JP4257757B2 - Process for producing ethylene-vinyl acetate copolymer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an ethylene-vinyl acetate copolymer, and more particularly to a method for producing a good ethylene-vinyl acetate copolymer with less generation (attachment) of scale to the inner wall of a reaction can.
[0002]
[Prior art]
Conventionally, in order to obtain an ethylene-vinyl acetate copolymer, ethylene and vinyl acetate (monomer) are polymerized together with a polymerization solvent by a method such as solution polymerization, nodule polymerization, suspension polymerization under pressure in a polymerization vessel. In these polymerization methods, it has been studied to obtain an ethylene-vinyl acetate copolymer more stably.
For example, Japanese Patent Publication No. 2-52922 discloses a method for continuously producing an ethylene-vinyl acetate copolymer, in which the polymerization catalyst should normally be charged into a polymerization tank. There is a description that it is used by dissolving in a part of the solvent.
[0003]
[Problems to be solved by the invention]
However, as a result of detailed studies on the method for charging the polymerization catalyst by the present inventor, the polymerization catalyst is not necessarily soluble in a polymerization solvent (lower aliphatic alcohol having 1 to 4 carbon atoms). However, it was found that there was a possibility that a high concentration portion was locally formed, a cross-linked product (gel) was likely to be generated and a scale was generated, and further improvement was necessary.
That is, the present invention aims at producing a good ethylene-vinyl acetate copolymer with less generation (adhesion) of scale on the inner wall of the reaction can during polymerization.
[0004]
[Means for Solving the Problems]
Therefore, as a result of intensive studies on the method of charging the polymerization catalyst in order to achieve the above object, the present inventor has previously dissolved the polymerization catalyst in a vinyl acetate monomer and then supplied it to the reaction system (polymerization can) to produce ethylene. When the amount of the polymerization catalyst dissolved in the vinyl acetate monomer is 0.002 to 50 parts by weight with respect to 100 parts by weight of the vinyl acetate monomer, Alternatively, when the charging temperature of the vinyl acetate monomer in which the polymerization catalyst is dissolved into the reaction system (polymerization can) is lower than the 1000-hour half-life temperature of the polymerization catalyst, it is found that the effect of the present invention is remarkably obtained. The invention has been completed.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
Usually, when ethylene and vinyl acetate (monomer) are copolymerized, ethylene, vinyl acetate, a polymerization solvent, a polymerization catalyst (polymerization initiator), etc. are charged into a polymerization (reaction) can. As a charging method, a polymerization solution which is a mixed solution of vinyl acetate, a polymerization solvent and a polymerization catalyst (polymerization initiator) is generally charged into a polymerization can and then ethylene gas is blown into a gas phase portion in the polymerization can. In the present invention, however, in this charging method, after the polymerization catalyst is previously dissolved in the vinyl acetate monomer, it is charged into the reaction system (polymerization can), in other words, the polymerization solution is mixed after mixing the vinyl acetate monomer and the polymerization catalyst. It is characterized by being charged to the polymerization can as a maximum, and if this charging method is satisfied, a known method can be adopted for other conditions, for example, Continuous, may be any of batch-wise, may be appropriately set polymerization conditions in accordance with the polymerization method.
[0006]
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. , Ethanol, propanol, etc., among which methanol is preferably used, and the amount of the solvent is preferably 1 to 60 parts by weight (more preferably 1 to 50 parts by weight) with respect to 100 parts by weight of vinyl acetate. 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, and it is difficult to control the polymerization. Conversely, if the amount exceeds 60 parts by weight, the resulting ethylene-vinyl acetate copolymer is polymerized. The degree is low and the physical properties become fragile, which is not preferable.
[0007]
The polymerization catalyst blended with the vinyl acetate monomer is not particularly limited as long as it is a radical initiator, but preferably 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2 ′. -Azo such as azobis- (2,4,4-trimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile) Compounds, alkyl peresters such as t-butylperoxyneodecanoate, t-butylperpivalate, bis- (4-t-butylcyclohexyl) peroxy-dicarbonate, di-cyclohexylperoxydicarbonate, Bis (2-ethylhexyl) di-sec-butylperoxy-di-carbonate, di-isopropylperoxy-di-carbonate Peroxy such Boneto - di - carbonates, acetyl peroxide, di - lauroyl peroxide, di - decanoyl peroxide, di - octanoylperoxide, di - such as peroxides such as propyl peroxide and the like.
[0008]
In the present invention, it is necessary to previously dissolve such a polymerization catalyst in a vinyl acetate monomer (in the present invention, the vinyl acetate monomer in which the polymerization catalyst is dissolved may be referred to as a monomer composition). As dissolution, 0.002 to 50 parts by weight (further 0.002 to 30 parts by weight, particularly 0.002 to 20 parts by weight) is preferable with respect to 100 parts by weight of vinyl acetate. The polymerization time may be too long or the polymerization may not proceed. On the other hand, if it exceeds 50 parts by weight, gel is likely to be generated, which is not preferable.
The polymerization catalyst does not necessarily need to be dissolved in the entire amount of vinyl acetate monomer to be used, and may be dissolved in a part of the vinyl acetate monomer within the range of the above-described dissolution amount.
[0009]
When the polymerization catalyst is dissolved in the total amount of vinyl acetate monomer, in the case of a batch system, it is preferable to dissolve 0.002 to 0.1 parts by weight of the polymerization catalyst with respect to 100 parts by weight of vinyl acetate. If the amount is less than 002 parts by weight, the catalyst efficiency may be poor and the polymerization time may be prolonged or the polymerization may not proceed. If the amount exceeds 0.1 parts by weight, it may be difficult to control the polymerization, or the catalyst may remain after completion of the polymerization. As a result, post-polymerization may occur. In the case of a continuous type, it is preferable to dissolve the polymerization catalyst in an amount of 0.002 to 0.06 parts by weight with respect to 100 parts by weight of vinyl acetate, and if it is less than 0.002 parts by weight, the catalyst efficiency is poor and the polymerization time is prolonged. In some cases, the polymerization does not proceed. If the amount exceeds 0.06 parts by weight, it is difficult to control the polymerization, or the catalyst may remain after the polymerization is completed, which is not preferable.
[0010]
The polymerization catalyst is dissolved in the vinyl acetate monomer, although it is not particularly limited, but it is preferable to dissolve the polymerization catalyst at 1000 hours or less half-life temperature of the polymerization catalyst (further lower by 10 ° C. than the half-life temperature).
Furthermore, in this invention, it is also possible to mix | blend a part of polymerization solvent with this monomer composition, As this compounding quantity, it is the range of 1-1000 weight part with respect to 100 weight part of vinyl acetate. .
[0011]
In the polymerization, the monomer composition and the polymerization solvent, and in some cases, the vinyl acetate monomer is charged into the polymerization can, and then the polymerization is performed by blowing ethylene gas. The monomer composition and the polymerization solvent, depending on circumstances. Arbitrary means are adopted as a method of charging the vinyl acetate monomer into the polymerization can. Typically, (1) the monomer composition and the polymerization solvent, and in some cases, the vinyl acetate monomer are mixed in advance, and then collectively. Method of charging, (2) Method of charging monomer composition (also vinyl acetate monomer in some cases) and polymerization solvent separately, (3) Charging monomer composition and polymerization solvent at once, and optionally adding vinyl acetate monomer separately Although a method etc. can be mentioned, it does not specifically limit.
[0012]
In the present invention, it is preferable that the charging temperature of the monomer composition at the time of the above charging is not more than the 1000 hour half-life temperature of the polymerization catalyst, and the polymerization catalyst reacts when the charging temperature exceeds the 1000 hour half-life temperature of the polymerization catalyst. The reaction may occur before entering the can, which is not preferable.
Thus, the monomer composition (vinyl acetate monomer and polymerization catalyst), the polymerization solvent and ethylene are charged into the polymerization can, and the polymerization starts, but the polymerization temperature is not particularly limited, but usually 40 to 80 ° C. (further 55 to 80 ° C. is preferable. If the temperature is lower than 40 ° C., it takes a long time to polymerize. If it is attempted to shorten the polymerization time, a large amount of catalyst is required. It is not preferable.
[0013]
In the case of a batch system, the polymerization time is preferably 4 to 10 hours (more preferably 6 to 9 hours). If the polymerization time is less than 4 hours, the polymerization temperature must be increased or the amount of catalyst must be set large. On the other hand, if it exceeds 10 hours, there is a problem in productivity, which is not preferable. In the case of the continuous type, the average residence time in the polymerization can is preferably 2 to 8 hours (more preferably 2 to 6 hours). If the residence time is less than 2 hours, the polymerization temperature is increased or the amount of the catalyst is set to be large. If it exceeds 8 hours, there is a problem in productivity, which is not preferable.
[0014]
The polymerization rate (vinyl acetate) is set as high as possible within the range in which polymerization can be controlled from the viewpoint of productivity, and is preferably 20 to 90%. 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. Conversely, if it exceeds 90%, polymerization control becomes difficult, which is not preferable.
[0015]
In the production method of the present invention, in addition to ethylene and vinyl acetate, it is also possible to copolymerize an ethylenically unsaturated monomer copolymerizable with these as a copolymerization component. For example, olefins such as propylene, isobutylene, α-octene, α-dodecene, α-octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, salts thereof, mono or Dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or salts thereof, alkyl vinyl ethers, N- Acrylamide methyltrimethylammoni Polyoxyalkylene (meth) allyl ethers such as muchloride, allyltrimethylammonium chloride, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether , Polyoxyalkylene (meth) acrylates such as polyoxyethylene (meth) acrylate and polyoxypropylene (meth) acrylate, polyoxyalkylene (meth) acrylamides such as 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, polyoxypropylene vinyl amine.
[0016]
Thus, in the production method of the present invention, there is little generation of scale, and a good ethylene-vinyl acetate copolymer is obtained. Such an ethylene-vinyl acetate copolymer is composed of an adhesive, a pressure-sensitive adhesive, a paint, a fiber, It is used for textile processing agents, paper / leather processing agents, binders for various materials, cement and mortar admixtures, etc., and is also particularly useful as a raw material for ethylene-vinyl acetate copolymer saponified products. A method for producing a saponified vinyl copolymer will be described below.
[0017]
The ethylene content of the ethylene-vinyl acetate copolymer used in the saponified ethylene-vinyl acetate copolymer is preferably 10 to 60 mol% (more preferably 20 to 55 mol%), and the content is 10 If it is less than mol%, when the saponified ethylene-vinyl acetate copolymer obtained is melt-molded, the melt moldability is lowered and the gas barrier property of the melt-formed product at high humidity is greatly reduced. When it exceeds mol%, when the saponified product is melt-molded, the mechanical strength and gas barrier properties of the obtained molded product are not sufficient, which is not preferable. The ethylene content may be controlled by the ethylene pressure in the polymerization can in the production method of the present invention.
[0018]
The ethylene-vinyl acetate copolymer obtained by the production method of the present invention is saponified to become a saponified ethylene-vinyl acetate copolymer. Such saponification reaction is carried out in the presence of a saponification catalyst. Is done.
In the saponification, the ethylene-vinyl acetate copolymer is dissolved in an alcohol (usually methanol is used) or an alcohol-containing medium to a concentration of about 30 to 60% by weight, and an alkali catalyst (usually hydroxylated) is used. Saponification reaction is performed at a temperature of 40 to 140 ° C. by adding an alkali metal hydroxide such as sodium or potassium hydroxide.
[0019]
By such saponification, the saponification degree of the vinyl acetate component of the saponified ethylene-vinyl acetate copolymer is preferably 80 to 100 mol% (further 90 to 100 mol%, particularly 95 to 100 mol%). When the degree of conversion is less than 80 mol%, the thermal stability in melt molding using the saponified ethylene-vinyl acetate copolymer is deteriorated, and the mechanical strength and gas barrier properties of the saponified product are greatly reduced. This is not preferable.
[0020]
Next, the alcohol solution of the ethylene-vinyl acetate copolymer saponified product obtained above may be used as it is, but preferably, water is added directly or after adding water, the concentration of the saponified alcohol solution is adjusted appropriately. Then, after forming a solution for producing a strand as an alcohol / water solution, the solution is extruded into a strand form in a coagulation bath such as water or a water / alcohol (mixed) solution and deposited.
[0021]
The precipitated strand is then cut into pellets and then washed with water. Such water-washed pellets are preferably chemically treated by a method such as immersion in an aqueous solution of a drug such as acid and / or salts thereof, such as formic acid, acetic acid, adipic acid, phosphoric acid, boric acid. Alternatively, salts thereof may be mentioned, and acetic acid is more preferably used.
[0022]
The pellets obtained as described above are melt-molded and formed into a desired molded product. The temperature condition during melt-molding is preferably about 160 to 260 ° C. In molding, a known additive such as a reinforcing material such as glass fiber and carbon fiber, a filler, a colorant, a stabilizer such as hydrotalcite, a foaming agent, and a desiccant may be appropriately blended as necessary. Further, an appropriate amount of a thermoplastic resin for modification can be blended in the saponified ethylene-vinyl acetate copolymer.
[0023]
As the melt molding method, any molding method such as an injection molding method, a compression molding method, and an extrusion molding method can be employed. Among these, the extrusion molding method includes a T-die method, a hollow molding method, a pipe extrusion method, a linear extrusion method, a deformed die extrusion method, an inflation method, etc., but molding of an ethylene-vinyl acetate copolymer saponified product alone. Coextrusion of not only products (films, sheets, tapes, bottles, pipes, filaments, profile cross-section extrudates, etc.) but also saponified ethylene-vinyl acetate copolymer layers and other thermoplastic resin layers is possible. .
[0024]
【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.
Example 1
Using a monomer composition in which 0.007 part of a polymerization catalyst (2,2′-azobisisobutyronitrile) was blended in advance with respect to 100 parts of vinyl acetate monomer, The ethylene-vinyl acetate copolymer was continuously polymerized under the following conditions.
Supply amount of monomer composition 480 g / hr
Charge temperature of monomer composition -20 ° C
Polymerization solvent (methanol) supply rate 40 g / hr
Polymerization temperature 77 ° C
Ethylene pressure 6.3 MPa
Average residence time 6 hr
The resulting ethylene-vinyl acetate copolymer had an ethylene content of 40 mol% and a vinyl acetate polymerization rate of 50%.
Under the above conditions, no scale adhesion was observed in the polymerization can after 10 days of continuous operation.
[0025]
Example 2
Polymerization with a stirrer having a capacity of 10 l using a monomer composition in which 0.033 part of a polymerization catalyst (2,2′-azobisisobutyronitrile) and 40 parts of methanol were previously blended with 100 parts of vinyl acetate monomer. The ethylene-vinyl acetate copolymer was continuously polymerized with a can under the following conditions.
Supply amount of monomer composition 140 g / hr
Charge temperature of monomer composition -20 ° C
Supply amount of vinyl acetate monomer 380 g / hr
Polymerization temperature 77 ° C
Ethylene pressure 6.3 MPa
Average residence time 6 hr
The resulting ethylene-vinyl acetate copolymer had an ethylene content of 40 mol% and a vinyl acetate polymerization rate of 50%.
Under the above conditions, no scale adhesion was observed in the polymerization can after 10 days of continuous operation.
[0026]
Example 3
Using a monomer composition in which 0.035 part of a polymerization catalyst (diisopropyl peroxydicarbonate) and 5 parts of methanol were blended in advance with respect to 100 parts of vinyl acetate monomer, a polymerization can with a capacity of 10 l, under the following conditions Then, ethylene-vinyl acetate copolymer was batch polymerized.
Charge amount of monomer composition 3000 g
Charge temperature of monomer composition -20 ° C
Charge amount of polymerization solvent (methanol) 143g
Polymerization temperature 65 ° C
Ethylene pressure 4.3MPa
Polymerization time 6hr
The ethylene content of the obtained ethylene-vinyl acetate copolymer was 33 mol%, and the polymerization rate of vinyl acetate was 55%.
Under the above conditions, no scale adhesion was observed in the polymerization can after 10 days of continuous operation.
[0027]
Example 4
In Example 3, a monomer composition in which 20 parts of a polymerization catalyst (diisopropyl peroxydicarbonate) and 100 parts of methanol were blended in advance with respect to 100 parts of vinyl acetate monomer was used, and the charge amount of the monomer composition was 110 g. The ethylene-vinyl acetate copolymer was continuously polymerized in the same manner except that 2806 g of vinyl acetate monomer and 236 g of polymerization solvent (methanol) were charged.
The ethylene content of the obtained ethylene-vinyl acetate copolymer was 33 mol%, and the polymerization rate of vinyl acetate was 55%.
Under the above conditions, no scale adhesion was observed in the polymerization can after 10 days of continuous operation.
[0028]
Example 5
In Example 1, it carried out similarly except having made ethylene pressure 4.3MPa, and obtained the ethylene-vinyl acetate copolymer with the ethylene content of 30 mol% and the polymerization rate of 50% of vinyl acetate.
Under the above conditions, no scale adhesion was observed in the polymerization can after 10 days of continuous operation.
[0029]
Comparative Example 1
In Example 1, an ethylene-vinyl acetate copolymer having an ethylene content of 40 mol% and a vinyl acetate polymerization rate of 50% was carried out in the same manner except that the polymerization catalyst was dissolved in a part of the polymerization solvent and fed into the polymerization vessel. Coalescence was obtained.
After continuous operation for 10 days, a large amount of scale was observed in the polymerization can.
[0030]
【The invention's effect】
In the present invention, since the polymerization catalyst is preliminarily dissolved in the vinyl acetate monomer and then charged into the reaction system (polymerization can), there is little adhesion of scale inside the polymerization (reaction) can.

Claims (3)

A method for producing an ethylene-vinyl acetate copolymer, wherein a polymerization catalyst is dissolved in a vinyl acetate monomer in advance and then supplied to a reaction system to carry out copolymerization with ethylene. 2. The method for producing an ethylene-vinyl acetate copolymer according to claim 1, wherein the amount of the polymerization catalyst dissolved in the vinyl acetate monomer is 0.002 to 50 parts by weight with respect to 100 parts by weight of the vinyl acetate monomer. . The method for producing an ethylene-vinyl acetate copolymer according to claim 1 or 2, wherein the charging temperature of the vinyl acetate monomer in which the polymerization catalyst is dissolved is equal to or lower than the 1000-hour half-life temperature of the polymerization catalyst. .