KR101138470B1 - A method of epoxy resins for a pulverulent body paints and a pulverulent body paints composition - Google Patents

Abstract

The present invention relates to a method for preparing an epoxy resin for thermosetting powder coating and a powder coating composition which can be cured at low temperature and has excellent flexibility after coating and adhesion to a substrate. More specifically, the present invention relates to a dimer of an aliphatic or aromatic epoxy resin in one step. Powder coating epoxy which can be used for baf coating, pipe coating and other metal surface coating, which is modified with acid and reacted with a good novolac epoxy resin that can fully satisfy the paint properties in two steps. It relates to a resin production method and a powder coating composition using an epoxy resin produced by the production method.

Description

Manufacturing method and powder coating composition of epoxy resin for powder coating excellent in low temperature cure {A METHOD OF EPOXY RESINS FOR A PULVERULENT BODY PAINTS AND A PULVERULENT BODY PAINTS COMPOSITION}

The present invention relates to a method for preparing an epoxy resin for thermosetting powder coating and a powder coating composition which can be cured at low temperature and has excellent flexibility after coating and adhesion to a substrate. More specifically, the present invention relates to a dimer of an aliphatic or aromatic epoxy resin in one step. Powder coating epoxy which can be used for baf coating, pipe coating and other metal surface coating, which is modified with acid and reacted with a good novolac epoxy resin that can fully satisfy the paint properties in two steps. It relates to a resin production method and a powder coating composition using an epoxy resin produced by the production method.

Conventionally, bisphenol-A (bisphenol-A) type epoxy resins and dicyandiamide curing agents were used as curing agents (US Pat. No. 3,882,064). However, when using dicyandiamide curing agents alone, they are sensitive to moisture. Not suitable for pipe coating.

In addition, bisphenol A type epoxy resin and a curing agent of acid anhydride or hydroxypyridine are used as a curing agent (US Pat. No. 3,819,564). However, when using a curing agent of hydroxypyridine, the fast curing and the negative electrode peelability are good. However, there is a disadvantage in that the flexibility is poor because of poor flexibility.

In addition, Japanese Patent Application Laid-Open No. 92-20605 discloses a method in which a bisphenol A type epoxy resin and a novolak type epoxy resin are mixed and a diphenol derivative is used as a curing agent. High and hard (HARD) has the disadvantage of lowering the flexibility after coating, there is room for improvement.

In addition, US Pat. No. 5,686,185 and US Pat. No. 5,077,355 describe the use of diphenol derivatives as bisphenol A epoxy resins and hardeners, which are excellent in flexibility and cathodic peeling but not yet sufficiently satisfactory. In particular, there is a problem that fast curing does not work.

The purpose of the present invention is to solve the problems of the prior art, it is possible to harden (less than 2 minutes) at low temperatures (less than 180 ℃), excellent mechanical strength, such as negative electrode peelability and impact resistance, flexibility, It is to provide a method for producing an epoxy resin for steel pipe and reinforcing film powder coating, and excellent powder coating composition, and a powder coating composition using the epoxy resin produced by the production method.

The method for producing an epoxy resin for powder coating of the present invention includes reacting a butadiene rubber or a dimer acid with an aliphatic or aromatic epoxy resin in one step, and reacting a novolak type epoxy resin and a polyhydric phenol in two steps. It is done.

Referring to the step-by-step detailed method for producing an epoxy resin for powder coating of the present invention.

In one step, the aliphatic or aromatic epoxy resin is reacted with butadiene rubber or dimer acid. An example of this reaction is represented by the following Chemical Formula 1.

[Formula 1]

In the production method of the epoxy resin for powder coating of the present invention, the aliphatic or aromatic epoxy resin used in the first step is used for the purpose of improving the flexibility and adhesion to the base material after coating, and as a specific example thereof Aliphatic epoxy resins such as polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylol ethene triglycidyl ether, and diglycidyl ether bisphenol A type, diglycidyl ether bisphenol F resin Aromatic epoxy resins, such as these, etc. are mentioned, These can be used individually or in mixture of 2 or more types. There is no particular limitation on the mixing ratio in the mixed use.

It is preferable that the weight average molecular weight of the said aliphatic epoxy and aromatic epoxy resin is 100-1000, but when it is less than 100, reactivity falls and it is unpreferable, and when it exceeds 1000, the storage stability of resin is bad and it is unpreferable.

Butadiene rubber and dimer acid used in the first step is used to improve the flexibility, it is preferable to have at least two carboxyl groups. In the case of butadiene rubber and dimer acid, when the long carbon chain of the main chain is used excessively, flexibility may be excellent, but there is a tendency of blockage during storage of the resin and the paint, and the short carbon chain of the main chain is used. If the storage property of the lower surface resin becomes good, but the flexibility is poor, there is a possibility that the flexibility is lowered. Therefore, the butadiene rubber or dimer acid preferably has an average molecular weight of 200 to 1000.

Specific examples of the butadiene rubber include carboxyl terminated butadiene acrylonitrile copolymer, butadiene homopolymer, and the like, and specific examples of the dimer acid include dimer fatty acid and hydrogenated dimer fatty acid.

The amount of the butadiene rubber or the dimer acid is preferably used in an amount of 20 to 70 parts by weight based on 100 parts by weight of the aliphatic or aromatic epoxy resin. The mechanical strength and flexibility may be improved, but the storage and reactivity may be reduced.

In step 1, butadiene rubber or dimer acid may be optionally used together with polyhydric phenol. Specific examples of polyhydric phenols are bisphenol A.

It is preferable that the usage-amount of the said polyhydric phenol is 30 weight part or less with respect to 100 weight part of said aliphatic or aromatic epoxy resins, but when the usage-amount exceeds the said usage-amount, its equivalent viscosity will be high, adhesive viscosity with a base material will fall, It is not windy as it may lower.

As a result of the first step, butadiene rubber or dimer acid-modified epoxy polyester resin is obtained, which epoxy equivalent is 200 ~ 1000g / eq, the number average molecular weight is preferably 400 ~ 1000.

The reaction of the first step is preferably carried out in an inert gas atmosphere, the reaction temperature is preferably 150 ~ 200 ℃.

In the method for producing an epoxy resin for powder coating of the present invention, in the second step, the epoxy resin for powder coating can be obtained by reacting the resultant obtained in the first step with a novolak-type epoxy resin and a polyhydric phenol in the presence of a catalyst. .

The novolak-type epoxy resin used in the second step, for example, may be represented by the following formula (2), 3 to 7 functional groups, the average molecular weight is 300 to 1500, the epoxy equivalent of 150 to 400 g / eq Preferably, 1 or more types chosen from a phenol novolak-type epoxy resin, a cresol novolak-type epoxy resin, etc. can be used.

[Formula 2]

The amount of the novolak-type epoxy resin is preferably used in an amount of 100 to 400 parts by weight based on 100 parts by weight of the modified epoxy polyester resin obtained in step 1. If the content is less than 100 parts by weight, the mechanical strength and flexibility may be improved. It has a bad effect on the adhesion to the substrate and the negative electrode peelability, and is not preferable because the solvent resistance, chemical resistance, etc. are lowered, and if it exceeds 400 parts by weight, the crosslinking degree is too high, the flexibility and mechanical strength is lowered, and the reaction proceeds during storage. Due to the bad effect on the paint properties, it is not preferable.

The polyhydric phenol is used to improve the flexibility and storage stability of the resin through a reaction with a novolac epoxy resin, a representative example is bisphenol A. The amount of the polyhydric phenol is preferably used 50 to 150 parts by weight based on 100 parts by weight of the modified epoxy polyester resin obtained in the first step, less than 50 parts by weight is not preferable, the storage stability of the resin is poor, 150 parts by weight If it exceeds, melt viscosity will become high and reactivity will tend to fall.

The catalyst is used for reaction activation, for example, phenyltrimethylammonium chloride, butyltriphenylphosphonium chloride, butyltriphenylphosphonium bromide, butyltriphenylphosphate oxalate, tetramethylammonium, 2-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, quaternary ammonium, 2-undecylimidazole and the like can be used, and can also be used after being dissolved in solvents.

The amount of the catalyst added is 0.05 to 1.0 equivalents based on 100 parts by weight of the modified epoxy polyester resin obtained in step 1. If the amount is less than 0.05 equivalents, the reaction is delayed and the desired equivalents are not obtained. It is undesirable because there is a risk of gelation during the reaction.

In the two-step reaction, each component is added at 150 to 170 ° C, and the reaction is preferably performed while maintaining the reactant temperature at 150 to 200 ° C.

The epoxy resin for powder coating obtained through the first and second steps as described above has 2 to 5 functional groups at the terminal, an epoxy equivalent of 500 to 2000 g / eq, a number average molecular weight of 1000 to 5000, and a softening point of 90 to 140. It is preferable that it is 10-40poise (200 degreeC) in degreeC and a viscosity.

The powder coating composition of the present invention is characterized by comprising an epoxy resin for a powder coating, a phenol curing agent, a flow improving agent, a curing accelerator, and a pigment obtained by using the above production method.

In the powder coating composition of the present invention, the phenol curing agent is used to improve heat resistance and moisture resistance, and epoxy equivalent is preferably 150 to 400 g / eq, and specific examples thereof include KK450 (manufactured by KCC).

The amount of the phenol curing agent used is 25 to 50 parts by weight based on 100 parts by weight of the epoxy resin for powder coating, and less than 25 parts by weight of the phenol curing agent is not preferable because the physical properties such as impact resistance and flexibility are lowered. If it exceeds, a crosslinking degree will become high and a coating film will fall easily, and there exists a tendency for flexibility to fall, and it is unpreferable.

In the powder coating composition of the present invention, the flow improver is used to provide an excellent flowability even at low temperatures by reducing the viscosity increase at low temperatures, and acrylic or silicone flow improvers may be used, and specific examples are all. Flow I (manufactured by Monsanto); Fib-5, piel-201 (by Willissa); Akronal-4F (made by BASF Corporation), etc. are mentioned.

The use amount of the flow improver is 0.5 to 1.5 parts by weight based on 100 parts by weight of the epoxy resin for powder coating, and if it is less than 0.5 parts by weight, the desired appearance cannot be obtained. not.

In the powder coating composition of the present invention, the curing accelerator is a catalyst for promoting the reaction between the epoxy resin and the curing agent. For example, an organic tin compound such as imidazoles, phosphonium compounds, or butyl tin dilaurate may be used. It may be used, and specific examples include CNZ00048 (manufactured by KCC).

The amount of the curing accelerator used is 0.1 to 0.6 parts by weight based on 100 parts by weight of the epoxy resin for powder coating, and if it is less than 0.1 part by weight, the curing rate decreases rapidly. Can be.

In the powder coating composition of the present invention, a pigment is used for coloring, and as a specific example, titanium dioxide may be used.

The usage-amount of the said pigment is 25-50 weight part with respect to 100 weight part of said epoxy resins for powder coatings, and when it is less than 25 weight part, hiding is bad, and when it exceeds 50 weight part, bendability falls.

In addition to the above components, fillers such as barium sulfate (BaS0 ₄ ), calcium carbonate (CaC0 ₃ ), silica (SiO ₂ ), and aluminum hydroxide (Al (OH) ₃ ) may be additionally used in the powder coating composition of the present invention. It is also possible to further include conventional additives, if necessary, without departing from the object of the present invention.

The present invention can be understood in more detail by the following examples and comparative examples, the following examples are only for illustrating the present invention, and are not intended to limit the protection scope of the present invention.

Example

Manufacturing example  1-6 and Comparative Production Example  1-3

Each component was blended in the blending ratio (weight ratio) shown in Table 1 below to prepare an epoxy resin for powder coating. The specific manufacturing method of the epoxy resin for powder coating is as follows.

As a first step, a modified bisphenol A-type epoxy resin, butadiene rubber or dimer acid, and optionally a polyhydric phenol were added to a flask at room temperature and reacted at 150 ° C under injection of an inert gas to prepare a modified epoxy polyester resin.

As a second step, a novolak-type epoxy resin, a catalyst and a polyhydric phenol were added to the modified epoxy polyester resin prepared in Step 1 at 170 ° C, and reacted while maintaining the reactant temperature at 180 ° C.

The physical properties of the epoxy resin for powder coating prepared as described above were measured and shown in Table 1.

TABLE 1

week)

1.R8828 (epoxy equivalent 194g / eq, manufactured by KCC)

2. CTBN (NOVEON Co.)

3. Pripol (product of UNICHEMA company)

4, 7.Bisphenol A

5.N8470 (epoxy equivalent 225g / eq, manufactured by KCC)

6.N8460 (manufactured by KCC Corporation)

8. 2-isopropylimidazole

9. Measured by 0.2N HCl-Dioxan method

10. Cone & Plate Viscosity, 200 ℃

11.Measure with Mettler FP 800

Example  1-6 and Comparative example  1-3

Using the epoxy resins for powder coating of Preparation Examples 1 to 6 and Comparative Preparation Examples 1 to 3 in Examples 1 to 6 and Comparative Examples 1 to 3, respectively, the components were blended in the mixing ratios (weight ratios) shown in Table 2. And uniformly mixed, melt mixed at 90-120 ° C. through an extruder of a kneader or uniform extruder (PLK 46, BUSS), and then using a grinder, an average particle size of 30-50 microns, particle distribution 10-100. A micron powder coating composition was prepared. The powder coating composition thus prepared was coated on a specimen preheated at 250 ° C. (250 ° C. × 60 minutes) and cured to prepare a coating film specimen having a thickness of 300 ± 50 μm. After evaluating the physical properties of this specimen, the results are shown in Table 3.

Table 2

week)

1.DEH 84 (product of DOW company)

2.PV-5 (Wally Corporation)

3. CNZ00048 (potential curing catalyst) (manufactured by KCC)

4. Benzoin

5. Titanium Dioxide

TABLE 3

As can be seen from the above, powder coating compositions made mainly of epoxy resins prepared using the method of preparing epoxy resins for powder coatings of the present invention are conventionally used in high-temperature fast curing when used on metal surfaces, especially pipes, rebar coatings, and the like. It satisfies general characteristics such as corrosion resistance and chemical resistance of the epoxy resin, and has excellent properties such as flexibility, negative electrode peelability and adhesion.

Claims (6)

(1) reacting an aliphatic or aromatic epoxy resin with butadiene rubber or dimer acid having a carboxyl group to obtain a modified epoxy polyester resin; (2) reacting the modified epoxy polyester resin obtained in step (1) with a novolak-type epoxy resin and a polyhydric phenol under a catalyst to obtain an epoxy resin for powder coating. Manufacturing method. The method for producing an epoxy resin for powder coating according to claim 1, wherein 20 to 70 parts by weight of the butadiene rubber or dimer acid is used based on 100 parts by weight of the aliphatic or aromatic epoxy resin. The method for producing an epoxy resin for powder coating according to claim 1, further comprising using a polyhydric phenol together with butadiene rubber or dimer acid in the step (1). The amount of the novolac epoxy resin is 100 to 400 parts by weight based on 100 parts by weight of the modified epoxy polyester resin, and the amount of the polyhydric phenol is 100 parts by weight based on 100 parts by weight of the modified epoxy polyester resin. Process for producing an epoxy resin for powder coating, characterized in that 50 to 150 parts by weight. The method of claim 1, wherein the catalyst is used in an amount of 0.05 to 1.0 equivalent based on 100 parts by weight of the modified epoxy polyester resin. 25 to 50 parts by weight of a phenol curing agent, 0.5 to 1.5 parts by weight of a flow improver, and 0.1 to 0.6 of a curing accelerator based on 100 parts by weight of the epoxy resin for powder coating prepared by the manufacturing method according to any one of claims 1 to 5. Powder coating composition comprising a part by weight and 25 to 50 parts by weight of pigment.