JPS581154B2 - Netsukasei acrylic - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermosetting acrylic powder coating composition that is excellent in weather resistance, flexibility, beautiful appearance of a coating film, and blocking resistance.

Traditionally, solvent-based paints, water-soluble paints, and emulsion paints in which synthetic resins and pigments are dispersed in a solvent have been widely used for coating metals, etc. However, in recent years, air pollution, water pollution, etc. Studies have been progressing on the development of various paint technologies from the viewpoint of making paints pollution-free and effectively utilizing the resources of paint manufacturing raw materials as a way to eliminate problems such as pollution problems and shortages of paint manufacturing raw materials. Among them, powder coatings are solvent-free coatings whose main components are resins and colorants, and they are attracting general attention from a practical standpoint.

Conventionally known powder coatings include, for example, epoxy resin powder coatings using an epoxy resin and a curing agent such as dicyandiamide, and acrylic resin powder coatings containing acrylic resin and hexamethoxymethylolmelamine resin. However, among these powder coatings, epoxy resin powder coatings do not have sufficiently satisfactory blocking resistance, and the weather resistance of the resulting coating film is extremely poor, and the flexibility is not very satisfactory. Moreover, it is difficult to recognize that the above-mentioned acrylic resin-based powder coatings are not necessarily satisfactory in terms of the beautiful appearance, flexibility, blocking resistance, etc. of the coating film.

Therefore, the present invention provides a coating material which is excellent enough to satisfy the various performances which are said to be insufficient in practical use in the known epoxy resin powder coatings and acrylic resin powder coatings as described above. The present invention relates to a novel thermosetting acrylic powder coating composition that has excellent performance and is extremely useful and valuable. 30% by weight or more of a monomer having a structure of alkyl group), (a-2), 4 to 40% by weight of a vinyl monomer containing a hydroxyl group, (a-3), the above (a-1) B. A polyvalent oxazolone compound is blended into a copolymer having a glass transition point of 20°C or higher obtained by copolymerizing (a-2) and 0 to 67% by weight of a copolymerizable vinyl monomer. This is a thermosetting acrylic powder coating composition obtained by

The composition of the present invention not only has excellent weather resistance, but also has excellent flexibility, beautiful appearance of the film, and blocking resistance, and greatly improves the quality of conventional thermosetting acrylic powder coatings. can do.

Examples of the monomer having the structure (a-1), which is a constituent raw material of the copolymer A, include methyl acrylate,
Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, Cyclohexyl methacrylate and the like are generally used to impart excellent properties in terms of weather resistance and aesthetic appearance to the cured coating film of the resulting thermosetting powder coating composition.

The amount of these monomers used is 30% by weight of the total comonomer.
If it is less than this, the excellent weather resistance of the film formed and the beautiful appearance of the coating film, which are the characteristics of the present invention, will deteriorate and the object of the present invention cannot be fully achieved.

Examples of the vinyl monomer (a-2) containing a hydroxyl group, which is a constituent raw material of the copolymer A, include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate. , 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, 10-hydroxyhexyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate , 6-hydroxyhexyl methacrylate, 10-hydroxydecyl methacrylate, etc. are generally used, and this vinyl monomer imparts a hydroxyl group to the side chain of the above-mentioned copolymer of A, and forms the multivalent monomer of B above. It reacts specifically with the oxazolone compound to provide a tough reticulated coating, and also forms a coating that has the excellent appearance and flexibility of the weather-resistant coating as described above.

As for the amount used in the copolymerization of the vinyl monomer containing a hydroxyl group (a-2), if it is less than 3% by weight of the total copolymerized monomer, crosslinking will be insufficient in practical use and the flexibility of the film will decrease. If the amount exceeds 40% by weight, the crosslinking reaction will proceed before heat melting is sufficient during the baking process after painting, resulting in poor thermal fluidity and poor surface smoothness. The appearance of the coating film is deteriorated and is therefore unsuitable.

Examples of the monomer shown in (a-3) above used in the present invention include styrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, and vinylidene chloride. If the amount exceeds 67% by weight of the copolymerization monomer used in the present invention, the weather resistance and flexibility of the formed film will deteriorate, making it impractical and unsuitable.

The copolymer A mentioned above in the present invention must have a glass transition point of 20° C. or higher.

If the glass transition point of the above-mentioned copolymer A is lower than 20° C., the blocking resistance will be significantly lowered and the powder coating will solidify during storage, making it unsuitable for practical use.

The above-mentioned glass transition point referred to in the present application is a numerical value defined as the temperature at the inflection point of the specific volume-temperature diagram measured by measuring the temperature change in specific volume using a dilatometer.

Further, the average molecular weight of the above-mentioned copolymer A is desirably in the range of 1,500 to 30,000 in terms of number average molecular weight.

The polyvalent oxazolone compound B mentioned above in the present invention has the general formula (wherein R1 and R2 are hydrogen or an alkyl group, R is a hydrocarbon such as a benzene nucleus, a cyclohexyl nucleus, or an alkylene group having 2 or more carbon atoms). residue, n is 1 or 2
(an integer of ) is preferable.

Particularly desirable polyvalent oxazolone compounds for use in the present invention include, for example, 2,2'-p-phenylenebis[(4H)oxazolone-5], 2,2'-m-phenylenebis[(4H)oxazolone-5], 2 ,2'-
p-phenylenebis[4-methyl(4H)oxazolone-5], 2,2'-m-phenylenebis[4-methyl(
4H) Oxazolone-512,2'-p-phenylenebis[4-isobutyl(4H)oxazolone-5], 2.
2'-p-phenylenebis[4,4dimethyl(4H)oxazolone-5], 2,2'-tetramethylenebis[(
4H) oxazolone-5], 2,2'-tetramethylenebis[4,4 dimethyl (4H) oxazolone-5], 2
, 2'-dimethylenebis[4,4dimethyl(4H)oxazolone-5], 1,2,4tris.2[4-methyl(
4H)5-oxazolonyl)benzene, 1,4bis・2
[4-methyl(4H)5oxazolonyl)cyclohexane, 1,2bis(4-methyl(4H)-5oxazolonyl)cyclohexane, and the like.

The above-mentioned polyvalent oxazolone compound B in the coating composition of the present invention is combined with the hydroxyl group contained in the above-mentioned copolymer A, and the temperature is usually 130°C to 250°C during the baking process when used in practical use as a powder coating. It undergoes a ring-opening reaction at temperatures such as 100 to 100 ml, forming a resin film with excellent weather resistance, flexibility, beautiful appearance, and anti-blocking properties.

In the coating composition of the present invention, the polyvalent oxazolone compound B undergoes a crosslinking reaction with the hydroxyl group contained in the copolymer A during the baking step to form a cured film, as described above. In this respect, for example, when the above compound is a polyvalent oxazolone compound represented by the above general formula, the crosslinking reaction (wherein R1 and R2 are hydrogen or an alkyl group, R is a benzene nucleus, a cyclohexyl nucleus, or a carbon number (residues consisting of two or more hydrocarbons such as alkylene groups).

The above-mentioned polyvalent oxazolone compound B usually has a molecular weight of 0.5 to 1.5 with respect to the hydroxyl group of the above-mentioned copolymer A.
It is preferable that they be blended in such a proportion that the amount becomes double equivalent.

The rod coating composition of the present invention usually contains metal oxides such as titanium oxide, iron oxide, chromium oxide, and lead chromate, and various pigments such as carbon black, phthalocyanine blue, phthalocyanine green, syncacia red, toluidine red, etc. and various so-called surface conditioners such as silicone oil, polyacrylic acid ester, fatty acid metal salt, fatty acid amide, higher aliphatic alcohol or wax, or fillers such as silica, talc, alumina, sodium metasilicate, glass powder, etc. Additives are mixed appropriately and rolled under a temperature condition of usually 70 to 120°C.
It is preferable to melt and knead the mixture using a kneader such as an extruder or a co-kneader, cool it, and then pulverize it to form a powder coating for practical use.

In addition to the above-mentioned materials that can be mixed into the coating composition of the present invention, an epoxy resin is blended in order to achieve more sufficient adhesion to the coating substrate, which is the object to be coated, and the coating composition is prepared as described above. It may be used for practical purposes as a powder coating.G)o The powder coating produced as described above is applied to the above-mentioned object by a method such as electrostatic powder coating, and is usually heated at 130 to 250°C.
A reticulated film with excellent weather resistance, flexibility, and beautiful appearance can be obtained by baking at a temperature of It is desirable to previously incorporate tertiary amines such as chloride, quaternary ammonium salts, or organometallic compounds such as dibutyltin oxide and zinc naphthenate into the coating composition of the present invention.

Examples will be described below.

Example (1) Production of solid copolymer: For each experiment number shown in Table 1, a solid acrylic copolymer was produced by the method shown below.

A flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with toluene in the amount shown in Table 1, heated to 90°C, and a mixture of various monomers and a polymerization initiator in the amounts shown in Table 1 was added over 3 hours. dropwise, while keeping the temperature inside the flask at 90-95℃.
After the dropwise addition was completed, the temperature was further maintained at the above temperature for 3 hours to complete the polymerization, and a toluene solution of the acrylic copolymer was obtained.

Next, the toluene solution of each acrylic copolymer obtained above was added to 5000 g of n-hexane, and each copolymer was precipitated and dried in vacuum. Solid acrylic copolymers of experiment numbers 1 to 4 having the properties shown were obtained.

Table 1 also lists the glass transition point of each solid acrylic copolymer and the equivalent weight of hydroxyl groups in 1000 g of the copolymer.

(2) Synthesis of polyvalent oxazolone: (2-1) Dissolve 100 g of DL-alanine and 50 g of magnesium oxide in water at 750°C, place in a flask equipped with a stirrer, and add 100 g of teref, tar acid dichloride.
was dissolved in 500 cc of dioxane and added dropwise over 2 hours at 20° C. with thorough stirring.

After the dropwise addition was completed, stirring was continued for 30 minutes at 20°C.

Next, add hydrochloric acid until the pH of the contents becomes 1.5, filter out the precipitated solids, wash the solids with water, vacuum dry,
An intermediate product was obtained.

800cc of this intermediate product heated to 50℃
of acetic anhydride and heat to 50°C while stirring thoroughly.
The reaction was carried out for 1 hour.

After the reaction was completed, the crystals were cooled to 20°C, separated by filtration, washed with water, dried in vacuum, and recrystallized from diethyl ether to give 2,2'-p-phenylenebis[4-methyl (4H
) Oxazolone-5] was obtained.

The melting point of this compound was 180°C.

(2-2) In the above (2-1), DL-alanine and terephthalic acid dichloride were used, but instead, glycine and isophthalic acid dichloride were used in the same manner as in the above (2-1). m-phenylenebis[(4H)oxazolone-5] was synthesized.

The melting point of this compound was 190°C.

(2-3) In (2-1) above, DL-alanine and terephthalic acid dichloride were used, but DL-α
2,2'tetramethylenebis(4,4-dimethyl(4H)oxazolone-5)] was synthesized using aminoisobutyric acid and adipic acid dichloride in the same manner as in (2-1) above.

The melting point of this compound was 107°C.

(3) Preparation of powder coating To each of the solid copolymers of Experiment Nos. 1 to 4 produced by the method described above, a polyvalent oxazolone compound, a pigment, a surface conditioner, or an epoxy resin shown in Table 2 was added. In addition, it was melt-kneaded for 10 minutes under heating conditions of 100°C with a hot roll, and after cooling,
The powder was pulverized using a pulverizer, and the fractions that passed through a sieve of 150 mesh were collected to obtain powder coatings for each of Experiment Nos. 1 to 4 (examples of the present invention).

As a comparative example for the example of the present invention, as shown in Table 2, Cymel #300 (A. A powder coating compounded with a pigment and a surface conditioner (product name manufactured by C.C. Co., Ltd.) and a powder coating compounded with an epoxy resin, its curing agent, a pigment, and a surface conditioner were tested according to the above-mentioned example of the present invention. Powder coatings of experiment numbers 5 and 6 were prepared in the same manner.

Evaluation test for powder coatings: (a) 50g of each of the powder coatings prepared in experiment numbers 1 to 6 prepared by the above method was placed in stoppered bottles with a radius of 50mm, and each was placed in a separate constant temperature bath at 30°C and 40°C. It was left for one week and its blocking resistance was tested.

The test results are shown in Table 3. (0) Also, each powder paint obtained from the above test was sprayed with an electrostatic powder spray gun to a size of 0.8 mm.
Each test plate having the film thickness shown in Table 3 was obtained by coating a thick zinc phosphate treated steel plate and baking it in a hot air dryer at 200°C for 30 minutes.

The evaluation results of the weather resistance, flexibility, and aesthetic appearance of the films formed on the test plates prepared using the powder coatings of Experiment Nos. 1 to 6 are also listed in Table 3.

Claims (1)

[Claims] 1A, (a-1), 30% by weight or more of a monomer having the structure of the general formula CH2 (Rl is H or CH3; R2 is an alkyl group or a cycloalkyl group), and (a -2), vinyl monomer 4 containing a hydroxyl group
~40% by weight, and (a-3), the glass transition point obtained by copolymerizing 0 to 67% by weight of a vinyl monomer copolymerizable with (a-1) and (a-2) above. 1. A composition for a thermosetting acrylic powder coating, comprising: B. a polyvalent oxazolone compound mixed with a copolymer having a temperature of 20° C. or higher.