JPS585946B2 - Netsukokaseifuntaiyoujiyushisoseibutsu - Google Patents

Description

[Detailed description of the invention] The present invention relates to a resin composition for thermosetting powder coatings.

In general, resin compositions for powder coating are solid at room temperature, are brittle and can be easily powdered, and have free flowability as powder without causing blocking at temperatures below 50°C. having a temperature of 130℃
When baking the above coating film, it is necessary to have the resin melt flow and appropriate gelation time necessary to form a coating film with a smooth surface, and premature crosslinking may occur at a flow temperature of around 100°C. It is required to be able to be kneaded with auxiliary agents such as pigments, spreading agents, and antistatic agents without any problems, and to have sufficient crosslinking density after baking.

It is clear that in order to satisfy such a wide range of requirements, the selection of the crosslinking agent as well as the properties of the base resin are important factors.

Epoxy resins are conventionally known as resins for powder coatings, but they lack weather resistance in applications that are exposed to the outdoors for long periods of time.

Also, acrylic resins using etherified melamine having 1 to 4 carbon atoms as a crosslinking agent are well known as resins with excellent weather resistance, but they suffer from blocking as the temperature rises in summer, resulting in insufficient storage stability. .

It has good storage stability without the above drawbacks, and the baked cured coating has high gloss without yellowing or other discoloration. It also exhibits good mechanical properties and is resistant to long-term weathering. A resin composition for powder coatings which has particularly good weather resistance has been filed as Japanese Patent Application No. 120358/1982, but the present invention further provides a resin composition for powder coatings which has particularly excellent adhesion and corrosion resistance. A resin composition is provided.

That is, the present invention is directed to: K A hydroxyl group-containing polyester resin having a softening point of 50 to 180°C and mainly based on aromatic polycarboxylic acid.

(B) at least one of an N-acyl polylactam compound and an N-acyl polyimide compound; and (C) an epoxy resin; Component (C) is added in an amount of 1 to 1 based on the total amount of components (A), (B), and (C) so that the group is 0.5 to 1.5 equivalents.
This invention relates to a thermosetting powder coating resin composition obtained by blending 5% by weight.

The hydroxyl group-containing polyester resin which is component (A) in the present invention has a softening point in the range of 50 to 180°C, and mainly uses an aromatic polycarboxylic acid as the polycarboxylic acid component.

Aromatic polycarboxylic acid is used in the carboxylic acid component in an amount of 80 to 10 to obtain a resin having the necessary glass transition point as a powder.
0 mol% used.

Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, dimethylterentalic acid, diethyltellentalic acid, trimellitic acid, pyromellitic acid, diphenolic acid, 2,2-bis-(4-carpoxy phenyl)
- Propane, etc., and their acid anhydrides, esters, etc. are used.

Other carboxylic acid components include alicyclic polycarboxylic acids such as methylcyclohexenetricarboxylic acid, tetrahydrophthalic acid, and hexahydrophthalic acid, heterocyclic polycarboxylic acids such as tris(2-carboxyethyl)in cyanurate, and malon. Aliphatic polycarboxylic acids such as acid succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dimer acid, etc., and their acid anhydrides, esters, etc. are used in less than 20 mol% of the carboxylic acid component. As the alcohol component to be polycondensed with a polycarboxylic acid to produce a hydroxyl group-containing polyester resin, it is preferable to mainly use a dihydric alcohol.

The dihydric or higher alcohol component can be used in part for the effect of imparting mechanical strength to the substantially linear polyester resin.

Suitable polyalcohols include ethylene glycol, propylene glycol, butylene gelylcol, n-hexylene glycol, neopentyl glycol, heptanediol, octadecanediol, cyethylene glycol, triethylene glycol, glycerin, trimethylolethane trimethylol. Propane, pentaerythritol, 1,4-cyclohexanediol, trisu2
-Hydroxyethyl isocyanurate and the like.

These can be used alone or as a mixture.

In order to produce the hydroxyl group-containing polyester resin (component (3)) by condensation polymerization of the above-mentioned polycarboxylic acid and polyalcohol, the reaction system is The materials are blended in proportions such that the alcohol has 1 to 2, preferably 1.02 to 1.5 equivalents of hydroxyl groups.

A normal condensation polymerization method is applied as a method for producing such a polyester resin.

For example, the reaction is carried out at a temperature of about 170 to 190° C. while blowing an inert gas, such as nitrogen gas, in the equivalent ratio of acid and alcohol to produce the polyester resin of the present invention as follows.

A large amount of water produced as a by-product in the reaction system is quickly distilled out of the system.

After several hours have elapsed from the start of the reaction, the temperature is raised to about 230-250°C and the reaction is continued.

The reaction is completed in about 15 hours.

The use of conventional polyesterification catalysts is effective to accelerate the reaction.

For example, metal acetates such as lead acetate, 0.01-0.2% by weight of umbrella alkoxides such as tetrabutyl titanate, and 0.01-1.0% by weight of oxides such as antimony dibutyltin oxide. Use.

Further, when a lower alkyl ester of an aromatic dihydric carbonic acid (for example, dimethyl terephthalate) is used as the acid component, the condensation reaction proceeds by transesterification.

The reaction is carried out at approximately 190 mL while blowing an inert gas such as nitrogen gas.
The reaction starts at a temperature of 0.degree. C., and a large amount of methanol produced as a by-product in the reaction system is quickly distilled out of the system.

Several hours after the start of the reaction, the temperature was increased to approximately 230-250°C.
and continue the reaction.

The reaction is completed in about 10 hours.

In order to promote the reaction, 0.01 to 0.2% by weight of metal acetate, metal alkoxide, and 0.0% of a catalyst such as an oxide are added.
It is effective to add 01 to 0.5% by weight.

The produced polyester resin as it is contains excessive alcohol, which lowers the softening point of the resin and may cause blocking during long-term storage as a powdered resin.

In such a case, it is possible to avoid the problem by distilling off the excess alcohol from the molten polyester resin under reduced pressure, or by pouring it into water or other liquid.

The N-acyl polylactam compound or N-acyl polyimide compound which is component (B) in the present invention is represented by the following general formula.

Here, R' is a divalent aliphatic hydrocarbon residue having 1 to 11 carbon atoms, preferably 3 to 8 carbon atoms, or 6 to 10 carbon atoms.
carbon atoms.

represents one or more optionally substituted divalent aromatic hydrocarbon residues, preferably one or more benzene residues; X1 and X2 are hydrogen atoms or 1 to 5 hydrogen atoms; It represents a monovalent aliphatic hydrocarbon residue having a carbon atom, and X1 and X2 may be the same or different.

n represents an integer from 2 to 4.

R has 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms, optionally interrupted or branched by 1 to 2 nitrogen atoms or 1 to 2 oxygen atoms, optionally partially unsaturated or has 6 to 10 carbon atoms.

one or more optionally substituted di- to tetravalent aromatic hydrocarbon residues, preferably 11 benzene residues, or 2 with 4 to 12, preferably 5 to 9 carbon atoms; Represents a valent or trivalent complex residue.

An example of a preferred N-acyl polylactam compound or N-acyl polyimide compound is terephthaloyl bis(N
- caprolactam), isophthaloyl bis(N-caprolactam), adipoyl bis(N-caprolactam),
Examples include adipoyl bis(N-succinimide) and isophthaloyl bis(N-succinimide).

The above crosslinking agent is synthesized by a dehydrochloric acid reaction between an acid chloride compound of a polybasic acid and a lactam compound or an imide compound, and in some cases an alkali metal salt thereof, and in some cases a desalination reaction.

As the epoxy resin which is component (C) in the present invention, a solid body having a melting point at least at room temperature or higher is mainly used.

Such epoxy resins include reaction products of bisphenol and epihalohydrin, such as Epicote 10.
01, bisphenol type epoxy resins such as Epicote 1004, Epicote 1007, and Epicote 1009 (all trade names of Shell Chemical Company), reaction products of hydrogenated bisphenol and epihalohydrin, such as EPS
Examples include alicyclic epoxy resins such as -4085 (Asahi Denka Kogyo ■ trade name) and Chissonox 313, 301 (both Chitsuso ■ trade names).

Components (A), (B) and (C) in the present invention are blended as follows.

(A) component and (B) component are the hydroxyl groups of component (A) 1
When a lactam group or an imide group or both are present, they are blended so that the total amount is 0.5 to 1.5 equivalents, preferably 0.8 to 1.2 equivalents.

When the amount is less than 0.5 equivalent, the crosslinking density of the resulting coating film decreases, and sufficient mechanical properties cannot be expected.

Moreover, if the amount exceeds 1.5 equivalents, unreacted curing agent remains in the coating film, resulting in a decrease in performance such as chemical resistance.

Component (C) is used in the resin composition for powder coating in an amount of 1 to 15% by weight, preferably 2 to 10% by weight.

If it is less than 1% by weight, the adhesion and corrosion resistance will be improved by addition, but if it exceeds 15% by weight, the blocking resistance and weather resistance of the resin composition for powder coatings will be deteriorated, which is not preferable.

The powder coating resin composition blended in this way is heated to 50°C.
There is no blocking at the following temperatures, and as the temperature rises, the reaction occurs rapidly, so the curing reaction occurs after the coated surface is completely melted, giving a good coated surface appearance and no discoloration such as yellowing.

A catalyst, a pigment, a filler, a fluidity regulator, etc. can be further added as appropriate to the resin composition according to the present invention.

As a catalyst, p-toluenesulfonic acid, naphthalene-
Sulfonic acids such as 1,5-disulfonic acid, tetraalkylammonium salts such as tetrabutylammonium bromide, tetrabutylammonium chloride, and tetrabutylammonium iodide, zinc nanthenate, cobalt naphthenate, dibutyltin dilaurate, lithium benzoate Metal end of carboxylic acids such as lithium hydroxide, alkali metal hydroxides such as lithium chloride, metal salts, tin halide compounds such as stannous chloride, dimethyltin chloride, dibutyltin chloride, dimethylaniline hydrochloride, semihydrochloride, etc. Examples include amine hydrochlorides such as chloride, monoethylamine complexes of boron trifluoride, boron fluoride complexes such as p-nitrobenzenediazonium fluoroborate, alcoholates of titanium, vanadium, zirconium, etc., and polymers thereof.

Examples of pigments include titanium dioxide, red iron oxide, and carbon black.

Examples of fillers include calcium carbonate, calcium sulfate, barium sulfate, and the like.

Examples of flow regulators include Modaflow (trade name of Mon-Into Chemical Co., Ltd.), Erosil (trade name of Tegusa Co., Ltd.), Acronal 4F (trade name of Bazuf Co., Ltd.), and the like.

When preparing a powder coating, the resin composition according to the present invention is melt-kneaded together with other components, and then pulverized and classified.

As a coating method, an electrostatic coating method, a fluidized dipping method, an electrostatic dynamic dipping method, etc. are used, and baking is performed at 130 to 220°C, preferably 140 to 220°C, for 5 to 30 minutes, preferably 10 to 2
The questions will be asked for 0 minutes.

Next, a synthesis example of component (4) of the resin composition according to the present invention will be shown.

Synthesis Example 1 Terephthalic acid 788.5g (4.75 mol), adipic acid 36.5g (0.25 mol), neopentyl glycol 353.6g (3.4 mol), 1,4-butanediol 76.5g ( 0.85 mol), 160.8 g (1.2 mol) of trimethylolpropane, and 8.61 g of dibutyltin oxide were heated to about 190°C, and the temperature was gradually increased while removing the water produced from the system. The reaction was allowed to proceed for 15 hours.

The temperature at the end of the reaction was 230°C.

The produced polyester resin was poured out into a tin plate, cooled, and then ground to an appropriate size.

The softening point of this polyester is 75-80°C. (KOHmg/g).

Synthesis Example 2 970 g (5.0 mol) of dimethyl terephthalate, 416 g (4.0 mol) of neopentyl glycol, 201 g (1.5 mol) of trimethylolpropane and 0.952 g of tetrabutyl titanate were mixed at about 180°C for 5 mols. The mixture was heated for a period of time, and the generated methanol was removed from the system.

Furthermore, in order to complete the transesterification reaction, the temperature was raised to 230°C, and this temperature was maintained for 10 hours to complete the reaction.

After the reaction was completed, the molten resin was poured into a tin plate, cooled, and pulverized to an appropriate size.

This polyester resin had a softening point of 76 to 81°C and a hydroxyl value of 100 (KOHmg/g).

Synthesis Example 3 Terephthalic acid 1.6 mol (265.6 g), adipic acid 0.4 mol (64.0 g) neopentyl glycol 1.
0 mol (104.0 g), 1,4-butanediol 1.
0 mol (90.0 g), trimethylolpropane 0.2
Mol (26.8 g) and 3.3 g of dibutyltin oxide were heated to about 190° C., and the temperature was gradually raised while removing the produced water from the system, and the reaction was carried out for 10 hours.

The temperature after the completion of the reaction was about 230°C.

The produced polyester resin was poured out into a tin plate, cooled, and then ground to an appropriate size.

This polyester resin has a softening point of 68 to 79°C, a hydroxyl value of 60 (KOHmg/g), and an acid value of 6 (KOHmg/g).
g).

Synthesis Example 4 Terephthalic acid 830g (5 mol), neopentyl glycol 442g (42.5 mol), glycerin 110.4
g (1.20 mol), dibutyltin oxide 6.9 g
(0.5% by weight based on the reactants) is heated to 180-190°C for 6 hours, and the water produced is removed from the system.

The temperature was further increased to 210-220°C, and heating was continued for 5 hours to complete the reaction.

The resin thus obtained is pale yellow and transparent, has a softening point of 74 to 81°C, and a hydroxyl value of 100 (KOHmg/
g), acid value 5.8 (KOHmg/g), reduced viscosity 0.1
6 dl/g (0.5 g resin/dl chloroform, 30°C
Met.

Next, a synthesis example of component (B) of the present invention will be shown.

Synthesis Example 5 Terephthaloyl chloride 1.
Charge 0 mol (203 g) and dissolve by adding 600 g of toluene.

Separately, 2.1 mol (237.3 g) of ε-caprolactam,
2.1 mol (254.1 g) of dimethylaniline was dissolved in 400 g of toluene, and this solution was added dropwise through the dropping funnel over 30 minutes.

The reaction proceeded exothermically and the temperature rose to about 50°C.

Subsequently, the temperature was raised to 80°C and the reaction was continued for 90 minutes.

The precipitated terephthaloyl bis(N-caprolactam) and dimethylaniline hydrochloride were separated by filtration, the dimethylaniline hydrochloride was washed away with dilute hydrochloric acid and water, and the mixture was dried to obtain terephthaloyl bis(N-caprolactam). Ta.

Yield: 302.6g Melting point: 194-197°C.

This compound has the following structural formula.

Original cumulative analysis result Calculated value C: 67.4%, H: 6.7%, N: 7.9% Actual value C: 67.5%, H: 6.6%, N: 7.8% Synthesis example 6 Into a 1L four-necked flask equipped with a thermometer, nitrogen gas blowing tube, and dropping rod, fill in an appropriate amount of nitrogen gas and add 678 g (6 moles) of dried ε-caprolactam and heat to 85°C to dissolve. urge

Isofucloyl chloride 203 while stirring well.
g (1 mol) is added little by little over 1 hour.

The reaction proceeded exothermically and the temperature rose to 90°C.

Subsequently, the reaction product was kept at 90° C. for 5 hours and then cooled to room temperature to solidify the reaction product.

Take it out and crush it well in a mortar to give 2.000g
Wash several times with water and then filter.

The powdered filtration residue was recrystallized from alcohol.

The structural formula of the obtained crystalline isophthaloyl bis(N-caprolactam) is as follows, the yield at this time was 150 g (theoretical yield 356 g), and the melting point was 138-14
It was 0°C.

Elemental analysis results Calculated values C: 67.4%, H: 6.7%, N: 7.9%O
: 18.0% Actual value C: 67.0%, H: 6.6%, N: 7.1% Synthesis example 7 1 ton with thermometer, nitrogen blowing pipe, dropping funnel, cooling pipe, and stirring rod 678 g (6 mol) of ε-caprolactam dried in a four-round flask with an appropriate amount of nitrogen gas sealed in it.
was heated to 85°C to dissolve it, and 183 g (1 mol) of adipoyl chloride was added dropwise from the dropping funnel over 1 hour while stirring well, generating heat and the temperature rose to 90°C.

Subsequently, the reaction product was kept at 90° C. for 3 hours and then cooled to the lowest temperature to solidify the reaction product.

The material was taken out, ground thoroughly in a mortar, washed several times with 200 g of water, and then filtered.

The powdered filtration residue was recrystallized with alcohol.

The yield of the obtained crystalline adipoyl bis(N-caprolactam) was 250 g (theoretical yield: 336 g), and the melting point was 72-7.
The temperature was 3°C.

The structural formula is shown below.

Calculated values C: 64.3%, H: 8.3%, N: 8.3%
O: 19.1% Actual value C: 64.0%, H: 8.9%, N: 8.3%
Synthesis Example 8 6.0 mol (5 mol) of succinimide was placed in a 2 L four-necked flask equipped with a thermometer, nitrogen gas blowing tube, dropping funnel, and stirring rod.
94g) and 400g of dehydrated and purified dimethylformamide
was charged and heated to 85°C to dissolve it.

While stirring well, add 1.0 mol of adiboyl chloride (
When 183g) was dropped through the dropping funnel, it generated heat and
The temperature rose to 0°C.

After being kept at 90°C for 3 hours, the mixture was cooled to room temperature.

This material was gradually dropped into 5,000 cc of water to obtain a white precipitate.

This precipitate was filtered, washed several times with 2,000 cc of water, and then recrystallized from ethyl alcohol to obtain adipoyl bis(N-succinimide).

The yield was 23.1 g (theoretical yield 308 g).

The structural formula is shown below. Elemental analysis result calculation values C: 54.5%, H: 5.2%, N: 9.1%
Actual value C: 55.2%, H: 6.1%, N: 9.0%
Next, examples of the present invention will be shown.

Examples 1 to 5 and Comparative Example 1 Each mixture having the formulation shown in Table 1 was charged into a Henschel mixer, mixed for 3 hours, and then melt-kneaded using a Co-kneader PR-46 manufactured by Buss.

At this time, the barrel temperature is 90℃ and the screw temperature is 78℃.
And the screw rotation speed was 40 RPM.

Average residence time was 60-100 seconds.

Immediately cool and solidify, coarsely crush and finely crush,
The particle size was adjusted to below μ.

The obtained powder coating was electrostatically sprayed onto a Bondilight #144 treated steel plate to a film thickness of 70 to 80 μm, and baked at 180° C. for 30 minutes.

The cured coating shows no discoloration such as yellowing, is flexible enough to not crack when bent, and does not dissolve in methanol or toluene.

General properties are shown in Table 2 for a 70μ thick coating.

In the cross-cut test, scratches reaching the substrate were made with a knife at intervals of one hole so that 100 squares were formed in the coating film, and then peeled off using cellophane tape.

In the table, the number of remaining squares is used as the numerator.

In the boiling water resistance test, the test piece was immersed in boiling water for 4 hours, and then a cross-cut test was performed.

The corrosion resistance test was conducted according to JIS-K-2371, and the tape peeling width is shown.

In the alkali resistance test, the test piece was immersed in a 5% NaOH aqueous solution for 120 hours, and then the state of the coating film surface was visually examined.

As is clear from Table 2, the resin composition for powder coating according to the present invention exhibits excellent general properties and is particularly excellent in adhesion such as boiling water resistance and corrosion resistance.

The resin composition for thermosetting powder coatings according to the present invention has sufficient free-flowing properties at room temperature, and can be coated on objects without causing blocking even when left at temperatures below 50°C for a long time. Later, in the baking process, the coating has sufficient fluidity and, after sufficient flow, the crosslinking reaction begins immediately, resulting in a coating film with excellent leveling properties and a sufficiently high gloss. Furthermore, the cured coating film obtained by baking has excellent mechanical properties, chemical resistance, weather resistance against long-term weathering, etc., and is particularly excellent in adhesion and corrosion resistance.

The thermosetting powder coating resin composition according to the present invention can be used to coat household appliances, metal parts for automobile manufacturing, and metal parts exposed to long-term weathering, such as automobile body decorative panels, pipes, and steelwork. It is also applied to covering equipment for agriculture and forestry.

Claims (1)

[Scope of Claims] 1(A) A hydroxyl group-containing polyester resin having a softening point of 50 to 180°C, which is mainly based on an aromatic polycarboxylic acid. (B) At least one of an N-acyl polylactam compound and an N-acyl polyimide compound and (C) an epoxy resin. 03) component has a lactam group and/or imide group per equivalent of hydroxyl group in component (4). Component (C) is added in an amount of 1 to 1 based on the total amount of components (A), (B), and (C) so that the amount is 0.5 to 1.5 equivalents.
A resin composition for thermosetting powder coating obtained by blending 5 parts by weight.