JPH039947B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a coating resin composition containing a high molecular weight polyester resin as a main component. More specifically, polyester precondensate [A] obtained by reaction of dihydric carboxylic acids and/or their alkyl esters with dihydric alcohols, polyepoxy compounds having at least two epoxy groups in one molecule The present invention relates to a method for producing a coating resin composition whose main component is a high molecular weight polyester resin obtained by reacting [B] and polycarboxylic anhydride [C]. Conventionally, it has been known that high molecular weight saturated polyesters made by reacting dibasic acids such as terephthalic acid and isophthalic acid with dihydric alcohols can be used for applications such as paints and adhesive inks. The method for producing is a transesterification method in which lower alkyl esters of dibasic acids such as terephthalic acid and isophthalic acid are transesterified with ethylene glycol, etc., purified, and then polycondensed, or dibasic acids such as terephthalic acid and isophthalic acid are A direct esterification method has been used in which an acid is directly esterified with a dihydric alcohol and then polycondensed, but both methods require a high degree of vacuum in the polycondensation reaction process, and industrially it is difficult to manufacture at a high degree of vacuum. The drawback was that it required equipment and ended up using expensive polyester. Furthermore, even if this type of high molecular weight linear polyester is used as a baking paint by blending it with a crosslinking agent such as an amino resin or a polyisocyanate compound, the functional group that participates in the reaction with the crosslinking agent is contained at the end of the molecule. However, there was a drawback that a sufficient crosslinking reaction did not occur and a coating film with excellent performance could not be obtained. It also has poor compatibility with amino resins, which are crosslinking agents. Several methods have been proposed to overcome these drawbacks. For example, according to JP-A No. 54-24998, a saturated dibasic acid and a glycol are reacted according to a known procedure to form an initial condensate, and a diisocyanate is added to this to increase the molecular weight. A method is proposed.
However, although such a method does not require high-vacuum production equipment, it only yields a polyester in which the functional groups that participate in the crosslinking reaction are located at the terminals of the molecule, and are unable to exhibit excellent coating film performance. Furthermore, according to JP-A-55-155060, ordinary esters are prepared by using an acid component consisting of an aromatic dibasic acid and an aliphatic saturated dibasic acid and an aliphatic saturated glycol having 2 to 10 carbon atoms. An initial polyester condensate is prepared by a chemical reaction, and an epoxy compound having two epoxy groups in one molecule is added to this so that the amount of epoxy groups is at least equivalent to the carboxyl group in the initial polyester condensate. A method has been proposed in which the molecular weight is increased by reacting at a certain ratio, and a hydroxyl group as a crosslinkable functional group is generated in the molecule by the reaction between a carboxyl group and an epoxy group. However, in this method, an equivalent or more amount of epoxy groups is reacted with the carboxyl groups in the initial polyester condensate, so the acid value of the final resin inevitably becomes a low value. For this reason, even if a crosslinking agent such as an amino resin is blended into a resin composition for coatings containing this high molecular weight saturated polyester as a main component, the effect of the acid value as an internal catalyst is small because the acid value of the resin is low. Sufficient coating performance cannot be obtained under normal baking conditions. In order to compensate for this drawback, external catalysts such as para-toluenesulfonic acid are sometimes used together, but such external catalysts have the disadvantage that their effectiveness gradually decreases during storage of the paint when used in combination with the paint. Furthermore, since the resin acid value is low, the compatibility with curing agents such as amino resins is also poor.
On the other hand, if an attempt is made to keep the acid value at a high value, the reaction stops before the reaction between carboxyl groups and epoxy groups has progressed sufficiently, making it impossible to obtain the desired polyester with a sufficiently high molecular weight. The present inventors have made intensive studies to overcome the above-mentioned drawbacks of conventional methods, and as a result, we have developed a polyester precondensate [A] and a polyepoxy compound [A] produced by the reaction of a dihydric carboxylic acid and a dihydric alcohol. A completed method for producing a coating resin composition whose main component is a high molecular weight polyester resin having an appropriate amount of carboxyl groups that exhibits an internal acid catalytic effect by reacting B] and polycarboxylic anhydride [C]. It is. The coating resin composition produced by the production method of the present invention is
One or more divalent carboxylic acids and/or their alkyl esters (a) that do not have ethylenically unsaturated double bonds and one or more divalent carboxylic acids and/or their alkyl esters (a)
Polyester precondensate [A] with an acid value of 3 to 20 obtained by condensation reaction with a hydrolic alcohol (b) at a molar ratio of (a)/(b) in the range of 0.9 to 1.1,
The main component is a high molecular weight polyester resin with an acid value of 5 to 30 obtained by reacting a polyepoxy compound [B] having at least two epoxy groups in one molecule and a polycarboxylic anhydride [C]. This is a characteristic feature. In addition, the acid value in the present invention is
It means the acid value based on non-volatile content. Polyester precondensate [A] in the present invention
The molar ratio of the dihydric carboxylic acid and/or its alkyl ester (a) to the dihydric alcohol (b) is such that (a)/(b) is in the range of 0.9 to 1.1, and this value is 0.9.
If it is less than 1.1, the molecular weight of the polyester precondensate [A] will become small and a high molecular weight polyester will not be obtained. The disadvantage is that it is difficult to set the range. The acid value of polyester precondensate [A] is 3 to 20
If the acid value is less than 3, polyepoxy compounds [B] and polyhydric carboxylic anhydrides [C]
Even when reacted, the amount of crosslinkable functional groups generated is insufficient and excellent performance is not exhibited. Also, the acid value is 20
If the molecular weight exceeds 100%, the molecular weight of the polyester precondensate becomes undesirable, and furthermore, the number of crosslinkable functional groups generated by the reaction with the polyepoxy compound [B] and the polycarboxylic anhydride [C] increases, resulting in poor performance. It is unfavorable in terms of balance, especially flexibility. Polyester precondensate [A] is prepared by combining dihydric carboxylic acids and/or their alkyl esters (a) and dihydric alcohols (b) according to conventionally known procedures.
It can be easily adjusted by carrying out a condensation reaction at a temperature of 160 to 260°C with or without an esterification catalyst. The ratio of the epoxy equivalent of the polyepoxy compound [B] to 1 carboxyl equivalent of the polyester precondensate [A] is 0.7 to 1.3, and if it is outside this range, a polyester resin with a high molecular weight cannot be prepared. The amount of polycarboxylic anhydride [C] used is such that the final high molecular weight polyester resin has an acid value in the range of 5 to 30. For example, when reacting polycarboxylic anhydride [C] with the reaction product of polyester precondensate [A] and polyepoxy compound [B], the equivalent proportion of acid anhydride groups of polycarboxylic anhydride [C] is less than 1.0 relative to the hydroxyl equivalent of the reaction product, and if it exceeds 1.0, it is unfavorable in terms of performance such as water resistance of the coating film. The acid value of the high molecular weight polyester resin in the present invention is within the range of 5 to 30. If the acid value is less than 5, the effect as an internal acid catalyst will be low, and the compatibility with curing agents such as amino resins will be poor, which is not preferable. . Also,
When the acid value exceeds 30, the storage stability as a coating resin composition is extremely poor. The divalent carboxylic acids and/or their alkyl esters (a) used in preparing the polyester precondensate [A] include aromatic divalent carboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, etc. Mention may be made of aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, acid anhydrides thereof, and alkyl esters thereof. It is preferable to use an aromatic divalent carboxylic acid and an aliphatic divalent carboxylic acid together. Dihydric alcohol (b) includes ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, butanediol, hexanediol,
1,4-cyclohexanedimethanol, alkylene oxide adduct of bisphenol A or hydrogenated bisphenol A, 2,2,4-trimethyl-1,3-pentanediol, hydroxy-2,
Examples include 2-dimethylpropionate, 3-methylpentane-1,5-diol,
One or more of these can be used effectively. The polyepoxy compound [B] is a compound having at least two epoxy groups in one molecule that are reactive with carboxyl groups. For example, “Epicote”
Bisphenol type epoxy compounds such as "828, 1001, 1004, 1007" (Ciel Chemicals), "Epicron 800, 1000, 4000" (Dainippon Ink Chemicals), "Denacol EX-211, EX-321, EX- 421,
Aliphatic ether type epoxy compounds such as “EX-611” (Nagase Kasei Kogyo products), “Yunox 201,
Examples include alicyclic epoxy compounds such as ``207'' (Union Carbide Products), ester type epoxy compounds such as diglycidyl phthalate, and epoxy compounds with a triazine nucleus such as TEPIC (Nissan Chemical Products). Among them, bisphenol type epoxy compounds can be particularly effectively used. Examples of polycarboxylic anhydride [C] include phthalic anhydride, succinic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexic anhydride, hymic anhydride, Trimellitic anhydride, etc. The high molecular weight polyester resin according to the present invention is obtained by reacting a polyester precondensate [A], a polyepoxy compound [B], and a polycarboxylic anhydride [C]. , the acid value is in the range of 5 to 30, and the number average molecular weight is in the range of 3,000 to 20,000.As for the reaction method, for example, polyester precondensate [A], polyepoxy compound [B] and anhydrous polyester A method of mixing and reacting a polyhydric carboxylic acid [C]; After reacting a polyester precondensate [A] and a polyepoxy compound [B], anhydrous polyhydric carboxylic acid [C] is added to the system containing the reaction product. Method of reacting by adding polyester precondensate [A] and polycarboxylic anhydride [C], and then adding polyepoxy compound [B] to the system containing the reaction product, etc. There are no particular restrictions.In this case, the reaction temperature is between 100℃ and 200℃.
can be in the range of Moreover, Solbetsuso (hydrocarbon solvent from Etsuso Co., Ltd.), xylene, etc. can be used as a reaction solvent if necessary. The reaction solvent can also be used as a part of the coating resin composition described below without being removed from the system after the reaction is completed. The coating resin composition according to the present invention has the high molecular weight polyester resin according to the present invention as a main component, and may optionally contain additives conventionally used in this type of composition, such as a flow control agent and a pigment dispersant. can be included. Since the high molecular weight polyester resin has a hydroxyl group and/or a carboxyl group as a crosslinkable functional group, a crosslinking agent such as an amino resin, a polyisocyanate compound, an epoxy compound, and a pigment are further added as necessary. In some cases, coatings with superior performance can be obtained without the use of external acid catalysts. Hereinafter, the present invention will be explained in more detail with reference to Examples. In addition, parts in the examples mean parts by weight, and acid values mean acid values based on nonvolatile content. Moreover, the molecular weight means the number average molecular weight measured by gel permeation chromatography (manufactured by Waterjet Co., Ltd.). Example 1 266 parts of terephthalic acid, 250 parts of isophthalic acid, 160 parts of sebacic acid, 124 parts of ethylene glycol, 204 parts of neopentyl glycol and dibutyltin oxide were placed in a reactor equipped with a stirrer, a condenser and a thermometer.
0.5 part was charged, the temperature was gradually raised from 160℃ to 240℃ under an inert gas atmosphere, and the reaction was carried out for 10 hours.
A polyester precondensate (hereinafter referred to as polyester-[I]) having an acid value of 15 was obtained. After dissolving 350 parts of this polyester-[I] in 161 parts of "Solbetsuso 150" (aromatic hydrocarbon solvent manufactured by Etsuso),
“Epicote 828” (bisphenol type epoxy compound manufactured by Ciel Chemical) 18 parts, triethylamine 0.5
1 part and 7.8 parts of phthalic anhydride were added and reacted at 150°C for 4 hours to obtain a high molecular weight polyester resin having a molecular weight of about 6000 and an acid value of 10.2. Next, “Sorbetso”
150'' and cellosolve acetate were added to obtain a coating resin composition having a nonvolatile content of 50.1%, an acid value of 10.2, and a Gardner viscosity of Z _1. Example 2 350 parts of the polyester-[I] of Example 1 was mixed with "Solbetsuso 150". After dissolving in 158 parts,
Add 18 parts of 828” and 0.5 parts of triethylamine.
Reacted at 150℃ for 4 hours, non-volatile content 70%, acid value 2.1
A reaction product (hereinafter referred to as reaction product-[I]) was obtained. 7.8 parts of phthalic anhydride and 3 parts of "Solbetsuso 150" were added to 526.5 parts of the reaction product [I] and reacted at 150 DEG C. for 1 hour to obtain a high molecular weight polyester resin having a molecular weight of about 6000 and an acid value of 10.0. Next, "Sorbetso 150" and cellosolve acetate were added to obtain a coating resin composition having a nonvolatile content of 49.8%, an acid value of 10.0, and a Gardner viscosity of Z ₁ . Example 3 350 parts of the polyester-[I] of Example 1 was dissolved in 161 parts of "Solbetsuso 150", and 7.8 parts of phthalic anhydride was dissolved.
After that, 18 parts of "Epikote 828" and 0.5 parts of triethylamine were added and reacted for 4 hours at 150°C to obtain a high molecular weight polyester resin with a molecular weight of 6100 and an acid value of 10.0. Ta. Next, "Sorbetso 150" and cellosolve acetate were added to obtain a coating resin composition having a nonvolatile content of 50.3%, an acid value of 10.0, and a Gardner viscosity of Z ₁ ⁺ . Example 4 166 parts of terephthalic acid, 322 parts of isophthalic acid, 292 parts of adipic acid, 124 parts of ethylene glycol, 312 parts of neopentyl glycol and 1 part of dibutyltin oxide were reacted in the same manner as in Example 1, and the acid value was 7.
A polyester precondensate was obtained. After dissolving 350 parts of this polyester precondensate in 156 parts of "Solbetsuso 150", 4.4 parts of "Denacol EX-211",
1.9 parts of "Denacol EX-421" (all manufactured by Nagase Chemical Industries, aliphatic ether type epoxy compound), 0.5 parts of dimethylbenzylamine and 7 parts of trimellitic anhydride were added and reacted at 170°C for 3 hours until the molecular weight was approximately 7300. A high molecular weight polyester resin with an acid value of 13.1 was obtained. Next, "Sotsubetsuso 150", cellosolve acetate and butyl cellosolve were added to obtain a coating resin composition having a nonvolatile content of 50.6%, an acid value of 13.1, and a Gardner viscosity of _Z2 . Example 5 322 parts of terephthalic acid, 322 parts of isophthalic acid, 146 parts of adipic acid, 124 parts of ethylene glycol, 312 parts of neopentyl glycol and 1 part of dibutyltin oxide were reacted in the same manner as in Example 1, and the acid value was 10.
A polyester precondensate was obtained. After dissolving 350 parts of this polyester precondensate in 167 parts of "Solbetsuso 150", 30 parts of "Epikote 1001", 0.5 parts of dimethylbenzylamine and maleic anhydride were added and reacted at 150°C for 4 hours, resulting in a molecular weight of 6880. A high molecular weight polyester resin with an acid value of 18.0 was obtained.
Then add “Sorbetso 150” cyclohexanone and methyl isobutyl ketone to reduce the non-volatile content to 49.7
%, an acid value of 18.0, and a Gardner viscosity of _Z4 . Example 6 Using the same method as Example 1, 498 parts of isophthalic acid, 62 parts of ethylene glycol, and 1,6 hexanediol were added.
236 parts and 0.5 part of dibutyltin oxide were reacted to obtain a polyester precondensate having an acid value of 16. 350 parts of this polyester precondensate was
After dissolving in 103 parts of “150”, “Epicote 1001”
56 parts of dimethylbenzylamine, 0.5 parts of dimethylbenzylamine, and 6.6 parts of succinic anhydride were added and reacted at 150°C for 4 hours to obtain a high molecular weight polyester resin with a molecular weight of about 5300 and an acid value of 6.0. Next, xylene and cellosolve acetate were added to obtain a coating resin composition having a nonvolatile content of 49.6%, an acid value of 6.0, and a Gardner viscosity of _Z1 . Example 7 Using the same method as in Example 1, 723 parts of adipic acid, 208 parts of neopentyl glycol, 288 parts of 1,4-cyclohexanedimethanol, 340 parts of ethylene oxide adduct of hydrogenated bisphenol A, and 1 part of dibutyltin oxide were added. were reacted to obtain a polyester precondensate having an acid value of 5. After dissolving 400 parts of this polyester precondensate in 105 parts of "Solbetsuso 150", 4.7 parts of "Denacol EX-321" and 7.2 parts of maleic anhydride were added and reacted at 180°C for 4 hours. A high molecular weight polyester resin with a valence of 11 was obtained. Next, "Sorbetso 150", methyl isobutyl ketone, and butyl cellosolve were added to obtain a coating resin composition having a nonvolatile content of 49.9%, an acid value of 11.0, and a Gardner viscosity of _Z4 . Comparative example 1 1 mm of polyester-[I] in Example 1
The condensation reaction proceeded under a Hg vacuum and a temperature of 240°C to obtain a comparatively high molecular weight polyester with an acid value of 2.0. Next, "Sorbetso 150" and cellosolve acetate were added to obtain a comparative coating resin composition having a nonvolatile content of 50.0%, an acid value of 2.0, and a Gardner viscosity of Z. Comparative Example 2 "Sorbetso 150" and cellosolve acetate were added to the reaction product-[I] in Example 2 to obtain a comparative coating resin composition having a nonvolatile content of 50.1%, an acid value of 2.1, and a Gardner viscosity of Z ₁ ^- . Comparative Example 3 After dissolving 350 parts of the polyester-[I] in Example 1 in 157 parts of "Solbetsuso 150", 18 parts of "Epicote 828", 0.5 part of triethylamine and 1 part of phthalic anhydride were added, and the mixture was heated at 150°C. time reaction,
A comparatively high molecular weight polyester resin having a molecular weight of approximately 5900 and an acid value of 2.9 was obtained. Next, add “Sorbetso 150” and cellosolve acetate to reduce the non-volatile content to 49.7.
%, an acid value of 2.9, and a Gardner viscosity of Z ₁ ^- . Comparative Example 4 After dissolving 350 parts of the polyester-[I] in Example 1 in 174 parts of "Solbetsuso 150", 18 parts of "Epikote 828", 0.5 part of triethylamine and 38 parts of phthalic anhydride were added, and the mixture was heated at 150°C. time reaction,
A comparatively high molecular weight polyester resin having a molecular weight of about 6100 and an acid value of 37 was obtained. Next, add “Sorbetso 150” and cellosolve acetate to reduce the non-volatile content to 50.3%.
A comparative coating resin composition having an acid value of 37.0 and a Gardner viscosity of Z ₂ ^- was obtained. Comparative Example 5 A polyester precondensate having an acid value of 30 was obtained using the same formulation and method as in Example 1. After dissolving 350 parts of this polyester precondensate in 169 parts of "Solbetsuso 150", 36 parts of "Epicoat 828" and triethylamine were added.
6 at 150℃ by adding 0.5 parts and 7.8 parts of phthalic anhydride.
A comparatively high molecular weight polyester resin having a molecular weight of about 5500 and an acid value of 11.2 was obtained by reacting for a period of time. Next, "Sorbetso 150" and cellosolve acetate were added to give a non-volatile content of 49.5, an acid value of 11.2, and a Gardner viscosity of Z _1.
A comparative coating resin composition was obtained. Example 8 Melamine as a crosslinking agent was added to each of the coating resin compositions obtained in Examples 1 to 7 and the comparative coating resin compositions obtained in Comparative Examples 1 to 5 according to the following procedure. Compatibility with resin was measured. The results were as shown in Table 1. ☆Compatibility with melamine resin The appearance of the composition when the latter is added to the former until the solid content ratio of the coating resin composition and the melamine resin becomes 80/20 is observed. ◎: Completely transparent ○: Slightly fluorescent. Δ: Slight turbidity. ×: Cloudy, sometimes separated. In addition, paints were prepared with the following formulations for each of the coating resin composition and the comparative coating resin composition, and coating films were formed by the following coating method, and coating film performance was measured. The results were as shown in Table 1. ☆Paint formulation Coating resin composition/“Super Betsucomin L-117” (melamine resin manufactured by Dainippon Ink Chemical Co., Ltd.) = 80/20 (solids weight ratio) PWC = 50% (titanium white is used as the pigment) Thinner (xylene/butyl cellosolve)
Dilute to coating viscosity ☆ Painting method, etc. Base material: 0.3mm thick "Bonderite #37" treated galvanized iron plate Bar coater coating: Dry film thickness approximately 20μ Baking conditions: 230℃ x 60 seconds

【table】

【table】

Claims (1)

[Scope of Claims] 1. One or more dihydric carboxylic acids and/or their alkyl esters (a) having no ethylenically unsaturated double bonds and one or more dihydric alcohols ( b) and the molar ratio of (a)/(b) is 0.9~
A polyester precondensate with an acid value of 3 to 20 obtained by a condensation reaction at a ratio of 1.1 [A], a polyepoxy compound having at least two epoxy groups in one molecule [B], and anhydrous Acid value 5 obtained by reacting polyhydric carboxylic acid [C]
A method for producing a coating resin composition containing a high molecular weight polyester resin of ~30 as a main component.