JPS5936945B2 - Method for dissolving polyvinyl alcohol resin powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dissolving polyvinyl alcohol-based resin powder which has been improved so that it can be immediately dispersed and dissolved without becoming lumpy even when the polyvinyl alcohol-based resin powder is poured into water. be.

Polyvinyl alcohol is useful as a main raw material for sizing agents such as warp sizing agents and household laundry starches.

However, it is surprisingly difficult to prepare a size solution by dissolving polyvinyl alcohol powder in water, and if the dissolution process is not done carefully, only the surface of the powder particles will swell rapidly, especially in fine powder grades. If the particles remain floating on the water surface and are not dispersed in the water, and stirring is performed to aid in dispersion, the particles may stick to each other, a so-called sticky state, which can make dissolution work extremely difficult. The solubility of polyvinyl alcohol powder in water can be judged in the following three stages.

(1) When a primary dispersion powder is put into water, does it disperse and settle without forming lumps? (2) Secondary dispersibility Then, after stirring the water, the stirring was stopped. Sometimes the particles do not stick to each other, or they form blocks and sink to the bottom.

(3) Solubility Does dissolution complete quickly and smoothly when stirring is continued?

The solubility of polyvinyl alcohol powder is as described in (1) and (2) above.
It is most desirable that both (2) and (3) are excellent; (iii) If any one of (2) and (3) is poor, this becomes a rate-limiting step and the process of dissolving polyvinyl alcohol becomes difficult. will not proceed smoothly.

Therefore, in order to increase the solubility of polyvinyl alcohol powder, methods have been proposed such as blending glyoxal with polyvinyl alcohol, blending dialdehyde starch, blending polyhydric alcohol, and blending dicarboxylic acid or its ester. However, although efforts have been made to some extent to prevent the occurrence of mako, that is, to improve primary dispersibility, the secondary dispersibility or dissolution rate has not yet been completely satisfied.

Although glyoxal gives relatively good results in the above method, it may not be possible to achieve the desired effect depending on the type or amount of the organic solvent used as a diluent when mixing the glyoxal solution with polyvinyl alcohol particles. There are times when this is not possible, which poses a practical problem. The present invention solves the above conventional problems by blending 0.1 to 10 parts by weight of glyoxylic acid to 100 parts by weight of polyvinyl alcohol resin.

The solubility of polyvinyl alcohol resin powder in water is determined by mixing glyoxylic acid with primary dispersion, secondary dispersion,
It exhibits a remarkable effect of greatly improving both the dissolution rate and the dissolution rate.

A wide variety of polyvinyl alcohol resins can be used as long as they are water-soluble, but those with a saponification degree of 75 to 98 mol% are particularly practical; Higher saponified or fully saponified polyvinyl alcohols may also be used.

This highly saponified polyvinyl alcohol originally has better primary dispersibility than partially saponified polyvinyl alcohol, but the idea is to improve secondary dispersibility by adding glyoxylic acid. The degree of polymerization of the partially saponified polyvinyl alcohol or completely saponified polyvinyl alcohol is not particularly limited, and those having a degree of polymerization of approximately 100 to 3,000 are used. It is also copolymerized and modified with acrylic acid, methacrylic acid, crotonic acid, maleic acid or their alkyl esters, α-olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, and sodium sulfonate. So-called modified polyvinyl alcohol can also be used. When blending glyoxylic acid with polyvinyl alcohol resin, glyoxylic acid is usually in the number 10.
Since it is often available as an aqueous solution with a concentration of Adopted.

Examples of such organic solvents include alcohols such as methanol, ethanol, propanol, and cyclohexanol, esters such as methyl acetate and ethyl acetate, ketones such as acetone and methyl ethyl ketone, diethyl ether,
Ethers such as dioxane, cellosolves, hydrocarbons such as benzene, toluene, xylene, and petroleum ether, halogenated hydrocarbons, and nitrogen-containing organic solvents are used. Is the degree of dilution with an organic solvent such that the concentration of glyoxylic acid is 0.1 to 20% by weight? Although the glyoxylic acid concentration is often kept at a low level, it may be high if the glyoxylic acid concentration is high. There is also no problem in directly mixing the glyoxylic acid aqueous solution with the polyvinyl alcohol particles, especially when the polyvinyl alcohol particles are wet particles, but in this case, sufficient care should be taken in the addition and mixing methods to ensure uniform mixing. Therefore, non-uniform mixing may impair the solubility of the polyvinyl alcohol resin powder. A typical method is to use 0.5 to 200 parts by weight of an organic solvent containing 0.1 to 10 parts by weight of glyoxylic acid to 100 parts by weight of polyvinyl alcohol resin particles (based on dry particles).
It is preferable to add parts by weight and mix. And at this time, there is no problem even if there is some water in it. After adding glyoxylic acid, dry it. Although heating is not necessarily required during drying, it is preferable to carry out the drying under heating conditions up to a maximum of about 150° C. in order to speed up the drying rate and to fix glyoxylic acid on the polyvinyl alcohol particles. The powder thus obtained can be used for textile glue, laundry glue, pigment binder in paper coating, paper manufacturing binder, urea resin adhesive modification, emulsifier, etc. by dissolving polyvinyl alcohol resin powder in water. It can be widely used in various fields. Next, the method of the present invention will be further explained with reference to Examples.

In the following, "parts" and "%" are expressed on a weight basis unless otherwise specified. Example 1 Degree of polymerization 170
0, degree of saponification 87.0 mol? To 100 parts of polyvinyl alcohol powder (particle size: 80-200 mesh product) was added 40 parts of a 40% aqueous solution of glyoxylic acid diluted with 7 times the amount of methanol, mixed well, and then heated to 80°C.
Dry with hot air.

The amount of glyoxylic acid deposited is 2 parts per 100 parts of polyvinyl alcohol. The thus obtained powder 109 was poured into water 5009 in a beaker, stirred, and heated to dissolve.

Table 1 shows the primary dispersibility, secondary dispersibility, and solubility. Control Examples 1 to 5 Control Examples 1 When the polyvinyl alcohol powder (without glyoxylic acid blended) in Example 1 was directly poured into water.

Control Example 2 To 100 parts of the polyvinyl alcohol powder in Example 1, 40 parts of a 40% aqueous solution of glyoxal diluted with 7 times the amount of methanol was added and mixed well, and then dried with hot air at a temperature of 80°C, and the mixture was poured into water. If you put it in.

Comparative Example 3 10 parts of a 20% aqueous solution of dialdehyde starch was added to 100 parts of the polyvinyl alcohol powder in Example 1, mixed well, and then dried with hot air at a temperature of 80° C., and the resultant mixture was poured into water.

Control Example 4 40 parts of a 5% methanol solution of ethylene glycol was added to 100 parts of the polyvinyl alcohol powder in Example 1, mixed well, and then dried with hot air at a temperature of 80° C., and the resultant mixture was poured into water.

Control Example 5 40 parts of a 5% methanol solution of oxalic acid was added to 100 parts of the polyvinyl alcohol powder in Example 1, mixed well, and then dried with hot air at a temperature of 80° C., and the resultant mixture was poured into water.

Experiments were conducted in the same manner as in Example 1 for the above Control Examples 1 to 5 as well.

The results are also shown in Table 1. Example 2 Degree of polymerization 1400
1 degree of saponification 87.0 moles? To 100 parts of polyvinyl alcohol powder, 100 parts of a 40% aqueous solution of glyoxylic acid diluted with 19 times the amount of methyl acetate was added and mixed well, and then dried with hot air at a temperature of 100°C.

The amount of glyoxylic acid attached is 100% of polyvinyl alcohol.
2 parts for 1 part. Using the thus obtained powder, primary dispersibility, secondary dispersibility, and dissolution rate were examined in the same manner as in Example 1.

The results are shown in Table 2. Example 3 Monomethyl maleate content 2.5 mol? 98 of the vinyl acetate component of the monomethyl maleate monovinyl acetate copolymer of
An experiment was conducted in the same manner as in Example 2 except that a powder of the saponified product obtained by alkali saponification of mol % was used in place of the polyvinyl alcohol in Example 2.

The results are shown in Table 2. Control Example 5 An experiment was conducted in the same manner as in Example 3, in which the saponified monomethyl maleate monovinyl acetate copolymer powder (without glyoxylic acid added) in Example 3 was directly poured into water.

The results are also shown in Table 2. Example 4 Sodium allylsulfonate content: 2.0 mol%, degree of saponification of vinyl acetate component: 99.0 mol? An experiment was carried out in the same manner as in Example 2 except that powder of the saponified product of sodium allylsulfonic acid and vinyl acetate copolymer was used in place of the polyvinyl alcohol in Example 2, except that glyoxylic acid was blended.

Claims (1)

[Claims] 1. A method for dissolving polyvinyl alcohol resin powder, which comprises dissolving in water a powder composition containing 100 parts by weight of polyvinyl alcohol resin and 0.1 to 10 parts by weight of glyoxylic acid.