JPS6250350A - Rubber composition - Google Patents

Abstract

PURPOSE:To provide a rubber compsn. having excellent resistance to wear and discoloration by light and suitable for use as a soling material, by adding white carbon having a high pH, a relatively large quantity of sulfur and a small quantity of a glycol vulcanization promoter to a rubber component contg. polybutadiene rubber. CONSTITUTION:20-60pts.wt. white carbon (A) having a pH of 9-12, 2-3pts.wt. sulfur (B) and 0.5-5wt% (based on the quantity of component B) glycol vulcanization promoter (C) (e.g., diethylene glycol) are added to 100pts.wt. rubber component (D) composed of 30-100wt% polybutadiene rubber and 70-0wt% natural rubber or isoprene rubber to obtain the desired compsn. suitable examples of the polybutadiene rubber are cis-1,4-polybutadiene rubber having a cis-1,4- structure unit content of 80% or above and polybutadiene rubber contg. 1-20wt% syndiotactic 1,2-polybutadiene and having a cis-1,4-structure unit content of 60% or above.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rubber composition containing polybutane rubber as a main component, which has improved prevention of discoloration due to light and excellent abrasion resistance. The rubber composition of the present invention is particularly suitable for use as a forming material for light-colored rubber shoe soles such as those for sports shoes.

[Conventional technology]

Natural rubber, polyisoprene rubber, styrene-butadiene rubber, and polybutadiene rubber are mainly used as materials for forming rubber soles.

In addition, polybutadiene rubber is used as the main material when particularly abrasion resistance is required, such as in the case of roughened sports shoe soles.

Most of the soles are bright colors to match the colorful skin, and black (contains carbon blank as a filler) is rare. The fillers used in light color formulations are
These include hydrated silica, anhydrous silica, calcium carbonate, magnesium carbonate, clay, talc, etc., but silica-based fillers are used when wear resistance is required. This silica-based filler slows down the vulcanization rate because it has a low pH (usually p 15 to 6) and has a small particle size and high surface activity, so it adsorbs and fixes vulcanization-promoting particles.

Therefore, the conventional light color formulation mentioned above uses amine-based formulations.

A glycol-based vulcanization activator is added to increase the vulcanization rate.

[Problems to be Solved by the Invention] The rubber shoe soles made of the conventional light-colored compound as described above turn yellow when exposed to ultraviolet rays from fluorescent lights, sunlight, etc. while the product is on display at a store.
There was a problem that the product value would be lost.

Therefore, an object of the present invention is to provide a light-colored rubber composition that is improved in preventing discoloration due to light and has excellent abrasion resistance.

[Means for solving problems]

In order to achieve the above object, the present inventors investigated the causes of photodiscoloration for each of the conventional light-colored compound materials, and found that the causes of photodiscoloration were determined from the test results shown in Table 1 below. It was found that this is mainly due to sulfur vulcanization. In particular, the effects of vulcanization activators and sulfur are large, and in particular, amine compounds such as Acting SL (manufactured by Yoshitomi Pharmaceutical Co., Ltd.) are often used because vulcanization activators have a large effect.
It was discovered that this compound is the most important cause of photodiscoloration.

Notes 1 to 5 in Table 1 below are as follows.

Moreover, the unit of the blending amount is parts by weight.

Note 1: UBEPOL-VCR412 (manufactured by Ube Industries@) Note 2; Nibutsuru VN3 (manufactured by Nippon Sirikani Corporation) Note 3
Nizy 2-henzothiazyl disulfide Note 4: Tetramethylthiuram monosulfide Note 5 = Test conditions are as follows.

Vulcanization = 160℃ 10 minutes Discoloration: Sunshine Weather Meter WE-3UN-T
C (manufactured by Suga Test Instruments) Black panel temperature: 63℃ Exposure time without rain: 15
Time evaluation Nigerley scale (JIS L 0804) No.
1 Table As a result of further intensive research based on the above study results, the present inventors used white carbon with a high pH as a filler in order to reduce the amount of vulcanization activator added, which is the main cause of photodiscoloration. In addition, photodiscoloration can be improved by using diethylene glycol as a vulcanization activator and adding more sulfur than the usual amount (1 to 2 phr); It has been found that in addition to additives, process oil, vulcanization accelerator, and anti-aging agent affect photodiscoloration, but the extent of this effect is not very large.

The present invention was made based on the above findings, and includes 30 to 100% by weight of polybutadiene rubber, preferably 40 to 80% by weight.
Rubber component 1 consisting of 70% to 0% by weight, preferably 60% to 20% by weight of natural rubber or polyisoprene rubber
00 parts by weight, p) 19 to 12 white carbon 2
0 to 60 parts by weight, 2 to 3 parts by weight of sulfur, and 0.5 to 5 parts of the above white carbon amount of glycol-based vulcanization activator.
The present invention provides a rubber composition in which a heavy stirring percentage is added.

The rubber composition of the present invention improves wear resistance by using a certain amount of polybutadiene rubber, and reduces the amount of vulcanization activator added by using white carbon with a high pH as a filler. To improve the degree of discoloration (yellowing) caused by ultraviolet rays from fluorescent lamps, etc., and to increase the crosslinking density by using a glycol-based vulcanization activator and using a slightly larger amount of sulfur. This further improves the degree of discoloration.

The rubber composition of the present invention will be explained in detail below.

The rubber component in the present invention is polybutadiene rubber 30~
It consists of 100% by weight, preferably 40-80% by weight, and 70-0% by weight, preferably 60-20% by weight of natural rubber or polyisoprene rubber, although the entire amount of the rubber component may be polybutadiene rubber, If the blend ratio of polybutadiene rubber is too low, the abrasion resistance will be poor, so the amount of polybutadiene rubber used in the rubber component must be 30% by weight or more.

The above-mentioned polybutadiene rubber has a cis-1゜4-structure content of 80% or more, preferably 90% or more.
,4-polybutadiene rubber (hereinafter referred to as BR), or syndiotactic l,2-polybutadiene from 1 to 20
Polybutadiene rubber (hereinafter referred to as VCR) having a cis-1,4-structure content of 60% or more is suitable.

In addition, the white carbon with a pH of 9 to 12 used in the present invention is used as a filler, and unlike the conventionally used low pH white carbon, it does not slow down the vulcanization rate, so it is not the main cause of photodiscoloration. This white carbon can reduce the amount of a vulcanization activator added, and examples of this white carbon include Nibcil NA (manufactured by Nippon Shirikani Gyougyo ■) and Carplex 1120 (Jiotsugi!!).
Commercially available products such as Tokuseal S (manufactured by Tokuyama Soda), VitaSeal #1200 (manufactured by Tamoto Kagaku) can be used.

If the pH of the white carbon is less than 9, the vulcanization rate will be slow, so it is practically impossible to reduce the amount of vulcanization activator added, and furthermore, the degree of photodiscoloration caused by the effect of the vulcanization activator cannot be improved. . Furthermore, those having a pH exceeding 12 are difficult to manufacture and have a small effect on the vulcanization rate, making it impossible to further reduce the amount of the vulcanization activator, making them impractical.

The amount of white carbon added is 100% of the above rubber component.
20 to 60 parts by weight, preferably 30 to 5 parts by weight
It is 0 parts by weight. If the amount added is less than 20 parts by weight, wear resistance and tensile strength will be poor.

Moreover, if it exceeds 60 parts by weight, the viscosity when unvulcanized becomes too high, resulting in poor moldability.

The amounts of polybutadiene rubber and white carbon used above are based on the physical properties of rubber shoe soles, i.e. hardness is the most common 6.
0, tensile strength is 150Kg/ which is required for high quality shoe soles.
- or more, and the abrasion resistance is 0.1 by Akron abrasion tester.
cc/ less than 1000 times.

Furthermore, the glycol-based vulcanization activator used in the present invention is
A vulcanization activator that has less adverse effect on photodiscoloration than amine-based vulcanization activators, and preferred examples of this vulcanization activator include:
You can give him diethylene glycol.

The amount of the vulcanization activator added is 0.5 to 5% by weight, preferably 1 to 3% by weight, based on the amount of white carbon. If the amount added is less than 0.5% by weight, the vulcanization rate will be too slow. Moreover, if it exceeds 5% by weight, photodiscoloration becomes large.

The sulfur used in the present invention is used as a vulcanizing agent, and the amount used is 2 to 3 parts by weight per 100 parts by weight of the rubber component. By using a larger amount than that used in the rubber compounding, the crosslinking density is increased and the degree of photodiscoloration is further improved.

The rubber composition of the present invention may further contain a process oil, a vulcanization accelerator, and an anti-aging agent, if necessary.

As the process oil, any light-colored naphthenic or paraffinic oil can be used, but it is preferable to use a paraffinic oil from the viewpoint of preventing photodiscoloration. The preferred amount of this process oil added is 10% of the rubber component.
The hardness of the rubber composition after vulcanization is 5 to 20 parts by weight relative to 0 parts by weight, depending on the amount of white carbon.
It may be adjusted appropriately so that it falls within the range of 5 to 65.

Further, as the vulcanization accelerator, it is preferable to use a non-staining sulfenamide or thiazole type accelerator, and it is more preferable to use a thiuram type in combination with this as a secondary accelerator. The amount of the vulcanization accelerator to be added may be appropriately determined in consideration of the vulcanization production conditions (temperature: 1 hour).

In addition, as the anti-aging side, 1 to 1 to 100 parts by weight of non-staining hindered phenol is added to 100 parts by weight of the rubber component.
It is preferable to add 3 parts by weight.

In addition, to the rubber composition of the present invention, vulcanization aids such as zinc white and stearic acid, pigments such as zinc white and titanium white, etc. are added in amounts used in ordinary rubber compounding. can do.

For the rubber composition of the present invention, there are no particular restrictions on the mixing method and vulcanization method for the ingredients, and conventional methods can be used.

〔Example〕

EXAMPLES The present invention will be explained in more detail by giving examples and comparative examples of the present invention below.

In addition, various physical properties of the rubber compositions in the following Examples and Comparative Examples were measured as follows.

■Sulfur rubber hardness, length Measured according to JIS K6301.

According to Akron Abrasion BS 903, with a load of 6 bonds and a sample angle of 15°, after 2000 pre-slides, the wear loss (c
c) was measured.

According to JIS LO842, the black panel temperature was 63℃ and exposed for 15 hours without rain using a carbon arc sunshine weather meter (manufactured by Suga Test Instruments), and the degree of discoloration was determined by JIS LO842.
Evaluated on Grace Scale according to IS LO804.

Under these test conditions, there is no problem if the grade is 3 to 4 or higher on the grace scale.

Example 1 A rubber composition of the present invention was obtained in the following manner using the formulations shown in Table 2 below.

The ingredients other than the vulcanization accelerator and sulfur were mixed for 5 minutes using a B-type Banbury mixer. Next, a vulcanization accelerator and sulfur were added using a roll to obtain a rubber composition of the present invention.

Regarding this rubber composition, the various physical properties described above were measured.

The results of these measurements are shown in Table 2 below.

The test piece used for the measurement was a 2IIIIn thick sheet with a thickness of 16
It was produced by vulcanization at 0°C for 6 minutes. However, the vulcanization time for the test pieces subjected to the Akron abrasion test was 10 minutes.

Example 2 As shown in Table 2 below, a rubber composition of the present invention was obtained in the same manner as in Example 1, except that VCR was used instead of BR, and white carbon and a vulcanization activator were used.

Regarding this rubber composition, various physical properties were measured in the same manner as in Example 1. The results of these measurements are shown in Table 2 below.

Comparative Examples 1 and 2 As shown in Table 2 below, the same procedure as Example 1 was carried out except that all the rubber components were NR (natural rubber) or SBR (styrene-butadiene rubber) and the amount of vulcanization accelerator was changed. Rubber compositions were obtained respectively.

Regarding these rubber compositions, various physical properties were measured in the same manner as in Example 1. The results of these measurements are shown in Table 2 below.

Comparative Example 3 As shown in Table 2 below, white carbon was
A rubber composition was obtained in the same manner as in Example 1, except that the rubber composition was changed to that of Example 6 and the amount of the vulcanization activator was increased.

Regarding this rubber composition, various physical properties were measured in the same manner as in Example 1. The results of these measurements are shown in Table 2 below.

Comparative Example 4 As shown in Table 2 below, sulfur was added to 1.5 parts by weight/J
A rubber composition was obtained in the same manner as in Example 1, except for the following steps.

Regarding this rubber composition, various physical properties were measured in the same manner as in Example 1. The results of these measurements are shown in Table 2 below.

Notes 1 to 8 in Table 2 below are as follows.

Moreover, the unit of the blending amount is parts by weight.

Note 1: UBEPOL-BRloo (manufactured by Ube Industries) Note 2: LIBEPOL-VCR412 (manufactured by Ube Industries)
(Manufactured by Nippon Silkani Industry) Note 3: Nibusyl NA (Manufactured by Nippon Silikani Industry) Note 4 =
Nibcil VN3 (manufactured by Nippon Silikani Industry ■) Note 5 Nidiethylene glycol Note 6 -N-oxydiethylene-2-penzothiazyl sulfenamide Note 7: Tetramethylthiuram disulfide Note 8: Other compounding agents include the following: The ingredients were blended.

3 parts by weight of zinc white, 1 part by weight of stearic acid, 5 parts by weight of paraffin oil, 10 parts by weight of titanium white, anti-aging agent (BI
T) 2 parts by weight.

Table 2 [Effects of the Invention] The rubber composition of the present invention has improved prevention of discoloration due to light,
It also has excellent abrasion resistance, and is particularly suitable for use as a forming material for light-colored rubber shoe soles such as sports shoes.

Claims (2)

[Claims] (1) To 100 parts by weight of a rubber component consisting of 30 to 100% by weight of polybutadiene rubber and 70 to 0% by weight of natural rubber or polyisoprene rubber, 20 to 60 parts by weight of white carbon with a pH of 9 to 12 and 2 to 3 parts by weight of sulfur. parts by weight, and glycol-based vulcanization activator to 0 of the above white carbon amount.
．． A rubber composition containing 5 to 5% by weight. (2) The polybutadiene rubber is cis-1,4-polybutadiene rubber with a cis-1,4-structure content of 80% or more, or syndiotactic 1,2-polybutadiene of 1 to 2
The rubber composition according to claim 1, which is a polybutadiene rubber containing 0% by weight and having a cis-1,4-structure content of 60% or more.