|Publication number||USH582 H|
|Application number||US 07/026,852|
|Publication date||Feb 7, 1989|
|Filing date||Mar 17, 1987|
|Priority date||Mar 17, 1987|
|Also published as||CA1321437C|
|Publication number||026852, 07026852, US H582 H, US H582H, US-H-H582, USH582 H, USH582H|
|Inventors||John H. Tucker|
|Export Citation||BiBTeX, EndNote, RefMan|
|Non-Patent Citations (3), Referenced by (3), Classifications (20), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This invention relates to blends of ethylene/carboxylic acid copolymers with high density polyethylene and inorganic fillers, which blends are useful for making films for skin packaging applications.
Skin packaging is a packaging method involving placing a product on a substrate material, such as paperboard, and draping heated plastic film over the product and substrate. A vacuum is then applied to draw the film down tightly to the board and around the product to make a secure and attractive package. One common application for skin packaging is industrial skin packaging used to protect products in transit. Products as divergent as computer tapes, lamps, service repair kits and table tops may be skin packaged instead of using die-cut corrugated, foam-in-place, foam peanuts and other stabilizing or dunnage materials. Skin packaging offers high throughputs and full visibility to check for tampering or missing components and also allows for quick identification, usually at significant cost reductions.
Low density polyethylene films are often used for skin packaging applications, but skin packaging films of ethylene/acid copolymers have been found to possess faster cycle times, better board adhesion, improved draw and better toughness than the low density polyethylene films. Oddly enough, one drawback of the ethylene/acid copolymer films is their relatively good optical properties since they more readily show the relatively unattractive packaging board used for the skin packaging of industrial items. Additionally, the industrial items themselves are often relatively unattractive. Thus, a method for affecting the optical properties of the ethylene/acid copolymer films, while not adversely affecting the desirable properties of such films, such as adhesion, was desired.
A method of modifying ethylene/acid copolymers by blending them with high density polyethylene and inorganic fillers has now been found which serves to degrade the optical properties of films made therefrom without degrading the adhesive and other desirable properties of such films. Surprisingly, this modification of the ethylene/acid copolymers leads to films which not only retain the adhesive properties of the unmodified copolymers, but in some cases leads to films with adhesive properties superior to that of the unmodified copolymers. Specifically, this invention relates to novel blends comprising:
(a) about 75 to 95.5% by weight of one or more ethylene/carboxylic acid copolymers;
(b) about 5 to 20% by weight of high density polyethylene; and
(c) about 0.5 to 5% by weight of a particulate inorganic filler, and to films made therefrom.
The ethylene/carboxylic acid copolymers which comprise the greatest part of the blends of this invention are copolymers of ethylene with an alpha, beta-ethylenically unsaturated carboxylic acid preferably having 3 to 8 carbon atoms. Examples of acid monomers include acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, maleic acid, fumaric acid, and monoesters of said dicarboxylic acids, such as methyl hydrogen fumarate, ethyl hydrogen fumarate and maleic anhydride. The concentration of acidic monomer in the copolymer is generally about 1 to 20 weight %, and preferably from about 3 to 15 weight %. Preferred copolymers are copolymers of ethylene with methacrylic acid or acrylic acid, or terpolymers of ethylene, maleic anhydride and esters of acrylic acid such as ethyl acrylate. The most preferred copolymer is a copolymer of ethylene with methacrylic acid, having an acid content of about 9 weight % and a melt index of about 1.5.
The particulate inorganic fillers useful in this invention are those fillers well known in the art for incorporation into films to improve handling characteristics. The preferred filler is calcium carbonate, but examples of other fillers which may be utilized include, but are not limited to, mica, aluminum silicate, magnesium silicate, and barium sulfate. Preferably, so as not to adversely affect the quality of the film, the filler is quite uniform in size; e.g., for the preferred calcium carbonate filler, a particle distribution would preferably range from about 0.3 to 50 microns, and more preferably from about 0.3 to 20 microns. Also, when it is desired to degrade the optical properties of the film (e.g., increase haze or reduce transparency), the refractive index of the filler preferably differs from that of the ethylene/acid copolymer and the high density polyethylene used in the blend.
The preferred high density polyethylene is a linear ethylene homopolymer of medium molecular weight distribution having a melt index of about 1.1.
A preferred composition comprises about 82 to 94% by weight of ethylene/acid copolymer, about 5 to 15% by weight high density polyethylene, and about 1 to 3 weight % inorganic filler.
The blends of this invention may be made and extruded into films by methods known in the art. The following examples illustrate blends and films of this invention.
A blend was made incorporating the following:
Component A: 88% by weight of ethylene/methacrylic acid copolymer having 9% methacrylic acid, a Melt Index of 1.5
Component B: 10% by weight of high density polyethylene hav:ng a Melt Index of 1.1
Component C: 2% by weight calcium carbonate, 3-5 micron average particle size and extruded into films 4 and 6 mil thick. Control films extruded from Component A alone and from low density polyethylene (LDPE) alone were also prepared. Properties for these films are presented in the following table. A description of the tests used follows the table.
TABLE______________________________________Film Properties BLEND A BLEND A A LDPEFilm 4 mil 4 mil 6 mil 6 mil 5 mil 5 mil______________________________________ADH,PP COR (g/in.)MD 729 681 873 736 771 811TD 629 581 718 651 703 694ADH,UPUP COR (g/in.)MD 314 308 356 363 395 201TD 333 296 364 349 411 218TEMPERATURE, F. 190 230 195 198 190 230HEAT UP, sec. 17 18 16.5 17.5 17.3 30HAZE -- -- 71 1.5 -- 12.8GLOSS -- -- 4 90 -- 18TRANSPARENCY -- -- 0.2 43 0.8ELMENDORF (g/mil)MD -- -- 209 224 -- 84TD -- -- 229 240 -- 101SPENCER IMPACT(in-lbs/mil) -- -- 3.1 4.3 -- 2TENSILE (psi)MD -- -- 3959 4331 -- 2814TD -- -- 3999 4266 -- 2947ELONGATION (%)MD -- -- 512 536 -- 540TD -- -- 502 574 -- 530______________________________________ ADH,PP COR Adhesion to primed printed corrugated board ADH,UPUP COR Adhesion to unprimed unprinted corrugated board TEMPERATURE Amount of heat retained in the film as it contacts the board to activate the primer or adhesive on the board for good adhesion HEAT UP The optimum amount of time required to soften the film for skin packaging, i.e., the amount of time required to "double drape" the film. HAZE ASTM D100361 GLOSS ASTM D245770 TRANSPARENCY ASTM D174670 ELMENDORF ASTM D192267 SPENCER IMPACT ASTM D342085 TENSILE ASTM D82283 ELONGATION ASTM D82283 MELT INDEX (Referred to elsewhere in this specification) D1238
The data in the table indicate that the films prepared from the blends of this invention possessed superior physical properties and better adhesion to unprimed corrugated board than the film of low density polyethylene. The films according to this invention, when compared to films prepared from ethylene/acid copolymer alone (Component A), also possessed a slight increase in adhesion to primed corrugated board, a reduction in film heat-up time, and no adverse reduction in film physical propeties.
|1||Copy of Contract between Du Pont and Stone Container Corp. (and related papers).|
|2||Misc. Shipment or Return Order dated 3-11-86.|
|3||Notebook page by Tucker dated 3/3/86 titled "Melt Blend for Industrial Skin Pkg."|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US6162852 *||Sep 4, 1997||Dec 19, 2000||Isolyser Company, Inc.||Degradable polymers|
|US20030144422 *||Jan 13, 2003||Jul 31, 2003||Isolyser Company, Inc.||Novel degradable polymers|
|WO1995013329A1 *||Nov 9, 1994||May 18, 1995||E.I. Du Pont De Nemours And Company||Multi-phase film and methods relating thereto|
|U.S. Classification||524/427, 525/221, 524/517, 525/207, 524/522|
|International Classification||C08L23/06, C08J5/18, C08L23/08, C08K3/26, C08K3/00|
|Cooperative Classification||C08J5/18, C08K3/0033, C08L23/06, C08L23/0869, C08K3/26, C08J2323/08|
|European Classification||C08J5/18, C08K3/00P5, C08K3/26, C08L23/08C3|
|May 20, 1987||AS||Assignment|
Owner name: E.I. DU PONT DE NEMOURS AND COMPANY, WILMINGTON, D
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:TUCKER, JOHN H.;REEL/FRAME:004721/0254
Effective date: 19870312