JP6885224B2 - Cross-linked rubber and golf balls - Google Patents

Description

The present invention relates to a crosslinked rubber, and more particularly to a crosslinked rubber using a novel cocrosslinking agent.

As a method of extending the flight distance of a golf ball on a driver shot, for example, there are a method of using a core having high resilience and a method of using a core having a hardness distribution in which the hardness increases from the center of the core toward the surface. The former has the effect of increasing the initial velocity of the golf ball, and the latter has the effect of increasing the launch angle and lowering the spin. A golf ball with a high launch angle and low spin has a large flight distance.

Examples of a method for obtaining a core having high resilience include a method in which the core has a multi-layer structure to control the physical properties of each layer, and a method in which a core is formed using a rubber composition having high resilience. As a method of controlling the physical properties of each layer of the core, for example, Patent Document 1 describes a multi-piece solid golf in which the elastic modulus of the inner layer core is 50 to 200 MPa and the elastic modulus of the outer layer of the core is 15 to 100 MPa lower than that of the inner layer core. A ball is described (see Patent Document 1 (Claim 1, 0020, 0022)). Further, in Patent Document 2, when the blending amounts of the organic sulfur compounds in the innermost layer and the outermost layer of the core are Hi and Ho, respectively, with respect to 100 parts by weight of the base rubber, the formula 0 ≦ Ho / Hi < A multi-piece solid golf ball satisfying No. 1 is described (see Patent Document 2 (Claim 1, paragraph 0019)).

In the method of forming a core using a rubber composition having high resilience, a technique for improving the base rubber blended in the rubber composition has been proposed. For example, Patent Documents 3 and 4 propose a rubber composition using high cis polybutadiene synthesized by using a cobalt-based catalyst as a base rubber (Patent Document 3 (Claim 1), Patent Document 1). 4 (see claim 1)). Patent Document 5 describes a rubber composition in which (A) high cis polybutadiene synthesized using a cobalt-based catalyst and (B) high cis polybutadiene synthesized using a catalyst other than cobalt-based catalyst are used in combination as a base rubber. A thing has been proposed (see Patent Document 5 (Claim 1, 0017, 0035)). Further, Patent Document 6 proposes a rubber composition in which (A) a polybutadiene rubber containing syndiotactic polybutadiene and a rubber other than (A) are used in combination as a base rubber (Patent Document 6 (claim). Item 1, paragraphs 0010, 0025)).

Japanese Unexamined Patent Publication No. 2001-87422 Japanese Unexamined Patent Publication No. 2001-161858 Patent No. 40623363 Japanese Unexamined Patent Publication No. 2004-292667 Japanese Unexamined Patent Publication No. 2006-241265 Patent No. 4811274

Various crosslinked rubbers with enhanced resilience have been proposed, but there is still room for improvement in resilience performance. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a crosslinked rubber having excellent resilience performance.

The crosslinked rubber of the present invention that could solve the above problems contains (a) a base rubber, (b) a co-crosslinking agent, and (c) a cross-linking initiator, and the (b) co-crosslinking agent is of the formula (b). A storage elastic modulus E'(which is formed from a rubber composition containing a complex represented by 1) and / or a complex represented by the formula (2) and measured using a dynamic viscoelastic device (tensile mode). It is characterized that Pa), the loss elastic modulus E ”(Pa), and the slab hardness (shore C) X ^{satisfy the relationship of │log (E'/ E” 2} ) │ / X × 100 ≦ 5.7. And.

［式（１）中、Ｍ¹は同一または異なって金属原子であり、Ｌ¹は式（３）で表されるカルボキシレートである。式（２）中、Ｍ²は同一または異なって金属原子であり、Ｌ²は式（３）で表されるカルボキシレート、ｘは１以上の整数である。式（３）中、Ｒは、水素原子、炭素数１〜１８のアルキル基、炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基であり、破線は共鳴構造を示す。式（１）および式（２）において、複数存在するＲは、それぞれ同一でも異なっていてもよい。ただし、式（１）および式（２）において、Ｒのうち少なくとも１個は炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基である。]

[In the formula (1), M ¹ is the same or different metal atom, and L ¹ is the carboxylate represented by the formula (3). In formula (2), M ² is the same or different metal atom, L ² is a carboxylate represented by formula (3), and x is an integer of 1 or more. In the formula (3), R is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms, and the broken line indicates a resonance structure. In the formulas (1) and (2), the plurality of Rs existing may be the same or different. However, in the formulas (1) and (2), at least one of R is an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms. ]

The complex represented by the formula (1) and the complex represented by the formula (2) have a high affinity with the base rubber (a) and a high dispersibility with respect to the base rubber (a). Therefore, the size of the cross-linking point after cross-linking becomes small (about 0.4 nm). Further, the complex represented by the formula (1) and the complex represented by the formula (2) have a structure of a cross-linking point formed in advance. Therefore, a cross-linking point can be formed only by the reaction with the base rubber, and the cross-linking efficiency is high. Further, the storage elastic modulus E'(Pa) and the loss elastic modulus E "(Pa) measured using the dynamic viscoelastic device (tensile mode) and the slab hardness (shore C) X are │log (E). '/ E ^"2) │ / cross-linked rubber which satisfies the relationship of X × 100 ≦ 5.7 is excellent in the resilience.

In the complex represented by the formula (1) and the complex represented by the formula (2), at least one of R is an alkenyl group having 2 to 8 carbon atoms or a terminal having a carbon-carbon double bond at the terminal. It is preferably an alkynyl group having 2 to 8 carbon atoms having a carbon-carbon triple bond. The oxidation number of the metal atom constituting the complex represented by the formula (1) and the complex represented by the formula (2) is preferably +2. The co-crosslinking agent (b) preferably contains 5% by mass or more of the complex represented by the formula (1) and / or the complex represented by the formula (2).

The base rubber (a) preferably contains a diene rubber or a natural rubber. The rubber composition preferably contains 1 part by mass to 50 parts by mass of the (b) co-crosslinking agent with respect to 100 parts by mass of the (a) base material rubber.

The present invention also includes a golf ball having a member made of the crosslinked rubber.

The crosslinked rubber of the present invention has excellent resilience performance.

It is a figure which shows the ASAP-MS spectrum of the acrylic acid oxo cluster. It is a figure which shows the ASAP-MS spectrum of the acrylic acid oxo cluster. It is a figure which shows the IR spectrum of the acrylic acid oxo cluster. It is a figure which shows the X-ray diffraction spectrum of an oxo cluster of acrylic acid. It is a figure which shows the IR spectrum of the acrylate hydroxocluster. It is a figure which shows the X-ray diffraction spectrum of an acrylate hydroxocluster. It is a figure which shows the structure of the acrylate hydroxocluster determined by the single crystal X-ray structure analysis. It is a figure which shows the relationship between the slab hardness of a crosslinked rubber and | log (E'/ E " ^{2) |.}

[Cross-linked rubber]
The crosslinked rubber of the present invention contains (a) a base rubber, (b) a co-crosslinking agent, and (c) a cross-linking initiator, and the (b) co-crosslinking agent is a complex represented by the formula (1) and /. Alternatively, the storage elastic modulus E'(Pa) and the loss elastic modulus E'(Pa) formed from the rubber composition containing the complex represented by the formula (2) and measured using a dynamic viscoelastic device (tensile mode) ( Pa) and the slab hardness (shore C) X are characterized in that they satisfy the relationship of ^{│log (E'/ E "2) │ / X × 100 ≦ 5.7.}

Conventionally, the metal salt of α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, which is often used as a co-crosslinking agent, is an ionic crystal and has a low affinity with the base rubber, and has a low affinity for the base rubber. Poor dispersibility. Further, such a metal salt of α, β-unsaturated carboxylic acid formed a graft chain by oligomerization between co-crosslinking agents and a reaction with a base rubber to form a cross-linking point. Therefore, the size of each cross-linking point was large (about 4 nm), and the cross-linking efficiency was low. On the other hand, the complex represented by the formula (1) and the complex represented by the formula (2) have high affinity with (a) base rubber and (a) high dispersibility with respect to the base rubber. .. Therefore, the size of the cross-linking point after cross-linking becomes small (about 0.4 nm). Further, the complex represented by the formula (1) and the complex represented by the formula (2) have a structure of a cross-linking point formed in advance. Therefore, a cross-linking point can be formed only by the reaction with the base rubber, and the cross-linking efficiency is high. Therefore, the crosslinked rubber of the present invention is excellent in resilience performance.

((A) Base rubber)
As the base material rubber (a), natural rubber and / or synthetic rubber can be used. Examples of the synthetic rubber include diene rubbers such as polybutadiene rubber (BR), polyisoprene rubber (IR), styrene polybutadiene rubber (SBR), chloroprene rubber (CR), butyl rubber (IIR), and acrylonitrile butadiene rubber (NBR). Examples include non-diene rubbers such as ethylene propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), urethane rubber, silicone rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, fluororubber, and chlorosulfonated polyethylene rubber. .. These may be used alone or in combination of two or more.

The base rubber (a) preferably contains a natural rubber and / or a diene rubber. The total content of the natural rubber and / or the diene-based rubber in the base rubber (a) is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass or more. It is also preferable that the base rubber (a) contains only natural rubber and / or diene rubber.

The base rubber (a) preferably contains a polybutadiene rubber. In particular, high cis polybutadiene having a cis-1,4-bond advantageous for repulsion of 40% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more is preferable. The content of high cis polybutadiene in the (a) base material rubber is preferably 50% by mass or more, more preferably 70% by mass or more.

The content of 1,2-vinyl bond in the high cis polybutadiene is preferably 2.0% by mass or less, more preferably 1.7% by mass or less, and further preferably 1.5% by mass or less. If the content of 1,2-vinyl bond is too large, the resilience may decrease.

The high cis polybutadiene is preferably synthesized with a rare earth element catalyst, and in particular, the use of a neodymium catalyst using a neodymium compound which is a lanthanum series rare earth element compound has a high content of 1,4-cis bond. , 1,2-vinyl bond is preferable because a polybutadiene rubber having a low content can be obtained with excellent polymerization activity.

As the high cis polybutadiene, the molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) is preferably 2.0 or more, more preferably 2.2 or more, still more preferably 2. It is 4 or more, most preferably 2.6 or more, preferably 6.0 or less, more preferably 5.0 or less, still more preferably 4.0 or less, and most preferably 3.4 or less. If the molecular weight distribution (Mw / Mn) of high cis polybutadiene is too small, workability may decrease, and if it is too large, resilience may decrease. The molecular weight distribution was determined by gel permeation chromatography (manufactured by Tosoh Corporation, "HLC-8120GPC") using a differential refractometer as a detector, column: GMHHXL (manufactured by Tosoh Corporation), column temperature: 40 ° C., mobile phase. : It is a value calculated under the condition of tetrahydrofuran and calculated as a standard polystyrene conversion value.

The high cis polybutadiene has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of preferably 30 or more, more preferably 32 or more, still more preferably 35 or more, preferably 140 or less, and more preferably. It is 120 or less, more preferably 100 or less, and most preferably 80 or less. _{The Mooney viscosity (ML 1 + 4} (100 ° C.)) referred to in the present invention is a condition of using an L rotor, a preheating time of 1 minute, a rotor rotation time of 4 minutes, and 100 ° C. according to JIS K6300. It is a value measured below.

((B) Co-crosslinking agent)
The co-crosslinking agent (b) is a complex having a carboxylate as a ligand, and contains a complex represented by the general formula (1) and / or a complex represented by the general formula (2).

［式（１）中、Ｍ¹は同一または異なって金属原子であり、Ｌ¹は構造式（３）で表されるカルボキシレートである。
式（２）中、Ｍ²は同一または異なって金属原子であり、Ｌ²は構造式（３）で表されるカルボキシレート、ｘは１以上の整数である。
式（３）中、Ｒは、水素原子、炭素数１〜１８のアルキル基、炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基であり、破線は共鳴構造を示す。
式（１）および式（２）において、複数存在するＲは、それぞれ同一でも異なっていてもよい。ただし、式（１）および式（２）において、Ｒのうち少なくとも１個は炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基である。]

[In the formula (1), M ¹ is the same or different metal atom, and L ¹ is the carboxylate represented by the structural formula (3).
In formula (2), M ² is the same or different metal atom, L ² is a carboxylate represented by structural formula (3), and x is an integer of 1 or more.
In the formula (3), R is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms, and the broken line indicates a resonance structure.
In the formulas (1) and (2), the plurality of Rs existing may be the same or different. However, in the formulas (1) and (2), at least one of R is an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms. ]

Examples of the metal atoms (M ¹ , M ² ) include alkali metals such as lithium, sodium, potassium, rubidium and cesium; alkaline earth metals such as calcium, strontium and barium; scandium, titanium, vanadium, chromium and manganese. , Iron, cobalt, nickel, copper, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, hafnium, tantalum, tungsten, renium, osmium, iridium, platinum, gold and other transition metals; , Aluminum, zinc, gallium, cadmium, indium, tin, tallium, lead, bismuth, polonium and other base metals. The metal atom may be used alone or in combination of two or more. Among these, the metal atom preferably has an oxidation number of +2, and more preferably beryllium, magnesium, calcium, zinc, barium, cadmium, and lead. In the formulas (1) and (2), the plurality of existing metal atoms (M ¹ , M ² ) may be the same or different, but it is preferable that they are all the same.

Examples of the alkyl group having 1 to 18 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group and a tridecyl group. Examples thereof include a group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group and an octadecyl group. The alkyl group having 1 to 18 carbon atoms may be linear, branched or cyclic, but linear is preferable.

Examples of the alkenyl group having 2 to 18 carbon atoms include an ethenyl group (vinyl group), a 1-propenyl group, a 2-propenyl group, an isopropenyl group, a 3-butenyl group, a 4-pentenyl group, a 5-hexenyl group, and 6 -Heptenyl group, 7-octenyl group, 8-nonenyl group, 9-decenyl group, 10-undecenyl group, 11-dodecenyl group, 8-tridecenyl group, 12-tridecenyl group, 13-tetradecenyl group, 8-pentadecenyl group, 14 Examples thereof include a-pentadecenyl group, a 15-hexadecenyl group, an 8-heptadecenyl group, a 10-heptadecenyl group, a 16-heptadecenyl group and a 17-octadecenyl group. The alkenyl group having 2 to 18 carbon atoms may be linear or branched, but linear is preferable. As the alkenyl group having 2 to 18 carbon atoms, one having one carbon-carbon double bond is preferable, and one having a carbon-carbon double bond at the terminal is preferable. The alkenyl group preferably has 8 or less carbon atoms, more preferably 6 or less, and further preferably 4 or less. As the alkenyl group having 2 to 18 carbon atoms, a vinyl group, an isopropenyl group, a 1-propenyl group and a 2-propenyl group are preferable.

Examples of the alkynyl group having 2 to 18 carbon atoms include an ethynyl group, a 1-propynyl group, a 2-propenyl group, a 3-butynyl group, a 4-pentynyl group, a 5-hexynyl group, a 6-heptinyl group and a 7-octynyl group. , 8-nonynyl group, 9-decynyl group, 10-undecynyl group, 11-dodecynyl group, 8-tridecynyl group, 12-tridecynyl group, 13-tetradecynyl group, 8-pentadecynyl group, 14-pentadecynyl group, 15-hexadecynyl group. , 8-Heptadecinyl group, 10-Heptadecinyl group, 16-Heptadecinyl group, 17-octadecynyl group. The alkynyl group having 2 to 18 carbon atoms may be linear or branched, but linear is preferable. As the alkynyl group having 2 to 18 carbon atoms, one having one carbon-carbon triple bond is preferable, and one having a carbon-carbon triple bond at the terminal is preferable. The alkynyl group preferably has 8 or less carbon atoms, more preferably 6 or less, and further preferably 4 or less. As the alkynyl group having 2 to 18 carbon atoms, an ethynyl group, a 1-propynyl group and a 2-propynyl group are preferable.

In formulas (1) and (2), at least one of R is an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms. That is, the complex represented by the formula (1) and the complex represented by the formula (2) have one or more carbon-carbon unsaturated bonds. Having one or more carbon-carbon unsaturated bonds can (a) react with the base rubber. In the formula (1), the number of the alkenyl group having 2 to 18 carbon atoms or the alkynyl group having 2 to 18 carbon atoms in the R is preferably 2 or more, more preferably 4 or more, still more preferably 5. More than one, especially preferably six. In the formula (2), the number of the alkenyl group having 2 to 18 carbon atoms or the alkynyl group having 2 to 18 carbon atoms in the R is preferably 2 or more, more preferably 4 or more, still more preferably 5. The number is 0 or more, particularly preferably 6 or more, and most preferably 8 or more. By having two or more carbon-carbon unsaturated bonds, (a) a plurality of molecular chains of the base rubber can be crosslinked.

In formulas (1) and (2), at least one of R is an alkenyl group having 2 to 18 carbon atoms having a carbon-carbon double bond at the terminal, or a carbon having a carbon-carbon triple bond at the terminal. It is preferably an alkynyl group of number 2-18. In the formula (1), the number of alkenyl groups having 2 to 18 carbon atoms having a carbon-carbon double bond at the end or alkynyl groups having 2 to 18 carbon atoms having a carbon-carbon triple bond at the end in the R. Is preferably 2 or more, more preferably 4 or more, still more preferably 5 or more, and particularly preferably 6 or more. In the formula (2), the number of alkenyl groups having 2 to 18 carbon atoms having a carbon-carbon double bond at the end or alkynyl groups having 2 to 18 carbon atoms having a carbon-carbon triple bond at the end in the R. Is preferably 2 or more, more preferably 4 or more, still more preferably 5 or more, particularly preferably 6 or more, and most preferably 8 or more.

In the formulas (1) and (2), the plurality of Rs existing may be the same or different, but it is preferable that they are all the same.

In the formula (2), the complex having x of 1 is the basic structural unit of the complex, and the complex having an integer of x of 2 or more is an integrated complex formed by accumulating the basic structural units. The x is an integer of 1 or more, and if x is 1 or more, a strong cross-linking point can be formed, and the durability of the obtained cross-linked rubber is improved. In the integrated complex (x is an integer of 2 or more), the upper limit of x is not particularly limited, but is preferably 100 million or less, more preferably 1 million or less, and further preferably 10,000 or less.

Examples of the complex represented by the formula (1) include a complex in which R is all vinyl groups and the metal atom (M ¹ ) is zinc (zinc oxocluster acrylate); R is all isopropenyl groups. Examples thereof include a complex (zinc oxocluster methacrylate) in which the metal atom (M ^{1) is zinc.}

Examples of the complex represented by the formula (2) include a complex in which R is all vinyl groups and the metal atom (M ² ) is zinc (zinc hydroxocluster acrylate); R is all isopropenyl groups. Examples thereof include a complex in which the metal atom (M ² ) is zinc (zinc methacrylate hydroxocluster).

The structure of the complex represented by the formula (1) is a structure in which four metal atoms (M ¹ ) are bonded to an oxygen atom (O) and a carboxylate group (formula (3)) is coordinated to the metal atoms. Can be mentioned. Examples of the arrangement mode of the four metal atoms bonded to the oxygen atom include a regular tetrahedron structure and a square planar structure. The coordination mode of the carboxylate group with respect to the metal atom is a bidentate coordination. The two oxygen atoms of the carboxylate group may be coordinated to different metal atoms or the same metal atom, but are preferably coordinated to different metal atoms.

The complex represented by the formula (1) is preferably a complex represented by the structural formula (4).

［式（４）において、Ｍ¹¹〜Ｍ¹⁴は同一または異なって金属原子であり、Ｒ¹¹〜Ｒ¹⁶は、それぞれ同一または異なって、水素原子、炭素数１〜１８のアルキル基、炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基を表す。Ｒ¹¹〜Ｒ¹⁶のうち少なくとも１個は炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基である。］

[In formula (4), M ^{11 to} M ¹⁴ are the same or different metal atoms, and R ^{11 to} R ¹⁶ are the same or different, respectively, a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and 2 carbon atoms. Represents an alkenyl group of ~ 18 or an alkynyl group of 2-18 carbon atoms. At ^{least one of R 11 to} R ¹⁶ is an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms. ]

In the structural formula (4), the bond with a broken line on the solid line indicates a hybrid bond of a carboxylate group. Further, in the structural formula (4), both the covalent bond and the coordination bond are shown by solid lines.

Examples of the metal atom represented by ^{M 11 to M 14} in the formula (4) include those similar to ^{M 1 in the formula (1).} Among these, the metal atom preferably has an oxidation number of +2, and more preferably beryllium, magnesium, calcium, zinc, barium, cadmium, and lead. The ^{metal atoms represented by M 11 to} M ¹⁴ may be different from each other, but it is preferable that they are all the same metal atom.

Examples of the alkyl group having 1 to 18 carbon atoms represented by ^{R 11 to} R ¹⁶ in the formula (4) are the same as those of R in the formula (1). The alkyl group having 1 to 18 carbon atoms may be linear, branched or cyclic, but linear is preferable.

Examples of the alkenyl group having 2 to 18 carbon atoms represented by ^{R 11 to} R ¹⁶ in the formula (4) are the same as those of R in the formula (1). The alkenyl group having 2 to 18 carbon atoms may be linear or branched, but linear is preferable. As the alkenyl group having 2 to 18 carbon atoms, those having a carbon-carbon double bond at the terminal are preferable. The alkenyl group preferably has 8 or less carbon atoms, more preferably 6 or less, and further preferably 4 or less. As the alkenyl group having 2 to 18 carbon atoms, a vinyl group, an isopropenyl group, a 1-propenyl group and a 2-propenyl group are preferable.

Examples of the alkynyl group having 2 to 18 carbon atoms represented by ^{R 11 to} R ¹⁶ in the formula (4) are the same as those in R in the formula (1). The alkynyl group having 2 to 18 carbon atoms may be linear or branched, but linear is preferable. The alkynyl group having 2 to 18 carbon atoms preferably has a carbon-carbon triple bond at the terminal. The alkynyl group preferably has 8 or less carbon atoms, more preferably 6 or less, and further preferably 4 or less. As the alkynyl group having 2 to 18 carbon atoms, an ethynyl group, a 1-propynyl group and a 2-propynyl group are preferable.

In the formula (4), ^{at least one of R 11 to} R ¹⁶ is an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms. The number of alkenyl groups having 2 to 18 carbon atoms or alkynyl groups having 2 to 18 carbon atoms in ^{R 11 to} R ^{16 is preferably 2 or more, more preferably 4 or more, still more preferably 5 or more.} , Most preferably six.

In the formula (4), ^{at least one of R 11 to} R ¹⁶ has an alkenyl group having 2 to 18 carbon atoms having a carbon-carbon double bond at the terminal or a carbon number having a carbon-carbon triple bond at the terminal. It is preferably 2 to 18 alkynyl groups. The number of alkenyl groups having 2 to 18 carbon atoms having a carbon-carbon double bond at the end or alkynyl groups having 2 to 18 carbon atoms having a carbon-carbon triple bond at the end in ^{R 11 to} R ^{16 is determined.} Two or more are preferable, four or more are more preferable, five or more are more preferable, and six are most preferable.

In the formula (4), R ^{11 to} R ¹⁶ may be the same or different, but it is preferable that they are all the same.

In the formula (4), R ^{11 to} R ¹⁶ are preferably vinyl groups or isopropenyl groups, and the metal atom preferably has an oxidation number of +2, more preferably zinc.

The complex represented by the formula (2) is preferably a complex having a structure represented by the structural formula (5).

［式（５）において、Ｍ²¹〜Ｍ²⁵は同一または異なって金属原子であり、Ｒ²¹〜Ｒ²⁸はそれぞれ同一または異なって、水素原子、炭素数１〜１８のアルキル基、炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基であり、ｘは１以上の整数である。Ｒ²¹〜Ｒ²⁸のうち少なくとも１個は炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基である。］

[In formula (5), M ^{21 to} M ²⁵ are the same or different metal atoms, and R ^{21 to} R ²⁸ are the same or different, respectively, a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and 2 to 2 carbon atoms. It is an alkenyl group of 18 or an alkynyl group having 2 to 18 carbon atoms, and x is an integer of 1 or more. At ^{least one of R 21 to} R ²⁸ is an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms. ]

In the above formula (5), atomic groups of adjacent constituent units are described outside the parentheses. In the structural formula (5), the bond with a broken line on the solid line indicates a hybrid bond of the carboxylate group. Further, in the structural formula (5), both the covalent bond and the coordination bond are shown by solid lines.

In the integrated complex (x is an integer of 2 or more), the upper limit of x is not particularly limited, but is preferably 100 million or less, more preferably 1 million or less, and further preferably 10,000 or less.

The integrated complex of the structural formula (5) has a three-dimensional structure represented by the following formulas (5-1) and (5-2). Formula (5-2) shows an ORTEP diagram (Oak Ridge Thermal-Ellipsoid Plot Program) of the crystal structure of the integrated complex. From these structural formulas, it can be seen that the integrated complex of the structural formula (5) has a three-dimensional structure in which four structural units are bonded to one structural unit.

Examples of the metal atom represented by ^{M 21 to M 25} in the formula (5) include those similar to ^{M 2 in the formula (2).} Among these, the metal atom preferably has an oxidation number of +2, and more preferably beryllium, magnesium, calcium, zinc, barium, cadmium, and lead. The ^{metal atoms represented by M 21 to} M ²⁵ may be different from each other, but it is preferable that they are all the same metal atom.

Further, the complex represented by the formula (2) is preferably a complex represented by the formula (6) when x is 1.

［式（６）において、Ｍ²¹〜Ｍ²⁵は同一または異なって金属原子であり、Ｒ²¹〜Ｒ²⁸はそれぞれ同一または異なって、水素原子、炭素数１〜１８のアルキル基、炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基を表す。Ｒ²¹〜Ｒ²⁸のうち少なくとも１個は炭素数２〜１８のアルケニル基または炭素数２〜１８のアルキニル基である。］

[In formula (6), M ^{21 to} M ²⁵ are the same or different metal atoms, and R ^{21 to} R ²⁸ are the same or different, respectively, a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and 2 to 2 carbon atoms. It represents 18 alkenyl groups or alkynyl groups with 2 to 18 carbon atoms. At ^{least one of R 21 to} R ²⁸ is an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms. ]

In the structural formula (6), the bond with a broken line on the solid line indicates a hybrid bond of a carboxylate group. Further, in the structural formula (6), both the covalent bond and the coordination bond are shown by solid lines.

The complex represented by the formula (6) is a basic structural unit. The integrated complex (x is an integer of 2 or more) in the formula (5) and the complex (x is 1) represented by the formula (6) exist in an equilibrium state in a solvent. The abundance ratio changes depending on the solvent, temperature, and concentration. The complex represented by the formula (6) changes to an integrated complex (x is an integer of 2 or more) in a more stable state. For example, in the solid state, a more stable integrated complex (x is an integer of 2 or more) can be obtained. Further, in a low-concentration solution, the ratio of the complex of the formula (6) is high because it is stabilized by the solvent.

Examples of the metal atom represented by ^{M 21 to M 25} in the formula (5) or (6) include those similar to ^{M 2 in the formula (2).} Among these, the metal atom preferably has an oxidation number of +2, and more preferably beryllium, magnesium, calcium, zinc, barium, cadmium, and lead. The ^{metal atoms represented by M 21 to} M ²⁵ may be different from each other, but it is preferable that they are all the same metal atom.

Examples of the alkyl group having 1 to 18 carbon atoms represented by ^{R 21 to} R ²⁸ in the formula (5) or (6) are the same as those of R in the formula (2). The alkyl group having 1 to 18 carbon atoms may be linear, branched or cyclic, but linear is preferable.

Examples of the alkenyl group having 2 to 18 carbon atoms represented by ^{R 21 to} R ²⁸ in the formula (5) or (6) are the same as those of R in the formula (2). The alkenyl group having 2 to 18 carbon atoms may be linear or branched, but linear is preferable. As the alkenyl group having 2 to 18 carbon atoms, those having a carbon-carbon double bond at the terminal are preferable. The alkenyl group preferably has 8 or less carbon atoms, more preferably 6 or less, and further preferably 4 or less. As the alkenyl group having 2 to 18 carbon atoms, a vinyl group, an isopropenyl group, a 1-propenyl group and a 2-propenyl group are preferable.

Examples of the alkynyl group having 2 to 18 carbon atoms represented by ^{R 21 to} R ²⁸ in the formula (5) or (6) are the same as those in R in the formula (2). The alkynyl group having 2 to 18 carbon atoms may be linear or branched, but linear is preferable. The alkynyl group having 2 to 18 carbon atoms preferably has a carbon-carbon triple bond at the terminal. The alkynyl group preferably has 8 or less carbon atoms, more preferably 6 or less, and further preferably 4 or less. As the alkynyl group having 2 to 18 carbon atoms, an ethynyl group, a 1-propynyl group and a 2-propynyl group are preferable.

In the formula (5) or (6), ^{at least one of R 21 to} R ²⁸ is an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms. The number of alkenyl groups having 2 to 18 carbon atoms or alkynyl groups having 2 to 18 carbon atoms in ^{R 21 to} R ^{28 is preferably 2 or more, more preferably 4 or more, still more preferably 5 or more.} , Especially preferably 6 or more, and most preferably 8 or more.

In formula (5) or (6), ^{at least one of R 21 to} R ²⁸ is an alkenyl group having 2 to 18 carbon atoms having a carbon-carbon double bond at the terminal, or a carbon-carbon triple bond at the end. It is preferably an alkynyl group having 2 to 18 carbon atoms. The number of alkenyl groups having 2 to 18 carbon atoms having a carbon-carbon double bond at the end or alkynyl groups having 2 to 18 carbon atoms having a carbon-carbon triple bond at the end in ^{R 21 to} R ^{28 is determined.} The number is preferably 2 or more, more preferably 4 or more, still more preferably 5 or more, particularly preferably 6 or more, and most preferably 8 or more.

In the formula (5) or (6), R ^{21 to} R ²⁸ may be the same or different, but it is preferable that they are all the same.

In the formula (5) or (6), R ^{21 to} R ²⁸ are preferably vinyl groups or isopropenyl groups, and the metal atom preferably has an oxidation number of +2, more preferably zinc.

The co-crosslinking agent (b) contains a complex represented by the general formula (1) and a co-crosslinking agent other than the complex represented by the formula (2) to the extent that the effect of the present invention is not impaired. You may. Examples of the other co-crosslinking agent include α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof. The α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof has an action of cross-linking the rubber molecule by graft-polymerizing the base rubber molecular chain. Examples of the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid and the like.

Examples of the metal constituting the metal salt of α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms include monovalent metal ions such as sodium, potassium and lithium; magnesium, calcium, zinc, barium and cadmium. Divalent metal ions; trivalent metal ions such as aluminum; other ions such as tin and zirconium. The metal component can also be used alone or as a mixture of two or more kinds. Among these, as the metal component, divalent metals such as magnesium, calcium, zinc, barium, and cadmium are preferable. This is because the use of a divalent metal salt of α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms facilitates metal cross-linking between rubber molecules.

When the other cross-linking agent is used, the content of the complex represented by the formula (1) and the complex represented by the formula (2) in the (b) co-crosslinking agent is 5% by mass or more. It is preferably 20% by mass or more, more preferably 50% by mass or more, and further preferably 80% by mass or more. When the co-crosslinking agent (b) contains either the complex represented by the formula (1) or the complex represented by the formula (2), the content thereof may be adjusted within the above range. When the co-crosslinking agent (b) contains both the complex represented by the formula (1) and the complex represented by the formula (2), the total content of them can be adjusted within the above range. Good. It is also preferable that the rubber composition contains only the complex represented by the formula (1) and / or the complex represented by the formula (2) as the co-crosslinking agent (b).

The content of the (b) co-crosslinking agent in the rubber composition is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 3 parts by mass or more, based on 100 parts by mass of the (a) base material rubber. It is 5 parts by mass or more, preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and further preferably 40 parts by mass or less. When the content of the (b) co-crosslinking agent is less than 1 part by mass, the amount of the (c) cross-linking initiator described later must be increased in order to make the member formed from the rubber composition have an appropriate hardness. However, the resilience of the crosslinked rubber molded product tends to decrease. On the other hand, when the content of (b) the co-crosslinking agent exceeds 50 parts by mass, the member formed from the rubber composition tends to be too hard.

((C) Crosslink initiator)
The (c) cross-linking initiator is formulated to cross-link the (a) base rubber component. (C) Organic peroxide is suitable as the cross-linking initiator. Examples of the organic peroxide include peroxyketal, dialkyl peroxide, diacyl peroxide, and peroxy ester. Examples of the peroxyketal include 1,1-di (t-hexylperoxy) cyclohexane, 1,1-di (t-butylperoxy) cyclohexane, and n-butyl 4,4-di- (t-butylperoxy). Valerate), 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane and the like. Examples of the dialkyl peroxide include dicumyl peroxide, di (2-t-butylperoxyisopropyl) benzene, t-butylcumyl peroxide, and 2,5-dimethyl-2,5-di (t-butylperoxy). Examples thereof include hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexin-3, and di-t-butyl peroxide. Examples of the peroxy ester include 2,5-dimethyl-2,5-di (benzoyl peroxy) hexane, t-hexyl peroxybenzoate, t-butyl peroxybenzoate and the like. These organic peroxides may be used alone or in combination of two or more. Of these, dicumyl peroxide is preferably used.

The content of the (c) cross-linking initiator is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 0.7 with respect to 100 parts by mass of the (a) base material rubber. It is 5 parts by mass or more, preferably 50 parts by mass or less, more preferably 45 parts by mass or less, further preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less. If the content of the cross-linking initiator (c) is less than 0.2 parts by mass, the member formed from the rubber composition tends to be too soft and the resilience of the cross-linked rubber molded body tends to decrease, and the mass is 50. If it exceeds the portion, it is necessary to reduce the amount of the above-mentioned (b) co-crosslinking agent used in order to make the member formed from the rubber composition appropriate hardness, and the resilience of the crosslinked rubber molded body is insufficient. There is a risk of rubber or durability deterioration.

((D) Metal compound)
The rubber composition may further contain (d) a metal compound. Examples of the metal compound (d) include metal hydroxides such as magnesium hydroxide, zinc hydroxide, calcium hydroxide, sodium hydroxide, lithium hydroxide, potassium hydroxide and copper hydroxide; magnesium oxide and calcium oxide. , Metal oxides such as zinc oxide and copper oxide; metal carbon oxides such as magnesium carbonate, zinc carbonate, calcium carbonate, sodium carbonate, lithium carbonate and potassium carbonate. (D) The metal compound may be used alone or in combination of two or more. As the metal compound (d), a metal oxide is preferable, and at least one selected from the group consisting of magnesium oxide, calcium oxide and zinc oxide is preferable.

The content of the (d) metal compound in the rubber composition is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and further preferably 1 with respect to 100 parts by mass of the base rubber (a). It is 5.5 parts by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 10 parts by mass or less.

((E) Carboxylic acid and / or salt thereof)
The rubber composition may contain (e) a carboxylic acid and / or a salt thereof. By containing the carboxylic acid (e) and / or a salt thereof, the hardness distribution of the obtained crosslinked rubber molded product can be controlled. Examples of the (e) carboxylic acid and / or a salt thereof include an aliphatic carboxylic acid, an aliphatic carboxylic acid salt, an aromatic carboxylic acid and an aromatic carboxylic acid salt. The (e) carboxylic acid and / or salt can also be used alone or as a mixture of two or more. The carboxylic acid and / or the salt thereof includes the complex represented by the formula (1) used as the co-crosslinking agent (b), the complex represented by the formula (2), and the number of carbon atoms of 3 to 3. Eight α, β-unsaturated carboxylic acids and / or metal salts thereof are not included.

The aliphatic carboxylic acid is either a saturated aliphatic carboxylic acid (hereinafter, may be referred to as “saturated fatty acid”) or an unsaturated aliphatic carboxylic acid (hereinafter, may be referred to as “unsaturated fatty acid”). It may be. Further, the aliphatic carboxylic acid may have a branched structure or a cyclic structure. The number of carbon atoms of the saturated fatty acid is preferably 6 or more, preferably 24 or less, more preferably 18 or less, still more preferably 13 or less. The unsaturated fatty acid has preferably 6 or more carbon atoms, more preferably 7 or more, still more preferably 8 or more, preferably 24 or less, more preferably 18 or less, still more preferably 13 or less.

Examples of the aromatic carboxylic acid include those having a benzene ring in the molecule and those having a heteroaromatic ring in the molecule. The aromatic carboxylic acid may be used alone or in combination of two or more. Examples of the carboxylic acid having a benzene ring include an aromatic carboxylic acid in which a carboxyl group is directly bonded to the benzene ring, an aromatic-aliphatic carboxylic acid in which an aliphatic carboxylic acid is bonded to the benzene ring, and a carboxyl group in the condensed benzene ring. Examples thereof include a directly bonded polynuclear aromatic carboxylic acid and a polynuclear aromatic-aliphatic carboxylic acid in which an aliphatic carboxylic acid is bonded to a condensed benzene ring. Examples of the carboxylic acid having a heteroaromatic ring include those in which a carboxyl group is directly bonded to the heteroaromatic ring.

As the aliphatic carboxylic acid salt or the aromatic carboxylic acid salt, the above-mentioned salts of the aliphatic carboxylic acid or the aromatic carboxylic acid can be used. Examples of the cationic component of these salts include metal ions, ammonium ions, and organic cations. The cationic component can also be used alone or as a mixture of two or more kinds. Examples of metal ions include monovalent metal ions such as sodium, potassium, lithium and silver; divalent metal ions such as magnesium, calcium, zinc, barium, cadmium, copper, cobalt, nickel and manganese; aluminum and iron. Trivalent metal ions such as; other ions such as tin, zirconium, titanium and the like. Among these, as the metal ion, a divalent metal ion is preferable, and magnesium, zinc, and calcium are more preferable.

The organic cation is a cation having a carbon chain. The organic cation is not particularly limited, and examples thereof include organic ammonium ion. Examples of the organic ammonium ion include primary ammonium ions such as stearyl ammonium ion, hexyl ammonium ion, octyl ammonium ion, and 2-ethylhexyl ammonium ion, and secondary ammonium ions such as dodecyl (lauryl) ammonium ion and octadecyl (stearyl) ammonium ion. Ammonium ion; tertiary ammonium ion such as trioctylammonium ion; quaternary ammonium ion such as dioctyldimethylammonium ion and distearyldimethylammonium ion. These organic cations may be used alone or in combination of two or more.

Examples of the aliphatic carboxylic acid and / or a salt thereof include saturated fatty acids and / or salts thereof, unsaturated fatty acids and / or salts thereof. The saturated fatty acids and / or salts thereof are preferable, and caprylic acid (octanoic acid), pelargonic acid (nonanoic acid), capric acid (decanoic acid), lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, or these. Potassium salt, magnesium salt, calcium salt, aluminum salt, zinc salt, iron salt, copper salt, nickel salt, and cobalt salt are preferable. Examples of the unsaturated fatty acid and / or a salt thereof include palmitoleic acid, oleic acid, linoleic acid or arachidonic acid, or potassium salts, magnesium salts, calcium salts, aluminum salts, zinc salts, iron salts, copper salts and nickel salts thereof. Salts and cobalt salts are preferred.

Examples of the aromatic carboxylic acid and / or a salt thereof include benzoic acid, butyl benzoic acid, anisic acid (methoxy benzoic acid), dimethoxy benzoic acid, trimethoxy benzoic acid, dimethylamino benzoic acid, chlorobenzoic acid, and dichlorobenzoic acid. , Trichlorobenzoic acid, acetoxybenzoic acid, biphenylcarboxylic acid, naphthalenecarboxylic acid, anthracenecarboxylic acid, furancarboxylic acid or tenoyl acid, or potassium salts, magnesium salts, calcium salts, aluminum salts, zinc salts, iron salts, Copper salt, nickel salt and cobalt salt are preferable.

The content of the (e) carboxylic acid and / or its salt is, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 with respect to 100 parts by mass of the base material rubber (a). It is 5 parts by mass or more, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less.

((F) Organic sulfur compound)
The rubber composition may further contain (f) an organic sulfur compound. (F) The organic sulfur compound comprises, for example, thiophenols, thionaphthols, polysulfides, thiurams, thiocarboxylic acids, dithiocarboxylic acids, sulfenamides, dithiocarbamates, thiazoles and metal salts thereof. At least one compound selected from the group can be mentioned. (F) As the organic sulfur compound, an organic sulfur compound having a thiol group (-SH) or a metal salt thereof is preferable, and thiophenols, thionaphthols, or metal salts thereof are preferable.

Examples of thiols include thiophenols and thionaphthols. Examples of the thiophenols include thiophenols; 4-fluorothiophenol, 2,5-difluorothiophenol, 2,6-difluorothiophenol, 2,4,5-trifluorothiophenol, 2,4,5. , 6-Tetrafluorothiophenols, pentafluorothiophenols and other fluorophenols substituted with fluorophenols; 2-chlorothiophenols, 4-chlorothiophenols, 2,4-dichlorothiophenols, 2,5-dichlorothiophenols Thiophenols substituted with chloro groups such as phenol, 2,6-dichlorothiophenol, 2,4,5-trichlorothiophenol, 2,4,5,6-tetrachlorothiophenol, pentachlorothiophenol; 4 -Bromothiophenol, 2,5-dibromothiophenol, 2,6-dibromothiophenol, 2,4,5-tribromothiophenol, 2,4,5,6-tetrabromothiophenol, pentabromothiophenol, etc. Thiophenols substituted with the bromo group of; 4-iodothiophenol, 2,5-diiodothiophenol, 2,6-diiodothiophenol, 2,4,5-triiodothiophenol, 2,4 Thiophenols substituted with iodo groups such as 5,6-tetraiodothiophenols, pentaiodothiophenols; or metal salts thereof. As the metal salt, a zinc salt is preferable.

Examples of the thionaphthols (naphthalenethiols) include 2-thionaphthol, 1-thionaphthol, 1-chloro-2-thionaphthol, 2-chloro-1-thionaphthol, 1-bromo-2-thionaphthol, and 2 -Bromo-1-thionaphthol, 1-fluoro-2-thionaphthol, 2-fluoro-1-thionaphthol, 1-cyano-2-thionaphthol, 2-cyano-1-thionaphthol, 1-acetyl-2- Thionaphthol, 2-acetyl-1-thionaphthol, or metal salts thereof can be mentioned, with 2-thionaphthol, 1-thionaphthol, or metal salts thereof being preferred. The metal salt is preferably a divalent metal salt, more preferably a zinc salt. Specific examples of the metal salt include a zinc salt of 1-thionaphthol and a zinc salt of 2-thionaphthol.

The polysulfides are organic sulfur compounds having a polysulfide bond, and examples thereof include disulfides, trisulfides, and tetrasulfides. As the polysulfides, diphenyl polysulfides are preferable.

Examples of diphenyl polysulfides include diphenyl disulfide, bis (4-fluorophenyl) disulfide, bis (2,5-difluorophenyl) disulfide, bis (2,6-difluorophenyl) disulfide, and bis (2,4,5-). Trifluorophenyl) disulfide, bis (2,4,5,6-tetrafluorophenyl) disulfide, bis (pentafluorophenyl) disulfide, bis (4-chlorophenyl) disulfide, bis (2,5-dichlorophenyl) disulfide, bis ( 2,6-dichlorophenyl) disulfide, bis (2,4,5-trichlorophenyl) disulfide, bis (2,4,5,6-tetrachlorophenyl) disulfide, bis (pentachlorophenyl) disulfide, bis (4-bromophenyl) Disulfide, bis (2,5-dibromophenyl) disulfide, bis (2,6-dibromophenyl) disulfide, bis (2,4,5-tribromophenyl) disulfide, bis (2,4,5,6-tetrabromo) Phenyl) disulfide, bis (pentabromophenyl) disulfide, bis (4-iodophenyl) disulfide, bis (2,5-diiodophenyl) disulfide, bis (2,6-diiodophenyl) disulfide, bis (2,4) , 5-Triiodophenyl) disulfides, bis (2,4,5,6-tetraiodophenyl) disulfides, bis (pentaiodophenyl) disulfides and other diphenyl disulfides substituted with halogen groups; bis (4-methylphenyl) ) Disulfide, bis (2,4,5-trimethylphenyl) disulfide, bis (pentamethylphenyl) disulfide, bis (4-t-butylphenyl) disulfide, bis (2,4,5-tri-t-butylphenyl) Examples thereof include diphenyl disulfides substituted with alkyl groups such as disulfide and bis (penta-t-butylphenyl) disulfide.

Examples of thiurams include thiuram monosulfides such as tetramethylthium monosulfide, thiuram disulfides such as tetramethylthium disulfide, tetraethyl thiuram disulfide, and tetrabutyl thiuram disulfide, and thiuram tetrasulfides such as dipentamethylene thiuram tetrasulfide. Can be mentioned. Examples of thiocarboxylic acids include naphthalene thiocarboxylic acids. Examples of dithiocarboxylic acids include naphthalene dithiocarboxylic acids. Examples of sulfenamides include N-cyclohexyl-2-benzothiazolesulfenamide, N-oxydiethylene-2-benzothiazolesulfenamide, and N-t-butyl-2-benzothiazolesulfenamide. Can be mentioned.

(F) The organic sulfur compound can be used alone or in combination of two or more. (F) As the organic sulfur compound, thiophenols and / or a metal salt thereof, thionaphthols and / or a metal salt thereof, diphenyl disulfides, thiuram disulfides are preferable, and 2,4-dichlorothiophenol, more preferably. 2,6-difluorothiophenol, 2,6-dichlorothiophenol, 2,6-dibromothiophenol, 2,6-diiodothiophenol, 2,4,5-trichlorothiophenol, pentachlorothiophenol, 1- Thiophenol, 2-thionaphthol, diphenyl disulfide, bis (2,6-difluorophenyl) disulfide, bis (2,6-dichlorophenyl) disulfide, bis (2,6-dibromophenyl) disulfide, bis (2,6-di) Thiophenol) disulfide and bis (pentabromophenyl) disulfide.

The content of the (f) organic sulfur compound is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and 5.0 parts by mass with respect to 100 parts by mass of the (a) base rubber. The amount is preferably 2 parts or less, more preferably 2.0 parts by mass or less. If the content of the (e) organic sulfur compound is less than 0.05 parts by mass, the effect of adding the (e) organic sulfur compound cannot be obtained, and the resilience of the golf ball may not be improved. Further, if the content of the organic sulfur compound (e) exceeds 5.0 parts by mass, the amount of compression deformation of the obtained golf ball may increase and the resilience may decrease.

(Other ingredients)
If necessary, the rubber composition may contain additives such as pigments, fillers for weight adjustment, anti-aging agents, deliquescent agents, and softeners. Further, the rubber composition may contain a core of a golf ball or a rubber powder obtained by crushing scraps generated during core production.

Examples of the pigment to be blended in the rubber composition include a white pigment, a blue pigment, a purple pigment and the like. It is preferable to use titanium oxide as the white pigment. The type of titanium oxide is not particularly limited, but it is preferable to use the rutile type because of its good hiding property. The content of titanium oxide is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and more preferably 8 parts by mass or less with respect to 100 parts by mass of (a) base rubber. It is preferably 5 parts by mass or less.

It is also a preferred embodiment that the rubber composition contains a white pigment and a blue pigment. The blue pigment is blended to make the white color appear vivid, and examples thereof include ultramarine blue, cobalt blue, and phthalocyanine blue. Examples of the purple pigment include anthraquinone violet, dioxazine violet, and methyl violet.

The filler used in the rubber composition is mainly blended as a weight adjusting agent for adjusting the weight of the crosslinked rubber molded product, and may be blended as necessary. Examples of the filler include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder. The content of the filler is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, preferably 30 parts by mass or less, and 25 parts by mass with respect to 100 parts by mass of the base rubber (a). More preferably, it is 20 parts by mass or less, and further preferably 20 parts by mass or less. This is because if the content of the filler is less than 0.5 parts by mass, it becomes difficult to adjust the weight, and if it exceeds 30 parts by mass, the weight fraction of the rubber component tends to be small and the resilience tends to decrease.

The content of the anti-aging agent is preferably 0.1 part by mass or more and 1 part by mass or less with respect to 100 parts by mass of (a) base rubber. The content of the deliquescent agent is preferably 0.1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of (a) base rubber.

(Physical characteristics)
The crosslinked rubber has a storage elastic modulus E'(Pa) and a loss elastic modulus E "(Pa) measured using a dynamic viscoelastic device (tensile mode), and a slab hardness (shore C) X. The relationship of log (E'/ E " ² ) │ / X × 100 ≦ 5.7 is satisfied. The crosslinked rubber satisfying the above relationship has high hardness and excellent resilience performance.

The storage elastic modulus E'(Pa), the loss elastic modulus E "(Pa), and the slab hardness (shore C) X of the crosslinked rubber are │log (E'/ E" ² ) │ / X × 100 ≦ 5. It is preferable to satisfy the relationship of .6, and more preferably to satisfy the relationship of │log (E'/ E " ² ) │ / X × 100 ≦ 5.5.

The slab hardness of the crosslinked rubber is the shore C hardness, preferably 20 or more, more preferably 25 or more, further preferably 30 or more, preferably 98 or less, more preferably 96 or less, still more preferably 95 or less. .. If the slab hardness is Shore C hardness of 20 or more, the crosslinked structure is sufficiently constructed, the durability of the crosslinked rubber is improved, and if it is 98 or less, the resilience of the crosslinked rubber is further improved.

The storage elastic modulus E'(Pa) of the crosslinked rubber ^{is preferably 3.0 × 10 7} Pa or more, more preferably 5.0 × 10 ⁷ Pa or more, still more preferably 10 × 10 ⁷ Pa or more, and 40. It is preferably × 10 ⁷ Pa or less, more preferably 35 × 10 ⁷ Pa or less, and further preferably 30 × 10 ⁷ Pa or less. When the storage elastic modulus E'(Pa) is 3.0 × 10 ⁷ Pa or more, the resilience of the crosslinked rubber is further improved, and when it is 40 × 10 ⁷ Pa or less, the crosslinked rubber has an appropriate hardness.

The loss elastic modulus E ”(Pa) of the crosslinked rubber ^{is preferably 0.001 × 10 7} Pa or more, more preferably 0.005 × 10 ⁷ Pa or more, and further preferably 0.01 × 10 ⁷ Pa or more. , 3.0 × 10 ⁷ Pa or less, more preferably 1.0 × 10 ⁷ Pa or less, still more preferably 0.5 × 10 ⁷ Pa or less. The loss elastic modulus E ”(Pa) is 0. If it is 001 × 10 ⁷ Pa or more, the crosslinked structure is sufficiently constructed and the durability of the crosslinked rubber is improved, ^{and if it is 3.0 × 10 7} Pa or less, the crosslinked rubber has appropriate viscosity and repulsion. The elastic modulus is improved.

[Manufacturing method of rubber composition]
(Preparation of complex represented by formula (1))
The complex represented by the formula (1) is obtained by contacting a fatty acid metal salt with a metal oxide. As a method for producing the complex represented by the formula (1), for example, a step of dissolving or dispersing a fatty acid metal salt and a metal oxide in a first solvent and stirring the reaction solution (reaction step); Examples thereof include a production method having a step of removing an insoluble matter from the reaction solution (insoluble matter removing step); and a step of removing a solvent from the reaction solution (drying step).

(Reaction process)
In the reaction step, the fatty acid metal salt and the metal oxide are dissolved or dispersed in the first solvent, and the reaction solution is stirred. In this step, the fatty acid metal salt and the metal oxide are brought into contact with each other in a solvent to form a complex represented by the formula (1).

The fatty acid metal salt is not particularly limited as long as it can form a ligand represented by the formula (3). The fatty acid metal salt may be used alone or in combination of two or more.

Examples of the fatty acid constituting the fatty acid metal salt include saturated fatty acids having 1 to 19 carbon atoms and unsaturated fatty acids having 3 to 20 carbon atoms. Examples of the saturated fatty acids include methanic acid, ethane acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid and tetradecanoic acid. Examples thereof include pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid and nonadecanic acid. Examples of the unsaturated fatty acid include propenoic acid (acrylic acid), 2-methylpropa-2-enoic acid (methacrylic acid), 2-butenoic acid, 3-butenoic acid, 4-pentenoic acid, 5-hexenoic acid, and 6. −Heptenoic acid, 7-octenoic acid, 8-nonenic acid, 9-decenoic acid, 10-undecenoic acid, 11-dodecenoic acid, 12-tridecenoic acid, 9-tetradecenoic acid, 13-tetradecenoic acid, 14-pentadecenoic acid, 9 Unsaturated fatty acids with carbon-carbon double bonds such as −hexadecenoic acid, 15-hexadecenoic acid, 16-heptadecenoic acid, 9-octadecenoic acid, 11-octadecenoic acid, 17-octadecenoic acid, 18-nonadecenoic acid; propic acid, 3-Buchiic acid, 4-Pentic acid, 5-Hexic acid, 6-Heptic acid, 7-Octic acid, 8-Nonic acid, 9-Decinic acid, 10-Undecic acid, 11-Dodecic acid, 12-Tridecic acid, 9-Tetradecic acid, 13-tetradecic acid, 14-pentadecic acid, 9-hexadecinic acid, 15-hexadecinic acid, 16-heptadecic acid, 9-octadecinic acid, 11-octadecinic acid, 17-octadecinic acid, 18-nonadecinic acid, etc. Examples thereof include unsaturated fatty acids having a carbon-carbon triple bond.

As the unsaturated fatty acid having a carbon-carbon double bond, one having one carbon-carbon double bond is preferable, and one having a carbon-carbon double bond at the terminal is preferable. As the unsaturated fatty acid having a carbon-carbon triple bond, one having one carbon-carbon triple bond is preferable, and one having a carbon-carbon triple bond at the terminal is preferable.

Examples of the metal atom constituting the fatty acid metal salt include alkali metals such as lithium, sodium, potassium, rubidium and cesium; alkaline earth metals such as calcium, strontium and barium; scandium, titanium, vanadium, chromium and manganese. Transition metals such as iron, cobalt, nickel, copper, ittrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, hafnium, tantalum, tungsten, renium, osmium, iridium, platinum, gold; beryllium, magnesium, Base metals such as aluminum, zinc, gallium, cadmium, indium, tin, tarium, lead, bismuth and polonium can be mentioned. Among these, as the metal atom, a metal atom capable of forming a divalent metal ion is preferable, and beryllium, magnesium, calcium, zinc, barium, cadmium, and lead are more preferable. The metal ions can also be used alone or as a mixture of two or more.

As the fatty acid metal salt, a metal salt of a divalent metal ion of a fatty acid is preferable, a metal salt of a divalent metal ion of an unsaturated fatty acid is more preferable, and a metal ion having a valence of acrylic acid or methacrylic acid is more preferable. A metal salt, particularly preferably zinc acrylate or zinc methacrylate.

When two or more kinds of the fatty acid metal salts are used in combination, the content of each fatty acid metal salt may be appropriately adjusted according to the desired complex. The content of unsaturated fatty acids in the fatty acids constituting the fatty acid metal salt is preferably 33 mol% or more, 50 mol% or more, and more preferably 66 mol% or more. It is also preferable that all the fatty acids constituting the fatty acid metal salt are unsaturated fatty acids. The content of unsaturated fatty acids having a carbon-carbon double bond in the fatty acids constituting the fatty acid metal salt is preferably 33 mol% or more, 50 mol% or more, and more preferably 66 mol% or more. It is also preferable that all the fatty acids constituting the fatty acid metal salt are unsaturated fatty acids having a carbon-carbon double bond. A plurality of types of fatty acids constituting the fatty acid metal salt may be used in combination, but one type is also preferable.

Examples of the fatty acid metal salt include one fatty acid and one metal ion; a plurality of fatty acids and one metal ion; one fatty acid and a plurality of metal ions. Aspects containing; Examples thereof include a plurality of types of fatty acids and a plurality of types of metal ions. Among these, an embodiment containing one type of fatty acid and one type of metal ion is preferable.

Examples of the metal oxide include alkali metal oxides such as lithium oxide, sodium oxide, potassium oxide, rubidium oxide, and cesium oxide; oxides of alkaline earth metals such as calcium oxide, strontium oxide, and barium oxide; Titanium oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, yttrium oxide, zirconium oxide, niobium oxide, molybdenum oxide, technetium oxide, ruthenium oxide, rhodium oxide, palladium oxide, silver oxide , Hafnium oxide, tantalum oxide, tungsten oxide, renium, osmium oxide, iridium oxide, platinum oxide, gold oxide and other transition metal oxides, berylium oxide, magnesium oxide, aluminum oxide, zinc oxide, gallium oxide, cadmium oxide, oxidation Examples thereof include oxides of base metals such as indium, tin oxide, tallium oxide, lead oxide, bismuth oxide, and polonium oxide. The metal oxide can also be used alone or as a mixture of two or more kinds. Among these, as the metal oxide, a divalent metal oxide is preferable, and beryllium oxide, magnesium oxide, calcium oxide, zinc oxide, barium oxide, cadmium oxide, and lead oxide are more preferable.

The combination of the fatty acid metal salt and the metal oxide is not particularly limited, but it is preferable that the metal constituting the fatty acid metal salt and the metal constituting the metal oxide are the same. As the combination of the fatty acid metal salt and the metal oxide, a combination of a fatty acid zinc salt and zinc oxide is preferable, a combination of an unsaturated fatty acid zinc salt and zinc oxide is more preferable, and zinc acrylate and / / Alternatively, it is a combination of zinc methacrylate and zinc oxide.

The first solvent is a solvent capable of dissolving the complex represented by the formula (1) produced by the reaction. Examples of the first solvent include dichloromethane, 1,2-dichloroethane, chloroform and the like.

The mixing ratio (molar ratio) (fatty acid / metal oxide) of the fatty acid in the fatty acid metal salt in the reaction solution to the metal oxide is preferably 1.0 or more, more preferably 1.5 or more, and further. It is preferably 2.0 or more, preferably 6.0 or less, more preferably 5.0 or less, still more preferably 4.0 or less. When the mixing ratio is within the above range, the desired complex can be produced in good yield.

The amount of the solvent used is preferably 1000 parts by mass or more, more preferably 2000 parts by mass or more, still more preferably 3000 parts by mass or more, based on 100 parts by mass of the total of the fatty acid metal salt and the metal oxide. It is preferably 10,000 parts by mass or less, more preferably 8,000 parts by mass or less, and further preferably 6000 parts by mass or less. When the amount of the solvent used is 1000 parts by mass or more, the yield of the complex is higher, and when it is 10,000 parts by mass or less, the amount of work during synthesis can be reduced.

The liquid temperature at the time of stirring the reaction solution is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, further preferably 20 ° C. or higher, preferably 100 ° C. or lower, more preferably 90 ° C. or lower, still more preferably. It is 80 ° C. or lower. When the liquid temperature is 0 ° C. or higher, the reaction rate is high and the yield of the complex is high, and when the liquid temperature is 100 ° C. or lower, the reaction of the unsaturated bond of the carboxylate is suppressed and the yield of the complex is higher. Become.

The time for stirring the reaction solution is preferably 1 hour or more, more preferably 3 hours or more, further preferably 12 hours or more, preferably 300 hours or less, more preferably 200 hours or less, still more preferably 100 hours or less. Is.

(Insoluble matter removal process)
In the insoluble matter removing step, the insoluble matter is removed from the reaction solution after the reaction. The insoluble matter is considered to be a metal oxide or a fatty acid metal salt that remains undissolved in the solvent. Further, when the liquid temperature at the time of reaction is high, it is considered that a polymer of an unsaturated fatty acid metal salt is also produced as an insoluble matter.

Examples of the method for removing the insoluble matter from the reaction solution after the reaction include a method of filtering the reaction solution.

(Drying process)
In the drying step, the solvent is removed from the reaction solution from which the insoluble matter has been removed. By removing the solvent, a mixture of the complex represented by the formula (1) and the fatty acid metal salt is obtained.

Examples of the method for removing the solvent include vacuum drying, heat drying and the like, and vacuum drying is preferable. The reaction solution may be heated when drying under reduced pressure. The temperature of the reaction solution at the time of drying is preferably 100 ° C. or lower, more preferably 80 ° C. or lower, and further preferably 60 ° C. or lower.

The production method may include a step for purifying the complex represented by the formula (1). If there is a step for purifying the complex, the insoluble matter removing step may be omitted. As a step for purification, in the above-mentioned production method, a method of removing the fatty acid metal salt from the reaction solution (a method including a purification step); the complex represented by the formula (1) and the fatty acid metal obtained by the above-mentioned production method. For the mixture with the salt, a method of reprecipitating (a method including a reprecipitation step); and the like can be mentioned. Among these, the method of removing the fatty acid metal salt from the reaction solution is preferable in the above-mentioned production method.

(Refining process)
In the purification step, in the above-mentioned production method, a second solvent is added to the reaction solution from which the insoluble matter has been removed, and the precipitate is removed. Impurities such as fatty acid metal salts are precipitated by adding a second solvent to the reaction solution. By removing this precipitate, the purity of the finally obtained complex represented by the formula (1) can be increased.

The second solvent is not particularly limited as long as it can selectively precipitate the fatty acid metal salt in the reaction solution. That is, the solubility of the complex represented by the formula (1) in the second solvent is higher than the solubility of the fatty acid metal salt in the second solvent. Examples of the second solvent include hydrocarbons such as hexane, pentane, cyclohexane, and heptane.

The amount of the second solvent added may be appropriately adjusted so that the fatty acid metal salt can be precipitated. The amount of the second solvent input is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 30 parts by mass or more, and 200 parts by mass with respect to 100 parts by mass of the amount of the first solvent used. It is preferably parts or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less.

Further, the fatty acid metal salt may be precipitated by removing a part of the first solvent and the second solvent after adding the second solvent. As a method for removing a part of the first solvent and the second solvent, drying under reduced pressure is preferable. The reaction solution may be heated when drying under reduced pressure. The temperature of the reaction solution at the time of drying is preferably 100 ° C. or lower, more preferably 80 ° C. or lower, and further preferably 60 ° C. or lower.

Examples of the method for removing the precipitated fatty acid metal salt include a method of filtering the reaction solution. From the reaction solution from which the precipitate has been removed, the complex represented by the formula (1) can be obtained by removing the first solvent and the second solvent in the drying step. The purification step may be performed a plurality of times depending on the desired purity of the complex represented by the formula (1).

(Reprecipitation process)
In the reprecipitation step, the mixture of the complex represented by the formula (1) obtained by the above production method and the fatty acid metal salt is reprecipitated. Specifically, after dissolving a mixture of the complex represented by the formula (1) obtained by the above production method and a fatty acid metal salt in a first solvent, a second solvent is added to this solution to add fatty acids. The metal salt is precipitated and the precipitate is removed.

As the first solvent and the second solvent used in the reprecipitation step, those exemplified in the reaction step and the purification step can be used. Further, the amount of the second solvent used and the preferred embodiment of the method for removing the precipitate are the same as in the purification step. By removing the solvent after removing the precipitate, the complex represented by the formula (1) can be obtained. A preferred embodiment of the solvent removing method is the same as the drying step. The reprecipitation step may be performed a plurality of times depending on the desired purity of the complex represented by the formula (1).

(Preparation of complex represented by formula (2))
Examples of the method for producing the complex represented by the formula (2) include a method of reacting the complex represented by the formula (1) with water. Examples of the method of reacting the precursor with water include a method of exposing the complex represented by the formula (1) to a high humidity atmosphere. The humidity of the high humidity atmosphere is preferably 40% RH or more, more preferably 50% RH or more, and even more preferably 60% RH or more. The temperature (air temperature) of the high humidity atmosphere is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, further preferably 20 ° C. or higher, preferably 100 ° C. or lower, more preferably 80 ° C. or lower, still more preferable. Is 60 ° C. or lower.

[Preparation of rubber composition]
The rubber composition comprises (a) a base rubber, (b) a co-crosslinking agent, (c) a cross-linking initiator,, if necessary, (d) a metal compound, (e) a carboxylic acid and / or a salt thereof, (f). ) It is obtained by mixing and kneading an organic sulfur compound and other additives. The kneading method is not particularly limited, and for example, a known kneading machine such as a kneading roll, a Banbury mixer, or a kneader may be used.

[Cross-linked rubber]
The crosslinked rubber of the present invention is characterized in that it is formed from the rubber composition. The crosslinked rubber can be obtained by molding the kneaded rubber composition in a mold. The molding temperature is preferably 120 ° C. or higher, more preferably 150 ° C. or higher, and preferably 250 ° C. or lower. The molding pressure is preferably 2.9 MPa to 11.8 MPa. The molding time is preferably 10 to 60 minutes.

Examples of the use of the crosslinked rubber include sporting goods such as golf balls, tennis balls and grips; industrial goods such as hoses, belts and mats; soles, tires, resin additives, anti-vibration rubbers and anti-frilling materials. .. Examples of the golf ball include those having a member made of the crosslinked rubber.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples, and changes and embodiments within the scope of the present invention are all described in the present invention. Included within range.

[Evaluation method]
(1) Direct introduction-mass spectrometry (DI-MS)
For mass spectrometry, a mass spectrometer (SynaptG2-S type manufactured by Waters) was used.
Ionization method: Atmospheric pressure solid sample probe (ASAP)
Measurement mode: Pos., Neg.
Measuring range: m / z = 50 to 1500

(2) CHN Elemental Analysis Elemental analysis was performed using an organic trace element analyzer (Microcoder JM10 type manufactured by J-Science Labs).

(3) Zinc content measurement Zinc oxocluster acrylate (0.1171 g) or zinc hydroxocluster acrylate (0.1057 g) was weighed in a 100 ml beaker, and 50 ml of distilled water was added to dissolve it. To this, add 10 ml of sodium acetate-sodium acetate (pH 5) buffer solution, and add a few drops of XO indicator (Wako Pure Chemical Industries, Ltd., 0.1 w / v% xylenol orange solution, 0.1 g / 100 ml for titration = 0.001396M). Was added. Finally, it was prepared to 100 ml with distilled water. This adjusted solution was titrated with a 0.05 mol / l EDTA standard solution (manufactured by Dojin Chemical Co., Ltd.).

(4) Infrared spectroscopic analysis Infrared spectroscopic analysis is performed by the total internal reflection absorption measurement method (ATR method) using diamond as a prism for total internal reflection absorption measurement, and is carried out by a Fourier converted infrared spectrophotometer (manufactured by Perkin Elmer Co., Ltd.). This was done using "Spectrom One").

(5) Powder X-ray diffraction The X-ray diffraction measurement was performed using a wide-angle X-ray diffractometer (“RINT-TTR III type” manufactured by Rigaku Co., Ltd.). The measurement sample was pulverized using an agate mortar. The measurement conditions are as follows.
X-ray source; CuKα tube voltage-tube current; 50kV-300mA
Step width; 0.02deg.
Measurement speed; 5deg./min
Slit system; divergence-light reception-scattering: 0.5deg.-open-0.5deg.
Monochromator; Diffraction line curved crystal monochromator

(6) Slab hardness (Shore C hardness)
Using the rubber composition, a sheet having a thickness of about 2 mm was prepared by heat molding and stored at 23 ° C. for 2 weeks. The heat molding was performed at the temperatures and times shown in Tables 1 and 2. The hardness was measured using an automatic hardness tester (Digitest II, manufactured by H. Burleys) in a state where three or more of these sheets were stacked so as not to be affected by the measuring substrate or the like. As the detector, "Shore C" was used.

(7) Lübke-type rebound resilience test The rebound resilience test was performed according to JIS K6255 (2013). Using the rubber composition, a sheet having a thickness of about 2 mm was produced by heat molding. The heat molding was performed at the temperatures and times shown in Tables 1 and 2. A columnar test piece having a thickness of about 12 mm and a diameter of 28 mm was prepared by stacking six sheets punched from the sheet into a circular shape having a diameter of 28 mm. The test piece was stored at a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5%. The storage time is the crosslinked rubber No. 1, 2, 8-11 and 12-17 were crosslinked rubber No. 1 for 12 hours. 3 to 7 were set to 24 hours. The rebound resilience of the prepared test piece was measured using a Lübke-type rebound resilience test measuring device (manufactured by Ueshima Seisakusho Co., Ltd.). The flat portion of the overlapped test piece is supported by a mechanical fixing method, and the measurement conditions are a temperature of 23 ° C., a relative humidity of 50%, a striking end diameter of 12.50 ± 0.05 mm, and a striking mass of 0.35 ± 0. The impact speed was 01 kg and the striking speed was 1.4 ± 0.01 m / s.

(8) Measurement of storage elastic modulus E'(Pa) and loss elastic modulus E "(Pa) The storage elastic modulus E'(Pa) and loss elastic modulus E" (Pa) of the crosslinked rubber were measured under the following conditions.
Device: Dynamic viscoelasticity measuring device "Rheogel-E4000" manufactured by UBM
Measurement sample: A sheet having a thickness of 0.5 mm was prepared from the rubber composition by press molding under the conditions shown in Tables 1 and 2, and a sample piece was cut out from this sheet so as to have a width of 4 mm and a distance between clamps of 20 mm.
Measurement mode: Tension Measurement temperature: 24 ° C
Vibration frequency: 10Hz
Measurement strain: 0.05%

[Manufacture of zinc acrylate oxocluster]
Zinc oxide (0.125 kg, 1.54 mol) and zinc acrylate (0.955 kg, 4.60 mol) were added to 24.9 kg of dichloromethane, and the mixture was stirred at 40 ° C. for 48 hours. The solvent was refluxed. After 48 hours, the reaction solution was filtered to remove the precipitate. 9.83 kg of hexane was added to the filtrate, and the mixture was concentrated under reduced pressure until the volume of the filtrate was reduced to about 1/4. The concentrated solution was filtered and the filtrate was concentrated and dried to obtain zinc acrylate oxoclusters (615 g, yield 57% by mass).

The zinc oxocluster obtained above was subjected to mass spectrometry, elemental analysis, zinc content measurement, X-ray diffraction measurement, and infrared spectroscopic analysis. The results of each test are shown below.

High-resolution ASAP-MS (positive) spectrum measurement result
Positive ion HR-ASAP-MS m / z: 632.7715
[M-CH ₂ CHCOO] ⁺ (calcd. For C ₁₅ H ₁₅ O ₁₁ Zn ₄ 632.7707 Δ1.2ppm
High-resolution ASAP-MS (negative) spectrum measurement results
Negative ion HR-ASAP-MS m / z: 735.7762
[M + O ₂ ] ^- (calcd. For C ₁₈ H ₁₈ O ₁₅ Zn ₄ 735.7740 Δ2.9ppm

Anal. Calcd for C ₁₈ H ₁₈ O ₁₃ Zn ₄ : C, 30.71; H, 2.58. Found: C, 30.72; H, 2.50.

IR spectrum ^{peaks: 520cm -1, 600cm -1, 675cm} -1, 828cm -1, 968cm -1, 1067cm -1, 1276cm -1, 1370cm -1, 1436cm -1, 1572cm -1, 1643cm -1

The ASAP-MS spectra of zinc acrylate oxoclusters are shown in FIGS. 1 and 2. In addition, the anions [Zn ₄ O (OCOCHCH ₃ ) ₆ O ₂ ] ^(-) _{estimated from Zn 4} O (OCOCHCH ₂ ) ₆ and the cations [Zn ₄ O (OCOCHCH ₃ ) ₅ ] ⁽⁺⁾ The ASAP-MS spectrum simulation patterns are shown in FIGS. 1 and 2. As shown in FIGS. 1 and 2, the ASAP-MS spectrum showed a pattern similar to the simulation pattern. The experimental values obtained were 632.7715 and 735.7762, which were cations [Zn ₄ O (OCOCHCH ₃ ) ₅ ] ⁽⁺⁾ : C ₁₅ H ₁₅ O ₁₁ Zn ₄ estimated values 632.7707 and anions [Zn]. ₄ O (OCOCHCH ₃ ) ₆ O ₂ ] ^(-) : C ₁₈ H ₁₈ O ₁₅ Zn _{4 The} estimated value was 735.7740, which was very close to the value. The measured value of zinc content was 36.8% by mass, which was very close to the theoretical value of 37.2% by mass. From these results, it was confirmed that the _{zinc oxocluster acrylate prepared above is a compound represented by Zn 4} O (OCOCHCH ₂ ) _6.

From the result of elemental analysis, the carbon content of zinc oxocluster acrylate was 30.72% by mass and the hydrogen content was 2.50% by mass. The difference between the analysis result and the estimated value was that the carbon content was 0.01% by mass and the hydrogen content was 0.08% by mass. Since the atomic composition is very close to the estimated value, it was confirmed that the purity of the _{zinc acrylate oxocluster (Zn 4} O (OCOCHCH ₂ ) _{6) is very high.}

The IR spectrum is shown in FIG. 3, and the X-ray diffraction spectrum is shown in FIG. From the IR spectrum, absorption derived from the vinyl group of acrylate and absorption derived from the vibration of _{Zn 4 O were confirmed.} It was also confirmed that the coordination state of the carboxylate group was different from that of zinc bisacrylate. From the X-ray diffraction spectrum, it was confirmed that the zinc acrylate oxocluster has a crystal structure different from that of zinc bisacrylate.

[Manufacturing of zinc acrylate hydroxocluster]
Zinc oxide (0.125 kg, 1.54 mol) and zinc acrylate (0.955 kg, 4.60 mol) were added to 24.9 kg of dichloromethane, and the mixture was stirred at 40 ° C. for 48 hours. The solvent was refluxed. After 48 hours, the reaction solution was filtered to remove the precipitate. 9.83 kg of hexane was added to the filtrate, and the mixture was concentrated under reduced pressure until the volume of the filtrate was reduced to about 1/4. The concentrate was filtered and the filtrate was concentrated and dried to obtain a precursor of hydroxocluster acrylate. This precursor was gradually reacted with water in an environment of 20 ° C. to 30 ° C. and a humidity of 50% or more to obtain zinc acrylate hydroxoclusters (631 g, yield 57% by mass).

The zinc hydroxocluster obtained above was subjected to infrared spectroscopic analysis, elemental analysis, zinc content measurement, and X-ray diffraction measurement. The results of each test are shown below.

IR spectrum ^{peaks: 413cm -1, 469cm -1, 688cm} -1, 829cm -1, 972cm -1, 1068cm -1, 1274cm -1, 1372cm -1, 1435cm -1, 1522cm -1, 1568cm -1, 1644cm - ¹

Anal. Calcd for C ₂₄ H ₂₆ O ₁₈ Zn ₅ : C, 31.02; H, 2.82. Found: C, 30.36; H, 2.77.

The IR spectrum is shown in FIG. From the IR spectrum, absorption derived from the vinyl group of the acrylate and absorption derived from the vibration of _{(HO) Zn 3 were confirmed.} In addition, two types of absorption due to vibration of carboxylate groups with different coordination states were confirmed. The measured value of zinc content was 35.7% by mass, which was very close to the theoretical value of 35.2% by mass. From these results, it was confirmed that the zinc acrylate hydroxocluster prepared above is a compound represented by ((CH ₂ CHCOO) ₈ Zn ₅ (OH) ₂ ) _n (n is an integer of 1 or more)). ..

From the result of elemental analysis, the carbon content of zinc oxocluster acrylate was 30.36% by mass and the hydrogen content was 2.77% by mass. The difference between the analysis result and the estimated value was that the carbon content was 0.66% by mass and the hydrogen content was 0.05% by mass. Since the atomic composition is very close to the estimated value, _{the purity of the zinc acrylate hydroxocluster (((CH 2} CHCOO) ₈ Zn ₅ (OH) ₂ ) _n (n is an integer of 1 or more)) is It was confirmed that it was expensive.

The X-ray diffraction spectrum is shown in FIG. From the X-ray diffraction spectrum, it was confirmed that the zinc acrylate hydroxocluster has a crystal structure different from that of zinc bisacrylate.

The structure of the hydroxocluster acrylate was determined by single crystal X-ray structural analysis. As a result, it was found to have the structure shown in FIG. In FIG. 7, the arrow indicates the center of symmetry of this structure, and the portion surrounded by the solid line is a part of the adjacent molecules that interact with each other.

[Preparation of rubber composition]
Each raw material was kneaded with the formulations shown in Tables 1 and 2 to prepare a rubber composition. The material temperature at the time of kneading the rubber composition was 60 ° C. to 125 ° C.

The materials used in Tables 1 and 2 are as follows.
BR730: JSR, high cis polybutadiene (cis-1,4-bond content = 96% by mass, 1,2-vinyl bond content = 1.3% by mass, Mooney viscosity (ML _{1 + 4} (100 ° C.)) ) = 55, molecular weight distribution (Mw / Mn) = 3)
ZN-DA90S: Zinc acrylate (10% by mass zinc stearate coated product) manufactured by Nikko Techno Fine Chemical Co., Ltd.
Zinc oxide: "Ginmine R" manufactured by Toho Zinc Co., Ltd.
Dikmil Peroxide: "Park Mill (registered trademark) D" manufactured by NOF CORPORATION

Tables 1 and 2 show the slab hardness, storage elastic modulus, and loss elastic modulus of the crosslinked rubber prepared from each rubber composition. Tables 1 and 2 show the contents of the cross-linking components ((b) acrylate group in the co-crosslinking agent, (b) co-crosslinking agent and (d) metal in the metal compound) contained in each rubber composition. It was. Further, FIG. 8 shows the relationship between the slab hardness of the crosslinked rubber and │log (E'/ E " ² ) │. In the crosslinked rubber Nos. 1 to 11, the cocrosslinking agent (b) of the rubber composition is used. It contains a complex represented by (1) and / or a complex represented by the formula (2), and has a storage elastic modulus E'(Pa), a loss elastic modulus E "(Pa), and a slab hardness (shore C) X. This is the case where │log (E'/ E " ² ) │ / X × 100 ≦ 5.7 is satisfied. These crosslinked rubbers are also excellent in resilience performance.

Crosslinked rubber No. 12 to 17 are cases where the (b) co-crosslinking agent of the rubber composition does not contain the complex represented by the formula (1) and the complex represented by the formula (2). These crosslinked rubbers are described in the crosslinked rubber No. When designed to have the same hardness as 1 to 11, the resilience is inferior.

The crosslinked rubber of the present invention has high hardness and excellent resilience performance. Therefore, the crosslinked rubber of the present invention is used for sports equipment such as golf balls, tennis balls and grips; industrial products such as hoses, belts and mats; it can.

Claims (18)

It contains (a) base rubber, (b) co-crosslinking agent, (c) cross-linking initiator, and the (b) co-crosslinking agent is represented by the complex represented by the formula (1) and / or the formula (2). Formed from a rubber composition containing the complex to be
The storage elastic modulus E'(Pa) and the loss elastic modulus E'(Pa) measured using the dynamic viscoelastic device (tensile mode) and the slab hardness (shore C) X are │log (E'/. A crosslinked rubber characterized by satisfying the relationship of E " ^{2) │ / X × 100 ≦ 5.7.}

[In the formula (1), M ¹ is a metal atom having the same or different oxidation number of +2, ^{and L 1} is a carboxylate represented by the formula (3).
In the formula (2), M ² is a metal atom having the same or different oxidation number of +2 ^{, L 2} is a carboxylate represented by the formula (3), and x is an integer of 1 or more.
In the formula (3), R is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms, and the broken line indicates a resonance structure.
In the formulas (1) and (2), a plurality of M ¹ , M ² and R may be the same or different from each other. However, in the formulas (1) and (2), at least 4 of R have an alkenyl group having 2 to 8 carbon atoms having a carbon-carbon double bond at the terminal or a carbon number having a carbon-carbon triple bond at the terminal. 2 to 8 alkynyl groups . ] The crosslinked rubber according to claim 1, wherein the (b) co-crosslinking agent contains 5% by mass or more of the complex represented by the formula (1) and / or the complex represented by the formula (2). The crosslinked rubber according to claim 1 or 2, wherein at least 4 of R in the complex represented by the formula (1) and the complex represented by the formula (2) are vinyl groups or isopropenyl groups. The co-crosslinking agent (b) is at least one complex selected from the group consisting of a complex represented by the formula (4), a complex represented by the formula (5), and a complex represented by the formula (6). The crosslinked rubber according to any one of claims 1 to 3.

[In the formula (4), M ^{11 to} M ¹⁴ are the same or different metal atoms having an oxidation number of +2, ^{and R 11 to} R ¹⁶ are the same or different hydrogen atoms and carbon atoms 1 to 18 respectively. It represents an alkyl group, an alkenyl group having 2 to 18 carbon atoms, or an alkynyl group having 2 to 18 carbon atoms. At least four ^{of R 11 to} R ¹⁶ are alkenyl groups having 2 to 8 carbon atoms having a carbon-carbon double bond at the end or alkynyl groups having 2 to 8 carbon atoms having a carbon-carbon triple bond at the end . ]

[In formula (5), M ^{21 to} M ²⁵ are the same or different metal atoms having an oxidation number of +2, ^{and R 21 to} R ²⁸ are the same or different, hydrogen atoms and alkyl having 1 to 18 carbon atoms. A group, an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms, and x is an integer of 1 or more. At least four ^{of R 21 to} R ²⁸ are alkenyl groups having 2 to 8 carbon atoms having a carbon-carbon double bond at the end or alkynyl groups having 2 to 8 carbon atoms having a carbon-carbon triple bond at the end . ]

[In formula (6), M ^{21 to} M ²⁵ are the same or different metal atoms having an oxidation number of +2, ^{and R 21 to} R ²⁸ are the same or different, hydrogen atoms and alkyl having 1 to 18 carbon atoms. A group represents an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms. At least four ^{of R 21 to} R ²⁸ are alkenyl groups having 2 to 8 carbon atoms having a carbon-carbon double bond at the end or alkynyl groups having 2 to 8 carbon atoms having a carbon-carbon triple bond at the end . ] The crosslinked rubber according to any one of claims 1 to 4, wherein the base rubber (a) contains a diene rubber or a natural rubber. The item according to any one of claims 1 to 5, wherein the rubber composition contains 1 part by mass to 50 parts by mass of the (b) cocrosslinking agent with respect to 100 parts by mass of the (a) base material rubber. Crosslinked rubber. Claims 1 to 6 wherein the metal atom constituting the complex represented by the formula (1) and the complex represented by the formula (2) is berylium, magnesium, calcium, zinc, barium, cadmium, or lead . The crosslinked rubber according to any one item. The crosslinked rubber according to any one of claims 1 to 7, wherein the rubber composition further contains (d) a metal compound. The crosslinked rubber according to claim 8, wherein the metal compound (d) is at least one metal oxide selected from the group consisting of calcium oxide, zinc oxide and magnesium oxide. The crosslinked rubber according to claim 8 or 9, wherein the rubber composition contains (a) 0.5 parts by mass to 20 parts by mass of the metal compound with respect to 100 parts by mass of the base rubber. The crosslinked rubber according to any one of claims 1 to 10, wherein the rubber composition further contains (e) a carboxylic acid and / or a salt thereof. The crosslinked rubber according to claim 11, wherein the rubber composition contains (a) 1 part by mass to 30 parts by mass of carboxylic acid and / or a salt thereof with respect to 100 parts by mass of the base rubber. The crosslinked rubber according to claim 11 or 12, wherein the fatty acid constituting the (e) carboxylic acid and / or a salt thereof is a saturated fatty acid having 6 to 24 carbon atoms or an unsaturated fatty acid having 6 to 24 carbon atoms. The invention according to any one of claims 11 to 13, wherein the (e) carboxylic acid and / or a salt thereof is a fatty acid metal salt, and the metal ion constituting the fatty acid metal salt is a divalent metal ion. Crosslinked rubber. The crosslinked rubber according to any one of claims 1 to 14, wherein the rubber composition further contains (f) an organic sulfur compound. The crosslinked rubber according to claim 15, wherein the rubber composition contains (a) 0.05 parts by mass to 5.0 parts by mass of an organic sulfur compound with respect to 100 parts by mass of the base rubber. Claim 15 or 16 that the (f) organic sulfur compound is at least one compound selected from the group consisting of thiophenols, diphenyl disulfides, thionaphthols, thiuram disulfides, and metal salts thereof. The crosslinked rubber described in. A golf ball having a member made of the crosslinked rubber according to any one of claims 1 to 17.

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