JPS60190474A - Aqueous coating composition for forming improved protecting film - Google Patents

Abstract

PURPOSE:The titled composition for providing a film usuful as a protecting film of a product, removable with an alkali, obtained by copolymerizing a monoethylenic unsaturated fatty acid with a specific hydrophilic monomer in an aqueous solvent, dispersing it into water. CONSTITUTION:(A) 3-15pts.wt. one or more alpha,beta-monoethylenic unsaturated acids is copolymerized with (B) 100pts.wt. polymerizable vinyl monomer containing one polymerizable unsaturated bond in the molecule, having polyoxyethylene chain having 1,500-15,000 average molecular weight, containing 1-15pts.wt. hydrophilic monomer having a terminal group consisting of H, or 1-4C alkyl group in (C) an aqueous organic solvent. The prepared vinyl copolymer is dispersed into water, to give the desired composition comprising a vinyl copolymer aqueous dispersion as an essential component.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved aqueous coating composition for forming a protective film, and more particularly, the present invention relates to an improved aqueous coating composition for forming a protective film, and more particularly, the present invention relates to an improved protective film-forming aqueous coating composition comprising a specified amount of an α,β-monoethylenically unsaturated acid and a specified hydrophilic monomer. Aqueous dispersion of vinyl copolymer obtained from polymerizable vinyl monomer (
Hereinafter, it is also referred to as an acrylic resin dispersion. ) as an essential component, which has excellent coating workability and protective properties, and which can be removed extremely easily with an alkaline aqueous solution even after long-term outdoor exposure. Therefore, the composition of the present invention is suitable for protecting objects to be coated, such as metals, glass, plastics, pre-painted objects, or plated objects, which are not affected by alkali treatment. It is extremely useful for protecting large objects such as mechanical parts and for primary rust prevention of metals such as steel, and is particularly suitable as a strippable paint.

By the way, before cars and other vehicles are delivered to consumers, they are usually exposed to dust, soot, soot, salts, iron powder, and in rare cases, bird excrement.

The surface can become contaminated due to direct sunlight, wind and rain, and it can also develop weirs, stains, discoloration, rust, and cracks. Further, among metal articles, steel in particular is an extremely important material in industry, but it is easily oxidized and rusts due to the action of moisture and oxygen in the air.

These often become a factor that significantly reduces product value, and removing them requires a great deal of effort and expense, so it is necessary to protect the surface of such products in advance. Become.

Many protection methods and compositions have been proposed for this purpose.

For example, there is a method of applying a protective composition and then mechanically peeling it off each time, but since most of these protective compositions are solvent-based, they pose a fire hazard and are toxic to the human body. Such peeling, especially when dealing with large objects, has the drawback of requiring a correspondingly large amount of effort.

Another method is to remove the protective composition with a solvent, but since it is a wax-based protective composition, it is usually difficult to store it for a long time or expose it to direct sunlight. If you do this, it may change in quality, so
The removal work can be said to be extremely difficult, and since a large amount of solvent is used in the removal process, this method poses a risk of fire and toxicity to the human body. This poses a major problem in the treatment of wastewater and wastewater.

Furthermore, as primary rust preventive agents for steel materials, oil, grease, wax, or small amounts of organic amines, zinc naphthenate, petroleum oxidation products, funnel oil, alkali metal salts, or alkaline earth wire mesh salts are added to these. Although rust preventive oils and the like are known, steel materials coated with such secondary rust preventive agents exhibit good rust preventive properties as long as they are not transported or stored for a short period of time. Although it can be easily removed by alkaline treatment after the next processing, these rust-preventing effects are almost impossible as recently, when it is often left piled up outdoors or stored under water droplets. It will no longer be possible to demonstrate your full potential.

In addition, since these anti-corrosion coatings are liquid coatings, they have poor mechanical strength and are easily damaged, and the anti-corrosion coatings may fall off from the surface of the steel due to contact with nearby objects. It also has the disadvantage that it is easy to rust, and therefore rust occurs in such areas.

In recent years, water-based resins have been developed as a method that is suitable for protecting large objects, has fewer problems with fire, toxicity, and wastewater treatment, is easy to remove, and provides good protection. JP-A-49-97835.50-19 also includes a method of using an alkaline aqueous solution in the removal process with a protective composition based on
835.50-89427 and 56-22368, but all of them are still sufficiently satisfactory in terms of paint workability, peelability, and physical properties of the coating film such as water resistance. It has not become.

However, in view of these circumstances, the inventors of the present invention have conducted intensive research to improve the coating workability, releasability, and physical properties of the coating film of an aqueous coating composition for forming a protective film. We have discovered an aqueous coating composition for forming a protective film, so-called stripper paint, which has the following characteristics and can be removed extremely easily with an alkaline aqueous solution even after long-term outdoor exposure.
The present invention was completed = 6-.

That is, the present invention comprises one or more α,β-monoethylenically unsaturated acids having 6 to 15 polyvalent moieties, one polymerizable unsaturated bond in the molecule, and an average molecular weight of 1,
100 of a polymerizable vinyl monomer having a polyoxyethylene chain of 500 to 15,000 and containing a hydrophilic monomer whose end group is a hydrogen atom or a C0 to C4 alkyl group in a proportion of 1 to 15 parts by weight. Particularly for painting work, comprising as an essential component an aqueous dispersion of a vinyl copolymer obtained by copolymerizing parts by weight in a water-soluble organic solvent and then dispersing the resulting vinyl copolymer in water. The present invention provides an aqueous coating composition for forming a protective film, which has significantly improved properties, protective properties, and coating performance after long-term outdoor exposure.

Here, the acrylic resin dispersion used to obtain the composition of the present invention is made by combining a polymer obtained by solution polymerization with a water-soluble organic solvent and a hydrophilic group without using emulsifiers or protective colloids that are commonly used. It is an aqueous dispersion that is stably dispersed in water due to the action of acrylic resin, and this eliminates problems such as sagging during painting, which is a drawback of acrylic resin.
It does not have problems such as foaming after coating, which is a disadvantage of emulsions, and is extremely advantageous in practical terms.

The acrylic resin dispersion is aliquified, for example, by the method described below.

First, one or two α,β-monoethylenically unsaturated acids
and one α,β-monoethylenically unsaturated bond (polymerizable vinyl group) in one molecule, and a hydrogen atom or a C, to C4 alkyl group as a terminal group, and an average molecular weight of i, so o~15. It is obtained by copolymerizing a polymerizable vinyl monomer containing ODD, a hydrophilic monomer having a polyoxyethylene chain, in a specific ratio in a hydrophilic organic solvent, and then dispersing it in water.

Here, typical examples of the α,β-monoethylenically unsaturated acids mentioned above include maleic acid, fumaric acid, itaconic acid, crotonic acid, and (meth)acrylic acid; Methacrylic acid is preferred.

The appropriate amount of the unsaturated acid used is 3 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of the total polymerizable vinyl monomer.

If the amount used is less than 6 parts by weight, the peelability of the protective film due to alkali tends to deteriorate;
If more than 5 parts by weight is used, no further improvement in strippability due to alkali can be expected, and it is not only uneconomical, but also the free carboxylic acid content increases and Both are rated 9- unfavorable because they adversely affect the painted surface.

On the other hand, a polyoxyethylene chain having one unsaturated bond in the molecule and having an average molecular weight of 1.500 to 15,000, whose end group is a hydrogen atom or C,%C
Examples of typical hydrophilic monomers with alkyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxy (meth)acrylate. - A compound obtained by adding ethylene oxide to a hydroxyl group-containing vinyl monomer such as n-butyl, or a compound with an average molecular weight of 1.500 to 15,000, in which one of the terminal groups is a hydrogen atom or a C1 to C4 alkyl group. a polyoxyethylene glycol derivative, the other of which is a hydroxyl group, and a vinyl group-containing carboxylic acid monomer (α,β-monoethylenically unsaturated acid) such as (meth)acrylic acid, cinnamic acid or itaconic acid. Compounds such as those obtained by esterification reaction of or (meth)acrylic acid-te
Examples include compounds obtained by transesterifying a vinyl group-containing ester monomer such as rt-butyl with the above-mentioned polyoxyethylene glycol derivatives.

The average molecular weight of the polyoxyethylene chain portion in the hydrophilic monomer must be within the range of 1.500 to 15,000.

If the molecular weight of this chain portion is less than 1.500, a sufficient effect cannot be expected in water dispersion of the resulting copolymer solution, and conversely, 15. Even when exceeding ODD,
The copolymerizable vinyl group (α) per unit molecular weight of the hydrophilic monomer.

Since the amount of (β-monoethylenically unsaturated bonds) is extremely reduced, the water dispersion effect of the copolymer solution is also significantly reduced, so both are unfavorable.

The average molecular weight of the polyoxyethylene chain portion of the monomer is preferably 2,000 to io, ooo, more preferably 3,000 to 8,000.

The amount of the monomer used is 1 to 15 parts by weight, preferably 2 parts by weight, based on 100 parts by weight of the total polymerizable vinyl monomer.
~10 parts by weight.

If the amount of the monomer used is less than 1 part by weight, the water dispersion effect of the resulting copolymer solution may not be sufficient, and therefore it becomes difficult to obtain a stable aqueous dispersion.
On the other hand, if the amount exceeds 15 parts by weight, the water dispersion effect of the obtained copolymer solution will not be expected to be any greater than that, and it will not only become uneconomical, but also the water resistance of the copolymer will deteriorate. Both of these are undesirable as they result in a decrease in

Furthermore, other polymerizable vinyl monomers that can be copolymerized with the above-mentioned α,β-monoethylenically unsaturated acids and hydrophilic polymers include methyl (meth)acrylate, (meth)acrylic acid, Ethyl, (meth)acrylic acid-
n-Butyl, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, (meth)acrylic acid
(meth)acrylic acid esters such as 2-hydroxyethyl, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-chloropropyl (meth)acrylate, and (β-methyl)glycidyl (meth)acrylate; Class;
α, β-monoethylenically unsaturated amides such as (meth)acrylamide, N-methyl (meth)acrylamide, N-methylol (meth)acrylamide; α,β-monoethylenically unsaturated nitriles such as (meth)acrylonitrile Typical examples include the following.

13- Vinyl chloride, vinyl halides such as vinylidene chloride, styrene, α-methylstyrene, vinyl Styrene derivatives such as toluene, vinyl acetate.

Vinyl propionate, vinyl esters such as "Beova" (a product of Shell, Netherlands), α-olefins such as ethylene and propylene, conjugated dienes such as butadiene, or maleic esters such as dimethyl maleate and dibutyl maleate. etc., and these may be used alone or in combination of two or more.

The acrylic resin dispersion, which is an essential component of the composition of the present invention, is prepared by mixing the various polymerizable vinyl monomers listed above in a water-soluble organic solvent as exemplified below. 1so-Proper Tools, n-
Alcohols such as propoxy 7'0 hanol, diacetone alcohol, 1so-phthalol, n-butanol, or propylene glycol monomethyl ether, methyl cellosolve, ethyl cellosolve, ethylene glycol mono-1so
These include monoether alcohols or ethers such as -7' lobil ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and dioxane, and these may be used alone or in combination of two or more.

The amount of the solvent to be used is not particularly limited, but it is normally within the range of 10 to 100 parts by weight per 100 parts by weight of the total polymerizable vinyl monomers mentioned above.

In preparing the acrylic resin dispersion, benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, tart-butyl peroctate, and
It is preferable to use a known and commonly used radical polymerization initiator such as an organic peroxide type such as art-butyl perbenzoate or acetyl peroxide, or a nitrile type such as azobisinbutyronitrile or azobisinvaleronitrile.

The method for preparing the vinyl copolymer solution to obtain the acrylic resin dispersion is not particularly limited, and the method of preparing the vinyl copolymer solution described above is not particularly limited. Alternatively, a method may be used in which a saturated acidic polymerizable monomer of α, β-monoethylenically oriented, and a radical polymerization initiator are dropped, or a method of dropping a water-soluble organic solvent, a radical polymerization initiator, a hydrophilic monomer, and a radical polymerization initiator may be used.
, β-monoethylenically unoriented saturated acidic polymerizable vinyl monomer may be simultaneously added dropwise in parallel, or α, β-
A method may also be used in which a monoethylenically unoriented saturated acidic polymerizable vinyl monomer is copolymerized with a radical polymerization initiator, and in the latter half of the copolymerization reaction, the remaining hydrophilic monomer is added and packed.

In order to prepare the desired acrylic resin dispersion using the vinyl copolymer solution obtained in this way, it is sufficient to add water to the vinyl copolymer solution, and by doing this, the desired dispersion can be easily prepared. is obtained.

The dispersion of the vinyl copolymer solution with water may be carried out by gradually adding and dispersing the copolymer solution while stirring the water, or conversely, by gradually adding water to the copolymer solution. Alternatively, a method may be used in which the emulsification is effected by adding the liquid to the liquid and emulsifying it by phase inversion.

Generally, the vinyl copolymer solution is heated to about 50 to 100'C.
It is more preferable to use a method of heating the mixture and gradually adding water dropwise while stirring well to effect phase inversion emulsification, since this makes it easier to obtain a stable acrylic resin dispersion having a fine particle size.

17- When the film obtained using the acrylic resin dispersion thus obtained and the aqueous dispersion of the divinyl copolymer is required to have better retention properties when exposed outdoors for a long period of time. In the present composition containing the aqueous vinyl copolymer dispersion as an essential component, phenyl salicylate, 4-tert-butylphenyl salicylate, 2,4-
One or more of various salicylic acid derivatives such as dihydroxybenzophenone, 2-oxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, benzophenone derivatives or ultraviolet absorbers such as benzophenone derivatives or IJ azole derivatives. is 0.2 to 0.2 based on the weight of the aqueous vinyl copolymer dispersion.
It can also be added within a range of 5%.

In addition, acid components (such as free carboxyl groups) present in the aqueous copolymer dispersion can be neutralized with a volatile alkali such as ammonia or morpholine, if necessary. may be added in a pre-dissolved form in the water added during the preparation of the aqueous dispersion, or
Alternatively, it is of course possible to add it directly to the aqueous dispersion after its preparation.

On the other hand, neutralizing the aqueous dispersion with sodium hydroxide, potassium hydroxide, or triethanolamine, which has a low volatilization rate, is not preferable because the water resistance of the formed film will be significantly reduced.

The aqueous coating composition of the present invention can be used to protect the surface of the object to be coated by a known and commonly used method such as coating with a roll coater, curtain flow coater, brush coating, flow coating, spraying or dipping. After coating on the substrate, it may be dried at room temperature or forced drying.

The thickness of the dry film at this time is suitably within the range of 5 to 70 .mu.m, preferably 10 to 30 .mu.m.

In order to remove the protective film of the composition of the present invention thus formed, an alkaline aqueous solution (alkaline agent) as exemplified below may be used, and it can be easily removed by the action of such an alkaline agent.

That is, a 0.2 to 5 weight solution of various basic compounds such as ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium metasilicate, and sodium orthosilicate heated to 10 to 80°C is applied. 10 on the object
It can be easily and completely removed by spraying for about 15 seconds to 10 minutes, preferably 15 seconds to 5 minutes, or by immersing the coated object in the basic aqueous solution for the above period of time.

The aqueous coating composition of the present invention can be applied to any substrate as long as it does not change in quality due to treatment with an alkaline agent (alkali treatment), such as steel, cast iron, stainless steel, etc. - Suitable for protecting steel, plated or chromated materials, glass, various plastics, or ceramics.
It is particularly effective as a so-called strippable paint for protecting large objects such as automobiles, vehicles, aircraft, or mechanical parts, and for primary rust prevention of gold wires such as steel materials.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. In the following, all parts and percentages are based on weight unless otherwise specified.

Example 1 In a 21 flask equipped with a stirrer, a thermometer, a dropping funnel, a reflux condenser, and an inert gas inlet, 300 parts of ethyl cellosolve as a solvent and a methyl terminal group were added.
and the average molecular weight of the polyoxyethene chain portion is (S, 0
65 parts of methyl acrylate derivative 00 was prepared, and 1
434 parts of methyl methacrylate, 210 parts of n-butyl acrylate, and 56 parts of methacrylic acid were separately mixed in advance as polymerizable vinyl monomers at a temperature of 30° C. part tart-
Butyl hydroperoxide was injected from a separate dropping funnel to carry out dropwise copolymerization over a period of 3 hours.

After the dropwise addition was completed, the same temperature was maintained for 6 hours to complete the polymerization reaction.

Next, the vinyl copolymer solution obtained in this way was heated to 80%
℃, 615 parts of water was dropped over about 2 hours at the same temperature, and then the temperature was lowered to 25℃ and the pH was made alkaline with 5% ammonia water. A desired aqueous dispersion was obtained.

The vinyl copolymer aqueous dispersion obtained here has a non-volatile content of 22- (NV) of 45.2% and a Pruck-field viscosity (hereinafter simply referred to as viscosity) at 25°C of 1.40.
0 cps, p) (is 8.2, and the average particle size is 0.2
It was less than μm.

This aqueous dispersion was then diluted with deionized water in a trench with an NV of 20%, and the resulting coating composition was applied to a polished mild steel plate (JI
Sc-3310) and forced drying at 150° C. for 10 minutes to form a primary rust-preventing film with a thickness of 12 μm.

No "sag" or foaming on the painted surface was observed during such painting, and when the various properties of the resulting protective film were investigated, the pencil hardness was H to 2, the base grain density was 100/10100 (1 cell Fantape peeling) and water whitening resistance are also excellent, and it has a rating of 4 in the salt spray test (JIS Z-2571-1955 method).
It was found that even after 8 hours, there was no accumulation of rust due to total heat, and the condition was extremely good.

Furthermore, when this protective film was immersed in a 3% sodium orthosilicate aqueous solution for 6 minutes and then washed with water, it was confirmed that the protective film was completely removed during the immersion.

Example 2 In a reactor similar to Example 1, 300 parts of n-butyl cellosolve and 21 parts of hydrogen atom at the end, and a polyoxyethylene chain having a half-average molecular weight of 8,000, and C.
An acrylate represented by the structural formula H,=CH-0CO(-CH2CH20肱-H was charged, and 1
While heating to 30°C, a mixture consisting of 6 parts of azobisisobutyronitrile, 330 parts of styrene, 300 parts of n-butyl acrylate, and 70 parts of methacrylic acid was added through a separate dropping port for about 6 hours. It took a while to drip.

After completing the dropwise addition, the same temperature was maintained for 10 hours to complete the copolymerization reaction, the resulting copolymer solution was cooled to 80°C, and 580 parts of water was added dropwise at the same temperature over about 2 hours. , then cooled to 25°C and adjusted to pH' with 5% ammonia water.
l When made alkaline, it becomes uniform with a slight bluish tinge, NV is 44.8%, viscosity is 1.140 cps, pH
An aqueous copolymer dispersion having a particle size of 86 and an average particle diameter of 02 μm or less was obtained.

Thereafter, the coating composition thus obtained has a 4'NV of 2.
The aqueous coating composition was diluted to 0% with deionized water, and then applied to a stainless steel plate (8US24BA) of 10 x 150 x 0.4 m11 to a dry film thickness of 5 μm, and dried at room temperature for 2 days. A primary anti-rust film was formed.

There was no 'sagging' during painting, and when we investigated the performance of the protective film, the pencil hardness was 2H and the base grain test was 100710.
0, has excellent water whitening resistance, and has a rating of 48 in the salt spray test.
It was found that an extremely good aqueous coating composition for forming a protective film was obtained, showing no signs of rusting even after a period of time had elapsed.

It was also confirmed that the protective film was completely dissolved and removed by simply immersing the protective film in a 2% aqueous sodium hydroxide solution at 60° C. for 2 minutes and then washing with water.

Example 6 3 of n-butyl cellosolve in a reactor similar to Example 1.
00 parts of tert-butylperoxy-2-ethylhexanoate, 160 parts of styrene, 240 parts of methyl methacrylate, and 2 parts of acrylic acid. -ethyl-, xyl 2
61 and 65 parts of acrylic acid was added dropwise from another dropping port over a period of 6 hours. 70 parts of methacrylate was divided into three parts, and divided injections were also made in parallel every 26 hours. After the dripping is completed, the temperature remains the same.8
After holding for a certain period of time, the copolymerization reaction was completed.

Next, the temperature of the obtained copolymer solution was cooled to 60°C in a trench, and 640 parts of water was added dropwise over about 2 hours. After the dropwise addition was completed, the copolymer solution was cooled to 25°C. T-N
v is 45.2%, viscosity is 3,060 ape s pH
An aqueous copolymer dispersion was obtained in which the particle diameter was 3.2 and the average particle diameter was 0.2 μm or less.

The aqueous coating composition was then diluted with deionized water to an NV of 20% and then diluted at 120x.
The paint was applied to a 200 x 2 mm ABS board using an airless sprayer to a dry film thickness of 20 μm.

There was no 'sagging' on the painted surface, and a good painted surface was obtained by hot air drying at 60°C for 30 minutes, but the hardness was H, the base grain test was 100/100, and it was immersed in water for 48 hours. It was confirmed that an extremely good protective film was formed without causing any whitening.

Comparative Example 1 In order to compare the performance with an acrylic copolymer emulsion obtained by an emulsion polymerization method, an emulsion having the following composition was prepared according to a conventional emulsion polymerization method.

Methyl methacrylate 441 parts n-butyl acrylate 210 〃 Methacrylic acid 49 # Lauryl mercaptan 0.1〃 Dodecylbenzenesulfone 1 Narrow sodium 28 〃Ammonium persulfate 2.1〃 1.825.0 The emulsion obtained here is NV The emulsion was 404%, the viscosity was 19Qcps, and the pH was 3.4. After diluting this emulsion with deionization to an NV of 20%, it was coated on an ABS plate of 120X200X2v+it so that the dry film thickness was 20μm. When sprayed with an airless sprayer, there were countless air bubbles in the painted surface, giving it the appearance of artificially finely foamed surfaces.

Furthermore, when the water resistance of the coating film was examined, the entire surface turned white after 24 hours of immersion, and blisters were also observed, indicating that it was by no means suitable for practical use as a protective coating.

Comparative Example 2 In order to compare the performance with a water-soluble acrylic resin, a control resin solution was obtained by carrying out copolymerization based on the following composition in a solvent using a conventional method, and then neutralizing and diluting with water. However, the horn property value of Kono was 40.5% for NY, and the viscosity was 2.3%.
00 cpa 29- Methyl methacrylate 650 parts n-butyl acrylate 280 methacrylic acid 70 n-butyl cellosolve 490 tert-butyl peroxybenzoate 7 triethanolamine 84 ion exchange water 490 1.771 and pH was 94.

Next, the solution of this water-soluble acrylic resin was heated to 20% NY.
When the solution was diluted with deionized water to a concentration of 10% and then sprayed onto a polished mild steel plate (see above), significant "sagging" occurred and a uniform coating could not be obtained.

Thereafter, forced drying was performed at 150° C. for 10 minutes to obtain a coating film. As for the performance of the coating film obtained here, the lead dark hardness was H and the base grain test was 97/100, but the water resistance was 30-, with severe blistering occurring after 48 hours. As a protective coating, it was by no means a product that could be put to practical use.

Agent Ben” Katsutoshi Takahashi 31- biq-

Claims (1)

[Claims] One or more α, β-monoethylenically unsaturated acids
6 to 15 parts by weight of hydrogen, one polymerizable unsaturated bond in the molecule, and an average molecular weight of 1.500 to 15.0
100 parts by weight of a polymerizable vinyl monomer containing 1 to 15 parts by weight of a hydrophilic monomer which also has a polyoxyethylene chain of 00 and whose terminal group is a hydrogen atom or a C8 to C4 alkyl group. An alkali-removable coating film comprising as an essential component an aqueous vinyl copolymer dispersion obtained by copolymerizing in a water-soluble organic solvent and then dispersing the resulting vinyl copolymer in water. An aqueous coating composition for forming an improved protective film.