JPH0365835B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating composition, and more particularly to a coating composition useful for metal applications, particularly metal can applications, which can form a coating film with excellent corrosion resistance by baking at high temperatures and short times. These coating compositions are desired to form excellent coating films under high temperature and short baking conditions in order to streamline the coating process, and this requirement is particularly severe when applied to metal cans. Taking one example of metal can applications, conventional metal cans include solder cans, adhesive cans, and welded cans, depending on the method of joining the can body, but the cost is low because the equipment space required for can manufacturing is small. Due to the surface advantage and the high mechanical strength of the can,
Welded cans are becoming increasingly popular. however,
In the case of welded cans, both cut ends of the can body material are welded overlapping (lap seam), so the cut ends are exposed to the inside of the can as painted, and if the material is electroplated tin, heat during welding Tin reflows when it is heated, and if it is a stain-free steel, corrosion is likely to occur from the metal surface that has been ground down to make it easier to weld. For this reason, in order to protect these welded parts, a method has traditionally been adopted in which a repair paint is applied to form a protective film.Generally, thermoplastic resin paints such as vinyl chloride copolymers, epoxy-amino paints,
Thermosetting resin coatings such as epoxy-phenolic and epoxy-acrylic are used. However, although it is possible to form a film in a short time with thermoplastic resin paints, in the case of food and beverages, they are not sufficiently resistant to acids and can be subjected to high-temperature retort treatment for sterilization. It has drawbacks in terms of corrosion resistance and content resistance. In addition, the above-mentioned epoxy-based thermosetting resin paint is
A coating film with excellent corrosion resistance will be formed if baked for a long time of about 1 minute, but if baked for a short time of 1 minute or less, especially 30 seconds or less, it will harden sufficiently even at high temperatures of about 240 to 260 degrees Celsius. Otherwise, a coating film with excellent corrosion resistance will not be obtained. Furthermore, the above-mentioned paint has the disadvantage that it cannot prevent sulfide blackening that occurs when the material is electroplated tin. In view of the above-mentioned current situation, the present invention provides a novel coating composition which has excellent content resistance and retort resistance and does not cause sulfide blackening, using baking conditions of high temperature and short time. That is, the present invention is obtained by reacting 5 to 100 parts by weight of a higher fatty acid with 100 parts by weight of a bisphenol type epoxy resin.
100 parts by weight of an epoxy ester resin composition obtained by partially modifying at least the above bisphenol type epoxy resin, 5 to 100 parts of a resol type phenol resin
This is a coating composition characterized by dissolving 5 to 100 parts by weight of an amino resin in an organic solvent. The epoxy ester resin composition used in the present invention is a bisphenol type epoxy resin represented by a bisphenol A type epoxy resin, a hydrogenated bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a saturated or unsaturated higher fatty acid. At least a portion of the resin is modified by esterification. Examples of the higher fatty acids include unsaturated fatty acids such as linoleic acid, linolenic acid, dehydrated castor oil fatty acid, soybean oil fatty acid, coconut oil fatty acid, tung oil fatty acid, sesame oil fatty acid, linseed oil fatty acid, and Hydiene (trade name of Soken Chemical Co., Ltd.). Higher fatty acids are preferred. In particular, when the iodine value is measured, higher fatty acids or mixtures having a value in the range of 80 to 190, more preferably 130 to 190 are used. The amount of higher fatty acids used is 5 to 100 parts by weight of higher fatty acids per 100 parts by weight of bisphenol type epoxy resin.
parts by weight, preferably from 300 to 70 parts by weight,
If the amount of higher fatty acid used is more than 100 parts by weight, the flavor suitability for the contents of the coating film will decrease, which is undesirable, while if it is less than 5 parts by weight, sulfide blackening is likely to occur. Modification of a bisphenol type epoxy resin with a higher fatty acid can be preferably carried out in an organic solvent at a reaction temperature of 200 to 230°C and a reaction time of 1 to 3 hours. The resol type phenolic resin in the present invention is obtained by reacting phenols and formalin in the presence of an alkali catalyst such as sodium hydroxide, magnesium hydroxide, lithium hydroxide, or ammonia. As the phenols, one or more phenols such as carbolic acid, p-cresol, o-cresol, m-cresol, bisphenol A, p-tert-butylphenol, p-phenylphenol, and xylenol can be used. Preferably, ammonia aresol using ammonia as a catalyst is used. The amino resin may be one obtained by reacting urea, melamine, a triazine compound, or a mixture thereof with formaldehyde, and etherified with a monohydric alcohol having 1 to 4 carbon atoms. The blending ratio of the epoxy ester resin composition and the resol type phenol resin is 5 to 100 parts by weight, preferably 5 to 50 parts by weight, of the resol type phenol resin to 100 parts by weight of the epoxy ester resin composition. If the amount of phenolic resin is less than 5 parts by weight, corrosion resistance, content resistance, and sulfide blackening will be reduced, and if it is more than 100 parts by weight, processability will be reduced. The blending ratio of the epoxy ester resin composition and the amino resin is 5 parts by weight to 100 parts by weight of the amino resin per 100 parts by weight of the epoxy ester resin composition.
Preferably, the amount is 5 to 50 parts by weight, and if the amino resin is less than 5 parts by weight, corrosion resistance and content resistance will be reduced, and if it is more than 100 parts by weight, processability will be reduced. When the coating composition of the present invention is used particularly as a repair coating, polyolefin resin, modified polyolefin resin, , polyester resin, polyamide resin, polyacetal resin, polycarbonate resin, acrylic resin, ABS resin,
Fine particles of thermoplastic resin such as styrene-acrylonitrile copolymer are used as a dispersion to reduce paint solid content to 100%.
It can be blended in an amount of 50 parts by weight or less. The most important feature of the present invention is that an epoxy ester resin obtained by modifying a bisphenol type epoxy resin with a higher fatty acid is cured and crosslinked with a resol type phenol resin and an amino resin. The reaction between epoxy ester resin and amino resin is faster than the self-condensation of epoxy ester resin and the reaction between epoxy ester resin and phenol resin, and the self-condensation of phenol resin itself is faster than the reaction with epoxy ester resin and amino resin. As a result, it is presumed that the phenol resin floats in the form of islands in the epoxy ester resin-amino resin crosslinked network structure, forming a structure crosslinked with the epoxy ester resin or amino resin. The above reaction is extremely fast, especially for epoxy ester resins and amino resins, so baking can be carried out in a short period of time.
Furthermore, the phenolic resin floats in the form of islands and has a high crosslinking density, so it has excellent corrosion resistance, and the double bonds (derived from unsaturated fatty acids) in the phenolic resin and epoxy ester resin mainly contain hydrogen sulfide generated from the contents. It reacts with sulfur compounds, and in combination with the shielding effect due to its high crosslinking density, it prevents the occurrence of sulfide blackening on the base and has excellent content resistance. The coating composition of the present invention dries at a high temperature of 240°C or higher for 60 seconds, in some cases for 25 seconds, and in a short time.
It can be baked, and the resulting coating film has excellent corrosion resistance and prevents the occurrence of blackening due to sulfide, making it useful as a repair paint for welded food cans, especially for fish and shellfish. This expands the uses of welded cans, mainly cans. The coating composition of the present invention contains acidic substances such as phosphoric acid, phosphoric acid esters, p-toluenesulfonic acid, and trimellitic acid, salts such as zinc octylate and zinc naphthenate, or aluminum alcoholates and alkyl titanates to accelerate curing. Organometallic compounds can be blended. Other conventional additives can be used in the coating compositions according to the invention, such as coloring dyes and pigments, rust-preventing pigments, fillers, surface-active substances, lubricants, etc. As a method for applying the coating composition of the present invention,
Known means such as spraying, roll coating, brush coating, flow coating, etc. can be used. The coating composition of the present invention is useful not only as a repair coating for welded cans, for repairing the inner and outer surfaces of side seams, but also for other products that require short baking times, such as coil coating coatings for beverage can lids, and architectural coatings. It is also useful as a paint for coating wood panels. Of course, it can also be applied to food cans and beverage cans as a baking paint for 10 to 20 minutes at 170°C to 220°C. The present invention will be specifically explained below with reference to Examples. In the examples, "parts" and "%" indicate "parts by weight" and "% by weight." Production of epoxy ester resin Bisphenol A type epoxy resin in flask
While stirring, add 100 parts of AER667 (manufactured by Asahi Kasei Corporation), 40 parts of soybean oil fatty acid, and 10 parts of xylene.
It was kept at 220°C for 3 hours. The reaction was terminated when the acid value became 10 or less, and 100 parts of Solbetsuso 100 was added.
and 100 parts of Solbetsuso 150 were added and cooled to obtain an epoxy ester resin (a) solution. Thereafter, solutions of epoxy ester resins (b), (c) and (d) were obtained using the raw materials and blending amounts shown in Table 1 by the same operations as above.

[Table] Production of phenolic resin 100 parts of p-cresol, 70 parts of formalin (30% aqueous solution), and 2 parts of a 20% aqueous solution of sodium hydroxide were placed in a flask and kept at 100°C for 2 hours with stirring. Next, 70 parts of xylene, 70 parts of n-butanol
and 70 parts of cyclohexanone and cooled.
After neutralization with hydrochloric acid, the aqueous layer was removed by decantation, the solvent layer was washed twice with the same amount of water, and then dehydrated by relaxing to obtain a solution of the phenol resin (e). Solutions of phenolic resins (f), (g), (h) and (j) were obtained by the same operation as above using the raw materials and blending amounts shown in Table 2.

[Table] Example Epoxy ester resin, resol type phenolic resin, and amino resin were mixed at the solid content ratio shown in Table 3, and after adding 0.3 parts of phosphoric acid as a curing aid, the viscosity was adjusted to #4 food cup for 220 seconds. (25℃)
Organic solvent (butyrocellosolve acetate/ethyl cellosolve acetate/Solbetsuso 100/xylene/isopropyl alcohol =
20/20/20/20/20) and used as a welding can repair paint. After the paints obtained in Examples 1 to 4 and Comparative Examples 1 to 8 were stored at room temperature for one month, the state of gluing and separation of the resin was observed (paint stability test). Next, cut out a section from the side seam of a 1 kg round tin can that was welded using a can making machine (manufactured by Sudronics), and apply these paints to the inner surface of the can with a brush to obtain a coating thickness of 15μ on the flat plate. Then, it was baked for 20 seconds using a gas burner. Baking was set so that the plate temperature reached 255°C after 20 seconds. The coated welded area was cut into 3 x 7 cm pieces to make test pieces, immersed in the contents of a well-ground salmon boiled can, re-made, retorted at 117°C for 90 minutes, and stored at 50°C for 20 days. The corrosion state and sulfide blackening state were evaluated (salmon can repacking test). In addition, a similar test piece was immersed in 1% saline solution, and 117
It was retorted at ℃ for 90 minutes and stored at 50℃ for 20 days to evaluate the corrosion state (body saline test). Next, the applied welded part was bent and the occurrence of cracks was observed (workability test). Table 4 shows the storage stability and coating film test results of the paints obtained in Examples and Comparative Examples. The paints obtained in Examples 1 to 4 showed no sulfide blackening and had excellent corrosion resistance and processability, whereas the paints obtained in Comparative Examples were particularly poor in corrosion resistance and processability. It is not practical as a welding can repair paint because of the poor balance between sulfide blackening, corrosion resistance, and workability. Example 5 20 parts of fine powder of nylon 11 having an average particle size of 10 μm was added to 100 parts of the solid content of the paint obtained in Example 1 while stirring at high speed to obtain a welding can repair paint. Example 6 40 parts of fine powder of nylon 11 having an average particle size of 10 μm was added to 100 parts of the solid content of the paint obtained in Example 1 while stirring at high speed to obtain a welding can repair paint. Example 7 20 parts of fine powder of nylon 12 having an average particle size of 10 μm was added to 100 parts of the solid content of the paint obtained in Example 2 while stirring at high speed to obtain a welding can repair paint. Example 8 40 parts of fine powder of nylon 12 having an average particle size of 10 μm was added to 100 parts of the solid content of the paint prepared in Example 2 while stirring at high speed to obtain a welding can repair paint. Example 9 15 parts of fine powder of carboxyl-modified polypropylene having an average particle size of 5 μm was added to 100 parts of the solid content of the paint obtained in Example 2 while stirring at high speed to obtain a welding can repair paint. The welded can repair paints obtained in Examples 5 to 9 were painted and baked in the same manner as in Example 1, and the film performance was examined. The results are shown in Table 5.

【table】

【table】

【table】

【table】

Claims (1)

[Claims] 1. 100 parts by weight of an epoxy ester resin composition obtained by reacting 5 to 100 parts by weight of a higher fatty acid with 100 parts by weight of a bisphenol-type epoxy resin, at least a part of which is modified from the bisphenol-type epoxy resin; 5 to 100 parts by weight of resol type phenolic resin and 5 to 100 parts by weight of amino resin
A coating composition characterized in that part by weight is dissolved in an organic solvent.