JPS63245479A - Polyester powder for coating - Google Patents

Abstract

PURPOSE:To obtain a polyester powder for coating, having excellent adhesiveness, impact resistance, film surface properties, and coating cycle, by uniformly compounding a specified polyester copolymer and polybutylene terephthalate. CONSTITUTION:A dicarboxylic acid component of which 30-80mol.% comprise terephthalic acid, and a diol component consisting of at least one 2-6C diol (e.g., 1,4-butanediol) are subjected to transesterification in the presence of a transesterification catalyst at 150-220 deg.C, which is then subjected to glycol removal reaction in the presence of a polymerization catalyst under a vacuum of 0.5mmHg or lower to give a polymer. This polymer is ejected into water and cut, thus giving a polyester copolymer. 100pts.wt. said polyester copolymer, 0.1-15pts.wt. polybutylene terephthalate, and if necessary, a nucleating agent, 0.05-2pts.wt. leveling agent, a filler, etc. are uniformly compounded at 220-240 deg.C, cooled, finely ground, and classified, thus giving a polyester powder for coating, having a particle diameter of 50-700mum.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a polyester powder for coating that has excellent performance as a powder coating.

Powder coatings are solvent-free, low pollution, and can be reused6
It has shown remarkable growth in recent years due to its advantages such as being able to coat a range of 50 to 700 microns in one coat.

Therefore, the present invention provides a polyester powder for coating that has excellent adhesion, impact resistance, coating surface properties, and coating cycle.

Conventional technology> E-polyester JiJnW is used as a powder coating, but it is mainly a thermosetting composition that is used in combination with epoxy compounds, isocyanate compounds, melamine compounds, etc. Although it is known that plastic polyester resins are used in fluidized dipping or electrostatic coating, there are very few examples of this being put to practical use.

Known examples of thermoplastic polyester resins used in aqueous dipping or electrostatic coating methods include poly (neopentyl terephthalate) and terephthalic acid and isophthalic acid 1.4-7.
JP-A-49-97023, which uses a mixture of a polyester selected from chlorohexylene dimethanol consortium and a magnetic fiber material such as acetyl butyl cellulose, is a polyethylene isophthalic acid component containing 8 to 20 mol%. JP-A-59-41367 consisting of a terephthalate copolymer,
There is JP-A-50-56424 which uses a polyester derived from 1°4-butanediol and terephthalic acid having a specific composition and specific physical properties.

These known examples include thermoplastic polyester resin, which has excellent weather resistance and other resin properties as a paint, but has poor adhesion to substrates, poor adhesion, and problems with cranking during rapid cooling and bending. It has been proposed in order to solve problems such as the tendency to occur, the glossiness of the coating film surface, etc.

A known example disclosed in JP-A No. 49-97023 improves the glossiness of the coating film surface by blending a cellulose compound into a polyester having a specific composition. Also, JP-A-59-
In the known example No. 56424, a predetermined ratio of isophthalic acid is combined with polyethylene terephthalate in order to improve the adhesion of the polyethylene terephthalate resin to metal surfaces and the bending workability.

However, even with these improvements, it is still not sufficient as a powder coating, and its adhesive properties, impact resistance, etc. are far from practical levels.

Further, the known example disclosed in JP-A-50-56424 attempts to improve the above-mentioned problems by specifying a specific combination composition and specific physical properties.

On the other hand, Japanese Patent Publication No. Sho 60-6215 discloses a molded product made by adding polybutylene terephthalate to a copolymerized polyester containing a polybutylene terephthalate component. It is different from the coating powder of the present invention.

<Problems to be solved by the invention> It is true that the coating powder of JP-A-50-56424, written by TjiJ, has been improved from various drawbacks and is close to a practical level, but
The adhesion and impact resistance after heat treatment and hot water treatment are still low, the surface characteristics of the coating film are insufficient, and it takes time to solidify after coating, which reduces work efficiency.
Moreover, during this process, there are problems in terms of coatability, such as the possibility of scratches on the coated surface.

The inventors of the present invention have attempted to improve the adhesion, impact resistance, and surface properties of the coating film, and to improve the properties of the coating film by improving its adhesion, impact resistance, and surface properties. The present invention was developed as a result of extensive research in order to obtain a coating powder with excellent coating properties.

<Means for solving the problems> That is, the present invention provides (A) 30 mol% or more and 80 mol%
tB) 0.1 parts of polybutylene terephthalate per 100 ff of copolyester obtained from a dicarboxylic acid component consisting of terephthalic acid and a diol component consisting of one or more diols having 2 to 6 carbon atoms. 1-1
The present invention provides a polyester powder for coating, the main component of which is a mixture of homogeneously mixed with 5 parts of heavy M.

The acid component of the copolymerized polyester (A) constituting the composition which is the main component of the powder of the present invention is a dicarboxylic acid component consisting of terephthalic acid at 30 mol% or more and 80 mol% or less. are isophthalic acid, orthophthalic acid, naphthalene-2,6-dicarboxylic acid, diphenyl-
Aromatic dicarboxylic acids such as 4゜4'-2 carboxylic acid, 3-sulfoisophthalic acid, aliphatic dicarboxylic acids such as succinic acid, 7-euric acid, adipic acid, sebacic acid, dodecanedioic acid, and l,4-cyclohexane. Mention may be made of alicyclic dicarboxylic acids such as dicarboxylic acids. Among these dicarboxylic acids, isophthalic acid, adipic acid, sebacic acid, and dodecanedioic acid are preferably used.

It is necessary to use terephthalic acid in an amount of 30 mol% or more and 80 mol% or less, preferably 40 mol% or more and 170 mol% or less. If it is less than 30 mol%, the melting temperature of the resin will be too low and the heat resistance of the coating film will be below the practical level,
-If it exceeds mol%, the adhesion pressure will decrease and the seizure will be
・Is this high temperature? Since it is necessary to rub, the resin tends to deteriorate and the physical properties of the wood coating are often impaired.

The diol component of the copolymerized polyester (A) constituting the composition which is the main component of the powder of the present invention is a diol consisting of one or more types of carbon' and 2-6 diols. Carcal diol components include ethylene glycol, propylene glyco/I'll l + 4-buta/diol, l
, 5-bentanediol, 1,6-hexanediol,
Examples include neopentyl glycol and diethylene glycol. Among these diols, ethylene glycol, 1,4-butanediol, and 1,6-hexanediol are preferably used. In particular, it is preferable to use 1,4-butanediol as an essential component.

The method of polymerizing the copolyester is not particularly limited. As a representative example, dimethyl terephthalate, another dicarboxylic acid component, and a diol component such as 1,4-butanediol are mixed together with a transesterification catalyst such as tetrabutyl titanate in one reaction vessel equipped with a stirrer. After charging and distilling methanol at a temperature of 150 to 220°C under a nitrogen atmosphere, a polymerization catalyst such as tetrabutyl titanate is added, and after gradually exhausting and raising the temperature, the mixture is heated to 250°C and 0.5ffHf. After proceeding with the deglycol reaction under the following vacuum and reaching a predetermined degree of polymerization, nitrogen gas is introduced to terminate the reaction, and the polymer is discharged from the bottom of the reaction vessel into water and cut to obtain pellets. There are several methods.

The composition which is the main component of the powder of the present invention can be obtained by homogeneously mixing the above #polymerized polyester V and (B) polybutylene terephthalate. Polybutylene terephthalate is used in pellet form or powder form, but powder form is more preferable. The amount of polybutylene terephthalate added is based on the copolymerized polyester loOm
ffi parts, 0.1-15 Arashi parts, preferably 0.1-15 Arashi parts.
It is a 5-10 heavy abrasive part. When the amount added is less than 0.1 weight and 1 part, the effect of improving the coating properties, which is the objective of the present invention, is not noticeable, and when it exceeds 15 parts, adhesion, impact resistance, etc. decrease, and the surface This is not preferable as it will also worsen the condition.

The method for obtaining the composition which is the main component of the powder of the present invention is to tri-blend copolymerized polyester pellets or powder, polybutylene terephthalate pellets or powder, and then use a l-screw or twin-screw extruder. Generally, a method is used in which polybutylene terephthalate is homogeneously mixed and dispersed in a copolyester at a temperature of 220 to 240° C. using a suitable mixer such as a Nigu, Pan Bali mixer, or roll.

Further, when a known crystal nucleating agent is added together with (B) polybutylene terephthalate, the effects of the present invention become even more remarkable. Examples of known crystal nucleating agents include talc, alkaline earth carbonates, aluminum oxide, higher fatty acid sodium salts, and sodium montan waxate.

To further improve the appearance of products powder coated with the polyester powders of the present invention, leveling agents can be added. As the leveling agent, silicone resin, fluororesin, acrylic copolymer, etc. can be used. especially,
A leveling agent prepared by adding powdered silica to an acrylic copolymer (manufactured as a registered trademark Modaflow) is preferably used. The amount added is 10% of the copolymerized polyester
It is preferably from 0.05 to 271 parts F. 2
At n11 parts or more, a decrease in adhesive strength is observed.

Furthermore, the polyester composition that is the main component of the powder of the present invention may contain antioxidants such as hindered phenol compounds, phosphite compounds, and thioether compounds, benzophenone light absorbers, and Ultraviolet stabilizers such as dirt amine light stabilizers, hydrolysis resistance improvers, coloring agents such as pigments and dyes, core-blocking agents, conductive agents, flame retardants, calcium carbonate, barium sulfate, clay, titanium oxide, oxidation Fillers such as silicon, mica powder, etc. can be added.

The method of turning the polyester composition used in the present invention into a powder for powder coating is not limited to this method, but the polyester composition is cooled with liquid nitrogen, crushed using a crusher, and classified to A method for obtaining coating powder having a particle size suitable for the 700 micron coating method is preferably used.

Powder coating using the polyester powder of the present invention is normally carried out! This can be done by LII dipping method or electrostatic coating method. As a typical example, in the fluidized immersion method, the substrate is preheated at 250 to 300°C, immersed in the fluidized powder for a few seconds, then post-heated at 180 to 200°C for several minutes, and slowly or rapidly cooled. One example is a method of obtaining a coated product.

Note that the preheating is preferably performed at a temperature such that the temperature of the substrate quickly becomes 230°C or less when immersed in the tM, wJJ powder, and the post-heating is also preferably performed at a temperature of 230°C or less.

<Example> The present invention will be explained in detail below using Examples.

The evaluation and testing of the coated products was conducted in the following manner.

Make a cut in the adhesive crab coating to reach the base material at 25 tm 1lln, and apply a peel strength of 180 degrees at a tensile speed of 50 fl.
/min.

Surface hardness: Pencil hardness was measured according to the JIS K-5401 method.

Impact strength: According to JIS K-5400 method, l
The strength was measured using a load of kq.

Gloss: Visually evaluated.

○: Glossy, △: Slightly glossy, ×: No gloss Surface Condition 2. The smoothness of the surface was determined by finger touch and visual inspection.

O: Good, △: Slightly uneven, ×: uneven Melting temperature: Differential scanning: Top of the melting peak when heated at a heating rate of lθ°C/min in a nitrogen gas atmosphere using an Affi meter Temperature was measured.

Reduced viscosity: Volima 0.25 f mixed with phenol/orthodichlorobenzene (60/40) 111M solvent 25w
The solution was dissolved in e and the a was determined at 25°C using an Ubbelohde viscometer.

Heat treatment: The completed coated product was placed in a hot air oven at 90°C and heat treated for 10 days.

Hot water treatment: The completed painted product is immersed in 80℃ hot water,
It was treated for 10 days.

Examples 1 to 3, Comparative Examples 1 to 2 Terephthalic acid 60 mol%, isophthalic acid 3 as acid components
A copolymerized polyester with a melting point of 149°C and a reduced viscosity (J,
A copolymerized polyester (1) of 92 (f/cc) was obtained.

After tri-blending 5 parts by weight or 10 parts by weight or 11 parts by weight of polybutylene terephthalate powder 2 with an average particle size of 200 microns with this polyester (Igloo heavy void part e), 30 with Dalmage IJ z- Using a flφ single screw extruder (manufactured by Plagiken), 2
After melt blending at 30° C. and pelletizing, three types of co]polyester compositions were obtained. The resulting composition was cooled with liquid nitrogen and ground. The obtained powder was classified using a sieve to obtain paint powder that passed through a 150 mesh sieve and remained on a 200 mesh sieve. This 2
50 x 100 x 2 heated at 50℃ for 20 molecules
Painted on a U rolled steel plate by the fluidized dipping method and heated at 200℃ for 2 hours.
After heating for a minute, the coated products were evaluated. As a comparative example, when polypterene terebutanate powder was not added and copolymerized polyester (1) 100 m
An evaluation was performed when a part of polybutylene terephthalate powder was added to the deposit, and the results are shown in Table 1 along with Examples.

Examples 4 to 9, Composite Examples 3 to 5 Terephthalic acid as acid component: 52 moJl/%, isophthalic acid: 48 mole%, diol component: l.

A copolyester consisting of 100 mol% of 4-butanoneol was produced, with a melting point of 129°C and a reduced viscosity of 0.81 (
17 cc) of copolymerized polyester (II) was obtained.

This copolymerized polyester (II) 1004 nail part,
Triblend L, each additive in the opening as shown in Table 2,
The mixture was kneaded and pelletized using an extruder with a 30 nφ screw set at 230°C, and i'
A fl product (N~(1)) was obtained.
The resulting composition was pulverized to obtain paint powder having an average particle size of 150 microns. Example 1 using these powders
Table 3 shows the results of the evaluation f+11i conducted in the same manner as in ~3.

<Effects of the Invention> The polyester powder for coating according to the present invention forms a coating film having excellent hardening properties, adhesive properties, and a beautiful surface in a short coating cycle.

Permit applicant Azuma Co., Ltd.

Claims (1)

[Claims] (A) For 100 parts by weight of a copolymerized polyester obtained from a dicarboxylic acid component in which 30 mol% or more and 80 mol% or less is terephthalic acid and a diol component consisting of one or more diols having 2 to 6 carbon atoms, (B) A polyester powder for coating, the main component of which is a composition homogeneously mixed with 0.1 to 15 parts by weight of polybutylene terephthalate.