JPH0655798B2 - Method for producing chloroprene copolymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a carboxyl-modified chloroprene polymer, more specifically acrylic acid and / or methacrylic acid and chloroprene (2-chloro-
1,3-butadiene) and an emulsion copolymerization method to obtain a chloroprene copolymer.

[Conventional technology]

A method for producing a chloroprene copolymer by emulsion polymerization of chloroprene and acrylic acid and / or methacrylic acid is known, for example, from Japanese Patent Publication No. 43-6067. When chloroprene and acrylic acid and / or methacrylic acid are emulsion-polymerized to obtain a chloroprene copolymer, there are the following problems as compared with the case of producing a normal chloroprene (co) polymer.

(1) Since the polymerization is carried out in an acidic atmosphere, the polymerization rate is extremely high and it is difficult to control the polymerization.

(2) Since the polymerization is carried out in an acidic atmosphere, an ordinary emulsifier mainly composed of rosin acid cannot be used.

(3) During the steps from polymerization to isolation of the polymer, the stability of the latex is poor, and precipitates are easily generated.

(4) When the copolymer is isolated by the freeze drum coagulation method, the coagulated film is washed with water, and water is squeezed with a squeezing roll to dry it. The problem occurs.

(5) When the copolymer is isolated by the freeze drum coagulation method, the coagulated film is washed with water, the water is squeezed with a squeezing roll, the film is attached to a moving canvas, and hot air is blown to dry the film. The film is peeled off by the hot air and a part which is not dried is generated, or the film is dropped from the canvas to cause a process stop, which causes a problem of workability and quality deterioration.

Regarding the problem (2), many patent publications in the past (for example, Japanese Patent Publication No. 40-9773, Japanese Patent Publication No. 38-1242, Japanese Patent Publication No. 43)
No. -6067, Japanese Patent Publication No. 44-9593, etc.) is covered by polymerization using a non-rosin acid salt.

Regarding (3), in JP-B-43-6067, a latex containing unreacted monomer is added to about 2% of a dilute aqueous solution of alkali metal hydroxide to adjust the pH to 7 to 12. It is known that the precipitation of a solidified product can be prevented when the unreacted residual monomer is removed by steam distillation.

Regarding (4), it is known from Japanese Patent Application Laid-Open No. 61-12710 that it can be improved by adding a rosin acid salt to the latex which has been polymerized.

However, a method capable of simultaneously improving the above problems (1) to (5) has not yet been known.

[Problems to be solved by the invention]

The present invention aims to simultaneously improve various problems in producing a chloroprene copolymer by emulsion polymerization of chloroprene and acrylic acid and / or methacrylic acid as described above, and more specifically, chloroprene and Emulsion polymerization of acrylic acid and / or methacrylic acid to produce a chloroprene copolymer, which does not require special equipment and operational changes, and can be produced in the same manner as a conventional chloroprene (co) polymer. With the goal.

[Means for solving problems]

That is, the present invention relates to chloroprene and acrylic acid and / or
Alternatively, in a method for producing a chloroprene copolymer by emulsion copolymerization of methacrylic acid, (1) as an emulsifier, an alkali metal salt of alkylbenzenesulfonic acid having an alkyl group having 6 to 18 carbon atoms and formalin of β-naphthalenesulfonic acid The following straight line (a), (b), the alkali metal salt of the condensate
Within the range enclosed by (c) and (d) (however, (a), (b), and
Including the line (c). The shaded area in FIG. ), (2) containing 5 to 30 ppm of a chloroprene polymerization inhibitor with respect to all monomers before the initiation of the polymerization reaction, and (3) polymerizing in the presence of dialkyl xanthogen disulfide. A method for producing a polymer, which is a fundamental improvement method in which the above problems (1) to (5) are simultaneously solved.

Straight line (a): y = 0.8x Straight line (b): y = -1.5x + 7.0 Straight line (c): y = -2.0x + 4.0 Straight line (d): y = 0 where y is 100 parts by weight of all monomers By weight of the alkali metal salt of alkylbenzene sulfonic acid with respect to x,
Is the part by weight of the alkali metal salt of the β-naphthalenesulfonic acid formalin condensate with respect to 100 parts by weight of all the monomers.

The monomers used in the present invention have chloroprene and acrylic acid and / or methacrylic acid as essential components, and acrylic acid and / or methacrylic acid is preferably 0.5 to 2.6 mol% of all monomers, and when less than 0.5 mol%, The amount of carboxyl groups in the polymer is extremely small and the characteristics of carboxyl modification cannot be exhibited. If it exceeds 2.6 mol%, the storage stability of the raw rubber is greatly deteriorated and it cannot be put to practical use.

As described above, the monomers used in the present invention include chloroprene and acrylic acid and / or methacrylic acid as essential components. In addition to these, 2,3-dichlorobutadiene-
1 selected from the group consisting of 1,3,1-chlorobutadiene-1,3, styrene, sulfur and methyl methacrylate
Copolymerization of 1.0% by weight or less of one or more monomers does not hinder the present invention.

The emulsifier used in the emulsion polymerization in the present invention is an alkali metal salt of alkylbenzene sulfonic acid (hereinafter referred to as ABS).
Is limited to the combination of alkali metal salt of formalin condensate of β-naphthalene sulfonic acid (hereinafter referred to as β-NS), and the combination or substitution of other emulsifiers lowers the polymerization activity, decreases the stability of latex, Alternatively, it is not preferable because it leads to a decrease in workability when the polymer is isolated from the latex. The amount of ABS and β-NS used is the shaded area in FIG. 1, that is, y ≦ 0.8x, y ≦ −1.5x + 7.0, y when ABS = y parts by weight and β-NS = x parts by weight. ≥-2.0x + 4.
It is limited to a section surrounded by straight lines of 0 and y> 0.
When y> 0.8x, the above problems (3), (4) or (5) cannot be improved. If y> -1.5x + 7.0, the above problem (4) or (5)
Can not be improved, and in a polymerization system containing a chloroprene polymerization inhibitor described below, there is a risk of delaying the polymerization. y
<-2.0x + 4.0 cannot solve the above problem (1) or (3).

The carbon number of the alkyl group of ABS is limited to 6 to 18, and if it is 5 or less and 19 or more, the above problem (3) cannot be improved.

Further, one of the greatest features of the present invention is that 5 to 30 ppm of a chloroprene polymerization inhibitor is added to all the monomers before the initiation of the polymerization reaction.

If it is less than 5 ppm, the above problem (1) cannot be improved, the reproducibility of the polymerization reaction is poor, and not only the physical properties of the obtained copolymer but also the reproducibility of the viscosity are not certain.

On the other hand, if it exceeds 30 ppm, the delay of the polymerization is large and the productivity is lowered.

Thiodiphenylamine is most preferable as the polymerization inhibitor of chloroprene, and can exhibit balanced polymerization behavior.

The molecular weight modifier is limited to dialkyl xanthogen disulfide, and the mercaptan compound causes an addition reaction with acrylic acid and / or methacrylic acid, which is not preferable in terms of viscosity reproducibility.

Other auxiliaries used in the polymerization include a trace amount of alkali metal hydroxides, but the total amount of the monomers 10
When it exceeds 0.4 parts by weight relative to 0 parts by weight, the conversion rate of methacrylic acid during emulsion polymerization is suppressed, which is not preferable.

Polymerization temperature, monomer conversion rate, etc. are not particularly limited,
The polymerization temperature is preferably in the range of 5 to 55 ° C., particularly in the range of 25 to 35 ° C. from the viewpoint of controllability of polymerization rate and storage stability of the obtained copolymer (raw rubber). Monomer conversion is 70-
90% is preferable. A polymerization terminator for stopping the polymerization at a predetermined conversion rate is, for example, thiodiphenylamine, 4
-tert-Butylcatechol, diethylhydroxylamine, etc. are used. In addition, various stabilizers such as epoxy compounds, phenol compounds, bisphenol compounds, etc. may be converted in order to improve the storage stability of raw rubber. .

The stability of the latex can be adjusted by adjusting the pH of the latex after the polymerization based on the method disclosed in Japanese Examined Patent Publication No. Sho 43-6067 to a pH of 8 or more, preferably 8 to 9 with a 2% aqueous sodium hydroxide solution. Are preferred for further improvement.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples and comparative examples. Unless otherwise specified, the numbers "%" and "parts" are parts by weight. Polymerization is 1
Polymerization was carried out in a 4-necked flask of 5 under the conditions shown in (1) in a nitrogen stream while stirring.

Polymerization was carried out while sequentially adding a 0.2% aqueous solution of formamidine sulfinic acid in order to control the increase of the specific gravity to 0.003 for 10 minutes.

When the polymerization reached a predetermined addition rate, 100 ppm of diethylhydroxyamine was added to all charged monomers to terminate the polymerization. While stirring the latex, add 2% NaOH aqueous solution to adjust the pH of the latex to 9.0.
The unreacted monomer was removed by a vacuum thin film dryer. The polymer was isolated by first adding 5% acetic acid aqueous solution to the latex and adjusting the pH to 7.0, and then performing the freeze-coagulation method in the usual manner.

The results of polymerization and polymer isolation are shown in Table 1.

The chemical properties of the chemicals used in Examples and Comparative Examples are as follows.

Chloroprene: 2-chloro-1,3-butadiene, purity = 99.8% Methacrylic acid: manufactured by Wako Pure Chemical Industries, Ltd. Thiodiphenylamine: manufactured by Seiko Chemical Co., Ltd. H ₂ O: ion-exchange resin, followed by distillation did.

DBS: Sodium dodecylbenzene sulfonate, manufactured by Kao Corporation, trade name "Neoperex 05 powder" β-NS: Sodium salt of formalin condensate of β-naphthalene sulfonic acid, manufactured by Kao Corporation, trade name "Demol N" Sodium hydroxide: manufactured by Wako Pure Chemical Industries, Ltd., special grade product DXD: diisopropyl xanthogen disulfide, manufactured by Kawaguchi Chemical Co., Ltd. (Examples 1 to 4) Examples included in the claims of the present invention. Therefore, there were few problems in manufacturing.

(Comparative Examples-1 and 2) This is an example in which the amount of the polymerization inhibitor added to the monomer before the initiation of polymerization is out of the scope of the claims, and it is difficult to control the polymerization rate and there is a problem in reproducibility of Mooney viscosity. I got it.

(Comparative Examples-3 to 7) The amount of the emulsifier added was outside the scope of the claims, and there was a problem in productivity.

[Effects of the Invention] As is clear from the above points, according to the present invention, (i) the polymerization can be carried out at an appropriate rate, and the reproducibility of the polymerization is good.

(Ii) The stability of the latex is good during the polymerization to polymer isolation steps.

(Iii) When performing polymer isolation by the freeze drum coagulation method,
Problems such as workability, yield, and environmental degradation can be prevented.

And the like, which is extremely superior to the conventional method for producing a carboxyl-modified chloroprene rubber, and is a technology which has a great inventive step in industry.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the addition amounts of an alkali metal salt of an alkylbenzene sulfonic acid and an alkali metal salt of a β-naphthalene sulfonic acid formalin condensate in the method of the present invention.

Claims (3)

[Claims] 1. A method for producing a chloroprene copolymer by emulsion-copolymerizing chloroprene and acrylic acid and / or methacrylic acid, wherein (1) an alkylbenzene sulfonic acid having an alkyl group having 6 to 18 carbon atoms is used as an emulsifier. The alkali metal salt of the formalin condensate of alkali metal salt and β-naphthalene sulfonic acid within the range surrounded by the following straight lines (a), (b), (c) and (d) (however, (a), (b ), And (including on the line of (c)), (2) contains 5 to 30 ppm of a chloroprene polymerization inhibitor before the start of the polymerization reaction with respect to all monomers,
(3) A method for producing a chloroprene copolymer, which comprises polymerizing in the presence of dialkylxanthogen disulfide. Straight line (a): y = 0.8x Straight line (b): y = -1.5x + 7.0 Straight line (c): y = -2.0x + 4.0 Straight line (d): y = 0 where y is all monomers It is the weight part of the alkali metal salt of alkylbenzene sulfonic acid with respect to 100 weight parts, and x
Is the part by weight of the alkali metal salt of the β-naphthalenesulfonic acid formalin condensate with respect to 100 parts by weight of all the monomers. 2. The method for producing a chloroprene copolymer according to claim 1, wherein acrylic acid and / or methacrylic acid account for 0.5 to 2.6 mol% of all monomers. 3. The method for producing a chloroprene copolymer according to claim 1, wherein the polymerization inhibitor of chloroprene added in advance to the monomer during the polymerization is thiodiphenylamine.