JPS588429B2 - Funtai Triyou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder coating, particularly a powder coating suitable for coating metal surfaces.

In recent years, the usefulness of powder coatings has attracted attention due to advances in electrostatic powder coating technology.

Powder coatings have the advantage of not using volatile solvents compared to solution-based coatings, and can also be applied thickly in one coat.
It has many advantages.

When the resin component of the powder coating is a thermoplastic resin, it must (a) have excellent adhesion to metals and flexibility, (0) have excellent weather resistance, and (c) the resin is easily crushed and easily powdered. (d) the powder is stable; (e)
Low melt viscosity; (f) no deterioration during melting;
(g) The necessary conditions include melting at a relatively low temperature.

Conventionally, epoxy resin, vinyl chloride resin, nylon resin,
Powder coatings using polyethylene, cellulose acetate butyrate, etc. are known, but at present no powder coating with excellent properties as a top coat for metals has yet been obtained.

In addition, attempts have been made to use thermoplastic polyester as a powder coating, but very few have been put to practical use. It has disadvantages such as (1) poor adhesion, (2) requiring high temperature for baking, and (2) difficulty in obtaining a smooth coating film due to insufficient flow during melting.

As a result of intensive research focusing on this point, the present inventor has discovered a glycol component containing ethylene glycol and neopentyl glycol in specific proportions, and a specific proportion of terephthalic acid and aliphatic dicarboxylic acid having 6 to 16 carbon atoms. Consists of a dicarboxylic acid component and has a reduced specific viscosity of 0.4 to 2.
．． Polyester No. 5 has excellent properties as a powder coating, that is, it is stable at room temperature, easily forms a uniform coating film by heating, and has excellent flexibility, weather resistance, and adhesion to metal. The present invention was developed based on the discovery that a coating film with good performance can be obtained.

That is, the present invention provides (4) at least 85 mol% of the glycol component is ethylene glycol and neopentyl glycol, and the ratio of neopentyl glycol to the sum of the ethylene glycol and neopentyl glycol is 40 to 90 mol%.
(B) At least 80 mol% of the acid component is terephthalic acid and has the general formula HOOC+CH2+nCOOH (where n is 4 to 1);
at least one aliphatic dicarboxylic acid represented by the integer 4), and the ratio of terephthalic acid to the sum of the terephthalic acid and aliphatic dicarboxylic acid is 60 to 98 mol%.
The present invention relates to a powder coating comprising a dicarboxylic acid component as a main component and a polyester having a reduced specific viscosity of 0.4 to 2.5.

The powder coating of the present invention has the following characteristics.

■The coating film has good flexibility and excellent impact resistance.

■Good flow during melting and easy baking.

■It has better weather resistance than epoxy resin powder coatings.

■Excellent adhesion to metals.

In the polyester mainly used in the powder coating of the present invention, at least 85 mol%, preferably 90 mol% or more, particularly 95 mol% or more of the glycol component thereof consists of ethylene glycol and neopentyl glycol, and the polyester contains ethylene glycol and neopentyl glycol. Neopentyl glycol is contained in a proportion of 40 to 90 mol%, preferably 50 to 85 mol%, particularly 60 to 80 mol%, based on the sum of pentyl glycol.

If the ratio of neopentyl glycol to the sum of ethylene glycol and neopentyl glycol is less than 40 mol%, the resin becomes brittle and its flexibility decreases, and in some cases, the resin crystallizes during baking of the coating film, making it difficult to apply the coating. The appearance of the membrane deteriorates.

Moreover, if it exceeds 90 mol%, the resin will become soft and the coating surface will be easily scratched.

When the sum of ethylene glycol and neopentyl glycol is less than 85 mol % of the total glycol components, the excellent properties exhibited by the combination of ethylene glycol and neopentyl glycol, ie, the excellent coating appearance and weather resistance, deteriorate.

In addition to the above-mentioned ethylene glycol and neopentyl glycol, the glycol component constituting the polyester may include other glycols such as 1,2-propanediol, 1
, 4-butanediol, ■, 6-hexanediol, cyclohexanedimethanol, cyclohexanediol,
■, 3-propanediol, polyethylene glycol,
Polyteramethylene glycol, 2,2-bis(hydroxyphenyl)propane, 2,2-bis(hydroxyethoxyphenyl)furopane, bis(hydroxyphenyl)sulfone, bis(hydroxyethoxyphenyl)sulfone, etc. One type or two or more types may be used in small proportions.

In addition, the dicarboxylic acid component constituting the polyester is at least 80 mol% of terephthalic acid and an aliphatic dicarboxylic acid represented by the general formula HOOC-(CH2)-nCOOH (where n is an integer from 4 to 14). and 60 to 98 mol% of terephthalic acid, preferably 7% by mole based on the sum of the terephthalic acid and aliphatic dicarboxylic acid.
It is contained in a proportion of 0 to 98 mol%, particularly 80 to 97 mol%.

Specific examples of aliphatic dicarboxylic acids represented by the above general formula include adipic acid, pimelic acid, superric acid, azelaic acid, sebacic acid, nonamethylene dicarboxylic acid,
Examples include decamethylene dicarboxylic acid, undecamethylene dicarboxylic acid, todecamethylene dicarboxylic acid, tridecamethylene dicarboxylic acid, and tetradecamethylene dicarboxylic acid.

Among these, aliphatic dicarboxylic acids having 9 or less carbon atoms particularly increase the surface hardness of the resulting resin.

Furthermore, aliphatic dicarboxylic acids having 11 or more carbon atoms particularly improve the powder stability of the resulting resin.

In particular, aliphatic dicarboxylic acids having 11 or 12 carbon atoms are characterized by significantly improving powder stability, coating surface hardness, and surface appearance.

The sum of terephthalic acid and aliphatic dicarboxylic acid accounts for 8 of the total acid components.
If it is less than 0 mol %, the excellent performance of the resin developed by the combination of terephthalic acid and aliphatic dicarboxylic acid, that is, one or both of high surface hardness and excellent flexibility will be reduced.

If the ratio of terephthalic acid to the sum of terephthalic acid and the aliphatic dicarboxylic acid is less than 60 mol%, the softening point of the polyester will decrease and the stability of the powder will deteriorate;
When the amount exceeds mol%, flexibility decreases.

As the dicarboxylic acid component constituting the polyester, in addition to the above-mentioned terephthalic acid and the aliphatic dicarboxylic acid represented by the above general formula, other dicarphonic acids such as isophthalic acid, phthalic acid, conocic acid, gnoretalic acid, cyclohexanedicarboxylic acid, A small proportion of one or more of diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, naphthalene dicarboxylic acid, sodium 3,5-dicarboxybenzenesulfonate, dibromo terefucuric acid, etc. Good too.

The polyester containing the above-mentioned dicarboxylic acid component and glycol component must have a reduced specific viscosity of 0.4 to 2.5, more preferably 0.45 to 1.7, particularly 0.5 to 1.
It is preferable that it is 4.

If the reduced specific viscosity of polyester is less than 0.4, the coating film will be brittle and have poor adhesion to metals, making it unsuitable for practical use; if it exceeds 2.5, the flow during baking will be poor, resulting in a smooth coating. It is difficult to obtain a coating film with good properties.

The reduced specific viscosity [ηSP/C] mentioned here is expressed by the following formula (however,
ηrel: relative viscosity, C2 concentration 1.2f/dI, solvent:
This is a value calculated from orthochlorphenol, measured at a temperature of 35°C ηSP: specific viscosity.

The polyester mainly used in the powder coating of the present invention is terephthalic acid, the aliphatic dicarphonic acid represented by the above general formula, and in some cases other dicarboxylic acids, or ester-forming derivatives thereof, ethylene glycol, neopentyl glycol, and In some cases, it can be obtained by reacting other glycols or their ester-forming derivatives in accordance with conventionally known polyester production methods.

Examples of the ester-forming derivatives of dicarboxylic acids include lower alkyl esters (eg, methyl ester), phenyl esters, anhydrides, and halides of dicarboxylic acids, with lower alkyl esters being particularly preferred.

Typical examples of these include dimethyl terephthalate and dimethyl adipic acid.

Examples of the ester-forming derivatives of glycols include lower fatty acid esters, carbonate esters, and alkylene oxides of glycols.

Examples of alkylene oxide include ethylene oxide.

The powder coating of the present invention may contain coating compounding agents as required.

Examples of such compounding agents include pigments, flow control agents, stabilizers, and the like.

The pigments include, for example, white pigments such as zinc white, lithobon, zirconium oxide, titanium oxide, etc.; black pigments such as carbon black, graphite, etc.; pallite, chalk, clay, talc, silica white, alumina white, slag, bentonite, etc. Extender pigments such as zinc powder, gray pigments such as lead zinc oxide, red lead, vermilion, molybdenum red, antimony red,
Red pigments such as toluidine red, etc. Brown pigments such as amber, iron oxide, etc. Yellow pigments such as Hansa yellow, penzidine yellow, yellow lead, synthetic orca, etc.: Copper cap cyanine green, chromium green, chromium oxide green , zinc green, etc.; blue pigments, such as copper-lid cyanine blue, navy blue, gunmai, cobalt blue, manganese blue, etc.; violet pigments, such as oxazine violet, manganese violet, dark cobalt violet, marus violet, etc.: Examples include metal powder pigments such as aluminum powder, copper powder, gold powder, brass powder, and the like.

Further, examples of the flow control agent include silicone resin, acrylic resin, silicon oxide fine powder, polyvinyl butyral, organic bentonite, aluminum stearate, zinc stearate, and the like.

Examples of the stabilizer include antioxidants, ultraviolet absorbers, and the like.

The blending ratio of such paint compounding agents can be arbitrarily selected depending on the type thereof, but the blending ratio conventionally used may be used, for example, the pigment content is 0.5 to 50% by weight, preferably 1 to 40% by weight based on the total composition. The flow control agent is present in an amount of 0.5 to 50% by weight, preferably 5 to 30% by weight, based on the total composition, and their total amount does not exceed 50% by weight.

The stabilizer is added in a proportion of not more than 5% by weight, preferably not more than 1% by weight, based on the total composition.

When adding the paint additives, such as pigments, flow control agents, stabilizers, etc. to the polyester, they are kneaded using a mixer such as an extruder or seconder at a temperature higher than the softening point of the polyester. is preferred.

Polyester or polyester compositions containing the above-mentioned ingredients are usually pulverized by mechanical methods.

In the case of mechanical methods, the first step is usually to coarsely grind the material using a grinder, and the second step is to produce a fine powder using a pulverizer.

When performing fine pulverization, it can be carried out at a low temperature of 0° C. or lower; for example, a fine powder can be easily obtained by pulverizing while cooling with liquid nitrogen or the like.

The powder coating thus obtained is stable at room temperature,
Plocking phenomenon does not occur.

The powder coating of the present invention can be applied using a powder coating method such as electrostatic spray coating.
It is applied to a pretreated metal surface by a fluidized dipping method, an electrostatic dynamic dipping method, a spraying method, etc.
It is baked at a temperature of 180-240°C, preferably 180-240°C.

Baking melts the resin and forms a uniform coating surface.

Hereinafter, the present invention will be explained in detail with reference to Examples.

The physical properties of the coating film were tested by the following method.

(1) Scratch test: Scratches are made with a record stylus on the painted surface in a grid pattern at 1-inch intervals vertically and horizontally until the metal surface is reached, and the paint film adheres closely to the metal surface without peeling off among 100 scratches. It is expressed by the number of pieces.

(2) Erichsen test: A coating film is formed on a metal plate with a thickness of 1 mm, and a punch with a diameter of 20 mm is extruded from the back side, and the extrusion distance is expressed as the extrusion distance when cracks or peeling occur in the coating film.

(Erichsen testing machine manufactured by Toyo Tester Industries) (3) Bending test: According to JIS-K-5400-1970.

(4) Pencil hardness: Based on JIS-K-5400-1970.

(Using Mitsubishi Pencil Uni) Examples 1 to 4 and Comparative Examples 1 to 3 Ethylene glycol 65 in a 5QQcc three-necked flask
f (1.05 mol), neopentyl glycol 109P
(1.05 mol) and the dicarboxylic acid ester shown in Table 1 and 0.176 g of calcium acetate hydrate were charged and heated to react while distilling methanol out of the system. When the distillation of methanol stopped, The transesterification reaction was completed.

The obtained reaction product was transferred to a polymerization flask equipped with a stirrer and the atmosphere was purged with nitrogen, and 0.0% of antimony trioxide was added. 0871 and trimethyl phosphate 0.1681 and heated to 250°C.
The reaction was carried out at normal pressure for 30 minutes, then the pressure was reduced to about 20 mmHf for 15 minutes, and then at 0.5 mmH? The reaction was carried out for a predetermined time under reduced pressure.

The acid component composition ratio, glycol component composition ratio, and reduced specific viscosity of the obtained polyester are as shown in Table 1.

The polyester was subjected to an impact pulverizer to produce a fine powder.

The obtained powder coating was applied to a steel plate with a thickness of 1 mm using an electrostatic coating machine, and then baked in a heating furnace at a temperature of 220° C. for 5 minutes to form a coating film.

The results are shown in Table 1.

DMT is the abbreviation for terephthalic acid dimethyl ester (DMA).
Z is the abbreviation for azelaic acid dimethyl ester DMA is the abbreviation for adipic acid dimethyl ester DMSB is the abbreviation for suberic acid dimethyl ester DMD is the abbreviation for decamethylene dicarboxylic acid dimethyl ester DMN is the abbreviation for 2,6-naphthalene dicarboxylic acid dimethyl ester DMSO is amber Abbreviation for acid dimethyl ester.

All of Comparative Examples 1 to 3 do not contain the aliphatic dicarboxylic acid represented by the above general formula, so the physical properties of the coating film are poor. In particular, Comparative Examples 1 and 2 have poor flexibility, and Comparative Example 3 has poor pencil hardness. is decreasing.

Examples 5 to 8 and Comparative Examples 4 to 5 Terephthalic acid dimethyl ester and various aliphatic dicarboxylic acid dimethyl esters in the amounts shown in Table 2, ethylene glycol 65P (1.05 mol) and neobentyl glycol 109P (1.05 mol) mol) in the same manner as in Example 1 to obtain a polyester.

A paint was prepared from the obtained polyester in the same manner as in Example 1, and baked.

The results are shown in Table 2.

TA is the abbreviation for terephthalic acid DDC is the abbreviation for decamethylene dicarboxylic acid EG is the abbreviation for ethylene glycol NPG is the abbreviation for neoduntyl glycol DDD is the abbreviation for dodecamethylene dicarboxylic acid dimethyl ester DODC is the abbreviation for dodecamethylene dicarboxylic acid DTD TDC is the abbreviation for tetradecamethylene dicarboxylic acid. TDC is the abbreviation for tetradecamethylene dicarboxylic acid.

In Comparative Examples 4 and 5, the surface hardness of the coating film was low because the content of decamethylene dicarboxylic acid was high.

In addition, the obtained powder caused blocking.

Examples 9, 10 and Comparative Examples 6-7 Terephthalic acid dimethyl ester 751 (0.9 mol) and azelaic acid dimethyl ester 221 (0.1 mol)
and ethylene glycol and neopentyl glycol in the amounts shown in Table 3 were reacted in the same manner as in Example 1 to obtain a polyester.

A paint was prepared from the obtained polyester in the same manner as in Example 1, and baked.

The results are shown in Table 3.

Note that AZ is an abbreviation for azelaic acid.

In Comparative Example 6, the surface hardness of the coating film was low due to the high neopentyl glycol content, and in Comparative Example 7, the flexibility was low due to the high ethylene glycol content.

Examples 11, 12 and Comparative Example 8 Terephthalic acid dimethyl ester 184P (0.95 mol) and decamethylene dicarboxylic acid dimethyl ester 13
P (0.05 mol) and ethylene glycol 65P (1.
05 mol) and neopentyl glycol 109P (1.
05 mol) in the same manner as in Example 1 to produce polyester.

A paint was prepared from the obtained polyester in the same manner as in Example 1, and baked.

The results are shown in Table 4.

In Comparative Example 8, since the reduced specific viscosity of the polyester is low, the adhesiveness to metals is poor and the flexibility is also low.

Example 13 Terephthalic acid dimethyl ester 175P (0.9 mol)
and decamethylene dicarboxylic acid dimethyl ester 26?
(0.1 mol) and ethylene glycol 65f (1.05 mol)
mol) and neopentyl glycol 1091 (1.05
mol) in the same manner as in Example 1 to produce polyester.

The composition of the acid component and glycol component of the obtained polyester was 90 mo1% terephthalic acid, 10 mo1% decamethylene dicarboxylic acid, and 32 mole ethylene glycol.
1% and neopentyl glycol 68mo1%,
The reduced specific viscosity was 0.88.

100 parts by weight of this polyester and 3 parts of rutile titanium oxide
0 parts by weight were heated and kneaded in an extruder.

After cooling, it was passed through an impact pulverizer to produce a fine powder.

A coating film was prepared from the obtained powder coating in the same manner as in Example 1.

The physical properties of the coating film are as follows.

Paint film physical properties Goban test 100/100 Erichsen test 9F1N/r'r1 pass bending test
2zm/m passing pencil hardness H Orange beam Almost none

Claims (1)

[Scope of Claims] 1 (A) At least 85 mol% of the glycol component is ethylene glycol and neopentyl glycol, and the ratio of neopentyl glycol to the sum of the ethylene glycol and neopentyl glycol is 40 to 90 mol%. At least 80 mol% of the glycol component and (8) acid component is terephthalic acid and has the general formula HOOC-{OH2)-nCOOH, where n is 4.
The dicarboxylic acid component is at least one aliphatic dicarboxylic acid represented by (an integer from A powder coating whose main component is polyester having a specific viscosity of 0.4 to 2.5.