US3423266A - Process for the production of a nonwoven web of a continuous filament yarn - Google Patents

Description

Jan. 21, 1969 B. L. DAVIES ET AL 3,423,266

PROCESS FOR THE PRODUCTION OF A NON-WOVEN WEB OF A CONTINUOUS FILAMENT YARN Sheet Filed Dec. 30, 1964 lnvenfnr BARR/E L/NTON DAV/5.5

By Q Q field/Q7 Attorney Jan. 21, 1969 5 D s ETAL 3,423,256

PROCESS FOR THE PRODUCTION OF A NON-WOVEN WEB OF A CONTINUOUS FILAMENT YARN Filed Dec. 30, 1964 Sheet 2 of 5 2f 2/ J2 J3 Inventor BARR/E LIA/TON DAV/E5 AL U 56240 09 :Allorney L- DAVIES ET AL 3,423,266

B PROCESS FOR THE PRODUCTION OF A NON-WOVEN WEB OF A CONTINUOUS FILAMENT YARN Jan. 21, 1969 Filed Dc. so, 1964 Sheet 3' of 5 yg aghw Atlorney United States Patent Office 3,423,266 Patented Jan. 21, 1969 1,229/ 64 US. 'Cl. 156-167 12 Claims Int. Cl. D0411 3/16 ABSTRACT OF THE DISCLOSURE A process for the manufacture of a nonwoven web for-med from a continuous filament yarn in which freshly spun filaments of synthetic high molecular weight polymers are attenuated and intermingled by the action of a fluid jet, and deposited on a receiving surface in a random loopy configuration while in the non-crystalline condition.

This invention is concerned with non-woven materials and in particular with non-woven materials comprising continuous filament yarns.

Non-woven materials formed from continuous filamentary materials which filaments have been laid in a random, loopy configuration are well known in the art. In the formation of such materials, which are commonly called webs by which title they will be referred to hereinafter, great care is frequently taken to ensure that the filaments are maintained apart from each other and that interfilament entanglement and the formation of filament aggregates is avoided.

We have now surprisingly found that a useful coherent stable web may consist of a continuous filament twistless yarn, comprising a plurality of intermingled filaments exhibiting a pattern of parallelism between the said filaments, disposed throughout the web in a random loopy manner, the filaments constituting the yarn being at least partially oriented and substantially non-crystalline at the time of deposition.

Accordingly therefore, from one aspect, the present invention provides a non-woven coherent stable web con sisting of a continuous filament twistless yarn disposed throughout the web in a random loopy configuration, which yarn comprises a plurality of intermingled filaments, formed from at least one synthetic high molecular weight polymer, exhibiting a pattern of parallelism therebetween, the said filaments being at least partially oriented and substantially non-crystalline at the time of deposition.

By intermingled filaments is meant the axial displacement of individual filaments in the yarn relative to each other such that the paths of two or more filaments cross and recross at random intervals throughout the length of the yarn.

A pattern of parallelism is said to exist between the filaments in a yarn when the average paths of those filaments, throughout the length of the yarn, are substantially parallel.

The coherent stable webs of this invention may be conveniently manufactured by a process wherein freshly spun filaments comprising one or more polymer components are subjected to the action of a high velocity fluid jet which attenuates and orients the filaments and intermingles them to form a twistless yarn, which yarn is forwarded by the fluid jet and deposited on a receiving surface in a random loopy manner.

A useful advantage of the webs of this invention is related to the fact that the filaments comprising the yarn are in a substantially non-crystalline state at the time of deposition. As a result the yarn is deposited in a flat state on the receiving surface to form a compact, stable and lifeless web which is easily controllable, the position of the yarn in the web being practically unaffected by extraneous air currents.

According to another aspect thereof, the present invention provides a process for the production of a nonwoven web of a continuous filament yarn wherein freshly spun filaments of synthetic high molecular weight polymers are subjected to the action of a high velocity fluid jet acting at an angle to the filament path to provide sufficient tension in the filaments above the point of application of the said fluid jet to attenuate and at least partially molecularly orient the filaments and to cause the said filaments to intermingle and form a yarn structure exhibiting a pattern of parallelism between the filaments, the said yarn being forwarded by the fluid jet and deposited on a receiving surface in a random loopy configuration whilst the filaments are in a substantially non-crystalline condition to form a stable coherent web.

In prior art webs individual filaments are normally laid in the crystalline state and as such tend to form bulky unstable webs which are diflicult to control owing to the lively nature of the filaments.

After formation the web is preferably treated to cause the filaments to crystallise which crystallisation tends to set the yarn in the form in which it was laid so that the compact stable nature of the web is retained.

Crystallisation may be effected by any of the known techniques, the method being dependent upon the polymer from which the filaments were formed. Thus in the case of polyamide filaments such as for example, polyhexamethylene adipamide filaments, crystallisation will proceed merely by allowing the web to remain in a humid ambient atmosphere. Acceleration of crystallisation may be achieved by heating or more particularly by the application of a swelling agent such as water, preferably in the form of steam. In the case of the polyesters crystallisation may be induced 'by heating or by the application of a suitable swelling agent.

Whilst the aforementioned filaments are in the substantially amorphous condition referred to above they lack, although molecularly oriented, elastic recovery and hence retain the shape into which they are formed during deposition. On subsequent crystallisation this shape is permanently set into the filament and hence stable webs are produced.

Owing to this method of formation the webs of this invention are inclined to lack bulk being very compact in form. Particularly useful webs are thus those which contain filaments having a potential crimp which can be developed after formation of the web and during or after crystallisation. Such webs have a desirable soft warm handle and enhanced covering power. Particularly useful in this respect are filaments composed of two or more polymer components, one component having a higher shrinkage than the other component, the components existing in an eccentric relationship along the length of the filament, e.g. in eccentric sheath and core of side-by-side relationship. Filaments of this type are generally referred to as composite or heterofilaments. If both components are polyamides for example, then the web may be allowed to crystallise under ambient condition and the potential crimp subsequently developed by a suitable relaxing treatment, eJg. by subjecting the web to a heat or steam treatment;

Conveniently the hereterofilaments used in the production of webs of this invention may have one component which has a significantly lower melting point than the other component or components and hence be of particular value if it is required in subsequent operations to bond the filaments in the web together e.g. by heating. Alternatively or in addition the component may be the more chemically reactive and use may be made of this property in subsequent bonding operations. It is to be understood that if heterofilaments of the sheath and core type are employed, i.e. Where one component is completely enclosed by one or more other components, the lower melting or more chemically reactive component should be exposed and therefore form the sheath portion.

Particularly suitable polyamide components for forming into heterofilaments include polyhexamethylene adipamide and a copolymer of polyhexamethylene adiparnide and polyepsilon caprolactam (80/20 in parts by weight), polyhexamethylene adipamide and polyaminoundecanoic acid and polyhexamethylene adipamide and polyhexamethylene sebacamide. The heat treatment employed to develop crimp in these filaments can also be utilised to simultaneously bond them together to yield a web of increased strength.

It is not necessary that all of the filaments in the yarn forming the web be the same. Thus the yarn may contain filaments formed from two or more different polymers, the so called heteroyarn, which polymers have different physical and/or chemical properties, e.g. lower melting points or greater solubility in solvents. These differences in properties may be utilised in bonding or in producing novel effects in dyeing etc.

In the production of webs from polyamide yarns the yarns may contain filaments of polyhexamethylene adipamide together with filaments of polyepsilon caprolactam, polyaminoundecanoic acid, polyhexamethylene sebacamide or a copolymer of polyhexamethylene adipamide and polyepsilon caprolactam as the lower melting filaments. Bonding may be achieved by subjecting the web to a suitable heat treatment or by treating it with a solvent which preferentially softens one of the types of filaments.

In addition to or in the place of the potential crimp exhibited by the filaments referred to above, a spontaneous random irregular crimp may in some circumstance be imparted to the filaments e.g. as a result of asymmetric quenching of the filaments by the fluid jet.

The invention will be more fully understood by reference to the accompanying drawings.

In the drawings: R

FIGURE I is a schematic representation of an apparatus useful for forming the webs of this invention.

FIGURE 11 is a cross-section of an aspirating jet suitable for use with apparatus of FIGURE 1.

FIGURE III is a schematic representation of an im proved apparatus useful for forming the web of this invention.

FIGURE 1V is a schematic representation of a novel method for the formation of a web.

Referring to FIGURE I freshly formed filaments 1 are spun through spinneret 2 and are converged into a bundle at thethroat 3 of the aspirating jet 4. Within the aspirating jet the filaments are acted upon by high velocity air which is supplied through theinlet 5, torroidal vortices, having their axes substantially perpendicular to the main axes of the filaments, are thought to be formed within the jet and to create a turbulent zone around the filaments causing them to be whipped from side to side and to intermingle with each other. The intermingled yarn obtained is forwarded by the blast of air issuing from the jet to the receiving surface 6 where it is laid in random loopy manner to form the web 7.

In FIGURE II, the aspirating jet comprises a hollow body portion 10 which is externally threaded at either end and has an air inlet pipe 11 attached thereto. A cover 12 containing ayarn inlet guide 13 is screwed onto the top of the body portion 10. A second cover 14 containing a yarn exhaust guide I15 is screwed onto the bottom of the body portion 10. The bottom and top ends of the inlet and exhaust guides respectively are chamfered to provide an annularair injector passageway 16. The angle of chamber on the guides is referred to as the injector half angle and is denoted by a in the diagram. The annular air injector passageway is arranged to direct the air downwards, i.e. in the direction of filament flow.

In operation the aspirating jet may conveniently be placed at some point below the spinneret plate such that the semi-solid filaments are converged together at the throat of the aspirating jet through which they are passed. In the aspirating jet the filaments are contacted by a jet of high velocity fluid which quenches the filaments, causing them to crimp in an irregular random manner. The turbulence resulting from the fiuid vortices which are thought to be formed within the jet then cause the filaments to intermingle, and form a coherent yarn. As the yarn issues with it forwards the yarn at substantially greater speed than the extrusion speed, i.e. it exerts a drag effect on the yarn, thus causing the filaments in the yarn to be attenuated and oriented. The attenuation and orientation does notfhowever, take place within the jet but at some point between the spinneret and the throat of the jet, i.e. the semi-molten filaments are attenuated. The drag effect of the fluid on the yarn continues for some distance below the mouth of the jet, and it is therefore important that the receiving surface is placed below the point at which the drag becomes insignificant in order to achieve maximum attenuating efficiency.

In practice the receiving surface 6 will normally take the form of a conveyor belt which moves at a predetermined constant speed. In order to obtain a uniformly thick web across the width of the belt means may be provided for traversing or deflecting the aspirating jet or its output across the belt, or belt itself may be oscillated from side to side.

In FIGURE III there is shown, diagrammatically, a system for ensuring the uniform lay of the yarn on the receiving surface and means for collecting the web so formed. Freshly formed filaments 21 are spun through thespinneret 22 and passed through the aspirating jet 23 where they are acted upon by a high velocity fluid jet which attenuates, orients and intermingles the filaments to form theyarn 24. Theyarn 24 is forwarded to the receivingsurface 25 which comprises a continuous moving sheet ofpaper 25 taken fromroll 27 onto a carrier roller 28. In order that uniform distribution of the yarn is obtained across the width of the paper thefluid inlet pipe 29, which is constrained to move in horizontal place at right angles to the direction of movement of thepaper 26 byrods 30 and 31, is acted upon by a traversing cam 32 of suitable shape driven by theconstant speed motor 33. Thepaper 26 carrying theweb 34 is collected in the form of aroll 35 which is peripherally driven by therollers 36 and 37 which are themselves driven by means of chain 28 operated by motor 39.

An alternative method of forming the web in FIGURE IV. A rotatingexhaust 50 is attached to the lower end of the aspiratingjet 51 in such a manner that it is able to freely rotate about the aspirating jet axes, Theend portion 52 of the exhaust is bent through approximately 40 to direct the yarn 53 onto theannular receiving plate 54. Owing to rotation of theexhaust 50 the yarn is laid in a random loopy manner around the receiving plate to form a tubular web 55, which web is withdrawn at a constant speed and wound up on the drivenpackage 56.

Referring back to FIGURE II, it is thought that the angle of incidence of the fluid jet and the filaments i.e. the injector half angle a must be large enough to provide a plurality of fluid vortices having their axes substantially perpendicular to the mean filament axes, and small enough to ensure that the component of motion of the jet in the direction of movement of the filaments has a high enough velocity to provide suflicient drag on the filaments to forward them at a speed greater than the speed of extrusion and thus attenuate and orient the filaments.

The effect of the fluid vortices is to provide a turbulent zone around the filaments which cause them to be whipped about and for the paths of the filaments to be made to cross and recross each other at random intervals and thus provide an interlaced coherent yarn.

The velocity of the fluid jet required to attenuate and orient the filaments to the desired amount, which velocity is a function of the air consumption (i.e. air pressure) an aspirating jet design, will vary depending upon the type of polymer being spun and the process conditions including; the emergent viscosity of the polymer, e.g. in the case of a melt spun polymer this will be the melt viscosity at the time of extrusion, the spun denier, the filament/fluid contact distance which provides the drag on the filament and the angle of incidence of the fluid jet and the filaments.

In general the velocity of the fluid jet must be sufiiciently high to provide a resultant tension in the filaments, above the point of action of the jet on the filaments, to attenuate and orient them to the required extent. This tension is most conveniently expressed in terms of grns. per denier of the attenuated filaments.

The aforementioned resultant tension is the sum of the tension applied to the filaments by the fluid jet acting to attenuate the filaments, and the tension caused by the melt viscosity of the polymer, surface tension effects and air drag above the point of action of the fluid jet, which act to resist attenuation of the filaments.

It is not necessary that the yarn forming the web be composed of filaments which are more than partially oriented. For some end uses it is a definite advantage for the web to contain filaments capable of further attenuation and orientation. Thus if a needle punching operating is applied to a web composed of partially oriented filaments, the action of the needles on the filaments punched through the web causes these filaments to be further attenuated and oriented without them breaking.

In order that the invention may be more fully understood the following examples are given, which examples are illustrative only and are in no way intended to limit the scope of the invention.

EXAMPLE 1 Polyhexamethylene adipamide having a relative viscosity of 32.6 and a melt viscosity of 475 poises at 290 C. (the spinning temperature) was spun through a 34 hole spinneret and the filaments converged into a bundle at the throat of an aspirating jet, of the type described with reference to FIGURE II, located 2 feet below the spinneret. The dimensions of the aspirating jet were as follows:

Inlet bore: internal diameter Ma, length 2" Exhaust bore: internal diameter A1", length 6" Injector /2 angle (a): 10

Air at ambient temperature and a constant pressure of 100 p.s.i. was used as the fluid. The consumption of air, which was used as a measure of its velocity, was fixed at cu. ft./min. by adjusting the size of the air injector passage, i.e. the distance apart of the inlet and exhaust bores. A coherent yarn of intermingled oriented filaments was obtained and laid in the form of a web on a moving belt of paper in the manner described with reference to FIGURE III. As laid the yarn was in an amorphous state and formed a uniform compact and stable web. The filaments forming the web were allowed to crystallise under ambient conditions the web retaining its compact and stable form.

In contrast to the above, an intermingled yarn produced under identical conditions except that the crystallisation of the filaments in the yarn was accelerated so that they were substantially fully crystallised before deposition on the belt could only be laid as a web with extreme difliculty and the web so formed was a bulky non-uniform, unstable and uncontrollable owing to the liveliness of the crystalline yarn.

6 EXAMPLE 2 Polyhexamethylene adipamide having a melt viscosity of 980 poises at 290 C. and a copolymer of polyhexamethylene adipamide and polyepsilon caprolactam parts to 20 parts by Weight) having a melt viscosity of 1050 poises at 290 C. were spun through a 34 hole spinneret into side-by-side heterofilaments, each filament consisting of substantially equal proportions of each component. The filaments were converged into a bundle at the throat of an aspirating jet, of the type described with reference to FIGURE II, located 2'6" below the spinneret. The aspirating jet had the dimensions quoted in Example 1. Air at ambient temperature was used as the fluid at a pressure of about 76 p.s.i. and a consumption of 6 cu. ft./min. and the web was laid from the oriented filaments in the manner described in Example 1.

A compact stable web was formed which was treated with high pressure steam to crystallise and develop the crimp in the heterofilament and bond the filaments together through the copolymer component. The resultant product was a compact and felt-like having a soft war-m handle and considerably more strength than the unbonded web.

EXAMPLE 3 Polyhexamethylene adipamide having a melt viscosity of 600 poises at 290 C. and polyaminoundecanoic acid having a melt viscosity of 463 poises were spun through a 34 hole spinneret into side-by-side heterofilaments, each filament consisting of substantially equal proportions of each component, and formed into a web in the manner described in Example 2. A compact stable web was obtained which was passed between heated rolls to bond and crystallise the filaments in the web. The final product was a dense felt-like structure.

EXAMPLE 4 The process of Example 3 was repeated using polyhexamethylene sebacamide as one component of the hetero and polyhexamethylene adipamide as the other component. The filaments in the product were allowed to crystallise at ambient temperature to yield a compact stable Web which could be handled without disruption.

Webs prepared by this process are suitable for a variety of end uses particularly in the manufacture of non-woven fabrics.

What we claim is:

1. A process for the production of a non-woven web of a continuous filamentyarn wherein freshly spun filaments of synthetic high molecular weight polymers are subjected to the action of a high velocity fluid jet acting at an angle to the filament path to provide sufficient tension in the filaments above the point of application of the said fluid jet to attenuate and at least partially molecularly orient the filaments and to cause the said filaments to intermingle and form a yarn structure exhibiting a pattern of parallelism between the filaments, the said yarn being forwarded by the fluid jet and deposited on a receiving surface in a random loopy configuration whilst the filaments are in a substantially non-crystalline condition.

2. A process according to claim 1 wherein at least one synthetic high molecular weight polymer is a polyamide and the polyamide filaments in the web subsequently crystallise in the form in which they were deposited.

3. A process according to claim 2 wherein the polyamide is polyhexamethylene adipamide.

4. A process according to claim 2 wherein the web is subjected to a steam treatment to crystalliset-he polyamide filaments.

5. A process according to claim 1 wherein a minor proportion of the filaments formed are potentially adhesive comprising activating said filaments after formation of the web to bond the filaments in the web together.

6. A process according toclaim 5 wherein the potentially adhesive filaments are formed from polymer from the group consisting of polya-minoundecanoic acid, polyepsilon caprolactam, polyhexamethylene sebacamide or an 80/20 copolymer of polyhexamethylene adipamide and polyepsilon caprolactam.

7. A process according to claim 2 wherein at least some of the filaments are extruded as hete rofilaments consisting of at least two different polymer components.

8. A process according to claim 7 wherein the heterofilaments are potentially crimpable.

9. A process according to claim 7 wherein the heterofilaments contain an exposed potentially adhesive component.

10. A process according to claim 7 wherein the potentially adhesive component is a polymer from the group consisting of polyaminoundecanoic acid, polyhexamethylene sebaca-mide polyepsiloncaprolactam or an 80/ 20 copolymer of polyhexamethylene adipamide and polyepsilon caprolactam.

11. A process according to claim 8 wherein the web is References Cited UNITED STATES PATENTS 3,017,686 l/1962 Breen et a1. 161-177 X 3,186,155 6/1965 Breen et a1. 161173 X 3,304,220 2/1967 McIntyre 16117O ROBERT F. BURNETT, Primary Examiner.

R. L. MAY, Assistant Examiner.

US. Cl. X.R.

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