JP2002338609A - Manufacturing method of vinyl acetate polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method capable of obtaining a vinyl acetate polymer sharper in distribution of molecular weight. SOLUTION: Upon manufacturing a vinyl acetate polymer, a manufacturing method of the vinyl acetate polymer comprises introducing an alcohol into the reaction solution when stopping the polymerization by adding a polymerization inhibitor after polymerization of the vinyl acetate polymer in a reaction drum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a vinyl acetate polymer, and more particularly to a method for producing a vinyl acetate polymer having a narrow (sharp) molecular weight distribution, particularly a vinyl alcohol polymer.

[0002]

2. Description of the Related Art Conventionally, vinyl alcohol-based polymers such as polyvinyl alcohol-based resins and saponified ethylene-vinyl acetate copolymers have been replaced by vinyl acetate-based polymers such as polyvinyl acetate and ethylene-vinyl acetate copolymer. It is manufactured by saponification. And in such a vinyl acetate polymer, especially in a vinyl alcohol polymer,
Its molecular weight distribution is also an important factor in properties.

That is, when characteristics such as improvement of thermal stability and improvement of mechanical properties of the obtained vinyl alcohol-based polymer are required, it is better that the molecular weight distribution is narrow (sharp). In addition, during the production of the polymer, a low molecular weight polymer may be mixed into the production waste liquid and adversely affect waste liquid treatment such as activated sludge treatment.In the production of a vinyl acetate polymer, such a molecular weight distribution is controlled. Have been tried to.

[0004] In general, a method has been performed in which a polymerization inhibitor is added in a step after the polymerization step to suppress the post-polymerization.

[0005]

However, in the above method, post-polymerization cannot be sufficiently suppressed only by adding a polymerization inhibitor, and it is not easy to obtain a polymer having a sharper molecular weight distribution. Did not. Further, depending on the type of the polymerization inhibitor, the addition conditions, and the like, the resulting polymer may be colored, so that sufficient consideration is required.

[0006]

Accordingly, the present inventors have conducted intensive studies in view of the above situation, and as a result, when producing a vinyl acetate polymer, a vinyl acetate monomer was polymerized in a reaction vessel. By introducing an alcohol into the reaction solution when adding a post-polymerization inhibitor to terminate the polymerization, a vinyl acetate-based polymer having a large post-polymerization inhibiting effect and a sharper molecular weight distribution can be obtained. And completed the present invention.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The method for producing a vinyl acetate-based polymer of the present invention comprises the steps of introducing an alcohol into a reaction solution when polymerizing a vinyl acetate-based monomer in a reaction vessel as described above and then adding a polymerization inhibitor to terminate the polymerization. It is characterized by doing. The polymerization of the vinyl acetate monomer is not particularly limited, and can be performed by a known method. For example,
The polymerization may be carried out by charging a vinyl acetate monomer alone or another copolymerizable monomer, a polymerization catalyst and a solvent into a reaction system such as a reaction vessel (polymerization vessel).

Examples of such other copolymerizable monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, acrylic acid, methacrylic acid, crotonic acid, maleic acid, and maleic anhydride. Acids, unsaturated acids such as itaconic acid or salts thereof or mono- or dialkyl esters, etc., nitriles such as acrylonitrile, methacrylonitrile, amides such as acrylamide, methacrylamide, ethylenesulfonic acid, allylsulfonic acid, methallylsulfonic acid Olefin sulfonic acids or salts thereof, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallylvinylketone, N-vinylpyrrolidone, chloride Polyoxyalkylene (meth) allyl ethers such as benzyl, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, polyoxyethylene (meth) acrylate, and polyoxypropylene (meth) acrylate. Polyoxyalkylene (meth) acrylamide, such as polyoxyalkylene (meth) acrylate, polyoxyethylene (meth) acrylamide, and polyoxypropylene (meth) acrylamide; polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ) Ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, It can be mentioned polyoxypropylene vinyl amine.

As the polymerization catalyst, any radical polymerization initiator can be used without any particular limitation.
2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobis- (2,4,4-trimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2 ' -Azobis- (4-methoxy-2,4-
Azo compounds such as dimethylvaleronitrile), t-butyl peroxy neodecanoate, t-butyl perpivale
Alkyl peresters, such as bis- (4-t-butylcyclohexyl) peroxy-di-carbonate, di-cyclohexylperoxy-di-carbonate, bis (2-ethylhexyl) di-sec-butylperoxy-di- Carbonates, peroxy-di-carbonates such as di-isopropylperoxy-di-carbonate,
Acetyl peroxide, di-lauroyl peroxide,
Peroxides such as di-decanoyl peroxide, di-octanoyl peroxide, di-propyl peroxide and the like can be mentioned, and one or more of these can be used.

The amount of the polymerization catalyst used is from 0.0001 to 1.0 with respect to 100 parts by weight of the vinyl acetate monomer.
Parts by weight, more preferably 0.001 to 1.0 parts by weight, especially 0.1 to 1.0 parts by weight.
0.01 to 0.1 parts by weight, preferably 0.000 to 0.1 parts by weight.
If the amount is less than 1 part by weight, the catalyst efficiency may be poor and the polymerization time may be extended, or the polymerization may not proceed. Is undesirably left to cause post-polymerization.

Further, as such a solvent (polymerization solvent),
An alcohol having 4 or less carbon atoms or a mixed solvent mainly containing an alcohol having 4 or less carbon atoms is preferably used. Examples of the alcohol include methanol, ethanol, and propanol. Among them, methanol is preferably used.
The amount of the solvent to be used is not particularly limited, but is preferably 1 to 100 parts by weight, more preferably 1 to 80 parts by weight, particularly preferably 1 to 50 parts by weight, based on 100 parts by weight of the vinyl acetate monomer. If the amount of the solvent is less than 1 part by weight, the viscosity of the polymerization solution is high and heat removal becomes difficult, and the control of polymerization becomes difficult. It is unpreferable because of low physical properties and brittleness.

In starting the polymerization, a vinyl acetate monomer or a vinyl acetate monomer and another copolymerizable monomer, a polymerization catalyst and a polymerization solvent are charged into a reaction vessel (polymerization vessel). Alternatively, any means may be adopted as a method for charging the vinyl acetate monomer and another copolymerizable monomer, a polymerization catalyst and a solvent, and typically, a vinyl acetate monomer or a vinyl acetate monomer and another copolymerizable monomer are used. , The polymerization catalyst and the solvent are all mixed in advance and then charged all at once. The polymerization catalyst dissolved in the solvent (a small amount), the vinyl acetate-based monomer or the vinyl acetate-based monomer and other copolymerizable monomers and the solvent are mixed. Separately charge vinyl acetate monomer or vinyl acetate monomer and other copolymerizable monomer, mixture of polymerization catalyst and solvent separately Method, a mixture of vinyl vinyl acetate monomer or acid-based monomers with other copolymerizable monomers and solvents, the polymerization catalyst and a method in which charged separately mixture of solvents thereof, but is not particularly limited. When the other copolymerizable monomer is a gaseous substance such as ethylene, it is preferable to charge the monomer by bubbling or adjusting the pressure while sealing.

Thus, a vinyl acetate monomer or a vinyl acetate monomer and another copolymerizable monomer are contained in the reaction vessel.
The polymerization is started by charging the polymerization catalyst and the solvent. The polymerization temperature is not particularly limited, but is usually 40 to 80.
° C, more preferably 55 to 80 ° C, and such a temperature is 40 ° C.
If the temperature is lower than 0 ° C, polymerization takes a long time and there is a problem in terms of productivity, and a large amount of a polymerization catalyst remains to easily cause post-polymerization. Also, there is no need to polymerize at a constant temperature until the end of the polymerization,
It may be changed together with the additional preparation of the catalyst.

The polymerization time is 4 to 20 in the case of a batch system.
Time, more preferably 6 to 12 hours, and the polymerization time is 4 hours.
If the time is less than the time, it is difficult to control the polymerization in order to obtain high productivity (high polymerization rate). In the case of the continuous type, the average residence time in the polymerization vessel is preferably 2 to 10 hours, more preferably 2 to 8 hours. If the residence time is less than 2 hours, high productivity (high polymerization rate) is obtained. Control becomes difficult, and if it exceeds 10 hours, there is a problem in productivity, which is not preferable.

The polymerization rate is not particularly limited, but is set as high as possible within the range where polymerization can be controlled from the viewpoint of productivity, and is preferably 20 to 95%. The polymerization rate is 20%
If it is less than 95%, there is a problem that the productivity is high and a large amount of unpolymerized vinyl acetate monomer is present.

Thus, the polymerization is completed and a vinyl acetate polymer solution is produced. In the present invention, when the polymerization is terminated by adding a polymerization inhibitor after polymerizing the vinyl acetate monomer, This method is characterized by introducing an alcohol into a reaction solution, and such a method will be described.

The polymerization inhibitor used in the present invention is not particularly restricted but includes, for example, hydroquinone, aniline, anthracene, nitrobenzene, dinitrobenzene, trinitrobenzene, benzonitrile, benzophenone, N,
N-dimethylformamide, cinnamic alcohol, cinnamic acid,
Sorbic acid and the like, and 1 to 200 ppm with respect to the reaction solution (a vinyl acetate polymer solution containing a monomer).
Further, it is preferable to add 5 to 100 ppm, especially 5 to 50 ppm. If the amount is less than 1 ppm, the action of inhibiting the polymerization is not sufficient, and if it exceeds 200 ppm, it may cause coloring or hygiene problems. It is not preferable because it occurs.

The alcohol used in the present invention is preferably an alcohol having 1 to 4 carbon atoms, and specific examples include methanol, ethanol, n-propanol, iso-propanol and n-butanol. preferable. The amount of the alcohol to be introduced is not particularly limited, but is preferably from 10 to 300 parts by weight, particularly preferably from 20 to 200 parts by weight, based on 100 parts by weight of the charged monomers. If the introduction amount is less than 10 parts by weight, the effect of terminating the polymerization becomes insufficient and
If the amount exceeds 00 parts by weight, the productivity will decrease in the subsequent step of demonomerization or saponification, which is not preferable.

In the present invention, such an alcohol is introduced when terminating the polymerization. In the introduction, the alcohol may be introduced directly into the reaction solution. Specifically, the introduction of the alcohol into the reaction solution is carried out. May be provided. The inlet in the reaction solution may be provided at the upper, lower, side, or the like of the reactor. Above all, it is particularly preferable to introduce alcohol from the lower part of the reactor in that a uniform solution can be obtained.

After the termination of the polymerization, the monomer is removed from the vinyl acetate polymer solution containing the monomer such as the vinyl acetate monomer obtained above by distillation. Thus, a vinyl acetate-based polymer having a sharper molecular weight distribution can be obtained by the production method of the present invention.

Examples of the vinyl acetate polymer obtained by the production method of the present invention include polyvinyl acetate, ethylene-
Vinyl acetate copolymers and the like can be mentioned, and these are
Used in adhesives, adhesives, paints, textile and textile processing agents, paper and leather processing agents, binders for various materials, admixtures of cement and mortar, etc., especially polyvinyl alcohol and ethylene-vinyl acetate copolymer ken It is also useful as a raw material of a compound, and a method for producing such polyvinyl alcohol will be described below.

In order to obtain polyvinyl alcohol from polyvinyl acetate, polyvinyl acetate may be saponified, and the saponification is performed by dissolving polyvinyl acetate in alcohol and in the presence of an alkali catalyst. Examples of the alcohol include methanol, ethanol, and butanol.

The concentration of the polymer in the alcohol is between 20 and 50.
It is selected from the range of weight%. As the saponification catalyst, sodium hydroxide, potassium hydroxide, sodium methylate,
It is necessary to use an alkali catalyst such as an alkali metal hydroxide or an alcoholate such as sodium ethylate or potassium methylate. The amount of the catalyst used is from 1 to 100 in order to obtain a desired saponification degree with respect to vinyl acetate.
It is necessary to make millimolar equivalents.

In such a case, the saponification temperature is not particularly limited, but is usually preferably selected from the range of 10 to 70 ° C, more preferably 25 to 50 ° C. The reaction is usually carried out for 0.5 to 3 hours, and the preferred degree of saponification is 10 to 100 mol%.
Particularly preferably, it is selected from the range of 50 to 100 mol%, particularly preferably 70 to 100 mol%.

Thus, a polyvinyl alcohol having a sharp molecular weight distribution can be obtained. Such a polyvinyl alcohol is less colored by heat treatment and the like, and is a dispersant, an adhesive, a sizing agent, an emulsifier, a suspending agent, a film, a fiber, a paper processing agent. And various coating applications.

[0026]

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 reaction vessel equipped with a condenser and a stirrer was charged with 7000 kg of vinyl acetate monomer and 3000 kg of methanol, and heated under reflux with stirring for 1 hour.
180 kg of a 1.5% methanol solution of acetyl peroxide was added as a polymerization catalyst, and polymerization was carried out for 6 hours under reflux. Thereafter, when the mixture was cooled and reflux was stopped, a 0.1% hydroquinone methanol solution 10 was used as a polymerization inhibitor.
At the same time, 0 kg was added from the upper part of the reaction vessel, and 3800 kg of methanol was introduced from the lower part of the reaction vessel and stirred, and a homogeneous solution (vinyl acetate conversion 90%, solids concentration 4
4.8%).

The resulting solution was distilled to remove unreacted monomers and adjusted to a solid concentration of 45%. The molecular weight distribution (Mw) of polyvinyl acetate in such a vinyl acetate polymer solution
/ Mn, Mw: weight average molecular weight, Mn: number average molecular weight)
Was measured by GPC and found to be Mw / Mn = 2.3.

Further, 83 kg of a 2% methanol solution of sodium hydroxide was added to 2000 kg of the vinyl acetate polymer solution (solid content: 45%) and saponified at 40 ° C.
And a degree of saponification of 99.1 mol% and a degree of polymerization of 110
Viscosity of 13.5 mPa · s when used as 0, 4% aqueous solution
(20 ° C.) polyvinyl alcohol was obtained. In addition, the molecular weight distribution (Mw / Mn, M
(w: weight average molecular weight, Mn: number average molecular weight) was re-acetylated and measured by GPC, and it was Mw / Mn = 2.1.

Example 2 A reaction vessel equipped with a condenser and a stirrer was charged with 8000 kg of vinyl acetate monomer and 2,000 kg of methanol, and heated under reflux with stirring for 1 hour.
87 kg of a 1.5% methanol solution of acetyl peroxide was added as a polymerization catalyst, and polymerization was carried out for 6 hours under reflux. Thereafter, when the mixture was cooled and reflux was stopped, a 0.1% hydroquinone methanol solution 80 as a polymerization inhibitor was used.
At the same time, 5200 kg of methanol was introduced from the bottom of the reaction vessel and stirred, and a homogeneous solution (vinyl acetate polymerization rate 80%, solid content concentration 41.kg) was added.
7%).

The resulting solution was distilled to remove unreacted monomers and adjusted to a solid concentration of 45%. The molecular weight distribution (Mw) of polyvinyl acetate in such a vinyl acetate polymer solution
/ Mn, Mw: weight average molecular weight, Mn: number average molecular weight)
Was measured by GPC and found to be Mw / Mn = 2.3.

Further, 56 kg of a 2% methanol solution of sodium hydroxide was added to 2000 kg of the vinyl acetate polymer solution (solid content: 45%), and saponified at 35 ° C.
With a degree of saponification of 87 mol%, a degree of polymerization of 1400 and 4
% Aqueous solution of polyvinyl alcohol having a viscosity of 22 mPa · s (20 ° C.). Further, the molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of the obtained polyvinyl alcohol is re-acetylated, and GPC is performed.
Was Mw / Mn = 2.1.

Example 3 A reaction vessel equipped with a condenser and a stirrer was charged with 6000 kg of vinyl acetate monomer and 750 kg of methanol, heated under reflux with stirring, and refluxed for 1 hour. 16 kg of a 5% methanol solution was added, and polymerization was performed under reflux for 6 hours.
Then, when the mixture was cooled and refluxed, 80 kg of a 0.1% methanol solution of hydroquinone was used as a polymerization inhibitor.
At the same time as adding methanol
70 kg was introduced from the lower part of the reaction vessel and stirred to obtain a uniform solution (vinyl acetate polymerization rate 65%, solid content concentration 33%).

The resulting solution was distilled to remove unreacted monomers and adjusted to a solid concentration of 32%. The molecular weight distribution (Mw) of polyvinyl acetate in such a vinyl acetate polymer solution
/ Mn, Mw: weight average molecular weight, Mn: number average molecular weight)
Was measured by GPC and found to be Mw / Mn = 2.2.

Further, 28 kg of a 2% methanol solution of sodium hydroxide was added to 2000 kg of the vinyl acetate polymer solution (solid content: 45%) and saponified at 40.degree.
With a degree of saponification of 87 mol% and a degree of polymerization of 2200,4
% Aqueous solution of polyvinyl alcohol having a viscosity of 52 mPa · s (20 ° C.). The molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of the obtained polyvinyl alcohol is re-acetylated, and GPC is performed.
Was Mw / Mn = 2.1.

Comparative Example 1 The procedure of Example 1 was repeated except that, after the completion of the polymerization, both the polymerization inhibitor and methanol were charged from the top of the reaction vessel (polymerization rate of vinyl acetate: 93%, solid content: 46.2).
%).

The resulting solution was distilled to remove unreacted monomers and adjusted to a solid concentration of 45%. The molecular weight distribution (Mw) of polyvinyl acetate in such a vinyl acetate polymer solution
/ Mn, Mw: weight average molecular weight, Mn: number average molecular weight)
Was measured by GPC and found to be Mw / Mn = 2.6.

Further, 83 kg of a 2% methanol solution of sodium hydroxide was added to 2000 kg of the vinyl acetate polymer solution (solid content: 45%), and saponified at 40 ° C.
And a degree of saponification of 99.2 mol% and a degree of polymerization of 105
Viscosity of 12.2 mPa · s when used as a 0, 4% aqueous solution
(20 ° C.) polyvinyl alcohol was obtained. In addition, the molecular weight distribution (Mw / Mn, M
(w: weight average molecular weight, Mn: number average molecular weight) was re-acetylated and measured by GPC to find that Mw / Mn = 2.5.

[0039]

According to the production method of the present invention, when a vinyl acetate polymer is produced, a polymerization inhibitor is added after a vinyl acetate monomer is polymerized in a reaction vessel to terminate the polymerization. Since the alcohol is introduced into the solution, the effect of inhibiting post-polymerization after the polymerization of the vinyl acetate-based monomer is large, and a vinyl acetate-based polymer having a sharper molecular weight distribution can be obtained.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Seiichi Nakamura 221 Tsukigo-cho, Uto-shi, Kumamoto Nippon Gohsei Chemical Industry Co., Ltd. Kumamoto Factory F-term (reference) 4J011 NA12 NA13 NA14 NA15 NA17 NA18 NA19 NA23 NB02 NB04 NC04 4J100 AD02P AG04P BA03H CA01 CA04 DA04 FA06 HA09

Claims (3)

[Claims] In producing a vinyl acetate polymer, an alcohol is introduced into a reaction solution when a polymerization inhibitor is added after polymerization of a vinyl acetate monomer in a reaction vessel to terminate the polymerization. A method for producing a vinyl acetate-based polymer, comprising: 2. The method for producing a vinyl acetate-based polymer according to claim 1, wherein alcohol is introduced from a lower part of the reaction vessel. 3. The method for producing a vinyl acetate polymer according to claim 1, wherein the alcohol is an alcohol having 1 to 4 carbon atoms.