Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-12-09
2003-03-18
Tarazano, D Lawrence (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S447000, C428S910000, C428S516000, C264S173150, C264S173190
Reexamination Certificate
active
06534153
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a matte surface film. More particularly, the present invention relates to a multilayer polyolefin matte surface film having improved matte appearance.
BACKGROUND OF THE INVENTION
Matte surface films have a variety of useful purposes. Primarily, they form a good background for displaying printed or artful images on the film. The images can be printed onto the matte surface film by any conventional plastic printing process.
Mobil Chemical Company film product “70 MLT” is a matte surface biaxially oriented multilayer film. The base layer is oriented polypropylene and the matte surface skin layer comprises a mixture of polyethylenes and an ethylene-propylene-butene-1 terpolymer. The matte surface film has a dull surface appearance; that is, it is not shiny or glossy. Such a surface appearance is not typical of most biaxially oriented films used in packaging but is advantageous in that it provides an unusual appearance when reverse printed on the side opposite to the matte surface.
While the above-described matte surface film is excellent in many respects, it would be desirable to produce a matte surface film that has an improved matte appearance.
U.S. Pat. No. 5,492,757 to Schuhmann, et al. discloses an opaque, matte, multilayer polypropylene film having at least one base layer and at least one interlayer, and an outer layer applied to this interlayer. The base layer includes polypropylene and fillers. The interlayer includes a mixture or blend of two components I and II, wherein component I is a propylene homopolymer or a copolymer of &agr;-olefins having 2 to 10 carbon atoms, or a terpolymer of &agr;-olefins having 2 to 10 carbon atoms, or a mixture or blend of these polymers and component II is a high density polyethylene (HDPE) or a blend of HDPE and a propylene homopolymer or copolymer of a copolymer of &agr;-olefins having 2 to 10 carbon atoms, or a terpolymer of &agr;-olefins having 2 to 10 carbon atoms, or a mixture or blend of these polymers. The outer layer essentially includes a copolymer of &agr;-olefins having 2 to 10 carbon atoms, or a terpolymer of &agr;-olefins having 2 to 10 carbon atoms, or a mixture or blend of these polymers.
U.S. Pat. No. 5,494,717 to Peiffer, et al. discloses a heat-sealable, shrinkable multilayer film which comprises at least one base layer containing a propylene polymer or a propylene polymer mixture and at least one outer layer which comprises a mixture or blend of two components I and II, wherein the mixture contains copolymers or terpolymers of &agr;-olefins having 2 to 10 carbon atoms and HDPE.
U.S. Pat. No. 5,496,600 to Peiffer, et al. discloses a multilayer polypropylene film which contains at least one base layer containing polypropylene or a polypropylene mixture and resin, and at least one outer layer which contains a mixture or blend of two components I and II.
U.S. Pat. No. 5,516,563 to Schumann, et al. discloses an opaque, matte, multilayer polypropylene film including at least one base layer comprising polypropylene or a polypropylene mixture and fillers, and at least one outer layer which contains a mixture or blend of two components I and II.
Similarly, U.S. Pat. No. 5,618,369 to Peiffer, et al. discloses a matte multilayer polypropylene film which includes at least one base layer containing polypropylene and migrating additives or a mixture of migrating additives, and at least one outer layer which includes a mixture or blend of two components I and II.
There remains a need in the art for new and improved methods for making matte films with new and improved properties.
SUMMARY OF THE INVENTION
The present invention is directed to a matte surface film comprising:
(a) a base layer comprising a polyolefin; and
(b) a matte surface layer comprising a blend of high molecular weight high density polyethylene (HMWHD PE) with at least one incompatible polyolefin.
The incompatible polyolefin in the matte surface layer may be selected from ethylene propylene (EP) copolymers, ethylene butylene propylene (EBP) terpolymers, and polypropylene.(PP) homopolymers, such as metallocene catalyzed isotactic polypropylene (m-iPP) and metallocene catalyzed syndiotatic polypropylene (m-sPP).
The matte surface layer may further comprise a low molecular weight high density polyethylene or medium molecular weight high density polyethylene.
The matte surface layer of the present invention may have an improved matte appearance. In particular, the surface texture of the matte surface layer may be nodular.
The present matte surface film is heat sealable and has improved processability in comparison with other types of matte films.
DETAILED DESCRIPTION OF THE INVENTION
The matte surface film of the present invention has a base layer comprising polyolefin and a matte surface layer comprising a blend of high molecular weight high density polyethylene with at least one incompatible polyolefin.
The base layer may comprise polypropylene or high density polyethylene (HDPE). Particularly useful HDPE polymers for producing the base layer include, but are not limited to, HDPE M6211 and HDPE M6030 sold by Lyondell Chemical Company, HD-6704.67 sold by Exxon Chemical Company, and the like.
The matte surface film may be an oriented polypropylene (OPP) film, and is preferably biaxially oriented.
The matte surface layer is formed by providing a blend of at least one incompatible polyolefin with high molecular weight high density polyethylene (HMWHD PE). Examples of suitable incompatible polyolefins include ethylene propylene copolymer (EP), ethylene butylene propylene terpolymer (EBP) or a polypropylene (PP) homopolymer, such as a metallocene catalyzed isotactic polypropylene (m-iPP) or metallocene catalyzed syndiotatic polypropylene (m-sPP).
High molecular weight high density polyethylene (HMWHD PE) polymers have a melt index of less than 1 and preferably less than 0.5. The HMWHD PE may have a density of about 0.940 to about 0.980 g/cm
3
, and a melting point of about 115 to about 140° C. For example, the HMWHD PE may have a density of about 0.95 to about 0.970 g/cm
3
, and a melting point of about 120 to about 134° C. Melt index may be measured in accordance with ASTM D1238 under a load of 2.16 kg at 190° C.
A matte surface may contain very small (e.g., microscopic) raised areas in the form of fibers (e.g., elongated ridges) and/or in the form of nodules (e.g., essentially spherically shaped mounds). Those surfaces which include primarily fibers may be described as fibrillar, whereas those including primarily nodules may be described as nodular.
When the incompatible polyolefin is a metallocene catalyzed polypropylene resin, the matte surface texture may be controlled. That is, when standard polypropylene is changed to metallocene catalyzed polypropylene, the surface texture :changes from a fibrillar nature to a nodular nature. This surface morphological change results in a dramatic improvement in the matte appearance of the film.
When the incompatible polyolefin is EP or EBP or m-sPP, the matte surface texture obtained with the blend of EP with HMWHD PE, EBP with HMWHD PE, and m-sPP with HMWHD PE, is nodular in nature and is also heat sealable. Gloss can be controlled by the ratio of sealable resin to HMWHD PE.
The matte surface layer may be a terblend system, for example, comprising a blend of high molecular weight high density polyethylene, either a low molecular weight high density polyethylene (LMWHD PE) or a medium molecular weight high density polyethylene (MMWHD PE), and at least one incompatible polyolefin. The incompatible polyolefin may be EP copolymer, EBP terpolymer or PP homopolymer. The blend of this embodiment provides films with an improved matte appearance, while mitigating lenses (clear spots resulting from unmelted high molecular weight species) and alleviating die buildup problems.
The copolymer of ethylene and propylene and the terpolymer of ethylene, propylene and butylene may be comprised predominantly of propylene. Such copolymer or terpolymer, may contain more than about 80% propylene. Th
Chu Shaw-Chang
Cretekos George F.
Larter John A.
Su Tien-Kuei
Wagner, Jr. John R.
Bell Keith A.
ExxonMobil Oil Corporation
James Rick F.
Tarazano D Lawrence
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