JPH11246708A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber compsn. for improving such a base rubber in the stain resistance that is used in the base part of a pneumatic type cushion tire for an industrial vehicle having an external appearance according to a color specification such as white, green, etc. SOLUTION: A rubber compsn., comprising a blend of a rubber component of a styrene/butadiene copolymer rubber having 40-50 wt.% of a natural rubber and bonding styrene content; a carbon black as the reinforcing agent; a phenolic resin; and a hexamethylene tetramine of a hardener for said phenolic resin, is characterized in that an age resistor used for said rubber compsn. belongs to aromatic secondary amine-based and amine/keton-based ones.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The product of the present invention is used for a base portion of a pneumatic cushion tire for industrial vehicles (hereinafter, also simply referred to as a color tire) having a color specification such as white or green in appearance. The present invention relates to a rubber composition of a base rubber.

[0002]

2. Description of the Related Art A pneumatic cushion tire for an industrial vehicle having a color specification is a conventional solid tire for a forklift. The rubber of a pneumatic cushion tire for an industrial vehicle is colored rubber such as white or green. This is a color tire which is used in a clean factory such as an epoxy or acrylic resin floor such as a food factory, mainly to prevent floor stains and the like caused by ordinary black rubber during running.

[0003] Although it is a color tire, it is also a pneumatic cushion tire for industrial vehicles for forklifts, and is often used under severe conditions such as various types, high loads, stationary cutting, and is used for tread rubber, side rubber, etc. Uses a color rubber which is a rubber material such as an ordinary diene and uses a reinforcing agent such as white carbon. The base rubber inside the base portion surrounded by the color rubber is disclosed in Japanese Patent Application No. 9-25 / 1997.
As shown in Japanese Patent No. 2802, a rubber made of natural rubber and SBR having a large amount of bound styrene, containing a phenolic resin, and having high hardness, excellent bending resistance, etc., and high durability was used.

In order to maintain the durability of the rubber, 6C (N-phenyl-N '-(1,3-dimethylmethyl) -p is used as described in Japanese Patent Application No. 9-252802. -Phenylenediamine), a strong amine-based anti-aging agent is used in a large amount.
Heat resistance, ozone resistance, etc. were maintained, and it was possible to fulfill the function as a base rubber.

[0005]

However, these anti-aging agents have a contaminating property, and the anti-aging agent migrates to the color rubber with the passage of time, that is, the anti-aging agent migrates and contaminates. The color changes to a brownish color, which is a very undesirable condition.

Without the use of an anti-aging agent, no contamination occurs, but an ozone-deteriorating crack is generated in a short period of time. In terms of physical properties, not only flex resistance and heat resistance but also elongation, which is another basic physical property of rubber, is obtained. In addition, deterioration of tensile strength, tear strength and the like also progresses, and the durability of the rubber is rapidly lost, so that the tire cannot function as a base rubber. There are also non-staining phenolic and other antioxidants, but their deterioration prevention performance is so small that they are not suitable for use.

[0007] The product of the present invention has been made in view of such circumstances, and an anti-aging agent which is non-contaminating and does not degrade ozone resistance, bending resistance, heat resistance and other basic physical properties as rubber. By using, the rubber composition as a base rubber for a pneumatic cushion tire for a pneumatic industrial vehicle of a color specification that does not cause discoloration in appearance even when used for a long period of time and can sufficiently satisfy the function as a base rubber. To provide.

[0008]

In order to achieve the above object, the present invention takes the following means to solve the problem. That is, it is composed of natural rubber and a rubbery component of a styrene-butadiene copolymer rubber having an amount of bound styrene of 40 to 50% by weight, carbon black as a reinforcing agent, a phenolic resin, and hexane as a curing agent for the phenolic resin. A rubber composition containing methylenetetramine is characterized in that the antioxidant used in the rubber composition is an aromatic secondary amine-based or amine-ketone-based. The aromatic secondary amine-based antioxidant may be a paraphenylenediamine, and the amine-ketone-based antioxidant may be a reaction product of diphenylamine and acetone.

[0009]

Embodiments of the present invention will be described below. FIG. 1 is a diagram for a new industrial vehicle using the rubber composition of the present invention.
1 shows a cross section of a mastic type cushion tire. The pneumatic cushion tire 1 for an industrial vehicle includes a base rubber 2 on a base portion on a rim side, a side rubber 3 on a side portion on a tire side, a tread rubber 4 on a tread portion on a running surface side, a base rubber 2 and a tread rubber 4. And a bead core 6 built in the base rubber 2. The rubber composition of the present invention comprises a base rubber 2
It is about. The middle rubber 5 does not have to improve the cushioning property, heat resistance and the like of the tire. The bead core 2 may be a bundled strand bead wire formed by winding a plurality of bead wires, or a single thick steel ring.

[0010] 1. Results of comparative test of contamination of various anti-aging agents in pure rubber compounding

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

[Table 3]

[0014] Vulcanized rubber plates of various contaminants having a thickness of 2 mm were prepared by adding various antioxidants to the pure rubber compound shown in Table 1, and a comparative contamination test was performed on non-contaminated materials.
The contamination results are shown in Tables 2 and 3. In Table 1, each numerical value indicates the blending number PHR. In Tables 2 and 3, the names of antioxidants, SP, and ADPAL are abbreviations of SRIS (Japanese Rubber Association Standards). For 8C, 8C-NS of Ouchi Shinko Chemical Industry Co., Ltd. was used. Contamination test is J
It was carried out according to the heating method of promoting contact and migration stain test of IS-K6267 ^-1996. Heating condition is 70 with gear aging tester.
At 24 ° C. for 24 hours, the secondary exposure is irradiation with a mercury lamp for 9 hours. The non-polluting material is a sulfur-vulcanized white rubber compounded board having a thickness of 2 mm, using natural rubber 70 PHR, 30 PHR of synthetic diene rubber of BR and SBR, using 50 PHR of white carbon as a reinforcing material, and adding 20 PHR of titanium oxide as a white pigment. Using.

Comparative Example 1 in Table 2 has no anti-aging agent and no contamination, but has no effect of preventing deterioration of ozone resistance, bending resistance, heat resistance, and other basic physical properties as a rubber. Not suitable for base rubber for color tires. The SPs and ODAs of Comparative Examples 2 and 8 are also unsuitable for use because they are anti-aging agents having a small stain-preventing effect but a small effect of preventing deterioration. In Comparative Examples 3 to 6, 6C (N-phenyl-N '-(1,3-dimethylmethyl) -p-phenylenediamine) and 8C (in which the alkyl group of 6C is further increased in molecular weight) are described in the above-mentioned patent application. As shown in Table 1 of Japanese Patent Application Laid-Open No. 9-252802, use of about 2 PHR, which is a practical use amount having a deteriorating effect, obviously causes migration contamination and is not suitable for use. ADPAL of Comparative Example 7 is also unsuitable for use at a general use amount of about 3 PHR, showing contamination. Also, as shown in Comparative Examples 9 to 12 in Table 3, 6C
Or it turns out that even if 8C and ADPAL are combined, they will still be contaminated.

2. Using natural rubber and a styrene-butadiene copolymer rubber having a bound styrene content of 46% by weight,
Comparative test results of various anti-aging agents in rubber compositions containing carbon black as a reinforcing agent, phenolic resin and hexamethylenetetramine as a curing agent.

[0017]

[Table 4]

[0018]

[Table 5]

[0019]

[Table 6]

Using natural rubber and a styrene-butadiene copolymer rubber having a bound styrene content of 46% by weight as shown in Table 4, carbon black as a reinforcing agent, a phenolic resin and hexamethylenetetramine as a curing agent thereof In the rubber composition blended with, to prepare various contaminating vulcanized rubber plate of thickness 2mm to which various antioxidants are added,
A comparative contamination test was performed on a non-contaminated material, and the results of the contamination are shown in Tables 5 and 6.

In Table 4, each numerical value indicates the blending number PHR. As the SBR, a solution polymerization type was used, but an emulsion polymerization type may be used. The phenolic resin used was a cashew oil-modified product, but may be another oil-modified or non-modified product. As for the sun crack inhibitor (wax), 2 PHR was uniformly added. The oil used was non-staining naphthenic oil, but other non-staining oils may be used. In Tables 5 and 6, antioxidant names, ADPAL, M
BI is an abbreviation for SRIS (Japanese Rubber Association Standard). 8C-N of Ouchi Shinko Chemical Industry Co., Ltd.
S was used. Test of contaminating was carried out according to the heating method of promoting contact and migration stain test of JIS-K6267 ^-1996. The heating condition is a gear aging tester at 70 ° C. for 24 hours, and the secondary exposure is irradiation with a mercury lamp for 9 hours. The non-polluting material is a natural rubber 70 PHR and a total of 100 PHR using a total of 100 PHR using a synthetic diene rubber of BR and SBR. A sulfur-vulcanized white rubber compounded board was used.

Although the anti-aging agent of Comparative Example 13 in Table 5 without addition of an anti-aging agent still does not show stainability, it is not suitable for use because it has no effect of preventing deterioration. As shown in Example 1, ADPA which is a reaction product of aromatic secondary amine-based paraphenylenediamines 6C, amine-ketone-based diphenylamine, and acetone as the rubber composition of the present invention.
It can be seen that the combination of L is slightly contaminated and has a degree of contamination in a range where there is no practical problem. Further, as shown in Example 2, even if 6C and ADPAL are further combined with an anti-aging agent such as MBI as a non-staining type secondary anti-aging agent, the effect of preventing deterioration can be further improved while maintaining micro contamination. . Similarly, as shown in Example 3 and Example 4 in Table 6, the combination of 8C and ADPAL, which are aromatic secondary amine-based paraphenylenediamines, as the rubber composition of the present invention was also fine. The contamination level was within a range where there was no problem in practical use. As shown in Examples 5 and 6, 8C and ADPAL were further added with a non-staining type secondary anti-aging agent MBI as an anti-aging agent.
Even if a combination of the above is combined, the deterioration prevention effect can be further improved while maintaining the fine pollution.

In addition to the present examples, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N '-(3
-Methacryloyloxy-2-human peroxyfluoro) -p-phenylenediamine and the like. Examples of other suitable amine-ketone antioxidants include 2,2,4-trimethyl-1,2-dichlorodiquinoline polymer and 6-ethoxy.
-1,2-dihydroxy-2,2,4, -trimethylquinoline and the like.

Although the effect of the rubber composition of the present invention for preventing contamination is not clearly understood, the amount of bound styrene is as large as 40 to 50% by weight as compared with ordinary SBR, and a phenolic resin is also added. Therefore, the amount of the aromatic ring contained therein is also large, and this has some interaction with the aromatic ring portion of the aromatic secondary amine-based and amine-ketone-based antioxidants, thereby inhibiting the movement of the antioxidants themselves. It is also conceivable that it leads to suppression.

In Examples 1 to 6, a 5.00-8 size color tire having the structure shown in FIG. 1 was actually manufactured and the contamination was confirmed. It turns out that there is no problem.

3. Using natural rubber and a styrene-butadiene copolymer rubber having a bound styrene content of 46% by weight,
Including carbon black and further phenolic resin as a reinforcing agent and hexamethylenetetramine which is a curing agent thereof,
Comparative test results of various physical properties of rubber compositions containing various anti-aging agents

[0027]

[Table 7]

[0028]

[Table 8]

[0029]

[Table 9]

Using natural rubber and a styrene-butadiene copolymer rubber having a bound styrene content of 46% by weight as shown in Table 4, carbon black as a reinforcing agent, a phenolic resin and hexamethylenetetramine as a curing agent thereof And a JIS A hardness, a Dematia flex test, a thermally degraded Dematia flex test, and a tensile test were performed on a vulcanized product of a rubber composition containing various antioxidants, and the results were shown in Tables 7 and 8. The results are shown in Table 9. Vulcanization conditions are JIS
A hardness and Dematia flex test are 150 ° C x 60 minutes, and tensile test is 150 ° C x 30 minutes.

The rubber hardness is a JIS A spring type hardness according to JIS- ^K6301-1975 . The tensile test was also performed using a ^tumbell -shaped No. 3 type test piece according to JIS- ^K6301-1975 . The bending test is also JIS-K6301
^{-1975 is} a Dematia bending test, except that the test piece is not drilled, the bending test is performed as it is, and the crack generated on the concave surface of the test piece spreads from end to end and the end of the bending test when both ends are connected And the numerical value (the number of times). The larger the value, the better the flex crack resistance. or,
Demachia bending test obtained by thermal degradation were subjected to bending test after the test piece was also to JIS-K6301 ^{-197 5} air heating aging test degradation 100 ° C. x 24 hours heat set at a gear type aging tester according to.

Each numerical value in Table 4 indicates the blending number PHR.
BR used a solution polymerization type, but it may be an emulsion polymerization type, and the phenolic resin used a cashew oil-modified product, but may be another oil-modified or unmodified product.
For sun crack inhibitor (wax), 2PH
R added. The oil used was non-staining naphthenic oil, but other non-staining oils may be used. SB
By setting the amount of R-bonded styrene to 40% by weight or more, the JIS A hardness required as a base rubber for this type of tire can be easily increased to 80 ° or more, and to 50% by weight or more. Conversely, the styrene portion having thermoplastic properties increases and the compression set of the rubber composition becomes too large, which is not preferable. Therefore, a range of 40 to 50% by weight is suitable. In Tables 7, 8, and 9, the names of antioxidants, ADPAL, and MBI are abbreviations of SRIS (Standards of the Rubber Association of Japan). For 8C, 8C-NS of Ouchi Shinko Chemical Industry Co., Ltd. was used. The rubber kneading is 6
The test roll was hand-kneaded.

As shown in Table 1 of Japanese Patent Application No. 9-252802, the results of the physical properties of Comparative Example 14 in Table 7 show that the antioxidant 6C, which is generally used for tires, has an effect of preventing deterioration. It is the result of adding 2PHR in a practical use amount having a certain amount. Using this as a physical property standard, comparison with other comparative examples and examples was performed. Regarding the bending test and the heat deterioration bending test, which are particularly important for the durability of the tire, the number of times of the bending test value and the number of the heat deterioration bending test values of Comparative Example 14 were set to 100 as reference indices, respectively. Every,
An index comparison with others was also performed for each thermal degradation bending test. The numerical values in parentheses in Tables 7, 8, and 9 are exponent values.

In the case of Comparative Example 15 containing no anti-aging agent in Table 7, the physical properties were greatly reduced, and particularly, the bending test value and the heat deterioration bending test value were significantly reduced, and were not suitable for use. SP (monophenols) of Comparative Example 16 also has a large decrease in physical properties and is not suitable for use. Example 7 is a combination of 6C and ADPAL, which is preferable because it has a small decrease in properties. Further, as shown in Example 8, good results can be obtained by further adding MBI. Since MBI is a non-staining type secondary anti-aging agent, there is no concern about contamination. Examples 7 and 8 correspond to Examples 1 and 2 and are not noticeable due to slight contamination, so that there is no practical problem. Examples 9 and 10 in Table 8 are a combination of 8C and ADPAL, and are preferable because physical properties decrease is small. Further, as shown in Example 11 and Example 12 in Table 9, it is possible to obtain a result in which MBI is further added. Embodiments 9, 10, 11, and 12 are Embodiment 3,
It corresponds to 4, 5, and 6 and is inconspicuous due to micro-contamination.

The present invention is not limited to such an embodiment at all, and can be implemented in various modes without departing from the gist of the present invention.

[0036]

As described in detail above, the rubber composition of the present invention has a natural rubber and an S
A rubbery component of BR, which contains carbon black as a reinforcing agent, phenolic resin and hexamethylenetetramine as a curing agent, and is combined with an aromatic secondary amine-based and amine-ketone-based antioxidant. It is a thing. By using the rubber composition of the present invention as a base rubber for a base portion of a color tire, contamination by an antioxidant can be prevented to a degree that does not cause a problem in appearance, and deterioration of rubber physical properties can also be effectively prevented. Color tires are mainly used in clean places such as color floors of food factories, etc., and by using tires using the rubber composition of the present invention, without impairing the beauty of the use environment and as a base rubber. Since it has excellent deterioration resistance, it can be used for a long period of time, and its economic efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a pneumatic cushion tire for an industrial vehicle using the rubber composition of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pneumatic type cushion tire for industrial vehicles 2 ... Base rubber 3 ... Side rubber 4
... Tread rubber 5 ... Middle layer rubber 6 ... Bead core

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Tanemura 1108 Otsubo, Dakuraku-cho, Kasugai-shi, Aichi Prefecture Inside the Kasugai Works of Aichi Tire Industry Co., Ltd. Aichi Tire Industry Co., Ltd.Kasugai Works (72) Inventor Haruyuki Morimoto 1108 Otsubo, Dakuru-cho, Kasugai City, Aichi Prefecture Aichi Tire Industry Co., Ltd.Kasugai Works, (72) Inventor Hisaki Kato 1108 Aichi Tire Industry Co., Ltd., Kasugai Works

Claims (3)

[Claims] (1) The amount of natural rubber and bound styrene is 40 to 50.
A rubber composition comprising a rubbery component of a styrene-butadiene copolymer rubber in an amount of 1% by weight, comprising carbon black as a reinforcing agent, phenolic resin, and hexamethylenetetramine as a curing agent for the phenolic resin. A rubber composition characterized in that the antioxidant used in the composition is an aromatic secondary amine-based or amine-ketone-based. 2. The rubber composition according to claim 1, wherein the aromatic secondary amine-based antioxidant is a paraphenylenediamine. 3. The rubber composition according to claim 1, wherein the amine-ketone antioxidant is a reaction product of diphenylamine and acetone.