CONFORMABLE SHEET

Abstract

A substantially planar sheet having two opposable surfaces, the sheet having at least one layer formed from a first optionally polymeric material and a second optionally polymeric material, the second material having a lower elasticity modulus (1% Secant) than the first material, incorporation of the second material producing a sheet having a tensile strength and/or elasticity modulus of about 90% or less of that of a sheet without such material when measured in any direction parallel to the sheet surface. Such conformable sheets and films are particularly useful for labelling and graphic art applications.

Claims

1. A substantially planar sheet having two opposable surfaces, the sheet comprising at least one layer comprising a first material and a second material characterised in that the second material has a lower elasticity modulus than that of the first material, incorporation of the second material producing a sheet having a tensile strength and/or elasticity modulus of about 90% or less of that of a sheet without such material measured in any direction parallel to the sheet surface.

2. A sheet according to claim 1 which has been stretched in at least one linear dimension (optionally in two substantially orthogonal directions more optionally in a machine direction and in a transverse direction) from an initial size to a final size and the at least one layer comprises as a bulk and/or continuous phase a first optionally polymeric material having an elasticity modulus from about 2000 to about 3000 MPa and a second optionally polymeric material of elasticity modulus from about 1000 to about 2500 MPa homogeneously dispersed or dissolved therein, the elasticity modulus of the second material being lower than the elasticity modulus of the first material, the second material being present in the conformability layer in an amount from about 5% to about 30% by weight of the first material; the sheet exhibiting one or more of the following properties: measured in the machine direction: (b) an elasticity modulus below about 2600 MPa; (c) a percentage elongation to break after manufacture below about 90%; (d) a percentage shrinkage after manufacture of below about 7% when the sheet is heated to 130° C. for one minute; measured in the transverse direction; (e) an elasticity modulus from about 1800 to about 2200 MPa; (f) a percentage elongation to break after manufacture of below about 120%; and/or (g) a percentage shrinkage after manufacture of below about 3.0% when the sheet is heated to 130° C. for one minute.

3. A sheet according to Claim either preceding claim, in which the first polymeric material comprises an homopolymer and/or a polymer of randomly oriented amorphous non-crystalline polymer chains.

4. A sheet according to any preceding claim, in which the first polymeric material comprises a polyolefin.

5. A sheet according to claim 4, in which the polyolefin comprises polypropylene optionally biaxially oriented.

6. A sheet according to any preceding claim, in which the second polymeric material comprises an elastomer and/or polyolefin.

7. A sheet according to claim 6, in which the second polymeric material comprises at least one polymer selected from at least one of the group consisting of homopolymers and copolymers including one or more repeat units derived from any ethylenic polymer precursor; copolymers including one or more repeat units derived from any propylenic polymer precursor; copolymers including one or more repeat units derived from any styrenic polymer precursor; copolymers including one or more repeat units derived from any CH.sub.2═CHR (R denotes any saturated C.sub.1-20 hydrocarbon group, preferably C.sub.1-10 alkyl) olefinic polymer precursor; and/or copolymers including one or more repeat units derived from any norbornenic polymer precursor.

8. A sheet according to any preceding claim in which the second polymeric material is present in the or each conformable layer(s) in amount of from about 5 to about 30% by weight of the first polymeric material.

9. A sheet according to any preceding claim comprising a plurality of layers.

10. A sheet according to claim 9, comprising at least three layers where the or each conformable layer is sandwiched between other layers such that none of the or each conformable layers forms either surface of the sheet.

11. A sheet according to any preceding claim, having an elasticity modulus of from about 1600 to about 2600 MPa measured in the machine direction.

12. A sheet according to any preceding claim, having an percentage elongation during manufacture of from about 60% about 85%. measured in the machine direction,

13. A sheet according to any preceding claim, having a percentage shrinkage after manufacture and heating at 130° C. for one minute of from about 5% to about 7% measured in the machine direction.

14. A sheet according to any preceding claim, having an elasticity modulus of from about 1200 to about 2200 Mpa measured in the transverse direction.

15. A sheet according to any preceding claim, having a percentage elongation after manufacture of from about 110% to about 115% measured in the transverse direction.

16. A sheet according to any preceding claim, having a percentage shrinkage after manufacture and heating to 130° C. for one minute of from about zero to about 2.5% measured in the transverse direction.

17. A sheet according to any preceding claim, having a mean thickness above about 75 μm.

18. A sheet according to any preceding claim, including a free radical scavenger and/or a UV attenuating material optionally located in the conformable layer (preferably in an amount of from about 0.1% to about 0.5% by weight of the first material) such that the sheet retains at least 50% of its mechanical properties after exposure to artificial weathering for 2500 hours.

19. A label, security, marking, graphic art and/or display device comprising a sheet according to any preceding Claim.

20. A label of optionally improved conformability, the label comprising a first backing sheet coated with a release layer on top of which is attached a second sheet according to any of claims 1 to 18, the second sheet being optionally provided with a printable coating on the side opposed to the first (backing) sheet.

21. Use of a sheet according to any of claims 1 to 18 in a method of manufacture of a label security, marking and/or display device.

22. Use of a sheet according to any of claims 1 to 18 in a method of labelling, security marking and/or display.

23. Use of a first and/or second polymeric material as defined in any of claims 1 to 18, for the purpose of enhancing in a sheet as claimed in any of claims 1 to 18, defined herein (optionally the sheet exhibiting improved conformability) one or more properties the properties being selected from: (a) tensile strength optionally from about 100 to about 250 Nm.sup.−2; (b) elasticity modulus optionally from about 2100 to about 3100 MPa; (c) percentage elongation optionally below about 150%; and/or (d) percentage shrinkage optionally below about 7%.

Description

COMPARATIVE EXAMPLE (Comp I)

[0112] A comparative BOPP film was prepared by the bubble process as described above, where Composition A was a stabilised propylene homopolymer suitable for film production with a melt flow index (MFI) measured at 230° C. and 2.16 kg of about 6.5 to about 9.0; Composition B was a propylene (95% w/w)/ethylene (5% w/w) copolymer; and Composition C was a propylene (82% w/w)/ethylene (1% w/w)/butylene-1 (17% w/w) terpolymer of low crystallinity.

[0113] It will be appreciated that other Examples (not necessarily tested herein) could be carried out by replacing any of Compositions A to C by other suitable compositions. For example Composition A could be replaced by a polymer of polypropylene containing a small concentration (from about 0.5% to about 1.0% w/w) of polyethylene, and/or Composition B could be replaced by a propylene (92% w/w)/ethylene (4% w/w)/butylene-1 (4% w/w) terpolymer.

Examples 1 to 5

[0114] Films of the invention were prepared as described in Comparative Example I, except that amounts (% by weight of the polypropylene) of the thermoplastic polyolefin (available commercially from Montell under the trade name Adflex X500F) shown in Table 1 were added to the propylene homopolymer forming composition A. Stable BOPP bubbles were achieved with Adflex X500F concentrations from 5 to 25% w/w. At each stage the bubble was allowed to settle and samples were taken.

[0115] The films were tested, and the results obtained are given in the following Tables 1 and 2, as follows:

TABLE-US-00001 TABLE 1 Amount Tensile Elasticity Elongation/ Shrinkage/ Adflex strength/Nm.sup.−2 Modulus/MPa % % Example X500F/wt % MD TD MD TD MD TD MD TD comp I — 228.4 187.4 2695 2397 86.40 122.6 7.6 1.5 1 5 168.9 147.4 2032 1882 78.16 107.4 5.1 1.7 2 10 163.4 141.9 1964 1486 75.51 108.7 6.6 2.1 3 15 168.0 136.1 1854 1670 70.84 108.9 5.9 2.3 4 20 146.9 115.4 1694 1391 70.11 109.4 6.9 2.5 5 25 144.8 111.8 1627 1230 65.07 119.0 7.2 3.2

TABLE-US-00002 TABLE 2 Av. Gloss/ Haze/ Clarity/ Yield/ thickness/ Example % % % kgm.sup.−2 μm Comp I 94.7 98.2 2.94 18.90 56.2 1 94.3 97.5 2.29 19.06 57.6 2 94.1 97.4 2.45 18.75 56.7 3 92.9 97.2 2.85 18.59 57.8 4 86.1 96.6 3.86 17.63 61.8 5 74.6 97.5 5.24 17.86 60.6

[0116] The test method used for gloss was ASTM D2457-70 and for haze and clarity were ASTM D1003 and D1044.

[0117] The addition of Adflex X500F to a conventional film (Comp I) was successfully at 5%, 10%, 15%, 20% and 25% w/w, and no delamination was observed for any of these films.

[0118] The optical properties of the modified films were within acceptable limits, although there was a slight reduction in clarity and gloss at Adflex levels from 15% to 25%. At concentrations of Adflex of from 20% to 25% there was a slight reduction in thermal stability and an increase in TD shrinkage was observed. Increasing levels of Adflex reduced the elasticity modulus (MD), elongation (MD) and tensile strength (MD and TD) leading to a more conformable film.

Examples 6 to 9

[0119] Films of the invention were prepared as described above except that the Adflex X500F was replaced as the modifying resin by various amounts of another resin, such as the saturated styrenic block copolymer (that available commercially from Asahi Chemicals under the trademark Tuftec®L515) as shown in Table 3.

TABLE-US-00003 TABLE 3 Amount of Tuftec Example L515/wt % 6 2 7 8 8 10 9 20 10 10 (another resin).sup.1

[0120] The modifying resin used was EMAC 2260 not Tuftec L515.

[0121] A comparative prior art OPP film Comp II (UCB code ref. C50) was prepared analogous to Comp I herein and also without any modifying resin. Some of these films were tested as described above and the results are given in Tables 4 &5 below.

TABLE-US-00004 TABLE 4 Flexural Tensile Elasticity stiffness: strength: Modulus: Elongation Shrinkage: Mn/m.sup.2 Nm.sup.−2 Mn/m.sup.2 at break % Example MD TD MD TD MD TD MD TD MD TD Comp II 2.147 1.956 219.9 193.3 2504 2348 85.34 107.6 4.84 −0.26  8 1.549 1.88 214.2 170.2 1936 1539 66.82 114.9 11.18 2.81  9 0.9283 1.315 218.1 129.5 1644 1054 58.12 109 8.7 −1.8 10 1.802 1.683 221.2 167.6 1789 1656 71.5 104.1 10.65 2.28

TABLE-US-00005 TABLE 5 (optical properties of film measured on a surface treated with a corona discharge) Example Gloss/% WAH/% NAH/% Comp II 92.7 1.6 5 to 10 8 87.4 1.8 2 to 3 9 86.9 2.6 2 10 85.0 2.7 13 to 14