US1808070A - Method of producing paper filled with alkaline filler - Google Patents

Description

Patented June 2, 1931 UNITED STATES PATENT OFFICE HAROLD R RAITON, or LAwRENoE, MASSACHUSETTS, ssIGNoR To .RAI'FOLD PROCESS CORPORATION, A conroaATIoN or MAssAcnUsETTs ifnrnon or rnomrcme rArnRrILLnn WITH ALKALINE FI LER No Drawing.

This invention relates to the manufacture of paper and more particularly to a method of producing paper filledwith alkaline filler. The principal object of my invention is to provide a method for the reduction,'elimination, prevention or alteration of foam in the manufacture of a substantially unsized paper filled with alkaline filler.

An important object of my invention is to improve machine operation in such manufacture, particularly as regards the dandy roll.

.Another object of my invention is to avoid the deterioration by alkaline filler of the effect of alum ,in a paper mix.

A further object of my invention is to avoid the deterioration in a substantially unsized paper filled-with alkaline filler of a precipitate of alum and an amount of rosin size in- ,suflicient toimpart a substantial degree of sizing to'the paper.

Y .-A further object of my invention is to I, avoid the deterioration in a substantially unsized paper filledwith alkaline filler of a precipitate formed from a soluble salt such as sodium silicate and a precipitant such asalum.

Afurther object of my invention is to provide a process of making substantially unsized paper filled with alkaline filler wherein alkaline filler. is added to the paper mix at such a point in the process that the time and intimacy of contact of the alkaline filler in.

the paper mix are materially limited.

A further object of my invention is to provide a process of making substantiallyunthe manufacture by a similar method of subby the additionof alum copending application Serial No.-

. Application filed November 24, 1928. Serial No. 32l, 75,3.

sitfintially unsized paper filled with alkaline As set forth in my c'opending ap lications Serial Nos. 304,171 and 304,174, oth filed September 5, 1928', I have found that, in the manufacture of substantially unsized papers filled'with alkaline filler it is highly desirable in order, to improve the runnin of the,

paper on the machine and in order to improve the quality of paper made to add alum atthe wet end of the papermachine, or to add rosin size in the beater, precipitate it with alum, and thereafter restore the effectiveness of the precipitate by a further addition of alum-at the wet end of the paper machine, or to add rosin size in the beater followed by the addition of alum at the wet end of the paper machine, in either of the two latter cases the size used being'in an amount insuflicient to impart a substantial degree of sizing to the paper. I

Likewise in my copending a plications Serial Nos. 319,7 19-and 319,720 lmth filed November 15, 1928, Idisclose and claim a method of incorporating soluble material such as sodium silicate into paper, either by the addition of sodium silicate in thebeater where it is precipitated as by alum, and the effective.

ness of the resulting precipitate restored-as by a further quantity of alum added at the wet end of the paper machine, or by the Eddl'.

tion of sodium silicate in the beater followed f at the wet end of the pa er machine.

. n the latter mentioned four copending a plications the presence of alkaline filler in t e relatively concentrated fibrous mix is recognized as being the cause of the necessity of adding alum at-the wet end of the paper machine in order to achieve the various results desired, and it is b this step that the desired effects are capa le of accomplishe ment. I have discovered, however, that these eflfects can be equally well attained by addin the alum, or rosin size, in an amount insu ficient to impart a substantial degree of sizing to the paper, and alum, or sodium silicate and alum, to the relatively concentrated fibrous mix as'in the beater, and then adding the alkaline filler at the wet end of the paper madamaging to these effects.

chine. By this method in the one case a substantially foam free paper and good machine operating conditions can be obtained, and in the other the beneficial effect of sodium silicate-alum precipitate in the stock and paper made therefrom can be'retained.

I have found that the .damaging or destructive efi'ect-of the alkaline filler to the above referred desired effects is a function of the time of contact of the alkaline filler with the constituents of the mix and also of its intimacy of contact with these constituents. I have also discovered that the intimacy of contact of the alkaline filler with the constituents of the mix resulting from high concentrations and/or agitation is particularly I have further found that if the time ofcontact be greatly reduced over that which normally would obtain in the ordinary papermaking process, and the conditions made. such that intimacy of contact is also greatly reduced, the tendency for the alkaline filler to 'in ure or destroy these effects is greatly reduced, if not entirely eliminated. s

The method which I employ consists substantially in adding an alkaline filler at a pointinthe p-apermaking process where the intimacy ofcontact and thetimeof contact of the alkaline filler and the constituents of the mix will be at a minimum. In accordance with my invention, I may add the alkaline filler at a point where the mix is still in a relatively concentrated condition provided that the time of contact in such condition is to be relatively short, but the preferred procedure is to add the alkaline filler at or subsequent to the point where the mix is diluted preparatory to its delivery to the web-forming device, i. e., at the wet end o f the paper machine. From this point. to the point of web formation the time of contact is short and the intimacy of. contact is practically at a minimum owing to the high dilution.

Inasmuch as the white water from a paper machine running on a stock containing alkaline filler contains a considerable quantity of this filler, it is preferable not to use such white watereither in the beater, the beater chest, at the Jordan, or in the machine chest, .as in any of these places the constituents of the mix in a relatively concentrated condition will come into contact with the alkaline filler for a relatively longperiod of time, and this will tend to injure or destroy the effects de sired. The exception to this case is where the white water to be employed has been clarified or filtered so that there is a" negligible quantity of the alkaline filter present in such purified water, and in this case such water may be used in the places which are stated above to be places at which it is preferable notto use the unpurified white water.

In the preferred practice of my invention I add to the beater or other similar machine,

all thefibrous'materials to be used, with the exception of those fibrous materials coming under the definition of alkaline filler hereinafter set forth and such fibrous material. as is present in the stock recovered from the white water; I also add to the beater alum, or rosin size, in an amountinsufiicient to impart a sub stantial degree of sizing to the paper, or sodium silicate and alum, or both rosin size and sodium silicate and alum. In any event I prefer to have an excess of alum present. Filler other than alkaline filler may be added ifkdesired, as well as coloring matter or the li e.

After the usual treatment in the beater, the mix is preferably passed through the beater chest, Jordan, and machine chest in the customary manner. This procedure and/or order of steps is not essential, and may vary considerably as will be apparent to one skilled in the art. The mix, still in relatively concentrated form, is now at the point where it is ready for dilution preparatory to delivery to the Web-forming end of the paper machine.

"As indicated above-all water used for dilution up to this point in the process is preferably either fresh water, or white water which has been purified so that it contains only a negligible amount of alkaline filler. However, at this point, untreated white water as obtained from the paper machine may be used as diluting water. During dilution at this point,-or subsequent thereto, the alkaline filler preferably in aqueous suspension is added continuously, due care being taken that adequate mixing is insured.

Accordingto the definition of alkaline filler hereinafter set forth, this. term includes fibrousmatter in combination with the mineral alkaline filler itself. In such cases the fibrous material must be properly "broken down in a suitable apparatus before addition as will be apparent. It may be refined separately if desired, but ordinarily this will be unnecessary as such fibres have already been once refined .in the previous papermaking procedure.

Moreover, the stock recovered from the white water contains alkaline filler and this stock preferably should not be added at a point prior to the point of dilution preparatory to delivery to the web-forming end of the paper machine as the content of alkaline fillerwould tend to injure or destroy the effects desired because of the relatively prolonged contact in a relatively concentrated condition.

Moreover, the recovery of the stock from the white water should take place as soon as possible after the production of the white water and such stock should preferably be returned promptly to its point of reuse so as to afford as little time as possible for contact between the alkaline filler and the constitu- 9 or the sulphate.

ents of the mix which have accompanied itin 7 settling system, a convenient way is to add the recovered stock directly from this settling system continuously at the mixing box at the point of dilution of the stock. If the stock venient method is to divert part or all of the stream-of concentrated fibrous stock just be fore its delivery to the mixing box, and utilize this as sweetener stock, delivering it after it has so functioned to the mixing box. In this way the stock containing the alkaline filler derived from the white water remains for only a brief interval in concentrated conldition, and is quickly diluted at themixing Of course-it is also possible to use the pro--' cedure of adding alkaline filler at the wet end ticing my invention is:

of the paper machine to a paper mix in which no alum or other material adversely afiected by alkaline filler is present. In such case of course this method of adding alkaline. filler would be chiefly of value in increasing the beater capacity inregard to fibrous constituents, and also in permitting beating to be accomplished more effectively, as the mechanicallyprotecting action of the fibre by the filler would be avoided.

Instead of rosin size, which may be referred to as sodium resinate. and which may therefore be termed an alkali metal sa1t, any

other size is suitable which is used in conjunction with a size precipitant as alum. One example of such a size is a soap, such as an oleate. Another is a wholly or partially saponified wax, such as beeswax.

Instead of alum, for example, as a precipitant for the rosin size, I may use acidic 'material such as sulphuric acid, or sodiumbisulphate (NaHSOQ or other salts of aluminum, but from the standpoints of efiiciency and cost I prefer alum. In the case of the use of alum as a precipitant for sodium silicate, I may also substitute in addition to the above, ammonium salts such as the chloride 7 It is thus apparent that other acidic material as sulphuric acid," or other metallic salts as sodium bisulphate, or salts of aluminum other than alum, or in certain cases ammonium salts'are equivalents of alum in the practice of my invention.

3 Instead of sodium silicate, I may use sodium stannate, or any of the other inorganic alkali metal salts with a pH:value greater than 7 .0, which are precipitable by material which depresses their hydroxyl ion concentration.

An illustrative furnish suitable for prac- Materials aaa'a beam" l Pounds Fibrous furnish (air dry basis), e. g. equal parts of sulphite pulp, soda Alkaline filler (bone. dry basis), e. g

calcium carbonate Pounds magnesium hydroxide 300 Another illustrative furnish is M aterz'al added in beater I Pounds Fibrous material (air dry basis), e. g.

equal parts of sulphite and soda pulps 1700 Rosin size a 6 Inorganic alkali metal salt, e. g.

B. sodium silicate 30 Alum V 60 Material added proportionately and continuoasly 0n dilution a j Pounds Alkaline filler (bone dry basis), e. g. calcium carbonate magnesium hyd-1'oxide i.

It is to be understood that the above furnishes are illustrative onlyand not limiting, as I have found that my 1nvent1on may be practiced with'a wide variety ofingredients in the furnish, with widely varymg proporpulp and old paper stock 1700 Alum .L Material added proportionately and eontz'n'aously on dilution Pounds Alkaline filler (bone dry basis), e. g. calcium carbonate magnesium hy droxide 300 Another illustrative furnish is:

Material added in beater 1 Pounds Fibrous furnish, (air dry basis), e. g. equal parts ofsulphite pulp, soda pulp and old paper stock 1700 Rosin size 6 Alum a 50 Material added-proportionately and continuously on dilution I Pounds Alkaline filler .(bonez. dry basis), e. g.

calcium carbonate magnesium hydroxide 300 Another illustrative furnish is:

Material added in beater Pounds Fibrous material (air dry basis), e. g. equal parts of sulphite. and soda -pul 1700 Inorganic alkali metal salt, e. g. 60 B. sodium silicate 30 Precipitant, e. g.. alum 45 tions of the several ingredients to one another, for making a wide variety of grades of paper.

.As will be apparent from the previous detailed description it is very desirable to be able to utilize in a paper mix both an acidic constituent, such as alum or a small amount of precipitated sodium resinate accompanied usually by excess alum, and a substantially water insoluble alkaline constituent, such as an alkaline filler. These-two constituents, however, under conditions obtaining in the ordinary method of paper manufacture, react chemically upon one another so that the effect of the acidic constituent is deteriorated if not completely destroyed. The primary object of this invention is to so adjust conditions as to substantially prevent the acidic constituent from reacting chemically with the alkaline filler and thus to preserve the desired effect of the acidic constituent in the papermaking mix. This result is attained as indicated above by adjusting conditions so that the alkaline filler is brought into contact with the paper mix containing the acidic constituent under circumstances which tend to prevent the chemical reaction between the alkaline filler and the acidic constituent, that is, under conditions favoring the minimizing of the time and intimacy of contact of the constituents of the mix, or specifically, at the wet end of the paper machine. It is thus obvious that conditions are adjusted to prevent rather than to obtain a chemical reaction between the acidic constituent and the alkaline filler.

A chemical reaction between acidicfmaterial and alkaline material which is to result in a final state which is substantially in the vicinity of neutrality obviously requires the employment of substantially chemically equivalent proportions of the two materials.

Thus if it were desired to effect such arechemically equivalent proportions of calcium carbonate and alum are used, but rather the amount of alkaline filler used is far in excess of the chemical equivalent of the alum used. This is made clear by reference to the illustrative furnishes given above. In these furnishes 40 to lbs. of alum and 300 lbs. of alkaline filler, in this instance calcium carbonate magnesium hydroxide, are employed. In some of the formulas, a considerable portion of the alum is used up in precipitating size and/or sodium silicate; hence for the purpose of this calculation it can be assumed that in the illustrative furnishes there would be present aproximately 40 to 50 lbs. of free, i. e. uncombined alum. Using the figure of 50 lbs. alum, this wouldgive therefore a ratio of alkaline filler, in this case calcium carbonate magnesium hydroxide, to uncombined or free alum of 17.4 to 2.9. Thus it is apparent that in this case there is present 17.4 times the amount of alkaline filler which would be the chemical equivalent of the alum, that is, 17.4 times theamount of alkaline filler necessary to react completely with the alum were conditions provided favorable for the consummationof reaction between the two.

It is thus apparent that I use an amount of alkaline filler far in excess of the chemical equivalent of alum employed. Thus even were conditions such that the alkaline filler were acted upon bythe alum, as is substantially not the case in my invention, under such conditions the unacted upon residual alkaline filler would only be slightly less in amount than that originally added and thus substantially the same amount as added (less, of course, the losses through the machine wire into the white water) would find its way into the paper. While I have not limited my invention to the addition of any definite amount of alkaline filler in relation to the total furnish, the examples of illustrative furnishes given indicate that the proportion of alkaline filler normally present constitutes a substantial percentage of the total furnish, and thus the paper produced by my process would contain a substantial percentage of alkaline. filler and would be what is considered as a paper filled with alkaline filler- .In order to compute the amount of alkaline filler that would be chemically equivalent in amount to the alum, it is only necessary to know how much alum is ordinarily used. Whereas I have not limited my invention to the addition of any definite amount of alum in relation to the total furnish, it is apparent from the examples of illustrative furnishes above, that the propor tion of free alum used on the total furnish normally runs in the vicinity of several percent. If, for example, I use 2 of free alum on the total furnish, which is approximately the amount given in the illustrative 4 (such as would be present if the alkaline filler to quantities of alum somewhat larger than were used in amounts chemically equivalent that given above) would be wholly inadeuate to impart any'substantial degree of filling tb the paper made with such furnish. Indeed in such case analytical procedures of fairly exact degree ofrefinement would have to beemployed to detect the presence of such minute quantity of alkaline 'filler that might find its way into the paper to distinguish it with certainty for instance from the small amounts of inorganic constituents naturally occurring in the fibres, such as sulphite or soda fibres. On the other hand the filler "in paper ordinarily known as filled paper, suchas that to which my in vention is directed, is present in so much larger amount that the normal inorganic constituents of the fibre are negligible in proportion thereto, and ordinary ashing of the paper by ignition gives a result indicating the filler content sufliciently accurately for practical paper millpurposes.

It is thus clearlyevident that I add alkaline filler at the wet end of the paper machine to prevent the chemical reactionbe tween the alkaline filler and the acidic constituent of the mix, and'therefore my invention is completely differentiated, from any papermaking procedure wherein alkaline filler would be added to a paper mix in proportion substantially chemically equivalent to the acidic constituent thereof, for chemically reacting purposes. L i

It is to be noted that in any papermaking procedure where it would have been .desired to add alkali for chemically reacting purposes at the dilute stage, for example for neutralizing the acidic content of a paper mix, 7 a proportion of alkali chemically equivalent to that of the acidic content would have been employed. This chemical equivalence would according to the prior knowledge of the art have been a necessary and limiting feature of such procedure. Were soluble alkali in excess of the chemical equivalent? of the acid added, the mix would have been alkalinized. No distinction would have been made according to prior knowledge between soluble and substantially insoluble alkali. According to known prior art, were substantially insoluble alkali used as a substitute for the soluble alkali, it would have been subject to the same limitationsas to quantity employed, and. were there used an amount of insoluble alkali, for example alkaline filler, inexcess of that chemically equivalent to the acidic content of the mix, the prior art would have taught that there would also have resulted an alkalinizing of the mix, thereb defeating the neutralizing purpose for whic the alkali would have been added. It was not until-the discovery herein disclosed that it was realized that an amount of alkaline filler greatly in excess of the chemical equivalent of the acidic constituent could be added ing or substantially deteriorating the effect of the acidic constituent in the mix. Hence the present invention distinctly difi'erentiates from any chemically reacting, i. e. neutralizing practice, as the addition ofalkali at the dilute stage in such practice would necessarily have been confined by previously existing knowledge to the addition of proportions at the dilute stage without-thereby destroychemically equivalent to the acidic constituent of the mix.

It is also clear that my invention is directed to the manufacture of paper filled-in .substantial degree with alkaline filler, and is thus completely differentiated from any papermaking procedure in which alkaline filler would be added in proportion substantially chemically equivalent to the acidic constituent, as in the latter case a commercially wholly inconsequential amount ofalkaline filler, if indeed any quantity at all detectable by ordinary analytical procedure, would be incorporated into the paper, and such paper could not be considered in the ordinary papermaking interpretation of the words as paper filled with alkaline filler.

When I use the expression alkali metal,

I mean 'to include the hypothetical alkali metal ammonium (NH J ,By the term alkaline filler I mean filler which when agitated in contact with freshly boiled distilled water, say for an hour, will impart a pH value to such water greater than 7.0, that is, which will be on the alkaline. side of the neutral point. Among fillers included in this group may be mentionedcalcium carbonate, of which lime mud from the causticizing process is one form; calcium carbonate magnesium basic carbonate employed in the paper disclosed in my U. S. Patent No. 1,595,416, issued August 10, 1926; calcium carbonate magnesium hydroxide disclosed in my U. S. Patent No. 1,415,391, issued May 9, 1922; and other substantially water insoluble normal or basic carbonates of alkaline earth metals (which expression is herein intended to include magnesium), or com.- pounds, double salts, or physically associated mixtures of these with one or more other.

terial such aspaper coating constituents or the like containing one or more compounds of the character referred to, such as old papers or similar papers, broke, or the like.

When I use the word paper herein, I use it in the broad sense to include products of manufacture of all types and of all weights and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are capable of being produced on \a Fourdrinier, cylinder, or other forming, felting, shaping or molding machine.

By the term wet end of the paper machine I-intend to include those instrumentalities employed in paper manufacture by which and/or in which a relatively concentrated paper mix is diluted, and treated, conveyed or fed up to the point of web-formation such as the mixing box, regulating and proportioning devices,'rifllers, troughs, screens, head boxes,inlets, and the like, including also instrumentalities used in the white water cycle.

While I have described in detail the preferred embodiment of my invention, it is to be understood that the details of procedure, the proportions of ingredients, and the arrangement of steps may be widely varied without departing from the spirit of my invention or the scope of the subjoined claims.

I claim:

1. That step in the method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount sufiicient to impart a substantial degree of filling to the resulting paper, to fibrous material under conditions favoring the minimizing of the time of contact of the alkaline filler and the fibrous material.

2. That step in the method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount sufficient to impart a substantial degree of filling to the resulting paper, to fibrous material -under conditions favoring the minimizing of the time and'intimacy of contact of the alkaline filler and the fibrous material.

3. The method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding to fibrous material previously mixed with alum alkaline filler, in an amount sufficient to impart a substantial degree of filling to the resulting paper under conditions favoring the minimizing of the time of contactof the alkaline filler and the fibrous mix, and thereafter making paper therefrom.

4..The method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding to fibrous material.

previously mixed with alum alkaline filler, in an amount suflicient to impart a substantial degree of filling to the resulting paper,

under conditions favoring the minimizing of the intimacy and time of contact of the alkaline filler and the fibrous mix, and thereafter making paper therefrom.

5. The method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount sufficient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to fibrous material previousl mixed with acidic material, and therea er making paper therefrom.

6. The method "of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount sufficient toimpart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to fibrous material previously mixed with a salt of aluminum, and thereafter making. paper therefrom.

7. The method of manufacturing a substantially unsized paper-filled with alkaline filler comprising adding alkaline filler, in an amount sufficient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to fibrous material previously mixed with alum, and thereafter making paper therefrom.

8. The method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount sufiicient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to a paper stock which has been previously mixed with a precipitant for an ingredient of said stock.

9. The method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount suflicient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to fibrous material previously mixed with soluble material and a precipitant therefor, and thereafter making paper therefrom.

10. The methodof manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount suflicient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to fibrous material previously mixed with alkali metal salt and a precipitant therefor, and thereafter making paper therefrom.

11. The method of manufacturing a substantially unsized paper filled with alkaline filler comprisingadding alkaline filler, in an amount suflicient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to fibrous material previously mixed with alkali metal salt comprising size, in an amount insufficient to' a precipitant therefor, and thereafter makwet end of the paper machine to ing paper therefrom.

12. The method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount sufficient to impart a substantial degree of filling to the resulting paper, at the brous material previously. mixed with alkali metal salt comprising rosin size, in an amount insufficient to produce a substantial degree of sizing, and a precipitant therefor, and thereafter makingpaper therefrom.

13. The. method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount sufficient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to fibrous material previously mixed with an inorganic alkali metal salt with a'pH value greater than .7 .0, which is precipitable by material which depresses its hydroxyl ion concentration, and alkali metal salt comprising size,

in an amount insufficient to produce a substantial degree of sizing, and precipitant for said alkali metal salts, and thereafter making paper therefrom.

14. The method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount'suificient to impart a substantial degree of filling to the resulting pa er, at the .wet end of the paper machine to brous material previously mixed with an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by material which depresses it hydroxyl' ion concentration, and alkali metal salt comprising rosin size, in an amount insuificient to produce a amount suflicient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to fibrous material previously mixed with sodium silicate and size, in an amount insufficient to produce a substantial degree of sizing, andprecipitant for said sodium silicate and said size, and thereafter making paper therefrom..

16. The method of manufacturing a substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount suflicient to impart a substantial degree of filling .to the resulting paper, atthe .wet end of the paper machine to fibrous material previously mixed with sodium silicate and rosin size, in an amount insufiicient to produce a substantial degree ofsizing, and precipitant for said sodium silicate and said size, and thereafter making paper therefrom.

gree of "filling to the resulting paper, at the wet end of the paper machine to fibrous material previously mixed with sodium silicate and rosin size, in an amount insufiicient to produce a substantial degree of sizing, and acidic material, and thereafter making paper therefrom.

18. The method of manufacturing a substantially unsized aper filled with alkaline filler comprising a ding alkaline filler, in an amount suflicient to impart a substantial degree of filling tothe resulting paper, at the wet end of the paper machine to fibrous material previously mixed with sodium silicate and rosin size, in an amount insuflicient to produce a substantial degree of sizing, and asalt of aluminum, and thereafter making paper therefrom.

19. The method of manufacturing a substantially unsized aper filled with alkaline filler comprising a ding alkaline filler, in an amount suificient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to fibrous ma terial previously mixed with sodium silicate and rosinsize, in an amount insulficient to produce a substantial degree of sizing, and alum, and thereafter making paper therefrom.

20. That step in the manufacture of substantially unsized paper filled with alkaline filler comprising the addition of alkaline filler to fibrous material at the wet end of the paper machine in an amount sufiicient to impart a substantial degree of filling to the resulting paper.

21. That step in the manufacture of substantially unsized paper filled with alkaline filler comprisingthe addition of alkaline filler consisting of al aline earth metal compound to fibrousmaterial at the wetend of the paper machine in an amount sufficient to impart a substantial degree of filling to the. resulting paper.

22. That step in the manufacture of substantially unsized paper filled with alkaline filler comprising the addition of alkaline filler consisting of calcium carbonate to fibrous material at the wet end of the paper machine in an amount suflicient to impart a substantial v end of the paper machine in an amount sufficient to im art a substantial degree of filling to the resu ting paper.

24. That step in the manufacture of substantially unsized paper filled with alkaline filler comprising the addition of alkaline filler consisting of calcium carbonate magnesium hydroxide to fibrous material at the wet end of the paper machine in an amount sufficient to impart a substantial degree of filling .to the resulting paper.

25. The cyclic procedure in the method of making substantially unsized paper filled with alkaline filler, comprising the addition of alkaline filler to fibrous material at the wet end of the paper machine in an amount sufficient to impart a substantial degree of filling to the resulting paper, and the returning of the material recovered from the white water to the Wet end of the paper machine.

26. The method of producing substantially unsized paper filled with alkaline filler comprising adding alkaline filler, in an amount suflicient to impart a substantial degree of filling to the resulting paper, to the paper .mix at a point not in advance of that at which the concentrated stock is ready for dilution.

tial degree of filling-to the resulting paper, at the wet end of thepaper machine to a fibrous. mix to which a metallic salt has been previously added, and thereafter making paper therefrom.

In testimony whereof I aifix my signature.

HAROLD ROBERT RAFTON.

27. The method of producing a substantially unsized paper filled with alkaline filler, comprising adding alkaline filler, in an amount suflicient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine to a fibrous mix to which a metallic salt has been previously added, and thereafter making paper therefrom.

28. The method of producing a substantially unsized paper filled with alkaline filler,

comprising adding alkaline filler consisting of alkaline earth metal compound, in an amount sufficient to impart asubstantlal degree of filling to the resulting paper, at the. wet end of the paper machine to a fibrous mix to which a metallic salt has been previously added, and thereafter making paper 4 therefrom.

29. The method of producing a substantially unsized paper filled with alkaline filler,

comprising adding alkaline fillerconsisting of calcium carbonate, in an amount sufficient to impart a substantialdegree of filling to the resulting paper, at the wet end of the paper machine to a fibrous mix to which a metallic salt has been previously added, and thereafter making paper therefrom.

30. The method of producing a substantially unsized paper filled with alkaline filler, comprising. adding alkaline filler consisting of calcium carbonate and magnesium compound, in an amount suflicient to impart a substantial degree of filling to theresulting paper,.at the wet end of the paper machine to a fibrous mix to which a metallic salt has been previously added, and thereafter make ing paper therefrom.

31. The method of producing.a substantially unsized paper filled with alkaline filler, comprising adding alkaline filler consisting of calcium carbonate magnesium hydroxide,

in an amount sufficient to impart a. substan-