JPS584071B2 - Huntai Toryouso Saibutsu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermosetting coating composition suitable for electrostatic powder spraying and fluidized dipping.

As is well known, powder coatings are produced by heating, melting, and kneading a resin composition, pigment, filler, viscosity modifier, and other additives, and then cooling and pulverizing the resulting solid material.

Therefore, when the resin component used is thermosetting, the resin component is stable when melted and mixed, but on the other hand, strict performance is required in the curing process after painting, in that it must be sufficiently cured by heating.

In addition, the resin component is required to have the ability to be easily melted and mixed, and the solid material after cooling can be easily crushed.

The present inventors previously applied for a composition of polyester resin, amine resin, and metal compound (Japanese Patent Application No. 48529/1989).
However, as a result of further research, it was discovered that a composition of polyester resin, epoxy resin, and metal compound had even better performance in terms of crushability, blocking resistance, storage stability, etc.

That is, the feature of the present invention is to synthesize a polyester having a carboxyl group as a functional group, to form an ionic bond between the carboxyl group and a metal compound, and to make it stable around room temperature and dissociate at high temperatures. It is possible to obtain a coating film that is sufficiently smooth and glossy and has excellent adhesion and impact resistance.

The composition of the present invention has (a) a softening point of 40 to 120°C, preferably 60 to 90°C, and an acid value of 30 to 200, preferably 50
~120 ioO parts of a polyester resin; (0) 4 to 50 parts, preferably 15 to 30 parts, of an epoxy resin containing at least two epoxy groups per average molecule; and (c) further,
Pigments, fillers, and viscosity are added to a composition prepared by adding 0.01 to 10 parts, preferably 2 to 5 parts, of a metal compound selected from oxides, hydroxides, acetates, and formates of monovalent and divalent metals. It contains regulators and other additives.

In the case of curing with an amine resin, the OH groups of the polyester are involved, but in the case of curing with an epoxy resin, as in the present application, the COOH groups are involved, so in order to obtain an appropriate crosslinking density, the acid value of the polyester should be 30 to 200. good.

Furthermore, the amount of epoxy resin corresponding to this is preferably 4 to 50 parts.

In order to obtain the polyester resin used in the present invention, it is sufficient to react appropriate amounts of a carboxylic acid component and a polyol component to provide the physical properties shown in (a) above, but as a result of studies conducted by the present inventors, The main raw materials recognized as usable are as follows.

(1) Carboxylic acids aliphatic, aromatic and oxygen-containing heterocyclic carboxylic acids, or halogen-substituted or hydrogenated derivatives of these acids, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydride anhydride Phthalic acid, succinic acid, adivic acid, azelaic acid, sebacic acid, tetrachloric phthalic anhydride, rosin maleic anhydride adduct trimellitic acid, etc. (2) Glycol ethylene glycol, propylene glycol, 1-4 butanediol, 1- 3-butanediol, 2,3-butanediol, diethylene glycol, triethylene N lagoon Al obentyl glycol, hydrogenated bisphenol A
1 Glycerin monocarboxylic acid ester, etc. (3) Polyhydric alcohols N lagoon serine, pentaerythritol, trimethylolpropane, dipentaerythritol, mannitol, sorbitol, etc. Also, whole or partial eboxidized products of these alcohols AN lagoon cidyl ester , glycidyl ether can also be used.

Examples include ethylene oxide or propylene oxide additives, glycidyl laurate, glycidyl benzoate, epoxidized soybean oil, phenol glycidyl ether, and the like.

It is possible to use any of these raw materials as long as the above conditions can be met by appropriately combining raw materials that can be converted into polyester.

Epoxide resins contain an average number of epoxy groups of at least two in their molecules, such as bisphenol A.
Type resins are common, but those containing an average of 3 or more epoxy groups are preferred.

For example, triglycidyl isocyanurate, but also various other well-known polyepoxide resins are required to contain at least two epoxy groups in the average molecule.

Oxides, hydroxides, acetates and formic acid of monovalent and divalent metals include oxides, hydroxides of lithium, sodium, J lagoon, magnesium, calcium, strontium, barium, zinc, cadmium, etc. These include acetate and formate.

The polyester resin in the present invention is synthesized by a common method.

Into a reaction vessel equipped with a thermometer, a stirrer, a cooling tube, and a decanter, 474 parts of terephthalic acid, 24 parts of adipic acid, 162 parts of trimethylolpropane, 231 parts of neopentyl glycol, and 1.0 part of tetrabutyl titanate were charged with nitrogen. It was heated to 180 DEG C. to 250 DEG C. in a gas atmosphere and maintained at this temperature with stirring, and the water of the esterification reaction was removed out of the yarn by bubbling nitrogen gas through the reaction mass.

The reaction was stopped when the acid value reached 5.0. The characteristics of the reactant were an acid value of 5.0, a hydroxyl value of 119.4, and a softening point of 62°C.

Next, 99 parts of hexahydride-based phthalic anhydride was added to 300 parts of the above reactant, and 150 to 170 parts of hexahydride phthalic anhydride was added in a nitrogen gas atmosphere.
℃ and stirred for 120 minutes.

The reaction product was cooled and solidified, and then pulverized.

The reactant had a hydroxyl value of 0, an acid value of 107.7, and a softening point of 65°C.

This polyester resin is designated as A.

In a reaction vessel similar to that used for polyester A, 388 parts of dimethyl terephthalate, 93 parts of ethylene glycol, 36 parts of trithimerolethane, and 115 parts of 1,3-butylene glycol were charged and melted by heating.

Once melted, stir and heat further until the temperature reaches 160℃.
When the temperature reached 180℃, add 1 part of lead oleate and further heat to 180℃.
Maintained at ˜250° C. under nitrogen.

During this time, methanol produced as a by-product was removed through a separator.

Next, 148 parts of ctaric anhydride was added to give a
The temperature was maintained at 0°C, and the reaction was stopped when the acid value was 16.3, the hydroxyl value was 85.2, and the softening point was 74°C.

Next, 71 parts of hexahydride-based phthalic anhydride was added to 300 parts of the above reactant into a reaction vessel, and 15 parts of
It was heated to 0-170°C and stirred for 120 minutes.

The reactant had a hydroxyl value of O, an acid value of 100.3, and a softening point of 82°C.

This polyester resin is designated as B.

Furthermore, polyester C also contains 166 parts of terephthalic acid,
68 parts of phenyl acetic acid, 74 parts of phthalic anhydride, 62 parts of ethylene glycol, and 96 parts of trimethylolmethane were subjected to a condensation reaction, and then 132 parts of hexahyde-based phthalic anhydride were reacted with 300 parts of the above reaction product.

The softening point was 76°C, the acid value was 139.3, and the hydroxyl value was 0.

Next, metal oxide M was added to 100 parts of polyester resin B.
After adding 4 parts of g0 and melting and mixing at 130° C. for 10 minutes, the mixture was cooled and the dynamic viscoelastic modulus was measured (by Vibron manufactured by Toyo Sokki Co., Ltd.) to check the crushability and powder stability (blocking ability).

The results are shown in FIG. 1, indicating that the system to which metal oxides were added had a high elastic modulus near room temperature and better powder properties.

Furthermore, the glass transition temperature (Tg) was increased by about 30° C. compared to the one without additives, indicating that the powder stability (blocking property) of the pulverized product was good.

Example 100 parts of polyester resin A, 5 parts of zinc oxide (ZnO), and 30 parts of titanium oxide were mixed using a hot roll to give a powder of 130 to 140 parts.
After kneading at 105°C for 10 minutes, 21 parts of epoxy resin (triglycidyl isocyanurate) was further added and kneading was performed at 105°C for 5 minutes.

The cooled and solidified material is crushed with a pin desk mill to a powder of 20 to 150
A particle with a particle size of μ was obtained.

This crushed paint was degreased using an electrostatic coating machine on a mild steel plate (20
0X100XO. 6 mm) to a film thickness of 100 μm, and baked at 160 to 180° C. for 20 minutes.

Good grindability and powder stability.

There are no coating defects such as pinholes or cissing, and the appearance is good.

The impact resistance value was 25 cr or more at % inch $500 g.

The powder stability and impact resistance values were measured by the following method.

Powder stability: 5 g of powder paint is placed in a 10 mmf test tube, and after being left at 40°C for 24 hours, the presence or absence of blocking is observed.

Impact resistance: A 1/2 inch f striking core and a pedestal are attached to a DuPont impact tester, and the test piece is sandwiched between them with the coated side facing upward.

A weight weighing 500g±1g is dropped from a predetermined height,
Check for damage to the painted surface.

The maximum height without damage is the impact value.

Comparative Example Polyester resin AI 00 parts Titanium oxide 30 parts 130 parts
The mixture was melt-mixed at ~140°C, cooled, and then ground.

Further, 21 parts of epoxy resin (triglyzyl isocyanurate) was added, melt-kneaded at 105° C. for 5 minutes, cooled, and then pulverized.

Since the pulverizability was not very good, the composition was pulverized after being cooled with dry ice, but the powder stability was poor and it was slightly sticky.

In addition, Example 1 was released in a constant temperature room at 25°C for one month and then re-pulverized.
It seems that either the electrostatic coating was carried out using the same method as above, or the composition was not sufficiently melted and curing had already progressed.

Other Examples 2 to 5 were stable for 3 months or more (25° C. room temperature).

The compositions and physical properties of these are listed in Tables 2 and 3.

[Brief explanation of the drawing]

FIG. 1 shows a comparison of the elastic modulus (solid line) and glass transition point (dotted line) between polyester resin B and polyester resin B to which 4 parts of M90 were added.

Claims (1)

[Claims] 1 Polyester resin ioog with an acid value of 30 to 200 and a softening point of 40 to 120°C, 4 to 50 parts of an epoxy resin having at least two epoxy groups per average molecule, and oxides of monovalent and divalent metals. , hydroxide, acetate, and formate, and an additive.