US3329633A - Polyamide and fibers derived therefrom - Google Patents

Description

United States Patent 3,329,633 POLYAMIDE AND FIBERS DERIVED THEREFROM Lawrence W. Crovatt, Jr., Raleigh, N.C., assignor to Monsanto Company, a corporation of Delaware No Drawing. Filed Oct. 15, 1964, Ser. No. 404,187 4 Claims. (Cl. 260-18) ABSTRACT OF THE DISCLOSURE The lubricity properties of polyhexamethylene adipamide fibers are improved by introducing into the polymer between 0.1 and 5.0 weight percent of oleic acid dimer.

Fibers obtained from the homopolymer prepared from the reaction of hexamethylene diamine and adipic acid (nylon 66) have obtained commercial importance and success. Although these fibers have much to commend them, there is still need and room for new and improved properties. It is known that this commercial polyamide is very hard and crystalline and quite difficult to handle in friction producing operations. For this reason and because end-uses such as tire-cord, ropes and cordages are greatly benefited by a reduced yarn-to-yarn friction, a permanent low-friction property as a characteristic of the polymer is highly desirable.

Presently, in the commercial production of nylon 66 fibers, the as-spun filaments are given a treatment to improve their lubricity and handling properties. This treatment usually consists of passing the filaments, while in the form of a bundle, through a bath of or over a wheel coated with the treating or finishing liquid. The finish, thus received by the filaments, is nothing more than a coating and is not necessarily of a permanent nature. Most, if not all, of the lubricating agent contained Within the finish bath, is often lost in subsequent processing of the filament such as by mechanical handling, heating, washing, scouring and dyeing. If the finish does remain on the fiber until the final end-product is produced, it

3,329,633 Patented July 4, 1967 terminator. Therefore, it is not necessary to use undesirable polyamide cross-linking agents or vacuum finish techniques in the polymerization reaction to keep the oleic acid dimer modified polyamide in a fiber-forming molecular weight range. Additionally, the more even distribution of the lubricity enhancing additive throughout the polyamide chain results in a more uniform fiber lubricity and greater fiber strength.

The modified polyamides described herein are prepared by procedures well known in the art and commonly employed in the manufacture of unmodified nylon 66 polymers. That is, the reactants are heated at a temperature of from 180 C. to 300 C., and preferably from 200 C. to 295 C., until the product has a sufficiently high molecular weight to exhibit fiber-forming properties. This condition is reached when the polyamide has an intrinsic often becomes less effective after the end-product is used for periods of time.

Therefore, what is needed is a lubricating agent of a permanent nature; one that is incorporated directly into the polymer and the filaments produced therefrom, in lieu of merely being coated on the outside of the. produced filaments. If an improvement of a permanent nature such as this could be obtained, it would lead to significant reductions in yarn processing difficulties and subsequent increased end-product quality. Such an improvement would cause large reductions in fiber-to-fiber friction and thus increase the maximum strength and'life obtainable in tire cords, ropes and cordages.

Accordingly, it is an object of the present invention to provide a modified polyhexamethylene adipamide polymer and fibers produced therefrom which possess high lubricity characteristics. 4

This and other objects and advantages will become apparent in the course of the following detailed description of the invention and the claims appended thereto.

In general, these objects are accomplished in accordance with this invention by adding a modifying agent to the polymer forming reactants during the course of polymerization. The modifying agent is oleic acid dimer and is used in an amount of from 0.1 to about 5.0 weight percent based on the weight of the polyamide forming monomer, and preferably from 0.1 to 2.0 weight percent.

Oleic acid dimer is an ideal modifying agent because it is a dibasic acid comonomer and is capable of being evenly distributed throughout the long polyamide molecular chains. Also this additive does not cause polymer stabilization difiiculties because it does not act as a chain viscosity of at least 0.4, the intrinsic viscosity being in which N is the relative viscosity of a dilute solution of the polymer in m-cresol in the same units at the same temperature and C is the concentration in grams of polymer per cc. of the solution. The reaction can be conducted at superatmospheric, atmospheric or subatmospheric pressure. Often it is desirable, especially the last stage of the reaction, to employ a reduced pressure to aid in the removal of the reaction by-product. Preferably, the reaction is carried out in the absence of oxygen, e.g., in an atmosphere of nitrogen. The hexamethylene diamine and adipic acid polyamide forming reactants are normally introduced into the autoclave as a preformed salt but may be in the form of uncombined diamine and diacid when added. The modifying agent or additive should be added to the polymerization reaction during the final polymer holding or finishing cycle in order to avoid -undesirable polymer foaming. V

The modified polyamides as described herein may be prepared, spun and drawn under conventional nylon forming production conditions. In addition to the aforedescribed additive, delustrants, anti-oxidants, plasticizers, viscosity stabilizers, chain terminators, and other like modifying agents may be used in the preparation of the polyamides of this invention.

In order to illustrate the invention and advantages thereof with greater particularity the following specific examples are given. It is to be understood that they are intended to be only illustrative and are in no way intended to limit the invention. Parts and percentages are given by weight unless otherwise indicated.

EXAMPLE I A solution of 147 parts of hexamethylenediammonium adipate (nylon 66 salt) dissolved in 153 parts of water was added to a stainless steel evaporator which had previously been purged of air with purified nitrogen. The evaporator was so positioned that the contents thereof could be piped into a high-pressure autoclave when desired. The solution was then heated under a nitrogen blanket at a pressure of 13 p.s.i.g. with the continuous removal of steam as condensate until the solution reached a temperature of 137 C. At this point the salt solution was charged to a stainless-steel high-pressure autoclave which had previously been purged of air by the use of purified nitrogen. The temperature and pressure were slowly raised until values of 220 C. and 250 p.s.i.g., respectively, were reached. The temperature was then further increased to 243 C. with the pressure being maintained at 250 p.s.i.g. by the removal of steam as condensate. At this point the pressure reduction cycle egan. The pressure was gradually reduced to atmosheric over a 25 minute period. When the pressure reached tmospheric, 0.5 weight percent (based on the weight of he polyamide forming monomer) of oleic acid dimer was added to the polymerization reaction. The polymer nelt was then allowed to equilibrate for 30 minutes at 278 C. This finished polymer had a relative viscosity If 37.5.

The resultant polymer was melt spun directly from the aottom of the autoclave through a -hole spinneret to rield a white multi-filament yarn. Upon being drawn this Iarn of 11.5 denier per filament exhibited a tenacity of 3.0 grams per denier at an elongation of 24 percent.

EXAMPLE II In this example a solution of 147 parts of hexamethylenediammonium adipate dissolved in 153 parts of water was added to a stainless steel evaporator which had previously been purged of air by the use of purified nitrogen. The evaporator was positioned above a stainless-steel high-pressure autoclave and equipped with means for dropping the contents thereof into the autoclave when desired. This solution was then heated under a nitrogen blanket at a pressure of 13 p.s.i.g. with the continuous removal of steam as condensate until the solution reached a temperature of 137 C. At this point the salt solution was charged to the autoclave. The temperature and pressure in the autoclave were slowly raised until values of 220 C. and 250 p.s.i.g., respectively, were reached. The temperature was then further increased to 243 C. and the pressure was maintained at 250 p.s.i.g. by the continuous removal of steam as condensate. At this point the pressure was gradually reduced to atmospheric during a 25 minute period; at the end of which 1.0 weight percent (based on the weight of polyamide forming monomer) of oleic acid dimer was added to the polymer melt by mixing and stirring over a period of 30' minutes during which the temperature was maintained at 278 C.

The final finished polymer of 38.3 relative viscosity was melt extruded directly from the bottom of the autoclave through a 10-hole spinneret to yield a white multifilament yarn. The yarn was godet drawn over a hot (90 C.) pin to yield filaments having a 10.7 denier per filament, a tenacity of 7.5 grams per denier, and an elongation of 27 percent.

The filaments obtained in the above examples were closely examined and compared with filaments obtained from the standard, unmodified polyamide, nylon 66. The filaments of this invention exhibited a much more waxy or lubrid feel to the hand than those prepared from the standard, unmodified nylon 66 polymer. Additionally, a high degree of lubricity was evidenced by the ability of the fibers to slide freely over one another in bundles.

As previously noted, the products obtained in the practice of this invention are particularly useful in the manufacture of tire cords, ropes and cordages, where polyamide filaments having low fiber-to-fiber friction are especially desirable. The products obtained in the practice of this invention may also be used to advantage in the manufacture of fabrics, film, and the like where the ultimate end-use intended would be benefited by the employment of a polymer having high lubricity characteristics.

This improvement in lubricity has been obtained without degradation of other physical properties. That is to say, physical properties such as tenacity, elongation, and relative viscosity of the fibers produced in accordance with this invention have been maintained at the same desirable levels as those exhibited by the standard commercially successful polyamide nylon 66.

As many widely diiferent embodiments of this invention may be made without departing with the spirit and scope thereof it is to be understood that the invention is not to be limited by the specific embodiments set forth herein but only by the claims which follow.

Having thus described my invention in detail what I claim as new and desire to secure by US. Letters Patent is:

1. A fiber-forming synthetic linear polyamide having improved lubricity when in fiber form which comprises the product obtained by reacting at a temperature of between C. and 300 C. reactants comprising, (A) a polyamide forming monomer consisting of the salt formed by substantially equimolecular proportions of adipic acid and hexamethylene diarnine, and (B) from 0.1 to about 5.0 weight percent based on the weight of the (A) of the additive oleic acid dimer.

2. The fiber-forming synthetic linear polyamide as set forth in claim 1, wherein said additive is present in an amount of from 0.1 to 2.0 weight percent based on the Weight of the polyamide forming monomer.

3. A textile fiber comprising the polyamide as defined in claim 2.

4. A fiber-forming synthetic linear polyamide having improved lubricity when in fiber form which comprises the product obtained by the process comprising polymerizing a polyamide-forming monomer consisting of the salt formed by substantially equimolecular proportions of adipic acid and hexamethylene diamine and adding to the polymer during the final polymerization stage thereof, from 0:1 to about 5.0 weight percent of oleic acid dimer.

References Cited UNITED STATES PATENTS 3,240,732 11/1966 Ham et al 260-18 DONALD E. CZAIA, Primary Examiner.

LEON J. BERCOVITZ, Examiner.

C W. IVY, Assistant Examiner.

Claims (1)

1. 4. A FIBER-FORMING SYNTHETIC LINEAR POLYAMIDE HAVING IMPROVED LUBRICITY WHEN IN FIBER FORM WHICH COMPRISES THE PRODUCT OBTAINED BY THE PROCESS COMPRISING POLYMERIZING A POLYAMIDE-FORMING MONOMER CONSISTING OF THE SALT FORMED BY SUBSTANTIALLY EQUIMOLECULAR PROPORTIONS OF ADIPIC ACID AND HEXAMETHYLENE DIAMINE AND ADDING TO THE POLYMER DURING THE FINAL POLYMERIZATION STAGE THEREOF, FROM 0.1 TO ABOUT 5.0 WEIGHT PERCENT OF OLEIC ACID DIMER.