JPH0377807B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a chloroprene copolymer, and further relates to an emulsion obtained by emulsion polymerizing a carboxyl group-containing vinyl monomer and a chloroprene monomer under acidic conditions. This is a method of adding rosin acid salt to. [Prior Art] A method for producing a carboxylic acid/chloroprene copolymer by emulsion polymerizing chloroprene and a vinyl monomer containing a carboxyl group such as acrylic acid or methacrylic acid in an acidic atmosphere is described, for example, in U.S. Pat. No. 2,724,707. No. Specification and Special Publication No. 43-6067
It is known from the publication number etc. Furthermore, when removing unreacted residual monomers from an acidic copolymer emulsion by steam distillation, there is a problem in that a large amount of coagulated material precipitates. Add the oxide aqueous solution and make the acidic copolymer emulsion.
It is also known that the pH can be adjusted to 7 to 12, thereby suppressing the precipitation of coagulum. However, even if this method is used, it has been found that there are still problems as described below. That is, (1) When a carboxylic acid/chloroprene copolymer is isolated by the freezing drum coagulation method, which is generally widely used for isolation of chloroprene polymer by emulsion polymerization method, the coagulated film is washed with water, and then squeezed using a squeeze roll. In the process of squeezing out the water and drying it, the washing water became extremely cloudy and the film sagged a lot.
This poses major problems in terms of wastewater treatment and workability, and is difficult to produce stably industrially. (2) When adding about 2% dilute alkali metal hydroxide aqueous solution to adjust the pH of the acidic copolymer emulsion to 7 to 12, a considerable amount of coagulation will precipitate if added at once. The addition must be done very slowly, which is cumbersome in operation. etc. [Problems to be Solved by the Invention] The object of the present invention is to solve the problems during the isolation of the above-mentioned carboxylic acid/chloroprene or further ethylenically unsaturated monomer copolymers in the preparation of the copolymers. The purpose is to solve the problems of turbidity of washing water and sagging of film. [Means for solving the problem] That is, the present invention solves the problem by adding a rosin acid salt to an acidic copolymer emulsion obtained by copolymerization.
The purpose of the present invention is to solve the above problems, and further, to perform emulsion polymerization of chloroprene and a vinyl monomer containing a carboxyl group in an acidic atmosphere, and to add an aqueous rosin acid salt solution to the acidic copolymer emulsion. It is characterized by The details of the present invention will be further explained below. There are no particular restrictions on the polymerization method for each monomer, and chloroprene and vinyl monomers containing carboxyl groups and, if necessary, other copolymerizable ethylenically unsaturated monomers are emulsified in an acidic atmosphere. All you have to do is polymerize. As a vinyl monomer containing a carboxyl group, which is a carboxylic acid, for example, unsaturated fatty acids such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid, etc., are added in an amount of 0.1 to 100 parts by weight of chloroprene.
~10 parts by weight are used, preferably 0.5 to 4 parts by weight. Examples of copolymerizable ethylenically unsaturated monomers include styrene, methyl methacrylate, acrylonitrile, 2,3-dichlorobutadiene, 1
- A monomer normally used for copolymerization of chloroprene, such as chlorobutadiene, is used in an amount of 20 parts by weight or less, if necessary. As the emulsifier, a sulfonic acid type emulsifier or a nonionic type emulsifier is used, for example, a carbon number of 8 to 20.
These include alkyl sulfonates, alkylaryl sulfates, condensates of sodium naphthalene sulfonate and formaldehyde, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenols, sorbitan fatty acid esters, polyoxyethylene acyl esters, and preferred examples include dodecyl Sodium benzenesulfonate, dodecylbenzenesulfonic acid triethanolamine salt, sodium lauryl sulfate, etc. are used. As the polymerization initiator, commonly used organic or inorganic peroxides such as benzoyl peroxide, potassium persulfate, ammonium persulfate, etc. may be used. The polymerization temperature can be carried out in the range of 0 to 80°C,
The preferred range is 8-50°C. As the polymerization terminator, commonly used terminators,
For example, phenothiazine, 2,6-di-tertiarybutylhydroxytoluene, etc. may be used. The rosin added to the acidic copolymer emulsion after completion of polymerization is used as an aqueous rosinate salt solution. The type of rosinate salt is not particularly limited, but alkali metal salts, ammonium metal salts, etc. of wood rosin, tall oil rosin, or disproportionated products thereof can be used, and potassium salts are particularly preferred. The concentration of the rosinate salt aqueous solution is also not particularly limited, but is 5 to 30
Weight percent is preferred. Also, add a small amount to this aqueous solution.
Alkali metal hydroxides such as NaOH and KOH can also be added. The amount used is about 1 to 10 parts by weight, preferably about 2 to 8 parts by weight, based on the rosin acid content per 100 parts by weight of the polymerized monomer. If the amount is less than about 1 part by weight or more than about 10 parts by weight, the effect of preventing washing water from becoming cloudy and film sagging will be small. [Effect] According to the present invention, surprisingly, by adding a relatively small amount of rosinate salt aqueous solution, the stability of the emulsion is improved when unreacted monomers are recovered, and the freeze-coagulated film is improved. It was found that the turbidity of the washing water and film sag during washing were significantly improved. It was also found that the storage stability of the obtained copolymer was significantly improved. A further remarkable effect is that the emulsion has good stability when adding an aqueous rosinate salt solution. When adding an aqueous alkali metal hydroxide solution such as NaOH, if the concentration is high (e.g. 5-10%)
A large amount of coagulum precipitated during addition, and the concentration was reduced to 2%.
If the solution is diluted to a certain degree, no coagulum precipitation will be observed, but the addition method must be carried out very gradually. If the addition is done rapidly, even about 2%
Even if diluted to a certain extent, a considerable amount of coagulum will precipitate. This tendency becomes more pronounced when the proportion of monomers containing carboxyl groups is increased. On the other hand, in the case of an aqueous rosinate salt solution, no coagulum precipitation is observed even if it is rapidly added. Furthermore, the stability of the emulsion during the recovery of residual monomer by the steam flash method is also different between the NaOH aqueous solution and the rosinate salt aqueous solution. When using a dilute NaOH aqueous solution, it is necessary to adjust the pH of the emulsion to 7 or higher by adding it;
Below, considerable coagulum precipitation is observed during recovery. On the other hand, the pH of rosin acid salt aqueous solution is 4 to 5.
Even when the emulsion is low, the stability of the emulsion during recovery is extremely good. From the above, the effect of adding the rosinate salt of the present invention has a completely different mechanism of action from the effect of adding an alkali metal hydroxide aqueous solution, which is brought about simply by adjusting the pH of the emulsion to a high level. This was discovered for the first time by the present invention. [Effects of the Invention] As is clear from the above description, according to the present invention, (1) turbidity of washing water when washing a freeze-solidified film can be improved. (2) It is possible to improve film sag when washing a freeze solidified film with water. (3) The stability of the emulsion when recovering unreacted residual monomers can be improved. (4) The rosinate salt aqueous solution can be added all at once without having to be added gradually. (5) The storage stability of the obtained copolymer can be significantly improved. The advantages are very great, and it is an industrially useful method. [Examples] The method of the present invention will be specifically explained below using Examples, but is not limited to these Examples. In addition, unless otherwise specified in the text, parts are parts by weight. Examples 1 to 5, Comparative Examples 1 to 4 Polymerization was carried out at 40° C. in a 10° autoclave equipped with a stirrer at the composition ratios shown in Table 1. Table 1 Chloroprene 98.7 parts Methacrylic acid 1.3〃 n-Dodecylmercaptan 1.8-2.0〃 Dodecylbenzenesulfonic acid sodium salt
1.0〃 Sodium salt of formaldehyde-naphthalene sulfonic acid condensate 0.7〃 Water 110〃 All polymerizations were carried out in a nitrogen atmosphere by continuously dropping an aqueous solution of potassium persulfate. When the conversion rate was about 90%, a terminator was added to stop the polymerization. The pH of the emulsion is approximately 2.0~
It was 2.2. In Examples 1 to 5, a 25% potassium rosinate aqueous solution was added to the obtained copolymer emulsion, and in Comparative Examples 2 to 4, a 2% NaOH aqueous solution was added. Comparative Example 1 contains no additives. Then, residual monomers were removed by a steam flash method, and the product was solidified in a freezing drum, washed with water, and dried. If the emulsion had a pH higher than 6, a 10% acetic acid aqueous solution was added to the emulsion to adjust the pH to 6.0 before solidification in a freezing drum, followed by freeze solidification. The results are summarized in Table 2.

【table】

[Table] As is clear from Table 2, compared to the comparative example, this example showed remarkable improvements in terms of turbidity of the washing water, film sag, and storage stability, as well as stability when adding potassium rosinate aqueous solution. Significant improvements were also seen in terms of stability, stability during residual monomer recovery, and stability during neutralization. In particular, the pH is 4.1 (Example 1) and 4.9 (Example 2)
Even if it is as low as 2%, the stability during collection is good.
It is clear that the effect is significantly different from that of NaOH aqueous solution. Examples 6 to 8, Comparative Examples 5 to 7 Table 4 summarizes the results of the same study as Examples 1 to 5 using the composition ratios shown in Table 3. Table 3 Chloroprene 95.0 parts 2,3-dichlorobutadiene 3.0 Methacrylic acid 2.0 n-dodecyl mercaptan 1.5-2.0 Sodium dodecylbenzenesulfonate 1.0 Sodium salt of formaldehyde-naphthalene sulfonic acid condensate 0.7 Water 110

[Table] As a result, methacrylic acid, a copolymer component,
If it is 2.0 parts, in a 2% NaOH aqueous solution, when recovering the monomer,
Although a considerable amount of coagulum was observed, it is clear that good results were obtained with the 25% potassium rosinate aqueous solution. Examples 9 to 11, Comparative Examples 8 to 9 Table 6 summarizes the results of the same study as in Examples 1 to 5 using the composition ratios shown in Table 5. Table 5 Chloroprene 99 parts Acrylic acid 1 Diisopropylxanthogen disulfide
2.5〃 Triethanolammonium dodecylbenzenesulfonate 1.0〃 Sodium salt of formaldehyde-naphthalenesulfonic acid condensate 0.7〃 Water 110〃

【table】

【table】 Good results were obtained in all of these Examples.

Claims (1)

[Claims] 1. A method of emulsion polymerizing a chloroprene monomer and a vinyl monomer containing a carboxyl group under acidic conditions, characterized by adding a rosinate salt to the obtained acidic copolymer emulsion. A method for producing a chloroprene copolymer. 2. The method according to claim 1, wherein an ethylenically unsaturated monomer is further added as a copolymer component.