US1762928A - Water-resistant paper - Google Patents

Description

Patented June 10, 1930 STATES NHTE PATENT oFFIcE WATER-RESISTANT PAPER No Drawing.

This invention relates to a water resistant paper, or one which is rendered sufliciently resistant to the ingress of moisture to serve Various applications where so-called water-- proof paper or boardis required, and relates particularly to paper containing a wax such as parafiin wax as the major or essential waterproofing agent, said paper having good strength and possessing what is known as crackle or rattle.

My invention comprises paper which is Waterproofed with such wax material, preferably incorporated with t e pulp, as, for example, in the beater engine, applied in the form of adispersion or emulsion. In one form of the invention I contemplate avoiding the employment of any resinous size such as ordinary rosin size. The latter is supposed to give stiffness and rattle to paper, while 2 paraflin wax is supposed to render paper limp. The rosin size is expected to give strength, while it is assumed that wax will tend to cause weakness. In carrying out the present invention I am enabled to produce, even without the employment of any rosin size, a relatively strong paper having a desirable rattle or crackle and a stiffness meeting commercial requirements.

The usual procedure in the sizing of paper pulp, with, for example, rosin size, is that of adding a rosin soap or mixture of rosin soap to the paper pulp in the beater engine and after mixing thoroughly with the pulp to add a precipitant or coagulant; alum being the material usually employed for such purposes. In acordanee with the present invention a product is obtained from a wax such as para- 'ffin wax which contains wax particles in so fine a form of division or in some peculiar form of dispersion, such that a precipitant is not necessarily required to secure adhesion of the articles of wax to the cellulose fibres.

e waxy element or ingredient of the composition preferably is essentially paraffin wax and for this purpose, in some cases, scale wax or other cheap grade of paraflin wax may be employed.

Wax preferably is first incorporated with, for example, a solution of silicate of soda and an emulsion produced, whereupon a quantity Application filed March 14, 1927. swarm. 175,440,

of a precipitant such as hydrated lime, alum, and the like, is added to react completely with the silicate of soda. By this rocedure the Wax is obtained in a dis ersed the property aforesaid o becoming occluded pr taken up by moist fibres of wood or celluose.

In some cases a protective colloid such as a small amount of glue, casein, and the like, may form an ingredient of the composition being added preferabl with the silicate o soda. In other cases t e wax may contain a small amount of oleic or stearic acid. In still other cases the wax may have incorporated with it a varying roportion of vegetable waxes such as can elilla or carnauba wax or an acidic mineral wax such as montan wax or montanic acid. The incorporation of.- such hard waxes with the parafiin wax serves to modify its melting point and to some extent its properties of dispersion.

The wax or mixture of waxes may be incorporated with the silicate of soda by melting the former and placing in an agitator, whereupon the solution of silicate of soda is added and the mixture thoroughly agitated for a short time. Then a precipitant, for example,,a quantity of alum equivalent to the sodium silicate is added and agitation continued for an additional brief period, Whereupon the dispersed wax composition is obtained ready for use. Preferably this composition should contain from 25 to 30 per cent of waxy material and preferably, though not necessarily, such compositions should be practic ally neutral to ordinary tests such as that with litmus. Its pH value preferably should range from 7 to 7.3.

Examples of such compositions are the following Example 1 Parts by weight Paraffin wax I... v 3 Silicate of sodai 4 Alum ..........I. a.=. 2 Glue 1 Water" The silicate of soda used 1n the above for- I mula is a commercial formof syrupy consistform having pared is about 17 F.

Example 2 Parts by H weight Parafiin wax 32. 5 M0ntan wax 0. 85

Silicate of soda 5 Alum 2. 75

Glue 0.4

Water 58. 5

In this case, as in Example 1, the silicate of soda specified is a syrup containing about 50 per cent of water.. In like manner this syrup is diluted with per cent of the total water and the alum is dissolved in the remainder of the water employed.

The glue is d;ssolved in the silicate of soda solution. It is desirable to add 1 or 2 per cent of phenol, based on the amount of glue, inorder to preserve the latter. The waxes are melted together and the silicate of soda solution containing the glue is added thereto with thorough agitation, the temperature being about 170 F. Thealum solution is then.

added and agitation continued for. a short time.

.' E mample 3 Parts by 1 weight Paraflin wax... 31 Montan wax 7 Silicate of soda 2. 65 Alum 1. 35 .Water 58 The silicate of soda syrup is diluted with a part of the water and the alum is diluted with the remainder, somewhat similar to the man- 'ner set forth in Examples 1 and 2. The waxes are melted together and the silicate of soda solution is added thereto with vigorous agitation at a working temperature of 170 F. When the incorporation is thoroughly effected the alum solution is introduced. A very fine Wax dispersion results.

Example 4' Parts by weight Parafiin wax- 37 Quick lime 1J7 Alum 4.6 \Vater 56. 7

The quick lime is treated with about 65 per cent of the total water and the alum is dissolved in the remaining water. The wax is melted and placed in an agitator and the.milk of lime is added. After stirring vigorously for about one minute the alum solution is added and agitation continued for two minutes, whenthe wax composition is ready for use. As in the foregoing, it is recommended that the working temperature in the preparation of the wax composition be about 17 0 F.

The foregoing compositions serve to illustrate the present invention, but it should be understood that these procedures are set forth solely for illustrative purposes and that various modifications with respect to proportions, temperatures and procedure and manner of incorporation may be utilized, also that substances of an equivalent character may replace one or more of the foregoing-constituents. I prefer to dilute the wax composition (which comes from the agitator containing approximately 30 per cent of waxy material) until it contains about 5 per cent of waxy material and add it in the diluted state to the beater through a screen of about GO mesh. I have found that this insures a better dispersion through the stockin the beater. When using waxes containing rosin soaps and free present invention is used that the acidity of the paper stock, after said composition is added, is not at all critical, and. may vary Lfrom an acidity corresponding to a pH value of 4.5 -to 7 without affecting the retention of the wax by the fibre. I have also found that the Wax composition can be added to the pulp if the pulp is acid, that is, corresponding to a pH value of from 5 to 6.5. In this case it is not necessary to add any further precipitant such as alum. This allows of a considerable saving of alum. The stock being less acid increases the life of the various parts of the system such as pumps, piping and Wires.

The following will serve as an illustration of the beneficial effect of the use of'this wax composition A plant engaged in the forming of pulp articles and using standard rosin size had considerable difliculty due to the rosin adhering to the wires on the forming machines, making a product which had badly formed edges. and holes. They also had trouble with their piping system and pumps on account of the acidity of the stock due to the use of the amount of alum necessary to precipitate the rosin size. In this plant when rosin size was discontinued and a Wax composition made in the manner above set forth was employed, no -t-rouble was experienced with the products sticking to the wires on the forming machine, and furthermore the production was increased at least 15 per cent, with the product being uniformly much cleaner on the edges and tougher, that is, not as brittle as previously.

As the pulp was nearly neutral to litmus when the Wax size wasused there would not be the expected deterioration of the pipings and pumps consequent on the procedure involved in using rosin size.

I have found that using wax composition mentioned above, a retention of the; wax on the fibres of from 7 5 per cent to 90 per cent, 1

depending on the nature of the stock, resulted. Moreover, any wax that is not retained on the fibre does not adhere to the felts or wires of the paper machine or forming machines, but is carried away with thewhite water. Wax which does not adhere to the pulp fibres must not adhere to the felt and to the wires, as this would prevent drainage of the pulp sheet and cause holes in the sheet, or

spots on the surface of the sheet.

I have found that the addition of only 1% per cent of wax will give water resisting qualities satisfactory for the ordinary uses to which paper porducts are put, although for special purposes the amount of wax can be increased to 4 M5 per cent. I have found that the addition of wax up to 5 per cent tends to increase'the strength and to improve the rattle or stiffness. This is a surprising result as parafiin wax has been supposed to have a lubricating action on fibres and thus yield a a weak limp paper. Paper containing this wax dispersion is not as susceptible to changes in atmospheric moisture, and for this reason is peculiarly adapted to use in the printing trade where it is necessary to register two or more impressions. I have found that paper containing 1 to 1% per cent of wax and 1 to 2 per cent of rosin, the rosin being added as or dinary rosin size, does not lose strength when subjected to the action of a greasy material as paper does when it is only sized with the ordinar rosin size. This property makes the use 0 emulsion ,in paper for food containers and greasy articles very valuable.

When the plant aforesaid was using rosin size it was necessary for them to use fresh water in the beater and to dilute the stock before it went to the forming machines. As this water was pumped from artesian wells it was an item of considerable expense. With the wax composition the plant could be worked in a closed system, that is, the water drained from the forming machines was returned to the heaters and the make-up chests. It is possible to do this when using the wax composition because the wax therein is not critical as regards the acidity of the stock in the beater when the said composition is added the acidity is very small. In the particular instance cited, less than one-tenth of the alum that was used with the rosin size was used with the wax composition.

The formation of a wax dispersion composition in the manner described above, that is, adding a precipitating substance to a mixture of wax, water and an emulsifying agent produces what may be termed a pre-set wax dispersion. Instead of forming an emulsion of Wax by means of an emulsifying substance such as soap, adding this emulsion to the pulp in the beater, and then introducing a precipitant, I prefer to accomplish apart at least of the precipitation in advance of introduction of the wax dispersion or emulsion into the paper pulp stock. By employing such a preset. or partially pre-set wax dispersion composition, preferably containing parafiin wax as the principal waxy component, I am enabled to produce a composition having the novel property of being absorbable by paper pulp stock in large proportion, that is, the major proportion of the wax is readily taken up by the pulp, with or without the addition of additional precipitant, and the minor proportion of said dispersion composition,usual- 1y representing only from 10,t0 20 per cent of the entire wax, being capable of passing through the screen, felt or other web (upon which the pulp is formed into a sheet) without fouling and obstructing said web. In this respect I believe that I have obtained a wax dispersion composition possessing qualities of great importance in the manufacture of iii/later resisting paper, pressboard, and the As indicated by the foregoing the water resistant paper is prepared by adding the wax dispersion composition to pulp at any suitable stage prior to formation of the pulp into a sheet. Thus the composition may be added to best advantage in the beater engine. The paper stock may be any suitable material such as sulphite pulp, sulphate pulp, or kraft stock, newsprint, ground wood, and the like, or mixtures of these. In some cases, rag stock may be added. Preferably, as indicated, the pro- \portion of wax in the finished paper may be from 1 to 2 per cent, to secure a considerable degree of water resistance and larger proportions of wax, such as 4 or 5 per cent, or, in some cases, even higher proportions, may be present. After the dispersion has been added, followed, if desired, by a precipitant such as 'alum, the pulp may in due course be formed into sheets, either continuous or. discontinuous, or, the pulp may be shaped in any suitable manner. The usual papermaking machines, such as the cylinder machine and the Fourdrinier machine, may be employed, thus forming a layer of the paper pulp and wax composition on a felt or wire support, as thecase may be. After drying the paper preferably is run through calender rolls. If pressboard is to be produced, this .may be prepared on board machines.

In some cases, as has been indicated, rosin size may be introduced into the charge in the beater engine and a composite effect obtained by the presence in the paper of the waxy material and the rosin size. When the latter is used, it is essential to add torthe pulp some substance such as alum, and the like, which will cause the rosin size to precipitate among the fibres. In such a case, therefore, I incorporate the pre-set wax dispersion com position and rosin size with the paper pulp. In the finished paper there may be present from, say, 1 to 3 per cent, of wax,'and a like amount of rosin size material. Paper of this character not only is notably water resistant in the sense the term is employed in the case of papers of this general character, but also it has the property of exhibiting a considerable resistance to the action of grease and hence-may be termed a grease-resistant and water-resistant paper product. A moderately heavy paper or light board made in this -manner may be employed to advantage in r the production of containers for greasy foods.

On the other hand there are numerous applications of paper products treated only with the pre-set wax dispersion composition and entirely free from rosin, which exhibit an unexpected strength and which have a desirable crackle, such paper products falling within the purview of my invetnion. I consider the preferred embodiment of my invention a water-resistant paper (which includes also pressboard, and the like) containing not to exceed about 5 per cent of paraflin wax, conferring such properties as have been noted above. I also include as a preferred embodiment a paper which is free, or substantially free from rosin size, yet has not only many characteristics engendered in paper by rosin size, but in addition has greater water resist- .ance than would be conferred upon paper sizedwith a corresponding amount of rosin size only. I

In copending case No. 17 5,427 filed March 14, 1927, there is claimed the method of introducing wax dispersion into paper pulp, while in copending case No. 175,428 filed on the same date there is claimed a specific type of paper having grease resistant properties.

What I claim is 1. A water-resistant paper containing not to exceed about 5 per cent of wax comprising paratfin Wax conferring strength and crackle thereto.

2. A water-resistant paper containing not to exceed about 5 per cent of wax comprising paraflin wax conferring strength and crackle thereto; said paper being free from rosin size.

3. A water resistant paper containing a pre-set wax.

said paper is substantially free from wax 7. A water resistant paper made from pulp containing a non-fouling wax composition containing glue whereby said paper substantially free from wax spots.

v 8. A paper made from fibrous pulp containing a waxy dispersion, the particles of wax being present under conditions such that fouling does not occur-under the usual conditions prevailing on paper-making machines. a

9. A paper made from fibrous pulp containing a wax emulsified in a medium containing an emulsifying agent under conditions to yield a non-fouling wax composition -under the usual conditions prevailing on paper-making machines.

. 10. A water resistant paper made from pulp containing a non-fouling mineral wax composition, whereby said paper is substantially free from wax spots.

11.- A paper made from fibrouspulp con taining a mineral wax dispersion, the particles of mineral wax being present under conditions such that fouling does not occur under the usual conditions prevailing on paper making machines.

GEORGE JAMES MANSON.

GERTIFICATE 0F CORRECTION.

Patent No. 1,762,928. Granted June 10, 1930, w

GEORGE JAMES MANSON.

It is hereby certified that error appears in. the printed specification of the above numbered patent requiring correction as follows: Page 1, line 31, before the word "soap" second occurrence insert the words "androsin"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of July, A. D. 1930.

Wm. A. Kinnan,

(Seal) Acting Commissioner of Patents.