JPH04161465A - Thermosetting resin composition for powder coating - Google Patents

Abstract

PURPOSE:To obtain the subject composition, containing a specific vinyl polymer and a curing catalyst, excellent in storage stability, acid and weather resistance, smoothness, etc., and useful for automotive car bodies, metallic coatings, etc. CONSTITUTION:The objective composition is obtained by blending (A) a vinyl polymer having >=2 groups of 2-oxo-1,3-dioxolan-4-yl expressed by the formula (R1 to R3 are H or 1-4C alkyl) in one molecule with (B) a curing catalyst (preferably trimethylvinylammonium bromide, etc.), (C) a compound (at least one selected from the group of polyester resins, vinylic copolymers and low- molecular compounds) having carboxyl and/or acid anhydride groups in one molecule and, as necessary, a leveling agent, an ultraviolet light absorber, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a new and useful thermosetting resin composition for powder coatings. More specifically, the present invention relates to a specific vinyl polymer having at least two 2-oxol-1,3-dioxolan-4-yl groups (hereinafter also referred to as cyclocarbonate groups) in one molecule. A curing system based on a resin and a specific curing catalyst characterized by this cyclocarbonate group curing catalyst; Another curing system based on a resin and the specific curing catalyst; and the specific resin, which is a vinyl polymer having at least two cyclocarbonate groups in one molecule, and a specific curing catalyst;
Furthermore, a thermosetting resin composition for powder coatings, which is a curing system based on a specific compound having at least two carboxyl groups and/or acid anhydride groups in one molecule, and which has particularly excellent storage stability. The present invention relates to a thermosetting resin composition for powder coatings that is extremely useful in terms of acid resistance, weather resistance, and coating film appearance such as smoothness.

The thermosetting resin composition for powder coatings of the present invention can be used in fields where acrylic polyol/melamine resin paints have traditionally been used, such as car bodies and metal coatings. It is something that will be done.

[Conventional technology]

Powder coatings, which were developed as low-pollution coatings, have been used in a wide range of fields in recent years.

In addition, thermosetting powder coatings used for such powder coatings include polyester resin powder coatings using blocked isocyanate compounds or triglycidyl isocyanurate as a curing agent, and glycidyl-based powder coatings using dibasic acids as a curing agent. Containing acrylic resin powder coating is used.

By the way, the former requires certain conditions for high-temperature baking, while the latter has the disadvantage of poor storage stability, so in the end it becomes difficult to bake in itself. There is a strong desire for the development of extremely useful powder coatings that cure at low temperatures and have excellent storage stability.

[Problem to be solved by the invention]

To this end, the present inventors have particularly found that it has good storage stability, excellent low-temperature curing properties, and in addition, excellent weather resistance and physical properties of the coating film, making it extremely useful and therefore extremely practical. We have begun intensive research with the aim of providing a highly thermosetting resin composition for powder coatings.

Therefore, the problem to be solved by the present invention is - In particular, it has good storage stability and excellent low-temperature curability, and in addition, it has excellent weather resistance and physical properties of the coating film. It is an object of the present invention to provide a thermosetting resin composition for powder coatings that is extremely useful and therefore highly practical.

[Means to solve the problem]

Therefore, the inventors of the present invention have endeavored to eliminate or solve the various drawbacks or problems in the prior art as described above, and have also begun earnest research to meet the demands as described above.

Therefore, the problem to be solved by the present invention is to provide a resin composition for a single-wave coating that has excellent storage stability, and that also has excellent acid resistance, weather resistance, and coating film appearance such as smoothness. An object of the present invention is to provide an extremely useful resin composition for coatings.

Therefore, the inventors of the present invention focused on the problems to be solved by the invention as described above, and as a result of intensive studies, the following results were obtained: 1. 3-dioxolane-4
-yl group, especially a group represented by the general formula % (hereinafter also referred to as cyclocarbonate group).

) and a curing catalyst for the cyclocarbonate groups as essential film-forming components, or a vinyl copolymer containing cyclocarbonate groups and a curing catalyst for the cyclocarbonate groups; A thermosetting resin composition comprising a compound having an acid anhydride group and a curing catalyst for a cyclocarbonate group as essential film-forming components has excellent storage stability and acid resistance. Of course, the present invention was completed based on the discovery that the present invention provides a coating film with excellent weather resistance and coating appearance.

That is, the present invention provides vinyl polymers (A-1) each having at least two cyclocarbonate groups in one molecule, particularly a specific group as represented by the general formula CI) as an essential component. and a curing catalyst (B); or the above vinyl polymer (A-1) and a curing catalyst (B); The present invention provides a thermosetting resin composition for powder coating, comprising a compound (C) having one carboxyl group and/or acid anhydride group.

Here, as the vinyl polymer (A-1) having at least two cyclocarbonate groups in one molecule, for example, one α,β-ethylenically unsaturated double bond ( (hereinafter also referred to as unsaturated bond),
A product obtained by a copolymerization reaction of a compound having at least one cyclocarbonate group, especially a cyclocarbonate group as shown in the above general formula [I], and another polymerizable unsaturated monomer. Alternatively, it may be obtained by addition-reacting a carbonate monoalcohol to a known and commonly used incyanate group-containing polymer such as incyanate ethyl (meth)acrylate copolymer, or a known and commonly used acid chloride group-containing polymer. It may be obtained by subjecting a polymer to an addition reaction with a carbonate monoalcohol, but in particular, one obtained by copolymerizing a compound having both an unsaturated bond and a cyclocarbonate group with a hydroxyl group-containing polymerizable unsaturated monomer, - layer, is particularly recommended because of its simplicity.

First, one polymerizable unsaturated double bond and a small number of (
To exemplify only particularly representative compounds having both one cyclocarbonate group and one cyclocarbonate group, 2,3-carbonate propyl (meth)acrylate, each represented by the general formula % [) , 2-methyl-2゜3-carbonate propyl (meth)acrylate, 3,4-carbonate butyl (meth)acrylate, 3-methyl-3,4
-carbonate butyl (meth)acrylate, 4-methyl-3,4-carbonate butyl (meth)acrylate, 4,5-carbonate pentyl (meth)acrylate, 6,7-carbonate hexyl (meth)acrylate, 5-ethyl-5 , 6-carbonate to beef sill (meth)
acrylate or octyl 7,8-carbonate (
acrylates such as meth)acrylates; or 2,
3-carbonate propyl vinyl ether, methyl-2
, 3-carbonate propyl malate or methyl-
These are vinyl compounds such as 2,3-carbonate propyl itaconate.

The amount of these compounds to be used is 1 to 70 parts by weight, preferably 5 to 50 parts by weight, more preferably 5 to 35 parts by weight, when the total monomer amount is 100 parts by weight. Within the range is appropriate.

If the amount is less than 1 part by weight, the effect of such a compound cannot be expected. On the other hand, if it is used in an excessively large amount exceeding 70 parts by weight, the remaining cyclocarbonate groups inevitably result in a hard and brittle coating film. The case is also unfavorable.

Next, other vinyl monomers copolymerizable with the unsaturated monomer containing a cyclocarbonate group include, but are not particularly limited to, unsaturated monomers containing a hydroxyl group and/or a carboxyl group as a functional group. Copolymerization of saturated monomers can enhance the effects of the present invention.

To exemplify only particularly representative hydroxyl group-containing unsaturated monomers, 2-hydroxyethyl (
β-hydroxyalkyl (meth)acrylates such as meth)acrylate, 4-hydroxybutyl (meth)acrylate; 2-hydrodiethyl vinyl ether, 4
- 2-hydroxyalkyl vinyl ethers such as hydroquine butyl vinyl ether; allyl compounds such as allyl alcohol or hydroxyethyl aryl ether; and hydroxyl group-containing unsaturated compounds obtained by adding ε-caprolactone to various suspended monomers. Monomers can be mentioned.

The introduction of hydroxyl groups causes a reaction with carbonate, which also induces an increase in crosslink density, which in turn improves solvent resistance and weather resistance.

Furthermore, carboxyl group-containing unsaturated monomers can also be used.

The use of such carboxyl group-containing unsaturated monomers is particularly effective because it significantly improves the compatibility with carboxyl group-containing or acid anhydride group-containing compounds.

Particularly representative examples of the carboxyl group-containing unsaturated monomer used in the present invention include α such as (meth)acrylic acid, maleic acid, fumaric acid, or itaconic acid.

β-ethylenically unsaturated mono- or dicarboxylic acids;
Esters of α, β-ethylenically unsaturated dicarboxylic acids and monohydric alcohols having 1 to 4 carbon atoms, such as diethyl maleate, dibutyl maleate, dibutyl fumarate, or diethyl itaconate; or 2-hydroxyethyl (meth) ) A carboxyl group-containing unsaturated monomer obtained by adding an acid anhydride such as phthalic anhydride to a hydroxyl group-containing vinyl monomer such as acrylate.

The cyclocarbonate group-containing vinyl polymer (A-1)
In some cases, if necessary, a glycidyl group-containing monomer such as glycidyl (meth)acrylate may be further used as a copolymerization component to introduce such a glycidyl group.

However, when considering the stability of the composition of the present invention, the amount of these glycidyl group-containing monomers used should be limited to 20 parts by weight when the total monomer amount is 100 parts by weight. Should.

Further, as other copolymerizable vinyl monomers, only typical examples include alkyl (meth)acrylates having an alkyl group having 1 to 22 carbon atoms;
Various (meth)acrylates without reactive polar groups, such as 2-ethoxyethyl (meth)acrylate or cyclohexyl (meth)acrylate; various (meth)acrylates containing reactive polar groups, such as glycidyl (meth)acrylate. ;Styrene, tertiary butylene/L/
Aromatic vinyl monomers such as (tert-butyl)styrene, α-methylstyrene or vinyltoluene; various (meth)acrylamides such as (meth)acrylamide or N-alco-remethylated meth)acrylamide;
Acrylamides; or (meth)acrylonitrile, vinyl acetate, or phosphoric acid group-containing (meth)acrylates.

To prepare the vinyl copolymer using the various monomers listed above, any known and commonly used polymerization method such as solution polymerization method or non-aqueous dispersion polymerization method can be applied. Radical polymerization is the simplest method.

Typical examples of solvents used here include hydrocarbon solvents such as toluene, xylene, cyclohexane, n-butylene or octane; methyl acetate, n-butyl acetate or Ester solvents such as amyl acetate; or ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone or cyclohexanone, and these may be used alone or in combination of two or more.

In addition, particularly typical radical polymerization initiators include known and commonly used ones, such as azo type represented by azobisisobutyronitrile and peroxide type represented by penzoyl pero beef side. It is. Furthermore, if necessary, lauryl mercaptan, octyl mercaptan, 2-mercaptoethanol,
Various known and commonly used chain transfer agents such as octyl thioglycolate, 3-mercaptopropionic acid or α-methylstyrene dimer can also be used.

The number average molecular weight of the vinyl copolymer resin thus obtained is suitably in the range of 800 to 50,000, preferably in the range of 1,500 to 50,000.

If it is less than 800, it will be difficult to obtain a product with the desired performance, while if it exceeds 50,000, it will inevitably have a negative effect on the appearance of the coating film, etc. Either case is not preferable.

Next, as the carboxyl group- and/or acid anhydride group-containing compound (C), at least one member selected from the group consisting of vinyl copolymers, polyester resins, and low-molecular compounds having such specific functional groups. Particularly representative examples include compounds such as

Among these, first, as a vinyl copolymer, a carboxyl group-containing unsaturated monomer and/or an acid anhydride group-containing unsaturated monomer is combined with other copolymerizable unsaturated monomers such as those listed above. It may be one obtained by copolymerizing with a body.

As such carboxyl group-containing unsaturated monomers, of course, various types as mentioned above can be used.

Further, the unsaturated monomer containing an acid anhydride group is one having both an acid anhydride group and an unsaturated group, typified by maleic anhydride, itafonic anhydride, and the like.

Other unsaturated monomers that can be copolymerized with the carboxyl group-containing unsaturated monomer and/or the acid anhydride group-containing unsaturated monomer include the above-mentioned cyclocarbonate group-containing unsaturated monomers. Various polymerizable unsaturated monomers can, of course, be used as such.

Carboxyl group-containing polyester resins include those obtained by reacting an acid component excessively with polyhydric alcohol, or those obtained by reacting acid anhydride groups with hydroxyl group-containing polyester resins. be.

The polyester resin referred to here is not a special one, but includes polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, adipic acid, maleic acid, or dimer acid, ethylene glycol, propylene glycol, and neopentyl glycol. Alternatively, it can be obtained by condensing a polyol such as trimethylolpropane according to a known and commonly used method.

More specifically, it can be obtained by adding an acid anhydride group-containing compound such as trimellitic acid to a hydroxyl-terminated polyester obtained by reacting under conditions where the polyol component is in excess, or it can be obtained by adding an acid anhydride group-containing compound such as trimellitic acid. Examples include carboxyl group-terminated polyester resins, such as those obtained by reaction under conditions where an excess of carboxylic acid is present. Furthermore, hydroxyl groups can also be introduced by adding an epoxy compound.

In addition, examples of the carboxyl group-containing low-molecular compound referred to in the present invention include adipic acid, phthalic acid, isophthalic acid, terephthalic acid, dimer acid, and double dodecane. It is also possible to use oxycarboxylic acids such as

On the other hand, examples of low-molecular compounds containing acid anhydride groups include trimellitic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, hetacetic anhydride, imic anhydride/%imic anhydride, maleic anhydride, itaconic anhydride, and pyromellitic anhydride. Can be mentioned.

Separately, as a particularly representative compound having at least two carboxyl groups in one molecule, among various compounds such as those excavated in the earth, there are compounds that exclusively have carboxyl groups as functional groups (reactive polar groups). Needless to say, there are also other forms of the term ``group-containing''.

These compounds (C) mainly act as a crosslinking agent for the vinyl polymer (A-1) having a cyclocarbonate group or the vinyl polymer (A-2) having both a cyclocarbonate group and a carboxyl group. be.

Next, examples of the curing catalyst (B) include ring-opening catalysts of cyclocarbonate groups, and also ring-opening catalysts of epoxy groups.

Among these catalysts, the former cyclocarbonate group ring-opening catalyst is mainly important for decarbonization (decarbonation) reactions based on cyclocarbonate groups, but To mention only, tetramethylammonium bromide, trimethylbenzylammonium hydroxide, 2-hydroxypyridine, trithimelbenzylammonium methoxide, phenyltrimethylammonium chloride, phenyltrimethylammonium bromide, phenyltrimethylammonium hydrochloride. , phenyltrimethylammonium iodite, phenyltrimethylammonium tribromide, phosphocholine chloride sodium salt, stearyl ammonium bromide, tetra-n-amylammonium iodite, tetra-n-butylammonium bromide, tetra-n
-butylammonium \hydroxide, tetra-
n-butylammonium phosphate, tetra-n-decylammonium trichloride, tetraethylammonium hydroxide, tetraethylammonium tetrafluoroborate, acetylcholine bromide,
Quaternary ammonium salts such as alkyldimethylbenzylammonium chloride, benzylcholine bromide, benzyl-n-butylammonium bromide, betaine, butyryl chloride, bis(tetra-n-butylammonium) dichromate or trimethylvinylammonium bromide; allyl Triphenylphosphonium chloride, n-amyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, bromomethyltriphenylphosphonium bromide, 2-dimethylaminoethyltriphenylphosphonium bromide, ethoxycarbonylphosphonium bromide, n-heptyltriphenylphosphonium furomite , methyltriphenylphosphonium bromide, tetrakis(hydroxymethyl)phosphonium sulfate or tetraphenylphosphonium bromide,
Phosphonium salts; acid catalysts such as phosphoric acid, p-toluenesulfonic acid or dimethyl sulfuric acid; or carbonates such as calcium carbonate.

The amount of the cyclocarbonate ring-opening catalyst used is 10% by weight of the solid content of the vinyl copolymer resin described above.
A range of 0101 to 5 parts by weight is suitable for 0 parts by weight.

The amount used greatly affects the temperature during baking of the above-mentioned vinyl copolymer resin and carboxyl group-containing and/or acid anhydride group-containing compound, but especially when it is less than 0.01 part by weight. On the other hand, if the amount exceeds 5 parts by weight, the storage stability of the thermosetting resin composition will be extremely reduced, and the water resistance of the coating film will deteriorate. Both cases are unfavorable since the performance and other properties will also be significantly reduced.

Epoxy group ring-opening catalysts are then also used to promote the reaction of epoxy groups with carboxyl group-containing and/or acid anhydride group-containing compounds, respectively, resulting from the decarboxylation reaction of cyclocarbonate groups. However, as such a component, in order to advance the esterification reaction, it is most preferable to use a commonly used basic catalyst. As the above-mentioned various quaternary ammonium salts are most preferred.

Further, the combination of triphenylphosphine and the like with the quaternary ammonium salt catalyst is also effective.

The appropriate amount of the epoxy ring-opening catalyst used is up to 5 parts by weight based on 100 parts of the solid content of the vinyl copolymer resin.

The thus obtained thermosetting resin composition for powder coatings of the present invention can be used as it is as a clear coating material, or can also be used as an enamel coating material by incorporating a pigment therein.

Further, the composition of the present invention may contain various known and commonly used additives such as a leveling agent, an ultraviolet absorber, or a pigment dispersant, if necessary.

Furthermore, known and commonly used cellulose compounds, plasticizers, polyester resins, and the like may be added to the composition of the present invention.

To prepare a powder coating using the thermosetting resin composition for powder coating of the present invention, any well-known method can be adopted, but usually, various components such as suspended are mixed. Thereafter, the mixture is sufficiently melted and kneaded at about 80 to 120° C. using a melt kneader such as a heating roll or an extruder, and then pulverized after cooling.

Further, as a method for applying the powder coating, known and commonly used methods such as electrostatic spraying and fluidized dipping can be employed.

Furthermore, the object to be coated with the powder coating is usually baked in a baking oven at about 140 to 210 DEG C. to obtain the desired cured coating film.

The thermosetting resin composition for powder coatings of the present invention can be used primarily for automobile top coats or various metal materials. In particular, in fields such as acrylic resin/melamine resin paint systems, which have not yet reached the required level in terms of acid resistance, weather resistance, and coating outside markings,
Significant effects can be expected.

〔Example〕

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

Reference Example 1 [Preparation example of a vinyl copolymer having both a cyclocarbonate group and a carboxyl group in the molecule] 66.7 parts of xylene was placed in a four-way flask equipped with a thermometer, cooling tube, stirrer, and nitrogen gas introduction tube. is added, the air in the reaction vessel is replaced with nitrogen, and the mixture is heated to reflux.

A mixture of monomers and a polymerization initiator as shown in Table 1 was added thereto over a period of 4 hours, and the mixture was further kept under reflux for 1 hour. After cooling, azobisisomer was added. 0.5 part of butyronitrile is added to complete the polymerization reaction at 80°C.

By removing the solvent from the polymerization solution thus obtained, a solid desired copolymer was obtained.

Reference Examples 2 to 4 (same as above) The desired copolymers were obtained in the same manner as in Reference Example 1, except that the monomers shown in Table 1 were used.

Reference Examples 5 and 6 (Example of Preparation of Vinyl Copolymer for Control) Copolymer for control was prepared in the same manner as Reference Example 1, except that the monomers shown in Table 1 were used. Obtained union.

Examples 1 to 5 and Comparative Examples 1 and 2 Each type of cyclocarbonate group-containing vinyl copolymer obtained in Reference Examples 1 to 6 as shown in Table 2 and a curing catalyst were Further, the mixture is melt-kneaded with a pigment, an acid group-containing compound and/or a flow control agent at 90°C using a hot roll, and then cooled and pulverized, and then classified using a 150-mesh sieve. , various powder coatings were prepared.

Each powder coating was then treated with zinc phosphate,
It was applied onto a 0.8 mm thick matte steel plate using an electrostatic spray coating machine for powder coatings, and baked at 180°C for 20 minutes to obtain a cured coating.

Thereafter, the storage stability of each powder coating material and the performance of each cured coating film were evaluated and studied, as shown in Table 3.

These evaluations were conducted in the following manner.

Storage stability: After storing the powder paint in a constant temperature bath at 40°C for one month, pelletize it into 10mm x 0.5g pellets, then pelletize at 180°C. Measure the flowability after baking for 20 minutes.

Observation of degree of viscosity change A: Extremely smooth B: Fairly smooth C: Poor smoothness Erichsen value: Measured using an Erichsen tester. 11. Displayed in "m".

Weather resistance: Displayed as gloss retention rate (%) after 3,000 hours on a Sunshine Weatherometer.

〔Effect of the invention〕

As described above, the thermosetting resin compositions for powder coatings of the present invention each contain 2-oxolan-1,3-dioxolane-4-
A vinyl polymer containing a specific group called yl group and a curing catalyst for the specific group, or the vinyl polymer and curing catalyst and a compound containing a carboxyl group and/or an acid anhydride group. Compared to existing powder coatings, it not only has superior storage stability, but also improves weather resistance and film appearance, especially smoothness. It is something that can be done.

Therefore, it can be said that the thermosetting resin composition of the present invention opens up new possibilities as a powder coating.

Claims (1)

[Claims] 1. At least two 2-oxo-1,3- in one molecule
Vinyl polymer having dioxolan-4-yl group (A-
1) and a curing catalyst (B). A thermosetting resin composition for powder coatings. 2. At least one 2-oxo-1,3- in one molecule
Vinyl polymer having dioxolan-4-yl group (A-
1), a curing catalyst (B), and a compound (C) having a carboxyl group and/or an acid anhydride group in one molecule. 3. 2-oxo-1,3-dioxolane-4- described above
The yl group has the general formula ▼ There are numerical formulas, chemical formulas, tables, etc. ▼ ... [ I ] However, R1, R2 and R3 in the formula are each a hydrogen atom or carbon, which may be the same or different. It represents an alkyl group having a number of 1 to 4. The composition according to claim 1 or 2, which is represented by: 4. The compound (C) having at least two carboxyl groups and/or acid anhydride groups in one molecule is at least one type selected from the group consisting of polyester resins, vinyl copolymers, and low molecular weight compounds. is something,
A composition according to claim 2.