US2758943A - Process of superficially saponifying a strip of cellulose ester - Google Patents

Abstract

A foil, film or the like of a fatty acid ester of cellulose which contains more than 1.5 but less than 3 molecules of combined fatty acid per glucose residue is subjected to superficial saponification in a bath containing an alkaline substance and an organic solvent, and when the saponification has proceeded to the desired depth the foil or other article is treated in one or more baths which terminate the saponification, at least one of these after-treatment baths being one which contains no aqueous solution of monobasic or dibasic acid but which is capable of reducing aqueous swelling of partially esterified cellulose having 0.5 to 1.5 molecules of combined fatty acid per glucose residue. Such an after-treatment bath may be a solution of a water-soluble sulphate, phosphate, sulphite, thiosulphate, carbonate, tartrate, citrate, acetate, lactate, fluoride or chloride. It may be an aqueous solution of a tribasic acid or of glycerol, glucose or a sugar. It may be a primary saturated alcohol having a straight chain of 4-11 carbon atoms, such as butanol-1. An after-treatment bath containing toluene, benzene, tetrahydronaphthalene or a liquid ether may be used. The treated films may be used for photographic purposes, e.g. the saponified layers may be impregnated with light-sensitive substances. If desired, plasticizers originally present in the films may be removed from the saponified layers by solvent treatment, e.g. by treatment with aqueous or alcoholic-aqueous solutions of dispersing agents such as salts of sulpho-ricinoleic acid, sodium oleate, sodium p-octylbenzene sulphonate, dodecylamine hydrochloride and lauryl ethers of polyethylene oxide. The substance for reducing aqueous swelling and the solvent for the plasticizer may be incorporated in a single treatment bath. In an example, a cellulose acetate tape is passed in succession through a solution of caustic potash in aqueous methanol, through two baths of butanol-1, through an aqueous solution of phosphoric acid and through two baths of circulating water.

Description

PROCESS OF 'SUPERFICIALLY SAPONIFYING A STRIP OF CELLULQSE Roelof Jan Hendrik Alink, Johannes Cornelis Antonius aSPe a i Will m Y B isSs f inm in el, Ein 'dhoven, Netherlands, assignors to Hartford Naonal Bank and Trust Company, Hartford, Conn, as .mlstee L, No Drawing. Original application June 6, 195, Serial o: 230,245, new Patent No;2;704,-262; dated March 15, 1955. Divided and this application January '13, 1955, Serial No. 481,714 r Claims priority, application Netherlands June 6, 1950 Claiuns. (Cl. 117-62) This invention relates to an improved method of making cellulosic and more particularly to cellulosic films which are to be subsequently impregnated with ig se itive system containing'a di'afzoniumcompound, and is 'a division of our 'co-pen'ding application, ,Ser. No; 230,- I-2 45,1fi1ed June 6, 19 1, new U Pat n No- 2,704,262. 'Fat'tyacidesters of cellulose film's containing from 1.5 to 3.0 radicals offatty acid per glucose unit were sa'ponified in order to regenerate a cellulosic outerlayer which'can be readily impregnated with aqueous solutions; Such had the undesirable feature that 'the outer layer swelled in aqueous solution while the unsaponified portion of the film did not swell, resulting stresses in the filrn withfsubsequent peeling of the outer -l yer.

United States Patent C) (I An o'bject'of the invention, therefore, is to provide a v fethod to shrink the outer layer and to prevent its subeq ent Peelin and further objects of my invention will appear as the'speciiication progresses. i "According to the invention, the cellulose strip after euperficial saponification thereof is immersed in one or more aftentreatrnent baths. One of theafter-treatments containsan anti-peeling agent which shrinksan'int'ermg diate partially 'saponified layer such that upon subsequent immersion of the strip in an aqueous solution, for instance when impregnating the strip with 'a water-soluble lightsensitive system no stresses are created in the saponified layer which would cause it to peel from the underlying unsaponified portion of the strip.

The invention is particularly applicable to cellulose diesters which are subject to peeling after saponification. For example a fatty ester of cellulose containing more than 1.5 and less than 3.0 fatty acid radicals per glucose residue after superficial saponification, i. e. by immersion of a strip of this material in a saponifying bath for a given period of time to saponify at least one side of the strip to a desired depth, is immersed in a bath containing an anti-peeling agent which is capable of shrinking a layer intermediate the outer surface of the strip and the unsaponified portion of the strip which contains 0.5 to 1.5 fatty acid radicals per glucose residue.

Anti-peeling agents suitable for the aforesaid purposes are: primary saturated alcohols having a main chain of from 4 to 11 carbon atoms, such as butanol-l; a mixture of about one part of butanol-l and about one part of either benzene or toluene; a mixture of about one part of butanol-l and about one part of tetrahydronaphthalene; a mixture of about one part of butanol-l and about one part of diethyl ether; a solution of about 1.5 n phosphoric acid and butanol-l.

Cellulosic films which initially contain ester plasticisers such as triphenylphosphate and tricresylphosphate, which upon the superficial saponification of tha fatty acid cellulose ester are not saponified completely. Particularly the intermediate layer may hold or subsequently attract from the substratum by diffusion a comparatively large Patented Aug. 14,

2 amount of plasticiser resulting in deposition or turbidity of particles of plasticiser on the surface ofthe film, foil or the like. It'ha's now been'found that the plasticjser still present after sapon'ific at'ion" in the totally sapz'mifi a layer and the intermediate layer of the rott'fil'mw'r the like can be removed with the use of solvents. Such solvents are, for example, solutions of so-called dispersion agents]? such as salt of a 'sulphated hy droxycarbdni c acid having at least 10 carbon atoms, for example, nium'or sodiunisalts of ricinolic acid 'esterified with s'ul} phu iC a id, in additionsodium oleate, the sodium s'altof pfoctylbenzenesulphonic acid, cationegenou's dispersion agents such as dodecylaminehydrochloride or compo nds derived therefrom and in addition nc'm-ion forming persion agentasuch as polyethers, derived from methylene for ethylene oxide, which at the end of the chain,'ar e eisterified, for example, witha lauryl alcohol. Solutionsof fr e? 5 to by We h o these on-f m d ers qn agents in' water are suited to free from plasticis'er saponified superficial layers of foils, films or the like made'of fatty acid cellulose esters. An after-treatment bath may contain both an antipeeling ag'ent for partially esterified cellulose containing from 0.5 to 1.5 radicals of fattyacid per glucose residue and a solvent for the plasticiser. It must be noted that'ja great number of non-ion-form'ing shrinking a'gent's'also have a dissolvingefiect on plasticisers. l

Since the intermediate layer formed during saponificationdoes notjswell appreciably'in the solution of the dis- ,Pi r' iQi a e ere r obabil f h apon fie layer peeling from the non-saponified substratum; "Th'r 'e s e o fe t l er y 'es d o h choic between treating the foil, film or the like upon saponificatio11" first with the use of the dispersionagent orlby treating it first 'the use of the anti-peeling agent. For th e"' sake" of p c y r t s agent nd t e s lven r th plasticiser maybe combined in one after-'treatment'bath.

"The'invention will now described in connectionf'with the followingexamples:

Exam I A mechanically moved web 130 ,u. thick and made of cellulose acetate containing about 2.3 radicals of acetic acid per glucose unit is saponified at 24 C. for 45 seconds on two sides in a solution of l n potassium hydroxide in a mixture of 66 parts by volume of methanol and 34 parts by volume of water, shrinking then taking place for a period of 45 seconds in a mixture of 1 part by volume of butanol-l and 1 part by volume of toluene. The web then passes during a period of 45 seconds through a stopper bath of 0.6 n acetic acid in butanol-l. Eventually the web is washed in circulating water for 2.5 minutes and after spraying with water and skimming dried with the use of warm air of about to C.

The thickness of the regenerated cellulose layer is 10 n and that of the intermediate layer 4 ,u. The adhesion of the saponified layer to the non-saponified substratum is excellent. The butanol-toluene mixture may be replaced with equally satisfactory results by a mixture of butanol-l with benzene or with tetrahydronaphthalene or with diethyl-ether.

Example II A web ,u. thick and made of cellulose acetate having an acetic acid content of 53.3% is passed mechanically at 23.5 C. at the rate of 60 seconds per bath in succession through the following baths:

use being made with advantage of the difierence in specific gravity between butanol-l and water so that the film upon immersion in bath ([1) repels the alcohol.

The web is then sprayed with water for 30 seconds and after skimming at 90 C. dried with a warm flow of air. The thickness of the regenerated cellulose layer is a and that of the intermediate layer 3 The adhesion of the saponified layer to the substratum is excellent.

Examp le III Cellulose diacetate foil was superficially saponified for 1 minute in a solution of l n-potassium hydroxide in a mixture of 2 parts by volume of methanol and 1 part by volume of water at 25 C. The web was then immediately inserted in a solution obtained by diluting 10 ccs. of 89% phosphoric acid with 300 cos. of butanol-l (this solution is about 1.5 .n). After immersion in this bath for 1 minute at 25 C. the foil was rinsed in water for 30 minutes and then dried in air. The saponified layer adheres most satisfactorily and the surface is smooth. It

is preferred that the concentration of phosphoric acid should not be excessive since otherwise the surface of the saponified layer, which in itself is readily adhesive, tends to become slightly shrivelled.

While the invention has been described with reference to specific examples and applications thereof, other modifications will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

What we claim is:

1. A process of superficially saponifying a strip of cellulose ester containing between 1.5 and 3.0 radicals of fatty acid per glucose residue, which comprises the steps of immersing said strip in a saponifying bath containing at least 0.1 normal solution of an alkali hydroxide and an alcoholic solvent to effect rapid saponification of said strip for a time sufficient to produce a partially saponified layer in said strip containing between 0.5 and 1.5 fatty acid radicals per glucose residue, and thereafter immersing said strip for at least 45 seconds in butanol-l.

2. A process of superficially saponifying a strip of cellulose ester containing between 1.5 and 3.0 radicals of fatty acid per glucose residue, which comprises the steps of immersing said strip in a saponifying bath containing at least 0.1 normal solution of an alkali hydroxide and I,

an alcoholic solvent to eflfect rapid saponification of said strip for a time suflicient to produce a partially saponified intermediate layer in said strip containing between 0.5 and 1.5 fatty acid radicals per glucose residue, and thereafter immersing said strip for at least seconds in a mixture of about one part of butano'l-l and about one part of a component having the formula CnH(2n-6), where n is one of the integers 6 and 7.

3. A process of superficially saponifying a strip of cellulose ester containing between 1.5 and 3.0 radicals of fatty acid per glucose residue, which comprises the steps of immersing said strip in a saponifying bath containing at least 0.1 normal solution of an alkali hydroxide and an alcoholic solvent to effect rapid saponification of said strip for a time sufiicient to produce a partially saponified intermediate layer in said strip containing between 0.5 and 1.5 fatty acid radicals per glucose residue, and thereafter immersing said strip for at least 45 seconds in a mixture of about one part of butanol-l and about one part of tetrahydronaphthalene.

4. A process of superficially saponifying a strip of cellulose ester containing between 1.5 and 3.0 radicals :of fatty acid per glucose residue, which comprises the steps of immersing said strip in a saponifying bath containing at least 0.1 normal solution of an alkali hydroxide and an alcoholic solvent to effect rapid saponification of said strip for a time sufiicient to produce a partially saponified intermediate layer in said strip containing between 0.5 and 1.5 fatty acid radicals per glucose residue, and thereafter immersing said strip for atleast 45 seconds in a mix-v ture of about one part of butanol-l and about one part of diethyl ether.

5. A process of superficially saponifying a strip of cellulose ester containing between 1.5 and 3.0 radicals of fatty acid per glucose residue, which comprises the steps of immersing said strip in a saponifying bath containing at least 0.1 normal solution of an alkali hydroxide and an alcoholic solvent to efiect rapid saponification of said strip for a time sufficient to produce a partially saponified intermediate layer in said strip containing between 0.5 and 1.5 fatty acid radicals per glucose residue, and thereafter immersing said strip for at least seconds in a solution of about 1.5 n phosphoric acid in butanol-l.

No references cited.

Claims (1)

1. A PROCESS OF SUPERFICIALLY SAPONIFYING A STRIP OF CELLULOSE ESTER CONTAINING BETWEEN 1.5 AND 3.0 RADICALS OF FATTY ACID PER GLUCOSE RESIDUE, WHICH COMPRISES THE STEPS OF IMERSING SAID STRIP IN A SAPONIFYING BATH CONTAINING AT LEAST 0.1 NORMAL SOLUTION OF AN ALKALI HYDROXIDE AND AN ALCOHOLIC SOLVENT TO EFFECT RAPID SAPONIFICATION OF SAID STRIP FOR A TIME SUFFICIENT TO PRODUCE A PARTIALLY SAPONIFED LAYER IN SAID STRIP CONTAINING BETWEEN 0.5 AND 1.5 FATTY ACID RADICALS PER GLUCOSE RESIDUE, AND THEREAFTER IMMERSING SAID STRIP FOR AT LEAST 45 SECONDS IN BUTANOL-1.