JPH07292165A - 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 having an excellent elastic modulus in addition to an excellent damping property same as in the conventional one. CONSTITUTION:This high-damping chloroprene rubber composition contains a solid chloroprene polymer and a low-molecular chloroprene polymer having 20000 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 invention, there is a problem that the elastic modulus is lowered by blending the liquid chloroprene polymer.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide chloroprene which is superior in elastic modulus to conventional chloroprene rubber while maintaining the balance of general rubber physical properties, weather resistance, heat resistance, cold resistance and the like. 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 having a specific number average molecular weight were obtained. The present inventors have found that the contained chloroprene rubber composition has an excellent elastic modulus as compared with the chloroprene rubber composition containing the liquid chloroprene rubber polymer of the prior art, and completed the present invention.

That is, the present invention relates to a high-damping chloroprene rubber composition comprising a solid chloroprene polymer and a low molecular weight chloroprene polymer having a number average molecular weight of more than 20,000 and not more than 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 more than 20,000 and 50,000.
It is the following. The use of this polymer enables to improve the elastic modulus, which has been a problem in the prior art. When the number average molecular weight is 20,000 or less, the effect of improving the damping property is recognized, but the elastic modulus cannot be improved. Further, if the number average molecular weight exceeds 50,000, the effect of improving the damping property is significantly reduced, which is not preferable. However, as the number average molecular weight increases, the elastic modulus increases, so by using a low molecular weight chloroprene polymer having a large number average molecular weight as much as possible within a range in which the effect of improving the damping property does not decrease, the elastic modulus is improved as compared with the conventional technique. It is possible to improve.

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, the more remarkable the effect of improving the damping property becomes, but the tensile strength and elastic modulus gradually increase. Since it decreases, it is preferable to adjust the content according to the required characteristics of the field of use. When particularly high tensile properties, elastic modulus, and damping properties are required, solid chloroprene polymer:
The low molecular weight chloroprene polymer has a weight ratio of 50: 50-
The range of 90:10 is preferable, and 60:40 to 80:20.
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.

To control the molecular weight of the solid chloroprene polymer and the low molecular weight chloroprene polymer of the present invention, a well-known molecular weight modifier may be used. As the molecular weight modifier, a compound containing at least one mercapto group in the molecule, for example, an alkyl mercaptan such as methyl mercaptan, ethyl mercaptan, n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan, 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-
Examples thereof include mercapto alcohols such as mercapto-1-butanol, 2-mercaptocyclohexynol, and 3-mercapto-1,2-propanediol, xanthogen disulfide, halogenated hydrocarbons such as carbon tetrachloride, but are not limited thereto. It is possible to select and use an appropriate one according to the purpose instead of the one.

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) Production of Chloroprene Polymer Using a 5-liter 4-necked flask as a reactor, emulsion polymerization was carried out by continuously dropping potassium persulfate under a nitrogen atmosphere in a polymerization recipe shown in Table 1. went. The molecular weight of the high molecular weight chloroprene polymer and the low molecular weight chloroprene polymer was adjusted by adjusting the amount of n-dodecyl mercaptan added. Immediately after the polymerization rate reached 65%, 100 pL of diethylhydroxylamine was added to all the charged monomers.
The polymerization reaction was stopped by adding pm. Unreacted monomer was removed using the steam stripping method.

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

The chloroprene polymers polymerized in Example 1 and Comparative Examples 1 to 3 (1) were mixed in an emulsified state as shown in Table 2. The mixing ratio is shown by the weight ratio of the polymer. The rubber thus obtained was blended according to the formulation shown in Table 3 with an open roll kneader, and then 15
It was press-vulcanized at 0 ° C. for 20 minutes to obtain a vulcanized sheet having a thickness of 2 mm.

Method for measuring physical properties of vulcanized rubber The static shear modulus (GS) [kgf / cm2] is JIS K
According to the low elongation stress test of 6301, the stress at 25% elongation was determined 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 these results, it is confirmed that the use of the low molecular weight chloroprene polymer increases the tan δ and the effect of improving the damping property. However, it is also clear that when the number average molecular weight of the low molecular weight chloroprene polymer exceeds 50,000, the effect of improving the damping property is significantly lowered, and when it is 20,000 or less, the elastic modulus is lowered. That is, within the scope of the present invention, both effects of high elastic modulus and high damping are achieved in a well-balanced manner.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

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 produced by the present invention has the general rubber physical properties, weather resistance, required for a seismic isolation rubber laminate.
Since it satisfies heat resistance, cold resistance, etc., and has excellent damping properties, it is not necessary to use a viscous damper, which has been conventionally required, and is optimal as a seismic isolation rubber laminate. In addition,
In comparison with a conventional chloroprene rubber composition containing a liquid chloroprene polymer having a number average molecular weight of 500 to 20,000 polymerized in the presence of a xanthogen disulfide compound,
The chloroprene rubber composition of the present invention is superior in elastic modulus.

Claims (1)

[Claims] 1. A high-damping chloroprene rubber composition comprising a solid chloroprene polymer and a low molecular weight chloroprene polymer having a number average molecular weight of more than 20,000 and not more than 50,000.