JP4061977B2 - White heat-shrinkable polystyrene resin film roll and method for producing the same - Google Patents

Description

主体樹脂
ＰＳ１：４−メチルスチレン共重合シンジオタクティックポリスチレン
ＰＳ２：アタクティックポリスチレン
ＰＳ３：シンジオタクティックポリスチレン
ゴム成分
Ｇ１：スチレン（４０ｗｔ％）−ブタジエン共重合体
改質剤
ａ：ハイスチレンゴム（スチレン８５ｗｔ％）
ｂ：スチレングラフト−スチレンブタジエンゴム
【表２】

【表３】

【表４】

[0001]
BACKGROUND OF THE INVENTION
The present invention is a white heat-shrinkable polystyrene resin film roll suitable as a packaging material used for coating, bundling, outer packaging, etc. of containers and the like, in particular, with a low temperature range suitable for shrinkage, to aseptic filling packaging and packaging in a short time. The present invention relates to a film roll formed by winding a white heat-shrinkable polystyrene resin film roll having excellent applicability.
[0002]
[Prior art]
Since the white heat-shrinkable film has a function of shrinkability, the white heat-shrinkable film can be laminated and integrated with an object by using the shrinkage force and shapeability of the film itself without using fixing means such as an adhesive or a fastener. Therefore, it has not only mechanical protection of the object by lamination or coating, but also functions such as binding and sealing. Furthermore, when the heat-shrinkable film itself has a special function, the special function can be added to the object later by lamination. This property is effectively used in the packaging field in which the main purpose is to protect the object during storage and distribution, and to provide display and design. For example, bottles including glass and plastic bottles, various containers such as cans, long objects such as pipes, bars, wood, various rod-like bodies, or sheet-like bodies, for covering, binding, exterior Used for use or sealing. Specifically, it is used for applications that cover a part or the whole of the cap part, shoulder part, and trunk part of the bottle for the purpose of improving the commercial value by displaying, protecting, binding, and functionalizing. Furthermore, it is also used for applications such as packing, packaging a plurality of packages, such as boxes, bottles, plates, sticks, notebooks, etc., and packaging with a film in close contact with the package (skin package). Used. At this time, if the display is preliminarily provided with a modeling for the purpose of design, the product is a label.
[0003]
As a material for the white heat-shrinkable film, polyvinyl chloride, polystyrene, polyester, polyamide, aliphatic polyolefin, derivatives thereof, hydrochloric acid rubber, and the like are used. Usually, a film made of these materials is formed into a tube shape and, for example, covered with a bottle or pipes are collected, and then heat shrinkage is performed for packaging and binding. However, all of the conventional white heat-shrinkable films have poor heat resistance and cannot withstand high temperature boiling or retort processing, so they cannot be sterilized at high temperatures when applied to food, sanitary goods, and pharmaceutical applications. There is a drawback. For example, when a retort process is performed, the conventional film has a problem that it is easily damaged during the process.
[0004]
In the case of the conventional white heat-shrinkable film, the film made of polyvinyl chloride resin has very good heat-shrinkage characteristics, but it has poor adhesion to the ink during printing when used as a label, etc. Since a gel-like product of the additive to be blended is easily generated, 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-based resin is excellent in heat resistance, dimensional stability, solvent resistance, etc., but in order to achieve desired heat shrinkage characteristics, adhesion, etc., precise manufacturing condition control technology is necessary, There was a problem such as cost.
[0005]
In addition, because of the usefulness of white heat-shrinkable films, white heat-shrinkable films are also used in fields where films and labels that are not white heat-shrinkable films have been used. In particular, many beverage container labels have been replaced with heat-shrinkable labels from affixed labels made of films that are not paper or white heat-shrinkable films. In particular, in the label field of plastic bottle containers, heat shrink labels are actively applied in relation to recycling problems, and various forms and systems of packaging designs are being implemented. Above all, the low-temperature moist heat shrinking process is a process used for aseptic filling packaging made possible by the combination of recent cleaning technology, sterilization technology, high-speed packaging technology, etc. Furthermore, packaging can be completed by a relatively short process at a relatively low temperature, and the contents can be prevented from being thermally deteriorated and the packaging efficiency can be improved. The heat-shrinkable film that can be used in the low-temperature wet heat shrinkage process needs to be excellent in shrinkability in a low-temperature region, and further, a relatively high shrinkage rate is advantageous from the viewpoint of shortening the process passage time. Conventionally, a heat-shrinkable polyester resin film has been used as a film having such characteristics. However, when the bottle and label need to be separated and collected, white heat-shrinkable polystyrene is difficult to separate and can be separated by specific gravity. The use of a resin-based resin film roll has been demanded. However, the conventional polystyrene resin has a glass transition temperature near 100 ° C. and has a problem that it is inferior in low-temperature shrinkage, and a method for solving this has been attempted. However, if the shrinkage temperature is set low, There have been problems such as the natural shrinkage of the resin being increased, and the heat resistance after the shrinkage is reduced.
[0006]
Moreover, because the demand for white heat-shrinkable polystyrene films for special applications as described above has increased, production of homogeneous film rolls capable of supplying films that function stably and with good reproducibility in any part of the roll shape Is required. In the case of a film roll with non-homogeneous quality, for example, if the fluctuation of the heat shrinkage rate is large in each unit of the label, the heating conditions in the tunnel are the same in the heat shrinkage process of the label, and thus the heat shrinkage rate is not appropriate Labels are generated, which cause poor appearance due to insufficient shrinkage, shrinkage spots, wrinkles, pattern distortion, vertical shading, and the like, and cannot be used as final products. Normally, since the same label for the final product is processed from one film roll, when the fluctuation amount of the heat shrinkage rate of the film constituting one film roll is large, in the heat shrinking process as described above The defective rate increases. Furthermore, since the adhesion stress when mounted on the container varies depending on the site, even if a film having excellent heat resistance in the hot warmer is used, poor heat resistance may occur.
[0007]
[Problems to be solved by the invention]
The present invention has a sufficiently high heat shrinkage rate even in the low temperature shrinking process, does not cause shrinkage unevenness in the film at the time of heat shrinking, has a beautiful appearance, and stabilizes the appearance even when exposed to high temperature conditions after shrinking. White heat-shrinkable polystyrene resin film roll that can be held in a stable manner, and insufficient shrinkage, shrinkage spots, wrinkles, distortion, vertical warping in the post-processing steps caused by fluctuations in the heat shrinkage rate in the film roll An object of the present invention is to provide a white heat-shrinkable polystyrene resin film roll that can reduce the occurrence of defects such as the above, and a method for producing the same.
[0008]
[Means for Solving the Problems]
The present invention is a film roll formed by winding a white heat-shrinkable polystyrene resin film roll, and the white heat-shrinkable polystyrene resin film roll is 10 seconds in hot water at a temperature of 65 ° C. in the main shrinkage direction. The heat shrinkage rate indicated by the rate of change in length with respect to the pretreatment after the immersion treatment is 5% or more, and the length with respect to the pretreatment after the treatment of dipping in hot water at 85 ° C. for 10 seconds in the main shrinkage direction. The rate of change in the heat shrinkage rate indicated by the rate of change for all rolls with respect to the average value of the heat shrinkage rate at each measurement point is all Within ± 3% The light transmittance is 50% or less, The rate of change in length with respect to the length before the treatment after the treatment in which the white heat-shrinkable polystyrene resin film is heated for 1 minute at each temperature from 100 ° C. to 150 ° C. in the main shrink direction. The maximum heat shrinkage rate, which is the maximum value of, is 60% or more, and the film length of the film roll is 1000 to 6000 m The white heat-shrinkable polystyrene-based resin film roll, and its manufacturing method.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The white heat-shrinkable polystyrene resin film roll forming the film roll of the present invention has a heat shrinkage indicated by a rate of change in length with respect to the pre-treatment after the treatment immersed in hot water at a temperature of 65 ° C. for 10 seconds in the main shrinkage direction. The rate is 5% or more. Preferably, the heat shrinkage rate is 10% or more, more preferably 20% or more. When the heat shrinkage rate is less than 5%, the low temperature shrinkability is lowered, and it cannot be used for aseptic packaging using the white heat shrinkable polystyrene resin film roll of the present invention.
[0010]
As a method for obtaining the desired heat shrinkage rate, it is possible to lower the glass transition temperature of the film by selecting the type and blending ratio of the polystyrene-based resin constituting the white heat-shrinkable film, blending the additive components, etc. Examples thereof include a decrease in stretching temperature corresponding to the glass transition temperature. 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 increases to lower the glass transition temperature to the shrinkage process temperature region. , Heat resistance and dimensional stability tend to decrease. When the resin composition constituting the film is incompatible, it shrinks in the vicinity of the glass transition temperature of the polystyrene resin, which is the main component, but the component is dispersed using a modifier for adjusting compatibility. 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.
[0011]
The white heat-shrinkable polystyrene resin film roll forming the film roll of the present invention has a heat shrinkage rate indicated by a rate of change in length with respect to the pre-treatment after the treatment immersed in hot water at 85 ° C. for 10 seconds in the main shrinkage direction. In all the rolls, the fluctuation rate with respect to the average value of the heat shrinkage rate at each measurement point must be within ± 5%. Preferably, the variation rate is within ± 3%, and more preferably within ± 2%. When the fluctuation rate is within ± 5%, the heat shrinkage rate fluctuation for each label produced from one film roll is reduced, and the defective rate in the heat shrinking process can be drastically reduced. Moreover, the change by the site | part of the adhesion stress at the time of mounting | wearing with a container becomes small, and the heat resistant defect in a hot warmer reduces.
[0012]
As described below, the method of setting the variation rate within ± 5% is adjustment of the film production conditions, in particular, homogenization of the blending state of the resin constituting the film, preheating step, stretching step, and heat treatment step. Examples include a method of adjusting the fluctuation range of the surface temperature of the film measured at an arbitrary time.
[0013]
The variation rate within ± 5% is suitable when the white heat-shrinkable polystyrene resin film roll forming the film roll has a width of 200 mm or more and a length of 300 m or more. This is because a film of the above size is excellent in processing suitability and handling properties from printing to a final product such as a label, but the film roll as a whole is greatly affected by an increase in defective rate due to fluctuations in thermal shrinkage rate. A film having a width of less than 200 mm is less affected by an increase in the defect rate because the processing suitability and handling properties are lowered. A film having a length of less than 300 m is less likely to cause an increase in defect rate due to fluctuations in heat shrinkage rate in the entire film roll. It is particularly suitable when the width of the white heat-shrinkable polystyrene resin film roll forming the film roll is 300 mm or more, and further suitable when it is 400 mm or more. Moreover, it is suitable when the length of the white heat-shrinkable polystyrene-based resin film roll forming the film roll is 400 m or longer, and further suitable when it is 500 m or longer. From the viewpoint of handleability, the width of the film is preferably 1500 mm or less, and the length is preferably 6,000 m or less when the thickness is 50 μm.
[0014]
The variation rate within ± 5% is suitable when the white heat-shrinkable polystyrene resin film roll forming the film roll is made of two or more different resins. This is because the film tends to increase in defective rate due to fluctuations in heat shrinkage rate in the entire film roll.
[0015]
Further, the white heat-shrinkable polystyrene resin film forming the film roll of the present invention is required to have a light transmittance of 50% or less, preferably 30% or less, more preferably 20% or less. If the light transmittance exceeds 50%, the back side will be seen through when printed on the front surface, resulting in poor design.
[0016]
Examples of the method of reducing the light transmittance to 50% or less include a method of adding inert particles represented by titanium dioxide, calcium carbonate, aluminum oxide, barium sulfate, talc, kaolin, crosslinked polystyrene, crosslinked acrylic, benzoguanamine and the like. It is done. Preferably, the addition amount is 3 parts by weight or more and 100 parts by weight or less, more preferably 10 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight in total of the polystyrene resin and the styrene copolymer resin constituting the white heat-shrinkable film. It is as follows. If it is less than 3 parts by weight, the light transmittance becomes too high, and if it exceeds 100 parts by weight, breakage during film formation frequently occurs.
[0017]
As another method for reducing the light transmittance to 50% or less, by adding inert particles and / or incompatible resin to the resin constituting the white heat-shrinkable film and stretching the resin, fine cavities are formed inside. And a method of causing light scattering at the interface between the cavity and the resin. Examples of the inactive particles include those described above. Examples of incompatible resins include polyolefin resins such as polymethylpentene, polypropylene, polyethylene, and cyclic polyolefin, and polyesters such as polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, and polynaphthalene terephthalate. Can be mentioned. Preferably, the total addition amount of the inert particles and the incompatible resin is 3 parts by weight or more and 100 parts by weight or less with respect to the total 100 parts by weight of the polystyrene resin and the styrene copolymer resin constituting the white heat-shrinkable film. More preferably, it is 10 parts by weight or more and 50 parts by weight or less. If it is less than 3 parts by weight, the light transmittance becomes too high, and if it exceeds 100 parts by weight, breakage during film formation frequently occurs.
[0018]
As described above, the apparent specific gravity when a fine cavity is formed inside is 0.5 or more and 1.0 or less, preferably 0.6 or more and 0.9 or less. If it is less than 0.5, breakage frequently occurs during film formation. When it exceeds 1.0, sufficient opacity is not exhibited. Further, as a secondary effect, by setting it to less than 1.0, the label composed of the film floats on water, and the resin used in the PET bottle and the label can be easily separated. Examples of the method for reducing the apparent specific gravity include a method of mixing EPS within 1% by weight during weight reduction.
[0019]
The apparent specific gravity is measured by accurately cutting out a white heat-shrinkable resin film into a 10 cm × 10 cm square to obtain a test piece, and measuring the thickness of the test piece at 50 points to obtain an average thickness t (unit: μm). Next, the weight of the test piece was measured to 0.1 mg and set to w (unit: g). And apparent specific gravity was calculated by the following formula 1.
Apparent specific gravity (−) = (w / t) × 10,000 Equation 1
[0020]
The white heat-shrinkable polystyrene-based resin film roll forming the film roll of the present invention is pre-treated after the treatment of heating for 1 minute at each temperature from 100 ° C. to 150 ° C. every 10 ° C. in the main shrink direction. It is preferable that the maximum heat shrinkage rate, which is the maximum value of the rate of change in length with respect to the length, is 40% or more. When the maximum heat shrinkage rate is less than 40%, the shrinkage is insufficient when used as a label (body label) of a generally used bottle body portion, and it is difficult to make it adhere to the bottle. More preferably, the maximum heat shrinkage rate is 50% or more. When the maximum heat shrinkage is 50% or more, insufficient shrinkage does not occur as a label of a PET bottle that requires high shrinkage. More preferably, the maximum heat shrinkage is 60% or more, and particularly preferably 70% or more. If the maximum heat shrinkage is in the above range, insufficient shrinkage does not occur even as a full label for a container having a complicated shape.
[0021]
Examples of the method of setting the maximum heat shrinkage ratio as the above range method include, for example, the types and blending ratios of resins constituting the white heat shrinkable film, blending of additives such as a plasticizer, adjustment of film production conditions, particularly high stretching. Examples of the method include magnification, reduction of heat fixation, and adjustment of the compatibility state of the constituent components.
[0022]
The white heat-shrinkable polystyrene resin film roll forming the film roll of the present invention is measured in the temperature range where the polystyrene-derived alpha dispersion is measured in the measurement of the dynamic viscoelasticity of the film. It is preferable. According to Nakatani, Yamada, et al., 44th Rheological Symposium Abstracts (1996) pp. 169-172, white heat-shrinkable polystyrene resin film rolls that measure dispersion other than alpha dispersion are alpha dispersion, Shrinkage occurs with the relaxation dispersion that causes the shrinkage phenomenon, and dispersion occurs due to crystallization, generation of a gel-like structure, and the like near the end of shrinkage. If dispersion occurs due to crystallization, generation of a 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 copolymers thereof.
[0023]
In the measurement of dynamic viscoelasticity of a film, a white heat-shrinkable polystyrene resin film roll in which dispersion other than alpha dispersion is measured in a temperature region where alpha dispersion derived from polystyrene is measured is, for example, dynamic viscoelastic In measurement, it is obtained by stretching an unstretched sheet in which dispersion other than alpha dispersion is measured in a temperature range where alpha dispersion derived from polystyrene is measured.
[0024]
The structure of the polystyrene resin constituting the white heat-shrinkable polystyrene resin film roll forming the film roll of the present invention is not particularly limited as long as it can exhibit the heat shrink characteristics described later, but preferably syndiotactic A polystyrene-based resin containing a polystyrene-based resin having a structure is preferable. More preferably, a polystyrene resin having a syndiotactic structure is used as the polystyrene resin. By using a polystyrene resin having a syndiotactic structure, mechanical strength and heat resistance are improved. By using such a polystyrene-based resin, in addition to the low density of polystyrene, which is advantageous for separation in the recycling process, it is excellent in heat resistance, particularly heat storage during heat storage, etc. The change in printing pitch due to shrinkage is reduced, and high-precision printing can be performed as a label. Furthermore, the durability against the solvent contained in the printing ink is improved, and the printability is excellent.
[0025]
The polystyrene resin having the syndiotactic structure is preferably 75% or more in terms of dyad (two constituent units) in the tacticity for quantifying the phenyl group and / or substituted phenyl group as a side chain by a nuclear magnetic resonance method. More preferably, it is 85% or more, and it is preferably 30% or more, more preferably 50% or more in pentad (5 structural units).
[0026]
Examples of the polystyrene component constituting the polystyrene resin used in the present invention include polystyrene, poly (p-, m-, or o-methylstyrene), poly (2,4-, 2,5-, 3,4-, Or 3,5-dimethylstyrene), poly (alkylstyrene) such as poly (p-tertiarybutylstyrene), poly (p-, m-, or o-chlorostyrene), poly (p-, m-, or o-bromostyrene), poly (p-, m-, or o-fluorostyrene), poly (halogenated styrene) such as poly (o-methyl-p-fluorostyrene), poly (p-, m-, or poly (halogenated substituted alkylstyrene) such as o-chloromethylstyrene), poly (p-, m-, or o-methoxystyrene), poly (p-, m-, or o-ethoxystyrene) Poly (alkoxy styrene), poly (p-, m-, or o-carboxymethyl styrene) and other poly (carboxyalkyl styrene) poly (p-vinylbenzylpropyl ether) and other poly (alkyl ether styrene), poly Examples include poly (alkylsilylstyrene) such as (p-trimethylsilylstyrene), and poly (vinylbenzyldimethoxyphosphide).
[0027]
The white heat-shrinkable polystyrene resin film roll used in the present invention is plasticized for the purpose of lowering the heat shrinkage starting temperature and improving the impact resistance of the polystyrene resin constituting at least one layer of the film. It is preferable to use an agent, a compatibilizing agent and the like which are blended with polystyrene or in a polymer.
[0028]
In the present invention, it is preferable to add a thermoplastic resin and / or a rubber component to the polystyrene resin. Examples of the thermoplastic resin include polystyrene resins such as polystyrene, AS resin, and ABS resin having an atactic structure, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, nylon 6, nylon 66, nylon 12, Examples thereof include polyamide resins such as 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 a constituent component, and examples thereof include random, block or graft copolymers obtained by copolymerizing one or more of styrene and a rubber component. . Examples of such rubber-like copolymers include styrene-butadiene copolymer rubber, styrene-isoprene block copolymer, rubber obtained by hydrogenating part or all of these butadiene moieties, and 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 rubbery copolymer containing a styrene compound as a constituent component has a styrene unit, and therefore has a good dispersibility with respect to a polystyrene resin mainly having a syndiotactic structure. As a result, the polystyrene resin Greatly improves physical properties. In particular, as the compatibility adjuster, a rubbery copolymer containing the above styrene compound as a constituent component is suitable.
[0029]
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, etc. Can be used.
[0030]
In the present invention, the polystyrene-based resin constituting the film preferably has a weight average molecular weight of 10,000 or more, more preferably 50,000 or more. When the weight average molecular weight is less than 10,000, the high elongation property and heat resistance of the film are likely to be lowered. The upper limit of the weight average molecular weight is not particularly limited, but if it is 1,500,000 or more, the occurrence of breakage or the like accompanying the increase in stretching tension may occur, so it is preferably less than 1,500,000.
[0031]
In the present invention, it is necessary to use a white pigment. As the white pigment used in the present invention, titanium oxide, barium sulfate, zinc oxide, zinc sulfide, calcium carbonate and the like can be used. In addition, white pigments subjected to various organic and inorganic surface treatments for the purpose of improving dispersibility in polystyrene resin and the like can be used as these white pigments. Among these, titanium oxide is particularly preferable for use as a substrate for information recording / printing materials and the like because it has a high refractive index and can exhibit high concealability even in a small amount. These white pigments may be added alone to the polystyrene resin, or two or more kinds may be mixed and added. The content of the white pigment is preferably 5 to 90% (corresponding to 4.8 to 47% by weight with respect to the film weight) with respect to the entire resin composition constituting the film. If the content is less than 5%, it is difficult to improve quality such as a high refractive index and high concealing property due to the inclusion of the white pigment, and if the content exceeds 90%, the stretchability of the film decreases.
[0032]
In the present invention, the white heat-shrinkable polystyrene-based resin film roll is improved in electrostatic adhesion, slipperiness, stretchability, processability, impact resistance, etc. For the purpose of weight reduction, other resins, plasticizers, compatibility adjusters, inorganic particles, organic particles, colorants, antioxidants, antistatic agents and the like can be appropriately blended.
[0033]
By using the polystyrene resin as described above as a material constituting the film of the present invention, it is excellent in various heat shrink characteristics, excellent in printability such as adhesiveness with ink at the time of label formation, etc. There are no pinholes on the surface. Furthermore, it is excellent in disposal and has little environmental impact when incinerated.
[0034]
The polystyrene-based resin constituting the film as described above is formed into a film by a method such as an extrusion method or a calendar method that is generally used conventionally. The shape of the film is, for example, a flat 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 any of sequential biaxial stretching, simultaneous biaxial stretching, uniaxial stretching, and combinations thereof. In the biaxial stretching, stretching in the vertical and horizontal directions may be performed at the same time, but sequential biaxial stretching in which one of them is performed first is effective, and either of the vertical and horizontal orders may be performed first. It shows below about preferable conditions in the case of manufacturing the white heat-shrinkable polystyrene-type resin film roll of this invention. The draw ratio is preferably 1.0 to 6.0 times, and the magnification in one predetermined direction and the magnification in the direction orthogonal to the direction may be the same or different. In the stretching step, it is preferable to perform preheating at a temperature not lower than the glass transition temperature (Tg) of the resin constituting the film and not higher than (Tg + 50) ° C. In heat setting after stretching, it is preferable to pass through a heating zone of 30 ° C. to 150 ° C. for about 1 to 30 seconds after stretching. Further, after the film is stretched and before or after the heat setting, the relaxation treatment may be performed to an appropriate degree. Furthermore, after the stretching, a step of cooling while applying a stress to the film while keeping the stretched or tensioned state, or a cooling step after releasing the tensioned state following the treatment may be added.
[0035]
As a factor that the thermal shrinkage rate of the long film forming the film roll varies depending on the part, the composition variation of the resin component of the film is considered as a major factor. In general, white heat-shrinkable polystyrene resin film rolls are made by blending two or more kinds of resins or using a resin composed of a plurality of copolymerization monomer components in order to achieve both heat shrinkage properties and strength. The characteristics are changed. When blending two or more kinds of resins, raw material chips of a plurality of kinds of resins having different structures are blended with a hopper or the like, then melt-kneaded and extruded from an extruder to form a film. For example, when there are three kinds of resins as raw materials, the respective raw material chips are continuously or intermittently supplied to three hoppers, and finally passed through a buffer hopper as needed, finally immediately before the extruder or While mixing three types of raw material chips with a hopper immediately above (hereinafter referred to as “final hopper”), the raw material chips are quantitatively supplied to the extruder according to the extrusion amount of the extruder to form a film. However, depending on the capacity or shape of the final hopper, when the amount of chips in the final hopper is large or when the remaining amount is small, the material segregation phenomenon that the mixing ratio of the chips supplied from the final hopper to the extruder varies. It's easy to do. This problem is particularly noticeable when the shape and specific gravity of the chip differ depending on the resin. In that case, the thermal shrinkage rate tends to fluctuate in a long film.
[0036]
Therefore, in order to obtain a film having a small variation in heat shrinkage rate in a long film forming one film roll, it is preferable to reduce the composition variation due to the site of the film. When using a resin, it is preferable to prevent the material segregation phenomenon in the final hopper by reducing the variation in the shape of the raw material chips. Specifically, when including a step of mixing and extruding a plurality of resins constituting the white heat-shrinkable polystyrene resin film roll, the shape of the raw material chip of each resin is a columnar shape and / or an elliptical columnar shape, The major axis, minor axis, and longitudinal length of the cross section perpendicular to the longitudinal direction of the other resin raw material chips with respect to the resin raw material chip with the largest blending amount are within ± 50% in terms of the difference in average value. Is preferable. The plane shape of the cross section perpendicular to the longitudinal direction in the “columnar shape” is not particularly limited, such as a square shape or a circular shape that can be measured. More preferably, the major axis, minor axis, and length in the longitudinal direction should be within ± 20% in terms of the average value, and particularly preferably within ± 15% in terms of the average value. Good. If there is a difference in the size and shape of the raw material chips, small chips tend to fall when the mixture of chips falls in the final hopper, so the ratio of large chips when the remaining amount of chips in the final hopper decreases. However, the segregation of the raw material can be reduced by aligning the size and shape of the chip as described above.
[0037]
In addition, in order to prevent the raw material segregation phenomenon in the final hopper, the resin constituting the white heat-shrinkable polystyrene resin film roll is mixed using an extruder equipped with a funnel-shaped hopper as a raw material chip supply part. When the step of melt extrusion is included, it is preferable that the inclination angle of the hopper formed by the funnel-shaped hypotenuse and the horizontal line segment is 65 degrees or more. By setting the tilt angle to 65 degrees or more, the chip can be easily dropped even if the shape varies, and the chip can be lowered while the upper surface is horizontal, which is effective in reducing raw material segregation. is there. More preferably, the inclination angle is 70 degrees or more. A plurality of hoppers may be used upstream of the final hopper, and in that case, the inclination angle is preferably 65 degrees or more, more preferably 70 degrees or more in any hopper.
[0038]
Further, since the fine powder generated due to the collapse or breakage of the raw material chips used promotes the occurrence of raw material segregation, it is also preferable to remove the fine powder generated in the process and reduce the ratio of the fine powder in the hopper. . Specifically, the ratio of the fine powder is preferably controlled within 1% by weight, more preferably within 0.5% by weight throughout the entire process until the raw material chips enter the extruder. Examples of the method for reducing the ratio of the fine powder include a method of removing the fine powder with a sieve when forming a chip with a strand cutter, and a method of removing with a cyclone air filter or the like when the raw material chips are air-fed.
[0039]
In addition, as a means for reducing raw material segregation in the hopper, a method of optimizing the capacity of the hopper to be used is also preferable. Specifically, the capacity of the hopper to be used is preferably 15 to 120% by weight, more preferably 20 to 100% by weight of the discharge amount per hour of the extruder.
[0040]
Furthermore, as a method of mixing the raw material chips of two or more kinds of resins, it is preferable to mix each raw material chip while continuously supplying the raw material chips to the extruder with a hopper (final hopper) directly above the extruder. Further, after mixing in advance the raw material chip size variation controlled within the above range, it may be supplied to the final hopper and the extruder via one or more intermediate (buffer) hoppers. When mixing multiple raw material chips, mix them in advance using a method that mixes raw material chips while quantitatively supplying multiple types of raw materials into the hopper, using a blender, etc. In the latter case, it is preferable to pay attention to the size of the raw material chip so that the raw material does not segregate when the mixture is discharged.
[0041]
As a factor that the thermal shrinkage rate of the long film forming the film roll varies depending on the part, in addition to the compositional fluctuation due to the resin part constituting the above-mentioned film, there are fluctuations in conditions in the process of stretching the film. Can be mentioned. In the present invention, as another method for reducing the fluctuation of the thermal shrinkage rate in the film roll, a method for suppressing the fluctuation of the surface temperature of the film by suppressing the temperature fluctuation in the step of stretching the film is also preferable. For example, when uniaxially stretching in the transverse direction using a tenter, there are a preheating step before stretching, a stretching step, a heat treatment step after stretching, a relaxation treatment step, a restretching treatment step, etc., in particular a preheating step, In the stretching step and the heat treatment step after stretching, the fluctuation range of the surface temperature of the film measured at an arbitrary point is preferably within the average temperature ± 1 ° C. over the entire film length, and more preferably the average temperature ± It should be within 0.5 ° C. When the fluctuation range of the surface temperature of the film is small, stretching and heat treatment are performed at the same temperature over the entire length of the film, and the heat shrinkage behavior becomes uniform. Temperature fluctuations during the preheating process, stretching process, and heat treatment process after stretching greatly affect fluctuations in the heat shrinkage rate. Therefore, temperature fluctuations can be achieved by using heating equipment and stretching equipment that allow strict temperature control. Is preferably suppressed. In addition, it is preferable to suppress temperature fluctuations in the preheating step and the heat treatment step after stretching.
[0042]
In the present invention, “the fluctuation range of the surface temperature of the film measured at an arbitrary time” is, for example, the time when the film surface temperature is continuously measured during the production of the film at the time when 2 m has elapsed after entering the stretching step. Measure by a method such as measuring. Since the average temperature can be calculated when the film production for one roll is completed, if the fluctuation range of the film surface temperature is within the average temperature ± 1 ° C., the film is stretched under the same conditions over the entire length of the film. The fluctuation of the heat shrinkage rate is reduced.
[0043]
In the present invention, the thickness of the white heat-shrinkable polystyrene resin film roll is not particularly limited, but is preferably in the range of 10 to 200 μm, and more preferably in the range of 20 to 100 μm.
[0044]
The film roll of the present invention is formed by winding the white heat-shrinkable polystyrene resin film roll. As the winding core, a core made of plastic or metal such as 3 inch, 6 inch, 8 inch or the like, which is generally used, can be used.
[0045]
The white heat-shrinkable polystyrene resin film roll obtained from the film roll of the present invention is suitably used as a packaging material used for coating, binding, exterior, etc. of containers, etc., and has a beautiful appearance by using the film of the present invention. Obtainable. In particular, the label constituted by the film of the present invention is excellent in coverage and suitable for packaging containers. In addition, the white heat-shrinkable polystyrene resin film roll of the present invention has excellent applicability to a heat storage container, and a container equipped with a label obtained from the film roll of the present invention is subjected to high temperature conditions after shrinkage. The label keeps its appearance stable even when exposed to. Moreover, it has excellent low-temperature shrinkability and has excellent applicability to aseptic filling packaging and packaging in a short time.
[0046]
Hereinafter, the present invention will be described more specifically with reference to test examples and examples, but the present invention is not limited thereto.
[0047]
Test example
Test method
(1) Thermal contraction rate
The white heat-shrinkable film is cut from any part of the film rolls of Examples 1 and 2 and Comparative Examples 1 to 6 so that the main shrinkage direction is the longitudinal direction and becomes a width of 15 mm, and is marked at intervals of 200 mm in the longitudinal direction. A line was marked to give a test piece. The test piece was soaked for 10 seconds in hot water in a water bath set at a temperature of 65 ° C. The distance between the marked lines (X: unit mm) was measured, and the length change rate D (unit%) with respect to the length before the treatment after the treatment was calculated using the following formula 2. Further, the “main shrinkage direction” was determined by measuring the following maximum heat shrinkage rate in the longitudinal direction and the transverse direction of the film, and taking the direction with the largest maximum heat shrinkage rate as the main shrinkage direction. In the films of Examples and Comparative Examples, the transverse direction was the main shrinkage direction.
D (%) = [(200−X) / 200] × 100 Formula 2
[0048]
(2) Maximum heat shrinkage
From the film rolls of Examples 1 and 2 and Comparative Examples 1 to 6, with the main shrinkage direction as the longitudinal direction, 6 white heat-shrinkable polystyrene resin film rolls having a width of 15 mm at approximately equal intervals are cut, Marks were marked at intervals of 200 mm in the longitudinal direction to obtain test pieces. The test piece is in the center of the incubator at 100 ° C to 150 ° C every 10 ° C in a hot air circulation thermostat (manufactured by Sakai Seisakusho, FX-1: damper closed, quick heater ON) Each was left to stand and heated for 1 minute. After taking out the specimen from the thermostat and cooling it, the distance between the marked lines (X ′: unit mm) is measured, and the length change rate D ′ (unit%) with respect to the length before processing after processing is calculated. It calculated using the following formula 3. Among the length change rates D ′, the maximum value was defined as the maximum heat shrinkage rate.
D ′ (%) = [(200−X ′) / 200] × 100 Formula 3
[0049]
(3) Dynamic viscoelasticity
Each unstretched sheet obtained in the production process of the white heat-shrinkable polystyrene resin film roll forming the film rolls of Examples 1 and 2 and Comparative Examples 1 to 6, with the MD direction as the longitudinal direction, a width of 5 mm, and the length of the measurement unit A test piece was cut to a thickness of 30 mm. About this test piece, dynamic viscoelasticity is measured under conditions of stretching mode, frequency of 50 Hz, temperature range of -20 to 250 ° C., temperature increase rate of 2 ° C./min, and temperature region where alpha dispersion derived from polystyrene is measured. Then, the presence or absence of dispersion other than alpha dispersion was confirmed.
[0050]
(4) Fluctuation rate of heat shrinkage rate across the entire roll
The white heat-shrinkable polystyrene resin film rolls constituting the film rolls of Examples 1 and 2 and Comparative Examples 1 to 6 are within 2 m from the end of film winding, and the first cut-out portion is within 2 m from the beginning of film winding. So that the final cutout part comes to about 100 m from the first cutout part (including an error range. For example, there may be a difference of about ± 1 m). A 10 cm × 10 cm square test piece having sides parallel to the longitudinal direction of the film and the direction perpendicular thereto is cut out. About each test piece, the process immersed in the hot water of the water bath set to the temperature of 85 degreeC for 10 second was performed. The length (An: unit mm) of one side (main shrinkage direction) contracted mainly was measured, and the rate of change in length Yn (unit%) with respect to the length before treatment after treatment as the thermal shrinkage rate was expressed by the following formula. After calculating using 4, the average value X ′ (unit:%) of the heat shrinkage rate of each test piece was determined, and X′−Yn was defined as the variation rate (unit:%) of the heat shrinkage rate. In Table 3, the maximum value of the absolute value | X′−Yn |
Yn (%) = [(10−An) / 10] × 100 Formula 4
In addition, said test method is demonstrated concretely. For example, in the case of a film roll composed of a film having a length of 498 m, the sample 1 is cut out within a range of 2 m from the end of winding of the film. When the sample 5 is cut out at the part separated by the sample 2,200m at the part distant from the sample 1 at the part where the sample 2,200m is separated and the part 4,300m is separated from the specimen 4, the remaining part is shorter than 100m, so the winding of the film starts. The sample 6 is cut out within a range of 2 m from. Since there is a high possibility that the end of winding and the beginning of winding of the film are more varied than the part of the heat-shrinking characteristic type, be sure to collect specimens within the range of 2 m each. Note that the fluctuation rate of thermal shrinkage is within ± 5% means that the difference of the thermal shrinkage rate Yn (%) of the sample piece n with respect to the average value X ′ of the thermal shrinkage rate of each test piece, | X′− Yn | means that both are smaller than 5%. That is, the difference | X′−Ymax | between the maximum values Ymax and X ′ of Yn and the difference | X′−Ymin | between the minimum values Ymin and X ′ of Yn may be within 5%.
[0051]
(5) Shrinkage finish
After performing three-color printing on the full length of the films constituting the film rolls of Examples 1 and 2 and Comparative Examples 1 to 6 using inks of three colors (grass color, gold, white) manufactured by Toyo Ink Manufacturing Co., Ltd. The film was slit, and using a center seal machine, a solvent was adhered with 1,3-dioxolane to form a tube, and the film was wound in a folded state. All the tubes were cut into a size that would be a full label for a PET bottle described later (the main shrinkage direction was a circular cross section, and the length in the non-shrinkage direction was 22 cm) to form a label. The label was put on a 1,000 ml PET bottle and allowed to pass through a steam tunnel (manufactured by Fuji Astec, SH-1500-L). The conditions for the steam tunnel were 67 ° C. in the first zone, 80 ° C. in the second zone, and a tunnel passage time of 10 seconds. All labels were similarly heat-shrinked, and the shrinkage finish was visually evaluated according to the following criteria. Further, 4 or more was “accepted” and 3 or less was “defective” according to the following criteria, and the defect rate was determined according to the following formula 5. Here, “defects” are wrinkles, label edge folding, color spots, and insufficient shrinkage.
[Evaluation criteria]
5: Best finish
4: Good finish
3: Within 2 defects
2: 3-6 defects
1: 6 or more defects
Defective rate = (number of “defective” / total number of labels) × 100 Equation 5
[0052]
(6) Heat storage resistance
To the bottle (after heating) equipped with a label comprising a white heat-shrinkable polystyrene resin film roll constituting the film rolls of Examples 1 and 2 and Comparative Examples 1 to 6 used for the shrinkage spot evaluation in (5) above. Air was removed as much as possible, filled with water, and sealed with a cap. The bottle was placed sideways on a laboratory hot plate heated to 110 ° C. and allowed to stand for 24 hours, and then the state of the label was visually evaluated according to the following criteria.
○: Good with little defect on the label
Δ: Defects are clearly recognized on the label, not good
×: Many labels are defective and defective
[0053]
(7) Ease of printing
Metallic surface printing was performed on the white heat-shrinkable resin films of Examples 1 and 2 and Comparative Examples 1 to 6, labels were formed as described above, and the state of the labels was visually evaluated according to the following criteria.
○: The printed material is easy to see without seeing through the bottom
Δ: The printed matter is slightly difficult to see
×: Hard to see printed matter
[0054]
(8) Light transmittance
Based on JIS K7105-1981, the total light transmittance of the white heat-shrinkable resin films of Examples 1 and 2 and Comparative Examples 1 to 6 was determined using NDH-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.
[0055]
(9) Raw material chip dimensions
100 chips were randomly collected from the raw material chips of each polymer used in the production of the white heat-shrinkable polystyrene resin film rolls constituting the film rolls of Examples 1 and 2 and Comparative Examples 1 to 6, respectively. Each of the dimensions, that is, the major axis and minor axis of the cross section perpendicular to the longitudinal direction and the length in the longitudinal direction (all units are mm) were measured to 1 digit after the decimal point using a caliper, and the average value was obtained. The difference between the average value of each dimension in the raw material chip of the main resin (the resin with the largest blending amount) and the average value of each dimension in the raw material chip of the other resin is obtained, and the average value of each dimension in the main chip of the main resin Percentage was calculated.
[0056]
2. Test results
The results of the tests (1) to (8) are shown in Tables 3 and 4, and (9) is shown in Table 2.
[0057]
【Example】
Example 1
Syndiotactic polystyrene (weight average molecular weight 300,000) obtained by copolymerizing 33 mol% of 4-methylstyrene as a constituent component, and 20 wt% of anatase-type titanium dioxide particles having an average particle diameter of 0.3 μm as a whitening agent The raw material chip of the main resin mixed and mixed, the raw material chip of a styrene-butadiene block copolymer (rubber component) obtained by copolymerizing styrene as a constituent component to 40 wt%, and for compatibility adjustment The raw material chip of high styrene rubber (styrene-butadiene copolymer rubber, containing styrene as 85% by weight) as a modifier is 55: 40: 5 by weight ratio (main resin / rubber component / modified) Is fed by a fixed screw feeder so as to be in the proportion of the material) and mixed in a hopper with an inclination angle of 70 degrees directly above the extruder. It was. This was melted at 250 ° C., extruded from a T die having a lip gap of 800 μm, adhered to a cooling roll at 40 ° C. by an air knife method, and solidified by cooling to obtain an amorphous sheet. At this time, 150 kg of raw material chips remained in the hopper. The amorphous sheet is preheated to 110 ° C., stretched at a stretching temperature of 90 ° C. in the transverse direction at a magnification of 6.0 times, and then heat-fixed at 60 ° C. for 15 seconds, continuously over 1,000 m. Thus, a white heat-shrinkable polystyrene resin film roll having a thickness of 50 μm was formed. The fluctuation range of the surface temperature during film formation was within the range of the average temperature ± 0.8 ° C in the preheating step, the average temperature ± 0.6 ° C in the stretching step, and the average temperature ± 0.5 ° C in the heat setting step. It was. The obtained film was slit into a width of 400 mm and a length of 1,000 m, wound up in a 3-inch paper can, and used as a film roll.
[0058]
Example 2
The shape and size of the raw material chips are as shown in Table 2, and the modifying agent is a styrene-grafted styrene-butadiene rubber obtained by graft copolymerization of styrene with a styrene-butadiene copolymer (styrene content 25% by weight) (graft rate 100% by weight). ), And the fluctuation range of the surface temperature during film formation is within the range of the average temperature ± 0.8 ° C in the preheating step, the average temperature ± 0.5 ° C in the stretching step, and the average temperature ± 0.8 ° C in the heat setting step A film roll was obtained in the same manner as in Example 1 except that the inside was used.
[0059]
Comparative Example 1
A film roll was obtained in the same manner as in Example 1 except that the shape and size of the raw material chips were as shown in Table 2 and the draw ratio was 2.0 times.
[0060]
Comparative Example 2
The shape and size of the raw material chips are as shown in Table 2, the main resin polystyrene is syndiotactic polystyrene containing no copolymerization component, and the mixing ratio of the main resin, rubber component and modifier is 50 pairs by weight. A film roll was obtained in the same manner as in Example 1 except that the ratio was 50 to 0 (main resin / rubber component / modifier).
[0061]
Comparative Example 3
A film roll was obtained in the same manner as in Example 1 except that the shape and size of the raw material chips were as shown in Table 2 and a hopper with an inclination angle of 60 degrees was used.
[0062]
Comparative Example 4
The shape and size of the raw material chips are as shown in Table 2, and the fluctuation range of the surface temperature during film formation is the average temperature ± 1.0 ° C. in the preheating step, the average temperature ± 2.5 ° C. in the stretching step, and the heat setting step A film roll was obtained in the same manner as in Example 1 except that the average temperature was within the range of ± 2.0 ° C.
[0063]
Comparative Example 5
The shape and size of the raw material chips are as shown in Table 2, and the fluctuation range of the surface temperature during film formation is the average temperature ± 1.0 ° C. in the preheating step, the average temperature ± 2.5 ° C. in the stretching step, and the heat setting step A film roll was obtained in the same manner as in Example 1 except that the average temperature was within the range of ± 2.0 ° C.
[0064]
Comparative Example 6
A film roll was obtained in the same manner as in Example 1 except that the shape and size of the raw material chips were as shown in Table 2 and the main resin polystyrene was atactic polystyrene.
[0065]
【The invention's effect】
The film obtained from the white heat-shrinkable polystyrene resin film roll of the present invention has a sufficient heat shrinkage rate in the low-temperature shrinkage step, and shrinks evenly during the heat shrinkage regardless of temperature fluctuations and non-uniformity in the shrinkage step. Thus, no contraction unevenness occurs and a beautiful appearance is exhibited. Further, even when exposed to high temperature conditions after shrinkage, no sagging or wrinkles are generated, and the appearance is stably maintained. With respect to the film obtained from any part of the film roll, the variation in the above characteristics is reduced, and the yield when used as a label or the like can be improved.
[Table 1]

Main resin
PS1: 4-methylstyrene copolymer syndiotactic polystyrene
PS2: Atactic polystyrene
PS3: Syndiotactic polystyrene
Rubber component
G1: Styrene (40 wt%)-butadiene copolymer
Modifier
a: High styrene rubber (styrene 85 wt%)
b: Styrene graft-styrene butadiene rubber
[Table 2]

[Table 3]

[Table 4]

Claims (6)

A film roll obtained by winding a white heat-shrinkable polystyrene resin film roll, wherein the white heat-shrinkable polystyrene resin film roll is immersed in hot water at a temperature of 65 ° C. for 10 seconds in the main shrinkage direction. The rate of thermal shrinkage indicated by the rate of change in length with respect to before treatment is 5% or more, and the rate of change in length with respect to before treatment after immersion in hot water at 85 ° C. for 10 seconds in the main shrinkage direction. In the entire roll of heat shrinkage rate, the variation rate with respect to the average value of the heat shrinkage rate at each measurement point is within ± 3% , the light transmittance is 50% or less, and the white heat shrinkable polystyrene resin film However, in the main shrinkage direction, the maximum value of the rate of change in length with respect to the length before the treatment after heating for 1 minute at each temperature from 100 ° C. to 150 ° C. every 10 ° C. That maximum heat shrinkage rate is 60% or more, and a white heat-shrinkable polystyrene based resin film roll, wherein the film length of the film roll is 1000～6000M. A film roll formed by winding a white heat-shrinkable polystyrene resin film roll, wherein the white heat-shrinkable polystyrene resin film roll is measured for polystyrene-derived alpha dispersion in the measurement of dynamic viscoelasticity of the film. The dispersion other than alpha dispersion is measured in the temperature region, and in the main shrinkage direction, the thermal shrinkage rate indicated by the rate of change in length with respect to the pretreatment after immersion in hot water of 65 ° C. for 10 seconds is 5% or more. And in the main shrinkage direction, the average of the heat shrinkage rate at each measurement point in the entire roll of the heat shrinkage rate indicated by the length change rate with respect to the pretreatment after immersion in hot water at 85 ° C. for 10 seconds. is within ± 3% variation rate are all relative values, and a light transmittance of 50% or less, the white Ironetsu shrinkable polystyrene based resin film, the main shrinkage direction In this case, 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, is 60% or more after the treatment of heating for 1 minute at each temperature from 100 ° C. to 150 ° C. every 10 ° C. A white heat-shrinkable polystyrene resin film roll, wherein the film length of the film roll is 1000 to 6000 m . 3. The white heat-shrinkable polystyrene resin film roll according to claim 1, wherein the white heat-shrinkable polystyrene resin film roll has a width of 200 mm or more and a length of 1000 m or more. . The white heat-shrinkable polystyrene resin film roll according to any one of claims 1 to 3 , comprising a polystyrene resin having a syndiotactic structure. The white heat-shrinkable polystyrene resin film roll according to any one of claims 1 to 4 , wherein the white heat-shrinkable polystyrene resin film roll is made of two or more different types of resins. 6. The method for producing a white heat-shrinkable polystyrene resin film roll according to claim 5, wherein the following (1) to (3) are satisfied.
(1) It includes a step of mixing and melt-extruding a resin constituting a white heat-shrinkable polystyrene resin film roll, and the shape of the raw material chip of each resin is a columnar shape and / or an elliptical columnar shape, and the blending amount is the largest. The major axis, minor axis, and longitudinal length of the cross section perpendicular to the longitudinal direction of the other resin raw material chips with respect to the resin raw material chips are within ± 50% of the difference in average value.
(2) including a step of mixing and melt-extruding a resin constituting the white heat-shrinkable polystyrene resin film roll using an extruder equipped with a funnel-shaped hopper as a feed portion of raw material chips, The inclination angle, which is the angle formed by the hypotenuse and the horizontal line segment, is 65 degrees or more
(3) Including the preheating step, stretching step, and heat treatment step, the fluctuation range of the surface temperature of the film measured at any point in each step is within the average temperature ± 1 ° C. over the entire length of the film ”