JP2007204537A - Resin for polyester-based powder coating and method for producing the resin, and polyester-based powder coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin for polyester-based powder coating highly adhesive to to-be-coated objects and containing no heavy metals in consideration of environmental pollution, and to provide such a polyester-based powder coating using the resin. <P>SOLUTION: The resin for polyester-based powder coating is made mainly from an aromatic dicarboxylic acid and a glycol. The resin has a hydroxyl number of 17-65 mgKOH/g. This resin is characterized in containing 100-400 ppm of a magnesium compound coated with titanic acid-based coating layer. A method for producing the above resin is provided, comprising using the above-mentioned magnesium compound as polymerization catalyst and incorporating the magnesium compound at 100-400 ppm based on the final resin. The polyester-based powder coating containing the above resin is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polyester powder coating resin that is excellent in weather resistance and adhesion and is environmentally friendly and does not contain heavy metals such as antimony, a method for producing the same, and a polyester powder coating material containing the resin. It is about.

Compared with solvent-based paints, powder paints are pollution-free paints that do not generate VOCs, can be thickly coated at once, can be used immediately after painting, In recent years, there has been a rapid increase in demand for protective decorative paints for components such as home appliances, building materials, and automobile parts, because they are unnecessary, relatively inexpensive, and can be recovered and used. .
As the powder coating, epoxy resin-based, acrylic resin-based, and polyester resin-based ones are mainly used, and among them, the polyester resin-based powder coating is a coating having a balanced coating film performance.

  Conventionally, antimony compounds represented by antimony trioxide have been widely used as polycondensation catalysts for producing polyester powder coating resins. Antimony trioxide is a polycondensation catalyst that is inexpensive and has excellent catalytic activity. However, in recent years, problems regarding the safety of antimony have been pointed out in Europe and the United States from an environmental viewpoint.

  Studies on polymerization catalysts to replace antimony catalysts such as antimony trioxide have also been conducted, and titanium compounds and tin compounds represented by tetraalkoxy titanates have already been proposed. Polyester powders produced using these compounds The resin for body paint has a problem that the coloring at the time of polymerization or baking of the coating film is intense.

  As an attempt to overcome the problems when such a titanium compound is used as a polymerization catalyst, for example, as disclosed in Patent Document 1, a method of using tetraalkoxy titanate as a polymerization catalyst simultaneously with a cobalt compound has been proposed. However, in these techniques, although coloring when tetraalkoxy titanate is used as a polymerization catalyst is reduced, it is not achieved to effectively suppress thermal decomposition of the resin for polyester powder coating. There is a problem that the film physical properties deteriorate. In addition, with respect to cobalt compounds as well as antimony trioxide, in recent years, safety problems have begun to be pointed out.

  Also, as another attempt to suppress thermal degradation of polyester polymerized using a titanium compound as a catalyst, a method of adding a phosphorus compound after polymerizing a polyester using a titanium compound as a catalyst is disclosed, as in Patent Document 2. ing. However, it is impractical to effectively mix the additives after polymerization, resulting in a complicated production process and cost increase.

Germanium compounds have already been put to practical use as polymerization catalysts that have excellent catalytic activity other than antimony compounds and are excellent in color tone and thermal stability. However, this catalyst is very expensive and is undergoing polymerization. However, since the catalyst concentration in the reaction system changes and polymerization control becomes difficult, there is a problem in using it as a catalyst main component.
JP-A-55-116722 JP-A-10-259296

  The problem to be solved is to provide a polyester-based powder coating resin that is free from heavy metals and is environmentally friendly.

The present invention solves the above-mentioned problems, and the gist thereof is as follows.
(1) A resin mainly composed of an aromatic dicarboxylic acid and glycol and having a hydroxyl value of 17 to 65 mgKOH / g and containing 100 to 400 ppm of a magnesium compound in which a coating layer made of titanic acid is formed. Polyester powder coating resin.
(2) A polyester powder coating composition according to (1), wherein a magnesium compound having a coating layer made of titanic acid is used as a polymerization catalyst, and the compound is added in an amount of 100 to 400 ppm to the resulting resin. Manufacturing method for resin.
(3) A polyester-based powder coating comprising the resin described in (1) above.

  ADVANTAGE OF THE INVENTION According to this invention, the resin for polyester type powder coating materials and polyester type powder coating materials which do not contain the heavy metal represented by antimony and are friendly are provided.

The present invention will be described in detail below.
In the present invention, as the aromatic dicarboxylic acid component, those mainly composed of aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, phthalic anhydride, phthalic acid, naphthalenedicarboxylic acid are used, and if necessary, adipic acid, Aliphatic dicarboxylic acids such as sebacic acid and dodecanedioic acid, and trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid can be used in combination.
Moreover, as a glycol component, what mainly has aliphatic glycols, such as ethylene glycol, diethylene glycol, propylene glycol, 1, 4- butanediol, 1, 6-hexanediol, neopentyl glycol, is used, as needed An alicyclic alcohol such as 1,4-cyclohexanedimethanol, and trihydric or higher alcohols such as trimethylolpropane, glycerin, and pentaerythritol can be used in combination. Moreover, you may use together hydroxycarboxylic acids, such as 4-hydroxybenzoic acid and (epsilon) -caprolactone, as needed.

  The polyester-based powder coating resin of the present invention needs to contain 100 to 400 ppm of a magnesium compound (hereinafter also referred to as a coating) on which a coating layer made of titanic acid is formed. When the polyester-based powder coating resin is added so that the coating is less than 100 ppm relative to the resin during the polymerization reaction, the activity as a polymerization catalyst is not sufficient. The color tone of the resulting polyester-based powder coating resin deteriorates, or the coated body aggregates in the polyester-based powder coating resin to cause foreign matters, thereby impairing the appearance of the coating film.

  In the present invention, a magnesium compound (coated body) having a coating layer made of titanic acid is a titanium compound in the presence of a magnesium compound at a temperature in the range of 5 to 100 ° C., preferably in the range of 15 to 70 ° C. Is hydrolyzed, and titanic acid is precipitated on the surface thereof, whereby the surface of the magnesium compound is provided with a coating layer made of titanic acid.

  Although a magnesium compound is not specifically limited, For example, magnesium hydroxide, magnesium carbonate, magnesium acetate, magnesium acetylacetonate, carboxylates other than acetic acid, etc. are mentioned, Especially magnesium hydroxide is preferable.

  Titanium halides, titanates, and titanium alkoxides are used as the titanium compound.

  The titanium compound and magnesium compound used in the present invention may be used as a coating by using two or more kinds of compounds in either one or both.

  The hydroxyl value of the polyester-based powder coating resin of the present invention is required to be 17 to 65 mgKOH / g. If the hydroxyl value of the polyester powder coating resin is less than 17 mgKOH / g, the molecular weight of the resin is high and the fluidity is lowered, so that not only the processability of the coating film is lowered but also the adhesion to the material is poor. Become. On the other hand, when the hydroxyl value exceeds 65 mgKOH / g, the amount of the curing agent added to the paint increases, resulting in an increase in cost. Moreover, since the crosslink density increases, the smoothness of the coating film decreases.

The polyester powder coating resin of the present invention can be produced, for example, as follows. Raw materials such as the carboxylic acid component and glycol component (including their ester-forming derivatives) are charged into an esterification reaction vessel, and the esterification reaction or the reaction is performed at a temperature of 200 to 280 ° C. in a nitrogen gas atmosphere for 2 to 10 hours. A transesterification reaction is performed. Subsequently, it is transferred to a polycondensation reaction tank, and a magnesium compound (covered body) in which a coating layer made of titanic acid is formed so as to have a concentration of 100 to 400 ppm is added, and the pressure is reduced to 200 to 300 ° C. and 5 hPa or less. A polycondensation reaction is carried out to obtain a polyester-based powder coating resin having a high degree of polymerization. Thereafter, a glycol component is added, and the polymer can be produced by depolymerization at a reaction temperature of 220 to 290 ° C. for 2 to 5 hours.
Alternatively, it can also be produced by adding a covering by the above method, performing a polycondensation reaction under a reduced pressure of a temperature of 200 to 300 ° C. and 100 hPa or less, and ending the polymerization when a predetermined molecular weight is reached.

  The addition method of the magnesium compound (coating body) on which the coating layer made of titanic acid is formed is not particularly limited, but it may be added at the time of the polycondensation reaction as a slurry in which the coating body is dispersed in a dispersion medium. preferable. In addition, 0.5-3 mass% is preferable for content of the coating body in a slurry. If the amount is less than 0.5% by mass, the amount of slurry added increases, and a large amount of distillate is generated during the polycondensation reaction, which tends to increase costs. On the other hand, when the content exceeds 3% by mass, the agglomeration of the coating tends to occur when the slurry is added to the polyester-based powder coating resin, and the coating tends to be coarse particles, which tends to impair the appearance of the coating film.

  The dispersion medium used for the slurry of the coating is ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-butylene glycol, 1,3-butylene. Examples thereof include glycol, 2,3-butylene glycol, and 1,4-butylene glycol. Among these, ethylene glycol is particularly preferable.

  Moreover, in order to prevent coating film appearance abnormality by agglomerating the coating in the polyester powder coating resin, and adding a predetermined amount of the coating to a dispersion medium such as ethylene glycol, stirring and mixing, It is preferable to perform ultrasonic treatment.

  In addition, the frequency of an ultrasonic wave may be a normal frequency region, and for example, a range of about 20 kHz to 100 kHz can be applied. As an oscillation source for generating ultrasonic waves, known means may be used, and examples thereof include a piezoelectric vibrator using crystal, an electrostrictive oscillator using nickel or ferrite, and the like. In addition, the ultrasonic treatment time is preferably in the range of 0.5 to 5 hours.

  Furthermore, if it does not inhibit the effect of the present invention, additives such as antioxidants such as hindered phenol compounds, color improvers such as fluorescent agents and dyes, and light resistance agents are used for polyester powder coatings. It may be contained in the resin.

Next, the manufacturing method of the polyester-type powder coating material of this invention is demonstrated.
It can be produced by adding a leveling agent, an additive, a curing agent, a curing catalyst, etc. to a polyester powder coating resin, and melt-kneading at 70 to 140 ° C. using a kneader or a roll. Then, it coats on a to-be-coated object, and a coating film is obtained by baking for 15-25 minutes normally at the temperature of 170-190 degreeC.

The curing agent used in the polyester powder coating material of the present invention is not particularly limited, but uretdione ring-bonded internal blocked isophorone diisocyanate (BF1540 manufactured by Huls) that does not generate lactam during curing is suitable. Other than this, for example, isophorone diisocyanate curing agent blocked with ε-caprolactam (Hestus Vestagon B-1530, Sumitomo Bayer Urethane Clerant UI), hydrogenated diphenylmethane diisocyanate curing agent blocked with ε-caprolactam (McWHORTER) It is possible to use hardeners, such as a product made from 24-2430) and a glycoluril type hardening | curing agent (POWDER LINK1174 by American Cyanamid Co., Ltd.).
The compounding amount of the curing agent is 0.5 to 1.5 times equivalent, preferably 0.8 to 1.2 times equivalent to the hydroxyl value of the polyester resin.
Further, a dioctyl tin maleate-based curing catalyst (“Stan OMF” manufactured by Sansha Co., Ltd.) may be added as a curing catalyst.

Next, the present invention will be specifically described with reference to examples and comparative examples.
(1) Hydroxyl value 3.0 g of a resin for polyester powder coating is dissolved in 50 ml of pyridine, 0.6 ml of acetic anhydride is added, the mixture is heated and acetylated, and a 0.5 mol / l potassium hydroxide methanol solution is used. Determined by titration.
(2) Color tone Using a color difference meter ND-Σ80 manufactured by Nippon Denka Kogyo Co., Ltd., the b value of a Hunter Lab colorimeter was determined and evaluated. The larger the b value, the stronger the yellow color, and the smaller the b value, the better unless it becomes extremely small.
○: b value is less than 15.0.
X: b value is 15.0 or more.
(3) Smoothness The smoothness and color of the coating film were visually evaluated.
○: The coating film has few unevenness, good smoothness, and good coating film color.
X: The coating film has large unevenness and the smoothness is not good, or the coating film has a poor color.
(4) Impact resistance According to JIS K 5400, a coated steel plate is sandwiched between a shooting mold having a spherical surface with a diameter of 1.27 cm and a cradle having a recess corresponding thereto, so that the coating film comes into contact with the spherical surface. A 0.5 kg weight was dropped vertically to determine the height at which the coating film was destroyed.
○: Even if the weight was dropped from a height of 15 cm, the coating film was not cracked.
X: When the weight was dropped from a height of 15 cm, the coating film was cracked.
(5) Eriksen Determined according to JIS Z 2247.
○: The film was not cracked or cracked even when extruded 2 mm.
X: When extruded 2 mm, the coating film was cracked or cracked.

Example 1
7.386 kmol (1227 kg) of terephthalic acid, 3.1626 kmol (526 kg) of isophthalic acid, and 13.187 kmol (1526 kg) of neopentyl glycol mixed with 10% by weight of water were charged into an esterification reaction tank, and the pressure was 0.25 MPa and the temperature was 260 ° C. A time esterification reaction was performed. After the obtained esterified product is transferred to a polycondensation reaction tank, the concentration of a coated body (a titanium coat MGZ manufactured by Sakai Chemical Industry Co., Ltd.) in which a coating layer made of titanic acid is formed on the surface of magnesium hydroxide as a polycondensation catalyst. 58.3 kg of ethylene glycol slurry prepared at 1.5% by mass (the content of the coating is 350 ppm with respect to the polyester powder coating resin), and the pressure is reduced to 0.5 hPa, and the weight is increased at 280 ° C. for 4 hours. A condensation reaction was performed to obtain a resin having an intrinsic viscosity of 0.45 dl / g. Next, 0.264 kmol (23.8 kg) of glycerin and 0.053 kmol (7.1 kg) of trimethylolpropane were added to this resin, and a depolymerization reaction was performed at 270 ° C. for 1 hour under normal pressure. The characteristic values shown in Table 1 were obtained. A polyester powder coating resin was obtained.
The resulting polyester-based resin for powder coatings is blended with uretdione ring-bonded internal blocked isophorone diisocyanate ("BF1540" from Huls), butylpolyacrylate leveling agent ("Acronal 4F" from BASF), benzoin , Rutile type titanium dioxide pigment (“Taipek CR-90” manufactured by Ishihara Sangyo Co., Ltd.) was added and dry blended with a Henschel mixer (“FM10B type” manufactured by Mitsui Miike Manufacturing Co., Ltd.). 46 type ") was melt-kneaded at 100 ° C, cooled, pulverized, and then classified with a 140 mesh (106 µm) wire mesh to obtain a powder coating material. The obtained powder coating material was electrostatically coated on a zinc phosphate-treated steel sheet so as to have a film thickness of 50 to 60 μm, and baked at 180 ° C. for 20 minutes. Table 1 shows the performance of the coating film.

Examples 2-5
In the same manner as in Example 1, the charge composition and the addition amount of the polymerization catalyst were changed to obtain a polyester powder coating resin as shown in Table 1. Further, a polyester powder coating material was obtained at the blending ratio shown in Table 1 using the obtained polyester powder coating resin.

Comparative Examples 1-4
In the same manner as in Examples 1 to 5, the charge composition and the addition amount of the polymerization catalyst were changed to obtain a polyester powder coating resin as shown in Table 1. Further, a polyester powder coating material was obtained at the blending ratio shown in Table 1 using the obtained polyester powder coating resin.

The color tone of the resin for polyester powder coating obtained in Examples 1 to 5 was good, and the polyester powder coating had good physical properties, flow property of coating film, and color.
In Comparative Example 1, the color tone of the polyester powder coating resin was poor and the color of the coating film was poor. In Comparative Example 2, the polyester-based powder coating resin had a high hydroxyl value, resulting in poor smoothness of the coating film. In Comparative Example 3, the hydroxyl value of the polyester-based powder coating resin was low, the smoothness of the coating film was poor, and the impact resistance and elixsen were poor. In Comparative Example 4, since the addition amount of the polymerization catalyst of the polyester powder coating resin was small, the degree of polymerization did not increase and the reaction was stopped midway.

Claims (3)

A polyester mainly composed of an aromatic dicarboxylic acid and a glycol and having a hydroxyl value of 17 to 65 mgKOH / g and containing 100 to 400 ppm of a magnesium compound having a coating layer made of titanic acid. -Based powder coating resin. 2. The polyester-based powder coating resin according to claim 1, wherein a magnesium compound having a coating layer made of titanic acid is used as a polymerization catalyst, and the compound is added in an amount of 100 to 400 ppm based on the resulting resin. Production method. A polyester-based powder paint comprising the resin according to claim 1.