JPH0730276B2 - Gold powder for gold ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention has a very excellent metallic luster as a printed matter,
In addition, the present invention relates to gold powder for gold ink, which does not discolor after being mixed with a vehicle and left for a long period of time and has an excellent metallic luster.

[Prior Art] For gold-colored printing using gold powder (flake-shaped brass metal powder), printing with gold-based ink in advance and sprinkling gold powder on it,
Alternatively, there is a method in which gold powder and hibicle are mixed immediately before printing to make gold ink and printing is performed.

However, from the viewpoint of work efficiency and environmental hygiene, a method of printing with gold ink in which gold powder and a vehicle are mixed in advance has been desired. However, since gold powder is a copper alloy powder in gold ink that is a mixture of gold powder and vehicle in advance, it is gradually oxidized by active acid groups such as free acid in the vehicle and trace amounts of water, and loses its metallic luster, resulting in long-term May cause discoloration. As a method of remedying these drawbacks, a gold ink composition in which a vehicle having little reaction with gold powder is used, or an amine compound is added as a rust preventive (JP-A-51-
No. 115105 and Japanese Patent Publication No. 55-27119) have been proposed.

However, according to the research conducted by the present inventor, although these gold inks are observed to have the effect of preventing discoloration of gold powder, they lose the metallic luster that is the greatest feature of gold inks quickly and are insufficient in storage stability. .

On the other hand, the metallic luster of the printed matter is that the gold powder in the vehicle rapidly emerges on the surface of the ink film due to interfacial tension and is arrayed (referred to as a leafing phenomenon), so that an excellent metallic luster is generated. For this reason, in gold-color printing, methods have been taken to maximize the leafing phenomenon of gold powder, such as slowing the printing speed, thickening the coating film, and printing twice. However, recently, the same printing method as other inks has been adopted due to automation of the printing process, speeding up of printing machines, economical reasons, etc., the leafing phenomenon of gold powder cannot be sufficiently obtained, and gold printed matter also has poor metallic luster. Has become.

Therefore, a gold powder capable of exhibiting a more leafing property than the conventional gold powder has been required in the vehicle, but such a gold powder has not been found yet.

[Problems to be solved by the invention]

The gold powder used for gold ink is a fine metal powder with an average particle size of 10 μm or less. For high-speed offset printing, very fine metal powder of 5 μm or less is used to improve printability.

In particular, the finer the metal powder containing copper as a main component, such as gold powder, the more easily it is oxidized, and when it is made into gold ink, it reacts with the vehicle and the like, and the metallic luster disappears in about one month in the summer. This is a problem in industrial use of gold ink, and it is necessary to maintain the initial metallic luster for at least 3 months.

Gold powder has conventionally been uniformly surface-treated with fatty acids (higher fatty acids such as stearic acid) in the manufacturing process.
This is the reason why the gold powder has an excellent metallic luster and a color tone close to that of pure gold, and has been widely used as a pigment for gold printing. However, the leafing performance obtained with fatty acids has become insufficient as gold powder for gold ink. In addition, the presence of trace amounts of active acid groups and water in the vehicle causes the fatty acid coating (which partially forms metal soap such as copper stearate) to be easily replaced, and the vehicle and gold powder are not compatible with the leafing phenomenon. have.

On the other hand, the method of treating gold powder with an organic rust preventive such as benzotriazole, tolyltriazole, or an amine compound is effective for coarse gold powder, but for fine gold powder of 10 μm or less, the rust protection On the contrary, the film could not be used as gold powder for gold ink because it changed the color tone of gold powder or hindered the leafing phenomenon.

The inventors of the present invention have found that when the gold powder surface is uniformly treated with a fatty acid (a part of copper reacts with the fatty acid to form metal soap), it retains an excellent color tone and luster, and when mixed with a vehicle. , The leafing property is better than the conventional gold powder, and the leafing phenomenon does not worsen even when contacted with the vehicle, and as a result of various studies to find a gold powder that maintains a metallic luster for a long time, the present invention has been completed. Is.

[Means for solving problems]

That is, the present invention is a gold ink coated with 0.5 to 10 parts by weight of polyethylene glycol and 0.5 to 10 parts by weight of a fatty acid ester, based on 100 parts by weight of a flaky brass metal powder having an average particle size of 10 μm or less treated with a fatty acid. It is gold powder for use.

The flaky brass metal powder treated with the fatty acid of the present invention is referred to as bronze powder or gold powder produced by a mechanical grinding method.

The particle size is set to 10 μm or less because it is not preferable for the particle size to be coarser than that, because the grain size of the plate or the printability is significantly deteriorated.

The polyethylene glycol of the present invention - [- CH ₂ CH ₂ O
-] A linear polyether represented by n-, specifically, polyethylene glycol # 200, polyethylene glycol # 300, polyethylene glycol # 400, polyethylene glycol # 600, polyethylene glycol # 1000, polyethylene glycol # 2000, polyethylene glycol #
4000 and the like.

The amount of polyethylene glycol is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of metal powder. If it is less than 0.5 part by weight, the sufficient leafing effect and the storage stability after mixing with the vehicle are not improved.

The larger the amount of polyethylene glycol, the better the leafing property in the vehicle, but if it is 10 parts by weight or more, the adhesion between the gold powder and the vehicle becomes problematic, and the gold powder is removed from the printing surface, which is not preferable.

The optimum addition amount of polyethylene glycol is 2 to 6 parts by weight with respect to 100 parts by weight of metal powder.

The coating method of polyethylene glycol on the metal powder should be changed according to the molecular weight of polyethylene glycol. That is, liquid polyethylene glycol having a molecular weight of 400 or less may be coated with a mixer such as a mixer. On the other hand, if it is a wax-like or wax-like solid polyethylene glycol having a higher molecular weight, it is better to coat it with a ball mill or an agitator mill.

The fatty acid ester of the present invention is preferably fatty acid methyl or ethyl ester, specifically, methyl palmitate,
Examples thereof include ethyl palmitate, methyl stearate, ethyl stearate, methyl behenate, ethyl behenate, and the like.

Fatty acid esters other than fatty acid methyl or ethyl esters are not preferred because they deteriorate the leafing property and color tone of the gold powder.

Among the fatty acid methyl or ethyl esters, a particularly preferred fatty acid ester is a fatty acid having 16 or more carbon atoms,
The following fatty acid esters have a slightly poor leafing property, and it is necessary to add more polyethylene glycol.

The amount of the fatty acid ester is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the metal powder. If less than 0.5 parts by weight, the smoothness of the coating film,
The dispersibility of gold powder does not improve. If the amount is 10 parts by weight or more, it is not preferable because it adversely affects the adhesion to paper as gold ink.

The reason why polyethylene glycol and fatty acid ester are used together is to improve the dispersibility of the gold powder in the vehicle and the smoothness of the coating film. That is, if polyethylene glycol alone is used, the compatibility with the vehicle is too poor, so that the vehicle and the gold powder are separated, the smoothness of the coating film surface of the printed matter is deteriorated, and the gold powder may be removed. The optimum amount of fatty acid ester is the same as that of polyethylene glycol, and is 2 to 6 parts by weight with respect to 100 parts by weight of metal powder.

[Action]

The reason why the gold powder for gold ink of the present invention exhibits excellent metallic luster and storage stability as a gold ink has not been fully clarified as to what kind of binding or action it is, but the following may be considered.

When the gold powder is coated with polyethylene glycol, it interacts with the fatty acid or metal soap formed on the surface in advance to form a protective film which is incompatible with the vehicle. When gold powder having such a protective film is mixed with a vehicle and printed, the gold powder rapidly floats and is arrayed on the surface of the ink film due to interfacial tension, and exhibits excellent metallic luster. The leafing property of the gold powder having the protective film of the present invention is stronger than the leafing property of the conventional gold powder treated with a fatty acid, and the gold powder floats up on the surface of the coating film very quickly, which may improve the metallic luster of the printed matter.

Further, the protective film of the present invention has an effect of preventing the vehicle and the gold powder from becoming compatible with each other even against the influence of active acid groups and water in the vehicle, and maintains the leafing property even when it is in contact with the vehicle for a long period of time. Ah

Polyethylene glycol has not only a very small corrosive effect on copper, but also a certain reducing effect, which may be the reason why storage stability is obtained for a long period of time.

The effect of the fatty acid ester is that when used in combination with polyethylene glycol, the gold powder can be smoothly arranged on the coating surface. That is, gold powder coated only with polyethylene glycol has a strong floating force on the surface of the coating film, but is not uniformly arranged on the surface of the coating film. However, when the fatty acid ester is added, the floating gold powder is evenly arranged laterally along the surface of the coating film, producing a smooth metallic luster. It is considered that this is because the fatty acid ester improves the dispersibility and orientation of the gold powder.

〔Example〕

The present invention will be specifically described below with reference to examples, but the use range of the gold powder for gold ink of the present invention is not limited thereby.

All the parts in the text are parts by weight, and the brass powder used is a product of Fukuda Metal Foil & Powder Co., Ltd.

Example (1) 0.5 parts of polyethylene glycol # 200 and 0.5 parts of methyl palmitate were added to 100 parts of brass metal powder (trade name No. 50) having an average particle size of 10 μm, and mixed with a mixer at 60 rpm for 60 minutes. Gold powder for gold ink was manufactured.

Example (2) 0.5 parts of polyethylene glycol # 200 and 0.5 parts of ethyl palmitate were added to 100 parts of brass metal powder (trade name No. 50) having an average particle size of 10 μm, and mixed with a mixer at 60 rpm for 60 minutes. Gold powder for gold ink was manufactured.

Example (3) 0.5 part of polyethylene glycol # 4000 and 0.5 part of methyl behenate were added to 100 parts of brass metal powder (trade name No. 70) having an average particle size of 10 μm, and the mixture was mixed with a ball mill using glass balls as a medium to give 30 r.
pm · 120 minutes mixed at 80 ℃ to produce gold powder for gold ink.

Example (4) 0.5 part of polyethylene glycol # 4000 and 0.5 part of ethyl behenate were added to 100 parts of brass metal powder (trade name No. 70) having an average particle size of 10 μm, and the mixture was mixed with a ball mill using glass balls as a medium at 30 r.
pm · 120 minutes mixed at 80 ℃ to produce gold powder for gold ink.

Example (5) 6 parts of polyethylene glycol # 300 and 6 parts of methyl stearate were added to 100 parts of brass metal powder (trade name No. 5550) having an average particle size of 3 μm, and mixed with a mixer at 60 rpm for 120 minutes. Gold powder for gold ink was manufactured.

Example (6) 6 parts of polyethylene glycol # 300 and 6 parts of ethyl stearate were added to 100 parts of brass metal powder (trade name No. 5550) having an average particle size of 3 μm, and mixed with a mixer at 60 rpm for 120 minutes. Gold powder for gold ink was manufactured.

Example (7) To 100 parts of brass metal powder (trade name No. 7770) having an average particle diameter of 3 μm, 10 parts of polyethylene glycol # 1000 and 10 parts of methyl behenate were added, and a ball mill using glass balls as a medium was used for 30 rp.
Gold powder for gold ink was manufactured by mixing at 80 ° C. for 120 minutes.

Example (8) 10 parts of polyethylene glycol # 600 and 5 parts of methyl stearate were added to 100 parts of brass metal powder (trade name No. 7770) having an average particle size of 3 μm, and a ball mill using glass balls as a medium was used.
Gold powder for gold ink was manufactured by mixing at 30 rpm for 60 minutes.

Example (9) 2 parts of polyethylene glycol # 300 and 2 parts of ethyl stearate were added to 100 parts of brass metal powder having an average particle size of 5 μm (trade name No. 5000) and mixed with a mixer at 60 rpm for 60 minutes. Gold powder for gold ink was manufactured.

Example (10) 2 parts of polyethylene glycol # 300 and 6 parts of methyl stearate were added to 100 parts of brass metal powder (trade name No. 7000) having an average particle size of 5 μm and mixed with a mixer at 60 rpm for 60 minutes. Gold powder for gold ink was manufactured.

As described above, in order to evaluate the performance of the gold powder for gold ink obtained in Examples (1) to (10), 50 parts of the vehicle dissolved in the alkylphenol-modified xylene resin No. 5 solvent was used in Examples (1) to (10). 50 parts of each of the obtained gold powder for gold ink was mixed to prepare gold ink.

As a result, the coating film printed on the paper with the gold ink using the gold powder for the gold ink of the present invention (the printing condition is by the RI tester) is the same printing method as the gravure printing, though it is a printing method according to the offset printing. It exhibited a luster.

Even when the gold ink was left standing at 25 ° C. for 90 days and then printed, a coating film having excellent metallic luster could be obtained. For comparison, a gold ink prepared by the above method using ordinary gold powder not subjected to the treatment of the present invention has a temperature of 25 ° C.
The metallic luster disappeared after 10 days, and discoloration was observed after 30 days.

[Advantages of the Invention] Recently, the number of cases where gold color printing is performed by offset printing has been increasing, but the fact that the metallic gloss is poor compared to gold color printing of gravure printing is a major drawback.

Until now, it has been common sense that in the industry it is not possible to produce the metallic luster of gravure printing by offset printing without any countermeasures.

However, when the gold powder for gold ink of the present invention is used, it is possible to obtain a metallic luster similar to that of gravure printing by offset printing, and storage stability is also very good. As a result, it can be stocked for a long time, and a printed matter having an excellent metallic luster can be printed at any time.

Further, since the leaf stuffing performance is better than that of the conventional gold powder, printed matter having excellent metallic luster can be produced even at high speed printing.

As described in detail above, the gold powder for gold ink of the present invention,
It is an epoch-making gold powder that shows excellent performance when used for gold ink.

Claims (2)

[Claims] 1. A gold ink coated with 0.5 to 10 parts by weight of polyethylene glycol and 0.5 to 10 parts by weight of a fatty acid ester per 100 parts by weight of a flaky brass metal powder having an average particle size of 10 μm or less treated with a fatty acid. For gold powder. 2. The fatty acid ester is a fatty acid methyl or ethyl ester.
Gold powder for gold ink according to the item.