Heat-shrinkable film

Abstract

The present invention provides a heat shrinkable film that has excellent heat shrinkability while preventing contamination in subsequent processes such as printing. The present invention relates to a heat shrinkable film that at least includes a front layer and/or a back layer. The front layer and the back layer each contain a cyclic olefin resin in an amount of 55 to 99.99% by weight and organic fine particles in an amount of 0.01 to 0.3% by weight.

Claims

1. A heat shrinkable film comprising: a front layer; a back layer; and an interlayer, laminated together, wherein the front layer and the back layer comprise a cyclic olefin resin in an amount from 55 to 74.9% by weight, organic fine particles in an amount from 0.03 to 0.2% by weight, and an ethylene resin in an amount from 0.1 to 25% by weight, the organic fine particles are crosslinked-organic resin fine particles and have an average particle size in a range from 1 to 5 m, and the crosslinked-organic resin fine particles are at least one particles selected from the group consisting of crosslinked acryl resin fine particles and crosslinked styrene resin fine particles, the interlayer comprises a propylene resin in an amount from 51 to 99% by weight and a cyclic olefin resin in an amount from 1 to 49% by weight, and the propylene resin comprises a propylene-a-olefin random copolymer.

2. The heat shrinkable film according to claim 1, wherein the interlayer further comprises a hydrocarbon resin.

3. The heat shrinkable film according to claim 1, wherein the interlayer further comprises an olefin elastomer in an amount from 1 to 20% by weight.

Description

DESCRIPTION OF EMBODIMENTS

(1) The embodiments of the present invention are described in detail below referring to examples. The present invention is not limited to these examples.

EXAMPLE 1

(2) An amount of 99.85% by weight of APL8008T (an ethylene-tetracyclododecen copolymer, glass transition temperature: 70 C., from Mitsui Chemicals, Inc.) as a cyclic olefin resin was mixed with 0.15% by weight of crosslinked styrene fine particles (SX, average particle size: 3.5 m, from Soken Chemical & Engineering Co., Ltd.) as organic fine particles.

(3) The mixture was melted in a uniaxial extruder at a barrel temperature of 210 C., extruded through a T-die, and cooled and solidified on a roll cooled to 30 C. Thus, an unstretched sheet was prepared. This unstretched sheet was stretched in TD (transverse direction) by 5 times with a tenter stretching machine at a temperature of 90 C. Thus, a film having a total thickness of 45 m was obtained.

EXAMPLE 2

(4) An amount of 45% by weight of APL6509T (anethylene-tetracyclododecen copolymer, glass transition temperature: 80 C., from Mitsui Chemicals, Inc.) and 14.9% by weight of APL8008T (an ethylene-tetracyclododecen copolymer, from Mitsui Chemicals, Inc.) as cyclic olefin resins, 40% by weight of linear low density polyethylene SP2320 (from Prime Polymer Co., Ltd.) as an ethylene resin, and 0.10% by weight of crosslinked polymethyl methacrylate fine particles (MBX series, average particle size: 5 m, from Sekisui Plastics Co., Ltd.) as organic fine particles were mixed.

(5) A film having a total thickness of 30 m was obtained in the same manner as in Example 1 except that this mixture was used.

EXAMPLE 3

(6) A material for the front layer and the back layer was prepared by mixing 84.85% by weight of 750R (a hydrogenated product of a norbornene ring-opening polymer, from Zeon Corp.) as an a cyclic olefin resin, 15% by weight of linear low density polyethylene SP1520 (from Prime Polymer Co., Ltd.) as an ethylene resin, and 0.15% by weight of crosslinked urethane fine particles (Art Pearl C from Negami Chemical Industrial Co., Ltd., average particle size: 6 m) as organic fine particles.

(7) A material for the interlayer was prepared by mixing 80% by weight of linear low density polyethylene SP2520 (from Prime Polymer Co., Ltd.) and 20% by weight of 750R (a hydrogenated product of a norbornene ring-opening polymer, from Zeon Corp.) as a cyclic olefin resin.

(8) The material for the front layer and the back layer was melted in a uniaxial extruder at a barrel temperature of 210 C., and the material for interlayer was melted in another uniaxial extruder at a barrel temperature of 180 C. The melted materials were extruded from a T-die and cooled and solidified on a roll cooled to 30 C. Thus, an unstretched sheet was prepared. This sheet was stretched in TD (transverse direction) by 5 times with a tenter stretching machine at a temperature of 90 C., whereby a film having a total thickness of 50 m was obtained. The front layer, the interlayer, and the back layer in the film had a thickness of 9 m, 32 m, and 9 m, respectively.

EXAMPLE 4

(9) A material for the front layer and the back layer was prepared by mixing 74.9% by weight of TOPAS9506 (an ethylene-norbornene copolymer from Polyplastics Co., Ltd.) as an cyclic olefin resin, 25% by weight of linear low density polyethylene SP2020 (from Prime Polymer Co., Ltd.) as an ethylene resin, and 0.10% by weight of crosslinked polymethyl methacrylate fine particles (Art Pearl J, average particle size: 3.3 m, from Negami Chemical Industrial Co., Ltd.) as organic fine particles.

(10) A material for the interlayer was prepared by mixing 90% by weight of a propylene-ethylene random copolymer (ethylene content=4.0% by weight, MFR (ASTM D 1238, 230 C., 2.16 kg)=2.5 g/10 min, density (ASTM D 1505)=0.90 g/cm.sup.3, DSC melting point=139 C.) and 10% by weight of TOPAS8007 (an ethylene-norbornene copolymer from Polyplastics Co., Ltd.) as a cyclic olefin resin.

(11) The material for the front layer and the back layer was melted in a uniaxial extruder at a barrel temperature of 210 C., and the material for the interlayer was melted in another uniaxial extruder at a barrel temperature of 200 C. The procedure was otherwise the same as in Example 3, and a film having a total thickness of 50 m was obtained. The front layer, the interlayer, and the back layer in the film had a thickness of 5 m, 40 m, and 5 m, respectively.

EXAMPLE 5

(12) A material for the front layer and the back layer was prepared by mixing 74.82% by weight of APL8008T (an ethylene-tetracyclododecen copolymer, glass transition temperature: 70 C., from Mitsui Chemicals, Inc.) as a cyclic olefin resin, 25% by weight of linear low density polyethylene SP2320 (from Prime Polymer Co., Ltd.) as an ethylene resin, and 0.18% by weight of crosslinked styrene fine particles (SX, average particle size: 3.5 m, from Soken Chemical & Engineering Co., Ltd.) as organic fine particles.

(13) A material for the interlayer was prepared by mixing 55% by weight of a propylene-ethylene random copolymer (ethylene content=4.0% by weight, MFR (ASTM D 1238, 230 C., 2.16 kg)=2.5 g/10 min, density (ASTM D 1505)=0.90 g/cm.sup.3, DSC melting point=139 C.), 25% by weight of APL8008T (an ethylene-tetracyclododecen copolymer, from Mitsui Chemicals, Inc.) as a cyclic olefin resin, and 20% by weight of a petroleum resin (ARKON P-140, alicyclic petroleum resin from Arakawa Chemical Industries Ltd.) as a hydrocarbon resin.

(14) A film having a total thickness of 40 m was obtained in the same manner as in Example 3 except that the materials thus prepared were used. The front layer, the interlayer, and the back layer in the film had a thickness of 8 m, 24 m, and 8 m, respectively.

COMPARATIVE EXAMPLE 1

(15) APL8008T (ethylene-tetracyclododecen copolymer, glass transition temperature: 70 C., from Mitsui Chemicals, Inc., 99.85% by weight) as a cyclic olefin resin was mixed with 0.15% by weight of synthetic alminosilicate fine particles having an average particle size of 3.5 m as fine particles.

(16) A film having a total thickness of 50 m was obtained in the same manner as in Example 1 except that this mixture was used.

COMPARATIVE EXAMPLE 2

(17) A material for the front layer and the back layer was prepared by mixing 74.9% by weight of APL8008T (an ethylene-tetracyclododecen copolymer, glass transition temperature: 70 C., from Mitsui Chemicals, Inc.) as a cyclic olefin resin, 25% by weight of linear low density polyethylene SP2320 (from Prime Polymer Co., Ltd.) as an ethylene resin, and 0.10% by weight of synthetic silica fine particles (average particle size: 2.0 m) as inorganic fine particles.

(18) A film having a total thickness of 40 m was obtained in the same manner as in Example 3 except that this mixture was used. The front layer, the interlayer, and the back layer in the film had a thickness of 8 m, 24 m, and 8 m, respectively.

COMPARATIVE EXAMPLE 3

(19) A material for the front layer and the back layer was prepared by mixing 85% by weight of APL8008T (an ethylene-tetracyclododecen copolymer, glass transition temperature: 70 C., from Mitsui Chemicals, Inc.) as a cyclic olefin resin and 15% by weight of linear low density polyethylene SP2320 (from Prime Polymer Co., Ltd.) as an ethylene resin.

(20) A film having a total thickness of 40 m was obtained in the same manner as in Example 3 except that the mixture was used. The front layer, the interlayer, and the back layer in the film had a thickness of 8 m, 24 m, and 8 m, respectively.

COMPARATIVE EXAMPLE 4

(21) APL8008T (ethylene-tetracyclododecen copolymer, glass transition temperature: 70 C., from Mitsui Chemicals, Inc., 99.5% by weight) as a cyclic olefin resin was mixed with 0.5% by weight of crosslinked styrene fine particles (SX, average particle size: 3.5 m, from Soken Chemical & Engineering Co., Ltd.) as organic fine particles.

(22) The mixture was melted in a uniaxial extruder at a barrel temperature of 210 C., extruded through a T-die, and cooled and solidified on a roll cooled to 30 C., whereby, an unstretched sheet was prepared. The unstretched sheet was stretched in TD (transverse direction) by 5 times with a tenter stretching machine at a temperature of 90 C., whereby a film having a total thickness of 45 m was obtained.

(23) (Evaluation)

(24) The heat shrinkable films obtained in the examples and the comparative examples were subjected to the following evaluations. The results are shown in Table 1.

(25) (1) Film Fouling

(26) One surface of each obtained film was printed in two colors with indigo and white printing inks using a gravure printing machine (from FUJI KIKAI KOGYO Co., Ltd.). Specifically, a 5 mm square grid pattern was printed with the indigo ink while the white ink was printed on the entire surface. The printing rate was 120 m/min.

(27) The film roll after the printing was rewound using a secondary slitter (from Kataoka Machine Co., Ltd.) at 150 m/min. During rewinding, the unprinted surface of the film was wiped with waste cloth on the first roll from the film roll unwinding unit upon contact of the printed surface with the roll. The waste cloth was pressed onto the unprinted surface with the index finger. The wiping was performed at film 1500 m/min.

(28) If the part of the film onto which the waste cloth was pressed blackened after the wiping at 1500 m/min, the film was evaluated as x (poor). If the part hardly blackened, the film was evaluated as o (good).

(29) (2) Coefficient of Dynamic Friction

(30) The coefficient of dynamic friction of each obtained film was determined with a surface property tester (HEIDON 14FW, from Shinto Scientific Co., Ltd.). In the measurement, the front layers of two pieces of the film were brought into contact with each other. The load was 200 g, and the travel speed was 100 mm/min.

(31) (3) Heat Shrinkage

(32) A specimen having a size of MD (machine direction) 100 mmTD (transverse direction) 100 mm was cut out of each obtained film. The specimen was immersed in 80 C. warm water for 10 seconds, and then taken out. The heat shrinkage in MD (machine direction) and TD (transverse direction) was calculated according to the following formula. This measurement was performed three times, and the shrinkage was the average value thereof.
Shrinkage(%)={(100L)/100}100
(4) Transparency

(33) The haze value of each obtained film was determined using NDHS000 (from NIPPON DENSHOKU INDUSTRIES CO., Ltd.) in accordance with JIS K 7136.

(34) TABLE-US-00001 TABLE 1 Coefficient of Heat shrinkage Haze Film fouling dynamic friction (%) (%) Example 1 0.48 55 4.6 Example 2 0.43 27 6.0 Example 3 0.47 40 5.7 Example 4 0.42 34 5.8 Example 5 0.47 38 5.6 Comparative X 0.43 55 4.4 Example 1 Comparative X 0.45 38 5.6 Example 2 Comparative 0.74 38 3.8 Example 3 Comparative 0.74 38 8.9 Example 4

(35) Comparison of the examples and the comparative examples 1 and 2 shows that the films of Comparative Examples 1 and 2 blackened although they were not greatly different from the films of the examples in the coefficient of dynamic friction. This was presumably caused by shaving of the control roll due to use of inorganic fine particles instead of organic fine particles.

(36) The film of Comparative Example 3, which was free of fine particles, had a larger coefficient of dynamic friction. This indicates that the film had lower surface smoothness. The film of Comparative Example 3, however, was not fouled. This shows that the surface smoothness of the film is not correlated with fouling of the film.

INDUSTRIAL APPLICABILITY

(37) The present invention can provide a heat shrinkable film that has excellent heat shrinkability while preventing contamination in subsequent processes such as printing.