US2183711A - Method of treating paper - Google Patents

Description

F.- DE WITT MET/fion oF ,HEATING PAPER Fil'ed Jan. 7, 1938 RN EYS Patented Dee. 19, 1939 UNITED STATES PATENT oFF-Ice 2,183,111 mamon' or mesme Paras Francis. ne wm,- New York, N. Y., signor u .Bei'vel Corpratlon, New York, N. Y., a corporation of Delaware Application January "l, 1'938, Serial No. 183,756

-4Claims.

-tile fabrics. y l

Paper has been andy is used for many types of manufactures, such as, for example, disposable tissues, hand towels, decorative articles, table covers and the like. The papers used forl these articles vary, but they have certain characteristics which render them unsuitable for 'more general usage. Papers which have aA soft texture are low in mechanical strength and therefore are not durable either dry vor wet. Papers having high mechanical strength are hard or harsh in texture and lack pliability or the feel that characterizes textile fabrics.

Recently papers have been develope'd, such as those disclosed in the Schur Patent No. 2,035,204. patented March 24, 1936. having so-called wet strengt These papers are substantially as strong and tear resistant when wet as whenv dry; However, they lack pliabillty or drapability and as a consequence are not satisfactory substitutes for cloth. When crushed or crumpled, creases of wrinkles are formed in wet strengt papers which cannot be readily removed and therefore their utility is restricted tothe disposable types of articles of manufacture. It has been suggested previously that man l types of papers can. be softened and rendered pliable by impregnation with glycerine or other polyhydric alcohols or derivatives of the` same.

These softening agents, however, are water sol-` uble and upon wetting may be dissolved and removed, allowing thepaper to become hard and harsh upon drying. The softening agents may also evaporate or be drawn from the paper if it is brought in contact with other absorbent materials.

The'principal object of this invention, therefore, is to provide a method of treating paper to render it pliable and soft in texture and capable ,of being moistened without losing these characeither wet or dry, and capable of being cut' and sewed in the manner oi' textile fabrics.

Other objects of the invention which will become apparent as typical embodiments of the invention, are vdescribed hereinafter.

In my co-p'ending application, Serial No. 183,800 flied the 7th day of January, 1938,- I have disclosed paper articles which are made in accordance with this invention. The paper articles obtained by practicing my novel process are characterized by good mechanical strength, pliability, flexibility and other characteristics, such as normally associated with textile fabrics of the smooth nish type. In addition to these characteristics, these novel papers are impervious to dust. 'Ihese papers may be used, for example, in the manufacture of hospital supplies, home supplies and ofiice supplies of which doctors aprons, dentists bibs, sheets, pillow cases, table linens, articles of apparel theatre decorations and costumes.

In my co-pending application, Serial No. 183,801 iiled the 7th day of January, 1938, I have dislclosed a sizing or impregnating composition which is used in practicing the process embodying this invention.l The sizing or impregnatng compoav sition is characterized by the presence of a paper softening agent, such as for example, polyhydroxy alcohols and derivatives ofthe same, such as glycerine, glycol, diethylene glycol andA the ethers and estersof polyhydroxy alcohols. 'I'hese paper softening agents are water soluble, are stable and have boiling points suiciently in excess ofor greater than water, .whereby they will be retainedin the paper even if it is heated as high or above the boiling point of water.

In addition to the paper softening agent, the sizing and coating composition contains water insoluble pulverulent ,mineral Ifiller which fixes' or anchors the paper softening agent in the paper by retaining it more tenaciously than is the tendency of the paper softening agent yto go into solution in water. The preferred type of mineral filler material may be one or more of the group of water insoluble calcium, magnesium or aluminum salts, of which the silicates, fiuorides,sul fates, salcylates of calcium and magnesium and the aluminum silicates, such as kaolin and -pumice,'are typical. In finely divided form these fillers may be distributedthroughout the papers in accordance with the process embodying the in,

vention and adhere tenaciously to the bers of the. paper and at the same time adsorb the paper softening agent so that it is retained even when the paper is wetted. I

In practice, the sizing or impregnatinur composition is applied in accordance with this invenafter removing the moisture from the paper by drying on drying drums or by festooning the -paper over suitable supports in a drying room.

The sizing bath consists of an aqueous solution of the paper softening agent, the water content of which may vary in accordance with the type of paper being treated 'and the degree of pliability or softness which it is desired to obtain.

IFor a better understanding of the present invention, reference may be had to the single figureof the drawing which discloses diagrammatically and in perspective a typical form of device for applying the sizing composition to the paper.

As illustrated in the drawing, the device may consist of a tank I having a tapered bottom' I2,

desired type which forces the liquid through a conduit I8 to a mixingtank 20 where the sizing and impregnating bathmay be strengthened or replenished. A suitable outlet conduit 22 allows the sizing composition to be returned from the mixing tank 20 to the tank I0 and is provided with a valve 24 for regulating the amount of sizing composition to be delivered to the tank I0.

'Ihe tank Ill-is provided with a roller 26 under which a sheet of paper 28 is passed in order to completely submerge the sheet in the sizing composition. The sheet of paper 28 may be delivered from a large roll 30 and looped around a pair of idling or driven rollers 32 for smoothing and removing bulges or wrinkles from the sheet. The sheet 28v passes through the sizing composition under the roll 26 and over and around a pair of driven drying rolls 3l and 36, which remove the excess water from the sheet. The dried sheet is then rewou'nd on a roll 38 at the back end of the machine. Since the ller material is a nely divided water insoluble mass it has a tendency to settle outA and therefore an agitator 40 driven in any suitable way, such as, for example,

.by electric motor 42, is provided for maintaining the filler in suspension.

Typical examples of the sizing and impregnating bath may be as follows:

Example I Glycerine uid ounces-- 28 70% denatured alcohol -do 4 28 Water do '72 Magnesium silicate ounces-- 14 These proportions may be varied as by varying the water content to vary the concentration of glycerine and magnesium silicate in the sizing composition whenlit is-desired to. apply a greate` or lesser amount of'these ingredients to the paper Forexample, a heavy, thick-bodied paper preferably will be treated with a greater concentration of glycerine and magnesium silicate in order to s'often it to a predetermined point than would be required to treat a'lighter paper or one naturally more soft to render it of the same degree of pliability and softness. 'Ihe alcohol has the effect of causing the paperto dry more rapidly after treatment, but is not an essential ingredient of the sizing bath. The filler material, magnesium silicate, may be replaced by magnesium fluoride or oxide or by calciumv carbonate, salicylate, or sulfate, or any water insoluble aluminum compound, such as the silicates of which kaolin, fullers earth and pumice are typical examples. If desired, mixtures of these compounds may be used with equal facility.

Another example which in actual practice has been found entirelysatisfactory is as follows:

Example II Glycerine uid ounces-; 28

Water do. 80

Magnesium silicate', or other water insoluble mineral ller of the type set forth in Example L ounces-- 16 The proportions of paper softening agent and filler material may be varied within narrow limits. An excess of glycerine over the adsorptive power of the filler will cause a change in the texture of the paper upon wetting. Likewise, an excessive amount of filler will tend to provide a harder and smoother surface on the paper which may or may not be desirable under certain circumstances.

'Ihe process consists generally of treating the papers, such as, for example wet strengt papers, by passingthe paper through or dipping it into a bath of the sizing composition above set forth, and thereafter drying the paper to dry off the moisture.

The resulting product is a flexible, pliable paper which has a soft, moist texture, and a durability which is at least equal to the durability of the same untreated paper. If the original untreated stock is Wet strength stock, the articles made therefrom may be moistened, stretched and smoothed without tearing and without any decrease of strength or pliability. Papers of this type are quite similar in texture to the smooth finish textile fabrics and. therefore can be cut and sewed by the same types of machines used in cutting and sewing the textile fabrics.

In addition, because of the pliability, drapability of the paper, it may be crumpled or crushed and thereafter smoothed without leaving any vis, ible Wrinklesor creases therein. This characteristic is of material importance in the production of such articles as b'ed linens and table linens, as well as other hospital and home supplies. The hospital supplies may, if desired, be sterilized because there are no ingredients therein which would be removed or deleteriously affected by heating or by the presence of suitable antiseptic agents, and they, therefore, have great utility in hospital usage.

It will be seen from the preceding description that through my method, I have been able to vproduce paper and paper manufactures which have many novel characteristics not found in other papers. It should be understood, of course, that the examples given are illustrative and are therefore not to be consideredas limiting the scope of the following claims. I

I claim:

1. The process of treating paper to render it soft an`d flexible comprising the steps of applying to the paper a solution containing, in the following proportions, about '72 to 80 fluid ounces of water and about 28 fluid ounces of a paper softening agent of the class of compounds consisting of water soluble, stable polyhydroxy alcohols and ethers and esters of polyhydroxy alcohols having boiling points higher than water and containing about 14 to 16 ounces avoirdupois of finely divided water-insoluble mineral filler capable of adsorbing the paper softening agent, and thereafter removing the water from the paper.

2. The process of treating paper to render it soft and pliable. comprising the steps oi' apply ing to a sheet of wet strengt paper having substantially l the same mechanical strength whether wet or dry a solution containing in the following proportions about 'I2 to 80 fluid ounces of water,v 28 fluid ounces of a paper softening agent and about '14 to 16 ounces avoirdupois of a water-insoluble mineral iller, and thereafter drying the paper to produce a paper having high u about the following proportions 28 fluid ounces of glycerine, 'I2-80 fluidounces of water and 14-16 ounces avoirdupois of a finely-divided water-insoluble mineral iller capable of adsorbing the glycerine and (2) removing the water from the paper.

4. The process of treating paper to render it soft and lpliable comprising applying an aqueous solution of a paper softening agent and containing a nely-divided water-insoluble mineral iiller and drying said paper, said solution containing inl the following proportions about 28 fluid ounces of paper soitening agent, 'I2-80 iiuid ounces of water and 14-16 ounces avoirdupois of filler. FRANCIS DE WITT. v

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