JPH08187776A - Stretched polystyrenic film, self-adhesive tape and easily tearing packing film - Google Patents

Abstract

PURPOSE: To provide a stretched SPS film excellent in easily tearing properties and having capacity excellent in dispenser cutting properties and hand cutting properties. CONSTITUTION: A stretched polystyrenic film, a self-adhesive tape based on a stretched polystyrenic film and an easily tearing packing film containing a stretched polystyrenic film as a constitutional component are composed of a styrenic resin compsn. containing 70-100wt.% of a styrenic polymer having a high degree of syndiotactic configuration and characterized in that the number of crazes with a length of 20μm or more present in at least two end parts thereof is 50 or less per a length of 10mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretched polystyrene film, an adhesive tape, and an easily tearable packaging film. More specifically, various tapes or films such as films for electrical insulation, films for writing, films for photography, and plates The present invention relates to a polystyrene-based stretched film excellent in easy tearability, which is also suitably used for a film, an optical film such as OHP, and the like.

[0002]

BACKGROUND OF THE INVENTION Styrene-based polymers having a syndiotactic structure (hereinafter referred to as
It may be abbreviated as "SPS". ) Is the mechanical strength,
Since it has excellent heat resistance, appearance, solvent resistance, etc., it is expected to be used for various purposes. In particular, various film, sheet or fiber extrusion techniques, molded products, applications, etc. have been proposed. In addition, many proposals have been made so far regarding a method for producing a stretched film, a stretched film having various physical properties, and its use. Since the SPS stretched film is easy to tear, this property is used to advantage.
No. 485 discloses an adhesive tape for simple packaging, which is disclosed in Japanese Patent Laid-Open No. 2-6.
No. 7328 discloses a packaging film.
However, when the conventional SPS stretched film is slit and trimmed by a general method, there is a problem that the hand-cutability of the left and right ends after slitting is different. Further, although the SPS stretched film has a small tear propagation resistance, there is a problem that the initial tension at the time of tearing is high and the tearability is insufficient as a packaging material. Up to now, regarding the SPS stretched film, a film suitable for slitting, trimming, etc. in the secondary processing has not been proposed.

The present invention has been made in view of the above situation. That is, the present inventors have made earnest studies on a film having excellent tearability and the like. Among them, SPS
It was found that the molded product of No. 1 is apt to cause craze, and that the tear propagation resistance is lowered by stretching. As a result of further investigation focusing on the occurrence of this craze, it was found that a craze at a film edge portion above a specific value is effective in solving problems such as easy tearing. Further, it has been found that this craze can be generated by using a slit blade having a specific temperature or lower and a specific width or higher. The present invention has been completed based on such findings to provide an SPS stretched film excellent in easy tearability and the like.

[0004]

That is, the present invention relates to a stretched film comprising a styrene resin composition containing 70 to 100% by weight of a styrene polymer having a high syndiotactic structure, which comprises at least one 2 at the end
It is intended to provide a polystyrene-based stretched film characterized in that the number of crazes having a length of 0 μm or more is 50 or more per 10 mm of the end portion. Also, the present invention
The present invention provides an adhesive tape based on the above stretched polystyrene-based film and an easily tearable packaging film containing the above stretched polystyrene-based film as a constituent component. Hereinafter, the present invention will be described in more detail.

First, the material of the stretched polystyrene film of the present invention will be described. The syndiotactic styrene-based polymer in the present invention means that the stereochemical structure is a syndiotactic structure, that is, a phenyl group or a substituted phenyl group, which is a side chain, alternates with respect to the main chain formed from carbon-carbon bonds. The tacticity is determined by the nuclear magnetic resonance method ( ¹³ C-NMR method) using isotope carbon. ¹³ C-
The tacticity measured by the NMR method can be indicated by the abundance ratio of a plurality of continuous constitutional units, for example, diad in the case of 2, triad in the case of 3, and pentad in the case of 5. The styrene-based polymer having a high syndiotactic structure referred to in the invention is usually 75% or more, preferably 85% or more in racemic dyad, or 30% or more in racemic pentad,
Preferably, polystyrene having a syndiotacticity of 50% or more, poly (alkylstyrene), poly (halogenated styrene), poly (alkoxystyrene), poly (
Vinyl benzoate), hydrogenated polymers thereof and mixtures thereof, or copolymers containing these structural units. Here, as poly (alkylstyrene), poly (methylstyrene), poly (ethylstyrene), poly (propylstyrene), poly (butylstyrene), poly (phenylstyrene), poly (vinylnaphthalene), poly ( Vinyl styrene), poly (acenaphthylene), etc.
(Chlorostyrene), poly (bromostyrene), poly (fluorostyrene), etc. Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene). Of these, particularly preferred styrene-based polymers are copolymers of styrene and p-methylstyrene, polystyrene, poly (p-methylstyrene), poly (m-methylstyrene), poly (p-tertiarybutylstyrene). ), Poly (p-chlorostyrene),
Examples thereof include poly (m-chlorostyrene) and poly (p-fluorostyrene) (JP-A-62-187708).
Issue).

Further, as the comonomer in the styrene-based copolymer, in addition to the above-mentioned styrene-based polymer monomers, olefin monomers such as ethylene, propylene, butene, hexene and octene, diene monomers such as butadiene and isoprene, and cyclic compounds. Examples thereof include diene monomers, polar vinyl monomers such as methyl methacrylate, maleic anhydride and acrylonitrile. In particular, a styrene-based polymer having a styrene repeating unit of 80 to 100 mol% and a p-methylstyrene repeating unit of 0 to 20 mol% is preferably used. The molecular weight of the styrene-based polymer is not particularly limited, but those having a weight average molecular weight of 10,000 or more and 3,000,000 or less are preferable, and those of 50,000 or more and 1,500,000 or less are more preferable. If the weight average molecular weight is less than 10,000, stretching may not be performed sufficiently. Further, the molecular weight distribution is not limited in its width and various kinds can be applied, but it is preferable that the weight average molecular weight (Mw) / number average molecular weight (Mn) is 1.5 or more and 8 or less. . The styrene-based polymer having the syndiotactic structure is remarkably excellent in heat resistance as compared with the conventional styrene-based polymer having the atactic structure. The styrene polymer having a high syndiotactic structure is contained in the stretched polystyrene film of the present invention in an amount of 70 to 100% by weight, preferably 80 to 100% by weight.

The polystyrene stretched film of the present invention contains a lubricant, another thermoplastic resin, an antioxidant, an inorganic filler, a rubber, a compatibilizer, a colorant, a cross-linking agent, and a cross-linking aid within a range that does not impair its purpose. Agents, nucleating agents, plasticizers, etc. can also be added. As the lubricant, for example, inorganic fine particles can be used. Here, the inorganic fine particles mean group IA, IIA
Tribe, IVA, VIA, VIIA, VIII, IB, IIB
Group, Group IIIB, Group IVB oxides, hydroxides, sulfides, nitrides, halides, carbonates, sulfates, acetates, phosphates, phosphites, organic carboxylates, silicates, Titanate, borate and their hydrous compounds, their complex compounds, and natural mineral particles are shown.

Specifically, Group IA element compounds such as lithium fluoride and borax (sodium borate hydrous salt), magnesium carbonate, magnesium phosphate, magnesium oxide (magnesia), magnesium chloride, magnesium acetate, magnesium fluoride, titanic acid Magnesium, magnesium silicate, magnesium silicate hydrous salt (talc), calcium carbonate, calcium phosphate, calcium phosphite, calcium sulfate (gypsum), calcium acetate, calcium terephthalate, calcium hydroxide, calcium silicate, calcium fluoride, calcium titanate , Strontium titanate, barium carbonate, barium phosphate, barium sulfate, barium phosphite, etc.
IIA group element compounds, titanium dioxide (titania), titanium monoxide, titanium nitride, zirconium dioxide (zirconia),
Group IVA element compounds such as zirconium monoxide, group VIA element compounds such as molybdenum dioxide, molybdenum trioxide and molybdenum sulfide, group VIIA element compounds such as manganese chloride and manganese acetate, group VIII element compounds such as cobalt chloride and cobalt acetate , Group IB element compounds such as cuprous iodide, Group IIB element compounds such as zinc oxide and zinc acetate, aluminum oxide
(Alumina), aluminum hydroxide, aluminum fluoride,
Group IIIB element compounds such as aluminosilicate (alumina silicate, kaolin, kaolinite), silicon oxide (silica,
Group IVB element compounds such as silica gel), graphite, carbon, graphite, glass, carnal stone, kainite, mica (
Particles of natural minerals such as mica, quinnemo) and birose ore are included. The average particle size of the inorganic fine particles used here is
There is no particular limitation, but it is preferably 0.001 to 3 μm, and the content in the molded product is 0.001 to 5% by weight, preferably 0.0
It is from 05 to 3% by weight. The inorganic fine particles are contained in the final molded article, but the method of containing them is not limited. For example, a method of adding or precipitating in an arbitrary process during polymerization, a method of adding in an arbitrary process of melt extrusion can be mentioned.

In the present invention, there are various kinds of other thermoplastic resins which can be added to the above-mentioned styrene-based polymer. For example, a styrene-based polymer having an atactic structure, a styrene-based polymer having an isotactic structure, Examples thereof include polyphenylene ether. These resins are easily compatible with the styrene-based polymer having the syndiotactic structure described above, are effective in controlling crystallization when creating a preform for stretching, and are improved in the stretchability after that, and the stretching condition A film that is easy to control and has excellent mechanical properties can be obtained. Among these, in the case of containing a styrene-based polymer having an atactic structure and / or an isotactic structure, those containing the same monomer as the styrene-based polymer having a syndiotactic structure are preferable. The content ratio of these compatible resin components is 1 to 70% by weight, especially 2 to 5%.
It may be 0% by weight. When the content of the compatible resin component exceeds 70% by weight, the heat resistance, which is an advantage of the styrene polymer having a syndiotactic structure, may be impaired, which is not preferable.

Other resins which can be added to the above-mentioned styrene polymer used in the present invention and which are incompatible resins include, for example, polyolefins such as polyethylene, polypropylene, polybutene and polypentene, polyethylene terephthalate, Polyester such as polybutylene terephthalate, polyethylene naphthalate, nylon-
Polyamide such as 6 or nylon 6,6, polythioether such as polyphenylene sulfide, polycarbonate, polyarylate, polysulfone, polyetheretherketone, polyethersulfone, polyimide, vinyl halide polymer such as Teflon, polymethylmethacrylate, etc. Examples of the acrylic polymer, polyvinyl alcohol, etc. other than the above compatible resins include cross-linking resins containing the above compatible resins. These resins are
Since it is incompatible with the styrene-based polymer having a syndiotactic structure used in the present invention, when contained in a small amount, it can be dispersed like islands in the styrene-based polymer having a syndiotactic structure, and after stretching. It is effective for giving moderate gloss and improving the surface slipperiness. The content ratio of these incompatible resin components is 2 to 50% by weight for the purpose of gloss, and 0 for the purpose of controlling the surface property.
001-5 weight% is preferable. Further, when the temperature used as a product is high, it is preferable to use an incompatible resin having relatively high heat resistance.

As the antioxidant, a phosphorus-based antioxidant, a phenol-based antioxidant and a sulfur-based antioxidant can be used. By using such an antioxidant,
A polystyrene resin composition having good heat stability can be obtained.
Here, various types of phosphorus-based antioxidants may be used, and they may be monophosphite, diphosphite, or the like. As monophosphite, tris (2,4-
Di-t-butylphenyl) phosphite; tris (mono- and di-nonylphenyl) phosphite and the like. The diphosphite has the general formula

[0012]

Embedded image

[In the formula, R ¹ and R ² may be the same or different and each is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms or 6 to 2 carbon atoms.
The aryl group of 0 is shown. ] A phosphite represented by the following formula is used, and specific examples thereof include distearyl pentaerythritol diphosphite; dioctyl pentaerythritol diphosphite; diphenyl pentaerythritol diphosphite; bis (2,4-di-t-butylphenyl) Pentaerythritol diphosphite; bis (2
6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite; dicyclohexyl pentaerythritol diphosphite; tris (2,4-di-t
-Butylphenyl) phosphite; tetrakis (2,4
-Di-t-butylphenyl) -4,4'-biphenylene phosphonite and the like. Among these, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite; bis (2,6-di-t-butyl-
4-methylphenyl) pentaerythritol diphosphite; tris (2,4-di-t-butylphenyl) phosphite; tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphonite Is preferably used.

Various kinds of phenolic antioxidants can be used, and specifically, dialkylphenol, trialkylphenol, diphenylmonoalkoxyphenol, tetraalkylphenol and the like are used. As dialkylphenol,
2,2'-methylenebis (6-t-butyl-4-methylphenol); 1,1-bis (5-t-butyl-4-hydroxy-2-methylphenyl) butane; 2,2'-methylenebis (4 -Methyl-6-cyclohexylphenol); 4,4'-thiobis (6-t-butyl-3-methylphenol); 2,2-bis (5-t-butyl-4-)
Hydroxy-2-methylphenyl) -4-n-dodecylmercapto-butane and the like can be mentioned. Examples of the trialkylphenol include 2,6-di-t-butyl-4-methylphenol; 2,2'-methylenebis (6-t-butyl-4-ethylphenol); 2,2'-methylenebis [4-methyl- 6- (α-methylcyclohexyl) phenol]; 2,2′-methylenebis (4-methyl-6-
Nonylphenol); 1,1,3-tris- (5-t-
Butyl-4-hydroxy-2-methylphenyl) butane; ethylene glycol-bis [3,3-bis (3-t
-Butyl-4-hydroxyphenyl) butyrate]; 1
-1-bis (3,5-dimethyl-2-hydroxyphenyl) -3- (n-dodecylthio) -butane; 1,3,5
-Tris (3,5-di-t-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene; 2,2-
Bis (3,5-di-t-butyl-4-hydroxybenzyl) malonic acid dioctadecyl ester; n-octadecyl-3- (4-hydroxy-3,5-di-t-butylphenyl) propionate; tetrakis [methylene (3,
5-di-t-butyl-4-hydroxyhydrocinnamate)] methane; 3,9-bis [1,1-dimethyl-2
-(Β- (3-t-Butyl-4-hydroxy-5-methylphenyl) propionyloxy) ethyl-2,4
8,10-Tetraoxaspiro [5,5] undecane;
Tris- (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate and the like can be mentioned. Examples of diphenylmonoalkoxyphenol include 2,6-diphenyl-4-methoxyphenol, and examples of tetraalkylphenol include tris- (4-t-butyl-2,6-di-methyl-3-hydroxybenzyl)-. Isocyanurate and the like can be mentioned.

Further, the sulfur type antioxidant is preferably a thioether type one, specifically, dilauryl-3,
3'-thiodipropionate; dimyristyl-3,3 '
-Thiodipropionate; distearyl-3,3'-thiodipropionate; pentaerythritol-tetrakis- (β-lauryl-thiopropionate); bis [2
-Methyl-4- (3-n-alkylthiopropionyloxy) -5-t-butylphenyl] sulfide; 2-mercaptobayzoimidazole and the like. Among these, especially pentaerythritol-tetrakis- (β-
Lauryl-thiopropionate) is preferred.

In the stretched polystyrene-based film of the present invention, if necessary, it has a --NH-- group and has a pH of 10,0.
Contains organic compounds having a molecular weight of less than 00. As such an organic compound, a compound in which an electron-withdrawing group is adjacent to an -NH- group is preferable, and examples of such an electron-withdrawing group include a benzene ring, a naphthalene ring, an anthracene ring, a pyridine ring, a triazine ring and an indenyl ring. And an aromatic ring or carbonyl structure such as a derivative thereof. The organic compound has a thermal decomposition temperature of 26
Those of 0 ° C. or higher are particularly preferable. Specifically, the following compounds, for example, 2,4-bis- (n-octylthio) -6
-(4-Hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-
Hydrocinnamide), N, N'-bis [3- (3,5-
Di-t-butyl-hydroxyphenyl) propionyl]
Hydrazine, 3- (N-salicyloyl) amino-1,
2,4-triazole, decamethylenedicarboxylic acid disalicyloyl hydrazide, isophthalic acid (2-phenoxypropionyl hydrazide), 2,2-oxazamide-bis [ethyl-3- (3,5-di-t-butyl-4] -Hydroxyphenyl) propionate], oxalyl-bis (benzylidene-hydrazide), N-formyl-N'-
Salicyloylhydrazine, 2-mercaptobenzimidazole, N, N'-di-2-naphthyl-p-phenylenediamine, 4,4'-bis (α, α-dimethylbenzyl) diphenylamine, 2-mercaptomethylbenzimidazole, Styrenated diphenylamine, octylated diphenylamine, N-phenyl-1-naphthylamine, poly (2,2,4-trimethyl-1,2-dihydroquinoline), 6-ethoxy-1,2-dihydro-2,
2,4-trimethylquinoline, N, N'-diphenyl-
p-phenylenediamine, N-phenyl-N '-(1,
3-dimethylbutyl) -p-phenylenediamine, N-
Phenyl-N '-(3-methacryloxy-2-hydroxypropyl) -p-phenylenediamine, thiodiphenylamine, p-aminodiphenylamine, N-salicyloyl-N'-aldehyde hydrazine, N-salicyloyl-N'-acetylhydrazine, N, N'-diphenyl-oxamide, N, N'-di (2-hydroxyphenyl) oxamide, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, N-phenyl-N'-
Isopropyl-p-phenylenediamine and the like can be mentioned. The above-mentioned organic compound having a -NH- group and having a molecular weight of less than 10,000 is optionally contained in the polystyrene stretched film of the present invention in an amount of less than 30% by weight.

The stretched polystyrene film according to the present invention is a stretched film comprising a styrene resin composition containing 70 to 100% by weight of the above-mentioned styrene polymer having a highly syndiotactic structure, and at least 1 Crazes with a length of 20 μm or more at one end
50 or more per 0 mm length, preferably 10 m at the end
It is 100 or more per m length, and a rolled stretched film is also included. If the number of crazes is less than 50 per 10 mm in length, the stretched film is not easily tearable, which is not preferable. When the easy tear property is insufficient, the dispenser cut property of the adhesive tape having the stretched film as a base becomes poor, and further, the easy tear property of the packaging film containing the stretched film becomes poor. I will end up. Further, the stretched polystyrene film of the present invention is a film in which at least one end has a specific number or more of Crazes having a length of 20 μm or more. When the length of the craze is less than 20 μm, the easy tearing property is insufficient, which is not preferable. The above physical properties of the stretched film can be measured, for example, by the following evaluations. That is, the presence or absence, length and number of crazes are confirmed by observing the end portion of the stretched film with a polarizing microscope or the like. Then, the stretched film cut to an appropriate length is evaluated by examining the dispenser cut property or the hand cut property. The polystyrene-based stretched film according to the present invention having such physical properties has excellent tearability, and dispenser cutability and hand tearability.

The pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape comprising the above-mentioned polystyrene stretched film as a base material, and has sufficient easy tearability, dispenser cutability and hand tearability of the polystyrene stretched film. Alive,
It is an adhesive tape having excellent easy tear properties. Furthermore, the easily tearable packaging film of the present invention is an easily tearable packaging film containing the above polystyrene-based stretched film as a constituent component, and has excellent easy tearability of the polystyrene-based stretched film, dispenser cuttability and It is an easily tearable film for packaging which also has excellent hand-cutting properties and the like, which makes full use of the hand-cutting properties.

Next, the method for producing the polystyrene stretched film of the present invention will be described. The polystyrene-based stretched film according to the present invention can be produced by various methods, but has excellent easy tearability, and in order to obtain a stretched film suitable for dispenser cutability and hand tearability, It is preferable to use the above method. The styrene-based resin composition used in the present invention can be produced by any method, that is, various methods used for conventional thermoplastic resins. For example, (A) the styrene-based polymer component and ( B) a method of mixing components other than the styrene-based polymer and melt-kneading with an extruder or the like, a method of adding the component (B) at any stage of the extrusion step of the component (A), a manufacturing process of the component (A) A method of adding the component (B) at any stage of
A method of melt-kneading the material in which the component (A) and the component (B) are mixed and the component (A) are applicable. When the stretched film of the present invention is produced using such a styrene-based resin composition, the method is not particularly limited, and for example, after heating and melting these materials, a preformed body is formed, followed by heating and stretching. It is obtained by slitting the stretched film obtained by subjecting it to a heat treatment or the like under specific conditions.

The operation from the heating and melting to the heat setting will be specifically described as follows. First, the styrene-based polymer obtained as described above is used as a molding material, and this is usually extrusion-molded to obtain a stretching preform (film, sheet or tube). In this molding, it is common to mold the heat-melted molding material into a predetermined shape with an extruder, but do not heat the molding material and mold it in a softened state. Good. The extruder used here may be either a single-screw extruder or a twin-screw extruder, and may or may not have a vent. If a suitable filter is used for the extruder,
It is possible to remove foreign matters and foreign substances. Further, the shape of the filter can be appropriately selected and used such as a flat plate shape or a cylindrical shape. The extrusion conditions here are not particularly limited,
The temperature may be appropriately selected according to various situations, but the temperature is preferably selected within a range of 50 ° C. higher than the melting point of the molding material to the decomposition temperature, and the shear stress is 5 × 10 ⁶ dyne / cm ² or less. The die used may be a T-die, an annular die or the like.

After the above extrusion molding, the obtained preform for stretching is cooled and solidified. At this time, various refrigerants such as gas, liquid and metal roll can be used. When a metal roll or the like is used, it is effective to prevent thickness unevenness and waviness according to methods such as an air knife, an air chamber, a touch roll, and electrostatic printing. The temperature for cooling and solidification is usually 0 ° C.
-The temperature is in the range of 30 ° C higher than the glass transition temperature of the preform for stretching, preferably in the range of 70 ° C lower than the glass transition temperature-glass transition temperature. The cooling rate is 20
It is appropriately selected within the range of 0 to 3 ° C / sec. In the case of biaxial stretching, the cooled and solidified preform may be simultaneously stretched in the machine direction and the transverse direction, but may be sequentially stretched in any order.
The stretching may be performed in one stage or in multiple stages.
The draw ratio is 2 times or more, preferably 3 times or more in terms of area ratio. When the stretching ratio is in this range, the crystallinity of the film is 25% or more, and a stretched film roll having favorable physical properties can be obtained.

As the stretching method, various methods such as a tenter method, a method of stretching between rolls, a method of bubbling utilizing gas pressure, and a method of rolling can be used. These can be appropriately selected or combined. You can apply. The stretching temperature may be generally set between the glass transition temperature and the melting point of the preform. The stretching speed is usually 1 × 10 to 1 × 10 ⁵ % / min, preferably 1
× 10 ³ to 1 × 10 ⁵ % / min. When the stretched film obtained by stretching under the above-mentioned conditions is required to have dimensional stability at high temperature, heat resistance, and strength balance in the plane of the film, it is preferable to further perform heat setting. The heat setting can be carried out by a commonly used method, but the stretched film is subjected to a tensioned state, a relaxed state or a restricted shrinking state, from the glass transition temperature to the melting point of the film, preferably 100 ° C. lower than the melting point. It may be carried out by maintaining the temperature in the temperature range from the temperature to immediately before the melting point for 0.5 to 120 seconds. The heat setting can be performed twice or more by changing the conditions within the above range. Further, this heat fixing may be performed in an atmosphere of an inert gas such as argon gas or nitrogen gas.

The stretched polystyrene film of the present invention is
It is obtained by slitting the stretched film roll obtained as described above under specific conditions. That is, the stretched film roll obtained by the above method is slit using a slit blade having a maximum thickness of 400 μm or more, preferably 450 μm or more. At the time of slitting, the temperature of the slit portion is 50 ° C or lower, preferably 40 ° C.
It is below ℃. Moreover, it is preferable that the cross-sectional shape of the slit blade is symmetrical. According to such a manufacturing method, it is possible to efficiently and reliably manufacture the polystyrene stretched film according to the present invention, which is excellent in easy tearing property, dispenser cutting property, hand cutting property and the like.

[0024]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Reference Example 1 17 g of copper sulfate pentahydrate (Cu SO ₄ .5H ₂ O) was placed in a glass container having an inner volume of 500 ml replaced with argon.
(71 mmol), 200 ml of toluene and 24 ml (250 mmol) of trimethylaluminum were added, and the mixture was reacted at 40 ° C. for 8 hours. Then, the solid portion was removed to obtain 6.7 g of a contact product. The molecular weight of this product was 610 as measured by the freezing point depression method.

Production Example 1 Production of Styrenic Polymer Having Syndiotactic Structure In a reaction vessel having an internal volume of 2 liters, the contact product obtained in Reference Example 1 above was added in an amount of 7.5 mmol as an aluminum atom,
Triisobutylaluminum 7.5 mmol, pentamethylcyclopentadienyl titanium trimethoxide
0.038 mmol and 1 liter of purified styrene were taken and a polymerization reaction was carried out at 90 ° C. for 5 hours. After completion of the reaction, after decomposing the catalyst component with a methanol solution of sodium hydroxide,
The product was washed repeatedly with methanol and dried to give a polymer.
466g was obtained. The weight average molecular weight of the obtained polymer was 1,
When measured by gel permeation chromatography at 130 ° C. using 2,4-trichlorobenzene as a solvent, it was 290000, and the weight average molecular weight / number average molecular weight was 2.72. Further melting point and ¹³ C-NMR
It was confirmed that the obtained polymer was polystyrene having a syndiotactic structure.

Example 1 0.1% by weight of spherical zeolite having a particle size of 1.5 μm was added to the styrene polymer having a syndiotactic structure obtained as in Production Example 1, and the mixture was melt-extruded at 300 ° C. , Pellets. The obtained pellets are melt-extruded by an extruder and adhered to a cooling roll at 30 ° C. by electrostatic pinning method to make 300μ.
A m pre-formed sheet for amorphous stretching was prepared. This amorphous stretch preform sheet was continuously and longitudinally stretched to 115
The stretched film roll was obtained by stretching the film at 3.2 ° C. to 3.2 times and transversely at 125 ° C. to 3 times and heat-treating at 235 ° C. The stretched film roll was slit into widths of 1.5 cm and 10 cm with a stainless cutter having a blade edge of 500 μm in thickness and a symmetrical cross-sectional shape to obtain a stretched film. The temperature of the slit part at this slit is 20
It was set to ° C. The edge of the obtained stretched film was observed with a polarization microscope, and crazes of 20 μm or more were counted.
Further, the difference in the left / right dispenser cuttability was examined using the stretched film having the width of 1.5 cm. Further, the stretched film having a width of 10 cm was subjected to corona treatment, and then made into a bag with a rubber adhesive, and the hand-cutability of the bag was examined. The results are shown in Table 1.

Example 2 A stretched film roll was prepared and slit to obtain a stretched film in the same manner as in Example 1 except that the amorphous stretching preform sheet of 900 μm was prepared. Then, the same evaluation as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 1 A stretched film was prepared in the same manner as in Example 1 except that a stainless cutter having a blade edge of 300 μm in thickness and an asymmetric cross-sectional shape was used and the slit temperature was set to 80 ° C. A roll was prepared and slit to obtain a stretched film. Then, the same evaluation as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 2 A stretched film roll was prepared and slit to obtain a stretched film in the same manner as in Comparative Example 1 except that the amorphous stretching preform sheet of Comparative Example 1 was prepared. Then, the same evaluation as in Example 1 was performed. The results are shown in Table 1.

[0030]

[Table 1] Note) 1) Dispenser cutability is good: It is possible to cut with the same force on the left and right Poor: The cut parts are not uniform due to the difference in the feel of the left and right cuts. Defective: The cutting position is not uniform and the cutting part is deformed.

[0031]

As described above in detail, the stretched polystyrene film according to the present invention has excellent tearability, dispenser cutability, and hand tearability. Further, the adhesive tape and the easily tearable packaging film according to the present invention have excellent tearability, and dispenser cutability and hand tearability. Such a polystyrene-based stretched film of the present invention can be suitably used for various tapes or films, for example, films for electrical insulation, films for writing, films for photography, films for plate making, optical films such as OHP, With the adhesive tape and the easily tearable packaging film of the present invention, the industrial utility value is extremely large.

Claims (3)

[Claims] 1. A stretched film comprising a styrene-based resin composition containing 70 to 100% by weight of a styrene-based polymer having a highly syndiotactic structure, the stretched film having a length of 20 μm or more at least at one end. A polystyrene-based stretched film, wherein the number of crazes is 50 or more per 10 mm length. 2. An adhesive tape comprising the stretched polystyrene film according to claim 1 as a base material. 3. An easily tearable packaging film containing the stretched polystyrene film according to claim 1 as a constituent component.