CA1041257A - Producing printing plates by covering polymeric coating with flexible sheet and applying pressure - Google Patents
Producing printing plates by covering polymeric coating with flexible sheet and applying pressureInfo
- Publication number
- CA1041257A CA1041257A CA191,271A CA191271A CA1041257A CA 1041257 A CA1041257 A CA 1041257A CA 191271 A CA191271 A CA 191271A CA 1041257 A CA1041257 A CA 1041257A
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- resin composition
- support structure
- sheet material
- layer
- resin
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Abstract
ABSTRACT OF THE DISCLOSURE
A process and apparatus are provided for making polymer plates that include a uniformly thick layer of a resin composition adhering to a base or support plate. The disclosed process in-cludes the steps of applying a resin composition to a base plate.
coating the surface of the resin composition with a sheet of thermoplastic material, rolling the covered resin composition and base plate with rollers, cooling the resultant plate, peeling off the sheet material and then drying the resultant polymer plate.
A process and apparatus are provided for making polymer plates that include a uniformly thick layer of a resin composition adhering to a base or support plate. The disclosed process in-cludes the steps of applying a resin composition to a base plate.
coating the surface of the resin composition with a sheet of thermoplastic material, rolling the covered resin composition and base plate with rollers, cooling the resultant plate, peeling off the sheet material and then drying the resultant polymer plate.
Description
~4~7 BACKGROUND OF THE INVENTION
- This invention relat~s generally to a process for making polymer plates and more specifically to a unique process ~or continuously manufacturing polymer plates having a layer of resin composition that is soluble in water and/or a vol-atile solvent and is useful, for example, as a photopolymeri-zable element for a printing plate.
A significant demand has developed in the printing and newspaper industries for photopolymer printing plates, sometimes referred to as cladplates, which include a supporting ;
structure, such as metal, and a photopolymerizable resin com-position rigidly secured to the supporting structure. Con-~` ventional techniques for making such plates involve the mold-ing, casting, extrusion and/or calendering of the resin com-position onto a support structure, such as aluminum, tin or steel. It is known, for example, t~hat resin compositions, having a water soluble or volatile solvent soluble polymer and a monomer compatible therewith as their primary com-ponents, can first be molded to form a plate or membrane, and then subsequently adhered onto a base or support plate, suGh as aluminum, tin or steel plates.
Besides requiring two distinct and, therefore, expensive steps, e.g., molding and then adhering, such tech-niques are not entirely satisfactory for use with the most desirable types of resin compositions useful as photopoly-merizable elements. It has been recognized, for example, that the most desirable types of resin compositions include highly reactive monomer components that are stimulated at temperatures of 80C. or more and, thus, generally cause the resin composition to assume a gelatin condition at com-monly used molding temperatures. Conventional molding tech-niques, therefore, had to be modified to operate at tem-peratures below 80C.
- This invention relat~s generally to a process for making polymer plates and more specifically to a unique process ~or continuously manufacturing polymer plates having a layer of resin composition that is soluble in water and/or a vol-atile solvent and is useful, for example, as a photopolymeri-zable element for a printing plate.
A significant demand has developed in the printing and newspaper industries for photopolymer printing plates, sometimes referred to as cladplates, which include a supporting ;
structure, such as metal, and a photopolymerizable resin com-position rigidly secured to the supporting structure. Con-~` ventional techniques for making such plates involve the mold-ing, casting, extrusion and/or calendering of the resin com-position onto a support structure, such as aluminum, tin or steel. It is known, for example, t~hat resin compositions, having a water soluble or volatile solvent soluble polymer and a monomer compatible therewith as their primary com-ponents, can first be molded to form a plate or membrane, and then subsequently adhered onto a base or support plate, suGh as aluminum, tin or steel plates.
Besides requiring two distinct and, therefore, expensive steps, e.g., molding and then adhering, such tech-niques are not entirely satisfactory for use with the most desirable types of resin compositions useful as photopoly-merizable elements. It has been recognized, for example, that the most desirable types of resin compositions include highly reactive monomer components that are stimulated at temperatures of 80C. or more and, thus, generally cause the resin composition to assume a gelatin condition at com-monly used molding temperatures. Conventional molding tech-niques, therefore, had to be modified to operate at tem-peratures below 80C.
2 --.
~lZ~7 In addition, ho~eyer, when the most desirable types of resin compositions are exposed to air at temperatures above 40C, their surfaces begin to dry and an undesirable skin is formed on the resin. Thus, conventional molding techniques have the further disadvantage of permitting such air exposure and skin formation on the resin compositions.
Finally~ it has also been recognized that the monomer component of such desired resin compositions shifts at tempera-tures below 20C and such shifts reduce the adhesion strength f the surface of such resin compositions to the base or support material.
Thus, there is a significant need for polymer plates utilizing such desired resin compositions and for a process for making such plates without the above-mentioned disadvantages of conventional molding techniques.
According to one apsect of the invention there is provided a process for the continuous production of photosensitive printing plates having a metallic support structure and a uniform layer of a photopolymerisable resin composition in adherent contact therewith, which process comprises: (a) applying to the support structure a coating of a paste-like photopolymerisable resin composition comprising a solution of a polymer and a com-patlble monomer in water and/or a volatile solvent, wherein the resin composition is reactive at a temperature of 80C or above, and wherein the temperature of the resin composition is maintained at a value in the range of from 50 to 70C during the time in which it is applied to the support structure; tb) covering the surface of the applied coating of photopolymerisable resin composition with a flexible thermoplastic sheet material; (c)
~lZ~7 In addition, ho~eyer, when the most desirable types of resin compositions are exposed to air at temperatures above 40C, their surfaces begin to dry and an undesirable skin is formed on the resin. Thus, conventional molding techniques have the further disadvantage of permitting such air exposure and skin formation on the resin compositions.
Finally~ it has also been recognized that the monomer component of such desired resin compositions shifts at tempera-tures below 20C and such shifts reduce the adhesion strength f the surface of such resin compositions to the base or support material.
Thus, there is a significant need for polymer plates utilizing such desired resin compositions and for a process for making such plates without the above-mentioned disadvantages of conventional molding techniques.
According to one apsect of the invention there is provided a process for the continuous production of photosensitive printing plates having a metallic support structure and a uniform layer of a photopolymerisable resin composition in adherent contact therewith, which process comprises: (a) applying to the support structure a coating of a paste-like photopolymerisable resin composition comprising a solution of a polymer and a com-patlble monomer in water and/or a volatile solvent, wherein the resin composition is reactive at a temperature of 80C or above, and wherein the temperature of the resin composition is maintained at a value in the range of from 50 to 70C during the time in which it is applied to the support structure; tb) covering the surface of the applied coating of photopolymerisable resin composition with a flexible thermoplastic sheet material; (c)
3~ applying pressure to the sheet material sufficient to make the coating of the photopolymerisable resin composition relatively _ 3 _ ..' ` 1634~125~
uniform; (d~ cooling~said layer of resin composition, said sheet material and said support structure; (e~ removing the sheet material from the photopolymerisable resin composition;
and (f) drying the result~ng layer of photopolymerisable resin composition and support struct`ure for a time sufficient to bring the resin into adherent contact with the support structure.
According to another aspect of the invention there is provided an apparatus for the continuous manufacture of photo-i:
polymer printing plates having a metallic support struc~ure anda photopolymerisable resin composition in adherent contact there-with comprising: (a) means for containing said resin composition and for dispensing said composition when desired; (b) means for continuously transporting said support structure with respect , to said resin containing and dispensing means to permit the deposit of a layer of resin composition on said support structure;
(c) means for applying a continuous sheet of flexible thermo-plastic sheet material to the surface of said resin composition;
(d) a:plurality of successive pairs of spaced apart pressure ~20 rollers arranged along the transporting means and disposed on opposite sides of said resin compos~it;ion layer for applying pressure to said layer of resin composition to uniformly spread ~sald layer over said support structure; (e) means for cooling said layer of resin composition, said thermoplastic sheet ~ ~ material and said support structure~; (f) means for removing said : sheet material from said layer of resin; and (g) means for drying said layer of resin composition and said support structure for a time sufficient to firmly secure said layer of resin to said support structure.
~ 3a -. .
Brief Description of the Drawings The process of the present invention will be better understood through reference to the accompanying drawings in which:
- Figure 1 is a diagrammatic axial sectional view of one example of an apparatus which can be used in practicing the process of this invention;
Figure 2 is an enlarged view of section A of the apparatus illustrated in Figure l;
Figure 3 is an enlarged view of section B of the apparatus illustrated in Figure l; and Figure 4 is an enlarged view of section C of the apparatus illustrated in Figure l; and Figure 5 is an alternative arrangement of the rollers sho~n in Figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Although any number of resin compositions are use-ful in the practice of this invention, it has been found that a~resin having a polymer soluble in water and/or a volatile 20 ~ solvent as one of its primarey components is especially use-- ful. Such polymer components include, for example, polyvinyl alcohol, partially saponified polyvinyl acetate, partial carbamoyl ester of polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl me~thyl cellulose phthalate, sodium carboxymethyl cellulose, gelatin, polyvinyl acetate, , . . .
polyvinyl acetal or nylon. The mon~omer component which is compatible with the polymer includes an acryla e or meth-- acrylate with a free hydroxyl group in the alcohol component of the esters, (e.g., B-hydroxyethyl acrylate, B-hydroxyethyl methacrylate, B-hydroxypropyl acrylate or B-hydroxypropyl methacrylate, or mixture thereof), or a half-ester of acrylic .
~ - 4 -or methacrylic acid with polyethylene glycol wherein the hy-droxyl group opposite the ester component is esterified or ; etherified (eg., methoxy polyethylene glycol monoacrylate, ; methoxy polyethylene glycol monomethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate). Water and/or a volatile solvent, for example, a lower alcohol such as ethyl ox methyl alcohol, are suitable as their solvents for such resins.
According to the present invention, a polymer plate can be continuously manufactured in either a water soluble type of resin composition or a volatile solvent-soluble type of resin composition. Thus, the process is ex-plained in detail below in relation to the water-soluble type of x~sin composition (hereinafter referred to as a water soluble resin composition)~ The water soluble resin composition is used herein to mean a resin composition having as primary components a polymer soluble in water and a monomer compatible therewith and including water (hereinafter referred to as a water inclusive resin composition) from which the water has ` 20 been removed.
The following is an example of the steps involved in the preparation of the water inclusive resin composition used in the practice of this invention: 40 to 60 parts by weight of a highly reactive and ~water soluble acrylic monomer is added dropwise to 100 parts by weight of a 50 to 70~ by weight aqueous solution of a polyvinyl alcohol tdegree of saponification: 78 to 98 ~ole %, average degree of polymeri-zation : 500 to 2000) and then the mixture is mixed in a kneader at a temperature of 60 to 80C fo~ 30 minutes. A~ter the mixing is completed, the mixture is subjected to defoaming under reduced pressure (liquid temperature: 60 to 80C.). The viscosity of water inclusive resin composition thus obtained is 30,000 to 100,000 cps.
This resin composition is then used in ~he process of this invention to continuously make a polymer plate. Speci-fically, the present process for the continuous manufacture of polymer plates having a uniformly thick layer of water soluble resin composition is one that utilizes the variation of the adhesion strength resulting from the variation of heat; and is characterized by applying the water inclusive resin composi-~; ton heated at about 50 o 70C. to a base plate, and then coating the surface with a sheet material in order to prevent the form-ation of a skin on the surface of the resin when it is rolled.
After coating the resin with sheet material, the resin is rolled to form a uniformly thick layer, cooled to about 20C. or below to reduce the adhesion strength between the surface and the sheet material, after which the sheet material is peeled off the resin. Thus, the present process consists of the con-tinuous steps comprising the application of the water inclusive res m composition to the base plate, the coating of the applied :`
plate with a sheet materia-l, the rolling of the resin into a uniform layer, the cooling of the resultant polymer plate so formed, the removal of thP sheet material, and the drying of the resultant polymer plate.
Figure 1 indicates one apparatus which can be used in the practice of this invention. The illustrated apparatus includes a base plate 23 and sheet 24 which are transported to subsequent processing continuously by a con-veyor 21 having a rubber or steel belt. A hopper 25 for con-taining the resin is provided, along with an assembly for supplying sheet material 24, a means for applying pressure 26, a cooling device 27, a means for peeling off the sheet mat-erial 28, and a drying device 29j all of which are arranged in order following the direction of the above conveyor 21.
~\
1~4~L257 Hopper 25 is provided with a valve 30 that controls the amount of the flow of the water inclusive resin composition in accordance with the width and speed o the base plate~ A
restraining board 31 is also provided to prevent protrusion of resin from the base plate 23 when it is applied to the base plate. In this way, the resin composition is utilized more efficiently.
Either a long or endless sheet 24 can be used in the apparatus illustrated in Figure 1. In the case of a long sheet, the sheet material is unwound by the reel-out roller 32 and after adhering the applied surface and being peeled off by the peeling roller 48 (which is one type of peeling off means 28) the sheet material is wound by the reel-in roller 33. Cleansing rollers 34 are furnished both upstream of the reel-out roller 32 and downstream of reel-in roller 33.
In all cases, the sheet material 24 operates synchronous to the conveying speed.
A number of individual press rollers 46 are at-tached above and below the conveyor as the pressing means 26 .
~20 to press from above and below the water inclusive resin com-;~ position inserted between the base plate 23 and the sheet materiàl 24. The press rollers 46 are maintained at a tem-perature of 60 to 70~C. by means of a hot water jacket in order to prevent the lowering of tha temperature of the water : .
inclusive resin composition at the time of rolling. These prèss rollers 46 are ordinary rollers and have a pressure of 1 to 10 kg/cm at the time of rolling. The thickness of polymer plates consisting of base plate and water inclusive resin composition can be controlled accurately by using many pairs of upper and lower rollers and arranging them in such a manner that the clearance between upper and lower rollers of each pair is gradually reduced. For example, 8 rollers having the same diameter are arranged in 4 pairs of upper and lower rollers.
The lower rollers are located in the same horizontal level, and the upper rollers are located respectively above the lower rollers in such a manner that the clearance between up-per and lower rollers is gradually reduced, as shown in Figure 5~ In practice, the difference (hereinafter termed as a gap) betwee~ the clearance of a pair of upper and lower rollers and the clearance of the next pair of rollers is adjusted within a range of 20 to 100 ~. In this case, polymer plates having thickness of lOOO~ can be produced with a precision of ~ 25~. It is desirable in the practice of this invention to remove air bubbles between the water inclusive resin composi-tion and the sheet material by adjusting the pressure at the time of rolling. This press~ure at the time of rolling is determined by the gap mentioned above. When the gap is ad-justed to more than 100~ , air is admitted and the air bubbles become more congested between the sheet and the water inclusive ~ ~ resin compositlon. It is desirable, therefore, for the gap ; ~ to be 20 to 100 ~. Furthermore, it is possiblè` to obtain ; polymer plates having a greater precision of thickness merely by increasing the number of pairs of upper and lower : ~
rollers from 10 to ao. In addition, it is possible to make the thickness of the water inclusive resin composition from 500 to 2000 ~ by adjusting the clearance between the final rolling rollers.
The cooling device 27 is generally an air circula-tion style cooling assembly with a 0 to 5C. temperature at the outlet of the air blower. It is typically divided into two ; chambers, a normal temperature chamber at 10 to 20C. and a cooled air chamber at 3 to 8C. The use of two chambers pre-vents water from forming when the polymer plate goes from the cooling device back to room temperature and also reduces the 257 - ~:
possibility of undesirable effects resulting from the reuse of the sheet material.
Because of the temperature of the resin com-position when the sheet material is peeled off, the surface of the resin may have waves. This will generally not occur under normal conditions, but even if it does, the polymer plate can be leveled before the drying process commences.
The drying device 29, which dries the polymer plate after the sheet material is peeled off, is indirectly operated by hot air circulation, so that the ultimate drying temperature is in the range of about 60 to 80C. Even though the polymer plate is dehydrated and contracts during this process, the final product desiréd can be easily obtained merely by calculating beforehand the contraction rate and ap-~`~ plying the resin composition accordingly. For example, when ~ the polymer plate is dried for 40 to 60 minutes at 80C. with "~ wind speed of 0.5 to 2.0 m/sec.~, and RH 1%, the contraction rate lS 7 to 10~. Since air bubbles will form on the surface of the resin adjoining the base plate when the drying tem-~perature is high, it is desirable that the plate be dried at ` a~temperature below the boiling point of the included volatile component.
,-It is also preferred that an assembly be provided ~` to regulate the movement of the base plate and sheet material - to prevent them from swerving. Moreover, a base plate supply :
device 35 that supplies the base plate is also provided in the illustrated apparatus.
It should be understood that each of the devices, means and mechanisms described above are linked together and are utilized with the base plate, water inclusive resin com-position and sheet in manufacturing polymer plate continuously.
Thus, the process of this invention for the _ g _ .
lZ57 continuous manufacture of polymer plates having a layer of uniform thickness of a water soluble resin composition can be illustrated through reference to the accompanying drawings.
The water inclusive resin composition prepared on the basis of the example described above is added into the hopper 25 and flow~d out in suitable portions onto the base plate 23 by controlling the valve 30. Thus, measured amounts of the resin composition can be applied between the base plate 23 and the sheet material 24 set between the upper and lower press rollers 46, 46'. At this time, the temperature of the water inclusive resin composition is maintained at 50 to 70C. In terms of limitations of thickness, mechanical propertles and prevention of chemical attack, the base plate may be preferably made from steel, aluminum, and other metals, and may even be a long coil plate or cut plate. In the case of cut plate, a sheet of kra~t paper of a thickness of 80 +
S ~ can~be used as an under sheet below the base plate and ;~ cellulose tape can be affixed between each sheet to make a continuous sheet in order to prevent the water inclusive resin composition from spilling under the base plate. In ; addition, in order to improve the adhesion of the surface of the base plate 23 to the water inclusive resin composition, the base plate can be sandpolished or pre-coated with an ad-hesive and then supplied continuously by the base plate supply device 35.
The sheet material covering the surface of the water inclusive resin composition in order to prevent a skin from forming thereon should desirably be of a constant thickness and smooth, flexible, toughl and readily removable. For ex-ample, a commercially available polyester sheet (thickness, 125 to 250 ~) or a rigid polyvinyl chloride sheet (thickness 200 to 300 ~) can be preferably used as a sheet material 24.
~4~2S7 The sandwich polymer plate made from the base plate, water inclusive resin composition and sheet is then rolled by passing it between the press rollers 46, 46'. Then the polymer plate of the water inclusive resin composition rolled to the prescribed thickness is conveyed to the cooling device and cooled. The temperature for the above composition is reduced from about 40C. to 65C., to approximately 20C.
at the tlme of rolling. Then, the sheet material 24 is peeled off the cooled sandwich polymer plate by the peelin~-off rolleræ 48. When the polymer plate from which the sheet has been peeled is dried by passing it through the drying device 29, a polymer plate having a layer of uniform thickness of a water inclusive resin composition is obtained. The drying ~` time for the polymer plate will vary according to the thickness and properties of the water inclusive composition, but generally drying can be accomplished in 100 to 120 minutes under the conditions where the thickness of the layer of the water in-clusive resin composition is 1.00 mm, the wind speed 1.5 to 2.0 w/sec., and the temperature 78C.
~:, ;~ 20 Finally, polymer plates having the required measurement are obtained merely by cutting the polymer plates , obtained above, that is, polymer plates having a layer of uniform thickness of a water soluble resin composition are cut to the required size.
As explained in detail above, according to the process of the invention, there is no need to previously mold the water or volatile solvent inclusive resin composition in the form of a plate or membrane, but instead it is possible, in accordance with this invention, to manufacture polymer plates having a layer of uniform thickness of a resin composi-:
tion soluble in water and/or a volatile solvent inexpensively and continuously. In addition, this process is especially 5i7 suited for industrial manufacture of such products as a water soluble photopolymer printing plate for printing mat-erial. For example, polymer plates containing, as the water inclusive resin composition, (a) 255.3 parts by weight of 33.6% aqueous solution of polyvinyl alcohol (degree of saponification: 82 mole %, average degree of polymerization:
500), (b) 213.2 parts by weight of ~-hydroxyethyl methacrylate, (c) 5.9 parts by weight of benzoin, and (d) 0.01 parts by weight of hydroquinone can be used in the practice of this invention ~o make excellent photopolymer printing plates.
According to the present invention, polymer plates can be manufactured at the relatively low temperature of 80C. or below, and therefore a resin composition that includes among its components a thermal polymerizable compound can be readily used in the practice of this invention at a temperature below that which will normally cause thermal ~: .
polymerization. The process of this invention has the further advantages of (a) being readily useable with water inclusive resin compositions, (b) being relatively inexpensive and . . .
(c) ~being capable of making polymer plates that have high adheeion between res-~n and base~plate, and thus forming ex-tremely strong polymer plates.
Although a number of specific embodiments of thi~ invention have baen disclosed herein, it should be under-stood that the present invention is in no way limited by the specific features of the disclosed embodiments. Rather, it is intended that various modifications and equivalents of the disclosed embodiments can be made without departing from the spirit and scope of this invention as defined by the following claims.
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uniform; (d~ cooling~said layer of resin composition, said sheet material and said support structure; (e~ removing the sheet material from the photopolymerisable resin composition;
and (f) drying the result~ng layer of photopolymerisable resin composition and support struct`ure for a time sufficient to bring the resin into adherent contact with the support structure.
According to another aspect of the invention there is provided an apparatus for the continuous manufacture of photo-i:
polymer printing plates having a metallic support struc~ure anda photopolymerisable resin composition in adherent contact there-with comprising: (a) means for containing said resin composition and for dispensing said composition when desired; (b) means for continuously transporting said support structure with respect , to said resin containing and dispensing means to permit the deposit of a layer of resin composition on said support structure;
(c) means for applying a continuous sheet of flexible thermo-plastic sheet material to the surface of said resin composition;
(d) a:plurality of successive pairs of spaced apart pressure ~20 rollers arranged along the transporting means and disposed on opposite sides of said resin compos~it;ion layer for applying pressure to said layer of resin composition to uniformly spread ~sald layer over said support structure; (e) means for cooling said layer of resin composition, said thermoplastic sheet ~ ~ material and said support structure~; (f) means for removing said : sheet material from said layer of resin; and (g) means for drying said layer of resin composition and said support structure for a time sufficient to firmly secure said layer of resin to said support structure.
~ 3a -. .
Brief Description of the Drawings The process of the present invention will be better understood through reference to the accompanying drawings in which:
- Figure 1 is a diagrammatic axial sectional view of one example of an apparatus which can be used in practicing the process of this invention;
Figure 2 is an enlarged view of section A of the apparatus illustrated in Figure l;
Figure 3 is an enlarged view of section B of the apparatus illustrated in Figure l; and Figure 4 is an enlarged view of section C of the apparatus illustrated in Figure l; and Figure 5 is an alternative arrangement of the rollers sho~n in Figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Although any number of resin compositions are use-ful in the practice of this invention, it has been found that a~resin having a polymer soluble in water and/or a volatile 20 ~ solvent as one of its primarey components is especially use-- ful. Such polymer components include, for example, polyvinyl alcohol, partially saponified polyvinyl acetate, partial carbamoyl ester of polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl me~thyl cellulose phthalate, sodium carboxymethyl cellulose, gelatin, polyvinyl acetate, , . . .
polyvinyl acetal or nylon. The mon~omer component which is compatible with the polymer includes an acryla e or meth-- acrylate with a free hydroxyl group in the alcohol component of the esters, (e.g., B-hydroxyethyl acrylate, B-hydroxyethyl methacrylate, B-hydroxypropyl acrylate or B-hydroxypropyl methacrylate, or mixture thereof), or a half-ester of acrylic .
~ - 4 -or methacrylic acid with polyethylene glycol wherein the hy-droxyl group opposite the ester component is esterified or ; etherified (eg., methoxy polyethylene glycol monoacrylate, ; methoxy polyethylene glycol monomethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate). Water and/or a volatile solvent, for example, a lower alcohol such as ethyl ox methyl alcohol, are suitable as their solvents for such resins.
According to the present invention, a polymer plate can be continuously manufactured in either a water soluble type of resin composition or a volatile solvent-soluble type of resin composition. Thus, the process is ex-plained in detail below in relation to the water-soluble type of x~sin composition (hereinafter referred to as a water soluble resin composition)~ The water soluble resin composition is used herein to mean a resin composition having as primary components a polymer soluble in water and a monomer compatible therewith and including water (hereinafter referred to as a water inclusive resin composition) from which the water has ` 20 been removed.
The following is an example of the steps involved in the preparation of the water inclusive resin composition used in the practice of this invention: 40 to 60 parts by weight of a highly reactive and ~water soluble acrylic monomer is added dropwise to 100 parts by weight of a 50 to 70~ by weight aqueous solution of a polyvinyl alcohol tdegree of saponification: 78 to 98 ~ole %, average degree of polymeri-zation : 500 to 2000) and then the mixture is mixed in a kneader at a temperature of 60 to 80C fo~ 30 minutes. A~ter the mixing is completed, the mixture is subjected to defoaming under reduced pressure (liquid temperature: 60 to 80C.). The viscosity of water inclusive resin composition thus obtained is 30,000 to 100,000 cps.
This resin composition is then used in ~he process of this invention to continuously make a polymer plate. Speci-fically, the present process for the continuous manufacture of polymer plates having a uniformly thick layer of water soluble resin composition is one that utilizes the variation of the adhesion strength resulting from the variation of heat; and is characterized by applying the water inclusive resin composi-~; ton heated at about 50 o 70C. to a base plate, and then coating the surface with a sheet material in order to prevent the form-ation of a skin on the surface of the resin when it is rolled.
After coating the resin with sheet material, the resin is rolled to form a uniformly thick layer, cooled to about 20C. or below to reduce the adhesion strength between the surface and the sheet material, after which the sheet material is peeled off the resin. Thus, the present process consists of the con-tinuous steps comprising the application of the water inclusive res m composition to the base plate, the coating of the applied :`
plate with a sheet materia-l, the rolling of the resin into a uniform layer, the cooling of the resultant polymer plate so formed, the removal of thP sheet material, and the drying of the resultant polymer plate.
Figure 1 indicates one apparatus which can be used in the practice of this invention. The illustrated apparatus includes a base plate 23 and sheet 24 which are transported to subsequent processing continuously by a con-veyor 21 having a rubber or steel belt. A hopper 25 for con-taining the resin is provided, along with an assembly for supplying sheet material 24, a means for applying pressure 26, a cooling device 27, a means for peeling off the sheet mat-erial 28, and a drying device 29j all of which are arranged in order following the direction of the above conveyor 21.
~\
1~4~L257 Hopper 25 is provided with a valve 30 that controls the amount of the flow of the water inclusive resin composition in accordance with the width and speed o the base plate~ A
restraining board 31 is also provided to prevent protrusion of resin from the base plate 23 when it is applied to the base plate. In this way, the resin composition is utilized more efficiently.
Either a long or endless sheet 24 can be used in the apparatus illustrated in Figure 1. In the case of a long sheet, the sheet material is unwound by the reel-out roller 32 and after adhering the applied surface and being peeled off by the peeling roller 48 (which is one type of peeling off means 28) the sheet material is wound by the reel-in roller 33. Cleansing rollers 34 are furnished both upstream of the reel-out roller 32 and downstream of reel-in roller 33.
In all cases, the sheet material 24 operates synchronous to the conveying speed.
A number of individual press rollers 46 are at-tached above and below the conveyor as the pressing means 26 .
~20 to press from above and below the water inclusive resin com-;~ position inserted between the base plate 23 and the sheet materiàl 24. The press rollers 46 are maintained at a tem-perature of 60 to 70~C. by means of a hot water jacket in order to prevent the lowering of tha temperature of the water : .
inclusive resin composition at the time of rolling. These prèss rollers 46 are ordinary rollers and have a pressure of 1 to 10 kg/cm at the time of rolling. The thickness of polymer plates consisting of base plate and water inclusive resin composition can be controlled accurately by using many pairs of upper and lower rollers and arranging them in such a manner that the clearance between upper and lower rollers of each pair is gradually reduced. For example, 8 rollers having the same diameter are arranged in 4 pairs of upper and lower rollers.
The lower rollers are located in the same horizontal level, and the upper rollers are located respectively above the lower rollers in such a manner that the clearance between up-per and lower rollers is gradually reduced, as shown in Figure 5~ In practice, the difference (hereinafter termed as a gap) betwee~ the clearance of a pair of upper and lower rollers and the clearance of the next pair of rollers is adjusted within a range of 20 to 100 ~. In this case, polymer plates having thickness of lOOO~ can be produced with a precision of ~ 25~. It is desirable in the practice of this invention to remove air bubbles between the water inclusive resin composi-tion and the sheet material by adjusting the pressure at the time of rolling. This press~ure at the time of rolling is determined by the gap mentioned above. When the gap is ad-justed to more than 100~ , air is admitted and the air bubbles become more congested between the sheet and the water inclusive ~ ~ resin compositlon. It is desirable, therefore, for the gap ; ~ to be 20 to 100 ~. Furthermore, it is possiblè` to obtain ; polymer plates having a greater precision of thickness merely by increasing the number of pairs of upper and lower : ~
rollers from 10 to ao. In addition, it is possible to make the thickness of the water inclusive resin composition from 500 to 2000 ~ by adjusting the clearance between the final rolling rollers.
The cooling device 27 is generally an air circula-tion style cooling assembly with a 0 to 5C. temperature at the outlet of the air blower. It is typically divided into two ; chambers, a normal temperature chamber at 10 to 20C. and a cooled air chamber at 3 to 8C. The use of two chambers pre-vents water from forming when the polymer plate goes from the cooling device back to room temperature and also reduces the 257 - ~:
possibility of undesirable effects resulting from the reuse of the sheet material.
Because of the temperature of the resin com-position when the sheet material is peeled off, the surface of the resin may have waves. This will generally not occur under normal conditions, but even if it does, the polymer plate can be leveled before the drying process commences.
The drying device 29, which dries the polymer plate after the sheet material is peeled off, is indirectly operated by hot air circulation, so that the ultimate drying temperature is in the range of about 60 to 80C. Even though the polymer plate is dehydrated and contracts during this process, the final product desiréd can be easily obtained merely by calculating beforehand the contraction rate and ap-~`~ plying the resin composition accordingly. For example, when ~ the polymer plate is dried for 40 to 60 minutes at 80C. with "~ wind speed of 0.5 to 2.0 m/sec.~, and RH 1%, the contraction rate lS 7 to 10~. Since air bubbles will form on the surface of the resin adjoining the base plate when the drying tem-~perature is high, it is desirable that the plate be dried at ` a~temperature below the boiling point of the included volatile component.
,-It is also preferred that an assembly be provided ~` to regulate the movement of the base plate and sheet material - to prevent them from swerving. Moreover, a base plate supply :
device 35 that supplies the base plate is also provided in the illustrated apparatus.
It should be understood that each of the devices, means and mechanisms described above are linked together and are utilized with the base plate, water inclusive resin com-position and sheet in manufacturing polymer plate continuously.
Thus, the process of this invention for the _ g _ .
lZ57 continuous manufacture of polymer plates having a layer of uniform thickness of a water soluble resin composition can be illustrated through reference to the accompanying drawings.
The water inclusive resin composition prepared on the basis of the example described above is added into the hopper 25 and flow~d out in suitable portions onto the base plate 23 by controlling the valve 30. Thus, measured amounts of the resin composition can be applied between the base plate 23 and the sheet material 24 set between the upper and lower press rollers 46, 46'. At this time, the temperature of the water inclusive resin composition is maintained at 50 to 70C. In terms of limitations of thickness, mechanical propertles and prevention of chemical attack, the base plate may be preferably made from steel, aluminum, and other metals, and may even be a long coil plate or cut plate. In the case of cut plate, a sheet of kra~t paper of a thickness of 80 +
S ~ can~be used as an under sheet below the base plate and ;~ cellulose tape can be affixed between each sheet to make a continuous sheet in order to prevent the water inclusive resin composition from spilling under the base plate. In ; addition, in order to improve the adhesion of the surface of the base plate 23 to the water inclusive resin composition, the base plate can be sandpolished or pre-coated with an ad-hesive and then supplied continuously by the base plate supply device 35.
The sheet material covering the surface of the water inclusive resin composition in order to prevent a skin from forming thereon should desirably be of a constant thickness and smooth, flexible, toughl and readily removable. For ex-ample, a commercially available polyester sheet (thickness, 125 to 250 ~) or a rigid polyvinyl chloride sheet (thickness 200 to 300 ~) can be preferably used as a sheet material 24.
~4~2S7 The sandwich polymer plate made from the base plate, water inclusive resin composition and sheet is then rolled by passing it between the press rollers 46, 46'. Then the polymer plate of the water inclusive resin composition rolled to the prescribed thickness is conveyed to the cooling device and cooled. The temperature for the above composition is reduced from about 40C. to 65C., to approximately 20C.
at the tlme of rolling. Then, the sheet material 24 is peeled off the cooled sandwich polymer plate by the peelin~-off rolleræ 48. When the polymer plate from which the sheet has been peeled is dried by passing it through the drying device 29, a polymer plate having a layer of uniform thickness of a water inclusive resin composition is obtained. The drying ~` time for the polymer plate will vary according to the thickness and properties of the water inclusive composition, but generally drying can be accomplished in 100 to 120 minutes under the conditions where the thickness of the layer of the water in-clusive resin composition is 1.00 mm, the wind speed 1.5 to 2.0 w/sec., and the temperature 78C.
~:, ;~ 20 Finally, polymer plates having the required measurement are obtained merely by cutting the polymer plates , obtained above, that is, polymer plates having a layer of uniform thickness of a water soluble resin composition are cut to the required size.
As explained in detail above, according to the process of the invention, there is no need to previously mold the water or volatile solvent inclusive resin composition in the form of a plate or membrane, but instead it is possible, in accordance with this invention, to manufacture polymer plates having a layer of uniform thickness of a resin composi-:
tion soluble in water and/or a volatile solvent inexpensively and continuously. In addition, this process is especially 5i7 suited for industrial manufacture of such products as a water soluble photopolymer printing plate for printing mat-erial. For example, polymer plates containing, as the water inclusive resin composition, (a) 255.3 parts by weight of 33.6% aqueous solution of polyvinyl alcohol (degree of saponification: 82 mole %, average degree of polymerization:
500), (b) 213.2 parts by weight of ~-hydroxyethyl methacrylate, (c) 5.9 parts by weight of benzoin, and (d) 0.01 parts by weight of hydroquinone can be used in the practice of this invention ~o make excellent photopolymer printing plates.
According to the present invention, polymer plates can be manufactured at the relatively low temperature of 80C. or below, and therefore a resin composition that includes among its components a thermal polymerizable compound can be readily used in the practice of this invention at a temperature below that which will normally cause thermal ~: .
polymerization. The process of this invention has the further advantages of (a) being readily useable with water inclusive resin compositions, (b) being relatively inexpensive and . . .
(c) ~being capable of making polymer plates that have high adheeion between res-~n and base~plate, and thus forming ex-tremely strong polymer plates.
Although a number of specific embodiments of thi~ invention have baen disclosed herein, it should be under-stood that the present invention is in no way limited by the specific features of the disclosed embodiments. Rather, it is intended that various modifications and equivalents of the disclosed embodiments can be made without departing from the spirit and scope of this invention as defined by the following claims.
- 12 _
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the continuous production of photo-sensitive printing plates having a metallic support structure and a uniform layer of a photopolymerisable resin composition in adherent contact therewith, which process comprises:
(a) applying to the support structure a coating of a paste-like photopolymerisable resin composition comprising a solution of a polymer and a compatible monomer in water and/or a volatile solvent, wherein the resin composition is reactive at a temperature of 80°C or above, and wherein the temperature of the resin composition is maintained at a value in the range of from 50 to 70°C during the time in which it is applied to the support structure;
(b) covering the surface of the applied coating of photo-polymerisable resin composition with a flexible thermoplastic sheet material;
(c) applying pressure to the sheet material sufficient to make the coating of the photopolymerisable resin composition relatively uniform;
(d) cooling said layer of resin composition, said sheet material and said support structure;
(e) removing the sheet material from the photopolymerisable resin composition; and (f) drying the resulting layer of photopolymerisable resin composition and support structure for a time sufficient to bring the resin into adherent contact with the support structure.
(a) applying to the support structure a coating of a paste-like photopolymerisable resin composition comprising a solution of a polymer and a compatible monomer in water and/or a volatile solvent, wherein the resin composition is reactive at a temperature of 80°C or above, and wherein the temperature of the resin composition is maintained at a value in the range of from 50 to 70°C during the time in which it is applied to the support structure;
(b) covering the surface of the applied coating of photo-polymerisable resin composition with a flexible thermoplastic sheet material;
(c) applying pressure to the sheet material sufficient to make the coating of the photopolymerisable resin composition relatively uniform;
(d) cooling said layer of resin composition, said sheet material and said support structure;
(e) removing the sheet material from the photopolymerisable resin composition; and (f) drying the resulting layer of photopolymerisable resin composition and support structure for a time sufficient to bring the resin into adherent contact with the support structure.
2. A process as claimed in claim 1, wherein the applica-tion of pressure to the coating of resin is accomplished by means of a plurality of successive pairs of spaced rollers arranged along the length of the coating of resin composition and the support structure.
3. A process as claimed in claim 1, wherein the sheet material is a continuous sheet of smooth thermoplastic resin material.
4. A process as claimed in any of claims 1 to 3, wherein the temperature of the resin composition and the support structure is maintained at 20°C or below after the application of pressure thereto.
5. A process as claimed in any of claims 1 to 3, in which the support structure is a continuous coil of material consisting of aluminium, tin or steel.
6. A process as claimed in any of claims 1 to 3, wherein the resin composition also includes a polymerisation initiator and a polymerisation inhibitor.
7. A process as claimed in any of claims 1 to 3, wherein the resin composition includes therein an aqueous solution of par-tially saponified polyvinyl acetate, a .beta.-hydroxyethyl methacrylate monomer, benzoin and a polymerisation inhibitor.
8. A process as claimed in any of claims 1 to 3, wherein the sheet material consists of polyester or polyvinyl chloride sheet materials.
9. A process as claimed in any of claims 1 to 3, wherein the sheet material has a thickness in the range of from 125 to 300 µ.
10. An apparatus for the continuous manufacture of photo-polymer printing plates having a metallic support structure and a photopolymerizable resin composition in adherent contact therewith comprising:
(a) means for containing said resin composition and for dispensing said composition when desired;
(b) means for continuously transporting said support structure with respect to said resin containing and dispensing means to permit the deposit of a layer of resin composition on said support structure;
(c) means for applying a continuous sheet of flexible thermoplastic sheet material to the surface of said resin composition layer;
(d) a plurality of successive pairs of spaced apart pressure rollers arranged along the transporting means and disposed on opposite sides of said resin composition layer for applying pressure to said layer of resin composition to uni-formly spread said layer over said support structure;
(e) means for cooling said layer of resin composition, said thermoplastic sheet material and said support structure;
(f) means for removing said sheet material from said layer of resin; and (g) means for drying said layer of resin composition and said support structure for a time sufficient to firmly secure said layer of resin to said support structure.
(a) means for containing said resin composition and for dispensing said composition when desired;
(b) means for continuously transporting said support structure with respect to said resin containing and dispensing means to permit the deposit of a layer of resin composition on said support structure;
(c) means for applying a continuous sheet of flexible thermoplastic sheet material to the surface of said resin composition layer;
(d) a plurality of successive pairs of spaced apart pressure rollers arranged along the transporting means and disposed on opposite sides of said resin composition layer for applying pressure to said layer of resin composition to uni-formly spread said layer over said support structure;
(e) means for cooling said layer of resin composition, said thermoplastic sheet material and said support structure;
(f) means for removing said sheet material from said layer of resin; and (g) means for drying said layer of resin composition and said support structure for a time sufficient to firmly secure said layer of resin to said support structure.
11. The apparatus of claim 10 wherein said means for applying and removing the continuous sheet of sheet material to and from the surface of said resin composition is a continuous loop of sheet material suspended by means of a pair of oppositely disposed rollers, said loop of sheet material being disposed along and covering the surface of said resin composition and passing between said plurality of successive pairs of spaced pressure rollers.
12. The apparatus of claim 10 wherein said support structure is a continuous coil of metallic material and said means for continuously transporting said support structure is an endless belt.
13. The apparatus of claim 10 wherein the cooling means comprises two separate cooling chambers which can be maintained at different temperatures.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA191,271A CA1041257A (en) | 1974-01-30 | 1974-01-30 | Producing printing plates by covering polymeric coating with flexible sheet and applying pressure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA191,271A CA1041257A (en) | 1974-01-30 | 1974-01-30 | Producing printing plates by covering polymeric coating with flexible sheet and applying pressure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1041257A true CA1041257A (en) | 1978-10-31 |
Family
ID=4099056
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA191,271A Expired CA1041257A (en) | 1974-01-30 | 1974-01-30 | Producing printing plates by covering polymeric coating with flexible sheet and applying pressure |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1041257A (en) |
-
1974
- 1974-01-30 CA CA191,271A patent/CA1041257A/en not_active Expired
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