NONWOVEN FABRICS MADE OF BICOMPONENT FIBERS

Abstract

The present invention relates to nonwoven fabrics comprising bicomponent fibers, wherein the bicomponent fibers comprise at least two distinct polymeric domains a) and b) in intimate adherence along the length of the fibers, and polymeric domain a) comprises a compound of formula (1), wherein the substituents are as defined in the specification, and polymeric domain b) is free of the compound of formula (1), as well as to the preparation of such nonwoven fabrics. Furthermore, the present invention is directed to corresponding bicomponent fibers.

##STR00001##

Claims

1: A nonwoven fabric, comprising bicomponent fibers, wherein the bicomponent fibers comprise at least two distinct polymeric domains a) and b) in intimate adherence along the length of the bicomponent fibers, and polymeric domain a) comprises a compound of formula (1), ##STR00007## wherein G.sub.1, G.sub.2, G.sub.3 and G.sub.4 are each independently C.sub.1-C.sub.4 alkyl, or G.sub.1 and G.sub.2 together or G.sub.3 and G.sub.4 together are pentamethylene; G.sub.5 and G.sub.6 are each independently hydrogen or C.sub.1-C.sub.4 alkyl; X is hydrogen, C.sub.1-C.sub.18 alkyl, C.sub.2-18 alkenyl, OC.sub.1-C.sub.18 alkyl, NHC.sub.1-C.sub.18 alkyl, N(C.sub.1-C.sub.6 alkyl).sub.2, phenyl, phenoxy or NH-phenyl; n is 1 or 2; and R.sub.1 is C.sub.2-C.sub.8 alkylene, C.sub.2-C.sub.8 hydroxyalkylene or C.sub.4-C.sub.36 acyloxyalkylene when n is 1, and (CH.sub.2).sub.2C(CH.sub.2).sub.2 when n is 2; and polymeric domain b) is free of the compound of formula (1).

2: The nonwoven fabric of claim 1, wherein G.sub.1, G.sub.2, G.sub.3 and G.sub.4 are each independently C.sub.1-C.sub.4 alkyl.

3: The nonwoven fabric of claim 1, wherein n is 1 and R.sub.1 is C.sub.4-C.sub.36 acyloxyalkylene.

4: The nonwoven fabric of claim 1, wherein X is hydrogen or C.sub.1-C.sub.18 alkyl.

5: The nonwoven fabric of claim 1, comprising a compound of formula ##STR00008##

6: The nonwoven fabric of claim 1, wherein polymeric domain a) comprises a compound of formula ##STR00009## and polymeric domain b) is free of the compound of formula (1).

7: The nonwoven fabric of claim 1, wherein polymeric domains a) and b) each independently comprise a polyolefin, a polyester, a polyamide, a polyvinyl chloride, a polyimide, a polyacrylonitrile, a polycarbonate or a polystyrene.

8: The nonwoven fabric of claim 1, wherein at least one of the polymeric domains a) and b) comprises a polyolefin.

9: The nonwoven fabric of claim 1, wherein each of the polymeric domains a) and b) comprises a polyolefin.

10: The nonwoven fabric of claim 1, wherein each of the polymeric domains a) and b) comprises a polypropylene.

11: The nonwoven fabric of claim 1, wherein the compound of formula (1) is present in polymeric domain a) in an amount of 0.001 to 5% by weight.

12: The nonwoven fabric of claim 11, wherein the compound of formula (1) is present in polymeric domain a) in an amount of 0.001 to 1% by weight.

13: A process for preparing nonwoven fabrics comprising bicomponent fibers having at least two distinct polymeric domains a) and b) in intimate adherence along the length of the fibers, the process comprising: i) separately melting at least two polymers wherein a first polymer comprises a compound of formula (1) as defined in claim 1, and a second polymer is free of the compound of formula (1), to obtain at least two melted polymers, ii) directing the at least two melted polymers through spinneret orifices, to form a plurality of bicomponent fibers, and iii) forming a layer from the plurality of bicomponent fibers.

14: A bicomponent fiber, comprising at least two distinct polymeric domains a) and b) in intimate adherence along the length of the bicomponent fibers, wherein polymeric domain a) comprises a compound of formula (1), ##STR00010## wherein G.sub.1, G.sub.2, G.sub.3 and G.sub.4 are each independently C.sub.1-C.sub.4 alkyl or G.sub.1 and G.sub.2 together or G.sub.3 and G.sub.4 together are pentamethylene; G.sub.5 and G.sub.6 are each independently hydrogen or C.sub.1-C.sub.4 alkyl; and X is hydrogen, C.sub.1-C.sub.18 alkyl, C.sub.2-18 alkenyl, OC.sub.1-C.sub.18 alkyl, NHC.sub.1-C.sub.18 alkyl, N(C.sub.1-C.sub.6 alkyl).sub.2, phenyl, phenoxy or NH-phenyl; n is 1 or 2; and R.sub.1 is C.sub.2-C.sub.8 alkylene, C.sub.2-C.sub.8 hydroxyalkylene or C.sub.4-C.sub.36 acyloxyalkylene when n is 1, and (CH.sub.2).sub.2C(CH.sub.2).sub.2 when n is 2; and polymeric domain b) is free of the compound of formula (1).

Description

EXAMPLES

A) Preparation of Nonwovens

[0079] Spunbond nonwovens are produced with polypropylene (Polypropylene HG475FB available from Borealis) with and without the Additive prepared as given below, on a 1 m wide Reicofil 4 line with a single beam having around 6800 holes per meter length. The holes have a diameter of 0.6 mm. Throughput per hole is set at 0.6 g/min. The line has a sheath-core configuration with 30% of the polymer in the sheath and 70% by weight of the polymer in the core. The Additive-containing fibers comprise the Additive only in the sheath, or for comparison purposes in all of the fiber. Furthermore for comparison fibers are prepared wherein both domains are free of the Additive. Nonwovens are produced with a fabric weight of 17 g/m.sup.2 (line speed: 235 m/min) and 70 g/m.sup.2 (line speed: 57 m/min), respectively. Target filament fineness is 2 dtex (dtex is a unit of measure for the linear mass density of fibers and is defined as the mass in grams per 10000 meters). The nonwovens are thermally bonded using an embossed roll.

[0080] The Additive given above and indicated in the following tables represents a mixture comprising 0.5% by weight of the compound of formula (3) and 99.5% by weight of polypropylene. Such mixture is prepared by mixing the compound of formula (3) with a polypropylene carrier (Moplen HP 561R) in a Berstorff twin screw extruder 25X32D at 200 C.

[0081] In case the Additive is used only in one polymeric domain, the given amount of Additive is based on the weight of only this polymeric domain (which in the examples is the weight of the sheath part).

[0082] In case the Additive is used in both polymeric domains, the given amount of Additive is based on the sum of the weight of both polymeric domains (which in the examples is the sum of the weight of the sheath and the core part).

[0083] Further processing conditions are given below: [0084] Extruder temperature is the temperature used for extrusion of the polypropylene or polypropylene/Additive blend on the Reicofil 4 line and is in all examples 250 C.; [0085] die temperature is the temperature of the polymer on the die and is in all examples 250 C.; [0086] cabin pressure is the pressure in the cabin after and below the die and is in all examples 4500 Pa; [0087] engraved and smooth rolls are rolls between which the fiber web is passed. [0088] nip pressure is the pressure between the engraved and smooth roll and is in all examples 80 N/mm

B) Evaluation of Mechanical Properties

[0089] The mechanical properties of the nonwoven fabrics are determined according to DIN EN 29073-3 with a sample clamping length of 100 mm, sample width of 50 mm, advance (deformation speed) of 200 mm/min.

[0090] Tensile Strength MD and Elongation MD are the corresponding maximum values measured in machine direction.

[0091] Tensile Strength MC and Elongation MC are the corresponding maximum values measured in a direction perpendicular to the machine direction.

C) Results

[0092]

TABLE-US-00001 TABLE 1 (fabric weight of nonwoven: 70 g/m.sup.2) Temperature of engraved roll: 153 C. Temperature of smooth roll: 150 C. Tensile Tensile strength strength Elongation Elongation MD [N] MC [N] MD [%] MC [%] No additive 87 55 30 38 2% by weight of 218 156 88 101 additive in all of the fibre, based on the weight of the whole fiber 2% by weight of 256 173 128 121 additive only in sheath, based on the weight of sheath part only.

TABLE-US-00002 TABLE 2 (fabric weight of nonwoven: 70 g/m.sup.2) Temperature of engraved roll: 147 C. Temperature of smooth roll: 144 C. Tensile Tensile strength strength Elongation Elongation MD [N] MC [N] MD [%] MC [%] No additive 66 43 21 33 2% by weight of 196 140 83 93 additive in all of the fibre, based on the weight of the whole fiber 2% by weight of 228 157 106 110 additive only in sheath, based on the weight of sheath part only.

TABLE-US-00003 TABLE 3 (fabric weight of nonwoven: 17 g/m.sup.2) Temperature of engraved roll: 153 C. Temperature of smooth roll: 150 C. Tensile Tensile strength strength Elongation Elongation MD [N] MC [N] MD [%] MC [%] No additive 38 22 68 69 2% by weight of 44 28 72 83 additive in all of the fibre, based on the weight of the whole fiber 2% by weight of 44 27 83 89 additive only in sheath, based on the weight of sheath part only.

[0093] The results clearly demonstrate the advantages of the present invention, according to which significantly better results can be obtained with respect to mechanical properties, when compared to the use of no Additive or the use of the Additive in the whole fiber. This, for example, provides the producer of nonwovens with the option to reduce weight while keeping still good mechanical performance of the product.

[0094] Compared to the use of the Additive in the whole fiber, the use in only one polymeric domain allows to use distinctive lower amounts of Additive.

[0095] In addition, the data also clearly show the improvement of processing safety, being able to run the process under more moderate conditions at lower thermobonding temperature (see temperature of engraved roll and smooth roll). At lower thermobonding temperature still good mechanical properties are obtained, which consequently allows to reduce thermobonding temperature. Furthermore, energy savings will be a secondary benefit.