JPH093389A - Hydrophilic coating - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a hydrophilic coating agent having excellent film-forming properties and storage stability. [Structure] Specific branched alkyl acrylamide
The main component is a novel polyvinyl alcohol resin containing 10 to 10 mol% and 0.1 to 10 mol% of at least one ethylenically unsaturated carboxylic acid or salt thereof.

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]

Means for Solving the Problems As a result of intensive studies to solve the above drawbacks, the present inventors have found that a branched alkyl acrylamide (A) represented by the following chemical formula 1 as a modifying component is 0.1 to 10 mol% ( Preferably 0.1-5 mol%),
Ethylenic monomer having hydrophilic group (preferably at least 1 of ethylenically unsaturated carboxylic acid or salt thereof)
Seed) (B) 0.1 to 10 mol% (preferably 0.1 to
The present inventors have found that a hydrophilic coating agent using a novel PVA-based resin obtained by copolymerization (5 mol%) 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 and R ₁ is hydrogen or a methyl group.
R _{2 to} R ₄ are hydrogen, an alkyl group or aryl
Each represents a group, and at the same time two or more are not hydrogen but R
The total number of carbon atoms of _{2 to} R ₄ is 4 or more. )

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) and (B) units as essential components as described above, and the (A) unit is represented by the above Chemical Formula 1. N, N-di-branched alkyl acrylamide components R _{1 to} R ₄
When the number of carbon atoms of the functional groups R _{2 to} R ₄ is less than 4, the stability of the modifying group during saponification and the storage stability of the hydrophilic coating agent are poor, and the number of carbon atoms is preferably Is 4-16
It is.

The copolymerizable monomer containing the (A) unit is N, N-diisobutylacrylamide,
N, N-di (2-ethylhexyl) acrylamide,
Examples thereof include N, N-diisoamylacrylamide, N, N-diisobutylmethacrylamide, N, N-di (2-ethylhexyl) methacrylamide, and N, N-diisoamylmethacrylamide, and preferably N, N-
Diisobutyl acrylamide is preferably used. Examples of the copolymerizable monomer containing the unit (B) include acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, aconitic acid, fumaric acid, maleic acid monoester, and itaconic acid monoester. Examples thereof include esters, citraconic acid monoesters, fumaric acid monoesters, maleic anhydride, itaconic anhydride, citraconic anhydride, and salts thereof.

Usually, in order to produce the modified PVA-based resin of the present invention, a vinyl ester-based copolymer obtained by copolymerizing (A) and (B) with a vinyl ester (C) is saponified.
Examples of (C) 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, the N, N-di-branched alkyl acrylamide unit (A) shown in Chemical formula 1 above is 0.1 to 10 mol%, preferably 0.1 to 5 mol%. Mol%, 0.1-10 mol% of the ethylenic monomer (B) having a hydrophilic group, preferably 0.1-
It is suitable that the total amount of 5 mol%, the vinyl ester unit (C) and the vinyl alcohol unit (D) is 80 to 99.8 mol%. The degree of saponification (the ratio of the vinyl alcohol unit (D) to the total amount of the vinyl ester unit (C) and the vinyl alcohol unit (D)) is not particularly limited, but when the formed film is water-soluble. 70 mol%
It is preferably at least above, and particularly preferably at least 75 mol%.

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 3.
If it is less than 00, the viscosity of the hydrophilic coating agent is lowered, and conversely it is 300.
If it exceeds 0, 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 comprises an N, N-di-branched alkyl acrylamide monomer having a specific structural unit represented by the above chemical formula 1 and an ethylenic monomer having a hydrophilic group (ethylenically unsaturated carboxylic acid). It is obtained by saponifying a copolymer of an acid or at least one salt thereof) and a vinyl ester. The copolymerization reaction can be arbitrarily selected from known polymerization methods in radical polymerization, such as 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 three components, such as alkyl vinyl ether, methacrylamide, ethylene, propylene, α-hexene, unless the purpose of the present invention is impaired, α
-Olefins such as octene, α-dodecene, α-octadodecene, nitriles such as acrylonitrile and methacrylonitrile, alkyl acrylates, alkyl methacrylates, alkyl crotonic acid esters, dialkyl maleates, dialkyl itaconic acid, citracone A small amount of 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 from the range of 10 to 60 ° C., preferably 20 to 50 ° C., and the saponification reaction is carried out for 5 to 240 minutes. The target modified PVA-based resin is obtained by neutralizing, washing with alcohol, etc., 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 containing the modified PVA-based resin.
-50% by weight, preferably 5-30% by weight. 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. Specifically, it is applied to the surface of the substrate by a gravure coater, a reverse roll coater, an air knife coater, a spray or the like. 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.

[0016]

[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.

[0017]

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-based resin) 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 raise azobisisobutyrate at 62 ° C. Ronitrile 0.
A solution prepared by dissolving 4 parts in 19.6 parts of methanol was added to initiate polymerization. From the polymerization initiation point, 8.0 parts of monomethyl maleate and N, N-diisobutylacrylamide 22.
Polymerization was performed while 61.2 parts of a methanol solution in which 6 parts were dissolved was continuously added dropwise over 5 hours, and the polymerization was terminated when the polymerization rate of vinyl acetate was 50%. 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 resulting modified PVA-based resin was extracted and washed with methanol using a Soxhlet extractor, and the modification degree with N, N-diisobutylacrylamide was analyzed by ¹ H-NMR. As a result, the modification degree was 2.0 mol%. . Further, the degree of modification of monomethyl maleate was analyzed by acid content determination by titration of the copolymer before saponification, the degree of modification was 1.0 mol%, and the degree of saponification of the modified PVA-based resin was The amount of alkali consumption required for the hydrolysis of the residual vinyl acetate unit was analyzed to be 90 mol%. The viscosity of the 4% aqueous solution of this modified PVA-based resin measured by a B-type viscometer is
The degree of polymerization was 1700 at 28.2 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 above coating agent was left at 40 ° C. for 1 month, the viscosity was measured in order 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 8 Copolymerization with vinyl acetate (in Comparative Example 8 in the same manner as in the above (Production of Modified PVA Resin)) with the components and charging amounts shown in Table 1. , Without adding a modifying monomer) and saponification to produce various modified PVA-based resins shown in Table 2,
Using the PVA-based resin, a hydrophilic coating agent was prepared in the same manner as in Example 1 and evaluated in the same manner. Table 3 shows the evaluation results of the examples and comparative examples.

[0022]

[Table 1] Type of monomer copolymerized with vinyl acetate, charged amount and polymerization rate (A) Monomer (B) Monomer polymerization rate Species Charged amount Species charged amount (%) (mol%) ( Mol%) Example 1 D-i-BAAm 2.0 3M 1.0 50 〃 2 D-i-BAAm 2.0 3M 1.0 50 〃 3 D-i-BAAm 8.0 3M 4.0 46 〃 4 D-i-BAAm 0.5 3M 0.5 54 〃 5 D-i-BAAm 2.0 Itaconic acid 1.0 52 〃 6 D-i-PAAm 2.0 3M 1.0 54 〃 7 D-EHAAm 2.0 3M 1.0 46 Comparative Example 1 D-i-BAAm 2.0 −−− 50 〃 2 Nn-OAAm 2.5 3M 1.0 47 〃 3 VeoVa-10 1.0 AS 1.0 55 〃 4 VeoVa-10 3.0 Itaconic acid 1.0 50 〃 5 MRM 3. 0 --- 55 〃 6 --- AMPS 2.0 55 〃 7 --- 3M 1.0 60 〃 8 --- --- --87

Note) The charged amount represents a charged mole fraction (mol%) of each of the monomers (A) or (B) with respect to the total charged amount of the monomers. Abbreviations are as follows. D-i-BAAm; N, N-diisobutyl acrylamide D-i-PAAm; N, N-diisopentyl acrylamide D-EHAAm; N, N-di (2 ethylhexyl) acrylamide Nn-OAAm; N-n- Octyl acrylamide 3M; monomethyl maleate AS; sodium allyl sulfonate MRM; mono (diisopropylmethyl) malate VeoVa-10; monomer shown by the following chemical formula 3

Embedded image _{(Wherein, R 1, R 2, R} 3 is R ₁ is hydrogen or an alkyl radical, R
The total number of carbon atoms of ₂ , R ₃ is 10 on average. ) AMPS; sodium N-sulfoisobutylene acrylamide

[0024]

TABLE 2 content of the content of denatured P V A saponification degree (A) the monomer (B) monomer of 4% Viscosity (mol%) (mol%) (mol%) (cps) Example 1 90 2.0 1.0 28.2 〃 2 80 2.0 1.0 2.0 29.0 〃 3 85 7.7 4.0 3.0 31.1 〃 4 90 0.5 0.5 27.7 〃 5 75 2.0 1.0 28.5 〃 6 90 2.0 2.0 18.0 〃 7 75 2.0 2.0 1.0 13.5 Comparative example 1 90 2.0-27.8 〃 2 85 2.0 1.0 28.3 〃 3 75 75 0.8 1.0 27.1 〃 4 90 90 2.0 1.0 25.3 〃 5 90 2.0-28.1 〃 6 90-2.0 29.1 〃 7 90-1.0 23.1 〃 8 90--27.8

[0025]

[Table 3]

[0026]

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 (2)

[Claims] 1. An N, N-dibranched alkyl acrylamide (A) represented by the following chemical formula 1 is 0.1 to 10 mol%, and an ethylenic monomer having a hydrophilic group (B) is 0.1 to 10: A hydrophilic coating agent comprising a polyvinyl alcohol-based resin as a main component, which is obtained by copolymerization in mol%. Embedded image Here, R ₀ is shown in Chemical formula 2. Embedded image (However, n is 1 to 3 and R ₁ is hydrogen or a methyl group.
R _{2 to} R ₄ are hydrogen, an alkyl group or aryl
Each represents a group, and at the same time two or more are not hydrogen but R
The total number of carbon atoms of _{2 to} R ₄ is 4 or more. ) 2. The hydrophilic coating agent according to claim 1, wherein the ethylenic monomer (B) having a hydrophilic group is at least one kind of ethylenically unsaturated carboxylic acid or a salt thereof.