JP3193428B2 - Rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition, and more particularly to a rubber composition applied to tires of automobiles and the like.

[0002]

2. Description of the Related Art Conventionally, butyl rubber (I) has been used as a rubber material for tire inner liners and tubes.
IR) or the like is mainly used, and a process oil is blended to improve the processability of the rubber material.

[0003]

By the way, the rubber material for a tire as described above is required to have elasticity and air barrier properties. However, since process oil is not originally blended for the purpose of air barrier properties, The fact is that such rubber materials do not provide sufficient air barrier properties.
It is thought that the air barrier property is increased by blending a polymer with a high glass transition temperature, etc., but according to this, the glass transition temperature of the rubber composition itself also increases, and the elasticity at low temperatures is impaired and the processability decreases. This is inconvenient. In view of the above, an object of the present invention is to provide a rubber composition which can improve the air barrier property and can avoid a large increase in the glass transition temperature, and has good processability, while paying attention to a softener. And

[0004]

In order to achieve the above object, the present invention relates to a rubber composition containing 30 to 100 parts by weight of a butyl rubber and 100 parts by weight of a rubber component.
Polymer containing isobutyl of 0 to 1500, acrylonitrile butadiene polymer having a weight average molecular weight of 5000 or less, ethylene propylene diene polymer, butadiene polymer, isoprene polymer and at least one low molecular weight polymer selected from the group consisting of styrene butadiene polymer (however, Excluding those having a hydroxyl group.)
It is characterized by being a sulfur vulcanization system containing up to 25 parts by weight.

[0005]

The butyl rubber is preferably isobutyl / isoprene rubber or halogenated isobutyl / isoprene rubber. The low molecular weight polymer is preferably a polymer containing isobutyl, and the content of isobutyl is not particularly limited, but is more preferably 20% by weight or more. Further, in order to secure the air barrier property and prevent the glass transition temperature from increasing, the weight average molecular weight of the polymer containing isobutyl is more preferably 380 to 1300, and 380 to 1300.
900 is more preferred. If the weight average molecular weight is less than 300, sufficient air barrier properties cannot be obtained, and 1500
A larger size is disadvantageous because the elasticity is reduced and the glass transition temperature is increased. Further, as for other low molecular weight polymers, the weight average molecular weight is more preferably in the range of 1,000 to 3,000. In the present specification, the weight average molecular weight is measured by GPC (gel permeation chromatography), and more specifically, HCL8020 manufactured by Toyo Soda Co., Ltd.
2000H × L and G3000H × L, R as detector
I (differential refractometer), THF (tetrahydrofuran) was used as a mobile phase, and a calibration curve was performed in terms of polystyrene.

Here, a method for measuring the air permeation index and the low-temperature embrittlement temperature will be described. Air Permeability Index One side of the thin rubber test piece is set to vacuum and the other side is set to atmospheric pressure. The amount of change in pressure (air permeation) per unit time on the vacuum side is calculated, and the relative change is calculated. The air permeation index was evaluated and evaluated. Low temperature embrittlement temperature The rubber test piece was cooled and hit with a constant force using a hammer or the like, and the temperature at which the test piece cracked was taken as the low temperature embrittlement temperature. According to the present invention, by adding a low molecular weight polymer to a rubber compound, air barrier properties can be improved without impairing the elasticity of rubber at low temperatures. In addition, workability was also good.

[0007]

EXAMPLES Examples of the present invention will be described below together with comparative examples. Example I Examples 1 to 9 will be described together with Comparative Examples 1 to 8 with reference to the following table.

[0008]

[Table 1]

Comparative Example 1 uses a paraffinic oil, Comparative Example 2 uses an aromatic oil, and 100 parts by weight of IIR (butyl rubber) as a rubber component. Comparative Examples 3 to 8 use a polymer containing isobutyl, but show cases where the weight average molecular weight or the compounding amount is not suitable. On the other hand, Examples 1 to 9 show that the polymer containing isobutyl contains It shows a case where the weight average molecular weight satisfies the range of 300 to 1500 and the compounding amount satisfies the range of 3 to 25 parts by weight. In addition, other compounds, namely, sulfur as a vulcanizing agent, DM (dibenzothiazole disulfide), TT (tetramethylthiuram disulfide), vulcanization accelerator or vulcanization accelerator, stearic acid and zinc white, and The same conditions were used for carbon black as a filler (however, the numbers in parentheses in the table indicate product numbers).

In order to evaluate the air barrier properties of each of these examples, the air permeability index at 25 ° C. is shown relative to the value of Comparative Example 1 as 100. The smaller the numerical value, the lower the air permeability. It indicates that the barrier property is good. Furthermore, in order to evaluate the elasticity, the actual low-temperature embrittlement temperature is measured and shown from the glass transition temperature, and the lower the temperature, the better the elasticity even at a low temperature. As a result, Comparative Examples 6 to 8 are excellent in terms of air barrier properties, but inferior in elasticity, and cannot achieve both properties. On the other hand, Examples 1 to 9 greatly enhance air barrier properties. In addition to being able to significantly increase the low-temperature embrittlement temperature, it exhibited an effective evaluation value in satisfying both characteristics, and was excellent in workability. In the above table, only those using IIR (butyl rubber) as the rubber component are shown.
Even when IR was used, similar good results could be obtained with the same composition as in Examples 1 to 9. As the polymer containing isobutyl, "Polybutene (trade name)" manufactured by Nippon Petrochemical Co., Ltd. was used.

Example II Referring to the following table, Example 11 was used together with Comparative Examples 11 and 12.
13, Examples 21 and 22 will be described together with Comparative Example 21, and Examples 31 and 32 will be described together with Comparative Example 31.

[0012]

[Table 2]

As rubber components, NR (natural rubber, in parentheses in the table indicates the product number), SBR (styrene butadiene rubber, in parentheses in the table indicates the product number), BR
(Butadiene rubber, where the number in parentheses in the table indicates the product number), IR (isoprene rubber, but the number in parentheses in the table indicates the product number) and IIR (butyl rubber, the product number is in parenthesis in the table). Two of them are used in combination.
Comparative Examples 11, 21 and 31 show a case where 10 parts by weight of paraffinic oil was used and Comparative Example 12 shows a case where 10 parts by weight of an isoprene polymer having a weight average molecular weight of 8000 were used with respect to 00 parts by weight. On the other hand, Examples 11 and 13 relate to isoprene polymer, and
1,22 are examples of butadiene polymer,
32 is a styrene butadiene polymer (styrene content 5
%), The case where their weight average molecular weight satisfies the range of 5000 or less and the blending amount satisfies the range of 3 to 25 parts by weight. Example 12 shows the case where 5 parts by weight of an isoprene polymer and a polymer containing isobutyl were used together. In addition, other compounds, namely, sulfur as a vulcanizing agent, DM (dibenzothiazole disulfide), TT (tetramethylthiuram disulfide), as a vulcanization accelerator or vulcanization accelerator,
The same conditions were used for stearic acid, zinc white and carbon black as a filler (however, the numbers in parentheses in the table indicate the product numbers).

In the same manner as in Example I, the air permeability index at 25 ° C. (Comparative Examples 11, 21, 31
It was set to 0 and compared with each example. ) And low temperature embrittlement temperature. As a result, each example exhibited an effective evaluation value in satisfying both characteristics, and was excellent in workability.

Example III Example 4 together with Comparative Examples 41 and 42 with reference to the table below.
1 and 42 will be described.

[0016]

[Table 3]

As rubber components, IIR (butyl rubber) and NBR (butadiene acrylonitrile rubber, where the number in parentheses in the table indicates the product number). Paraffin-based oil is used in Comparative Example 41 with respect to 100 parts by weight. Comparative Example 42 shows the case where the weight average molecular weight of the acrylonitrile butadiene polymer was 8000, while Examples 41 and 42 showed that the weight average molecular weight of the acrylonitrile butadiene polymer was 5000 or less. The case where the range is satisfied and the blending amount satisfies the range of 3 to 25 parts by weight is shown. In addition, other compounds, that is, sulfur as a vulcanizing agent,
MBTS (dibenzothiazyl-disulfide) as a vulcanization accelerator or vulcanization accelerator, stearic acid and zinc white, carbon black as a filler (however, parentheses in the table indicate the product number), and an antioxidant D (phenyl-
β-naphthylamine) and the like were set to the same conditions. In the same manner as in Example I, the air permeation index at 25 ° C. (Comparative Example 41 was set to 100 and compared with each Example) and the low-temperature embrittlement temperature were evaluated. As a result, Examples 41 and 42 exhibited an effective evaluation value in satisfying both characteristics, and were also excellent in workability.
In the above table, only those using IIR (butyl rubber) as the rubber component are shown. Even when the halogenated IIR is used, the same good results can be obtained with the same composition as in Examples 41 and 42. I got it.

Example IV Referring to the table below, Example 51 together with Comparative Examples 51 to 54 was used.
To 55 will be described.

[0019]

[Table 4]

EPR (ethylene propylene rubber, where parentheses in the table indicate product numbers) and IIR as rubber components
(Butyl rubber, the number in parentheses in the table indicates the product number), and Comparative Example 51 used a paraffinic oil. Comparative Examples 52 to 54 used an ethylene propylene diene polymer having a weight average molecular weight of 2500 or 9000
In this case, the case of Example 51 is shown.
-55 satisfy the weight average molecular weight of the ethylene propylene diene polymer in the range of 5000 or less;
In addition, Example 55 shows a case where the compounding amount satisfies the range of 3 to 25 parts by weight. Further, Example 55 shows a polymer containing isobutyl in addition to the ethylene propylene diene polymer (weight average molecular weight 2500) (weight average molecular weight 380). 5
The case where the weight part is blended is shown. In addition, other compounds, namely, sulfur as a vulcanizing agent, TT (tetramethylthiuram disulfide), MBT (2-mercaptobenzothiazole), stearic acid and zinc white as a vulcanization accelerator or a vulcanization accelerator. The same conditions were used for carbon black as a filler (however, the number in parentheses in the table indicates the product number).

In the same manner as in the Examples, the air permeability index at 25 ° C. (Comparative Example 51 was set to 100 and compared with each Example) and the low-temperature embrittlement temperature were evaluated. As a result, Examples 51 to 55 exhibited effective evaluation values in that both characteristics were satisfied, and were also excellent in workability. In addition, as a polymer containing isobutyl having a weight average molecular weight of 380, LV-25 of "Polybutene" (trade name) manufactured by Nippon Petrochemical Co., Ltd. was used.

[0022]

As described above, according to the present invention,
It is possible to provide a rubber composition which improves the air barrier property and does not impair the low-temperature elasticity and has good processability.

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 21/00 C08L 9/00 C08L 23/16

Claims (2)

(57) [Claims] 1. A weight-average molecular weight of 300 per 100 parts by weight of a rubber component containing 30 to 100 parts by weight of a butyl rubber.
At least one low-molecular-weight polymer selected from the group consisting of a polymer containing isobutyl of ~ 1500, an acrylonitrile butadiene polymer having a weight average molecular weight of 3)
A rubber composition characterized by being a sulfur vulcanized composition containing up to 25 parts by weight. 2. The rubber composition according to claim 1, which is applied to an inner liner of a tire.