JP4547105B2 - Method for producing vinyl acetate polymer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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]
[Prior art]
Conventionally, vinyl alcohol polymers such as polyvinyl alcohol resins and saponified ethylene-vinyl acetate copolymers have been obtained by saponifying vinyl acetate polymers such as polyvinyl acetate and ethylene-vinyl acetate copolymers. It is manufactured.
In such vinyl acetate polymers, particularly vinyl alcohol polymers, the molecular weight distribution is also an important factor in characteristics.
[0003]
That is, when the obtained vinyl alcohol polymer is required to have characteristics such as improvement in thermal stability and improvement in mechanical properties, the molecular weight distribution is preferably narrow (sharp). In addition, when the polymer is produced, the low molecular weight polymer may be mixed into the production waste liquid and adversely affect the waste liquid treatment such as activated sludge treatment. The molecular weight distribution is controlled during the production of the vinyl acetate polymer. It has been tried to do.
[0004]
In general, a method of suppressing post-polymerization by adding a polymerization inhibitor is performed after the polymerization step.
[0005]
[Problems to be solved by the invention]
However, in the above method, the post-polymerization cannot be sufficiently suppressed only by adding a polymerization inhibitor, and it has not been easy to obtain a polymer having a sharper molecular weight distribution. Further, depending on the type of polymerization inhibitor, the addition conditions, and the like, the resulting polymer may be colored, and sufficient consideration is required.
[0006]
[Means for Solving the Problems]
Therefore, as a result of intensive research in view of the above-mentioned present situation, the present inventors have added a polymerization inhibitor after polymerizing a vinyl acetate monomer in a reaction vessel in producing a vinyl acetate polymer. When the polymerization was stopped, it was found that by introducing alcohol into the reaction solution from the bottom of the reaction vessel, a post-polymerization inhibition effect was large, and a vinyl acetate polymer having a sharper molecular weight distribution was obtained. The invention has been completed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. Method for producing a vinyl acetate polymer of the present invention, when stopping the polymerization by adding a polymerization inhibitor after the polymerization of vinyl acetate monomer in the reaction vessel as described above, the reaction solution from the bottom of the reaction vessel It is characterized by introducing alcohol into it. The polymerization of the vinyl acetate monomer is not particularly limited and can be performed by a known method. For example, a vinyl acetate monomer alone or other copolymerizable monomer, a polymerization catalyst, and a solvent may be charged into a reaction system such as a reaction vessel (polymerization vessel) for polymerization.
[0008]
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, maleic anhydride, and itacone. Unsaturated acids such as acids or salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, olefins such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid Sulfonic acid or its salts, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, chloride Polyoxyalkylenes such as Nilidene, Polyoxyethylene (meth) allyl ether, Polyoxyalkylene (meth) allyl ether such as polyoxypropylene (meth) allyl ether, Polyoxyethylene (meth) acrylate, Polyoxypropylene (meth) acrylate, etc. (Meth) acrylate, polyoxyethylene (meth) acrylamide, polyoxyalkylene (meth) acrylamide such as polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, Polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene Can pyrene vinyl amine.
[0009]
The polymerization catalyst is not particularly limited as long as it is a radical polymerization initiator, but preferably 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobis- (2, 4,4-trimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile) and other azo compounds, t-butylper Oxyneodecanoate, alkyl peresters such as t-butyl perpivalate, bis- (4-tert-butylcyclohexyl) peroxy-dicarbonate, di-cyclohexylperoxy-dicarbonate, bis (2-ethylhexyl) Peroxy-di, such as di-sec-butyl peroxy-di-carbonate, di-isopropyl peroxy-di-carbonate Peroxides such as carbonates, acetyl peroxide, di-lauroyl peroxide, di-decanoyl peroxide, di-octanoyl peroxide, di-propyl peroxide, etc. can be mentioned, one or two of these The above can be used.
[0010]
The amount of the polymerization catalyst used is 0.0001 to 1.0 parts by weight, more preferably 0.001 to 1.0 parts by weight, and particularly 0.01 to 0.1 parts by weight with respect to 100 parts by weight of the vinyl acetate monomer. The amount is preferably parts by weight. If the amount is less than 0.0001 part by weight, the catalyst efficiency may be poor and the polymerization time may be prolonged or the polymerization may not proceed. This is not preferable because it may be difficult or the catalyst may remain after polymerization is completed, causing post-polymerization.
[0011]
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 suitably used, and examples of the alcohol include methanol, ethanol, propanol and the like. Of these, methanol is preferably used.
The amount of the solvent used is not particularly limited, but is preferably 1 to 100 parts by weight, more preferably 1 to 80 parts by weight, and particularly preferably 1 to 50 parts by weight with respect to 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 it is difficult to remove the heat, so that the control of the polymerization is difficult. Conversely, if the amount exceeds 100 parts by weight, the degree of polymerization of the resulting vinyl acetate polymer is increased. It is not preferable because it is low and brittle in physical properties.
[0012]
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 can (polymerization can). Such a vinyl acetate monomer or vinyl acetate Arbitrary means are used as a method for charging the monomer and other copolymerizable monomer, the polymerization catalyst and the solvent. Typically, (1) vinyl acetate monomer or vinyl acetate monomer and other copolymerizable monomer are used. , Polymerization catalyst, Method of charging all after solvent is mixed in advance, (2) Polymerization catalyst dissolved in (small amount) solvent, vinyl acetate monomer or vinyl acetate monomer and other copolymerizable monomer , Method of charging solvent separately, (3) Separate vinyl acetate monomer or vinyl acetate monomer and other copolymerizable monomer, mixture of polymerization catalyst and solvent Examples of the charging method include (4) a vinyl acetate monomer or a mixed solution of a vinyl acetate monomer and another copolymerizable monomer and a solvent, a method of separately charging a mixed solution of a polymerization catalyst and a solvent, and the like. It is not a thing.
When the other copolymerizable monomer is a gaseous substance such as ethylene, it is preferable to charge the monomer with bubbling or hermetically adjusting the pressure.
[0013]
Thus, the vinyl acetate monomer or the vinyl acetate monomer and other copolymerizable monomer, the polymerization catalyst and the solvent are charged into the reaction can and the polymerization starts.
Although the polymerization temperature is not particularly limited, it is usually preferably 40 to 80 ° C., more preferably 55 to 80 ° C. If the temperature is less than 40 ° C., the polymerization takes a long time, and there is a problem in terms of productivity. A large amount of the residual amount tends to cause post-polymerization. On the other hand, when the temperature exceeds 80 ° C., the polymerization control becomes difficult, which is not preferable. Moreover, it is not necessary to polymerize at a constant temperature until the polymerization is completed, and it may be changed as the catalyst is added.
[0014]
The polymerization time is preferably 4 to 20 hours, more preferably 6 to 12 hours in the case of a batch system. If the polymerization time is less than 4 hours, it is difficult to control the polymerization if high productivity (high polymerization rate) is to be obtained. On the other hand, if it exceeds 20 hours, there is a problem in productivity, which is not preferable. In the case of a continuous type, the average residence time in the polymerization can is preferably 2 to 10 hours, more preferably 2 to 8 hours, and if the residence time is less than 2 hours, polymerization is attempted to obtain high productivity (high polymerization rate). Control becomes difficult, and if it exceeds 10 hours, there is a problem in productivity, which is not preferable.
[0015]
The polymerization rate is not particularly limited, but is set as high as possible within a range in which polymerization can be controlled from the viewpoint of productivity, and is preferably 20 to 95%. If the polymerization rate is less than 20%, there are problems such as productivity and the presence of a large amount of unpolymerized vinyl acetate monomer. Conversely, if it exceeds 95%, the molecular weight distribution tends to be widened, which is not preferable.
[0016]
Thus, the polymerization is completed, and a vinyl acetate polymer solution is formed. In the present invention, after the polymerization of the vinyl acetate monomer, the polymerization inhibitor is added to stop the polymerization . This method is characterized by introducing alcohol into the reaction solution from below, and this method will be described.
[0017]
The polymerization inhibitor used in the present invention is not particularly limited. For example, hydroquinone, aniline, anthracene, nitrobenzene, dinitrobenzene, trinitrobenzene, benzonitrile, benzophenone, N, N-dimethylformamide, cinnamic alcohol, cinnamic acid, sorbin An acid etc. are mentioned, and it is preferable to add 1 to 200 ppm, more preferably 5 to 100 ppm, particularly 5 to 50 ppm to the reaction liquid (vinyl acetate polymer liquid containing the monomer). The inhibitory action of polymerization is not sufficient. Conversely, if it exceeds 200 ppm, it is not preferable because it may cause coloring or cause sanitary problems.
[0018]
The alcohol used in the present invention is preferably an alcohol having 1 to 4 carbon atoms, and specifically includes methanol, ethanol, n-propanol, iso-propanol, n-butanol, etc. Among them, methanol is most preferable.
The amount of the alcohol introduced is not particularly limited, but is preferably 10 to 300 parts by weight, particularly preferably 20 to 200 parts by weight with respect to 100 parts by weight of the charged monomer. If the amount introduced is less than 10 parts by weight, the polymerization stopping effect is insufficient, and if it exceeds 300 parts by weight, productivity is reduced in the subsequent monomer removal or saponification step.
[0019]
In the present invention, such an alcohol is introduced when the polymerization is stopped. For the introduction, the alcohol may be directly introduced into the reaction solution, specifically, an introduction port is provided in the reaction solution. do it. The introduction port in the reaction solution may be provided at the bottom of the reaction can.
[0020]
After the polymerization is stopped, the monomer is removed from the vinyl acetate polymer solution containing monomers such as vinyl acetate monomer obtained above by distillation.
Thus, with the production method of the present invention, a vinyl acetate polymer having a sharper molecular weight distribution can be obtained.
[0021]
Specific examples of the vinyl acetate polymer obtained by the production method of the present invention include polyvinyl acetate, ethylene-vinyl acetate copolymer, and the like. These include adhesives, pressure-sensitive adhesives, paints, fibers, It is used for textile processing agents, paper / leather processing agents, binders for various materials, cement and mortar admixtures, etc., and is particularly useful as a raw material for polyvinyl alcohol and saponified ethylene-vinyl acetate copolymers. A method for producing polyvinyl alcohol will be described below.
[0022]
In obtaining polyvinyl alcohol from polyvinyl acetate, it is only necessary to saponify the polyvinyl acetate. In the saponification, the polyvinyl acetate is dissolved in alcohol and carried out in the presence of an alkali catalyst. Examples of the alcohol include methanol, ethanol, butanol and the like.
[0023]
The concentration of the polymer in the alcohol is selected from the range of 20 to 50% by weight. As the saponification catalyst, it is necessary to use an alkali catalyst such as an alkali metal hydroxide or alcoholate such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate or potassium methylate. The amount of the catalyst used is required to be 1 to 100 millimolar equivalent with respect to vinyl acetate in order to obtain a desired degree of saponification.
[0024]
In such a case, the saponification temperature is not particularly limited, but is usually 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 saponification degree is selected from the range of 10 to 100 mol%, particularly preferably 50 to 100 mol%, particularly preferably 70 to 100 mol%.
[0025]
Thus, polyvinyl alcohol having a sharp molecular weight distribution is obtained, and such polyvinyl alcohol is less colored by heat treatment and the like, and is a dispersant, adhesive, paste, emulsifier, suspension, film, fiber, paper processing agent, various coatings. It can be used for applications.
[0026]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples.
In the examples, “parts” and “%” are based on weight unless otherwise specified.
[0027]
Example 1
A reactor equipped with a condenser and a stirrer was charged with 7000 kg of vinyl acetate monomer and 3000 kg of methanol, heated with stirring and refluxed for 1 hour, and then 180 kg of a 1.5% acetyl peroxide methanol solution as a polymerization catalyst. And polymerization was carried out under reflux for 6 hours. Thereafter, when the mixture was cooled and refluxed, 100 kg of hydroquinone 0.1% methanol solution was added as a polymerization inhibitor from the top of the reaction vessel. At the same time, 3800 kg of methanol was introduced from the bottom of the reaction vessel and stirred to obtain a uniform solution ( A polymerization rate of vinyl acetate of 90% and a solid content concentration of 44.8%) was obtained.
[0028]
The resulting solution was distilled to remove unreacted monomers and adjusted to a solid content concentration of 45%. When the molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of polyvinyl acetate in the vinyl acetate polymer solution was measured by GPC, it was Mw / Mn = 2.3.
[0029]
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%), saponified at 40 ° C., dried at 105 ° C., and saponification degree 99.1 mol%. Polyvinyl alcohol having a degree of polymerization of 1100 and a viscosity of 13.5 mPa · s (20 ° C.) in a 4% aqueous solution was obtained.
In addition, the molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of the obtained polyvinyl alcohol was re-acetylated and measured by GPC, Mw / Mn = 2.1. .
[0030]
Example 2
A reactor equipped with a condenser and a stirrer was charged with 8000 kg of vinyl acetate monomer and 2000 kg of methanol, heated with stirring and refluxed for 1 hour, and then 87 kg of a 1.5% acetyl peroxide methanol solution was added as a polymerization catalyst. And polymerization was carried out under reflux for 6 hours. Then, after cooling and refluxing, 80 kg of hydroquinone 0.1% methanol solution was added as a polymerization inhibitor from the upper part of the reaction vessel, and at the same time, 5200 kg of methanol was introduced from the lower part of the reaction vessel and stirred to obtain a uniform solution ( A polymerization rate of vinyl acetate of 80% and a solid content concentration of 41.7%) was obtained.
[0031]
The resulting solution was distilled to remove unreacted monomers and adjusted to a solid content concentration of 45%. When the molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of polyvinyl acetate in the vinyl acetate polymer solution was measured by GPC, it was Mw / Mn = 2.3.
[0032]
Further, 2000 kg of the vinyl acetate polymer solution (solid content: 45%) was added with 56 kg of a 2% methanol solution of sodium hydroxide, saponified at 35 ° C. and dried at 105 ° C., and the degree of saponification was 87 mol%. Polyvinyl alcohol having a viscosity of 22 mPa · s (20 ° C.) in the case of a 1400 degree and 4% aqueous solution was obtained.
In addition, the molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of the obtained polyvinyl alcohol was re-acetylated and measured by GPC, Mw / Mn = 2.1. .
[0033]
Example 3
A reactor equipped with a condenser and a stirrer was charged with 6000 kg of vinyl acetate monomer and 750 kg of methanol, heated with stirring and refluxed for 1 hour, and then 16 kg of a 1.5% acetyl peroxide methanol solution as a polymerization catalyst. And polymerization was carried out under reflux for 6 hours. Thereafter, when the mixture was cooled and refluxed, 80 kg of hydroquinone 0.1% methanol solution was added as a polymerization inhibitor from the top of the reactor, and simultaneously 4970 kg of methanol was introduced from the bottom of the reactor and stirred to obtain a uniform solution ( A polymerization rate of vinyl acetate of 65% and a solid content concentration of 33%) was obtained.
[0034]
The resulting solution was distilled to remove unreacted monomers and adjusted to a solid content concentration of 32%. When the molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of polyvinyl acetate in the vinyl acetate polymer solution was measured by GPC, it was Mw / Mn = 2.2.
[0035]
Furthermore, 28 kg of a 2% methanol solution of sodium hydroxide was added to 2000 kg of the vinyl acetate polymer solution (solid content: 45%), saponified at 40 ° C., dried at 105 ° C., and saponification degree was 87 mol%. Polyvinyl alcohol having a viscosity of 52 mPa · s (20 ° C.) in the case of a 2200 degree and 4% aqueous solution was obtained.
Further, the molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of the obtained polyvinyl alcohol was re-acetylated and measured by GPC, and Mw / Mn = 2.1. .
[0036]
Comparative Example 1
In Example 1, the same procedure was carried out except that both the polymerization inhibitor and methanol were added from the top of the reaction vessel after the completion of the polymerization (polymerization rate of vinyl acetate 93%, solid content concentration 46.2%).
[0037]
The resulting solution was distilled to remove unreacted monomers and adjusted to a solid content concentration of 45%. When the molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of polyvinyl acetate in the vinyl acetate polymer solution was measured by GPC, it was Mw / Mn = 2.6.
[0038]
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%), saponified at 40 ° C., dried at 105 ° C., and saponification degree 99.2 mol%. Polyvinyl alcohol having a degree of polymerization of 1050 and a viscosity of 12.2 mPa · s (20 ° C.) in a 4% aqueous solution was obtained.
Further, the molecular weight distribution (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of the obtained polyvinyl alcohol was re-acetylated and measured by GPC, and Mw / Mn = 2.5. .
[0039]
【The invention's effect】
In the production method of the present invention, when a vinyl acetate polymer is produced, a polymerization inhibitor is added after polymerization of a vinyl acetate monomer in a reaction can, and then the polymerization is stopped by stopping the polymerization from the bottom of the reaction can. Since the alcohol is introduced into the liquid, it is possible to obtain a vinyl acetate polymer having a large effect of inhibiting post-polymerization after the polymerization of the vinyl acetate monomer and a sharper molecular weight distribution.

Claims (2)

In producing a vinyl acetate polymer, an alcohol is introduced into the reaction solution from the bottom of the reaction can when a polymerization inhibitor is added after the polymerization of the vinyl acetate monomer in the reaction can to stop the polymerization. A method for producing a vinyl acetate polymer. Alcohol The method of claim 1 Symbol placement of vinyl acetate polymer, characterized in that an alcohol having 1 to 4 carbon atoms.