JPH011770A - Resin composition for powder coating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a resin composition for powder coatings that provides a semi-matte coating film.

(Prior art) Currently, epoxy, acrylic, and polyester-based powder coatings are mainly known, but among these, polyester-based powder coatings, especially isocyanate-cured powder coatings,
Powder coatings made of polyester mainly having hydroxyl groups at the ends have excellent weather resistance, corrosion resistance, and mechanical strength. Known as a well-balanced paint.

Powder coatings are currently used for home appliances, automobiles, and building materials.

It is used in many fields, but when a painted surface requires gloss from an aesthetic point of view (60 specular gloss 90
~100%), matte (approximately 30% or less) or semi-matte (approximately 30-70%) may be required. Conventionally, methods for preparing such matte powder coatings include adding a large amount of two coarse pigment particles, and tri-blending two types of powder coatings: polyester powder coating and acrylic powder coating. (Japanese Patent Publication No. 61-19668) is 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 tri-blending two types of powder paints cannot produce a matte paint at the - stage of paint formation.
In addition to increasing the manufacturing cost of the paint, there are problems such as non-uniformity of the blend and changes in the blending ratio during recovery and use.

It is an object of the present invention to solve these problems and provide a resin composition for powder coatings that provides a semi-matte or matte coating film with excellent mechanical strength and that can be easily produced. It is something.

(Means for solving the problem) In response to this situation, the present inventors have conducted repeated research to develop a resin composition that does not have the above problems, and as a result, they have developed a polyester resin having a specific hydroxyl value. The present inventors have discovered that by blending the following, it is possible to easily obtain a resin composition for semi-matte or matte powder coatings that provides a coating film with excellent mechanical strength, smoothness, and weather resistance.2.

That is, in the present invention, the hydroxyl value is 1200geq/10
6g or more of substantially non-gelled polyester,
It consists of a polyester (B) having a hydroxyl value of 200-1000 geq/10& and a blocked incyanate curing agent, and the blending ratio of the polyester and polyester (B) is 70:30 to 1O:90 in terms of weight ratio.

The object of the present invention is to provide a resin composition for powder coating in which each polyester satisfies the following formula (f).

1t (A) - t (n months > 3 (minutes) (I) (however,
1 (~9 t(B) indicates the gelation time of the polyester and polyester (B), respectively.) In the uninvented resin composition, the hydroxyl value of the polyester (A) is 1200ge (1/10'51 or more). , preferably 200
The hydroxyl value of polyester 03) needs to be 200 to 10009 eq/I 09.

The hydroxyl value of polyester (A) is 1200! je(1/
10! If it is less than j, it is difficult to obtain a good matting effect. Also,
The hydroxyl value of polyester) is less than 200geq/IOg.

Large irregularities occur on the surface of the coating film, which tends to reduce smoothness, and 100100O/10. ! If it exceeds 7,
The mechanical strength of the coating film may decrease or the matting effect may not be sufficient.

The polyester (A) needs to be a polyester that is not substantially gelled. What does "substantially non-gelled polyester" refer to here?

It can be pulverized with a general pulverizer and has fluidity when melted. If it is substantially gelled, it is difficult to form it into a paint, and it is impossible to form a uniform surface when it is formed into a film.

In the present invention, the appearance of the coating film is used as a curing agent.

Incyanate compounds from the viewpoint of low temperature curing properties, etc.

In particular, blocked isocyanates are used. Preferred blocked isocyanates include inphorone diisocyanate blocked with ε-caglolactam, such as B-1065 and B-1530 manufactured by Huls.

It is appropriate that the amount of the curing agent used corresponds to the amount of hydroxyl groups in the polyester resin, preferably in the range of 1.0:0.8 to 1.0:1.2.

In the present invention, it is necessary that the difference in gelation time between the polyester matrix and (B) be within a range that satisfies the above formula (1), and a highly matte coating surface (6
0 specular gloss of 20% or less) and then preferably for 5 minutes or more. A blend of resins outside this range will not provide a sufficient matting effect.

Note that the term "gelling time" as used in the present invention means a value determined by Brabender-Plustuder according to the method described below.

In the resin composition of the present invention, the weight ratio of polyester to polyester (8) is 70:30 to 10.
:90. The preferred ratio is 40:60 and 2:8. If the blending ratio is outside this range, the matting effect will not be sufficient.

In the present invention, the hydroxyl value of the polyester.

It is possible to control the degree of matting by changing the blending ratio of polyester (4) and a3) and the difference in gelation time. For example, the hydroxyl value of polyester is approximately 3o.
oopeq/xrf'i or higher, polyester (A)/
If the mixing ratio of
If the resin composition is ~4 minutes, the specular gloss will be 50-600 semi-matte, and if the left side is about 5 minutes, it will be 20.
Similarly, if the left side is 6 minutes or more, it is possible to obtain a completely matte coating surface of 10 or less.

The carboxylic acid component of the polyester (A) is not particularly limited, but mainly consists of terephthalic acid (hereinafter abbreviated as TPA) or isophthalic acid (hereinafter abbreviated as IPA),
Other polycarboxylic acids as required.

For example, aromatic dicarboxylic acids such as 2,6-naphthalene dicarboxylic acid, aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, cycloaliphatic dicarboxylic acids, and optionally trimellitic acid.

Those containing a small amount of trivalent or higher carboxylic acid such as pyromellitic acid are suitable. In addition, as the alcohol component, trifunctional alcohols are preferred 9 For example, trimethylolethane, trimethylolpropane (hereinafter abbreviated as TP), 3-methylpentane-1,3,5-to-IJol, etc. Examples include glycerin, but if necessary, other dihydric alcohols, such as ethylene glycol (hereinafter referred to as E
It is abbreviated as C.

Diethylene glycol C is abbreviated as DEC. ).

It may also contain small amounts of aliphatic glycols such as turf-propanediol and neopentyl glycol (hereinafter abbreviated as NPC), and tetrahydric alcohols such as pentaerythritol. Furthermore, it may contain a small amount of oxycarboxylic acid such as paraoxybenzoic acid or tartaric acid.

The carboxylic acid component of polyester (B) is TPA and/or
Or mainly IPA, but other aromatic dicarboxylic acids such as 2,6-naphthalene dicarboxylic acid.

Aliphatic dicarboxylic acids and alicyclic dicarboxylic acids such as succinic acid, adipic acid, and azelaic acid can be used as copolymerization components in amounts as required.

The alcohol component is mainly composed of EG and neopentyl glycol, but other aliphatic glycols such as DEC and 1,2-propanediol can also be used. In addition, trivalent or higher alcohols such as trimethylolethane, TP, glycerin, pentaerythritol, etc. and/or trivalent or higher carboxylic acids such as trimellitic acid, pyromellitic acid, trimesic acid, etc. may be contained within a range that does not substantially cause gelation. It can be used in the world. As mentioned above, polyester that is not substantially gelled.

If it is gelled, it will not be possible to make it into a paint. Furthermore, if necessary, oxycarboxylic acids such as paraoxybenzoic acid and tartaric acid may be included.

Moreover, the average degree of polymerization of the polyester powder and polyester (B) is preferably in the range of 4 to 50, which allows for powderization. Further, since they are used in powder coatings, their softening points are preferably in the range of 50 to 150°C. Softening point is 50
If the temperature is below 150°C, the powdered resin tends to aggregate and solidify, and the blocking resistance tends to be poor. On the other hand, if it exceeds 150°C, the kneading temperature will be high and the curing agent will not mix well with the curing agent when forming a coating. The reaction progresses, and as a result, the smoothness and mechanical strength of the coating film tend to decrease.

After performing a known esterification reaction or transesterification reaction using the above carboxylic acid and/or its alkyl ester and alcohol as raw materials.

If necessary, a polycondensation reaction can be carried out to prepare a polyester powder and a polyester CB).

Using a kneader or roll, the polyester powder obtained in this way, the polyester), and a curing agent were mixed at 70 to 100%
By kneading at 50°C, the resin composition for powder coating of the present invention can be obtained.

The resin composition of the present invention may contain pigments such as titanium oxide and carbon black, a curing catalyst, and other additives, if necessary.

(Example) Next, the present invention will be specifically explained using Examples and Comparative Examples.

Note that the characteristic values in the nine examples were measured by the method shown below.

Average degree of polymerization: Determined by gel permeation kubutograph method.

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

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

Smoothness: The smoothness of the coating film was visually evaluated.

60 Specular gloss: Determined according to JIS K 5400K.

Pencil hardness: Determined according to JIS K 5400.

Accelerated weather resistance: Determined according to JIS K5400.

(200 hours) Gelation time: A curing agent (manufactured by Hüls B) was added to each polyester.
A sample of RTC
A curing curve was determined using a Brabender plasticizer (Brapender M) at +o, p and a temperature of 200°C, and the time up to the inflection point was defined as the gelation time.

Reference Example 1 [Preparation of Polyester Container] The compounds shown in Table 1 were charged in the amounts shown in Table 1 into a stainless steel reactor, heated to 230°C, and the produced water was continuously removed from the reaction system. Next, the degree of vacuum was reduced to 600 mmI (g
The mixture was kept for 3 hours to obtain Polyester 1.

In Table 9, DMT is dimethyl terephthalate.

DMI stands for dimethyl inphthalate.

Reference Example 2 [Preparation of Polyester Container] The compounds shown in Table 1 were charged in the amounts shown in Table 1 into a stainless steel reactor, heated to 250°C, and the produced water was continuously removed from the reaction system. Subsequently, 5,84 parts of antimony trioxide was added as a catalyst, and while the degree of vacuum was maintained at 0.5 mHg or less, polycondensation reaction was carried out at 280 ° C. for 4 hours to obtain a polyester resin with a high degree of polymerization. .

The temperature was lowered to 270°C, the compounds shown in Table 2 were added in the amounts shown in Table 2, and polyester 2 was obtained by depolymerization reaction under closed conditions.

Reference Examples 3 and 4 [Preparation of polyester (B)] The compounds shown in Table 1 were placed in the amount shown in Table 1 in a stainless steel reactor, and 2
The resulting water was removed from the reaction system by heating to 50°C. Subsequently, 5.84 parts by weight of antimony trioxide was added as a catalyst, the degree of vacuum was maintained at 10 to 0.5 Hg, and 270
A polycondensation reaction was carried out at °C for 2 hours to obtain polyesters 3 and 4.

Reference Examples 5 and 6 [Preparation of polyesters] Polyesters 5 and 6 were prepared in the same manner as Reference J 2 and Sono except that the type or amount of the compound used was changed as shown in Tables 1 and 2. Obtained.

Reference Example 7.8 [Preparation of polyester (B)] The compounds shown in Table 1 in the amounts shown in Table 1 and 4.39 parts by weight of zinc acetate as a catalyst were placed in a stainless steel reactor and heated to 220°C. The generated methanol was continuously pumped out of the reaction system. Then, 5.84 ml of antimony trienhide was added as a catalyst.
Add L ft part and reduce the pressure to 0.5■H! After performing a polycondensation reaction at 280° C. for 4 hours while maintaining the temperature below i to obtain a polyester resin with a high degree of polymerization.

The temperature was lowered to 270°C, the compounds shown in Table 2 were added in the amounts shown in Table 2, and polyesters 7 and 8 were obtained by depolymerization reaction under closed conditions.

The characteristic values of each polyester were as shown in Table 3.

t″′ table (parts by weight) Table 3 LOL Examples 1-7. Comparative examples 1 to 4 Polyesters and curing agents shown in Tables 4 and 5.

A leveling agent, benzoin, and titanium oxide were taken in the proportions shown in Tables 4 and 5, and after tri-blending with an FM20B Henschel mixer (manufactured by Mitsui Miike Seisakusho), P
After melt-kneading at 100° C. using an R-42 type co-kneader (manufactured by Busu Co., Ltd.), cooling and pulverizing.

The mixture was separated using a wire mesh of 145 mesh to obtain a powder coating of 145 mesh or less.

The obtained powder coating was applied onto a zinc phosphate treated steel plate at a film thickness of 5.
Electrostatically coated to a thickness of 0 to 60 μm and heated at 200°C for 20
Baking was performed for a minute.

The performance of each coating film was evaluated and the results shown in Tables 6 and 7 were obtained.

fil Product name B-153Of21 manufactured by Huls
BASF company product name Acronal 4F Table 6 Table 7 fil 1/2 inφ 5001 As is clear from Table 5, Comparative Examples 1 to 6 were polyester (4), gelation time difference (lt I), hydroxyl value, or their blending ratio are outside the range defined in the present invention, so the matte and semi-matte effects are inferior, whereas Examples 1 to 7 have excellent matte and semi-matte effects. 9 Provides a good coating film with well-balanced mechanical strength and appearance.

(Effects of the Invention) According to the present invention, it is possible to easily obtain a resin composition for powder coating that can provide a completely matte or semi-matte coating surface with excellent mechanical strength.

Patent applicant: Nihon Ester Co., Ltd.

Claims (1)

[Claims] (1) A substantially non-gelled polyester (A) with a hydroxyl value of 1200 geq/10^6 g or more, a polyester (B) with a hydroxyl value of 200 to 1000 geq/10^6 g, and a blocked isocyanate curing agent. A resin composition for powder coatings in which the blending ratio of polyester (A) and polyester (B) is 70:30 to 10:90 by weight, and each polyester satisfies the following formula (I). thing. |t(A)-t(B)|>3(min)(I) (However, t(A) and t(B) are each polyester (
The gelation time of A) and polyester (B) is shown. )