JPS6034564B2 - Method for saponifying ethylene-vinyl acetate copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for saponifying ethylene-vinyl acetate copolymer, and its purpose is to produce an economical particulate ethylene-vinyl acetate copolymer that does not require special operations such as reprecipitation after the saponification reaction. An object of the present invention is to provide a method for producing a saponified polymer.

Generally, the saponification reaction of ethylene-vinyl acetate copolymer is
Dissolve the copolymer in a good solvent for polymers such as xylene,
This is carried out by adding alcohol and an alkaline catalyst such as alkali hydroxide to the solution.

However, in such a method, in order to obtain a product, it is necessary to add a large amount of a non-solvent such as methanol to reprecipitate the saponified product after the saponification reaction is completed, and the good solvent, non-solvent, and reaction This cannot be said to be an economical method because it requires a complicated process of separating and recovering the acetate produced as a by-product. In addition, as a method for saponifying ethylene-vinyl acetate copolymer that does not require the operation of adding undissolved soot to reprecipitate the saponified product after the saponification reaction is completed, there is a method of saponifying the ethylene-vinyl acetate copolymer using an alkali or acid catalyst in alcohol soot. (British Patent No. 1095204, Tokkoku Sho 51-686
No. 93) A method of obtaining a powdered product by saponifying a saturated hydrocarbon-methanol-alkali hydroxide system with a boiling point of 30°C to 120°C above the melting point of the copolymer and then cooling it (Japanese Patent Publication No. 45-33065) A method of obtaining a powdery saponified product by saponifying a copolymer dispersed in water at a high temperature and pressure of 22,000 ml using an alkali catalyst, and then depressurizing the reaction product by injecting it through a valve etc. (East German Patent No. 88404) ) etc. are known.

In the first method, that is, saponification in an alcohol medium, it is generally difficult to control the degree of saponification, and when saponifying at a temperature above the softening point of the copolymer, it takes a long time to cool the reaction mixture, about 2 hours after the reaction. Otherwise, a good saponified powder cannot be obtained, and when the saponification reaction is carried out at a temperature below the melting point of the copolymer, the reaction rate is slow and it takes 6 to 6 hours to obtain a saponified product with a lazy saponification degree. This method required a reaction time of several days, and in order to shorten the reaction time a step was required to make the ethylene-vinyl acetate copolymer into a fine powder, which could not be said to be an economical method. In addition, the method of saponification using a saturated hydrocarbon-alcohol-alkali hydroxide IJ system has the advantage of easily obtaining a powdery saponified product, but in order to precipitate the saponified product in a powdery state, ethylene -A large amount of solvent is used for the vinyl acetate copolymer, and a large amount of heat is required for its recovery and purification.

Furthermore, in the method of saponifying a copolymer dispersed in high-temperature, high-pressure water with an alkali, a considerable proportion of the saponified material is blown out from the reactor when the saponified material is pulverized by depressurizing the water through a valve, etc. It has the serious disadvantage that it remains in the reactor in the form of a lump, and this lump must be separately removed and powdered by some method.

The present inventors have taken note of the above problems and have developed a new ethylene-
As a result of intensive research on the saponification method of vinyl acetate copolymer, we found that if the saponification is carried out in a mixture of alcohol with a certain carbon number range and water at a certain ratio, the reaction rate is high, and the ethylene-vinyl acetate copolymer is saponified. At temperatures above their melting point, the coalescence and its saponified products are dispersed in the liquid as fine particles due to agglomeration (because they do not dissolve in the mixed liquid but swell with the mixed liquid), and this dispersion is dropped into the liquid by flies. The inventors have discovered that when a copolymer and its saponified material are cooled to a temperature below the softening point, the saponified material solidifies into particles that are easy to handle without agglomerating into large lumps, leading to the present invention.

That is, the present invention is a method for saponifying an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 5% by weight using an alkali hydroxide as a catalyst, and in which the saponification reaction is carried out in a method in which the saponification reaction is carried out using a carbon acetate of 2 to 5% by weight.
The main components are alcohol and water, and the mixing ratio of water to alcohol is 10 parts by volume of alcohol to 50 parts by volume of water.
The present invention relates to a method characterized in that the process is carried out in a mixed solution in the range of 100 parts by volume at a temperature equal to or higher than the melting point of the ethylene-vinyl acetate copolymer. The alcohol used as a component of the mixed solution for saponification in the present invention has 2 to 4 carbon atoms, and specifically includes ethanol, n-propanol, and isof.

Ro/gunol, n-butanol, sec-butanol,
The most preferred alcohol among these is isopropanol. Alcohols with carbon numbers of 2 or less, that is, methanol, have a small swelling ability for polymers, so the ethylene-vinyl acetate copolymer or its saponified product does not disperse in the liquid, and alcohols with carbon numbers of 5 or more do not dissolve the copolymer or its saponified products. The saponified product dissolves in the alcohol, increasing the liquid viscosity, and furthermore, the compatibility between alcohol and water decreases, so the copolymer saponified product is dispersed in the liquid, resulting in a granular saponified powder. Undesirable and undesirable. In the present invention, the ratio of the raw material ethylene-vinyl acetate copolymer to the mixed liquid in which it is dispersed is such that if the ratio of the mixed liquid to the copolymer is small, the dispersion of the copolymer and the saponified product, which is the reaction product, is difficult. The saponified product tends to clump together when cooled after the completion of the reaction, making it difficult to obtain a particulate saponified product. Also, if the ratio of the mixed liquid is too large, it is uneconomical. Therefore, in the present invention, the copolymer is 1
100 to 100 parts by weight of water-alcohol mixture
0 parts by weight, preferably 150 to 40 parts by weight are employed.

In the present invention, the mixing ratio of alcohol and water in the water-alcohol mixture is 2000% by volume, alcohol 1
It is necessary that the volume of water be in the range of 50 to 100 parts by volume per 00 parts by volume of water. If the amount of water is less than 50 parts by volume per 10 parts by volume of alcohol, the dispersion of the ethylene-vinyl acetate copolymer and its saponified product in the liquid will be poor, and not only will particulate saponified products not be obtained, but side reactions will occur. Therefore, the hue of the saponified product produced becomes poor, and if water exceeds 100 parts by volume, the saponification reaction rate is slow, and the dispersion of the ethylene-vinyl acetate copolymer and its saponified product in the liquid becomes poor.
The desired particulate saponified product cannot be obtained, and both are unfavorable.

In the present invention, it is particularly preferable to use 80 to 40 parts by volume of water per 100 parts by volume of alcohol.

The amount of alkali hydroxide used as a catalyst for the saponification reaction is 1.5 stoichiometric amount necessary to saponify the acetyl groups of the ethylene-vinyl acetate copolymer to the desired degree of saponification.
The amount is preferably 0 to 1.2 times.

, Furthermore, when saponifying the ethylene-vinyl acetate copolymer in the above-mentioned mixed solution, the saponification reaction needs to be carried out in the liquid phase at a temperature higher than the melting point of the copolymer.
It is preferable to conduct the reaction at a temperature of 00 to 250°C, preferably 110 to 250°C, and more preferably 130 to 220qo. If the saponification reaction is carried out at a temperature below the melting point, the saponification reaction rate will be slow, saponification will take more than one field hour, and side reactions will occur and the hue of the saponified product will deteriorate.

Further, at a temperature of 25,000 or higher, the ethylene-pinyl acetate copolymer and its saponified product begin to decompose, so the reaction at a temperature higher than this is not preferred. The reaction pressure may be any pressure that maintains the reaction system in a liquid phase, that is, a pressure higher than the vapor pressure of the dispersed liquid mixture at the saponification temperature, and the saponification reaction is usually carried out under the vapor pressure of the mixed liquid. The reaction time varies depending on the reaction temperature, but is usually 20 minutes to 2 hours.

Furthermore, it is necessary to drain the reaction solution during the saponification reaction, and the speed at the tip of the saponification blade is preferably 100 m/min or more. After the saponification reaction is completed, the reaction solution containing the particulate saponified material is cooled to below the softening point of the saponified material, preferably below 7000, while the reaction solution containing the particulate saponified material is cooled to a temperature below the softening point of the saponified material, preferably below 7000 skin/min. It solidifies in the state of
Thereafter, the reaction solution is separated from the saponified material by filtration or centrifugation to obtain a saponified product. This particulate saponified material further contains 6
It is desirable to wash the product with water or a mixed solution of water and alcohol of 0.030 or less to remove coloring and alkali metal acetate, which is a side reaction product, and then separate and dry the product.

The obtained saponified product has excellent mechanical properties such as tensile strength, chemical properties such as oil resistance, transparency, and color. The method of the present invention has several advantages over conventional saponification reactions using liquids consisting only of water or only alcohol.

In other words, when saponifying in a liquid consisting only of water, the ethylene-vinyl acetate copolymer or its saponified product does not swell with the liquid during the reaction, and the molten polymer does not swell due to the liquid surface tension being higher than the surface tension of the polymer. Not only do they tend to aggregate easily, but the viscosity of the reaction liquid system is high, making it difficult to pour water into the altar, and the reaction rate is also slow. In addition, when the polymer is made into a manan in a solution consisting only of alcohol, the polymer easily dissolves in the alcohol, and the liquid clay rises, making it difficult to coat, and furthermore, the product is significantly colored. On the other hand, as in the present invention, water. When saponification is carried out in an alcohol-based solution, the polymer does not dissolve in the reaction solution but swells during the reaction, and the surface tension of the solution is lower than that of the polymer due to the action of the alcohol, so it is difficult to react. The polymer is easily dispersed in the liquid in the form of droplets, and since the liquid viscosity is low, it is easy to form pseudo-azusa, and the reaction rate is high.

Furthermore, if the reaction is carried out in a water-only system, the polymer will coagulate and solidify as a lump when it is cooled after the reaction, and in an alcohol-only system, alcohols with carbon numbers of 2 or less will cause the same phenomenon as with water. In contrast, in the case of alcohols with 3 or more carbon atoms, the swelling of the polymer undergoes significant solid-liquid separation even after cooling, resulting in a single saponified product.In contrast, in the present invention, the polymer solidifies in a state close to a dispersed state, resulting in particulate saponified matter. A compound is obtained.

The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples. Examples 1 to 4 Ethylene-acetic acid copolymer pellets (Mitsui Polychemical Co., Ltd. (trade name: Evaflex), isopropanol, water, and sodium hydroxide.

Heat the autoclave in an oil bath at a rotation speed of 800 RPM (Takaazusa blade tip speed 137.6 m/min) while heating the autoclave to 150 qo in about 30 minutes.
The mixture was kept for 1 minute to 1 hour for reaction. Thereafter, the autoclave was taken out from the oil bath, water was poured onto the outside of the autoclave under the fly at a rotational speed of 1000 RPM (Takaazusa blade tip speed 172/min), and the autoclave was cooled to 50 oo over about 20 minutes.

When I took out the contents of the autoclave, it was 0.1 ~
5. Saponified particles of skin were dispersed in the liquid. After solid-liquid separation by filtration, the saponified product was washed for 30 minutes with 50 oo warm water of about three times the amount of the saponified product, and after solid-liquid separation again, it was dried to obtain white saponified particles. The results are shown in Table 1. table ·
*1 Amount of acetic acid scraped 27.7% by weight Melt index 369 *4, ×5×2 Amount of acetic acid scraped
28.0% by weight Melt index 149
All at 20℃ *3 Acetic acid pyrolysis amount 34
．． 0 weight* Melt index 33 Capacity comparison examples 1 to 3 In the autoclave used in Examples 1 to 4, ethylene-vinyl acetate copolymer (vinyl acetate amount 28.1%, meltin Dex 421) Isopropanol, water, and sodium hydroxide were charged.

The autoclave was heated in an oil bath at a rotational speed of 80 PM while heating to 150 qo to 180°C in about 30 minutes, and then kept at this temperature for 0.5 to 1 hour for reaction. After that, remove the autoclave from the oil bath and
Water was poured onto the outside of the fly-dropping autoclave at a rotational speed of 0 RPM [concentrated floating blade tip speed of 172/min], and the water was sprayed approximately every 2 vessels.
It was cooled to 0o0. When the contents were removed from the autoclave, the reaction product formed large clumps and no dispersed particle shape was obtained. The results are shown in Table 2.
Table 2 *1, *2 Capacity Examples 5 to 8 Both at 20°C. Ethylene-vinyl acetate copolymer (Evaflex-210,
Vinyl acetate content 28.1% by weight, melt index 4
21) for 50 minutes, isopropanol for 50 minutes, water for 100 minutes.
and sodium hydroxide were added according to the target degree of saponification as shown in Table 3.

The autoclave was placed in an electric furnace and heated at a temperature of about 2 powders from 110 qo to 220 qo while stirring at a rotation speed of 1500 RPM (floating blade tip speed 225/min).
Thereafter, the autoclave was taken out of the electric furnace and cooled down to room temperature under a fly pestle for about 10 minutes while being cooled with water. When the autoclave was opened, a coarsely particulate reacted polymer with a particle size of 100 French or more was obtained. When the degree of saponification of the polymer was measured after drying, it was found that the degree of saponification corresponded to the amount of sodium hydroxide added. The results are shown in Table 3. Table 3 Examples 9 to 11 Examples except that the alcohol shown in Table 6 was used instead of isopropanol as the alcohol in Example 5, and the type of ethylene-wart vinyl copolymer and the amount of sodium hydroxide were changed. Table 5 shows the results obtained in the same manner as in Example 5.

Table 5 *1 Trade name, Evaflex-220 manufactured by Mitsui Polychemicals Vinyl acetate Content 28.2% by weight Melt index 149 Comparative example 4 Ethylene-acetic acid was added to the autoclave used in Examples 1 to 4 in the proportions shown in Table 4. vinyl copolymer pellet, water,
Sodium hydroxide and a surfactant (sodium laurylbenzenesulfonate) were charged.

The autoclave was heated to 220 oo in an oil bath, and the reaction was carried out at this temperature for 2 hours at a rotational speed of 1200 RPM (sea bream tip speed 2064/min). After the reaction is complete, use the needle valve (caliber 3 sail) attached to the autoclave at the reaction temperature and pressure (approximately 22 k9/g).
was opened and the autoclave contents were squirted out into a container of cold water. The reacted polymer was present in powder form in the ejected material. When the autoclave was opened after the ejection was completed, about half of the reacted polymer remained in the autoclave without being ejected. The results are shown in Table 4. Comparative Example 5 After carrying out the saponification reaction in the same manner as in Comparative Example 4, except that the reaction time was changed to 3 minutes, the autoclave was heated to room temperature while rotating at a rotation speed of 1000 RPM (the speed of the blade tip was 172 m/min). Cooled.

When the autoclave was opened, the reacted polymer was present as one large lump within the autoclave and was not granulated. The results are shown in Table 4. Table 4 *1 Pinyl acetate content 28.1% by weight Melt index 421 Comparative example 6 Saponification reaction was carried out using the same equipment and operation as in Example 9, except that isoamyl alcohol was used as the alcohol in the charging liquid composition in Example 9. I did it.

After the reaction was completed, the autoclave was opened after cooling under condensation, and the reaction product was found to be present in large lumps and not dispersed in the liquid. The results are shown in Table 6. Table 6 *1 Vinyl acetate content 28.2% by weight Melt index 149 Comparative examples 7 to 10 In the autoclave used in Examples 1 to 4, ethylene-vinyl acetate copolymer (Ebaflex-210, vinyl acetate content 28 .1% by weight, melt index 42
1) 500 yen, alcohol of the type shown in Table 6 1200 yen
of sodium methylate, heated in an oil bath, and heated at a reaction temperature of 15,000 °C for 10 minutes.
The reaction was carried out at a rotational speed of 000 RPM (rope pestle blade tip speed 172 m/min).

After the reaction was completed, the autoclave was cooled to room temperature for 20 minutes at a speed of 1000 RPM, and when the autoclave was opened, the reaction polymer, which was colored yellow or brown, swelled with the liquid and became a large lump. It was present and did not become particulate. The results are shown in Table 7. Table 7

Claims (1)

[Claims] 1 In a method of saponifying an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 50% by weight using an alkali hydroxide as a catalyst, the saponification reaction is carried out using an alcohol having 2 to 4 carbon atoms and water as main components, and The mixing ratio of water is 50 to 1000 parts by volume of alcohol to 100 parts by volume of alcohol.
The ethylene-
A method characterized in that it is carried out at a temperature equal to or higher than the melting point of the vinyl acetate copolymer.