JPS61252210A - Styrene/conjugated diene copolymer rubber - Google Patents

Abstract

PURPOSE:The titled rubber having a large hysteresis loss and excellent breaking strength and elongation breaking behavior and being suitable as a vibrationproof material, comprising styrene/conjugated diene copolymer obtained by emulsion polymerization and having a specified combined styrene content and a specified intrinsic viscosity. CONSTITUTION:A styrene/conjugated diene copolymer rubber obtained by emulsion polymerization and having an average combined styrene content of 40-70wt%, a distribution range of the composition of the combined styrene >=30%, said copolymer being distributed over the entire range of this composition distribution, and an intrinsic viscosity (in toluene at 30 deg.C) of 0.1-6dl/g. When the distribution range of the composition of the combined styrene in said copolymer rubber is narrower than 30%, the temperature dependency of the hysteresis loss of the rubber increases, which is undesirable for vibrationproof performance. The particularly desirable conjugated diene of the copolymer rubber is butadiene.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a large hysteresis loss, that is, a small impact resilience, and a small temperature dependence thereof, and has excellent fracture characteristics such as fracture strength and elongation. Styrene-conjugated chef 1 suitable as a vibration isolating material! Regarding composite rubber.

[Conventional technology]

In recent years, rubber materials with excellent vibration damping properties have been required to prevent noise and vibration from transportation means such as automobiles and motorcycles, as well as industrial machinery. Since they are used under extremely harsh conditions, so-called tough materials with large hysteresis loss and excellent fracture properties are required.

Conventionally, materials used to meet these requirements include natural rubber or synthetic rubber mixed with large amounts of oil and carbon black), or materials with relatively low glass transition temperatures (Tg).
It has been used as a blend of polymers with high

Generally, when oil is blended, impact resilience is small and vibration damping properties are improved, but compression set and fracture properties are reduced. Further, if a large amount of carbon black is used, there is a drawback that the workability during cross-wiring and molding, and the heat generation properties of the vulcanizate are reduced.

Furthermore, when a polymer having a relatively high Tg is blended, there is a drawback that the temperature dependence of hysteresis loss is large and the low-temperature properties are poor.

On the other hand, when looking at the practical conditions of vibration isolating materials, the operating temperatures thereof are increasing over a wide range, and as a result, vibration isolating materials with low temperature dependence of hysteresis loss are required.

[Problem that the invention seeks to solve]

The present inventors have found a method that does not have such drawbacks, that is, has good fracture properties, large hysteresis loss, and low temperature dependence, without reducing workability during kneading and molding. Intensive research was carried out to obtain a rubber particularly suitable for use as vibration damping materials.

[Ninth way to solve the problem]

As a result, it was found that a styrene-conjugated diene polymer rubber obtained by emulsion polymerization that satisfies the following requirements has excellent vibration damping properties, and based on this knowledge, the present invention was achieved.

The homogeneously bound styrene content exceeds ω weight St- and is 70% by weight or less, the composition distribution width of bound styrene is 3011I11 or more, the copolymer is distributed over the entire composition distribution width, and the intrinsic viscosity (in toluene, 9)℃) is 0.1~6
The object of the present invention is to provide a styrene-conjugated diene copolymer rubber suitable as a vibration damping material, which is characterized by a dt/f.

Describing the present invention in detail below, the average bound styrene content in the copolymer rubber of the present invention is more than 70% by weight and less than 70% by weight, preferably 45 to 65% by weight, more preferably 50 to 60% by weight. Particularly excellent effects can be obtained with a weight of -.

Further, the composition distribution width of bound styrene in the copolymer rubber of the present invention is 3 o or more, preferably 40 or more. If the mosquito distribution width is narrower than 30%, the temperature dependence of the hysteresis loss of the rubber will become large, which is unfavorable in terms of vibration damping properties. Furthermore, in the present invention, it is necessary that the copolymer is distributed over the entire composition distribution width of the bonded styrene, otherwise the effects of the present invention cannot be obtained.

The composition distribution of bonded styrene in the present invention is 5HNYA
TERAMACHI method (J, Macromol
Set.

Cross-fractionation was carried out using a cyclohexane/in-octane mixed solvent and benzene/methyl ethyl ketone according to Chew, 4 [8) 1785, 1970].

The styrene content in the polymer was determined by H-NMRK and expressed as a weight fraction.

Next, from the viewpoint of processability, the molecular weight of the copolymer rubber of the present invention is determined in terms of intrinsic viscosity (in toluene, aO°C) from 0.1 to 6d4/1.
1 Preferably 0.5 to 4 d4/f s Mooney 100°C Viscosity (ML1+4) preferably 20 to 150,
Particularly preferably, the range is from 30 to 100.

The amount of vinyl bonds in the microstructure of the conjugated diene moiety in the copolymer rubber of the present invention is not particularly defined, but the copolymer rubber of the present invention is obtained by an emulsion polymerization method. Therefore, as is well known, its value is much smaller than that of the additive.

Examples of the conjugated diene for the copolymer rubber of the present invention include butadiene, isoprene, pentadiene, etc., but butadiene is preferred.

To describe the method for producing the copolymer rubber of the present invention, specifically, after adding emulsion polymerization chemicals excluding part or all of styrene to a reactor, styrene is continuously added at the same time as polymerization starts until the end of the reaction. It can be obtained by adding a conjugated diene up to K at the end of the reaction, or by adding it to a reactor and polymerizing it while continuously changing the composition ratio of styrene and conjugated diene.

The copolymer rubber of the present invention can be used in a blend with other diene rubbers. Other diene rubbers include natural rubber, cis-polyisoprene rubber, other emulsion polymerized SBR,
Examples include cispolybutadiene, ethylene-propylene-diene rubber, butyl rubber, and halogenated butyl rubber.

Aromatic oils, naphthenic oils, and paraffinic oils can be added to the copolymer rubber of the present invention as extender oils, and aromatic oils are particularly preferred from the viewpoint of the physical properties targeted by the present invention. Highly aromatic oil is preferable in terms of vibration damping properties because it increases the hysteresis loss e of the rubber and reduces its temperature dependence.

The amount of extension oil added is 200 parts by weight per 100 parts by weight of rubber.
Parts by weight or less, preferably 10 to 100 parts by weight.

Carbon black, calcium carbonate, silica, etc. are used as reinforcing agents, and other ordinary compounding agents for rubber can be used for kneading and vulcanization.

[Effect]

Although the mechanism by which the copolymer rubber of the present invention produces the above-mentioned properties is not clear, it is thought that the interaction of the above-mentioned requirements of the present invention provides excellent vibration-proofing properties and fracture properties.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following examples as long as they do not exceed the gist of the invention.

In the Examples and Comparative Examples, the fracture properties were evaluated by fracture strength and fracture elongation, and the vibration damping properties were evaluated by rebound resilience at 25'C, 150℃, and 80℃. In good condition.

Processability was evaluated using the following scores: ■Shape of the compound when extruded using an extruder, and ■Wrapability during roll processing. (The numbers in Table 3 are the sum of ■ and ■. value).

■ Shape of the compound at the time of extrusion, good soldering ← → Bad ■ Rolling property good ← → Bad Note that in Examples and Comparative Examples, parts indicating proportions are based on weight.

Example 1 According to the basic emulsion polymerization recipe shown in Table 1, a volume of 10
0 t polymerization reaction vessel K 42 parts of 1,3-butadiene and 0.25 part of t-dodecylmercaptan were added. The reactor temperature was set to 7°C, and 0.10 part of paramenthane hydroperoxide was added to initiate polymerization. Immediately after the start of polymerization until the conversion reached 62%, 58 parts of styrene was continuously added at a constant rate.

When the conversion rate reached 62 cm, 0.15 parts of diethylhydroxylamine was added to stop the reaction.

Next, unreacted upper sludge was collected according to a conventional method, and the polymer was coagulated into crumbs using sulfuric acid and salt, and then dehydrated and dried to obtain rubber. The compositional distribution of bound styrene for the nine rubbers obtained was determined by the method described above and is shown in FIG. In FIG. 1, the composition distribution width of bound styrene is wide, and the copolymer is distributed over the entire composition distribution width.

Further, the mixture was kneaded in a 250ee plastomill according to the formulation shown in Table 2, and fractional press vulcanization was performed at 145°C. The physical property evaluation results are shown in Table 3.

Example 2 The amount of 1.3-butadiene added was set as the bottom, the amount of t-dodecylmercaptan added was set as 0.21 parts, and the amount of styrene added was set as t.
The same process as in Example 1 was performed except that -65 parts were used. The composition distribution of bound styrene was measured using the obtained rubber trap, and the results are shown in FIG. In FIG. 2, the composition distribution width of bound styrene is wide, and the copolymer is distributed over the entire composition distribution width. In addition, the physical properties were evaluated in the same manner as in Example 1, and the results are shown in Table 3.

Example 3 The same treatment as in Example 2 was carried out using V, G, C, 1, 16 as the extender oil during kneading, except for the following.

The physical properties of the rubber obtained in the same manner as in Example 1 were evaluated, and the results are shown in Table 3.

Comparative Example 1 The amount of 1.3-butadiene added was 63 parts, the amount of t-dodecylmercaptan added was 0.28 parts, and the amount of stainless steel added was 3
The same treatment as in Example 1 was performed except that 7 parts were removed. The physical properties of the rubber obtained were evaluated in the same manner as in Example 1, and the results are shown in Table 3.

Comparative Example 2 The amount of 1.3-butadiene added was 13 parts, and the amount of t-dodecylmercaptan added was 0-ODHt! , the amount of styrene added was 8
The same treatment as in Example 1 was carried out except that 7 parts were used. The physical properties of the rubber obtained were evaluated in the same manner as in Example 1, and the results are shown in Table i@3.

Comparative Example 3 1.3-butadiene addition amount is 1.3-butadiene addition amount is
The same treatment as in Example 1 was carried out, except that the amount of t-dodecyl mercaptan added was 0.21 parts, and the 7-mercaptan was added all at once. The physical properties of the rubber obtained were evaluated in the same manner as in Example 1, and the results are shown in Table 3.

Comparative Example 4 The amount of 1.3-butadiene added was 61.2 parts, the amount of t-dodecyl mercaptan added was t-0.14 parts, 0.10 part of para-menthane hydrover oxide was added, and the temperature was
Be sure to start emulsion polymerization under conditions of ℃. When the reaction reached 49 cm, 38.8 parts of styrene was added to continue the reaction.
The reaction was stopped when the conversion rate of edible sugar reached 60%.

The composition distribution of bound styrene was measured on the obtained rubber, and the results are shown in FIG. In FIG. 3, the composition distribution width is extremely narrow. Further, the physical properties of the rubber were evaluated in the same manner as in Example 1, and the results are shown in Table 3.

Table 2 $I V, G, C, -0,96O aromatic extender oil However,
In Example 3, V, G, C, = 1.16 F) was used.

*2 N-Cyclohexyl-2-benzothiazolylsulfenamide *3 2-mercaptobenzothiazole 14 1,3-diphenylguanidine [Effects of the invention] As is clear from Table 3, Examples 1 and 2.3 are comparative Compared to Example 3 (small composition distribution width of bonded styrene), the impact resilience is smaller, that is, the hysteresis loss is larger, and its temperature dependence is smaller, as well as good vibration isolation material properties with improved fracture characteristics and workability. shows. Comparative Examples 1 and 4 have a small average amount of bonded styrene, so the hysteresis loss is extremely small, and Comparative Example 2 has a large average amount of bonded styrene, so the fracture properties are significantly inferior.

The present invention is a styrene-conjugated diene copolymer rubber suitable for use as a vibration damping material, which has a large hysteresis loss, that is, a small impact resilience, a small temperature dependence, and excellent fracture properties in terms of fracture strength and elongation. It provides:

[Brief explanation of drawings]

FIG. 1 is a bar graph showing the composition distribution of bound styrene in the copolymer rubbers obtained in Example 1.2 and Comparative Example 4, respectively, where the horizontal axis shows the amount of bound styrene and the vertical axis shows the weight percentage.

Claims (1)

[Claims] A copolymer of styrene and conjugated diene obtained by emulsion polymerization, the average bound styrene content of which is 40% by weight.
exceeding 70% by weight, the composition distribution width of bound styrene is 30% or more, the copolymer is distributed over the entire composition distribution width, and the intrinsic viscosity (in toluene, 30°C) is 0. A styrene-conjugated diene copolymer rubber suitable as a vibration isolating material, characterized in that it has a vibration absorption of 1 to 6 dl/g.