JP3294709B2 - Method for producing high damping chloroprene rubber composition - Google Patents

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 high damping chloroprene rubber composition capable of efficiently absorbing vibrational energy.

[0002]

2. Description of the Related Art In recent years, devices for absorbing vibration energy, that is, vibration isolation, vibration isolation, seismic isolation devices, and the like have been rapidly spreading. For example, seismic isolation construction methods for protecting buildings from earthquakes use seismic isolation rubber laminates. That is, the rubber layer and the iron plate are alternately combined to absorb vibration energy due to the earthquake between the ground and the building.

[0003] However, the conventionally used seismic isolation rubber laminate has insufficient damping performance of the rubber composition itself used and has a small effect of absorbing vibration energy. I was Therefore, there have been problems such as a complicated structure and high cost.

In general, 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 measuring the viscoelasticity of a material is used. The higher the attenuation, the higher the attenuation. As the rubber having a high damping property, butyl rubber is best known, but it has problems such as large compression set, easy settling, poor workability, and low vulcanization rate, and its use field has been limited.

On the other hand, chloroprene rubber is known as a rubber material suitable for seismic isolation rubber laminates and the like because of its excellent balance of physical properties such as general rubber properties, weather resistance, heat resistance and cold resistance. Chloroprene rubber laminates are used for bearings on road bridges. However, since chloroprene rubber does not have sufficient damping performance, its improvement has been demanded.

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

However, in the above invention, the method of producing liquid rubber is significantly different from ordinary solid rubber, and the production cost is high, the mixing of solid rubber and liquid rubber is not easy, and the viscosity of liquid rubber is large. Has a problem that it is difficult.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a chloroprene rubber having a balance of general rubber properties, weather resistance, heat resistance, cold resistance, etc., while maintaining the balance of damping performance, elastic modulus, etc. It is an object of the present invention to provide an industrially advantageous method for producing a chloroprene rubber composition having excellent heat resistance.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies and as a result, have obtained 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. A chloroprene rubber composition produced by emulsion polymerization and mixing them in an emulsified state, respectively, exhibits high damping properties like a chloroprene rubber composition obtained by mixing a liquid chloroprene polymer with a solid chloroprene polymer, which is a conventional technique. The present inventors have found that mixing in a state of emulsification also eliminates the difficulty of mixing a solid rubber and a liquid rubber, and reached the present invention.

That is, the present invention provides a GPC (gel permeation)
Chromatography) Measured in styrene conversion
A high molecular weight chloroprene polymer having a number average molecular weight of 100,000 or more and GPC (gel permeation powder )
A low-molecular-weight chloroprene polymer having a number average molecular weight of 500 to 50,000 , as determined in terms of styrene by measurement (chromatography), is produced by an emulsion polymerization method, and then these are mixed in an emulsified state. The present invention relates to a method for producing a highly damping chloroprene rubber composition.

The chloroprene polymer in the present invention is:
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, as the other monomer, 2-chloro
There is no particular limitation as long as it can be copolymerized with -1,3-butadiene, for example, styrene, acrylonitrile, 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, acrylic acid, acrylic Acid esters, methacrylic acid, methacrylic acid esters, isoprene, 1,3-butadiene and the like can be mentioned.

The high molecular weight chloroprene polymer of the present invention has a number average molecular weight of 100,000 or more. Generally, when the number average molecular weight of the chloroprene polymer decreases,
Physical properties such as elastic modulus, tensile strength and compression set are reduced. In particular, when a low-molecular-weight chloroprene polymer is mixed as in the present invention, the physical properties thereof are remarkably reduced, and the viscosity of the rubber after mixing is too low, so that the workability is remarkably lowered 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 needs to have a number average molecular weight of 500 to 50,000. When the number average molecular weight is less than 500, it merely functions as a softening agent and has no effect of improving the damping property. When it exceeds 50,000, the effect of improving the damping property is reduced.

In the present invention, the higher the content of the low-molecular-weight chloroprene polymer in the chloroprene rubber composition, the more the effect of improving the damping property becomes remarkable. It is preferable to adjust the content in accordance with the required characteristics of. When particularly high tensile properties, elastic modulus, and damping property are also required, the high-molecular-weight chloroprene polymer: low-molecular-weight chloroprene polymer is preferably in a weight ratio of 50:50 to 90:10, and 60:60. The range of 40 to 80:20 is more preferable.

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

The advantage of mixing the chloroprene polymer of the present invention in a latex state is that an extremely high molecular weight chloroprene polymer and an extremely low molecular weight chloroprene polymer can be easily mixed at an arbitrary ratio. is there. In addition, when a low-molecular-weight chloroprene polymer having a number-average molecular weight of 500 to 50,000 is produced alone, a special production step is usually required (for example, Japanese Patent Application Laid-Open No.
-85292), and in the case of the present invention, it can be easily produced by the same method as that for ordinary chloroprene rubber.

Emulsion polymerization may be carried out by a usual method, and as a polymerization initiator, a usual radical initiator such as a peroxide, an azo compound, a sulfate, a redox initiator can be used. As the emulsifier, an anionic, cationic, nonionic or amphoteric surfactant can be used. Specific surfactants include fatty acid salts such as sodium oleate, rosin and rosin derivatives, sulfate salts such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, arylsulfonic acids, and arylsulfonic acids. Anionic surfactants such as formaldehyde condensates, nonionic surfactants such as polyethylene glycol and alkyl esters of polyethylene glycol, and one or more kinds of polyvinyl alcohols can be used in combination. 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 in the present invention, a known molecular weight regulator may be used. As the molecular weight regulator, compounds containing at least one mercapto group in the molecule, for example, alkyl mercaptans such as methyl mercaptan, ethyl mercaptan, n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, Compounds containing at least one mercapto group and at least one hydroxyl group in the molecule, such as 2-mercapto-1
-Ethanol, 3-mercapto-1-propanol, 4
- mercapto-1-butanol, 2-mercapto-cyclo <br/> hexane hexanol, 3-mercapto alcohol-mercapto-1,2-propanediol, xanthogen disulfide, halogenated hydrocarbons such as carbon tetrachloride However, the present invention is not limited to these, and an appropriate one can be selected and used depending on the purpose.

The chloroprene rubber composition of the present invention is used after 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 and rubbers can be blended as long as the physical properties are not impaired. There is no limitation on the compounding method and vulcanization method, and general operations on rubber can be performed.

The chloroprene rubber composition obtained according to the present invention has the general rubber properties characteristic of chloroprene rubber,
Excellent damping properties are obtained without impairing the balance of physical properties such as weather resistance, heat resistance, and cold resistance.It is suitable for seismic isolation rubber, such as foundation bearings for buildings and road bridges. Although it is suitable for a member for the purpose of absorbing vibration energy in the automobile field and the like, the present invention makes it possible to industrially easily produce such a high-damping rubber.

[0021]

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

Production Example 1 (1) Production of chloroprene polymer Emulsion polymerization was carried out using a 5-liter four-necked flask as a reactor under the polymerization recipe shown in Table 1 while continuously dropping potassium persulfate under a nitrogen atmosphere. Was done. 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-dodecylmercaptan. As soon as the polymerization rate reached 65%, 100p of diethylhydroxylamine was added to all charged monomers.
pm was added to stop the polymerization reaction. Unreacted monomers were removed using a 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 by GPC (gel permeation chromatography) in terms of styrene.

Production Example 2 (1) Low molecular weight chloroprene polymer (B5) 2-chloro-chloroprene polymer was placed in a 5-liter four-necked flask equipped with a stirrer.
900 parts by weight of 1,3-butadiene, 2,3-dichloro-
1,3-butadiene 10 parts by weight, toluene 25 parts by weight,
After charging a solution containing 18 parts by weight of diisopropylxanthogen disulfide and raising the temperature to 55 ° C., 1 part of 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 parts by weight. The polymerization was continued at 55 ° C., and after 15 hours, 0.02% by weight of p-tert-butylcatechol was used.
1 part by weight of a toluene solution containing was added to terminate the polymerization. The conversion of 2-chloro-1,3-butadiene is 72%.
Met. Next, a large excess of methanol was added to isolate the polymer. Thereafter, the purification operation of benzene dissolution-methanol coagulation was repeated three times, and then 11 times using a thin film evaporator.
The polymer was isolated by evaporating the residual solvent at 0 ° C and 1-2 mmHgabs, and the polymer was designated as B5. This was liquid at normal temperature, and had a number average molecular weight of 4,900 as determined by GPC measurement.

Examples 1-4, Comparative Example 1 The chloroprene polymer obtained in Production Example 1 was mixed in an emulsified state at the ratio shown in Table 2. The mixing ratio was shown by the weight ratio of the polymer. The chloroprene rubber thus obtained was kneaded with an open roll kneader according to the formulation shown in Table 3, 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 a high molecular weight polymer, and B5 was used as a low molecular weight chloroprene polymer. The mixture was kneaded with an open roll kneader according to the formulation shown in Table 4, and then pressed at 150 ° C. for 20 minutes. Vulcanization was performed to obtain a vulcanized sheet having a thickness of 2 mm.

In both the examples and comparative examples, the kneading operation was carried out using an open roll, and the workability at that time is shown in Table 5 as the difficulty of compounding.

Method for measuring physical properties of vulcanized rubber Breaking strength [kgf / cm2], breaking elongation [%], hardness (JIS-A)
[Point], Compression set (CS) is JIS K6301
It measured according to. Static shear modulus (GS) [kgf / cm2]
Is 2 according to the low elongation stress test of JIS K6301.
The stress at 5% elongation was determined and calculated according to the following equation. Static shear modulus (GS) = stress at 25% elongation × 1.
639 The loss factor (tan δ) is 38 m longer than the vulcanized sheet.
m, a width of 4 mm, and a thickness of 2 mm were punched out and a room temperature (23 ° C.), amplitude ± 1%, using a rheovibron DDV-25F (manufactured by Orientec) as a viscoelasticity measuring device.
The measurement was performed at a preload of 30 g and frequencies of 0.5 Hz and 15 Hz.

Table 5 shows the measurement results of the above physical properties. From the 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 a large tan δ is exhibited and excellent attenuation is exhibited. In Comparative Example 2 in which a liquid rubber is blended, it takes time to mix the liquid rubber, and the liquid rubber is a viscous liquid, which is difficult to handle. On the other hand, in the present invention, there is no such a problem. Compounding could be performed in a similar manner.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

As described above, the production method of the present invention makes it possible to industrially produce a highly damping chloroprene rubber composition easily and inexpensively. 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 according to the present invention satisfies the general rubber properties, weather resistance, heat resistance, cold resistance, and the like required for the seismic isolation rubber laminate, and has excellent damping properties. Therefore, it is not necessary to use a conventionally required viscous damper, so that it is optimal as a seismic isolation rubber laminate.

────────────────────────────────────────────────── (5) References JP-A-51-124145 (JP, A) JP-A-55-3425 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 11/00 C08F 2/22

Claims (1)

(57) [Claims] 1. GPC (gel permeation chromatography)
Chloroprene polymer having a number-average molecular weight of 100,000 or more as determined by styrene conversion by measurement , and GPC (gel permeation chromatography).
-) The number average molecular weight obtained by measurement in terms of styrene is 5
A low-molecular-weight chloroprene polymer having a molecular weight of from 0.00 to 50,000,
A method for producing a high-damping chloroprene rubber composition, wherein each of them is produced by an emulsion polymerization method, and then these are mixed in an emulsified state.