JP2018048320A - Stretched sheet, packaging container, and methods of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretched sheet excellent in mold releasability and stacking preventing properties between containers in addition to moldability, heat resistance, and oil resistance.SOLUTION: The stretched sheet includes a resin layer obtained by stretching a resin composition which contains: a copolymer (A) containing an aromatic vinyl compound and a vinyl cyanide compound as monomer units; and a graft copolymer (B) obtained by graft-polymerizing an aromatic vinyl compound onto a rubber component. When the Vicat softening point of the copolymer (A) is Ta(°C), the Vicat softening point of the graft copolymer (B) is Tb(°C), the volume median particle diameter of rubbery dispersed particles in the graft copolymer (B) is Db (μm), and the volume average particle diameter of rubbery dispersed particles in the stretched sheet is Ds (μm), the following expressions (a)-(d) are satisfied: 102≤Ta≤112 (a); 10≤Ta-Tb≤30 (b); 1≤Db≤4 (c); and 1.5≤Ds/Db≤3 (d).SELECTED DRAWING: None

Description

  The present invention relates to stretched sheets and packaging containers, and methods for producing them.

  Conventionally, a packaging container made of a synthetic resin sheet has been used as a container used when selling foods, processed foods, and the like in stores such as supermarkets, convenience stores, department stores, and lunch boxes.

  Biaxially stretched polystyrene sheets are widely used in the food packaging field because of their excellent transparency and high rigidity, but they have the disadvantage of low oil resistance. Then, the styrene-type extending | stretching sheet which improved oil resistance by copolymerizing vinyl cyanide compounds, such as acrylonitrile, with styrene is reported (patent document 1, 2).

  The stretched sheet made of a styrene-acrylonitrile copolymer described in Patent Documents 1 and 2 has a high rigidity, and the packaging container obtained therefrom has a feature that the shape stability against a load is high. On the other hand, if containers are stacked, there is a concern that stacking will occur as in the case of sheets made of general-purpose polystyrene, and the force to peel off the stacked containers will be greater than that of sheets made of polystyrene. Troubles such as turning over multiple sheets when peeling off.

  In addition, the stretched sheet made of a copolymer of styrene and a vinyl cyanide compound has high adhesion to the metal above the glass transition point due to the presence of the vinyl cyanide compound, in addition to the difficulty of peeling, When thermoforming using a mold, there is a great concern that it may lead to defective appearance from the mold, and defects such as scratches and dents when released.

  In view of the above problems, it is necessary to design a stretched sheet having mold releasability and container stacking prevention. Known methods for imparting these performances to a stretched polystyrene sheet include a method using polystyrene with high impact polystyrene added (Patent Document 3), a method of applying a release agent to the surface layer of the stretched sheet (Patent Document 4), and the like. It has been. Although these methods are effective for general-purpose styrene-based stretched sheets, it is difficult to impart sufficient peelability to stretched sheets formed by copolymerization with a vinyl cyanide compound.

Japanese Patent Laid-Open No. 10-7817 Japanese Patent Laid-Open No. 2001-104589 JP-A-50-74649 Japanese Patent Laid-Open No. 53-115781

  In view of these current situations, the present invention provides a stretched sheet that is excellent in mold releasability and anti-stacking property between containers in addition to moldability, heat resistance and oil resistance, and packaging obtained by molding the same. It aims at providing a container and those manufacturing methods.

The present invention provides stretched sheets and packaging containers shown below, and methods for producing them.
(1) A resin containing a copolymer (A) containing an aromatic vinyl compound and a vinyl cyanide compound as monomer units, and a graft copolymer (B) obtained by graft-polymerizing an aromatic vinyl compound to a rubber component A stretched sheet comprising a resin layer formed by stretching the composition, wherein the Vicat softening point of the copolymer (A) is Ta (° C), the Vicat softening point of the graft copolymer (B) is Tb (° C), When the volume median particle diameter of the rubber-like dispersed particles in the graft copolymer (B) is Db (μm) and the volume average particle diameter of the rubber-like dispersed particles in the stretched sheet is Ds (μm), the following formula ( A stretched sheet satisfying a) to (d).
102 ≦ Ta ≦ 112 (a)
10 ≦ Ta−Tb ≦ 30 (b)
1 ≦ Db ≦ 4 (c)
1.5 ≦ Ds / Db ≦ 3 (d)
(2) The stretched sheet according to (1), wherein the arithmetic average roughness Sa of at least one surface of the stretched sheet is 0.005 to 0.25 μm and the root mean square roughness Sq is 0.01 to 0.5 μm. .
(3) The stretched sheet according to (1) or (2), wherein the shrinkage start temperature of the stretched sheet is 10 to 30 ° C. higher than Tb.
(4) The stretched sheet according to any one of (1) to (3), wherein the stretch ratio determined from the heat shrinkage ratio of the stretched sheet is 1.8 to 3.2 times.
(5) The stretched sheet according to any one of (1) to (4), further comprising a release agent layer containing polydimethylsiloxane on at least one surface of the resin layer.
(6) The stretched sheet according to any one of (1) to (5), wherein the total volatile content in the stretched sheet is 3000 ppm or less, the oligomer amount is 3000 ppm or less, and the vinyl cyanide compound monomer content is 50 ppm or less.
(7) The stretched sheet according to any one of (1) to (6), wherein the stretched sheet has a total light transmittance of 80 to 99% and HAZE of 0.3 to 3%.
(8) The stretched sheet according to any one of (1) to (7), wherein the color coordinate b * value of the stretched sheet is 0 to 8.
(9) The stretched sheet according to any one of (1) to (8), wherein the solvent-soluble component in the stretched sheet has a weight average molecular weight (Mw) of 100,000 to 250,000.
(10) The stretched sheet according to any one of (1) to (9), wherein the gel content in the stretched sheet is 0.05 to 1.5% by mass.
(11) A method for producing a stretched sheet according to any one of (1) to (10), wherein a resin composition containing a copolymer (A) and a graft copolymer (B) is biaxially stretched. The manufacturing method of a stretched sheet provided with the process to do.
(12) A packaging container formed of the stretched sheet according to any one of (1) to (10).
(13) The packaging container according to (12), wherein the shrinkage start temperature is 100 to 112 ° C.
(14) A method for manufacturing a packaging container according to (12) or (13), comprising a step of forming the stretched sheet according to any one of (1) to (10).
(15) The method for producing a packaging container according to (14), wherein the molding is hot plate molding.

  According to the present invention, in addition to moldability, heat resistance and oil resistance, a stretched sheet excellent in mold releasability and anti-stacking property between containers, and a packaging container obtained by molding the same, and those The manufacturing method of can be provided.

  Hereinafter, embodiments of the present invention will be described in detail.

  The stretched sheet of this embodiment includes a copolymer (A) containing an aromatic vinyl compound and a vinyl cyanide compound as monomer units, a graft copolymer (B) obtained by graft-polymerizing an aromatic vinyl compound to a rubber component, and The resin layer formed by extending | stretching the resin composition containing these is provided.

  Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile, but acrylonitrile is preferred. These vinyl cyanide compounds may be used alone or in combination of two or more.

  Examples of the aromatic vinyl compound include styrene, α-methyl styrene, p-methyl styrene, o-methyl styrene, m-methyl styrene, ethyl styrene, pt-butyl styrene, etc., preferably styrene. is there. These aromatic vinyl compounds may be used alone or in combination of two or more.

  The copolymer (A) containing an aromatic vinyl compound and a vinyl cyanide compound as monomer units may be a copolymer composed of any combination of the above monomer units, but the aromatic vinyl compound is styrene, Most preferably, the vinyl cyanide compound is an acrylonitrile-styrene copolymer which is acrylonitrile.

  In this embodiment, a stretched sheet having excellent heat resistance and oil resistance can be obtained by using a resin composition containing a copolymer (A) containing an aromatic vinyl compound and a vinyl cyanide compound as monomer units. .

  In the copolymer (A), the content of the vinyl cyanide compound monomer unit is preferably 9 to 39% by mass, more preferably 12 to 36% by mass, and still more preferably 18 to 30%, based on the total amount of monomer units. % By mass.

  In the copolymer (A), the content of the aromatic vinyl compound monomer unit is preferably 61 to 91% by mass, more preferably 64 to 88% by mass, and still more preferably 70, based on the total amount of monomer units. It is -82 mass%.

  The Vicat softening point (Ta) of the copolymer (A) is essential to be 102 ° C. or higher and 112 ° C. or lower, preferably 103 ° C. or higher and 111 ° C. or lower, more preferably 104 ° C. or higher and 110 ° C. or lower. When the Vicat softening point is 102 ° C. or higher, the stretched sheet and its molded container are excellent in heat resistance and oil resistance. When the Vicat softening point is 112 ° C. or lower, when a stretched sheet is formed, defective molding and defective release from the mold are suppressed, and the intended packaging container is easily obtained.

  Examples of the method for adjusting the Vicat softening point include selection of an aromatic vinyl compound and a vinyl cyanide compound during polymerization, adjustment of the blending amount, and addition of a third component. The Vicat softening point is measured in accordance with JIS K7206 (1999) using an injection molded product having a thickness of 3.2 mm as a test piece at a load of 9.8 N and a heating rate of 2 ° C./min.

  The content of the copolymer (A) is preferably 97 to 99.9% by mass, more preferably 98 to 99.7% by mass, and still more preferably 98.5 to 99.5% by mass based on the total amount of the resin composition. %. When the content is not less than the above lower limit, the transparency is more excellent. When the content is not more than the above upper limit value, it is more excellent in terms of mold releasability and anti-stacking property.

  The copolymer (A) may contain other vinyl monomer units copolymerizable with the aromatic vinyl compound and the vinyl cyanide compound as necessary. Other vinyl monomer units include, for example, acrylic acid, methacrylic acid, maleic anhydride, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dicyclopentanyl methacrylate, isobornyl methacrylate and other methacrylate esters, Examples include units such as acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, and decyl acrylate. The content of the other vinyl monomer units is not particularly limited, but the content of the monomer units of the vinyl cyanide compound and the aromatic vinyl compound is preferably in a range that does not deviate from the above range.

  The copolymer (A) can be obtained by polymerizing an aromatic vinyl compound and a vinyl cyanide compound. The polymerization method is not particularly limited, but bulk continuous polymerization or solution continuous polymerization is preferable.

  Although known examples can be adopted as the bulk continuous polymerization or solution continuous polymerization method, 10 to 40 parts by mass of a solvent such as ethylbenzene, toluene and methyl ethyl ketone is added to 100 parts by mass in total of the aromatic vinyl compound and the vinyl cyanide compound. It is more preferable to polymerize them.

  During polymerization, t-butyl peroxybenzoate, t-butyl peroxy-2-ethylhexanoate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (T-butylperoxy) -cyclohexane, 2,2-bis (4,4-di-butylperoxycyclohexyl) propane, t-butylperoxyisopropyl monocarbonate, di-t-butyl peroxide, dicumyl peroxide Further, a known organic peroxide such as ethyl-3,3-di- (t-butylperoxy) butyrate may be added, and 4-methyl-2,4-diphenylpentene-1, t- A known molecular weight modifier such as dodecyl mercaptan or n-dodecyl mercaptan may be added.

  The polymerization temperature is preferably 80 to 170 ° C, more preferably 100 to 160 ° C.

  The weight average molecular weight of the copolymer (A) is a polystyrene equivalent weight average molecular weight measured by the SEC method. The weight average molecular weight is preferably 100,000 to 250,000, and more preferably 12 to 200,000. When the weight average molecular weight is 250,000 or more, appearance defects called rain drops are less likely to occur when hot-plate forming a stretched sheet into a packaging container. When the weight average molecular weight is less than 100,000, appearance defects called bridges are less likely to occur.

  The number average molecular weight of the copolymer (A) is preferably 50,000 to 100,000, and the Z average molecular weight is preferably 200,000 to 450,000. When the number average molecular weight is 50,000 or more or the Z average molecular weight is 200,000 or more, raindrops are less likely to occur, and when the number average molecular weight is 100,000 or less or the Z average molecular weight is 450,000 or less, more bridges are generated. It becomes difficult to do.

  Here, raindrop refers to a phenomenon in which an unheated portion generated by entraining air between a hot plate and a sheet looks like a water droplet. The bridge refers to a phenomenon in which a heated sheet at the time of hot plate forming is locally deformed when peeled off from the hot plate, and a portion formed with the sheets overlapped on the mold remains as a trace.

The SEC measurement is performed under the following conditions.
Apparatus: Shodex “SYSTEM-21” manufactured by Showa Denko KK
Column: PLgel MIXED-B
Temperature: 40 ° C
Solvent: Tetrahydrofuran Flow rate: 1.0 ml / min Detection: RI
Concentration: 0.2% by mass
Injection volume: 100 μl
Calibration curve: Standard polystyrene (manufactured by Polymer Laboratories) is used, and the relationship between elution time and elution amount is converted to molecular weight to obtain various average molecular weights.

  The melt mass flow rate (MFR) of the copolymer (A) measured at 200 ° C. and a load of 49 N is preferably 1 to 5 g / 10 minutes, more preferably 2 to 4 g / 10 minutes.

  The graft copolymer (B) of this embodiment is a graft copolymer obtained by graft-polymerizing an aromatic vinyl compound to a rubber component. When styrene is used as the aromatic vinyl compound, the graft copolymer (B) is also called a rubber-modified styrene resin. The graft copolymer (B) can be obtained, for example, by graft polymerization of an aromatic vinyl compound in the presence of a rubber-like polymer. The polymerization method may be a known method such as a bulk polymerization method, a bulk / suspension two-stage polymerization method, or a solution polymerization method.

  In this embodiment, by using the resin composition containing the graft copolymer (B), the rubber-like dispersed particles form irregularities on the sheet surface, thereby preventing stacking and mold releasability during molding. An excellent stretched sheet can be obtained.

  Examples of the aromatic vinyl compound include styrene, alkyl styrene (eg, o-, m-, and p-isomers such as methyl styrene, ethyl styrene, isopropyl styrene, butyl styrene, and tertiary butyl styrene), and alpha alkyl. Styrene (eg, alphamethyl styrene, alpha ethyl styrene, etc.), monohalogenated styrene (eg, o-, m-, and p-isomers such as chlorostyrene, bromostyrene, and fluorostyrene), dihalogenated styrene (eg, Isomers such as dichlorostyrene, dibromostyrene, difluorostyrene and chlorobromostyrene), trihalogenated styrene (eg, trichlorostyrene, tribromostyrene, trifluorostyrene, dichlorobromostyrene, dibromochloros) Nuclei substituted isomers such as len and difluorochlorostyrene), tetrahalogenated styrene (e.g., each nucleosubstituted isomer such as tetrachlorostyrene, tetrabromostyrene, tetrafluorostyrene and dichlorodibromostyrene), pentahalogenated styrene ( For example, each nucleus-substituted isomer such as pentachlorostyrene, pentabromostyrene, trichlorodibromostyrene, and trifluorodichlorostyrene), alpha- and beta-halogen-substituted styrenes (eg, alphachlorostyrene, alphabromostyrene, beta-chlorostyrene, and beta-bromo) Styrene) and the like, and styrene is preferable. These monomers may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the rubber component include one or more conjugated 1,3-dienes (for example, butadiene, isoprene, 2-chloro-1,3 butadiene, 1-chloro-1,3 butadiene, piperylene, etc.) Co) polymer, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, butadiene-styrene-acrylonitrile copolymer, isobutylene-acrylate copolymer, butyl rubber and ethylene-propylene-terpolymer (EPDM) Among them, a butadiene polymer (polybutadiene) is preferable. These rubber components may be used individually by 1 type, and may be used in combination of 2 or more type.

  Further, as the polybutadiene, either high-cis polybutadiene or low-cis polybutadiene may be used, or a mixture of both may be used.

  It is essential that the Vicat softening point (Tb) of the graft copolymer (B) is lower than the Vicat softening point of the copolymer (A). When the sheet is stretched, the rubber-like dispersed particles of the graft copolymer (B) are stretched together. However, since the Vicat softening point of the graft copolymer (B) is lower than that of the copolymer (A), the sheet is cooled. In the process, re-shrinkage of the rubber-like dispersed particles occurs, and many fine irregularities are formed on the sheet surface, so that excellent anti-stacking property and mold releasability are exhibited.

  The difference (Ta−Tb) between the Vicat softening point (Ta) of the copolymer (A) and the Vicat softening point (Tb) of the graft copolymer (B) must be 10 ° C. or higher and 30 ° C. or lower. 13 ° C. or higher and 27 ° C. or lower is preferable, and 15 ° C. or higher and 25 ° C. or lower is more preferable. If this difference is 10 ° C. or more, re-shrinkage of the rubber-like dispersed particles is likely to occur, and sufficient unevenness is easily obtained on the sheet surface. Therefore, adhesion of the molding container to the mold is suppressed, and separation from the mold is suppressed. Improves moldability. Further, stacking prevention properties are also improved. In addition, when this difference is 30 ° C. or less, it is possible to suppress the rubber-like dispersed particles from being stretched again when the stretched sheet is molded and the unevenness to disappear, and to prevent the molding container from being in close contact with the mold. The releasability from is improved. Further, stacking prevention properties are also improved.

  Examples of methods for adjusting the Vicat softening point include a method using rubber particles having different softening points, a method of changing the blending amount of rubber particles, and a method of adding a plasticizer such as white oil. The Vicat softening point is measured in accordance with JIS K7206 using an injection molded product having a thickness of 3.2 mm as a test piece at a load of 9.8 N and a heating rate of 2 ° C./min.

  The volume median particle diameter (Db) of the rubber-like dispersed particles in the graft copolymer (B) used in the present embodiment is 1 μm or more and 4 μm or less, preferably 2 μm or more and 3 μm or less. When the volume median particle diameter is 1 μm or more, the release property from the mold when the obtained stretched sheet is molded is further improved, and stacking hardly occurs when the molded containers are laminated. In the case of 4 μm or less, it is possible to suppress the occurrence of small spherical defects called “fish eyes” in the resulting stretched sheet, which are caused by imperfect mixing in the resin, and to suppress a decrease in oil resistance.

  Examples of the method for adjusting the particle diameter include a method for adjusting the stirring speed in the phase transition region of the rubber particles in the polymerization step, a method for adjusting the amount of the chain transfer initiator in the raw material liquid, and the like. The volume median particle size of the rubber-like dispersed particles in the graft copolymer (B) is determined by dissolving the graft copolymer (B) in an electrolytic solution (3% tetra-n-butylammonium / 97% dimethylformamide solution). The volume-based particle size distribution curve determined by the Coulter multisizer method (Multisizer II manufactured by Coulter Co., Ltd .: Aperture tube orifice diameter 30 μm) is defined as 50 volume% particle diameter.

The gel content of the graft copolymer (B) used in the present embodiment is, for example, 15 to 55% by mass, and preferably 20 to 45% by mass. Examples of the method for adjusting the gel content include a method for adjusting the rubber content in the polymerization step, a method for adjusting the initiator amount, and a method for adjusting by blending with a styrene homopolymer after polymerization. The gel content is the ratio of the rubber-like dispersed particles in the graft copolymer (B). The weight of 1.00 g of the graft copolymer (B) is precisely weighed (W), and 35 ml of methyl ethyl ketone is added and dissolved. The solution was centrifuged at 10,000 rpm for 30 minutes in a centrifuge (Kokusan H-2000B (rotor: H)) to settle the insoluble matter, and the supernatant was removed by decantation to obtain an insoluble matter. Pre-dried in an oven at 90 ° C. for 2 hours, further dried under reduced pressure at 120 ° C. for 1 hour in a vacuum dryer, cooled in a desiccator for 20 minutes, and then measured the mass G of the dried insoluble matter as follows. Can be requested.
Gel content (mass%) = (G / W) × 100

The graft ratio of the rubber-like dispersed particles of the graft copolymer (B) used in the present embodiment is preferably 1 to 5. As a method of adjusting the graft ratio, there is a method of reducing the amount of the initiator in the polymerization step, but it varies depending on the type of the reactor and the type of rubber used. The graft ratio of the rubber-like dispersed particles of the graft copolymer (B) is determined from the gel content (mass%) in the graft copolymer (B) and the rubber content R (mass%) in the graft copolymer (B). It can be obtained as follows.
Graft rate = {(G / W) × 100-R) / R

  The rubber content in the graft copolymer (B) is obtained by dissolving the graft copolymer (B) in chloroform, adding a certain amount of iodine monochloride / carbon tetrachloride solution and leaving it in the dark for about 1 hour. Potassium iodide solution is added, excess iodine monochloride is titrated with 0.1N sodium thiosulfate / ethanol aqueous solution, and the amount of iodine monochloride added can be determined.

The swelling degree SI of the rubber-like dispersed particles of the graft copolymer (B) used in the present embodiment is preferably 10-30. The degree of swelling SI of the rubber-like dispersed particles of the graft copolymer (B) was determined by accurately weighing 1.00 g of the graft copolymer (B), adding 30 ml of toluene, and dissolving the solution. (Kokusan H-2000B (rotor: H)) was centrifuged at 10,000 rpm for 30 minutes to settle the insoluble matter, the supernatant liquid was removed by decantation, and the mass S of the insoluble matter swollen with toluene was determined. Then, the insoluble matter swollen with toluene is preliminarily dried in a safety oven at 90 ° C. for 2 hours, further dried under reduced pressure at 120 ° C. for 1 hour in a vacuum dryer, dried in a desiccator for 20 minutes, and then insoluble. The dry mass D of the minute can be measured and determined as follows.
Swelling degree SI = S / D

It is preferable that the methanol soluble part of the graft copolymer (B) of this embodiment is 1-6 mass%. The methanol-soluble component here means a component soluble in methanol in the graft copolymer (B), for example, an aromatic vinyl by-produced in the polymerization step or devolatilization step of the graft copolymer (B). In addition to compound oligomers (for example, styrene dimer and styrene trimer), various additives such as liquid paraffin and silicone oil, residual styrene monomer, and low molecular weight components such as a polymerization solvent are included. As a method for adjusting the methanol-soluble content, a method for adjusting the amount of oligomers (dimer, trimer) generated as a by-product in the polymerization step according to the type and amount of the initiator, and a method for adjusting the amount of liquid paraffin and silicone oil added. Methods and the like. In addition, methanol-soluble matter is obtained by accurately weighing 1.00 g of graft copolymer (B) (P), adding 40 ml of methyl ethyl ketone to dissolve, and rapidly adding 400 ml of methanol to insoluble methanol (resin component). Is precipitated and precipitated. After leaving still for about 10 minutes, it was gradually filtered through a glass filter to separate methanol-soluble components, dried under reduced pressure at 120 ° C. for 2 hours in a vacuum dryer, allowed to cool in a desiccator for 25 minutes, and dried. The mass N of the insoluble matter in methanol can be measured and determined as follows.
Methanol-soluble content (mass%) = (P−N) / P × 100

  The melt mass flow rate (MFR) measured at 200 ° C. and 49 N load of the graft copolymer (B) of this embodiment is preferably 1 to 5 g / 10 minutes, more preferably 2 to 4 g / 10 minutes. .

  In the resin layer of this embodiment, an ultraviolet absorber, a light stabilizer, an antioxidant, a lubricant, a plasticizer, a colorant, an antistatic agent, a flame retardant, mineral oil, and other additives, glass fiber, carbon, etc. Reinforcing fibers such as fibers and aramid fibers, fillers such as talc, silica, mica, and calcium carbonate may be further contained as long as the performance of the stretched sheet is not impaired.

The volume average particle diameter (Ds) of the rubber-like dispersed particles in the stretched sheet of the present embodiment is different from the volume median particle diameter (Db) of the rubber-like dispersed particles in the graft copolymer (B). The volume average particle diameter (Ds) in the stretched sheet is cut by an ultra-thin section method so that the observation surface is parallel to the main surface of the stretched sheet, and the rubber component is dyed with osmium tetroxide (OsO ₄ ). After that, the particle diameter of 100 particles is measured with a transmission microscope and calculated by the following formula.

  Ratio (Ds / Db) between the volume average particle diameter (Ds) of the rubber-like dispersed particles in the stretched sheet of the present embodiment and the volume median particle diameter (Db) of the rubber-like dispersed particles in the graft copolymer (B). ) Must be 1.5 or more and 3 or less, preferably 1.7 or more and 3 or less, and more preferably 2 or more and 3 or less. When this ratio is 1.5 or more, the rubber-like dispersed particles easily re-shrink, and sufficient unevenness is easily obtained on the sheet surface, so that the mold releasability and stacking prevention properties are excellent. Further, if this ratio is 3 or less, microcracks are less likely to occur at the interface between the rubber-like dispersed particles in the stretched sheet and the outer resin composition, and at the time of molding or mold release due to the cracks. It can suppress that a crack generate | occur | produces or oil resistance falls.

The weight average molecular weight (Mw) of the solvent-soluble component of the stretched sheet in this embodiment is preferably 100,000 to 250,000, and more preferably 12 to 200,000. When the weight average molecular weight is 250,000 or less, appearance defects called rain drops are less likely to occur when a stretched sheet is hot plate molded to obtain a packaging container. When the weight average molecular weight is 100,000 or more, an appearance defect called a bridge hardly occurs. The weight-average molecular weight of the solvent-soluble component in the stretched sheet was determined by accurately weighing 10 mg of sample, adding 5 g of tetrahydrofuran and dissolving it, and then filtering with a 0.45 μm membrane filter. The weight average molecular weight in terms of polystyrene measured by The SEC measurement is performed under the following conditions.
Apparatus: Shodex “SYSTEM-21” manufactured by Showa Denko KK
Column: PLgel MIXED-B
Temperature: 40 ° C
Solvent: Tetrahydrofuran Flow rate: 1.0 ml / min Detection: RI
Injection volume: 100 μl

  The stretch ratio of MD (Machine Direction; sheet flow direction) and the stretch ratio of TD (Transverse Direction; direction perpendicular to the sheet flow direction) of the stretched sheet in this embodiment are preferably 1.8 to 3.2, respectively. Times, more preferably 2 to 3 times, still more preferably 2.2 to 2.8 times.

  In this embodiment, the draw ratio is a ratio at which the test piece of the stretched sheet changes before and after heating. Specifically, the stretch formula is a value calculated by the following formula, that is, stretch ratio = Y / Z, unit [times]. means. In this formula, Y indicates the length [mm] of the straight line drawn on MD and TD on the surface of the stretched sheet before heating, and Z indicates the shrinkage of the test piece left in an oven at a temperature of 150 ° C. for 60 minutes. It shows the length [mm] of the straight line after being made.

  Moreover, it is preferable that the thermal contraction stress of MD and TD of a stretched sheet is 0.35-1.2 MPa. In addition, the heat shrinkage stress adopts the peak value of the stress obtained by measuring in 150 ° C. silicone oil according to ASTM D-1504.

  Moreover, the shrinkage start temperature of the stretched sheet is preferably 10 to 30 ° C higher, more preferably 15 to 25 ° C higher, and still more preferably 17 to 23 ° C higher than the Vicat softening point Tb of the graft copolymer (B). . If the difference from Tb is less than 10 ° C., the stretching temperature setting range for obtaining sufficient irregularities on the sheet surface may be narrowed. Moreover, when this difference exceeds 30 degreeC, there exists a possibility that the shaping | molding temperature setting range for a shaping | molding container obtaining sufficient unevenness | corrugation on the surface at the time of shaping | molding of a stretched sheet may become narrow. The shrinkage start temperature is a dimension before heating by placing a test piece of a stretched sheet in silicone oil heated at a heating rate of 2 ° C./min with a heat shrinkage measuring device (Tester Sangyo Co., Ltd.). The temperature at which MD or TD shrinks by 5% is adopted.

  Sa of arithmetic average roughness which is a roughness parameter of the stretched sheet is preferably 0.005 to 0.25 μm, more preferably 0.025 to 0.2 μm, and still more preferably 0.05 to 0.15 μm. The root mean square roughness Sq of the stretched sheet is preferably 0.01 to 0.5 μm, more preferably 0.05 to 0.4 μm, and still more preferably 0.1 to 0.3 μm. When it is at least the above lower limit, the stacking prevention property is further improved, and when it is at most the above upper limit, the transparency is further improved. In at least one surface of the stretched sheet, the roughness parameters Sa and Sq may be within the above range. When the stretched sheet further includes other layers such as a release agent layer, it is preferable that the roughness parameters Sa and Sq are within the above-mentioned range on the surface on which the other layers are provided.

The roughness parameters Sa and Sq are measured using a 3D image of the sheet surface photographed under the following conditions based on the method defined in ISO 25178.
Apparatus: 3D measurement laser microscope LEXT OLS4000 (Olympus)
Objective lens: MPLAPONLEXT50
Image size: 260μm × 250μm
Number of pixels: 1024 × 1024
Cut-off period λc: 0.80 mm λs: None λf: None Filter: Gaussian filter

  The total volatile content in the stretched sheet is preferably 3000 ppm or less, more preferably 2000 ppm or less, and still more preferably 1000 ppm or less. The amount of oligomer in the stretched sheet is preferably 3000 ppm or less, more preferably 2000 ppm or less, and still more preferably 1000 ppm or less. The content of the vinyl cyanide compound monomer in the stretched sheet is preferably 50 ppm or less, more preferably 30 ppm or less, and still more preferably 20 ppm or less. If these values are less than or equal to the above upper limit value, rain drops are less likely to occur during molding.

Here, the total volatile content refers to the total value of the volatile content of aromatic vinyl monomer, ethylbenzene, toluene, n-propylbenzene, and i-propylbenzene. The oligomer amount refers to the total value of the aromatic vinyl dimer, aromatic vinyl linear trimer, and aromatic vinyl cyclic trimer. In addition, the measurement method uses a gas chromatography method and performs the measurement under the following conditions.
Device name: GC-12A (Shimadzu Corporation)
Column: Glass column φ3 [mm] x 3 [m]
Quantitative method: Internal standard method (cyclopentanol)

The total light transmittance of the stretched sheet is preferably 80 to 99%, more preferably 85 to 98%, and still more preferably 90 to 97%. HAZE of the stretched sheet is preferably 0.3 to 3%, more preferably 0.4 to 2.5%, and still more preferably 0.5 to 2%. When the total light reduction rate is 80% or more or the HAZE is 3% or less, the transparency of the molded product is further improved. In addition, a total light transmittance and HAZE are measured on condition as follows according to JISK-7361-1.
Sample: Stretched sheet device: Haze meter NDH5000 (Nippon Denshoku)

The color coordinate b * value of the stretched sheet is preferably 0 to 8, more preferably 1 to 7, and further preferably 2 to 6. It is preferable that When the b * value exceeds 8, when the molded product is used as a packaging container, the content looks yellowish, and the appearance of the content is impaired. If the b * value is less than 0, the contents appear bluish, and the appearance of the contents is impaired. The b * value is the color coordinate b * of the L * a * b * color space defined by the CIE. The b * value is measured using a spectrocolorimeter under the following conditions.
Sample: Lamination of stretched sheets Total thickness 4.5mm
Apparatus: Spectral colorimeter CM-2500d (Konica Minolta)
Measurement method: SCI method (including regular reflection light)

  The gel content in the stretched sheet of the present embodiment is preferably 0.05 to 1.5% by mass. When the gel content is 1.5% by mass or less, small spherical defects, which are called fish eyes at the time of forming a sheet and are not completely mixed in the resin, are less likely to occur. Further, when the gel content is 0.05% by mass or more, surface unevenness due to the graft copolymer (B) is likely to occur, and the mold releasability and stacking prevention properties are further improved. The gel content in the stretched sheet is preferably 0.2% by mass or more, 0.21% by mass or more, 0.22% by mass or more, 0.23% by mass or more, from the viewpoint of particularly excellent stacking prevention properties. 24 mass% or more, 0.25 mass% or more, 0.26 mass% or more, 0.27 mass% or more, 0.28 mass% or more, 0.29 mass% or more, or 0.3 mass% or more, Moreover, Preferably, it is 1.0 mass% or less, or 0.6 mass% or less. The gel content in the stretched sheet is more preferably 0.2 to 1.0% by mass, and still more preferably 0.3 to 0.6% by mass, from the viewpoint of particularly excellent stacking prevention properties.

As a method of adjusting the gel content, a method of adjusting the type and addition amount of the graft copolymer (B), a method of adding a third component insoluble in the solvent, and changing the extrusion conditions at the time of forming the sheet And a method for producing a component insoluble in a solvent. For the gel content, 1.00 g of a stretched sheet was precisely weighed (W), 35 ml of methyl ethyl ketone was added and dissolved, and the solution was centrifuged at 10,000 rpm with a centrifuge (H-2000B manufactured by Kokusan Co., Ltd.). Centrifugation for 5 minutes to settle the insoluble matter, remove the supernatant by decantation to obtain the insoluble matter, pre-dry at 90 ° C for 2 hours in a safety oven, and further reduce pressure at 120 ° C for 1 hour in a vacuum dryer After drying and cooling in a desiccator for 20 minutes, the mass G of the dried insoluble matter can be measured and determined as follows.
Gel content (mass%) = (G / W) × 100

  The rubber content (R) of the stretched sheet of this embodiment is preferably 0.05 to 0.36% by mass. For rubber, dissolve the sheet in chloroform, add a certain amount of iodine monochloride / carbon tetrachloride solution, leave it in the dark for about 1 hour, add potassium iodide solution, and add excess iodine monochloride to 0.1N thiol. Titration with a sodium sulfate / ethanol aqueous solution can be performed from the amount of iodine monochloride added.

It is preferable that the methanol soluble part of the stretched sheet of this embodiment is 1% by mass or less. The methanol-soluble component herein refers to a component soluble in methanol of the stretched sheet, for example, a styrene oligomer (styrene dimer, styrene trimer) by-produced in the polymerization step or devolatilization step of the graft copolymer (B). In addition, various additives such as liquid paraffin and silicone oil, residual styrene monomer, and low molecular weight components such as a polymerization solvent are included. The methanol-soluble matter is precisely weighed 1.00 g of the stretched sheet (P), 40 ml of methyl ethyl ketone is added and dissolved, and 400 ml of methanol is added rapidly to precipitate and precipitate the methanol-insoluble matter (resin component). . After leaving still for about 10 minutes, it was gradually filtered through a glass filter to separate methanol-soluble components, dried under reduced pressure at 120 ° C. for 2 hours in a vacuum dryer, allowed to cool in a desiccator for 25 minutes, and dried. The mass (N) of the methanol insoluble matter can be measured and determined as follows.
Methanol-soluble content (mass%) = (P−N) / P × 100

  The stretched sheet of this embodiment may further include other layers on the surface of the resin layer. The other layer may be, for example, a release agent layer containing silicone oil, paraffin wax, microcrystalline wax or the like, or a surfactant layer containing glycerin fatty acid ester, sucrose fatty acid ester, sorbitan fatty acid ester or the like. Since the stretched sheet improves stacking prevention and mold releasability and is excellent in terms of food safety, it is further provided with a release agent layer containing polydimethylsiloxane on at least one surface of the resin layer. Is preferred.

  The thickness of the stretched sheet is not particularly limited, but is usually 0.01 mm or more and less than 1 mm, preferably 0.1 mm or more and less than 0.5 mm.

  The stretched sheet described above is obtained, for example, by a production method including a step of biaxially stretching a resin composition containing the copolymer (A) and the graft copolymer (B). More specifically, in this production method, the resin composition is melt-kneaded with an extruder, extruded from a die (particularly, a T-die), and then stretched sequentially or simultaneously in the biaxial direction. Get.

  In the case where the stretched sheet further includes the above-mentioned other layers in addition to the resin layer, the stretched sheet is produced by, for example, applying a general-purpose coating on the resin layer obtained in the step of biaxially stretching the resin composition. The method further includes the step of forming another layer using the method. Examples of the coating method include a normal rotation roll coater, a reverse roll coater, a gravure roll coater, a spray coater, a kiss roll coater, a bar coater, a knife coater, a comma roll coater, and a die coater. A gravure roll coater and a spray coater are preferable, and a spray coater is particularly preferable because a sheet having excellent mold releasability and blocking resistance can be obtained by efficiently providing a coating layer having a coating layer.

  The stretched sheet according to the present embodiment can be used for molded products such as packaging containers by molding. As the molded product, a food packaging container (that is, a packaging container containing food as a content) or a lid for the food packaging container is suitable, and particularly suitable when the food is a food containing fats and oils. Moreover, the food packaging container and the lid of the food packaging container can be used for heating a microwave oven or for refrigeration. When stretched sheets are used as lids for food packaging containers, the raw materials used for stretched sheets are publicly sanitary and stable, such as registered in the Food Additives Official Statement and the Polyolefin Hygiene Council Positive List. It is preferable to use a material that is recognized for its properties.

  It is preferable that the shrinkage | contraction start temperature of the packaging container of this embodiment is 100-112 degreeC. The shrinkage start temperature of the packaging container is determined based on the dimensions of the packaging container before heating when the test piece of the packaging container is left in an oven heated at a rate of 2 ° C./min. The temperature at which either of them contracts by 5% is adopted.

  An example of a molding method for obtaining a molded product from a stretched sheet is hot plate molding using a commercially available general hot plate pressure forming machine. The molding machine to be used is preferably of a type that can set the time during which the sheet is pressed against the hot plate, the time for molding by pressure air, the time lag for switching from sheet pressure welding to pressure air molding, the molding cycle, and the like. These methods are described in, for example, “Plastic Processing Technology Handbook” edited by The Society of Polymer Science, Nikkan Kogyo Shimbun (1995).

  Production examples (experimental examples) of the acrylonitrile-styrene copolymer used as the copolymer (A) and the graft copolymer (B) used as the graft copolymer (B) are shown below.

{Experimental Example 1: Production of acrylonitrile-styrene copolymer (AS-1)}
A devolatilizing tank in which a first reactor which is a fully mixed stirring tank having a capacity of about 20 L and a second reactor which is a tower-type plug flow reactor with a stirring capacity of about 40 L are connected in series, and a preheater is further attached. Two units were connected in series. As shown in Table 1, on the basis of the total amount of monomers, 15 parts by mass of ethylbenzene, t-butylperoxyisopropyl monocarbonate 0.01% with respect to 85 parts by mass of a monomer solution containing 12% by mass of acrylonitrile and 88% by mass of styrene Mass parts and 0.25 parts by mass of n-dodecyl mercaptan were mixed to obtain a raw material solution. This raw material solution was introduced into a first reactor controlled at 125 ° C. at 6.0 kg per hour. The reaction solution was continuously withdrawn from the first reactor, and this reaction solution was introduced into a second reactor adjusted to have a gradient from 125 ° C. to 160 ° C. in the flow direction. Next, after heating to 160 ° C. with a preheater, it was introduced into the first devolatilization tank reduced to 67 kPa, and further heated to 230 ° C. with a preheater and then introduced into the second devolatilization tank reduced to 1.3 kPa. Residual monomer and solvent were removed. This was extruded and cut into strands to obtain pellet-shaped acrylonitrile-styrene copolymer (AS-1). Table 1 shows the resin composition, Vicat softening point, and weight average molecular weight (Mw) of the obtained AS-1.

{Experimental Examples 2 to 9: Production of acrylonitrile-styrene copolymer (AS-2 to 9)}
Acrylonitrile-styrene resins (AS-2 to 9) were obtained in the same manner as in Experimental Example 1, except that the amounts of acrylonitrile and styrene were changed as shown in Table 1. Table 1 shows the resin composition, Vicat softening point, and weight average molecular weight (Mw) of AS-2 to 9 obtained.

{Experimental Example 10: Production of graft copolymer (B) (HI-1)}
As a rubbery polymer, 3.4% by mass of low-cis polybutadiene rubber (trade name: Diene 55AE, manufactured by Asahi Kasei) and 91.6% by mass of styrene were dissolved in 5.0% by mass of ethylbenzene. Moreover, 0.1 mass part of antioxidant (made by Ciba Geigy, trade name Irganox 1076) of rubber was added. This polymerization raw material was supplied at 12.5 [kg / hr] to a 14-liter jacketed reactor (R-01) equipped with a vertical stirring blade having a blade diameter d = 0.285 [m]. The reaction temperature was 140 ° C., N3d2 was 0.83 [m ² / s ³ ], and the resin ratio was 25%. The obtained resin solution was introduced into two jacketed plug flow reactors having an internal volume of 21 liters arranged in series. In the first plug flow reactor (R-02), the reaction temperature is 120 to 140 ° C. in the flow direction of the resin liquid. In the second plug flow reactor (R-03), the reaction temperature is The jacket temperature was adjusted so as to have a gradient of 130 ° C. to 160 ° C. in the flow direction of the resin liquid. The resin rate at the R-02 outlet was 50%, and the resin rate at the R-03 outlet was 70%. The obtained resin liquid is heated to 230 ° C., sent to a devolatilization tank with a vacuum degree of 5 [torr], unreacted monomers and solvents are separated and recovered, then extracted from the devolatilization tank with a gear pump, and then die plate This was extruded into a strand and cut into a pellet. Next, 0.3% by mass of white oil is added to the resin obtained by polymerization, blended uniformly using a twin screw extruder, extruded into a strand, and cut to form a pellet-shaped graft copolymer. Combined (B) (HI-1) was obtained. The monomer content in 100% by mass of the copolymer of the obtained graft copolymer (B) (HI-1) is 89.9% by mass of styrene, 10.1% by mass of butadiene, and 100% by mass of the resin composition. The amount of white oil was 0.3% by mass. The gel content was 30% by mass, the Vicat softening point was 87 ° C., and the volume median diameter (Db) of the rubber-like dispersed particles was 2.7 μm. These values are shown in Table 2.

{Experimental Examples 11-18: Production of Graft Copolymer (B) (HI-2-9)}
Various raw material charging amounts and stirring conditions in Experimental Example 10 were adjusted, and graft copolymers (B) HI-2 to 9 shown in Table 2 were obtained. Table 2 shows the monomer content, white oil amount, gel content, Vicat softening point, and volume median particle size (Db) of the obtained graft copolymer (B) HI-2 to 9.

<Example 1>
As a copolymer (A), 99.0% by mass of AS-2 obtained in the experimental example and 1.0% by mass of HI-2 obtained in the experimental example as a graft copolymer (B) were preliminarily prepared using a Henschel mixer. Using a sheet extruder (T-die width 500 mm, φ40 mm extruder (manufactured by Tanabe Plastic Machinery Co., Ltd.)), it was kneaded and extruded at an extrusion temperature of 230 ° C. and a rotation speed of 50 rpm to obtain a sheet having a thickness of 1.2 mm. . This sheet was stretched by a batch type biaxial stretching machine (manufactured by Toyo Seiki Co., Ltd.) at a stretching temperature of 137 ° C. and a strain rate of 0.1 / sec to MD 2.5 times and TD 2.5 times, and further using a bar coater. A polydimethylsiloxane emulsion (SM7025EX manufactured by Toray Dow Corning Co., Ltd.) was applied to one surface, dried in a dryer at 105 ° C., and after drying, a release agent layer having a coating amount of 20 mg / m ² was formed. A stretched sheet having a thickness of 0.20 mm was obtained.

  When the obtained stretched sheet was observed with a transmission electron microscope, the volume average particle diameter (Ds) of the rubber-like dispersed particles was 4.8 μm. The calculated average roughness (Sa) of the sheet is 0.111 μm, the root mean square height (Sq) is 0.211 μm, the total light transmittance is 90.0%, HAZE is 1.0%, and the b * value is 4.0. The shrinkage start temperature of the sheet was 106 ° C., the heat shrinkage rate was 59.3%, and the draw ratio determined from the heat shrinkage rate was 2.5 times. Furthermore, the amount of oligomer determined from gas chromatography was 1390 ppm, the total amount of volatile components was 1160 ppm, the amount of acrylonitrile was 20 ppm, the weight average molecular weight (Mw) of the solvent-soluble component of the resin composition was 148,000, and the gel content was 0.30. It was mass%.

<Examples 2 to 17>
AS-1,2,3,6,7,8,9 obtained in the experimental example as the copolymer (A) and HI-1,2,3 obtained in the experimental example as the graft copolymer (B) 4, 5, 8, and 9 were used to obtain stretched sheets by the same method as in Example 1 except that the blending amounts shown in Tables 3 and 4 were used. Thickness of the obtained stretched sheet, volume average particle diameter (Ds) of rubber-like dispersed particles, calculated average roughness (Sa) of sheet surface, root mean square height (Sq), total light transmittance, HAZE, b * Value, sheet shrinkage start temperature, thermal shrinkage rate and stretch ratio, oligomer amount determined from gas chromatography, total volatile content and acrylonitrile content, weight average molecular weight (Mw) of solvent-soluble content of stretched resin composition, gel content The measured values are shown in Tables 3 and 4.

<Comparative Examples 1-6>
AS-1,2,3,4,5 obtained in the experimental example as the copolymer (A) and HI-1,2,3,4,6 obtained in the experimental example as the graft copolymer (B) 7 was used to obtain a stretched sheet in the same manner as in Example 1 except that the blending amounts shown in Table 5 were used. Thickness of the obtained stretched sheet, volume average particle diameter (Ds) of rubber-like dispersed particles, calculated average roughness (Sa) of sheet surface, root mean square height (Sq), total light transmittance, HAZE, b * Value, sheet shrinkage start temperature, thermal shrinkage rate and stretch ratio, oligomer amount determined from gas chromatography, total volatile content and acrylonitrile content, weight average molecular weight (Mw) of solvent-soluble content of stretched resin composition, gel content The measured values are shown in Table 5.

<Examples 18 to 21>
Using AS-2 obtained in the experimental example as the copolymer (A) and HI-2 obtained in the experimental example as the graft copolymer (B), the blending amounts, extrusion temperatures, and rotational speeds shown in Table 6 are used. A stretched sheet was obtained in the same manner as in Example 1 except that it was changed. Thickness of the obtained stretched sheet, volume average particle diameter (Ds) of rubber-like dispersed particles, calculated average roughness (Sa) of sheet surface, root mean square height (Sq), total light transmittance, HAZE, b * Value, sheet shrinkage start temperature, thermal shrinkage rate and stretch ratio, oligomer amount determined from gas chromatography, total volatile content and acrylonitrile content, weight average molecular weight (Mw) of solvent-soluble content of stretched resin composition, gel content The measured values are shown in Table 6.

<Examples 22 to 25, Comparative Examples 7 and 8>
Using AS-2 obtained in the experimental example as the copolymer (A) and HI-2 obtained in the experimental example as the graft copolymer (B), the blending amounts, extrusion temperatures, and rotational speeds shown in Table 6 are used. A stretched sheet was obtained in the same manner as in Example 1 except that it was changed. Thickness of the obtained stretched sheet, volume average particle diameter (Ds) of rubber-like dispersed particles, calculated average roughness (Sa) of sheet surface, root mean square height (Sq), total light transmittance, HAZE, b * Value, sheet shrinkage start temperature, thermal shrinkage rate and stretch ratio, oligomer amount determined from gas chromatography, total volatile content and acrylonitrile content, weight average molecular weight (Mw) of solvent-soluble content of stretched resin composition, gel content The measured values are shown in Table 6.

<Examples 26 to 31>
Using the AS-2 obtained in the experimental example as the copolymer (A) and the HI-2 obtained in the experimental example as the graft copolymer (B), the compounding amounts shown in Table 7 are obtained, and the release agent layer Polydimethylsiloxane A (viscosity 10000 mm ² / s SM7025EX manufactured by Toray Dow Corning), polydimethylsiloxane B (viscosity 1000 mm2 / s KM-9737A manufactured by Shin-Etsu Silicone), monoglycerin fatty acid (DM-100 manufactured by Riken Vitamin Co., Ltd.) It apply | coated with the application quantity of Table 7, and it was made to dry with 105 degreeC drying machine, and the stretched sheet was obtained.

  The stretched sheet obtained in the examples was heated by a hot plate molding machine HPT-400A (manufactured by Wakisaka Engineering) with a hot plate temperature of 137 ° C., a mold temperature of 95 ° C., a preheating time of 2.0 seconds, and a molding time of 3.0 seconds. Under the conditions, a packaging container (hood pack with hinge: 241 mm long × 193 mm wide × 10 mm lid height / 28 mm body depth) was molded, and the physical properties of the obtained packaging container were measured and evaluated by the following methods. The results are shown in Tables 3-7.

[Formability]
When forming a packaging container, A is the one that is out of shape and has no appearance defect. Drop (droplet-like appearance defect), bridge (streaky appearance defect), fish eye (fish-eye appearance), etc. Part B was observed but no problem was designated as B, and one that was difficult to mold due to defective mold or crack was designated as C. If it is A or B, it can be said that the moldability is excellent.

[Mold releasability]
After the packaging container was molded, when it was peeled from the mold, A was designated as not causing scratches, cracks or whitening, B was designated as scratches, and C was designated as cracking or whitening. If it is A or B, it can be said that the mold releasability is excellent.

[transparency]
100 molded packaging containers were stacked and placed on paper on which 5 mm × 5 mm squares were written, and when the squares were viewed from above the containers, the visibility of the squares was evaluated as follows. If it is A, B or C, it can be said that it is excellent in transparency.
A: The whole is easily visible B: A part is covered with defects and cloudiness, but it is almost easily visible C: The whole is covered with defects and cloudiness, but can be visually recognized D: Not visible

[Stacking prevention]
After stacking 100 molded packaging containers, a load of 1 kgf was applied for 60 minutes, and then the number of sheets peeled when turning in order from the top was measured. When all 100 sheets were peeled off, the maximum number of sheets was listed if one or two sheets were peeled off and one or more sheets were peeled off. If the maximum number is 5 or less, it can be said that the stacking prevention property is excellent.

[Heat-resistant]
After leaving the packaging container in an oven at a predetermined temperature for 15 minutes, the change in container height was measured. This measurement was performed at each temperature while increasing the predetermined temperature in increments of 2 ° C. The heat resistance was evaluated by the minimum temperature at which the container height decreased by 5% or more from the container height before heating. If the minimum temperature is 102 ° C. or higher, it can be said that the heat resistance is excellent.

[Oil resistance]
In a state where the hinge portion of the packaging container is bent at a radius of curvature R = 1.0, 2 ml of a 3: 1 mixture of fatty acid triglyceride (Coconard ML Kao) and mint oil (Taiyo Pharmaceutical) is soaked. A set of gauze 10 × 10 mm was attached and allowed to stand at room temperature, and the container was observed. The time from pasting the gauze until whitening or cracking was observed was measured. The measurement was performed after 1, 3, 6, 12, 24, 48, and 72 hours had elapsed since the gauze was attached. If the said time is 12 hours or more, it can be said that it is excellent in oil resistance.

Claims (15)

A resin composition comprising a copolymer (A) containing an aromatic vinyl compound and a vinyl cyanide compound as monomer units, and a graft copolymer (B) obtained by graft-polymerizing an aromatic vinyl compound to a rubber component. A stretched sheet comprising a stretched resin layer,
The Vicat softening point of the copolymer (A) is Ta (° C.), the Vicat softening point of the graft copolymer (B) is Tb (° C.), and the rubber-like dispersed particles in the graft copolymer (B) A stretched sheet that satisfies the following formulas (a) to (d), where Db (μm) is the volume median particle diameter and Ds (μm) is the volume average particle diameter of the rubber-like dispersed particles in the stretched sheet.
102 ≦ Ta ≦ 112 (a)
10 ≦ Ta−Tb ≦ 30 (b)
1 ≦ Db ≦ 4 (c)
1.5 ≦ Ds / Db ≦ 3 (d)   2. The stretched sheet according to claim 1, wherein an arithmetic average roughness Sa of at least one surface of the stretched sheet is 0.005 to 0.25 μm and a root mean square roughness Sq is 0.01 to 0.5 μm.   The stretched sheet according to claim 1 or 2, wherein a shrinkage start temperature of the stretched sheet is 10 to 30 ° C higher than the Tb.   The stretched sheet according to any one of claims 1 to 3, wherein a stretch ratio determined from a heat shrinkage rate of the stretched sheet is 1.8 to 3.2 times.   The stretched sheet according to any one of claims 1 to 4, further comprising a release agent layer containing polydimethylsiloxane on at least one surface of the resin layer.   The stretched sheet according to any one of claims 1 to 5, wherein the stretched sheet has a total volatile content of 3000 ppm or less, an oligomer amount of 3000 ppm or less, and a vinyl cyanide compound monomer content of 50 ppm or less.   The stretched sheet according to any one of claims 1 to 6, wherein the stretched sheet has a total light transmittance of 80 to 99% and HAZE of 0.3 to 3%.   The stretched sheet according to any one of claims 1 to 7, wherein the stretched sheet has a color coordinate b * value of 0 to 8.   The stretched sheet according to any one of claims 1 to 8, wherein the solvent-soluble component in the stretched sheet has a weight average molecular weight (Mw) of 100,000 to 250,000.   The stretched sheet according to any one of claims 1 to 9, wherein the gel content in the stretched sheet is 0.05 to 1.5 mass%. It is a manufacturing method of the extension sheet given in any 1 paragraph of Claims 1-10,
The manufacturing method of an extending | stretching sheet | seat provided with the process of biaxially stretching the resin composition containing the said copolymer (A) and the said graft copolymer (B).   The packaging container formed with the extending | stretching sheet of any one of Claims 1-10.   The packaging container of Claim 12 whose shrinkage | contraction start temperature is 100-112 degreeC. It is a manufacturing method of the packaging container according to claim 12 or 13,
The manufacturing method of a packaging container provided with the process of shape | molding the stretched sheet of any one of Claims 1-10.   The method for manufacturing a packaging container according to claim 14, wherein the forming is hot plate forming.