JPH07233338A - Aqueous strippable paint - Google Patents

Abstract

PURPOSE:To obtain an aqueous strippable paint useful for surface protection, excellent in release characteristics, having good adhesiveness after an outdoor exposure for a 1ong.period by allowing to consist of an aqueous dispersion of a copolymer consisting of a (meth)acrylate having a specific structural unit and a copolymerizable monomer with the same. CONSTITUTION:This paint comprises an aqueous dispersion of a copolymer consisting of (A) 10-40wt.% (metln)acrvlate of a long chain 12-30C aliphatic monoalcohol as a structural unit [e.g. lauryl (meth)acrylate, mvristvl (meth) acrylate, etc.] and (B) 60-99wt.% polymerizable monomer [preferably, at least, one of (meth)acrylate of 1-8C aliphatic monoalcohols and styrenel capable of copolymerizing with the component A. The glass transition temperature of the copolymer is 0-40 deg.C and tensile break strength of the dried coating is at least 30kgf/cm<2>. Here, the aqueous dispersion can be obtained by an emulsion polymerization using an emulsifier containing a specific nonionic surfactant.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to waterborne strippable paints. More specifically, the present invention relates to a water-based strippable paint having excellent releasability, which is used for protecting a painted surface or a surface of a plastic molded product.

[0002]

2. Description of the Related Art Conventionally, a so-called strippable paint that is used as a film by painting for the purpose of temporarily protecting the exterior coating surface of automobiles and preventing dirt from ventilation fans, etc., and that can be peeled off when it is no longer needed. Is used. There are water-based and oil-based strippable paints,
From the viewpoints of worker safety and health, fire hazard, pollution problems, etc., water-based materials are desired. This water-based strippable paint is a polyolefin-based paint used as a so-called coating wax (Japanese Patent Publication No. 53-37257).
JP-A No. 2-182768), a polymer containing a carboxyl group-containing polymer (JP-B-55-50517), an oil-soluble polymer (JP-A-2-182768), and the like. The products are of a type that can be peeled and removed by washing with water, alkaline water or an organic solvent, and both require waste liquid treatment after washing, which is not preferable from the viewpoint of pollution problems. Therefore, it is desired that even a water-based strippable paint can be peeled off as a continuous film especially after use. As an aqueous strippable paint that can be peeled off and discarded as such a continuous film, for example, a strippable paint comprising an aqueous dispersion of a copolymer of an acrylic monomer having acrylonitrile as an essential monomer (for example, Japanese Patent Publication No. 44-29593). JP-B-49-28889), an aqueous strippable paint obtained by emulsion copolymerizing butyl acrylate and methyl methacrylate in water (for example, JP-B-45-14671), a hard monomer and a soft monomer. A water-based strippable paint (for example, Japanese Patent Application Laid-Open No. 03-140373) containing the constituent acrylic copolymer and a water repellent as essential components has been proposed.

[0003]

[Problems to be Solved] However, the above-mentioned water-based strippable paint has a problem that harmful cyan gas is generated when incinerating and discarding a paint film which has become unnecessary after peeling. However, there is a drawback in that the adhesiveness to the paint-coated surface of the base material increases with time due to outdoor exposure and the peelability decreases. In addition, the water-repellent agent is incompatible with the film, so that the film becomes cloudy and does not become a transparent film, which is not preferable in appearance.

[0004]

Means for Solving the Problems The present inventors did not include an acrylonitrile-based polymer, which accompanies the generation of cyan gas at the time of extinction, and the adhesive strength to the painted surface of the substrate did not change even when exposed outdoors, and the appearance was transparent. The present invention has been accomplished as a result of extensive studies to obtain an aqueous strippable pane that can form a uniform film with and can be easily peeled off in the form of a continuous film.

That is, the present invention comprises 1 to 40% by weight of (meth) acrylate (A) of a long-chain aliphatic monoalcohol having 12 to 30 carbon atoms as a constitutional unit and a polymerizable monomer which is copolymerizable with the (A). A copolymer (B) comprising 60 to 99% by weight of an aqueous dispersion of a copolymer, having a glass transition point of 0 to 40 ° C., and a dry film having a tensile breaking strength of at least 30 kgf / cm ² . It is an aqueous strippable paint characterized by the fact that it is present.

Constituting the copolymer in the present invention (A)
Is a (meth) acrylate of a long-chain aliphatic monoalcohol having 12 to 30 carbon atoms, and the hydrocarbon group of the aliphatic alcohol may be linear or branched. Specific examples of the (A) include lauryl (meth)
Examples thereof include acrylate, myristyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, oleyl (meth) acrylate and a mixture of two or more thereof.

(B) is another polymerizable monomer copolymerizable with the above (A), and includes, for example, the following monomers (a) to (i). Can be used together. (A) Ester of unsaturated carboxylic acid An alkyl ester of (meth) acrylic acid having an alkyl group having 1 to 11 carbon atoms; a dialkyl ester or monoalkyl ester of maleic acid, fumaric acid and itaconic acid. (B) Styrene and its derivatives Styrene, alkyl group-substituted styrene (α-methylstyrene, p-methylstyrene, vinyltoluene, etc.), halogen-substituted styrene (monochlorostyrene, etc.), and the like. (C) Hydroxyl group-containing monomer 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and the like. (D) Halogen atom-containing monomer Vinyl chloride, vinylidene chloride, chloroprene, etc. (E) Aliphatic hydrocarbon monomer such as butadiene and isoprene. (F) Vinyl ester and / or (meth) allyl ester vinyl acetate, vinyl propionate, allyl acetate and the like. (G) Amino group-containing monomer (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N-methylol (meth) acrylamide, N-butyrol (meth) acrylamide and the like. (H) Unsaturated carboxylic acid (salt) (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid and salts thereof (alkali metal salts, alkaline earth metal salts, ammonium salts, amine salts, etc.) and the like. (I) Polyvinyl monomer Divinyl monomer (divinylbenzene, divinylphthalate, diallylphthalate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate ethylene glycol di (meth) acrylate, etc.) , Trivinyl monomer (trimethylolpropane tri (meth) acrylate, glycerin tri (meth) acrylate, etc.), tetravinyl monomer (pentaestritotetra (meth) acrylate, etc.), etc.

Of the materials exemplified in (a) to (i) above, (g) to (i) are usually used in combination with any of (a) to (f). Among those exemplified above in (a) to (i), preferable ones are (meth) acrylates of aliphatic monoalcohols having 1 to 8 carbon atoms and styrene, and particularly preferable ones are methyl methacrylate, ethyl acrylate, They are -n-butyl acrylate, 2-ethylhexyl acrylate and styrene.

Constituting the copolymer in the present invention (A)
The weight ratio of (B) to (B) is usually (1:99) to (40: 6).
0), preferably (2:98) to (30:70). When the ratio of (A) is less than 1, the peelability after weathering is insufficient, and when it exceeds 40, the strength of the film is insufficient.

The glass transition point of the copolymer of (A) and (B) in the present invention is usually 0 to 40 ° C., preferably 5 to
It is 30 ° C. If the glass transition point is less than 0 ° C, the film becomes too soft and the strength of the film becomes insufficient, and if it exceeds 40 ° C, the minimum film forming temperature becomes too high and it becomes difficult to form the film at a temperature around room temperature. The tensile strength at break of the dry film is usually 30 kgf / cm ² or more, preferably 50 kgf / cm ^2.
cm ² or more. If the tensile strength at break is less than 30 kgf / cm ² , the coating film does not become a continuous film at the time of peeling and it is difficult to peel smoothly. The glass transition temperature (Tg) in the present invention is calculated by the Fox method represented by the following formula (1). 1 / Tg = W ₁ / Tg ₁ + W ₂ / Tg ₂ + ... + W _n / Tg _n (1) [In the formula, Tg is the glass transition temperature (absolute temperature display) of the copolymer, Tg ₁ and Tg ₂ weight · · · Tg _n is the glass transition temperature of a homopolymer of each monomer component of each polymer (absolute temperature _{display), W 1, W 2 ···} W n each monomer component respectively Indicates the fraction. ]

The aqueous dispersion of the copolymer in the present invention is
Usually, a method of emulsion-polymerizing a monomer mixture consisting of (A) and (B) in an aqueous solvent in the presence of a polymerization initiator and a surfactant, or after polymerizing in an organic solvent, solvent substitution with water. However, the emulsion polymerization method is preferable. As an emulsion polymerization method, a known method (collective charging method, monomer dropping method, monomer emulsion dropping method, etc.) can be used.

Examples of the surfactant (emulsifier) used in the case of the emulsion polymerization method include one or more known surfactants listed in (a) to (d) below. The amount of the emulsifier used is usually 1 to 1 with respect to the total amount of the monomers.
It is 0% by weight. (A) Nonionic surfactant Aliphatic alcohol alkylene oxide adduct (for example, lauryl alcohol alkylene oxide adduct, myristyl alcohol alkylene oxide adduct, cetyl alcohol alkylene oxide adduct,
Alkylene oxide adduct of stearyl alcohol,
Oleyl alcohol alkylene oxide adduct, etc.); Alkylphenol alkylene oxide adduct (eg, octylphenol alkylene oxide adduct, nonylphenol alkylene oxide adduct, dodecylphenol alkylene oxide adduct, etc.); Fatty acid alkylene oxide adduct ( For example, lauric acid alkylene oxide adduct, stearic acid alkylene oxide adduct and the like); alkylene oxide adduct of polyhydric alcohol fatty acid ester (for example, polyalkylene glycol oleic acid monoester, polyalkylene glycol oleic acid diester,
Polyalkylene glycol lauric acid diester, etc.);
Alkylene oxide adducts of higher alkyl amines; Alkylene oxide adducts of fatty acid amides; Alkylene oxide adducts of fats and oils; Ethylene oxide adducts of polypropylene glycols; Fatty acid esters of glycerol; Fatty acid esters of pentaerythritol; Fatty acid esters of sorbitol and sorbitan; Fatty acid esters of sucrose; alkyl esters of polyhydric alcohols; fatty acid amides of alkanolamines. In the above, as the alkylene oxide, ethylene oxide,
Examples thereof include propylene oxide, and ethylene oxide is preferable. (B) Anionic surfactant Sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium alkyldiphenyl ether disulfonate, sodium polyoxyethylene alkyl ether sulfate, etc. (C) Cationic surfactant Stearylbenzyldimethylammonium chloride, distearylbenzyldimethylammonium chloride and the like. (D) Reactive surfactant Sodium alkylallyl sulfosuccinate, sodium (meth) acryloyl polyoxyalkylene sulfate, etc.

Of the above (a) to (d), nonionic surfactants are preferable, and HLB is particularly preferable.
A combination of a nonionic surfactant (C1) having an HLB of 8 to 12 and a nonionic surfactant having an HLB of more than 12 and up to 16 (C2); and a combination of both and a sulfonic acid type anionic surfactant. Is. The weight ratio of (C1) to (C2) is usually (10:90) to (90: 1).
0), preferably (30:70) to (70:30). The HLB is the Grif expressed by the following equation (2).
It is a numerical value calculated by the fin method. HLB = (molecular weight of hydrophilic group in surfactant) / (molecular weight of whole surfactant) × (100/5) (2)

As the polymerization initiator, for example, known ones listed in the following can be used. Persulfate Ammonium persulfate, sodium persulfate, potassium persulfate, etc. Peroxide compounds Benzoyl peroxide, lauryl peroxide, t-
Butyl hydroperoxide, hydrogen peroxide, etc. Azo compounds azobisisobutyronitrile, azobisisovaleronitrile, azobisamidinopropane-2 hydrochloride, azobiscyanovaleric acid, azobis {2-methyl-N- [1,1-
Bis (hydroxymethyl) -2-hydroxyethyl]}
Propionamide, azobis [2-methyl-N- (hydroxyethyl)] propionamide and the like. Redox initiators Combinations of peroxides and reducing (bis) sulfites such as ammonium persulfate and sodium bisulfite; Combinations of peroxides and amine-based compounds such as ammonium persulfate and dimethylaminoethanol; Combination of peroxide and polyvalent metal salt such as hydrogen peroxide and Fe ²⁺ .

As the aqueous medium, water alone may be used, or a water-miscible organic solvent (methanol, isopropanol, acetone, etc.) may be used together with water. If necessary, a chain transfer agent (such as mercaptan), an electrolyte (sodium hydrogen carbonate, sodium tripolyphosphate, etc.) may be added to the polymerization reaction.
For example, potassium chloride) or a pH adjuster (ammonia, sodium hydroxide aqueous solution, etc.) may be used.

The water-based strippable paint of the present invention is
It usually consists of the emulsion polymer described above. The concentration of the polymer is usually 30 to 60% by weight, and the resin concentration may be adjusted after the emulsion polymerization if necessary. If necessary, known film-forming aids (ethylene glycol, dibutyl phthalate, etc.), thickeners (hydroxyethyl cellulose, polyvinyl alcohol, etc.), dispersants, defoamers, leveling agents,
Preservatives, deterioration inhibitors, etc. may be contained.

[0017]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. In the following, "%" indicates% by weight.

Example 1 107 g of water, 1 g of sodium persulfate, 0.4 g of sodium tripolyphosphate, 2 g of sodium dodecylbenzenesulfonate, 2 g of nonylphenol polyoxy were placed in a reaction vessel equipped with a stirrer, a nitrogen gas introduction tube, a thermometer, and a reflux condenser. 2 g of ethylene (6 mol) adduct (HLB = 10.9) and 2 g of nonylphenol polyoxyethylene (12 mol) adduct (HLB = 14.1) were charged, and then 100 g of the monomer mixture shown in Table 1 was charged. The inside of the system was replaced with nitrogen gas with stirring, the temperature was raised to 70 ° C., and the reaction was carried out for about 4 hours. The reaction product was cooled to 30 ° C. and adjusted to pH 7 with 25% aqueous ammonia to obtain an aqueous strippable paint of the present invention composed of an emulsion polymer having a solid content of 49.7%. This product is applied to a metal steel plate coated with a coating (acrylic melamine-based) for automobile outer panels with a film thickness of 40 μm using an applicator so that the dry film thickness is 100 μm, and then at 40 ° C. for 24 hours.
Peel strength was measured using test pieces that had been dried for a period of time.
The peel strength was measured before and after weathering and comparatively evaluated. The exposure condition of the weather resistance test is 100 hours with a sunshine weatherometer. Further, the tensile strength at break of the dry film was measured according to JIS K6301. The results of these evaluations are shown in Table 1.

Example 2 107 g of water, 1 g of sodium persulfate, 0.4 g of sodium tripolyphosphate, and a reactive emulsifier (Eleminol JS-2; manufactured by Sanyo Chemical Industry Co., Ltd.) 2 were placed in the same reaction vessel as in Example 1.
g, 2 g of nonylphenol polyoxyethylene (6 mol) adduct and 2 g of nonylphenol polyoxyethylene (12 mol) adduct, and then 100 g of the monomer mixture shown in Table 1. The inside of the system was replaced with nitrogen gas with stirring, the temperature was raised to 70 ° C., and the reaction was carried out for about 4 hours. The reaction product was treated in the same manner as in Example 1 to obtain an aqueous strippable paint of the present invention composed of an emulsion polymer having a solid content of 49.8%. Table 1 shows the results of evaluation of this product in the same manner as in Example 1.

Examples 3 to 5 Under the same conditions as in Example 2, the polymerization reaction was carried out with the mixed composition shown in Table 1 only for the monomer composition, and the aqueous strippable of the present invention consisting of an emulsion copolymer having a solid content of 50.0%. Got the paint. Table 1 shows the results of evaluation of this product in the same manner as in Example 1.

Comparative Example 1 107 g of water, 1 g of sodium persulfate, 0.4 g of sodium tripolyphosphate, 2 g of sodium dodecylbensonsulfonate, 2 g of nonylphenol polyoxyethylene (6 mol) adduct and 2 g of nonylphenol were placed in the same reactor as in Example 1. 2 g of polyoxyethylene (12 mol) adduct
Then, 100 g of the monomer mixture shown in Table 2 was charged. The inside of the system was replaced with nitrogen gas with stirring, the temperature was raised to 70 ° C., and the reaction was carried out for about 4 hours. The reaction was performed under the same conditions as in Example 1 to obtain a comparative aqueous strippable paint composed of an emulsion polymer having a solid content of 49.5%. Table 2 shows the results of evaluation of this product in the same manner as in Example 1.

Comparative Example 2 The same reactor as in Example 1 was charged with 107 g of water, 1 g of sodium persulfate, 0.4 g of sodium tripolyphosphate, and 2 g of a reactive emulsifier (Eleminol JS-2; manufactured by Sanyo Kasei Co., Ltd.). 100 g of the monomer mixture shown in 2 was charged. The inside of the system was replaced with nitrogen gas with stirring, the temperature was raised to 70 ° C., and the reaction was carried out for about 4 hours. The reaction was performed under the same conditions as in Example 1 to obtain a comparative aqueous strippable paint composed of an emulsion polymer having a solid content of 49.5%. Table 2 shows the results of evaluation of this product in the same manner as in Example 1.

Comparative Examples 3 and 4 Under the same conditions as in Comparative Example 2, a polymerization reaction was carried out with the mixed composition shown in Table 2 only for the monomer composition, and a comparative aqueous strippable comprising an emulsion copolymer having a solid content of 50.0%. Got the paint. Table 2 shows the results of evaluating these in the same manner as in Example 1.

Comparative Example 5 Under the same conditions as in Comparative Example 2, a polymerization reaction was carried out with only the monomer composition having a mixed composition shown in Table 2 to obtain an emulsion copolymer having a solid content of 50.0%. A paraffin wax emulsion was added to this as a water repellent at a ratio of 5% by weight based on the solid content to obtain a comparative aqueous strippable paint. The results of evaluation of this product in the same manner as in Example 1 are shown in Table 2. The dry film coated with this emulsion mixture had no transparency and was cloudy and non-uniform.

[0025]

[Table 1] * 1 MMA: Methyl methacrylate C12A: Lauryl acrylate BA: Butyl acrylate C18A: Stearyl acrylate 2EHA: 2-Ethylhexyl acrylate C18M: Stearyl methacrylate St: Styrene * 2: Compliant with JIS K 6301 (180 degree peeling) , Pulling speed 50m
m / min)

[0026]

[Table 2] * 3 AN: Acrylonitrile C12M: Lauryl methacrylate (other abbreviations are the same as in Table 1)

[0027]

The water-based strippable paint of the present invention has the following effects. (1) Adhesiveness to a substrate such as a painted surface does not change even after long-term outdoor exposure, and peelability is good. (2) Since the composition does not contain a nitrile group, no harmful cyan gas is generated when incinerating the film after peeling. (3) Since the dry film has an appropriate strength, it can be easily peeled off in the state of a continuous film. (4) It is water-based and safe to handle. Because of the above effects, the water-based strippable paint of the present invention is extremely useful especially as a paint for coating surfaces of vehicles, building materials and the like, and as a surface protection coating for plastics molded articles and the like.

Claims (3)

[Claims] 1. A (meth) acrylate (A) 1 of a long-chain aliphatic monoalcohol having 12 to 30 carbon atoms as a structural unit.
To 40% by weight and 60 to 99% by weight of the polymerizable monomer (B) copolymerizable with the (A), the aqueous dispersion of the copolymer, wherein the glass transition point of the copolymer is 0 to 40 ° C. and the tensile strength at break of the dry film is at least 30 kgf
/ Cm ² Aqueous strippable paint. 2. The aqueous strippable paint according to claim 1, wherein the (B) is at least one selected from (meth) acrylates of aliphatic monoalcohols having 1 to 8 carbon atoms and styrene. 3. The aqueous dispersion comprises (A) and (B)
A nonionic surfactant having an HLB of 8 to 12 (C1)
The aqueous strippable paint according to claim 1 or 2, which is an aqueous dispersion obtained by emulsion polymerization using an emulsifier essentially containing a nonionic surfactant (C2) having an HLB of more than 12 and up to 16.