TW201842030A - Additive for rubber, rubber composition, producing method of additive for rubber and rubber product - Google Patents

Abstract

The present invention provides an additive for rubber which can impart excellent heat resistance and durability, and which can be easily handled at the time of producing a rubber product. The additive for rubber of the present invention comprises a chain sulfide compound having a repeating unit (1) represented by the following formula. [In the formula, x is 2, 3 or 4, R1 and R2 are each independently a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, or a substituted or unsubstituted oxyalkylene group having 2 to 4 carbon atoms.].

Description

 Rubber additive, rubber composition, rubber additive manufacturing method, and rubber product  

The present invention relates to an additive for rubber, a rubber composition, a method for producing an additive for rubber, and a rubber product.

In order to improve the properties of rubber articles, it is known to use, for example, sulfur as a vulcanizing agent. In recent years, in order to improve the physical properties of rubber products, an additive containing benzothiazole (for example, Patent Document 1) or an additive containing a cyclic polysulfide (for example, Patent Document 2) has been disclosed.

 [Previous Technical Literature]    [Patent Literature]  

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei 11-293036.

Patent Document 2: Japanese Laid-Open Patent Publication No. 2014-210870.

However, additives containing a benzene-containing thiazole structure may have long-term adverse effects on, for example, organisms and plants due to their structure. Therefore, it is preferred to reduce the amount of the additive containing the benzene-containing thiazole structure. In addition, rubber products are required to have excellent heat resistance and mechanical properties depending on their use. Further, since the cyclic polysulfide-containing additive disclosed in Patent Document 2 has a small molecular weight, it is likely to generate an odor during production. Further, in the production step of the additive containing a cyclic polysulfide, a large amount of salt is generated as a by-product, so that the additive to be produced is also mixed with a salt, and the mechanical properties of the rubber are inferior. Further, since the cyclic polysulfide is a highly viscous oily substance, workability is deteriorated, and it is difficult to use it when manufacturing a rubber product.

An object of the present invention is to provide an additive for rubber which is excellent in heat resistance and durability and which is easy to handle when manufacturing a rubber product.

The inventors of the present invention have tried hard to review it in the past, and found that the rubber product obtained by using the rubber additive having a specific structure has excellent heat resistance and durability, and is easy to handle when manufacturing a rubber product by using the rubber additive. . That is, the present invention provides the invention described in the following items.

A rubber additive comprising a chain sulfur compound having a repeating unit (1) represented by the following formula (1).

Wherein x is 2, 3 or 4, and R ¹ and R ² are each independently a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, or a substituted or unsubstituted alkyl 2 to 4 alkyloxy group; .

2. The additive for rubber according to the above item 1, wherein the sulfur compound is 100 moles per unit of the total amount of the repeating unit (1), and the amount of the repeating unit (1) of x=3 is 45 moles. In parts or more, the number n of repeating units (1) is from 1 to 1,000.

3. The process according to item 1 or 2 of the rubber of the additive, wherein, R & lt ¹ and R ² of a substituted or unsubstituted alkylene group having a carbon number of 2-4.

The additive for rubber according to any one of the above items 1 to 3, wherein the sulfur compound is 100 moles in total of the amount of the repeating unit (1), and the repeating unit of x=3 (1) The amount is 50 moles or more.

The rubber additive according to any one of the above items 1 to 4, wherein the sulfur compound is a total of 100 mole parts relative to the amount of the repeating unit (1), and x = 2 repeating unit (1) The amount is 30 moles or less.

The additive for rubber according to any one of the above items 1 to 5, wherein the total amount of the sulfur compound is 100 moles with respect to the amount of the repeating unit (1), and the repeating unit of x=4 (1) The amount is 30 moles or less.

A rubber composition comprising the rubber additive according to any one of items 1 to 6, and a natural rubber and/or a synthetic rubber.

A method for producing a rubber additive according to any one of the items 1 to 6, wherein the method comprises the step of reacting a dithiol compound with sulfur dichloride.

A rubber product obtained by vulcanizing a rubber composition according to the above item 7.

According to the present invention, there is provided an additive for rubber which can impart excellent heat resistance and durability to a rubber product. Further, there is provided an additive for rubber which is easy to handle when manufacturing a rubber article.

Fig. 1 is a graph showing the vulcanization curve of the rubber composition of Example 1.

Fig. 2 is a graph showing the vulcanization curve of the rubber composition of Comparative Example 1.

In the present invention, the rubber additive contains a chain sulfur compound having a repeating unit (also referred to as a repeating unit (1)) represented by the formula (1).

Wherein x is 2, 3 or 4, and R ¹ and R ² are each independently a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, or a substituted or unsubstituted alkyl 2 to 4 alkylene oxide base. ]

In the present specification, the molar amount of "the amount of the repeating unit (1)" means the number of units (ratio) of x = 2, 3 or 4 which are present in the sulfur compound having the repeating unit (1). The chain sulfur compound having the repeating unit (1) will be described below.

In the formula (1), R ¹ and R ² are each independently a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, or a substituted or unsubstituted oxygen alkyl group having 2 to 4 carbon atoms. By making R ¹ and R ² into the above groups, the durability of the rubber product after crosslinking can be improved.

The aforementioned alkylene group having 2 to 4 carbon atoms may be substituted or unsubstituted, and is preferably unsubstituted. The substituent having a C 2 to 4 carbon alkyl group may, for example, be an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a carboxyl group, a halogen atom, an amine group, a decyl group or a cyano group. The nitro group, the pendant oxy group, the phenyl group and the like are preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

The above-mentioned alkylene group having 2 to 4 carbon atoms may be linear or branched, for example, an ethyl group, a propyl group, a n-butyl group, an isobutyl group or the like.

The above oxygen alkyl group having 2 to 4 carbon atoms may be substituted or unsubstituted, and is preferably unsubstituted. Examples of the substituent having an alkylene group having 2 to 4 carbon atoms include an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a carboxyl group, a halogen atom, an amine group, an anthracenyl group, and a cyano group. The nitro group, the pendant oxy group, the phenyl group and the like are preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

The above oxygen alkyl group having 2 to 4 carbon atoms is preferably -(CH ₂ )mO(CH ₂ )m-.

Wherein m is independently an integer of from 1 to 3 in each (CH ₂ ) unit. Each of the one oxygen alkyl groups may be the same or different. For example, the oxygen alkyl group is -CH ₂ CH ₂ -OCH ₂ CH ₂ -, -CH ₂ CH ₂ -OCH ₂ -, etc., preferably -CH ₂ CH ₂ -OCH ₂ CH ₂ -.

In the present invention, the above R ¹ and R ² may be the same or different, and are preferably the same from the viewpoint of crystallinity. By increasing the crystallinity, the obtained sulfur compound is liable to be in a powder state.

The above R ¹ and R ^{2 are} preferably a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, more preferably an unsubstituted alkylene group having 2 to 4 carbon atoms, and still more preferably an extended ethyl group.

The sulfur compound having the repeating unit (1) is chain-like (linear or branched). The terminal of the sulfur compound may be a hydrogen atom.

In the sulfur compound having the repeating unit (1) of the present invention, the number n of repeating units is preferably from 1 to 1,000. By making the number n of the repeating units from 1 to 1,000, the dispersibility of the rubber additive in the rubber composition is good. A preferred lower limit of the number n of the repeating units (1) contained in the sulfur compound having the repeating unit (1) is 2, more preferably 6, and still more preferably 10. Further, the upper limit of the number n of the repeating units (1) contained in the sulfur compound having the repeating unit (1) is preferably 800, more preferably 600, still more preferably 500.

The weight average molecular weight of the sulfur compound having the repeating unit (1) in the present invention is measured by GPC (gel permeation chromatography) and is usually 150 to 200,000, preferably 300 to 150,000, in terms of standard polystyrene. More preferably from 1,000 to 110,000, still more preferably from 2,000 to 90,000 (e.g., 5,000 to 75,000, 10,000 to 50,000, 15,000 to 40,000, etc.).

In the present invention, the rubber additive may contain any sulfur compound in addition to the sulfur compound of the repeating unit (1). The optional sulfur compound is a sulfur compound other than the sulfur compound having the repeating unit (1), and may be another chain-like or cyclic sulfur compound. For example, in the present invention, the rubber additive may have an integer (for example, x=5 or x=6, etc.) in which x is 0 or 5 or more in the formula (1), in addition to the sulfur compound having the repeating unit (1). A repeating unit of a chain sulfur compound.

In the present invention, the amount of the sulfur compound having the repeating unit (1) contained in the rubber additive is usually 75% by mass or more, preferably 90% by mass or more, based on the rubber additive. In the present invention, the rubber additive may be composed only of the sulfur compound having the repeating unit (1).

In the present invention, the amount of the repeating unit (1) of x = 3 is usually 45 moles per 100 parts by mole of the total amount of the repeating unit (1) contained in the sulfur compound having the repeating unit (1). the above.

By setting the amount of the repeating unit (1) of x = 3 to 45 mol parts or more, an additive for rubber which can provide more excellent heat resistance and durability can be obtained.

In the sulfur compound having the repeating unit (1), the total amount of the repeating unit (1) with respect to the repeating unit (1) is preferably 100 mol% or more, more preferably 50 mol parts or more, more preferably 55 moles or more, more preferably 60 moles or more, further preferably 75 moles or more. The upper limit of the amount of the repeating unit (1) of x = 3 is preferably 100 mole parts or less, more preferably 99 mole parts or less, still more preferably 95 mole parts or less, and particularly preferably 85 mole parts or less.

From the viewpoint of heat resistance, the content of the repeating unit (1) of x = 2 is preferably in a total amount of 100 moles relative to the total amount of the repeating unit (1) contained in the sulfur compound having the repeating unit (1). It is 30 moles or less, more preferably 25 moles or less. If it is the said range, the fall of bridge|crosslinking density can be reduced. It is preferably from 0.1 moles to 27.5 moles, more preferably from 0.1 moles to 25 moles, still more preferably from 1 mole to 25 moles, still more preferably from 2.5 to 25 moles. , especially good for 5 to 25 moles.

The content of the repeating unit (1) of x=4 is preferably 30 mol or less with respect to 100 parts by mole of the total amount of the repeating unit (1) contained in the sulfur compound having the repeating unit (1), and more preferably Good for 25 moles or less. If it is in the above range, the reduction by reduction can be reduced. More preferably from 0.1 moles to 25 moles, more preferably from 1 mole to 17.5 moles, still more preferably from 1 mole to 14.5 moles, and particularly preferably from 2.5 moles to 12.5 parts. Moer.

In the present invention, the amount of the repeating unit (1) contained in the sulfur compound having the repeating unit (1) is the amount of the repeating unit (1) contained in the sulfur compound having the repeating unit (1) The total of 100 moles, preferably x=2, of repeating unit (1) is from 1 mole to 25 moles, and x=3 of repeating unit (1) is from 45 moles to 95 Moer.

More preferably, it is 100 moles of the total amount of the repeating unit (1) contained in the sulfur compound having the repeating unit (1), and the amount of the repeating unit (1) of x=2 is 1 mole to 25 parts. For the molar fraction, the amount of the repeating unit (1) of x = 3 is from 55 moles to 95 moles.

In the present invention, in the sulfur compound having the repeating unit (1), the amount of the repeating unit (1) of x = 4 is preferably less than the amount of the repeating unit (1) of x = 2, more preferably x = 2 The amount of the repeating unit (1): the molar ratio of the amount of the repeating unit (1) of x = 4 is in the range of 10:1 to 1.1:1. By using the repeating unit (1) containing the molar ratio of the above x=2 and x=4, it is possible to obtain an additive for rubber which can impart more excellent durability and heat resistance.

In the present invention, in the sulfur compound having the repeating unit (1), the amount of the repeating unit (1) in which x = 2 and x = 4 is determined such that the amount of the repeating unit (1) of x = 3 is within the above range. .

When the amount of the repeating unit (1) is in the above range, an additive for rubber which can impart more excellent heat resistance and can provide more excellent durability can be obtained. Further, an additive for rubber which is improved in sulfur reduction resistance can be obtained.

In the present invention, the chain sulfur compound having the repeating unit (1) may further have a repeating unit (also referred to as a repeating unit (2)) represented by the formula (2).

[wherein, y is 0 or an integer of 5 or more, and R ¹ and R ² are each independently a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, or a substituted or unsubstituted carbon having 2 to 4 carbon atoms; Alkyl. ]

The sulfur compound having the repeating unit (1) is usually 100 moles per part of the amount of the repeating unit (1), and the amount of the repeating unit (2) is usually 50 mole parts or less, preferably 30 mole parts or less. More preferably, it is 25 moles or less, and more preferably 15 moles or less.

In the present invention, a method for producing a chain sulfur compound having a repeating unit (1) includes, for example, a step of reacting a dithiol compound with sulfur dichloride. More specifically, examples of the method for producing a sulfur compound having a repeating unit (1) include a solvent in which a dithiol compound represented by the following formula (A) and sulfur dichloride are preferably inert with respect to a reaction raw material. In the step of carrying out the reaction, the dithiol compound represented by the formula (A) is, for example, a bis(nonylalkyl) sulfide (for example, bis(2-mercaptoethyl) sulfide or the like), bis(nonylalkoxyalkyl). Sulfide, etc. Sulfur dichloride can be prepared by reacting sulfur monochloride with chlorine gas.

HS-R ¹ -SR ² -SH (A) wherein R ¹ and R ² are independently substituted or unsubstituted alkylene groups having 2 to 4 carbon atoms, or substituted or unsubstituted carbon numbers 2 to 4 Oxygen alkyl group. ]

When the above production method is used, the amount of sulfur chloride relative to the thiol group of the dithiol compound is adjusted, whereby the total of 100 moles of the amount of the above sulfur compound relative to the repeating unit (1) can be adjusted. 2, 3 or 4 of the repeat unit (1) of the moles. The sulfur dichloride may be used, for example, in an amount of 0.1 to 1.1 mol, preferably 0.15 to 0.75 mol, more preferably 0.22 to 0.60 mol, based on the thiol group 1 mol of the dithiol compound. By setting the above range, the total amount of the repeating unit (1) of x = 3 can be adjusted to be more than 45 moles of the preferred range with respect to the total of 100 moles of the amount of the repeating unit (1).

Examples of the inert solvent include hydrocarbon-based organic solvents such as hexane, benzene, toluene, and xylene; ether-based organic solvents such as diethyl ether and tetrahydrofuran; halogenated hydrocarbon-based organic solvents such as dichloromethane, chloroform, and monochlorobenzene; and acetonitrile. Wait.

The rubber additive of the present invention can be carried on cerium oxide as needed. Further, it is preferably used by diluting an organic compound or the like which does not inhibit the rubber additive effect such as oil.

The rubber additive of the present invention can be used as a vulcanizing agent which can improve the heat resistance of a rubber product and can impart excellent durability, depending on its excellent properties.

The method of using the rubber additive of the present invention is not particularly limited. For example, the rubber additive of the present invention is blended with natural rubber and/or synthetic rubber to be used as a rubber composition.

In the present invention, the rubber composition contains at least an additive for rubber containing the sulfur compound having the above repeating unit (1), and a rubber component belonging to natural rubber and/or synthetic rubber.

The rubber additive containing the sulfur compound having the repeating unit (1) is usually contained in an amount of from 0.5 to 20 parts by mass based on 100 parts by mass of the rubber component, and is preferably contained in the rubber composition from the viewpoint of heat resistance and durability. It is preferably 1 to 10 parts by mass, based on 1 to 15 parts by mass of the rubber additive. The aforementioned addition amount of the rubber additive can be appropriately selected depending on the type of natural rubber and/or synthetic rubber to be used and the desired physical properties.

 [rubber component]  

The rubber component is preferably natural rubber and/or synthetic rubber (especially natural rubber). The synthetic rubber is preferably a diene-based synthetic rubber. Examples of the diene synthetic rubber include polyisoprene synthetic rubber (IR), polybutadiene rubber (BR), styrene/butadiene copolymer rubber (SBR), and acrylonitrile-butadiene copolymer rubber. (NBR), chloroprene rubber (CR), butyl rubber (IIR), and the like. The rubber rubber or the diene-based synthetic rubber may be used singly or in combination of two or more.

 [Additives / Filling Materials]  

The rubber composition of the present invention contains a rubber additive containing the above-mentioned chain sulfur compound having a repeating unit (1), and a natural rubber and/or a synthetic rubber, and may contain a known additive and/or a filler.

In the rubber composition of the present invention, the total amount of the additive and/or the filler is preferably from 10 to 160 parts by mass based on 100 parts by mass of the rubber component. The additive and/or the filler may be used singly or in combination of two or more.

The aforementioned additives may be used in the art, and include, for example, a vulcanizing agent, a vulcanization accelerator, a vulcanization aid (vulcanization accelerator), an anti-aging agent, an ozone crack inhibitor, a heat resistance improver, and a plasticizer (softening). Agent), viscosity modifier, molecular weight regulator, stabilizer, processing aid, white filler, reactive monomer and foaming agent.

The vulcanizing agent is, for example, sulfur other than a sulfur compound having a repeating unit (1), a sulfur compound, an anthracene, a nitroso compound, a polyamine, an organic peroxide or the like. The vulcanizing agent to be used in combination may be used alone or in combination of two or more. It is possible to use only the sulfur compound having the repeating unit (1) as a vulcanizing agent.

The vulcanization accelerator may be, for example, anthracene, aldehyde-amine, aldehyde-ammonia, thiazole, sulfenamide, thiourea, thiuram, dithiocarbamate, xanthate Esters and the like. The vulcanization accelerator may be used alone or in combination of two or more.

In the rubber composition, the amount of the vulcanization accelerator is usually 0.1 to 15 parts by mass, preferably 0.3 to 10 parts by mass, more preferably 0.5 to 7.5 parts by mass, based on 100 parts by mass of the rubber component.

The vulcanization aid is, for example, a long-chain fatty acid having 12 or more carbon atoms such as stearic acid, oleic acid or palmitic acid, a metal oxide such as zinc oxide, magnesium oxide or lead oxide. One or more kinds of the above-mentioned vulcanization aids can be used. Particularly preferred is a combination of a long chain fatty acid and a metal oxide.

In the rubber composition, the amount of the vulcanization aid may be 0.1 to 15 parts by mass, preferably 0.3 to 10 parts by mass, more preferably 0.5 to 7.5 parts by mass, based on 100 parts by mass of the rubber component.

The anti-aging agent may be, for example, an amine, a quinoline, a hydroquinone derivative, a monophenol, a polyphenol, a thiobisphenol, a hindered phenol, a phosphite or the like. The anti-aging agent may be used alone or in combination of two or more.

In the rubber composition, the amount of the anti-aging agent is usually 0.1 to 10 parts by mass, preferably 0.3 to 5 parts by mass, per 100 parts by mass of the rubber component.

The plasticizer (softener) may be, for example, an alkane-based softener, a naphthenic-based softener, an aromatic softener, or the like. The plasticizer (softener) may be used alone or in combination of two or more.

In the rubber composition, the amount of the plasticizer (softener) is usually 0.1 to 15 parts by mass, preferably 0.3 to 7.5 parts by mass, based on 100 parts by mass of the rubber component.

The filler may be, for example, an inorganic filler such as cerium oxide or carbon black.

The cerium oxide may be, for example, a wet-type cerium oxide cerium oxide or a dry-type cerium oxide, and particularly preferably a wet-type cerium oxide cerium oxide.

In order to improve mechanical properties and improve workability, carbon black can be used, and a known carbon black having a range of I ₂ adsorption amount, CTAB specific surface area, N ₂ adsorption amount, DBP adsorption amount, or the like can be selected. The type of carbon black can be suitably selected, for example, from SAF, ISAF, ISAF-LS, HAF, HAF-HS, HAF-LS, and the like. From the viewpoint of abrasion resistance, it is preferably ISAF, SAF, HAF.

For the filler, for example, cerium oxide may be used alone or in combination with carbon black and cerium oxide.

In the rubber composition, the amount of the filler is usually 5 to 150 parts by mass, preferably 10 to 100 parts by mass, more preferably 30 to 80 parts by mass, per 100 parts by mass of the rubber component.

The rubber composition containing the sulfur compound having the repeating unit (1), the natural rubber and/or the synthetic rubber, and optionally other additives and/or fillers are kneaded by a known method to prepare the rubber composition of the present invention. . It is preferred to knead the rubber composition in a range of preferably from 20 to 100 ° C, more preferably from 20 to 80 ° C. By kneading in the above temperature range, it is possible to carry out the preparation without causing crosslinking by the rubber additive of the present invention.

The rubber additive of the present invention can impart excellent mechanical properties such as tensile stress, elongation at the time of cutting, compression set, and the like, and can impart excellent physical properties such as heat resistance, cold resistance, aging resistance, ozone resistance, and the like. It can also impart excellent electrical properties, oil resistance and chemical resistance.

The rubber composition of the present invention can be used as a raw material of various rubber products. The rubber composition of the present invention is subjected to a heat treatment or the like and vulcanized, whereby a rubber product having improved mechanical properties can be obtained. The rubber product includes, for example, an engine mount, a stabilizer bush, a suspension bush, and the like, which are used for vibration-proof rubber, automobile vehicles, and the like, and a hard disk of a computer. Controlling vibration damping dampers for general household electrical appliances such as dampers and washing machines, shock-absorbing (vibration) devices such as vibration-damping devices for buildings in the field of building houses, and vibration-damping devices, and even Including automotive parts, tires, shoes, hoses, belts, air springs, anti-slip sheets and other general and industrial products. The rubber composition of the present invention contains an additive for rubber containing a chain sulfur compound having a repeating unit (1), whereby it can have excellent heat resistance, durability, and mechanical properties, and is preferably applied to an automobile. Anti-vibration materials such as engine feet used in vehicles and the like.

(Example)

The invention will be more specifically described below by way of examples. In the examples, "parts" and "%" are based on a quality standard unless otherwise specified.

 (Synthesis Example 1)  

80 g of sulfur monochloride and 0.02 g of iron powder were placed in a 100 mL four-necked flask, and the liquid temperature was set to 20 °C. Next, while maintaining the liquid temperature at 20 ° C, 43 g of chlorine gas was blown for 3 hours. Thereafter, the reaction liquid was stirred at the same temperature for 2 hours. After stirring, the reaction liquid was filtered, whereby iron powder was removed to obtain 118 g of sulfur dichloride. In addition, as a result of analysis by GC (gas chromatography, manufactured by Shimadzu Corporation, column: TAKU-1 (filling material: SHIMALITE F), detector: TCD), sulfur dichloride contained 20% by mass of monochlorinated chlorine. Sulfur.

Next, 170 g (1.1 mol) of bis(2-mercaptoethyl) sulfide and 370 g of monochlorobenzene were placed in a 1000 mL four-necked flask, and the liquid temperature was set to 20 °C. Next, 112 g of sulfur dichloride obtained in the above step was added dropwise to the mixture of the above bis(2-mercaptoethyl) sulfide and monochlorobenzene while maintaining the liquid temperature at 20 ° C for 4 hours. The solvent was removed by distillation under reduced pressure from the obtained reaction liquid to obtain a sulfur compound solid having a repeating unit (1). The structure of the sulfur compound was confirmed by IR (manufactured by Thermo Nicolet Japan Co., Ltd., trade name: AVATAR360).

Further, the weight average molecular weight of the obtained sulfur compound was 20,000. The weight average molecular weight of the obtained sulfur compound is determined by the GPC method and is calculated based on standard polystyrene. The measurement conditions are as follows.

Device name: LC-10Asystem, manufactured by Shimadzu Corporation.

Column name: Linked to Shodex KF804, KF803, KF802 and KF801 (all manufactured by Showa Denko Co., Ltd.).

Lysis solution: tetrahydrofuran.

Column temperature: 40 ° C.

The ratio of each repeating unit in the obtained sulfur compound is 100 moles with respect to the total of each repeating unit of x=2 to 4 in the sulfur compound, and 15 moles of x=2 in the formula (1), In the formula (1), x = 3 is 75 mole parts, and in the formula (1), x = 4 is 10 mole parts. In addition, the ratio of each repeating unit in the sulfur compound was confirmed by IR (manufactured by Thermo Nicolet Japan Co., Ltd., trade name: AVATAR360).

 (Synthesis Example 2)  

80 g of sulfur monochloride and 0.02 g of iron powder were placed in a 100 mL four-necked flask, and the liquid temperature was set to 20 °C. Next, while maintaining the liquid temperature at 20 ° C, 30 g of chlorine gas was blown for 3 hours. Thereafter, the reaction liquid was stirred at the same temperature for 2 hours. After stirring, the reaction liquid was filtered, whereby iron powder was removed to obtain 110 g of sulfur dichloride. In addition, GC (gas chromatography, manufactured by Shimadzu Corporation, column: TAKU-1 (filling material: SHIMALITE F), detector: TCD) analysis results, sulfur dichloride containing 30% by mass of monochlorinated sulfur.

Next, 170 g (1.1 mol) of bis(2-mercaptoethyl) sulfide and 370 g of monochlorobenzene were placed in a 1000 mL four-necked flask, and the liquid temperature was set to 20 °C. Next, 112 g of sulfur dichloride obtained in the above step was added dropwise to the mixture of the above bis(2-mercaptoethyl) sulfide and monochlorobenzene while maintaining the liquid temperature at 20 ° C for 4 hours. The solvent was removed by distillation under reduced pressure from the obtained reaction liquid to obtain a sulfur compound solid having a repeating unit (1). The structure of the sulfur compound is confirmed by IR.

Further, the weight average molecular weight of the obtained sulfur compound was 25,000 in terms of standard polystyrene.

As a result of the above analysis, the ratio of each repeating unit in the obtained sulfur compound is 100 moles of the total of x repeating units of x=2 to 4 in the sulfur compound, and the repeating unit of x=2 (1) The amount is 20 moles, the amount of repeating unit (1) of x=3 is 65 mole parts, and the amount of repeating unit (1) of x=4 is 15 mole parts. Further, the ratio of each repeating unit in the sulfur compound was confirmed by IR.

 (Synthesis Example 3)  

170 g (1.1 mol) of bis(2-mercaptoethyl) sulfide and 370 g of monochlorobenzene were placed in a 1000 mL four-necked flask, and the liquid temperature was set to 20 °C. Next, 147 g of sulfur monochloride was added dropwise to the mixture of the above bis(2-mercaptoethyl) sulfide and monochlorobenzene while maintaining the liquid temperature at 20 ° C for 4 hours. The solvent was removed by distillation under reduced pressure from the obtained reaction liquid to obtain a sulfur compound solid having a repeating unit (1). The structure of the sulfur compound is confirmed by IR.

Further, the weight average molecular weight of the obtained sulfur compound was 30,000 in terms of standard polystyrene.

As a result of the above analysis, the ratio of each repeating unit in the obtained sulfur compound is 100 moles of the total of each repeating unit of x=2 to 4 in the sulfur compound, and the repetition of x=2 in the formula (1) The unit is 2 moles, the repeating unit of x=3 in the formula (1) is 23 mole parts, and the repeating unit of x=4 in the formula (1) is 75 mole parts. Further, the ratio of each repeating unit in the sulfur compound was confirmed by IR.

 (Examples 1 to 3, Comparative Example 1)  

Making rubber composition

Using the sulfur compounds obtained in the above Synthesis Example 1, Synthesis Example 2, and Synthesis Example 3, rubber compositions (Examples 1, 2, and 3, respectively) were prepared, and the properties as a vulcanizing agent were evaluated. A rubber composition (Comparative Example 1) was prepared as a comparative example, and sulfur was added as a rubber additive in place of the sulfur compound obtained in the synthesis example. Each of the rubber compositions was mixed and prepared according to the blending ratio of Table 1. Further, "TBBS" in the table is an abbreviation for N-(t-butyl)-2-benzothiazole sulfoximine, and "ODPA" is an abbreviation for octylated diphenylamine.

In the evaluation of the mechanical properties, a rubber test sample was produced from the obtained rubber composition in accordance with JIS K 6299-2012.

 [Evaluation of vulcanization reduction]  

The test method of the vulcanization characteristics by the vulcanization tester was measured in accordance with JIS K 6300-2-2001. More specifically, for the obtained rubber composition, a rotorless vulcanization tester is used as a rheometer according to JIS K 6300-2-2001, and the torque is plotted on the vertical axis and the vulcanization time is plotted on the horizontal axis at a predetermined test temperature. Vulcanization curve. Further, the test temperature of the composition containing natural rubber (NR) was set to 160 °C.

Fig. 1 shows the vulcanization curve of the rubber composition of Example 1, and Fig. 2 shows the vulcanization curve of the rubber composition of Comparative Example 1. The vulcanization curve of the rubber composition of Comparative Example 1 gradually decreased after the torque reached the peak value, and it was considered that vulcanization reduction occurred. On the other hand, in the vulcanization curve of the rubber composition of Example 1, no torque reduction was observed, and it was found that the rubber-reducing property was improved by the rubber additive of the present invention. The vulcanization curves of the rubber compositions of Example 2 and Example 3 also showed the same vulcanization curves as in Example 1.

 [Evaluation of mechanical properties]  

The tensile strength, 100% tensile stress, and elongation at the time of vulcanization rubber were measured in accordance with JIS K 6251-1993, and the hardness of the vulcanized rubber was measured in accordance with JIS K 6253-1997. Further, the test piece was a dumbbell-shaped No. 3 shape. The measurement results of the respective samples are shown in Table 1.

The aging test of each sample was carried out in accordance with JIS K 6257-1993. For example, the heat aging of a sample containing natural rubber (NR) is measured in an environment of 100 ° C for 72 hours.

Here, the "change amount (MPa)" and "change rate (%)" described in the table are calculated in accordance with JIS K 6257-1993.

The rubber additive of the present invention can impart excellent heat resistance and can impart excellent durability. Further, the rubber additive of the present invention does not produce or hardly causes sulfide reduction. Further, since the rubber additive of the present invention does not contain benzothiazole in the structure, the load on the environment can be reduced.

Further, the rubber product containing the rubber additive of the present invention may have excellent heat resistance and durability.

 (industrial use)  

The rubber additive of the present invention can impart excellent heat resistance, durability, and the like to a rubber product such as a tire.

Claims (9)

An additive for rubber containing a chain sulfur compound having a repeating unit (1) represented by the following formula (1), Wherein x is 2, 3 or 4, and R ¹ and R ² are each independently a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, or a substituted or unsubstituted alkyl 2 to 4 alkyloxy group; .  The rubber additive according to claim 1, wherein the sulfur compound has a total of 100 moles relative to the amount of the repeating unit (1), and the amount of the repeating unit (1) of x=3 is 45. Above the moles, the number n of repeating units (1) is from 1 to 1,000.   The rubber additive according to claim 1 or 2, wherein R ¹ and R ² are a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms.  The additive for rubber according to any one of claims 1 to 3, wherein, in the sulfur compound, a total of 100 moles and a repeating unit of x=3 with respect to the amount of the repeating unit (1) 1) The amount is 50 moles or more.    The additive for rubber according to any one of claims 1 to 4, wherein, in the sulfur compound, a total of 100 moles and a repeating unit of x=2 with respect to the amount of the repeating unit (1) 1) The amount is 30 moles or less.    The additive for rubber according to any one of claims 1 to 5, wherein, in the sulfur compound, a total of 100 moles and a repeating unit of x=4 with respect to the amount of the repeating unit (1) 1) The amount is 30 moles or less.    A rubber composition comprising the rubber additive according to any one of claims 1 to 6, and a natural rubber and/or a synthetic rubber.    A method for producing a rubber additive according to any one of claims 1 to 6, which has a step of reacting a dithiol compound with sulfur dichloride.    A rubber product obtained by vulcanizing a rubber composition as described in claim 7 of the patent application.