the mixture is kneaded. 17 . A rubber product comprising the rubber composition according to claim 13 .

18. The rubber product according to claim 17, which is a tire.

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