JPH0514746B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an aqueous cleaning liquid for washing flexographic printing ink adhering to printing rolls, ink supply circulation pipes, flexographic plates, etc. when changing lots in a flexographic printing machine. . [Prior Art] A flexo printing machine using water-soluble ink is preferably used as a high-speed printing machine for corrugated boards and the like. Since flexographic ink is water-based, it dries quickly and enables high-speed printing. In this flexo printing machine, when changing lots and changing ink colors, the ink and ink adhering to rolls and covers such as the plate, ink roll, doctor roll, and printing roll are supplied and the excess ink is removed. It is necessary to completely wash the ink in the ink circulation system to be recovered.
118808, 56-86757). As a cleaning liquid for such flexographic printing ink, an aromatic hydrocarbon solvent such as kerosene or xylene is emulsified and dispersed in an aqueous sodium silicate solution using a surfactant such as sorbitan monooleate or an organic dibasic acid alkyl ester sulfonide. A cleaning solution is known (Japanese Unexamined Patent Publication No. 53-2509). [Problems with the prior art] The composition of flexographic printing ink is mainly composed of a maleic acid resin binder such as an amine salt of a styrene-maleic acid copolymer or an amine salt of maleic acid grafted rodine, a pigment, ethyl alcohol, and water. It is something. When the above-mentioned flexographic printing ink is dried after printing, amines such as ammonia and diethanolamine with small molecular weight are liberated from the carboxyl group and scattered into the air, and the maleic acid resin, which was previously water-soluble, becomes water-insoluble. be. When printing is completed using this flexo printing ink, a large amount of ink remains on the printing press. Some of it dries and remains attached to the ink distribution channels of printing machines, plates, etc. At the end of this dry residue, no water-soluble amine remains. Naturally, this cannot be washed away with water, which is the solvent for ink. This is because the amine is scattered and free carboxylic acid appears at the end. In the cleaning solution disclosed in JP-A No. 53-2509, sodium silicate, which is alkaline and has excellent pigment adsorption ability, is used to make the maleic acid resin water-soluble. The cleaning liquid contains about 50% by weight of kerosene, xylene, etc., which acts to prevent rust from forming on the printing machine and swells the dry ink, so after cleaning, the kerosene, etc. is separated. The wastewater needs to be drained away, and wastewater treatment equipment costs a lot of money. [Specific means for solving the problem] The present invention uses a water-soluble lower amine such as monoethanolamine as a salt to neutralize a binder resin containing a carboxyl group, and In a washing machine, we use an aqueous cleaning solution containing an antifoaming agent that can be dispersed in water, such as silicone oil or amide, to prevent the foaming of the cleaning solution that occurs when the cleaning solution circulates in pipes, etc., when the plate is transferred by rolling, and when the plate is brushed. This is what we provide. [Structure of the Invention] The present invention provides component (A): monoethanolamine or diethanolamine.
0.05 to 35% by weight (B) Component: Water-dispersible antifoaming agent 0.001 to 1.0% by weight (C) Component: Water-soluble aliphatic monoalcohol having 1 to 4 carbon atoms 0 to 75% by weight (D) Ingredients: Water 25-96% by weight The present invention provides a flexographic printing ink cleaning liquid containing the above components (A), (B), (C), and (D). (Amine) The amine of component (A) reacts with the hydrophobic maleic acid resin to form a water-soluble salt. Tertiary amines such as triethanolamine are not sufficient to render the solidified ink into a water-soluble salt. These amines are 0.05 to 35% by weight in the cleaning solution.
It is preferably used in a proportion of 0.5 to 5% by weight.
Less than 0.05% by weight is not sufficient to make the solidified ink water-soluble. Even if 35% by weight or more is added, no further improvement in water solubility can be expected, which is disadvantageous in terms of cost. (Anti-foaming agent) An anti-foaming agent is an anti-foaming agent that can be used by itself or with the aid of surfactants or protective colloids to dissolve up to 3 microns in water.
Preferably, it is one that can be dispersed into particles of 0.005 to 1 micron, and the following can be used. Metallic soaps: e.g. aluminum stearate, calcium oleate. Silicone oil; silicone paste, fluorosilicone oil,

[Formula] etc. Usually, an inorganic filler such as calcium carbonate or silica or a surfactant is used as a dispersant to reduce the particle size. Amides; polyoxyalkylene amide, acrylate polyamine, ethylene bisstearyl amide, amide obtained by reacting alkylene amine with fatty acid, butane dicetyl amide, etc. Alcohols having 6 or more carbon atoms; for example, octyl alcohol, hexadecyl alcohol, polyoxyalkylene glycol, pluronic alcohol, modified polyether urethane, etc. These may be used alone or as a mixture of two or more. (Polyhydric Alcohol) Since an aqueous polyhydric alcohol acts as an antifoaming agent, it may be added as an optional component. Such polyhydric alcohols include ethylene glycol,
Diethylene glycol, propanediol, butanediol, triethylene glycol, tetraethylene glycol, pentadiol, hexanediol, glycerin, pentaerythritol, trimethylolpropane, polyethylene glycol, polypropylene glycol, etc., with a molecular weight of 500
The following water-soluble aliphatic polyhydric alcohols can be mentioned. This polyhydric alcohol is used in a proportion of 0 to 75% by weight, preferably 25% by weight or less in the cleaning liquid. (Monoalcohol) The water-soluble monoalcohol may be blended arbitrarily. The blending of this monoalcohol facilitates the release of the resin from the plate and has a foam-breaking effect. As such monoalcohols, water-soluble ones such as methanol, ethanol, propyl alcohol, butanol can be used, and are used in a proportion of 75% by weight or less of the cleaning liquid. (Water) Water is used as an inexpensive solvent in a proportion of 25 to 96% by weight, preferably 85 to 96% by weight in the cleaning liquid. If the water content exceeds 96% by weight, there will be problems in detergency and antifoaming properties. A cleaning device for rolls, plates, etc. of a flexo printing machine is described in Japanese Patent Application Laid-open Nos. 118808-1980 and 86757-56. The solidified flexographic printing ink is cleaned by spraying or immersing it in the cleaning liquid of the present invention. Hereinafter, the present invention will be explained in detail with reference to Examples. Examples 1 to 6, Comparative Examples 1 to 8 Cleaning liquids having the compositions shown in Table 1 were prepared. 8 ml of this cleaning liquid was collected in a 10 ml glass bottle, and then 0.08 g of solidified pulverized flexographic printing ink with an aqueous maleic acid resin made by Dainippon Ink and Chemicals Co., Ltd. as a binder was added. was evaluated based on the following criteria. ◎: Dissolved within 1 minute ○: Dissolved within 1 minute to 0.5 hours △: Dissolved within 0.5 to 5 hours ×: Not dissolved even after 5 hours The defoaming effect when placed was evaluated based on the following criteria. ◎: Foaming disappears within 10 seconds 〇: Foaming disappears within 1 minute △: Foaming disappears within 1 to 5 minutes ×: Foaming does not disappear even after 5 minutes have passed. The results are shown in the same table.

【table】

Claims (1)

[Claims] 1. Component (A): monoethanolamine or diethanolamine
0.05 to 35% by weight (B) Component: Water-dispersible antifoaming agent 0.001 to 1.0% by weight (C) Component: Water-soluble aliphatic monoalcohol having 1 to 4 carbon atoms 0 to 75% by weight (D) Ingredients: Water 25-96% by weight A cleaning liquid for flexographic printing ink containing the above components (A), (B), (C) and (D). 2. The cleaning liquid according to claim 1, wherein component (A) is monoethanolamine. 3. The cleaning liquid according to claim 1, wherein the antifoaming agent is metal soap, silicone oil, polyoxyalkylene amide, or pluronic alcohol.