US1878228A - Paper manufacture - Google Patents

Description

Sept. 20, 1932. w. J. ZIMMERMAN PAPER MANUFACTURE Filed Aug. 16, 1928 Patented Sept. 20', 1932 UNITED .sTAras 'WALTER iLflZIMMERMAN, OF lDAYTON, 'OHIO, ASSIGNOR '10 MEAD PAPERIBOARD CO PATENT orFIcE 1 PORATION, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE PAPER MANUFACTURE This invention relates tothe manufacture of paper, and the like, andparticularly to the preparation of'pulp for use-infsuch manufacture.

One of the-principal objects of this invention is to provide a method of treating fibrous materials to forma superior pulp having unusual strength with a large yield, and in which desired uniformity of the pulp product is obtained. a I

Another object of this invention is to provide a method of pulping fibrous materials, such as hard woods which have heretofore been difficult and impractical to treat with the hitherto known pulping'processes, to form a satisfactory pulp with a high yield for the manufacture of paper or board and the like.

Another object-of this invention is to provide apparatus .for carrying out the above method, which apparatus is simple in construction, and highly effective and readily controlled in operation.

Other objects and advantages of this invention will be apparent from the following description and a from the accompanying drawing, and the appended claims.

In the drawing, the single figure is a; diagrammatic view of apparatus constructed for carrying out the method of this invention.

According to this invention the fibrousmaterials are first cooked, or otherwise treated with chemicals, to loosen the bonding material holding the fibers in their natural asso-- ciated form, after which the treated fibrous materials are subjected to mechanical disintegration or defibering to so separate the fibers that they will form a suitable pulp, this mechanical defibering action being controlled in accordance with operating variations in the characteristics of the treated fibrous materials and coordinated therewith to give an ultimate pulped product of substantially uniform characteristics. For purposes of illustration of preferred embodiment of the method and apparatus for practicing the method, the invention is hereinafter described in connection with the treatment of chestnut wood,and more particularly of leached chestnut chips from which tannic acid has been e tracted. z

Application filed August '16, 1928. Serial No. 299,982.

In treating such materials the chestnut chips are first given a chemical treatment or cooking which is effective to soften them, but is purposely so limited in its eifects that any considerable defibering or separating of the Wood into its ultimate fibers does not result, with resulting high strength and yield of the ultimate product. In actual commercial operations according to this invention, this treatment is what is called an incomplete digestion and it is so controlled that the I chips retain substantially their original form, but may be thereafter readily defibered with properly coordinated mechanical treatment. This incomplete digestion may vary considerably depending upon the fibrous material being treated and the ultimate product desired; but in the commercial operations referred to a so-called semi-chemical cook, hereinafter point such as is possible where a substantially complete digestion is effected and the incrustants are primarily dissolved leaving the fibers in separated condition. In fact different batches of the same material subjected to this semi-cooking may vary considerably in character, due to variations in the cooking action resulting from variable factors wh1ch.are I practically indeterminate and not easily controlled. The character of the cooked material may vary considerably from a more complete- 1y cooked material or one in which more of the incrustants and lignins have been removed and a higher degree of hydration of the fibers has been effected, and which is hereinafter termed a ft cook, to a less completely cooked material or one in which a larger percentage of the incrustants and-lignins remain in the material and a lesser degree of hydration of the fibers has been effected, and which is hereinafter termed a hard cook.

The fibrous material resulting from the semi-cook is then subjected to mechanical i treatment to complete the pulping of the material and to provide a pulp product of desired uniformity irrespective of varlatlons in the characteristics of the cooked material.

- This is accomplished by-subjecting the cooked the cooked material to the action of a rodm ll,

after which it is passed through a Jordan engine. The rod mill effects apoundlng,

' rubbing and shredding action which disintegrates the material and hydrates the fibers without objectionable cutting of the fibers. Thesubsequent Jordan treatment effects what may be termed a brushing out treatment, which sufficiently separates the material into its ultimate fibers, and prepares it for proper\ formation on the paper machine. These treatments are coordinated in accordance with the characteristics of the cooked material as received from the cooking digester, or the like, to secure a final pulp product of the desired uniform characteristics. Vhere the cooking treatment produces a hard cook, or one in which a lesser degree of hyd ation of the fibers is obtained, the degree of the rodmilling treatment is increased by relatively prolonging the time of such treament to complete the hydration of the fibers to a-desired point, and the degree of ordaning treatment is lessened by freeing or opening up the setting of the Jordan. Conversely when a soft cook is obtained, the degree of treatment in the rod mill is reduced by relatively shortening the time of such treatment, while the setting of the Jordan is tightened up to give a more rigorous action on the fibers to thereby produce a stock in which the lumps are effec: tively reduced, producing a more uniform consistency of the fibrous stock. I By a proper control and coordination of these mechanical treatments in accordance with the. character of the cooked material, a final pulp product of substantially uniform characteristics is obtained which is adapted to be formed directly into paper or board of uniform quality.

Referring to the drawing, in which a preferred embodiment of apparatus for carry ing out the above method is disclosed, a conveyor for raw fibrous materials is indicated cores and the like, which have heretofore proved extremely difiicult and impractical to treat by conventional pulping processes to give a satisfactory grade of pulp of sufficient strength and yield. This invention opens up a field of use for waste wood, such as from furniture factories which contains a propor- The raw fibrous material is cooked, preferably with an incomplete digestion .or semichemical cook which gives an exceedingly high yield and a product of unusual strength. In the semi-chemical cook, Ver satisfactory results are secured with an aqueous solution of a normal sulphite containing a salt of a weekly ionized polybasic acid, such as a mixture of sodium sulphite and sodium bicarbonate. The cook is carried out in two stages. The charge of wood chips is added to the digester and the chips after being preferably steamed for about half a ho to remove air from the wood to faciliw ii npregnation with liquor are then submerged in the cook ing liquor and the temperature is brought up to approximately C. to (3.. with steam for a length of time to secure desired impregnation of the liquor within the Wood, this being termed the impregnation stage.

A treating time of about two hours gives satisfactory results inthisfirst stage. The unabsorbed liquor is then drawn off .and the liquor-saturated material remaining in the a digester is then raised to a temperature of approximately C. to C. for a period action with the incrustants and ligneous material takes place with resultant softening of the chips. According to the length of time and temperature of this final heating treatment, the characteristics of the fibrous stock are determined such as whether it can be easily hydrated or not, its bulkiness, and whether it will form a hard or soft sheet, andthe like. V

Reference is herein made to the patent to FrancisG. Rawling, 1,673,089, issued June 12, 1928, which discloses and claims a semichemical cook of thisccharacter.

In practical operation, the character of the cooked material produced by such a semichemical cook varies. This is due to certaiii variable factors in the cooking, such as the character of the steam as to whether it is dry. wet or superheated, the moisture content of the chips charged into the digester, the, amount of CO formation in the digester during the coking which sets up what is termed a false pressure or a pressure which is not the result of the introduction of steam, and other factors which so far it has been found commercially impracticable to control within suitably narrow limits. The result is that the characteristics of the cooked materials'vary from a hard cook to a soft cook, which varying characteristics would show up in the finished pulp to give objectionable variationsin the freeness of the stock, the hardness, its degree of hydration, and the like to give a paper or board of non-uniform quality. These variations may be compensated for and a uniform final product obtainedby coordinating the steps ofthe subsequent defibering, by coordinating the rod milling and ordaning treatments.

The cooked material is discharged from the digester'into a dump tank 15. The ma whereby it is easily handled at high consistency. The mass of softened chips discharged into the dump tank 15 is then washed to remove residual liquor. This is preferably accomplished by introducing wash water into thedigester and then permitting this liquor to discharge upon the chips within the dump tank 15. The washing is completed by the introduction of any additional wash water neededas by a hose onto the surface of the chips in the'dump tank. These chipsare supported upon a perforatedbottom, which may be a lattice work as indicatedat 16, the wash liquor draining through the lattice work and escaping to sewer or. recovery through the p1pe 17 The dump tank 15 is provided with means for feeding the softened and drained chips at a controlled rate to the rod mill. As illustrated, the bottom of the dump tank is pro- 7 vided with an opening 20 located adjacent the periphery of the tank. This opening is closed by a valve (not shown) during the dumping and washing operations, and is then opened to permit the feeding of softened chips, at a controlled rate onto an endless conveyor 22. Positioned Within the dump tank is What is termed a leach caster. which comprises a central vertical shaft 24 supported in suitable bearings and driven through gears 25 and 26 from a drive shaft 27 which in turn is driven at a controlledrate from any suitable source of power.

\ mounted on the shaft 24 for vertical movement thereon and is keyed thereto so as to rotate with the shaft 24. The stirring arm carries a plurality of depending inclined blades or fingers 31 which are constructed to move the chips toward the periphery of the tank upon rotation oftheshaft 24 and arm 30. The construction is such that the arm slides up and down the shaft 24 in accordance with the A stirring arm 30 is slidablyv level of chips within the dump tank so that the arm rests on the surfaceof the chips. The rate at which the chips are fed to the periphery of the tank is controlled by the rate of rotation of the shaft 24, this in turn control ling the rate at which the chips are fed through the opening 20 onto the conveyor 22. The conveyor 22 discharges chips into a receiving hopper 35 feeding intoan endless bucket elevator 36, which in turn discharges onto an endless conveyor 37 feeding into the inlet 38 of a rod mill 40. controlled supply of dilution liquid, which is generally white water from the forming machine, is admitted concomitantly with the softened chips through a supply pipe 42. The dilution liquid is generally controlled to provide a stock consistency of about 5% to 8% within the rod mill, this consistency range being found to be very satisfactory for the rod-milling-of pulp of this character.

- The rod mill comprises an outer rotary shell 41 which containstherein a plurality of loose parallely arranged rods extending substantia ly throughout the length of the shell. The

contracted ends 43 and 44 of the shell are supported in suitable bearings (not shown), and the body of the shell is provided with an annular gear 45 which is driven through gearing from a suitable power shaft (not shown). The softened chips are simultaneously fed into the inlet 38 with dilution liquid from the pipe. 42, and the stock feeds from the inlet 38 to the discharge 44 as the casing 41 is rotated to provide a tumbling and cascading of'the rods within the casing to thereby give a thorough pounding, rubbing and shredding treatment to the fibrous material. This serves to effectively pulp the softened chips and to hydrate the fibers without. objectionable cutting of the fibers. While a rod mill is disclosed herein, it is to be understood that other types of disintegrating mills can be used to give this effective pounding, rubbing and shredding treatment, such,-for.example, as a swinghammer type of mill inwhich the pounding elements are mounted therein-for swinging and impacting movement. In disintegrating mills of this character provided with swinging or loose impacting element's,*the unreduced bundles or lumps of fibrous material receive substantiallv the entire action of the movable elements. such as the rods, while the portions that are suflicientlv reduced are protected bythe lumps against further reducion ,and cut ing action.

The weight of the rods within a rod mill and the speed of rotation of the mill are selected to provide for the most effective treatment. In a mill having a shell 12 feet long and 6 feet in diameter, a weight of 40,000 pounds of rods is found to give very satisfactory results when treating leached chestnut chips. But this may be varied within considerable limits to suit the characteristics of the particular pulp or fibrous material being treated. The speed of rotationof the rod mill is preferably controlled so that the rods merely cascade or roll over one another and there is substantially no throwing or free falling 7 "of the rods. This cascading efl'ect gives the desireddisintegrating and hydrating treatment without the more-forceful collision effect of a freely falling rod which is apt to w cut the fibers. In a mill of the size above mena-nce with the rate at which fresh material is fed into the mill. the time of treatment within the rod mill being thereby'controlled by the rate of feed. Inasmuch as the rate of feed is controlled by the leach caster of the dump tank, effective .control of. the time of treatment in the rod mill is obtained by con "trol of the speed of rotation of the shaft 24 of the leach caster, which may be obtained by control of the speed of the drive shaft 27 in 30 any suitable conventional manner, such as by a variable speed motor with rheostat control.

The discharge from the rod mill is fed to a stock chest 50 provided with suitable agitating mechanism such as a driven horizontal shaft 51 having stirring arms 52- At this point, additional dilution liquid, such as white water, may be added through a pipe 54 t reduce the consistency of the stock within the chest to a point such that it can be readily puinpe'd'through conduits, a consistencv range of about 3% to 5% giving satisfactory results. Stock is withdrawn from the chest 50 through pipe 56 by a suitable pump such as a centrifugal pump57, which feeds it through pipe 58 to overflow box 60. This overflow box may be of any suitable'and conventional construction adapted to regulate the supply of stock to the jordan, the excess supplied by the pump 57 being returned to the stock chest 50. As shown, the overflow tank 60 is divided by partitions 61 and 62 into three compartments 63, 64 and 65. The pump 57 feeds the stock through pipe 58 into the central compartment 64. The compartment 63 is connected by pipe 67 which returns the excess stock, to the stock chest 50. The compartment is connected by pipe 69 which feeds a regulated supply into the jordan 7 5. The partition 61 is of a fixed height, while the partition 62'is provided with an adjustable weir 70 to control the amount of stock feeding over the weir and thence to the jordan. The provision of a stock chest inter mediate the rod mill and jordan permits the 65 rod mill and jordan to be driven at separate rates, and to have different capacities, thus .out treatment to the stock passing therethrough serving to refine and separate sufliciently the pulped material into its ultimate fibers. An adjusting shaft provided with a hand wheel 81 is rotatably mounted in a fixed bearingtnot shown) and is threadedly received within the end wall of the casing 76 to effect upon rotation of the shaft longitudina l adjustment of the casing and plug relatively to each other, to secure the desired setting of the respective knives to regulate the degre of brushing-out treatment effected by the jordan. As any conventional means maybe used to control the jordan setting, further illustration is thought unnecessary. )Vhile a jordan is illustrated herein, it is to be understood that other types of refiners may be used, such as a claflin.

The stock treated in the jordan 75 discharges through pipe 85 into a second stock chest 86 having an agitating shaft 87 and stirring arms 88. The stock is withdrawn from the chest 86 through pipe 89 by pump 90 and fed through pipe 91 to a second overflow .box 92 which is similar in construction to the overflow box 60. A regulated supply of stock is fed from the overflow box through pipe 94 to the inlet of a cylinder mold tank of a suitable forming machine (not shown), or to other treating apparatus. The over flow from the box 92 passes through return pipe 95 back to the stock chest 86. The construction is such that the overflow is returned to the system on the far side of the jordan so that thisoverflow is not subjected again to a j ordaning treatment with the result that the fibers are not shortened or cut up additionally, and the stock is uniformly treated.

In practice the operator at the forming machine tests the stock from time to time to determine its relative hardness or softness. This is determined in practice by the feel of the stock in the light of the'experience of the operator. If he finds, for example, that the cooked material received from the digester is a harder cook than previously, the time of treatment in the rod mill is increased by reducing the rate of feed at the leach caster. At the same time, the jordaning treatment is coordinated therewith by proportionately freeing up the jordan setting to increase the clearance of the knives of the plug from the interior knives of the surrounding casing. Conversely,. when he finds the pulp softer than previously; the time of treatment in the rod mill is reduced by speeding up the rate of feed of the leach caster, and at the same d the following is given.

time the jordan setting is tightened up to reduce the clearance of the knives. By a proper coordination of the control of the respective mechanical treatments, a stock of substantially uniform characteristics is ob tained. The combination of the rod-milling treatment with the jordaning treatment for pulp of this character isfound to considerably reduce the work on each machine, and the proper coordination as above described effects an increase in capacity of both machines as well as an increase intbe quality of the pulp. An average yield of 70% to 85% on the dry weight of the wood has been obtained by this method ,and apparatus in actual practice with leached chestnut chips; and corrugating board produced from such chestnut chip pulp is found to be substantially twice as strong as ordinary strawboard as heretofore manufactured in the industry.

As an example of a pulping treatment carried out in accordance with this invention, A cooking liquor consisting of 1800 pounds of sodium sulphite and 700 pounds of sodium bicarbonate (both calculated as sodium carbonate) is added to the digester together with 14,000 pounds of wood (dry basis), this charge practically filling the digester. The charge is brought up to approximately 125 C. with steam, the cooking being continued at this temperature for approximately two hours. Then the liquor in the digester is blown back into a closed receiving tank where fresh liquor is added to bring it up to strength, and this liquor may then be used to cook a second charge. The chips impregnated withthe liquor and which remain in the digester, are then steamed until the temperature is brought upv to approximately 160 C., this temperature together with the absorbed cooking liquor serving to effect the softening of the chips. This second stage of the cooking is generally carried on for about f hours. While the cooking is generally carried out under certain set conditions, certain variables enten in as above described, to give a cooked material which varies in characteristics with different batches. The cooked chips are then dumped into the dump tank and washed, the plug valve for the outlet 20 being closed. The plug valve is then opened and the shaft 24 of the leach caster driven to feed the softened chips at a controlled rate to the rod mill 40. With a mill of the size above mentioned, the rate. of feed of the chips is generally controlled to give an output of about 13 tons to 18 tons of rodmilled stock in 24 hours. The j ordan setting is coordinated therewith to give a regulated brushing-out treatment, the clearance between the blades being generally varied between 0.005 of an-inch to about of an inch.-

erated at a rate of about 15 tons a day, and

the jordan is given an intermediate setting within the limits above mentioned. Should the cook from the digester be a hard cook, the

leach caster is slowed down-to provide fora reduced feeding rate approaching 13 tons a day to the rod mill, and at the same time the jordan is given a freer setting by opening up the clearance to approach a clearance of about 1 3' of an inch. On the other hand, when a soft cook is obtained from the digester, the time of treatment in the rod mill is reduced by increasing'the rate of feed to approach 18 tons .a day, and the jordan is tightenedup to reduce the clearance to approach .005 of an inch.

,While the method herein described, and the form of apparatus for carrying this method into effect, constitute preferred -emprecise method and'form of apparatus, and

that changes may be made ineither without departing. from the scope of the invention which is defined in the appended claims.

What is claimed is: 1. In the manufacture of pulp, the method which comprises cooking fibrous material with an incomplete chemical cooking treatment to soften the fibrous material without pulping thereof, whereby a cooked material of characteristics varying substantially from a morevcompletely cooked -material or soft cook to a less completely cooked material or hard cook is produced, mechanically disintegrating the softened and unpulped material, mechanically refining the disintegrated material, and coordinating the disintegrating treatment with" the refining treatment in accordance with the character of the cooked material, by providing a more rigorous disin- I tegrating treatment and a less rigorous refining treatment for a hard cook, and a less rigorous disintegrating treatment and a more rigorous refining treatment for a soft cook.

2. In the manufacture of pulp, the method which comprises cooking fibrous material with an incomplete chemical cooking treatment to soften the fibrous material without pulping thereof, whereby a cooked material of characteristics varying substantially from a more completely cooked material or soft cook to a less completely cooked material or hard cook is produced, rod-milling the softened and unpulped material, jordaning the rod-milled material, and coordinating the time of rod-milling treatment with the degree of jordaning treatment in accordance with the character of the cooked material, by providing a longer time of rod-milling treatment and a freer setting of the jordan for a hard cook, and a shorter time of rodmilling treatment and a tighter setting of the jordan for a soft cook.

trolled rate, introducing the stream of ma-' terial of low moisture content concomitantly with dilution liquid into a rod mill, rodmilling the cooked fibrous material admixed with dilution liquid, and controllng the rate of feed and introduction of the drained material and the introduction of the dilution liquid into the rod mill to thereby control the time of' rod-milling treatment.

4. Apparatus of the character described, comprising in combination, a dump tank adapted to receive a mass of partially cooked undefibered fibrous material and having provisions for efiecting draining of material received therein, rotary means for discharging .material continuously from the mass of drained material in said dump tank, a mechanical disintegrator, and means for continuously feeding the material discharged by said rotary means into said mechanical disintegrator.

5. Apparatus of the character described, comprising in combination, a dump tank adapted to receive partially cooked undefibered' wood chips and having provisions of chips received for effecting drainin therein, said dump tan having a discharge opening adjacent the periphery thereof, a rotary arm for continuously feeding drained alkali metal carbonate to soften the wood without pulping while maintaining its chip form, subjecting the softened chip material to a mechanical disintegration by a pound ing treatment of impact elements, mechanically refining the disintegrated material,

'and coordinating the disintegrating treatment with the refining treatment in accordance with the character of the cooked mate-- rial by providing a more rigorous distinte- 5 gratingtreatment and a less rigorous refining treatment for a h rd cook, and a less rigorous disintegrating treatment and a more rigorous refining treatment for a soft cook. 7

8. In'the manufacture of pulp from wood 80 chips, the method. which comprises cooking the chips with an incomplete chemical cooking treatment to soften the chips without pulping while maintaining the chip form thereof, dumping the cooked chips without blowing, permitting the cooked chips to drain, feeding the drained chips from the drained mass in a continuously moving' stream of chips and at a controlled rate, introducing the softened chips and a dilution liquid concomitantly and continuously into a disintegrator, and mechanically disintegrating the softened chips in the prs ence of dilution liquid by a pounding treatment o'fimpact elements.

In testimony whereof I hereto aflix my signature.

. WALTER J. ZIMMERMAN.

' chips from the mass confined in said dump tank through said" discharge opening, a mechanical disintegrator, means for continuously introducing chips fed through said discharge opening into said mechanical disintegrator, and means for varying the rate of discharge feed of said arm to thereby vary the rate of feed to said mechanical disintegrator.

6. Apparatus of the character described, comprising in combination, a dump tank for receiving a mass of partially cooked unde fibered fibrous material and for draining liquor from the same, means for discharging drained fibrous material at a controlled rate from the mass in. said dump tank, means for continuously transporting drained material of low moisture content in a continuously Ill moving nonliquid stream,"a disintegrating mill, and means for concomitantly introducing the transported material and dilution liquid into said disintegrating mill. I

7; In the manufacture of pulpjfrom hard deciduous wood,'such as chestnut, the method which comprises. cooking the deciduous wood in chip form with an incomplete chemical cooking treatment with a cooking liquor containing an alkali metal sulphite and an

Images