MXPA00001105A - Soft nonwoven fabric made by melt extrusion - Google Patents

Abstract

A nonwoven fabric (2) having one or more layers of melt-extruded fibers (4, 6, 8) and having improved softness. The softness of the fabric (2) is improved by the addition of a softness-enhancing agent to a polyolefin melt prior to extrusion. The softness-enhancing agent is titanium dioxide (TiO2) or an additive having an active ingredient which is an oligomeric ester or both. If TiO2 is the only softness-enhancing agent in the polyolefin melt, then the percentage loading of the TiO2 is preferably 1-10%to achieve a desired enhanced softness. The TiO2 is preferably rutile or anitase grade. The percentage loading of the oligomeric ester additive in the polyolefin melt is preferably 0.2-10%to achieve a desired enhanced softness. The softness-enhancing agent can be added during the manufacture of a spunbond fabric, a spunbond/meltblown laminate, a spunond/spunbond laminate, and SMS laminate or any other composite formed from spunbond and/or meltblown layers.

Description

SOFT NON-WOVEN FABRIC MADE BY EXTRUSION OF CAST MATERIAL RELATED REQUEST This application claims the benefit of provisional application No. 60 / 054,081, filed on July 29, 1997.

FIELD OF THE INVENTION The invention relates to nonwoven fabric suitable for use as a component in a disposable diaper. In particular, the invention relates to non-woven fabric containing one or more layers of extruded fibers in the molten state.

BACKGROUND OF THE INVENTION The non-woven fabrics and laminated materials thereof have applications in a variety of disposable products, including wipes, garments, medical wipes and absorbent articles such as diapers. A class of non-woven mesh laminate materials is commonly referred to as spunbonded / meltblown / spunbond (SMS) laminates. These laminated materials SMS & amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; As used herein, the term "non-woven mesh" refers to a mesh that has a structure of individual fibers or filaments which are interspersed, but not in a repeating pattern that can be identified. As used herein, the term "spunbonded fibers" refers to fibers that are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries of a spinner. The cooling air is fed to an extinguishing chamber where the filaments are cooled. The cooling air is then sucked through a nozzle, which accelerates the flow of air. The friction between the air flow and the filaments creates a force that stretches the filaments, that is, decreases the filaments to a smaller diameter. The stretched filaments are then passed through a diffuser and deposited on a conveyor belt to form a non-woven mesh. A conventional spinning bonding technique is described in the patent E.U.A. No. 4,340,563 for Appel. As used herein, the term "meltblown fibers" refers to fibers that are formed by extruding molten thermoplastic material as threads or filaments through a plurality of thin, usually circular, capillaries of a die. A stream of high speed gas, normally heated (eg air), decreases the filaments of thermoplastic material in the molten state to reduce its diameter. After this, the fibers in the molten state are carried by the heated high-speed gas stream and are deposited on a collecting surface to form a mesh of randomly dispersed molten-fiber fibers. A conventional meltblowing technique is described in the patent E.U.A. No. 4,707,398 for Boggs. The meltblown fibers differ from the spunbond fibers in that the extruded polymer yarns have much finer diameters. These filaments of finer diameter are easily dispersed by the forced current of hot air before being deposited on the collecting surface. In addition, the meltblown fibers are substantially cooled by air so that they do not bind significantly. The binding of the mesh to retain the integrity and resistance is presented as a separate downstream operation. SMS fabrics lack the softness and feel of woven fabrics. The main problem is the presence of the melt-blown core layer, which causes the SMS structure to become stiff / rough after calendoring. Although the softness of the mixed SMS material can be improved by reducing the content of the meltblown material, i.e., by reducing the basis weight of the meltblown layer, there is a need to further increase the softness of the mixed SMS material. In addition, there is a need to improve the smoothness of the spunbond nonwoven fabric.

BRIEF DESCRIPTION OF THE INVENTION The present invention is a non-woven fabric containing one or more layers of extruded fibers in the molten state and having improved softness. The softness of the fabric is improved by adding a softness enhancing agent to a molten polyolefin material before ext noise. The softness enhancing agent according to a preferred embodiment is titanium dioxide (TiO2). If T 2 O 2 is the only softness enhancing agent in the molten polyolefin material, then the loading percentage of T 2 O 2 is preferably 1-10% to achieve a desired increase in softness. The TiO2 is preferably rutile or anitane grade. The softness enhancing agent according to another preferred embodiment is an additive having an active ingredient which is an oligomeric ester. The loading percentage of this additive in the molten polyolefin material is preferably 0.2-10% to achieve a desired increase in softness. The oligomeric ester preferably belongs to the class that increases the hydrophilic character of the polyolefin fibers. Alternatively, the oligomeric ester may belong to the class that increases the hydrophobic character of the polyolefin fibers. According to a further preferred embodiment of the invention, both the TiO2 and the oligomeric ester-based agent are added to the molten polyolefin material before extrusion. In this case the charge of TiO2 can be reduced to 0.2-4%. The invention can be applied in the manufacture of a spunbond fabric, a spunbond / spin-bonded laminate, an SMS laminate or any other mixed material formed from spunbond and / or meltblown layers. In accordance with the preferred embodiment of an SMS fabric, the softness-enhancing agents are added only to the melt-bonded melt materials. Alternatively, the softness enhancing agents can also be added to the meltblown melt material. The addition of TiO2 by itself, according to the invention, results in a fabric having increased softness and increased opacity. The addition of both TiO2 and the hydrophilic oligomeric ester-based agent according to the invention produces a fabric having increased softness, increased opacity, decreased coefficient of friction and increased hydrophilicity. The addition of both TiO2 and hydrophobic oligomeric ester-based agent according to the invention produces a fabric having increased softness, increased opacity, decreased coefficient of friction and increased hydrophobicity.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing the conventional laminate material construction of spunbond / meltblown / spunbonded fiber. Figure 2 is a schematic diagram showing the essential components of a system for continuously producing non-woven mesh material having increased softness in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention can be incorporated in a non-woven mixed material 2 of the type shown in Figure 1. This mixed non-woven material 2 contains a layer of meltblown fabric 4 of thermoplastic polymeric microfibers sandwiched between two layers of spunbonded fabric. and 8, each made from thermoplastic polymer filaments. According to a preferred embodiment, only the spin-bonded layers contain the softness-enhancing agents of the present invention. Alternatively, the softness enhancing agents can be added to the meltblown polymer. The meltblown fabric layer 4 can be prepared by extruding a base resin of a fiber-forming thermoplastic polymer in molten form through a plurality of fine capillaries., usually circular of a die. A stream of gas at high speed, normally heated (for example air) decreases the filaments of the molten thermoplastic material to reduce its diameter. Thereafter, the meltblown fibers are transported by the high velocity, heated gas stream and are deposited on a collecting surface to form a non-woven mesh of randomly dispersed meltblown fibers. In accordance with the preferred embodiment, the thermoplastic polymeric microfibers of the meltblown fabric layer 4 are polypropylene. Polymers other than polypropylene, such as nylon, polyethylene, polyester and copolymers and combinations thereof, can also be used. Each of the spunbond fabric layers 6 and 8 can be produced by continuously extruding a thermoplastic polymer through a plurality of fine, normally circular, capillaries of a spinner. Pressurized cooled air is fed to an extinguishing chamber where the filaments are cooled. The cooling air is then accelerated through a nozzle by positive air pressure. The friction between the air flow and the filaments creates a force that stretches the filaments, that is, decreases the filaments to a smaller diameter. The filaments are stretched to achieve molecular orientation and tenacity. The continuous filaments are then deposited in a substantially random form to form a mesh of molecularly oriented filaments substantially continuous and randomly arranged. The preferred thermoplastic polymer used to make the layers 6 and 8 of spunbonded fabric is polypropylene, although nylon, polyethylene, polyester and copolymers and combinations thereof can also be used. In accordance with the conventional structure of an SMS fabric as seen in Figure 1, the meltblown (MB) 4 fabric layer is sandwiched between two spunbonded fabric layers (SB) 6 and 8. All of these three layers of fabrics are joined by application of heat and pressure to form the fabric laminate material SMS 2. Figure 2 shows a production line 10 for producing a fabric laminate material SMS 2 according to the present invention. This production line can work at a speed in the range of 250 to 600 m / min, preferably around 375 m / min. The equipment of the production line 10 consists of an endless foraminous forming band 12 wrapped around the rollers 14 and 16. The band 12 is driven in the direction shown by the arrows. The production line 10 includes a forming machine which has three stations: spunbonding station 18, meltblowing station 20 and spunbonding station 22. First, the spunbonding station 18 places an 8th mesh spunbonded fibers 28 on the conveyor belt 12. Then the meltblowing station 20 places a mesh 4 of meltblown fibers 26 on the spunbonded mesh 8. Finally, the spinning junction station 22 places a 6-mesh net. of spunbonded fibers 30 on the meltblown web 4. Alternatively, each of the component layers of the web can be formed separately, rolled and subsequently converted to the SMS web laminate off-line. The spunbonding stations 18 and 22 are conventional extruders with spinners forming continuous filaments of a polymer and depositing those filaments on the forming band 12 in a random interlaced manner. Each spunbonding station can include one or more spinning heads depending on the speed of the process and the particular polymer that is being used. The formation of spunbonded material is a conventional process well known in the art. The meltblowing station 20 consists of a die 24 which is used to form microfibers 26. As the thermoplastic polymer leaves the die 24, the polymer threads are diminished and spread by high pressure fluid, usually air, to form the microfibers 26. The microfibers 26 are randomly deposited on the spunbond layer 8 and form a melt blown layer 4. The construction and operation of the meltblowing station 20 to form microfibers 26 is well known in the art. In accordance with the broad concept of the present invention, the basis weight of the melt-blown fabric layer may be in the range of 0.5 to 15.0 gm2, while the total basis weight of the spunbond fabric layers may be in the range of 0.5 to 15.0 gm2. the interval from 5.0 to 50.0 gm2. In addition, according to the invention, the melt-blown fibers have an average diameter of 1-10 μm, preferably 3-5 μm, while the fibers spun-bonded have an average diameter of 10-30 μm, preferably 12. -20 μm. The SMS fabric laminate according to the preferred embodiment has an average pore size in the range of 15-50 μm, preferably around 30-40 μm. The molten polypropylene used to make the meltblown fibers has a molecular weight distribution in the range of about 1.8-5.0, preferably 3.6, and a melt flow rate in the range of about 400-3000 grams / 10 minutes. , preferably of about 1000 grams / 10 minutes, while the molten polypropylene used to make the spunbonded fibers has a molecular weight distribution in the range of about 1.8-5.0, preferably 2.5-2.7, and a speed of melt flow in the range of about 10-100 grams / 10 minutes, preferably about 35 grams / 10 minutes. Outside the forming machine, the fabric laminate mesh SMS 2 (see Figure 2) is then fed through bonding rolls 32 and 34. The surface of the bonding rolls 32 and 34 are provided with a pattern of portions high which apply heat and pressure to thermally bond the three layers together. The bonding rolls are heated to a temperature that causes the meltblown polymer to soften. As the melt-blown mesh 4 passes between the heated bonding rolls 32 and 34, the bonding rolls compress and heat the mixed material in accordance with the pattern on the rolls to create a pattern of discrete bonding areas. Such discrete area or spot bonding is well known in the art and can be performed by means of heated rolls or by ultrasonic bonding. The bonding pattern is selected to provide the desired strength characteristics for the fabric. The bond pattern area is not limited in accordance with the present invention, although patterns of bond area in the range of 5-25%, preferably 14-19%, of the total area of the fabric are possible. Alternatively, the laminate may be ultrasonically knitted or bonded by melt rolling / adhesive glue. According to a further preferred embodiment of the invention, a spunbonded / spunbonded (SS) web laminate is formed by operating only spinning stations 18 and 22, i.e., meltblowing station 20. turns off. The softness enhancing agents of the present invention can be added to either or both spinning bundles. In this case, the nip rolls 32 and 34 must be heated to a temperature that causes the spin-bond polymer to soften. The SS fabric laminate will have the same tensile and stretch strength as an SMS fabric laminate having the same spunbonded layers since the meltblown layer does not contribute to these physical properties. According to a preferred embodiment of the invention, a spunbonded monolayer having increased softness can be manufactured. In this case, both the meltblowing station 20 and the second spinning joint station are turned off, and the softness enhancing agent is added to the polymer being fed to the spinning bonding station in operation. In accordance with a manufacturing method of the invention, the TiO2 is mixed with a base resin to form a master batch. This masterbatch is then mixed at a low percentage with the primary resin that is being supplied to one or more stations. The primary and base resins may be different or the same. According to a second manufacturing method of the invention, a hydrophilic additive is mixed with a base resin to form a masterbatch, which is then mixed at a low percentage with the primary resin that is being supplied to one or more stations. Alternatively, the masterbatch can be formed by mixing both the T¡O 2 and the hydrophilic additive with a base resin and then mixing the masterbatch with the main resin before feeding the molten polymeric material to the extruder. The preferred base and primary resins are polyolefins. In particular, the primary resin is preferably polypropylene, while the base resin is preferably either polyethylene or polypropylene. In a first test run, a master batch consisting of 70% T0O2 and 30% polyethylene (PE) was blended with molten polypropylene (PP) to produce spunbonded samples having a basis weight of 25 gm2 . The reduction was 4%, giving a composition of molten material of 2.8% TiO2, 1.2% polyethylene and 96% polypropylene. The softness and opacity of the fabric, as evaluated subjectively, were considerably greater than those of a control sample of 100% polypropylene (i.e., 0% TiO 2) spun bonded. The processing conditions during this test were similar for the control samples and the master lot samples of TiO2 / PE. The Uniformity of the fabric was also comparable. A second test run was made to evaluate the influence of TiO2 in an SMS configuration. A master batch consisting of 70% TiO 2 and 30% polyethylene (PE) was mixed with molten polypropylene (PP) only in cast spin bonding materials. The meltblown layer was formed from polypropylene or polyethylene without TiO2. Mixed SMS materials were produced having a variable base weight meltblowing layer, as indicated in the following table: TABLE I Total weight (gm2) Weight of MB (gm) Weight of SB (gm **) 18. 0 1.0 17.0 15.5 2.5 13.0 15.5 1.0 14.5 12.0 0.6 11.4 In addition, a mixed SMS material with a total basis weight of 15.5 gm2 was produced with a meltblowing layer of 2.5 gm2 using a master batch consisting of 70% TiO2 and 30% polypropylene at reductions of 2% and 4%. say the melt compositions for spunbonding were, respectively, 1.4 T02 / 98.6% polypropylene (2% reduction) and 2.8% TiO2 / 97.2% polypropylene (4% reduction). There was a significant improvement in softness for all SMS samples in which the spin-bonded layers incorporated T0O2. However, the uniformity of the fabric was more deficient compared to SMS control samples made with 0.27% T0O2. In order to study the influence of polyethylene only on the softness of the molten extruded polypropylene based fabric, a master batch consisting of 50% polypropylene and 50% polyethylene with molten polypropylene at 6% reduction was mixed to the melt-cast materials for spun bonding, ie, the melt composition for spin-bonding was 3.0% polyethylene / 97% polypropylene. Again the molten material for meltblowing consisted of polypropylene or polyethylene without T¡O2. These molten materials were used to produce mixed SMS materials having a total basis weight of 15.5 gm2 with meltblown base weights of 2.5 and 1.0 gm2, respectively. No significant improvement in softness was observed compared to polypropylene-based control samples. In another test run, a master batch consisting of 50% T0O2 and 50% polyethylene was blended with polypropylene to produce spunbonded fabric samples having a basis weight of 20 gm2. Reductions of 6%, 4% and 2% were used, giving compositions of molten material of 3.0% TiO2 / 3.0% polyethylene / 94% polypropylene, 2.0% TiO2 / 2.0% polyethylene / 96% polypropylene, and 1% TiO2 / 1.0% polyethylene / 98% polypropylene, respectively. Similarly, spunbond fabric was made from a masterbatch consisting of 50% TiO2 and 50% polypropylene blended with polypropylene at reductions of 6%, 4% and 2%. In these cases, the melt compositions were 3.0% TiO2 / 97% polypropylene, 2.0% TiO2 / 98% polypropylene and 1.0% TiO2 / 99% polypropylene, respectively. Again significant improvements in smoothness and opacity were observed. In accordance with the present invention, the TiO2 filler may be in the range of 1-10%, with about 2% being preferred. T0O2 of any of the rutile or anitase types can be used. The tests showed that master batches consisting of TiO2 mixed with either polyethylene or polypropylene provided improved softness when added to a melt-spinning material based on polypropylene. Initial observations indicated that the polyethylene-based masterbatch provided better softness than that provided by the polypropylene-based masterbatch. In addition, the softness of a mixed SMS material can be enhanced by adding TiO2 to one of the spunbonded layers but not to the other spunbonded layers and not to the meltblown layer. In addition, similarly, the smoothness of a mixed material SS can be improved by adding TiO2 to one but not to the other of the spunbond layers. According to a further preferred embodiment of the invention, the softness of the fabrics joined by spinning, SMS or other fabrics extruded in the molten state can be improved by using a molten additive which migrates to the surface during fiber formation. In particular, an oligomeric ester based additive was used to improve the softness of a spunbonded polypropylene based fabric. This additive increased the softness to a level of 0.5% or more. The molten additive was durable since it was not leached after the first attack. A test run was made in which a masterbatch consisting of 25% additive based on hydrophilic oligomeric ester and 75% polypropylene was mixed, with a final melt flow rate of approximately 60 grams / 10 minutes (PPM 11186). from Techmar PM, Rancho Dominguez, California), with polypropylene to produce samples of spunbonded cloth having a basis weight of approximately 24 gm2. Two levels of reduction were used: 2% and 10%, giving a final concentration of additive based on hydrophilic oligomeric ester in the meltbond material for spin bonding of 0.5% and 2.5%, respectively. The performance of the spinning joint station was 0.35 gm / hr / min; the fabric unit by spinning was joined by points with temperatures of 133.3 ° C and 131.6 ° C for the upper and lower connecting rollers, respectively. The resulting spunbonded fabrics had improved smoothness compared to the control samples made from polypropylene without additive based on hydrophilic oligomeric ester and the smoothness improved with increasing levels of additive. The physical properties of the samples that incorporate the additive based on the hydrophilic oligomeric ester are listed in Table 2: TABLE 2 Concentration of hydrophilic additive Property 0% 0.5% 2.5% Base weight (grn ^) 25.4 23.4 23.8 Thickness (mm) 0.2783 0.2350 0.2100 Resistance MD to traction (gm / 2.54 cm) 3010 2946 2750 Stretch MD @ rupture (%) 44.7 82 97 Resistance CD to the traction (gm / 2.54 cm) 1336 1543 1512 Stretch CD @ rupture (%) 58? 81.6 93.1 In accordance with a further aspect of the present invention, both the TiO2 and the hydrophilic additive can be added to the masterbatch to further increase the softness of a melt extrudate, for example, spin-bonded. To demonstrate this point, a test run was made in which a master batch consisting of 30% hydrophilic additive, 20% T0O2 and 50% polypropylene was mixed with polypropylene to produce spunbonded fabric samples having a basis weight of approximately 23 gm2. Two levels of reduction were used: 4% and 7.5%, giving a final concentration of hydrophilic additive in the melted material bonded by spinning of 1.2% and 2.2%, respectively and a final concentration of TiO2 in the melted material bonded by spinning of 0.8 % and 1.5%, respectively. The performance of the spinning joint station was 0.30 gm / hr / min; the spunbonded web was joined by dots with a temperature of 133.3 ° C for the upper and lower link rolls.

The performance of the second test was 0.30 gm / hr / min compared to 0.35 mg / hr / min for the first test. In addition, the softness and opacity were considerably better compared to the previous test run due to the addition of TIO2. The physical properties of the spin-bonded fabric that incorporates both the hydrophilic oligomeric additive and T TO2 are listed in Table 3: TABLE 3 Concentration of hydrophilic additive Property 0% L2% 2.2% Base weight (gm ^) 23O 22.6 23.2 Thickness (mm) 0.1675 0.2075 0.2100 MD resistance to traction (gm / 2.54 cm) 3006 3329 3351 MD stretch @ break (%) 50.4 79.5 93.9 DC resistance to traction (gm / 2.54 cm) 1141 1412 1505 Stretching CD @ rupture (%) 57.1 87.6 109.6 Coefficient of friction 0.63 0.33 0.3 The coefficient of friction was measured in accordance with ASTM Standard D 1894-75, "Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting," American Society for Testing and Materials, Part 35 (1977), p. 575-580. Compared to the coefficient of friction value of 0.63 for the control sample, the samples with 1.2% hydrophilic additive based on oligomeric ester had a coefficient of friction of 0.33 and the samples with 2.2% of hydrophilic additive based on ester oligomeric had a coefficient of friction of 0.3, indicating a significant improvement in smoothness. For the unit-by-spin fabric, the preferred levels for the hydrophilic additive based on oligomeric ester and TIO2 are 0.2-10% and 0.2-4%, respectively. When SMS fabrics are made, different levels of hydrophilic additive based on oligomeric ester can be incorporated into the melt and spinning beams to improve the penetration and rewet properties. In addition, hydrophilic agents can be applied topically to further improve hydrophilicity. To further test the concept of adding hydrophilic agents based on oligomeric ester to improve softness, test runs were conducted in which SS fabrics were made and spun-bonded. In the test runs, SS mixed materials with base weights of 10.45, 11.87 and 14.21 gm2 were manufactured using a master batch consisting of 30% hydrophilic additive, 20% T0O2 and 50% polypropylene (PPM 11253 from Techmar PM). The master batch was combined with polypropylene or both spinning bundles at a 4% reduction, giving final concentrations of hydrophilic additive based on oligomeric ester and Ti 2 in the spin-bonded melt of 1.2% and 0.8%, respectively. The same masterbatch of hydrophilic agent / Ti? 2 was used to produce a mixed SS material with a basis weight of 11.87 gm2, except that the master batch was combined with polypropylene or both spinning bundles at a 2.5% reduction, giving final concentrations of hydrophilic additive based on oligomeric ester and TiO2 in the spin-bonded melts of 0.75% and 0.5%, respectively . In addition, SS control samples without softness-enhancing agents were manufactured with base weights of 10.45, 11.87 and 14.21 gm2. The SS mixed materials with oligomeric ester and TiO2 additives had significantly improved softness compared to the control samples. The physical properties of the SS control samples and of the spin-bonded and SS prior fabrics are listed in Tables 4 and 5 respectively: TABLE 4 Controls Final concentration of UNCLE? Property 0.5% 0.5% 0.5% Base weight (gm ') 10.45 1 1 .88 14.21 Thickness (mm) 0.2025 0.2125 0.2325 MD resistance to traction (gm / 2.54 cm) 1412 1848 1764 Stretching MD @ rupture (%) 69 90 80 DC resistance to traction (gm / 2.54 cm) 535 741 1 156 Stretching CD @ rupture (%) 77 82 95 Coefficient of friction 0.57 0.54 0.62 TABLE 5 With additive in both beams Final concentration of Additive Property TÍO2 0.8% 0.8% 0.8% 0.8% Additive 1.2% 1.2% 1.2% 0.75% Base weight (gm¿) 10.45 11.88 14.21 11.88 Thickness (mm) 0.1825 0.1800 0.2350 0.1750 MD resistance to traction (gm / 2.54 cm) 1364 1463 1364 1559 MD stretch @ rupture (%) 87 85 103 81 Tensile strength CD (gm / 2.54 cm) 484 655 861 715 Stretching CD @ rupture (%) 72 87 196 85 Coefficient of friction 0.23 0.28 0.26 0.25 TABLE 6 Additive only! in a beam Final concentration of TiO? Property Make 1 - Additive 0.15% 0.15% 0.15% Make 2 - Ti02 0.75% 0.75% 0.75% - Additive 0.5% 0.5% 0.5% Base weight (gm ^) 10.45 11.87 14.21 Thickness (mm) 0.1950 0.1900 0.2500 MD resistance to traction (gm / 2.54 cm) 1475 1496 2018 Stretching MD @ break (%) 87 87 97 Resistance CD to the traction (gm / 2.54 cm) 614 502 941 Stretching CD @ rupture (%) 79 69 93 Coefficient of friction 0.32 0.33 0.34 Additional run runs were made in which SS fabric was made with a spinning yarn containing poopylene with 0.15% TiO2 and no oligomeric ester and the other spinning yarn comprising poopylene mixed with a master batch consisting of 30% hydrophilic additive base of oligomeric ester, 20% TiO2 and 50% poopylene. The masterbatch was combined with poopylene at a 5-0% reduction. The final concentration of hydrophilic additive based on oligomeric ester and TIO2 in the spin-bonded material was 0.75% and 0.5%, respectively. The softness at the level of 5% in one beam was lower than for the 2.5% in the two beams. The physical properties of the above SS fabric are listed in Table 6. Additional runs of test were made to test the effect of adding hydrophilic agents based on oligomeric ester to improve softness characteristics in mixed SMS materials. In these runs, SMS mixed materials with base weights of 10.86 and 9.62 gm2 were manufactured using a master batch consisting of 25% hydrophilic additive and 75% poopylene (11186 from Techmar PM) at reduction rates of 3% and 5% in both bundles of union by spinning giving final concentrations of 0.75% and 1.25%, respectively. The hydrophilic additive was not used in the meltblown material bundle. A white masterbatch of 50% TiO2 and 50% poopylene was used together with hydrophilic additive at a reduction rate of 0.33%, giving a final concentration of 0.17%, respectively. No TIO2 was used in the meltblown material bundle. Samples were also produced containing TiO2 but without hydrophilic additive with base weights of 10.86 and 9.62 gm2. The physical properties of the SMS fabric of 10.86 gm2 containing TiO2 with and without the hydrophilic additive are listed in table 7.

TABLE 7 Concentration of hydrophilic additive Property 0% 0.75% 1.25% Base weight (grn ^) 10.86 11.1 10.80 Thickness (mm) 0.1700 0.1893 0.1843 MD resistance to traction (gm / 2.54 cm) 1600 1715 1644 MD stretch @ rupture (%) 65 59 56 DC tensile strength (mg / 2.54 cm) 838 814 791 Stretching CD @ rupture (%) 68 58 58 Coefficient of friction 0.56 0.35 0.34 Mixed SMS materials with oligomeric ester and TiO2 had significantly improved softness characteristics as measured by the coefficient of friction. The samples with 0.75% and 1.25% had coefficients of friction of 0.35 and 0.34 respectively, compared to 0. 56 for the sample without additive. The reduction and final concentration of the oligomeric ester can be adjusted to affect the hydrophobic or hydrophilic properties. In this case, the hydrophobic character of SMS mixed materials with oligomeric ester were comparable with mixed materials SMS that do not have oligomeric ester. The level of hydrophilic additive based on oligomeric ester can be increased in order to achieve hydrophilic properties. In addition, hydrophilic agents can be used to treat the fabrics topically to further increase the hydrophilic character. Preferred embodiments of the invention have been described for illustrative purposes. Variations and modifications of the described preferred embodiments that fall within the scope of this invention will be readily apparent to those skilled in the art. It is intended that such variations and modifications be encompassed by the claims set forth hereinafter.

Claims (6)

NOVELTY OF THE INVENTION CLAIMS

1. - A nonwoven fabric containing a first layer of polyolefin fibers extruded in the molten state incorporating an additive based on oligomeric ester in an amount in the range of 0.2% to 10% of the weight of said fibers.

2. The non-woven fabric according to claim 1, further characterized in that said polyolemic fibers extruded in the molten state further incorporate TiO2 in an amount in the range of 0.2% to 4% of the weight of said fibers.

3. The non-woven fabric according to claim 1, further characterized in that said polyolefin fibers extruded in the molten state are spun-bonded.

4. The non-woven fabric according to claim 1, further characterized in that said polyolefin fibers extruded in the molten state are blown by fusion.

5. The non-woven fabric according to claim 3, further characterized in that it contains a second non-woven layer of spun-bonded polyolefin fibers laminated to said first non-woven layer.

6. The non-woven fabric according to claim 3, further characterized in that it contains a second non-woven layer of melt-blown polyolefin fibers laminated to said first non-woven layer. 7 .- The nonwoven fabric according to claim 6, further characterized in that it contains a third nonwoven layer of polyolefin fibers joined by spinning laminated to said second nonwoven layer. 8. The non-woven fabric according to claim 1, further characterized in that said additive based on oligomeric ester is hydrophilic. 9. The non-woven fabric according to claim 1, further characterized in that said additive based on oligomeric ester is hydrophobic. 10. The non-woven fabric according to claim 1, further characterized in that said fabric has a coefficient of friction of less than 0.5. 11. A method for manufacturing a non-woven mesh having improved softness, comprising the steps of: mixing an oligomeric ester-based additive with a base resin to form a masterbatch; mixing said masterbatch at a predetermined percentage with a primary resin to form a molten material; extruding said molten material through a plurality of capillaries of a molten material extrusion device to form a plurality of filaments; and depositing said filaments on a collecting surface to form a non-woven mesh of randomly dispersed fibers, characterized in that said base resin and said primary resin are polyolefins, said base additive being present j'-i of oligomeric ester in said molten material in an amount in the range of 0.2% to 10% by weight of said molten material. 12. The method according to claim 11, further characterized in that said additive based on oligomeric ester is hydrophilic. 13. The method according to claim 11, further characterized in that said additive based on oligomeric ester is hydrophobic. 14. The method according to claim 11, further characterized in that it comprises the step of mixing TiO2 with said base resin to form said masterbatch, the TiO2 being present in said molten material in an amount in the range of 0.2% to 4%. % of the weight of said molten material. 15. The method according to claim 11, further characterized in that said base resin is polyethylene and said primary resin is polypropylene.