US3848023A - Antistatic composition and fiber made therefrom - Google Patents

Abstract

1. AN ANTISTATIC COMPOSITION OF MATTER COMPRISING A HIGH MOLECULAR WEIGHT FIBER-FORMING POLYCARBONAMIDE WHEREIN THE RECURRING CARBONAMIDE LINKAGES ARE AN INTEGRAL PART OF THE POLYMER CHAIN, SAID POLYCARBONAMIDE BEING EITHER A COPOLYMER OF AT LEAST TWO DIFFERENT POLYCARBONAMIDE-FORMING SUBSTANCES OR A MELT BLEND OF AT LEAST TWO DIFFERENT POLYCARBONAMIDE POLYMERS, SAID POLYCARBONAMIDE BEING COMPOSED OF ABOUT 6-24 WEIGHT PERCENT AROMATIC NUCLEI AND A HIGH MOLECULAR WEIGHT POLY(ALKYLENE ETHER) AS A DISTINCT PHASE IN THE FORM OF SMAALL ELONGGATED PARRTICLES FROM 1 TO 15 PERCENT BASED ON THE WEIGHT OF THE COMPOSITION FORMED BY THE ESTER INTERCHANGE REACTION OF

R-OOC-Y-COO-R

WHEREIN R IS AN ALKYL RADICAL OF 1 TO 4 CARBON ATOMS AND Y IS A DIVALENT ORGANIC RADICAL SELECTED FROM THE GROUP CONSISTING OF

-(PHENYLENE)-, -(NAPHTHALYENE)-

AND A LINEAR OR BRANCHED ALKYLENE RADICAL OF 1 TO 20 CARBON ATOMS; AND

(HO-(A-O)N-R''(-R")(-X))2-N-R''-(O-A)N-OH

WHEREIN R'' IS A LINEAR OR BRANCHED C2-C4 ALKYLENE RADICAL, R" IS A C12-C24 ALKYL RADICAL, A IS A LINEAR OR BRANCHED C2-C4 ALKYLENE RADICAL, THE SUM OF THE N''S IS ABOUT 25 TO 7575, X IS HYDROGEN OR AN ALKYL RADICAL OF 1 TO 4 CARBON ATOMS; AND THE MOL RATIO OF (A) TO (B) IS FROM ABOUT 1:9 TO ABOUT 1:1.

Description

United States Patent US. Cl. 260-857 PG 7 Claims ABSTRACT OF THE DISCLOSURE An antistatic composition is provided suitable for being shaped by melt spinning into resilient fibers. Such fibers can be used to make an antistatic carpet structure having a maximum body voltage for a human Walking thereon and wearing leather shoes of less than 3,000 volts at 20% relative humidity and 72 F. The antistatic composition is composed of a high molecular weight fiberforming polycarbonamide composed of about 6-24 weight percent aromatic nuclei and a high molecular weight non-fiber-forming poly(alkylene ether) compound. The polycarbonamide is either a copolymer of at least two different polycarbonamide-forming substances or a melt blend of at least two difierent polycarbonamide polymers. The polyether is present in amount of about 115 percent based on the weight of the composition and is dispersed in the composition as a distinct phase in the form of small elongated particles. At least 50% of the molecular weight of the poly(alkylene ether) compound is composed of repeating alkylene oxide units.

BACKGROUND OF THE INVENTION It is well known that static electricity is generated and transferred as one walks on conventional carpet structures made from either synthetic fibrous material or natural fibrous material. The more severe problems occur when the carpet pile is made of a synthetic polymer, such as nylon which is a fiber-forming polycarbonamide wherein the recurring carbonamide linkages are an integral part of the polymer chain. As one walks on a carpet structure, electron transfer occurs. When a person walking across such a surface later becomes grounded, a discharge of electrons occurs through that part of the individuals body which by chance comes in contact with the ground. The discharge may occur by touching a door knob, metal bookcase or the like. When the voltage build-up exceeds, 3,000 volts, the electric shock can cause personal discomfort.

The tendency for static electricity to build-up on a carpet greatly increases as the relatively humidity of the ambient air decreases. Many approaches have been taken to reduce the static problems of carpets made of synthetic filaments or fibers. None of these have provided an entirely suitable carpet structure which is lastingly essentially static free at 20% or less relative humidity. Substances have been placed on the surface of the fiber, but the elfectiveness of such treatment is only temporary. Many different antistatic additives have been incorporated in carpet yarn with varying degrees of success. Unfortunately, when the carpet is constructed of such yarn, voltages above 3,000 volts at 20% relative humidity will occur on a person walking thereover, unless an undesirable amount of antistatic additive is placed in the polymer. As one adds more and more antistatic additive, the voltage build-up is accordingly reduced. But, as more and more antistatic additive is used, the spinnability of the polymer is significantly reduced; and the fibers made therefrom become easily matted down because the resistance to crushing of the pile is very much lowered. It has been suggested to randomly intermingle metal fibers among the synthetic fibers. This approach gives rise to considerable added cost and product non-uniformities. It has been taught in the art to incorporate electrically conductive carbon black in latex applied to the underside of the carpet backing with the pile of the carpet containing or not containing an antistatic additive. Using conductive carbon black in the latex alone without modifying the pile fibers helps but does not reduce the electric build-up to below the 3,000 volt level referred to above; On the other hand, using conductive carbon black in the latex and a pile made of synthetic polymer fibers having known antistatic additives incorporated therein is not only expensive but when suificient amount of the additive is used the fibers lose their resiliency.

In accordance with the present invention, a polymeradditive combination is provided so that the composition thereof is not only lastingly antistatic but fibers made therefrom are at least as resilient as nylon fibers to which no antistatic additive has been incorporated.

SUMMARY OF THE INVENTION The antistatic composition of the present invention can be shaped into films and filaments. Such filaments are characterized by having resistance to matting and can be used as the pile material in a conventional carpet structure that provides a maximum body voltage build-up for a human walking thereover of at most 3,000 volts even at relative humidities as low as 20% at 72 F. The com-- position is composed of a high molecular weight fiberforming polycarbonamide and a high molecular weight non-fiber-forming poly(alkylene ether) compound. The molecular weight can range from 600 to 30,000 and higher. The polycarbonamide is composed of about 6-24- weight percent aromatic radicals. The polycarbonamide is a copolymer of at least two different polycarbonamideforming substances or a melt blend of at least two different polycarbonamide polymers. The polyether is present in amount of l-l5 percent based on the weight of the composition and is dispersed in the composition as a distinct phase in the form of small elongated particles.

DETAILED DESCRIPTION OF THE INVENTION The composition of the present invention is basically a specific class of polycarbonamides rendered antistatic by having incorporated therein poly(al'kylene ether) compounds. It is important to the attaining of the unexpected low levels of static build-up and the high resistance to matting in fiber form that the polycarbonamide is fiberforrning and is either a copolymer of at least two different polycarbonamide-forming substances or a melt blend of at least two ditferent polycarbonamides. As indicated above, polycarbonamides may generically be called nylons and have recurring carbonamide linkages as an integral part of the polymer chain. It is also important that 6-24 weight percent of the polycarbonamide be composed of aromatic nuclei. The presence of the aromatic radicals surprisingly contributes to the improved electrical properties as Well as' to the resistance to matting of filaments made therefrom.

The aromatic moieties of the polycarbonamides may be a single ring, a fused ring or a multi-nuclear aromatic ring system which can be either homocyclic or heterocyclic. Preferably, it is homocyclic and more preferably it is carbocyclic. Representative of the divalent aromatic radicals constituting a substantial part of polycarbonamide are the following:

C-- NE NH- ---O NH- etc. Preferably the functional aromatic radical is The polycarbonamide can be a random copolyamide formed from at least two different polycarbonamideforming substances. Among these substances that are preferred are:

Also included are random copolymers of p-aminobenzoic acid and hexamethylene adipamide. Instead of hexamethylene diamine one may use in whole or in part pphenylene diamine.

The polycarbonamides can be a melt blend or dispersion of two or more fiber-forming polymers. Among the blends that are preferred are:

(a) polyhexamethylene adipamide and polyhexamethylene terephthalamide;

(-b) polyhexamethylene adipamide and polyhexamethylene isophthalamide;

(c) polycaproamide and polyhexamethylene terephthalamide;

(d) polycaproamide and polyhexamethylene isophthalamide;

(e) polyhexamethylene adipamide, polyhexamethylene terephthalamide, and polyhexamethylene isophthalamide;

(f) polycaproamide, polyhexamethylene terephthalamide, and polyhexamethylene isophthalamide; and (g) polyhexamethylene adipamide, caproamide, and polyhexamethylene terephthalamide.

Dispersed as a separate and distinct phase in the polycarbonamide is a high molecular weight non-fiber-forming poly(alkylene ether) compound. The compound in the polycarbonamide matrix takes the form of elongated particles of 0.05 to 1.5 microns in diameter and at least 15 microns long. The poly(alkylene ether) may be added prior to, during or after the polycondensing of the polycarbonamide-forming substances. In order to obtain the high antistatic performance, the p0ly(alkylene ether) compound should be made up of at least 50% by weight of repeating alkylene oxide units. The alkylene oxide units may be ethylene oxide, propylene oxide, butylene oxide, etc.

The most preferred poly(alkylene ether) additive is formed by the ester interchange reaction of where R is an alkyl radical of 1 to 4 carbon atoms and Y is a divalent organic radical selected from the group of and a linear or branched alkylene radical of 1 to 20 carbon atoms; and

wherein R is a linear or branched C -C alkylene radical, R" is a C -C alkyl radical, A is a linear or branched C -C alkylene radical, the sum of ns is about 25 to 75, X is hydrogen or an alkyl radical of l to 4 carbon atoms; and the mol ratio of (a) to (-b) is from 1:9 to about 1:1.

The static measurement tests used in the following examples were conducted as follows. The testing was done in a controlled humidity room (20 RH.) maintained at 72i2 F. A 3 ft. x 12 ft. carpet was placed on a conventional waffie rubber carpet pad which lay on the concrete floor of the testing room. The human subject, wearing shoes with leather soles and heels, walked on the carpet sample. The subject carried a 1000:1 kv. voltage divider probe. From the probe a lead run to the input of a Keithley 610 C electrometer. The output of the electrometer was then fed to a strip chart recorder. As the subject walked, the voltage increased to a steady-state maximum voltage after 20 to 30 steps. The data given below are the average body build-up measurements on two subjects.

EXAMPLE I A random copolymer of hexamethylene adipamide and hexamethylene terephthalamide was prepared in an autoclave. The copolymer contained 20 weight percent hexamethylene terephthalamide units and had a relative viscosity of 32 when measured in formic acid at 25 C. The polymer was cut into flake suitable for feeding a conventional screw melter-extruder.

A poly(alkylene ether) wax (molecular weight-6250) compound was formed by the ester interchange reaction and wherein R is a C -C saturated aliphatic radical, n is an integer, the sum of the ns being about 50, the mol ratio of (a) to (b) being 1:1.

The flake of the random copolymer was introduced into a melt screw extruder device. Both the rate of introduction of flake and the poly(alkylene ether) compound and extrusion of the molten polymer were maintained at 355 pounds per hour. The flake was fed to the inlet end of the screw extruder and heated to 285 C. to melt the same. The poly(alkylene ether) compound was metered into the molten polymer near the exit end of the screw extruder in an amount to provide in the polymer 7.2% by weight of the poly(alkylene ether) compound. The compound became dispersed as a separate phase in the polymer. The resulting molten composition was forced through trifurcated holes in a spinnerette of a conventional spinning machine to form a threadline composed of 136 filaments having an ultimate drawn total denier of 2460. A small amount of lubricant was applied to the surface of the filaments. The undrawn filaments of trilobal cross section were collected on bobbins. The bobbins were stocked on a multiple position gear-texturing machine as shown in US. Pat. 3,456,610. The yarn was draw-textured on this machine and collected. The yarn was then tufted into a non-woven polypropylene carpet backing to form a pile fabric. The backing had a reinforcing scrim. The pile was level loop of A in. pile height and weighed 22 ounces per square yard. An aqueous dispersion of conventional latex was applied to the backing which was thereafter dried.

The carpet was tested for static build-up on a human subject in accordance with the procedure given above. The voltage build-up was only 2,600 volts. The carpet had an excellent appearance and had noticeable resistance to matting.

EXAMPLE II In comparison, a homopolymer of hexamethylene adipamide was prepared and spun into similar filaments. The filaments were draw-textured and tufted into carpet of the same structure as Example I. It was found that under similar test conditions the voltage build-up on the carpet was 15,000 volts.

EXAMPLE III In this example a random copolymer of hexamethylene adipamide and hexamethylene terephthalamide was prepared as in Example I but the content of the latter substance was increased to 28 weight percent. The same poly- (alkylene ether) wax in the same amount as in Example I was incorporated into the copolymer prior to being spun into filaments. The filaments were draw-textured and tufted into a carpet as in Example I. It was found under similar test conditions that the voltage build-up on the carpet was 1,960 volts.

EXAMPLE IV In this example the random copolymer was 80% hexamethylene adipamide and hexamethylene terephthalamide. The same poly(alkylene ether) wax was added to the copolymer as in Example I. However, in this case the amount of wax was reduced to 5.5 weight percent. Filaments were spun therefrom, draw-textured and tufted into a carpet as in Example I. It was found that under similar test conditions the voltage build-up on the carpet was 2,900 volts.

EXAMPLE V In this example the random copolymer was 80% hexamethylene adipamide and 20% hexamethylene terephthalamide. The same poly(alkylene ether) wax was added to the copolymer as in Example I. The amount of wax was 7.2% by weight. However, 75 p.p.m. copper in compound form was added to the polymer. Filaments were spun therefrom, draw-textured and tufted into carpet as in Example I. It was found that under similar test conditions the voltage build-up on the carpet was 2,300 volts.

What is claimed is:

1. An antistatic composition of matter comprising a high molecular weight fiber-forming polycarbonamide wherein the recurring carbonamide linkages are an integral part of the polymer chain, said polycarbonamide being either a copolymer of at least two different polycarbonamide-forming substances or a melt blend of at least two different polycarbonamide polymers, said polycarbonamide being composed of about 6-24 weight percent aromatic nuclei and a high molecular weight poly(alkylene ether) as a distinct phase in the form of small elongated particles from 1 to 15 percent based on the weight of the composition formed by the ester interchange reaction of (a) ROCYCOR wherein R is an alkyl radical of 1 to 4 carbon atoms and Y is a divalent organic radical selected from the group consisting of and a linear or branched alkylene radical of 1 to 20 carbon atoms; and

' to about 1:1.

2. The composition of claim 1 wherein the aromatic nuclei is 3. The composition of claim 1 wherein the polycarbonamide is a random copolyamide formed from the polycarbonamide-forming substances selected from the group consisting of (a) hexamethylene adipamide and hexamethylene terephthalamide;

(b) hexamethylene adipamide and hexamethylene isophthalamide;

(c) caproamide and hexamethylene terephthalamide;

(d) caproamide and hexamethylene isophthalamide;

(e) hexamethylene adipamide, hexamethylene terephthalamide and hexamethylene isophthalamide;

(f) caproamide, hexamethylene terephthalamide and hexamethylene isophthalamide; and

(g) hexamethylene terephthalamide, caproamide and hexamethylene terephthalamide.

4. The composition of claim 1 wherein the polycarbonamide is a melt blend of polymers selected from the group consisting of (a) polyhexamethylene adipamide and polyhexamethylene terephthalamide;

(b) polyhexamethylene adipamide and polyhexamethylene isophthalamide;

7 '(c) polycap'r'oamide and polyhexamethylene terephthal'amide;

' (d) polycaproamide and polyhexamethylene isophthalamide;' (e) polyhexamethylene adipamide, polyhexamethylene terephthalamide, and polyhexamethylene isophthalamide; (flpolycaproamide, polyhexamethylene terephthalamide, and polyhexamethylene isophthalamide; and (g) polyhexarnethylene adipamide, polycaproamide and polyhexamethylene terephthalamide. 5. antistatic composition of matter comprising a 'polycar'bonamide consisting essentially of a random copolymer of hexamethylene adipamide and hexamethylene terephthalamide, said copolymer containing 6-24 weight percent. aromatic nuclei; and as a distinct phase in the form of small elongated particles from about 1 to 15 percent based on the weight of the composition, a high molecular weight poly(alkylene ether) compound formed by the ester interchange reaction of CH3OCCOGH3 8 8 and wherein R is a C -C saturated aliphatic radical, n is an integer, the sum of the ns being 25 to 75, the mol ratio of (a) to (b) being 1:9 to 1:1. I

6. A fiber shaped from the composition of claim 1. 7. A carpet whose pile is made at least in part of the References Cited UNITED STATES PATENTS Magat 260-857 PG Ohno 260-857 PG Garforth 2'608S7 PG Lofquist 260857 PE FOREIGN PATENTS Great Britain 260-857 PG Canada 260857 PG Netherlands 260857 PG Japan 260857 PG Japan 260857 PG Japan 260-857 PG PAUL LIEBERMAN, Primary Examiner fiber of claim 6.

US. Cl. X.R.

Claims (1)

1. AN ANTISTATIC COMPOSITION OF MATTER COMPRISING A HIGH MOLECULAR WEIGHT FIBER-FORMING POLYCARBONAMIDE WHEREIN THE RECURRING CARBONAMIDE LINKAGES ARE AN INTEGRAL PART OF THE POLYMER CHAIN, SAID POLYCARBONAMIDE BEING EITHER A COPOLYMER OF AT LEAST TWO DIFFERENT POLYCARBONAMIDE-FORMING SUBSTANCES OR A MELT BLEND OF AT LEAST TWO DIFFERENT POLYCARBONAMIDE POLYMERS, SAID POLYCARBONAMIDE BEING COMPOSED OF ABOUT 6-24 WEIGHT PERCENT AROMATIC NUCLEI AND A HIGH MOLECULAR WEIGHT POLY(ALKYLENE ETHER) AS A DISTINCT PHASE IN THE FORM OF SMAALL ELONGGATED PARRTICLES FROM 1 TO 15 PERCENT BASED ON THE WEIGHT OF THE COMPOSITION FORMED BY THE ESTER INTERCHANGE REACTION OF