JPH1112536A - Polyester resin composition for powder coating and powder coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject curing catalyst addition type resin composition low in coloration degree and excellent in thermal stability, smoothness, mechanical characteristics, etc., by including a specific polyester resin and a specific organic phosphine halide compound. SOLUTION: This polyester resin composition comprises 100 pts.wt. of a polyester resin having carboxyl groups as main terminal groups and having an acid value of 20-100, preferably 20-80 mgKOH/g and a softening point of 90-140 deg.C, preferably 100-130 deg.C, and 0.1-5 pts.wt. of an organic phosphine halide compound of the formula: R'R3 P<+> X<-> (R is phenyl, butyl; R' is a 1-4C alkyl, phenyl, etc.; X is a halogen) (e.g. methyltriphenylphosphonium bromide).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin composition for powder coatings and a powder coating containing the polyester resin composition. The present invention relates to a polyester resin composition for a powder coating having a low curing catalyst addition type and a powder coating containing the polyester resin composition.

[0002]

2. Description of the Related Art Among thermosetting powder coatings, powder coatings comprising a polyester resin having a carboxyl group as a main terminal group and an epoxy compound are excellent in coating appearance and relatively low in cost. It is used in many fields including home appliances and building materials.

[0003] However, this powder coating requires high-temperature and long-time baking, and in order to enable low-temperature baking to reduce energy cost, a method such as adding a curing catalyst is required. Has been used. Conventionally, organic phosphine compounds such as triphenylphosphine, imidazoline, and imidazole which have been used as such curing catalysts have poor thermal stability and exhibit considerable coloring when producing resins or baking at high temperatures after coating. was there.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a powder which is excellent in thermal stability, has a low degree of coloring even during resin production and high-temperature baking, has good smoothness and excellent mechanical properties. An object of the present invention is to provide a polyester resin composition for body paint and a powder paint.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that when a specific organic phosphine halogen compound is used in combination with a polyester resin composition as a curing catalyst,
The inventors have found that the above problems can be solved, and have reached the present invention.

[0006] Powder coating polyester resin composition of the present invention, a polyester resin, the following general formula R'R ₃ P ⁺ X ^- (wherein R phenyl group or a butyl group, R 'is C ₁ -C _Four
And X represents a halogen), and an organic phosphine halogen compound represented by the following formula:

Preferably, in the polyester resin composition, the organic phosphine halogen compound is contained in a ratio of 0.1 to 5 parts by weight based on 100 parts by weight of the polyester resin.

Preferably, in the polyester resin composition, the main terminal group of the polyester resin is a carboxyl group, the acid value is 20 to 100 mgKOH / g, and the softening point is 90 to 140 ° C.

[0009] The powder coating of the present invention is characterized by comprising the above-mentioned polyester resin composition.

Preferably, the powder coating further comprises an epoxy resin.

[0011]

Organic phosphine halide used in the present invention DETAILED DESCRIPTION OF THE INVENTION, the general formula R'R ₃ P ⁺ X ^- (wherein, R represents a phenyl group or a butyl group, R 'is C ₁ -C
₄ , an alkyl group, a phenyl group or a benzyl group, and X represents a halogen), which is blended as a curing catalyst.

As the organic phosphine halogen compound represented by the general formula (1), for example, methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, propyltriphenylphosphonium bromide, isopropyltriphenylphosphonium bromide, butyltriphenylphosphonium chloride, Isobutyltriphenylphosphonium chloride,
Examples include tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, benzyltriphenylphosphonium chloride, and benzyltriphenylphosphonium bromide.

The compounding amount of the organic phosphine halogen compound as a curing catalyst is as follows.
It is preferably 0.1 to 5 parts by weight based on parts by weight. If the amount is less than 0.1 part by weight, sufficient curability cannot be obtained, and if the amount exceeds 5 parts by weight, curing is too fast, which causes a problem in the appearance of the coating film. A particularly desirable amount is 0.3 to 2 parts by weight.

The main terminal group of the polyester resin used in the present invention is preferably a carboxyl group. The proportion of the carboxyl group in all the terminal groups is preferably 60 mol% or more, and if it is less than 60 mol%, when the powder coating material is used, the mechanical strength is lowered due to the decrease in crosslink density, which is not preferable. Regarding the upper limit of the carboxyl group content, the total amount of the terminal groups in the polyester resin may be used as the carboxyl group.

The acid value of the above polyester resin is measured by titration with 1/10 normal alcoholic KOH solution using pyridine as a solvent, and preferably 20 to 100 mg.
KOH / g, particularly preferably 20 to 80 mg KOH / g
It is. When the acid value is lower than 20 mgKOH / g,
Since an effective cross-linking density cannot be obtained, it is difficult to obtain sufficient mechanical properties of the coating film, and if it exceeds 100 mgKOH / g, it is necessary to lower the molecular weight relatively.

The softening point of the polyester resin is measured by a ring and ball method (JIS K 2207), and is preferably in the range of 90 to 140 ° C, particularly preferably 100 to 130 ° C. When the softening point is lower than 90 ° C, the powder coating has drawbacks such as easy blocking during storage, and when the softening point is higher than 140 ° C, the coating film has smoothness and adhesion. This results in significantly poorer properties.

As the acid component which is a constituent component of the polyester resin, aromatic, aliphatic and / or alicyclic polybasic acids and derivatives thereof can be used. Specifically, terephthalic acid, isophthalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic anhydride, fumaric acid, maleic anhydride And trimellitic anhydride can be exemplified, and these are used as one kind or as a mixture of two or more kinds.

As the polyhydric alcohol component, which is another essential component of the polyester resin, those commonly used can be used, for example, ethylene glycol, neopentyl glycol, diethylene glycol,
1,2-propanediol, 1,3-propanediol, dipropylene glycol, 2-methyl-1,3-propanediol, 2-ethylpropanediol, 2-ethyl-2-butylpropanediol, 2-butylpropanediol , 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,
5-pentanediol, 1,5-pentanediol,
Examples thereof include 1,6-hexanediol, 2,5-hexanediol, ester diol 204 (manufactured by Union Carbide), 1,4-cyclohexanedimethanol, hydrogenated bisphenol A, and the like. It can be used as a mixture of the above.

The branching agent can obtain sufficient performance without using it, but can be used to increase the acid value to supplement the reactivity. The above components may be polybasic acids or polyols, and the content thereof can be appropriately set according to the target hydroxyl value and softening point of the polyester resin in the above ranges.

The tri- or tetrafunctional component serving as a branching agent includes:
Examples include trimellitic anhydride, pyromellitic anhydride, trimethylolpropane, trimethylolethane, glycerin, pentaerythritol and the like.

Regarding the method for producing the polyester resin,
Any of the known and commonly used direct esterification methods or transesterification methods can be applied. Specifically, the acid component and the alcohol component described above are polycondensed with an excess of the acid component, or prepared by adding a carboxylic anhydride or the like to a polyester resin having a hydroxyl terminal by polycondensation under an excess of a hydroxyl group. You can also. Further, as a method of accelerating the reaction, a method of increasing the reaction temperature while preventing the dissipative loss by increasing the boiling point of the polyol by applying pressure, or by applying a reduced pressure operation or by passing an inert gas through the reaction. There are ways to promote

Specifically, in the direct esterification method by pressurization, the entire amount of the polyol component is charged in the first stage, and after heating and melting, the temperature is raised to about 160 ° C., and the total acid component
About 60% of the acid is charged. This is because if the entire amount of the acid component is charged in the first stage, the mixture loses fluidity and it becomes difficult to stir, and if the amount is about 50 to 60%, the slurry is easily stirred. As the reaction catalyst to be charged in the first stage, di-n-butyltin oxide, stannous oxalate, antimony trioxide and the like can be used, and the amount of addition is 0.01 to 0.1 mol% based on the total acid components. Appropriate. Next, the process proceeds to a pressurizing operation, in which the reaction temperature is promptly increased by increasing the boiling point of the polyol, thereby accelerating the reaction.

Also, industrially, a direct esterification method is usually used, but when an apparatus which cannot carry out a pressure reaction is used, an ester using dimethyl terephthalate having good reactivity as a terephthalic acid component is used. An exchange method is used. In this case, as the transesterification catalyst used, metal acetates such as zinc acetate, manganese acetate and calcium acetate are generally used.

Further, the promotion of the reaction by the decompression operation is such that at the end of the reaction, the unreacted polyol almost disappears,
It is applied when the removal of generated water outside the system is delayed. The promotion of the reaction by passing an inert gas can be applied to any part of the reaction, in such an amount that the dissipation of the polyol out of the system is minimized.

The polyester resin composition of the present invention is obtained by adding a predetermined amount of an organic phosphine halogen compound as a curing catalyst to the polyester resin thus produced and stirring the mixture to sufficiently disperse it. The polyester resin may have a branched structure or a linear structure.

As the epoxy compound used in the powder coating material of the present invention, a commonly used epoxy compound such as bisphenol A cricidyl type epoxy resin, hydrogenated bisphenol type epoxy resin, alicyclic epoxy resin compound, triglycidyl isocyanurate and the like are used. be able to.

The powder coating of the present invention comprises the above-mentioned polyester resin composition and is obtained by blending the above-mentioned polyester resin with an epoxy compound. The ratio of the epoxy group equivalent number B of the compound (functional group ratio of epoxy group to acid) is in the range of 0.9 to 1.5 from the viewpoint of stably realizing excellent coating performance. preferable.

The powder coating of the present invention may be a powder coating capable of obtaining a transparent coating film without adding a pigment, or may be a pigment for coloring or other fillers, a flow regulator. And a powder coating to which a pinhole inhibitor or the like is added.

Specifically, titanium dioxide or carbon black is used as a pigment, calcium carbonate is used as a filler,
Barium sulfate and the like are used as flow regulators, acrylic low molecular weight polymers such as Acronal 4F (BASF) and Polyflow S (Kyoeisha Chemical Co., Ltd.), and benzoin and the like are used as pinhole inhibitors.

In producing a powder coating, for example, the above fillers and additives, the polyester resin composition and the epoxy compound are mixed with a Henschel mixer or a super mixer having a high-speed rotor or a NOW having a low-speed rotor. And dry-mixed. Next, the mixture is melt-mixed using a uniaxial co-kneader (for example, Buss Co., Ltd.) or a biaxial kneading extruder, etc.
Pulverize with a pin mill or other impact-type pulverizer, classify it with a vibrating sieve or the like, and collect powder having a specific particle size range to produce a powder coating.

The powder coating obtained in this manner is used by being coated and baked on a substrate by a known electrostatic coating method or a fluid immersion coating method.

[0032]

The present invention will be described with reference to the following examples and comparative examples. In the following Examples and Comparative Examples, unless otherwise specified, "parts"
Indicates "parts by weight". In preparing Table 1 of Example 1～3,5～6 polyester resin composition (A-1~3,5~6), each of polyols in Examples 1-3 and 5-6, stirrer, heating The apparatus, a thermometer, a fractionating apparatus and a stainless steel reactor having an inlet for an inert gas were charged.
The temperature was raised to 160 ° C. with stirring to melt the contents.

Next, dimethyl terephthalate (hereinafter abbreviated as “DMT”) and zinc acetate dihydrate (hereinafter abbreviated as “ZAC”) were charged into the stainless steel reactor, and the temperature at the top of the fractionation apparatus was 66 ° C. While removing the produced methanol out of the system so as not to exceed, the content is gradually reduced to 21.
The temperature was raised to 0 ° C. to carry out a transesterification reaction. After the amount of methanol distilled became 90% or more of the theoretical amount, the content was cooled to 180 ° C. or less, and terephthalic acid (hereinafter abbreviated as “TA”) and di-butyltin oxide (hereinafter abbreviated as “TA”) at the ratios shown in Table 1. (Abbreviated as “DTO”), and gradually remove the condensed water generated by the nitrogen gas stream out of the system so that the temperature at the top of the fractionating device does not exceed 100 ° C.
The esterification reaction was continued at that temperature.

In the course of the reaction, a sample of the reaction product was appropriately taken, and the acid value of the reaction product was determined by using pyridine as a solvent.
Measured by titration with a 10N alcoholic KOH solution. After this value becomes 25 mgKOH / g or less, the content is cooled to 200 ° C or less, and isophthalic acid (hereinafter abbreviated as “IPA”) is added. Then, similarly to the reaction in the second stage, the temperature was gradually raised to 240 ° C. while removing the condensed water generated by the nitrogen gas stream out of the system, and the esterification reaction was continued at that temperature.

During the reaction, a sample of the reactant is appropriately collected, and the acid value of the reactant is determined by the same method as described above.
The softening point was measured by the ring and ball method (JIS K2207). After adjusting these values so as to fall within the predetermined range of the present invention, the content was cooled to 200 ° C., and the curing catalyst shown in Table 1 was added. Polyester resin composition (A-1 to 3,5-
6) was prepared. The obtained polyester resin composition (A
Tables 1 to 3 show composition and characteristic values.

Preparation of Powder Coating (A'-1 to 3,5-6) The above-mentioned polyester resin (A'-1 to 3,5-6) and epoxy resin Epicoat 1003F (Yuka Kasei Co., Ltd.)
Henchel mixer (Mitsui Miike), titanium dioxide Taipaque CR-90 (Ishihara Sangyo Co., Ltd.), pinhole inhibitor benzoin, and flow control agent Polyflow S (Kyoeisha Chemical Co., Ltd.) in the proportions shown in Table 1. Dry Blending, then uniaxial Coneda PL
K-46 (manufactured by Buss Co., Ltd.) performs melt kneading at a screw temperature of 50 ° C. and a barrel temperature of 90 ° C., cools, pulverizes and classifies, collects a 150 mesh sieve, and collects the powder coating material of the present invention ( A'-1 to 3, 5 to 6). Table 1 shows the composition of the obtained powder coatings (A'-1 to 3, 5 to 6).

Example 4 Preparation of Polyester Resin Composition (A-4) Adipic acid (hereinafter abbreviated as “ADA”) instead of IPA
Was performed in the same manner as in Example 1 to obtain a polyester resin composition (A-4) of the present invention. Table 1 shows the composition and characteristic values of the obtained polyester resin composition (A-4).

Preparation of Powder Coating (A'-4) The powder of the present invention was prepared in the same manner as in Example 1 except that the polyester resin composition (A-4) was used in the mixing ratio shown in Table 1. A paint (A'-4) was obtained. Table 1 shows the composition of the obtained powder coating material (A'-4).

Examples 7-8 Preparation of polyester resin composition (A-7-8) Trimellitic anhydride (hereinafter referred to as "T
MA "), and carried out in the same manner as in Example 1 in accordance with Table 1 to obtain a polyester resin composition of the present invention (A-6 to A-6).
7) was obtained. The obtained polyester resin composition (A-
Table 1 shows the composition and characteristic values of 4).

Preparation of Powder Coatings (A'-7 to 8) Using the polyester resin composition (A'-6, 7), Table 1
The powder coatings (A'-6 to 7) of the present invention were obtained in the same manner as in Example 1 except that they were blended at the blending ratios shown in Table 1. Table 1 shows the composition of the obtained powder coating material (A'-6 to 7).

Examples 9 to 10 Preparation of Polyester Resins (A-9 to 10) In Table 1, the polyols shown in Examples 9 to 10 were mixed with a stirring device, a heating device, a thermometer, an inert gas inlet, The reactor was charged into a stainless steel pressure-resistant reactor having a reservoir and a distillate storage tank connected to the reservoir, and the temperature was raised to 160 ° C. while stirring to melt the contents.

Next, the stainless steel pressure-resistant reactor was put on the table.
The reactor was charged with a half amount of TA and DTO in 1
Is sealed as a unit, and pressurized nitrogen gas is introduced to introduce 2 kg /
cm ^TwoPressurized. As the temperature inside the reactor rises,
The pressure in the reactor also increases, but when it reaches 240 ° C
Pressure is 3.5kg / cm^TwoPressurized nitrogen gas so that
The pressure in the reactor was adjusted during the introduction. Fractionation device top
Temperature and pressure in the reactor so that the temperature of
Adjust the power and transfer the condensed water to the distillate storage tank.
While accumulating, the esterification reaction was continued at that temperature. Warm
1.5 hours after the temperature reaches 240 ° C,
When the output exceeds 90% of the logical value, the cooling is performed.
When the temperature reached ° C, the system pressure was released.

Next, the remaining TA was charged into the stainless steel pressure-resistant reactor, and the condensed water produced was reacted with a nitrogen gas stream at a normal pressure so that the temperature at the top of the distillation apparatus did not exceed 100 ° C. While removing the contents outside the system, the content was gradually heated to 240 ° C., and the esterification reaction was continued at that temperature.

In the course of the reaction, a sample of the reaction product was appropriately collected, and the acid value of the reaction product was measured by using pyridine as a solvent.
Measured by titration with a 10N alcoholic KOH solution. After this value becomes 25 mgKOH / g or less, the content is cooled to 200 ° C. or less, IP is further added, and the Similarly, while removing the condensed water generated by the nitrogen gas stream out of the system, the temperature was gradually raised to 240 ° C., and the esterification reaction was continued at that temperature.

During the reaction, a sample of the reactant is appropriately collected, and the acid value and softening point of the reactant are measured by the same method as in Example 1, so that these values fall within the predetermined ranges of the present invention. After the content was adjusted to 200 ° C., the content was cooled to 200 ° C., the curing catalyst shown in Table 1 was added, and the mixture was stirred for 60 minutes to sufficiently disperse the polyester resin composition of the present invention (A
-9 to 10). Table 1 shows the composition and characteristic values of the obtained polyester resin compositions (A-9 to 10).

Preparation of Powder Coating (A'-9-10) Using the polyester resin composition (A-9-10), Table 1
The powder coatings (A'-9 to 10) of the present invention were obtained in the same manner as in Example 1 except that they were blended at the blending ratios shown in Table 1. Table 1 shows the composition of the obtained powder coating materials (A'-9 to 10).

Comparative Examples 1 to 4 Preparation of Polyester Resin Composition (B-1 to 4) In preparing the polyester resin composition, the preparation was carried out in accordance with Example 1 according to Table 1, and the polyester resin composition (B1 to 4) I got The obtained polyester resin (B-
Table 1 shows the compositions and characteristic values of 1) to 4).

Preparation of Powder Coatings (B'-1 to 4) Powder coatings (B'-1 to 4) were prepared in the same manner as in Example 1 except that the polyester resin compositions (B1 to 4) were mixed in the mixing ratio shown in Table 1. Paints (B'-1 to 4) were obtained. Table 1 shows the compositions and characteristic values of the obtained powder coating materials (B'-1 to 4).

[0049]

[Table 1]

Test Example Each of the powder coatings obtained in Examples 1 to 10 and Comparative Examples 1 to 4 was coated on a zinc phosphate mild steel sheet so as to have a thickness of 40 to 60 μm. Baking was performed at 160 ° C. for 20 minutes in a heating furnace to obtain a cured coating film. The following properties were examined for each of the coating films thus obtained.

The 60 ° gloss was obtained by specular reflection at 60 ° using a gloss meter (VGS-300, manufactured by Nippon Denshoku Industries Co., Ltd.), and the smoothness was determined by Yupica coat GV-230 (Yupika Japan Co., Ltd.).
Exelin is an exelin tester (made by excelin tester). The steel ball was extruded at a speed of 0.1 mm / sec by using Tayu Kiki Co., Ltd., and the extrusion just before cracking or peeling was observed was measured at a distance.
The coated plate was baked at 160 ° C. for 20 minutes and baked at 200 ° C. for 20 minutes, and evaluated by the color difference measured by a color difference meter (Z-300A, manufactured by Nippon Denshoku Industries Co., Ltd.). Table 2 shows the results.

[0052]

[Table 2]

From Table 2, it can be seen that the cured coating film of the powder coating of the present invention obtained from the polyester resin composition for a powder coating of the present invention was compared with that obtained in the comparative example, and The effect was confirmed.

[0054]

The powder coating of the present invention obtained by using the polyester resin composition for powder coating of the present invention comprises:
It is possible to give a coating film that has a low degree of coloring at high temperatures, has excellent coloring during polyester resin production and yellowing resistance during baking of the coating film, has good thermal stability, and has excellent smoothness and mechanical properties. it can.

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Claims (5)

[Claims] 1. A polyester resin of the general formula R'R ₃ P ⁺ X ^- (wherein, R represents a phenyl group or a butyl group, R 'is C ₁ -C
₍₄₎ an alkyl group, a phenyl group or a benzyl group, and X represents a halogen). 2. The polyester resin composition according to claim 1, wherein the organic phosphine halogen compound is contained in a ratio of 0.1 to 5 parts by weight based on 100 parts by weight of the polyester resin. 3. The polyester resin has a carboxyl group at a main terminal group and an acid value of 20 to 100 mgKOH /
g. The polyester resin composition for powder coating according to claim 1 or 2, wherein the softening point is 90 to 140C. 4. A powder coating comprising the polyester resin composition for powder coating according to claim 1. 5. The powder coating according to claim 4, further comprising an epoxy resin.