JPS6146503B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides an aqueous coating composition, more specifically, a cocondensate of a hydroxyl group-containing polycarboxylic acid resin and a water-insoluble amino resin as a base resin, which can be used as a reactive diluent in an amino resin curable composition system. The present invention relates to a thermosetting aqueous coating composition mixed with a polyether polyol. Conventionally, a polyvalent carboxylic acid resin having an acid value of 20 to 100 and having a hydroxyl group and a carboxyl group in its molecule is neutralized with an organic or inorganic base to form an aqueous solution or aqueous dispersion, and in order to impart thermosetting properties to the base resin. Paint systems containing water-soluble amino resins that can cross-link with the hydroxyl groups present in polyhydric carboxylic acid resins are superior to conventional solvent-based paints in several respects, including gloss, physical properties, and chemical stability. However, it has some drawbacks, namely, the use of low molecular weight water-soluble amino resins, which tend to cause repellency in the coating, and to solve this problem, the addition of an anti-repellent agent was introduced. Measures have been taken, but this is due to a decrease in non-sand interlayer adhesion (interlayer adhesion when the same coating is layered without surface sanding), and water-soluble amino resins are difficult to separate due to coagulation and precipitation. Therefore, there are disadvantages such as the need for separate wastewater treatment equipment, and in order to solve this problem, a co-condensate of a hydroxyl group-containing polycarboxylic acid resin and a water-insoluble amino resin is used. By baking at a lower temperature than conventional water-based paints, it produces a coating film with excellent gloss, smoothness, and durability.
A thermosetting coating composition has been found which is free from defects such as repellency and which greatly facilitates wastewater treatment. However, in the case of a co-condensate, which is a type of ion-dissociable water-soluble resin, the viscosity rapidly increases at the phase change point during baking, and has the disadvantage that wrinkles are likely to occur. The present invention has been made to solve this problem, and by mixing polyether polyol, which is a non-ionically dissociable water-soluble resin, to prevent phase transformation, it is possible to create a solution-based coating material with solution behavior. It has properties close to those of painting workability. The polyether polyol used here has the following general formula [H-(OCH ₂ CH ₂ ) _o -O-R- O-(CH ₂ CH ₂ O) _o -H where R in the general formula is

[expression] or

[Formula] n is an integer from 2 to 10. ] It is indicated by. By mixing 5 to 120 parts by weight, preferably 10 to 100 parts by weight, of this to 100 parts by weight of the cocondensate, an aqueous coating composition having excellent performance can be obtained. The hydroxyl group-containing polycarboxylic acid resin used in the present invention has an acid value of 20 to 100 and a hydroxyl value of 20 to 100.
Any resin having a molecular weight of 200 can be used, including all conventionally known water-soluble resins, and typical examples include the following. (1) Carboxyl group-containing polymerizable unsaturated monomers such as (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, hydroxyalkyl (meth)acrylates (the number of carbon atoms in the alkyl group is 2 to 4,
For example, hydroxyl group-containing polymerizable unsaturated monomers such as (meth)acrylate-2-hydroxyethyl, -2-hydroxypropyl, -2-hydroxybutyl, etc.) and polymerizable monomers copolymerizable with these. It is obtained by copolymerizing. Preferably, an acrylic resin or a vinyl resin having a number average depth weight of 5,000 to 40,000. (2) Ethylene glycol, diethylene glycol, propylene glycol, butanediol,
Polyhydric alcohols such as pentanediol, 2,2-dimethylpropanediol, glycerin, trimethylolpropane, pentaerythritol, and monohydric alcohols used in combination as necessary, or monoepoxy compounds having one glycidyl group in the molecule (e.g. , Karjiura E
(Product name, manufactured by Ciel Chemical Co., Ltd.)" as an alcohol component, phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic anhydride, succinic anhydride, adipic acid, sebacic acid, trimerizanhydride. An oil obtained by condensing the above alcohol component and the above acid component with a polybasic acid such as acid, pyromellitic anhydride, and a monobasic acid such as benzoic acid or t-butylbenzoic acid used in combination as necessary. Free alkyd resin, or in addition to the above alcohol component and the above acid component, castor oil, dehydrated castor oil, tung oil, safflower oil, soybean oil, linseed oil, tall oil, coconut oil, etc., and one type of fatty acid thereof. Or an oil-modified alkyd resin obtained by adding an oil component which is a mixture of two or more types to the above acid component and an alcohol component and reacting the three components, and preferably has a number average molecular weight of 500 to 10,000. . (3) A graft copolymer obtained by grafting an acrylic resin or a vinyl resin onto an alkyd resin, preferably having a number average molecular weight of 5,000 to 20,000, for example, an alkyd resin having a polymerizable unsaturated group and a vinyl monomer and/or Or a graft copolymer obtained by reacting acrylic monomers.
In addition, phenolic resins and epoxy resins having an acid value of 20 to 100 and a hydroxyl value of 20 to 200 can also be used. The acid value of these hydroxyl group-containing polycarboxylic acid resins is 20 to 100, and the hydroxyl value is 20 to 200, but if both the acid value and the hydroxyl value are less than 20, the resulting cocondensation composition may be aqueous. This is not preferable because it is difficult to achieve this and the stability is further reduced. Furthermore, if the acid value exceeds 100 or the hydroxyl value exceeds 200, it is not preferable because gelation or insolubilization may occur during the cocondensation reaction described below. These hydroxyl group-containing polycarboxylic acid resins are usually subjected to a reaction with a water-insoluble amino resin as a solution with a solid content of 40 to 90% by weight, and the solvent in this case is, for example, methyl-, ethyl-, Alcohol solvents such as isopropyl, n-propyl, and butyl alcohol; Ether alcohol solvents such as methyl cellosolve, cellosolve, and butyl cellosolve; Ester solvents such as methyl cellosolve acetate and cellosolve acetate; and ketone solvents such as acetone. Organic solvents that are freely miscible with water are used. The water-insoluble amino resin used in the present invention is, for example, a melamine resin etherified with a higher aliphatic alcohol having 4 or more carbon atoms, such as n-butyl, isobutyl, or hexyl etherified melamine resin, or hexamethylol melamine. In addition, melamine-urea cocondensation resins, urea-formaldehyde resins, and guanamines such as benzoguanamine can be mentioned. These can be used alone or in the form of a mixture of two or more. In the present invention, in order to produce a co-condensation composition of a hydroxyl group-containing polycarboxylic acid resin (component A) and a water-insoluble amino resin (component B), 5 to 5 parts by weight per 100 parts by weight of component A in terms of solid content are required. 70 parts by weight of component B is blended and the temperature is usually 40 to 120°C, preferably 50 to 80°C.
What is necessary is to react for 0.5 to 5 hours. When producing the co-condensation composition, if the amount of component B blended is less than 5 parts by weight per 100 parts by weight of component A, crosslinking properties will be insufficient and sufficient coating performance cannot be expected. If Component B is used in an amount exceeding 70 parts by weight, the amino resin may become gelled or insolubilized due to self-condensation, making it difficult to produce the aqueous co-condensation composition of the present invention. The reaction temperature when producing the co-condensation composition is 40°C.
If the amount is less than that, the cocondensation reaction will be slow and it will be difficult to obtain the desired cocondensation composition. On the other hand, 120℃
If it exceeds this amount, gelation tends to occur during the cocondensation reaction. It goes without saying that the cocondensation temperature is important in producing a stable cocondensation resin, but the present invention is characterized in that it is cocondensed without adding a neutralizing agent. That is, if a neutralizing agent is added during co-condensation, the co-condensation does not proceed and if a paint is formed, the water-insoluble amino resin may separate in the liquid, causing a change in viscosity or separation into two layers during storage. Such defects do not occur in the present invention. The basic substances used to neutralize the co-condensation composition include ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, dimethylethanolamine, diethanolamine,
Examples include triethanolamine. The amount of neutralization of carboxyl groups in the cocondensate is preferably 50% or more. Using the thus obtained aqueous solution or aqueous dispersion of the co-condensed composition as a base resin, the polyether polyol and, if necessary, various inorganic pigments, organic pigments, fillers and/or additives, etc. are blended. By doing so, the aqueous coating composition targeted by the present invention can be obtained. The thermosetting water-based coating composition of the present invention is used for electrodeposition paints, intermediate coatings, water-based baking paints for top coats, water-based baking paints for base coatings, and the like. The method for applying the coating composition of the present invention includes:
In addition to air spray painting, airless spray painting, brush painting, dipping painting, electrostatic painting, roller painting,
Alternatively, an electrodeposition coating method or the like can be used. In addition, the heat treatment conditions after coating the coating composition of the present invention are such that an excellent coating film can be obtained by heat treatment for 10 to 60 minutes at an appropriate temperature in the range of usually 80 to 250°C, preferably 100 to 180°C. can be caused to form. The feature of the present invention is that the coating workability is significantly improved by using a water-insoluble amino resin as a crosslinking agent and mixing polyether polyol. In other words, most of the amino resins conventionally used as crosslinking agents have a low molecular weight (generally, they are mononuclear) to make them water-soluble, and they have the disadvantage of being susceptible to defects such as cissing. It was hot. In order to solve this problem, anti-cissing agents are added, but this often has negative effects such as a decrease in adhesion or the formation of wrinkles during baking. However, since water-insoluble amino resins can be used in water-based paint compositions as in the present invention, high molecular weight (polynuclear) melamine resins,
Alternatively, since a butyl etherified melamine resin can be used, not only coating film defects such as repellency peculiar to water-based baking paints are significantly improved, but also non-sand adhesion is significantly improved. Furthermore, when considering wastewater treatment in coating systems, most conventional water-based baking paints use water-soluble amino resins, making it difficult to separate the resin by coagulation and sedimentation. By using a water-insoluble amino resin, it is possible to separate the amino resin, which is a crosslinking agent, from the base resin at the same time as the base resin through coagulation and precipitation by adding an acid, which is economical in terms of wastewater treatment. It's advantageous. Furthermore, by mixing polyether polyol as a reactive diluent, it is possible to reduce the amount of organic solvent neutralizing agent, which is effective in saving resources.Additionally, by mixing the above polyol, it exhibits solution behavior, has good flow, and can be used during painting. The nonvolatile content is increased, and gloss and painting workability are improved. In addition, physical properties, hardness, moisture resistance, and corrosion resistance are improved. The present invention will be described below with reference to Examples, but these are merely illustrative of one embodiment of the present invention, and the present invention is not limited to these. All parts and percentages hereinafter are based on weight unless otherwise specified. Example 1 After reacting 26 parts of neopentyl glycol, 20 parts of trimethylolpropane, 40 parts of adipic acid, and 14 parts of trimellitic anhydride at 200 to 230°C for 5 hours, 11 parts of phthalic anhydride was added and further reacted at 160°C for 1 hour. An oil-free alkyd resin A having a molecular weight of 7,000, an acid value of 88, and a hydroxyl value of 62 was obtained. Add 20 parts of Cellosolve and 61 parts of Yuban 20SE (70% butanol solution) [trade name manufactured by Mitsui Toatsu Co., Ltd.], which is a type of butoxymethylated melamine resin, to 100 parts of resin A, and heat at 70°C.
After carrying out the cocondensation reaction for 2 hours, 10.5 parts of diethylamine was added to remove the carboxyl groups in the resin.
Neutralized 100%. Titanium white JR-600E (trade name manufactured by Teikoku Kako Co., Ltd.) per 100 parts of solid content of this varnish.
and After blending 50 parts of the polyether polyol shown in the formula, kneading it in a pebble mill for 7 hours, adding water and adjusting it for 50 seconds with a food cup #4, and spraying it on a partially painted iron plate, the coating workability was excellent. By heat treatment at 150℃ for 30 minutes, we were able to obtain a glossy, smooth film with no defects such as repellents or wrinkles, and excellent coating performance such as water resistance, chemical resistance, and weather resistance. Example 2 1,6-hexanediol 27 parts Cardiula E [trade name manufactured by Schiel Kagaku Co., Ltd.] 22 Trimethylolpropane 12 Phthalic anhydride 39 Trimellitic anhydride 11 were reacted at 200 to 230°C for 5 hours to obtain a molecular weight of 800. ,
An alkyd resin having an acid value of 32 and a hydroxyl value of 181 was obtained. After adding 20 parts of butyl carbitol and 16 parts of Euban 20SE to 100 parts of the above resin B and carrying out a co-condensation reaction at 50°C for 3 hours, dimethylaminoethanol
5.1 parts were added to neutralize 100% of the carboxyl groups in the resin. To 90 parts of the solid content of this varnish, 10 parts of the polyether polyol used in Example 1, Titanium White JR
-600E and 12 parts of Sumimaru HM-100 (83% butyl cellosolve solution) [trade name manufactured by Sumitomo Chemical Co., Ltd.], which is a water-soluble melamine resin, were mixed together, and 8 parts were mixed in a ball mill.
After kneading for an hour, water/isopropyl alcohol =
It was diluted with 3/1 thinner and adjusted to 50 seconds using a #4 food cup, painted in the same manner as in Example 1, and heat-treated, resulting in gloss, smoothness, and coating performance with no defects such as repelling or wrinkling. An excellent coating was obtained. Example 3 Neopentyl glycol 31 parts Trimethylolpropane 7 Phthalic anhydride 24 Tetrahydrophthalic anhydride 17 Trimerite anhydride 5 Tall oil fatty acid 15 After reacting at 200 to 230°C for 5 hours, 8 parts of phthalic anhydride was added, Further, the reaction was carried out at 180° C. for 1 hour to obtain alkyd resin C having a molecular weight of 5,600, an acid value of 45, and a hydroxyl value of 32. 100 parts of the above resin, 15 parts of methyl carbitol, and Supervecamine J-820 (70% butanol solution), a type of butoxymethylated melamine resin [trade name manufactured by Nippon Reichhold Co., Ltd.]
After adding 48 parts and carrying out a cocondensation reaction at 60°C for 1 hour, 6.7 parts of diethanolamine was added to neutralize 80% of the carboxyl groups in the resin. For 100 parts of solid content of this varnish 100 parts of polyether polyol shown by, 80 parts of titanium white JR-600E, 20 parts of precipitated barium sulfate,
Neo Spectra Beads AG〔Columbia Carbon
Co. product name] 1 part and kneaded in a ball mill for 8 hours, then diluted with water and placed in a food cup #4.
When adjusted to 60 seconds and spray-painted on a steel plate, the coating workability was excellent, and when heat-treated at 140℃ for 30 minutes, it had no defects such as repelling or wrinkling, and had excellent gloss, smoothness, and coating performance. A coating film with significantly improved non-sand interlayer adhesion was obtained. Example 4 Styrene 30 parts n-butyl acrylate 38 2-hydroxyethyl methacrylate 25 acrylic acid 7 azobisisobutyronitrile 3 were dropped into 50 parts of butyl cellosolve heated to 120°C and polymerized over 7 hours. Acrylic resin D (67% butyl cellosolve solution) having an acid value of 54, a hydroxyl value of 107, and a molecular weight of 20,000 was obtained. Add 150 parts of this solution to Melan X-28 (70% isobutanol solution), a type of butoxymethylated melamine resin [Hitachi Chemical
Co., Ltd. product name] was added and a co-condensation reaction was carried out at 90°C for 2 hours, and then 7.8 parts of triethylamine was added to neutralize 80% of the carboxyl groups in the resin.
119 parts were added to obtain an aqueous dispersion with a solid content of 40%. For 100 parts of solid content of this aqueous dispersion Mix 30 parts of polyether polyol and 8 parts of aluminum pigment, disperse with a disperser for 1 hour, add water, adjust the time with a #4 food cup for 30 seconds, spray paint on an iron plate, and apply it at 150℃ for 30 minutes. The heat treatment made it possible to obtain a film with good coating performance, which was free from defects such as repellency and wrinkles, and had excellent gloss, metallic feel, and smoothness. Example 5 100 parts of alkyd resin C obtained in Example 3 was dissolved in 133 parts of methyl cellosolve, and while heating to 120°C Styrene 18 parts Methyl methacrylate 12 i-Butyl acrylate 24 2-ethylhexyl methacrylate 32 Acrylic A mixture of 4 2-hydroxyethyl acrylic acids, 10 t-butyl perbenzoate, and 8 t-butyl perbenzoates was added dropwise and graft polymerized over 7 hours to obtain acrylic graft alkyd resin F (70% methyl cellosolve solution) was obtained. After adding 67 parts of Supervecamine J-820 to 100 parts of this solution and causing a co-condensation reaction at 110°C for 30 minutes, 100% of the carboxyl groups in the resin were neutralized with 7.7 parts of triethylamine. Titanium white JR− per 100 parts of solid content of this varnish.
80 parts of 600E and Mapico Yellow XLO (color pigment)
[Product name manufactured by Titan Kogyo Co., Ltd.] 20 parts were mixed and kneaded in a pebble mill for 5 hours. Adding 70 parts of the polyether polyol shown in the formula, diluting it further with water, adjusting the coating time using a #4 food cup for 50 seconds, painting in the same manner as in Example 1, and heat treating resulted in gloss and smoothness with no defects such as creases or wrinkles. A film with excellent coating performance was obtained.

Claims (1)

[Claims] 1. Cocondensation of 100 parts by weight of a hydroxyl group-containing polycarboxylic acid resin with an acid value of 20 to 100 and a hydroxyl value of 20 to 200 and 5 to 70 parts by weight of a water-insoluble amino resin that is compatible with the above resin. For 100 parts by weight of the compound, the following general formula [H(OCH ₂ CH ₂ ) _o -O-R-O- (CH ₂ CH ₂ O) _o H In the general formula, R is [Formula] or [Formula] n is an integer from 2 to 10. ] A thermosetting aqueous coating composition containing 5 to 120 parts by weight of the polyether polyol shown below.