US1797048A - Method of imparting high finish to paper - Google Patents

Description

March 17,1931. A, CLAPP 1,797,048

METHOD OF IMPARTING HIGH FINISH TO PAPER Filed F'eb.` 19, 1925 Patented VMal. 17, 1931 UNITED STATES PATENT OFFICE" ALBERT L. CLAPP, OF DANVERS, MASSACHUSETTS, ASSIGNOR TO BENNETT, INCOR- PORATED, F BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS METHOD 0F IMPARTING HIGHYFINISH TO PAPER Application filed February 19, 1926. Serial No. 89,502.

This invention relates to a method of imparting a high finish or glaze to paper in the course of its manufacture, without the necessity of subjecting the paper to a super-calendering or friction-calendering operation, and

Without the use of special machinery.

In producing a paper having superior finish to that which may be made by only the usual calendering operation which takes place after the drying of the paper, the practice is to pass the paper successively between pairs of rolls of a series of contacting, superposed, supercalendering rolls, or friction rolls made alternately of chilled, polished steel and highly compressed paper or cotton. The finish may be enhanced by applying moisture in the form of a steam shower or water spray to either or both sides of the paper, the effect produced by calendering being similar to that produced in ironing amoistened shirt or collar. Further to augment the finish, a small quantity of wax, such as carnauba, is sometimes applied to the paper during the super calendering or friction-calendering operations.

have 4found that a paper 'having a high finish or glaze may be produced if a dispersion comprising a glazing. or polishing wax, such as carnauba, and a wax of lower melting point, such as paraffin, is applied to the paper prior to or during the usual calendering operation, after the paper has been dried. Such a dispersion melts readily at the temperature of the\calenders, penetrates the surface of the paper, and permits the paper to be highly polished after the drying operation, by the usual calenders, without the necessity of a subsequent supercalendering or friction-calendering operation.

The dispersion may be prepared by heating and melting the waxes and while in molten condition mixing with vigorous stirring with a hot, concentrated aqueous soap solution, and continuing the stirring at a temperature above the melting point of the Wa-xes until the dispersion has been effected, whereupon the dispersion is allowed to cool. The dispersion consists of finely divided, congealed particles of the paraiin and carnauba Wax, enveloped or protected by the soap dispersing solution, which prevents the coalescence of the finely divided,- di-screte particles into larger particles while the particles are in molten condition and after they have become congealed, so that when the dispersion is subsequently1 diluted in water, there is very little tendency for the particles to separate or iioat out.

Another method which may be employed in the preparation of the dispersion may be about as follows. The waxes are melted and While in molten condition are mixed with a hot solution of sodium silicate. The entire mass is thoroughly stirred until the molten materials have been reduced to a finely dispersed or divided condition, whereupon the dispersion is cooled. Preferably the cooling is effected by suddenly chilling the dispersion, as by adding cold water thereto or'by jacketing the dispersing kettle with a cooling medium, so that the waxes are frozen or congealed in finely divided condition, without allow- Y ing any material saponification of the waxes to take place, and also reducing the tendency to coalescence of the particles into larger agglomerates while they are in molten condition. The dispersion comprises minute particles of the dispersed waxes in substantially unchanged condition in the silicate solution. If desired, a solution comprising a mixture of both sodium silicate and soap may be used as the dispersing agent.

The sodium silicate dispersion is preferably employed in the practiceof the method set forth in the present invention, since I have found that better results may be obtained therewith than when the dispersion is effe-cted with a soap solution, the soap lowering somewhat the glaze which may be produced by substantially unsaponilied waxes alone and causing a gummy condition on the calenders and also a slight. discoloration of the paper when white paper is being polished.

A typical dispersion which may be used in glazing the paper may be composed, for example, of 90 parts of parafhn aud l0 parts of carnauba dispersed in sodium silicate solution. The paraffin, which has a melting point of 118o F. to 120o F., fluxes readily withthe carnauba wax, which melts at about 180 to 183 F., the mixture melting readily at the temperature of the calender rolls (about 130 to 135 FJ and producing a very smooth surface or glaze on the paper.

A dispersion may be prepared by melting a mixture composed of 90 parts of paraffin wax and parts of earnaubawax, land raising it to a temperature of from 300 to 360" F. The melt is mixed with a hot solution of sodium silicate at about 200 F'., composed' of parts of sodium silicate (60 Baume) and 15,0 parts of water. The materials are frap'idly and intimately stirred until a complete dispersion of the waxes has-been effected, whereupon the mass is cooled to a temperature below the melting point of the waxes, preferably by the rapid addition of cold water thereto or by j'acketing the dispersing vessel with a cooling medium. The dispersion so made is of a heavy or cre my consistency, and before being used as a lazing agent at the calender rolls is diluted, as for example, with 100to 500 times its weight of water, depending on the degree of finish desired.

The invention may be best understood from the following further description thereof, when considered in conjunction with the accompanying drawings, wherein Figure 1 illustrates in side elevation a portion of the dryers and a stack of calender rolls, certain of which rolls receive the dispersion from receptacles and apply it tothe surface of the paper.

Figure 2- represents a plan view of the calenders.

Figure 3 is a section through the two up.- per calender rolls, on the line 3-3 of Figure 2.

Figure 4 shows a section through a sheet of glazed paper as made herein.

Referring vto the drawings, the sheet of paper S passes from the dryer rolls 7 under the guide roll 8 to the top of the calender stack, and thence successively between the super-posed rolls, passing from the bottom 0f the stack ready forfurther treatment, for example, as cutting or reeling, as may be desired. The dispersion is applied to the iron side of either or both of the two upper calender rolls 9, 9a, from receptacles or tanks 10. Each receptacle is provided with a bottom 10a and ends 10b, which conform accurately to the contour of the roll so that a supply of the wax dispersion may be maintained in the receptacle, and is supported at its ends by the brackets 11 secured to the frame work 12. In rotating, each of the rolls 9, 9a picks up a fil-m or coating of the wax dispersion from the supply maintained in its respective receptacle, and applies it to the surface of the paper with which it contacts. The thickness of the film picked up by each of the rolls is determined by thev clearance between the roll and a' doctor 13 vextending across the tank 10a at its top.

While I have described one method of applying the wax dispersion to they surface of the paper during the calendering operation, it should be obvious that other methods may be used for the application of the dispersion prior to or during such calendering, as by sprayingthe dispersion onto the paper in line form, by means of suitable spraying devices. Thefilm of wax dispersion is thus applied to each side of the paper, and the paper moistened, therewith, upon being calendered, is highly polished or glazed, the waxes permeating the surface of the paper, imparting additional water resistance to the surface portion a, a thereof, and thus serving as a Waterproofing or surface-sizing agent.

Furthermore, thewater associated with the wax dispersion gives all the advantages incident to the usual water finishing of pa r.

If desired, I may add a greaseproo g agent, such as glue, to the dispersion, so as to give the paper a grease-resisting surface. Thus, I may apply a composition comprising about one part of glue to about one part of dispersed waxes. I may also incorporate coloring agents, such as pigments and dyes together with the dispersed waxes, to impart the desired surface color to the paper. Ordinarily, when dyes andV pigments are used at the calenders, a smooched surface results, but when used together with a fusible wax dispersion such as herein provided, produce a uniform color over the entire' surface. The

finished paper thus'produced simulates sol called vat lined paper composed of a plurality of plies, one or more of which are formed from coloredv stock.

I .may use dispersions containing various .proportions of para-ihn and carnauba wax,

the carnauba by equivalent waxes, such as Y Montan; or a mixture of such wares may be employed. Montan, however, has the disadvantage that it does not impart a permanent glaze to the paper.

As previously stated, it is essentialsthat paraiiin or other wax of lower melting point be employed with carnauba, since when carnauba alone is employed Qat the. calender rolls it produces streaks in the paper. The streaky efect is doubtless produced because carnauba does not melt at the temperature of the calender rolls', and is consequently crushed therebetween and forced into the paper unp evenly,-rathe'rA thanei'ecting an even penetration. I may, however, use parain only at the calenders, and increase the waterproof qualities of the paper, but, since it does not produce ahigh glaze, I preferably use a glazeproducing wax, such as carnauba, therewith.

When papers surface-finished in accordance with this invention are employed for writing or printing purposes, there is a decreased ink consumption, and because of the low spread of ink the writing or printing stands out very clearly.

By the term calenders, as employed in the appended claims, I mean the usual hot calenders which are located at the dry end, i. e., after the driers, of the paper machine, in contradistinction to supercalenders or friction calenders which are sometimes employed for calendering paper subsequent to the usual calendering operation.

Having thus described this invention, it should be obvious that it is capable of various changes and modifications Without dearting from its spirit or scope as defined y the appended claims.

I claim:

1. A method of treating paper in the course of its manufacture, which comprises applying to the surface of the paper after the drying operation an aqueous dispersion of solid particles of waxes fiuxible at the calendering temperature of the usual hot calender rolls at the dry end of the paper machine, and hot calendering the paper.

2. A method of treating paper in the course of its manufacture, which comprises applying to the surface of the paper after the drying operation an aqueous sodium silicate dispersion of solid particles of waxes fluiible at the calendering temperature of the usual hot calender rolls at the dry end of the paper machine, and hot calendering the paper.

3. A method of treating paper in the course of its manufacture, which comprises applying to the surface of the paper after the drying operation an aqueous dispersion of solid particles of paraffin uxible at the calendering temperature of the usual hot calender rolls at the dry end of the paper machine, and hot calendering the paper.

4. A method'of treating paper in the course of its manufacture, which comprises applying to the surface of the paper after the drying operation an aqueous dispersion of solid articles of carnauba and paraffin waxes uxible at the calendering temperature of the usual hot calender rolls at the dry end of the paper machine, and hot calendering the a er.

A method of treating paper in the course `of its manufacture, which comprises applyrying to the surface of the paper after the ing operation an aqueous dispersion of sohd particles of waxes containing a greaseproofing agent and fluxible at the calenderlng temperature of the usual hot calender rolls at the dry end of the paper machine, and hot calendering the paper.

6. A method of treatmg paper 1n the course of its manufacture, which comprises applying to the surface of the paper after the drying operation an aqueous dispersion of solid particles of waxes containing glue fluxible at the calendering temperature of the usual hot calender rolls at the dry end of the paper machine, and hot calendering the paper.

7. A method of treating paper in the course of its manufacture, which comprises applying to certain rolls of the usual hot calender stack at the dry end of the paper machine, an aqueous dispersion of waxes fluxible at the calendering telnperature, and passing the paper between the rolls of the stack after the drying operation.

' 8. In the manufacture'of paper from fluid, fibrous pulp, the process of applying to the surface of the advancing formed paper sheet, after it has been dried but before it has been calendered, a solution containing an emulsion of paraffin.

9. In the manufacture of paper in a continuous 'web or sheet, a process for finishing said sheet whichconsists in applying a thin solution containing paraffin to the surface of the advancing sheet after is has passed the drying rolls and as or before it enters the calendering rolls.

101 In the manufacture of paper in a continuous web or sheet, aV process for finishing said sheet which consists in applying a thin solution of parafn emulsion to the surface nature.

ALBERT L. CLAPP.

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