JPS621963B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of acetoacetylating a PVA resin, ie, a powdered PVA resin, or a molded PVA resin by directly contacting the polyvinyl alcohol (PVA) resin with diketene gas.

As a conventional technique for producing acetoacetylated PVA (AA-PVA)-based resin by reacting PVA-based resin with diketene gas,
Dispersion systems such as dispersing PVA resin and adding diketene gas to it, or dissolving PVA resin in a solvent such as dimethylformamide or dioxane in advance and adding diketene to it, and homogeneous systems. Acetoacetylation method using diketene is known.

However, in such conventional technology, in order to obtain the reaction product from the reaction system, a precipitant is added to the reaction product to precipitate the product, and then the product and the mother liquor are separated, and the separated mother liquor is Many complicated steps are essential, such as recovering the solvent and precipitant from the product and removing the solvent and precipitant from the separated product, and these steps inevitably affect the product cost, making it economically disadvantageous for industrialization. It invites

Furthermore, it is impossible to acetoacetylate PVA resin molded products such as films, sheets, fibers, etc. in their original state using conventional techniques.

However, the present inventors have repeatedly investigated a method for easily acetoacetylating PVA resin in its original state, and found that by bringing diketene gas into direct contact with PVA resin,
It was discovered that acetoacetylation can be easily carried out, and the present invention was completed.

According to the present invention, the following remarkable effects can be obtained.

1 Unreacted diketene is easily removed by degassing the product under reduced pressure or passing an inert gas through it.

2. Unreacted diketene can also be decomposed and removed by hydrolysis or steaming.

By simplifying the manufacturing process, especially the post-processing process, equipment efficiency increases and manufacturing costs are reduced.

3 PVA resin molded products can be acetoacetylated in their original state, and only the surface of the molded product is acetoacetylated.
While maintaining the original characteristics of PVA resin,
Furthermore, chemical reactivity is imparted.

When acetoacetylating a powdered PVA resin, the resin may be brought into contact with diketene gas under reduced pressure, normal pressure, or even under increased pressure while maintaining the resin in a fluidized or stirred state.

The contact temperature is 30 to 250°C, preferably 50 to 200°C, and it is preferable to bring the gaseous diketene into contact with the resin under temperature and diketene partial pressure conditions at which it does not liquefy upon contact with the resin. There is no problem with it becoming a drop.

The contact time is appropriately selected from the range of 1 minute to 6 hours depending on the contact temperature, that is, when the temperature is low, the time may be long, and when the temperature is high, the time may be short.

When diketene gas is supplied, diketene gas may be used as it is, or a mixed gas of diketene gas and inert gas may be used, or the gas may be absorbed into powdered PVA resin and then heated. It is preferable to contact the gas after heating while heating.

It is preferable to use the powdered PVA resin to be subjected to acetoacetylation after removing volatile components, since water, methanol, etc. consume diketene. The finer the resin, the better, with a particle size of 10 to 450.
Mesh, preferably 60 mesh.

Since PVA resin powder usually contains sodium acetate, it is often not necessary to add a catalyst, but the amount of sodium acetate is 0.01 to 2.0%, preferably 0.1 to 1.0%.

Next, when acetoacetylating a PVA resin molded product, do the same as in the case of powdered PVA resin, but use basic compounds such as sodium acetate, potassium acetate, primary amine, secondary amine, or tertiary amine. It is preferable to use it after adsorbing it to the surface of the molded article, if necessary.

In the present invention, PVA-based resins include PVA obtained by saponifying a lower alcohol solution of polyvinyl acetate with a saponification catalyst such as an alkali, and its derivatives, as well as monomers copolymerizable with vinyl acetate. It is a saponified copolymer of vinyl acetate and vinyl acetate.

The monomers include (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth)acrylic acid and other unsaturated carboxylic acids and their esters;
α-olefins such as ethylene and propylene;
Olefin sulfonic acids such as (meth)allylsulfonic acid, ethylenesulfonic acid, sulfonic acid malate, sodium (meth)allylsulfonate, sodium ethylenesulfonate, sodium sulfonate (meth)
Olefin sulfonic acid alkali salts such as acrylate, sodium sulfonate (monoalkyl maleate), sodium disulfonate alkyl maleate, N
Examples include amide group-containing monomers such as -methylol acrylamide and alkali salts of acrylamide alkyl sulfonic acids, as well as N-vinylpyrrolidone and N-vinylpyrrolidone derivatives.

When carrying out the present invention, it is sufficient to use a device that can heat the powder and is equipped with a stirrer. Examples include kneaders, Henschel mixers, various other blenders, and stirring dryers.

In the case of PVA resin molded products such as films, sheets, fibers, etc., this is achieved by exposing these molded products to a diketene gas atmosphere.

The acetoacetylated product obtained in the present invention can be used in a wide range of applications, including the production of gels, photographic materials, chelate exchange resins, molding materials, and paper strength enhancers.

Next, the present invention will be specifically explained with reference to Examples. In the examples, "parts" and "%" represent "parts by weight" and "% by weight."

Example 1 Partially saponified PVA containing 0.3% sodium acetate
(Saponification degree: 88 mol%) 196 parts of fine powder was charged into a reactor, and while the temperature was raised to 90°C over 1 hour with stirring, 15 parts of diketene gas generated in the evaporator was flowed into the reactor. Ta. After raising the temperature to 90°C and stirring for an additional 30 minutes, the powder was sprayed with 10 parts of water and analyzed, and it was found to be 3.1 mol% acetoacetylated. When this powder was dissolved in hot water, most of it was dissolved.

Example 2 Fill the bottom of a desiccator with liquid diketene,
A vinylon film with a thickness of 30 microns was hung on top, and after being left at 60°C overnight, the film was taken out and left to stand until the diketene odor disappeared, and analysis revealed that acetoacetylation was 0.5 mol%. This film was insoluble in hot water.

Example 3 Reacted with diketene gas in the same manner as in Example 1 except that a saponified copolymer of maleic acid monomethyl ester and vinyl acetate containing 3 mol % of maleic acid monomethyl ester was used instead of polyvinyl alcohol. , degree of acetoacetylation 1.5
Mol% of acetoacetylated derivative was obtained.

Claims (1)

[Scope of Claims] 1. A method for acetoacetylation of polyvinyl alcohol resin, which comprises bringing diketene gas into direct contact with polyvinyl alcohol resin. 2. The acetoacetylation method according to claim 1, wherein the polyvinyl alcohol resin is a powdered polyvinyl alcohol resin. 3 Claim 1 in which the polyvinyl alcohol resin is a polyvinyl alcohol resin molded product
Acetoacetylation method described in section.