JPS5812905B2 - rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ethylene-propylene rubber composition with improved oil resistance.

Ethylene-propylene rubber has superior heat resistance, weather resistance, electrical properties, etc. compared to other synthetic rubbers, and taking advantage of these characteristics, it is used in a variety of applications such as automobile parts, industrial products, electric wires, and heat-resistant belts.

However, on the other hand, it has poor oil resistance, which prevents its use in fields that require such physical properties.

To improve the oil resistance of ethylene-propylene rubber,
Blends of acrylonitrile-butadiene copolymer rubber (NBR), which has excellent oil resistance, are used as modifiers, but polar polymers such as NBR and non-polar polymers such as ethylene-propylene rubber are different. The compatibility is very poor, and blends of these rubbers are used in extremely limited blending ratios without being sufficiently compatible. has not yet been reached.

The present inventors have focused on this point, and have developed a rubber that retains the characteristics of ethylene-propylene rubber, has better oil resistance than ethylene-propylene rubber, and has good compatibility with NBR, allowing for a wide range of blending applications. The present invention was achieved by developing a composition that has better oil resistance than conventional ethylene-propylene rubber/NBR blends and can be used in a wide range of fields.

That is, the present invention is a rubber composition A obtained by mixing 25 to 90% by weight of ethylene-propylene rubber and 10 to 75% by weight of a graft copolymer of ethylene-propylene rubber and vinyl chloride; 75% by weight or less of N in A
This is a rubber composition B mixed with BR.

The present invention will be explained in detail below.

The present inventors focused on the fact that polyvinyl chloride has excellent oil resistance due to a specific polar group (Cl group) in its structure, and blended polyvinyl chloride with ethylene-propylene rubber to improve the As a result of examining the quality method, it was possible to improve the oil resistance of ethylene-propylene rubber, but other physical properties were significantly reduced.

In other words, the polar states of polyvinyl chloride and ethylene-propylene rubber are greatly different, and as the blend ratio of polyvinyl chloride to ethylene-propylene rubber increases, the compatibility decreases, resulting in a drastic decline in physical properties, making the material impractical. It became clear that.

Therefore, as a result of intensive investigation into various methods to improve this compatibility and maintain oil resistance, we found that the SP value of polyvinyl chloride (
As a method to bring the solubility parameter (solubility index) closer to ethylene-propylene rubber, by using a graft copolymer of ethylene-propylene rubber and vinyl chloride (hereinafter abbreviated as "EVG"), the ethylene- A composition A was obtained in which the propylene rubber part and the ethylene-propylene rubber were compatible and the polyvinyl chloride part could improve oil resistance.

EVG can be made by polymerizing vinyl chloride in the presence of ethylene-propylene rubber.

In the EVG used in the present invention, if the ethylene-propylene rubber content is too low, the compatibility with the ethylene-propylene rubber will deteriorate, and if it is too high, the polyvinyl chloride portion in the EVG will be reduced. Since the oil resistance modification effect is weakened, EVG is subject to self-regulation, and EVG with an ethylene-propylene rubber content of 4 to 60% by weight is used, but for example, a graft polymer with a content of 20% by weight or less is used. When the amount of ethylene-propylene rubber in Composition A is more than 50% by weight, it is desirable to blend the ethylene-propylene rubber in Composition A to a larger amount within the range of the composition of the present invention. It is desirable that the amount of propylene rubber be blended in a smaller amount than in the composition of the present invention.

Generally, the preferred range for the ethylene-propylene rubber content in EVG is 20 to 50% by weight.

Composition A of the present invention usually has flame retardancy when the amount of EVG is 50% by weight or more, and its effect is self-extinguishing or non-flammable even without the use of ordinary flame retardants.

Furthermore, the ethylene-propylene rubber used in the present invention is saturated ethylene-propylene copolymer rubber (EPM) or unsaturated ethylene-propylene-diene terpolymer rubber (EPDM), and the type of third component and The content, molecular weight, propylene content, etc. are not particularly limited, and can be arbitrarily selected and used.

Ethylene propylene rubber is more susceptible to the blooming phenomenon of compounded chemicals than other synthetic rubbers, and it may be necessary to select compounded chemicals depending on the application.

On the other hand, Composition A of the present invention has an SP value close to that of the compounded drug used, and therefore has good compatibility with the compounded drug.
The blooming phenomenon is very small, and the selection range of compounded chemicals is wide, allowing a wide range of compounded chemicals to be used.

In addition, the present inventors have developed a blend system of Composition A and NBR with the aim of further enhancing this effect and providing a composition that can be applied to a wide range of applications requiring oil resistance and ozone resistance. We also investigated and compared its effectiveness with that of an ethylene-propylene rubber/NBR blend.

As a result, compared to conventional ethylene-propylene rubber/NBR blends, both compatibility and oil resistance can be greatly improved.
This led to the invention of composition B, which also has the same ozone resistance.

The NBR used in composition B is not particularly limited, and any commercially available normal NBR can be used.

Composition A of the present invention becomes a very hard composition at room temperature when the proportion of ethylene-propylene rubber in the composition is less than 25% by weight, and it becomes difficult to knead when adding general rubber compounding chemicals. -If the propylene rubber content exceeds 90% by weight, the oil resistance modification effect will be weakened, so composition A
is weight% ethylene-propylene rubber/EVG=25~
It can be obtained by physically mixing EVG with ethylene-propylene rubber in a kneader while maintaining the melting temperature of EVG at an arbitrary blending ratio within the blending ratio range of 90/10 to 75.

Regarding Composition B, if the blend ratio of NBR in the composition exceeds 75% by weight, the effect of improving oil resistance and compatibility will not be sufficient compared to conventional ethylene-propylene rubber and NBR blends, and the N in Composition B is impractical due to the inability to obtain an ozone-modifying effect.
The amount of BR can be obtained by physically blending any blend ratio within the blend ratio range of up to 75% by weight using a general rubber compounding and kneading machine.

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 (1) Production of a composition of ethylene-propylene rubber and EVG or polyvinyl chloride Composition No. Except for 5, ethylene-propylene rubber and EVG or polyvinyl chloride (
EVG or PVC) for 8 to 10 minutes each.
After confirming that the VC was sufficiently melted and mixed with the ethylene-propylene rubber, the kneading was completed and the mixture was heated at 70°C for 24 minutes.
After cooling with a 6-inch roll at 34 rpm and a nip of 2 m/m, the sheets were taken out to give ethylene-propylene rubber/EVG and ethylene-propylene rubber/PVC compositions.

(2) Examination of the oil resistance improvement effect of ethylene-propylene rubber Each composition in Table 1 and ethylene-propylene rubber (N
o. 5) to compare its characteristics with 70°C and 7.
Using a 1L pressure kneader preset at 0 rpm, experiment No. 1 was prepared according to the formulation shown in Table 2. After kneading the compositions or polymers of Nos. 1 to 8 for 1 minute, fillers and additives were added, and after kneading for 3 minutes, sulfur was added and kneaded for 30 seconds.

Thereafter, the vulcanization accelerator was added to each compound for 3 to 5 minutes using a 6-inch roll set at 70°C, 22/34 rpm, and a roll nip of 2 m/m.
Thinning was carried out 8 times at m.

After leaving this mixture overnight, take out a sheet at about 2% and hold it at 150°C.
Press vulcanization was performed at an arbitrary vulcanization time to prepare samples for compatibility and oil resistance studies.

Using the vulcanized rubber thus obtained, first, in order to examine its compatibility, comparisons were made with ethylene-propylene rubber alone, ethylene-propylene rubber/EVG blend compositions in various proportions, and ethylene-propylene rubber/PVC blend compositions in various proportions. A tensile test and a tear test (Type B) were conducted in accordance with JISK-6301.

As shown in Table 3 and Figures 1 to 3, the results show that when the blend ratio of the ethylene-propylene rubber/PVC composition reaches 50,750, TB (tensile strength), EB (elongation), and TR (tensile strength) increase. extremely low.

*On the other hand, in the case of ethylene-propylene rubber/EVG composition, TB increases as EVG increases, and no decrease in TR is observed, and compatibility with ethylene-propylene rubber is much better than that of ethylene-propylene rubber/PVC. It can be seen that TB and TR are not inferior to rubber alone and have sufficient practicality.

In addition, in order to examine the oil resistance, which is a feature of the present invention, using the vulcanized rubber obtained by the method described above, test pieces of 2 x 2 x 0.2 cfrL were cut out according to the JIS K-6301 oil resistance test method. was immersed in JIS test grade &3 oil at 100°C for 70 hours, and the degree of swelling was measured based on the change in volume.

The results are shown in Table 3 and Figure 4. As the amount of EVG in the ethylene-propylene rubber/EVG composition increases, the oil resistance tends to improve, especially when ethylene-propylene rubber/EVG=50/50. When the EVG increases, oil resistance is greatly improved compared to ethylene-propylene rubber alone.

Furthermore, although the ethylene-propylene/PVC composition as a comparative example has better oil resistance than the ethylene-propylene rubber/EVG composition, other physical properties are extremely poor, making it a material with poor practicality. .

Example 2 Tests were conducted according to Example 1 using various ethylene-propylene rubbers.

The above composition was manufactured in the same manner as in Example 1, added with fillers, additives, and vulcanizing agents in the same manner as in Example 1 according to the formulation shown in Table 5, and press-vulcanized at 150°C. did.

Using the obtained vulcanizate, tensile test, tear test, oil resistance, and ozone resistance were conducted in the same manner as in Example 1 according to JISK-6301.
As shown in Table 6, ethylene-
It can be seen that the rubber composition of the present invention has excellent oil resistance and other physical properties regardless of the type of propylene rubber.

Example 3 The effect of the composition obtained in Example 1 was further enhanced, and the oil resistance and
In order to provide a polymer that can be applied to a wide range of applications requiring ozone resistance, Composition A2 obtained in Example 1 was blended with NBR and compared with conventional ethylene-propylene rubber/NBR blends. We compared them and looked at their effects.

After kneading EPDM/NBR and Composition A2/NBR for 1 minute according to the formulation shown in Table 7 in a 1L pressurized kneader preset at 70°C and 70 rpm, fillers and additives were added and kneaded for 3 minutes. After mixing, sulfur was added and kneaded for an additional 30 seconds.

A vulcanizing agent was added to this kneaded material for 3 to 5 minutes using a 6-inch roll set at 70° C., 24/34 rpm, and a roll nip of 2 mm, and then thinning was performed 8 times using a roll nip of 0.3 mm.

This mixture was left overnight and sheeted out at about 2 m/m.
It was press-cured at 150°C and used as a sample for examination.

Using the thus obtained vulcanized rubber, both samples were subjected to a tensile test and a tear test (Type B) in accordance with JISK-6301 in order to compare their compatibility.

The results are as shown in Table 8 and Figures 5 and 7.
EPDM/NBR blends have NBR content of 30-50
A large sagging phenomenon is observed at the weight percentage.

In contrast, the composition of the present invention A. The sagging phenomenon in the 2/NBR blend is very small as shown in the correlation graph.

Furthermore, in order to examine oil resistance, which is a feature of the present invention, both blends were compared in accordance with JISK-6301 using vulcanized rubber obtained in the same manner as in the above tensile test.

As shown in Table 8 and FIG. 8, the composition of the present invention No. 1 compared with the ethylene-propylene rubber/NBR blend. The 2/NBR blend has much better oil resistance, and when blends with the same NBR content are compared, the oil resistance improvement effect is approximately twice as high.

In addition, in order to confirm the retention of ozone resistance, which is one of the characteristics of ethylene propylene rubber, in accordance with JISK-6301, we used a standard ozone tester manufactured by Toyo Seiki at a test temperature of 40 ± 1 ° C and an ozone concentration of 100 ppm. , static extension 2
The state of ozone crack occurrence was observed after 5 days and 10 days under the 0% condition.

As a result, as shown in Table 8, when comparing blends with the same NBR content, ozone cracking was observed in both blends with an NBR content of 75%, and the ozone cracking state was almost the same.

From this, the composition A of the present invention is recognized to have an ozone resistance modification effect on NBR that is almost equivalent to that of ethylene propylene rubber, and the present invention provides a rubber composition with a very wide range of uses.

[Brief explanation of the drawing]

Figures 1 to 4 show the relationship between the ethylene-propylene rubber content, tensile strength, elongation, tear strength, and oil resistance of rubber composition A of Example 1 of the present invention in comparison with conventional compositions. It is. Moreover, FIGS. 5 to 8 show rubber composition B of Example 3 of the present invention.
The relationship between the NBR content and the above-mentioned physical properties is shown in comparison with conventional compositions.

Claims (1)

[Scope of Claims] 1. A rubber composition prepared by mixing 25 to 90% by weight of ethylene-propylene rubber and 10 to 75% by weight of a graft copolymer of ethylene-propylene rubber and vinyl chloride. 2. A rubber composition prepared by mixing 25 to 90% by weight of ethylene-propylene rubber and 10 to 75% by weight of a graft copolymer of ethylene-propylene rubber and vinyl chloride,
A rubber composition comprising 5% by weight or less of acrylonitrile-butadiene copolymer rubber.