JP2787813B2 - Fine polyvinyl alcohol resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a finely divided polyvinyl alcohol resin having an average degree of polymerization of 500 or less and an average particle size of 30 μm or less.

[Prior Art] Polyvinyl alcohol is widely used in dispersants, adhesives, sizing agents and the like by utilizing its unique property of water solubility.

Polyvinyl alcohol has a wide variety of properties depending on the average degree of polymerization, average degree of saponification, average particle size, etc. It is used for

[Problems to be Solved by the Invention] So far, polyvinyl alcohols having a very low molecular weight of about 50 in terms of the average degree of polymerization to high molecular weights of 6000 or more have been known. It is well known that a completely saponified product having a degree of saponification of 100 mol% to a partially saponified product having several tens mol%.

Furthermore, from the aspect of average particle size, ordinary industrial products are 200 to 1000
It is on the order of μ, and is crushed into fine particles of about 200 μ or less for use in special applications.

From this point, it is needless to say that the combination of the average polymerization degree, the average saponification degree, and the average particle size also has a wide variety of performances, and the combination has a novel performance which has not been known until now. The finding of a polyvinyl alcohol having the formula (1) expands the industrial range of use, and therefore it must be said that it is extremely useful in industry.

[Means for Solving the Problems] The present inventors have conducted intensive studies and found that the average degree of polymerization was
500 or less, preferably 300 or less, particularly preferably 100 or less, the average particle size is 30μ or less, preferably 20μ or less, particularly preferably 10μ or less fine polyvinyl alcohol has a unique performance not found in conventional polyvinyl alcohol This led to the completion of the present invention. That is, the particulate polyvinyl alcohol of the present invention has the following characteristics.

(1) Since it has a high degree of crystallinity, for example, when used in a hot melt adhesive or the like, the melting behavior is sharp, that is, the temperature range in which uniform melting is possible is narrow.

(2) Since the distribution of the degree of polymerization is sharp, the product can be made uniform.

(3) By the heat treatment, the swellability in (cold) water can be controlled, and the dispersibility in an aqueous medium becomes good. Therefore, a stable water / polyvinyl alcohol slurry can be obtained by using the finely divided polyvinyl alcohol of the present invention, and a high-concentration polyvinyl alcohol can be prepared by heating and dissolving the slurry. The behavior is also sharp.

(4) The effect of the heat treatment greatly affects water solubility. In the case of conventional polyvinyl alcohol, it is common that completely saponified products are insoluble in cold water and soluble in warm water, and partially saponified products are soluble in cold water. Therefore, the degree of saponification is inevitably limited in applications where the solubility in water is used naturally, whereas in the case of the present invention, the solubility in water can be controlled by heat treatment, It is possible to adjust the dissolution behavior in water with a degree of saponification of, and to diversify the product.

(5) When producing polyvinyl alcohol industrially,
Regardless of the degree of polymerization, it is usually obtained in the form of coarse particles of about 200 to 1000 µ.

Therefore, when producing finely divided polyvinyl alcohol, mechanical pulverization or the like is necessary, but polyvinyl alcohol in the degree of polymerization of the present application is very easy to pulverize, the product yield is high, There are also other advantages such as a sharp particle size distribution. In addition, an ultrafine product of 10 μm or less, which cannot be produced with conventional polyvinyl alcohol, can be easily obtained.

The finely divided polyvinyl alcohol of the present invention is usually first produced as a coarse particle of polyvinyl alcohol by a known method, and is obtained by pulverizing the same by a mechanical pulverization method.

As a method for producing coarse particles, a polymerization solution of polyvinyl acetate having a low polymerization degree obtained by polymerizing vinyl acetate in an alcohol having a large chain transfer constant as described in JP-A-51-87594 is heated. A method in which the solvent is expelled underneath, the polyvinyl acetate in a molten state is mixed with anhydrous methanol, and the methanol solution is added with an alkali to carry out deacetation, as described in JP-A-57-28121. A method in which mercaptans are used as a transfer agent and the mercaptans are added to a specific amount polymerization system before the start of polymerization, and when the polymerization is substantially started, vinyl acetate is further polymerized while continuously supplying the mercaptan to the polymerization system. The method described in JP-A-63-278911 is advantageously carried out.

That is, the vinyl acetate monomer is polymerized in a solvent having a chain transfer constant of 2 × 10 ^{−4 to} 2000 × 10 ⁻⁴ under the temperature at the time of polymerization,
Then, when producing polyvinyl alcohol having a low degree of polymerization by saponifying the obtained polyvinyl acetate, the above polymerization is carried out while sequentially charging a vinyl acetate monomer.

The polyvinyl alcohol of the present invention includes not only partially saponified or completely saponified polyvinyl acetate, but also a vinyl ester and a monomer copolymerizable therewith, such as ethylene, propylene, isobutylene, α-octene, α-dodecene, Olefins such as α-octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid and salts thereof, and mono- or dialkyl esters, etc., nitriles such as acrylonitrile and methacrylonitrile Amides such as acrylamide and methacrylamide, olefinsulfonic acids such as ethylene sulfones, allyl sulfones and methallyl sulfonic acid or salts thereof, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyl Trimethyl ammonium chloride, dimethyl diallyl vinyl ketone, N- vinylpyrrolidone, vinyl chloride, a copolymer saponified vinylidene chloride and the like, but is not limited thereto.

Thus, polyvinyl alcohol is obtained as coarse particles of about 200 to 300 μm, and is then pulverized by mechanical pulverization.

The pulverization method is not particularly limited, and any method may be employed. For example, a roll mill, a stamp mill, an edge runner, a cutting / shearing mill, a rod mill, a self-made pulverizer, a roller mill, a high-speed rotary pulverizer (hammer mill, cage mill, pin mill, Disintegrators, screen mills, turbo mills, centrifugal classifier mills, etc., ball mills (rolling mills, vibrating ball mills, planetary mills), stirring mills (tower mills, stirring tank mills, flow tube mills, annular mills), jet mills , A shear mill, a compression grinding type pulverizer, a colloid mill and the like are used.

It is advantageous that the average particle diameter is 30 μm or less, preferably 20 μm or less, particularly preferably 10 μm or less. If the average particle diameter is more than such, the effect of the present invention is hardly obtained.

The finely divided polyvinyl alcohol thus obtained is used for any purpose.

 Specific applications include the following.

(1) Molded materials Fibers, films, sheets, pipes, tubes, leak-proof films, provisional films, water-soluble fibers for chemical lace, separation functional materials, water-based gels (2) Adhesive materials Wood, paper, aluminum foil, plastic, etc. Adhesives, adhesives, re-wetting agents, nonwoven fabric binders, fibrous binders,
Binders for various building materials such as gypsum board and fiberboard, binders for various powder granulations, additives for cement and mortar, hot melt type adhesives, pressure sensitive adhesives, fixing agents for anionic dyes (3) Coating agents Clear coating agent for paper, pigment coating agent for paper, internal sizing agent for paper, sizing agent for textile products, warp sizing agent, textile processing agent, leather finishing agent, paint, cloud inhibitor, metal corrosion inhibitor, plating Brightener, antistatic agent, conductive agent (4) Blending agent for hydrophobic resin Antistatic agent for hydrophobic resin, hydrophilicity imparting agent, composite fiber, film and other additives for molded products (5) Dispersion for suspension Stabilizers Pigment dispersion stabilizers such as paints, inks, watercolor colors, and adhesives, and dispersion stabilizers for suspension polymerization of various vinyl compounds such as vinyl chloride, vinylidene chloride, (meth) acrylate, and vinyl acetate (6 ) Emulsifiers Emulsifiers for emulsion polymerization of ethylenically unsaturated compounds and butadiene compounds, hydrophobic resins such as polyolefins and polyester resins, post-emulsifiers such as epoxy resins, paraffins and bitumen (7) Viscosity regulators Viscosity modifiers for various emulsions (8) Coagulant Aqueous coagulant for suspensions and dissolved substances in water, water improver for pulp slurry (9) Soil improver (10) Photosensitizer, electrosensitizer, cosmetic additive (11) Others Ion-exchange resin, ion-exchange membrane-related chelating resin [Action] The finely divided polyvinyl alcohol of the present invention has various properties not found in conventional polyvinyl alcohol, such as high crystallinity, dispersibility in water, and water dissolution behavior. Have.

EXAMPLES Next, the present invention will be described in detail with reference to examples.

Example 1 1000 g of isopropanol, 100 g of vinyl acetate monomer and azobisisobutyronitrile as an initiator were charged, and the reaction was carried out while maintaining the system at a temperature of 80 ° C.

After the start of the polymerization reaction, polymerization was carried out at a rate of 250 g / hr for 12 hours while dropping vinyl acetate monomer. System S / M
Was kept almost constant throughout the entire polymerization period. The final conversion was 88%.

After removing isopropanol from the polymerization reaction product, it was converted to a methanol solution, and then alkali-saponified by a conventional method to obtain an average degree of polymerization of 47, a degree of saponification of 99.5 mol%, and an average particle size of 430 μm.
Was obtained.

The measurement of the average degree of polymerization, the degree of saponification, and the average particle size are as follows. (The same shall apply hereinafter.) 1. Average degree of polymerization; re-acetylation and purification of the sample by a conventional method;
According to JISK6725.

2. Degree of saponification: According to JISK6726.

3. Average particle size: Using the JIS standard section, a 50% particle size was determined from a plot of a rosin-Rammler particle size diagram and defined as an average particle size.

Next, 50 g of the coarse particles were fed from a feeder of a jet mill [LABO JET LJ, supersonic jet crusher manufactured by Nippon Pneumatic Industries, Inc., AFS-10CA, an arcuate feeder].
It was supplied at a rate of 1.4 to 1.8 g / min into the aircraft under an airflow of Mach 2.5 or more. After the completion of the charging, the idle operation was performed for 40 minutes as it was, and the remaining particles in the machine were discharged.

The average particle size of the obtained polyvinyl alcohol was 3.5 μm, and the viscosity distribution was as shown in Table 1.

Further, the obtained particles were subjected to a heat treatment, and the degree of swelling in water and dissolution behavior were observed. The results are also shown in Table 1.

In Comparative Example 1, the average degree of polymerization was 1100 and the average degree of saponification was 9
A 9.5 mol% polyvinyl alcohol having an average particle size of 260 μm was subjected to jet mill pulverization under the same conditions as in Example 1 to obtain particles having an average particle size of 22 μm.

The particles having an average particle diameter of 3.5 μm were divided from these particles, and the particles were subjected to the same heat treatment as in Example 1 to obtain a degree of water swelling.
Water solubility was observed. These results are also shown in Table 1.

However, the degree of swelling in water is 10 g of fine-grain polyvinyl alcohol.
Was immersed in 100 g of ion-exchanged water, allowed to stand at room temperature for 24 hours, and represented by the rate of increase (times) in the weight of particles after immersion compared to before immersion.

Regarding the dissolution behavior in water, 450 g of 5 ° C. ion-exchanged water was placed in a 500 ml beaker, 5 g of a sample was charged and dispersed, and the temperature was immediately raised at 1 ° C./min while stirring with a magnetic stirrer.

 The water temperature at which the liquid became transparent was taken as the water dissolution temperature.

Example 2 200 g of the same polyvinyl alcohol coarse particles as in Example 1 were charged into a Victor Mill (manufactured by Hosokawa Iron Works) at a rate of 34 to 40 g / min, and pulverized (blade rotation speed 10,000 rpm, screen opening 0.22 mm). The results are shown in Table 2.

Examples 3 to 5 Coarse particles of polyvinyl alcohol were produced according to Example 1, and pulverized by a jet mill. Table 2 shows the results.

[Effects] The finely divided polyvinyl alcohol of the present invention has characteristics not found in conventional polyvinyl alcohol particles.

Claims (3)

(57) [Claims] 1. A finely divided polyvinyl alcohol resin having an average degree of polymerization of 500 or less and an average particle size of 30 μ or less. 2. The resin according to claim 1, having an average degree of polymerization of 300 or less and an average particle size of 20 μ or less. 3. The resin according to claim 1, having an average degree of polymerization of 100 or less and an average particle size of 10 μ or less.