JPH07292164A - High-damping chloroprene rubber composition - Google Patents

Abstract

PURPOSE:To obtain a chloroprene rubber composition keeping well-balanced properties of general rubber properties essential to chloroprene rubber, weatherability, heat resistance, cold resistance, etc., and more excellent in damping properties than the conventional one. CONSTITUTION:This high-damping chloroprene rubber composition contains a solid chloroprene polymer and a low-molecular chloroprene polymer synthesized by polymerization in the presence of an alkylmercaptane and/or mercaptoalcohol and having 500 to 50000 number-average molecular weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high damping chloroprene rubber composition capable of efficiently absorbing vibration energy.

[0002]

2. Description of the Related Art In recent years, vibration energy absorbing devices, that is, vibration isolator, vibration isolator, seismic isolation device and the like have been rapidly spread. For example, in a seismic isolation construction method for protecting a building from an earthquake, a seismic isolation rubber laminate is used. That is, the rubber layers and the iron plates are alternately combined to absorb the vibration energy caused by the earthquake between the ground and the structure.

However, the conventional seismic isolation rubber laminate has a lack of damping performance of the rubber composition used and has a small effect of absorbing vibration energy. Therefore, a viscous damper or the like is used to absorb the vibration. Was there. Therefore, there are problems such as a complicated structure and high cost.

Generally, as a method for evaluating the damping performance of a rubber composition, a loss coefficient (tan δ = loss elastic modulus / storage elastic modulus) obtained by viscoelasticity measurement of a material is used, and a loss coefficient with a large value is used. The higher the attenuation, the higher the judgment. Butyl rubber is best known as a rubber having a high damping property, but its use fields are limited because of problems such as large compression set, easy set, poor processability, and low vulcanization rate.

On the other hand, chloroprene rubber has an excellent balance of physical properties such as general rubber physical properties, weather resistance, heat resistance and cold resistance, and is therefore known as a suitable rubber material for seismic isolation rubber laminates. The chloroprene rubber laminate is used for the support of road bridges. However, since chloroprene rubber has insufficient damping performance, its improvement has been demanded.

As a means for improving the damping performance of chloroprene rubber, JP-A-63-245449 discloses a chloroprene polymer and a number average molecular weight of 500 to 20,000 polymerized in the presence of a xanthogen disulfide compound.
There is disclosed a chloroprene rubber composition for vibration-proof rubber, which comprises the liquid chloroprene polymer.

However, in the above-mentioned invention, there is a problem that the elastic modulus is lowered by the blending of the liquid chloroprene polymer, and therefore the blending amount of the liquid chloroprene polymer is naturally limited, so that sufficient damping performance cannot be obtained. It was

[0008]

An object of the present invention is to provide chloroprene which is superior in damping performance to conventional ones while maintaining the balance of general rubber physical properties, weather resistance, heat resistance, cold resistance, etc. possessed by chloroprene rubber. To provide a rubber composition.

[0009]

[Means for Solving the Problems] In order to solve the above problems, as a result of intensive studies by the present inventors, a solid chloroprene polymer and a low molecular weight chloroprene polymer polymerized in the presence of a specific compound were obtained. The inventors have found that the chloroprene rubber composition containing ## STR3 ## has superior damping performance as compared with the chloroprene rubber composition containing the liquid chloroprene rubber polymer of the prior art, and have reached the present invention.

That is, the present invention has a number average molecular weight of 50 obtained by polymerizing a solid chloroprene polymer with an alkyl mercaptan and / or mercapto alcohol.
The present invention relates to a high-damping chloroprene rubber composition containing a low molecular weight chloroprene polymer of 0 to 50,000.

The chloroprene polymer in the present invention means
Both the solid chloroprene polymer and the low molecular weight chloroprene polymer refer to a homopolymer of 2-chloro-1,3-butadiene or a copolymer of 2-chloro-1,3-butadiene and another monomer. Here, other monomers include 2-chloro-1,3
-It is not particularly limited as long as it can be copolymerized with butadiene, for example, styrene, acrylonitrile, 2,3-dichloro-1,3
-Butadiene, 1-chloro-1,3-butadiene, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, isoprene, 1,3-butadiene and the like.

As the solid chloroprene polymer in the present invention, a solid chloroprene polymer which is solid at room temperature and can be used for general vulcanized rubber can be used, but it is required to have high general rubber physical properties and compression set characteristics. In this case, those having a high molecular weight are preferable, and those having a number average molecular weight of 100,000 or more, more preferably 150,000 or more are preferable.

The low molecular weight chloroprene polymer in the present invention has a number average molecular weight of 5 obtained by polymerization in the presence of alkyl mercaptan and / or mercapto alcohol.
It is a polymer of 00 to 50,000, and by using this polymer, it is possible to improve the damping property, which was a problem in the prior art. As the alkyl mercaptan, a compound containing at least one mercapto group in the molecule,
For example, methyl mercaptan, ethyl mercaptan, n
-Butyl mercaptan, n-octyl mercaptan, n
-Dodecyl mercaptan, t-dodecyl mercaptan, etc. are mentioned, but not limited thereto. As the mercapto alcohol, a compound containing at least one mercapto group and at least one hydroxyl group in the molecule, for example, 2-mercapto-1-ethanol, 3-mercapto-1-propanol, 4-mercapto-1-butanol, Examples thereof include 2-mercaptocyclohexynol and 3-mercapto-1,2-propanediol, but are not limited thereto. When the number average molecular weight is less than 500, there is no effect of improving the damping property, and when it exceeds 50,000, the damping property is deteriorated.

The low molecular weight chloroprene polymer obtained by polymerizing in the presence of alkyl mercaptan and / or mercapto alcohol has a chemically stable molecular end, and has an alkyl group and / or a hydroxyl group which hardly reacts during rubber vulcanization. Become. On the other hand, in the case of a low molecular weight chloroprene polymer obtained by polymerizing in the presence of a conventional xanthogen disulfide compound, the molecular end of the polymer becomes a reactive xantogen end, and the molecular end becomes a cross-linking reaction during rubber vulcanization. It is considered that the effect of improving the damping property is not sufficiently exhibited because of the above. For this reason, as a low molecular weight chloroprene polymer, an alkyl group and // whose molecular terminal is chemically stable and hardly reacts during rubber vulcanization
Alternatively, it is considered that a low molecular weight chloroprene polymer having a hydroxyl group provides better damping properties.

In the chloroprene rubber composition of the present invention, the higher the content of the low molecular weight chloroprene polymer in the chloroprene rubber composition is, the more remarkable the effect of improving the damping property becomes, but on the other hand, the tensile strength and the elastic modulus are Since it gradually decreases, it is preferable to adjust its content according to the required characteristics of the field of use. When particularly high tensile properties, elastic moduli and damping properties are required together, the solid chloroprene polymer: low molecular weight chloroprene polymer is used in a weight ratio of 50: 5.
The range of 0 to 90:10 is preferable, and 60:40 to 80:
The range of 20 is more preferable.

The chloroprene can be polymerized by any of emulsion polymerization, solution polymerization and the like. As a method of mixing the solid chloroprene polymer and the low molecular weight chloroprene polymer, the latex state obtained by emulsion polymerization can be used. In the present invention, both solid chloroprene polymer and low molecular weight chloroprene polymer are produced by emulsion polymerization. It is preferable to mix in the obtained latex state.

The chloroprene rubber composition of the present invention is used by adding a vulcanizing agent and vulcanizing. Carbon black,
Fillers such as silica and clay, as well as process oils, plasticizers, antioxidants, lubricants and the like may be added. If necessary, other resins, rubbers, etc. may be blended within a range that does not impair the physical properties. There is no limitation on the compounding method and the vulcanizing method, and general rubber operations can be performed.

The chloroprene rubber composition obtained by the present invention has general rubber physical properties which are characteristic of chloroprene rubber,
It has excellent damping properties without impairing the balance of physical properties such as weather resistance, heat resistance, cold resistance, etc., and is suitable for building base support, road bridge support applications, etc. for seismic isolation rubber, precision electronics field, It is suitable as a member for absorbing vibration energy in the automobile field and the like.

[0019]

The present invention will be described in detail below with reference to examples.

Production Example 1 (1) Low molecular weight chloroprene polymer (B1) In a 5 l four-necked flask equipped with a stirrer, 2-chloro-
900 parts by weight of 1,3-butadiene, 2,3-dichloro-
1,3-butadiene 10 parts by weight, toluene 25 parts by weight,
A solution containing 12 parts by weight of n-dodecyl mercaptan as an alkyl mercaptan was charged and heated to 55 ° C., and then 0.5% by weight of α, α′-azobis-2,4-dimethylvaleronitrile was used as a polymerization initiator. The reaction was started by adding 1.5 parts by weight of a toluene solution. Polymerization was continued at 55 ° C., and 15 hours later, 1 part by weight of a toluene solution containing 0.02% by weight of p-tert-butylcatechol was added to terminate the polymerization. The polymerization rate of 2-chloro-1,3-butadiene was 72%. Next, a large excess of methanol was added to isolate the polymer, and then the purification operation of benzene dissolution-methanol coagulation was repeated three times, and then the residual solvent was evaporated at 110 ° C and 1-2 mmHgabs using a thin film evaporator. A false polymer was isolated and designated as B1.

(2) Low molecular weight chloroprene polymer (B2) A polymer was produced in the same manner as in Production Example (1) except that 4 parts by weight of 2-mercaptoethanol was used as a mercapto alcohol instead of 12 parts by weight of n-dodecyl mercaptan. Was obtained, and this polymer was designated as B2.

(3) Low molecular weight chloroprene polymer (B3) A polymer was obtained in the same manner as in Production Example (1) except that 18 parts by weight of diisopropylxanthogen disulfide was used instead of n-dodecyl mercaptan, and this polymer was obtained. To B3
And

(4) Method for measuring number average molecular weight of low molecular weight chloroprene polymer The number average molecular weight of chloroprene polymers B1 to B3 is GP.
The results obtained in terms of styrene by the C (gel permeation chromatography) method are shown in Table 1.

Production Example 2 (1) Production of solid chloroprene polymer (A1) Using a 5 liter 4-necked flask as a reactor and using the polymerization recipe shown in Table 2, potassium persulfate was continuously added dropwise under a nitrogen atmosphere. While carrying out emulsion polymerization. When the rate of polymerization reached 65%, 100 ppm of diethylhydroxylamine was immediately added to all charged monomers to terminate the polymerization reaction. Unreacted monomer was removed using the steam stripping method.

Molecular Weight Measurement Method of Solid Chloroprene Polymer (A1) The number average molecular weight of the chloroprene polymer obtained by (1) was determined in terms of styrene by GPC (gel permeation chromatography) method.

Example 1 A polymer A1 was used as a solid chloroprene polymer and a polymer B1 was used as a low molecular weight chloroprene polymer, and the composition and formulation shown in Table 3 (each numerical value is parts by weight) were applied to an open roll kneader. After kneading, the mixture was press-vulcanized at 150 ° C. for 20 minutes to obtain a vulcanized sheet having a thickness of 2 mm.

Example 2 A vulcanized sheet was obtained in the same manner as in Example 1 except that B2 was used as the low molecular weight chloroprene polymer.

Comparative Example 1 A vulcanized sheet was obtained in the same manner as in Example 1 except that B3 was used as the low molecular weight chloroprene polymer.

Comparative Example 2 A1 was used as the solid chloroprene polymer, and the vulcanized sheet was obtained in the same manner as in Example 1 without using the low molecular weight chloroprene polymer.

Method for measuring physical properties of vulcanized rubber Break strength [kgf / cm2], Break elongation [%], Hardness (JIS-A)
[Point], compression set (CS) is JIS K 6301
It was measured according to. Static shear modulus (GS) [kgf / cm2]
Is 2 in accordance with the JIS K 6301 low elongation stress test.
The stress at 5% elongation was calculated and calculated according to the following formula. Static shear modulus (GS) = stress at 25% elongation × 1.
639 Loss factor (tan δ) is 38m longer than vulcanized sheet
m, width 4 mm, thickness 2 mm, a test piece was punched out, and a rheovibron DDV-25F (manufactured by Orientec Co., Ltd.), which is a viscoelasticity measuring device, was used to room temperature (23 ° C.), amplitude ± 1%,
The measurement was performed at a preload of 30 g and frequencies of 0.5 Hz and 15 Hz.

Table 4 shows the results of measuring the above physical properties. From the results of Examples and Comparative Examples, it is confirmed that the use of the low molecular weight chloroprene polymer significantly improves tan δ and the effect of improving the damping property. Further, when using a low molecular weight chloroprene polymer, when using a hydroxyl terminal and an alkyl terminal than the xanthogen terminal,
It is clear that the effect of improving the damping property is excellent, and the improvement of compression set is also recognized.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

As described above, the chloroprene rubber composition produced according to the present invention has excellent physical properties such as damping property, elastic modulus and general rubber physical properties. Therefore,
The chloroprene rubber composition satisfies the general rubber physical properties, weather resistance, heat resistance, cold resistance, etc. required for a seismic isolation rubber laminate and, at the same time, is excellent in damping property, and therefore has a conventional viscosity. It is most suitable as a seismic isolation rubber laminate without the need to use a damper. In addition, the number average molecular weight of 500 to be polymerized in the presence of a conventional xanthogen disulfide compound
The damping performance of the chloroprene rubber composition of the present invention is superior to that of the chloroprene rubber composition containing 20,000 liquid chloroprene polymers.

Claims (1)

[Claims] 1. A number average molecular weight obtained by polymerizing a solid chloroprene polymer in the presence of an alkyl mercaptan and / or a mercapto alcohol is 500 to 50,000.
A high-damping chloroprene rubber composition comprising a low molecular weight chloroprene polymer of 0.