JPH083271A - Production of epoxy-modified polyester resin and powder coating composition - Google Patents

Abstract

PURPOSE:To obtain a powder coating composition excellent in weatherability and storage stability by using a modified polyester resin obtained by modifying a polyester resin having a carboxyl or hydroxyl group at each end with a specific epoxy resin. CONSTITUTION:A polyester resin (A) having a carboxyl or hydroxyl group at each end is melt-kneaded together with a polyfunctional epoxy resin (B) to produce an epoxy-modified polyester resin having a polyester structure as the central part. The resin (A) has an acid value of 10-250KOHmg/g, a softening point of 60-150 deg.C, and a number-average mol.wt. of 500-12,000. The resin (B) has a functionality of 2 or higher, preferably 3 to 10, and is represented by formula I or II. An alicyclic epoxy resin is desirable as the resin (B) from the standpoint of heat resistance. This modified polyester resin is blended with a polyester resin having a carboxyl or hydroxyl group at each end, and a cationic catalyst (e.g. an amine complex of BF3) and other ingredients are incorporated into the blend to produce the objective a powder coating composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an epoxy resin having a polyester structure in the center and a resin composition for powder coatings containing the epoxy resin and a polyester resin containing a carboxyl group or a hydroxyl group as essential components. is there.

[0002]

2. Description of the Related Art Powder coatings are non-polluting coatings, can be used immediately after coating, do not require multi-layer coating, and are relatively inexpensive as compared with conventional solvent-based coatings. In addition, it has been recognized that it can be collected and reused, and is applied to members such as home electric appliances, building materials, and automobile parts, and the demand for it is rapidly expanding in recent years.

As a curing system which has been applied to conventional powder coatings, there is a curing reaction of a carboxyl group and an epoxy group represented by a TGIC system and a hybrid system.

[0004]

However, the use of TGIC systems has been drastically reduced due to their skin irritation problems. In the latter case, since the weather resistance is poor, the applicable range is limited to indoor use. Currently, the most used system for outdoor applications is a polyurethane system using block isocyanate, but this has the problems of armpits and tars.

Further, for example, as disclosed in Japanese Examined Patent Publication No. 10471/1992, the main skeleton has a cyclohexane ring bonded by an ether bond, and the side chain of the cyclohexane ring has three kinds of functional groups, namely, , Epoxy group, vinyl group,
EHPE, which is an alicyclic epoxy resin having an ester group
Application of a cycloaliphatic epoxy resin manufactured by Daicel Chemical Industries Ltd. in combination with a polyester resin having a plurality of carboxyl groups to a powder coating [JP-A-63-262129 and JP-A-2-191680]. Has excellent weather resistance, alkali resistance, etc., but has some problems in storage stability (blocking property) as a powder coating.

[0006]

It is an object of the present invention to solve the problem of blocking properties of the epoxy resin as a raw material, to prevent the occurrence of cracks and tars, and to have excellent weather resistance, and to provide a functional group-containing polyester resin containing 3 It is an object of the present invention to provide a powder coating resin composition containing a resin modified with a functional or higher epoxy resin, which has excellent coating film properties and powder properties, and which is cured at a relatively low temperature.

The inventors of the present invention have made earnest studies to achieve the above-mentioned object, and as a result, by using an epoxy resin having a polyester structure in the central part, which is obtained by modifying a carboxyl group- or hydroxyl group-containing polyester resin with an epoxy group. The inventors have found that the above drawbacks can be remedied and reached the present invention.

[0008]

That is, the present invention is
"A method for producing an epoxy-modified polyester resin having a polyester structure in the central portion, characterized by modifying a polyester resin having a carboxyl group or a hydroxyl group at both ends with an epoxy resin" and "(A) Carboxyl group at both ends Alternatively, an epoxy-modified polyester resin having a polyester structure in the central part, which is obtained by modifying a hydroxyl group-containing polyester resin with a bifunctional or higher epoxy resin,
(B) contains a carboxyl group- or hydroxyl group-containing polyester resin as an essential component, and optionally (C)
It is a powder coating composition containing a surface preparation agent, a curing catalyst, a pigment or a dye ”.

The resin produced by the production method of the present invention comprises a polyester resin having a carboxyl group or a hydroxyl group at both ends, which is one starting material, and an epoxy group of a bifunctional or more functional epoxy resin which is another starting material. It is an epoxy resin modified by, that is, having a polyester structure in the center.

Therefore, the term "modified" means chemically binding a bifunctional or higher functional epoxy resin to a carboxyl group- or hydroxyl group-containing polyester resin, and simply blending the bifunctional or higher functional epoxy resin with the polyester resin. Not a thing. The carboxyl group- or hydroxyl group-containing polyester resin, which is one of the raw materials for the epoxy-modified polyester resin produced by the production method of the present invention, is not special, and phthalic acid, isophthalic acid, and terephthalic acid, which are usually used, , Aromatic dicarboxylic acids such as naphthalene dicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid and sebacic acid, unsaturated dicarboxylic acids such as maleic acid and fumaric acid, fats such as hexahydroterephthalic acid and hexahydroisophthalic acid With various carboxylic acids such as polycarboxylic acids such as cyclic dicarboxylic acid, trimellitic acid and pyromellitic acid,
Ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol, glycerin, pentaerythritol, neopentylglycol −
And various polyhydric alcohols (polyols) such as trimethylolpropane can be obtained by condensing according to a well-known and commonly used method described below, or a commercially available product can be used, but is preferable. Acid component is aromatic dicarboxylic acid (isophthalic acid, terephthalic acid, etc.), alcohol component is aliphatic glycol (ethylene glycol, neopentyl glycol, 1,6-hexanediol, etc.) A linear type resin composed of a combination thereof, more preferably a branching type resin formed by using a polyhydric alcohol such as trimethylolpropane.

In one of the starting materials in the present invention, "a polyester resin containing carboxyl groups or hydroxyl groups at both ends", for example, a polymer obtained by a transesterification method or a direct esterification method is polycondensed to have a high molecular weight. After that, it is produced by carrying out a depolymerization reaction if necessary.

For example, it can be manufactured under the following conditions.

The polyester resin having a carboxyl group can be obtained by reacting (n + 1) mol of a polybasic acid or an anhydride thereof with n mol of a polyvalent alcohol.

For example, the reaction formula in the case of a reaction between a dibasic acid and a divalent alcohol, and the polyester resin obtained are represented by the following structural formulas.

[0015] On the other hand, the polyester resin having a hydroxyl group is, contrary to the above, a mixture of n mol of polybasic acid or their anhydride (n + 1)
Obtained by reacting with moles of polyhydric alcohol. The reaction is performed as follows.

First, a reactor is charged with a polybasic acid or an anhydride thereof and a polyhydric alcohol. Then, the reaction temperature is set to 150 to 250 ° C. to distill off the water produced as the reaction proceeds. However, when an acid anhydride is used, water is not generated. A catalyst can be used in the reaction.

The catalyst which can be used is a catalyst which is usually used in the esterification reaction, specifically, para-toluenesulfonic acid, sulfuric acid, tin compounds such as tetrabutyl titanate and the like.

The amount of catalyst used is from 1 to the starting material.
It is 1000 ppm, preferably 100 to 200 ppm. The carboxyl group-containing polyester resin used in the powder coating composition of the present invention preferably has an acid value in the range of 15 to 250, more preferably 30 to 100.
Is.

Both the carboxyl group-containing and hydroxyl group-containing polyester resins have a number average molecular weight of 500 to 1200.
The range is 0, preferably 1000 to 5000. If the number average molecular weight is less than 500, the softening temperature of the resin is low, and the storage stability during powder coating is poor. On the contrary, if it exceeds 12000, the softening temperature becomes too high, which is not suitable as a resin for powder coating. Neither is preferable.

When the acid value is less than 10, the reactivity is low and the crosslink density does not increase in the coating film.

On the contrary, when the acid value exceeds 250, not only is the molecular weight so low that a solid product is difficult to obtain, but
When the epoxy resin is blended in an equivalent amount, it becomes meaningless to use it because the content of the polyester resin becomes small.

The acid value of the polyester resin has a relative relationship with the molecular weight, and the lower the acid value, the higher the molecular weight. On the contrary, those having a high acid value have a low molecular weight. The polyester resin used is preferably solid at room temperature and has a glass transition temperature in the range of 40 to 80 ° C. The carboxyl group-containing and hydroxyl group-containing polyester resins having the above glass transition temperatures have a softening point of 60 to 150.
The temperature range is 0 ° C, preferably 80 to 110 ° C. If the softening point is less than 60 ° C, the storage stability during powder coating is adversely affected, while if it exceeds 150 ° C, the heat melting behavior becomes dull, and the appearance of the coating film tends to deteriorate. Neither is preferable.

The bifunctional or higher functional epoxy resin, which is the other starting material used for epoxy-modifying the above-mentioned carboxyl group- or hydroxyl group-containing polyester resin, is not special and is preferably a 3- to 10-functional epoxy resin. It is a resin.

More preferred bifunctional or higher functional epoxy resins are those of general formula (I)

Embedded image Or general formula (II)

[Chemical 4] It contains at least one of the structures shown in.

Examples of the bifunctional or higher functional epoxy resin containing the structure of the general formula (I) include the general formula (III)

Embedded image There is an epoxy resin represented by. Further, as an example of the bifunctional or more functional epoxy resin containing the structure of the general formula (II),
General formula (IV)

[Chemical 6] There is an epoxy resin represented by.

Specific examples thereof include Celoxide 2021, manufactured by Daicel Chemical Industries, Ltd., Epolide GT, EHPE, and the like. Further, for example, a commercially available bisphenol-based epoxy resin having a glycidyl group, and an epicoal made of oleic shell
828, Arubaito GT700 manufactured by Ciba-Geigy
4, CY179, etc. can be used. Of these, an alicyclic epoxy resin is preferable. The reason is that it is excellent in heat resistance.

The reaction of the "polyester resin having carboxyl groups or hydroxyl groups at both ends" with the various "bifunctional or more functional epoxy resins" is carried out as follows. That is, the epoxy-modified polyester resin is prepared by mixing the bifunctional or higher functional epoxy resin and the acid-terminated or hydroxyl-terminated polyester resin as described above with a mixer and then extruding the mixture under a temperature condition of 50 to 150 ° C. It can be obtained by melt-kneading with a kneader, cooling and pulverizing.

Further, in a state where the polyester resin is melted in advance, an epoxy resin is added, and the temperature is 50 to 150 ° C.
It can also be obtained after stirring for a predetermined time under temperature conditions in the range. If the temperature at the time of melt-kneading is less than 50 ° C., the polyester resin is difficult to melt, and even if melted, the reaction with the epoxy resin does not proceed, and the epoxy modification intended by the present invention cannot be performed. On the other hand, at a temperature above 150 ° C., the reaction between the polyester resin and the epoxy resin progresses too much and a gel is partially generated, and the original function of the epoxy-modified polyester resin as the curing agent in the meaning of the present invention is Both are not preferable because they disappear.

By the above reaction, "epoxy-modified polyester resin having a polyester structure in the central portion"
Is obtained.

Next, the "epoxy-modified polyester resin having a polyester structure in the central part" and the "polyester resin having a carboxyl group or a hydroxyl group at both ends" obtained as described above are blended to prepare the present invention. Prepare the powder coating composition.

The compounding ratio of "epoxy-modified polyester resin having a polyester structure in the central part" and "polyester resin having carboxyl groups or hydroxyl groups at both ends" is 1 to 1 epoxy resin per polyester molecule.
10 molecules, preferably 3 to 5 molecules. When the compounding amount of the epoxy resin is less than 1 molecule, the ratio of the functional groups remaining in the polyester resin increases, and when the compounding amount of the epoxy resin is more than 10 molecules, the epoxy resin does not react with the polyester resin. such resin are many residual resistance Bed <br/> locking worsens, not suitable for this purpose.

The epoxy-modified polyester resin thus obtained can be used as a curing agent for acid-terminated polyesters and as a curing agent for hydroxyl-terminated polyesters. In the latter case, the epoxy resin used for modification is preferably an alicyclic type, and it is preferable to add a cationic catalyst.

As the cation catalyst, an amine complex of BF ₃ , specifically, a BF ₃ amine complex such as n-hexylamine, monoethylamine and benzylamine, a sulfonium salt having a benzyl group, an ammonium salt, a pyridinium salt, And phosphonium salts, etc., and BF ₄ , AsF ₆ , PF ₆ , SbF ₆ as counter-ions.
And so on. Among them, those having SbF ₆ as a counter ion show high catalytic activity.

The resin composition for powder coatings of the present invention contains, if necessary, inorganic pigments such as titanium dioxide, carbon black, iron oxide and lead, organic pigments such as cyaning line and cyanimble, and sulfuric acid. Extender pigments such as barium, mica, talc, zinc oxide, metal powders such as aluminum powder, copper powder, nickel powder, dyes, pigment dispersants, surface preparation agents, phosphorus-based and imidazole-based catalysts and other additives 0.01 to 1.0 part by weight, preferably 0.30 to 0.60 part by weight can be added.

The composition of the present invention can be obtained by a known method such as a known method, dry blending, melt-kneading with an extruder, cooling, crushing and filtering.

[0036]

EFFECTS OF THE INVENTION A powder coating obtained by applying the epoxy-modified polyester resin of the present invention to a powder coating gives a coating film having excellent weather resistance, storage stability and smoothness. This will be specifically described.

<Example 1> As an acid group-containing polyester resin, Crylcoat CC800 (manufactured by UCB, polyester resin having a terminal carboxyl group obtained by using a dicarboxylic acid mixture and a diol mixture, AV: 33KO)
Hmg / g, Mn: 2500, Tg: 60 ° C.) 100 parts by weight, EHPE-3050 as an epoxy resin for modification
[Daicel Chemical Industry Co., Ltd., which is disclosed in JP-B-4-10471, has a trimethylolpropane residue at the end, and has a cyclohexane ring bonded to the main skeleton with an ether bond, Epoxy resin having a skeleton having three kinds of functional groups in the side chain of the cyclohexane ring, that is, an epoxy group, a vinyl group and an ester group, WPE: 124
g / mol] 38 parts by weight was pre-kneaded using a Henschel mixer [manufactured by Mitsui Kako Co., Ltd.], melt-kneaded at 120 ° C. using an extruder, cooled, and then pulverized to obtain an epoxy-modified polyester resin ( A1) was obtained. The residual acid value is 5.2.
(KOH mg / g).

<Example 2> As the polyester resin containing an acid group, the same rylcoat CC800 (UCB) as in Example 1 was used.
Manufactured by AV, 33 KOHmg / g, Mn: 2500, T
g: 60 ° C.) 100 parts by weight, GT-301 as a modified epoxy resin [described in Japanese Patent Application Laid-Open No. 4-69360, manufactured by Daicel Chemical Industries, Ltd., 3,4-epoxycyclohexyl group in the skeleton] Epoxy resin having 3 units / tetrahydrophthalic anhydride and 3-cyclohexene methanol as starting materials to synthesize an ester compound, to which ε-caprolactone monomer was added to further epoxidize the 3 cyclohexene moieties Compound, WPE: 1
73] 32 parts by weight was prepared in the same manner as in Example 1 to obtain an epoxy-modified polyester resin (A2). The residual acid value is 2.
It was 4 (KOHmg / g).

<Example 3> As an acid group-containing polyester resin, Crylcoat CC800 (manufactured by UCB, AV: 33)
KOHmg / g, Mn: 2500, Tg: 60 ° C) 10
0 parts by weight, EHPE-3 as an epoxy resin for modification
030 [manufactured by Daicel Kagaku Kogyo Co., Ltd., disclosed in Japanese Patent Publication No. 4-10471, having a trimethylolpropane residue at the end and a cyclohexane ring bonded to the main skeleton through an ether bond] , An epoxy resin having a skeleton having three kinds of functional groups in the side chain of the cyclohexane ring, that is, an epoxy group, a vinyl group, and an ester group, WPE:
98 g / mol] 30 parts by weight was prepared in the same manner as in Example 1 to obtain an epoxy-modified polyester resin (A3). The residual acid value was 4.2 (KOHmg / g).

<Example 4> Crylcoat CC800 (manufactured by UCB, AV: 33) as an acid group-containing polyester resin
KOHmg / g, Mn: 2500, Tg: 60 ° C) 10
0 parts by weight, EHPE-1 as an epoxy resin for modification
050 [manufactured by Daicel Chemical Industries, Ltd., disclosed in Japanese Patent Publication No. 4-10471, having a methanol residue in the main skeleton and having a cyclohexane ring bonded by an ether bond, Epoxy resin having a skeleton with three types of functional groups in the side chain of the ring, namely, epoxy group, vinyl group, ester group, WPE: 113 g / mol]
34 parts by weight were prepared in the same manner as in Example 1 to obtain an epoxy-modified polyester resin (A4). The residual acid value is 3.9.
(KOH mg / g).

<Example 5> As a hydroxyl group-containing polyester resin, Crylcoat CC690 (manufactured by UCB, OHV:
30KOHmg / g, Mn: 2500, Tg: 55 ° C)
100 parts by weight, GT-30 as an epoxy resin for modification
1 [manufactured by Daicel Chemical Industries, Ltd., WPE: 173] 31
Parts by weight were prepared in the same manner as in Example 1 to obtain an epoxy-modified polyester resin (A5). The residual hydroxyl value is 2.8 (K
OH mg / g).

Table 1 shows the properties of the epoxy-modified polyester resin.

Table 1 WPE (g / mol) Tg (° C.) A1 720 47.7 A2 870 40.2 A3 640 43.5 A4 670 38.3 A5 850 37.2 <Examples 6 to 10> According to the formulation shown, the mixture was pre-kneaded using a Henschel mixer [manufactured by Mitsui Kako Co., Ltd.], melt-kneaded at 115 ° C. using an extruder, cooled, pulverized, filtered with 150 mesh, and powdered. Got body paint. The powder coating thus obtained is applied to a zinc phosphate-treated steel sheet to a film thickness of 50.
Electrostatically coated to ~ 60 microns 15 at 170 ° C
It was baked for a minute to form a coating film. Table 3 shows the results of evaluating the performance of the coating film.

Table 2 Raw material components Example 6 7 8 9 10 Polyester resin 70 66 73 73 72 -CC800 CC690 ----- 68 Epoxy modified polyester A1 30 ----- A2-34 --- A3 --- 27 --A4 − − − 28 − A5 − − − − 32 Additive Modaflo − 0.5 0.5 0.5 0.5 0.5 Benzoin 0.5 0.5 0.5 0.5 0.5 Catalyst TPP 0.5 0.5 0.5 0.5 − SI-L145 − − − 0.5 Pigment CR90 40 40 40 40 40 40 TPP: Triphenylphosphine SI-L145: Sanshin Chemical Co., Ltd. thermal latent catalyst CR90: Ishihara Sangyo Co., Ltd. titanium oxide Table 3 Example 6 7 8 9 10 Smoothness ◎ ◎ ◎ ◎ ◎ Gloss (60 degrees) (%) 98 97 97 97 96 98 Impact resistance (cm)>80>80>80>80> 80 (1/2 inch φ1 kg) Erik Down (mm)>9>8>10>9> 7 accelerated weathering test 92 90 93 93 94 300hr (SWO ) 76 73 70 76 78 500hr ( retention%) 45 48 42 47 51 1000hr smoothness: Visual impact Properties: JIS K 5400 Gloss: JIS K 5400 Erichsen: JIS K 5400 (hereinafter blank space)

Claims (5)

[Claims] 1. A process for producing an epoxy-modified polyester resin having a polyester structure in the center, which comprises modifying a polyester resin having a carboxyl group or a hydroxyl group at both ends with a bifunctional or higher functional epoxy resin. 2. The acid value of the polyester resin containing carboxyl groups at both ends is 10 to 250 KOHmg / g,
The polyester structure according to claim 1, which has a softening point of 60 to 150 ° C., is a resin which is solid at room temperature and has an average of 2 or more carboxyl groups per molecule, and has a number average molecular weight of 500 to 12000. For producing an epoxy-modified polyester resin having a central part. 3. A polyester resin having hydroxyl groups at both ends has a hydroxyl value of 10 to 250 KOHmg / g, a softening point of 60 to 150 ° C., and has an average of 2 or more hydroxyl groups per molecule at room temperature. The method for producing an epoxy-modified polyester resin having a polyester structure in the central portion according to claim 1, which is a solid resin and has a number average molecular weight of 500 to 12000. 4. The bifunctional or higher functional epoxy resin as the starting material according to claim 1 has the following general formula (I): Or the general formula (II), 2. A resin containing at least one structure of
A method for producing the epoxy-modified polyester resin described. 5. (A) Epoxy-modified polyester resin having a polyester structure in the central part, which is obtained by modifying a polyester resin having carboxyl groups or hydroxyl groups at both ends with a bifunctional or higher functional epoxy resin, and (B) carboxyl group or hydroxyl group. Contains a contained polyester resin as an essential component, and optionally (C) a surface preparation agent, a curing catalyst,
A powder coating composition containing a pigment or a dye.