JP3331524B2 - Epoxy resin composition for powder coating and production method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin cured product obtained by incorporating an elastomer component into a solid epoxy resin to improve the stress relaxation characteristics of the epoxy resin cured product.
The present invention relates to an epoxy resin powder coating composition excellent in mechanical impact, thermal impact, and coating aging.

[0002]

2. Description of the Related Art Epoxy resin powder coatings are used to coat heavy-duty corrosion-resistant coatings on steel frames and reinforcing bars, as well as decorative coatings for household appliances and steel furniture, protective coatings, and insulating coatings for electrical and electronic components. It is widely used as a coating method with less environmental pollution for the intended use. These are due to the excellent adhesion, rust prevention and electrical properties of the epoxy resin, but at the same time, the cured epoxy resin is hard and brittle, weak to mechanical or thermal shock, However, there are disadvantages such as generation of internal stress due to cooling after curing of the epoxy resin. To solve these problems, a method of modifying the epoxy resin by using an elastomer has been used.

[0003] This reforming method is disclosed in Japanese Patent Application Laid-Open No. 55-92.
No. 750 discloses a method using a carboxy-terminated butadiene-acrylonitrile copolymer. However, a cured product of an epoxy resin modified by this method has a low Tg and is incompatible with a component used as an elastomer. Since it contains a saturated double bond, it is inferior in high-temperature heat resistance and weather resistance even if it has an effect on mechanical impact resistance, and it is difficult to improve both impact resistance and high-temperature heat resistance. there were.
In the method using a carboxy-modified butadiene-styrene block copolymer disclosed in Japanese Patent Application No. 63-308027, the modified epoxy resin may separate from the elastomer component during long-term storage at room temperature. It has been found that it has disadvantages and is accompanied by a drawback of giving non-uniformity to the cured epoxy resin.

Another reforming method is disclosed in Japanese Patent Publication No. 51-449.
No. 73, JP-A-62-60361, JP-A-62-633
No. 69, JP-A-64-85216, JP-A-2-117
No. 948 and JP-A-2-206656 propose a method of dispersing acrylic polymer particles in an uncured epoxy resin. However, these methods produce a liquid epoxy resin having a low molecular weight, but are limited to powder coating applications. Further, JP-A-63-23078
No. 0 discloses that an epoxy resin is modified by mixing a powder rubber. In this case, the rubber powder is mixed with a filler such as calcium carbonate to improve dispersibility in the molten epoxy resin. There was a drawback that had to be used in.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to form an epoxy resin powder coating film useful for coating by using a solid epoxy resin at room temperature which is efficiently modified by an elastomer. It is excellent in mechanical and thermal shock resistance, weather resistance, and aging resistance by relaxing the stress of epoxy resin cured product without sacrificing the strength and heat resistance of epoxy resin cured product. It is intended to provide an epoxy resin powder coating excellent in the above.

[0006]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a liquid
(Meth) acrylic acid ester-based cross-linked polymer for epoxy resin
After the fine particle component is dispersed, the presence of the chain extender and catalyst
Reacting in the presence, the softening point is 60 ~ 150 ℃
(Meth) acrylate crosslinked polymer fine particle component
2-30 parts by weight are uniformly dispersed and solid at room temperature
Epoxy for powder coatings characterized by using epoxy resin
This is a method for producing a resin composition.
Characterized by using the obtained epoxy resin composition
Epoxy resin powder coating. And the (meth) a
2 μm or less of the acrylate ester crosslinked polymer fine particle component
And the glass transition temperature is preferably room temperature or lower.
New

Hereinafter, the present invention will be described in detail. The liquid epoxy resin in which the (meth) acrylate polymer fine particles used in the present invention are uniformly dispersed can be produced by a known method. For example, a (meth) acrylate polymer produced by various conventional polymerization methods such as an emulsion polymerization method, a suspension polymerization method, and a solution polymerization method, and a liquid epoxy resin are forcibly stirred under a shearing force, and then water Or a method of removing a solvent, a method of heating and mixing powdery polymer fine particles in an epoxy resin, and a method of removing an acrylic monomer in an epoxy resin.
And a method of adding an aqueous dispersion of a (meth) acrylate polymer obtained by emulsion polymerization to an epoxy resin, forcibly stirring under a shearing force, and then dehydrating. It is industrially advantageous.

The epoxy resin used in the present invention is preferably a polyfunctional type having two or more epoxy groups in one molecule, and diglycidyl ethers such as bisphenols of bisphenol A and bisphenol F. Polyglycidyl ethers of alcohols such as polyethylene glycol and polypropylene glycol; polyglycidyl esters such as hexahydrophthalic acid and dimer acid; polyglycidylamines such as diaminodiphenylmethane; phenol novolak , Novolak-type polyglycidyl ethers such as orthocresol-lenovolak, diglycidyl ethers such as hydrogenated bisphenol, and alicyclic epoxies such as 3,4-epoxycyclohexylmethyl-3,4 epoxycyclohexylcarboxylate. Compound 1
Alternatively, a mixture of several types may be used.

The monomers used for producing the (meth) acrylate-based polymer fine particles include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylic acid. Butyl,
Isoamyl (meth) acrylate, (meth) acrylic acid 2
-Acrylic esters such as ethylhexyl and decyl (meth) acrylate, and corresponding alkyl esters of (meth) acrylic acid, and monomers having a functional group include carboxy groups such as (meth) acrylic acid. Monomers, hydroxyl-containing monomers such as hydroxypropyl acrylate and hydroxypropyl methacrylate, N
-Methylol group-containing monomers such as methylol acrylamide and dimethylol acrylamide; alkoxymethyl-containing monomers such as N-butoxymethyl acrylamide; glycidyl (meth) acrylate; (meth) acryl glycidyl ether; Epoxy group-containing monomers, acrylonitrile, methacrylonitrile, cyano group-containing monomers such as azobisisobutylnitrile, and divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate and the like as crosslinking monomers. can do.

A conventionally known method can be applied to emulsion polymerization of a monomer. For example, a method in which an emulsifier, water, a polymerization catalyst, and a monomer are mixed together and polymerized, a method in which a monomer is added later, a pre-emulsion method in which a monomer is emulsified in advance, a decomposable or polymerizable surfactant, The so-free emulsion polymerization method used and the multi-stage polymerization method for forming a multilayer structure are used.

As the catalyst used in the emulsion polymerization, for example, those generally used in emulsion polymerization such as potassium persulfate, ammonium persulfate and hydrogen peroxide can be used. As the emulsifier, anionic, nonionic, cationic and amphoteric emulsifiers can be used alone or in combination. The polymerization is usually performed at a temperature of 30 to 90 ° C., and the reaction time is 2 to 10 hours.

An aqueous dispersion of a (meth) acrylate polymer obtained by emulsion polymerization is mixed with a liquid epoxy resin under a shearing force, and then the mixture is heated at a temperature of 80 to 200 ° C. under a reduced pressure of 200 torr or less. A liquid epoxy resin in which the polymer is uniformly dispersed can be produced by dehydration. A polyaddition reaction between the obtained liquid epoxy resin (meth) acrylate-based polymer particles dispersed therein (hereinafter simply referred to as acrylic rubber-dispersed epoxy resin), phenols and / or alcohols, and a carboxy-containing compound; Thus, a solid epoxy resin having a desired molecular weight at normal temperature can be obtained. Examples of phenols include monovalent phenols such as nonyl phenol and butyl phenol.
Resorcin, Hydolquinone, Catechol, Pyrogallo-
Divalent and trivalent mononuclear phenols such as phenol, divalent phenols such as biphenol and bisphenol, and phenol-aldehyde novolak resins such as phenol novolak resin. Examples of the alcohols include polyols, polyester polyols, and polyether polyols. Examples of the carboxy compound include addition of hydrogenated bisphenol A and hexahydrophthalic anhydride. Products, acidic polyesters and the like. These can be used alone or as a mixture of several types.

Examples of the catalyst used in the polyaddition reaction include tertiary amines such as benzyldimethylamine, triethylamine and benzylamine, imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole, and water. Alkali metal hydroxides such as sodium oxide and potassium hydroxide,
Examples include quaternary ammonium compounds such as benzyltrimethylammonium chloride and tetraammonium chloride, phosphines such as triphenylphosphine and tributylphosphine, and phosphonium salts such as n-butyltriphenylphosphonium bromide. The catalyst is 10 ppm to 0.5% based on the acrylic rubber dispersed liquid epoxy resin.
60-200 ° C., preferably 120-180 ° C.
React at 1 ° C. for 1-10 hours.

(Meth) in the epoxy resin composition of the present invention
The content of the acrylic acid ester-based polymer fine particles is preferably 2 parts by weight to 30 parts by weight. When the amount is less than 2 parts by weight, a desired coating film having excellent impact resistance and stress relaxation property cannot be obtained, and when the amount is more than 30 parts by weight, there is a problem that the melt viscosity of the resin increases. Further, the diameter of the polymer fine particles is 2 μm or less, preferably 0.5 μm or less in order to uniformly and stably exist as a dispersed phase in the epoxy resin. When the polymer has a glass transition temperature of room temperature or higher, the properties of the coating film aimed at by the present invention are not improved.
For this reason, in the production of the polymer, it is necessary to consider the types and combinations of the monomers described above.

In the epoxy resin composition of the present invention, a hardening agent is added to the resin when forming a coating film. The curing agent to be used is not particularly limited, and generally used curing agents, for example, aliphatic amines, aromatic amines, acid anhydrides, imidazoles, hydrazides, dicyandiamides And phenolic hydroxyl group-containing compounds. Examples of the aliphatic amines include ethylenediamine, diethylenetriamine, and triethylenetetramine. Tetraethylenepentamine, hexamethylenediamine, N, N-dimethylpropylenediamine, N, N
-Diethylpropylene diamine and the like. As the aromatic amines, m-xylylenediamine, m-phenylenediamine, p-phenylenediamine, bis (4-
Aminophenyl) methane, bis (4-aminophenyl)
Sulfone and the like. Other amine-based curing agents include adducts of monoepoxy compounds with the amines,
An adduct of bisphenol A and / or bisphenol F type epoxy resin, an adduct of alicyclic epoxy resin, an addition condensation polymer of dimer acid and the like can also be used. Examples of the acid anhydride include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, and succinic anhydride. As imidazoles, 2-methylimidazo-
And 2-methyl-4-ethylimidazole. The hydrazides include adipic hydrazide, sebacic hydrazide, phthalic hydrazide and the like. Further, a phenolic hydroxyl group-containing compound (TH-4000, TH-4100 manufactured by Toto Kasei Co., Ltd.)
Phenolic hydroxyl group-containing epoxy resin curing agent) and acid-terminated polyester resin (carboxy terminal type saturated polyester such as ER-8100, ER-8101 manufactured by Nippon Ester Co., Ltd.). .

The composition of the present invention contains various additives such as fillers such as silica, quartz powder, calcium carbonate, talc, alumina, titanium oxide, silicate compounds, mica, molybdenum compounds and antimony compounds, and antioxidants. Agents, leveling agents such as acrylate oligomers, and the like. In order to prepare the epoxy resin powder coating of the present invention, a usual method may be used. Raw materials having a predetermined composition ratio are sufficiently mixed by a mixer, and then mixed with an extruder of a twin screw. A method of melt-kneading and then pulverizing with a pulverizer and then removing coarse particles with a sieve or the like is exemplified. Examples of the method for applying the powder coating composition of the present invention to a coating material include general powders such as a fluid immersion method, an electrostatic fluid immersion method, a hot spray method, an electrostatic spray method, and a frictional electrostatic spray method. The coating layer can be easily formed by any of the coating methods. Hereinafter, the present invention will be described in detail with reference to examples, but it is needless to say that the present invention is not limited to only these examples. still,
"Parts" means parts by weight unless otherwise specified.

[0017]

[Examples and Comparative Examples]

Reference Example As a monomer component, methacrylic acid 6 parts, butadiene 6
7 parts, 25 parts of acrylonitrile and 2 parts of divinylbenzene were added to 250 parts of water, 1 part of sodium dodecylbenzenesulfonate, 0.45 part of tertiary dodecylmercaptan, 0.27 parts of potassium persulfate, and cyanoethylation. 0.15 parts of diethanolamine and 0.1 part of potassium hydroxide were added, and the mixture was added at 20 ° C. in an autoclave according to a conventional method.
Was used for copolymerization. When the polymerization conversion reached 70% or more, 0.2 parts of hydroxyamine sulfate was added to terminate the polymerization, and the remaining unreacted monomer was removed by steam distillation to remove the acrylic rubber aqueous dispersion. I got

Next, a liquid epoxy resin YD-128 (manufactured by Toto Kasei Co., Ltd., epoxy equivalent: 1) was placed in a reaction vessel equipped with a stirrer, thermometer, condenser and nitrogen gas supply device.
86.5 g / eq) of 300 g was added, 300 g of the acrylic rubber aqueous dispersion obtained by the above method was added, and the mixture was gradually heated and heated to 150 ° C. while dewatering. Next, 100t
After sufficiently dehydrating under a reduced pressure of orr, the mixture was filtered through a 100-mesh wire net to obtain a white liquid epoxy resin in which acrylic rubber was uniformly dispersed. The epoxy equivalent of this is 2
33 g / eq, viscosity at 25 ° C. is 2000 ps, acrylic rubber content is 20% based on the epoxy resin composition (epoxy resin + acrylic rubber), and particle size of fine particle acrylic rubber is 0.3 ± 0.1 μm. The glass transition temperature of the rubber was -30C.

Example 1 A stirring device, a nitrogen gas supply device, a condenser, a thermometer,
1000 g of the acrylic rubber-dispersed liquid epoxy resin obtained in Reference Example and 240.6 g of bisphenol A were charged into a four-neck separable flask installed in a polymerization tester equipped with a heating / cooling device, and gradually heated to 120 ° C. The mixture was heated to a uniform temperature and stirred continuously, and 0.004 g of 2-ethyl-4-methylimidazole was added.
It was kept at 0 ° C. to make the whole uniform. Thereafter, the mixture was gradually heated to 170 ° C. and reacted at 170 ° C. ± 1 ° C. for 4 hours. The product obtained has an epoxy equivalent of 552 g / e.
q, softening point 77.5 ° C, 16% acrylic rubber component to epoxy resin composition (epoxy resin + acrylic rubber)
Was solid at room temperature at milky white.

Example 2 In the same manner as in Example 1, 1000 g of the acrylic rubber-dispersed epoxy resin obtained in Reference Example and 305.5 of bisphenol A were used.
Then, 0.014 g of the catalyst used in Example 1 was added thereto and reacted at 170 ° C. ± 1 ° C. for 4 hours. The obtained product was a milky white solid containing 15.3% of an acrylic rubber component based on an epoxy resin composition (epoxy resin + acrylic rubber) with an epoxy equivalent of 791 g / eq, a softening point of 102 ° C., and was solid.

Example 3 In the same manner as in Example 1, 1000 g of the acrylic rubber-dispersed epoxy resin obtained in Reference Example and 337.1 of bisphenol A were used.
Then, 0.017 g of the catalyst used in Example 1 was added thereto and reacted at 170 ° C. ± 1 ° C. for 4 hours. The obtained product was an epoxide equivalent of 951 g / eq, a softening point of 105 ° C., and a milky white solid containing 14.9% of an acrylic rubber component based on the epoxy resin composition (epoxy resin + acrylic rubber), and was solid at room temperature.

Example 4 Acrylic rubber-dispersed epoxy resin 10 obtained in Example 1
After dry blending 0 parts, 3.8 parts of dicyandiamide, 0.2 parts of 2-methylimidazole, 40 parts of titanium oxide, and 0.5 parts of Modaflow (manufactured by Monsanto Co.) as a flow regulator, an extruder (Ikegai) is used. The mixture was melt-kneaded with PCM-30 manufactured by Tekko Co., Ltd., cooled, pulverized, and sieved with a 100-mesh wire net to obtain a powder coating. The melt kneading of the extruder was performed under the following conditions. Cylinder-1: Cooling, Cylinder-2: 80 ° C, Cylinder-3: 90 ° C Head: 110 ° C, Main screw: 200 rpm,
Feed screw: 20 rpm The obtained powder coating is subjected to electrostatic powder coating on a mild steel plate (150 × 70 × 1.2 mm) subjected to sandblasting.
Baking was performed for 20 minutes in a hot air circulating oven at 200 ° C. to obtain a coating test plate having a thickness of 100 μm. The physical properties of the coating film of the painted test plate were measured, and the results are shown in Table 1.

Example 5 Acrylic rubber-dispersed epoxy resin 10 obtained in Example 2
Using 0 part, 2.7 parts of dicyandiamide, 0.2 part of 2-ethylimidazole, 40 parts of titanium oxide, and 0.5 part of modafuro, a powder coating was prepared in the same manner as in Example 4 to perform a coating test. I got a board.

Example 6 Acrylic rubber-dispersed epoxy resin 10 obtained in Example 3
Using 0 part, 2.2 parts of dicyandiamide, 0.2 parts of 2-ethylimidazole, 40 parts of titanium oxide, and 0.5 parts of Modaflow, a powder coating was prepared in the same manner as in Example 4 to perform a coating test. I got a board.

Comparative Example 1 100 parts of YD-902 (a bisphenol A type epoxy resin manufactured by Toto Kasei Co., Ltd., epoxy equivalent: 665 g / eq), 3.2 parts of dicyandiamide, 0.2 part of 2-ethylimidazole, A powder coating was prepared in the same manner as in Example 4 using 40 parts of titanium oxide and 0.5 part of Modaflow to obtain a coated test plate.

Comparative Example 2 100 parts of YD-904 (bisphenol A type epoxy resin manufactured by Toto Kasei Co., Ltd., epoxy equivalent: 950 g / eq), 2.2 parts of dicyandiamide, 0.2 part of 2-ethylimidazole, A powder coating was prepared in the same manner as in Example 4 using 40 parts of titanium oxide and 0.5 part of Modaflow to obtain a coated test plate.

Comparative Example 3 50 parts of YD-904 and YR-450 (Toto Kasei Co., Ltd.)
(Butadiene-acrylonitrile liquid rubber-modified bisphenol A type epoxy resin) 50 parts, 3.4 parts of dicyandiamide, 0.2 parts of 2-ethylimidazole, 40 parts of titanium oxide, and 0.5 parts of modafuro. A powder coating was prepared in the same manner as in Example 4 to obtain a coated test plate. Example 4
Table 1 shows the results of measuring the physical properties of the coating films of the coated test plates of Comparative Examples 1 to 6 and Comparative Examples 1 to 3.

[0028]

[Table 1]

The physical properties of the coating film were measured by the following methods. [Impact resistance] In accordance with JIS K 5400, using a Dupont type impact tester, drop a 1 kg weight using a 1/4 inch bomb and a corresponding base, and do not crack or peel off the paint film. Was measured for height. [Cross-grid adhesion] Based on JIS K 5400. An evaluation point of 10 indicates that the grid adhesion is the best. [Erichsen test] According to JIS K 5400, the indentation distance until the coating film was cracked was measured by an Erichsen tester.

[Glass transition point Tg] The midpoint of the glass transition of the coating film measured by DSC. [Adhesion] Degreasing test piece (mild steel plate SPCC-S
D 1.6 t × 25 × 100 mm) were heated to about 200 ° C., and the upper surface (width 2
(5 mm, length 12.5 mm) by sprinkling a powder coating onto it, adhering and melting it, fixing the two tips to each other, fixing them with clips, curing in a hot air circulating oven at 200 ° C. for 20 minutes, and bringing them to room temperature After standing for 24 hours, JIS K6
The shear bond strength was measured according to 850. [Heat resistance] The adhesive test piece obtained by the above adhesiveness was left in an atmosphere at 200 ° C. for 30 days, and then cooled to room temperature, and the shear adhesive strength was measured. The heat resistance was determined by the following equation (1).

[0031]

(Equation 1)

[Flowability] 0.50 g of the powder coating was weighed and pressed at room temperature under a pressure of 20 kg / cm 2 to obtain a 13 m
m tablets were created. A mild steel plate (SPCC-SB) with this tablet adjusted to an angle of 45 ° with the horizontal
0.6 mmt) and left in a hot air circulating oven at 180 ° C. to measure the flow distance (Fmm) of the paint,
The flowability was determined by the following equation (2).

[0033]

(Equation 2)

[Blocking Resistance] 50 g of the powder coating material was placed in a glass dish and left in a thermo-hygrostat set at 40.degree. C. and 80% RH for 7 days to visually check the formation of lumps. a: not in a lump state but with fluidity b: not in a large lump state but without fluidity c: in a lump state and lacking fluidity

[0035]

By using the epoxy resin powder coating of the present invention, it is possible to obtain a coating film having excellent adhesiveness and impact resistance and greatly improved heat resistance. The anti-blocking property is greatly improved.

────────────────────────────────────────────────── ─── Continuation of the front page Examiner Hiroko Fujiwara (56) References JP-A-59-230068 (JP, A) JP-A-4-359972 (JP, A) JP-A-4-224818 (JP, A) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) C09D 163/00-163/10 C09D 133/00-133/26 C09D 5/03 C08L 33/00-33/26 C08L 63/00-63 / Ten

Claims (4)

(57) [Claims] 1. A (meth) acrylate crosslinked polymer fine particle component is dispersed in a liquid epoxy resin and then reacted in the presence of a chain extender and a catalyst to have a softening point of 60.
An epoxy resin for a powder coating, wherein the epoxy resin is a solid epoxy resin at room temperature, wherein the epoxy resin has a temperature of from 150 to 150 ° C and 2 to 30 parts by weight of a (meth) acrylate-based crosslinked polymer fine particle component are uniformly dispersed. A method for producing a resin composition. 2. An epoxy resin powder coating comprising the epoxy resin composition obtained by the method according to claim 1. 3. The method according to claim 1, wherein the component of the (meth) acrylate crosslinked polymer fine particles is 2 μm or less, and the glass transition temperature is room temperature or less .
The obtained epoxy resin composition for powder coatings. 4. A (meth) acrylate-based crosslinked polymer
The fine particle component is 2 μm or less, and the glass transition temperature is room temperature.
3. The epoxy according to claim 2, wherein the temperature is not higher than the temperature.
Resin powder paint.