CA2340662A1 - Blends containing linear low density polyethylene, high density polyethylene, and low density polyethylene particularly suitable for extrusion coating and films - Google Patents
Blends containing linear low density polyethylene, high density polyethylene, and low density polyethylene particularly suitable for extrusion coating and films Download PDFInfo
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- CA2340662A1 CA2340662A1 CA002340662A CA2340662A CA2340662A1 CA 2340662 A1 CA2340662 A1 CA 2340662A1 CA 002340662 A CA002340662 A CA 002340662A CA 2340662 A CA2340662 A CA 2340662A CA 2340662 A1 CA2340662 A1 CA 2340662A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/10—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of paper or cardboard
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B29/00—Layered products comprising a layer of paper or cardboard
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/06—Polyethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/08—Copolymers of ethene
- C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
- C08L23/0815—Copolymers of ethene with aliphatic 1-olefins
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2270/00—Resin or rubber layer containing a blend of at least two different polymers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2439/00—Containers; Receptacles
- B32B2439/70—Food packaging
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2323/04—Homopolymers or copolymers of ethene
- C08J2323/08—Copolymers of ethene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2423/04—Homopolymers or copolymers of ethene
- C08J2423/08—Copolymers of ethene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
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- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Laminated Bodies (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
A novel composition of at least three different polyethylene-based component s is provided. The blend comprises a linear low density polyethylene, a high density polyethylene and a low density polyethylene. The composition can be used in extrusion coating, in preparing films, cast or blown included, and other applications, such as laminates.
Description
WO 00/11075 PCT/US9911$G05 BLENDS CONTAINING LINEAR LOW DENSITY POLYETHYLENE, HIGH DENSITY POLYETHYLENE, AND LOW DENSITY POLYETHYLENE
PARTICULARLY SUITABLE FOR EXTRUSION COATING AND FILMS
FIELD OF THE INVENTION
The present invention relates to a composition comprising a blend of at least three polyethylene components particularly useful for extrusion coating, a process using such blends for extrusion coating, and the composite produced thereby.
The invention also relates to f Ims produced from the blends.
BACKGROUND OF THE INVENTION
Prior art polyolefin blends, containing linear low density polyethylene as a component, are useful in certain extrusion coating applications. One such prior art blend is Dow Chemical's Dowlex 3010 linear low density polyethylene, which contains at least 80 weight percent linear low density polyethylene. Examples of extrusion coating applications are structures such as flexible polymeric film/paper packages for foods, arid metallized polymeric film balloons. The linear low density polyethylene component in'the prior art blends provides strong heat seals (coating-to-coating); strong tensile properties of coatings; strong resistance of coatings to tear; high resistance o:P coatings to missile, or dart, impact; resistance of coatings to puncture; and coating stress crack resistance. These properties are generally not attainable with polyolefin blends which contain no linear low density polyethylene.
However, these prior art blends containing linear low density polyethylene exhibit certain undesirable processing problems.
The prior art blends, that contain high levels of linear low density polyethylene, i.e., 80 weight percent and greater, generally require excessive power (extruder motor drive watts) to be extruded during the extrusion coating operation.
Frequently, the production rates of an extrusion coating operation must be slowed _2-so as not to exceed the limits of the extruder drive motors. In many cases, productivity is so low as to result in economic losses.
Further, the prior art blends, that contain high levels, i.e., 80 weight percent and greater, of linear low density polyethylene, generally exhibit excessive extrudate edge bead, manifested by excessive neck-in of the molten extrudate.
This is a problem readily known to those skilled in the art of extrusion coating.
Excessive edge bead must be trimmed away and disposed of as scrap. Otherwise, a final coated structure will not exhibit a uniform thickness.
It would obviously be desirable in an extrusion coating operation to utilize a polyolefin composition containing linear low density polyethylene as a component which would extrude at significantly lower power requirements and with significantly less edge bead. It would further be desirable for that same polyolefin 1 b composition containing linear low density polyethylene as a component to retain the desired coating properties exhibited by the prior art two component polyolefin blends containing linear low density polyethylene as the major component of the two components. The properties include strong heat seals (coating-to-coating);
strong tensile properties of coatings; strong resistance of coatings to tear;
high resistance of coatings to missile, or dart, impact; coating puncture resistance; and resistance of coatings to stress cracking.
The present inventors have unexpectedly discovered an improved extrusion coating polyolefin composition comprising a blend of a linear low density polyethylene, a high density polyethylene, and a low density polyethylene. The composition of the present invention desirably extrudes with lower power requirements (extruder drive motor watts) than the prior art two component blends containing linear low density polyethylene. This occurs even though the compositions of the present invention require significantly more thermal energy per unit of mass to melt than is required by the prior art blends. The compositions of the present invention exhibit significantly less neck-in (less edge bead) than that exhibited by the prior art compositions.
The compositiion according to the present invention is a polyolefin blend comprising at least the following three components. The first component is a linear low density polyethylene which generally provides coating-to-coating heat seal strength, toughness, tear resistance, and puncture resistance. In general, the properties are essentially equal to those exhibited by the prior art compositions.
The second component is a high density polyethylene copolymer which generally provides tensile strength and stress crack resistance properties. The properties are generally substantially equal to the prior art compositions. The third component is a low density polyethylene homopolymer which generally contributes to a reduced edge bead by providing a lower neck-in of the molten extrudate. Generally, this property of neck-in is superior to the prior art compositions. Moreover, the third component also generally provides good wetting of the substrate surface to which the blend is coated, for good coating-to-substrate bonding. Accordingly, the present invention that contains a lower amount of linear low density polyethylene than prior art compo:>itions is utilized without a loss in coating properties that would be normally expected with a reduction in linear low density polyethylene content.
The present invention is also directed to an improved extrusion coating process comprising the use of the above-mentioned composition of at least a linear low density polyethylene, a high density polyethylene, and a low density polyethylene. Furthf;r, the present invention is also directed to a coated article or composite comprising a substrate, either primed or unprimed, having the aforementioned composition coated thereon, preferably by means of an extrusion coating process. Thc; primer used to provide bonding to a substrate is preferably a water-soluble primer, more preferably a polyethyleneimine primer. Furthermore, WO 00/11075 PCT/US9911$605 the present invention includes laminates wherein a layer of the aforementioned three component composition is utilized between two similar or dissimilar substrates, optionally including a primer layer between the polyethylene blend and each substrate. The resultant composite or laminate may be formed into an article, such as a package for food, having good barner properties, that is, the package is generally impermeable to liquids and gases. The present invention is also directed to films prepared from the novel compositions, particularly by means of cast or blown film techniques.
It is, therefore, an object of the invention to provide novel compositions comprising a blend of at least a linear low density polyethylene, a high density polyethylene, and a low density polyethylene.
Another object of the invention is to provide an improved extrusion coating process wherein there is utilized as the extrusion coating, the novel compositions comprising the blends of the present invention as defined herein.
It is a further object of this invention to provide a coated substrate or a composite wherein the coating composition comprises the novel blends of the present invention as defined herein.
A still further. object of this invention is to provide a coated substrate or a composite wherein tile coating composition comprising the novel blends of the present invention is applied onto the substrate by an extrusion coating process.
These and otlher objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description, preferred embodiments, specific examples, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures 1 and 2 are obtained using differential scanning calorimetry (1.~SC) to determine melting point profiles, in particular, the maximum melting point and the thermal energy pf;r unit mass required to melt the mass. The melting point profile and pertinent calorimetry data of the prior art two component blend is shown in Figure 1. The melting point profile and pertinent calorimetry data of a three component blend of the present invention is shown in Figure 2.
DETAILED DESCRIPTION OF THE INVENTION
The novel compositions of the present invention comprise blends of a linear low density polyethylene, a high density polyethylene, and a low density polyethylene.
The linear low density polyethylene component of the blend is known to generally provide heat seal strength, toughness, tear resistance and puncture resistance properties to an extruded coating. The linear Iow density polyethylene component of the composition is a low density polyethylene copolymer comprising ethylene and a C3-Coo alpha-olefin comonomer. The alpha-olefin comonomer is preferably a C6-Cs alpha-olefin, and more preferably an ethylene-hexene or ethylene-octene copolymer. The alpha-olefin comonomer is present in an amount of about 5 to about 12 percent by weight of the ethylene-alpha olefin copolymer, more preferably an amount of from about 7 to about 10 percent by weight. The ethylene-alpha olefin copolymer component is further characterized by having a melt index value measured at 190°C, of about 0.5 dglmin. to about 10 dg/riiin., more preferably from about 1 dglmin. to about 3 dg/min., and most preferably is about 2 dg/min.; a swell ratio of about 1.0 to about 1.2; an annealed density of about 0.90 g/cc to about 0.93 g/cc; and a polydispersity index of about 1 to about 4.
The ethylene-alpha olefin linear low density copolymers may be produced by any method known in the art such as, for example, described in U. S. Patent No.
4,339,507.
The linear low density ethylene copolymer component of the blend of the present invention is present in an amount of about 25 to about 40 weight percent, based on the weight of the blend, more preferably in an amount of from about 30 to about 35 weight percent, and most preferably, in an amount of about 33 weight percent, based on the weight of the blend.
The high density polyethylene component of the blend is known to generally provide tensile strength and stress crack resistance to the blend of the present invention. The high density polyethylene component of the novel composition is a homopolyrner of ethylene or a copolymer of ethylene and an alpha olefin comonorner. T'he alpha olefin comonomer preferably has about 3 to about 10 carbon atoms. The alpha olef n comonomer is present in an amount of about 0.2 to about 1 percent by weight of the copolymer, more preferably about 0.4 to about 1.5 0.7 percent by weight, and still more preferably in an amount of about 0.5 percent by weight, based on the weight of the copolymer. The preferred comanorner is hexene. The high density polyethylene component is further characterized as having an annealed density of at least 0.940 g/cc to about 0.97 g/cc, more preferably from about 0.95 g/cc to about 0.97 g/cc; a malt index of about 6 dglmin. to about 20 dg/min., more preferably about 14 dg/min. to about dg/min., and most preferred about 16 dg/min., measured at 190°C. The high density polyethylene component may be produced by any method known in the art, such as, for example, that described in U.S. Patent No. 4,339,507.
The high density polyethylene component of the blend of the present invention is present in an amount of from about 25 to about 40 weight percent, based on the weight of the blend, more preferably, in an amount of from about to about 35 weight percent, and most preferably in an amount of about 33 weight percent, based on the; weight of the blend.
The low densiity polyethylene component of the blend of the present invention generally provides good wetting of a substrate to allow a good bonding to the substrate. The low density polyethylene component of the novel composition is a polyethylene of broad molecular weight distribution, as indicated by having a polydispersity index above 9 to about I2. The low density polyethylene is further characterized by having a melt index value of about 3 dg/min. to about 40 dglmin., more preferably from about 6 dg/min. to about 30 dglmin., still more preferably from about I8 dg/min. to about 22 dg/min., and most preferably about 20 dg/min., measured at 190°C. The low density polyethylene is further characterized by having an annealed density of from about 0.90 glcc to about 0.93 g/cc.
The low density polyethylene component of the blend of the present invention is present in an amount of from about 25 to about 40 weight percent, based on the weight of the blend, more preferably in an amount of from about 30 to about 35 weight percent, and most preferably, in an amount of about 33 weight percent, based on the; weight of the blend.
The novel compositions of the present invention may be prepared using any method known in the art. Fax example, the compositions may be prepared by dry blending or tumbling in any conventional equipment or by mixing in any conventional mixing equipment such as single and twin screw extruders, Werner Pfleiderer mixers, Banbury mixers or the like.
As will become apparent hereinafter, it has been found that less power is required to extrude the compositions of the present invention than the prior art blends. This is quite; unexpected since the novel compositions of the present invention require a greater amount of thermal energy to be melted than is necessary to melt the prior art blends.
_$.
The substrate to which the blend of the present invention is applied is preferably a primed substrate. The primer is preferably a water-soluble primer.
More preferably, the :>ubstrate is primed with polyethyleneimine. After priming, the primed surface is then extrusion coated with the blend. The polyethyleneimine used to prime the various substrates to be extrusion coated with the blends of the present invention is most preferably MICA Corporation's A-131-X
polyethyleneimine primer. Extrusion coating methods are well known in the art.
One skilled in tt~e art can readily extrusion coat or extrusion laminate a composition of the present invention onto primed or unprimed surfaces to prepare a composite or laminate.
The composition of the present invention may be extrusion coated to a substrate or extrusion iarninated between two substrates. Extrusion coating and laminating means and methods are well known in the art, and it is expected that any of such methods may be utilized. in the present invention. It is also possible to coextrusion coat the novel compositions to a structure of at least one or more substrates. The laminating process may further include the step of preparing a film from the composition of the present invention. The film may be, for instance, a cast or blown film. 'lChe skilled artisan would be well aware of the methods available in the art to~ prepare a film from the blends of the present invention.
There are many metriods known in the art for preparing film using cast or blown film techniques.
The substrate to which the blends of the present invention may be coated or laminated may be any substrate to which polyolef ns are normally coated.
Examples of suitable; substrates include, but are not limited to, paper or paperboard (printed or unprintedl), coated, e.g. clay-coated or uncoated, metal foils, plastic films and the like. These surfaces may be primed or unprimed, with a preference for primed surfaces.
_g_ A laminate according to the present invention comprises two substrates, each of which may bc~ independently primed or unprimed on the surface facing the other substrate, with the composition of the present invention between the substrates. In such a laminate, the substrates may be similar or dissimilar.
For example, the substrates may both be paper or one substrate may be paper and the other substrate may be a polymeric film.
The skilled a~~tisan can determine optimum conditions for coating or laminating without difficulty.
Films may bE; produced from the novel compositions of the present invention by any known technique. Preferred herein are the cast and blown film techniques, both of which are well known in the art.
The composition of the present invention can contain other ingredients;
such as additional polyethylene components, fillers, slip agents, tackifiers, pigments, and the like, as known in the art, provided the compositions are not adversely affected.
The invention will be more readily understood by reference to the following examples. There are, of course, many other forms of this invention which will become obvious to one skilled in the art, once the invention has been fully disclosed, and it will accordingly be recognized that these examples are given for the purpose of illustration only, and are not to be construed as limiting the scope of this invention in any way.
EXAMPLES
In the following examples the test procedures listed below were used in evaluating the analytical properties of the polyethylenes herein and in evaluating the physical properties of the compositions of the examples.
wo oomo~s rcT~s~9nssos Melt Index, dglmin., was determined in accordance with ASTM D 123 $-62T
at 190°C {374°F).
Swell Ratio is defined as the ratio of the extrudate over that of the orifice diameter of the extrusion plastorneter in ASTM D1238-62T. The diameter of the specimen is measured in the area between 0.159-cm and 0.952-cm of the initial portion of the specimen as it emerges from the extrusion plastometer.
Measurements were made by standard methods according to ASTM D374.
Annealed Density, g/cc, was determined in accordance with ASTM D1505.
Polydispersity Index is the ratio of the weight-average molecular weight, Mw, to number-average molecular weight, Mn. Mw and Mn were obtained by size-exclusion chromatography on a Waters 150C gel permeation chromatograph equipped with the standard refractomefer detector and a Viscotek 1 SOR
differential viscometer system. The 3-column set consisted of Waters' 103, 104, and linear-mixed bed (10~, 10', and 103) Micro-Styragel HT columns. The samples were run as 0.125% weight-to-volume solutions in ortho-dichlorobenzene at 140°C.
The data were interpreted using Viscotek Unical software (V4.02), by universal calibration using NBS 1475 (linear polyethylene) and NBS 1476 {branched polyethylene) for any polyethylene sample.
Differential Scanning Calorimetry maximum melting points, °C, and the energy required to melt a given mass of polyolefin, expressed in Joules/gram, were determined in accordance with ASTM D341$.
Neck-in, inches/edge or cm/edge was determined by first measuring the width of an extrusion coating, W, on a substrate, and then subtracting that measurement from the width of the extrusion coating die, D. The difference, (D-V~ is then divided by 2, i.e. (D-V~/2, resulting in the amount of extrudate neck-in per edge.
Ultimate Heat; Seal Strength, grams force, was determined on a Theller Model HT tack heat sealer as described in U.S. Patent No. 5,331,858.
Tensile Properties, tensile strength at fracture and tensile strength at yield, both expressed in lb/in2 (or megapascals); and elongation at break, expressed in percent, were determined in accordance with ASTM D882.
Tear Strength, expressed in grams-force, or millinewtons, was determined in accordance with A.STM D1992.
Dart Impact Resistance, grams at 50% failure, was determined in accordance with ASTM D 1709A.
Puncture Resistance, ib/mil, was determined in accordance with ASTM
D4649.
Stress Crack, hours to 50% failure (Fso) was determined in accordance with ASTM D 1693-94.
Example 1 (Comparative) In this example, the composition utilized was Dow Chemical Company's Dowlex 3010 polyethylene, which is believed to be a blend of about 80 weight percent ethylene-octene copolymer, containing about 7 to about 10 weight percent octene, and about 2C1 weight percent low density polyethylene. Further, the blend has a melt index of '.i.8 dglmin. at 190°C and an annealed density of 0.922 g/cc.
Pellets of the Dowlex 3010 blend were tested using differential scanning calorimetxy to deterrniine the melting point profile, particularly the maximum melting point and the thermal energy per unit mass required to melt the mass.
The melting point profile and calorimetry data obtained for the Dowlex 3010 blend are shown in Figure 1.
The Dowlex 3010 blend was extrusion coated, a process well known in the art, to a 40 pound natiural Kraft paper. The Dowlex 3010 blend was applied to the Kraft paper at a melt temperature of 601 °F (3I7°C), from a 3.5 inch diameter extruder with its barrel heaters set at 397°F (203°C), 500°F (260°C), 600°F
(315°C) and 645°F (340°C). The extrusion die throughput rate was maintained constant at 10 lb/inch/hr (1.8 kglcm/hr) of die width. Extruder power, measured in percent motor load, and kilowatts required to extrude the Dowlex 3010 blend, at the constant extruder throughput rate, are shown in Table I. Also shown in Table I
is the energy required to melt a given mass of the Dowlex 3010 blend, as well as the maximum melting point of the Dowlex 3010 blend.
Example 2 A composition of the present invention was prepared by dry blending the following components:
(a) 33 weight percent of Eastman Chemical Company's CM 27057-F
linear low density polyethylene, based on the weight of the composition. The linear Iow density polyethylene is an ethylene-hexene copolymer containing about 8% by weight of hexene having a melt index of about 2.0 dg/min. at 190°C, an annealed density of about; 0.910 g/cc, a swell ratio of about 1.2, and a polydispersity index: of about 3.
(b) 33 weight percent of Eastman Chemical Company's HT 7011-X
high density polyethylene, based on the weight of the composition.
WO 00/11075 PCTICIS99/i8605 The high density polyethylene is an ethylene-hexene copolymer containing about 0.7 weight % hexene, having a melt index of 16 dgJmin. at 190°C and an annealed density of 0.96 g/cc; and (c) 33 weight percent of Eastman Chemical Company's 811A low density polyethylene, based on the weight of the composition. The low density polyethylene is a polyethylene homopolymer having a melt index of about 20 dglmin. at 190°C and an annealed density of about 0.92 g/cc. The low density polyethylene is further characterized as having a broad molecular weight distribution as reflected in a polydispersity index of about 10.
The resultant. blend of the three components, which is an exemplary composition of the present invention, is characterized by having a melt index of about 5.5 dglmin. at 190°C and an annealed density of about 0.922 g/cc.
Pellets of the; composition of this example were tested using differential scanning calorimetry to determine its melting point profile, particularly the maximum melting point of the blend and the thermal energy per unit mass of the composition required to melt the mass. The melting point profile and calorimetry data of the blend of this example is shown in Figure 2.
The resultant blend of this example was extrusion coated to natural 40 lb.
Kraft paper. The blend was applied at a melt temperature of 596°F
{313°C) to the Kraft paper from a 3.5 inch diameter extruder with its barrel heaters set at 398°F
{203°C), 499°F (259°C), 600°F (315°C) and 639°F (338°C). The extrusion screw was single-flighted with a compression ratio of 3.5: I , providing a uniform output through the die. The extrusion die throughput rate was held constant at 10 lb/inch/hr (1.8 kg/cm/hr) of die width. Extruder power, measured in percent motor Ioad and kilowatts required to extrude the blend of this Example 2, noted at the constant extruder throughput rate, are reported in Table I. Also reported in Table I
is the energy required to melt a given mass of the blend of this Example 2, as v~iell as the maximum melting point of the blend.
Table 1 Property Property UnitsBlend of ExampleBlend of Example Motor Load Percent 87 76 Drive Motor Kilowatts 16.0 I4.0 Power Energy RequiredJoules/gram 79.7 93.56 to Melt Maximum MeltingC 123.01 128.28 Point of Pellets From the data in Table I, the following observations can be made. The novel composition of Example 2, typical of the present invention, can be extruded using a lower extrudex drive motor load than is required for the prior art blend of Example 1. In this instance; the reduction in extruder drive motor load is 12 percent.
Further, the blend of Example 2 can be extruded using less extruder drive motor power than is required for the prior art blend of Example I . The reduction herein was 12 percent in extruder drive motor power. The lowering of extruder drive motor power permits an extrusion coating operation to produce product with greater latitude in power requirements before maximum drive motor load is exceeded.
The reduction in power requirements accompanying usage of the compositions of the lxesent invention is quite unexpected since the data in Table I
reveals that the energy required to melt a given mass of the composition of Example 2 is 15 percent greater than is required to melt a mass of the blend of Example I (the prior art blend}. Based on the difference in thermal energies required to melt the blends of Examples I and 2, one would have predicted the opposite result, narnc~ly, a higher power requirement accompanying a composition _15_ of the present invention, as typified by the blend of Example 2, when compared with the prior art blend of Example 1.
Example 3 (COMPARATIVE) In this examplle was used the same composition as in Example l, namely Dow Chemical Company's Dowlex 3010 blend. The Dowlex 3010 blend was extrusion coated to natural 40 lb. Kraft paper. The Dowlex 3010 blend was applied to the Kraft paper at a melt temperature of 60I °F (317°C) from a 3.5 inch diameter extruder with its barrel heaters set at 397°F (203°C), 500°F {260°C), 600°F
(315°C) and 645°F (340°C). The extrusion die throughput rate was held constant at 10 lb/inch/hr (1.8 kg/cm/hr) of die width. The die to nip air gap was 5.25 inches (6.4 cm). Samples of the coated Kraft paper were obtained at 600 fpm (185 rn/min.) and at 1000 fpm (305 rn/min.) and neck-in measurements of the prior art Dowlex 3010 blend coatings were taken at each speed. The results are reported in Table II.
Example 4 The same composition as described in Example 2 herein was extrusion coated to natural 40 lb. Kraft paper. The composition was applied to the natural Kraft paper at a melt temperature of 596°F (313°C), from a 3.5 inch diameter extruder with its barrel heaters set at 398°F (203°C), 499°F (259°C), 600°F
(315°C), and 639°F (338°C). The extrusion die throughput rate was held constant at 10 lb/inch/hr ( 1.8 kg/cm/hr) of die width.. The die to nip air gap was 5.25 inches (6.4 cm). Samples of the coated Kraft paper were obtained at 600 fpm (185 m/min.
) and at 1000 fpm {305 m/min.), and neck-in measurements of the coating of the blend of Example 2 (typical of the present invention) were taken at each speed.
The results are reported in Table II.
Table TI
Properly Properly UnitsBlend of ExampleBlend of Example Neck-in at 600 Inches(cm)Bdge2.55(6.50) 2.40(6.10) fpm Neck-in at 1000Inches(cm)IEdge2.50(6.35) 2.30(5.85) fpm A review of th.e data in Table II permits the (allowing abservations to be made. The compositions of the present invention, as typified by Example 4, offer lower, and therefore superior, neck-in values when compared to the prior art blend of.Example 3. Lower neck-in values result in a wider extnzsion coating and a reduced edge bead of the molten extrudate. Edge beads are normally slit and discarded as scrap, resulting in an economic loss. Accordingly since the compositions of the present invention are characterized by lower neck-in, and reduced edge bead, the economic loss is decreased since Iess is discarded as edge bead scrap when compared with use of the prior art blend of Example 3.
Example 5 1 b The same composition of Example 1 herein, namely Dow Chemical Company's Dowlex 3010 blend, was cast into film by known techniques at a melt temperature of 603°F (3I8°C) and at a sufficient haul-off speed to obtain a film thickness of 0.001 inch (0.0254 mm). The resultant cast film was tested for heat seal strength (film to :elm); tensile properties; resistance to tear;
resistance to missile, or dart, impact; and puncture resistance. In addition, pellets of the Dowlex 3010 blend were pressed into sheets and tested for stress crack resistance.
The results are reported in. Table III.
Following the aforementioned procedure, the composition of Example 2 was formed into cast film at a melt temperature of 603°F (318°C}
at a sufficient haul-off speed to obtain a film thickness of 0.001 inch (0.0254 mm). The resultant cast film was tested for heat seal strength (film to film}; tensile properties;
resistance to tear; resistance to missile, or dart, impact; and puncture resistance.
Pellets of the composition of Example 2 were pressed into sheets and tested for stress crack resistance;. The properties are reported in Table III.
Table III
Property Property UnitsBlend of ExampleBlend of Example Tensile StrengthIblin2 (kPa) 4230-517.0 4032-4928 at Break (Machine (29200-35600) (27600-34000) Direction) Tensile StrengthIb/in2 (kPa) 1764-2156 2385-2915 at Yield (Machine (12400-14900} (16500-21000) Direction) Elongation Percent 689-76I 599-661 (Machine Direction) 'Tensile StrengthIb/inz (kPa) 3150-3850 2625-3209 at Break (Transverse (21800-26600) (I8100-22100) Direction) Tensile Strengthlblin2 (k Pa) 1013-1237 1738-2124 at Yield(Transverse (7000-8500) (11900-14600) Direction) Elongation Percent 836-924 839-927 (Transverse Direction) Tear Strength Grams 82-100 83-93 (Machine Direction) Tear Strength Grams 547-667 642-784 (Transverse Direction) Dart Impact Grams at 26-inches46-68 36-54 {63 cm) Puncture ResistanceIb/mil 4.04-5.46 4.26-5.76 (N/cm2) (367-484) (378-510) Stress Crack Hours (F5o) >312 >312 Resistance Ultimate Heat Grams Force 520 510 Seal Strength -1$-A review of the data in Table III reveals that the film/coating properties obtained when using the novel compositions of the present invention are substantially similar to those obtained when using the prior art blend of Example I .
Example 6 The composition of Example 2 was used herein to produce blown film.
Processes for producing blown film are well known in the art. In more detail, the composition of Example 2 was extruded from a 2.5 inch (6.4 cm) diameter extruder having a length to diameter ratio of 24:1, and equipped with 5 zones of heating.
The annular extrusion die had a diameter of 6 inches (I5.3 cm), and the die's land to land separation was uniformly set to 0.088 inch (0.224 mm). The extrudate temperature was 385°:E (196°C). The extrudate output rate was 89 lb/hr (41 kg/hr), and the blown film's haul-off speed was 78 fpm (24 rn/min.) The film blow up ratio was 2.5, resulting in a tubular lay flat width of 22.5 inch (57 cm), and a uniform film thickness of 0.001 inch (0.0254 mm). The resultant film blown from the composition of Example 2 was uniform in thickness and of overall excellent quality.
From all of the foregoing it is apparent that the novel compositions of the present invention have many applications. For example, the novel compositions may be formed into cast and blown films, using any of the well known techniques for forming cast or blown film. In addition, the novel compositions of the present invention may be used in preparing extrusion coatings having substantially equivalent fiim/coating properties compared to prior art compositions, but with improved processing properties, namely, a lower extruder motor drive power requirement and a lower neck-in, that is, less edge bead.
The invention has been described above in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and WO 00/11075 PCT/US99/1$605 ~Q~'~....r.:....,., ..+l..o.. +l.n., n.. .....on:~nnll« .lnc.n,.;l.nl1 hn..o;"
no.~. l.o o~~ i.+o.i ..>:+1.:,. +t.e
PARTICULARLY SUITABLE FOR EXTRUSION COATING AND FILMS
FIELD OF THE INVENTION
The present invention relates to a composition comprising a blend of at least three polyethylene components particularly useful for extrusion coating, a process using such blends for extrusion coating, and the composite produced thereby.
The invention also relates to f Ims produced from the blends.
BACKGROUND OF THE INVENTION
Prior art polyolefin blends, containing linear low density polyethylene as a component, are useful in certain extrusion coating applications. One such prior art blend is Dow Chemical's Dowlex 3010 linear low density polyethylene, which contains at least 80 weight percent linear low density polyethylene. Examples of extrusion coating applications are structures such as flexible polymeric film/paper packages for foods, arid metallized polymeric film balloons. The linear low density polyethylene component in'the prior art blends provides strong heat seals (coating-to-coating); strong tensile properties of coatings; strong resistance of coatings to tear; high resistance o:P coatings to missile, or dart, impact; resistance of coatings to puncture; and coating stress crack resistance. These properties are generally not attainable with polyolefin blends which contain no linear low density polyethylene.
However, these prior art blends containing linear low density polyethylene exhibit certain undesirable processing problems.
The prior art blends, that contain high levels of linear low density polyethylene, i.e., 80 weight percent and greater, generally require excessive power (extruder motor drive watts) to be extruded during the extrusion coating operation.
Frequently, the production rates of an extrusion coating operation must be slowed _2-so as not to exceed the limits of the extruder drive motors. In many cases, productivity is so low as to result in economic losses.
Further, the prior art blends, that contain high levels, i.e., 80 weight percent and greater, of linear low density polyethylene, generally exhibit excessive extrudate edge bead, manifested by excessive neck-in of the molten extrudate.
This is a problem readily known to those skilled in the art of extrusion coating.
Excessive edge bead must be trimmed away and disposed of as scrap. Otherwise, a final coated structure will not exhibit a uniform thickness.
It would obviously be desirable in an extrusion coating operation to utilize a polyolefin composition containing linear low density polyethylene as a component which would extrude at significantly lower power requirements and with significantly less edge bead. It would further be desirable for that same polyolefin 1 b composition containing linear low density polyethylene as a component to retain the desired coating properties exhibited by the prior art two component polyolefin blends containing linear low density polyethylene as the major component of the two components. The properties include strong heat seals (coating-to-coating);
strong tensile properties of coatings; strong resistance of coatings to tear;
high resistance of coatings to missile, or dart, impact; coating puncture resistance; and resistance of coatings to stress cracking.
The present inventors have unexpectedly discovered an improved extrusion coating polyolefin composition comprising a blend of a linear low density polyethylene, a high density polyethylene, and a low density polyethylene. The composition of the present invention desirably extrudes with lower power requirements (extruder drive motor watts) than the prior art two component blends containing linear low density polyethylene. This occurs even though the compositions of the present invention require significantly more thermal energy per unit of mass to melt than is required by the prior art blends. The compositions of the present invention exhibit significantly less neck-in (less edge bead) than that exhibited by the prior art compositions.
The compositiion according to the present invention is a polyolefin blend comprising at least the following three components. The first component is a linear low density polyethylene which generally provides coating-to-coating heat seal strength, toughness, tear resistance, and puncture resistance. In general, the properties are essentially equal to those exhibited by the prior art compositions.
The second component is a high density polyethylene copolymer which generally provides tensile strength and stress crack resistance properties. The properties are generally substantially equal to the prior art compositions. The third component is a low density polyethylene homopolymer which generally contributes to a reduced edge bead by providing a lower neck-in of the molten extrudate. Generally, this property of neck-in is superior to the prior art compositions. Moreover, the third component also generally provides good wetting of the substrate surface to which the blend is coated, for good coating-to-substrate bonding. Accordingly, the present invention that contains a lower amount of linear low density polyethylene than prior art compo:>itions is utilized without a loss in coating properties that would be normally expected with a reduction in linear low density polyethylene content.
The present invention is also directed to an improved extrusion coating process comprising the use of the above-mentioned composition of at least a linear low density polyethylene, a high density polyethylene, and a low density polyethylene. Furthf;r, the present invention is also directed to a coated article or composite comprising a substrate, either primed or unprimed, having the aforementioned composition coated thereon, preferably by means of an extrusion coating process. Thc; primer used to provide bonding to a substrate is preferably a water-soluble primer, more preferably a polyethyleneimine primer. Furthermore, WO 00/11075 PCT/US9911$605 the present invention includes laminates wherein a layer of the aforementioned three component composition is utilized between two similar or dissimilar substrates, optionally including a primer layer between the polyethylene blend and each substrate. The resultant composite or laminate may be formed into an article, such as a package for food, having good barner properties, that is, the package is generally impermeable to liquids and gases. The present invention is also directed to films prepared from the novel compositions, particularly by means of cast or blown film techniques.
It is, therefore, an object of the invention to provide novel compositions comprising a blend of at least a linear low density polyethylene, a high density polyethylene, and a low density polyethylene.
Another object of the invention is to provide an improved extrusion coating process wherein there is utilized as the extrusion coating, the novel compositions comprising the blends of the present invention as defined herein.
It is a further object of this invention to provide a coated substrate or a composite wherein the coating composition comprises the novel blends of the present invention as defined herein.
A still further. object of this invention is to provide a coated substrate or a composite wherein tile coating composition comprising the novel blends of the present invention is applied onto the substrate by an extrusion coating process.
These and otlher objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description, preferred embodiments, specific examples, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures 1 and 2 are obtained using differential scanning calorimetry (1.~SC) to determine melting point profiles, in particular, the maximum melting point and the thermal energy pf;r unit mass required to melt the mass. The melting point profile and pertinent calorimetry data of the prior art two component blend is shown in Figure 1. The melting point profile and pertinent calorimetry data of a three component blend of the present invention is shown in Figure 2.
DETAILED DESCRIPTION OF THE INVENTION
The novel compositions of the present invention comprise blends of a linear low density polyethylene, a high density polyethylene, and a low density polyethylene.
The linear low density polyethylene component of the blend is known to generally provide heat seal strength, toughness, tear resistance and puncture resistance properties to an extruded coating. The linear Iow density polyethylene component of the composition is a low density polyethylene copolymer comprising ethylene and a C3-Coo alpha-olefin comonomer. The alpha-olefin comonomer is preferably a C6-Cs alpha-olefin, and more preferably an ethylene-hexene or ethylene-octene copolymer. The alpha-olefin comonomer is present in an amount of about 5 to about 12 percent by weight of the ethylene-alpha olefin copolymer, more preferably an amount of from about 7 to about 10 percent by weight. The ethylene-alpha olefin copolymer component is further characterized by having a melt index value measured at 190°C, of about 0.5 dglmin. to about 10 dg/riiin., more preferably from about 1 dglmin. to about 3 dg/min., and most preferably is about 2 dg/min.; a swell ratio of about 1.0 to about 1.2; an annealed density of about 0.90 g/cc to about 0.93 g/cc; and a polydispersity index of about 1 to about 4.
The ethylene-alpha olefin linear low density copolymers may be produced by any method known in the art such as, for example, described in U. S. Patent No.
4,339,507.
The linear low density ethylene copolymer component of the blend of the present invention is present in an amount of about 25 to about 40 weight percent, based on the weight of the blend, more preferably in an amount of from about 30 to about 35 weight percent, and most preferably, in an amount of about 33 weight percent, based on the weight of the blend.
The high density polyethylene component of the blend is known to generally provide tensile strength and stress crack resistance to the blend of the present invention. The high density polyethylene component of the novel composition is a homopolyrner of ethylene or a copolymer of ethylene and an alpha olefin comonorner. T'he alpha olefin comonomer preferably has about 3 to about 10 carbon atoms. The alpha olef n comonomer is present in an amount of about 0.2 to about 1 percent by weight of the copolymer, more preferably about 0.4 to about 1.5 0.7 percent by weight, and still more preferably in an amount of about 0.5 percent by weight, based on the weight of the copolymer. The preferred comanorner is hexene. The high density polyethylene component is further characterized as having an annealed density of at least 0.940 g/cc to about 0.97 g/cc, more preferably from about 0.95 g/cc to about 0.97 g/cc; a malt index of about 6 dglmin. to about 20 dg/min., more preferably about 14 dg/min. to about dg/min., and most preferred about 16 dg/min., measured at 190°C. The high density polyethylene component may be produced by any method known in the art, such as, for example, that described in U.S. Patent No. 4,339,507.
The high density polyethylene component of the blend of the present invention is present in an amount of from about 25 to about 40 weight percent, based on the weight of the blend, more preferably, in an amount of from about to about 35 weight percent, and most preferably in an amount of about 33 weight percent, based on the; weight of the blend.
The low densiity polyethylene component of the blend of the present invention generally provides good wetting of a substrate to allow a good bonding to the substrate. The low density polyethylene component of the novel composition is a polyethylene of broad molecular weight distribution, as indicated by having a polydispersity index above 9 to about I2. The low density polyethylene is further characterized by having a melt index value of about 3 dg/min. to about 40 dglmin., more preferably from about 6 dg/min. to about 30 dglmin., still more preferably from about I8 dg/min. to about 22 dg/min., and most preferably about 20 dg/min., measured at 190°C. The low density polyethylene is further characterized by having an annealed density of from about 0.90 glcc to about 0.93 g/cc.
The low density polyethylene component of the blend of the present invention is present in an amount of from about 25 to about 40 weight percent, based on the weight of the blend, more preferably in an amount of from about 30 to about 35 weight percent, and most preferably, in an amount of about 33 weight percent, based on the; weight of the blend.
The novel compositions of the present invention may be prepared using any method known in the art. Fax example, the compositions may be prepared by dry blending or tumbling in any conventional equipment or by mixing in any conventional mixing equipment such as single and twin screw extruders, Werner Pfleiderer mixers, Banbury mixers or the like.
As will become apparent hereinafter, it has been found that less power is required to extrude the compositions of the present invention than the prior art blends. This is quite; unexpected since the novel compositions of the present invention require a greater amount of thermal energy to be melted than is necessary to melt the prior art blends.
_$.
The substrate to which the blend of the present invention is applied is preferably a primed substrate. The primer is preferably a water-soluble primer.
More preferably, the :>ubstrate is primed with polyethyleneimine. After priming, the primed surface is then extrusion coated with the blend. The polyethyleneimine used to prime the various substrates to be extrusion coated with the blends of the present invention is most preferably MICA Corporation's A-131-X
polyethyleneimine primer. Extrusion coating methods are well known in the art.
One skilled in tt~e art can readily extrusion coat or extrusion laminate a composition of the present invention onto primed or unprimed surfaces to prepare a composite or laminate.
The composition of the present invention may be extrusion coated to a substrate or extrusion iarninated between two substrates. Extrusion coating and laminating means and methods are well known in the art, and it is expected that any of such methods may be utilized. in the present invention. It is also possible to coextrusion coat the novel compositions to a structure of at least one or more substrates. The laminating process may further include the step of preparing a film from the composition of the present invention. The film may be, for instance, a cast or blown film. 'lChe skilled artisan would be well aware of the methods available in the art to~ prepare a film from the blends of the present invention.
There are many metriods known in the art for preparing film using cast or blown film techniques.
The substrate to which the blends of the present invention may be coated or laminated may be any substrate to which polyolef ns are normally coated.
Examples of suitable; substrates include, but are not limited to, paper or paperboard (printed or unprintedl), coated, e.g. clay-coated or uncoated, metal foils, plastic films and the like. These surfaces may be primed or unprimed, with a preference for primed surfaces.
_g_ A laminate according to the present invention comprises two substrates, each of which may bc~ independently primed or unprimed on the surface facing the other substrate, with the composition of the present invention between the substrates. In such a laminate, the substrates may be similar or dissimilar.
For example, the substrates may both be paper or one substrate may be paper and the other substrate may be a polymeric film.
The skilled a~~tisan can determine optimum conditions for coating or laminating without difficulty.
Films may bE; produced from the novel compositions of the present invention by any known technique. Preferred herein are the cast and blown film techniques, both of which are well known in the art.
The composition of the present invention can contain other ingredients;
such as additional polyethylene components, fillers, slip agents, tackifiers, pigments, and the like, as known in the art, provided the compositions are not adversely affected.
The invention will be more readily understood by reference to the following examples. There are, of course, many other forms of this invention which will become obvious to one skilled in the art, once the invention has been fully disclosed, and it will accordingly be recognized that these examples are given for the purpose of illustration only, and are not to be construed as limiting the scope of this invention in any way.
EXAMPLES
In the following examples the test procedures listed below were used in evaluating the analytical properties of the polyethylenes herein and in evaluating the physical properties of the compositions of the examples.
wo oomo~s rcT~s~9nssos Melt Index, dglmin., was determined in accordance with ASTM D 123 $-62T
at 190°C {374°F).
Swell Ratio is defined as the ratio of the extrudate over that of the orifice diameter of the extrusion plastorneter in ASTM D1238-62T. The diameter of the specimen is measured in the area between 0.159-cm and 0.952-cm of the initial portion of the specimen as it emerges from the extrusion plastometer.
Measurements were made by standard methods according to ASTM D374.
Annealed Density, g/cc, was determined in accordance with ASTM D1505.
Polydispersity Index is the ratio of the weight-average molecular weight, Mw, to number-average molecular weight, Mn. Mw and Mn were obtained by size-exclusion chromatography on a Waters 150C gel permeation chromatograph equipped with the standard refractomefer detector and a Viscotek 1 SOR
differential viscometer system. The 3-column set consisted of Waters' 103, 104, and linear-mixed bed (10~, 10', and 103) Micro-Styragel HT columns. The samples were run as 0.125% weight-to-volume solutions in ortho-dichlorobenzene at 140°C.
The data were interpreted using Viscotek Unical software (V4.02), by universal calibration using NBS 1475 (linear polyethylene) and NBS 1476 {branched polyethylene) for any polyethylene sample.
Differential Scanning Calorimetry maximum melting points, °C, and the energy required to melt a given mass of polyolefin, expressed in Joules/gram, were determined in accordance with ASTM D341$.
Neck-in, inches/edge or cm/edge was determined by first measuring the width of an extrusion coating, W, on a substrate, and then subtracting that measurement from the width of the extrusion coating die, D. The difference, (D-V~ is then divided by 2, i.e. (D-V~/2, resulting in the amount of extrudate neck-in per edge.
Ultimate Heat; Seal Strength, grams force, was determined on a Theller Model HT tack heat sealer as described in U.S. Patent No. 5,331,858.
Tensile Properties, tensile strength at fracture and tensile strength at yield, both expressed in lb/in2 (or megapascals); and elongation at break, expressed in percent, were determined in accordance with ASTM D882.
Tear Strength, expressed in grams-force, or millinewtons, was determined in accordance with A.STM D1992.
Dart Impact Resistance, grams at 50% failure, was determined in accordance with ASTM D 1709A.
Puncture Resistance, ib/mil, was determined in accordance with ASTM
D4649.
Stress Crack, hours to 50% failure (Fso) was determined in accordance with ASTM D 1693-94.
Example 1 (Comparative) In this example, the composition utilized was Dow Chemical Company's Dowlex 3010 polyethylene, which is believed to be a blend of about 80 weight percent ethylene-octene copolymer, containing about 7 to about 10 weight percent octene, and about 2C1 weight percent low density polyethylene. Further, the blend has a melt index of '.i.8 dglmin. at 190°C and an annealed density of 0.922 g/cc.
Pellets of the Dowlex 3010 blend were tested using differential scanning calorimetxy to deterrniine the melting point profile, particularly the maximum melting point and the thermal energy per unit mass required to melt the mass.
The melting point profile and calorimetry data obtained for the Dowlex 3010 blend are shown in Figure 1.
The Dowlex 3010 blend was extrusion coated, a process well known in the art, to a 40 pound natiural Kraft paper. The Dowlex 3010 blend was applied to the Kraft paper at a melt temperature of 601 °F (3I7°C), from a 3.5 inch diameter extruder with its barrel heaters set at 397°F (203°C), 500°F (260°C), 600°F
(315°C) and 645°F (340°C). The extrusion die throughput rate was maintained constant at 10 lb/inch/hr (1.8 kglcm/hr) of die width. Extruder power, measured in percent motor load, and kilowatts required to extrude the Dowlex 3010 blend, at the constant extruder throughput rate, are shown in Table I. Also shown in Table I
is the energy required to melt a given mass of the Dowlex 3010 blend, as well as the maximum melting point of the Dowlex 3010 blend.
Example 2 A composition of the present invention was prepared by dry blending the following components:
(a) 33 weight percent of Eastman Chemical Company's CM 27057-F
linear low density polyethylene, based on the weight of the composition. The linear Iow density polyethylene is an ethylene-hexene copolymer containing about 8% by weight of hexene having a melt index of about 2.0 dg/min. at 190°C, an annealed density of about; 0.910 g/cc, a swell ratio of about 1.2, and a polydispersity index: of about 3.
(b) 33 weight percent of Eastman Chemical Company's HT 7011-X
high density polyethylene, based on the weight of the composition.
WO 00/11075 PCTICIS99/i8605 The high density polyethylene is an ethylene-hexene copolymer containing about 0.7 weight % hexene, having a melt index of 16 dgJmin. at 190°C and an annealed density of 0.96 g/cc; and (c) 33 weight percent of Eastman Chemical Company's 811A low density polyethylene, based on the weight of the composition. The low density polyethylene is a polyethylene homopolymer having a melt index of about 20 dglmin. at 190°C and an annealed density of about 0.92 g/cc. The low density polyethylene is further characterized as having a broad molecular weight distribution as reflected in a polydispersity index of about 10.
The resultant. blend of the three components, which is an exemplary composition of the present invention, is characterized by having a melt index of about 5.5 dglmin. at 190°C and an annealed density of about 0.922 g/cc.
Pellets of the; composition of this example were tested using differential scanning calorimetry to determine its melting point profile, particularly the maximum melting point of the blend and the thermal energy per unit mass of the composition required to melt the mass. The melting point profile and calorimetry data of the blend of this example is shown in Figure 2.
The resultant blend of this example was extrusion coated to natural 40 lb.
Kraft paper. The blend was applied at a melt temperature of 596°F
{313°C) to the Kraft paper from a 3.5 inch diameter extruder with its barrel heaters set at 398°F
{203°C), 499°F (259°C), 600°F (315°C) and 639°F (338°C). The extrusion screw was single-flighted with a compression ratio of 3.5: I , providing a uniform output through the die. The extrusion die throughput rate was held constant at 10 lb/inch/hr (1.8 kg/cm/hr) of die width. Extruder power, measured in percent motor Ioad and kilowatts required to extrude the blend of this Example 2, noted at the constant extruder throughput rate, are reported in Table I. Also reported in Table I
is the energy required to melt a given mass of the blend of this Example 2, as v~iell as the maximum melting point of the blend.
Table 1 Property Property UnitsBlend of ExampleBlend of Example Motor Load Percent 87 76 Drive Motor Kilowatts 16.0 I4.0 Power Energy RequiredJoules/gram 79.7 93.56 to Melt Maximum MeltingC 123.01 128.28 Point of Pellets From the data in Table I, the following observations can be made. The novel composition of Example 2, typical of the present invention, can be extruded using a lower extrudex drive motor load than is required for the prior art blend of Example 1. In this instance; the reduction in extruder drive motor load is 12 percent.
Further, the blend of Example 2 can be extruded using less extruder drive motor power than is required for the prior art blend of Example I . The reduction herein was 12 percent in extruder drive motor power. The lowering of extruder drive motor power permits an extrusion coating operation to produce product with greater latitude in power requirements before maximum drive motor load is exceeded.
The reduction in power requirements accompanying usage of the compositions of the lxesent invention is quite unexpected since the data in Table I
reveals that the energy required to melt a given mass of the composition of Example 2 is 15 percent greater than is required to melt a mass of the blend of Example I (the prior art blend}. Based on the difference in thermal energies required to melt the blends of Examples I and 2, one would have predicted the opposite result, narnc~ly, a higher power requirement accompanying a composition _15_ of the present invention, as typified by the blend of Example 2, when compared with the prior art blend of Example 1.
Example 3 (COMPARATIVE) In this examplle was used the same composition as in Example l, namely Dow Chemical Company's Dowlex 3010 blend. The Dowlex 3010 blend was extrusion coated to natural 40 lb. Kraft paper. The Dowlex 3010 blend was applied to the Kraft paper at a melt temperature of 60I °F (317°C) from a 3.5 inch diameter extruder with its barrel heaters set at 397°F (203°C), 500°F {260°C), 600°F
(315°C) and 645°F (340°C). The extrusion die throughput rate was held constant at 10 lb/inch/hr (1.8 kg/cm/hr) of die width. The die to nip air gap was 5.25 inches (6.4 cm). Samples of the coated Kraft paper were obtained at 600 fpm (185 rn/min.) and at 1000 fpm (305 rn/min.) and neck-in measurements of the prior art Dowlex 3010 blend coatings were taken at each speed. The results are reported in Table II.
Example 4 The same composition as described in Example 2 herein was extrusion coated to natural 40 lb. Kraft paper. The composition was applied to the natural Kraft paper at a melt temperature of 596°F (313°C), from a 3.5 inch diameter extruder with its barrel heaters set at 398°F (203°C), 499°F (259°C), 600°F
(315°C), and 639°F (338°C). The extrusion die throughput rate was held constant at 10 lb/inch/hr ( 1.8 kg/cm/hr) of die width.. The die to nip air gap was 5.25 inches (6.4 cm). Samples of the coated Kraft paper were obtained at 600 fpm (185 m/min.
) and at 1000 fpm {305 m/min.), and neck-in measurements of the coating of the blend of Example 2 (typical of the present invention) were taken at each speed.
The results are reported in Table II.
Table TI
Properly Properly UnitsBlend of ExampleBlend of Example Neck-in at 600 Inches(cm)Bdge2.55(6.50) 2.40(6.10) fpm Neck-in at 1000Inches(cm)IEdge2.50(6.35) 2.30(5.85) fpm A review of th.e data in Table II permits the (allowing abservations to be made. The compositions of the present invention, as typified by Example 4, offer lower, and therefore superior, neck-in values when compared to the prior art blend of.Example 3. Lower neck-in values result in a wider extnzsion coating and a reduced edge bead of the molten extrudate. Edge beads are normally slit and discarded as scrap, resulting in an economic loss. Accordingly since the compositions of the present invention are characterized by lower neck-in, and reduced edge bead, the economic loss is decreased since Iess is discarded as edge bead scrap when compared with use of the prior art blend of Example 3.
Example 5 1 b The same composition of Example 1 herein, namely Dow Chemical Company's Dowlex 3010 blend, was cast into film by known techniques at a melt temperature of 603°F (3I8°C) and at a sufficient haul-off speed to obtain a film thickness of 0.001 inch (0.0254 mm). The resultant cast film was tested for heat seal strength (film to :elm); tensile properties; resistance to tear;
resistance to missile, or dart, impact; and puncture resistance. In addition, pellets of the Dowlex 3010 blend were pressed into sheets and tested for stress crack resistance.
The results are reported in. Table III.
Following the aforementioned procedure, the composition of Example 2 was formed into cast film at a melt temperature of 603°F (318°C}
at a sufficient haul-off speed to obtain a film thickness of 0.001 inch (0.0254 mm). The resultant cast film was tested for heat seal strength (film to film}; tensile properties;
resistance to tear; resistance to missile, or dart, impact; and puncture resistance.
Pellets of the composition of Example 2 were pressed into sheets and tested for stress crack resistance;. The properties are reported in Table III.
Table III
Property Property UnitsBlend of ExampleBlend of Example Tensile StrengthIblin2 (kPa) 4230-517.0 4032-4928 at Break (Machine (29200-35600) (27600-34000) Direction) Tensile StrengthIb/in2 (kPa) 1764-2156 2385-2915 at Yield (Machine (12400-14900} (16500-21000) Direction) Elongation Percent 689-76I 599-661 (Machine Direction) 'Tensile StrengthIb/inz (kPa) 3150-3850 2625-3209 at Break (Transverse (21800-26600) (I8100-22100) Direction) Tensile Strengthlblin2 (k Pa) 1013-1237 1738-2124 at Yield(Transverse (7000-8500) (11900-14600) Direction) Elongation Percent 836-924 839-927 (Transverse Direction) Tear Strength Grams 82-100 83-93 (Machine Direction) Tear Strength Grams 547-667 642-784 (Transverse Direction) Dart Impact Grams at 26-inches46-68 36-54 {63 cm) Puncture ResistanceIb/mil 4.04-5.46 4.26-5.76 (N/cm2) (367-484) (378-510) Stress Crack Hours (F5o) >312 >312 Resistance Ultimate Heat Grams Force 520 510 Seal Strength -1$-A review of the data in Table III reveals that the film/coating properties obtained when using the novel compositions of the present invention are substantially similar to those obtained when using the prior art blend of Example I .
Example 6 The composition of Example 2 was used herein to produce blown film.
Processes for producing blown film are well known in the art. In more detail, the composition of Example 2 was extruded from a 2.5 inch (6.4 cm) diameter extruder having a length to diameter ratio of 24:1, and equipped with 5 zones of heating.
The annular extrusion die had a diameter of 6 inches (I5.3 cm), and the die's land to land separation was uniformly set to 0.088 inch (0.224 mm). The extrudate temperature was 385°:E (196°C). The extrudate output rate was 89 lb/hr (41 kg/hr), and the blown film's haul-off speed was 78 fpm (24 rn/min.) The film blow up ratio was 2.5, resulting in a tubular lay flat width of 22.5 inch (57 cm), and a uniform film thickness of 0.001 inch (0.0254 mm). The resultant film blown from the composition of Example 2 was uniform in thickness and of overall excellent quality.
From all of the foregoing it is apparent that the novel compositions of the present invention have many applications. For example, the novel compositions may be formed into cast and blown films, using any of the well known techniques for forming cast or blown film. In addition, the novel compositions of the present invention may be used in preparing extrusion coatings having substantially equivalent fiim/coating properties compared to prior art compositions, but with improved processing properties, namely, a lower extruder motor drive power requirement and a lower neck-in, that is, less edge bead.
The invention has been described above in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and WO 00/11075 PCT/US99/1$605 ~Q~'~....r.:....,., ..+l..o.. +l.n., n.. .....on:~nnll« .lnc.n,.;l.nl1 hn..o;"
no.~. l.o o~~ i.+o.i ..>:+1.:,. +t.e
Claims (10)
1. A polymer blend composition comprising:
(a) from 25 to 40 weight percent based on the weight of the composition, of a first copolymer of ethylene and a C3-C10 alpha-olefin comonomer wherein the alpha olefin comonomer is present in an amount of from 5 to 12 weight percent, based on the weight of the first copolymer, and further wherein the first ethylene alpha-olefin copolymer has a melt index, at 190C, of 0.5 to 10 dg/min., a swell ratio of 1.0 to 1.2, an annealed density of 0.90 to 0.93 g/cc, and a polydispersity index of 1 to 4;
(b) from 25 to 40 weight percent, based on the weight of the composition, of a first homopolymer of ethylene or a second copolymer of ethylene and a C3-C10 alpha-olefin comonomer wherein the alpha-olefin comonomer is present in an amount of 0.2 to 1 percent by weight, based on the weight of the second ethylene-alpha olefin copolymer, and further wherein the first homopolymer of ethylene and the second ethylene-alpha olefin copolymer have an annealed density of at least 0.940 g/cc to 0.97 g/cc, and a melt index at 190ÀC, of from 6 to 20 dg/min.; and (c) from 25 to 40 weight percent, based on the weight of the composition, of a second homopolymer of ethylene having a polydispersity index greater than 9 to 12, a melt index, at 190ÀC, of from 3 to 40 dg/min., and an annealed density of from 0.90 to 0.93 g/cc.
(a) from 25 to 40 weight percent based on the weight of the composition, of a first copolymer of ethylene and a C3-C10 alpha-olefin comonomer wherein the alpha olefin comonomer is present in an amount of from 5 to 12 weight percent, based on the weight of the first copolymer, and further wherein the first ethylene alpha-olefin copolymer has a melt index, at 190C, of 0.5 to 10 dg/min., a swell ratio of 1.0 to 1.2, an annealed density of 0.90 to 0.93 g/cc, and a polydispersity index of 1 to 4;
(b) from 25 to 40 weight percent, based on the weight of the composition, of a first homopolymer of ethylene or a second copolymer of ethylene and a C3-C10 alpha-olefin comonomer wherein the alpha-olefin comonomer is present in an amount of 0.2 to 1 percent by weight, based on the weight of the second ethylene-alpha olefin copolymer, and further wherein the first homopolymer of ethylene and the second ethylene-alpha olefin copolymer have an annealed density of at least 0.940 g/cc to 0.97 g/cc, and a melt index at 190ÀC, of from 6 to 20 dg/min.; and (c) from 25 to 40 weight percent, based on the weight of the composition, of a second homopolymer of ethylene having a polydispersity index greater than 9 to 12, a melt index, at 190ÀC, of from 3 to 40 dg/min., and an annealed density of from 0.90 to 0.93 g/cc.
2. The composition according to Claim 1 wherein the alpha olefin comonomer of the first ethylene-alpha olefin copolymer has 6 to 8 carbon atoms, and wherein the first ethylene-alpha olefin copolymer has a melt index of from 1 to 3 dg/min., at 190ÀC.
3. The composition according to Claim 1 wherein the first homopolymer of ethylene and the second ethylene-alpha olefin copolymer have an annealed density of from 0.95 to 0.97 g/cc and a melt index, at 190ÀC; of from 14 to 18 dg/min.
4. The composition according to Claim 1 wherein the second homopolymer of ethylene has a melt index, at 190ÀC, of from 18 to 22 dg/min.
5. The composition according to Claim 1 wherein each of (a), (b) and (c) is present in an amount of from 30 to 35 percent by weight, based on the weight of the composition.
6. A process comprising extrusion coating onto a substrate a composition according to Claim 1.
7. An article comprising a substrate and a coating thereon wherein the coating comprises the composition according to Claim 1.
8. The article of Claim 7 prepared by extrusion coating the composition according to Claim 1 onto the substrate.
9. A film formed from the composition according to Claim 1.
10. An article wherein a film produced from the composition according to Claim 1 is a component of a multi laminate structure.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US9699598P | 1998-08-18 | 1998-08-18 | |
| US60/096,995 | 1998-08-18 | ||
| US29179399A | 1999-04-14 | 1999-04-14 | |
| US09/291,793 | 1999-04-14 | ||
| PCT/US1999/018605 WO2000011075A1 (en) | 1998-08-18 | 1999-08-16 | Blends containing linear low density polyethylene, high density polyethylene, and low density polyethylene particularly suitable for extrusion coating and films |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2340662A1 true CA2340662A1 (en) | 2000-03-02 |
Family
ID=26792267
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002340662A Abandoned CA2340662A1 (en) | 1998-08-18 | 1999-08-16 | Blends containing linear low density polyethylene, high density polyethylene, and low density polyethylene particularly suitable for extrusion coating and films |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP1112322A1 (en) |
| JP (1) | JP2002523542A (en) |
| KR (1) | KR20010072727A (en) |
| CA (1) | CA2340662A1 (en) |
| MX (1) | MXPA01001472A (en) |
| WO (1) | WO2000011075A1 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6509106B1 (en) * | 1998-08-18 | 2003-01-21 | Eastman Chemical Company | Blends containing linear low density polyethylene, high density polyethylene, and low density polyethylene particularly suitable for extrusion coating and films |
| MXPA06002483A (en) * | 2003-09-05 | 2006-06-20 | Dow Global Technologies Inc | Improved resin compositions for extrusion coating. |
| EP1777238B1 (en) | 2005-10-18 | 2007-05-02 | Borealis Technology Oy | Polyethylene blend component and blends containing the same |
| SE538048C2 (en) | 2012-11-30 | 2016-02-23 | Stora Enso Oyj | Process for making a packaging material |
| SE538498C2 (en) * | 2014-02-19 | 2016-08-09 | Stora Enso Oyj | Process for making a packaging material |
| WO2017114705A1 (en) * | 2015-12-28 | 2017-07-06 | Sig Technology Ag | Sheet-like composite, especially packaging laminate for dimensionally stable foodstuff containers, having a polymeric internal layer characterized by differential scanning calorimetry |
| JP6827892B2 (en) * | 2017-07-24 | 2021-02-10 | 大日本印刷株式会社 | Polyolefin resin film |
| JP6738568B2 (en) * | 2019-06-21 | 2020-08-12 | 大日本印刷株式会社 | Polyethylene resin film |
| CN112442223B (en) * | 2019-09-04 | 2023-02-28 | 中国石油化工股份有限公司 | Polyethylene composition and polyethylene film |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4728325A (en) * | 1986-04-03 | 1988-03-01 | Exxon Chemical Patents Inc. | Diaper backsheet |
| JP2643348B2 (en) * | 1988-09-01 | 1997-08-20 | 三井石油化学工業株式会社 | Polyethylene resin composition and film |
| JP3375780B2 (en) * | 1995-03-29 | 2003-02-10 | 三井化学株式会社 | Polyethylene resin composition for heavy packaging bags and polyethylene resin film for heavy packaging bags comprising the composition |
-
1999
- 1999-08-16 JP JP2000566340A patent/JP2002523542A/en active Pending
- 1999-08-16 WO PCT/US1999/018605 patent/WO2000011075A1/en not_active Application Discontinuation
- 1999-08-16 CA CA002340662A patent/CA2340662A1/en not_active Abandoned
- 1999-08-16 MX MXPA01001472A patent/MXPA01001472A/en unknown
- 1999-08-16 KR KR1020017002040A patent/KR20010072727A/en not_active Application Discontinuation
- 1999-08-16 EP EP99942218A patent/EP1112322A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| WO2000011075A1 (en) | 2000-03-02 |
| MXPA01001472A (en) | 2002-05-08 |
| JP2002523542A (en) | 2002-07-30 |
| EP1112322A1 (en) | 2001-07-04 |
| KR20010072727A (en) | 2001-07-31 |
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| EEER | Examination request | ||
| FZDE | Discontinued |