JP2003089739A - Method for producing vinyl acetate polymer and its saponified product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a vinyl acetate polymer and its saponified product developing little fisheye defect in molding, having suppressed discoloration and odor and exhibiting suppressed formation of fisheye and discoloration in molding even in the case of using a recycled material. SOLUTION: The vinyl acetate polymer is produced by homopolymerizing vinyl acetate or copolymerizing vinyl acetate and other unsaturated monomer and adding an N,N-dialkylhydroxylamine and preferably further one or more compounds selected from styrene derivatives, hydroquinone derivatives, quinone derivatives and piperidine derivatives to the obtained polymer solution.

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-based polymer, more specifically, a vinyl acetate-based polymer in which generation of fish eyes during molding is small, coloration is suppressed, and odor is also suppressed. The present invention relates to a method for producing a polymer, particularly a vinyl alcohol polymer.

[0002]

2. Description of the Related Art Conventionally, a vinyl alcohol polymer such as a polyvinyl alcohol resin or a saponified product of an ethylene-vinyl acetate copolymer can be melt-molded and is used for various purposes by such molding. In particular, it is formed into a film or sheet, and is often used for packaging foods, clothes, and the like. Examples of the required performance when used for such purposes include suppression of fish eyes, suppression of coloring, suppression of odor during molding. In order to satisfy the required performance, it has been attempted to add a salt, an acid or the like to the obtained vinyl alcohol polymer,
Polymerization catalysts used for polymerization, regulators of polymerization degree, and the like are also being studied. For example, Japanese Patent Application Laid-Open No. 9-71620 discloses a method for producing a vinyl acetate-based polymer in which a conjugated polyene compound having a boiling point of 20 ° C. or higher is added after polymerizing one or more kinds of monomers containing vinyl acetate. The applicant also proposed in Japanese Patent Laid-Open No. 61-197603 to add a specific phenyl group-containing olefin derivative to a vinyl ester copolymer solution which has reached a predetermined polymerization rate.

[0003]

However, as a result of a detailed study of the above method by the present inventor, the former method does not sufficiently suppress fish eyes and coloring of the molded product of the vinyl alcohol polymer, and Such a problem tends to occur when the molded product is recycled, and the latter method is not sufficient in terms of suppression of minute fish eyes of the molded product, and further, against severe demands for odor control of recent years. However, it turned out that there is room for improvement.

[0004]

Therefore, as a result of intensive studies in view of the above situation, the present inventors have found that vinyl acetate alone or after polymerizing vinyl acetate and another unsaturated monomer,
When N, N-dialkylhydroxylamine is preferably used in combination with at least one compound selected from the group consisting of styrene derivative, hydroquinone derivative, quinone derivative and piperidine derivative, suppression of fish eye, suppression of coloration and suppression of odor during molding. Etc. to obtain a vinyl acetate-based polymer (particularly a vinyl alcohol-based polymer), and further, by using an organic peroxide as a polymerization catalyst during the polymerization and coexisting with a hydroxylactone or a hydroxycarboxylic acid. The present invention has been completed by finding that the above effects of the present invention can be remarkably exhibited.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The method for producing a vinyl acetate polymer of the present invention comprises the steps of polymerizing vinyl acetate alone or vinyl acetate and another unsaturated monomer as described above, and then adding N, N-dialkylhydroxylamine to the resulting polymer solution. It is characterized by doing. N,
As N-dialkylhydroxylamine, N, N-dimethylhydroxylamine, N, N-diethylhydroxylamine, N, N-dipropylhydroxylamine,
N, N-dibutylhydroxylamine and the like,
N, N-diethylhydroxylamine is preferably used. In the present invention, further improvement of the effect can be expected by using N, N-dialkylhydroxylamine together with at least one compound selected from styrene derivative, hydroquinone derivative, quinone derivative and piperidine derivative.

As the styrene derivative, cinnamic alcohol,
Examples include at least one selected from cinnamic acid and its derivatives. In addition to cinnamic alcohol and cinnamic acid, cinnamic acid ester (ethyl cinnamate, methyl cinnamate, etc.), cinnamic acid chloride (cinnamoyl chloride, etc.), cinnamic acid amide, Examples thereof include cinnamic acid nitrile and cinnamic acid salts (sodium cinnamate, calcium cinnamate, etc.), and cinnamic alcohol and cinnamic acid are preferably used.

Examples of the hydroquinone derivative include hydroquinone, hydroquinone monomethyl ether, dipentylhydroquinone, p-butoxyphenol, p-pentoxyphenol and monobenzone. Examples of the quinone derivative are o-benzoquinone, p-benzoquinone, diphenoquinone, 1,4. -Naphthoquinone, anthraquinone and the like are 4-hydroxyl-as the piperidine derivative.
2,2,6,6-tetramethylpiperidine-1-oxyl, hexahydrodipicolinic acid, hexahydroquinolinic acid, hexahydrocincomeronic acid and the like can be mentioned, respectively. In addition, within a range not impairing the gist of the present invention, 2,4-
Diphenyl-4-methyl-1-pentene, 1,3-diphenyl-1-butene and the like, phenyl group-containing olefin derivatives described in JP-A-61-197603, sorbic acid and the like, described in JP-A-9-71620. Boiling point of 20 ℃
The above conjugated polyene compounds can also be used.

The polymerization method of vinyl acetate in the production method of the present invention will be specifically described. In polymerizing vinyl acetate alone or other unsaturated monomer, for example, vinyl acetate alone or vinyl acetate and another unsaturated monomer are charged in a reaction system such as a polymerization vessel together with a polymerization catalyst and a solvent for polymerization. Should be done.

Examples of such other unsaturated monomers include ethylene, propylene, isobutylene, α-octene,
Olefins such as α-dodecene and α-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, methacrylonitrile, etc. Nitriles such as acrylamide, 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-acrylamidomethyl trimethyl ammonium chloride, allyl trimethyl ammonium Chloride, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether Polyoxyalkylene (meth) allyl ethers such as ter, polyoxyethylene (meth)
Acrylates, polyoxyalkylene (meth) acrylates such as polyoxypropylene (meth) acrylate,
Polyoxyethylene (meth) acrylamide, polyoxyalkylene (meth) acrylamide such as polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether,
Examples thereof include polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine and polyoxypropylene vinylamine.

As the catalyst, any radical initiator can be used without particular limitation, but preferably 2,2 '.
-Azobis- (2,4-dimethylvaleronitrile),
2,2'-azobis- (2,4,4-trimethylvaleronitrile), 2,2'-azobisisobutyronitrile,
Azo compounds such as 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile), dimethyl 2,2'-azobisisobutyrate, t-butyl peroxyneodecanoate, t-butyl Peroxypivalate, t-
Butyl peroxy-2-ethyl hexanoate, α,
α'bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxy neodecanoate, 1,
1,3,3-Tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyisobutyrate ,
Peroxyesters such as t-hexyl peroxypivalate, di-n-butyl peroxydicarbonate, bis- (4-t-butylcyclohexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate, bis (2-ethylhexyl) ) Di-sec-butylperoxydicarbonate, di-n-propylperoxydicarbonate, di-iso-propylperoxydicarbonate, di-sec-butylperoxydicarbonate, bis (4-t-butylcyclohexyl) Peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, dimethoxybutyl peroxydicarbonate, di (3-methyl-3-methoxybutylperoxy) dicarbonate Peroxydicarbonate such etc.,
Dibenzoyl peroxide, distearoyl peroxide, dilauroyl peroxide, dioctanoyl peroxide, didecanoyl peroxide, 3,3,5-trimethylhexanoyl peroxide, diisobutyryl peroxide, dipropyl peroxide, diacetyl Examples thereof include diacyl peroxides such as peroxides.

The half-life at 60 ° C. is preferably 0.1 to
An organic peroxide for 50 hours is used, and specifically,
t-Butylperoxy neodecanoate [half-life 1.8
Time], t-butylperoxypivalate [half-life 5.
0 hours], α, α'bis (neodecanoylperoxy)
Diisopropylbenzene [half-life 0.5 hours], cumyl peroxyneodecanoate [half-life 0.5 hours],
1,1,3,3, -tetramethylbutylperoxy neodecanoate [half-life 0.7 hours], 1-cyclohexyl-1-methylethylperoxy neodecanoate [half-life 0.8 hours], Peroxyesters such as t-hexyl peroxy neodecanoate [half-life 1.4 hours], t-hexyl peroxypivalate [half-life 4.2 hours], di-n-propyl peroxydicarbonate [ Half-life 0.7 hours], di-iso-propyl peroxydicarbonate [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) Le) peroxydicarbonate [half-life 0.9 hours, dimethoxybutyl peroxydicarbonate [half-life 1.6 hours, di (3-methyl-3-
Peroxydicarbonates such as methoxybutylperoxy) dicarbonate [half-life 1.9 hours], 3,
Examples of diacyl peroxides such as 3,5-trimethylhexanoyl peroxide [half-life 9.2 hours], diisobutyryl peroxide [half-life 0.3 hours], lauroyl peroxide [half-life 12 hours], etc. You can The half-life here is measured in benzene or the like at 60 ° C.

In the case of the batch type, the amount of such a catalyst used is 0.002 to 0.5 part by weight (more preferably 0.005 to 0.1 part by weight, particularly preferably 0. 0
07-0.08 parts by weight) is preferable, and if it is less than 0.002 parts by weight, the catalyst efficiency may be poor and the polymerization time may be long or the polymerization may not proceed. Is difficult, or the catalyst may remain after the polymerization to cause post-polymerization, which is not preferable. In the case of the continuous type, 0.002-based on 100 parts by weight of vinyl acetate
0.1 parts by weight (further 0.005 to 0.07 parts by weight, particularly 0.01 to 0.05 parts by weight) is preferred, and 0.00
If it is less than 2 parts by weight, the catalyst efficiency may be poor and the polymerization time may be long or the polymerization may not proceed. If it exceeds 0.1 parts by weight, the control of the polymerization may be difficult or the catalyst may remain after the completion of the polymerization. And post-polymerization may occur, which is not preferable. From the viewpoint of safety in handling, these catalysts are preferably diluted with a suitable solvent and then charged into the polymerization system. Examples of such a solvent include aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic esters or these. It is preferable to use a mixed solvent of. Depending on the purpose, it is possible to use vinyl acetate as a diluting solvent, but it is desirable to mix it with another solvent so that the concentration of vinyl acetate is 40% by weight or less in order to avoid the risk of polymerization. These catalysts can also be introduced into the polymerization system in the form of an aqueous emulsion.

In the present invention, it is also preferable to coexist a hydroxylactone compound or a hydroxycarboxylic acid together with the above catalyst, and the hydroxylactone compound 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, etc. can be mentioned, L-ascorbic acid and erythorbic acid are preferably used, and as the hydroxycarboxylic acid,
Glycolic acid, lactic acid, glyceric acid, malic acid, tartaric acid, citric acid, salicylic acid and the like can be mentioned, and citric acid is preferably used.

The amount of the hydroxy lactone compound or hydroxy carboxylic acid used is 0. 0 with respect to 100 parts by weight of vinyl acetate in both the batch system and the continuous system.
0001 to 0.1 parts by weight (further 0.0005 to 0.0
5 parts by weight, particularly 0.001 to 0.03 part by weight) is preferable, and if the amount used is less than 0.0001 part by weight, the effect of the present invention may not be obtained, and conversely, 0.1 part by weight may be added. If it exceeds the above range, the polymerization of vinyl acetate is hindered, which is not preferable. When charging such a compound into the polymerization system, it is not particularly limited, but usually it is diluted with a solvent such as an aliphatic ester containing a lower aliphatic alcohol or vinyl acetate or water, or a mixed solvent thereof and charged into the polymerization reaction system. .

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, and examples of the alcohol include methanol, ethanol, propanol and the like. Among them, methanol is preferably used. The amount of the solvent is 100 parts by weight of vinyl acetate,
1 to 100 parts by weight (further 1 to 80 parts by weight, especially 1 to
60 parts by weight) is preferable, and when 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 to control the polymerization. Conversely, when it exceeds 100 parts by weight, a vinyl acetate-based product obtained is obtained. The degree of polymerization of the polymer is low and the physical properties become brittle, which is not preferable.

To start the polymerization, vinyl acetate alone or vinyl acetate and another unsaturated monomer, a polymerization catalyst (if necessary, a hydroxylactone compound or a hydroxycarboxylic acid together) and a polymerization solvent are subjected to a (polymerization) reaction. Although it is charged in a can, any means is adopted as a charging method, and typically, vinyl acetate alone or vinyl acetate and other unsaturated monomer, polymerization catalyst, and solvent are all mixed in advance. Then, batch charging, polymerization catalyst dissolved in (a small amount) solvent, vinyl acetate alone or vinyl acetate and other unsaturated monomers, separately charging solvent, vinyl acetate alone or vinyl acetate and other Unsaturated monomer, a method of separately charging a mixture of a polymerization catalyst and a solvent,
Examples thereof include a method in which vinyl acetate alone or a mixed solution of vinyl acetate and another unsaturated monomer and a solvent, a method of separately charging a mixed solution of a polymerization catalyst and a solvent are used, but the method is not particularly limited.
When the other unsaturated monomer is a gaseous substance such as ethylene, it is preferable to adjust the pressure under bubbling or sealing.

Thus, vinyl acetate alone or vinyl acetate and another unsaturated monomer, a polymerization catalyst and a solvent are charged in the polymerization vessel to start the polymerization, but the polymerization temperature is not particularly limited, but is usually 50-70 ° C (further 55-8
0 ° C) is preferable, and if the temperature is lower than 40 ° C, it takes a long time for the polymerization, which is a problem in terms of productivity. A large amount of the polymerization catalyst remains and post-polymerization easily occurs. It is not preferable because the polymerization control becomes difficult. Further, it is not necessary to carry out the polymerization at a constant temperature until the completion of the polymerization, and it may be changed with the additional charging of the catalyst.

In the case of a batch system, the polymerization time is 4 to 2
0 hour (more preferably 6 to 12 hours) is preferable, and when the polymerization time is less than 4 hours, it is difficult to control the polymerization when trying to obtain high productivity (high polymerization rate). There is a problem in terms of aspect and it is not preferable. In the case of the continuous system, the average residence time in the polymerization vessel is preferably 2 to 10 hours (further, 2 to 8 hours), and if the residence time is less than 2 hours, high productivity (high polymerization rate) will be obtained. Polymerization control becomes difficult,
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 80%. The polymerization rate is 20%
When it is less than 80%, there is a problem in terms of productivity and the presence of a large amount of unpolymerized vinyl acetate. On the contrary, when it exceeds 80%, the molecular weight distribution tends to be broad, which is not preferable.

Thus, the polymerization is completed to produce a vinyl acetate polymer solution. In the present invention, unreacted vinyl acetate monomer and unreacted copolymerizable monomer such as ethylene are appropriately added. The greatest feature is the addition of N, N-dialkylhydroxylamine to such a polymer solution with or without removal. The N,
The method of adding N-dialkylhydroxylamine is not particularly limited, but is usually 0.005 to 10% by weight (further 0.005 to 5% by weight, particularly 0.005% by weight).
Up to 2% by weight) in an alcohol (solvent at the time of polymerization) solution, etc.
001 to 0.05 parts by weight (further 0.0001 to 0.0
2 parts by weight, particularly 0.0001 to 0.01 parts by weight) is preferably added, and the addition amount is 0.1.
If it is less than 0001 parts by weight, it is difficult to obtain the effects of the present invention,
On the contrary, if it exceeds 0.05 parts by weight, it may cause an odor, which is not preferable. When a styrene derivative, a hydroquinone derivative, a quinone derivative or a piperidine derivative is used together with N, N-dialkylhydroxylamine,
Similar to the above, usually 0.005 to 10% by weight (further 0.005 to 5% by weight, particularly 0.005 to 2% by weight)
Alcohol (solvent at the time of polymerization) solution of 0.0001-0.
05 parts by weight (further 0.0001 to 0.02 parts by weight, particularly 0.0001 to 0.01 parts by weight) is added.

Thus, a vinyl acetate-based polymer can be obtained. Specific examples of the vinyl acetate-based polymer include polyvinyl acetate, ethylene-vinyl acetate copolymer, and the like. Used in adhesives, adhesives, paints, textile / textile finishing agents, paper / leather finishing agents, binders for various materials, cement / mortar admixtures, etc., especially polyvinyl alcohol and ethylene-vinyl acetate copolymer It is also useful as a raw material for a compound, and a method for producing the saponified ethylene-vinyl acetate copolymer will be described below.

The ethylene content of the ethylene-vinyl acetate copolymer used as a raw material for the saponified product of the ethylene-vinyl acetate copolymer is 5 to 60 mol% (more preferably 20 to 5%).
5 mol%) is preferable, and when such a content is less than 10 mol%, when the saponified product of the obtained ethylene-vinyl acetate copolymer is melt-molded, the melt moldability is deteriorated, and
The gas-barrier property of the melt-molded product at high humidity is significantly lowered, and conversely, when it exceeds 60 mol%, when the saponified product is melt-molded, the mechanical strength and gas-barrier property of the resulting molded product are not sufficient, which is not preferable. . In the production method of the present invention, the ethylene content may be controlled by the ethylene pressure in the polymerization vessel or the like.

The ethylene-vinyl acetate copolymer obtained by the production method of the present invention is saponified to give a saponified ethylene-vinyl acetate copolymer. In the saponification reaction, a saponification catalyst coexists. Carried out below. 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. Alkali metal hydroxides such as sodium and potassium hydroxide are used) and the saponification reaction is carried out at a temperature of 40 to 140 ° C.

By the saponification, the saponification degree of the vinyl acetate component of the saponified ethylene-vinyl acetate copolymer is 80 to
100 mol% (further 90-100 mol%, especially 95-1
If the degree of saponification is less than 80 mol%, the heat stability of the melt-molded product using the saponified ethylene-vinyl acetate copolymer will be poor and the saponification will be The mechanical strength and gas barrier properties of the compound are greatly reduced, which is not preferable.

Next, the alcohol solution of the saponified product of the ethylene-vinyl acetate copolymer obtained above may be used as it is, but preferably water is added directly, or water is added and then the alcohol solution of the saponified product is added. Is adjusted to an alcohol / water solution to prepare a solution for producing a strand, and then extruded in a strand shape into a coagulation bath of water or a water / alcohol (mixed) solution to deposit the solution.

The deposited strands are then cut into pellets and then washed with water. Such washed pellets are preferably chemically treated by a method such as immersing in an aqueous solution of a chemical such as acid and / or a salt thereof, and such chemicals include formic acid, acetic acid, adipic acid, phosphoric acid and boric acid. Alternatively, salts thereof and the like can be mentioned, and acetic acid is more preferably used.

The pellets obtained as described above are melt-molded to be molded into a desired molded product, and the temperature condition for melt-molding is preferably about 160 to 260 ° C. Upon molding, if necessary, known additives such as a reinforcing material such as glass fiber and carbon fiber, a filler, a coloring agent, a stabilizer such as hydrotalcite, a foaming agent and a desiccant may be appropriately added. Further, the saponified ethylene-vinyl acetate copolymer may be blended with an appropriate amount of a modifying thermoplastic resin.

As the melt molding method, any molding method such as injection molding method, compression molding method and extrusion molding method can be adopted. Among them, examples of the extrusion molding method include a T-die method, a hollow molding method, a pipe extrusion method, a linear extrusion method, a profile die extrusion method, an inflation method, and the like, and a molding of a saponified ethylene-vinyl acetate copolymer alone. Thing (film, sheet, tape,
(Bottles, pipes, filaments, atypical cross-section extrudates, etc.)
Not only is it possible to coextrude the saponified ethylene-vinyl acetate copolymer layer with another thermoplastic resin layer.

To obtain polyvinyl alcohol from polyvinyl acetate, it is sufficient to saponify polyvinyl acetate. Saponification is carried out by dissolving polyvinyl acetate in alcohol and in the presence of an alkali catalyst. Examples of alcohols include methanol, ethanol, butanol and the like.

The concentration of the polymer in alcohol is 20-50.
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 metal hydroxide such as sodium ethylate or potassium methylate, or an alkali catalyst such as alcoholate. It is necessary to use the catalyst in an amount of 1 to 100 millimole equivalent to vinyl acetate.

In such a case, the saponification temperature is not particularly limited, but it is usually selected from the range of 10 to 70 ° C, preferably 30 to 50 ° C. The reaction is usually carried out for 0.5 to 3 hours, and the preferable saponification degree is 10 to 100 mol%.
In particular, it is preferably selected from the range of 50 to 100 mol%, particularly preferably 70 to 100 mol%.

[0032]

EXAMPLES 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 An ethylene-vinyl acetate copolymer was continuously polymerized under the following conditions using a polymerization vessel equipped with a stirrer and having a capacity of 10 liters and having an external cooling jacket. Vinyl acetate supply amount 1300 g / hr Methanol supply amount 200 g / hr Lauroyl peroxide (catalyst) supply amount 480 mg / hr L-ascorbic acid supply amount 65 mg / hr (0.005 parts by weight per 100 parts by weight vinyl acetate) Polymerization temperature 67 ° C. Ethylene pressure 4.5 MPa Average residence time 4 hr

The polymerization solution obtained above was continuously discharged from the polymerization vessel, and at the same time, 0.01% N,
N-diethylhydroxylamine and 4-hydroxyl-
A methanol solution of a mixture with 2,2,6,6-tetramethylpiperidine-1-oxyl (mixing weight ratio 65/35) was added at a rate of 1.95 g / hr (charged vinyl acetate 100
(g ratio of 1.5 mg). After that, unreacted ethylene and vinyl acetate monomers were removed to give an ethylene content of 35 mol% and a vinyl acetate polymerization rate of 38.
% Ethylene-vinyl acetate copolymer was obtained.

Next, alkali saponification was carried out by a conventional method to obtain a methanol solution of a saponified ethylene-vinyl acetate copolymer having an ethylene content of 35 mol% and a saponification degree of 99.5 mol%. Water was added to this solution to prepare a solution of saponified ethylene-vinyl acetate copolymer in methanol / water (mixing ratio: 6/4), which was extruded in a strand shape into a water tank at 5 ° C through a nozzle having a hole diameter of 4 mm. After the strand is sufficiently solidified, it is cut with a cutter to have a diameter of 4 mm and a length of 4
mm pellets were obtained. After washing the pellets with an aqueous solution of acetic acid, the pellets were poured into an aqueous solution of boric acid / acetic acid / sodium acetate,
Pellets containing 0.03 part of boric acid (boron conversion), 0.009 part of acetic acid, and 0.1 part of sodium acetate (conversion of sodium) per 100 parts of saponified ethylene-vinyl acetate copolymer after treatment and drying. Got Ethylene obtained
The saponified vinyl acetate copolymer pellets were evaluated for moldability, colorability and odor in the following manner.

(Moldability) The obtained saponified ethylene-vinyl acetate copolymer pellets were molded into a film having a thickness of 50 μm using a single-screw extruder under the following conditions, and a state of fish eye generation was obtained. Was evaluated as follows.

[0037] [Film forming conditions with a single screw extruder]     Screw inner diameter 40 mm     L / D 28     Screw compression ratio 3.2     Screw rotation speed 60 rpm     T-die coat hanger type     Die width 450mm     Extrusion temperature C1: 190 ° C, H: 210 ° C                       C2: 210 ° C, D: 210 ° C                       C3: 220 ° C,                       C4: 220 ° C

[Observation of Fish Eyes] The film (10 cm × 10 cm) immediately after molding was visually observed for the appearance of fish eyes having a diameter of 0.01 mm or more, and evaluated as follows. ◎ ・ ・ ・ 0-9 pieces ○ ・ ・ ・ 10-39 pieces △ ・ ・ ・ 40-79 pieces × ・ ・ ・ 80 pieces or more

(Colorability) Using an injection molding machine, a plate having a thickness of 3 mm was molded under the following conditions, and the color tone (ΔE value) of the obtained plate was measured.

[Molding conditions of plate by injection molding machine] Injection time 8 seconds Cooling time 15 seconds Cycle time 29 seconds Injection speed 25 mm / sec Injection pressure 1095 kg / cm ² Cylinder temperature 210 ° C Mold temperature 60 ° C

[Measurement of color tone] The obtained plate was evaluated for ΔE value using a color difference meter (“SZ-Σ80” manufactured by Nippon Denshoku Industries Co., Ltd.) and evaluated as follows. ○ ・ ・ ・ 15 or less △ ・ ・ ・ 16 to 20 × ・ ・ ・ 21 or more

(Odor) At the time of molding the above film and 15
The presence or absence of odor was confirmed after standing for 5 hours in an atmosphere of 0 ° C. ○: No odor in any case △: Slight odor in any case ×: Significant odor in any case

Further, the saponified pellets of the obtained ethylene-vinyl acetate copolymer were repelletized using a single screw extruder, and the moldability and the colorability were evaluated in the same manner as above. The re-pellet conditions are as follows.

[Repellet conditions] Screw inner diameter 40 mm L / D 28 Screw rotation speed 60 rpm Processing temperature (MAX) 230 ℃

Example 2 The procedure of Example 1 was repeated except that L-ascorbic acid was replaced by citric acid at a rate of 52 mg / hr to polymerize ethylene and vinyl acetate, and 4-hydroxyl-2,2,6,6.
-Tetramethylpiperidine-1-oxyl was replaced with a cinnamic acid mixture (mixing weight ratio 17/83) in methanol at a rate of 7.8 g / hr (charged vinyl acetate 100 g).
Was continuously added at a rate of 6 mg) to obtain an ethylene-vinyl acetate copolymer having an ethylene content of 35 mol% and a vinyl acetate conversion rate of 38% to obtain an ethylene-vinyl acetate copolymer. The saponified polymer (saponification degree: 99.5 mol%) pellets were obtained and evaluated in the same manner.

Example 3 In Example 1, 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile) was charged in place of lauroyl peroxide at a rate of 200 mg / hr, and ethylene and acetic acid were added. Polymerizes vinyl and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-
Mixture with cinnamic acid instead of oxyl (mixing weight ratio 17 /
83) using a methanol solution of
The same procedure was performed except that an ethylene-vinyl acetate copolymer having a mol% and a vinyl acetate conversion rate of 37% was obtained to obtain saponified ethylene-vinyl acetate copolymer (saponification degree: 99.5 mol%) pellets. , And similarly evaluated.

Example 4 A 10 liter capacity polymerization vessel equipped with a stirrer was charged in the following manner, and polymerization was carried out under the following conditions. Charge amount of vinyl acetate 4000 g Charge amount of polymerization solvent (methanol) 320 g Charge amount of lauroyl peroxide 220 mg Charge amount of L-ascorbic acid 160 mg (0.004 parts by weight per 100 parts by weight of vinyl acetate) Polymerization temperature 60 ° C. Ethylene Pressure 3.9MPa Polymerization time 7hr

After the above polymerization, 0.01% N,
A solution of N-diethylhydroxylamine in methanol was added 1
After adding 0 g (a ratio of 2.5 mg of amine to 100 g of charged vinyl acetate) to obtain an ethylene-vinyl acetate copolymer having an ethylene content of 33 mol% and a vinyl acetate conversion rate of 49%, the procedure of Example 1 was repeated. Saponification was carried out by the same method to obtain saponified ethylene-vinyl acetate copolymer pellets. The obtained saponified product of ethylene-vinyl acetate copolymer (saponification degree: 99.5 mol%) was evaluated in the same manner as in Example 1.

Examples 5 to 7 In Example 4, 10 g of 0.01% cinnamic alcohol methanol solution (Example 5) and N, N-diethylhydroxylamine in methanol solution of hydroquinone monomethyl ether (Example 6) were used. ) 10 g of a methanol solution of p-benzoquinone (Example 7) was used in the same manner as in Example 2 to obtain saponified ethylene-vinyl acetate copolymer pellets (saponification degree: 95.0 mol%). Was evaluated.

Comparative Example 1 The same as in Example 1 except that N, N-diethylhydroxylamine and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl were not added to the polymerization solution. The experiment was conducted to obtain saponified ethylene-vinyl acetate copolymer pellets, and the same evaluation was performed.

Comparative Example 2 In Example 1, 0.03% methanol sorbate was used instead of N, N-diethylhydroxylamine and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl. Except for using the solution, the same procedure was performed to obtain saponified ethylene-vinyl acetate copolymer pellets, and the same evaluation was performed.

Comparative Example 3 In Example 1, substituting N, N-diethylhydroxylamine and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl for 0.06% of 2,
Except for using a methanol solution of 4-diphenyl-4-methyl-1-pentene, the same procedure was performed to obtain saponified ethylene-vinyl acetate copolymer pellets, and the same evaluation was performed. Table 1 shows the evaluation results of the examples and comparative examples.

[Table 1] Moldability Coloring Odor Moldability * Coloring * Example 1 ◎ ◎ ◎ ◎ ◎ ◎ 〃 2 ◎ ◎ ○ ◎ ◎ ◎ 〃 3 ◎ ○ ○ ◎ ◎ 〃 4 ◎ ○ ○ ◎ ○ 〃 5 ◎ ◎ ○ ◎ ◎ 〃 6 ◎ ◎ ○ ◎ ○ 〃 7 ◎ ○ ◎ ◎ ○ Comparative Example 1 × × × × × 〃 2 △ ○ ○ △ △ 〃 3 △ ○ △ △ △ * Evaluation result after re-pelleting

[0054]

According to the production method of the present invention, there are few fish eyes at the time of molding, coloration and odor are suppressed, and further,
It is possible to obtain a vinyl acetate polymer and a saponified product thereof in which fish eyes and coloration during molding are suppressed even during recycling.

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Claims (6)

[Claims] 1. A process for producing a vinyl acetate-based polymer, which comprises adding vinyl acetate alone or vinyl acetate and another unsaturated monomer, and then adding N, N-dialkylhydroxylamine. 2. The vinyl acetate-based heavy polymer according to claim 1, wherein at least one compound selected from a styrene derivative, a hydroquinone derivative, a quinone derivative and a piperidine derivative is used together with N, N-dialkylhydroxylamine. How to make a coalesce. 3. An organic peroxide is used as a polymerization catalyst during polymerization, and a hydroxylactone compound or a hydroxycarboxylic acid is allowed to coexist.
2. The method for producing a vinyl acetate-based polymer as described in 2 above. 4. An azo compound is used as a polymerization catalyst during the polymerization, and a hydroxylactone compound or a hydroxycarboxylic acid is allowed to coexist.
The method for producing a vinyl acetate polymer according to any one of the items. 5. A method for producing a saponified vinyl acetate polymer, characterized by saponifying the vinyl acetate polymer produced in any one of claims 1 to 4. 6. The method for producing a vinyl acetate polymer or a saponified product thereof according to claim 1, wherein the other unsaturated monomer is an olefin monomer.