Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
1999-05-07
2001-11-27
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S516000, C428S910000, C428S195100, C264S173150, C264S173190
Reexamination Certificate
active
06322894
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 cuttability.
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 can be easily cut through and yet is suitable for a variety of applications (e.g., packaging or label applications).
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.
None of these references, however, disclose or suggest a matte surface film having improved cuttability in which the base layer contains HDPE.
SUMMARY OF THE INVENTION
The present invention is directed to a matte surface film comprising:
(a) a base layer comprising high density polyethylene (HDPE); and
(b) a matte surface layer comprising a blend of two or more incompatible polyolefins.
In a preferred embodiment of the present invention, the blend of the incompatible polyolefins contained in the matte surface layer comprises (i) a propylene homopolymer or propylene interpolymer and (ii) an ethylene homopolymer or ethylene interpolymer.
It is an object of the invention to produce a film having a matte surface layer, which has easy or improved cuttability.
It is a further object of this invention to produce a matte surface film having easy cuttability and yet is suitable for various applications such as packaging and labels.
It is also an object to produce a matte surface film, which has easy or improved cuttability, as well as a rough surface and low gloss.
DETAILED DESCRIPTION OF THE INVENTION
The easy or improved cuttability of the matte surface film of the present invention is achieved by providing a base layer comprising a HDPE. In general, the HDPE that may be used in the present invention has a density of about 0.940 to about 0.980 g/cm
3
, a melting point of about 115 to about 140° C., and a melt index of about 0.5 to about 12 g/10 minutes (measured in accordance with ASTM D 1238 under a load of 2.16 kg at 190° C.). Most preferably, the HDPE contained in the base layer has a density of about 0.950 to about 0.970 g/cm
3,
a melting point of about 120 to about 134° C., and a melt index of about 1 to about 6 g/10 minutes.
Particularly useful HDPE polymers for producing the base layer include, but are not limited to, HDPE M6211 and HDPE M-6030 sold by Lyondell Chemical Company, HD-6704.67 sold by Exxon Chemical Company, and the like.
The matte surface layer is formed by providing any blend of two or more incompatible polyolefins. Examples of suitable blends include a HDPE/ethylene-propylene-butylene (EPB) terpolymer blend, a polypropylene (PP)/HDPE blend, a PP/EPB terpolymer blend, an ethylene-propylene (EP) copolymer/polyethylene blend, and a PP/polyethylene/EPB terpolymer blend. In particular, the matte surface layer comprises a blend of: (i) a propylene homopolymer or propylene interpolymer; and (ii) an ethylene homopolymer or ethylene interpolymer. For purposes of the present invention, the term “interpolymer” includes various polymers other than homopolymers, such as random copolymers, terpolymers, etc., as well as block polymers, graft polymers, etc.
In the present invention, the polymer blend of the matte surface layer which has demonstrated effectiveness comprises a blend of (i) at least one of (1) a copolymer of ethylene and propylene or (2) a terpolymer of ethylene, propylene, and a C
4
to C
10
alpha-olefin or (3) propylene homopolymer; and (ii) an ethylene polymer.
Typically the copolymer of ethylene and propylene and the terpolymer of ethylene, propylene and a C
4
to C
10
alpha-olefin are comprised predominantly of propylene. Such copolymer or terpolymer, typically contains more than about 80% propylene. The ethylene polymer (ii) may include a copolymer or a blend of different kinds of ethylene polymers. For example, the ethylene polymer may be a blend of two or more ethylene polymers each having different densities. In one embodiment that is contemplated, the ethylene polymer comprises at least a first ethylene polymer having a density of at least about 0.91 g/cm
3
and a second ethylene polymer having a density which is different from the density of the first ethylene polymer. For example, the blend may comprise high density polyethylene and low density polyethylene or linear low density polyethylene. The ratio of the blend will vary depending upon the polyethylene components of the blend and the desired characteristics of the surface layer. In general, a blend in which an equal proportion of each component is employed, such as a 50:50 blend, may be useful. However, a useful blend has been found to be of 50% ethylene-propylene-butene-1 terpolymer, 40% high density polyethylene (0.95 g/cm
3
), and 10% of a lower density polyethylene (approx. 0.92 g/cm
3
).
Specific examples of useful polymer blends are described in U.S. Pat. Nos. 4,487,871; 4,508,786 or 5,451,468.
In U.S. Pat. Nos. 4,487,871 and 4,508,786, a film is describe
Harley Lyle J.
Lu Pang-Chia
ExxonMobil Oil Corporation
Santini Dennis P.
Tarazano D Lawrence
Thibodeau Paul
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