JPH11302569A - Spherical thermosetting powder clear coating particles, method for producing spherical thermosetting powder clear coating particles, method for forming multilayer coating film, and multilayer coating film obtained therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a clear coating powder particle having good anti-blocking properties and smoothness of a coating film obtained therefrom, and further obtaining a coating film having sufficient acid resistance. I will provide a. SOLUTION: The spherical thermosetting powder clear paint particles containing acrylic resin A and acrylic resin B, wherein (a)
(SP value of acrylic resin A)-(SP value of acrylic resin B)
(B) (T of acrylic resin A)
g)-(Tg of acrylic resin B) is 10 ° C or more, (c)
The Tg of the acrylic resin A is 40 to 100 ° C., the Tg of the acrylic resin B is 20 to 50 ° C., (d) the number average molecular weight of the acrylic resin A is 2000 to 4000, and the number average molecular weight of the acrylic resin B is 5000 to 10000; ) The ratio of the solid content weight of acrylic resin A / acrylic resin B is 5/95 to 5
0/50 spherical thermosetting powder clear coating particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing thermosetting powder clear coating particles, spherical thermosetting powder clear coating particles, a method for forming a multilayer coating film, and a multilayer coating film obtained therefrom.

[0002]

2. Description of the Related Art Powder coatings have attracted attention in recent years as environmentally friendly coatings because there is no organic solvent released into the atmosphere. Among them, a thermosetting powder coating is required from the viewpoint of weather resistance. However, in the thermosetting powder coatings so far, blocking resistance, which is one of storage stability, often becomes a problem. It is generally well known that increasing the Tg of a resin used in a powder coating improves blocking resistance.
However, since the increase in the amount leads to a decrease in the smoothness of the coating film, it has been a reality that powder coating cannot be applied to the coating of an automobile body requiring a high appearance.

In recent years, along with changes in the environment surrounding us, durability against acid rain, so-called acid resistance, has been required for coating films, particularly for clear top coats for automobiles.

[0004] In powder coatings, various curing systems have been used to improve acid resistance, but those having sufficient acid resistance have not been obtained because of the low molecular weight between crosslinks of the resulting coating films. .

On the other hand, a so-called wet method for producing powder coating particles in an aqueous medium has recently been proposed. For example, Japanese Patent Application Laid-Open No. Hei 9-100414 discloses the production of thermosetting powder coating particles having a narrow particle system distribution using a wet method, but the improvement of blocking resistance and the smoothness of a coating film are disclosed. Had not been resolved.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a spherical thermosetting powder having good blocking resistance and good smoothness of a coating film obtained therefrom, and a coating film having sufficient acid resistance can be obtained. It is intended to provide a body clear paint particle and a method for producing the same.

[0007]

The present invention relates to spherical thermosetting powder clear paint particles containing acrylic resin A and acrylic resin B, wherein (a) (SP value of acrylic resin A)
(SP value of acrylic resin B) is 0.5 to 1.5, (b)
(Tg of acrylic resin A)-(Tg of acrylic resin B)
Is 10 ° C. or more, and (c) Tg of the acrylic resin A is 40 to
00 ° C and Tg of acrylic resin B is 20 to 50 ° C,
(D) Acrylic resin A has a number average molecular weight of 2000 to 40
00 and the number average molecular weight of the acrylic resin B 5,000 to 10
000, (e) a spherical thermosetting powder clear paint particle characterized in that the ratio of the solid content weight of acrylic resin A / acrylic resin B is 5/95 to 50/50.

The present invention also provides a method for producing spherical thermosetting powder clear coating particles from a suspension obtained by adding a thermosetting resin solution to an aqueous solution containing a water-soluble polymer,
The thermosetting resin solution contains an acrylic resin A, an acrylic resin B and an organic solvent, and the acrylic resin A and the acrylic resin B are (a) (SP of the acrylic resin A).
Value)-(SP value of acrylic resin B) is 0.5 to 1.5,
(B) (Tg of acrylic resin A) − (Tg of acrylic resin B) is 10 ° C. or more, and (c) Tg of acrylic resin A is 4
0-100 ° C and Tg of acrylic resin B is 20-50
℃, (d) the number average molecular weight of the acrylic resin A is 2000
4000 and the number average molecular weight of acrylic resin B is 5,000 to 5,000.
10,000, (e) a method for producing spherical thermosetting powder clear paint particles, wherein the ratio of the solid content weight of acrylic resin A / acrylic resin B is 5/95 to 50/50. is there.

Further, the present invention provides a step of applying a base paint on an undercoated or undercoated and intermediate-coated substrate, and a step of applying a powder clear paint on the substrate coated with the base paint obtained in the above step. And a step of heating the substrate on which the base paint and the powder clear paint are applied, wherein the powder clear paint comprises the spherical thermosetting powder clear. An object of the present invention is to provide a method for forming a multilayer coating film, which is a coating particle, and a multilayer coating film obtained by the method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Spherical thermosetting powder clear coating particles The spherical thermosetting powder clear coating particles of the present invention contain an acrylic resin A and an acrylic resin B, and (a) (acrylic resin A (SP value of acrylic resin B) is 0.3 to 1.5, (b) (Tg of acrylic resin A)
(Tg of acrylic resin B) is 10 ° C. or more, (c) Tg of acrylic resin A is 40 to 100 ° C., Tg of acrylic resin B is 20 to 50 ° C., (d) Number average molecular weight of acrylic resin A is 2000 to 2000 4000 and the number average molecular weight of acrylic resin B is 5,000 to 10,000, (e) acrylic resin A /
The ratio of the solid content weight of the acrylic resin B is 5/95 to 50/5
0.

The acrylic resin A and the acrylic resin B undergo a curing reaction by heating, or when the spherical thermosetting powder clear coating particles of the present invention further contain a curing agent, this curing is performed. The agent and the acrylic resin A and / or the acrylic resin B have a property of undergoing a curing reaction by heating.

When (SP value of acrylic resin A)-(SP value of acrylic resin B) is smaller than 0.5, the blocking resistance at the time of storage is lowered, and when larger than 1.5, the cured product has a low resistance. The appearance of the coating deteriorates.

The SP value of the acrylic resin A and the acrylic resin B used in the present invention must satisfy the above relationship, but is usually 9.0 to 12.0, preferably 9.0 to 11 0.0, more preferably 9.5-11.
0. The SP value in the present invention is determined by a method well known by those skilled in the art such as a turbidity method.

On the other hand, when (Tg of acrylic resin A)-(Tg of acrylic resin B) is smaller than 10 ° C., the blocking resistance is reduced. At this time, Tg of acrylic resin A
Is 40 to 100 ° C. and the Tg of the acrylic resin B is
Is 20 to 50 ° C. Here, Tg of acrylic resin A
Is less than 40 ° C., the blocking resistance during storage decreases, and if it is more than 100 ° C., the smoothness of the coating film decreases. When the Tg of the acrylic resin B is 20 ° C. or lower, the blocking resistance during storage decreases, and when it is higher than 50 ° C., the smoothness of the coating film decreases. In the present invention, Tg is a glass transition temperature, which can be determined by a differential scanning calorimeter (DSC). In the case of an acrylic resin, the Tg is determined from the ratio of a monomer having a known Tg constituting a copolymer. , Can be obtained by simultaneous equations.

The acrylic resin A used in the present invention has a number average molecular weight of 2,000 to 4,000, and the acrylic resin B
Has a number average molecular weight of 5,000 to 10,000. If the molecular weight is lower than this, good acid resistance cannot be obtained, and if it is higher than this, the smoothness of the coating film may be reduced.

As the specific acrylic resin A and acrylic resin B, an acrylic monomer or an aromatic monomer having a functional group capable of undergoing a curing reaction and a neutral acrylic monomer or an aromatic monomer not involved in the curing reaction are used in accordance with a usual method. And copolymerized products can be used. Examples of such a monomer having a functional group that undergoes a curing reaction include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl acrylate, glycidyl acrylate, and glycidyl methacrylate. On the other hand, as the neutral monomer, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, Ethylhexyl (meth) acrylate, styrene,
Examples include methylstyrene dimer, vinyltoluene, p-chlorostyrene and the like.

The ratio of the solid content weight of the acrylic resin A / the solid content weight of the acrylic resin B contained in the spherical thermosetting powder clear coating particles of the present invention is from 5/95 to 50/50. When the ratio is less than 5/95, the blocking resistance decreases, and when the ratio is more than 50/50, the smoothness of the coating film decreases.

When the spherical thermosetting powder clear coating particles of the present invention contain a curing agent, it is preferable to use a curing agent other than melamine from the viewpoint of acid resistance. As a curing agent other than melamine, acrylic resin A
Alternatively, depending on the functional group of the acrylic resin B, those well known in the field of powder coatings can be used, but those having a melting point of 50 to 150 ° C are preferably used. 50
When the temperature is lower than 150 ° C., the blocking resistance of the obtained particles decreases, and when it is higher than 150 ° C., the smoothness of the coating film may decrease. As a specific type, it is preferable to use an aliphatic polycarboxylic acid or a blocked isocyanate from the viewpoint of acid resistance. Examples of the aliphatic polycarboxylic acid include decane dicarboxylic acid and sebacic acid.
Examples of the blocked isocyanate include “Cleran UI” (trade name, manufactured by Sumitomo Bayer Urethane Co., Ltd.). From the viewpoint of the smoothness of the obtained coating film, it is more preferable to use an aliphatic polycarboxylic acid.

In consideration of the smoothness of the coating film, the spherical thermosetting powder clear coating particles of the present invention can be used as acrylic resin A having a hydroxyl group and an epoxy group, acrylic resin B having an epoxy group, and a curing agent. It preferably contains a polyvalent carboxylic acid.

When the spherical thermosetting powder clear coating particles of the present invention contain a curing agent, the ratio of the sum of the solid contents of the acrylic resin A and the acrylic resin B / the solid content of the curing agent is as follows. 60/40 to 90/1 from the viewpoint of film physical properties and curability
A range of 0 is preferred.

The spherical thermosetting powder clear coating particles of the present invention may contain, if necessary, additives usually used in powder coatings. In addition, as additives, silicones such as dimethyl silicone and methyl silicone and surface modifiers such as acrylic oligomers, foam inhibitors such as benzoins such as benzoin and benzoin derivatives, curing accelerators (or curing catalysts), Plasticizer,
Examples include an antistatic agent, an antioxidant, a pigment dispersant, a flame retardant, a fluidity-imparting agent, a curing accelerator (or a curing catalyst) such as an amine compound, an imidazole compound, and a cationic polymerization catalyst.

The spherical thermosetting powder clear coating particles of the present invention have a volume average particle diameter of 5 to 30 μm. 5 μm
If it is smaller, the coating efficiency is reduced, and if it is larger than 30 μm, the smoothness of the coating film is reduced.

On the other hand, the particle diameter distribution standard deviation of the spherical thermosetting powder clear coating particles of the present invention is preferably 10 μm or less. If it is larger than 10 μm, coarse powder and fine powder increase,
Coating workability such as coating efficiency and transportability is reduced. The volume average particle size and the standard deviation of the particle size distribution used in the present invention can be determined by a particle size measuring device using a laser light scattering method generally used in the field of powder coatings. The spherical thermosetting powder clear coating particles of the present invention can be obtained by the production method described below.

Method for producing spherical thermosetting powder clear coating particles
Method The method for producing the spherical thermosetting powder clear coating particles of the present invention comprises a step of preparing a spherical thermosetting powder coating particle from a suspension obtained by adding a thermosetting resin solution to an aqueous solution containing a water-soluble polymer. It is a method of manufacturing.

The thermosetting resin solution used in the method for producing spherical thermosetting powder coating particles of the present invention contains acrylic resin A, acrylic resin B and an organic solvent, and may further contain a curing agent. Good. In addition, additives that are usually used in powder coatings may be included as needed.
Here, the details of the acrylic resin A, the acrylic resin B, the curing agent, the pigment, and the additive are the same as those described for the spherical thermosetting powder clear paint particles.

On the other hand, the organic solvent contained in the thermosetting resin solution used in the present invention is substantially water-immiscible, ie, has a solubility in water of 10% or less and a boiling point of less than 100 ° C. at normal pressure. A substance or a substance having an azeotropic property with water is used. Specifically, xylene, toluene,
Examples include cyclohexane and ethyl acetate.

The water-soluble polymer used in the method for producing the spherical thermosetting powder clear coating particles of the present invention is classified into two types. One is a water-soluble polymer showing no cloud point, and the other is a water-soluble polymer showing a cloud point in the range of 30 to 90 ° C.

Examples of the water-soluble polymer having no cloud point include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol having a degree of saponification of 85% or more, and aqueous solutions of ethyl cellulose, hydroxyethyl cellulose, polyethylene glycol and the like. Is used that does not exhibit the cloud point phenomenon even when the material is heated.

On the other hand, as the water-soluble polymer having a cloud point in the range of 30 to 90 ° C., polyvinyl alcohol partially saponified, partially formalized,
Polyvinyl alcohol polymers partially containing hydrophobic groups such as ethylene-vinyl alcohol copolymers, cellulose derivatives such as methyl cellulose and hydroxypropyl cellulose, polyethylene glycol alkyl ethers, and ethylene glycol propylene glycol block copolymers The aqueous solution is heated to 30 to 9
Those exhibiting a cloud point phenomenon within the range of 0 ° C are used. Further, it is also possible to add an electrolyte to the above-mentioned water-soluble polymer which does not show a cloud point by itself to give a cloud point in the range of 30 to 90 ° C. The water-soluble polymer exhibiting a cloud point within the range of 30 to 90 ° C. may be used in combination of two or more as needed.

As described below, the operation procedure and the particle size and particle size distribution of the obtained two types of water-soluble polymers depend on the case where each is used alone and the case where the two types are used in combination. It will be different.

<When a water-soluble polymer is used alone> In the production of the thermosetting clear powder coating particles of the present invention, the water-soluble polymer may be a water-soluble polymer having no cloud point or 30 to 30%.
When only one type of water-soluble polymer showing a cloud point within the range of 90 ° C. is used, the following procedure is performed.

First, an aqueous solution of a water-soluble polymer is prepared in a reaction vessel equipped with a stirrer. Next, a thermosetting resin solution containing acrylic resin A, acrylic resin B and an organic solvent is added to the aqueous solution containing the water-soluble polymer. The ratio of the solid content weight of the acrylic resin A / the solid content weight of the acrylic resin B in the thermosetting resin solution is set in the range of 5/95 to 50/50. When the ratio is less than 5/95, the blocking resistance decreases, and when the ratio is more than 50/50, the smoothness of the coating film decreases. When the thermosetting resin solution contains a curing agent, the ratio of the sum of the solid content weights of the acrylic resin A and the acrylic resin B / the solid content weight of the curing agent is 60/60 from the viewpoint of coating film properties and curability. The range of 40 to 90/10 is preferred.

The mixing ratio of the thermosetting resin solution to the aqueous solution containing the water-soluble polymer is such that the weight of the aqueous solution containing the water-soluble polymer / the weight of the solid content of the thermosetting resin solution is 0 from the viewpoint of mixing properties. It is preferably set to be 0.5 / 1 to 3/1. The suspension thus obtained is diluted with ion-exchanged water as required, and finally a suspension containing 10 to 50% by weight of a thermosetting resin solution is obtained.

The mixed liquid thus obtained is suspended by stirring with a stirrer according to the viscosity of the mixed liquid and well known to those skilled in the art to form particles. Since these particles contain an organic solvent, an operation for distilling off the organic solvent is performed.

The distillation of the organic solvent can be carried out by raising the temperature and / or the pressure. However, in consideration of the fact that the obtained particles have thermosetting properties, by reducing the pressure of the system,
It is preferable to lower the temperature at which the organic solvent is distilled off. Further, it is preferable to carry out the distillation of the organic solvent until the particles are solidified.

The solidified particles thus obtained are isolated using a conventional solid-liquid separation method such as filtration or centrifugation. This is washed with water and dried to finally obtain spherical thermosetting clear powder coating particles. The finally obtained thermosetting powder clear coating particles have a volume average particle diameter of 5 to 40 μm, preferably 5 to 30 μm.
m, more preferably 5 to 20 μm.

<When Two Types of Water-Soluble Polymers are Used> When a water-soluble polymer having no cloud point and a water-soluble polymer having a cloud point within the range of 30 to 90 ° C. are used, the present invention The method for producing thermosetting clear powder coating particles comprises the following three steps.

(1) Suspension Step The first step is to add a water-soluble polymer having no cloud point to 30 to 9
A thermosetting resin solution containing an acrylic resin A, an acrylic resin B and an organic solvent is added to an aqueous solution containing a water-soluble polymer having a cloud point in the range of 0 ° C., and suspended at a temperature lower than the cloud point. It is a process.

As a procedure in the first step, first, a water-soluble polymer having no cloud point as a dispersion stabilizer and a water-soluble polymer having a cloud point within a range of 30 to 90 ° C. are placed in a reaction vessel equipped with a stirrer. An aqueous solution containing a polymer is prepared. The ratio of the weight of the solid content of the water-soluble polymer showing no cloud point / the weight of the solid content of the water-soluble polymer showing the cloud point in the range of 30 to 90 ° C. is 99/1.
It is preferably in the range of 10 to 90. Outside of this range, it may be difficult to control the particle size of the secondary particles. The concentration of the water-soluble polymer in the aqueous solution is preferably from 0.02 to 20% by weight from the viewpoint of miscibility.

Next, a thermosetting resin solution containing acrylic resin A, acrylic resin B and an organic solvent is added to the aqueous solution containing the water-soluble polymer. The ratio of the acrylic resin A and the acrylic resin B in the thermosetting resin solution and the ratio in the case of including the curing agent are the same as those described in <When the water-soluble polymer is used alone>.

The mixing ratio of the thermosetting resin solution to the aqueous solution containing the water-soluble polymer is such that the mixing ratio of the weight of the aqueous solution containing the water-soluble polymer / the weight of the solid content of the thermosetting resin solution is 0 from the viewpoint of miscibility. It is preferably set to be 0.5 / 1 to 3/1.

The mixture thus obtained is suspended by stirring at a temperature lower than the cloud point. If the thermosetting resin solution cannot be suspended in the aqueous solution containing the above two types of water-soluble polymers due to the components contained in the thermosetting resin solution, only the water-soluble polymer that does not show a cloud point or the surface activity thereof After preparing a suspension using an aqueous solution containing the agent, a water-soluble polymer exhibiting a cloud point within the range of 30 to 90 ° C. may be added. The suspension thus obtained is diluted with ion-exchanged water as required, and finally a suspension containing 10 to 50% by weight of a thermosetting resin solution is obtained.

(2) Step of Obtaining Primary Particles The second step is a step of raising the temperature of the suspension obtained in the first step below the cloud point to obtain primary particles. The volume average particle diameter of the primary particles obtained in the second step is 1
It is preferably 5 μm or less, more preferably 10 μm or less. The particle size of the primary particles can be determined by sampling and measuring the particle size.

(3) Step of Obtaining Secondary Particles The third step is a step of raising the temperature of the suspension obtained in the second step at a temperature higher than the above cloud point to obtain secondary particles.

In this step, the temperature of the suspension is raised to a temperature higher than the above cloud point. This temperature depends on the type of the water-soluble polymer used and the properties of the resin solution containing the thermosetting resin composition.

When the temperature of the suspension is raised to a temperature equal to or higher than the above cloud point, the primary particles are agglomerated with the elapse of time as the temperature rises to form secondary particles. The secondary particles are sampled from the suspension to measure the particle size, and the third step can be completed when the target particle size is reached.

In order to obtain the desired particle size, other than the method of adjusting the weight ratio of the water-soluble polymer having no cloud point and the water-soluble polymer having a cloud point within the range of 30 to 90 ° C. When the secondary particles are formed to a desired particle size, a method of cooling the suspension to a temperature lower than the cloud point of the water-soluble polymer and stopping the growth of the secondary particles due to aggregation can be used. .

Further, due to the properties of the obtained spherical thermosetting powder coating particles, it is preferable to evaporate the organic solvent out of the system by raising the temperature. This operation can be performed in the above-described second or third step. The details of the distillation of the organic solvent are the same as those described in <When the water-soluble polymer is used alone>. When this is performed in the second step, the amount of the organic solvent in the primary particles is 0.01 to 3
It is preferably 0% by weight, preferably 0.01 to 10% by weight, more preferably 0.01 to 5% by weight.

The secondary particles thus obtained are isolated using a conventional solid-liquid separation method such as filtration or centrifugation. By washing and drying this, thermosetting clear powder coating particles can be finally obtained.

The volume average particle diameter of the obtained thermosetting clear powder coating particles is 5 to 40 μm, preferably 5 to 30 μm.
m, more preferably 5 to 20 μm. When two types of water-soluble polymers are used, the standard deviation of the particle size distribution can be made 10 μm or less as compared with the case where only one type is used.

The method for forming a multilayer coating according to the present invention comprises a step of applying a base coating on an undercoat or a substrate on which an undercoat and an intermediate coating have been applied; A step of applying the spherical thermosetting powder clear coating particles of the present invention on the coated substrate, and a step of heating the base coating and the substrate coated with the spherical thermosetting powder clear coating particles. This is a method for forming a multilayer coating film.

The substrate used in the method for forming a multilayer coating film of the present invention has been subjected to an undercoat or an undercoat and an intermediate coat. Substrates include plastic and iron plates,
Steel plates, aluminum plates, and the like can be given. As the undercoat paint and the intermediate paint, known paints such as an electrodeposition paint and a chipping primer can be used.

The base paint is not particularly limited, such as a solvent-based paint or an aqueous paint, but it is preferable to use an aqueous paint from the viewpoint of environmental protection. The base paint is applied to the substrate on which the above-mentioned undercoating or undercoating and intermediate coating has been performed by an electrostatic coating machine with a coating film thickness of 10 to 20 μm.

After preliminarily heating the substrate coated with the base coating at 60 to 100 ° C. for about 5 to 10 minutes by IR or hot air, the thermosetting powder coating particles of the present invention are coated by electrostatic coating or the like. After coating with a film thickness of 40 to 80 μm, it is cured by baking. Baking temperature is 90 ~
The temperature is 250 ° C, preferably 100 to 200 ° C, more preferably 120 to 180 ° C. The baking time can be appropriately adjusted depending on the baking temperature. Thus, a multilayer coating film can be obtained by the multilayer coating film forming method of the present invention.

[0055]

EXAMPLES Production Example 1 Production of Resin A-1 63 parts by weight of xylene was charged into a reaction vessel equipped with a stirrer, a temperature controller and a reflux tube, heated to 130 ° C., and placed under a nitrogen atmosphere for 3 hours. The following mixture was added dropwise.

Glycidyl methacrylate 40 parts by weight Styrene 20 parts by weight Methyl methacrylate 35 parts by weight 2-hydroxyethyl methacrylate 5 parts by weight t-butyl peroctoate 7 parts by weight

After keeping the temperature for 3 hours after dropping, the mixture was cooled to room temperature to obtain a resin A-1 solution (solid content concentration: 60% by weight). Further, a part of the resin A-1 solution was heated under reduced pressure to distill off xylene, thereby obtaining a resin A-1. T of the obtained resin A-1
g was measured by DSC (differential scanning calorimeter).
0 ° C, and the SP value was measured by the turbidity method.
0.9. The number average molecular weight measured by GPC (gel permeation chromatography) is 3500
Met.

Production Example 2 Production of Resin B-1 63 parts by weight of xylene were charged into the same reaction solution as in Production Example 1,
, And the following mixture was added dropwise over 3 hours under a nitrogen atmosphere.

Glycidyl methacrylate 40 parts by weight Styrene 20 parts by weight Methyl methacrylate 20 parts by weight 2-ethylhexyl methacrylate 20 parts by weight t-butyl peroctoate 2 parts by weight

After keeping the temperature for 3 hours after dropping, the mixture was cooled to room temperature to obtain a resin B-1 solution (solid content concentration: 60% by weight). Further, a part of the resin B-1 solution was heated under reduced pressure to distill off xylene, thereby obtaining a resin B-1. T of the obtained resin B-1
g was measured by DSC (differential scanning calorimeter).
It was 5 ° C and the SP value was measured by a turbidity method.
It was 8. The number average molecular weight measured by GPC (gel permeation chromatography) was 8,500.

Production Examples 3 to 6 Resins A-2 to 3, B-2 to
Production Example 3 of Production Example 1 and 2 and the same method 3 Production Example 6
(Resins A-2 and A-3, Resins B-2 and B-3)
I got With respect to each of the obtained resins, special values of the resins were measured in the same manner as in Production Example 1. Table 1 shows the composition and special values of each resin.

[0062]

[Table 1]

Example 1 Production of Spherical Thermosetting Powder Clear Coating Particles Resin A-1 solution (solid content concentration: 60% by weight) 14.7 parts by weight Resin B-1 solution (solid content concentration: 60% by weight) 0 parts by weight 1,10-decanedicarboxylic acid 12.7 parts by weight YF-1939 0.1 parts by weight (polysiloxane surface conditioner manufactured by Toshiba Silicone Co., Ltd.) Benzoin 0.3 parts by weight UV absorber 1.2 parts by weight Hindered amine 1.0 part by weight of a system antioxidant The above ingredients were mixed in a sand grind mill to prepare a thermosetting resin solution.

Next, the above-mentioned thermosetting resin solution was added to an aqueous polymer solution comprising 8 parts by weight of Gohsenol GH-20 (polyvinyl alcohol manufactured by Nippon Synthetic Chemical Company, saponification degree: 88%) and 90 parts by weight of ion-exchanged water. Was. A suspension was prepared by mixing the obtained mixture using a homogenizer. Subsequently, 300 parts by weight of ion-exchanged water was added to the obtained suspension to dilute it, and this was transferred to a container equipped with a stirrer, a temperature controller, a reflux tube, and a decompression device.

After the pressure of this suspension was reduced to 140 Torr, the temperature was raised to 60 ° C., and the solvent in the dispersed phase was completely distilled out of the system. After cooling the suspension, the particles obtained by suction filtration were dried at 30 ° C. using a vacuum dryer to obtain spherical thermosetting powder clear coating particles. When the particle diameter of the obtained powder coating particles was measured using a Coulter counter (manufactured by Coulter Electronics Co., Ltd.), the volume average particle diameter was 10.1 μm and the number average particle diameter was 3.5 μm.

Example 2 Spherical thermosetting powder clear paint particles
The thermosetting resin solution produced in Example 1 was prepared using Gohsenol GH-20 (polyvinyl alcohol, manufactured by Nippon Synthetic Chemical Co., Ltd.).
6% by weight, Gohsenol KL-05
(Polyvinyl alcohol manufactured by Nippon Synthetic Chemical Company, saponification degree 8
(0%) 3 parts by weight, 1 part by weight of hydroxypropyl cellulose, and 90 parts by weight of ion-exchanged water. The obtained mixture was mixed using a homogenizer to prepare a suspension having a weight average particle size of 4.2 μm. Subsequently, 300 parts by weight of ion-exchanged water was added to the obtained suspension to dilute it, and this was transferred to a container equipped with a stirrer, a temperature controller, a reflux tube, and a decompression device.

After the pressure of this suspension was reduced to 140 Torr, the temperature was raised to 60 ° C., and the solvent in the dispersed phase was completely distilled off. After cooling the suspension, the particles obtained by suction filtration were dried at 30 ° C. using a vacuum dryer to obtain spherical thermosetting powder clear coating particles. The particle diameter of the obtained powder coating particles was measured by the same method as in Example 1, and it was found that the volume average particle diameter was 13.3 μm and the number average particle diameter was 10.5 μm.

Example 3 Spherical thermosetting powder clear paint particles
Instead of manufacturing the resin A-1 solution of the child, except for using the resin A-2 solution corresponding to the same solids weight resin A-1 solution, producing a thermosetting resin solution in the same manner as in Example 1 did. Using this thermosetting resin solution, spherical thermosetting powder clear paint particles were produced in the same manner as in Example 2. The volume average particle size of the obtained powder coating particles was 12.9 μm, and the number average particle size was 7.6 μm.

Comparative Example 1 Thermosetting powder not included in the present invention
Production of Body Coating Particles Thermosetting resin composition was prepared in the same manner as in Example 1 except that a resin A-3 solution corresponding to the same solid content weight as the resin A-1 solution was used instead of the resin A-1 solution. Was prepared. Using this thermosetting resin composition solution, thermosetting powder coating particles were prepared in the same manner as in Example 2. When the particle diameter of the obtained powder coating particles was measured by the same method as in Example 1, the volume average particle diameter was 14.0 μm and the number average particle diameter was 10.2 μm.

Comparative Example 2 Thermosetting powder not included in the present invention
Production of Body Coating Particles Thermosetting resin solution in the same manner as in Example 1 except that a resin B-2 solution corresponding to the same solid content weight as the resin B-1 solution is used instead of the resin B-1 solution. Was manufactured. Using this thermosetting resin solution, spherical thermosetting powder coating particles were produced in the same manner as in Example 2. The particle size of the obtained powder coating particles was measured by the same method as in Example 1.
The volume average particle diameter is 15.7 μm, and the number average particle diameter is 9.
It was 8 μm.

Comparative Example 3 Production of thermosetting powder coating particles not included in the present invention 8.2 parts by weight of resin A-1 solution (solid content concentration 60% by weight) Resin B-3 solution (solid content concentration 60 weight%) %) 76.5 parts by weight 1,10-decanedicarboxylic acid 12.7 parts by weight YF-1939 0.1 parts by weight (polysiloxane surface conditioner manufactured by Toshiba Silicone Co., Ltd.) Benzoin 0.3 parts by weight UV absorber 1. 2 parts by weight Hindered amine antioxidant 1.0 part by weight The above ingredients were mixed using a Henschel mixer to prepare a thermosetting composition.

Next, 5 parts by weight of Gohsenol GH-20 (polyvinyl alcohol manufactured by Nippon Synthetic Chemical Company, saponification degree: 88%) and 4 parts by weight of Gohsenol KL-05 (polyvinyl alcohol manufactured by Nippon Synthetic Chemical Company, 80% saponification degree) Parts and 2 parts by weight of hydroxypropylcellulose, ion-exchanged water 90
A polymer aqueous solution consisting of parts by weight was added to the thermosetting resin solution. A suspension was prepared by mixing the obtained mixture using a homogenizer. Subsequently, 300 parts by weight of ion-exchanged water was added to the obtained suspension to dilute it, and this was transferred to a container equipped with a stirrer, a temperature controller, a reflux tube, and a decompression device.

After the pressure of this suspension was reduced to 140 Torr, the temperature was raised to 60 ° C., and the solvent in the dispersed phase was completely distilled off.
After cooling the suspension, the particles obtained by suction filtration were dried at 30 ° C. using a vacuum dryer to obtain spherical thermosetting powder coating particles. When the particle diameter of the obtained powder coating particles was measured by the same method as in Example 1, the volume average particle diameter was 1
2.3 μm, and the number average particle diameter was 8.4 μm.

Comparative Example 4 Production of Thermosetting Powder Coating Particles Not Included in the Present Invention Resin A-1 Solution (Solid Content Concentration: 60% by Weight) 9.1 Parts by Weight Resin B-1 Solution (Solid Content Concentration: 60% by Weight) %) 37.2 parts by weight 1,10-decanedicarboxylic acid 12.7 parts by weight Polysiloxane-based surface conditioner 0.1 part by weight (YF-1939, manufactured by Toshiba Silicone Co., Ltd.) Benzoin 0.3 part by weight UV absorber 1 .2 parts by weight Hindered amine-based antioxidant 1.0 part by weight The above components were mixed using a Henschel mixer to prepare a thermosetting composition.

The resulting mixture was melt-kneaded and dispersed using a buscon kneader, crushed again with a Henschel mixer, crushed with a hammer mill, and then finely crushed with a jet mill to obtain thermosetting powder coating particles. Was prepared. The particle diameter of the obtained powder coating particles was measured by the same method as in Example 1, and it was found that the volume average particle diameter was 13 μm and the number average particle diameter was 2.8 μm.

Example 4 Production of Spherical Thermosetting Powder Clear Coating Particles Resin A-1 solution (solid content concentration: 60% by weight) 8.2 parts by weight Resin B-1 solution (solid content concentration: 60% by weight) 5 parts by weight 1,10-decanedicarboxylic acid 12.7 parts by weight YF-1939 0.1 parts by weight (polysiloxane surface conditioner manufactured by Toshiba Silicone Co., Ltd.) Benzoin 0.3 parts by weight UV absorber 1.2 parts by weight Hindered amine 1.0 part by weight of a system antioxidant The above ingredients were mixed in a sand grind mill to prepare a thermosetting resin solution.

Next, 5 parts by weight of Gohsenol GH-20 (polyvinyl alcohol manufactured by Nippon Synthetic Chemical Company, saponification degree: 88%) and 4 parts by weight of Gohsenol KL-05 (polyvinyl alcohol manufactured by Nippon Synthetic Chemical Company, 80% saponification degree) Parts and 2 parts by weight of hydroxypropylcellulose, ion-exchanged water 90
A polymer aqueous solution consisting of parts by weight was added to the thermosetting resin solution. A suspension was prepared by mixing the obtained mixture using a homogenizer. Subsequently, 300 parts by weight of ion-exchanged water was added to the obtained suspension to dilute it, and this was transferred to a container equipped with a stirrer, a temperature controller, a reflux tube, and a decompression device.

After the pressure of this suspension was reduced to 140 Torr, the temperature was raised to 60 ° C., and the solvent in the dispersed phase was completely distilled off.
After cooling the suspension, the particles obtained by suction filtration were dried at 30 ° C. using a vacuum dryer to obtain spherical thermosetting powder coating particles. When the particle diameter of the obtained powder coating particles was measured by the same method as in Example 1, the volume average particle diameter was 1
2.3 μm and the number average particle diameter was 8.4 μm.

Comparative Example 5 Production of thermosetting powder coating particles not included in the present invention Resin B-1 solution (solid content concentration: 60% by weight) 84.7 parts by weight 1,10-decanedicarboxylic acid 12.7 parts by weight Part YF-1939 0.1 part by weight (polysiloxane surface modifier manufactured by Toshiba Silicone Co., Ltd.) Benzoin 0.3 part by weight UV absorber 1.2 part by weight Hindered amine antioxidant 1.0 part by weight The mixture was mixed with a sand grind mill to prepare a thermosetting resin solution.

Next, 6 parts by weight of Gohsenol GH-20 (polyvinyl alcohol, manufactured by Nippon Synthetic Chemical Company, saponification degree: 88%) and 3 parts by weight of Gohsenol KL-05 (polyvinyl alcohol, manufactured by Nippon Synthetic Chemical Company, 80% saponification degree) Parts and 1 part by weight of hydroxypropylcellulose, ion-exchanged water 90
A polymer aqueous solution consisting of parts by weight was added to the thermosetting resin solution. A suspension was prepared by mixing the obtained mixture using a homogenizer. Subsequently, 300 parts by weight of ion-exchanged water was added to the obtained suspension to dilute it, and this was transferred to a container equipped with a stirrer, a temperature controller, a reflux tube, and a decompression device.

After the pressure of this suspension was reduced to 140 Torr, the temperature was raised to 60 ° C., and the solvent in the dispersed phase was completely distilled off.
After cooling the suspension, the particles obtained by suction filtration were dried at 30 ° C. using a vacuum dryer to obtain spherical thermosetting powder coating particles. When the particle size of the obtained spherical powder coating particles was measured by the same method as in Example 1, the volume uniform particle size was 1
The number average particle diameter was 5.1 μm and the number average particle diameter was 9.8 μm.

Comparative Example 6 Production of Thermosetting Powder Coating Particles Not Included in the Present Invention Resin A-1 solution (solid content concentration 60% by weight) 44.7 parts by weight Resin B-1 solution (solid content concentration 60% by weight) %) 40.0 parts by weight 1,10-decanedicarboxylic acid 12.7 parts by weight Polysiloxane surface conditioner 0.1 part by weight (YF-1939, manufactured by Toshiba Silicone Co., Ltd.) Benzoin 0.3 part by weight UV absorber 1 .2 parts by weight Hindered amine antioxidant 1.0 part by weight The above components were mixed in a sand grind mill to prepare a thermosetting resin solution.

Next, thermosetting powder coating particles were prepared in the same manner as in Example 1 using the obtained thermosetting composition solution. The particle size of the obtained powder coating particles was measured by the same method as in Example 1 to find that the volume average particle size was 12.4 μm.
m, the number average particle diameter was 8.5 μm.

Evaluation Test The thermosetting powder coating particles obtained in Examples 1 to 4 and Comparative Examples 1 to 6 were evaluated for the following items. Table 2 shows the results.

1. Smoothness 1) Smoothness of coating film on iron plate Thermosetting powder coating particles are applied to iron plate by electrostatic coating,
Baking was performed at 145 ° C. for 25 minutes to form a coating film having a thickness of 50 μm. The appearance of the obtained coating film was evaluated by an NSIC value (%) measured by a mapping sharpness measuring device (manufactured by Suga Test Instruments Co., Ltd.).
70% was accepted.

2) Smoothness on aqueous base An aqueous metallic base (manufactured by Nippon Paint Co., Ltd., trade name: “Super Rack M260 Silver”) was placed on the intermediate-coated substrate so that the dry film thickness became 10 to 20 μm. It was electrocoated and preheated in a hot air drying oven at 80 ° C. for 10 minutes. After cooling the substrate to room temperature, thermosetting powder coating particles were electrostatically coated to a thickness of 50 μm and baked in a hot air drying oven at 145 ° C. for 25 minutes. After the completion of baking, the substrate was taken out, and when the substrate temperature reached room temperature, the smoothness of the obtained coating film was measured by an NSIC value (%) measured by a mapping sharpness measuring device (manufactured by Suga Test Instruments Co., Ltd.). The evaluation was made, and 65% or more was regarded as a pass.

The intermediate-coated substrate was obtained by coating a galvanized steel sheet treated with zinc phosphate with an electrodeposition paint for automobiles (trade name “Power Top U-50” manufactured by Nippon Paint Co., Ltd.) to a dry film thickness of about 25 μm. After baking at 160 ° C. for 30 minutes, an intermediate coating (Nippon Paint Co., Ltd., trade name “Olga P-2”) is electrostatically coated to a dry film thickness of about 40 μm. Then, it was manufactured by baking at 140 ° C. for 30 minutes.

2. Blocking Resistance The thermosetting powder coating particles after storage at 30 ° C. for 2 months in an incubator were sieved using a vibrating sieve, and the coating passed 95% or more through 150 mesh was accepted.

3. For the thermosetting powder coating particles stored at 30 ° C. for 2 months, the rate of change of the weight average molecular weight was evaluated by GPC, and the smoothness of the coating film on the iron plate was evaluated. N
If the SIC value did not decrease by 5% or more, it was judged as acceptable.

4. Evaluation of crosslink density of coating film From a coating film having a thickness of 50 μm obtained by baking thermosetting powder coating particles at 145 ° C. for 25 minutes, a width of 5 mm × length of 20
A free film having a size of 11 mm was prepared using a forced stretching vibration type viscoelasticity measuring device (trade name “Vibron DDV-II” manufactured by Toyo Baldwin Co., Ltd.).
The crosslink density of the coating film was measured under the conditions of ° C / min.

5. Acid Resistance Test A polyethylene ring having a diameter of 2 cm to 3 cm was fixed on a coating film formed in the same manner as in the above-described evaluation of smoothness on an iron plate, and 2 ml of a 1 / 10N sulfuric acid aqueous solution was dropped into the opening, and 20 g After standing for 24 hours at ± 2 ° C., an effective humidity of 75% and no wind, the ring was removed, the coating film was washed with air and dried, and the acid resistance was visually evaluated based on the following evaluation criteria.

Evaluation criteria ○: Traces are hardly visible △: Traces are visible ×: Traces are visible, and the coating film is significantly discolored

[0093]

[Table 2]

[0094]

Since the spherical thermosetting powder clear coating particles of the present invention are synthesized in an aqueous medium using two kinds of acrylic resins having specific special values, they have good blocking resistance. Besides, the smoothness of the coating film obtained by using this is good, and it has a sufficient acid resistance.

It is considered that this may be because the particles obtained by the method for producing spherical thermosetting powder clear coating particles of the present invention have the following structure. That is, in the outer shell of the particles that are in contact with the dispersion medium water,
It is considered that the concentration of the acrylic resin A having a higher SP value than that of the acrylic resin B is higher than the concentration of the acrylic resin B. As a result, it is expected that the outer shell of the spherical thermosetting powder clear coating particles of the present invention has a higher Tg than the inner shell, thereby improving the blocking resistance. On the other hand, the Tg of the spherical thermosetting powder clear coating particles as a whole is naturally lower than the Tg of the outer shell, and thus it is considered that the smoothness of the coating film can be maintained. Further, since a resin having a higher molecular weight than that of a normal powder coating is used, a coating film having excellent acid resistance can be obtained.

Furthermore, since the spherical thermosetting powder clear coating particles of the present invention are produced in an aqueous medium, less heat is applied to the powder coating raw material during production than in the conventionally well-known melt-kneading method. Therefore, the solid phase resistance is also excellent. Also,
The spherical thermosetting powder clear coating particles of the present invention have a spherical shape and a uniform particle size distribution, so that the amount of fine powder is extremely small, and the recovered powder can be used similarly to the new coating material. It is also excellent in coating workability such as transportability and coating efficiency. In addition, even when coated with a thin film, a coating film having a good appearance can be obtained.

Since the method for forming a multilayer coating film of the present invention uses a powder coating material, it is possible to reduce the amount of solvent used, especially when an aqueous coating is used as the base coating material. Is big.

The multilayer coating film obtained by the method for forming a multilayer coating film of the present invention is excellent in the smoothness of the coating film, so that it can be applied to an automobile top coat requiring a high appearance. it can.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 133/06 C09D 133/06 163/00 163/00

Claims (11)

[Claims] 1. Spherical thermosetting powder clear paint particles containing acrylic resin A and acrylic resin B, wherein (a) (SP value of acrylic resin A)-(acrylic resin B)
(SP value of acrylic resin A)-0.5 to 1.5, (b) (Tg of acrylic resin A)-(Tg of acrylic resin B) is 10 ° C or more, (c) Tg of acrylic resin A is 40 to 100 ° C and The Tg of the acrylic resin B is 20 to 50 ° C., (d) the number average molecular weight of the acrylic resin A is 2000 to 40
00 and the number average molecular weight of the acrylic resin B 5,000 to 10
(E) spherical thermosetting powder clear paint particles, characterized in that the ratio of the solid content weight of acrylic resin A / acrylic resin B is 5/95 to 50/50. 2. A volume average particle size of 5 to 30 μm.
The spherical thermosetting powder clear coating particles according to claim 1. 3. The spherical thermosetting powder clear coating particles according to claim 1, wherein the standard deviation of the particle size distribution is 10 μm or less. 4. The thermosetting powder clear coating particles according to claim 1, further comprising a curing agent. 5. The thermosetting powder clear coating particles according to claim 4, wherein the acrylic resin A and the acrylic resin B have an epoxy group, and the curing agent is a polycarboxylic acid. 6. A method for producing spherical thermosetting powder clear coating particles from a suspension obtained by adding a thermosetting resin solution to an aqueous solution containing a water-soluble polymer, wherein The resin solution contains an acrylic resin A, an acrylic resin B, and an organic solvent, and the acrylic resin A and the acrylic resin B are: (a) (SP value of the acrylic resin A) − (acrylic resin B)
(SP value of acrylic resin A)-0.5 to 1.5, (b) (Tg of acrylic resin A)-(Tg of acrylic resin B) is 10 ° C or more, (c) Tg of acrylic resin A is 40 to 100 ° C and The Tg of the acrylic resin B is 20 to 50 ° C., (d) the number average molecular weight of the acrylic resin A is 2000 to 40
00 and the number average molecular weight of the acrylic resin B 5,000 to 10
(E) A method for producing spherical thermosetting powder clear paint particles, wherein the ratio of the solid content weight of acrylic resin A / acrylic resin B is 5/95 to 50/50. 7. The method for producing spherical thermosetting powder clear paint particles according to claim 6, wherein the thermosetting resin solution further contains a curing agent. 8. The water-soluble polymer is a mixture of a water-soluble polymer having no cloud point and a water-soluble polymer having a cloud point in the range of 30 to 90 ° C., A step of suspending the liquid at a temperature lower than the cloud point; (2) a step of raising the temperature of the suspension obtained in the first step at a temperature lower than the cloud point to obtain primary particles; The spherical thermosetting powder clear according to claim 6 or 7, further comprising a step of raising the temperature of the suspension obtained in the step (2) above the cloud point to obtain secondary particles. Method for producing paint particles. 9. The method for producing spherical thermosetting powder clear coating particles according to claim 8, wherein in the second step or the third step, the organic solvent is distilled out of the system. . 10. A step of applying a base paint on a substrate on which an undercoat or an undercoat and an intermediate coat have been applied, on the substrate on which the base paint obtained in the above step has been applied,
2. A method for forming a multilayer coating film comprising a step of applying a powder clear paint, and a step of heating a substrate to which the base paint and the powder clear paint are applied, wherein the powder clear paint is used. 5. A method for forming a multi-layer coating film comprising the spherical thermosetting powder clear coating particles according to any one of the above-mentioned items. 11. A multilayer coating film obtained by the method for forming a multilayer coating film according to claim 10.