JP3525012B2 - Transparent film with excellent gloss and moisture - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a transparent film having excellent gloss and wet feeling.

[0002]

2. Description of the Related Art Polystyrene resins, thermoplastic styrene butadiene block copolymers (hereinafter referred to as SB block copolymers), or vinyl chloride have been mainly used for films required to have transparency and gloss. In particular, vinyl chloride tends to be voluntarily not used by manufacturers in recent years because waste produces hydrogen chloride gas when it burns. In addition, since polystyrene is a rigid film, it is not easy to use (cracks and breaks occur). The strength is improved by mixing the styrene resin and the SB block copolymer to improve such a problem, but the tensile strength of the resin tends to be anisotropic in the take-up direction and the lateral direction. There is a method of using transparent high-impact polystyrene to improve anisotropy. By this method, the anisotropy is certainly improved, but due to the difference in viscoelasticity between the resin matrix phase and the rubber dispersed phase on the film surface, unevenness is generated on the 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-based resin that does not contain a rubber cross-linking dispersed phase, but in order to improve the impact resistance and tear strength of the film, Not enough.

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

[0004]

SUMMARY OF THE INVENTION The present invention provides a transparent styrenic resin film which has both impact resistance and tear strength.

[0005]

SUMMARY OF THE INVENTION Namely, the present invention is styrene
Thermoplastic elastomer layer A composed of a butadiene block copolymer, a transparent styrene resin layer B composed of a rubber dispersed phase polymerized in the presence of rubber and a resin mother phase, and styrene butadiene
A film having a thickness of 0.001 to 0.2 mm, which has a three-layer structure of a thermoplastic elastomer layer C made of an enblock copolymer , and has a layer thickness of A layer + C layer ≦ B.
The transparent film is a layer having a rubber-dispersed particle size of 0.14 to 1.5 μm and a Vicat softening point of the rubber-dispersed transparent styrene resin of 62 to 98 ° C. Preferably, the particle size of the rubber dispersion is 0.2 to 1.5 μm.
and the Vicat softening point of the rubber-dispersed transparent styrene resin is 65 to 98 ° C. Since the transparent styrenic resin layer B composed of the rubber dispersed phase and the resin matrix phase is an intermediate layer, the surface irregularities do not directly appear, and therefore high transparency can be maintained. In addition, styrene butadiene block
The anisotropy, which is a drawback of the polymer-made thermoplastic elastomer layer, is complemented by the intermediate layer. In addition, the three-layer structure allows light to pass through the styrene-butadiene block.
Thermoplastic elastomer composed of polymer (hereinafter, elastomer
When passing through the ( mer) layer and the transparent styrenic resin layer, a part thereof is reflected on the surface at the interface, and a wet feeling is visually observed. It is preferable that the composition ratio of the surface layer and the intermediate layer is A + B ≦ C at the point of giving a wet feeling.

Since it has a three-layer structure of an elastomer layer and a transparent styrene 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 heated and processed. The rubber dispersed particles have a particle size of 0.2 to 1.5 μm, and further 0.2 to
It is preferably 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 lowered. On the other hand, if it exceeds 1.5 μm, even if the elastomer is coated on the surface, unevenness of the rubber dispersed particles appears on the surface, which is not preferable. The unevenness of the surface not only deteriorates the transparency of the resin but also causes uneven application of ink during gravure printing.

The coating of the SB block copolymer on the surface greatly contributes to the improvement of printing characteristics. A thin film having only a transparent styrenic resin layer is significantly eroded by the ink solvent when gravure printing. This is because the ester-based, ketone-based, and alcohol-based solvents used in the ink solvent have strong penetrability due to the structure of the transparent styrene resin. In order to improve the printability, an SB block copolymer having relatively good solvent resistance is preferable. Further, when the back surface printing is performed for the purpose of imparting a design property, since the colors of the printing pigments are observed through the three-layer structure, red, green,
The color black is very moist and very luxurious. Therefore, this three-layer structure is very interesting as a packaging material and as a highly-designable material .

Since the film structure of the three-layer structure is thin, viscoelasticity exhibits an intermediate behavior between the rubber-dispersed transparent styrene resin and the elastomer layer. Of course, by utilizing this characteristic, it can be applied to a heat-shrinkable stretched film and a heat-shrinkable label. The rubber component of the rubber dispersed phase is butadiene 8
0-45% by weight, aromatic vinyl compound 20-55% by weight
Is a styrene-butadiene block copolymer consisting of
The low temperature peak value of tan δ is −80 to −30 ° C., the monomer composition of the polymer constituting the resin mother phase is 20 to 80% by weight of methyl methacrylate, alkyl acrylate (alkyl group having 2 to 4 carbon atoms) 0 0.5 to 20% by weight, aromatic vinyl compound 20 to 79.5% by weight, rubber
It is preferably composed of a rubber-dispersed transparent styrene resin in which the dispersed phase is 5 to 15% by weight and the resin matrix phase is 5 to 95% by weight.

Further, the rubber component of the rubber dispersed phase is a styrene-butadiene block copolymer comprising 30 to 55% by weight of butadiene and 70 to 45% by weight of an aromatic vinyl compound, and the low temperature peak value of tan δ is -80 to-. At 50 ° C., the monomer composition of the polymer constituting the resin mother phase is 25 to 50% by weight of methyl methacrylate, 1 to 15% by weight of alkyl acrylate (having 2 to 4 carbon atoms in the alkyl group), and aromatic vinyl compound 35. It is preferable that the rubber-dispersed transparent styrenic resin comprises 5 to 15% by weight of the rubber dispersed phase and 5 to 95% by weight of the resin mother phase.
To adjust the refractive index of the rubber dispersed phase and the resin matrix is required to be within the above composition ratio.

When the low temperature peak value of tan δ is lower than -80 ° C, the impact strength is lowered, which is not preferable. -30 again
If the temperature exceeds ℃, when the film is stretched, irregularities are likely to appear on the surface, and the transparency of the film is lowered, such being undesirable.
The thermoplastic elastomer layer constituting the A and C layers is preferably a styrene-butadiene block copolymer,
Furthermore, 30 to 70% by weight of styrene and 70 to 70% of butadiene
The block copolymer is preferably 30% by weight. Specifically, Asaflex 815 and 816 Tuffprene 125 and 126 manufactured by Asahi Kasei Kogyo Co., Ltd. are preferred.

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

This terpenoid derivative may be mixed with the transparent styrenic resin composition, or may be present together during the polymerization of the transparent styrenic resin. Examples of the terpenoid derivative include pinene, limonene, phenyl addition compounds thereof, and vinylphenyl compounds. Specifically, Yasuhara Chemical Co., Ltd. product name, Clearon 115, etc. are mentioned. The terpenoid derivative is preferable because it does not easily impair the transparency when the film of the present invention is stretched. (Japanese Patent Laid-Open No. 8-109304) A multi-layer extruder is used to form a film, and a 0.3 mm sheet is once extruded with a T-die and stretched at 90 to 120 ° C. in the length and width directions by 350% or more.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The methods for measuring the physical properties of a film are shown below. The rubber particle size was measured by a laser scattering method using LPA3000 manufactured by Otsuka Electronics Co., Ltd. with 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 measuring instrument RMS800 manufactured by Rheometrics. The Vicat softening point was measured by the method of ASTM D1525. The DuPont impact value is a load of 500 g to 1 on a 0.3 mm sheet.
A kg missile having a diameter of 12.6 mm was dropped and the value of 50% of the potential energy required for destruction was measured.

Haze is JIS K6714.
Was measured by the method. For solvent resistance, one drop of solvent is dropped onto the film with a dropper and the appearance is judged visually. The back side printability is
Offset printing was performed on the surface of the film with the following three types of ink, and visually evaluated. The ink is a mixed solvent of ethyl acetate 50% by weight and isopropyl alcohol 50% by weight.
For 0 g, 17 g of Stylon 680, 5 g of each of three types of pigments of red (red iron oxide), yellow (cadmium yellow) and black (carbon) were used.

As for the tensile strength, the film was cut into 20 × 70 mm, the chuck distance was 50 mm, and the pulling speed was 5 mm /
Measured in seconds. The tear strength is the sheet take-up direction (M
D) and transverse direction (TD) were measured by the Elmendorf method.

[0017]

Examples 1 to 12 and Comparative Examples 1 to 9 The resin compositions for the B layer used in the examples are shown in Table 1 as Resins 1 to 6. Here, it can be seen that the rubber particle size in the resin changes depending on the styrene content of the rubber component, and the resin composition becomes turbid due to the monomer composition of the resin composition. The elastomer of the thermoplastic elastomer A and C layers 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 Chemical Industry Co., Ltd.)
Manufactured by Asaflex 815].

For the production of the film, a multi-layer extruder is used to prepare a sheet having a thickness of 0.3 mm.
A film was formed by biaxially stretching 3 to 5 times 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]

INDUSTRIAL APPLICABILITY The transparent film of the present invention is excellent in impact resistance, tear strength and design, and is suitable as a packaging film.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-201919 (JP, A) JP-A-3-227326 (JP, A) JP-A-8-34861 (JP, A) JP-A-8- 109304 (JP, A) JP 61-43643 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C08L 25/00-25/18

Claims (5)

(57) [Claims] 1. A styrene-butadiene block copolymer
A three-layered structure of thermoplastic elastomer layer C consisting Ranaru thermoplastic elastomer layer A and the rubber dispersed phase and made of a resin matrix phase transparent styrene-based resin layer was polymerized in the presence of the rubber B and styrene butadiene block copolymer , Thickness 0.
The film has a thickness of 001 to 0.2 mm, the layer thickness of the film is A layer + C layer ≦ B layer, the particle diameter of the rubber dispersion is 0.14 to 1.5 μm, and the vicat of the rubber dispersion transparent styrene resin is A transparent film having a softening point of 62 to 98 ° C. 2. The particle size of the rubber dispersion is 0.2 to 1.5 μm.
And the Vicat softening point of the rubber-dispersed transparent styrene resin is 65 to 98 ° C. 3. A styrene-butadiene block copolymer having a rubber dispersed phase of 80 to 45% by weight of butadiene and 20 to 55% by weight of an aromatic vinyl compound and having a low temperature peak value of tan δ of −80 to −30 ° C. Moreover, the monomer composition of the polymer constituting the resin mother phase is methyl methacrylate 20.
To 80% by weight, alkyl acrylate (alkyl group having 2 to 4 carbon atoms) 0.5 to 20% by weight, aromatic vinyl compound 2
3. A rubber-dispersed transparent styrenic resin comprising 0 to 79.5% by weight, a rubber dispersed phase of 5 to 15% by weight, and a resin matrix phase of 85 to 95% by weight. Film. 4. The film according to claim 3, wherein the terpenoid derivative is contained in the rubber-dispersed transparent styrene resin in an amount of 2 to 10% by weight. 5. Styrene butadiene constituting the A and C layers
The film according to claim 1 or 2, wherein the composition of the thermoplastic elastomer layer made of a block copolymer is a block copolymer made of 30 to 70% by weight of styrene and 70 to 30% by weight of butadiene, respectively.