DK172001B1 - Method of production of flexographic printing formes - Google Patents

Description

in DK 172001 B1

The invention relates to a process for the preparation of photopolymerization crosslinked flexo printing forms, whereby certain developer solvents are used to wash out the non-crosslinked parts of the layers.

5

The preparation of flexo printing forms by photopolymerizable or photo-crosslinkable relief forming layers is illuminated imaged with actinic light during crosslinking of the illuminated layer portions and subsequent leaching of the non-crosslinked portions of the layers in developer solvents. Usually, as the developing solvent, chlorinated hydrocarbons such as trichloroethylene, tetrachlorethylene, aromatic hydrocarbons such as benzene, toluene, saturated cyclic and acyclic hydrocarbons such as hexane, cyclohexane, unsaturated cyclic hydrocarbons such as terpenoid compounds, limones, limonene, limonene, limones, , methylene ethyl ketone, if added in admixture with an alcohol, e.g. butanol in a proportion of approx. 20% by volume.

20

The frequently used leaching solutions for flexo printing plates, which consist of approx. 80 volumes of tetrachlorethylene and 20 volumes of n-butanol and trichloroethane respectively cause problems in the operation of washing machines due to their toxicity. Therefore, in order to achieve proper operation, a suction is required and the released air must be freed from chlorinated hydrocarbons before release. Disposing of the used leach solution is also problematic. Other problems manifest themselves through the large swelling that the illuminated layers undergo during the leaching. The large swelling of layers causes damage to the photopolymerized structure, ie. breakage, release of small items, etc., as well as poor resistance to washing.

The use of alternative leaching agents such as aromatic and aliphatic hydrocarbons causes problems with combustion. These solvents exhibit flash points below 21 ° C and, as a result, must be used in explosion-proof systems. This also applies to the low molecular weight solvents from the ketone group.

5

Terpenoid hydrocarbons such as e.g. Although limons possess a sufficiently high flash point, their use as a washout solution is limited by their intense, often irritating odor.

10

The use of various oil fractions containing few aromatics and commercially available to induce photochemically crosslinked photoresists is known from US Patent No. 3,887,373. However, these photoresists are used to prepare semiconductor products, i.e. microchips.

Thus, US Patent No. 3,887,373 relates to a technical field far beyond the scope of the present invention, and does not give the person skilled in the art how to photopolymerize and use flexo printing forms.

It is therefore the object of the present invention to find a leaching agent whose flash point is significantly above room temperature and which only needs a little washout time for flexo printing plates, causes only a slight swelling of the flexo printing mold, and exhibits only a slight toxicity as well as a slight pleasant smell.

30

Surprisingly, it has been found that these properties can be met for leaching agents containing as hydrocarbon solvent certain hydrated oil fractions.

The object of the present invention is a process for the preparation of photopolymerization 35 3 DK 172001 B1 crosslinked flexo printing forms of the kind mentioned in the preamble of claim 1, which are peculiar to that of the characterizing part of claim 1. .

Hydrated oil fractions generally have an aromatic content according to DIN 51 378 which is less than 1%. It is preferred that such hydrated oil fractions exhibit a naphthenic proportion also determined by DIN 51 378 of between 0.5 and 50%.

10

Laundry detergents according to the invention may also contain additives of odor enhancing and / or surfactants.

15 Aromatic hydrocarbon solvents having an aromatic content greater than 10% are also suitable as leaching agents for pressure plates and resistors respectively, but they have a significantly lower OEL value and an unpleasant odor.

20

Pure paraffinic solvents such as e.g. synthetic isoparaffins, on the other hand, are hardly suitable for leaching of pressure plates and resists. The same goes for high-boiling n-paraffin blends.

25

Dearomatized hydrocarbon solvents with a boiling range above 230 eC are also not suitable as pressure leaching agents for pressure plates or resistors due to excessive wash-out times.

30

The preferred hydrated oil fractions in particular are those which, in addition to an aromatics content of less than 1% and a flash point greater than 45 eC, exhibit a boiling range of 170 to 220 ° C, especially 180-210 ° C, and a proportion of naphthenic hydrocarbons from 0.5 to 50%, especially from 10 to 40% (according to DIN 51 378).

4 DK 172001 B1

Examples of suitable hydrated oil fractions are ShellsolØD 60 from the company Shell and Exxsol®D 60 from the company Esso, which exhibit a boiling range of approx. 180 to 210 eC, a flash point of approx. 60 eC, an aromatic content of approx. 0.5%, as well as a content of naphthenic hydrocarbons from 30%. Furthermore, these products are virtually completely odorless and exhibit high OEL values (OEL = "occupational exposure limit").

Since flexo printing pads generally have a multilayer structure (about 3000 µm thick relief layers are frequently a thin about 5 µm thick polyamide coating), it may be advantageous to add an alcohol component to the hydrated oil fraction used in the invention.

15

As a suitable alcohol component, alcohols appear with a number of carbon atoms from 4 to 8 such as n-butanol, n-pentanol, iso-butanol, hexanol and others. In order to obtain a sufficient solubility of the polyamide coating, the proportion of the alcohol component must be at least 5% by volume, preferably 20% by volume. In the presence of alcohol, the flash point of the pure hydrocarbon solvent is lowered from 10 to 20 eC. The flash point of the formulated leaching solutions is therefore at approx. 40 ° C As a result, the wash-out solutions can be processed in appliances without explosion protection.

Furthermore, as already mentioned above, the leaching solutions may contain surfactants which accelerate the dissolution of non-illuminated materials and which contain proportions of odor enhancing substances.

Speaking as surfactants are, for example, alkyl sulfonates and their salts, alkylammonium salts or ethoxylated fatty alcohols, fatty alcohol ether sulfates and their salts as well as fatty alcohol phosphoric esters and their salts. The surfactant components can be added in the usual manner to the leach solution in an amount of 0-2% by weight.

Speaking as odor-enhancing additives, for example, the naturally occurring terpenoid compounds, limonene, pines, citronellol, etc., depending on the desired intensity of the aromatic odor, can be added to the leach solution in a proportion of 0 to a maximum of 10% by weight.

10

The development and leaching of the photo-illuminated photopolymer layers are dried in the usual manner in the known sprinkler, brush and rubbing washers at temperatures of 20 to 50 ° C. Thus, it has been found that the leaching time required for a specific leaching depth in the case of leaching solutions according to the invention is only substantially longer than in the case of conventional leaching agents, but that the absorption of solvent in the illuminated portions of the relief layer in the case of the leaching solution according to the invention is drastically reduced. Thereby, the resistance to overwashing of the structures produced by car-lighting is greatly improved, ie. also, when the washout times required for a certain relief height are exceeded, error-free structures can be obtained. This is primarily of importance for thin layers with thicknesses less than 0.7 mm, which are increasingly used in high-quality lattice flexo printing.

Also, the burst stability of the imagery-illuminated structures through the use of the hydrated oil fractions described in accordance with the invention above is greatly improved. This is particularly important for thick soft elastic pressure plates with high relief structures (approx. 3 mm), such as e.g. used in cardboard 35 and corrugated paper printing.

6 DK 172001 B1

A further surprising advantage of the leaching solution used according to the invention relates to the surface goodness of the image-illuminated and leached layers. Especially when leaching flexo printing plates with the usual flexo solvents, there is often an undesirable surface structure in the form of wrinkles (the so-called orange skin) which is not seen when leaching with solvents according to the invention exhibit a uniform smooth surface .

10

A further surprising advantage of using leaching solutions according to the invention is the fact that despite the high boiling ranges of the present hydrated oil fractions in comparison with leaching solutions with tetrachlorethylene, extended drying time after leaching is not necessary.

It is further advantageous that the leaching agent of the present invention can be used in non-explosion protected leaching apparatus. Due to the low odor of the hydrated oil fraction used according to the invention, the extraction of leaching apparatus can be greatly reduced. After completion, the flexo printing forms are odorless.

It is further advantageous that the leaching solutions of the invention can be successfully applied to numerous known cross-linked layers by photopolymerization.

Thus, e.g. short wash-out times for photopolymerizable layers containing as a binder block mix polymer isates of vinyl aromatic / alkadiene such as styrene-isoprene-styrene, styrene-butadiene-styrene, styrene-isoprene-styrene / butadiene, etc., as well as layers which binder contains copad polymerases of alkadiene / acrylonitrile such as butadiene-acrylonitrile, fluorine gums such as vinylidene, chloride-hexafluoropropylene copolymers, natural rubber, silicone polymers and polysulfide gums. Furthermore, short wash-out times are obtained for recording materials containing ethylene-propylene-diene terpolymer as a binder.

The advantages of the leaching agent according to the invention for flexo printing plates are illustrated in the following examples and comparative examples.

10

The crude layers used had the following composition (% by weight) 1. Plate Type 1 (One Layer Plate) 15 3-block of styrene / isoprene / styrene-butadiene 87.592% according to EP-A-27 612. Example 2

Paraffin oil 5%:

Hexanediol diacrylate 5% Benzyl dimethyl ketal 1.2% 2.6-di-tert-butyl-p-cresol 1.2%

Dye "Solvent Black" (C.I. 26,150) 0.008%

Layer thicknesses of 2700 µm were coated on a 125 µm thick polyethylene terephthalate film coated with a polyurethane adhesive coating.

2. Plate type 2 (multilayer plate) 3-block rubber as for plate type A 93.596%

Hexanediol diacrylate 5%

Benzildimethylketal 0.4% 2.6-di-tert.-butyl-p-cresol 1.0%

Dye "Solvent Black" (C.I. 26,150) 0.004%

700 µm layer thicknesses were coated on a 125 µm thick polyethylene terephthalate film coated with a polyurethane coating. As a support layer, a photo-crosslinkable layer was also used on the basis of an elastomer binder (thickness 2000 µm).

5 3. Plate type 3

Terpolymer of ethylene / propylene / ethylidene- 78% norbornene (proportions: 50% ethylene; 8 double bonds per 100 C atoms) 10 Dioctyl adipate 10%

Dihydrocyclopentadiene acrylate 6%

Isobornyl acrylate 4%

Benzild dimethyl ketal 2% Coat thicknesses of 2700 µm were coated on a 125 µm thick polyethylene terephthalate film coated with a polyurethane adhesive coating.

EXAMPLE 1 20

A flex plate (plate type 1) was prepared in the usual manner.

The flexo printing plate was then illuminated from the rear over its full surface in a fluorescent light illuminator within 65 seconds, after which it was illuminated incrementally imaged by illumination (illumination times per use of the negative from 6-20 min) and at room temperature for 5 minutes. a non-explosion-proof low air extraction brush washer 3 30 (about 10 m / h) was washed out. The washer contained a leach solution with 80 parts by volume of hydrated oil fraction (naphthen content 35%, boiling range from 180 to 217 eC) and 20 parts by volume of n-butanol.

35 To achieve a desired relief height of 700 µm, the optimum wash time was 6 minutes.

DK 172001 B1 9

Already at 6 minutes illumination time, all test elements of the obtained flexo printing form were completely and properly finished.

The flexo printing mold was dried for 2 hours at 65 ° C, lightly allowed to stand for 15 hours at room temperature, pulled through a usual after-treatment with an aqueous bromine solution, and dried again.

The flexo printing form, upon completion, exhibited a uniform smooth surface. No orange skin could be observed. After manufacture, the printing form was odorless.

The post-processed flexo print was clamped on a 15-cylinder in a flexo mill and provided excellent print results that in no way showed any loss of information relative to the original for the negative.

EXAMPLE 2 20

Using the same procedure as in Example 1, only n-pentanol (20 parts by volume) was added to the leach solution as alcohol components instead of n-butanol. The leaching test was again conducted in a non-explosion-protected brush extractor with low suction (about 10 m / h).

The optimal wash-out time was 6 minutes. All test elements were already fully and properly finished at an illumination time of 6 min 30. After the finishing, the flexo printing form again showed a uniform smooth surface, good printing properties and it was odorless.

Comparative Example 1

A procedure was used as in Example 1, only a mixture of 80 parts by volume of tetrachlorethylene and 20 parts by volume of η-butanol was used as a leach solution.

The leaching tests were conducted in a non-explosion protected but with strong air extraction (approx. 100 3 m / h) brushed washers.

The optimum wash-out time was 5 minutes. The test elements were first finished without error after an illumination time of more than 12 minutes. At shorter illumination times, outbursts were detected at the test elements, especially in the grid and raster fields.

After drying and finishing, the printing forms exhibited a uniformly textured surface (orange skin).

Comparative Example 2

The same procedure was used as in Example 1, 20 only a mixture of 80 parts by volume of gasoline (aromatics content 25%, boiling range from 187 to 216 ° C) and 20 parts by volume of n-butanol were used as the leach solution. The leaching experiments were carried out in a non-explosion-proof washer with heavy suction (approx.

25 m3 / h).

The optimum wash-out time was 5 minutes. The flexo printing forms possessed an unpleasant odor after their completion.

30

Comparative Example 3

The same procedure was used as in Example 1, only a mixture of 80 parts by volume of test gasoline (aromatics content 25%, boiling range of 155-185 ° C) and 20 parts by volume of n-butanol were used as a leach solution. The experiments were carried out in an explosion-proof washer 3 with strong suction (approx. 100 m / h).

The optimal wash-out time for a 700 µm relief was 6 min. The printing molds, after their preparation, had an unpleasant odor.

Comparative Example 4

Using the same procedure as in Example 1, 10 only a mixture of 80 parts by volume of hydrated mineral foil (boiling range from 220 to 255 ° C, naphthenic proportion of about 30%) and 20 parts by volume of n-butanol were used as the leaching agent. The experiments were conducted in a non-explosion-proof low-vacuum brush washer (approximately 10 15 m3 / h).

The washout time for a 700 wm thick relief was 17 min. EXAMPLE 3 20

Using the same procedure as in Example 2, only a multilayer plate type 2 with a predetermined relief height of 700 μΐη was used instead of a plate type 1. The experiments were conducted in a non-explosion-protected, low-suction wash (approximately 10). m / h).

The optimal wash-out time was 6 minutes. At a 100% wash, ie at a total wash-out time of 12 minutes, no damage to the relief structure could be observed or sample elements found to be defective. The flexo printing forms were odorless.

Comparative Example 5 35 The same procedure was used as in Example 3, but only one wash solution of 80 parts by volume of tetrachlorethylene and 20 parts by volume of n-butanol was used.

The experiments were conducted in a non-explosion-protected 3 washer with strong suction (approx. 100 m / h).

The optimum wash-out time was 5 minutes. A 100% over-5 wash was now noticed by errors in critical test elements (freestanding points and lines) and in bursts in raster fields and grids.

EXAMPLE 4 10

For a plate type 1 flexo pressure made of plate type 1, the drying process was measured in a ventilated drying cabinet at 65 eC as a function of time.

15 Immediately after the leaching, the weight swelling was 2%.

After a drying time of 2 hours at 65 ° C, the weight swelling had returned to -0.1% of the starting weight. After a drying time of 24 hours, the extracted proportion examined amounted to 0.3% of the starting weight.

20

Comparative Example 6

The same procedure was used as in Example 4, only a mixture of 80 parts by volume of tetrachloroethyl and 20 parts by volume of n-butanol was used as a leaching solvent.

Immediately after leaching, the weight swelling was 8%.

However, after a drying time of 2 hours, the weight swelling had also fallen back to -0.1%, however, the extracted proportion was 1.7% of the starting weight.

EXAMPLE 5 35 As flexo printing plate, plate type 3 was used. After pre-illumination from the rear, the flexo printing plate was illuminated from the front through a test negative (illumination time 13 DK 172001 B1 20 min) and subsequently developed in a flex brush printing machine. As a leach solution, a mixture of 80 parts by volume of hydrated oil fraction (naphthenic content 35%, paraffin content 65%, boiling range from 186 to 217 ° C, aromatic content less than 1% according to DIN 51 378) was used and 20 parts by volume of n-butanol.

The optimum wash time for a relief height of 700 µm was 12 minutes. All test elements were properly finished-formed and no objections could be raised against any of them. After a post-treatment, flexo printing molds were obtained which exhibited a uniform smooth surface.

Comparative Example 7 15

A procedure was used as in Example 5, only a mixture of 80 parts by volume of tetrachlorethylene and 20 parts by volume of n-butanol was used as a leaching agent.

20 for a relief height of 700 μπι optimal wash time was again 12 min. Outbreaks were detected at the edge and in the raster fields. After finishing, flexo printing forms were obtained which exhibited a disjointly damaged surface.

EXAMPLE 6

The same procedure as in Example 1 was used, only a mixture of 75 parts by volume of hydrated oil fraction (boiling range from 160 to 195 ° C, naphthene content 35%), 20 parts by volume of n-butanol and 5 parts by volume of limonene was used as leaching solution.

The leaching experiments were carried out in a non-explosion-proof, low suction brush washer (approx. 10 m / h).

The optimal wash-out time for an approx. 700 µm thick relief lasted 5 min. The flexo print forms showed a pleasant orange-like smell.

Claims (5)

A method of preparing photopolymerization crosslinked flexo printing forms by photopolymerization crosslinkable layers are illuminated imaged with active light during crosslinking of the illuminated layer portions and leaching of the non-crosslinked portions of the hydrocarbon solvent layers or with mixtures of hydrocarbon solvent and alcohols, characterized in that the cross-linking layers as a binder contain block-mix polymers of vinyl aromatic / alkadiene, copolymers of alkadiene / acrylonitrile and / or ethylene-polypropylene-diene polymer and for the leaching 15 as the hydrocarbon solvent, hydrated oil fractions exhibiting a flash point greater than 45 ° C and a boiling range between 160 and 220 ° C are used. Process according to claim 1, characterized in that the hydrated oil fraction exhibits an aromatic content less than 1% according to DIN 51 378. Process according to claim 1 or 2, characterized in that the hydrated oil fraction exhibits a naphthenic proportion between 0.5 and 50% according to DIN 51 378. Process according to any one of the preceding claims, characterized in that the hydrated oil fraction contains an addition of an odor-enhancing substance. Process according to any one of the preceding claims, characterized in that the hydrated oil fraction contains an addition of a surfactant. DK 172001 B1 It is hereby declared that this description and claims correspond to the original description of claims PCT / EP89 / 00478 with replacement pages 1, 1a, 2, 4, 6, 7, 8, 9, 10 and 11, with the exception of claim 1 is bounded to crosslinkable layers containing as a binder block vinyl aromatics / alkadiene block copolymers, alkadiene / acrylonitrile copolymers and / or ethylene-propylene-diene terre polymers based on the original description page 5 , lines 5-13. 10 20 25 30 35