JPH0352969A - Matte powder coating - Google Patents

Abstract

PURPOSE:To obtain a matte powder coating, capable of providing films excellent in smoothness, water, heat and impact resistance and adhesion to metals and suitable for household appliances, building materials, etc., by blending specific two kinds of polyester resins in a prescribed proportion and further adding a curing agent thereto. CONSTITUTION:The objective coating obtained by blending (A) a polyester prepared by polycondensing (i) a diol component containing 5-100wt.% 2-butyl-2- ethyl-1,3-propanediol and/or 2,2-diethyl-1,3-propanediol and (ii) a carboxylic acid component consisting essentially of terephthalic acid and/or isophthalic acid as principal components with (B) a polyester composed of isophthalic acid and trimethylolpropane or a component consisting essentially thereof without substantially gelling and (C) a curing agent, such as a blocked isocyanate, at (30:70)-(85:15) blending weight ratio of the aforementioned components (A) to (B).

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a matte coating film made of polyester resin, and a matte powder that has excellent adhesion to metal, water resistance, heat resistance, and impact resistance. It concerns body paint.

(Conventional technology) Powder coatings began to be used in Japan in 1973-1973.
Around 8 years old. At that time, it was put to practical use in electrical equipment, kitchen equipment, fire extinguishers, fences, maritime containers, etc., and gradually came to be used in the home appliance industry and automobile exterior panels.

Powder coatings can be broadly classified into thermosetting resin powder coatings and thermoplastic resin powder coatings, depending on the characteristics of the synthetic resin used as the raw material. The resin used in thermosetting resin powder coatings is
These include epoxy resin, acrylic resin, polyester resin, and polyurethane resin. The resin used in thermoplastic resin powder coatings is vinyl chloride resin, and other materials such as polyamide and polyester are also used.

Powder coatings are currently used in many fields, including home appliances, automobiles, and building materials, but there are cases in which the painted surface is required to be glossy from an aesthetic point of view, and in some cases, matte or semi-matte is required. may be done. Conventionally, methods for preparing such matte powder coating materials include adding a large amount of coarse pigment, or dry blending two types of powder coatings: polyester powder coating and acrylic powder coating. A method (Japanese Patent Publication No. 61-19688) and a powder coating containing polyester containing neopentyl glycol (Japanese Patent Application Laid-Open Nos. 63-154771 and 58-8429) are known.

(Problems to be Solved by the Invention) However, when a large amount of coarse pigment is added, there is a problem that the smoothness and mechanical strength of the coating film decrease. In addition, the method of dry blending two types of powder coatings does not allow a matte coating to be obtained in one step, increases the coating manufacturing cost, and has problems such as changes in the blending ratio.

In addition, polyester using neopentyl glycol,
Although it was possible to make it into a one-step paint and the problem of blending ratio was solved, it still cannot be said to be sufficient in terms of water resistance, heat resistance, adhesion to metals, and impact resistance.

(Means for solving the problem) As a result of intensive research focusing on this point, the present inventors found that
By blending a specific polyester resin, ti! has excellent smoothness, water resistance, heat resistance, adhesion to metals, and impact resistance. ! It was discovered that a matte powder coating that forms a film can be easily obtained, leading to the present invention.

That is, the present invention provides 2-butyl-2-ethyl-1.3
-propanediol or 2,2-diethyl-1,3-
A polyester (A) which is polymerized with a diol component containing 5 to 100 fIffi% of at least one diol selected from propanediol and at least one carboxylic acid component selected from terephthalic acid or isophthalic acid as main components; Substantially non-gelled polyester (B) consisting of inftanoleic acid and trimethylolpropane or components mainly composed of these, and a curing agent (C)
The present invention relates to a matte powder coating in which the weight ratio of component (A) to component (B) is 30:70 to 85:15.

The glycol component constituting the polyester (A) is at least one diol selected from 2-butyl-2-ethyl-1,3-propanediol or 2,2-diethyl-1,3-propanediol. . In addition to this diol, other glycols such as ethylene glycol, diethylene glycol, 1.
2-propanediol, 1,3-propanediol,
Neopentyl glycol, 1,4-butanediol, 1
, 5-benzene diol, 1,8-hexane diol,
2, 2. Aliphatic glycols such as 4-}limethyl-1,3-pentanediol, glycerin,
A small amount of trivalent or higher polyol such as ester erythritol may be included. The carboxylic acid component is mainly composed of at least one carboxylic acid component selected from terephthalic acid or isophthalic acid. 6-
Other aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, adipic acid, bimelic acid, suberic acid, azelaic acid, cepacic acid, nonamethylene dicarboxylic acid, decamethylene dicarboxylic acid, undecamethylene dicarboxylic acid, dodecamethylene dicarboxylic acid , aliphatic dicarboxylic acids such as tridecamethylene dicarboxylic acid and tetradecamethylene dicanolebonic acid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and in some cases trimellitic acid and pyromellitic acid. An aromatic carboxylic acid having a valence of 3 or more can be used as a copolymerization component in an amount as required.

The carboxylic acid component of the polyester (B) is mainly composed of isophthalic acid, but if necessary, other carboxylic acids such as terephthalic acid, other aromatic dicarboxylic acids such as 2,6-naphthalene dicarboxylic acid, adivic acid, Fats such as bimelic acid, suberic acid, azelaic acid, sepacic acid, nonamethylene dicarboxylic acid, decamethylene dicanolebonic acid, undecamethylene dicarboxylic acid, dodecamethylene dicarboxylic acid, tridecamethylene dicarboxylic acid, tetradecamethylene dicarboxylic acid group dicarboxylic acids, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid,
In some cases, trivalent or higher aromatic carboxylic acids such as trimellitic acid and biromellitic acid may be used as a copolymerization component in an amount as required. In addition, the glycol component is mainly trimethylolpropane,
If necessary, other polyhydric alcohols such as ethylene glycol, diethylene glycol, 1. 2-propanediol, 1. 3-propanediol, neopentyl glyconol, 1. 4-butanediol, 1
．． 5-pentanediol, 1. 6-hexanediol, 2. 2. A small amount of aliphatic glycols such as 4-}trimethyl-1,3-pentanediol and trivalent or higher valent polyols such as glycerin and pentaerythritol may also be included.

The polyester (B) needs to be a polyester that is not substantially gelled. The term "substantially non-gelled polyester" as used herein refers to polyester that can be pulverized with a general pulverizer and has fluidity when melted. If it is substantially gelled, it is difficult to make it into a paint.
Also, when it is formed into a coating, it cannot be made into a uniform surface.

In the present invention, the molecular weight of polyester (A) is 500
A range of 20,000 to 20,000 is desirable. If it is less than 500, the mechanical strength of the coating film tends to decrease or the matting effect is insufficient, and if it exceeds 20,000, large irregularities occur on the surface of the coating film and the smoothness decreases. Tend.

Furthermore, the softening points of polyester (A) and polyester (B) are preferably in the range of 60 to 150°C. If the softening point is less than 50°C, the powdered resin tends to condense and solidify, and the blocking resistance tends to be poor.
If it exceeds 0°C, the kneading temperature will be increased, and the reaction with the curing agent will proceed during the coating process, resulting in a tendency for the smoothness and mechanical strength of the coating film to decrease.

In the polyester of the matte powder coating of the present invention, the weight ratio of polyester (A) to polyester (B) is 30:70 to 85:15, preferably 40:
60 to 20:80.

If the blending ratio is outside this range, the matting effect will not be sufficient.

After performing a known esterification reaction or transesterification reaction using the above carboxylic acid and/or its alkyl ester and glycol as raw materials, a polycondensation reaction is performed as necessary to prepare polyester (A) and polyester (B). can do.

Examples of the ester-forming derivatives of the carboxylic acids include lower alkyl esters (eg, methyl esters), phenyl esters, anhydrides, and halides of dicarboxylic acids, with lower alkyl esters being particularly preferred. Typical examples of these include dimethyl terephthalate, dimethyl adibate, and the like.

As the curing agent (C), inocyanate compounds, melamine compounds, anhydrides, etc. can be used, but isocyanate compounds, particularly blocked isocyanates, are preferred from the viewpoint of the appearance of the coating film, low temperature curability, etc. Preferred blocked isocyanates include isophorone diisocyanate blocked with ε-cabrolactam, such as B-1085 and B-1530 manufactured by Huls.

The amount of curing agent (C) used needs to be an amount of functional groups that approximately corresponds to the amount of hydroxyl groups in the polyester resin, preferably 1. O: 0. 8-1.0:
1. The range is 2.

The matte powder coating of the present invention may contain paint additives, if necessary. Examples of such compounding agents include pigments, flow control agents, stabilizers, and the like.

The pigments include, for example, white pigments such as zinc white, lithobon, zirconium oxide, titanium oxide, etc., black pigments such as carbon black, graphite, etc., pallite, chalk, clay talc, silica white, alumina white, gypsum, betonite, etc. Extender pigments such as: Gray pigments such as zinc powder, lead zinc oxide, etc.: Red pigments such as Henkara, red lead, vermilion, molybdenum red, antimony red, toluidine red, etc.; Brown pigments such as amber, iron oxide, etc.: Hansa yellow. , Penzidine Yellow Yellow pigments such as yellow lead, synthetic orca, etc. Green pigments such as copper-phthalocyanine green, chromium green, chromium oxide green, zinc green, etc. Copper-phthalocyanine blue Navy L Ultramarine blue, cobalt blue, manganese blue, etc. Blue pigments such as: Oxazine violet, manganese violet, cobalt violet, Mars violet, etc. Purple pigments: Aluminum powder, copper powder, gold powder,
Examples include metal powder pigments such as cypress powder and the like. Examples of the flow control agent include silicone resin, acrylic resin, fine silicon oxide powder, polyvinyl butyral, organic betonite, zinc aluminum stearate, and zinc stearate. Examples of the stabilizer include antioxidants, ultraviolet absorbers, and the like. The blending ratio of such paint compounding agents can be arbitrarily selected depending on the type, but the blending ratio that has been conventionally used is usually sufficient.
For example, the amount of pigment is 0.5 to 50% by weight, preferably 1 to 40% by weight based on the total composition, and the amount of flow control agent is 0.5% to 50% by weight, preferably 1 to 40% by weight based on the total composition. 5-50% by weight, preferably 5-30 mai
1%, and their total amount does not exceed 50m%. The stabilizer is added in a proportion of not more than 5% by weight, preferably not more than 1% by weight, based on the total composition.

To illustrate the method for producing the matte powder coating of the present invention, the obtained polyester (A), polyester (B) and curing agent (C
) and a coating composition are uniformly mixed, then kneaded at 70-150°C using a mill or roll, and then pulverized by a conventional mechanical method. In the case of mechanical methods, the first step is usually a pulverizer for coarse pulverization, and the second step is a pulverizer to produce fine powder. When performing fine pulverization, it can also be performed at a low temperature of 0° C. or lower.

For example, a fine powder can be easily obtained by crushing while cooling with liquid nitrogen or the like.

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

The powder coating of the present invention is applied to a pretreated metal surface by a powder coating method, such as electrostatic spraying, fluidized dipping, electrostatic dipping, or spraying, and coats the surface with a coating of 150-300%.
The resin is baked at a temperature of 18°C to 240°C, preferably 180 to 240°C. The baking melts the resin and forms a uniform coating surface.

(Example) Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. In addition, the characteristic values in the examples were measured by the method shown below.

Average molecular weight: Determined from the ester value determined by alkaline hydrolysis.

Hydroxyl value: Determined by titration with potassium hydroxide solution after acetylation.

Softening point: Determined by visual observation after heating on a hot bench.

A coating film of 50 to 60 μm was formed on a metal plate with a thickness of 1 mm, and the following evaluations were performed.

Smoothness: *The smoothness of the film was determined visually.

80' specular gloss; determined according to JIS K 5400. Pencil hardness: Determined according to JIS K 5400.

Scratch test: Scratch the painted surface with a cutter knife at 1 mm intervals vertically and horizontally until it reaches the metal surface, and check if the paint film adheres closely to the metal surface without peeling out of 100 scratches. Expressed in number.

Erichsen test; a coating film is formed on a metal plate with a thickness of 1 mm,
I pushed out a punch with a diameter of 20mm from the back side and cracked the paint film.
It is expressed as the pushing distance when peeling occurs.

Water resistance: When the coating film test piece was immersed in running water (room temperature) for one week, compared to before immersion! ! ! Mark 0 indicates that there is no change in the state of the film, and mark Δ if there is some change.
Those that have changed markedly are marked with an x mark.

Heat-resistant;! ! ! When the mock test piece was left in a vertical position at a temperature of 200℃ for 1 hour, no change was observed in the state of the coating film compared to before heating, and the mark O indicates that some changes were observed. Those with significant changes are marked with Δ, and those with significant changes are marked with ×.

Impact resistance: A coating film test piece was placed horizontally, and a 500 g striking core with a 1/2 inch spherical tip was dropped from a predetermined height to determine the height when there was no significant change.

Synthesis Example Preparation of Polyester (A) The compounds shown in Table 1 were placed in a stainless steel reactor, and 25
The reaction system was heated to 0° C., and the produced water was continuously removed from the reaction system. Next, 5.84ff of antimony dioxide was added as a catalyst.
Add i part and keep the degree of vacuum below 0.5 mmHg to 28
A polycondensation reaction was carried out at 0° C. for 4 hours to obtain polyester resins 2 and 3 with a high degree of polymerization.

Preparation of polyester (B) Compounds shown in Table 1 and zinc acetate 4.39% as a catalyst
A weight part was taken into a stainless steel reactor and heated to 230''C, and the generated water was continuously removed from the reaction system. Subsequently, the degree of vacuum was maintained at 800 mmHg for 3 hours to obtain polyester resin 4.

Preparation of polyester (D) Polyester resin 1 was obtained using the compounds shown in Table 1 in accordance with polyester (A).

The physical properties of each synthesized polyester resin are also listed in Table 1. Examples 1 to 2, Comparative Examples 1 to 2 The polyester resin, curing agent, leveling agent, benzoin, and titanium oxide shown in Table 2 were taken in the proportions shown in Table 3, and after dry blending with a Henschel mixer, 10
The mixture was melt-kneaded at 0° C., cooled, pulverized, and separated through a 145-mesh sieve to obtain a powder coating with a size of 145 mesh or less.

The obtained powder coating was coated on a zinc phosphate steel plate to a film thickness of 50~
Baking was performed at 200''C for 20 minutes so that the thickness became eoμm.

The performance of each coating film was evaluated and the results shown in Table 3 were obtained.

As is clear from Table 3, both Examples 1 and 2 have a matting effect and have superior coating film properties compared to the comparative example.

(Effects of the Invention) The specific powder coating of the present invention has various physical properties that cannot be obtained with conventional matte powder coatings, such as adhesion to metal, water resistance, and heat resistance, while maintaining good matting properties. It can produce coatings with excellent properties such as durability and impact resistance, and can be used in many fields including home appliances, automobiles, and building materials.

Table 1 Table 2 (1) Manufactured by Huls (2) Manufactured by BASF Product name Product name B-1530 Acronal 4F Table 3 that's all September 1989 8 Day

Claims (2)

[Claims] (1) At least one diol selected from 2-butyl-2-ethyl-1,3-propanediol or 2,2-diethyl-1,3-propanediol for 5 to 10
A polyester (A) which is polycondensed with a diol component included in the weight of 0 and at least one carboxylic acid component selected from terephthalic acid or isophthalic acid as a main component, and isophthalic acid and trimethylolpropane, or a component mainly composed of these. (A) is made by blending a substantially non-gelled polyester (B) and a curing agent (C).
A matte powder coating in which the weight ratio of component and component (B) is 30:70 to 85:15. (2) The molecular weight of the polyester (A) of the first claim is 50
0 to 20,000, and the curing agent (C) is a block isocyanate.