DE1470932C - Photopolymerizable mass - Google Patents

Description

Photopolymer printing plates are now increasingly used in the printing industry. you will be obtained by a material comprising a photosensitive, a polymerizable monomer and having a suitable photoinitiator for the polymerization-containing layer, exposed imagewise. Under the influence of actinic light, the photoinitiator is activated so that it initiates the polymerization of the monomer induced. In this way, polymerized and non-polymerized material will be polymerized in the exposed material Areas in an image-wise distribution corresponding to the light and dark areas of the for Exposure pattern used. By treatment with a suitable solvent that the unpolymerized material in the unexposed areas, but not the polymer in the exposed areas Dissolves image areas, then relief printing plates are obtained.

For use in printing presses you need photopolymer printing plates with a relief image, its raised areas after the application of printing ink against a suitable surface, e.g. B. a sheet of paper, can be printed to obtain an imprint. These photopolymer printing plates have a very high quality standard achieved. Recorded materials and photopolymerizable elements therefor Purpose are the subject of U.S. patents 2,760,863, 2,791,504, 2,927,022, 2,927,023, 2,902,365, 2,948,611 and 2,972,540. The preferred compositions contain a polymerizable monomer, a Photoinitiator and an organic, polymeric binder or filler, preferably a mixed cellulose ester such as cellulose acetate hydrogen succinate. The manufacture of such masses is the subject of the USA patents 2 923 673 and 3 012 952.

A convenient method for making photopolymerizable elements in which masses according to the mentioned patents are used, is to apply the material at elevated temperatures To calender films of uniform thickness. A suitable film is then covered with this film Layer carrier, for example one made of steel, aluminum, plastic, cardboard, etc. The The mass can also be calendered directly onto the substrate.

In order to be able to work properly in the calender, the mass must be sufficient at an elevated temperature Possess plasticity. Materials with a low degree of plasticity tend to get stuck in the nip of the Calender to form a non-cohesive crumbly mass instead of a homogeneous mass. Such friable masses provide inadequate films, imperfections and areas of mismatch Have thickness.

Another, in calendering photopolymer films Occurring error is in the presence of small, shallow surface depressions or »hollows« see. These latter phenomena are related to the tearing off of the outer layer of the Mass or the mixture comb or bead formed by the photopolymerizable material, which is under constant tension and continuously due to the nature of the polymer flow at the nip of the calender is stretched. Are the polymer beads in a smooth form and free of tears before, so no hollows can occur.

The invention is based on the object of eliminating these difficulties arising during calendering.

switch on and provide a photopolymerizable mass available that delivers flawless films. The invention relates to a photopolymerizable composition consisting of

a) 10 to 60 parts by weight of an addition polymerizable monomers with at least one terminal ethylenic _(CH2 = Cc) group and one lying above 100 ⁰ C boiling point at atmospheric pressure, which is capable initiated 'via free radical, is a chain-like propagating addition polymerization of a high polymer to form with a molecular weight up to 1500,

b) 40 to 90 parts by weight of cellulose acetate hydrogen succinate,

c) aliphatic carboxylic acids,

d) a polymerization exciter for addition polymerization,

e) an inhibitor for thermal addition polymerization.

It is characteristic that as component (c) 0.1 to 10 parts by weight of maleic acid, glycolic acid, lactic acid, Citric acid or glutaric acid are present. According to one embodiment of the invention is the aliphatic carboxylic acid corresponding to (c) glutaric acid.

The calendering is carried out by verfonnt the photopolymerizable composition according to a) to e) into a web and these calendered at temperatures between 70 and about 12O ⁰ C.

One can the photopolymerizable compositions of the invention by simply mixing together the Manufacture individual components. A method of operation in accordance with the USA patents has proven particularly useful 3 012 952 and 2 923 673, according to which the introduction of the succinic acid residue by implementation of cellulose acetate with succinic anhydride in the melt and in the presence of an esterification catalyst, a monomeric compound, a photoinitiator and an inhibitor for thermal polymerization takes place. You add the organic acids of the photopolymerizable composition to be incorporated according to the invention are expediently am End of the reaction with succinic anhydride and before the mass is calendered to one Foil or a layer is deformed to. You can ■ the desired amount of organic acid accordingly c) add in this embodiment, while the mass in a suitable grinding device 5 to Milled for 10 minutes at 85 to 150 ° C. It is also possible to add the organic acid during or at the beginning of the reaction with succinic anhydride. Although free succinic acid has a plasticizing effect on the photopolymerizable mass, it is only sparingly soluble in the plastic mass and tends to become photopolymerizable when the finished product is stored Crystallize plate. This is due to the formation of a fog on the plate surface recognize. Other acids have an effect on the between metallic substrate and photopolymerizable Layer lying adhesive layer in the opposite sense from or diffuse through the adhesive layer through and attack the metallic substrate. Still other acids cause instantaneous Polymerization of the mass. On the other hand, these disadvantages occur when those listed under c) are incorporated Acids, their use also provides

Further advantages over the other acids mentioned including sulfuric acid, or acetic acid Oxalic acid.

. The polymerization exciter, which can be activated by actinic light and below 185 ° C thermally is inactive, is preferably used in amounts of 0.001 to 10 parts by weight, based on the mass itself. Preferred pathogens are described in U.S. Patent 2,951,758.

As a thermal polymerization inhibitor is p-Methöxyphenyl has proven particularly useful in the intended amounts of from 0.001 ° to 6 ° / _0, based on the weight of the ethylenically unsaturated compound present.

Other suitable inhibitors are: hydroquinone and alkyl- and aryl-substituted hydroquinones, tert. Butyl catechol, pyrogallol, copper resinate, naphthylamine, ^ -Naphthol, copper (I) chloride, 2,6-di-tert-butyl-p-cresol, Phenothiazine, pyridine, nitrobenzene and dinitrobenzene. Other useful inhibitors: p-Toiuchinon and Chloranil.

Diethylcyclohexylamine has proven particularly useful as an esterification catalyst in the reaction with succinic acid proven. Other esterification catalysts, in amounts up to 20%, based on the weight of the Reaction partners that can be added are described in US Pat. No. 3,012,952: pyridine, Triethylamine, tributylamine, triamyiamine, trimethylamine acetate and pyridine acetate. In addition, inorganic Catalysts are used such as sodium carbonate, sodium phosphate, sodium borate, Sodium acetate, lithium acetate, calcium acetate, potassium acetate, magnesium acetate and potassium carbonate.

The invention is important for the production of photosensitive addition-polymerizable compositions, which are particularly suitable for the production of photopolymerizable Printing materials, for example printed reliefs, are suitable, as described in the USA patent 2,760,863.

The compositions according to the invention can also be used in elements for thermal transfer printing processes U.S. Patents 3,060,025, 3,060,024 and 3,060,023 as well as the Belgian patent Use 626 525. They can also be used to make phosphors stick to surfaces to raise and thereby. Produce screens for color television and diagrams for printed Manufacture circuits.

The photopolymerizable compositions of the invention show improved behavior in the calendering process and provide photopolymerizable printing plates with excellent surface properties. on in this way, in turn, prints of high quality can be achieved with these printing plates.

The following examples illustrate the invention. Unless otherwise stated, all are Quantities, weights.

Example L

According to the US Pat. No. 3,012,952, a photopolymerizable composition was made up of the following Components manufactured:

Cellulose acetate 2400 g

Polyethylene glycol diacrylate 1680 g

Succinic anhydride 910 g

'p-methoxyphenol 6.72 g

2-ethyl anthraquinone 6.72 g

The degree of acetyl substitution of the cellulose acetate was 1.85, the acetate was in a finely powdered form so that the particles could pass through a 0.25 mm sieve Openings went through. The polyethylene glycol diacrylate was made from a diol forerun with a average molecular weight of 300 obtained.

The ingredients were mixed thoroughly in a planetary mixer for 5 minutes and then one

ίο 2-roller rubber mill supplied (length of the rollers: 50.8 cm, roller diameter: 25.4 cm). The rollers had been preheated ^{to 135 ° C. with steam.}

The mixture was worked through for 10 minutes at a roll temperature of 135 ° C to drive out all moisture and obtain a uniform mass.

Then 160 cm ^{3 of} diethylcyclohexylamine were added with further milling. The meal

ao process was continued for a further 15 minutes then, during which time the reaction proceeded with succinic anhydride and the temperature of the mass rose to 140 to 15O ⁰ C. In a small sample now taken, the degree of substitution of succinic acid for the cellulose acetate was determined in accordance with Example 1 of US Pat. No. 3,012,952, a value of 0.81 being found.

At the end of the reaction time of 15 minutes, 160 g of dry glutaric acid were added to the reaction product, which was still in the mill, and it was ground for a further 5 minutes. The photopolymerizable mass present at the end was then removed from the mill and fed to a 4-roll L-calender, in which the four calender rolls were arranged like an upside-down L (length of the calender rolls: 40.64 cm, diameter: 20, 32 cm). The rollers were kept at temperatures of 105 to 110 ^° C., and calendering was carried out at a speed of 1.83 m / minute. A 0.38 mm thick film was molded and coated with a 0.30 mm thick layer support made of steel which was coated with an adhesive. The coating was carried out by rolling under pressure at room temperature, followed by curing in an oven at about 120 ⁰ C. The composition of the adhesive is described in Example 5 of US Pat. No. 3,036,913. The physical properties of the photopolymerizable composition were found to be excellent during the calendering process. The bead rotated freely and the calendered film showed no surface defects or pits.

The coated photopolymerizable material was placed in a vacuum frame and the polymer surface was brought into contact with a photographic negative comprising lines and halftone areas. The evacuated vacuum frame containing plate and negative was placed under a 1800 watt high pressure mercury vapor lamp and exposed ^{to actinic light of 0.272 watt / cm 2 for 14 seconds.} After exposure, the negative was stripped from the plate and the unexposed areas of the plate were removed by spray washing for 5 minutes with a 0.04 η aqueous NaOH solution. A clear relief image that adhered firmly to the substrate and corresponded to the clear areas of the negative was obtained. The printing plate produced in this way had excellent image quality and, when printed using

flat printing presses have a long service life.

A comparison plate manufactured using the same process, in which the same ingredients are used with the exception of the incorporated glutaric acid showed surface defects. In the calender, the bead did not rotate freely, and the resulting one Polymer film had many small surface depressions or depressions. After exposure and washing out a printing plate with an equally good service life was obtained, but its surface defects Imperfection in the image reproduction.

The procedure described was repeated, but using the glutaric acid present at the beginning Mixture was added before the start of the reaction with succinic anhydride. The results were similar.

Example 2

Example 1 was repeated, but instead of glutaric acid, the same amounts of dry glycolic acid incorporated. Similar favorable physical properties were observed, and those on the basis Printing plates made from these masses were of very good quality.

The procedure of Example 1 was repeated again, but the glycolic acid before the start of Reaction with succinic acid added to the reaction mixture. Similar results were obtained receive.

Example 3

Two photopolymerizable masses were prepared, one of which, exactly as described in Example 1, with a content of 3% glutaric acid and the other was made with the same amount of succinic acid. Both mixtures passed Calendering processes excellently and did not result in any surface defects when coated on substrates. After 3 weeks of storage, the plate containing succinic acid showed on the surface however, a fitting consisting of crystallized succinic acid. The one containing glutaric acid The plate still showed no fogging after 4 months of storage.

Example 4

layered photopolymerizable plates have good surface properties. After 4 months of storage, no fogging had formed, and flawless relief printing plates could also be produced.
5

Example 5

Two milling batches of 22.7 kg each were prepared according to Example 1 while maintaining the proportions, but no acid was added. The mixing took place in a cylindrical double mixer with a capacity of 141 l. The mixture contained 1.18 ° / ₀ during the grinding succinic acid formed. From this mixture, 5 batches of 9.1 kg were made, each containing 9.1 kg of the mixture and 54 g of one of the following acids:

Glutaric acid,
Adipic acid,
Maleic acid,
Citric acid.

The acids were uniformly dispersed in each mixture by 15 minutes grinding of the mass at 130 ⁰ C by means of a 25.4 / 50.8-cm rubber mill.

Each of the blends was then granulated and the granules fed to a 61/137 cm calender fed, the rollers of which were kept at 90 ° C. A 1.1 mm thick sheet was formed and 2.6 mm thick aluminum substrate coated with an adhesive at room temperature combined. All five masses could be processed perfectly by calendering in the same way and delivered trough-free films.

35

40

45

As in Example 1, three polymerizable compositions were prepared, but glutaric acid replaced by the following organic acids:

1. 2.5% maleic acid,

2. 3,3 ° / ₀ citric acid,

3. 3,3 ° / ₀ lactic acid.

The three masses could easily be ground and processed in calenders. They also have

55

Claims (1)

Claim: Photopolymerizable composition consisting of a) 10 to 60 parts by weight of an addition polymerizable monomer with at least one terminal ethylenic (CH ₂ = C =:) group and a boiling point above 100 ° C at normal pressure, which is capable of chain-based addition polymerization initiated by free radicals To form high polymers with a molecular weight of up to 1500, b) 40 to 90 parts by weight of cellulose acetate hydrogen succinate, c) aliphatic carboxylic acids, d) a polymerization exciter for addition polymerization, e) an inhibitor for thermal addition polymerization, characterized in that as component (c) 0.1 to 10 parts by weight of maleic acid, Glycolic acid, lactic acid, citric acid, or glutaric acid are present.