Low emissivity film

Abstract

The present invention concerns a functional film material comprising a substrate layer and a coating layer, the coating layer comprising a block copolymeric binder and a particulate metal pigment therein, the ratio of pigment to binder in the coating layer being selected with reference to the coat weight to provide the functional film material with an emissivity of less than 0.5, and the substrate and coating layer being selected to provide the film with a VWTR (ambient) in excess 400 gm.sup.−2 d.sup.−1 bar.sup.−1.

Claims

1. A functional film material for providing an insulation regime facilitated by low emissivity comprising: a substrate layer selected from cellulose acetate, cellulose and derivatives thereof; and a coating layer forming the outermost layer of the film, the coating layer comprising: a block copolymeric binder, and a particulate metal pigment therein, a ratio of pigment to binder in the coating layer being selected with reference to a coat weight and to be within a range from 3:1 to 1:10 to provide the functional film material with an emissivity 0.5 or less; the substrate and coating layer being selected to provide the film with an ambient water vapor transmission rate (WVTR (ambient)) in excess of 400 gm.sup.−2 d.sup.−1 bar.sup.−1, wherein the WVTR of the substrate is at least 10 gm.sup.−2 d.sup.−1 bar.sup.−1 higher than the coating layer and wherein the substrate layer has a higher WVTR than the coating layer, such that the determining factor of the WVTR of the film as a whole is the coating layer.

2. The functional film material according to claim 1 wherein the substrate layer has a WVTR (ambient) in excess of 400 gm.sup.−2 d.sup.−1 bar.sup.−1.

3. The functional film material according to claim 1 wherein the substrate layer has an oxygen permeability (OTR) of less than about 30 cm.sup.3 m.sup.−2 d.sup.−1 bar.sup.−1.

4. The functional film material according to claim 1 wherein the substrate layer is cellulose acetate.

5. The functional film material according to claim 1 wherein the substrate layer is regenerated cellulose.

6. The functional film material according to claim 1 wherein the block copolymeric binder is selected from materials comprising a hard and soft segment polymer of the type configured for fabrics allowing breathability.

7. The functional film material according to claim 6 wherein the block copolymeric binder is selected from hydrophilic polyurethanes.

8. The functional film material according to claim 1 wherein the particulate metal material is a polished metal material.

9. The functional film material according to claim 8 wherein the polished metal material is selected from the group consisting of aluminium, bronze, stainless steel, brass, gold, nickel, silver, silver coated glass, tin, copper, and mixtures of two or more thereof.

10. The functional film material according to claim 1 wherein the particulate metal material has a predominantly lamellar or plate-like form.

11. The functional film material according to claim 10 wherein a median aspect ratio of the particulate metal material is at least about 10:1.

12. The functional film according claim 1 wherein the emissivity of the film is less than about 0.45.

13. The functional film according to claim 12 wherein the emissivity of the film is less than about 0.4.

14. The functional film according to claim 1 wherein the film substrate layer has a WVTR (ambient) in excess of 400 gm.sup.−2 d.sup.−1 bar.sup.−1 and the coating layer is at least one of the group consisting of: a semi-permeable membrane and a microporous layer.

15. The functional film according to claim 1 wherein the coat weight is from about 0.8 to about 2.5 gm.sup.−2.

16. The functional film material according to claim 15 wherein at least one of the film and the substrate layer has a WVTR (ambient) in excess of 1000 gm.sup.−2 d.sup.−1 bar.sup.−1.

17. The functional film material according to claim 1 wherein at least one of the film and the substrate layer has a WVTR (ambient) in excess of 500 gm.sup.−2 d.sup.−1 bar.sup.−1.

18. The functional film material according to claim 1 wherein at least one of the substrate and the coating is a semi-permeable membrane.

19. The functional film material according to claim 1 wherein at least one of the substrate and the coating is microporous.

Description

EXAMPLES

(1) Films in accordance with the invention were prepared (lab and pilot) by coating regenerated cellulose films (thickness of around 35 μm) with a coating comprising a polyurethane binder and a pigment. The coatings were applied by direct gravure coating to produce the films identified in Table 1 and with the properties identified therein. In the plant trials the coatings were applied to a cellulose acetate substrate available from Clarifoil, PO Box 5, Spondon, Derby, UK, DE21 7BP. W

(2) TABLE-US-00001 TABLE 1 Coat Pigment weight Emissivity WVTR* Sample Type Polyurethane Pigment Type P:B (g/m.sup.2) (ctd side) (g/m.sup.2/day) Cellophane 0.83 (comparative) Lab Cytec Silberline.sup.# Non - 0.67:1  0.8 0.20 1282 {circumflex over ( )}XPR571 Starbrite 2100 Leafing Lab Cytec{circumflex over ( )} Silberline.sup.# Non - 0.67:1  0.8 0.28 1391 XPR571 Starbrite 2100 Leafing Lab Cytec{circumflex over ( )} Silberline.sup.# Non - 0.4:1 1.5 0.49 1312 NPU433 LT20727 Leafing Lab Bayer Miraroto.sup.+ Non - 0.4:1 1.5 0.48 1216 Impraperm TF4679 Leafing 43189 Lab Bayer Miraroto.sup.+ Leafing 0.4:1 0.8 0.24 1116 Impraperm TF4679 43189 Lab Cytec{circumflex over ( )} Miraroto.sup.+ Non - 1.5:1 1.1 0.50 1449 XPR571 TF4679 Leafing Lab Cytec Miraroto.sup.+ Non - 1.5:1 1.4 0.44 1377 {circumflex over ( )}XPR571 TF4679 Leafing Lab Cytec{circumflex over ( )} Miraroto.sup.+ Non - .sup. 2:1 0.85 0.50 1449 XPR571 TF4679 Leafing Lab Cytec Miraroto.sup.+ Non - .sup. 2:1 1.1 0.45 1394 {circumflex over ( )}XPR571 TF4679 Leafing Pilot Cytec{circumflex over ( )} Miraroto.sup.+ Non - .sup. 1:1 0.9 0.42 1444 XPR571 TF4679 Leafing Pilot Cytec{circumflex over ( )} Miraroto.sup.+ Non - .sup. 1:1 2.2 0.26 1163 {circumflex over ( )}XPR571 TF4679 Leafing Pilot Cytec Miraroto.sup.+ Non - .sup. 1:1 1.7 0.30 1216 {circumflex over ( )}XPR571 TF4679 Leafing Pilot Cytec{circumflex over ( )} Miraroto.sup.+ Non - 1.5:1 2.2 0.24 1158 XPR571 TF4679 Leafing Pilot Cytec{circumflex over ( )} Miraroto.sup.+ Non - 1.5:1 1.7 0.21 1168 XPR571 TF4679 Leafing Plant Cytec{circumflex over ( )} RotoVario.sup.+ Non - 1.5:1 1.41 0.21 625 XPR571 530925 + Leafing Bricosoll.sup.~ Yellow KRV Plant Cytec{circumflex over ( )} Miraroto Non - 1.5:1 1.57 0.22 519 XPR571 TF4679 + Leafing Bricosoll.sup.~ Yellow KRV Plant Cytec{circumflex over ( )} Miraroto.sup.+ Non - 1.5:1 1.16 0.19 595 XPR571 TF4679 Leafing Bricosoll.sup.~ Yellow KRV *measured by the Standard Test Methods for Water Vapor Transmission of Material - ASTM E96/E96M-04 .sup.#from Silberline Manufacturing Co., Inc., 130 Lincoln Drive, P.O. Box B, Tamaqua, Pennsylvania 18252 {circumflex over ( )}from Cytec Surface Specialties S.A., Anderlechtstraat 33 - Rue d'Anderlecht, 1620 Drogenbos .sup.+from Eckart GmbH & Co. KG, Guentersthal, 91235 Velden, Germany *from Albion Colours, High Level Way, Halifax, HX1 4PN