JP2007211133A - External coating composition for deep drawn food can and deep drawn food can having coating layer comprising the composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an external coating composition for steel or aluminium deep drawn food cans, having design exhibiting high luminance, forming a coating film having punching resistance, retort resistance, hot water immersion steam treatment resistance and adhesion. <P>SOLUTION: The external coating composition for deep drawn food cans comprises a glass flake pigment (A) silver-plated on the surface and a binder resin (B) comprising a polyester resin (a) containing no bisphenol type-originated material, having 5-15 hydroxyl value of a solid, <10 acid value of the solid and 13,000-18,000 number-average molecular weight as a main agent, and a methyl butyl mixed etherification benzoguanamine-melamine copolycondensation resin (b) containing no bisphenol type-originated material, and alicyclic polyisocyanate (c) as curing agents. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used as a base coat layer on the outer surface of steel or aluminum deep-drawn food cans, gives a design with vivid golden high brightness with a glittering feeling, and is excellent in retort resistance and high workability. The present invention relates to an environment-friendly deep-drawn food can outer coating composition that retains the physical properties of the coated film and a steel or aluminum deep-drawn food can having a dry paint film layer on the can wall.

  2. Description of the Related Art Conventionally, a coating material that forms a coating film having a glittering property with an emphasis on designability has been adopted in cosmetic and beverage 3P cans. In recent years, a high-gloss design has been required for the base coat layer on the outer surface of steel or aluminum deep-drawn food cans, and metal pigments such as aluminum paste and aluminum flakes have been used. In the case of a base coat layer on the outer surface of a steel or aluminum deep-drawn food can, pressurized steam treatment is performed to sterilize the contents, so the coating film is resistant to such treatment (retort resistance). In addition, solvent-based paints mainly composed of organic solvent solutions such as epoxy-amino resins, acrylic-amino resins, and polyester-amino resins are used.

  However, in this method, an epoxy resin made from bisphenol A, which has a suspected endocrine problem, is used as an essential component. One of the major problems of many existing can coatings is the endocrine problem. This is because, if the internal paint of the can contains a component made of bisphenol A, which is suspected of having an endocrine problem, the compound was eluted from the cured coating into the contents and ingested. It has become a social problem by the theory that it has a negative effect on human endocrine secretion. The coating on the outer surface of the can does not directly contact the contents, but it cannot be denied that the components of the outer surface coating may adhere to the inner surface during the can-making process such as baking in an oven. Against this background, the can manufacturing industry has announced a policy to eliminate bisphenol A from the raw materials for can coating materials, and paint manufacturers are conducting technical studies for that purpose.

  Conventionally, epoxy resins made of bisphenol A as raw materials have been heavily used as paints for cans containing foods and the like as the most useful components to satisfy the processability, adhesion, retort resistance, etc. required for coating films. It was. It was a very difficult task to satisfy the above-mentioned coating film performance without using this bisphenol A type epoxy resin. In recent years, paints that do not contain bisphenol A have been developed as exterior paints for 3P welding cans (see, for example, Patent Documents 1 and 2). However, the paints introduced in these documents are used for 3P welding cans, and the processing after the coating film formation is about the neck processing. However, to apply to deep-drawn food cans made of steel or aluminum, where the plate is processed into a container shape by deep drawing after the coating is formed, the punching resistance, etc., as an important condition, is satisfied. It was not something to let

  In addition, it has been difficult to achieve both high-gloss design properties and characteristics required for food cans such as processability and retort resistance. There is an example in which a high luster pigment obtained by coating a glass flake with a metal thin film by a sputtering method is used for automobile body painting, home appliance painting, etc. (see, for example, Patent Documents 3 and 4), but has high workability and retort resistance. There is no known steel or aluminum deep-drawn food can coating that retains.

JP 2001-14669 A JP 2003-246966 A JP 2004-314152 A JP-A-9-188830

  An object of the present invention is to solve the above-mentioned problems of the prior art, and has a design property that exhibits high brightness as a condition of a deep drawn food can made of steel or aluminum, and has punching resistance and retort resistance. Steel or aluminum deep-drawn food can outer coating that can form excellent coatings with high performance of heat resistance, immersion in steam and heat treatment, and adhesion and processability that can be processed into various can forms An object of the present invention is to provide a steel or aluminum deep-drawn food can having a composition and a dry coating layer of the coating composition.

  As a result of intensive studies, the inventors of the present invention do not contain a bisphenol-type raw material that is suspected of having an endocrine problem, and have a high brightness with a specific surface treatment with a specific polyester resin, benzoguanamine resin and alicyclic polyisocyanate. By using the present glass flake pigment, as a base coat layer for the outer surface of deep-drawn food cans made of steel or aluminum, it combines coating performance such as punching resistance, retort resistance, and hot water immersion steam treatment, and high brightness. A coating composition for the outer surface of an environment-friendly steel or aluminum deep-drawn food can capable of forming a coated film and a steel or aluminum deep-drawn food can having a dry paint film layer thereof have been found and the present invention has been achieved.

  That is, the present invention first includes a glass flake pigment (A) plated with silver on its surface, does not contain a bisphenol-type raw material, has a solid content hydroxyl value of 5 to 15, a solid content acid value of less than 10, and a number average molecular weight. A polyester resin (a) having a molecular weight of 13,000 to 18,000, which is blocked by an oxime-based blocking agent and a methylbutyl mixed etherified benzoguanamine-melamine cocondensation resin (b) containing no bisphenol-type raw material A deep-drawn food can outer coating composition comprising a binder resin (B) having an alicyclic polyisocyanate (c) as a curing agent.

  Secondly, the present invention provides a deep-drawn food can characterized by having a dry coating layer of the above-described deep-drawn food can outer coating composition on the outer surface of the side wall of the food can.

  According to the present invention, it is an environmentally friendly paint composition for the outer surface of a can that has a design property that exhibits a glittering golden luster, does not contain a bisphenol type-derived raw material, and has no fear of an endocrine problem, Even for severe processing of deep drawing, a coating composition for can outer surface having performances such as punching resistance, retort resistance, hot water immersion steam processing property, and steel having an excellent coating film or A deep-drawn food can made of aluminum can be provided.

  The deep-drawn food can outer coating composition of the present invention has a glass flake pigment (A) plated with silver on its surface, does not contain a bisphenol-type raw material, has a solid content hydroxyl value of 5 to 15, and a solid content acid value of 10 Less than, a polyester resin (a) having a number average molecular weight of 13,000 to 18,000, and containing no bisphenol-type raw material, a methylbutyl mixed etherified benzoguanamine-melamine cocondensation resin (b), and an oxime block Containing the binder resin (B) having the alicyclic polyisocyanate (c) blocked with the agent as a curing agent, and the average particle diameter R (μm) of the pigment (A) is 10 to 50 μm. A range is preferable. In addition, an average particle diameter shall be represented by median D50.

When the average particle diameter R (μm) of the pigment (A) is 10 to 25 μm, the pigment content is preferably 10 to 90 parts by mass with respect to 100 parts by mass of the solid content of the binder resin (B). Moreover, when the average particle diameter R (micrometer) of an above described pigment (A) is 25-50 micrometers, it is preferable that content of the pigment with respect to 100 mass parts of binder resin (B) solid content is 10-60 mass parts.

  The glass flake pigment (A) having a surface plated with silver used in the deep-drawn food can outer coating composition of the present invention is plated with silver on glass flakes having a thickness of about 1 to 2 μm and an average particle size of about 10 to 50 μm. The glass flake pigment thus obtained is preferred, and the silver surface may be further subjected to a surface coating treatment with a silane coupling agent or the like, and may be a glass flake pigment exhibiting more water resistance. If the average particle size is less than 10 μm, sufficient high brightness cannot be obtained, and if it exceeds 50 μm, high brightness can be obtained, but damage to the rubber roll or scraper tends to occur due to restrictions on coating conditions.

  The preferable average particle diameter and content of the pigment described above are in the range of 25 to 40 μm, and the content of the pigment with respect to 100 parts by mass of the coating composition is about 5 to 30% by mass.

  The above-mentioned pigment component surface-treated with a silane coupling agent or the like includes, for example, the following products as commercially available products (all are manufactured by Nippon Sheet Glass Co., Ltd., “Metashine” is registered by the company) Trademark).

  Examples of silver-coated products include Metashine MC5480PS-A1 (average particle size: 480 μm, and the parentheses are the average particle size indicated by Median D50), Metashine MC5230PS-A1 (230 μm), Metashine MC5150PS- A1 (150 μm), Metashine MC5090PS-A1 (90 μm), Metashine MC5030PS-A1 (30 μm), Metashine MC2080PS-A1 (80 μm), Metashine ME2040PS-A1 (40 μm), Metashine ME2025PS-A1 (25 μm), etc. Is mentioned.

  As the nickel silver coated products, Metashine MC5480NS-A1 (480 μm), Metashine MC5230NS-A1 (230 μm), Metashine MC5150NS-A1 (150 μm), Metashine MC5090NS-A1 (90 μm), Metashine MC5030NS-A1 (30 μm) ) And the like.

  As the nickel black coat products, Metashine MC5480NB-A1 (480 μm), Metashine MC5230NB-A1 (230 μm), Metashine MC5150NB-A1 (150 μm), Metashine MC5090NB-A1 (90 μm), Metashine MC5030NB-A1 (30 μm) ), Metashine MC1040NB-A1 (40 μm), Metashine MC1020NB-A1 (20 μm), and the like.

  As silver color products, Metashine MC5030RS-A1 (30 μm), Metashine MC5090RS-A1 (90 μm), Metashine MCK500RS-A1 (500 μm), Metashine MC1080RS-A1 (80 μm), Metashine MC1040RS-A1 (40 μm) And Metashine MC1020RS-A1 (20 μm).

  Examples of yellow products include Metashine MC5090RY-A1 (90 μm), Metashine MC1080RY-A1 (80 μm), Metashine MC1040RY-A1 (40 μm), Metashine MC1020RY-A1 (20 μm), and the like.

  Examples of red products include Metashine MC5090RR-A1 (90 μm), Metashine MC1080RR-A1 (80 μm), Metashine MC1040RR-A1 (40 μm), Metashine MC1020RR-A1 (20 μm), and the like.

  Examples of purple products include Metashine MC5090RV-A1 (90 μm).

  Examples of blue products include Metashine MC5090RB-A1 (90 μm), Metashine MC1080RB-A1 (80 μm), Metashine MC1040RB-A1 (40 μm), Metashine MC1020RB-A1 (20 μm), and the like.

  Examples of green products include Metashine MC5090RG-A1 (90 μm), Metashine MC1080RG-A1 (80 μm), Metashine MC1040RG-A1 (40 μm), Metashine MC1020RG-A1 (20 μm), and the like.

  All the pigments subjected to these surface treatments can be used. Preferably, for example, Metashine ME2025PS-A1 (Median D50: 20 μm), Metashine ME2040PS-A1 (Median D50: 33 μm), etc. These have a glass thickness of about 1 μm and a silver plating thickness of about 0.05 μm.

  The polyester resin used in the deep-drawn food can outer coating composition of the present invention has a solid content hydroxyl value of 5 to 15 (mg KOH / g), a solid content acid value of less than 10 (mg KOH / g), and several A polyester resin having an average molecular weight of 13,000 to 18,000 and containing no bisphenol-derived raw material.

  When a typical polyester resin is exemplified, for example, a polyol and a polycarboxylic acid (anhydride) are heated and melted, and the reaction product has an acid value of about 1 to 40 at a reaction temperature of about 160 to 270 ° C. And the like, if necessary, by dehydrating condensation under reduced pressure to obtain a dehydrating condensate having a number average molecular weight of about 500 to 25,000 and then dissolving it in various organic solvents. .

Typical examples of polyols used in preparing the polyester resin include ethylene glycol, propylene glycol, 1.3-butylene glycol, 1.4-butylene glycol, 1.6-hexanediol or diethylene glycol, or Various dihydric alcohols such as dipropylene glycol, neopentyl glycol, triethylene glycol; and glycerin, trimethylolethane, trimethylolpropane, trishydroxymethylaminomethane, pentaerythritol, dipentaerythritol or diglycerin Such as various trivalent or higher alcohols,
2-methyl 1,3-propanediol, cyclohexanedimethanol, and trimethylolpropane are preferred.

Typical examples of the polycarboxylic acid (anhydride) used in preparing the polyester resin include propanetricarboxylic acid, butanetetracarboxylic acid, adipic acid, phthalic acid, terephthalic acid or trimellitic acid. And various aliphatic or aromatic polycarboxylic acids, (anhydrous) trimellitic acid, methylcyclohexentricarboxylic acid (anhydride) or (anhydrous) pyromellitic acid. Furthermore, if necessary, various monobasic acids such as benzoic acid and tert-butylbenzoic acid can be used in combination as the acid component.
Terephthalic acid and isophthalic acid are preferred.

  The benzoguanamine resin used as a curing agent in the deep-drawn food can outer coating composition of the present invention is a methylbutyl mixed etherified benzoguanamine-melamine cocondensation resin that does not contain a bisphenol-type raw material.

  The blocked alicyclic polyisocyanate used as a curing agent in the deep-drawn food can outer coating composition of the present invention has a blocked NCO content of about 8% by weight and a free NCO content of less than 0.1% by weight. The dissociation temperature is 130 ° C., and it is an alicyclic polyisocyanate resin blocked with an oxime blocking agent.

  Considering the balance between the curability of the coating film and the processability, in particular, the methyl butyl etherified benzoguanamine resin is 5 to 15 parts by mass with respect to 100 parts by mass of the polyester resin component, and the block type alicyclic polyisocyanate resin is 5 to 15 parts by mass is preferable.

  The deep-drawn food can outer coating composition of the present invention is preferably used as a solvent-type paint in which a paint constituent is dissolved in a water-insoluble solvent. Any known organic solvent can be used, but Solvesso 100, Solvesso 150, butyl cellosolve acetate and the like are desirable. These may be used alone or in combination of two or more.

  The deep-drawn food can outer coating composition according to the present invention may be various acid catalysts such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthylene disulfonic acid, or phosphoric acid, if necessary. Various amine salts and the like may be added as a curing catalyst. The amount of the curing catalyst is usually about 0.1 to 1.0 part by mass with respect to 100 parts by mass of the resin solid content.

  Furthermore, various additives such as leveling agents, antifoaming agents, and lubricants that are usually used in paints can be blended in the deeply drawn food can outer coating composition of the present invention.

  The deep-drawn food can outer coating composition of the present invention can be produced by a conventional method using, for example, a mixing device such as a turbo mill or a dispersion stirrer.

  It is preferable that a part of the above-described polyester resin is prepared in advance with a precipitated barium sulfate base that has been kneaded with a roll mill or the like using a solvent such as butyl cellosolve together with precipitated barium sulfate.

  The deep-drawn food can outer coating composition of the present invention can be applied to a steel or aluminum deep-drawn food can as a base coat layer. After providing a base layer, a printing layer, etc. on the outer surface of a steel or aluminum sheet, for example, using a roller or the like with a 9-inch coater or the like, the deep-drawn food can outer coating composition of the present invention is used as a base coat layer. The target cured coating film can be formed by applying and baking at a temperature of about 180 ° C. for about 10 minutes.

  The coating film thus obtained has high luster, excellent workability, adhesion and the like while maintaining excellent golden luster, and is suitable as a base coat for steel or aluminum deep-drawn food cans.

  Hereinafter, the present invention will be described specifically by way of examples. Unless otherwise specified, “part” and “%” in the examples represent “part by mass” and “% by mass”.

(Preparation of precipitated barium sulfate base)
Polyester resin Byron GK36CS not containing bisphenol A (Toyobo Co., Ltd .: solid content hydroxyl value 8, solid content acid value 5, number average molecular weight 15,000) 60.0 parts, precipitated barium sulfate 30.0 parts, 10.0 parts of butyl cellosolve was blended and kneaded with a roll mill or the like to obtain a precipitated barium sulfate base.

(Preparation of Example Paint-Paint Base 1)
As a polyester resin not containing bisphenol A, 47.0 parts Byron GK36CS (manufactured by Toyobo Co., Ltd.) and as a methylbutyl mixed etherified benzoguanamine-melamine cocondensation resin not containing bisphenol A, Mycoat 101 (Nippon Cytec Industry Co., Ltd.) 3.0 parts), block type alicyclic polyisocyanate resin is 3.5 parts VESTANAT B1370 (manufactured by Huls Japan Co., Ltd.), 0.01 part silicone aid that imparts spot coating suitability and defoaming properties Furthermore, 20.0 parts of the precipitated barium sulfate base described above, 0.08 parts of leveling agent, 4.0 parts of PGM-AC, 4.0 parts of Solvesso 150, and 2.0 parts of Solvesso 100 Weigh accurately to 60 ° C ± while stirring and dispersing with a turbo mixer. ℃ was MadeNoboru temperature. After naturally cooling to about 40 ° C., 1.0 part of an acid catalyst was added while mixing and stirring in a vat tank equipped with a dispersion stirrer to obtain a paint base (1). Next, Metashine ME2040PS-A1 (manufactured by Nippon Sheet Glass Co., Ltd.) was added in an amount described in Table 1 below, and Solvesso 100 was added while adjusting to an appropriate viscosity to obtain each coating composition.

(Preparation of Example Paint-Paint Base 2)
As polyester resin not containing bisphenol A, 59.0 parts Byron GK36CS (manufactured by Toyobo Co., Ltd.), methylbutyl mixed etherified benzoguanamine-melamine co-condensation resin not containing bisphenol A, Mycoat 101 (Nippon Cytec Industry Co., Ltd.) 3.0 parts), block type alicyclic polyisocyanate resin is 3.5 parts VESTANAT B1370 (manufactured by Huls Japan Co., Ltd.), 0.01 part silicone aid that imparts spot coating suitability and defoaming properties 4.0 parts of PGM-AC, 4.0 parts of Solvesso 150, and 2.0 parts of Solvesso 100 are precisely weighed in a bat tank and heated to 60 ° C. ± 5 ° C. while being dispersed and stirred with a turbo mixer. It was. After naturally cooling to about 40 ° C., 1.0 part of an acid catalyst was added while mixing and stirring in a vat tank equipped with a dispersion stirrer to obtain a paint base (2). Next, Metashine ME2040PS-A1 (manufactured by Nippon Sheet Glass Co., Ltd.) was added in an amount described in Table 1 below, and Solvesso 100 was added while adjusting to an appropriate viscosity to obtain each coating composition.

(Preparation of comparative paint-paint base 3)
As a polyester resin not containing bisphenol A, 41.0 parts of Byron GK36CS (manufactured by Toyobo Co., Ltd.) and as a methylbutyl mixed etherified benzoguanamine-melamine cocondensation resin not containing bisphenol A, Mycoat 101 (Nippon Cytec Industry Co., Ltd.) 12.5 parts), 0.01 part of a silicone aid that imparts spot coating suitability and antifoaming property, 20.0 parts of the above-described precipitated barium sulfate base, 0.08 parts of leveling agent, PGM -4.0 parts of AC, 4.0 parts of Solvesso 150, and 2.0 parts of Solvesso 100 were precisely weighed in a bat tank and heated to 60 ° C ± 5 ° C while being dispersed and stirred with a turbo mixer. It was allowed to cool to about 40 ° C. to obtain a paint base (3). Next, Metashine ME2040PS-A1 (manufactured by Nippon Sheet Glass Co., Ltd.) was added in an amount described in Table 1 below, and Solvesso 100 was added while adjusting to an appropriate viscosity to obtain each coating composition.

Using the 9-inch test coater, the coating compositions of the Examples and Comparative Examples obtained above were dried on the outer surface of a TFS base plate (tin-free steel plate, thickness 0.19 mm) for can manufacturing. After coating so that the film amount was 75 mg / dm ² , the film was cured by heating in a hot air circulating gas oven at 180 ° C. for 10 minutes. The thickness of the obtained coating film was about 6 μm. What used this panel as the test piece was used for the next test.

  (High luminance): Based on visual evaluation.

  (Missing property): A black paper is placed before and after the composition roll using a 9-inch test coater as a testing machine. The coater is rotated at 80 rpm in the same manner as painting. Mist was collected on black paper for 1 minute and evaluated visually.

  (Flow property): Paint on a TFS board with a 9-inch test coater, and bake the paint board in a hot air circulation oven (set time 0 minutes). The flowability of the cured coating film surface is visually determined.

  (Scraper scratch resistance): A scraper polished and smoothed by a grindstone is set on a 9-inch coater, and the coater is operated in the same manner as painting. Lightly touch the scraper with the impression roll and scrape the paint. Immediately after the start, paint is applied to the TFS board 5 minutes later and 10 minutes later. Visually judge the backside dirt (dirty back) of the paint plate and scratching of the scraper blade according to the scratching of the scraper

  (Cap processability test): A cap process test was performed with a 12-ton press.

  (Cap processing roto mat test): After cap processing with a 12-ton press, the cap was immersed in 130 ° C. hot water in a pressurized container for 30 minutes, and then the state of the coating film was evaluated.

  (Bendability test): Using a DuPont impact tester, the cracked state of the coated film was evaluated under the conditions of 1 kg-50 cm on a 1/10 tilt table.

  (Impact resistance test) The state of the coating film after the DuPont impact test was evaluated under the conditions of 1 kg-10 cm, 20 cm, and 30 cm.

The evaluation criteria for the above evaluation items regarding workability are as follows.
○: Good, △: Somewhat bad, ×: Bad

The coating composition of the present invention can impart high glossiness of golden luster to steel and aluminum plates, and can form a tough base coat film that can withstand deep drawing, and can be used for food cans such as tuna cans. It can be widely deployed.

Claims (7)

Glass flake pigment (A) plated with silver on the surface, does not contain bisphenol-type raw material, solid content hydroxyl value is 5 to 15, solid content acid value is less than 10, number average molecular weight is 13,000 to 18,000 A methyl butyl mixed etherified benzoguanamine-melamine co-condensation resin (b) and a cycloaliphatic polyisocyanate (c) blocked with an oxime-based blocking agent, which contains a certain polyester resin (a) as a main ingredient and does not contain a bisphenol-type raw material. A deep-drawn food can outer coating composition comprising a binder resin (B) as a curing agent. The average particle diameter R (micrometer) of the above-mentioned pigment (A) is 10-25 micrometers, and content of the pigment with respect to 100 mass parts of binder resin (B) solid content is 10-90 mass parts. Deep-drawn food can outer coating composition. The average particle diameter R (micrometer) of the above-mentioned pigment (A) is 25-50 micrometers, Content of the pigment with respect to 100 mass parts of binder resin (B) solid content is 10-60 mass parts. Deep-drawn food can outer coating composition. The deep-drawn food can outer coating composition according to any one of claims 1 to 3, comprising a precipitated barium sulfate base containing the polyester resin, precipitated barium sulfate, and a solvent. A deep-drawn food can comprising a dry-coating layer of the paint composition for an outer surface of a deep-drawn food can described in claim 1 on an outer surface of the side wall of the food can. The deep-drawn food can according to claim 5, wherein the amount of the dried coating film of the deep-drawn food can outer coating composition is 40 to 180 mg / dm ² . The deep-drawn food can according to claim 5 or 6, wherein the deep-drawn food can has a desired printed layer on the bottom surface and the outer surface of the side wall.