RU2164969C2 - Fibers and textile materials from high-density polyethylene and method of manufacture thereof - Google Patents

Abstract

FIELD: polymer fibers. SUBSTANCE: for manufacture of fibers with melting index 4 to 1000 and M_z/M_w ratio below 2.2, both homopolymers and copolymers of ethylene can be used. Manufacture can be performed by stapling, blow molding from melt, or spinning from melt. Fibers can be used for fabricating textile materials and wear products. EFFECT: improved mechanical properties of fibers. 18 cl, 6 tbl

Description

The invention relates to fibers and textile materials made from polyethylene. The present invention also relates to a method for manufacturing such fibers and textile materials. In particular, the present invention relates to fibers and textile materials made from high density polyethylene (exceeding 0.940 g / cm ³ ), as well as to methods for their manufacture.

To date, the range of polyethylene used for the manufacture of fibers and textile materials has been largely limited to linear low density polyethylene (LLDPE). LLDPE is a copolymer of ethylene with another olefin or diene, the density of which is less than 0.940 g / cm ³ .

 Typically, polyethylene fibers and textile materials lack the strength properties of fibers and textile materials made from polypropylene. It is well known in the art that certain mechanical properties, such as tensile strength, of a given polymer with a change in density and molecular weight of this polymer change. Thus, for example, the difference between the strength properties of polyethylene and polypropylene could be partially eliminated if higher density and / or higher molecular weight polyethylene resins were used in the manufacture of fibers and textile materials. Moreover, in some applications, polyethylene textile materials are preferable to polypropylene. For example, items of clothing for medical personnel are often sterilized by gamma radiation. It is well known that, unlike polyethylene polypropylene textile materials, when they are treated with gamma radiation, they become brittle and emit a smell. Polyethylene textile materials, in addition, are more suitable for use in ultraviolet and beta radiation than polypropylene.

A variety of methods have been developed for the polymerization of olefins. In the 1940s Free radical polymerization processes have been developed. Upon receipt of such polymers as polyethylene, in accordance with this technology, the use of high pressures, high temperatures and initiators of free radical polymerization, in particular peroxides, is provided. However, in free radical polymerization processes, low density polyethylene (LDPE) is usually obtained, characterized by a degree of disordered branching with side groups of different lengths and densities ranging from about 0.910 to about 0.936 g / cm ³ .

In the late 1950s and early 1960s. Ziegler-Natta catalysts were widely used. These catalysts are used in a wide variety of processes, including low, medium and high pressure processes. Typically, the polymerization of ethylene using Ziegler-Natta catalysts produces a “linear” product, the polymer molecules of which are usually almost unbranched. Such linear polyolefins, as a rule, have a relatively high density of from about 0.941 to about 0.965 g / cm ³ , which is due to the denser packing of the polymer molecules and the minimum degree of entanglement compared to those characteristic of higher branched and less dense materials. When ethylene and a higher molecular weight α-olefin are copolymerized using Ziegler-Natta catalysts as a comonomer, a product can be obtained that does not contain detectable long side chains, but whose density decreases with increasing number of introduced units of a higher molecular weight α-olefin comonomer. The density of such linear low density polyethylene (LLDPE) can be from 0.860 to 0.940 g / cm ³ . One of the characteristics of polymer products obtained using Ziegler-Natta catalysts is their wide molecular weight distribution (MMP).

 Recently, technological difficulties in obtaining fibers from high density polyethylene resins have consisted in the fact that, with this MMP, such fibers more often tend to break or form "bumps" during molding than fibers from low density polyethylene. "Cones" are globules of polymer or foreign material that form on the surface on the front side of the die or on the thread itself when it is spun during passage through the die. The result of such breaks or bumps is low-quality textile materials, which can cause the shutdown of technological equipment, leading to loss of working time and cost of production.

 The presence in the polyethylene obtained with a Ziegler-Natta type catalyst, a relatively large number of materials of very low molecular weight and materials of very high molecular weight, causes the technological difficulties encountered in the processing of high density polyethylene. The presence in the polyethylene of a relatively large number of materials of very high molecular weight also creates difficulties in the spinneret drawing of threads to an acceptable small diameter due to an increase in the degree of entanglement, which leads to breakage of the thread. Another problem associated with the manufacture of fibers and textile materials from high density polyethylene is that such fibers tend to become dense and stiff, which makes the textile material coarse or "stiff". Such fibers may also be brittle. Therefore, the manufacture of fiber from high-density polyethylene resins obtained using Ziegler-Natta catalysts is traditionally considered technically impractical.

US Pat. No. 4,830,907 to Sawer et al. Describes the processing of LLDPE obtained using Ziegler-Natta catalysts into low linear density fibers. Sawer et al. Offer a complex material with a linear density of less than about 15 denier, obtained from LLDPE copolymer, the density of which is from about 0.86 to about 0.95 g / cm ³ , but they do not describe an example of such material from LLDPE- resin, the density of which exceeds 0.926 g / cm ³ .

For Kubo et al., US Pat. No. 5,068,141 describes a textile material made from LLDPE ethylene / octene-1 copolymers, the density of which is 0.900-0.940 g / cm ³ . However, Kubo et al. Deliberately limited the density of the LLDPE used according to their invention to 0.940 in order to achieve an acceptable reduction in the weight of the formed filaments, and the density of the resins from which the fibers were obtained was indicated as an example of 0.937 g / cm ³ .

 The use of catalysts with a single active site, such as metallocenes, instead of Ziegler-Natta catalysts in the polymerization process allows solving some problems of processing high density polyethylene. Polyethylene obtained using a metallocene catalyst system is characterized by a narrower molecular weight distribution and a more uniform distribution of comonomer units in comparison with polyethylene obtained using Ziegler-Natta catalysts. Although polyethylenes with such a narrow molecular weight distribution usually have a high average molecular weight, they effectively provide the formation of a polymer that does not contain a low molecular weight fraction, which causes technological difficulties in the formation of single strands. These products with a narrow molecular weight distribution are usually characterized by a higher level of crystallinity, because do not contain a low molecular weight fraction. However, since such polyethylenes do not include a large fraction of high molecular weight components, it is easier to stretch the filaments to smaller diameters than in the case of the known high-density polyethylenes, as a result of which they are characterized by acceptable softness and do not hamper body movements.

For Davey et al., US Pat. No. 5,322,728 describes the use of LLDPE obtained using a metallocene catalyst system for forming fibers, but the resin density is limited to a range of from about 0.86 to about 0.93 g / cm ³ .

 Thus, there is a need to create fibers and textile materials from high-density polyethylene resin in order to improve mechanical properties compared with the properties of fibers molded from low-density polyethylene resins without compromising processability or quality of the textile material.

In accordance with the present invention, new fibers are proposed either from an ethylene homopolymer or from a copolymer of ethylene and comonomer, the polymer density being at least 0.940 g / cm ³ , the MMP value is less than about 3.6, the melt index is in the range of about 4 to about 1000, and the ratio of M _z / M _w is less than about 2.2; and also offers textile materials, in the composition of which such fibers are used. The present invention also provides new methods for the manufacture of such fibers and textile materials. These fibers and textile materials are characterized by improved manufacturability and mechanical properties, as well as an improved fingerboard in comparison with fibers and textile materials made from polyethylene resins having a similar melt index and density, but obtained using a Ziegler-Natta catalyst. Unlike polypropylene fibers, these fibers are able to withstand sterilization by gamma irradiation, making them particularly effective for medical use. These fibers and textile materials made from them, unlike polypropylene fibers and textile materials, can also withstand the effects of ultraviolet and beta radiation. Good processability allows the formation of finer yarns than polyethylene yarns made using Ziegler-Natta catalysts, which makes it possible to produce a softer, more drapable textile material. High density also allows you to maximize some mechanical properties without compromising processability or quality of textile material. These fibers can be made in several ways, including melt spinning, melt blow molding, and staple fiber manufacturing. At relatively high processing speeds, these fibers are also characterized by fewer strand breaks and fewer bumps than polyethylene fibers made using Ziegler-Natta catalysts.

 Unexpectedly, these polyethylene fibers can be easily molded from resins of such a high density. It is also unexpected that the fibers of the invention form a soft, drapeable textile material and have increased strength and higher elongation compared to polymers having similar melt indices and densities obtained using Ziegler-Natta catalyst systems or other systems with many active sites. An advantage is also the improved characteristics of the process in comparison with the characteristics of processes using a similar material made from polymers obtained using catalysts with many active sites.

Description of Preferred Options
Resin Catalyst
The polyethylene resins used in the present invention are preferably prepared using a supported metallocene catalyst. Metallocene catalysts, as a rule, are such compounds of the transition metal with a bulky ligand, which can be obtained from products of the formula:
[L] _m M [A] _n ,
where L is a bulky ligand; A denotes at least one halogen leaving group, M denotes a transition metal, and the values of m and n are such that the total valency of the ligand corresponds to the valency of the transition metal. In a preferred embodiment, the catalyst is four-coordinated, whereby the compound is able to ionize to a 1 ⁺ charge state.

 Ligands L and A can be connected by a bridge, and in the presence of two ligands L and / or A, they can be connected by bridges. Such metallocene compounds may be full-sandwich compounds containing two or more L ligands, which may be cyclopentadienyl ligands or ligands derived from cyclopentadienes, or semi-sandwich compounds comprising one L ligand, which is a cyclopentadienyl ligand or derivatized ligand.

 Metallocene compounds contain many bonded atoms, preferably carbon atoms, forming a group that may be cyclic. The bulky ligand may be a cyclopentadienyl ligand or a ligand derived from cyclopentadienyl, which may be mono- or polycyclic or any other ligand capable of forming an η -5 bond to a transition metal atom. One or more bulky ligands may be π-bonded to a transition metal atom. As the transition metal atom, a transition metal atom of group 4, 5 or 6 and / or a transition metal atom from a number of lanthanides or actinides can be used. Other ligands may be bonded to the transition metal, such as at least one halogen as a leaving group that is capable of being separated from the transition metal. Non-limiting examples of metallocene catalysts and catalytic systems are described, for example, in US Pat. 93/08199.

 In the polymerization method of the present invention, a metallocene type catalyst system of various forms can be used. Examples of the development of metallocene catalysts in the art for ethylene polymerization are presented in US Pat. Nos. 4,871,705 issued to Hoel, 4,937,299 issued to Ewen et al., European Application A-0129368, published July 26, 1989, as well as US Patents. 5017714 and 5120867 issued to Welborn, Jr. These publications deal with the structure of metallocene catalysts and the inclusion of aluminoxane as a cocatalyst. There are various methods for preparing alumoxane, one of which is described in US Pat. No. 4,665,208.

 In addition, the metallocene catalyst component of the invention may be a heteroatom-containing monocyclopentadienyl compound. This heteroatom is activated either with alumoxane alone or with alumoxane with an ionizing activator to form an active polymerization catalyst system for producing polymers, which can be used according to the present invention. Catalytic systems of these types are described, for example, in publications WO 92 / 00333.94 / 07928 and 91/04257, in US patents 5057475, 5096867, 5055438 and 5227440 and in European application A-0420436. Moreover, metallocene catalysts that can be used according to the present invention may include non-cyclopentadienyl catalyst components or auxiliary ligands, such as boroles or carbolides, in combination with a transition metal. In addition, the scope of the present invention includes such catalysts and catalytic systems, which may be the products described in US patent 5064802 and publications WO 93/08221 and 93/08199 of April 29, 1993

 Preferred transition metals as components of the catalyst of the invention are Group 4 metals, in particular zirconium, titanium and hafnium. Such a transition metal may be in any oxidation state, preferably +3 or +4, or in a mixed oxidation state. All catalyst systems of the invention can be prepolymerized or used in conjunction with an additive or impurity-removing component to increase catalytic performance.

In the context of this description, the term "metallocene" is defined as indicating the content of one or more unsubstituted or substituted cyclopentadienyls or cyclopentadienyl residues in combination with a transition metal. In one embodiment, the metallocene catalyst component corresponds to the general formula (C _p ) _m MeR _n R ' _p , where at least one C _p is an unsubstituted or preferably substituted cyclopentadienyl ring, more preferably a monosubstituted cyclopentadienyl ring; Me is a transition metal of group 4, 5 or 6; R and R ′ are independently halogen, a hydrocarbyl group or a hydrocarboxyl group containing 1-20 carbon atoms; m is 1-3, n is 0-3 and p is 0-3, and the sum of m + n + p is equal to the oxidation state of Me.

In another embodiment, the metallocene catalyst component corresponds to the formulas
(C ₅ R ' _m ) _p R'' _s (C ₅ R' _m ) MeQ _3-px and
R '' _s (C ₅ R ' _m ) ₂ MeQ',
where Me is a transition metal of group 4, 5 or 6; C ₅ R ' _m is substituted cyclopentadienyl, each of R', which may be the same or different, is hydrogen, an alkyl, alkenyl, aryl, alkylaryl or arylalkyl radical containing 1-20 carbon atoms or two carbon atoms bonded to each other the formation of a part of a C ₄ -C ₂₀ ring, R ″, denotes a radical that bridges two rings (C ₅ R R _m ) or one ring (C ₅ R _{m m} ) with Me and contains one, several, or a combination of such representatives carbon, germanium, silicon, phosphorus or nitrogen atoms when p is m 0 and x denotes 1, and in other cases, "x" is always 0, each Q, which may be the same or different, denotes an aryl, alkyl, alkenyl, alkylaryl or arylalkyl radical containing 1-20 carbon atoms, or halogen , Q 'is an alkylidene radical containing 1-20 carbon atoms, s is 0 or 1, and when s is 0, m is 5, and p is 0, 1 or 2, and when s is 1, m is 4, and p is 1.

Although any metallocene catalyst component can be used according to the present invention, monosubstituted metallocenes are preferred over disubstituted. However, disubstituted and polysubstituted metallocenes are nevertheless better than equivalent catalytic systems, such as Ziegler-Natta systems, which are prepared in accordance with previously known methods. In yet another embodiment, a preferred metallocene catalyst component according to the invention corresponds to the formulas
(C ₅ H _n R ') R'' _s (C ₅ H _n R') MeQ ₂ and
R '' (C ₅ H _n R ') ₂ MeQ',
where Me is a transition metal of group 4, 5 or 6, each of R ', which may be the same or different, is hydrogen, an alkyl, alkenyl, aryl, alkylaryl or arylalkyl radical containing 1-20 carbon atoms, R "is a radical connecting two rings by a bridge (C ₅ H _n R ') and containing one, several, or a combination of such representatives as carbon, germanium, silicon, phosphorus, and nitrogen atoms, each of Q, which may be the same or different, denotes aryl, alkyl alkenyl, alkylaryl or a a rilalkyl radical containing 1-20 carbon atoms, or halogen, Q 'is an alkylidene radical containing 1-20 carbon atoms, s is 0 or 1, and when s is 1, n is 3, and when s is 0, n is 4.

In another embodiment, the metallocene catalyst component corresponds to the formula
R '' (C ₅ H ₃ R ') ₂ MeQ ₂ ,
where Me denotes a transition metal of groups 4, 5 or 6, each of R ', which may be the same or different, denotes hydrogen, alkyl, alkenyl, aryl, alkylaryl or arylalkyl radical containing 1-20 carbon atoms, R "denotes a radical connecting a single ring (C ₅ R ′ _m ) to Me with a bridge and containing one, several, or a combination of representatives such as carbon, germanium, silicon, phosphorus, and nitrogen atoms, each of Q, which may be the same or different, means aryl, alkyl, alkenyl, alkylaryl and whether an arylalkyl radical containing 1-20 carbon atoms, or halogen.

 In the context of this description, the terms “cocatalysts” and “activators” are used interchangeably and refer to any compound or component that is capable of activating a transition metal compound with a bulky ligand, or metallocene, as defined above. In addition to the use of alumoxane, the scope of the present invention includes the use of ionizing ionic activators or compounds, such as tri (n-butyl) ammonium tetra (pentafluorophenyl) boron, which ionizes a neutral metallocene compound. Such ionizing compounds may contain an active proton or some other cation that is bound but does not form a coordination bond with the remaining ion, or is very poorly coordinated with respect to this ion of the ionizing ionic compound. These compounds and their like are described in European applications 0520732, 0277003 and 0277004 and in US patents 5153157, 5198401 and 5241025.

 In the context of this description, the terms “carrier” and “substrate” are used interchangeably and can mean any carrier, preferably a porous carrier, capable of containing absorbed or adsorbed water, for example, such as talc, inorganic oxides, inorganic chlorides and tar carriers, such as polyolefin and other polymeric compounds or other organic carriers.

 Preferred carriers are inorganic oxide materials, which include those consisting of metal oxides of groups 2, 3, 4, 5, 13 and 14 of the Periodic Table of the Elements. In a preferred embodiment, the catalyst supports include silica, alumina, silica-alumina, and mixtures thereof. Other inorganic oxides that can be used either individually or in combination with silica, alumina or silica-alumina include magnesium oxide, titanium dioxide, zirconia, and the like. Other suitable carriers may be used, such as micronized polyolefins, such as polyethylene, and other polymeric compounds and inorganic compounds, such as magnesium dichloride and the like.

 In accordance with the present invention, the preferred moisture content of the carrier is from about 3 to about 27 wt.% Of the total weight of the carrier and the moisture contained therein, preferably in the range of from about 7 to about 15 wt.% And most preferably in the range of from about 9 up to about 14 wt.%. The amount of moisture contained in the carrier can be measured by a method that is well known in the art, for example, such as the calcination weight loss method (PVP).

Preparation of the catalyst used to obtain the resins
In the method for preparing the preferred catalyst system of the invention, the carrier is first contacted with a component capable of forming an activator for the metallocene catalyst component, as described above.

 In one embodiment, the preferred component is a compound with organometallic alkyls, alkoxides and halides and metals of groups 1, 2, 3, and 4. Preferred organometallic compounds are lithium alkyls, magnesium alkyls, magnesium alkyl halides, aluminum alkyls, silicon alkyls, silicon alkoxides, and silicon alkyl halides. More preferred organometallic compounds are aluminum alkyls and magnesium alkyls. The most preferred organometallic compounds are aluminum alkyls, for example, triethylaluminum (TEAL), trimethylaluminum (TALA), triisobutylaluminum (TIBAL), tri-n-hexylaluminum (TNGAL) and the like.

Most preferred are organometallic compounds which, when contacted with moisture contained in the carrier of the invention, form an oxygen-containing organometallic compound of the general formula
(R-AI-O) _n ,
which is a cyclic compound, as well as a compound of the general formula
R (R-Al-O) _n AlR ₂ ,
which is a linear or non-cyclic compound and mixtures thereof, including multidimensional structures. In this general formula, R is a C ₁ -C ₁₂ alkyl group, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, and n is an integer of 1-20. The most preferred oxo-containing organometallic compounds are aluminoxanes, for example methylaluminoxane and / or ethylaluminoxane.

 In a preferred embodiment, the carrier is introduced into the solution of the organometallic compound so that the temperature of the solution containing the organometal compound remains practically constant throughout the process of introducing the carrier, so that the temperature is always in the temperature ranges below.

In a liter flask equipped with a mechanical stirrer, 180 ml of TMAL in a heptane solution (concentration of 15 wt.%) And 90 ml of heptane were charged. This solution was cooled and kept at a temperature of 45 ^o F (7.2 ^o C). A 40-gram silica gel sample (Davison D-948 with an average particle size of 70 micrometers), which contained 12.5 wt.% Water, was slowly added to the flask over 70 minutes. The molar ratio of TMAL / H ₂ O was 0.91. Then, 0.9 g of (n-butylcyclopentyldienyl) ₂ ZrCl _{2 was} suspended in 20 ml of heptane, followed by addition to the vessel. The mixture was allowed to stand for 1 hour to give rise to a reaction at 165 ^° F (74 ^° C). Upon completion of the reaction, the solid was dried in a stream of nitrogen. After the preparation process, a free-flowing solid was obtained.

Resin Process
The resins used in the present invention are preferably prepared by a continuous suspension process. Such continuous suspension polymerization processes are well known to those skilled in the art. In the process of suspension polymerization, usually a pressure in the range of from about 1 to about 507 bar (from about 1 to about 500 atmospheres) and higher is maintained and a temperature in the range of from -60 to about 280 ^° C. is maintained. a suspension of solid polymer particles into which ethylene and comonomers are introduced, as well as often hydrogen together with the catalyst. A preferred liquid used in the polymerization medium is an alkane, cycloalkane or an aromatic hydrocarbon such as toluene, ethylbenzene or xylene. Under polymerization conditions, this medium should be a liquid that is relatively inert. In a preferred embodiment, hexane or isobutane is used. The operating parameters maintained in the process of obtaining varieties of polyethylene resin for carrying out the invention (resin A and resin B) are given in table. 1. It should be noted that resin A and resin B contain small amounts of hexene comonomer units. It will be apparent to those skilled in the art that other polymerization processes can be used to produce these resins, such as high pressure, medium pressure, and low pressure processes with polymerization in the bulk phase, gas phase, and solution phase.

Characterization of resins
In a preferred embodiment, the present invention provides a fiber consisting of a copolymer of ethylene with one or more comonomers, the density of this copolymer exceeding 0.940 g / cm ³ , preferably exceeding 0.945 g / cm ³ and most preferably exceeding 0.950 g / cm ³ , the MMP is less than 3.6; and a melt index [TS, according to ASTM D-1238 (E)] is from about 4 to about 1000. Those skilled in the art will recognize that a homopolymer having the same characteristics can also be used.

 In the case of the use of a comonomer in a preferred embodiment, each such comonomer contains 3-20, more preferably 3-10 carbon atoms and may be, for example, propylene, butene, hexene, octene, 4-methyl-1-pentene, styrene or combinations thereof. Preferred resins generally do not contain measurable long side chains.

Typically, in the manufacture of the fiber, the better, the narrower the MMP or the polydispersity index (M _w / M _n ), as a result of which the preferred MMP range is below about 3.6; more preferably, the MMP value is from 1.8 to 3.5, and most preferably from 2.0 to 3.1.

The ratio between the values of the third parameter (M _z ) and the second parameter (M _w ) on the curve for the molecular weight distribution is a measure of the fractions of very high molecular weight and very low molecular weight chains contained in the polymer. As indicated above, a polymer with a large fraction of relatively very low molecular weight chains tends to form cones during the spinning process, while the presence of a large fraction of relatively very high molecular weight chains causes low quality textile material and technological difficulties when drawing yarns of acceptable small diameters. Thus, the smaller the ratio M _z / M _w , the better for spinning. The preferred ratio M _z / M _w for the fibers and textile materials of the present invention is less than about 2.2. A ratio of M _z / M _{w of} less than about 2.0 is more preferred, and a ratio of M _z / M _{w of} less than about 1.9 is most preferred.

 In addition to the possibility of achieving such an extremely important factor as ensuring the target molecular weight distribution in the polymer resin molecules, the advantage of using metallocene-type catalysts is also that it allows more uniformly introduced units of comonomers of various sizes into the main polymer chain than in the case of Ziegler-Natta catalysts. In addition, metallocene-type catalysts can be effectively used in several different polymerization processes, including, for example, high pressure, medium pressure and low pressure polymerization, in the solution phase, bulk phase, suspension phase and gas phase.

 The preferred value of the IR of the polymer depends on the method by which the fiber is to be made. The fibers of the present invention can be formed by various methods well known in the art, including methods of stapling, melt blow molding and melt spinning. For staple molding, a preferred range is 4-60, with an IR of about 15 to about 35 being more preferred, and an IR range of about 25 to about 30 is most preferred. For the melt-blow molding method, the MI is preferably from about 10 to about 1000. For the melt-spinning method, the MI is preferably from about 4 to about 150. In the table. II provides melting point, molecular weight and molecular weight distribution data for the resins used in the present invention, as well as some comparative commercially available resins. All melt index and density values were determined according to ASTM D-1238 (E) and ASTM D-1505, respectively.

As shown in the table. II, the MMP values for resin A and resin B are 3.1 and 3.3, respectively, as opposed to 4.0 for high density polyethylene resin obtained using a Ziegler-Natta catalyst (product HD-6705 supplied by Exxon Chemical Company, Houston , Texas). In addition, the “marginal fractions” or the high and low molecular weight end portions of the molecular weight distribution curves for resins A and B are significantly smaller than the same fractions of polyethylene obtained using a Ziegler-Natta catalyst. It should be noted that the values of M _z / M _w for resin A and resin B are 1.81 and 1.86, respectively, while the M _z / M _w value for resin HD-6705 is 2.74.

Specialists in the art know that there are several methods for determining the MMP of a polyethylene sample. The values of molecular weights indicated in the table. II, was determined using a Waters gel permeation chromatography apparatus equipped with ultrastyrogel columns operating at 145 ^° C. Trichlorobenzene was used as an elution solvent. Sixteen polystyrenes of precisely known molecular weights, which were in the range from 500 to 5.2 million, were used as calibration standards. NBS 1475 polystyrene was also used as a calibration standard.

 The fibers of the invention are preferably used in the manufacture of textile materials, especially non-woven textile materials. It was found that textile materials made from such fibers have good mechanical properties and good drapability. Such fibers can be used to make garments, for example, surgical sheets and napkins, medical gowns and diaper linings, as well as filters and absorbents.

Properties of fibers and textile materials made from resins
Fibers were formed from resins A and B using melt stapling and blow molding processes. Resin fibers HD-6705 and EXACT ^™ 4023 were also molded for comparative purposes. EXACT ^™ 4023 was an ethylene-butene copolymer prepared using a metallocene catalyst and manufactured by Exxon Chemical Company, Houston, pc. Texas. The conditions for the stapling process are presented in table. III. Non-woven textile materials made of staple fiber were manufactured using a 1 meter Reicofil ^TM production line from Reifenhauser Company. The extruder size was 7 cm (2.75 inches) with a ratio between length and diameter of 30: 1. 3719 holes were provided in the die head, each of which had a diameter of 0.4 mm and a length to diameter ratio of 4: 1. The staple method is well known in the fabrication of textile materials. Usually continuous filaments are extruded, laid on an endless ribbon and then fastened together, usually with a hot calender roll. An overview of stapling techniques can be found at Wadsworth LC and Goswami BC in Non-Woven Fabrics: Spunbonded and Meltblown Processes, Materials from the Eighth Annual Non-Wovens Workshop, July 30-August 3, 1990, hosted by TANDEC, U. Tennessee, Knoxville.

 Staple fibers made from resin A and resin B, according to a number of parameters, had several advantages over fibers and textile materials based on resins obtained using Ziegler-Natta catalysts. In the table. III shows the data for two samples of products of stapling processes using each of the tested resins. Presented in the table. III data show that the normal operating conditions of the process using high density polyethylene resins of the present invention lasted longer with less technological difficulties than in the case of using comparative material based on resins obtained using Ziegler-Natta catalysts (0 cones for resin A in comparison with 2 cones for resin HD-6705 for longer periods of normal operation in the case of resin A). In general, the process of spinning fibers from the resins of the present invention proceeded well, confirming a qualitatively simpler spinning of fibers than in the case of processing resins obtained using Ziegler-Natta catalysts.

 In addition, the textile material made from these molded fibers was less coarse than the textile material from resin fibers obtained using Ziegler-Natta catalysts and did not give the impression of “greasy” touch, which is usually characteristic of fibers and textile materials from low density polyethylene.

 The results of the test to determine the physical properties of textile materials made in the process of stapling are shown in table. IV. The tensile force for the strip and the elongation at break were measured in accordance with ASTM D-1682-75. Measurements for stapled textile materials were performed using a United Model SSTM-1-E-PC tensile testing machine with a 13 cm (5 in) gap between the clamps and a 13 cm / min (5 in / min) slider speed. The overall signature of the neck was determined using a fingerboard and carcass of model 211-5 textile material in accordance with the TAPPI 4998 CM-85 test method with a gap of 0.64 cm (0.25 in) on a sample measuring 20 cm x 20 cm (8 inches x 8 inches).

From the data table. IV, it is obvious that with this weight characteristic of the textile material, the resins of the present invention make it possible to produce fibers having a higher tensile strength (tensile strength) and higher elongation at break than those made from an equivalent material obtained using a catalyst Ziegler-Natta, with similar melt index and density. Thus, the textile materials of the present invention are stronger and more “stretchable” than textile materials made from resins made using Ziegler-Natta catalysts. The fibers of the invention are characterized by improved mechanical properties compared to the properties of EXACT ^™ fibers.

 Further tests were carried out by spinning the fibers in accordance with the melt blow molding method. In the table. V shows the conditions of the process according to the method of blow molding from the melt. The technology of melt blow molding is well known in the art of manufacturing textile materials. An overview of such a technique can be found in Wadsworth L. C. and Goswami B.C. in "Non-Woven Fabrics: Spunbonded and Meltblown Processes", materials from the Eighth Annual Non-Wovens Workshop, July 30 - August 3, 1990, hosted by TANDEC, Universit. Tennessee, Knoxville, and the Meltblown Process, Meltblown Technology Today, Miller Freeman Publications, Inc., San Francisco, pc. California, 1989, pp. 7-12. Typically, in a melt-blow molding process, continuous filaments are extruded, typically at high speed and drawn by hot air, followed by collection on a collector drum. These filaments are typically held together by a combination of fiber coalescence and thermal bonding provided by the residual heat of extrusion and extraction by hot air. Depending on the end use of the textile materials, additional post-extrusion bonding may or may not be necessary. This test was carried out using a 51-cm (20-inch) Accurate Products Meltblown production line. The Davis Standard extruder was 5 cm (2 in) with a ratio between length and diameter of 30: 1. A 501 hole was provided in the die head. The diameter of each of the holes was 0.4 mm (0.015 in.). The length to diameter ratio in the die was 15: 1, and the air gap was set to 1.5 mm (0.060 inches).

In the table. VI shows the results of determining the physical properties of textile materials made by the method of spinning by melt-blow molding. The tensile strength test and relative removal of textile material from meltblown fiber was carried out in accordance with ASTM Standard 1682-75 (the same procedure as for textile materials made from staple fibers) using a tensile testing machine United System C Model 7-VI. The overall bar index was determined using the same instrument and method as for testing textile materials made of stapled fibers. As shown in the table. VI, textile materials made using resins A and B have the same or improved mechanical properties compared to the properties of textile materials from resins made using Ziegler-Natta catalysts, even with a much higher melt index (IR 64 for resin B in comparison with IR 20 for resin HD-6705). In addition, the fibers of the present invention were thinner than fibers made from resins prepared using Ziegler-Natta catalysts. This is the result of a narrower MMP and lower M _z / M _w ratio for resin B compared to its equivalent obtained using multiple site catalysts (HD-6705). The lower viscosity of resin B also contributed to the formation of thinner fibers. In such a process, a combination of both narrow MWD and low viscosity would be ideal (IR> 100).

 In the manufacture of fibers, it is preferable to use almost 100% by weight polyethylene homopolymers or copolymers. However, it must be borne in mind that resins A and B could be mixed with a wide variety of polar and non-polar polyolefins and thermoplastic rubbers, such as LLDPE, PP, EVA, EMA, EPA, EPDM, SBS, SIS, SEBS, etc. ., without departing from the scope of the present invention. The high density polyethylene resins of the present invention may also include additives, such as process improvers, pigments, dyes, stabilizers and flame retardants.

Claims (18)

1. Fibers comprising a polyethylene-based polymer, characterized in that the polymer density is at least 0.940 g / cm ³ , preferably at least 0.945 g / cm ³ and more preferably at least 0.950 g / cm ³ , the MMP is less than 3.6, preferably from 1.8 to 3.5, more preferably from 2.0 to 3.1, the melt index is from 4 to 1000, and the ratio M _z / M _w is less than 2.2, preferably less than 2 0 and more preferably less than 1.9. 2. The fiber according to claim 1, where the polymer is a copolymer of ethylene with at least one C ₃ -C ₂₀ alpha-olefin comonomer obtained using a metallocene catalyst.  3. The fibers of claim 2, wherein the comonomer is selected from the group consisting of propylene, butene, hexene, octene and 4-methyl-1-pentene.  4. Fibers according to any one of the preceding paragraphs, where the polymer is obtained by conducting a suspension process.  5. Fibers according to any one of the preceding paragraphs, where the polymer does not contain detectable long side chains. 6. A method of manufacturing a polymer fiber, comprising the step of extruding a polyethylene-based polymer through an opening, characterized in that the density of the copolymer is at least 0.940 g / cm ³ , preferably at least 0.945 g / cm ³ and more preferably at least 0.950 g / cm ³ , the MMP is less than 3.6, preferably from 1.8 to 3.5, more preferably from 2.0 to 3.1, the melt index is from 4 to 1000, and the ratio M _z / M _w is less than 2.2, preferably less than 2.0, and more preferably less than 1.9.  7. The method according to claim 6, where the polymer is obtained by conducting a suspension process.  8. The method according to any one of claims 6 to 7, wherein the polymer does not contain detectable long side chains. 9. The method according to any one of claims 6 to 8, wherein the polymer is a copolymer of ethylene with at least one C ₃ -C ₂₀ alpha-olefin comonomer obtained using a metallocene catalyst. 10. A method of manufacturing a textile material, comprising the steps of extruding the polymer through a plurality of holes to form a plurality of fibers, collecting these fibers using a collector device, and manufacturing a textile material comprising these fibers, the polymer being a polyethylene-based polymer, characterized in that the density the polymer is more than 0.940 g / cm ³ , preferably at least 0.945 g / cm ³ and more preferably at least 0.950 g / cm ³ , the MMP value is less than 3.6, preferably about from 1.8 to 3.5, more preferably from 2.0 to 3.1, the melt index is from 4 to 1000, the ratio of M _z / M _w is less than 2.2.  11. The method according to p. 10, where the polymer is obtained by conducting a suspension process.  12. The method according to any one of claims 10 and 11, wherein the polymer does not contain detectable long side chains. 13. The method according to any one of claims 10 to 12, where the polymer is a copolymer of ethylene with at least one C ₃ -C ₂₀ alpha-olefin comonomer obtained using a metallocene catalyst.  14. The method according to any one of paragraphs. 10 to 13, where the process is a stapling process, and the melt index is from 4 to 60, preferably from 15 to 35, and more preferably from 25 to 30.  15. The method according to any one of claims 10 to 13, where the process is a melt blow molding process, and the melt index is from 10 to 1000.  16. The method according to any one of claims 10 to 13, where the process is a melt spinning process, and the melt index is from 4 to 150.  17. A textile material comprising fibers according to any one of claims 1 to 5.  18. The product, which is a textile material according to 17.

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