US3839496A - Manufacture of filaments or fibers of polyamides - Google Patents

Abstract

1. A PROCESS FOR THE MANUFACTURE OF ANTISTATIC POL AMIDE FILAMENTS WHICH COMPRISES: FORMING A MOLTEN MIXTURE OF (A) A FILAMENT-FORMING SYNTHETIC LINEAR ALIPHATIC POLYAMIDE HAVING RECURRING AMIDE GROUPS IN THE BACKBONE AND HAVING A RELATIE VISOSITY IN THE RANGE OF 1.5 TO 2.9, MEASURED AS A 1% W./W TOGETHER WITH (B) FROM 2 TO 15% BY WEIGHT, BASED ON THE FILAMENTS OR FIBERS, OF AN ALKOXYLATED POLYAMIDE MANUFACTURED BY REACTION OF A OLYMIDE SELECTED FROM THE CONSISTING OF THE POLYCONDENSATES OF LACTAMS OF 4 TO 12 CARBON ATOMS AND POLYCONDENSATES OF THE SALTS OF DIAMINES CONDENSATES OF LACTAMS OF 4 TO 12 CARBON ATOMS AND DICARBOXYLIC ACIDS OF 4 TO 12 CARBONS ATOMS WITH A 1,2-ALKYLENE OXIDE IN A WEIGHT RATIO FO FROM 1:2 TO 1-5 AND TO PROVIDE A TOTAL MOLECULAR WEIGHT OF 10,000, COMPONENTS (A) AND (B) BEING SO THROUGHLY MIXED THAT SAID ALKOXYLATED POLYAMIDE IS PRESENT IN THE FINISHED FILAMENTS IN THE FORM OF PARTICLES HAVING A DIAMETER OF NOT MORE THAN 0.1; AND FINISHED FILAMENTS IN THE FORM OF PARTICLES HAVING A FILTER HAVING A PORE WIDTH OF NOT MORE THAN 20; AND SUBSEQUENTLY MELT SPINING SAID MIXTURE BEING MAINTAIND IN THIS MENTS, THE MOLTEN MIXTURE BEING MAINTAINED IN THIS PROCESS AT ELEVATE TEMPERATURES OF UP TO NOT MORE THAN 290*C. FOR A TOTAL PERIOD OF NOT MORE THAN 30 MINUT4S.

Description

United States Patent US. Cl. 260857 TW 4 Claims ABSTRACT OF THE DISCLOSURE Manufacture of filaments or fibers of synthetic linear polyamides containing from 2 to 15% by weight of alkoxylated polyamides using certain conditions concerning the fineness of subdivision, filtration and shaping.

This invention relates to a process for the manufacture of filaments or fibers containing alkoxylated polyamides.

It is well known that textiles and carpets of synthetic fibers including polyamides build up an electrostatic charge due to friction occurring in use. Such electrostatic charges, in the case of textiles, may produce an unpleasant feel when said textiles are in contact with the human body or, in the case of carpets, persons walking thereon may receive highly unpleasant shocks due to electrostatic discharges. These phenomena are particularly observed when the relative humidity is low.

There has been no lack of attempts to obviate these undesirable properties. For example, attempts have been made to increase the surface conductivity of polyamide filaments by applying antistatic agents thereto, either together with the lubricant or in a subsequent step. Such agents are usually water-soluble, however, and consequently their effectiveness disappears on washing. The effect may be made more permanent by incorporating the agents in the polymer. This method is described in US. Pat. 3,329,557, which teaches the incorporation of polyethylene glycols into polyamide filaments. However, the results obtained could still be improved upon, since the said polyethylene glycols are extracted on repeated washing. These well-known disadvantages may, in theory, be overcome by subsequent cross-linking with, say, X-rays', but this solution is hardly economical.

It is an object of the invention to manufacture filaments or fibers which show a permanent greatly reduced tendency to antistatic build-up without the other properties of the fibers, such as their mechanical or tinctorial properties, being substantially impaired.

This object is achieved by a method of making filaments or fibers of filament-forming synthetic linear polyamides containing alkoxylated polyamides in an amount of from 2 to 15%, on the weight of the filaments or fibers, Wherein a molten mixture of the filament-forming synthetic linear polyamides and alkoxylated polyamides is subjected to thorough mixing so that the alkoxylated polyamides are present in the finished filaments in the form; of particles having a diameter of not more than 0.1,u., and the molten mixture is filtered at least once through a filter having a pore width of not more than 2071, the mixture is converted to chip form if desired, and the mixture is melt spun, the molten mixture being maintained at temperatures of up to not more than 290 C. for a total period of not more than 30 minutes.

By filament-forming synthetic linear polyamides of high molecular weight we mean those having recurring amide groups in the backbone.

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Suitable filament-forming or fiber-forming synthetic linear polyamides are, for example, the polycondensates of lactams having from 4 to 12 carbon atoms, such as e-caprolactam, octolactam, dodecanolactam or mixtures of said lactams, and the polycondensates of salts of diamines and dicarboxylic acids having from 4 to 12 carbon atoms, such as the salts of adipic acid, suberic acid or sebacic acid, and hexamethylene diamine, octamethylene diamine or dodecamethylene diamine or mixed condensates of said polyamide-forming materials. Particularly suitable are polycaprolactam; and polyhexamethylene adipamide. The filament-forming or fiber-forming polyamides may contain an excess of Basic groups or they may have a content of sulfo groups or alkali metal sulfonate groups. Conveniently, the polyamides to be modified ha've relative viscosities in the range 1.5 to 2.9.

Polyamides alkoxylated with 1,2-alkylene oxides may be manufactured by known processes, for example by the method described in Belgian Pat. 665,018 comprising the reaction of 1,2-alkylene oxides, for example ethylene oxide and/ or 1,2-propylene oxide, with polyamides under pressure and at elevated temperatures, in particular at temperatures ranging from 60 to C. The reaction may be carried out in the presence or absence of organic solvents and/or reducing or oxidizing agents, the alkylene oxides being reacted with the polyamides preferably in a ratio of from 2 to 5:1 by weight. It has been found advantageous to use alkoxylated polyamides having a total molecular weight of at least 10,000 and in particular from 20,000 to 80,000.

Suitable polyamides from which the alkoxylated polyamide antistatic agents may be manufactured are for example conventionally produced polycondensates of lactams having from 4 to 12 carbon atoms, such as e-caprolactam, octolactam, dodecanolactam or mixtures of said lactams, the polycondensates of salts of diamines and dicarboxylic acids having from 4 to 12 carbon atoms, such as the salts of adipic acid, suberic acid or sebacic acid, and hexamethylene diamine, octamethylene diamine or dodecamethylene diamine or copolyamides of said polyamide-forming materials. Particularly suitable are all those polyamides which have low crystallinity, for example copolyamides or polyamides which have been prepared by quenching the polymer melt, for example molten polycaprolactam.

The amount of alkoxylated polyamides used is conveniently from 2 to 15% and in particular from 4 to 10% w./w. of the weight of the filaments or fibers. It is possible to use larger proportions, but this leads to changes in the properties of the filaments or fibers.

The solid components, i.e. the filament-forming polyamides and the alkoxylated polyamides, may be melted separately or together. The components may be mixed in a conventional single-worm or twin-worm extruder, of which one or both of the worms may be axially displaceable if desired. Static mixers having stationary conducting elements may also be used to advantage. Adequate mixing is usually obtained using static mixers having 15 or more elements. Static mixers of this kind are described for example in US. Pats. 3,286,992 and 3,404,689 and German Published Application 1,178,404. Conditions should be such as to achieve such thorough mixing that the alkoxylated polyamides, which form a separate phase in the filaments after cooling and drawing, have a particle diameter of not more than 0.1 4. The degree of mixing required to achieve this end may be previously found by simple experiment. The length of the separate particles of alkoxylated polyamides in the filaments after drawing is generally a multiple of their diameter, for example about 111 or more. It is an important feature of the process of the invention that filtration of the molten mixture of components is carried out at least once through filters having pore widths or not more than 201L- Examples of suitable filters are metal sieves or, in particular, sintered metal filters such as sintered metal plates or sintered metal tubelets.

Following the thorough mixing and filtration, the molten mixture may, if desired, be converted to chips and subsequently melt-spun to filaments or fibers. Alternatively, the molten mixture may be thoroughly mixed and filtered and immediately melt-spun to filaments or fibers without intermediate conversion to chip form. Another alternative is to carry out mixing and filtration in the spinning apparatus by using a spinning extruder capable of providing thorough mixing and placing a filter having a pore width of less than 20g immediately downstream of the spinning nozzle, which filter is advantageously an appropriate sintered metal filter.

It is important that the molten mixture of filamentforming polyamide and alkoxylated polyamide is maintained at temperatures of not more than 290 C. and generally at from 250 to 290 C. for a total period of not more than 30 minutes including the melt-spinning time. The time during which the mixture may be in chip form in a colder state is, of course, not included.

The filaments are made using conventional spinning systems wherein, of course, the conditions usually observed in the manufacture of polyamide filaments, such as the exclusion of oxygen and the use of certain low moisture contents, must be met. The filaments or fibers produced by melt-spinning may have a round crosssection or a profiled cross-section such as a trilobate or tetralobate cross-section. The filaments may be in the form of two-component filaments with other filamentforming materials. Conveniently, the filaments or fibers of the invention are stretched, for example at a draw ratio of from 1:2.5 to 1:4.5. The filaments or fibers may also be texturized, for example by the false-twist or stutter-box method or by texturizing in moving gas media.

The filaments or fibers may incorporate conventional additives such as pigments, for example titanium dioxide, or light stabilizers, heat stabilizers, and stabilizers to prevent the degradation of polyether chains.

The filaments or fibers produced by the method of the invention are distinguished by their greatly reduced tendency to build up electrostatic charges. This good antistatic behavior remains after repeated washing.

Electrostatic build-up on textile articles may be determined by the method proposed by Heyl & Liittgens (Kunststoife, Vol. 56, 1966, p. 51). A suitable method as regards carpets is the stroll test (Test Method for Determining the Static Propensity of Carpets, Report American Carpet Institute, Aug. 19, 1968).

It is a great advantage that the good antistatic properties of the filaments or fibers produced by the method of the invention are not obtained at the expense of the mechanical and tinctorial properties of the filaments or fibers. The process of the invention is distinguished in that the yields produced in spinning and drawing are high as compared with unmodified polyamides, which means that the number of defects found in the subsequent stages of warping and knitting is low. The same applies to the use of the filaments in the manufacture of carpets, where great advantage are found, for example, in the steps of texturizing and tufting. The quality of the filaments is tested by the conventional technological tests on mechanical properties and dyeability. The values found for the filaments produced by the invention hardly differ from those provided by the corresponding unmodified polyamides. Indeed, the filaments modified by the present invention can usually by dyed deeper and more level shades a frequently desirable feature. Since the streak-free dyeing of conventional polyamides remains a problem, the above improvement as concerns dyeability is particularly advantageous.

The filaments made in accordance with the present invention may be woven or knitted to textile articles such as underwear and shirts with advantageous results. The quality required in such articles is particularly high and the measures of the invention are therefore especially efiective for this application. Filaments made in the manner proposed by the present invention may also be used successfully in carpets, both in the form of continuous filaments and as staple fibers. A distinct improvement in the quality of the filaments is achieved as compared with prior art modifying processes for the manufacture of twophase antistatic fibers.

In the following Example the parts and percentages are by weight. The relative viscosities (1 are measured on a 1% w./w. solution in 98% H at 20 C.

EXAMPLE A Werner & Pfieiderer twin-worm extruder ZSK 53 is fed with 92.5 parts of extracted and dried polycaprolactam chips having a relative viscosity (1 of 2.4 and delustered with 1.6% of TiO and simultaneously with 7.5 parts of an ethoxylated polycaprolactam showing a ratio of polycaprolactam to ethylene oxide of 1:3.6 by weight. Heating is effected so that the temperature of the molten mixture rises from 220 C. at the feed end to from 266 to 268 C. at the output end of the extruder. At a speed of rpm. the throughput is 80 kg./hr. The residence time of the melt in the extruder is about 2 minutes. t

At the end of the screws there is provided a filter unit which is heated at 25 0 C. and is fitted with metal sieves of 17 mesh. The filtered molten mixture is extruded in four strands which are cooled in a water bath and then granulated. The granules are dried to a water content of less than 0.1% and then melt-spun to filaments 144 f 10 dtex. using an extruder provided with a sintered metal filter having an average pore width of about 18 The residence time of the molten mixture in the spinning system is about 15 minutes. The resulting filaments are then stretched at a draw ratio of 113.28 to form filaments 44 f 10 dtex. The drawing yield is 96% based on cops weighing 1 kg.

Table 1 below gives the results of tests in comparison with unmodified polycaprolactam filaments:

This table shows that there are no substantial differences between the two types of filament.

The ethoxylated polycaprolactam is present in the filaments as a separate phase in the form of very small rods having a diameter of not more than 0.1 4. Using the apparatus described by Heyl & Liittgens (10c. cit.) for measuring the electrostatic build-up, knitted material made from the filaments of the invention and which has been washed five times has a field strength of only 60 volts/ cm. when measured at 50% relative humidity after being rubbed for 4 minutes against a knitted fabric of unmodified polycaprolactam. Unmodified polycaprolactam in the form of knitted fabric which has been washed five times shows a field of strength of 2,400 volts/cm. when measured under similar conditions.

Knitted fabric made from the filaments of the invention shows very uniform affinity for acid dyes as well as disperse dyes and also shows a distinctly higher color yield than unmodified polycaprolactam material.

We claim: 1. A process for the manufacture of antistatic polyamide filaments which comprises: forming a molten mixture of (a) a. filament-forming synthetic linear aliphatic polyamide having recurring amide groups in the backbone and having a relative viscosity in the range of 1.5 to 2.9, measured as a 1% w./w. solution in 98% H 80 at 20 C.,

together with (b) from 2 to 15% by weight, based on the filaments or fibers, of an alkoxylated polyamide manufactured by reaction of a polyamide selected from the group consisting of the polycondensates of lactams of 4 to 12 carbon atoms and polycondensates of the salts of diamines and dicarboxylic acids of 4 to 12 carbon atoms with a 1,2-alkylene oxide in a weight ratio of from 1:2 to 1:5 and to provide a total molecular weight of 10,000 to 80,000,

components (a) and (b) being so thoroughly mixed that said alkoxylated polyamide is present in the finished filaments in the form of particles having a diameter of not more than 0.1 1.; and

filtering said molten mixture at least once through a filter having a pore width of not more than 20 and subsequently melt spinning said mixture into solid filaments, the molten mixture being maintained in this process at elevated temperatures of up to not more than 290 C. for a total period of not more than 30 minutes.

2. A process as claimed in Claim 1, wherein the filament-forming linear polyamide (a) is thoroughly mixed with from 4 to 10% by weight of alkoxylated polyamide (b). a

3. A process as claimed in Claim 1 wherein the mixture is converted into chip form or granulated intermediate the filtering step and the melt spinning step.

4. The filamentary product obtained by the process of Claim 1.

References Cited UNITED STATES PATENTS 3,099,067 7 1963 Merriam et al 264-210 F 3,329,557 7/1967 Mag-at et a1. 161--172 3,577,308 5/1971 Drunen et a1. 264-171 3,632,666 1/1972 Okazaki et al 260857 PE 3,639,502 2/1972 Okazaki et a1. 260857 PE 3,707,341 12/ 1972 Fontiju et a1 264176 F 3,725,503 4/1973 Kunde et al 260-857 PG JAY H. WOO, Primary Examiner US. Cl. X.R.

260-78 SC; 264-176 F

Claims (1)

1. A PROCESS FOR THE MANUFACTURE OF ANTISTATIC POL AMIDE FILAMENTS WHICH COMPRISES: FORMING A MOLTEN MIXTURE OF (A) A FILAMENT-FORMING SYNTHETIC LINEAR ALIPHATIC POLYAMIDE HAVING RECURRING AMIDE GROUPS IN THE BACKBONE AND HAVING A RELATIE VISOSITY IN THE RANGE OF 1.5 TO 2.9, MEASURED AS A 1% W./W TOGETHER WITH (B) FROM 2 TO 15% BY WEIGHT, BASED ON THE FILAMENTS OR FIBERS, OF AN ALKOXYLATED POLYAMIDE MANUFACTURED BY REACTION OF A OLYMIDE SELECTED FROM THE CONSISTING OF THE POLYCONDENSATES OF LACTAMS OF 4 TO 12 CARBON ATOMS AND POLYCONDENSATES OF THE SALTS OF DIAMINES CONDENSATES OF LACTAMS OF 4 TO 12 CARBON ATOMS AND DICARBOXYLIC ACIDS OF 4 TO 12 CARBONS ATOMS WITH A 1,2-ALKYLENE OXIDE IN A WEIGHT RATIO FO FROM 1:2 TO 1-5 AND TO PROVIDE A TOTAL MOLECULAR WEIGHT OF 10,000, COMPONENTS (A) AND (B) BEING SO THROUGHLY MIXED THAT SAID ALKOXYLATED POLYAMIDE IS PRESENT IN THE FINISHED FILAMENTS IN THE FORM OF PARTICLES HAVING A DIAMETER OF NOT MORE THAN 0.1; AND FINISHED FILAMENTS IN THE FORM OF PARTICLES HAVING A FILTER HAVING A PORE WIDTH OF NOT MORE THAN 20; AND SUBSEQUENTLY MELT SPINING SAID MIXTURE BEING MAINTAIND IN THIS MENTS, THE MOLTEN MIXTURE BEING MAINTAINED IN THIS PROCESS AT ELEVATE TEMPERATURES OF UP TO NOT MORE THAN 290*C. FOR A TOTAL PERIOD OF NOT MORE THAN 30 MINUT4S.