JPS5835231B2 - Triyouno Tosohouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing yellowing of a coating film that is prone to yellowing.

Nitrocellulose has excellent features such as quick drying, pigment dispersibility, gloss, and compatibility with resins, so it is widely used as a raw material for nitrocellulose lacquer, modified acrylic lacquer, modified urethane paint, etc.

In these paints, nitrocellulose exhibits high functionality as the above-mentioned characteristic imparting agent, but in the case of paints, nitrocellulose itself has the property of being easily yellowed by ultraviolet rays, so yellowing resistance is required. In the case of paints, nitrocellulose was often subject to restrictions on the amount of use.

Therefore, attempts have been made to overcome the yellowing of such nitrocellulose paints for many years, and many proposals have been made in this regard, the most common method being the addition of ultraviolet absorbers.

However, it is effective, practical, and economical when used in combination with paints with a high nitrocellulose content such as nitrocellulose lacquers, or resins that easily yellow, such as nitrocellulose-modified tolylene diisocyanate-based polyurethane paints. The Preventive Power Act is still not a distant relative.

However, as mentioned above, nitrocellulose has excellent features that other synthetic resins do not have, so there has been a strong desire for an effective solution to the restrictions on the amount of nitrocellulose used.

As a result of many years of research aimed at solving this problem, the present inventors have completed the present invention.

In the present invention, a polyurethane paint or a polyurethane paint modified with nitrocellulose is used as a second layer on a coating film containing nitrocellulose (hereinafter referred to as the first layer) coated as the first layer. This is a coating method that increases the yellowing resistance of the first layer by overcoating with a composition containing an absorbent.

The substituted acrylonitrile-based external radiation absorber used in the method of the present invention refers to a compound represented by the general formula, and more specifically, the following 3
It refers to an ultraviolet absorber selected from alkylidene cyanoacetate and its alkyl ester [I] represented by the following structural formulas, alkylidene malononitrile C11), and alkyl-α-cyanoacrylamide (1).

[Here, Ar11 Ar2, Arl', Ar2'
, Ar1″.

and A r 2'' is an unsaturated hydrocarbon group selected from a phenyl group, a substituted phenyl group, and a heterocyclic hydrocarbon group, and has a conjugated double viscosity in the functional group.

More specifically, substituted phenyl group refers to alkyl (C-1-1
0), alkoxy (C=1-10), halogen (Br.

Refers to mono-, di-, and tri-substituted products consisting of c1λ and combinations thereof.

A heterocyclic hydrogen group is one or two S, N in the ring.
, refers to a 4- to 6-membered ring having an O atom and at least one set of conjugated double bonds, such as a chenyl group, a pyridyl group, or a pyrimidyl group.

A r 3 refers to an H atom, a straight or branched alkyl group with c=1 to 10, and a phenyl group.

Since this ultraviolet absorber has a maximum absorption wavelength of 250 to 310 millimicrons, it is effective in stabilizing nitrocellulose, which is easily yellowed by ultraviolet rays of 280 to 320 millimicrons.

If the paint to be applied as the second layer is a polyurethane paint, the amount of these ultraviolet absorbers to be added may be 0.1 to 5% based on the solid content of the paint, and if the content in the solid content of the paint is 5%.
In the case of a nitrocellulose-modified polyurethane paint that is formulated to have a content of 0% or less, it is preferably 5 to 30% based on the amount of nitrocellulose.

In addition, when this composition is applied as the second layer of a coating film on top of the first layer, it is possible to apply the composition to a thickness of at least 5 microns without impairing the durability of the composition itself. It can also effectively prevent yellowing.

Nitrocellulose used in the present invention has a nitrogen content of 10 to 12.
5% and an average degree of polymerization of 30 to 500. Any nitrogen content of 10.7 to 12.2% and an average degree of polymerization of 35 to 100 is preferable, but the present invention is limited to this. It's not a thing.

Polyurethane paint refers to a paint designed to form urethane bonds and polymerize through the reaction between isocyanate compounds and polyol compounds, and nitrocellulose-modified polyurethane is a paint that is further added with nitrocellulose as a film-forming agent. Paints are usually used as two-component paints.

Isocyanate compounds include hexamethylene diisocyanate (HMD i ), xylidene diisocyanate)
(XDi), diphenylmethane diisocyanate (Ml
) i), lysine diisocyanate (LDi), and inphorone diisocyanate (ipDi), among which HMDi is particularly preferred and has excellent effects.

Polyol compounds include polyester polyols and acrylic polyols, and the effects of the present invention are remarkable and the objectives can be fully achieved no matter which of them is used.

In addition, the polyurethane paint and hinitrocellulose-modified polyurethane paint applied as the second layer contain plasticizers, dyes,
Although extender pigments, abrasives, matting agents, etc. may be included in the present invention, there is no problem in the case where these substances are included, and the usefulness of the present invention is rather enhanced.

In addition to nitrocellulose as film-forming elements, the paint to be applied to the first layer includes vegetable oils such as coconut oil, soybean oil, and castor oil, alkyd resins modified with fatty acids, rosin, phenol, and styrene, butylated melamine resins, etc. Acrylic resins polymerized from butylated urea resins, natural resin-modified maleic acid resins, methacrylic acid, methacrylic esters, acrylic acid, and acrylic ester monomers, or obtained by copolymerizing these with styrene monomers, alkyd resins, etc. , a two-component polyurethane obtained by mixing an incyanate compound and a polyol compound, and one or a combination of two or more resins selected from urethane resins modified with linseed oil, safflower oil, etc. It is a paint containing a solvent and, if necessary, film-forming elements such as a plasticizer, a glossing agent, a matting agent, a leveling agent, and an anti-sag agent, and a pigment.

The present invention will be explained in detail by the following examples.

Parts shown in Examples are parts by weight unless otherwise specified.

The yellowing test results for each example were obtained by subjecting the test piece to a 50-hour accelerated exposure test using a sunshine weather meter, and were expressed as changes in yellowing using the following formula.

Change in yellowing degree = (yellowing degree after 50 hours of irradiation) - (yellowing degree before irradiation) Example 1 An undercoat paint (hereinafter referred to as undercoat paint I) forming the first layer was adjusted as follows.

Nitrocellulose (H1/2 seconds dry cotton equivalent) 6 parts Coconut oil modified alkyd resin (solid content equivalent) 6 parts Pesocozole 1323 manufactured by Inu Nippon Ink) Rosin modified maleic acid resin 6 parts (Veracasite 1111 parts manufactured by Nippon Ink) Dibutyl phthalate
2 parts ethyl acetate
12 parts Butyl acetate
8 part isoproper tool
8 parts n-butanol
4 parts Butyl Cellosol 4 parts Toluene 32 parts Next, a top coat to form the second layer was prepared as follows.

Nitrocellulose (H1/2 second dry cotton) 5 parts Hexamethylene diisocyanate 5 parts (adduct) Acrylic polyol (dry equivalent) 15 parts (
Acridic A301: Dainippon Ink) Methyl ethyl ketone 30 parts Butyl acetate
15 parts cellosolve acetate
7.5 parts xylene
22.5 parts (however, the solvent brought in from the polyol was divided into methyl ethyl ketone and xylene) The preparation according to the above composition was designated as composition A, and 0.5 part of ethyl α-cyano β-phenyl cinnamate was added to composition A. was designated as Composition B.

Next, on a mild steel plate coated with white enamel, the previously prepared undercoat paint I was spray-coated to a film thickness of 50 microns, and after drying at room temperature for 5 hours, Composition B was further spray-painted to a film thickness of 10 microns. An overcoat was applied.

A 50-hour accelerated exposure test was conducted on panels that had been painted for 3 days.

The results are shown in Table 1 together with the results for the panel with only the undercoat paint and the panel with Composition A applied on the undercoat film.

Example 2 Top coating composition Nitrocellulose (H1/2 second dry cotton) 5 parts Hexamethylene diisocyanate 7 parts (adduct) Polyester polyol 13 parts (Bayer Tesmofen 651 [F]) Methyl ethyl ketone
30 parts butyl acetate
15 parts cellosolve acetate
7.5 parts xylene
22.5 parts This composition was designated as a C composition, and 0.45 part of α-cyanoβ-methoxyphenylcinnamate 2-ethylhexyl was added to this C composition as a D composition.
It was coated on a white enamel-coated mild steel plate in exactly the same manner as in 1, and a 50-hour accelerated exposure test was conducted.

The results are shown in Table-2.

Example 3 Undercoat paint with the following composition (hereinafter referred to as undercoat paint)
adjusted.

Nitrocellulose (F (1 part 2 seconds dry cotton) 5 parts Tolylene diisocyanate adduct 5
parts (Japan Polyurethane "Coronet L") Polyester Polyol 15 parts Methyl ethyl ketone 30 parts Butyl acetate 15 parts Cellosolve acetate 7.5 parts Xylene
22.5 parts of this paint was spray-coated to a thickness of 50 microns on a mild steel plate coated with white enamel and dried for 3 days at room temperature.

Furthermore, composition A and composition B used in Example-1 were displayed on this panel.
The change in yellowing degree was measured by a 50-hour accelerated exposure test of panels obtained by painting the compositions C and D compositions used in Example-2 according to the previous example, and the results were as follows:
It was as shown in Table-3.

Example 4 Composition E was prepared by adding 0.5 part of diphenylmethylene malononitrile to composition A used in Example-1.
After a 50-hour accelerated exposure test, the change in yellowing degree of the paint film obtained by overcoating this EJ, fl monochrome by 20 microns over the undercoat paints I and ① was 0.02 when combined with the undercoat paint I. In the case of undercoat paint (■), it was 0.04.

Example 5 A composition F was prepared by adding 0.5 part of α-cyano-β-monochlorinated phenylcinnamate 2-ethylhexyl to the C composition used in Example-2. to 3
After a 50-hour accelerated exposure test, the yellowing degree change of the coating film obtained with a 0 micron overcoat was 0.04.

Example 6 Two types of undercoat paints were prepared with the following compositions (undercoat paint
, and undercoat ■) Undercoat ■ Nitrocellulose (H1/2 second dry cotton equivalent) 8 parts Coconut oil modified alkyd resin 10 parts Dibutyl phthalate 2 parts Ethyl acetate
12 parts Butyl acetate
8 part no 7° mouth Tsumano nno
Free n-butanol
4 parts Butyl cellosolve 4 parts Toluene 32 Undercoat ■ Nitrocellulose (H1/2 second dry cotton) 9 parts Tolylene diisocyanate 4 parts Polyester polyol 12 parts Methyl ethyl ketone 30 parts Butylacetate 7
15 parts cellosolve acetate
7.5 parts xylene
22.5 Undercoat paint ■ and undercoat paint ■ were applied to a white enamel coated mild steel plate to a thickness of 40 microns each, and after drying at room temperature for 4 hours, the B composition used in Example-1 was applied to a thickness of 30 microns. It was overcoated to a film thickness of .

The change in yellowing degree in a 50-hour accelerated exposure test of a paint film dried for 3 days with room salt after painting was 0.03 for those using undercoat ■ as the undercoat, and 0.0 for those using undercoat ■.
It was 4.

Example 7 The undercoat paint (undercoat ■) prepared in Example 3 was spray coated onto a mild steel plate coated with white enamel to a thickness of 50 microns, and dried for two days at room temperature.

I adjusted the topcoat paint using the string shown below.

Hexamethylene diisocyanate 5 parts (adduct) Acrylic polyol (dry equivalent) 15 parts (Acridic A301: manufactured by Dainippon Ink) Methyl ethyl ketone 24 parts Butyl acetate
12 parts cellosolve acetate
6 parts xylene
18 parts A top coat with the above composition was used as a G composition, and 0.3 parts of αtuanoβ phenyl ethyl cinnamate was added to this G composition as a H composition and sprayed on a panel coated with the above undercoat paint. A 10 micron overcoat (second layer) was applied.

After the coating film was left at room temperature for 3 days, an accelerated exposure test for 50 hours was conducted.

The results are shown in Table 4. Example 8 Composition I was prepared by adding 0.5 part of α-cyano-β-phenylcinnamic acid to composition A used in Example-1, and this one composition was applied to undercoat I and The change in yellowing degree after a 50-hour accelerated exposure test of the coating film obtained with micron overcoat was 0.02 when combined with primer paint I.
It was 0.03 in the case of combination with undercoat paint (■).

Example 9 A J composition was prepared by adding 0.5 part of benzyl α-cyano-β-phenylcinnamate to the C composition used in Example-2, and this J composition was applied on top of the undercoat paint (■). After a 50-hour accelerated exposure test, the yellowing index change of the coating film obtained with a 30 micron overcoat was 0.04.

Example 10 A composition was prepared by adding 0.4 part of α-cyano-β-phenylcinnamic acid amide to the A composition used in Example-1, and this composition was applied onto the undercoat I. After a 50 hour accelerated exposure test, the yellowing index change of the coating film obtained with a 20 micron overcoat was 0.04.

As explained above, the coating method of the present invention provides a film on the surface of the coating film in which an ultraviolet absorber is added to a polyurethane paint or a nitrocellulose-modified polyurethane paint. Nitrocellulose, which is subject to quantitative restrictions on use, can be added in any proportion, and at the same time its yellowing resistance is improved by 10 to 20 times, making it ideal for indoor use or applications where yellowing resistance is relatively unrequired. It is possible to dramatically expand the applications of paints that are used in a limited manner.

Claims (1)

[Scope of Claims] 1. When applying a paint, a coating film containing nitrocellulose applied as the first layer is coated as a second layer with the general formula % [However, R1 and R2 are phenyl groups, alkyl groups (C 21～
10), alkoxy group (C-1-10), halogen group (
cl, Br) or a combination thereof,
Indicates a di- or tri-substituted phenyl group. R3 is C0OR, (here R4 is H atom, C=1-10
), CN, and CONH2. )] is added to a hexamethylene diisocyanate-based polyurethane paint, or a composition in which 0.1 to 30% of the above UV absorber is added to a drying methylene diisocyanate polyurethane paint modified with 1 to 30% nitrocellulose. A method for applying a paint, characterized by overcoating with a composition containing 10%.