JPS61223049A - Vulcanized rubber composition - Google Patents

Abstract

PURPOSE:A vulcanized rubber composition having improved mechanical strength, especially low-temperature characteristics, obtained by subjecting a paraffin mineral oil and polyethylene to copolymerization in the presence of a peroxide to give a copolymer process oil, and mixing ethylene propylene rubber with the copolymer process oil. CONSTITUTION:(A) 100pts.wt. paraffin mineral oil having preferably 5-800cSt and 2-40cSt kinematic viscosity at 40 deg.C and 100 deg.C, respectively, and 70-140 deg.C aniline point, especially secondary hydrogenated oil is blended with (B) 5-35pts. wt. polyethylene having 20,000-500,000 viscosity-average molecular weight, the component B is dissolved at 185-225 deg.C, cooled to 120-150 deg.C, blended with (C) 5-10wt% based on the component B of a peroxide, preferably dicumyl peroxide, reheated at 200 deg.C, they are copolymerized to give a copolymer process oil. 100pts.wt. ethylene oil is blended with 30-200pts.wt. copolymer process oil, kneaded, and mixed with sulfur and a vulcanization promoter by open rolls.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vulcanized rubber composition, and more particularly to a vulcanized rubber composition that has excellent mechanical strength, particularly its low temperature properties.

[Technical background of the invention and its problems] A maleated polyolefin wax obtained by graft polymerizing a maleic acid compound to a polyolefin wax is used as a vulcanizing agent for ethylene propylene rubber.

Vulcanized rubber compositions blended with vulcanization aids and vulcanization accelerators are known (see Japanese Patent Publication No. 1111213/1983), and paraffin-based process oils are mixed in the presence of a peroxide crosslinking agent. Rubber compositions containing modified rubber compositions are also known (see Japanese Patent Publication No. 58-48217), and rubber compositions containing mineral oil and process oil dissolved in polyethylene are also known.

However, both of the former two vulcanized rubber compositions do not have sufficient mechanical strength, and especially have insufficient rubber elasticity at low temperatures.

Other rubber compositions are superior to the first two in terms of mechanical strength, but they still do not necessarily have satisfactory properties.

[Object of the Invention] The object of the present invention is to eliminate the drawbacks of the conventional vulcanized rubber compositions described above and to provide a vulcanized rubber composition that has excellent mechanical strength properties, especially its low-temperature properties.

[Summary of the Invention] In order to achieve the above object, the present inventors have conducted intensive research on process oils to be blended during the production of rubber compositions, and as a result, the copolymerized process oil produced by the method described below has achieved the above object. We discovered that the vulcanized rubber composition of the present invention is extremely effective in achieving the following.

That is, the vulcanized rubber composition of the present invention contains 100 parts by weight of ethylene propylene rubber and 30 to 200 parts by weight of a copolymerized process oil obtained by copolymerizing paraffinic mineral oil and polyethylene in the presence of a peroxide. It is characterized by what it did.

This copolymerization process oil can be produced as follows. First, paraffinic mineral oil is selected as the base oil and polyethylene is dissolved in it. Any paraffinic mineral oil that has been conventionally used as a process oil for rubber products may be used, but
Kinematic viscosity at ℃ and 100℃ is 5 to 8 QOcS, respectively.
Mineral oils having a kinematic viscosity of 2 to 40 cSt and an aniline point of 70 to 145°C are preferred; those with a kinematic viscosity smaller than the above lower limit will increase the amount of bleeding of rubber products, and those larger than the above upper limit will increase the viscosity. If the aniline point becomes too high, it becomes difficult to blend uniformly into rubber, leading to a decrease in processability.Also, if the aniline point drops below 70°C, the aging resistance of the rubber product, such as weather resistance, deteriorates. If it exceeds this, the compatibility with rubber will deteriorate and at the same time, bleeding will increase.

One of these paraffinic mineral oils, for example, Diana Process Oil PW380. Diana Process Oil PW-
Secondary hydrogenated oil commercially available as LV (all trade names manufactured by Idemitsu Kosan) is particularly suitable.

As polyethylene, the viscosity average molecular weight is 20.000
The above values are preferred; if polyethylene with a value smaller than 10,000 is used, the hardness of the obtained rubber product will decrease and at the same time bleeding will increase. However, polyethylene with a viscosity average molecular weight that is too large has a lower solubility in the paraffinic mineral oil, so the upper limit thereof is preferably 500,000, particularly 50,000.
000 to 300,000 is suitable. Melting of polyethylene is usually carried out at a temperature of 185-225°C.

The amount of polyethylene to be dissolved is 5 to 35 parts by weight per 100 parts by weight of paraffinic mineral oil as the base oil. If it is less than 5 parts by weight, the rubber elasticity of the obtained rubber product at low temperature will decrease, and if it is more than 35 parts by weight, it will decrease the mechanical strength of the rubber product. This is because it causes an increase in bleeding.

Then, peroxide was added to the obtained solution.
Proceed with radical polymerization. Peroxides used at this time include dicumyl peroxide, t-butylcumyl peroxide, 1.3-bis(t-butylperoxy-isopropyl)-benzene, 2.5-dimethyl-2,5-
Dialkyl peroxides such as di(t-butylperoxy)-hexane, dibutyl peroxide, 2,5-dimethyl-2,5-(t-butylperoxy)-hexyne-3; 1,4.4-) ref. Tylpentyl-2-hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-
Preferred are organic peroxides such as hydroperoxides such as butyl hydroperoxide, or a combination of two or more thereof. Dicumyl peroxide is particularly suitable.

To add peroxide, once the solution obtained in the previous step is
A preferred method is to cool the mixture to 120-150°C and then gradually add peroxide thereto.

The amount of peroxide added at this time is preferably 5 to 10% by weight based on the weight of the polyethylene dissolved in the above step. If it is less than 5% by weight, radical polymerization will not proceed smoothly. If the amount exceeds 10% by weight, not only will the effect of the addition be reduced, but also problems such as excessive hardening of the rubber will occur as the thermal history progresses.

If the product obtained by copolymerization in this manner is subjected to a stripping treatment to separate and remove peroxide decomposition components, a copolymerization process oil that is effective for use in the present invention can be obtained. The conditions for the stripping process are a pressure of 1 to 2 m.
-I1g, temperature 185-225°C, 9 hours and about 2 hours.

This reactive rubber compounding oil is added in an amount of 30 to 200 parts by weight to 100 parts by weight of the above-mentioned ethylene propylene rubber. The mechanical strength of
If the amount exceeds 0.00 parts by weight, the mechanical strength of the vulcanized rubber composition will decrease and problems such as oil bleeding will occur, making it unsuitable.

The vulcanized rubber composition of the present invention usually contains reinforcing agents such as carbon black, zinc white, stearic acid, sulfur, peroxide, and other vulcanizing agents and vulcanization accelerators, as well as titanium white, talc, and calcium carbonate. There is no problem in adding a predetermined amount of other known additives such as inorganic fillers, anti-aging agents, and antistatic agents.

The vulcanized rubber composition of the present invention can be produced as follows. Namely, the aforementioned ethylene propylene rubber and copolymerization process oil.

Predetermined amounts of carbon black, zinc white, and stearic acid are sufficiently kneaded using, for example, a Pampari mixer.

A predetermined amount of sulfur pods and a vulcanization accelerator are added to the obtained mixed material using an oven roll whose surface is heated to 80° C., and then press-molded to obtain a vulcanized molded article of the rubber composition of the present invention. be able to.

[Examples of the Invention] Examples 1 to 4 (1) Production of copolymerized process oil First, Diana Process Oil PW380 and Diana Process Oil PIll-LV (both trade names) having properties shown in Table 1 as paraffinic mineral oils were prepared. , secondary hydrogenated oil manufactured by Idemitsu Kosan ■) was prepared, and the second hydrogenated oil was prepared as polyethylene.
Polyethylene LO114H (product name,
(manufactured by Idemitsu Petrochemical ■) and Hetrocene PE208 (trade name, manufactured by Toyo Soda ■) were prepared.

100 parts by weight of each of the mineral oils listed in Table 1 and 25 parts by weight of each of the polyethylenes listed in Table 2 were placed in a stainless steel container and heated to 200°C to dissolve the polyethylene. .

After the solution was cooled to 130°C, 5 parts by weight of dicumyl peroxide (manufactured by Tokyo Kasei, reagent grade 1') was gradually added thereto until the entire amount was dissolved, and then heated again to 200°C to approx. The radical polymerization reaction was allowed to proceed under stirring for 2 hours.

After the reaction is completed, the temperature is kept at 200°C and the pressure is about 2 mmHg.
The copolymerized process oil 4 according to the present invention is time-stripped to remove low-boiling substances such as peroxide fragments.
Got the kind.

That is, Diana Process Oil PW380-Polyethylene L-0114H, Diana Process Oil PW3
It is a process oil obtained by a combination such as 80-Hetrocene PH208, Diana Process Oil PW-LV-Polyethylene L-0114H, Diana Process Oil PW-LV-Hetrocene PE208. Each is referred to in this order as 'E4ZMi@1 oil, 1-C Example 2 oil, Example 3 oil, and Example 4 oil.

For comparison, process oil P%1I3801
00 parts by weight of polyethylene L-0114H or Petrocene PH20825 parts by weight (referred to as Comparative Example 1 oil and Comparative Example 2 oil, respectively), process oil pw-tv 100 parts by weight of polyethylene L-0114H or Petrosen PE20825
Parts by weight were simply dissolved to produce products (referred to as Comparative Example 3 oil and Comparative Example 4 oil, respectively).

In addition, process oil PW380 was used as Comparative Example 5 oil.

Process oil Pill-LV was used as Comparative Example 6 oil.

(2) Production of vulcanized rubber ethylene propylene rubber (product name: EPT4095,
100 parts by weight of carbon black (manufactured by Mitsui Petrochemical Co., Ltd.),
Product name: Asahi Carbon lllOH, MAF type, manufactured by Asahi Carbon #s) 140 parts by weight, zinc white (No. 1, JISK
-1410-1982), 1 part by weight of stearic acid (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent), and 140 parts by weight of the various process oils mentioned above were put into a Banbury mixer and kneaded at 120°C for 5 minutes. did.

The obtained kneaded product was transferred to a mixing roller with a surface temperature of 80°C, and 8.2-mercaptobenzothiazole I (1 weight part) and 1.5 parts by weight of tetramethylthiuram monosulfide (1 weight part) were added thereto, and then mixed 8 times. Let it pass;
Finally, it was press-molded at 180°C for 15 minutes to obtain a vulcanized rubber specimen.

The physical properties of each sample obtained at room temperature were measured according to the following specifications.

Hardness (Hs): Based on JISK-8301, type A
Tensile test: Based on JISK-8301 ■Tensile modulus:
Tensile modulus at 100% strain "100100 (
/ad) value ■Tensile strength: Stress at break (TB: kgf
/cyj) ■Tensile elongation: (EB, %) Dynamic viscoelasticity: Measurement temperature range from liquid nitrogen temperature to 80°C using a Pyblon M type device manufactured by Toyo Baldwin ■.

Heating rate 2℃/min 9 frequencies (vibration) Dynamic frequency) Measured under the condition of 110Hz The temperature at which tanδ reaches its peak value is Judging by degrees The above results are summarized in Table 3.

[Effects of the Invention] As is clear from the results in Table 3, the vulcanized rubber composition of the present invention has a tan δ peak temperature 5 to 15°C lower than the rubber compositions of the comparative examples, and has excellent low-temperature properties. ing. This is because the blended copolymerized process oil has partial mobility of the polyethylene molecular chain (MICR) due to the bond between the constituent molecules of the mineral oil and the polyethylene.

This can be said to be due to an increase in brown ability. In fact, process oil PW38 is used as the base oil.
Process oil PW-LV with better low-temperature fluidity than 0
When the tan δ peak temperature of the rubber specimen was replaced by It is clear that there are

Thus, the vulcanized rubber composition of the present invention has high mechanical strength, particularly excellent low-temperature properties, and can be expected to be used in various fields, and has great industrial value.

Claims (1)

[Claims] A vulcanized rubber composition characterized in that 100 parts by weight of ethylene propylene rubber is blended with 30 to 200 parts by weight of a copolymerized process oil obtained by copolymerizing paraffinic mineral oil and polyethylene in the presence of a peroxide.