JP4531553B2 - Polyvinyl alcohol resin and use thereof - Google Patents

Description

  The present invention relates to a novel polyvinyl alcohol resin and use thereof, and more specifically, viscosity stability of aqueous solution, reactivity with a crosslinking agent, water solubility when used as a film, stretchability, gas barrier property, and emulsifier. It is related with the polyvinyl alcohol-type resin excellent in the standing stability of the emulsion at the time, and its use.

Conventionally, polyvinyl alcohol resins (hereinafter, polyvinyl alcohol is abbreviated as PVA) are dispersed using their excellent water solubility, interface properties, film properties (film forming properties, strength, oil resistance, etc.), etc. Widely used in agents, emulsifiers, suspending agents, fiber processing agents, paper processing agents, binders, adhesives, films and the like. And except for special cases, it is usually used as an aqueous solution.
Depending on the purpose, PVA resins with various saponification degrees are used. In the case of PVA resins with a relatively high saponification degree, the viscosity of the aqueous solution increases with time in winter when the water temperature is low. However, in extreme cases, it may gel and lose its fluidity at all. In recent years, high-speed coating properties have become an important issue for paper processing applications. However, such high-saponification degree PVA-based resin aqueous solutions are thickened at high shear rates and have high coating properties. There was a problem that it decreased.

  On the other hand, the partially saponified PVA resin has few such problems. However, when the aqueous solution is easily foamed or used as a molding material such as a film, the food has an odor of acetic acid derived from residual acetyl groups. There is a problem that it cannot be used as packaging materials for cosmetics and cosmetics.

  In addition, a film made of a PVA-based resin exhibits excellent gas barrier properties, and this feature can be further improved by highly stretching a film made of a highly saponified PVA-based resin. The high saponification degree PVA resin has a problem that the stretchability is poor and the film lacks flexibility.

Various modified PVAs have been studied for the purpose of improving the low-temperature viscosity stability and high-speed coating properties of the above-mentioned problems, particularly high-saponification degree PVA-based resin aqueous solutions. For example, polymerization of aliphatic vinyl esters In this case, the pressure in the polymerization machine is maintained at a pressure higher than atmospheric pressure, polymerization is performed at a temperature 2-80 ° C. higher than the boiling point of the reaction solution under atmospheric pressure, and the resulting aliphatic polyvinyl ester is saponified. A PVA-based resin (see, for example, Patent Document 1) and a PVA-based paper coating agent that has such a PVA-based resin as a main component and is excellent in high-speed coating properties (for example, see Patent Document 2) have been proposed.
The present applicant has also proposed a PVA-based resin containing a 1,2-glycol component in the side chain (see, for example, Patent Document 3 and Patent Document 4).
JP-A-11-279210 JP-A-11-279986 JP 2002-284818 A JP 2004-285143 A

  However, in the disclosed techniques of Patent Document 1 and Patent Document 2, since it is necessary to pressurize in order to increase the polymerization temperature, there is a problem that a pressurization facility must be provided for the production, and the obtained PVA system Since the resin has a 1,2-glycol bond in its main chain, it has a drawback of poor heat resistance and easy coloration. Furthermore, the control of the amount of 1,2-glycol that can be introduced is not easy, and the viscosity stability of the aqueous solution and the coating property at the time of high-speed coating are still not satisfactory, and further improvement is required. Further, since all the hydroxyl groups present are secondary alcohols, the reactivity with a crosslinking agent or the like is not sufficient.

In addition, the PVA resin disclosed in Patent Document 3 and Patent Document 4 is a modified PVA resin having a structural unit represented by the following general formula (3), which is excellent in viscosity stability and viscosity stability of an aqueous solution, Good fluidity even at high shear rates during high-speed coating, high reactivity with crosslinking agents due to the presence of primary hydroxyl groups, and intramolecular and intermolecular hydrogen despite low crystallinity Although the bonding strength is maintained and a film excellent in water resistance can be obtained, since there is one primary hydroxyl group per structural unit of the general formula (3) introduced by copolymerization, it is desirable. In order to obtain the above characteristics, there remains a problem that the amount of modification must be increased.

However, as a result of intensive studies in view of such circumstances, the present inventor has found that a novel PVA-based resin containing a structural unit represented by the following general formula (1) meets the above purpose, and completed the present invention. did.
(Wherein R ¹ and R ² are each independently an alkylene group having 1 to 3 carbon atoms which may have an alkyl group)

The novel PVA-based resin of the present invention has a specific structural unit, and even if it is a highly saponified product, it has low crystallinity, so it is excellent in water solubility, aqueous solution viscosity stability, and high-speed coating property. Excellent stretchability when formed into a film, hydrogen bonding strength is maintained despite low crystallinity, excellent gas barrier properties, and excellent reactivity with various cross-linking agents. Adhesives and molding Suitable for applications such as products, water-soluble films for packaging materials, coating agents, paper processing agents, emulsifiers, suspending agents, gas barrier films and polarizing films.
Further, since two primary hydroxyl groups are present in the structural unit represented by the general formula (1), the above-mentioned characteristics can be obtained with a relatively small amount of modification, so that there is a great economic advantage.

Hereinafter, the present invention will be described in detail.
The novel PVA resin of the present invention is a PVA resin having a structural unit represented by the following general formula (1).
In the general formula (1), R ¹ and R ² are each independently an alkylene group having 1 to 3 carbon atoms which may have an alkyl group.

In obtaining such a PVA-based resin, although not particularly limited, a method of saponifying a copolymer of a vinyl ester monomer and a compound represented by the following general formula (2) is preferably used.
[Chemical formula 4]
R ³ O—R ¹ —CH═CH—R ² —OR ⁴ (2)
In the general formula (2), R ¹ and R ² are each independently an alkylene group having 1 to 3 carbon atoms which may have an alkyl group, and R ³ and R ⁴ are each independently hydrogen. An atom or —CO—R ⁵ group (wherein R ⁵ is an alkyl group, preferably a methyl group, a propyl group, a butyl group, a hexyl group or an octyl group, and such an alkyl group is optionally a halogen group, And may have a substituent such as a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group.
Specific examples of the compound represented by the general formula (2) include 1,4-dihydroxy-2-butene, 1,4-diacyloxy-2-butene, 1-hydroxy-4-acyloxy-2-butene, 1,4 -Diacyloxy-1-methyl-2-butene, 1,5-diacyloxy-2-pentene, 1,6-diacyloxy-2-hexene, 1,6-diacyloxy-3-hexene, among others, copolymerization 1,4-diasiloxy-2 in which R ¹ and R ² are methylene groups, R ³ and R ⁴ are —CO—R ⁵ , and R ⁵ is an alkyl group in that they are excellent in reactivity and industrial handling -Butene is preferable, and 1,4-diacetoxy-2-butene in which R ³ is a methyl group is particularly preferable.

  Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, Examples include vinyl versatate. Of these, vinyl acetate is preferably used from the economical viewpoint.

  Further, in the present invention, in addition to the above copolymerization component, other monomers can be copolymerized in an amount of about 0.5 to 10 mol% within a range that does not impair the object of the present invention. Olefins such as propylene, isobutylene, α-octene, α-dodecene, α-octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid or salts thereof, mono- or dialkyl Esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as diacetone acrylamide, acrylamide and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid, or salts thereof, alkyl vinyl ethers, Dimethylallyl vinyl ketone N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxyalkylene (meth) allyl ether such as polyoxypropylene (meth) allyl ether, polyoxyethylene (meth) acrylate, polyoxypropylene Polyoxyalkylene (meth) acrylates such as (meth) acrylate, polyoxyalkylene (meth) acrylamides such as polyoxyethylene (meth) acrylamide, polyoxypropylene (meth) acrylamide, and polyoxyethylene (1- (meth) acrylamide- 1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, poly Carboxymethyl ethylene vinyl amine, polyoxypropylene vinyl amine.

  Furthermore, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidopropyltrimethylammonium chloride, 2-acryloxyethyltrimethylammonium chloride, 2-methacryloxyethyltrimethylammonium chloride, 2-hydroxy-3- Cationic group-containing monomers such as methacryloyloxypropyltrimethylammonium chloride, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, 3-butenetrimethylammonium chloride, dimethyldiallylammonium chloride, diethyldiallylammonium chloride, acetoacetyl group-containing monomers, 3, 4 -Diacetoxy- - butene, ethylene carbonate, vinyl ethylene carbonate, glycerin monoallyl ether, isopropenyl acetate, also 1-methoxy-vinyl acetate, and the like.

The method for copolymerizing the above vinyl ester monomer and the compound represented by the general formula (2) (and other monomers) is not particularly limited, and includes bulk polymerization, solution polymerization, suspension polymerization, A known method such as dispersion polymerization or emulsion polymerization can be employed, but solution polymerization is usually performed.
The charging method of the monomer component at the time of copolymerization is not particularly limited, and any method such as batch charging, split charging, continuous charging and the like can be adopted, but the structural unit represented by the general formula (1) is a copolymer. In view of being uniformly distributed in the molecular chain, drop polymerization is preferable, and a polymerization method based on the HANNA method is particularly preferable.
In addition, various chain transfer agents such as aldehyde compounds such as acetaldehyde and propionaldehyde, and mercaptan compounds such as thioacetic acid, dodecyl mercaptan and lauryl mercaptan can be used for the purpose of adjusting the degree of polymerization and modifying the end group. .

Examples of the solvent used in such copolymerization include usually lower alcohols such as methanol, ethanol, isopropyl alcohol, n-propanol and butanol, and ketones such as acetone and methyl ethyl ketone, and industrially preferred is methanol. used.
The amount of the solvent used may be appropriately selected in consideration of the chain transfer constant of the solvent in accordance with the degree of polymerization of the target copolymer. For example, when the solvent is methanol, S (solvent) / M ( Monomer) = 0.01 to 10 (weight ratio), preferably 0.05 to 3 (weight ratio).

For the copolymerization, a polymerization catalyst is used. Examples of the polymerization catalyst include known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, lauryl peroxide, azobisdimethylvaleronitrile, azo Examples include low-temperature active radical polymerization catalysts such as bismethoxydimethylvaleronitrile, and the amount of polymerization catalyst used varies depending on the type of catalyst and cannot be determined unconditionally, but is arbitrarily selected according to the polymerization rate. For example, when azoisobutyronitrile or acetyl peroxide is used, 0.01 to 0.2 mol% is preferable with respect to the vinyl ester monomer, and 0.02 to 0.15 mol% is particularly preferable.
The reaction temperature of the copolymerization reaction is about 30 ° C. to the boiling point, more specifically 35 to 150 ° C., preferably 40 to 75 ° C.

  In the present invention, the copolymerization ratio of the compound represented by the general formula (2) is not particularly limited, but the copolymerization ratio may be determined in accordance with the introduction amount of the structural unit represented by the general formula (1) described later. .

  The obtained copolymer is then saponified. In such saponification, the copolymer obtained above is dissolved in an alcohol or a hydrous alcohol, and the reaction is carried out using an alkali catalyst or an acid catalyst. . Examples of the alcohol include methanol, ethanol, propanol, tert-butanol and the like, and methanol is particularly preferably used. The concentration of the copolymer in the alcohol is appropriately selected depending on the viscosity of the system, but is usually selected from the range of 10 to 60% by weight. Catalysts used for saponification include alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate, lithium methylate, etc., sulfuric acid, Examples include acid catalysts such as hydrochloric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resin.

The amount of the saponification catalyst used is appropriately selected depending on the saponification method, the target degree of saponification, and the like. When an alkali catalyst is used, the vinyl ester monomer and the general formula (2) are usually used. A ratio of 0.1 to 30 mmol, preferably 2 to 15 mmol, is suitable for 1 mol of the total amount of the compounds shown.
The reaction temperature for the saponification reaction is not particularly limited, but is preferably 10 to 60 ° C (particularly 20 to 50 ° C).

  The average degree of polymerization (measured in accordance with JIS K6726) of the PVA-based resin of the present invention is appropriately selected depending on the purpose of use and is not particularly limited, but is usually 300 to 4000 (more preferably 300 to 2600, particularly 500 to 2200). When the average degree of polymerization is less than 300, the coating film and the film strength may be lowered, which is not preferable. When it exceeds 4000, the introduction amount of the structural unit represented by the general formula (1) is not limited. This is not preferable because it may be difficult to increase the amount to the extent that the effect of the invention can be obtained, or the polymerization rate may become extremely slow.

  Further, the degree of saponification of the PVA-based resin is not particularly limited and is appropriately selected depending on the purpose of use, but is usually 60 mol% or more (further 70 mol% or more, particularly 80 mol% or more). Preferably, when the saponification degree is less than 60 mol%, the water solubility becomes low, which is not preferable.

  In addition, the content of the structural unit represented by the general formula (1) in the PVA resin of the present invention is not particularly limited, but is 0.1 to 20 mol% (more preferably 0.5 to 15 mol%, particularly 1). 10 mol%). When the content of the structural unit represented by the general formula (1) is less than 0.1 mol%, the effect of the present invention cannot be sufficiently obtained. The degree of polymerization is lowered, and as a result, sufficient coating strength and film strength cannot be obtained, and water resistance may be insufficient.

  The PVA-based resin containing the structural unit represented by the general formula (1) thus obtained has a low crystallinity even if it has a high saponification degree. Therefore, the dissolution rate in water is large and the viscosity stability of the aqueous solution is improved. It has excellent coating properties without thickening even at high shear rates during high-speed coating.

  The PVA resin of the present invention can impart water resistance by using various organic and inorganic crosslinking agents in combination. Such organic crosslinking agents include aldehyde compounds (formaldehyde, glyoxal, glutardialdehyde, etc.), amino resins (urea resins, guanamine resins, melamine resins), methylol compounds (methylolated melamine, methylolated urea, methylolated bisphenol S). Etc.), epoxy compounds (water-soluble epoxy resin, polyamide polyamine epichlorohydrin, etc.), hydrazide compounds (adipic acid dihydrazide, carbodihydrazide, polyhydrazide, etc.), isocyanate compounds and the like. Examples of inorganic crosslinking agents include boric acid, borates (borax, etc.), titanium compounds (tetraalkoxy titanate, etc.), aluminum compounds (aluminum sulfate, aluminum chloride, aluminum nitrate, etc.), phosphorus compounds (phosphorous acid) Esters, bisphenol A-modified polyphosphoric acid, etc.), silicone compounds having reactive functional groups such as alkoxy groups and glycidyl groups, and metal-based cross-linking agents such as zirconium compounds are effective. Of these, isocyanate compounds and zirconium compounds are preferred. .

  Examples of the isocyanate compound include tolylene diisocyanate (TDI), hydrogenated TDI, trimethylolpropane-TDI adduct (for example, “Desmodur L” manufactured by Bayer), triphenylmethane triisocyanate, methylenebisdiphenyl isocyanate (MDI), Examples include hydrogenated MDI, polymerized MDI, hexamethylene diisocyanate, xylylene diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and isophorone diisocyanate. In addition, a prepolymer having a terminal group having an isocyanate group, which is previously polymerized with an excess of polyisocyanate in a polyol, is also included. As a blending ratio of the isocyanate compound, it is preferable that the molar ratio of isocyanate group to hydroxyl group (NCO / OH) is 0.1 to 2.

Examples of the zirconium compound include zirconium chloride, zirconium acetate, zirconyl acetate, zirconium nitrate, zirconyl nitrate, zirconium sulfate, zirconyl sulfate, zirconium acetylacetonate, ammonium zirconium carbonate, potassium zirconium carbonate, zirconyl octylate, zirconium oxychloride, Examples include hydroxy zirconium chloride and hydroxy zirconyl chloride. Of these, zirconium ammonium carbonate and potassium zirconyl carbonate are preferable.
Examples of applications utilizing water resistance by the PVA resin and the crosslinking agent of the present invention include an aqueous vinyl urethane type adhesive using an isocyanate compound as a crosslinking agent, a protective layer for a thermal recording medium, an inkjet recording medium (ink) Receiving layer, gloss layer) and the like.

  Furthermore, since the film obtained by forming the PVA resin of the present invention is excellent in water solubility, water-soluble packaging for various articles such as agricultural chemicals, detergents, laundry clothes, civil engineering additives, bactericides, dyes, pigments, etc. Useful as a material. The saponification degree of the PVA resin when used for such water-soluble packaging is preferably 65 to 98 mol%. However, when packaging an acidic substance or an alkaline substance, the saponification degree is preferably 98.1 to 100 mol%, and more preferably 99 to 100 mol%. This is because if the degree of saponification is less than 98.1 mol%, the water solubility of the film may decrease over time when an acidic substance or an alkaline substance is packaged and stored.

Further, such a PVA-based resin film is excellent in stretchability, and the uniaxially stretched film has flexibility and gas barrier properties, and is therefore suitable for packaging material materials such as clothing and food.
In addition, the PVA-based resin film is subjected to a dehydration treatment with a dehydration accelerator such as a protonic acid, then stretched by a known method such as dry heat stretching or wet stretching, and further fixed with a boron compound. A PVA film having a polyvinylene structure is obtained, and such a PVA film is useful as a polarizing film.

  The PVA-based resin of the present invention is excellent as a dispersant for various inorganic particles. Examples of applications utilizing such properties include binders for paper pigment coating and inorganic fine particle binders for inkjet recording media. Such an ink jet recording medium is obtained by coating a coating liquid containing the PVA resin of the present invention and inorganic fine particles on a supporting substrate such as paper, film, resin-coated paper, an ink receiving layer, It can be applied to any of the glossy layers, and the inorganic fine particles in this case include amorphous silica in the case of the ink receiving layer, and vapor phase silica, colloidal silica, alumina sol in the case of the glossy layer. In particular, when used in the gloss layer, excellent gloss can be obtained.

The PVA-based resin of the present invention can be used for various applications by utilizing its characteristics, and some of the applications have been described above, but other specific examples include the following.
(1) Adhesive-related adhesives such as wood, paper, aluminum foil, plastics, adhesives, rehumidifiers, binders for non-woven fabrics, binders for various building materials such as gypsum boards and fiber boards, various binders for granulating powder, Additives for cement and mortar, hot melt adhesive, pressure sensitive adhesive, anionic paint fixing agent, etc.

(2) Molded fibers, films, sheets, pipes, tubes, leak-proof membranes, temporary coatings, water-soluble fibers for chemical lace, additives for modifying various films for the purpose of reducing crystallization and improving stretchability, etc. .

(3) Coating-related paper clear coating agent, paper sizing agent, textile product sizing agent, warp glue, fiber processing agent, leather finishing agent, paint, antifogging agent, metal corrosion inhibitor, gloss for galvanizing Agent, antistatic agent, conductive agent, ship bottom paint, anti-scaling agent, etc.

(4) Emulsifier relationship Ethylenically unsaturated compounds, butadiene compounds, emulsifiers for emulsion polymerization of various acrylic monomers, hydrophobic resins such as polyolefins and polyester resins, post-emulsifiers such as epoxy resins, paraffin and bitumen, and the like.

(5) Suspension-related dispersion stability for various types of vinyl compounds such as paint dispersion stabilizers such as paints, ink, water color, adhesives, vinyl chloride, vinylidene chloride, styrene, (meth) acrylate, vinyl acetate Agents, etc.

(6) Hydrophobic resin blending agent-related hydrophobic resin antistatic agent, hydrophilicity-imparting agent, composite fiber, film and other additives for molded articles, and the like.
(7) Coagulant-related suspensions in water and coagulants for dissolved substances, pulp, slurries, etc.
(8) Thickener-related various aqueous solutions and emulsion thickeners, etc.

(9) Soil improver-related (10) Photosensitizer, electrosensitive relationship, photosensitive resist resin, etc.
(11) Other ion exchange resins, ion exchange membrane relations, chelate exchange resins, etc.
Among the above, its usefulness is particularly expected for the uses (1) to (7).

In addition, when applying to various uses, it is preferable to add a plasticizer as necessary. As the plasticizer, trivalent to hexavalent polyhydric alcohols (glycerin, trimethylolpropane, diglycerin, pentaerythritol). Xylol, arabinose, ribulose, sorbitol, etc.) and various alkylene oxides (ethylene oxide, propylene oxide, mixed adducts of ethylene oxide and propylene oxide, etc.).

Hereinafter, the present invention will be specifically described with reference to examples. In the examples, “parts” and “%” mean weight basis unless otherwise specified.
Example 1
To a reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer, 1300 g of vinyl acetate, 520 g of methanol, 1,4-diacetoxy-2-butene (R ¹ and R ² are methylene groups, R ³ and R ⁴ are —CO in -R ^{5, R 5} is charged methyl group) 52.0 g (2 mol%), 0.1 mol% of azobisisobutyronitrile (vs. the charged vinyl acetate) were charged, under a nitrogen stream at stirring Polymerization was carried out at an elevated temperature.
Thereafter, when the polymerization rate of vinyl acetate reached 83.6%, a polymerization inhibitor was added to complete the polymerization. Subsequently, unreacted vinyl acetate monomer was removed out of the system by a method of blowing methanol vapor to obtain a methanol solution of the copolymer.

  Next, the solution was diluted with methanol to a concentration of 40% and charged into a kneader. While maintaining the solution temperature at 40 ° C., a 2% methanol solution of sodium hydroxide was added to 1 mol of vinyl acetate in the copolymer. Saponification was carried out at a rate of 8 mmol. Saponification progressed as saponification progressed, and finally became particulate. The produced PVA-based resin was separated by filtration, washed well with methanol, and dried in a hot air dryer to obtain the desired product.

  The saponification degree of the obtained PVA-based resin was 99.7 mol% when analyzed by the alkali consumption required for hydrolysis of the residual vinyl acetate unit, and the polymerization degree was analyzed according to JIS K 6726. Was 840. The viscosity of a 4% aqueous solution of the PVA-based resin (I) was 8.9 mPa · s (20 ° C.) as measured by a Heppler viscometer, and the amount of modification was 2.0 mol as calculated from NMR measurement. %Met.

Assignment of IR spectrum and ¹ H-NMR (solvent: DMSO-d6) spectrum of the obtained PVA resin was as follows. The IR chart is shown in FIG. 1, and the ¹ H-NMR chart is shown in FIG.

[IR] (see FIG. 1)
3360 cm ⁻¹ : OH (strong)
2950, 2910 cm ⁻¹ : methylene (strong)
1440 cm ⁻¹ : methylene (strong)
1240 cm ⁻¹ : methine (weak)
1144 cm ⁻¹ : Crystal band (between H and OH, strong)
1100 cm ⁻¹ : C—O (medium)
850 cm ⁻¹ : methylene (medium)
660 cm ⁻¹ : OH (medium broadcast)

[ ¹ H-NMR] (see FIG. 2)
1.2-1.6 ppm: Methylene proton, methine proton (due to modified species)
3.4-3.5 ppm: Methylene proton (due to modified species)
3.8 to 3.9 ppm: Methine proton 4.1 to 4.6 ppm: Hydroxyl group

  The following evaluation was performed about the obtained PVA-type resin. The results are shown in Tables 1-4.

[Viscosity stability of aqueous solution]
An 8% aqueous solution of PVA-based resin was placed in a glass container, and the temperature of the aqueous solution was 20 ° C. Next, the glass container was left in a constant temperature water bath at 5 ° C., the viscosity after being left for 1 hour and 24 hours was measured, the thickening ratio was determined and evaluated as follows.
○ ・ ・ ・ Thickening ratio is less than 1.5 times △ ・ ・ ・ Thickening ratio is 1.5 times or more and less than 2.5 times × ・ ・ ・ Thickening ratio is 2.5 times or more Is calculated from the following equation.
Thickening factor = (viscosity after 24 hours at 5 ° C.) / (Viscosity after 1 hour at 5 ° C.)

[Foaming properties of aqueous solution]
Place 250 ml of 1% aqueous solution of PVA resin in a 1 L capacity graduated cylinder, adjust the temperature to 40 ° C., place a diffuser stone in the bottom of the liquid, and blow it with air at 0.2 L / min. The combined volume of the aqueous solution and foam was measured and evaluated as follows.
○ ... Volume is less than 400 ml Δ: Volume is 400 ml or more, less than 1000 ml × ... Volume is 1000 ml or more

[High speed coatability]
The increase in viscosity of a 10% aqueous solution of PVA resin under a high shear rate at 30 ° C. was measured and evaluated as follows. As a measuring device, a flow tester CFT-500C manufactured by Shimadzu Corporation was used.
○: When the shear rate is 6 × 10 ⁶ / s or more and the viscosity increase shows a maximum value ×… When the shear rate is less than 6 × 10 ⁶ / s and the viscosity increase shows a maximum value

[Wood adhesion performance]
After the PVA resin is stirred and completely dissolved in distilled water at 80 ° C., an aqueous solution with a concentration of about 15% is prepared, and the PVA resin aqueous solution and an isocyanate compound (MDI, isocyanate as a crosslinking agent) are prepared in a Teflon mold. Base amount: 6.71 × 10 ⁻³ mol / g) was added to prepare an adhesive.
In addition, the compounding ratio of the isocyanate compound and the PVA resin was blended so that the ratio of the hydroxyl group in the isocyanate group and the PVA resin was 1: 5.
The obtained adhesive was applied to an adherend (merkaba: average specific gravity 0.73, moisture content about 12%) so that the application amount was 220 g / m ^2, and after application, 20 ° C. × 1 at about 1 MPa. The sample was clamped by day and heat-treated at 120 ° C. for 2 hours. A single lap tensile shear type test piece was subjected to a tensile test at a crosshead speed of 10 mm / min and evaluated as follows.
○ ··· adhesive strength is 40Kgf / cm ² or more △ ··· adhesive strength is 30kgf / cm ² or more, 40kgf / cm ² less than × ··· adhesive strength is less than 30Kgf / cm ²

[Left stability of emulsion]
In a separable flask equipped with a stirrer, reflux condenser, dropping funnel, thermometer, 140 parts of water, 10 parts of PVA resin, 0.02 part of sodium acetate as pH adjuster, polymerization monomer (methyl methacrylate / n-acrylic acid n- 12.5 parts of butyl = 60/40 (weight ratio) was charged, and the temperature in the flask was raised to 60 ° C. while stirring. Meanwhile, while replacing the inside of the flask with nitrogen gas, 5 parts of a 1% ammonium persulfate aqueous solution was added to initiate polymerization. Initial polymerization was performed for 30 minutes, 112.5 parts of the remaining polymerization monomer was added dropwise over 4 hours, and 5 parts of a 1% ammonium persulfate aqueous solution was further added 4 times every hour for polymerization. Then, after aging at 75 ° C. for 1 hour, the mixture was cooled to obtain an aqueous emulsion of a methyl methacrylate / n-butyl acrylate copolymer having a solid content of 45%.
After putting 300 g of the obtained emulsion into a 450 ml mayonnaise bottle, the emulsion viscosity (V ₀ ) at 25 ° C. was measured with a BROOFIELD type viscometer, and further left in a constant temperature bath at 60 ° C. for 10 days. The viscosity of the emulsion (V ₁₀ ) was measured and the viscosity ratio (V ₁₀ / V ₀ ) was determined.

[Glossiness of inkjet recording medium]
Colloidal silica ("Ludox AS-40" manufactured by WR Grace Co., Ltd., particle size 20 nm, solid content 40%) is dissolved in 85 parts of water by dissolving 15 parts of PVA resin in PVA resin / colloidal silica = 1/2. (Solid content weight ratio) The mixture was mixed, and stirred at 5000 rpm for 5 minutes with a homogenizer (“TK ROBOMICS” manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a coating solution having a solid content of 15%.
The aqueous dispersion is coated on high-quality paper having a basis weight of 270 g / m ^{2 with} a 50 μm applicator and dried in a hot air dryer at 105 ° C. for 5 minutes to form a coating layer having a thickness of 7.5 μm. A recording medium was obtained.
The glossiness of 60 degrees with respect to the normal line of the obtained inkjet recording medium was measured using a goniophotometer (“VG-Σ80” manufactured by Nippon Denshoku Industries Co., Ltd.).

[Water solubility of film]
A cast film having a thickness of 30 μm was prepared by casting a 10% aqueous solution of a PVA resin on a hot roll at 60 ° C. The film was cut into 40 mm × 40 mm, sandwiched between slide mounts, immersed in water stirred at 20 ° C., the time (seconds) until the film was completely dissolved was measured and evaluated according to the following criteria.
○ ... 30 seconds or less △ ... 30 seconds or more, less than 60 seconds × ... 60 seconds or more

[Film stretchability]
A 10% aqueous solution of PVA resin was cast on a hot roll at 60 ° C. to prepare a cast film having a thickness of 100 μm. A 200 mm × 40 mm test piece was cut out from the film and stretched by a precision universal testing machine (“Autograph IS-5000” manufactured by Shimadzu Corporation) at 150 ° C. at a speed of 200 mm / min until the length became 6 times. The evaluation was based on the following criteria.
○ ・ ・ ・ The film does not break ×× The film breaks

[Gas barrier properties of film]
A 10% aqueous solution of PVA resin was cast on a PET film, allowed to stand for 48 hours in an atmosphere of 23 ° C. and 50% RH, left to stand in a desiccator containing phosphorus pentoxide for 2 weeks, and dried to a thickness of 3 μm. And a 20 μm cast film was prepared. Using a film with a thickness of 3 μm, the oxygen permeability at 0% RH was measured using an oxygen permeability measuring device (“OXTRAN 2/20” manufactured by MOCON). The oxygen permeability at 37% RH and 52% RH was measured. It measured using the oxygen permeability measuring apparatus ("OXTRAN TWIN" by MOCON). Further, using a 20 μm-thick film, the oxygen permeability at a humidity of 81% RH was measured using an oxygen permeability measuring device (“OXTRAN TWIN” manufactured by MOCON) and converted to a value of 3 μm thickness.

Example 2
To a reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer, 1300 g of vinyl acetate, 104 g of methanol, 1,4-diacetoxy-2-butene (R ¹ and R ² are methylene groups, R ³ and R ⁴ are —CO in -R ^{5, R 5} is charged methyl group) 27.6 g (1.06 mol%), 0.1 mol% of azobisisobutyronitrile (vs. the charged vinyl acetate monomer) were charged, stirred and While raising the temperature under a nitrogen stream, the polymerization was started at 67 ° C., and at the same time, charging of a 20% methanol solution of 1,4-diacetoxy-2-butene was started according to the HANNA method, and the polymerization rate reached 80.5%. 46 ml was charged.
When the polymerization rate of vinyl acetate reaches 80.5%, the polymerization is terminated, and then unreacted vinyl acetate monomer is removed out of the system by blowing methanol vapor to a methanol solution of the copolymer. Got.

  Next, the solution was diluted with methanol to a concentration of 40% and charged into a kneader. While maintaining the solution temperature at 40 ° C., a 2% methanol solution of sodium hydroxide was added to 1 mol of vinyl acetate in the copolymer. Saponification was carried out by adding an amount of 7 mmol. Saponification progressed as saponification progressed, and finally became particulate. The produced PVA-based resin was separated by filtration, washed well with methanol, and dried in a hot air dryer to obtain the desired product.

The degree of saponification of the obtained PVA-based resin was 99.2 mol% when analyzed by the alkali consumption required for hydrolysis of the residual vinyl acetate units, and the degree of polymerization was in accordance with JIS K 6726. It was 1290 when the analysis was conducted. The viscosity of a 4% aqueous solution of the PVA resin was 17.0 mPa · s (20 ° C.) as measured with a Heppler viscometer, and the amount of modification was 1.5 mol% as calculated from NMR measurement. It was.
Evaluation similar to Example 1 was performed about the obtained PVA-type resin. The results are shown in Tables 1-4.

Example 3
To a reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer, 1300 g of vinyl acetate, 65 g of methanol, 1,4-diacetoxy-2-butene (R ¹ , R ² methylene group, R ³ and R ⁴ are —CO— in R ^{5, R 5} is charged methyl group) 154.6 g (6 mol%), azobisisobutyronitrile and 0.1 mol% (relative to charged vinyl acetate) turned temperature under a nitrogen stream while stirring Was raised to carry out polymerization.
Thereafter, when the polymerization rate of vinyl acetate reached 65.2%, a polymerization inhibitor was added to complete the polymerization. Subsequently, unreacted vinyl acetate monomer was removed out of the system by a method of blowing methanol vapor to obtain a methanol solution of the copolymer.

  Next, the solution was diluted with methanol to a concentration of 40% and charged into a kneader. While maintaining the solution temperature at 40 ° C., a 2% methanol solution of sodium hydroxide was added to 1 mol of vinyl acetate in the copolymer. Saponification was carried out at a rate of 7 mmol. Saponification progressed as saponification progressed, and finally became particulate. The produced PVA-based resin was separated by filtration, washed well with methanol, and dried in a hot air dryer to obtain the desired product.

  The saponification degree of the obtained PVA-based resin was analyzed by the alkali consumption required for hydrolysis of the residual vinyl acetate unit. As a result, it was 99.3 mol%, and the polymerization degree was analyzed according to JIS K 6726. Was 690. The viscosity of a 4% aqueous solution of the PVA-based resin (I) was 6.9 mPa · s (20 ° C.) as measured with a Heppler viscometer, and the amount of modification was calculated as 5.9 mol from NMR measurement. %Met.

Comparative Example 1
In Example 1, except that 1,4-diacetoxy-2-butene was not charged and only vinyl acetate was polymerized (S / M = 0.8, S: methanol, M: vinyl acetate), and saponification was performed. Was carried out in the same manner to obtain a PVA resin.
The degree of saponification of the obtained PVA-based resin was 99.5 mol% when analyzed by the alkali consumption required for hydrolysis of the remaining vinyl acetate units, and the degree of polymerization was analyzed according to JIS K 6726. Was 860. The viscosity of a 4% aqueous solution of the PVA resin (I) was 9.1 mPa · s (20 ° C.) as measured by a Heppler viscometer.
Evaluation similar to Example 1 was performed about the obtained PVA-type resin. The results are shown in Tables 1-4.

Comparative Example 2
In Example 1, the amount of methanol charged was 845 g, 3,4-diacetoxy-1-butene was used instead of 1,4-diacetoxy-2-butene, and azobisisobutyronitrile was 0.08 mol%. (Various charged vinyl acetate) was charged, and polymerization and saponification were carried out in the same manner as in Example 1 except that a polymerization inhibitor was charged when the polymerization rate of vinyl acetate reached 91.2% to obtain a PVA resin. .
The saponification degree of the obtained PVA-based resin was 99.6 mol% when analyzed by the alkali consumption required for hydrolysis of the residual vinyl acetate unit, and the polymerization degree was analyzed according to JIS K 6726. Was 850. The viscosity of a 4% aqueous solution of the PVA-based resin (I) was 9.0 mPa · s (20 ° C.) as measured with a Heppler viscometer, and the amount of modification was 2.1 mol as calculated from NMR measurement. %Met.
Evaluation similar to Example 1 was performed about the obtained PVA-type resin. The results are shown in Tables 1-4.

  The PVA-based resin of the present invention is excellent in water solubility, aqueous solution viscosity stability, high-speed coating properties, excellent stretchability, flexibility and gas barrier properties when made into a film, and further reactive with various crosslinking agents. Useful for applications such as adhesives, molded products, water-soluble films for packaging materials, coating agents, paper processing agents, inorganic fine particle binders for inkjet recording media, emulsifiers, suspending agents, gas barrier films, polarizing films, etc. is there.

2 is an IR spectrum chart of the PVA resin obtained in Example 1. FIG. 1 is a ¹ H-NMR spectrum chart of a PVA resin obtained in Example 1. FIG.

Claims (10)

A polyvinyl alcohol-based resin comprising a structural unit represented by the general formula (1).

(Wherein R ¹ and R ² are each independently an alkylene group having 1 to 3 carbon atoms which may have an alkyl group) The polyvinyl alcohol resin according to claim 1, wherein the copolymer is a saponified copolymer of a vinyl ester monomer and a compound represented by the general formula (2).
(In the formula, R ¹ and R ² are each independently an alkylene group having 1 to 3 carbon atoms which may have an alkyl group, and R ³ and R ⁴ are each independently a hydrogen atom or —CO 2. a -R ⁵ group, ^{R 5} represents an alkyl group)   The polyvinyl alcohol resin according to claim 1 or 2, wherein the content of the structural unit represented by the general formula (1) is 0.1 to 20 mol%.   An adhesive comprising the novel polyvinyl alcohol resin according to any one of claims 1 to 3.   A molded article using the novel polyvinyl alcohol resin according to any one of claims 1 to 3.   A water-soluble film using the polyvinyl alcohol resin according to claim 1. The coating agent characterized by using the polyvinyl alcohol-type resin in any one of Claims 1-3.   The paper processing agent characterized by using the polyvinyl alcohol-type resin in any one of Claims 1-3.   The polyvinyl alcohol-type resin in any one of Claims 1-3 is used, The emulsifier characterized by the above-mentioned. A suspending agent comprising the polyvinyl alcohol resin according to any one of claims 1 to 3.