JPH1121474A - Powdered paint composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder paint composition that has cold setting properties, excellent thermal stability, develops reduced discoloration on the resin production and high-temperature baking and gives good smoothness and mechanical characteristics. SOLUTION: This composition contains an acid-terminated polyester resin, epoxy resin, triphenylphosphine and/or triallyl phosphite bearing one or more meta- or para-substituents and polycarboxylic acid and/or its anhydride. The content of the triphenyl phosphine and/or triaryl phosphine bearing one or more m- or p-substituents is 0.1-5 pts.wt. per 100 pts.wt. of the acid-terminated polyester resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating composition, and more particularly to a powder coating composition which has a low degree of coloring at high temperature baking and can be cured at a low temperature in a short time.

[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 thermosetting powder coating has a high temperature,
Since long-time baking is required, a method such as addition of a curing catalyst has been used to enable low-temperature baking to reduce energy costs. Conventionally, triphenylphosphine, imidazoline, imidazole, and the like used as such a curing catalyst have poor thermal stability and have a problem that they exhibit considerable coloring when baking after coating.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide low-temperature curability, excellent thermal stability, low coloring even at high-temperature baking, good smoothness, and low mechanical properties. An object of the present invention is to provide an excellent powder coating composition.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that, when a powder coating composition comprising an acid-terminated polyester resin and an epoxy resin is cured, triphenylphosphine and / or a meta- or para-position resin is cured. When the triarylphosphine having a substituent in any one or more thereof is used as a curing catalyst, the above problem can be solved by coexisting at least one selected from polycarboxylic acids and / or anhydrides thereof. Heading, the present invention has been reached.

The powder coating composition of the present invention comprises an acid-terminated polyester resin, an epoxy resin, triphenylphosphine and / or a triarylphosphine having a substituent at one or more meta or para position, and a polycarboxylic acid. And / or an anhydride thereof.

[0007] Preferably, in the powder coating composition, triphenylphosphine and / or triarylphosphine having a substituent at one or more of meta or para positions is added to 100 parts by weight of the acid-terminated polyester resin. 0.1 to 5 parts by weight.

More preferably, in the powder coating composition, the polycarboxylic acid and / or polycarboxylic anhydride is triphenylphosphine and / or triphenylphosphine having a substituent at one or more meta or para position. The total amount of the polyester resin and the acid value of the polycarboxylic acid and / or its anhydride is 20 to 120 mg, which is contained at a ratio of 3 to 400 mol per 1 mol of the phosphorus atom in the reel phosphine.
KOH /.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The curing catalyst used in the present invention is triphenylphosphine and / or triarylphosphine having a substituent at one or more meta or rose positions. Specifically, tris-3-methoxyphenylphosphine, tris-4-methoxyphenylphosphine,
Trimethatoryl phosphine, triparatolyl phosphine and the like are used.

The amount of the curing catalyst is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the polyester resin. If the amount is less than 0.1 part by weight, sufficient curability cannot be obtained, and if the amount is more than 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
~ 2 parts by weight.

The acid-terminated polyester resin used in the present invention preferably has a main terminal group as a carboxyl group. The proportion of carboxyl groups in all terminal groups is 60
% Is preferable, and if it is less than 60%, it is not preferable because when the powder coating material is used, the mechanical strength is lowered due to a decrease in crosslink density. 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 softening point of the polyester resin is measured by the 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 used in 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,
Examples thereof include 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic anhydride, fumaric acid, maleic anhydride, and trimellitic anhydride, and as one or a mixture of two or more of these. Used.

As the polyhydric alcohol component used in 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, 1,6-hexanediol, 2,5-hexanediol, ester Diol 2
04 (union carbide product), 1,4-cyclooxane dimethanol, hydrogenated bisphenol A, and the like, and these can be used alone or as a mixture of two or more.

[0015] The branching agent can obtain sufficient performance without particularly using it, but can also 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.

As the epoxy compound used in the present invention, a commonly used epoxy compound such as a bisphenol type epoxy resin, a hydrogenated bisphenol type epoxy resin, an alicyclic epoxy resin compound, and triglycidyl isocyanurate can be used.

The ratio of the epoxy compound equivalent number B of the epoxy compound to the acid equivalent number A of the polyester resin (ratio of epoxy group to acid) is 0.9 to 1.5. Is preferable from the viewpoint of stably realizing excellent coating film performance.

As the polycarboxylic acid and its anhydride used in the present invention, aromatic, aliphatic and / or alicyclic polybasic acids and their derivatives can be used. Specific examples thereof include isophthalic acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, hexahydrophthalic anhydride, (phthalic anhydride), and trimellitic acid (anhydride). Used as a mixture of two or more.

The polycarboxylic acid and its anhydride are used in an amount of 3 to 400 mol per 1 mol of phosphorus atoms in triphenylphosphine and / or triarylphosphine having a substituent at one or more meta or para position. Included in percentage.

In order to obtain a coating film having a good balance between smoothness and mechanical strength, the total of the acid value of the polyester resin and the acid value of the polycarboxylic acid is 20 to 120 mg.
It needs to be in the range of KOH / g. If it is less than 3 moles, sufficient anti-yellowing effect cannot be obtained during baking, and if it is more than 400 moles, the acid value is 120 mgK.
Since it is higher than OH / g, the smoothness is lowered, and the epoxy resin is crosslinked with a low molecular weight polycarboxylic acid, and the mechanical strength is lowered, which is not preferable.

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 an acid component, or a carboxylic acid anhydride, for example, maleic anhydride, an anhydride of a polyester resin which has been polycondensed under an excess of a hydroxyl group and has been terminated with a hydroxyl group. It can also be prepared by the addition reaction of trimellitic acid or the like. As a method of accelerating the reaction,
There is a method of increasing the reaction temperature while preventing the dissipation loss by increasing the boiling point of the polyol by applying pressure, a method of applying a reduced pressure operation, or a method of accelerating the reaction by passing an inert gas.

Specifically, in the direct esterification method by pressurization, the whole 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.

Further, industrially, the direct esterification method is usually used. However, 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.

To the polyester resin thus produced, a predetermined amount of triphenylphosphine as a curing catalyst and / or a triarylphosphine having a substituent at one or more meta or para position and a polycarboxylic acid An acid and / or an anhydride thereof are added, and the mixture is stirred and sufficiently dispersed. The polyester resin may have a branched structure or a linear structure.

The powder coating composition of the present invention comprises triphenylphosphine and / or triarylphosphine having a substituent at one or more meta or para position and polycarboxylic acid and / or an anhydride thereof. The powder coating composition of the present invention can be obtained by blending the above-mentioned polyester resin and epoxy compound, and the blending ratio is a ratio of the epoxy group equivalent number B of the epoxy compound to the acid equivalent number A of the polyester resin. It is preferable that the (functional group ratio of the epoxy group to the acid) be in the range of 0.8 to 1.5 from the viewpoint of stably realizing excellent coating performance.

The powder coating composition 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 powder coating composition to which a flow regulator, a pinhole inhibitor and the like are added can also be used.

Further, titanium dioxide and carbon black are used as pigments, calcium carbonate and barium sulfate are used as fillers, and Acronal 4F is used as a flow regulator.
(BASF), polyflow S (Kyoeisha Chemical Co., Ltd.), etc., and a low molecular weight acrylic polymer, and benzoin or the like is used as a pinhole inhibitor.

In producing the powder coating composition, for example, these fillers and additives are combined with triphenylphosphine and / or triarylphosphine having a substituent at one or more meta or para position. The polyester resin composition and the epoxy compound to which the polycarboxylic acid and / or its anhydride are added in advance are put into a Henschel mixer or a super mixer having a high-speed rotor or a Nauta mixer having a low-speed rotor, and are dry-dried. Mix. Then, melt and mix using a single-screw kneader (for example, Buss Co.) or a twin-screw kneading extruder, pulverize with a hammer mill, pin mill or other impact-type pulverizer, classify with a vibration sieve, etc., and specify Are collected to produce a powder coating composition.

The powder coating composition thus obtained is used by being coated and baked on an object to be coated by a known electrostatic coating method or fluid immersion coating method.

Instead of the above preparation method, triphenylphosphine and / or triarylphosphine having a substituent at one or more meta or para position and polycarboxylic acid and / or anhydride thereof are previously melted in a polyester resin. Instead of mixing, they can be mixed in a rough mixing step in preparing the powder coating composition.

[0033]

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". Examples 1,4,6-12 Preparation of polyester resin composition (A-1,4,6-12)
Among Ltd. Table 1, were charged each polyol in Examples 1, 4 and 6 to 12, stirrer, heater, thermometer, a stainless steel reactor having an inlet fractionator and inert gas, stirring While the temperature was raised to 160 ° C., the contents were melted.

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 fractionator 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 collected, and the acid value of the reaction product was determined by using 1 /
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.

In the course of the reaction, a sample of the reactant is appropriately collected, and the acid value of the reactant is determined in the same manner as described above.
The softening point was measured by the ring and ball method (JIS K2207). After adjusting these values to fall within the predetermined range of the present invention, the content is cooled to 180 ° C., and a curing catalyst,
By adding polycarboxylic acid and / or its anhydride,
After stirring for minutes, the mixture was sufficiently dispersed to prepare a polyester resin composition (A-1, 4, 6 to 12). Table 1 shows the composition and characteristic values of the obtained polyester resin composition (A-1, 4, 6 to 12).

Powder coating composition (A'-1,4,6-1)
2) Preparation of the above polyester resin (A-1,4,6 to 12), epoxy resin Epicoat 1003F (Yuka Kasei Co., Ltd.)
Henchel Mixer (Mitsui Miike), Titanium Dioxide Taipaque CR-90 (manufactured by Ishihara Sangyo Co., Ltd.), pinhole inhibitor benzoin, and flow control agent Polyflow S (manufactured by Kyoeisha Chemical Co., Ltd.) in the proportions shown in Table 2. Dry blend) and then uniaxial co-kneader P
LK-46 (manufactured by Buss Company) with a screw temperature of 50 ° C.
The mixture was melt-kneaded at a barrel temperature of 90 ° C., cooled, pulverized and classified, and the amount passed through a 150-mesh sieve was collected to obtain a powder coating (A′-1,4,6 to 12) of the present invention. Table 2 shows the composition of the obtained powder coating composition (A'-1,4,6 to 12).

Example 2 Preparation of Polyester Resin Composition (A-2) Instead of IPA, adipic acid (hereinafter abbreviated as “ADA”)
And in the same manner as in Example 1 according to Table 1 to obtain a polyester resin composition (A-2). Table 1 shows the composition and characteristic values of the obtained polyester resin composition (A-2).

Preparation of Powder Coating Composition (A'-2) Powder coating composition (A'-2) was prepared in the same manner as in Example 1 except that the polyester resin composition (A-2) was blended in the mixing ratio shown in Table 2. A composition (A′-2) was obtained. Table 2 shows the composition of the obtained powder coating composition (A'-4).

Example 3 Preparation of Polyester Resin Composition (A-3) Trimellitic anhydride (hereinafter referred to as "T
MA "), and carried out in the same manner as in Example 1 according to Table 1 to obtain a polyester resin composition (A-3).
Table 1 shows the composition and characteristic values of the obtained polyester resin composition (A-4).

Preparation of Powder Coating Composition (A'-3) The powder was prepared in the same manner as in Example 1 except that the polyester resin composition (A'-3) was used in the mixing ratio shown in Table 2. A coating composition (A'-3) was obtained. Table 2 shows the composition of the obtained powder coating composition (A'-3).

Example 5 Preparation of Polyester Resin (A-5) In Table 1, the polyol shown in Example 5 was mixed with a stirring device, a heating device, a thermometer, an inlet for an inert gas, a fractionating device and connected thereto. The mixture was charged into a stainless steel pressure-resistant reactor having a storage tank for distillate, 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 is charged into this stainless steel pressure-resistant reactor, and the condensed water produced is reacted with a nitrogen gas stream at normal pressure so that the temperature at the top of the distillation apparatus does 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 determined 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., a curing catalyst was added, and the mixture was stirred for 60 minutes and sufficiently dispersed to obtain a polyester resin composition (A-5). Table 1 shows the composition and characteristic values of the obtained polyester resin composition (A-5).

Preparation of Powder Coating Composition (A'-5) The same procedure as in Example 1 was carried out except that the polyester resin composition (A-5) was used in the mixing ratio shown in Table 2. A powder coating composition (A'-5) was obtained. Table 2 shows the composition of the obtained powder coating composition (A'-5).

Examples 13 and 14 Preparation of polyester resin (A-13, A-14) The polyester resin composition (A-13, A-14) was prepared in the same manner as in Example 5 in accordance with Table 1 without using a curing catalyst. 1
4) was obtained. The obtained polyester resin composition (A-1)
Table 1 shows the composition and characteristic values of (3, A-14).

Powder coating composition (A'-13, A'-1)
Preparation of 4) Polyester resin (A-13, A-14), epoxy resin epicoat 1003F (manufactured by Yuka Shell Co., Ltd.), curing catalyst, trimellitic acid, pinhole inhibitor benzoin, flow regulator Polyflow S (Kyoeisha) Chemical Co., Ltd.)
Was charged into a Henschel mixer (manufactured by Mitsui Miike Seisakusho) at the blending amounts shown in Table 2 and dry blended. The mixture was melt-kneaded, cooled, pulverized and classified, and a 150 mesh sieve was collected to obtain a powder coating composition of the present invention. Table 2 shows the composition of the obtained powder coating composition (A'-13, A'-14).
Shown in

Comparative Examples 1 to 3 Preparation of Polyester Resin Composition (B-1 to 3) In preparing the polyester resin composition, the preparation was carried out in accordance with Example 1 in accordance with Table 1, and the polyester resin composition (B1 to 3) I got Table 1 shows the compositions and characteristic values of the obtained polyester resin compositions (B-1 to 3).

Preparation of Powder Coating Compositions (B'-1 to 3) The procedure was the same as in Example 1 except that the polyester resin compositions (B1 to 3) were used in the mixing ratio shown in Table 2. Powder coating compositions (B'-1 to 3) were obtained. Table 2 shows the compositions of the obtained powder coating compositions (B'-1 to 3).

Comparative Example 4 Preparation of Polyester Resin Composition (B-4) The preparation of the polyester resin composition was carried out in accordance with Example 3 in accordance with Table 1 to obtain a polyester resin composition (B-4). Table 1 shows the composition and characteristic values of the obtained polyester resin composition (B-4).

Preparation of Powder Coating Composition (B′-4) Powder coating composition (B′-4) was prepared in the same manner as in Example 3 except that the polyester resin (B-4) was mixed at the mixing ratio shown in Table 2. A product (B′-4) was obtained. Table 2 shows the composition of the obtained powder coating composition (B'-4).

Comparative Example 5 Preparation of Polyester Resin Composition (B-5) A polyester resin composition was prepared in the same manner as in Example 13 in accordance with Table 1 to obtain a polyester resin composition (B-5). Table 1 shows the composition and characteristic values of the obtained polyester resin composition (B-5).

Preparation of Powder Coating Composition (B'-5) The procedure of Example 13 was repeated in accordance with Table 2 except that trimellitic acid was not used.
5) was obtained. Table 2 shows the composition of the obtained powder coating composition (B'-5).

[0056]

[Table 1]

[0057]

[Table 2]

Test Example Each of the powder coating compositions obtained in Examples 1 to 14 and Comparative Examples 1 to 5 was applied to a zinc phosphate mild steel sheet so as to have a thickness of 40 to 60 μm. The composition was applied with an electrostatic coating machine and baked in a hot-air heating furnace at 160 ° C. for 20 minutes to obtain a cured coating film. The following properties were examined for each of the coating films thus obtained.

The 60 ° gloss was measured by a 60-degree specular reflection by a gloss meter (VGS-300, manufactured by Nippon Denshoku Industries Co., Ltd.), the smoothness was evaluated by visual comparison, and the adhesion was measured with a cutter at 1 mm intervals. Exelin was prepared by using an exelin tester (manufactured by Taiyu Kiki Co., Ltd.) at a rate of 0.1 mm.
The steel ball was extruded at a speed of / sec, and the extrusion immediately before cracking or peeling was observed was measured at a distance.
A color difference meter (Z-300A, Nippon Denshoku Industries Co., Ltd.) of the coated plate which was baked for 20 minutes and baked at 200 ° C. for 20 minutes.
By the color difference measured according to the formula (1). Table 3 shows the results.

[0060]

[Table 3]

From Table 3, the cured coating film of the powder coating composition of the present invention was able to confirm the effects of the present invention described later as compared with those obtained in Comparative Examples.

[0062]

The powder coating composition of the present invention has a low degree of coloring at high temperatures, has excellent yellowing resistance during baking of a coating film, has good thermal stability, and has excellent smoothness and mechanical properties. A coating can be applied.

Claims (3)

[Claims] 1. An acid-terminated polyester resin, an epoxy resin, triphenylphosphine and / or a triarylphosphine having a substituent at one or more meta or para positions, and a polycarboxylic acid and / or an anhydride thereof. A powder coating composition comprising: 2. An acid-terminated polyester resin comprising triphenylphosphine and / or triarylphosphine having a substituent at one or more meta or para positions.
The powder coating composition according to claim 1, which is contained in an amount of 0.1 to 5 parts by weight based on 00 parts by weight. 3. The polycarboxylic acid and / or anhydride thereof is used in an amount of 3 to 1 mol of phosphorus atoms in triphenylphosphine and / or triarylphosphine having a substituent at one or more meta or para positions. And the total acid value of the polyester resin and the polycarboxylic acid and / or anhydride thereof is 20 to 120 m.
The powder coating composition according to claim 1, wherein the ratio is gKOH /.