Heat shrinkable polyolefin film and a preparation method thereof

Abstract

The present invention relates to a biaxially oriented polyolefin multilayer heat shrinkable film, which is a multilayer heat shrinkable film with at least three laminated layers, and has internal and external surface layers of a resin composition comprising 70-80 wt % of an ethylene-norbornene copolymer having a glass-transition temperature (Tg) of 138 C. and a norbornene content of 76 wt %, and 20-30 wt % of an ethylene-propylene random copolymer having a melting point (Tm) of 140 C.; and a core layer comprising 54 wt % of an ethylene-propylene random copolymer having Tm of 140 C., 8 wt % of an ethylene-butylene random copolymer having Tm of 66 C., 20 wt % of an ethylene-norbornene copolymer having Tg of 78 C. and norbornene content of 65 wt %, and 18 wt % of a hydrogenated petroleum resin having softening point (Ts) of 140 C. The present invention provides a polyolefin heat shrinkable film and a method for preparing the same, the film has good temperature resistance, high transversal heat shrinkage rate, solves the problem that labels among bottles are easy to adhere between each other during hot filling drink or the problem about adhesion between labels and PE heat-shrinkable film in bundle-shrink pack of a group of bottles using the PE heat-shrinkable film, and is suitably used as label substrate material for contoured bottles.

Claims

1. A multilayer heat shrinkable film, which is a heat shrinkable polyolefin film with at least three laminated layers, wherein the multilayer heat shrinkable film is obtained by biaxial orienting, wherein the multilayer heat shrinkable film has a middle layer as a core layer, two sides of the core layer each have a surface layer, and the surface layer comprises 70-80 wt % of a first ethylene-norbornene copolymer having a glass-transition temperature Tg of 138 C. and 20-30 wt % of a first ethylene-propylene random copolymer having a melting point Tm of 140 C., and wherein the core layer comprises 54 wt % of a second ethylene-propylene random copolymer (A) having a melting point Tm of 140 C., 8 wt % of an ethylene-butylene random copolymer (B) having a melting point Tm of 66 C., 20 wt % of a second ethylene-norbornene copolymer (C) having a glass-transition temperature Tg of 78 C., and 18 wt % of a first hydrogenated petroleum resin (D) having a softening point Ts of 140 C.

2. The multilayer heat shrinkable film according to claim 1, further comprising: sub-surface layers disposed between the core layers and the surface layer, wherein the sub-surface layers each comprise 60-90 wt % of a third ethylene-norbornene copolymer having a glass-transition temperature Tg of 78 C., and 10-40 wt % of a second hydrogenated petroleum resin having softening point Ts of 140 C.

3. The multilayer heat shrinkable film according to claim 1, wherein the first and second ethylene-propylene random copolymers have an ethylene content of 6.5 wt %, and the ethylene-butylene random copolymer has a butylene content of 25 wt %.

4. The multilayer heat shrinkable film according to claim 2, wherein the second ethylene-norbornene copolymer in the core layer and third ethylene-norbornene copolymer in the sub-surface layers are the same, the second and third ethylene-norbornene copolymers each have a norbornene content of 65 wt % and a glass-transition temperature Tg of 78 C., and the ethylene-norbornene copolymer in the surface layers has a norbornene content of 76 wt % and glass-transition temperature Tg of 138 C.

5. The multilayer heat shrinkable film according to claim 1, wherein the multilayer heat shrinkable film has a transversal heat shrinkage rate of not less than 40% under the condition that the multilayer heat shrinkable film is dipped in 90 C. water for 10 seconds.

6. The multilayer heat shrinkable film according to claim 1, wherein the multilayer heat shrinkable film has a longitudinal fracture nominal strain of 282-289%.

7. The multilayer heat shrinkable film according to claim 1, wherein the multilayer heat shrinkable film has a transversal tensile strength of 115-134 MPa.

8. The multilayer heat shrinkable film according to claim 1, wherein the multilayer heat shrinkable film has a transversal tensile elastic modulus of 1419-1530 MPa.

9. A container, comprising: a container body; and a multilayer heat shrinkable polyolefin film attached to the container body by heat shrinking, wherein the multilayer heat shrinkable polyolefin film includes at least three laminated layers obtained by biaxial orienting, wherein the multilayer heat shrinkable polyolefin film has a middle layer as a core layer, sides of the core layer each having a surface layer, the surface layer comprising 70-80 wt % of a first ethylene-norbornene copolymer having a glass-transition temperature Tg of 138 C. and 20-30 wt % of a first ethylene-propylene random copolymer having a melting point Tm of 140 C.; and wherein the core layer comprises 54 wt % of a second ethylene-propylene random copolymer (A) having a melting point Tm of 140 C., 8 wt % of an ethylene-butylene random copolymer (B) having a melting point Tm of 66 C., 20 wt % of a second ethylene-norbornene copolymer (C) having a glass-transition temperature Tg of 78 C., and 18 wt % of a first hydrogenated petroleum resin (D) having a softening point Ts of 140 C.

10. The container according to claim 9, wherein the multilayer heat shrinkable film further has sub-surface layers disposed between the core layer and the surface layer, and the sub-surface layers each comprise 60-90 wt % of a third ethylene-norbornene copolymer having a glass-transition temperature Tg of 78 C., and 10-40 wt % of a second hydrogenated petroleum resin having a softening point of 140 C.

11. The container according to claim 9, wherein the first and second ethylene-propylene random copolymers have an ethylene content of 6.5 wt %, and the ethylene-butylene random copolymer has a butylene content of 25 wt %.

12. The container according to claim 10, wherein the second ethylene-norbornene copolymer in the core layer and third ethylene-norbornene copolymer in the sub-surface layers are the same, the second and third ethylene-norbornene copolymers each have a norbornene content of 65 wt % and a glass-transition temperature Tg of 78 C.; and the first ethylene-norbornene copolymer in the surface layer has a norbornene content of 76 wt % and a glass-transition temperature Tg of 138 C.

13. The container according to claim 9, wherein the multilayer heat shrinkable film has a transversal heat shrinkage rate of not less than 40% under the condition that the multilayer heat shrinkable film is dipped in 90 C. water for 10 seconds.

14. The container according to claim 9, wherein the multilayer heat shrinkable film has a longitudinal fracture nominal strain of 282-289%.

15. The container according to claim 9, wherein the multilayer heat shrinkable film has a transversal tensile strength of 115-134 MPa.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1: a schematic diagram of overlapping heat shrinkable label sheet at joints to form a sleeve.

(2) 1coating head, 2press roll, 3overlap joint, 4direction of machine run.

(3) FIG. 2: a schematic diagram of bundle-pack of filled PET bottles using PE heat-shrinkable film.

(4) 1heat shrinkable sleeve labels, 2PE heat-shrinkable film.

(5) FIG. 3: a structural diagram of the multilayer heat shrinkable film of a preferable example of the present invention.

(6) 1external surface layer, 2external sub-surface layer, 3core layer, 4internal sub-surface layer, 5internal surface layer.

(7) FIG. 4: a structural diagram of the multilayer heat shrinkable film of Example 4 of the present invention.

(8) 1external surface layer, 3core layer, 5internal surface layer.

MODE FOR CARRYING OUT THE INVENTION

EXAMPLE 1

(9) A polyolefin heat shrinkable film had a five-layered co-extrusion structure (see: FIG. 3), comprising internal and external surface layers, internal and external sub-surface layers and core layer. The internal and external surface layers were composed of 70 wt % of ethylene-norbornene copolymer having Tg of 138 C. and norbornene content of 76 wt % (manufactured by Treasure Plastic Co., Ltd, TOPAS 6013F-04), and 30 wt % of ethylene-propylene random copolymer having Tm of 140 C. (manufactured by Lyondell Basell Company, CLYRELL RC1890). The internal and external sub-surface layers were composed of 90 wt % of ethylene-norbornene copolymer having Tg of 78 C. and norbornene content of 65 wt % (manufactured by Treasure Plastic Co., Ltd, TOPAS 8007F-400), and 10 wt % of hydrogenated petroleum resin having Ts of 140 C. (manufactured by Idemitsu Kosan Co., Ltd, P140). The core layer composition was composed of 54 wt % of ethylene-propylene random copolymer having Tm of 140 C. (manufactured by Lyondell Basell Company, CLYRELL RC1890), 20 wt % of ethylene-norbornene copolymer having Tg of 78 C. and norbornene content of 65 wt % (manufactured by Treasure Plastic Co., Ltd, TOPAS 8007F-400), 8 wt % of ethylene-butylene random copolymer having Tm of 66 C. (manufactured by Mitsui Chemicals Inc, A4085S), and 18 wt % of a hydrogenated petroleum resin having Ts of 140 C. (manufactured by Idemitsu Kosan Co., Ltd, P 140).

(10) The polyolefin heat shrinkable film was prepared by the following method: raw materials for blending were separately poured into extruder at 250 C., co-extruded through a 5-layers T-die, cooled with chill roll at 25 C., then longitudinal stretching was performed, the pre-heating temperature and stretching temperature for longitudinal stretching were both 100 C., annealing temperature was 110 C., and stretch rate was 1.2; then transversal stretching was performed, the pre-heating temperature for transversal stretching was 115 C., stretching temperature was 85 C., annealing temperature was 70 C., wind cooling temperature was 25 C., and stretch rate was 5.5, then the obtained film was subjected to corona treatment so that the film surface had a surface tension of 43 dyne/cm, following winding and slitting, and finally packed and stored.

(11) The film had the following thicknesses: the external and internal surface layers separately had thickness of 2 m, the external and internal sub-surface layers separately had thickness of 5 m, the core layer had thickness of 31 m, and the total thickness was 45 m. The longitudinal and transversal tensile strengths, longitudinal and transversal fracture nominal strains, longitudinal and transversal shrinkage rates, fraction coefficient, stretch elastic modulus in longitudinal and transversal directions, surface tension, haze and glossiness of the film were shown in Table 1.

EXAMPLE 2

(12) The composition for internal and external surface layers was composed of 80 wt % of ethylene-norbornene copolymer having Tg of 138 C. and norbornene content of 76 wt % (manufactured by Treasure Plastic Co., Ltd, TOPAS 6013F-04), and 20 wt % of ethylene-propylene random copolymer having Tm of 140 C. (manufactured by Lyondell Basell Company, CLYRELL RC1890); while the internal and external sub-surface layers, the core layer and the preparation method were the same as Example 1.

(13) The film had the following thicknesses: the external and internal surface layers separately had thickness of 2 m, the external and internal sub-surface layers separately had thickness of 5 m, the core layer had thickness of 31 m, and the total thickness was 45 m. The longitudinal and transversal tensile strengths, longitudinal and transversal fracture nominal strains, longitudinal and transversal shrinkage rates, fraction coefficient, stretch elastic modulus in longitudinal and transversal directions, surface tension, haze and glossiness of the film were shown in Table 1.

EXAMPLE 3

(14) The composition for internal and external sub-surface layers was composed of 60 wt % of ethylene-norbornene copolymer having Tg of 78 C. and norbornene content of 65 wt % (manufactured by Treasure Plastic Co., Ltd, TOPAS 8007F-400), and 40 wt % of hydrogenated petroleum resin having softening point of 140 C. (manufactured by Idemitsu Kosan Co., Ltd, P140); while the internal and external surface layers, the core layer and the preparation method were the same as Example 1.

(15) The film had the following thicknesses: the external and internal surface layers separately had thickness of 2 m, the external and internal sub-surface layers separately had thickness of 5 m, the core layer had thickness of 31 m, and the total thickness was 45 m. The longitudinal and transversal tensile strengths, longitudinal and transversal fracture nominal strains, longitudinal and transversal shrinkage rates, fraction coefficient, stretch elastic modulus in longitudinal and transversal directions, surface tension, haze and glossiness of the film were shown in Table 1.

EXAMPLE 4

(16) A three-layered co-extrusion structure was used, which specific structure was as follows: internal and external surface layers were composed of 70 wt % of ethylene-norbornene copolymer having Tg of 138 C. and norbornene content of 76 wt % (manufactured by Treasure Plastic Co., Ltd, TOPAS 6013F-04), and 30 wt % of ethylene-propylene random copolymer having Tm of 140 C. (manufactured by Lyondell Basell Company, CLYRELL RC1890).

(17) The core layer composition was composed of 54 wt % of ethylene-propylene random copolymer having Tm of 140 C. (manufactured by Lyondell Basell Company, CLYRELL RC1890), 20 wt % of ethylene-norbornene copolymer having Tg of 78 C. and norbornene content of 65 wt % (manufactured by Treasure Plastic Co., Ltd, TOPAS 8007F-400), 8 wt % of ethylene-butylene random copolymer having Tm of 66 C. (manufactured by Mitsui Chemicals Inc, A4085S), and 18 wt % of a hydrogenated petroleum resin having Ts of 140 C. (manufactured by Idemitsu Kosan Co., Ltd, P140).

(18) The polyolefin heat shrinkable film was prepared by the following method: raw materials for blending were separately poured into extruder at 185-250 C., co-extruded through a 3-layers T-die, cooled with chill roll at 25 C., then longitudinal stretching was performed, the pre-heating temperature and stretching temperature for longitudinal stretching were both 100 C., annealing temperature was 110 C., and stretch rate was 1.2; then transversal stretching was performed, the pre-heating temperature for transversal stretching was 115 C., stretching temperature was 85 C., annealing temperature was 70 C., wind cooling temperature was 25 C., and stretch rate was 5.5, then the obtained film was subjected to corona treatment so that the film surface had a surface tension of 43 dyne/cm, following winding and slitting, and finally packed and stored.

(19) The film had the following thicknesses: the external and internal surface layers separately had thickness of 7 m, the core layer had thickness of 31 m, and the total thickness was 45 m. The longitudinal and transversal tensile strengths, longitudinal and transversal fracture nominal strains, longitudinal and transversal shrinkage rates, fraction coefficient, stretch elastic modulus in longitudinal and transversal directions, surface tension, haze and glossiness of the film were shown in Table 1.

COMPARATIVE EXAMPLE 1

(20) A three-layered co-extrusion structure was used, which specific structure was as follows: internal and external surface layers were composed of 70 wt % of ethylene-norbornene copolymer having Tg of 78 C. and norbornene content of 65 wt % (manufactured by Treasure Plastic Co., Ltd, TOPAS 8007F-400), and 30 wt % of LLDPE (manufactured by Mitsui Chemical Inc., SP3020), while the core layer and the preparation method were the same as Example 4.

(21) The film had the following thicknesses: the external and internal surface layers separately had thickness of 7 m, the core layer had thickness of 31 m, and the total thickness was 45 m. The longitudinal and transversal tensile strengths, longitudinal and transversal fracture nominal strains, longitudinal and transversal shrinkage rates, fraction coefficient, stretch elastic modulus in longitudinal and transversal directions, surface tension, haze and glossiness of the film were shown in Table 1.

(22) As can be seen from the comparison, there is an obvious adhesion by using polyolefin heat shrinkable film of Comparative Example 1 in bundle-shrink pack using PE heat-shrinkable film, which do not meet appearance quality requirement for heat shrinkable sleeve label of canned drink.

(23) TABLE-US-00001 TABLE 1 Comparative Example 1 Example 2 Example 3 Example 4 Example 1 Tensile strength Longitudinal 40 46 42 47 36 (MPa) Transversal 115 127 117 134 107 Fracture nominal Longitudinal 289 288 289 282 291 strain (%) Transversal 24 21 22 21 32 Heat shrinkage Longitudinal 3 3 3 3 3 rate (%) Transversal 41.5 41 43 40.5 46 Friction Static 0.45 0.44 0.45 0.45 0.44 coefficient Dynamic 0.39 0.38 0.39 0.38 0.39 Stretch elastic Longitudinal 896 939 912 945 874 modulus (MPa) Transversal 1419 1503 1485 1530 1397 Surface tension, (mN/m) 43 43 43 43 43 Haze (%) 6.5 5.6 5.1 6.8 4.5 Glossiness (%) 61 65 65 60 69 Adhesion test of bundle-shrink x pack using PE heat-shrinkable film Notation: represents that no adhesion with PE heat-shrinkable film was confirmed; x represents that adhesion with PE heat-shrinkable film was confirmed.