JPS58122903A - Production of ethylene/vinyl acetate copolymer saponificate - Google Patents

Abstract

PURPOSE:To avoid blockage of a multi-stage tower and thereby produce a saponificate in good efficiency, by employing a specified mixed solvent in carrying out the continuous saponification of an ethylene/vinyl acetate copolymer (EVA) by use of a multi-stage tower. CONSTITUTION:Use is made of a solvent prepared by mixing a polyalcohol (e.g., ethylene glycol) with a lower aliphatic alcohol (e.g., methanol) in a weight ratio of 1/99-65/35. Namely, a solution of EVA (ethylene content 15-60mol%) is the above mixed solvent and an alkali catalyst (e.g., sodium hydroxide) are introduced from the overhead into a multi-stage tower (including a packed tower as well as a plate column) and, on the other hand, vapor of a lower aliphatic alcohol is blown into the tower from the bottom to thereby saponify the EVA. The acetate ester formed, together with the low aliphatic alcohol, is distilled off from the overhead, and the solution of EVA saponificate is withdrawn from the bottom.

Description

[Detailed description of the invention] Misfire F! J4 relates to a method of continuously saponifying ethylene-vinyl acetate copolymer using a multi-stage column.

Using a multi-stage column, a methanol solution of ethylene-vinyl acetate copolymer and an alkali catalyst are supplied from the top of the column, while methanol vapor is blown into the bottom of the column to form a homogeneous liquid phase in the column to produce ethylene. - Methods for saponifying vinyl acetate copolymers are disclosed in Japanese Patent Publication No. 45-149588, Japanese Patent Publication No. 45-40547Ji+, Japanese Patent Publication No. 47-48558.
It is known from the publication no. However, in these methods, the degree of saponification of the ethylene-vinyl acetate copolymer is set to 9.
If you try to increase it to 9 mol% or more, saponified products tend to precipitate and block the perforated plate in the middle of the column. If less than 55 mol% is used, there is a tendency for column blockage to occur before the degree of saponification increases. Such troubles can be resolved by increasing the temperature inside the tower (for example, 96 to 155 degrees Celsius) and the pressure inside the tower (for example, 1 to 9.5 atmospheres), but the operation at the start and stop of operation is difficult. In addition, high temperatures adversely affect the quality of the obtained polymer, and high pressures are undesirable from the standpoint of safety and equipment cost.

The present invention uses a specific mixed solvent as the solvent for the ethylene-vinyl acetate copolymer solution supplied to the multistage column, that is, the weight ratio of polyhydric alcohol/lower aliphatic alcohol is 1/99 to 65.
By using a mixed solvent of No. 155, the above problems are completely solved.

That is, +1 in the present invention] The target ethylene-vinyl acetate copolymer has an ethylene content in a wide range of 15 to 60 mol%, but it is particularly prone to precipitate during the saponification reaction (ethylene content, which was considered difficult to implement). The content is 15-56 mol%, especially 1
A smooth saponification reaction can be carried out on 5 to 25 mol% of ethylene-vinyl acetate copolymer.

(2) Highly saponified products with a degree of saponification of 99 mol% or more are easily seen.

(3) As the reaction conditions, mild conditions such as a relatively low temperature inside the column of 75° C. or less and a substantially normal pressure can be adopted.

(4) Even under the above-mentioned reaction conditions, a homogeneous solution state can be maintained throughout the entire process of the saponification reaction, so the reaction operation is easy.

(5) As a result, a high quality saponified product with less thermal history can be obtained.

This can have a profound effect.

In the present invention, the raw material polymer has an ethylene content of 1
5 to 60 mol% of ethylene-vinyl acetate copolymer is used. If the ethylene content is outside this range, the oxygen barrier properties of the saponified product may be poor, and therefore they are not the object of the present invention. Among the above reassembly, the ethylene content is 15~
It was conventionally thought that 55 mol%, especially 15 to 26 mol%, could not be saponified in a multi-stage column at normal pressure.
In the present invention, even materials having an ethylene content of 15 to 55 mol% can be saponified to a high saponification degree of 99 mol% or more under normal pressure.

The above ethylene-vinyl acetate copolymer is a polyhydric alcohol/
Trout in the form of a mixed solvent solution of lower aliphatic alcohols is fed to the top of the multi-stage column.

Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,5-butanediol, glycerin, and trimethylene glycol. , tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, etc. Among these, ethylene glycol is most suitable.

Examples of lower aliphatic alcohols include methanol, ffl/
-ol, globanol, butanol, etc.
Methanol is particularly preferred from an industrial standpoint.

The ratio of polyhydric alcohol to lower aliphatic alcohol is 1/99 to 65155 by weight, preferably 2/98 to 5015.
If the ratio of polyhydric alcohol is too small, saponified particles may precipitate during the saponification reaction and cause blockage of the column, while if the ratio of polyhydric alcohol is too large, the saponification rate will be reduced. If it is slow, it will be disadvantageous in terms of industry. In relation to the ethylene content of the ethylene-vinyl acetate copolymer, it is desirable to increase the proportion of polyhydric alcohol within the above range as the ethylene content is smaller. For example, for a copolymer containing 124 to 65 mol% of ethylene, #i22/
A range of 78 to 65155 is desirable.

Along with the solution of the ethylene-vinyl acetate copolymer in the above mixed solvent, an alkali catalyst is also supplied from the upper part of the column.

It is desirable that both be mixed in advance before being supplied to the tower.

As the alkali catalyst, alkali hydroxides such as sodium hydroxide and potassium hydroxide, alcolades of alkali metals, and the like are used.

Note that multi-stage towers include ordinary plate towers such as perforated plate towers and bubble bell towers, as well as packed towers.

Next, lower aliphatic alcohol vapor is blown into the column from the lower part or the bottom of the column. As the lower aliphatic alcohol, those mentioned above are used, and methanol is particularly important.

A homogeneous liquid phase is formed within the tower, and the saponification reaction of the ethylene-vinyl acetate copolymer proceeds. The acetic acid ester produced by the pycnification is elevated together with the lower aliphatic alkyl, and is usually distilled off continuously from the top of the column. It is continuously taken out from the bottom of the column in the form of a mixed solvent solution.

The degree of saponification can be determined arbitrarily, but it exceeds 99 mol% and 10
A feature of the present invention is that saponified products do not precipitate in the column even when the content is increased to nearly 0 mol %.

In order to precipitate the saponified product from the resulting saponified solution, it is sufficient to add a non-solvent for the saponified product to this solution, such as an acetate/class aliphatic compound distilled from the n+1 column. It is industrially advantageous to use a distillate consisting of alcohol.

Of course, other non-solvents such as acetic acid esters, ketones, etc. may also be used.

Although some polyhydric alcohol remains in the precipitated saponified product, this residual polyhydric alcohol can be easily removed by washing the saponified product with water or a solvent. However, when the saponified product is subjected to melt molding, the moldability will be better if it contains some polyhydric alcohol, so in such a case, an appropriate amount of the polyhydric alcohol may remain in the saponified product.

Regarding the temperature and pressure conditions in the column during the saponification reaction, a discharge temperature of less than 75° C. and normal pressure are sufficient, and the temperature and pressure cannot be increased beyond these.

Next, the method of the present invention will be further explained with reference to Examples. Hereinafter, "%" means % by weight unless otherwise specified.

Example 1 50% methanol g solution of ethylene-vinyl acetate copolymer containing ethylene @ 26.7 mol% 150%, 7% ethylene glycol, 42%. ”, 9 and 79 of sodium hydroxide
After mixing 6 methanol solution + s and 4 Ky with a mixer,
Charged at a rate of 205.7 Kg/hr to the top of a plate column with 56 plates, while l 5 D Kg/hr was charged from the bottom of the column.
Methanol vapor was charged at a rate below the boiling point. The temperature inside the column is 68℃ at the bottom and 58℃ at the top, and the bottom is IO50mH20.
Met. 192Kg from the bottom of the tower 65 minutes after the start of preparation
The reaction liquid was taken out at a rate of 1/by, and a distillate with a weight ratio of methyl acetate/methanol of 24/76 was taken out from the top of the column.
It was distilled at a rate of 65.4 Kl//hr.

The reaction solution obtained from the bottom of the tower was a completely transparent homogeneous solution, with a composition of 22.0% saponified ethylene-vinyl acetate copolymer;
Methyl acetate 0.9%, ethylene glycol 22.0%,
The degree of pycnicity of the vinyl acetate unit of the ethylene-vinyl acetate copolymer pycnic acid was 99.
It was 4 mol%.

This reaction solution was continuously fed into a mixed solvent of 5 times its weight of methyl acetate/methanol with a weight ratio of 515 to precipitate saponified particles, which were then crushed and centrifuged to remove volatile matter of 55%. %, and then dried at a temperature of 80° C. for 2 hours to obtain a saponified product in the form of translucent chips containing 4.5% ethylene glycol.

By feeding this saponified product as it is to a commonly used molding machine such as an injection molding machine or an extrusion molding machine without any special post-treatment, it was possible to obtain a molded product with no coloration at a cylinder temperature of 210°C. .

When the wet particles after solid-liquid content Ni were poured into water at 25°C, washed once at a bath ratio of 20, and then dried, saponified particles containing no ethylene glycol were obtained.

Comparative Example When a poppy conversion reaction was carried out under the same conditions as described in Example 1 except for ethylene glycol, the bottom of the column rose rapidly 15 minutes after the start of charging, making it impossible to continue charging. It became. When the bath was dismantled and examined after the charging was stopped, it was found that the perforated plate in the middle of the tower was clogged with precipitated particles. The degree of pycnicity of the precipitated particles was 98.1 mol%.

Example 2 In addition to using glycerin instead of ethylene glycol
i Saponification was carried out in the same manner as in Example 1.

The pycnification proceeded smoothly, and a reaction solution having a composition of 22% ethylene-vinyl acetate copolymer pycnide, 0.4% methyl acetate, 22% glycerin, and 55.6% methanol was taken out from the bottom of the column. The degree of saponification of vinyl acetate units in the saponified ethylene-vinyl acetate copolymer was 99.5 mol%.

Example Filter Ethylene Content Filter After mixing 2.4 mol% 50% methanol solution of ethylene-vinyl acetate copolymer 1150, 26 kg of ethylene glycol, and 7% methanol solution of sodium hydroxide + 7.2 kg, a tray column was added. I 95 at the top of
．． Charged at a rate of 2 Kg/hr, while 180 kg was charged from the bottom of the column.
Methanol vapor was charged at a rate of Kg/hr under heating to boiling point. In steady state, the temperature inside the column is 66℃ at the bottom and 58℃ at the top.
A reaction solution was taken at a rate of 7 Ky/hr, and a distillate with a weight ratio of methyl acetate/methanol of 27/75 was distilled from the top of the column at a rate of 56.2 Kg/br. did.

The reaction liquid obtained from the bottom of the tower was a completely transparent homogeneous solution, and its composition was 20% saponified ethylene-vinyl acetate copolymer, 0.08% methyl acetate, 12.0% ethylene glycol, and 68.0% methanol. , and the degree of saponification of the vinyl acetate unit of the saponified ethylene-vinyl acetate copolymer is 99.7.
It was mol%.

Claims (1)

[Claims] 1. Ethylene content in the upper part of the multistage column is 15 to 60 mol%
An ethylene-vinyl acetate copolymer acid solution and an alkali catalyst are supplied, vapor of lower aliphatic alcohol is blown into the lower part of the column or the bottom of the column, and acetic acid ester produced by a saponification reaction is added to the column from the top of the column together with the lower aliphatic alcohol. In this method, a solution of the saponified ethylene-vinyl acetate copolymer is taken out from the bottom of the column by distilling the ethylene-vinyl acetate copolymer to form a homogeneous liquid phase in the column to proceed with the saponification reaction of the ethylene-vinyl acetate copolymer. As a solvent for the supplied ethylene-vinyl acetate copolymer, the weight ratio of polyhydric alcohol/lower aliphatic alcohol is 179.
A method for producing a saponified ethylene-vinyl acetate copolymer, characterized in that a mixed solvent of 9 to 65155 is used. 2. The method according to claim 1, wherein the ethylene-vinyl acetate copolymer has an ethylene content of 15 to 35 mol%.