CA2017497A1 - Filling and/or sealing orifices, cavities or voids in printing plates mounted on plate cylinders - Google Patents
Filling and/or sealing orifices, cavities or voids in printing plates mounted on plate cylindersInfo
- Publication number
- CA2017497A1 CA2017497A1 CA 2017497 CA2017497A CA2017497A1 CA 2017497 A1 CA2017497 A1 CA 2017497A1 CA 2017497 CA2017497 CA 2017497 CA 2017497 A CA2017497 A CA 2017497A CA 2017497 A1 CA2017497 A1 CA 2017497A1
- Authority
- CA
- Canada
- Prior art keywords
- filling
- sealing
- printing
- component
- filling compound
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
- B41N6/00—Mounting boards; Sleeves Make-ready devices, e.g. underlays, overlays; Attaching by chemical means, e.g. vulcanising
- B41N6/02—Chemical means for fastening printing formes on mounting boards
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41F—PRINTING MACHINES OR PRESSES
- B41F27/00—Devices for attaching printing elements or formes to supports
- B41F27/12—Devices for attaching printing elements or formes to supports for attaching flexible printing formes
- B41F27/1293—Devices for filling up the cylinder gap; Devices for removing the filler
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Sealing Material Composition (AREA)
- Inks, Pencil-Leads, Or Crayons (AREA)
- Macromonomer-Based Addition Polymer (AREA)
- Supply, Installation And Extraction Of Printed Sheets Or Plates (AREA)
Abstract
- 22 - O.Z. 0050/40893 Abstract of the Disclosure: Orifices, cavities or voids which are formed when printing plates resistant to alcoholic printing ink solvents are mounted on a plate cylinder are filled and/or sealed by means of a photo-curable sealing or filling compound consisting of one or more photopolymerizable, ethylenically unsaturated low molecular weight compounds (a), one or more polymeric binders (b) which are compatible with the photopolymeriz-able low molecular weight compounds of component (a), one or more photopolymerization initiators (c) and conventional assistants and additives (d). After it has been applied, this sealing or filling compound is cured by exposure to light and may be machined.
Description
2 0 ~
- Z . 0050/40893 Fillin~ and/or saaling orif ices, cavitie~ or voids in ~rintinq plates mount~3d on plate cylinders The present inv~ntion relate~ to a method fo~
filling and/or sealing orifices, cavities or voids such 5as occur when printing plates are mounted on plate cylin-ders, in particular in the region of the end or edge ssctions of the printing platss, by mean~ of a sealing or filling compound. The method according to the invention is particularly suitabla for filling and/or sealing such 10orifices, cavities or voids in gravure printing plate~
which are mounted on plate cylinders and are resi~tant to alcoholic printing ink ~olvent~.
For the production of rotary printing plates, it is known that flat printing plate~ can be wrapped around 15plate cylinder~ and fa~tened to the latter in a suitable manner, for example by adhe~ive bonding or magnetically or mechanically by means of ~uitable retaining and clamp-ing elements. In this way, only one printin~ plate or a plurality of printing plates, one behind the other and/or 20side by side, can be mounted on the surface of a plate cylinder. ~his method for the production of rotary printing plates is becoming increasingly importan~ par-ticularly in rotary gravure printing, owing to the simple and economical production and handling of wrap-around 25gravure printing plates. The wrap-around gravure print-ing plates are preferably mounted on the plate cylinder by bending over one or both o~ their end sections and hooking these bent-ovar region~ into a groove r provided for this purpose, in the cylinder, with simultaneous 30clamping of said plate.
When flat printing plates are mounted on a plate cylinder, an interruption in th~ printing surface occur~
on the plate cylinder, in the fo~m of gaps~ clamping slots or other voids or cavities, between the opposite 35ends or end regions of a printing plate, which ends or end regions may be bent over, or, when a plurality of ~rinting plates are mounted one behind the other and/or . , .
, 2 ~ '~ 7 ~ rl - 2 - O.Z. 0050/40893 side by side on a plate cylinder, be~ween the abutting edges of the end and/or lateral regions of the printing plates. Such orifices or void~ which form when prlnting plates are mounted on plate cylinder~ must be filled in a suitable manner to avoid penetration of printing ink, which, for example, may lead to loss of bonding of the printing plate to the plate cylinder or, particularly in the case of gravure printing, to spraying of ~he printing ink and to an undesirable Lmpre~sion of the gap, and furthermore to ensure quiet running of the doctor blade and thus to prevent damage to the doctor blade and the printing plate surface. Orifices and voids, which have to be sealed again~t pen~tration of printing ink or for other reasons in order to avoid problems during printing, may also be formed at the end faces of plate cylinders, between the pla~e cylinder surface and the lateral regions of the mounted printing plate or between the printing plate surface and metal rings placed a~ the sides of the printing cylinder and defining the printing surface, as is generally the case in rotary gravure printing.
It has already been proposed that the gap or clamping slot formed when wrap-around gravure printing plates are mechanically clamped on printing cylinders be filled by mean of sealing Strip9~ sealing tap s or seal-ing cords of resilient or plastically deformable mater-ials (cf. for example US-A-2 056 991, US-A-2 285 116, D~-A-25 45 124 or DE-A-26 33 445). This method of gap filling is only of limited u~e and expen~ive to carry out and frequently presents con~iderable difficulties owing to the adaptation of the seal profiles to the shape o the orifice or ~oint to be filled and possible subsequent surface machining.
I~ i3 also known that the gap~, clamping slots or other orifices and void~ which are formed when printing plates are mounted on plate cylinders can be filled with materials which reach the ~tate required for their - .
- ' - ~ : '.'. .
- ~ , ~.
. .
2 ~ 7 - 3 - O.Z. 0050/40893 function only through chemical reaction, heat, drying or the like, for example adhesives, thermoplastic~, hotmelt adhesives, heat-curable or photocurable reaction resins or reaction foams or liquid photopolymerizable materials.
The use of ~uch filling compounds for printing plates mounted on plate cylinders is described in, for example, Deutschex Drucker, No . 41 (1975), pages 17-22, DE-A-25 45 618, EP-A-118 866, EP-A-174 568, EP-A-175 189 or GB-A-2 160 882. These filling compounds generally present no problems with regard to shape adaptation but often have insufficient resistance to the printing ink solvents and/or exhibit mechanical weaknesse~ under the ctre~ses of the printing process, in particular under the action of the impression cylinder, the printed medium and, in the case of gravure printing, also the doctor blade.
Some of these known filling material~ tend to exhibit embrittlement, so that small cracks form in the gap region after a short time and may fill with ink. It is precisely the combined action of printing ink solvents and mechanical forces which not infrequently lead to damage or even destruction of these filling compo~nds.
However, even when these filling compounds have suf-ficient chemical and mechanical resis~ance to meet the requirements, their application and the establishment of the required properties are as a rul~ tedious and expensive and their use is mainly restricted to the filling of relatively wide or large gap~, orifices or other cavities or voids.
It is an ob~ect o~ ~he present invention rapidly and effectively to seal andJor to fill the orifices and voids, for example gap~, joints, hole~, cavities and the like, which form when printing plates are mounted and fixed on plate cylinders, while avoiding the disadvan- :
tage~ known from the prior art but incurring no great expense, to give a printing plate surface which is un-interrupted all round and which withstands the mechanical and chemical stresse~ occurring during printing. ~-~, - .
.
'~
2 ~
- Z . 0050/40893 Fillin~ and/or saaling orif ices, cavitie~ or voids in ~rintinq plates mount~3d on plate cylinders The present inv~ntion relate~ to a method fo~
filling and/or sealing orifices, cavities or voids such 5as occur when printing plates are mounted on plate cylin-ders, in particular in the region of the end or edge ssctions of the printing platss, by mean~ of a sealing or filling compound. The method according to the invention is particularly suitabla for filling and/or sealing such 10orifices, cavities or voids in gravure printing plate~
which are mounted on plate cylinders and are resi~tant to alcoholic printing ink ~olvent~.
For the production of rotary printing plates, it is known that flat printing plate~ can be wrapped around 15plate cylinder~ and fa~tened to the latter in a suitable manner, for example by adhe~ive bonding or magnetically or mechanically by means of ~uitable retaining and clamp-ing elements. In this way, only one printin~ plate or a plurality of printing plates, one behind the other and/or 20side by side, can be mounted on the surface of a plate cylinder. ~his method for the production of rotary printing plates is becoming increasingly importan~ par-ticularly in rotary gravure printing, owing to the simple and economical production and handling of wrap-around 25gravure printing plates. The wrap-around gravure print-ing plates are preferably mounted on the plate cylinder by bending over one or both o~ their end sections and hooking these bent-ovar region~ into a groove r provided for this purpose, in the cylinder, with simultaneous 30clamping of said plate.
When flat printing plates are mounted on a plate cylinder, an interruption in th~ printing surface occur~
on the plate cylinder, in the fo~m of gaps~ clamping slots or other voids or cavities, between the opposite 35ends or end regions of a printing plate, which ends or end regions may be bent over, or, when a plurality of ~rinting plates are mounted one behind the other and/or . , .
, 2 ~ '~ 7 ~ rl - 2 - O.Z. 0050/40893 side by side on a plate cylinder, be~ween the abutting edges of the end and/or lateral regions of the printing plates. Such orifices or void~ which form when prlnting plates are mounted on plate cylinder~ must be filled in a suitable manner to avoid penetration of printing ink, which, for example, may lead to loss of bonding of the printing plate to the plate cylinder or, particularly in the case of gravure printing, to spraying of ~he printing ink and to an undesirable Lmpre~sion of the gap, and furthermore to ensure quiet running of the doctor blade and thus to prevent damage to the doctor blade and the printing plate surface. Orifices and voids, which have to be sealed again~t pen~tration of printing ink or for other reasons in order to avoid problems during printing, may also be formed at the end faces of plate cylinders, between the pla~e cylinder surface and the lateral regions of the mounted printing plate or between the printing plate surface and metal rings placed a~ the sides of the printing cylinder and defining the printing surface, as is generally the case in rotary gravure printing.
It has already been proposed that the gap or clamping slot formed when wrap-around gravure printing plates are mechanically clamped on printing cylinders be filled by mean of sealing Strip9~ sealing tap s or seal-ing cords of resilient or plastically deformable mater-ials (cf. for example US-A-2 056 991, US-A-2 285 116, D~-A-25 45 124 or DE-A-26 33 445). This method of gap filling is only of limited u~e and expen~ive to carry out and frequently presents con~iderable difficulties owing to the adaptation of the seal profiles to the shape o the orifice or ~oint to be filled and possible subsequent surface machining.
I~ i3 also known that the gap~, clamping slots or other orifices and void~ which are formed when printing plates are mounted on plate cylinders can be filled with materials which reach the ~tate required for their - .
- ' - ~ : '.'. .
- ~ , ~.
. .
2 ~ 7 - 3 - O.Z. 0050/40893 function only through chemical reaction, heat, drying or the like, for example adhesives, thermoplastic~, hotmelt adhesives, heat-curable or photocurable reaction resins or reaction foams or liquid photopolymerizable materials.
The use of ~uch filling compounds for printing plates mounted on plate cylinders is described in, for example, Deutschex Drucker, No . 41 (1975), pages 17-22, DE-A-25 45 618, EP-A-118 866, EP-A-174 568, EP-A-175 189 or GB-A-2 160 882. These filling compounds generally present no problems with regard to shape adaptation but often have insufficient resistance to the printing ink solvents and/or exhibit mechanical weaknesse~ under the ctre~ses of the printing process, in particular under the action of the impression cylinder, the printed medium and, in the case of gravure printing, also the doctor blade.
Some of these known filling material~ tend to exhibit embrittlement, so that small cracks form in the gap region after a short time and may fill with ink. It is precisely the combined action of printing ink solvents and mechanical forces which not infrequently lead to damage or even destruction of these filling compo~nds.
However, even when these filling compounds have suf-ficient chemical and mechanical resis~ance to meet the requirements, their application and the establishment of the required properties are as a rul~ tedious and expensive and their use is mainly restricted to the filling of relatively wide or large gap~, orifices or other cavities or voids.
It is an ob~ect o~ ~he present invention rapidly and effectively to seal andJor to fill the orifices and voids, for example gap~, joints, hole~, cavities and the like, which form when printing plates are mounted and fixed on plate cylinders, while avoiding the disadvan- :
tage~ known from the prior art but incurring no great expense, to give a printing plate surface which is un-interrupted all round and which withstands the mechanical and chemical stresse~ occurring during printing. ~-~, - .
.
'~
2 ~
- 4 - O.Z. 0050/40893 The method described in DE-A-37 36 180 has considerable advantages in this respect but is not very suitable when alcoholic printing ink sol~ents are used.
It is an objec~ of ~he present invention to provide a method which makes it possible to adapt ~he sealing or filling compound to plate type~ which are resistant to alcoholic printing ink solvents, the adhesion of ~hese compounds in the cured state in the plate gap being sufficiently high to perform their function during the printing process. ~oroever, the sealing and filling compound should be capable of being removed cleanly and completely from the plate after the printing process, without the printing plate being damaged during the procedure.
We have found, surprisingly, tha~ this object is achieved in a very ad~antageous manner by a method in which sealing or filling compounds of a certain composi-tion which are photocurable at room temperature are used.
The present invention relates to a method for filling and/or sealing orifices, cavitie~ or voids, which are formed when printing plates resistant ~o alcoholic printing ink sol~ent~ are mounted on a plate cylinder, by means of a sealing or filling compound, wherein the seal-ing or filling compound used is a material which is photocurable at room temperature and essentially consists of a photopolymerizable mixture of (a) from 10 to 60~ by weight of one or more photopoly-merizable, ethylenically unsaturated low molecular weight compounds and (b) from 90 to 40% by weight of one or more copolymeriz-able oligomeric or polymeric binders which are com-patible with the photopolymerizable low molecular weight compounds of component (a), the sum of the percentages stated under (a) and ~b) bein~
lO0, and ~dditionally (c) from Q.01 to 10~ by weight, based on the total ., .
2~P~7 - 5 - O.Z. 0050/40893 amoun~ of componen~s (a) and (b), of one or more photopolymerization initiators, with or without (d) conventional assistants and additives in an amount such that, as a mixture with components (a) to (c)~
they give mixtures which are tran~parent to long-wave W light, and which, after application in or on the orifices, cavities or voids to be filled or sealed, is cured by exposure to light and may then be machined.
For the novel method, the sealing or filling com-pounds may additionally contain a thermal polymerization inhibitor and from 0.1 to 2~ by weight, based on the total amount of component~ (a) + (b), of a paraffin.
Component (a) used for the novel method prefer-ably comprise~ one or more compounds from the group con-sisting of the vinylaromatics and of the hydroxyl-free ester~ of acrylic acid or methac~ylic acid with mono-hydric or polyhydric alcohols, ~tyrene and/or esters of acrylic acid or methacrylic acid with a monoalkanol of 1 to 12 carbon atoms being parti~ularly preferred.
Copolymerizable oligomeric or polymeric binders which are preferred as componen~ tb) are unsaturated polyestQrs and esterification produ~t~ of di- or poly-epoxides with acrylic acid or methacrylic acid.
Finely divided oxidic filler~ which are also advantageous for the novel method are aluminum hydroxida and silica having particle diameters of from 0.01 to 10 ~m, prefQrably from 0.01 to 5 ~m.
Although the novel method i8 applicable to all types of printing plate~ mounted on plate cylinder~, for example letterpres3 and flexographic printing plates, it has proven particularly advan~ageous for qravure printing plates which are mounted on plate cylinder3 and are resistant to alcoholic printing ink ~olvent~. For the purposes of the pre~ent invention, alcoholic printing ink solvent~ are flexographic or gravure printing ink .
.
.
~ ` ?
.. : .
, - :, 2 ~ 7 - 6 - O.Z. 0050/40893 solvents which predominantly consist of lower alcohols, preferably of ethanol, and may contain from 5 to 20% by weight of an alkyl acetate, preferably ethyl, n-propyl or isopropyl acet~te, or water. By employing the ~ealing or filling compounds to be used according to the invention, penetration of even low-viscosity printing ink into the stated orifices, cavities or voids is also prevented, avoiding the resulting disadvantages The adhesion of the sealing and filling compounds, used according to the invention, in the cured state in the plate gap ens~re~
problem-free printing. After the printing proce~, how-ever, the sealing and filling compound can be removed cleanly and completely from the plate without damaging the latter. It was also surprising that the orifices, lS cavities or voids filled and/or sealed by the novel method have excellent chemical and mechanical re istance and durability under the requiremQnts and stresses encountered during printing and do not exhibit any weak-nesses, and that the rotary gravure printing plates produced by the novel method permit an even, quiet and smooth sliding of the doctor blade over the printing plate ~urface without damaging the latter. The novel method is particularly advantageous because it is univer-sally applicable. The sealing or filling compound to be used according to the invention can be simply and readily processed in the novel method. On the one hand it can be uniformly distributed in the gap cavity while on the other hand the gap cavity at the end face3 of the cylin-der can be sealed without additional expen ive measure~
having to be taken. Although the novel method i~ suit-able for filling and/or sealing any type of orifices, cavities or voids in printing plates mounted on plate cylinders, it is particularly suitable and can be used without difficulty and advantageously for filling and/or sealing small or narrow gaps, ~oints, other orifice , voids and the like.
Among the conventional photopolymerizable, .
2 ~
_ 7 - O.Z. 0050/~0893 ethylenically unsaturated, low molecu]ar weight com-pounds, in particular those having boiling points a~ove 100C, vinylaromatics, such as styrene, esters of acrylic acid and/or methacrylic acid, preferably those with mono-alcohols of 1 to 12, in particular 1 to 8, carbon atoms, are suitable as component (a) for the novel method, such compounds being known per se. Monomers whose photopoly-merizable, ethylenic double bonds are activated by con~ugation or by being adjacent to O, N or S atoms are preferred. The photopolymerizable, ethylenically unsaturated low molecular weight compounds (a) to be used according to tha invention may be either monofunctional or polyfunctional, ie. they may contain one or more photopolymerizable, ethylenic double bonds in the molecule.
The photopolymerizable, ethylenically unsaturated low molecular weight compound~ to be used according to the invention as component (a) of the filling compounds include the N-vinyl compounds and the deriYatives of ~
2n olefinically un~aturated mono- or dicarboxylic acids.
Among the ~ olefinically unsaturated carboxylic acids, acrylic acid and methacrylic acid are particularly impor-tant. Particularly advantageous photopolymerizable mono-mers are derivatives of the ~ olefinically un~aturated carboxylic acids, in particular derivati~es of acrylic or methacrylic acid, such as their hydroxyl-free e~ters with polyhydric alcoholq, eg. hexanediol diacrylate, butane-diol dimethacrylate, trimethylolpropane triacrylate and/or tripropylene glycol diacrylata.
The choice of the photopolymerizable low molecu-lar weight compound~ used as component (a) depends, inter alia, on the type of polymeric binder which is present as component (b) and with which the photopolymerizable low molecular weight compoundYishould be compatible, and also on the desired properties of the cured filling compound.
The photopolymeri~able low moleeular weight compounds can be usad alone or a~ a mixture with one another. For .. . ,. . .,,, ~, ~ . . ' i .~ :
~ ~3 ~
- 8 - O.Z. 0050/40893 example, it is possible for the mechanical propertie~ of the cured filling compound and the gap filled therewith to be varied an~ adjusted to the desired extent via the type and amount of monomer~ used or, where monomer mix-tures are employed, also via the ratio in which themonomers are mixed with one another. The filling com-pounds to be used for the novel method contain in general from 10 to 60, preferably from 20 to 50, % by weight, based on the total ~mount of components (a) + (b), of the photopolymerizable low molecular weight compounds (a).
The viscosity of the filling compound can also be ad-~usted and varied via the amount of said compounds (a).
In addition, the filling compounds to be used for the novel method contain, as component (b), one or more copolymerizable oligomeric or polymeric binders which are compatibie with the photopolymerizable low molecular weight compounds of component (a). The polymeric binder is chosen so that it is resistant to the conventional alcoholic printing ink solvents usually used in gravure printing.
Unsaturated polyesters have proven u~eful as co-polymerizable polymeric binder~ ~b) which are particular-ly advantageous for the novel method.
Unsaturated polyesters can usually be prepared by polycondensation of a-unsaturated polybasic carboxylic acid~, in particular dicarboxylic acid~ or their anhyd-rides, with polyhydric, preferably dihydric, alcohol~.
Soma of the ~-unsaturated dicarboxylic acids can be replaced by aromatic and~or saturated dicarbo~ylic acids.
Example~ of suitable unsaturated dicarboxylic acid3 are maleic acid, fumaric acid, itaconic acid, citraconic acid and mesaconic acid. Examples of suitable aromatic di-carboxylic acids are phthalic acid, isophthalic acid and terephthalic acid. Suitable ~aturated dicarboxylic acids are, for example, succinic acid, glutaric acid, ~-methyl-glutaric acid, adipic acid a~d sebacic acid.
Particularly suitable polyh~dric alcohol~ for the . ~ :
It is an objec~ of ~he present invention to provide a method which makes it possible to adapt ~he sealing or filling compound to plate type~ which are resistant to alcoholic printing ink solvents, the adhesion of ~hese compounds in the cured state in the plate gap being sufficiently high to perform their function during the printing process. ~oroever, the sealing and filling compound should be capable of being removed cleanly and completely from the plate after the printing process, without the printing plate being damaged during the procedure.
We have found, surprisingly, tha~ this object is achieved in a very ad~antageous manner by a method in which sealing or filling compounds of a certain composi-tion which are photocurable at room temperature are used.
The present invention relates to a method for filling and/or sealing orifices, cavitie~ or voids, which are formed when printing plates resistant ~o alcoholic printing ink sol~ent~ are mounted on a plate cylinder, by means of a sealing or filling compound, wherein the seal-ing or filling compound used is a material which is photocurable at room temperature and essentially consists of a photopolymerizable mixture of (a) from 10 to 60~ by weight of one or more photopoly-merizable, ethylenically unsaturated low molecular weight compounds and (b) from 90 to 40% by weight of one or more copolymeriz-able oligomeric or polymeric binders which are com-patible with the photopolymerizable low molecular weight compounds of component (a), the sum of the percentages stated under (a) and ~b) bein~
lO0, and ~dditionally (c) from Q.01 to 10~ by weight, based on the total ., .
2~P~7 - 5 - O.Z. 0050/40893 amoun~ of componen~s (a) and (b), of one or more photopolymerization initiators, with or without (d) conventional assistants and additives in an amount such that, as a mixture with components (a) to (c)~
they give mixtures which are tran~parent to long-wave W light, and which, after application in or on the orifices, cavities or voids to be filled or sealed, is cured by exposure to light and may then be machined.
For the novel method, the sealing or filling com-pounds may additionally contain a thermal polymerization inhibitor and from 0.1 to 2~ by weight, based on the total amount of component~ (a) + (b), of a paraffin.
Component (a) used for the novel method prefer-ably comprise~ one or more compounds from the group con-sisting of the vinylaromatics and of the hydroxyl-free ester~ of acrylic acid or methac~ylic acid with mono-hydric or polyhydric alcohols, ~tyrene and/or esters of acrylic acid or methacrylic acid with a monoalkanol of 1 to 12 carbon atoms being parti~ularly preferred.
Copolymerizable oligomeric or polymeric binders which are preferred as componen~ tb) are unsaturated polyestQrs and esterification produ~t~ of di- or poly-epoxides with acrylic acid or methacrylic acid.
Finely divided oxidic filler~ which are also advantageous for the novel method are aluminum hydroxida and silica having particle diameters of from 0.01 to 10 ~m, prefQrably from 0.01 to 5 ~m.
Although the novel method i8 applicable to all types of printing plate~ mounted on plate cylinder~, for example letterpres3 and flexographic printing plates, it has proven particularly advan~ageous for qravure printing plates which are mounted on plate cylinder3 and are resistant to alcoholic printing ink ~olvent~. For the purposes of the pre~ent invention, alcoholic printing ink solvent~ are flexographic or gravure printing ink .
.
.
~ ` ?
.. : .
, - :, 2 ~ 7 - 6 - O.Z. 0050/40893 solvents which predominantly consist of lower alcohols, preferably of ethanol, and may contain from 5 to 20% by weight of an alkyl acetate, preferably ethyl, n-propyl or isopropyl acet~te, or water. By employing the ~ealing or filling compounds to be used according to the invention, penetration of even low-viscosity printing ink into the stated orifices, cavities or voids is also prevented, avoiding the resulting disadvantages The adhesion of the sealing and filling compounds, used according to the invention, in the cured state in the plate gap ens~re~
problem-free printing. After the printing proce~, how-ever, the sealing and filling compound can be removed cleanly and completely from the plate without damaging the latter. It was also surprising that the orifices, lS cavities or voids filled and/or sealed by the novel method have excellent chemical and mechanical re istance and durability under the requiremQnts and stresses encountered during printing and do not exhibit any weak-nesses, and that the rotary gravure printing plates produced by the novel method permit an even, quiet and smooth sliding of the doctor blade over the printing plate ~urface without damaging the latter. The novel method is particularly advantageous because it is univer-sally applicable. The sealing or filling compound to be used according to the invention can be simply and readily processed in the novel method. On the one hand it can be uniformly distributed in the gap cavity while on the other hand the gap cavity at the end face3 of the cylin-der can be sealed without additional expen ive measure~
having to be taken. Although the novel method i~ suit-able for filling and/or sealing any type of orifices, cavities or voids in printing plates mounted on plate cylinders, it is particularly suitable and can be used without difficulty and advantageously for filling and/or sealing small or narrow gaps, ~oints, other orifice , voids and the like.
Among the conventional photopolymerizable, .
2 ~
_ 7 - O.Z. 0050/~0893 ethylenically unsaturated, low molecu]ar weight com-pounds, in particular those having boiling points a~ove 100C, vinylaromatics, such as styrene, esters of acrylic acid and/or methacrylic acid, preferably those with mono-alcohols of 1 to 12, in particular 1 to 8, carbon atoms, are suitable as component (a) for the novel method, such compounds being known per se. Monomers whose photopoly-merizable, ethylenic double bonds are activated by con~ugation or by being adjacent to O, N or S atoms are preferred. The photopolymerizable, ethylenically unsaturated low molecular weight compounds (a) to be used according to tha invention may be either monofunctional or polyfunctional, ie. they may contain one or more photopolymerizable, ethylenic double bonds in the molecule.
The photopolymerizable, ethylenically unsaturated low molecular weight compound~ to be used according to the invention as component (a) of the filling compounds include the N-vinyl compounds and the deriYatives of ~
2n olefinically un~aturated mono- or dicarboxylic acids.
Among the ~ olefinically unsaturated carboxylic acids, acrylic acid and methacrylic acid are particularly impor-tant. Particularly advantageous photopolymerizable mono-mers are derivatives of the ~ olefinically un~aturated carboxylic acids, in particular derivati~es of acrylic or methacrylic acid, such as their hydroxyl-free e~ters with polyhydric alcoholq, eg. hexanediol diacrylate, butane-diol dimethacrylate, trimethylolpropane triacrylate and/or tripropylene glycol diacrylata.
The choice of the photopolymerizable low molecu-lar weight compound~ used as component (a) depends, inter alia, on the type of polymeric binder which is present as component (b) and with which the photopolymerizable low molecular weight compoundYishould be compatible, and also on the desired properties of the cured filling compound.
The photopolymeri~able low moleeular weight compounds can be usad alone or a~ a mixture with one another. For .. . ,. . .,,, ~, ~ . . ' i .~ :
~ ~3 ~
- 8 - O.Z. 0050/40893 example, it is possible for the mechanical propertie~ of the cured filling compound and the gap filled therewith to be varied an~ adjusted to the desired extent via the type and amount of monomer~ used or, where monomer mix-tures are employed, also via the ratio in which themonomers are mixed with one another. The filling com-pounds to be used for the novel method contain in general from 10 to 60, preferably from 20 to 50, % by weight, based on the total ~mount of components (a) + (b), of the photopolymerizable low molecular weight compounds (a).
The viscosity of the filling compound can also be ad-~usted and varied via the amount of said compounds (a).
In addition, the filling compounds to be used for the novel method contain, as component (b), one or more copolymerizable oligomeric or polymeric binders which are compatibie with the photopolymerizable low molecular weight compounds of component (a). The polymeric binder is chosen so that it is resistant to the conventional alcoholic printing ink solvents usually used in gravure printing.
Unsaturated polyesters have proven u~eful as co-polymerizable polymeric binder~ ~b) which are particular-ly advantageous for the novel method.
Unsaturated polyesters can usually be prepared by polycondensation of a-unsaturated polybasic carboxylic acid~, in particular dicarboxylic acid~ or their anhyd-rides, with polyhydric, preferably dihydric, alcohol~.
Soma of the ~-unsaturated dicarboxylic acids can be replaced by aromatic and~or saturated dicarbo~ylic acids.
Example~ of suitable unsaturated dicarboxylic acid3 are maleic acid, fumaric acid, itaconic acid, citraconic acid and mesaconic acid. Examples of suitable aromatic di-carboxylic acids are phthalic acid, isophthalic acid and terephthalic acid. Suitable ~aturated dicarboxylic acids are, for example, succinic acid, glutaric acid, ~-methyl-glutaric acid, adipic acid a~d sebacic acid.
Particularly suitable polyh~dric alcohol~ for the . ~ :
7 ~ ~ ~
- 9 - O.Z. 0050/40893 preparation of the polyesters are the conventional di-hydric alcohols, eg. ethylene glycol, 1,2-propylene glycol, l,3-butylene glycol, butane-1,4-diol, hexane-1,6-diol, diethylene glycol, dipropylene glycol, triethylene glycol or 2,2-dimethylpropane-1,3-diol, and, in certain amounts, also alcohols of higher functionality, eg.
~lycerol, pentaerythritol or trimethylolpropane.
Particularly preferred unsaturated polyesters are those based on phthalic acid/maleic acid/ethylene glycol/propylene glycol, which, for example, are commer-cially available in solution in styrene (having a styrene content of about 35% by weight).
Such standard polyester resin~ generally have viscosities of from 300 to 2,000 mPa.s (at 23C) in the form of 30-50~ strength solutions in styrene and can be elastified and rendered flexible by mixing with o~her polyester resins, for example those based on adipic acid/phthalic acid~maleic acid/dipropylene glycol/
propylene glycol, which are likewise commercially avail-able in solution in styrene (for example having a styrenecontent of about 25% by weigh~) and, af~er polymeriza-tion, themselves have substantially lower tensile strengths and glass transition temperatures which are below room tèmperature, the skilled worker being familiar with this procedure. Mixtures of these two ~ypes of polye~ters are preferred.
Particularly suitable copolymerizable oligomeric binders (b) are e~terification products of di- or poly-epoxide~ with acrylic acid and/or methacrylic acid. Di-and polyepoxides on which these esterification productsare based are, in particular, tho~e which axe derived from bisphenol A, as are obtained, for example, by condensation of not les8 than 2 moles of epichlorohydrin per mole of bisphenol A, and which can be subjected to chain extension using dicarboxylic acids, eg. phthalic acid. However, other suitable di- or polyepoxide~ are tho~e basad on other diol3 or polyol-~.
.. . . . .
'' :, , ~ ~ I r~
- 10 - O.Z. 0050/40893 The di- or polyepoxides ca~ be reacted with acrylic acid and/or methacrylic acid to give the abovementioned esterification products, which are prefer-ably fre~ of epoxy groups and then contain on average about two (meth)acrylate groups per molecule.
Preferred components (b~ are copolymerizable oligomeric and polymeric binders which are soluble in the photopolymerizable, ethylenically unsaturated low molecular weight compounds used as component (a). ~ow-ever, it is also possible to use, as component (b), co-polymerizable oligomeric and/or polymeric binder~ which are dispersible in the photopolymerizable low molecular weight compounds of component (a) only if the photopoly-merizable low molecular weight compounds and the oligo-meric and/or polymeric binders are compatible with oneanother and can be processed to give a homogeneous free-flowing mixture. The amount of the copolymeriæable oligomeric and/or polymeric binders (component (b)) in the total ~mount of components (a) ~ (b) is in general ~0 from 90 to 40, in particulax from 80 ~o 50, % by weight, based on the total amount of components (a) + (b).
In addition to the photopolymerizable low molecular weight compounds (a) and the copolymerizable oligomeric and/or polymeric binder~ (b), the filling com~
pounds to be used for the novel method contain, a~ com-ponent (c), one or more photopolymerization initiators, in particular in an amount of from 0.01 to 10, preferably from 0.01 to 2, % by weight, based on the total amount of components ~a) ~ (b). According to the invention, the compounds known per se and conventionally used a~ photo-initiators for photocurable materials are ~uitable for this purpose. These include in particular benzoin and benzoin derivative~, for example b~nzoin alkyl ethers, in particular where alkyl i5 of 1 to 8 carbon atoms, eg.
benzoin monomethyl ether or benzoin i~opropyl ether, ~-hydroxymethyl~enzoin and its al~yl ether~, such as ~-hydroxymethylbenzoin methyl ether, or ~-methylbenzoin and 2~:~7l~7 ~ O.Z. 0050/~0893 its ethers; benzil and benzil derivatives, in particular benzil monoketals, ~uch as benzil dimethyl ketal, benzil methyl ethyl ketal or benzil methyl benzyl ketal; the acylphosphine compounds which are effective photo-5initiators, as described, for example, in German Laid-Open Applications DOS 2,830,927, DO5 2,909,994, DOS
3,020,092, DOS 3,034,697, DOS 3,114,314 and DOS
3,133,419, and of which 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphos-10phinate and 2,4,6-trimethylbenzoylbis-o-toluylphosphine oxide are typical examples; derivatives of ~-hydroxy-acetophenone, eg. l-phenyl-2-hydroxy-2-methyl-1-propan-one, l-(p-isopropylphenyl)-2-hydroxy-2-methyl-1-propanone and l-hydroxy-l-benzoylcyclohexane;andalsobenzophenone, 15Michler's ketone, fluorenone, anthraquinone, xanthone, thioxanthone and acridone and those derivatives of these compounds which are conventionally used and known photo-initiators. The photopolymerization initiators may be present alone or as a mix~ure with one another in the 20filling compounds to be used according to the invention;
they can also be used together wi~h the activators known per se for these photoinitiators, suitable activa~ors being mainly amine compounds.
Conventional assistants and additives may be used 25as component (d) in amounts such that, when mixed with component~ (a) to (c), they give mixtures which are transparent to long-wave W light. Examples of suitable substan~es are finely divided oxidic fillers, the particle si2e of these filler~ being in general from 0.01 30to 10 ~m, preferably from 0.01 ~o 5 ~m. Examples of such fillers are colloidal or hydrophobic silica, microtalc, micromica, kaolin, aluminas and aluminum hydroxides.
Silica (eg. Aerosil~ from Degussa) and aluminum hydroxide (eg. Nartinal~ from Nzrtinswerk) and mixtures thereof are 35particularly suitable.
The use of aluminum hydroxide of the hydrargil-lite type may be particularly advantageous, if i~ has, ' ~
.
~ ~ `
2 ~ ~ 7 ~
- 12 - O.Z. 0~50/40893 for example, particle sizes (up to 80%) of from 0.2 to 3.0 ~m or a lamellar structure. Apart from the fact that this reduces the polymerization shrinkage and increases the strength, smooth surfaces and a substantially reduced tendency to crack during curing result. Moreo~er, there are only small differences between the refractive index of aluminum hydroxide and that of ~he resin component (b) or of its mixture with component (a).
The addition of finely divided silica may also help to thicken the mixture of components (a) + (b) and Lmpart thixotropic properties to said mixture, may serve as a sedimentation inhibi~or for other filler~ and may result in increased str~ngth on curing. Finely divided hydrophilic and hydrophobic silica grade~ which, for example, have particle sizes of about 12 or 14 nm may be particularly advantageous. The finely divided hydro-phobic silica grades are generally preferred for un-saturated polyester resins.
Fillers may in general be added in amounts of not more than 70% by weight, based on the total amount of the filling compound.
Other a~sistant~ and additive3, such ag paraffin (for example a paraffin having a solidification point of from 56 to 58C), in general in amounts of from 0.1 to 2%
by weight, based on the total amount of components (a) +
(b), or polymerization inhibitors, for example thermal polymerization inhibitors, such as hydroquinone, hydro-quinone derivatives, 2,6-di-tert-butyl-p-cresol, nitro-phenols, N-nitrosamines, such as N-nitrosodiphenylamine, or the salts, in particular the alkali metal and aluminum salts, of N-nitrosocyclohe~ylhydroxylamine, may be added to the materials to be used according to the invention.
Pigment~ and dyes may be u~eful for visual obsexvation during gap filling and for evaluation of gap filling. By adding plasticizers, the vi~cosity and the flow behavior of the novel pho~ocurable filling compounds can be ~aried and controlled and mechanical properties of the cured gap .
.
7~
- 13 - O.Z. 0050/40893 filling, for example toughness and resilience, can be influenced. Particularly suitable plasticizers are low molecular weight compounds, for example the known phthal-ates, or hydroxyl-containing compounds, eg. glycerol, ethylene glycol and the like, which are compatible with the components (a) and (b) of the novel filling compounds.
The photocurable filling compounds to be used for the novel method are suitable for gap filling in all gravure printing plates which can be clamped on ~he plate cylinder of a sheet-fed or web-fed rotary gravure print-ing press, for example the conventional metal gravure printing plates. However, the novel filling compounds are particularly advantageous for gap filling in gravure printing plates which are clamped on plate cylinders and have plastic printing layers which are resistant to alcoholic printing ink solvents. In the gravure printing plates having plastic printing layers, a plastic layer is applied to a suitable printing layer substrate, ink-carrying inden ations (wells) being incorporated in saidplastic layer. These wells may have been formed in the plastic printing layer by mechanical engraving or laser engraving ~cf. for example DE-A-27 52 500 or D~-A-30 28 098) or, in the case of photopolymer~c gravure printing plates, may have been incorporated in the photosensitive plastic printing layer by imagewise exposure and develop-ment (cf. DE-A-20 61 287, DE-A-31 2~ 949 and DE-A-31 28 951). The photocuxable filling compound to be used according to the invention can be very advantageously used in wrap-around gravure printing plates for filling the gap formed between the ends of ~he gravur~ printing plate when these wrap~around plates are clamped on a plate cylinder. However, it i also suitable for filling the gaps formed between the end regions and/or lateral edges of the individual gravure printing plates when a plurality of said plates a e mounted one behind the other and/or side hy sida on a single plate cylinder/ for `
2 ~
- 14 - O.Z. 0050/40893 example by means of saddle constructions known per se and suitable for this purpose. For the purposes of th~
present invention, gravure printing plates are both the ready-prepared gravure printing plates in which the ink-conveying indentations have already been introduced, and the gravure printing plate blanks in which the wells have not yet been formed. Thus, it is also possible to clamp a ready-prepared gravure printing plate on the plate cylinder and then to fill the resulting gap~ with the filling compound to be used according to the invention, or first to clamp gravure printing plate blanks on the plate cylinder, then to fill the resulting gaps with the filling compound and only thereafter to introduce the wells into the printing layer of the printing plates.
Clamping of the gravure printing plates on the plate cylinder is known per s~ and is carried out, for example, by means of permanent magnets or by mechanical means for fastening and clamping printing plates. Plate cylinders used for this purpose are in general those where the gravure printing plates are fastened and clamped by hooking in and anchoring one plate end, preferably both plate ends, which is or are bent over for thi~ purpose, in an anchoring groove or channel in the cylinder.
In the novel method, the filling compound for filling the gap~ formed when the gravure printing plate~
are clamped on the plate cylinder can be introduced into the gap by any ~uitable methods or processes, provided that uniform and complete filling of the gap cavity is ensured.
Application of the photocurable materials to be used as sealing or filling compounds in the novel method can be effected, for example, in a very simple manner by straightforward application of the material~, for example from a tube, cartridge or sLmilar metering apparatus, onto those areas of the printing plates andJor plate cylinders which are to be ~ealed, and simple mechanical pressing onto or into the orifice~ or cavities ~o be . ri~ Pl - 15 - o.Z. 0050/~0893 filled, for example by means of a spatula, a scraper or the like. Excess filling material can then be readily removed by sLmply wiping it off from the printing plate surface or from the end faces of the printing plate cylinder thus obtained. According to the invention, no spPcial equipment or procedure i~ thus necessary for filling and/or sealing the orifices and gap~. Subsequent machining is often unnecessary; as a rule, however, it is advantageous to smooth the surface of the cured compound by subsequent machining, for example by grinding, milling and/or polishing, and to adapt it to the contour of the cylinder. To remove the printing plates from the plate cylinder, no special apparatuses or expensive procedures are required. The extent of the adhesion (gap filling compound/printing plate) can be controlled by changing the mixing ratioR of component~ (a) + (b), preferably the various amounts of polymers in components (b). This too is a particular advantage of the novel method~ Printing plates which have been used can be reused without restriction.
After the gap~ have been filled, the photocurable filling compound i9 exposed to actinic light for curing.
All known light sources capable of emitting light in the actinic wavelength range effective for the filling com-pounds, in particular in the wavelength range from about250 to 450 nm, can be used for this pu~pose, fox example carbon arc lamps, actinic or ~uperactinic fluore~cent tubes, low pressure, medium pressure or high pressure mercury lamps, which may be doped, xenon lamps or even laser3 having a hiqh W content.
The materials to be used according to the invention for filling and/or sealing orifices, cavities or voids in printing plate~ moun~ed on pla~e cylinder~
ha~e both high stability to the solvent~ and solvent mixtures usually used in printing inks, in particular polar solvents or ~olvent mixtures of this type, such as alcohols r e~ter~ and ketones, and wide variability in : ' :
,' '~ . ' , ' ': ' "
r~
- 16 - O. Z . 0050/408g3 relation to the application (flow behavior, spreadability, adhesion, surface ~moothnes-~ and machining) as a result of the addition of different amounts of one or more oxidic fillers.
5The physical properties of the materials to be used according to the invention, before and after curing, can be adapted within par~icularly wide limits to the practical requirements.
In the Examples, parts and percentages are by 10weight, unless stated otherwise.
114 g of an esterification product of methacrylic acid (2 moles) with a reaction product ~1 mole) contain-ing about two epoxy groups in ~he molecule and obtained 15from bisphenol A and epichlorohydrin and 130 g of an un-saturated polyester of maleic acid/phthalic acid/adipic acid/neopentyl glycol (molar ratio 2.15 : 1 : 6 : 9.5) were dissolved in 156 g of styrene. 2.61 g of ben~il di-methyl ketal and 1.28 g of trimethylbenzoyldiphenylphos-20phine oxide were added to the solution. The resulting mixture was homogenized and devolatilized under reduced pressure. The gap filling compound thus obtained can readily be in~ected into the cavities to be filled in a gravure printing cylinder.
25The material was cured by expo~ure to ultraviolet light.
~he mechanical properties and the adhe~ion of the gap filling ~hu~ produced were ~o good that it withstood long print runs without problem~. It has to be mechani-30cally 3eparated in order to remove the plate.
21.7 g of a finely divided silica and 229 g of a finely divided aluminum hydroxide were inc~rporatedl while stirring, into the liquid photosensitive mixture 35described in Example 1. The pasty material obtained afte~ complete homogenization and devolatilization could readily be introduced into tho cavities and joint~ to be ,. . ~ .
" ~
: : . . .:
20~7~3rJ
17 - O.Z. 0050t40893 filled, by means of a trowel or with the aid of a tube.
Curing of the gap filling compound was effect~d as described in Example 1.
132 g of a polyether obtained from bisphenol A
and epichlorohydrin and esterified with methacrylic acid and 148 g of an unsaturated polyester of 8 parts of maleic anhydride, 12 parts of phthalic anhydride, 14 parts of adipic acid, 12 parts of pxopylene glycol and 26 parts of dipropylene glycol were dissolved in 174 g of styrene. 2.96 g of benzil dimethyl ketal and 1.46 g of trimethylbenzoyldiphenylphosphine oxide were added to this solution.
After devolatilization, the syrupy material thus obtained could be used for fillin~ joints and cavities.
It could readily be applied by in~ection. Curing was effected by exposure to ultraviolet li~ht.
225 g of a polyethar obtained from bisphenol A
and epichloroh~ydrin and esterified with methacrylic acid were di-~solved in 200 g of hexanediol diacrylate. 0.7 g of the pota~sium salt o~ N-nitro~ocyclohexylhydroxyl-amine, in the ~orm of a 30~ strength methanolic ~olution, - was then added. Finally, 0.85 g of trimethylbenzoyldi-phenylphosphine oxide was stirred in.
~he material was devolatilized in the usual manner. It could particularly readily be injected into the ~oint-q to ba filled and, after curing by mean~ of W
light, exhibited very good resistance to ethanol.
6.0 g of trimethylbenzoyldiphenylphosphin~ oxide, 1.5 g of benzil dimethyl ketal, 0.2 g of hydroquinone monomethyl ether and 3.8 g of paraffin (solidification point 56-58C), dissolved in 34 g of styrene, wer~ added to a solution of 1,070 g of a polyether, obtained from bisphenol A and epichlorohydrin and esterifled with meth-acrylic acid, in 810 g o~ ~tyrene.
. ~ .: . .. .
. ........................... . . .
.
: :. .: . .
2 ~ ~ r~ 7 - 18 - O.Z. 0050/40893 The only slightly syrupy mix~ure was homogenized and devolatilized under reduced pressure. The photopolymerizable ma~erial thus obtained wa~ used for filling the orifice ~etween the two ends of a printing S plate clamped on a cylinder. Because of its good flow behavior, the material is particularly suitable for injection by means of a hose or tube ~y~tem into narrow and/or poorly accessible cavities or orifices.
The material was prepared essentially as des-cribed in Example 5. In addition, 40 g of a finely divided silica were added before the homogenization and devolatilization step.
The material thus Dbtained had a somewhat higher lS viscosity. It wa~ used in a manner similar to that de~-cribed in Example 5.
A photopolymerizable filling compound wa~ prep-ared on the basi~ of the formulation of Example 5, using 80 g of a finely divided ~ilica.
In ~pite of the substantially increased ViSC08-ity, this material could still be in~ected through suitable pipe apparatuseC into the cavitie~ to b~ filled.
The higher visco~ity has the advantage that slight leaks in the syst~m cause no problems.
80 g of a finely divided silica and 860 g of a finely divided aluminum hydroxide were added to the mixture of the organic component~ of Example 5 before the homogenization and devolatilization step.
~ he viscous material thus obtained can be intro-duced into the cavities to be filled, not only by means of wide-bore application systems but also by mean3 of a trowel. In the cured state, it exhibits excellent adhec-ion to polymeric layers and vexy good machiningproperties.
-, , ~ . . .
- , ~
- . :
2 ~ .~L 7 ~
- 19 - O.Z. ~050J40893 The basic mixture from Example 5 was thickened by the addition of 80 g of a finely divided silica and 2,000 g of a finely divided aluminum hydroxide.
5The photocurable filling compound thus obtained could conveniently be applied from a tube.
The basic mixture from Example 5 was modified by the addition of 80 g of a finely divided silica and 3,000 g of a finely divided aluminum hydroxide.
The pasty filling compound thus obtained could be particularly readily applied by means of a trowel. In the cured state, it had excellent mechanical propertie~.
.:
- 9 - O.Z. 0050/40893 preparation of the polyesters are the conventional di-hydric alcohols, eg. ethylene glycol, 1,2-propylene glycol, l,3-butylene glycol, butane-1,4-diol, hexane-1,6-diol, diethylene glycol, dipropylene glycol, triethylene glycol or 2,2-dimethylpropane-1,3-diol, and, in certain amounts, also alcohols of higher functionality, eg.
~lycerol, pentaerythritol or trimethylolpropane.
Particularly preferred unsaturated polyesters are those based on phthalic acid/maleic acid/ethylene glycol/propylene glycol, which, for example, are commer-cially available in solution in styrene (having a styrene content of about 35% by weight).
Such standard polyester resin~ generally have viscosities of from 300 to 2,000 mPa.s (at 23C) in the form of 30-50~ strength solutions in styrene and can be elastified and rendered flexible by mixing with o~her polyester resins, for example those based on adipic acid/phthalic acid~maleic acid/dipropylene glycol/
propylene glycol, which are likewise commercially avail-able in solution in styrene (for example having a styrenecontent of about 25% by weigh~) and, af~er polymeriza-tion, themselves have substantially lower tensile strengths and glass transition temperatures which are below room tèmperature, the skilled worker being familiar with this procedure. Mixtures of these two ~ypes of polye~ters are preferred.
Particularly suitable copolymerizable oligomeric binders (b) are e~terification products of di- or poly-epoxide~ with acrylic acid and/or methacrylic acid. Di-and polyepoxides on which these esterification productsare based are, in particular, tho~e which axe derived from bisphenol A, as are obtained, for example, by condensation of not les8 than 2 moles of epichlorohydrin per mole of bisphenol A, and which can be subjected to chain extension using dicarboxylic acids, eg. phthalic acid. However, other suitable di- or polyepoxide~ are tho~e basad on other diol3 or polyol-~.
.. . . . .
'' :, , ~ ~ I r~
- 10 - O.Z. 0050/40893 The di- or polyepoxides ca~ be reacted with acrylic acid and/or methacrylic acid to give the abovementioned esterification products, which are prefer-ably fre~ of epoxy groups and then contain on average about two (meth)acrylate groups per molecule.
Preferred components (b~ are copolymerizable oligomeric and polymeric binders which are soluble in the photopolymerizable, ethylenically unsaturated low molecular weight compounds used as component (a). ~ow-ever, it is also possible to use, as component (b), co-polymerizable oligomeric and/or polymeric binder~ which are dispersible in the photopolymerizable low molecular weight compounds of component (a) only if the photopoly-merizable low molecular weight compounds and the oligo-meric and/or polymeric binders are compatible with oneanother and can be processed to give a homogeneous free-flowing mixture. The amount of the copolymeriæable oligomeric and/or polymeric binders (component (b)) in the total ~mount of components (a) ~ (b) is in general ~0 from 90 to 40, in particulax from 80 ~o 50, % by weight, based on the total amount of components (a) + (b).
In addition to the photopolymerizable low molecular weight compounds (a) and the copolymerizable oligomeric and/or polymeric binder~ (b), the filling com~
pounds to be used for the novel method contain, a~ com-ponent (c), one or more photopolymerization initiators, in particular in an amount of from 0.01 to 10, preferably from 0.01 to 2, % by weight, based on the total amount of components ~a) ~ (b). According to the invention, the compounds known per se and conventionally used a~ photo-initiators for photocurable materials are ~uitable for this purpose. These include in particular benzoin and benzoin derivative~, for example b~nzoin alkyl ethers, in particular where alkyl i5 of 1 to 8 carbon atoms, eg.
benzoin monomethyl ether or benzoin i~opropyl ether, ~-hydroxymethyl~enzoin and its al~yl ether~, such as ~-hydroxymethylbenzoin methyl ether, or ~-methylbenzoin and 2~:~7l~7 ~ O.Z. 0050/~0893 its ethers; benzil and benzil derivatives, in particular benzil monoketals, ~uch as benzil dimethyl ketal, benzil methyl ethyl ketal or benzil methyl benzyl ketal; the acylphosphine compounds which are effective photo-5initiators, as described, for example, in German Laid-Open Applications DOS 2,830,927, DO5 2,909,994, DOS
3,020,092, DOS 3,034,697, DOS 3,114,314 and DOS
3,133,419, and of which 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphos-10phinate and 2,4,6-trimethylbenzoylbis-o-toluylphosphine oxide are typical examples; derivatives of ~-hydroxy-acetophenone, eg. l-phenyl-2-hydroxy-2-methyl-1-propan-one, l-(p-isopropylphenyl)-2-hydroxy-2-methyl-1-propanone and l-hydroxy-l-benzoylcyclohexane;andalsobenzophenone, 15Michler's ketone, fluorenone, anthraquinone, xanthone, thioxanthone and acridone and those derivatives of these compounds which are conventionally used and known photo-initiators. The photopolymerization initiators may be present alone or as a mix~ure with one another in the 20filling compounds to be used according to the invention;
they can also be used together wi~h the activators known per se for these photoinitiators, suitable activa~ors being mainly amine compounds.
Conventional assistants and additives may be used 25as component (d) in amounts such that, when mixed with component~ (a) to (c), they give mixtures which are transparent to long-wave W light. Examples of suitable substan~es are finely divided oxidic fillers, the particle si2e of these filler~ being in general from 0.01 30to 10 ~m, preferably from 0.01 ~o 5 ~m. Examples of such fillers are colloidal or hydrophobic silica, microtalc, micromica, kaolin, aluminas and aluminum hydroxides.
Silica (eg. Aerosil~ from Degussa) and aluminum hydroxide (eg. Nartinal~ from Nzrtinswerk) and mixtures thereof are 35particularly suitable.
The use of aluminum hydroxide of the hydrargil-lite type may be particularly advantageous, if i~ has, ' ~
.
~ ~ `
2 ~ ~ 7 ~
- 12 - O.Z. 0~50/40893 for example, particle sizes (up to 80%) of from 0.2 to 3.0 ~m or a lamellar structure. Apart from the fact that this reduces the polymerization shrinkage and increases the strength, smooth surfaces and a substantially reduced tendency to crack during curing result. Moreo~er, there are only small differences between the refractive index of aluminum hydroxide and that of ~he resin component (b) or of its mixture with component (a).
The addition of finely divided silica may also help to thicken the mixture of components (a) + (b) and Lmpart thixotropic properties to said mixture, may serve as a sedimentation inhibi~or for other filler~ and may result in increased str~ngth on curing. Finely divided hydrophilic and hydrophobic silica grade~ which, for example, have particle sizes of about 12 or 14 nm may be particularly advantageous. The finely divided hydro-phobic silica grades are generally preferred for un-saturated polyester resins.
Fillers may in general be added in amounts of not more than 70% by weight, based on the total amount of the filling compound.
Other a~sistant~ and additive3, such ag paraffin (for example a paraffin having a solidification point of from 56 to 58C), in general in amounts of from 0.1 to 2%
by weight, based on the total amount of components (a) +
(b), or polymerization inhibitors, for example thermal polymerization inhibitors, such as hydroquinone, hydro-quinone derivatives, 2,6-di-tert-butyl-p-cresol, nitro-phenols, N-nitrosamines, such as N-nitrosodiphenylamine, or the salts, in particular the alkali metal and aluminum salts, of N-nitrosocyclohe~ylhydroxylamine, may be added to the materials to be used according to the invention.
Pigment~ and dyes may be u~eful for visual obsexvation during gap filling and for evaluation of gap filling. By adding plasticizers, the vi~cosity and the flow behavior of the novel pho~ocurable filling compounds can be ~aried and controlled and mechanical properties of the cured gap .
.
7~
- 13 - O.Z. 0050/40893 filling, for example toughness and resilience, can be influenced. Particularly suitable plasticizers are low molecular weight compounds, for example the known phthal-ates, or hydroxyl-containing compounds, eg. glycerol, ethylene glycol and the like, which are compatible with the components (a) and (b) of the novel filling compounds.
The photocurable filling compounds to be used for the novel method are suitable for gap filling in all gravure printing plates which can be clamped on ~he plate cylinder of a sheet-fed or web-fed rotary gravure print-ing press, for example the conventional metal gravure printing plates. However, the novel filling compounds are particularly advantageous for gap filling in gravure printing plates which are clamped on plate cylinders and have plastic printing layers which are resistant to alcoholic printing ink solvents. In the gravure printing plates having plastic printing layers, a plastic layer is applied to a suitable printing layer substrate, ink-carrying inden ations (wells) being incorporated in saidplastic layer. These wells may have been formed in the plastic printing layer by mechanical engraving or laser engraving ~cf. for example DE-A-27 52 500 or D~-A-30 28 098) or, in the case of photopolymer~c gravure printing plates, may have been incorporated in the photosensitive plastic printing layer by imagewise exposure and develop-ment (cf. DE-A-20 61 287, DE-A-31 2~ 949 and DE-A-31 28 951). The photocuxable filling compound to be used according to the invention can be very advantageously used in wrap-around gravure printing plates for filling the gap formed between the ends of ~he gravur~ printing plate when these wrap~around plates are clamped on a plate cylinder. However, it i also suitable for filling the gaps formed between the end regions and/or lateral edges of the individual gravure printing plates when a plurality of said plates a e mounted one behind the other and/or side hy sida on a single plate cylinder/ for `
2 ~
- 14 - O.Z. 0050/40893 example by means of saddle constructions known per se and suitable for this purpose. For the purposes of th~
present invention, gravure printing plates are both the ready-prepared gravure printing plates in which the ink-conveying indentations have already been introduced, and the gravure printing plate blanks in which the wells have not yet been formed. Thus, it is also possible to clamp a ready-prepared gravure printing plate on the plate cylinder and then to fill the resulting gap~ with the filling compound to be used according to the invention, or first to clamp gravure printing plate blanks on the plate cylinder, then to fill the resulting gaps with the filling compound and only thereafter to introduce the wells into the printing layer of the printing plates.
Clamping of the gravure printing plates on the plate cylinder is known per s~ and is carried out, for example, by means of permanent magnets or by mechanical means for fastening and clamping printing plates. Plate cylinders used for this purpose are in general those where the gravure printing plates are fastened and clamped by hooking in and anchoring one plate end, preferably both plate ends, which is or are bent over for thi~ purpose, in an anchoring groove or channel in the cylinder.
In the novel method, the filling compound for filling the gap~ formed when the gravure printing plate~
are clamped on the plate cylinder can be introduced into the gap by any ~uitable methods or processes, provided that uniform and complete filling of the gap cavity is ensured.
Application of the photocurable materials to be used as sealing or filling compounds in the novel method can be effected, for example, in a very simple manner by straightforward application of the material~, for example from a tube, cartridge or sLmilar metering apparatus, onto those areas of the printing plates andJor plate cylinders which are to be ~ealed, and simple mechanical pressing onto or into the orifice~ or cavities ~o be . ri~ Pl - 15 - o.Z. 0050/~0893 filled, for example by means of a spatula, a scraper or the like. Excess filling material can then be readily removed by sLmply wiping it off from the printing plate surface or from the end faces of the printing plate cylinder thus obtained. According to the invention, no spPcial equipment or procedure i~ thus necessary for filling and/or sealing the orifices and gap~. Subsequent machining is often unnecessary; as a rule, however, it is advantageous to smooth the surface of the cured compound by subsequent machining, for example by grinding, milling and/or polishing, and to adapt it to the contour of the cylinder. To remove the printing plates from the plate cylinder, no special apparatuses or expensive procedures are required. The extent of the adhesion (gap filling compound/printing plate) can be controlled by changing the mixing ratioR of component~ (a) + (b), preferably the various amounts of polymers in components (b). This too is a particular advantage of the novel method~ Printing plates which have been used can be reused without restriction.
After the gap~ have been filled, the photocurable filling compound i9 exposed to actinic light for curing.
All known light sources capable of emitting light in the actinic wavelength range effective for the filling com-pounds, in particular in the wavelength range from about250 to 450 nm, can be used for this pu~pose, fox example carbon arc lamps, actinic or ~uperactinic fluore~cent tubes, low pressure, medium pressure or high pressure mercury lamps, which may be doped, xenon lamps or even laser3 having a hiqh W content.
The materials to be used according to the invention for filling and/or sealing orifices, cavities or voids in printing plate~ moun~ed on pla~e cylinder~
ha~e both high stability to the solvent~ and solvent mixtures usually used in printing inks, in particular polar solvents or ~olvent mixtures of this type, such as alcohols r e~ter~ and ketones, and wide variability in : ' :
,' '~ . ' , ' ': ' "
r~
- 16 - O. Z . 0050/408g3 relation to the application (flow behavior, spreadability, adhesion, surface ~moothnes-~ and machining) as a result of the addition of different amounts of one or more oxidic fillers.
5The physical properties of the materials to be used according to the invention, before and after curing, can be adapted within par~icularly wide limits to the practical requirements.
In the Examples, parts and percentages are by 10weight, unless stated otherwise.
114 g of an esterification product of methacrylic acid (2 moles) with a reaction product ~1 mole) contain-ing about two epoxy groups in ~he molecule and obtained 15from bisphenol A and epichlorohydrin and 130 g of an un-saturated polyester of maleic acid/phthalic acid/adipic acid/neopentyl glycol (molar ratio 2.15 : 1 : 6 : 9.5) were dissolved in 156 g of styrene. 2.61 g of ben~il di-methyl ketal and 1.28 g of trimethylbenzoyldiphenylphos-20phine oxide were added to the solution. The resulting mixture was homogenized and devolatilized under reduced pressure. The gap filling compound thus obtained can readily be in~ected into the cavities to be filled in a gravure printing cylinder.
25The material was cured by expo~ure to ultraviolet light.
~he mechanical properties and the adhe~ion of the gap filling ~hu~ produced were ~o good that it withstood long print runs without problem~. It has to be mechani-30cally 3eparated in order to remove the plate.
21.7 g of a finely divided silica and 229 g of a finely divided aluminum hydroxide were inc~rporatedl while stirring, into the liquid photosensitive mixture 35described in Example 1. The pasty material obtained afte~ complete homogenization and devolatilization could readily be introduced into tho cavities and joint~ to be ,. . ~ .
" ~
: : . . .:
20~7~3rJ
17 - O.Z. 0050t40893 filled, by means of a trowel or with the aid of a tube.
Curing of the gap filling compound was effect~d as described in Example 1.
132 g of a polyether obtained from bisphenol A
and epichlorohydrin and esterified with methacrylic acid and 148 g of an unsaturated polyester of 8 parts of maleic anhydride, 12 parts of phthalic anhydride, 14 parts of adipic acid, 12 parts of pxopylene glycol and 26 parts of dipropylene glycol were dissolved in 174 g of styrene. 2.96 g of benzil dimethyl ketal and 1.46 g of trimethylbenzoyldiphenylphosphine oxide were added to this solution.
After devolatilization, the syrupy material thus obtained could be used for fillin~ joints and cavities.
It could readily be applied by in~ection. Curing was effected by exposure to ultraviolet li~ht.
225 g of a polyethar obtained from bisphenol A
and epichloroh~ydrin and esterified with methacrylic acid were di-~solved in 200 g of hexanediol diacrylate. 0.7 g of the pota~sium salt o~ N-nitro~ocyclohexylhydroxyl-amine, in the ~orm of a 30~ strength methanolic ~olution, - was then added. Finally, 0.85 g of trimethylbenzoyldi-phenylphosphine oxide was stirred in.
~he material was devolatilized in the usual manner. It could particularly readily be injected into the ~oint-q to ba filled and, after curing by mean~ of W
light, exhibited very good resistance to ethanol.
6.0 g of trimethylbenzoyldiphenylphosphin~ oxide, 1.5 g of benzil dimethyl ketal, 0.2 g of hydroquinone monomethyl ether and 3.8 g of paraffin (solidification point 56-58C), dissolved in 34 g of styrene, wer~ added to a solution of 1,070 g of a polyether, obtained from bisphenol A and epichlorohydrin and esterifled with meth-acrylic acid, in 810 g o~ ~tyrene.
. ~ .: . .. .
. ........................... . . .
.
: :. .: . .
2 ~ ~ r~ 7 - 18 - O.Z. 0050/40893 The only slightly syrupy mix~ure was homogenized and devolatilized under reduced pressure. The photopolymerizable ma~erial thus obtained wa~ used for filling the orifice ~etween the two ends of a printing S plate clamped on a cylinder. Because of its good flow behavior, the material is particularly suitable for injection by means of a hose or tube ~y~tem into narrow and/or poorly accessible cavities or orifices.
The material was prepared essentially as des-cribed in Example 5. In addition, 40 g of a finely divided silica were added before the homogenization and devolatilization step.
The material thus Dbtained had a somewhat higher lS viscosity. It wa~ used in a manner similar to that de~-cribed in Example 5.
A photopolymerizable filling compound wa~ prep-ared on the basi~ of the formulation of Example 5, using 80 g of a finely divided ~ilica.
In ~pite of the substantially increased ViSC08-ity, this material could still be in~ected through suitable pipe apparatuseC into the cavitie~ to b~ filled.
The higher visco~ity has the advantage that slight leaks in the syst~m cause no problems.
80 g of a finely divided silica and 860 g of a finely divided aluminum hydroxide were added to the mixture of the organic component~ of Example 5 before the homogenization and devolatilization step.
~ he viscous material thus obtained can be intro-duced into the cavities to be filled, not only by means of wide-bore application systems but also by mean3 of a trowel. In the cured state, it exhibits excellent adhec-ion to polymeric layers and vexy good machiningproperties.
-, , ~ . . .
- , ~
- . :
2 ~ .~L 7 ~
- 19 - O.Z. ~050J40893 The basic mixture from Example 5 was thickened by the addition of 80 g of a finely divided silica and 2,000 g of a finely divided aluminum hydroxide.
5The photocurable filling compound thus obtained could conveniently be applied from a tube.
The basic mixture from Example 5 was modified by the addition of 80 g of a finely divided silica and 3,000 g of a finely divided aluminum hydroxide.
The pasty filling compound thus obtained could be particularly readily applied by means of a trowel. In the cured state, it had excellent mechanical propertie~.
.:
Claims (8)
1. A method for filling and/or sealing orifices, cavities or voids, which are formed when printing plates resistant to alcoholic printing ink solvents are mounted on a plate cylinder, by means of a sealing or filling compound, wherein the sealing or filling compound used is a material which is photocurable at room temperature and essentially consists of a photopolymerizable mixture of (a) from 10 to 60% by weight of one or more photopoly-merizable, ethylenically unsaturated low molecular weight compounds and (b) from 90 to 40% by weight of one or more copolymeriz-able oligomeric or polymeric binders which are com-patible with the photopolymerizable low molecular weight compounds of component (a), the sum of the percentages stated under (a) and (b) being 100, and additionally (c) from 0.01 to 10% by weight, based on the total amount of components (a) and (b), of one or more photopolymerization initiators, with or without (d) conventional assistants and additives in an amount such that, as a mixture with components (a) to (c), they give mixtures which are transparent to long-wave UV light, and which, after application in and on the orifices, cavities or voids to be filled or sealed, is cured by exposure to light and may then be machined.
2. A method as claimed in claim 1, wherein the sealing or filling compound additionally contains a thermal polymerization inhibitor.
3. A method as claimed in claim 1 or 2, wherein from 0.1 to 2% by weight, based on the total amount of components (a) + (b), of a paraffin are added to the sealing or filling compound.
- 21 - O.Z. 0050/40893
- 21 - O.Z. 0050/40893
4. A method as claimed in any of the preceding claims, wherein one or more compounds from the group consisting of the vinylaromatics and of the hydroxyl-free esters of acrylic acid or methacrylic acid with mono-hydric or polyhydric alcohols are used as component (a).
5. A method as claimed in claim 4, wherein styrene is used as component (a).
6. A method as claimed in claim 4, wherein one or more esters of acrylic acid or methacrylic acid with a monoalkanol of 1 to 12 carbon atoms are used as component (a).
7. A method as claimed in any of the preceding claims, wherein one or more copolymerizable oligomeric or polymeric binders from the group consisting of the unsaturated polyesters and the esterification products of di- or polyepoxides with acrylic acid or methacrylic acid are used as component (b).
8. A method as claimed in any of the preceding claims, wherein finely divided oxidic fillers from the group consisting of aluminum hydroxide and silica are added to the sealing or filling compound.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3920093.0 | 1989-06-20 | ||
| DE19893920093 DE3920093A1 (en) | 1989-06-20 | 1989-06-20 | METHOD FOR CLOSING AND / OR SEALING OPENINGS, CAVES OR SPACES IN PRINTING PLATES APPLIED ON FORM CYLINDERS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2017497A1 true CA2017497A1 (en) | 1990-12-20 |
Family
ID=6383115
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2017497 Abandoned CA2017497A1 (en) | 1989-06-20 | 1990-05-24 | Filling and/or sealing orifices, cavities or voids in printing plates mounted on plate cylinders |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0406585A3 (en) |
| JP (1) | JPH0334855A (en) |
| CA (1) | CA2017497A1 (en) |
| DE (1) | DE3920093A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5998098A (en) * | 1996-12-23 | 1999-12-07 | E. I. Du Pont De Nemours And Company | Process for adhering the edges of photopolymerizable printing plates or photopolymer printing forms for flexographic printing |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7201336B2 (en) * | 2003-12-30 | 2007-04-10 | 3M Innovative Properties Company | Liquid spray gun with non-circular horn air outlet passageways and apertures |
| DE102011001315A1 (en) * | 2011-03-16 | 2012-09-20 | Contitech Elastomer-Beschichtungen Gmbh | System consisting of a blanket cylinder and a blanket |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8416571D0 (en) * | 1984-06-29 | 1984-08-01 | Asahi Chemical Industry Uk Ltd | Flexographic printing |
| DE3710146A1 (en) * | 1987-03-31 | 1988-10-13 | Basf Ag | METHOD FOR CLOSING AND / OR SEALING OPENINGS, CAVES OR SPACES IN PRINTING PLATES APPLIED ON FORM CYLINDERS |
| DE3712070A1 (en) * | 1987-04-09 | 1988-10-20 | Basf Ag | METHOD FOR JOINING THE CUT EDGES OF PHOTOPOLYMERIZED FLEXO PRINTING FORMS |
| DE3736180A1 (en) * | 1987-10-26 | 1989-05-03 | Basf Ag | METHOD FOR CLOSING AND / OR SEALING OPENINGS, CAVES OR SPACES IN PRINTING PLATES APPLIED ON FORM CYLINDERS |
-
1989
- 1989-06-20 DE DE19893920093 patent/DE3920093A1/en not_active Withdrawn
-
1990
- 1990-05-24 CA CA 2017497 patent/CA2017497A1/en not_active Abandoned
- 1990-06-11 EP EP19900110994 patent/EP0406585A3/en not_active Withdrawn
- 1990-06-13 JP JP15290590A patent/JPH0334855A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5998098A (en) * | 1996-12-23 | 1999-12-07 | E. I. Du Pont De Nemours And Company | Process for adhering the edges of photopolymerizable printing plates or photopolymer printing forms for flexographic printing |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3920093A1 (en) | 1991-01-03 |
| JPH0334855A (en) | 1991-02-14 |
| EP0406585A3 (en) | 1991-07-31 |
| EP0406585A2 (en) | 1991-01-09 |
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