US2739068A

US2739068A - Stereotype mat

Info

Publication number: US2739068A
Application number: US481009A
Authority: US
Inventors: Russell R Eichmeier
Original assignee: Burgess Cellulose Co
Current assignee: Burgess Cellulose Co
Priority date: 1950-06-23
Filing date: 1955-01-10
Publication date: 1956-03-20
Anticipated expiration: 1973-03-20

Description

United States Patent STEREOTYPE MAT Russell 'R. Eichmeier, Freeport, 111., assignor to B urgess Cellulose Company, Freeport, Ill.,1a corporation of Delaware No Drawing. Continuation .of application Serial No. 170,030, June 23,1950. This application January 10, 1955, Serial No. 481,009

8 Claims. (Cl. 106-385) This invention relates to improvements in stereotype mats and particularly to an improvement in the composition of stereotype mats wherebythe molding and casting properties thereof are improved.

The stereotype mat of the type which is in common use and to which the present invention relates consists of a relatively thick sheet of felted cellulose fibers, such as rag stock, cotton linters, chemical wood pulp, such as alpha, sulphite or soda pulp, or the like. The stereotype mat usually contains a filler, such as powdered clay, talc, etc. mixed with the fibers in the body of the mat. A stereotype mat of this general character is described in ice type mat is composed of felted cellulose fibers. Cellulose v fibers, in themselves, possess only a limited amount of plasticity, the impression being accomplished by reason of the compression and stretch undergone by the felted mass of ,the'fibers. A sheet of felted cellulose fibers normally exhibits characteristic limitations with respect to such compression and stretch, and the present invention has for its principal purpose the modification of the mat whereby its plasticity when moist is substantiallyimproved. .The result is that during manufacture the surface of the mat is readily made smooth and free of projecting fibers and United States Patent 1,524,155. The surface ofvthe mat which is'to receive the impression of the form may have a coating applied to it to enhance its smoothness and uniformity. The coating composition may consist of an aqueous suspension of starch, dextrin, clay or the like, a suitable composition for this purpose being described in United States Patent 1,863,731.

An essential property of a stereotype mat is that it readily absorbs water, and it is usually stored shipped .in humidified condition with a water content of about 10% to 50%, based on the total weight of the mat. In this moistened condition it is ready for use and the form or pattern containing the type, cuts, etc., is impressed upon it. Its moist-plasticity enables it to take a well-defined impression of the form, including the details thereof.

After the impression has .been taken, the mat .is dried by subjecting it to heat in what is called a scorcher. In this operation all of the moisture is rapidly driven out of the mat. An important property of the mat is that it permits the moisture to escape readily during this drying operation. After it is dry, the surface carrying the impression is hard and very smooth for the reception of the molten type metal. Reproductions of the original form are then made by casting molten type metal against such surface and allowing the metal-to solidify in that position. Since most printing work is done on cylindrical presses, the dried mat is placed in a curved casting box and is bent or curved to conform to the shape of the box. It is highly desirable to make as many reproductions as possible from the same stereotype mat and this is the reason why the surface should be hard and smooth. If there is any roughness or fractures, the fibers of the mat project from the surface and become embedded in the cast molten metal. After the casting operation the solidified metal and the mat are separated and if fibers or any portion of the mat surface adheres to the metal the surface is torn andithe useful life of the mat is at an end.

It is the principal object of the present invention to provide a stereotype mat of' increased plasticity when moist so as to receive with a minimum of pressure and without fracture a full, exact and faithful impression of the type, half-tones, illustrations etc. from the metal form, and to retain this impression without change during the casting operation whereby a stereotype printing plate is formed which .is an exact and faithful duplicate of the original form. As has been stated heretofore, the stereoduring use it takes a full and exact impression from the form without fracture, whereby a minimum of wear or damage is caused by casting molten metal against the mat and'the latter has the ability to take a large number of casts of superior quality. This is of especial importance in newspaper work where a large number of stereotype plate reproductions are required from each original form.

"It is a further object of the invention to provide a stereotype mat having the above improved properties and which possesses the full amount of strength for mats of this general character and undergoes the normal amount of shrinkage while being dried.

It is a further object of the invention to provide a mat having the improved properties described above in which the'moisture is more readily released during drying of the molded mat, whereby'the latter is more quickly and easily rendered completely dry and capable of forming a perfect stereotype platereproduction.

It is a furtherobject of theinvention to provide a stereotype mat of the character described which, after it has been molded and dried, possesses increased flexibility,

without sacrifice of strength or toughness, whereby it more readily conforms to the curvature of the casting box. 7

Other objects and advantages will become apparent as the following description progresses.

The objects are obtained by incorporating in the body of the stereotype mat a finely divided precipitated alkaline earth metal silicate, that is, a chemically precipitated silicate of barium, calcium, magnesium, or strontium. The silicate may be used in place of the filler normally used in a stereotype mat. It is permissible to use a small amount of normal filler, but this is not necessary when the alkaline earth metal silicate is incorporated in accordance with the present invention.

There are a number of natural silicates of the alkaline earth metals which have been formed by fusion and other natural processes, and these silicates are not suitable for the present invention. The precipitated silicates are formed by preparing an aqueous solution of a water soluble alkaline earth metal compound, and treating the solution with a water soluble alkali metal silicate. The soluble alkaline earth metal compound may be an alkaline earth metal salt or hydroxide, an example of a salt being an alkaline earth metal chloride. Examples of suitable water soluble alkali metal silicates are sodium silicate and potassium silicate. A precipitate of the alkaline earth metal silicate is thereby formed, which is separated from the solution, washed with water, dried and ground to a finely divided condition. Finely divided precipitated alkaline earth metal silicates which are suitable for use are also available upon the market.

In accordance with the present invention, it has been discovered that when a substantial amount of an alkaline earth metal silicate of the character described is incorporated in a' stereotype mat of felted cellulose fibers a pronounced increase in the moist-plasticity of the mat is obtained, together with the other benefits of improved smoothness of surface, release of moisture during drying, flexibility when dry, etc., Without any sacrifice in other desirable properties such as strength, toughness, hardness of surface when dry, normal shrinkage, etc.

The proportion of alkaline earth metal silicate may vary within relatively wide limits. Amounts from about to about based on the dry weight of the stereotype mat, have been used with satisfactory results.

The following are several examples of the preparation of a stereotype mat in accordance with the present invention. It is to be understood that these specific examples are illustrative only and that the invention is not limited thereto but changes and modifications may be made as will occur to those skilled in the art.

Example 1 Calcium silicate is prepared by dissolving 8 parts by weight of calcium chloride, CaClz, in 235 parts of water and slowly adding to this 83 parts of a water solution of sodium silicate containing 7.3 parts of the sodium silicate having the oxides present in the ratio 1 NazO, 3.3 SiOz. The reaction solution is heated to boiling. A precipitate of calcium silicate is formed having substantially the ratio 1 CaO, 3.3 SiOz. After' the reaction is complete, the precipitate is separated from the solution by filtering and is washed and dried. It is then reduced by grinding to finely divided particles, a suitable apparatus for this purpose being a ball mill. While the particle size is not critical, a fineness of the order of that of paper-makers clay is preferred.

Certain characteristics are given herein for the calcium silicate so formed and for other alkaline earth metal silicates disclosed herein, said characteristics being specific surface area and the presence of a substantial amount of the silicate in the amorphous state. The specific surface area is given in terms of square meters per gram and is determined by the low temperature nitrogen adsorption method which is described in the article by S. Brunauer, P. H. Emmett and E. Teller at pages 309 to 319 of vol. 60 of the Journal of the American Chemical Society. The fact that a substantial amount of the silicate is in the amorphous state is determined by obtaining an X-ray ditfraction pattern of the material by the Hull-Debye-Scherrer method described at pages 391 to 419 of X-rays in Practice by Wayne T. Sproull. published in 1946 by McGraw-Hill Book Company, Inc. In such a pattern the presence of a so-called amorphous ring shows that a substantial amount of the silicate is in the amorphous state.

The calcium silicate formed by the method described has a specific surface area of 45.4 square meters per gram, and a substantial amount of said silicate is in the amorphous state.

The stereotype mat is then formed by a procedure the manipulative steps of which, except for the inclusion of the alkaline earth metal silicate, follow well known procedure for making stereotype mats. A quantity of an aqueous slurry of coniferous alpha pulp is placed in a beater and beaten until the fibers are well separated and there is a suitable hydration thereof. Calcium silicate such as has been described heretofore is mixed with the beaten fibers in the water suspension, the proportions, on a dry weight basis, being 100 parts of fibers and 23 parts of calcium silicate. The mass is agitated to form a thorough, intimate mixture of the fibers and calcium silicate, and it is then transferred to a paper-making wet machine where it is placed in the usual form of a liquid suspension in water. The mixture of fibers and calcium silicate is felted out in the form of a web upon the screen of the wet machine and the web is transferred to a roll upon which it is wound until a sufiicient number of layers have been built up to form a sheet of the desired thickness. The sheet is then removed from the roll and dried and compressed to the desired thickness for the stereotype mat. In usual practice, the thickness of a stereotype mat is about .015 inch to .040 inch. The dry stereotype mat may have a coating such as has been described heretofore applied to the surface thereof which is to take the impression from the form.

For use, the resulting stereotype mat is moistened, so as to contain about 10% to of water, based on the total weight of the mat, whereby it is rendered plastic. A moisture content of about 20% is usually satisfactory for this purpose. The stereotype mat containing the calcium silicate is highly plastic and is of uniform texture and has a very smooth surface, whereby it takes a deep and exact impression of the printing form with a moderate amount of pressure. In addition, it readily releases the moisture upon drying following the taking of the impression, and has a smooth, hard surface to receive the cast molten metal, which surface is free from roughness,

fractures and projecting fibers, whereby a large number of faithful and exact stereotype reproductions may be made from a single stereotype mat, which reproductions carry in sharp definition the details of the original form. in all of these respects, the stereotype mat of the present invention is superior to one which does not contain the calcium silicate but rather contains an ordinary filler.

Example 2 A stereotype mat was made by a procedure similar to that of Example 1 except that calcium hydroxide, Ca(OH)z, was used in place of calcium chloride, CaClz, in the preparation of the calcium silicate. The product so formed has a specific surface area of 10.7 square meters per gram, and a substantial amount of the silicate is in the amorphous state.

Example 3 A stereotype mat was made by a procedure similar to that of Example 1 with the exception that sodium metasilicate, having the ratio 1 NazO, l SiOz was used in place of the sodium silicate having the ratio 1 NazO, 3.3 SiOz.

The calcium silicate formed by this method has a specific surface area of 105 square meters per gram, and a substantial amount of the silicate is in the amorphous state.

In the some way, stereotype mats were made by the procedures of Examples 1 and 2 in which the NazO to SiOz ratio of the sodium silicate was varied from 1 NazO, 1 SiOz to 1 NazO, 3.75 SiOz. The CaO to SiOz ratio in the resulting calcium silicate corresponded substantially to the N820 to SiOz ratio in the sodium silicate. In every case a satisfactory, improved stereotype mat was obtained. The calcium silicate formed by using the 1' NazO, 3.75 SiOz ratio has a specific surface area of 54.3 square meters per gram, and a substantial amount of said silicate is in the amorphous state.

In the same way, stereotype mats were made by the procedures described heretofore employing barium silicate, magnesium silicate, and strontium silicate in place of calcium silicate, said silicates being made by substituting the corresponding water soluble barium, magnesium or strontium compound for the water soluble calcium compound used in the described procedures. The barium silicate formed by using barium chloride and sodium silicate having the ratio of 1 NazO, 3.3 SiOz has a specific surface area of 25.9 square meters per gram, and a substantial'amount of said barium silicate is in the amorphous state. The magnesium silicate formed by using magnesium chloride and sodium silicate having the ratio 1 NazO, 3.3 SiOz has a specific surface area of 525 square meters per gram, and a substantial amount of said magnesium silicate is in the amorphous state. The strontium silicate formed by using strontium chloride and sodium silicate having the ratio 1 NazO, 3.3 SiOz has a specific surface area of 28.2 square meters per gram, and a substantial amount of said strontium silicate is in the amorphous state. Also, stereotype mats were made by the procedure described in Example 1 in which calcium and magnesium silicates obtained commercially upon the market were used in place of the calcium silicate prepared by the precipitation step as described in connection with Example 1. Such commercially available silicates are prepared by precipitation out of an aqueous solution of a calcium or magnesium compound, as the case may be. In all cases the stereotype mat had the superior properties which have been described heretofore.

One such commercially available calcium silicate which has been used is that sold under the trademark Silene EF, which has a specific surface area of 68.5 square meters per gram, and a substatnial amount of which is in,

meters per gram, and a substantial amount of which is in the amorphous state. As stated heretofore, theproportions of the alkaline earth metal silicate may vary over a considerable range,

and about to 25%, based on the dry weight of the stereotype mat, has been found to be suitable. With respect to the silicates, the ratio of alkaline earth metal oxide to SiOr; may vary in the same manner as explained heretofore in connection with calcium silicate. Also, instead of a single alkaline earth metal silicate, a mixture of several such silicates may be used in the stereotype mat. Also, the stereotype mat may be composed'of cellulose fibers different from the coniferous alpha fibers used in Example 1, as is explained in the early part of this specification.

This application is a continuation of my copending application Serial No. 170,030, filed June 23, 1950, now abandoned.

What is claimed is:

l. A stereotype dry mat comprised uniformly throughout the thickness thereof of a co-felted mixture of cellulose fibers and discrete particles of a filler, said filler containing as an essential constituent, a synthetic precipitated alkaline earth metal silicate, said stereotype mat being characterized by high plasticity when moist.

2. A stereotype dry mat comprised uniformly throughout the thickness thereof of a co-felted mixture of cellulose fibers and discrete particles of a filler, said filler containing, as an essential constituent, a synthetic precipitated silicate of a metal from the group consisting of barium, calcium, magnesium and strontium, said stereotype mat being characterized by high plasticity when moist.

3. A stereotype dry mat comprised uniformly throughout the thickness thereof of a co-felted mixture of cellulose fibers and discrete particles of a filler, said filler containing as an essential constituent, a synthetic precipitated alkaline earth metal silicate, the amount of said filler being about 10 percent to 25 percent, based on the dry weight of said mat, said stereotype mat being characterized by high plasticity when moist.

4. A stereotype dry mat comprised uniformly throughout the thickness thereof of a co-felted mixture of cellulose fibers and discrete particles of a filler and having a water content of about 10 percent to 50 percent based on the total weight of said mat, said filler containing as an essential constituent, a synthetic precipitated alkaline earth metal silicate, the amount of said filler being about.

10 percent to 25 percent, based on the dry weight of said mat, said stereotype mat being characterized by high plas ticity when moist.

5. A stereotype dry mat comprised uniformly throughout the thickness thereof of a co-felted mixture of cellu-' 1 lose fibers and discrete particles of a filler, said filler containing as anessential constituent, a synthetic alkaline earth metal silicate precipitated from an aqueous solution of an alkaline earth metal compound by an alkali metal silicate, said stereotype mat being characterized by high plasticity when moist.

6. A stereotype dry mat comprised uniformly throughout the thickness thereof of a co-felted mixture of cellulose fibers and discrete particles of a filler, said filler containing as an essential constituent, a synthetic precipitated alkaline earth metal silicate which has been dried and.

ground, said stereotype mat being characterized by-high plasticity when moist. v v

7'. A stereotype dry mat comprised uniformly through-. out the thickness thereof ,of a co-felted mixture .of cellulose fibers and discrete particles of a filler, said filler con taining as an essential constituent, a synthetic precipitated alkaline earth metal silicate, said stereotype mat having a release-promoting coating upon the molding and casting surface thereof, said stereotype mat being characterized by high plasticity when moist.

8. A stereotype dry mat comprised uniformly throughout the thickness thereof of a co-felted mixture of cellulose fibers and discrete particles of a filler, of said filler containing, as an essential constituent, a synthetic alkaline earth metal silicate exhibiting the following characteristics: a surface area of at least 10 square meters per gram as determined by the low temperature nitrogen adsorption method, and a substantial amount of said silicate being in the amorphous state as determined by the presence of an amorphous ring on the'X-ray diffraction pattern, said stereotype mat being characterized by high plasticity when moist.

References Cited in the fileof this patent UNITED STATES PATENTS

Claims

8. A STEREOTYPE DRY MAT COMPRISED UNIFORMLY THROUGHOUT THE THICKNESS THEREOF OF A CO-FELTED MIXTURE OF CELLULOSE FIBERS AND DISCRETE PARTICLES OF A FILLER, OF SAID FILLER CONTAINING, AS AN ESSENTIAL CONSITUTENT, A SYNTHETIC ALKALINE EARTH METAL SILICATE EXHIBITING THE FOLLOWING CHARACTERISTICS: A SURFACE AREA OF AT LEAST 10 SQUARE METERS PER GRAM AS DETERMINED BY THE LOW TEMPERATURE NITROGEN ADSORPTION METHOD, AND A SUBSTANTIAL AMOUNT OF SAID SILICATE BEING IN THE AMORPHOUS STATE AS DETERMINED BY THE PRESENCE OF AN AMORPHOUS RING ON THE X-RAY DIFFRACTION PATTERN, SAID STEREOTYPE MAT BEING CHARACTERIZED BY HIGH PLASTICITY WHEN MOIST.