Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins

Definitions

• the present invention relates to a sheet of plastic material which feels like and has at least some of the properties of paper, such as oxygen transmission rate, water vapor transmission rate and coefficient of friction, a process of producing same, as well as a composition for use in producing said sheet material. More particularly, the invention is concerned with a product which somewhat behaves and feels like paper, advantageously replaces food wrapping paper sheet material, can be used to replace stitched multi-wall paper bags, and finally is less expensive than paper. b) Description of Prior Art
• the sheet of plastic material according to the invention comprises a multilayer sheet having an outer layer, a middle layer, and an inner layer.
• the outer layer comprises between about 15 to 35 weight percent
• the middle layer comprises between about 30 and 70 weight percent
• the inner layer comprises between about 15 to 35 weight percent, all with respect to the entire weight of the multilayer sheet.
• the outer layer comprises between about 40 to 90 weight percent polyethylene and/or polypropylene, between about 5 and 50 weight percent of a finely granulated material adapted to give a feel of paper to the multilayer sheet, and between about 5 and 10 weight percent of a pigment.
• the middle layer comprises between about 60 and 95 weight percent polyethylene and/or polypropylene, between about 0 and 20 weight percent of the finely granulated material, and between about 5 and 20 weight percent of pigment.
• the inner layer comprises between about 70 and 98 weight percent polyethylene and/or polypropylene, between about 0 and 10 weight percent of filler, and between about 0 and 20 weight percent of pigment.
• the different layers may comprise linear low polyethylene, high density polyethylene, or a mixture thereof.
• the choice of the finely granulated material is left to one skilled in the art, the preferred product for its convenience being calcium carbonate.
• a product which is of interest is a particulate calcium carbonate dispersed in a high density polyethylene base.
• the preferred material is titanium dioxide in powder form, although it may also include a beige pigment.
• Some layers of the multilayer sheet according to the invention may include a filler as mentioned above.
• a preferred filler combination includes an anti-blocking agent which is chosen depending on the conditions prevailing in the extruder, silica, talc, diatomaceous earth, and any mixtures thereof.
• the outer layer preferably comprises a linear low polyethylene
• the middle layer preferably comprises a high density polyethylene
• the inner layer preferably comprises a linear low polyethylene
• the outer layer may comprise between about one layer and about one layer of the outer layer.
• the outer layer may comprise between about one layer and about one layer of the outer layer.
• the middle layer may comprise high density polyethylene, preferably in an amount between about 75 and 85 weight percent, between about 10 and 20 weight percent of a particulate calcium carbonate dispersed in a high density polyethylene base, and titanium dioxide powder, preferably in an amount between 8 and 12 weight percent.
• the inner layer may comprise linear low polyethylene, for example between about 90 and 98 weight percent, and a filler comprising an anti-blocking agent, talc, silica, and diatomaceous earth, preferably in an amount between about 2 and 10 weight percent.
• the outer layer is made of high density polyethylene, preferably between about 80 and 90 weight percent, particulate calcium carbonate dispersed in a high density polyethylene, preferably between about 5 and 10 weight percent, and titanium dioxide powder, preferably between about 5 and 10 weight percent.
• the middle layer may comprise between about 80 and 90 weight percent low linear polyethylene, and between about 10 and 20 weight percent titanium dioxide pigment.
• the inner layer in this case may comprise between about 60 and 80 weight percent high density polyethylene, between about 10 and 20 weight percent low linear polyethylene, and between about 10 and 20 weight percent titanium dioxide pigment.
• a preferred sheet material according to the invention has the following physical properties: an oxygen transmission rate between about 60 and 80 weight percent high density polyethylene, between about 10 and 20 weight percent low linear polyethylene, and between about 10 and 20 weight percent titanium dioxide pigment.
• the sheet material according to the invention has an oxygen transmission rate between about 30 and 50 cc/100in 2 /24 hours, and a coefficient of friction between about 0.4 and 0.5.
• the sheet of plastic material according to the invention may be used as a pet food packaging film, and in this case, it has the following properties: film thickness between about 4.0 to 7.0 mils; a tensile yield strength in longitudinal direction between about 1400 and 1800 lb Jin 2 ; an Elmendorf tear strength of between about 450 and 650 grams in longitudinal direction and between about 500 and 1000 grams in transverse direction; a dart drop impact between about 250 and 500 grams; a coefficient of friction between 0.35 and 0.8; a water vapor transmission rate between 0.30 and 0.01 g./lOO in 2 /24 hours; and an oxygen transmission rate between 20.0 and 38.0 cc/100 in 2 /24 hours.
• the invention also relates to a process of preparing a sheet multilayer sheet of plastic material which feels like and has at least some of the properties of paper, which comprises providing a first composition comprising between about 40 and 90 weight percent polyethylene and/or polypropylene, between about 5 and 50 weight percent of a finely granulated material adapted to give a feel of paper to the multilayer sheet, and between about 5 and 10 weight percent of a pigment, providing a second composition comprising between about 60 and 95 weight percent polyethyleneand/or polypropylene, between about 0 to 20 weight percent of the finely granulated material, and between about 5 and 20 weight percent of the pigment, and providing a third composition comprising between about 80 and 100 weight percent polyethylene and/or polypropylene, between about 0 and 10 weight percent of a filler, and between about 0 and 20 weight percent of the pigment, separately coextruding the first, second and third compositions and feeding the coextruded compositions to a die, and laminating same to constitute said multilayer sheet of plastic material
• Example 1 A laminating device consisting of an automatic raw supply for film outer later, an automatic raw supply for film middle layer, and an automatic raw supply for film inner layer, three corresponding extruders, and a multilayer sheet producing die were provided.
• the automatic raw supply for film outer layer contains 60 weight percent linear low polyethylene, and 40 weight percent Papermatch® (which is a highly concentrated additive of particulate calcium carbonate and titanium dioxide in a high density polyethylene base, sold by A Schulman Inc. of Akron, Ohio).
• the automatic supply is adjusted to feed 25 weight percent of the total weight of multilayer sheet to the corresponding extruder.
• the automatic raw supply for film middle layer contains 75 weight percent high density polyethylene, 10 weight percent titanium dioxide and 15 weight percent calcium carbonate. It is adjusted to feed 50 weight percent of the total weight of the multilayer sheet to the corresponding extruder.
• the automatic raw supply for film inner layer contains 96 weight percent low linear polyethylene, and 4 weight percent of a mixture comprising an anti-blocking agent, talc, silica and diatomaceous earth. The three extruders feed to the die which produces a multilayer sheet in a manner known to those skilled in the art. The multilayer sheet which is obtained feels and behaves like paper but is much more resistant than a normal sheet of paper.
• the procedure as in example 1 was repeated with the following ingredients and percentages.
• the outer layer consists of 45 weight percent high density polyethylene, 42 weight percent Papermatch ® and 13 weight percent beige pigment.
• the middle layer consists of 85 weight percent linear low density polyethylene and 15 weight percent particulate calcium carbonate.
• the inner layer consists of 80 weight percent high density polyethylene, 16 weight percent beige pigment and 4 weight percent of an anti-blocking agent. The film obtained was excellent to make boutique bags.
• the procedure as in example 1 was repeated with the following ingredients.
• the outer layer consists of 47 weight percent linear low density polyethylene (low slip), 44 weight percent Papermatch®, 5 weight percent white titanium dioxide pigment and 4 weight percent PPA (polymer processing aid).
• the middle layer consists of 61 weight percent linear low density polyethylene, 34 weight percent high density polyethylene and 5 weight percent white titanium dioxide pigment.
• the inner layer consists of 100 weight percent linear low density polyethylene (high slip).
• the film obtained was excellent for producing bags for wrapping sugar.
• the procedure as in example 1 was repeated with the following ingredients.
• the outer layer consists of 92 weight percent linear low density polyethylene and 8 weight percent Papermatch®.
• the middle layer consists of 56 weight percent linear low density polyethylene, 34 weight percent high density polyethylene and 10 weight percent calcium carbonate.
• the inner layer consists of 78.2 weight percent linear low density polyethylene, 15 weight percent low density polyethylene, 5 weight percent gray pigment and 1.8 weight percent slip/anti-blocking agent.
• the film obtained was excellent for producing paper like courier envelopes.

Landscapes

• Laminated Bodies (AREA)
• Wrappers (AREA)

Applications Claiming Priority (5)

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• 1999
  • 1999-05-06 WO PCT/CA1999/000413 patent/WO1999058336A1/en not_active Application Discontinuation
  • 1999-05-06 AU AU38047/99A patent/AU3804799A/en not_active Abandoned
  • 1999-05-06 EP EP99920474A patent/EP1076607A1/de not_active Withdrawn

Non-Patent Citations (1)

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