US2229146A - Drawsheet - Google Patents

Description

Jan. 21, 1941. R. E. THOMAS 2,229,146

DRAWSHEET Filed Sept. 6, 1939 [90291220124115 712012262! INVENTOR BY M C 7 ATTORNEY Patented Jan. 21, 1941 UNITED STATES PATENT OFFICE 2,229,146 DRAWSHEET Raymond E. Thomas, Newburgh, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application September 6, 1939, Serial No 293,545

1 Claim. (Cl. 154-545) This invention relates to newspaper printing drawsheet, the outer surface of which is relativeand more particularly to a new and improved ly hard but flexibleq and non-penetrable by inks coated drawsheet for impression cylinders of roor moisture, cleansing solvents such as hydrocartary printing presses. bons, carbon tetrachloride, etc.,'which' are used In the standard newspaper printing press the in the printing art. cylinder which carries the type is called the plate A further object is to produce a drawsheet cylinder. The cylinder which presses the sheet the base of which is exceptionally smooth, strong, being printed against the plate cylinder is called and sufficiently firm in texture to prevent stretchthe impression cylinder. ing, but resilient and-having the property to re- Impression cylinders of rotary printing presses turn to its normal smooth surface, that is, the po- 10 are made of hard unyielding materials, such as sition it occupies before being struck by the plate metal. In the printing of paper sheets, it is neccylinder carrying the type. essary to cover the face of the impression cylinder A still further object is to provide a drawsheet with a resilient cushion such as 0011;, in order to with improved anchorage of the coating to a new compensate for any irregularities in the printing fabric base in which case the said coating is exelements, to produce an even printing impression ceptionally smooth, dry, flexible, non-tacky, and

over the entire surface being printed. resistant to cracking and peeling when vsubjected The covering for the impression cylinder must to repeated pressure of great force. I be smooth, resilient, non-penetrable by printing The objectives of this invention are accominks, possess a hard non-cracking and non-peelplished by emp yi as a base material a fabric 20 ing surface capable of withstanding pressure apthe individual threads of which are composed of plication of great force by the plate cylinders with a great multiplicity of small continuous synthetic millions of repetitions. Therefore, it is necessary filaments twisted to and Woven into a to cover the resilient cork cushion with sheet tile fabric, and coating the fabric with a pluralmaterial called a drawsheet having these desirity of different cellulose-derivative coating com- 25 able properties. positions. Other objects will appear hereinafter. It has also been the practice in the printing These objects are accomplished by preparing art to employ a press blanket which comprises a drawsheet with a special type of fabric which a thick felted sheet which has previously been has no slugs or misweaves and which is resilient coated with a suitable coating for covering for and elastic. The base fabric is coated with a 30 the impression cylinder, instead of the cork plurality of compositions which make the finished sheet which is covered with the drawsheet. The product smooth and strong and also enhances coated felt blankets are several times more exthe strength of the original fabric. pensive than the cork sheet covered with a draw- A suitable fabric for the present invention is sheet since the latter may be replaced several strpng rayon, by which I mean a rayon'prepared 35 times for the cost of a single press blanket. from a regenerated cellulose yarn or cellulosic At present it is common to employ woven cotyarn wherein not more than. one hydroxyl group ton fabrics as a base for drawsheets. Such 'cotof each Co group is substituted, said yarn having ton fabrics are made from threads being coma strength of at least 2.5 grams per denier.

together to form a single thread.- The short tice is about 3 grams per denier which is nearly fi when. twisted into a Single fi me a twice the strength 'of ordinary rayon. m ny Sh rt protruding fibres commonly referred Suitable fabrics prepared "from the above de-. to as lint- In additmn the lint, due to the scribed yarn will probably be apparent to those 5 fact that the cotton fibres are relatively short, skilled in the am However, it has been found the individual threads are not smooth 81 1d have t fabrics having a construction of 0 x 4 g' g gggg g fig i yi g g 140 denier, 60 filament, regenerated cellulose are imperfections in the woven fabric referred l i: suitable provided g f -gg a g 2.5 grams per e er. 0 er cons ruc ion- 5355 3 3 ,35 gggggggggg g .which has been found suitable is 120 x as with 100 ing and result in a somewhat irregular surface. denier 100 filament regenerated cellulose a The drawsheets constructed a cotton f b i In these designations the first number refers to base are therefore undesirable for these reasons. the threads P inch in the Warp, While the Throughout t specification and claim t 0nd figures relate to the filling threads per inch. 55

term drawsheet is used tomean a coated heet, It is also desirable to select fabrics which have material which is drawn over a resilient sheet a fi am nt size of n t m re than 2.5 denier. previously attached to a rotary impression cyl- It has been found that a synthetic fabric having inder used in the printing industry. a thread count of 85 in the warp direction and r The object of this invention is to produce a 68 in the filler, weigh g Ounces 1 1 q re 00 40 posed of a number of small cotton fibres twisted Usually the strength of the fabric used in prac- 4o yard is very satisfactory for the purpose indicated.

The above described fabric, hereinafter referred to as synthetic fabric, is provided with non-cracking, non-peeling, ink resistant coating,.comprising a cellulose derivative as the film forming component. of a resin-cellulose nitrate solution. The following is given as an example, with the understanding that variations may be made without departing from the scope of this invention.

In the drawing the Figures 1 and 2 represent a diagrammatic section through the coated fabric. In both figures the basejabric is shown as I, the base coating comprising cellulose nitrate and resin is indicated by 2; the intermediate pigment is indicated by 3; and 4 surface lacquer. In Figure 2 a plasticized coat on the opposite side is shown as 5. This coat may have a slight tack. These coatings will be described in detail hereinafter.

Frnsr COATING COMPOSITION Example A Per cent by wt. 36 oz. cellulose nitrate solution (24.07% cellulose nitrate dispersed in 1 part ethyl alcohol and 1 part ethyl acetate) 59.3 65% solution of urea-formaldehyde resin dispersed in isobutyl alcohol 10.9 60% solution of alkyd resin-castor oil modified dispersed in toluol -1 12.3 Butyl acetate 17.5.

The urea-formaldehyde resin may be prepared in accordance with U. S. application Serial No. 58,000, filed January 7, 1936, by D. E. Edgar, et al.

The cellulose nitrate employed in the above coating composition has a nitrogen content of 12.3% to 12.5%. The viscosity characteristic is 90 to 110 seconds as determined by the A. S. T. M. D301-33. The urea-formaldehyde resin solution acts as a penetrating agent which assists the composition to penetrate into the threads of the synthetic fabric. The alkyd resin is a plasticizer for the urea-formaldehyde resin and cellulose nitrate.

Another example of the -first coating composition is as follows:

Fmsr COATING COMPOSITION Example B Per cent 36 oz. cellulose nitrate solution (24.07% cellulose nitrate dispersed in 1 part ethyl a1- cohol and 1 part ethyl acetate); 44.4 60% solution of alkyd resin-castor oil modified dispersed in toluol 40.6 A Butyl acetate 15.0

Two coats of either of. the above compositions are ap ied to the synthetic fabric by means of a doctor knife. Approximately two ounces of the first coating composition are deposited per square yard of fabric. After each coat the material passes through a heated drying tunnel to expel the volatile components.

After the first coating composition is applied, there is deposited a plurality of coats ,of a plasticized, pigmented, intermediate coating composition, prepared in the following manner: The dry pigments are ground in "Paraplex RG2 resin in the following preparation:

The first two coats consist Mni. BASE (PigmentResin grind) Per cent Lithopone 36.10 Yellow ochre 12.04 Bone black 6.26

resin (castor oil modifled sebacic acid glycerol condensation product) in 60% toluol solution 45.60

The above ingredients are ground in a ball INTERMEDIATE COATING Comosrrron Per cent by wt. Mill base n 17.3 24 oz. cellulose nitrate sol. (17.44% solution in 1 part ethyl alcohol-1 part ethyl acetate) 61.0

resin. (60% solution in toluol) rolls to improve the anchorage of the coating to the synthetic fabric, and also to smooth out any unevenness in the coated surface. Followmg the first embossing, four coats of the intercomposition, the coated surface is sprayed with a low concentration surface lacquer containing aluminum particles or flakes. The formula for this surface lacquer is as follows:

SURFACE LACQUEB Example A tion in 1 part ethyl alcoholand 1 part ethyl acetate) Butyl acetate 29.3 Ethyl acetate 1 13.31 Flat aluminum particles or flakes 3.69

a surface lacquer which in a dry matte finish is as follows:

Another example of results Per cent. 24 oz. cellulose nitrate sol. (17.44% solu- The method of preparation of the above composition is disclosed in U. S. Patent 2,169,200, filed November 6, 1937, by F. G. Uhler, and also in U. S. Patent 2,169,199, filed July 22, 1937 by R. E. Thomas. 6

Approximately two ounces of either' of the above surface lacquers are applied per square yard.

, ate coating and expelling the volatile solvents,

the drawsheet is finished and ready for use, or it may be further treated by applying a nonslipping coating composition to the uncoated side or back of the drawsheet as hereinafter described.

In practice an impression too wide to be covered with a single drawsheet, and two separate drawsheets are stretched over the cork covered impression cylinder, and the edge of one sheet is abutted with the edge of the other sheet in the middle of the cylinder. Durcylinder is usually ing the continuous pounding of plate cylinderv against the drawsheet stretched tautly over the impression cylinder, there is a tendency for the two drawsheets to slip toward the edges of the impression cylinder and become separated due to. the smoothness of the continuous rayon filaments which form the back of the drawsheet. The slipping of the drawsheet more than of an inch is objectionable since this is usually the distance of the printed material from the edge of the paper being printed.

In order to prevent slipping of the drawsheet on the cork covered impression cylinder a suitable coating having non-slipping properties is applied on the back side of the fabric which contacts the cork covered impression cylinder. By the way of illustration and not limitation, the following composition has been found satisfactory to apply on the back side of the drawsheet after the face coating has been completed, to prevent the slipping of the drawsheets on the cork covered impression cylinder:

Per cent Polyvinyl acetal resin 19.3 Castor oil 12.8 Toluol 24.3 Ethyl alcohol 43.6

A plurality of coats of the above .composition are applied to the back side of drawsheet. Approximately four ounces of the above composition are suits from the use of the synthetic deposited per yard of material 40" wide, which corresponds to 1.3 ounces of the non-volatile components. Other film forming as other vinyl resins and cellulose derivatives suitably plasticized, which have a slight tack under pressure, may also be satisfactorily used for the non-slipping coating applied on the back side of the rayon fabric. has been described with refer- The invention ence to specific coating compositions which have been given by the way of illustration and not limitation. It is within the purview of this invention to use other types of coating compositions employing other cellulose ester derivatives such cellulose acetate, cellulose butyrate, cellulose formate, etc. as well as cellulose ether derivatives, e. 'g., ethyl cellulose, benzyl cellulose, etc. The drawsheet may be any thickness as long as a substantially plane surface is obtained.

An outstanding advantage of a drawsheet produced in accordance with the disclosure of this invention is the extremely firmbond of the coating to the woven base. The resin-cellulose nitrate first coating composition is intended to penetrate into the interstices of the synthetic fabric, and as a result of the penetration of the coating into the fabric, the strength of the bond of the coating to the fabric base is increased.

A still further advantage is the high tensile strength of the coated synthetic fabric which allows the coated fabric to be drawn tautly over the cork sheet covering the impression cylinder and while in this taut condition is capable of sustaining pressure application of great force by the printing plates with millions of repetitions without the fibres of the fabric or coating being broken.

A still further advantage is the substantially plane surface of the coated drawsheet which refabric having a substantially plane surface resulting from the absence of lint, misweaves, and slugs.

Astill further advantage is the ing composition for the synthetic fabric. The coating is dry, flexible, non-tacky and substantially resistant to cracking and peeling when subjected to repeated pressure of great force.

While the invention has beendescribed in detall with specific examples, such examples areiilustrative and are not given as limitations, since other modifications within the spirit and scope of the invention will be apparent to those skilled in the art. Hence, the invention is to be understood as limited only as indicated, in the appended claim, in which the intent is to set forth all the novelty over the prior art.

I claim:

A drawsheet comprising a. base fabric prepared from threads of regenerated cellulose of uniform denier, on one side of said fabric .a base coat comprising a cellulose derivative and an' alkyd resin, an intermediate coat comprising a cellulose derivative,- alkyd resin and pigment and a materials sucli surface coat of a dull cellulose derivative compo- RAYMOND E. THOMAS.

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