US2438281A

US2438281A - Method for processing plastic sheets

Info

Publication number: US2438281A
Application number: US634044A
Authority: US
Inventors: Gordon Sheldon
Original assignee: US SEC WAR
Current assignee: United States, WAR, Secretary of; US SEC WAR
Priority date: 1945-12-10
Filing date: 1945-12-10
Publication date: 1948-03-23
Anticipated expiration: 1965-03-23

Description

Patented Mar. 23, 1948 ...Marmor .Eon PRo srnnrl:

CESSSINGfPI-IASTIC Sheldon LfGordom lMadison, 3W-is., assigner, "by -imesne assignments, :.to the `EUnited States --Lf rmericar-asirepresented by the Secretary ofivar i ApplieationDeeniber 10, 1945,.SerialfNo. 1,634,044

2 claims. (ciers-@2181 This invention relates tothe-rolling of plastic materials and, more particularly, to a method of rupturing il.bubbles*formed#duringrolling of hazardous plastic compositions.

In the manufacture'of-smokelessfpowder, vdiffr taining nitrocellulose -and gnitroglycerin. -ilhe y-rnixturemis `dumped onto 'horizontally disposed Lheated differential--ro-llsas-a-wetepaste an, O lied tobringI about-the -formation of -acolloided heet Von ithe-f faster roll. -During,-thisfhazardous :proces`s, protruding -bubblesofsteam" are formed 4-between the sheet and the faster roll as the moisture in the charge is rapidly dissipated by the heated roll in combination with the heat generated by the rolling operation.

The formation of these bubbles presents a considerable re hazard in the rolling of smokeless powder. 'I'he compression of the bubbles as they pass into the bite of the rolls causes them to burst and a fire frequently results. The theory has been advanced that escaping steam under a relatively high pressure passing through a small break in the wall of a large bubble frictionally generates enough heat to cause ignition of the charge.

Thus, the prevention of the compression of bubbles in the bite of the rolls is a very desirable step in the diierential rolling of smokeless powder as well as any other rolling operation where undesirable bubbles are likely to be formed.

An object of the present invention is to provide a method for rupturing protruding bubbles attaining a predetermined height in plastic composition during rolling to prevent such bubbles from entering the bite of the rolls.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

Generally described, the present invention comprises a method of rupturing and deiiating protruding bubbles which are undesirably formed in a plastic sheet material and means for rupturing bubbles in said plastic sheet material.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawing forming a part of the specification, wherein reference symbols refer to like parts wherever they occur.

Fig. 1 is a front elevational view of a preferred form of apparatus for the embodiment of the invention.

Fig. 2 is a transverse sectional view of the ap- V`pamaztus illustrated "infFi'g, "lgjshowinfg ajplastic .Sheet beine formed h*on 'one "of' the rolls of the apparatus.

,Figr' fis Ian .enlarged sectional` v iew 'of a portion 1'offthe apparatusitakenalong,line 3-.3 of `F'g. 1.

`With referenceto the 'drawing fa; conventional type diierential speed mill I0 with 'heated rolls -hasavliigjh speedrll-II 'ad'jacentto ailow vspeed ',rollF-,I-Z. f'Aibar'IiS'is rigidly supported at each 'endfbyffframeemembersjof'the milll. The bar k-Il3 :is gsuperposed 'infjuxtaposition 'to lfthe y high speed-rondt -The"bar"l3iis'provided with sharp bubble rupturing projections or pins Ill at a predetermined distance from and at suitable increments along the face of the high speed roll II. The pins I4, as shown in Fig. 3, are preferably formed of a shank I5 rigidly secured in the bar I3, a sharp point I6, and a sharp barb I'I adjacent to the point I6.

As illustrated in Fig, 2, during rolling of a wet charge I8, such as smokeless powder, bubbles I9 are formed as the moisture is rapidly.

evaporated from the charge being worked on the heated high speed roll II. The charge I8 being formed into a plastic sheet is carried under the bar I3 in the direction indicated by arrow 2o and bubbles I9 protruding above the surface of said plastic sheet are ruptured by the pins ld before entering the bite of the rolls. The rupturing of the bubbles I9 is greatly facilitated by the barbs I1 placed in a forward position as shown.

An example of the operation of the invention is given for the colloiding of a smokeless powder. The rolling mill utilized was of the type illustrated in the drawing and had the following characteristics Constant ro11 temperature 105 C.

Gap between the rolls.. .023 inch Peripheral speed of faster roll-- Approx. 113 it.

per min.

Peripheral speed of slower roll-. Approx. ft.

per min.

Roll diameters 14 inches Roll lengths 30 inches The smokeless powder composition had the following formulation:

Parts by weight Nitrocellulose 49.50 Nitroglycerin 41.50 Ethyl centralite 9.00 Candelilla, wax 0.08

The above composition, properly mixed in water, blended, dewatered and dried to a moisture content o1 approximately 13% by weight, was placed on the rolls of the mill in charges of predetermined weights suitable to the length of the rolls and size of sheet desired. The mill was provided with bubble rupturing means as illustrated in the drawing. Protruding bubbles, formed as the charge was worked on the faster roll, were eciently and eiectively ruptured by the pins set two inches apart and 0.4 inch above the faster roll.

In comparison with rolling operations not em- ,v

rembodiment of the invention, a plurality of knives, pins without barbs, circular cutters and the like similarly arranged over the plastic ma.- terial may be mentioned among alternating bubble rupturing means. y

It will be seen, therefore, that the advantages of the present invention reside particularly in the processing of hazardous plastic material, but that advantages also reside in any process where the bursting of protruding bubbles in a rolling 4 operation is required to improve the end product or the processing operation.

What I claim and desire to protect by Letters Patentis:

1. In the process of rolling an ignitable colloidable material, wherein protruding bubbles are undesirably formed and present a potential ignition hazard if compressed between the rolls,

- the improvement which comprises rupturing and deflating the bubbles reaching a predetermined height before entry into the bite of the rolls.

2. In the process of diierential rolling smokeless powder wherein protruding bubbles are undesirably formed and present a potential ignition hazard if compressed between the rolls, the improvement which comprises rupturing `and deating the bubbles reaching a predetermined height before entry into the bite of the rolls.

' SHELDON GORDON.

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

UNITED STATES PATENTS Number Name Date 1,184,016 Price May 23, 1916 2,055,002 Chandler Sept. 22, 1936 2,186,771 Smith Jan. 9, 1940 2,309,543 Sawyer Jan. 26, 1943 2,383,694 Steiner Aug. 28, 1945 2,408,729 Brackett Oct. 8, 1946