US1792202A - Process for treating the bagasse of sugar cane - Google Patents

Description

stares meals Parser ares- EARNESE GEAR-LE? EEMMER- VALET, 011" 'MEXIGO CITY, MEKIGQ, ASSIGNOR T0 QELU;

LOSE EEMMERVALET, SGGIEDAD ANION 03:? MEXIIGG CITY, MEXICO, A CORPO- RATIGN 0F MEXIQG PROGESSFOE TREATING TEE BAG-ASSE OF SUGAR CANE No Drawing. Application filed June 8, was, Serial No, 869,525, and in Germany March 23, 192?.

My invention comprises a complete process by which the bagasse of sugar cane may be treated to produce therefrom an excellent grade of cellulose. My invention is an 1mprovement over that disclosed and claimed in my Patent No. 1,630,142, dated May 24;, 1927, an application for a reissue of which is now pending. The present application 1s a continuation in part of United States application Serial No. 192,785, filed May 19, 1927.

Attempts to manufacture cellulose from the bagasse of sugar cane have heretofore en.-

- tailed considerable expense and have likewise Lil resulted in a product that was not readily bleachable except with such strong bleachmoisture content of the bagasse as it-comes from the mill and thereafter separate the longer fibres suitable for cellulose ;manufacture from the epidermis, parenchyma, and shorter fibres.

The drying of the bagasse andthe subsequent separation of the fibres is preferably carried out by the process described and claimed in my co-opending application-Serial No. 366,825 filed May 29, 1929. This process comprises air drying of the bagasse over a period of one or two weeks in a building provided with perforated floors and side walls open to the atmosphere, the bagasse being loosely spread about one or two' feet deep on the perforated floors and a' gentle current of air forced throu l1 and over the bagasse. The bagasse 1s then "treated preferably in a hammer-mill which breaks up the hard epidermis into a powdery form and partially opens up the fibrous art to detach the parenchyma and smaller fi res from the longer fibres. By means of screens and air flotation the longer fibre is then separated from the other parts of the bagasse I and further separation of the smaller fibres The materials are then ready for chemical 7 treatment by my improved process. In order to make clear the present process I will describe a treatment of a specific quantity of bagasse fibres togetherwith specific quanti ties of the various chemicals to be employed. I wish it understood, however,t hat the various quantities given are representative only and are not to be taken as limiting my invention except as so limited in my claims. To a quantity of about 300 kilograms of dry bagasse fibre, separated from other ingredients by the preliminary process above described, I add about 1200 to 1500 liters of a clear saturated solution of lime. I heatthe fibres and lime solution together for about one-half hour preferably first by steam allowed to enter directly into the solution, and then by passage of steam through heating coils, while maintaining the temperature be-' low the boiling point, referably eta-term perature of about 90 This treatment of the fibres is of particularvalue as a step in the elimination of the natural coloring matters and of the sugar content, which latter amounts to about one-and one-half to three per cent. or evenmore of the weight of the dry bagasse fibres. It is absolutely essential in order to obtain a good grade of paper stock for the sugar to be completely eliminated as otherwise it is impossible to bleach to'a. pure white product. After the lime treatment', and while the fibres are still immersed in the lime solution I add a cold solution containing sodium sulphite. With the quantities above mentioned I add 300 to 500 liters of the sodium ,sulphite solution, the amount of the sulphite in solution bein about onehalf to two per cent. of the fibre weight. Preferably the entire quantity of sodium sulphite amounting to about one and onehalf to six kilograms, is dissolved in about 100 liters of water, and 200 to 400 liters of water are added coldto the solution in the cooker to reduce the temperature thereof to sulphite solution, the mixture is now heated matters.

up to the initial temperature by means of steam for about one-half to one hour which time I have found sufiicient for my purposes. I have found that this treatment of the fibres,

first with clear saturated lime solution and then with the sulphite and lime solution, insures substantially complete elimination of the sugar content and also of the natural coloring matters. I believe this to be due to the partial opening up of the fibre by the alkaline solution to permit the sugars to go into solution and perhaps also to the enhanced solubility of the sugars in the res ence of lime. The sulphite solution, Thelieve to be of particular value in connection with the elimination of the natural coloring After this treatment I draw ofi so much of the solution as may be readily removed from the fibres, which amounts to about 1000 liters or two-thirds of the total employed. The fibers are then washed with addition to the washed fibre of a weak causcaustic tic solution, comprising about 1,000 liters of otash, caustic soda and sodium or other suitable sulphite in the proportions of about .3 to .6% caustic potash, 3 to 5% caustic soda and to 1 of the sulphite. The mixture is now heated by the addition of live steam in quantity suflicient to add about 200 liters of water to the solution and the temperature maintained around 130 C. for from four toeight hours. The treatment is .efi'ected in\a closed cooker, the pressure within which is accordingly raised to about 1 to 2 atmospheres.

The particular proportions of the various chemicals depend upon the age of the bagasse and also upon the soil in which the sugar cane is grown. In place of the caustic soda additional caustic potash could be used, but this is not preferred on account of the greater expense involved. During this treatment the silica is removed by the caustic poash, the vegetable glue is dissolved, the last traces of the coloring matterare destroyed, the resinous matter and vegetable iqeaaoa wax are saponified oremulsified by the combination of chemicals used, and any epidermis or parenchyma remaining with the fibres has been so acted upon as to render them harmless during the further treatment and manufacture of the cellulose. At the end of the cooking process samples of the solution and of the fibre are taken in order to ascertain whether the proper stage of purity of the cellulose has been reached, and if it has the pressure is reduced to about one atmosphere and the solution, which I will call solution B, drawn off "and saved for byproduct manufacture. The fibre is then washed with hot water or steam until'the water runs practically clear. The fibre is then removed from the cooker and placed in hollanders or beaters where it is beaten in a lukewarm solution of about 28 C. to 33 C.

of soap preferably of the type of Marseilles soap; about one to three kilograms of the dry soap being in solution in about 1,000 liters of water. The material in solution is then heated in the heaters to about 507 0 C. The soap solution washes out the last traces of the resins, waxes and gums. This solution is then removed and may, if desired, be

saved for by-product manufacture. The fibre remaining is then thoroughly washed with lukewarm water having a temperature of 30 C. to 35 C. in the same heaters and bleached in any well known manner.

I have found it of particular importance that the lime'solutionand the solution of sulphite added in the initial part of my above described process be added separately wit-1h suiiicient time elapsing before the sulphite solution is added, to insure the full respective effects of these reagents. By the separate addition of these solutions I am able to eliminate substantially all of the sugar and coloring matter and hence obtain 'a' cellulose that can be readily bleached without loss of strength of the resulting material.

In the latter part of my process it is-of particular importance to add the soap solution after the removal of the caustic solution and, the subsequent washing of the fibres. If the soap solution is added while the caustic solution is still in the cooker a kind of wax soap is formed which adheres in lumps to the cellulose and is most difiicult to. remove therefrom, requiring an immense quantity of hot water, and even after all this washing the fibres remain slippery to the touch, and are therefore not readily workable with the usual paper making machinery.

The recouery of by-products is of impor-; tance in my novel process as it substantially lowers the cost thereof. By-products obtainable from my process include high grade cellulose from theshort fibres of the bagasse, when these are not added to the longer fibres in the above process, sweetening syrups, fertilizers, filling material for the plastic arts or aveaaoa for explosives, waxes, resins, glues, etc. A description of the various processes by means of which these by-productsmay be obtained will now be given.

In my above mentioned-'copending application, theseparation of the short fibres from the parenchyma and epidermis is described.

This separation, briefly, is effected by air flow tation methods to first remove the powdered epidermis and dust, followed by screening,

using slit screens through which the shorter fibres pass, leaving the parenchyma behind.- I have found that a very excellent grade of cellulose, very high in alpha content, may be obtained from these separatedshort fibres. According to marketing conditions these may be added directly to the long fibres and treated therewith by my above described process or treated separately for by-product manufacture. These shorter. fibres when separated in the above manner are freer from adhering parenchyma, etc. than are the longer fibres, and I have found that they are particularly suitable for the production of a special high grade of alpha cellulose from which artificial silk of a quality superiorto that hitherto producedmay be manufactured. When treated for the production of such high grade cellulose, the short fibres are ents.

treated separately by a process similar to that described for the longer fibres. As by my process hereinafter described, I recover sweeteningsyrup from solution A and resins, waxes, glues, etc., from solution B, I prefer to use these solutions'intreating the short fibres, inorder to make those solutions as rich as possible in the'recoverable ingredi- In treating the short fibres tor the production of artificial silk, I first use solution A just as it comes from the cooker after treatment of the long fibres, and then recondition it by the addition of clear lime solution and,

after the treatment with this solution add be obtained from exhaust steam of the plant,

I may obtain a b product from the short fibres of considera is strength and of a very good light color, suitable, without bleaching, for newspapers or the like or suitable when bleached for other uses oficellulose. It is not essential to use solution A in this case, but its use is preferred in order to enrich the solution with the sugar from the fibres...

When using the unconditioned solutions, I agitate the short fibres for from four to six hours in solution B, maintain the temperature at about C. by exhaust steam of the plant and then wash them, using preferably the wash water from the longer fibresand finally treat the fibres with the soap solution, which may also be that used in the treatment of the longer fibres. I

Vegetable waxes, glues, and resins are precipitated by the use of acids or in any other known manner from the alkali solution afte its use in treating the fibres.

The parenchyma, separated in the first part of my process from the other-components oi the'bagasse, may be sold without treatment as a filler for explosives, or, if desired, the sugar contents contained therein may be recovered,

and the remaining material used for other purposes.

The sugars, which amount to about 3% to 5% of the total, may be removed from the parenchyma by treatment with so much of solution A with or without addition of fresh lime andsulphite solution as is necessary to bring the sugars into solution. This solution is then drawn oil combined with all of solution A remaining from the treatment of the long or short fibres, which solutioncontains the sugars removed from ths fibres and added to the molasses ofthe sugar plant in such proportions as to reduce the specific gravity to 8 to 12 Be, This miXture'I then pass through filter presses, condense the filtrate to about 33 Be, bleaching at the same time to a crystal clear syrup containing the sugars. This syrupis of value'as a sweetening, material for edible products. It hasa peculiar and pleasant aroma and fiavor,

-'wh ich I believe to be distinctive to my particular process and to the materials from which it is produced.

The parenchyma, after the above extraction of the sugars, may besold separately as filling material for the plastic arts, or may be added to the separated epidermis and dust and the whole used as a "fertilizer, as may also be used the filter cakes remaining in the presses after filtrationof the sugar containing solution. l have now described my novel process in considerable detail, and given a re resenta== tive treatment of a particular quantity of the bagasse. I have described as well various methods by which each of the constituents of the bagasse may be utilized in by product;

manufacture with a minimum of waste not only or the bagasse but also of the various chemicals employed. Certain of the by-prodnets and processes for their recovery disclosed herein are not claimed in the present application, as they form the subject matter of applications hereinafter to be filed. The particular by-products produced, and consequently the treatment therefor, will depend to a great extent upon the proximity to the plant of markets for the products and upon the facilities of the plant for storage, etc. Also the cost of manufacture of chemicals in chemicals are concerned, but giving a poorer all) grade cellulose, whereas at other times it may prove more economical to condition solutions A and B in order to produce cellulose for artificial silk. Similarly, in some instances it may be preferable to sell the parenchyma without treatment, while again, recovery of the sugars therein maybe expedient.

The cellulose obtained by my improved process is of a particularly fine quality. It has a high. alpha rcontent and is readily bleachable to a pure white color.

I claim:

1. A-process for treating bagasse fibres which comprises first treating the fibres .in a clear saturated solution of lime, later adding thereto a solution containing a suitable sulphite then treating the fibres in a solution containin caustic potash and a suitable sulphite and S11 sequently washing the fibres in a soap solution.

2. A process for treating bagasse fibres which comprises first treating the fibres in a clear saturated solution of lime, later adding thereto a solution of sodium sulphite, then treating the fibres in a solution containing caustic potash, caustic soda and sodium sulphite and subsequently washing the fibres in a soap solution. 3. A. process for treating the bagasse of sugar cane which comprises first separating epidermis, parenchyma, and, other foreign materials from the fibres, then treating the separated fibres in a clear lime solution and heating the same while maintaining the temperature below the boiling point, then reducing the temperature While adding an alkaline solution containing sulphite ions and again heating to a temperature below the boiling point, then removing the solution and thereafter treating the fibres with a weak alkali solution.

l. A. step in the process for treatin the bagasse of sugar cane which comprises ieating bagasse fibres with a clear lime solution to a temperature in the neighborhood of 90 0., then reducing the temperature to about C. by the addition of cold Water and thereafter adding a solution of sodium sulphite and raising the temperature to its initial value.

5. process for treating the bagasse of sugar cane, comprising first separating short fibres, epidermis, dust and parenchyma from the longer fibres, then treating the separated moaaea longer fibres in a clearsaturated solution of lime, followed by the addition thereto of a solution of sodium sulphi-te, then removing the solution, washing the fibres and then heating the same in a solution, containing caustic potash, caustic soda and sodium sulphite, then removing the solution and again washing the fibres, and finally beating the fibres in a heated solution of soap.

6. Additional steps in the process according to claim 5 comprising separating the shorter fibres from the other material separated from the longer fibres, then heating the separated short fibres with the-alkali solution removed after the treatment of the longer fibres, then washing the shorter fibres moisture content of the bagasse, then mechanically separating the longer fibres from the remainder of the bagasse, treating the separated fibres in a clear lime solution to which a solution of sodium sulphite is added thereafter, then removing the solution from the fibres, washing the fibres and subsequent ly treating the fibres in a weak caustic solution. I

9. A step in the process of treating the ba gasse of sugar cane which comprises treat ng separated fibres? of ,bagasse in a clear lime solution while maintaining the temperature below the boiling point of the solution, then adding a cold solution of a suitable sulphite andreheating the mixture to a temperature below the boiling point.

10. The process according to claim 9 wherein the sulphite solution is sodium sulphi-te in amount equal to about one-half to two percent of the weight of the bagasse fibres.

In testimony whereof, I have signed my name to this specification.

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