US 1829157 A
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Oct. 27, 1931. G. A. R|HTER 1,829,157
COMPOSITE SHEET MATERIAL Filed Sept. 29, 1928 Patented Oct. 27, 1931 UNITED STATES PATENT OFFICE GEORGE A. RICHTER, OF BERLIN, NEW HAMLPSHIRE, ASSIGNOR TO BROWN COMPANY, DIE BERLIN, NEW'HAMPSEERE, A CORPORATION OF IvIAIN'E COMPOSITE SHEET MATERIAL This invention deals with the manufacture of composite sheet material made of plies of cellulose fibers having diflerent characteristics and intended for use as a raw material in the production ofvarious products.
When cellulose fiber such as wood-pulp is used asa raw material in the manufacture of webs designed for treatment with liquid materials, such as liquid impregnating agents or chemical solutions, it has sometimes been found desirable to felt the fibers in substantially unbeaten condition on machinery of the papermaking type into a more or less fluffy web capable of being rapidly and uniformly penetrated by the liquid material and of absorbing a large amount of such mate rial. By using the pulp in substantially unbeaten condition, the fibers may be loosely felted into a light, fiuify web or waterlaid sheet of high absorptivity, particularly when the original pulp is of high absorptivity and is felted and dried without being subjected to substantial pressures, such as .used in cus-- tomary papermaking practice. One serious disadvantage of awaterlaidweb so made,however, is that it is unsuitable for use as a raw material in a process which places it under much stress as it tends to break. In accordance with the present invention, this disad-' vantage is overcome by adhesively uniting it face to face with a much stronger web of paper to produce a composite sheet of sufiicient strength to be handled without breaking under the stresses to which it is subjected in the usual treatments with liquid materials. If desired, two flufiy webs may be so united with the opposite faces of a paper web to produce a composite sheet which is interiorly reinforced. Where a composite sheet is produced as described with a paper web formed of gelatinized pulp, produced for example by hard-beating, it may be made of suflicfent strength, for instance, to be drawn through baths of liquid treating material quite satisfactorily, the material rapidly penetrating through and being absorbed in large quantity by the fluffy web material. For instance, when the composite sheet is passed through a rubber-containing bath, e. g. rubber latex, an artificial aqueous rubber dis- For instance, whereas the breaking length of the rubber-impregnated, fiuify web alone may be about 1,000 to 1,500 yards, the breaking length of the paper web impregnated with a lower proportion of rubber maybe about4,000 yards, so that the composite sheet, after impregnation, may have a breaking length of about 2,500 to 4,000 yards, andthus compare favorably with leather which may have a breaking length Breaking length is the length of paper which if freely suspended would break as a result of its own weight. The fluffy web, material after impregnation with agents such as rubber or lacquers of the nitrocellulose type, affords an excellent embossing surface, owing to the permanent displacement or give in 'the material under embossing action before the impregnating agent sets.
With these and other features in view, the invention may be best understood from the following more complete description thereof when considered in conjunction with the accompanying drawings, wherein Figure 1 illustrates more or less diagrammatically and conventionally a method of forming a two-ply composite sheet.
Figure 2 illustrates a method of forming and treating a three-ply composite sheet.
Figures 3 and 4 show in perspective impregnated and embossed fragments of composite sheets produced respectively as illustrated in Figures 1 and 2.
Referring to Figure 1 of the drawings, 1 represents a rolled fluffy web of felted cellulose fibers, and 2 a rolled paper web, these webs having the characteristics hereinbefore described. Both webs may be simultaneous- 1y unwound, the paper web being treated of about 3,000 yards.
with suitable adhesive on its upper face, as
by an adhesive-applying roll 3, whereupon the two webs may be united face to face un-., der a roll 4. Or an internally reinforced, composite sheet may be formed as illustrated in Figure 2, two rolled fluify webs 5 and a rolled paper web 6 beingsimultaneously unwound, the paper web being treated with three-ply sheet taking a downward loop extending from a roll 10, under a roll 11 in a bath of liquid material 9, to a roll 12. If
, the sheet is being treated in an aqueous bath the characterdescribed, as it is not necessary lose, such as shellac.
or in one "containing an organic solvent, the liquid content of thesheet may be removed by passing it over one or more heating rolls 13, but if the bath is made up of molten thermoplastic impregnating agents such as asphalt, waxes, or the like, the rolls 13 may be cooled to congeal these agents in the sheet.
Cellulose fibers of various origins may be employed in producing a composite sheet of that the fiuify ply and the paper ply be made with fiber of the same origin. Preferably, a refined wood fiber of high alpha cellulose content in substantially unbeaten condition is employed as the raw material for making the fluffy web, as the resulting web is of especially high absorptivity, owing not only to the loosely felted condition of the fibers, but also to the high absorptivity of the fiber itself.-
lhe paper web may be formed of similar beaten fiber, or from rag, sulphite, kraft, or manila stock, the fiber being well beaten to produce paper of the desired strength. Thus, whereas the substantially unbeaten fiber employed as a raw material for the flufi'y web may have a slowness of about one minute, the beaten fiber employed for. making the paper web may have a slowness of about forty The paper web may also containv the usual sizing or filling materials, or may be impregnated before being united with one or more fiuify webs as described, the impregnating material being similar to or different from a material subsequently used for impregnating the composite sheet. When the paper web is-to be impregnated with a material such as rubber, which does not bond well with a material such as nitrocellulose with which the composite sheet is to be impregnated, the adhesive employed for uniting the webs is preferably one which efiects a good bond between rubber and nitrocellu- A composite sheet such as described may of cellulose derivative'such as v1scose,whereupon, if desired, regenerated cellulose may be produced in sit-u in the sheet by passing it through a cellulose-regenerating solutlon such as a niter' cake solution, and the sheet then washed and dried. Or it may be passed through baths of parchmentizing reagents such as a zinc chloride or a sulphuric acid solution, then washed and dried.
Having thus described certain embodiments of this invention, it should be evident to those skilled in the art that various changes and modifications might be made therein without departing from the spirit and scopeof invention as defined by the appended claims.
1. Com osite sheet material comprising a waterlald ply of substantially unbeaten cellulose fibers in a loosely felted condition, and a ply of cellulose fibers bonded together with gelatinized cellulose.
2. Composite sheet material comprising a waterlaid ply of substantially unbeaten wood fibers of high alpha cellulose content in a loosely felted condition, and a much stronger ply of cellulose fibers bonded together with gelatinized cellulose.
3. impregnated composite sheet material comprising a ply of substantially unbeaten fibers in a loosely felted condition, and a paper ply, one of the plies carrying rubber as the impregnating agent and the other carrying nitrocellulose.
4:. impregnated composite sheet material comprising a ply of substantially unbeaten fibers in a loosely felted condition, and a paper ply, one of the plies carrying rubber as the impregnating agent and the other carrying nitrocellulose, said plies being .united by an adhesive bonding the rubber to the nitrocellulose.
5.-l[mpregnated composite sheet material comprising a ply of substantially unbeaten condition and a ply of cellulose fibers bonded together with gelatinized cellulose, the ply ofsubstantially unbeaten cellulose fibers car- -ry1ng a ma ing agent.
jor proportion of the impregnat- In testimony whereof I have aflixe d my signature.
GEORGE A. RICHTER.