JP2011012043A - New vulcanization accelerator imparting dynamic durability to vulcanized rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vulcanization accelerator imparting dynamic durability to a vulcanized rubber composition.SOLUTION: The rubber composition is obtained by compounding 100 pts.wt. of rubber with 0.5-20 pts.wt. of a compound represented by the formula (wherein Rto Rrepresent each the same or different aliphatic or aromatic hydrocarbon containing 1-18C alicycle; x represents an integer of ≥2 and ≤6; and n represents an integer of ≥1 and ≤3).

Description

  The present invention relates to a rubber vulcanization accelerator and relates to a technique for imparting dynamic durability to a vulcanized rubber composition.

  When vulcanizing the rubber composition, sulfur is not added or limited to a small amount. When a sulfur-donating vulcanizing agent and a vulcanizing accelerator are used in combination or a sulfur-donating vulcanizing accelerator is used, It is known that an improved vulcanized rubber composition can be obtained, which is called a sulfur-free vulcanization method, a low sulfur vulcanization method or an effective vulcanization method, and is widely used as a practical vulcanization method. Yes. Typical sulfur-donating vulcanization accelerators are thiuram di (poly) sulfide compounds, and sulfur-donating vulcanizing agents include dialkyldi (poly) sulfides, both of which are mono- or disulfide-type bridges. It is said that the formation of the structure contributes to the improvement of heat resistance of the vulcanized rubber composition. However, on the other hand, there is a defect derived from a crosslinked structure in which dynamic durability such as flex resistance is lowered, and it is difficult to achieve both heat resistance and dynamic durability, which is a technical problem.

  On the other hand, a vulcanizing agent for vulcanizing rubber with a flexible cross-linked structure has been developed as a means for satisfying this problem, that is, heat resistance and dynamic durability of the vulcanized rubber composition. The polysulfide polymer (chain polymer, cyclic polymer) to be used is the same. These vulcanize rubber compositions with mono- and disulfide-type crosslinked structures and dioxaoctanedithiol-type crosslinked structures, and the latter structure corresponds to a flexible crosslinked structure. An improvement in sex is achieved. However, these are vulcanizing agents and require a vulcanization accelerator separately.

JP 58-167634 A JP 58-122944

  An object of the present invention is to provide a vulcanization accelerator that improves the dynamic durability of a vulcanized rubber composition.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, by mixing 0.5 to 20 parts by weight of the compound represented by Chemical Formula 1 with respect to 100 parts by weight of rubber, the above-mentioned problems have been solved and the present invention has been completed.

（式中、Ｒ^１〜Ｒ^４は同一又は異なる炭素数１〜１８の脂環式を含む脂肪族又は芳香族の炭化水素基を示す。またｘは２以上６以下の整数，ｎは１以上３以下の整数を示す。）

(In the formula, R ^{1 to} R ⁴ represent the same or different aliphatic or aromatic hydrocarbon groups containing an alicyclic group having 1 to 18 carbon atoms. X is an integer of 2 to 6, and n is 1 or more. Indicates an integer of 3 or less.)

  According to the present invention, if a compound represented by Chemical Formula 1 is used as a vulcanization accelerator and a vulcanized rubber composition is obtained according to a general formulation, both heat resistance and dynamic durability can be achieved.

The infrared absorption spectrum chart of the compound represented by Chemical formula 2 is shown. The infrared absorption spectrum chart of the compound represented by Chemical formula 3 is shown.

Hereinafter, the present invention will be described in more detail with specific embodiments.
In the structural formula of the compound represented by Chemical Formula ¹ , R ^{1 to} R ⁴ represent the same or different aliphatic or aromatic hydrocarbon groups containing an alicyclic group having 1 to 18 carbon atoms. The amino group structure at both ends of the structure is preferably a dibenzylamino group, a di-2-ethylhexylamino group or the like because of the vulcanization promoting action. X is represented by an integer from 2 to 6. When x is 1, the crosslinking efficiency by dioxaoctanedithiol is lowered, and when it is 3 or more, the stability of the compound in the normal state is lowered. Therefore, x is most preferably 2. n is an integer from 1 to 3, and n is limited to 3 or less because the intermediate stress of the vulcanized rubber composition decreases as the value of n increases.

Since the compound represented by Chemical Formula 1 is structurally similar to a thiuram compound commercially available as a vulcanization accelerator, the vulcanization acceleration action can also be achieved by completely or partially substituting those compounds. it can. Specifically, 0.5 to 20 parts by weight of the compound of Chemical Formula 1 is blended with respect to 100 parts by weight of rubber, and sulfur for rubber, that is, cyclic sulfur (S ₈ ) or polysulfide-type insoluble sulfur is 0.01 to 1. Blend 5 parts by weight and vulcanize the rubber. If the compound of Chemical Formula 1 is less than 0.5 parts by weight, the crosslinking concentration by dioxaoctanedithiol decreases, and if the sulfur exceeds 1.5 parts by weight, the low sulfur vulcanization system deviates. It becomes difficult to achieve both dynamic durability and heat resistance of an object.

  In addition, those commercially available as rubber vulcanization accelerators, such as thiazole compounds, sulfenamide compounds, thiuram compounds, thiourea compounds, guanidine compounds, dithiocarbamates, xanthates, dithiophosphates, etc. are commonly used. There is no limitation in the case where it is used, and the combined use of a thiazole compound and a sulfenamide compound is preferable in terms of improving the physical properties of the vulcanized rubber composition.

  Other commercially available vulcanizing agents such as sulfur-donating dialkyl disulfide compounds and dialkyl polysulfide compounds, polyfunctional monomers such as bismaleimide compounds and acrylic or methacrylic acid metal salts are commonly used. There is no restriction in the range of use, and in particular, when it is necessary to improve the rubber hardness and intermediate stress of the vulcanized rubber composition by the sulfur-free vulcanization method, the combined use of a dialkyl disulfide compound or a dialkyl polysulfide compound is preferable.

  Examples of vulcanization aids include stearic acid, zinc oxide, and zinc stearate, which are preferably blended in an appropriate amount for the purpose of improving the efficiency of the vulcanization reaction.

  In addition, carbon black for rubber that is not directly involved in vulcanization, reinforcing agents such as silica, softeners such as organic and inorganic fillers, mineral oil and synthetic plasticizers, anti-aging agents, processing aids, and other auxiliary materials There is no particular limitation.

  Hereinafter, although an example is given and it explains still more concretely, of course, the present invention is not limited at all by the example.

Example 1
Synthesis example of compound represented by Chemical formula 2

  Dibenzylamine 19.73 g (100 mmol) and sodium hydroxide 4.00 g (100 mmol) were dissolved in 25 ml of water, and 8.00 g (10.5 mmol) of carbon disulfide was added dropwise. After stirring for 2 hours, the reaction solution was concentrated to obtain 27.44 g of a dithiocarbamate salt (yield 93.0%). 19.3 g (50 mmol) of 3,6-dioxaoctane-1,8-bis-thiosulfonate disodium salt is dissolved in 50 ml of water, 100 ml of toluene, 2.1 g (25 mmol) of sodium bicarbonate, 2.14 g of formalin ( 25 mmol) was added. Subsequently, an aqueous solution in which 14.75 g (50 mmol) of dithiocarbamate salt was dissolved in 50 ml of water was added dropwise and stirred for 12 hours. The organic phase was washed with water, dried over magnesium sulfate, and concentrated to obtain 12.04 g of Compound 2 (yield 66.4%). FIG. 1 shows an infrared absorption spectrum chart of the compound represented by Chemical Formula 2 obtained.

Example 2
Synthesis example of compound represented by Chemical formula 3

  24.15 g (100 mmol) of bis (2-ethylhexyl) amine and 4.00 g (100 mmol) of sodium hydroxide were dissolved in 50 ml of water, and 7.61 g (100 mmol) of carbon disulfide was added dropwise. After stirring for 10 minutes, 20 ml of methanol was added and stirred for 50 minutes. This reaction solution is designated as reaction solution A. 19.3 g (50 mmol) of 3,6-dioxaoctane-1,8-bis-thiosulfonate disodium salt is dissolved in 100 ml of water, 100 ml of toluene, 2.1 g (25 mmol) of sodium bicarbonate, 2.14 g of formalin ( 25 mmol) was added. Subsequently, the reaction solution A was stirred for 12 hours after dropping. The organic phase was washed with water, dried over magnesium sulfate, and concentrated to obtain 22.00 g of Compound 3 (yield 54.1%). FIG. 2 shows an infrared absorption spectrum chart of the compound represented by Chemical Formula 3 obtained.

Rubber test results of the compounds of Example 1 and Example 2 Table 1 shows the compounding and unvulcanized rubber test results.
Each compounding is carried out according to a general kneading method using a Banbury mixer and an open roll mill. Specifically, NR and carbon black and below, an anti-aging agent are added and kneaded in a Banbury mixer, and then sulfur is used in an open roll mill. A vulcanization accelerator was added.

  Each rubber composition obtained was subjected to a physical test method for unvulcanized rubber (JIS K6300), and the Mooney scorch test was measured with a Mooney viscometer manufactured by Toyo Seiki Seisakusho and vulcanized using a vibratory vulcanization tester. Manufactured by Alpha Technologies, Inc. D. R. Measured for 30 minutes using 2000.

From the measurement results shown in Table 1, it was confirmed that both Examples 1 and 2 exhibited a vulcanization promoting action [M _HF , tc (90)] and were relatively excellent in scorch stability (t ₅ ). .

Table 2 shows the vulcanized rubber test results.
Each obtained unvulcanized vulcanized rubber composition was vulcanized under predetermined conditions and then measured according to each vulcanized rubber test method (JIS K6251, 6252, 6253, 6257, 6260, 6263).

  From the results of the vulcanized rubber test shown in Table 2, it was confirmed that Examples 1 and 2 had a heat resistance equal to or higher than that of the Comparative Example, but the flex resistance was greatly improved. . Therefore, it was shown that the heat resistance and the dynamic durability can be achieved by using the compounds of the examples. Incidentally, in terms of compression set resistance and the like, only the rigid cross-linked form, that is, the mono- and disulfide cross-linked structure is advantageous, and the compound according to the present invention is not suitable for these requirements.

Claims (2)

A compound represented by formula 1.

(In the formula, R ^{1 to} R ⁴ represent the same or different aliphatic or aromatic hydrocarbon groups containing an alicyclic group having 1 to 18 carbon atoms. X is an integer of 2 to 6, and n is 1 or more. Indicates an integer of 3 or less.)   A rubber composition comprising 0.5 to 20 parts by weight of the compound represented by Chemical Formula 1 according to claim 1 with respect to 100 parts by weight of rubber.

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