US2844491A - Paper-like pellicle and method for producing same - Google Patents

Description

Jly'fzz, 195s J. KQHUBBARD' 2,844,491 :PAPER-LIKE PELLICLE AND' rvmiHouFoRv PRonuING SAME .i Filed April 29', i955-A v INVENTOR JAMES K.v HUBBARD 'I L/Qg United States Patent 'O PAPER-LIKE PELLICLE AND NIETHOD FOR PRODUCING SAME James K. Hubbard, Longview, Wash., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Application April 29, 1955, Serial No. 505,040 6 Claims. (Cl. 117-65) This invention relates to a new article of manufacture. More particularly it is concerned with paper and paperlike products from nylon fibers.

Despite the inherent desirable properties of the wholly synthetic fibers which have been commercialized in recent years, these fibers have not begun to replace cellulose in the manufacture of paper-like structures. The high wet strength, toughness, chemical durability, excellent dimensional stability and ageing qualities of these fibers, should make them particularly applicable to the field of paper-like products. One factor which has hindered the development of the wholly synthetic fibers in this field is the inability of the fibers to fibrillate and bond to themselves in the manner of beaten cellulose fibers. In addition, in many cases, commercial papermaking techniques either are not applicable or must be expensively modilied to accommodate the bonding process.

It is an object of this invention to provide a new paper structure from nylon fibers.

A further object is to provide a nylon paper-like pellicle of high fold endurance.

Another object is to provide a process for the manufacture of nylon fiber paper which is readily adaptable to commercial paper-making equipment.

These and other objects will become apparent i-n the course of the following specication and claims.

In accordance with the present invention a paper-like pellicle ofan unwoven mass of molecularly oriented synthetic condensation polyamide fibers is bonded with an N-alkoxymethyl polyamide resin. Such materials are described in Cairns, United States Patent No. 2,467,186. The `bonding of the polyamide fibers is readily accomplished on commercial paper-making equipment by impregnating an unwoven web or waterleaf of the polyamide fibers With an aqueous dispersion of the N-alkoxymethyl polyamide, squeezing to remove the excess liquid, drying the impregnated web and thereafter pressing. The resulting product, while exhibiting the mechanical and chemical properties of polyamides, possesses folding endurance values in the order of 700,000 to 1,000,000 cycles and higher.

By an N-alkoxymethyl polyamide resin is meant a polyamide containing recurring units of the formula:

C o-N- ClHn-O-R wherein R is the non-hydroxyl portion of an alcohol, preferably alkyl or hydrocarbon. Such materials and their aqueous dispersions are described in United States Patent No. 2,467,186.

By a polyamide fiber is meant la funicular structurehaving molecular orientation, such as a fiber, filament, staple and the like produced from a synthetic linear polyamide, e. g. as described in United States Patent No. 2,071,253 and 2,130,948, by the conventional methods. Among the specific polyamides included Within the present invention are those formed by the condensation polymerization of a dibasic acid or anamide-forming de- Patented July 22, 1958 ICC Z rivative thereof, such as adipic, sebacic, suberic, azelaic acids or the like, and a diamine such as piperazine, bisamino cyclohexane, ethylene, tertamethylene, pentamethylene, hexamethylene, decamethylene, paraxylylene diamines and the like. Such materials may also be formed by other well known methods such as by polymerization of amino acids or caprolactam.

Figure l is a diagrammatical sketch of a paper-like pellicle produced'in accordance with the present invention.

Figure 2 is a diagrammatical sketch of an enlarged section of the paper-like pellicle of Figure l.

In Figure l, the fibrous nature of the pellicle has been emphasized, for in many instances the pellicle has a paper-like finish and the fibers are not apparent.

In Figure 2, the fibers 1 are bonded together by the N-alkoxymethyl polyamide bonding agent 2 of the present invention.

The following examples are cited to illustrate the invention. They are not intended to limit it in any manner.

All test results to which reference is made in the examples are obtained by following the procedures reported in TAPPI Standards. Fold endurance tests are made on an M. I. T. Folding Endurance Tester manufactured by the Tinius Olsen Testing Machine Company).

EXAMPLE I Four grams of 5A; inch, 3 denier per filament staple of polyhexamethylene adipamide is suspended in a 6- liter aqueous solution containing 3 grams of sodium carboxymetbyl cellulose. The suspension is dispersed on a Rice-Barton Dyno pulper having two five-inch concave discs countercurrently stirring at 5000 revolutions per minute at opposite ends of a 5 gallon reservoir. Homogeneity is attained after 2 minutes. Thereafter the aqueous dispersion is filtered over an 8" X 8" square of 80 mesh screen, producing a randomly disposed mat of fibers referred to hereinafter as a waterleaff A vacuum of 350 mm. is employed to facilitate moisture removal and to avert bubble entrainment. The waterleaf is gently showered with 2.0 liters of water to wash out residual sodium carboxymethyl cellulose. The dry waterleaf is then dipped in a 20% solids aqueous dispersion of N-methoxymethyl polyhexamethylene adipamide having 45% of its amide groups substituted with methoxymethyl groups. The impregnated sheet is put through squeeze rolls to remove the excess dispersion and dried. It is thereafter pressed for 30 seconds at 160 C. under a pressure -of 200 pounds per square inch. The resulting paper-like pellicle, comprising 89% polyamide bers and 11% by weight `of bonding agent has a tensile strength of 35 pounds per inch, a burst strength of 140 pounds per square inch, elongation of 60%, a tearl strength of better than 3200 grams and a folding endurance of 777,329 cycles.

Table l below is a summary of various other fibrous polyhexamethylene adipamide pellicle preparations illustrating other polymeric dispersions in comparison with the N-alkoxymethyl polyamide dispersion in various concentrations. The fibers, the condition-s and the technique of Example I are employed in each example. They average about 2.5 ounces per square yard.v The impregnated sheets average about 5-8 mils in thickness. Hycar Acrylic Rubber #1551 is the trademark of B. F. Goodrich Chemical Co. for a colloidal suspension of an oilresistant butadiene/acryl-onitrile copolymer rubber in a water emulsion. Chemigum 245AHS is the trademark of Goodyear Tire and Rubber Co. for a colloidal suspension of an oil resistant butadiene/ acrylonitrile copolymer rubber in a water emulsion. Geon Latex #552 is the trademark of B.l F. Goodrich Chemical Co. for a stable water dispersion of a modified polyvinyl chloride resin of Example-8 isa low softeningplastictypefrnade fromv hexamethylene diamine, adipicacid, sebacic acid and caprolactam to yield a copolymer of approximately 35% or dropped upon a surface, or a continuous lament maybe crosslapped-on -a surface; The funicularv-structure may be crimped or uncrimped and of circular or irregular cross section.

polyhexamethylene adipamideunits;v 38%'epsilon-an1ino- 5 Among N-alkoxymethyl polyamides which are suitable caproamide units and 27% polyhexamethylene sebacamide in the process of the present invention may be mentioned units.N Polystyrene Emulsion P VVis an aqueous dis- N-methoxymethylpolyhexamethylenesebacamide,--N-isopersion lof plasticizedpolystyrene-produced by Koppersm'. butoxymethyl polyhexamethyleneadipamide, N-allyloxy- Co- Inc:1 methyl polyhexamethyleneadipamide, the N-benzyloxy- Table I Solidsin F1ber:Binder Tensile Fold En- Exam'yle Binder Dispersion' (Ratio)` Strength durances.:

(percenty (lbs/ln.) (Cycles) Sameas fEx. 1 5 1:0. 2 33 700,000 to 1,000,000 SameasEX. 1 10 1:0. 7 47 HfglAcrylie- Rubber 1:0.5 7.9 576 ohemium 24-5 Ana.; 5 110.35 1 8.2 l. 1, 638 `PtJlystyyrene Emulsion 5 1:0. 76 14.3 2, 486 Geo'Latex #552 5 1:0.23 f 26 15,000 'r Copolyamde 5 1 :0. 34 40 5,

In general the mechanics `of the process described herein methyl1 polyamide:4 derivedr-from afmixtureof hexamethyl-A are analogous to those of paper making. Thus the process 25 ene vdiammoniurn .adipatefand hexamethylen'ediammonium1:v is readily adaptable to paper-.making equipment, although sebacate, N-furyloxymethylsebacamide, N(betahydroxy):= notlimited thereto. In one embodiment a batt of bers is ethoxymethyladipamide, and the like.: formedon a movingscreen. Since the iiberstock can be y. ThefaqueousI dispersion of the N-alkoxymethyl polyf t added from a liquid suspension, the Fourdrinier machine; amide `bonding-agentz-is4 appliedto preformed batt in any is convenient for this operation. The N-alkoxymethyl 30 suitable manner: 'The amount of bondingresin retainedrf-'r polyamide dispersion, however, should be appliedto the by thebatt Will depend, of course, on the density of the Y batt `after. its formationon the endless screen. ,Addition batt,;-,;the solids. concentration of the dispersion and the of tliepolyamidedispersion to the beater or mixer will methodof removing'the excess dispersion. Vacuum ltrav not produce the outstanding products of this invention. tion of the-freshly impregnated batt yields the lowest ratio Adequate heat and pressure for completing the bonding of binder to fiber in the finished product, all other condiof iib'ersis supplied conveniently, by passing the .impreg-v tionsbeingequalgi.The simplest method for controlling natedbatt through. heated calender rolls. Manufacture. porosity of the paper-like productis through variation-ofmayalso be performed-on the cylinder paper machineby the solidstcontent of the aqueous dispersion of N-alkox-y- Similarmodication. methyl polyamide. Binder to liber ratios of less than 1-:1A

The method employed in forming the batt is not critical. 40 are generally; preferred if a product with any degree of It isfnot necessary that the molecularly oriented bers be y. porosityfiis desired.y If the product contains `as much suspended, in a liquid and beaten prior to battformation binder as fiber, it is nlm like and hasflow -tearfstrengtlrl since.adherence1among the iibers :does not depend on Thebinderato berratiomay be as low as 0.05 :1* and brillation as is the case in cellulose paper manufacture. provide adequatebonding for many4 purposes. lIn general; However, ,to attain uniform distribution it is convenient. the iratiozwill be between 0.2:1 Aand 0.7:fl for maximum to suspend .a known weight of fibers or the like in a. v utility.: To obtain these ratios, theaqueous'dispersionm measured quantity'of liquid and agitate. Machines usedl willfvary Vin solidsc'ontent'between 1 and 10%',"Clepending` in paper making'such as the Hollander Beater, the Tugf V to some extent'upon the method of removingthe excess boat..Pulper,.-jordans and the like are all suitable. Y To dispersionfromvthe impregnated batt. assist -dispersion the viscosity of the liquid may be raised-.50 The bonding step is generally accomplished Aby kex- This fmay. -be accomplished by supplying an additiveto posure of the/resin impregnated batt of nylon'ibersl to v water7 such as sodium carboxymethyl cellulose, -partiallyI elevated temperature and pressure. The optimumtem-V hydrolyzed polyvinyl acetate (such as Elvano172-51 peratureiwillvary with the speciicN-alkoxymethyl poly.-` manufactured by E. I. du Pont de Nemours and Co. of amidelused, the pressure upon `the ba-tt and the period of Wilmington, Delaware), the condensation product of exposure'. For a contact-period'of aboutthirty seconds i ethanolamine with mixed long chain acids (such as Ninola temperature within the` range of from about Vto 2012A, manufactured by Ninol Laboratories of Chicago, g.- aboutfl70 `-(l. is usuallyf'adequate. While longerhea't- Illinois), or the like, or by employingy a high viscosity'f ing periods/-When'foperating within this .temperature range liquidsuchas glycerine, ethylene-glycol, t-butyl alcohol may be employed Without deleterious eleets short Peor the like. 'The optimum viscosity will vary ,with'the 60 riOds of three minutes-or less are preferred to facilitate type of mixing or beating, the ber denier, and, similar commercial operations. lTemperatures suilicient to inducel factors. In choosing the suspending media'and thickener,l molecular r a-ndornl221ton Cause'e-*Weelenlug of the Prodtherefore, care must `be' exercised to avoid substancesz; not and loss of fleXbllltY- .For the Production 0f a which ;cannot be subsequently removed fromxthe formed; lllghstrengtll, hard Surface PaPerrllle PellCle, e Pressurec batt withfease since certain foreign'substances.such'asfor 65 Wltlllnerange 'of from about 50 to about 500 Pounds v instance sodium carboxymethylcellulose, even yin minutey L Per 'Squal'elnoll 1's usually employed-"AfA loWer Pressure.. concentrations, have been found to interferewith -thex- (0 t0 5 lbSJ Produoes a bulkler Product 0f softer Surface. formation of the join.t In batt formationfrom a' liquid The Product Vis a tough, leXble, Coherent Paper-likel suspension the use of staple having a lengthbelow about..l Pelllolel" lt S useful' in the-making of Peperv money,as 1 inchwith a denief per-1ament within the range of y.70 a nlte'rmedia,:as a non-woven fabric,.in the manufacture. from about'lo to about 6'is preferred. Howeverthese.v of reinforced Plastic, as body armor@ .Condenser Paper; values mayvary. Fibers of mixed length and denier in high frequency electronicV circuits,` printed electrical are suitable.l Fibers as short as l; inch are satisfactory. circuits, stencils,.,permanent- 1edger,..wallpaper.4 and lthe Instead of-laying the batt from liquid suspension, staple; 1ike..`Whilel the. invention has.l been `exemplied `in the fiber-'or nlamentin wetfor dry condition may be blown 75 productionof atstructures. it is obvious :that shaped 5 articles may be similarly formed by depositing the batt or leaf over a form and thereafter applying the necessary heat and pressure. The seamless cones, bags, apparel and the like may be made.

Many-equivalent modificati-Ons within the inventive concept will be apparent to those skilled in the art from a reading of the foregoing description without a departure from the inventive concept.

What is claimed is:

1. A process of preparing a paper-like pellicle which comprises impregnating an unwoven web of a molecularly oriented synthetic condensation polyamide fiber with an aqueous dispersion of an N-alkoxymethylpolyarnide and thereafter subjecting the impregnated mass to heat and pressure. y

2. The process of claim 1 wherein the polyamide ber is hexamethylene adipamide.

3. The process of claim 1 wherein the N-afkoxymethylpolyamide is N-methoxymethyl polyhexamethylene adipamide.

4. A paper-like pellicle comprising an unwoven mass' of a molecularly oriented synthetic condensation polyamide fiber adhered at points of fiber intersection with N-alkoxymethylpolyamide.

5. The product of claim 4 wherein the ber is hexamethylene adipamide.

6. The product of claim 4 wherein the N-alkoxymethylpolyamide is N-methoxymethyl polyhexamethylene adipamide.

References Cited in the le of this patent UNTTED STATES PATENTS 2,714,075 Watson et al. July 26, 1955 2,714,097 Watson et al. July 26, 1955 2,715,588 Graham et a1 Aug. 16, 1955 2,774,687 Nottebohm et al Dec. 18, 1956 OTHER REFERENCES Merriam-Websters New International Dictionary, 2nd ed. page 2894, item Web.

Claims (1)

1. A PROCESS OF PREPARING A PAPER-LIKE PELLICLE WHICH COMPRISES IMPREGNATING AN UNWOVEN WEB OF A MOLECULARLY ORIENTED SYNTHETIC CONDENSATION POLYAMIDE FIBER WITH AN AQUEOUS DISPERSION OF AN N-ALKOXYMETHYLPOLYAMIDE AND THEREAFTER SUBJECTING THE IMPREGNATED MASS TO HEAT AND PRESSURE.

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