JP7568498B2 - Modified copolymer, rubber composition, resin composition, tire and resin article - Google Patents

Description

The present invention relates to a modified copolymer, a rubber composition, a resin composition, a tire, and a resin article.

In general, durability is required for rubber products such as tires, conveyor belts, rubber crawlers, hoses, vibration-proof rubber used in vibration isolation devices, and seismic isolation rubber used in seismic isolation devices, and in order to meet such requirements, rubber materials with high durability are used.

For example, Patent Document 1 discloses a multicomponent copolymer having conjugated diene units, non-conjugated olefin units, and aromatic vinyl units as such a highly durable rubber material, and discloses that the use of the multicomponent copolymer in rubber products can improve durability such as crack growth resistance.

International Publication No. 2015/190072

In recent years, the performance requirements for the various rubber products mentioned above have become increasingly strict, and low heat generation is being sought as an additional performance requirement. However, the multicomponent copolymer described in Patent Document 1 above may not be sufficient to meet these requirements, and further improvements in terms of low heat generation are required.

Therefore, an object of the present invention is to provide a copolymer that can exhibit excellent low heat build-up properties as well as high durability.
Another object of the present invention is to provide a rubber composition, a resin composition, a tire, and a resin article each containing the copolymer.

As a result of extensive research, the inventors discovered that a copolymer modified in a specific manner, i.e., a modified copolymer, improves low heat generation, which led to the invention.

The gist of the present invention, which solves the above problems, is as follows:

The copolymer of the present invention is a modified copolymer having a conjugated diene unit, a non-conjugated olefin unit and an aromatic vinyl unit, and having no butylene unit,
The aromatic vinyl unit comprises an alkylstyrene unit,
The aromatic vinyl unit is characterized in that a modifying group having at least one of a carbonyl moiety (-C(=O)-) and a thiocarbonyl moiety (-C(=S)-) is bonded to the aromatic vinyl unit.
The modified copolymer of the present invention can exhibit excellent low heat build-up properties as well as high durability.

In the modified copolymer of the present invention, it is preferable that the aromatic vinyl unit contains a p-methylstyrene unit. In this case, the affinity of the copolymer with the filler can be further improved.

In the modified copolymer of the present invention, the proportion of the conjugated diene units is preferably 10 mol% or more and 80 mol% or less. In this case, the elongation and strength can be sufficiently improved, and the weather resistance can be improved. In addition, by combining with other units, the durability and low heat generation can be easily improved.

In the modified copolymer of the present invention, the proportion of the non-conjugated olefin units is preferably 10 mol% or more and 80 mol% or less. In this case, the weather resistance of the composition and the like is improved, the fracture properties (particularly the breaking strength (Tb)) are improved, and the fracture properties at high temperatures of the rubber composition and the like (particularly the breaking elongation (Eb)) are improved. Furthermore, by combining with other units, the durability and low heat build-up properties are likely to be improved.

In the modified copolymer of the present invention, the proportion of the aromatic vinyl units is preferably 0.1 mol% or more and 20 mol% or less. In this case, durability such as the fracture properties at high temperatures of the rubber composition is improved, and by combining with other units, durability and low heat build-up are likely to be improved.

The modified copolymer of the present invention preferably has a crystallinity of 0.5% or more and 30% or less. In this case, crack resistance and strength are further improved, workability during kneading and the like is improved, and the tackiness of the modified copolymer is also improved.

In the modified copolymer of the present invention, from the viewpoint of manufacturability and more effectively improving low heat generation properties, it is preferable that the modifying group has at least one of an ester bond (-C(=O)O-) and a dithioester bond (-C(=S)S-).

In the modified copolymer of the present invention, from the viewpoint of manufacturability and more effectively improving low heat generation properties, it is preferable that the modifying group is a group represented by -C(=O)OM or -C(=S)SM (M is an alkali metal atom).

In the modified copolymer of the present invention, the proportion of the modifying group is preferably 0.1% by mass or more and 10.0% by mass or less. In this case, the affinity is sufficiently increased, and high durability and excellent low heat generation can be more reliably exhibited, and gelation due to reaction between the modifying groups can be sufficiently suppressed.

The rubber composition of the present invention is characterized by containing a rubber component that includes the modified copolymer described above. The rubber composition of the present invention has high durability and excellent low heat generation properties.

The rubber composition of the present invention preferably further contains a filler. In this case, durability, reinforcement, etc. can be further improved.

The resin composition of the present invention is characterized by containing the modified copolymer described above. By combining the modified copolymer with other resin components, the inherent properties of the other resin components, such as durability and impact resistance, are improved.

The tire of the present invention is characterized by using the above-mentioned rubber composition. Such a tire of the present invention has high durability and low heat generation.

The resin article of the present invention is characterized by using the resin composition described above. Such a resin article of the present invention has high durability and low heat generation.

According to the present invention, it is possible to provide a copolymer that can exhibit excellent low heat build-up properties as well as high durability.
Furthermore, according to the present invention, it is possible to provide a rubber composition, a resin composition, a tire, and a resin article each containing the above copolymer.

The present invention will be described in detail below based on the embodiments.

(Modified copolymer)
A modified copolymer according to one embodiment of the present invention (hereinafter, sometimes referred to as "the modified copolymer according to the present embodiment") is a copolymer having conjugated diene units, non-conjugated olefin units and aromatic vinyl units, but no butylene units, characterized in that the aromatic vinyl units contain alkylstyrene units, and a modifying group having at least one of a carbonyl moiety (-C(=O)-) and a thiocarbonyl moiety (-C(=S)-) is bonded to the aromatic vinyl units.

The modified copolymer of this embodiment is obtained by bonding a specific modified group to the polymer chain of a copolymer having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit. Conventional copolymers having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit have been capable of exhibiting high durability, but when used in a rubber composition, in particular, there is a demand for further improving the performance in terms of low heat generation in relation to the affinity with fillers such as carbon black and silica contained in the rubber composition. In contrast, in this embodiment, it has been found that by adding a specific modified group having affinity with a filler to the polymer chain of the copolymer, the affinity of the resulting copolymer with the filler is improved, and as a result, it is possible to exhibit both high durability and excellent low heat generation. In addition, the modified copolymer of this embodiment can exhibit both high durability and excellent low heat generation even when used in a resin composition.

Moreover, in the modified copolymer of this embodiment, what is particularly noteworthy is that at least a part of the aromatic vinyl units is an alkylstyrene unit, and a specific modifying group is bonded to the aromatic vinyl units. Therefore, in this embodiment, unlike grafting (graft polymerization), it is possible to modify the polymer without consuming the double bonds in the main chain. As a result, the modified copolymer of this embodiment has the advantage that the effect of having the above-mentioned modifying group can be well expressed without reducing the effect of having a conjugated diene unit (especially a conjugated diene unit having a double bond in the main chain).

The conjugated diene unit is a unit that enables the vulcanization of the copolymer and can improve the elongation and strength of the rubber. The non-conjugated olefin unit is a unit that can improve durability such as fracture properties by dissipating energy when the non-conjugated olefin unit is significantly distorted. The aromatic vinyl unit is a unit that can improve the workability of the copolymer. The modified copolymer of this embodiment is a combination of these units, and when used in a rubber composition or a resin composition, it can exhibit particularly excellent performance in terms of durability such as fracture properties.

The conjugated diene unit is a structural unit derived from a conjugated diene compound as a monomer. Here, the conjugated diene compound means a conjugated diene compound. The conjugated diene compound preferably has 4 to 8 carbon atoms, and specific examples of such conjugated diene compounds include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc. The conjugated diene compound may be a single type or a combination of two or more types. From the viewpoint of effectively improving the durability of a composition using the resulting copolymer, the conjugated diene compound as a monomer of the modified copolymer preferably contains at least one type selected from 1,3-butadiene and isoprene, more preferably consists of at least one type selected from 1,3-butadiene and isoprene, and even more preferably consists of only 1,3-butadiene. In other words, the conjugated diene units in the modified copolymer preferably contain at least one selected from 1,3-butadiene units and isoprene units, more preferably consist of at least one selected from 1,3-butadiene units and isoprene units, and even more preferably consist of only 1,3-butadiene units. Furthermore, such conjugated diene units, when combined with other units, tend to improve durability and low heat generation.

The proportion of the conjugated diene unit in the modified copolymer is preferably 10 mol% or more and 80 mol% or less. If it is 10 mol% or more, elongation and strength can be sufficiently improved. If it is 80 mol% or less, weather resistance can be improved, and by combining with other units, durability and low heat build-up can be easily improved. From the same viewpoint, the proportion of the conjugated diene unit in the modified copolymer is more preferably 20 mol% or more, even more preferably 25 mol% or more, and more preferably 70 mol% or less, and even more preferably 65 mol% or less.
The ratio of units such as conjugated diene units in the modified copolymer is substantially the same as the ratio of units such as conjugated diene units in the corresponding copolymer before modification.

The non-conjugated olefin unit is a structural unit derived from a non-conjugated olefin compound as a monomer. Here, the non-conjugated olefin compound means an aliphatic unsaturated hydrocarbon compound having one or more carbon-carbon double bonds. The non-conjugated olefin compound preferably has 2 to 10 carbon atoms, and specific examples of such non-conjugated olefin compounds include α-olefins such as ethylene, propylene, 1-pentene, 1-hexene, 1-heptene, and 1-octene, and heteroatom-substituted alkene compounds such as vinyl pivalate, 1-phenylthioethene, and N-vinylpyrrolidone. The non-conjugated olefin compound may be one type alone or a combination of two or more types. From the viewpoint of further improving the weather resistance of the composition using the obtained copolymer, the non-conjugated olefin compound as a monomer of the modified copolymer is preferably an acyclic non-conjugated olefin compound, and the non-cyclic non-conjugated olefin compound is more preferably an α-olefin, even more preferably an α-olefin containing ethylene, and particularly preferably composed of only ethylene. In other words, the non-conjugated olefin units in the modified copolymer are preferably non-cyclic non-conjugated olefin units, and the non-cyclic non-conjugated olefin units are more preferably α-olefin units, even more preferably α-olefin units containing ethylene units, and particularly preferably composed of only ethylene units. Furthermore, such non-conjugated olefin units, when combined with other units, tend to improve durability and low heat generation.

The proportion of non-conjugated olefin units in the modified copolymer is preferably 10 mol% or more and 80 mol% or less. If it is 10 mol% or more, the proportion of conjugated diene units or aromatic vinyl units will decrease, improving the weather resistance of the composition and improving the fracture properties (particularly, the breaking strength (Tb)). If it is 80 mol% or less, the proportion of conjugated diene units or aromatic vinyl units will increase, improving the fracture properties at high temperatures of the rubber composition (particularly, the breaking elongation (Eb)). In addition, by combining with other units, it becomes easier to improve the durability and low heat generation properties. From the same viewpoint, the proportion of non-conjugated olefin units in the modified copolymer is more preferably 20 mol% or more, even more preferably 25 mol% or more, and even more preferably 70 mol% or less, and even more preferably 65 mol% or less.

The aromatic vinyl unit is a structural unit derived from an aromatic vinyl compound as a monomer. Here, the aromatic vinyl compound means an aromatic compound substituted with at least a vinyl group, and is not included in the conjugated diene compound. In addition, in the modified copolymer of this embodiment, it is necessary to have at least an alkylstyrene unit as the aromatic vinyl unit from the viewpoint of manufacturability. In other words, at least an alkylstyrene is used as the aromatic vinyl compound used as a monomer. By using an alkylstyrene as a monomer of the modified copolymer, a predetermined modifying group can be easily and in large quantities introduced during the production of the modified copolymer. Examples of the alkylstyrene include methylstyrenes such as α-methylstyrene, o-methylstyrene (2-methylstyrene), m-methylstyrene (3-methylstyrene), and p-methylstyrene (4-methylstyrene); o,p-dimethylstyrene; and ethylstyrenes such as o-ethylstyrene, m-ethylstyrene, and p-ethylstyrene. The alkylstyrene unit (and the alkylstyrene as a monomer) may be one type alone or two or more types in combination.
When a modifying group is introduced into a copolymer having an alkylstyrene unit, it is believed that the modifying group is preferentially introduced to the primary carbon atom (terminal carbon atom) of the alkyl portion of the alkylstyrene unit.

In particular, in the modified copolymer of this embodiment, it is preferable that the aromatic vinyl unit contains a p-methylstyrene unit. The methyl group portion of the p-methylstyrene unit contributes less steric hindrance to the copolymer than the main chain portion of the copolymer, so that the modified group can be introduced more easily and in large quantities, and thus the affinity of the copolymer with the filler can be further improved.

The modified copolymer of this embodiment may have an aromatic vinyl unit other than an alkylstyrene unit (e.g., a styrene unit, etc.) as an aromatic vinyl unit. However, from the viewpoint of obtaining the above-mentioned effect more fully, in the modified copolymer of this embodiment, the ratio of the alkylstyrene unit in the aromatic vinyl unit is preferably 80% or more, more preferably 90% or more, and even more preferably 100% (i.e., the aromatic vinyl unit is composed only of an alkylstyrene unit). In other words, the ratio of the alkylstyrene in the aromatic vinyl compound used as a monomer is preferably 80% or more, more preferably 90% or more, and even more preferably 100% (i.e., the aromatic vinyl compound as a monomer is composed only of an alkylstyrene).

The aromatic rings in the aromatic vinyl units are not included in the main chain of the copolymer unless they are bonded to adjacent units.

The proportion of aromatic vinyl units in the modified copolymer is preferably 0.1 mol% or more and 20 mol% or less. If it is 0.1 mol% or more, durability such as fracture properties at high temperatures of rubber compositions and the like is improved. If it is 20 mol% or less, the effects of the conjugated diene units and non-conjugated olefin units become significant, and the combination with other units makes it easier to improve durability and low heat generation. From the same perspective, the proportion of aromatic vinyl units in the modified copolymer is more preferably 0.3 mol% or more, even more preferably 0.5 mol% or more, and even more preferably 10 mol% or less, and even more preferably 5 mol% or less.

The modified copolymer does not contain butylene units in order to reliably obtain the desired effect. In other words, it is preferable that the modified copolymer does not contain, for example, a polymer obtained by hydrogenating butadiene or a hydrogenated product of a styrene-butadiene copolymer, such as styrene-ethylene/butylene-styrene (SEBS).

The modified copolymer may have other structural units in addition to the conjugated diene units, non-conjugated olefin units, and aromatic vinyl units. However, from the viewpoint of obtaining the desired effect, the ratio of other structural units to the entire copolymer is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and particularly preferably 0 mol% (i.e., the modified copolymer is composed only of conjugated diene units, non-conjugated olefin units, and aromatic vinyl units).

The modified copolymer preferably has a polystyrene-equivalent weight average molecular weight (Mw) of 10,000 or more and 10,000,000 or less. When the modified copolymer has an Mw of 10,000 or more, sufficient mechanical strength can be ensured, and when the Mw is 10,000,000 or less, high workability can be maintained. From the same viewpoint, the Mw of the modified copolymer is more preferably 100,000 or more, even more preferably 150,000 or more, and more preferably 9,000,000 or less, and even more preferably 8,000,000 or less.

The modified copolymer preferably has a polystyrene-equivalent number average molecular weight (Mn) of 10,000 or more and 10,000,000 or less. When the modified copolymer has an Mn of 10,000 or more, sufficient mechanical strength can be ensured, and when the Mn is 10,000,000 or less, high workability can be maintained. From the same viewpoint, the modified copolymer preferably has an Mn of 50,000 or more, more preferably 100,000 or more, more preferably 9,000,000 or less, and even more preferably 8,000,000 or less.

The molecular weight distribution of the modified copolymer [Mw/Mn (weight average molecular weight/number average molecular weight)] is preferably 1.00 or more and 4.00 or less. If the molecular weight distribution of the modified copolymer is 4.00 or less, sufficient homogeneity can be achieved in the physical properties of the modified copolymer. From the same viewpoint, the molecular weight distribution of the modified copolymer is more preferably 3.50 or less, and even more preferably 3.00 or less. In addition, the molecular weight distribution of the modified copolymer is more preferably 1.50 or more, and even more preferably 1.80 or more.

The weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) mentioned above are determined by gel permeation chromatography (GPC) using polystyrene as a standard substance.

The modified copolymer preferably has a melting point of 30°C or higher, and preferably 180°C or lower, as measured by a differential scanning calorimeter (DSC). If the melting point of the modified copolymer is 30°C or higher, the crystallinity of the modified copolymer is high, and crack resistance is further improved. If the melting point is 180°C or lower, there is no need to excessively increase the heating temperature during heating, and workability is further improved. From the same viewpoint, it is more preferable that the melting point of the modified copolymer is 140°C or lower. If the copolymer has two or more melting points, the highest melting point is used.

The modified copolymer preferably has a crystallinity (ΔH/ΔH ₀ ×100, also called "crystal amount") of 0.5% or more, and more preferably 30% or less. If the crystallinity of the modified copolymer is 0.5% or more, the crystallinity due to the non-conjugated olefin unit is sufficiently secured, and the crack resistance and strength are further improved. If the crystallinity of the modified copolymer is 30% or less, the workability during kneading and the like is improved, and the tackiness of the modified copolymer is improved, so that, for example, the workability when attaching rubber members made from the rubber composition to each other to form rubber articles such as tires is improved. From the same viewpoint, the crystallinity of the modified copolymer is more preferably 1% or more, more preferably 1.5% or more, more preferably 25% or less, and even more preferably 20% or less.
The degree of crystallinity can be determined as the ratio (ΔH/ΔH _{× 100} ) of the endothermic peak energy (ΔH) of the target copolymer to the crystalline melting energy (ΔH) of 100% crystalline polyethylene, measured by differential scanning calorimetry (DSC). The crystalline melting heat (crystalline melting energy) of polyethylene is ₂₉₃ J/g.

The main chain of the modified copolymer may have a cyclic structure, or the main chain may be composed of only a non-cyclic structure. When the main chain is composed of only a non-cyclic structure, the wear resistance of the rubber composition and the durability after crosslinking can be further improved. In addition, it becomes easier to introduce a predetermined modifying group into the copolymer. In addition, NMR is used as a main measurement means to confirm whether the main chain of the copolymer has a cyclic structure or not. Specifically, when a peak derived from the cyclic structure present in the main chain (for example, for three-membered to five-membered rings, a peak appearing at 10 to 24 ppm in a ¹³ C-NMR spectrum chart) is not observed, it indicates that the main chain of the copolymer is composed of only a non-cyclic structure. On the other hand, when the peak is observed, it indicates that the main chain of the copolymer has a cyclic structure.

The modified copolymer of this embodiment can be preferably produced by introducing a modifying group into a predetermined position of an (unmodified) copolymer having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit. In this case, the copolymer described in WO2017/065301A1, for example, can be preferably used as the (unmodified) copolymer having a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit.

The modified copolymer of this embodiment has a modified group having at least one of a carbonyl portion (-C(=O)-) and a thiocarbonyl portion (-C(=S)-), and the modified group is bonded to an aromatic vinyl unit in the copolymer. From the viewpoint of manufacturability and more effectively improving low heat generation, the modified group preferably has at least one of an ester bond (-C(=O)O-) and a dithioester bond (-C(=S)S-). Examples of such modified groups include groups corresponding to carboxylates, i.e., -C(=O)OR (R is any group), and groups corresponding to dithiocarboxylates, i.e., -C(=S)SR (R is any group). Furthermore, from the viewpoint of manufacturability and more effectively improving low heat generation, the modified group is more preferably a group represented by -C(=O)OM or -C(=S)SM (M is an alkali metal atom). In short, such modifying groups are groups equivalent to metal carboxylates or metal dithiocarboxylates.

In the modified copolymer of this embodiment, the modifying group may be further bonded to any position other than the alkylstyrene unit.

Methods for producing such modified copolymers are not particularly limited, and include (i) a step of adding an alkali metal compound to a copolymer (unmodified) having conjugated diene units, non-conjugated olefin units, and aromatic vinyl units containing at least alkylstyrene units, but no butylene units, and (ii) a step of reacting the product obtained in step (i) with a specific modifying agent to introduce a modifying group into the copolymer.

As described above, the copolymer before modification can be prepared, for example, according to the method described in WO2017/065301A1.

Examples of the alkali metal atom (M) of the alkali metal compound added in step (i) above include Li, Na, K, Rb, and Cs. Examples of the alkali metal compound include organic alkali metal compounds and organic alkaline earth metal compounds. As the alkali metal compound, organic alkali metal compounds are preferred.

Examples of organic alkali metal compounds include hydrocarbyl lithium and lithium amide compounds.

Preferable examples of hydrocarbyl lithium include those having a hydrocarbyl group having 2 to 20 carbon atoms, such as ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, isobutyl lithium, sec-butyl lithium, tert-butyl lithium, tert-octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butylphenyl lithium, 4-phenylbutyl lithium, cyclohexyl lithium, cyclopentyl lithium, and the reaction product of diisopropenylbenzene and butyl lithium.

Examples of lithium amide compounds include lithium hexamethylene imide, lithium pyrrolidide, lithium piperidide, lithium heptamethylene imide, lithium dodecamethylene imide, lithium dimethylamide, lithium diethylamide, lithium dibutylamide, lithium dipropylamide, lithium diheptylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium N-methylpiberazide, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, and lithium methylphenethylamide.

From the viewpoint of more efficiently introducing the modifying group into the copolymer, the alkali metal compound used in step (i) is preferably sec-butyllithium.

By adding an alkali metal compound in step (i), an alkali metal atom is introduced into the polymer main chain of the copolymer (such as in the middle of the polymer main chain) other than one end (hydrogen atoms in the hydrocarbon chain are replaced with alkali metal atoms), and the introduced alkali metal atom reacts with the modifying agent to introduce a modifying group.

The portion into which the alkali metal atom is introduced in step (i) can be, for example, the tertiary carbon atom at the bond between the alkylstyrene unit and the polymer main chain, and the primary carbon atom (terminal carbon atom) of the alkyl portion. However, in this case, the primary carbon atom has less steric hindrance than the tertiary carbon atom, so it is believed that the alkali metal atom is preferentially introduced into the primary carbon atom.

Examples of the modifying agent used in step (ii) include carbon dioxide gas and carbon disulfide. In particular, the use of carbon dioxide gas makes it easier to introduce the modifying group. When carbon dioxide gas is used as the modifying agent, the modifying group introduced into the copolymer can be -C(=O)OM (M is an alkali metal atom). When carbon disulfide is used as the modifying agent, the modifying group introduced into the copolymer can be -C(=S)SM (M is an alkali metal atom).

Another method for producing modified copolymers is to copolymerize a basic monomer such as a conjugated diene compound, a non-conjugated olefin compound, or an aromatic vinyl compound including alkylstyrene, to which a modifying group has been added in advance.

The proportion of the modified group in the modified copolymer is preferably 0.1% by mass or more and 10.0% by mass or less. If the proportion of the modified group is 0.1% by mass or more, the affinity is sufficiently increased, and high durability and excellent low heat generation can be more reliably expressed. In addition, if the proportion of the modified group is 10.0% by mass or less, gelation due to the reaction between the modified groups can be sufficiently suppressed. The above proportion is not limited to the modified group bonded to the alkylstyrene unit, but means the proportion of the modified group present in the modified copolymer. From the same viewpoint, the proportion of the modified group in the modified copolymer is more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, and more preferably 7.0% by mass or less, even more preferably 5.0% by mass or less, and even more preferably 3.0% by mass or less.
The proportion of the modifying group in the modified copolymer can be increased, for example, by increasing the amount of the modifier added, increasing the amount of the alkali metal compound added, increasing the amount of aromatic vinyl units in the copolymer, or further increasing the amount of alkylstyrene units as aromatic vinyl units.
The proportion of the modifying group in the modified copolymer can be calculated from the ¹ H-NMR spectrum.

The modified copolymer of this embodiment exhibits high durability and low heat generation, and is therefore suitable for use in rubber compositions and resin compositions, which will be described later. In particular, the rubber composition using the modified copolymer of this embodiment has high durability and low heat generation, and is therefore suitable for use in rubber products such as tires, conveyor belts, rubber crawlers, hoses, anti-vibration rubber used in anti-vibration devices, and seismic isolation rubber used in seismic isolation devices.

(Rubber composition)
A rubber composition according to one embodiment of the present invention (hereinafter, sometimes referred to as "rubber composition according to the present embodiment") contains a rubber component including the modified copolymer described above. Since the rubber composition according to the present embodiment contains the modified copolymer described above, it has high durability and excellent low heat generation properties.

The rubber composition of this embodiment may contain other rubber components in addition to the modified copolymer described above. Examples of other rubber components include natural rubber (NR) such as RSS and TSR, modified natural rubber such as high-purity natural rubber, epoxidized natural rubber, hydroxylated natural rubber, hydrogenated natural rubber, and grafted natural rubber, butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), butyl rubber, ethylene-propylene rubber (EPM), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), polysulfide rubber, silicone rubber, fluororubber, and urethane rubber. These other rubber components may be used alone or in combination of two or more.

The butadiene rubber (BR) may contain high-cis polybutadiene rubber in consideration of improving abrasion resistance. High-cis polybutadiene rubber is high-cis polybutadiene rubber in which the cis-1,4 bond content in the 1,3-butadiene units is 90% or more and 99% or less when measured by FT-IR. The cis-1,4 bond content in the 1,3-butadiene units of high-cis polybutadiene rubber is preferably 95% or more and 99% or less.

There are no particular limitations on the method for producing high-cis polybutadiene rubber, and it may be produced by a known method, such as a method of polymerizing butadiene using a neodymium-based catalyst. High-cis polybutadiene rubber is also commercially available, such as "BR01" and "T700" (both manufactured by JSR Corporation) and "Ubepol BR150L" (manufactured by Ube Industries, Ltd.).

From the viewpoint of reliably obtaining the effects of durability and low heat generation, the proportion of the modified copolymer of this embodiment in the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass, i.e., the entire amount is the modified copolymer.

The rubber composition of this embodiment preferably further contains a filler. By containing a filler, durability, reinforcement, and the like can be further improved. Examples of fillers include silica, carbon black, aluminum oxide, clay, alumina, talc, mica, kaolin, glass balloons, glass beads, calcium carbonate, magnesium carbonate, magnesium hydroxide, calcium carbonate, magnesium oxide, titanium oxide, potassium titanate, barium sulfate, and the like. The filler may be used alone or in combination of two or more types. From the viewpoint of improving dispersibility in the modified copolymer, it is preferable that the filler contains at least one type selected from silica and carbon black.

The carbon black is not particularly limited, and examples thereof include SAF, ISAF, HAF, FF, FEF, GPF, SRF, CF, FT, and MT grade carbon black. Carbon black may be used alone or in combination of two or more types. Among these, SAF, ISAF, and HAF grade carbon black are preferred.

The silica is not particularly limited, and examples thereof include wet silica, dry silica, colloidal silica, and the like. Silica may be used alone or in combination of two or more types. Among these, wet silica is preferred.

The content of the filler in the rubber composition of this embodiment is preferably 30 to 100 parts by mass per 100 parts by mass of the rubber component. By making the content 30 parts by mass or more, it is possible to further improve durability and abrasion resistance, and by making the content 100 parts by mass or less, it is possible to satisfactorily maintain low loss properties and high elastic modulus.

When silica is used as a filler, the rubber composition of this embodiment preferably contains a silane coupling agent from the viewpoint of improving the compounding effect of the silica. Examples of the silane coupling agent include vinyl triethoxysilane, vinyl tris (β-methoxyethoxy) silane, γ-methacryloxypropyl trimethoxysilane, vinyl triacetoxysilane, γ-glycidoxypropyl trimethoxysilane, γ-glycidoxypropyl triethoxysilane, β- (3,4-epoxycyclohexyl) ethyl trimethoxysilane, γ-chloropropyl methoxysilane, vinyl trichlorosilane, γ-mercaptopropyl trimethoxysilane, γ-aminopropyl triethoxysilane, N-β- (aminoethyl) -γ-aminopropyl trimethoxysilane, bis-triethoxysilylpropyl tetrasulfide, and bis-triethoxysilylpropyl disulfide. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is not particularly limited, but is preferably 1 to 12% by mass, and more preferably 3 to 10% by mass, relative to the content of silica as a filler. When the content of the silane coupling agent is 1% by mass or more relative to the content of silica in the filler, it becomes easier to obtain the effect of improving the dispersibility of the filler, and when it is 12% by mass or less, the incorporation of too much silane coupling agent is suppressed, and the effect of adding it can be obtained efficiently, which is also economically advantageous.

Furthermore, the rubber composition of this embodiment may contain components such as crosslinking agents (including vulcanizing agents such as sulfur), crosslinking accelerators (vulcanization accelerators), crosslinking acceleration assistants (vulcanization acceleration assistants), anti-aging agents, zinc oxide (ZnO), softeners, waxes, antioxidants, foaming agents, plasticizers, lubricants, tackifiers, petroleum-based resins, ultraviolet absorbers, dispersants, compatibilizers, homogenizers, etc., as necessary, within the scope of the invention, as long as the effects of the invention are not impaired.

The rubber composition of this embodiment has high durability and low heat generation, and is therefore suitable for use in rubber products such as tires, which will be described later, as well as conveyor belts, rubber crawlers, hoses, vibration-proof rubber used in vibration-proof devices, and seismic isolation rubber used in seismic isolation devices.

The method for producing the rubber composition of this embodiment is not particularly limited, and for example, the rubber composition can be produced by kneading the above-mentioned components using a kneading machine such as a Banbury mixer, roll, or internal mixer. Here, when compounding and kneading, all the components may be compounded and kneaded at once, or each component may be compounded and kneaded in multiple stages, such as two or three stages. Note that when kneading, a kneading machine such as a roll, internal mixer, or Banbury rotor can be used. Furthermore, when molding the rubber composition into a sheet or strip, a known molding machine such as an extrusion molding machine or a press machine can be used.

The rubber composition of this embodiment may also be produced by crosslinking (vulcanization). There are no particular restrictions on the crosslinking conditions, and typically a temperature of 140 to 180°C and a time of 5 to 120 minutes can be used.

(Resin composition and resin article)
A resin composition according to one embodiment of the present invention contains the modified copolymer described above. By combining the modified copolymer with other resin components, the inherent properties of the other resin components, such as durability and impact resistance, are improved. Furthermore, a resin article according to one embodiment of the present invention uses the resin composition described above. The resin article has high durability and low heat generation.

The resin component to be combined with the modified copolymer is not particularly limited, and various resin components can be used, and may be appropriately selected according to the performance desired for the resin article. Examples of such resin components include homopolymers such as polyethylene, polypropylene, polybutene, and polystyrene, copolymers such as ethylene-propylene copolymers, ethylene-methacrylic acid copolymers, ethylene-ethyl acrylate copolymers, ethylene-propylene-diene terpolymers, and ethylene-vinyl acetate copolymers, and polyolefin resins such as ionomer resins thereof, polyvinyl alcohol resins such as vinyl alcohol homopolymers and ethylene-vinyl alcohol copolymers, poly(meth)acrylic acid resins and their ester resins, polyamide resins such as aliphatic polyamide resins and aromatic polyamide resins, polyethylene glycol resins, carboxyvinyl copolymers, styrene-maleic acid copolymers, polyvinylpyrrolidone resins such as vinylpyrrolidone homopolymers and vinylpyrrolidone-vinyl acetate copolymers, polyester resins, cellulose resins, mercaptomethanol, hydrogenated styrene-butadiene, syndiotactic polybutadiene, trans-polybutadiene, and trans-polyisobutadiene. Among these, the resin component is preferably a polyolefin resin containing a non-conjugated olefin unit contained in a modified copolymer. Furthermore, the resin component is more preferably polyethylene, polypropylene, or polybutene.

In the above resin composition, the content of the modified copolymer relative to the total resin components can be adjusted appropriately depending on the other resins to be combined, the desired properties, etc., and is usually about 1 to 99% by mass, and preferably 5 to 90% by mass.

The resin composition may contain various additives depending on the desired performance. The various additives are not particularly limited, and additives that are usually contained in resin compositions may be used, such as UV absorbers, weathering agents such as light stabilizers, antioxidants, fillers exemplified as fillers that may be contained in the rubber composition, softeners, colorants, flame retardants, plasticizers, antistatic agents, etc.

(tire)
A tire according to an embodiment of the present invention uses the above-mentioned rubber composition. Since the tire uses the rubber composition according to the present embodiment, the tire has high durability and low heat generation.
The application site of the rubber composition of the present embodiment in a tire is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include tread, base tread, sidewall, belt coating rubber, ply coating rubber, side reinforcing rubber, and bead filler. From the viewpoint of effectively utilizing the excellent effect of the rubber composition of the present embodiment, which has high durability and low heat generation, the application site is preferably the tread, and particularly the tread of a studless tire. In addition, since it is also suitable for application as an adhesive with metal, application to belt coating rubber is also preferable.

Conventional methods can be used to manufacture the above tire. For example, components that are normally used in tire manufacturing, such as a carcass layer, a belt layer, and a tread layer, each composed of the unvulcanized rubber composition of this embodiment and/or cords, are laminated on a tire building drum, and the drum is removed to produce a green tire. The green tire is then heated and vulcanized in a conventional manner to manufacture the desired tire (e.g., a pneumatic tire).

(Products other than tires)
The above-mentioned rubber composition and resin composition can be applied to various rubber articles and resin articles other than tires.
For example, the above-mentioned composition can be preferably applied to automobile parts (automobile seats, automobile batteries (lithium ion batteries, etc.), weather strips, hose tubes, anti-vibration rubbers, cables, sealing materials, etc.).
In addition, the above-mentioned compositions can be used in a wide variety of applications, including conveyor belts, crawlers, anti-vibration rubber, hoses, resin piping, sound-absorbing materials, bedding, precision parts for office equipment (OA (office automation) rollers), bicycle frames, golf balls, tennis rackets, golf shafts, resin additives, filters, adhesives, pressure sensitive adhesives, inks, medical instruments (medical tubes, bags, microneedles, rubber sleeves, artificial organs, caps, packings, syringe gaskets, medicine stoppers, artificial legs, artificial limbs), cosmetics (UV (ultraviolet) powders, puffs, containers, wax, shampoos, conditioners), detergents, building materials (flooring materials, vibration-damping rubber, seismic isolation rubber, building films, sound-absorbing materials, waterproof sheets, heat insulating materials, joint materials, sealing materials), packaging materials, liquid crystal materials, organic EL (electro- The present invention can also be preferably applied to various applications, such as (luminescence) materials, organic semiconductor materials, electronic materials, electronic devices, communication equipment, aircraft parts, machine parts, electronic parts, agricultural materials, electric wires, cables, textiles (wearable bases), daily necessities (toothbrushes, shoe soles, eyeglasses, artificial bait, binoculars, toys, dust masks, garden hoses), robot parts, optical parts, road materials (asphalt, guardrails, poles, signs), protective equipment (shoes, bulletproof vests), electrical equipment exterior parts, office automation exterior parts, soles, and sealing materials.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples and may be modified as appropriate without departing from the spirit and scope of the invention.

(Preparation of Modified Copolymer A1)
Into a thoroughly dried 2000 mL pressure-resistant stainless steel reactor, 16 g of styrene as an aromatic vinyl compound and 364 g of toluene were placed.
In a glove box under a nitrogen atmosphere, 0.025 mmol of mono(bis(1,3-tert-butyldimethylsilyl)indenyl)bis(bis(dimethylsilyl)amide)gadolinium complex (1,3-[(t-Bu)Me ₂ Si] ₂ C ₉ H ₅ Gd[N(SiHMe ₂ ) ₂ ] ₂ ), 0.025 mmol of trityltetrakis(pentafluorophenyl)borate [Ph ₃ CB(C ₆ F ₅ ) ₄ ], and 0.75 mmol of triisobutylaluminum were charged into a glass vessel, and 15 mL of toluene was added to prepare a catalyst solution. The catalyst solution was added to the pressure-resistant stainless steel reactor and heated to 60°C.
Next, ethylene as a non-conjugated olefin compound was charged into the pressure-resistant stainless steel reactor at a pressure of 0.6 MPa, and copolymerization was carried out for 61 minutes at 75° C. In addition, 260 g of a toluene solution containing 80 g of 1,3-butadiene as a conjugated diene compound was continuously added at a rate of 4.0 to 7.0 mL/min.
Next, 1 mL of a 5% by mass solution of 2,2'-methylene-bis(4-ethyl-6-t-butylphenol) (NS-5) in isopropanol was added to the pressure-resistant stainless steel reactor to terminate the reaction. Then, separation was performed using a large amount of methanol and vacuum drying at 50°C to obtain copolymer A0 (before the introduction of a modifying group).
That is, in preparing the copolymer A0, no alkylstyrene was used as a monomer.

20 g of the copolymer and 380 g of cyclohexane were added to a 1 L glass bottle, and the mixture was stirred in a water bath at 80° C. for 2 hours to dissolve the copolymer in cyclohexane. Next, a hexane solution containing 3.4 mmol of sec-butyl lithium and 3.4 mmol of tetramethylethylenediamine were added to the glass bottle, and the mixture was reacted at 80° C. for 1 hour. After the reaction, the glass bottle was removed from the water bath, and carbon dioxide gas (CO ₂ ) was added to the reacted solution by bubbling for 1 minute. Then, the mixture was left at room temperature overnight to complete the modification reaction. Then, separation was performed using a large amount of methanol, and vacuum drying was performed at 50° C., and finally, a copolymer A1 having a modified group (-C(=O)OLi) (especially, mainly on the tertiary carbon atom of the bond portion with the polymer main chain of the styrene unit) was obtained.

(Preparation of Modified Copolymer B1)
Into a thoroughly dried 2000 mL pressure-resistant stainless steel reactor, 7 g of p-methylstyrene as an aromatic vinyl compound and 373 g of toluene were placed.
In a glove box under a nitrogen atmosphere, 0.025 mmol of mono(bis(1,3-tert-butyldimethylsilyl)indenyl)bis(bis(dimethylsilyl)amide)gadolinium complex (1,3-[(t-Bu)Me ₂ Si] ₂ C ₉ H ₅ Gd[N(SiHMe ₂ ) ₂ ] ₂ ), 0.025 mmol of trityltetrakis(pentafluorophenyl)borate [Ph ₃ CB(C ₆ F ₅ ) ₄ ], and 0.75 mmol of triisobutylaluminum were charged into a glass vessel, and 15 mL of toluene was added to prepare a catalyst solution. The catalyst solution was added to the pressure-resistant stainless steel reactor and heated to 60°C.
Next, ethylene as a non-conjugated olefin compound was charged into the pressure-resistant stainless steel reactor at a pressure of 0.6 MPa, and copolymerization was carried out for 117 minutes at 75° C. In addition, 260 g of a toluene solution containing 80 g of 1,3-butadiene as a conjugated diene compound was continuously added at a rate of 2.0 to 4.0 mL/min.
Next, 1 mL of a 5% by mass solution of 2,2'-methylene-bis(4-ethyl-6-t-butylphenol) (NS-5) in isopropanol was added to the pressure-resistant stainless steel reactor to terminate the reaction. Then, separation was performed using a large amount of methanol and vacuum drying at 50°C to obtain copolymer B0 (before the introduction of a modifying group).

20 g of the copolymer and 380 g of cyclohexane were added to a 1 L glass bottle, and the mixture was stirred in a water bath at 80° C. for 2 hours to dissolve the copolymer in cyclohexane. Next, a hexane solution containing 3.4 mmol of sec-butyl lithium and 3.4 mmol of tetramethylethylenediamine were added to the glass bottle, and the mixture was reacted at 80° C. for 1 hour. After the reaction, the glass bottle was removed from the water bath, and carbon dioxide gas (CO ₂ ) was added to the reacted solution by bubbling for 1 minute. Then, the mixture was left to stand overnight at room temperature to complete the modification reaction. Then, separation was performed using a large amount of methanol, and vacuum drying was performed at 50° C., and finally, a copolymer B1 having a modified group (-C(=O)OLi) (especially, mainly in the methyl portion at the 4th position of the p-methylstyrene unit) was obtained.

The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw/Mn) of the copolymer in terms of polystyrene were determined by gel permeation chromatography [GPC: HLC-8220GPC/HT manufactured by Tosoh Corporation, column: GMH _HR -H(S)HT x 2 manufactured by Tosoh Corporation, detector: differential refractometer (RI)] using monodisperse polystyrene as a standard. The measurement temperature was 140°C. The results are shown in Table 1.

Further, using a differential scanning calorimeter (DSC, manufactured by TA Instruments Japan, "DSCQ2000"), the copolymer was heated from -150°C to 150°C at a rate of 10°C/min, and the endothermic peak energy (ΔH ₁ ) from 0°C to 100°C and the endothermic peak energy (ΔH ₂ ) from 100°C to 150°C were measured. Then, using the value of the crystalline melting energy (ΔH ₀ ) of the 100% crystalline polyethylene, the crystallinity of the copolymer from 0°C to 100°C and the crystallinity from 100°C to 150°C were calculated from the ratio of the endothermic peak energy of the copolymer to the crystalline melting energy (ΔH ₀ ) of the polyethylene ((ΔH ₁ /ΔH ₀ )×100, (ΔH ₂ /ΔH ₀ )×100). The results are shown in Table 1. The above crystallinity is the crystallinity in the range of 0 to 150°C. For example, when the crystallinity is described separately as 0 to 100°C and 100 to 150°C, the sum of these is the crystallinity in the range of 0 to 150°C.

The proportions (mol %) of conjugated diene units (1,3-butadiene units), non-conjugated olefins (ethylene units), and aromatic vinyl units (styrene units, p-methylstyrene units) in the copolymer were determined from the integral ratios of each peak in the ¹ H-NMR spectrum (100° C., d-tetrachloroethane standard: 6 ppm). The results are shown in Table 1.

The proportion of modified groups in the copolymer was calculated from the ¹ H-NMR spectrum. The results are shown in Table 1.

Further, the ¹³ C-NMR spectrum of the copolymer was measured. In the obtained ¹³ C-NMR spectrum chart, no peak was observed at 10 to 24 ppm. From this, it was confirmed that the main chain of all the synthesized copolymers was composed only of acyclic structures.

According to the present invention, it is possible to provide a copolymer that can exhibit excellent low heat build-up properties as well as high durability.
Furthermore, according to the present invention, it is possible to provide a rubber composition, a resin composition, a tire, and a resin article each containing the above copolymer.

Claims (10)

A modified copolymer having a conjugated diene unit, a non-conjugated olefin unit and an aromatic vinyl unit, and having no butylene unit,
The aromatic vinyl unit comprises an alkylstyrene unit,
a modifying group having at least one of a carbonyl moiety (-C(=O)-) and a thiocarbonyl moiety (-C(=S)-) is bonded to the alkylstyrene unit ;
The proportion of the non-conjugated olefin units is 25 mol % or more and 80 mol % or less,
The ratio of the conjugated diene units is 10 mol % or more and 65 mol % or less,
The ratio of the aromatic vinyl unit is 0.1 mol % or more and 10 mol % or less,
The crystallinity is 0.5% or more and 30% or less.
A modified copolymer, characterized in that: The modified copolymer according to claim 1, wherein the aromatic vinyl units include p-methylstyrene units. The modified copolymer according to claim 1 or 2, wherein the modified group has at least one of an ester bond (-C(=O)O-) and a dithioester bond (-C(=S)S-). The modified copolymer according to any one of claims 1 to 3, wherein the modifying group is a group represented by -C(=O)OM or -C(=S)SM (M is an alkali metal atom). The modified copolymer according to any one of claims 1 to 4, wherein the proportion of the modifying group is 0.1% by mass or more and 10.0% by mass or less. A rubber composition comprising a rubber component containing the modified copolymer according to any one of claims 1 to 5. The rubber composition according to claim 6, further comprising a filler. A resin composition comprising the modified copolymer according to any one of claims 1 to 5. A tire characterized by using the rubber composition according to claim 6 or 7. A resin article made using the resin composition according to claim 8.