JP2002037802A - Method for producing vinyl acetate polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a useful vinyl acetate polymer to give a saponified vinyl acetate polymer which is excellent in transparency and solubility and has less distribution of polymerization degree. SOLUTION: In the homopolymerization or copolymerization of vinyl acetate monomer, the polymerization is carried out by subjecting the monomer preblended with a polymerization catalyst to a polymerization system, or by subjecting a prepared solution obtained by dissolving of monomer blended with the catalyst in a polymerization solvent to the system. Alternatively, it is carried out by blending the catalyst with the prepared solution wherein the monomer and the solvent are premixed to obtain the system.

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 acetate polymer, and more particularly, to a method for obtaining a saponified vinyl acetate polymer having excellent transparency and solubility and having less unevenness in polymerization degree. The present invention relates to a method for producing a useful vinyl acetate polymer.

[0002]

2. Description of the Related Art Conventionally, polyvinyl acetate and ethylene-
In obtaining a vinyl acetate-based polymer such as a vinyl acetate copolymer, a solution of a vinyl acetate monomer or a monomer and a copolymerizable monomer such as ethylene together with a polymerization solvent under pressure in a polymerization (reaction) canister. , Nodule polymerization, suspension polymerization and the like, and in these polymerization methods, obtaining a better vinyl acetate polymer has been studied.

[0003] For example, Japanese Patent Application Laid-Open No. 9-316110 discloses that a half-life at 60 ° C of 10 to 110 minutes is obtained in order to obtain a polyvinyl acetate saponified product having a small amount of undissolved material, improved transparency and low odor. It is described that an organic peroxide is used as a polymerization catalyst and a hydroxycarboxylic acid coexists in a polymerization solution. Japanese Patent Application Laid-Open No. 9-71620 discloses that, in the event that coloration is low, gel-like buttocks are formed at the time of molding. It is described that a conjugated polyene compound is added after polymerization using a polymerization catalyst having a half-life in methanol at 60 ° C. of 5 hours or less in order to obtain a small amount of saponified ethylene-vinyl acetate copolymer.

In Japanese Patent Publication No. 2-52922,
A method for continuously producing an ethylene-vinyl acetate copolymer is disclosed, in which a polymerization catalyst is used, usually, a polymerization catalyst is used by being dissolved in a part of a solvent to be charged in a polymerization tank and charged. There is a statement to the effect.

[0005]

However, the technique disclosed in Japanese Patent Application Laid-Open No. 9-316110 and the method disclosed in Japanese Patent Application Laid-Open
In the technology disclosed in Japanese Patent No. 1620, when the (co) polymer obtained after a long production is performed, unevenness in the degree of polymerization may occur. Therefore, a method for producing a vinyl acetate polymer that can stably produce high-quality products over a long period of time is desired.
As for the technique disclosed in Japanese Patent Application Laid-Open Publication No. H11-209, as a result of a detailed study of the method for charging the polymerization catalyst described above, the solubility of the polymerization catalyst in a polymerization solvent (lower aliphatic alcohol having 1 to 4 carbon atoms) is not necessarily good. In addition, it was found that the polymerization catalyst was charged in an undissolved state, a high concentration portion was locally formed, a crosslinked product (gel) was likely to be generated, and there was a risk of generating scale, and further improvement was necessary. became. That is,
An object of the present invention is to provide a method for producing a vinyl acetate-based polymer which is excellent in transparency and solubility and is useful for obtaining a saponified vinyl acetate-based polymer having a small degree of polymerization unevenness.

[0006]

In order to achieve the above object, the present inventors have conducted intensive studies on a method for charging a polymerization catalyst, and as a result, have found that vinyl acetate monomers can be homopolymerized or copolymerized (copolymerized with ethylene). When the copolymerization ratio of ethylene is less than 10 mol%), the polymerization is carried out by charging a vinyl acetate monomer in which a polymerization catalyst has been previously blended into the polymerization system, or when homopolymerizing or copolymerizing the vinyl acetate monomer. A polymerization liquid is prepared by dissolving a vinyl acetate monomer in a polymerization solvent in which a polymerization catalyst is blended, and a polymerization system is charged into the polymerization system to perform polymerization, or a polymerization catalyst is blended in a preparation liquid in which a vinyl acetate monomer and a polymerization solvent are previously mixed. The inventors have found that the above-mentioned object can be achieved when the polymerization is carried out by charging the mixture into a polymerization system, and the present invention has been completed.

[0007] Further, in the present invention, the charging temperature of the vinyl acetate monomer or the charging solution containing the polymerization catalyst into the polymerization system satisfies the following conditions;
It is also a preferred embodiment to use an organic peroxide having a half life at 60 ° C. of 5 hours or less and to allow a hydroxylactone compound to coexist during polymerization. (10 hour half-life temperature of catalyst-80) / log (10 hour half-life temperature of catalyst) ≥ charging temperature

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
Usually, when producing a vinyl acetate polymer, polymerization is carried out by charging a vinyl acetate monomer or a vinyl acetate monomer and other monomers, a polymerization solvent and a polymerization catalyst (polymerization initiator) in a polymerization (reaction) can. As a charging method at this time, it is general to charge a polymerization solution, which is a mixture of a vinyl acetate monomer, a polymerization solvent, and a polymerization catalyst (polymerization initiator), into a polymerization vessel, but in the present invention, In this charging method, 1) charging a vinyl acetate monomer in which a polymerization catalyst is previously mixed into a polymerization system (polymerization can); 2) charging a vinyl acetate monomer in which a polymerization catalyst is mixed in a polymerization solvent; It is best to charge the liquid into the polymerization system, or 3) mix the polymerization catalyst with the liquid in which the vinyl acetate monomer and the polymerization solvent have been previously mixed and then charge the polymerization tank. If this charging method is satisfied, other conditions can be adopted by a known method.For example, a continuous method or a batch method may be used. Other polymerization conditions may be set as appropriate.

More specifically, as a solvent (polymerization solvent) used at the time of polymerization, an alcohol having 4 or less carbon atoms or a mixed solvent mainly containing an alcohol having 4 or less carbon atoms is suitably used. Include methanol, ethanol, propanol and the like. Among them, methanol is preferably used, and the amount of the solvent is 1 to 60 parts by weight relative to 100 parts by weight of vinyl acetate (further 1 to 60 parts by weight).
When the amount of such a solvent is less than 1 part by weight, the viscosity of the polymerization solution is high and heat removal becomes difficult, making it difficult to control the polymerization. Conversely, when the amount exceeds 60 parts by weight, the obtained vinyl acetate is used. A system polymer is not preferable because it has a low degree of polymerization and is brittle in physical properties.

The polymerization catalyst used in the present invention is not particularly limited as long as it is a radical initiator, but is preferably 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobis- (2,4-dimethylvaleronitrile). '-Azobis- (2,4,
Azo compounds such as 4-trimethylvaleronitrile), 2,2'-azobisisobutyronitrile, and 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile), t-butylperoxyneo Alkyl peresters such as decanoate and t-butyl perpivalate;
(4-t-butylcyclohexyl) peroxy-di-carbonate, di-cyclohexylperoxy-di-carbonate, bis (2-ethylhexyl) di-sec-butylperoxy-di-carbonate, di-isopropylperoxy-di- Peroxy-di-carbonates such as carbonate, peroxides such as acetyl peroxide, di-lauroyl peroxide, di-decanoyl peroxide, di-octanoyl peroxide, di-propyl peroxide and the like can be mentioned.

In the present invention, the half-life at 60 ° C. is 5 in consideration of the effect of preventing scale during the production (polymerization) of a vinyl acetate polymer and the odor during melt molding of a saponified product of the polymer. Time or less organic peroxide is preferably used,
Specifically, t-butyl peroxy neodecanoate [half-life 1.8 hours], t-butyl peroxypivalate [half-life 5.0 hours], α, α'bis (neodecanoylperoxy) ) Diisopropylbenzene [half-life 0.5
Hours], cumyl peroxy neodecanoate [half-life 0.5 hours], 1,1,3,3-tetramethylbutyl peroxy neodecanoate [half-life 0.7 hours], 1
-Cyclohexyl-1-methylethyl peroxy neodecanoate [half-life 0.8 hours], t-hexyl peroxy neodecanoate [half-life 1.4 hours], t-hexyl peroxypivalate [half-life] 4.2 hours], di-n-propylperoxydicarbonate [half-life 0.7 hours], di-iso-propylperoxydicarbonate [half-life 0.6 hours], di- sec-butyl peroxydicarbonate [half-life 0.7 hours], bis (4-t-butylcyclohexyl)
Peroxydicarbonate [half-life 0.7 hours], di-
2-ethoxyethyl peroxydicarbonate [half-life 0.9 hours], di (2-ethylhexyl) peroxydicarbonate [half-life 0.9 hours], dimethoxybutyl peroxydicarbonate [half-life 1.6 hours] Peroxydicarbonates such as di (3-methyl-3-methoxybutylperoxy) dicarbonate [half-life 1.9 hours], 3,3,5-trimethylhexanoyl peroxide [half-life 9.2 hours] And diacyl peroxides such as diisobutyryl peroxide [half-life 0.3 hours].

In the present invention, 1) charging a vinyl acetate monomer in which a polymerization catalyst is previously blended into a polymerization can;
2) A polymerization liquid is prepared by dissolving a vinyl acetate monomer containing a polymerization catalyst in a polymerization solvent, or 3) A polymerization catalyst is mixed with a preparation liquid in which a vinyl acetate monomer and a polymerization solvent are previously mixed. After that, the method is charged into a polymerization can. First, the method 1) will be described more specifically.

The method 1) requires that a polymerization catalyst be dissolved in a vinyl acetate monomer in advance (in the present invention, a vinyl acetate monomer in which a polymerization catalyst is dissolved is sometimes referred to as a monomer composition). The amount of the polymerization catalyst to be dissolved is 10 to 100 parts by weight of the vinyl acetate monomer.
Not more than 7 parts by weight (more preferably not more than 7 parts by weight, especially not more than 5 parts by weight)
If it exceeds 10 parts by weight, gel is likely to be generated, which is not preferred.

The above-mentioned polymerization catalyst does not necessarily need to be dissolved in the entire amount of the vinyl acetate monomer to be used, but may be dissolved in a part of the vinyl acetate monomer within the above-mentioned range of the dissolved amount. At this time, the vinyl acetate monomer not used for dissolution may be charged alone or in combination with the polymerization catalyst. In dissolving the polymerization catalyst in the vinyl acetate monomer, there is no particular limitation, but it is preferable that the polymerization catalyst be dissolved at a liquid temperature or lower at the time of preparation.

Next, the method 2) will be described. 2)
The method of 1) can be carried out by, in the method of 1) above, adding a polymerization solvent to the monomer composition to prepare a charged solution, and then charging the mixture into a polymerization system. The amount of the polymerization catalyst in the monomer composition is 20 parts by weight or less (more preferably 15 parts by weight or less, particularly 10 parts by weight based on 100 parts by weight of the vinyl acetate monomer).
(By weight) or less), and if the amount exceeds 20 parts by weight, gel is easily generated, which is not preferable. Similarly to the method 1), the polymerization catalyst does not necessarily need to be dissolved in the entire amount of the vinyl acetate monomer to be used, and may be dissolved in a part of the vinyl acetate monomer within the above-mentioned range of the amount of the polymerization.

The monomer composition described above does not necessarily need to contain the entire amount of the polymerization solvent to be used, but may also contain a part of the polymerization solvent. At that time, the vinyl acetate monomer not used for dissolving the polymerization catalyst and the polymerization solvent not mixed with the monomer composition may be charged alone or in combination.

Further, the method 3) will be described. 3)
In the method (1), it is necessary to mix a polymerization catalyst in a charged solution in which a vinyl acetate monomer and a polymerization solvent are previously mixed, and the mixing ratio of the vinyl acetate monomer and the polymerization solvent is not particularly limited.

The amount of the polymerization catalyst to be blended in the obtained preparation liquid may be the same as the amount of the above 2). Incidentally, it is not always necessary to mix the polymerization catalyst into the preparation liquid in which the whole amount of the vinyl acetate monomer and the polymerization solvent are mixed, and it is not necessary to mix the whole amount of the vinyl acetate monomer within the range of the amount of the polymerization catalyst dissolved. Alternatively, an arbitrary amount of the polymerization solvent may be mixed.
In the present invention, a charged liquid containing a vinyl acetate monomer and a polymerization catalyst is prepared by any one of the above methods 1) to 3), and the charged liquid is supplied to a polymerization system to start polymerization. Is what you do.

In the polymerization, in the above method 1), the charge (vinyl acetate monomer and the polymerization catalyst) and the polymerization solvent may be charged into the polymerization system, and the order of the charge is not particularly limited. It is preferable to adopt the method described above. That is, it is preferable that the monomer composition and the polymerization solvent are preliminarily mixed and charged into a polymerization system as a charging liquid.

In the method 3), the charged solution (vinyl acetate monomer + polymerization solvent + polymerization catalyst) may be charged as it is to the polymerization system. In some cases, in any of the methods, it is also possible to additionally charge a part of the vinyl acetate monomer and the polymerization solvent.

In the present invention, in any of the above methods, it is preferable to adjust the charging temperature of the charging liquid so as to satisfy the following conditions. (10 hour half-life temperature of catalyst-80) / log (10 hour half-life temperature of catalyst) ≥ charging temperature

Thus, the polymerization starts when the vinyl acetate monomer, the polymerization catalyst and the polymerization solvent are charged into the polymerization vessel. In the present invention, it is also preferable to coexist a hydroxylactone compound during the polymerization. Is not particularly limited as long as it is a compound having a lactone ring and a hydroxyl group in the molecule, for example, L-ascorbic acid, erythorbic acid, glucono delta lactone and the like, and preferably L-ascorbic acid, Erythorbic acid or the like is used.

The amount of the hydroxylactone compound used is 0.0001 to 0.1 part by weight (further 0.0005 to 0.1 part by weight) with respect to 100 parts by weight of the vinyl acetate monomer in both the batch system and the continuous system. 05 parts by weight, particularly 0.001 to 0.03 parts by weight), and when the amount is less than 0.0001 part by weight, the color tone of the obtained saponified vinyl acetate polymer may be deteriorated. If it exceeds 0.1 part by weight, the polymerization of vinyl acetate is inhibited, which is not preferable. In charging such a compound into the polymerization system, although not particularly limited, it is usually diluted with a solvent such as an aliphatic ester containing a lower aliphatic alcohol or a vinyl acetate monomer or water or a mixed solvent thereof and charged into the polymerization reaction system. It is.

The polymerization temperature during the polymerization is not particularly limited,
Usually, 40 to 80 ° C. (more preferably 55 to 80 ° C.) is preferable, and if the temperature is lower than 40 ° C., a long time is required for polymerization,
In order to shorten the polymerization time, a large amount of the catalyst is required. On the other hand, when the temperature exceeds 80 ° C., the polymerization control becomes difficult, which is not preferable.

The polymerization time is 4 to 1 in the case of a batch system.
0 hours (more preferably 6 to 9 hours) is preferable. If the polymerization time is less than 4 hours, the polymerization temperature must be increased or the amount of catalyst must be set higher. There is a problem and it is not preferable. In the case of a continuous system, the average residence time in the polymerization vessel is preferably 2 to 8 hours (more preferably 2 to 6 hours). If the residence time is less than 2 hours, the polymerization temperature may be raised or the amount of catalyst may be set large. If the time exceeds 8 hours, there is a problem in productivity, which is not preferable.

The polymerization rate (vinyl acetate) is set as high as possible within the range where the polymerization can be controlled from the viewpoint of productivity, and is preferably 20 to 90%. When the polymerization rate is less than 20%,
There are also problems such as productivity and the presence of a large amount of unpolymerized vinyl acetate monomer. Conversely, if it exceeds 90%, polymerization control becomes difficult, which is not preferable.

In the production method of the present invention, in addition to the vinyl acetate monomer, an ethylenically unsaturated monomer copolymerizable therewith can be copolymerized as a copolymer component. Is, for example, ethylene, propylene, isobutylene, α-octene, α-dodecene, α
-Olefins such as octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride and itaconic acid or salts or mono- or dialkyl esters thereof; acrylonitrile; nitriles such as methacrylonitrile; Amides such as acrylamide and methacrylamide, olefinsulfonic acids such as ethylenesulfonic acid, allylsulfonic acid and methallylsulfonic acid or salts thereof, alkyl vinyl ethers, N-
Polyoxyalkylenes such as acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallylvinylketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, and polyoxypropylene (meth) allyl ether; Polyoxyalkylene (meth) acrylates such as (meth) allyl ether, polyoxyethylene (meth) acrylate, and polyoxypropylene (meth) acrylate; polyoxyalkylenes such as polyoxyethylene (meth) acrylamide and polyoxypropylene (meth) acrylamide (Meta)
Acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester,
Examples thereof include polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

Thus, the production method of the present invention can provide a vinyl acetate-based polymer which is excellent in transparency and solubility and is useful for obtaining a saponified vinyl acetate-based polymer with less unevenness in polymerization degree. , Such a vinyl acetate polymer is an adhesive,
It can also be used for adhesives, paints, textile / textile processing agents, paper / leather processing agents, binders for various materials, cement / mortar admixtures, and the like. In order to obtain such a saponified vinyl acetate polymer, a known method can be employed.

For example, saponification may be carried out by adding a saponification catalyst to the obtained vinyl acetate polymer. Examples of such a saponification catalyst include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, and potassium methylate, alkali catalysts such as alcoholate, sulfuric acid, p-toluenesulfonic acid, and hydrochloric acid. And the like, and sodium hydroxide is preferably used.

The amount of the saponification catalyst used is 2 to 20 mmol% based on the vinyl ester units of the vinyl acetate polymer.
What is necessary is just to select from the range of a degree. The saponification temperature is usually preferably selected from the range of 10 to 70 ° C., and the saponification reaction is usually performed for 0.5 to 3 hours.

The saponification as described above can be performed either continuously or batchwise, and examples of such a batch type saponification degree apparatus include a kneader and a ribbon blender. Thus, a saponified vinyl acetate polymer having excellent transparency and solubility and having less unevenness in polymerization degree can be obtained.

[0032]

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 A charged solution was prepared by previously mixing 0.012 parts of a polymerization catalyst (di-iso-propylperoxydicarbonate [half-life 0.6 hours]) with 100 parts of vinyl acetate monomer. The temperature of the charged solution was set to −30 ° C., charged in a polymerization vessel having a capacity of 10 l with a stirrer, and methanol was simultaneously charged as a polymerization solvent to carry out continuous polymerization in the following manner.

Supply amount of charged liquid 480 g / hr Supply temperature of charged liquid −30 ° C. Supply amount of polymerization solvent (methanol) 60 g / hr Polymerization temperature 55 ° C. Average residence time 5 hr The obtained polyvinyl acetate has a polymerization rate of 40%. Met.

The obtained polyvinyl acetate was saponified by a conventional method to obtain polyvinyl alcohol, and the transparency, solubility and uneven polymerization of the polyvinyl alcohol were evaluated in the following manner.

(Transparency) Using a 4% aqueous solution of the obtained polyvinyl alcohol, the transmittance A (%) at a wavelength of 430 nm was measured at 30 ° C. using a spectrophotometer. Was measured in the same manner, and the transparency (%) was calculated from the following equation to evaluate the transparency. Transparency (%) = Transmittance A + (100−Transmittance B) The evaluation criteria are as follows. ◎ ・ ・ ・ 97% or more ○ ・ ・ ・ 94% or more and less than 97% △ ・ ・ ・ 90% or more and less than 94% × ・ ・ ・ less than 90%

(Solubility) The obtained polyvinyl alcohol was converted into a 5% aqueous solution, stirred at 90 ° C. for 1 hour, filtered through a wire mesh having an opening of 45 μm, and the weight of undissolved material remaining on the wire mesh was measured. Then, the amount (ppm) of the undissolved substance in the polyvinyl alcohol was calculated, and the solubility was evaluated. The evaluation criteria are as shown below. ◎: less than 100 ppm ○: 100 ppm or more and less than 250 ppm △: 250 ppm or more and less than 500 ppm × ・ ・ ・ 500 ppm or more

(Polymerization Degree Unevenness) The degree of polymerization of the obtained polyvinyl alcohol was measured to examine its variation. Specifically, with respect to the vinyl acetate-based polymer obtained by continuous polymerization, the respective vinyl acetate-based polymers were sampled at 5 hours, 15 hours, and 25 hours after the start of polymerization, and saponified. Polyvinyl alcohol was used, and the degree of polymerization of the polyvinyl alcohol was measured. Based on the degree of polymerization of the polyvinyl alcohol obtained from the vinyl acetate polymer 5 hours after the initiation of polymerization, the acetic acid at the 15th and 25th hours was used as a reference. The variation in the degree of polymerization of the polyvinyl alcohol obtained from the vinyl polymer was examined to evaluate the unevenness in the degree of polymerization. As for the vinyl acetate-based polymer obtained by the batch polymerization, the first, fifth, and tenth batches of the vinyl acetate-based polymer were sampled in the same manner as described above, and the samples were saponified to obtain polyvinyl acetate. Alcohol, the degree of polymerization of the polyvinyl alcohol was measured, and based on the degree of polymerization of the polyvinyl alcohol obtained from the vinyl acetate polymer of the first batch, the vinyl acetate weight of the fifth batch and the tenth batch was determined. The variation in the degree of polymerization of the polyvinyl alcohol obtained from the coalescence was examined, and the degree of polymerization degree unevenness was evaluated. The degree of polymerization was measured by an Ostwald viscometer based on the relative viscosity of a 0.8% aqueous solution. The evaluation criteria are as shown below. ◎: less than ± 5% ○: ± 5% or more and less than ± 10% △: ± 10% or more and less than ± 15% ×: ± 15% or more

Example 2 Polymerization was carried out in the same manner as in Example 1 except that L-ascorbic acid was allowed to coexist during the polymerization, and the same evaluation was carried out. In addition, it supplied so that the coexistence amount of L-ascorbic acid might be set to 0.004 part with respect to 100 parts of vinyl acetate monomers.

Example 3 Polymerization was carried out in the same manner as in Example 1 except that the ethylene pressure was changed to 8 MPa, and the same evaluation was conducted.

Example 4 Polymerization was performed in the same manner as in Example 2 except that the ethylene pressure was changed to 8 MPa, and the same evaluation was performed.

Example 5 The liquid prepared in Example 1 was subjected to batch polymerization in a 10-liter polymerization vessel equipped with a stirrer under the following conditions. Charge amount of charge solution 3000 g Charge temperature of charge solution -30 ° C Charge amount of polymerization solvent (methanol) 250 g Polymerization temperature 60 ° C Polymerization time 6 hr The polymerization rate of the obtained polyvinyl acetate was 50%. The obtained polyvinyl acetate was evaluated in the same manner as in Example 1.

Example 6 Polymerization was carried out in the same manner as in Example 5 except that L-ascorbic acid was allowed to coexist during the polymerization, and the same evaluation was performed. In addition, it supplied so that the coexistence amount of L-ascorbic acid might be set to 0.004 part with respect to 100 parts of vinyl acetate monomers.

Example 7 0.012 parts of a polymerization catalyst (di-iso-propylperoxydicarbonate [half-life: 0.6 hours]) and 12.5 parts of a polymerization solvent (methanol) were added to 100 parts of a vinyl acetate monomer in advance. A charge was prepared by blending the above components, and continuous polymerization was carried out using the charge in the same manner as in Example 1, and the same evaluation was performed.

Example 8 0.012 parts of a polymerization catalyst (di-iso-propylperoxydicarbonate [half-life 0.6 hours]) and 12.5 parts of a polymerization solvent (methanol) were added to 100 parts of a vinyl acetate monomer in advance. A charge was prepared by blending the above components, and continuous polymerization was carried out using the charge in the same manner as in Example 2, and the same evaluation was performed.

Example 9 0.012 parts of a polymerization catalyst (di-iso-propylperoxydicarbonate [half-life 0.6 hours]) and a polymerization solvent (methanol) 8.3 were previously added to 100 parts of a vinyl acetate monomer. The prepared liquid was prepared by mixing the components, and batch polymerization was carried out using the prepared liquid in the same manner as in Example 5, and the same evaluation was performed.

Comparative Example 1 12.5 parts of a polymerization solvent (methanol) and a polymerization catalyst (di-i
So-propyl peroxydicarbonate [half-life 0.5.
6 hours]) At the same time, 0.012 part was charged into the polymerization system, and at the same time, 100 parts of a vinyl acetate monomer was charged, and continuous polymerization was carried out in the same manner as in Example 1, and the evaluation was performed in the same manner. Table 1 shows the evaluation results of the examples and the comparative examples.

[0048]

[0049]

According to the present invention, in homopolymerizing or copolymerizing a vinyl acetate monomer, a vinyl acetate monomer containing a polymerization catalyst is charged into a polymerization system to carry out polymerization, or the vinyl acetate monomer and a polymerization solvent are prepared in advance. Since the polymerization is carried out after charging the polymerization catalyst into the mixed solution prepared by mixing with the polymerization solution, it is excellent in transparency and solubility, and in order to obtain a saponified vinyl acetate polymer having less unevenness in polymerization degree. A useful vinyl acetate polymer can be obtained.

Claims (6)

[Claims] When a vinyl acetate monomer is homopolymerized or copolymerized (copolymerization ratio of ethylene is less than 10 mol% when copolymerized with ethylene), a vinyl acetate monomer preliminarily containing a polymerization catalyst is converted into a polymerization system. A method for producing a vinyl acetate polymer, comprising charging and performing polymerization. 2. A method for homopolymerizing or copolymerizing a vinyl acetate monomer, wherein a polymerization solution is prepared by dissolving a vinyl acetate monomer containing a polymerization catalyst in a polymerization solvent, and polymerization is carried out. For producing a vinyl acetate polymer. 3. The homopolymerization or copolymerization of a vinyl acetate monomer is characterized in that a polymerization catalyst is blended in advance with a liquid mixture in which a vinyl acetate monomer and a polymerization solvent are mixed and then charged into a polymerization system to carry out polymerization. A method for producing a vinyl acetate polymer. 4. The process for producing a vinyl acetate polymer according to any one of claims 1 to 3, wherein the temperature of charging the vinyl acetate monomer or the charged solution containing the polymerization catalyst into the polymerization system satisfies the following conditions. Law. (10 hour half-life temperature of catalyst -8
0) / log (10-hour half-life temperature of catalyst) ≥ charging temperature 5. The method for producing a vinyl acetate polymer according to any one of claims 1 to 4, wherein the polymerization catalyst is an organic peroxide having a half life at 60 ° C. of 5 hours or less. 6. The method for producing a vinyl acetate polymer according to any one of claims 1 to 5, wherein a hydroxylactone compound is allowed to coexist during the polymerization.