EP0009924A1

EP0009924A1 - Thermoplastic twines and method and apparatus for their manufacture

Info

Publication number: EP0009924A1
Application number: EP79301995A
Authority: EP
Inventors: William Dewhurst; John Bernard O'neil
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1978-09-28
Filing date: 1979-09-25
Publication date: 1980-04-16
Also published as: ES246564U; ES485639A1; ES484513A1; ES246564Y

Abstract

A twine comprised of a core bundle of synthetic monofilaments (4) twisted along the length of the twine and a synthetic binder material (18) in thin band form spirally wound about the monofilaments in a direction opposite to the core bundle twist.

A method of producing such twine comprises, passing a bundle of thermoplastic monofilaments (4) continuously along a path, imparting a false twist of 3 to 30 turns per linear foot to said bundle, applying a compatible molten thermop- lasticspiral band (18) to said twisted bundle as a spiral band to fuse said spiral band to the outer monofilaments (16), and recovering a twine having a portion of said false twist captured therein by fusion of the spiral band thereon.

The apparatus for obtaining this twine consists of a path along which a bundle (4) of thermoplastic synthetic monofilaments having a false twist therein can be continuously moved, means (5) to direct a molten compatible thermoplastic onto said twisted bundle to form one or more spiral bands (18) on said bundle and to fuse the outer monofilaments (16) of the bundle to the spiral band (18) and means (8) for imparting a false twist to said bundle at a point prior to said directing means.

Description

This invention relates to synthetic monofilament twines. More particularly, this invention relates to synthetic monofilament twines produced from a bundle of oriented thermoplastic monofilaments which are twisted along the length of the twine and which are bound by a thermoplastic material which extends around the bundle in spiral form.
Another aspect of the present invention relates to a method and apparatus for producing the twine described above from thermoplastic materials.
U.S. Patent No. 2,552,210 to W. B. Parker discloses a ply yarn comprising a bundle of natural fibers entwined together with a fine filament nylon yarn. The ply yarn has a twist imoarted to it.
U.S: Patent No. 3,315,454 to Enerza discloses a synthetic twine suitable for forming knots in baling, tying and other automatic knot tying machines. The twine comprises a plurality of filaments of a thermoplastic resin and containing dispersed therein a gas so as to produce foamed filaments.
U.S. Patent No. 3,446,002 to Kip^pan discloses a twine comprised of a bundle of substantially parallel synthetic monofilaments with a synthetic binder material in thin band form wrapped around and fused to the outer monofilaments.
U.S. Patent No. 3,577,873 discloses a core yarn comprising a core component of set false twisted synthetic continuous multifilaments and at least one wrapping component of synthetic continuous filaments formed in helices around the core components, the direction of the helices being reversed at intervals along the yarn.
U.S. Patent No. 3,769,787 to Rosenstein et al discloses a multiple filament yarn of synthetic textile useful for knitting, winding and weaving which multi-filament textile yarn has continuously disposed thereabout two special wrapper filaments wrapoed in a generally helical path about the core filaments of the yarn, one wrapper being disposed in a clockwise manner and the other wrapper being disposed in a counterclockwise manner.
U.S. Patent No. 3,851,457 to Waters discloses a ore yarn comorised of a set false twisted core and a wrapoer of filaments formed in reversing helices.
U.S. Patent No. 3,415,919 to KioDan discloses a method of oroducing a twine by extruding a thermoplastic material in a spiral onto an untwisted bundle of oriented thermoplastic monofilaments. According to Kippan prior art fiber twine of necessity is twisted in order to transmit stress fro one fiber to another and develop the continuity of tensile strength of the cord. The patentee notes that monofilament twine prior to his development was twisted so that the monofilaments contained themselves by intertwined helixes to form a unit twine or cord.
Kippan notes several disadvantages of twisted twine The primary disadvantage is a weaker twine, since the helixes are able to assume only a portion of an applied tensile load, whereas in a oarallel alignment of monofilaments each filament is able to fully bear an applied tensile load. In theor at least, the tensile strength of a twine having all of the monofilaments aligned is the sum of the tensile strengths of each filament (in practice tensile strength is slightly less)
Another disadvantage of the twisted cord according to Kiooan is that it tends to untwist when it is slack, forming snarls which can cause problems in mechanical hay balers.
The following patents are also part of the publishe prior art.
U.S. Patent 2,953,418 shows the use of a composite yarn of Teflon and Dacron or nylon in the preparation of a molded resin bearing.
U.S. Patent 2,281,647 deals with a method whereby staple fibers are firmly anchored in the body of yarn containing said fiber utilizing a technique whereby one or more relatively fine threads which carry a solvent or softening agent are embedded in the structure of the spun yarn.
U.S. Patent 4,095,403 discloses a method in which two yarns, one of which is a cord yarn and one an effect yarn, are fed to a junction point and then fed together through a heat treatment zone and assembled into a fancy yarn in a false twisting step, the cord yarn being provided with a thermoplastic binder upstream of the junction point, the heat treatment in the zone being sufficient to develop the hot melt adhesive properties of the thermoplastic binder.
U.S. Patent 3,315,455 discloses a synthetic rope having improved structure comprising a core of unfoamed synthetic filaments and an enclosing layer of foamed polymer filaments.
U.S. Patent 3,332,228 discloses polypropylene baling twine which is certainly pertinent in its broad terminology to the present claimed invention. However, the twine is made from strips or ribbons of unidirectionally oriented isotactic polypropylene film, which are fibrillated by the act of twisting the strip or strips which set the film as a twine. This patent discloses the possibility of using a foam poly^pro- pylene in preparing the twine.
U.S. Patent 3,593,509 relates to an apparatus and method for stranding a twisted unit of cable.
U.S. Patents 2,463,619 and 3,609,953 are also mentioned.
It has been found that twine or cord such as described by Kippan having parallel monofilaments bound by an extruded binder, also is disadvantageous in mechanical balers. The straight monofilaments can be deformed in the knotting operations such that individual fibers break out between the spiral binding. The structure becomes less homogeneous in the knotting step and a protruding monofilament may catch in the mechanism.
It is an object of the present invention to provide synthetic monofilament twines which have suoerior knotting characteristics as comoared with the synthetic twines heretofore known.
It is a further object of the invention to provide twines having consistent characteristics throughout the length thereof, and which are rot resistant and resistant to ultraviolet radiation. It is a further object of the invention to provide a synthetic twine having monofilaments twisted with resoeon to each other along the length of the twine, and a means ror retaining the monofilaments in their twisted relationship to each other without interfering with the flexibility of the twine.
Accordingly, in accordance with the invention there is provided a twine comprising a core bundle of continuous synthetic oriented monofilaments extending lengthwise and twisted so as to contain from 3 to about 30 turns per linear foot of monofilament twine and a synthetic binder in thin band form made from a material compatible with the monofilament material and spirally wound in a direction reverse to the core bundle twist so as to contain from about 8 to 30 spirals per linear foot of the twisted monofilaments, the spirally wound band being adhered to the monofilaments along the length of the twisted core bundle.
The twist imparted into the core bundle of monofilaments generally is of the false twist tyoe. A "false twist" as the term is generally used and understood herein is a twist which is applied to a filament or a bundle of filaments by a torque apolied thereto, which will reverse and return to the zero twist upon release of the torque. In accordance with a preferred embodiment of this invention, it has been found that imparting a false twist to a bundle of thermoplastic monofilaments and thereafter extruding a band or a binder about the bundie, in a direction o^poosite to the twist, provides a more homogeneous structure in the sense that the twine has consistent characteristics throughout its length and additionally that the yarn has improved knot strength over yarns made from, for example, parallel monofilaments spirally encapsulated.
In accordance with another aspect of the invention, the method of making twine according to the oresent invention comprises continuously drawing a bundle of substantially parallel synthetic monofilaments along a path, imparting a false twist to said bundle to monofilaments, and directing a stream of molten synthetic material, which is compatible with the monofilament material, onto the outer surface of said moving, twisted monofilament bundle to form a spiral band therearound.
The molten material is directed onto the surface of the bundle at a temperature and pressure sufficient to cause the band which is formed to fuse to the contacted monofilaments, but without materially affecting the strength of the fused monofilaments. The monofilaments on the inside of the bundle are free to move relative to each other.
In accordance with another of its aspects the apparatus of the invention comprises a oath along which a bundle of substantially parallel synthetic monofilaments having a false twist therein can be continuously drawn, means for directing a continuous stream of molten synthetic material which is compatible with said monofilament material onto the outer monofilaments of the twisted moving bundle, thereby forming a spiral band therearound, means for supplying said molten synthetic material to said directing means at a temperature and pressure sufficient to cause the formed spiral band to fuse with said outer monofilaments without materially affecting the strength of said outer monofilaments, whereby the other monofilaments of said bundle are left free to move relative to each other, and a false twisting means for imparting a false twist to said bundle of monofilaments at a noint prior to said directing means whereby said bundle is characterized as having a false twist therein along said path.
The term twine as used herein is understood to include twine, cord, yarn and the like.
The yarns of the oresent invention are preferably made from synthetic thermoplastic resins and the present apparatus and process are particularly suited for the use of preferred synthetic thermoplastic materials, such as polyethylene, polypropylene and their copolymers. Various other synthetic materials which may be employed include oolyamides, e.g., poly (hexamethylene adioamide), polyesters, such as polymers of terephthalic acid or isoohthalic acid and a lower glycol, e. g., ooly (ethylene-terephthalate), poly (hexahydro-p-xylene tercphthate): polyalkylene generally, e.g., polyethylene: polyvinyl chloride: polyacrylics, e.g., poly-acrylonitrile and the copolymers of acrylonitrile with other comonomers and other synthetic continuous filement materials, regardless of denier per filament and regardless of the cross-section or total denier of the product.
The binder band must be formed of a material that is compatible with the monofilament material such that they both react to heat in substantially the same manner. Hence, the spiral binders are prepared from thermoolastic resins or thermoplastic rubbers, such as, for examole, polypropylene, polyethylene, pclyamide, polyesters, polycarbonates, polyvinyl tyoes, copolymers of ethylene and propylene and ethylene-propylene rubbers. Especially preferred are blends of ethylenepropylene rubber with polypropylene modified with oil and carbon black and sold under the trademark VISTAFLEX^R by Exxon Chemical Company. Another preferred rubber is a block copolymer comprising polystyrene end blocks with polyolefin rubbers as the midblock such as KRATONR oroduced by Shell Chemical Company.
The filaments may have a wide variety of cross-sections in addition to the usual circular cross-section, such as, eliolical, Y-shaped, triangular, heart-shaoed, square and the like.
The number of continuous monofilaments emoloyed in the twine can be from about 40 to about 340 and preferably from about 95 to 195 monofilaments per twine bundle. Most preferably, the twine bundle comprises about 130 continuous monofilaments. The monofilaments are generally wound about with one continuous spiral band.
Generally, the twine will have a denier in the range of 5000 to 50,000 more preferably about 20,000 to about 40,000 with each monofilament falling in the range of 50 to about 1000 denier, and preferably about 200 denier.
The false twist will generally be applied at a rate of 3 to 30 turns per linear foot of monofilament, preferably about 5 to 15 turns per linear foot most preferably 6 turns. The binder band will be applied at the rate of 8 to 30 spirals per linear foot of twines, and preferably about 10 to about 16 spirals per linear foot of twine. The monofilament bundle will generally be drawn through the apparatus at 200 to 2000 feet per minute, preferably about 500 to 1500 feet per minute.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic representation of one form of apparatus according to the present invention.
Fig. 2 is an enlarged view of a piece of twine made according to the present invention.
Fig. 3 is an enlarged partial cross sectional elevation of extruder and crosshead die 2 of Fig. 1.
Fig. 4 is a cross section taken on the line, 4-4 of Fig. 3.
Fig. 5 is a cross section taken on the line 5-5 of Fig. 3.
Fig. 6 is an enlarged partial cross sectional ele- vatinn of the twister 8 of Fig. 1.
Fig. 7 is a perspective view of the twine twisting element shown in Fig. 6.

Fig. 1 shows a process line according to the present invention. A plurality of thermoplastic monofilaments 4 are conveyed along a path, the axis A-A, through a die assembly 5 attached to an extruder 2, hence through cooler tank 6 through false twisting means 8 and into drawing apparatus 12 through which the completed twine 10 is passed to the take up apparatus (not shown). The principal difference in this apparatus and that which would ordinarily be found in facilities making monofilament twine according to the prior art is the twister 8.
Briefly, the thermoplastic monofilament is conventionally extruded by means well known in the art and which forms no part of this invention. Preferably the filaments are oriented along the axis of the twine in known manner. The monofilaments 4 are preferably made of a bundle of substantially parallel, oriented thermoplastic monofilaments; the oresent bundle 4 is twisted at a point 3 prior to entry into die assembly 5, so that a bundle having 3 to 30 turns per linear foot oasses into die assembly 5 wherein a continuous spiral band 18 of a compatible thermoplastic material is aoplied to the twisted bundle of monofilaments 4.
The spiral band is comprised of a material which is compatible with the monofilament material and is applied at a temperature and pressure, so as to fuse the band to only the outer layer of monofilaments.
The twisted and banded monofilament oreferably passes through a conventional cooling section, such as that shown, having a water quench 6, drying soonges 7 and air drying means 9, which is employed to solidify the extruded spiral band 18. The cooling of band 18 which is fused to the outer monofilaments serves to entrap some of the false twist or the characteristics of the twisted monofilament bundle.
The twist in the monofilament bundle 4 is obtained by having a false twisting means 8 downstream of the extruder 2. The twist is obtained by the false twister grasping the banded monofilament bundle 4, as for examole with the arrangement shown in Fig. 6, and continuously rotating the grasoing portion of the false twister 360° around an axis parallel to the axis A-A of the monofilament bundle 4, thereby extending the twist upstream along the bundle 4, through the cooler 6, through the die assembly 5 and back to ooint 3 upstream of the extruder 2. As the twine 4 passes out of false twister 8, the twisted monofilaments are freed of the torque from the false twister and would normally return to their untwisted, longitudinal state, which is also their tendency here, but for the band 18 which is fused to the outer monofilaments.
Referring to Fig. 2, a segment of twine 10 produced according to the present invention is illustrated. The monofilaments 14 (inner) and 16 (outer) are shown to have a Z twist, which is a counterclockwise twist. The spiral band 18 (in this embodiment) has an S twist, which is clockwise. As noted above, since a false twist was apolied, the twist would normally not be present in the twine, unless it were heat treated to set the twist in the monofilament. However, the psiral band or binder 18 is fused to the twisted outer monofilaments, thereby capturing at least some of the twist in the final product 10. Thereis a slight torque thus captured in the monofilaments which are seeking to return to their static or dead untorqued state.
It should be aopreciated that the spiral band 18 could have the same twist configuration as the monofilaments, and it would also capture some torque in the monofilaments in the same fashion, since the sDiral band 18, is itself in the static or dead state and will resist the movement of the torqued monofilaments, to which it is bound. Similarly, either the monofilament bundle or the binder may be S or Z when different configurations are desired. When the monofilament bundle and binder have the same twist configuration, i.e., both S or both Z twist, the product has been found to be a very flat band of monofilaments with the binder therearound.
Although the soiral band or binder 18 is illustrated as a single band, it should be appreciated that two or more bands may be used and in fact normally two bands would be emoloyed.
Figs. 3-5 illustrate the die assembly 5 and show the relationship of the monofilament bundle 4 and the twist beginning at point 3 prior to the die assembly 5. The die assembly 5 includes a crosshead 28 having a die passage 22 extending therethrough. An elongated die 24 is rotatably mounted in and extends through passage 22. This die has an axial bore 46 extending therethrough which is just large enough to accommodate a moving monofilament bundle 4 which has been oreviously formed by conventional means not shown and which may be twisted in a counterclockwise direction and which may be drawn through the bore in any suitable manner. such as by the drawing apparatus 12 (which must be located down stream of the twister 8).
Die 24 is rotated around the longitudinal axis thereof in any suitable manner. To produce the preferred yarn mentioned above, the direction of rotation is opposite to the twist direction. For example, a pulley 38 may be mounted on an elongated tubular drive shaft 44 rotatably mounted in bearing 36 of a plurality of support blocks 42. Pulley 38 is rotated by a drive belt 40 which, in turn, extends to an appropriate motor means (not shown).
Suitable means is provided for directing one or more streams of molten synthetic material through rotating die 24 into bore 46 thereof and onto the outer surface of bundle 4, as the latter moves linearly through said bore. An annular groove 50 is formed in the outer surface of die 24, and one or more passages 52, extend from said groove 50 inwardly and open into bore 46. These passages or noxxles are oreferably taoered inwardly from the groove towards the bore.
The molten synthetic material is directed into annular groove 50 through passage 48 extending through crosshead 28. The molten material is fed to passage 48 by a standard plastic extruder 2.
Since there is sufficient clearance in nassage 22 to permit die 24 to rotate, there is a tendency for the molten thermoplastic to flow axially along the outer surface of the die. In order to avoid seizing of the die by this material, annular grooves 26 and 34 are provided in the outer surface of die 24 on opposite sides of groove 50. Passages 30 and 32 in crosshead 28 communicate with grooves 26 and 34, respectively and extend downward therefrom, and may be connected by pipes to extend away from the apparatus.
The false twisting means 8 as shown in Fig. 6, consist of housing 60 affixed to a suooort 62 by support members 64. Each support member 64 is attached to the supoort 62 and housing 60 on opposite sides of the housing. Each support member 64 has a bore 72 therethrough, a support bearing 66 and a biased bearing 70, both of said bores 72 being aligned with each other.
A rotatably mounte_'d shaft 76 having a bore 80 therethrough and a pulley 78 mounted thereon extends through the bore 72 of one support member into housing 60. A second rotatably mounted shaft 82 having a bore 84 therethrough extends through the bore 72 of the other support member 64 into housing 60, the bores 80 and 84 being aligned. Mounted between the two shafts 76 and 82 is plate 86. Rotatably mounted to said plates are two sheaves or rollers 74. The rollers 74 are mounted diagonally on opposite sides of the axis of the bores 80 and 84, by means of oins 75, so that rollers 75 are free to rotate. The bearings 70 are biased by means 68 against shafts 76 and 82 respectively. Pulley 78 is rotated by a drive belt 88, which in turn is connected to an appropriate motor (not shown).
In operation the bundle 4 which has had the spiral band 18 applied in the crosshead 5 enters the housing 60 through the bore 80 of shaft 76, passes around one roller 74 then around the other roller 74 and hence out of the housing through bore 84 of shaft 82. A slight tension on the twine 10 by the drawing apparatus 12, allows the twine 10 to be gripped in this manner so that as the shaft 76 is rotated the entire assembly comprised of the two shafts 76 and 82, the attached plate 86 and the rollers 74 mounted thereon, rotates about the longitudinal axis A-A of the twine thereby twisting the twine 10. Bushing 90 tightly abuts the twine thereby forcing the twisting to extend upstream to point 3 on the bundle 4. This is only one means of twisting the monofilament bundle and any means which will achieve this function may be employed.
In operation there may be more than one monofilament bundle on a sheave, for example, two or three independent bundles may be on one sheave provided the sheaves or rollers 74 are wide enough. The twist is extended down each bundle and the bundles may be twisted about one another, however, this has no adverse effect. The individual oroduct twines separate as they leave the twister 8 and are taken up seoarately. This allows for an economy of equipment, since only one cooling section and twister are required for the oreoaration of a plurality of twines.
During operation of the die assembly 5, die 24 is rotated at a desired speed. The monofilament bundle 4 is continuously drawn through the bore of the die by the drawing aooaratus 12 and twisted by twisting means 8 such that a bundle of monofilaments having a desired number of turns per foot is passed into the die. The compatible synthetic material is directed to the extruder 2 through oassage 48 and annular passage 50 into radial passages or nozzles 52 in the rotating die. The two passages form two spiral bands on the twisted bundle 4.
The compatible molten material is at a temperature and pressure to fuse to the outer monofilaments it contacts. Any molten material moving along bore 22 over the outer surface of die 24 drains off through low pressure passages 30 and 32.
The temoerature of the molten thermoplastic extruded onto the twisted monofilament bundle must be adjusted to ore- vent damage or degradation of the monofilaments, which those operating the process need to routinely determine for the materials emoloyed. Similarly, the adjustment of the rate of speed at which the monofilament bundle is drawn along its oath, the rate of twist in relation thereto and the rate of spiral band application are all adjustable as desired or required for any particular thermoplastics employed.
Referring to Table I, it is shown that the knot strength and the general tying performance of the twisted twine is superior to that of conventional synthetic twine comprising parallel monofilaments.
In accordance with an aspect of this invention the monofilaments and band material can be foamed by dispersion of gas through the filaments at about 16 to about 66% by volume based on the volume of the resin and more preferably, at about 32% by volume based on the volume of the resin. The spiral band can be foamed alone or both the monofilaments and the spiral band can be foamed. Processes for preparing the foaming resin are well known and such processes are disclosed in, for example, U.S. Patent No. 3,214,234 of Bottom- ley and U.S. Patent No. 3,315,454 of Carranza.
Suitable stabilizer or pigments can be added to the resins which form the monofilaments and binder in order to protect them against ultraviolet degradation. Furthermore suitable fillers and blowing agents may be added to the resins for monofilament and binder in order to change the density or bulkiness prooerty.
The term "monofilament" as used in the specification and the following claims is intended to include monofilaments of any desired cross section. The binder bands also can be of any desired cross section, although it is preferably to use bands of rectangular or oval cross section.
It is readily aoparent that other soecific crosshead die assemblies and twisting means may be employed with the same function and result as those illustrated.
Thus, the present invention provides a means to produce a twine which has some loss of tensile strength but which has better characteristics for use, especially in tying the knot and knot strength, than prior art twine made without the false twist.

Claims

1. A twine comorising a core bundle of continuous synthetic oriented monofilaments extending lengthwise of the twine and a synthetic binder in thin band form made from a material compatible with the monofilaments material, spirally wound about the twisted monofilaments, the soirally wound band being adhered to the outer monofilaments along the length of the twisted core bundle, characterized in that the monofilaments are twisted so as to contain from 3 to 30 turns per linear foot of monofilament twine and that the spiral band is wound in a direction reverse to that of the twist of the filaments and containing about 8 to 30 spirals per linear foot of the twisted monofilaments.

2. A twine according to claim 1 characterized in that the core bundle contains from 40 to 340 monofilaments.

3. A twine according to claim 2- characterized in that the core bundle contains from 95 to 195 monofilaments.

4. A twine aecording to claims 1-3 characterized in that the core bundle of monofilaments is soirally encapsulated while in a false twisted condition.

5. A twine according to claims 1-4 wherein said core filaments are twisted so as to contain from about 5 to 15 turns per linear foot of monofilament twine.

6. A twine according to claim 5 wherein said core filaments contain about 6 turns per linear foot of monofilaments and said soiral bond contains about 10 to about 16 soi- rals per linear foot of monofilaments.

7. A twine according to claims 1-6 characterized in that the synthetic monofilaments and spiral binder are tnermo- plastic resins, including oolyolefins, oolyamides, oolyesters, oolycarbonates and polyvinyl types.

8. A twine according to claim 7 characterized in that the thermoplastic resins are polyolefins and the binder thermoplastic polyolefin resins or thermoolastic rubber.

9. A twine aecording to claim 8 characterized in that the polyolefins are selected from polypropylene, polyethylene and copolymers of ethylene and propylene.

10. A twine according to claim 9 characterized in that the synthetic monofilaments and binder are polypropylene.

11. A twine according to claims 1-10 characterized in that said monofilaments have a denier of about 50 to 1000 and the twine is in the range of about 5000 to 50,000 denier and the denier of the spiral band is in the range of 10% to 25% of the denier of the total twine denier.

12. A twine according to claim 11 characterized in that said twine is in the range of about 20,000 to 40,000 denier, said monofilaments are about 200 denier and the denier of the spiral band is about 15% of the total twine denier.

13. A twine according to claims 1-12 characterized in that the spiral band is foamed.

14. A twine according to claims 1-12 characterized in that the monofilaments and spiral band are foamed.

15. A twine according to claim 13 characterized in that the spiral band contains a gas dispersed therein at about 16 to about 66% of volume, based on the volume of the resin.

16. A twine according to claim 14 characterized in that the monofilaments and band contain a gas dispersed therein at about 16 to about 66% volume based on the volume of the resin.

17. A twine according to claims 13 or 14 characterized in that the gas is present at about 32% by volume based on the volume of the resin.

18. A method of making twine comorising continuously drawing a bundle of substantially parallel synthetic monofilaments along a path imparting a twist to said bundle of monofilaments and directing a stream of molten synthetic material onto the outer surface of said moving, monofilament bundle to form a spiral band therearound, the molten material being directed onto the surface of said bundle at a temperature and pressure sufficient to cause the band which is formed to fuse to the contact monofilaments without material affecting the strength of the fused monofilaments. Characterized in that the twist which is a false twist is at the rate of about 3 to about 38'turns per linear foot and that the molten material is directed onto the twisted bundle.

19. A method according to claim 18 characterized in that the monofilaments on the inside of said bundle are free to move relative to each other.

20. A method according to claims 18 or 19 characterized in that synthetic materials are thermoplastic.

21. An apparatus for producing twine from a bundle of synthetic monofilament, comprising:

a path along which a bundle of substantially parallel synthetic monofilaments can be continuously drawn,

means for directing a continuous stream of molten synthetic material, which is compatible with said monofilament material, onto the outer monofilaments of the twisted moving bundle, thereby forming a spiral band therearound,

means for supplying said molten synthetic material to said directing means at a temperature and pressure sufficient to cause the formed spiral band to fuse with the said outer monofilaments without materially affecting the strength of said outer monofilaments of said bundle, whereby the other monofilaments of said bundle are left free to move relative to each other, and characterized by

a false twisting means for imparting a false twist to said bundle of monofilaments effective at a point prior to said directing means, whereby said bundle of monofilaments is characterized as having a false twist therein along said path.

22. An apparatus according to claim 21 characterized in that false twisting means is located downstream of said directing means along said path.

23. An apparatus according to claim 21 or 22 characterized in that said false twisting means comprises means for grasping said bundle of monofilaments having a spiral band therearound'and rotating said bundle about a longitudinal axis, whereby said bundle of monofilaments is twisted along said path to a point on said path, prior to said directing means.

24. An apparatus according to claims 21-23 characterized by a rotatably mounted frame mounted in said path, at least one rotatably mounted sheave mounted tangentially to said path, for passing said banded bundle of monofilaments around said sheave thereby securing said banded bundle such that rotation of said frame causes said banded bundle to twist.

25. An apparatus according to claims 21-24 characterized by a pair of rotatably mounted sheaves are diagonally mounted in said frame tangential to said oath whereby said banded bundle passes around both sheaves.

26. An apparatus according to claims 21-25 characterized in that said directing means comprises at least one nozzle directed toward said path and caoable of moving circumferentially about said path.