Патент USA US2112999код для вставки
Patented Apr. /5’, 1938 > 2,112,999_' = UNITED STATES" PATENT "OFFICE CONDITIONING or cELnuLo'sE FIBER FOB CONVERSION m'ro- CELLULOSE acn TATE ~ George A. Richter, Berlin, N. 11.,» assignor to Brown Company, Berlin, N. 11., a corporation _ of Maine No Drawing. Application May z, 1936, ' - Serial No. 77,612 - r: Claims. v(c1. zso-ioi) This invention relates to the conditioning .of cellulose ?ber for conversion'into cellulose ace tate and more particularly to a conditioning tions prepared from the acetylated product for such purposes as arti?cial silk and mm manu facture.- Moreover, I have found‘that such a treatment that activates and otherwise improves - mixture can render cellulose ?ber of the refrac the cellulose for the acetylating reaction. While tory character ,hereinbefore described satisfac- 5,’ not limited thereto, the conditioning treatment‘ torily. acetylatable by the usual acetylating re agents. '_I‘he conditioning or activating treat of the present invention is of especial useful ness when applied to cellulose ?ber which is more, ment hereof presents the ‘important advantage or. less refractory toward acetylatingireagents. Wood‘ pulp which has been puri?ed to high alpha cellulose content in alkaline liq’uors are apt to acquire passivity toward acetylating re agents; and the stronger the alkaline liquor, the more passive is the pulpapt to become. In deed, wood pulp which has been re?ned in alkav line liquor of sufficient strength to be mercer— / that there is no'need for washing or otherwise removing the activating reagents, inasmuch‘ as 10 the hydrogen peroxide leaves no undesirable res idues in the ?ber and the‘acetic acid ‘can take part in the'subsequent acetylation. While vari ous percentages of hydrogen ‘peroxide may be used in admixture with acetic acid for the acti- 15 vating treatment hereof, it is preferable to use' izing, say, caustic soda solution'of about 18% or - aqueous hydrogen peroxide solution. -in such greaterv strength, generally becomes so passive amount and in such highly concentrated condi as to require an activating treatment -.;of some ' tion together with glacial acetic acid as to dis kind before it can be acetylated with the desired‘ pense with the ~step of dehydrating or drying of 20 20 the activated ?ber, preparatory to acetylation. smoothness or uniformity of reaction. Again, sheeted cellulose ?ber, such as pulpboard and Unlike the hydrogen peroxide solution usually waterleaf paper, ‘is' sometimes poorly responsive _ employed for medicinal or antiseptic purposes, to acetylation even when it is ?nely shredded 25 prior to acetylation; and its poor responsiveness may be attributable largely to its overdried con - dition rather than‘ to the nature of its cellulose which is of about 3% hydrogen peroxide content, the hydrogen peroxide solution used herein is 25 ' preferably of much greater strength. Although. it is di?icult and expensive to preparevery strong ?ber. In this connection, it might be observed _ hydrogen peroxide solutions, aqueous solutions that it is quite desirable that cellulose ?ber to of about 30% hydrogen peroxide content are; commercially available at a cost reasonable for 30 be acetylated contain very little moisture,.pref erably not much' more than about 2% of its dry the purpose hereof, wherefore, I may advan tageously'use such solutions. To be sure, such . weight, so as to avoid undue dilution of the acet ylating reagents. However, in drying pulpboard lsolutions=contain more than twice as‘ much water or waterleaf'paper to the desired low residual moisture content, as on the usual steam-heated‘ drier drums of a. papermaking machine, it is fre quently the case that in getting-'maximum out put on the machine, ‘the sheet is broughtto a bone-dry condition, 1. e. overdried, particularly 40 on its surface,‘ Just as it is undesirable to have much more than about 2% water present in the cellulose to be acetylated, so a bone-dry condi solutions in the activating treatment and to add 40, so little water to the ?ber as to avoid practically any drying or dehydratiomot the activated ?ber may spell'a shrunken and dense ?ber structure _ prior to its acetylation. An illustrative example of the'practice of the resistant‘ to '.acetylation. In accordance withthe present invention, cel-, lulose ?ber to be acetylated is ?rst put through lows. Pulpboard or waterleaf paper of a mois ture content of about 1% or less and umatisi'ac tion therein is to be avoided, as bone-dryness an activating treatment .with a mixture of hy '50 as hydrogen peroxide, but because only a very. small percentage of hydrogen peroxide, based 35 on dry ?ber,‘ is su?icient when admixed' ‘with’ glacial acetic acid to cause the desired activation or improvement of cellulose ?ber, it becomes possible to use such aqueous hydrogen peroxide drogen peroxide and acetic acid, the mixture preferably containing as- it's acetic acid compo-‘ nent a fraction of the glacial acetic-acid subse quently to enter into the acetylating‘reaction. I have found that such a mixturenot'only ‘greatly improves the acetylatability of/the ?ber but also enhances the color and clarity of the usual solu present invention may be ‘substantially as fol- 45 torily .responsive to 'acetylating reagents may constitute the raw material. Besides being bone dry on its surfaces, such sheeted ?ber may be so composed of wood pulp or cotton ?ber, which,‘ on account of puri?cation in an'alkaline liquor,; _ has taken on passivity‘ toward acetylating . agents. For instance, the sheeted ?ber may be composed of white, highly purified wood pulp, 66 2 9,119,999 speci?cally, mercerized wood pulp which has glacial acetic acid to appear in the acetylating been brought to an alpha cellulose content up reagent together with the catalyst of such re wards of about 96% in a caustic, soda solution agent; and this larger portion not. only ensures of 18% or greater strength. Such'a sheet may - a uniform distribution of the peroxide through be wetted with hydrogen peroxide-acetic, acid out the sheet, but assists in the attainment of mixture prepared by mixing 3 to 10 parts by a ?nal sheet uniformly and well activated for 1 weight of hydrogen peroxide solution of about the acetylating reaction. Thus, the sheet may 30% strength with 97 to 90 parts by weight of be sprayed or otherwise treated continuously glacial acetic acid; and about 20 parts of such with the activating mixture as it is coming '10 a mixture may be substantially uniformly ap from a papermaking, machine or from a roll plied to the surfaces of about 100 parts by weight accumulation, whereupon it may be accumu'-~ 10 of the sheeted ?ber. The application of the lated as a roll and kept for a period; or the sheet mixture may be effected as by spraying the wetted with the activating mixture may be ex sheet surfaces therewith or by transferring the posed in festoon form to the air either at room 15 mixture to the sheet surfaces from the periph or elevated temperature. The sheeted ?ber may 15 ery of a so-called "kissing" roll. The treated then be' impregnated with a large additional a ‘sheet containing less than 2% added water, about amount of glacial acetic acid containing the 0.2 to 0.6% added hydrogen peroxide, and about catalyst/of acetylation. as by running the sheet 17% acetic acid, based on the dry weight of ?ber, continuously through a bath of such acid or by 20 may be kept for about two to eight or even-more dipping separate sheets thereinto. After keeping 20 hours at about 20° to 40° C. to effect the desired the acid-soaked sheet ?ber at a suitable tem activation of the cellulose, after which period it perature for a substantial period of time, for, is desirable to add to the sheet as such or after instance, at 40° C. for four or more hours, it may it has been disintegrated more .of the glacial be acetylated, as hereinbefore described. 25 acetic. acid later to form part of the acetylating vIt is possible to apply the conditioning or acti 25 - reagents, for instance, as much as about 400%, vating treatment hereof to bulk or shredded based on the dry weight of the ?ber, together‘ cellulose ?ber, in which case, a substantially uni with the desired amount of catalyst for the form wetting of the ?ber with the activating mix acetylating reagent, for instance, about 1 to 2% ture of hydrogen peroxide and glacial acetic acid 30 sulphuric acid, based on the dry weight of the can be had only when a comparatively large 30 ?ber. After the second portion of acetic acid' amount of the mixture, say, about 100% or more, together with catalyst has been added, it is based on the dry weight of ?ber, is sprayed or preferable to keep the sheet at about 40° C. for otherwise applied to the- ?ber while fresh ?ber about 30 to 60 minutes, during ,which time surfaces are being exposed to the spray, for in 35 catalyst ' is given an opportunity to diffuse stance, while the ?ber is being stirred or tumbled throughout the sheet and to combine substan as the spray impinges thereon. In'_ such case, the tially uniformly with the individual ?bers or hydrogen peroxide content or concentration in ?ber walls. The soaked sheet may then be dis ' the glacial acetic acid may be reduced so as not integrated or shredded, if this has not already. to incorporate an excessive amount of hydrogen 40 been done, and admixed with acetic anhydrlde peroxide or water into the ?ber. A very uniform 40 and more acetic acid to produce the usual acety- I’ and e?ective' treatment of bulk ?ber with the ac lating bath or mixture,_ the last addition of tivating mixture can be realized by suspending glacial acetic acid giving a total glacial acetic the ?ber in many times its own weight of the acid content of, say, about r100%, based -on the ,. activating mixture; and,’ after a substantially 45 dry weight of the ?ber. As the ?ber is stirred uniform ?ber suspension has been prepared, as in the acetylating reagents, it undergoes smooth much as possible of the activating mixture may , and ‘uniform acetylation so that’ the original be removed by a centrifuge, squeezing, or simi ~thick ?brous suspension gradually becomes a lar extracting operation. The latter treatment of ' ‘ substantially clear cellulose acetate solution the bulk ?ber may be accompanied by the addi 50 from which the cellulose acetate is. precipitated and‘ recovered as customarily. The foregoing example lends itself ‘to wide modi?cation’ as to the concentration of the tion to the ?ber of so much more than the ap proximately 2% water content desired in ?ber intended for acetylation that provision must be vating mixture applied to the sheeted _ ?ber made to evaporate or otherwise remove from the ?ber water in excess of about 2%. This may, as already indicated, be accomplished by exposing _ and/or as to the amount of the mixture infused the centrifuged or pressed ?ber to the dehydrat into the ?ber. ing action of warm air currents. aqueous hydrogen peroxide ‘solution in the acti If such concentration and/or amount is such as to produce in the sheet a total water content of much greater ‘than about 60 2 to 3%, say 5% or more, basedcn the dry weight of ?ber, the treated sheet may be exposed to warm air currents for a su?lcient period of time to reduce the water content to about 2% and thus to avoid undesirable dilution of the 65 acetylating reagents in which the ?ber is ?nally acetylated. It is generally; preferable to keep ' the hydrogen peroxide concentration in the acti vating mixture as high as possible compatible with the'incorporation into the sheeted ?ber of 70 activating mixture in amount to impart to they sheet a moisture content not much in excess of 2% of the dry weight of ?ber. After keep ' It is possible that the mixture of hydrogen peroxide and acetic acid herein used for the purpose of conditioning or activating cellulose 60 ?ber for acetylation owes its eifectiveness to a partial reaction between the acetic acid and the hydrogen peroxide productive of 'peraoetic acid. Irrespective of whether peracetic acid is or is not present in the activating mixture, cellulose 65 ?ber is greatly improved in its acetylatability by such a mixture and, when of a refractory nature, is transformed thereby toa satisfactory‘ acetylatable state. I claim:— ' . 70 1. A process which comprises treating cellulose ?ber with a mixture of hydrogen peroxide and ing the sheet moistened with the mixture for a acetic acid and then acetylating the treated ?ber ‘while, it .is, as already indicated, desirable to in the presence of not much more than about 2% 75 add thereto ‘another much larger portion of the ‘ water, based on the dry weight of cellulose ?ber. 75 2,112,999 - 2. A process which comprises treating ceilu-_ ' lose ?ber with a mixture of concentrated aqueous adding glacial acetic,acid to the fiber, andacety-' ' lating the resulting ?ber._ _ " , 10. As a step-product especially adapted for , acid and then acetylating the treated ?ber in.‘ conversion into cellulose. acetate, cellulose ?ber ._ the presence of not much more than about 2% treated with a mixture composed-substantially 01! water, based on the dry weight of cellulose ?ber. - ‘hydrogen peroxide, acetic acid, and only a small 3. A process which comprises treating cellulose percentage of- water, based on the dry weight of _ ?ber with a mixture of concentrated aqueous 11. As a step-product especially adapted for hydrogen peroxide solution and glacial acetic 10 acid, adding more glacial acetic acid to the ?ber, conversion into cellulose acetate, cellulose, ?ber and acetylating the ?ber in the presence of not ‘treated with amixture of hydrogen peroxide-and much more than about 2% water, based on the glacial acetic acid and containing not much more dry weight of cellulose ?ber. than about 2% ‘water, basedvon the dry weight . 4. A process which comprises treating cellu of'?ben' . hydrogen peroxide solution and glacial acetic ?ber. 15 lose ?ber with a mixture of glacial acetic acid . and a smaller amount of aqueous hydrogen peroxide solution of about 30% strength and ~ g a ' '~ 12. As a step-productespecially adapted for 15 conversion into cellulose acetate, wood pulp of high alpha cellulose content treated with a mix then acetylating the treated ?ber in the presence . ture of hydrogen peroxide and acetic acid and of not much more than about 2% water, based. containing not much more than about 2% mois ture, based on the dry weight oi pulp.‘ , 13. As a stop-product especially adapted for 5. A process which comprises treating cellu 20 on the dry weight ‘of cellulose ?ber. 20 lose ?ber with a mixture of glacial .acetic acid - conversion ‘into cellulose acetate, white mer- ‘ and a smaller amount of aqueous hydrogen per- . cerized wood, pulp of an alpha cellulose content oxide solution of about 30% strength, adding ' upwards of about 96% treated with a mixture more glacial acetic acid to the ?ber, and acetylat-~ of hydrogen peroxide and acetic acidand con 25' ingthe ?ber in the presence of not much more taining not much more than about 2% moisture, ' based on thedry weight of pulp. ’ than'about 2% water, based on the dry weight of cellulose ?ber. ' 6. A process which comprises treating a sub stantially dry sheet of cellulose ?ber with a mix ture of glacial acetic acid and concentrated aqueous hydrogen peroxide solution in amount to add to the sheet not much more than about 2% water, based on the dry weight of ?ber, and acetylating the treated ?ber constituting "said sheet. ' '7. A process which comprises treating a‘ sub- stantially dry sheet of cellulose ?ber with a 14. As a step-product especially’ adapted for‘ conversion into cellulose acetate, a sheet of cellu lose ?ber treated with a- mixture of aqueous hy-' drogen peroxide solution of about 30% strength and a larger amount of glacial acetic acid but containing not much more than about 2.% water, based on the dry weight off the ?ber. 15. As a step-product-especi'ally adapted .for 35 conversion into cellulose acetate, a sheet of wood pulp‘of high alpha cellulose content treated with 1 a mixture of aqueous hydrogen peroxide solution mixture of glacial acetic acid and concentrated ~ of about 30% strength and a larger amount of _ 40 aqueous hydrogen peroxide solution in amount to glacial acetic acid but containing ‘not much more 40. than about 2% water, based on the dry weight ‘ add to ,the sheet not much more than about 2% water, based on the dry weight of ?ber, adding more glacial acetic acid to the sheet,‘and acety lating the treated ?ber constituting said sheet. 8. A process which comprises treating cellu 45 lose ?ber with a mixture of acetic acid and aque ous hydrogen peroxide solution of suchv water . content and in such amount to associate with the ?ber considerably more than 2% water, based on the dry weight of ?ber, evaporating from the ?ber its water content in excess of about/2%. of’ pulp. - 16. As a step-product ‘especially adapteddor Y conversion into cellulose acetate, a sheet of white mercerized wood pulp of an alpha cellulose con 45 tent upwards' of about 96% and treated with a mixture‘ of aqueous hydrogen peroxide solution of about 30%~strength and -a larger amount or glacial acetic acid but containing not muchY more than about 2% ‘water,’ based on the dry weight of pulp. ' 1 , 1'7. A process which comprises in more _9-. A process which comprises treating cellu aqueous hydrogen peroxide solutio into sub-1 stantially dry cellulose while'keepingthe water lose ?ber with a mixture of acetic acid and aque ous hydrogen peroxide solution of such water‘ content of the cellulose at not muchymore than 55 ‘content and in such amount to associate with the about 2%, based on the dry weight or cellu ?ber‘considerably more than 2% water, based lose’, and acetylating the cellulose in the presence _ ‘ on the dry weight of ?ber, evaporatingirom the “of such hydrogen peroxide." ?ber its water content in excess of about'3%,' GEQRGE A. RICHTER. - _ and acetylating the resulting ?ber. '