JPS584070B2 - Huntai Toryouso Saibutsu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to thermosetting resin compositions for use in powder coatings, particularly electrostatic coatings and flow dipping.

There are many characteristics necessary for a thermosetting resin powder coating, but
It can be roughly summarized into the following items.

b) Easy to manufacture.

Stable when stored. → Easily becomes smooth when painted and hardens quickly.

→The physical properties of the coating film are good, etc.

For this reason, polyester/amino resin powder coatings are made by blending amine resin with polyester resin that has a relatively high softening point and high hydroxyl value, and adding pigments, fillers, viscosity modifiers, and other additives. After heating and melting and kneading,
It is well known that it is manufactured by pulverizing the solid material obtained by cooling, but it has not yet come into general use because it is difficult to make something that completely satisfies the above requirements. .

In other words, if a polyester resin with a low softening point is used, it is difficult to powder it, or even if it can be powdered, it is likely to cause blocking, and if a polyester resin with a high softening point is used, high temperature kneading is required, so The methylol group of the amino resin and the OH group of the polyester tend to react and gel, making it difficult to operate, and even if a powder coating is obtained, the gelation time is short, so the coating hardens and becomes smooth before it becomes smooth. It is difficult to create a smooth surface.

In addition, adding a large amount of amino resin increases the blocking properties of the powder, so only a small amount can be added, and there are also problems in terms of flexibility and impact resistance.

The present inventors came up with the idea that carboxyl groups play a role as a catalyst in the curing reaction, and as a result of investigation, they added oxides of monovalent and divalent metals to thermosetting polyester/amine resin compositions. The composition to which at least one compound among hydroxide and acetate is added has the characteristics necessary as a resin composition for powder coatings, that is, it is stable during the kneading process, has excellent storage stability, and does not block. We have discovered that a coating film with smoothness and photoselectivity can be obtained by baking.

By adding the above compound, carboxyl groups can be masked during the kneading process and curing can be prevented.

At room temperature during kneading, metal ions are crosslinked, but at high temperatures during baking, the crosslinks are removed, making painting easier.

The first advantage of the present invention is that even polyester resins with low softening points, for example those around 40° C., can have their softening points raised by ionic crosslinking, making it easier to powder them.

Moreover, since the crosslinks are removed when melted, the viscosity does not increase much.

However, if a material with a high softening point is raised further, it cannot be used as a paint, so there will be restrictions on the softening temperature range.Compared to conventional technology, which is limited to an extremely narrow temperature range, the choice of resin is far greater. Easy to use.

The second effect is that it becomes possible to increase the amount of amino resin mixed, and a coating film with sufficient smoothness and gloss and excellent adhesion and impact resistance can be obtained.

According to the above, the present invention has an oxidation value of 30 or less and a hydroxyl value of 50 or less.
500, polyester resin with a softening point of 40 to 120°C, 5 to 40 parts of loamino resin, and oxides of halogen and divalent metals,
At least one compound selected from hydroxide and acetate 0
．． This relates to a thermosetting resin composition for coatings obtained by powdering a resin composition mainly containing 1 to 10 parts of 0.01 to 10 parts. This is necessary to prevent blocking and to provide a smooth and sufficient coating film properties upon baking, but a composition consisting only of A and A cannot satisfy the above-mentioned properties necessary for a powder coating.

In order to obtain the polyester resin used in the present invention, it is sufficient to react a suitable combination of a carboxylic acid component and a polyol component to provide the physical properties shown in (a) above, but it can be used as a result of studies conducted by the present inventors. The main raw materials recognized as such 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, hexadohydroanhydride Phthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetraphthalic anhydride, rosin maleic anhydride adduct trimellitic acid, etc. (2) Glycol G'ren N lagcol At propylene glycol, 1-4 butane Diol, 1-3 butanediol, 2,3 butanediol, diethylene glycol, ethylene glycol, neopentyl glycol A, hydrogenated bisphenol A
, glycerin monocarboxylic acid esters, etc. (3) Polyhydric alcohols glycerin, pentaerythritol, trimethylolpropane, dipentaerythritol, mannitol, sorbitol, etc. Also, full or partial epoxidized products of these alcohols, glycidyl esters, glycidyl ethers, can also be used.

For example, 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.

The amine resin is a condensate of an aldehyde, preferably formaldehyde, and melamine, urea, guanamine, etc., with a carbon number of 1.
It is obtained by etherification with ~6 aliphatic alcohols.

The most preferred among these is hexamethoxymethylmelamine.

Oxides, hydroxides and acetates of monovalent and divalent metals include lithium, sodium, potassium, magnesium,
These include oxides, hydroxides, acetates, etc. of calcium, strontium, barium, zinc, cadmium, etc.

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

A reaction vessel equipped with a thermometer, stirrer, reflux condenser, inert gas inlet and outlet was charged with 46 parts by weight of ethylene glycol, 46 parts by weight of glycerin, 128 parts by weight of glycidyl laurate, and 249 parts by weight of terephthalic acid. do.

The contents of the container are heated to about 200-260C, maintained at this temperature with stirring, and heated with nitrogen gas until the acid number reaches about 9.

The obtained polyester resin has a softening point of 87C and a hydroxyl value of 1.
It was 426.

This was designated as polyester resin A.

Other polyester resins B, C, and D were also synthesized by the same method and using the same equipment using the components summarized in Table 1.

The acid value, hydroxyl value, and softening point of the obtained polyester resin are also shown in Table 1. Example 1 100 parts by weight of polyester resin A, magnesium oxide (
After kneading 0.5 parts by weight of MgO and 25 parts by weight of titanium oxide at 150C for 10 minutes using a hot roll, 20 parts by weight of hexamethoxymethylmelamine (HMMM) was further added and kneading was carried out at 130C for 10 minutes.

The cooled and solidified product was pulverized to obtain a product having a particle size of 50 μm or less.

This powder paint was degreased using an electrostatic coating machine to give a 0.6Wtm
Painted on a mild steel plate with a film thickness of 100μ,
Baking was performed at 0°C for 30 minutes.

Good grindability and powder stability. "Pinhole""Hajiki"
There are no paint film defects such as, and the appearance is good.

The impact resistance value was 25α or more at 1 inch of $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 mm 5 test tube, left at 40° C. for 24 hours, and checked for blocking.

Attach the striking core and pedestal, and apply the test piece. Place it in between with the sides facing up.

Predetermined weight with a weight of 500g ± 1g If the paint surface is damaged by dropping it from a height of Examine nothingness.

The highest height without damage is the impact value.

Example 2-7 and Comparative Example 1-3 Using the same method as in Example 1, polyester resin B. C.
A powder coating composition was prepared for D and shown in Table 2.

Next, a coating test was similarly conducted on these compositions, and the results are shown in Table 3.

Comparative Examples 1 and 2.3 were obtained by omitting the metal compound from Examples 1 and 2.3.

Claims (1)

[Claims] 1 Acid value 30 or less, hydroxyl value 50-500, softening, point 4
100 parts of polyester resin at 0 to 120°C, 5 to 40 parts of amino resin, and at least one compound selected from monovalent and divalent metal oxides, hydroxides, and acetates.
A resin composition for powder coating comprising 01 to 10 parts and an additive.