USRE46911E1 - Machine direction oriented polymeric films and methods of making the same - Google Patents

Machine direction oriented polymeric films and methods of making the same Download PDF

Info

Publication number
USRE46911E1
USRE46911E1 US14/950,596 US201514950596A USRE46911E US RE46911 E1 USRE46911 E1 US RE46911E1 US 201514950596 A US201514950596 A US 201514950596A US RE46911 E USRE46911 E US RE46911E
Authority
US
United States
Prior art keywords
labelstock
layer
copolymer
film
propylene
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
US14/950,596
Inventor
Kevin O. Henderson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Avery Dennison Corp
Original Assignee
Avery Dennison Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US39198302P priority Critical
Priority to US42488302P priority
Priority to US10/606,461 priority patent/US7217463B2/en
Application filed by Avery Dennison Corp filed Critical Avery Dennison Corp
Priority to US14/950,596 priority patent/USRE46911E1/en
Application granted granted Critical
Publication of USRE46911E1 publication Critical patent/USRE46911E1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00Layered products comprising a layer of synthetic resin
    • B32B27/32Layered products comprising a layer of synthetic resin comprising polyolefins
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04Interconnection of layers
    • B32B7/12Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18Manufacture of films or sheets
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02Compositions 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
    • C08L23/10Homopolymers or copolymers of propene
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02Compositions 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
    • C08L23/10Homopolymers or copolymers of propene
    • C08L23/12Polypropene
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02Compositions 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
    • C08L23/10Homopolymers or copolymers of propene
    • C08L23/14Copolymers of propene
    • C08L23/142Copolymers of propene at least partially crystalline copolymers of propene with other olefins
    • C09J7/0271
    • C09J7/0296
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/20Adhesives in the form of films or foils characterised by their carriers
    • C09J7/22Plastics; Metallised plastics
    • C09J7/24Plastics; Metallised plastics based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
    • C09J7/241Polyolefin, e.g.rubber
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/20Adhesives in the form of films or foils characterised by their carriers
    • C09J7/29Laminated material
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02Characterised 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
    • C08J2323/10Homopolymers or copolymers of propene
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02Compositions 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
    • C08L23/04Homopolymers or copolymers of ethene
    • C08L23/08Copolymers of ethene
    • C08L23/0807Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
    • C08L23/0815Copolymers of ethene with aliphatic 1-olefins
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02Compositions 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
    • C08L23/16Elastomeric ethene-propene or ethene-propene-diene copolymers, e.g. EPR and EPDM rubbers
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2666/00Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
    • C08L2666/02Organic macromolecular compounds, natural resins, waxes or and bituminous materials
    • C08L2666/04Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
    • C08L2666/06Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2203/00Applications of adhesives in processes or use of adhesives in the form of films or foils
    • C09J2203/334Applications of adhesives in processes or use of adhesives in the form of films or foils as a label
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2423/00Presence of polyolefin
    • C09J2423/006Presence of polyolefin in the substrate
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00Stock material or miscellaneous articles
    • Y10S428/901Printed circuit
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/249921Web or sheet containing structurally defined element or component
    • Y10T428/249953Composite having voids in a component [e.g., porous, cellular, etc.]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/28Web or sheet containing structurally defined element or component and having an adhesive outermost layer
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/28Web or sheet containing structurally defined element or component and having an adhesive outermost layer
    • Y10T428/2848Three or more layers
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/31504Composite [nonstructural laminate]
    • Y10T428/31855Of addition polymer from unsaturated monomers
    • Y10T428/31909Next to second addition polymer from unsaturated monomers
    • Y10T428/31913Monoolefin polymer

Abstract

This invention relates to a film comprising a machine direction oriented polymeric film prepared from (A) at least one propylene homopolymer or copolymer or lend of two or more thereof, wherein (A) has a melt flow rate from about 6 to about 30 and (B) an olefin elastomer having a melt flow rate of 0.5 to 10. In one embodiment, the film also contains a nucleating agent. In one embodiment, these films are clear. The films have good stiffness and clarity with low haze. These films are useful in preparing labels and may be used as a monolayer film or in a multilayer film. In one embodiment, the films are printable. Die-cut labels are also described which comprise a composite comprising the extruded, machine-direction oriented polypropylene copolymer films of the present invention in combination with an adhesive associated with said copolymer films for adhering said label to a substrate. Multilayer composites also are described which comprise as label facestock material comprising an extruded oriented multilayer film of the present invention, an adhesive layer associated with said facestock material, and a release-coated liner or carrier. Combinations of the labels of the present invention joined with layer of adhesive to a substrate such as glass bottles also are described.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority from provisional application U.S. Ser. No. 60/391,953 filed Jun. 26, 2002 and provisional application U.S. Ser. No. 60/424,883 filed Nov. 8, 2002. The provisional applications are hereby incorporated by reference in their entirety.
FIELD OF THE INVENTION
This invention relates to a method of preparing machine-direction oriented monolayer or multilayer films, and methods of making the same. The invention also relates to the preparation of labels and other composites using such machine-direction oriented polymer films.
BACKGROUND OF THE INVENTION
It has long been known to manufacture and distribute pressure-sensitive adhesive stock for labels by providing a layer of face or facestock material for the label or sign backed by a layer of pressure-sensitive adhesive which in mm is covered by a release liner or carrier. The liner or carrier protects the adhesive during shipment and storage and allows for efficient handling of an array of individual labels after the labels are die-cut and the matrix is stripped from the layer of facestock material and up to the point where the individual labels are dispensed in sequence on a labeling line. During the time from die-cutting to dispensing, the liner or carrier remains uncut and may be rolled and unrolled for storage, transit and deployment of the array of individual labels carried thereon.
In many label applications, it is desirable that the facestock material be a film of polymeric material which can provide properties lacking in paper, such as clarity, durability, strength, water-resistance, abrasion-resistance, gloss and other properties. Historically, facestock material of thicknesses greater than about 3 mils have been used in order to assure dispensability in automatic labeling apparatuses. However, it is desirable to reduce the thickness or “down-gauge” the facestock material in order to attain savings in material costs. Such reduction in label thickness often has resulted in reduced stiffness and the inability to dispense the labels in a reliable commercially acceptable manner using automatic machinery.
Failure to reliably dispense is typically characterized by the label following the carrier around a peel plate without dispensing or “standing-off” from the carrier for application to the substrate. Such failure to dispense is believed to be associated with excessive release values between the label facestock material and the liner. The release level also is dependent upon the stiffness of the facestock. Failure to dispense may also be characterized by the wrinkling of the label due to lack of label stiffness at the dispensing speed as it is transferred from the carrier to the substrate. Another particular need in many labeling applications is the ability to apply polymeric-film labels as high line speeds, since an increase in line speed has obvious cost saving advantages.
Recently, to achieve the cost savings afforded by down-gauged film, polymeric materials which have been suggested in the prior art as useful in preparing labels include polymeric biaxially-oriented polypropylene (“BOPP”) of thicknesses down to about 2.0 mils which is relatively inexpensive and dispenses well. Such films tend to have sufficient stiffness for dispensing, but they also generally have unacceptable conformability characteristics. When the biaxially-oriented films are applied to rigid substrates such as glass bottles, the application is not completely successful due to the tendency of the relatively stiff label to bridge surface depressions and mold seams resulting from bottle-forming processes which results in an undesirable surface appearance simulating trapped air bubbles. This has impeded the use of pressure-sensitive adhesive labels to replace prior glass bottle labeling techniques such as ceramic ink directly bonded to the bottle surface during glass bottle manufacturing processes, Such ceramic ink techniques are environmentally undesirable due to objectionable ink components and the contamination by the ink of the crushed bottle glass in recycling processing.
Other useful materials are unoriented polyethylene and polypropylene films that are also relatively inexpensive and conformable. However, both of these films are difficult to die-cut and do not dispense well at low calipers.
It is also desirable in some instances to use labels which are clear and essentially transparent on glass bottles. Many facestocks currently available for labels lack sufficiently low levels of opacity and haze to qualify for such uses. Resinous film-forming materials which are blends of “soft” polar additives (“SPA”) such as ethylene vinyl acetate copolymer (EVA) with low-cost oleic base materials such as polypropylene, polyethylene, or combinations thereof including propylene-ethylene copolymers, blends of polyethylene and polypropylene with each other, or blends of either or both of them with polypropylene-polyethylene copolymer have been suggested as useful in preparing die-cut labels. In U.S. Pat. No. 5,186,782, extruded heat-set polymeric films are described which are die-cut into labels and applied to deformable or squeezable workpieces after being treated differently in their lengthwise and cross directions so as to have different stiffness in the respective directions. The polymeric films described in the '782 patent include heat-set unilayer films, and specifically films of polyethylene, as well as multilayer films which may comprise a coextrudate including an inner layer, a skin layer on the face side of the coextrudate, and optionally a skin layer on the inside of the coextrudate opposite the face side. A pressure-sensitive adhesive layer is generally applied to the inner side of the coextrudate. Preferred materials disclosed for use in the skin and inner layers comprise physical blends of (1) polypropylene or copolymers of propylene and ethylene and (2) ethylene vinyl acetate (EVA) in weight ratios ranging from 50/50 to 60/40. The core material also may be polyethylene of low, medium or high density between about 0.915 and 0.965 specific gravity. Films made of olefin-SPA blends have too high a haze for use on certain glass bottle substrates.
The machine-direction-oriented labels of the present invention are to be contrasted with shrink-films consisting of stretched, unannealed films. Examples of such shrink film labels are found in U.S. Pat. Nos. 4,581,262 and 4,585,679. The tendency to shrink causes such film to tend to withdraw from any borders leaving exposed adhesive. The exposed adhesive presents a particular disadvantage in die-cut label applications since the exposed adhesive is unsightly and tends to catch dust.
SUMMARY OF THE INVENTION
This invention relates to a film comprising a machine direction oriented polymeric film prepared from (A) at least one propylene homopolymer, propylene copolymer or blend of two or more thereof, wherein (A) has a melt flow rate from about 5 to about 40 and (B) an olefin elastomer, wherein (A) is not the same as (B). In one embodiment, the film is nucleated. In one embodiment, the films are clear. In another embodiment, the films have good stiffness and clarity with low haze. The films are useful in preparing labels and may be used as a monolayer film or in a multilayer film. In one embodiment, the films are printable.
Die-cut labels are also described which comprise a composite comprising the extruded, machine-direction oriented polypropylene copolymer films of the present invention in combination with an adhesive associated with said copolymer films for adhering said label to a substrate.
Multilayer composites also are described which comprise a label facestock material comprising an extruded oriented multilayer film of the present invention, an adhesive layer associated with said facestock material, and a release-coated liner or carrier. The labels of the present invention may be joined with layer of adhesive to a substrate such as glass bottles or deformable substrates like squeezable bottles.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view of a label prepared with a monolayer film of the present invention.
FIG. 2 is a cross sectional view of a multilayer film of the present invention.
FIG. 3 is a cross sectional view of a multilayer film of the present invention.
FIG. 4 is a cross sectional view of a label prepared with a multilayer film of the present invention.
FIG. 5 is a cross sectional view of a label prepared with a multilayer film of the present invention.
FIG. 6A is a schematic illustration of film extrusion.
FIG. 6B is a schematic illustration of film hot stretching.
FIG. 6C is a schematic illustration of film be taken into roll form.
FIG. 7A is a schematic illustration of coating adhesion or release coating manufacturing steps.
FIG. 7B is a schematic illustration of the manufacturing step of joining liner or carrier with a facestock.
FIG. 7C is a schematic illustration of the die cutting.
FIG. 7D is a schematic illustration of the application of labels to a workpiece.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The films of the present invention are derived from a combination of (A) at least one propylene homopolymer, propylene copolymer or blend of two or more thereof and (B) at least one olefin elastomer, provided that (A) and (B) are not the same. The films may be used as a monolayer film or as one or more parts of a multilayer film. In one embodiment, the films are clear, even crystal clear. In one embodiment, the films have a haze of less than 10%. Haze is measured in the BYK Gardner hazemeter. The oriented propylene films of the present invention have an opacity of about 10% or less.
(A) Propylene Polymers
The present invention relates to films prepared from propylene polymers. The films are prepared from (A) at least one propylene homopolymer, propylene copolymer or blend of two or more thereof, wherein (A) has a melt flow rate from about 5 to about 40, or from about 6 to about 32, or from about 6 to about 30, or from about 8 to about 25. The melt flow rate is determined by ASTM test D-1238. In one embodiment, the melt flow rate of the polymer (A) is from about 8 to about 26, or from about 10 to about 22. Here and elsewhere in the specification and claims, the range and ratio limits may be combined.
As noted above, the machine direction oriented film comprises (A) at least one propylene homopolymer, copolymer, or a blend of two or more thereof. In one embodiment, (A) is generally present in an amount from about 40% to about 98%, or from about 45% to about 90%, or from about 50% to about 85%, or from about 55% to about 80% by weight of the polymers in the film. In one embodiment, (A) is a blend of two or more polymers having the melt flow described herein. The blend can comprise a blend of two or more propylene homopolymers, a blend of a propylene homopolymer and a propylene copolymer, a blend of two or more propylene homopolymers with a propylene copolymer, or a blend of two or more propylene copolymers with a propylene homopolymer.
In one embodiment, the propylene films (A) may be nucleated. These films may contain one or more nucleating agents. In a particularly useful embodiment, the nucleating agent is blended into the propylene polymers (A). Various nucleating agents can be incorporated into the film formulations of the present invention, and the amount of nucleating agent added should be an amount sufficient to provide the desired modification of the crystal structure while not having an adverse effect on the desired optical properties of the film. It is generally desired to utilize a nucleating agent to modify the crystal structure and provide a large number of considerably smaller crystals or spherulites to improve the transparency (clarity) of the film. The amount of nucleating agent added to the film formulation should not have a deleterious affect on the clarity of the film. The amounts of nucleating agent incorporated into the film formulations of the present invention are generally quite small and range from about 500, or from about 750 or from about 850 ppm. The nucleating agents may be present in an amount up to 5000, or up to about 3000, or up to about 1000.
Nucleating agents which have been used heretofore for polymer films include mineral nucleating agents and organic nucleating agents. Examples of mineral nucleating agents include carbon black, silica, kaolin and talc. Among the organic nucleating agents which have been suggested as useful in polyolefin films include salts of aliphatic mono-basic or di-basic acids or arylalkyl acids such as sodium succinate, sodium glutarate, sodium caproate, sodium 4-methylvalerate, aluminum phenyl acetate, and sodium cinnamate. Alkali metal and aluminum salts of aromatic and alicyclic carboxylic acids such as aluminum benzoate, sodium or potassium benzoate, sodium beta-naphtholate, lithium benzoate and aluminum tertiary-butyl benzoate also are useful organic nucleating agents. Wijga in U.S. Pat. Nos. 3,207,735, 3,207,736, and 3,207,738, and Wales in U.S. Pat. Nos. 3,207,737 and 3,207,739, all patented Sep. 21, 1966, suggest that aliphatic, cycloaliphatic, and aromatic carboxylic, dicarboxylic or higher polycarboxylic acids, corresponding anhydrides and metal salts are effective nucleating agents for polyolefin. They further state that benzoic acid type compounds, in particular sodium benzoate, are the best embodiment of the nucleating agents.
In one embodiment, the nucleating agents are sorbitol derivatives or organic phosphates. Substituted sorbitol derivatives such as bis (benzylidene) and bis (alkylbenzilidine) sorbitols wherein the alkyl groups contain from about 2 to about 18 carbon atoms are useful nucleating agents. More particularly, sorbitol derivatives such as 1,3,2,4-dibenzylidene sorbitol, and 1,3,2,4-di-para-methylbenzylidene sorbitol are effective nucleating agents for polypropylenes. Useful nucleating agents are commercially available from a number of sources. Millad 8C-41-10, Milled 3988 and Millad 3905 are sorbitol nucleating agents available from Milliken Chemical Co.
Other acetals of sorbitol and xylitol are typical nucleators for polyolefins and other thermoplastics as well. Dibenzylidene sorbitol (DBS) was first disclosed in U.S. Pat. No. 4,016,118 by Hamada, et al. as an effective nucleating and clarifying agents for polyolefin. Since then, large number of acetals of sorbitol and xylitol have been disclosed. Representative US patents include: Kawai, et al., U.S. Pat. No. 4,314,039 on di(alkylbenzylidene) sorbitols; Mahaffey, Jr., U.S. Pat. No. 4,371,645 on di-acetals of sorbitol having at least one chlorine or bromine substituent; Kobayashi, et al., U.S. Pat. No. 4,532,280 on di(methyl or ethyl substituted benzylidene) sorbitol; Rekers, U.S. Pat. No. 5,049,605 on bis(3,4-dialkylbenzylidene) sorbitols including substituents forming a carbocyclic ring. These patents are hereby incorporated by reference. These patents are hereby incorporated by reference.
Another class of nucleating agents described by Nakahara, et al. in U.S. Pat. No. 4,463,113, in which cyclic bis-phenol phosphates was disclosed as nucleating and clarifying agents for polyolefin resins. Kimura, et al. then describes in U.S. Pat. No. 5,342,868 that the addition of an alkali metal carboxylate to basic polyvalent metal salt of cyclic organophosphoric ester can further improve the clarification effects of such additives. Compounds that are based upon this technologies are marketed under the trade name NA-11 and NA-21. These patents are hereby incorporated by reference.
A number of useful propylene homopolymers are available commercially from a variety of sources. Some of the useful homopolymers are listed and described in the following Table I.
TABLE I
Commercial Propylene Homopolymers
Commercial Melt Flow Density
Designation Company g/10 min (g/cm3)
5390N Dow Chemical 12.0 0.90
SE66R Dow Chemical 8.8 0.90
3622 Atofina 12.0 0.90
3576X Atofina 9.0 0.90
Moplen HP400N Basell 12.0 0.90
P4G4K-038* Huntsman 12 0.90
9074*MED Exxon Mobil 24 0.90
*contains a nucleating agent
In another embodiment, (A) may be a propylene copolymer. Propylene copolymers generally comprise polymers of propylene and up to about 40% by weight of at least one alpha-olefin selected from ethylene and alpha-olefins containing from 4 to about 12, or from 4 to about 8 carbon atoms. Examples of useful alpha-olefins include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. In one embodiment, the polymers of propylene which are utilized in the present invention comprise polymers of propylene with ethylene, 1-butene, 1-hexene or 1-octene. The propylene alpha-olefin polymers useful in the present invention include random as well as block copolymers although the random copolymers generally are particularly useful. In one embodiment, the films are free of impact copolymers. Blends of two or more propylene copolymers as well as blends of the propylene copolymers with propylene homopolymers can be utilized.
In one embodiment, the propylene copolymers are propylene-ethylene copolymers with ethylenic contents from about 0.2% to about 10% by weight. In another embodiment, the ethylene content is from about 3% to about 10% by weight, or from about 3% to about 6% by weight. With regard to the propylene-1-butene copolymers, 1-butene contents of up to about 15% by weight are useful. In one embodiment, the 1-butene content generally may range from about 3% by weight up to about 15% by weight, and in other embodiments, the range may be from about 5% to about 15% by weight. Propylene-1-hexene copolymers may contain up to about 35% by weight 1-hexene. In one embodiment, the amount of 1-hexene is up to about 25% by weight. Propylene-1-octene copolymers useful in the present invention may contain up to about 40% by weight of 1-octene. More often, the propylene-1-octene copolymers will contain up to about 20% by weight of 1-octene.
A list of some useful commercially available propylene copolymers is found in the following Table II.
TABLE II
Commercial Propylene Copolymers
Melt Flow Rate
Commercial Name Source (g/10 mins)
DS6D21 Dow Chemical 8.0
KB4560 BP Amoco 10
KB4586 BP Amoco 10
KB4986 BP Amoco 30
9433* BP Amoco 12
13T25A Huntsman 25
P5M4K-046* Huntsman 10
P5M5K-047 Huntsman 20
*contains nucleating agent
In one embodiment, the propylene copolymer contains a nucleating agent as described above for the propylene homopolymer.
The propylene copolymers useful in preparing the film facestock of the present invention may be prepared by techniques well known to those skilled in the art, and many such copolymers are available commercially. For example, the copolymers useful in the present invention may be obtained by copolymerization of propylene with an alpha-olefin such as ethylene or 1-butene using single-site metallocene catalysts. In one embodiment, the propylene polymer (A) are free of antistatic agents.
(B) Olefin Elastomers
As described herein, the film compositions include (B) at least one olefin elastomer. Olefin elastomers have been referred to as plastomers. In one embodiment, the olefin elastomers have a melt flow index from about 1 to about 40, or from about 3 to about 35, or from about 5 to about 25 g/10 min. The melt flow index is determined by ASTM test D-1238 at 190 degrees C. In one embodiment, the melt flow indix for (B) is in the range from about 1 to about 25, or from about 2 to about 10 g/10 min. The olefin elastomer is typically present in an amount from about 2% to about 55%, or from about 10% to about 50%, or from about 15% to about 45% of the polymers in the film.
In one embodiment, the olefin elastomers (B) typically have a molecular weight distribution (Mw/Mn) of about 1.5 to 2.4, where Mw is weight average molecular weight and Mn is number average molecular weight. In one embodiment, the olefin elastomers have a density of about 0.82 to about 0.98 0.91, or of about 0.84 to about 0.97 0.91, or of about 0.86 to about 0.91 g/cc, or of about 0.87 g/cc to about 0.91 g/cc. In another embodiment, the olefin elastomers have a molecular weight of about 5,000 to about 50,000, or of about 20,000 to about 30,000.
The olefin elastomers include polyolefin polymers which exhibit both thermoplastic and elastomeric characteristics. The polymers include copolymers and terpolymers of ethylene or propylene with an alpha-olefin. The polymer typically comprises from about 2% to about 30%, or from about 5% to about 25%, or from about 10% to about 20% by weight of the alpha-olefin. The alpha olefins have been described above. The alpha olefins include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 1-dodecene. Particularly useful alpha olefins include 1-butene and 1-hexene. Olefin elastomers include but are not limited to ethylene-butene copolymers, ethylene-octene copolymers, ethylene-hexene copolymers, and ethylene-hexene-butene terpolymers, as well as mixtures thereof.
In another embodiment, the olefin elastomers which may be employed in the invention include copolymers of ethylene and at least one C3-C20 alpha-olefin, or a C4-C8 alpha-olefin present in an amount of about 5 to about 32 mole %, or of about 7 to about 22 mole %, or of about 9 to about 18 mole %.
For example, the copolymers may be obtained by copolymerization of ethylene or propylene with an alpha olefin, such as 1-butene, using single-site metallocene catalysts. Such copolymers are available from Exxon Mobil Chemical Company, Basell and Dow Chemical Company. Another useful propylene and 1-butene copolymer is available commercially from Basell under the trade designation EP3C30HF. This copolymer has 14% butylene and a melt flow index of about 5.5 g/10 min.
Non-limiting examples of olefin elastomers include linear ethylene-butene copolymers such as EXACT 3024 having a density of about 0.905 gms/cc (ASTM D-1505) and a melt index of about 4.5 g/10 min. (ASTM D-1238); EXACT 3027 having a density of about 0.900 gms/cc (ASTM D-1505) and a melt index of about 3.5 g/10 min. (ASTM D-1238); EXACT 4011 having a density of about 0.888 gms/cc (ASTM D-1505) and a melt index of about 2.2 g/10 min. (ASTM D-1238); and EXACT 4049 having a density of about 0.873 gms/cc (ASTM D-1505) and a melt index of about 4.5 g/10 min. (ASTM D-1238); and ethylene-hexene copolymers such as EXACT 4150 having a density of about 0.895 gms/cc (ASTM D-1505) and a melt index of about 3.5 g/10 min. (ASTM D-1238). Other non-limiting examples of useful EXACT plastomers are EXACT 3017 and EXACT 4053. Terpolymers of e.g. ethylene, butene and hexene also can be used. All of the above EXACT series plastomers are available from EXXON Chemical Co.
Examples of terpolymers are Exxon's Exact 3006 (an ethylene-butene-hexene terpolymer with a density of 0.910 g/cm3 (g/cc) and M.F.I. of 1.2 g/10 min (g/10′); Exact 3016 (an ethylene-butene-hexene terpolymer having a density of 0.910 g/cm3 (g/cc) and a M.F.I. of 4.5 g/10 min (g/10′)); Exact 3033 (an ethylene-butene-hexene terpolymer having a density of 0.900 g/cm3 (g/cc) and a M.F.I. of 1.2 g/10 min (g/10′)); Exact 3034 (an ethylene-butene-hexene terpolymer having a density of 0.900 g/cm3 (g/cc) and a M.F.I. of 3.5 g/10 min (g/10′)); Dow Affinity PL 1840 (an ethylene-propylene-butylene terpolymer); Dow Affinity PL 1845 (an ethylene-propylene-butylene terpolymer); Dow Affinity PL 1850 (an ethylene-propylene-butylene terpolymer); and Exxon Mobil ZCE 2005 (an ethylene-propylene-butylene terpolymer).
In one embodiment, EXACT plastomers independently have a molecular weight distribution (Mw/Mn) of about 1.5 to 2.4, where Mw is weight average molecular weight and Mn is number average molecular weight, a density of about 0.86 to about 0.91 g/cc, or about 0.87 g/cc to about 0.91 g/cc, a molecular weight of about 5,000 to about 50,000, or about 20,000 to about 30,000, a melting point of about 140-220 F., and a melt flow index above about 0.50 g/10 mins, or about 1-10 g/10 mins as determined by ASTM D-1238, condition E.
Plastomers such as those sold by Dow Chemical Co. under the tradename Affinity also may be employed in the invention. These plastomers are believed to be produced in accordance with U.S. Pat. No. 5,272,236, the teachings of which are incorporated herein in their entirety by reference. In one embodiment, these plastomers are substantially linear polymers having a density of about 0.85 gms/cc to about 0.97 0.91 g/cc measured in accordance with ASTM D-792, a melt index (“MI”) of about 0.01 gms/10 minutes to about 1000 grams/10 minutes, a melt flow ratio (I10/I2) of about 7 to about 20, where I10 is measured in accordance with ASTM D-1238 (190/10) and I2 is measured in accordance with ASTM D-1238 (190/2.16), and a molecular weight distribution Mw/Mn which or is less than 5, and or is less than about 3.5 and or is from about 1.5 to about 2.5. These plastomers include homopolymers of C2-C20 olefins such as ethylene, propylene, 4-methyl-1-pentene, and the like, or they can be interpolymers of ethylene with at least one C3-C20 alpha-olefin and/or C2-C20 acetylenically unsaturated monomer and/or C4-C18 alpha-olefins. These plastomers generally have a polymer backbone that is either unsubstituted or substituted with up to 3 long chain branches/1000 carbons. As used herein, long chain branching means a chain length of at least about 6 carbons, above which the length cannot be distinguished using 13 C nuclear magnetic resonance spectroscopy. Useful Affinity plastomers are characterized by a saturated ethylene-octene backbone, a narrow molecular weight distribution Mw/Mn of about 2, and a narrow level of crystallinity. These plastomers also are compatible with pigments, brightening agents, fillers such as carbon black, calcium carbonate and silica, as well as with plasticizers such as paraffinic process oil and naphthenic process oil. Other commercially available plastomers may be useful in the invention, including those manufactured by Mitsui.
In one embodiment, the molecular weight distribution, (Mw/Mn), of plastomers made in accordance with U.S. Pat. No. 5,272,236 is about 2.0. Non-limiting examples of these plastomers include Affinity PF 1140 having a density of about 0.897 gms/cc, and a melt flow index of about 0.5 g/10 mins; Affinity PF 1146 having a density of about 0.90 gms/cc, and a melt index of about 1 gms/10 min; Affinity PL 1880 having a density of about 0.902 gms/cc, and melt index of about 1.0 gms/10 min; Affinity EG 8100 having a density of about 0.87 gms/cc, and a melt index of about 1 gms/10 min.; Affinity EG 8150 having a density of about 0.868 gms/cc, and a melt index of about 0.5 gms/10 min,; Affinity EG 8200 having a density of about 0.87 gms/cc, and a melt index of about 5 g/10 min.; and Affinity KC 8552 having a density of about 0.87 gms/cc, and a melt index of about 5 g/10 min.
In one embodiment, the olefin elastomers include those formed by a single-site metallocene catalyst such as those disclosed in EP 29368, U.S. Pat. Nos, 4,752,597, 4,808,561, and 4,937,299, the teachings of which are incorporated herein by reference. As is known in the art, plastomers can be produced by metallocene catalysis using a high pressure process by polymerizing ethylene in combination with other monomers such as butene-1, hexene-1, octene-1 and 4-methyl-1-pentene in the presence of catalyst system comprising a cyclopentadienyl-transition metal compound and an alumoxane.
(C) Nucleating Agents
In one embodiment, the films include a nucleating agent. The nucleating agents are described above. The nucleating agents may be incorporated in any or all of the layers of the multilayer films of the invention. As described above, the nucleating agent maybe incorporated into propylene polymer (A) or as a separate component of the formulation used to make the film. Nucleating agents may also be pre-compounded in propylene polymer (A) or olefin elastomer (B) and added as a separate component of the film formulation. Generally, the total amount of nucleating agent incorporated into the film formulations of the present invention are generally quite small and range from about 500 or 1000 to 3000 or 5000 ppm. The amount of nucleating agent may be evenly or unevenly divided between being pre-compounded in (A) or (B) and present as a separate component (C).
The monolayer and multilayer films of the present invention may also contain antiblocking agents. The addition of antiblocking agents to the film formulations reduces the tendency of the films to block during windup, regulates the slip and anti-static properties of the films and allows a smooth unwinding from the reels. Any of the antiblocking agents described in the prior art as useful additives modifying the properties of polymer films, and in particular, olefin polymer films, can be included in the film formulations of the present invention. Silicas with average particle sizes of about 2 microns or less can be utilized for this purpose, and only small amounts (for example, 1000 to 5000 ppm) of the fine silica are needed. Several antiblocking agents based on synthetic silica are available from A. Schulman, Inc., Akron, Ohio, under the general trade designation Polybatch®. These materials are antiblocking masterbatches and comprise free-flowing pellets comprising propylene homopolymers or copolymers and the synthetic silica. For example, Polybatch ABPP-05 comprises 5% synthetic silica in a propylene homopolymer; ABPP-10 comprises 10% synthetic silica in a propylene homopolymer; and ABPP-05SC comprises 5% synthetic silica and a random propylene copolymer. When the antiblocking agents are to be utilized in the preparation of the multilayer films of the present invention, the antiblocking agent generally is added to the skin layer formulations only. Useful antiblocking agents are Ampacet's Seablock 1 and Seablock 4.
In another embodiment, the film compositions contain at least one processing aid. The processing aid acts to facilitate extrusion. These processing aids include hexafluorocarbon polymers. An example of a commercially available processing aid that can be used is Ampacet 10919 which is a product of Ampacet Corporation identified as a hexafluoro carbon polymer. Another example of a useful processing aid is Ampacet 401198. The processing aids are typically used at concentrations of up to about 1.5% or form about 0.5% to about 1.2% by wight. In another embodiment, the processing aid is present in an amount up to about 0.25% by weight, and in one embodiment about 0.03% to about 0.15% by weight.
The films may be prepared by means known to those in the art. For instance the films may be prepared by extrusion. Typically the films are extruded at temperatures between 250 to about 550, or about 300 to about 500 degrees F. A useful procedure for preparing the films is extrusion at 450 degrees F.
The following examples relate to polymer compositions which can be used to prepare the polymeric films. Unless otherwise indicated, amounts are in parts by weight, temperature is in degrees Celsius and pressure is ambient pressure.
TABLE III
1 2 3 4 5 6 7 8 9 10 11 12
Huntsman propylene homopolymer 50 60 65 15 65
P4G4K-038# (MFR 12)
Huntsman propylene copolymer 65 90
P5M4K-046# (MFR 10)
BP Amoco propylene copolymer 55 65 52
KB4986 (MFR 30)
Dow propylene copolymer 80 65 50
D56D21 (MFR 8)
Exact 3025 olefin elastomer (MFI 1.2) 45 10 20
Exact 4049 olefin elastomer (MFI 4.5) 35 10 40 35 35 48 15
Affinity 8500 olefin elastomer (MFI 5.0) 50 20 25 35
Sodium benzoate Nucleating agent 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
calcium stearate 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1