JPH1058603A - Transparent film with superior brightness and adequate moisture feel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide impact properties and tear strength by forming a three-layer structure of transparent film consisting of a thermoplastic elastomer layer, a transparent styrene resin layer consisting of a rubber dispersion phase polymerized in the presence of rubber and a resin matrix layer and a thermoplastic elastomer layer, to the specific thickness. SOLUTION: A transparent film consisting of a three-layer structure such as a thermoplastic elastomer layer, a transparent styrene resin layer of a rubber dispersion phase polymerized in the presence of rubber and a resin matrix phase, and a thermoplastic elastomer layer, is formed to the thickness of 0.001-0.2mm. The transparent styrene resin layer consisting of the rubber dispersion phase and the resin matrix phase is an intermediate layer and does not reveal a surface unevenness directly, so that its high transparency is maintained. In addition, anisotropy, the shortcoming of the thermoplastic elastomer layer is compensated for by the intermediate layer. Further, the three-layer structure is responsible for the partial reflection of light to the surface by the interface between the thermoplastic elastomer layer and the transparent styrene resin layer when the light passes through both layers and thus the moisture feel is visually created.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent film having excellent gloss and moisture.

[0002]

2. Description of the Prior Art Polystyrene resins, thermoplastic styrene-butadiene block copolymers (hereinafter, SB block copolymers), or vinyl chloride have been mainly used for films requiring transparency and gloss. In particular, in recent years, vinyl chloride tends to not be used voluntarily by manufacturers because waste generates hydrogen chloride gas during combustion. Further, the use of polystyrene alone is poor (breaks and cuts) because the film is hard. By mixing a styrenic resin and an SB block copolymer to improve such problems, the strength is improved, but the resin tends to exhibit anisotropy in the tensile direction and the transverse direction in tensile strength. There is a method of using transparent high-impact polystyrene to improve anisotropy. Although the anisotropy is certainly improved by this method, irregularities are generated on the surface due to the difference in viscoelasticity between the resin matrix and the phase separation on the film surface, and the transparency is significantly impaired. As a method for solving these problems, Japanese Patent Application Laid-Open No. 8-34861 discloses a method of coating a styrene resin containing no rubber cross-linked dispersed phase. However, in order to improve the impact strength and tear strength of the film, Not enough.

On the other hand, comparing the viscoelasticity of the resin and the SB block copolymer, it is difficult to control the stretching because the properties of the resin rapidly change near the glass transition temperature. The latter is easy to control because the change in elastic modulus and change in elongational viscosity are gentle. Further, even when the film is shrunk to be used for a label or the like, a resin having a moderate temperature change rate of the resin characteristic is preferable. Therefore, it is important that an ideal film has both properties.

[0004]

SUMMARY OF THE INVENTION The present invention provides a transparent styrene resin film having both impact strength and tear strength.

[0005]

That is, the present invention relates to a thermoplastic elastomer layer A, a transparent styrene resin layer B comprising a rubber dispersed phase polymerized in the presence of rubber and a resin matrix, and a thermoplastic elastomer layer C. 0.001 thickness consisting of three layers
It is a transparent film of about 0.2 mm. Since the transparent styrene-based resin layer B composed of the rubber dispersed phase and the resin matrix is an intermediate layer, high transparency can be maintained because surface irregularities do not appear directly. Further, the anisotropy, which is a disadvantage of the thermoplastic elastomer layer, is complemented by the intermediate layer. In addition, when light passes through the thermoplastic elastomer layer and the transparent styrene resin layer due to these three-layer structure, a part of the light is reflected on the surface at the interface, and the moisture is visually observed. It is preferable that the composition ratio of the surface layer and the intermediate layer satisfy A + B ≦ C at the point of giving this wet feeling.

Further, since it has a three-layer structure of an elastomer layer and a transparent styrene-based resin layer, the softening temperature is preferably 65 to 85 ° C., more preferably 68 to 75 ° C. in terms of Vicat softening point. If it is out of this range, for example, peeling will occur at the interface when the film is processed by applying heat. The particle size of the rubber dispersion particles is 0.2 to 1.5 μm, and more preferably 0.2 to 1.5 μm.
Preferably it is 0.8 μm. If it is less than 0.2 μm, the transparency is improved, but the tensile strength and impact strength of the resin are reduced. On the other hand, if it exceeds 1.5 μm, even if the surface is coated with the elastomer, the irregularities of the rubber dispersed particles appear on the surface, which is not preferable. Irregularities on the surface not only impair the transparency of the resin, but also cause uneven application of the ink during gravure printing.

[0007] Coating the surface with an SB block copolymer greatly contributes to the improvement of printing characteristics. In the case of a thin film having only a transparent styrene resin layer, gravure printing significantly erodes the ink solvent. This is because ester-based, ketone-based, and alcohol-based solvents used in the ink solvent have strong permeability due to the structure of the transparent styrene-based resin. In order to improve the printability, SB block copolymers having relatively high solvent resistance are preferred. In addition, in the case where the back side printing is performed for the purpose of imparting designability, since the color of the printing pigment is observed through the three-layer structure, red, green,
The shade of black gives it a very luxurious look rich in moisture. Therefore, this three-layer structure is very interesting as a packaging material and a material with high design. The same effect can be obtained with a methacryl butadiene styrene copolymer (for example, Kanace A) MBS obtained by further copolymerizing an acrylic ester with the refractive index of the resin component coated on the surface.

Since the three-layer structure has a thin film structure, the three-layer structure shows an intermediate behavior between the rubber-dispersed transparent styrene resin and the elastomer layer in terms of viscoelasticity. Of course, by utilizing this characteristic, application to a heat-shrinkable stretched film or a heat-shrinkable label is also possible. The rubber component of the rubber phase is butadiene 80 ~
A styrene butadiene block copolymer comprising 45% by weight and 20 to 55% by weight of an aromatic vinyl compound;
The low-temperature peak value of nδ is −80 to −30 ° C., the monomer composition of the polymer constituting the mother phase is 20 to 80% by weight of methyl methacrylate, and the alkyl acrylate (the alkyl group has 2 to 4 carbon atoms). 5 to 20% by weight, an aromatic vinyl compound of 20 to 79.5% by weight, and a rubber phase of 5 to 1%.
It is preferable to use a rubber-dispersed transparent styrene-based resin having 5% by weight and a mother phase of 5 to 95% by weight.

Furthermore, the rubber component of the rubber phase is butadiene 3
0 to 55% by weight, 70 to 45% by weight of an aromatic vinyl compound
A styrene butadiene block copolymer consisting of
The low-temperature peak value of tan δ is −80 to −50 ° C., and the monomer composition of the polymer constituting the mother phase is 25 to 50% by weight of methyl methacrylate, 1 to alkyl acrylate (2 to 4 carbon atoms in the alkyl group) It is preferable to use a rubber-dispersed transparent styrene resin having 15% by weight, 35 to 74% by weight of an aromatic vinyl compound, 5 to 15% by weight of a rubber phase and 5 to 95% by weight of a mother phase. In order to match the refractive indices of the rubber dispersed phase and the mother phase, it is necessary that the above composition ratio does not exist.

When the low-temperature peak value of tan δ is lower than -80 ° C., the impact strength is undesirably reduced. Also -30
If the temperature exceeds ℃, when the film is stretched, irregularities are likely to be formed on the surface, and the transparency of the film is undesirably reduced.
The thermoplastic elastomer layers constituting the A and C layers are preferably a styrene-butadiene block copolymer,
Further, styrene 30-70% by weight, butadiene 70-70%
The block copolymer is preferably 30% by weight. Specifically, Asaflex 815, 816 made by Asahi Kasei Kogyo Co., Ltd.
6. Kane-Ace a, manufactured by Kanegafuchi Kogyo Co., Ltd., is preferred.

When the butadiene content exceeds 70% by weight, that is, the multilayer extrusion temperature of 200 to 220 ° C. is too high to be suitable. If the butadiene content is less than 30% by weight, the strength of the resin cannot be maintained. It is preferable that the rubber-dispersed transparent styrene resin contains a terpenoid derivative in an amount of 2 to 10% by weight. If the content is less than 2% by weight, the effect of improving the transparency of the transparent styrene resin composition is not sufficiently exhibited, which is not preferable. On the other hand, when the content exceeds 10% by weight, when the transparent styrene resin composition is stretched into a film, cracks in the stretching direction occur with the lapse of time, which is not preferable.

The terpenoid derivative may be mixed with a transparent styrene resin composition or may be present at the time of polymerization of the transparent styrene resin. Examples of the terpenoid derivative include pinene, limonene, a phenyl addition compound thereof, and a vinylphenyl compound. Specific examples include Clearon 115 (trade name, manufactured by Yashara Chemical Co., Ltd.). The terpenoid derivative is preferred because it does not easily impair the transparency when the film of the present invention is stretched. (Japanese Unexamined Patent Publication No. H08-109304) A film is prepared by using a multilayer extruder, extruding a 0.3 mm sheet once with a T die, and stretching at 90 to 120 ° C. by 350% or more in each of length and width.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A method for measuring physical properties of a film is described below. The rubber particle diameter was measured by a laser scattering method using LPA3000 manufactured by Otsuka Electronics Co., Ltd. using tetrahydrofuran as a solvent at a concentration of 10 mg / 10 ml at 23 ° C.

The tan δ value was measured by a dynamic viscoelasticity analyzer RMS800 manufactured by Rheometrics. The Vicat softening point was measured according to the method of ASTM D1525. Dupont impact value is from 500g to 1 load on 0.3mm sheet.
kg, a missile having a diameter of 12.6 mm was dropped, and the value of 50% of the potential energy required for breaking was measured.

The haze (HAZE) is based on JIS K6714.
Was measured by the following method. The solvent resistance was determined by visually dropping one drop of the solvent with a dropper on the film. Back side printability
Offset printing was performed on the film surface with the following three inks, and the film was visually evaluated. The ink is a mixed solvent of 50% by weight of ethyl acetate and 50% by weight of isopropyl alcohol.
A mixture of 17 g of Stylon 680 and 5 g of each of three kinds of pigments of red (red iron), yellow (cadmium yellow), and black (carbon) with respect to 0 g was used.

The tensile strength was determined by cutting a film into a size of 20 × 70 mm, a distance between chucks of 50 mm, and a tensile speed of 5 mm /
Measured in seconds. The tear strength is determined by the sheet taking-off direction (M
D) The transverse direction (TD) was measured by the Elmendorf method.

[0017]

Examples 1 to 12 and Comparative Examples 1 to 9 The resin compositions of the layer B used in the examples are shown in Table 1 as resins 1 to 6. Here, it is understood that the rubber particle diameter in the resin changes depending on the styrene content of the rubber component, and that the resin becomes cloudy depending on the monomer composition of the resin composition. The elastomer of the thermoplastic elastomer A, C layer is 65% by weight of styrene,
Type 4 block copolymer consisting of 35% by weight of butadiene [MFR 6.2 g / 10 mm (JIS K6871 method, load 5 kg, temperature 200 ° C.) (Asahi Kasei Corporation)
Manufactured by Asaflex 815].

For the production of the film, a sheet having a thickness of 0.3 mm is prepared using a multilayer extruder, and the sheet is formed at an ambient temperature of 12 mm.
The film was formed by stretching 3 to 5 times biaxially at 0 to 130 ° C. The evaluation results are shown in Tables 2 and 3.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

The transparent film of the present invention has excellent impact resistance, tear strength and design, and is suitable for packaging films.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B32B 27/30 B32B 27/30 B B65D 65/40 B65D 65/40 A

Claims (7)

[Claims] 1. A transparent styrene resin layer B comprising a thermoplastic elastomer layer A, a rubber dispersed phase polymerized in the presence of rubber and a resin matrix, and a thermoplastic elastomer layer C having a three-layer structure. 001-0.2 mm transparent film. 2. The film according to claim 1, wherein the thickness of the film layer is A layer + C layer ≦ B layer. 3. The rubber dispersion has a particle size of 0.2 to 1.5 μm.
The film according to claim 1, wherein 4. The rubber-dispersed transparent styrene resin has a Vicat softening point of 65 to 98 ° C.
The film as described. 5. The rubber phase has a butadiene content of 80 to 45% by weight,
A styrene-butadiene block copolymer composed of 20 to 55% by weight of an aromatic vinyl compound, having a low-temperature peak value of tan δ of −80 to −30 ° C., and having a monomer composition of methyl methacrylate 20 to 80% by weight, alkyl acrylate (alkyl group having 2 to 2 carbon atoms)
4) 0.5 to 20% by weight, aromatic vinyl compound 20 to 7
2. The film according to claim 1, comprising 9.5% by weight, a rubber-dispersed transparent styrene resin having a rubber phase of 5 to 15% by weight and a mother phase of 85 to 95% by weight. 6. The film according to claim 5, wherein the rubber-dispersed transparent styrene resin contains a terpenoid derivative in an amount of 2 to 10% by weight. 7. The composition according to claim 1, wherein the composition of the elastomer layers constituting the A and C layers is a block copolymer comprising 30 to 70% by weight of styrene and 70 to 30% by weight of butadiene, respectively. the film.