Gold paste for aqueous ink and aqueous gold ink formed by dispersing the paste

Abstract

To provide a golden paste for aqueous ink which enables manufacture of aqueous golden ink that exhibits good dispersibility to a vehicle for acrylic aqueous ink, is not gelled over a long period of time of 1 months or longer and is excellent in storage stability, provides a printed matter printed using the aqueous golden ink showing excellent metallic glossiness, is suitably usable for high precision printing, and enables manufacture of aqueous golden ink having high safety and low environmental load.SOLUTION: A golden paste for aqueous ink contains, with respect to 100 pts.wt. of flaky yellow copper powder coated with a fatty acid, 0.5 pt.wt. or more and 10 pts.wt. or less of a non-ionic surface active agent having an HLB value of 13 to 17, 15 pts.wt. or more and 45 pts.wt. or less of glycols, and 3 pts.wt. or more and 10 pts.wt. of less of aqueous wax emulsion aqueous solution.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a gold paste for aqueous ink. Specifically, it is a gold paste that can be dispersed in a vehicle for aqueous ink to produce a gold ink, which can be well dispersed in a vehicle for acrylic aqueous ink without gelling, and can produce an aqueous gold ink with excellent storage stability. When printed using the aqueous gold ink, a printed matter with excellent metallic luster is obtained, and it can also be preferably used for high-definition printing such as gravure printing and flexographic printing, and relates to a gold paste that can produce an aqueous gold ink with a low environmental load.

Background Art

[0002] Generally, flaky brass powder is used as a metal pigment in printing gold ink for gold printing.

[0003] Flaky brass powder is mainly an alloy powder of copper and zinc, and is generally sometimes called bronze powder or gold powder.

[0004] Since the surface of flaky brass powder is coated with fatty acid, most of the gold inks in which flaky brass powder is dispersed are organic solvent-based gold inks using an organic solvent-based vehicle for ink.

[0005] However, since organic solvents have problems such as air pollution, in recent years, there has been an increasing demand for aqueous gold inks using a vehicle for aqueous ink. However, flaky brass powder coated with fatty acid is difficult to disperse in a vehicle for aqueous ink and has poor wettability. Therefore, there is a problem that an aqueous gold ink in which flaky brass powder is dispersed cannot obtain a gold printed coating film with excellent metallic luster like an organic solvent-based gold ink.

[0006] Flaky brass powder particles with improved dispersibility in a vehicle for aqueous ink have been developed by coating the surface of flaky brass powder particles coated with fatty acid with a surfactant. However, in the prior art, uneven treatment is likely to occur, and there is a problem that the surface of flaky brass powder particles is not sufficiently and firmly coated with the surfactant.

[0007] Flaky brass powder whose surface is not sufficiently coated with a surfactant may gel when dispersed in a vehicle for acrylic-based aqueous ink or the like.

[0008] In addition, if flaky brass powder whose surface is not sufficiently coated with a surfactant is stored for a long period of one month or more in a state of being dispersed in a vehicle for acrylic-based aqueous ink or the like, the vehicle and the flaky brass powder gradually react, and after separating into two layers of a flaky brass powder layer and a vehicle layer, there is a problem that the flaky brass powder particles aggregate with each other.

[0009] Even if it is separated into two layers of a flaky brass powder layer and a vehicle layer, it is possible to remix it as long as it is not strongly aggregated. However, when printing using the mixed gold ink, the metallic luster of the printed coating film may deteriorate.

[0010] Therefore, there is a need to develop a gold paste that can be dispersed in a vehicle for acrylic-based aqueous ink without gelling to produce an aqueous gold ink. The produced gold ink is difficult to separate into two layers of a flaky brass powder layer and a vehicle layer and has storage stability. Also, it can be mixed even after separation. Moreover, it is desired to develop a gold paste that can produce an aqueous gold ink that exhibits excellent metallic luster equivalent to that of an organic solvent-based gold ink, not only immediately after ink production but also after long-term storage.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0012] Patent Document 1 describes an aqueous gold ink that does not gel even after several months of storage by surface-treating the surface of flaky brass powder particles with a surfactant and dispersing them in an aqueous polyurethane resin.

[0013] Patent Document 2 describes flaky brass powder for aqueous ink in which the surface of flaky brass powder treated with a fatty acid is coated with a nonionic surfactant.

[0014] The flaky brass powder for aqueous ink described in Patent Document 2 exhibits a metallic luster equivalent to that of an organic solvent-based gold ink, but has a problem that it gels during long-term storage and becomes unusable.

[0015] Patent Document 3 describes flaky brass powder for aqueous printing ink in which the surface of flaky brass powder particles treated with a fatty acid is coated with a nonionic surfactant having an HLB value of 13 to 17 and a hydrophobic group composed of fatty acids such as monostearic acid and isostearic acid.

[0016] However, the flaky brass powder for aqueous ink described in Patent Document 3 contains alcohol when coated with a surfactant, and has poor stability over time with respect to a specific acrylic-based aqueous ink vehicle. There are problems such as gelation on the surface, formation of verdigris, and generation of bubbles immediately after ink preparation, and then the whole gels and becomes unusable.

[0017] The present invention aims to solve the above problems as a technical challenge. As a result of numerous trial productions and experiments, for 100 parts by weight of flaky brass powder whose surface is coated with fatty acid, 0.5 parts by weight or more and 10 parts by weight or less of a nonionic surfactant with an HLB value of 13 to 17, 15 parts by weight or more and 45 parts by weight or less of glycols, and 3 parts by weight or more and 10 parts by weight or less of an aqueous wax emulsion aqueous solution are contained. If it is a gold paste for aqueous ink, even if it is a vehicle for acrylic aqueous ink, it can be stored stably for more than one month without gelling, and can be mixed even after being separated into two layers of a flaky brass powder layer and a vehicle layer. Moreover, not only immediately after the ink is produced, but also after long-term storage, the printed coating film of the aqueous gold ink exhibits an excellent golden color with metallic luster, and the above technical challenge has been achieved.

Means for Solving the Problems

[0018] The above technical challenge can be solved by the present invention as follows.

[0019] The present invention is a gold paste for aqueous ink, and the gold paste contains 0.5 parts by weight or more and 10 parts by weight or less of a nonionic surfactant with an HLB value of 13 to 17, 15 parts by weight or more and 45 parts by weight or less of glycols, and 3 parts by weight or more and 10 parts by weight or less of an aqueous wax emulsion aqueous solution with respect to 100 parts by weight of flaky brass powder whose surface is coated with fatty acid.

[0020] Moreover, the present invention is the above gold paste for aqueous ink, wherein the average particle diameter of the flaky brass powder particles is 2 μm or more and 20 μm or less.

[0021] Moreover, the present invention is an aqueous gold ink obtained by dispersing the above gold paste in a vehicle for aqueous ink.

[0022] Moreover, the present invention is the above aqueous gold ink, wherein the vehicle for aqueous ink is a vehicle for acrylic aqueous ink.

[0023] The present invention also relates to a method for producing the above-described gold paste for aqueous ink.

Effects of the Invention

[0024] Since the present invention contains 0.5 to 10 parts by weight of a nonionic surfactant having an HLB value of 13 to 17 and 15 to 45 parts by weight of glycols with respect to 100 parts by weight of flaky brass powder coated with fatty acid, unevenness in the treatment of the surface of the flaky brass powder particles is less likely to occur, and the surface of the flaky brass powder particles can be uniformly and firmly coated with a nonionic surfactant. Therefore, even in the case of a vehicle for acrylic aqueous ink, a gold paste can be produced that can form an aqueous gold ink that does not gel immediately after mixing or during storage.

[0025] In addition, since the present invention contains 3 to 10 parts by weight of an aqueous wax emulsion aqueous solution with respect to 100 parts by weight of flaky brass powder, it is a gold paste that can produce an aqueous gold ink with excellent storage stability and can be mixed without gelling over a long period of time.

[0026] Further, if the average particle diameter of the flaky brass powder particles is 2 μm to 20 μm, an aqueous gold ink exhibiting more excellent metallic luster can be produced, and a gold ink suitable for high-definition printing inks such as gravure printing and flexographic printing can be produced.

Embodiments for Carrying Out the Invention

[0027] The present invention is a gold paste for aqueous ink containing flaky brass powder coated with fatty acid.

[0028] The flaky brass powder is an alloy of copper and zinc produced by a mechanical pulverization method. In the present invention, an alloy of 75% copper and 25% zinc that exhibits a gold color close to gold, or an alloy of 90% copper and 10% zinc that exhibits a gold color with a slightly stronger red tone is suitable, but is not limited thereto.

[0029] The average particle diameter of the flaky brass powder particles is preferably 2 μm to 20 μm.

[0030] If the average particle diameter is less than 2 μm, a printing coating film with excellent metallic luster cannot be obtained because the flaky brass powder does not uniformly float on the printing coating film surface. If it is greater than 20 μm, when used in high-definition printing such as gravure printing or flexographic printing, it is difficult to transfer to the printing plate in the ink, resulting in poor printability.

[0031] The gold paste in the present invention contains a nonionic surfactant with an HLB (Hydrophile-Lipophile-Balance) value of 13 to 17.

[0032] The HLB value is a numerical value representing the balance between the hydrophilicity and hydrophobicity strengths in the surfactant molecule, and the larger the numerical value, the higher the hydrophilicity.

[0033] As the surfactant used in the gold paste, a nonionic surfactant that does not ionize when dissolved in water is preferred.

[0034] This is because anionic surfactants and cationic surfactants that ionize into ions easily cause the flaky brass powder to discolor, resulting in a printing coating film with poor metallic luster.

[0035] For nonionic surfactants with an HLB value of less than 13, it is difficult to disperse in a printing ink vehicle that is nearly completely aqueous, and it is difficult to transfer to the printing plate, resulting in a printing coating film with poor hiding power.

[0036] Also, when the HLB value exceeds 17, there are more solid nonionic surfactants, and it is difficult to disperse the solid surfactants in the ink.

[0037] There is also a nonionic surfactant adjusted to an aqueous solution type, but the aqueous solution type does not mix well with the fatty acid film on the surface of the flaky brass powder particles, and there is a possibility of forming a printing coating film that does not exhibit excellent metallic luster.

[0038] If the HLB value is in the range of 13 to 17, the nonionic surfactant is not particularly limited.

[0039] Examples of the nonionic surfactant in the present invention include polyoxyalkylene alkyl ether, polyoxyethylene sorbitan monolaurate, and polyoxyethylene coconut oil fatty acid sorbitan.

[0040] The content of the nonionic surfactant is preferably 0.5 to 10 parts by weight, more preferably 3 to 7 parts by weight, based on 100 parts by weight of the flaky brass powder.

[0041] If it is less than 0.5 part by weight, it becomes difficult to uniformly coat the flaky brass powder, resulting in a decrease in dispersibility in the vehicle for aqueous ink. Also, if it is more than 10 parts by weight, the foaming property becomes large, leading to a decrease in coating film performance and a possible decrease in printing suitability such as drying property.

[0042] The gold paste in the present invention preferably contains 15 to 45 parts by weight, more preferably 25 to 35 parts by weight, of glycols based on 100 parts by weight of the flaky brass powder.

[0043] In the present invention, it is preferable to mix the flaky brass powder in a solution in which glycols, a nonionic surfactant, and an aqueous wax emulsion are mixed and stir to coat the surface of the flaky brass powder particles with the nonionic surfactant. This is because if the amount of glycols is less than 15 parts by weight, the nonionic surfactant may not uniformly and firmly coat the surface of the flaky brass powder particles.

[0044] Also, an aqueous gold ink containing a gold paste with more than 45 parts by weight of glycols has a reduced drying property.

[0045] The glycols are not particularly limited, but low molecular weight glycols such as ethylene glycol, propylene glycol, and diethylene glycol are preferred.

[0046] This is because high molecular weight glycols such as polyethylene glycol may reduce the metallic luster and storage stability of the printed coating film of the aqueous gold ink.

[0047] From the viewpoints of safety and environmental impact, propylene glycol is preferred.

[0048] The gold paste for aqueous ink in the present invention contains an aqueous wax emulsion.

[0049] The aqueous wax emulsion is a wax emulsion of a copolymer and an aqueous solvent, and it causes steric hindrance in the aqueous gold ink, so the dispersibility of the flaky brass powder is improved and sedimentation can be suppressed.

[0050] The aqueous wax emulsion is not particularly limited, and examples thereof include an emulsion of an ethylene vinyl acetate copolymer and AQUATIX (registered trademark) 8421 (manufactured by BYK).

[0051] The content of the aqueous wax emulsion in the present invention is preferably 3 to 10 parts by weight, more preferably 5 to 8 parts by weight, based on 100 parts by weight of the flaky brass powder.

[0052] If it is less than 3 parts by weight, sedimentation of the flaky brass powder may not be sufficiently suppressed. If it exceeds 10 parts by weight, the property of the flaky brass powder floating on the printed coating film surface may be inhibited, and the metallic luster of the printed matter may be reduced.

[0053] Since the present invention is a gold paste in which the surface of the flaky brass powder particles is uniformly and firmly coated with a nonionic surfactant, it is a gold paste for aqueous ink that can be well dispersed in the vehicle for aqueous ink and mixed without gelling.

[0054] The vehicle for aqueous ink for dispersing the gold paste in the present invention is not particularly limited.

[0055] Examples of the vehicle for aqueous ink include a vehicle for urethane-based aqueous ink and a vehicle for acrylic-based aqueous ink.

[0056] In addition, since the gold paste in the present invention has excellent dispersibility, it does not gel even when dispersed in a vehicle for acrylic-based aqueous ink, and the flaky brass powder layer and the vehicle layer can be stored in a state where they can be mixed for a long period of one month or more.

[0057] The gold paste for aqueous ink in the present invention can be mixed with a vehicle for aqueous ink at a desired weight ratio, but the ratio of gold paste:vehicle is preferably 3:7 to 5:5.

Examples

[0058] Examples of the present invention are shown, but the present invention is not limited thereto.

[0059] (Example 1) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 7 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan with an HLB value of 16 (manufactured by Nippon Emulsion Co., Ltd.) was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for gold paste.

[0060] To the obtained solution, 100 parts by weight of flaky brass powder (75% by weight of copper, 25% by weight of zinc) with an average particle diameter of 9 μm was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0061] 40 parts by weight of the obtained gold paste was mixed with 60 parts by weight of a vehicle for acrylic-based aqueous ink, stirred to prepare an aqueous gold ink, and then gravure printing was performed. As a result of visual observation, it was confirmed that a gold printed matter having a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0062] When the prepared aqueous gold ink was stored at 25°C for 2 months, it did not gel and could be mixed even after separation. Also, when gravure printing was performed with the gold ink after 2 months, it was confirmed that a gold printed matter having a good metallic luster close to that immediately after ink preparation was obtained.

[0063] (Example 2) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 7 parts by weight of polyoxyethylene sorbitan monolaurate (manufactured by Kao Corporation) with an HLB value of 17 was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0064] To the obtained solution, 100 parts by weight of flaky brass powder (75% by weight of copper, 25% by weight of zinc) with an average particle diameter of 9 μm was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0065] 40 parts by weight of the obtained gold paste was mixed and stirred with 60 parts by weight of a vehicle for acrylic aqueous ink to prepare an aqueous gold ink. Then, gravure printing was performed and observed visually. As a result, it was confirmed that a gold printed matter exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0066] When the prepared gold ink was stored at 25°C for 2 months, it did not gel, could be remixed after separation, and when gravure printing was performed with the gold ink after 2 months, it was confirmed that a gold printed matter exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0067] (Example 3) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 7 parts by weight of polyoxyalkylene alkyl ether (manufactured by Sanyo Chemical Industries, Ltd.) with an HLB value of 13 was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0068] To the obtained solution, 100 parts by weight of flaky brass powder (75% by weight of copper, 25% by weight of zinc) with an average particle diameter of 9 μm was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0069] 60 parts by weight of a vehicle for an acrylic-based aqueous ink and 40 parts by weight of a gold paste obtained were mixed and stirred to prepare an aqueous gold ink. After performing gravure printing and observing visually, it was confirmed that a gold printed matter exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0070] When the prepared gold ink was stored at 25°C for 2 months, gelation did not occur, mixing was possible even after separation, and when gravure printing was performed with the gold ink after 2 months, it was confirmed that a gold printed matter exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0071] (Example 4) To 15 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 7 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan with an HLB value of 16 (manufactured by Nippon Emulsion Co., Ltd.) was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX (registered trademark) 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0072] To the obtained solution, 100 parts by weight of flaky brass powder with an average particle diameter of 9 μm (75% by weight of copper, 25% by weight of zinc) was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0073] 60 parts by weight of a vehicle for an acrylic-based aqueous ink and 40 parts by weight of a gold paste obtained were mixed and stirred to prepare an aqueous gold ink. After performing gravure printing and observing visually, it was confirmed that a gold printed matter exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0074] When the prepared gold ink was stored at 25°C for 2 months, gelation did not occur, mixing was possible even after separation, and when gravure printing was performed with the gold ink after 2 months, it was confirmed that a gold printed matter exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0075] (Example 5) To 45 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 7 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan with an HLB value of 16 (manufactured by Nippon Emulsion Co., Ltd.) was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0076] To the obtained solution, 100 parts by weight of flaky brass powder with an average particle diameter of 9 μm (75% by weight of copper, 25% by weight of zinc) was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0077] 40 parts by weight of the obtained gold paste was mixed and stirred with 60 parts by weight of a vehicle for acrylic-based aqueous ink to prepare an aqueous gold ink. After performing gravure printing and observing visually, it was confirmed that a printed matter with a gold color exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0078] When the prepared gold ink was stored at 25°C for 2 months, it did not gel, could be remixed after separation, and when gravure printing was performed with the gold ink after 2 months, it was confirmed that a printed matter with a gold color exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0079] (Example 6) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 7 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan with an HLB value of 16 (manufactured by Nippon Emulsion Co., Ltd.) was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0080] To the obtained solution, 100 parts by weight of flaky brass powder with an average particle diameter of 6 μm (90% by weight of copper, 10% by weight of zinc) was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0081] 60 parts by weight of a vehicle for acrylic-based aqueous ink was mixed with 40 parts by weight of a gold paste obtained, and stirred to prepare an aqueous gold ink. After performing gravure printing and observing visually, it was confirmed that a gold printed matter exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0082] When the prepared gold ink was stored at 25°C for 2 months, it did not gel, and could be remixed even after separation. Also, when gravure printing was performed with the gold ink after 2 months, it was confirmed that a gold printed matter exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0083] (Example 7) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 10 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan with an HLB value of 16 (manufactured by Nippon Emulsion Co., Ltd.) was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for gold paste.

[0084] To the obtained solution, 100 parts by weight of flaky brass powder with an average particle diameter of 2 μm (90% by weight copper, 10% by weight zinc) was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0085] 60 parts by weight of a vehicle for acrylic-based aqueous ink was mixed with 40 parts by weight of a gold paste obtained, and stirred to prepare an aqueous gold ink. After performing gravure printing and observing visually, it was confirmed that a gold printed matter exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0086] When the prepared gold ink was stored at 25°C for 2 months, it did not gel, and could be remixed even after separation. Also, when gravure printing was performed with the gold ink after 2 months, it was confirmed that a gold printed matter exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0087] (Example 8) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 3 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan with an HLB value of 16 (manufactured by Nippon Emulsion Co., Ltd.) was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0088] To the obtained solution, 100 parts by weight of flaky brass powder with an average particle diameter of 12 μm (90% by weight copper, 10% by weight zinc) was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0089] 40 parts by weight of the obtained gold paste was mixed and stirred with 60 parts by weight of a vehicle for acrylic-based aqueous ink to prepare an aqueous gold ink. Then, gravure printing was performed and, as a result of visual observation, it was confirmed that a gold printed matter exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0090] When the prepared gold ink was stored at 25°C for 2 months, it did not gel, could be remixed after separation, and when gravure printing was performed with the gold ink after 2 months, it was confirmed that a gold printed matter exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0091] (Example 9) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 0.5 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan with an HLB value of 16 (manufactured by Nippon Emulsion Co., Ltd.) was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0092] To the obtained solution, 100 parts by weight of flaky brass powder with an average particle diameter of 20 μm (90% by weight copper, 10% by weight zinc) was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0093] 40 parts by weight of a gold paste obtained in 60 parts by weight of a vehicle for an acrylic-based aqueous ink were mixed and stirred to prepare an aqueous gold ink. After performing gravure printing and observing visually, it was confirmed that a printed matter having a gold color exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0094] When the prepared gold ink was stored at 25°C for 2 months, it did not gel, and it was possible to mix it even after separation. Also, when gravure printing was performed with the gold ink after 2 months, it was confirmed that a printed matter having a gold color exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0095] (Example 10) After adding and mixing 7 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan (manufactured by Nippon Emulsion Co., Ltd.) having an HLB value of 16 to 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 3 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX (registered trademark) 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0096] 100 parts by weight of flaky brass powder having an average particle diameter of 9 μm (75% by weight of copper, 25% by weight of zinc) was added to the obtained solution and mixed with a mixer for 10 minutes to prepare a gold paste.

[0097] 40 parts by weight of a gold paste obtained in 60 parts by weight of a vehicle for an acrylic-based aqueous ink were mixed and stirred to prepare an aqueous gold ink. After performing gravure printing and observing visually, it was confirmed that a printed matter having a gold color exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0098] When the prepared gold ink was stored at 25°C for 2 months, it did not gel, and it was possible to mix it even after separation. Also, when gravure printing was performed with the gold ink after 2 months, it was confirmed that a printed matter having a gold color exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0099] (Example 11) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 7 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan with an HLB value of 16 (manufactured by Nippon Emulsion Co., Ltd.) was added and mixed. Then, 10 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0100] To the obtained solution, 100 parts by weight of flaky brass powder with an average particle size of 9 μm (75% by weight of copper, 25% by weight of zinc) was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0101] 40 parts by weight of the obtained gold paste was mixed and stirred with 60 parts by weight of a vehicle for acrylic-based aqueous ink to prepare an aqueous gold ink. Then, gravure printing was performed and the result was observed visually. It was confirmed that a gold printed matter exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained.

[0102] When the prepared gold ink was stored at 25°C for 2 months, it did not gel, could be remixed after separation, and when gravure printing was performed with the gold ink after 2 months, it was confirmed that a gold printed matter exhibiting a good metallic luster close to that immediately after ink preparation was obtained.

[0103] (Comparative Example 1) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 7 parts by weight of polyoxyethylene glyceryl isostearate with an HLB value of 12 (manufactured by Nippon Emulsion Co., Ltd.) was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0104] To the obtained solution, 100 parts by weight of flaky brass powder with an average particle size of 9 μm (75% by weight of copper, 25% by weight of zinc) was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0105] 60 parts by weight of an acrylic-based aqueous ink vehicle was mixed with 40 parts by weight of a gold paste obtained, and stirred to prepare an aqueous gold ink. After performing gravure printing and observing visually, a printed matter with a metallic luster equivalent to that of an organic solvent-based gold ink was obtained. However, when the prepared gold ink was stored at 25°C for 2 months, the surface of the ink was completely cured and could not be mixed, and it became impossible to use for printing.

[0106] (Comparative Example 2) To 30 parts by weight of propylene glycol (manufactured by Kanto Chemical Co., Inc.), 7 parts by weight of a polyoxyethylene alkyl ether with an HLB value of 18 (manufactured by Kao Corporation) was added and mixed. Then, 7 parts by weight of an aqueous solution of an aqueous wax emulsion (trade name: AQUATIX® 8421, manufactured by BYK) was added and thoroughly mixed with a mixer to obtain a solution for a gold paste.

[0107] To the obtained solution, 100 parts by weight of flaky brass powder with an average particle size of 9 μm (75% by weight of copper, 25% by weight of zinc) was added and mixed with a mixer for 10 minutes to prepare a gold paste.

[0108] 60 parts by weight of an acrylic-based aqueous ink vehicle was mixed with 40 parts by weight of the obtained gold paste and stirred to prepare an aqueous gold ink. After performing gravure printing and observing visually, a printed matter showing gold color was obtained, but the metallic luster of the printed coating film was poor.

[0109] Also, when the prepared gold ink was stored at 25°C for 2 months, it did not gel, and even after separating into a flaky brass powder layer and a vehicle layer, mixing was possible. However, as in immediately after ink preparation, the metallic luster of the printed coating film after gravure printing was poor.

[0110] (Comparative Example 3) To 100 parts by weight of flaky brass powder with an average particle size of 9 μm (75% by weight of copper, 25% by weight of zinc), 5.5 parts by weight of polyoxyethylene coconut oil fatty acid sorbitan with an HLB value of 16 (manufactured by Nippon Emulsion Co., Ltd.) and 5.5 parts by weight of isopropyl alcohol (manufactured by Kanto Chemical Co., Inc.) were added and mixed, and thoroughly mixed with a mixer to prepare a gold paste.

[0111] 40 parts by weight of a gold paste obtained was mixed with 60 parts by weight of a vehicle for an acrylic-based aqueous ink and stirred to prepare an aqueous gold ink. After gravure printing was performed and visually observed, as a result, immediately after the ink was prepared, a printed matter of gold color exhibiting a metallic luster equivalent to that of an organic solvent-based gold ink was obtained. However, when the prepared gold ink was stored at 25°C for 1 day, a film formed on the surface of the ink, and then, when stored at 25°C for 1 week, gelation occurred and printing became impossible.

[0112] (Comparative Example 4) To 100 parts by weight of flaky brass powder having an average particle diameter of 9 μm (75% by weight of copper, 25% by weight of zinc), 2 parts by weight of polyoxyethylene nonylphenyl ether (manufactured by Sanyo Chemical Industries, Ltd.) having an HLB value of 11 was added and mixed, and sufficiently mixed with a mixer to obtain a gold paste.

[0113] 40 parts by weight of the obtained gold paste was mixed with 60 parts by weight of a vehicle for an acrylic-based aqueous ink and stirred to prepare an aqueous gold ink. After gravure printing was performed and the printed matter was visually observed, as a result, immediately after the gold ink was prepared, a gold printed matter could be printed. However, when the prepared gold ink was stored at 25°C for 1 day, a film formed on the surface of the ink, and then, when stored at 25°C for 1 week, gelation occurred and printing became impossible.

[0114] The results of the examples are shown in Table 1, and the results of the comparative examples are shown in Table 2.

[0115] In the table, in the column of "luster" immediately after the ink was prepared, those in which the printed matter exhibited a metallic luster equivalent to that of an organic solvent-based gold ink were indicated as ◎, those in which the metallic luster was slightly inferior to that of an organic solvent-based gold ink were indicated as 〇, and those in which it was very inferior were indicated as ×.

[0116] Regarding the change over time, in the "State" column, for those in which gelation was not observed after two months and the flaky brass powder layer and the vehicle layer were mixable, it was marked as ○, and those in which the ink surface hardened or gelled were marked as ×. In the "Luster" column, those showing a metallic luster equivalent to the metallic luster immediately after printing were marked as 〇, those with poor metallic luster were marked as ×, and those that could not be printed were marked as "not possible".

[0117]

Table 1

Table 2

[0118] The gold paste in the present invention shows good dispersibility with respect to the vehicle for acrylic-based aqueous ink, does not cause gelation, and even after two months, it is possible to mix the flaky brass powder layer and the vehicle layer, proving that an aqueous gold ink with good metallic luster can be produced even after printing.

Industrial Applicability

[0119] The present invention is a gold paste that can be dispersed in a vehicle for aqueous ink to produce an aqueous gold ink, shows good dispersibility with respect to the vehicle for acrylic-based aqueous ink without causing gelation, and can produce an aqueous gold ink with excellent storage stability in that it is possible to mix the flaky brass powder layer and the vehicle layer over a long period of one month or more. In addition, a printed matter printed using the aqueous gold ink obtained by dispersing the gold paste in the present invention becomes a printed matter showing excellent metallic luster equivalent to that of a conventional organic solvent-based gold ink. Not only immediately after ink production, but also after storage, the printed coating film of the aqueous gold ink shows a gold color with excellent metallic luster and can be used suitably for high-definition printing such as gravure printing and flexographic printing. It is a gold paste that can produce an aqueous gold ink. Moreover, since a vehicle for aqueous ink is used, an aqueous gold ink with high safety and low environmental load can be produced. Therefore, the present invention is an invention with high industrial applicability.

Claims

1. A gold paste for aqueous ink, wherein the gold paste contains, per 100 parts by weight of flaky brass powder having a surface coated with fatty acid, 0.5 part by weight or more and 10 parts by weight or less of a nonionic surfactant having an HLB value of 13 to 17, 15 parts by weight or more and 45 parts by weight or less of glycols, and 3 parts by weight or more and 10 parts by weight or less of an aqueous wax emulsion aqueous solution.

2. The gold paste for aqueous ink according to Claim 1, wherein the average particle diameter of the flaky brass powder particles is 2 μm or more and 20 μm or less.

3. An aqueous gold ink obtained by dispersing the gold paste according to Claim 1 or 2 in a vehicle for aqueous ink.

4. The aqueous gold ink according to Claim 3, wherein the vehicle for aqueous ink is an acrylic-based vehicle for aqueous ink.

5. A method for producing the gold paste for aqueous ink according to Claim 1 or 2.

Images