JPH0428002B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is characterized in that the reaction proceeds in a solution system using a water-soluble solvent, and the introduction ratio of isocyanate compounds can be arbitrarily controlled. The present invention relates to a method for producing a carbamate-based peeling treatment agent. BACKGROUND TECHNOLOGY Conventionally, as a method for producing a vinyl carbamate-based stripping agent made of a reaction product of an ethylene/vinyl alcohol copolymer and an alkyl isocyanate, an ethylene/vinyl alcohol copolymer with an ethylene copolymerization ratio of 0.1 to 0.9 has been used. A method was known in which a polymer is dissolved or dispersed in a water-insoluble solvent such as toluene or xylene, and then an alkyl isocyanate having 8 or more carbon atoms is added and reacted (Japanese Patent Publication No. 60-30355). ). Problems to be Solved by the Invention However, with the above method using only a water-insoluble solvent, it is impossible to use an ethylene-vinyl alcohol copolymer that has a high degree of saponification and therefore has a high content of hydroxyl groups. The inability to arbitrarily control the introduction ratio of isocyanate compounds;
Therefore, there have been problems such as difficulty in preparing a releasable treatment agent that has excellent adhesion to hydrophilic substrates such as cellophane or paper, and that the resulting releasable treatment agent has poor heat resistance. In addition, when using the dispersion method, there were other problems such as when an ethylene/vinyl alcohol copolymer having an average degree of polymerization of 2000 or more was used, the reaction rate became extremely slow, making it impractical. Means for Solving the Problems The present inventors have overcome the above problems and have improved the degree of saponification,
Ethylene/vinyl alcohol copolymers with a high average degree of polymerization can also be used, and the introduction ratio of isocyanate compounds can be controlled arbitrarily, so that the resulting release treatment agent has good heat resistance and adhesion to the substrate. As a result of intensive research to develop a method for producing a vinyl carbamate-based stripping agent with excellent properties, it was surprisingly possible to dissolve ethylene and vinyl alcohol in a water-soluble solvent, add an isocyanate compound to this solution, and react. The present inventors have discovered that the object can be achieved by allowing the process to proceed while maintaining the solution state, and have thus completed the present invention. That is, the present invention provides a method for producing a stripping agent made of a reaction product of an ethylene/vinyl alcohol copolymer and an isocyanate having an alkyl group having 8 or more carbon atoms. Provided is a method for producing a stripping treatment agent, which comprises reacting an ethylene-vinyl alcohol copolymer and an alkyl isosuccinate in a solution state from the start of the reaction to the end of the reaction, including intermediate products. It is something to do. The ethylene/vinyl alcohol copolymer used in the present invention is soluble in a water-soluble solvent. Generally, from the viewpoint of water solubility, a copolymerization ratio of vinyl alcohol of about 20 mol % or more, particularly 30 to 95 mol %, is used. The degree of saponification is not particularly limited as long as the condition of being soluble in a water-soluble solvent is satisfied, but the present invention is advantageous as a homogeneous dissolution method when the degree of saponification is 80 mol% or more. is demonstrated. Therefore, those having an ethylene copolymerization ratio of about 80 mol % or less, particularly 70 to 5 mol %, are generally used. The average degree of polymerization of the copolymer is suitably from 100 to 5,000, particularly from 500 to 2,500. If the average degree of polymerization is less than 100, the resulting releasable treatment agent will have poor film strength and heat resistance, and if it exceeds 5,000, it will have poor solubility, which is undesirable for reaction work. On the other hand, the water-soluble solvents mentioned above include dimethyl sulfoxide, tetrahydrofuran, N-methylpyrrolidone, dioxane, acetylacetone, diethylene glycol dimethyl ether, sulfolane, butyllactone, triethyl phosphate, methyl lactate, and the like. In addition,
Aqueous solvents having a boiling point above the reaction temperature are generally preferably used. The alkyl isocyanate used in the present invention has an alkyl group having 8 or more carbon atoms. Among these, those having an alkyl group having 12 to 30 carbon atoms are preferably used from the viewpoint of ability to impart releasability or easy availability. Typical examples include octyl, nonyl, decyl, undecyl,
Dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl,
docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, octacosyl, nacosyl,
Examples include isocyanates having long-chain alkyl groups such as triacontyl. In the present invention, it is necessary to react the ethylene/vinyl alcohol copolymer and the alkyl isocyanate in a solution state using a water-soluble solvent, and the process including the intermediate products from the start to the end of the reaction is necessary. It is necessary to carry out the reaction under solution conditions. This makes it possible to carry out a reaction using an ethylene/vinyl alcohol copolymer with a high degree of saponification and a high degree of polymerization, and also to arbitrarily control the proportion of the isocyanate compound introduced. The above reaction generally begins with a predetermined amount of ethylene.
The vinyl alcohol copolymer is dissolved in at least the amount necessary to dissolve it, usually 3 to 8 times the weight of the water-soluble solvent, and a predetermined amount of alkyl isocyanate is added to this solution, followed by heating.
At that time, in order to dissolve the intermediate product as necessary, that is, to prevent the intermediate product from precipitating in the reaction system, a water-insoluble solvent such as xylene or toluene may be added as appropriate to the reaction system. It is necessary to maintain the solution state until the end of the reaction. This achieves the object of the invention. Therefore, the object of the present invention cannot be achieved by a method in which the reaction is started in a dispersion state using a water-insoluble solvent of ethylene/vinyl alcohol, or a method in which precipitation of an intermediate product is allowed to occur. The end point of the reaction is determined by the disappearance of isocyanate groups in the reaction system. Further, during the reaction, a catalyst typified by, for example, an organic tin compound, which promotes the reaction between the hydroxyl group and the isocyanate group, may be used as necessary. On the other hand, the amount of alkyl isocyanate to be used is appropriately determined depending on the intended introduction ratio. Generally, it is used in an amount of 0.1 to 1.1 equivalent to the hydroxyl group in ethylene/vinyl alcohol. It is advantageous to leave hydroxyl groups in view of adhesion to hydrophilic substrates such as cellophane substrates and paper substrates. The obtained reaction product is usually poured into a medium such as methanol to precipitate it, then washed, and the pulverized product is dissolved in toluene etc. and used as a solution for practical purposes such as stripping treatment. . Effects of the Invention According to the present invention, since a solution reaction system using a water-soluble solvent is used, an ethylene-vinyl alcohol copolymer with a high degree of saponification and a high degree of polymerization can be used as a reactant. The introduction ratio of the isocyanate compound can be easily controlled. In addition, it also has the advantage of being able to efficiently obtain a releasable treatment agent with excellent adhesion to the substrate and excellent thermal stability (heat resistance) of peeling properties with a simple operation. Examples Examples 1 to 4 Put ethylene-vinyl alcohol copolymer into a 1000 c.c. four-necked flask equipped with a reflux condenser and water content receiver, add dimethyl sulfoxide and stir to form a solution. do. Next, xylene was added to this solution, and the mixture was refluxed at 140° C. for 2 hours while stirring to remove water. Then, after cooling the system to 100°C, octadecyl isocyanate is added and reacted. The system is constantly maintained in a homogeneous solution state by adding xylene at appropriate times as the reaction progresses, and the reaction is allowed to proceed at 120°C for about 5 hours. During this time, the amount of isocyanate groups remaining in the system is quantified, and the point at which the remaining amount disappears is defined as the end point of the reaction. After the reaction is completed, the reaction solution is poured into 5 times the weight of methanol to precipitate a white precipitate, which is filtered, washed with methanol, and dried and ground to obtain the desired product. The target product consisting of the reactants shown in the table is obtained in the above manner. Comparative Example 1 10 parts (by weight, the same applies hereinafter) of ethylene/vinyl alcohol copolymer (ethylene copolymerization ratio 0.5, average degree of polymerization 1700) was dispersed in 50 parts of xylene, and 45 parts of octadecyl isosuccinate was added to this to make 120 parts. ℃
The reaction is allowed to proceed until the remaining isocyanate groups disappear, and the resulting reaction solution is treated in the same manner as in Examples to obtain the desired product. Comparative Example 2 Using 20 parts of polyvinyl alcohol (degree of saponification 88 mol%, average degree of polymerization 1400), 204 parts of xylene, and 116 parts of octadecyl isocyanate, the desired product was obtained by processing according to Comparative Example 1. Comparative Example 3 Ethylene/vinyl alcohol copolymer (ethylene copolymerization ratio 0.8, vinyl alcohol copolymerization ratio
Although the same operation as in the example was carried out using an average polymerization degree of 0.2 and 1000, the objective could not be achieved as it did not dissolve in dimethyl sulfoxide. Evaluation test A 1% by weight solution was prepared by dissolving the stripping agent as a reaction product obtained in Examples and Comparative Examples in toluene, and this was applied to a cellophane film (thickness: 36 μm).
It is coated on top (solid matter: 0.05 g/m ² ) and dried to obtain a release-treated film. Next, apply cellophane adhesive tape (No. 29, manufactured by Nitto Electric Industry Co., Ltd.) to the treated surface of the release-treated film, weighing 2 kg.
Press with a rubber roller, heat this in an atmosphere of 20°C or 50°C for 24 hours, and then measure the peeling force by 180 degree peel (pulling speed 300 mm/min). however,
For the products heated at 50°C, they were left in an atmosphere at 20°C for 4 hours after heating. The results are shown in the table.

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Claims (1)

[Claims] 1. In producing a stripping treatment agent made of a reaction product of an ethylene/vinyl alcohol copolymer and an isocyanate having an alkyl group having 8 or more carbon atoms, a solution is prepared using a water-soluble solvent. Ethylene
A method for producing a stripping treatment agent, which comprises reacting a vinyl alcohol copolymer and an alkyl isocyanate in a solution state, including their intermediate products, from the start of the reaction to the end of the reaction.