JPH08325515A - Water-soluble protecting coating agent and coating with the same - Google Patents

Abstract

PURPOSE: To obtain a water-soluble protecting coating agent, excellent in moisture resistance, having protecting functions on the product surface in use and capable of manifesting the adhesive strength so as not to readily peel and easily removable after use by washing by blending a polydioxolane therein. CONSTITUTION: The water-soluble protecting coating agent is obtained by placing 1,3-dioxolane in a four neck flask equipped with a stirrer, a cooler, a thermometer and a nitrogen introduction pipe, dropping a 5wt.% solution of phosphotungtic acid in methyl ethyl ketone as an initiator thereinto under cooling with ice, heating the mixture at 50 deg.C, polymerizing the 1,3-dioxolane, then adding triethylamine thereto, terminating the reaction, providing a polydioxolane having >=60wt.% structural unit of the formula [(n) is an integer of >=1] in the molecule, subsequently diluting the polydioxolane with water and affording a 30% aqueous solution. Thereby, the resultant coating agent is capable of forming a coating layer, excellent in moisture resistance, has protecting functions on the product surface in use and the adhesion strength so as not to readily peel and easily peelable and removable by washing with water after the use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-soluble protective coating agent and a coating method using the same.

A water-soluble protective coating agent is used for the purpose of preventing damage to the product surface of a plastic such as polyethylene, polymethylmethacrylate or melamine resin, or a metal plate such as mild steel or stainless steel during secondary processing, transportation or storage. It's being used.

[0003]

2. Description of the Related Art Conventionally, as these protective coating methods, generally, polyethylene, polypropylene, polyethylene terephthalate, etc. are adhered to a substrate via an adhesive layer, methyl vinyl pyridine / methyl acrylate / methacrylic acid copolymer, There has been a method of forming a coating layer by dissolving a film-forming polymer compound such as ethyl cellulose in an organic solvent having high volatility, applying the solution, and then drying the solvent. However, in the case of the former method,
There is a problem that the adhesive force between the pressure-sensitive adhesive layer and the base material increases with time, and a part of the pressure-sensitive adhesive layer remains on the base material side upon peeling,
Further, in the latter method, since an organic solvent is used, there is a problem in that safety is required and a large amount of cost is required for exhaust equipment in a workplace.

As a means for solving the above problems, for example, JP-A-2-68176 proposes a method of forming a coating layer by applying a coating agent comprising an acrylic emulsion or a polyvinyl alcohol aqueous solution and then drying it. Has been done. However, the coating method as described above is effective for protecting the surface of a product having a simple shape such as a flat plate, but in a product having a complicated shape, the coating agent remains in the recessed portion after application,
There is a problem that the formed coating layer is difficult to remove. If the coating layer is water-insoluble, it is necessary to use an organic solvent in order to remove the coating layer, which is unfavorable for safety and hygiene. Further, if the coating layer is water-soluble, the coating layer can be removed by washing with water, but the stability of the formed coating layer under high humidity is poor and the surface exhibits tackiness. There was a problem.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has excellent moisture resistance,
At the same time, it has a function of protecting the product surface during use, has an adhesive strength that does not easily peel off, and is water-soluble to form a coating layer that is easy to peel off and remove by washing after use. It is to provide a protective coating agent.

Another invention of the present invention is excellent in moisture resistance,
At the same time, it has a function of protecting the surface of the product when in use, has an adhesive strength to the extent that it cannot be easily peeled off, and is suitable for forming a coating layer that is easy to peel off and remove by washing after use. It is to provide a coating method.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above problems can be solved by using a water-soluble protective coating agent containing polydioxolane, and complete the present invention. Came to.

That is, the present invention is a water-soluble protective coating agent containing polydioxolane.

Another aspect of the present invention is a coating method, which comprises applying the water-soluble protective coating agent to a substrate.

[0010]

The water-soluble protective coating agent of the present invention includes
In addition to homopolymers of polydioxolane, block or random copolymers obtained by copolymerizing 1,3-dioxolane and 1,3-dioxolane with a copolymerizable monomer,
The homopolymers and / or copolymers with other resin composition obtained by mixing the polymer and the like, in particular, the following general formula (1): - (- CH 2 -O-CH 2 CH 2 -O-) n It is preferable that 60% by weight or more of the structural unit represented by the formula (in the formula, n represents an integer of 1 or more) is contained in the molecule for sufficient water solubility and moisture resistance.

Examples of the monomer copolymerizable with 1,3-dioxolane include unsaturated hydrocarbons such as styrene, ethylene and propylene; (meth) acrylic acid such as (meth) acrylic acid and (meth) acrylic acid ester. Compounds: vinyl acetate; cyclic ethers such as trioxane, ethylene oxide, propylene oxide and tetrahydrofuran; lactones such as γ-butyrolactone, glycolide, lactide, ε-caprolactone, ε-caprolactam and lactams. Examples of the polymer used as a mixture with the dioxolane homopolymer and copolymer include:
Examples thereof include poly (meth) acrylic acid, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, starch, chitin, chitosan, carboxymethyl cellulose, and cellulose acetate.

The protective coating agent of the present invention may be the above polydioxolane as it is, but is usually prepared by diluting with a solvent. The solvent when diluted with a solvent is not particularly limited, but water, acetone, isopropyl alcohol, toluene, tetrahydrofuran, chloroform, dioxane and other highly volatile solvents are preferable, and among them, water, isopropyl alcohol, and toluene are It is particularly preferable because it has high safety. The polydioxolane concentration in that case is not particularly limited, but is usually 5 to 60% by weight, preferably 10 to 50% by weight. If the solution concentration is less than 5% by weight or higher than 60% by weight, the coatability and handleability may deteriorate.

The coating method of the protective coating agent of the present invention is not particularly limited, but usually a coater,
A method of applying using a spray, a method of melt applying,
There is a method of sticking via an adhesive layer. However, in the case of interposing the pressure-sensitive adhesive layer, it is desirable to use a water-soluble pressure-sensitive adhesive in order to facilitate peeling and washing after use.

The protective coating agent containing the polydioxolane of the present invention may be used in a state of being mixed with additives such as various stabilizers and nucleating agents.

The protective coating method of the present invention is characterized by applying the protective coating agent to a substrate.

The method for applying the protective coating agent to various substrates is not particularly limited, but usually, the protective coating agent of the present invention is diluted with a solvent and the protective coating agent of the present invention is melted. And the like. The coating method is also not particularly limited, and means such as gravure coating, roll coating, air knife coating and spray coating can be used. The concentration of the solution used when the protective coating agent is diluted with a solvent is not particularly limited as described above, but is usually 5 to 60% by weight, preferably 10 to 50% by weight.
The melting temperature when the protective coating agent is used by melting is not particularly limited, but usually 70 ° C to 180 ° C.
C, preferably 80 to 150 ° C. Melting temperature is 7
When the temperature is lower than 0 ° C, the melt viscosity is remarkably high, and when the temperature is higher than 180 ° C, the melt viscosity is remarkably lowered, and thus the coatability may be deteriorated.

The thickness of the protective coating layer formed on the surface of the substrate is 5 to 50 μm, preferably 2 when dry.
It is 0 to 30 μm. If the thickness is less than 5 μm, the strength as a protective film may be insufficient, while
If the thickness exceeds 50 μm, the coatability may deteriorate.

The base material which can be coated with the protective coating agent of the present invention is not particularly limited, but polyethylene, polypropylene, polyethylene terephthalate, polymethylmethacrylate, rigid polyvinyl chloride, melamine resin, ABS resin, urethane resin and the like can be used. plastic,
Examples include metals such as mild steel, stainless steel, and aluminum.

[0019]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

<Example 1> 60.00 g of 1,3-dioxolane (manufactured by Osaka Organic Chemical Industry Co., Ltd.) was placed in a four-necked flask equipped with a stirrer, a cooler, a thermometer and a nitrogen inlet tube.
The internal temperature was adjusted to 3 ° C with an ice water bath at 0 ° C. To this, 0.6 ml of a 5 wt% methyl ethyl ketone solution of phosphotungstic acid obtained by drying at 120 ° C. for 20 hours under reduced pressure was added as a polymerization initiator with stirring. The polymerization started immediately after the addition of the initiator, and reached an exothermic peak of 45 ° C. in about 6 minutes. After changing the ice water bath to a warm water bath at 50 ° C. and keeping the reactor warm to age the polymer for 15 minutes, 5 ml of a 1,3-dioxolane solution of triethylamine having a concentration of 0.1 wt% was added to stop the reaction. . The obtained reaction product was reacted at 110 ° C. for 5 hours at 1 Torr using a vacuum dryer to remove volatile matter. The polystyrene equivalent number average molecular weight of the obtained polydioxolane measured by size exclusion chromatography was 230,000.

The polydioxolane (1) obtained as described above was diluted with water to give a 30% aqueous solution, which was used as a protective coating agent (1).

60 mm of the protective coating agent (1)
10 x 120 mm x 5 mm rigid polyvinyl chloride substrate
After applying using a mil applicator, 23 ° C, 6
The protective coating layer of Example 1 was obtained by air-drying at 0% RH for 24 hours.

The resulting protective coating layer was applied at 25 ° C. and 9
It was placed in a thermo-hygrostat of 5% RH, and the state of change of the coating layer surface was observed with time. The measurement results are shown in Table 1.

Comparative Example 1 A 30% aqueous solution of polyethylene oxide (“R-150” manufactured by Meisei Chemical Co., Ltd.) was used in place of the protective coating agent (1) obtained in Example 1. Is the same as Example 1 and Comparative Example 1
A protective coating layer of

The resulting protective coating layer was applied at 25 ° C. and 9
It was placed in a thermo-hygrostat of 5% RH, and the state of change of the coating layer surface was observed with time. The measurement results are shown in Table 1.

Example 2 The protective coating agent (1) obtained in Example 1 was applied to a 60 mm × 120 mm × 1 mm mild steel plate using a 10 mil applicator and then at 23 ° C. and 60% RH for 24 hours. The protective coating layer of Example 2 was obtained by air-drying. The resulting protective coating layer was placed in a thermo-hygrostat at 25 ° C. and 95% RH, and the state of change of the coating layer surface was observed over time. The measurement results are shown in Table 1.

<Comparative Example 2> The procedure of Example 2 was repeated except that a 30% aqueous solution of polyethylene oxide (manufactured by Meisei Chemical Industry Co., Ltd., "R-150") was used in place of the protective coating agent obtained in Example 2. A protective coating layer of Comparative Example 1 was obtained in the same manner as in Example 2.

The resulting protective coating layer was applied at 25 ° C. and 9
It was placed in a thermo-hygrostat of 5% RH, and the state of change of the coating layer surface was observed with time. The measurement results are shown in Table 1.

[0029]

[Table 1]

[0030]

From the above Examples and Comparative Examples, the water-soluble protective coating layer formed by using the protective coating agent of the present invention has the same level of product surface protection as conventional products when used, and is easy to use. It is clear that the adhesive strength is such that it does not peel off and the moisture resistance is also excellent.

Therefore, when the protective coating agent of the present invention is used, a protective coating layer having excellent water solubility and moisture resistance can be formed on the surface of the base material, and even if the base material has a complicated shape, It is easy and hygienic to safely remove the protective coating agent and remove the protective coating layer by washing with water.

Further, by using the coating method of the present invention, it is possible to form a water-soluble and moisture-resistant protective coating layer on the surface of a substrate, and even if the substrate has a complicated shape, the protective coating after use can be formed. The protective coating layer can be easily removed by peeling off the layer and washing with water, and can be carried out safely in hygiene.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroya Kobayashi 5-8 Nishimitabicho, Suita City, Osaka Prefecture Nippon Shokubai Co., Ltd.

Claims (3)

[Claims] 1. A water-soluble protective coating agent comprising polydioxolane. 2. The polydioxolane is represented by the following general formula (1): — (— CH ₂ —O—CH ₂ CH ₂ —O—) _n — (wherein n represents an integer of 1 or more). The water-soluble protective coating agent according to claim 1, which is a polymer having a structural unit of 60% by weight or more in the molecule. 3. A coating method, which comprises applying the water-soluble protective coating agent according to claim 1 or 2 to a substrate.