JP2003073486A - Heat-shrinkable polystyrene-based resin film, label and container using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable polystyrene-based resin film suitable for packaging to be used for wrapping, bundling, external package, etc., of containers or the like having especially low optimum temperature range of shrinkage, excellent adaptability to an aseptic filling packing or a short time packing, further having appropriate stiffness in a proprietary processing stage such as fitting stage in which the film is put over a bottle, and to provide a label and a container using the film. SOLUTION: This heat-shrinkable polystyrene-based resin film is characterized in that the heat shrinkage expressed by the change rate in length in the principal shrinking direction after the treatment of dipping in a warm water of 65 deg.C for 10 seconds to that before the treatment is >=5%, and the vertical compressive force in a cylindrical body is >=5,000 mN when the film is formed in a label form with 175 mm layflat size and 120 mm in the direction perpendicular to the principal shrinking shrinking direction axis, and is made the label into the cylindrical body having a square bottom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polystyrene resin film suitable as a packaging material used for covering, binding, and packaging containers, etc. Heat-shrinkable polystyrene-based resin film, which has excellent flexibility for packaging and has a waist strength that is suitable when undergoing a specific process such as mounting on a bottle, label and container using the same Regarding

[0002]

2. Description of the Related Art Since a heat-shrinkable film has a function of shrinkability, it does not use a fixing means such as an adhesive or a fastener,
It can be laminated and integrated with an object by the shrinkage force and shapeability of the film itself. Therefore, it not only has a function of mechanically protecting the object by stacking or coating, but also has a function of binding and sealing. Further, when the heat-shrinkable film itself has a special function, the special function can be added to the object later by laminating. This property is effectively used in the packaging field whose main purpose is to protect objects during storage and distribution, and to impart displayability and design. For example, bottles including glass and plastic bottles, various containers such as cans, and long objects such as pipes, rods, wood, various rod-shaped bodies, or sheet-like bodies for covering, binding, and exterior. It is used as a seal or a seal. In particular,
It is used for covering a part or the whole of the cap, shoulder, and body of a bottle for the purpose of labeling, protection, bundling, and enhancement of commercial value through functionalization. further,
It is also used for the purpose of packing a plurality of items to be packed such as boxes, bottles, plates, rods, notebooks, etc., and for the purpose of bringing a film into close contact with the item to be packed and packaging it with the film (skin package). . At this time, when the film is preliminarily displayed and shaped for the purpose of design, it becomes a product called a label.

Materials for the heat-shrinkable film include polyvinyl chloride, polystyrene, polyester, polyamide,
Aliphatic polyolefins and their derivatives, hydrochloric acid rubber, etc. are used. Usually, a film made of these materials is formed into a tube shape, for example, by covering it with a bottle,
After accumulating pipes, etc., they are heat-shrinked to be packaged and bound. However, conventional heat-shrinkable films have poor heat resistance and cannot withstand boil treatment or retort treatment at high temperatures, and therefore cannot be sterilized at high temperatures when applied to food, hygiene products, and pharmaceutical applications. There are drawbacks. For example, when the retort treatment is performed, the conventional film has a problem that it is easily damaged during the treatment.

In the case of a conventional heat-shrinkable film, a film made of a polyvinyl chloride resin has a very good heat-shrinkage property, but has a poor adhesion to ink during printing such as a label. Since it is easy to form a gel material of the additive to be added when forming a film, pinholes are easily generated on the printed surface. Furthermore, there is a problem that disposal and incineration are difficult from the environmental point of view. A film made of a polyester resin is excellent in heat resistance, dimensional stability, solvent resistance, etc., but it requires precise control of manufacturing conditions in order to achieve desired heat shrinkage characteristics, adhesiveness, etc. There were problems such as cost.

Further, because of the usefulness of the heat-shrinkable film, the heat-shrinkable film has come to be used also in the field where films and labels which are not heat-shrinkable films have been used conventionally. In particular, many labels for beverage containers have been replaced with a heat-shrinkable label from a sticking label made of paper or a film that is not a heat-shrinkable film. In particular,
In the field of labels for plastic bottle containers, the application of heat-shrinkable labels has been active in connection with the problem of recycling, and various forms and methods of packaging design have been implemented. Among them, the low temperature wet heat shrinkage process is the latest clean technology, sterilization technology,
This is a process used for aseptic filling and packaging made possible by a combination of high-speed packaging technology, etc., which allows sterilization of beverages etc. for a short period of time and then completes the packaging in a relatively short time at a relatively low temperature. It is possible to prevent the heat deterioration of the contents and improve the packaging efficiency. The heat-shrinkable film that can be used in the low temperature wet heat shrinkage process needs to have excellent shrinkability in the low temperature range, and the relatively high shrinkage rate is also advantageous from the viewpoint of shortening the process passage time. Conventionally, a heat-shrinkable polyester-based resin film has been used as a film having such characteristics, but when it is necessary to separately collect bottles and labels, it is difficult to separate the heat-shrinkable polystyrene-based polystyrene film. The use of resin films has been sought. However, conventional polystyrene resins have a glass transition temperature of around 100 ° C. and are inferior in low-temperature shrinkability. A method for solving this problem has been attempted. However, there have been problems such as a large natural shrinkage and a decrease in heat resistance after shrinking and mounting.

Further, the packaging line using the heat-shrinkable film tends to be speeded up, and as a tube-shaped label shape, the label is opened in a cylindrical shape, and a low-temperature shrinkable type film is often used in a mounting process for covering the bottle. In the case of so-called weak film, the label is attached in a bent state due to the impact when it contacts the bottle, or in the worst case, the label is compressed between the attachment device and the bottle and becomes a buckled state, and it is attached. In some cases it was impossible.

[0007]

DISCLOSURE OF THE INVENTION The present invention has a waist strength suitable for a peculiar process such as a mounting process for covering a bottle, excellent low temperature shrinkability, and heat shrink even in the low temperature shrink process. The heat-shrinkable polystyrene resin film has a sufficiently high rate, does not cause uneven shrinkage in the film during heat shrinkage, has a beautiful appearance, and retains its appearance stably even after being exposed to high temperature conditions after shrinking. , And a label and a container using the same.

[0008]

According to the present invention, in the main shrinkage direction, the heat shrinkage ratio shown by the rate of change in length after the process of dipping in hot water at a temperature of 65 ° C. for 10 seconds before the process is 5%.
When the label has a folding diameter of 175 mm and a length of 120 mm in the direction orthogonal to the main contraction axis direction, and the label has a rectangular bottom surface, the vertical compression strength of the cylinder is 5000 mN or more. In the measurement of the dynamic viscoelasticity of the heat-shrinkable polystyrene-based resin film characterized by being present, and at least one layer constituting the film or film, in the temperature range where the alpha dispersion derived from polystyrene is measured, other than alpha dispersion Dispersion was measured, folding diameter 175 mm, length 1 in the direction orthogonal to the main contraction axis direction
When the label has a shape of 20 mm and the label has a rectangular bottom surface, the vertical compressive strength of the cylinder is 5000.
A heat-shrinkable polystyrene-based resin film characterized by having a mN or more, and a label and a container using these.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The constitution of the polystyrene resin constituting the film of the present invention is not particularly limited as long as the shrinkage characteristics described later can be exhibited, but it is preferable to use a polystyrene resin having a syndiotactic structure. It is preferable that the contained polystyrene resin. More preferably,
As the polystyrene resin, it is preferable to use a polystyrene resin having a syndiotactic structure. By using a polystyrene resin having a syndiotactic structure, mechanical strength and heat resistance are improved. By using such a polystyrene-based resin, the density of polystyrene is low, and in addition to being advantageous for separation in the recycling step, it is excellent in heat resistance, particularly heat resistance during heat storage, and after the film formation, Changes in the printing pitch due to contraction are reduced, and high-precision printing can be performed as a label. Further, the durability against the solvent contained in the printing ink is improved, and the printability is excellent.

The polystyrene resin having the syndiotactic structure is preferably 75 diads (two constitutional units) in the tacticity of quantifying side chain phenyl groups and / or substituted phenyl groups by a nuclear magnetic resonance method. % Or more, more preferably 85% or more, and pentad (5 units) is preferably 30% or more, more preferably 50% or more.

As the polystyrene component constituting the polystyrene resin used in the present invention, polystyrene, poly (p-, m-, or o-methylstyrene), poly (2,4-, 2,5-, 3, 4- or 3,5-dimethylstyrene), poly (p-tertiarybutylstyrene), and other poly (alkylstyrene), poly (p-, m)
-Or o-chlorostyrene), poly (p-, m-,
Or poly (halogenated styrene) such as o-bromostyrene), poly (p-, m-, or o-fluorostyrene), poly (o-methyl-p-fluorostyrene), poly (p-, m-, Or poly (halogenated substituted alkylstyrene) such as o-chloromethylstyrene), poly (p
-, M-, or o-methoxystyrene), poly (p
-(M-, or o-ethoxystyrene) or other poly (alkoxystyrene), poly (p-, m-, or o-carboxymethylstyrene) or other poly (carboxyalkylstyrene) poly (p-vinylbenzylpropyl ether) ) Etc., poly (alkyl ether styrene), poly (p
-Trimethylsilylstyrene) and other poly (alkylsilylstyrenes), as well as poly (vinylbenzyldimethoxyphosphide) and the like.

The heat-shrinkable polystyrene-based resin film of the present invention is a plasticizer for the polystyrene-based resin forming at least one layer of the film for the purpose of lowering the heat-shrinking start temperature and improving impact resistance. It is preferable that the compatibilizing agent and the like be used during polystyrene polymerization or blended with the polymer.

In the present invention, it is particularly preferable to add a thermoplastic resin and / or a rubber component to the polystyrene resin constituting at least one layer of the film. Examples of the thermoplastic resin include polystyrene-based resins having an atactic structure such as polystyrene, AS resin and ABS resin, polyester-based resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate, nylon 6, nylon 66,
Examples thereof include polyamide resins such as nylon 12, nylon 4 and polyhexamethylene adipamide, and polyolefin resins such as polyethylene, polypropylene and polybutene. The rubber component is preferably a rubbery copolymer containing a styrene compound as its constituent component, and examples thereof include random, block or graft copolymers obtained by copolymerizing at least one selected from styrene and the rubber component. . Examples of such a rubber-like copolymer include styrene-butadiene copolymer rubber, styrene-isoprene block copolymer, rubber obtained by hydrogenating a part or all of these butadiene moieties, methyl acrylate-butadiene- Examples thereof include styrene copolymer rubber, acrylonitrile-butadiene-styrene copolymer rubber, acrylonitrile-alkyl acrylate-butadiene-styrene copolymer rubber, and methyl methacrylate-alkyl acrylate-butadiene-styrene copolymer rubber. The above rubber-like copolymer containing a styrene compound as its constituent component has a styrene unit,
The dispersibility in polystyrene resin mainly having a syndiotactic structure is good, and as a result, the effect of improving physical properties in polystyrene resin is large. In particular, as the compatibility modifier, a rubbery copolymer containing the above-mentioned styrene compound as its constituent component is suitable.

Other rubber components include natural rubber, polybutadiene, polyisoprene, polyisobutylene, neoprene, ethylene-propylene copolymer rubber, urethane rubber, silicone rubber, acrylic rubber, polyether-
Ester rubber, polyester-ester rubber and the like can be used.

The weight average molecular weight of the polystyrene resin constituting the film of the present invention is preferably 10,000 or more, more preferably 50,000 or more. When the weight average molecular weight is less than 10,000, the strength / elongation property and heat resistance of the film are likely to decrease. The upper limit of the weight average molecular weight is not particularly limited, but if it is 1,500,000 or more, breakage may occur due to an increase in stretching tension, so that it is preferably less than 1,500,000.

The heat-shrinkable polystyrene resin film of the present invention is used for improving electrostatic adhesion, slipperiness, stretchability, processability, impact resistance, etc., roughening, opacifying, and hollowing. , Other resins, plasticizers, compatibility modifiers, inorganic particles, organic particles, colorants, antioxidants, for the purpose of weight reduction,
An antistatic agent or the like can be appropriately added.

As the material constituting the film of the present invention,
By using a polystyrene resin as described above,
Excellent in various heat shrinkage properties, excellent printability such as adhesion to ink when forming a label, and no pinholes are formed on the printed surface of the film. Furthermore, it has excellent disposability and has little impact on the environment when incinerated.

The heat-shrinkable polystyrene resin film of the present invention preferably has a multi-layer structure of two or more layers. By adopting a multi-layer structure, uniform shrinkability, heat resistance under high temperature conditions after shrinkage, and waist strength are improved. In particular, the heat-shrinkable polystyrene-based resin film of the present invention preferably has a multilayer structure of two or more layers each made of a polystyrene-based resin, and at least one layer contains a polystyrene-based resin having a syndiotactic structure. preferable.

In the case of a multi-layered structure having two or more layers, the laminating method is not particularly limited,
The films may be formed separately and then laminated. When laminating after film formation separately, before or after stretching the film, a coating method of applying a resin dissolved in the film, a dry laminating method of adhering a plurality of films or sheets, a thermal laminating method, an extrusion method to the film Examples thereof include an extrusion laminating method of laminating, and when laminating simultaneously with film formation, a method of melt coextruding a plurality of layers (CCF method) and the like can be mentioned. When each layer is made of a resin having physical properties close to each other, a method of laminating by a CCF method before stretching the film is preferable.

In the case of a multilayer structure having two or more layers, the layer structure and thickness ratio of each layer are not particularly limited, but when the surface layer has three or more layers and each surface layer is made of a resin having the same composition, the central layer is the surface layer. It is preferably thicker.

The polystyrene resin constituting the film of the present invention as described above is formed into a film by a conventionally used method such as an extrusion method or a calender method. The shape of the film is, for example, a plane shape or a tube shape, and is not particularly limited. As the stretching method, conventionally used methods such as a roll stretching method, a long gap stretching method, a tenter stretching method and a tubular stretching method can be used. In any of the above methods, stretching may be performed by sequential biaxial stretching, simultaneous biaxial stretching, uniaxial stretching, or a combination thereof. In the above-mentioned biaxial stretching, stretching in the longitudinal and transverse directions may be performed simultaneously, but sequential biaxial stretching in which either one is performed first is effective, and the longitudinal and lateral directions may be performed first. Preferred conditions for producing the heat-shrinkable polystyrene resin film of the present invention are shown below.
The draw ratio is preferably 1.0 to 6.0 times,
The predetermined one direction magnification and the direction orthogonal to the predetermined direction may be the same or different. In the stretching step, the glass transition temperature (Tg) of the resin forming the film
Preheating is preferably performed at a temperature of (Tg + 50) ° C. or less. In heat setting after stretching, after stretching, 30 ° C
It is preferred to pass a heating zone of ~ 150 ° C for about 1 to 30 seconds. Further, after the film is stretched and before or after the heat setting, the relaxation treatment may be performed to an appropriate degree. Further, after the stretching, a step of cooling the film while applying a stress to the film while keeping it in a stretched or tensioned state, or a cooling step after releasing the tensioned state following the treatment may be added.

The total thickness of the heat-shrinkable polystyrene resin film of the present invention is not particularly limited, but is 6 to 250 μm.
The range is preferably.

The heat-shrinkable polystyrene-based resin film of the present invention has a primary shrinkage direction of 1 in hot water of 65.degree.
The heat shrinkage ratio, which is indicated by the rate of change in length after the treatment of dipping for 0 seconds before the treatment, is 5% or more. Preferably, the heat shrinkage is 10% or more, more preferably 20% or more. When the heat shrinkage is less than 5%, the low temperature shrinkability is lowered, and the heat shrinkable polystyrene resin film of the present invention cannot be used for aseptic filling packaging and the like.

As a method for obtaining the desired heat shrinkage ratio, the glass transition temperature of the film is lowered by selecting the kind and compounding ratio of the polystyrene resin constituting the heat shrinkable film, and mixing the additive components. Further, a decrease in the stretching temperature corresponding to the glass transition temperature and the like can be mentioned. When the resin composition constituting the film is a completely compatible system, the glass transition temperature becomes a weighted average value of each constituent component, so that the use of additional components is increased in order to lower the glass transition temperature to the shrinking process temperature region. , Heat resistance and dimensional stability tend to decrease. When the resin composition that constitutes the film is an incompatible system, it shrinks near the glass transition temperature of the polystyrene resin, which is the main component, but using a modifier for compatibility adjustment, the dispersed state of the components By adjusting
The glass transition temperature of the film can be lowered to the glass transition temperature of the additive component while maintaining the heat resistance of the polystyrene resin.

The heat-shrinkable polystyrene resin film of the present invention has a label shape having a folding diameter of 175 mm and a length of 120 mm in a direction perpendicular to the main shrinkage axis direction, and the label is a cylinder having a square bottom surface. The vertical compressive strength of the body must be 5000 mN or more. Compressive strength is 50
When it is less than 00 mN, it becomes unusable due to a tubular label shape, the label is opened into a cylindrical shape, and in the mounting step of covering the bottle, the label is bent or the buckling state between the mounting device and the bottle causes the label to become unmountable. Become. When the compressive strength is 6000 mN or more, it is possible to prevent displacement of the label due to deformation such as slight bending of the waist, which is preferable.

As a method of setting the compressive strength to the above range method, for example, a method of increasing the film thickness can be mentioned, but from the viewpoint of cost, the film thickness is 65 μm.
It is preferably not more than 55 μm, more preferably not more than 55 μm, and particularly preferably not more than 45 μm in consideration of transparency. Therefore, in order to set the compressive strength to the above range method, a method of hardening the raw material resin, for example, adjustment of the type and compounding ratio of the resin constituting the heat-shrinkable film, and two layers made of a resin having each characteristic The method of making the above-mentioned multilayer structure is mentioned. There is also a method of using a resin with high stereoregularity, but in order to maintain low temperature shrinkability and high shrinkability, a method of adjusting the type and mixing ratio of the resin, especially the type and mixing ratio of the rubber component such as SBR. And a method of forming a multilayer structure is preferable.

In the heat-shrinkable polystyrene resin film of the present invention, at least one layer constituting the film or the film is in a temperature range in which the alpha dispersion derived from polystyrene is measured in the measurement of dynamic viscoelasticity, and other than alpha dispersion. Dispersion is measured, and the label has a folding diameter of 175 mm and a length of 120 mm in a direction orthogonal to the main contraction axis direction, and the label has a rectangular bottom surface, the vertical compression strength of the cylinder body is It may be a heat-shrinkable polystyrene resin film of 5000 mN or more. Nakatani,
Proceedings of the 44th Rheology Conference, Yamada, et al. (19
96) According to pages 169 to 172, a heat-shrinkable polystyrene resin film in which dispersion other than alpha dispersion is measured, shrinks together with alpha dispersion, that is, relaxation dispersion causing the heat shrinkage phenomenon, and at the end of shrinkage. Dispersion occurs in the vicinity due to crystallization or generation of gel-like structure. When dispersion occurs due to crystallization, generation of gel-like structure, etc., heat resistance and dimensional stability after shrinkage are excellent. Dispersions other than alpha dispersion are often found in syndiotactic polystyrene and its copolymers.

In the dynamic viscoelasticity measurement of the film or at least one layer constituting the film, a heat-shrinkable polystyrene resin film in which dispersion other than alpha dispersion is measured in a temperature range where alpha dispersion derived from polystyrene is measured. Has at least one layer obtained by stretching an unstretched sheet for which dispersion other than alpha dispersion is measured in a temperature region where alpha dispersion derived from polystyrene is measured in dynamic viscoelasticity measurement.

The heat-shrinkable polystyrene resin film of the present invention is preferably used in the temperature range in which alpha dispersion derived from polystyrene is measured in the dynamic viscoelasticity measurement of the film or at least one layer constituting the film. Dispersions other than the dispersion were measured, and in the main shrinkage direction, the heat shrinkage ratio indicated by the length change rate after the process of dipping in hot water at a temperature of 65 ° C. for 10 seconds before the process was 5% or more, and the fold diameter was 175 mm. When the label has a length of 120 mm in a direction perpendicular to the main contraction axis direction and the label is a rectangular bottomed cylinder, the vertical compression strength of the cylinder is preferably 5000 mN or more.

The heat-shrinkable polystyrene resin film of the present invention has a primary shrinkage direction of 1 at every 70 ° C to 10 ° C.
The maximum heat shrinkage rate, which is the maximum value of the rate of change in length with respect to the length before the treatment, after the treatment of heating for 1 minute at each temperature up to 00 ° C. is preferably 40% or more. When the maximum heat shrinkage ratio is less than 40%, the shrinkage is insufficient when used as a label (body label) for a body portion of a bottle that is generally used, and it becomes difficult to adhere the bottle to the bottle. More preferably, the maximum heat shrinkage is 50% or more. PE with high shrinkability if the maximum heat shrinkage is 50% or more
Even when used as a T bottle label, insufficient shrinkage does not occur. The maximum heat shrinkage is more preferably 60% or more, and particularly preferably 70% or more. When the maximum heat shrinkage ratio is within the above range, insufficient shrinkage does not occur even as a full label for a container having a complicated shape.

Examples of the method for setting the maximum heat shrinkage ratio within the above range include, for example, adjusting the type and blending ratio of the resin forming the heat shrinkable film, especially the compatibility state of the materials forming the heat shrinkable film, Examples of the method include adjusting the production conditions of the film, particularly increasing the stretching ratio, reducing heat setting, and performing crystallization treatment during preheating and then stretching to increase the strain of the polymer chain.

The heat-shrinkable polystyrene resin film of the present invention is preferably used as a packaging material used for covering, binding, and packaging containers and the like, and a beautiful appearance can be obtained by using the film of the present invention. it can. In particular, the label composed of the film of the present invention has excellent coverage and is suitable for packaging containers. Further, the heat-shrinkable polystyrene-based resin film of the present invention has excellent applicability to a heat storage container, and a container equipped with a label composed of the film of the present invention is exposed to high temperature conditions after shrinkage. Even if it is, the label keeps its appearance stable.
Further, it has a waist strength suitable for a specific process such as a mounting process for covering a bottle, and an excellent shrink finish appearance can be obtained even after a high-speed packaging process. Further, it has excellent low-temperature shrinkability, and has excellent applicability to aseptic filling packaging and short-time packaging.

The present invention will be described in more detail below with reference to test examples and examples, but the present invention is not limited to these.

Test Example 1. Test method Compressive strength The heat-shrinkable polystyrene resin films of Examples 1 to 6 and Comparative Examples 1 to 3 were formed into a label shape having a folding diameter of 175 mm and a length of 120 mm in a direction orthogonal to the main shrinkage axis direction (non-shrinkage direction). Then, five pieces of cylinders each having a quadrangular bottom face were prepared by folding the label. Vertical compression strength of each cylinder (unit:
mN) is a strograph (manufactured by Toyo Seiki Co., Ltd., model: V
10-C), the compression mode was measured at a crosshead speed of 200 mm / min, and the maximum value was taken as the compression strength of the film.

(2) Heat Shrinkage Ratio The heat shrinkable polystyrene resin films of Examples 1 to 6 and Comparative Examples 1 to 3 have a width of 15 with the main shrinkage direction as the longitudinal direction.
The test piece was cut into pieces each having a length of 200 mm, and marked lines were set at intervals of 200 mm in the longitudinal direction. The test piece was immersed in warm water of a water bath set at a temperature of 65 ° C. for 10 seconds. The distance (X: unit mm) between the marked lines was measured, and the rate of change in length D (unit%) after the treatment with respect to the length before the treatment was calculated using the following formula 1. Also, "main contraction direction"
Was measured in the machine direction and the transverse direction of the film, and the following maximum heat shrinkage was measured, and the direction in which the maximum heat shrinkage was large was taken as the main shrinkage direction. In the films of Examples and Comparative Examples, the lateral direction was the main shrinkage direction. D (%) = [(200−X) / 200] × 100 Formula 1

(3) Maximum Heat Shrinkage Ratio The heat shrinkable polystyrene resin films of Examples 1 to 6 and Comparative Examples 1 to 3 were each made to have a width of 15 mm with the longitudinal direction and the transverse direction of the film as the longitudinal directions. The test piece was cut and marked with marks at 200 mm intervals in the longitudinal direction.
The test piece was placed in the center of the incubator in a hot air circulation type incubator (manufactured by Peng Co., Ltd., FX-1: damper closed, quick heater ON) set to each temperature from 70 ° C to 100 ° C in every 10 ° C. Were allowed to stand and were heated for 1 minute. After the test piece was taken out of the incubator and cooled, the distance between the marked lines (X ': unit mm) was measured, and the length change rate D' (unit:%) after the treatment to the length before the treatment was measured. It was calculated using the following Equation 2. The maximum value of the length change rate D ′ was defined as the maximum heat shrinkage rate. D ′ (%) = {(200−X ′) / 200} × 100 Formula 2

(3) Dynamic Viscoelasticity Each unstretched sheet obtained in the process of producing the heat-shrinkable polystyrene resin film of Examples 1 to 6 and Comparative Examples 1 to 3 was
Width 5 mm, measurement part length 30 with MD direction as longitudinal direction
A test piece was cut to have a size of mm. About the test piece, expansion mode, frequency 50 Hz, -20 to 250 ° C
The dynamic viscoelasticity was measured under the conditions of the temperature range and the heating rate of 2 ° C./min, and the presence or absence of dispersion other than the alpha dispersion was confirmed in the temperature region where the alpha dispersion derived from polystyrene was measured.

(4) Shrinkage unevenness The heat-shrinkable polystyrene-based resin films of Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to metallic back-printing to give a size for a rectangular heat-resistant PET bottle label (main shrinkage direction is It has a circular cross section, and the length in the direction perpendicular to the main contraction direction is 1
The label was formed by forming a tube into a cylindrical shape (6 cm).
The label was put on a 350 cc square heat-resistant PET bottle up to the neck and passed through a shrink tunnel. The conditions in the shrink tunnel were such that the first zone was 70 ° C. and the residence time was 4.5 seconds, and the second zone was 80 ° C. and the residence time was 5 seconds. After passing through the shrink tunnel, the print density due to uneven shrinkage of the heat-shrinkable label was visually evaluated according to the following criteria. ⊚: Defects such as unevenness, wrinkles, and looseness are not recognized, and very good ○: Defects such as unevenness, wrinkles, and looseness are hardly recognized, and good Δ: Defects such as unevenness, wrinkles, and looseness are clearly recognized Poor, bad; many defects such as unevenness, wrinkles, looseness, etc.

2. Test results Table 2 shows the results of the above tests (1) to (4).

[0040]

EXAMPLES [Raw material resin] Each resin composition (compositions A to H) having the composition shown in Table 1 was previously compounded and melt-kneaded.
It was extruded, pelletized, made into chips and dried.

Example 1 Composition B and Composition G in Table 1 were each 30 m
The composition B was charged into a single-screw extruder of mφ, and the composition B was added to the central layer (b
Layer) and the composition G constitutes three layers which are both surface layers (a layer, c layer), and the thickness ratio is a layer: b layer: c layer = 1: 4: 1. Melt-extruded at 255 ° C., adhered to a 40 ° C. cooling roll by an air knife method, and cooled and solidified to obtain an amorphous sheet. The amorphous sheet was preheated to 110 ° C., stretched at a stretching temperature of 80 ° C. in the transverse direction at a draw ratio of 6.0 times, and then heat-set at 60 ° C. for 15 seconds to obtain a heat-shrinkable film having a thickness of 50 μm. Got
An image was formed on the entire surface of one side of the film by halftone printing and used as an example.

Example 2 Composition B and Composition A in Table 1 were each 30 m
The composition B was charged into a single-screw extruder of mφ, and the composition B was added to the central layer (b
Layer) and the composition A was configured to form three layers which are both surface layers (layer a, layer c), and a heat-shrinkable film having a thickness of 50 μm was obtained in the same manner as in Example 1.

Example 3 Composition C and Composition A in Table 1 were each 30 m
The composition C was charged into a single-screw extruder of mφ, and the composition C was added to the central layer (b
Layer) and the composition A was configured to form three layers which are both surface layers (layer a, layer c), and a heat-shrinkable film having a thickness of 50 μm was obtained in the same manner as in Example 1.

Example 4 Composition D and Composition A in Table 1 were each 30 m
The composition D was charged into a single-screw extruder of mφ, and the composition D was added to the central layer (b
Layer) and the composition A was configured to form three layers which are both surface layers (layer a, layer c), and a heat-shrinkable film having a thickness of 50 μm was obtained in the same manner as in Example 1.

Example 5 Composition E and Composition A in Table 1 were each 30 m
The composition E was charged into a single-screw extruder of mφ, and the composition E was added to the central layer (b
Layer) and the composition A was configured to form three layers which are both surface layers (layer a, layer c), and a heat-shrinkable film having a thickness of 50 μm was obtained in the same manner as in Example 1.

Example 6 Composition F and composition A in Table 1 were each 30 m
The composition F was put into a single-screw extruder of mφ, and the composition F was mixed with the central layer (b
Layer) and the composition A was configured to form three layers which are both surface layers (layer a, layer c), and a heat-shrinkable film having a thickness of 50 μm was obtained in the same manner as in Example 1.

Comparative Example 1 Only the composition F in Table 1 was charged into a single-screw extruder having a diameter of 30 mm, and the center layer (layer b) and both surface layers (layer a,
A heat-shrinkable film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the three layers (c layer) were formed.

Comparative Example 2 Only the composition G in Table 1 was charged into a single-screw extruder having a diameter of 30 mm, and the center layer (layer b) and both surface layers (layer a).
A heat-shrinkable film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the three layers (c layer) were formed.

Comparative Example 3 Only the composition H in Table 1 was charged into a single screw extruder having a diameter of 30 mm, and the central layer (layer b) and both surface layers (layer a,
A heat-shrinkable film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the three layers (c layer) were formed.

[0050]

EFFECTS OF THE INVENTION The heat-shrinkable polystyrene resin film of the present invention has a waist strength suitable for a specific process such as a mounting process for covering a bottle, and a sufficient heat shrinkage rate in the low-temperature shrinkage process. When heat-shrinking, the film uniformly shrinks regardless of temperature fluctuations and non-uniformity in the shrinking step, so that uneven shrinkage does not occur and a beautiful appearance is exhibited. Even after being exposed to high temperature conditions after shrinkage, slack and wrinkles do not occur, its appearance is stably maintained, and it can be suitably used when it is attached to a container as a label and used.

[Table 1] Rubber component (G) G1: Styrene (25 wt%)-butadiene block copolymer modifier: Compatibility modifier, 5 parts by weight compounding lubricant: 1 μm diameter, 0.05 parts by weight compounding

[Table 2]

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B29K 25:00 B29K 25:00 105: 02 105: 02 B29L 7:00 B29L 7:00 9:00 9:00 C08L 25:04 C08L 25:04 (72) Inventor Satoshi Hayakawa 344 Maebata, Kizu character, Inuyama City, Aichi Prefecture Toyobo Co., Ltd. Inuyama factory (72) Inventor Nori Tabota Kizu, Inuyama City, Aichi Prefecture 344 Maebatahata Toyobo Co., Ltd. Inuyama Factory (72) Inventor Shigeru Yoneda 2-8 Dojimahama 2-chome, Kita-ku, Osaka City, Osaka Prefecture Toyobo Co., Ltd. (72) Inventor Katsuhiko Nose Osaka City, Kita Osaka 2-8-2 Dojimahama-ku, Toyobo Co., Ltd. Main company F-term (reference) 3E062 AA09 AC02 JA01 JA08 JB05 JB26 JC07 4F071 AA22 AF18Y AF61Y AH04 BA01 BC01 4F100 AK12A AK12B AK12C BA03 BA06 BA10B BA1 0C BA16 EH20 EJ38 GB16 GB90 JA03 YY00 4F210 AA13 AE01 AG01 AG03 RA03 RC02 RG02 RG04 RG09 RG43

Claims (10)

[Claims] 1. In the main shrinkage direction, the heat shrinkage ratio, which is represented by the rate of change in length after the process of dipping in hot water at a temperature of 65 ° C. for 10 seconds before the process, is 5% or more, and the fold diameter 175.
mm, a length of 120 mm in a direction perpendicular to the main contraction axis direction, and when the label has a rectangular bottom surface, the vertical compression strength of the cylinder is 5000 mN or more. Heat shrinkable polystyrene resin film. 2. In the main shrinkage direction, the heat shrinkage ratio, which is represented by the rate of change in length after the process of dipping in hot water at a temperature of 65 ° C. for 10 seconds before the process, is 5% or more, and the fold diameter 175.
mm, a label shape having a length of 120 mm in a direction perpendicular to the main contraction axis direction, and in the case where the label has a rectangular bottom surface, the vertical compression strength of the tube body is 6000 mN or more. Heat shrinkable polystyrene resin film. 3. In measurement of dynamic viscoelasticity of a film or at least one layer constituting the film, dispersion other than alpha dispersion is measured in a temperature region where alpha dispersion derived from polystyrene is measured, and a folding diameter is 175 mm, A heat-shrinkability, which has a label shape having a length of 120 mm in a direction orthogonal to the shrinkage axis direction, and has a vertical compressive strength of 5000 mN or more when the label has a rectangular bottom surface. Polystyrene resin film. 4. In measurement of dynamic viscoelasticity of a film or at least one layer constituting the film, dispersion other than alpha dispersion is measured in a temperature region where alpha dispersion derived from polystyrene is measured, and in a main shrinkage direction, The heat shrinkage ratio, which is represented by the rate of change in length after the treatment of dipping in hot water at a temperature of 65 ° C. for 10 seconds, is 5% or more,
When the label has a folding diameter of 175 mm and a length of 120 mm in the direction orthogonal to the main contraction axis direction, and the label has a rectangular bottom surface, the vertical compression strength of the cylinder is 500.
A heat-shrinkable polystyrene-based resin film, which is 0 mN or more. 5. In the dynamic viscoelasticity measurement, at least one layer is formed by stretching an unstretched sheet whose dispersion other than alpha dispersion is measured in a temperature range where alpha dispersion derived from polystyrene is measured. The heat-shrinkable polystyrene resin film according to claim 3 or 4. 6. 70 ° C. to 10 ° C. in the main shrinkage direction
The maximum heat shrinkage rate, which is the maximum value of the rate of change in length with respect to the length before the treatment, after the treatment of heating for 1 minute at each temperature up to 100 ° C. is 40% or more. Item 6. The heat-shrinkable polystyrene resin film according to any one of items 1 to 5. 7. A polystyrene resin 2
The heat-shrinkable polystyrene resin film according to any one of claims 1 to 6, wherein the heat-shrinkable polystyrene-based resin film has a multi-layered structure including at least one layer. 8. Each of which is made of polystyrene resin
The heat-shrinkable polystyrene-based resin film according to any one of claims 1 to 7, wherein the heat-shrinkable polystyrene-based resin film has a multilayer structure including at least one layer and at least one layer contains a polystyrene-based resin having a syndiotactic structure. 9. A label comprising the heat-shrinkable polystyrene resin film according to any one of claims 1 to 8. 10. A container provided with the label according to claim 9.