US1773419A - Sulphite wood pulp and method of making the same - Google Patents

Description

Aug. 19, 1930. w. E. B. BAKER n 1,773,419

SULPHITE WOOD PULP AND METHOD OF MAKING THE SAME Filed June 3, 1926 Patented Aug. 1e, 1930 y d 1,7 73,419v

UNITED STATES PATENT OFFICE WEBSTER E. BYRON BAKER, OF BROOKLYN, NEW YORK SULPIEIITE WOOD PULP AND METHOD OF MAKING THE SAIE Application filed June '3, 1926. Serial No. 118,408.

The principalobjects of the present invendigesters. As shown these means comprise a. tion are to increase the yield and improve the closed receptacle 8 in a closed valved pipe quality and strength of unbleached sulphite circuit Q, which includes a pump 10 and pulp suitable for making wrapping and bag which communicates by valved branches 11 U paper; to improvethe fibers; to shorten they with the digesters, and there is also a valved 55 sulpliite cooking period; and to provide an connectionI 12 between each of the digesters. economical and effective process for obtain'- The method or improvement of the inveninG the foregoing objects. tion may be described in connection with the Itated generally, the invention consists in apparatus above referred to as follows:

10 treating wood chips with alkali solutions In the description reference will be made 30y adapted to render'their alpha li nin insoluble at first to one digester, for. example 3. The in bisulphite cooking liquor be ore digesting digester is properly supplied with wood chips the chips in bisulphite cooking liquor. and the chips are subjected to weak alkali The invention also comprises rendering solution and steam by wa ofthe connections 15 the alpha lignin `insoluble in the subsequent 4 and 11. The result o this is that alpha 55 step of cooking with bisulphite acid solution lignin is rendered insoluble Ain the cooking by treating thewood chips with an alkali acid employed at a later stageof the process solution containing or consisting of free act.- and in the usual way. An example of weak ing ammonia which, augmenting the vapor alkali solutions are solutions of caustic soda,

pressure at the tempera-ture employed in the barium hydrate and the like. A' descriptive 7 digester, forces the alkali solution into the but not limiting example of temperature is pores of the chips, l 90'to 100 C. more or less and as a descriptive,

The invention also comprises sulphite pulp but not limiting, example of an alkali solucharacterized by abnormally high lignin contion adapted to render alpha lignininsoluble tent and by the strength and flexibility of its in the subsequent cooking step, reference may 75 bers, be made to one differing only by a few hun- The invention also comprises the imiplilgovedredths specific gravity departure from waments to be presently described and ally ter, more or less. Stronger solutions of alkali claimed, and in the following description effect economy in time` at the expense of 30. reference will be made to the accompanying economies in chemical consumption. The 8u drawing forming part hereof and in which duration or length of the treatment varies, the Single figure, more or less diagrammatibut descriptively reference may be made to cally,` illustrates one form 0f apparatus 1n one or two hours. The described treatment connection with which the invention may be of the wood chips in the digesterA may well 8, practiced. i be carried on in the presence 4of ammonia. thIIl the dlnllg 1, dalll aiglgesri which, creating relatively high vapor prese genera ype 11S g P sure at the temperature employed, forces the Wd Rulll) lzomlwood chllps lydookngphll solution into they pores of the wood. The Wlth blsu p lte' lquor' ac lges er 1S ammonia can be supplied along with the al- 9o ted with steam'connections 4 leading to the` top and bottom and provided with valves kali solution in the manner described or 1t and also. with valved Vblow olf or dischar may. be. lnlected /mto .the digester Upoll connections 5, and also with valved connefl; comllletlon of the fiescnbed Stel) the alkall tions 6 for bis'ulphite cooking acid, and also Solutlon, may be Wflflhdlawll by Way 0f the 5 with valved relief connections 7 for air, sul- Connectlon 11g OLT 1t may be Passed by Way 95 phurous acid gas or vapor, SO2, and bisulofthe connection 12 'into the digester 2 filled pliite cooking acid. There isv ynothing new with wood chipsgaiid used in the treatment involved in the a pa: atus above described. of the chips in the digester '2, and in the There are means or introducing and withlattercase an economy is effected in that the 5 drawing weak alkali solutions to and from the heat of the alkali solution is imparted tothe o chips in the digester 2 and is not wasted or 10st. 4

The next step is the well known step of cooking the chips for example in any of the 5' digesters shown, or in digester with bisulphite liquor or cooking acid which step is too well understood tolrequire detail description. The pulp is finally discharged as at 5 and it of course contains the alpha lignin so that the-yield is increased and the fibers are improved by having been subjected to the swelling effect of hydroxyl ions in the first treatment and to the-shrinking effect of acid in the second treatment or step. In respect to the step of cooking in acid liquor there are advantages due to the primary treatment of the wood chips in the digester with an alkali solution as described,

and lamong these' advantages reference may i anbe made to the fact that the discharge of the weak alkali solution from the digester leaves a partial vacuum which'promotes the penetration of the chips by the cooking acid. Resin saponiication and elimination from 5 the wood by the weak alkali solution treatment previous to cooking facilitates penetration of the cooking acid into the porespf the chips. The resultv of these factors is that the sulphite cooking periods are made shorter,

jjo thus effecting Aan economy additional to the economyeected by increased 'eld while at thevsame time the quality of t e wood pulp is improved in regard to strength, flexibility and otherwise for. uses and purposesof which v u ba and wra ping paper are examples. twill be o viousl to thoseskilledinthe art that modifications may bemade in'details of procedure and in thel ifchoice of the alkali solution or ofthe ori 'nal raw material with- 40 out departin from t e spirit of the invention which is not limited in'those respects or otherwise than as'the prior artand the appended claims may requlre. I claim:

1. In the' manufacture of sulphite wood pulp the improvement which consists in rendering the alpha lignin insoluble in the subsequent step of cookingivvith bisulphite acidy liquor by primarily treating wood chips in a digester with an alkali` solution including free acting ammonia which creating relative- 1y high vapor pressure at the temperature employed forcesthe alkali'solution into the pores of the wood. l v

2. In he manufacture' of sulphite wood pulp'the improvement `which consists in establishinga plurality .digesters containing wood chips, primarilyl treating the wood 50 chips -in one digesterl alkali solution i fl introducing isulphite acid cooking adapted to render alpha lignin insoluble,

transferring the solution while hot from the first dlgester to a Second-.digester and there treatlng chi s with the hot solutio and l1liquor ter and thereby creating a partial vacuum,

and introducing bisulphite cooking liquor and cooking the chips.

4. In the manufacture of 'sulphite wood pulp the improvement which consists in treatlng wood chips in a digester with alkali solution includin free acting ammonia, removing the solutlon and thereby creating a partial vacuum, and introducing bisulphlte cooking liquor into the partial vacuum and cooking the chips.

5. Sulphite pulp characterized by abnormally high alpha lignin content.

6. Sulphite pulp characterized by abnormally hlgh alpha lignin content and by strength and flexibility of its fibers exceedin that where the beta lignin is present.

Sulphite wood pul contalning alphal lignin in a form insolub e in bisulphite acid cooking liquor.

8. Sulphite wood ul of low resin content and containing alpha lignin in a form insoluble in bisulphite acid cooking liquor.

9. In the manufacturepof sulphite wood pulpthe improvement which consists in initially-preparing the wood chips for cooking by treatin them in a digester with alkali solutionan limiting the action of the alkali by'-flow temperature and low concentration `such that none of the lignin is cooked and the alpha lignin is rendered insoluble in the subsequent step of cooking withbisulphite liquor, and then pulping the so treated chips by cooking them with bisulphite liquor.

10. In the manufacture of-sulphite wood pulp the improvement which consists in primarily treating the wood chips in a digester with an alkall solution differing only by a few hundredths specific avity departure from water to render the' pha lignin insoluble in the subsequent step of cooking Vwith bisulphite li uor, and then pulpin the so ireated chips y cooking them with bisulphite quor. v 11. A process for manufacturing pulp in twostages of which the Erst is a treatment of the wood chips with alkali solution differing only by a few hundredths specific avity departure from water, and of whic 'the secon comprises anacid treatment of the chips resultm in the production of, ulp. W'EBS'I'ER E. BYRON B uns`

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