JPH0222774B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, by room temperature curing or low temperature heating curing,
The present invention relates to a coating film forming method that provides a high-performance coating film with excellent appearance, physical performance, gasoline resistance, weather resistance, etc. In recent years, due to problems such as pollution and resource conservation, as well as from the direction of labor saving, there has been a demand for paints that are easy to apply, non-polluting, and low cost. It is a high-solids type that uses less solvent, is non-toxic, low-cost, and easy to apply manually, even for paints for areas that cannot be treated at high temperatures, such as building materials such as plastics and wood concrete, and metals such as automobile repair applications. There is a demand for something that does not require a lot of energy. Currently, in these fields, there are air-drying types that do not involve cross-linking reactions in the paint film, such as acrylic paints or melamine paints (so-called high-solid paints) that have added nitrified cotton, and cross-linked paints such as so-called phthalic acid enamels and urethane paints. type is used. In addition to the inherent problem that the air-drying type is unsuitable when high performance is required, it is also necessary to increase the degree of polymerization of the resin component in the paint, making it difficult to obtain a high-solid type and requiring manual labor. There are many drawbacks. Phthalate enamel is excellent in that it is easy to paint, but there are problems with film performance such as hardness, while urethane paint has excellent film performance and is quite easy to paint, but it is harmful and has problems due to isocyanate. There are handling issues and price issues. Therefore, the inventors of the present invention thought that it would be difficult to satisfy all of these requirements using an air-drying method, and as a result of intensive research into a new crosslinking method, we developed a high-performance crosslinking method previously announced in JP-A-52-76338. We have invented a coating film forming method that is easy to handle and saves labor. This method consists of (1) 0.2 to 30 percent by weight of a basic nitrogen-containing acrylic monomer, (2) acrylic acid or methacrylic acid, and aliphatic 1
Acrylic monomer () consisting of 35 to 99.8 weight percent of ester with alcohol or mixture thereof (3) and 0 to 60 weight percent of other copolymerizable monomers with two or more epoxy groups per molecule. This is a coating film forming method characterized by blending a compound or resin () having the following properties and applying it to an object to be coated. Although this method was revolutionary as a new coating film formation method, as it was put into practical use, it was discovered that there were a few problems. One of them is that when a tertiary amine monomer such as dimethylaminoethyl methacrylate or diethylaminoethyl methacrylate is used as a basic nitrogen-containing acrylic monomer, the produced acrylic resin solution becomes colored when stored for a long period of time. The second reason is that it tends to turn yellow when painted over a base paint that uses a large amount of nitrified cotton, and the third reason is that a hindered phenol ultraviolet absorber is usually used to improve weather resistance. Or, when mixed, at least temporarily becomes yellow or colored. The inventors of the present invention have further studied the solution to these problems, and as a result, have invented an improved coating film forming method that solves the above-mentioned problems. That is, the present invention comprises (1) 0.2 to 30 weight percent of a basic nitrogen-containing acrylic monomer, (2) acrylic acid or methacrylic acid, and an aliphatic monomer.
Acrylic polymer () consisting of 35 to 99.8 weight percent of ester with alcohol or a mixture thereof (3) and 0 to 50 weight percent of other copolymerizable monomers with two or more epoxy groups per molecule Compounds or resins () and carboxylic acids activated by double bonds and/or hydroxyl groups ()
This is a coating film forming method characterized by blending and applying the mixture to the object to be coated. Acrylic copolymer used in the present invention ()
As component (1), acrylic acid and/or methacrylic acid derivatives such as dimethylaminoethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate, t-butylaminoethyl acrylate or methacrylate are preferably used; Acrylamide or methacrylamide derivatives such as aminoethylacrylamide or methacrylamide, N-diethylaminoethylacrylamide or methacrylamide, etc. can also be used. The amount of these used is 0.2-30% by weight, but 0.5-15% by weight
is preferred for performance and cost reasons. As component (2) of the acrylic copolymer (2), esters of acrylic acid or methacrylic acid and monovalent acyclic or cyclic aliphatic monohydric alcohols are suitable, particularly methanol, ethanol, propanol, butanol, Esters or mixtures thereof with lauryl alcohol, stearyl alcohol, etc. are preferred, and 35-99.8%, preferably 50-80% by weight of the polymeric monomers are used. As component (3) of the acrylic copolymer (), styrene and a small amount of acrylic acid and/or methacrylic acid are preferably used, but other materials include α-methylstyrene, vinyltoluene, acrylonitrile, vinyl acetate, and 2-hydroxyethyl. or propyl acrylate or methacrylate,
acrylamide, methacrylamide, n-butoxymethyl or ethyl acrylamide or methacrylamide and their methylol compounds,
Itaconic acid, 2-vinylpyridine, etc. (1) and (2)
Anything that can be copolymerized with the components can be used, and the amount used is 0 to 50% by weight, preferably 20 to 45% by weight.
It is. The acrylic copolymer () can be polymerized by any polymerization method, but solution radical polymerization is preferably used.
That is, aromatic solvents such as toluene, and/
Alternatively, polymerization is preferably carried out by a conventional method using a polymerization initiator such as an azobis type and/or peroxide type in the presence of an alcohol solvent such as isobutanol and/or an ester solvent such as ethyl acetate. It is also possible to use chain transfer agents such as mercaptans for the purpose of controlling the degree of polymerization.
As the compound or resin () having two or more epoxy groups per molecule used in the present invention, any substance having two or more epoxy groups per molecule can be used. Glycidyl ethers of polyhydric alcohols are preferably used. Specific examples include ethylene glycol diglycidyl ether, glycerol polyglycidyl ether, and sorbitol polyglycidyl ether. Furthermore, as the resin having an epoxy group, an acrylic resin copolymerized with glycidyl acrylate or methacrylate is preferably used. The blending ratio of the acrylic copolymer () and the epoxy compound or resin () is: basic nitrogen atom (gram atom) in the acrylic copolymer ()/oxygen atom (of the epoxy group in the epoxy compound or resin ()) Gram atom) = preferably about 0.1 to 6, more preferably 0.5 to 6
3, but is not limited to this. The carboxylic acids activated by a double bond and/or a hydroxyl group used in the present invention include benzoic acid, various toluic acids, o- or p-hydroxybenzoic acid, maleic anhydride, itaconic acid,
Examples include lactic acid and derivatives thereof. It is activated by double bonds and/or hydroxyl groups to more easily dissociate as an acid than normal aliphatic carboxylic acids,
Preferably used are those that are easily soluble in toluene, xylene, and other common paint solvents. The amount of the carboxylic acid () to be used is preferably 0.1 to 5% by weight, more preferably 0.5 to 3% by weight, based on the solid content of the acrylic resin (), but is not limited thereto. Further, it is preferable that the acrylic resin (2) is blended during the production of the acrylic resin (2), but is not limited thereto. As for the blending method, it is desirable to add and mix the epoxy compound or resin () to the mixture of the acrylic copolymer () and the carboxylic acid () immediately before applying it to the object to be coated. In other words, a composition containing an acrylic copolymer () and a carboxylic acid () to which pigments, additives, solvents, etc. are added if necessary, and an epoxy compound or resin () to which solvents and others are added if necessary. It is preferable to add a solvent and other additives, if necessary, and apply the mixture to the object without stirring and leaving it for a long time. The applied coating film is left at room temperature or, if necessary, heated to a relatively low temperature to dry and form a cured coating film through a crosslinking reaction. The first effect of the present invention is that the composition itself is less colored. This is based on the fact that by allowing the acrylic resin (2) to coexist with the carboxylic acid (2), it is possible to prevent the basic nitrogen in the acrylic resin (2) from discoloring over time. In particular, this method has a particularly large effect on the apparent commercial value of the composition when used for light-colored or colorless coatings. The second effect of the present invention is that when a coating film is formed on a base containing nitrified cotton, there is no coloration.
Particularly in automobile repair applications, base paints containing nitrified cotton are often used, and there are cases in which paints containing nitrified cotton have already been applied during repair even if no base paint is used. The present invention has improved the disadvantages of coloring, and as a result, it has become possible to paint without the need for prior consideration of the base, which has a significant effect in simplifying the work. The reason for this effect is that the coloring reaction (considered to be a diazotization reaction) caused by the coexistence of basic nitrogen, nitrified cotton, and epoxy groups in the acrylic resin can be prevented by the action of a specific carboxylic acid (). by. The third effect of the present invention is that it does not cause coloration in the coexistence of a hindered phenol ultraviolet absorber and does not inhibit the reaction between the compound or resin (2) having an epoxy group and the acrylic resin (2). In the reaction between an acrylic resin () and a compound or resin () having an epoxy group, there appears to be an intermediate that is considered to be a strong base. That is, when phenolphthalene is added to a mixture of acrylic resin () and a compound or resin () having an epoxy group, and left at room temperature, 1 to 2
Phenolphthalene coloration is observed after a few days, and the coloring disappears after being left for one to several weeks. This is thought to be because a base that colors phenolphthalene is generated during the reaction.
Even if a hindered phenol ultraviolet absorber is added instead of phenolphthalene, the color will vary depending on the ultraviolet absorber, but generally a yellow coloration will be observed with the same tendency. This coloring can generally be prevented by adding acid, but adding common fatty acids such as acetic acid and butyric acid requires a fairly large amount to suppress the coloring, and in this case, the performance as a coating film may also be affected. It also inhibits the reaction between the acrylic resin () and the compound or resin () having an epoxy group. Furthermore, when a strong acid such as para-toluenesulfonic acid or phosphoric acid is used, the reaction between the acrylic resin (2) and the compound or resin (2) having an epoxy group is significantly inhibited. The carboxylic acid (2) of the present invention suppresses coloring and does not inhibit the reaction between the acrylic resin (2) and the compound or resin (2) having an epoxy group. The present invention can be particularly preferably used to form coating films in fields that cannot be subjected to high temperature treatment, such as building materials such as plastics, wood, and concrete, and metal materials, particularly for automobile repair applications. In addition, it can also be used to form coating films in fields that can be processed at high temperatures. It can also be used for adhering objects by taking advantage of the good adhesion of acrylic resin.
It can also be applied to textile processing, etc. Examples are shown below to clarify the effects of the present invention. Example 1 80 parts of toluene, 20 parts of isoptanol, 5 parts of hydroxymethacrylate, 1 part of acrylamide, 12 parts of dimethylaminoethyl methacrylate, 58 parts of methyl methacrylate, acrylic acid in a flask equipped with a condenser, thermometer and stirrer. Add 30 parts of butyl, 1 part of n-dodecyl mercaptan, and 1 part of azohisisobutyronitrile, stir at 80°C for 2 hours, and then add azohisisobutyronitrile 3 times every 2 hours.
After adding 0.2 parts, polymerization was completed in 12 hours to obtain an acrylic copolymer (). 1.5 parts of p-hydroxybenzoic acid and 20 parts of xylene were added to this acrylic copolymer (2) and stirred to prepare a solution A. Separately, take 10 parts of sorbitol polyglycidyl ether (manufactured by Nagase Sangyo Co., Ltd.),
Toluene/butyl cellosolve = 9/1 mixed solvent
10 parts were added and stirred to obtain Solution B. Take 50 parts of liquid A and add Alpaste 1500MA to it.
(manufactured by Toyo Aluminum Co., Ltd.), add 10 parts of liquid B, and stir well.
Sorbetsuso #100/Cellosolve Acetate=3/
Diluted with 6/1 thinner and spray painted on a steel plate coated with a commercially available nitrified cotton lacquer, and then
A composition prepared by mixing 50 parts of liquid, Tinubini 328 (sold by Nippon Ciba Geigy Co., Ltd.) and 10 parts of liquid B and diluting it with the above-mentioned thinner was spray coated and dried at 60°C for 30 minutes to give a metallic finish. This painted object is 1
Even after being left for several months, no discoloration was observed. Also A
Even if the liquid was left to stand for a long time, the color tone remained below the Gardner color number of 1. If lactic acid is not added when producing Part A, the painted surface with a metallic finish will be heated to 60℃ for 30 minutes.
After drying for several minutes, it was colored yellow-green, and when it was left at room temperature for about a week, the strong yellow-green color faded, but a faint yellow color still remained. In this case, the color of Solution A changed after it was left for two months. Three days after coating, the hardness, gasoline resistance, and xylene resistance were examined and found to be good, with no difference compared to when no p-hydroxybenzoic acid was added during the production of Liquid A. Example 2 In Example 1, p-hydroxybenzoic acid 1.5
various amounts of p-hydroxybenzoic acid in place of parts;
Similar experiments were carried out using benzoic acid, lactic acid, maleic anhydride, and for comparison purposes such as butyric acid and p-toluenesulfonic acid. The results are shown in Table 1.

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【table】

Claims (1)

[Scope of Claims] 1. Basic nitrogen-containing acrylic monomer 0.2 to 30% by weight 2. Acrylic acid or methacrylic acid and aliphatic 1
Esters or mixtures thereof with alcohols
35 to 99.8 weight percent 3 Other copolymerizable monomers Compounds or resins () having two or more epoxy groups per molecule in an acrylic polymer () consisting of 0 to 50 weight percent, and double bonds and A method for forming a coating film, which comprises blending a carboxylic acid () activated by a hydroxyl group and applying the mixture to an object to be coated.