JP4520544B2 - 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 specifically, relates to a method for producing an ethylene-vinyl acetate copolymer with little generation (attachment) of scale to the inner wall of a reaction can and stable quality. .
[0002]
[Prior art]
Conventionally, in order to obtain an ethylene-vinyl acetate copolymer, ethylene and vinyl acetate are polymerized together with a polymerization solvent by a method such as solution polymerization, nodule polymerization, suspension polymerization under pressure in a polymerization can. In this polymerization method, it has been studied to obtain an ethylene-vinyl acetate copolymer more stably.
For example, Japanese Patent Publication No. 2-52922 discloses a continuous production method of an ethylene-vinyl acetate copolymer including a step of absorbing and dissolving ethylene in a vinyl acetate or vinyl acetate solvent solution.
[0003]
[Problems to be solved by the invention]
However, as a result of detailed examination of the above production method by the present inventor, although the effect of preventing the occurrence of scale in the reaction can is recognized, the distribution of ethylene composition of the obtained ethylene-vinyl acetate copolymer is wide, and distribution unevenness is observed. It has been found that this is possible, and further improvements have been required for the recent higher performance quality requirements.
That is, the present invention is directed to a method for producing a stable ethylene-vinyl acetate copolymer of low quality with little generation (adhesion) of scale on the inner wall of a reaction can during polymerization and less uneven distribution of ethylene composition. It is.
[0004]
[Means for Solving the Problems]
Therefore, the present inventor has conducted extensive research to achieve the above object, and as a result, ethylene-vinyl acetate copolymer is characterized by copolymerizing ethylene and vinyl acetate using a radical initiator as a polymerization catalyst. In the production method, the above-mentioned object can be achieved by copolymerizing ethylene and vinyl acetate while charging ethylene in the polymerization solution, and further, the pressure P (MPa) at the time of charging ethylene is set at this time. By adjusting so as to satisfy the following formula (1), the inventors have found that the effects of the present invention can be remarkably obtained and have completed the present invention.
[Expression 2]
logP ≦ {(S + M) / (M × 0.01C)} − 1.5 (1)
(However, S represents the polymerization solvent charge (kg), M represents vinyl acetate charge (kg), and C represents the polymerization rate (%)).
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
Usually, when ethylene and vinyl acetate are copolymerized, ethylene, vinyl acetate, a polymerization solvent, a polymerization catalyst (polymerization initiator), etc. are charged into a polymerization (reaction) can, but as a charging method at this time In general, vinyl acetate, a polymerization solvent, a polymerization catalyst (polymerization initiator), and the like are charged into a polymerization can and ethylene gas is blown into a gas phase portion in the polymerization can. In this method, ethylene gas is directly charged into the polymerization solution, and a known method can be adopted for other conditions as long as this charging method is satisfied. The method of the present invention may be either a continuous type or a batch type, but the continuous type can remarkably obtain the effects of the present invention.
More specifically, as the solvent used in the polymerization, 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, and the amount of the solvent may be adjusted so as to satisfy the following formula (1).
[0006]
The polymerization catalyst is not particularly limited as long as it is a radical 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-butylperoxy Alkyl peresters such as neodecanoate, t-butyl perpivalate, bis- (4-t-butylcyclohexyl) peroxy-dicarbonate, di-cyclohexylperoxy-dicarbonate, bis (2-ethylhexyl) di -Peroxy-di- such as -sec-butylperoxy-dicarbonate, di-isopropylperoxy-dicarbonate Boneto acids, acetyl peroxide, di - lauroyl peroxide, di - decanoyl peroxide, di - octanoylperoxide, di - such as peroxides such as propyl peroxide and the like.
[0007]
The amount of the catalyst used is preferably 0.002 to 0.2 parts by weight (more preferably 0.002 to 0.1 parts by weight) with respect to 100 parts by weight of vinyl acetate. The efficiency is poor and the polymerization time may be prolonged or the polymerization may not proceed. If the amount exceeds 0.2 parts by weight, the control of the polymerization becomes difficult, or the catalyst remains after the completion of the polymerization to cause the subsequent polymerization. Is not preferable.
In the polymerization, as described at the beginning, it is sufficient that ethylene gas is charged (injected) into the polymerization solution in the polymerization can, and any method for charging the vinyl acetate, solvent and catalyst into the polymerization can is used. Typically, (1) a method in which all vinyl acetate, solvent, and catalyst are mixed in advance and then charged together, (2) catalyst, vinyl acetate, and solvent dissolved in the solvent are charged separately. Method, (3) vinyl acetate, a method in which a mixture of a catalyst and a solvent is separately added, (4) a method in which a mixture of vinyl acetate and a solvent, a method in which a mixture of a catalyst and a solvent is separately added, etc. Is not to be done.
[0008]
On the other hand, the pressure P (MPa) of the ethylene gas charged (blown) into the polymerization solution is set according to the ethylene content of the required ethylene-vinyl acetate copolymer. It is preferable to adjust the pressure so that the following equation (1) is satisfied.
[Equation 3]
logP ≦ {(S + M) / (M × 0.01C)} − 1.5 (1)
Here, S represents the polymerization solvent charge (kg), M represents vinyl acetate charge (kg), and C represents the polymerization rate (%).
That is, in the above equation (1), when the pressure becomes such that the left side is larger than the right side, the scale is remarkably generated, which is not preferable. The ethylene gas charging (blowing) method is not particularly limited as long as ethylene gas is charged into the polymerization solution in the polymerization can.
[0009]
According to the method of the present invention, vinyl acetate, a solvent, a catalyst, and ethylene are charged into a polymerization can and polymerization starts. However, the polymerization temperature is not particularly limited, but is usually 40 to 80 ° C. (more preferably 55 to 80 ° C.). When the temperature is less than 40 ° C., it takes a long time for the polymerization. If the polymerization time is to be shortened, a large amount of catalyst is required. On the other hand, if it exceeds 80 ° C., the polymerization control becomes difficult, which is not preferable.
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.
[0010]
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.
[0011]
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.
[0012]
Thus, the production method of the present invention yields an ethylene-vinyl acetate copolymer with little generation of scale and excellent quality stability. Such an ethylene-vinyl acetate copolymer is used as an adhesive, an adhesive, and an adhesive. It is used as a raw material for saponified products of ethylene-vinyl acetate copolymer, especially as an additive for paints, paints, textiles and fabrics, paper and leather, binders for various materials, cement and mortar admixtures, etc. A method for producing such a saponified ethylene-vinyl acetate copolymer will be described below.
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 60 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.
[0013]
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.
[0014]
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.
[0015]
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.
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.
[0016]
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.
[0017]
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. .
[0018]
【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
While supplying the following polymerization solution (vinyl acetate, methanol, catalyst) into a polymerization can with a stirrer having a capacity of 10 l, ethylene gas was blown into the polymerization solution to a pressure of 4.0 MPa. The ethylene-vinyl acetate copolymer was continuously polymerized.
Vinyl acetate supply 1350 g / hr
Methanol supply rate 200g / hr
Benzoyl peroxide (catalyst) supply amount 810 mg / hr
Polymerization temperature 67 ° C
Average residence time 4 hr
[0019]
The ethylene content of the obtained ethylene-vinyl acetate copolymer was 33 mol%, and the polymerization rate of vinyl acetate was 36%.
Further, when the pressure at the time of charging ethylene, the charged amount of vinyl acetate, the charged amount of the polymerization solvent, and the polymerization rate are substituted into the formula (1) in the text, the left side = log P = log 4.0 = 0.60, the right side = {(S + M) / (M × 0.01C)} − 1.5 = {(0.2 + 1.35) / (1.35 × 0.01 × 36)} − 1.5 = 1.69, The left side ≦ the right side was satisfied.
Under the above conditions, no scale adherence was observed at the top of the polymerization can after 10 days of continuous operation.
Further, regarding the distribution unevenness of the ethylene composition of the obtained ethylene-vinyl acetate copolymer, the ethylene-vinyl acetate copolymer was completely saponified by a conventional method to obtain a DSC (differential scanning calorimeter: manufactured by Elmer Perkin Co., Ltd.). (DSC-7)) measured at a heating rate of 10 ° C./min, held at 230 ° C. for 1 minute, and then measured at a cooling rate of 10 ° C./min. It was a very good ethylene-vinyl acetate copolymer with a low distribution of 2 ° C.
[0020]
Example 2
While supplying the following polymerization solution (vinyl acetate, methanol, catalyst) into a polymerization can equipped with a stirrer having a capacity of 10 l, ethylene gas was blown into the polymerization solution to a pressure of 4.8 MPa, and the following conditions were satisfied. The ethylene-vinyl acetate copolymer was continuously polymerized.
Vinyl acetate supply rate 1045 g / hr
Methanol supply rate 155 g / hr
2,2'-Azobisisobutyronitrile (catalyst) supply amount 68 mg / hr
Polymerization temperature 77 ° C
Average residence time 5 hr
[0021]
The ethylene content of the obtained ethylene-vinyl acetate copolymer was 34 mol%, and the polymerization rate of vinyl acetate was 36%.
Further, when the pressure at the time of charging ethylene, the charged amount of vinyl acetate, the charged amount of the polymerization solvent, and the polymerization rate are substituted into the formula (1) in the text, the left side = log P = log 4.8 = 0.68, the right side = {(S + M) / (M × 0.01C)} − 1.5 = {(0.155 + 1.045) / (1.045 × 0.01 × 36} −1.5 = 1.69, the left side ≦ Right side was satisfied.
Under the above conditions, no scale adherence was observed at the top of the polymerization can after 10 days of continuous operation.
In addition, the distribution distribution of ethylene composition of the obtained ethylene-vinyl acetate copolymer was examined in the same manner. As a result, it was 5.5 ° C. and it was a very good ethylene-vinyl acetate copolymer with little distribution. It was.
[0022]
Example 3
While supplying the following polymerization solution (vinyl acetate, methanol, catalyst) into a polymerization vessel equipped with a stirrer having a capacity of 10 l, ethylene gas was blown into the polymerization solution to a pressure of 6.1 MPa, and the following conditions were satisfied. The ethylene-vinyl acetate copolymer was continuously polymerized.
Vinyl acetate supply 1190 g / hr
Methanol supply rate 85g / hr
2,2'-Azobisisobutyronitrile (catalyst) supply amount 68 mg / hr
Polymerization temperature 77 ° C
Average residence time 5 hr
[0023]
The ethylene content of the obtained ethylene-vinyl acetate copolymer was 40 mol%, and the polymerization rate of vinyl acetate was 32%.
Further, when the above ethylene charging pressure, vinyl acetate charging amount, polymerization solvent charging amount, and polymerization rate are substituted into the formula (1) in the text, the left side = logP = log6.1 = 0.79, the right side = { (S + M) / (M × 0.01C)} − 1.5 = {(0.085 + 1.19) / (1.19 × 0.01 × 32)} − 1.5 = 1.85, left side ≦ The right side was satisfied.
Under the above conditions, no scale adherence was observed at the top of the polymerization can after 10 days of continuous operation.
In addition, the distribution distribution of ethylene composition of the obtained ethylene-vinyl acetate copolymer was examined in the same manner. As a result, it was 5.5 ° C. and it was a very good ethylene-vinyl acetate copolymer with little distribution. It was.
[0024]
Comparative Example 1
In Example 1, polymerization was carried out in the same manner except that ethylene was charged in the gas phase portion in the polymerization can.
The obtained ethylene-vinyl acetate copolymer had an ethylene content of 32 mol% and a vinyl acetate polymerization rate of 36%.
After 10 days of continuous operation, scale adhesion was observed in the polymerization can.
Further, when the distribution unevenness of the ethylene composition of the obtained ethylene-vinyl acetate copolymer was examined in the same manner, it was 7.2 ° C., and the ethylene-vinyl acetate copolymer had a very large distribution unevenness of the ethylene composition. Met.
[0025]
Comparative Example 2
In Example 1, polymerization was carried out in the same manner except that ethylene was charged into the gas phase portion in the polymerization can and the polymerization temperature was 77 ° C.
The ethylene content of the obtained ethylene-vinyl acetate copolymer was 32 mol%, and the polymerization rate of vinyl acetate was 55%.
After 10 days of continuous operation, scale adhesion was observed in the polymerization can.
Further, when the distribution unevenness of the ethylene composition of the obtained ethylene-vinyl acetate copolymer was examined in the same manner, it was 8.0 ° C., and the ethylene-vinyl acetate copolymer had a very large distribution unevenness of the ethylene composition. Met.
[0026]
【The invention's effect】
In the present invention, in a method for producing an ethylene-vinyl acetate copolymer, wherein ethylene and vinyl acetate are copolymerized using a radical initiator as a polymerization catalyst, ethylene and vinyl acetate are charged while ethylene is charged into the polymerization solution. Therefore, a stable ethylene-vinyl acetate copolymer having a low quality and less uneven distribution of the ethylene composition can be obtained.

Claims (2)

In a process for producing an ethylene-vinyl acetate copolymer, wherein ethylene and vinyl acetate are copolymerized using a radical initiator as a polymerization catalyst, ethylene and vinyl acetate are copolymerized while charging ethylene into the polymerization solution. A process for producing an ethylene-vinyl acetate copolymer. Preparation of vinyl acetate copolymer - ethylene according to claim 1, characterized in that the polymerization continuously ethylene and vinyl acetate.