LAMINATED POLYPROPYLENE FILM

Abstract

The present invention provides a laminated polypropylene film having good transferability and adhesiveness to printing ink, less electrically charged, and excellent in transparency. The laminated polypropylene film includes a resin layer on at least one side of a polypropylene film substrate, and the resin layer includes at least a polyurethane resin, an ethylene-based copolymer resin and an antistatic agent; and the ethylene-based copolymer is 5 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the polyurethane resin.

Claims

1. A laminated polypropylene film comprising: a polypropylene film substrate; and a resin layer disposed on at least one side of the polypropylene film substrate, the resin layer comprising at least a polyurethane resin, an ethylene-based copolymer resin, and an antistatic agent, wherein the resin layer includes 5 parts by mass or more and 50 parts by mass or less of ethylene-based copolymer resin based on 100 parts by mass of polyurethane resin.

2. The laminated polypropylene film according to claim 1, wherein the resin layer includes polyurethane resin having a glass transition temperature of 40° C. or lower.

3. The laminated polypropylene film according to claim 1, the resin layer has a thickness of 0.03 μm or more and 0.20 μm or less.

4. The laminated polypropylene film according to claim 2, the resin layer has a thickness of 0.03 μm or more and 0.20 μm or less.

Description

EXAMPLES

[0070] Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. The present invention, however, is not limited by the following examples. Film properties obtained in examples are measured and evaluated in accordance with the following methods.

[0071] (Evaluation Method)

[0072] (1) Thickness of Resin Layer

[0073] Samples prepared with the following process were observed with a transmission electron microscope. First, a piece of obtained polypropylene film including a resin layer was cut out in the direction perpendicular to the longitudinal direction of the film, and the piece was embedded in epoxy resin. The epoxy resin was prepared by thoroughly mixing LUVEAK-812, LUVEAK-MNA (both of which are manufactured by Nacalai Tesque, Inc.), and DMP30 (manufactured by TAAB Laboratories Equipment Ltd.) at a ratio by weight of 100:89:3. The sample film was embedded in the epoxy resin, which was then left in an oven the temperature of which was set at 60° C. for 16 hours to cure the epoxy resin, and an embedded block was obtained.

[0074] The obtained embedded block was set to Ultracut manufactured by Nissei Sangyo to produce an ultrathin section. First, the embedded block was trimmed with a glass knife so that a cross-sectional surface of the portion that was expected to be observed emerged on the surface of the resin. Next, the ultrathin section was cut out with a diamond knife (Sumi Knife SK2045, manufactured by Sumitomo Electric Industries, Ltd.). The cut ultrathin section was collected on a mesh, and then carbon was thinly vapor deposited.

[0075] The cross-sectional surface of the film was observed by the transmission electron microscope JEM-2010 manufactured by JEOL Ltd. under the condition of accelerating voltage of 200 kV to obtain an image, from which the thickness of the resin layer was determined.

[0076] (2) Glass Transformation Temperature

[0077] In accordance with JIS K7121, using a differential scanning calorimeter (DSC6200, manufactured by Seiko Instruments Inc.), 10 mg of urethane resin sample was heated in a temperature range of 25° C. to 300° C. at a rate of 20° C./min to obtain an extrapolated glass transition onset temperature from a DSC curve, which was determined to be a glass transition temperature.

[0078] (3) Surface Free Energy

[0079] A sample of the polypropylene film including a resin layer was left under the condition of relative humidity of 50% for 24 hours, and then, using a FACE contact angle meter (CA-X, manufactured by Kyowa Interface Science Co., Ltd.), a contact angle of distilled water and a contact angle of diiodomethane after being dropped on the side of the resin layer were measured. The contact angles were determined by measuring contact angle of each sample five times, eliminating the largest value and the smallest value, and averaging the remaining three values. From the contact angle of distilled water and the contact angle of diiodomethane, surface free energy γs was calculated, and it was determined that the sample with the surface free energy γs of 45 to 60 mN/m had wettability.

[0080] (4) Haze

[0081] In accordance with JIS K7136, using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.), haze was measured.

[0082] (5) Surface Resistance

[0083] Using a surface resistivity meter (Loresta-UP MCP-HT450, manufactured by Mitsubishi Chemical Corporation), a surface resistance of a surface of the resin layer of the polypropylene film including the resin layer was measured under the condition of 20° C., 55% RH at applied voltage of 500 V. If the surface resistance was 14.0 log(Ω/□) or less, it was determined that the sample has antistatic property, and especially, the case in which the surface resistance was 13.0 log(Ω/□) or less was determined to be good.

[0084] (6) Transferability

[0085] Using a RI tester (model RI-3, manufactured by Mei Seisakusho Co., Ltd.), a printed sample was obtained by printing UV ink (BESTCURE UV161 indigo S, manufactured by T&K TOKA Co., Ltd.) on a surface of the resin layer of the polypropylene film including the resin layer, and getting the printed film passed under a high-pressure mercury lamp with an output of 120 W/cm by 20 cm (accumulated light quantity of 100 mJ/cm.sup.2) at a rate of 10 m/min. The degree of printing appearance of the printed sample was visually observed, and samples showing good transferability with no fading of the ink or uneven printing were classified as rank A, samples with fading of the ink or uneven printing in the area less than 10% of the printed area were classified as rank B, and samples with fading of the ink or uneven printing in the area more than 10% of the printed area were classified as rank C. Samples classified as rank A or rank B were determined to have printability, and especially, samples classified as rank A were determined to have good printability.

[0086] (7) Adhesiveness

[0087] One hundred of cuts having a chessboard pattern that arrived at the polypropylene film including the resin layer through the ink layer were made on the printed sample obtained by the abovementioned way with a cutter guide having a gap of 2 mm. Then, adhesive cellophane tape (No. 405, 24 mm width, manufactured by Nichiban Co., Ltd.) was attached on the surface having chessboard patterned cuts, which was rubbed with an eraser to make the adhesive cellophane tape completely stick with the surface. Subsequently, the adhesive cellophane tape was vertically rip from the surface of the ink layer for one time, and the number of peeled squares from the surface of the ink layer of the printed sample was visually counted, and the adhesiveness of the ink layer and the polypropylene film including the resin layer was obtained according to the below-mentioned equation. Note that partially peeled squares were counted as peeled squares, and the samples were classified on the basis set forth below.

Adhesiveness (%)=(1−the number of peeled squares/100)×100

[0088] A: 100%, or break of the ink layer

[0089] B: 99 to 70%

[0090] C: 69 to 0%

[0091] Samples classified as rank A or B were determined to have adhesiveness, and especially, samples classified as rank A were determined to have good adhesiveness.

[0092] Resins, compounds, and solvent used in the resin layer is as follows.

[0093] (A-1: Water Dispersible Polyurethane Resin)

[0094] HYDRAN AP-201 (manufactured by DIC Corporation, glass-transition temperature: 10° C., polyester-urethane obtained from tolylene diisocyanate and polyol consisting of terephthalic acid, isophthalic acid, sebacic acid, and adipic acid)

[0095] HYDRAN AP-40N (manufactured by DIC Corporation, glass-transition temperature: 40° C., polyester-urethane obtained from tolylene diisocyanate and polyol consisting of terephthalic acid, isophthalic acid, sebacic acid, and adipic acid)

[0096] HYDRAN AP-30F (manufactured by DIC Corporation, glass-transition temperature: 60° C., polyester-urethane obtained from tolylene diisocyanate and polyol consisting of terephthalic acid, isophthalic acid, sebacic acid, and adipic acid)

[0097] (A-2: Acrylic Resin)

[0098] Joncryl PDX-6102B (manufactured by BASF Ltd., glass-transition temperature: 25° C., styrene-acrylic acid copolymer)

[0099] (B: Ethylene-Based Copolymer Resin)

[0100] Hi-tech S-9201 (manufactured by TOHO Chemical Industries Co., Ltd., ethylene-methacrylic acid-1-alkene copolymer)

[0101] (C: Antistatic Agent)

[0102] ELECUT C-048 (manufactured by Takemoto Oil & Fat Co. Ltd., quaternary ammonium chloride)

[0103] (D: Solvent)

[0104] water/isopropanol=70/30 solution

Examples 1 to 6, Comparative Examples 1 to 5

[0105] Polypropylene films including a resin layer of Examples 1 to 6 and Comparative Exampled 1 to 5 were obtained by applying application liquid used for forming the resin layer by gravure coating on a corona treated surface of a biaxially-oriented polypropylene film (P2108, manufactured by TOYOBO Co. Ltd., thickness of 40 μm), and drying them at 100° C. for 30 seconds.

[0106] Composition of the application liquid used for forming the resin layer and thickness of the resin layer after applying and after drying are shown in Table 1.

[0107] Properties of the obtained laminated polypropylene film are also shown in Table 1.

[0108] The laminated polypropylene film of Example 1 to 6 had antistatic property, and also satisfied transferability of UV ink and adhesiveness to UV ink.

[0109] On the other hand, Comparative Example 1 and Comparative Example 4 did not satisfy transferability of UV ink due to no urethane resin.

[0110] Comparative Example 2 did not satisfy transferability of UV ink due to high proportion of ethylene-based resin to urethane resin.

[0111] Comparative Example 3 did not satisfy adhesiveness to UV ink due to no ethylene-based resin.

[0112] Comparative Example 5 did not have antistatic property due to no antistatic agent.

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 resin, compound, A-1: urethane resin AP-201 AP-40N AP-30F AP-201 AP-201 AP-201 solvent used in blend ratio (% by mass, 55 55 55 65   47.5 55 application liquid in the whole solid content) for forming resin A-2: acrylic resin — — — — — — layer blend ratio (% by mass, — — — — — — in the whole solid content) B: ethylene-based copolymer S-9201 S-9201 S-9201 S-9201 S-9201 S-9201 resin blend ratio (% by mass, 25 25 25  5   22.5 25 in the whole solid content) C: antistatic agent C-048 C-048 C-048 C-048 C-048 C-048 blend ratio (% by mass, 20 20 20 30 30 20 in the whole solid content) D: solvent water/isopropanol = same as same as same as same as same as 70/30 (% by weight) the left the sett the left the left the left blend ratio (% by mass, 20 20 20 30 30 20 in the whole solid content) ratio of ethylene-based 20 45 45 45  8 47 copolymer to 100 parts by mass of urethane resin (part by mass) properties of thickness (μm)    0.10    0.10    0.10    0.10    0.03    0.20 laminate grass-transition temperature 10 40 60 10 10 10 of urethane resin (° C.) surface free energy (mN/m) 53 47 45 49 46 59 haze (%)   1.8   1.9   1.9   1.8   1.5   1.9 surface resistance (Ω/□)   10.8   11.9   13.6   11.7   12.9   10.2 transferability A A B A A A adhesiveness A A B A A A Comparative Example 1 2 3 4 5 resin, compound, A-1: urethane resin — AP-201 AP-201 — AP-201 solvent used in blend ratio (% by mass, — 40 80 — 75 application liquid in the whole solid content) for forming resin A-2: acrylic resin PDX-6102B — — — — layer blend ratio (% by mass, 55 — — — — in the whole solid content) B: ethylene-based copolymer S-9201 S-9201 S-9201 S-9201 resin blend ratio (% by mass, 25 40 80 25 in the whole solid content) C: antistatic agent C-048 C-048 C-048 C-048 blend ratio (% by mass, 20 20 20 20 in the whole solid content) D: solvent same as seme as same as same as same as the left the left the left the left the left blend ratio (% by mass, 20 20 20 20 in the whole solid content) ratio of ethylene-based — 100   0 — 33 copolymer to 100 parts by mass of urethane resin (part by mass) properties of thickness (μm)    0.10    0.10    0.10    0.10    0.10 laminate grass-transition temperature — — 10 10 10 of urethane resin (° C.) surface free energy (mN/m) 44 61 53 63 36 haze (%)   2.2   1.8   1.8   1.8   1.8 surface resistance (Ω/□)   11.5   11.1  >14.0   10.2  >14.0 transferability B C A C A adhesiveness C B C C A

INDUSTRIAL APPLICABILITY

[0113] The laminated polypropylene film of the present invention has good transferability and adhesiveness to printing ink, and can be also given antistatic property without deteriorating the former properties, which makes it possible for the film to be versatilely and widely used in the packaging field thanks to its superiority in transparency and design as packaging materials, at the same time to be easily treated when printing.