JPH09111156A - Peelable coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a peelable coating compsn. which gives a coating film easily peelable, excellent in water resistance and strengths, and easily treated after being peeled by using as the main ingredient an emulsion obtd. by the emulsion polymn. of a mixture of three specific monomers. SOLUTION: This compsn. is prepd. by adding an acetylene glycol deriv. to a copolymer which has a glass transition point of -40 deg.C to 40 deg.C and is obtd. by the emulsion copolymn. of 3-50wt.% at least one ethylenically unsatd. monomer having a water solubility lower than 0.10g/100g water at 25 deg.C and capable of forming a homopolymer having a glass transition point of 50-130 deg.C, 35-96.5wt.% at least one ethylenically unsatd. monomer having a water solubility of 0.10g/100g water or higher at 25 deg.C, and 0.5-15wt.% at least one ethylenically unsatd. monomer having a functional group in the pressure of 0.01-5wt.% (based on the sum of all the monomers) free-radical polymn. initiator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a peelable coating composition which is excellent in water resistance and peeling property and does not leave stains on the surface of an object to be protected after peeling. , Vehicle, aircraft, machine parts, metal household appliances, etc. are useful for the purpose of temporary surface protection.

[0002]

2. Description of the Related Art Painting for the purpose of temporary protection of the exterior coating surface of automobiles and prevention of stains on metal household appliances such as ventilation fans, etc., provided that these products can be completely peeled off immediately before use. There are so-called peelable coating materials. There are water-based and oil-based peelable coating materials, but oil-based coating materials cause blistering and stains on the base paint, so they cannot be used on painted surfaces, and From the viewpoints of safety and health, fire risk, and pollution problems, water-based peelable coating materials are desired. As this water-based peelable coating material, JP-B-44-29593, JP-A-7-26175, JP-A-7-26176, an acrylic resin water dispersion composition containing acrylonitrile as an essential component is proposed. However, although these coating films can be tentatively evaluated in terms of peelability, there is a big problem that when incinerating an unnecessary coating film, cyan gas is generated. Also, Japanese Patent Publication No. 45-14671 proposes a butyl acrylate-methyl methacrylate acrylic resin composition containing no acrylonitrile, but this coating film has a poor peeling property because of its brittle film.

[0003]

In view of the above situation, the present invention provides a coating film having excellent water resistance and strength when applied to the surface of a product requiring temporary protection as a long-term protective film. In addition to playing a role, this coating film is easy to peel off when peeled off, does not leave stains on the surface of the protected object after peeling, and has no problem in treating the coating film after peeling. It was made in an attempt to provide a composition.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a monomer is used in a specific range and a reactive surfactant is used as a surfactant to initiate radical polymerization. It was found that the problem could be solved by using as a main component a copolymer emulsion in a specific range which was emulsion-polymerized in the presence of an agent, and further tested for the type and amount of monomer and reactive surfactant. The present invention has been carried out.

That is, the peelable coating composition of the present invention solves the above-mentioned problems by: (a) its solubility in water at 25 ° C. is less than 0.10 g / 100 g of water, and One or more monomers selected from ethylenically unsaturated monomers having a homopolymer glass transition temperature of 50 to 130 ° C 3 to 50% by weight (b) Solubility in water at 25 ° C 0.10 g / 100 g or more of water One or more monomers selected from ethylenically unsaturated monomers 35 to 96.5% by weight (c) Selected from ethylenically unsaturated monomers having functional groups Obtained by emulsion polymerization of a monomer mixture containing 0.5 to 15% by weight of one or more kinds of monomers to be used, using a reactive surfactant as a surfactant in the presence of a radical polymerization initiator. The main component is a copolymer emulsion having a glass transition temperature of -40 to 40 ° C. .

Hereinafter, the present invention will be described in detail. The coating film formed from the coating composition of the present invention is peeled off after the purpose of its purpose of temporary protection is reached, but the peeling is smooth and does not leave stains on the surface of the protected object. In the copolymer emulsion which is the main component of the composition, it is necessary that the copolymer in the emulsion particles contains a monomer unit having a high glass transition temperature of the homopolymer. It was found that the body units should be unevenly distributed inside the emulsion particles rather than on the surface layer. It is presumed that such uneven distribution can provide a coating film that is tough and has good peelability.

In the coating composition of the present invention, the ethylenically unsaturated monomer as the component (a) is a monomer for introducing this monomer unit, and in order to achieve the purpose, The glass transition temperature of homopolymer is 50-130 ℃,
The solubility in water at ℃ is less than 0.10 g / 100 g of water, preferably less than 0.05 g / 100 g of water. The amount of this monomer used is 3 to 50% by weight, preferably 5 to 45% by weight, based on the total amount of the monomer. The glass transition temperature is 50 to 1
Solubility in water at 25 ℃ is 0.10g / at 30 ℃
If the amount of water is 100 g or more, it is difficult to obtain the required properties, but it is considered that this is because components having a high glass transition temperature cannot be unevenly distributed inside the particles. On the other hand, when the glass transition temperature is low, the coating film becomes soft and toughness cannot be obtained. Therefore, it is necessary to select a monomer having both properties.

Examples of such a monomer include styrene, styrene derivatives, alkyl methacrylate having an alkyl group having 3 or 4 carbon atoms, benzyl (meth) acrylate, aryl such as phenyl (meth) acrylate. Examples thereof include (meth) acrylic acid ester having a group, vinyl chloride and the like, and only one of them or two or more thereof can be used at the same time. The component (a) does not have the functional group of the component (c) described later.

The component (b) has a solubility in water at 25 ° C. of 0.10 g.
/ 100 g or more of water, preferably 0.2 to 8 g / 100 g of water, which is an ethylenically unsaturated monomer and does not have a functional group possessed by the component (C) described later. This component (b) is used to develop appropriate adhesiveness and flexibility in the coating film, and its amount is 35 to 96.5% by weight, preferably 50 to 92% by weight, based on the total amount of the monomers. %. Also, (b)
It has been found that it is preferable to form the surface layer part of the emulsion particles by the components in order to impart appropriate adhesiveness and flexibility to the coating film. Such monomers include:
For example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acetate, vinyl propionate, etc. are exemplified, and among these, only one kind or two or more kinds at the same time is used. Can be used.

The ethylenically unsaturated monomer having a functional group as the component (c) means, in one molecule, in addition to the ethylenically unsaturated group, a carboxyl group or its anhydride, a hydroxyl group, an amido group, an amino group. , An alkoxyl group or a glycidyl group, or one or more ethylenically unsaturated groups. Examples of such a monomer include carboxyl group-containing monomers such as acrylic acid, methacrylic acid and maleic anhydride, or anhydride monomers thereof, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth). Hydroxyl group-containing monomer such as acrylate, (meth) acrylamide, N-methylol (meth)
Acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide,
Amide group-containing monomers such as diacetone (meth) acrylamide, dimethylaminoethyl (meth) acrylate,
Amino group-containing monomers such as diethylaminoethyl (meth) acrylate, methoxyethyl (meth) acrylate,
Alkoxyl group-containing monomer such as butoxyethyl (meth) acrylate, glycidyl (meth) acrylate, glycidyl group-containing monomer such as glycidyl allyl ether, divinylbenzene, allyl (meth) acrylate, ethylene glycol di (meth) acrylate, Examples thereof include monomers having two or more ethylenically unsaturated groups in one molecule such as diethylene glycol di (meth) acrylate and trimethylolpropane tri (meth) acrylate. The ethylenically unsaturated monomer having a functional group may be used alone or in combination of two or more.
This monomer is used to improve the stability of the emulsion and the water resistance of the coating film due to the reaction of the functional groups, etc. Of these, 0.5 to 15% by weight, preferably 1 to 10% by weight.

If necessary, the ethylenically unsaturated monomer other than the above-mentioned components (a) to (c) may be added in order to impart physical properties and coating film characteristics which cannot be exhibited only by the components (a) to (c). Can be used. Examples of such a monomer include 2-ethylhexyl acrylate, decyl acrylate, stearyl acrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate and the like. These are used in an amount of 15% by weight or less based on the total amount of the monomers so as not to impair the object of the present invention.

Further, in order to improve the water resistance of the coating film obtained from the coating composition, and further to eliminate the contamination of the surface of the object to be protected which remains after peeling the coating film, a surfactant (emulsifier) is used. It has been found to be advantageous to use a reactive surfactant. Examples of this reactive surfactant include:

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[0013]

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And the like, or a cationic reactive surfactant having a radical polymerizable group and a group in the form of a quaternary ammonium salt or a tertiary amine salt. This reactive surfactant can also be obtained from a commercial product. This reactive surfactant may be used alone or in combination of two or more kinds, but if the amount is too small, many agglomerates will be generated in the produced emulsion, and the resulting coating film will be obtained. Also does not show good physical properties. Also, when the amount is too large, the particle size of the emulsion becomes small, the viscosity of the emulsion increases and the polymerization rate decreases, and the water resistance of the film also deteriorates. Therefore, an appropriate amount of this reactive surfactant is
It is 0.5 to 15% by weight, particularly preferably 1 to 7% by weight. Further, as long as this reactive surfactant does not impair the object of the present invention, it is possible to use a combination of surfactants used in ordinary emulsion polymerization within 20% by weight of the amount used. is there. Examples of such a surfactant include anionic surfactants such as alkyl or alkylallyl sulfates, alkyl or alkylallyl sulfonates, and dialkyl sulfosuccinates, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl ethers. Examples thereof include nonionic surfactants such as oxyethylene carboxylic acid ester.

As the radical polymerization initiator for producing the emulsion used in the present invention, potassium persulfate,
Persulfates such as ammonium persulfate, hydrogen peroxide solution, t-
Water-soluble types such as butyl hydroperoxide, azobisamidinopropane hydrochloride, benzoyl peroxide, cumene hydroperoxide, dibutyl peroxide, diisopropyl peroxydicarbonate, cumyl peroxyneodecanoate, cumyl peroxy octoate Oil-soluble types such as azobisisobutyronitrile and the like. Further, if necessary, N, N-dimethylaniline, acidic sodium sulfite, Rongalit,
A redox system in which a reducing agent such as L-ascorbic acid is also used can be used. The amount of the polymerization initiator used is usually 0.01 to 5% by weight based on all the monomers,
It is more preferably 0.05 to 2% by weight.

To produce the emulsion used in the present invention, first, the above-mentioned various monomers are mixed, a reactive surfactant is added thereto, and a polymerization initiator and the like are further combined to carry out emulsion polymerization in an aqueous system. In this case, methods such as batch charge polymerization and polymerization while continuously supplying each component can be applied. The polymerization is usually carried out at a temperature of 10 to 90 ° C with stirring. The solid content of the polymerized emulsion is in the range of 30 to 70% by weight. Even by this ordinary polymerization method, it is judged that the component having a high glass transition temperature can be unevenly distributed inside the emulsion particles due to the balance of the hydrophobicity and hydrophilicity of the monomers (difference in solubility in water described above). But,
For even more certainty, core-shell polymerization may be performed. That is, for example, after adding a surfactant and a polymerization initiator to the monomer of the component (a) and emulsion-polymerizing the mixture in an aqueous system to form a core part, the system further contains a surfactant, a polymerization initiator and The above (B), (C), and a monomer used as necessary are added, and emulsion polymerization is performed to form a shell portion.

The glass transition temperature of the copolymer obtained by polymerization must be in the range of -40 ° C to 40 ° C.
When the temperature is lower than -40 ° C, the coating film obtained from the coating composition becomes too soft, and when the temperature is higher than 40 ° C, it becomes too brittle, and in either case, good peeling cannot be obtained when the film is peeled off. . It is preferably in the range of -20 to 30 ° C. However, this glass transition temperature is obtained by the following formula based on the monomer used. Actually, as described above, it is unevenly distributed inside the emulsion particles. 1 / Tg = Σ (wi / Tgi) Tg: Glass transition temperature of copolymer (absolute temperature display) Tgi: Glass transition temperature of homopolymer of monomer component (i) (absolute temperature display) wi: Copolymer weight Weight fraction of component (i) in coalescence

If necessary, the composition of the present invention may be mixed with additives commonly used in ordinary coating compositions such as thickeners, defoamers, pigments, dispersants and film-forming aids. it can.
Among them, in particular, the addition of the acetylene glycol derivative represented by the following general formula (1) allows the characteristics of the composition of the present invention to be exhibited without causing defects such as cracks, cissing and bubbles in the film. Is effective for.

Embedded image (However, R ¹ and R ² in the formula are each a hydrogen atom or a carbon number 1
~ 5 alkyl groups, the sum of n and m is 0-30. )

Examples of such acetylene glycol derivatives include 2,5-dimethyl-3-hexyne-2,5-diol and 2,4,7,9-tetramethyl-5-decyne-
4,7-diol, 2,4,7,9-tetramethyl-5
Examples thereof include ethylene oxide adducts of -decyne-4,7-diol, and these can be obtained from commercial products (manufactured by Air Products and Chemicals, trade name Olfine or Surfynol). Only one of these acetylene glycol derivatives can be used, or two or more of them can be used at the same time. The amount of acetylene glycol derivative used is 0.1 to 10 per 100 parts by weight of the total solid content of the emulsion in order to prevent film defects. It should be added in the range of parts by weight.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with examples. In addition, the part and% in an example show a weight part and weight%, respectively. Example 1 Deionized water was placed in a polymerization vessel equipped with a stirrer, a cooler and a thermometer.
40 parts were charged, 10% of the total amount of a mixed liquid (hereinafter referred to as liquid A) consisting of 40 parts of the monomer, surfactant and deionized water shown in Table 1 was added, and then heated to 80 ° C., Further, a mixed solution of 0.1 part of ammonium persulfate and 20 parts of deionized water was added, and seed polymerization was carried out for 1 hour. Then, the remaining A at 80 ℃ for 3 hours
The solution was added dropwise. After the dropping of the liquid A was completed, the inside of the polymerization vessel was kept at 80 ° C. for another 2 hours to complete the reaction. The solid content concentration of the obtained emulsion was 50%. This emulsion
100 parts, modified polysodium acrylate 15% aqueous solution 0.5 parts,
A peelable coating composition was prepared by sequentially mixing 7 parts of titanium oxide. This coating composition is applied to the surface of a metal steel sheet, which is spray-coated with an acrylic melamine-based paint so as to have a dry film thickness of 40 μm, by using an applicator so that the dry film thickness is 100 μm. The test piece was dried for 10 minutes. With respect to the obtained test piece, peelability, heat-resistant peelability, heat resistance, water resistance, tensile elongation at break and strength were measured. The results were as shown in Table 2. In addition, the measurement of each characteristic was performed as follows.

A. Peelability When a coating film of the peelable coating composition was peeled from a test piece in an atmosphere at a temperature of 20 ° C, the ease of peeling was evaluated. b. Heat-Resistant Peeling Resistance A test piece was left in an atmosphere of a temperature of 80 ° C. for 20 days and then taken out, and the ease of peeling when the coating film of the peelable coating composition was peeled from the test piece was evaluated. c. Heat resistance (change in appearance) The change in appearance of the coating film tested in the above b was compared with that before the test. ◯: No change from the initial stage, △: A slight change is recognized,
X: A remarkable change is recognized d. Immerse the water resistant test piece in water at a temperature of 40 ° C for 10 days and then remove it.
The state of the coating film of the peelable coating composition and the appearance change of the coated metal steel sheet surface after the coating film was peeled off were compared with those before the test. (D-1) State of coating film ◯: Good as before, Δ: Partially peeled off, ×: Whole surface peeled off (d-2) Appearance change of coated metal steel plate surface ◯: Same as initial, Δ: Slightly Change is recognized,
X: Significant change is recognized e. Tensile Break Elongation The peelable coating composition was applied onto a glass plate using an applicator so that the dry film thickness was 80 μm, and dried at 50 ° C. for 10 minutes. Peel off the resulting coating from the glass plate, 25 mm
A test piece was obtained by cutting it into strips each having a width, and the breaking elongation at the time of a tensile test was measured at a temperature of 20 ° C. and a pulling speed of 300 mm / min. f. Tensile breaking strength The breaking strength at the time of the tensile test in the above e was measured.

Example 2, Comparative Examples 1 to 3 Polymerization was carried out in the same manner as in Example 1 with the types and amounts of the monomers and surfactants shown in Table 1, and the emulsions obtained were used in Examples. A composition was prepared by the same formulation as in Example 1, test pieces were prepared and evaluated in the same manner, and the results are shown in Table 2.

Example 3 Deionized water was placed in a polymerization vessel equipped with a stirrer, a cooler and a thermometer.
After charging 80 parts, after adding the component (a) of the monomers shown in Table 1 and the surfactant, the mixture was heated to 80 ° C, and a mixed solution of 0.1 part of ammonium persulfate and 10 parts of deionized water was added. After addition, the inside of the polymerization vessel was kept at 80 ° C. for 2 hours to polymerize the core portion. Then, after adding a mixed solution of 0.1 part of ammonium persulfate and 10 parts of deionized water, the remaining monomers shown in Table 1 were added dropwise at 80 ° C. over 3 hours. After the completion of the dropping, the inside of the polymerization vessel was kept at 80 ° C. for 2 hours to complete the reaction.
The solid content concentration of the obtained emulsion was 50%. Using the obtained emulsion, a composition was prepared by the same formulation as in Example 1, and test pieces were prepared and evaluated by the same method, and the results are shown in Table 2.

Examples 4 and 5 Polymerization was carried out in the same manner as in Example 3 with the types and amounts of the monomers and surfactants shown in Table 1, and the obtained emulsion was used to carry out the same procedure as in Example 1. A composition was prepared by blending, test pieces were prepared and evaluated by the same method, and the results are shown in Table 2.

Example 6 Total solids of the strippable coating composition prepared in Example 1 100
1.5 parts by weight of ethylene oxide (1.7 mol) adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol with respect to parts by weight (trade name: Surfynol 420 manufactured by Air Products and Chemicals) ) Was mixed uniformly. Using this, the state of the coating film obtained by coating on the same coated metal steel sheet surface as used in Example 1 was evaluated. The results were as shown in Table 3. ◯: Good coating film without cracks and craters, Δ: Some cracks and craters are observed, ×: Cracks on the entire surface,
Repelling is recognized

Examples 7, 8 and Comparative Examples 4, 5 In the same manner as in Example 6, the acetylene glycol derivative was uniformly mixed with the type and amount of the coating composition shown in Table 3 in the type and amount shown in Table 3. And the state of the coating film obtained by coating the same coated steel sheet surface as used in Example 1 with this was evaluated. The results were as shown in Table 3.

[0027]

[Table 1] Tg in Table 1 indicates the glass transition temperature (° C.) of the homopolymer, and the solubility in water indicates the solubility of the monomer in water (g / water 100 g),
In addition, the name of the manufacturer is shown in parentheses in the surfactant column.

The reactive surfactants in Table 1 have the following structures.

Embedded image Further, Emal O is sodium lauryl sulfate, and Neugen EA-170 is polyethylene glycol nonyl phenyl ether.

[0029]

[Table 2]

[0030]

[Table 3] Surfynol 485 (trade name, manufactured by Air Products and Chemicals, Inc.) in Table 3 is an ethylene oxide (30 mol) adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol.

[0031]

EFFECTS OF THE INVENTION The peelable coating composition of the present invention, when applied to the surface of a product requiring temporary protection, exhibits excellent water resistance and strength and thus exhibits a role as a long-term protective coating film. Furthermore, it is easy to peel off when peeling off this coating film and does not leave stains on the surface of the protected object after peeling off. Further, there is no problem in the treatment of the coating film after peeling. Due to this characteristic, the peelable coating composition of the present invention is extremely advantageous practically.

Claims (3)

[Claims] 1. A) selected from ethylenically unsaturated monomers whose solubility in water at 25 ° C. is less than 0.10 g / 100 g of water, and whose homopolymer has a glass transition temperature of 50 to 130 ° C. 1 to 2 or more monomers 3 to 50% by weight (b) 1 or 2 selected from ethylenically unsaturated monomers having a solubility in water at 25 ° C of 0.10 g / water 100 g or more 35 to 96.5% by weight of one or more monomers (c) Monomer mixture consisting of 0.5 to 15% by weight of one or more monomers selected from ethylenically unsaturated monomers having a functional group Is obtained by emulsion polymerization in the presence of a radical polymerization initiator using a reactive surfactant as a surfactant, and may contain a copolymer emulsion having a glass transition temperature of −40 to 40 ° C. as a main component. A peelable coating composition. 2. A copolymer emulsion, wherein the monomer of component (a) is used in the core part and the monomers of (b) and (c) are used in the shell part, and the emulsion is used as a surfactant. An emulsion having a core-shell particle structure having a glass transition temperature of -40 to 40 ° C., which is obtained by emulsion polymerization using a reactive surfactant in the presence of a radical polymerization initiator.
A peelable coating composition as described in 1. 3. The peelable coating composition according to claim 1, which contains an acetylene glycol derivative represented by the following general formula (1). Embedded image (However, R ¹ and R ² in the formula are each a hydrogen atom or a carbon number 1
~ 5 alkyl groups, the sum of n and m is 0-30. )