US1592294A - Method of making waterproof paper or fiber board - Google Patents

Description

Patented July 13, 1926.

ALBERT L. CLAPP, or nauvnns, MAssAcsrusn rrs.

METHOD OF MAKING WATERPROOF PAPER 0R FIBER ZBOARD.

W0 Drawing.

This invention relates to waterproof paper or fiber board, such for example as is suitable for use as a wrapper or container for food products.

It also relates to the method of manufacture of this paper or fiber board 'by which the Waterproofing material is incorporated in the paper stock so that the waterproof paper is completely formed on the paper machine, no subsequent saturation with the waterproofing material being necessary. By thismethod it is possible to form paper with a waterproof liner backed by other kinds of paper. This is of advantage, as for example, in the manufacture of paper pails and boxes, such as are commonly used for oysters, ice cream, etc., the waterproof liner being on the inside of the container where it contacts with the food and the outside of the container being of a nature to readily receive printing thereon, since printing can not be satisfactorily done on the waterproofed paper. The outside liner may also be made of-cheap material such as news- I paper, thus materially cheapening the material without in any way impairing its suitability for the purpose intended.

Heretofore it has been proposed to incor:

porate waterproofing material such as parafiin in the beater stock by forming an emulsion of the paratfin in a more or less saponified aqueous mixture. In practice, however, it has been found commercially impossible to run such a stock on a paper machine, as

' the emulsion forms a sticky mass which clogs the cylinder mold or Fourdrinier wire, and

sticks to the blankets. The saponified mix-' ture holds much water in combination and aside from the trouble from sticking it is a diliicult matter to drive this off by the ac tion of the drying rolls of the paper machine. The paraffin is also contaminated by a comparatively large amount of saponified salts and so fails to be wholly effective in waterproofing the paper.

A fine dispersion of parafiin or other waterproof material, however, may be made in an aqueous solution of a nature which permits the waterproofing material to be fixed as fine particles or granules to the fibers of a paper stock and without the production of any sticky substances which may stick to the blankets of the paper machine or clog the cylinder molds or Fourdrinier wire by the method described and claimed in Applicaticnfiled November 6,1923. Serial- No. 673,215.

my application for patent entitled Disper-.

comprising 200 parts of silicate of soda and 1500 parts of water, the mass being thoroughly stirred and agitated while the mixture is being efi'ected. lVhile continuing the stirring the mixture is then cooled suddenly i belowthe melting points of the waxes and rosin as by means of the addition of 2250 parts of cool or cold water, the stirring being continued until the wax and rosin appears as finely dispersed particles in the solution. While the parafiin in itself may be dispersed in the aqueous solution, yet the Montan or carnauba wax, being of greater penetrability and of lower surface tension than the paraffin, acts to permit a fine dispersion of the wax in thesolution.

By the present method, therefore, the paraffin and Montan or carnauba waxes and the rosin are dispersed in finely divided or granular form in a silicate of soda solution, the mixture being non-sticky. This mixture has the physical characteristics of inert granu- I do not herein claim per se the method of effecting a dispersion of the paralfin or other water-immiscible compound or composition.

The procedure in the production of the paper may be as follows: 5 to 45 parts of paralfin dispersion product, made according to a method heretofore described, are added to 55 to parts of beaten sulphite pulp and thoroughly mixed therewith, 5 to 25 parts of alum or other precipitant may then be added and mixed in for a few minutes to form a flocculent precipitate with the silicate which acts to fix the dispersed material on the pulp. The sodium silicate acts as a coagulant to fix the dispersed particles over the fibers. The stock may then be run off on the paper machine and may be passed over heated calender rolls which causes the dispersed grains to flux together throughout the material. This stock is found to run as well or better on the paper machine than lar material in a sodium silicate solution.

therefore, is not only waterproof, butis water repellent comparable in this respect to paper which has been dipped in melted paraffin. z

So far as I am aware I am the first to produce a paper having these characteristics where the paraflin is incorporated in the pulp before it is sheeted on the paper mach ne. The product is quitedifi'erent from a paper water-proofed by size such as rosin size. The rosin soap in rosin size is precipitated on the fibers in the form of a resinate which is incapable of-being fiuxed without great heat'so as to form a coating entirely encasing each fiber. By the method of this invention, however, the wares, and nearly all of the rosin as free rosin is deposited on the fiber as such and may therefore be fluxed to encase the fibers as hereinbefore described.

Not only does the method of this invention produce a paper directly on the paper machine as waterproof and water repellent as that dipped in melted paraflin, but this is accomplished with much less wax than is necessary in the dipping process and Without the presence of an apparent coating of wax on the surface.

Other cellulosic, material besides sulphite pulp might, of course, be used, but this is a stock. preeminently suited for the manufacture of food containers, particularly when bleached, because of its freedom from substances which might contaminate the food.

In place of'forming the entire board or paper with the paraflin therein, it may be 'formed with two or more plies, one or more plies, which are intended to be in contact with the food being formed of stock containing the parafiin, and the outer ply or plies not having the paraffin therein. This may be done on a multi-cylinder machine, the stock for some of the cylinder molds containing the dispersed waterproofing material and the stock for the other molds having no such -material. The waterproofing material being in dispersed condition in the stock in no way hinders the interfelting of i the two or more plies, as they are formed and brought together on the multi-cylinder machine, so that a proper felted union of the waterproofed and non-waterproofed plies of the finished product is assured. For example, the inner liner may be made of stock comprising 70 to 90 parts of sulphite pulp, 5

to 30 parts of the paraffin dispersion product, and parts of silicate of soda, to which 5 to parts of alum may ,be added before the stock is run in order to precipitate the parafiin on the pulp. The 10 parts of silicate of soda are merely added to insure sufiieient silicate to properly coagulate and bring down the parafi'in on the pulp and can be omitted in case the silicate in the-dispersion product. appears to be suflicient to produce the desired action.- The outer liner may be formed of any suitable cellulosic stock, such for example, as 100 parts of sulphite-pulp, 5 parts of rosin size, 5 parts of alum.

A somewhat cheaper grade of paper or board suitable for oyster pails and the like may be made by the use of cheaper cellulose fiber in the outer ply,- suchfor example, as newspaper pulp. A board particularly suitable, for instance, for milk bottle caps,may have-its cellulosic material composed of parts of easily bleached sulphite pulp and 30 parts of ground wood pulp. v A sanitary Waterproof wrapping paper for food products may be produced from parts of sulphate pulpand 35 parts of paraffin dispersion product.

lVhile various waxes, gums, rosins' or resins may be dispersed by subjecting them to treatment similar to that hereinbefore described, paraflin is preferable for food containers or wrappers because of its chemical purity, its ability to stand low temperatures without becoming excessively brittle, its clean appearance, and its compliance with all of the various pure food laws.

A very desirable building paper, or boxboard, may be produced by employing the parafiin or other waterproofing dispersion product in the outer plies of the board or paper and in the inner plies using a cheaper waterproofing agent, such. as asphalt emulsion, for example, the emulsion known to the trade as K-B emulsion which comprises an emulsion of asphalt with a colloidal clay solution. Thus the furnish for the top and bottom liners may comprise 50 parts of newspaper, 50 partsmagazine stock, 20 parts of paraffin dispersion product, and 20 parts of alum, while the middle filler may comprise parts of news, 100 parts of K-B emulsion (dry or 200 parts wet), 15 parts of silicate of soda,*20 parts of alum. Such paper is waterproof throughout and can be run readily on the paper machine. Where asphalt emulsion alone is employed as p a waterproofing agent, it is usually necessary to apply top and bottom liners Without the emulsion in order to prevent the material from sticking to the blanket and the drying 1011s of themachine. As before noted the paraffin dispersion product promotes rather than hinders the proper running of'the paper in the machine, since it acts as a Inbricant and prevents sticking to the parts of the machine with which it comes into contact.

A dispersion product suitable for waterroofing paper by the method hereinbeore described but containing a large proportion of carnauba wax may be made by substituting for paraflin and rosin in the example heretofore given, 500 parts of rosin and 500 parts of carnauba wax. It is also possible to form a dispersion of carnauba wax alone in the silicate of soda solution by the hereinbefore described method, though the presence of some rosin or Montan wax causes the dispersion to be somewhat finer.

Similarly the amount of paraflin may be decreased and the amount of rosin increased, 500 parts of paratfin and 500 parts of rosin and 50 .parts of Montan wax being satisfactory.

I do not hereindescribed, this subject matter having been divided out from this application and being claimed in my application Serial Number 22,394 filed June 1, 1926, nor do I claim herein the aqueous dispersions or the process for making these dispersions, these subjects matter being claimed in my application Serial Number 673,216 hereinbefore mentiond.

Having thus described this invention it should be evident that many modifications and changes might be made therein without departing from its spirit or scope as defined by the appended claims.

I claim:

1. The method which comprises mixing with beater stock a dispersion product of water-proofing material in an aqueous solution of sodium silicate, adding a recipitant, and running off on a paper mac inc.

2. The method which comprises mixing with beater stock, a dispersion product of paraifin in sodium silicate, adding a precipitant, and running off on a paper machine.

3. The method of producing a waterproof and water repellent paper, which comprises melting a waterproof and water repellent material, adding the melted materials to a hot aqueous solution while it is being thoroughly stirred, suddenly cooling the mixture below the melting point of the material to solidify it in finely dispersed condition, adding the resultant product to fibrous beater stock, recipitating the dispersed material on the fibers, running ofi on a paper machine, and fiuxing the dispersed material.

4. The method of producin a waterproof and water repellent pa er, w ich comprises melting waterproof an water repellent material, adding the melted material to a hot aqueous solution of sodium silicate while agitating the same, and thoroughly mixing, and then suddenly chilling the mixture to herein claim the paper products solidify the material in finely dispersed condition, adding the resultant product to fibrous beater stock, adding another precipitant to form a coagulant with the silicate of soda to fix the dispersed material on the fibers, running off on a paper machine and subecting to a temperature above the melting point of the material until it is fiuxed and coalesced about the fibers.

5. The method of producin a waterproof and water repellent paper, w ich comprises melting paraiiin and dispersing agent, adding the melted mass to a hot aqueous solution and thoroughly mixing therewith, rapidly chilling the mixture below the melting point of the parattin while continuing the agitation to solidify the paraffin and dispersing agent in dispersed condition, adding the product to fibrous beater stock, precipitating the dispersed material on the fibers, sheeting on a paper machine, and subjecting the sheet to a temperature above the melting point of the paraffin and dispersing agent whereby they are fiuxed and coalesced throughout the sheet.

6. The method of producin a waterproof and water repellent paper, w ich comprises melting together paraiiin and a wax having a higher penetrability and a lower surface tension than the paraflin, adding the melted mixture to a hot solution of silicate of soda while it is being agitated, then cooling the mixture below the melting point of the parafiin and wax while the agitation is continued to cause the parafiin and wax to become solidified in finely dispersed condition, adding the resultant product to fibrous beater stock, adding a precipitant capable of coagulating with the silicate of soda and fixing the dispersed material on the fibers,

sheeting on a paper machine, and subjecting the sheet to a temperature above the melting point of the parafiin'and wax to cause them to coalesce throughout the sheet.

7. The method of producing a waterproof and water repellent paper, which comprises melting together parafiin, rosin and Montan wax, pouring the melted mixture into a hot silicate of soda solution while agitating the same, and adding cold water while continuing the agitation to solidify the parafiin, rosin and Montan wax in finely dispersed condition, adding the resultant product to fibrous beater stock, adding aprecipitant capable of coagulating with the silicate of soda to fix the dispersed materials on the fibers, sheeting on a paper machine, and subjecting the sheet to a temperature above the melting point of the paraifin, rosin and Montan wax to cause them to coalesce throughout the sheet.

In testimony whereof I have aflixed my signature.