US1748998A - Composite sheeting and method of making - Google Patents

Description

March 4, 1930. G. A. RlCHTER COMPOSITE SHEETING AND METHOD OF MAKII ING Filed Oct. 6, 1928 Patented Mar. 1939' UNITED. STATES PATENT OFFICE?" GEORGE -A. RICHTER, OF BERLIN, NEW HAMPSHIRE, ASSIGNOR 1'0 BROWN- COMPANY,

' BERLIN, NEW HAMPSHIRE, CORPORATION 015' MAIN E comrosrrn snnn'rine AND..METHOD or MAKING 'Application filed October 6, 1928. Serial No. 310,710.

This invention has to do with the manufacture of composite sheet material'made with cellulose fiber such as wood pulp as a raw material, and intended for various 6 uses, being especially serviceable as a base or foundation for the production of coated or impregnated products,

. When cellulose fiber such as wood pulp is used as a raw material for the manufacture times been desirable to felt the fibers into a more or less fluify web on'machinery of the paper-making type, so that the web may be capable of quickly absorbing a large amount of liquid impregnating materials, such as rubber latex, for instance. A sheet of especially high absorptivity is produced when refined wood pulp of high alpha cellulose content in substantially unbeaten condition is used, and the webformed without being subjected to high pressure during felting or drying, as in such case the resulting sheet is highly absorbent, not only because of the loosely felted condition in which the fibers exist but also because of the absorbency of the fiber itself. One of the serious disadvantages of a web so made, however, is that it is comparatively weak and is hence likely to be broken when subjected to the stresses of usual treating operations, as for instance, when drawn in continuous form through a bath of liquid impregnating agents. In accordance with the present invention, this diificulty is overcome by reinforcing the fiuify web with a flexible metallic backing, which may take the form. of strands of wire arranged in generally parallel relationship with or without lateral tying or filling strands, wire cloth or screening, or highly flexible, thin sheet metal with or without perforations therein. When wire screening is used as the backing material, reinforcement of the web may be effected by felting the pulp fibers to one side of the screening while it is being supported as on a ible metallic backing. Acomposite web thus flexible metallic backing. If the pulp fibers have been deposited on wire screening, they are felted 'to'and entangled in the screening, although some entanglement is efiectedeven when a fluffy web is adhes'ively secured to wire screening. A' fiuify web reinforced as described may be used as a raw material in various processes, being sufficiently strong to be handled in continuous sheet form without likelihood of breaking. For instance, it may be successfully drawn through baths of liquid materials, the web absorbing a large amount of such material, owing'to itshigh absorptivity. While not limited thereto, a com posite web of this kind is especially suitable for use as a raw material in the manufacture of artificial leather suitable for use.

Where the characteristics of flexibility, high strength, and low stretch are desired, as, for instance, in the manufacture of belting. By passing the composite web through a rubber-containing bath, e. g., a rubber-benzene solution, rubber latex, or an artificial aqueous dispersion of rubber, and then removing the liquid rubber vehicle, an artificial leather of this type may be produced. The surface of the flufi'y web may be embossed quite satisfactorily,fowing to the permanent displacement or give in thematerial when subjected to embossing action before the liquid rubber vehicle is removed. The composite web also lends itself well to coating or impregnation with thermo-plastic materials such as asphalt, or waxes such as Montan'and carnauba, with varnishes or lacquers of the nitro-cellulose type, and withother materials. With these and other features in view, the invention may be best understood from the following more detailed -descrip- Figures 3 and 4 represent enlarged sections through composite webs formed by the methods shown in Figures 1 and 2, respectively.

Figure 5 illustrates a method of reinforcing pre-formed webs with any suitable flexible metallic backing.

Referring in detail first to Figure 1 of the drawings, 1 indicates a cylinder mould which rotates in a pulp suspension malntamed 1n a vat 2. Wire screening 3 of, say, about 40 mesh, made of high grade steel or other suitable metal, may be progressively unwound from a roll 4 and passed into contact with and then around the submerged portion of the mould on which it is supported. The pulp suspension fed into the vat 2 is preferably of very dilute consistency, containing say about 0.005% to 0.01% fiber, preferably in an unbeaten condition, especially when a highly absorbent web is desired. As the wire screening passes into the pulp suspension, pulp fibers are deposited thereon while water is passing into the cylinder mould and being removed, so that when the wire movesout of the suspension it carries a wet pulp layer the fibers of which are entangled therein, as illustrated in Figure 2. The wet pulp layer is preferably dewatered without being subjected to heavy pressure, this being shown as accomplished by passing the screening with the wet web carried thereon around a drum drier 5, from which the dry composite web is removed and wound into a roll 6.

If an interiorly reinforced web is desired, the method illustrated in Figure 2 may be practised. According to this method, aroll 7 of suitable wire screening 3 may be pro gressively unwound and passed around the submerged portion of a cylinder mould 9 rotating in a vat 10 being supplied with pulp suspension. This screening leaves the vat 10 with a wet pulp layer on its under side, and is guided successively over rolls 11 and 12, thence around the submerged portion of a second cylinder mould 13, with the pulp layer in contact with the periphery of the mould, which rotates in a vat 14 supplied with pulp suspension. -As the screening with its inner pulp layer proceeds through the pulp suspension, pulp fibers are deposited on the outer side of the screening, so that the screening passes out of the pulp vat 14 with wet pulp layers on both sides. The screening and pulp may then be guided over rollsv 15 and over a drum drier 16, from which the dry composite web is removed and wound into a roll 17.

If desired, the wire screening or other suitable flexible metallic backing may be adhesively united with one or more flufly webs of the character described, which have been formed Without reinforcement. Figure 5 illustrates such a method, according to which two rolled flufi'y webs 18 and rolled backing 19 are simultaneously unwound, the backing being guided through a bath 20 of suitable adhesive such as rubber latex, whereupon the fluffy webs may be united with the opposlte faces of the backing as by passing'the three in superposed relation into the nip of a air of press rolls 21, the resulting composite s eet being wound into a roll 22.

Cellulose fibers of various origins may be employed inpro'ducing the flufiy web hereinbefore described, but it is preferable to employ a refined wood fiber of high alpha cellulose content in substantially unbeaten condltion. It is further preferable to felt the fibers loosely, this being accomplished b forming the web and drying it without su jecting it to heavy pressures. The resulting web, when thus formed, is of especiall high absorptivity, owing to the loosely elted condition of the fibers and also to the high absorptivity of the fiber itself.

The composite sheet may be successfully subjected to various treating operations in continuous sheet form, it being especially useful as a foundation for the manufacture of artificial leather, as the fluffy web material may be able to absorb in the order of magnitude of 100% to 200% rubber, based on the dry Weight of fiber. An artificial leather thus produced serves well in the manufacture of power belts, owing to its high strength and low stretch characteristics.

Having thus described an embodiment of this invention, it should be evident to those skilled in the art that it is capable of various changes and modifications without departing from the spirit or scope of invention as defined by the appended claims.

I claim:

1. Rubber impregnated composite sheet material comprising substantiall unbeaten cellulose fibers in a loosely felte condition, united with flexible metallic screening.

2. Rubber impregnated composite sheet material comprising flexible metallic screening faced on opposite sides with substantially unbeaten pulp fibers in loosely felted condition.

3. A method of making a reinforced pulp web, which com rises progressively passing wire screening a out a cylinder mould rotating in a pulp suspension to deposit a layer of pulp on one side of the screening, progressively passing it about asecon'd cylinder mould rotating in a pulp suspension with the layer of pulp thereon contacting with the mould to deposit a layer of pulp on the other side of the screening, and drying the resulting composite web.

In testimony whereof I have aflixed my sig-

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