JPH047992B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a metal-polypropylene film laminate made by laminating a polypropylene film with good corrosion resistance to a metal plate, and its main purpose is to provide excellent adhesive workability and corrosion resistance. An object of the present invention is to provide a resin-coated metal plate having the following properties. (Prior Art) Conventionally, a metal-polyolefin laminate in which a polyolefin in film such as polyethylene or polypropylene is formed on a metal plate via an adhesive layer such as an adhesive or a modified olefin composition has been manufactured based on the characteristics of the polyolefin in film, such as normal chemical resistance,
Taking advantage of its properties such as solvent resistance and heat resistance, it is mainly applied to container materials and indoor and outdoor building materials. Several methods have been proposed for producing this metal-polyolefin film laminate. For example, a method in which a film containing a carboxyl group-modified polyolefin is bonded onto a metal substrate by thermocompression, and a method in which a three-layer structure of an epoxy resin primer, a modified polyolefin, and an olefin film is bonded onto a metal surface (JP-A-Show)
56-117642), a method of adhering a polyolefin film to a metal substrate using an adhesive prepared by dispersing carboxyl-modified polyolefin powder in an epoxy resin containing a curing agent (Japanese Patent Laid-Open No. 53-133242)
(Japanese Patent Application Laid-open No. 1982-12481), and a method using an adhesive prepared by reacting a saturated hydrocarbon having a carboxyl group with an epoxy resin (Japanese Patent Application Laid-open No. 124812/1982). The metal-polyolefin film laminate produced by these methods has sufficient adhesive strength and exhibits good corrosion resistance and durability against common chemicals and solvents. (Problem to be solved by the invention) However, ordinary polyolefin films such as polyethylene and polypropylene have the property of relatively quickly absorbing and permeating lower fatty acids such as acetic acid and butyric acid, and chlorinated solvents such as carbon tetrachloride. It also has a relatively high oxygen gas permeability, so if the polyolefin side is exposed to substances containing these for a long period of time, these acids and oxygen will permeate through the film in a very short period of time depending on the conditions. It may reach metal surfaces and cause corrosion. Such a phenomenon cannot be prevented even by the above-mentioned prior art method of using an epoxy resin as a primer or dispersing carboxyl group polyolefin powder in an epoxy resin. Therefore, for example, when a metal-polyolefin laminate is used as a container material, this drawback significantly limits its range of application as a container. (Means for Solving the Problems) The present inventors have conducted intensive studies to solve the characteristic problem of permeation of corrosive substances such as organic acids into the film in metal-polypropylene laminates. In an adhesive composition composed of an epoxy ester resin, a resol type phenolic resin, and a carboxyl group-modified polypropylene, it is possible to penetrate the film layer by imparting flexibility to the epoxy ester resin and keeping the acid value of the resulting resin low. We have discovered that the adhesive layer exhibits a powerful barrier ability against corrosive substances. As will be shown in the Examples below, by doing so, the corrosion resistance of the entire coating layer is significantly improved without impairing process adhesion. That is, the present invention provides a laminate in which a multilayer film of an adhesive film layer containing a carboxyl group-modified polypropylene resin and an unmodified polypropylene resin is laminated via an adhesive layer formed on a metal base material. The layer is bisphenol A
100 parts by weight of type epoxy resin and 1 to 20 parts of saturated dibasic acid
Composition (A) of epoxy ester resin having an oxidation value of 10 or less, modified using parts by weight (A) 90 to 40% by weight
and 100 parts by weight of a solvent-soluble resin consisting of 10 to 60% by weight of resol type phenolic resin (B), and 0 to 100 parts by weight of dispersed carboxyl group-modified polypropylene resin (C), which was baked and hardened. The coating film is a metal-polypropylene film laminate. Next, explanation will be given with reference to the drawings. As shown in FIG. 1, the present invention comprises laminating a multilayer film 5 consisting of an adhesive film layer 3 containing carboxyl group-modified polypropylene and unmodified polypropylene 4 via an adhesive layer 2 formed on a metal base material 1. In the laminate made of
The adhesive layer is made of bisphenol A type epoxy resin.
A composition of epoxy ester resin having an acid value of 10 or less obtained by modifying 100 parts by weight with 1 to 20 parts by weight of a saturated dibasic acid (A) 90 to 40% by weight, and a resol type phenol resin (B) A metal-polypropylene film laminate which is a bake-hardened coating film containing 0 to 100 parts by weight of dispersed carboxyl group-modified polypropylene (C) to 100 parts by weight of a solvent-soluble resin consisting of 10 to 60% by weight. It is. FIG. 2 shows the process of co-pressing and laminating carboxyl group polypropylene and unmodified polypropylene via an adhesive layer on the metal base material 1. The bisphenol A type epoxy resin in the present invention refers to epichlorohydrin and 2,2-bis(4-
It is obtained by the reaction of hydroxyphenyl)propane, and the average molecular weight calculated from the epoxy equivalent is
Although those having an average molecular weight of 800 or more can be used, those having an average molecular weight of 2,000 to 4,000 are preferable. Composition (A) of epoxy ester resin in the present invention
is a resin composition made by partially modifying a bisphenol A type epoxy resin with a fatty acid, for example, a resin epoxy esterified with a saturated dibasic acid such as adipic acid, suberic acid, azelaic acid, or sebacic acid. be. The method for epoxy esterification is 1 to 20 parts by weight per 100 parts by weight of epoxy resin.
Add parts by weight of fatty acids and heat at a temperature of 100 to 200℃.
Allow to react for 8 hours. At this time, the acid value of the resin produced by esterification has a strong influence on the barrier ability of the adhesive composition finally prepared against lower fatty acids that penetrate, for example, a polypropylene film. In the present invention, when the acid value of the epoxy ester is set to 10 or less, preferably 3 or less, remarkable effects are obtained. The resol type phenolic resin (B) in the present invention is obtained by a known method of addition-condensing formaldehyde to phenols under a catalyst, and also includes those modified with phenolic hydroxyl groups or alcoholic hydroxyl groups. In addition, the phenols include phenol, o-cresol, m-cresol,
P-cresol, p-tert-butylphenol,
p-nonylphenol, p-octylphenol, p-phenylphenol, methylphenol, ethylphenol, propylphenol, isopropylphenol, butylphenol, p-
tert-amylphenol, 4,4'-sec-butylidenephenol, p-cyclohexylphenol,
4,4'-isopropylidene-diphenol (bisphenol A), xylenol, phenyl-o-
Cresol etc. may be used alone or in combination of two or more, and as a catalyst, organic amines such as ammonia, ethylamine, butylamine, diethanolamine, etc.
Basic compounds such as sodium hydroxide, magnesium hydroxide, calcium hydroxide, and barium hydroxide are used, and as formaldehyde, a 37% aqueous solution or a 40% butanol solution is used. The solvent-soluble resin according to the present invention is composed of an epoxy ester resin composition (A) of 90 to 40% by weight and a resol type phenolic resin (B) of 10 to 60% by weight.
When the amount of epoxy ester resin (A) exceeds 90% by weight, the barrier of the coating film decreases;
If the amount is less than this, the processability of the coating film decreases, which is not preferable. The carboxyl group-modified polypropylene (C) in the present invention is polypropylene graft-polymerized with an unsaturated carboxylic acid such as maleic acid or maleic anhydride, or an acid anhydride thereof. A carboxyl group-modified polypropylene dispersion can be produced by physically crushing carboxyl group-modified polypropylene and dispersing it in an appropriate solvent, or by dissolving it in a solvent such as xylene while hot, and then cooling it to disperse the resin in the solvent. It can also be obtained by a method of In the adhesive composition of the present invention, the dispersion of carboxyl group-modified polypropylene (C) is used in an amount of 0 to 100 parts by weight, preferably 3 to 50 parts by weight, based on 100 parts by weight of the solvent-soluble resin. . Resin (C)
If the amount is more than 100 parts by weight, the anticorrosion properties of the solvent-soluble resin will be relatively reduced, which is not preferable. Examples of organic solvents used in the adhesive composition of the present invention include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone, aromatics such as benzene, toluene, xylene, and other alkylbenzenes, methyl cellosolve, and ethyl Cellosolve, cellosolves such as butyl cellosolve, methyl cellosolve acetate, butyl cellosolve acetate, esters such as ethyl acetate, butyl acetate, isopropyl alcohol,
Alcohols such as butyl alcohol and diacetone alcohol, or a mixed solvent thereof can be used. The multilayer polypropylene film used in the present invention includes polypropylene containing carboxyl group-modified polypropylene, a homopolymer of polypropylene, a copolymer of ethylene or butene, etc.
It is produced by a conventional coextrusion method or lamination method using a polymer blend with polyisobutylene or butadiene rubber or the like. The thickness of the polypropylene layer containing carboxyl-modified polypropylene used as the adhesive side is generally in the range of about 5 to 20 μm, and the overall thickness is in the range of 30 to 300 μm for general use and practical use. On the other hand, the base metal plates include cold-rolled steel plates, electric or hot-dip galvanized steel plates, steel plates coated with their alloys, electrolytic chromic acid treated steel plates, tin-plated steel plates, stainless steel plates, aluminum plates, copper plates, or foils thereof. etc., and these can be used as they are or those to which a commonly used chemical conversion treatment has been applied. In order to obtain a metal-polypropylene film laminate using the adhesive composition according to the present invention, the adhesive composition is coated on a metal plate by a conventional method such as roll coating or curtain flow coating, so that the coating thickness after drying is After applying it to a thickness of 1 to 50 μm,
Heat and dry for about 0.3 to 20 minutes so that the metal plate temperature becomes 180 to 280℃. Immediately thereafter, the polypropylene film described above is laminated using a roll lamination method. The bonding pressure may be about 0.1 to 20 kg/cm ² . Thereafter, it is cooled to obtain a coated metal plate. (Function) The metal-polypropylene film laminate thus obtained has good adhesion as well as excellent heat resistance, corrosion resistance, and chemical resistance, so it can be used not only as a general building material but also in fields that require relatively high corrosion resistance, such as containers. It is believed that it can be fully applied to materials, etc. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 100 parts by weight of Epicote 1007 (bisphenol A type epoxy resin manufactured by Yuka Ciel Epoxy Co., Ltd.) and 5 parts by weight of sebacic acid were dissolved in 105 parts by weight of cellosolve acetate, and N,N dimethylbenzylamine was dissolved.
Add 0.22 parts by weight, react at 150℃ for 4 hours,
An epoxy ester resin composition with a solid content of 50% was synthesized. The acid value of the epoxy ester resin composition produced at this time was 2.1 mg KOH/g. Next, 0.3 mol of bisphenol A and 0.7 mol of p-tert-butylphenol were added to formaldehyde (37%
Aqueous solution) was dissolved in 2.4 mol, 0.2 mol of ammonia (25% aqueous ammonia) was added, and the mixture was reacted at 95°C for 3 hours.
The resulting condensate was extracted with a mixed solvent consisting of 30 parts by weight of methyl isobutyketone, 30 parts by weight of cyclohexanone, and 40 parts by weight of xylene, washed with water, left to stand for one day, and the aqueous layer was separated to obtain a solid content of 60%. A solution of resol type phenolic resin was synthesized. Then, 77 parts by weight of the epoxy ester resin composition as a solid content was mixed with 23 parts by weight of a resol type phenol resin as a solid content to prepare an epoxy phenol resin solution with a solid content of 52%. To 100 parts by weight of the solvent-soluble resin as a solid content, 12 parts by weight of a solvent dispersion of carboxyl group-modified polypropylene (manufactured by Toyo Ink Mfg. Co., Ltd., trade name: Lioflex 4188, solid content 10%) was added. An adhesive with a concentration of 35.9% by weight was prepared. The adhesive obtained in this way was applied to one side of a 0.32 m/m thick piece of stain-free steel (manufactured by Nippon Steel Corporation, trade name: Can Super) in an amount of 5 ml after drying.
It was coated using a reverse roll coater so that the coating amount was g/m ² . Next, the steel plate was dried and heated in a gas oven for 30 seconds to reach a temperature of 240°C, and then, while maintaining the same temperature, a roll laminator was immediately used to coat the steel plate with a 10 μm layer of carboxyl group-modified polypropylene. 60 μm thick coextruded polypropylene film (manufactured by Idemitsu Petrochemical Co., Ltd.)
F-200S/M-100 (trade name) was laminated at a pressure of 4 kg/cm ² and immediately cooled to produce a metal-polypropylene laminate. Example 2 100 parts by weight of Epicote 1009 (manufactured by Yuka Ciel Epoxy Co., Ltd., bisphenol A type epoxy resin) and 4 parts by weight of azelaic acid were dissolved in 104 parts by weight of cellosolve acetate, and 0.25 parts by weight of N,N-dimethylbenzylamine was dissolved. Parts by weight were added and reacted at 150°C for 5 hours to synthesize an epoxy ester resin composition with a solid content of 50%. The acid value of the epoxy ester resin composition produced at this time was 1.8 mgKOH/g resin. On the other hand, the synthesis and blending of resol type phenolic resin and the solvent dispersion of carboxyl group-modified polypropylene were carried out in the same manner as in Example 1.
A 35.9% by weight adhesive was prepared. A metal-polypropylene film laminate was produced using this adhesive composition in the same manner as in Example 1. Example 3 A metal-polypropylene film laminate was prepared in the same manner as in Example 1 using only the solvent-soluble resin prepared from the epoxy ester resin synthesized in Example 1 and the resol type phenol resin. Example 4 A metal-polypropylene film laminate was produced in the same manner as in Example 1, except that the amount of carboxyl group-modified polypropylene used in Example 1 was changed to 95 parts by weight, and an adhesive was prepared in the same manner as in Example 1. Comparative Example 1 In the synthesis of the epoxy ester resin composition in Example 1, N,N-dimethylbenzylamine was changed to 0.11 parts by weight and the reaction was carried out for 3 hours. The acid value of the epoxy ester resin composition obtained was 13.5. mg
KOH/g resin. Using the epoxy ester resin composition, an adhesive was prepared in the same manner as in Example 1, and a metal-polypropylene film laminate was produced. Comparative Example 2 In place of the azelaic acid used in Example 2, 5 parts by weight of stearic acid was used to synthesize an epoxy ester resin composition. The acid value of the epoxy ester resin composition produced at this time was 3.5 mg.
KOH/mg resin. Using the epoxy resin composition, an adhesive was prepared in the same manner as in Example 1, and a metal-polypropylene film laminate was produced in the same manner as in Example 1. Comparative Example 3 In Example 1, instead of the epoxy ester resin composition solution, a resin solution in which Epicote 1007 was dissolved in cellosolve acetate to a solid content of 50% was used, and the other conditions were the same as in Example 1. A metal-polypropylene film laminate was produced in the same manner as in Example 1. Comparative Example 4 A metal-polypropylene film laminate was produced in the same manner as in Example 1 except that only the stain-free steel was heated without using an adhesive. Comparative Example 5 A metal-polypropylene film laminate was produced in the same manner as in Example 1, using only the dispersed carboxyl group-modified polypropylene used in Example 1 as an adhesive. The processing adhesion of the metal-polypropylene film laminates produced in Examples 1 to 4 and Comparative Examples 1 to 5 was measured by an Erichsen test according to JIS K-6744. Then, in order to examine the corrosion resistance including the processed parts, a Dupont impact test (1/2 inch diameter, 500 g load, 30 cm height) was performed from the back at a temperature of 20°C, and then immersed in a 5% acetic acid aqueous solution at 37°C. At
After 480 hours had elapsed, the state of rust on the flat and convex parts was visually observed and evaluated. These results are summarized in Table 1. This also shows that the product of the present invention has sufficient adhesion processability and corrosion resistance. It is also found that among the epoxy ester resin compositions, the lower the acid value, the better the corrosion resistance.

【table】

[Table] (Effects of the Invention) The adhesive layer of the present invention is made by modifying the epoxy resin component with a fatty acid, thereby increasing the molecular weight of the epoxy resin and imparting flexibility. Even if it is formed and processed like a general metal plate, cracks in the adhesive layer at the processed parts are prevented from occurring. The modified product also has high barrier properties against corrosive substances, and can be covered with an adhesive layer against corrosive substances that penetrate the polypropylene film. Therefore, it can be fully applied to the modification of cans, whose application has been delayed due to large restrictions on contents.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram illustrating the layer structure of a laminate according to the present invention. FIG. 2 is a schematic diagram illustrating the process of obtaining the laminate of the present invention. 1... Metal base material, 2... Adhesive layer, 3... Adhesive film layer containing carboxyl group-modified polypropylene, 4
...Unmodified polypropylene, 5...Multilayer film.

Claims (1)

[Claims] 1. Via an adhesive layer formed on a metal base material,
In a laminate formed by laminating a multilayer film of an adhesive film layer containing a carboxyl group-modified polypropylene and an unmodified polypropylene, the adhesive layer contains 100 parts by weight of a bisphenol A type epoxy resin and 1 to 20 parts by weight of a saturated dibasic acid. A solvent-soluble resin 100 consisting of 90 to 40% by weight of an epoxy ester resin composition (A) having an acid value of 10 or less and 10 to 60% by weight of a resol type phenolic resin (B).
A metal-polypropylene film laminate which is a bake-hardened coating film containing 0 to 100 parts by weight of dispersed carboxyl group-modified polypropylene (C). 2. The metal-polypropylene film laminate according to claim 1, wherein the dispersion of the carboxyl group-modified polypropylene resin (C) is blended in an amount of 3 to 50 parts by weight.