US2067501A - Parchment paper and method of making same - Google Patents

Description

Patented Jan. 12, 1937 PABCHMENT PAPER AND METHOD OF MAKING SAME John A. Newman, Edgeley, Pa... asaignor to Paterson Parchment Paper Company, Bristol, Pa.. a corporation of New Jersey No Drawing. Application July '1, 1934, Serial No. 734,201

11 Claims. (CI. 91-88) The invention relates to the production of a web of parchmentized vegetable fiber which is waterproof and resistant to dialysis, capable of retarding evaporation of moisture from articles wrapped therein and possessing a surface which will readily receive and retain printer's ink on either surface.

In the standard vegetable parchment paper on .the market, the vegetable fibres of the paper web are converted by a chemical treatment to a gelatinous substance known as amyloid which dissolves as it were or envelops each individual fibre, completely filling the interstices and by a cementing action bonds the whole into a homogeneous mass. As the result of the process of parchmentizing the original paper undergoes such modification that it no longer softens or separates into its original fibres on being soaked or even boiled in water but retains its coherence, being impervious to water, and also retains its newly acquired properties when redried. The conversion is strictly chemical and the result is a product which is both odorless and tasteless and insoluble. These qualities render it particularly suitable for many commercial uses. Although the product is impervious to water, it readily absorbs moisture due to the hygroscopicity of the material. Accordingly, although ordinary parchment paper, due to its imperviousness to water, might seem to be an ideal mate-' rial for purposes of wrapping articles of food or the like, it has not proven itself to be entirely satisfactory for such uses and it has therefore been a customary practice in preparing parch- I ment paper for the purpose of serving as wrapping material for moisture-containing products, to place a surfacing coat of wax or paraffin upon the parchment paper. Due to the solid character of the parchment paper the wax appears as a coating only and is necessarily the product of a wet-wax process, it being impossible to dry-wax v the ordinary parchment paper. A sheet of wetwaxed parchment paper, .because of its waxed surface, does not readily take on printers ink and the amount of wax required is necessarily relatively large.

It is the object of the present invention to pro-- duce a dry-waxed parchment paper which will Confronted with the generalh! accepted fact that vegetable parchment was supposed not to be capable of responding to a dry-wax process, I

conceived the idea that if the parchmentizing treatment were not carried to the full extent used in making the standard paper, there might be a possibility of establishing in the paper a certain porosity sufllcient to permit the paper to become subject to a dry-wax process and still retain the advantages of a parchmentized surface. Experiments based on this idea resulted in the discovery that if in the parchmentizing process the period of exposure to the chemicals was shortened or the chemicals were somewhat weakened, or retarded in their action upon the interior fibres of the paper web, or a combination of any of these conditions were employed, a product would result which, while possessing a well parchmentized surface, was sufficiently porous or absorbent to take up wax or paraffin in its interior structure between the outer parchmentized surfaces in the interior fibres which had been at best but feebly parchmentized, leaving the outer surfaces relatively free of wax.

This is accomplished by passing one surface a of the porous parchmentized web over a roll which applies fluid parafiine and then passing the web between heated drums under slight compression. The waxed paper is then wound on a roll and, being quite hot, the roll is permitted to stand for several hours and in the process of cooling in the tightly wound state the wax is apparently further driven into the fibrous portions of the web and away from the parchmentized surfaces.

The outer surfaces of the thus dry-waxed parchment paper can be readily printed upon and such printing isnot smudged or blurred by reason of the presence of the wax within the body of the paper. The thickness of the paper is not materially increased and due to the fact that there is thus created a continuous barrier or sheet of wax throughout the entire interior portions of the parchment, the moisture contained in articles wrapped in such paper will not be transmitted through the paper and whatever moisture is taken up by the parchmentized portion of the paper on one surface thereof cannot.

readily pass through to the other because of the interposed barrier or dam of wax. The new drywaxed product, to all appearances, is ordinary parchment paper. It does not possess the feel of waxed paper. The interior film of wax is so thin that a paper parchmentized according to the new method which prior to the parchmentizparchment.

ing treatment weighs 27% pounds per 500 24" x 36" sheets, will take up only about three pounds of paraflin per ream. In making the new dry-waxed parchment paper the web may, after the completion of the parchmentizing operation, be treated with a softener or plasticizer such as glycerine for rendering the sheets flexible and pliable and the presence of the glycerine does not interfere with the capacity of the interior unparchmentized or feebly parchmentized fibrous section of the product from absorbing the paraffin. The new product retains the essential characteristics of vegetable parchment and is useful for wrapping, for box linings, and it retards evaporation or escape of moisture as in the case of butter, soap, and other products, and prevents dialysis as is the case of butter containing salt and has many other advantages readily apparent to many classes of users.

A special advantageous feature of the new product is that it can readily be attached to other objects or to portions of itself by means of glue or other cementing material without any difficulty such as is experienced in attempting to glue together waxed paper or wet-waxed In view of the fact that no injurious ingredients are employed, the paper can be safely used in connection with food stuffs.

The process of manufacturing ordinary vegetable parchment involves the initialJmanufacture or use of a paper such as water leaf which contains no sizing and is very soft and absorbent, these qualities being essential for the success of the parchmentizing or chemical step. The parchmentizing or chemical process consists in subjecting the paper web to the action of chemicals such as sulphuric acid, phosphoric acid, zinc chloride, or other agents which will convert the flbresof the paper into a gelatinous substance. A customary strength of acid is about 55 B. (69.65% H2804 at 60 F.)' to'56" B. (71.17% H2804 at 60 F.) but the range is, of course, subject to considerable fluctuation as to acid strength and temperature. A typical speed at which the paper is'passe'd through the acid, for example, in the case of a paper weighing 27 pounds for 500 24" x 36" sheets, is about 350 feet per minute. As the thickness of the paper increases, the run is correspondingly. slower. When the acid-treated paper leaves the acid bath, the adhering acid is washed oif and the paper passes over drying drums and is then finished parchment paper.

A typical example of making the new-paper involves a reduction in the strength of acid to for example 53 B. (65.49% H2804 at 60 F.) with or without an increase in the speed of the machine or maintaining the speed constant, reducing the amount of paper which passes through the bath perunit of time. In any event, the correlation of the factors referred to should be such as to produce a sheet of a porous nature in which a lightly parchmentized web is secured whose top and bottom surfaces are both lightly parchmentizedwhile the interior consists of unparchmentized or but very feebly parchmentized fibres. Inasmuch as the pulp from which the paper is made varies somewhat and some paper is denser or more compressed than other paper of the same weight, the process will be subject to adjustment from time to time whenever the desired result is not obtained. These adjustments are very readily made, preferably by a control of .the speed of the paper through the .acid and/or the control. of the length of paper immersed at any moment in the acid bath. Controls such as these are well understood by those skilled in the art.

In the preferred process the control manipulations just referred to are the only ones 'employed, while the strength of the acid is allowed to remain the same as that used for making standard parchment paper because in that event the same acid can be used for all parchmentizing operations used in the plant including the new process, and for all weights of paper.

Because of the light parchmentization resulting from the new practice, a condition is set up in the product which makes it possible to drive something into a sheet which, if it had been subjected to the standard parchmentization paper.

In the new process the desired result may also be obtained with parchmentizing agents other 7 than sulphuric acid such for example as phosphoric acid, zinc chloride, or other chemicals "effecting a similar conversion of vegetable fibres into a parchmentized product. It is also possible in connection with the new process to load the raw material with pigments, for example, titanium oxide, or opaque pigments, or sizing material for the purpose of retarding the parchmentizing effect of the acids used with the result that acids of the standard or higher concentrations can be used to obtain the result aimed at.

The wax-filled parchment paper is also capable of being used to produce special effects by the application of heat and pressure. In case, for instance, the point of a hot metal instrument is drawn over the sheet under pressure, the path of the instrument remains visible on the sheet as a transparent track.

It is understood that the invention is not restricted to any particular or prescribed method or process of parchmentizing and is not limited i to any particular or specific form of wax or waxed material, but is directed broadly to the! production of a dry-waxed parchmentized paper in which dry-waxing has been 'made possible by limiting the parchmentizing effects of the chemicals used in the parchmentizing treatment, to a condition where the paper is still sufllciently porous to absorb wax-like substances in its interior fibrous structure and the web has not yet become so completely parchmentized as to be impervious to access by fluid waxy substances into its interior. I

Furthermore, the impregnating substance need not necessarilybe wax or paraflln but may be a substance such as rubber latex or medicated material or any other substance which is'absorbable by' the parchmentized web and is capable of remaining in the web up to the time of the use for which the impregnating substance is selected. For the purposes of my broader claims any such substances are to be regarded as the equivalents of wax or paraflln.

When it is stated in some of the claims that one or both surfaces of the paper are substantially free from wax, it is not intended to indicate that no wax can be located on such surfaces. The phrase is employed to convey the thought that while there may be some small amounts of wax on the surfaces, wax is not present in such amounts as to impart a waxy feel to the paper, or to prevent the surfaces from being capable of receiving and retaining printer's ink, or to prevent ordinary glue from exerting a strong binding effect when used to join two sheets together.

I claim:

1.'A vegetable parchment paper having relatively light parchmentized exterior surfaces and.

a fibrous interior section substantially unparchmentized, porous with respect to the entry into the interior thereof of extraneously applied wax,

the fibrous interior section being impregnated with a wax, the finished product forming a drywaxed parchmentized paper at least one surface of which is capable of receiving and retaining printers ink.

2. A vegetable parchment web having relatively lightly parchmentized top and bottom sur- 4. A vegetable parchment web having rela-' tively light parchmentized top and bottom surfaces, an interior fibrous structure substantially unparchmentized, and a plasticizer such as glycerin diffused throughout the web, the interior fibrous structure being impregnated with wax, at least one'of the surfaces of the paper being substantially free from wax.

5. A vegetable parchment web having relatively light parchmentized top and bottom surfaces, an interior fibrous structure substantially unparchmentized, and ,a retarder of parchmentizing effects such as pigments or sizing described throughout the web, the interior fibrous structure being impregnated with a wax, at least one surface of the paper .being substantially free from wax.

6. A vegetable parchment web having relatively lightly parchmentized top and bottom surfaces and an interior fibrous structure substantially unparchmentized, the latter being impregnated with paraflin, at least one of the surfaces of said Web being free from paraffin.

. '7. The process of producing vegetable. parchment paper which consists in passing a porous paper web through an acid bath to cause parchmentization of the exterior surfaces of the. web, removing the acid and drying, and in the parchmentizing treatment limiting the extent of parchmentization so that the same shall effect an active parchmentization of the surface portions of the web but shall not proceed beyond the stage where the web, when subsequently washed and dried, is no longer sufficiently porous to absorb in its interior wax or parafiin applied by a dry-wax process, and impregnating the interior structure of said web with a wax by a dry-waxing process.

8. A method of making dry-waxed paraflin paper which comprises passing a porous paper web through an acid bath, regulating the effect of the said action onthe web to limit the treatment to a light parchmentization, leaving the web porous'and its interior still fibrous and substantially unparchmentized, removing the acid,

drying, subjecting the dry porous web to a drywax process, impregnating the interior fibrous structure of the web with wax and leaving the outer parchmentized surfaces of the web relatively uncoated, and causing the impregnated wax to congeal in the-web.

9. The method of making dry-waxed paraffin paper which comprises passing a porous paper web through an acid bath, regulating the effect of the said action on the web to limit the treatment to a light parchmentization leaving the web porous and its interior still fibrous and substantially unparchmentized, removing the acid, drying, bringing the dried web into contact with a wax by a dry-wax process to impregnate the fibrous interior of. the web while leaving the surfaces of the webs substantially free and uncoated, subjecting the resultant product to simultaneously applied heat and pressure, rolling up the thus treated web while still hot into rolls and causing dissipation of the heat from the hot web while in the rolled-up condition.

10. The method of making dry-waxed paraffin in the rolled-up condition, whereby the interior structure is impregnated with the wax andv the surfaces are substantially unaffected.

11. The method of making dry-waxed parafiln paper which comprises passing a porous paper web through an acid bath, regulating the effect of the said action on the web to limit the treatment of a light parchmentization, leaving the web porous and its interior still fibrous and substantially unparchmentized, removing the acid, drying, subjecting the dried porous web to a dry-wax ,process to impregnate the interior fibrous structure of the web with wax and leaving the outer parchmentized surfaces of the web relatively uncoated, causing the wax to congeal in the web and locally applying heat under pressure to'create patterns of greater transparency at the localities where said heat and pressure are applied.

JOHN A. NEWMAN.