JPS62213879A - Improved partial painting method - Google Patents

Abstract

PURPOSE:To simply and beautifully perform even in partial painting of a complicated shape, by using an org. solvent solution containing a polyurethane resin having specific tensile strength and specific elongation at break as an essential component as masking paint. CONSTITUTION:An org. solvent solution of a polyurethane resin used as masking paint is a composition containing only the polyurethane resin having a film characteristic such that the tensile strength is 150kg/cm<2> or more and the elongation at break is 300% or a resin mixture of said resin and at least one of a vinyl chloride resin, a vinyl acetate resin and nitrocellulose etc. as an essential component in an amount of 3-50wt%. This composition is applied to an article as the masking paint and, subsequently, the paint film of an area to be partially painted is released by cutting while desired partial painting is applied to the released area. As a final step, the remaining masking paint is released and removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a new and useful partial painting method, and more particularly, the present invention relates to a new and useful partial painting method, in which a specific masking paint is pre-applied,
This invention relates to an improved method comprising cutting a part to be partially painted, applying this partial coating to the peeled area, and then peeling off other non-coated parts to obtain a desired partial system product. .

[Problems to be solved by conventional technology and invention]

Conventionally, when dividing an article to be painted into different colors, the method used is to use masking tape to cover the areas to be painted with other colors (other color areas) before painting. .

However, when using such a masking tape, it is relatively easy to mask a flat surface, but it is extremely inconvenient to mask a curved surface or a curved surface.

There is also a method of using a jig to cover parts that do not need painting, but in this case.

There is a problem in that it is difficult to seal the parting lines, and it is no longer possible to completely coat objects with complex shapes.

In addition to this method, recently there is a method of painting the Ω part using masking paint.

For example, in Japanese Patent Publication No. 59-35671.

A method is disclosed for partially painting the surface of a plastic article using a masking paint obtained from polyvinyl acetate or polyvinyl chloride. However, since it contains a relatively large amount of plasticizer as a component that maintains the stability of the resin, it is inevitable that the solvent resistance will be poor, so the film based on masking paint can be peeled off by cutting. A solvent contained in the paint that is subsequently applied.

In particular, it was found that the parting lines were easily swollen by ketones and esters, so the parting lines were deformed during the painting operation, and as a result, the masking itself became useless.

In particular, if such masking (cutting and painting is performed while the surface is not sufficiently dry), deformation of such parting lines is likely to occur, which particularly limits the painting time. In cases such as line painting, the disadvantages are that the type of paint that can be used is severely limited, and the use of masking paint is often virtually impossible.

[Rounding method to solve problems]

However, in view of the various drawbacks of the prior art as described above, the inventors of the present invention conducted extensive studies to solve these problems, and found that
In particular, it is possible to easily apply partial coating to objects with any complex shape, and the resistance to commonly used painting solvents (solvent resistance) is extremely high. Therefore, even if the masking paint itself is not sufficiently or completely dried in a short drying time, it has sufficient masking performance and cutting performance even before the nails are completely dry. Problems such as deformation can be resolved,
Moreover, it can be used satisfactorily for line painting in factories. We have discovered a versatile and innovative partial painting method using masking paint, and have completed the present invention.

In other words, the present invention first coats the surface of the article to be coated with a material having a tensile strength of 150 kyl or more and an elongation of 30 when cut.
At least one selected from the group consisting of polyurethane resin alone, or polyurethane resin and vinyl chloride resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer resin, nitrocellulose, and cellulose acetate sotylate, having a film property of 0%. A resin (composition) in the form of a mixture with a seed resin is used as an essential film-forming component.
An organic solvent solution of a resin (composition) containing ~50 gk% by weight is used as a masking paint to apply the paint, and then the paint film in the area to be partially coated is cut out and peeled off, and then, The method consists of applying a desired partial coating to the area thus peeled off, and then peeling off the film of the area where no partial painting has been applied and therefore the masking paint is still applied. This article attempts to provide an improved partial painting method.

Here, first, the organic solvent solution of polyurethane resin used as the above-mentioned masking paint has a tensile strength of 150 to 97 tm2 or more as a film formed, and an elongation at break of 300% or more. These polyurethane resins include polyurethane resins with a high molecular weight (20,000 to 300,000, preferably 30,000 to 100,000) obtained by ordinary solution polymerization or bulk polymerization. can be mentioned.

That is, a solution or bulk (agglomerate) of a resin having a linear structure obtained by polymerizing a polymeric diol, an organic diisocyanate, and a chain extender in the presence or absence of an organic solvent by a conventional method. ), preferred polyurethane resins for carrying out the method of the present invention are polyurethane resins in which the tensile strength (breaking strength) of the film obtained from the resin is 150 kyl>' or more, and Suitable materials have physical properties (values) such that the elongation at break is 300 inches or more.

First, polymer diols are I having hydroxyl groups at both ends.
Lyester diol or? This is synonymous with riether diol, and any known and commonly used polymer diols can be used, but representative polyester diols include succinic acid and adipino acid.

Various dibasic acids such as glutaric acid, azelaic acid, sepatic acid or phthalic acid, as well as unsaturated dibasic acids such as ffleic acid, fumaric acid or itaconic acid, ethylene glycol, furopylene gellicol, 1.4- butane fall. 1. Polycondensates with various diols such as 6-hexanediol or diethylene glycol; or ring-opened heavy metal compounds of various caprolactones such as ε-caprolactone or alkyl-substituted C-casirolactone.

On the other hand, typical polyether diols include:
19 Litetramethylene glycol, polyzo c1♂ lengelicol, polyethylene glycol, etc. are 0.
The polymeric diols listed above are just a few examples, and therefore other types may of course be used depending on the purpose and application.

Next, known and commonly used organic diisocyanates mentioned above can be used as they are, and among them, representative ones include 4,4'-diphenylmethane diisocyanate *-),
Phenyl diisocyanate.

Xylylene diisocyanate, inphorone diisocyanate, 1.6-hexamethylene diisocyanate, 1.
4-tetramethylene diisocyanate.

Examples include tolylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, and hydrogenated tolylene diisocyanate.

Furthermore, the chain extender mentioned above is hydrazine.

Ethylenecyamine, py(razone, propylene diamine,
Various diamines such as xylylene diamine or isophorone cyamine; Difunctional compounds with active hydrogen may be mentioned, such as oyster glycols; or amino alcohols such as monoethanolamine or dimethylethanolamine.

The tensile strength of the film obtained from the polyurethane resin is 15
If it is less than 0 kg/cm, masking 4
When applying India and then cutting and peeling off the coated film, it became impossible to peel off as a continuous film and the film split midway and was cut into pieces. Resistance to solvents of paint applied to the masking paint area (mainly near the boundary with the area to be partially painted, although it is not necessary to paint this area, it is applied when painting one part) The properties (solvent resistance) deteriorated, and the parting line portion became deformed. On the other hand, if the elongation at break of the film obtained from the resin is less than 300%, the film becomes brittle and does not form a continuous film when it peels off. This is undesirable because it tends to result in cleavage or fragmentation in the middle of the process.

The organic solvent solution of the polyurethane resin is prepared by reacting the polyurethane resin in the form of a solution in the presence of an organic solvent, or by dissolving a previously prepared polyurethane resin in an organic solvent. can get.

Organic solvents used for this purpose include acetone, methyl ethyl ketone, methyl isobutyl ketone,
Typical examples include toluene, xylene, ethyl acetate, and butyl acetate, and it goes without saying that these may be used alone or in combination of two or more. Among these, it is preferable to use methyl ethyl ketone.

The organic solvent solution of the urethane resin obtained in this way is
Usually, it is used as a non-volatile content (solid content temperature) of 3 to 50% by weight.

If the concentration is less than 3% by weight, the concentration is too low and only an extremely thin and brittle film can be formed, or multiple coatings may be required, which is undesirable.On the other hand, if it exceeds 50% by weight, Polyurethane resins are undesirable because they thicken to the point that they become difficult to handle.In order to avoid this thickening problem, the molecular weight of the polyurethane resin can be made extremely low to create sufficient tensile strength and strength at break to withstand peeling. This is also undesirable since it becomes impossible to obtain a film with good elongation.

A particularly desirable range for the nonvolatile content (solid content concentration) of the -urethane resin solution is 5 to 401! It's quantity.

In addition, the solvents used to prepare the resin solution include the above-mentioned 9 solvents, and each of the solvents listed above is one representative example.

All of these are indispensable, and what can be obtained if such specific organic solvents are not used at all? The polyurethane resin solution may become cloudy, the polyurethane resin may precipitate and separate over time, or the drying rate of the resin solution may become extremely slow, or furthermore, the cost may become high and it may become impractical. Problematic and undesirable.

The preferred proportion of the above-mentioned essential organic solvents is within the range of 50 to 100% by weight of the total organic solvents, therefore, within the range of 0 to 50% by weight, n-!
Tanol, imbutanol.

ffl alcohols such as isoglono-9ol, ethanol or methanol; various ethers such as ethylene glycol monoethyl ether, ethylene glycol moptyl ether or diethylene glycol monomethyl ether; amides such as trimethylformamide or dimethylacetamide; or tetrahydrofuran or Cyclic ether compounds such as dioxane, etc.
It can be used as other solvents.

Masking as described above (in India, in addition to the above-mentioned organic solvent solution of only polyurethane resin, 5 to 100 ii
Vinyl chloride resin (I-vinyl chloride),
When vinyl acetate resin (vinyl acetate), vinyl chloride-vinyl acetate copolymer resin, nitrocellulose and/or Tahcel a-acetate butyrate are used in combination within a range that does not significantly impair the solvent resistance of the resulting film. However, it goes without saying that even in the case of V bonding by such combination, the resulting film must have a tensile strength of 150 kg7cm2 or more and an elongation at break of 300% or more.

A particularly desirable resin to be used in combination is vinyl chloride.
It is a vinyl acetate copolymer resin.

An organic solvent solution of the polyurethane resin obtained in this way or an organic solvent solution of a mixture of the d IJ urethane resin and the above-mentioned specific resin is used as a masking method and the resin solution is applied to the surface of the article to be coated. For coating, it is applied to the surface of the partially coated article by a known and commonly used coating method such as brush coating, spray coating, O-layer coating, or dipping coating, and then the solvent is applied by air drying or forced drying. The masking paint film on the area to be coated is then removed by cutting the area to be painted, and then the area is partially coated using a conventional coating method.

Here, the articles to be coated, that is, the objects to be coated, include iron or non-ferrous metal products (including raw materials and processed products), wood products (same), glass products (same), thermosetting materials and thermoplastic materials. plastic molded products (same) or rubber products (same)
Among them, thermosetting plastic molded products include phenol resin and melamine resin.

Typical examples include molded products obtained from various resins such as urea resin, 2-epoxy resin, unsaturated I-lyester resin, and vinyl ester resin (2-d-oxyacrylate resin).On the other hand, thermoplastic Plastic molded products include polyethylene, polypropylene, and polyester resin (PE
Also includes T and PBT. ), vinyl chloride resin (polyvinyl chloride), vinyl chloride-vinyl acetate copolymer resin, polystyrene resin, AS resin, ABS resin, methacrylic acid resin, polyurethane resin, ethylene-vinyl acetate copolymer resin, polyphenylene sulfide resin. Typical molded products are molded products made from various resins such as recarbonate resin, but polypropylene or polyurethane is particularly mentioned, and in particular, polypropylene automobile pancakes or polyurethane split automobile bumpers are mentioned.

In addition, paints used for partial painting include various synthetic resin paints such as acrylic-urethane paints, acrylic-melamine paints, alkyd-melamine paints, epoxy resin paints, and polyester-melamine paints. Water-based baking paint.

Alternatively, general-purpose paints such as oil-based paints using drying oil are typical.

Then, after the partial coating has been applied in this way, ie before or after drying of the partial coating area.

The masking-indica coating on the remaining portions, which have not been painted, is peeled off to complete the desired partial painting.

The film obtained from the masking paint (masking paint film) used in carrying out the method of the present invention has excellent film strength and elongation, and moreover, it has excellent film strength and elongation. It also has sufficient solvent resistance to the solvents used in paints, so even if it dries for a relatively short time, there will be no damage to the paint during the partial painting process that is carried out after cutting the masking paint film. The serious problem that the masking paint film swells due to the presence of the solvent and the parting line portions become deformed, rendering it useless as a mask, has been solved.

As a result, even if the workpiece has a complex shape, the parting line can be easily and reliably maintained, making it possible to safely and extremely easily paint the desired part even if it is L or with high precision. can be done.

〔Example〕

Next Washing 1 The present invention will be specifically explained with reference to Reference Examples, Examples, and Comparative Examples. In the following, all parts and weights are based on weight unless otherwise specified.

Reference example 1 (class example of organic solvent solution of polyurethane resin)
In a glass reaction vessel equipped with a cooling tube, a thermometer, a blowing device, and a stirring device, 1 having a hydroxyl group equivalent of 503,
4-Butanediol-adipic acid system, I? 100 parts of IJ ester diol and 6 parts of ethylene glycol were charged, and the temperature was raised to 80°C. Traditionally, 100 parts of methyl ethyl ketone was added and then 49 parts of 4,4'-diphenylmethane diisocyanate were also charged and reacted at 75-85°C in a nitrogen stream.

As the viscosity increased, the reaction was continued while diluting with methyl ethyl ketone until the final resin concentration was 30.
Brookfield viscosity (
) is 38,000 cps? A solution of urethane resin in methyl ethyl ketone was obtained. Below, this is P
It is abbreviated as U-1.

Next, this resin solution was cast onto a glass plate.

Dry H to about 100 μm after drying at 80°C for 30 minutes
A polyurethane resin film with a thick thickness was prepared.

The tensile strength of the film thus obtained was 437 kg/cm2, and the elongation at break was 650 inches.

Reference Example 2 (same as above) In a device similar to Reference Example 1, 100 parts of polyoxypropylene glycol having a hydroxyl group at of 300 and 2+4-/
2+6-Trilene with an isomer weight mixing ratio of 80/20.
29 parts of diisocyanate were charged, and 100 parts of a mixed solvent of xylene/methyl ethyl ketone = 1/1 (weight ratio) were also charged, and the mixture was reacted at 75 to 85°C under a nitrogen atmosphere.

At that time, as the viscosity increased, the reaction was continued while diluting with a mixed solvent of xylene/methyl ethyl ketone = 171 (weight ratio). & Eventually the tree's ma degree is 45
．． The purpose is to have a viscosity of 27,000 cps with a weight of 6 yen (
A mixed solvent solution of resin xylene/methyl ethyl ketone=171 (weight ratio) was obtained.

Hereinafter, this will be abbreviated as PU-2.

Next, this resin solution was cast onto a glass plate and dried at 80° C. for 30 minutes to produce a polyurethane resin film having a dry film thickness of about 100 P/ML.

The film thus obtained has a tensile strength of 296'Q/cm2.
The elongation at break was 540%.

Reference Example 3 (same as above) Using the same apparatus as Reference Example 1, methyl ethyl ketone/dimethylformamide = 8/2 (weight ratio ), 34.8 parts of 1,6-hexamethylene diisocyanate were added, and 75 parts of the mixed solvent was added under a nitrogen atmosphere.
After reacting at ~85°C, 17 parts of isophorone diisocyanate dissolved in methyl ethyl ketone was slowly added dropwise and the same temperature was maintained at VC for 1 hour after the completion of one drop.
Then methyl ethyl ketone/trimethylformamide=1
Diluted with a mixed solvent of /1 (f [quantity ratio)], the resin concentration was 40.1%, and the viscosity was 32.000 cps.
A desired resin solution was obtained. Hereinafter, this will be abbreviated as PU-3.

Afterwards, this resin solution was cast onto a glass plate, and
The dry film thickness is approximately 100 μm after drying at ℃ for 30 minutes. A urethane resin film was produced.

The tensile strength and elongation at break of the film thus obtained were 383 kg/cm and 430 cm, respectively.

Examples 1 to 8 and Comparative Examples 1 to 3 Each polyurethane resin solution obtained in Reference Examples 1 to 3 was
Masking 4 India was prepared by diluting with the solvents listed in the table.

Resin solutions containing pond-type resins were also prepared according to those listed in the same table and used as masking paints.

Next, each of the masking paints obtained in this way is applied to the entire surface of the unsaturated polyester resin molded product, and then the area to be partially coated is cut out and peeled off using a cutter, and then the area to be partially coated (
At this point, the surface of the molded article is exposed. ) is coated with one layer of primer and then with one layer of clear or enamel obtained from acrylic-tarethane resin, and then
Baking was carried out at 0°C for 30 minutes to completely peel off the remaining masking paint film on the masked area to obtain the desired partially coated article. The results determined by visual inspection are summarized in the same table.

The object to be coated is an automobile pan made of polypropylene and polyurethane, which is a typical example of a thermoplastic synthetic resin molded product.
It was confirmed that similar results could be obtained even if the same partial painting method was repeated.

〔Effect of the invention〕

As is clear from the results in Table 1, when the method of the present invention is followed, the resistance (solvability) to commonly used coating solvents is extremely excellent.

Moreover, it is known that it has sufficient masking properties and cutting properties.

Claims (1)

[Claims] 1. The surface of the article to be coated has a tensile strength of 150 kg/c.
As a masking paint, an organic solvent solution of a polyurethane resin having film properties of m^2 or more and an elongation at break of 300% or more is contained as an essential film-forming component in an amount of 3 to 50% by weight. Then, the masking paint area to be partially coated is cut out and peeled off, and then the partially coated area is partially coated, and this masking paint area is left uncoated. An improved partial painting method characterized by stripping a certain masking paint film. 2. The method according to claim 1, wherein the article to be coated is a thermosetting resin molded article. 3. The method according to claim 1, wherein the article to be coated is a thermoplastic resin molded article. 4. The method according to claim 1 or 3, wherein the article to be painted is an automobile bumper made of polypropylene. 5. The method according to claim 1 or 3, wherein the article to be painted is an automobile bumper made of polyurethane. 6. The method according to claim 1, wherein the organic solvent solution of the resin containing the polyurethane resin as an essential film-forming component is an organic solvent solution of the polyurethane resin. 7. An organic solvent solution of a resin containing the above-mentioned polyurethane resin as an essential film-forming component is mixed with vinyl chloride resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer resin, nitro-based Claim 1, which is an organic solvent solution of a mixture comprising 5 to 100 parts by weight of at least one selected from the group consisting of cellulose and cellulose acetate butyrate. Method. 8. A patent characterized in that the organic solvent solution of the resin containing the polyurethane resin as an essential film-forming component is an organic solvent solution of a mixture of a polyurethane resin and a vinyl chloride-vinyl acetate copolymer resin. Claim 1
or the method described in paragraph 7. 9. The organic solvent described above is characterized in that it contains as an essential compound at least one member selected from the group consisting of acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, ethyl acetate, and butyl acetate. , the method according to claim 1. 10. The method according to claim 1, wherein the organic solvent contains methyl ethyl ketone as an essential compound.