US2056209A - Paper manufacture - Google Patents

Description

matter, and of which the present application is of paper filled with an alkaline filler.

Patented Got. 6, 1936 IPAPER MANUFACTURE Harold Robert Rafton, Andover, Mass, assignor to Rafiold Process Corporation, a corporation of Massachusetts No Drawing. Application October 29, 1932, Serial No. 640,330

22 Claims.

This invention relates to the manufacture-of paper filled with alkaline filler.

The principal object of this invention is the manufacture of substantially unsized paper filled with alkaline filler.

An important object-is the use of saponifiable material in substantially or preponderatingly unsaponified form in such paper.

A further object is the use of rosin in substantially or preponderatingly unsaponified form in such paper. 1

A further object is the employment of the principle of adding materials under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix in connection withthe manufacture of paper filled with alkaline filler employing material comprising saponifiable material in substantially or preponderatingly unsaponified form.

Other objects and advantages of this invention will become apparent during the course of the following description.

Cross reference is hereby made to my copending application Serial No. 584,012, filed December 30, 1931, now matured into Patent No. 1,886,120, issued November 1, 1932, having related subject a continuation in part.

In numerous of my patents, for example No. 1,819,441, issued August 18, 1931, and Nos. 1,803,645, 1,803,648, 1,803,651, and 1,803,652, issued May 5, 1931, I have disclosed the sizing of paper filled with alkaline filler by the employment of a substantially unsaponifiable material such as paraffin in emulsified form. Moreover in No. 1,848,658, issuedMarch 8, 1932, I have disclosed the manufacture of substantially unsized paper in which emulsified parafiin is employed. In other of my patents, for example Nos. 1,803,643 and 1,803,647, issued May 5, 1931, I broadly cover the addition of alum or the like at the wet end of the paper machine, or in the beater and at the wet end of the paper machine, in the practice of the sizing, with any suitable size,

Particularly'I disclose therein the use as sizes of partially or completely saponifiable materials in saponified form, and preferably the use of size such as ordinary rosin size. Likewise in Nos. 1,803,646 and rosin present, and although it is perhaps considered theoretically feasible to make a usable soap with as high as 55 per cent. free rosin, in practice 45 per cent. may be said to be the upper limit. It will thus be noted that where rosin 5 size is employed in alkaline filler paper mixes in the processes as disclosed in my prior Patents Nos. 1,803,643; 1,803,646; 1,803,647, and 1,803,649,

a certain amount of rosin in unsaponified form may be present, which in the case of high free 10 rosin soaps may amount to the theoretically possible 55 per cent. of the total rosin present as explained above.

In the present application I disclose a process comprising the use of sizes comprising saponifiable material in substantially completely unsaponified or preponderatingly unsaponified form in the manufacture of substantially unsized papers filled with alkaline filler. In its preferred practice the present process is a modification of the procedures covered broadly by my prior patents, Nos. 1,803,646 and 1,803,649 above referred to. Saponifiable materials of any type whether partially or wholly saponifiable may be used in the present process. Examples are: fatty acids, esters particularly glyceryl esters of saturated and unsaturated acids, and esters of the high molecular fatty acids with alcohol, saponifiable gums, resins and the like, all whether chemically pure or occurring commercially in combination or association with other materials. In the class of saponifiable materials, however, I do not intend to include such black or substantially black colored materials of a pitchy nature which, be-- cause of their color, are not feasible for use in white papers, or even in papers which are somewhat colored such as kraft or the like.

I preferably use saponifiable materials which aresolid or substantially solid at ordinary or room temperature and from the standpoint of cost I prefer to use rosin. In the'present invention as stated I use either substantially all the saponifiable material such as rosin in unsaponified form; or,'as in the case where saponified material as rosin is also additionally present in 45 the furnish, I use the unsaponified material such as rosin in a substantially preponderating amount over that of the rosin present in saponified form, which differentiates from my prior disclosure.

The advantage of using saponifiable material in completely or preponderatingly unsaponified form rather than in saponified form is that in certain cases there is less tendency tofoam formation. This is particularly useful in the case where coated broke is employed in the furnish.

' Also there is less tendency in certain cases for the web to stick to the press rolls or the like'on the paper machine. There is also a tendency for the precipitated size to be less aifected by the deteriorating influence of alkaline filler.

Moreover the use of saponifiable material such as rosin in completely or preponderatingly unsaponified form has an advantage over the use of paraflin, which is a substantially unsaponifiable material, (the use of which in substantially unsized paper is described in No. 1,848,658 above referred to), because parafiin, although advantageous from the standpoint of increasing the' flexibility of the sheet, has a tendency to weaken the sheet in respect to certain of its strength tests, such as the bursting or Mullen test. This disadvantage rosin does not have, rosin in fact exerting substantially no deleterious effect on the strength of the sheet.

As has been fully described in my Patents Nos. 1,803,643, 1,803,646, 1,808,647, and 1,803,649 above referred to, when an acidic agent such as alum is utilized with a size in a relatively concentrated fibrous mix in the presence of an alkaline filler, there takes place a deterioration or destruction of the size precipitate by' alkaline filler. This is avoided if materials are added to the mix according to the minimizing principle. The phenomena on which this principle is based have been described by me in great detail in those patents as well as in numerous other of my issued patents. 1 i

' Briefly the situation is that alkaline filler, which always is present in the stock from which paper filled with alkaline filler is made in great stoichiometrical excess over the acidic constituent, acts upon the acidic constituent to the ultimate destruction thereof and/or the destruction of the effect maintained by such constituent. (The acidic constituent so-called may be one which is actively acid, and/or one, such as a size precipitate, which is capable of being affected or deteriorated by an alkaline material.) The action just referred to has been found to depend upon the time of contact of the acidic and alkaline constituents and also upon the intimacy of contact of these constituents. Agitation such as normally occurs in papermaking procedure in stuff chests .or the like accelerates the rate of thereby is substantially preserved in an alkaline filler mix. With the present types of paper machines and the present arrangement of equipment usually employed in paper machine operation, the contact of the acidic materiaf and the alkaline constituent at any time prior to the passage of the stock from the last stuff chest, which is commonly called the machine chest, results in great deterioration or complete destruction of the acidic material; Addition of one or both of these constituents, as well as other materials such as size, sodium silicate, starch, or the like, asset forth in my various issued patents, at a point subsequent to the passage of the stock from the machine chest, after which point according to present day operating practice the stock remains in concentrated condition only for a very brief interval of time, or addition preferably at or subsequent to the point of dilution, 1. e.

utilize in the practice of my invention. It is obvious that the above description of the minimizing principle is merely a condensation of the full discussion given in a number of my prior patents, and indicates the practice by which the optimiun results may be obtained. It is to be understood, of course, that minimizing of the time may be practiced,-without so completely satisfactory results to be sure,-by addition of material late in the process, but earlier than under the optimum conditions, such as in the chest or the like, see my patents, Re. 18,983, 1,803,642, etc.

In the preferred practice of my invention, there is prepared in any suitable container such as a beater, a fibrous mix of any desired fibrous constituents, to which is added alkaline filler, and size, insumcient in amount to impart a substantial degree of sizing to the resulting paper. This size may be for example rosin in substantially or preponderatingly unsaponified form, preferably as an aqueous emulsion. A precipitant such as an acidic material, preferably alum, may then be added. A variation which is sometimes desirable to practice is to add the size and alum to the fibre prior to the addition of the alkaline filler. After any further desired treatment of the mix such as is customary to prepare it for use, is then diluted preparatory to running off on the webforming device. Preferably at this point a further amount of acidic material as alum may be added; or the original addition of alum may be omitted if desired and alum added only at the dilute stage. In the first instance the alum added at the dilute stage acts as a restoring agent, in the second as the original precipitating or fixing agent. Various other orders of addition of materials may be used in accordance with the minimizing principle as has been set forth in my various patents or copending applications. For example, the alkaline filler, alum, and/or size may be added at the dilute stage, as well as other constituents of the mix. The mix is then run over a web-forming device and through the remainder of the customary equipment of a paper machine, such as driers, and calendars, if desired, producing thereby a substantially unsized paper filled with alkaline filler.

The advantages of using such small amount of v the described size in the paper as will produce a substantially unsized paper, compared with the practice of making paper without any size therein, may vary with varying stocks and machine conditions, but they may include the elimination or diminution of foam, cleanerdandy operation,

I ample as those to be described below, may in certain cases be used directly with the alkaline filler in the fibrous mixture and run off on a web-forming device without the addition of alum according to the minimizing principle. In such case,

however, the emulsions are not fixed on the fibre,

and thus much of the emulsion is lost in the white water, substantially the only amount remaining in the sheet being that which is mechanically retained by the web. When alum is employed as in the preferred practice of my invention outlined above, this suffices to fix certain of the emulsions very satisfactorily on the fibre, and others of them with a fair degree of satisfaction. However it is sometimes desirable to employ instead of alum, or additionally therewith, fixing agents such as two mutually precipitating or fiocculating materials. As alum itself is an excellent material for use as one of the mutually fiocculating agents, it is some times convenient to employ with alum only one other material which with alum will form a fiocculate or precipitate. Examples of mutually flocculating materials which may be employed are: soluble salts such as sodium silicate and acidic material as hydrochloric acid; barium chloride and sodium sulphate; and the like. Examples of materials which fiocculate with alum are sodium hydroxide, sodium silicate, soap such as rosin soap; and the like. These may be added in the beater and/0r dilute stage, but it is desirable that when the precipitation or flocculation takes place the emulsion I employ should be already present in the mix.

It is to be understood thatmy invention may be practiced without employing the minimizing principle. Thus the emulsion may be added with the fibre and alkaline'filler in the concentrated stage of the paper making operation as in the beater, without alum as described above, or in the beater with alum and with or without other flocculating materials. While in certain cases moderately satisfactory results can thus be obtained, I- prefer however to employ the minimizing principle as superior results are usually obtained thereby.

In order that rosin in substantially or preponderatingly unsaponified form, such as I employ in the practice of my invention, may be used in a fibrous mix, it is necessary that the rosin be introduced in extremely finely divided condition,

preferably as a finely divided suspension or emulsion. Such suspensions or emulsions of rosin may be prepared in a number of ways.

For example, rosin may be thus emulsified by mechanical dispersion with a small percentage, for example about 2 per cent. of a protective colloid such as alkali casein according to the so-called Bewoid process to form the so-called Bewoid size, (see Canadian Patent No. 305,650 of November 11, 1930). When alkali casein is used for emulsifying rosin according to the Bewoid process an amount of alkali is usually employed with the casein which is somewhat more than that required to completely dissolve the casein. Thus a certain amount of unacted upon alkali comes in contact with the rosin which may result in the conversion of a small amount of the resin into soap form. However this may be, it is within the bounds of reasonable commercial accuracy to state i that the rosin in Bewoid size is present substantially completely in unsaponified form.

Another suitable method is to emulsify rosin with a substantially insoluble type emulsifying agent, for example such method as is described for parafiin in my issued Patents Nos. 1,803,651 and 1,803,652. This may be done by melting rosin and vigorously mixing the melted rosin with a paste formed of emulsifying material and a liqnid such as water, whereby the rosin becomes the'disperse phase of the emulsion, the particles of rosin being substantially surrounded by the substantially in soluble emulsifying agent. Various emulsifying agents may be used, such for example as clay, more advantageously colloidal clay such as bentonite. A modification of this method is where the substantially insoluble emulsifying agent is formed by precipitation in the presence of finely dispersed particles of molten rosin in liquid suspension.

Still another suitable way in which rosin may be emulsified is by making a substantially nonbreakable emulsion therewith'such for example as is described for paraffin in my issued patents, Nos. 1,803,645 and 1,803,648. In this case the melted rosin is emulsified with a solution of a gum preferably substantially water soluble such as gum ghatti and other additive agents may be employed such as d'extrin. One such emulsion may be made by the use (by weight) of 15 parts of rosin, 1 part gum ghatti, and 1 part dextrin, suitably with 83 parts water to give it a convenient concentration. The emulsion may be made in a colloid mill or homogenizer. Owing to the fact that rosin below the boiling point of water is very viscous and thus comparatively diflicult to emulsify, it is preferable to employ temperatures higher than 100 C. for its emulsification, that is, the system should conveniently be kept under pressure in order to keep the water used in. liquid condition at the elevated temperature desirable to employ.

In order to overcome the desirability of using such high temperatures as will make the rosin very fluid, it is sometimes feasible to utilize other materials which will lower the melting point or increase the fluidity of the rosin melt when in admixture therewith. These constituents may be used in any desired amount but owing to cost considerations, it is generally desirable to use only a minor amount, and such a minor amount is normally all that is necessary, 5 to 25 per cent. usually suificing. Suitable materials to use in conjunction with the rosin are parafiin, rosin oil, petrolatum, or any other liquids, oils or fiuxible solids which will lower the melting point or decrease the viscosity of the rosin melt.

Other methods of preparing suitable emulsions are possible but these examples will suffice.

An example of a furnish suitable for carrying out my invention is as follows:

Added in the beater Pounds Fibrous furnish, e. g. sulphite pulp, soda pulp and old paper stock 1000 Alkaline filler, e. g. calcium carbonate magnesium hydroxide 200 Emulsion of saponifiable material in substantially unsaponified form, e. g. rosin, (based on weight of sosin) 5 Added continuouslydnd proportionately at dilute stage of the papermaking process Pounds Acidic material, e. g. alum 15 Another example is:

Added in the beater Pounds Sulphite and soda pulps 700 Coated broke (containing about fibre)- 430 Alkalinefiller, e. g; calcium carbonate mag-' Acidic material, e. g. alum..-.. 15

*ing process is one form; calcium carbonate mag- Another example is:

. Added in the beater V POllIidS Sulphite and soda pulps 700 Coated broke (containing about 70% fibre)- 430 Bewoid size (based on weight of rosin 'present) -5 Acidic material, e.,g. hydrochloric acid .5 Alkaline filler, e. g. calcium carbonate 100 Added continuously and proportionately at dilute stage Pounds Acidic material, e. g. alum 15 It is to be understood of course that these furnishes are to be taken only as illustrative examples of my invention, and that they are in no way limiting, as it is possible to vary these formulas-widely both as to ingredients and proportions and order of addition, and still obtain satisfactory results.

Instead of, or in addition to, introducing my emulsion into the fibrous 'mix, I may apply it to the web, by which is intended to be included the web either during the process of its formation or after it has been formed. This application to the web may take place either on the paper machine or subsequently. If desired, a precipitant or mutually flocculating precipitants may be applied to the emulsion prior to its application to the web, or a precipitant or mutually fiocculating precipitants may be applied to the web at the same time as the emulsion, or independently thereof. Any known method of making such application is suitable.

' The application to the web of an amount of size insuflicient to impart a substantial degree of sizing to the paper has in certain cases additional advantages which may vary with different stocks and machine conditions, but which may include the improvement of the printing and/or physical characteristics of the sheet. 1

According to customary usage in the art, as

pointed out in my Patent No. 1,819,441 (page 2,

lines 83-84), the term sized paper" designates paper which is resistant in varying degree to ordi- V nary aqueous writing ink. Thus, the term substantially unsized paper is used herein as it is customarily used in the art, namely, to designate paper having substantially no resistance to the penetration of aqueous writing ink.

Where I use the'word rosin, I intend to include not only the natural resin, but any synthetic resin acid or acids.

In place of alum I may use otheraluminum salts or other metallic salts such as zinc sulphate or the like, or other acidic materials such as acid, sodiumbisulphate or the like.

By the term "alkaline filler I mean substantially water insoluble 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 magnesium hydroxide disclosed in my United States 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 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 thick nesses, which contain as an essential constituent a considerable amount of prepared fibreand which are capable of being produced on a Fourdriner, cylinder, or other forming, felting, shaping or molding machine, and-which are of the classes known as printing, news, magazine, book, catalog and similar papers.

By the term wet endof 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,

stood that the details of procedure, the proportions of ingredients, and the arrangement of steps may be widely varied without departing fromthe spirit of my invention or the scope of the 'subjoined claims.

,I claim:

1. In a process of manufacturing substantially unsizedpaper wherein a paper mix containing fibrous material and alkaline filler is prepared and then run off on a web-forming device, the step of adding saponifiable material in an amount insufficient to impart to said paper any substantial degree of resistance to the penetration of aqueous writingink, more than of the total amount of said saponifiable material being in unsaponifled form.

2. In-amethod of manufacturing substantially unsized paper filled 'with alkaline filler, the step of adding to the papermix from which said paper is to be made an emulsion -of saponifiable material of which more than 55% of the total amount is presentdn unsaponified form, in an amount insumcient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink.

3. In a method of manufacturing substantially unsized paper filled with alkaline filler, the steps of adding to the paper mix from which said paper is to be made an emulsion of saponifiable material of which more than 55% of the total amount is present in unsaponified form, in an amount insufficient to impart to said paper any substan-' tial degree of resistance to the penetration of aqueous writing ink, and acidic material.

4. A method according to claim 2 wherein the saponifiable material is rosin.

5. In a method of manufacturing substantially unsized paper filled with alkaline filler, the step of adding to the paper mix from which said paper is to be made saponifiable material substantially completely in unsaponified form, in an amount insufficient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink.

6. A method according to claim 5 in which the saponifiable material is rosin.

7. A method according to claim 5 wherein the saponifiable material substantially completely in unsaponified form is Bewoid size.

8. In a method of manufacturing substantially unsized paper filled with alkaline filler, the step of adding to the paper mix from which said paper is to be made an emulsion of saponifiable material substantially completely in unsaponified form, in an amount insuificient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink.

9. In a method of manufacturing substantially unsized paper filled with alkaline filler, the steps of adding to the paper mix from which said paper is to be made saponifiable material substantially completely in unsaponified form, in an amount insufficient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink, and acidic material.

10. In a method of manufacturing substantially unsized paper filled with alkaline filler, the steps of adding to the paper mix from which said paper is to be made saponifiable material substantially completely in unsaponified form, in an amount insufiicient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink, and alum.

11. In a method of manufacturing substantially unsized paper filled with alkaline filler, the steps of adding to the paper mix from which said paper is to be made an emulsion of saponifiable material substantially completely in unsaponified form, in an amount insufficient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink, and a precipitant therefor.

12. In a method of manufacturing substantially unsized paper filled with alkaline filler wherein a fibrous mix is prepared and then run off on a webforming device, the step comprising applying to the fibrous web containing alkaline filler saponifiable material of which more than 55% of the total amount is in unsaponified form, in an amount insuflicient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink.

13. In a method of manufacturing substantially unsized paper filled with alkaline filler wherein a fibrous mix is prepared and then run off on a webforming device, the step comprising applying to the fibrous web containing alkaline filler an emulsion of saponifiable material of which more than 55% of the total amount is in unsaponified form,

in an amount insufiicient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink.

14. In a method of manufacturing substantially unsized paper filled with alkaline filler wherein a fibrous mix is prepared and then run off on a web-forming device, the step comprising applying to the fibrous web containing alkaline filler an emulsion of rosin in a substantially water-soluble gum solution, in an amount insufficient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink.

15. In a method of manufacturing substantially unsized paper filled with alkaline filler wherein a fibrous mix is prepared and then run off on a web-forming device, the step comprising applying Bewoid size, in an amount insufficient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink, to the fibrous web containing alkaline filler.

16. Substantially unsized filled paper comprising fibrous material, alkaline filler, and substantially water insoluble saponifiable material substantially completely in unsaponified form, in an amount insufi'icient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink.

17. A product according to claim 16 wherein the saponifiable material is rosin.

18. Substantially unsized filled paper comprising fibrous material, alkaline filler, and substantially water insoluble saponifiable material on the surface, said saponifiable material being substantially completely in unsaponified form, and being in an amount insufficient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink, and being so distributed on the surface as not to impart to any substantial portion thereof any substantial degree of resistance to the penetration'of aqueous writing ink.

19. A product according to claim 18 wherein the saponifiable material" is rosin.

'20. Substantially unsized filled paper comprising fibrous material, alkaline filler, colloidal mat'erial and substantially water insoluble saponifiable material substantially completely in unsaponified form, in an amount insufiicient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink.

21. Substantially unsized filled paper comprising fibrous material, alkaline'filler, and colloidal material and rosin derived from Bewoid size, in an amount insufficient to impart to said paper any substantial degree of resistance of the penetration of aqueous writing ink.

22. Substantially unsized filled paper comprising fibrous material, alkaline filler, and a gum and rosin derived from an emulsion of the rosin in a substantially water-soluble gum solution, in an amount insufiic'ient to impart to said paper any substantial degree of resistance to the penetration of aqueous writing ink.

HAROLD ROBERT RAFTON.