CA2107095A1 - Polymeric material and clear film produced therefrom - Google Patents

Abstract

The present invention is directed to a novel polymer which in one embodiment, was formed by extruding an admixture (either a physical blend of solids, or a compounded melt) of a high molecular weight high density polyethylene (HMW-HDPE) resin and a high molecular weight low density polyethylene (HMW-LDPE) resin. Also disclosed is the direct reactor formation of this polymer. The new polymer can be used to manufacture high gloss, low haze films and to form easy to open bags. The present invention is also directed to a method of improving the haze properties of clear plastic films prepared from high molecular weight high density polyethylene (HMW-HDPE) resins, which method comprises adding a haze reducing amount of a high molecular weight low density polyethylene (HMW-LDPE) resin to said HMW-HDPE resins and forming films from the blended and extruded resin mixture.

Description

~92/17539 PCT/US92/02557 :
~10 1 095 POLYMERIC ~ATERIAL AND CLEAR FILM PRODUCED THEREFROM

CROSS-REFERENCE TO RELATED APPLICATIONS

In the ~nited States Patent and Trademark Office, this application is a continuation-in-part of copending 15application Serial No. 07/677,534, filed 29 March 1991, the disclosure of which is hereby incorporated herein by reference.
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BACKGROUND OF THE INVENTION
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The present invention is directed to improvements ; in high density, and par~icularly, high density, high molecular weight polyethylene polymers, the use of such improved polymers in film and bag applications, and to a method of producing such improved polymers.

~ igh density polyethylene (HDPE) polymers have traditionally not been employed in the production of thin plastic films, plastic bags, and the like, which require high clarity, because these materials do not possess the requisite degree of clarity most commonly desired for many thin plastic film uses. Thus, when clear ~or semi-clear) plastic (i.e., polymeric) films .

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W~92~17~39 PCT/US92/02557~

2~0~09~ - 2 -or bags are formed, they are usually formed from low density polyethylene (LDPE) or mixtures of low density polyethylene polymers. Conventional HDPE films and/or bags, unliXe LDPE films and/or bags have little or no gloss in their overall appearance, often making them undesirable to wholesale and retail consumers alike.
In the United States, the following companies produce the ~ulk of HDPE; Phillips 66, Exxon/Paxon, Occidental Chemical, Quantum Chemical, Solvay Polymers, Chevron Chemical, Union Carbide, Dow Chemical, and Hoechst Celanese. See, Chemical & Enqineerina News, Vol. 70, No~ 12, pp. 9-l0, March 23, 1992.

Thin, clear plastic films and thin clear plastic bags, such as plastic produce bags, have traditionally been prepared from low density polyethylene (LDPE) films. These materials are generally used because they can be cheaply formed into films, and the bags produced therefrom can also be made easily and at relatively low cost. However, the LDPE materials are not without their drawbacks. LDPE films and bags produced therefrom are typically very clingy, thus maklng the bags hard to open. LDPE films and bags produced therefrom are not as strong as HDPE films and bags at an equivalent thickness. In addition, LDPE films are more flexible than HDPE films, which can make LDPE more difficult to run through machinery. The higher stiffness of HDPE films is one very desirable characteristic of this type of product, but the lack of high gloss and clarity has limited its applications.

The present invention represents a dramatic breakthrough in the use of high density polyethylene polymers ~or the formation of clear, strong thin films .. : .
' W~92/17539 PCT/US92/025~7 ~L073~

and bags. The present invention affords a high densi~y polyethylene material which can be formed into a thin film having many of the desirable qualities of both high and low density polyethylene materials, without 5 the disadvantages associated with either class of material.

Being a high density product, the film and/or bags produced therefrom are stronger at an equivalent thickness, have the requisite high clarity, and have less cling than those films and/or bags formed from traditional low density polyethylene polymers. Since the polymer of the present invention is a high density polyethylene, less polymer is required to form a film or bag having superior strength characteristics in comparison to the traditional low density polymers. In addition, since the polymer of the present invention is a high molecular weight, high density material, it yields a stiffer film and/or bag at comparable thicknesses to a conventional LDPE polymer, which makes the processing of the film through machinery better, and extends the applications of the material beyond that traditionally envisioned for LDPE films and/or bags.
INFORMATIOM DISCLOSURE

Applicants wish to cite the following patents as representative prior art with respect to the invention claimed herein.

U.S. Patent No. 2,983,704 (Roedel) describes a film of polyethylene comprising 2 solid e~hylene polymer having a density of 0.9137 at 25C, and from lO to ;
.

. ' . ' . , . -WO92/17539 PC~/US92/02557,~

' ' ~i 21~ D~5 - 4 -50% by weight of an ethylene polymer having a density of 0.9757 at 2sc.

U.S. Patent No. 1,234,567 (Tritsch) describes a pressure-sensitive adhesive tape having a molecularly oriented polyethylene film backing and a pressure-sensitive adhesive mass on at least one side thereof, said backing comprising a blend of high density polyethylene having a density of from about 0.95 to about 0.98 and low density polyethylene having a density of about 0.92 w~erein said high ~ensity polyethylene is present in an amount from about 5% to less than about 20 percent of the blend.

lS U.S. Patent No. 3,125,548 (Anderson) describes a polyethylene blend comprising 20 to 45 weight percent of a polyethylene having a density of less than 0.920 g/cc, 30 to 60 weight percent of a polyethylene resin having a density of 0.1924 to 0.933 g/cc and at least 10 weight percent of a polyethylëne resin having a density above 0.945 g/cc.

U.S. Patent No. 3,176,051 (Gregorian et al.) describes a blended composition, comprising 25 polyethylene having a density in the range 0.94 to 0.9 and a melt index in the range 0.5 to 10 and a minor amount, i.e., between o.l to lo~ by weight of said composition of an a~ditive member of the group consisting of polyethylene having a reduced viscosity : 30 in the range 2.9 to 10 and a copolymer of ethylene and 1-butene having a reduced viscosity in the range ~.0 to 10 .

U.S. Patent No. 3,340,328 (Brindell 2t al.) `
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W~92/17539 ~CT/US92/02557 ,",,,,. 21~7095 describes a homogeneous, polyethylene composition comprising a blend of (a) from 15 percent to 25 percent by weight of a straight chain polyethylene characterized as having a density of from 0.95 g/cc, to 0.96 g/cc, at 23C, and in having a melt index in the range of 3 to 15 g/10 minutes through a 2.1 mm oriflce at 190C, and under a 2.16 kg weight; and (b) ~rom 85 percent to 75 percent of a linear polyethylene having an average molecular weight exceeding 750,000 and characterized as having a density of between approximately 0.925 g/cc, and 0.935 g/cc, at 23C, a melt index of about 0. 30 g/10 minutes at 250C, and 2,740 p. s. i., and an initial melting point of between 186C, and 220C .
U.S. Patent No. 3,231,636 (Snyder) describes a composition possessing improved shear strength and resistance to thermal embrittlement comprising 50 to 85 parts by weight of a polyethylene resin having a specific gravity above 0.945 and a melt index between about 0.02 and 8.0 and 50 to 15 parts by weight of a polyethylene resin having a specific gravity between about 0. 915 and 0. 925 and a melt index between about 0.02 to 25Ø
U.S. Patent No. 3,375,303 (Joyce) describes a composition comprising low density polyethylene having a density of from about 0. 915 to about 0. 925 and from about 1 to about 9 percent by weight, based on the weight of the composition of high density, high molecular weight polyethylene of narrow molecular weight distribution having a density of from about 0.930 to about 0.965, a melt index of not more than 0.1 decigrams per minute measured at 4~ p.s.i. and 190C, : . . , ~ : ' . ;, -~ ' - ' WO92/17539 PCT/US92/02~S,7 and a melt flow of not more than lo d~cigrams per minute measured at 440 p.s.i. and 190c, the melt index of said low density polyethylene bP.ing no greater than about 30 times the melt index of the high density polyethylene.

U.S. Patent No. 3,3~1,060 (Peacock) describes a composition e~hibiting freedom from melt fracture comprising low density polyethylene having a density of from about 0.915 to about 0.925, from about 0.3 to about 8 percent by weight of a first high density polyethylene having a density of from about o. 930 to about o. 965, a melt index of not more than 0.1 decigram per minute measured at 44 p.s.i. and 190C, and a melt flow of not more than 10 decigrams per minute measured at 440 p.s.i. and 190C, and from about 1 to about 33 percent by weight of a second high density polyethylene having a density of from about 0.930 to about 0.965, a melt index of greater than 0.1 decigram per minute measured at 44 p.s.i. and 190C, and a melt flow of greater-than 10 decigrams per~minute measured at 440 p.s.i. and 190C, the melt index of said low density polyethylene being no greater than about 250 times the melt index of said first high density polyethylene.

The following literature references deal with the potential correlations of polyethylene film rheological properties with other physical properties, especially film optical properties.

S. Onogi, et al., Polvmer Journal, 7 (4), 467-480 (1975) entitled 'IRheo-Optical Studies of Drawn Polyethylene Films." This reference describes how , -.:. :: . :
. . ~ . . . ;.

W~92/17539 21 0 7 0 9 ~ PCT/US92/02557 birefringence and stress relaxation were measured simultaneously on low density polyethylene (LDPE) films drawn to various extents. For undrawn and wea~ly drawn films, the strain-optical coefficient increased with increasing time; for highly drawn films, it decreased with increasing time; indicating that highly drawn films do r.ot exhibit the mechanism of crystalline orientation. No melt rheology was performed.

M. Shida, et al., Polvmer Enqineerina and Science, 17 (11), 769-77~ (1977), entitled "Correlation of Low Density Rheological Measurements with Optical an Processing Properties." This paper describes physical properties such as film haze and gloss of low density lS polyethylene (LDPF), which were correlated with rheological functions and the level of long-chain branching.

M. Rokudai, et al., Journal of APPlied Polvmer Science, 23, 3289-3294 (1979), entitled, "Influence of Shearing History on the Rheological Properties and Processability of Branched Polymers. II. Optical Properties of Low-Density Polyethylene Blown Films."
In this paper, the authors discuss the rheological and optical properties of six (6) different LDPE resins, which were determined on both f-esh samples and samples that had been extruded five (5) times to determine the effects of extrusion shearing. The modifications effected by shearing were correlated with a rheological property called the "processing index" (PI).

F.C. Stehling, et al., Macromolecules, 1~, 698-708 (1981), entitled "Causes of Haze of Low-Density Polyethylene Blown Films." Tn ,his paper, static and , W092/17~3~ PCT/US~2/025 on-line haze, low-angle light scattering, and microscopic measurements showed that ha~e of LDPE films is caused mainly by scattering from rough fllm surfaces that are formed by two mechanisms:
1. melt flow disturbances at the die exit (extrusion haze) 2. stress-induced crystallization close to the film surface (crystallization haze).
Haze from melt flow disturbances can be reduced by selecting resins that contain relatively low concentrations of large molecules and by intense mechanical deformation of the melt before extrusion.
Melt index swell decreased with number of extrusions and correlated well with degree of haze reduction.

H. H. Winter, Pure Appl. Chem., 55 (6), 943-976 (1983), entitlPd, "A Collaborative Study on the Relation Between Film Blowing Performance and Rheological Properties of Two Low-Density and Two High-Density Polyethylene Sampl~s." In this paper two pairs of polyethylenes (HDPE an LDPE) were studied in 14 laboratories. The experiments concentrated on film blowing and laboratory tests. The resins were chosen so that their shear flow behavior was similar, but 2S their film blowing properties differed. Laboratory tests included the following:
l. Crystallization from the melt 2. Shear viscosity (steady and time dependent) 3. Storage and loss moduli 4. Relaxation modulus 5. Entrance pressure correction 6. Melt flow index-7. Extrudate swell ~ : . ......... -, -~'~92/17539 PCT/US92/025~7 - 9 - 2107~9~

8. Uniaxial extensional creep and recovery afterward 9. Tensile test on extrudate The author claimed that extensional flow tests were the most sensitive, but other sensi.tive rheological tests included those that were dominated by long time constants. This includes the complex modulus.

S.A. Montes, Polvmer En~ineerina and Science, 2~
(4), 259-263 (1984), entitled "Rheological Properties of Blown Film Low-Density Polyethylene Resins." In this paper the author found that viscoelasticity played a dominant role in the behavior of three blown film-grade low density polyethylene resins. He mentioned, for instance, that there was general agreement that haze in LDPE film increases as extrudate swell, a measure of elasticity, increases. He also mentioned that rough films are generated by two mechanisms: extrusion haze and crystallization haze.
Extrusion haze involves melt flow disturbances at the die exit and is, therefore, related to the rheological properties of the resin.

H. Ashizawa, et al., Polymer Enaineerin~ and ~sir~5~, 24, (13), 305-1042 (1984), entitled, "An Investigation of Optical Clarity and Crystalline Orientation in Polyethylene Tubular Film." In this paper the authors claim that the majority of light scattered from LDPE, LLDPE and HDPE film was from the surface and not from the interior.

M.S. Pucci et al., Polvmer En~ineerina and Science, 26 (8), 569-575 (1986), entitled "Correlation of Blown Film Optical Properties with Resin Properties. In this WO92/17539 PCT/US92/025~-21~7()9~

paper it was shown that for LDPE blown films, resins with higher melt elasticity consistently resulted in films with poorer optical properties.

~. Audureau, et al., Journal of Plastic Film &
Sheetinq, 2, 298-309 tl986), entitled "Prediction and Improvement of Surface Properties of Tubular Low Density Polyethylene Films." In this paper, the authors found a correlation between surface haze and the ratio of freeze time to average rheological relaxation time. The average rheological relaxation time was obtained from dynamic melt rheological data.

W. Minoshima et al., Journal of Non-Newtonian Fluid Mechanics, 19, 275-302 (1986), entitled, "Instability Phenomena in Tubular Film, an Melt Spinning of Rheologically Characterized High Density, Low Density and Linear Low Density Polyethylenes."

D.L. Cooke et al., Journal of Plastic Film &
Sheetinq, 5, 290-307 (1989), entitled "Addition of Branched Molecules and High Molecular Weight Molecules to Improve Optical Properti~s of LLDPE Film." In this paper the authors mention that haze and gloss of LLDPE
films are determined largely ~y the roughness of the film surface. The LLDPE crystallization process that is responsible for the roughness can be disrupted by blending a small amount of a second PE resin. The resins used for blending with LLDPE included high gloss-low haze LDPE, low qloss-high haze LDPE, and HDPE. The authors suggest that a blending resin that has a high molecular weight tail in its MWD is most effective in improving LLDPE optical properties.

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wn 92/17539 PCT/US92/02557 - 1l 2~7~

Rheometrics APplication Bulletin, No. ll (undated), entitled, "Melt Elasticity & PE Blown-Film Optics." In this bulletin prepared by a commercial manufacturer of rheslogy instrumentation, the author reports correlations between the haze in low density polyethylene films and the storage modulus, G ' . The differences in the G' values were greatest in the low frequency region, 0.1 to 1 rad/sec.

From the art discussed above, there is certainly an interest in the production of clear plastic films, such as those described and claimed herein.
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SUMMARY OF THE INVENTION

The present invention is directed to a high molecular weight, high density polyethylene (HMW-HDPE) polymer which can be formed into a thin film having many of the desirable qualities of both high and low density polyethylene materials, without the disadvantages commonly associated with either class or material.

The HMW-HDPE polymer of the present invention has a molecular weight range of about 450,000 to 650,000, a density range of from about 0.9~1 to 0.950, and a melt index of about 0.5 g/10 min.

Thin films produced from this composition have the following physical properties:

(a) Low haze (i.e., high clarity); the percentage of haze in the films of the present . . . , : ;~

WO92/17539 ~lO 7 ~ ~ ~ PCT/US92/025~7 invention is less than about 50 percenl, preferably less than about 35 percent, and most preferably less than about 20 percent, as measured by ASTM D-lOo3. Conventional HDPE
polymer based films have haze values typically in excess of 50, 60 and/or 70 percent when measured in this manner. (See Table I and II, infra).

(b) High Gloss (45): the 45 gloss values of the films of the present inven~ion are at least about 20, preferably at least about 30 and most preferably at least about 40, as measured by ASTM D-2457. Conventional 1~ HDPE polymer based films have gloss values typically below about 15 and/or lO when measured in this manner. (see Table I and II, infra).

(c) High Light Transmission: the percen~age of light transmission for the films of the present invention are at least about 85 percent, preferably at least about 90 pe~cent, as measured by ASTM D-lO0~. Conventional HDPr polymer based films have similar high light transmission percentages. Thus, the HDPE
polymer of the present invention retains this favorable characteristic. (See Table I and II, infra).
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(d) Variation of Moisture Vapor Transmission; the films of the present invention show variation in moisture vapcr transmission (MVTR) values when compared to :' . . ~. ' '' ,, ~ ': "' :
,', .. '. ' "' "-; . . ' '' . : ' : ':

~'~92/17539 PCT/US92/02557 ! .~

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conventional HMW-HDPE polymer films as measured using ASTM F-372. In some cases the MVTR values increased from about 3 to 20 percent; while in other cases MVTR values decreased up to about lo percent. (See Table I and II, infra).

(e) Increased Nitrogen Ga~ Permeation; the films of the present invention show an lo increase in N2 gas per.meation values when compared to conventional HMW-HDPE polymer films ranging from about 1.5% up to about 17.2% as measured using ASTM D-3985. (See Table I and II, infra).
~f) Increased Oxygen Gas Permeation; the films of the present invention show an increase in 2 gas permeation values when compared to conventional HMW-HDPE polymer films ranging from about 3% up to about 22% as measured using ASTM D-3985. (see Table I and II, infra).

(g) Low Coefficient of Friction; the films of the present invention have a low coeffi~ient of friction as measured using ASTM
D-1894.

: ~ As used herein, the term "thin films" is defined :: ~ 30 as a film having a thickness of less than 1.5 Mil, : preferably less than 1.0 Mil, and most preferably less than 0.75 Mil.

In one preferred embodiment, it has been discovered ~: ~

..... " . :, WO92/17~39 PC~/US92/025;~
Zi07 95 ~

that by blending and extruding a mixture comprising a high molecular weight, hlgh density polyethylene (ab~reviated HMW-HDPE) resin (e.g., Novacor Chemical's Novapol, Product Number HD-4045, also know as HF-W648-H) and a high molecular weight low density polye~hylene (a~breviated HMW-LDPE) resin (e.g., Quantum USI's Petrothene, Product Number NA 355) a novel polymeric material is produced.

While not wishing to be bound by theory, it is believed that the resulting polymer formed by the above described blending and extrusion is not merely a mixture of the individual ingredients. It is believed that during the extrusion process, the crystalline structure of the two individual polymers is modified, resulting in the formation of a new polymer. Such change is believed due to the action of the heat and pressure of the extruder. This new polymer affords films and/or bags exhibiting high strength, high clarity, high gloss, low haze, and high slip. The film and/or bags prepared from this new polymer have exceptional strength, high gloss or sheen, and bet~er transparency than conventional HMW-HDPE film based bags.
It has further been discovered that the addition of a HMW-LDPE resin to any HMW-HDPE resin significantly reduces the haze value of ~he combination polymer, while concomitantly raising the gloss value of a film produced therefrom. Thus this invention is also directed to a method of improving the haze properties of clPar films prepared from high molecular weight high density polyethylene resins, which method comprises adding a haze reducing amount of a high molecular W~92/17539 PCT/US92/02~57 21 0709~

weight low density polyethylene resin to said HMW-HDPE
resins and forming films from the blended resin mixture.

The above described i~proved physical properties of films and bags prepared from a blend of HMW-HDPE resins and XMW-LDPE resins are essential for the commercial and customer acceptance of thin film materials, particularly thin film clear bags, such as produce and bakery bags, dry cleaning bags, and the like.

Through experimentation ît has been determined that one of the most preferred formulations of the aforementioned blend of a HMW-HDPE resin and a LDPE
resin in this invention is 80% (by weight) of Novacor's Novapol HD-4045 and 20% (by weight) of Quantum USI's Petrothene NA 355. The ranges of these materials which can be effectively used to make the film and/or bags of the present invention are as follows:
Novapol HDPE No. HD-4045 90% - 10% (by weight) Quantum LDPE No. NA 355 10% - 90% (by weight) A second preferred polymer blend formulation which has been developed herein is 79% Novacor's Novapol HD-4045, 20~ USI's Petrothene NA 355 and 1%
Archer Daniels Midland's Polyclean II 20835. It should be noted that USI's Petrothene NA351 can be substituted for the NA 355. Also, USI's Petrothene NA357 is another acceptable material.

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WO 92/17S39 2 1 ~ 7 ~ 9 ~ PCr/US92/02557 ~.

DETAIIJED D~;SCRIPTION OF THE PREFERRED El~lBODIMENTs As described above, the present invention is directed to improvements in high density polyethylene (HDPE) polymers, the use of such improved polymers in film and bag applications, and to a method of producing such improved polymers.

More particularly, the present invention is directed to a novel polymeric material and most particularly to films and/or thin, strong, high clarity bags, (e.g., produce and bakery bags) produced fror~, this polymeric material.

The physical properties for various HMWW-HDPE
polymers and blended compositions useful herein are presented below in Tables I and II. These data are for films produced at a 4:1 blow-up ratio, which is adequate for purposes of the present invention. The currently preferred blow-up ratio for film production in this invention is 5:1, and at that ratio, most of the properties described in the data Tables are improved. With the exception of Example F-1 in ~able I, the mixed film compositions recited were produced by a physical blendins (mixing) of the solid polymers, followed by extrusion. In the case of Example F-', the polymers were compounded together (melted together) prior to extrusion. From these data and the general level of skill in this field of art, the skilled ar~isan will be capable of determining, without resort to undue experimentation, other suitable materials which will yield a film and/or bag having the properties described herein.

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wn 92/17539 ` 2~ g PCT/US92/02557 ~7 TABI.E I

Physical Properties for various HMWW-HDPi and FRESH-SAC Formula~ions A i~ C D E F
1 00% 80% 80Yo USI 100% 100% Mitsui 100/0Novacor LY- Chev Cain 20% Mitsui 20%

Dart Impact G/Mil 281 1251 !254 !48 1214 125.7 Puncture J/mm 43.8 142.4 162.5 146.8 183 148.5 Elmendorf Tear G/Mil I_ I . I
MD 8.8 19.0 ~ 6 17.8 18.9 19.3 TD 206 193 +203 1425 1~69 ¦35 MVTR1100sq in/24 hrs 1.59 11.67 !1~44 11.68 !~--4 !2.~0 Gas Permeation N2=cc 239 1239 ¦188 ¦212_ ~ ~8 N21100 in2/24 hrs Gas Permeation 02=CC 303 !874 8û9 1871 693 1997 .-021100 in2/24 hrs ~
Gloss (450) 6.4 ~.0 17.1 136.9 111.1 140.7 Ha~e ~%) 72.1 159.9 l70.; 117.7 158.7 119.2 Light Transmission (%) 192.0 191.6 192.8 !92.1 192.8 I ~
ensile Yield PSI ~

i I
L
Tensile S~rength I
MD 11165 i9625 i8511 _ l12905 il O295 !9570 TD 6104 16148 15Ei55 14C22 16133 14886 _ ¦
I . _ I I ,.
Elongation ~
MD 335 1263 1324 !232 !242 !306 .
TD 571 1539 1533 ¦601 l537 1605 I :
Secant Modulus ¦ . I .. I
MD 133545 ¦130790 1112955 1151380 ¦159935 195_55 TD 13g345 1147345 ~134415 1153265_ 1188210_1127890 Thickness (Mil) .5~ 1.61 _1.63 h~,7 1.58 1.67 .. .. . . . .

WO 92/17539 PCr/US92/0255~7~, . ,:

2~0 ~095 TA3LE I

Physical Properties tor various HMWW-HDPE and FPESH-SAC Formulalions Compounded 80% 80Yo 80Yo 70Ch 80Yo 8û~ Novacor Cain LY600 Che~ Mitsui Mitsui 20% Cluantum 20% 20Yo 20~o 30Yo 20%
ySI NA3_5 NA355 NA35~ NA-~5~ NA355. Reo Dart Impacl G/Mil 65 139-2_ 138.3 132 j116 1400 Punc~ure J/mm 57 53 8 ~ ~ 4: 7 ¦49.4 177.2 ElmendortTear G/Mii I I I I i MD 6.4 18.6 i7.5 i7.4 i7.6 i8.4 TD 143 13~5 1396 1~51 ¦380 1230 MVTR/100sq in/24 hrs ~ 9 1~.44 1.51_ ¦1 49 11.46 Gas Permeation N2=cc '' 1227 1243 1241 ¦215 1210 N21100 in2/24 hrs Gas Permeation 02=Cc ~....... 703 939 1901 !886 1705 02~100 iri2/24 hrs Gloss (450) 55.0 ¦27.8 _ 25.6 139.1 ¦33.9 113.2 Haze (%) 7-9 _ ¦27-2 130.5 _ 118.1 116-3 161.2 Ligh~ Transmission (/0) 93.0 192.7 192.4 191.9 193.1 191.9 Tensile Yield PSI l _ MD 4626 _ 155B2 i4611 13764 6131 15462 TD 3045 13461 13582 ¦3314 3320 14120 Tensile Strength MD 105a5 111078 110251 9438 111B41 19895 TD 4495 l498a 14999 4899 !4462 ~41 Elongation l I
MD i172 1200_ 1286 298_ 229 1252 TD 578 559 ~541 1583 1648 1601 I _ I I
Secant Modulus i i MD 93815 _ 111795 ¦148896 93286 j153380 l160921 TD 113680 141230 ¦134621 ¦125290 ¦155271 ¦188231 Thickness(Mil) 54 1.59 _1.60_ 1.59 j.58 _ i-60 .

~; 92/17~39 ~ PC~US92/0~557 TABLE I

Physical Propsr~ies tor various HMWW-HDPE and FF/ESH-SAC Formulations L M N O P
1 ûO% 80% 80Yo 100% American American 100% Formosa Novacor Hoechst Hoechst Formosa 905(F) HFW945-H GM9255 20C~o NA:~55 905(F1 20% NA355 , ~
Dart Impact GlMil 400 1481 174.1 j234 li67 Puncture J/mm 172 ~0 161,0 j70.0 145.
Elmendort Tear G/Mil ~
MD15 10.61 14.8 Ig.o 7.9 TD143 1134 _ 1249 1226.0 231.û
MVI'R/1 OOsq in/24 hrs 1.66 1~ .
Gas Permeation N2=CC 240 T
N2/100 in2124 hrs _ ~ t _i Gas Permeation 02=cc 869 021100 ir~2124 hrs ~ +
Gloss (45O) 1~1.2 ¦a.o 13q.3 ¦8.a 1i31.0 Haze (%) 154~3 163.7 ~ i62.û 122.9 Light Transmission (Yo) . 91.9 19~7 - 192.7 1i92.0 1i93.0 .
Tensile Yield PSI

Ti~ 3928 !i4350 1460û 13524 12958_ Tensile Strength ¦ i t I _ MD 9300 19410 19730 !89-76 19034_ TD 7000 !7177 15307 15031 14456 I .
1, I I
Elonga~ion ~
MD 300 1241 1222 1313 _ _2 TD 600 !555 1545 1589 591 .
Secant Modulus ~ -TD 11~000 1156895 1166460 1126730 132240 Thickness (Mil) 1.50 _ 1.s5 1.60 i I .¦

,, ~ , . ... .

WO 92/1 7539 PCI /I JS92/02~7,~.
~ o709~ - 20 -TABLE I

P~ysical Propenies ~or various HMWW-HDPE and FRESH-SAC Formulation 80%
100YO Formoss 908(F) Formosa 20% OuanSum 908(F~ USI NA35~i Dart Impact GlMil 207 !
_ I
Puncture J/mm 58.0 lS0.0 Elmendort Tear G/Mil I
MD 9.S 17.3_ TD ¦173.0 1324.0 MVrP,l1OOsq in/24 hrs ¦' I ^ i I
Gas Permeation N2=cc ~
N21100 in2t24 hrs I _ Gas Permeation 02=cc 02/100 in2/24 hrs Gloss(450) j7.7_~ !30.0 i Haze (%) 70.0 !2.. 9 Light Transmission (Yo) 92.0 j93.0 Tensile Yield PSI

TD 3350 ~3219 Tensile Strength 1- ~

TD
:~ _ 1, Elongation _ I _ MD 298 _ l231 TD ~81 _ô33 Secant Modulus - !--=
MD 105415 179750_ TD 1~3545 l128905 _ I
Thickness (Mil) 49 ~ 1.56_ .

WO 92/17~39 2 ~ ~ 7 ~ 9 ~ P~/lJS92/025s7 , ., - .

FOOTNO~E TO TABLE I

A~ 100% Quantum USI IY6000 B- 100% Chevron 9890 C~ 100% Cain L5005 D- 80% Mitsui 7000F
20% Quantum USI NA355 E~ 100% Mitsui 7000F
F 80% Novacor HFW-945-H
20% Quantum USI NA355 F-1~ Compound~d 80% Novacor 20% Quantum USI NA355 G- 80% Cain L-6005 20% C)uantum USI NA355 H- 80% Quantum USI LY6000 20% Quantum USI NA356 I- 80% Chevron 9690 20% Quantum USI NA356 Jn 70% Mltsui 7000F
30% Quantum USI NA355 K~ . 80% Mitsui 7000F
. 20% Repro. Novacor HFW-g46-H
L~ 100% Novacor HFW-945-H
M~ 100% American Hoechst GM9256 N- 80% American Hoechst ~M 9255 20% Quantum USI NA365 O~ 100% Formosa 905(F) P~ 80% Formosa gO5~F) 20% Quantum USI NA355 Q- 100% Formosa 908~F) R~ 80% Formosa 908~F) 20% Quantum USI NA3~6 :

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WO92/17539 PCT/US92/025; ~

- 21~70~ - 22 -Table II provides additional physical data for some of the polymeric formulations described in Table I.

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21Q7;~9S - 24 -As shown in Tables I and II, either compounding (i.e., co-melting and mixing) or blending (i.e., solid mixing) of the various polymeric starting materials may be conducted prior to extrusion, and following extrusion the new polymeric material is obtained. In one case, the new polymer may be formed during the compounding, in the other, it is clearly formed in situ (i.e., in t~e extruder).

While one route used to prepare the novel polymeric composition of the present invention is based upon the physical blending of two (or more) materials together, followed by extrusion of the blend to produce the novel polymeric product, it is envisioned other processes may be employed. For example, given the physical properties of the presently claimed polymeric composition, those artisans having ordinary skill in the polymer art will be able to prepare the same polymeric product, having the described desired properties, using a variety of different techniques, e.g., in a polymer reactor vessel. In other woràs, the present inventors anticipate that artisans having ordinary skill in this field will be able to avoia the blending step described above, and still produce the presently claimed polymeric composition. Such progress is a typical development in the production of polymers, and is one that is clearly envisioned by the present inventors to represent the ultimate best mode for producing the presently claimed polymer composition.
In fact, Exxon and Dow Chemical have recently published technical literature wherein the describe new catalysts that permit them to tailor specific resins having specific properties in polymer reactor vessels.

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~092/17539 PCT~US~2tO2~57 2~ ~70'~5 Thus, any high molecular weight polyethylene based polymer exhibiting the previously described properties, prepared by whatever means, is deemed to be encompassed by the present application and the present claims.

As discussed above, clear produce and bakery bags manufactured from conventional HDPE resins could be produced using up to 50% less polymer resin than used for conventional LDPE produce and bakery plastic bags, but the HDPE resins have not generally been used in such thin bag applications because previously existing HDPE products were unable to match the clarity of the LDPE product. There is a general consensus that grocery store customers and check-out personnel need to see the contents of the bag without resort to opening the same, particularly in today's fast paced checkout lanes. The bags and film of the present invention provide the level of clarity necessary for this marke~, preferably in an easy-to-open T-shirt type bag form.
The novel polymer of the present invention has exceptional properties, which allows its use in numerous film and/or bag applica~ions, including:

(a) as a substrate for adhesive laminating, e.g., for pouch packages where high clarity, high strength at reduced gauge, high modulus and heat stability are important.

(b) as a l'can-liner'l for garbage or recycling cans or bins, which represents the first high clarity, HMW HDPE product of its type:
particularly for municipal recycling programs.

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2107~9~ - 26 -(c) as a carton liner, where high clarity, high barrier (gas) properties are important, e.g., in baking dough transfer and the like.

(d) a variety of clear, strong bag constructions, including for example, side weld, bottom gussett, tubular, and the like, for use as lettuce bags, various food packs, e.g., deli pouches, garment bags, e.g., dry cleaning bags, and the like.

(e) as a clear and strong film wrapper, e.g., fox newspapers, automatic packaging machines, and the like.
(f) as a heat sealable (hermetically sealable) single-ply replacement for polyester and/or polypropylene film/bag applications.

(g) as a substrate film for metallization and high moisture, light and air barrier food bags prepared therefrom (e.g., coffee, snack foods, such as candy, chips, peanuts, etc.) traditionally formed from polyester and/or two-layer polypropylene products.

h) as a heat stable film material, e.g., to be used to cover food f or microwave warming, heating and cooking.
(i~ as a solari~ation film for agricultural uses e.g., as a crop or ground cover wherein radiant heat energy from the sun is captured and directed to plants and/or the soil, . .. :

W092/17539 PCT/US92/025~7 f ..
210709~

promoting physical, chemical and/or biological changes therein.

Upon consid~ration of this disclosure, the skilled artisan in this field will readily be capable of determining additional uses for the polymer, film and bags of the present invention.

For instance, the mixture of HMW-HDPE (e.g., Novapol's HD-4045) and the H~W-LDPE (e.g., Quantum's NA
355) can be run through a commercial blown film extruder to produce films ranging in thickness from about 0.000275 inches to about 0.0005 inches.

l~ Quantum's NA 355, one of the preferred resins used heréin includes the following guidelines for its use:

A long-stalk bubble shape is recommended if HMW-LDPE films under l.5 mil are being extruded. In this technique, the extrudate above the die is kept at the same diameter as the die until the ~ubble expands to its final diameter just below the frost line, the point where the molten resin solidifies. The long stalk is maintained by a single-lip air ring around the die.

The rapid expansion of the bubble immediately below the frost line creates an orientation in the melt which optimizes the resultant film's impact strength~ This further enhances HMW-LDPE's strength properties, .
partlcularly at thln gauges.

Drawdown is also increased when long-stalk extrusion is used. Field trails have shown that .

WO92/17539 PCT/US92/02557~
210.7.0~

Quantum's HMW-LDPE resins can be drawn down to 0.5 mil . and retain their high strength and clarity properties, provided they are extruded using the long-st~lk technique. Table III lists other properties of Quantum~s HMW-LDPE resins for film when blown under lo~g-stalk co~ditions.

TABLE III

. . _ . ..... --Propory Unl~s ASTM Ts3~ NA 351-226 NA 35~196 HA 357-103 . Muthod . . . . . .. . . .. .. .. . ..
~Ro~ln Melt Index 9/10 min. D 1238 0.3 0.5 0.25 Density g/cm3 D 1505 0.925 0.925 0.930 ~myl Ace~ate Incorporated ~ 4.5 Film H~e ~ D 1003 6.0 5.8 8.0 Qloss, 45 D 2457 67 69 60 Dart Drop, F50 9 D 1709 310 300 350 TEDD, eody ~b D 4272 2.1 2.0 3.8 Crease f~b D 4272 2.0 1.9 3.8 Ins~on Puncture S~en0th, hrc~ newtons 27 24 24 Eneroy J 0.44 0.42 0.42 2 5 Tensile Prcperties Break, MD psi D 882 5300 5400 5200 TD psi D 882 5100 5200 5~00 Yleld, MD psi D 882 1900 1840 2200 TD psi D 882 1900 1860 1500 Elongation, MD % D 882 210 200 310 TD ~ D 382 340 340 310 3 o 1~b S~cant Modulus, MD psi D 882 37,500 32,400 22,800 1~ psi D 882 42,100 36,4D0 26,60û
~1 film prop~rties obtained on 1 mil film extruded with a long stalk and 3:1 blow-up ralio.

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W~92/17~39 PCTt~S92/02557 21~7~)9~
~ 29 -Novapol HD-4045 is a high molecular weight, high density film resin for thin gauge, high-strength film applications. This material ls advertized by its manufacturer as being designed to be drawn as low as 13 microns (0.5 mil). HD-4045-H offers the film processor high output rates for demanding film applications such as merchandise bags, T-shirt bags, can liners, mailing envelopes and other paper replacement end-uses.

HD-4045-H is said to process well on blown film lines designed for high denslty polyethylene extrusion, as well as on low shear, low L/D grooved barrel extruders. Film produced from this resin can readily be treated, printed and heat sealed on a variety of converting equipment.
.

Table IV outlines physical properties of HD-4045-H
of importance in the present invention.

.

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WO 92/17S39 PCT/~92/02557 2 i ~ r~ 53 ~3 ,~j `' ' ' TABLE IV

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W~92/17;39 210 7 0 9 ~ PCT/US92/02557 11 While these two materials are especially preferred herein, as shown in Tables I-II, other commercially available high molecular weight high molecular weight high density polyethylenes (HMW-HDPE) can be employed to provide films and/or bags having properties described herein. Such materials include:

Petrothene(R) high density polyethylene resins for blown and cast films (U.S. Industrial ~o Chemicals Co.,) such as LY 600.

High density polyethylene HD-7000F blown film resin (~xxon Chemical co.) Alathon(R) L5005 HDPE resin, a high molecular weight HDPE resin (Cain Chemical Inc.) whose broad bimodal molecular weight distribution (MWD) can be controlled by production technology.

Hostalen(R) "H" Series HMW HDPE film resins (Hoechst Celanese Co.) have optimal strength in both the machine direction (MD) and transverse direction (TD). Films produced from this resin series are said to possess a naturally slippery surface, allowing for easy opening of thin gauge products.

While a number of HMW HDPE resins have been described, it is similarly believed that the skilled artisa~ will readily see that NA 355 is not the only HMW-LDPE resin which can be used to improve the gloss and haze values of films and bags prepared from HMW-HDPE resins. Upon consideration of the present disclosure, the skilled artisan will readily be capable - - .. ; , .-.- . . . ..... .
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of determining substitute, equivalent, and/or superior materials for formulating polymers, films and/or bags having the unique properties described herein.

Physical analysis of several films prepared according to the present invention (see Tables I-II) has revealed several critical properties, including the following:

DSC crystallinity measurements of several films prepared according to the present invention reveal that film clarity and haze are not related to the degree of crystallinity of the final film.

Polymer crystal size is also not related to film clarity and haze, as demonstrated by polarized light microscopy and interference microscopy of microtomed cross sections of film.

Haze and clarity were found to be related solely to irregular polymer surface features on the inside and outside surfaces of the films. This was initially indicated by interference microscopical examination of film surfacPs. This was confirmed by the films becoming optically clear when their surfaces were treated with an immersion oil having a refractive index of 1.5150, similar to polyethylene.

Optical microscopy revealed surface s~riations on all of the films, even the 100% B film. These straitens, however, are not the cause of haze.
:
To better characterize the surface irregularities .~

WO92/17539 '~l O ~ 0 9 a PCT/US92/02~57 ~ 33 -on the films, both inside and outside film surfaces were examined using Scanning Electron Microscopy '(SEM). Inside and outside surfaces of all films were examined at lOOX and 500X. Both film surfaces were also examined at lOOOX for A/B blend ratios of lOo/o and 85/l5. An analysis of the SEM studies reveal significant differences in surface smoothness and irregularities between inside versus outside surfaces in blend ratios. The degree of surface roughness displayed in these photomicrographs correlates with the loss of clarity for individual films. Film clarity was ,ranked by measuring how far the film could be lifted off printed material and be legible.
The present invention will be further illustrated with reference to the following examples which aid in the understanding of the present invention, but which are not to be construed as limitations thereof. All percentages reported herein, unless otherwise specifLed, are pe'rcent by weight. All temperatures are expressed in degrees Celsius.

The Novapol HD-4045 and Petrothene NA 355 are blended together in a 4:1 ratio (i.e., 80% - 20%) respectively. The blend is then run through a blown ::; 30 film extruder at a 4:1 blow-up ratio and produces a 8"
' X 5" X .0005" X 20,000 foot film roll, [It has been found that a 5:l blow-up ratio provides better results for most of the physical characteristics.] The film is then printed on by means of a flexographic printing :- , .` : ' . .

W092/17~39 PCT/U~92/02557 ~
f .....

~70~5- - 34 ~
press. The film is then converted into a T-shirt sack by a conventional T-shirt bag machine.

Example 1 is repeated, but the formulation comprises 79% Novacor's Novapol HD-4045, 20% USI's Petrothene NA 355 and 1% Archer Daniels Midland's Polyclean II 20835.

Example 1 is repeated, but ~SI's Petrothene NA 351 is substituted for the NA 355.

Example 1 is repeated, but USI's Petrothene NA 357 is substituted for the NA 355.

Ten films made from various ratios of two polyethylene resins, Novacor's 40/45 (HMW-HDPE) and Petrothene NA 355 (HMW-LDPE), which were designated as Sample A and Sample B, respectively. The blended materials as well as pure pellets of the two components were also submitted for dynamic mechanical testing on the polymer melt, using ASTM D 4440:

Instrument: Rheometrics System 4 Temperature: 190C
Environment: Nitrogen Test Geometry: Parallel Plate - 25 mm diameter, with a typical gap height of 1 to 2 mm.
Test Frequencies: 0.1 to 100 rad/sec; 5 points per decade ,. , . . . ~ .,, - . -. . . - . . ~ ;: . . -i ~ 210709~

strain Level: 25%
Equilibration time at test conditions: >5 minutes 1 to 1.5 grams of each polymeric material were used for each experiment. Test specimens were loaded at temperatures ranqing from 25C to 70C. After loading, the temperature was raised in order to melt the specimen. Initially, the specimens underwent thermal expansion and exerted an outward normal force on the parallel plates. Therefore, the gap setting had to be adjusted periodically to avoid a normal force overload to the instrument.

When the temperature reached about 140C, the test specimens began to melt, and the normal forces decreased. The test material was then compressed between the parallel plates until it clearly filled the entire gap. Next, the excess material was trimmed from the edge of the plates. Finally, the test specimen was compressed again, with the operator making sure that the entire gap was filled with polymer melt. Once the temperature of the specimen reached the desired level, the specimen was allowed to equilibrate for 5 minutes before testing was begun.

In pxeliminary testing, it was determined that a strain level of 25% was suitable for the planned experiments. This selection was based on three criteria:

1. The materials did not exert an excessive torque at the highest test frequency (100 rad/sec).

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W092/17539 ; pCT/US9 ~A .

2. The ma$erials did exert a sufficient toraue at the lowest test frequency (0.1 rad/sec) 3. The materials appeared to be in the linear viscoelastic region, meaning that their - rheological properties were not dependent on the strain level.

Multiple runs were performed on each sample until the degree of reproducibility was acceptable (abou~ 5%
difference or less between runs). For some materials, it was sufficient to perform duplicate runs; for others, triplicate runs were necessary.

Tables with data from representative runs for each material are provided below. Since differences be~ween the different samples should be the most noticeable at the low frequencies, this was the region that focused on. The data at the lowest test frequency, 0.1 rad/sec, were somewhat scattered, possibly due to a low torque level or else variations associated with the start-up of the experiment. The scatter at the second-lowest frequency, 0.158; rad/sec, was accep~ably low, so this was the frequency that was used for comparing the different materials.

The results from multiple tests on the unblen~ed materials are given below in Table V. G' refers to the s~orage modulus; G" refers to the loss modulus.

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WO92/17539 ~ O~ S PCT/US92/02~57 -TABLE v G' 2 G" 2 EXpt.(dy/cm ) (dy/cm ) Material Form No. (*lE-4~ (*lE-4) S
_ Pellets 407 7.287 8.337 408 7.500 8.622 409 7.723 8.749 410 7.291 8.510 A Film 404 6.581 7.834 405 . 6.958 8.316 406 6.928 8.378 Avg. 6.822 8.176 Std. 0.171 0.15 Cov.(%) 3 3 B Pellets 412 . 1.061 3.28~
413 0.987 3.008 414 1.016 3.080 Avg. 1.021 3.124 Std. 0.030 0.117 Cov.(%) 3 4 B Film 415 1.002 3.060 417 0.998 2.992 Avg.1. 000 3.026 Std.o. 002 0.034 Cov. (%) o o .

The overall degree of reproducibility was from 2 to 3%. This is considered good.

SUBSrlTUTE S~ET

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Analysis of the storage modulus versus frequency curves of the pellets and films of material A and the pellets and films of material B showed good agreement (data not shown). The corresponding loss modulus values for pellets and films of materials A and B also showed good agreement (data not shown).

3. The Dependence of Rheological Properties on Composition and Correlations with Clarity Data The storage and loss moduli for the various compositions at 0.1585 rad/sec are given in Table VI
below.

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WO92/17539 ~ iO 7 ~ 9 ~ PCT/US92/025~7 The correlations of both storage and loss modulus with composition are very good. The equations from linear regression are the following:

Storage Modulus = 588 * (%A) + 4615 r = 0.948 Loss Modulus = 513 ~ (%A) T 26477 r = 0.938 However, neither of these quantities correlated with the clarity rankings. Therefore, the unexpected ranking of the clarity of these films cannot be explained by the rheological data, even though correlations between rheological data and clarity have been proposed in several prior art references (supra).

The present invention has been described in detail, including the preferred embodiments thereof. However, it will be appreciated that those skilled in the art, upon consideration of the present disclosure, may make modifications and/or improvements on this invention and still be within the scope and spirit of this invention as set forth in the following claims.

; ~ ' ' '' ' ' ' '

Claims

WHAT IS CLAIMED IS:

1. A high molecular weight, high density polyethylene polymer (HMW-HDPE) which has the following physical properties:

molecular weight range of about 450,000 to 650,000, density range of from about 0.941 to 0.950, and melt index of about 0.5 g/10 min.

2. A method of producing a high molecular weight, high density polyethylene polymer (HMW-HDPE) having the following physical properties:

molecular weight range of about 450,000 to 650,000, density range of from about 0.941 to 0.950, and melt index of about 0.5 g/10 min.;

which method comprises the steps of mixing from about 10 to 90 percent by weight of a high molecular weight high density polyethylene polymer with from 10 to 90 percent by weight of a high molecular weight low density polyethylene polymer, and extruding the mixed materials to form the polymer having the recited physical properties.

3. The method of Claim 2, wherein the mixing is conducted by physically blending the solid HMW-HDPE
polymer and the solid HMW-LDPE, to form a solid admixture which is then extruded.

4. The method of Claim 2, wherein the mixing is conducted by physically compounding the solid HMW-HDPE
polymer and the solid HMW-LDPE, to form a melted admixture which is then extruded.

5. Thin films produced from the polymer of Claim 1 having the following physical properties:

(a) Low haze (i.e., high clarity); the percentage of haze is less than about 50 percent, as measured by ASTM D-1003;

(b) High Gloss (45°); the 45° gloss values are at least about 20, as measured by ASTM D-2457;

(c) High Light Transmission; the percentage of light transmission is at least about 85 percent, as measured by ASTM D-1003;

(d) Variation of Moisture Vapor Transmission; the films show variation in moisture vapor transmission (MVTR) values when compared to conventional HMW-HDPE polymer films as measured using ASTM F-372;

(e) Increased Nitrogen Gas Permeation; the films show an increase in N2 gas permeation values when compared to conventional HMW-HDPE
polymer films ranging from about 1.5% up to about 17.2% as measured using ASTM D-3985;

(f) Increased Oxygen Gas Permeation; the films show an increase in O2 gas permeation values when compared to conventional HMW-HDPE
polymer films ranging from about 3% up to about 22% as measured using ASTM D-3985; and (g) Low Coefficient of Friction; the films have a low coefficient of friction as measured using ASTM D-1894.

6. The thin films of Claim 5, which have the following physical properties:

(aa) Low haze (i.e., high clarity); the percentage of haze is less than about 35 percent, as measured by ASTM D-1003;

(bb) High Gloss (45°); the 45° gloss values of the films are at least about 30, as measured by ASTM D-2457; and (cc) High Light Transmission; the percentage of light transmission is at least about 90 percent, as measured by ASTM D-1003.

7. The thin films of Claim 5, which have the following physical properties:

(aaa) Low haze (i.e., high clarity); the percentage of haze is less than about 20 percent, as measured by ASTM D-1003; and (bbb) High Gloss (45°); the 45° gloss values of the films are at least about 40, as measured by ASTM D-2457.

8. A film of Claim 5, which is prepared by extruding a physical blend of from about 90% to about 10% by weight of a high molecular weight high density polyethylene (HMW-HDPE) and from about 10% to about 90%
by weight of a high molecular weight low density polyethylene (HMW-LDPE) at a blow-up ratio ranging from about 4:1 to about 5:1.

9. The film of Claim 8, wherein the physical blend of polymers is a blend of polymer solids.

10. The film of Claim 8, wherein the physical blend of polymers is a melt blend.

11. The film of Claim 8, 9, or 10, wherein the HMW-HDPE is present in the blend at from about 80% to about 50% by weight.

12. The film of Claim 8, 9, or 10, wherein the HMW-HDPE is present in the blend at from about 80% to about 70% by weight.

13. Clear bags having exceptional strength, high sheen, and better transparency than conventional HDPE
film based bags, prepared from the films of Claim 5, 6, 7, 8, 9, 10, 11 or 12.

14. A method of improving the haze properties of clear plastic films prepared from high molecular weight high density polyethylene (HMW-HDPE) resins, which method comprises adding a haze reducing amount of a high molecular weight low density polyethylene (HMW-LDPE) resin to said HMW-HDPE resins and forming films from the blended and extruded resin mixture.

15. The method of Claim 14, wherein the blending of the polymers is conducted by admixing the individual solid polymer species.

16. The method of Claim 14, wherein the blending of the polymers is conducted by melt-mixing the individual polymer species.

18. The method of Claim 14, 15, or 16, wherein the haze reducing amount of the HMW-LDPE is from about 10%
to about 90% by weight.

19. The method of Claim 14, 15, or 16, wherein the haze reducing amount of the HMW-LDPE is from about 20%
to about 50% by weight.

20. The method of Claim 14, 15, or 16, wherein the haze reducing amount of HMW-LDPE is from about 20% to about 30% by weight.