JPH093391A - Hydrophilic coating - Google Patents

Abstract

PURPOSE: To prepare a hydrophilic coating agent having excellent film forming properties and storage stability by using as a main component a polyvinyl alcohol resin (PVA) prepd. by copolymerizing a particular ethylenically unsatd. dicarboxylic acid monoamide (A) in a particular proportion. CONSTITUTION: A vinyl ester copolymer prepd. by copolymerizing 0.1 to 20mol% component (A) represented by the formula I [R0 represents the formula II (n is 1 to 3; R1 to R3 represent H, an alkyl, or aryl, provided that they do not simultaneously represents H and the total number of carbon atoms of R1 to R3 is 4 or more)], e.g. N,N-diisobutylmaleic acid monoamide, and a component (B) of a vinyl ester, e.g. vinyl acetate, is saponified to prepare a hydrophilic coating compound. The proportion of the component (B) is pref. 80 to 99.9mol%. A copolymerization catalyst, e.g. azobisisobutyronitrile, is used. NaOH or the like may be used as a catalyst in the saponification. The saponification may be carried out at 10 to 60 deg.C. The degree of saponification, when the formation of a water-soluble film is contemplated, is pref. 70mol% or more. The degree of polymerization is pref. 300 to 3,000.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrophilic coating agent using polyvinyl alcohol (hereinafter abbreviated as PVA), and more specifically, to a film-forming property and a storage stability using a novel PVA resin. It relates to an excellent hydrophilic coating agent.

[0002]

2. Description of the Related Art Conventionally, a hydrophilic coating agent using PVA has various properties such as antistatic property, antifogging property and water solubility, so that it has been used for coating plastic materials for building materials and agricultural films. It is widely used for film forming applications such as coatings for cosmetics, cosmetics packs, and temporary coatings for surface protection of various substrates such as metals and plastics.

[0003]

However, the physical properties of the formed film are improved by various means such as modification of PVA, which is the main component of the coating agent, but the storage stability of the hydrophilic coating agent comprising an aqueous solution of PVA is improved. There was still room for improvement in properties and film formation speed during film formation.

[0004]

As a result of intensive studies to solve the above drawbacks, the present inventor has found that an ethylenic compound containing an N, N-dibranched alkylamide component represented by the following chemical formula 1 as a modifying component. Saturated dicarboxylic acid monoamide (A)
PVA containing 0.1 to 20 mol% of a copolymer component
The present inventors have found that a hydrophilic coating agent using a base resin has excellent storage stability and a good film-forming rate, and has reached the present invention.

Embedded image Here, R ₀ is shown in Chemical formula 2.

Embedded image (However, n is 1 to 3, R _{1 to} R ₃ are each hydrogen or an alkyl group or an aryl group, and two or more are not hydrogen at the same time, and the total number of carbon atoms of R _{1 to} R ₃ is 4 That is all.)

Hereinafter, the present invention will be described in detail. The modified PVA (hereinafter sometimes simply referred to as modified PVA) -based resin of the present invention contains the (A) unit as an essential component as described above, and the (A) unit is the N, N-dicarboxylic acid represented by Chemical Formula 1 above. modified carbon number of functional groups of R ₁ to R ₃ in having the functional group of R ₁ to R ₃ in ethylenically unsaturated dicarboxylic acid monoamide units containing branched alkyl amide component, during saponification is less than 4 The stability of the group and the storage stability of the hydrophilic coating agent are poor, and the carbon number is preferably 4 to 16.

As the copolymerizable monomer containing the (A) unit, N, N-diisobutyl maleic acid monoamide, N, N-diisoamyl maleic acid monoamide, N, N
N-di (2-ethylhexyl) maleic acid monoamide,
N, N-diisobutyl fumaric acid monoamide, N, N-diisoamyl fumaric acid monoamide, N, N-di (2-ethylhexyl) fumaric acid monoamide, N, N-diisobutylitaconic acid monoamide, N, N-diisoamylitaconic acid Monoamide, N, N-di (2-ethylhexyl) itaconic acid monoamide, N, N-diisobutyl citraconic acid monoamide, N, N-diisoamyl citraconic acid monoamide, N, N-di (2-ethylhexyl) citraconic acid monoamide, etc. Of these, N, N-diisobutyl maleic acid monoamide is preferably used. The carboxylic acid component in the unit (A) of the modified PVA-based resin of the present invention is a free carboxyl group or a salt thereof.

Usually, in order to produce the PVA resin of the present invention, the vinyl ester copolymer obtained by copolymerizing (A) and the vinyl ester (B) is saponified. Examples of (B) include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, and the like, and vinyl acetate is preferable from the economical viewpoint.

With respect to the ratio of each unit of the modified PVA-based resin, 0.1 to 0.1 of the ethylenically unsaturated dicarboxylic acid monoamide unit (A) containing the N, N-dibranched alkylamide component shown in Chemical formula 1 above is used. 20 mol%, preferably 0.3 to 10 mol%, and the total range of vinyl ester unit (B) and vinyl alcohol unit (C) is suitably 80 to 99.9 mol%. The degree of saponification (the ratio of the vinyl alcohol unit (C) to the total amount of the vinyl ester unit (B) and the vinyl alcohol unit (C)) is not particularly limited, but when the formed film is water-soluble. It is preferably 70 mol% or more, and particularly preferably 75 mol% or more.

The degree of polymerization of the modified PVA resin used in the present invention is not particularly limited, but is preferably 300 to 3000, more preferably 500 to 2500, and the degree of polymerization is 30.
If it is less than 0, the viscosity of the hydrophilic coating agent decreases, and conversely 3000
If it exceeds, the viscosity of the hydrophilic coating agent increases, and in either case, workability tends to be poor.

Next, the method for producing the modified PVA resin of the present invention will be described. The modified PVA-based resin of the present invention saponifies the copolymer of the above-mentioned ethylenically unsaturated dicarboxylic acid monoamide monomer containing the N, N-dibranched alkylamide component represented by Chemical Formula 1 and vinyl ester. Obtained by

Such ethylenically unsaturated dicarboxylic acid monoamides (A) include maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid,
An ethylenically unsaturated dicarboxylic acid such as citraconic anhydride or an anhydride thereof, or an acid halide thereof is used with a secondary amine represented by Chemical formula 3 without catalyst or with a suitable acid catalyst (sulfuric acid,
It can be obtained by reacting in the presence of hydrochloric acid, a protonic acid such as P-toluenesulfonic acid). Such amines include diisobutylamine, diisoamylamine,
Di (2-ethylhexyl) amine may be mentioned.

Embedded image Here, R ₀ is shown in Chemical formula 2.

Embedded image (However, n is 1 to 3, R _{1 to} R ₃ are each hydrogen or an alkyl group or an aryl group, and two or more are not hydrogen at the same time, and the total number of carbon atoms of R _{1 to} R ₃ is 4 or more.)

The copolymerization reaction can be arbitrarily selected from known polymerization methods such as radical polymerization, for example, bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc., but solution polymerization is preferred from the industrial viewpoint. Further, any method such as batch polymerization and continuous polymerization can be adopted. There are no particular restrictions on the method of charging the monomers during the polymerization, and any method such as batch charging, divided charging, continuous charging may be employed. Branched alkyl acrylamide and ethylenically unsaturated carboxylic acid or salts thereof are used as PVA molecules. A divided charging method or a continuous charging method is advantageous in that it can be uniformly introduced into the inside.

As a catalyst for the copolymerization, known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, and lauryl peroxide, and low-temperature catalysts such as azobisdimethylvaleronitrile and azobismethoxydimethylvaleronitrile. An active radical catalyst or the like is used. Further, the reaction temperature is not particularly limited and is appropriately selected from the range well known to those skilled in the art.

In such polymerization, other unsaturated monomers copolymerizable with the monomers other than the above-mentioned two components, such as alkyl vinyl ether, methacrylamide, ethylene, propylene and α, can be used as long as they do not impair the gist of the present invention. −
Olefin such as hexene, α-octene, α-dodecene, α-octadodecene, nitriles such as acrylonitrile and methacrylonitrile, alkyl acrylate, alkyl methacrylate, alkyl crotonic acid, dialkyl maleate, dialkyl itaconate A small amount of ester, citraconic acid dialkyl ester, fumaric acid dialkyl ester and the like may be copolymerized.

The copolymer obtained by such a method is then saponified. As the saponification method, any method such as kneader saponification, continuous saponification, and pearl saponification can be adopted. In the saponification step, the residual monomer is expelled as necessary, and then saponification is performed according to a conventional method. To be done. Examples of the catalyst used for saponification include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate, alkali catalysts such as alcoholate, sulfuric acid, hydrochloric acid and the like. An acid catalyst is used.

The saponification reaction temperature is not particularly limited and is usually selected in the range of 10 to 60 ° C, preferably 20 to 50 ° C. After the saponification reaction is completed, the target modified PVA-based resin is obtained by neutralizing, washing with alcohol or the like, if necessary, and drying. Next, a hydrophilic coating agent using the obtained modified PVA-based resin will be described. The hydrophilic coating agent of the present invention is an aqueous solution using the modified PVA-based resin, and contains 1 to 50% by weight, preferably 5 to 30% by weight of the PVA-based resin. Further, in the hydrophilic coating agent of the present invention, as a solvent other than the above, alcohol such as methanol and ethanol is used as a solvent for the purpose of shortening the drying time and the like, and a cellulose derivative is blended when peelability is required. In some cases, as other additives, plasticizers (glycols such as ethylene glycol, propylene glycol, glycerin, polyethylene glycol and their fatty acid esters), perfumes and bactericides may be contained in appropriate amounts.

In forming a film using such a hydrophilic coating agent, a known method can be adopted, and specifically, a gravure coater, a reverse roll coater, an air knife coater, a spray or the like is applied to the surface of the substrate. Examples thereof include a coating method, a method of forming a film on the surface of an object such as a base material by dipping, and a method of applying by hand like a cosmetic pack. The hydrophilic film obtained by such a method is excellent in film forming property, and it is a film for coating of plastic materials for building materials and agricultural films, cosmetic pack agents, surface protection of various base materials such as metals and plastics. Very useful for coating applications such as temporary coatings.

[0018]

[Working] The hydrophilic coating material of the present invention is made of a specific modified PVA.
Since it uses a system resin, it has excellent film-forming properties and storage stability. It can be used as a coating for building materials or packaging plastic materials, coating films for agricultural films, cosmetic packs, and various base materials such as metals and plastics. It is very useful for coating formation such as temporary coating for surface protection of materials.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, “%” and “part” mean on a weight basis unless otherwise specified. (Production of modified PVA resin) 500 parts of maleic anhydride,
65.9 parts of diisobutylamine was charged into a flask, and the reaction was carried out at 60 ° C. for 2 hours while stirring. After completion of the reaction, the reaction product was recrystallized to obtain the compound represented by Chemical formula 4.

Embedded image R ₀ is shown in Chemical formula 5.

Embedded image The yield was 95%.

A polymerization vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 1000 parts of vinyl acetate and 450 parts of methanol, and the temperature was raised under a nitrogen stream while stirring to obtain 0.6 of azobisisobutyronitrile at 62 ° C. A solution prepared by dissolving 1 part in 19.4 parts of methanol was added to initiate polymerization.
Polymerization was performed while continuously adding dropwise 272 parts of a methanol solution containing 27.2 parts of the compound N, N-diisobutylmaleic acid monoamide obtained above from the polymerization initiation point over 5 hours while the vinyl acetate ester polymerization rate was 50%. The polymerization was terminated when the percentage reached. Then, the 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. Then, the solution was diluted with methanol to adjust the concentration to 30% and charged in a kneader, and sodium hydroxide was added to neutralize while keeping the solution temperature at 35 ° C. To this, sodium hydroxide was further added in an amount of 30 mmol with respect to the vinyl acetate unit in the polymer and kneaded. As the saponification reaction proceeded, a saponified product was deposited and finally became a particulate form. The resulting modified PVA-based resin was filtered, washed well with methanol, and dried in a hot air drier to obtain the desired product. The modified PVA resin thus obtained was extracted and washed with methanol using a Soxhlet extractor, and the degree of modification with diisobutyl maleic acid monoamide was ¹ H-N.
As a result of analysis by MR, the degree of modification was 2.0 mol%.
The saponification degree of the modified PVA-based resin was 90 mol% when analyzed by quantifying the amount of alkali consumption required for hydrolysis of the residual vinyl acetate unit. This modified PV
The viscosity of a 4% aqueous solution of A type resin measured by B type viscometer is 2
The polymerization degree was 1700 at 7.1 cps / 20 ° C.

Example 1 100 parts of the above-mentioned modified PVA-based resin, 20 parts of glycerin,
An aqueous PVA solution containing 20 parts of hydroxyethyl cellulose, 50 parts of ethanol and 550 parts of water was prepared to obtain the hydrophilic coating agent of the present invention. Next, the coating agent is applied to the surface of the corrugated board by a bar coater so that the dry thickness is about 100 μm, and the coating is left at 20 ° C. and 65% RH to examine the rate of film formation. The sex was evaluated. ○ --- The film formation is completed in less than 10 minutes, and the film surface is not sticky. × −−− Even after 10 minutes or more, the film formation was insufficient and the film surface remained sticky.

After the coating agent was left at 40 ° C. for 1 month, the viscosity was measured to examine the storage stability of the aqueous solution and evaluated as follows. ○ --- Viscosity change is less than 5% △ --- Viscosity change is 5 to less than 20% X --- Viscosity change is 20% or more The viscosity change (%) is the treatment for the viscosity before the treatment. The change rate (%) of the viscosity afterwards is shown. When the face was packed using the coating agent as a pack, the drying property was good and the skin became glossy.

Examples 2 to 7 and Comparative Examples 1 to 6 Ethylenically unsaturated dicarboxylic acid monoamides were synthesized under the components and conditions shown in Table 1, and various ethylenically unsaturated dicarboxylic acid monoamides and vinyl acetate were obtained. The copolymerization of the above-mentioned (modified PV
Various modified PVA-based resins shown in Table 2 were copolymerized with vinyl acetate (in Comparative Example 6, no modifying monomer was added) and saponified by the same procedure as in (Production of A-based resin). A hydrophilic coating agent was prepared in the same manner as in Example 1 using the PVA-based resin, and evaluated in the same manner. Table 4 shows the evaluation results of the examples and the comparative examples.

[0024]

[Table 1] Synthetic conditions of ethylenically unsaturated dicarboxylic acid monoamide Synthetic monoamic acid amine Temperature time Yield (part) (part) (° C) (hr) (%) Di-BMMAm Diisobutylamine maleic acid 60 2 95 Di- BIMAm Itaconic anhydride Diisobutylamine 60 295 Di-AMMAm Maleic anhydride Diisoamylamine 60 2 97 D-EHMMAm Maleic anhydride Di (2 ethylhexyl) amine 60 2 92 Dn-DMMAm Maleic anhydride di-n-Fluoroylamine 60 2 95 N-n-OMMAm n-octylamine maleic anhydride 60 290 Note) Abbreviations are as follows. D-i-BMMAm; N, N-diisobutyl maleic acid monoamide D-i-BIMAm; N, N-diisobutylitaconic acid monoamide D-i-AMMAm; N, N-diisoamyl maleic acid monoamide D-EHMMAm; N, N -Di (2 ethylhexyl) maleic acid monoamide D-n-DMMAm; N, N-di-n-propyl maleic acid monoamide N-n-OMMAm; N-n-octyl maleic acid monoamide

[0025]

[Table 2] Type of monomer copolymerized with vinyl acetate, charged amount and polymerization rate (A) Monomer Polymerized rate type Charged amount (mol%) (%) Example 1 D-i-BMMAm 2. 0 50 〃 2 D-i-BMMAm 0.5 60 〃 3 D-i-BMMAm 8.0 47 〃 4 D-i-BIMAm 2.0 50 50 〃 5 D-i-AMMAm 2.0 55 〃 6 D- EHMMAm 2.0 45 〃 7 D-BMMAm 2.0 50 Comparative Example 1 D-n-DMMAm 2.4 53 〃 2 N-n-OMMAm 2.5 52 〃 3 MRM 3.0 55 〃 4 AMPS 2.0 55 〃 5 3M 2.0 60 〃 6 --- 87

Note) The charged amount represents the charged mole fraction (mol%) of the monomer (A) with respect to the total charged amount of the monomers. Abbreviations are as follows. D-i-BMMAm; N, N-diisobutyl maleic acid monoamide D-i-BIMAm; N, N-diisobutylitaconic acid monoamide D-i-AMMAm; N, N-diisoamyl maleic acid monoamide D-EHMMAm; N, N -Di (2 ethylhexyl) maleic acid monoamide D-n-DMMAm; N, N-di-n-propyl maleic acid monoamide N-n-OMMAm; N-n-octyl maleic acid monoamide 3M; monomethyl maleate MRM; mono ( Diisopropylmethyl) malate AMPS; N-sulfoisobutylene acrylamide sodium

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

The hydrophilic coating agent of the present invention has a specific modified P content.
Since it uses VA-based resin, it has excellent film-forming properties and storage stability. It is a coating film for plastic materials for construction materials or packaging, coating films for agricultural products, cosmetic packs,
It is very useful for film formation applications such as temporary films for surface protection of various substrates such as metals and plastics.

Claims (1)

[Claims] 1. A polyvinyl alcohol-based polymer containing the ethylenically unsaturated dicarboxylic acid monoamide (A) represented by the following chemical formula 1 as a copolymerization component in an amount of 0.1 to 20 mol%, wherein the ethylenically unsaturated dicarboxylic acid is A hydrophilic coating material comprising a polyvinyl alcohol-based resin as a main component, which is obtained by copolymerizing a monoamide (A). Embedded image Here, R ₀ is shown in Chemical formula 2. Embedded image (However, n is 1 to 3, R _{1 to} R ₃ are each hydrogen or an alkyl group or an aryl group, and two or more are not hydrogen at the same time, and the total number of carbon atoms of R _{1 to} R ₃ is 4 That is all.)