US2024600A

US2024600A - Manufacture of impregnated fiber articles or sheets

Info

Publication number: US2024600A
Application number: US631496A
Authority: US
Inventors: George A Richter; Milton O Schur
Original assignee: Brown Co
Current assignee: Brown Co
Priority date: 1932-09-02
Filing date: 1932-09-02
Publication date: 1935-12-17
Anticipated expiration: 1952-12-17

Description

Patented Dec. 17, 1935 I UNITED STATES PATENT OFFICE MANUFACTURE OF IMPREGNA'I'ED FIBER- ARTICLES OB SHEETS No Drawing.

8 Claims.

'butthis invention is concerned more especially with webs prepared on machinery of the paper- 15 making type, such as so-called Fourdrinier or cylinder machines,- from cellulose fibers like preliberated wood pulp.

In accordance with the present invention, we first associate with the fiber articles or sheets so-called regenerated cellulose as an impregnating phase while still preserving, if desired, residual porosity in such articles or sheets. We then associate with such articles or sheets a solid, water-repellent phase in fluxed condition distinct from and enveloping the regenerated cellulose phase, for instance a fluxed, water-repellent phase of rubber, asphalt, rosin, wax, celluloid, or any other water-repellent material which can be liquefied and fluxed by heat or by organic solvents. The secondary enveloping phase may be an impregnating and/or coating one and impart primarily such qualities as water-repellency and body or stiffness to the web, if desired. In any event, however, the secondary phase is preferably present in dominating proportion over the primary impregnating phase of regenerated cellulose, which may, in fact, constitute only a small fraction by weight of the secondary phase. The regenerated cellulose is characterized by its inertness for all practical purposes toward the liquefied and fiuxed bodies which we use for the articles or sheets. This is true whether the bodies are liquefied and fluxed by heat or by solution in an organic solvent. Indeed, regenerated cellulose is more or less like cellulose fiber in its quality of inertness.

The principles of the present invention may be availed of in various connections. Thus, the regeneratedcellulose phase may serve as a valuable one in fibrous articles or sheets which are to undergo impregnation with, liquefied and fluxed, water-insoluble bodies. For example, when one; uses waterlaidwebs of cellulose fiber 'as the foundations to be impregnated, it is de:

sirable that such websbe highly porous and thus Application September 2-, 1932, Serial No. 631,496

be able to imbibe the liquefied impregnant quick-- ly and uniformly. For many impregnated foundations, the best kind of waterlaid web is one which has substantially the same compactness as deposited from aqueous suspension and dried. In 5 other words, the web may undergo the application of little, if any, outside pressure during its traverse of both the wet and dry ends of the papermaking machine on which it is prepared. The fibers of such a web are hence only loosely interfelted because, other thanthe action of surface tension in drawing together the fib'ers during drying, they have been compacted only slightly, if at all. The web is hence bulky, highly porous, and able to imbibe readily large quantities of liquid impregnant, for instance a quantity by weight twice or even more than the weight of the dry web. The raw or waterleaf web is, however, tender or lacking in much tensile strength. By associating only a. small amount of regenerated cellulose with such a web so as to preserve most, I if not substantially all, of its porosity, the web is improved vastly for impregnation with various liquefied and fluxed impregnants. The regenerated-cellulose-containing web has much less tendency to disintegrate when it is drawn under stress as a continuous sheet through one or more baths of the fiuxed, water-insoluble impregnants. It can be passed continuously through an organic solvent solution of rubber, e. g., a rubber-benzol solution, and then dried without danger of breaking in its journey to produce a finished product having high tear resistance, toughness, waterrepellency, and other leather-simulating qualities.

The increased strength imparted to the web by the regenerated cellulose is not lost when the web is impregnated with heat-liquefied impregnants, e. g., molten asphalt, rosin, waxes, or similar thermoplastic bodies, as the regenerated cellulose is stable at those temperatures which 40 render these bodies sufliciently fluid to enter into and through the web readily. The web can be impregnated with large quantities of asphalt or other bitumens to produce an impregnated sheet containing upwards of 250% asphalt, based on 4 fiber; and thus highly serviceable for roofing, fiooring, or other building purposes on account of its high tear resistance, water repellency, and weathering capacity. The impregnation of the web with molten rosin alone or together, if desired, with molten asphalt or similar thermoplastic agents followed by cooling of the impregnated web results in a stiff, resilient sheet eminently satisfactory for use in making socalled thermoplastic shoe stiffener parts, e. g.,

box toe blanks, which are molded in a heatsoftened condition to the desired shape in the shoe. When the web is to undergo impregnation with a heat-liquefied impregnant, e. g., asphalt, at least a portion of its fiber content may be asbestos and/or wool and/or other non-cellulosic fiber which is heat-resistant.

Nor is the increased strength imparted to the web by the regenerated cellulose lost when the web is dipped into baths made up of the heatfusible impregnants mentioned, or of resins (natural or synthetic) nitrocellulose, cellulose acetate, celluloid, or other cellulose derivatives dissolved in suitable organic solvents. In fact, the regenerated cellulose is insoluble in the common organic solvents like alcohol, ether, ethyl acetate, benzol, toluol, carbon tetrachloride, chloroform, or the like. The web may, for example, be impregnated with a nitrocellulose, cellulose acetate, or celluloid solution, and the solvent then evaporated to produce a stiffened, resilient, flexible, and waterproof sheet suitable for various purposes in the arts. Box toe blanks may be cut from such a sheet and assembled with the shoe uppers in limp, solvent-treated condition and then allowed to set or stiffen in place in the shoes.

The association of the regenerated cellulose with the web may be accomplished in various ways, but. we prefer to regenerate the cellulose from a cellulose xanthate or viscose solution because of the low cost of this cellulose derivative and the comparative ease with which the cellulose may be regenerated therefrom. The viscose solution may be added to the aqueous fiber suspension from which the web is made, but we prefer to add this solution to the web at any suitable stage of its travel on the papermaking machine or to the prefabricated web. The concentration and the amount of viscose solution added may be adjusted to deposit, say, about 1% regenerated cellulose in the web, based on the weight of fiber, although, if desired, this percentage may be somewhat lower or as high as 3% or even much higher. Ordinarily, however, about 1% regenerated cellulose is ample to effect the desired strengthening of the web; and this percentage does not detract appreciably from the web absorbency.

The cellulose may be regenerated in the web by subjecting the viscose-treated web to the action of suitable regenerating chemicals such as acid or acid salt solutions and/or to the action of heat. Thus, the drying of the viscose-treated web under heat regenerates the cellulose therein: If desired, the viscose solution used as the initial impregnant for the web may be treated with such acids as boric or acetic, which can be added to the viscose solution in such amount as to neutralize part of the alkali in the solution without causing a gelling of the solution. The partly neutralized viscose solution may then be applied as the primary impregnant to the web. The addition of such acids to a viscose solution promotes the subsequent regeneration of the cellulose therefrom in the web, When the viscose solution is used in treating a prefabricated dried web, it may be applied, as by a spraying or coating device, to only one face of the web so as to effect only a partial impregnation; or it may be applied in such a way as to produce a substantially uniformly impregnated web. For instance, the dried, prefabricated web may be passed through a bath of the viscose solution, or the viscose solution may be applied to one face of the web and then passed over a suction box, to cause a penetration bleached or in substantially unbleached condition.

We prefer to use refined wood pulps of an alpha cellulose content of about 93% to 96% when we 15 are seeking webs of the highest absorbency, for

in such case we can readily prepare waterlaid webs of a compactness of about 30 to 55 when the papermaking machine for fabricating the webs are operated in such a way as to exert no sub- 20 stantial pressure on the webs at any stage of their journey on the machine. The foregoing values of compactness are obtained by dividing the basis weight in pounds by the thickness in inches and multiplying by the factor 10 The 25 expression basis weight as known in papermaking circles represents weight in pounds of 480 sheets whose dimensions are 24 x 36 inches, this being equivalent to 2880 square feet of sheet materiaL- In other words the compactness value 30 really represents the weight of fiber per unit volume of sheet material.

In some instances, the fiber article being treated in accordance with our invention may advantageously be a paper made from beaten pulp as 35 ordinarily and with which regenerated cellulose has been associated at any suitable stage of papermaking. In fact, such paper maybe associated additionally with sizing ingredients, such as glue or rosin. The glue or other sizing agent 40 may be incorporated into the paper at the same stage of paper manufacture as is the regenerated ellulose or at some different stage of paper manufacture. For instance, a mixed glue and viscose solution, a mixed rosin size and viscose solution, 45 or a viscose solution containing both glue and rosin size may be used as the impregnant for a pre-fabricated, waterleaf web of paper. When glue as well as regenerated cellulose is incorporated into the paper, suitable modifying agents may 50 be added to the paper. For instance, glycerine may be added to the mixed glue and viscose solution to impart pliancy to the resulting paper. So, too, insolubilizing agents, such as formaldehyde, alum, tannic acid or the like may be added to-the 55 mixed impregnating solution for the purpose of converting the glue to water-insoluble condiiton when it is dried or set in the paper. Should a glue solution be used independently of the viscose solution as an impregnant, the modifying agents 60 may be added to the glue solution itself or after the paper has been impregnated with the glue solution or with both. the glue and viscose solutions. In the event that the paper containing the regenerated cellulose has been made from 65 well-beaten stock and contains sizing agents, such as glue and/ or rosin, subsequent treatment of the paper with fluxed, water-repellent bodies in heatliquefied or dissolved condition is accomanied by only surface penetration of the paper on account 70 of its density and impermeability. In other words, the water-repellent body will deposit essentially as a continuous coating on the surface of the paper on account of the comparatively dense, non-absorptive character acquired by the 75 paper through the beating of the papermaking stock and/or sizing of its fibers. In thwe instances when it is desired to-produce essentialy a water-repellent paper by coating with organic solvent solutions of cellulose derivatives, such as nitrocellulose, cellulose acetate, or the like, or with molten thermoplastic waterproofing agents, such as waxes, bitumens, or the like, the dense, non-absortive character of the paper is desirable in that the water-repellent body is confined largely to the surface of the paper where it can exercise most effectively its water-shedding ability. A paper which contains regenerated cellulose in its interior and is enveloped .by a fluxed, 1 solid phase of water-repellent material existing either as a coating and/or as a partial or complete impregnant for the body of the paper can withstand most effectively the disintegrating action of water, for even should the fluxed phase of water-repellent material be abraded, cracked or otherwise injured, the paper resists rupture on account of the high wet strength imparted thereto by the internal phase of regenerated cellulose.

We have spoken about the solid phase of waterrepellent material as being in fluxed condition when it exists primarily in the body of the fibrous article and/or on its surface. By fluxed condition, we, mean the condition of continuity attained in the water-repellent material through i the action of heat or suitable organic solvents, thereupon. Water-repellent materials do not exercise their maximum potential water-repellency when deposited from aqueous suspension or 5 dispersion, as by mere drying. Indeed, unless drying is accomplished under such elevated temperature conditionsas will fuse the dispersed particles, assuming that' they are fusible, or unless drying is followed by treatment with suitable or- 40 ganic solvents, the dispersed particles will not impart maximum water-repellency to the fiber articles into which they are incorporated. This is true even of aqueous rubber dispersions, such as latex, whose dispersed particles tend to coalesce 45 upon drying. Consequently even when aqueous dispersions of solid, water-repellent materials are used to impregnate a. fiber article containing regenerated cellulose, the dispersed particles are, in accordance with our invention, fluxed by the 50 action of heat or a suitable organic solvent. It is, however, more direct and economical to use organic solvent solutions of the water-repellent body or to use the body in fused or molten condition, when it is fusible, in bringing. about the im- .pregnation and/or coating of the fiber articles containing the regenerated cellulose so as to realize the articles of the present invention.

We do not claim herein specifically the subject matter of our application Serial No. 631,497, filed of even date herewith (now Patent No. 1,971,274, dated Aug. 21, 1934), wherein we have disclosed and claimed specifically the use of wax for coating or enveloping substantially all of the surfaces of a fibrous article containing regenerated cellu- 65 lose as an impregenating phase.

We claim:

1. A fibrous article carrying a small percentage of regenerated cellulose as an added primary impregnating phase in the pores and interstices 70 between the fibers as well as on the fibers and a separately added secondary impregnating phase of solid, fluxed, water-repellent material enveloping substantially all of the surfaces of said F article, said article being possessed of residual porosity substantially throughout after the addition of' the primary impregnating phase but before the addition of the secondary impregnating phase.

2. A fibrous article carrying a small percentage of regenerated cellulose as an added primary im- .5

' porosity substantially throughout after the addition of the primary impregnating phase but before the addition of the secondary impregnating phase. I

3. A fibrous article carrying a small percentage of regenerated cellulose as an added primary impregnating phase in the pores andinterstices between the fibers as well as on the fibers and a separately added secondary phase of solid, sol- 20 vent-fluxed, water-repellent cellulose ester enveloping substantially all of the surfaces of said article, said article being possessed of residual porosity substantially throughout after the addition of the primary impregnating phase but be- 25 fore the addition of the secondary impregnating phase.

4. A fibrous article carrying a small percentage of regenerated cellulose as an added primary impregnating phase in the pores and interstices between the fibers as well as on the fibers and a separately added secondary impregnating phase of solid, heat-fluxed, water-repellent material enveloping substantially all of the surfaces of said article, said article being possessed of residual porosity substantially throughout after the addition of the primary impregnating phase but before the addition of the secondary impregnating phase.

5. A fibrous article carrying a small percentage of regenerated cellulose as an added primary impregnating phase in the pores and interstices between the fibers as well as on the fibers and a separately added secondary impregnating phase of fluxed asphalt enveloping substantially all of the surfaces of said article, said article being possessed of residual porosity substantially throughout after the addition of the primary impregnating phase but before the addition of the secondary impregnating phase.

6. A fibrous article carrying a small percentage of regenerated cellulose as an added primary impregnating phase in the pores and interstices between the fibers as well as on the fibers and a. separately added secondary impregnating phase of fluxed rosin enveloping substantially all of the surfaces of said article, said article being possessed of residual porosity substantially throughout after the addition of the primary impregnating phase but before the addition of the secondary impregnating phase.

7. A fibrous article, at least a portion of whose fiber content is noncellulosic, carrying a small percentage of regenerated cellulose as an added primary impregnating phase in the pores and 6 interstices between the fibers as well as on the fibers and a separately added secondary impregnating phase of solid,fluxed,,water-repellent material enveloping substantially all of the surfaces of said article, said article being possessed of residual porosity substantially throughout after the addition of the primary impregnating phase but before the addition of the secondary impregnating phase.

8. A fibrous article, at least a portion of whose fiber content is asbestos, carrying a small percentage of regenerated cellulose as an added primary impregnating phase in the pores and interstiees between the fibers as well as on the fibers 5 and a separately added secondary impregnating phase of solid, fluxed, water-repellent material enveloping substantially all of the surfaces of said article, said article being possessed of residual porosity substantially throughout aft-er the addition of the primary impregnating phase but before the addition of the secondary impregnating phase.

GEORGE A. RICHTER. MILTON O. SCHUR.