JPH1177674A - Manufacture of pellet of saponified ethylene-vinyl acetate copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously manufacturing pellets of saponified ethylene-vinyl acetate copolymer having excellent accuracy of size. SOLUTION: In the method for continuously manufacturing pellets of saponified ethylene-vinyl acetate copolymer comprising the steps of continuously extruding solution of saponified ethylene-vinyl acetate copolymer in a strand-like state in solidified solution, and then cutting the strand, a weight ratio (solidified liquid/strand of saponified ethylene-vinyl acetate copolymer) of the solidified liquid to the strand of the saponified ethylene-vinyl acetate copolymer is set to 50 to 10000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a saponified ethylene-vinyl acetate copolymer pellet which is capable of continuously producing saponified ethylene-vinyl acetate copolymer pellets and having excellent size accuracy of the saponified pellet. Related to manufacturing method.

[0002]

2. Description of the Related Art Saponified ethylene-vinyl acetate copolymers are widely used in various applications such as films, sheets, containers and fibers because of their excellent properties such as oxygen barrier properties and mechanical strength. As a method for producing the saponified ethylene-vinyl acetate copolymer pellets, a method of extruding a solution of the saponified ethylene-vinyl acetate copolymer into a coagulating liquid in a strand form, and then cutting the strand to produce pellets is as follows. It is known.

[0003]

However, in the above-mentioned prior art, the weight ratio of the coagulating liquid and the strand of the saponified ethylene-vinyl acetate copolymer is not specified, and the weight ratio is usually reduced by the amount of solvent. 5 to prevent resin loss
It was set as small as less than 0, and it became clear that in that case, there were disadvantages such as breakage of the strand and poor accuracy of the pellet size. Furthermore, when the pellets obtained by the known technique are used for extrusion molding, fluctuations in charging to the extruder, fluctuations in the load of the extruder, etc. occur, making it difficult to carry out a stable molding operation, and therefore, the shape is uniform. There is a need for saponified ethylene-vinyl acetate copolymer pellets.

[0004]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, continuously extruded a solution of a saponified ethylene-vinyl acetate copolymer into a coagulating solution in a strand form. Then, in a method for continuously producing pellets by cutting the strand, the weight ratio of the coagulating liquid and the strand of the saponified ethylene-vinyl acetate copolymer (coagulating liquid / saponified ethylene-vinyl acetate copolymer) is used. It was found that when the (strand) is 50 to 10000, the desired saponified ethylene-vinyl acetate copolymer pellet was obtained, and the present invention was completed.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The ethylene-vinyl acetate copolymer used as a raw material of the saponified ethylene-vinyl acetate copolymer used in the present invention is not particularly limited in ethylene content, but is preferably 15 to 60 mol%, and more preferably 20 to 55 mol%.

[0006] When the ethylene content is less than 15 mol%, precipitation in a strand form in a coagulation solution is incomplete,
A part of the strand is eluted, which is not preferable in terms of operation, and it is not preferable because it is necessary to pressurize or heat to a high temperature in order to keep the ethylene-vinyl acetate copolymer solution in a uniform solution state.

On the other hand, if it exceeds 60 mol%, it is difficult to prepare a homogeneous solution when the saponified ethylene-vinyl acetate copolymer is used, and the desired strand cannot be formed.

The ethylene-vinyl acetate copolymer may contain, as well as ethylene and vinyl acetate, an ethylenically unsaturated monomer copolymerizable therewith as a copolymer component. Examples of the monomer include olefins such as propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; and unsaturated monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid. Acids or salts or mono- or dialkyl esters thereof, acrylonitrile, nitriles such as methacrylonitrile, acrylamide, amides such as methacrylamide, ethylenesulfonic acid, allylsulfonic acid, olefinsulfonic acid such as methallylsulfonic acid or a salt thereof, Alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallylvinylketone, N-vinylpyrrolidone, vinyl chloride,
Polyoxyalkylene (meth) allyl ethers such as vinylidene chloride, polyoxyethylene (meth) allyl ether, and polyoxypropylene (meth) allyl ether;
Polyoxyethylene (meth) acrylate, polyoxyalkylene (meth) acrylate 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, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinyl Amines and the like.

The saponified ethylene-vinyl acetate copolymer used in the present invention is obtained by saponifying the above-described ethylene-vinyl acetate copolymer. The saponification reaction is carried out in the presence of an alkali catalyst. As the alkali catalyst, a conventionally known catalyst used for a saponification reaction of polyvinyl acetate or an ethylene-vinyl acetate copolymer with an alkali catalyst can be used as it is. Specifically, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali metal alcoholates such as sodium methylate and potassium t-butoxy;
8-diazabicyclo [5,4,10] undecene-7
Examples thereof include a cobasic amine represented by (DBU), and further, an alkali metal carbonate, an alkali metal hydrogencarbonate and the like. Of these, use of sodium hydroxide is preferred from the viewpoint of easy handling, catalyst cost and the like.

The amount of the catalyst used depends on the required degree of saponification, the reaction temperature and the like, but is used in an amount of 0.05 equivalent or less, preferably 0.03 equivalent, based on the remaining acetic acid groups in the ethylene-vinyl acetate copolymer. It is as follows. Further, instead of the alkali catalyst, an acid catalyst such as hydrochloric acid and sulfuric acid can be used.

In the saponification, the ethylene-vinyl acetate copolymer is dissolved in an alcohol or an alcohol-containing medium so as to have a concentration of usually about 20 to 60% by weight, and an alkali catalyst or an acid catalyst is added. 40-1
React at a temperature of 40 ° C. The concentration of the saponified product is not particularly limited as long as the saponified product of the ethylene-vinyl acetate copolymer is not precipitated at the solution temperature, but usually the concentration of the saponified product is 10 to 55% by weight, preferably 15% by weight.
What is necessary is just to make it 50% by weight.

The saponification degree of the vinyl acetate component of the saponified ethylene-vinyl acetate copolymer obtained by the saponification is preferably from 70 to 100 mol%, more preferably from 80 to 100 mol%. . When the saponification degree is less than 70 mol%, the thermal stability when melt-molding using the saponified ethylene-vinyl acetate copolymer pellets becomes poor.

Next, the alcohol solution of the saponified ethylene-vinyl acetate copolymer obtained as described above may be used as it is, but preferably, water is added directly, or the saponified solution is appropriately concentrated or diluted before water is added. In addition, a solution for strand production is prepared. At this point the saturated aliphatic amide
(E.g., stearic acid amide), unsaturated fatty acid amide
(E.g., olefin amides), bisfatty acid amides (e.g., ethylene bisstearic acid amide), fatty acid metal salts (e.g., calcium stearate, etc.), and low molecular weight polyolefins (e.g., having a molecular weight of 500 to 10,000).
Low-molecular-weight polyethylene or low-molecular-weight polypropylene, etc.), inorganic salts (eg, hydrotalcite, etc.), plasticizers (eg, aliphatic polyhydric alcohols such as ethylene glycol, glycerin, hexanediol, etc.) and the like. .

The concentration of the saponified product in the solution of the saponified ethylene-vinyl acetate copolymer is preferably 10 to 5
It is 5% by weight, more preferably 20 to 50% by weight. If the amount is less than 10% by weight, coagulation in a coagulating liquid becomes difficult, while if it exceeds 55% by weight, the porosity of the pellets is reduced, which adversely affects the thermal stability during molding. The weight ratio of alcohol and water in the solution of the saponified product is 9/1 to 3/7, preferably 8/2 to 4/6.
It is desirable to adjust so that When the ratio of alcohol to water exceeds 9/1, the solution becomes slightly unstable, and the porosity at the time of strand deposition is slightly reduced. On the other hand, when the ratio is less than 3/7, the solution becomes unstable and the precipitation of saponified substances may be caused. is there.

Next, the solution of the saponified ethylene-vinyl acetate copolymer is extruded into a coagulating solution in the form of a strand to precipitate the solution. Examples of the coagulating solution include water or a mixed solvent of water / alcohol and aromatic solvents such as benzene. Hydrocarbons, ketones such as acetone and methyl ethyl ketone, ethers such as dipropyl ether, organic acid esters such as methyl acetate, ethyl acetate and methyl propionate are used, but water or a mixed solvent of water / alcohol is preferred.

The alcohol concentration when alcohol is used is preferably equal to or lower than the alcohol content of the alcohol / water mixture in the saponified copolymer solution. If the alcohol content is exceeded, strand precipitation in the coagulation solution is caused. The polymer loss at the time increases, which is not preferable. As the alcohol, alcohols such as methanol, ethanol, and propanol are used, and preferably, methanol is used.

In the present invention, when the above-mentioned solution of the saponified ethylene-vinyl acetate copolymer is continuously extruded into a coagulating liquid in a strand form, the coagulating liquid and the ethylene-vinyl acetate copolymer are extruded.
The biggest feature is to adjust the weight ratio to the strand of the saponified vinyl acetate copolymer (coagulating liquid / strand of the saponified ethylene-vinyl acetate copolymer).
The weight ratio needs to be 50 to 10000, preferably 100 to 1000. The weight ratio is 5
If it is less than 0, the curing time of the strand in the coagulation liquid is delayed, and if it exceeds 10,000, resin loss into the coagulation liquid becomes large, which is inappropriate.

The contact time between the coagulation liquid and the saponified ethylene-vinyl acetate copolymer is preferably from 10 seconds to 60 minutes, and more preferably from 15 seconds to 100 seconds. If the contact time is less than 10 seconds, the curing of the strand in the coagulating liquid is insufficient, and if it exceeds 60 minutes, the resin loss into the coagulating liquid tends to increase, which is not preferable.

The temperature at which the solution of the saponified ethylene-vinyl acetate copolymer is brought into contact with the coagulating liquid is from -10 to 40 ° C, preferably from 0 to 20 ° C. Since the above-mentioned organic solvent is a non-solvent for the saponified product, there is almost no fear that the saponified product dissolves in the coagulation liquid to cause resin loss, but operation at a low temperature is safe as much as possible.

The solution of the saponified ethylene-vinyl acetate copolymer is extruded into a coagulating solution in a strand form by a nozzle having an arbitrary shape, usually a circular hole. The shape of the nozzle is not particularly limited, but is preferably a cylindrical shape, and the length at that time is 1 to 100 cm, preferably 3 to 30 cm, and the inner diameter is 0.1 to 10 cm.
Preferably it is 0.2 to 5.0 cm. In particular, it is preferable that the nozzle has a cylindrical shape having a length-to-inner diameter ratio (length / inner diameter) of 8 to 40, and the nozzle has a thickness of 0.01 to 0.5 c.
m, preferably 0.1-0.3 cm.

The cross-sectional shape of the nozzle is preferably circular as described above, but may be elliptical, square, rhombic, star-shaped or the like in some cases.

Thus, the saponified ethylene-vinyl acetate copolymer is extruded from the nozzle in the form of a strand. The number of strands is not necessarily limited to one, and any number of strands ranging from several to several hundreds can be used. Can be extruded.

Next, the saponified ethylene-vinyl acetate copolymer extruded into a strand is cut, pelletized, and usually washed with water after coagulation has sufficiently proceeded.

The washing conditions are as follows:
Wash in a water bath at ６０60 ° C. By washing with water, ethylene
Oligomers and impurities in the saponified vinyl acetate copolymer are removed, and in particular, sodium acetate is removed to 0.5% by weight or less.

The washed pellets are preferably subjected to an acid treatment, for example, acetoacetic acid, formic acid, acetic acid, adipic acid, phosphoric acid, boric acid and the like. More preferably, acetic acid is used. The condition of the acid treatment is, for example, 3% by weight.
Washing is performed in the following acetic acid aqueous solution, and treatment is performed so that the pH of the washing solution becomes 3 to 8. The shape of the strand is not particularly limited, but is preferably 2-5 mm in diameter and 2-5 mm in length in the case of a cylindrical shape in terms of workability and handling during molding.
In the case of a spherical shape, one having a diameter of about 2 to 5 mm is practical.

Thus, according to the method of the present invention, saponified ethylene-vinyl acetate copolymer pellets can be continuously produced, and saponified ethylene-vinyl acetate copolymer excellent in size accuracy of the saponified pellets can be obtained. .

The pellets obtained by the production method of the present invention are melt-molded and molded into a desired molded product. The temperature conditions for the melt molding are about 160 to 260 ° C.
It is desirable that At the time of molding, an appropriate amount of a known additive such as a reinforcing material such as glass fiber or carbon fiber, a filler, a coloring agent, a stabilizer such as hydrotalcite, a foaming agent, or a drying agent may be added as needed. Also, ethylene-
The saponified vinyl acetate copolymer may be blended with a suitable amount of a modifying thermoplastic resin.

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 adopted. Examples of the extrusion molding method include a T-die method, a hollow molding method, a pipe extrusion method, a linear extrusion method, a deformed die extrusion method, an inflation method and the like, and a molding of a saponified ethylene-vinyl acetate copolymer alone. Objects (films, sheets, tapes,
Bottles, pipes, filaments, extruded shaped sections, etc.)
In addition, coextrusion molding of the saponified ethylene-vinyl acetate copolymer layer and another thermoplastic resin layer is also possible.

[0029]

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 To 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content of 35 mol% was added 0.017 equivalent of sodium hydroxide to the acetic acid group in the copolymer. And 150 parts of methanol. Next, 60 parts of an aqueous methanol solution mixed at a ratio of 50 parts of water to 100 parts of methanol was supplied at an azeotropic point. The reaction temperature is 128-140 ° C and the pressure is 5 kg /
cm ² G. The resulting saponified ethylene-vinyl acetate copolymer solution (resin concentration 40%) was a completely transparent homogeneous solution, and the saponification degree of the vinyl acetate component of the saponified ethylene-vinyl acetate copolymer was 99.8 mol. %Met.

Subsequently, the solution of the saponified ethylene-vinyl acetate copolymer was dissolved in methanol 5 at a rate of 10 kg / hour.
83 kg of coagulation liquid maintained at 5 ° C.
In the coagulation liquid tank containing the pore diameter 0.4cm, length 0.3cm,
It was extruded into a strand form from a 6.0 cm thick cylindrical nozzle, brought into contact with the coagulation liquid for 30 seconds by a take-off roller attached to the end of the coagulation liquid tank, and then the strand was drawn out of the coagulation liquid. (Weight ratio of coagulation liquid and saponified ethylene-vinyl acetate copolymer strand was 1000) The strand was cut with a cutter to obtain porous pellets. The obtained pellets were uniform in shape and had no deformation. The porous pellet was washed in a water bath at a temperature of 30 ° C. for 1 hour, and this was repeated four times to remove sodium acetate. After washing in an aqueous solution of acetic acid at a temperature of 30 ° C. for 1 hour, the resultant was dried and dried. Inventive pellet (diameter 3.8m)
m, a white pellet of the present invention having a length of 4 mm). The following items were evaluated in the above manufacturing process.

(1) Evaluation of strand Hardening time The hardness of the strand immediately after being pulled out of the coagulating solution was determined by JI
According to SK6301, the hardness was measured with a spring-type hardness tester (Shimadzu Corporation) and evaluated as follows. ○ ・ ・ ・ 30 or more △ ・ ・ ・ 25 to less than 30 × ・ ・ ・ less than 25

The number of breaks of the strand during the 72-hour operation was measured, and there were 10 series of the strands, and the number of breaks per 10 series was expressed.

Accuracy of pellet size The diameter and length of 100 pellets of the present invention were measured with a vernier caliper, and the ratio of pellets whose diameter and length were within ± 0.2 mm was determined as follows. Was evaluated. ◎ ・ ・ ・ 95% or more ○ ・ ・ ・ 80 to less than 95% △ ・ ・ ・ 60 to less than 80% × ・ ・ ・ less than 60%

Example 2 In Example 1, the amount of the coagulating liquid was adjusted and the weight ratio of the coagulating liquid / saponified ethylene-vinyl acetate copolymer was set to 5000.
A pellet of the present invention was produced and evaluated in the same manner as in Example 1 except for the above.

Example 3 In Example 1, the contact time between the strand and the coagulating liquid was changed to 5 times.
The pellets of the present invention were produced and evaluated in the same manner as in Example 1 except that the weight of the coagulated liquid and the saponified ethylene-vinyl acetate copolymer was 100.

Example 4 In Example 1, the contact time between the strand and the coagulating liquid was set to 2
Example 1 except that the time was 0 second (the weight ratio of the coagulating solution to the saponified ethylene-vinyl acetate copolymer was 1490).
The pellets of the present invention were produced in the same manner as described above, and were similarly evaluated.

Comparative Example 1 In Example 1, the amount of the coagulating liquid was reduced and the weight ratio of the coagulating liquid to the saponified ethylene-vinyl acetate copolymer (coagulating liquid / strand of the saponified ethylene-vinyl acetate copolymer) was used. The pellets of the present invention were produced and evaluated in the same manner as in Example 1, except that 30 was used.

Comparative Example 2 In Example 1, the amount of the coagulating liquid was increased and the weight ratio of the coagulating liquid to the saponified ethylene-vinyl acetate copolymer (coagulating liquid / strand of the saponified ethylene-vinyl acetate copolymer) was used. Was set to 12000, and a pellet of the present invention was produced in the same manner as in Example 1 and evaluated in the same manner. Examples 1-4,
Table 1 shows the evaluation results of Comparative Examples 1 and 2.

[0040]

[Table 1] Curing time Strand Cut of pellets (times) Size accuracy Example 1 ○ 0 ◎ Example 2 ○ 0 ◎ Example 3 ○ 0 ○ Example 4 ○ 0 ◎ Comparative Example 1 × 8 × Comparative Example 2 ○ 0 x

[0041]

According to the present invention, there is provided a method of continuously extruding a solution of a saponified ethylene-vinyl acetate copolymer into a coagulating liquid in the form of a strand and then cutting the strand to continuously produce pellets. By setting the weight ratio of the coagulating liquid to the saponified ethylene-vinyl acetate copolymer strand (coagulating liquid / strand of the saponified ethylene-vinyl acetate copolymer) to 50 to 10000, the accuracy of the size is continuously increased. Excellent saponified ethylene-vinyl acetate copolymer pellets can be produced.

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[Procedure amendment]

[Submission date] April 24, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

The saponified ethylene-vinyl acetate copolymer used in the present invention is obtained by saponifying the above-described ethylene-vinyl acetate copolymer. The saponification reaction is carried out in the presence of an alkali catalyst. As the alkali catalyst, a conventionally known catalyst used for a saponification reaction of polyvinyl acetate or an ethylene-vinyl acetate copolymer with an alkali catalyst can be used as it is. Specifically, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali metal alcoholates such as sodium methylate and potassium t-butoxy;
8-diazabicyclo [5,4,10] undecene-7
Strongly basic amines represented by (DBU), more alkali metal carbonates, the like alkali metal bicarbonate salts, ease of handling, the use of sodium hydroxide from the catalyst cost and the like are preferable.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

Example 1 To 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content of 35 mol% was added 0.017 equivalent of sodium hydroxide to the acetic acid group in the copolymer. The methanol solution containing the solution and 150 parts of methanol were supplied and saponified . Next, 100 parts of methanol and 5 parts of water
60 parts of an aqueous methanol solution mixed at a ratio of 0 parts was supplied at an azeotropic point. The reaction temperature was 128 to 140 ° C., and the pressure was 5 kg / cm ² G. The resulting saponified ethylene-vinyl acetate copolymer solution (resin concentration 40%) was a completely transparent homogeneous solution, and the saponification degree of the vinyl acetate component of the saponified ethylene-vinyl acetate copolymer was 99.8 mol. %Met.

Claims (5)

[Claims] 1. A solution of a saponified ethylene-vinyl acetate copolymer is continuously extruded into a coagulating solution in a strand form,
Next, in a method of continuously producing pellets by cutting the strand, the weight ratio of the coagulating liquid and the strand of the saponified ethylene-vinyl acetate copolymer (coagulating liquid / strand of the saponified ethylene-vinyl acetate copolymer) is used. 50 to
A method for producing saponified ethylene-vinyl acetate copolymer pellets, wherein the pellet is 10,000. 2. A method for producing saponified ethylene-vinyl acetate copolymer pellets, wherein the weight ratio of the coagulating liquid to the strand of saponified ethylene-vinyl acetate copolymer is 100 to 1,000. 3. The method for producing saponified ethylene-vinyl acetate copolymer pellets according to claim 1, wherein the coagulating liquid is water or a water / methanol mixed solution. 4. The ethylene-vinyl acetate copolymer according to claim 1, wherein the contact time between the coagulation liquid and the strand of the saponified ethylene-vinyl acetate copolymer is 10 seconds to 60 minutes. Method for producing saponified polymer pellets. 5. The method for producing saponified ethylene-vinyl acetate copolymer pellets according to claim 1, wherein the solution is methanol or a mixed solution of methanol and water.