JPH0425316B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved coating resin composition,
More specifically, a specific partially crosslinked urethanized polyester is used as an essential component, or this partially crosslinked urethanized polyester and an aminoaldehyde resin and/or a blocked polyisocyanate compound are used as essential components. In particular, it relates to a resin composition that is excellent in processability, coating hardness, and stain resistance. The object of the present invention is to maintain the excellent processability that is the advantage of conventional oil-free polyester/aminoaldehyde resin paints, while also providing coatings with high hardness and excellent stain resistance. It is an object of the present invention to provide an improved oil-free polyester/aminoaldehyde resin based coating composition that provides a film, and further to provide a resin composition suitable for a precoated metal coating. Conventionally, there have been many types of pre-coated metal paints of this type, such as amino-alkyd resin systems, amino-oil-free polyester resin systems, amino-acrylic resin systems, and vinyl resin systems. The current situation is that if emphasis is placed on workability, other properties become inferior, which is why there are restrictions on its use. In particular, electric products in the category called light electrical products, such as refrigerators and washing machines, require high hardness and excellent stain resistance and water resistance, so conventional pre-coated metal paints cannot be used. The reality is that these demands cannot be met. Even when looking at oil-free polyester/amino aldehyde resin paints, if the hardness exceeds a certain level, processability becomes insufficient, and in addition, it becomes extremely difficult to balance physical properties. It is. By the way, the present inventors added these to a so-called uncrosslinked urethane-modified polyester obtained without partially crosslinking an aminoaldehyde resin and/or a blocked polyisocyanate compound using a specific polyester-forming component and an organic diisocyanate. It was discovered that the desired object could be achieved by blending the aminoaldehyde resin and/or blocked polyisocyanate compound, and patent application No. 58-84038 was filed.
We have already filed an application for this patent, but we have learned that there are problems with the storage stability of the urethane-modified polyester itself, and there are also problems with the smoothness of the coating film, especially the repellency of the coating surface. However, as a result of intensive studies to solve these problems, the inventors of the present invention found that by using a modified polyester resin in which the urethane-modified polyester is partially cross-linked with an aminoaldehyde resin as a coating film-forming component. , significantly improves the smoothness of the coating film while maintaining the coating performance of the resin composition for paint described in the invention related to the above-mentioned Japanese Patent Application No. 58-84038 (see Japanese Patent Application Laid-open No. 59-210977). The inventors have now completed the present invention by discovering that the storage stability of the urethane-modified polyester resin solution can be dramatically improved. That is, the present invention involves reacting an aromatic dibasic acid, if necessary, another dibasic acid, a saturated glycol, a trivalent or higher valent polyol and/or a polycarboxylic acid, and an organic diisocyanate. with a hydroxyl value of 10 to 150,
In addition, a modified polyester resin A obtained by partially crosslinking a urethane modified polyester (a-1) having a number average molecular weight of 2,000 to 15,000 and an aminoaldehyde resin (a-2) is an essential coating film forming component. or a modified polyester resin A obtained by partially crosslinking the resin composition as an essential coating film-forming component, and further comprising an aminoaldehyde resin B and a blocked polyisocyanate compound C. A coating resin composition comprising at least one compound selected from the group consisting of as an essential curing agent component, the urethane-modified polyester (a-1)
Aromatic dibasic acids account for at least 50 mol% of the total acid components constituting the composition, and the ratio of the organic diisocyanate to the total acid components is 3 to 50 mol%.
It is an object of the present invention to provide a resin composition for coating material comprising the following. Although it is not clear why the storage stability of the modified polyester resin solution is improved by partial crosslinking of the aminoaldehyde resin, the polyester has a low molecular weight that is extremely polar through the urethanization reaction. This is thought to be due to the fact that such polar low molecular weight substances are incorporated into the aminoaldehyde resin.
It is thought that the stability of the resin solution is improved, and in the same way, the smoothness of the coating film is also thought to be significantly improved. The present invention provides that the urethane-modified polyester (a-1) contains at least 50 mol%, more preferably at least 75 mol% of the total acid component constituting the polyester (a-1), At the same time as the acid occupies, the number of moles of the organic diisocyanate per mole of the total acid component is 0.03 to 0.5 mole, preferably 0.1 to 0.2 mole, that is, the ratio of the organic diisocyanate to the total acid component is 3 to 50 mole%. is characteristic in that it is preferably 10 to 20 mol%, but if the amount (mol%) of aromatic dibasic acid based on the total acid components is less than 50 mol%, the coating film On the other hand, if the amount (mol%) of organic diisocyanate based on the total acid component is less than 3 mol%, the coating film has both high hardness and good stain resistance. On the other hand, if the amount exceeds 50 mol %, it will not be possible to obtain a product with good processability, and the solubility in solvents will also be poor. The hydroxyl value of the urethane-modified polyester (a-1) needs to be in the range of 10 to 150, preferably in the range of 30 to 100.
If it is less than 10, the coating film will inevitably be insufficiently cured, and if it exceeds 150, workability will deteriorate. Further, the number average molecular weight ( ) of the polyester (a-1) needs to be in the range of 2,000 to 15,000, preferably in the range of 4,000 to 10,000. If it is less than 2,000, sufficient processability cannot be obtained, and if it exceeds 15,000, it becomes difficult to dissolve in solvents. Representative examples of the aromatic dibasic acids that are one of the constituents of the polyester (a-1) include isophthalic acid, terephthalic acid and orthophthalic acid, as well as 2,6-dinaphthalene dicarboxylic acid and 4,4' -diphenyldicarboxylic acid and the like. Also included are reactive derivatives such as alkyl esters and anhydrides of these aromatic dibasic acids,
From the viewpoint of coating film properties and economic efficiency, it is preferable to use orthophthalic acid, isophthalic acid, or terephthalic acid. Next, in the present invention, representative examples of the other dibasic acids that may be used as necessary include tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexahydrophthalic acid, hexahydroterephthalic acid, methyl Hexahydrophthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, pimelic acid,
Speric acid, sebacic acid, dimeric fatty acid, etc., and these dibasic acids are appropriately used in consideration of coating film properties, economical efficiency, and the like. In addition, the urethane-modified polyester (a-
Typical saturated glycols that are one of the forming components of 1) include ethylene glycol, propylene glycol, trimethylene glycol,
These include alkylene glycols such as 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, or neopentyl glycol, but also 1,4-cyclohexanedimethanol. Aromatic glycols or alicyclic glycols such as , pishydroxyethyl terephthalate, hydrogenated bisphenol A, or alkylene oxide adducts of bisphenol A can also be used in appropriate amounts as necessary, and monoepoxy compounds can also be used. It goes without saying that it can also be used in combination as an alcohol component. Furthermore, the trivalent or higher polyol and/or polycarboxylic acid described above are one of the essential forming components of the polyester (a-1), and particularly maintain a balance between processability, hardness of the coating film, and stain resistance. It is an extremely important ingredient. Typical such polyols include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol or mannitol, while typical polycarboxylic acids include trimellitic acid, pyromellitic acid, etc. , trimesic acid or cyclopentanetetracarboxylic acid, but in addition to these, polyepoxy compounds can also be used in combination as this type of polyfunctional raw material. The amount used is 5% of the total amount of the various alcohol components listed above, including trivalent or higher polyols, that is, 5% of the total weight of all alcohol components.
It should be at least 7% by weight, preferably at least 7%, and for trivalent or higher polycarboxylic acids, it is necessary to use at least 5% by weight based on the total dibasic acid component, preferably at least 7%. It is appropriate to use % by weight or more, and even when using trivalent or higher polyols and trivalent or higher polycarboxylic acids together, it is appropriate to use % by weight or more based on the total usage of the total alcohol component and the total dibasic acid component. It is necessary that the total amount of these trivalent or higher polyols and trivalent or higher polycarboxylic acids used is 5% by weight or more, preferably 7% by weight or more. When the amount of the so-called polyfunctional raw material component, which is trivalent or higher polyol and/or trivalent or higher polycarboxylic acid, is less than 5% by weight, the resulting urethane-modified polyester (a-1) is substantially linear. This structure results in poor curing, and as a result, the hardness and stain resistance of the coating film are also significantly reduced. On the other hand, typical examples of the organic diisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; cycloaliphatic diisocyanates such as xylylene diisocyanate and isophorone diisocyanate; or tolylene diisocyanate and 4,4'-diphthalate diisocyanate; Examples include aromatic diisocyanates such as enylmethane diisocyanate, but it goes without saying that these may also be used in combination. From the viewpoint of yellowing resistance of the coating film, it is preferable to use an aliphatic diisocyanate. There are various methods for preparing the urethane-modified polyester (a-1) using the raw material components listed above, but a typical method is to first prepare a dibasic acid component and a glycol component. There is a method in which the total amount of each polyol and/or polycarboxylic acid is esterified at 200 to 250°C, and then urethanized with an organic diisocyanate, or in which the alcohol component is There is a method in which a portion of the alcohol component is removed in advance, the esterified product (polyester) and this portion of the alcohol component are mixed, and an organic diisocyanate is added thereto to perform a urethanization reaction. There are methods of esterifying the adduct with the remaining components, and any method may be selected. In each of these esterification reactions, the pressure may be normal pressure, increased pressure, or reduced pressure. Known and commonly used esterification catalysts including various tin-based compounds such as esters and the like may be used. In addition, as for the usage ratio of each forming component of the polyester (a-1), the total number of moles of each raw material component listed above is Y, and among each raw material component, aromatic dibasic acid, organic diisocyanate, and When the total number of equivalents of other acid components is defined as X, it is necessary that the ratio Y/X be 1 or more. The reaction can also be carried out in the presence of an organic solvent such as xylene, and the presence of this organic solvent is particularly recommended as a means for removing water produced during the esterification reaction. On the other hand, when carrying out the urethanization reaction with an organic diisocyanate, the polyester (esterification reaction product) and/or glycol component is dissolved using an organic solvent that does not have active hydrogen.
It is preferable to use a method in which an organic diisocyanate is dropped therein. The organic solvent used in this case is toluene, xylene, "Solbetsuso 100 or 150" [Exxon Chemical Co., Ltd.]
products]; ester solvents such as cellosolve acetate, ethyl acetate, and butyl acetate; and ketone solvents such as cyclohexanone and methyl isobutyl ketone; however, aromatic and ester solvents are preferred. It is a mixed solvent with ketone type. Further, in this urethanization reaction, it is preferable to use a known and commonly used catalyst such as a tin-based compound, and the reaction temperature is 30 to 150°C, preferably 60°C.
A range of ~100°C is suitable. After the urethanization reaction is completed, unreacted organic diisocyanate is completely removed, and methanol, ethanol, n-butanol, i-butanol, or butyl cellosolve is added to prevent thickening over time and gelation. It is preferable to add an alcohol solvent. In the present invention, the urethane-modified polyester (a-1) thus obtained and the aminoaldehyde resin (a-2) listed below are partially crosslinked to form a coating film forming component of the composition of the present invention. A partially crosslinked modified polyester resin A is obtained, and representative aminoaldehyde resins (a-2) include amino groups such as melamine, urea, acetoguanamine, benzoguanamine, steroguanamine, or spiroguanamine. A condensate obtained by reacting the containing compound component with an aldehyde compound component such as formaldehyde, paraformaldehyde, acetaldehyde or glyoxal by a known and commonly used method, or a condensate obtained by etherifying each of these condensates with an alcohol. However, any material that is normally used for paint can be used. Therefore, hexamethoxymethylmelamine and melamine resins in which some of the methoxy groups thereof are partially substituted with C4 _or higher alcohols are also used, but when such resins are used, known resins such as para-toluenesulfonic acid Preference is given to adding customary curing catalysts. Among these, melamine/formaldehyde resin is the most desirable from the viewpoint of weather resistance of the coating film. The ratio of the resin (a-2) to the urethane-modified polyester (a-1) is 95:5 to 60:40, preferably 90:10 to 70:
A solid content weight ratio of 30 is suitable. In addition, the reaction conditions for partially crosslinking the urethane-modified polyester (a-1) and the aminoaldehyde resin (a-2) are as follows:
At the initial stage of this partial crosslinking, these (a-1) and (a
-2) If the number average molecular weight measured by gas vermiaction chromatography (GPC) when both component compounds are mixed is assumed to be 1, the rate of increase in the number average molecular weight after partial crosslinking is
It is preferably within the range of 1.01 to 2. If it is 1 or more and less than 1.01, the degree of partial crosslinking will be insufficient, whereas if it exceeds 2, it will impede the coating workability and increase the risk of gelation, which is not preferable. The reaction conditions for carrying out such a partial crosslinking reaction include the above-mentioned urethane-modified polyester (a
-1) and aminoaldehyde resin (a-2) are mixed and heated and stirred at a temperature of 60 to 120°C. “Betsukamin P-198” [Dainippon Ink Chemical Co., Ltd. product]
It is also possible to add a catalyst such as. On the other hand, as the aminoaldehyde resin B which is a curing agent component, urethane modified polyester (a-
The aminoaldehyde resin (a-2) for partial crosslinking of 1) can be appropriately selected from among the aminoaldehyde resins (a-2) listed above, taking into consideration the physical properties of the coating film and economical efficiency. The usage ratio of aminoaldehyde resin (a-2) to resin (a-1) is as follows: Resin B for curing agent and resin (a-2) for partial crosslinking are combined, a-
1):Resin B+Resin (a-2)=Solid content weight ratio of 95:5 to 60:40, preferably 90:10 to 70:30, is suitable. In addition, the purpose of using the above-mentioned blocked polyisocyanate C is that the resin itself is added alone in order to improve the drawbacks of the above-mentioned aminoaldehyde resin B, or it is added in a form that eliminates the drawbacks. The point is that the addition of the C component further improves the finish and chemical resistance of the coating film. A typical example of the blocked polyisocyanate C is "Burnock D-550" [Dainippon Ink Co., Ltd.], which is a polyisocyanate compound obtained by blocking a so-called non-yellowing polyisocyanate using a known and commonly used blocking agent. Kagaku Kogyo Co., Ltd. product], “Takenate B815-N” [Takeda Pharmaceutical Co., Ltd. product] or “ADDITOL VXL-80” [Hoechst Synthetic Co., Ltd. product]
etc. And the urethane modified polyester resin A
The blending ratio of the blocked polyisocyanate C to the polyisocyanate is 95:5 to 60:40, preferably
A solid weight ratio of 90:10 to 70:30 is suitable. When blending the urethane-modified polyester resin A with these aminoaldehyde resins B and/or blocked polyisocyanate C, if the proportion of the component A exceeds 95% by weight, the desired stain resistance cannot be achieved. A coating film with unpredictable properties and hardness will be obtained, and conversely, if it is less than 60% by weight, processability will deteriorate, so both are not preferred. As described above, the composition of the present invention may contain the urethane-modified polyester resin A as an essential coating film-forming component, or may contain this modified polyester resin A and each as an essential curing agent component. , the above-mentioned aminoaldehyde resin B
and/or the above-mentioned blocked polyisocyanate compound C. When blending these components, an organic solvent such as "Sorbetso 100 or 150", cellosolve acetate or butyl cellosolve is used as a diluent. It is best to use it in moderation. Such diluent components are appropriately selected in consideration of solvency (solubility), evaporation rate (drying rate), etc., but are preferably combinations of aromatic hydrocarbons and ester, ketone, and/or alcohol solvents. It is appropriate to use them together. Although the composition of the present invention obtained in this way has sufficient performance by simply applying it to a steel plate and baking it, it is recommended that the composition of the present invention be applied with a primer for applications that particularly require corrosion resistance.
It is preferable to adopt a two-coat bake method. Furthermore, additives such as coloring pigments such as titanium oxide and wax may also be added to the composition of the present invention, depending on the purpose and use. In preparing the composition of the present invention, a kneading machine such as a roll kneader, a ball mill, or a blender is used, and in coating with the composition of the present invention, roll coating, coating with a roll coater, Spray painting or electrostatic painting may be used. The composition of the present invention is applied to a steel plate or the like and baked to provide a coating film with excellent corrosion resistance and hardness, and the composition of the present invention has extremely excellent workability or painting workability. Next, the present invention will be specifically explained with reference to Reference Examples, Examples, and Comparative Examples, where all parts and percentages are based on weight unless otherwise specified. Reference Example 1 [Preparation example of urethane-modified polyester resin A] 426 parts of isophthalic acid, 153 parts of neopentyl glycol, and trimethylol were placed in a reaction tank equipped with a heating device, a stirrer, a reflux device, a thermometer, a water separator, and a dropping device. 63 parts of propane and 250 parts of 1,6-hexanediol were charged and heated in the presence of an inert gas. Once the raw materials have melted and stirring is possible, start stirring and add 0.5% of dibutyltin oxide.
The temperature was raised to 230°C. During this time, the condensed water produced was removed from the system, and once the temperature reached the same temperature, stirring was continued for 2 hours while keeping the temperature constant. Next, chiresin was added into the reaction tank, and the reaction was continued in the presence of a solvent. When the acid value reached 5, the reaction was terminated and the tank was cooled. After cooling, 500 parts of "Sorbetso 100" and 500 parts of cyclohexanone were added to obtain a polyester melt. Thereafter, 200 parts of hexamethylene diisocyanate was added dropwise to this melt at 80°C in the presence of an inert gas over 1 hour, and the same temperature was further maintained for 4 hours to determine the Gardner viscosity at 25°C (hereinafter the same applies). ) is T-U, the acid value is 0.5, the hydroxyl value is 60,
A urethane-modified polyester (a-1) having a number average molecular weight (n) of 5200 was obtained. Hereinafter, this will be abbreviated as polyester (a-1-1). Next, this polyester (a-1-1)
100 parts of "Super Betsukamine L-117-60" [Butylated melamine resin from Dainippon Ink and Chemicals Co., Ltd.]
A resin solution with a viscosity of S (n= by GPC) was prepared by adding 4.7 parts of
4990) and heated and stirred at 80°C for 4 hours to cause partial crosslinking, resulting in a viscosity of T-U ²
A solution of target resin A (n=5400 by GPC) was obtained. Hereinafter, this will be abbreviated as resin (A-1). Reference Examples 2 to 7 (same as above) Various urethane-modified polyesters (a-1) and a control urethane-modified polyester ( a'-1), urethane-modified polyester resin A, and urethane-modified polyester A' for control were obtained. Example 1 55.5 parts of titanium oxide was added to 100 parts of resin (A-1).
1 part, 9.3 parts of "Super Betsukamine L-105-60" [methyl etherified melamine resin manufactured by Dainippon Ink & Chemicals Co., Ltd.; non-volatile content = 60%], 9.3 parts of "Super Betsukamine L-105-60" [Methyl etherified melamine resin manufactured by Dainippon Ink and Chemicals Co., Ltd.; 0.1 part and 0.04 part of "Polyflow S" (leveling agent manufactured by Kyoeisha Yushi Co., Ltd.) were added and kneaded in a boat mill to obtain a resin composition for paint. Next, this was applied to a 0.3 mm thick zinc phosphate treated galvanized iron plate to a film thickness of 15 to 20 μm, and then baked at 220° C. for 1 minute to obtain a coating film. The results of the performance test for this coating are shown in the second
Shown in the table. Examples 2 to 7 and Comparative Examples 1 to 6 Various resin compositions for coatings were obtained in the same manner as in Example 1, except that the curing agent shown in Table 2 was used as the curing agent component. Ta. However, Example 2 uses no curing agent at all, Comparative Examples 4 and 5 use commercially available baking paints, and Comparative Example 6 uses urethane-modified polyester resin ( a-1) is used. Using each of the obtained paint resin compositions,
Each coating film was obtained in the same manner as in Example 1, and then the coating film performance test was performed, and the results are summarized in the same table.

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Claims (1)

[Claims] 1. An aromatic dibasic acid, if necessary, another dibasic acid, a saturated glycol, a trivalent or higher valent polyol and/or polycarboxylic acid, and an organic diisocyanate. The resulting product has a hydroxyl value of 10 to 150 and a number average molecular weight of 2000 to 2000.
15000 urethane modified polyester (a-1)
and an aminoaldehyde resin (a-2) as an essential coating film-forming component. Aromatic dibasic acid accounts for at least 50 mol% of the total acid components constituting a-1), and the ratio of the organic diisocyanate to the total acid components is 3 to 50 mol%, The above resin composition for paint. 2 A hydroxyl value obtained by reacting an aromatic dibasic acid, if necessary, another dibasic acid, a saturated glycol, a trivalent or higher polyol and/or polycarboxylic acid, and an organic diisocyanate. 10 to 150, and the number average molecular weight is 2000 to
15000 urethane modified polyester (a-1)
and an aminoaldehyde resin (a-2), the modified polyester resin A obtained by partially crosslinking is an essential coating film-forming component, and the group further consists of an aminoaldehyde resin B and a blocked polyisocyanate compound C. A coating resin composition comprising at least one compound selected from the following as an essential curing agent component, wherein at least 50 mol% of the total acid component constituting the urethane-modified polyester (a-1) is aromatic. The organic diisocyanate is characterized in that the proportion of the organic diisocyanate based on the total acid component is 3 to 50 mol %. The above resin composition for paint.