BACKGROUND ART It would be advantageous to provide a product from polymeric material in order to combine the look, stiffness, feel and dead fold characteristics of paper with the strength, waterproofing, and other advantages of polymeric sheeting.

It is an object of the present invention to provide a strong polymeric sheet material which has a definite paper feel and which can be used to great advantage in many typical applications of paper, such as bags, wrapping, packaging, stationery, bookbinding material and many others.

In the replacement of paper by the product of the present invention, the environmental advantage will be apparent in that trees may be saved instead of used for paper manufacture. Furthermore, the by-products derived during the paper manufacture process impacts negatively on the environment. In addition, the product of the invention is recyclable and reusable, or may be disposed of without creating an environmentally dangerous or unpleasant waste product. It can also be safely incinerated without forming any noxious or unpleasant gases.

DISCLOSURE OF THE INVENTION According to the invention in its broadest aspect a polymeric film is produced which contains a polymer, or blend of polymers which provide adequate strength and flexibility for use as a paper substitute and which also contains an extender in finely

divided form to provide a product which has a coefficient of friction similar to that of natural paper and which has a dead fold property similar to that of natural paper.

In a preferred form of the invention the extender is calcium carbonate which should be easily dispersible in a molten polymeric medium such as the medium chosen for the present invention. Thus, for example, a calcium carbonate product provided in the form of pellets in a polymeric binder which melts at operating temperatures allowing the calcium carbonate to disperse unifonnly into the polymer or polymer blend is preferred.

It will, of course, be appreciated that many possible extenders may be used in the process of the present invention, but calcium carbonate has been found to be best substance for this purpose. The calcium carbonate should be present in an amount of between about 10 percent and 50 percent of the mass of the polymer.

One of the main considerations in the choice of extender is the particle size as this will have a great effect on the feel of the product which should not be too coarse, nor too smooth, otherwise it will not have the characteristic paper like feel.

The invention is preferably in the form of multilayer product which is formed by co-extrusion of two or more different compositions chosen for particular end uses of the product formed.

High density polyethylene has been found to be a suitable polymeric material and when mixed with about 20 percent by mass of calcium carbonate, forms an excellent product which has the properties required. The upper limit of calcium carbonate is about 50 percent.

As mentioned above the invention may be provided in multilayer constructions, one or both of the outer layers having a composition for the required paper like feel while the internal layers may have compositions to provide adhesion between adjacent layers, to provide strength and waterproofing and/or degree of air or vapour permeability.

It has been found that the intermediate layer/s should contain the extender to certain degree because this ensures that the product will exhibit the dead fold property which polymer sheeting never does because of the inherent memory of the polymer. It seems that the extender, and in particular calcium carbonate at the correct percentage guarantees that this desirable property is achieved.

It has been found that the outside layers provide the desired properties if extruded from high density or medium density polyethylene (density between 0.94 and 0.96g/cm3) while the intermediate layers should have a certain amount of low density polyethylene and particularly linear low density polyethylene. The latter has a beneficial effect on the bonding of adjacent layers so that the blown coextrusion of the various layers is effectively carried out.

It has been found that a film or layer having about 60 percent of high density polyethylene and containing above 20 percent of calcium carbonate has a density of about 1.1 and is very similar in all respects to paper of the same of similar thickness, except that the layer or film of the invention is infinitely stronger than the paper equivalent.

It will be appreciated that the coextrusion method involved may be predetermined to produce products having different colours front and back, or different feels-for example for certain types of packaging or bags (cement bags, dog food bags and others for example). One product of the invention may have a paper like feel on one side and a perfectly smooth feel on the other. it In a particular example of the invention a three layer product is prepared, the outer layers comprising 60 percent high density polyethylene and 20 to 30 percent calcium carbonate and the core layer comprising a blend of high density polyethylene and linear low density polyethylene with 20 percent of calcium carbonate.

In an example of the invention a film was obtained having the following parameters.

TYPICAL VALUES BASED ON 50xnn FILM PROPERTIES UNIT VALUE Density (final product) g/cm 1. 1 Melt Flow Index (190/2.16) g/lOmin. 0. 133 Moisture Vapour Transmission Rate G/m2/24hrs (38°C 8.60 and 75-100% RH Tensile strength at break MD Mpa 32.9 TD Mpa 18.9 Elongation MD % 400 TD % 106 Storage Conditions Must be stored away from direct sunlight. Storage conditions must be clean and dry. Storage temperatures must be below 25°C. Food Contact This material complies with F & DA regulations.

Variations of the coefficent of friction with increasing amounts of calcium carbonate are shown in the following Table % CaC03 vs C. O. F

% CaCO3 10% 15% 20% 25% 30% 35% 40% 45% 50% C. o. F 0.32 0. 33 0.34 0. 36 0. 38 0.39 0.41 0. 42 0.44 Other parameters of films according to the invention of increasing thickness are shown in the following Table Paperlike Films Analysis

30 mic 50 mic 80 mic 100 mic 120 mic DENSITY 1.1 g/cm3 1.1 g/cm3 1.1 g/cm3 1.1 g/cm3 1.1 g/cm3 MVTR 12. 6 8. 6 5. 7 6. 7 3.3 ELONGATION : MD 340% 401% 453% 495% 556% TD 106% 106% 105% 107% 106% TENSILE: MD 31. 14 32.95 32.49 30.33 32.49 TD 18. 01 18. 9 20.74 27.04 35.04 The films of the invention may be corona treated on either or both sides to a level of 40 Dyne which is ideally suited for printing and laminating. Due to its low water absorbency, solvent based inks are recommended for printing and it has been found that the quality of printing is excellent.