JPH08134386A - Aqueous composition for releasing uncured coating film - Google Patents

Abstract

PURPOSE: To obtain an aqueous composition capable of efficiently removing uncured coatings adhering to coating utensils such as masking jigs without any problem such as occupational hygiene or environmental pollution, containing each specified amount of film-forming water-soluble polymer compound(s) and builder. CONSTITUTION: This composition having the above-mentioned advantages is obtained by dissolving in water 3-20wt.% of at least one kind of film-forming water-soluble polymer compound selected from among acrylic resins, polyvinyl alcohol, methyl cellulose, polyethylene oxide, cellulose acetate, polyvinyl butyral, polyvinyl formal, hydroxypropyl cellulose, and derivatives therefrom, and 0.1-15wt.% of a builder such as a phosphate such as sodium orthophosphate, carbonate such as sodium carbonate, silicate such as sodium metasilicate or organic acid salt such as sodium gluconate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-curing coating film peeling aqueous solution which enables efficient removal of a pre-curing coating film adhering to coating equipment used in the coating process of various coated objects. It relates to a composition.

[0002]

2. Description of the Related Art As a method for removing coating films before curing adhered to coating equipment used in a coating process for coating an object to be coated, such as masking jigs, slats and coating booths, (i) dichloromethane A method of using a non-aqueous cleaning agent having an organic solvent as a main component, such as thinner, (ii) a method of using an aqueous cleaning agent having a caustic alkali as a main component by heating, (iii) a method of incineration treatment, And (iv) methods of applying physical vibration or shock have been conventionally used.

However, in the case of the method (i), there are many problems in terms of work hygiene such as toxicity, odor, flammability and waste liquid treatment and environmental pollution, and in the case of the method (ii), safety is also high. There is a problem in terms of wastewater treatment, etc., and there is a problem in terms of air pollution because of the method (iii) generation of toxic exhaust gas.In addition, in the case of method (iv), the coating equipment is deformed. Not only is there a high risk of damage, but the work efficiency is extremely low.

[0004]

SUMMARY OF THE INVENTION In view of such circumstances in the field, the present invention has almost no problems in terms of work hygiene and environmental pollution, and also has a pre-cured coating film that adheres to coating equipment. It was made in order to provide the means to remove efficiently.

[0005]

That is, the present invention relates to an aqueous composition for stripping a coating film before curing, which contains 3 to 20% by weight of a water-soluble film-forming polymer compound and 0.1 to 15% by weight of a builder.

Examples of the water-soluble film-forming polymer compound used in the present invention include acrylic resins, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose,
Examples thereof include polyethylene oxide, cellulose acetate, polyvinyl butyral, polyvinyl formal, hydroxypropyl cellulose, and various derivatives of these polymer compounds, but acrylic resins and polyvinyl alcohols, particularly acrylic resins are preferable.
The molecular weight of these polymer compounds is not particularly limited, but is generally about 10,000 to about 100,000, preferably about 30,000 to about 50,000.

The amount of the above water-soluble film-forming polymer compound is usually 3 to 20% by weight, preferably 5 to 10%.
If the amount is less than 3% by weight, it becomes difficult to form a sufficient film on the surface of the coating equipment, and conversely,
If it is more than 20% by weight, the viscosity of the aqueous composition becomes too high, spraying becomes difficult, and the formed film becomes thick, so that it takes time to dry the film and then remove it by washing. Not only is it uneconomical.

Examples of the builder used in the present invention include phosphates (for example, sodium orthophosphate, sodium pyrophosphate, sodium tripolyphosphate, sodium tetraphosphate and sodium hexametaphosphate) and carbonates (for example,
Examples thereof include sodium carbonate, sodium bicarbonate and sodium sesquicarbonate), silicates (eg sodium metasilicate and sodium orthosilicate), and organic acid salts (eg sodium gluconate and sodium EDTA).

The compounding amount of the above-mentioned builder depends on the kind of the builder and the kind of paint adhered to the coating equipment, but it is usually 0.1 to 15% by weight, preferably 0.5.
If it is less than 0.1% by weight, effective detergency cannot be obtained. On the other hand, if it exceeds 15% by weight, the formation of a polymer film is hindered, which is not preferable.

If desired, the aqueous composition for stripping off a coating film before curing according to the present invention may further contain a nonionic surfactant or anionic surfactant known per se. Nonionic surfactants include higher alcohol-ethylene oxide adducts, alkylphenol-ethylene oxide adducts, higher alkylamine-ethylene oxide adducts, propylene glycol-ethylene oxide adducts, alkyl ethers of polyhydric alcohols, and fatty acid amides of alkanolamines. Etc. are illustrated. Also,
Examples of anionic surfactants include fatty acid salts, higher alcohol sulfates, higher alkyl ether sulfates, sulfates such as sulfated olefins, sulfonates such as alkylbenzene sulfonates, and higher alcohol phosphates. Examples thereof include phosphoric acid ester. The amount of the above-mentioned surfactant is usually 0.1 to 10
% By weight, preferably 1 to 3% by weight.

The coating equipment is pretreated with the above-mentioned aqueous composition according to the invention before it is used in the coating process. That is, by attaching the aqueous composition to the surface of coating equipment by a spraying method, a dipping method, or the like, and then evaporating water by natural drying or heat drying (for example, 60 ° C. to 90 ° C.), A polymer film is formed on the surface. The thickness of the polymer film is not particularly limited, but is usually 10 to 100 μm, preferably 15 to 50 μm. If the film thickness is too thin, the film effect cannot be obtained and the paint cannot be completely erased. . On the other hand, if it is too thick, the drying property is deteriorated and the removability of the film itself is deteriorated.

When coating equipment having a polymer film on the surface is used in a coating process according to each purpose, a pre-cured coating layer is formed on the surface of the polymer coating. The substances are subjected to a cleaning treatment such as a spraying method or a dipping method. As the cleaning liquid, an aqueous cleaning liquid is used from the viewpoint of work hygiene and environmental pollution. In this cleaning treatment, since the water-soluble polymer film is solubilized, the coating film before curing formed on the polymer film is efficiently peeled and removed. In this case, as the aqueous cleaning liquid, an aqueous cleaning liquid containing the aforementioned builder or surfactant may be appropriately used, but from the viewpoint of reuse of coating equipment and work efficiency, curing by the present invention It is preferable to use the aqueous composition for removing the pre-coating film as a cleaning liquid. That is, when the coating equipment after peeling off the coating film before curing using the aqueous composition is naturally dried or dried by heating, a polymer film is re-formed on the surface of the coating equipment, The coating equipment can be used as it is in the next coating process, and is extremely efficient.

The aqueous composition according to the present invention can be applied to general pre-curing coating films attached to coating equipment, but particularly urethane coating films, melamine coating films, acrylic coating films and the like. Effective for peeling and removing.

[0014]

EXAMPLES The present invention will be further described below with reference to examples. Example 1 A water-based composition 1 prepared by the following formulation was adhered to the surface of a masking jig for coating by a dipping method, and this was subjected to a drying treatment to form a water-soluble polymer film on the surface. . Ingredients Ingredient amount (wt%) Polyvinyl alcohol (number average molecular weight: 30,000) 10 Sodium metasilicate 5 Water 85 After using this masking jig, spray coating with urethane paint for automobile bumper was performed 20 times, and then 9
Using the aqueous composition 1 heated to 0 ° C., a masking jig having a pre-cured coating layer formed on its surface was spray-washed (spray pressure: 5 kg / cm ² ) to completely remove the pre-cured coating layer. The time until peeling and removal was measured. After the washed masking jig was subjected to a drying treatment, it was used in the same spray coating as above, and then subjected to a spray washing treatment, and the time until the coating film before curing was completely peeled off was measured. This operation was repeated once more. The results obtained (washing time until the coating layer before curing is completely peeled off) are shown in Table 1. The same coating process and cleaning process as above were performed except that the aqueous composition 1 at room temperature was used as the cleaning liquid.
The obtained results are shown in Table 2.

Example 2 The same operation as in Example 1 was conducted except that the aqueous composition 2 prepared by the following formulation was used in place of the aqueous composition 1, and the results are shown in Tables 1 and 2. Blending ingredients Blending amount (wt%) Acrylic resin (number average molecular weight: 20,000) 10 Sodium paratonene sulfonate 5 Water 85

Comparative Example 1 The same operation as in Example 1 was performed except that a masking jig that was not pretreated with the aqueous composition was used, and that a 25 wt% caustic potash aqueous solution was used as the cleaning liquid (temperature of the cleaning liquid). : 90 ° C). The results obtained are shown in Table 1.

Comparative Example 2 The same operation as in Comparative Example 1 was carried out except that a 5% by weight aqueous sodium metasilicate solution was used as the cleaning liquid. The obtained results are shown in Tables 1 and 2.

Comparative Example 3 The same operation as in Comparative Example 1 was performed except that dichloromethane was used as the cleaning liquid and the rocking dipping method was adopted as the cleaning method (temperature of the cleaning liquid: normal temperature). The obtained results are shown in Table 2.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

EFFECTS OF THE INVENTION By using the aqueous composition of the present invention, it adheres to coating equipment without causing problems such as work hygiene and environmental pollution (in particular, it does not require caustic alkali which is dangerous to handle). The coating film before curing can be efficiently removed.

Claims (5)

[Claims] 1. A water-soluble film-forming polymer compound 3 to 2
An aqueous composition for removing a coating film before curing, containing 0% by weight and 0.1 to 15% by weight of a builder. 2. The aqueous composition according to claim 1, wherein the film-forming polymer compound is a water-soluble acrylic resin. 3. The method according to claim 1, which contains a surfactant.
The aqueous composition described. 4. A coating device having a polymer film formed on the surface thereof by previously depositing and drying the pre-curing coating film-peeling aqueous composition according to claim 1 is applied. A method for cleaning coating equipment, which comprises treating with an aqueous cleaning solution after being used in a process. 5. The method according to claim 4, wherein the aqueous cleaning liquid is the aqueous composition according to any one of claims 1 to 3.