JP2000159825A - Production of vinyl ester polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a vinyl ester polymer exhibiting no dispersion in average degree of polymerization and having a stable quality by polymerizing a vinyl ester monomer in the presence of dimethylacetal. SOLUTION: This process is applicable to any polymerization method, such as solution, emulsion, suspension, or bulk polymerization. The amount of dimethylacetal present is preferably 0.001-10 wt.% of than of a vinyl ester monomer. Preferably, an organic peroxide having a half line of 10-180 min at the polymerization temperature, as a polymerization initiator, is present in the polymerization system. The presence of a hydroxycarboxylic acid and/or a polycarboxylic acid is also preferable, suitably a hydroxypolycarboxylic acid such as citric acid. The hydroxycarboxylic acid and/or the polycarboxylic acid is added preferably in an amount of 5-30 ppm based on the vinyl ester monomer.

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 vinyl ester polymer, and more particularly, to a method for producing a vinyl ester polymer having a stable quality without variation in the average degree of polymerization. Related to manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in obtaining a vinyl ester polymer such as a vinyl acetate resin, a vinyl ester monomer such as vinyl acetate is polymerized by a method such as solution polymerization, bulk polymerization, suspension polymerization and the like. In this case, polymerization initiators such as persulfates such as potassium persulfate, azo compounds such as azobisisobutyronitrile, and organic peroxides such as benzoyl peroxide are used.

[0003]

However, when a vinyl ester monomer is polymerized in the coexistence of the conventional polymerization initiator as described above, the resulting polymer has a variation in the average degree of polymerization. It was found that it would occur, and in particular it was found that it was necessary to finely adjust the production conditions in order to control the variation in the average degree of polymerization between lots, responding to recent demands for further quality improvement in the market. Is where is desired.

[0004]

In view of the above situation, the present inventors have conducted intensive studies on a method for producing a vinyl ester-based copolymer, and as a result, have found that a vinyl ester-based monomer can be obtained in the presence of dimethyl acetal. The above problems can be solved by polymerizing the polymer, and in particular, by coexisting a polymerization initiator (organic peroxide) having a half-life at a temperature during polymerization of 10 to 180 minutes, the present invention The present inventors have found that the effect of the present invention is remarkable, and have completed the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As the vinyl ester monomer used in the present invention,
Examples include vinyl formate, vinyl acetate, vinyl propionate, vinyl stearate, saturated branched fatty acid vinyl, and vinyl benzoate. Practically, vinyl acetate is important, but is not limited thereto.

It is also possible to use these vinyl ester monomers together with monomers copolymerizable therewith, such as ethylene, propion, isobutylene, α-octene, α-octene and the like. Dodecene, olefins such as α-octadecene, acrylic acid, methacrylic acid, crotonic acid, unsaturated carboxylic acids such as maleic acid or salts thereof or alkyl esters thereof, acrylonitrile,
Nitriles such as methacrylonitrile, acrylamide,
Amides such as methacrylamide, ethylene sulfonic acid,
Olefinsulfonic acids such as allylsulfonic acid and methallylsulfonic acid or salts thereof, N-vinylimidazole,
-, 3- or 4-vinylpyridine, basic monomers such as dimethylaminoethyl acrylate, mono (2-hydroxyethyl acrylate) acid phosphate, mono
(2-hydroxyethyl methacrylate) phosphoric acid-containing monomers such as acid phosphate, vinyl ether, vinyl ketone, N-vinylpyrrolidone, vinyl halide or vinylidene halide, and the like. The proportion of the monomer in the copolymer obtained is not particularly limited, but is preferably 50% by weight or less, particularly preferably 20% by weight or less.

In the production method of the present invention, alcohol,
Ester, a solution polymerization method in which polymerization is performed in an organic solvent such as an aromatic hydrocarbon, an emulsion polymerization method in which monomers are dispersed in an aqueous medium and polymerization, a suspension polymerization method, a bulk polymerization method, and the like. It is possible to apply.

The main feature of the present invention is to allow dimethyl acetal to coexist during the polymerization of the vinyl ester monomer. The object of the present invention is achieved by coexisting such dimethyl acetal. You can do it.

The coexistence amount of the dimethyl acetal is not particularly limited.
001 to 10% by weight (further preferably 0.01 to 7% by weight, particularly 0.1 to 5% by weight, especially 1 to 5% by weight). It is difficult to obtain the effects of the present invention, and if it exceeds 10% by weight, it may be difficult to obtain a polymer having a high degree of polymerization, which is not preferable.

As a method of adding such dimethyl acetal, for example, a method of adding it to a polymerization system as it is, a method of dissolving it in a solvent used for polymerization in advance and then adding it to the polymerization system,
A method of adding beforehand to the monomer to be polymerized, a method of adding it before mixing with other additives, a method of adding it separately, a method of adding it to the polymerization system simultaneously with the monomer and the solvent And the like, but are not limited thereto.

The production method of the present invention is not limited by the polymerization method and the like as described above, and various polymerization conditions are not particularly limited, but the polymerization temperature is preferably set to 40 to 70 ° C. (furthermore, 55 to 65 ° C.). If the temperature is lower than 40 ° C., the polymerization takes a long time, and if it is higher than 70 ° C., it becomes difficult to remove the heat of polymerization, which is not preferable.

In the present invention, in addition to the above-mentioned dimethyl acetal, a half-life at a temperature during polymerization is 10 minutes.
To 180 minutes (further 10 to 120 minutes, especially 20 to 120 minutes
It is also preferable to coexist the polymerization initiator of (ii), and as such a polymerization initiator, an organic peroxide is preferable, and specifically, isobutyl peroxide, diisopropyl peroxydicarbonate, diallyl peroxydicarbonate, di-n -Propyl peroxydicarbonate, dimyristyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, di (2-ethoxyhexyl) peroxydicarbonate, di (methoxyisopropyl) peroxydicarbonate, and the like. be able to.

The half-life is determined by using a solution inert to radicals such as benzene, preparing a 0.1 mol / l polymerization initiator solution, and enclosing the solution in a nitrogen-substituted glass tube. Immersed in a thermostat set at 60 ° C., and thermally decomposed for measurement. The coexistence amount of the polymerization initiator is not particularly limited, but the polymerization time is 2 to 20.
It is preferable to adjust such a coexistence amount so as to be time. If the polymerization time is less than 2 hours, it is difficult to remove the heat of polymerization. Conversely, if the polymerization time is more than 20 hours, industrial productivity is disadvantageous, which is not preferable.

Further, in the present invention, coexistence of a hydroxycarboxylic acid and / or a polyvalent carboxylic acid is also preferable in that generation of by-products can be suppressed. Such a hydroxycarboxylic acid or polyvalent carboxylic acid is preferably glycolic acid. Lactic acid, glycerin, malic acid, tartaric acid, citric acid, salicylic acid, malonic acid, succinic acid, maleic acid, phthalic acid, oxalic acid, glutaric acid, etc., and carboxylic acids such as citric acid are preferably used. . The amount of such a hydroxycarboxylic acid or polyvalent carboxylic acid to be present is not particularly limited, but is usually 5 to 5 parts per vinyl ester monomer.
It is preferable to add in the range of -30 ppm.

The method of adding the polymerization initiator and the carboxylic acid compound is not particularly limited, and the same addition method as that for dimethyl acetal can be employed. Thus,
According to the production method of the present invention, a vinyl ester polymer excellent in quality with little variation in molecular weight can be obtained, but the production method of the present invention is used for any polymerization such as batch polymerization and continuous polymerization. be able to.

The vinyl ester polymer obtained by the method of the present invention can be, of course, commercialized as it is,
For example, polyvinyl acetate obtained by polymerizing vinyl acetate can be used as a raw material of a polyvinyl alcohol-based resin, and the polyvinyl alcohol-based resin obtained by saponifying the polyvinyl acetate obtained by the method of the present invention has a hue. It is good (white) and excellent in solubility in water, and is useful for various uses.

[0017]

The present invention will be specifically described below with reference to examples. In the Examples, “parts” and “%” are based on weight unless otherwise specified. Example 1 100 parts of vinyl acetate, 28 parts of methanol, a polymerization initiator (benzoyl peroxide; half-life at 60 ° C. is 300)
Minutes) (200 ppm based on vinyl acetate) and 4 parts of dimethyl acetal (4% based on vinyl acetate) were charged into a reaction vessel equipped with a condenser and a paddle type stirring device.
Polymerization was carried out at 60 ° C. for 6 hours while rotating the paddle at 60 rpm to obtain a vinyl acetate polymer.

The obtained vinyl acetate polymer is saponified by an ordinary method using an alkali catalyst to give a saponification degree of 99.9.
A mole% of a polyvinyl alcohol resin was obtained, and the average degree of polymerization of the resin was 1,800 as measured according to JIS K 6726. Further, under the same conditions as above, two lots were further polymerized, and the average degree of polymerization was measured in the same manner. However, there was almost no variation among lots at 1800 and 1810, respectively. Further, the following evaluation was performed using the vinyl acetate polymer obtained in the first lot. The evaluation results are shown in Table 1.

(Hue) The obtained vinyl acetate polymer was saponified by an ordinary method using an alkali catalyst to give a saponification degree of 9
A polyvinyl alcohol-based resin of 9.9 mol% was obtained, and the hue of the polyvinyl alcohol-based resin was visually observed and evaluated as follows. ○ −−− White × −−− Ivory color (slightly yellowish) (Solubility) 10 parts of the polyvinyl alcohol-based resin obtained above and 90 parts of water were placed in a beaker and placed at 30 ° C. for 30 minutes. After stirring for 30 minutes (a stirrer rotation speed of 60 rpm), the temperature was raised to 90 ° C., and stirring was performed for 30 minutes in the same manner. ○ −−− No undissolved matter is observed at all △ −−− Fine undissolved matter is observed × −−− Gel of undissolved matter is observed

Example 2 In Example 1, the amount of dimethyl acetal was changed to 2.
A vinyl acetate polymer was obtained in the same manner except that the amount was changed to 2 parts (2.2% based on vinyl acetate). The average degree of polymerization of the obtained vinyl acetate polymer was measured in the same manner.
800. Further, under the same conditions as above, two lots of polymerization were further carried out, and the average degree of polymerization was measured in the same manner. Evaluation was performed in the same manner as in Example 1 using the vinyl acetate polymer obtained in the first lot. The evaluation results are shown in Table 1.

Example 3 In Example 1, the charged amount of dimethyl acetal was changed to 4 parts (4% based on vinyl acetate), and citric acid was further added to 5 p.
A vinyl acetate polymer was obtained in the same manner except that pm was added. When the average degree of polymerization of the obtained vinyl acetate polymer was measured in the same manner, it was 1,800. Further, under the same conditions as above, polymerization was further performed on two lots, and the average degree of polymerization was measured in the same manner. However, there was almost no variation among the lots at 1810 and 1800, respectively. Evaluation was performed in the same manner as in Example 1 using the vinyl acetate polymer obtained in the first lot. The evaluation results are shown in Table 1.

Example 4 In Example 1, the charged amount of dimethyl acetal was changed to 4 parts (4% based on vinyl acetate), and citric acid was further added to 10 parts.
A vinyl acetate polymer was obtained in the same manner except that ppm was added. When the average degree of polymerization of the obtained vinyl acetate polymer was measured in the same manner, it was 1,790. Further, under the same conditions as above, two lots of polymerization were further performed, and the average degree of polymerization was measured in the same manner.
There was almost no variation among lots. Evaluation was performed in the same manner as in Example 1 using the vinyl acetate polymer obtained in the first lot. The evaluation results are shown in Table 1.

Example 5 Example 1 was repeated except that di-n-propylperoxydicarbonate (half-life at 60 ° C .: 40 minutes) was charged as a polymerization initiator so as to be 80 ppm based on vinyl acetate. In the same manner, a vinyl acetate polymer was obtained. When the average degree of polymerization of the obtained vinyl acetate polymer was measured in the same manner, it was 1,800. Further, under the same conditions as above, polymerization was further performed on two lots, and the average degree of polymerization was measured in the same manner. However, no variation was observed between the lots at 1800 and 1800, respectively. Evaluation was performed in the same manner as in Example 1 using the vinyl acetate polymer obtained in the first lot. The evaluation results are shown in Table 1.

Comparative Example 1 A vinyl acetate polymer was obtained in the same manner as in Example 1 except that dimethyl acetal was not charged. When the average degree of polymerization of the obtained vinyl acetate polymer was measured in the same manner, it was 1,850. Further, under the same conditions as above, polymerization was further performed for two lots, and the average degree of polymerization was measured in the same manner. However, there was considerable variation among lots at 1880 and 1750, respectively. Evaluation was performed in the same manner as in Example 1 using the vinyl acetate polymer obtained in the first lot. The evaluation results are shown in Table 1.

[0025]

[Table 1]

[0026]

According to the production method of the present invention, a good quality vinyl ester polymer having a stable average polymerization degree can be obtained. It is also useful as a raw material for obtaining a resin.

Claims (5)

[Claims] 1. A method for producing a vinyl ester polymer, comprising polymerizing a vinyl ester monomer in the presence of dimethyl acetal. 2. The process for producing a vinyl ester polymer according to claim 1, wherein the coexisting amount of dimethyl acetal is 0.001 to 10% by weight based on the vinyl ester monomer. 3. The method according to claim 1, wherein the half-life at the temperature during the polymerization is 1
The method for producing a vinyl ester-based polymer according to claim 1 or 2, wherein a polymerization initiator for 0 to 180 minutes is allowed to coexist. 4. A half-life at a temperature during polymerization of 10 to 1
4. The method for producing a vinyl ester polymer according to claim 3, wherein the polymerization initiator for 80 minutes is an organic peroxide. 5. The method for producing a vinyl ester polymer according to claim 1, further comprising coexisting a hydroxycarboxylic acid and / or a polycarboxylic acid.