JPS6211003B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is an ethylene-vinyl acetate copolymer (hereinafter referred to as
This method relates to a method for saponifying EVA (abbreviated as EVA) in granular or powder form. In general, saponified EVA has superior thermal stability, mechanical properties, solvent resistance, gas barrier properties, etc. compared to EVA, and can be used as a powder, film, or molded product as a fiber adhesive, powder coating, or adhesive. film,
It is a useful resin used for composite films, etc. Conventionally, the saponification method of EVA is usually carried out by dissolving EVA in a good solvent for EVA such as toluene or xylene, and adding an alkali catalyst such as sodium hydroxide, potassium hydroxide, or sodium methylate in a solution state. This is a so-called homogeneous saponification method. According to this method, it is not only necessary to add a large amount of non-solvent such as methanol or ethanol to precipitate the saponified EVA after the reaction, but also
Isolation and recovery become very complicated, and this is not a preferred method from an economic point of view. On the other hand, a method of saponification using an alkaline catalyst in a non-solvent such as methanol or ethanol is also known. This is the so-called heterogeneous saponification method,
Generally, the saponification reaction of EVA occurs from the solid surface of the copolymer, so if only a low-boiling alcohol is used, saponification will occur to different degrees on the solid surface and inside, making uniform saponification difficult. The saponification reaction necessarily takes a long time and is not an industrially preferred method. This drawback is particularly noticeable when trying to obtain a highly saponified pellet-like EVA product. In order to improve this drawback, attempts have been made to add n-butanol or t-butanol to low-boiling alcohols such as methanol or ethanol, to swell EVA and shorten the reaction time while maintaining the original shape of EVA. ing. (Japanese Patent Publication No. 44-27902) However, according to this method, if n-butanol or t-butanol is used in an amount of 5wt% or more based on EVA, fusion will occur between particles, and more than 90% of EVA can be saponified. Can not. In order to obtain a saponification rate of 90% or more, higher alcohols must be used, but in this case, fusion between particles occurs, which is inconvenient. On the other hand, Japanese Patent Publication No. 49-6551 uses a mixture of methanol and n-propanol or i-propanol alone or as a mixture.
We have proposed a method to easily saponify EVA to a saponification rate of 90% or higher, but this method must be carried out using an autoclave under nitrogen purge. The present inventors investigated in order to improve the drawbacks of the conventional saponification method for EVA with a vinyl acetate content of 50% by weight or less, and developed a mixed solvent system of sec-butanol and a low boiling point alcohol such as methanol. When used
The present invention was completed by the discovery that the reaction proceeds smoothly at normal pressure without causing any fusion between particles of EVA or/and EVA saponified product, and that a saponified product with a saponification rate of 90% or more can be easily obtained. did. That is, when saponifying an ethylene-vinyl acetate copolymer having a vinyl acetate content of 50% by weight or less in a heterogeneous state, the present invention uses methanol or/and ethanol and sec-butanol for 100 parts by weight of the granular copolymer. (The mixing ratio of sec-butanol in the mixture is 15-80% by weight) 150-1000
A method for saponifying an ethylene-vinyl acetate copolymer, which comprises adding parts by weight and 0.05 to 10 equivalents of a catalyst and reacting at a temperature of 90°C or lower, thereby causing the reaction to occur without causing fusion between the copolymers. be. In the present invention, the saponification reaction is carried out using a mixed solvent in which sec-butanol is added to a lower alcohol. In order to swell both the saponified products well, the saponification reaction proceeds in a state close to a homogeneous method even though it is a heterogeneous method. As a result, a highly saponified EVA product in the form of granules or powder can be obtained in a short time under normal pressure, so the method of the present invention can be said to be industrially very advantageous. The EVA used in the present invention has a vinyl acetate content of 50% by weight or less, preferably 35% by weight or less. If the vinyl acetate content exceeds 50% by weight, fusion between particles tends to occur, making it unsuitable for application to the method of the present invention. The melt index of EVA is not particularly limited, but is usually in the range of 1 to 500% and 10 minutes. The mixed solvent used in the saponification method of the present invention is methanol or ethanol or a mixture thereof and sec-
However, the mixing ratio of sec-butanol in the mixed solvent is 15 to 80% by weight, preferably
It is 30-70% by weight. 15% by weight or less
EVA and saponified EVA do not fully swell, which is insufficient to exhibit the effects of the present invention, and if it exceeds 80% by weight, the EVA will fuse with each other due to heating, which is not preferable. The amount of mixed solvent is usually
It is used in an amount of 150 to 1000 parts by weight, preferably 250 to 600 parts by weight, based on 100 parts by weight of EVA.
If it is less than 150 parts by weight, it is difficult to carry out saponification, and if it exceeds 1,000 parts by weight, there is virtually no merit, and if it is less than 1,000 parts by weight, the purpose is sufficiently achieved. The catalyst used in the saponification method of the present invention is an alkali catalyst, and examples thereof include sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, and the like. Its usage is against EVA
It is 0.05 to 10 times equivalent, preferably 0.1 to 3 times equivalent. The reaction temperature in the saponification method of the present invention is
Although it varies depending on the vinyl acetate content and melt index of EVA, it is usually carried out at 50 to 90°C. 90
At temperatures above ℃, mutual fusion of EVA saponified substances is observed.
If the temperature is below 50°C, the reaction time will be long, which is not preferable. The saponification reaction of the present invention is usually carried out in a reactor equipped with a stirring device under normal pressure near the boiling point of the mixed solvent, but the reaction can be carried out in an autoclave while controlling the temperature to prevent mutual fusion of EVA saponified products. You can do it. In the present invention, the amount of sec-butanol used is as described above, but when looking at the amount of sec-butanol in terms of the amount ratio to EVA, if it is less than 20% by weight relative to EVA, it has almost no swelling effect. The results showed that it was preferable to use an amount several hundred times as large as that of EVA to achieve the effects of the present invention. This is known as the conventional method n-
In the EVA saponification method that uses butanol or t-butanol mixed with methanol, if n-butanol or t-butanol is added in an amount of 5% or more by weight of EVA, it is said that fusion will occur between EVA particles. This was surprising considering the fact that Furthermore, compared to the adhesive strength, dry cleaning resistance, etc. of saponified products with a low saponification rate when EVA is saponified in a methanol alone medium or a methanol and n-butanol mixed medium, respectively,
The saponified product saponified by the method of the present invention is
It was also found that the properties of saponified products with low saponification rates were significantly improved. The method of the present invention will be explained below using examples. In the example, the adhesive strength test of saponified EVA was conducted in the following manner. Spread EVA saponification at a rate of 20 g/m ² on No. 60 broad cloth of 150 x 200 mm, layer the same size cloth, and then apply the mixture at a temperature of 140°C, a pressure of 0.2 Kg/cm ² and a time of 10 seconds. Press and adhere to create a basic test piece. (1) Initial adhesive strength The above basic test piece was cut vertically to a width of 25 mm to create 5 test pieces, and each was peeled using a tensile testing machine at a gripping interval of 50 mm and a tensile speed of 200 mm/min. According to JIS-L-1089, 3 items with the highest maximum value and 3 items with the lowest maximum value are taken for a total of 6 items.
Calculate the average value of 5 test pieces, and calculate the average value of 5 test pieces in g
It was expressed as (2) Dry creeling resistance Pressure stitch with a sewing machine 5mm from the edge of the above basic test piece. In accordance with JIS-L-0860-1965 (dry cleaning test), three test pieces with a width of 25 mm and a length of 130 mm were collected after treatment with perchlorethylene at 40°C for 1 hour and air drying.
The test pieces were peeled off according to the initial adhesive strength test (1) and expressed as the average value g of the three test pieces. (3) Washing resistance As with dry cleaning resistance, press-stitch with a sewing machine at 5 mm from the edge of the basic test piece.
Put it in the washing machine so that it weighs 1kg with additional cloth,
Add a solution containing 0.1% powdered soap to 60℃ hot water, wash for 30 minutes, drain, and rinse with 40℃ hot water.
Wash for 15 minutes, dehydrate, air dry, width 25mm, length
Three test pieces of 130 mm were cut and subjected to a peel test according to the strength test method (1), and the average value of the three pieces was expressed in g. Example 1 In a glass reaction vessel with a stirrer and a capacity of 500 ml, 75 g of EVA pellets with a vinyl acetate content of 25.5% by weight and a melt index of 150 g/10 minutes, 150 g of methanol, 150 g of sec-butanol, 10.4 g of sodium hydroxide, Cyanoacetic acid methyl ester 0.3g
was charged, the temperature was raised over 20 minutes, and the reaction was carried out for 4 hours while refluxing the solvent at the boiling point temperature. After the reaction is completed, cool it down, filter it, and wash it with methanol.
It was dried in a dryer at ℃ overnight. The obtained pellets had a saponification degree of 96%. Table 1 shows the results of an adhesive strength test using this pellet. Example 2 An experiment was conducted in the same manner as in Example 1 except that the reaction time was changed to 2.5 hours, and the degree of saponification was
An 85% white pellet was obtained. The adhesive strength of this product was measured and the results are shown in Table 1. Comparative Example 1 The same operation as in Example 1 was carried out except that sec-butanol was not used in Example 1 and 300 g of methanol alone was charged and reacted at the boiling point for 16 hours. The obtained pellets were in the form of white pellets, and the degree of saponification was 85%. Comparative Example 2 Using the reactor used in Example 1, vinyl acetate content 25.5% by weight, melt index 150g/10
75g of EVA pellets, 3g of n-butanol,
300g of methanol and 7g of sodium hydroxide were charged, boiled for 30 minutes, reacted at the boiling point for 5 hours, and then treated in the same manner as in Example 1 to obtain a white saponification degree.
Got 84% stuff. Table 1 shows the adhesive strength test results for the pellets obtained in Comparative Examples 1 and 2.

[Table] Example 3 Methanol 175 was used as the mixed solvent in Example 1.
The same operation as in Example 1 was carried out except that 50 g of sec-butanol was used instead. The reaction was carried out at the boiling point for 5 hours, yielding white pellets with a saponification degree of 91%. Example 4 In Example 1, the mixed solvent was methanol 100%
The procedure was repeated in the same manner as in Example 1 except that 200 g of sec-butanol was used, and white pellets with a saponification degree of 99% were obtained by reaction at the boiling point for 4 hours. Example 5 In Example 1, the mixed solvent was ethanol 100%
The same procedure as in Example 1 was carried out except that 150 g of sec-butanol was used, and the reaction was carried out at the boiling point for 5 hours to obtain white pellets with a saponification rate of 99%.

Claims (1)

[Claims] 1 When saponifying an ethylene-vinyl acetate copolymer with a vinyl acetate content of 50% by weight or less in a heterogeneous state, methanol or/and a mixture of ethanol and sec-butanol (mixture The mixing ratio of sec-butanol in the copolymer is 15-80% by weight) 150-1000 parts by weight and 0.05-10 equivalents of catalyst are added and reacted at a temperature of 90°C or less without causing fusion between the copolymers. A method for saponifying an ethylene-vinyl acetate copolymer, which comprises causing a reaction.