TW202118801A - Copolymer, rubber composition and tire - Google Patents

Abstract

An objective of the present invention is to provide a copolymer having an excellent effect of reducing rolling resistance of tires, a rubber composition containing the copolymer, and a tire.

As a solution, the copolymer of the present invention has in its molecule a polymer A containing at least butadiene as a constituent unit and a polymer B of a monomer b containing N-vinyl-2-pyrrolidone. The polymer A preferably contains polybutadiene or modified polybutadiene. Since the copolymer of the present invention has an excellent effect of reducing rolling resistance of tires, for example, it can be suitably used as an additive for rubber.

Description

Copolymer and rubber composition and tire

The present invention relates to copolymers and rubber compositions and tires.

At this stage when the issue of global warming has been raised, the industry is actively investing in countermeasures to suppress the emission of carbon dioxide into the atmosphere. For example, in the automobile industry, improving the fuel consumption of automobiles can effectively reduce carbon dioxide emissions, so relevant technology development is actively carried out all over the world. Especially in automobiles, the rolling resistance of tires has a great impact on fuel consumption. For example, a person who improves the rolling resistance by 20% is considered to improve fuel consumption by about 5%. Therefore, those who improve the performance of automobile tires are extremely important from the viewpoint of improving the fuel consumption of automobiles.

From this point of view, in recent years, the demand for fuel-efficient tires that further reduce the rolling resistance of tires, so-called energy-saving tires, has increased. Generally speaking, energy-saving tires use both carbon black and silicon dioxide as reinforcing materials to reduce rolling resistance. Recently, it has also been proposed that instead of using carbon materials, energy-saving tires should be replaced with 100% silicon dioxide.

In such tires containing silicon dioxide, it is important to more uniformly disperse reinforcing materials such as silicon dioxide in the tire. In response to this, silane coupling agents are generally used to improve the dispersibility of silica in tires, but the dispersibility is still insufficient in most cases. Therefore, for example, by using an active agent in combination, silicon dioxide and carbon are uniformly dispersed. In addition, various additions to improve the dispersion of silica are also discussed Agent. For example, in Patent Document 1, an amine-based compound having a specific structure is added to a rubber composition to improve the dispersibility of silicon dioxide in the tire and reduce the rolling resistance of the tire.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] JP 2013-87185 A

However, from the viewpoint of further improvement in fuel consumption in recent years, it is expected to further reduce the rolling resistance of tires, and it is difficult for the aforementioned conventional rubber compositions and the like to respond to such high demands.

For example, in terms of improving the dispersibility of silicon dioxide and carbon, and the rolling resistance of tires, it is also considered to use polyvinyl pyrrolidone (PVP; polyvinyl pyrrolidone), which has excellent dispersibility of silicon dioxide. However, due to the poor compatibility of PVP and rubber, the sufficient dispersing power of PVP in rubber cannot be exerted, and on the contrary, the rolling resistance of the tire is deteriorated.

The present invention was made in view of the above circumstances, and its object is to provide a copolymer having an excellent effect of reducing the rolling resistance of a tire, a rubber composition containing the copolymer, and a tire.

The inventors of the present invention conducted intensive studies in order to achieve the above-mentioned object, and found that by using a copolymer of a polymer containing butadiene as a constituent unit and poly(N-vinyl-2-pyrrolidone) , The above-mentioned object can be achieved, and the present invention can be completed.

That is, the present invention includes, for example, the subjects described in the following items.

Item 1

A copolymer having in its molecule: polymer A containing at least butadiene as a constituent unit, and polymer B containing monomer b of N-vinyl-2-pyrrolidone.

Item 2

The copolymer according to item 1, wherein the aforementioned polymer A comprises polybutadiene or modified polybutadiene.

Item 3

The copolymer as described in item 1 or 2, which is a graft polymer in which the aforementioned polymer A is used as the backbone polymer and the aforementioned polymer B is used as the branch polymer.

Item 4

The copolymer according to any one of items 1 to 3, which is used as an additive for rubber.

Item 5

A rubber composition containing at least the copolymer described in item 4 and a diene rubber.

Item 6

A tire comprising the rubber composition described in item 5.

According to the copolymer of the present invention, since it has an excellent effect of reducing the rolling resistance of a tire, it can be suitably used as, for example, an additive for rubber.

The following describes the implementation of the present invention in detail. In this manual, the expressions of "contains" and "contains" include the concepts of "contains", "contains", "substantially constituted by", and "constituted only by".

1. Copolymer

The copolymer of the present invention has, in its molecule, polymer A containing at least butadiene as a constituent unit, and polymer B containing monomer b of N-vinyl-2-pyrrolidone. In more detail, the copolymer of the present invention is a copolymer having polymer A as a unit portion and polymer B as a unit portion. Hereinafter, in this specification, the copolymer of the present invention is described as "copolymer C". For example, in the case of being applied to tires as an additive for rubber, copolymer C can reduce the rolling resistance of the tire.

(Polymer A)

Copolymer C has polymer A in the molecule. The polymer A is a polymer containing butadiene as a constituent unit.

The polymer A is not particularly limited as long as it contains butadiene as a structural unit. For example, the polymer A can be a homopolymer of butadiene (that is, polybutadiene) or a modified polybutadiene. The so-called modified polybutadiene refers to a polymer in which a part of butadiene units in the butadiene unit is modified (modified) with functional groups, or a structural unit in which a part of butadiene units is contained with functional groups (butadiene) Polymers substituted with structural units other than diene structural units). Therefore, copolymers of butadiene and monomers other than butadiene are also included in the modified polybutadiene. In addition, a structural unit in which a butadiene unit is modified with a functional group or the like or a structural unit containing a functional group (a structural unit other than the butadiene structural unit) may be referred to as a "modified butadiene unit".

In the case where the polymer A is modified polybutadiene, the type thereof is not particularly limited. For example, conventional modified polybutadiene can be widely used.

Specific examples of modified polybutadiene include: carboxyl modified polybutadiene, epoxy modified polybutadiene, hydroxyl modified polybutadiene, acrylic modified polybutadiene, and amino modified polybutadiene. High-quality polybutadiene, isocyanate-based modified polybutadiene, etc. Examples of the carboxyl modified polybutadiene include maleic acid modified polybutadiene. Examples of the hydroxyl-modified polybutadiene include polybutadiene diol, polybutadiene having a hydroxyl group at the terminal, and the like. Acrylic-modified polybutadiene includes polybutadienediol acrylate and the like. Examples of the isocyanate group-modified polybutadiene include polybutadiene having an isocyanate group at the terminal, and the like.

In addition, the polymer A can also exemplify a copolymer having a butadiene skeleton, such as a styrene-butadiene random copolymer.

Polymer A preferably contains polybutadiene or modified polybutadiene, and particularly preferably contains modified polybutadiene. In the case where polymer A contains modified polybutadiene, for example, when copolymer C is used as an additive for rubber, since it has excellent affinity with rubber components, silicon dioxide and the like are present in the rubber The time is easy to be dispersed, and it is easy to improve the effect of reducing the rolling resistance of the tire. In addition, when the polymer A contains modified polybutadiene, the polymer B described later can be easily introduced into the copolymer C, and the copolymer C can be easily produced.

Among them, the modified polybutadiene is preferably a carboxyl modified polybutadiene, and particularly preferably a maleic acid modified polybutadiene. Among them, maleic acid-modified polybutadiene is, for example, a polymer composed of butadiene units and maleic acid units.

In the modified polybutadiene, the introduction ratio of the modified butadiene unit is not particularly limited. For example, from the viewpoint of not being easily damaged and compatibility with rubber, the introduction ratio of the modified butadiene unit is preferably 0.1 to 80% by weight, more preferably 0.1 to 80% by weight, relative to all the structural units of the modified polybutadiene 0.5 to 70 weight%. Especially when the modified polybutadiene is a maleic acid-modified polybutadiene, the introduction of maleic acid units is relative to all the constituent units of the maleic acid-modified polybutadiene The ratio is preferably 1 to 50% by weight, more preferably 2 to 40% by weight, particularly preferably 3 to 30% by weight. Although modified polybutadiene has no restrictions on random polymers, block polymers, etc., it is usually a random polymer.

From the viewpoint of easy reduction in rolling resistance, the number average molecular weight of polymer A is preferably 500 to 100,000, more preferably 1,000 to 50,000, still more preferably 1,500 to 10,000, and particularly preferably 2,000 to 8,000. In this specification, the number average molecular weight of polymer A means the value measured by gel permeation chromatography (GPC). However, when the polymer A is a commercially available product, etc., the catalog value or product guarantee value can also be used as the number average molecular weight of the polymer A.

To the extent that the effects of the present invention are not impaired, polymer A may have other constituent units in addition to butadiene units and modified butadiene units, and polymer A may also consist of butadiene units and modified butadiene units only. The quality of butadiene unit is formed. In the case where the polymer A has other structural units, relative to all the structural units of the polymer A, the content ratio of the other structural units can be set to 5 mol% or less, preferably 1 mol% or less, more preferably 0.1 Mole% or less, particularly preferably 0.05 Mole% or less.

(Polymer B)

Copolymer C has polymer B in the molecule. The polymer B is a polymer containing monomer b of N-vinyl-2-pyrrolidone. Hereinafter, N-vinyl-2-pyrrolidone is abbreviated as "NVP".

Monomer b may only be NVP, or may include NVP and other polymerizable monomers. In the case where the monomer b contains other polymerizable monomers, relative to the total mass of the monomer b, the content ratio of the other polymerizable monomers can be set to 5% by mass or less, preferably 1% by mass or less, more preferably 0.1% by mass or less, particularly preferably 0.05% by mass or less.

In the case where monomer b is only NVP, polymer B is a homopolymer of polyvinylpyrrolidone. On the other hand, when the monomer b contains polymerizable monomers other than NVP, polymer B is a copolymer of NVP and other polymerizable monomers, and in this case, it is usually a random copolymer.

From the viewpoint of easy reduction of rolling resistance, the number average molecular weight of polymer B is preferably 10 to 1.5 million, more preferably 30 to 800,000, still more preferably 50 to 500,000, particularly preferably 10,000 to 100,000 . In addition, in the copolymer C, the range of the preferred number average molecular weight of the aforementioned polymer A and the preferred range of the number average molecular weight of the polymer B can be arbitrarily combined.

(Copolymer C)

Copolymer C has polymer A and polymer B in the molecule. Specifically, the copolymer C forms a molecule by bonding the polymer A and the polymer B through chemical bonds (especially covalent bonds). Therefore, copolymer C is a high molecular compound having a block of polymer A and a block of polymer B. In this case, the block of polymer A and the block of polymer B can be directly chemically bonded, or there are other functional groups intervening between polymer A and polymer B.

Further specific examples of the copolymer C include a graft polymer in which the polymer A is the main stem polymer and the polymer B is the branch polymer. In the case where copolymer C forms such a graft polymer, the affinity of copolymer C with rubber components is particularly excellent, and it is easier to disperse silicon dioxide when silicon dioxide or the like is present in the rubber. As a result, the effect of reducing the rolling resistance of the tire is particularly improved. In addition, in the case where the copolymer C is the aforementioned graft polymer, it is also easy to produce the copolymer C. Among them, when the polymer A is modified polybutadiene, it is easy to manufacture copolymer C, which is a graft polymer.

In the case where the copolymer C is a graft polymer, the polymer B belonging to the branch polymer can be grafted from any part of the polymer A, and its position is not limited. Especially when polymer A is modified polymer In the case of butadiene, the polymer B is easily grafted from the main chain portion of the modified butadiene unit. Specifically, in the case where the modified polybutadiene belonging to the polymer A has maleic anhydride units, the copolymer C may have: the hydrogen of the carbon atom bonded to the carboxyl group of the maleic anhydride Structure replaced by polymer B.

In addition, whether or not the copolymer C is a graft polymer can ^{be judged from, for example, 13} C-NMR measurement.

In the copolymer C, the content ratio of the polymer A and the polymer B is not particularly limited. For example, in the copolymer C, the content ratio of the polymer B can be set to 3 to 95% by mass relative to the total mass of the polymer A and the polymer B. In this case, the copolymer C has a high affinity with rubber components. In addition, when silica or the like is present in the rubber, the silica is easier to disperse, which can fully exert the effect of reducing the rolling resistance of the tire. In copolymer C, relative to the total mass of polymer A and polymer B, the content ratio of polymer B is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably 30% by mass or more , Particularly preferably more than 40% by mass. In addition, in copolymer C, relative to the total mass of polymer A and polymer B, the content ratio of polymer B is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass. % Or less, particularly preferably 60% by mass or less.

When the copolymer C is used as an additive for rubber in tires, it can reduce the rolling resistance of the tire and improve the fuel efficiency of automobiles. In particular, the copolymer C has a polymer A with polybutadiene as the main component and a polymer B with polyvinylpyrrolidone as the main component in the molecule, so it has high compatibility with the rubber component and makes the dioxide The dispersing performance of silicon and carbon is also high. Therefore, by using the copolymer C as an additive for tires, the copolymer C can be uniformly present in the rubber, and the reinforcing materials such as silicon dioxide or carbon sometimes contained in the tire can be dispersed well. It can further reduce the rolling resistance of tires than before.

2. Manufacturing method of copolymer

The method of manufacturing copolymer C is not particularly limited, and various manufacturing methods can be adopted. For example, the copolymer C can be obtained by a manufacturing method having the following steps, which is to make the aforementioned polymer A and N-vinyl-2-pyrrolidone (NVP) in the presence of a polymerization initiator The monomer b reacts. Hereinafter, this process is abbreviated as "process 1".

The polymer A used in step 1 is the same as the aforementioned polymer A. Therefore, the polymer A used in step 1 preferably contains modified polybutadiene, and preferably contains maleic acid modified polybutadiene. Polymer A can be used individually by 1 type or in combination of 2 or more types.

The polymer A used in step 1 can be obtained by a conventional method. Alternatively, the polymer A used in step 1 can also be obtained from a commercially available product or the like.

The monomer b used in step 1 is the same as the aforementioned monomer b. Therefore, the monomer b may only be NVP, or may include NVP and other polymerizable monomers. The manufacturing method of the NVP contained in the monomer b is also not particularly limited. For example, it can be obtained by a conventional method, or it can also be obtained from a commercially available product.

In step 1, the use ratio of polymer A and NVP is not particularly limited, and can be appropriately determined according to the chain length of polymer A and polymer B, etc. For example, relative to the total mass of polymer A and NVP, the use ratio of NVP can be set to 3 to 95% by mass. In this case, the obtained copolymer C has a high affinity with rubber components. In addition, when silicon dioxide or the like is present in the rubber, the silicon dioxide is easily dispersed, which can fully exert the effect of reducing the rolling resistance of the tire. . Relative to the total mass of polymer A and NVP, the use ratio of NVP is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and particularly preferably 40% by mass or more. In addition, relative to the total mass of polymer A and NVP, the use ratio of NVP is preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass or less, and particularly preferably 60% by mass or less.

In step 1, the type of polymerization initiator is not particularly limited, and, for example, conventional polymerization initiators can be widely used. Specific examples of the polymerization initiator include persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate; organic peroxides such as benzyl peroxide, dicumyl peroxide, and lauryl peroxide. Oxide; 2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-amidinopropane) dihydrochloride, etc. Azo compounds; 2,2'-azobis(2,4-dimethylbutyronitrile), 2,2'-azobis(2-isopropylbutyronitrile), 2,2'-azo Water-insoluble azo compounds such as bis(2,4-dimethylvaleronitrile) and the like. Other examples include redox initiators using hydrogen peroxide and the like. Among them, from the viewpoint that the polymer A has excellent hydrogen abstraction ability and facilitates the polymerization reaction of the monomer b, persulfate, organic peroxide, etc. are preferred, and persulfate is particularly preferred.

The amount of the polymerization initiator is not particularly limited, and can be appropriately set according to the properties such as the half-life temperature of the polymerization initiator used. For example, per 100 parts by mass of the total mass of polymer A and monomer b, the amount of the polymerization initiator can be set to 0.01 to 15 parts by mass.

The reaction of Step 1 can be carried out in a reaction solvent as needed. The reaction solvent can be water or various organic solvents. Examples include: aliphatic hydrocarbons such as hexane and heptane; alicyclic hydrocarbons such as cyclohexane; ketone solvents such as acetone and methyl ethyl ketone; Aromatic hydrocarbons such as toluene; chlorinated hydrocarbons such as chloroform and 1,2-dichloroethane; alcohols such as methanol, ethanol, isopropanol and tertiary butanol; nitrile compounds such as acetonitrile, etc. The organic solvent can be used alone or in a mixture of two or more kinds.

In the reaction of step 1, the amount of the reaction solvent is not particularly limited. For example, per 100 parts by mass of the total mass of polymer A and monomer b, the amount of the reaction solvent can be set to 50 to 800 parts by mass.

The reaction temperature in step 1 is not particularly limited, and can be appropriately set in accordance with the properties such as the half-life temperature of the polymerization initiator used. For example, the reaction temperature in step 1 can be set to 40 to 230°C.

The method for reacting the polymer A with the monomer b containing N-vinyl-2-pyrrolidone (NVP) is not particularly limited, and conventional methods can be widely used. For example, a method of dropping a solution in which the polymerization initiator and the monomer b are dissolved into the solution of the polymer A can be used. In this case, the type of solvent used to prepare the two solutions is not limited, and can be appropriately selected in consideration of solubility and the like. For example, it can be suitably selected from the aforementioned reaction solvents. The solvents of the two solutions can be the same or different.

The reaction in step 1 can be carried out under atmospheric pressure, under reduced pressure, and under increased pressure, and can also be carried out in an inert gas environment such as nitrogen as necessary. The reaction vessel, reaction device, etc. used in the reaction are also not limited.

Through the reaction in step 1, for example, the polymerization of NVP is carried out with polymer A as the starting point, and a block polymer of polymer A and polyvinylpyrrolidone (polymer B) can be produced. Especially when the polymer A is modified polybutadiene such as maleic acid modified polybutadiene, as mentioned above, polyvinylpyrrolidone (polymer B) is easy to change from the modified butadiene unit The main chain part of the growth, as a result, it is easy to form a graft polymer with polymer A as the backbone polymer and polymer B as the branch polymer. Therefore, in the case of using modified polybutadiene as the polymer A, the copolymer C having a graft structure can be easily obtained in step 1.

After the completion of the reaction in Step 1, by performing purification treatment or the like by appropriate means, the intended copolymer C can be obtained.

In addition, in step 1, not all of the polyvinylpyrrolidone (PVP) produced by the polymerization is bound (for example, grafted) to the polymer A, and a part of it may exist alone. The PVP produced in this way can be removed by an appropriate method, or copolymer C can be obtained in a state of being mixed into the target copolymer C.

3. Rubber composition

The rubber composition of the present invention contains at least the aforementioned copolymer C and diene rubber. Since the rubber composition of the present invention contains the copolymer C, it can reduce the rolling resistance of the tire when it is formed into a tire.

The type of diene rubber is not particularly limited. For example, a wide range of conventional diene rubbers used for forming tires can be cited. For example, the diene rubber includes natural rubber and diene synthetic rubber. Diene-based synthetic rubbers include: polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), butyl rubber (IIR), ethylene -Propylene copolymer etc. The diene rubber contained in the rubber composition may be a single type or any of two or more types.

The rubber composition may further include silicon dioxide as a reinforcing material. The type of silicon dioxide is not particularly limited. For example, silicon dioxide used in conventional rubber compositions can be widely used. For example, wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), colloidal silica, etc. can be cited, and wet silica is preferred.

The content of the copolymer C contained in the rubber composition is not particularly limited. For example, from the viewpoint of easily exhibiting the effect of reducing the rolling resistance by the copolymer C, the content of the copolymer C can be 0.1 to 30 parts by mass per 100 parts by mass of the diene rubber. It is preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass, still more preferably 2 to 8 parts by mass, and particularly preferably 3 to 6 parts by mass.

In addition, when the rubber composition contains silicon dioxide, the content of copolymer C contained in the rubber composition is preferably 0.1 to 25 parts by mass, more preferably 0.5 parts by mass based on 100 parts by mass of silicon dioxide. To 20 parts by mass, more preferably 1 to 15 parts by mass, particularly preferably 3 to 10 parts by mass.

Here, in addition to the copolymer C, the rubber composition may also include: polyvinylpyrrolidone (PVP) that is by-produced during the manufacture of the copolymer C as described above, that is, it is not bonded to the polymer A And the PVP that exists alone.

In addition, in the case where the rubber composition contains silicon dioxide, the content of silicon dioxide is not particularly limited. For example, from the viewpoint of improving low loss properties, relative to 100 parts by mass of diene rubber, the content of silicon dioxide is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more , Particularly preferably at least 40 parts by mass. In addition, from the viewpoint of improving processability, the content of silicon dioxide is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 120 parts by mass or less relative to 100 parts by mass of the diene rubber , Particularly preferably 100 parts by mass or less.

In addition to copolymer C, diene rubber, and optionally added silica, the rubber composition may also contain various additives. Examples of additives include reinforcing materials other than silica, silane coupling agents, lubricating oils, anti-aging agents, light stabilizers, antioxidants, preservatives, flame retardants, pigments, colorants, and anti-mold agents. Examples of the reinforcing material include carbon black, talc, calcium carbonate, aluminum hydroxide, and magnesium carbonate. The content of these additives is not particularly limited, and for example, various additives may be included in the same content as that of conventional rubber compositions. For example, the compounding amount of the silane coupling agent may be 1 to 20 parts by mass, preferably 6 to 12 parts by mass relative to 100 parts by mass of silica.

Using the rubber composition of the present invention, a rubber molded body such as a tire can be produced. More specifically, a rubber molded body can be produced by a method including a first kneading step for preparing the rubber composition and a second kneading step for mixing the rubber composition and a vulcanizing agent.

In the first kneading step, the copolymer C, the diene rubber, the silica and the aforementioned additives are kneaded in a predetermined mixing amount to prepare a rubber composition. Mixer No. 1 The kneading method in the sequence is not particularly limited. For example, the kneading can be performed by a conventional mixing method. The mixer used in the first kneading step is also not limited, and conventional mixers can be widely used.

In the second kneading step, a vulcanizing agent or the like is added to the rubber composition prepared in the first kneading step. The type of vulcanizing agent is not particularly limited, and for example, conventional vulcanizing agents can be widely used.

Examples of the vulcanizing agent include sulfur-based vulcanizing agents. Examples of sulfur-based vulcanizing agents include sulfur such as powdered sulfur and colloidal sulfur; sulfur-containing compounds such as sulfur chloride and sulfur dichloride.

In the second kneading step, in addition to the vulcanizing agent, a vulcanization accelerator may be formulated. As the vulcanization accelerator, for example, conventional vulcanization accelerators used for the vulcanization of rubber can be widely used.

In the second kneading step, the blending amounts of the vulcanizing agent and the vulcanization accelerator are also not particularly limited. For example, per 100 parts by mass of the diene rubber in the rubber composition, the total amount of the vulcanizing agent and the vulcanization accelerator may be 3 to 20 parts by mass, preferably 5 to 15 parts by mass.

After the second kneading step, a vulcanization treatment is performed to obtain a rubber molded body. The method of the vulcanization treatment is not particularly limited, and for example, it can be made the same as the conventional vulcanization method.

The shape of the rubber molded body is also not particularly limited. In addition to tires, it can also be molded into a desired shape in response to various rubber products. In particular, the rubber molded body is preferably a tire. Since the tire is formed by using the rubber composition of the present invention, it has low rolling resistance and can contribute to the improvement of automobile fuel consumption.

[Example]

The following examples illustrate the present invention in more detail, but the present invention is not limited to the aspects of these examples.

(Example 1)

Dissolve 80 g of maleic acid-modified polybutadiene (“Ricon156MA17” manufactured by CRAY VALLY, with a number-average molecular weight of 2500) in 800 g of acetonitrile, deoxygenate by purging with nitrogen and mix simultaneously Together, a solution of polymer A is obtained. While maintaining this solution at 80°C, monomer b in which 80 g of NVP and 6.4 g of ammonium persulfate were dissolved in 64 g of isopropanol was dropped into this solution for 1.5 hours to perform polymerization reaction (Step 1). In this step 1, the blending mass ratio of maleic acid-modified polybutadiene and NVP is set to 50:50 (the Mn of the produced PVP is 51000). After the reaction, the solvent was removed by vacuum drying to obtain copolymer C.

(Example 2)

Except that the blending mass ratio of maleic acid-modified polybutadiene and NVP was changed to 70:30, the copolymer C was obtained by the same method as in Example 1.

(Example 3)

Except that the blending mass ratio of maleic acid-modified polybutadiene and NVP was changed to 30:70, the copolymer C was obtained by the same method as in Example 1.

(Example 4)

Except that the maleic acid-modified polybutadiene was changed to a number average molecular weight of 9,100, the copolymer C was obtained by the same method as in Example 1.

(Example 5)

The copolymer C was obtained by the same method as in Example 1, except that the maleic acid-modified polybutadiene was changed to a number average molecular weight of 5000.

(Example 6)

Except that the amount of ammonium persulfate was adjusted so that the number average molecular weight Mn of PVP was 650,000, the copolymer C was obtained by the same method as in Example 1.

(Example 7)

Except that the amount of ammonium persulfate was adjusted so that the number average molecular weight Mn of PVP was 5000, the copolymer C was obtained by the same method as in Example 1.

(Analysis of copolymer C)

When the structure of the graft copolymer obtained in each example was confirmed by ¹³ C-NMR measurement, it was observed around 41 ppm from "Due to PVP grafted to maleic acid modified polybutadiene The chain is derived from the "fourth grade carbon" peak produced by the tertiary carbon of maleic acid. From this result, it was confirmed that vinylpyrrolidone was graft-polymerized to maleic acid-modified polybutadiene. That is, the copolymer C-based backbone polymer obtained in Examples 1 to 7 is modified polybutadiene (polymer A), and the branched polymer is PVP (polymer B; polyvinylpyrrolidone ) Of grafts.

In addition, in the copolymer obtained in Example 1, the number average molecular weight of the PVP site was 51,000, and in the copolymer obtained in Example 2, the number average molecular weight of the PVP site was 50,000. In Example 3 In the copolymer obtained in, the number average molecular weight of the PVP site is 52,000. In addition, the number average molecular weight of the PVP site was determined by gel permeation chromatography (GPC) according to the following steps.

<Measurement of the number average degree of polymerization of the PVP site (polymer B)>

The copolymer C obtained in the example was added to diethyl ether, and the insoluble matter was removed by filtration or the like, and then the diethyl ether was distilled off to obtain a solid content. The solid content obtained was determined by gel permeation chromatography (GPC). The measurement conditions of GPC are as follows.

‧GPC device: HLC-8020 RI detection (manufactured by TOSOH)

‧Column: TSK guard column PWXL, TSKgel G2500 PWXL, TSKgel G3000PWXL, TSKgel G4000 PWXL, TSKgel G6000 PWXL (manufactured by TOSOH)

‧Eluent: 0.08M sodium acetate aqueous solution/acetonitrile (50/50vol%)

‧Flow rate: 0.7mL/min

‧Temperature: 40℃

Next, the obtained copolymer C was used as an additive for rubber, and a rubber composition was prepared by the method described in the following preparation examples and comparative examples, and the rubber composition was vulcanized to produce a rubber molded body.

(Modulation example 1)

4 parts by mass of the copolymer C obtained in Example 1, 70 parts by mass of styrene-butadiene copolymer rubber (SBR), 30 parts by mass of polybutadiene rubber (BR), 60 parts by mass Parts of silicon dioxide, 4.9 parts by mass of silane coupling agent, 15 parts by mass of oil, 2 parts by mass of stearic acid, and 1 part by mass of anti-aging agent are mixed to obtain a rubber composition (first mixing process) . 4 parts by mass of zinc oxide, 2 parts by mass of vulcanization accelerator DPG, 1.8 parts by mass of vulcanization accelerator CBS, and 1.5 parts by mass of sulfur were blended in the resulting rubber composition and mixed to obtain molding raw materials (No. 2. Mixing process). The obtained raw material for molding was vulcanized to obtain a 16 cm square (thickness about 2 mm) rubber molded body. The raw materials used in each preparation example are as follows.

SBR: SL552 made by JSR

BR: BR54 manufactured by JSR Corporation

Silicon dioxide: Nipsil AQ manufactured by TOSOH Co., Ltd.

Silane coupling agent: Cabrus-2 manufactured by Osaka Soda Co., Ltd.

Oil: Sunthene 415 manufactured by Japan Sun Oil Co., Ltd.

Stearic acid: manufactured by FUJIFILM Wako Pure Chemical Co., Ltd.

Anti-aging agent: N-phenyl-1-naphthylamine manufactured by Tokyo Chemical Industry Co., Ltd.

Zinc oxide: Zinc oxide manufactured by FUJIFILM Wako Pure Chemical Co., Ltd.

Vulcanization accelerator DPG: N,N-Diphenylguanidine manufactured by FUJIFILM Wako Pure Chemical Co., Ltd.

Vulcanization accelerator CBS: N-cyclohexyl-2-benzothiazolylsulfenamide manufactured by Tokyo Chemical Industry Co., Ltd.

Sulfur: manufactured by FUJIFILM Wako Pure Chemical Co., Ltd.

(Modulation example 2)

Except that the copolymer C obtained in Example 1 was changed to 2 parts by mass, a rubber molded body was obtained by the same method as in Preparation Example 1.

(Modulation example 3)

Except that the copolymer C obtained in Example 1 was changed to 8 parts by mass, a rubber molded body was obtained by the same method as in Preparation Example 1.

(Modulation example 4)

Except that the copolymer C obtained in Example 1 was changed to the copolymer C obtained in Example 2, the rubber molding was obtained by the same method as in Preparation Example 1.

(Modulation example 5)

Except that the copolymer C obtained in Example 1 was changed to the copolymer C obtained in Example 3, the rubber molded body was obtained by the same method as in Preparation Example 1.

(Modulation example 6)

Except that the copolymer C obtained in Example 1 was changed to the copolymer C obtained in Example 4, the rubber molded body was obtained by the same method as in Preparation Example 1.

(Modulation example 7)

Except that the copolymer C obtained in Example 1 was changed to the copolymer C obtained in Example 5, a rubber molded body was obtained by the same method as in Preparation Example 1.

(Modulation example 8)

Except that the copolymer C obtained in Example 1 was changed to the copolymer C obtained in Example 6, the rubber molding was obtained by the same method as in Preparation Example 1.

(Modulation example 9)

Except that the copolymer C obtained in Example 1 was changed to the copolymer C obtained in Example 7, the rubber molding was obtained by the same method as in Preparation Example 1.

(Comparative example 1)

In addition to changing the copolymer C obtained in Example 1 to a PVP homopolymer (“Pitzcol K-50” manufactured by Daiichi Kogyo Co., Ltd., with a number average molecular weight of 77,000), other methods and preparation examples 1 The same method is used to obtain the rubber molding.

(Comparative example 2)

Except that the copolymer C obtained in Example 1 was changed to maleic acid-modified polybutadiene ("Riconl56MA17" manufactured by CRAY VALLY, with a number average molecular weight of 2500), other methods and preparation examples 1 The same method is used to obtain a rubber molded body.

(Evaluation of rolling resistance)

A viscoelasticity measuring device ("Rheogel-E4000" manufactured by UBM Corporation) was used to evaluate the rolling resistance of the rubber moldings obtained in the respective preparation examples and comparative examples. With this viscoelasticity measuring device, tanδ was measured at 60°C, dynamic strain 5%, and frequency 15Hz. In addition, for comparison, "a rubber molded body formed by the same method as Preparation Example 1 except that the copolymer C obtained in Example 1 was not used" was taken as a reference. Set the reciprocal of the tanδ of this reference material to 100, and based on the relative value based on this, follow the following criteria to evaluate the rolling of the rubber molded body obtained in each preparation example resistance. The larger the relative value, the lower the rolling resistance. Therefore, it can be said that the rolling resistance reduction effects of A, B and C are high (especially A is excellent), and the rolling resistance reduction effect of D is poor.

<Judgment Criteria>

A: 110 or more

B: 105 or more and less than 110

C: more than 100 and less than 105

D: less than 100

Table 1 shows the blending conditions and results of each preparation example.

[Table 1]

From Table 1, it can be seen that the rubber molded body obtained by using the rubber composition containing the copolymer C obtained in the example has low rolling resistance.

Claims (6)

A copolymer having in its molecule: polymer A containing at least butadiene as a constituent unit, and polymer B containing monomer b of N-vinyl-2-pyrrolidone. The copolymer according to claim 1, wherein the aforementioned polymer A contains polybutadiene or modified polybutadiene. The copolymer according to claim 1 or 2, which is a graft polymer in which the aforementioned polymer A is used as a backbone polymer and the aforementioned polymer B is used as a branch polymer. The copolymer according to any one of claims 1 to 3, which is used as an additive for rubber. A rubber composition containing at least the copolymer described in claim 4 and a diene rubber. A tire comprising the rubber composition described in claim 5.