US1791248A - Felted-cellulose-fiber product - Google Patents

Description

G. L. SCHWARTZ FELTED CELLULOSE FIBER PRODUCT Filed Sept. 22, 1928 Feb. 3, 1931.

. Patented Feb. 3, 1931 UNITED STATES PATENT OFFICE GEORGE L. SCHWARTZ OF WILMINGTON, DELAWARE, ASSIGNOB TO E. I. DU PON'I DE NEMOURS & COMPANY, OF WILMINGTON, DELAWARE; A CORPORATION OF DELA'L WARE FELTED-CELLULOSE-FIBER PRODUCT Application filed September 22, 1928. Serial No. 307,760.

, This invention relates to the art of cellulose products and more particularly to the art of felted cellulosefiber products.

Many attempts have been made to produce cellulose fiber products by compacting" the fibers into a felt but the results achieved by previous processes have been subject to various objections. In the prior processes it has been customary to use binding materials to unite the fibers but this is objectionable because it gives a product of low porosity, On the other hand, when a binding material has not been used in the previous processes, the resulting felt has been inherently weak. Also, the products resulting from previous processes have often been stiff and horn-like, because the gelatinizing action of the substances used for treating the fibers, such as aqueous solutions of' caustic soda or zinc chloride, has not been stopped by heat.

It is an object of the present invention to produce felted cellulose fiber products without the use of auxiliary binding materials.

It is another object of the present invention to produce cellulose fiber products havinga high degree of pliability. I i

It is a further object of the present invention to so produce. these products that they shall have a greatly increased wet strength.

It is a still further object of the present invention to produce such products having an increased dry strength without being susceptible to the customary paper break.

It is a still further object of the present invention to produce eellulose fiber products having increased wetfanddry strength without impairing their wetting properties or reducing their porosity. With the above and other objects in view,

-ceeds, '1 have set forth my invention in'the following specification and illustrated it in the accompanying drawing, in which:

Fig. is a-diagrammatic side'elevation of an diipparatus for carrying out my invention, an

Fig. 2 is a diagrammatic planview thereof.

In the accompanyin drawing 10 designates a continuous roll of elt composed of fibersso that amended and kinked and which has which will be apparent as the description promounted in any convenient manner,as by susthereby beenmade in any desired manner. This may be" accomplished,'for example, as set forth in the copendin application of McCormick and Schwartz, erial No. 283,445, filed June 6, 1928, the process consisting, briefly, in treating cellulose fibers with a solution of caustic alkali for example 8 to 35% sodium hydroxide, at temperatures from slightly below 5 C. to C. This pulp can then be converted into a continuous roll of felt by any standard paper machinery, such as a Fourdrinier machine.

The roll of felt 10, mounted in any desired manner, passes over a guide roll 11 and is fed on to a wire screen conveyor 12, which may be made of any suitable material, such as Monel metal, and is supported by guide rolls 13, 14, 15, 16 and 17, and a drum which willbe described hereinafter.

The conveyor 12 propels the felt 10 forwardly into a bath of cold caustic solution 18, which is kept in circulation through an overflow connection 19 between a main caustic tank 20 and an overflow tank 21, and by providing the latter with a gravity outflow pipe 22 at a point slightly above its bottom. From I thispipe the solution flows into a pump 23, driven by any suitable means, which forces the solution up to a supply tank 24, from which it flows by gravity back to the tank so 20. The supply tank 24 may be cooled by any well known means, such as brine or electric refrigeration (not shown).-

Immersion of the felt 10 in the caustic solution 18 is effected by the passage of the conveyor 12 and the felt 10 over guide roll 14 and under a second guide roll 31, both of which are adjustable to vary the period of immersion of the. -felt. Guide roll .14 is pending it from a cross bar (not shown), which is carried in a parallel take-up mecha nism 33-that has adjusting screws 34 for varying its horizontal distance from guide roll 31 I, I

efi'ecting an earlier or later im- 'mersion of the felt. Guide roll 31 is mounted in bearings 35, which are adjustable vertically by hand-wheels 36 to vary the depth to which the felt is immersed in tank20. Guide rolls 16 and 17 are provided with adjusting hand- 1 the latter being submerged caust c bath 62 contained in a "SOllltIOIl 1s of relatively high concentration wheels 37 and 38, respectively, for taking up or providing slack in the conveyor 12 as guide roll 31 is raised or lowered.

This immersion causes the felt to become impregnated with the caustic solution so that its fibers are swollen and their surfaces are sli htly gelatinized.

he impregnated felt 10, supported on the conveyor 12, is passed between guide roll 15 and a second guide roll 39, the latter being adjustably mounted with respect to the former. to permit the variation of the space betweenthem by hand-wheels 40 and the exertion of any desired intense pressure. These rolls squeeze the excess caustic solution from the felt 10, and form it into a rubber-like but very weak sheet, the expelled caustic flowing back into tank 20.

A second wire screen conveyor 41, supported by a series of guide rolls 42, 43, 44, 45, and 46, mounted in a framework 47, and provided with tightening adjustments 48: and conveyor aligning adjustments 48', is mounted above the path of travel of the conveyor 12 and felt 10 to exert a predetermined and regulable' pressure on the upper surface of the felt'to remove excess caustic solution.

The felt 10 supported on the conveyor 12,

passes over a drum 49 that is perforated at 50 and heated by any desired means, such as steam supplied to a series of spray pipes 51. A suction hood 52 is preferably mounted on the framework 47 to remove the uncondensed steam, As the felt 10 and conveyor 12 reach the circumference of the drum 49, conveyor 41 is brought into contact with felt 10 and steam is injected through the latter, thus stopping the gelatinizing action of the cold caustic solution and, with the aid of the pressure applied by the upper screen,

' molding the fibers into a compact felt 53, in

situ. 1

As the felt 53 leaves the drum 49 .it also leaves the conveyors 12 and 41 and is received on a third wire screen conveyor 54, supported by a series of guide ' rolls 55, 56, 57, and 58, as well as by certain press rolls which will be described hereinafter.

Conveyor 54 carries the felt 53 over guide rolls 55 and 56 and under a guide roll 61, in an aqueous tank 63. This and is maintained at-a high temperature in any suitable manner, as by gas or oil burners 64. This treatment reduces the swelling of fthefibers and causes, them to acquire more .definite'kinks and curls, accompanied by some shrinkage the area of the felt.

The latteris now very strong and requires only-com lete washing to free it from caustic,.-andor this purpose it passes through a .seriesofrubber covered press rolls which I are independentlyadjustable at'.66 to exert .anydesiredpressure and squeeze out the exmamas frame (not shown), and is wound up on a roll (not shown) or fed to other apparatus (not shown) which fits it for the speclal uses to which it is to be applied.

'The apparatus is driven by any suitable mechanism, such as a sprocket chain 72 which engages a sprocket wheel 73 on the axis of drum 49 and a series of sprocket Wheels 74 on the driving shafts of the press rolls 65. These sprocket wheels are of any desired size, and power is transmitted to sprocket wheel 7 3y from any suitable source (not shown). The power thus transmitted to the drum 49 is sufficient to create a friction drive for the various wire screen conveyors and to feed the untreated felt 10 forwardly into contact with conveyor 12. I have found it desirable to provide scraper knives 75, 76, and 77 in the vicinity of roll 31, roll 39, and drum 49, respectively, to overcome any tendency of the felt to follow the contour of these rotary members.

I have also found it desirable to provide the roll 31 with a series of staggered slots 78 and to cover it with a Monel metal screen 79 to break the vacuum which tends to form between it and the gelatinized fibers, although any equivalent means might be used.

Although the apparatus described herein is one I have found satisfactory for carrying and pass it into a 10-11% aqueous sodium. hydroxide solution at --5 C. for a 5-second treatment, and for the second caustic treatment 1 use an 18% sodium hydroxide solution at 100 to 104 C. for 5 seconds or longer.

If a sheet of unsized kraft, made from fibers that have not been curled and kinked, is used as the raw material a considerably lon er time is required for impregnation wit the cold caustic solution.

If the starting material is a sheet made from 5-hour cooked cotton linters it should remain in the cold caustic solution 6 seconds, whereas-if the sheet is made from 20-hour cooked linters this time may be reduced to 3 seconds.

.To'produce a relatively stilt felt the time of impregnation in the cold caustic bath is increased, but if a relatively pliable felt is teria'l used and i ficial fibers,

desired the time of impregnation is decreased.

' Consequently, according to the raw mathe degree of pliability desired in the final product the time of impregnation with the cold caustic bath will vary from 1 to 30 seconds. If it is desired to give a longer treatment in the cold caustic solution the concentration of the latter may be reduced as low as 8%, and I have found that a range of from 8 to concentration of sodium hydroxide is satisfactory for most purposes, although still higher concentrations may be used with sheets from certain fibers such as cotton, rag, or wood pulp fibers that have been cooked a long time, or arti such as rayon.

The duration of the period in which pres-. sure is exerted by the cold rolls may vary from 1 to seconds, the upper limit being utilized for fibers that are not very reactive, such as slightly cooked wood fibers. The duration of the exertion of pressure on the perforated hot drum may also be varied, but usually corresponds to the time of pressing with the cold rolls.

The degree of pressure exerted by both the cold rolls and the hot drum may also be varied, a greater pressure being used for fibers that are only shghtly reactive than for fibers that are very reactive."

The temperature of heating may be varied i but the best results are obtained when steam is liberated on to the sheet with a pressure of at least 10 pounds. The best results are obtainedwhen there is a very sudden change from the highly swollen to the final swollen state. This is accomplished by heating the sheet as quickly as possible. While this may be accomplished by merely passing the sheet over a heated roll, this is too slow for optimum results, hence it is preferable to an ment the heating by injecting'steam throng the sheet.

The concentration of the hot caustic bath may be varied, using any concentration but the 18% concentration is.

above 15%, preferable because the quality of the product with this concentration is near the optimum, and because of economy in caustic.

The temperature of the hot caustic bath may be varied from 80 C. to the boiling the solution, but the best results are obtained when it is near the latter point, although with. certain ty es of fibers a lower temperature'is prefera le.-to avoid appreciable degradation of the cellulose and weakening of the felt. In general I have found that the best temperature range is from 100 to 104 C.

The time of passage through the hot caustic bath may vary from 2 .to 20 seconds, al-

though the latter period causes deterioration of some types of fibers.

As an example of the increase in strength stiff and boardy.

develo ed a process of making felted celluappreciableat the line of crease when such papers were creased, whereas felt made by this process suffers no decrease in strength even after repeated creasing. Likewise, sheets made from kraft fibers subjected to my process are less stifi' than kraft papers which have not been so treated and are free from the decided paper break which is characteristic of the untreated kraft papers.

My treatment also produces a marked increase in the wet strength of kraft apers and felts subjected thereto, raising t e wet tensile strength from 2% of the dry; strength to 20% or more of the dry strengt I desire to have it understood that I may use sheets or mats of any cellulose fibers, such as kraft fibers, linters, sulfite treated fibers, rope fibers, cotton fibers, including those reclaimed from tires, burlap fibers, or a, mixture of two,or more types of fibers, such as a mixture of kraft and rope fibers or 'kraft fibers and linters. In sheets made from such mixed fibers the greater length of rope fibers adds strength to the finished product and the kraft fibers give an increased pliability. Linters that are free from very short fibers give a product of similar strengthdto long rope fibers. Fibers from wood, in general, give they be unsized.

Where high density is required more reactive fibers should be used.

Although I have referred herein to caustic solutions and have mentioned caustic soda in particular,it will be understoodthat caustic potash or other fixed caustic alkali may be used. 1

I have found that it is desirable toheat the material while it is still under 'pressure to prevent the 'final product from becoming Although the pas age through the hot caustic bath can be omitted, I-have also found that this increases the strength of the final roduct and improves the felting.

It will therefore be apparent that I have lose fi er roducts in which the fibers are held toget er in a sheet form by interlneshing, kinking and curling of the fibers instead of by the use of binding materials, such as Y products whose 'stren h varies as the length of the fibers.

resins, glues, pyroxylin and rubber compo- Wide variety of below 5 C.

sitions; that my products are more pliable than products made by other processes; and that my products have a greatly increased wet strength, and an equal or greater dry strength" than paper without being subject to the characteristic paper break Felted cellulose fiber products'made in accordance with my invention are useful for apurposes, including a base for subjection to coating or impregnating processes with pyroxylin, rubber or other materials, as in the formation of fabrikoid or artificial leather; for impregnation in single or multiple layer thicknesses with solutions of phenolic condensation products; and without impregnation, as for felt hats, containers shoe counters or box toes.

As many apparently widely difi'erent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended patent claims. a claim:

1. The process of making felted cellulose fiber products, which comprises gelatinizing continuous bands of cellulose fibers with g caustic alkali,

subjecting these gelatinized bers to pressure and heat, and washing.

e process of making felted cellulose 2. fiber products, which comprises treating cellul'ose fibers in sheet or mat form with caustic alkali to elatinize these fibers without dispers ng t em, pressing heatlng While maintaming pressure, and washlng. The process of claim 2, in which the caustlc alkali solution is cold.

- he process of fibers are subjected to a treatment with hot caustic alkali before the washing. e process of making. felted cellulose fiber products, which comprises treating cellulose; fibers in sheet or mat form with an 8 claim '2, in .which the menace 5 seconds to gelatinize the fibers without dis- Eersing the cellulose, pressing the gelatinized bers,-1ncreasing the temperature while still maintaining the pressure, move the caustic alkali.

' 10. The process of claim 9, in which the heating is facilitated by the application of steam under an initial pressure of at least 10 pounds.

11. The process of claim 9, in which the matis passed through an 18% solution of sodium hydroxide at 100 to 104 C. for 5 seconds prior to the washing, to reduce the swelling of the fibers and facilitate their kinhn and curling.- I v 12. strong flexible compressed felted non-woven cellulose fiber product comprising artificially an intensely curled and k'inked fibers held to gether fibers.

13. A product comprising artificially curled and kinked cellulose fibers associated and washing to reby gelatinization of the in a non-woven sheet form without other while gelatinized,

to 15% solution of caustic alkali to gelatinize H these fibers without dispersing them, pressing 'whlle gelatinized, heating pressure, and w hing.

The process of claim 5;, caustic alkali is maintained at and treatment in which the a temperature with caustic al' kali is continued. for from 1 to'30 seconds.

7 The process of claim 5, in which the fibers are subjected to treatment with an 18% solution of hot caustic soda for from 2 to 20 seconds before the washing.

8. The process of claim 5, in which the caustic alkali is maintained at a temperature below 5C. and treatment with this caustic alkali is continued for from 1 to' 30 seconds, and in which there is a subsequent treatment W1th a hot 18% caustic alkali solution before washing. V

9. The process of making a felted cellulose while maintaining a wet tensile strength i ion

Images