US1834903A - Manufacture of paper - Google Patents

Description

Patented Eco, 1, 1931 PATET orrics HARQLD coarser RAFTON', Z5 ANDQVER, MASSACHUSETTS, ASEJGNQR TQ BAI'FQLD PROCESS CORPOMEIUN, A CQRIEORATION 0F MASSfiGE'USFETfi l lo Drawing,

This invention relates to the manufacture taining alkaline filler.

The principal object of this invention is to provide a novel method of using starch in paper made With alkaline filler.

An important object is to provide a method of using starch which will measurably avoid decomposition oi the starch in the paper-mahing process.

A further object is to provide a method oi using starch wherein the maximum Viscous properties of the starch are retained.

Other objects arid advantages of tli vention will become apparent during course of the following description.

Starch has been used for years as a constituent of paper mixes to impart stitiening, a firmer "feel, and the like qualities paper made therewith,

As I hays disclosed in thy copending aopli cation Serial No, 202,453, filed June 29, 1927, starch is also particularly valuable incerta cases Where alkaline iillersare used in pa making, for substantially eliminating the loam-forming tendency f om otherwise foam-forming mixes. lln the alcove referred to application the use starch in conjunction with alum is also recommended,

Where starch has heen employed heretofore as a constituent of paper mixes it has been the customary practice to mix it a compounding and/or treating device, such as a heater or the hire, with an aqueous susoension of fihrous material and such other material as may he employedv in paperrnaking such as filler, size, for example rosin size, size preci itant, for example alum, tinting and the lil e. This mix usually has a dry solid con tent of approximately 5%, more or less. The mix after subjection to suficient treatment in the heater, is then ordinarily discharged into a container commonly called a heater chest, additional Water usually losing added. Thereafter the mix may he transferred from may be approximately point commonly being referred to as the coir:-

the beater chest to a suitable refining en ine, usually a Jordan, at a dry solid content W ich 131 the neighborhood Application filed February 5, 1930. Serial Ito. 426,199,

of 4%. ln common practice the mix is this point usually diluted somewhat by the addition of Water, and the diluted mix alter jordaning is ordinarily conducted from the Jordan to another container commonly known as machine chest, From the inschine chest the mix is transferred to a point near the Web forming end of a paper machine Where it is largely diluted' with Water, this mg hex, Water hein here added ordinarily in such to provide a dry content zimat to 1% or slightly higher, hut casually not in excess of li The in such h1g3 dilute condition is then passe 1 rs or the like desired d 6;. ough screens and through the H the paper niachin on to the rose is wire, into a rat, dc 1 ing' upon Wl a Fonrdrinier or a cy machine is i ycd; and during this passage additional amounts water are ads 5. in the form a sprays or otherwise.

This exact procedure is not always ioh lowed hut in some ins nces is modified i accordance with the of paper lasing made. F or example, in the manufacture of certain types of paper the heating process is almost it not entirely dispensed with, the ingredients losing merely mixed together prior to jordaning. some instances the step of rehning or ordanine may be partially if not Wholly dispensed with. Moreover in some cases the arrangement or? steps is difierent; for example, the jordaning may take place subsequent to the machine chest, the stool: passing directly from the Jordan to the mixing box. gometimes also the arrangement.

till

- subject to'attack by molds and the like, and

in the'course of its assage through the beater, chests, and J or an, up to the point of dilution, the length of time is such that. the

starch remains sufficiently long, in the system for these deterioratingagencies to act thereon to a'considerable extent. The deterioration seems to be particularly pronounced in certain instances where the system is alkaline as would be the case where alkaline filler is employed, particularly where it is added in the beater. The putrescent condition is aggravated if there be present in the inix other putrescible materials such as old paper stock (reworked old papers), particularly if such contain reworked coated papers containing casein. If in addition there be other elements which prolong the continuance of contact of the starch with the other ingredients of the mix such as is customary in modern papermaking equipment, this tendency toward decomposition is much more manifest. An example of such elements which maintain the other ingredients of the mix in contact with the starch for longer times is where recovery systems are used in the white water cycle. Sedimentation systems are common for use on the excess white water,

and in such instances the recovered stock,

which in this case would contain starch, is returned to the papermaking operation, commonly to the beater. Another type of recovery system commonly used and which illustrates the point satisfactorily is the filtration type whichngrmally mixes the excess white water from the machine with the so-called sweetener stock usually taken fromv the heater or machine chest, and returns the material filtered from the excess white water together with the sweetener stock back into one or the other chests. This filtration cycle, as is apparent, returns part of the starch which would ordinarily escape with the white waters back into the papermaking operation and thus prolongs the contact of the starch with the other constituents of the mix and promotes its decomposition.

As a result of the decomposition, not only is the starch in part deteriorated or destroyed, but there is a considerable opinion that such decomposition of the starch is very njurious in promoting slime in the paper and also as being in certain cases an agency which promotes the formation of soft lumps on the paper machine, which in turn greatly interfere with production and reduce the quality of the paper made under such conditions.

Another disadvantage inherent in the method heretofore employed in using starch is the fact that even though the system were kept entirely sterile so that no growth of molds or micro-organisms could take place,

nevertheless the constant agitation such as c less proportional to the amount of agitation it receives.

Ihave discovered that the disadvantages inherent in the method of utilizing starch hitherto. employed, can be overcome to a very great extent by minimizing the time and/or intimacy of contact of the starch with the other constituents of the paper mix and I have deviseda method whereby my discovery can be practically utilized in the papermaking operation.

Briefly, I add the starch to the mix at a point late in the papermaking process, for example, subsequent to the passage of the mix through the machine chest and preferably at the wet end of the paper machine, whereby the time of'contact of the starch with the other constituents of the mix is greatly minimized. Moreover the'addition of the starch in the dilute stage of the papermaking process acts to decrease greatly the intimacy of contact of the constituents of the mix and thereby prevents deterioration of the viscous quality of the starch by diminishing the frictional action to which the starch is subjected.

Of course, in certain cases such as where the refining engine is placed between the final stock chest and the paper machine, the starch may be added subseguent to the delivery of the stock from this nal chest. In this case the Jordan acts as an eflicient incorporating means for the starch with the paper mix, and inasmuch as the time of contact in the concentrated condition. is only very brief, the results are in certain cases wholly satisfactory; However, in most cases I have found it preferable to effect the mixing of thestarch at the wet end of the paper machine, usually at the mixing boxor at any point which may be convenient prior to the delivery of the mix on to the Web-forming device.

nesaeos It will thus be apparent that my method of utilizing starch in the papermaking process avoids to a great extent the deterioratinginfiuences formerly inherent in the method of adding starch in the beater, removes the starch as a source of putrescence from the earlier part of the papermaking operation, tends to prevent in certain cases in a consid erable measure the formation of slime and lumps in the papermaking process, and prevents the deterioration of the valuable viscous quality of the starch owing to the prevention of prolonged agitation of the starch in contact with the other constituents of the mix.

As will be apparent this makes for the more efiicient use of the starch and lesser amounts than formerly were required to give certain desired properties to the paper mix or resulting paper can now he used. It is thus apparent that my process is very beneficial from the standpoint of starch economy.

In those cases as indicated above where settling or filtration cycles on the excess white waters return the material recovered from the excess white water to the earlier stage in the process either the heaters as is sometimes done with settling systems or to the chests as is sometimes done with filtration systems it will be apparent that part of the starch in the furnish will he returned to an earlier stage of the process. This, as has been indicated ahove, is not theoretically the most advantageous procedure. However, owing to fact that the starch originally introduced is highly viscous owing to undeteriorated condition, as well as to the fact a lesser amount of starch may he employed than for merly, less of the starch than was formerly the case will tend-to be present in the white water coming from the machine and thus only a relatively small quantity will he reintroduced at an earlier stage in the process. As this quantity is small compared with the original amount of starch employed, and especially it it he reintroduced, as is preferable, in the latter part of the system such as in the machine chest, serious detriment will be incurred from the presence of this minor quantity of starch in the system prior to the passage of the mix from the machine chest. However, if it he feasible, it is especially advantageous in this connection to employ the machine cycle disclosed in my copending application Serial No. 4238,6544, filed March 24, 1930, whereby substantially all of recovered material is returned to the papermaking operation just prior to or at the dilute stage.

y invention may be conveniently employed in the manufacture either of sized or substantially unsized papers. Moreover, it may be carried out satisfactorily in connection with the processes disclosed in various of my copending applications, that is, the starch may be the onlymaterial added at the wet Substantially 'u/naz'zed paper Pounds Sulphite pulp 350 Soda pulp 435 Reworked old magazine papers (deinked) 600 Broke (defective paper to bereworked) 180 Alkaline filler (e. g. llaCO Mg (@H) 720 Alum '50 Starch 75 In the above furnish the starch is added, preferably continuously, at the wet end of the paper machine. lhe filler and/or alum may either be added in the heater with the fibrous. constituents, or at the Wet end of the paper machine.

Another suitable furnish is as follows:

Sized paper Pounds Sulphiteand soda pulps 2709 Size (e. rosin sis-c l5 Alkaline filler (e. g. waC@ l /lg(@ll) 300 Size precipitant (e. alum) Starch 5G in the above furnish starch is added, pref erably continuously. at the wet end of the paper machine. "ei erahly least oi the alum should also be added at that point. T he iiller and/or the size may either he added in the heater, or at the wet end of the paper machine.

in ooth the above furnishes weights of the size and alkaline filler'refer to the bone dry basis; the weights of all other constituents refer to the air dry basis.

It will be understood of course that the above furnishes intended as illustrative only and in no sense as restrictiye, as widely (littering furnishes give satisfactory results. The starch used may vary widely in amount. Practically speaking, however, although i do not restrict myself thereto,i less than one percent. has lout little effect on the finished paper and starch is seldom use in lesser amount in papermaking.

As is well known, starch is customarily employed in the papermaking process by treating raw starch in such a manner as to produce a viscous solution. This may be suitably accomplished by heating starch and Water to the point where the starch is cooked, i. e., where it becomes a substantially homogeneous viscous colloidal solution. This solution is then usually allowed to cool. It is in such condition that 1 preferably employ starch in my process. However, starch, i. e.,

unmodified starch, is not always emplo ed in papermaking; sometimes the so-ca led modified starches are used. A great variety of these with difierent properties are on the market, e. g., some are dlrectl soluble in cold water, others give thin boilmg solutions. My process, as will be apparent, is also useful-with modified starches for although the questionv of maintaining the viscosity ma not be of such great importance with suc this group may be mentioned calcium car-.

bonate, 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, dated August 10, 1926; calcium carbonate magnesium hydroxide disclosed in my U. S. Patent No. 1,415,391, dated 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 compounds,

'double salts, or physically associated mixtures of these with one or more other acid soluble materials of a substantially water insoluble nature.

By the term alkaline filler I also intend to include fibrous material and/or other material such as paper 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 ca able of being produced on a Fourdrinier, cy inder, 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, rifilers, troughs, screens, head boxes, inlets, and the like, including also instrumentalities used in the white water cycle.

In my copending application Serial No.

' 304,167, filed September 5, 1928, I have disclosed but not claimed the addition of starch to a fibrous mix at the wet end of the paper machine in the manufacture of paper filled with an alkaline filler.

In my copending application Serial No. 304,175, filed September 5, 1928, I have disclosed and claimed a method for sizing paper filled with an alkaline filler in which size such as rosin size and size precipitant such as alum are mixed in the presence of starch, and the resulting product is added to the fibrous mix at the wet end of the paper machine. Moreover, in my copending applica tion Serial No. 319,721, filed November 15, 1928, I have disclosed and claimed a method of incorporating into pa er filled with alkaline filler an inorganic al ali metal salt with a pH value greater than 7.0, for example sodium silicate which is precipitable by material which depresses its hydro 1 ion concentration, by mixing said alkali metal salt with a precipitant therefor in the presence of starch, and adding the resulting product to the fibrous mix at the wet end of the paper machine. I therefore exclude from the scope of the present specification and claims the addition of starch, in the manufacture of paper filled with alkaline filler, to a fibrous mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix in the cases where such starch has had previously added to ita size or an alkali metal salt such as described in this paragraph, together with a precipitant therefor.

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. The step in the method of manufacturing paper filled with alkaline filler comprising adding starch to a fibrous mix under conditions favoring the minimizing of the time of contact of the starch with the constituents of the mix. 1

2. The step in'the method of manufacturing pa er filled with alkaline filler comprising ad ing starch to a fibrous mix under conditions favoring the minimizing of the time and intimacy of contact of the starch with the constituents of the mix.

3. The step in the method of manufacturing paper filled with alkaline filler comprising adding starch to a fibrous mix subsequent to the passage of the mix from the machine chest. 7

4. The step in the method of manufacturing paper filled with alkaline filler comprising adding starch to a fibrous mix at the wet end of the paper machine.

5. The step in the method of manufacturing paper filled with alkaline filler comprising adding starch and alum to a fibrous m1x at the wet end of the paper machine.

6. The method of manufacturing paper filled with alkaline filler comprising adding starch, alum, and alkaline filler to a fibrous mix at the. wet end of the paper machine,

and thereafter making paper therefrom.

7. The method of manufacturing paper filled with alkaline filler comprising adding starch, alum, alkaline filler, and size to a fibrous mix at the wet end of the paper machine, and thereafter making paper therefrom.

8. The step in the method of manufacturing paper filled with alkaline filler comprising calcium carbonate, which comprises adding starch to a fibrous mix under conditions favoring the minimizing .of the time of con- 2 tact of the starch with the constituents of the mix.

9. The step in the method of manufactur ing paper filled with alkaline filler comprising calcium carbonate and magnesium compound, which comprises adding starch to a fibrous mix under conditions favoring the minimizing of the time of contact of the starch with the constituents of the mix.

10. The step in the method of manufacturing paper filled with alkaline filler comprising calcium carbonate magnesium hydroxide, which comprises adding starch to a fibrous mix under conditions favoring the minimizing of the time of contact of the starch with 3 the constituents of the mix.

11. The step in the method of manufacturing paper filled with alkaline filler comprising calcium carbonate maghesium hydroxide, which comprises'adding starch to a fibrous mix under conditions favoring the minimizing of the intimacy and time of contact of the starch with the constituents ofthe mix.

12. The step in the method of manufacturing paper filled with alkaline filler comprising calcium carbonate magnesium hydroxide, which comprises adding starch to a fibrous mix at the wet end of the paper machine.

13. The step in the method of manufacturing paper filled with alkaline filler, comprising adding starch at the wet end of the paper 'maclliline to a fibrousmix containing old paper stoc 14. The step in the method of manufactur-" ing paper filled with alkaline filler, comprising adding starch at the wet end of the paper machine to a fibrousmix containing casein bearing constituent.

15. The method of minimizing the putrescence of starch in the manufacture of paper L filled with alkaline filler comprising withholding the addition of the starch until late in the process of stock preparation.

16. The method of manufacturing paper filled with alkaline filler, comprising mixmg fibrous material and alkaline filler in the beater, and adding to the resulting mix starch at the wet end of the paper machine.

In testimony whereof I aflix my signature.

HAROLD ROBERT RAFTON.