JP4897733B2 - Seamless can printing ink composition - Google Patents

Description

  The present invention relates to a seamless can printing ink composition, and has a printing property such as excellent transferability and on-machine stability and coating stability, and a seamless can printing ink composition that gives good film properties, and an ink thereof. The present invention relates to a method for coating a used seamless can.

  Seamless cans are widely used as packaging containers for fruit juice drinks, soft drinks, carbonated drinks, alcoholic drinks such as beer, and foods. The outer peripheral surface of the seamless can is printed and painted on a cylindrical metal can for the purpose of enhancing the product value and preventing corrosion.

  In addition, the surface of the seamless can may be printed after being coated with a silver coat or white coat for the purpose of decorating and wet coated with an overcoat varnish. Therefore, the ink used for seamless cans is required to adhere to various base materials.

  By the way, the conventional seamless can uses a wax when punching a metal material such as an aluminum plate or an iron plate into a cup shape and ironing it into a cylindrical shape. For this reason, a washing step is required after molding, and a large amount of water is used.

  In recent years, seamless cans using polyester-coated steel sheets in which polyester is laminated to iron plates or aluminum plates have been developed as environmentally friendly can containers that do not require this cleaning process. Has been developed.

  However, especially in printing systems that use water-based overprint varnishes for seamless cans made of polyester-coated steel sheets, conventional metal printing inks containing fatty acid-modified polyesters have both good printability and good film properties. It has become difficult.

  That is, in a seamless can printing coating system using a polyester-coated steel sheet as a metal substrate, a phenomenon occurs in which ink agglomerates and density unevenness occurs in a process of wet-coating and baking the aqueous overprint varnish after printing.

  For example, as a metal printing ink having suitability for a water-based overprint varnish, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent as examples of obtaining water-based varnish suitability by a diluent component Reference 5 and Patent Document 6 are cited.

  However, these use a highly hydrophilic diluent component to achieve wet suitability with an aqueous overprint varnish. However, inks using these diluent solvents generate a large amount of mist during printing, and can be used in printed paint cans. The work environment is deteriorated by causing dirt.

  Examples of obtaining the suitability for water-based varnish by the resin component include, for example, Patent Document 7 and Patent Document 8.

  In Patent Document 7, a monohydric alcohol having 6 to 26 carbon atoms and a polyvalent carboxylic acid anhydride are first reacted, and then further reacted with the polyhydric alcohol to leave a large amount of hydroxyl groups, thereby printing on an aqueous overprint varnish. Appropriate and improve misting.

  In Patent Document 8, monovalent branched saturated carboxylic acid, polyhydric alcohol and polyhydric carboxylic acid are used, leaving a large amount of hydroxyl groups to give printing suitability for aqueous overprint varnish and improving misting. . In these methods, the wettability with respect to the aqueous overprint varnish is improved, but the dispersion state of the pigment in the ink cannot be sufficiently stabilized, and aggregation occurs depending on the use conditions.

JP-A 62-295974 JP-A-62-295975 JP-A-62-295976 JP-A 64-060670 Japanese Patent Laid-Open No. 03-273068 Japanese Patent Laid-Open No. 04-106166 JP 02-127484 A Japanese Patent Laid-Open No. 02-127485

  In the printing ink composition mainly composed of a pigment, a resin, and a solvent, the polybasic acid-added fatty acid-modified polyester obtained by adding a polybasic acid intramolecular anhydride to the terminal of the fatty acid-modified polyester, It has been found that the terminal carboxyl group acts as an anchor agent for the pigment, improves the pigment dispersion stability in the ink, and at the same time improves the wettability with the base and improves the adhesion to the base.

  The present invention is a seamless can printing coating system using a metal substrate such as a polyester-coated steel sheet, and has excellent printability such as excellent transferability and on-machine stability and excellent suitability for an overprint varnish wet coat, It is an object of the present invention to provide a seamless can printing ink composition that gives good film properties and a method for coating a seamless can.

  That is, the present invention is a polybasic acid addition having a fatty acid modification amount of 35 to 65% by mass, a hydroxyl value of 60 to 200 mgKOH / g and an acid value of 10 to 60 mgKOH / g, and a styrene equivalent weight average molecular weight of 3000 to 30000. The present invention relates to a seamless can printing ink composition containing a fatty acid-modified polyester (A).

  The polybasic acid addition fatty acid modified polyester (A) is a polybasic acid addition fatty acid modification obtained by adding an intramolecular acid anhydride of a polybasic acid to a fatty acid modified polyester (B) having an acid value of less than 10 mgKOH / g. Polyester is preferable because it works as an anchoring agent for the pigment and the dispersion stability of the pigment is good.

  The polybasic acid-added fatty acid-modified polyester (A) is obtained by reacting a fatty acid-modified polyester (B) having an acid value of less than 10 mgKOH / g with an intramolecular acid anhydride of a polybasic acid at 100 ° C to 200 ° C. Polybasic acid-added fatty acid-modified polyesters are preferred because the target acid value can be controlled without substantially increasing the molecular weight of the resin.

  The ink composition of the present invention usually contains a pigment component and a solvent component.

  Furthermore, the present invention provides a can body by punching a metal base material, a printing layer is provided on the surface of the can body by the seamless can printing ink composition of the present invention, and a thermosetting varnish for overprinting on the printing layer. It is related also to the coating method of the seamless can which apply | coats and then heat-hardens.

  A preferred example of the metal substrate is a polyester-coated steel sheet.

  According to the present invention, in a printing coating system for seamless cans, a printing ink composition that can suppress aggregation of ink even when using an aqueous overprint varnish, and can provide stable wet coat suitability and good film properties, Can provide a method for coating a metal substrate with an ink composition.

  Polybasic acid addition fatty acid modified polyester (A) used for this invention can be manufactured, for example with the following method.

  First, a fatty acid-modified polyester (B) using a fatty acid or vegetable oil as a raw material is synthesized using a known fatty acid method or transesterification method. By adding an intramolecular acid anhydride of a polybasic acid to the hydroxyl terminal of the raw material fatty acid-modified polyester (B), a carboxyl group is introduced to the terminal of the fatty acid-modified polyester, and the polybasic acid-added fatty acid-modified polyester (A) is obtained. To manufacture.

  Next, the raw material fatty acid-modified polyester (B) and the polybasic acid addition fatty acid-modified polyester (A) will be specifically described.

  The raw material fatty acid-modified polyester (B) can be produced, for example, by reacting a polyhydric alcohol, a polybasic acid and a fatty acid. It can also be produced by transesterifying a fatty acid ester with a polyester obtained by reacting a polyhydric alcohol and a polybasic acid.

  Examples of the polyhydric alcohol include dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,6-hexanediol, bisphenol A, and hydrogenated bisphenol A; trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane. Tetrahydric or higher alcohols such as pentaerythritol and dipentaerythritol can be used.

  Examples of the polybasic acid used in the production of the raw material fatty acid-modified polyester (B) include phthalic anhydride, isophthalic acid, terephthalic acid, succinic anhydride, adipic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic anhydride and the like. Dibasic acids of the following: Tribasic acids such as trimellitic anhydride and methylcyclohexenticarboxylic anhydride can be used.

  Examples of the modifying fatty acid include decanoic acid, lauric acid, myristic acid, octanoic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, linolenic acid, and eleostearic acid. Synthetic fatty acids; vegetable oils such as soybean oil, castor oil, coconut oil, linseed oil, safflower oil, dehydrated castor oil, tall oil, rice bran oil and the like. These fatty acids may be used alone or in combination of two or more. Moreover, monobasic acids other than these fatty acids, for example, benzoic acid, pt-butylbenzoic acid, abietic acid and the like can be used in combination.

  The fatty acid is added so that the amount of fatty acid modification in the polybasic acid-added fatty acid-modified polyester (A) is 35 to 65% by mass, preferably 40 to 60% by mass.

  When the amount of fatty acid modification is less than 35% by mass, the transferability and on-machine stability of the ink composition obtained are lowered. If it exceeds 65% by mass, mechanical properties such as ink film hardness are lowered, so that it is necessary to add other additives such as a curing agent, particularly an amino resin-based curing agent.

  The raw material fatty acid-modified polyester (B) is blended so that the total hydroxyl equivalent of the polyhydric alcohol is greater than the total acid equivalent (total carboxyl group equivalent) of the monobasic acid and polybasic acid containing the above fatty acid. Perform the chemical reaction.

  The amount of the polyhydric alcohol, polybasic acid and fatty acid is adjusted so that the obtained raw material fatty acid-modified polyester (B) has a hydroxyl value of 70 to 250 mgKOH / g and a styrene equivalent weight average molecular weight of 3000 to 30000.

  When the hydroxyl value of the raw material fatty acid-modified polyester (B) is larger than 250 mgKOH / g, the polybasic acid-added fatty acid-modified polyester (A) has too many hydroxyl groups, so that the adhesiveness to the polyester-coated steel sheet is deteriorated, whereas 70 mgKOH / If it is less than g, the wettability with the aqueous overprint varnish becomes insufficient, and when the aqueous overprint varnish is wet coated, aggregation occurs in the printing ink.

  The weight average molecular weight in terms of styrene is preferably 3000 to 30000, more preferably 6000 to 16000. When the molecular weight is too small, the cohesive force of the target polybasic acid-added fatty acid-modified polyester (A) is too small and the strength of the ink film is insufficient. On the other hand, when the molecular weight is too large, the viscosity of the polybasic acid-added fatty acid-modified polyester (A) is too high, and the ink cannot be prepared in a predetermined shape.

  In the reaction system, since the amount of hydroxyl group (polyhydric alcohol) is larger, the acid value of the obtained raw material fatty acid-modified polyester (B) is small and less than 10 mgKOH / g. In the case of the fatty acid-modified polyester having an acid value of less than 10 mgKOH / g, even if the hydroxyl value is 70 to 250 mgKOH / g and the styrene-converted weight average molecular weight is 3000 to 30000, the wetness with the aqueous overprint varnish is improved. The dispersion stability of the pigment is insufficient and the object of the present invention cannot be achieved.

  In addition, when the raw material fatty acid-modified polyester is produced with an excess of acid (polybasic acid and fatty acid), the acid value is increased, but the hydroxyl value is smaller than the above range, even if the polybasic acid is reacted in the next step. A polybasic acid-added fatty acid-modified polyester having a target hydroxyl value cannot be obtained.

  Furthermore, it is conceivable to control the acid value by stopping the esterification reaction halfway, but it is actually difficult to control the reaction in order to control the acid value and the hydroxyl value.

  The polybasic acid-added fatty acid-modified polyester (A) can be produced by adding an intramolecular acid anhydride of a polybasic acid to the terminal hydroxyl group of the raw material fatty acid-modified polyester (B).

  When the polybasic acid to be reacted is a polybasic acid that is not an intramolecular acid anhydride (an acid in which all carboxyl groups are free carboxyl groups), the reaction with the terminal hydroxyl group of the starting fatty acid-modified polyester (B) is not an addition reaction but dehydration. This is not preferable because the esterification reaction is accompanied by a polybasic acid that joins the terminal hydroxyl groups of the fatty acid-modified polyester (B), resulting in a rapid increase in molecular weight and difficulty in introducing a carboxyl group. On the other hand, when an intramolecular acid anhydride is used as the polybasic acid to be reacted, the reaction occurs at a lower temperature, so that the reaction with the terminal hydroxyl group of the raw fatty acid-modified polyester (B) becomes only an addition reaction, and the molecular weight is almost increased. It is preferable because a carboxyl group can be easily introduced.

  Examples of intramolecular acid anhydrides of polybasic acids include dibasic acid anhydrides such as phthalic anhydride, succinic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and maleic anhydride; trimellitic anhydride, methylcyclohextricarboxylic Tribasic acid anhydrides such as acid anhydrides can be used. By adding these intramolecular acid anhydrides, the acid value and the hydroxyl value, particularly the acid value, can be adjusted with almost no change in the weight average molecular weight. Particularly preferred intramolecular acid anhydrides of polybasic acids are trimellitic anhydride and phthalic anhydride from the viewpoint of good solubility in the resin and misting when inked.

  The reaction is preferably performed at 100 ° C to 200 ° C. When the reaction temperature is lower than 100 ° C., the solubility of the intramolecular acid anhydride of the polybasic acid in the raw fatty acid-modified polyester (B) is small, and the addition reaction with the terminal hydroxyl group of the raw fatty acid-modified polyester (B) hardly occurs. The intramolecular acid anhydride of the polybasic acid may remain as a solid.

  When the reaction temperature exceeds 200 ° C., the carboxyl group produced by the addition reaction of the intramolecular acid anhydride of the polybasic acid or the other carboxyl group contained in the trivalent or higher intramolecular acid anhydride is further converted into the starting fatty acid-modified polyester ( B) an esterification reaction with the hydroxyl group of the resulting polybasic acid-added fatty acid-modified polyester is reduced in acid value and hydroxyl value, and the desired acid value and hydroxyl value cannot be obtained, or the molecular weight is excessively increased. There is also a case of causing.

  The hydroxyl value of the polybasic acid-added fatty acid-modified polyester (A) is 60 to 200 mgKOH / g, preferably 80 to 180 mgKOH / g. When the hydroxyl value is larger than 200 mgKOH / g, the adhesion to the polyester-coated steel sheet is deteriorated due to excessive hydroxyl groups. On the other hand, when the hydroxyl value is less than 60 mgKOH / g, the wettability with the aqueous overprint varnish becomes insufficient. When the varnish is wet coated, aggregation occurs in the printing ink.

  The acid value of the polybasic acid-added fatty acid-modified polyester (A) is 10 to 60 mgKOH / g, preferably 15 to 40 mgKOH / g. When the acid value is too small, the dispersion stability of the pigment becomes insufficient. In particular, when a water-based overprint varnish is wet-coated, the pigment in the ink may cause agglomeration depending on the type. If the acid value is too high, the polarity of the resin becomes too high, so that the fluidity of the ink is lowered and the transferability is deteriorated.

  The polybasic acid-added fatty acid-modified polyester (A) has a styrene-converted weight average molecular weight of 3000 to 30000, preferably 6000 to 16000. When the molecular weight is too small, the cohesive force of the polybasic acid-added fatty acid-modified polyester (A) is too small and the strength of the ink film is insufficient. On the other hand, when the molecular weight is too large, the viscosity of the polybasic acid-added fatty acid-modified polyester (A) is too high, and the ink cannot be prepared in a predetermined shape.

  The polybasic acid addition fatty acid modified polyester (A) of the present invention can be made into a seamless can printing ink composition, for example, by mixing with a pigment component and a solvent component.

  The printing ink composition for seamless cans of the present invention comprises a polybasic acid-added fatty acid-modified polyester (A) and other components such as a pigment component and a solvent component.

  Any pigment that has been conventionally used in metal printing inks can be used as long as it has heat resistance, light resistance, and retort resistance. Examples thereof include inorganic pigments such as titanium oxide, silica and carbon black; organic pigments such as phthalocyanine blue, watching red, quinacridone, diketopyrrolopyrrole and quinophthalone.

  Although the compounding quantity of a pigment changes with kinds and purposes, it should just select normally in the range of 10-60 mass% in an ink composition.

  As the solvent, known solvents used in metal printing inks can be used. Examples thereof include aliphatic hydrocarbons having a boiling point range of about 230 ° C. to 400 ° C., aromatic hydrocarbons such as alicyclic hydrocarbons and alkylbenzenes, and higher alcohols.

  Moreover, it is also possible to use other resin normally used for metal printing ink together. Examples of the resin that can be used in combination include petroleum resin, epoxy resin, ketone resin, rosin-modified maleic acid resin, amino resin, benzoguanamine resin, oil-free polyester, and rosin phenol resin. In addition, usual additives such as a lubricant, a curing catalyst, and a dispersing agent can be added as necessary.

  The viscosity of the ink composition of the present invention can be appropriately selected by adjusting the amount of solvent in accordance with the printing method. For example, it is adjusted in the range of tack value (JIS K5701-1) 4 to 12 and flow value (JIS K5701-1) 27 to 47 for letterpress offset printing, and has a higher viscosity than ordinary ink for waterless planographic printing. It is preferable to adjust to a tack value of 6 to 15 and a flow value of 25 to 45.

  The ink composition of the present invention can be prepared by a conventional method using a roll mill, a ball mill, a bead mill or the like.

  The seamless can printing ink composition of the present invention can be used in a dry offset method using a resin relief plate, which is a normal printing method, or an offset using a waterless lithographic plate. The film thickness of the ink is arbitrary, but may be in the range of 0.5 to 6 μm.

  The present invention also provides an overprint varnish which is formed by punching a metal substrate, forming a can body, providing a printing layer on the surface of the can body with the seamless can printing ink composition of the present invention, and being thermosetting on the printing layer. It is related also to the coating method of the seamless can which apply | coats and then heat-hardens.

  The seamless can on which the ink composition of the present invention is applied is obtained by punching a metal substrate into a can shape. As the metal substrate, an aluminum plate, an iron plate, and a coated plate obtained by laminating a polyester film or the like are used. These base materials may be subjected to chemical conversion treatment, plating treatment, size painting, white coating, silver coating, or the like.

  The ink composition thus prepared can be used on the outer peripheral surface of the seamless can without limitation by a conventionally known printing method as described above.

  The present invention is particularly effective when applied to a polyester-coated substrate as a metal substrate.

  Then, without printing the printed ink layer, a thermosetting overprint varnish is applied and finally baked and cured to complete the printing of the seamless can. The baking conditions are not particularly limited, but in general, heating at a temperature of 160 to 260 ° C. for 20 seconds to 10 minutes is preferable.

  The thermosetting overprint varnish is not particularly limited and conventionally known varnishes can be used. Specifically, for example, solvent-based or aqueous polyester-melamine-based, polyester-epoxy-melamine-based, polyester-acrylic-based, Examples include melamine varnish.

  Next, the present invention will be described based on production examples, examples and comparative examples, but the present invention is not limited to these examples. In the following, “parts” and “%” are both “parts by mass” and “% by mass”.

Production Example 1 [Production of Raw Fatty Acid-Modified Polyester (B-1)]
Charge 29.0 parts of phthalic anhydride, 18.0 parts of trimethylolpropane, 18.0 parts of pentaerythritol, 42.0 parts of coconut oil fatty acid, 10.0 parts of xylol into a four-necked flask equipped with a stirrer, and a nitrogen stream The esterification reaction was carried out at a temperature of 220 to 230 ° C. while circulating xylol until the acid value reached 2 mgKOH / g. After completion of the reaction, xylol was distilled at 240 ° C. to obtain a liquid raw material fatty acid-modified polyester (B-1).

  Table 1 shows the fatty acid modification amount (%), acid value (mgKOH / g), and hydroxyl value (mgKOH / g) of this raw material fatty acid-modified polyester.

Production Examples 2 to 12 [Production of Raw Material Fatty Acid-Modified Polyesters (B-2) to (B-12)]
Raw material fatty acid-modified polyesters (B-2) to (B-12) using the intramolecular acid anhydrides, polyhydric alcohols and fatty acids shown in Table 1 under the same conditions as the production conditions of (B-1). ) Was manufactured.

  Table 1 shows the fatty acid modification amount (%), acid value (mgKOH / g) and hydroxyl value (mgKOH / g) of these raw material fatty acid-modified polyesters.

Production Example 13 [Production of Polybasic Acid-Added Fatty Acid-Modified Polyester (A-1)]
Put 95.2 parts of raw fatty acid-modified polyester (B-1) in a four-necked flask, add 4.8 parts of trimellitic anhydride at a temperature of 170 ° C. with stirring, and carry out an addition reaction for 10 minutes. A transparent liquid polybasic acid-added fatty acid-modified polyester (A-1) having an amount of 40.0%, a hydroxyl value of 172 mgKOH / g, an acid value of 27 mgKOH / g, and a weight average molecular weight of 6000 in terms of styrene was produced.

Production Example 14 [Production of Polybasic Acid-Added Fatty Acid-Modified Polyester (A-2)]
91.4 parts of raw material fatty acid-modified polyester (B-1) was put into a four-necked flask, and 8.6 parts of trimellitic anhydride was added at 170 ° C. with stirring, followed by addition reaction for 10 minutes, to modify the fatty acid. A transparent liquid polybasic acid-added fatty acid-modified polyester (A-2) having an amount of 38.4%, a hydroxyl value of 153 mgKOH / g, an acid value of 50 mgKOH / g, and a weight-average molecular weight of 6200 in terms of styrene was produced.

Production Example 15 [Production of Polybasic Acid-Added Fatty Acid-Modified Polyester (A-3)]
94.8 parts of raw material fatty acid-modified polyester (B-2) was put into a four-necked flask, 5.2 parts of trimellitic anhydride was added at 170 ° C. with stirring, and an addition reaction was carried out for 10 minutes. A transparent liquid polybasic acid-added fatty acid-modified polyester (A-3) having an amount of 55%, a hydroxyl value of 135 mgKOH / g, an acid value of 30 mgKOH / g, and a weight average molecular weight of 6000 in terms of styrene was produced.

Production Example 16 [Production of polybasic acid-added fatty acid-modified polyester (A-4)]
Put 95.2 parts of raw fatty acid-modified polyester (B-3) in a four-necked flask, add 4.8 parts of trimellitic anhydride at a temperature of 170 ° C. with stirring, and carry out an addition reaction for 10 minutes to modify the fatty acid. A transparent liquid polybasic acid-added fatty acid-modified polyester (A-4) having an amount of 45%, a hydroxyl value of 70 mgKOH / g, an acid value of 26 mgKOH / g, and a styrene-equivalent weight average molecular weight of 6500 was produced.

Production Example 17 [Production of polybasic acid-added fatty acid-modified polyester (A-5)]
95.2 parts of raw material fatty acid-modified polyester (B-4) was put into a four-necked flask, and 4.8 parts of trimellitic anhydride was added at 170 ° C. with stirring, followed by addition reaction for 10 minutes, to modify the fatty acid. A transparent liquid polybasic acid-added fatty acid-modified polyester (A-5) having an amount of 45%, a hydroxyl value of 120 mgKOH / g, an acid value of 27 mgKOH / g, and a styrene-converted weight average molecular weight of 6500 was produced.

Production Example 18 [Production of polybasic acid-added fatty acid-modified polyester (A-6)]
95.2 parts of raw fatty acid-modified polyester (B-5) was placed in a four-necked flask, and 4.8 parts of trimellitic anhydride was added at 170 ° C. with stirring, followed by addition reaction for 10 minutes to modify the fatty acid. A transparent liquid polybasic acid-added fatty acid-modified polyester (A-6) having an amount of 40%, a hydroxyl value of 142 mgKOH / g, an acid value of 28 mgKOH / g, and a weight average molecular weight of 25,000 in terms of styrene was produced.

Production Example 19 [Production of polybasic acid-added fatty acid-modified polyester (A-7)]
Raw material fatty acid-modified polyester (B-6) 95.2 parts was placed in a four-necked flask, and while stirring, 4.8 parts of trimellitic anhydride was added at a temperature of 170 ° C., and an addition reaction was carried out for 10 minutes. A transparent liquid polybasic acid-added fatty acid-modified polyester (A-7) having an amount of 40%, a hydroxyl value of 168 mgKOH / g, an acid value of 28 mgKOH / g, and a weight-average molecular weight of 6500 in terms of styrene was produced.

Production Example 20 [Production of polybasic acid-added fatty acid-modified polyester (A-8)]
Except that 6.8 parts of phthalic anhydride was added to 93.2 parts of the raw fatty acid-modified polyester (B-1), an addition reaction was carried out under the same conditions as the production conditions of (A-1), and the amount of fatty acid modification was 39.1. %, A hydroxyl value of 168 mg KOH / g, an acid value of 27 mg KOH / g, and a transparent liquid polybasic acid-added fatty acid-modified polyester (A-8) having a weight-average molecular weight of 6100 in terms of styrene was produced.

Comparative production examples 1 to 8 [Production of polybasic acid-added fatty acid-modified polyesters (A-9) to (A-16)]
Under the same conditions as the production conditions of (A-1) except that trimellitic anhydride was added to the raw material fatty acid-modified polyesters (B-1) and (B-7) to (B-12) in the proportions shown in Table 3. An addition reaction was carried out to produce transparent liquid polybasic acid addition fatty acid modified polyesters (A-9) to (A-16). Table 3 shows the fatty acid modification amount, hydroxyl value, acid value, and styrene equivalent weight average molecular weight.

Comparative production example 9
The addition reaction was carried out under the same conditions as the production conditions of (A-1) except that the reaction temperature was 80 ° C. However, even if the reaction was carried out for 2 hours, a solid unreacted substance remained and a transparent liquid ink composition The product could not be manufactured. This is probably because trimellitic anhydride did not react because it did not dissolve in the resin.

Comparative production example 10
The addition reaction was carried out under the same production conditions as in (A-1) except that the reaction temperature was 230 ° C., but the condensation reaction of the carboxyl group of trimellitic anhydride and the hydroxyl group of the starting fatty acid-modified polyester (B-1) As a result, the composition changed to a rubbery shape and a normal ink composition could not be produced.

Examples 1-8
Polybasic acid addition fatty acid modified polyesters (A-1) to (A-8) and carbon black (manufactured by Cabot Specialty Chemicals, Inc .: REGAL 400) shown in Table 2 as binder resins, and high-boiling aromatic hydrocarbons ( Nippon Oil Co., Ltd .: Alkene L) was blended in the proportions shown in Table 4, and kneaded with three rolls to prepare a printing ink composition.

Comparative Example 1
A printing ink composition was prepared in the same manner as in Example 1 except that the raw material fatty acid-modified polyester (B-1) to which no acid anhydride was added was used as the binder resin.

Comparative Examples 2-9
Printing ink as in Example 1, except that the polybasic acid-added fatty acid-modified polyesters (A-9) to (A-16) shown in Table 3 were blended with pigments and high-boiling aromatic hydrocarbons in the proportions shown in Table 5. A composition was prepared.

  About the printing ink composition prepared in these Examples 1-8 and Comparative Examples 1-9, printability (transferability, wet coat property), adhesiveness, and surface hardness were investigated by the following methods. The results are shown in Table 4 and Table 5.

(1) Printability (transferability test)
Using a high-speed printing aptitude tester (PM904PT manufactured by SMT Co., Ltd.), the printing ink composition is uniformly transferred onto a test rubber roll so that the thickness of the ink film in the wet state becomes 2 μm, and then two pieces of aluminum Transfer is performed at a printing speed of 8 m / s using a can (seamless can, wall thickness: 50 to 100 μm).

About this printed seamless can, the printing state (ink transfer state) is visually evaluated according to the following criteria.
A: The ink transfer property and the surface smoothness of the ink film are good.
B: The transferability of the ink and the surface smoothness of the ink film are slightly inferior to A, so that the color tone reproduction becomes difficult and the quality is problematic.
C: The amount of ink transferred is small, and the surface smoothness of the ink film is significantly different from A, and cannot be used as a product.

(Wet coat properties of overprint varnish)
Using a high-speed printing aptitude tester (manufactured by SMT Co., Ltd.), the printing ink composition is uniformly copied onto a test rubber roll so that the thickness of the wet ink film becomes 1.5 μm, and then a seamless silver coat can (Thickness 50-100 μm) is used for transfer at a printing speed of 8 m / s.

Immediately after the transfer, 55 parts of water-soluble acrylic resin (Almatec WA41 from Mitsui Chemicals), 15 parts of methylated melamine resin (Cymel 303 from Nippon Cytec Industries, Ltd.) as a curing agent, 20 parts of deionized water and ethylene glycol An aqueous overprint varnish consisting of 10 parts of monoisopropyl ether is applied to the entire printed surface (application amount 50 mg / 100 cm ² ) and baked at 220 ° C. for 2 minutes to produce a lithographically printed seamless can.

About this printed seamless can, the printing state (ink transfer state) is visually evaluated according to the following criteria.
A: The surface of the ink film is not different from that before wet coating the overprint varnish.
B: Compared with the surface of the ink film before wet-coating the overprint varnish, the tendency to agglomerate was confirmed visually and cannot be used as a product.
C: The surface of the ink film is remarkably different before and after the overprint varnish is wet-coated, and cannot be used as a product.

(Adhesiveness)
Evaluation is made by a cross cut test specified in JIS K5600-5-6. (surface hardness)
Gardner Cross Cut Tester Cat. No. Using 5123, the printed test piece is cross-cut by the method defined in JIS, and then the adhesion test is performed using a transparent pressure-sensitive adhesive tape having a width of 25 mm.

  Adhesion was evaluated as follows in accordance with JIS K5600-5-6.

Classification 0: The cut line is completely smooth, and there is no peeling in any lattice eye.
1: There is a small peeling in the coating film at the intersection of the cuts. It is clearly not more than 5% that the crosscut is affected.
2: Peeling along the edge of the coating film cut and / or at the intersection. The cross-cut part is clearly affected by more than 5% but not more than 15%.
3: Large or partial peeling occurs along the edges of the cut of the coating film, or various parts of the eyes are partially or completely peeled off. The cross-cut part is clearly affected by more than 15% but not more than 35%.
4: Along with the cut of the coating film, large or partial peeling has occurred, and / or several places have been partially or completely peeled off. It is clearly over 35% that they are affected at the crosscut.

(Pencil hardness)
Evaluation is based on JIS-A hardness (pencil hardness) specified in JIS K5600-5-4. The hardness of the hardest pencil that did not cause a scratch was called pencil hardness by performing a scratch test so that the core of the pencil touches the printed test piece at 45 ° C. by a method defined by JIS standards.

  From the results of Tables 4 and 5, it can be seen that the effect of the present invention in the printing system for seamless cans is obvious and is extremely useful in industry.

Claims (6)

Polybasic acid-added fatty acid-modified polyester having a fatty acid modification amount of 35 to 65% by mass, a hydroxyl value of 60 to 200 mgKOH / g and an acid value of 10 to 60 mgKOH / g and a styrene-converted weight average molecular weight of 3000 to 30000 ) Seamless can printing ink composition. Polybasic acid addition fatty acid modified polyester (A) obtained by adding an intramolecular acid anhydride of a polybasic acid to fatty acid modified polyester (B) having an acid value of less than 10 mgKOH / g The seamless can printing ink composition according to claim 1. A polybasic acid-added fatty acid-modified polyester (A) was obtained by reacting a fatty acid-modified polyester (B) having an acid value of less than 10 mgKOH / g with an intramolecular acid anhydride of a polybasic acid at 100 ° C to 200 ° C. The seamless can printing ink composition according to claim 2, which is a base acid-added fatty acid-modified polyester. The seamless can printing ink composition according to any one of claims 1 to 3, further comprising a pigment component and a solvent component. A can body is formed by punching a metal substrate, and a printing layer is provided on the surface of the can body with the seamless can printing ink composition according to any one of claims 1 to 4, and a thermosetting overcoat is formed on the printing layer. A seamless can coating method in which a varnish for printing is applied and then heat-cured. The method for coating a seamless can according to claim 5, wherein the metal substrate is a polyester-coated steel sheet.