DE2623801A1 - Laminated relief printing plate - comprises a photosensitive styrene-isoprene block copolymer initiator and monomer, stabilising and support layers - Google Patents

Abstract

Laminated plate for the prepn. of relief printing plates, as described in the parent patent, comprises a layer (I) of photoinitiator and opt. other conventional additives in a developer soluble photocrosslinkable compsn. (II), an underlayer (III) of a developer insoluble, non-photocrosslinkable elastomer having a Shore A hardness of 15-70 and a developer insoluble, non-photocrosslinkable stabilising layer (IV). In this addition (II) comprises >=1 soluble diblock copolymer (V) and >=1 photocrosslinkable unsatd. monomer. (V) comprises 75-85 wt. % 4-6C diene units of which >50 wt. % are isoprene units and 15-25 wt. % styrene units and has a viscosity of 150-250 ml/g (measured as a 5 wt. % soln. in toluene at 25 degrees C). The copolymer shows a sharp transition between the polystyrene segment and the polyisoprene segment and contains 4 wt. % homopolymer. (V) Can be easily synthesised in two steps, has good solvent and melt processability and can be cast or extruded to low tolerances of thickness.

Description

Multi-layer composite panels for the production of flexographic printing plates The subject of the main patent OO O0 eoo (patent application P 24 56 439off4) are multilayer composite panels for the production of relief printing forms which have a) a layer RS Basis of a photoinitiator and possibly a mixture of al) containing customary additives at least one soluble two-block copolymer P from 30 to 95% by weight of a diene hydrocarbon and 5 to 70% by weight of a monomer CH2 = CRR ', where R = H or CH3, R' = optionally

alkyl substituted phenyl, with a viscosity number from 60 to 350 ml / g or a partial hydrogenation product thereof and a2) one with the Monomers M compatible with polymers P with at least one photocrosslinkable C-C double bond, b) a non-photocrosslinkable and in the developer solvent for the layer RS non-soluble elastomeric sub-layer U with a hardness of 15 to 70 Shore A and c) a non-crosslinkable and insoluble in the developer solvent for the layer RS Stabilization layer ST.

In a further development of the invention of the main patent it has now been found that printing forms that are particularly stable and have high elasticity and good resistance against in particular ester-containing printing ink solvents are obtained if in the multilayer composite panels of the main patent as a two-block copolymer P is a two-lock copolymer of 75-85 weight units of a diene hydrocarbon with 4 = 6 carbon atoms with a proportion of more than 50% by weight of isoprene units and 15-25 GewO; Styrene units that have a viscosity number of 150-250 ml / g (measured at 250C as a 0.5 GewO5Sige solution in toluene) # a sharply separated transition between the polystyrene segment and the polydiene # segment and a homopolymer content of less than 4 wt> S. The present invention relates to multi-layer composites Plates according to claim 1 You have compared to multilayer composite plates with styrene = IsoX pren-styrene or styrene-butadiene-styrene triblock copolymers as elastomers in Some advantages of the photopolymerizable layer This is how it is made of diblock copolymers in just two synthesis it is easier to classify an advantage of Two lock copolymers are also better processability from the melt or highly concentrated solution, since they are not like the triblock copolymers Have restoring forces due to the physical networking. The diblock copolymers can thus be smoothly formed into layers with only very small thickness tolerances Pour the solution or extrude it from the melt. Surprisingly, the according to the invention in the layers RS contained two-block copolymers a higher dynamic elasticity (measured as impact elasticity according to DIN 43512) as the corresponding Commercially available styrene-isoprene-styrene triblock copolymers, although per se because of In the absence of physical crosslinking, the two-block copolymers have a high level of tack and plasticity would have been expected. Your compliance against compression deformation is greater than that of the three-block copolymers mentioned. The layer strength of the multilayer composite panels according to the invention is high enough that they are not difficult stored, shipped and handled can be, you surrender to Exposure and development of particularly high-quality relief printing forms with good Elasticity and very good resistance to printing ink solvents containing esters.

The production of styrene-diene two-block copolymers is known per se and, for example, in U.S. Patent 3,149,182. For making the invention diblock copolymers used is expediently with the polymerization of the Styrene started, after its termination the isoprene as a sharply separated second Polymer block is polymerized with this sequence he maintains a narrow molecular weight and composition distribution since the copolymerization step is very rapid. The styrene unit content of the diblock copolymers is 15-25 and in particular 18-22% by weight, the content of diene units 75-85 and in particular 78-82% by weight, X, where more than 50 and preferably 70-100% of the diene component is formed from isoprene other diene hydrocarbons with 4-6 C atoms that can be used in a mixture with isoprene Above all butadiene should be mentioned The range of the molecular weight (viscosity average the molecular weight: Mv) should preferably be between about 150,000 and 270,000. Its viscosity number, measured as a 0.5 weight, gige solder in toluene, is 250 cm correspondingly in the range of 150-250 and in particular 170-220 ml / g.

The diblock copolymers are expediently prepared by Solution polymerization in cycloaliphatic hydrocarbons such as cyclohexane or Mixtures of cycloaliphatic and aliphatic hydrocarbons. Of special The advantage is the solutions of the block copolymers produced by solution polymerization directly or concentrated - after adding the other layer components - to the To use the photocrosslinkable layer RS by potting. Using Cyclohexane is recommended as a solvent in the preparation of the copolymers the use of sec -butyllithium as an initiator since he the styrene polymerization starts quickly and is fully implemented.

About the formation of homopolystyrene or homopolyisoprene proportions to avoid, the anionic polymerization should start from starting materials which are largely free of proton-active compounds. The in the invention Multi-layer composite panels should contain two-block copolymers in the layer RS each have a homopolymer content of less than 4% by weight. Very suitable Mixtures of polymers P with monomers M for the photocrosslinkable layer RS contain 70 to 95 and in particular 80 to 95 Ges0% of polymers P and 5 to 30 and in particular 5 to 20 Ges .; of monomers M. As monomers largely compatible with the polymer P M with at least one photocrosslinkable or photopolymerizable C-C double bond the esters of acrylic acid and / or methacrylic acid with mono- or may be mentioned in particular polyhydric alcohols such as n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate and methacrylate, 1,6-hexanediol diacrylate and dimethacrylate, 1,1, 1-trimethylolpropane triacrylate, Pentaerythritol tetraacrylate, diethylene glycol diacrylate and methacrylate, lauryl acrylate, Hydroxypropyl acrylate etc, N-vinyl compounds such as N-vinylpyrrolidone are also suitable, Vinyl esters of aliphatic monocarboxylic acids such as vinyl oleate, vinyl ethers of diols such as 1,4-butanediol-1, 4-diviny ethers, as well as allyl ethers and allyl esters, the same applies for the reaction products of di- or polyepoxides, such as 1,4-butanediol diglycidyl ether or bisphenol A dig # yc idyl ether with (meth) acrylic acid, provided that they are sufficiently compatible with the polymer P are a mixture of acrylic acid and methacrylic acid derivatives is to improve the elastic values, the elongation at break values of the relief printing forms as well as the adhesive connection between the layers RS and ST are particularly advantageous In general, by suitable choice of the monomers or mixtures of them, the Properties of the photopolymerizable layers RS modified for the special purpose will The layer RS also usually contains a photoinitiator, generally in an amount of 0.01 to 10 and in particular 0.01 to 5 gels, such as benzoin or benzoin derivatives, zOBo benzoin methyl or isopropyl ether Layer RS can also contain other customary additives, such as inhibitors thermal polymerization, such as p-methoxyphenol, hydroquinone, N nitroso compounds, Dyes, photochromic substances, antioxidants or plasticizers (for better Processability of the mixture of the layer).

The thickness of the layer RS is expediently 200 to 3000 μm and in particular 300 to 2000 μm. Preferred layers RS show after the photo-crosslinking by total exposure to actinic light a hardness of 30 to 90 and in particular 40 to 70 Shore A and are equally hard or harder in the photo-crosslinked state than the related lower class U.

The photocrosslinkable layers RS are particularly advantageous their solutions in suitable solvents such as cyclohexane, toluene, xylene or tetrahydrofuran, produced by casting the stabilization layer ST as well as the sub-layer U as well as one as below specified in more detail - with the coating layer S provided protective film are used. If necessary A permanent connection can be achieved by means of suitable pressure-sensitive adhesives or intermediate adhesive layers of layers can be achieved.

It is often advantageous for the multilayer composite panels on which photocrosslinkable layer RS also has a firmly bonded, thin, non-stick coating layer S to be applied, which is preferably made of a hard, tack-free, transparent and tear-resistant Film-forming polymers such as a polyamide soluble in the developer solvent or copolyamide or from a mixture of such a polymer with a low Amount (not more than 10 percent by weight) of a photopolymerizable monomer as well as photo initiator and optionally inhibitor consists of the strength this coating layer S is expediently about 0.5 to 20 μm through Coating layer S is a negative overlay in the production of relief printing plates from the multi-layer composite panels without the risk of air bubble inclusions and impressions possible without any problems if the imagewise exposure is carried out using commercially available Exposure devices is made in which with the help of a slight negative pressure a vacuum film presses the negative onto the plate to be exposed during development of the exposed portions of the layer RS to the relief layer is generally the Coating layer S washed away together with the uncrosslinked parts of the layer.

It is also often advantageous, the coating layer S with a to provide removable protective film such as a polyester film, these also together with the coating layer S can be applied to the layer RS The protective film is generally peeled off before the imagewise exposure of the layer RS, while In general, the coating layer S remains on the layer RS.

The elastomeric lower layer U has a hardness of 15 to 70 Shore A. and preferably from 25 to 60 Shore A and is generally 0.5 to 6 mm and in particular about 1 to 4 mm thick. The hardness of the sub-layer U is in the preferred embodiment of the multilayer composite panels equal to or lower than the hardness of the layer RS in the photo-networked state.

Suitable elastomeric materials for the backsheet U are e.g.

Natural rubber, polybutadienes, butadiene-aeryl nitrile copolymers, butadiene-styrene copolymers, Silicone rubber, polysulphide rubber, vinyl chloride chloride, hexafluoropropylene copo lpolymer, isoprene-styrene and butadiene-styrene block copolymers and in particular Polyurethane elastomers, which are made in a known manner from higher molecular weight polyhydroxyl compounds, like polyesters or polyethers, optionally low molecular weight Polyols and polyisocyanates, especially diisocyanates, can be obtained, Reference is made, for example, to the information in the book Saunders-Frisch Polyurethanes, Part II, Chapter IX, Interscience Publishers Inch, New York, 1964o The materials for the layer U should expediently be processable into low-tolerance layers, z. B. by casting and hardening in molds or heatable centrifuges or in the case thermoplastic materials e.g. by calendering. Preferably layers and methods as given in DT-OS 22 59 360 are used. The carrier layer can also be made of the same material as the layer RS, if this processed to the required dry film thickness and then by total exposure has been photocrosslinked. It is also possible, the layer U made of foam-like To produce materials or to use foams for them, provided that they meet the requirements have suitable elasticity and they do not have a sponge effect (absorbent effect) the inks or developing solvents exercise. The materials are preferred of layer U in the developer solvents used for layer P are not or only sparingly soluble.

The stabilization layer ST should ensure perfect dimensional stability ensure the plate and warping of the pressure plate during assembly prevent the printing cylinder, so that a precise work with multi-color printing is possible.

The layer ST can here in the layer sequence RS-U-ST under the elastomeric lower layer U lie, in the preferred embodiment of the invention Multi-layer panels, however, the stabilization layer ST is firmly adhered between the photopolymerizable layer RS and the elastomeric sub-layer U arranged. This embodiment has the additional advantage that the sub-layer U during the wet development of the relief not exposed to the action of the washout agent is and thus a swelling of the layer U and the need for a subsequent one prolonged drying is avoided. In the preferred position of the layer ST, it has generally a strength of about 5 to 500 and especially from 50 to 125 / umO The hardness of the stabilization layer ST should be compared to the other layers be significantly higher, it expediently has a modulus of elasticity (measured according to DIN 53 457) from 1 x 103 to 2.1 x 106 and preferably from 5 x 10³ to 2s1 x 106 Kp / cm. As materials for the stabilization layer ST, for example. Plastic films, metal layers or cross-linked lacquer layers that also go through Fabrics such as fiberglass fabrics or textile fabrics can be reinforced, serve. Preferred Plastic films such as polyester films are used. The layers U, ST and RS or the relief layer are firmly bonded to one another when using suitable and in particular chemically structured polymer materials is such a firmly adhering one Connection z, B. by lamination under the action of suitable, the layers dissolving organic solvents easily accessible, however, it is often necessary to a firm connection between the respective layers by one or both sides Application of thin layers of adhesion promoters or adhesives and firm bonding of the layers, which then creates thin layers of adhesive between the layers arise that are, however, less than 100 μm and preferably less than 30 μm thick Commercially available one- and two-component adhesives can be used for the adhesive layers are used, the type of which depends on the type of the layers U, ST as well as RS used materials or types of polymer aligns. As an often suitable adhesive are the commercially available reactive adhesives based on polyurethane and polychloroprene called, by substrateing or pouring in a suitable layer thickness to the connecting layers can be applied, in some cases it has in the arrangement of the layer ST between the layers RS and U, if the elastomeric lower layer U on the side facing away from the layer ST a 0.1 to 20 and in particular 0.2 to 10 / µm thick coating layer S 'based on a non-tacky polymers0 Often the same polymers are suitable for this purpose, as they can be used for the production of the coating layer S, too the coating layer S 'should preferably be permeable to actinic light.

The multilayer boards according to the invention can be per se known way by imagewise exposure of the layer RS and subsequent removal, in particular washing out the unexposed or uncrosslinked portions of the layer Process RS to relief printing forms, especially for flexographic printing Exposure, which can take the form of a flat exposure or circular exposure, the usual light sources of actinic light are suitable as commercially available UV fluorescent tubes or high pressure mercury lamps O The emitted wavelength should preferably be at 300 to 400 mXu or on the self-absorption of the in the Layer RS contained photoinitiator be matched examples of suitable developer solvents for washing out the uncrosslinked parts of the RS layer for relief development are chlorinated hydrocarbons such as trichloroethane, sym, tetrachloroethane, tetrachlorethylene, Hydrocarbons such as hexane, toluene or other organic solvents such as N-methylpyrrolidone or mixtures of such solvents with lower alcohols to control the washout effect.

The parts and percentages given in the examples below relate unless otherwise stated, based on weight.

Parts by volume relate to parts like liters to kilograms, for example 1 a. In a 10,000 volume pressure autoclave with a stirrer are under inert gas 5,200 parts by volume of cyclohexane, which is proton-active by distillation over butyllithium Impurities was freed, and submitted 317 parts by volume of styrene unstabilized. At 30 ° C, 0.1 molar sec-butyllithium solution is used until it remains weak Yellow color titrated to the end. Then 85 parts by volume of L = g are added as initiator. The solution is heated to 45 ° C. and kept at this temperature for 1 hour. Thereafter a sample is drained for analytical purposes. The conversion is approx. 98%, the viscosity number (0.5 # in toluene at 250C) is 21 (corresponds to Mv = 35 000).

1,880 parts by volume of isoprene are added to the living polystyrene solution, which is freed from stabilizer by distillation and over a with aluminum oxide The filled column was dried. It is kept at approx. 70 = 80 ° C. until the isoprene polymerization after about 1 hour the conversion is 100%. The end point can also be optical can be determined by the deepening of the color from almost colorless to yellow-orange Solution of the living diblock copolymer is released under protective gas, with a few Drops of isopropanol are added and 0.25 (based on the solid substance) 2,6-Ditert .-Butyl-4-methyl-phenol stabilized Analysis of the end product: 18% styrene 82% Isoprene viscosity number 189 ml / g content of homopolystyrene: 1.8% The product is in the form of a 3 mm thick pressed plate, crystal clear.

b. From 210 parts of the two-block copolymer prepared according to a), 0.12 parts of 2,6-di-tert, butyl-4-methyl-phenol and 540 parts of toluene are added at approx 80 ° C produced a clear solution, to which 30 parts of benzoin isopropyl ether, 25 parts 1,6-hexanediol diacrylate, 12.5 parts lauryl acrylate and 0.05 part dye solvent Black 34 (such as 12195) dissolved in a methanol-toluene mixture can be added After homogenization, the solution is concentrated to a 45% solution in vacuo and on a 12.5 μm thick polyethylene terephthalate film (protective film) in layers poured on the previously with a 5 μm thin layer of an alcohol-soluble polyamide (Layer S) had been provided, After evaporation of the solvent, the unexposed Layer RS with the free layer side using a commercially available two-component polyurethane adhesive varnish of 20 #um thickness on a transparent polyethylene terephthalate film of 50 #um thickness applied, the other side by means of a similar adhesive varnish is connected to a 2 mm thick elastomeric sub-layer U, which consists of a polyester glycol Toluylene diisocyanate and activator had been formed and cured at 130 0C The lower layer U has a hardness of 32 Shore A and a rebound resilience of 45%.

c. The protective film is used to produce a print-ready printing form peeled off, the polyamide film due to better adhesion on the unexposed Relief layer RS remains and thus a non-sticky, bubble-free application of a negative allows for imagewise or grid-shaped exposure, after 40 seconds permanent rear full-surface pre-exposure of the relief layer RS by the Through the lower layer U (lower layer U facing the light source) became the relief layer RS image-wise through a negative original (with writing and halftone) about 15 minutes exposed, In a spray washer, the relief was then with a mixture of trichlorethylene and isopropanol (70:30 by volume) developed for 5 minutes. After a short drying time at 90 ° C. and post-exposure over the entire area for 10 minutes, the relief layer side became treated the printing form for a few minutes with acidified sodium hypochlorite solution, The relief printing form obtained shows very good reproduction of everything in the original contained image elements and perfect printing behavior.

Example 2 a. The two-block copolymer is produced up to at the end of the styrene polymerization according to the information in Example la. The viscosity number of the polystyrene is 22 ml / g (corresponds to Mv = 38,000) o The temperature of the solution of the living polystyrene is increased to 70 ° C. and 1,880 parts by volume become isoprene metered in over 45 minutes via a pressure vessel with a level indicator. By cooling will be an increase the temperature of the solution to over 900C prevented0 The end product has a homopolystyrene content of 0.7% and a viscosity number of 185 ml / g (measured as a 0.5% solution in toluene at 250C), the end product is crystal clear in a 15 mm thick layer.

b. Analogously to that given in Example Ib, 168 parts of the according to diblock copolymers produced in the preceding paragraph, 20 parts of 1,6-hexanediol diacrylate, 10 parts of 1,6-hexanediol dimethacrylate, 20 parts of N-methylolbenzoin methyl ether, 0.02 Parts of the dye Solvent Black 3 (CoIo 26150), 0.1 part of 2,5-di-tert-butyl-4-methyl-phenol a photocrosslinkable layer RS prepared in a solution in toluene, according to the information in example lb is further processed from the resulting multilayer composite panel gives a relief printing form with very good mechanical properties of the relief and very good printing behavior,

Claims (1)

Claims 1. Multi-layer composite panels for the production of Relief printing forms which have a) a layer RS based on a photoinitiator and optionally containing conventional additives, medium-soluble in a developer solvent photo-crosslinkable mixture of al) at least one soluble two-block copolymer P from 30-95% by weight of a diene hydrocarbon and 5-70% by weight of a monomer of Formula CH2: CRR 'where R .-. H or CH3 and R' = optionally alkyl-substituted phenyl, with a viscosity number of 60-350 ml / g and a2) at least one with the diblock copolymer P compatible monomers M with at least one photocrosslinkable C-C double bond, b) a non-photocrosslinkable and in the developer solvent for the layer RS non-soluble elastomeric sub-layer U with a hardness of 15 to 70 Shore A, c) a non-photocrosslinkable and insoluble in the developer solvent for the layer RS Stabilization layer ST, according to patent O. OO OOO (patent application P 24 56 439.4), characterized in that the diblock copolymer P in the layer RS from 75-85 % By weight of units of a diene hydrocarbon with 4 to 6 carbon atoms, of which more than 50 GewO; of the units represent isoprene units, and 15-25% by weight of styrene units consists; the diblock copolymer P has a viscosity number of 150-250 ml / g (measured as a 0.5% by weight solution in toluene at 2500), a sharply separated one transition between the polystyrene segment and the polyisoprene segment and a share of homopolymer of less than 4% by weight has 2 multilayer composite panels according to claim 1s characterized by marked that the stabilizing layer ST 5 to 500 / µm thick and firmly bonded to the neighboring layers between the photocrosslinkable Layer RS and the elastomeric sub-layer U is located