JP2782726B2 - Resin composition for powder coating - Google Patents

Description

The present invention relates to a novel and useful resin composition for powder coatings. More specifically, the present invention provides a so-called fluororesin system comprising a hydroxyl group-containing fluoroolefin copolymer as a base resin component, a hydroxyl reactive compound as a curing agent component, and a curing catalyst, respectively. The present invention relates to a resin composition for a powder coating.

[Conventional technology]

As this kind of resin for powder coating of a fluorine resin type, there is a thermoplastic type resin containing vinylidene fluoride as a main component.

Fluororesins (fluoroolefin copolymers) are widely used because of their good heat resistance, abrasion resistance, non-adhesion and weather resistance, including chemical resistance, but on the other hand, Because of its high melting point, special equipment is required for pulverization and melt baking at high temperature is also required.Therefore, it has hardly been used as a powder coating. That is the current situation.

On the other hand, acrylic powder coatings as thermosetting powder coatings are widely used because of their excellent weather resistance, stain resistance or appearance, but require long-term weather resistance. There is a need for a practical application of a thermosetting, highly weather-resistant powder coating in a form easily handled by a conventional production method, which is insufficient for use.

[Problems to be solved by the invention]

In view of the above-mentioned various drawbacks in the prior art, the present inventors have considered that a fluororesin-based resin which can be cured under commonly used curing conditions, that is, under the same curing conditions as in a general-purpose powder coating material. As a result of intensive studies aimed at obtaining a powder coating, a fluoroolefin copolymer having a specific molecular weight and softening point and containing a hydroxyl group as a reactive group (functional group), It has been found that a composition that is combined with a curing agent that is capable of reacting with the composition has excellent curability, so that it provides a cured coating film with excellent weather resistance as well as excellent solvent resistance. The invention has been completed.

That is, the present invention basically provides, as an essential (film-forming) component, a hydroxyl group-containing fluoropolymer having a number average molecular weight of 1,000 to 100,000 and a softening point of 60 to 150 ° C. measured by a ring and ball method. Olefin copolymer (A)
And a curing agent (B) having reactivity with a hydroxyl group, for promoting a crosslinking reaction between the hydroxyl group-containing fluoroolefin copolymer (A) and the hydroxyl group-reactive curing agent (B), respectively. An object of the present invention is to provide a resin composition for a powder coating, which comprises a so-called curing catalyst (C).

Here, as the above-mentioned fluoroolefin copolymer (A), for example, vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, bromotrifluoroethylene, chlorotrifluoroethylene, pentafluoropropylene, hexafluoropropylene It contains a fluoroolefin unit as an essential constituent unit, such as propylene or a (per) fluoroalkyl trifluorovinyl ether in which a (per) fluoroalkyl group has 1 to 18 carbon atoms, and also contains a hydroxyl group in a side chain. The fluoroolefin copolymer (A) is a fluoroolefin as described above [hereinafter referred to as one reaction component (a-1). ]
And a monomer containing a hydroxyl group [hereinafter, this will be referred to as one reaction component (a-2)]. ]
And another monomer copolymerizable with the fluoroolefin (a-1) and the hydroxyl group-containing monomer (a-2) [this is hereinafter referred to as one reaction component (a-3)]. Or a previously prepared fluoroolefin (a-1) and one of the other copolymerizable monomers (a-3), vinyl carboxylate A copolymer containing an ester as an essential reaction component is disclosed in
As disclosed in JP-A-219372 and JP-A-60-158209, it can be prepared by a method of hydrolysis or the like, but the method described above is particularly convenient and preferable.

Representative examples of the hydroxyl group-containing monomer (a-2) used for preparing the desired fluoroolefin copolymer (A) by such a method include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-
Hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 1-hydroxymethyl-4-vinyloxymethylcyclohexane, 2-hydroxyethyl allyl ether , 3-hydroxypropyl allyl ether, 4-hydroxybutyl allyl ether, 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate.

Among the hydroxyl group-containing monomers (a-2), from the viewpoint of copolymerizability, vinyl ether-based monomers are most desirable, while acrylic-based monomers are compatible with the above-mentioned fluoroolefin (a-1). Since the copolymerizability is insufficient, their amount should be kept within a range that does not lower the conversion of the target copolymer (A).

Further, fluoroolefins (a-
Representative examples of 1) and other monomers (a-3) copolymerizable with the hydroxyl group-containing monomer (a-2) include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, and n- Alkyl vinyl ethers such as butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, n-pentyl vinyl, n-hexyl vinyl ether, n-octyl vinyl ether or 2-ethylhexyl vinyl ether; cycloalkyl vinyl ethers such as cyclopentyl vinyl ether, cyclohexyl vinyl ether or methylcyclohexyl vinyl ether Aralkyl vinyl ethers such as benzyl vinyl ether or phenethyl vinyl ether; 2,2,3,3-
Tetrafluoropropyl vinyl ether, 2,2,3,3,4,4,
5,5-octafluoropentyl vinyl ether, 2,2,3,
3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononyl vinyl ether, perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoropropyl vinyl ether, perfluorooctyl (Per) fluoroalkyl vinyl ethers such as vinyl ether or perfluorocyclohexyl vinyl ether; or vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, Vinyl stearate, vinyl benzoate, p-tert-
Examples include vinyl carboxylate esters such as vinyl butyl benzoate, vinyl salicylate and vinyl cyclohexanecarboxylate, and further, ethylene, propylene, vinyl chloride, vinylidene chloride, (meth) acrylonitrile or various (meth) acrylic esters. And the like can also be used.

Among the other copolymerizable monomers (a-3), alkyl vinyl ethers are preferred from the viewpoint of improving the polymerization rate and improving the weather resistance of the coating film when preparing the target copolymer (A). It is preferable to use at least one member selected from the group consisting of cycloalkyl vinyl ethers and carboxylic acid vinyl esters, and in particular, in terms of storage stability (blocking resistance) of the obtained paint and hardness of the coating film. From cycloalkyl vinyl ethers or vinyl cyclohexanecarboxylate, vinyl acetate, vinyl benzoate or vinyl p-tert-butyl benzoate, or C ₅ to C ₅ having a carboxyl group bonded to a tertiary carbon atom.
It is desirable to use at least one selected from the group consisting of vinyl esters of aliphatic carboxylic acids of _C18 .

In order to obtain the target fluoroolefin copolymer (A) from the various reaction components listed above, 15 to 70% by weight of the fluoroolefin (a-1) and the hydroxyl group-containing monomer (a-2) ) And 5 to 84% by weight of the other copolymerizable monomer (a-3), preferably (a-
20 to 60% by weight of (1), 2 to 25% by weight of (a-2) and 10 to 77% by weight of (a-3) are combined so that the total amount of all the reaction components becomes 100% by weight. What is necessary is just to polymerize.

When the amount of the fluoroolefin (a-1) is less than 15% by weight, the weather resistance is insufficient, and when it exceeds 70% by weight, the gloss of the coating film is not reduced.
None of them is preferred, and the hydroxyl-containing monomer (a-
If the use amount of 2) is less than 1% by weight, the curability is inevitably low, and the solvent resistance of the obtained coating film is insufficient, while if it exceeds 30% by weight, the use of the curing agent (B) However, the amount of the other monomer (a-3) which is copolymerizable is less than 5% by weight. In such a case, the gloss of the coating film tends to be insufficient, while if it exceeds 84% by weight, the weather resistance is inevitably reduced, and neither is preferred.

The fluoroolefin copolymer (A) is prepared by a known method such as bulk polymerization, solution (pressure) polymerization, suspension polymerization or emulsion polymerization in the presence of a radical polymerization initiator. , Batch, semi-continuous or continuous operation.

Examples of the radical polymerization initiator include diacyl peroxides such as acetyl peroxide and benzoyl peroxide; ketone-based peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; hydrogen peroxide and tert-oxide.
Hydroperoxides such as butyl hydroperoxide; dialkyl peroxides such as di-tert-butyl peroxide or dicumyl peroxide; tert-butyl peroxyacetate or tert-butyl peroxide
Representative examples include alkyl peroxy esters such as butyl peroxy pivalate; or persulfates such as potassium persulfate or ammonium persulfate; or azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile. However, if necessary, they may be used in combination with an inorganic reducing agent such as sodium hydrogen sulfite or sodium pyrosulfite, or an organic reducing agent such as cobalt naphthenate or dimethylaniline.

As the copolymerization reaction method, among the various methods described above, the solution polymerization method is the simplest. Typical solvents used for this purpose include toluene, xylene,
Hydrocarbons such as cyclohexane, n-hexane or octane; esters such as methyl acetate, ethyl acetate or butyl acetate; acetone, methyl ethyl ketone;
Ketones such as methyl isobutyl ketone or cyclohexanone; amides such as dimethylformamide or dimethylacetamide; or alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol or ethylene glycol monoalkyl ether; These include mixtures.

In carrying out such a copolymerization reaction, various chain transfer agents such as lauryl mercaptan, octyl mercaptan, 2-mercaptoethanol or α-methylstyrene dimer can be used as a molecular weight regulator.

In carrying out the copolymerization reaction,
A temperature within the range of 150 ° C is appropriate, and approximately 100kg / cm ²
The following reaction pressures are suitable.

Depending on such reaction conditions, the hydroxyl group-containing monomer (a-
In the case where 2) is copolymerized with the fluoroolefin (a-1), there is a case where a gel often occurs, but from the viewpoint of preventing such gelation, tertiary amines and solid bases such as It is desirable to carry out the copolymerization reaction in the presence of a so-called basic substance.

As a method for removing water or a solvent as a medium from the dispersion or solution of the fluoroolefin copolymer (A) thus obtained, any of known methods can be used. A method of heating and distilling at a high temperature can be recommended.

And the number average molecular weight of the obtained copolymer (A) is usually 1,000 to 100,000, preferably 3,000 to 2
The hydroxyl value of the copolymer (A) is usually from 5 to 200, preferably from 10 to 100, respectively.

Further, the softening point of the fluoroolefin copolymer (A) is usually from 60 to 150 ° C, preferably from 80 to 130 ° C.
A range within is appropriate.

When the softening point is less than 60 ° C, difficulties are likely to appear in the blocking resistance of the powder coating,
If the temperature is excessively higher than ℃, the smoothness of the coating film is inevitably deteriorated.

Next, typical examples of the above-mentioned hydroxyl-reactive curing agent (B), that is, a curing agent having reactivity with a hydroxyl group in the fluoroolefin copolymer (A) include aminoplasts, block polyisocyanate compounds, and polybasic compounds. Acids (anhydrides) and the like can be used, and of course, these various curing agents can be used in combination.

Among them, first, as typical examples of aminoplasts, melamine, urea, acetoguanamine, benzoguanamine, steroguanamine or spiroguanamine, an amino group-containing compound component, and formaldehyde, paraformaldehyde, aldehyde-based compound component such as acetaldehyde or glyoxal, Condensates obtained by reacting by a known and common method, and those obtained by etherifying each of these condensates with alcohols, and the like, include those usually used for powder coatings. Of course, any can be used.

The blocked polyisocyanate compound is, of course, a compound obtained by blocking various polyisocyanate compounds having at least two isocyanate groups in one molecule with a known and commonly used blocking agent. Representative examples of the isocyanate compound include aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; cycloaliphatic diisocyanates such as hydrogenated xylylene diisocyanate or isophorone diisocyanate (alicyclic diisocyanates); or tolylene diisocyanate Or, organic diisocyanate compounds such as aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, or various organic diisocyanates thereof. An adduct of a catenate compound with a polyhydric alcohol, a low molecular weight polyester resin or water, and the above-mentioned polymers of organic diisocyanate compounds and isocyanate / biuret compounds, among which isophorone diisocyanate (IPDI )
Alternatively, it is desirable to use a so-called isophorone diisocyanate-based polyisocyanate blocked with ε-caprolactam, such as an adduct of IPDI and various polyol compounds.

In addition, a compound such as a uretdione bond that regenerates an isocyanate group by heat can be used.

Further, as a representative example of the above-mentioned polybasic acid curing agent,
An acrylic resin having two or more carboxyl groups in one molecule, a polyester resin having two or more carboxyl groups in one molecule, or pyromellitic acid, and the like, while a polybasic anhydride curing agent As typical examples, are acrylic resins having two or more acid anhydride groups in one molecule, trimellitic anhydride, pyromellitic anhydride, and the like.

Among the various curing agent (B) component compounds listed above, especially physical properties and storage stability (blocking resistance)
From the viewpoint of, for example, it is desirable to use a blocked polyisocyanate compound.

Further, as typical examples of the above-mentioned curing catalyst (C), when the above-mentioned blocked polyisocyanate compound is used as the curing agent (B), dibutyltin diacetate, dibutyltin dioctate, dibutyltin dilaurate, triethylamine or dimethylamine Examples of the curing catalyst (C) when aminoplast is used as the curing agent (B) include para-toluenesulfonic acid, phosphoric acid, or an alkyl ester of phosphoric acid, or “Beckamine P- 198 ”(product of Dainippon Ink and Chemicals, Inc.) or“ Nailure ”
155, 2500X, X-49-110, 5225 or 3525 "(manufactured by King Co., USA), dinonylnaphthalenedicarboxylic acid, dodecylbenzenesulfonic acid, or blocked organic amines thereof.

The resin composition for powder coating of the present invention thus obtained further includes, if necessary, a pigment, various resins, a flow control agent, an antioxidant, an ultraviolet absorber, a silane coupling agent, and the like, known and used. Of course, various additives can be added.

Then, the composition of the present invention, each component as described above, by a kneading machine such as a hot roll or a kneader,
It is obtained by melt-kneading at a temperature of about 80 to 150 ° C. and then pulverizing.

〔Example〕

Next, the present invention will be described more specifically with reference examples, examples and comparative examples. In the following, all parts and percentages are by weight unless otherwise specified.

Reference Examples 1 to 9 [Preparation Example of Fluoroolefin Copolymer (A)] In a stainless steel pressure vessel having an internal volume of 1, 400 g of methyl isobutyl ketone and “Perbutyl PV” [manufactured by NOF Corporation 8g of peroxide radical polymerization initiator)
And 5 g of bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, ethyl vinyl ether (EVE), cyclohexyl vinyl ether (CHVE), and 4-hydroxy as shown in Table 1. Butyl vinyl ether (HBVE), 6-hydroxyhexyl vinyl ether (HH
VE), vinyl pivalate (PIV), "VeoVa 9" (The Netherlands Shell Co., vinyl esters of aliphatic carboxylic acids of C ₉ having a carboxyl group bound to a tertiary carbon atom; hereinafter, VV-9 ), Vinylcyclohexanecarboxylate (VCHC), vinylbenzoate (VBZ) or p-tert-butylvinylbenzoate (VPTBZ), and cooled to -70 ° C in a dry ice / methanol bath. The air in the pressure vessel was replaced by blowing gas.

Next, chlorinated chlorotrifluoroethylene (CTFE) or hexafluoropropylene (HFP) was charged at a weight ratio as shown in the same table and sealed. On the other hand, when tetrafluoroethylene (TFE) was used, After using a pressure vessel with a valve and charging each raw material in the same manner as described above, the TFE cylinder
The FE was sealed under pressure and then weighed after closing the valve.

Thereafter, each of these pressure-resistant containers was placed in a rotating thermostatic water bath heated to 60 ° C., and the reaction was carried out for 16 hours. By distilling off the components, various target copolymers were obtained.

When each characteristic value was measured for each fluoroolefin copolymer (A), the results shown in the same table were obtained.

Examples 1 to 10 The respective fluoroolefin copolymers (A) obtained in the respective reference examples were mixed with a curing agent (B) and a filler in a weight ratio as shown in Table 2, or The curing agent (B), the curing catalyst (C) and the filler were mixed, cooled, pulverized, and then classified with a 150-mesh wire net to obtain a powder coating.

Next, each powder coating was applied to a 0.8 mm thick bonderite-treated steel sheet by electrostatic coating separately so that the film thickness after baking would be 60 to 70 microns, and baked at 180 ° C for 20 minutes. A cured coating was obtained.

After evaluating various physical properties of each coating film,
The results as shown in the table were obtained.

The procedure and criteria for evaluating each physical property are as follows.

Smoothness: Visually determined Gloss: Conforms to 6.7 of JIS K5400 Erichsen: Conforms to JIS Z-2247 The larger the Erichsen value, the better the flexibility.

Blocking resistance: 15 g of powder-resistant paint is collected in a test tube of 40 mmφ, left under a load of 20 g / cm ² at 35 ° C for 240 hours, and then the sample is taken out. Was evaluated as "good", and when blocking was observed, it was evaluated as "poor".

Weather resistance: 1,00 on sunshine weatherometer
The gloss retention rate after 0 hour is indicated, and the higher the numerical value, the better the weather resistance.

[Effects of the Invention] As is clear from the results in Table 2, the resin composition for a powder coating according to the present invention exhibits weatherability far exceeding that of a conventional powder coating and has various physical properties. It's easy to find out that it can be balanced.

Claims (4)

(57) [Claims] 1. An essential film-forming component having a number average molecular weight of 1,000 to 100,000 and a softening point (ring and ball method) of 60 to 15
0 ° C., a hydroxyl group-containing fluoroolefin copolymer (A), a hydroxyl group-reactive curing agent (B), and the above-mentioned hydroxyl group-containing fluoroolefin copolymer (A) and a hydroxyl group, respectively. A resin composition for powder coating, comprising: a curing catalyst (C) for promoting a crosslinking reaction with a reactive curing agent (B). 2. The method according to claim 1, wherein said hydroxyl group-containing fluoroolefin copolymer (A) is 15 to 15 of fluoroolefin (a-1).
70% by weight and 1 to 30 of the hydroxyl group-containing monomer (a-2)
% By weight and 5 to 84 of the other copolymerizable monomer (a-3).
% By weight, and the total amount of all these reaction components is 100% by weight.
The resin composition for a powder coating according to claim 1, which is obtained by copolymerizing so as to be as follows. 3. A method according to claim 1, wherein said hydroxyl group-containing fluoroolefin copolymer (A) is 15 to 15
70% by weight and 1 to 30 of the hydroxyl group-containing monomer (a-2)
% By weight and 5 to 84 of the other copolymerizable monomer (a-3).
% By weight, and the total amount of all these reaction components is 100% by weight.
The other copolymerizable monomer (a-3) is obtained by using vinyl carboxylate as an essential copolymerization component as the above-mentioned other copolymerizable monomer (a-3). The resin composition for a powder coating according to claim 1, which is: 4. The method according to claim 1, wherein said hydroxyl-reactive curing agent (B) is a blocked polyisocyanate compound.
Or the resin composition for powder coating according to 3.