US2544169A - Method of bonding metal printing plates to wooden supports - Google Patents

Description

Mam}! 1951 J. F. MANNING ETAL 2,544,159

METHOD OF BONDING METAL PRINTING PLATE TO WOODEN SUPPORTS Filed Oct. 10, 1945 &9 2 5 [n uerztors Joseph FMarzrzz'rzg Malcolm Seymour 5 their Attome Patented Mar. 6, 1951 METHOD OF BONDING METAL PRINTING PLATES ,TO WOODEN SUPPORTS Joseph F. Manning, Newton, and Malcolm Seymour, Boston, Mass assignors to B. B. Chemical 00., Boston, Man, a corporation of Mallachusetts Y Application October 10, 1945, Serial No. 621,520 1 Claim. (Cl. 154-429) This invention relates to printing members comprising a wooden supporting block and a metal late fastened thereto by a thermoplastic cement, and to a method of making such a printing member.

For convenience. the invention will be described in connection with its use in the making of photoengraving plates mounted upon wooden blocks. An establishment equipped for making photo-engraving plates and printing from such plates customarily first makes the plates and then fastens the finished plates to wooden blocks, which are clamped on a platen, and over which inking rollers pass during the printing operation.

The plates are commonly fastened to the blocks by nails alone. although cement has been employed, said cement being a two-way cement, by which is meant a cement in the ibrm of a liquid composition which is applied both to the plate and to the block, allowed to stand until enough of the liquid has evaporated so that tacky films of the cement form on the plate and on the block, after which the two members are pressed together. difllculties are liable to be encountered. For example, if the plates are large. nails are required in the middle portion of such plates in addition to the usual nails in the margins, in order to prevent the plates from loosening from their supports, such location of nails in the middle portions of the plates being often impractical. Regardless of whether a plate is large or small, a certain width of margin must be left around the plate; and this prevents the setting of type close to the edge of the plate.

When a two-way cement is used, the procedure When nails are used the following According to the present invention the wooden v blocks are coated on their plate-attaching faces with a solution of a thermoplastic cement, and the solvent of the cement caused to dry (for example. by being exposed to the atmosphere) until a hard, non-tacky film results. The metal plate is heated to a temperature sufilcient to soften and render tacky the cement when the plate is pressed against the film. whereupon the heated plate is pressed for a short interval against the film or coat of cement on the block. It is common to acquire the block material in the form of boards of the requisite thickness and to cut from these boards blocks of the desired shape to fit'given plates as soon as these plates have been finished and are ready to be printed. In such case the supporting block material may be coated on its plate-attaching face with the solution, and the solvent caused to evaporate, as stated above with respect to a separate block. In either case the coated article, be it a block or a board from which blocks are to be cut, may be stored for a considerable time and in the case of boards may be cut into the desired shape and size when coated blocks are needed.

The plate should be heated to a temperature sufficient, when pressed against the film of cement on the block, to soften the surface of the cement and with a pressure of enough magnitude to insure good contact; and the plate and cementcoated block should be maintained under pressure for a short interval, say 2 or 3 minutes. to permit the cold block to cool and thereby set the thermoplastic cement. A temperature indicator may be used in heating the plate to the desired temperature; and the pressure may be conveniently applied bythe use of a press. The printing member (the plate with'its attached supporting block) may then be removed from the press,

Referring to the accompanying drawing,

Figure 1 is a perspective of a printing plate fastened by a thermoplastic cement to its supporting block; and

Figure 2 is an end view on an enlarged scale of a portion of the printing member of Figure 1.

The method of the invention may be carried out as follows:

1. Apply a thermoplastic cement in the form of a liquid composition to the plate-attaching face of a properly shaped blocki or of the blockmaterial in the form of boards. Cause the liquid to evaporate until a film or coating of dry nontacky cement results. Put this coated material aside for future use.

2. When a plate 1 is ready for use in a printing press, select a cement-coated block to fit it, or cut a properly shaped block from the cementcoated block-material.

3. Heat the uncoated printing plate uniformly .to a proper temperature to soften the cement and render it tacky.

4. Locate the heated plate properly on the cement-coated block, press the plate firmly against the" film, and maintain the pressure for a short interval. the purpose being first to soften the thermoplastic cement and then to permit it to cool somewhat while the pressure is maintained. In Figure 2 the cooled film of thermoplastic cement is indicated at 9. In this figure Parts by weight Hycar OR 100,

- VYNS 25 Durez resin 1'75 50 Dixie clay 25 Methyl ethyl ketone 700-900 Hycar OR, a synthetic rubber marketed by the Hycar Chemical Co. of Akron, Ohio, is an oil resistant copolymer of butadiene and acrylonitrile containing about 25% by weight of acrylonitrile. VYNS is a copolymer of vinyl chloride and vinyl acetate containing about 88% by weight of vinyl chloride. Durez resin 175 is an oil resistant phenol-formaldehyde resin marketed by General Plastics Inc. of North Tonawanda, N. Y. Dixie clay is a filler. Methyl ethyl ketone is a volatile organic solvent for the synthetic rubber and the resin. The cement should be an oil resistant cement because the plates, after they have been used, are cleaned of the ink, deposited upon them by the printing rollers, by washing them with a hydrocarbon oil, benzol being commonly used. It is desirable that the thermoplastic cement should include, as it does in the example given above, a resin which is thermosetting, that is, a resin such as the phenolformaldehyde resin which will be partially cured by the heat and pressure treatment described above. The eilect is to increase the set of the cement. However, the cement is still thermoplastic after it has been subjected to heat and pressure as described, the only difference between its condition in the finished printing member and its condition as applied to the block being that its activating temperature has been raised somewhat.

4 A metal printing plate may by the above method be firmly attached to its wooden supporting block without the use of nails; and without the delay caused by the coating and drying procedure, since the coating and'drying may be done long beforehand, the blocks, or the material from which they are cut, being ready coated at hand. The plate itself is, of course, not inJured in any way by being heated to a temperature high enough to soften the thermoplastic cement.

Having described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

A method of firmly attaching a metal printing plate to a wooden supporting block, said method including the forming of an adherent dry film of a thermoplastic cement on the wooden block, said cement comprising a large proportion of an oil-resistant synthetic rubber, a smaller proportion of a thermosetting phenolic resin, and a mineral filler, heating the metal plate out of contact with the cement, pressing the heated plate against the dry film of cement adhering to the block to fuse the cement solely by the heat contained in the plate at.the time of contact, and maintaining the pressure until i a strong bond is formed by cooling and hardening of the cement.

JOSEPH F. MANNING. MALCOLM SEYMOUR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 843,483 McGovern Feb. 5, 1907 961,550 Stanley June 14, 1910 1,909,862 Honegger May 16, 1933 2,154,143 Whelan 1 Apr. 11, 1939 2,226,589 Smyers Dec. 31, 1940 2,246,795 Daniels June 24, 1941 2,348,696 Schabacker May 9, 1944 2,355,949 Boutwell Aug. 15, 1944 2,376,854 Saunders May 22, 1945 2,401,987 Taylor et a1 June 11, 1946 2,423,869 Blessing July 15, 1947 2,459,739 Groten Jan. 18, 1949 FOREIGN PATENTS Number Country Date 551,180 Great Britain Feb. 11, 1943

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