JPS586750B2 - Polyester materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester resin composition for powder coatings having improved heat flow properties and anti-blocking properties.

Powder coatings have shown remarkable growth in recent years as anti-pollution coatings and resource-saving coatings.

In order to use a resin composition as a material for a powder coating, the following properties are required.

(1) Easily pulverized into fine powder.

(2) Do not block during transportation, storage or use.

(3) Scales that flow at relatively low temperatures and can be easily turned into paints.

(4) Scales that provide a smooth and beautiful coating by painting and baking.

(5) The resulting coating film should be excellent in various properties such as weather resistance, solvent resistance, water resistance, heat resistance, and toughness.

Among various materials for powder coatings, a polyester resin composition using an N-methylol ether compound as a curing agent is one of the particularly preferred materials.
Although it is known from Japanese Patent Publication No. 7152, Japanese Patent Publication No. 48-6615, Japanese Patent Application Laid-open No. 48-86952, and Japanese Patent Application Publication No. 49-96023, an ideal material that satisfies all of the above characteristics is Is not yet.

In particular, there is currently no material that has both blocking resistance and heat flow properties.

That is, N- such as hexamethoxymethylmelamine
In most cases, the methylol ether compound is liquid at a low temperature of 40° C. or lower, and it significantly impairs the blocking resistance of the polyester resin composition for powder coatings obtained by mixing it with the polyester resin.

Conventionally, various methods have been proposed for improving the blocking resistance of polyester resin compositions for powder coatings using N-methylol ether compounds as curing agents.

For example, (1) a polyester resin composition for powder coatings is prepared using a polyester resin that has a relatively high degree of polymerization and a low content of terminal hydroxyl groups so as to be curable with a small amount of curing agent.

(2) As described in JP-A-48-86952, a polyester resin composition for powder coating is prepared by mixing a polyester resin and a curing agent and allowing them to partially react until a certain softening point is reached. thing.

However, the former method uses a polyester resin with a relatively high degree of polymerization, that is, a polyester resin with poor heat flow properties, which not only has poor workability when turning into a paint, but also allows the paint to be obtained by painting or baking. The smoothness of the film is poor and it is difficult to obtain a beautiful painted surface.

On the other hand, the latter method involves partially reacting hexakis(methoxymethyl)melamine with a polyester resin to prepare a powderable composition with a relatively high softening point; It is extremely difficult to prepare polyester resin compositions of the same quality.
It is extremely difficult to use it industrially.

The present inventors have conducted extensive research to develop a polyester resin composition for powder coatings that has both blocking resistance and heat flow properties and can be stably prepared industrially. A secondary rearrangement point obtained by reacting the polyester resin (1) with at least one molecule of an N-methylol ether compound represented by the following structural formula per end group of the polyester resin (1) at 100 to 180°C. An average degree of polymerization of 5 to 60°C obtained by copolymerizing a polyester resin composition at 20 to 60°C and a trihydric or higher polycarboxylic acid or/and a polyhydric alcohol mainly consisting of dicarboxylic acid and dialcohol in an amount that does not cause gelling. 50, secondary dislocation point 40-60℃, softening point 6
A polyester resin composition for powder coating was prepared by mixing polyester Kikawa (1) of 0 to 120° C. in an amount satisfying the following formula, and this objective was achieved very effectively.

(However, R is a monovalent organic residue such as an alkyl group, an aryl group, or a cycloalkyl group.

) [wherein r is R contained in the polyester resin composition (
The equivalent number of monovalent organic residues), h is the number of equivalents of the polyester resin (I
) Equivalent number of hydroxyl groups contained in polyester resin (1)
The reaction between N-methylolether compound and N-methylolether compound proceeds as follows, for example.

That is, since the N-methylol ether compound reacts with the terminal hydroxyl group or terminal carboxyl group of the polyester Jugetsu (1) and is introduced into the molecular terminal of the polyester resin, the secondary rearrangement point of the polyester resin composition is set at 20 to 60°C.
It is possible to maintain the temperature preferably in the range of 30 to 50°C, and for this reason, it is possible to prepare a polyester resin composition for powder coating that has preferable blocking resistance when kneaded with the polyester resin (9). Become.

Further, the N-methylol ether compound and the polyester resin (I) are heated at 100 to 180°C, preferably at 120 to 160°C.
A polyester resin composition mainly composed of a reaction product obtained by reacting at 0°C for 1 to 10 hours has a temperature of 100 to 100°C because it does not substantially contain terminal hydroxyl groups or terminal carboxyl groups that can react with the N-methylol ether compound. 18
It is stable even if left at 0°C for an extended period of time, and it is possible to repeatedly and stably produce products of the same quality.

Furthermore, by using the polyester resin composition used in the present invention as a curing agent, it is possible to use a polyester resin (1) with a relatively low degree of polymerization, and furthermore, it has good blocking resistance and good heat flow properties. It is possible to prepare a polyester resin composition for powder coatings having the following properties.

The polyester resin (I) used in the present invention is a polyester resin mainly consisting of dicarboxylic acid and dialcohol.

Such polyester resin (I) can be prepared by a conventionally known method, but it can be particularly preferably prepared, for example, by the following method.

That is, one or two of benzene dicarboxylic acids such as terephthalic acid, isophthalic acid, and phthalic acid, saturated aliphatic dicarboxylic acids such as naphthalene dicarboxylic acid, succinic acid, adipic acid, azelaic acid, and sepacic acid, or lower alkyl esters thereof. and ethylene glycol,
1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol,
Esterification or / and transesterification reaction, followed by addition of a polycondensation reaction catalyst such as antimony trioxide, and 2 hours under reduced pressure.
After carrying out a polycondensation reaction at 50 to 280°C to prepare a polyester with a high degree of polymerization having an intrinsic viscosity (measured at 20°C using a mixed solvent of phenol/tetrachloroethane = 1/1 equal weight) of 0.4 or more, Using one or more of the aforementioned dialcohols at 250 to 280°C under normal pressure or increased pressure.
It can be prepared by depolymerization reaction for 5 hours.

In the depolymerization reaction, an ester such as pis-β-hydroxyethyl terephthalate, pis-β-hydroxyisophthalate or pis-β-hydroxyphthalate may be used in part or all in place of the above-mentioned dialcohol.

The polyester resin (I) used in the present invention is mainly composed of dicarboxylic acid and dialcohol, and is obtained by copolymerizing trivalent or higher polyhydric carboxylic acid or/and polyhydric alcohol in an amount that does not cause gelation, and has an average polymerization degree of 5 to 50. , a polyester resin having a secondary dislocation point of 40 to 60°C and a softening point of 60 to 120°C.

Such polyester resin (I) can be prepared by a conventionally known method, but it can be particularly preferably prepared, for example, by the following method.

That is, polyester with a high degree of polymerization and having an intrinsic viscosity of 0.4 or more obtained in the same manner as in the production of polyester resin (I) is mainly used as a polyester such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, mannitol, etc. It can be prepared by depolymerizing alcohol or an ester such as tris-β-hydroxyethyl trimellitate or bis-β-hydroxyethyl terephthalate at 250 to 280° C. for 1 to 5 hours under normal pressure or increased pressure.

N-methylol ether compounds that can be used in the present invention are compounds represented by the above-mentioned structural formulas, such as hexamethoxymethylmelamine and hexabutoxymethylmelamine.

The polyester resin composition obtained by reacting the polyester resin (I) with the N-methylol ether compound and the polyester resin (I) may be kneaded with a pigment such as titanium oxide, carbon black, red iron oxide, or talc, if necessary.
It can be carried out at a temperature of 150°C or less, preferably 90 to 120°C, using a kneader, roll, or reaction can together with a coating surface conditioner or a curing catalyst.

The thus obtained polyester resin composition for powder coating can be ideally used as a powder coating having both desirable blocking resistance and heat flow properties.

Next, the present invention will be specifically explained by showing examples and reference examples.

Example 1 Dimethyl terephthalate (hereinafter abbreviated as DMT), dimethyl isophthalate (hereinafter abbreviated as DMI), ethylene glycol (hereinafter abbreviated as EG), and neobentyl glycol (hereinafter abbreviated as NPC) were added to stainless steel in the amounts shown in Table 1. After adding 0.01 mol of zinc acetate as a catalyst and carrying out a transesterification reaction at 150 to 250°C under normal pressure to remove the theoretical amount of methanol from the reaction system, add sepacic acid if necessary. (hereinafter abbreviated as SEA) was added to undergo an esterification reaction, and then 0.02 mol of trimethyl phosphate and 0.02 mol of antimony trioxide were added and a polycondensation reaction was performed at 270°C under reduced pressure to obtain an intrinsic viscosity of 0.65. A polyester with a high degree of polymerization of ~0.66 was prepared.

Next, NPC, bis-β-hydroxyethyl terephthalate (hereinafter abbreviated as BHET), trimethylolpropane (hereinafter abbreviated as TP), and pentaerythritol (hereinafter abbreviated as PE) were added in the amounts shown in Table 1 to give 0.5k9/cm2. A depolymerization reaction was carried out at 270° C. under nitrogen pressure to prepare polyester resin (■) and polyester resin (1) shown in Table 2.

Hexamethoxymethylmelamine (hereinafter abbreviated as HMM) was added to each polyester tree arm (1) shown in Table 2 and reacted under the conditions shown in Table 3 to prepare a polyester resin composition shown in Table 4.

Subsequently, succinic anhydride (hereinafter abbreviated as SUD) or trimellitic anhydride (hereinafter abbreviated as TMAD) was added to each polyester resin (I) shown in Table 2 and reacted at 150°C for 60 minutes to produce the products shown in Table 5. The acid value was adjusted accordingly.

Each polyester resin (I) shown in Table 5 has a corresponding No. 1 shown in Table 4. Polyester resin composition, rutile titanium oxide and regulator (YF- manufactured by Toshiba Silicone Co., Ltd.)
3860) in the amounts shown in Table 6 and kneaded at 100° C. using a three-roll roll to prepare a polyester resin composition for powder coating.

After pulverizing each obtained polyester resin composition for powder coating using a Micron Victory Mill VP-1 type pulverizer,
The blocking resistance and the coating film performance after electrostatic coating to a film thickness of 80μ on a 100x200x0.8 (unit: m/m) steel plate and baking at 190°C for 30 minutes were evaluated using the methods shown below. The following results were obtained.

(1) Blocking resistance test: Leave at 40°C for 7 days.

(2) Eriksen test: Based on JIS Z2247.

(3) Impact resistance test: DuPont type 1/4'-500g
.

(4) Boiling water resistance test: Erichsen test 2 hours after boiling water treatment.

(5) Acetone resistance test: According to JIS K6911.

(6) 60° specular reflectance: According to JIS Z8741.

(7) Weather resistance test: Sunshine Weather-Ometer 5
Gloss retention after 00 hours exposure.

Example 2 1,2.28 kg of the polyester resin (I) of Example 1
and 0.86 kg of hexabutoxymethyl melamine and 15
Polyester resin composition 6 was prepared by reacting at 0° C. for 6 hours.

The number of moles of hexabutoxymethylmelamine/the number of end group Durham equivalents of polyester resin (I)-1.0, and the secondary rearrangement point of polyester resin composition 6 was 30°C.

Next, using polyester resin (1) 2 shown in Table 5, Example 1 was prepared with the following formulation so that r/h = 1.2.
It was also made into paint.

The obtained polyester resin composition for powder coating was prepared in Example 1.
Evaluation was performed in the same manner as above, and the results shown below were obtained.

Blocking resistance Good Erichsen >9 m/m Impact resistance 40 cm Boiling water resistance >9 m/m Acetone resistance Good 60° specular reflectance 100 Weather resistance 95% Polyester resin composition 3 shown in Table 3 of Example 1 was produced. The reaction was carried out under the same conditions as for 0 (control example).
, 2, 4, 6, 8, and 10 hours, 0.5 g of each sample was dissolved in 100 ml of tetrahydrofuran, and the amount of unreacted HMM was measured using a Toyo Soda HLC-801A liquid chromatograph. was quantified, and the results shown in Table 8 were obtained.

Reference Example 1 The same conditions as for producing polyester resin composition 3 shown in Table 3 of Example 1 were used, but the amount of HMM was changed to 0.12k.
When the reaction was carried out with the number of moles of HMM and the number of terminal Durham equivalents of the polyester resin (1) = 0.23, gelation occurred 45 minutes after the start of the reaction.

Reference Example 2 Using the polyester Jugetsu (1) 3 shown in Example 10 Table 5, however, HMM was used as a curing agent in place of the polyester resin composition so that r/h = 1.2, and the following formulation was used. A paint was prepared in the same manner as in Example 1.

PoJ ester resin (I) 3 94.1 parts by weight HMM
5.9 parts by weight Rutile titanium oxide
50 parts by weight Adjusting agent 2 parts by weight The obtained polyester resin composition for powder coating was prepared in Example 1.
After being pulverized in the same manner as above, a blocking resistance test was conducted at 40°C and the result was a failure.

Reference Example 3 When the reaction was carried out under the same conditions as for producing polyester resin composition 3 shown in Table 3 of Example 1, but at a reaction temperature of 200°C, the reaction product gelled in 2 hours and 30 minutes.

Reference Example 4 The same conditions as for producing polyester resin composition 3 shown in Table 3 of Example 1 were used, but the amount of HMM was changed to 1.56k.
The reaction was carried out by increasing the number of moles of HMM/the number of end group Durham equivalents of polyester resin (1) by 3.00 to prepare polyester resin composition 7 having a secondary rearrangement point of 18°C.

Next, the polyester resin shown in Table 5 of Example 1 (1
) was used to make a paint in the same manner as in Example 1 with the following formulation so that r/h = 1.2.

Polyester tree axillary (2) 85.9 parts by weight Polyester resin composition 7 14.1 parts by weight Rutile type titanium oxide 50 parts by weight Conditioner
2 parts by weight of the obtained polyester resin composition for powder coating was prepared in Example 1.
After being pulverized in the same manner as above, a blocking resistance test was conducted at 40°C and the result was a failure.

As is clear from a comparison of Examples and Reference Examples, the polyester resin composition for powder coatings of the present invention can be manufactured stably industrially, and has improved heat floss consistency and blocking resistance. It is an ideal material for powder coatings.

That is, by reacting an N-methylol ether compound with polyester resin (I) to prepare a polyester resin composition, the blocking resistance of the polyester resin composition for powder coating can be improved without impairing the function as a curing agent. Maintenance is possible.

Therefore, polyester resin with a relatively low degree of polymerization (2
), and it is also possible to improve the heat flow properties of polyester resin compositions for powder coatings.

The average degree of polymerization, secondary rearrangement point and softening point of the polyester resin (I) are 5 to 50, 40 to 60°C and 60°C, respectively.
Controlling the temperature within the range of ~120°C is essential in order to maintain the crushability of the polyester resin composition for powder coatings and the workability of forming into paints, and in preparing the polyester resin composition for powder coatings, In order to maintain the coating performance after painting baking, the polyester resin (I) and the polyester resin composition as a curing agent must be mixed within a range that satisfies the formula 0.5≦r/h≦2.0. Must be.

Claims (1)

[Scope of Claims] 1. A polyester resin (I) mainly consisting of a dicarboxylic acid and a dialcohol;
At least one molecule of N-methylol ether compound represented by the following structural formula per terminal group of 100 to 18
A polyester resin composition having a secondary rearrangement point of 20 to 60°C obtained by reacting at 0°C, and a polyhydric carboxylic acid or/and polyhydric alcohol consisting of a trihydric or higher hydric carboxylic acid and/or polyhydric alcohol in an amount that does not cause gelling. Powder obtained by copolymerizing polyester resin (1) with an average degree of polymerization of 5 to 50 and a secondary rearrangement point of 40 to 60°C and a softening point of 60 to 120°C that satisfies the following formula. Polyester resin composition for paint. (However, R is one organic residue such as an alkyl group, an aryl group, or a cycloalkyl group.) [In the formula, r is R contained in the polyester resin composition.
(monovalent organic residue) equivalent number, h is the polyester resin (
The number of equivalents of hydroxyl groups contained in 1)].