JP6753333B2 - Method for manufacturing crosslinked structure and inkjet recording medium - Google Patents

Description

The present invention relates to a method for producing a crosslinked structure of a polyvinyl alcohol-based resin, and more particularly to a crosslinked structure having excellent water resistance and particularly effective for an inkjet recording medium, and such an inkjet recording medium.

Polyvinyl alcohol-based resins (hereinafter, may be abbreviated as PVA-based resins) have been conventionally used as water-soluble resins for various purposes.
Further, the PVA-based resin is also known as a resin that is difficult to melt-mold, and the PVA-based resin is usually used after being dissolved in water.
In the manufacturing process, it is used as an aqueous solution by taking advantage of its water solubility, but when it becomes a product, it is finally dried and often used as a film. On the other hand, when used as a coating film, there are many applications where water resistance is required.

For example, when used for an ink receiving layer or an adhesive of an inkjet recording medium, water solubility is required in the coating process, but high water resistance is required when it is dried. In order to meet such demands, attempts have been made to add a cross-linking agent to a PVA-based resin to form a cross-linked structure and improve water resistance.

When forming a crosslinked structure, it is preferable to use a modified PVA-based resin having reactivity in order to increase the crosslinking efficiency and form a strong crosslinked structure. For example, an acetacetyl group-containing PVA-based resin (hereinafter referred to as “Crosslinkable PVA” resin) , Acetacetyl group-containing PVA-based resin may be abbreviated as AA-modified PVA-based resin.) Modified group-containing PVA-based resin having an active methylene group (hereinafter, abbreviated as active methylene group-containing PVA-based resin). There is.) Is used.

It is known that the AA-modified PVA-based resin is highly reactive with a cross-linking agent and a strong cross-linked structure can be obtained. Various compounds are known as cross-linking agents for such AA-modified PVA-based resins. Among them, hydrazine compounds and aldehyde compounds have excellent reactivity with acetoacetyl groups, and the cross-linking reaction proceeds at a relatively low temperature. Widely used in applications.

However, although the crosslinked structure of the AA-modified PVA resin and a hydrazine compound such as adipic acid dihydrazide or an aldehyde compound such as glyoxal or glyoxylic acid has excellent water resistance, there is a problem that it is colored with time.
Therefore, as a cross-linking agent for an AA-modified PVA-based resin, a cross-linking agent containing a glyoxylate having an aldehyde group as an effective functional group has been proposed (see, for example, Patent Document 1). As a result, a crosslinked polymer having characteristics of excellent stability of the mixed solution with the AA-modified PVA-based resin, excellent water resistance, and less coloring over time can be obtained. Further, among the glyoxyphosphates, especially when an alkali metal salt of glyoxylic acid or an alkaline earth metal salt of glyoxylic acid is used as a cross-linking agent, the water resistance of the cross-linked polymer obtained by cross-linking the AA-modified PVA-based resin It is also described as excellent.

Further, as a resin composition having further excellent water adhesion resistance, a composition in which a composition of AA-modified PVA-based resin and glyoxyphosphate further contains a metal-based cross-linking agent has been proposed (see, for example, Patent Document 2). .).

Japanese Unexamined Patent Publication No. 2010-77385 JP-A-2017-32813

However, the cross-linked structure of the AA-modified PVA-based resin and the glyoxylate obtained by the disclosed techniques of Patent Documents 1 and 2 and the cross-linked structure further containing the metal-based cross-linking agent cause the coated surface to be colored over time. However, cracks on the coated surface after drying have become a problem, and further improvements are required in achieving both color resistance that suppresses coloring over time and crack resistance that prevents cracks after drying. There is.

Therefore, it is an object of the present invention to provide a method for producing a crosslinked structure that has both color resistance that suppresses coloring over time and crack resistance that prevents cracks after drying under such a background. Is what you do.

However, as a result of diligent studies in view of the above circumstances, the present inventors have suppressed coloring over time by reacting a modified group-containing PVA resin containing an active methylene group, glyoxylic acid and a zirconium compound (a3). We have found that it is possible to obtain a crosslinked structure that has both color resistance and crack resistance that prevents cracking after drying, and completed the present invention.

That is, the gist of the present invention is to react the active methylene group-containing PVA resin (a1), glyoxylic acid (a2) and the zirconium compound (a3) in the method for producing the crosslinked structure (A) of the PVA resin. The present invention relates to a method for producing a characteristic crosslinked structure (A).

Further, the present invention also provides an inkjet recording medium using the crosslinked structure (A).

Although the mechanism for obtaining the above effects has not been clarified in detail, the ligand of zirconium is replaced with glyoxylic acid by mixing glyoxylic acid (a2) and the zirconium compound (a3). Glyoxylic acid (a2) reacts with the active methylene group of the modified group-containing PVA-based resin having an active methylene group to form a crosslinked structure. Further, it is presumed that a stronger crosslinked structure is formed by the effect of chelate crosslinking of the zirconium atom of the zirconium compound with the modifying group having an active methylene group. Therefore, when such a crosslinked structure is used, cracks do not occur on the coated surface, which is particularly useful for an inkjet recording medium.

According to the production method of the present invention, the obtained crosslinked structure (A) has excellent color resistance and crack resistance, and is useful for various coatings and the like. For example, ink receiving of an inkjet recording medium. It is effective for various applications such as layers, protective layers for heat-sensitive recording media, and adhesives. Above all, it is particularly suitable for the ink receiving layer of an inkjet recording medium.

Hereinafter, the present invention will be described in detail.
The production method of the present invention is a production method in which an active methylene group-containing PVA-based resin (a1), glyoxylic acid (a2) and a zirconium compound (a3) are reacted.

[Active methylene group-containing PVA-based resin (a1)]
First, the active methylene group-containing PVA-based resin (a1) used in the present invention will be described.
The active methylene group of the present invention represents a methylene group having increased acidity, such as a methylene group adjacent to a carbonyl group. The protons on the methylene group cause a cross-linking reaction in the resonance-stabilized portion.
Examples of the active methylene group-containing PVA-based resin (a1) as described above include PVA-based resins having a modifying group such as a ketone, a carboxylic acid, or a carboxylic acid ester. Specific examples thereof include PVA-based resins having an acetoacetyl group and a diacetone group. Among them, AA-modified PVA-based resin (a1-1) and diacetone acrylamide structural unit-containing PVA-based resin are preferable, and further, AA-modified PVA-based resin (a1-1) is preferable from the viewpoint of water resistance.

The active methylene group-containing PVA-based resin (a1) used in the present invention contains a structural unit having a modifying group having an active methylene group, and a vinyl alcohol structural unit is used in addition to the structural unit having such an active methylene group. It has, and if necessary, a vinyl ester structural unit of an unsaken portion.
As a method for producing the active methylene group-containing PVA-based resin (a1), (i) a modified group-containing monomer having an active methylene group and a vinyl ester-based compound are copolymerized, and the obtained copolymer is saponified. (Ii) A method of polymerizing a vinyl ester-based compound, saponifying the obtained polymer, and post-modifying the obtained PVA-based resin.

Examples of the vinyl ester compound include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyric acid, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and benzoic acid. Vinyl, vinyl versaticate and the like can be mentioned, but vinyl acetate is preferably used from the viewpoint of economy.

Examples of the monomer having an active methylene group include vinyl acetate, acetoacetoxyalkyl (meth) acrylate, and diacetone acrylamide.
Moreover, as a method of post-denaturation, a method of reacting a PVA resin with a ketone such as diketene can be mentioned.

Further, as the PVA-based resin, a saponified product of a copolymer of a vinyl ester-based compound and a copolymer having copolymerizability can be used to the extent that the effect of the present invention is not impaired. For example, olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene; 3-butene-1-ol, 4-pentene-1-ol, 5-hexene-1-ol, 3, Hydroxy group-containing α-olefins such as 4-dihydroxy-1-butene and derivatives such as acylated products thereof; unsaturated acids such as acryloacid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undesylene acid. , Its salts, monoesters, or dialkyl esters; nitriles such as acrylonitrile and metaacrylonitrile; amides such as diacetoneacrylamide, acrylamide and methacrylicamide; olefin sulfonic acids such as ethylenesulfonic acid, allylsulfonic acid and metaallylsulfonic acid. Or salts thereof; vinyl compounds such as alkyl vinyl ethers, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, etc. Substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate; vinylidene chloride, 1,4-diacetoxy-2-butene, 1,4-dihydroxy-2-butene, vinylene carbonate and the like.

The amount of the copolymerizable compound introduced varies depending on the type of compound and cannot be unequivocally determined. However, it is usually 10 mol% or less, particularly 5 mol% or less of all structural units, and if it is too large, it is water-soluble. The properties may be impaired or the compatibility with the cross-linking agent may be reduced.

The average degree of polymerization of the active methylene group-containing PVA-based resin (a1) is usually 300 to 4000, and particularly 400 to 3000, more preferably 500 to 2500 is preferably used. If the average degree of polymerization is too small, sufficient water resistance tends not to be obtained or a sufficient cross-linking rate tends not to be obtained. On the contrary, if it is too large, the viscosity of the aqueous solution becomes too high and the substrate is coated. When doing so, coating tends to be difficult.

The degree of saponification of the active methylene group-containing PVA-based resin (a1) is usually 80 to 100 mol%, and more preferably 85 to 99.9 mol%, particularly 90 to 99.8 mol%. Used.
If the degree of saponification is too low, the water solubility tends to decrease, making it difficult to make an aqueous solution, the stability of the aqueous solution decreases, and the water resistance of the obtained adhesive tends to decrease.
The average degree of polymerization and the degree of saponification are measured in accordance with JIS K6726. The following is performed in the same manner.

The modification amount of the active methylene group-containing PVA-based resin (a1) is usually 0.1 to 20 mol%, more preferably 1 to 15 mol%, and particularly preferably 2 to 10 mol%. If the content is too small, the water resistance tends to decrease or a sufficient cross-linking rate tends to be obtained, and conversely, if the content is too large, the water solubility tends to decrease and the stability of the aqueous solution tends to decrease.

[AA-formed PVA-based resin (a1-1)]
Next, the AA-modified PVA-based resin (a1-1) preferably used in the present invention will be described.
The AA-modified PVA-based resin (a1-1) used in the present invention has an acetoacetyl group (AA group) bonded directly to the main chain of the PVA-based resin, or via an oxygen atom or a linking group. Examples thereof include PVA-based resins containing a structural unit having an AA group represented by the general formula (1). The AA-modified PVA-based resin (a1-1) has a vinyl alcohol structural unit in addition to the structural unit having an AA group, and further has a vinyl ester structural unit of an unsaken portion, if necessary.

The PVA-based resin is obtained by polymerizing a vinyl ester-based compound and saponifying the obtained polymer. Examples of the vinyl ester compound include the same compounds as described above.

Further, a saponified product of a copolymer of a vinyl ester compound and a compound having copolymerizability can also be used, and examples of such a copolymerizable compound include the same as described above.

The amount of the copolymerizable compound introduced varies depending on the type of compound and cannot be unequivocally determined. However, it is usually 10 mol% or less, particularly 5 mol% or less of all structural units, and if it is too large, it is water-soluble. The properties may be impaired or the compatibility with the cross-linking agent may be reduced.

The average degree of polymerization of the AA-modified PVA-based resin (a1-1) may be appropriately selected depending on the intended use, but is usually 300 to 4000, particularly 400 to 3000, and more preferably 500 to 2500. Be done. If the average degree of polymerization is too small, sufficient water resistance tends not to be obtained or a sufficient cross-linking rate tends to be obtained. On the contrary, if it is too large, the viscosity of the coating liquid becomes too high and the substrate is coated. It tends to be difficult to coat.

The degree of saponification of the AA-modified PVA-based resin (a1-1) is usually 80 to 100 mol%, and further 85 to 99.9 mol%, particularly 90 to 99.8 mol%, particularly. 95 to 99.8 mol% is preferably used. If the degree of saponification is too low, the water resistance of the obtained crosslinked structure tends to decrease.

The AA group content (hereinafter, may be abbreviated as the degree of AA conversion) in the AA-modified PVA-based resin (a1-1) is usually 0.1 to 20 mol%, and further 1 to 1 It is preferably 15 mol%, particularly preferably 3-10 mol%. If the content is too small, the water resistance tends to decrease or a sufficient cross-linking rate tends to be obtained, and conversely, if the content is too large, the stability of the aqueous solution tends to decrease.

In the present invention, it is preferable that all of the PVA-based resins used are AA-modified PVA-based resins (a1-1), but PVA-based resins other than AA-modified PVA-based resins (a1-1) are used in combination. The content thereof is usually 20% by weight or less, particularly preferably 10% by weight or less, and further preferably 5% by weight or less, based on the AA-modified PVA-based resin (a1-1).
Examples of the PVA-based resin other than the AA-modified PVA-based resin (a1-1) include unmodified PVA-based resins and various modified PVAs obtained by copolymerizing various monomers copolymerizable with vinyl ester-based monomers. A system resin can be mentioned.

Further, the AA-modified PVA-based resin (a1-1) used in the present invention contains an acetate of an alkali metal such as sodium acetate used or by-produced in the manufacturing process (mainly, alkali metal hydroxide used as a saponification catalyst). Organic acids such as acetic acid (derived from the reaction product of acetic acid produced by saponification of polyvinyl acetate) and acetic acid (when an acetic acid ester group is introduced into a PVA-based resin, it is stored in PVA during the reaction with diketen. (Derived from organic acids, etc.), organic solvents such as methanol and methyl acetate (derived from reaction solvents for PVA-based resins, cleaning solvents for producing AA-modified PVA-based resins, etc.) may remain in part.

As a method for producing the AA-modified PVA-based resin (a1-1), for example, it can be produced according to the methods described in paragraphs [0059] to [0065] of JP2010-077385.

[Glyoxylic acid (a2)]
Glyoxylic acid (a2) used in the present invention will be described.
As a method for producing glyoxylic acid (a2) used in the present invention, a known method can be used. Examples thereof include a method of converting glycolic acid into glyoxylic acid by a microorganism. In particular, the method (1) is preferably used in terms of production efficiency.
The glyoxylic acid (a2) produced above is a liquid.

The aldehyde group of glyoxylic acid (a2) in the present invention is acetalized by an alcohol having 3 or less carbon atoms such as methanol and ethanol, and a diol having 3 or less carbon atoms such as ethylene glycol and propylene glycol, and hemiacetal. It includes the modified compounds. The acetal group and the hemiacetal group are easily desorbed from alcohol in water or at high temperature to be in equilibrium with the aldehyde group, and thus react with various monomers and functional groups in the same manner as the aldehyde group to form a cross-linking agent. It functions as.

Glyoxylic acid (a2) used in the present invention may contain raw materials used for its production, impurities contained in the raw materials, by-products during production, and the like, for example, metal hydroxides and fats. It may contain group carboxylic acid salts, glyoxal, oxalic acid, oxalates, glycolic acid, glycolate and the like.

Glyoxal, which is a by-product of the production of glyoxylic acid (a2), may be contained, and the content of such glyoxal is most preferably 0% by weight, but 5% by weight or less, particularly 2% by weight. Hereinafter, it is more preferably 1% by weight or less. When the content of glyoxal is high, for example, the stability of the aqueous solution mixed with the AA-modified PVA-based resin (a1) is lowered, the pot life is shortened, or the crosslinked structure of the obtained AA-modified PVA-based resin (a1) is shortened. However, depending on the storage conditions, it may be colored over time.

[Zirconium compound (a3)]
The zirconium compound (a3) used in the present invention will be described.
Examples of the zirconium compound (a3) used in the present invention include zirconium difluoride, zirconium trifluoride, zirconium tetrafluoride, hexafluorozirconium acid salt (for example, potassium salt), and heptafluorozirconium acid acid salt (for example, Sodium salt, potassium salt or ammonium salt), octafluorozirconium acid salt (eg lithium salt), zirconium fluoride oxide, zirconium dichloride, zirconium trichloride, zirconium tetrachloride, hexachlorozirconium acid salt (eg sodium salt or potassium) Salt), zirconium acetate (zirconyl chloride), zirconium dibromide, zirconium tribromide, zirconium tetrabromide, zirconium bromide, zirconium triiodide, zirconium tetraiodide, zirconium peroxide, zirconium hydroxide, sulfide Zirconium, zirconium sulfate, zirconium p-toluenesulfonate, zirconium sulfate, sodium zirconyl sulfate, acidic zirconium sulfate trihydrate, potassium zirconium sulfate, zirconium selenate, zirconium nitrate, zirconium nitrate, zirconium phosphate, zirconium carbonate, zirconium carbonate Ammonium, zirconium acetate, zirconium acetate, zirconyl ammonium acetate, zirconyl lactate, zirconyl citrate, zirconium stearate, zirconium phosphate, zirconium oxalate, zirconium isopropylate, zirconium butyrate, zirconium acetylacetonate, acetylacetone zirconium butyrate, stear Examples thereof include zirconium acid butyrate, bis (acetylacetonato) dichlorozirconium, and tris (acetylacetonato) chlorozirconium.
Among these compounds, from the viewpoint of reactivity, zirconyl chloride, zirconyl sulfate, sodium zirconyl sulfate, acidic zirconyl sulfate trihydrate, zirconyl nitrate, zirconyl carbonate, zirconyl ammonium carbonate, zirconyl acetate, zirconyl ammonium acetate, zirconyl stearate Is preferable, zirconyl carbonate, ammonium zirconyl carbonate, zirconyl acetate, zirconyl nitrate and zirconyl chloride are more preferable, and zirconyl ammonium carbonate, zirconyl chloride and zirconyl acetate are more preferable.
Further, as the zirconium compound, if it is a solid such as zirconium oxide, it cannot be used in an aqueous coating solution, so a water-soluble compound is usually used.

As the zirconium compound (a3), a commercially available product may be used, or a synthetic product may be used. Specific examples of commercially available products include zircozol ZA-20 (zirconyl acetate), zircozol ZC-2 (zirconyl chloride), zircozol ZN (zirconyl nitrate) (all manufactured by Daiichi Rare Element Chemical Industry Co., Ltd.) and the like. Be done.

[Cross-linked structure (A)]
The crosslinked structure (A) of the present invention is obtained by reacting an active methylene group-containing PVA-based resin (a1), glyoxylic acid (a2) and a zirconium compound (a3).

As a method for producing the crosslinked structure (A), an aqueous solution containing all the components is usually prepared and dried. Examples of the method for mixing the aqueous solution include (i) a method of dissolving each component in water and mixing, and (ii) (a1) to (a3) one or more components are dissolved in water to obtain an aqueous solution. In the method of blending the remaining components into, (iii) (a1) to (a3), one or more of the components are dissolved in water and coated on the base material as a coating liquid to form a coated surface, and the remaining components are formed. Examples of the coating liquid include a method in which the components are also dissolved in water and the coating liquid is applied to the coated surface. Above all, the method (i) is preferable from the viewpoint of viscosity stability of the coating liquid.

The content of glyoxylic acid (a2) used in the present invention is preferably 0.1 to 20 parts by weight, more preferably 0, with respect to 100 parts by weight of the active methylene group-containing PVA-based resin (a1). It is 5 to 10 parts by weight, particularly preferably 1 to 8 parts by weight. If the content of glyoxylic acid (a2) is too high or too low, the water resistance tends to decrease.

The content of the zirconium compound (a3) is preferably 0.1 to 100 parts by weight, particularly 0.5 to 50 parts by weight, and further 1 to 30 parts by weight with respect to 1 part by weight of glyoxylic acid (a2). Parts by weight, particularly 1 to 10 parts by weight, are preferred.
The molar ratio of glyoxylic acid (a2) to zirconium compound (a3) is preferably 1/10 to 10/1 for glyoxylic acid (a2) / zirconium compound (a3), and more preferably 1/5 to 5 It is 1/1, particularly preferably 1/2 to 4/1.
If the content of the zirconium compound (a3) is too small, a sufficient effect tends not to be obtained, and conversely, if it is too large, the water resistance tends to decrease.

The concentration of the aqueous solution of the active methylene group-containing PVA-based resin (a1) used in the present invention is usually 0.05 to 40% by weight, more preferably 0.1 to 30% by weight, and particularly 1 to 20% by weight. The% range is preferably used. If the concentration is too high, the viscosity becomes too high, which may make it difficult to coat the base material or apply it to various processes. On the other hand, if the concentration is too low, the amount of resin tends to be insufficient or it takes a long time to dry.

The concentration of the aqueous solution of glyoxylic acid (a2) is usually preferably in the range of 1 to 50% by weight, particularly 5 to 30% by weight. If the concentration is too low, the amount of water in the obtained mixed aqueous solution increases and it tends to take a long time to dry. On the contrary, if the concentration is too high, the reaction with the AA-modified PVA resin occurs quickly and the mixture is sufficiently mixed. It may not be possible.

The concentration of the aqueous solution of the zirconium compound (a3) is usually 0.1 to 50% by weight, particularly preferably in the range of 0.5 to 15% by weight. If the concentration is too low, it tends to be difficult to adjust the concentration, and if it is too high, it cannot be sufficiently dispersed and the reaction tends not to proceed.

Thus, a crosslinked structure (A) obtained by reacting the active methylene group-containing PVA resin (a1), glyoxylic acid (a2) and the zirconium compound (a3) can be obtained.

The crosslinked structure (A) of the present invention is useful for various applications requiring water resistance, and is particularly suitable for an ink receiving layer of an inkjet recording medium, various adhesive applications, binder applications, coating agent applications, and the like. is there. Above all, the ink receiving layer of the inkjet recording medium is preferably used from the viewpoint of color resistance and crack resistance.

[Inkjet recording medium]
Next, an inkjet recording medium having at least one layer containing the crosslinked structure (A) of the present invention will be described.
The layer containing the crosslinked structure (A) of the present invention is usually used as an ink receiving layer, and if necessary, further contains a pigment such as an inorganic pigment or an organic pigment. The content of the pigment at this time is 50 to 1000 parts by weight with respect to 100 parts by weight of the crosslinked structure (A).

Examples of the above pigments include inorganic pigments such as calcium carbonate, silica, zinc oxide, aluminum oxide, aluminum hydroxide, titanium dioxide, talc, kaolin and clay, nylon resin fillers, urea / formarin resin fillers, and organic starch particles. Pigments are mentioned, and in particular, when imparting gloss to the ink receiving layer, inorganic fine particles such as colloidal silica, vapor phase method silica, and alumina sol are preferably used.

The average particle size of the above-mentioned inorganic fine particles is usually 3 to 200 nm, more preferably 3 to 100 nm, particularly 10 to 50 nm, and if the average particle size is too small, the writing property and the stamping property may be deteriorated. On the contrary, if it is too large, the smoothness of the surface of the glossy layer may be impaired and the glossiness may be lowered.

The coating liquid for the ink receiving layer can be applied by any means such as a roll coater method, an air doctor method, a blade coater method, a bar coater method, a size press method, and a gate roll method. The amount of work is preferably about 0.5 to 10 g / m ² in terms of dry weight, and after coating, the target coating layer is formed by air-drying or light heat treatment.

The inkjet recording medium of the present invention has at least one of the above ink receiving layers, and the other has a supporting base material and other intermediate layers.

Examples of the supporting base material used in the inkjet recording medium of the present invention include paper (paperboards such as Manila balls, white balls, and liners, printing papers such as general high-quality paper, medium-quality paper, and gravure paper, and upper / middle / lower grades. Paper, newspaper paper, release paper, carbon paper, non-carbon paper, glassin paper, synthetic paper, etc.), non-woven fabric, plastic film (polyester film, nylon film, polyolefin film, polyvinyl chloride film, and laminates thereof, etc.), Alternatively, these composite sheets can be used, such as synthetic resin laminated paper.

The thickness of the ink receiving layer is usually preferably adjusted to be 3 to 100 μm, more preferably 5 to 80 μm, and particularly preferably 10 to 50 μm. If the thickness is too thick, the ink receiving layer tends to be cracked, or the weight of the product increases, which is uneconomical. On the contrary, if the thickness is too thin, the ink absorbency tends to decrease.

In the present invention, in addition to the above-mentioned ink receiving layer for an inkjet recording medium, the crosslinked structure (A) can be applied to applications requiring water resistance, and specific examples thereof are as follows. Things can be mentioned.
(1) Paper processing agents Undercoat layer and backcoat layer of various processed papers, color development layer and intermediate layer of sublimation type heat-sensitive writing medium, inorganic fine particle binder of void type inkjet recording medium, ink of swelling type inkjet recording medium Receiving layer, clear coating agent for paper, pigment binder for coated paper, pigment binder for recording medium for electrophotographic, surface coating agent and pigment binder for release paper, heat-resistant ink receiving layer for thermal transfer recording medium, etc.
(2) Adhesive Two-component adhesive, honeymoon type adhesive, adhesive, re-wetting agent, binder for non-woven fabric, binder for building materials (plaster board, fiberboard, etc.), binder for various powder granulation, pressure-sensitive adhesive Agents, adhesives for anionic paints, etc.
(3) Aqueous gel Wastewater treatment carrier, water retention agent, ice pack, bioreactor, air freshener, ground strengthening agent, organ model, artificial joint, artificial muscle, artificial bait, etc.
(4) Coating agent Fiber processing agent, leather finishing agent, paint, antifogging agent, metal corrosion inhibitor, brightener for galvanizing, antistatic agent, conductive agent, temporary paint, temporary protective film, etc.
(5) Films, films, fibers Electrolyte films, packaging films, non-woven fabrics for separators, non-woven fabrics for organic solvent filters, non-woven fabrics for sound absorbing materials, non-woven fabrics for packaging, nanofiber non-woven fabrics, etc.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.
In the example, "part" and "%" mean a weight standard.
The degree of saponification and the degree of polymerization are numerical values measured according to JIS K 6726.

<Example 1>
[Manufacturing of AA-modified PVA-based resin (a1-1)]
3600 parts of PVA (sakenization degree 98 mol%, average degree of polymerization 2400) was charged in a kneader, 540 parts of acetic acid was added thereto, and the mixture was swollen and heated to 60 ° C. with stirring at a rotation speed of 20 rpm, and then diketene 420. The portion was added dropwise over 3 hours and allowed to react for another 1 hour. After completion of the reaction, the mixture was washed with methanol and dried at 70 ° C. for 6 hours to obtain an AA-modified PVA-based resin (a1-1). The degree of AA conversion of the AA-modified PVA-based resin (a1-1) is 4 mol%, the degree of saponification is 98 mol%, and the average degree of polymerization is 2400.

[Preparation of coating liquid for ink receiving layer]
87.5 parts of 10% aqueous solution of AA-modified PVA resin (a1-1) obtained above, 100 parts of fumed silica 35% dispersion, 5.3 parts of 10% aqueous solution of glyoxylic acid (a2), zirconium compound. As (a3), 12.3 parts of a 10% aqueous solution of zirconium acetate was mixed to prepare a coating liquid for an ink receiving layer.

[Preparation of evaluation inkjet recording medium]
As an inkjet recording medium for evaluation, a laminate was prepared by coating on a resin-coated paper as follows. That is, the coating liquid for the ink receiving layer obtained above was applied onto the resin-coated paper and dried at 80 ° C. for 3 minutes to form an ink receiving layer having a film thickness of 20 μm.
The obtained laminate was humidity-controlled for one day in an environment of 23 ° C. and 50% RH to obtain an inkjet recording medium for evaluation. The following evaluation was performed on the obtained evaluation inkjet recording medium.

(Crack resistance)
The ink receiving layer forming surface of the obtained evaluation inkjet recording medium was observed with a microscope and evaluated as follows. The results are shown in Table 1.
Surface crack evaluation method 〇: No cracks are observed ×: Cracks are observed

(Color resistance)
The evaluation inkjet recording medium obtained above was left to stand in an environment of 40 ° C. and 90% RH for 28 days to promote coloring, and then color measurement was performed with a colorimeter. As a measuring device, a spectrocolorimeter CM-3600A (manufactured by Konica Minolta Sensing) was used, and the average value of the transmission method light source D-65 N = 3 was evaluated.
The results are shown in Table 1.

Comparative Example 1
An evaluation inkjet recording medium was obtained in the same manner as in Example 1 except that it did not contain glyoxylic acid (a2), and evaluation was performed in the same manner. The results are shown in Table 1.

Comparative example 2
An evaluation inkjet recording medium was obtained in the same manner as in Example 1 except that 5 parts of a 10% aqueous solution of sodium glyoxylate was blended in place of glyoxylic acid (a2), and evaluation was performed in the same manner. The results are shown in Table 1.

Comparative Example 3
An evaluation inkjet recording medium was obtained in the same manner as in Example 1 except that 5 parts of a 10% aqueous solution of sodium glyoxylate was blended in place of glyoxylic acid (a2), and evaluation was performed in the same manner. The results are shown in Table 1.

Comparative Example 4
An evaluation inkjet recording medium was obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1 except that 5 parts of a 10% aqueous solution of adipic acid dihydrazide was blended in place of glyoxylic acid (a2). The results are shown in Table 1.

Example 1 containing glyoxylic acid and zirconium acetate as a cross-linking agent was excellent in crack resistance and color resistance. On the other hand, Comparative Example 1 in which glyoxylic acid was not blended, Comparative Example 2 in which sodium glyoxylate was contained instead of glyoxylic acid, and Comparative Example 3 were inferior in crack resistance and contained adipic acid dihydrazide as a cross-linking agent. Example 4 was inferior in color resistance.

The crosslinked structure obtained by the production method of the present invention has excellent crack resistance and color resistance, and is extremely suitable as a coating for various substrates, particularly as an ink receiving layer for an inkjet recording medium.

Claims (5)

In the method for producing a crosslinked structure (A) of a polyvinyl alcohol-based resin,
A method for producing a crosslinked structure (A), which comprises reacting a modifying group-containing polyvinyl alcohol resin (a1) having an active methylene group, glyoxylic acid (a2) and a zirconium compound (a3). The production method according to claim 1, wherein the zirconium compound (a3) is zirconium acetate. Claim 1 or claim 1, wherein the content of glyoxylic acid (a2) is 0.1 to 20 parts by weight with respect to 100 parts by weight of the modifying group-containing polyvinyl alcohol-based resin (a1) having an active methylene group. 2. The manufacturing method according to 2. The production method according to any one of claims 1 to 3, wherein the content of the zirconium compound (a3) is usually 0.1 to 100 parts by weight with respect to 1 part by weight of the glyoxylic acid (a2). An inkjet recording medium having at least one layer containing a crosslinked structure (A) obtained by the production method according to any one of claims 1 to 4.