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1. WO1993017863 - FILMS THERMOPLASTIQUES THERMOSOUDABLES

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

CLAIMS :

1. A film structure comprising a thermoplastic base layer having a heat sealable layer on at least one side which, on heat sealing, forms a seal
which is separable at the original seal surface without film tear, or by delamination of the
sealant material from the base layer.

2. A film structure according to claim 1 in which the heat sealable layer has a seal strength of
100 to 500 grams per inch (170° to 250°F seal
temperature, 20 psi, 0.75 sec. dwell time).

3. A film structure according to claim 1 or 2 in
which the heat sealable layer comprises a ternary blend of:
a) a random copolymer of ethylene and propylene and/or a random terpolymer of ethylene,
propylene and butylene; and
b) low density polyethylene; and
c) polybutene,
there being no less than 10 wt%, and no more than

50 wt%, of any one component a), b) or c) present in the blend, the weight percentage being by
weight of the total blend.

4. A film structure according to claim 3 in which one of the components a) , b) or c) is present in the blend in an amount from 30 to 50 wt%, the
other two components each being present in the blend in an amount from 10 to 30 wt%, the weight percentage being by weight of the total blend.

5. A film structure according to claim 3 or 4 in
which the random copolymer of ethylene and
propylene has a propylene content from 75 to 85 weight percent.

6. A film structure according to any one of claims
3, 4 or 5 in which the random copolymer of
ethylene and propylene has a random ethylene
content from 2 to 10 weight percent.

7. A film structure according to claim 3 or 4 in
which random terpolymer of ethylene, propylene and butylene has a random ethylene content from 1 to 5 weight percent and a random butylene content from 10 to 25 weight percent.

8. A film structure according to any one of claims 3 to 7 in which component a) has a melt flow rate from 5 to 10 with a density of 0.9 and a melting point from 115° to 135°C.

9. A film structure according to any one of claims 3 to 8 in which the low density polyethylene
component comprises a linear low density
polyethylene.

10. A film structure according to any preceding claim wherein the base layer comprises high density
polyethylene (HDPE) .

11. A film structure according to claim 10 wherein the HDPE has a density of at least 0.96.

12. A film structure according to claim 10 in which the base layer comprises an HDPE blend of two or more polymers each of which has a density of at least 0.96.

13. A film structure according to claim 12 in which the HDPE blend comprises a major proportion of
HDPE having a melt index of 0.5 to 10.

14. A film structure according to claim 12 or 13 in which the HDPE blend comprises a terblend of:
i) 50 to 98 weight percent of HDPE having a
density of at least 0.96 and a melt index
greater than 0.5 to about 2;
ii) 1 to 25 weight percent of HDPE having a
density of at least 0.96 and a melt index
from 0.1 to 0.5;
iii) 1 to 25 weight percent of HDPE having a
density of at least 0.96 and a melt index
greater than 2 to 8, the weight percentage
being by weight of the total HDPE blend.

15. A film structure according to any one of claims
10 to 14 wherein the base layer is oriented in the solid state to a deformation ratio from 1.1:1 to 2:1 in the machine direction, and to a
deformation ratio from 6:1 to 12:1 in the
transverse direction.

16. A heat seal composition for oriented films which comprises a blend of components a) , b) and c) as defined in claim 3 or 4.

17. Use of a composition defined in claim 16 for
forming heat seals in biaxially oriented film
structures comprising high density polyethylene.