JPH11116622A - Production of sulfur-modified chloroprene polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject polymer capable of giving cured rubber with high tack abrasion resistance, by homopolymerization of a chlorobutadiene or its copolymerization with another monomer in the presence of a specific amount of sulfur based on the total amount of the monomer(s) followed by terminal modification of the resultant polymer so as to leave a specified amount of a free specific disulfide after the (co)polymerization. SOLUTION: This modified polymer is obtained by (A) homopolymerization of 2-chloro-1,3-butadiene or (B) copolymerization between 85-99.9 wt.% of 2- chloro-1,3-butadiene and 0.1-15 wt.% of another monomer copolymerizable therewith, in the presence of 0.4-1.2 wt.% of sulfur based on the total amount of the monomer(s), followed by terminal modification of the resultant polymer with (C) a 1-6C alkyl-bearing tetraalkyl thiuram disulfide and/or (D) a dialkyl xanthogenic disulfide so as to leave the free component(s) C and/or D at 0.2-1.1 wt.% based on the final polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a sulfur-modified chloroprene polymer having excellent adhesive and abrasion resistance suitable for use in, for example, automobiles, general industrial rolls and belts.

[0002]

2. Description of the Related Art Conventionally, vulcanized rubber made of sulfur-modified chloroprene polymer has been used as a material for belts and rolls because of its high tear strength and high bending fatigue resistance. But,
When used for a long period of time, the belt or roll is worn, and the generated sticky abrasion powder adheres to the sliding portion of the belt or roll, which is likely to cause vibration and noise. Conventional techniques for preventing this phenomenon (hereinafter referred to as adhesive wear) include the following techniques.

(1) In order to sufficiently perform vulcanization, there are methods such as strict vulcanization conditions (temperature and time), use of a vulcanization accelerator having high vulcanization, and addition of a filler. But,
As a result, the elastic modulus of the final product is increased, and the required quality is not satisfied. In addition, other mechanical properties such as tensile strength have to be sacrificed.

(2) There is a method in which short fibers are blended in an appropriate amount and exposed from the rubber surface to reduce the coefficient of friction to prevent sticking and abrasion. I do.

(3) As a method for improving the raw rubber itself, there is a method in which a crosslinked gel is contained. However, although the tackiness such as peeling of a roll in an unvulcanized state is improved, the effect of preventing the adhesive wear after vulcanization is improved. Is small.

[0006]

According to the prior art, a sulfur-modified chloroprene polymer suitable for obtaining a vulcanized rubber having excellent adhesive and abrasion resistance has not yet been obtained.

[0007] As a result of solving the above problems, the present inventor has found a method for producing a sulfur-modified chloroprene polymer which can provide a vulcanized rubber having excellent adhesive and abrasion resistance.

[0008]

Thus, according to the present invention, in producing a sulfur-modified chloroprene polymer,
(I) Homopolymerization of 2-chloro-1,3-butadiene in the presence of 0.4 to 1.2% by weight of sulfur based on the total amount of monomers or 85 to 99.9% by weight of 2-chloro- 1,3-butadiene and 0.1 to 15% by weight of a monomer copolymerizable therewith are copolymerized, and after polymerization, tetraalkylthiuram disulfide (a) having an alkyl group having 1 to 6 carbon atoms and End-modified with dialkylxanthogen disulfide (b) such that 0.2-1.1% by weight of free (a) and / or (b) remains with respect to the resulting polymer, or (II) Homopolymerization of 2-chloro-1,3-butadiene in the presence of sulfur or 8
5 to 99.9% by weight of 2-chloro-1,3-butadiene and 0.1 to 15% by weight of a monomer copolymerizable therewith are copolymerized. The terminal is modified with a tetraalkylthiuram disulfide having an alkyl group (a) and / or a dialkylxanthogen disulfide (b). At this time, the polymerization temperature (T ° C.) and the amount of elemental sulfur used (S %) And the amount of free (a) and / or (b) based on the total amount of the polymer (P% by weight) are expressed by the following formulas (1) to (3). (2) 0.6 ≦ S ≦ 1.2 Equation (3) All of 38 ≦ T ≦ 52 are satisfied, and Equations (4) to (6) are satisfied.
0.2 ≦ P ≦ 1.1 Equation (5) 0.8 ≦ S ≦ 1.2 Equation (6) 42 ≦ T ≦ 52 Selection is made so as to satisfy at least one of the following. Is provided.

For example, P = 1.8, S = 0.6, T = 4
In the case of 0, under the above conditions, (1), (2), (3)
Although the condition of the expression is satisfied, none of the conditions of the expressions (4), (5), and (6) are satisfied. Satisfaction of any one of the formulas (4), (5) and (6) means that the amount of the plasticizer (a) and / or (b) (P) is smaller than that of the conventional method.
Lowering the amount of sulfur, increasing the amount of sulfur (S), or increasing the polymerization temperature (T) means that at least one of the methods is adopted. Can be realized.

In the method of the present invention, when the polymerization is carried out according to an emulsion polymerization method using rosin soap containing at least 40% by weight of abietic acid as an emulsifier, a vulcanized rubber having excellent adhesive and abrasion resistance is obtained. Can be obtained.

[0011] In the present invention, the polymer is a compound having 1 carbon atom.
A tetraalkylthiuram disulfide (a) and / or a dialkylxanthogen disulfide (b) having an alkyl group of from 6 to 0.2,
Even if only terminal modification is carried out so that 1.1% by weight of free (a) and / or (b) remains, an improvement in adhesive wear resistance can be obtained. If the amount of elemental sulfur, the amount of (a) and / or (b) and the polymerization temperature are limited as in (1), the effect is further enhanced.

The procedure of the method for producing a sulfur-modified chloroprene polymer according to the present invention may be the same as the ordinary production method.
For example, when manufacturing by emulsion polymerization, chloroprene alone,
Alternatively, polymerization is carried out after emulsifying both chloroprene and a mixture of monomers copolymerizable with chloroprene and sulfur.

As the emulsifier in the emulsion polymerization method, ordinary rosin acid soap can be used. To further improve the abrasion resistance, rosin acid containing at least 40% by weight of abietic acid as a rosin acid component is used. Preference is given to using sodium and / or potassium salts. The use amount of the rosin soap is preferably 3 to 8% by weight, more preferably 4 to 7% by weight, based on 100 of the monomer. When the content is less than 3% by weight, poor emulsification is apt to occur, and problems such as deterioration of heat generation control of polymerization and formation of aggregates are liable to occur. When the content is more than 8% by weight, the polymer is liable to stick due to the residual rosin acid, and the separation and drying of the polymer from the emulsion, the processing with a roll, a Banbury mixer, etc., and the operability are deteriorated. Absent.

The monomer copolymerizable with chloroprene is not particularly limited. For example, 2,3-dichloro-1,3
-Butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, styrene, acrylonitrile, acrylic acid and its esters, methacrylic acid and its esters, and the like, and if necessary, two or more kinds may be used. Absent. The monomer copolymerizable with 2-chloro-1,3-butadiene is used at 15% by weight or less. If it exceeds 15%, the adhesive and abrasion resistance is reduced, and depending on the type, for example, tensile strength, elongation, oil resistance and the like are undesirably reduced.

The sulfur is not particularly limited, but colloidal sulfur is preferred from the viewpoint of solubility and dispersibility in the 2-chloro-1,3-butadiene monomer. The amount of sulfur used during polymerization is in the range of 0.4 to 1.2% by weight, preferably 0.6 to 1.2% by weight, based on the amount of 2-chloro-1,3-butadiene monomer. , More preferably from 0.8 to 1.2% by weight. 0.
If it is less than 4% by weight, the effect of improving the adhesive wear resistance is small, and if it is more than 1.2% by weight, heat resistance after vulcanization, bending fatigue resistance and the like are reduced.

The polymerization temperature is from 38 to 52.degree.
2 to 52 ° C is preferred. When the polymerization temperature is lower than 38 ° C., the effect of improving the adhesive wear resistance is small, and when the polymerization temperature is higher than 52 ° C., the vapor pressure of the 2-chloro-1,3-butadiene monomer increases, so that the polymerization operation is very difficult. Become difficult,
Since large-scale capital investment such as using a pressure-resistant container for the polymerization reactor is required, it is not preferable.

As a polymerization initiator, a usual radical polymerization initiator can be used. For example, in the case of emulsion polymerization, ordinary benzoyl peroxide, potassium persulfate,
Organic or inorganic peroxides such as ammonium persulfate,
An azo compound such as azobisisobutyronitrile is used.

In general, in the production of a chloroprene polymer, a polymerization terminator is added to stop the reaction when a predetermined polymerization rate is reached in order to prevent gel formation. There is no particular limitation on the polymerization terminator, and usually used terminators such as phenothiazine, tetraethylthiuram disulfide,
Hydroquinone monomethyl ether, diethylhydroxylamine and the like can be used.

The degree of polymerization is preferably in the range of 70 to 85%. If it is 70% or less, the copolymerization ratio with sulfur is too low, so that mechanical properties such as tensile strength and tear strength are insufficient, which is not preferable. If it is 85% or more, a branched structure or a gel is formed, so that the plasticization rate in the plasticizing step in the production of a general sulfur-modified chloroprene polymer described below decreases, resulting in poor processability of the polymer, It is not preferable because productivity is reduced.

The sulfur-modified chloroprene polymer obtained as described above generally has a high viscosity immediately after polymerization and has extremely poor processability. Therefore, the viscosity is reduced by cutting the polymer chain, which is called “plasticization”. Perform lowering operation. As a plasticizer for this purpose, dialkyldithiocarbamates and the like are usually used in combination with tetraalkylthiuram disulfides and dialkylxanthogen disulfides. As the kind of the tetraalkylthiuram disulfide and / or the dialkylxanthogen disulfide, those having an alkyl group having 1 to 6 carbon atoms are preferable. If the number of carbon atoms is larger than 6, the plasticization rate in "plasticization" to be described later is slowed down, and the productivity is lowered. Examples thereof include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, diethylxanthogen disulfide, diisopropylxanthogen disulfide and the like. The terminal modification of the polymer by plasticization
The reaction is carried out in such a manner that 0.2 to 2.0% by weight, preferably 0.2 to 1.1% by weight, of free tetraalkylthiuram disulfide and / or dialkylxanthogen disulfide remains based on the produced polymer. Below 0.2% by weight, while the rigidity of the vulcanized rubber increases, the elongation,
It is not preferable because the strength is reduced and the bending fatigue resistance is reduced. When the content is 2.0% by weight or more, the abrasion resistance deteriorates, which is not preferable.

[0021] The sulfur-modified chloroprene polymer produced under the above conditions exhibits excellent adhesive and abrasion resistance. As an evaluation method, visual observation is common, for example,
In the Taber abrasion test after vulcanization, it can be quantified by the particle size of the sandpaper of the mating material (which is smaller than that of the conventional technique) at which the adhesive wear starts to visually occur at a constant load and a constant number of shears. In this case, the smaller the numerical value, the greater the adhesive resistance, which is preferable.

The analysis method and the measurement method are as follows.

Analysis of free plasticizer For the quantitative analysis of tetraalkylthiuram disulfide and / or dialkylxanthogen disulfide used as a plasticizer, extraction of acetone from a polymer at room temperature and titration of the extract with aqueous sodium sulfide solution (Discoloration point: from yellow to green-blue). The calculated value is a value converted to tetraethylthiuram disulfide.

Evaluation of Adhesive Abrasion Resistance Among the methods of JIS K6264, a Taber abrasion test was adopted, and JIS was used as an abrasive instead of ordinary stone.
Using sandpapers of various particle sizes shown in the method of R6001, the maximum [center] particle size (μm) of the sandpaper when adhesion was observed by visual observation after 500 gf of load and 500 times of shearing was measured. The number of the used sandpaper and its central particle size (μm) are as follows.
The smaller the value, the less likely it is to stick (higher abrasion resistance).

[0025] Measurement of physical properties of vulcanized rubber Normal condition and tensile test after heat aging (100 ° C, 30 minutes)
According to JIS K6301, bending fatigue resistance is J
It was measured according to ISK6260.

[0026]

EXAMPLES The present invention will be described in detail below with reference to examples and test examples, but the present invention is not limited to these examples.

Example 1 Using a reactor having an internal volume of 60 liters, 20 kg of chloroprene monomer, 25 kg of pure water, 0.8 k of rosin acid (Rosin HTR manufactured by Harima Kasei; abietic acid content: 44%)
g, sulfur 120 g, sodium hydroxide 160 g and β-
After charging and emulsifying 300 g of a sodium salt of a naphthalenesulfonic acid formalin condensate, polymerization was carried out at 44 ° C. under a nitrogen atmosphere using potassium persulfate as an initiator. As soon as the polymerization rate reached 82%, the emulsion was stopped by adding a milk suspension of phenothiazine. Next, a plasticizer emulsion (A) having the following composition was added.

Plasticizer emulsified liquid (A) toluene 300 g tetraethylthiuram disulfide 240 g 4,4'-thiobis (2-methyl-6-t-butylphenol) 10 g pure water 300 g β-naphthalenesulfonic acid formalin sodium salt 20 g 30 g of sodium lauryl sulfate Then, 220 g of sodium dibutyldithiocarbamate was added as a plasticization accelerator. Thereafter, unreacted monomers were removed by steam stripping, and plasticized at 30 ° C. for 25 hours.
A chloroprene polymer was obtained. The results are shown in Table 1 together with the analysis value of the amount of the free plasticizer. The obtained polymer was blended according to the blending recipe shown in Table 2 and press-vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized product.

Examples 2 to 8 and Comparative Examples 1 to 7 Polymers were produced by changing the amount of plasticizer, the amount of sulfur, the type and amount of rosin acid, the amount of sodium hydroxide and the polymerization temperature. Table 1 summarizes the results. In Comparative Examples 6 and 7,
A polymer could not be obtained for the reasons described in the table.

Test Examples Each of the polymers produced in Examples 1 to 8 and Comparative Examples 1 to 5 was roll-kneaded according to the formulation shown in Table 2 and then roll-kneaded.
Press vulcanization was performed at 30 ° C. for 30 minutes to produce a vulcanized rubber sheet. Table 3 shows the physical property evaluation results of these vulcanized rubber sheets.

[0031]

As can be seen from the results of the examples and test examples, according to the present invention, it is possible to produce a sulfur-modified chloroprene polymer which exhibits excellent adhesive and abrasion resistance when vulcanized. It is possible.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

Claims (3)

[Claims] 1. Homopolymerization of 2-chloro-1,3-butadiene in the presence of 0.4 to 1.2% by weight of sulfur with respect to the total amount of monomers or 85 to 99.9% by weight of 2- Chloro-
1,3-butadiene and 0.1 to 15% by weight of a monomer copolymerizable therewith are copolymerized.
A tetraalkylthiuram disulfide (a) and / or a dialkylxanthogen disulfide (b) having an alkyl group of 6 to 0.2 to 1.
A method for producing a sulfur-modified chloroprene polymer, wherein the terminal is modified so that 1% by weight of free (a) and / or (b) remains. 2. Homopolymerization of 2-chloro-1,3-butadiene in the presence of sulfur or 85-99.9% by weight of 2-
Chloro-1,3-butadiene and 0.1 to 15% by weight of a monomer copolymerizable therewith are copolymerized, and after polymerization, tetraalkylthiuram disulfide (a) having an alkyl group having 1 to 6 carbon atoms is obtained. ) And / or terminally modified with dialkylxanthogen disulfide (b), wherein the polymerization temperature (T ° C.), the amount of elemental sulfur used relative to the total amount of monomer during polymerization (S wt%) and the amount of free The amount (P weight%) of (a) and / or (b) is calculated according to the following formulas (1) to (3): formula (1) 0.2 ≦ P ≦ 2.0 formula (2) 0.6 ≦ S ≦ 1 .2 Formula (3) 38 ≦ T ≦ 52, and Formulas (4) to (6) Formula (4) 0.2 ≦ P ≦ 1.1 Formula (5) 0.8 ≦ S ≦ 1 .2, which is selected so as to satisfy at least one of the following expressions (6): 42 ≦ T ≦ 52. Method for producing a modified chloroprene polymers. 3. The polymerization is carried out by using abietic acid as an emulsifier.
The method for producing a sulfur-modified chloroprene polymer according to claim 1 or 2, wherein the method is carried out by emulsion polymerization using rosin soap containing 0% by weight or more.