JPH10279838A - Epoxy resin composition for powder coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powdery epoxy resin composition excellent in impact resistance, flexibility and blocking resistance. SOLUTION: This composition comprises a reaction product comprising 40-95 pts.wt. solid epoxy resin having at least two epoxy groups in the molecule, an epoxy equivalent of 400-2,500 and a softening point of 50-150 deg.C and 5-60 pts.wt. isocyanate-modified polydiene polymer being a reaction product of a polydiene polymer having one prim. hydroxyl group at one molecular terminal with a difunctional isocyanate compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition for powder coating used for powder coating of civil engineering and architectural materials, home electric appliances, heavy electrical equipment, road materials, steel furniture, automobile parts, water supply materials and the like.

[0002]

2. Description of the Related Art Conventionally used powder coatings containing an epoxy resin and a curing agent thereof as main components are used in the above-mentioned fields, and are generally excellent in chemical resistance, adhesion, surface hardness and the like. However, it has a disadvantage of poor flexibility and impact resistance.

[0003]

SUMMARY OF THE INVENTION Accordingly, the present inventors have
Develop an epoxy resin for powder coatings that gives a coating film with improved flexibility and impact resistance without impairing the chemical resistance, adhesion, and surface hardness, etc., characteristics of epoxy resin-based powder coatings. As a result of diligent research for the purpose of the present invention, an epoxy resin composition for powder coating which can achieve these objects was found, and the present invention was completed.

[0004]

According to the present invention, there is provided a composition comprising: (1, (a) a molecule having at least two epoxy groups in one molecule, an epoxy equivalent of 400 to 2500 and a softening point of 50 to 150 ° C. Solid epoxy resin 40-9
Reaction product comprising 5 parts by weight and (b) 5 to 60 parts by weight of an isocyanate-modified polydiene polymer which is a reaction product of a polydiene polymer having one primary hydroxyl group at the terminal of the molecule and a bifunctional isocyanate compound An epoxy resin composition for powder coatings. 2. The solid epoxy resin has a glycidyl ether obtained by reacting an aromatic compound having at least two hydroxyl groups with epichlorohydrin under alkaline reaction conditions, or has at least two or more epoxy groups, and has an epoxy equivalent of 160 to 400, a relatively low molecular weight epoxy resin having a molecular weight of 300 to 800, and at least two epoxy resins obtained by adding and polymerizing an aromatic compound having at least two hydroxyl groups in the presence of a catalyst to form a polymer. A compound having the above epoxy group,
2. The epoxy resin composition for powder coatings according to claim 1. 3. The molecular weight of the isocyanate-modified polydiene polymer (b) having one primary hydroxyl group at the terminal of the molecule is 500 to 500.
3. The epoxy resin composition for powder coatings according to paragraph 1 or 2, which is a reaction product of 20,000 polydiene polymer and bifunctional isocyanate. 4. (B) Reaction product of a polydiene polymer having one primary hydroxyl group at a terminal of a molecule used for producing an isocyanate-modified polydiene polymer and having an aliphatic double bond hydrogenated, and a bifunctional isocyanate 2. The epoxy resin composition for powder coatings according to item 1, wherein 5. (B) a composition in which the isocyanate group equivalent number is 0.8 to 1.2 times with respect to 1 equivalent of the hydroxyl group of the polydiene polymer having one primary hydroxyl group at the terminal of the molecule. 2. The epoxy resin composition for powder coating according to item 1, wherein the epoxy resin composition is obtained by reacting a bifunctional isocyanate. About.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the composition of the present invention, the solid epoxy resin as the component (a) has at least two components per molecule.
Having at least two epoxy groups and an epoxy equivalent of 400 to 2
It is an epoxy resin having a softening point of 50 to 150 ° C., preferably 70 to 130 ° C., preferably 500 to 2000. If the epoxy equivalent is less than 400, the stability during the production and storage of the powder coating will be poor, while 25
If it exceeds 00, the cured coating film cannot obtain desired performance in corrosion resistance, chemical resistance and the like. Further, if the softening point is less than 50 ° C, the powder coating tends to block during storage, while if it exceeds 150 ° C, the heat fluidity during heat curing of the powder coating deteriorates, and a smooth coating film cannot be obtained. .

The solid epoxy resin can be produced by reacting an aromatic compound having at least two hydroxyl groups with epichlorohydrin under alkaline reaction conditions to effect glycidyl etherification (commonly known as a one-step method), or at least two methods.
Having at least two epoxy groups and an epoxy equivalent of 160 to 4
A method of subjecting a relatively low-molecular-weight epoxy resin having a molecular weight of 300 to 800 and an aromatic compound having at least two hydroxyl groups to addition polymerization in the presence of a catalyst to polymerize to a desired molecular weight (commonly referred to as “Nitrogen-based epoxy resin”). Step method).

A typical example of the aromatic compound having at least two hydroxyl groups is a bisphenol compound. For example, 2,2'-bis (4,4'-hydroxyphenyl) propane (commonly known as bisphenol A) ), Halogenated bisphenol A, 2,2'-bis (4,4'-
(Hydroxyphenyl) methane (commonly known as bisphenol F), 2,2'-bis (4,4'-hydroxyphenyl) ethane, and 2,2'-bis (4,4'-hydroxyphenyl) sulfone (commonly known as bisphenol S) be able to. Also, alkylphenol novolak resins such as phenol novolak resins and cresol novolak resins, and bisphenol A novolak resins can be used.

As a specific example of the solid epoxy resin of the component (a) by the one-step method, for example, Epicoat 1001 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.) obtained by reacting bisphenol A with epichlorohydrin under alkaline reaction conditions.
(Epoxy equivalent 450-500), 1002 (epoxy equivalent 600-700), 1003 (epoxy equivalent 670)
770), 1004 (epoxy equivalent 875-97)
5), 1007 (epoxy equivalent of 1750 to 2200) and the like.

As a specific example of the solid epoxy resin of the component (a) obtained by the two-step method, for example, a low molecular weight bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.)
Epicoat 1003F (epoxy equivalent: 700-800), 1004F (epoxy equivalent: 875, manufactured by Yuka Shell Epoxy Co., Ltd.) obtained by addition polymerization of bisphenol A in the presence of a catalyst.
975), 1005F (epoxy equivalent 950-105)
0). Further, a low molecular weight bisphenol A type epoxy resin and bisphenol A, and further added as a third component phenol novolak resin, alkylphenol novolak resin, bisphenol A novolak resin or a glycidyl etherified product of these novolak resins,
There is also a copolymer type epoxy resin obtained by addition polymerization in the presence of a catalyst. As the catalyst for the two-stage method, inorganic alkalis such as sodium hydroxide, potassium hydroxide and sodium carbonate, phosphorus-based compounds such as triphenylphosphine, and amine-based compounds such as trialkylamine and tetraalkylammonium halide are used. The (b) component isocyanate-modified polydiene polymer can be obtained by reacting a polydiene polymer having one primary hydroxyl group at the terminal of the molecule with a bifunctional isocyanate compound. The polydiene polymer having one primary hydroxyl group at the terminal of the molecule is a kind of one or more olefin compounds, in particular, a homopolymerization of a diolefin or an aromatic hydrocarbon having a diolefin and one or more alkenyl groups. Obtained by copolymerization with a monomer. The copolymer may be a random copolymer or a block copolymer or a combination thereof. These polydiene polymers are adjusted by an anionic polymerization initiator (or catalyst). These polydiene polymers can be obtained in the form of a powder or a small solid or liquid by bulk polymerization, solution polymerization, or emulsion polymerization. Polydiene polymers can also be purchased from several manufacturers. Generally, in solution anionic polymerization, anionic polymerization initiators such as Group IA metals, their alkyl compounds, amide compounds, silanolate compounds, naphthalide compounds,
A biphenyl compound, an anthracenyl compound, or the like is used, and a polydiene polymer is obtained by simultaneously or sequentially polymerizing a diolefin monomer or an aromatic hydrocarbon monomer having an alkenyl group. The polymerization reaction is carried out in a suitable solvent in the range of about -150 ° C to about 300 ° C.
More preferably, it is carried out in a temperature range of about 0 ° C to 100 ° C. As the anionic polymerization initiator, organic alkali metal compounds are preferable, and an organic lithium compound represented by the following formula is particularly preferable. RLi Here, R is an aliphatic hydrocarbon cable having 1 to 20 carbon atoms, a cycloaliphatic hydrocarbon, an aromatic hydrocarbon or an aromatic hydrocarbon substituted with an alkyl group, and n is from 1 to 4 is an integer.

The conjugated diolefin used in the anionic polymerization has 4 to 24 carbon atoms, and specific examples are 1,3-butadiene, isoprene, piperylene, methylpentadiene, phenylbutadiene, and 3.4-dimethyl-. 1,3-hexadiene, 4,5-diethyl-1,
3-octanediene and the like. Of these, isoprene and butadiene are preferred because of relatively stable price and availability. The aromatic hydrocarbon having an alkenyl group used for copolymerization is a vinyl allyl compound such as styrene, various styrene substituted with an alkyl group, styrene substituted with an alkoxy group, vinyl naphthalene, and vinyl naphthalene substituted with an alkyl group. One primary hydroxyl group at the terminal of the molecule can be obtained by terminating the polydiene polymer by adding ethylene oxide. Anionic polymerization is terminated by adding water to remove lithium as lithium hydroxide or by adding alcohol to form lithium alkoxide. The polydiene polymer used in the production of the (b) isocyanate-modified polydiene polymer used in the present invention has a molecular weight of 500 to 20,000.
Those in the range of 0 are preferred. If it is less than 500, the molecular weight is too low and sufficient physical properties cannot be obtained, and if it is more than 20,000, the viscosity is too high and the handling becomes difficult, which is not preferable.

The polydiene polymer used in the production of the (b) isocyanate-modified polydiene polymer used in the present invention may be hydrogenated, and there is a method in which hydrogenation is performed under high pressure using a nickel catalyst. The preferred nickel catalyst is a mixture of nickel 2-ethylhexanoate and triethylaluminum. A polydiene polymer having one primary hydroxyl group at a terminal is sealed and modified with a bifunctional isocyanate. Preferably, in a composition in which the equivalent number of isocyanate groups is 0.8 to 1.2 times with respect to 1 equivalent of hydroxyl groups of a polydiene polymer having one primary hydroxyl group at the terminal.
The functional isocyanate is reacted, and a commonly used catalyst such as dibutyltin dilaurate may be used at this time.
Tolylene diisocyanate as an example of a bifunctional isocyanate. Examples thereof include aromatic diisocyanates such as diphenylmethane diisocyanate, aliphatic diisocyanates such as hexamethylene diisocyanate, dicyclohexylsylmethane diisocyanate, and isophorone diisocyanate.

The composition of the present invention is a reaction product having a weight ratio of component (a) / component (b) in the range of 95/5 to 40/60. When the ratio is 40/60 or more, the curability is poor and a sufficient coating film cannot be obtained, which is not preferable. Although the method for obtaining the composition of the present invention is not particularly limited, a reaction vessel with a heating device and a stirring device, a melt kneader using a melt kneader such as a Banbury mixer or an extruder, to obtain a reaction product. Is preferred. At this time, a commonly used catalyst such as dibutyltin dilaurate may be used. The progress of the reaction is monitored by infrared spectrum and by quantification of the absorption spectrum of the NCO group.

When the composition of the present invention is used as a powder coating, the curing agent is not particularly limited. For example, novolak type phenol resins, dicyandiamide, imidazoles, hydrazides, aromatic amines, and the like can be used. Acid anhydrides and the like can be used. When the composition of the present invention is used as a powder coating, the curing agent is not particularly limited, and is generally used, for example, a novolak type phenol resin, dicyandiamide, imidazoles, hydrazides, aromatic amines, and acid anhydrides. Or the like can be used. When the composition according to the invention is used as a powder coating, the addition of extenders, flow regulators, reinforcing agents, fillers and pigments is possible. Examples of these additives include:
Glass fiber, asbestos fiber, carbon fiber, polyethylene powder, quartz powder, mineral silicate, asbestos powder and slate powder, kaolin, aluminum oxide, aluminum hydroxide, antimony trioxide, silica, titanium dioxide, carbon black, oxide Examples thereof include color pigments, metal powders, polyester resins, and acrylic resins. When the composition of the present invention is used as a powder coating, the method of forming a powder coating may be a method of producing a normal powder coating, and the epoxy resin composition of the present invention, a curing agent and necessary additives, for example, The mixture is melt-kneaded by a usual kneader or extruder under conditions of temperature and time (usually 50 to 160 ° C. for 3 to 60 seconds) at which no thickening or gelling occurs, and after cooling, pulverized and subjected to a classifier. As a result, a powder coating having a desired particle size distribution can be obtained. It is generally desirable that the particle size of the powder coating material be about 1 to 80 microns. The application of the powder coating using the composition of the present invention is not particularly limited, and powder coating for civil engineering building materials, home appliances, heavy electrical equipment, road materials, steel furniture, automobile parts, water supply materials, and the like. Can be used widely.

[0014]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited to the Examples. In each of Examples and Comparative Examples, the following solid epoxy resin and isocyanate-modified polydiene polymer were used. Solid epoxy resin As the solid epoxy resin, Bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd., Epicoat 1
004 (E-1004) and Epicoat 1003F (E
-1003F). E-1004 had an epoxy equivalent of 915 g / eq and a softening point of 98 ° C.
03F had an epoxy equivalent of 747 g / eq and a softening point of 93 ° C. Isocyanate-modified polydiene polymer

Synthesis Example 1 As a polydiene polymer having one primary hydroxyl group at a molecular end, Liquid Krato manufactured by Shell Chemical Co., Ltd.
nPolymer HPVM1201 was used. HP
VM1201 is a hydrogenated 1,3-butadiene polymer having one primary hydroxyl group at the terminal of the molecule, and has a hydroxyl equivalent of 3,000 g / eq and a glass transition temperature of -63 ° C.
300.0 g of this HPVH1201 and 8.7 g of tolylene diisocyanate (isocyanate equivalent 87 g / eq) as a bifunctional isocyanate were added to DABCO T-1.
2 (Dibutyltin dilaurate manufactured by Air Products) was used as a catalyst in a nitrogen atmosphere at 80 ° C. for 4 hours to obtain a reactant C. Reactant C has a viscosity of 3
It was 66 poise (25 ° C.).

Synthesis Example 2 HPVH1201 300.0 as polydiene polymer
g and hexamethylene diisocyanate as a bifunctional isocyanate (isocyanate equivalent: 84.1 g / eq)
A reaction product D was obtained in the same manner as in Synthesis Example 1 except that 84.1 g of DABCO T-12 was used as a catalyst. Reactant D had a viscosity of 354 poise (25 ° C.).

Example 1 As a solid epoxy resin, Bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd., Epicoat 10
04 (E-1004), and the reactant C prepared in Synthesis Example 1 was used as an isocyanate-modified polydiene polymer. 90 parts by weight of the solid epoxy resin and 10 parts by weight of the isocyanate-modified polydiene polymer were mixed and kneaded with a three-roll mill at 100 ° C. for 30 minutes. After cooling the reaction product, it is pulverized with a hammer mill and the particle size is 150 to
A powdered epoxy resin composition containing 250 mesh as a main component was obtained. In the infrared spectrum of this reaction product, NC
No absorption spectrum of the O group was confirmed.

Example 2 The procedure of Example 1 was repeated except that 80 parts by weight of E-1004 was used as the solid epoxy resin and 20 parts by weight of the reactant C prepared in Synthesis Example 1 was used as the isocyanate-modified polydiene polymer. A powdery epoxy resin composition was obtained.

Example 3 The procedure of Example 1 was repeated except that 70 parts by weight of E-1004 was used as the solid epoxy resin and 30 parts by weight of the reactant C prepared in Synthesis Example 1 was used as the isocyanate-modified polydiene polymer. A powdery epoxy resin composition was obtained.

Example 4 The procedure of Example 1 was repeated except for using 60 parts by weight of E-1004 as a solid epoxy resin and 40 parts by weight of the reactant C prepared in Synthesis Example 1 as an isocyanate-modified polydiene polymer. A powdery epoxy resin composition was obtained.

Example 5 The procedure of Example 1 was repeated except that 80 parts by weight of E-1004 was used as the solid epoxy resin and 20 parts by weight of the reactant D prepared in Synthesis Example 1 was used as the isocyanate-modified polydiene polymer. A powdery epoxy resin composition was obtained.

Example 6 80 parts by weight of E-1003F as a solid epoxy resin,
Synthesis Example 1 as an isocyanate-modified polydiene polymer
A powdered epoxy resin composition was obtained in the same manner as in Example 1 except that 20 parts by weight of the reactant C prepared in the above was used.

Example 7 The procedure of Example 1 was repeated except that 75 parts by weight of E-1004 was used as the solid epoxy resin and 25 parts by weight of the reactant C prepared in Synthesis Example 1 was used as the isocyanate-modified polydiene polymer. A powdery epoxy resin composition was obtained.

Comparative Example 1 E-1004 was crushed by a hammer mill alone to obtain a powder having a standard particle size of 150 to 250 mesh as a main component.

Comparative Example 2 The procedure of Example 1 was repeated except that 30 parts by weight of E-1004 was used as a solid epoxy resin and 70 parts by weight of the reactant C prepared in Synthesis Example 1 was used as an isocyanate-modified polydiene polymer. A powdery epoxy resin composition was obtained.

Comparative Example 3 E-1003F was singly pulverized with a hammer mill to obtain a powder having a standard particle size of 150 to 250 mesh as a main component. The epoxy resin compositions of Examples 1 to 7 and Comparative Examples 1 to 3 were subjected to the following paint storage stability test (blocking resistance test) as a powder paint by the following powder paint preparation method. Are shown in Table 1.

[0027]

[Table 1]

Preparation of Body Coating The epoxy resin compositions of Examples 1 to 7 and Comparative Examples 1 to 3 were further blended with a curing agent, a curing accelerator, an inorganic filler and a flow control agent according to the composition shown in Table 2. Barrel temperature of 11 obtained by dry blending with a super mixer using a twin screw extruder MP-2015 manufactured by APV Chemical Machinery Co., Ltd.
Melt kneading was performed at 0 ° C. for a residence time of 20 seconds. After cooling the kneaded material, it is pulverized with a hammer mill, and the particle size is 150 to 2 with a standard sieve.
A powder mainly composed of 50 mesh was used. Paint Storage Stability Test (Blocking Resistance Test) After each of the powder coatings adjusted as described above was left in a constant temperature bath at 40 ° C. for one week, the presence or absence of blocking of the coating was visually observed. Further, using the powder coating materials adjusted as described above, coating film test pieces were prepared by the following methods, and the following coating film tests were performed. The results are shown in Table 1.

Preparation of Coating Film Specimen Preparation of coating film test pieces was performed in accordance with JIS K5400. That is, a 150 × 70 × 0.8 mm steel plate was used for the Erichsen test, the adhesion test, and the salt spray resistance test, and a 150 × 50 × 0.3 mm steel plate was used for the flex resistance test. 200 × 100 × for impact test
A 0.6 mm steel plate is used as a test plate and is JIS standard K5
The pretreatment described in No. 400 was performed. Among them, a rust preventive paint was applied to the back side of the test plate for the salt spray test and dried. These test plates are heated to 180 to 200 ° C. in advance, and the powder coating prepared by the above method is applied using an electrostatic coating machine. The coated test plates were further post-cured at 200 ° C. for 10 minutes to obtain coating film test pieces having a coating thickness of 180 to 220 μ.

Coating film test The following coating film test was carried out using the above-mentioned coating film test piece in accordance with JIS K5.
400. I. Ecrisen Test Using an Ecrisen tester, when a steel ball is extruded from the back surface of a test piece to deform the test piece, the extrusion distance until cracking and peeling of the coating film is recorded. The greater the number of extrusion distance, the better. B. Adhesion test (cross-cut tape method) Using a cutter, a cut is made to penetrate the coating film on the test piece and reach the bare ground to make 100 cross-cuts. A cellophane adhesive tape is adhered onto the grid and the number n of grids remaining as a coating film on the test piece even after strong peeling is represented by n
Record at / 100. The greater n is, the better. C. Flex resistance test Using a bending tester described in JIS K5400, changing the diameter of the mandrel, bending the test piece with the coating outward, and recording the minimum diameter of the mandrel without peeling and peeling off the coating. . The smaller the number of the diameter, the better. D. Dupont Impact Resistance Test Using a Dupont impact resistance tester, when a weight of 500 g is dropped from a certain height, the maximum height at which no cracking or peeling of the coating film is recognized is recorded. The higher the number, the better. E. Salt spray resistance test JIS Z2371 using a spray device specified in
Under the salt spray resistance test conditions described in K5400, 50
After spraying with salt water for 0 hour, the presence and degree of rust on the coating film and swelling and peeling of the coating film are visually observed and recorded.

[0031]

The epoxy resin composition for powder coating of the present invention has excellent impact resistance, flexibility and blocking resistance.
The surface hardness also has a high effect.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08G 59/06 C08G 59/06

Claims (5)

[Claims] 1. A solid epoxy resin 4 having at least two epoxy groups in one molecule, having an epoxy equivalent of 400 to 2500 and a softening point of 50 to 150 ° C.
A reaction comprising 0 to 95 parts by weight and (b) 5 to 60 parts by weight of an isocyanate-modified polydiene polymer which is a reaction product of a polydiene polymer having one primary hydroxyl group at the terminal of the molecule and a bifunctional isocyanate compound. The product is an epoxy resin composition for powder coatings. 2. A solid epoxy resin having a glycidyl ether obtained by reacting an aromatic compound having at least two hydroxyl groups with epichlorohydrin under alkaline reaction conditions, or having at least two or more epoxy groups, Epoxy equivalent is 160-400,
Epoxy resin having a molecular weight of 300 to 800, and at least two epoxy resins obtained by subjecting an aromatic compound having at least two hydroxyl groups to addition polymerization in the presence of a catalyst to polymerize the same. The epoxy resin composition for a powder coating according to claim 1, which is a compound having a group. 3. The isocyanate-modified polydiene polymer (b) is a reaction product of a polydiene polymer having a molecular weight of 500 to 20,000 having one primary hydroxyl group at a molecular terminal and a bifunctional isocyanate. Item 3. The epoxy resin composition for powder coatings according to Item 1 or 2. 4. A polydiene polymer having one primary hydroxyl group at a terminal of a molecule used to produce the isocyanate-modified polydiene polymer (b) and having an aliphatic double bond hydrogenated, and a bifunctional polymer. Is a reaction product of isocyanate,
The epoxy resin composition for powder coating according to claim 1. 5. The isocyanate-modified polydiene polymer (b) has an isocyanate group equivalent number of 0.8 to 1.2 times with respect to 1 equivalent of a hydroxyl group of a polydiene polymer having one primary hydroxyl group at a molecular terminal. The epoxy resin composition for powder coating according to claim 1, wherein the epoxy resin composition is obtained by reacting a bifunctional isocyanate with a composition having the following composition.