US3555139A - Method for melt spinning polycaprolactam into a low humidity environment - Google Patents

Abstract

POLYCAPROLACTAM, DRIED TO A MOISTURE CONTENT OF LESS THAN 1%, IS MELT SPUN INTO AN ENCLOSURE IN WHICH RELATIVE HUMIDITY IS KEPT LESS THAN 50%. WHILE STILL WITHIN THE ENCLOSURE, A NON-AQUEOUS FINISHING COMPOSITION IS APPLIED TO THE FILAMENTS AFTER THEY SOLIDIFY. THE FILAMENTS ARE THEREAFTER, STILL IN SAID ENCLOSURE IN WHICH THE FILAMENTS ARE SHIELDED FROM HUMIDITY, AND WITHOUT ANY INTERMEDIATE COOLING OR AGING STEP, DRAWN WITH A DRAW RATIO OF GREATER THAN 5.0:1. THE RESULTING FILAMENTS HAVE A TENACITY ON THE ORDER OF 10 GRAMS PER DENIER.

Description

Jan. 12, 1971 WATERS ETAL 3,555,139

METHOD FOR MELT SPINNING POLYCAPROLACTAM INTO A LOW HUMIDITY ENVIRONMENT Original Filed June 28. 1965 United States Patent O 3,555,139 METHOD FOR MELT SPINNING POLYCAPROLAC- TAM INTO A LOW HUMIDITY ENVIRONMENT Herbert Waters, Chester, and Sterling M. Nichols, Hopewell, Va., assignors to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio Continuation of application Ser. No. 467,532, June 28, 1965. This application Aug. 20, 1969, Ser. No. 853,820 Int. Cl. D01d 5/12 US. Cl. 264-210 2 Claims ABSTRACT OF THE DISCLOSURE Polycaprolactam, dried to a moisture content of less than 1%, is melt spun into an enclosure in which relative humidity is kept less than 50%. While still within the enclosure, a non-aqueous finishing composition is applied to the filaments after they solidify. The filaments are thereafter, still in said enclosure in which the filaments are shielded from humidity, and without any intermediate cooling or aging step, drawn with a draw ratio of greater than 5.0: 1. The resulting filaments have a tenacity on the order of grams per denier.

This is continuation of SN. 467,532 filed June 28, 1965 and now abandoned.

This invention relates to a process for the production of filaments from polycaprolactam wherein the filaments are spun from a melt of polycaprolactam and directly thereafter, without intermediate windup or storage, drawn to orient it to its final oriented-crystalline state.

Prospectively, the concept of direct spinning and drawing of nylon 6 to directly form oriented-crystalline filaments would appear to be highly attractive due to the presumable greater compactness of the equipment and elimination of extra handling of the intermediate undrawn filament. However it has heretofore been considered that polycaprolactam filaments required an aging time in undrawn state before being sujected to drawing to convert them to their final oriented-crystalline state, see A. Reichle and A. Prietzschk, Angewandte Chemie 74, 562569. It has therefore heretofore been necessary to first melt spin the polycaprolactam into unoriented filaments; to collect these filaments upon bobbins; to store these bobbins for an extended aging time; to transfer these bobbins to drawing machines; and finally to draw the filaments into final oriented-crystalline form. If this aging step was omitted, it was impossible to draw the filaments beyond a ratio of ca. 4.5 :1, and consequently impossible to attain desirably high degrees of tenacity, above say 7 grams/denier. The cumbersome nature of this procedure, involving considerable labor in the transfer and re-transfer of the undrawn filament to and from storage, and the sprawling nature of the plant, with its separate spinning units, storage, and drawing machinery, is very evident, but up to the present time unavoidable.

Accordingly it is an object of the invention to minimize the labor and handling involved in the production of polycaprolactam filaments.

Another object is to provide a more compact plant for the manufacture of polycaprolactam filament than has heretofore been possible.

A further object is to provide a process for the manufacture of polycaprolactam filament wherein the filament is melt spun and the unoriented filaments continuously and directly taken from the melt-spinning operation to the drawing operation, without intermediate spooling and aging.

SYNOPSIS OF THE INVENTION The above and other objects are secured, in accordance with this invention, in a process and apparatus wherein the polycaprolactam, carefully dried to a moisture content less than 1%, based on the weight of the polycaprolactam plus moisture, is melt-spun into an enclosure in which the relative humidity is kept extremely low, say less than 50% at room temperature, and a non-aqueous finishing composition is applied to the filaments as they solidify. The filaments are thereafter, still in an enclosure in which the filaments are shielded from humidity, drawn with a draw ratio of greater than 5.0:1, say in the range of 5.4:1 to 7.5 :1. Under these conditions, which have been found to enable the high draw ratios cited even without an aging step, filaments are obtained having tenacities on the order of 10 grams per denier.

The invention is illustrated in the attached drawing, which is a diagrammatic view of an apparatus for the carrying out of this invention.

THE APPARATUS Referring more particularly to the drawing, there is shown a reservoir and melter 10 into which polycaprolactam resin is introduced, a pump 12 receiving the molten polycaprolactam from the reservoir 10 and spinning it out through a spinneret 14 into the form of filaments 16. The filaments 16 pass downwardly through an enclosing chimney 18 in a direction opposite to the flow of lowhumidity quenching air indicated by the arrow 20. At the bottom of the chimney the filaments impinge upon a revolving applicator roll 22 which applies a non-aqueous finishing liquid composition thereto, the finishing composition being supplied to the roll 22 by a pickup roll 24 bearing against the applicator roll and dipping into a trough 26 containing a supply of the finishing composition. From their impingement upon the applicator roll, the filaments pass to a pair of heated and rotating feeding and braking rolls 28, 30 around which they are wrapped back and forth from roll 28 to roll 30 so that the speed of these rolls controls the speed of withdrawal of the filaments from the spinneret 14 and also the speed at which the filaments are fed to the further processing. From the feeding rolls 28, 30, the filaments pass to a pair of heated, revolving drawing rolls 32, 34, around which they are wrapped back and forth, the rolls 32, 34 having a greater peripheral speed than the rolls 28, 30, so that the filaments are drawn and stretch-oriented in their reach 36 between the two sets of rolls. From the drawing rolls 32, 34 the filaments are passed to a final windup (not shown) for storage and shipment. The feed and drawing rolls 28, 30, 32 and 34 are disposed within an enclosure 38, and during the passage through the enclosure any solvents in the finishing agent applied at 22 is evaporated.

EXEMPLARY CONDITIONS OF OPERATION It 'will be understood that the specific conditions of operation set out hereinbelow are given by way of example only, and that departures therefrom are permissible twithin the scope of the invention as set forth hereinbelow. In a typical run, the spinneret 14 had 204 orifices therein, each .010 in diameter by .015" in length. The spinneret was operated at 515 F. 'with a throughput of 30 lb./hr. of polycaprolactam. The chimney 18 was cylindrical in form and had a height of 20 feet and a diameter of 8 inches. Air at F. and 45% relative humidity entered the apparatus at 40 and passed up the chimney 18 and out at 42 at the rate of 35 cubic feet per minute. The finishing composition applied by the roll 22 was a solution comprising of a deodorized kerosene and 15% of Textolene 4018, (an anionic tire cord oil manufactured by Sonneborn Chemical and Refining Company, Division of Witco Chemical Company, Inc., having a Saybolt viscosity at 100 F. of 960 seconds, a density of 7.9 lbs./ gal. Cloud point 20 F., Pour point l F. and pH in 5% solution of 7.5), the kerosene being substantially completely evaporated during the passage of the filaments through the enclosure 38. The feed rolls 28, 30 are 6 inches in diameter and are operated at 730 rpm. with an internal temperature of 240 F., the filaments being wrapped 8 times therearound. The drawing rolls 32, 34 are also 6 inches in diameter, are operated at 3825 r.p.m. with, an internal temperature of 375 F., the filaments being Wrapped 18 times therearound. The draw ratio is thus approximately 5.25: 1, and no excessive breakage has been encountered. The product filaments had a tenacity of 10 grams per denier. By way of contrast, if it is attempted to operate with aqueous finishing agents and without shielding from moisture and without aging, an impractical rate of breakage is encountered with draw ratios of this order of magnitude.

From the foregoing general discussion and detailed specific example of the carrying out of this invention, it will be evident that this invention provides a novel procedure whereby polycaprolactam may be melt spun and drawn into its final oriented crystalline form with high draw ratios productive of high tenacities, all in a single unitary process and apparatus.

What is claimed is:

1. Process which comprises melting polycaprolactam which has previously been dried to a moisture content of less than 1% spinning the molten polycaprolactam into filaments in an enclosure in which a flow of cooling gas is maintained in a direction opposed to the direction of movement of said filaments, to cause said filaments to solidify maintaining said cooling gas at a temperature of 75 F.

and a relative humidity of applying to said filaments a non-aqueous finishing agent while still in said enclosure and without any intermediate spooling or aging step passing said filaments, while still within said enclosure and without any intermediate spooling or aging step, over a set of draw rolls to draw said filaments to a draw ratio of from 5.0:1 to 7.511.

2. Process according to claim 1 wherein said draw ratio is from 5.111 to 7.0:1.

References Cited UNITED STATES PATENTS 2,733,122 1/1956 Herele et al 264-2101 2,918,347 12/ 1959' Notarbartolo et a1. 264-2101 3,118,012 1/1964 Kilian 2641 76F 3,156,750 11/1964 Cuculo 264-210F 3,317,980 5/ 1967 Jaeggli.

JULIUS FROME, Primary Examiner J. H. WOO, Assistant Examiner US. Cl. X.R.

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