MXPA97005613A - Fabric of conjugated fiber of poliolefina-poliam - Google Patents

Abstract

The present invention relates to a non-woven fabric comprising conjugated fibers, said conjugated fibers comprise a polyolefin and a polyamide selected from polycaprolactam, copolymers of caprolactam and hexamethylene adipamide, hydrophilic copolymers of caprolactam and ethylene oxide diamine, and mixtures thereof, in wherein said polyamide has a number average molecular weight of up to about 16.5

Description

FABRIC OF CONJUGATED FIBER OF POLIOLEFINA-POLIAMIDA CROSS REFERENCE TO THE RELATED APPLICATION This application is a continuation in part of the application of the United States of North America No. 5,424,115 granted on June 13, 1995.

BACKGROUND OF THE INVENTION The present invention relates to conjugated fibers of two different thermoplastic polymers and to the non-woven fabrics produced therewith. More specifically, this invention relates to conjugated fibers and non-woven fabrics of a polyolefin and a polyamide.

The conjugated fibers contain at least two component compositions that occupy different cross-sections along essentially the entire length of the fibers, and these are produced by simultaneously and contiguously extruding a plurality of polymeric melt-fiber-forming compositions to the holes. of spinning of a spinning organ to form unitary filament yarns. In general, the component compositions for the conjugated fibers are selected from different polymers having different shrinkage properties and / or complementary advantageous physical and chemical properties. Component polymers having different shrinkage properties are typically used to impart frill in the conjugated fibers, and the component polymers having different advantageous properties are used to impart different functionalities in the fibers.

Since the different polymers have different melting and processing temperatures as well as having different rheological melting properties, it is usually necessary or desirable to process and maintain the component polymer compositions for the conjugated fibers at different temperatures just prior to combining. polymer compositions melted as unitary filament yarns. In many cases, when different melted polymers are combined to form the unit yarns, numerous processing difficulties arise such as the non-uniformity of the yarns, the spinning breaks and the phenomenon of bending of the non-solidified yarns at the tip of the organ. spinner. Such processing difficulties prevent the proper formation of the fibers, and therefore, of the non-woven fabrics. In addition, especially for the fiber spinning processes employing the pneumatic pulling steps, for example, the meltblown fibers and the spunbonded fibers, the filament yarns emerging from the spinner tend to be tied or hoiled during the process of pulling unless the processing conditions are carefully made for each polymer combination. Such controlled processing conditions ensure, for example, adequate cooling of the component polymers forming the filament yarns and separation of the extruded yarns until they are deposited on the forming surface. There have been many approaches to solve these processing difficulties in conjugate spinning fibers of different polymer compositions. For example, British Patent No. 965,729 discloses a spinner organ containing angularly positioned holes that is inclined in the direction opposite to the direction of bending of the conjugate and extruded fiber yarns. However, the teaching of the patent can only be practical for large production runs since a specific spinner organ has to be constructed for each different polymer combination. U.S. Patent No. 3,536,802 to Uraya et al. Discloses a method for separately extruding and maintaining component polymer compositions at different temperatures just before combining and extruding the unit fiber strands in order to alleviate processing difficulties. by maintaining the melt viscosities of the component polymer compositions essentially at the same level. The teaching of Uraya et al. Uses the fact that linear thermoplastic polymers generally decrease their melt viscosity by increasing the temperature of the melt. Nevertheless, the processes for securing the thermal profile of each of the component polymer melts requires a set of a stubborn or complex spinner organ containing insulating layers. In addition, the temperature difference of the polymer components of the unitary filament yarns create process difficulties in the handling of the extruded filaments. For example, component polymers having different melting temperatures tend to solidify at different rates, and insufficiently cooled polymer components of the conjugated filaments tend to cause random fusion or etching of the filament yarns before the filaments can be deposited properly on the forming surface.

Of the various conjugated fibers having different polymers, the conjugated fibers of a combination of polyolefin and polyamide are highly useful. U.S. Patent No. 3,788,940 issued to Ogata et al., For example, describes conjugate fibers containing a polyolefin and a long carbon chain polyamide, e.g., nylon-11, nylon-12, nylon 11 / 10, nylon 11/11 or nylon 11/12. The long carbon chain polyamides have melting and processing temperatures that are lower than the most commonly available and conventional nylons, for example nylon 6 and nylon 6/6. The melting and processing temperatures of these long carbon chain polyamides are practically comparable to those of the polyolefins so that these polyamides and the polyolefins can be easily processed to form conjugate fibers. In contrast, the most economical and conventional polyamides, for example, nylon 6 and nylon 6/6, have significantly higher melting points, and therefore, have to be processed with melting at a higher processing temperature range than polyolefins typical Furthermore, as is known in the art, a thermoplastic polymer is processed with melt typically at a temperature significantly higher than the melting point of the polymer in order to accommodate the temperature fluctuation typical of the melt processing equipment, for example a extruder and therefore to prevent an accidental solidification or freezing of the polymers in the melt processing equipment and to provide a melted composition having a melt viscosity suitably processable. In general, when a melted composition is improperly heated, the melt has an elongation viscosity or a melt elasticity that is too high to allow proper pulling of the extruded filaments; and when a melted one overheats, the filaments extruded from the melted can not be cooled adequately and sufficiently. Consequently, the superheated and not sufficiently heated melts do not adequately form useful filaments, for example, they cause spinning breaks and form fused and / or stacked fibers. Thus, conventional polyamides and polyolefins have been processed with melt at different processing temperatures, and therefore, typically have required specialized processing equipment to produce the conjugate fibers.

There is still a need to provide polymer compositions for the conjugated polyolefin / polyamide fibers that can be processed with conventional polyolefin processing equipment and that can contain polymer components which do not require processing at different processing temperatures.

SYNTHESIS OF THE INVENTION A conjugated fiber containing a polyolefin and a polyamide selected from polycaprolactam, copolymers of caprolactam and hexamethylene adipamide, hydrophilic copolymers of caprolactam and ethylene oxide diamine, and mixtures thereof, wherein the polyamide has a average molecular weight of number up to around 16,500. A non-woven fabric produced from the conjugated fiber is additionally provided.

The present invention further provides a desired method for producing conjugated fibers and non-woven fabrics containing a fiber-forming polyolefin and a polyamide selected from polycaprolactam, copolymers of caprolactam, and hexamethylene adipamide, hydroplic copolymers of caprolactam and ethylene oxide diamine, and mixtures thereof, wherein the polyamide has a number average molecular weight of up to about 16,500. The method contains the steps of extruding with melted polyolefin, extruding with melted polyamide, supplying the polyolefin and polyamide extruded to an orifice of a spinning organ to form a unitary filament where the melted polyolefin and polyamide entering the orifice they are processed with melt to have melting temperatures between the melting point of the polyamide and about 240 << * C.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1-6 illustrate the cross-sectional configurations of conjugate fiber example.

Figure 7 shows a non-woven fabric of conjugated fiber that was produced according to the present invention.

Figure 8 shows a non-woven fabric that was produced with a conventional polycaprolactam.

Figure 9 shows another non-woven fabric of conjugated fiber that was produced according to the present invention.

Figure 10 shows another nonwoven fabric that was produced with a conventional polycaprolactam.

DETAILED DESCRIPTION OF THE INVENTION The present invention describes the conjugate fibers having a polyolefin and a polyamide, and the non-woven fabrics produced from the conjugated fibers. Conjugated fibers and non-woven fabrics exhibit improved sgth properties, for example tensile sgth and tear resistance; abrasion resistance; junction characteristics, for example a wider junction temperature range; and functionalities, for example, dyeability and hydrophilicity, on the polyolefin fibers and the non-woven fabrics thereof. In addition, the non-woven fabric contains functional chemical groups, for example amide groups, which can be chemically modified to introduce various surface functionalities onto the non-woven fabric. The component polymer compositions of the conjugated fibers present, unlike the conventional short carbon chain polyamide compositions of the conjugated fibers of the prior art, can be processed at a temperature which is typically used to process the polyolefins with melted and can processed with a conventional non-insulated conjugated fiber spinning apparatus.

Polyamides, otherwise known as "nylons" suitable for the present invention include polycaprolactam (nylon 6), the copolymers of caprolactam and hexamethylene adipamide (nylon 6.6 / 6), and the hydrophilic copolymers of caprolactam and ethylene oxide diamine , as well as mixtures thereof. Of these, the most desirable polyamide for the present invention is a polycaprolactam. In accordance with the present invention, suitable polyamides are low molecular weight polyamides having an average number-average molecular weight, or less than about 16,500; desirably from between about 10,000 and about 16,200; more desirably from between about 11,000 and about 16,000; most desirably of between about 11,500 and about 15,000. It is believed that suitable polyamides having a low number average molecular weight of 5,000 or even less can be extruded with melt within: the conjugated fibers of the present invention. Polyamides particularly suitable for the present invention have a viscosity relative to formic acid of between about 1.8 and about 2.15, more particularly between about 1.85 and about 2, as measured in accordance with ASTM D789-66, and has a melt flow rate of between about 48 g / 10 minutes and about 100 g / 10 minutes, more particularly between about 65 g / 10 minutes and 95 g / 10 minutes, as measured in accordance with ASTM D1238-90b standard. Condition 230 / 2.16. Optionally, the polyamide composition for the conjugated fibers may contain a small amount of a processing lubricant to improve the processability of the polyamides. For example, a small amount of a metal or mineral stearate, for example calcium, sodium, lead, barium, cadmium, zinc or magnesium stearate, can be mixed within the polyamide composition to increase its melt flow rate and reduce its melt viscosity. Desirably, up to about 5%, more desirably between about 0.01% and about 4%, based on the weight of the polymer, of a stearate compound is mixed within the polymer composition.

It has been found that; the polyamides suitable for the present invention can be melt processed to the conventional processing temperature range for the polyolefins without undergoing processing difficulties, such as bending and etching of the extruded conjugated filament yarns. Desirably, the polyarylene is processed with melt to have a melting temperature between the melting point of the polyamide and about 240 ° C more desirably of between about 215 ° C and about 238 ° C, more desirably between 225 ° C and about 235 ° C, especially when the conjugated fibers joined by spinning are produced. The term "melting temperature" as used herein indicates the temperature of the melt of polymer composition entering the spin pack. It should be noted that the processing temperature suitable for the present invention is significantly lower than the conventional processing temperature range for the polycaprolactam and is not significantly higher than the melting point of the polyamide. While not wishing to be bound by any theory, it is believed that the unique low molecular weight of the polyamides suitable for the present invention provides the required melt viscosity even at the melt processing temperature range under present. In contrast, commercially available fiber class polycaprolactams have to be processed with melt at a temperature range in excess of the processing temperature range of typical polyolefins in order to obtain the proper melt flow characteristics that are compatible with polyolefins. processed with melted. Accordingly, the conjugated fiber component compositions containing the present polyamide can be processed with a conventional spinning organ assembly which is maintained in the conventional operating temperature range typically used for the polyolefins.

Polyolefins suitable for the present inventions include polyethylene, for example, high density polyethylene, medium density polyethylene, low density polyethylene and linear low density polyethylene; polypropylene, for example isotactic polypropylene and atactic polypropylene; polybutylene, for example poly (l-butene) and poly (2-butene); polypentene, for example, poly (2-pentene) and poly (4-methyl-1-pentene), - polyvinyl acetate; polyvinyl chloride; polystyrene; and the copolymers thereof, for example the ethylene-propylene copolymer, thus COITO mixtures thereof. Of these, the most desirable polyolefins are polypropylene, polyethylene, polybutylene, polypentene, polyvinyl acetate, and copolymers and mixtures thereof. The most desirable polyolefins for the present invention are polyolefins conventionally used in the production of non-woven fabrics, including polypropylene, polyethylene, polypropylene and polyethylene copolymers, and mixtures thereof; more particularly, isotactic polypropylene, mixtures of isotactic polypropylene and atactic polypropylene, syndiotactic polypropylene, high density polyethylene, linear low density polyethylene and mixtures thereof. In addition, the polyolefin component may also contain minor amounts of compatibilizing agents, abrasion resistance improving agents, curling inducing agents and the like. Illustrative examples of such agents include the acrylic polymer, for example, ethylene alkyl acrylate copolymers; polyvinyl acetate; ethylene vinyl acetate; polyvinyl alcohol; ethylene vinyl alcohol and the like.

The component polymer compositions of the present invention may additionally contain other additives and processing aids. For example, nucleating agents, dyes, pigments, wetting agents, surfactants, antistatics, odor absorbers, germicides, lubricants and the like. These additives can be, for example, dry or stirred mixed with the polymer pellets of the component polymers before the pellets are processed with melt.

Suitable processes for producing conjugated fibers are known in the art. In general, at least two polymer compositions component processed fluiblemente are fed through spinning orifices of a spinner member to form unitary filaments having distinct cross sections along substantially the entire length of the filaments that are occupied by polymer compositions. The conjugated fibers can be prepared to have ripples or latent rizability. Although it is not desired to be bound by any theory, it is believed that conjugated fibers containing component polymers of different shrinkage properties subsequently possess an activatable "latent rizability". When such conjugated fibers are exposed to a heat treatment or a mechanical pulling process, the integrity of the shrinkage between the component polymers of the conjugate fibers causes the fibers to ripple. An exemplary process for producing conjugated fibers highly suitable for the present invention is disclosed in commonly assigned U.S. Patent 5,382,400 to Pike et al., Which is incorporated herein by reference in its entirety. Briefly, the process for making a fabric conjugate fiber crimped, more specifically a woven fiber spunbonded, described in the patent includes the steps of spinning with melted polymeric filaments of multicomponent continuous, cooling at least partially filaments multicomponent so that the filaments have a latent rizability, activate the latent rizability and pull the filaments by applying heated drawn air, and then deposit the pulled and crimped filaments on a forming surface to constitute a non-woven fabric. In general, a higher pull air temperature results in a higher number of crimps. Optionally, the unheated ambient air can be used during the pull step to suppress the activation of the latent rizability and to produce non-crimped conjugated fibers. The multi-component melt-blown conjugate fiber and the methods for making same are described in, for example, U.S. Patent Nos. 5,238,733; 5,232,770; 4,547,420; 4,729,371 and 4,795,668.

The conjugated fibers of the present invention can have a wide variety of conjugate fiber configurations. Figures 1-6 illustrate examples of suitable conjugate fiber configurations. Suitable conjugate fiber configurations include a side-by-side configuration (Figure 1), an eccentric sheath-core configuration (Figure 2), a concentric sheath-core configuration (Figure 3), a core-wedge configuration (Figure 2). 5) and an island configuration at sea (Figure 6). The conjugated fibers can also be hollow fibers. The single molecular weight polycaprolactams of the present invention can be extruded-melted at polyolefin processing temperatures and, therefore, have a cooling profile similar to that of the polyolefin component of the conjugate fibers. Furthermore, the melting polyamides compositions of low molecular weight exhibit a reduced melt elasticity or elongational viscosity, improving the compatibility of the polyamide and polyolefin components of the fibers and pulled conjugate of the extruded filaments. It is believed also that the melting of the polycaprolactams single molecular weight exhibit reduced viscoelastic properties and improved even when melted is cooled to a temperature near or below the melting point, for example, even after the melt starts solidify, further facilitating the pulling of the extruded conjugate filaments. The present polyamide component can be conveniently processed under processing settings adapted for polyolefins, thereby eliminating the processing difficulties and problems associated with the production of conjugated fibers of polymer components of different processing temperatures and different viscosities. melted.

Non-woven fabrics or fabrics are produced from the conjugate fibers by depositing the fibers on a forming surface. Typically, the fibers are deposited randomly and isotropically to form a non-woven fabric having a uniform fiber coverage. If the conjugated fibers are not self-adhesive at the time of the formation of the non-woven fabric, said non-woven fabric has to be joined to impart physical integrity and strength. For example, typical meltblown fibers are not completely cooled or solidified when they are deposited on a forming surface, and therefore, the fibers constitute autogenous interfiber bonds as they are deposited to form a fabric of fibers formed by blowing the melted. In contrast, the spunbonded fibers and the short fibers are completely or essentially completely cooled when deposited to form a nonwoven fabric. Consequently, the resulting non-woven fabric requires being joined in a separate bonding step. Suitable bonding processes include compression joining processes, for example, calendering bonding, spot bonding and pattern bonding processes; and the processes of union without compression, for example, the union with furnace, the infrared union and the processes of union through air. Compression-bonding processes typically apply a combination of heat and pressure to effect bonding between fibers; for example by passing a non-woven fabric through the clamping point formed by a smooth or heated pattern roller and a smooth anvil roller. The non-compression bonding processes raise the temperature of the non-woven fabric until at least one component of the conjugate fibers forming the non-woven fabric melts and becomes adhesive, forming autogenous interfiber bonds at the cross-over contact points. the fibers.

According to another embodiment of the present invention, the non-woven fabrics of the present invention can be laminated to form a composite material. For example, a spin-linked conjugate fiber fabric and a meltblown fiber fabric of the present invention can be superposed or formed in sequence and then thermally or adhesively bonded to form a composite fabric having the strength properties of the bonded fabric. by spinning and the barrier properties of the melt blown fabric. By An example process for producing such composite materials is described in United States Patent No. 4,041,203 issued to Brock et al., Which is incorporated herein by reference.

According to still another embodiment of the present invention, the non-woven fabrics of the present invention can be laminated to a non-woven fabric of conventional monocomponent fiber or to a film. For example, a conjugate fiber fabric of the present invention can be laminated to a polymeric film and then thermally bonded to form a high strength cloth type liquid barrier laminate. Such a barrier laminate is highly useful as, for example, a fabric for protective garments and outer cover materials for diapers and other personal care articles.

As stated above, the non-woven polyamide / polyolefin conjugate fiber fabric of the present invention exhibits advantageous properties including improved tensile strength, dyeing, chemical functionalities and improved wettability. The non-woven fabric is highly suitable for producing protective garments, for example, medical examination gowns and surgical gowns; protective covers, for example, car covers and boat covers; disposable articles, for example liners for diapers; and similar.

The present invention is further illustrated with reference to the following examples. Nevertheless, the examples should not be considered as limiting the invention to them. EXAMPLES: EXAMPLE 1 A non-woven fabric spun-bonded of 1 ounce per square yard (ozy), 34 g / m 2, of conjugate fibers of 50% by weight polypropylene / 50% by weight of polycaprolactam was prepared side by side. The polypropylene used was Exxon PD3445, which had a melt flow rate of 35 g / 10 minutes, and the polycaprolactam used (nylon 6) was wire jacket class, 401-D, which had a relative viscosity of formic acid of 1.97, a number average molecular weight of about 13,800 and a melt flow rate of 85 g / 10 minutes. The relative viscosity of formic acid was tested in accordance with ASTM D789-66, and the melt flow rate was tested according to ASTM D 1238-90b, Condition 230 / 2.16. The nylon 6 resins were obtained from Custom Resins, of Henderson, Ky, a division of Bernis Company, Inc. The polypropylene was mixed with 2% by weight of a concentrate of Ti02 containing 50% by weight of Ti02 and 50% by weight of a polypropylene, and the mixture was fed into a single screw extruder having three zones. The nylon 6 was mixed with 2% by weight of a concentrate of Ti02 containing 25% by weight of Ti02 and 75% by weight of nylon 6, and the mixture was fed into a second single screw extruder having four zones. The extruded polymers were fed to a bicomponent spinning matrix through the heated transfer tubes and spun into round bicomponent fibers. The bicomponent spinning die had a spin hole diameter of 0.6 millimeters and a L / D ratio of 4: 1. The production rate of the spin hole was 0.7 grams / hole / minute. The spinning matrix was maintained at a constant temperature and, therefore, both of the melted component compositions were exposed to temperature. The processing temperature placement profile of the extruders, the transfer tubes and the spinner is shown in Table 1. The bicomponent fibers that come out of the spinning die were cooled by an air flow having a cup of flow of 45 SCFM / inch spinner organ width and a temperature of 65oF. The cooling air was applied to about 5 inches below the spinner and the cooled fibers were pulled into a suction unit of the type which is described in U.S. Patent No. 3,802,817 issued to Matsuki et al. The cooled fibers were pulled with the ambient air in the suction unit to achieve 2.5 denier fibers. Then, the pulled fibers were deposited on a foraminous forming surface with the aid of a vacuum flow to form a non-woven fiber fabric.

The non-woven fabric was knitted together by feeding the fabric into a clamping point of a steel calendering roller and a steel anvil roller. The calendering roller had about 310 square bond points highlighted per square inch (48 points / cm2). The bonding rolls were heated to about 143oc and a clamping point pressure of about 15.5 kg / linear centimeter was applied.

Table 1 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 216 166 Zone 2 241 199 Zone 3 224 221 Zone 4 229 Zone 5 230 Transfer Tube 229 221 Spinning Organ 232 Example 2 (Ex2) Example 1 was repeated except that a different processing temperature profile was used, as indicated in Table 2.

Table 2 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 216 171 Zone 2 241 222 Zone 3 224 229 Zone 4 229 Zone 5 230 Transfer tube 229 229 Spinning organ 234 The non-tremolo knitted weave from Examples 1 and 2 containing the low molecular weight polyamide, which was processed with melting at a non-conventionally low temperature and having a melting temperature that is close to or is at melting temperature of the polyolefin component, had a uniform fiber coverage and a caliper that are similar to those of conventional non-woven fiber fabrics of monocomponent fiber.

Comparative Example 1 (Cl) A one-ounce polypropylene monocomponent single-strand woven fabric was prepared using polypropylene PD3445 according to the procedure delineated in example 1, except that the polypropylene was melt-processed in both of the extruders and a concentric sheath-core spin pack was used. The processing temperature profile was as indicated in Table 3.

The resulting non-woven fabric was tested in relation to its grip strength resistance and tear resistance. Grip tension resistance was tested in accordance with federal standard methods 191 A, Method 5100 (1978), and tear strength was tested in accordance with the Trapezoidal Tear Test as described in ASTM D1117-80, Method 14. The results are shown in Table 12.

Table 3 Temperature Placement (° C) Position Extruder 1 Extruder 2 Extruder Zone 1 171 171 Zone 2 199 198 Zone 3 220 221 Zone 4 222 Zone 5 222 Transfer tube 230 230 Spinner organ 229 Comparative Example 2 (C2) A polypropylene / nylon 6 bicomponent conjugate fiber fabric of a fiber class polyamide was produced. The nylon 6 spinning sheets available from DSM and from Exxon PD3445 polypropylene according to the procedure outlined in example 1 and the processing temperature profile shown in Table 4. The nylon 6 had a relative viscosity of formic acid of 2.45. and a number average molecular weight of about 19,700. The high processing temperature profile of the polyamide was selected according to the processing recommendation and the polyamide manufacturer's guidance.

Table 4 Temperature Placement (oQ Position Nylon 6 Polypropylene Extruder Zone 1 219 171 Zone 2 266 199 Zone 3 263 221 Zone 4 263 - Zone 5 263 Transfer tube 263 221 Spinner 262 Fiber class nylon 6 could not be properly spun into conjugate fibers. The polymer yarns emerging from the spinning organ were significantly bent, and the yarns were randomly melted and holed during the pulling process. A non-woven fabric was not prepared since the tied fibers would not constitute a useful non-woven fabric.

Comparative Example 3 (C3) Comparative Example 2 was repeated except that the melt processing temperature of nylon 6 was raised so as to decrease the melt viscosity of the polymer composition. The processing temperature profile was as indicated in Table 5.

Table 5 Temperature Placement (oQ Position Nylon 6 Polypropylene Extruder Zone 1 221 171 Zone 2 268 199 Zone 3 291 221 Zone 4 288 Zone 5 288 Transfer tube 287 221 Spinning organ 265 Raising the melting temperature of the nylon composition, in order to affect the viscosity of the melt of the polymer, it does not alleviate the problem of fusion and etching. The filaments were melted and etched.

Comparative Example 4 (C4) Comparative Example 3 was repeated except for the processing temperature of the nylon composition which was further elevated in order to further reduce the melt viscosity of the composition. The resulting fibers were formed into a non-woven fabric according to Example 1. The processing temperature profile was as indicated in Table 6. Table 6 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 221 171 Zone 2 291 199 Zone 3 303 215 Zone 4 299 Zone 5 299 Transfer tube 299 215 Spinning organ 264 Again, raising the processing temperature did not cure the phenomenon of melting and etching and in fact, the problem of hacking was more severe. It is believed that not only the difference in melt viscosity between the component compositions but also the melt temperature disparity and therefore insufficient cooling of the nylon composition further contributed to the etching problem. As expected, the non-woven fabric produced had a highly non-uniform fiber covering due to the stapled fibers.

Example 3 (Ex 3) Example 1 was repeated except that the sheath-core conjugate fibers were produced using a concentric sheath-core spin pack. The processing temperature profile was shown in Table 7. Table 7 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 219 171 Zone 2 239 199 Zone 3 242 221 Zone 4 229 Zone 5 230 Transfer tube 230 221 Spinning organ 229 FIG. 7 is a photograph of the knitted nonwoven fabric produced in this example. As can be seen from Figure 7, the non-woven fabric had a highly uniform fiber coverage.

Comparative Example 5 (C5) Comparative Example 2 was repeated except that the sheath-core conjugate fibers were produced using a concentric sheath-core spin pack. The processing temperature profile was as shown in Table 8.

Table 8 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 218 171 Zone 2 291 199 Zone 3 298 221 Zone 4 299 Zone 5 298 Transfer tube 299 221 Spinner 238 The resulting conjugate fibers were fused and smoothed during the pulling process. The high molecular weight of the polyamide caused the problem of spinning even when the processing temperatures of the polyamide component were significantly raised to influence the melt flow properties of the component. Figure 8 is a photograph of the non-woven fabric. The photograph clearly shows the melted and smoothed fibers and uneven coverage of the fibers forming the non-woven fabric.

Example 4 (Ex4) Example 3 was repeated and the processing temperature profile was as shown in Table 9. Three non-woven fabrics were produced having conjugated fibers of different proportions of polymer component. The proportions of the polymer component were 50:50, 40:60 and 60:40 by weight of nylon 6 of polypropylene.

Table 9 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 171 171 Zone 2 214 198 Zone 3 239 221 Zone 4 229 Zone 5 230 Transfer tube 229 229 Spinning organ 229 All three component polymer proportions resulted in uniformly extruded and pulled conjugate fibers, and correspondingly, non-woven fabrics having a uniform fiber coverage and an even gauge. Figure 9 is a photograph of the non-woven fabric which was produced from the conjugate fibers having nylon 6 and 50:50 polypropylene components. The photograph shows the fibers of the non-woven fabric placed isotropically and uniformly.

The fabric shown in Figure 9 was also tested for its grip strength and tear properties according to the procedures outlined in Comparative Example 1. The results are shown in Table 12.

Comparative Example 6 (C6) Comparative Example 5 was repeated except that a nylon 6 of different fiber class was used. Nylon 6 was a polycaprolactam of low molecular weight fiber class DSM 1130, which had a relative viscosity of formic acid of 2.22, a number average molecular weight of about 16,700 and a melt flow rate of 42 g / 10 minutes. The processing temperature profile was as shown in Table 10. The resulting fabric was tested for its grip strength and tear properties according to the procedures delineated in Comparative Example 1. The results are shown in the Table 12 Table 10 Temperature Placement (° C) Position Nvlon 6 Polypropylene Extruder Zone 1171171 Zone 2214198 Zone 3241221 Zone 4 229 - Zone 5 230 - Transfer tube 229 229 Body spinner 229 During the filament spinning, breakings of yarn were observed, and fibers extruded from Comparative Example 6 were melted and etched during the pulling process. Even when the conjugated fibers of Example 4 and Comparative Example 6 were prepared under virtually the same processing condition, only the polyamide having the low molecular weight (from Example 4) was spun appropriately on conjugated fibers. The comparison of the results of the Example 4 and Comparative Example 6 clearly demonstrate that the low molecular weight polycaprolactam is uniquely suited for forming the conjugated fibers in conjunction with the polyolefins that are typically used to produce the nonwoven fabrics.

Figure 10 shows the nonwoven fabric produced in this comparative example. The melted and smoothed fibers are clearly visible and as expected, the fiber coverage is highly inadequate, forming many sections without fiber coverage.

Example 5 (Ex5) Example 3 was repeated except that linear low density polyethylene (LLDPE) was used instead of polypropylene. Linear low density polyethylene, class 6811 A, is commercially available from Dow Chemical. The LLDPE had a melt flow rate of about 43 g / 10 minutes, as measured in accordance with ASTM D1238-90b. Condition 230 / 2.16. In addition, the non-woven fabric was joined with a bonding roll having a different bonding pattern. The bonding roller had bonding points that covered about 25% of the total surface area and had a junction point density of about 200 regularly spaced points per square inch (31 points / cm2). The processing temperature profile was shown in Table 11, and the resulting fabric was tested for its properties of resistance to gripping and tearing according to the procedures delineated in Comparative Example 1. The results are shown in Table 12 .

Table 11 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 172 166 Zone 2 216 194 Zone 3 238 221 Zone 4 231 Zone 5 230 Transfer tube 229 229 Spinning organ 229 Table 12 Resistance to stress (Rq) Resistance to scratching (Ks) Use MD CD CD Ex4 15. 1 11. 5 3. 5 3. 2 Ex5 14. 2 7. 2 5. 7 2. 6 Cl 2.5 2.4 1.9 1.5 C6 5.4 2.5 1.8 1.5 MD = address to the machine CD = direction transverse to the machine The strength data given above clearly demonstrates that the conjugate fiber fabrics of the present invention have superior strength properties, such as tensile and tear strength properties over uncomposed single-component fiber fabrics and conjugate fiber fabrics produced from a conventional fiber class polycaprolactam.

Example 6 (Ex6) Example 3 was repeated except that nylon 6 used was Capron® 1767. Capron® 1767 was obtained from AlliedSignal Inc., and had a relative viscosity of formic acid of 2.1, a number average molecular weight of about 16,100 and a melt flow rate of 49 g / 10 min. The processing temperature profile was as shown in Table 13.

Table 13 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 171 171 Zone 2 218 199 Zone 3 241 229 Zone 4 229 Zone 5 229 Transfer tube 229 229 Spinner 231 The conjugated fibers were produced and a knitted non-woven was prepared even when there was a minor amount of etching observed.

Example 7 (Ex7) Example 6 was repeated, except that the polyamide was modified to contain sodium stearate and 6811 LLDPE was used in place of the polypropylene. The stearate was powder coated topically on the polyamide pellets, and it is believed that the amount of sodium stearate applied was less than 1% by weight of the pellets. In addition, a wedge spin pack was used, and the binding pattern of example 5 was used. The wedge spinning pack contained 16 identically formed wedges, similar to FIG. 5, and the two polymer components were arranged to alternately occupy the wedges. The processing temperature profile was as shown in Table 14.

Table 14 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 240 205 Zone 2 239 210 Zone 3 238 229 Zone 4 237 Zone 5 237 Transfer tube 238 229 Spinner 239 A knitted non-woven fabric was produced, and it was observed that the addition of the lubricant, sodium stearate, improved the processability of the polyamide.

Example 8 (Ex8) A nonwoven fabric bonded through air of nylon 6 / LLDPE wedge conjugate fibers was produced, which had the conjugate fiber configuration described in Example 7. The nylon 6 used was a polymerized polycaprolactam made up , which was produced by Nyltech, NH, and had a relative viscosity of formic acid of 1.85, a number average molecular weight of about 12,500 and a melt flow rate of 94 g / 10 min. The LLDPE used was 6811 A LLDPE. The conjugated fibers were produced and deposited to form a non-woven fabric spun-bonded according to example 7. The processing temperature profile was as shown in Table 15.

The non-woven fabric joined by spinning was attached by passing the fabric through a junction through air which was equipped with a source of heated air. The via-air linker is described in greater detail in the aforementioned United States patent No. 5,382,400. The heated air velocity and the heated air temperature were 200 feet / minute (61 m / minute) and 133 cm, respectively. The dwell time of the fabric on the cover was around 1 second. The resulting bonded fabric had a thickness of about 0.9 millimeters and a basis weight of about 85 g / m2.

Table 15 Temperature Placement (° C) Position Nylon 6 Polypropylene Extruder Zone 1 221 166 Zone 2 241 203 Zone 3 230 230 Zone 4 228 Zone 5 230 Transfer tube 229 230 Spinning organ 234 The non-woven fabric bonded through air had excellent uniform fiber coverage and exhibited good flexibility and elasticity.

As can be seen from the examples, the low molecular weight polyamide of the present invention can be processed with melt with polyolefins under melt processing conditions which are typically used to process the polyolefins, especially for producing polyolefin non-woven fabrics. This is highly unexpected since the melting points and the melt processing temperature of conventional polyamides are significantly higher than those of the polyolefins.

L asfib ra sc on polyolefin / polycaprolactam plays and the non-woven fabrics produced therefrom exhibit a combination of highly desirable properties, including tensile strength, tear resistance, abrasion resistance, a wider bonding temperature range , dyeing and hydrophilicity on polyolefin fibers and non-woven fabrics.

Claims (21)

1. A conjugated fiber comprising a polyolefin and a polyamide selected from polycaprolactam, copolymers of caprolactam and hexarnetylene adipamide, hydrophilic copolymers of caprolactam and ethylene oxide diamine, and mixtures thereof, wherein said polyamide has a number average molecular weight of up to about of 16,500.

2. The conjugated fiber as claimed in clause 1 characterized in that said polyamide is a polycaprolactam.

3. The conjugate fiber as claimed in clause 1 characterized in that it has a configuration selected from the side-by-side, sheath-core-concentric, eccentric sheath-core, wedge, core-wedge and island configurations in the sea.

4. The conjugated fiber as claimed in clause 3, characterized in that it has a hollow configuration.

5. The conjugated fiber as claimed in clause 1 characterized in that said polyamide has a number average molecular weight of between about 10,000 and about 16,200.

6. The conjugated fiber as claimed in clause 1 characterized in that it is a fiber bonded by spinning.

7. The conjugated fiber as claimed in clause 1 characterized in that it is a meltblown fiber.

8. The conjugated fiber as claimed in clause 1 characterized in that said polyolefin is selected from polyethylene, polypropylene, polybutylene, polypentene, polyvinyl acetate, polyvinyl chloride, polystyrene, and copolymers and mixtures thereof.

9. The conjugated fiber as claimed in clause 8 characterized in that said polyolefin. it is selected from high density polyethylene, linear low density polyethylene, isotactic polypropylene, mixtures of isotactic polypropylene and atactic polypropylene, syndiotactic polypropylene, and mixtures thereof.

10. A non-woven fabric comprising conjugated fibers, said conjugated fibers comprise a polyolefin and a polyamide selected from polycaprolactam, copolymers of caprolactam and hexamethylene adipamide, hydrophilic copolymers of caprolactam and ethylene oxide diamine, and mixtures thereof, wherein said polyamide has a Average molecular weight of number up to about 16,500.

11. The nonwoven fabric as claimed in clause 10 characterized in that said polyamide is a polycaprolactam.

12. The non-woven fabric as claimed in clause 10 characterized in that said polyolefin is selected from polyethylene, polypropylene, polybutylene, polypentene, polyvinyl acetate, polyvinyl chloride, polystyrene, and copolymers and mixtures thereof.

13. The nonwoven fabric as claimed in clause 10 characterized in that said conjugate fibers have a configuration selected from the side-by-side, concentric sheath-core, eccentric-sheath, wedge, core-wedge and of islands in the sea.

14. The nonwoven fabric as claimed in clause 10 characterized in that said polyamide has a number average molecular weight of between about 10,000 and about 16,200.

15. The non-woven fabric as claimed in clause 10, characterized in that said conjugated fibers are fibers joined by spinning.

16. The non-woven fabric as claimed in clause 10 characterized in that said conjugated fibers are meltblown fibers.

17. A laminate comprising the non-woven fabric as claimed in clause 10 and a film.

18. A laminate comprising the non-woven fabric as claimed in clause 10 and an additional non-woven fabric.

19. A process for producing a conjugated fiber comprising a polyolefin and a polyamide, which comprises the steps of: (a) extruding with melt a fiber-forming polyolefin; (b) extruding with melted polyamide selected from polycaprolactam, copolymers of caprolactam and hexamethylene adipamide, hydrophilic copolymers of caprolactam and ethylene oxide diamine, and mixtures thereof, said polyamide having a number average molecular weight of up to about 16,500; (c) supplying the extruded polyolefin and polyamide to an orifice of a spinning organ to form a unitary filament, wherein the melted polyolefin and polyamide entering said orifice are processed with melting to have melting temperatures from the point of melted from said polyamide and around 240oc.

20. The process as claimed in clause 19 characterized in that said polyamide is a polycaprolactam.

21. The process as claimed in clause 19 characterized in that said polyolefin is selected from polyethylene, polypropylene, polybutylene, polypentene, polyvinyl acetate, polyvinyl chloride, polystyrene, and copolymers and mixtures thereof.