JPH07292166A - Production of high-damping chloroprene rubber composition - Google Patents

Abstract

PURPOSE:To provide an industrially advantageous method for production of 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, elastic modulus, etc., than the conventional one. CONSTITUTION:This method for production of a high-damping chloroprene rubber composition is carried out by synthesizing a high-molecular chloroprene polymer having >=100000 number-average molecular weight and a low-molecular chloroprene polymer having 500 to 50000 number-average molecular weight respectively according to the emulsion polymerization method and subsequently blending them in an emulsion state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a highly dampening 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, the manufacturing method of the liquid rubber is very different from the usual solid rubber, the manufacturing cost is high, the mixing of the solid rubber and the liquid rubber is not easy, and the viscosity of the liquid rubber is large. It is difficult to do so.

[0008]

The object of the present invention is to maintain the balance of general rubber physical properties, weather resistance, heat resistance, cold resistance and the like of chloroprene rubber, while at the same time providing damping performance, elastic modulus, etc. Another object of the present invention is to provide an industrially advantageous method for producing a chloroprene rubber composition having excellent properties.

[0009]

[Means for Solving the Problems] In order to solve the above problems, the inventors of the present invention have conducted extensive research and as a result, have found that a high molecular weight chloroprene polymer having a specific molecular weight or more and a low molecular weight chloroprene polymer having a specific molecular weight are used. , Each produced by emulsion polymerization, a chloroprene rubber composition obtained by mixing these in an emulsion state shows high damping property similarly to a chloroprene rubber composition obtained by mixing a liquid chloroprene polymer with a solid chloroprene polymer which is a conventional technique, and further The inventors have found that the difficulty of mixing the solid rubber and the liquid rubber can be eliminated by mixing them in an emulsified state, and have reached the present invention.

That is, the present invention has a number average molecular weight of 100,
000 or more high molecular weight chloroprene polymer and a low molecular weight chloroprene polymer having a number average molecular weight of 500 to 50,000 are produced by an emulsion polymerization method, respectively, and then these are mixed in an emulsion state. The present invention relates to a method for producing a high-damping chloroprene rubber composition.

The chloroprene polymer in the present invention means
Both the high molecular weight 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, the other monomer is 2-chloro.
There is no particular limitation as long as it can be copolymerized with -1,3-butadiene, and examples thereof include styrene, acrylonitrile, 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, acrylic acid, and acrylic. Examples thereof include acid esters, methacrylic acid, methacrylic acid esters, isoprene, and 1,3-butadiene.

The high molecular weight chloroprene polymer in the present invention has a number average molecular weight of 100,000 or more. Generally, when the number average molecular weight of a chloroprene polymer becomes low,
Physical properties such as elastic modulus, tensile strength and compression set deteriorate. In particular, when a low-molecular-weight chloroprene polymer is mixed as in the present invention, the physical properties of the polymer are remarkably deteriorated, and the viscosity of the rubber after mixing is excessively decreased, so that the workability is significantly decreased in the compounding step. Therefore, the high molecular weight chloroprene polymer in the present invention needs to have a number average molecular weight of 100,000 or more, and more preferably 150,000 or more.

Next, the low molecular weight chloroprene polymer in the present invention is required to have a number average molecular weight of 500 to 50,000. When the number average molecular weight is less than 500, it merely acts as a softening agent and does not have the effect of improving the damping property, and when it exceeds 50,000, the effect of improving the damping property decreases.

In 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 the elastic modulus gradually decrease, but the field of use is increased. It is preferable to adjust the content according to the required characteristics of. When particularly high tensile properties, elastic modulus, and damping properties are required together, the high molecular weight chloroprene polymer: low molecular weight chloroprene polymer is preferably in a weight ratio range of 50:50 to 90:10, and 60: The range of 40 to 80:20 is more preferable.

As a method of polymerizing chloroprene, it is essential to carry out emulsion polymerization for both high molecular weight and low molecular weight and to mix both in the obtained latex state.

The advantage of mixing the chloroprene polymer of the present invention in a latex state is that it becomes possible to easily mix an extremely high molecular weight chloroprene polymer and an extremely low molecular weight chloroprene polymer at any ratio. is there. Further, when a low molecular weight chloroprene polymer having a number average molecular weight of 500 to 50,000 is produced alone, a special production process is usually required (see, for example, JP-A-54).
In the case of the present invention, it can be easily produced by a method similar to that of ordinary chloroprene rubber.

The emulsion polymerization may be carried out by a usual method, and as the polymerization initiator, a usual radical initiator such as a peroxide, an azo compound, a sulphate or a redox type initiator may be used. As the emulsifier, anionic, cationic, nonionic or amphoteric surfactants can be used. Specific surfactants include fatty acid salts such as sodium oleate, rosin and rosin derivatives, sulfate ester salts such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, aryl sulfonic acid, aryl sulfonic acid. It is possible to use one kind or a mixture of two or more kinds of anionic surfactants such as formaldehyde condensate, nonionic surfactants such as polyethylene glycol, alkyl ester of polyethylene glycol, polyvinyl alcohol and the like. It is not limited.

In order to control the molecular weight of the high molecular weight chloroprene polymer and the low molecular weight chloroprene polymer of the present invention, a well-known molecular weight adjusting agent 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, Compounds 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, 2-mercaptocyclohexynol, mercapto alcohols such as 3-mercapto-1,2-propanediol, xanthogen disulfide, halogenated hydrocarbons such as carbon tetrachloride, and the like, 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 after vulcanization by adding a vulcanizing agent. 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, Although it is suitable for a member intended to absorb vibration energy in the automobile field and the like, the present invention makes it possible to easily manufacture such a high damping rubber industrially.

[0021]

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

Production Example 1 (1) Production of chloroprene polymer Emulsion polymerization was carried out by continuously adding dropwise potassium persulfate under a nitrogen atmosphere with a polymerization recipe shown in Table 1 using a 5-liter 4-necked flask as a reactor. I 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.

Production Example 2 (1) Low molecular weight chloroprene polymer (B5) 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 18 parts by weight of diisopropylxanthogen disulfide was charged, the temperature was raised to 55 ° C., and then a toluene solution containing 0.5% by weight of α, α′-azobis-2,4-dimethylvaleronitrile as a polymerization initiator was added. The reaction was started by adding 0.5 part by weight. Polymerization was continued at 55 ° C. and after 15 hours p-tert-butylcatechol 0.02% by weight
Polymerization was stopped by adding 1 part by weight of a toluene solution containing The polymerization rate of 2-chloro-1,3-butadiene is 72%
Met. Next, a large excess of methanol was added to isolate the polymer, and then the purification operation of benzene dissolution-methanol coagulation was repeated 3 times, and then using a thin film evaporator, 11
The residual solvent was evaporated at 0 ° C and 1-2 mmHgabs to isolate the polymer, which was designated as B5. This product was liquid at room temperature, and the number average molecular weight determined by GPC measurement was 4,900.

Examples 1 to 4 and Comparative Example 1 The chloroprene polymers obtained in Production Example 1 were mixed in the ratio shown in Table 2 in an emulsified state. The mixing ratio is shown by the weight ratio of the polymer. The thus-obtained chloroprene rubber was kneaded with the compounding recipe shown in Table 3 using an open roll kneader, and then press vulcanized at 150 ° C. for 20 minutes to obtain a vulcanized sheet having a thickness of 2 mm. .

Comparative Example 2 A1 was used as the high molecular weight polymer and B5 was used as the low molecular weight chloroprene polymer. The compounding recipe shown in Table 4 was followed by kneading with an open roll kneader, followed by pressing at 150 ° C. for 20 minutes. It was vulcanized to obtain a vulcanized sheet having a thickness of 2 mm.

The kneading work was carried out with an open roll in both Examples and Comparative Examples, and the workability at that time is shown in Table 5 as the degree of difficulty of compounding.

Method of 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 5 shows the results of measuring the above physical properties. From Examples and Comparative Examples, a chloroprene rubber composition containing a high molecular weight chloroprene polymer produced according to the present invention and a low molecular weight chloroprene polymer having a specific number average molecular weight,
It can be seen that it exhibits a large tan δ and exhibits excellent damping properties. Further, in Comparative Example 2 in which the liquid rubber is blended, it takes time to mix the liquid rubber and the liquid rubber is a viscous liquid and is difficult to handle. Blending could be done similarly.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

As described above, according to the production method of the present invention, it becomes possible to industrially produce a chloroprene rubber composition having a high damping property at low cost. The chloroprene rubber composition produced by the present invention has excellent physical properties such as damping properties, elastic modulus, and general rubber physical properties. Therefore, the chloroprene rubber composition produced according to the present invention satisfies the general rubber physical properties, weather resistance, heat resistance, cold resistance, etc. required for the base-isolated rubber laminate, and at the same time, has excellent damping properties. Therefore, it is not necessary to use the viscous damper that has been conventionally required, and it is optimal as a seismic isolation rubber laminate.

Claims (1)

[Claims] 1. A high molecular weight chloroprene polymer having a number average molecular weight of 100,000 or more and a number average molecular weight of 500 to 500.
A method for producing a high-damping chloroprene rubber composition, which comprises producing 50,000 low molecular weight chloroprene polymers by an emulsion polymerization method, respectively, and then mixing these in an emulsion state.