US2623875A - Wood pulp and method of producing same - Google Patents

Description

Patented Dec. 30, 1 952 2,623,875 WOOD PULP AND METHOD OF PRODUCING SAME Paul Henry Schlosser and Kenneth Russell Gray,

Shelton, Wash., assignors to Rayonier Incorporated, Shelton, Wash., a corporation of Delaware No Drawing.

Application September 9, 1950,

Serial No. 184,108

4 Claims. (Cl. 260-212) This invention relates to the production of cellulosic products and has for its general object the provision of certain improvements in carrying out one or more of the processing steps used in the production of such products. The invention aims particularly to minimize inactivation effects in the production of a substantially dry sheet of refined wood pulp from a slurry of wet fibers. The invention further contemplates, as a new article of manufacture, substantially dry refined wood pulp in sheet form having incorporated therein a mixed ether containing a polyethylene oxide radical and an aliphatic hydrocarbon radical containing more than 7 carbon atoms.

In one of its important aspects, the invention involves the use of substantially dry refined wood pulp as a source of cellulose in the preparation of cellulosic derivatives, and has for a particular object incorporating mixed ethers in the pulp prior to completion of drying at an elevated temperature, whereby inactivation of the pulp as regards production of cellulosic derivatives is greatly minimized.

As used in this specification substantially dry refers to pulp either dried bone dry or containing that small moisture content which pulp being a hydroscopic substance would take up from the air. Roughly this will refer to pulp containing from zero to ten percent moisture.

In the preparation of refined wood pulp, the purified fibers are first obtained in the form of a slurry in water. In this undried state, the refined wood pulp fibers are extremely reactive. This is evidenced by the fact that in conversion processes taking place in non-aqueous media, such as in the production of cellulose acetate, if the water associated with the wet fibers is first displaced by organic solvents, the fibers are very reactive. place in an aqueous medium, such as the conversion to cellulose xanthate in the viscose process, the wet fibers may be very readily converted by treatment in slurry form without drying.

For practical reasons, however, it is generally necessary to form the pulp fibers into a dry pulp sheet, using heat to remove practically all the water. In such dry sheet form, the pulp may be readily shipped to distant factories for conversion into various derivatives. Also, in such relatively dry form, the pulp may be used in nonaqueous conversion processes without the need for expensive displacement of water by organic solvents.

However, in the formation of the pulp sheet Again in conversion processes taking and the drying at elevated temperature, the pulp fibers undergo various degrees of inactivation.

As regards use in the cellulose acetate process, such inactivation effects probably result largely from the drying at elevated temperature.

As regards use in conversion processes taking place in aqueous media, we find that inactivation is due in large part to mechanical effects of sheet formation. Such type of inactivity may be due to mechanical compacting which makes it difficult in subsequent processing to completely comminute the sheet without excessive damage to the fibers. We further find that such inactivity of dry pulp in sheet form toward aqueous processing is not particularly a function of the drying temperature but rather results from the substantial removal in pulp purification of the impurities removable by organic solvents, as for example, by ether, benzene, alcohol, etc. These impurities, often loosely called resins, are mainly of the natureof waxes, fats and true resins, the latter often being present in a relatively small amount.

One of the main objects in the manufacture of a highly refined pulp for the viscose process is to remove as much as possible of the noncellulosic impurities, so that a whiter, purer pulp results, which is capable, in the manufacture of rayon, of producing a higher grade yarn.

We find, however, that not all of the noncellulosic impurities which can be removed are undesirable, and in fact, certain of such impurities, normally present in small amounts, are highly beneficial in minimizing inactivity in the dry pulp sheet as regards processing the pulp into derivatives in aqueous solution. These impurities are particularly beneficial in promoting reactivity in the viscose process, especially as regards producing a reactive shredded alkali cellulose. The beneficial impurities which aid the shredding operation are probably of the nature of fiber lubricants which permit the steeped and pressed pulp sheets to be thoroughly shredded into a fluffy condition more readily and without mechanical damage to the alkali cellulose fibers, which would cause them to react incompletely with carbon bisulfide.

Pulp sheets which may tend to be unreactive toward processing into derivatives in aqueous solution will in general be characterized by having an ether extract of not more than about 0.15% where such values refer to the amount of natural ether-extractable material left in the P -P after the purification process. Such unre-.-

activity will tend to increase as the residual ether extract approaches zero.

We have discovered certain compounds, not normally present in pulp, which when added to the pulp in minute quantities prior to completion of drying, greatly minimize inactivation effects in the production of a dry pulp sheet from the wet fiber slurry. The compounds of our invention minimize both that inactivity primarily due to heat, as regards use in cellulose acetate preparation, and that inactivity due to sheet formation in pulp of low ether extract, as regards use in aqueous conversion processes (e. g, formation of a reactive alkali cellulose in the viscose or cellulose ether processes).

In accordance with the invention a small quantity of a mixed ether containing a polyethylene oxide radical and an aliphatic hydrocarbon radical containing more than '7 carbon atoms is incorporated in the pulp. Inthe preferred. form of the invention the compounds are incorporated in the pulp prior to completion of drying the pulp at an elevated temperature on the sheet forming machine.

For minimizing inactivity in the acetylation and other esterification processes carried out in non-aqueous solution, for satisfactory benefit it is necessary that at least the surfaces of the sheet be completely treated prior to final drying at elevated temperature. For use in the viscose process (or in other aqueous processes in which a shredded alkali cellulose is produced at an intermediate step) while the same manner of application is very satisfactory, nevertheless, substantial improvements may also be obtained by treating only portions of the sheet and even by application after drying on the machine is completed.

The compounds which we discovered for use in the invention are very effective in preventing loss of reactivity of the fibers during the formation of the dry pulp sheet and accordingly can be used in very small quantities.

The treated pulp of our invention containing the mixed ethers may be used with particular advantages in the The treated pulp, however, may be used forv the production of other cellulose derivatives such as cellulose xanthate in the viscose process.

For convenient application in our invention the mixed ethers are preferably substantially soluble in water, Such compounds will generally contain a polyethylene oxide radical, having at least half as many ethenoxy groups as there are carbon atoms in the hydrocarbon radical. Practica'lly, it is believed there is no upper limit for the number of ethenoxy groups in the polyethyl ene oxide radical. We have successfully used materials with a polyethylene oxide group containing up to 157 ethenoxy groups.

While the mixed ethers used in our invention are preferably substantially water soluble, it is possible however to use compounds of only slight solubility. Thus mixed ethers containing the simplest possible polyethylene oxide radical composed of two ethenoxy groups, i. e. a diethylene glycol ether group, may be used. Even though such products do not have a great solubility they still possess a sufiicient tendency tov emulsify so that they may be applied to the pulp in the form of an emulsion. If, however, a high degree of "solubility in water is desired with such compounds, as for example, in the preparation of concentrated stock solutions for application to the pulp or in the viscose process, it may be advantageous to combine them with dispersing production of cellulose acetate.

2,623,875 Y I f oxide radical so that the products will be substantially water soluble without the aid of any additional dispersing agents.

Further, from the standpoint of eifectiveness the most preferred class of compounds are mixed ethers containing a polyethylene radical with from 8 to 50 ethenoxy groups and a normal primary aliphatic hydrocarbon radical with from 8 to 20 carbon atoms.

The mixed ethers used in the invention may be prepared by any of the known methods for reacting ethylene oxide with a fatty alcohol. These methods include warming the fatty alcohol with the appropriate quantity of ethylene oxide while employing a catalyst such as an alkali which may be present either as a strong aqueous solu-' tion or as an alkali metal alcoholate. 'Again the mixed ethers maybe prepared by etherifying the fatty alcohols with polyethylene glycols, as for example, by reacting the sodium salt of the fatty alcohol with a halogen hydrin of the polyethylene glycol. I

We prefer, however, to react ethylene oxide at moderate temperatures with aliphatic fatty alcohols containing more than 7 carbon atoms, incorporating an alkali as catalystwith the alcohol. Suitable methods for incorporation of the alkali include:

(1) Addition of a small amount of concentrated caustic soda to the alcohol, e. g., about 0.25 to 1.5% by weight of 48% caustic soda. This is an inexpensive method particularly suited to the preparation of derivatives containing a relatively short polyethylene oxide chain.

(2) Dissolving metallic sodium in the molten fatty alcohol. We prefer to use about 0.1 to 4% of sodium by weight. I

(3) Addition of a solution of sodium in anhydrous liquid ammonia to a solution of the fatty alcohol in ether (or addition of liquid ammonia to an ether solution of the fatty alcohol followed by a subsequent addition of metallic sodium This method enables the preparation of sodium salts containing a theoretical amount of sodium. Since such salts contain much more sodium than can be introduced by method 2, they react much more rapidly with the ethylene oxide. 1

A convenient laboratory method for prepara tion of small quantities of the compounds follows: After incorporating alkali by one of the three methods described above, the fatty alcohol and the required amount of ethylene oxide are placed in an autoclave and heated with agitation until the pressure drops substantially to zero. When alkali has been incorporated by the first two methods and when using at least nine mols of ethylene oxide per mol of alcohol, a temperature of Bil-100 C. is usually a suitable reaction temperature. When using a theoretical sodium salt prepared by the third method or when incorporating alkali by any of the three methods and using less than nine mols of ethylene oxide, the reaction should be carried out at a considerably lower temperature, for example 50-80 C.;

' may proceed too rapidly and surge to completion with explosive violence, resulting in a less pure product. After completion of the reaction, the residual alkali may be neutralized with 30 H2804 or concentrated HCl.

1 oxide.

etfor the' preparation of the materials-on a large scale'the procedure will be'similar to that out-1- lined except that it will usually be preferable to introduce ethylene oxide in gaseous form at a relatively low'. pressure from an external. container during the course of the reaction. In this way the possibility of uncontrolled reaction may beavoided and, if desired, somewhat highe'r'reaction temperatures may be used.

For the purposes of our invention no subsequent purification will be usually required. Where an extremely-light-colored product is desired, however, thecompounds may be given subsequent treatment involving decolorizing with charcoal according to the methods well known to the art. A process used satisfactorily by us for both decolorizing the products and freeing them from inorganicsalt-consisted in dissolving the neutralized product. in benzene, decolorizing the benzene solution with' charcoal, drying the decolorized benzene solutioniby addition of sodium sulphate and by evaporating off the benzene, finally applying vacuum.

.When the alkaline catalyst used consists of a small amount of 48% aqueous caustic soda all of the ethylene oxide will probably not be consumed in extending the length ofthe polyether chain on the fatty alcohol, but a portion will be consumed with the formation of polyethylene v The presence of polyethyleneoxide is, however, not harmful to our invention, and is in fact in some cases even beneficial.

It is obvious that the fatty alcohols used for making the mixed ethers may be prepared by any desired method; for example, synthetic fatty alcohols containing more than 7 carbon atoms and built up from smaller molecules may be used. Such compounds are usually essentially branched chain molecules. We prefer, however, to use fatty alcohols prepared by catalytic reduction by hydrogen of vegetable or animal oils according to well known practices, which are substantially straight chain compounds. It is, however, not necessary to use pure fatty alcohols. Indeed,

highermolecular weight alcohols prepared by hydrogeneration of fats and oils are generally, if notv always offered in commercial quantities in the form of mixtures of different alcohols. Thus in place of pure lauryl alcohol, technical lauryl alcohol may be used. essentially a mixture of C10, C12, C14, C16 and C18, carbon length chains with the C12 chain predominating. These mixtures of alcohols function in substantially the identical manner as mixed tually, however, when using such a mixture in which lauryl alcohol predominates, the result is almost identical, as if pure 'lauryl alcohol itself were used. Also, instead of using pure stearyl alcohol it is satisfactory to use a technical mixture of saturated highermolecular weight fatty alcohols and in which stearyl alcohol predominates. In place of ,pure oleyl alcohol, technical oleyl alcohol as sold under the trade name of Ocenol may be used very satisfactorily. In condensing such technical mixtures of fatty alcohols with ethylene oxide, it is quite satisfactory to basethe desired molar ratio of. ethylene oxide on the assumption that the entire weight of fatty alcohol hasthe same molecular weight as the predominating fatty alcohol in the mixture. Thismay be done since small variations in the ratio. of ethenoxy in the products do not produce very great; differences in the properties. Furthermore, even when using pure. fatty alcohols it is not nee- This is considered to be ethers of the individual pure alcohols. Ac-

'e's'sary to use .e'xact stoichlometrical"proportions of ethylene oxide. Thus, for example,'if pure lauryl alcohol were treated with 12.5 mols of ethylene oxide, mixtures of mixed ethers would be obtained in which chains of 12 and 13 ethenoxy groups would predominate.

Condensation products prepared by the meth ods described, and which have been used satisfactorily include: v

The mixed ethers may be incorporated in the W006. pulp at any stage in the production of dry sheet pulp from the wet fiber slurry. For treating the pulp, the compounds may be incorporated either in the bulk pulp before sheet formation or in the sheet at any stage of the drying as by spraying the pulp with an aqueous solution or dispersion. A most practical and convenient method of securing the incorporation of the mixed ethers prior to completion of drying is to incorporate the mixed ether in the refined wood pulp while it is on the sheet forming machine by means of sprays or a rotating roll. Such application may be made to the wet pulp web subsequent to removal of the mechanically removable water by pressing, or later at any stage while it is passing through the hot dryer rolls prior to completion of drying.

When pulp is dried in a conventional manner on hot dryer rolls, inactivation of the fibers is greatest on the surface of the sheets. Thus, if desired, the treatment of the pulp sheet with the compounds may be applied by spray or a rotating roll in such a manner that the mixed ethers are largely incorporated near one or both surfaces of the sheet. Thus application is made largely to those fibers which would otherwise have the greatest tendency toward inactivation. In any event there is produced a substantially dry sheet of pulp containing a mixed ether incorporated prior to completion of drying.

While theinvention will be most usually applied in the drying of the pulp on the sheet forming machine as described above, it may also be applied to the reactivation of the pulp fibers in a sheet which has been already dried at an elevated temperature. In such case the dried sheet pulp will have at least one or both surfaces treated with a water solution of a mixed ether, as by spraying, or the dried pulp will be completely treated by dipping. The sheet thus treated with a water solution of a mixed ether will be r e-dried using such heat as may be practically required. In such method of application it is believed that the reactivation is brought about at least in part by the rewetting of the sheet with the water and that one function of the mixed ethers is to prevent or minimize loss during the second drying of the improved activity obtained by the rewetting'operaion. Obviously,

however, where possible it-will be economically preferable to carry out the treatment with the mixed ethers during the original drying on the sheet forming machine so that rewetting and redrying will be unnecessary.

The eifective proportion of the mixed ethers incorporated in the wood pulp during the production of dry pulp from a Wet slurry or in any reactivation treatment is from 0.015 to 0.5% based on the weight of bone dry pulp. Above this range in general no additional advantages are obtained and there are disadvantages in that the pulp sheet will tend to become undesirably soft and dusty and will undesirably contaminate the end product from the pulp. The quantities which would be preferred in practice for treating pulp intended for acetylation will, however, frequently be considerably less than 0.5% and will depend both on the method of application and the economics. If essentially only the surfaces of the sheet are treated, less compound will be required for eifecting a given amount of improvement than if the whole sheet is treated. This is because only those fibers would be treated which would have the greatest tendency to become unreactive.

For pulp intended for viscose processing, it will generally be preferred to use somewhat lower quantities of compounds than that given as the maximum for pulp intended for acetylation. The preferred range for pulp intended for viscose use is from 0.015% to 0.2%. In general, quantities greater than this will not be required for the purposes of the invention and their use may give rise to certain disadvantages such as foaming in the viscose and difficulty in obtaining completely ole-aerated viscose which is absolutely necessary for satisfactory spinning.

We find that sheet wood pulp dried in the presence of the mixed others has markedly improved acetylation reactivity as compared with pulp dried in a conventional manner in the absence of these additives. This may be demonstrated by the following convenient and rapid laboratory test for comparing the aoetylation reactivity of samples of sheeted Wood pulp fibers:

Small specimens of the pulps to be examined are treated with a solution of the mixed ether or With distilled water and dried in a circulating oven at a selected controlled elevated temperature to dry them under comparable conditions. An accurately Weighed sample of 0.5 gram of this pulp is torn into small bits and placed in a 35 ml. vial. A flattened glass rod is placed in the vial through'a hole in the cap and the vial and sample set in a Water bath at 20 C. 1

The acetylating mixture is prepared by mixing 2.50 gms. H2804, 88.0 ml. acetic anhydride, and 175.0 ml. acetic acid. This mixture is unstable and should be freshly prepared every two days.

To the sample vial in the water bath 15 ml. of the acetylating mixture are added from a pipette. The pulp and acid are mixed with the glass rod, which remains in the vial. The vials are stored in the water bath and the mixing repeated every 15-20 minutes. It is important to include a standard sample with each group of unknowns and to handle and agitate all samples alike.

As the pulp samples are acetylated by the mixture they dissolve to a clear solution. The time required for this solution to take place, the relative clarity and residual undissolved fibers, and the relative appearance during the reaction time will indicate whether any of the samples is more or less reactive than the standard.

TABLE I Acetylation reactivity of acetate wood pulps treated with polyethenomy alkyl ethers Dis- Treated solving .Appear- Residual P 1111 CB With time, ancc Fibers hrs.

water only 6.5 clear-.. Mauy,largc. A 5 None. B 5.5 Few, small C 5 do Veryiew small. Southern Pine". wateronly 6 "do Many, large.

Do C 5 do Few, small.

1 A-dodecaethenoxy ether oilaury] alcohol; B-nonadecaethenoxy other of oleyl alcohol; C-Brij (commercially prepared polyethenoxy ether of lauryl alcohol) In the usual viscose process the sheets of wood pulp are first subjected to a steeping .step' to convert the cellulose to alkali cellulose-and the pressed sheets of alkali cellulose are then shredded to form a fluffy mass of fibers. The fluffy mass is xantha'ted, dissolved in dilute caustic soda and the solution commonly known as viscose filtered to remove undissolved fibers and gel-like materials and ripened to impart the desired properties for satisfactory spinning.

While highly refined wood pulps are advantageous in the viscose process for the production of high grade yarns of superior strength and color, the reaction of the shredded alkali cellulose from such pulps with carbon bisulfide is frequently incomplete. This impairment inthe xanthating activity of the shredded alkali cellulose in the viscose process may be due on the one hand to some damage to the fibers during, the shredding operation or on the other hand to incomplete comminution of the alkali cellulose sheet or to formation of compressed fiber bundles. This difiiculty in efiecting satisfactory comminution of the alkali cellulose from highly refined pulp without damage is overcome, in our invention, by carrying out the operation with pulp treated with the polyethenoxy alkyl ethers.

When the invention is practiced for effecting the hereinbeforementioned improvements in shredding'in the viscoseprocess, certain further economies are effected in the subsequent steps of xanthating, dissolving and filtering. In viscose solutions there i usually a certain amount of undissolved fibers and gel-like material due to the incomplete reaction of the cellulose with the carbon bisulfide during xanthation. Prior to spinning, the viscose solutions are filtered several times to remove these gels and undissolved fibers. In the event that the viscose solutions, contain excessive amounts of undissolved and partially dissolved fibers, filtration is an expensive operation. In such cases the filters become rapidly clogged and the filter media must be changed frequently in order that the viscose will pass through in a reasonable time. Frequent changing of the filter medi is expensive, not only as regards consumption of filter cloth but also in I view .of the very considerable amount of labor involved and also since a certain amount of visaccepts-- 9 T cosef lost every time. the filteriis opened up. Furthermore, when the viscose solutionscontain very large proportions of gel-like materiaL'filtration is usually not altogether satisfactory in that some of the smaller gel-like particles tend to pass through the pores of the cloth with adverse effect upon the spinning operation.

It has heretofore been the cose industry, when processing pulps which tend to yield viscose solutions high in undissolved material and having poor filtration properties, to minimize such dimculties by carrying out the xanthation with amounts of carbon bisulfide considerably in excess of that normally required. Use of excess carbon bisulfide is expensive and in addition' is technically undesirable in that it may adversely anect certain properties such as the ripening of the viscose and yarn characteristics. We have found that when processing highly purified pulps which would normally tend to'give poorly filtering viscose solutions, the addition of minute amounts of the polyethenoxy alkyl ethersuto the pulp so improves the shredding operation that the alkali cellulose subsequently reacts much more completely with carbon bisulfide and yields a viscose solution very free from undissolved and partially dissolved cellulose particles and having good filtration properties. This result can be accomplished not only without the use of excess carbon bisulfide, but in many cases satisfactory viscose solutions can be obtained using amounts of carbon bisulfide very substantially less than the amounts normally required.

When the polyethenoxy alkyl ethers are incorporated in the wood pulp, by the pulp manufacturer thereof, the pulp sheets come to the rayon manufacturer in a form calculated to secure the full advantages of the invention in the preparation and processing of the viscose into high grade rayon yarns.

While it is our preferred practice to incorporate the polyethenoxy alkyl ethers in the drying on the machine of the wood pulp, preferably a highly refined pulp containing not more than about 0.15% of ether-extractable material, for use in viscose the presence of the compound in the pulp sheets may be secured in any other appropriate manner. Moreover for use in viscose, the compound need not be incorporated in every sheet. It may also be added to only a portion or the sheet as for example in strips on the pulp sheets. However, for use in acetylation it should be noted it is necessary to incorporate the polyethenoxy alkyl ether prior to drying at elevated temperature and in a manner so that at least the surfaces of the pulp sheet are completely treated.

The following small scale laboratory test may be conveniently used to compare the reactivity of dry sheet pulp in the viscose process:

A bundle of 10" x 10" pulp sheets weighing approximately 650 gms. is steeped in caustic soda solution containing 18.5% NaOH and about 1.5% hemicellulose for 30 minutes at 30 C., and then pressed to a weight of 2.70 times the original weight'of pulp.

The pressed sheets of alkali cellulose are shredded 60 minutes at 30 C. At the end of the shredding, the alkali cellulose is analyzed for percent NaOH and percent cellulose, and the apparent density of the alkali cellulose is measured.

The shredded alkali cellulose is then placed in V gallon glass top fruit jars sealed with rubber rings andaged 24 to 48 hours at 3 C. under conditions predetermined to give viscose of about 35 seconds viscosity (time for practice in the vis- 10- fall 20 cm)" at the time it is subjected to testing.

The aged alkali cellulose is then xanthated in the glass Jars using 31% CS: based on cellulose in alkali cellulose and rotating the jars on rollers for minutes at 30 C. The xanthate is mixed with caustic soda and Water for minutes at 15 C. to give a viscose solution with composition 8.5% cellulose and 5.25% NaOI-I.

After standing 24 hours at 20 C., a filtration test is made on the viscose. In this filtration test a plugging value is determined by filtering through a standard cotton batting filter medium, taking rate measurement at increasing time increments.

The plugging value is calculated by extrapolation from these measurements as the amount of viscose which would pass through one unit of filter area when the filter would be completely plugged. The higher the plugging value the bet-- ter the viscose. Under the standard conditions of the test the plugging value therefore indicates the relative reactivity of the pulp sample proc essed.

A viscose-type wood pulp having an ether ex tract of 0.1 was tested by the above procedure after treatment with a solution of a polyethenoxy alkyl ether. The samples and the test observations are shown in the following Table II. The wood pulp sheets, dried on the manufacturing machine, were later treated by spraying with a water solution of the agent named and redried at 10 0.

TABLE II Reactivity of viscose wood pulp treated with a polyethenomy alkyl ether Temperature of g ggf Plugging Treat Drying Cellulose Value 01' Arter D 1; Viscose 'lreat ensl y r Untreated Control 0.149 440 100 0. 148 410 100 0. 132 860 B-nonadecaethenoxy ether of oleyl alcohol.

. When viscose rayon is delustered by incorporatmg a suitable opacifying agent in the spinning solution, usually an oil or a pigment such as titanium dioxide, it is necessary in order to get a uniform emulsifioation or dispersion of the agent throughout the body of .the viscose solution to use an emulsifying or dispersing agent. The treated pulp of the invention produces viscose with exceptionally good emulsifioation and dispersion properties which is quite remarkable in view of the small quantities of ethers used in the treatment of the pulp. The emulsifioation is characterized by the uniformity of size of oil particles so that the resulting viscose solution is substantially free from even small numbers of large oil globules which weaken the filaments on spinning. The treated pulp therefore gives special advantages not only in regard to the reactivity in the viscose process but also gives a viscose solution characterized by improved properties, as for example improved emulsifioation properties in the preparation of delustered rayon.

We claim:

1. As a new article of manufacture relatively dry refined wood pulp in sheet form having incorporated therein from 0.02 to 0.50 percent by weight based on the bone dry weight of the pulp A steel ball t 7 of a water-soluble mixed ether containing a poly- 11 ethylene oxide radical and an aliphatic hydrocarbon radical containing more than '7 carbon atoms.

2, An article of manufacture according to claim 1 in which the mixed ether contains a polyethylene oxide radical with from 8 to 50 ethenoxy residues and a normal primary aliphatic hydrocarbon radical with from 8 to 20 carbon atoms.

3. In the preparation of mechanically compacted pulp sheets dried at an elevated temperature and formed of refined pulp relatively low in ether extractable matter, the improvement which comprises adding at a stage prior to completion of drying from 0.02 to 0.50 percent by weight based on the bone dry weight of the pulp of a water-soluble mixed ether containing a polyethylene oxide radical and an aliphatic hydrocarbon radical containing more than 7 carbon atoms to minimize inactivation in producing the treated sheets.

4. In the preparation of mechanically compacted pulp sheets dried at an elevated temperature and formed of refined pulp relatively low in ether extractable matter, the improvement which comprises adding at a stage prior to completion of drying from 0.02 tov 0.50 percent by weight based upon the bone dry weight of the. cellulose of a mixed ether containing a polyethylene. oxide radical with 8 to 50 ethenoxy residues and a normal primary aliphatic hydrocarbon radical containing from 8 to 20 carbon atoms tominimize.

inactivation in producing the treated sheets-l PAUL HENRY SCI-E O SSER. 4 I

KENNETH n ssELL AY.

REFERENCES CITED The following referencesv file of this patent:

UNITED STATES PATENTS are. of record. in the

Claims (1)

1. AS A NEW ARTICLE OF MANUFACTURE RELATIVELY FRY REFINED WOOD PULP IN SHEET FORM HAVING INCORPORATIED THEREIN FROM 0.02 TO 0.50 PERCENT BY WEIGHT BASED ON THE BONE DRY WEIGHT OF THE PULP OF A WATER-SOLUBLE MIXED ETHER CONTAINING A POLYETHYLENE OXIDE RADICAL AND AN ALIPHATIC HYDROCARBON RADICAL CONTAINING MORE THAN 7 CARBON ATOMS.