US3436798A - Treatment of continuous multifilament threads and relative threads having a controllably labile cohesion - Google Patents

Description

D. NICITA April 8, 1969 3,436,798 TREATMENT OF CONTINUOUS MUL-TIFILAMENT THREADS AND RELATIVE THREADS HAVING A CONTROLLABLY LABILE COHESION Filed Oct. 10. 1966 FIG. 2

FIG.

INVENTOR DOHENICO NICITA US. Cl. 281 3 Claims ABSTRACT OF THE DESCLOSURE Multifilament synthetic yarns are produced in which the filaments adhere to one another initially sufficiently to effect successful textile operations thereon, as, for instance, warp-setting, but will lose their coherence in subsequent mechanical treatments, such as weaving. These results are achieved by feeding the filaments alonga path defined by two aligned spaced thread guides while directing an air stream against the filaments to deflect them against a convex surface, the feed rate, spacing of the guides, position and curvature of the convex surface, etc. being determined to achieve the desired results. The filaments of yarns produced according to the present invention have a labile cohesion which disappears or decreases in substantial degree after a mechanical strain such as that due to a weaving operation.

This invention relates to an improvement in man-made and synthetic threads formed by a plurality of continuous monofilaments, and, more particularly, this invention relates to an improvement in the treatment of threads, intended to achieve a substantial cohesion among the individual components so as to improve the textile workability thereof. This invention also includes the articles of manufacture which can be obtained with the improved process and, more particularly, continuous multifilamentary yarns, both man-made and synthetic, having substantial cohesion features, as will be set forth in more detail hereinafter.

It is known that the individual monofilarnents of multifilamentary yarns must be bound together, at least to certain minimal requirements, in order that the involved textile processes, more particularly warp setting and picking, be practical. It is also well known that twisting provides the desired binding action between monofilaments. However, with more updated and favorable methods having in view economy of production, twisting has partly, or entirely been replaced by other processing steps or treatments conducive to the so-called cohesion of the yarn which latter is dubbed, in this case, a cohered yarn.

The degree of cohesion is generally determined by the artificial formation of so-called false knots or pseudoknots which can be ascertained by causing a needle or a hook to be slid along the cohered yarn, or between the monofilaments which compose it, and noting the average number of times that the needle is arrested in its sliding motion within a unitary span, for example one meter. Actually, said stops or hindrances to the hook motion are atent O due to the fact that the filaments, which are more or less ravelled, due to the effect of the treatment, give rise to knotted spots.

It has been ascertained, on the other hand, that the kind of cohesion of the yarns considered, in spite of the advantages afforded thereby from an economical standpoint over the conventional twisting procedures, may lead to trouble in the fabrics produced from said yarns. As a matter of fact, said knotted spots give rise to lumps or irregular spots in the fabric which are detrimental to structural evenness and to the capability of the fabric to be regularly and evenly dyed.

-It has also been noted that, in a finished fabric, the cohesion has no bearing in and as itself; conversely, for the reasons aforementioned, such a condition can be re garded as undesirable.

It should also be borne in mind that the degree of cohesion (which is expressed, as a general rule, by the number of pseudo-knots formed within a span of one meter of yarn) which is necessary for the textile operations, is different according to the individual textile operations and, more particularly, while for picking or shuttle weaving non-cohered or slightly cohered yarns can be used, the degree of cohesion should be higher for obtaining a good warp setting.

Therefore, by considering the textile procedure in its entirety, conflicting requirements should be theoretically fulfilled, namely:

For a successful textile o it is desirable to have highl having a considerable num as measured in the above For evenness of fabric a the other hand, it is desir play any irregularity in th of their individual 'monofi ditions, it is desirable th hered yarns.

It should be noted, finally, that the requirements demanded by the operation of formation of the warp are sharply different from those of the Weft, in that the yarn,

coming from a single take-up, covers, in the weft, the whole width of the fabric thus limited length in the piece, whil a considerable length but in a single thread. Possibly, tween yarns coming clined to different dy respectively.

It could thus be surmised that the most favorable c0nditions would be obtained by resorting to a multifilamentary yarn which is cohered to the extent which is amply sufficient to facilitate or assure the correct performance of the picking and, more particularly warp setting operations, but which is non-cohered, in practice, in the finished fabrics.

According to the present invention, it has been surprisingly ascertained that it is possible, with a yarn treatment similar to the one described in the joint application of the present invention and Piero Giacobone Ser. No. 257,274, now Patent No. 3,238,590, by abiding by certain quantitative specifications as to the variables of the process, to obtain yarns possessing to a considerable extent the above described properties and permitting the above recited practical effects and commercial achieveperation, such as warp setting, y cohered yarns, that is, yarns ber of pseudo knots per meter, outlined manner;

nd the tinctorial operations, on able that the yarns do not dise essential parallel arrangement laments, that is, in limiting conat the fabrics comprise non-c0- e in warp it extends along n area corresponding to a even the slightest, difference, befrom different take-ups, are thus ineing effects in the weft and the Warp,

ments. Such results could not have been forecast in the light of current technical knowledge; and contrarywise according to current ideas, to obtain such results would have required simultaneous compliance to conflicting requirements, something deemed impossible of attainment.

Stated alternatively, it is an object of the present invention to provide an improvement in the treatment of man-made or synthetic multifilamentary yarns, of the kind suitable to the uses described, which will provide a new article of manufacture which can be defined as a labile-cohesion yarn, in the sense that said yarn possesses the degree of cohesion which is necessary for assuring a satisfactory outcome of the textile processing, while said cohesion, or, better to speak, the conditions of knotting or interlinking between the individual monofilaments disappear or anyhow cannot practically be detected in the components of the weave of the fabrics produced therefrom.

The inventive improvement thus has for its object the end production of a composite yarn endowed with the above listed properties.

More particularly, it has been ascertained that devices, constructed and operated according to the above mentioned patent application, upon suitable adaption and observation of certain critical conditions and parameters, produce a cohering effect which can be properly defined as a labile or temporary cohesion, and that said cohesion is established and maintained in the degree and to the extent which are necessary to ensure the performance of the textile steps and which, partly at least, is subsequently destroyed or attenuated due to the effect of the particular mechanical actions and stresses to which the cohered yarns are subjected during progress of weaving.

According to this invention, therefore, yarns can be profitably and advantageously used in textile operations, whose degree of cohesion can be expressed, for example, by the number of pseudo-knots per lineal meter (or other length unit), with two numerical values, both corresponding to the number of pseudo-knots per unit length, but determined on at least two yarns which have undergone very much the same cohering operations, but either of which has also undergone a certain mechanical stress in correlation to the stresses or to the actions and treatments normally undergone by such yarns when they are subsequently employed in the production of fabrics.

In a preferred and more complete embodiment of this invention, standard conditions of mechanical treatment, or of non-mechanical treatment, can be set, correlated to the effect induced by the weaving operations and, typically, to those operations which are conducive to the formation of the warp and of the weft, respectively. These standard conditions may correspond, for example, to one or more passes of labile-cohesion yarns through thread-guides or other surfaces having a preselected shape, at a predetermined speed, under a predetermined tension, while compelling the yarn to travel a predetermined path including a given number of deviations of preselected angular amplitude.

It is thus possible to plot, for each labile-cohesion yarn, a characteristic curve of reduction or attenuation of the degree of cohesion, until cohesion disappears, said curve showing the several values of said degree (expressed as the number of pseudo-knots) as a function of the intensity of the subsequent mechanical handling, for example of the number of passes of said yarn through said path, under the standard conditions aforesaid.

In the practice of this invention, it is thus possible to produce labile-cohesion yarns under such conditions as to exhibit two predetermined service conditions which can be reproduced with a satisfactory uniformity, viz.:

(1) The degree of initial cohesion, which will be selected, in each individual case, to the most suitable value to ensure satisfactory outcome of the textile operations degree will be obviously different for different uses and, typically, according to whether the yarn is to be used as a warp thread or a weft thread;

(2) The degree of lability, that is, the ability to lose said cohesion due to the effect of subsequent mechanical treatments, corresponding to determined standard rules. This degree of lability, in turn, can vary because of the different initial cohesions necessary to achieve the maximum degree of residual cohesion which can be tolerated or is desirable in the yarn forming the fabric; said degree can also be desirably nil.

It should be borne in mind that said two values are to be regarded as entirely independent variables. As a matter of fact, while the former (initial cohesion) must correspond to the minimum which is necessary for a satisfactory outcome of the textile operations, and which depends upon the characteristics of the yarn, the textile machinery, the kind of weave and other factors, the latter should be determined as a function of the intensity and the kind of the mechanical action the yarn is to undergo during weaving. It is possible therefore that in a production run intended for different and specific commercial applications, the ratios between said two values are sharply different from one another.

For example, the case can be contemplated in which a strong initial cohesion is required, accompanied, however, by a high degree of lability (that is to say, said strong initial cohesion can be annulled or greatly reduced under a limited mechanical stress) or, conversely, the yarn may have a relatively limited initial cohesion, but should retain this cohesion or, at least, resist a comparatively intensive mechanical treatment.

Thus, yarns produced according to the invention exhibit a predetermined degree of initial cohesion along with a predetermined lability rating of said cohesion, expressed in terms of a mechanical standard treatment or of a sequence of such treatments. The invention comprises means and conditions for determination of both said characteristics, within limits and tolerances which are acceptable for commercial use of the yarns.

The features of the invention can be better understood by reference to the accompanying drawing, wherein:

FIG. 1 is a perspective view, in diagrammatic form, showing means for practicing the invention and how it is practiced, and

FIG. 2 illustrates, in diagrammatic and highly exaggerated form, a yarn staple having a labile cohesion imparted by using said means.

As shown in FIG. 1, the inventive apparatus includes means for guidedly feeding a non-cohered yarn A comprising a plurality of substantially parallel continuous monofilaments, said yarn being non-twisted or only slightly twisted. Said feeding means can comprise thread guides 10 and 11, separated by a preselected gap I and defining, with their connecting line, a predetermined rectilinear path or trajectory P. Intermediate between said thread guides, a nozzle 12 is located, which is adapted to throw a jet of a gas, at a determined speed V, intersecting said path P as well as the back of a member, for example an essentially rod-like member 1 arranged at right angles with respect to said path P, opposite to the nozzle 12. The member 14 has a convex surface 13 spaced a certain distance F from the rectilinear path P. This distance determines the curvature the yarn A can undergo under the action of the jet emitted by the nozzle 12. The nozzle, in turn, is spaced a predetermined distance D from said rectilinear path P, said path being obviously, a merely theoretical path. On considering the spatial arrangement of the above enumerated members, it can be seen that the yarn A is caused to be advanced between the thread guides 10 and 11 along an axis XX intersecting the axis YY of the gas jet, said two axes defining a plane. The convex surface 13 defines, in turn, With its top generating line, an axis ZZ which intersects at right angles the axis YY of the gas jet, the two axes YY and ZZ defining a second plane at right angles (or substantially so) to the plane defined by the axes XX and YY.

For practical purposes, the convex surface 13 can be assumed as coinciding with a line lying on a plane at right angles with the plane on which the yarn is caused to advance. Actually, said surface can be assimilated to an elongate area which is extremely narrow. The effective width of said restricted area, for all practical purposes, is a function of the radius of curvature of the convex surface 13. Thus, the yarn A is braked, in its displacement from the theoretically rectilinear path P under the urge of the gas jet, by bi-dimensional members which lie in said plane YY-ZZ. Furthermore, the jet emitted by the nozzle 12 can be regarded in turn, as being braked exclusively by two members which are essentially bi-dimensional also, that is by the yarn A lying in the plane XX-YY and by the convex surface 13, lying in the plane YY-ZZ, said essentially bi-dimensional members intersecting one another on the axis YY of said jet.

The threads which are at a discrete distance from said point of intersection, can be considered practically as being undisturbed since the disturbing effects due to the physical presence of the rod-like member 14, which has necessarily a certain transverse size, have no influence on the device since the disturbing action takes place downstream of the environment in which said jet acts upon the yarn A and on the back portion of the convex surface 13. Thus the geometrical configuration of the cross-section of the member 14 is immaterial providing that said member has a convex surface confronting the jet and intended to come into contact with the yarn.

Said device has substantial differences over the known means, used or suggested and disclosed in the pertinent technical and patent literature, in that said means, when using gaseous streams or jets which intersect or are intended to impinge on a multifilamentary yarn and are operated against surfaces shaped in any way, require, always and in any case, that these surfaces extend in both directions in a plane perpendicular to the axis of the jet. Moreover, the conventional means provide in any case that at least a part of the components of the yarn be struck by fluid streams having different velocities and/or at least two different directions generally opposed to one another or, at least, strongly contrasting.

In the device described above, on the other hand, the filaments of the yarn A are struck by gaseous streams which are parallel or virtually parallel to the axis of the jet, and said streams are deflected exclusively in the plane XXYY which contains said yarn. Furthermore, said deflection takes place in practice downstream of the yarn, that is upon completion of the action of the jet on said filaments. It can thus be assumed that the predominant deflecting action exerted by the jet on the filaments takes place in the plane YY-ZZ and in the direction defined by the axis YY.

Actually, since the convex surface 13 cannot practically have a nil width, phenomena of invention of the fluid streams belonging to the gas jet can occur, and occur in reality, that is there is a turbulence phenomena due to the hindrance offered to said jet by the convex surface 13. On the other hand, said phenomena take place only on the fringe portions of the gaseous jet impinging on the convex surface, that is, in areas which are definitely displaced at the sides of the yarn; and the filaments in these areas, therefore, are struck exclusively by gaseous particles travelling over paths which are substantially parallel to axis YY. For a more complete analysis of the resulting phenomena, it must be remembered that the components of the yarn are of extremely tiny size, a size which is in the order of very, very few microns, since, in general yarns ranging from 15 to 2,100 deniers are involved, and from 1.5 to deniers per monofilament, and comprising a high number of monofilaments, in general from 3 to 68 monofilaments.

As a matter of fact, the air or other gases emitted from nozzle 12 are under relatively low pressure, generally ranging from 1.5 and 2.5 kgs./ sq. cm. Hence, the velocity of the gaseous particles is relatively low. Considering the specific gravity of air at room temperature and the very tiny transverse dimensions of the filaments, the result is that the conditions of resistance to the jet are of a mainly viscous character, for the monofilaments, on account of the very low Reynolds number, do not in themselves offer much resistance. These conditions, conversely, are modified, however, if, by chance, a few filaments are closely adjacent one another to form together a physical obstruction having a transverse size such as to cause the occurrence of a local turbulent flow with consequent reduction of the entraining efficacy of the gaseous jet.

This offers an explanation as to the surprising effects which can be obtained with the above described device. With a merely random form, but which is uniformly reproduced from a statistical standpoint, the individual filaments, more or less clustered in the yarn A, are differently displaced in the plane YY-ZZ, and a part of those filaments comes into sliding contact with the convex surface 13. The phenomena of mutual aerodynamic masking which take place among the several components of the yarn, generate, in turn, a transverse oscillatory state in the plane YYZZ and the result is a mutual superimposition of the kind depicted in FIG. 2, without however producing substantial entanglements and without the individual filaments undergoing any substantial deviation from the direction defined by the axis of the yarn.

To this phenomenon, perhaps, the new and surprising result of labile cohesion can be ascribed, which is characteristic of the products obtained according to the invention. Said cohesion is obtained, to the desired extent, as a function of the number and the magnitude of the superimpositions and straddlings, but said superimpositions and straddlings, in turn, are suited to be unravelled and annulled under mechanical action, particularly a sliding action, which tends to restore the filaments to their substantially parallel initial posture.

As is obvious, in order that the desired degree of initial cohesion and of cohesion lability may be obtained, many variables have to be considered, namely:

(1) The gap I between the thread-guides 1t} and 11 which defines the free path of the yarn under the section of the jet and against the convex surface 13. (The gap preferably ranges from 20 to 60 mms.).

(2) The distance D between the nozzle and the theoretical rectilinear path P (this is preferably very small).

(3) The velocity V of the jet, a function of the working pressure, plus the size and the shape of the nozzle 12.

These three variables, moreover, determine the effective cross-section of the jet at a point where the jet intersects the yarn and the convex surface 13.

(4) The distance F between the theoretical rectilinear path P and the convex surface 13, that is the sag undergone by the yarn under the action of the jet, a distance which preferably ranges from 1 to 5 mms.

(5) The radius of curvature, ranging from 0.5 to 10 mms., and the geometrical configuration of the cross-sec tion of the convex surface 13, in its area which influences the jet and the movement of the filaments, under the action of the jet, preferably between and 600 meters/ minute.

(6) The feeding speed of the yarn A.

(7) The overall tension to which the yarn is subjected during its advance, a tension which can be expressed in terms of counter-tension or resistance encountered by the yarn as it enters the apparatus, and which is preferably not less than 10 grammes.

As a standard for defining the treatments which are conductive to the annulment of cohesion or to a substantial reduction thereof, that is, in order to express the degree of lability of the yarn cohesion, which is characteristic of this invention, it si advantageous to utilize a typical weaving treatment, so as to obtain values susceptible of being immediately utilized for industrial useof the novel yarns of this invention.

Thus, standard conditions are assumed to be those which are effective for a textile utilization of said yarns on a straight loom, with the formation of a satin-type fabric with a number of picks which is proportional to the denier count of the yarn, and is generally in the order of 50-60 picks per cm.

The measures giving the number of pseudo-knots have been made on threads taken from the warp and from fabrics produced under said standard conditions. The numerical values indicated in the following examples have been obtained from tests repeated to an extent sutficient to ascertain that said values actually are a statistical mean calculated with a narrow tolerance.

The new and surprising effects of the invention will become fully apparent from the non-limiting examples set forth hereinafter, from which the possibility can be seen of producing, according to the invention, labile cohesion yarns which are particularly suited for being used both as Warp and weft threads, so as to obtain a fabric having uniform textile and tinctorial properties and in which the textile components have no substantial cohesion, and none of the unevenness, notoriously attendant thereon, either.

The measurements of the initial cohesion degree and of the cohesion after a standard treatment, were made under conventional conditions and precisely by causing a thin hook inserted between the filaments and loaded by a weight proportional to the denier count of the individual filaments, preferably 1 grm./denier, to slide in vertically suspended yarn. The degree of cohesion is calculated by taking into account the average distances travelled by said hook before it is stopped due to the formation of a ravelling or to a superimposition of filaments which cannot be unravelled with the aid of the weight of the hook.

Example I A nylon-6 yarn comprising 18 filaments and having an overall denier count of 60 deniers (thus formed by individual 3.3-denier filaments), practically untwisted, has been treated under the following conditions:

(1) Feeding the yarn at a speed of 450 meters/minute under a tension of about 15 grams (thus, of 0.25 gram/ denier) between two thread guides 10 and 11 arranged at a distance of 37 mms. over a member 14 having a convex surface 13 of a 2 mm. curvature radius, spaced 3 mms. from the alignment as defined by said two thread guides. The member 14 was formed of sintered ceramic material (rose Diamantex) and placed perpendicularly to said alignment, midway between said thread guides.

(2) By a circular nozzle having a diameter of 1 mm. and disposed at a distance of 1 mm. from said alignment, the axis of said nozzle intersecting said alignment and the center of the convex surface.

(3) An air jet under a pressure of 1.9 atmospheres and at a rate of flow of 1.3 cu. meters an hour was projected against said yarn.

Immediately after the treatment, the cohesion of the yarn was measured and the degree of initial cohesion was 15 pseudo-knots per lineal meter.

The cohered thread was used for the formation of a satin type fabric for linings, under said standard conditions.

A sample of the cloth piece was undone after having been scoured. The warp threads exhibited no pseudo-knots and the weft threads exhibited an average value of 0.24 pseudo-knots. Another sample of the same piece of fabric, after scouring and dyeing, was undone. The warp threads had no pseudo-knots, the weft threads had 1.6 pseudoknots per lineal meter.

Example II A nylon-66 thread formed by 28 filaments and having an overall denier count of (thus formed of individual filaments of about 3.5 deniers each) and practically untwisted, has been treated under the following conditions:

(1) Feed at a speed of 400 meters/minute under a tension of about 16 grammes (therefore, 0.16 gr./den.) between two thread guides 10 and 11 arranged at a distance of 38 mms., over a member 14 having a convex surface 13 with a radius of curvature of 2.5 mms. and spaced 3 mms. from the line P defined by said thread guides. The member 14 was formed of a ceramic material and placed midway between said thread guides.

(2) A nozzle having a circular cross-section of 1 mm. diameter, with its axis intersecting the line P and the center of the convex surface 13 at a distance of 1 mm. therefrom, a jet of air being projected against said yarn under a pressure of 2 atmospheres and with a rate of flow of 1.36 cu. meters an hour.

Immediately upon completion of the treatment, the cohesion of said thread was measured and the degree of initial cohesion was found to be 18 pseudo-knots per linear meter. The cohered thread was used for the formation of a satin-type fabric under standard conditions. A sample of the fabric was subjected to scouring and dyeing treatment, whereafter it was undone. The warp threads had 0.1 pseudo-knot and the weft threads had 3 pseudoknots per linear meter.

What is claimed is:

1. A process for producing a multifilament synthetic yarn having the filaments adhered to one another in such labile fashion that when subsequently subjected to a weaving operation, the cohesion of the individual filaments to one another will be materially reduced or eliminated entirely, which comprises advancing a yarn, having at least three filaments, each having a denier count between 1.5 and 20 deniers, along a path defined by aligned spaced guiding means and in front of a convex surface whose generatrix extends at a right angle to the direction of said path,

subjecting the yarn while it is traveling along said path to the action of a gaseous jet which is disposed at the opposite side of said path from said convex surface and whose axis intersects said path at substantially a right angle at a point intermediate said guide means, and whose axis also intersects said generating line at substantially a right angle,

the radius of curvature of said surface being between 0.5 and 10 mms.,

said guiding means being spaced between 20 and 60 mms. from one another along said path,

the distance of said path from said convex surface being between 1 and 5 mms., said gaseous jet being emitted from a nozzle under a pressure between 1.5 and 2.5 kgs./sq. cm., and said yarn being advanced along said path at a speed between 100 and 600 meters/minute under an overall tension ranging from 10 to 20 grams.

2. The yarn produced according to the method of claim 1.

3. Apparatus for producing a multifilament synthetic yarn having the filaments adhered to one another in such labile fashion that, when subjected to a subsequent weaving operation, the cohesion of the individual filaments will be materially reduced or eliminated entirely, comprising two spaced longitudinally-aligned guide members between which the filaments travel,

a stationary member having a convex surface supported in spaced relation to and at one side of the path of travel of the filaments from one guide member to the other,

a nozzle disposed at the opposite side of said path and connected to a source of pressurized gaseous medium to blow said gaseous medium against the filaments and toward said convex surface as the filaments travel from one guide member to the other,

9 18 said nozzle means having a bore the axis of which speed between 100 and 600 meters/minute under an intersects essentially at right angles both said path overall tension ranging from 10 to 30 grams. and said convex surface, whereby said gaseous medium is blown at right angles to said path and to References Cited sald Surface, 5 UNITED STATES PATENTS said surface being disposed at a distance between 1 and 5 rnms. from said path, and the radius of curvature of said surface being between 0.5 and 10 Tums, said guide members being spaced from one another a distance between 20 and 60 rnms., said gaseous 10 JOHN PETRAKES Pmnmy Examme" medium being pressurized to be emitted from said Us CL nozzle under a pressure between 1.5 and 2.5 kgs./ sq. 4 157 cm., and said yarn being fed along said path at a 3,238,590 3/1966 Nicita et al 281 3,262,179 7/1966 Sparling 28-1

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