EP1082228B1 - Method for cleaning printing machines and printing moulds - Google Patents

Abstract

A process is proposed for cleaning printing machines or printing plates by removing the contaminants from the surfaces to be cleaned by washing them with a microemulsion comprising water, a surfactant, and a water-immiscible organic solvent.

Description

The invention relates to a method for cleaning printing machines and Printing forms, in particular for removing printing inks, for example from Oil-based inks or radiation-curable inks, of which Cylinders and rollers of printing machines, especially flat or offset printing machines, as well as printing forms, for example when the Printing.

For the purposes mentioned, cleaning agents are generally based organic solvents and / or aqueous solutions used. Thereby in Print shops with long machine downtimes or with a color change parts of the printing press contacted with the printing ink are freed of ink residues. Likewise, printing forms, especially planographic printing forms, must be used for one Interruption of the printing process carefully cleaned of ink residues and for Preservation of the hydrophilicity of the non-image areas with preservation solutions Based on hydrophilic polymers are coated. Cleaner, the organic solvent contain mostly volatile organic components (VOC = volatile organic compounds) that pollute the atmosphere and occupationally and ecologically are of concern. Cleaners made exclusively or predominantly from non-polar Organic solvents exist, also have the disadvantage that the parts to be cleaned, for example pressure rollers, adhering solvent residues do not wash off with water after cleaning. There is a clean platen roller however, a prerequisite for good wetting with the printing ink and good Ink transfer. With some printing forms, the color-guiding printing template can also be used detached from the cleaning agent and thereby damaged or even become unusable.

DE-B 27 24 557 describes a cleaning agent for lithographic printing plates described, which contains water and water-miscible organic solvents. Its cleaning effect against viscous inks is oil-based naturally limited.

GB-A 2 089 289 describes oil-in-water and water-in-oil emulsions as Cleaner described. The disadvantage here is the relatively high interfacial tension between water and oil phase, so that for example lipophilic, highly hydrophobic offset inks because of their high interfacial energy compared to the water-continuous cleaning solution only slowly and only slightly Dimensions of this are included.

The same applies to emulsions, such as those in WO-A 90/03419 or EP-A 0 498 545.

Emulsions of this type are otherwise only kinetic, but not thermodynamic stable, so that they can separate, especially in the case of temperature fluctuations [Creaming (sitting down), thickening, flocculation] tend and thereby in their Applicability will be affected.

The removal of offset curable by UV radiation is particularly difficult or high-pressure inks based on polymerizable monomers or oligomeric acrylates. To remove them, esters or Mixtures of esters and mineral oil are used.

The object of the invention was to provide a cleaning method and a liquid To provide cleaning agents that allow printing inks to be quick and effectively peel off without the environment becoming more volatile organic through vapors Components loaded or the printing template is attacked by printing forms.

EP-A-0527315 discloses a water-in-oil microemulsion as blanket detergent from ethoxylated partial glycerides of caprylic / capric acid, 1,2-bis (oxazolin-2) ethane and at least one saturated fatty acid methyl ester.

The invention is based on a method for cleaning printing machines or printing forms in which the contaminants are removed from the surface Wash away with a liquid.

The process according to the invention is characterized in that the liquid is a bicontinuous microemulsion, the water surfactant and as an oil phase an organic water-immiscible Contains solvents in the proportions as in claim 1 are defined.

In the context of the present description, a microemulsion is to be understood as a liquid, bicontinuous mixture of water and oil phase with an extremely low interfacial tension between the water and oil phase, i.e. an interfacial tension that is up to three orders of magnitude lower than that of a conventional water-in -Oil or oil-in-water emulsion. For microemulsions this interfacial tension is in the range of 10 ^-4 to 10 ^-6 N / m, for emulsions it is usually in the range of 10 ^-3 to 10 ^-2 N / m. A microemulsion in the sense of the present description is thermodynamically stable, visually transparent and preferably of low viscosity.

Conventional conventional emulsions can contain oil and water phases in very different proportions by volume. They have a continuous and a disperse phase, which is present in the continuous phase as very small spheres stabilized by coating with surfactants. Depending on the nature of the continuous phase, one speaks of oil-in-water or water-in-oil emulsions. In the ideal case, these emulsions are kinetically stable, ie they remain intact for a long time, but not indefinitely. In particular in the case of temperature fluctuations, they can tend to phase separation by sitting, creaming, thickening or flaking.
Bicontinuous microemulsions contain two phases, a water phase and an oil phase, in the form of extended domains lying next to one another and intertwined, at the interface of which stabilizing surfactant surfactants are enriched in a monomolecular layer. Bicontinuous microemulsions form very easily, usually because of the very low interfacial tension, if the individual components, water, oil and a suitable surfactant system, are mixed. Since the domains have only very small dimensions in the order of nanometers in at least one dimension, the microemulsions appear visually transparent and, depending on the surface-active system used, are thermodynamically stable in a certain temperature range, ie for an unlimited period.

For example, bicontinuous microemulsions are in the article "Microemulsions - a scientific and technical treasure trove? "by H.-F. Eicke in SÖFW-Journal 118 (1992), pages 311 to 314.

To achieve the required low interfacial tension on the Phase boundaries, the microemulsions contain certain amphiphiles, i.e. surfactants, and electrolytes often dissolved in their aqueous phase and optionally other auxiliaries. Especially then electrolytes added if the amphiphiles partially or exclusively ionic surfactants are.

The use of microemulsions for the extraction of organic pollutants contaminated soils is described in WO 94/04289. Also the Tertiary oil production is known as an area of application for microemulsions become.

It is also known from EP-A-0 498 545, microemulsions as Detergents, e.g. B. for painted or bare metal sheets, plastics and other surfaces, especially for pre-treatment for subsequent ones To use coatings.

The components of the microemulsion should be selected so that they mechanical properties of device parts or sealing materials Rubber or similar materials, such as elasticity, flexibility, Dimensional stability etc., by swelling or shrinking (swelling) Don `t change.

Organic solvents which are immiscible with water are advantageously those with a boiling range above 100, preferably above 150 ° C., in particular from 200 used up to 400 ° C. In general, organic solvents are used Flash points above 100 ° C used. Under "organic solvents" are among other fats and oils, e.g. Beet oil, fatty acid esters, ethers, ketones, aldehydes and understand hydrocarbons.

Alkyl esters of longer-chain fatty acids are for the process according to the invention suitable. The alkyl group of the alcohol component has 1 to 20, preferably 1 to 16 carbon atoms. The fatty acid component normally has 6 to 25, preferably 8 to 18 carbon atoms and can be linear or branched, be saturated or unsaturated and up to three double bonds in the molecule contain. The esters generally have an iodine number ranging from 0 to about 150, preferably from 0 to 40. Compounds with a higher content Double bonds often show a tendency to resinify and thus to Separation of unwanted substances. Such connections are therefore if at all, added only in small proportions. Examples of suitable esters are methyl, ethyl, isopropyl, n-butyl, n-hexyl, 2-ethylhexyl esters and / or Isooctyl esters of fatty acids or fatty acid mixtures, for example octanoic acid, 2-ethylhexanoic acid, capric acid, lauric acid. Myristic acid, palmitic acid, Oleic acid, linoleic acid, behenic acid or soybean oil, coconut oil, palm kernel oil, palm oil, Sunflower oil, sperm oil, tall oil, rapeseed oil, castor oil or tallow fatty acids. Individual typical esters are, for example, 2-ethylhexyl coconut fatty acid, Tall oil fatty acid n-hexyl ester, rapeseed methyl ester, oleic acid methyl ester, stearic acid methyl ester, Isopropyl palmitate, ethyl laurate, 2-ethylhexanoic acid 2- ethylhexyl ester and octanoic acid n-octyl ester. Besides these Esters are also high boiling range ethers, e.g. Dioctyl ether, as well Tricylycerides, such as rapeseed oil, coconut oil or soybean oil, are suitable.

The esters are characterized by a very low vapor pressure, so that at no pollution of the atmosphere occurs during their use. As is the case with bicontinuous Microemulsions are the rule, the volume fractions are aqueous and organic Phase approximately in the same order of magnitude, i.e. the volume ratio of Water to organic phase 40:60 to 60:40.

As surfactants, hereinafter also referred to as surfactants basically such different amphiphilic characters are used, thus anionic, cationic, amphoteric and nonionic surfactants or their Mixtures.

Suitable anionic surfactants are C ₁₀ to C ₂₀ , preferably C ₁₂ to C ₁₆ alkyl sulfates, for example sodium dodecyl sulfate; C ₁₀ to C ₂₀ , preferably C ₁₂ to C ₁₆ alkyl polyether sulfates, for example sodium dodecyloxypolyethoxy sulfate; Alkali salts of diisooctylsulfosuccinic acid; Alkali salts of alkylbenzenesulfonic acids, for example sodium dodecylbenzenesulfonate, of dialkyl phosphates, and of carboxylates, for example of fatty alkyl ether carboxylates. Some anionic surfactants, for example sodium dodecyl sulfate, are often used together with alkanols such as butanol, pentanol or hexanol as co-surfactants and / or with alkali or alkaline earth metal salts, for example sodium chloride, sodium sulfate or calcium chloride, or with other electrolytes, for example NaOH, KOH , Phosphates or silicates used.

Furthermore, the microemulsions used according to the invention can still Complexing agents such as ethylenediaminetetraacetic acid, nitrilotriacetic acid or Methylglycinediacetic acid, corrosion inhibitors and / or preservatives contain.

The alkanols can be present in amounts of up to 20, preferably up to 10% by weight Electrolytes can be added in amounts of up to 10, preferably up to 5% by weight.

Cationic surfactants can be used, for example, to produce microemulsions Alkyltrimethylammonium halides with alkyl chain lengths of about 8 up to 18 carbon atoms and / or quaternized imidazolinium or pyridinium salts be used.

Suitable nonionic or nonionic surfactants are polyglycol monoalkyl ethers with alkyl chain lengths of C ₈ to C _18, preferably C ₁₀ to C ₁₆ , and 2 to 20, preferably 3 to 15 oxyalkylene, in particular ethylene, propylene and / or butylene units, or block copolymers from these units. C ₁₀ to C ₁₅ alkyl ethers of polyglycols with 3 to 10 oxyalkylene units are frequently used. These are mostly technical products with a more or less broad molecular weight distribution. Surfactants with a narrow molecular weight distribution produced using special casters can also be used. Triglyceride alkoxylates, for example reaction products of 1 mol of triglyceride with 1 to 50 mol of alkylene oxide, particularly 10 to 50 mol of ethylene oxide, are also suitable. In addition, surfactants based on saccharides, for example alkyl polyglucosides or glucosamides, can be used.

The microemulsions used according to the invention preferably contain anionic ones Surfactants, usually in combination with one or more nonionic surfactants. However, microemulsions can also be produced using nonionic surfactants alone become.

To achieve an optimal cleaning effect, in each individual case Combination of organic solvent, surfactant or surfactants and optionally determined electrolytes and complexing agents in aqueous solution relatively narrow ranges of proportions of the individual components required, which are can be determined by simple routine tests. According to the invention, the proportion is Total surfactants in the microemulsion in the range of 7 to 25% by weight. If the surfactant content is too high, Cleaning problems arise, or the drying of the printing rollers can To cause difficulties.

In general, 1 to 20, preferably 3 to 15 and in particular 5 to 10 % By weight anionic surfactant; 1 to 20% by weight polyethylene glycol monoalkyl ether; 0.1 to 10, preferably 0.5 to 5 wt .-% reaction product of triglyceride with Ethylene oxide and 1 to 20 wt .-% polyalkylene glycol monoalkyl ether Oxyethylene and / or oxypropylene units used.

The microemulsions used according to the invention contain 20 to 60 wt .-% water-immiscible organic Solvent and 30 to 60 wt .-% water. All information in % By weight is based on the total weight of the finished microemulsion based.

Each microemulsion is thermodynamic in a certain temperature range stable. Those microemulsions which are preferred at room temperature and among them are thermodynamically stable. In many cases, however, it can also Microemulsions are used with success, their stability range above Room temperature, for example between 50 and 60 ° C.

High concentrations of surfactants in known cleaning fluids often lead to poor ink release. associated with surfactant deposits on the Printing rollers; these disadvantages occur with those used according to the invention Microemulsions not.

When carrying out the cleaning process according to the invention, the Microemulsion applied to the parts of the press to be cleaned. The Surface of the printing ink is wetted quickly, evenly and completely, so that the printing ink is quickly absorbed and dissolved by the cleaning liquid or is emulsified. Leave the remaining remains of the microemulsion easily removed by washing with water. The same goes for the after Interruption of pressure on one to be cleaned and preserved Printing form, in particular an ink or offset form remaining ink residue. The most important thing here is the complete removal of paint residues from the Non-image or background areas of the printing form, on which, for example, the Flat or offset printing the required when resuming printing Hydrophilicity must be preserved. As a printing form is part of this Description A printable printing plate referred to, usually by Exposing and developing a photosensitive printing plate is obtained.

The microemulsions used according to the invention are also suitable for Cleaning of other substances, e.g. B. of plastics, old paintwork, Primers and bare metal sheets. You can e.g. B. as a cleaning agent used in the field of car refinishing and as a brush cleaner become.

The following examples illustrate embodiments of the invention Process and for the microemulsions used and their preparation.

Production Example 1

By mixing 10 g of dioctyl sulfosuccinate (sodium salt), 7 g of a polyglycol monoalkyl ether mixture with about 5 oxyethylene units and a C ₁₀ -C ₁₃ alkyl ether group. 46 g of a C ₈ -C ₁₈ fatty acid methyl ester mixture, 37 g water and 0.07 g calcium chloride and brief shaking of the mixture gave a low viscosity thermodynamically stable and visually transparent microemulsion.

Production Example 2

A microemulsion which is stable at room temperature was described as in Preparation Example 1, but from 8 g of dioctyl sulfosuccinate,
16 g of the same polyglycol monoalkyl ether mixture, 15 g of rapeseed oil fatty acid methyl ester, 15 g of coconut fatty acid 2-ethyl-hexyl ester, 46 g of water and
0.07 g calcium chloride prepared.

Production Example 3

14 g of dioctyl sulfosuccinate, 34.5 g of soybean oil and 51.5 g of water were used Mix as in Preparation Example 1 to obtain a microemulsion. She was in Temperature range from 55 to 58 ° C thermodynamically stable and visually transparent.

Production Example 4

17.0 g of dioctyl sulfosuccinate were dissolved in 41.5 g of water and the solution with 415 g of decane mixed. The mixture forms in the temperature range from 51 to 56 ° C a thermodynamically stable visually transparent microemulsion lower Viscosity.

The microemulsions of Preparation Examples 3 and 4 are outside of specified temperature ranges are not permanently stable and separate Standing for a long time at room temperature in an oil and a water phase. The Microemulsions of Preparation Examples 1 and 2, on the other hand, allow one Use for an unlimited period at room temperature.

Application example 5

The rollers of a rotary offset printing press were used in a comparative test after every 100,000 prints with commercially available offset printing ink Oil base with white spirit (mainly with aliphatic hydrocarbons a boiling range of 80 to 250 ° C) and once with the microemulsion of Preparation example 1 cleaned. In both cases the cleaning performance, i.e. the removal of the ink, essentially the same. When using the After cleaning, the rollers were cleaner and drier than in the microemulsion Use of white spirit. The remains of the microemulsion could easily and can be removed without residue by simply rinsing with water.

In the same way, the offset printing form used in the printing process was included treated both cleaning liquids. In both cases, a clean, from Preserved printing stencil free of paint residues. The one cleaned with the microemulsion Printing form was from the subsequently applied aqueous solution of rubber arabicum smoothly and completely wetted, while this solution also from the The non-image-bearing support surface of the white spirit cleaned Printing form difficult and accepted only after a long intensive treatment has been.

Claims (7)

1. A process for cleaning printing machines or printing plates by removing the contaminants from the surfaces to be cleaned by washing them with a liquid, wherein said liquid is a bicontinuous microemulsion comprising

   a) from 20 to 60% by weight of a C₁-C₂₀ alkyl ester of a saturated or unsaturated C₆-C₂₅ fatty acid as a water-immiscible organic solvent,

   b) from 30 to 60% by weight of water,

   c) from 7 to 25% by weight of surfactant,

   where the volume ratio of water to organic phase is 40:60 to 60:40 and the interfacial tension between water and organic phase is from 10^-4 to 10^-6 N/m.
2. A process as claimed in claim I, wherein said washing is conducted in a temperature range within which the microemulsion is thermodynamically stable.
3. A process as claimed in claim 1 or 2, wherein said surfactant is an anionic surfactant.
4. A process as claimed in one of claims 1 - 3, wherein said microemulsion additionally comprises a nonionic surfactant.
5. A process as claimed in one of claims 1 - 4, wherein an electrolyte is present in solution in said water.
6. A process as claimed in claim 5, wherein said electrolyte is a water-soluble alkali metal salt or alkaline earth metal salt.
7. A process as claimed in one of claims 1 - 6, wherein a complexing agent or a corrosion inhibitor is present in solution in said water.