Polymer composition for producing gel extruded articles and polymer articles made therefrom

Abstract

To provide a polymer composition for producing gel extruded articles.SOLUTION: A polymer composition contains polyethylene particles combined with a plasticizer. The polyethylene particles are particularly selected so that the particles rapidly form a homogeneous gel-like material when combined with the plasticizer during gel processing. In one embodiment, the polyethylene used to produce the particles has a relatively low bulk density. Alternatively or in addition, the particles can have a carefully controlled particle size distribution. Polymer articles such as fibers and films can be produced having little to no imperfections.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001]

[0001] This application claims priority to U.S. Provisional Application No. 62 / 546,857, filed on August 17, 2017, the entire disclosure of which is incorporated herein by reference.

Background Art

[0002]

[0002] Polyethylene polymers have many diverse uses and applications. For example, high-density polyethylene is a valuable engineering plastic with a unique combination of abrasion resistance, surface lubricity, chemical resistance, and impact strength. They have found use in the manufacture of high-strength fibers for use in ropes and ballistic moldings, as well as in the manufacture of other elongated articles such as membranes for lithium batteries. However, since the fluidity of these materials in the molten state decreases as the molecular weight increases, processing by conventional techniques such as melt extrusion is not always possible.

[0003]

[0003] Another method for manufacturing fibers and other elongated parts from polyethylene polymers is by gel processing, in which the polymer is mixed with a solvent. The resulting gel can be extruded into fibers or membranes and stretched in one or two directions. Also, some or all of the solvent can be removed from the product.

[0004] However, in the past, there have been problems with gel-processed polyethylene polymers. For example, during the gel extrusion of polyethylene polymers, the physical properties of the resulting product may be impaired by the appearance of gel specks. Gel specks generally refer to polyethylene polymers that are not completely dissolved or not intimately mixed with the solvent in other forms during the extrusion process. For example, when forming a film, these gel specks can render the product unusable for some applications such as battery separator applications. In the past, to remove gel specks, gel processing has been carried out using lower molecular weight polymers, which may reduce the strength of the resulting product. Alternatively, the processing time can be increased to preferably eliminate gel specks before extrusion. However, an increase in processing time reduces throughput and increases the cost of the process.

[0005] In view of the above, there is a need for an improved polyethylene composition that can be gel spun or gel extruded at a relatively fast rate without forming gel specks or other impurities. There is also a need for an improved method for manufacturing extruded articles from polyethylene polymers using gel processing. SUMMARY OF THE INVENTION

[0006] Generally, the present invention relates to a polyethylene composition well-suited for gel processing applications. The polyethylene composition can be used, for example, to manufacture elongated articles such as films, membranes, fibers, and the like. According to the present invention, polyethylene such as high-density polyethylene resin is mixed with a plasticizer to form a gel-like material. According to the present invention, the polyethylene resin is specifically selected to have a carefully controlled bulk density and / or a carefully controlled particle size distribution. This characteristic of the polyethylene resin has been found to dramatically improve the rapid formation of the gel-like material without residual gel specks or impurities that can cause defects in the product when the composition is extruded.

[0007]

[0007] For example, in one embodiment, the present invention relates to a polymer composition for manufacturing a gel extruded article. The polymer composition includes a plasticizer blended with a polyethylene resin. The polyethylene resin can be formed from high density polyethylene such as high molecular weight polyethylene. In one embodiment, for example, the resin is formed from ultra-high molecular weight polyethylene. The polyethylene resin is mixed with a plasticizer to produce an extrudable gel-like composition. According to the present invention, the polyethylene resin has the following characteristics: (1) A bulk density of less than about 0.35 g / cm 3 ; and / or (2) A median particle size (d50) of less than 125 microns, where 90% of the particles have a particle size of less than about 180 microns; and has at least one of the above. In one embodiment, the polyethylene resin particles include both of the above characteristics. It has been found that the above polyethylene particles dramatically improve the gel processability of the polyethylene polymer. For example, it has been found that polyethylene particles having at least one of the above characteristics can be rapidly mixed with a plasticizer to produce a uniform gel-like material. Therefore, the above composition can be placed in an extruder to produce a gel-like composition in a very short time and without forming gel specs or other small particles that are not dissolved or not uniformly blended with the plasticizer in other forms.

[0008]

[0008] As described above, in one embodiment, the high density polyethylene particles may have a relatively low bulk density to improve the blend with the plasticizer. The bulk density may be, for example, in one embodiment, less than about 0.3 g / cm 3 , for example less than about 0.28 g / cm 3 , for example less than about 0.26 g / cm 3 . The bulk density is generally higher than about 0.15 g / cm 3 .

[0009] Alternatively, in addition to having a low bulk density, the polyethylene particles may also have a relatively small median size (d50). For example, the polyethylene particles may have a median particle size (d50) from about 60 microns to less than 125 microns, such as from about 70 microns to about 110 microns. Further, 90% of the high density polyethylene particles may have a particle size of less than about 170 microns, such as less than about 165 microns, such as less than about 160 microns, such as less than about 155 microns, such as less than about 150 microns, such as less than about 145 microns, such as less than about 140 microns.

[0010]

[0010] The high density polyethylene particles of the present invention have been found to rapidly mix with a plasticizer under heating to form a uniform gel-like material. For example, when tested according to the solubility test described in more detail below, the high density polyethylene particles may have a solubility of less than about 3 minutes, such as less than about 2.5 minutes, such as less than about 2 minutes.

[0011]

[0011] Generally, the polymer composition contains a high density polyethylene resin in an amount of about 50% by weight or less. The plasticizer can be present in the composition, for example, in an amount greater than about 50% by weight, such as greater than about 60% by weight, such as greater than about 70% by weight, such as greater than about 80% by weight, such as greater than about 90% by weight. Various different materials can be used as the plasticizer. For example, the plasticizer can include mineral oil, paraffin oil, hydrocarbon oil, alcohol, etc. For example, the plasticizer can include decalin, xylene, dioctyl phthalate, dibutyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, diphenyl ether, n-decane, n-dodecane, or a mixture thereof. In one embodiment, the plasticizer can include C5-C 12 saturated hydrocarbons such as C5-C 12 hydrocarbons. For example, the plasticizer can include heptane, hexane, etc.

[0012] In one embodiment, the polyethylene used to produce the particles may have a relatively high molecular weight. In fact, one of the advantages of the present invention is the ability to rapidly blend relatively high molecular weight polyethylene particles with a plasticizer without forming a gel spec. In one embodiment, the use of higher molecular weight polyethylene particles may be beneficial, particularly in applications where higher strength properties are required or desired. For example, the polyethylene used to produce the particles may have a molecular weight higher than about 500,000 g / mol, such as higher than about 1,000,000 g / mol, such as higher than about 1,500,000 g / mol, such as higher than about 2,000,000 g / mol, such as higher than about 2,500,000 g / mol, such as higher than about 3,000,000 g / mol, such as higher than about 3,500,000 g / mol, such as higher than about 4,000,000 g / mol. In one embodiment, the polyethylene used to produce the particles comprises Ziegler-Natta catalyzed ultra-high molecular weight polyethylene.

[0013]

[0013] The present invention also relates to polymer articles formed from the above polymer composition. The polymer articles can be manufactured by a gel extrusion or gel spinning process. Examples of polymer articles manufactured in accordance with the present invention include fibers, films, membranes, and the like.

[0014]

[0014] The present invention also relates to a method of manufacturing a polymer article. The method includes the step of forming a gel composition from the above polymer composition. Next, the gel composition is extruded through a die to form a polymer article. The polymer article may include, for example, a fiber, a film, or a membrane. During the formation of the polymer article, at least a portion of the plasticizer is separated and removed from the polyethylene particles. For example, in one embodiment, more than 80%, such as more than 90%, such as more than 95%, such as more than 98% of the plasticizer is removed during the formation of the polymer article.

[0015] Other features and aspects of the present invention are discussed in more detail below.

[0016] In the remainder of the specification, including the reference to the accompanying drawings, a more detailed disclosure of a complete and practicable disclosure of the present invention is shown.

Brief Description of the Drawings

[0016]

Figure 1

Modes for Carrying Out the Invention

[0017]

[0017] The repeated use of reference symbols in this specification and the drawings is intended to represent the same or similar features or components of the present invention.

[0018] It will be understood by those skilled in the art that this discussion is merely illustrative of exemplary embodiments and is not intended to limit the broader aspects of the present invention.

[0018]

[0019] In general, the present invention relates to a polymer composition well suited for manufacturing gel extrusion articles such as fibers, films, and membranes. The polymer composition includes a polyethylene resin such as high-density polyethylene particles mixed with a plasticizer. According to the present invention, the polyethylene particles are specifically configured such that when the particles are mixed with the plasticizer and heated, a uniform gel-like material is rapidly formed.

[0019]

[0020] In the past, there have been various problems in the gel processing of polyethylene polymers. For example, various polyethylene polymers may require a significant amount of time to dissolve in a processing solvent during extrusion. If the residence time in the extruder is not long enough to allow for complete dissolution of the polymer resin, defects may be formed in the polymer article being formed. Defects that can result from the presence of gel specs can lead to difficulties in manufacturing the article or a reduced quality of the resulting article. Ultimately, longer dissolution times or incomplete dissolution can limit the capabilities of the product. Further, these problems can result in a lower capacity of the gel processing manufacturing line.

[0020]

[0021] However, the present invention relates to selecting a specific polyethylene resin that is more suitable for rapidly blending with a plasticizer to form a uniform gel-like material. In particular, the polyethylene particles of the present invention are thought to provide a larger interaction area between the plasticizer and the polymer, reduce the dissolution time, thereby eliminating gel specs and preventing defects from occurring in the extruded polymer article. In one embodiment, the method of the present invention enables the use of relatively high molecular weight polymers that can result in polymer articles having improved physical properties such as strength characteristics.

[0021]

[0022] According to the present invention, the polyethylene resin selected to be mixed with the plasticizer may have at least one of two physical characteristics. In one embodiment, for example, the resin is formed from a polyethylene polymer having a relatively low bulk density. The lower bulk density has been found to unexpectedly and dramatically shorten the time required for the polymer to dissolve in the plasticizer or otherwise form a uniform gel-like material. In other embodiments, or in addition to having a relatively low bulk density, the polyethylene resin particles may have a unique particle size distribution (which has also been found to dramatically improve the dissolution time).

[0022]

[0023] According to the present invention, the polymer composition comprises a polyethylene polymer. As used herein, the polyethylene polymer refers to a polymer formed from more than 90% ethylene-derived units, such as more than 95% ethylene-derived units, or 100% ethylene-derived units. Polyethylene may be a homopolymer or a copolymer (including terpolymers) having other monomer units. In one embodiment, the polyethylene particles are formed from high density polyethylene. High density polyethylene has a density of about 0.93 g / cm 3 or greater. The polyethylene used to produce the particles can include high molecular weight polyethylene, ultra-high molecular weight polyethylene, and / or ultra-high molecular weight polyethylene. "High molecular weight polyethylene" refers to at least about 3×10 5Refers to a polyethylene composition having a weight average molecular weight of g / mol, and when used herein, is intended to include ultra-high molecular weight polyethylene and ultra-high molecular weight polyethylene. For the purposes of this specification, the molecular weights referred to herein are determined according to the Margolies formula (Margolies molecular weight).

[0023]

[0024] "Ultra-high molecular weight polyethylene" refers to a polyethylene composition having a weight average molecular weight of less than about 3×10 6 g / mol and higher than about 1×10 6 g / mol. In some embodiments, the molecular weight of the ultra-high molecular weight polyethylene composition is from about 2×10 6 g / mol to less than about 3×10 6 g / mol.

[0024]

[0025] "Ultra-high molecular weight polyethylene" refers to a polyethylene composition having a weight average molecular weight of at least about 3×10 6 g / mol. In some embodiments, the molecular weight of the ultra-high molecular weight polyethylene composition is from about 3×10 6 g / mol to about 30×10 6 g / mol, or from about 3×10 6 g / mol to about 20×10 6 g / mol, or from about 3×10 6 g / mol to about 10×10 6 g / mol, or from about 3×10 6 g / mol to about 6×10 6 g / mol.

[0025]

[0026] As described above, in one embodiment, the polyethylene is a homopolymer of ethylene. In other embodiments, the polyethylene may be a copolymer. For example, the polyethylene may be a copolymer of ethylene and another olefin containing 3 to 16 carbon atoms, such as 3 to 10 carbon atoms, such as 3 to 8 carbon atoms. These other olefins include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene, etc. In the present invention, 1,3-he xadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohex-1-ene, 1,5-cyclooctadiene, 5-vinylidene-2-norbornene, and polyene comonomers such as 5-vinyl-2-norbornene can also be used. However, when present, the amount of one or more non-ethylene monomers in the copolymer may be less than about 10 mol%, such as less than about 5 mol%, such as less than about 2.5 mol%, such as less than about 1 mol%, where mol% is based on the total number of moles of monomers in the polymer.

[0026]

[0027] In one embodiment, the polyethylene may have a unimodal molecular weight distribution. Alternatively, the polyethylene may exhibit a bimodal molecular weight distribution. For example, a bimodal distribution generally refers to a polymer having distinct higher and lower molecular weights (e.g., two distinct peaks) on a size exclusion chromatography or gel permeation chromatography curve. In other embodiments, the polyethylene may exhibit more than two molecular weight distribution peaks such that the polyethylene has a multimodal (e.g., trimodal, tetramodal, etc.) distribution. Alternatively, the polyethylene may exhibit a broad molecular weight distribution, where the polyethylene is composed of a blend of higher molecular weight and lower molecular weight components and the size exclusion chromatography or gel permeation chromatography curve does not show at least two distinct peaks, but instead shows one distinct peak broader than the individual component peaks.

[0027]

[0028] In one embodiment, the composition may be composed of more than one type of polyethylene, each having a different molecular weight and / or molecular weight distribution. For example, the molecular weight distribution may be within the defined range of the average molecular weight given above.

[0028]

[0029] Furthermore, the composition may be composed of a blend of one or more polyethylene polymers or copolymers with other thermoplastic polymers such as polypropylene, polybutylene, polymethylpentene, linear low density polyethylene, or mixtures thereof. However, the amount of one or more non-polyethylene polymers in the composition is less than about 10 wt%, for example less than about 5 wt%, for example less than about 2.5 wt%, for example less than about 1 wt%, where wt% is based on the total weight of the composition.

[0029]

[0030] Polyethylene can be synthesized using any method known in the art. Polyethylene powder is usually produced by the catalytic polymerization of ethylene monomers using a heterogeneous catalyst and an organoaluminum or magnesium compound as a cocatalyst, or in some cases by the catalytic polymerization with one or more other 1-olefin comonomers (the 1-olefin content in the final polymer is 10% or less of the ethylene content). Ethylene is usually polymerized in the gas phase or slurry phase at relatively low temperatures and pressures. The polymerization reaction can be carried out at a temperature between 50 °C and 100 °C and a pressure in the range of 0.02 - 2 MPa.

[0030]

[0031] The molecular weight of polyethylene can be adjusted by adding hydrogen. Also, the molecular weight can be finely adjusted by changing the temperature and / or the type and concentration of the cocatalyst. Furthermore, this reaction can be carried out in the presence of an antistatic agent to avoid fouling and product contamination.

[0031]

[0032] Suitable catalyst systems include, but are not limited to, Ziegler-Natta type catalysts. Usually, Ziegler-Natta type catalysts are derived by combining transition metal compounds of Groups 4-8 of the Periodic Table with alkyl or hydride derivatives of metals of Groups 1-3 of the Periodic Table. Commonly used transition metal derivatives include metal halides or esters or combinations thereof. Representative Ziegler-Natta catalysts include, for example, aluminum or magnesium alkyls (but are not limited thereto) Those based on the reaction products of organic aluminum or magnesium compounds such as with titanium, vanadium, or chromium halides or esters. The heterogeneous catalyst can be non-supported or supported on a porous particulate material such as silica or magnesium chloride. Such a support can be added during the synthesis of the catalyst or can be obtained as a chemical reaction product of the catalyst synthesis itself.

[0032]

[0033] As will be explained in more detail below, particularly advantageously, the polyethylene particles produced according to the present invention can be rapidly blended or dissolved with a plasticizer even when the polyethylene polymer is produced using a Ziegler-Natta catalyst. In the past, for example, there have been problems in rapidly forming a homogeneous gel-like material for gel processing using Ziegler-Natta catalyst polyethylene polymers, particularly high molecular weight polymers.

[0033]

[0034] In one embodiment, a suitable catalyst system can be obtained by reacting a titanium(IV) compound with a trialkylaluminum compound in an inert organic solvent at a temperature in the range of -40°C to 100°C, preferably -20°C to 50°C. The concentration of the starting materials is in the range of 0.1 to 9 mol / L, preferably 0.2 to 5 mol / L for the titanium(IV) compound, and 0.01 to 1 mol / L, preferably 0.02 to 0.2 mol / L for the trialkylaluminum compound. The titanium component is added to the aluminum component over 0.1 minute to 60 minutes, preferably 1 minute to 30 minutes, and the molar ratio of titanium to aluminum in the final mixture is in the range of 1:0.01 to 1:4.

[0034]

[0035] In other embodiments, a suitable catalyst system is obtained by a one-step or two-step reaction of a titanium(IV) compound with a trialkylaluminum compound in an inert organic solvent at a temperature in the range of -40°C to 200°C, preferably -20°C to 150°C. In the first step, the titanium(IV) compound is reacted with the trialkylaluminum compound at a temperature in the range of -40°C to 100°C, preferably -20°C to 50°C, using a molar ratio of titanium to aluminum in the range of 1:0.1 to 1:0.8. The concentration of the starting materials is in the range of 0.1 to 9.1 mol / L, preferably 5 to 9.1 mol / L for the titanium(IV) compound, and 0.05 to 1 mol / L, preferably 0.1 to 0.9 mol / L for the trialkylaluminum compound. The titanium component is added to the aluminum compound over 0.1 minute to 800 minutes, preferably 30 minutes to 600 minutes. When used, in the second step, the reaction product obtained in the first step is treated with a trialkylaluminum compound at a temperature in the range of -10°C to 150°C, preferably 10°C to 130°C, using a molar ratio of titanium to aluminum in the range of 1:0.01 to 1:5.

[0035]

[0036] In still other embodiments, a suitable catalyst system is obtained by a procedure of reacting magnesium alcoholate with titanium chloride in an inert hydrocarbon at a temperature of 50 °C to 100 °C in the first reaction stage. In the second reaction stage, the formed reaction mixture is heat-treated at a temperature of 110 °C to 200 °C for about 10 to 100 hours (generating alkyl chloride until no further alkyl chloride is released), and then the soluble reaction products are removed from the solid by washing several times with a hydrocarbon.

[0036]

[0037] In a further embodiment, a catalyst supported on silica, such as the commercially available catalyst system Sylopol 5917, can also be used.

[0038] When using such a catalyst system, the polymerization is usually carried out in one or more steps, continuously or batchwise, in suspension, at low pressure and low temperature. The polymerization temperature is usually in the range of 30 °C to 130 °C, preferably in the range of 50 °C to 90 °C, and the ethylene partial pressure is usually less than 10 MPa, preferably 0.05 to 5 MPa. Trialkylaluminums such as, for example, isoprenylaluminum and triisobutylaluminum (but not limited thereto) are used as co-catalysts such that the ratio of Al:Ti (co-catalyst:catalyst) is in the range of 0.01 to 100:1, more preferably in the range of 0.03 to 50:1. The solvent is an inert organic solvent as commonly used for Ziegler-type polymerization. Examples are butane, pentane, hexane, cyclohexene, octane, nonane, decane, their isomers and their mixtures. The molecular weight of the polymer is controlled by supplying hydrogen. The ratio of the hydrogen partial pressure to the ethylene partial pressure is in the range of 0 to 50, preferably in the range of 0 to 10. The polymer is isolated and dried under nitrogen in a fluidized bed dryer. The solvent can be removed by steam distillation when using a high-boiling solvent. Salts of long-chain fatty acids can be added as stabilizers. Typical examples are calcium, magnesium, and zinc stearates.

[0037]

[0039] In some cases, other catalysts such as Phillips catalysts, metallocenes, and post-metallocenes can be used. Generally, cocatalysts such as alumoxanes or alkylaluminum or alkylmagnesium compounds can also be used. Other suitable catalyst systems include Group 4 metal complexes of phenolate ether ligands.

[0038]

[0040] According to the present invention, the polyethylene polymer is formed into particles and mixed with a plasticizer. The polyethylene is specifically selected to have at least one of two physical characteristics in order to dramatically and unexpectedly increase the dissolution rate into the plasticizer and / or to rapidly form a uniform gel-like material. In one embodiment, for example, the polyethylene particles are formed from a polyethylene polymer having a relatively low bulk density as measured according to DIN-53466. For example, in one embodiment, the bulk density is generally less than about 0.4 g / cm 3 less, for example, about 0.35 g / cm 3 less, for example, about 0.33 g / cm 3 less, for example, about 0.3 g / cm 3 less, for example, about 0.28 g / cm 3 less, for example, about 0.26 g / cm 3 less. The bulk density is generally greater than about 0.1 g / cm 3 greater, for example, about 0.15 g / cm 3 greater. In one embodiment, the polymer has a bulk density of about 0.2 g / cm 3 to about 0.27 g / cm 3 .

[0039]

[0041] Alternatively, in addition to having a relatively low bulk density, the polyethylene particles may have a controlled particle size distribution (which has also been found to dramatically improve the dissolution time into the plasticizer when heated). In one embodiment, for example, the polyethylene particles may be a free-flowing powder. According to the present invention, the particles may have a median particle size (d50) of less than 125 microns. For example, the median particle size (d50) of the polyethylene particles may be less than about 110 microns, such as less than about 105 microns, such as less than about 100 microns, such as less than about 95 microns. The median particle size (d50) is generally greater than about 60 microns. For example, the median particle size (d50) may be from about 60 microns to less than 125 microns, such as from about 70 microns to about 110 microns. The particle size of the powder can be measured using the laser diffraction method in accordance with ISO-13320.

[0040]

[0042] In addition to having a median particle size within the above range, the particle size distribution of the polyethylene polymer particles can also be controlled such that it contains relatively few or no larger particles. For example, in one embodiment, 90% of the polyethylene particles may have a particle size of less than about 180 microns. In other embodiments, 90% of the polyethylene particles may have a particle size of less than about 170 microns, such as less than about 165 microns, such as less than about 160 microns, such as less than about 155 microns, such as less than about 150 microns, such as less than about 145 microns, such as less than about 140 microns, such as less than about 135 microns, such as less than about 130 microns, such as less than about 125 microns, such as less than about 120 microns.

[0041]

[0043] The above physical characteristics blend with the plasticizer to form a uniform solution during gel processing It has been found that the ability of polymer particles can be dramatically improved. In one embodiment, the polyethylene polymer selected for use in a polymer composition may have a relatively high molecular weight. For example, the molecular weight may be relatively high with respect to the bulk density of the polymer. Particularly advantageously, it has been found that even relatively high molecular weight polymers can be rapidly blended with plasticizers and can have extremely short dissolution times. For example, in some applications, the use of relatively high molecular weight polymers may be preferred. The use of high molecular weight polymers can improve various physical properties of the resulting product, such as the strength properties of the resulting product.

[0042]

[0044] The polyethylene polymer may have an average molecular weight determined, for example, according to the Margolies formula. The molecular weight can be determined by first measuring the viscosity number according to DIN-EN-ISO test 1628. Measure the dry powder flow rate using a 25 mm nozzle. Next, from the viscosity number, using the Margolies formula, a molecular weight of at least about 500,000 g / mol, or greater, such as greater than about 1,000,000 g / mol, such as greater than about 1,500,000 g / mol, such as greater than about 2,000,000 g / mol, such as greater than about 2,500,000 g / mol, such as greater than about 3,000,000 g / mol, such as greater than about 3,500,000 g / mol, such as greater than about 4,000,000 g / mol is calculated. The average molecular weight is generally less than about 12,000,000 g / mol, such as less than about 10,000,000 g / mol.

[0043]

[0045] Polyethylene is determined using a concentration in decahydronaphthalene of 0.0002 g / mL in accordance with ISO-1628, Part 3, and has an intrinsic viscosity of at least 100 mL / g, such as at least 500 mL / g, such as at least 1,500 mL / g, such as at least 2,000 mL / g, such as at least 4,000 mL / g, and less than about 6,000 mL / g, such as less than about 5,000 mL / g, such as less than about 4,000 mL / g, such as less than about 3,000 mL / g, such as less than about 1,000 mL / g.

[0044]

[0046] Polyethylene may have a crystallinity of at least about 40% to 85%, such as 45% to 80%.

[0047] To form a polymer article by a gel spinning or extrusion process, the above polyethylene particles are mixed with a plasticizer to form a polymer composition. Generally, the polyethylene particles are present in the polymer composition in an amount of about 50 wt% or less. For example, the polyethylene particles can be present in the polymer composition in an amount of less than about 45 wt%, such as less than about 40 wt%, such as less than about 35 wt%, such as less than about 30 wt%, such as less than about 25 wt%, such as less than about 20 wt%, such as less than about 15 wt%, such as less than about 10 wt%, such as less than about 5 wt%. The polyethylene particles can be present in the composition in an amount greater than about 1 wt%, such as greater than about 3 wt%, such as greater than about 5 wt%, such as greater than about 10 wt%, such as greater than about 15 wt%, such as greater than about 20 wt%, such as greater than about 25 wt%. During gel processing, the plasticizer can be substantially or completely removed when forming the polymer article. For example, in one embodiment, the resulting polymer article can contain a polyethylene polymer in an amount greater than about 70 wt%, such as greater than about 80 wt%, such as greater than about 85 wt%, such as greater than about 90 wt%, such as greater than about 95 wt%, such as greater than about 98 wt%, such as greater than about 99 wt%.

[0045]

[0048] Generally, any suitable plasticizer can be mixed with the polyethylene particles as long as the plasticizer can form a gel-like material suitable for gel spinning or extrusion. The plasticizer may include, for example, hydrocarbon oils, alcohols, ethers, esters such as diesters, or mixtures thereof. For example, suitable plasticizers include mineral oil, paraffin oil, decalin, etc. Other plasticizers include xylene, dioctyl phthalate, dib tyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, diphenyl ether, n-decane, n-dodecane, octane, nonane, kerosene, toluene, naphthalene, tetralin, etc. In one embodiment, the plasticizer may include halogenated hydrocarbons such as monochlorobenzene. Cycloalkanes and cycloalkenes such as camphene, methane, dipentene, methylcyclopentadiene, tricyclodecane, 1,2,4,5-tetramethyl-1,4-cyclohexadiene, etc. can also be used. The plasticizer may further include any of the above mixtures and combinations.

[0046]

[0049] The plasticizer is generally present in the composition used to form the polymer article in an amount greater than about 50% by weight, for example greater than about 55% by weight, for example greater than about 60% by weight, for example greater than about 65% by weight, for example greater than about 70% by weight, for example greater than about 75% by weight, for example greater than about 80% by weight, for example greater than about 85% by weight, for example greater than about 90% by weight, for example greater than about 95% by weight, for example greater than about 98% by weight. In fact, the plasticizer can be present in an amount of about 99.5% by weight or less.

[0047]

[0050] When the polyethylene particles produced according to the present invention are mixed with a plasticizer, the particles rapidly blend with the plasticizer to form a uniform gel-like material. For example, the polyethylene particles produced according to the present invention may have a solubility of less than about 3 minutes, such as less than about 2.5 minutes, such as less than about 2 minutes, and even less than about 1.8 minutes when tested according to the solubility test described in the following examples. The solubility is generally greater than about 0.1 minute.

[0048]

[0051] To form a polymer article according to the present invention, polyethylene particles are mixed with a plasticizer and extruded through a die of a desired shape. In one embodiment, the composition can be heated in an extruder. For example, the plasticizer can be mixed with the polyethylene particles and fed into the extruder. According to the present invention, the plasticizer and the polyethylene particles form a uniform gel-like material before being discharged from the extruder to form a polymer article having little or no impurities.

[0049]

[0052] In one embodiment, an elongated article is formed during the gel spinning or extrusion process. The polymer article can be in the form of, for example, a fiber, a film, or a membrane.

[0053] During this process, at least a portion of the plasticizer is removed from the final product. The plasticizer removal process can be carried out by evaporation when a relatively volatile plasticizer is used. In another form, an extractant can be used to remove the plasticizer. In one embodiment, both evaporation and extraction are used.

[0050]

[0054] If desired, the resulting polymeric article can be stretched at an elevated temperature below the melting point of the polyethylene polymer to increase strength and modulus. Suitable temperatures for stretching range from about ambient temperature to about 155°C. The stretch ratio can generally be greater than about 4, such as greater than about 6, such as greater than about 8, such as greater than about 10, such as greater than about 15, such as greater than about 20, such as greater than about 25, such as greater than about 30. In some embodiments, the stretch ratio can be greater than about 50, such as greater than about 100, such as greater than about 110, such as greater than about 120, such as greater than about 130, such as greater than about 140, such as greater than about 150. The stretch ratio is generally less than about 1,000, such as less than about 800, such as less than about 600, such as less than about 400. In one embodiment, a lower stretch ratio such as from about 4 to about 10 is used. The polymeric article can be uniaxially or biaxially oriented.

[0051]

[0055] The polymeric articles produced according to the present invention have numerous uses and applications. For example, in one embodiment, the present method is used to produce membranes. The membranes can be used, for example, in battery separators. Alternatively, the membrane can be used as a microfilter. When producing fibers, the fibers can be used to produce nonwoven fabrics, ropes, nets, etc. In one embodiment, the fibers can be used as a filler material in bulletproof vests.

[0052]

[0056] The polymeric compositions and articles produced according to the present invention may contain a variety of other additives such as heat stabilizers, light stabilizers, UV absorbers, flame retardants, lubricants, colorants, acid scavengers, and the like.

[0053]

[0057] In one embodiment, a heat stabilizer can be present in the composition. The heat stabilizer can include, but is not limited to, a phosphite, an amine antioxidant, a phenolic antioxidant, or any combination thereof.

[0054]

[0058] In one embodiment, an antioxidant can be present in the composition. Examples of the antioxidant include, but are not limited to, secondary aromatic amines, benzofuranones, sterically hindered phenols, or any combination thereof.

[0055]

[0059] In one embodiment, a light stabilizer can be present in the composition. Examples of the light stabilizer include, but are not limited to, 2-(2'-hydroxyphenyl)benzotriazoles, 2-hydroxy-4-alkoxybenzophenones, nickel-containing light stabilizers, 3,5-di-tert-butyl-4-hydroxybenzoates, sterically hindered amines (HALS), or any combination thereof.

[0056]

[0060] In one embodiment, instead of or in addition to the light stabilizer, a UV absorber can be present in the composition. Examples of the UV absorber include, but are not limited to, benzotriazoles, benzoates, or combinations thereof, or any combination thereof.

[0057]

[0061] In one embodiment, a halogenated flame retardant can be present in the composition. Examples of the halogenated flame retardant include, but are not limited to, tetrabromobisphenol A (TBBA), tetrabromophthalic anhydride, dodecachloropentacyclooctadecadiene (dechlorane), hexabromocyclododecane, chlorinated paraffin, or any combination thereof.

[0058]

[0062] In one embodiment, a non-halogenated flame retardant can be present in the composition. Examples of non-halogenated flame retardants include, but are not limited to, resorcinol bis(diphenyl phosphate) (RDP), ammonium polyphosphate (APP), phosphinic acid derivatives, triaryl phosphates, trichloropropyl phosphate (TCPP), magnesium hydroxide, aluminum trihydroxide, and antimony trioxide.

[0059]

[0063] In one embodiment, a lubricant can be present in the composition. Examples of lubricants include, but are not limited to, silicone oil, wax, molybdenum disulfide, or any combination thereof.

[0060]

[0064] In one embodiment, a colorant can be present in the composition. Examples of colorants include, but are not limited to, inorganic and organic coloring pigments.

[0065] In one embodiment, an acid scavenger can be present in the composition. An example of an acid scavenger is, for example, calcium stearate.

[0061]

[0066] These additives can be used alone or in any combination thereof. Generally, unless otherwise indicated, when using additives, they are present in an amount of at least about 0.05 wt%, such as at least about 0.1 wt%, such as at least about 0.25 wt%, such as at least about 0.5 wt%, such as at least about 1 wt%, and generally less than about 20 wt%, such as less than about 10 wt%, such as less than about 5 wt%, such as less than about 4 wt%, such as less than about 2 wt%. The sum of the weight percentages of all components (including additives if present) used in the polymer composition is 100 wt%.

Examples

[0062]

[0067] The present invention can be better understood with reference to the following examples. The following examples are given below for illustrative purposes and not for purposes of limitation. The following experiments were conducted to demonstrate some of the advantages and benefits of the present invention.

[0063] Example 1

[0068] Three grades of high-density polyethylene with equivalent molecular weights (4 to 4.5 million grams / mole) and different bulk densities were selected. The samples were sieved so as to obtain an intermediate fraction with a particle size of 100 to 125 micrometers. Thus, samples with equivalent molecular weights and particle sizes but different values of bulk density were obtained. The bulk density was determined according to the international standard ISO-60.

[0064]

[0069] A solubility test was conducted to determine the dissolution time in mineral oil. Solubility test

[0070] The following solubility test was used to determine the dissolution time for different samples. Polymer particles were mixed with oil under defined conditions while monitoring the torque applied on the screw.

[0065]

[0071] When the resin dissolves in the oil, the viscosity of the fluid increases due to the polymer chains (the same principle as the VN test), resulting in an increase in torque. When all the resin has dissolved in the oil, the torque reaches an equilibrium level. The time required to reach the equilibrium torque is a measure of the dissolution time of the resin.

[0066]

[0072] Apparatus used: Haake RheoStress 600 equipped with a screw agitator.

[0073] Preparation of samples Weigh 1.80 g of processing oil, 450 mg of Irganox B215, and 225 mg of resin powder into a weighing bowl.

[0067] 2. Attach the bowl to the Rheostress and start the measurement program.

[0074] Test program 1. Heat the bowl to 180°C.

[0068] 2. Once the temperature is reached, set the screw rpm to 130 rpm. 3. Continue stirring for 150 minutes while recording the torque reading.

[0075] Data evaluation 1. Identify the region where the torque (viscosity) is constant.

[0069] 2. Create a linear fit (horizontal line) within this region (usually 140 - 160 minutes). 3. Calculate the confidence interval for the fit line. 4. Identify the first data point within the confidence interval to determine the dissolution time.

[0070] 5. For the final viscosity, determine the average viscosity in the linear fit region.

[0076] The viscosity tests of four samples are shown in Figure 1. The dissolution times are shown in the table below.

[0071]

Table 1

[0072]

[0077] As shown above, the samples with lower bulk density unexpectedly and dramatically reduced the dissolution time.

[0073] Example 2

[0078] The following examples were conducted to demonstrate that the particle size distribution can have a dramatic effect on the dissolution time.

[0074]

[0079] Two different samples of high - density polyethylene powder were selected. Sample No. 1 had an average particle size (d50) of 98 microns, and Sample No. 2 had an average particle size (d50) of 135 microns. Except for the particle size distribution, the polyethylene polymers used in the samples were relatively equivalent.

[0075]

[0080] Different samples were subjected to the above solubility test. Further, the polyethylene particles were gel extruded and the resulting polymer articles were tested for various properties. The following results were obtained.

[0076]

Table 2

[0077]

[0081] As shown above, Sample No. 1 with a different particle size distribution had a dissolution time that was more than 50% shorter than that of Sample No. 2.

[0082] These and other modifications and variations to the present invention can be made by those skilled in the art without departing from the spirit and scope of the invention as more particularly shown in the appended claims. Further, it should be understood that the various forms of the plurality of aspects can be replaced in whole or in part. Furthermore, those skilled in the art will recognize that the above description is for illustrative purposes only and is not intended to further limit the invention described in the appended claims. The description of the claims of the original application of this application is transcribed below. [Aspect 1] A polymer composition for manufacturing a gel extruded article, a plasticizer; and high density polyethylene particles mixed with the plasticizer; comprising; the high density polyethylene particles have the following characteristics: (a) a bulk density of less than about 0.35 g / cm 3 ; and / or (b) a median particle size (d50) of less than 125 microns, where 90% of the particles have a particle size of less than about 180 microns; having at least one of, and the high density polyethylene has an average molecular weight higher than about 1,500,000 g / mol, the polymer composition. [Aspect 2] The polymer composition according to Aspect 1, wherein the high density polyethylene particles have a bulk density of less than about 0.33 g / cm 3 . [Aspect 3] The high-density polyethylene particles have a bulk density of less than about 0.3 g / cm 3 and, for example, less than about 0.28 g / cm 3 and, for example, less than about 0.26 g / cm 3 and are higher than about 0.15 g / cm, and are the polymer composition according to Aspect 1. 3 [Aspect 4] The polymer composition according to Aspect 1, wherein the high-density polyethylene particles have a median particle size (d50) of less than about 100 microns. [Aspect 5] The polymer composition according to Aspect 1, wherein the high-density polyethylene particles have a median particle size (d50) of from about 60 microns to less than 110 microns, for example from about 70 microns to about 100 microns. [Aspect 6] The polymer composition according to any one of Aspects 1 to 5, wherein 90% of the high-density polyethylene particles have a particle size of less than about 170 microns, for example less than about 165 microns. [Aspect 7] The polymer composition according to any one of Aspects 1 to 6, wherein the high-density polyethylene particles have a solubility of less than about 3 minutes, for example less than about 2.5 minutes, for example less than about 2 minutes, when tested according to a solubility test. [Aspect 8] The polymer composition according to Aspect 1, wherein the high-density polyethylene particles have both the features (a) and (b). [Aspect 9] The polymer composition according to any one of Aspects 1 to 8, wherein the high-density polyethylene particles are present in the composition in an amount of about 50% by weight or less. [Aspect 10] The polymer composition according to any one of Aspects 1 to 9, wherein the plasticizer comprises mineral oil, paraffin oil, hydrocarbon, alcohol, ether, ester, or a mixture thereof. [Aspect 11] The polymer composition according to any one of aspects 1 to 10, wherein the high-density polyethylene has a molecular weight greater than about 2,000,000 g / mol, for example greater than about 2,500,000 g / mol, for example greater than about 3,000,000 g / mol, for example greater than about 3,500,000 g / mol, for example greater than about 4,000,000 g / mol. [Aspect 12] The polymer composition according to any one of aspects 1 to 11, wherein the high-density polyethylene is a Ziegler-Natta catalyst ultra-high molecular weight polyethylene. [Aspect 13] The polymer composition according to any one of aspects 1 to 12, wherein the plasticizer comprises decalin, xylene, dioctyl phthalate, dibutyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, diphenyl ether, n-decane, n-dodecane, octane, nonane, kerosene, toluene, naphthalene, tetralin, monochlorobenzene, camphene, methane, dipentene, methylcyclopentadiene, tricyclodecane, 1,2,4,5-tetramethyl-1,4-cyclohexadiene, or a mixture thereof. [Aspect 14] A method for manufacturing a polymer article, comprising: forming the polymer composition according to any one of aspects 1 to 13 into a gel composition; extruding the gel composition through a die to form a polymer article, wherein the polymer article comprises a fiber, a film, or a membrane; The method as described above. [Aspect 15] The method according to aspect 14, further comprising removing at least a portion of the plasticizer from the polymer article. [Aspect 16] A polymer article comprising a fiber, a film, or a membrane, wherein the polymer article is formed by mixing a plasticizer and high-density polyethylene particles to form a gel composition, wherein the high-density polyethylene particles have the following characteristics: (a) a bulk density of less than about 0.35 g / cm 3 and / or (b) a median particle size (d50) of less than 125 microns, wherein 90% of said particles have a particle size of less than about 180 microns; having at least one of, said high density polyethylene having an average molecular weight higher than about 1,500,000 g / mol; and extruding said gel-like composition through a die to form said polymeric article; said polymeric article produced thereby. [Aspect 17] said high density polyethylene particles having a bulk density of less than about 0.3 g / cm 3 less than, for example, about 0.28 g / cm 3 less than, for example, about 0.26 g / cm3 and higher than about 0.15 g / cm3, the polymeric article according to Aspect 16. [Aspect 18] said high density polyethylene particles having a median particle size (d50) from about 60 microns to less than 110 microns, for example from about 70 microns to about 100 microns, the polymeric article according to Aspect 16. [Aspect 19] said high density polyethylene particles having both said characteristics (a) and (b), the polymeric article according to Aspect 16. [Aspect 20] said polymeric article comprising a film, the polymeric article according to Aspect 16. [Aspect 21] said polymeric article comprising fibers, the polymeric article according to Aspect 16.

Claims

1. A polymer composition for manufacturing a gel-extruded article, comprising a plasticizer, and high-density polyethylene particles mixed with the plasticizer , wherein the high-density polyethylene is a Ziegler-Natta catalyst ultra-high molecular weight polyethylene, and the high-density polyethylene particles have a median particle size (d50) greater than 60 μm, the high-density polyethylene has an average molecular weight higher than 500,000 g / mol when calculated using the Margolies formula from the viscosity number measured according to DIN-EN-ISO test 1628, the gel-extruded article is a fiber, film, or membrane, and the polymer composition.

2. The high-density polyethylene particles have a bulk density of less than 0.28 g / cm ３ The polymer composition according to claim 1, having a bulk density of less than 0.28 g / cm.

3. The high-density polyethylene particles have a bulk density higher than 0.15 g / cm ３ The polymer composition according to claim 1, which has a bulk density higher than ３ .

4. The polymer composition according to any one of claims 1 to 3, wherein the high-density polyethylene particles have a median particle size (d50) of less than 125 μm.

5. The polymer composition according to claim 1, wherein the high-density polyethylene particles have a median particle size (d50) of 70 μm to 100 μm.

6. The polymer composition according to any one of claims 1 to 5, wherein 90% of the high-density polyethylene particles have a particle size of less than 180 μm.

7. The polymer composition according to claim 1, wherein the high-density polyethylene particles have a solubility of less than 3 minutes when tested according to a solubility test.

8. The polymer composition according to claim 1, wherein the high-density polyethylene particles are present in the composition in an amount of 50% by weight or less.

9. The polymer composition according to claim 1, wherein the plasticizer comprises mineral oil, paraffin oil, hydrocarbon, alcohol, ether, ester, or a mixture thereof.

10. The polymer composition according to claim 1, wherein the plasticizer comprises decalin, xylene, dioctyl phthalate, dibutyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, diphenyl ether, n-decane, n-dodecane, octane, nonane, kerosene, toluene, naphthalene, tetralin, monochlorobenzene, camphene, methane, dipentene, methylcyclopentadiene, tricyclodecane, 1,2,4,5-tetramethyl-1,4-cyclohexadiene, or a mixture thereof.

11. A method for manufacturing a polymer article, comprising a step of forming the polymer composition according to claim 1 into a gel composition, and A step of extruding the gel composition through a die to form a polymer article The method comprising the above.

12. The method according to claim 11, further comprising a step of removing at least a part of the plasticizer from the polymer article.

13. A polymer article, wherein the polymer article mixes a plasticizer and high-density polyethylene particles to form a gel composition, and extrudes the gel composition through a die to form the polymer article is manufactured by the high-density polyethylene is Ziegler-Natta catalyst ultra-high molecular weight polyethylene, the high-density polyethylene particles have a median particle size (d50) greater than 60 μm, the high-density polyethylene has an average molecular weight higher than 500,000 g / mol when calculated using the Margolies formula from the viscosity number measured according to DIN-EN-ISO test 1628, the polymer article is a fiber, a film, or a membrane, the polymer article.

14. The high-density polyethylene particles have a bulk density greater than 0.15 g / cm ３ The polymeric article according to claim 13, having a bulk density greater than ３ .

15. The polymer article according to claim 13 or 14, wherein the high-density polyethylene particles have a median particle size (d50) of less than 125 μm.

16. The polymer article according to any one of claims 13 to 15, wherein the polymer article is a film.

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