JPS627229B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating composition containing a saturated polyester as a coating film-forming component, and more specifically to a high molecular weight saturated coating composition produced by reacting a hydroxyl group-containing saturated polyester of a dibasic acid and a dihydric alcohol with an organic diisocyanate compound. polyester,
The present invention relates to a coating composition containing it as a coating film-forming component. Traditionally, there are two types of paint for cans: inner can paint and can outer paint.Inner paint is applied to the inner surface of the can to prevent food from corroding the can material and metals from the can material leaching into the food. The exterior paint is applied to the outside of the can to prevent corrosion and give the outside of the can a beautiful appearance. Therefore, as an inner surface coating, the coating film must be harmless, do not give off an odor to the food, or inhibit the flavor, can prevent metals from being leached from the can stock into the food, and have good coating workability and drying properties. The coating film should adhere well to the substrate, have good flexibility, abrasion resistance, and impact resistance, and should withstand processing deformation during the can manufacturing process. It is required that no whitening occurs. The performance requirements for can exterior paint include painting workability,
Good drying properties, little yellowing of the paint film, repaintability and no backing, good adhesion to substrates, undercoats, and ink films, and the ability of the paint film to withstand processing deformation during the can manufacturing process. In this case, the ink should not bleed or change color, the coating should not peel, blister, whiten, yellow, etc. during the sterilization process of canned goods, and the coating should have a good gloss. It goes without saying that both the interior and exterior paints have good storage stability as paints. Based on these required characteristics, various resins are used as the main component of paints for the inside and outside of cans, depending on the application. Therefore, there is a problem that there are a large number of varieties, and it has been desired to develop a resin that simultaneously satisfies the above requirements. For example, paints used for caps, aerosol cans, etc. are processed into the shape of the can after being painted with a roll coater, so they are mainly made of vinyl chloride copolymer, which has good processability and has no abnormality in film properties even after being processed after painting. So-called vinyl-based paints are mainly used.
However, among vinyl chloride resins, vinyl chloride
Vinyl acetate copolymers have poor adhesion to metals, and further, when steam sterilized, deterioration of gloss, blistering, and peeling of the coating occur, resulting in poor steam sterilization resistance. Modified versions of vinyl chloride-vinyl acetate copolymers such as phenolic resins, epoxy resins, or amino resins tend to cause yellowing of the paint film during baking and have poor steam sterilization resistance. It lacks gloss and has poor solvent solubility resistance. In addition, vinylated alkyd resins and oil-free alkyd resin-amino resin modified products, which are commonly used as white coats for can exterior paints, are well-balanced in terms of appearance, solvent solubility, yellowing, steam sterilization resistance, and processability. However, the processability is insufficient to replace the above-mentioned vinyl chloride resin. In addition, thermosetting acrylic resins, which are mainly used as finishing varnishes, have little yellowing and excellent steam sterilization resistance, but are insufficient in processability to replace the above-mentioned vinyl chloride resins. Therefore, the present inventors have found that it has processability comparable to that of vinyl chloride resin, adhesion to metals, steam sterilization resistance,
We developed a resin with good gloss and less yellowing of the coating film upon baking, and discovered that urethane-modified saturated polyester satisfies these requirements, resulting in the present invention. The coating composition according to the present invention has particularly excellent processability. Therefore, it is useful not only as a paint for cans as described above, but also as a color tin paint that requires processability, and is generally useful in fields where objects to be painted (particularly metals) are processed after being painted. That is, the present invention is a method of urethanizing an initial condensate obtained by condensing (a) a dibasic acid having no ethylenically unsaturated bond or an alkyl ester thereof and (b) a dihydric alcohol with (c) an organic diisocyanate. , and the molar ratio of (a) dibasic acid or its alkyl ester, (b) dihydric alcohol, and (c) organic diisocyanate, and (b)/{(a)+(c)} is 1 to
1.1 and (a)/(c) of 5 to 100. The present invention relates to a coating composition containing, as a film-forming component, a high molecular weight saturated polyester obtained by reacting so that (a)/(c) is 5 to 100. Dibasic acid component [component (a)] of urethane-modified saturated polyester, which is the main component of the coating composition of the present invention.
Examples include dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, adipic acid, sebacic acid, and naphthalene dicarboxylic acid, their acid anhydrides, and their alkyl esters. Dihydric alcohol components [component (b)] include polyethylene glycols such as ethylene glycol and diethylene glycol, polypropylene glycols such as propylene glycol and dipropylene glycol, neopentyl glycol, butanediol, 2,2
-bis(p-2-oxyphenyl)propane and the like. Organic diisocyanates [component (c)] include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate, cycloaliphatic diisocyanates such as xylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, etc. aromatic diisocyanates, and the above compounds may be used in combination. Aliphatic diisocyanates are preferred from the viewpoint of yellowing resistance, but aromatic diisocyanates are preferred from the viewpoint of addition reaction rate. The production method first involves heating a dibasic acid and a dihydric alcohol at 150 to 280°C, preferably at 200°C.
React for 5-15 hours at ~260°C. At this time, there is no problem in using a known ester catalyst, such as dibutyltin oxide, dibutyltin dilaurate, etc., at a rate of 0.05 to
1% by weight is sufficient to achieve the purpose. The reaction can be carried out under normal pressure or under increased pressure, but
At this time, it can also be carried out in the presence of an organic solvent such as xylene. Next, in the urethanization reaction with an organic diisocyanate, in order to perform the reaction uniformly, preferably toluene, methyl ethyl ketone, ethyl acetate, xylene, cellosolve acetate, Solbetsuso 100, Solbetsuso 150 (trade name: Etsuso Standard Oil Co., Ltd. It is preferable to dissolve the above-mentioned condensate in the presence of an organic solvent such as an aromatic solvent manufactured by A. The reaction temperature is
Preferably, a suitable amount of a known catalyst such as a metal compound such as tin may be added to further promote the reaction at a temperature of 50°C to 150°C. For example, dibutyltin oxide used as an esterification catalyst can also be used as a catalyst in the urethanization reaction. The above (a), (b) and (c) components have a molar ratio (b)/{(a)+
(c)} is blended so that it is 1 to 1.1. If it is less than 1, unreacted isocyanate groups remain after urethanization, which is unfavorable in terms of coating film properties, and if it exceeds 1.1, it becomes difficult to increase the molecular weight. Further, components (a) and (c) are blended so that the molar ratio (a)/(c) is 5 to 100. If it is less than 5, the concentration of the urethane moiety in the obtained linear saturated polyester becomes high, the solubility in the solvent decreases, and the molar ratio decreases.
If it exceeds 100, it becomes difficult to increase the molecular weight. Preferably (a)/(c) (molar ratio) is 10 or less. In addition, you may use less than 5 weight% of trifunctional or more polyhydric alcohols in an alcohol component. 5% by weight
If it exceeds this amount, it becomes impossible to increase the molecular weight. The coating composition of the present invention uses an organic solvent such as xylene, Solbetsuso 100 (trade name of Etsuso Standard Oil Co., Ltd.), Solbetsuso 150 (trade name of Etsuso Standard Oil Co., Ltd.), cellosolve acetate, butyl cellosolve, etc. as a diluting solvent. Use as appropriate. Furthermore, an amino resin such as a melamine resin or a benzoguanamine resin may be used as a curing agent (eg, 50% by weight or less based on the urethane-modified saturated polyester). An acidic catalyst such as para-toluenesulfonic acid may be used to accelerate the reaction (eg, 1% by weight or less based on the total amount of urethane-modified saturated polyester and amino resin). Furthermore, color pigments such as titanium white, lead oxide, yellow lead, phthalocyanine blue, and phthalocyanine green may be added. Furthermore, a modifier such as an epoxy resin may be added. Examples of the present invention will be shown below. Parts are by weight. Example 1 <Esterification reaction> 249 parts of terephthalic acid, 249 parts of isophthalic acid, 93 parts of ethylene glycol, neopentyl glycol
176.8 parts were reacted at 240° C. for 10 hours under a blanket of inert gas to obtain an initial condensate (A) with an acid value of 5. At this time, 1.1 parts of dibutyltin oxide was used as a catalyst. <Urethane compound> 400 parts of the above initial condensate (A) was mixed with 600 parts of a mixed solvent of xylene/cellosolve acetate = 1/1 (weight ratio).
After dissolving in 100 ml, under inert gas atmosphere,
20 parts of hexamethylene diisocyanate was added dropwise at ℃. After dripping for 1 hour, it was kept at a constant temperature for 2 hours, and saturated polyester (A) with a Gardner viscosity of Z-Z ₁ was added.
I got it. The (b)/{(a)+(c)} molar ratio was 1.00, the (a)/(c) molar ratio was 15, and the acid value was 2 and the hydroxyl value was 5. <Painting> Saturated polyester (A)/Melan 326 (product name: amino resin manufactured by Hitachi Chemical Co., Ltd.)/Titanium white =
The mixture was mixed to have a weight ratio of 80/20/100 (solid content), and the nonvolatile content was adjusted to 50% with thinner (xylene/cellosolve acetate). Example 2 <Esterification reaction> 249 parts of terephthalic acid, 249 parts of isophthalic acid, 1,
310.5 parts of 4-butanediol and 1.1 parts of dibutyltin oxide were reacted at 240°C under an inert gas atmosphere to obtain an initial condensate (B) with an acid value of 5 in 10 hours. <Urethanization reaction> After 400 parts of the initial condensate (B) was dissolved in 600 parts of a mixed solvent of xylene/cellosolve acetate = 1/1 (weight ratio), 40 parts of hexamethylene diisocyanate was added dropwise at 100°C over 1 hour. Thereafter, the mixture was reacted for 2 hours to obtain a saturated polyester (B) having a Gardner viscosity of Z-Z ₁ . The (b)/{(a)+(c)} molar ratio was 1.01 and the (a)/(c) molar ratio was 7.2, with an acid value of 1 and a hydroxyl value of 5. The coating was made according to Example 1. Comparative Example 1 VAGH as vinyl chloride-vinyl acetate copolymer
(trade name: vinyl chloride resin manufactured by Union Carbide) was dissolved in a mixed solvent of toluene/methyl isobutyl ketone. <Painting> VAGH/Melan 326B/Titanium white = 80/20/100
(solid content weight ratio) and adjusted with thinner (toluene/methyl isobutyl ketone/isopropanol) to have a nonvolatile content of 40%. Comparative Example 2 Phthalkyd as vinylated alkyd resin
A paint was prepared using 903B (trade name: alkyd resin manufactured by Hitachi Chemical Co., Ltd.) and the same paint formulation as in Example 1. Comparative example 3 Phthalkyd as oil-free alkyd resin
A paint was prepared using SP×103 (trade name: alkyd resin manufactured by Hitachi Chemical Co., Ltd.) with the same paint formulation as in Example 1. Comparative Example 4 Hytaloid 2605 as thermosetting alkyl resin
(Product name: Acrylic resin manufactured by Hitachi Chemical Co., Ltd.) was used. <Painting> Hitaloid 2605 and titanium white
2605/Titanium White = 100/100 (weight ratio of solid content) was blended, and the nonvolatile content was adjusted to 50% by weight with thinner (xylene/cellosolve acetate) to make a paint. Comparative Example 5 Using the initial condensate (A) of Example 1, a polycondensation reaction was carried out in the following manner. 500 parts of the initial condensate (A) at a vacuum level of 1 mmHg and a temperature of 240
React for 180 minutes at ℃, acid 1.0, intrinsic viscosity 0.53 (30℃,
Phenol/tetrachloroethane = 6/4, 0.5
A saturated polyester (D) having properties of %) was obtained. Then, a paint was prepared using the same paint formulation as in Example 1. Table 1 shows the results of tests using the paints obtained in Examples 1-2 and Comparative Examples 1-5.

[Table] The coating film properties in Table 1 were measured as follows. Coating conditions and test methods Coating method Roll to coat a 0.25mm tin plate with a film thickness of 150mg/
It was painted to a size of 100cm ² and baked at 180℃ for 10 minutes. Coating film test method Γ adhesion 100 1 mm square squares were extruded for 6 mm using an Erichsen tester, then peeled off with cellophane tape, and the remaining squares were shown as molecules. Γ Yellowing Color difference was measured using a color difference meter. However, the baking conditions were 210°C for 60 minutes. Γ Processing method A test piece was punched out using a cap punching tester with a diameter of 20 mm and a depth of 40 mm, and the degree of peeling was determined. Γ Steam sterilization resistance Processability tested caps and flat plates were 1.5
Put it in an atmospheric pressure steam sterilizer and steam sterilize it for 60 minutes.
The gloss retention rate, degree of blistering, and peeling of the paint film were evaluated. Example 3 400 parts of the initial condensate (A) of Example 1 was added to a mixed solvent of toluene/methyl ethyl ketone = 8/2 (weight ratio).
After dissolving in 600 parts, under an inert gas atmosphere,
20 parts of hexamethylene diisocyanate was added dropwise at 80°C. The mixture was added dropwise for 1 hour and kept at a constant temperature for 2 hours to obtain a saturated polyester (A) having a Gardner viscosity of 15 seconds (25°C). Example 4 400 parts of the initial condensate (B) of Example 2 was added to a mixed solvent of toluene/methyl ethyl ketone = 8/2 (weight ratio).
After dissolving the mixture in 600 parts, 40 parts of hexamethylene diisocyanate was added dropwise at 80°C over 1 hour, and the mixture was reacted for 2 hours to obtain a saturated polyester (B) having a Gardner viscosity of 15 seconds (25°C). Example 5 400 parts of the initial condensate (A) of Example 1 was added to a mixed solvent of toluene/methyl ethyl ketone = 8/2 (weight ratio).
After dissolving in 600 parts, under an inert gas atmosphere, 80 parts
15 parts of hexamethylene diisocyanate was added dropwise in the same manner as in Example 1. Gardna viscosity 10 seconds (25
A saturated polyester (C) was obtained. Comparative Example 6 Using the initial condensate (B) of Example 1, a polycondensation reaction was carried out in the following manner. 500 parts of the initial condensate (A) at a vacuum level of 1 mmHg and a temperature of 240
The reaction was carried out at ℃ for 180 minutes, with an acid value of 2.0 and an intrinsic viscosity of 0.53 (30
°C), phenol/tetrachloroethane = 6/
A saturated polyester resin (D) having properties of 4.0.5%) was obtained. Comparative Example 7 249 parts of isophthalic acid, 219 parts of adipic acid, 1,6
118 parts of hexanediol and 260 parts of trimethylolpropane were reacted at 240°C under an inert gas atmosphere to obtain an oil-free alkyd (E) with an acid value of about 10. Comparative Example 8 <Esterification reaction> 249 parts of terephthalic acid, 249 parts of isophthalic acid, 214 parts of ethylene glycol, trimethylolpropane
67 parts were reacted at 240°C under an inert gas atmosphere to obtain an initial condensate (D) with an acid value of about 3. <Urethanization reaction> After dissolving 400 parts of the initial condensate (D) in 600 parts of a mixed solvent of toluene/methyl ethyl ketone = 8/2 (weight ratio), 63 parts of hexamethylene diisocyanate was added dropwise at 80°C over 1 hour. The mixture was reacted for 2 hours to obtain a urethanized oil-free alkyd resin (F). Comparative Example 9 <Esterification reaction> 249 parts of terephthalic acid, 249 parts of isophthalic acid, 1,
405 parts of 4-butanediol and 1.1 parts of dibutyltin oxide were reacted at 240°C under an atmosphere of inert gas.
An initial condensate (E) with an acid value of 5 was obtained in 10 hours. <Urethanization reaction> After dissolving 400 parts of the initial condensate (E) in 600 parts of a mixed solvent of toluene/methyl ethyl ketone = 8/2 (weight ratio), 252 parts of hexamethylene diisocyanate was added dropwise at 80°C over 2 hours. The reaction was carried out for 3 hours to obtain a saturated polyester resin (G). However, the solubility was poor at room temperature and it took on a gel-like appearance. Saturated polyester resin thus obtained
Table 2 shows the resin properties and coating film properties of (A) to (G). The coating film properties in Table 2 were measured as follows. Painting conditions and test methods Paint formulation Γ resin/Melan 28 (product name: melamine resin manufactured by Hitachi Chemical Co., Ltd.)/Titanium white = 80/20/
100 (weight ratio of solids) ΓP.WC=50% Γ thinner (xylene/cellosolve acetate)
Adjust the non-volatile content to 50%. Coating method Roll coating Film thickness 20μ Base material: 0.25mm tin plate Baking temperature 180℃ 10 minutes Coating film test method Γ Water resistance: 100 x 200mm test plate in boiling water at 100℃
After soaking for 10 hours, changes in gloss and degree of blistering were compared. Blister evaluation 5 points No abnormality (ASTM D714-54T) 3 points 8F 1 point 6F

[Table] Γ Workability A 70 x 40 mm test piece was bent from the center in the vertical direction, and a 0.25 mm tin plate was used as a spacer with scissors and bent and pressed at 180°C. 5 points: No cracks 3 points: Approximately 1/3 crack 1 point: Fully cracked As is clear from the above, the coating composition of the present invention has good yellowing resistance, adhesion, gloss, and blocking properties, and in particular has good processability. Remarkably superior. Furthermore, it has excellent steam sterilization resistance.

Claims (1)

[Claims] 1. An initial condensate obtained by condensation reaction of (a) a dibasic acid having no ethylenically unsaturated bond or its alkyl ester and (b) a dihydric alcohol is urethanized with (c) an organic diisocyanate, and the above-mentioned
(a) dibasic acid or its alkyl ester, (b) dihydric alcohol, and (c) organic diisocyanate in molar ratio, (b)/{(a)+(c)} from 1 to 1.1 and (a)/ A coating composition containing, as a film-forming component, a high molecular weight saturated polyester obtained by reaction such that (c) is 5 to 100.