JP2011026404A - Metal printing ink composition and covering method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal printing ink composition that has a high degree of whiteness and high designability and gives an elution amount with an aqueous alcoholic solution of a benzoxazole derivative sufficiently lower than the tolerance limit based on the U.S. Food and Drug Administration (hereinafter referred to as "FDA"), and a covering method using the same. <P>SOLUTION: The metal printing ink composition includes a pigment, an alkyd resin, a hydrocarbon solvent and a benzoxazole derivative. The covering method for a metal substrate includes applying the metal printing ink composition onto a metal substrate, subsequently coating it with a thermosetting overprinting varnish and thermosetting the varnish. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  In the field of metal printing inks, in particular, beverage cans and two-piece printing inks, benzoxazole has been recognized as having high whiteness and high design, and in a dissolution test from a dry film. It is an object of the present invention to provide a metal printing ink composition with a very small amount of derivative elution and a coating method using the same.

  Currently, beverage cans, especially two-piece cans, are often printed based on white, such as beer, happoshu, and third beer. Each manufacturer demands white ink with high whiteness for the purpose of eye catching. However, in order to increase the whiteness with a metal printing ink composition comprising current titanium oxide, alkyd resin, hydrocarbon solvent, etc., the film thickness of the ink must be increased. However, in the two-piece can printing method that performs curved surface printing, the occurrence of misting during printing becomes significant by increasing the film thickness. In addition, there are problems such as unclear reproduction of image lines, it is difficult to increase the printing speed, and the productivity is extremely poor. In addition, attempts have been made to add substances other than titanium oxide to improve the hiding property and improve the whiteness. (For example, refer to Patent Document 1) However, this attempt is an attempt to maintain the concealing property that is lowered when the aqueous overprint varnish is used, and does not attempt to positively improve the whiteness. . A benzoxazole derivative is used as an optical brightener in an ink visualized by UV irradiation (for example, see Patent Document 2). Although the whiteness is improved by adding a benzoxazole derivative, in the case of an alcoholic beverage can or the like, an ink with extremely little elution of the benzoxazole derivative has been demanded.

JP-A-6-279722 JP-A-8-199101

  An object of the present invention is a metal printing ink composition having a high whiteness and high design, and an elution amount of a benzoxazole derivative with an alcohol aqueous solution sufficiently lower than an allowable limit of the standards of the US Food and Drug Administration (hereinafter referred to as FDA). And it is providing the coating method using the same.

  As a result of intensive studies, the present inventors have found that a metal printing ink composition containing a benzoxazole derivative in a specific alkyd resin binder solves the above problems, and has completed the present invention.

  That is, the present invention provides a metal printing ink composition comprising a pigment, an alkyd resin, a hydrocarbon solvent, and a benzoxazole derivative represented by the general formula (1). Furthermore, this invention provides the coating method using this metal printing ink composition.

（Ｒ、Ｒ１、Ｒ２は、任意の有機化合物。）

(R, R1, and R2 are arbitrary organic compounds.)

  The metal printing ink composition characterized by containing the benzoxazole derivative of the present invention has equivalent printability as compared with a metal printing ink composition not containing a benzoxazole derivative, and has high whiteness and high design. Can be obtained. In addition, for the alcohol elution test required by the FDA in applications that directly touch food (equivalent to the inner surface of the can), the elution amount of the benzoxazole derivative from the dried film is 0.5 ppb or less. It was confirmed that the amount of elution was an extremely low level that was not necessary, and the possibility of expansion to can outer surface applications was also obtained.

  Hereinafter, each component used for this invention is demonstrated in detail. The alkyd resin used in the present invention is a resin modified with an oil, a fatty acid or a hydrogenated product thereof, a monovalent acid, a monovalent alcohol, etc., based on a condensate of a polybasic acid and a polyhydric alcohol. Yes, it can be modified with epoxy resin or acrylic resin. Each component has an oil length of 20 to 60, desirably 25 to 55, more desirably 30 to 50, and a hydroxyl value of 50 to 200, desirably 80 to 190, more desirably. What is necessary is just to be able to adjust to 100-185. If the oil length is less than 20, the transferability is lowered and whiteness is hardly obtained. If it exceeds 60, after the overprint varnish coating, the hardness especially in hot water is lowered, and the surface of the can print coating surface is easily damaged. On the other hand, when the hydroxyl value is less than 50, after coating the varnish for overprinting, the hardness particularly in hot water is lowered, and the surface of the can print coating is easily damaged. If it exceeds 200, the transferability is lowered, and it is difficult to obtain whiteness. In the alkyd resin of the present invention, raw materials that can be used for the synthesis of alkyd resins can be used, and there is no particular limitation. Polybasic acids include adipic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic anhydride, azelaic acid, sebacic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, anhydrous Examples thereof include het acid, hymic anhydride, maleic anhydride, fumaric acid, itaconic acid, trimellitic anhydride, methylcyclohexeric carboxylic anhydride, pyromellitic anhydride, and the like. These can be used alone or in combination. Polyhydric alcohols include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, butylene glycol, hexanediol, neopentyl glycol, octanediol, butylethylpropanediol, bisphenol A, hydrogenated bisphenol A, bisphenol F, glycerin, tri Examples include methylolethane, trimethylolpropane, trishydroxymethylaminomethane, pentaerythritol, dipentaerythritol and the like, and these can be used alone or in combination.

  The non-drying oil and non-drying oil fatty acid used for synthesizing the alkyd resin used in the present invention have an oil length in the range of 20 to 60, preferably 25 to 55, more preferably 30 to 50, and There is no particular limitation as long as the hydroxyl value can be adjusted to 50 to 200, preferably 80 to 190, and more preferably 100 to 185. Non-drying oils and non-drying oil fatty acids usually used for synthesizing alkyd resins can be used. Examples of non-drying oils and non-drying oil fatty acids include castor oil, palm oil, coconut oil, castor oil fatty acid, palm oil fatty acid, coconut oil fatty acid and the like. In view of easiness, etc., it is desirable to use coconut oil and / or coconut oil fatty acid.

  Examples of the monovalent acid include benzoic acid, p-tertiary butyl benzoic acid, rosin acid, hydrogenated rosin acid, and the like, which can be used alone or in combination. Examples of monohydric alcohols include octyl alcohol, decanol, lauryl alcohol, cetyl alcohol, stearyl alcohol, isostearyl alcohol, glycol esters, glycol ethers such as phenyl glycol, rosin alcohol, hydrogenated rosin alcohol, and the like. Can be used in combination. As the epoxy modification, it is also possible to form an epoxy ester with a compound having a monovalent and / or polyvalent epoxy group for modification. Acrylic modification is carried out by graft polymerization of a vinyl compound such as acrylate or styrene onto the unsaturated double bond of the fatty acid-modified polyester resin or oil-modified alkyd resin produced by the condensation reaction using a radical polymerization initiator. Is done.

  The addition amount of the alkyd resin in the metal printing ink composition of the present invention is arbitrary, but is usually in the range of 5 to 90% by mass as a nonvolatile content.

  As the hydrocarbon solvent used in the metal printing ink composition of the present invention, there can be used a solvent used for ordinary ink having a boiling range of 200 to 400 ° C., and there is no particular limitation. If the boiling point is less than 200 ° C., there may be a problem with on-press stability on a printing press. If it exceeds 400 ° C., a solvent may remain in the coating during baking and drying, which may cause a problem with physical properties. .

  As the hydrocarbon solvent, an ordinary petroleum solvent is used. Examples of petroleum solvents include AF5, 6, 7 Solvent of Shin Nippon Oil Co., Ltd., Genlex 57 of Mobil Petroleum Co., Ltd., etc., and alkyd resins in the metal printing ink composition of the present invention. In view of the solubility in water, an alkylbenzene solvent which is an aromatic hydrocarbon is preferable. Examples include Alkene L, 200P, etc., from Nippon Petrochemical Co., Ltd., which can be used alone or in combination, and can be mixed with hydrocarbons that do not contain aromatics.

  The amount of the hydrocarbon-based solvent used in the present invention is the T.I. There is no particular limitation as long as V can be adjusted in the range of 5 to 50, but it is usually in the range of 5 to 60% by mass.

  The benzoxazole derivatives used in the present invention can be used alone or in combination. Among the benzoxazole derivatives, 2,5-bis (5'-t-butylbenzooxolyl-2 ') thiophene is preferably used as a substance that is particularly likely to reduce the amount of elution with an aqueous ethanol solution. As the benzoxazole derivative, 0.1 to 5% by mass, more preferably 0.5 to 4% by mass, and particularly preferably 1 to 3% by mass in the ink.

  As the pigment used in the metal printing ink composition of the present invention, any inorganic and organic pigments can be used alone or in combination. In particular, the combined use of titanium oxide and particulate silica having a particle system of 100 nm or less and having a silanol group on the surface thereof is preferable. As a compounding quantity of a titanium oxide, 20-60 mass% in an ink, More preferably, it is 25-55 mass%, Especially preferably, what is necessary is just to mix | blend 30-45 mass%. The blending amount of the particulate silica may be 0.5 to 20% by mass, more preferably 5 to 15% by mass, and particularly preferably 6 to 12% by mass in the ink.

  As other components of the metal printing ink composition of the present invention, a pigment dispersant, a dryer, an acid catalyst, an auxiliary resin, an auxiliary solvent and the like can be added as necessary.

  As the auxiliary resin, any resin can be used singly or in combination, depending on the printability, physical properties and the like. Examples thereof include rosin-modified phenol resin, oil-free polyester resin, petroleum resin, epoxy resin, ketone resin, rosin-modified maleic acid resin, amino resin, and benzoguanamine resin.

  As an auxiliary solvent, it can be used individually or in mixture according to printability and the coating property of the overprint varnish. Examples include glycol-based, glycol ether-based, glycol ester-based, and higher alcohol-based solvents.

  The printing ink composition of the present invention can be easily printed on a metal substrate by a usual two-piece can printing method such as a resin letterpress offset method or a waterless planographic offset method. Although the ink film thickness is arbitrary, it may be performed, for example, in the range of 0.3 to 6 μm.

  As the base metal substrate used for printing the metal substrate, a two-piece can obtained by molding a metal into a cylindrical can shape or an unpainted or painted metal plate is used and there is no particular limitation. The base metal can be exemplified by aluminum, iron or the like, and may be applied with chemical conversion treatment, plating treatment, size paint, white coating, etc., or may be laminated with pet film or the like.

  As the overprint varnish to be combined with the metal printing ink composition of the present invention, any aqueous type or solvent type overprint varnish that is cured by heating can be used, and there is no particular limitation.

  The method for curing the metal printing ink composition of the present invention may be the same as that for ordinary metal ink, and is not particularly limited. For example, after only ink is baked and dried at a temperature of 100 to 200 ° C. for 5 seconds to 15 minutes, an overprint varnish may be applied, or after an overprint varnish is applied by a wet-on-wet method, 150 to You may bake and dry at 450 degreeC for about 1 second-15 minutes. The coating method of the overprint varnish combined with the metal printing ink composition of the present invention can be performed by a normal coater method. The film thickness of the overprint varnish is arbitrary, but may be in the range of 5 to 10 μm, for example.

  Hereinafter, in order to facilitate understanding of the present invention, the present invention will be specifically described by way of examples. In the examples, parts and% are based on mass.

(Resin-1: Synthesis of alkyd resin)
40.0 parts of coconut oil, 33.7 parts of phthalic anhydride, 8.5 parts of trimethylolpropane, and 17.2 parts of pentaerythritol are esterified by a conventional method to obtain a liquid having an oil length of 40, an acid value of 8 and a hydroxyl value of 148. An alkyd resin (resin-1) was obtained.

(Preparation of ink-1)
44 parts of titanium oxide CR50 (made by Ishihara Sangyo), 5 parts of particulate silica (Aerosil 200: made by Nippon Aerosil), 1 part of 2,5-bis (5′-t-butylbenzoxazolyl-2 ′) thiophene, 30 parts of Resin-1 and 20 parts of Alkene L (alkylbenzene: manufactured by Nippon Petrochemical Co., Ltd.) were kneaded with a normal three-roll mill to obtain a white ink (ink-1) for metal printing.

(Preparation of ink-2)
Usually, 45 parts of titanium oxide CR50 (made by Ishihara Sangyo), 5 parts of particulate silica (Aerosil 200: made by Nippon Aerosil), 30 parts of (Resin-1) and 20 parts of Alkene L (alkylbenzene: made by Nippon Nippon Petrochemical) Were mixed with a three-roll mill to obtain a white ink for metal printing (ink-2).

(Print test)
Using the prepared white ink for metal printing (ink-1) and (ink-2), printing on aluminum two-piece can (thickness 50-100 μm) by dry offset method so that the wet ink film is 1.5 μm Then, the printing state is observed, and those having good transferability are evaluated as ◯, and those having poor transfer are evaluated as ×. Following printing, 55 parts of water-soluble acrylic resin (Almatex WA41: made by Mitsui Chemicals), 15 parts methylated melamine resin (made by Cymel 303 Mitsui Cytex), 20 parts deionized water, ethylene glycol monoisopropyl as overprint varnish Using 10 parts of ether, the entire surface was coated with a coating amount of 50 mg / 100 cm ² , baked at 200 ° C. for 1 minute, and the whiteness was visually determined. A product having a high whiteness and having a high design is evaluated as “度”, a product having a normal whiteness is evaluated as “◯”, and a product having a low whiteness is evaluated as “X”.

(Dissolution test)
Using the prepared white ink for metal (ink-1) and (ink-2), printing on an aluminum plate (plate thickness 0.2 mm) using an RI tester so that the wet ink film is 2 μm, for overprinting Varnish 1WB306 (manufactured by DIC) is applied at 40 mg / 100 cm ² and then baked and dried at 190 ° C., 70 seconds + 200 ° C. for 90 seconds.

(Elution conditions)
The test piece prepared above (ink printing area: 322 cm ² ) was immersed in 322 ml of 10% ethanol solution so that the printing area was completely immersed, and elution was performed under the following two conditions.
・ Elution condition (1): “100 ° C., 30 minutes” + “40 ° C., 240 hours” elution condition (2): “66 ° C., 30 minutes” + “40 ° C., 240 hours” elution (2 ) Elution conditions in the US Food and Drug Administration (FDA) preparation of premarket submissions for food contact materials: preparation of pre-market notifications for food contact materials: recommended chemical tests This was carried out as a condition conforming to the d condition (assuming a can alcoholic beverage) of the selected dissolution test protocol in Appendix II. As the elution condition of (1) above, 100 ° C. was adopted as a more severe condition than (2).

(2. Analysis of eluate)
322 ml of the eluate was removed from the solvent, dried and solidified, and then eluted with 3.5 ml of acetone to obtain a test solution (concentration 100 times), which was measured by the SIM method. Since the detection limit of the benzoxazole derivative in this measurement is 100 ppb and 100-fold concentration, the detection limit of the eluate is 1 ppb. The quantitative results are shown in Table 2.

(Evaluation conditions and concentration in the eluate after conversion)
The FDA elutes with 10 ml of solvent per square inch (6.45 cm ² ) and requires a value obtained by multiplying the concentration obtained by a distribution coefficient and a consumption coefficient. In this test, elution was performed with 322 ml of solvent per 322 cm ² (that is, 10 ml per 10 cm ² ), so the solution elution concentration was 1 (ppb) × 6.45 ÷ 10 = 0. This corresponds to 645 (ppb). The distribution coefficient is “1” because the solvent is one kind of ethanol, the consumption coefficient is “0.17” when “Metal-Polymer Coated” is selected, and the required elution amount is 0.645 (ppb ) × 1 × 0.17 = 0.11 (ppb). When the area ratio is not considered, it is 0.17 ppb. Table 3 shows the concentration in the eluate after conversion.

The converted concentration was evaluated according to the following criteria described in the IV Recommended Safety Test in the FDA Pre-Marketing Notification for Food Contact Substances: Recommended Toxicity Test document.
(1) If the elution amount is less than 0.5 ppb (concentration in food (referring to 0.5 ppb is 0.0005 mg per kg of food), no further test [safety test] is required.
(2) If the elution amount is 0.5 ppb or more and less than 50 ppb, the Ames test “reversion mutation test using bacteria” and “mouse lymphoma test” are required.

  From the results in Table 3, the metal printing ink composition of the present invention is more suitable for the FDA requirement that the elution amount of the benzoxazole derivative from the dried film when printed on a metal substrate is 0.5 ppb or less. It was confirmed that the elution amount was at a very low level without the need for a test.

  When the metal printing ink composition of the present invention is printed on a metal substrate, it can obtain a highly designable coating film having sufficient whiteness compared to conventional inks, and elution of benzoxazole derivatives from the dried film The amount of (elution) is also an extremely low level of elution, and the possibility of development for can outer surface use is obtained.

Claims (8)

A metal printing ink composition comprising a pigment, an alkyd resin, a hydrocarbon solvent, and a benzoxazole derivative represented by the general formula (1).

(R, R1, and R2 are arbitrary organic compounds.) The metal printing ink composition according to claim 1, wherein the alkyd resin is an alkyd resin having an oil length in the range of 20 to 60 and a hydroxyl value of 50 to 200. The metal printing ink composition according to claim 1 or 2, wherein the oil and / or fatty acid used in the alkyd resin is coconut oil and / or coconut oil fatty acid. The metal printing ink composition according to any one of claims 1 to 3, wherein the hydrocarbon-based solvent includes an aromatic hydrocarbon. The metal printing ink composition according to any one of claims 1 to 4, wherein the benzoxazole derivative is 2,5-bis (5'-t-butylbenzooxolyl-2 ') thiophene. The metal printing ink composition according to any one of claims 1 to 5, wherein the pigment includes titanium oxide and particulate silica having an average particle system of 100 nm or less having a silanol group on the surface. The metal printing ink composition according to claim 1, which is used for coating an outer surface of an alcoholic beverage can. A metal substrate, wherein the metal printing ink composition according to any one of claims 1 to 7 is printed on a metal substrate, and then a thermosetting overprint varnish is applied and heat cured. Material coating method.