Bi-component fiber

Abstract

The present invention relates to a bi-component fiber having a core-sheath construction wherein the core comprises a polypropylene composition and the sheath comprises a first polyethylene composition and a second polyethylene composition wherein the first polyethylene composition has a melt flow index determined according to ISO 1133-1: 2011 at 190 DEG C and 2.16 kg of 5.0-14 dg / min and comprises a high density polyethylene (HDPE) and / or a linear low density polyethylene (LLDPE), and the second polyethylene composition has a melt flow index of from 15 to 50 dg / min as determined according to ISO 1133-1: 2011 at 190 DEG C and 2.16 kg.

Description

[0001] The present invention relates to bicomponent fibers, methods for making such bicomponent fibers, nonwoven fabrics comprising such bicomponent fibers, methods for making such nonwoven fabrics, and articles comprising such nonwoven fabrics.

[0002] As a well-known thermoplastic, polyolefins have been widely used in clothing fibers, filter fibers, and especially nonwoven fabrics in the hygiene and medical fields, such as diapers, incontinence pads, sanitary wipes, and surgical gowns and surgical drapes. Compared with single-component systems (100% polypropylene (PP)-based polymers), the development of bicomponent fibers / nonwovens (such as combinations of polypropylene (PP), polyester (PET) and / or polyamide (PA) with polyethylene (PE)) has led to increasing demand from the industry and customers because such combinations can provide sufficient mechanical properties and other desired physical properties. During the bicomponent fiber processing, the molten polymers (such as PE and PP) meet each other at the outlet of the spinneret in a designed configuration, such as a sheath-core configuration.

[0003] WO2011115702 discloses a bicomponent fiber comprising a core and a sheath, wherein the core comprises a first component comprising polypropylene, and the sheath comprises a second component comprising a polyethylene composition, wherein the polyethylene composition has a density in the range of 0.945 to 0.965 g / cm, a molecular weight distribution (Mw / Mn) in the range of 1.70 to 3.5, a melt index (I2) in the range of 0.2 to 150 g / 10 min, a molecular weight distribution (Mz / Mw) in the range of less than 2.5, and a vinyl unsaturation in the range of less than 0.1 vinyl groups per 1000 carbon atoms present in the main chain of the composition.

[0004] EP1942213 discloses a fiber comprising a first polymer component and a second polymer component, wherein the first and second polymer components differ in at least one property, and wherein the second polymer component comprises a fiber having a density of 0.945-0.965 g / cm 3 and an ethylene-α-olefin copolymer having an MFR2 of 15-45 g / 10min.

[0005] An important property of nonwoven fabrics is skin feel, such as softness, smoothness and stiffness. Good mechanical properties, such as tensile strength and elongation, are also important for nonwoven fabrics. What is more important is that the fibers from which nonwoven fabrics are made can be produced in a stable manner.

[0006] The object of the present invention is to provide a fiber by which the above-mentioned and / or other problems can be solved.

[0007] Thus, the present invention provides a bicomponent fiber having a core-sheath configuration, wherein

[0008] The core comprises a polypropylene composition, and

[0009] The sheath comprises a first polyethylene composition and a second polyethylene composition, wherein

[0010] The first polyethylene composition has a melt flow index of 5.0 to 14 dg / min as measured according to ISO 1133-1:2011 at 190°C and 2.16 kg and comprises a high density polyethylene (HDPE) and / or a linear low density polyethylene (LLDPE), and

[0011] The second polyethylene composition has a melt flow index of 15 to 50 dg / min, measured according to ISO 1133-1:2011 at 190°C and 2.16 kg.

[0012] The invention further provides a nonwoven fabric comprising the fibers according to the invention.

[0013] Surprisingly, the fibers according to the invention can be produced in a stable manner, and the nonwoven fabrics produced according to the invention have a good skin feel as well as good mechanical properties.

[0014] Bicomponent Fibers

[0015] The bicomponent fibers according to the present invention have a core-sheath configuration.

[0016] Preferably, the weight ratio between core and sheath in the bicomponent fiber is from 85:15 to 40:60, such as from 80:20 to 50:50.

[0017] nuclear

[0018] The core of the bicomponent fiber comprises a polypropylene composition.

[0019] The amount of the polypropylene composition relative to the core may for example be at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.9 wt% or 100 wt%.

[0020] The polypropylene composition of the core comprises polypropylene. The polypropylene may be a propylene homopolymer, a propylene copolymer such as a propylene alpha olefin copolymer, or a random copolymer polypropylene.

[0021] The polypropylene and / or the polypropylene composition may have a melt flow index determined according to ISO 1133-1:2011 at 230°C and 2.16 kg of, for example, 5.0 to 50 dg / min, such as 15 to 35 dg / min.

[0022] The polypropylene composition may include additives such as nucleating agents and clarifying agents, stabilizers, fillers, plasticizers, antioxidants, lubricants, antistatic agents, anti-scratch agents, impact modifiers, acid scavengers, circulation additives, coupling agents, antimicrobial agents, anti-fog additives, slip additives, anti-blocking additives, polymer processing aids, flame retardants, colorants and the like. Such additives are well known in the art. Preferred additives include Irganox 1010, Irganox 168, Irganox 3114 and vitamin E. The amount of the additive may be, for example, 0-5% by weight.

[0023] The amount of polypropylene relative to the polypropylene composition may be, for example, at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.9 wt% or 100 wt%. Preferably, the total amount of polypropylene and additives is 100 wt% relative to the polypropylene composition.

[0024] sheath

[0025] The sheath of the bicomponent fiber comprises a first polyethylene composition and a second polyethylene composition.

[0026] The total amount of the first polyethylene composition and the second polyethylene composition relative to the sheath may be, for example, at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.9 wt% or 100 wt%.

[0027] Preferably, the weight ratio between the first polyethylene composition and the second polyethylene composition is 95:5-60:40, more preferably 90:10-70:30, even more preferably 85:15-75:25. This leads to particularly good properties of the nonwoven fabric according to the invention while ensuring high processability of the fibers according to the invention.

[0028] The first polyethylene composition and / or the second polyethylene composition may comprise additives. Examples of suitable additives are those mentioned as additives for the polypropylene composition. The amount of the additive may for example be 0-5 wt%.

[0029] The amount of polyethylene relative to the first polyethylene composition may be, for example, at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.9 wt% or 100 wt%. Preferably, the total amount of polyethylene and additives is 100 wt% relative to the first polypropylene composition.

[0030] The amount of polyethylene relative to the second polyethylene composition may be, for example, at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.9 wt% or 100 wt%. Preferably, the total amount of polyethylene and additives is 100 wt% relative to the second polypropylene composition.

[0031] First polyethylene composition

[0032] The first polyethylene composition has a melt flow index of 5.0-14 dg / min measured according to ISO 1133-1:2011 at 190°C and 2.16 kg. The melt flow index measured according to ISO 1133-1:2011 at 190°C and 2.16 kg is preferably 7.5-10 dg / min. This is advantageous for obtaining a nonwoven fabric with good mechanical properties.

[0033] The first polyethylene composition comprises high density polyethylene (HDPE) and / or linear low density polyethylene (LLDPE).

[0034] In some embodiments, the amount of HDPE relative to the first polyethylene composition is at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.9 wt% or 100 wt%. The use of HDPE in the sheath of the fiber results in good abrasion resistance of the nonwoven fabric made from the fiber according to the present invention.

[0035] In some embodiments, the amount of LLDPE relative to the first polyethylene composition is at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.9 wt%, or 100 wt%.Using LLDPE in the sheath of the fiber results in lower temperatures required for fiber bonding in making nonwoven fabrics.

[0036] Second polyethylene composition

[0037] The second polyethylene composition has a melt flow index measured according to ISO 1133-1:2011 at 190°C and 2.16 kg of 15 to 50 dg / min, preferably 20 to 30 dg / min.

[0038] The second polyethylene composition may comprise at least one of linear density polyethylene (LDPE), HDPE and LLDPE. Preferably, the second polyethylene composition comprises LDPE. The use of LDPE in combination with HDPE and / or LLDPE of the first polyethylene composition results in a lower temperature required for fiber bonding in making a nonwoven fabric. In addition, the use of LDPE in combination with HDPE and / or LLDPE of the first polyethylene composition ensures good spinnability, which ensures that fibers according to the present invention can be made in a stable manner.

[0039] In some embodiments, the amount of LDPE relative to the second polyethylene composition is at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.9 wt%, or 100 wt%.

[0040] HDPE, LLDPE, LDPE

[0041] The production methods of HDPE, LLDPE and LDPE are summarized in Andrew Peacock's Handbook of Polyethylene (2000; Dekker; ISBN 0824795466), pages 43-66.

[0042] HDPE

[0043] HDPE has a linear structure with almost no branches.

[0044] HDPE may be an ethylene homopolymer or may be an ethylene copolymer with, for example, butene or hexene as a comonomer.

[0045] Preferably, HDPE has a mass of 941-970 kg / m 3 , more preferably 950-967kg / m 3 , more preferably 960-967kg / m 3 The density is measured according to ISO1183.

[0046] Preferably, the HDPE has a melt flow index measured according to ISO 1133-1:2011 at 190°C and 2.16 kg of 5.0-14 dg / min, more preferably 7.5-10 dg / min.

[0047] Preferably, the HDPE has a molecular weight (Mw) of 80-150 kDa.

[0048] Preferably, the HDPE has a molecular weight distribution (Mw / Mn) of 7-30.

[0049] LLDPE

[0050] LLDPE has a linear structure with a large number of short branches.

[0051] Suitable technologies for the preparation of LLDPE include gas phase fluidized bed polymerization, solution polymerization, polymerization in the polymer melt under very high ethylene pressure and slurry polymerization.

[0052] LLDPE comprises ethylene and a C3-C10 α-olefin comonomer (ethylene-α-olefin copolymer). Suitable α-olefin comonomers include 1-butene, 1-hexene, 4-methylpentene and 1-octene. The preferred comonomer is 1-butene.

[0053] Preferably, the amount of units derived from the comonomer in the copolymer is from 1.0 to 5.0% by weight.

[0054] Preferably, LLDPE has a mass of 910-940 kg / m 3, more preferably 920-940kg / m 3 , more preferably 925-935kg / m 3 The density is measured according to ISO1183.

[0055] Preferably, the LLDPE has a melt flow index measured according to ISO 1133-1:2011 at 190°C and 2.16 kg of 5.0-14 dg / min, more preferably 7.5-10 dg / min.

[0056] Preferably, the LLDPE has a molecular weight (Mw) of 50-100 kDa.

[0057] Preferably, the LLDPE has a molecular weight distribution (Mw / Mn) of 1.1-8.0.

[0058] LDPE

[0059] LDPE has a long chain branched structure.

[0060] LDPE can be produced by using autoclave high pressure technology and by tubular reactor technology.LDPE may be an ethylene homopolymer or may contain comonomers such as 1-butene or 1-hexene.

[0061] Preferably, LDPE has a mass of 910-940 kg / m 3 , more preferably 913-935kg / m 3 , more preferably 915-925kg / m 3 The density is measured according to ISO1183.

[0062] Preferably, the LDPE has a melt flow index measured according to ISO 1133-1:2011 at 190°C and 2.16 kg of 15-50 dg / min, preferably 20-30 dg / min.

[0063] Preferably, the LDPE has a molecular weight (Mw) of 50-200 kDa.

[0064] Preferably, LDPE has a molecular weight distribution (Mw / Mn) of 4-30.

[0065] The bicomponent fibers according to the present invention can be prepared in any desired thickness depending on the desired end use. Typical thicknesses are known to the skilled person and may be, for example, 0.5-100 denier, such as 1-50 denier.

[0066] Other aspects

[0067] The present invention further provides a method for making a bicomponent fiber according to the present invention, comprising the following steps:

[0068] providing a melt of a polypropylene composition and melts of a first polyethylene composition and a second polyethylene composition, and

[0069] The melt of the polypropylene composition and the melts of the first polyethylene composition and the second polyethylene composition are extruded through a spinneret to obtain bicomponent fibers.

[0070] The first polyethylene composition and the second polyethylene can be dry blended, then fed to an extruder and melted therein to obtain a melt of the first polyethylene composition and the second polyethylene composition. Alternatively, each of the first polyethylene composition and the second polyethylene composition can be fed to an extruder and melt mixed together to obtain a melt of the first polyethylene composition and the second polyethylene composition.

[0071] The invention further provides a nonwoven fabric comprising the fibers according to the invention.The nonwoven fabric according to the invention may have a fabric weight of, for example, 10 to 25 gsm.

[0072] The present invention further provides an article comprising the nonwoven fabric according to the present invention. Preferably, the article is selected from upholstery, apparel, wall coverings, carpets, diaper topsheets, diaper backsheets, medical fabrics, surgical wraps, hospital gowns, wipes, textiles, and geotextiles.

[0073] The invention further provides a process for making a nonwoven fabric according to the invention, which comprises providing fibers according to the invention and bonding the fibers to obtain a nonwoven fabric.

[0074] The present invention further provides the use of an LDPE having a melt flow index of 15-50 dg / min, measured according to ISO 1133-1:2011 at 190° C. and 2.16 kg, for improving the smoothness of a nonwoven fabric comprising bicomponent fibers having a core-sheath configuration, wherein the core comprises a polypropylene composition and the sheath comprises a first polyethylene composition and a second polyethylene composition, wherein the first polyethylene composition has a melt flow index of 5.0-14 dg / min, measured according to ISO 1133-1:2011 at 190° C. and 2.16 kg and comprises a high density polyethylene (HDPE) and / or a linear low density polyethylene (LLDPE), and the second polyethylene composition comprises LDPE.

[0075] It is to be noted that the present invention relates to the subject matter defined in the independent claims, alone or in combination with any possible combination of features described herein, with particular preference given to those combinations of features present in the claims. It will therefore be appreciated that all combinations of features relating to the composition according to the invention; all combinations of features relating to the method according to the invention as well as all combinations of features relating to the composition according to the invention and all combinations of features relating to the method according to the invention are described herein.

[0076] It is also noted that the term "comprising / including / containing" does not exclude the presence of other elements. However, it is also understood that a description of a product / composition comprising certain components also discloses a product / composition consisting of these components. A product / composition consisting of these components may be advantageous because it provides a simpler and more economical method for preparing the product / composition. Similarly, it is also understood that a description of a method comprising certain steps also discloses a method consisting of these steps. A method consisting of these steps may be advantageous because it provides a simpler and more economical method.

[0077] When the values ​​of the lower limit and the upper limit of a parameter are mentioned, it should also be understood that the range formed by the combination of the value of the lower limit and the value of the upper limit is disclosed.

[0078] The invention will now be illustrated by the following examples without being limited thereto. Example

[0079] Table 1

[0080]

[0081]

[0082] The MFI of PP is measured according to ISO 1133-1:2011 at 230°C and 2.16 kg; the MFI of PE is measured according to ISO 1133-1:2011 at 190°C and 2.16 kg.

[0083] Dow Aspun 6834 and Dow Aspun 6850 are polyethylene materials commercially available from Dow as fiber grade resins.

[0084] PP1, HDPE1, HDPE2, Dow Aspun 6834 and 6850 and LLDPE1 contain standard stabilizers.

[0085] Bicomponent fibers and spunbond nonwoven fabrics having a core-sheath structure were produced using the materials in Table 1. Process conditions were set according to Table 2 so that bicomponent fibers were obtained from the composition of Table 3, and a spunbond nonwoven fabric of about 20 gsm was produced from the obtained fibers.

[0086] Table 2 shows the spinnability of the fibers and whether dripping problems occurred during the spinning process.

[0087] The following properties were measured for the obtained spunbonded nonwoven fabrics and are shown in Table 3:

[0088] Measure tensile strength in machine direction (MD) and cross direction (CD) according to ASTM D5035-11

[0089] Elongation in the machine direction (MD) and cross direction (CD) was measured according to ASTM D5035-11

[0090] Smoothness measured by the standards in TSA (Towel Softness Analyzer) Leaflet Collection No. 11, November 13, 2014, emtec Electronic GmbH, Leipzig, Germany.

[0091]

[0092]

[0093] It can be appreciated that the nonwoven fabrics made of bicomponent fibers having a PP core / PE sheath configuration (CEx2-11 and Ex12-15) have better smoothness than the nonwoven fabric made of fibers made of only PP (CEx1).

[0094] When the sheath was made of DOW ASPUN 6850 or 6834 (CEx 2-3), the fiber had good spinnability and no dripping problem occurred. However, the nonwoven fabric did not show good smoothness.

[0095] When the sheath was made of LDPE 2-4 (CEx 4-6), the fibers had good spinnability and no dripping problems occurred. The nonwoven fabric showed good smoothness. However, the fibers showed poor adhesion and the nonwoven fabric had low mechanical properties.

[0096] When the sheath was made of LDPE1 with a relatively low MFI (CEx 7), the fiber had poor spinnability and dripping problems occurred.

[0097] When the sheath was made of LLDPE1 (CEx 8 and CEx 11), the fiber had good spinnability but a dripping problem occurred. Adding LDPE4 to LLDPE1 (Ex 12) solved the dripping problem. The nonwoven fabric of Ex 12 showed sufficiently high mechanical properties and very good smoothness.

[0098] When the sheath was made of HDPE1 with a relatively low MFI (CEx 10), the fiber had poor spinnability and dripping problems occurred.

[0099] When the sheath was made of HDPE2 (CEx 9), the fiber had good spinnability, but a dripping problem occurred. Adding LDPE4 to HDPE2 (Ex 13-15) solved the dripping problem. The nonwoven fabrics of Ex 13-15 showed sufficiently high mechanical properties and very good smoothness. In particular, Ex 14 using 16% HDPE / 4% LDPE led to excellent results.

[0100] It was thus found that adding LDPE to HDPE or LLDPE in the sheath of the fiber significantly improves the processability of the polyethylene composition and prevents dripping during fiber production. The nonwoven fabric has excellent smoothness.

Claims

1. A bicomponent fiber having a core-sheath structure, wherein The core comprises a polypropylene composition, and The sheath comprises a first polyethylene composition and a second polyethylene composition, wherein The first polyethylene composition has a melt flow index of 5.0-14 dg / min measured according to ISO 1133-1:2011 at 190°C and 2.16 kg and comprises a high density polyethylene (HDPE) and / or a linear low density polyethylene (LLDPE), and The second polyethylene composition has a melt flow index of 15-50 dg / min measured according to ISO 1133-1:2011 at 190° C. and 2.16 kg, wherein the second polyethylene composition comprises a low density polyethylene (LDPE), wherein the LDPE has a melt flow index of 910-940 kg / m 3 The density is measured according to ISO1183.

2. The bicomponent fiber according to claim 1, wherein the LDPE has a molecular weight of 913-935 kg / m 3 , preferably 915-925kg / m 3 The density is determined according to ISO 1183, preferably wherein LDPE is an ethylene homopolymer.

3. The bicomponent fiber according to any one of the preceding claims, wherein the first polyethylene composition has a melt flow index of 7.5 to 10 dg / min, measured according to ISO 1133-1:2011 at 190°C and 2.16 kg.

4. The bicomponent fiber according to any one of the preceding claims, wherein the first polyethylene composition comprises HDPE and the HDPE has a strength of 941-970 kg / m 3 , more preferably 950-967kg / m 3 , more preferably 960-967kg / m 3 The density is determined according to ISO 1183, preferably wherein HDPE is an ethylene homopolymer.

5. The bicomponent fiber according to any one of the preceding claims, wherein the first polyethylene composition comprises LLDPE and the LLDPE has a molecular weight of 910-940 kg / m 3 , more preferably 920-940kg / m 3 , more preferably 925-935kg / m 3 The density is determined according to ISO 1183, preferably wherein the LLDPE is a copolymer of ethylene and 1-butene, preferably wherein the amount of units derived from 1-butene in the copolymer is 1.0-5.0 wt%.

6. The bicomponent fiber according to any one of the preceding claims, wherein the weight ratio between the first polyethylene composition and the second polyethylene composition is from 95:5 to 60:40, preferably from 90:10 to 70:

30.

7. The bicomponent fiber according to any one of the preceding claims, wherein the weight ratio between the first polyethylene composition and the second polyethylene composition is from 85:15 to 75:

25.

8. A bicomponent fiber according to any one of the preceding claims, wherein the weight ratio between the core and the sheath is from 85:15 to 40:60, such as from 80:20 to 50:

50.

9. A method for making a fiber according to any one of the preceding claims, comprising the steps of providing a melt of the polypropylene composition and a melt of the first polyethylene composition and the second polyethylene composition, and extruding the melt of the polypropylene composition and the melt of the first polyethylene composition and the second polyethylene composition through a spinneret to obtain the fiber.

10. A nonwoven fabric comprising the fibers according to any one of claims 1 to 8.

11. The nonwoven fabric according to claim 10, wherein the nonwoven fabric has a smoothness of at most 110, more preferably at most 104, more preferably at most 95, measured according to the standards in TSA (Tissue Softness Analyzer) Information Booklet No. 11, published on November 13, 2014 by emtec Electronic GmbH, Leipzig, Germany.

12. A method for making a nonwoven fabric according to claim 10 or 11, comprising providing fibers according to any one of claims 1 to 9 and bonding the fibers to obtain the nonwoven fabric.

13. An article comprising the nonwoven fabric according to claim 10 or 11, preferably wherein the article is selected from the group consisting of upholstery, apparel, wall coverings, carpets, diaper topsheets, diaper backsheets, medical fabrics, surgical wraps, hospital gowns, wipes, textiles, and geotextiles.

14. Use of LDPE having a melt flow index of 15-50 dg / min, measured according to ISO 1133-1:2011 at 190° C. and 2.16 kg, for improving the smoothness of nonwoven fabrics comprising bicomponent fibers having a core-sheath configuration, wherein The core comprises a polypropylene composition, and the sheath comprises a first polyethylene composition and a second polyethylene composition, wherein The first polyethylene composition has a melt flow index of 5.0-14 dg / min measured according to ISO 1133-1:2011 at 190°C and 2.16 kg and comprises a high density polyethylene (HDPE) and / or a linear low density polyethylene (LLDPE), and The second polyethylene composition comprises LDPE.

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