US3357352A

US3357352A - Paper base planographic printing plates

Info

Publication number: US3357352A
Application number: US479343A
Authority: US
Inventors: Jr Henry P Williams; Donald A Rosenbohm; William H Page
Original assignee: Appleton Coated Paper Co
Current assignee: Appleton Coated Paper Co; Appvion Operations Inc
Priority date: 1964-01-24
Filing date: 1965-08-12
Publication date: 1967-12-12
Anticipated expiration: 1984-12-12
Also published as: DE1571877A1; DE1571877B2; BE685359A; GB1148577A

Description

United States Patent Ofi ice Patented Dec. 12, 1967 3,357,352 PAPER BASE PLANOGRAPHIC PRINTING PLATES Henry P. Williams, Jr., Combined Locks, and Donald A.

Rosenbohm and William H. Page, Appleton, Wis., assignors to Appleton Coated Paper Company, Appleton, Wis., a corporation of Wisconsin No Drawing. Filed Aug. 12, 1965, Ser. No. 479,343 13 Claims. (Cl. l01462) This application is a continuation-in-part of our prior co-pending application Ser. No. 339,888, filed Jan. 24, 1964, now abandoned.

This invention relates, generally, to innovations and improvements in paper base, planographic printing plates or paper masters, and methods of making the same.

Paper base planographic printing plates, and the methods of making and using the same, are well known to those skilled in the art pertaining thereto, having been first commercially introduced over 20 years ago, Planographic printing is a form of lithography and therefore depends upon the immiscibility of greasy lithographic printing inks and aqueous etch or lithographic solutions. In use, a paper lithographic or planographic printing plate is first imaged in known manner with the typed, Written, or drawn copy material to be reproduced so as to deposit a grease-receptive imaging material which makes imaged areas inkreceptive and water-repellent (i.e. hydrophobic). The non-imaged areas are water-receptive and ink-repellent (i.e. hydrophillic). The imaged plate is then placed on the plate cylinder of an offset duplicating press. The over-all surface of the plate is then treated with an aqueous wet-out liquid, such as a solution of glycerin slightly acidified with phosphoric acid, acid phosphate, ammonium nitrate, or other known substances. The aqueous wet-out liquid will wet all portions of the plate surface except those that have been imaged and are water-repellent. The press inking roll then passes over the surface of the plate and deposits a film of ink only upon the ink-receptive imaged areas. In the printing operation the ink from the imaged areas is transferred in reverse to the rubber offset blanket which in turn prints directly onto the paper sheet so as to form each copy.

A number of different coating formulations and techniques have been utilized in the past to provide paper base sheets or webs with suitable planographic printing surfaces. Normally, multiple coating layers or depositions are used in the production of planographic printing plates or paper masters of the class described. For example, a so-called black coat may be applied to one side (back) of the paper web so as to impart dimensional stability to the plate and prevent curling. On the opposite side (front) a seal or barrier coat is applied. Over the barrier coat on the front side a face coat can be applied which becomes the printing surface. Then, a wash coat is applied over the base coat for the purpose of insolubilizing the face coat. After each coating layer is applied it has to be dried. It will be appreciated that each coating requires the web to be run through a separate coating station and the machine time and labor required comprise an important portion of the cost of the finished plates or masters.

It has been found in accordance with the present invention that printing plates of good quality can be made in which the multiple coats or layers normally applied to the printing or functional side of the paper web are reduced to a single coating layer or deposit. Similar proposals may have been made before but it is not known that any of these prior proposals has gained commercial acceptance. In one embodiment of the present invention the functional or front coating formulation may also be used as the back coating and the two coatings applied in a two-side coater so that only one pass through the machine is required.

The object of the invention, generally stated, is the provision of planographic or lithographic paper base, printing plates or paper masters wherein the usual multiple coating layers, (cg. the seal or barrier coat, the face coat and the wash coat) are consolidated into one functional coat or layer.

A further object of the invention is the provision of coating formulations which contain all of the ingredients necessary to provide a good quality planographic or lithographic printing surface in a single coating application on one side of a paper base sheet or web.

Certain other objects of the invention will, in part, be

obvious and in part appear hereinafter.

For a more complete understanding of the nature and scope of the invention reference may now be had to the following detailed description thereof wherein a working example and certain permissible variations therein are set forth whereby the invention may be practiced on a commercial scale.

Example I The paper base sheet or web may be any of the suitable known types or grades of raw stock heretofore used for making planographic printing plates.

Step ].-A paper web having a basis weight of approximately 50 pounds based on a ream of 500 sheets cut to a size of 25 x 38 inches in first coated on one side with about 10 pounds dry weight per ream of a functional coating composition having the following formulation, the coating being dried in known manner so as to achieve a web temperature of at least about 100 0.:

Lbs. Water 94.8 Polyvinyl alcohol (PVA powder) 6.2 Cypel Resin Emulsion No. 205 3.1 50% Stellar Clay Slip (kaolin clay) 49.6 Melamine formaldehyde (Parez Resin No. 613) 2.3 Salt solution containing 7.5% aluminum chloride and 1.5% zinc acetate 43.0

In the above formulation the Cypel Resin Emulsion contains approximately 43 to 45% solids which comprise a mixture of approximately 63% (by weight) ethyl acrylate, 35% acrylonitrile, and about 2% methacrylic acid. This preparation is currently available under the proprietary name Cypel Resin Emulsion No. 205 from American Cyanamid Company.

The foregoing coating composition may be formulated from the specified ingredients in accordance with the following make-down procedure:

The PVA powder is first thoroughly dispersed in cool or cold water. The temperature of the dispersion is raised to C. and held between 90-95" C. for at least 30 minutes. To the resulting PVA solution, the Cypel Resin Emulsion, pigment slurry, Parez Resin solution, and salt solution are added in the order named, with moderate agitation. A suitable defoamer may be added if needed, following adition of the Parez Resin solution. After each ingredient is added, preferably a short period of mixing is allowed before addition of the next ingredient.

After all the ingredients have been added and sufiicient mixing time for thorough blending has been allowed, the temperature of the blended admixture is raised to 90 C. after which the blend may be allowed to cool to room temperature on standing. Alternately, after being held at 90 C. for 30 minutes the batch may be cooled rapidly as by the addition of ice.

Step 2.To the previously uncoated (i.e. back) nonprinting side of the paper web their is next applied a back After the back coating has been applied, dried and calendered, the formation of the paper masters or printing plates is complete except for slitting and cutting the rolled web into individual plates of the desired size.

The proportions of the constitutents in the foregoing functional coating formulation for the printing surface of the plate may be varied within the limits indicated in the following general formulation wherein the values are on a dry basis weight:

Parts dry Polyvinyl alcohol to Cypel resin 0.3 to 10 Pigment (kaolin clay) 18 to 60 Mela-mine formaldehyde 0.2 to 5 Salts (aluminum chloride and zinc acetate) 1.5 to 30 The total solids may range between %25% with the viscosity ranging from 400 to 800 centipoises. If there is an excess of water strike-through of the web may occur and there may be difficulty in drying. If there is too little water the mixture will be too viscous and will not flow properly in the equipment.

Certain procedural and formulation changes may be made in Step One of the foregoing example. The solu tion of aluminum chloride and zinc acetate can be held out and added at the end of the make-down procedure. Similarly the Cypel Resin Emulsion may be held out and added after the heating or cooking step provided that it is added prior to the addition of the salt solution. Up to about 75% of the melamine formaldehyde may be replaced with melamine provided a small amount up to about of the melamine formaldehyde is added after cooking but prior to the addition of the salts.

The following examples represent preferred functional coating formulations:

Example 2 Parts dry PVA 10 Cypel (63% ethylacrylate, acrylonitrile, 2% methacrylic acid) Pigment (kaolin clay) Melamine formaldehyde 3 Aluminum chloride 5 line acetate 5 Water to give 20% solids.

4 Example 5 Parts dry PVA 5 Parez 0.2 Cypel 1 Salts 3 Pigment 18 Example 6 PVA 10 Parez 5 Cypel 2 Salts 30 Pigment 60 Example 7 PVA 5 Parez l5 Cypel 0 3 Salts 15 Pigment 40 Example 8 PVA 10 Parez 3 Cypel l0 Salts 3O Pigment 46 Example 9 PVA 5 Paraez 1.5 Cypel 1 Salts 1.5 Pigment 22 Example 10 PVA 1O Parez 3 Cypel 10 Salts 30 Pigment 6 Example 11 PVA 5 Parez 0.2 Cypel 15 Salts 13 Pigment 18 Example 12 PVA 10 Parez 5 Cypel 2 Salts 3O Pigment 60 The following are additional preferred examples of the formulation for Step 1.

The formulation of this Example 14 is prepared generally as described for Step 1 of Example 1 with these changes-(1) the melamine resin solution is added where the Parez resin solution is added; (2) the salt solution is withheld and not added until after cooling; and (3) the melamine formaldehyde resin solution is also added after cooling but prior to the salt addition.

In the foregoing formulations a preferred form of the polyvinyl alcohol (PVA) is one that contains approximately 3% polyvinyl acetate for viscosity control, this grade of polyvinyl alcohol being available commercially from Shawinigan Chemicals, Inc., under the proprietary product named Gelvatol 391. The PVA functions in this system primarily as a protective colloid which prevents coagulation of the Cypel Resin by the salts and the melamine formaldehyde. While PVA may also act as a filmformer, it does not account for the hydrophillic properties of the functional coating. Thus, if the Cypel is omitted the plate does not remain hydrophillic but becomes, hydrophobic. Accordingly, PVA and Cypel do not perform the same function in the single functional coating.

The PVA may be replaced in whole or part with hydroxyethylated starch, e.g., Penford Gum 280 or Pencoat, on a weight for-weight basis.

The Cypel Resin Emulsion No. 205 may be replaced With similar formulation wherein the ethyl acrylate content ranges from 55 to 85 parts by weight, the acrylonitrile from 45 to 20 parts by weight and the methacrylic acid from 0.5 to 4 parts by weight.

Melamine formaldehyde resin is used to insolubilize the polyvinyl alcohol or hydroxyethylated starch, thereby contributing to the barrier properties of the coating and help control the imaging properties of the resulting coatings. This material is available commercially, one source being under the proprietary name Parez Resin from American Cyanamid Company or as Resloom M75 from Monsanto. The melamine formaldehyde may be replaced with other cross-linking agents, such for example as dimethylol urea (DMU), glyoxal, or glutaraldehyde. In such replacement these agents will be substituted in amounts stoichiometrically equivalent to the melamine formaldehyde on the basis of the formaldehyde content.

The formaldehyde resin may be largely replaced with melamine resin provided sufficient formaldehyde resin is added prior to the solution of salts to impart the desired imaging characteristics to the plates. Recrystallized melamine commercially available from American Cyanimid Company may be used. This variation is illustrated in Example 14.

The zinc acetate and aluminum chloride salts act to modify the image quality of the printing coat. These salts may be used in diiferent ratios of one to the other, and in different proportions to the other ingredients to achieve various known imaging effects.

More specifically, the ratio of zinc acetate to aluminum chloride may range from about 1 part of zinc acetate to 1 part of aluminum chloride to 4 parts of zinc acetate to 1 part of aluminum chloride. The aluminum chloride may be replaced with stoichiometric equivalents of ferric chloride and chromium chloride.

In the foregoing formulations the pigment provides the proper grain to the printing surface which acts to retain the moisture in the non-imaged areas. The kaolin clay may be replaced in whole or part, by one or more other inert mineral pigment materials such as blanc fixe, zinc oxide, titanium dioxide, or other fine pigments.

It will be appreciated that the back and functional coatings may be applied on any of the various types of known coating equipment in use for applying coatings to paper and other webs. The planographic printing plates provided in accordance with the foregoing examples may be used in known manner as direct image masters and have the advantage of being capable of being imaged by other reproduction process of known type such as that performed in one of the ufrently available Xerox copying machines.

What is claimed as new is:

1. A planographic printing plate comprising a paper base having applied directly onto at least one surface a dried and insolubilized coating layer thereon derived from a single coating application and providing a planographic printing surface, said coating being formed from an aqueous dispersion of from about 5 to 10 parts by weight of a protective colloid selected from the group consisting of polyvinyl alcohol and hydroxyethylated starch; from about 0.3 to 10 parts by weight of a mixture containing from about 55 to parts by weight ethyl acrylate, from about 45 to 20 parts by weight acrylonitrile and from about 0.5 to 4 parts by Weight of methaccrylic acid; from about 18 to 60 parts by weight of inert mineral pigment; from about 0.2 to 5 parts by weight of a resin material selected from the group comprising melamine formaldehyde resin alone and melamine resin plus melamine formaldehyde resin; and from about 1.5 to 30 parts by weight of a mixture containing from about 1 to 4 parts of zinc acetate and a salt selected from the group consisting of 1 part of aluminum chloride, about 1.2 part of ferric chloride and about 1.2 part of chromium chloride.

2. A planographic printing plate comprising a paper base having applied directly onto at least one surface a dried and insolubilized coating layer thereon derived from a single coating application and providing a planographic printing surface, said coating being formed from an aqueous dispersion containing from about 5 to 10 parts by weight of polyvinyl alcohol, from about 0.3 to 10 parts by weight of a mixture containing approximately 63% by weight ethyl acrylate, about 35% by weight acrylon'itrile and about 2% by weight methacrylic acid, from about 18 to 60 parts by weight of inert mineral pigment, from about 0.2 to 5 parts by weight of melamine formaldehyde resin, and from about 1.5 to 30 parts by weight of a mixture containing 1 part of zinc acetate and from about 1 to 4 parts of aluminum chloride.

3. The planographic printing plate of claim 2 wherein said inert mineral pigment is kaolin clay.

4. The planographic printing plate of claim 3 wherein said dried and insolubilized coating is provided on one side of the paper base, and the opposite side is provided with a coating to prevent curl and impart dimensional stability.

5. A planographic printing plate comprising a paper base having applied directly onto at least one surface a dried and insolubilized coating layer thereon derived from a single coating application and providing a planographic printing surface, said coating being formed from an aqueous dispersion containing about 10 parts by Weight of polyvinyl alcohol, about 2 parts by weight of a mixture containing approximately 63% by weight ethyl acrylate, 35 by weight acrylonitrile and about 2% by weight methacrylic acid, about 45 parts by weight of inert mineral pigment, about 3 parts of melamine formaldehyde resin, about 5 parts by weight of aluminum chloride and about 5 parts by weight of zinc acetate.

6. The planographic printing plate of claim 5 wherein said inert mineral pigment is kaolin clay.

7. The planographic printing plate of claim 5 wherein said dried and insolubilized coating is provided on one side of the paper base and the opposite side is provided with a coating to prevent curl and impart dimensional stability.

8. The method of making a planographic printing plate which comprises: coating a paper base web with a single application of an aqueous dispersion having a solids content ranging between about 15 to 25% by weight and containing from about 5 to 10 parts by weight of a protective colloid selected from the group consisting of polyvinyl alcohol and hydroxyethylated starch; from about 0.3 to 10 parts by weight of a mixture containing from about 55 to 85 parts by weight ethyl acrylate, from about 45 to 20 parts by weight acrylonitrile and from about 0.5 to 4 parts by weight of methyacrylic acid; from about 18 to 60 parts by weight of inert mineral pigment; from about 0.2 to 5 parts by weight of a resin material selected from the group comprising melamine formaldehyde resin alone and melamine resin plus melamine formaldehyde resin; and from about 1.5 to 30 parts by weight of a mixture containing from about 1 to 4 parts of zinc acetate and a salt selected from the group consisting of 1 part of aluminum chloride, about 1.2 part of ferric chloride and about 1.2 part of chromium chloride; and, drying said coating.

9. The method of claim 8 wherein said aqueous dispersion is coated and dried on one side of the paper base web and a second coating is applied and dried on the opposite side to prevent curl and impart dimensional stability.

10. The method of making a planographic printing plate which comprises coating a paper base Web with a single application of an aqueous dispersion having a solids content ranging between about 15 to 25% by weight and containing from about 5 to parts by weight of. polyvinyl alcohol, from about 0.3 to 10 parts by weight of mixture containing approximately 63% by weight ethyl acrylate, about 35%" by weight acrylonitrile and about 2% by weight methacrylic acid, from about 18 to 60 parts by weight of inert mineral pigment, from about 0.2 to 5 parts by weight of melamine formaldehyde resin, and from about 1.5 to 30 parts by weight of a mixture containing approximately 1 part of zinc acetate and from about 1 to 4 parts of aluminum chloride, and drying said coating.

11. The method of making a planographic printing plate which comprises coating a paper base web with a single application of an aqueous dispersion having a solids content ranging between about to by weight and containing about 10 parts by weight of polyvinyl alby weight of a mixture containing. approximately 63% by weight ethyl acrylate, by' weight acrylonitrile and about 2% by weight methacrylic; acid, about parts by weight of inert mineral pigment, about 3 parts by weight of melamine formaldehyde resin, about 5 parts by weight of aluminum chloride and about 5 parts by weight of zinc acetate, and drying said coating.

12. The method of claim 11 wherein said aqueous dispersion is coated and dried on one side of the paper base web and a second coating is applied and dried on the opposite side to prevent curl and impart dimensional stability.

13. A planographic printing plate comprising a paper base having applied directly onto at least one surface a dried and insolubilized coating layer thereon derived from a single coating application and providing a pianographic printing surface, said coating being formed from an aqueous dispersion containing from about 5 to 10 parts by weight of polyvinyl alcohol, from about 0.3 to 10 parts by weight of a mixture containing approximately 63% by weight ethyl acrylate, about 35 by weight acryloni trile and about 2% by weight methacrylic acid, from about 18 to parts by weight of inert mineral pigment, a suflicient quantity of a formaldehyde donor to insolubilize the polyvinyl alcohol, and a sufficient quantity of at least one polyvalent salt to impart predetermined imaging effects.

cohol, about 2 parts References Cited UNITED STATES PATENTS 2,635,537 4/1953 Worthen 101-1492 2,889,299 6/1959 Ritson. 2,994,676 8/1961 Kucsan et al. 3,006,274 10/ 1961 Oransky et al 101-149.2 3,020,839 2/1962 Richard 101-1492 ROBERT E. PULFREY, Primary Examiner.

J. A. BELL, Assistant Examiner.

Claims

1. A PLANOGRAPHIC PRINTING PLATE COMPRISING A PAPER BASE HAVING APPLIED DIRECTLY ONTO AT LEAST ONE SURFACE A DRIED AND INSOLUBILIZED COATING LAYER THEREON DERIVED FROM A SINGLE COATING APPLICATION AND PROVIDING A PLANOGRAPHIC PRINTING SURFACE, SAID COATING BENG FORMED FROM AN AQUEOUS DISPERSION OF FROM ABOUT 5 TO 10 PARTS BY WEIGHT OF A PROTECTIVE COLLOID SELECTED FROM THE GROUP CONSISTING OF POLYVINYL ALCOHOL AND HYDROXYETHYLATED STARCH; FROM ABOUT 0.3 TO 10 PARTS BY WEIGHT OF A MIXTURE CONTAINING FROM ABOUT 55 TO 85 PARTS BY WEIGHT ETHYL ACRYLATE, FROM ABOUT 45 TO 20 PARTS BY WEIGHT ACRYLONITRILE AND FROM ABOUT 0.5 TO 4 PARTS BY WEIGHT OF METHACCRYLIC ACID; FROM ABOUT 18 TO 60 PARTS BY WEIGHT OF INERT MINERAL PEGMENT; FROM ABOUT 0.2 TO 5 PARTS BY WEIGHT OF A RESIN MATERIAL SELECTED FROM THE GROUP COMPRISING MELAMINE FORMALDEHYDE RESIN ALONE AND MELAMINE RESIN PLUS MELAMINE FORMALDEHYDE RESIN; AND FROM ABOUT 1.5 TO 30 PARTS BY WEIGHT OF A MIXTURE CONTAINING FROM ABOUT 1 TO 4 PARTS OF ZINC ACETATE AND A SALT SELECTED FROM THE GROUP CONSISTING OF 1 PART OF ALUMINUM CHLORIDE, ABOUT 1.2 PART OF FERRIC CHLORIDE AND ABOUT 1.2 PART OF CHROMIUM CHLORIDE.