JP3228375B2 - Laminated polystyrene film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excellent gas barrier property, a retort resistance and a gelling property. The present invention relates to a laminated syndiotactic polystyrene film.

[0002]

2. Description of the Related Art A polystyrene-based polymer having a syndiotactic structure has been developed and is known to be a material having excellent crystallinity and excellent heat resistance and solvent resistance. (Japanese Patent Publication No. 3-7685). Stretched films using these have also been developed (JP-A-1-110122, JP-A-1-168709,
1-182346, 2-79731, 3-74437, 3-1094
No. 53, No. 3-99828, No. 3-124427, No. 3-316444).
These syndiotactic polystyrene films have excellent electrical properties such as mechanical properties, transparency, chemical resistance, dielectric loss and dielectric constant, and are expected to be applied to various industrial and packaging films. However, there is a problem that the syndiotactic polystyrene film has poor gas barrier properties. Films having excellent gas barrier properties include those obtained by laminating aluminum on a plastic film, and those coated with vinylidene chloride or ethylene vinyl alcohol copolymer. Further, as a device using an inorganic thin film, a device in which a silicon oxide, an aluminum oxide thin film, or the like is laminated is known.

[0003]

When a polyester film or a polyamide film is used as a base film of a gas barrier film, there is a problem that hydrolysis occurs under high temperature and high humidity or high temperature water. .
Further, in such an environment, the film may be curled due to humidity expansion, or if the environment repeatedly changes, the inorganic thin film layer or the like may be peeled or cracked, and the gas barrier property may be reduced.

The conventional gas barrier film has the following problems. Although the aluminum laminate is excellent in economics and gas barrier properties, it is opaque, so that the contents at the time of packaging cannot be seen, and it does not transmit microwaves, so that a microwave oven cannot be used. Those coated with vinylidene chloride or ethylene vinyl alcohol copolymer do not have sufficient gas barrier properties against water vapor, oxygen, etc., and the decrease is remarkable especially at high temperature treatment. In addition, with respect to vinylidene chloride, there is generation of chlorine gas at the time of incineration, and there is also a concern about the influence on the global environment. On the other hand, visible contents, as a gas barrier film that can be used in the microwave oven, in JP-B-51-48511, a gas barrier film formed by depositing a Si _x O _y (e.g., SiO ₂₎ in the synthetic resin surface is proposed However, the SiO _x system (x = 1.3 to 1.8) having a good gas barrier property has a slightly brown color and is insufficient as a transparent gas barrier film.

[0005] As those mainly composed of aluminum oxide
(Japanese Patent Application Laid-Open No. 62-101428)
Oxygen barrier properties are insufficient, and there is also a problem of bending resistance.
Further, A as a gas barrier film having retort properties
l_TwoO_Three・ SiO_TwoExamples of the system include (Japanese Patent Laid-Open No.
Although there is a proposal in 4), Al_TwoO_ThreeAnd SiO _Two
Are stacked, and the device becomes large-scale.
In addition, for these thin-film gas barrier films,
Its gas barrier properties and flex resistance are still insufficient
It is. In other words, to have retort resistance,
The thickness of the thin film is required
On the other hand, to improve bending resistance,
Has the problem that
Items that require careful handling are used
It is. Thus, sufficient oxygen barrier and water vapor barrier
, Retort-resistant, highly flexible and transparent
At present, there is no gas barrier film.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aluminum oxide / silicon oxide based gas barrier film which is excellent in gas barrier properties and retort resistance and has high bending resistance. That is, the present invention provides a gas barrier film in which an aluminum oxide / silicon oxide thin film is formed on a film made of a resin composition containing a polystyrene-based polymer having a syndiotactic structure. 20% by weight or more
The relationship between the specific gravity of the thin film and the aluminum oxide composition ratio in the thin film is D = 0.01A + b (D: specific gravity of the thin film, A: weight% of aluminum oxide in the thin film). When expressed, the specific gravity of the thin film is 1.6 ≦ b ≦ 2.2
A laminated polystyrene film characterized by being within the range determined by:

In the polystyrene polymer having a stereoregular syndiotactic structure used in the present invention, the phenyl group or the substituted phenyl group, which is a side chain, is quantified by nuclear magnetic resonance. 85% or more for 2) and 50 for pentad (5 constituent units)
% Or more of the syndiotactic structure. As the polystyrene-based polymer, polystyrene,
Poly (p-, m- or o-methylstyrene), poly (2,4-, 2,
5- (3,4- or 3,5-dimethylstyrene), poly (alkylstyrene) such as poly (p-tert-butylstyrene), poly (p-, m- or o-chlorostyrene), poly (p
-(M- or o-bromostyrene), poly (p-, m- or o-fluorostyrene), poly (halogenated styrene) such as poly (o-methyl-p-fluorostyrene), poly (p-, Poly (halogen-substituted alkylstyrene) such as m- or o-chloromethylstyrene, poly (p-, m- or o-methoxystyrene), and poly (p-, m- or o-ethoxystyrene) Poly (carboxyalkylstyrene) such as alkoxy (styrene), poly (p-, m- or o-carboxymethylstyrene), poly (alkyletherstyrene) such as poly (p-vinylbenzylpropylether), poly (p-trimethylsilylstyrene) ), And poly (vinylbenzyldimethoxyphosphide). In the present invention, among the polystyrene-based polymers, polystyrene is particularly preferred. Further, the polystyrene-based polymer having a syndiotactic structure used in the present invention does not necessarily need to be a single compound, and a polystyrene-based polymer having an atactic structure or an isotactic structure as long as the syndiotacticity is within the above range. It may be a mixture with a coalescence, a copolymer or a mixture thereof.

The polystyrene-based polymer used in the present invention has a weight average molecular weight of 10,000 or more, more preferably 50,000 or more.
00 or more. When the weight average molecular weight is less than 10,000, a film having excellent elongation characteristics and heat resistance cannot be obtained. The upper limit of the weight-average molecular weight is not particularly limited. However, when the weight-average molecular weight is 1500,000 or more, breakage may occur due to an increase in the stretching tension, which is not preferred.

The polystyrene-based polymer used in the present invention contains other resins, inorganic particles, organic particles, plasticizers, etc. in order to improve electrostatic adhesion, lubricity, stretchability, workability, impact resistance and the like. It is possible to use a compound in which an appropriate amount of a compatibilizer, a colorant, an antioxidant, an antistatic agent, and the like are blended, and the transparency is not particularly limited. However, when used as a transparent gas barrier film, 50% or more is used. Is preferred.

It is important to optimize the type and amount of lubricant particles in order to achieve both easy lubricity, workability and transparency, and the number of protrusions per unit area on the central surface of roughness PCC
It is preferable that the value and the three-dimensional surface roughness SRa satisfy the relationship of PCC value ≧ 20000 × SRa. For that purpose, as lubricant particles to be added, silica, titanium dioxide, talc, metal oxides such as kaolinite, calcium carbonate, calcium phosphate, metal salts such as barium sulfate or cross-linked polystyrene resin, cross-linked acrylic resin, silicon resin, and Examples include particles that are inert to syndiotactic polystyrene-based polymers, such as particles composed of an organic polymer such as a crosslinked polyester resin. These lubricants may be used alone or in combination of two or more, but the average particle system of the lubricant used is 0.01 μm or more.
The particle size variation (the ratio of the standard deviation to the average particle size) is preferably 25% or less, and the amount of addition is 0.005% to 2.0% by weight based on 100% by weight of the syndiotactic polystyrene-based polymer. The content is preferably not more than 1.0% by weight. In addition, it is preferable in terms of running characteristics that the shape of the lubricant particles includes one or more types having an area shape factor of 60% or more.

Further, the syndiotactic polystyrene-based film of the present invention can be prepared by a known method, for example, a sequential biaxial stretching method in which longitudinal stretching and transverse stretching are sequentially performed, as well as a transverse / longitudinal / longitudinal stretching method.
Stretching methods such as longitudinal stretching, longitudinal / horizontal / longitudinal stretching, and longitudinal / longitudinal / horizontal stretching can be employed. The syndiotactic polystyrene film in the present invention may be required to be a film having excellent heat resistance at high temperatures. As for the heat resistance, the heat shrinkage at 150 ° C. is preferably 3% or less. In that case, in addition to the selection of these stretching methods, the conditions of the stretching greatly affect, and in order to obtain excellent heat resistance, it is preferable to perform a heat fixing treatment, a longitudinal relaxation treatment, a horizontal relaxation treatment, or the like. .

As long as the object of the present invention is not impaired, the plastic film of the present invention is subjected to corona discharge treatment, glow discharge treatment and other surface roughening treatment prior to lamination of the thin film layer. Or a known anchor coat treatment, printing, or decoration. The thickness of the plastic film of the present invention is preferably in the range of 5 to 500 μm, more preferably 8 to 500 μm.
300300 μm.

It is considered that the aluminum oxide / silicon oxide thin film is composed of a mixture or a compound of aluminum oxide and silicon oxide. The aluminum oxide referred to herein, Al, AlO, consists of a mixture of various aluminum oxides Al ₂ O or the like, each of the content, such as in the aluminum oxide differs create conditions. Silicon oxide is considered to be composed of Si, SiO, SiO _{2 and the} like, and their ratios also differ depending on the preparation conditions. In the present invention, the ratio of aluminum oxide in the thin film is 20% by weight or more and 99% by weight or less, preferably 30% by weight or more and 95% by weight or less. Also, this component may contain a trace amount (up to 3% of all components) of other components as long as the properties are not impaired. As the thickness of the thin film,
Although not particularly limited, it is preferably from 50 to 8000 °, more preferably from 70 to 5000 °, from the viewpoint of gas barrier properties and flexibility.

In order to form such an aluminum oxide / silicon oxide thin film, a vacuum deposition method, a sputtering method, an ion
PVD method (physical vapor deposition method) such as ting, or C
A VD method (chemical vapor deposition method) or the like is appropriately used. For example,
In the vacuum deposition method, Al ₂ O ₃ and S
iO ₂ or a mixture of Al and SiO ₂ is used also as a heating method, resistance heating, high frequency induction heating, electron beam -
Heating or the like can be used. In addition, as a reactive gas, oxygen, nitrogen, water vapor, etc. are introduced, ozone is added,
Reactive deposition using means such as ion assist may be used. Further, the production conditions may be changed as long as the object of the present invention is not impaired, such as applying a bias to the substrate, increasing the substrate temperature, or cooling. The same applies to other production methods such as a sputtering method and a CVD method.

The product of the present invention may be used as it is, or may be used by laminating or coating a film or a thin layer of another organic polymer.

The specific gravity referred to in the present invention refers to the ratio of the mass of a substance occupying a certain volume at a certain temperature to the mass of a standard substance having the same volume (water at 4 ° C.). The measurement of specific gravity is
Normally, the mass and volume of the object may be measured, and the ratio of the mass to the same volume of water at 4 ° C. may be obtained. However, it is difficult to measure the volume in the measurement of the thin film of the present invention. Then, first, the thin film is peeled off from the substrate or only the substrate is dissolved to form a single film consisting of only the thin film.
It is desirable to use a specific gravity measurement method as described in 7112). For example, in the flotation method, a sample is immersed in a solution having a known specific gravity, and the specific gravity of the thin film can be measured from the flotation state. As this solution, a mixed solution of carbon tetrachloride and bromoform, methylene iodide, or the like can be used. The specific gravity value can also be measured by a density gradient tube method in which a single film is immersed in a solution having a continuous density gradient.

The relationship between the specific gravity value of the thin film thus obtained and the weight% of aluminum oxide in the thin film is expressed by D
= 0.01A + b (D: specific gravity of the thin film, A: weight% of aluminum oxide in the thin film), the value of b is 1.6
If the area is smaller than the above range, the structure of the aluminum oxide / silicon oxide thin film becomes coarse and sufficient gas barrier properties cannot be obtained. In addition, when the value of the specific gravity of the thin film is in a region where the b value is larger than 2.2, the initial gas barrier properties after film formation are excellent, but the film is too hard, and the mechanical properties, particularly the gelbo properties are inferior. The gas barrier property after treatment is greatly reduced, and is not suitable for use as a gas barrier film. For the above reasons, the specific gravity of the aluminum oxide / silicon oxide thin film, which is preferable as the gas barrier film, is expressed by the following formula: D = D
When the relational expression of 0.01A + b (D: specific gravity of the thin film, A: weight% of aluminum oxide in the thin film) is expressed by the value of b,
1.6 to 2.2, more preferably 1.7 to 2.1.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to only these examples. Hereinafter, a method for measuring the characteristics of the polystyrene-based transparent gas barrier films prepared in Examples and Comparative Examples and the inert particles used will be described.

(1) Thermal Shrinkage at 150 ° C. The shrinkage of the film was measured for 30 minutes in an atmosphere of 150 ° C. in an untensioned state.

(2) Three-dimensional surface roughness SRa The film surface was measured using a stylus type three-dimensional surface roughness meter (SE-3AK, manufactured by Kosaka Laboratory Co., Ltd.) with a needle radius of 2 μm and a load.
A cut-off value of 0 in the longitudinal direction of the film with a condition of 30 mg.
Measured over a measurement length of 1 mm at 25 mm,
It is divided into 00 points, and the height of each point is determined by a three-dimensional roughness analyzer (SPA).
-11). The same operation was continuously performed 150 times at intervals of 2 μm in the width direction of the film, that is, over 0.3 mm in the width direction of the film, and the data was taken into the analyzer. Next, SRa was determined using an analyzer.

(4) From the reference plane having the reference height when calculating the PCC value SRa, 0.00
The number of protrusions having a 625 [mu] m or more in height that represents the per 1 mm ^2.

(4) Average particle size The lubricant particles were observed with a scanning electron microscope (S-510, manufactured by Hitachi, Ltd.), and the photograph was enlarged and copied, and the outer shape of the lubricant was traced and arbitrarily determined. Individual particles were painted black. This image was measured for the horizontal Feret diameter of each particle using a Luzex 500 image analyzer manufactured by Nicole Co., Ltd., and the average value was defined as the average particle diameter. Also,
The degree of dispersion of the particle diameter was calculated by the following equation. Variation = (standard deviation of particle size / average particle size) x 10
0 (%)

(5) Area Shape Coefficient An arbitrary 20 particles are selected from the trace image used for measuring the average particle diameter, and the projected cross-sectional area of each particle is measured using the image analyzer used in (4). did. Further, the area of a circle circumscribing the particles was calculated, and calculated by the following equation. Area shape factor = (projected cross-sectional area of particle / area of circle circumscribing the particle) x 100 (%)

(6) Method of Measuring Oxygen Permeability The oxygen permeability of the prepared gas barrier film was measured using an oxygen permeability measuring device (OX-TRAN manufactured by Modern Controls).
100).

(7) Test method for flex fatigue resistance (hereinafter referred to as gelbo property) The flex fatigue resistance was evaluated using a so-called gelbo flex tester (manufactured by Rigaku Corporation). The conditions are (MIL-B131H), a sample piece of 11.2 inch × 8 inch is made into a cylindrical shape having a diameter of 3 (１ ／) inch, both ends are held, an initial holding interval is 7 inch, and a stroke is 3 (１ ／). The reciprocation of this operation was performed at a speed of 40 times / min at 20 ° C. and a relative humidity of 65% using an inch with a twist of 400 degrees.

Example 1 As a lubricant, an average particle size of 1.0
A polymer chip containing 1.0% by weight of 100% by weight of syndiotactic polystyrene (weight average molecular weight: 300,000) and a polymer chip without a lubricant added to 100% by weight of calcium carbonate having μm, a dispersion of 20%, and an area shape coefficient of 80%. After mixing at a weight ratio of 0.5 to 9.5, dry and mix
Melted at 0 ° C, extruded from T-die with lip gap of 800μm, and adhered to cooling roll at 50 ° C by electrostatic imprinting method.
After cooling and solidification, an amorphous sheet of 135 μm was obtained.

The amorphous sheet was first preheated to 95 ° C. with a cellulomicrol, heated to 138 ° C. with a silicone rubber roll, stretched 3.5 times in the machine direction, and then placed between a ceramic roll at 120 ° C. and a metal roll at 40 ° C. After 20% longitudinal relaxation, the film is preheated to 120 ° C by a tenter, stretched 1.8 times in the transverse direction at 120 ° C, and further stretched in the transverse direction at 180 ° C.
The film was stretched 9 times and heat-set at 250 ° C. for 12 seconds. Then 21
It was subjected to a 3% transverse relaxation treatment at 5 ° C. and a 2% longitudinal relaxation treatment at 210 ° C. The thickness of the obtained film was 14 μm. 150 ° C
Was 2.5%.

In the obtained film, 3 to 3
Particulate Al with a size of about 5 mm _TwoO_Three(Purity 99.5%)
And SiO_Two(Purity 99.9%) using electron beam evaporation
Thus, an aluminum oxide silicon oxide thin film was formed. Steam
The dressing materials are not mixed, and the inside of the heart is halved with a carbon plate.
One electron gun (hereinafter EB gun) as a partition and heating source
Used, Al_TwoO_ThreeAnd SiO_TwoEach in a time-sharing manner
Was. The emission current of the EB gun at that time is 0.8 to 2.2 A
And Al_TwoO_ThreeAnd SiO_TwoHeating ratio to 20:10
組成 50:10 and the composition was changed. Film feed speed
Is changed to 30-120 m / min, and 500-5000 mm thick
Made a membrane. Also, the vapor pressure changes the supply amount of oxygen gas.
1 × 10^-Five~ 8 × 10^-3Change the conditions until Torr
Was.

The film obtained has a coefficient of humidity expansion of 5 × 10 5
^It shows a very low value of ^-7 /% RH, and the coefficient of thermal expansion is 2 ×
Because of the good value of 10 ^-5 / ° C, it is excellent in dimensional stability due to environmental changes during processing and use after forming the thin film layer, and the thin film layer can be peeled, cracked, warped, wavy, etc. due to environmental changes. No defects occurred. The specific gravity of the thus obtained film was measured by dissolving the syndiotactic polystyrene film and then using the floatation / sedimentation method.

Further, an unstretched polypropylene film (OPP film) having a thickness of 40 μm was dried on the composite film on the syndiotactic polystyrene using a two-component curing type polyurethane adhesive (2 μm in thickness). To obtain a plastic film for packaging according to the present invention. This packaging film is subjected to retort treatment (120 degrees x 30 minutes) or gelbo treatment,
The oxygen barrier properties were measured.

The oxygen permeability measured in this way is 1.
It was very good, around 0 cc. Further, the result after the 200 times gelbo test also showed a rise of only about 2 to 3 cc, and a gas barrier film having excellent overall characteristics was obtained. (Table 1,
2)

Comparative Example 1 A transparent gas barrier thin film of aluminum oxide silicon oxide was prepared by EB vapor deposition in the same manner as in Example 1, and the obtained sample was subjected to specific gravity measurement and retort treatment or gelbo treatment. The oxygen barrier properties were measured. As a result, one of the oxygen barrier properties, retort resistance, and gelbo properties became insufficient, and the overall judgment was poor. (Tables 1 and 2)

Comparative Example 2 An aluminum oxide silicon oxide-based transparent gas barrier thin film was formed by EB deposition in the same manner as in Example 1 except that a polyethylene terephthalate film (Toyobo Co., Ltd .: E5007) was used instead of the syndiotactic polystyrene film. Was made. The specific gravity of the thus obtained film was measured by dissolving the syndiotactic polystyrene film and then using the floatation / sedimentation method. as a result,
Oxygen barrier properties, retort resistance, or gelbo properties were sufficient, but the polyethylene terephthalate film used had a humidity expansion coefficient of 120 × 10 ^-7 /%
Since it is RH and the humidity expansion is larger than that of the syndiotactic polystyrene film, the film was warped due to humidity change and retort treatment during processing or use after the formation of the thin film layer, and the overall judgment was poor.

Comparative Example 3 E was the same as in Example 1 except that a polyamide film (Toyobo Co., Ltd .: N1100) was used instead of the syndiotactic polystyrene film.
An aluminum-silicon oxide-based transparent gas barrier thin film was prepared by B vapor deposition, and the obtained sample was measured for specific gravity and oxygen barrier properties after retort treatment or gelbo treatment. As a result, the oxygen barrier properties, retort resistance, or gelbo properties were sufficient, but the humidity expansion coefficient of the polyamide film used was 10%.
It is 00 × 10 ^-7 /% RH, and its humidity expansion is much larger than that of syndiotactic polystyrene film.Therefore, the film will curl due to humidity change and retort processing during processing or use after forming the thin film layer. , The overall judgment was poor.

[0035]

As described above, in a gas barrier film in which an aluminum oxide / silicon oxide thin film is formed on a film made of a resin composition containing a polystyrene polymer having a syndiotactic structure, the ratio of aluminum oxide in the thin film Is not less than 20% by weight and not more than 99% by weight, and the relation between the specific gravity of the thin film and the composition ratio of aluminum oxide in the thin film is D = 0.01A + b (D: specific gravity of the thin film, A: weight% of aluminum oxide in the thin film) )), By setting the specific gravity of the thin film within the range represented by 1.6 ≦ b ≦ 2.2, the thin film has excellent gas barrier properties, high retort resistance, high flexibility, and overall practical characteristics. An excellent aluminum oxide / silicon oxide based gas barrier film can be provided.

[0036]

[Table 1]

[0037]

[Table 2]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-103375 (JP, A) JP-A-2-1433851 (JP, A) JP-A-60-23037 (JP, A) JP-A-4- 99165 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (1)

(57) [Claims] 1. A gas barrier film comprising an aluminum oxide / silicon oxide thin film formed on a film made of a resin composition containing a polystyrene polymer having a syndiotactic structure, wherein the ratio of aluminum oxide in the thin film is A laminated polystyrene-based film, wherein the specific gravity of the thin film satisfies the following formula: not less than 20% by weight and not more than 99% by weight. D = 0.01A + b, where D: specific gravity of the thin film, A: weight% of aluminum oxide in the thin film 1.6 ≦ b ≦ 2.2