KR20180112439A - High-Strength polyethylene packing film and manufacturing method - Google Patents

Abstract

Therefore, there is a need to produce a polyethylene blown film having both high sharpness and high vapor barrier properties. Blown films and methods of forming the same are described herein. The blown films generally include high density polyethylene having approximately 1.5 to 8.0 of molecular weight distribution and 0.94-0.96 g/cc of density.

Description

TECHNICAL FIELD [0001] The present invention relates to a high-strength polyethylene film,

Embodiments of the invention generally relate to polyethylene films. More specifically, embodiments of the present invention provide improved

To a high density polyethylene blown film having clarity and vapor barrier properties.

Historically, polyethylene resins have found wide applicability in the manufacture of blown films. Certain characteristics of the film, such as sharpness and vapor barrier properties, depend, for example, on both the type of polyethylene used and the method of production. However, it is difficult to achieve a specific combination of properties, since improving one characteristic can have side effects on another characteristic. For example, medium density polyethylene (MDPE) and high density polyethylene (PDPE) can be used to produce blown films. Generally, MDPE has a high clarity but forms a blown film with low vapor barrier properties, while HDPE produces a blown film with low clarity but high vapor barrier properties.

Therefore, there is a need to produce a polyethylene blown film having both high sharpness and high vapor barrier properties.

An embodiment of the present invention includes a blown film. Blown films generally include high density polyethylene having a molecular weight distribution of from about 1.5 to about 8.0 and a density of from 0.94 g / cc to less than 0.96 g / cc.

 Embodiments of the invention further include a method of forming a blown film. In one or more embodiments, the process generally comprises providing a high density polyethylene exhibiting a molecular weight distribution of from about 1.5 to about 8.0 and a density of from 0.94 g / cc to less than 0.97 g / cc, and blowing the high density polyethylene to a film .

 In another embodiment, the process generally comprises contacting ethylene monomers in a continuous stirred tank reactor in the presence of a catalyst system under conditions sufficient to polymerize ethylene monomers and form polyethylene, to produce a high density polyethylene having a molecular weight distribution from about 1.5 to about 8.0 And blowing the polyethylene into a film exhibiting an oxygen vapor transmission rate of less than about 280cc * mil / 100in2 / day.

The present invention has the effect of producing a polyethylene blown film having both high sharpness and high vapor barrier properties.

From now on, a detailed description will be provided. The appended claims define separate inventions, each of which is deemed to include equivalents or limitations to the various elements set forth in the claims for infringement purposes. Depending on the context, all the following references to "invention" may in some cases relate only to a specific embodiment. In other instances, it will be appreciated that references to "invention" will relate to the subject matter set forth in one or more of the claims, but not necessarily all. While the invention will be described in more detail below with reference to specific embodiments, variations and examples, it is to be understood that the invention is not limited to the particular embodiments disclosed, It is not limited to these embodiments, modifications, and examples.

 Various terms as used herein are described below. To the extent that the terms used in the claims are not defined below, the broadest definition should be provided at the time of filing to provide those terms as reflected in the published publications and patents of the persons skilled in the art. In addition, unless otherwise specified, all of the compounds described herein may be substituted or unsubstituted, and the list of compounds includes derivatives thereof.

In addition, various ranges and / or numerical limitations can be clearly defined below. Unless defined otherwise, it should be recognized that the endpoints are intended to be compatible. Additionally, any range includes similarly sized repeating ranges within clearly defined ranges or limits.

 Embodiments of the present invention generally provide unpredictable polymers and methods for forming polyethylene films, particularly polyethylene blend films having both high clarity and high vapor barrier properties.

 Catalyst system

 Useful catalyst systems for polymerizing olefin monomers include any suitable catalyst system. For example, the catalyst system may comprise a chromium-based catalyst system, a single-site transition metal catalyst system comprising a metallocene catalyst system, a Ziegler-Natta catalyst system, or a combination thereof. For example, the catalyst may be activated for subsequent polymerization and may or may not be associated with the support material. A brief description of such catalyst systems is included below, but is not intended to limit the scope of the invention with such catalysts.

 For example, a Ziegler-Natta catalyst system is generally produced from a combination of a metal component (e.g., a catalyst) and one or more additional components such as, for example, a catalyst support, cocatalyst and / or one or more electron donors .

 In at least one embodiment, the Ziegler-Natta catalyst system comprises a magnesium-supported catalyst system. For example, a magnesium-supported Ziegler-Natta catalyst can be prepared by a non-limiting exemplary process having three or more sequential steps: (1)

Preparing a metal dialkoxide as a reaction product of an alkyl and an alcohol; (2) preparing a soluble catalyst precursor as a reaction product of a metal dialkoxide and a halogenating agent / titanating agent; And (3) preparing a final solid catalyst component as a reaction product of the soluble catalyst precursor and the precipitant. The precipitant may also be a halogenating agent / titanating agent in some embodiments. The process may include additional steps such as, for example, additional halogenation / titanation steps.

 The metal dialkyl may comprise Group IIA metal dialkyl. In one or more embodiments, the metal dialkyl includes, for example, magnesium dialkyl. The magnesium dialkyl can include, for example, diethylmagnesium, dipropylmagnesium, dibutylmagnesium, butylethylmagnesium (BEM), and combinations thereof.

 The metallocene catalyst generally comprises at least one cyclopentadienyl group (Cp) group (which may be substituted or unsubstituted, each substituent may be the same or different) coordinated to the transition metal through a pi bond May be characterized by coordination compounds. The substituent on Cp may be, for example, a linear, branched or cyclic hydrocarbyl radical. The cyclic hydrocarbyl radicals can also produce other adjacent ring structures including, for example, indenyl, azulenyl and fluorenyl groups. These adjacent ring structures may also be substituted or unsubstituted, for example, by hydrocarbyl radicals such as C1 to C20 hydrocarbyl radicals.

 Polymerization process

 As indicated elsewhere herein, catalyst systems are used to form polyolefin compositions. Once the catalyst system is prepared, a variety of processes can be performed using the composition, as described above and / or as known to those skilled in the art. The equipment, process conditions, reactants, additives, and other materials used in the polymerization process are preferably

Will vary in a given process depending on the composition and properties. Such processes may include, for example, solution phase, gas phase, slurry phase, bulk phase, high pressure process, or combinations thereof (see, US Patent No. 6,359,072, US Patent No. 6,346,586, US Patent No. 6,340,730, US Patent No. 6,339,134, US Patent No. 6,300,436, US Patent No. 6,274,684, US Patent No. 6,271,323, US Patent No. 6,248,845, No. 6,245,868; U.S. Patent No. 6,245,705; U.S. Patent Nos. 6,242; 545; U.S. Patent No. 6,211,105; U.S. Patent No. 6,207,606; U.S. Patent Nos. 6,180,735 and U.S. Patent No. 6,147,173).

 In certain embodiments, the processes described above generally comprise polymerizing one or more olefin monomers to form a polymer. The olefinic monomers may include C2 to C30 olefin monomers or C2 to C12 olefin monomers such as ethylene, propylene, butene, pentene, methylpentene, hexene, octene and decene. The monomers may include olefinically unsaturated monomers, such as C4 to C18 diolefins, conjugated or non-conjugated dienes, polyenes, vinyl monomers and cyclic olefins. Non-limiting examples of other monomers include, for example, norbornene, norbornadiene, isobutylene, isoprene, vinylbenzocyclobutane, styrene, alkyl substituted styrene, ethylidene norbornene, dicyclopentadiene, and cyclo Pentene. The resulting polymer may, for example, comprise a homopolymer, a copolymer or a trimer.

Examples of solution processes are described in U.S. Pat. No. 4,271,060, U.S. Pat. No. 5,001,205, U.S. Pat. No. 5,236,998, and U.S. Pat. No. 5,589,555, all of which are incorporated herein by reference.

 An example of a gas phase polymerization process includes a continuous cycle system wherein a circulating gas stream (otherwise known as a recycle stream or flow medium) is heated by the polymerization heat in the reactor. Heat is removed from the circulating gas stream in another part of the circulation by the cooling system outside the reactor. A circulating gas stream containing one or more monomers can be continuously circulated through the fluidized bed in the presence of a catalyst under reaction conditions. The circulating gas stream is generally discharged from the fluidized bed and recycled back into the reactor. At the same time, the polymer product can be discharged from the reactor, and new monomers can be added to replace the polymerized monomers. The reactor pressure in the gas phase process may be, for example, from about 100 psig to about 500 psig, or from about 200 psig to about 400 psig, or from about 250 psig to about 350 psig. In a gas phase process, the reactor temperature may be, for example, from about 30 캜 to about 120 캜, or from about 60 캜 to about 115 캜, or from about 70 캜 to about 110 캜, or from about 70 캜 to about 95 캜 U.S. Patent Nos. 5,353,999; U.S. Patent Nos. 5,436,304; U.S. Pat. Nos. 5,436,304; U.S. Pat. U.S. Pat. No. 5,456,471; U.S. Pat. No. 5,462,999; U.S. Pat. No. 5,616,661; U.S. Pat. No. 5,627,242; U.S. Pat. No. 5,665,818; U.S. Pat. No. 5,677,375 and U.S. Pat. No. 5,668,228).

 The slurry phase process generally involves forming a suspension of solid particulate polymer in a liquid polymerization medium with monomers and optionally hydrogen added together with the catalyst. The suspension (which may include a diluent) may be removed intermittently or continuously from the reactor, where the volatile components are separated from the polymer and optionally recycled to the reactor after distillation. The liquefied diluent used in the polymerization medium may comprise, for example, a C3 to C7 alkane (e. G., Hexane or isobutane). The medium used is generally liquid under polymerization conditions and is relatively inert. The bulk phase process is similar to the slurry process except that the liquid medium is also a reactant (e.g., a monomer) in the bulk phase process. However, the process can be, for example, a bulk process, a slurry process, or a bulk slurry process.

 In certain embodiments, the slurry process or the bulk process may be performed continuously in one or more loop reactors. As a slurry or dry free flowing powder, the catalyst may be injected regularly into a reactor loop that can be self-filled with, for example, a circulating slurry of growing polymer particles in a diluent. Optionally, hydrogen may be added to the process, such as for molecular weight control of the resulting polymer. The loop reactor may be maintained at a pressure of, for example, from about 27 bar to about 50 bar or from about 35 bar to about 45 bar and a temperature of from about 38 ° C to about 121 ° C. The heat of reaction can be removed through the loop wall through any suitable method, such as, for example, through a double jacketed pipe or heat exchanger.

 In certain embodiments, the slurry process may be performed in a stirred reactor such as a continuous stirred tank reactor (CSTR).

 Alternatively, other types of polymerization processes may be used, such as, for example, a stirred reactor in series, in parallel, or a combination thereof. Upon removal from the reactor, the polymer may pass through the polymer recovery system for further processing, such as, for example, addition of additives and / or extrusion.

 Polymer product

 Polymers (and combinations thereof) formed through the processes described herein include, for example, linear low density polyethylene, elastomers, plastomers, high density polyethylene, low density polyethylene, medium density polyethylene, polypropylene and polypropylene copolymers But is not limited thereto.

 Unless otherwise stipulated herein, all test methods are current methods at the time of filing.

 In one or more embodiments, the polymer exhibits a un-modal molecular weight distribution. As used herein, the term "uni-modal" means a polymer composition that exhibits a single peak on a molecular weight distribution plot. In contrast, multi-modal polymer compositions generally exhibit multiple peaks on a molecular weight distribution plot.

 In one or more embodiments, the polymer comprises an ethylene-based polymer. As used herein, the term "ethylene based" is used interchangeably with the term "ethylene polymer" or "polyethylene ", for example, Or about 70% or more, or about 75% or more, or about 80%

By weight or more, or about 85% by weight or more, or about 90% by weight or more.

The ethylene polymer may have a narrow molecular weight distribution. As used herein, the term "narrow molecular weight distribution" refers to a polymer having a molecular weight distribution of, for example, from about 1.5 to about 8, or from about 2.0 to about 7.5, or from about 2.0 to about 7.0, or from about 4.5 to about 7.0. ≪ / RTI > The molecular weight distribution is represented here by the "dispersion index" (D) which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn); D = Mw / Mn. The dispersion index also means "polydispersity" and is measured by gel permeation chromatography (GPC).

 The ethylene polymer may have a molecular weight of from about 0.86 g / cc to about 0.98 g / cc, or from about 0.88 g / cc to about 0.965 g / cc, or from about 0.90 g / cc to about 0.965 g / / cc to about 0.97 g / cc (as measured by ASTM D-792).

The ethylene polymer may be used in an amount of, for example, from about 0.01 dg / min to about 100 dg / min, or from about 0.01 dg / min to about 25 dg / min, or from about 0.03 dg / min to about 15 dg / (MI2) (measured by ASTM D-1238) of from about 0.05 dg / min to about 10 dg / min.

 In at least one embodiment, the polymer comprises high density polyethylene. As used herein, the term "high density polyethylene" refers to polyethylene having a density of from about 0.94 g / cc to 0.97 g / cc, or from about 0.95 g / cc to 0.97 g / cc or from 0.95 g / cc to 0.96 g / lt; RTI ID = 0.0 > cc. < / RTI >

 In at least one embodiment, the polymer comprises a medium density polyethylene. As used herein, the term "medium density polyethylene" refers to an ethylene polymer having a density of, for example, from about 0.92 g / cc to 0.94 g / cc.

 Product use

 Polymers and blends thereof are useful in applications known to those skilled in the art such as molding operations (e.g., film, sheet, pipe and fiber extrusion and coextrusion as well as blow molding, injection molding and rotational molding). Films can be used in the fields of food contact and non-food contact applications such as shrink films, kling films, stretch films, sealing films, stretch films, snack packaging, sturdy bags, grocery colors, baking and frozen food packaging, Films which are useful as industrial liners and films, blown, oriented or cast formed by extrusion or co-extrusion or by lamination. The fibers may be in the form of slits, films, monofilaments, or woven fabrics for use in the form of fabrics or nonwoven fabrics for making color, bags, ropes, strings, carpet backings, carpet threads, filters, diaper fabrics, Melt spinning, solution spinning, and melt blown fiber working. The extruded article may be, for example, a medical tube, wire and cable sheath, sheet, thermoformed sheet,

And a fishing port liner. Molded articles include, for example, bottles, tanks, large hollow articles, hard food containers and toys in the form of single and multi-layered articles.

 In at least one embodiment, the polymer and blends thereof are used to prepare a blown film. The blown film can be produced by a known process such as drawing the molten polymer upward at a speed of the nip roller that determines the thickness of the film, and upward from the die by the nip roller over the die. The air-ring surrounding the die can cool the film as it moves upward. The air outlet pushes the compressed air into the center of the extruded circular polymer to expand the extruded circular cross section to a ratio of " blow-up ratio "of 200% or less of the original diameter,

Bubble. "The resulting film is characterized by a variety of properties both physical and functional, and the desired properties are knotted by the intended use.

 In one or more embodiments, the blown film exhibits a haze of, for example, about 20% or less, or about 15% or less, or about 10% or less. As used herein, the term "haze" means the ratio of transmitted light through the film and is measured using a haze meter according to standard ASTM-D1003. Embodiments of the invention form a blown film having improved clarity over a blown film formed from a high density polyethylene (e.g., "comparative polyethylene") having a density greater than 0.960 g / cc, and in one or more embodiments , Which has unexpectedly similar sharpness than films formed from medium density polyethylene.

 In one or more embodiments, the blown film formed from an embodiment of the present invention exhibits improved vapor barrier properties over a blown film formed from medium density polyethylene, and in one or more embodiments has a high density with a density greater than 0.960 g / cc Exhibit higher vapor barrier properties than polyethylene. The vapor barrier properties are measured by determining the vapor permeability per unit area of the film per unit time. Representative vapors thus characterized include oxygen (O 2) and water (H 2 O) vapors.

In one or more embodiments, the blown film exhibits an oxygen transmission rate of, for example, about 300 cc * mil / 100 in 2 / day or less or about 280 cc / 100 in 2 / day or less. In one or more embodiments, the blown film exhibits a water vapor transmission rate of, for example, less than about 0.8 g * mil / m 2 / day, or less than 0.6 g * mil / m 2 /

Claims (9)

In a blown film,
In a blown film comprising a high density polyethylene exhibiting a molecular weight distribution of from about 1.5 to about 8.0 and a density of from 0.94 g / cc to less than 0.96 g / cc,
Wherein the film exhibits lower haze and lower oxygen permeability than the blown film formed from the comparative high density polyethylene. The blown film of claim 1, wherein the high density polyethylene exhibits a molecular weight distribution from about 4.0 to about 7.0. The blown film of claim 1, wherein the 1.0 mil film has a haze of about 20% or less. The blown film of claim 1, wherein the 1.0 mil thick film exhibits an O2 permeability of about 300 cc / 100 in 2 / day or less. The blown film of claim 1, wherein the 1.0 mil thick film exhibits an O2 permeability of about 280 cc / 100 in2 / day or less. The blown film of claim 1, wherein the 1.0 mil thick film exhibits a water vapor transmission rate of about 0.8 cc / 100 in2 / day or less. A method for forming a blown film,
Providing a high density polyethylene having a molecular weight distribution of from about 1.5 to about 8.0 and a density of from 0.94 g / cc to less than 0.96 g / cc;
And blowing the high-density polyethylene to a film. A method for forming a blown film,
Providing a high density polyethylene having a molecular weight distribution of from about 1.5 to about 8.0 and a density of from 0.94 g / cc to less than 0.96 g / cc;
And blowing the high-density polyethylene into a film,
Wherein the film exhibits lower haze and lower oxygen permeability than the blown film formed from the comparative high density polyethylene. 9. The method of claim 8, wherein the high density polyethylene exhibits a molecular weight distribution from about 4.0 to about 7.0.