JP2022124614A - Strippable paint and coating layer thereof - Google Patents

Abstract

To provide a strippable paint that is well spread without containing a plasticizer and also has high peelability without contaminating the surface of a component, and a coating layer thereof.SOLUTION: A strippable paint according to the present disclosure contains a polyvinyl alcohol, a styrene-butadiene rubber, an alcoholic solvent, and water, The polyvinyl alcohol has a degree of saponification of 90 mol% or less, and a degree of polymerization of 500 or more and less than 2000. The mass ratio between the polyvinyl alcohol and the styrene-butadiene rubber is more than 30/70 and 60/40 or less, and the content of the alcoholic solvent is 5-15 wt.%.SELECTED DRAWING: None

Description

The present disclosure relates to a strippable paint that can be applied on a plastic substrate or a plastic substrate coated with an acrylic resin-based paint, and that can be peeled off without leaving a trace after drying and forming a film, and a coating film thereof. It is.

Plastic parts of industrial products are sometimes affixed with a film such as PVC at the time of shipment for protection, but if the part has a complicated shape, affixing the film is difficult and takes a long time. There is also a strippable paint that can protect plastic parts with a film that is dried after coating and formed into a film, but the peelability tends to decrease due to the effects of heat and organic solvents. For example, a strippable paint using PVA has been proposed (see Patent Documents 1 and 2, for example). For example, Patent Document 1 or Patent Document 2 discloses a strippable paint using PVA and a plasticizer.

JP-A-57-098571 JP-A-56-049764

However, since the strippable paints disclosed in Patent Documents 1 and 2 use a plasticizer, migration matters remain on the surface of the component after peeling, contaminating the surface of the component. In view of the above circumstances, it is desired to develop a strippable paint in which the film dried after coating is not affected by heat, organic solvents, or the like. However, the strippable paint disclosed in Patent Literature 2 also contains the use of methanol and ethanol, so it damages the surface of the plastic substrate.

An object of the present disclosure is to provide a strippable paint and its coating film which are stretchable even without containing a plasticizer and have good releasability without contaminating the surfaces of parts.

The strippable paint according to the present invention contains polyvinyl alcohol, styrene-butadiene rubber, an alcoholic solvent, and water, and the polyvinyl alcohol has a saponification degree of 90 mol% or less and a polymerization degree of It is 500 or more and less than 2000, the mass ratio of the polyvinyl alcohol and the styrene-butadiene rubber is more than 30/70 and 60/40 or less, and the content of the alcohol solvent is 5 to 15 wt%. and

In the strippable paint according to the present invention, the alcohol solvent includes isopropyl alcohol.

The strippable paint according to the invention preferably does not contain plasticizers. A coating film of such a strippable paint leaves no migrated matter on the surface of the article to be coated after peeling, and does not contaminate the surface of the article to be coated after peeling.

The coating film according to the present invention is characterized by comprising a cured product of the strippable paint according to the present invention.

The coating film according to the present invention has a breaking strength of 0.1 MPa or more measured in accordance with JIS K 7161-1:2014 "Plastics-Determination of tensile properties-Part 1: General rules", and an ambient temperature It is preferable that the elongation measured at 25° C. and a tensile speed of 20 mm/min is 200% or more. It can be peeled off more reliably.

ADVANTAGE OF THE INVENTION According to this disclosure, it is possible to provide a strippable paint and its coating film which have good elongation even without containing a plasticizer and have good releasability without contaminating the surface of parts.

One embodiment of the present invention is described below. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. Various modifications may be made as long as the effects of the present invention are achieved.

The strippable paint according to the present embodiment contains polyvinyl alcohol, styrene-butadiene rubber, an alcoholic solvent, and water, and the polyvinyl alcohol has a saponification degree of 90 mol% or less, and a polymerization degree of It is 500 or more and less than 2000, the mass ratio of polyvinyl alcohol and styrene-butadiene rubber is more than 30/70 and 60/40 or less, and the content of the alcoholic solvent is 5 to 15 wt%.

A strippable paint is a coating composition that is applied to the surface of an object to be coated for the purpose of preventing contamination or damage to the object. A coating film made of a cured strippable paint protects the surface of an object to be coated and can be peeled off at any time. Here, the object to be coated includes the surface of a base material such as plastic and the surface of a coating film formed on the surface of the base material.

Polyvinyl alcohol is a saponified polyvinyl ester obtained by polymerizing one or more of vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl laurate, vinyl stearate and vinyl benzoate. is.

The degree of saponification of polyvinyl alcohol is 90 mol % or less. If the degree of saponification exceeds 90 mol %, the solubility in the solvent decreases and the storage stability decreases. Although the lower limit of the degree of saponification of polyvinyl alcohol is not particularly limited, it is preferably 70 mol % or more.

The degree of polymerization of polyvinyl alcohol is 500 or more. If the degree of polymerization is less than 500, the strength of the coating film will be low and the peeling workability will be low. The upper limit of the degree of polymerization of polyvinyl alcohol is less than 2,000. If the degree of polymerization is 2000 or more, the toughness of the resulting coating film is lowered, and the viscosity of the solution is significantly increased, resulting in reduced workability.

Styrene-butadiene rubber is a copolymer obtained by emulsion polymerization using styrene and butadiene.

In the strippable paint according to this embodiment, the alcohol-based solvent includes isopropyl alcohol. The alcoholic solvent may be isopropyl alcohol or butanol such as n-butanol or i-butanol. From the viewpoint of drying property, the alcohol solvent is more preferably isopropyl alcohol.

Water is blended as a solvent for polyvinyl alcohol and a dispersion medium for styrene-butadiene rubber. Also, water may be blended for viscosity adjustment.

With respect to the total mass of polyvinyl alcohol and styrene-butadiene rubber of 100 wt% (mass%), the mass ratio of polyvinyl alcohol is more than 30.0 wt% and 60.0 wt% or less, and 34.0 wt% or more and 60.0 wt% or less. and more preferably 49.0 wt % or more and 60.0 wt % or less. By setting the mass ratio of polyvinyl alcohol to 49.0 wt% or more and 60.0 wt% or less, the organic solvent resistance and heat resistance are further improved. If the mass ratio of polyvinyl alcohol is 30.0 wt % or less, the organic solvent resistance and heat resistance are lowered, and when used as a mask, the peelability is deteriorated. When the mass ratio of polyvinyl alcohol exceeds 60 wt %, the elongation of the resulting coating film becomes small, and when used as a mask, the releasability becomes poor.

The content of the alcohol-based solvent is 5 to 15 wt%, more preferably 8 to 15 wt%, with respect to 100 wt% (mass%) of the entire strippable paint. If the alcohol-based solvent content is less than 5 wt %, the dryness to the touch is poor. When the content of the alcoholic solvent exceeds 15 wt%, the storage stability decreases.

The strippable paint according to this embodiment preferably does not contain a plasticizer. A coating film of such a strippable paint leaves no migrated matter on the surface of the article to be coated after peeling, and does not contaminate the surface of the article to be coated after peeling. Plasticizers are, for example, ethylene glycol, glycerin or polyethylene glycol. By containing a predetermined amount of styrene-butadiene rubber, the strippable paint according to the present embodiment has elongation without containing a plasticizer, and can be used as a masking application with good peelability without contaminating the surface of parts. .

Known extender pigments, color pigments, metallic pigments, and dyes may be added to the strippable paint according to the present embodiment, if necessary.

The coating film according to this embodiment is composed of a cured product of the strippable paint according to the present invention. Although the film thickness of the coating film is not particularly limited, it is preferably, for example, 10 to 100 μm, more preferably 20 to 50 μm.

The coating film according to the present embodiment has a breaking strength of 0.1 MPa or more measured according to JIS K 7161-1:2014 "Plastics - Determination of tensile properties - Part 1: General rule", and It is preferable that the elongation measured at a temperature of 25° C. and a tensile speed of 20 mm/min is 200% or more. It can be peeled off more reliably. If the breaking strength is less than 0.1 MPa, peelability may deteriorate when used as a mask. If the elongation percentage is less than 200%, the releasability will be poor when used as a mask.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. In addition, "parts" and "%" in the examples indicate "mass parts" and "mass%", respectively, unless otherwise specified. The number of parts to be added is a value in terms of solid content.

(Example 1)
After charging 850 g of pure water in a 1-liter round-bottomed three-necked flask equipped with a thermometer, a cooling tube, and a stirrer, the temperature inside the flask was kept at 90 ° C. while stirring, and polyvinyl alcohol (hereinafter referred to as PVA ) 150 g of powder (degree of saponification: 87 mol%, degree of polymerization: 500) was added and dissolved to obtain an aqueous PVA solution. 65 g of the prepared PVA aqueous solution, 20 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber (hereinafter sometimes referred to as SBR) aqueous dispersion, 8 g of isopropyl alcohol, and 7 g of pure water were thoroughly mixed using a stirrer to obtain a strippable paint. The mass ratio of PVA to styrene-butadiene rubber (PVA/SBR mass ratio) was 49.37/50.63. The content of isopropyl alcohol (alcoholic solvent) was 8% by mass.

(Example 2)
A PVA aqueous solution was prepared in the same manner as in Example 1. 55 g of the prepared PVA aqueous solution, 32 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber aqueous dispersion, 8 g of isopropyl alcohol, and 5 g of pure water were sufficiently mixed using a stirrer, Got a strippable paint. The mass ratio between PVA and styrene-butadiene rubber was 34.02/65.98. The content of isopropyl alcohol (alcoholic solvent) was 8% by mass.

(Example 3)
A PVA aqueous solution was prepared in the same manner as in Example 1. 75 g of the prepared PVA aqueous solution, 15 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber aqueous dispersion, 8 g of isopropyl alcohol, and 2 g of pure water were sufficiently mixed using a stirrer, Got a strippable paint. The mass ratio between PVA and styrene-butadiene rubber was 60.00/40.00. The content of isopropyl alcohol (alcoholic solvent) was 8% by mass.

(Example 4)
A PVA aqueous solution was prepared in the same manner as in Example 1. 65 g of the prepared PVA aqueous solution, 20 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber aqueous dispersion, and 15 g of isopropyl alcohol were sufficiently mixed using a stirrer to obtain a strippable paint. . The mass ratio of PVA and styrene-butadiene rubber was 49.37/50.63. The content of isopropyl alcohol (alcoholic solvent) was 15% by mass.

(Example 5)
A PVA aqueous solution was prepared in the same manner as in Example 1. 65 g of the prepared PVA aqueous solution, 20 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber aqueous dispersion, 5 g of isopropyl alcohol, and 10 g of pure water were sufficiently mixed using a stirrer, Got a strippable paint. The weight ratio of PVA to styrene-butadiene rubber was 49.37/50.63. The content of isopropyl alcohol (alcoholic solvent) was 5% by mass.

(Example 6)
A PVA aqueous solution was prepared in the same manner as in Example 1, except that PVA powder (degree of saponification: 87 mol%, degree of polymerization: 500) was changed to PVA powder (degree of saponification: 79 mol%, degree of polymerization: 500). 65 g of the prepared PVA aqueous solution, 20 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber aqueous dispersion, 8 g of isopropyl alcohol, and 7 g of pure water were sufficiently mixed using a stirrer, Got a strippable paint. The mass ratio of PVA and styrene-butadiene rubber was 49.37/50.63. The content of isopropyl alcohol (alcoholic solvent) was 8% by mass.

(Comparative example 1)
A strippable paint was obtained in the same manner as in Example 1, except that PVA powder (degree of saponification: 87 mol%, degree of polymerization: 500) was changed to PVA powder (degree of saponification: 97 mol%, degree of polymerization: 500). The mass ratio of PVA and styrene-butadiene rubber was 49.37/50.63. The content of isopropyl alcohol (alcoholic solvent) was 8% by mass.

(Comparative example 2)
A strippable paint was obtained in the same manner as in Example 1, except that PVA powder (degree of saponification: 87 mol%, degree of polymerization: 500) was changed to PVA powder (degree of saponification: 87 mol%, degree of polymerization: 2,000). The mass ratio of PVA and styrene-butadiene rubber was 49.37/50.63. The content of isopropyl alcohol (alcoholic solvent) was 8% by mass.

(Comparative Example 3)
A PVA aqueous solution was prepared in the same manner as in Example 1. 50 g of the prepared PVA aqueous solution, 35 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber aqueous dispersion, 8 g of isopropyl alcohol, and 7 g of pure water were thoroughly mixed using a stirrer, Got a strippable paint. The mass ratio between PVA and styrene-butadiene rubber was 30.00/70.00. The content of isopropyl alcohol (alcoholic solvent) was 8% by mass.

(Comparative Example 4)
A PVA aqueous solution was prepared in the same manner as in Example 1. 74 g of the prepared PVA aqueous solution, 12 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber aqueous dispersion, 7 g of isopropyl alcohol, and 7 g of pure water were sufficiently mixed using a stirrer, and a stripper was used. Got a bull paint. The weight ratio of PVA to styrene-butadiene rubber was 64.91/35.09. The content of isopropyl alcohol (alcoholic solvent) was 7% by mass.

(Comparative Example 5)
A PVA aqueous solution was prepared in the same manner as in Example 1. 65 g of the prepared PVA aqueous solution, 20 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber aqueous dispersion, and 15 g of pure water were thoroughly mixed using a stirrer to obtain a strippable paint. . The mass ratio of PVA and styrene-butadiene rubber was 49.37/50.63. The content of isopropyl alcohol (alcoholic solvent) was 0% by mass.

(Comparative Example 6)
A PVA aqueous solution was prepared in the same manner as in Example 1. 61 g of the prepared PVA aqueous solution, 19 g of Nipol LX426 (manufactured by Nippon Zeon Co., Ltd., solid content: 50 wt %) as a styrene-butadiene rubber aqueous dispersion, and 20 g of isopropyl alcohol were sufficiently mixed using a stirrer to obtain a strippable paint. rice field. The mass ratio between PVA and styrene-butadiene rubber was 49.06/50.94. The content of isopropyl alcohol (alcoholic solvent) was 20% by mass.

(Preparation of test piece)
The strippable paint of each example and each comparative example was brush-coated on an ABS resin substrate (50 mm wide, 150 mm long, 1 mm thick) so that the thickness of the coating film when dried would be 20 μm. After the coating was completed, the product was allowed to stand at room temperature for 24 hours to obtain an article in which a cured product (coating film) of the strippable paint was formed on the substrate. This article was used as a specimen for initial evaluation. On the coating film of the test piece for initial evaluation, an organic solvent-based two-part paint (Econet EY manufactured by Origin Co., Ltd.) was sprayed so that the thickness of the coating film after drying was 20 μm. . A test piece for secondary evaluation was obtained by forcibly drying with .

The strippable paints of each example and each comparative example prepared under the above conditions were evaluated. The evaluation test method and evaluation criteria are as follows. Table 1 shows the evaluation results.

(Breaking strength)
In the process of creating a test piece for initial evaluation in the above "Creating a test piece", the method of applying the strippable paint is changed from brush coating to spray coating to create a test piece for initial evaluation, and in this test piece for initial evaluation The cured product (coating film) of the strippable paint was peeled off from the substrate by hand. The breaking strength of the coating film of the strippable paint thus obtained was measured according to JIS K 7161-1:2014 "Plastics-Determination of tensile properties-Part 1: General rule". A value of 0.1 MPa or more was judged to be a practical level, and a value of less than 0.1 MPa was judged to be an unsuitable level for practical use.

(Growth rate)
In the process of creating a test piece for initial evaluation in the above "Creating a test piece", the method of applying the strippable paint is changed from brush coating to spray coating to create a test piece for initial evaluation, and in this test piece for initial evaluation The cured product (coating film) of the strippable paint was peeled off from the substrate by hand. For the coating film of the strippable paint thus obtained, using a small desktop tester (SHIMADZU EZ-S, manufactured by Shimadzu Corporation), the elongation rate of the coating film was measured at an ambient temperature of 25 ° C. and a tensile speed of 20 mm / min. was measured. An elongation rate of 200% or more was judged to be a practical level, and a rate of less than 200% was judged to be an unsuitable level for practical use.

(Initial peeling evaluation)
A peel evaluation was performed using a test piece for initial evaluation. A test for peel evaluation was performed by manually peeling the strippable paint from the ABS resin substrate on the initial test specimen. Evaluation criteria are as follows.
⊚: The strippable paint film is not broken during peeling, and the peelability is good (practical level).
◯: Part of the strippable paint film was broken during peeling, but peeling was possible (practical lower limit level).
x: The strippable paint film was broken during peeling and could not be peeled off (practically unsuitable level).

(Secondary peeling evaluation)
A secondary peel evaluation was performed using the test piece for secondary evaluation. A secondary peel evaluation test was performed by manually peeling the strippable paint from the ABS resin substrate on the initial test specimen. Evaluation criteria are as follows.
⊚: Good resistance to the organic solvent in the topcoat solvent-based paint, the strippable paint does not soften, and the organic solvent does not seep out and migrate to the substrate. As a result, there is no breakage of the strippable paint film during peeling, and the peelability is good (practical level).
Good: Slightly inferior resistance to the organic solvent in the topcoat solvent-based paint, the strippable paint softens slightly, and the organic solvent oozes out and migrates slightly to the base material. As a result, the film of the strippable paint partly breaks during peeling, but since it can be peeled off, there is no practical problem (lower limit level for practical use).
x: Resistance to the organic solvent in the topcoat solvent-based paint is poor, the strippable paint softens, and the organic solvent oozes out and migrates to the substrate. As a result, the strippable paint film breaks during peeling and cannot be peeled off, which poses a practical problem (unsuitable level for practical use).

(Workability evaluation)
Workability evaluation was performed as follows. The strippable paint of each example and each comparative example was brush-coated or spray-coated on an ABS resin substrate (50 mm wide, 150 mm long, 1 mm thick) so that the thickness of the coating film when dried was 20 μm, Left at room temperature. After that, the dry state was confirmed by touching the coated surface with a finger. Evaluation criteria are as follows.
○: Can be applied by spraying or brushing, and the drying time to the touch is within 30 minutes (practical level)
×: Spray coating is not possible or the drying time to the touch is 2 hours or more (practical unsuitable level)

(Evaluation of storage stability)
The strippable paints of each example and each comparative example were evaluated for separation and white turbidity after being left at room temperature for 7 days. Evaluation criteria are as follows.
〇: No separation or aggregation (practical level)
×: Separation and aggregation (unsuitable for practical use)

All evaluations of the strippable paints of the examples were of a practical level, and they spread well even without containing a plasticizer, and had good releasability without staining the surfaces of parts. In Comparative Example 1, the saponification degree of PVA was 95 mol %, and the saponification degree exceeded 90 mol %. Therefore, no further evaluation was performed. In Comparative Example 2, the degree of polymerization of PVA was 2,000, and since the degree of polymerization was 2,000 or more, the secondary peelability and workability were at a practically unsuitable level. Further, in Comparative Example 2, the elongation rate was 41%, and the elongation rate was less than 200%. In Comparative Example 3, the mass ratio of polyvinyl alcohol and styrene-butadiene rubber was 30/70, and the mass ratio was 30/70 or more. rice field. Moreover, Comparative Example 3 had a breaking strength of 0.08 MPa, and a breaking strength of less than 0.1 MPa. In Comparative Example 4, the mass ratio of polyvinyl alcohol and styrene-butadiene rubber was 64.91/35.09, and the mass ratio exceeded 60/40. was at a practically unsuitable level. Further, Comparative Example 4 had an elongation rate of 172% and an elongation rate of less than 200%. In Comparative Example 5, the content of the alcoholic solvent was 0% by mass, and the content was less than 5% by mass, so the workability was at an unsuitable level for practical use. In Comparative Example 6, the content of the alcoholic solvent was 20% by mass, and the content exceeded 15% by mass, so the storage stability was at a practically unsuitable level. Therefore, no further evaluation was performed.

Claims (5)

containing polyvinyl alcohol, styrene-butadiene rubber, an alcoholic solvent, and water,
The polyvinyl alcohol has a saponification degree of 90 mol% or less and a polymerization degree of 500 or more and less than 2000,
The mass ratio of the polyvinyl alcohol and the styrene-butadiene rubber is more than 30/70 and 60/40 or less,
A strippable paint, wherein the content of the alcoholic solvent is 5 to 15 wt%. The strippable paint of Claim 1, wherein the alcoholic solvent is isopropyl alcohol. 3. A strippable paint according to claim 1 or 2, characterized in that it contains no plasticizer. A coating film comprising a cured product of the strippable paint according to any one of claims 1 to 3. The coating film has a breaking strength of 0.1 MPa or more measured in accordance with JIS K 7161-1:2014 "Plastics - Determination of tensile properties - Part 1: General rules", and an ambient temperature of 25 ° C., tensile 5. The coating film according to claim 4, which has an elongation of 200% or more when measured at a speed of 20 mm/min.