JP5377819B2 - Easy-cut film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film having especially high tearing property in the width direction of the film, for more detail, a film readily teared in the width direction of the film by a hand and being linearly teared. <P>SOLUTION: The present invention provides a biaxially oriented film composed of a polystyrene-based resin and having 3-20 ratio of heat shrinkage stress in the flow direction to the width direction of the film and 1,000-8,000 kPa heat shrinkage stress in the width direction. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a film that is easy to tear in the width direction and a laminated film thereof. More specifically, food packaging materials, pharmaceutical packaging materials, bags for making packaging materials for miscellaneous goods, tape-like materials, films constituting sheet-like materials, especially tearing easily in the width direction of the film, and linear It relates to a film that can be torn.

  Various films are used for packaging foods, pharmaceuticals, miscellaneous goods and the like. Conventionally, cellophane is often used for the purpose of easily opening a packaging material made of a film. The laminated film of cellophane and polyethylene laminated is positioned so that the cellophane is on the outside of the bag and the polyethylene film is on the inside of the bag, and the two laminated films are heat sealed to form a packaging bag. Can be cut from the edge compared to bags using as a surface material, and is used as an easy-open bag.

However, the openability of the bag is insufficient, the cut surface may deviate in a direction different from the opened direction, and the contents are spilled and difficult to take out. Cellophane is generally easy to tear in the flow direction of the film, but difficult to tear in the width direction. As a packaging material, a bag that is long in the flow direction: For example, when opening a bag such as stick packaging or pillow packaging, if the bag is opened in the width direction, the contents are spilled by tearing in the flow direction.
Attempts were made to use polyethylene, polypropylene, polyester, and other films instead of cellophane, but these films were not always easy to open when made into bags due to the low rigidity of the original film. . For this reason, a notch or notch has been made in the bag, but it cannot be easily opened from anywhere in the bag, and the contents may be damaged at the processing stage. Furthermore, among these films, there were films that were easy to tear in the flow direction, but none were easy to tear in the width direction. In general, in order to produce a film, a molten resin is extruded, so that the resin is oriented in the direction of extruding the resin, that is, in the flow direction in which the film is wound, so that it is easy to tear in the flow direction but difficult to tear in the width direction.

In order to improve the cut property and the goodness of the waist, the invention of an easily cut film has been made. For example, an improved polyester film (Patent Documents 1 to 3), other resin films (Patent Document 4), an invention of an improved laminated film by combining these (Patent Document 5), and the like have been made. Moreover, invention of the adhesive tape with easy cut property (patent documents 6 and 7) is also made.
However, these inventions also have insufficient tearability, poor propagation of tears, and are used as film materials in the easy-cut field even though cellophane has poor properties. In addition, they have not yet invented a film that can be easily cut in the width direction.

  As an alternative material for cellophane, an invention has been made even with a polystyrene resin film having the same waist as cellophane (Patent Document 8). In this invention, a laminated film is formed by laminating a biaxially stretched polystyrene film using a general polystyrene resin and a polyolefin film having heat sealability, and the two laminated films are heat sealed to form an easy-open bag. There is a technical disclosure.

However, the tearability is still insufficient, and when these laminated films are used, there is a problem that a difference in melting point between the resin polystyrene used and general polyolefin is small, and heat sealing is difficult. That is, the above-mentioned laminated film made of cellophane and polyethylene is generally used as a pharmaceutical packaging bag, but the machine for making these is basically a machine designed with cellophane that does not melt. For this reason, the heat sealing temperature does not match, and even when heat sealing, the heat sealed part shrinks and does not form a good bag, and even if it is made into a bag, the resin that produces the film solidifies by melting the polystyrene resin It was a bag that could not be opened easily. If a bag is made at a lower heat seal temperature in order to obtain a bag, the bag-making speed is reduced and the efficiency is lowered. For this reason, the precious invention has not actually been used for these purposes.
Japanese Patent Publication No. 56-50692 JP 51-124163 A JP 2002-53675 A JP 2000-202956 A JP 2002-264237 A Japanese Patent Publication No.55-8551 Japanese Patent Publication No.55-20514 JP 63-79 A

  An object of this invention is to provide the film which is easy to tear especially in the width direction, and its laminated | multilayer film. More specifically, an object is to provide a film that can be easily opened in the width direction and linearly opened in the same direction as the opened direction.

As a result of intensive studies to solve the above problems, the present inventors have made the present invention.
The present invention is as follows.
1. A biaxially stretched polystyrene resin film, wherein the polystyrene resin is a styrene copolymer resin composed of a styrene-methacrylic acid copolymer resin, and the biaxially stretched polystyrene resin film comprises high impact polystyrene, styrene- It contains 2 wt% to 35.0 wt% of at least one copolymer elastomer selected from a conjugated diene copolymer and a styrene-aliphatic carboxylic acid copolymer, and a heat shrinkage stress ratio in the flow direction with respect to the width direction is 3 to 3. 20, the film heat shrinkage stress in the width direction 1000～8000KPa, tear strength of width direction of the film represented by JIS P-8116 is Ri 5~40mN der, wherein the thickness is 5 to 60 m.
2. 1. Vicat softening temperature is 100 to 155 ° C. Film .

3 . The biaxially oriented polystyrene resin film has a HAZE of 50% or less as measured by ASTM-D1003. Or 2 . Film.
4 . 1. A straight tear value in the width direction is 10 mm or less. ~ 3 . The film of any one of these.
5 . 1. ~ 4 . A laminated film, wherein the biaxially stretched polystyrene resin film according to any one of the above and a polyethylene resin film are bonded.
6 . 1. ~ 4 . A laminated film in which the biaxially stretched polystyrene resin film, polyethylene resin film, and aluminum foil according to any one of the above are joined.

  The present invention can provide a film having good tearability in the width direction. More specifically, it is possible to provide a film that can be easily torn by hand in the width direction and linearly torn in the width direction.

The present invention will be described in detail below, focusing on particularly preferred embodiments.
The present invention, heat shrinkage stress ratio in the flow direction from 3 to 20 with respect to the width direction, heat shrinkage stress in the width direction 1000～8000KPa, the width direction of the tear strength of the film represented by JIS P-8116 is at 5~40mN It is a biaxially stretched polystyrene resin film characterized by being.
The Vicat softening temperature of the biaxially stretched polystyrene resin film of the present invention is not particularly limited, but is preferably 100 ° C to 155 ° C, more preferably 110 to 155 ° C, and further preferably 120 to 150 ° C.

The Vicat softening temperature of the film is measured according to ASTM-D-1525. When the Vicat softening temperature is 100 ° C or higher, the rigidity of the film is moderately high, and the tearing straightness and tearing properties (tearability that can be easily torn by hand without notching the film) are particularly good. Become. Moreover, when making a bag for packaging using this film, it is generally subjected to polylamination with a polyethylene film that becomes a heat seal layer. When heat-sealing, etc., heat shrinkage is unlikely to occur in the heat-sealed portion, and bag shape distortion and pinholes are unlikely to occur in the heat-sealed portion.
When the Vicat softening temperature of the film is 155 ° C. or lower, moderate film toughness is obtained, and when an impact is applied to the film, it is not easily broken and pinholes are unlikely to occur. In addition, the straight tearability and tearability of the film are improved.

The polystyrene resin used for the biaxially stretched polystyrene resin film of the present invention may be a styrene resin alone, or various resins and additives as described later may be added to the styrene resin. Preferably, it is a styrene copolymer resin.
The styrene copolymer resin is obtained by copolymerizing a styrene monomer and an arbitrary monomer. Examples of the optional monomer include o-methylstyrene, m-methylstyrene, p-methylstyrene, t-butylstyrene, and α-methyl. Styrene derivatives such as styrene, β-methylstyrene and diphenylethylene, conjugated dienes such as butadiene and isoprene, alkyl-substituted methacrylate compounds such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate and cyclohexyl methacrylate, methyl acrylate, Alkyl-substituted acrylate compounds such as ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate, methacrylic acid, acrylic Examples thereof include vinyl monomers such as acid, maleic anhydride, N-substituted maleimide anhydride, acrylonitrile, methacrylonitrile, chlorostyrene, and bromostyrene. These monomers can be used alone or in combination of two or more. . In the present invention, these styrene copolymer resins may be used alone or in combination of two or more.

In order to give heat resistance and further improve the tearability of the obtained film, styrene-acrylic acid copolymer resin, styrene-methacrylic acid copolymer resin, styrene-maleic anhydride copolymer resin, and styrene- More preferred is at least one copolymer resin selected from α-methylstyrene copolymer resins.
The polymerization rate of styrene in the polystyrene resin is not particularly limited, but is preferably 50 wt% or more.

  What is necessary is just to select suitably the monomer unit content copolymerized with the polystyrene used for this invention. As a preferred resin to be copolymerized with polystyrene, for example, when acrylic acid, methacrylic acid or maleic anhydride is used, the range of 3 to 30 wt% is preferred. Similarly, for example, when α-methylstyrene is used, the range of 9 to 50 wt% is preferable. When these copolymerization ratios are within a preferable range, the rigidity of the resin is high and the tearability is improved. Further, when a film obtained from these resins is joined to a polyethylene resin and heat-sealed, the heat resistance is improved, and there is no generation of wrinkles during heat-sealing, which is preferable.

  The polystyrene resin used in the present invention is preferably amorphous. The structure of the resin is not particularly limited. Examples of the structure include an atactic structure, an isotactic structure, and a syndiotactic structure. Amorphous atactic structure polystyrene is more preferable from the viewpoint of improving the transparency of the film and the processability of the film to a bag or package.

  In the present invention, the term “amorphous” means that the crystallinity is 10% or less. The degree of crystallinity is preferably 5% or less, and the closer to complete amorphousness, the better. The degree of crystallinity can be measured by a differential scanning calorimetry method (DSC method) that can be generally calculated from the crystal melting exotherm. If the polystyrene resin has low crystallinity, it will not be whitened when producing films, and when it is processed with polyethylene resin and polylamination, or when making bags, it does not cause crystallization due to heat, and is highly transparent and tough. Is preferable because of the increase. Furthermore, when it is non-crystalline, it can solve problems such as whitening due to recrystallization when it is processed into a bag, and heat shrinkability and tearability are improved, so that it can be easily torn by hand.

  In this invention, the manufacturing method of a polystyrene-type resin is not specifically limited, A well-known manufacturing method can be used. Examples of general styrene polymer polymerization methods include radical solution polymerization using radical heat and initiator, radical suspension polymerization, radical emulsion polymerization, anionic polymerization using an organometallic compound, and coordination anion using a transition metal complex. There are methods such as polymerization and cationic polymerization using a Lewis acid. Commercially available resins can also be used. For example, as styrene-methacrylic acid copolymer resin, trade name: G9001 manufactured by PS Japan Co., Ltd., Ryulex (registered trademark) A- 14. Examples of styrene-maleic anhydride copolymer resins include DYLARK (registered trademark) 232 and 332 manufactured by NOVA. However, it is not limited to these resins.

The molecular weight of the polystyrene-based resin is not particularly limited as long as a sufficient melt viscosity can be obtained when forming a film. Further, styrene-based low molecular weight components such as monomers, dimers, and trimers remaining in the obtained biaxially stretched polystyrene resin film are not limited. However, when the film is processed into a bag-like material, the content is a pharmaceutical or food. Considering this, the lower one is preferable, and 10,000 ppm or less is preferable.
Various resins may be added to the polystyrene-based resin for the purpose of providing film-forming properties and impact resistance when processed into a film. The various resins may be any resin that is compatible with the polystyrene resin, and examples thereof include ABS resin, PPE resin, polystyrene-based styrene resin having impact resistance, and polystyrene-based elastomer. From the viewpoint of compatibility, polystyrene-based impact-resistant styrene-based resins and polystyrene-based elastomers are preferable.

Polystyrene elastomer is a substance that imparts film-forming properties and impact resistance to polystyrene resin, and generally refers to a substance that has a rubber-elastic part at room temperature. ). The Vicat softening temperature of the polystyrene-based styrene resin or polystyrene elastomer of the present invention is lower than the Vicat softening temperature (105 ° C.) of polystyrene, and generally lower than 90 ° C.
Examples of polystyrene-based impact-resistant styrene-based resins and polystyrene-based elastomers include high-impact polystyrene, styrene-conjugated diene copolymers, styrene-aliphatic carboxylic acid copolymers, and polystyrene. Besides, it may have a soft segment such as polybutadiene, polyisoprene, hydrogenated polybutadiene, hydrogenated polyisoprene, hydrogenated butadiene rubber, etc. It is more possible to add at least one polystyrene elastomer or resin selected from these preferable.

  The addition of the polystyrene-based elastomer may be performed by selecting the type and amount when producing the film, and it is preferable for the party to appropriately select within the scope of achieving the object of the present invention. Styrenic resin with polystyrene-based elastomer or polystyrene-based impact resistance due to film-forming properties when manufacturing film, impact resistance, heat resistance, balance with waist, and impact on transparency. Is preferably added in an amount of 0.5 to 35.0 wt%, more preferably 1.0 to 30.0 wt% in the biaxially stretched polystyrene resin film. When the addition amount is 0.5 wt% or more, the film forming property is stabilized when forming a film, and the impact resistance of the obtained film is improved. When the addition amount is 35.0 wt% or less, the film has good tearability, heat resistance, waist, and high transparency.

It is also effective to add stabilizers such as heat stabilizers, antioxidants, light-proofing agents, and antistatic agents to polystyrene resins in order to increase heat stability, mechanical stability, weather resistance, and light resistance. is there. Examples of heat stabilizers, antioxidants, and light stabilizers include phenolic, amine-based, phosphorus-based, sulfur-based, hindered amine-based stabilizers, and the like, so long as they do not impair the purpose and characteristics of the present invention. It is preferable to add the stabilizer.
In addition to the above stabilizers, known additives such as fine particle antiblocking agents such as inorganic fine particles and organic fine particles, plasticizers, lubricants, colorants, antistatic agents, etc., do not impair the requirements and characteristics of the present invention. You may mix | blend in the range.

The tear strength in the width direction indicated by JIS P-8116 of the biaxially stretched polystyrene resin film of the present invention is 5 to 40 mN. When the tear strength is less than 5 mN, the film is easily broken during processing, and the storage stability in the final product is deteriorated. When the tear strength is 40 mN or more, it becomes difficult to tear and the tearability by hand is inferior. Preferably it is 10-30 mN .

  As an index representing tearability, a method of expressing the orientation of resin molecules using a birefringence index is known (Patent Document 2: Japanese Patent Laid-Open No. 51-124163), and generally anisotropy in tearability. In the case of a film having a film, an attempt is made to express this value. However, in the case of polystyrene resin, optical alignment of the resin occurs in the direction perpendicular to the stretching direction, which is difficult to express with this index, and because of the rigidity of polystyrene resin molecules, the tearability of polystyrene resin film is good It becomes. In addition, it is very different from a polyester film or a polyethylene resin film that is difficult to make an easy-cut film if it does not have anisotropy, and a polystyrene resin film can be used in the present invention without having anisotropy in the orientation of resin molecules. If it is in the range of the heat shrinkage stress, it can be easily torn by hand. Moreover, tearability can also propagate the cut surface of the film linearly, and is the greatest advantage of the polystyrene resin film of the present invention.

In order to improve the tearability in the width direction, which is an important object of the present invention, the heat shrinkage stress of the biaxially stretched polystyrene resin film of the present invention has a heat shrinkage stress ratio of 3 to 20 in the flow direction with respect to the width direction. The heat shrinkage stress in the width direction is 1000 to 8000 KPa.
In order to express the tearability of the biaxially stretched polystyrene film of the present invention, the heat shrinkage stress of the obtained film is an important point (the heat shrinkage stress is measured by a method described later).

  The heat shrinkage stress of the film of the present invention is 1000 to 8000 KPa in the width direction, preferably 1500 to 6000 KPa, and more preferably 2000 to 4000 KPa. The straightness and tearability of tearing are caused by the molecular orientation of the resin. In the present invention, heat shrinkage stress is used as an index that can quantitatively represent the molecular orientation. That is, when the heat shrinkage stress of the polystyrene resin film of the present invention is 1000 KPa or more, since the orientation of the polymer of the resin is sufficiently obtained, the straight tearing property and tearing property of the film are good, and easily A film that can be torn by hand is obtained. In addition, the impact strength and flexural bending strength of the film are good, and the film is easy to handle and process because it is not easily bent or broken against external force. In the case of 8000 KPa or less, the tearability is good and the film is not torn when the film is handled or processed.

  The ratio of the flow direction to the width direction of the heat shrinkage stress of the film of the present invention is 3 to 20, preferably 4 to 10. When the ratio of the heat shrinkage stress is 3 or more, since the orientation of the polymer is aligned in the width direction, it is easy to tear in the width direction, can be easily torn by hand, and can be torn straightly. When the ratio of the heat shrinkage stress is 20 or less, the tearability is moderately good, and the film is not torn during handling or secondary processing.

  There is no particular limitation on the heat shrinkage stress in the film flow direction, but when increasing the stiffness and toughness of the film and when making final products using these films, there is no film tearing or pinholes, In order to increase the processing speed, the heat shrinkage stress in the flow direction is preferably 100 to 1000 KPa. When the heat shrinkage stress in the flow direction is 100 KPa or more, the film is difficult to tear in the flow direction during film formation or during secondary processing. In the case of 1000 KPa or less, the tearability in the width direction and the straightness of tearing are further improved.

The straight tear value of the film of the present invention is preferably 10 mm or less. If the straight tear value is 10 mm or less, the product (for example, a bag) using the film of the present invention can be opened straight, and the contents are not spilled or damaged. Also, when the bag is opened, the tear surface is straight and easy to use.
Although the thermal contraction rate of the biaxially stretched polystyrene resin film used in the present invention is not particularly limited, 0 to 10% is preferable, and 0 to 7% is more preferable. A heat shrinkage of 10% or less is preferred because no wrinkles or the like are generated when the film is processed. Further, the ratio of the heat shrinkage rate to the width direction is not particularly limited, but since the film of the present invention has a high orientation of the resin in the width direction, the heat shrinkage also increases in the width direction. The shrinkage rate is preferably 0 to 7%.

  The thickness of the biaxially stretched polystyrene resin film of the present invention is preferably 5 to 60 μm. More preferably, it is 10-50 micrometers from the balance of tearability and the waist | hip | lumbar property and impact property of a film, More preferably, it is 15-40 micrometers. When the thickness of the film is 5 μm or more, the film is not easily torn, and further, the film is firm and has good workability and workability. When the thickness of the film is 60 μm or less, the film has good tearability and can be easily torn by hand.

  The HAZE of the film of the present invention is preferably 50% or less, more preferably 30% or less. If HAZE is 50% or less, when the film is processed into a product such as a bag, it is preferable because information on the type, color, shape, etc. of the medicine or food contained in the bag can be easily read. In particular, in the case of a bag of a medicine or the like using this film, it is easy to check the contained medicine. Since transparency is an important factor for confirming the identification number and color of a pharmaceutical product, the film is more preferably colorless. However, when aluminum is laminated, transparency is not required.

  The manufacturing method of a biaxially stretched polystyrene resin film is not limited, and can be prepared by a tenter method, an inflation method, or the like. However, in order to improve the tearability (hand tearability) in the width direction in the present invention and to express the straight cut property, the resin is melted and extruded from a T-die or the like, and the raw fabric is flowed with a stretching roll. A tenter method of stretching in the width direction with a tenter after stretching in the direction is preferred, and a tenter method in the flow direction of sequential biaxial stretching is more preferred.

  In order to achieve easy tearing, which is an important object of the present invention, it is necessary to perform biaxial stretching. That is, the present invention uses polystyrene resins and further controls the orientation of the molecules of these resins, so that it can be easily torn in the width direction by hand, and the straightness of tearing in the width direction becomes good. If the orientation of the molecules of the resin is high, it can be easily torn by hand, and the orientation of the molecules in the direction of tearing makes the tear straightness good. In addition, due to the higher order structure of the polystyrene-based resin used, a fine weak portion is created in the film, which becomes a starting point and can be easily torn by hand. By the presence of fine weak portions in the orientation of the resin and the film, the tear portion propagates linearly and the film can be torn straight.

In this invention, the draw ratio which forms a film is not specifically limited. For example, when stretching using a sequential biaxial tenter stretching method, the stretching ratio is preferably 5 times or more in the width direction, and more preferably 6 times or more. On the other hand, 1.3 to 4 times is preferable in the flow direction, and 1.5 to 3 times is more preferable. 2.5-8 are preferable and, as for the ratio of the draw ratio of the width direction with respect to a flow direction, 3-5 are more preferable. A ratio of the draw ratio of 2.5 or more is preferable because the tearability in the width direction is good, the degree of stretch orientation is moderate, and the impact resistance of the film is high. A ratio of the draw ratio of 8 or less is also preferable because the degree of orientation is moderate and the film does not shrink during polylamination processing or bag making processing.

  In the present invention, the stretching temperature for forming the film is not particularly limited. Generally, when the draw ratio is low, the heat shrinkage stress is small, and when the draw ratio is large, the heat shrinkage stress is also large. Even in the case of the same draw ratio, the heat shrinkage stress becomes small when the drawing temperature is high, and the heat shrinkage stress becomes large when the drawing temperature is low. Controlling the stretching temperature and the stretching ratio is an important point in producing a film. When the stretching temperature is low, the melt viscosity of the resin is high, and even when the draw ratio is low, the orientation of the resin molecules is high. On the other hand, when the stretching temperature is high, the melt viscosity of the resin is low, and even when the stretching ratio is high, the orientation of the resin molecules is low. Therefore, the stretching temperature is not limited. In the present invention, it is important to control the orientation of the resin molecules, which is directly related to the heat shrinkage stress of the biaxially stretched polystyrene film. Further, as a method for controlling the heat shrinkage stress, it is also preferable to heat set after obtaining a film. These heat sets may be fixed length or free, and the set temperature may be appropriately selected.

  A laminated film may be obtained by bonding a polyethylene resin film to the biaxially stretched polystyrene resin film of the present invention as a heat seal layer. The method for laminating is not particularly limited. A biaxially stretched polystyrene resin film and a polyethylene resin film prepared in advance may be laminated and laminated, or melted polyethylene may be extruded onto a biaxially stretched polystyrene film and coated (polylamination). From the viewpoint of ease of processing, polylamination is preferred because it is simpler and can further enhance the adhesion of the laminated film. At the time of polylamination, it is preferable to use a film in which the adhesiveness of the biaxially stretched polystyrene film is increased in advance. A method of increasing the activity of polyethylene resin by ozone treatment or radiation treatment (oxidizing the resin layer to be bonded to increase the adhesiveness), or a method of aging the laminated film after laminating (put it in a heat treatment furnace for a while) Is also preferable. The higher the temperature at which the polyethylene-based resin is melt-extruded at the time of polylamination, the higher the adhesiveness, and generally 280 to 300 ° C is preferable.

  In the film of the present invention, an antistatic agent or an antifogging agent may be attached to one side or both sides for the purpose of imparting functions such as antistatic properties, antifogging properties, and oil resistance of products and molded products. Moreover, in order to increase the adhesiveness of the biaxially stretched film with the obtained polystyrene-based resin, it is a more preferable aspect to perform electrical discharge machining such as corona treatment or plasma treatment in order to increase the surface tension and enhance the adhesiveness. is there. Similarly, it is a more preferable aspect that the anchor coating agent is applied in advance before laminating for the purpose of improving adhesiveness. The anchor coating agent is not particularly limited as long as it enhances the adhesion between the polystyrene resin and the polyethylene resin. For example, urethane, imine, butadiene, natural rubber, casein, polyvinyl alcohol, polyacrylamide, Anchor coating agents such as ether-maleic anhydride copolymers, styrene polymers, polyphenylene ether copolymers and the like can be used.

  In the case where the solvent or diluent for dissolving the anchor coating agent is applied to a polystyrene resin, it is more preferable to use an alcoholic or aqueous solvent in order to prevent the film from being violated by the solvent. In any case, the measure for enhancing the adhesiveness should be selected appropriately by the practitioner, whether physically or chemically. Further, for the purpose of producing the final product, the film may be processed on one side or both sides.

  The adhesiveness of the polystyrene resin film of the present invention is preferably 35 mN / m or more, and more preferably 40 mN / m or more, as the surface tension. These surface tension values are achieved by the physical method and / or chemical method described above, but if the adhesiveness is high, the high tearability of the polystyrene-based resin film described above is utilized, and polyethylene The tearability of the film laminated with the base resin film is improved. On the other hand, if the adhesiveness is poor, the tearability of the polystyrene-based resin film is not utilized, and peeling occurs at the interface between the polystyrene-based resin film and the polyethylene-based resin film (delamination occurs), and the tearability of the laminated film is reduced. . A product such as a bag to be finally used may be printed on the surface. In order to improve the printability, it is also preferable to perform physical processing such as electric discharge processing or coating.

  The kind of polyethylene resin used as a heat seal layer is not limited. As the polyethylene resin, linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE) and the like can be used, and a mixture thereof may be used. These resins are heat-sealable ethylene-vinyl acetate copolymers, ethylene-acrylic ester copolymers, and acid copolymer ions for the purpose of increasing adhesion and controlling the softening point and heat seal temperature of the resin. A copolymer of ethylene and an α-olefin produced using a cross-linked product (ionomer) or a single site catalyst (metallocene catalyst) is preferable, and it may be a composition alone or mixed with another olefin resin.

  If the thickness of a polyethylene-type resin film functions as a heat seal layer, the thickness can be selected suitably, Preferably it is 5-70 micrometers, More preferably, it is 10-50 micrometers, More preferably, it is 15-30 micrometers. When the thickness is 5 μm or more, sufficient adhesive strength is obtained, and adhesion failure and pinholes are less likely to occur when a bag is formed. Moreover, when it is 70 micrometers or less, cost is lowered and the tearability of the laminated film is improved.

  The melting point of the polyethylene resin used as the heat seal layer is not particularly limited, but is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, and further preferably 20 ° C. or higher is lower than the Vicat softening temperature of the polystyrene resin. When the temperature is lower by 5 ° C. or more, a wide temperature range capable of heat sealing is obtained, and a good laminated film can be obtained.

  It is preferable that the tensile elongation of the polyethylene resin film to be the heat seal layer is low. When the tensile elongation of the polyethylene resin film is low, it becomes easy to tear the laminated film and the bag made from these. That is, when the elongation of the polyethylene-based resin film is increased and the laminated film is torn, only the film made of the polyethylene-based resin is stretched, peeling occurs between the layers, and the tearability of the biaxially stretched polystyrene-based resin film is present. This hinders the height and makes it difficult to tear. For this reason, the tensile elongation of the polyethylene-based resin film is preferably 900% or less, and more preferably 700% or less. On the other hand, it is better that the elastic modulus of the polyethylene resin film is high, and the obtained laminated film is easy to tear. Therefore, the bending elastic modulus of the polyethylene resin is preferably 50 MPa or more, more preferably 100 MPa or more. These tensile properties are measured according to JIS K7113, and the flexural modulus is measured according to JIS K7203.

  When making a bag-like product using laminated film, if the medicine or food to be put in the bag is in powder form, when filling and packaging, it will prevent the powder from being charged and difficult to enter or fill from the bag In order to make it easy to take out the powder, a method of kneading or coating an antistatic agent in a polyethylene resin or polystyrene resin is a more preferable embodiment. In particular, the antistatic agent is preferably in the inner layer where the contents come into direct contact. Furthermore, if the content is a pharmaceutical product, a method by kneading into a resin is more preferable than a method of applying to the surface, and the content does not remain inside when used. In particular, when the content is a pharmaceutical product, the amount of intake should be limited. Therefore, it is more preferable to apply an antistatic treatment to the inner layer.

  In the present invention, a biaxially stretched polystyrene resin film, a polyethylene resin film, and an aluminum foil are preferably joined to form a laminated film. By arranging the aluminum foil between the biaxially stretched polystyrene resin film and the polyethylene resin film, the moisture-proof effect of the bag made of the laminated film of the present invention can be improved, and the storage stability of the contents can be increased. .

  The aluminum foil used in the present invention is preferably 1N30 in the class shown for aluminum and aluminum alloy foil according to JIS 4160. Aluminum foils are roughly classified into hard foils and soft foils. However, when soft foils are used, it is necessary to consider the rolling oil remaining on the surface because they affect the adhesiveness of the laminated film. The thickness of the aluminum foil is preferably 3 to 70 μm, more preferably 5 to 50 μm, considering gas barrier properties and tearability. Those having a thickness of 3 μm or more have sufficient gas barrier properties and no pinholes. Moreover, the thing of 70 micrometers or less has good tearability, and it becomes easier to tear by hand.

Aluminum foil can be applied with an anchor coating agent such as urethane, imine, or butadiene in the lamination with these films in order to increase the adhesive strength with biaxially stretched polystyrene resin film and polyethylene resin film. preferable.
The aluminum foil and the biaxially stretched polystyrene resin film can be bonded by a wet laminating method, a dry laminating method, a solventless laminating method, an extrusion laminating method, or the like. When the biaxially stretched polystyrene resin film and the aluminum foil are bonded together with an adhesive, it is preferable to apply the adhesive to the aluminum foil side and bond the dried one to the biaxial polystyrene resin film.

  The film of the present invention can be used for products in any field and application as long as it has good tearing properties such as hand tearing and straight cut ability, and the application is not particularly limited. Examples include adhesive tape, bags for medicines and foods, and the like. It is suitable to use as a bag which is long in the flow direction, such as pillow packaging or stick packaging. These bags are long in the flow direction, and the contents are powder cake, granules, liquids and the like. The contents are generally enclosed in the flow direction during the molding of the bag, and the contents can be enclosed at a lower cost. For this reason, in the case of a bag that is long in the flow direction, the opening is generally made in the width direction. In conventional general films and cellophane, even if the film is torn in the width direction, the tear has propagated in the flow direction and the contents have spilled. In order to eliminate this, notches were physically made in the width direction, small cuts and physical defects were made in the film and processed into bags. However, during physical processing such as notching or making small scratches, the contents were affected and the efficiency of making the product was significantly reduced. In particular, a bag of medicines whose amount to be taken into the body is preferable because the unsealed portion can be torn straightly only in the width direction, and there is no spillage of the contents.

  When the film of the present invention is used as an adhesive tape, it can be obtained, for example, by laminating polyethylene, ethylene vinyl acetate copolymer or the like on one side or both sides of the film of the present invention and applying an adhesive to this. The pressure-sensitive adhesive is a pressure-sensitive adhesive having viscoelastic properties even at room temperature, and includes, for example, an adhesive base made of rosin, hydrogenated rosin ester, petroleum resin, etc. on an elastomer base of natural rubber or synthetic rubber. Can generally be used.

  When used for the above purposes and applications, if necessary, gas barrier properties such as water vapor and oxygen can be improved by coating the surface of the film, combining with other films, and the like. For this purpose, a coating such as vinylidene chloride or ethylene vinyl alcohol (EVOH) may be applied, or an evaporation such as aluminum, alumina oxide, or silicon oxide may be applied. Furthermore, you may laminate | stack with films with high barrier properties, such as a cyclic olefin film, such as a nylon film and COC.

Next, although an example and a comparative example explain the present invention, the present invention is not limited to these examples. The film flow direction was MD, and the width direction was TD.
First, a method for producing a film used in Examples and Comparative Examples and a processing method for evaluating the performance of the final product using the obtained film are described.

<Making method of polystyrene resin film>
After a parison extruded from a T-die is stretched with a roll-heated MD stretcher with an extruder having a 65 mmφ screw with L / D = 32, a polystyrene resin is stretched with a tenter and cooled by TD stretching. To obtain the desired film. The thickness of the film is appropriately adjusted according to the die slit width and the draw ratio. The resin composition, die temperature and stretching temperature are shown in Table 1.

<Method for creating laminated film>
One side of the film was electrodischarge processed, the contact angle was 33 degrees as the surface wetting index, and an imine anchor coating agent (EL-420 (trade name) manufactured by Toyo Morton Co., Ltd.) was dried and applied to the electrodischarge processed side of the film. After coating and drying to an amount of about 4 mg / m ² , Suntech L2340 (trade name) manufactured by Asahi Kasei Chemicals Co., Ltd. as a polyethylene resin on the polystyrene film so that the die temperature is 320 ° C. and the thickness is 20 μm. To make a laminated film.

<Making packaging bags>
A packaging bag was prepared with the polyethylene-based resin films of the prototype laminated film facing each other. The bag was long in the MD direction of the film, 10 cm in the MD direction, 5 cm in the TD direction, bent in the TD direction, heat-sealed in three directions, and contained 3 g of salt inside. Heat seal is performed at a seal width of 7 mm, a seal time of 0.2 seconds, a seal strength of 1 kg / cm ² , and a seal temperature of 115 ° C.

Next, evaluation methods and determination criteria used in Examples and Comparative Examples will be described below.
(1) Heat shrinkage stress (ORS)
In accordance with ASTM-D-1504, each sample (biaxially stretched polystyrene resin film) in the TD direction and MD direction is relaxed in a silicone oil bath at a temperature 15 ° C. higher than the Vicat softening point temperature of each resin. Measure the peak value of stress and round off to a positive value.
(2) Vicat softening temperature (hereinafter referred to as Vsp)
Measured in accordance with ASTM-D-1525 (load 9.8 N, heating rate 5 ° C./min).

(3) HAZE
Measured according to ASTM-D1003, rounded to one decimal place.
(4) tear strength of JIS P of the film - conforms to 8116 to prepare a test piece, a measurement of the TD direction and the MD direction of the film. However, the measurement is performed for each film, this measurement is repeated 5 times, and the average value is obtained by an integer value (rounded off to the first decimal place).

(5) Hand tearability of the film The sample size is 100 mm × 100 mm, this is folded in half in the MD direction of the film, and the film is torn by hand perpendicularly to the TD direction of the film from the fold. The feeling of tearing by hand is determined according to the following criteria.
○: tear easily by hand.
Δ: A tear is finally applied by applying force.
X: Not torn.

(6) Straight tear value of film The sample size is set to 50 mm × 100 mm, a sample is prepared according to the tearability evaluation test (JIS P8116), and the MD direction of the film is measured. A notch is made perpendicular to the MD direction at the center of the test piece in the TD direction (50 mm) (position 25 mm from the end), and the test piece is torn in the MD direction (100 mm). Repeat the test a total of 5 times for each sheet. Evaluation is made by measuring the width of the tear start point and end point, calculating the difference (measuring the deviation from the center), and judging according to the following criteria.
○: 0 to 5 mm
Δ: 5 to 10 mm
X: It cut | disconnected on the way, without reaching 10 mm or more or the end point of a test piece.

(7) Cutability (easy opening) of packaging bags made from film
A bag-processed bag 5 sample is cut by hand in the TD direction (TD direction of the film) of the bag, and the one showing the best openability is determined as a standard, and the following evaluation criteria are used. Moreover, the tearing part is implemented from the heat-sealed part and the part which just bent the film.
○: It tears easily.
Δ: A little resistance to tearing.
X: It does not tear easily.

(8) Cutability of packaging bags made from film (straight openability)
Ten samples of the bag-made bag are torn by hand in the direction perpendicular to the edge of the bag, and whether or not the tear surface has propagated linearly in the opening direction is determined according to the following evaluation criteria.
○: All 10 sheets are torn linearly.
Δ: 1 to 2 sheets, the tear plane is shifted.
X: The tear surface is shifted when three or more sheets are used.

(9) Heat shrinkage rate A sample was prepared according to ASTM-D-1504, immersed in a silicone oil bath at a temperature of 120 ° C. for 10 seconds, and the shrinkage rate (from the initial sample length and the sample length after immersion) %).
The evaluation results of Examples and Comparative Examples are shown in Table 2.

[Example 1]
As polystyrene resin, styrene-methacrylic acid copolymer resin manufactured by Dainippon Ink and Chemicals, Lurex (registered trademark) A-14 (crystallinity: 0%) was used, and methyl methacrylate manufactured by PS Japan Co., Ltd. was used. / Butadiene / styrene copolymer elastomer, SX100 (trade name), HIPS and HT478 (trade name) manufactured by PS Japan Co., Ltd. were sequentially chip-blended at a weight ratio of 80:10:10, extruded, and formed by the tenter method. . The film forming conditions are shown in Table 1. The obtained film had a Vicat softening temperature of 128 ° C., and the average film thickness was 22 μm. The resulting film properties (thickness, Vsp, ORS, HAZE, tear strength every time, hand tear resistance, tear linearity) shown in Table 2.
Using this film, a laminated film was prepared and made into a bag under predetermined conditions, and the tearability and tear straightness were evaluated.

[Example 2]
A styrene-methacrylic acid copolymer resin, Rurex (registered trademark) A-14 (crystallinity: 0%) manufactured by Dainippon Ink & Chemicals, Inc. was used as the polystyrene resin to form a film by the tenter method. The film forming conditions are shown in Table 1. Moreover, evaluation similar to Example 1 was implemented and these results are summarized in Table 2.

[Example 3]
PS polystyrene styrene-methacrylic acid copolymer resin, G9001 (trade name) (crystallinity: 0%) was used as the polystyrene resin, and PS Japan butyl acrylate / styrene copolymer elastomer, SC004. (Product name) was high-impact polystyrene (HIPS) manufactured by PS Japan Co., Ltd. and HT478 (product name) were sequentially chip-blended at a weight ratio of 75:10:15, extruded, and formed into a film by the tenter method. The film forming conditions are shown in Table 1. Moreover, evaluation similar to Example 1 was implemented and these results are summarized in Table 2.

[Example 4]
As polystyrene resin, polystyrene resin manufactured by PS Japan: 685 (crystallinity: 0%), high impact polystyrene (HIPS) manufactured by PS Japan, and HT478 (trade name) in that order 98: 2 wt ratio. Chip blending, extrusion, and film formation by the tenter method. The film forming conditions are shown in Table 1. Moreover, evaluation similar to Example 1 was implemented and these results are summarized in Table 2.

[Examples 5 to 7]
Using the same resin as in Example 1, the film was formed by the tenter method while changing the film forming conditions. The film forming conditions are shown in Table 1. Moreover, evaluation similar to Example 1 was implemented and these results are summarized in Table 2.

[Example 8]
Using the film obtained in Example 1, one surface was subjected to electrical discharge machining, and a polystyrene resin film was prepared with a contact angle of 33 degrees as the surface wetting index. Next, an imine anchor coating agent (EL-420 (trade name) manufactured by Toyo Morton Co., Ltd.) is applied to the side of the obtained polystyrene resin film subjected to electric discharge machining so that the dry coating amount is about 4 mg / m ^2. And dried to obtain a polystyrene resin film (PS-8). Next, the same anchor coating agent was applied to 9 μm aluminum foil (SA30 (trade name) manufactured by Sumitomo Light Metal Co., Ltd.) so that the dry coating amount was about 40 mg / m ² and dried (AL-1). Next, between PS-8 and AL-1 obtained, polyethylene as a polyethylene resin, L2340 (trade name) (PE-1), manufactured by Asahi Kasei Chemicals Co., Ltd., was formed so that the temperature immediately below the die was 320 ° C. and the thickness was 15 μm. While ozone treatment was performed on the system resin, it was extruded into a film and PS-1 and AL-1 were sand-laminated. Next, on the aluminum foil of the obtained laminated film (PS-8 / PE-1 / AL-1), the same polyethylene resin as described above was extruded under the same conditions so as to have a thickness of 30 μm, and a heat seal layer (PE- 1 ′) was formed. The obtained laminated film (PS-8 / PE-1 / AL-1 / PE-1 ′) can be easily torn by hand in a direction substantially perpendicular to the TD direction of the film, and the tearing surface can also be straightened. did it.

  The obtained laminated film (PS-8 / PE-1 / AL-1 / PE-1 ′) is combined with the polyethylene side, heat sealed at 150 ° C. for 0.2 seconds, and a four-side sealed bag is obtained. Had made. The bag had a good appearance, and the bag could be easily torn by hand in the direction substantially perpendicular to the TD direction of the film with respect to the heat seal line, and the tear surface could also be torn straight.

[Example 9]
Using the film (PS-9) obtained in Example 3, a laminated film (PS-9 / PE-1 / AL-1 / PE-1 ′) with an aluminum foil interposed as in Example 8 was prepared. did. The obtained laminated film (PS-9 / PE-1 / AL-1 / PE-1 ′) can be easily torn by hand in a direction substantially perpendicular to the width direction of the film, and the tear surface can be torn straightly. did it.
Further, a four-side sealed bag was made from this laminated film in the same manner as in Example 8. The bag had a good appearance, and the bag was easily prepared by hand in the direction substantially perpendicular to the film width direction with respect to the heat seal line, and the tear surface could be torn straight.

[Comparative Example 1]
Cellophane (Futamura Chemical Co., Ltd., Dazai (registered trademark) PF-3, thickness 21 μm) was used instead of the polystyrene resin film, and this was laminated with a polyethylene resin film and polylamination in the same manner as in Example 1. Turned into. Further, this film was used as a bag under predetermined conditions, and the tearing property and straight tearing property were evaluated.
The quality of the bag-making product was good, but the tearability was not good. In particular, tearing by hand from the TD direction of the film could not be torn unless considerable force was applied. When the film was opened from the TD direction, most of the film was not cut straight, the tear surface was bent, and sometimes the contents spilled.

[Comparative Example 2]
Instead of the polystyrene resin film, a polypropylene film (manufactured by Tokyo Cellophane, Tosero OP (registered trademark), thickness 20 μm) was used, and this was laminated with a polyethylene resin film and polylamination in the same manner as in Example 1. Turned into. Using this film, it was made into a bag under predetermined conditions, and the tearability and straight tearability were evaluated.
The appearance of the bag-made product was impaired due to wrinkles on the heat seal surface of the bag. The film can hardly be torn by hand from the TD direction, and can only be torn when the notch is punched. Most of them do not cut straight, and the tear surface is bent or stretched, sometimes the contents Things spilled.

[Comparative Example 3]
As polystyrene resin film, Oishi Sangyo Co., Ltd., Cellomer (registered trademark) 30 (crystallinity: 0%), thickness 30 μm was used, and this was made into a laminated film by polylamination processing in the same manner as in Example 1. The laminated film was made into a bag under predetermined conditions, and tearability and tear straightness were evaluated. As for polyrami, the film shrunk and a good quality was not obtained. Moreover, although bag making was implemented with the obtained laminated | multilayer film, a favorable bag was not obtained, respectively.
Bag-made products can hardly be torn by hand from the TD direction of the film, and can only be torn when the notch is punched. Most of the tear surface is not straight, and the tear surface is extreme. Bent in the MD direction and almost spilled the contents.

[Comparative Example 4]
Using the same resin as in Example 1, the film was formed by the tenter method while changing the film forming conditions. The film forming conditions are shown in Table 1. Moreover, the same evaluation as Example 1 was implemented and these results are summarized in Table 2.

[Comparative Example 5]
Using the same resin as in Example 1, the film was formed by the tenter method while changing the film forming conditions. The film forming conditions are shown in Table 1. Further, the same evaluation as in Example 1 was performed, and the results are summarized in Table 2.

  According to the present invention, a film having high tearability in the width direction of the film can be obtained (can be easily torn by hand and can be torn from the torn portion in a straight line), and therefore tearability is required only in the width direction. Used in food packaging materials, pharmaceutical packaging materials, miscellaneous goods packaging materials, adhesive tapes, etc.

Claims (6)

A biaxially oriented polystyrene resin film,
The polystyrene resin is a styrene copolymer resin composed of a styrene-methacrylic acid copolymer resin,
The biaxially stretched polystyrene resin film comprises 2 wt% to 35.0 wt% of at least one copolymer elastomer selected from high impact polystyrene, styrene-conjugated diene copolymer, and styrene-aliphatic carboxylic acid copolymer. Including
The heat shrinkage stress ratio in the width direction with respect to the flow direction is 3 to 20, the heat shrinkage stress in the width direction is 1000 to 8000 KPa, the tear strength in the width direction of the film represented by JIS P-8116 is 5 to 40 mN, and the thickness is 5 A film, which is ˜60 μm.   The Vicat softening temperature is 100 to 155 ° C.   3. The film according to claim 1, wherein the biaxially stretched polystyrene resin film has a HAZE of 50% or less as measured by ASTM-D1003.   The film according to any one of claims 1 to 3, wherein a straight tear value in the width direction is 10 mm or less.   The laminated film characterized by joining the biaxially-stretched polystyrene-type resin film of any one of Claims 1-4, and a polyethylene-type resin film.   A laminated film, wherein the biaxially stretched polystyrene resin film, polyethylene resin film, and aluminum foil according to any one of claims 1 to 4 are joined.