US1803642A - Paper product and method of making the same - Google Patents

Description

Patented May 5, 1931 UNITED STATES PATENT OFFICE HAROLD ROBERT RAFTON, OF LAWRENCE, MASSACHUSETTS, ASSIGNOR TO BAFI'OLD PROCESS CORPORATION, A CORPORATION OF MASSACHUSETTS PAPER PRODUCT AND METHOD OF MAKING THE SAME No Drawing.

, This invention relates to the manufacture of paper and more particularly to an improved sized paper containing a carbonate filler and to a method of making the same.

The principal object of this invention is to provide a sized paper made with a carbonate filler in such manner that deterioration by thecarbonate filler of the sizing agent or agents employed is substantially avoided.

An important object of this invention is to provide a simple and efiicient process of making an improved sized paper wherein rosin size and alum are employed in sizing the paper mix and wherein a carbonate filler is added to the sized paper mix when the latter is in relatively dilute condition.

Another object of this invention is to provide a process of making sized paper wherein a carbonate filler is added to a sized paper mix at such a point in the rocess that the time of contact between the car onate filler and the sized paper mix is materially limited.

A further object of this invention is to provide a process of making sized paper wherein a sized paper mix is treated with a carbonate filler in such manner that there is a minimum of intimacy of contact of the sized paper the like at a dry solid content of approximately 5 per cent. or slightly higher, and are subjected to a beating treatment in the beater, the amount of such treatment depending upon the type of paper which is to be made. The paper mix is then ordinarily discharged from the heater and introduced into a container commonly called a beater chest, additional water usually being added. Thereafter the mix is pumped from the beater chest to a suitable refining engine, usually Application filed September 5, 1928. Serial No. 304,167.

a jordan, at a dry solid content of approximately 4 per cent. In common practice the mix is usually diluted somewhat by the addition of water, and the diluted mix is ordinarily conducted from the jordan to another container commonly known as a machine chest. From the machine chest the mix is pumped to a point near the web-forming end of the paper machine where it is largely diluted with water, water being added ordi-' tional amounts of water are usually added in the form of sprays or otherwise. This exact procedure is not always followed but in some instances is modified in accordance with the type of paper being made. For example, in the manufacture of certain types of paper, the heating process is almost or entirely dispensed with, the ingredients of the stock being merely mixed prior to jordaning. In some instances the step of refining or jordaning may be partially or wholly dispensed with. Moreover, the arrangement of the chests in respect to the mechanical treating apparatus is not in all cases precisely as described above.

The time consumed from the point of mixing the ingredients in relatively concentrated state up to thew-point where the stock is to be diluted for delivery to the web-forming end of the machine is relatively long in comparison with the time during which the stock exists in dilute condition prior to its delivery to the web-forming end of the paper machine. The length of time during which the mix remains in a relatively concentrated condition may vary, of course, according to conditions, but it may be anywhere from as little as 15 or more minutes, as in certain extreme cases, upto a matter of a number of hours. On the other hand, the time during which the mix exists in a dilute stage prior to its delivery to the web-forming end of the machine is in some cases a matter of only a few seconds and ordinarily not over a minute. Even under extreme conditions the time would never be in excess of 5 minutes.

In many instances the water supplied to the heater and also the water employed for dilution at the jordan as well as for the final dilution of the mix before delivering to the web-forming end of the paper machine consists in whole or in part of white water by which term is meant to be included all efilucuts from the web-forming end of the pa 7 or machine. It will be apparent therefore t at this water functions cyclically in the process and that there may be reintroduced into the earlier stages of the process part of the material Which was derived from the web-forming stage of the process, such material being returned through the medium of the white water.

Moreover in modern papermaking practice there is a tendency to reclaim the ingredients contained in the white water, sometimes merely from that portion of it which is in excess of that which can be or is to be used cylically in the process, or sometimes from a portion or from all of that which is to be used cylically, or both, by subjecting the white water to some suitable procedure, as filtration, such for instance as deckering or actual passage through a filtering machine, or sedimentation or the like, whereby passing out the substantially purified aqueous efliuent to waste, or for further use in the pulp or papermaking process, with the simultaneous return of the recovered material to the papermaking process. In some installations this recovered material may be returned to the beater, while in others it may be returned to the beater chest, machine chest, or other point in the process if desired.

It will therefore be apparent that independent of the exact type of apparatus and procedure employed, the following operations are normally employed in' the papermaking process: the mixing of the ingredients in relatively concentrated form; their contact in such concentrated form for a relatively long period of time; their subsequent dilution to a concentration suitable for delivery to the web-forming end of the paper machine; their remaining in such dilute condition-a. relatively short period of time; and the recontacting of the mixture of the ingredients prior to its delivery to the webforming end of the paper machine with the cylically returned white water and/or material recovered therefrom. Under these conditions, where carbonate fillers have been employed in the papermak'ing process, it has been found in some cases that the sizing effect has been appreciably affected, or more commonly that the sizing efiect has been completel destroyed.

Although the practical sizing results of the use of alum and rosin size in ordinary papermaking practice have been known for a long period of time, nevertheless there is as yet no unanimity of pinion as to the exact chemistry of the sizing process. Some workers in this field assert that the sizing is due purely to the adsorption of the rosin from the sizing material by the cellulose fibre and the fixing of it thereon by the oppositely charged aluminum compound. Others maintain that a precipitate of aluminum resinate i responsibe for the sizing, and still others hold that the free rosin in the size is the major or entire sizing factor. Inasmuch as there is no generally accepted view as to the chemistry of sizing. it is difficult to explain chemically the exact effect of carbonate fillers on rosin sizing. However, whatever may be the reason which theory may assign for this effect, the actual results obtained in some cases where carbonate fillers have been employed are as described in the preceding paragraph.

As a result of careful experiments I have discovered that the damaging or destruction of the sizing by the carbonate filler is a function of the time of contact of the carbonate filler with the material constituting the sizing and also of the intimacy of contact of these constituents. I have also discovered that the intimacy of contact of the carbonate filler with the material constituting the sizing resulting from high concentrations and/or agitation is particularly deleterious to the sizing. I have further discovered that it the time of contact be greatly reduced over that which normally would obtain in the ordinary papermaking process, and the conditions be made such that intimacy of contact is also greatly reduced, the tendency for the carbonate filler to injure or destroy the sizing is greatly reduced, if not entirely eliminated, and I have devised a method whereby these discoveries may be practically applied to paper mill operation and sized carbonate filled papers be reliable produced thereby.

The preferred method which I employ consists substantially in adding a carbonate filler at a point in the papermaking process where the intimacy of contact and the time of contact of the carbonate filler and the sized fibre will be at a minimum. It should be here stated,of course, that the material constituting the sizing is ordinarily considered to be deposited on the fibre, and fibre having this deposit thereon is termed sized fibre. In accordance with my invention, I may add the carbonate filler at a point where the mix is still in a relatively concentrated condition provided that the time of contact is to be relatively short at that point, but the preferred procedure is to add the carbonate filler at or subse uent to the point where the mix is diluted for delivery to the web-forming end of the paper machine. From this point to the point of web formation the time of contact is extremely 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 carbonate filler contains a considerable quantit of this filler, it is preferable not to use sue white water either in the beater, the beater chest, at the jordan, or in the machine chest, as in any ofthese places the sized'fibre will come into contact with the carbonatefiller in a relatively concentrated condition and for a relatively long period of time, and this will tend to in ure or destroy the sizing. 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 carbonate filler 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 not to use the unpurified white water.

Moreover, the stock recovered from the white water contains carbonate 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 carbonate filler will tend to injure or destroy the sizing because of the relatively prolonged contact in a relatively concentrated condition, which addition at a point prior to this would bring about. 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 carbonate filler and the material constituting the sizing which has accompanied it in the white water.

In the preferred practice of my invention I add to the beater or other similar or mixing or compounding or disintegrating or treating machine, all the fibrous materials, with the exception of those fibrous materials coming under the definition of carbonate filler hereinafter set forth and such fibrous material as is present in the stock recovered from the white water, and then add a suitable sizing agent, such as rosin size, and a size precipitant, such as alum. In order to secure suitable sizing in the finished paper I employ sufficient size and size precipitant to size adequately the entire quantity of fibre and filler which will be present in the final paper, which amounts of size and size precipitant will stherefore be somewhat more than if I were merely adding sufficient to size the fibres in the beater. Under s'omeconditions, as for instance when the time of contact with the carbonate filler is to be greater than the minimum here proposed as preferable, I may add somewhat more size and size precipitant and/or may increase the proportion of" the size precipitant to the size present.

It is to be understood that'I do not restrict myself to the above order of the addition of the fibre, size, and size precipitant in the beater since I may use any order of addition which is suitable in papermaking practice. Furthermore I may add the ingredients in one or more parts or steps at any point prior to'the addition of the carbonate filler. For example, as is sometimes customary in papermaking practice where there is an ob'ectionable presence of hard water, I may rst add part of the size precipitant such as alum to the fibre and water to render harmless to the size the injurious ingredients in thehard Water, and thereafter add the size followed subsequently by the remainder of the size precipitant. Furthermore, fillers of types other than carbonate fillers may be also added in the beater if it be desired to have them present in conjunction with the carbonate fillers in the paper, as well as coloring materials and other substances which are normally added in the papermaking process.

After usual treatment in the beater the mix is preferably passed through the beater chest, jordan, and machine chest in the usual and well known manner. 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 carbonate filler. However, at this point antreated white water as obtained from the paper machine may be used as diluting water. During dilution at this point, or subsequent thereto, the carbonate filler is added continuously, the precaution being taken that adequate mixing of the carbonate filler, white water, other water if added, and the relatively concentrated mix coming from the machine chest is assured. A separate mixing box may be provided if desired, but under ordinary machine practice this is unnecessary, as there is usually adequate provision made to insure the thorough mixing of the relatively concentrated mix with the diluting water;-and even if the carbonate filler be Tadded at a subsequent point in the process the screens of the paper machine will effect a very thorough mixing. If, however, the carbonate filler is added actually at the headbox or inlet of the machine subsequent to the screens then care should be taken that proper distribution and mixing of the ingrefiller hereinafter set forth this term includes fibrous matter in combination with the mineral'earbonate 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 even be refined separately if desired, but ordinarily this will be unnecessary as such fibres have already been once refined in the previous pa ermaking procedure.

- Rn illustrative furnish which advantageously may be used in practicing my invention is as follows:

Materials added in beater Fibrous furnish, e. g. sulphite and soda pulps 1700 Size, e. g. rosin size 60 Size precipitant. e. g. alum MateH'aZ added to min. pmpm'f-iorazely and continuously on. dilution Pounds Pounds Carbonate. filled, e. g. Calcium carbonate magnesium hydroxide I 300 Another illustrative furnish is as follows:

Materials added in beater Pounds Fibrous furnish. e. g. sulphite and soda pulps 1530 Size, e. g. rosin size 60 Size preci itnnt. e. g. alum (Al=( 0.) -,.18H O) 90 Materz'ais added proportionately and continuously on dilution Pounds "Broke", e. g. fibrous material containing carbonate fillcr 170 Carbonate filler, e. g. calcium carbonate magnesium hydroxide 300 In the above formulae the weights of size and carbonate filler refer to the bone dry basis, the weights of all other ingredients being given on the air dry basis.

In either of the above furnishes starch may be used, attention Hi this connection being directed to my copending application Serial No. 202,453, filed June 29, 1927. The starch may be added either in the beater, or subsequently while the mix is still relatively concentrated, or at any time in the dilute stage where thorough mixing can be insured. Because of ease of operation, however, it is convenient to add it in the beater. Suitable V coloring matter may also be added if desired.

The illustrative furnishes given above produce a satisfactory sized paper, and of course the sizing can be increased or decreased as constituent, such as precipitated size accompanied usually b excess alum, and a substantially water insoluble alkaline constituent, carbonate filler. These twvo constituents, however, under conditions obtaining in the ordinary method of paper manufacture, react chemically upon one another so that the sizing 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 carbonate filler and thusto preserve the desired effect of the acidic constituent in the papermaking mix. This result is attained as indicatedabove by adjusting conditions so that the carbonate filler is brought into contact with the paper mix containing the acidic constituent under circumstances which tend to prevent the chemical reaction between the carbonate 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 carbonate filler.

A chemical reaction between acidic mate rial 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 eflect such a reaction between the more activepart of the acidic constituent, i. e. the excess alum, and carbonate filler, substantially chemical equivalents of each would have to be employed. A stoicliioinetrical calculation shows that if for example calcium carbonate were to be the carbonate filler used, one part thereof would be chemically equivalent to 2.2 parts of commercial alum. If calcium carbonate magnesium hydroxide (of equimolecular proportions) were to be the carbonate filler used, one part thereof would be chemically equivalent to 2.9 parts of alum.

In the present invention, however, no such chemically equivalent proportions of calcium carbonate and alum are used, but rather the amount of carbonate 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 60 lbs. of size, 90 lbs. of alum and 300 lbs. of carbonate filler, in this instance calcium carbonate magnesium hydroxide, are employed. Under ordinary circumstances it may be stated that approximately 2 lbs. of alum will throw down 10 lbs. of rosin size so that the 60 lbs. of rosin size used in the above formulae would use up approximately 12 lbs. of alum. This would leave an excess of alum of approximately 78 lbs. This would give therefore a ratio of carbonate filler, in this case calcium carbonate magnesium hydroxide, to uncombined or free alum of 11.1 to 2.9. Thus it is apparent that in this'case there is present 11.1 times the amount of carbonate filler which would be the chemical equivalent of the alum, that is, 11.1 times the amount of carbonate filler necessary to react completely with the alum were conditions provided favorable for the consummation of reaction between the two.

It is thus apparent that I use an amount of carbonate filler far in excess of the chemical equivalent of alum employed. Thus even were conditions such that the carbonate filler were acted upon by the alum, as is substantially not the case in my invention, under such conditions the unactcd upon residual carbonate 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 carbonate filler in relation to the total furnish, the examples of illustrative furnishes given indicate that the proportion of carbonate 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 carbonate filler and would be what is known in the art as paper filled with carbonate filler.

On the other hand if instead of using carbonate filler as is my practice in an amount far in excess of the alum used, carbonate filler were employed only in an amount chemically equivalent to the free alum present, it can be readily seen from the followin computation that such an amount of car onate filler would not produce a paper which would be considered as a paper filled with carbonate filler. In order to compute the amount of carbonate 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 proportion of free alum used on the total furnish normally runs in the vicinity of several per. cent. If, for example, I use 4% of free alum on the total furnish, which is approximately the amount given in the illustrative furnishes above, the amount of carbonate filler chemically equivalentthereto would be, in the case of calcium carbonate, 1.8%, and in the case of calcium carbonate ma esium hydroxide 1.4% on the total furnis The resulting paper would of course contain smaller percentages of filler owing to losses of filler through the machine wire into the white waters. Such amounts of filler there fore or even amounts in some excess thereof such as would be present if the carbonate ller were used in amounts chemically equivalent to quantities of alum somewhat lar er than that given above) would be wholly madequate to impart any substantial de of filling to the aper made with such furnish. Indeed in suc' case anal tical procedures of fairly exact degree of refinement would have to be employed to detect the presence of such minute quantity of carbonate filler that might find its way into the paper to distinguish it with certainty for instance from the small amounts of inorganic constituents naturall occurring in the fibres, such as sulphite or soda fibres. On the other hand the filler in paper ordinarily known as filled paper, such as that to which my invention is directed, is present in so much larger amount that the normal inorganic constitutents of the fibre are negligible in proportion thereto, and ordinary ashing of the pa er by ignition gives a result indicating t e filler content sufficiently accurately for practical paper mill purposes.

It is thus clearly evident that I add .car-

' bonate filler at the wet end of the paper machine to prevent the chemical reaction between the carbonate filler and the acidic constituent of the mix, and therefore my invention is completely differentiated from any papermaking procedure wherein carbonate filler would be added to a paper mix in proportion substantially chemically equivalent to the acidic constituent thereof, for chemically reacting purposes.

It is to be noted that in any papermaln'ng 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 for the purpose of improving the sizing, 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 rocedure. Were soluble alkali in excess 0 the chemical equivalent of the acid added, the sizing would have been substantially deteri-' orated if not destroyed. 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 limitations as to the quantity employed, and

were there used an amount of insoluble alkali, for example carbonate filler, in excess of that chemically equivalent to the acidic content of the mix, prior art would have taught that there would have resulted an alkahnizing of the mix to such an extent as to deteriorate or destroy the sizing, thereby defeating the purpose for which the alkali would have been added. It was not until the discovery herein disclosed that it was realized that an amount of carbonate filler greatly in excess of the chemical equivalent of the acidic constituent could be added at the dilute stage without thereby destroying the sizing. Hence the present invention is distinctly differentiated from any chemically reacting i. e. neutralizing practice, as the addition of alkali at the dilute stage in such practice would necessarily have been confined by previously existing knowledge to the addition of proportions chemically 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 carbonate filler, and is thus completely differentiated from any papermakmg procedure in which carbonate filler would be added in proportion substantially chemically equivalent to the acidic constituent, as in the latter case a commercially wholly inconsequential amount of carbonate 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 wordsas paper filled with carbonated filler.

While I have described herein the use of rosin size as a size and alum as a size precipitant to produce the desired sizing effect, and have shown a method for the prevention of the deterioration or destruction of this sizing effect by carbonate fillers it is to be understood that sizes other than rosin size may be employed for sizing. For example, any size is suitable which is used in conjunction with a size precipitant, such 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.

Others will readily occur to one skilled in the art. The material constituting the sizing formed from such sizes and size precipitant as alum is affected by carbonate fillers similarly to the material constituting the sizing formed from rosin size and alum and by my method of using carbonate filler the deterioration or destructionof the sizing when using such sizes is avoided. I consider, therefore, that the use of any such size and any suitable size precipitant such as alum, sodium bisulphate or the like, to impart sizing to a paper in which my method is used for the employment of carbonate filler, falls within the scope of my invention.

Although there have been proposals for sizing paper containing carbonate filler with the use of rosin (see for example, Loshs British Patent No. 2,664 of 1859, and Cap-.

pazas British Patent No. 5,776 of 1899) the method which I employ is wholly different from those disclosed in the above referred to patents as will be apparent or from any other method which has to my knowledge yet been proposed.

This invention may be used alone in producing a sized carbonate filled paper, or in connection with other of my copendingapplications, e. g. Serial No. 364,168 filed Sept. 5, 1928, and Serial No. 304,170 filed Sept. 5, 1928 By the term carbonate filler as employed herein is meant the substantially water insoluble normal or basic carbonates of alkaline earth metals (which expression is herein intended to include magnesium), or compounds, or double salts, or physically associated mixtures of these with one or more other acid soluble materials of a substantially water insoluble nature, these fillers whether simple or complex as above, being characterized by the fact that, when agitated in contact with freshly boiled distilled water in concentrated suspension for say an hour, they impart to the water a pH value which is on the alkaline side of the neutral point, and also by the fact that they give off carbon dioxide gas when brought into contact with an aqueous mineral acid, e. g. hydrochloric acid. Examples of such fillers are calcium 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 of August 10, 1926; and calcium carbonate magnesium hydroxide, disclosed in my U. S. Patent No. 1,415,391 of May 9, 1922. As will be apparent, these fillers are referred to not only in their chemically pure form but also in commercial form containing such impurities as may occur in such commercial products; and also when present with other material, so that they constitute only a part, either major or minor, of the whole. It should be stated that any given filler of the type referred to is not necessarily of uniform particle size; nor are the average particle sizes of the fillers necessarily alike. as some of the fillers of the type referred to have relatively coarse grain particles, whereas others are much more finely divided, and some are so finely divided that they may be said to approach or be in the colloidal condition.

Moreover, by the term carbonate filler, I mean to include not only the case where the carbonate filler is added as such in the papermaking rocess, but also the case where it may be ad ed wholly or inpart incorporated with fibrous material and/or other material' such as paper coating constituents or the like. Such a case would be where aper made with carbonate filler, either as a filling or coating constituent, or both, is reused in the papermaking process. Such papers may be those known to the trade as old papers or old waste papers or waste papers in any form, or returned trimmings or damaged paper or the like, or they may be the broke, that is, the partially made, the imperfect, or the waste paper which accompanies the papermaking, finishing, storing, packing,

shipping, or the like operations in a paper mill, and which is reworked either in the same or some other mill. Such papers are sometimes reworked by themselves and added in broken down or in pulp form in the papermaking process, being treated or cooked in some cases with or without chemicals and washed if desired, this reworking meaning to include the process of deinking if such is practiced or of bleaching or of both deinking and bleaching or sometimes they are added directly in the papermaking process and broken down to pulp form therein. In any event they are a source of carbonate filler in the paper to be made, and are included in the term carbonate filler as used'herein.

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 ma-.

chine.

Although the expression wet end of the paper machine may at times be used to con.

vey various meanings, where I use the expression in the description or the claims I intend it to include those instrumentalities provided in paper manufacture by which and/or in which the relatively concentrated mix is diluted, and treated, conveyed or fed up to the point of web formation, such as the mixing box, regulating and proportioning des vices, rifilers, troughs, screens, machine headboxes, inlets, and the like, including also instrumentalities used in the white water cycle, but I do not intend to include in this definition the web-forming device itself, that is, the moving wire in the case of a Fourdrinier machine or the cylinder mold in the case of a cylinder machine.

Although I have described in detail several illustrative furnishes I donot intend to be limited thereby, as my invention may be practicedwith a broad variety of formulae, using various materials customarily employed for various grades of paper in any suitableproportions. Moreover, various changes in procedure, ingredients, and arrangement of steps may be resorted to in the practice of my invention without departing from the spirit of my invention or the scope of the subjoined claims.

Having described my invention, I claim 1. The method of manufacturing a sized paper filled with carbonate filler comprising adding carbonate filler, in an amount suflicient to impart a substantial degree of filling to the resulting paper, to previously sized fibre in the p-apermakmg process under conditions favoring the minimizing of time of contact between the carbonate filler and the previously sized fibre, and thereafter making paper therefrom. Y v

2. The method of manufacturing a sized paper filled with carbonate filler comprising adding carbonate filler, in an amount sufficient to impart a substantial degree of filling to the resulting paper, to previously sized fibr-c in the paper-making process under conditions favoring the minimizing of intimacy and time of contact between the carbonate filler and the previously sized fibre, and making paper therefrom.

3. The step in a method of manufacturing a sized paper filled with carbonate filler comprising adding carbonate filler, in an amount sufficient to impart a. substantial degree of filling to the resulting paper, to previously sized fibre in the papermaking process subsequent to the passage of the fibre from the machine chest.

4. The step in avmethod of manufacturing a sized paper filled with carbonate filler com prising adding carbonate filler, in an amount sufficient to impart a substantial degree of filling to the resulting paper, to previously sized fibre in the papermaking process at a point subsequent to that at which the previously sized fibre exists in relatively concentrated form. a

5. The step in a method of manufacturing a sized paper filled with carbonate filler comprising adding carbonate filler, in an amount sulficient to impart a substantial degree of filling to the resulting paper, to previously sized fibre in the papermaking process at a point where the concentration of the solids is not over one and one half per cent. on the dry basis.

6. The step in a method of manufacturing a sized paper filled with carbonate filler comprising adding carbonate filler, in an amount sufiicient to impart a substantial degree of filling to the resulting paper, to previously sized fibre in the papermaking process not more than five minutes prior to web formatiou.

7. The step in a method of manufacturing a sized paper filled with carbonate filler comprising adding carbonate filler, in an amount sulficient to impart a substantial degree of filling to the resulting paper, to previously sized fibre at the point at which such fibre is diluted prior to Web formation. 8. The step in a method of manufacturing a sized paper filled with carbonate filler comprising adding a carbonate filler,- in an amount sufficient to impart a substantial de- 'fibre and subsequently adding car 9. The steps in ameth'od of manufacturing a sized paper filled with carbonate filler comprising adding size and size precipitant to the onate filler, in an amount suflicient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine.

10. The steps in a methodof manufacturing a sized paper filled with carbonate filler comprising adding size and alum to the fibre and subsequently adding .carbonate filler, in an amount sufiicient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine.

11. The steps in a method of manufacturing a sized paper filled with carbonate filler comprising adding rosin size and alum to the fibre and subsequently adding carbonate filler, in an amount sufiicient to impart a substantial degree of filling to the resulting paper, at the wet end of the papermachine.

12. The steps in a method of manufacturing a sized paper filled with carbonate filler comprising adding rosin size and alum to the fibre in the heater and subsequently adding carbonate filler, in an amount sufiicient to impart a substantial degree of filling to the resulting paper, at the wet end of the paper machine.

13. The step in a method of manufacturinga sized paper filled with carbonate filler which consists in adding carbonate filler comprising an alkaline earth metal carbonate, in an amount sufficient to impart a substantial degree of filling to the resulting paper, to previously sized. fibre at the wet end of the paper machine.

14. The step in a method of manufacturing a sized paper filled with carbonate filler which consists in adding carbonate filler comprising calcium carbonate, in an amount sufiicient to impart a substantial degree of filling to the resulting paper, to previously sized fibre at the wet end ofthe paper machine.

15. The step in a method of manufacturing a sized paper filled with carbonate filler which consists in adding carbonate filler comprising calcium carbonate and a magnesium com ound, in an amount sufficient to impart a su stantial degree of filling to the resulting paper, to previously sized fibre at the wet end of the paper machine.

16. The step in a method of manufacturing a sized paper filled with carbonate filler which consists in adding carbonate filler comprising calcium carbonate magnesium hydroxide, in an amount sufficient to impart a substantial degree of filling to the resulting paper, to previously sized fibre at the wet end of the paper machine.

17. A sized paper comprising fibrous material, carbonate filler comprising calcium carbonate and magnesium compound, and silzing comprising rosin size precipitated by a um.

terial, carbonate filler comprising calcium carbonate magnesium hydroxide, and sizing comprising rosin size precipitated by alum.

19. The step in the method of manufacturing a sized paper filled with carbonate filler, in an amount sutficient to impart a substantial degree of filling to the resulting paper, comprising adding carbonate filler at the wet end of the paper machine.

20. The cyclic procedure in the method of making sized paper filled with carbonate filler, comprising the addition at the wet end of the paper machine of carbonate filler, 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.

In testimony whereof I afiix my signature.

HAROLD ROBERT RAFTON.

18. A' sized paper comprising fibrous ma.-

CERTIFICATE or CORRECTION.

Patent No. 1', 803,642. Granted May 5, 1931, to

HAROLD ROBERT RAFTON.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, lines 29 and 31, for the misspelled word "cylically" read cyclically; line 35, for "whereby" read thereby; line 60, for the misspelled word "'cylically" read cyclically; line 73, for "pinion" read opinion, and line 114, for "reliable" read reliably; page 4, line 25, for "filled" read filler, and line 55, for "satisfactory" read satisfactorily; page 6, line 31, for "carbonated" read carbonate; page 8, line 25. claim 12' for "heater" read beater; same page, lines 72 and 73, claim 19, strike out the words "in an amount sufficient to impart a substantial degree of filling to the resulting paper,"

and insert same to follow the word "filler" in line 74, of same claim; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of August, A. D. 1931.

Wm. A. Kinnan, Acting Commissioner of Patents.