Elastomer composition

Abstract

To provide an elastomer composition that improves dispersibility of silica and expresses superior mechanical characteristics, specifically the elastomer composition that ensures superior dispersion of silica particles in a low polar elastomer and facilitates an improved balance between mechanical strength and elongation.SOLUTION: An elastomer composition contains a diene-based polymer, silica, and 1-dienyl-2-pyrrolidone. Silica is preferably polyvinyl pyrrolidone-coated silica. A group at a nitrogen atom in 1-dienyl-2-pyrrolidone is preferably a C4-15 substituted or unsubstituted conjugated dienyl group.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an elastomer composition. More specifically, it relates to an elastomer composition containing a diene polymer, silica, and N-dienylpyrrolidone.

Background Art

[0005] However, the technologies described in Patent Documents 1-4 do not always demonstrate sufficient affinity and dispersibility of silica to elastomers, and mechanical properties may not be improved. Furthermore, applying these technologies to sulfur-crosslinked diene rubbers may adversely affect the vulcanization behavior. The method of modifying polymer ends is only applicable to certain elastomers.

[0006] The technique of coating the silica surface with a polymer can improve dispersibility and even reinforcement effects in various elastomers. For example, the mechanical strength of an elastomer can be greatly improved by incorporating silica coated with polyvinylpyrrolidone or the like. However, even if only such polymer-coated silica is incorporated into an elastomer, while the strength increases, the elongation often decreases.

[0007] The present invention has been made in view of the above problems, and aims to provide an elastomer composition in which silica dispersibility is improved and excellent mechanical properties are exhibited, in particular an elastomer composition in which silica particles are well dispersed in a low-polarity elastomer and both mechanical strength and elongation are improved in a well-balanced manner. [Means for solving the problem]

[0008] As a result of diligent research, the inventors have found that by further incorporating 1-dienyl-2-pyrrolidone compounds into an elastomer composition containing a diene polymer and silica, the dispersibility of silica can be improved, thereby enhancing both strength and elongation.

[0009] In other words, the present invention provides the following (1) to (6). (1) An elastomer composition containing a diene polymer, silica, and 1-dienyl-2-pyrrolidone. (2) The elastomer composition according to (1), wherein the group on the nitrogen atom in 1-dienyl-2-pyrrolidone is a substituted or unsubstituted conjugated dienyl group having 4 to 15 carbon atoms. (3) The elastomer composition according to (1) or (2) above, wherein the content of 1-dienyl-2-pyrrolidone is 10 to 150 parts by mass per 100 parts by mass of silica. (4) The elastomer composition according to any one of (1) to (3) above, wherein the silica is polyvinylpyrrolidone coated silica. (5) The elastomer composition according to any one of (1) to (4) above, wherein the silica is rod-shaped silica particles having a length of 1 to 2 μm and a thickness of 100 to 300 nm. (6) The elastomer composition according to any one of (1) to (5) above, wherein the diene polymer is one or more polymers selected from the group consisting of styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene copolymer, hydrogenated styrene-isoprene-styrene block copolymer, hydrogenated polybutadiene, and hydrogenated butadiene-isoprene block copolymer. [Effects of the Invention]

[0010] In the elastomer composition of the present invention, the dispersibility of silica is significantly improved. As a result, the elastomer composition of the present invention exhibits excellent mechanical properties, resulting in an elastic body with improved strength and elongation. The effects of the present invention are particularly pronounced in elastomer compositions containing silica coated with a polymer such as polyvinylpyrrolidone, especially silica nanoparticles such as rod-shaped silica or silica colloids, in a low-polarity elastomer. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows the AFM analysis results of the elastomer composition of Example 1 according to one embodiment of the present invention. [Figure 2]This figure shows the AFM analysis results for the elastomer composition of Comparative Example 2. [Figure 3] This is an SEM image of rod-shaped silica particles prepared by the inventors in the silica preparation example. [Figure 4] This is the 1H-NMR spectrum of 1-(1,3-pentadienyl)-2-pyrrolidone synthesized by the inventors in the synthesis example. [Modes for carrying out the invention]

[0012] The elastomer compositions of the present invention will be described in detail below based on embodiments, but the present invention is not limited to these embodiments.

[0013] Elastomer composition The elastomer composition of the present invention contains a diene polymer, silica, and 1-dienyl-2-pyrrolidone. The inclusion of 1-dienyl-2-pyrrolidone (also known as N-dienyl-2-pyrrolidone) is a crucial requirement of the present invention. The presence of 1-dienyl-2-pyrrolidone improves the dispersibility of silica in the diene polymer. In a typical embodiment, as shown in the AFM analysis results in Figure 1, the elastomer composition exhibits a nearly uniform distribution of silica. Furthermore, it is possible to suppress the aggregation of silica particles, as seen in the AFM analysis results in Figure 2. Therefore, the elastomer composition of the present invention exhibits excellent mechanical properties such as strength and elongation. The main components of the elastomer composition are described below.

[0014] <Diene polymers> In the present invention, the diene polymer includes all polymers having diene compounds such as butadiene and isoprene as monomer components. Examples include homopolymers such as polybutadiene, polyisoprene, and polychloroprene; copolymers such as copolymers of styrene and butadiene, copolymers of styrene and isoprene, copolymers of acrylonitrile and butadiene, and copolymers of acrylonitrile and isoprene; and further hydrides thereof, etc., but are not limited thereto. It may have a small amount of a structure derived from phospholipids, fatty acids, etc. like natural rubber, or may be a modified polymer such as epoxidized natural rubber or carboxylated styrene-butadiene copolymer. It is also possible to use a plurality of diene polymers in combination.

[0015] There is no particular limitation on the bonding form of each monomer component in the diene polymer. For example, in polybutadiene and polyisoprene homopolymers, each monomer may be cis- or trans-1,4-bonded, or may be vinyl-bonded such as 1,2-bond or 3,4-bond, or a mixed bonding form thereof may be present. There is no limitation on the copolymerization form, and various random copolymers and block copolymers can be used as desired. Also, the copolymerization ratio of each monomer component in the copolymer is not particularly limited. There is no limitation on the molecular weight of the diene polymer, and for example, a polymer having a mass average molecular weight of about 50,000 to 500,000, particularly about 100,000 to 200,000, may be used. Polymers with such molecular weights generally have an excellent balance between physical properties such as mechanical strength and moldability, and are particularly suitable as the diene polymer of the present invention.

[0016] Further specific examples of the diene polymer include poly-1,4-butadiene (BR), polyisoprene (IR) including natural rubber (NR), 1,4-chloroprene copolymer (CR), styrene-butadiene random copolymer (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), acrylonitrile-butadiene random copolymer (NBR), acrylonitrile-isoprene random copolymer (NIR), acrylonitrile-butadiene-styrene copolymer (ABS), etc. Furthermore, hydrides (hydrogenated polymers) of these polymers are included, but are not limited thereto. Among these polymers, styrene copolymers are preferred. Generally, styrene copolymers have excellent mechanical properties in a well-balanced manner, showing high strength and flexibility, and are thus suitable as the polymer component in the elastomer composition of the present invention.

[0017] [Thermoplastic Elastomer] Among the above diene polymers, further, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene copolymer (HSBR), hydrogenated styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene copolymer, hydrogenated styrene-isoprene-styrene block copolymer, hydrogenated polybutadiene, hydrogenated butadiene-isoprene block copolymer, etc. are preferred. These polymers function as so-called thermoplastic elastomers, showing elasticity at room temperature and at the same time being capable of thermally melting and molding like a resin. Therefore, processes such as crosslinking are not required, and molded products of various shapes can be produced simply and at low cost.

[0018] More preferably, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, and / or their hydrogenated products are used. These copolymers generally exhibit excellent mechanical properties such as strength and elongation. Among them, copolymers with a styrene content of 10 to 70% by mass, and particularly 20 to 35% by mass, offer an excellent balance of strength and flexibility and are suitable as diene polymers in the present invention. In these copolymers, the ratio of vinyl bonds in the butadiene units is preferably about 5 to 20% by mass for non-hydrogenated polymers and about 30 to 40% by mass for hydrogenated polymers. Polymers with such a vinyl bond ratio have the advantage of easily exhibiting flexibility and elasticity as elastomers.

[0019] Here, when using a hydride as the diene polymer, there are no particular restrictions on its hydrogenation rate. For example, unhydrogenated styrene-butadiene-styrene block copolymer (SBS) or styrene-isoprene-styrene block copolymer (SIS), SEBS in which some of the butadiene units in SBS are hydrogenated to form ethylene units, SEP in which the isoprene units in the styrene-isoprene copolymer are hydrogenated, and SEPS or SEEPS in which the isoprene units in SIS are hydrogenated can be used, but are not limited to these. In addition, in some of the above hydrogenated polymers, the ethylene units E may form crystals C, so abbreviations such as SBC are also used. For example, the above-mentioned hydrogenated polybutadiene may be abbreviated as CEBC, and hydrogenated butadiene-isoprene block copolymer may be abbreviated as CEPC or CIC.

[0020] [Liquid polymer latex] The above-mentioned diene polymers are generally supplied as solid pellets or pails, but it is also possible to use polymers in liquid or latex form.

[0021] <Silica> While silica generally refers to silicon dioxide (SiO2), in this invention it also includes substances that are partially hydrated or hydroxylated, such as silicic acid (salt), silica colloid, and silica gel. There are no particular restrictions on its chemical structure and shape, and various known silicas can be used. Examples include anhydrous silicic acid produced by the dry method, such as Rheorosil (registered trademark) from Tokuyama Corporation and Aerosil (registered trademark) from Evonik Operations GmbH; silica produced by the wet method, such as Carplex (registered trademark) from DSL. Japan Co., Ltd., Toxil (registered trademark) from Oriental Silicas Corporation, Nipsil (registered trademark) from Tosoh Silica Co., Ltd., and Silton (registered trademark) from Mizusawa Chemical Industries, Ltd.; synthetic silicate silica, such as Silmos (registered trademark) from Shiraishi Industries Co., Ltd.; colloidal silica, such as Snowtex (registered trademark) from Nissan Chemical Corporation; and fuzzy silica, but are not limited to these.

[0022] There are no particular restrictions on the shape or size of the silica particles. For example, silica particles with an average particle size of approximately 1-5 μm, 5-10 μm, 10-20 μm, 20-40 μm, 40-100 μm, and even silica particles with an average particle size of approximately 100 μm or more can be used.

[0023] Furthermore, it is possible to use so-called silica nanoparticles with an average particle size of approximately 1 μm or less, for example, around 10 to 100 nm. In addition to spherical shapes, rod-shaped silica particles can also be used.

[0024] [Silica nanoparticles] Silica nanoparticles are nanoparticles made of silica and exhibit a particularly strong reinforcing effect on polymers such as rubber. Therefore, they are suitable as silica components in the elastomer composition of the present invention. Typical examples include, but are not limited to, fumed silica nanoparticles produced by the flame method, and colloidal silica nanoparticles produced by the water glass method or alkoxide hydrolysis method.

[0025] Because nanoparticles have a large surface area per unit mass, surface-related properties become prominent. For example, colloidal silica has a high proportion of ionic bonding between elements on its surface, and the surface is often covered with polarized oxygen atoms, which adsorb water and stabilize by forming silanol groups. As a result, it is particularly prone to aggregation among silicas, making dispersion in elastomers difficult. Therefore, the effect of containing 1-dienyl-2-pyrrolidone, as described later in this invention, becomes particularly pronounced.

[0026] [Rod-shaped silica particles] Silica particles may be rod-shaped or fibrous. Rod-shaped silica particles have an aspect ratio of about 2 to 150, a length in the long axis direction of generally about 1 to 1000 μm, for example about 1 to 10 μm, particularly about 1 to 2 μm, and a thickness (diameter) in the short axis direction of about 100 to 300 nm, for example about 100 to 250 nm, particularly about 100 to 200 nm. When silica particles are rod-shaped, the orientation characteristics of the silica provide the advantage of improved elongation compared to spherical silica.

[0027] The rod-shaped silica particles may also be rod-shaped nanosilica particles with a length in the long axis direction of approximately 1 to 2 μm, particularly approximately 1 to 1.1 μm, and a thickness (diameter) in the short axis direction of approximately 50 to 200 nm, particularly approximately 100 to 150 nm.

[0028] Rod-shaped silica particles can be produced, for example, from an alkoxysilane and a quaternary ammonium salt, or from an alkali silicate and a nonionic surfactant. By adjusting the concentration of the raw materials and the stirring speed during production, rod-shaped silica particles with a desired aspect ratio and size can be obtained.

[0029] [Surface coating silica] To further enhance the effects of 1-dienyl-2-pyrrolidone in the present invention, silica coated with a resin or coupling agent may be used. As described above, silica generally tends to aggregate and is difficult to disperse in elastomers, so silica coated with various materials has been used conventionally. Such coated silica can also be preferably used in the present invention. Examples of materials for coating silica include, but are not limited to, resins such as phenolic resins, surfactants such as amine-based and polyethylene oxide-based surfactants, and silane coupling agents such as mercapto-based and polysulfide-based surfactants.

[0030] (Polyvinylpyrrolidone-coated silica) More preferably, polyvinylpyrrolidone-coated silica is used as the silica. Polyvinylpyrrolidone-coated silica disperses well in diene polymers, including SBS, and can exhibit excellent reinforcing effects. Furthermore, because it has pyrrolidyl groups on its surface, it readily undergoes the compatibilization effect of 1-dienyl-2-pyrrolidone, which will be described later. For this reason, it is particularly useful as a silica component in the elastomer composition of the present invention. It is also possible to use polyvinylpolypyrrolidone (PVPP), in which the pyrrolidone moiety is crosslinked, as the polyvinylpyrrolidone (PVP).

[0031] There are no particular restrictions on the method for producing polyvinylpyrrolidone-coated silica. For example, it may be produced by applying a PVP solution to the surface of commercially available silica particles and then drying them, or by hydrolyzing an alkoxysilane in the presence of polyvinylpyrrolidone. The latter hydrolysis method is effective when producing silica nanoparticles, especially rod-shaped silica nanoparticles.

[0032] Specifically, silica particles coated with PVP, such as rod-shaped silica (nano) particles, can be obtained by adding an acid or alkali to a solution containing an alkoxysilane such as tetraethoxysilane (TEOS) and PVP to hydrolyze the TEOS. However, the method for producing polyvinylpyrrolidone-coated silica used in the present invention is not limited to this method.

[0033] [Silica content] In the elastomer composition of the present invention, the silica described above is preferably blended in an amount of about 5 to 50 parts by mass, more preferably 7 to 40 parts by mass, and even more preferably about 10 to 25 parts by mass per 100 parts by mass of the diene polymer. If the silica content is about 5 parts by mass or more per 100 parts by mass of the diene polymer, the reinforcing effect of the elastomer by silica is easily exhibited, and if it is about 50 parts by mass or less, it is easy to maintain good flexibility of the elastomer. In the case of coated silica, the amount of silica blended here is based on the mass of silica including polymer components such as polyvinylpyrrolidone.

[0034] <1-Dienyl-2-pyrrolidone> An important requirement of the present invention is that the elastomer composition contains 1-dienyl-2-pyrrolidone, as described above. This suppresses silica aggregation and significantly improves the dispersibility of silica in the elastomer composition, resulting in improved mechanical properties such as strength and elongation.

[0035] Although this invention is not limited by any particular theory, the reason why the dispersibility of silica in diene polymers is improved is thought to be that the dienyl group and the 2-pyrrolidone ring in 1-dienyl-2-pyrrolidone have excellent affinity for diene polymers and silica, respectively. The polar 2-pyrrolidone ring interacts with silica, and the low polarity of the dienyl group improves compatibility with diene polymers, so 1-dienyl-2-pyrrolidone may be functioning as if it were a surfactant or coupling agent.

[0036] 1-Dienyl-2-pyrrolidone (or N-Dienyl-2-pyrrolidone) itself is well known. It is a compound with a structure in which one dienyl group is attached to the nitrogen atom of a 2-pyrrolidone ring, and can be prepared, for example, by the reaction of 2-pyrrolidone with an alkenyl aldehyde. Here, the group on the nitrogen atom can be any dienyl group, and there are no particular restrictions on its structure. For example, it can be a substituted or unsubstituted linear, branched, or cyclic dienyl group. Furthermore, there are no particular restrictions on the structure around the double bond in the dienyl group, and each can be in a cis or trans configuration. There are also no particular restrictions on the type of substituent or the number of carbon atoms in the dienyl group.

[0037] From the viewpoint of further improving the dispersibility of silica in diene polymers, the substituents in the dienyl group are preferably hydrocarbon groups such as alkyl, alkenyl, alkynyl, aryl, arylalkyl, and alaryl groups. Furthermore, it is preferable that the carbon atoms in the 2-pyrrolidone ring are unsubstituted. 1-Dienyl-2-pyrrolidone with this structure exhibits higher affinity for diene polymers and silica, making it suitable as a component of elastomer compositions.

[0038] Furthermore, considering the affinity with diene monomer units in diene polymers, the dienyl group in the diene polymer is preferably a substituted or unsubstituted conjugated dienyl group having 4 to 15 carbon atoms. More preferably, it is an unsubstituted linear conjugated dienyl group having 4 to 12 carbon atoms, and even more preferably, 4 to 8 carbon atoms. Since such a structure is close to the structure of the diene component, which is often a major component in diene polymers, the effect of silica on improving the dispersibility of the diene polymer can be further enhanced. Particularly preferred is a compound in which the dienyl group is a 1,3-pentadienyl group, i.e., 1-(1,3-pentadienyl)-2-pyrrolidone.

[0039] [Amount of 1-dienyl-2-pyrrolidone] In the elastomer composition of the present invention, the amount of 1-dienyl-2-pyrrolidone is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, and even more preferably 50 to 120 parts by mass, per 100 parts by mass of silica. When the amount of 1-dienyl-2-pyrrolidone is within this range, the effect of improving the dispersibility of silica with respect to diene polymers becomes even more readily apparent.

[0040] The elastomer composition of the present invention preferably contains 5 to 50 parts by mass of silica, more preferably 7 to 40 parts by mass, and more preferably 10 to 25 parts by mass of silica, and 1 to 50 parts by mass of 1-dienyl-2-pyrrolidone, more preferably 5 to 30 parts by mass, and more preferably 7 to 15 parts by mass, per 100 parts by mass of diene polymer. With such a formulation, the mechanical properties are further improved while maintaining a balance between strength and elongation.

[0041] <Other additives> The elastomer composition of the present invention may optionally contain additives other than those listed above. For example, crosslinking agents and crosslinking accelerators may be added, as may fillers other than silica such as carbon black and calcium carbonate, and polymers other than diene polymers, such as resins such as polyolefins, polyamides, and polyesters; rubbers such as butyl rubber, EP (DM), acrylic rubber, urethane rubber, epichlorohydrin rubber, silicone rubber, and fluororubber; and even olefin-based, polyamide-based, polyester-based, and polyurethane-based thermoplastic elastomers may be added. Other additives include, but are not limited to, anti-aging agents, antioxidants, UV absorbers, colorants, lubricants, plasticizers, flow modifiers (flow modifiers), dispersants, flame retardants, stabilizers, antistatic agents, foaming agents, tackifiers, and coupling agents.

[0042] [Crosslinking agent] In particular, when using polymers such as NR, IR, BR, SBR, NBR, and CR as diene polymers, it is preferable to incorporate a crosslinking agent to crosslink the polymer. There are no particular restrictions on the type of crosslinking agent, and examples include, but are not limited to, sulfur and / or sulfur compounds, such as tetramethylthiuram disulfide, morpholine dithiobenzothiazole, sulfur dichloride, high molecular weight polysulfides; peroxides, such as dicumyl peroxide, 2,5-dimethyl-2,5-dibutylperoxyhexane, bis(butylperoxyisopropyl)benzene; phenolic resins, polyamines, oximes, etc.

[0043] When sulfur is used as a crosslinking agent, it is preferable to use a vulcanization accelerator in combination with zinc oxide (zinc oxide) or stearic acid. There are no particular restrictions on the type of vulcanization accelerator, and include guanidine-based accelerators such as diphenylguanidine and dioltotolylguanidine; thiazole-based accelerators such as 2-mercaptobenzothiazole and its salts, dibenzothiadyl disulfide, and morpholinodithiobenzothiazole; sulfenamide-based accelerators such as N-cyclohexyl-2-benzothiadylsulfenamide and N,N-dicyclohexyl-2-benzothiadylsulfenamide; and thiourea-based accelerators such as thiocarbanilide and ethylenethiourea. Examples of vulcanization accelerators include, but are not limited to, dibutylthiourea; thiram-based accelerators, such as tetramethylthiram monosulfide, tetramethylthiram disulfide, tetraethylthiram disulfide, and tetrabutylthiram disulfide; dithiocarbamate-based accelerators, such as dimethyldithiocarbamate and dibenzyldithiocarbamate; aldehyde ammonia-based accelerators such as hexamethylenetetramine; aldehyde amine-based accelerators; xantate-based accelerators; and 4,4'-dithiomorpholine. Multiple vulcanization accelerators can also be used in combination.

[0044] When using peroxides as crosslinking agents, crosslinking aids such as triallyl isocyanurate, trimethylolpropane trimethacrylate, and phenylenedimaleimide may be further added.

[0045] [Amount of other additives] When a crosslinking agent and / or a vulcanization accelerator or crosslinking aid is included, the amount of these is preferably 0.5 to 3 parts by mass, particularly 1 to 2 parts by mass, per 100 parts by mass of the diene polymer. When sulfur is included, the amount of zinc oxide is preferably 1 to 8 parts by mass, particularly 3 to 6 parts by mass, per 100 parts by mass of the diene polymer.

[0046] If the elastomer composition of the present invention contains a polymer other than a diene polymer, the amount is preferably 50 parts by mass or less, for example 5 to 40 parts by mass, and particularly about 10 to 30 parts by mass, per 100 parts by mass of the diene polymer. If the content of other polymers is 50 parts by mass or less, there is no risk of impairing the mechanical properties of the elastomer composition, and if the content is about 5 parts by mass or more, novel properties corresponding to the type of polymer added are more likely to be expressed. However, since the diene polymers used in the present invention generally have well-balanced and excellent mechanical properties, the elastomer composition of the present invention may also be a composition that does not contain other polymers and whose polymer component consists of a diene polymer.

[0047] If the elastomer composition of the present invention contains a filler other than silica, the amount is preferably 50 parts by mass or less, for example 5 to 40 parts by mass, and particularly about 10 to 30 parts by mass, per 100 parts by mass of the diene polymer. If the amount of filler is 50 parts by mass or less, there is no risk of impairing the flexibility of the elastomer composition, and if the amount of filler is about 5 parts by mass or more, the strength of the elastomer composition can be further improved. However, since the elastomer composition of the present invention can exhibit excellent mechanical strength due to the inclusion of silica and 1-dienyl-2-pyrrolidone, it may also be a composition that does not contain fillers other than silica, or contains only a small amount, for example, about 1 part by mass or less.

[0048] The content of additives other than those mentioned above, such as antioxidants and lubricants, can be arbitrarily set according to the desired physical properties and processability, but it is preferable that each of these additives be at least 10% by mass, for example, about 0.05 to 10% by mass, particularly about 0.2 to 5% by mass, relative to 100% by mass of the total of the diene polymer, silica, and 1-dienyl-2-pyrrolidone, and that the total amount of these other additives as a whole be at least 20% by mass, for example, about 0.05 to 20% by mass, particularly about 0.5 to 10% by mass.

[0049] ≪Method for producing elastomer compositions≫ The elastomer composition of the present invention can be produced by mixing the above-mentioned components, and there are no particular limitations on the method of production. Examples include, but are not limited to, a method of kneading a diene polymer with silica and 1-dienyl-2-pyrrolidone, as well as any desired additive, in a kneader such as a kneading roll, Banbury mixer, kneader, or unscrewed or twin-screw extruder; a method of mixing a solution of a diene polymer with a suspension of silica and a solution of 1-dienyl-2-pyrrolidone, etc., and drying or precipitating the mixture; and a method of mixing a latex of a diene polymer with a suspension of silica and a solution of 1-dienyl-2-pyrrolidone, etc., and drying or precipitating the mixture. Since pyrrolidone compounds are generally water-soluble, they can be used without problems in production methods using water-based latex.

[0050] There are no particular restrictions on the mixing order of each component. For example, the diene polymer, silica, 1-dienyl-2-pyrrolidone, and other optional additives may be mixed simultaneously; some of the components used may be pre-mixed or treated. For example, a coupling agent may be applied to the silica surface beforehand and then mixed with other components. Silica and 1-dienyl-2-pyrrolidone may be mixed first. It is also possible to mix the diene polymer, silica, and 1-dienyl-2-pyrrolidone in the first step, and then mix the other additives in the second step. In particular, when crosslinking agents or crosslinking accelerators are included, it is preferable to mix these additives in the second step from the viewpoint of preventing unintended crosslinking reactions, so-called scorching.

[0051] When mixing diene polymers, silica, and 1-dienyl-2-pyrrolidone in liquid form (for example, when using a polymer solution or latex), it is preferable to mix other optional additives separately in the second stage. Alternatively, silica and 1-dienyl-2-pyrrolidone may be mixed first to prepare a liquid, and this liquid may be mixed with the diene polymer solution. It is also possible to mix the diene polymer latex and silica suspension in the first stage, add salt or acid to induce salting out, and then mix the resulting solid (silica-containing polymer) with 1-dienyl-2-pyrrolidone and other optional additives in a kneader.

[0052] Furthermore, if the diene polymer is a thermoplastic elastomer such as SBS, heating may be used during mixing. For example, heating to a temperature of 50-180°C, particularly 80-120°C, facilitates the kneading of silica and other additives.

[0053] Molding of Elastomer Compositions The elastomer composition of the present invention can be molded into a desired shape by any method. There are no particular restrictions on the molding method, and various conventional methods such as injection molding, extrusion molding, roll molding, press molding, transfer molding, blow molding, and inflation molding can be used.

[0054] Depending on the components of the elastomer composition and the shape of the molded product, it is possible to mix the components and mold them simultaneously. For example, the components can be mixed in an extruder and extruded to form molded products in the shape of sheets, tubes, etc. Alternatively, the kneaded material can be extruded, for example, into strands, then cut and molded into pellets, and then molded in another extruder or injection molding machine. It may also be compounded with other materials by calendering or other methods.

[0055] Elastomer compositions containing a crosslinking agent and / or a vulcanization accelerator may undergo secondary crosslinking in a heated oven or the like after crosslinking by hot pressing or the like. On the other hand, compositions containing diene polymers that can become thermoplastic elastomers, such as SBS, SIS, HSBR, SEBS, SEP, SEPS, SEEPS, CEBS, CEPC, and CIC, can be easily molded into various shapes by melt molding methods such as injection molding.

[0056] Film-like molded products may be manufactured by solution casting. For example, various components can be mixed in solution or suspension, then the mixture can be poured onto a flat plate or drum and heated and dried to form a film. Casting solvents include, but are not limited to, aromatic hydrocarbon solvents such as toluene and xylene, halogen-containing solvents such as chloroform, ether solvents such as tetrahydrofuran (THF) and dioxane, ester solvents such as ethyl acetate, and amide solvents such as methylpyrrolidone. Furthermore, a mixture using latex can be applied to, for example, a handprint and dried or solidified to form a glove or similar shape.

[0057] In the elastomer composition of the present invention, the dispersibility of silica is significantly improved, so that the molded articles exhibit excellent mechanical properties and become elastic bodies with improved strength and elongation. Therefore, these molded articles are suitable for use as industrial materials such as belts, tubes, cable coverings, and sealing materials; daily necessities such as stationery, toys, and bath products; housings for home appliances; and polymer materials for transportation equipment such as tires, constant velocity joint boots, weatherstrips, and cushioning materials. [Examples]

[0058] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples except as specified above.

[0059] In the following examples, styrene-butadiene-styrene copolymer (SBS), polyvinylpyrrolidone-coated rod-shaped silica particles, and 1-(1,3-pentadienyl)-2-pyrrolidone, a type of 1-dienyl-2-pyrrolidone, were used as raw materials to prepare elastomer films by solution mixing and casting methods. The obtained films were subjected to tensile tests to measure tensile strength and elongation at break. AFM analysis of the film surface was also performed on some samples.

[0060] For the SBS (Styrene Bicarbonate), we used a polymer manufactured by Aldrich (styrene content 30%, mass-average molecular weight 140,000). The tensile test was performed in accordance with JIS K6251 at a tensile speed of 10 mm / min. AFM analysis was performed using a NANOSCOPEV from VEECo.

[0061] [Example of silica preparation] Polyvinylpyrrolidone (PVP) coated rod-shaped silica particles were prepared as follows. Approximately 30 g of polyvinylpyrrolidone and 300 ml of 1-pentanol were added to a 500 ml round-bottom flask, and sonication was performed for approximately 5 hours to dissolve the compounds. Next, the flask was transferred to a dry box, and 30 ml of anhydrous ethanol (ethanol dehydrated with molecular sieves), 8.4 ml of pure water, 2 ml of 0.18 M trisodium citrate aqueous solution, 6.75 ml of ammonia water, and 3 ml of tetraethoxysilane (TEOS) were added. After mixing, the mixture was allowed to stand overnight to react.

[0062] The mixed solution was transferred to a centrifuge tube and centrifuged at 3100 rpm for 1 hour. The supernatant was removed, and ethanol was added to the precipitated material and it was washed by centrifugation at 3100 rpm for 15 minutes. The precipitated silica after washing was stored in the form of an ethanol suspension, and the dispersion medium was converted to chloroform before the preparation of the elastomer composition described later. The conversion of the dispersion medium was performed by repeating the procedure of centrifugation at 3100 rpm for 15 minutes and adding 20 ml of chloroform to the obtained silica twice.

[0063] Furthermore, a portion of the obtained silica was dried and observed and photographed using a scanning electron microscope (SEM). An example of the obtained SEM image is shown in Figure 3. It can be seen that it is rod-shaped with a length of approximately 1 to 1.5 μm and a width of approximately 100 to 200 nm. The dried silica was also subjected to the AFM analysis described above, and it was confirmed that it consisted of rod-shaped particles with an average length of approximately 3 μm and an average width of approximately 1 μm.

[0064] [Example of combination] 1-(1,3-pentadienyl)-2-pyrrolidone was synthesized in a draft box as follows: In a 50 ml two-necked round-bottom flask fitted with a Dean-Stark trap and condenser, approximately 28.5 g of p-toluenesulfonic acid (p-TsOH), 5.5 ml of 2-pyrrolidone, and 85 ml of dry toluene (dehydrated with molecular sieves) were added and stirred under an argon stream for 30 minutes to dissolve. Then, 5.8 ml of trans-2-pentenal was added dropwise using a hypodermic needle, and the mixture was heated in an oil bath to 130°C and refluxed for 6 hours.

[0065] The refluxed solution was cooled and transferred to a separatory funnel. It was extracted once with 45 ml of saturated sodium bicarbonate aqueous solution, and then three times with 45 ml of purified water. The resulting aqueous phase was then extracted three times with 45 ml of diethyl ether. The extracted diethyl ether phase was dried over anhydrous magnesium sulfate, concentrated, and then purified by column chromatography (ethyl acetate:hexane volume ratio = 7:3) to obtain the product.

[0066] The structure of the obtained product is, 1 The product was identified by 1H-NMR measurement. 1 The H-NMR spectrum is shown in Figure 4. A peak of approximately 3H, attributed to carbon atom a, was observed around δ=1.7~1.8 ppm; peaks of 1H each, attributed to carbon atoms b~e, were observed around 5.4~7.2 ppm; and peaks of 2H each, attributed to carbon atoms f~h, were observed around 2.0~3.7 ppm. This confirmed that the target 1-(1,3-pentadienyl)-2-pyrrolidone was obtained. Although only the trans structure is shown in Figure 4 for convenience, the presence of two peaks attributed to carbon atom b suggests that the obtained product is a mixture of trans and cis structures.

[0067] [Example 1] 1.00 g of SBS was placed in a sample vial, 11.87 ml of chloroform was added, and the mixture was stirred to dissolve it. Separately, 7.81 ml of a chloroform dispersion of the PVP-coated rod-shaped silica particles prepared above (amount of coated silica particles: 0.10 g) was placed in a screw-cap tube, and 0.10 g of 1-(1,3-pentadienyl)-2-pyrrolidone was added and mixed. Next, the two liquids were mixed and transferred to a coupling petri dish, then placed in a drying oven and dried overnight at room temperature (23.6°C) to obtain a sheet-like sample.

[0068] Tensile tests and AFM analysis were performed on the obtained sheet-like samples. The results are shown in Table 1 and Figure 1 below.

[0069] [Comparative Example 1] A sheet-like sample was prepared by the same procedure as in Example 1, except that PVP-coated rod-shaped silica particles and 1-(1,3-pentadienyl)-2-pyrrolidone were not used. The tensile test results of the obtained sheet-like samples are shown in Table 1 below.

[0070] [Comparative Example 2] A sheet-like sample was prepared using the same procedure as in Example 1, except that 1-(1,3-pentadienyl)-2-pyrrolidone was not used. The tensile test results and AFM analysis results of the obtained sheet-like samples are shown in Table 1 and Figure 2 below.

[0071] [Comparative Example 3] A sheet-like sample was prepared by the same procedure as in Example 1, except that PVP-coated rod-shaped silica particles were not used. The tensile test results of the obtained sheet-like samples are shown in Table 1.

[0072] [Table 1]

[0073] As shown in Table 1, the elastomer composition of Example 1, which contains silica and 1-dienyl-2-pyrrolidone according to the present invention, showed improved tensile strength and elongation at break compared to the raw material SBS (Comparative Example 1), exhibiting excellent mechanical properties. On the other hand, the elastomer composition of Comparative Example 2, which contained only silica, showed significantly higher tensile strength, but its elongation at break was lower than that of the raw material SBS (Comparative Example 1), failing to achieve a balanced improvement in mechanical properties. The elastomer composition of Comparative Example 3, which contained only 1-dienyl-2-pyrrolidone, showed lower tensile strength and elongation at break compared to the raw material SBS (Comparative Example 1).

[0074] AFM analysis results show that in the elastomer composition of Comparative Example 2, which contains only silica, large protrusions presumably caused by silica aggregates are observed in places (Figure 2). On the other hand, in the elastomer composition of Example 1, which contains silica and 1-dienyl-2-pyrrolidone according to the present invention, no such aggregates were observed, and the silica particles were distributed almost evenly throughout (Figure 1).

[0075] As described above, it was found that by incorporating 1-dienyl-2-pyrrolidone together with silica into a diene polymer, silica aggregation is suppressed, and the dispersibility of silica in the elastomer composition is significantly improved, resulting in a well-balanced improvement in mechanical properties such as strength and elongation.

Claims

1. An elastomer composition containing a diene polymer, silica, and 1-dienyl-2-pyrrolidone.

2. The elastomer composition according to claim 1, wherein the group on the nitrogen atom in the 1-dienyl-2-pyrrolidone is a substituted or unsubstituted conjugated dienyl group having 4 to 15 carbon atoms.

3. The elastomer composition according to claim 1 or 2, wherein the content of 1-dinyl-2-pyrrolidone is 10 to 150 parts by mass per 100 parts by mass of silica.

4. The elastomer composition according to claim 1 or 2, wherein the silica is polyvinylpyrrolidone-coated silica.

5. The elastomer composition according to claim 1 or 2, wherein the silica is rod-shaped silica particles having a length of 1 to 2 μm and a thickness of 100 to 300 nm.

6. The elastomer composition according to claim 1 or 2, wherein the diene polymer is one or more polymers selected from the group consisting of styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene copolymer, hydrogenated styrene-isoprene-styrene block copolymer, hydrogenated polybutadiene, and hydrogenated butadiene-isoprene block copolymer.

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