US1836946A

US1836946A - Plastic film or sheet containing cellulose nitrate

Info

Publication number: US1836946A
Application number: US321759A
Authority: US
Inventors: James F Walsh; Thomas E Alcorn
Original assignee: Celluloid Corp
Current assignee: Celluloid Corp
Priority date: 1928-11-24
Filing date: 1928-11-24
Publication date: 1931-12-15
Anticipated expiration: 1948-12-15
Also published as: GB343962A

Description

Patented] 15, 1931 j UNl-TED STATES PATENT OFFICE mime E'jwALsn, 0E EAST ORANGE, AND THOMAS E. ALCORN, '0]? MA'rLEwoon, NEW

JERSEY, nssrenoas TO cE LUEoIn coaromrron, A coaroannon 0E NEW JERSEY rms'rrc mm on SHEET con'mmiie cELLuLosE nirnarn Ho Drawing.

This invention relates to the reparation of films or sheets containing celliilose nitrate and relates more particularly to the use of cellulose nitrate of comparatively low nitrogen content and of low viscosity characteristics in the preparation of films or sheets.

An object of our invention is to prepare films or sheets containing cellulose nitrate of low viscosity characteristics, and preferably of relatively low nitrogen content whereby films or sheets may be produced which have properties that are superior to those found in sheets orfilms heretofore made. Other objects of our, invention will appear from the following detailed description.

Heretofore cellulose nitrate films have been prepared by spreading or flowing viscous solutions of the same onto metallic or other surfaces, and after suitable exposure to cause evaporation of the volatile solvents, the dry or partially dry film was stripped for use or other treatment. i

. However in this process, it has been necessary'. to employ a cellulose nitrate or pyroxylin of about 12% nitrogen content produced by'the reaction of a mixture of sulphuric acid and nitric acid on cellulose, without further treatment to alter the viscosity or solubility characteristics of the cellulose nitrate after such nitration. Films formed in this manner have been limited in Ino their commercial application because of their lack of plasticity under heat and their'sluggish res onse to c'gmenting operations.

er to overcome the diificulties when such cellulose nitrate was empolyed, it has been necessary to use'large proportions of camphor or equivalent plastifiers-and' also certain modifiers such as fusel oil or similar-high boilers,all of which tended to distort the films'or to impart to them an undesirable degree of softness.

'We have discovered. hat all ficulties encountered in making a plastic film containing cellulose nitrate may be obviated by the use of a cellulosenitrate or pyroxylin of lower nitrogen content and of lower viscosity. 1

- In accordance with our invention, we pre-v pare films or sheets from solutions of celluface and are of the viscosity .Applicaticin filed November 24, 1928. Serial No. 321,759.

lose mtrate or pyroxylm of a comparatlvely low degree of nitration and having low viscosity characteristics, preferably lowering this viscosity by chemical and/or physical as is used for forming films, and the volatile means of a heated atmosphere. Theamount of solution flowed onto-the surface is such solvent is caused to evaporate preferably by that itproduces fihns or sheets ranging in thickness from that of ordinary films to. that of the comparatively thick sheets which heretofore have been made by cutting from blocks of plastic masses of cellulose nitrate. The films are then stripped from the surgiven any subsequent treatment desired.

. Therellulose nitrate or pyroxylin to be employed in our process is preferably one that has a nitrogen content of 10.7 to 11.35%- and preferably 11%. The viscosity characteristics of the cellulose nitrate employed is preferably from 10' to 7 5 seconds. ;Th1s viscosity is determined by measuring the time required for a steel ball having a diameter of3/32 of an inch to fall the distance of 11.44

inches through a solution maintained at a temperature of 25 (1, which [solution is formed by dissolving one part of the cellulose'nitrate in 9 parts of a mixture'of equal 'weights'of 188 proof ethyl alcohol and acetone. This low viscosity cellulose nitrate may be made in any suitable manner known to the pyroxylin art; However we prefer to prepare it by treating a cellulose nitrate after it has been formed by nitration'of. cellulose of these .dif-

with hot water under pressure in the presence of or the absence of chemical agents such as catalysts that promote the reduction characteristics ofythe cellulose nitrate.

Any suitable volatile solvent may be employed inmaking the solution, examples of which' are acetone, a mixture ofethyl alcohol if or methyl alcohol with ether, or a mixture of ethyl alcohol or methyl alcohol with acetone.

.While we prefer to employ camphor as the to the surfaces, which were not intended to be removed from such surfaces. Moreover even if such films were to be detached from the surfaces to which they are applied,

plastifier, other suitable plastifiers such as dithey would be found to be very brittle, and ethyl phthalate or dibutyl phthalate may be employed. The amount of plastifier used is generally within the range of that'employed for making sheets from plastic compositions. As an example of the quantity ,of plastifier that is suitable, it is pointed out that for 100 parts of cellulose nitrate 40 to 50 parts 0 camphor may be used.

By the use of our process, films or sheets may be produced which are clean and readily moldable and yet have all the desirable properties of films made from cellulose nitrate or pyroxylin having a nitrogen content of 12% and of normal viscosity. An important application of our invention is the formation of comparatively thick films or sheets of pyroxylin. Heretofore the preparation of sheets or thick films by flowing solutions of the same on polished surfaces has been extremely diflicult, if not impossible. Because --of the low viscosity characteristics of the cellulose nitrate employed, the solution of the same may be cast in such thickness, that the films or sheets resulting from the evaporation of the volatile solvent thereof have thicknesses equal to that of the thinner sheets formed by cutting from solid blocks of plastic composition Thus by our process, flowed sheets may be formed that have a thickn es's of .015 inch gauge-a result that has not been attainable heretofore.

The sheets or films produced by our process have smooth andhighly polished surfaces and may be as readil shaped by molding and embosslng as sheets ormed by planing blocks of pastic masses containing cellulose nitrate. Unlike sheets formed by planing, the sheets made by our process are free of ploughed lines, so that even when heat or a solvent is a plied to our films or sheets, the highly g ossed surfaces are unafiected. These sheets or films have a clarityand transparency superior to those heretofore made, have a high degree of plasticity, and may be readily cemented to other surfaces.

purposes for which films have been heretoore used, such as photographic films, and

" may also be put to the use to which planed sheets have been put. An importantapplication of the films or sheets produced by our process is in the making of laminated glass.

We are aware of the fact that varnish films have been formed on metallic or other Because of these properties, they are eminently suited for all subscribed our s Parts Cellulose nitrate of.11% nitrogen content and 15 seconds viscosity 100 Camphor -50, Urea 1 Acetone 00 0 This solution is carefully filtered to clarify the same and to remove foreign matter. The

solution is flowed on the rim of a slowly rotating large wheel in required thicknesses and the acetone is caused to evaporate y exposure to the air. The films or sheets thus produced are stripped from the wheel.

It is to be understood that theforegoing detailed description is given merely by way of illustration and that many variations may 'be made therein'without departing from the spirit of our invention.

Having described our invention what we claim and desire to secure by Letters Patent is: k

'1. Method of preparing films or sheets comprising applying 'a solution containing 'a volatile solvent and cellulose nitrate hav-' ing a viscosity of 10 to 7 5 seconds and a nitrogen content 9f 10.7 to 11.35%v to a surface,'permitting the volatile solvent to evaporate and then stripping the film or sheet thus formed from the surface.

2. A flowcd sheet or'film containing cellulose nitrate of a viscosity of 10 to 75 seconds and having a nitrogen content of 10.7 to

3. A composition of matter ada ted to be applied to a surface in the manu acture of 'films or sheets, containing cellulose nitrate having a viscosity of 10 to 75 seconds and a nitrogen content of 10.7 to 11.35% and a vol- .atile solvent.

In testimony whereof, we have hereunto names.

JAMES F. WALSH. THOMAS E. ALOORN.

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