US1891337A

US1891337A - Process of producing cellulose

Info

Publication number: US1891337A
Application number: US419729A
Authority: US
Inventors: Seaman Stewart Elmer
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1930-01-09
Filing date: 1930-01-09
Publication date: 1932-12-20
Anticipated expiration: 1949-12-20

Description

" Patented D... 20, 1932 ufacturing cellulose pup by the use of aquebus ammonia and ammonium salts.

UNITED STATES PA/TENT 1 OFFICE.

srnwanr. Emma SEAMAN, or BUFFALO, NEW YORK, assreuon. ro E. I. no PON'I. mz

nmrouns & COMPANY, or WILMINGTON, DELAWARE, A CORPORATIOII orpm- WARE 2N0 Drawing.

This invention relates to the manufacture of cellulose pulp and more particularly to an alkaline, neutral or non-acid process of man- This inventionhas as an object, a prociess for the production of cellulose pulp which results 'in a better yield, a higher percentage of alpha cellulose and a whiter color than that resulting from the processes now used involving the usual alkaline or neutral alkali salt treatments. A still further object is the provision of a purification process in.

which the recovery of the alkali may be more economically efi'ected than when caustic soda and other sodium salts are used. Other objects will appear hereinafter.

These objects are accomplished by the fol-' salts, under conditions of temperature and concentration most favorable for the production of high grade pulp, and in which the ammonia may be recovered for'further utilization as a cooking agent.

sulphide The material utilized for the production of high grade cellulose pulp in accordance with the present invention may b'e crude cellulose such ascotton linters, hull fiber, wood, chips, bagassee, cornsta'lks, esparto,

straw, flax, jute,-ramie, hemp, etc., either unbleached or partly or completely bleached. Ammonia may be used alone as the pulping reagent but for many purposes 'and with cellulose material from some origins I find that certain-ammoniumsalts or mixtures thereof or ammonia and-an ammonium salt '5.' Ammonia and ammonium sulphide Z u 6. Ammonium sulphite and ammonium bleach will be required.

PROCESS OF PRODUCING CELLULQSE Application med-J nuar 9, i930. SeriaL No. 419,729.

- Ewa-mple I hull fiber or, a mixture 0 the two,,as second cut cotton linters, for instance, government gradings, #6 or #7, or certain mmercial hull fiber. The cotton fiber is charged to the usual vertical type of digester used for sis that purpose and seven parts by weight of a' cooking liquor composed of approximately 0.7 concentration (NH basis) is added for each part by Weight of cotton. The temperature of the digester is then raised to ap-- I blown to the wash tank. The blow tank, pit or wash tank is in the present process provided with a tight cover and is piped to the ammonia recovery system. "The ammonia may be recovered direct from the digester upon completion of the cooking or in order to prevent the gas pressure from rising, the ammonia may be conducted to scrubbing towers as will be readily understood. The ammonia may alsobe recovered from spent cooking liquors or wash waters by adding enough lime to replace the ammonia and then driving oil". the ammonia by heating and recovering it in towers. With a revolving or tumbling type of digester the ratio of cooking liquor may be reduced In some instancesas little as 2.5 parts of liquor to one part of cotton may be used with consequent saving of ammonia. -The ,visco'sity of the product will be increased by lowering the cooking proximately 320 F. and maintained there" for fourhours after which the charge is temperature or shortening the cooking time.

The unbleached lint may then bebleached anid finished in the usual manner but less Example -.I I

When purifying a numberifive grade of linters (mill run) for producing a high viscosity pulp suitable for *acetylation or nitration with minimum of resistant fibres, the Y lint is-first thoroughly washed to remove dirt and hull particles after which it is charged to the digester with seven parts of cooking -liquor composed of 0.3% ammonia (NH,

thedig'ester the pulp may be washed, bleached basis) with 1.7% ammonium carbonate and 0.5% rosin and is cooked for three hours at approximately 230 F. after which the cooking liquor is blown off through 'a. perforated plate and the pulp in the digester, is further boiled for-onehour with water and is then drained and given a cold water wash. The

pulp is then dumped from the revolving di-.

gester or may be blown out by steam pressure. It i3 then bleached, washed and dried as desire It is to be understood however, that in the above and following examples the conditions may be varied, as understood byithose skilled in the art, in accordance with the difiere nt raw materials and with the different types of digesters and with the characteristics des red in the product. In the purification of cotton linters or hull fiber it is usually desired to get the highest possible alpha cellulose content with the minimum soda solubility, ash, ether extract with the whitest I color, to ether with some predetermined vis-- cosityen prepared for v dynamite or smokeless powder the purified cotton is not usually bleached and whiteness therefore is not a factor. When purifying however, for rayon, lacquer, safety glass, plastics'etc., brilliant whiteness is wanted. For dynamite the cellulose viscosity must be high, for lacquer preferably low, for plastics medium and for these reasons it must be borne in mind that the example here submitted canbe varied by one skilled in the purification of linters when preparing pulp forany one of the particular products mentioned. a

Example I I I lulose content, spruce, western hemlock, pop

lar, cotton wood, yvhite maple, gum or other woods are chipped in t e usual manner and charged in this case to t e tumbling end for end type of soda or sulphate digester. Five parts of cooking liquor composed of approximately two percent ammonia (NH basis) to each part by weight of the wood are added to the digester and the charge cooked for seven hours at approximately 330 F. including about two hours for bringing the charge to that temperature. The quantity of liquor to.pulp is varied based on the percentage of moisture in the chips but the percent of ammonia to wood will remain approximately constant. Difl'erent species of wood will require difi'erent quantities of ammonia, for

. example, spruce may be cooked with about 1.5% ammonia (NH basis); After blowing and dried in the usual manner.

v I Emafhplel V A variation in the procedure reierred to in ExampleIII for producing a high grade so-called soda pulp with further improvement in color. and yield may be had by cooking the chips with five parts of a cooking liquor composed of about 4.5% ammonium sulphite slightly on the alkaline side for six hours at a temperature of approximately 330 F. The quantity of liquor to pulp may be varied based on the per cent of moisture in the chips but the per cent of ammonium sulphite to the-wood will remain approximately constant. After blowing the digester, the pulp may be washed, bleached and dried in the usual manner, but bleach requirements will be reduced over the process described in Example III. Ea'ample V To produce a'pulp of maximum strength,

E wample VI To produce a high grade pulp of improved color, yield and alpha cellulose content from cornstalks, bagassee and similar fibrous materials, the pith is first separated mechanically from the fibrous material by any of the usual means such as a shredder and duster, is washed to remove sugar and after charging the disintegrated fibrous matter to a d1- gester, six parts ofa cookingliquor composed of approximately 4% ammoniumsulphite slightly on the alkaline side is added and cooked for four or five hours at approximately 280 F. after w'hichthe di ester is blown and the pulp is washed, bleac ed and dried in the usual manner as desired. Stalk, raw cellulose and s1milar materials require varying treatmetnts and often, benefit in the coo ng by the addition of an excess of ammonia,and addition of ammonium sulphide and in the same procedurejust mentioned there may be substltuted six parts of a liquor composed of 4% ammonium sulphite with.

9.7% ammonium sulphide and 9.16% ammonia (NH, basis).

Ewariple Y] I I To produce a pulp particularly high in alpha cellulose with maximum yield and excellent whiteness from relatively high ligno cellulose base raw materials, such as wood, the chips are preferably cooked with ammonium acid sulphite and sulphurous acid, the aqueous cooking liquor containing 3.5% of ammonium bisulphite and 1.5% sulphurous acid, raising the temperature gradually to about 230 F. when cooking spruce or to 250 F. when cooking western hemlock in' 2 to 3 hours and then further gradually raised to not over 320 F. in four hours and the temperature held for one hour and when .tests indicate the cook to be completed, itiis then blown with the usual S0 recovery and in addition the NH; may be recovered from the spent 'sulphite liquors. The pulp is washed then submittedto a secondary cooking preferably in a rotating tumbling endto end type of .digester with a solution co sisting of seven parts of approximately .3%

ammonia (NH basis) to each part of pulp for ninety minutes at approximately 280 F.

p The temperature maybe reduced to the boiling point 'or even slightly less dependent upon the viscosity wanted as the alpha cellulose content will not be materially improved having already been raised about as high as it can bemade from wood pulp The digester is then blown and the pulp is'washed and bleached with the small amount required and dried in the usual manner desired.

The last example is the most desired process for very high alpha content wood cellulose of outstanding whiteness particularly for the production of nitro and acetate cellulose products, cupra ammonium and viscose rayon, etc., and it is mentioned that the acid pretreatment may be accomplished by other ratios of ammonium bisulphite and sulphurous acid in the mixture and the pressures,

secondar rayon, nitro cellulose or cellulose acetate sotemperatures, and time of treatment may be varied or even the more broadly known sul- Ehite processes withlime or dolomite or soda ase bisulphite cooksmay be used and the treatment may be modified by substitutin the neutral ammonium sulphite, or ammonium sul hite and ammonia, with or without ammonium sulphide, or with ammonium carbonate or ammonium'carbonate and ammonia, or other mixtures of ammonium base salts and ammonia. A treatment with a small amount of bleach liquor or chlomine water of the pulp resulting from the first lutions,.and for the production of lac uers, plastics, explosives and for various gra es of paper. The brilliancy and whiteness of the product makes it es ecially desirable f0 ra on, lacquer and sa ety glass.

, e rocess of the present invention accomplis es a more complete removal of the non-alpha cellulose matter, producing a pulp of greater purity with a brightercolor and higher yield than that made when employing other alkalies as a base. -This process has also the-outstanding advantage over gxed alkali processes in that the alkaline base ay be recovered readily because of its ready conversion into a gas by replacement from its compounds. The ammonia is readily recoverable with a cheap base like lime and is recovered in purer state with less loss and at cheaper cost with less costly equipment than is possible the recovery of the base when other alkalies are used. The cooking time mayalso be shortened by taking advantage of the increased pressure due to the formation' of ammonia gas upon heating.

As many apparently widely different embodiments of th s invention may be made without departing from its spirit and scope thereof,- it isto be understood that I do not llnllt myself to the specific embodiments thereof except'as defined in the appended patent claims.

Iclainn 1. A-p rocess of purifying cellulose which compr'ses cooking vegetable fibrous material with an aqueous solution cbr 'nprising a mixture of ammonium sulphite and ammonium sulphide.

2. A process of purifying cellulose which comprises cooking vegetable fibrous material with an aqueous solution comprising a mixture of ammonium sulphite, ammonium .sul-

phide and ammonia. v p

3. A process of purifying cellulose wh ch comprises cooking vegetable fibrous material with an aqueous bisulphite'solution and sul phurous acid removingthe bisulphite soIu-' tion and cooking further with aqueous ammoma. a p

4. A process of purifying cellulose which comprisescooking vegetable fibrous material with an aqueous bisulphite solution and sulphurous acid removing-the bisulphite solution and cookng further with an aqueous solution of an ammonia compound.

5. A process of .purifying cellulose which" comprises cooking vegetable fibrous material with. an aqueous bisulphite solution and sul-' tion, and cook'ng further with an aqueous solution containing ammonia and an .ammonium salt. I J

6. A process of purifying cellulose which comprises cooking vegetable fibrous-material with an aqueous bisulphite solution and sulphurous acid removing the b sulphite-solution and cooking further with an aqueous solution of ammonium sulphite.

. 7. A process of purifying cellulose which comprises cooking vegetable fibrous material with an aqueous bisulphite solution and sulphurous acid removing the bisulphite'solution and cooking further with an aqueous solution comprising a mixture of ammonia and ammonium sulphite.

phurous acid removing the bisulphite soluaqueous ammonia 10. A process of purify'ng cellulose which comprises cooking vegetable fibrous material with a li uor consistin of a mixture of ammonium isulphite an sulphurous acid, re: moving the liquor and cooking further with an. aqueous solution of an ammon'a'compound. I

' 11. A process of purifying cellulose which comprises cooking vegetable fibrous'm'aterial with a liquor consisting of amixture of ammonium bisulphite and sulphurous acid, removing the l'quor' and cooking further with an aqueous solution comprising a mixture of ammonia and an ammonium salt 12. A process of purifying cellulose which comprises cookin vegetable fibrous material with an aqueous %isulphite solution and sulphurous acid, at least partially bleaching the cellulose before further re-cooking, removing the bisulphite solution and cooking. further with a ueous ammonia. 13. 2 process of purifying cellulose which comprises cooking vegetable fibrous material with an aqueous bisulphite solution and sulphurous acid, at least partially bleaching .the cellulose before further re-cooking, re-

moving the bisulphite solution and cooking further with aqueous ammonia.

14. A process of purifying cellulose Wl'llCl'l comprises cooking, vegetable fibrous material with'an aqueous bisulphite solution and sulphurous acid, at least partially bleaching the cellulose before further re-cooking, removing the bisulphitesolution, and cooking further with an aqueous solution containing ammonia and an ammonium salt.)

15. A process of purifying cellulose which comprises cooking vegetable fibrousmaterial with an aqueous bisulphite solution and sulphurous acid, at least partially bleaching the cellulose before further re-cooking, removingthe bisulphite solution and cooking further with an. aqueous solution of. ammonium sulphite. I Q 5 16. A process of purifying cellulose which comprises cooking vegetable fibrous material I with an aqueous bisulphite solution and sulphurous acid, at least partially bleaching the cellulose before further re-cooking, removing the bisulphite solution and cooking-further cellulose before further re-cookin remov--.

ing the bisulphite solution and coo g further with an aqueous solution comprising mixture of ammonia, ammonium sulphite and ammonium sulphide,

' 18. A process of purifying cellulose which comprises cooking veg'etable fibrousmaterial i with an-aqueous sulphitesolution and sul-' .phurous acid, at least partiall bleaching the cellulose before further re-coo g, removing the bisulphite solution and cooking' further with an aqueous solution ,of ammonium sulphide. I x

19. A prooess of purifying cellulose which comprises cooking vegetable fibrous material with a liquor consisting of a mixture ofammonium bisulphite and sulphurous acid at least partially bleaching the cellulose be ore further re-cooking, removing the liquor and cooking further with aqueous ammonia.

20. A process of purifying cellulose which comprises cooking vegetable fibrous material with a li uor consisting of a mixture of ammonium" isulphite and sulphurous acid at least partially bleachingthe cellulose be ore further re-cooking, removing the liquor and cooking further with an aqueous solution of an ammonia compound.

21. A process of purifying cellulose which comprises cooking vegetable fibrous material with a liquor consisting of a mixture of ammonium bisulphite and sulphurous acid at least partially bleaching the cellulose be ore further re-cooking, removing the liquor and cookin further with an aqueous solution comprising a mixture of ammonia and an ammonium salt.

22. The process of obtaining cellulose from a fibrous vegetable material which comprises cooking the fibrous vegetable material in an acid bath and thereafter cooking the fibrous material with an' aqueous solution of an ammonia compound.

23. The process of obtaining cellulose from a fibrous vegetable material which comprises cooking the fibrous vegetable-material with an acid solution, bleaching, and thereafter cooking with an aqueous solution of an ammonia compound.

Intestimonywhereof, I aflix my s' v STEWART E: SE N,

' 'ature.

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