JPH0120192B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new and useful resin composition for coatings, and more specifically, the present invention relates to a polyfunctional high molecular weight polyester resin obtained by reacting a high molecular weight branched polyester resin with a diepoxide, and a curing agent for the multifunctional high molecular weight polyester resin. The present invention relates to a coating resin composition to which an amino resin and/or a polyisocyanate compound is added. It is generally well known that a resin composition prepared by blending a polymeric linear polyester resin with an amino resin as a curing agent is used as a baking paint. However, in such a polyester resin, the hydroxyl groups that participate in the crosslinking and curing reaction with the curing agent amino resin are only contained at the molecular terminals, and therefore, even if the composition with this amino resin is heated, The curing reaction of the amino resin alone takes priority, and the crosslinking reaction between these two resins is difficult to occur.
As a result, it was not possible to obtain an excellent coating film. On the other hand, according to the specification of Japanese Patent Publication No. 49-40863, an amino resin or a polyisocyanate compound is blended as a curing agent into a polyfunctional polyester resin obtained by reacting a linear polyester resin with a diepoxide. A technique has been proposed in which the above-mentioned drawbacks are improved using a composition obtained by using a paint composition, and a coating composition that provides an excellent coating film is provided. When producing polyfunctional polyester resin, when adding trifunctional or higher functional polyester components in a specific ratio, a coating film with excellent corrosion resistance, flexibility, and hardness can be obtained. Moreover, it has been found that it is also possible to improve the turbidity of the resin solution over time. Here, trifunctional or higher-functional polycarboxylic acid and/or
Alternatively, the proportion of polyol (a-3) used is in the range of 0.3 to 7 mol% in the total acid component in the case of the polycarboxylic acid, and 0.1 to 7 mol% in the total alcohol component in the case of the polyol. range of %,
The optimum usage range is 0.5 for both components.
~5 mol%. The polycarboxylic acid or the polyol is less than 0.3 mol% or 0.1 mol%, respectively.
If the amount is less than mol%, the effect of suppressing turbidity of the resin solution over time cannot be obtained. On the other hand, when the proportion of each component used exceeds 7 mol %, flexibility deteriorates and there is also a risk of gelation during resin production or storage of the resin solution. The above-mentioned "trifunctional or higher functional polycarboxylic acid"
Typical examples of these include trimellitic acid, pyromellitic acid, trimesic acid, and cyclopentanetetracarboxylic acid.On the other hand, typical examples of the above-mentioned "trifunctional or higher functional polyols" include glycerin, trimethylol, etc. Ethane, trimethylolpropane, pentaerythritol,
Examples include dipentaerythritol or mannitol. The multifunctional high molecular weight branched polyester resin (A) constituting the composition of the present invention uses an aromatic dicarboxylic acid (a-1) containing terephthalic acid and/or isophthalic acid as an essential dicarboxylic acid component. and, if necessary, further aliphatic and/or
Alternatively, an alicyclic dicarboxylic acid (a-4) is also used, and on the other hand, a dihydric alcohol mainly composed of alkylene glycol (a-4) is used as the dihydric alcohol component.
-2), and the above-mentioned trifunctional or higher functional polycarboxylic acid and/or polyol (a-
Branched polyester resin (A-1) obtained by polyesterification using 3) according to a conventional method
is obtained by further reacting with diepoxide (A-2), but the polyester resin (A-1) has a ratio of the number of terminal acid groups to the number of terminal hydroxyl groups of 0.2 or more, and a number of The average molecular weight is in the range of 2,000 to 10,000, preferably 3,000 to 8,000. This terminal acid group (number)/terminal hydroxyl group (number) ratio is
If it is less than 0.2, the following diepoxide (A-
The reactivity with 2) deteriorates, making it impossible to sufficiently increase the molecular weight of this branched polyester resin (A-1). In addition, this intermediate polyester resin (A-1)
When the molecular weight of the resin (A-
The amount of diepoxide (A-2) used to increase the molecular weight of 1) will increase, and as a result, the number of functional groups in the multifunctional high molecular weight branched polyester resin (A) itself will increase. If the amount is too large, there is a problem in painting workability. On the other hand, if this molecular weight becomes too large, exceeding 10,000, the number of functional groups in the resulting multifunctional high molecular weight branched polyester resin (A) will be too small, making it impossible to achieve the desired purpose. , is inappropriate. Here, the above-mentioned terephthalic acid and/or
Or, as the aromatic dicarboxylic acid (a-1) that essentially includes isophthalic acid, terephthalic acid or isophthalic acid should be used alone or in combination, and in addition to these, phthalic acid It can also be used in a form that includes various compounds other than terephthalic acid and isophthalic acid, such as methyl terephthalic acid, ethyl terephthalic acid or naphthalene dicarboxylic acid,
Furthermore, so-called reactive derivatives such as the above-mentioned anhydrides or alkyl esters of aromatic dicarboxylic acids can also be used. Aromatic dicarboxylic acid (a-1) within this range
By using terephthalic acid and/or isophthalic acid as essential dicarboxylic acids, the physical properties of the coating film of the composition of the present invention, especially the corrosion resistance and weather resistance, are significantly improved. In addition, in the present invention, representative examples of the aliphatic and/or alicyclic dicarboxylic acids (a-4) that may be added as necessary include tetrahydrophthalic acid, methyltetrahydrophthalic acid, and hexahydrophthalic acid. , hexahydroterephthalic acid, methylhexahydrophthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid; maleic acid, fumaric acid,
These include itaconic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, pimelic acid, suberic acid, sebacic acid, and dimeric fatty acids. These aliphatic and/or cycloaliphatic dicarboxylic acids (a-
4) can be used in combination as necessary, taking into consideration mechanical coating film properties such as flexibility and economical efficiency. On the other hand, typical dihydric alcohols (a-2) are ethylene glycol, propylene glycol, trimethylene glycol, 1,4
-butanediol, 1,3-butanediol,
Alkylene glycols such as 1,5-pentanediol, isopentyl glycol, 1,6-hexanediol or neopentyl glycol; in addition to these, 1,4-cyclohexanedimethanol, bishydroxyethyl terephthalate, hydrogenated bisphenol. A, an alkylene oxide adduct of hydrogenated bisphenol A, an aromatic glycol such as diethylene glycol, an alicyclic glycol, or an aliphatic glycol other than the alkylene glycols listed above may also be used in appropriate amounts as necessary. . Moreover, it goes without saying that a monoepoxy compound can also be used in combination as a glycol component. Furthermore, the diepoxide (A-2) to be reacted with the branched polyester resin (A-1) is
It refers to a resin that has two epoxy groups in its molecule that are reactive with the carboxyl group in the resin (A-1).
828”, “1001” or “1004” (both
Bisphenol-type epoxides such as Glycerin diglycidyl ether or neopentyl glycol diglycidyl ether (products of Siel, Netherlands); aliphatic ether-type diepoxides such as glycerin diglycidyl ether or neopentyl glycol diglycidyl ether; and ester-type diepoxides such as diglycidyl phthalate, diglycidyl tetrahydrophthalate, and diglycidyl ester of dimer acid. In order to cause this diepoxide (A-2) to undergo an addition reaction with the above-mentioned intermediate polyester resin (A-1), the number of terminal carboxyl groups in the resin (A-1) must be Diepoxide (A
-2) is appropriate. In addition, the appropriate temperature for this epoxy addition reaction is generally a temperature of 140°C or less, but the esterification of the secondary hydroxyl group and the terminal carboxyl group that are generated in the addition reaction between the terminal carboxyl group and the epoxy group To prevent a reaction, you need to
It is desirable to carry out the epoxy addition reaction at a temperature of about 110 to 130°C. In addition, the above-mentioned intermediate polyester resin (A-
The reaction to obtain 1) can be carried out by either the melt method or the solvent method, and it goes without saying that this reaction can be carried out using a conventionally known esterification catalyst. However, in reality,
Monobutyltin oxide, dibutyltin oxide or “Fascat 4100” (USA M &
The use of tin compounds such as T (monobutyl stannic acid manufactured by M & T) is effective and their use is particularly recommended. In addition, this intermediate polyester resin (A-1)
The organic solvent used in the reaction with diepoxide (A-2) is aromatic hydrocarbons such as benzene, toluene, xylol, and "Solbetsuso 100" and "Solbetsuso 150" (all products of Etsuso). ,
Methyl ethyl ketone, methyl isobutyl ketone,
Examples include ketones such as cyclohexanone and isophorone, as well as esters such as ethyl acetate, butyl acetate, cellosolve acetate, cellosolve, n-butanol, octanol, 3-methyl-3-methoxy-butanol, butyl carbitol, Alcohols such as diethyl carbitol and butyl celorsobu can be used in combination. Furthermore, ethers can also be used if necessary. However, if an alcoholic solvent is used as a solvent for carrying out this epoxy addition reaction, it will delay the reaction or cause side reactions, and therefore their use should be avoided. The preferred blending ratio of the polyfunctional branched polyester resin (A) thus obtained and the above-mentioned amino resin and/or polyisocyanate compound (B) as its curing agent is 99:1 to 60:40 by weight. Yes, and more preferably within the range of 95:5 to 75:25. Here, typical examples of the amino resin (B-1) include aminotriazine compounds such as melamine and benzoguanamine, or urea,
These include condensates obtained by reacting urea-based compounds such as thiourea with formaldehyde or its equivalent substances by known methods, or those obtained by etherifying these condensates with alcohols.On the other hand, the above-mentioned Examples of polyisocyanate compounds include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; aromatic diisocyanates such as xylylene diisocyanate and tolylene diisocyanate, or nuclear hydrogenated products of these aromatic diisocyanates; and isophorone diisocyanate. Representative examples include alicyclic diisocyanates, and further examples include polymers of these diisocyanates or adducts with polyhydric alcohols. Blocked diisocyanates can also be used, and the blocking agents include phenols, lactams, active methylenes, alcohols, mercaptans, acid amide, imide, amine, , amidazole type, amine type, urea type, oxime type and sulfite type. Furthermore, as dissociation catalysts for such blocked diisocyanates, conventional ones containing tin compounds such as dibutyltin dilaurate can be used. When an amino resin (B-1) is used as a curing agent, a coating film with high hardness is formed, while when a polyisocyanate compound (B-2) is used, a coating film with high flexibility and impact resistance is formed. Since an excellent coating film can be formed, both of these resins can be appropriately selected in order to balance the coating film performance depending on the required performance. Thus, in order to obtain the composition of the present invention from the above-described multifunctional high molecular weight branched polyester resin (A) and curing agent (B), a mixer such as a roll kneader, ball mill or blender is used to mix them. Both components may be mixed. The composition of the present invention thus obtained can be coated by roller coating, roll coater, spray coating, electrostatic coating, or the like, as appropriate. The composition of the present invention has excellent storage stability, especially the ability to prevent or suppress clouding of resin solutions over time during storage, and the coating film obtained by baking has excellent solvent resistance, corrosion resistance, etc. It is also possible to balance hardness and flexibility. Next, the present invention will be specifically explained using examples. Hereinafter, all parts and percentages are based on weight unless otherwise specified. Reference Example 1 [Example of preparation of polyfunctional high molecular weight branched polyester resin (A)] 228 parts of terephthalic acid, 76 parts of isophthalic acid, 92 parts of sebacic acid, 69 parts of ethylene glycol, 113 parts of neopentyl glycol, 3 parts of trimethylolpropane 1 part and 0.5 part of monobutyltin oxide were charged into a reaction vessel, and the mixture was heated within 6 hours under a nitrogen gas stream.
Gradually raise the temperature to 220℃, and keep it at the same temperature for 4 hours.
Hold time. Next, 15 parts of xylene was added dropwise under reflux to promote dehydration, and the reaction was continued while maintaining the reaction temperature at 220°C to obtain an intermediate polyester resin having an acid value of 15 and a hydroxyl value of 4. The number average molecular weight of this product was 6,200. After that, this intermediate polyester resin was dissolved in "Swasol 1500" (Maruzen Oil Co., Ltd. product) - cyclohexanone mixed solvent (weight ratio 85/15) to adjust the nonvolatile content to 50%, and "Deconal EX" was added to this.
-211'' (diglycidyl ether of neopentyl glycol sold by Nagase Sangyo Co., Ltd.) 17.5 parts and 0.2 parts of 2-methyl-imidazole were added,
The temperature was raised to 125°C and a heating reaction was carried out for 10 hours. After the reaction, add "Swazol 1500" and cyclohexanone to make the nonvolatile content 40% and the acid value 1.2 without
A multifunctional high molecular weight branched polyester resin solution having a number average molecular weight of 12,500 was obtained. The viscosity of this resin solution was between Z ₄ and _{Z 5} according to the Gardner method. Hereinafter, this will be referred to as "polyester resin solution (A-)"
It is abbreviated as Note that this resin solution (A-) still remained transparent even after being left at room temperature for 180 days after production. Reference Example 2 (Same as above) The polyesterified components were 60 parts of terephthalic acid, 60 parts of isophthalic acid, 247 parts of adipic acid, 44 parts of ethylene glycol, 74 parts of neopentyl glycol, 1.
Reference Example 1 except that 82 parts of 6-hexanediol and 15 parts of trimethylolpropane were used.
In the same manner as above, an intermediate polyester resin having an acid value of 28, a hydroxyl value of 9, and a number average molecular weight of 3,040 was obtained. Since then, "Epicron 1050-70X" (Dainippon Ink Chemical Industry Co., Ltd.) has been used instead of "Denacol EX-211".
Except for 173 parts of high melting point epoxy resin manufactured by Co., Ltd.
Repeat the same operation as in Reference Example 1 until the non-volatile content is 40
%, Gardner viscosity is Z ₅ , acid number 1.2,
A multifunctional high molecular weight branched polyester resin (A-) having a number average molecular weight of 8,600 was obtained. Incidentally, like the resin solution (A-) in Reference Example 1, this resin solution (A-) also showed no turbidity and had good storage stability. Reference Example 3 (Same as above) The composition of the polyester component was changed to 231 parts of terephthalic acid, 77 parts of isophthalic acid, 89 parts of sebacic acid, 4 parts of trimellitic anhydride, 85 parts of ethylene glycol, and 95 parts of neopentyl glycol, and An intermediate polyester resin having an acid value of 10, a hydroxyl value of 4, and a number average molecular weight of 7160 was obtained in the same manner as in Reference Example 1, except that the same amount of "Fascat 4100" was used in place of butyltin oxide. Thereafter, the same procedure as in Reference Example 1 was repeated except that the amount of "Deconal EX-211" was 12.5 parts and the heating time was ₆ hours. A multifunctional high molecular weight branched polyester resin solution (A-) having an acid value and a number average molecular weight of 1.0 and 12,700, respectively, was obtained. Note that, similarly to the resin solution (A-) in Reference Example 1, this resin solution (A-) also showed no turbidity and had good storage stability. Reference Example 4 (Same as above) The polyester component was changed to a composition of 192 parts of terephthalic acid, 192 parts of isophthalic acid, 74 parts of ethylene glycol, 122 parts of neopentyl glycol, and 3 parts of trimethylolpropane, and replaced with monobutyltin oxide. An intermediate polyester resin having an acid value of 10, a hydroxyl value of 18, and a number average molecular weight of 3,080 was obtained in the same manner as in Reference Example 1, except that the same amount of "Fascat 4100" was used. From now on, 12 will be replaced with "Denacol EX-211"
The procedure was carried out in the same manner as in Reference Example 1, except that "NER-010" (glycerin diglycidyl ether sold by Nagase Sangyo Co., Ltd.) was used. ₄ , and a multifunctional high molecular weight branched polyester resin (A-) having an acid value and a number average molecular weight of 9700, respectively, was obtained. Note that, similarly to the resin solution (A-) in Reference Example 1, no turbidity was observed in this resin solution (A-), and it was confirmed that it had good storage stability. Reference Example 5 (Preparation example of polyester resin for comparison) 226 parts of terephthalic acid, 75 parts of isophthalic acid, 92 parts of sebacic acid, 70 parts of ethylene glycol, 115 parts of neopentyl glycol, 3 parts of trimethylolpropane, and 0.5 parts of "Fascat4100". The mixture was charged into a reaction vessel, and the temperature was raised to 220°C over 6 hours under a nitrogen gas flow, and the temperature was then maintained at the same temperature for 4 hours. Next, 15 parts of xylol was added dropwise under reflux, and the reaction was further continued at 220°C for 16 hours.
A polyester resin having an acid value of 5 and a hydroxyl value of 6 was obtained. The number average molecular weight of this product was 11,200. After that, this polyester resin was mixed with "Swazol 1500"/cyclohexanone mixed solvent (weight ratio
When the non-volatile content was adjusted to 40%, a polyester resin solution (A'-) with a Gardner viscosity of _Z1 was obtained. Note that this resin solution (A'-) had already precipitated and separated into two layers after 5 days of being left at room temperature after production. Reference example 6 (same as above) The polyester component and its composition were changed to terephthalic acid.
141 parts of isophthalic acid, 106 parts of adipic acid, and 123 parts of neopentyl glycol.
14, a hydroxyl value of 5, and a number average molecular weight of 4,480. From now on, except for changing the heating temperature to 120℃,
Repeat the same operation as in Reference Example 1 to reduce the non-volatile content to 40
%, a Gardner viscosity of Z ₃ -Z ₄ , and an acid value and a number average molecular weight of 1.0 and 10,700, respectively, a polyester resin solution (A') was obtained. This resin solution (A'-) also has poor storage stability like the resin solution (A'-) obtained in Reference Example 5, and it precipitates into two layers when left at room temperature for 5 days after production. It was separated.

[Table] Examples 1 to 7 and Comparative Examples 1 to 3 Each multifunctional high molecular weight polyester resin solution obtained in Reference Examples 1 to 4 (A-), (A-),
For 100 parts each of (A-) and (A-) and the polyester resin solutions (A'-) and (A'-) obtained in Reference Examples 5 and 6, amino resin or polyisocyanate as a curing agent was added. Add the specified amount of resin to Table 2,
plus 20 parts zinc chromate and 20 parts titanium oxide
10 parts were added and kneaded for 2 hours in a ball mill to obtain a total of 10 types of coating compositions. These coating compositions were then applied to separate zinc phosphate treated steel sheets each having a thickness of 0.6 mm to a film thickness of 15 to 20 μm.
After painting it so that it looked like this, it was baked at 260℃ for 1 minute. Physical property tests were conducted on each of the coating films thus obtained. The results are summarized in Table 2.

【table】

【table】

Claims (1)

[Scope of Claims] 1 (A) Aromatic dicarboxylic acid (a-1) containing terephthalic acid and/or isophthalic acid as essential
and dihydric alcohol (a-2) mainly composed of alkylene glycol as the main polyesterification components, and further added with a proportion of 0.3 to 0.3 to
0.1 to 7 based on 7 mol% trifunctional or higher functional polycarboxylic acid and/or total alcohol component
mol % of trifunctional or higher functional polyol (a-3) is also used, and if necessary, aliphatic dicarboxylic acid and/or alicyclic diol (a-4) is also used.
is also present, and the ratio of the number of terminal acid groups to the number of terminal hydroxyl groups is 0.2 or more, and the number average molecular weight is 2000 or more, obtained by polyesterifying these.
(B) Amino A resin composition for coatings, which contains one or more curing agents selected from the group consisting of resin (B-1) and polyisocyanate compounds.