TWI631166B - Styrene biaxially stretched sheet, biaxially stretched sheet with antifogging agent layer, packaging container and heating conditioning method - Google Patents

Abstract

The present invention provides a styrene-based biaxially stretched sheet comprising 97.0 to 99.9% by mass of a styrene resin and 0.1 to 3.0% by mass of a diene rubber-modified polystyrene based on the total amount of the resin composition. The resin composition is formed by biaxial stretching.

Description

Styrene biaxially stretched sheet, biaxially stretched sheet with antifogging agent layer, packaging container and heating conditioning method

The present invention relates to a styrene biaxially stretched sheet, a biaxially stretched sheet with an antifogging agent layer, a packaging container, and a heating conditioning method.

Conventionally, in a supermarket, a convenience store, a department store, a restaurant, and the like, as a container for selling food or processed food, a packaging container including a cover including a synthetic resin sheet and a container body is used.

Since the biaxially stretched polystyrene sheet is excellent in transparency and high in rigidity, it is widely used in the field of food packaging containers, but if it is stored for a long time in the state in which the oil adheres, whitening of the surface of the sheet occurs. A biaxially stretched polystyrene sheet which improves oil resistance has been sought (for example, Patent Documents 1 and 2).

Further, as described in Patent Documents 1 and 2, in addition to oil resistance, biaxially stretched polystyrene sheets are required to have mechanical strength, impact resistance, heat resistance, oil resistance, transparency, thermoformability, and the like. Various features.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 10-7817

Patent Document 2: Japanese Patent Laid-Open Publication No. 2001-105489

An object of the present invention is to provide a styrene-based biaxially stretched sheet, a biaxially stretched sheet with an antifogging agent layer, and a packaging container which are all excellent in transparency, slipperiness, and antifogging property.

The present invention provides a styrene-based biaxially stretched sheet, a biaxially stretched sheet with an antifogging agent layer, a packaging container, and a heating and conditioning method.

(1) A styrene-based biaxially stretched sheet comprising 97.0% by mass to 99.9% by mass of a styrene-based resin and a diene rubber-modified polystyrene 0.1 to 3.0 based on the total amount of the resin composition. The mass% of the resin composition is biaxially stretched.

(2) The styrene-based biaxially stretched sheet of (1), which comprises diene rubber particles having an average rubber particle diameter of 1.0 to 9.0 μm as a diene rubber.

(3) The styrene-based biaxially stretched sheet of (1) or (2), wherein the styrene-based resin is a copolymer comprising styrene and acrylonitrile as monomer units, and based on the total amount of monomer units The content of styrene is 64 to 88% by mass, and the content of acrylonitrile is 12 to 36% by mass.

(4) The styrene-based biaxially stretched sheet according to any one of (1) to (3) wherein the content of the diene rubber component is 0.005 based on the total amount of the styrene biaxially stretched sheet. 0.36 mass%.

(5) The styrene-based biaxially stretched sheet according to any one of (1) to (4), wherein the biaxially extending surface ratio is 4 to 11 times, and the maximum alignment relaxation stress is 0.2 to 0.8 MPa, and the MD direction is The absolute value of the difference between the maximum alignment relaxation stress and the maximum alignment relaxation stress in the TD direction is 0.2 MPa or less.

(6) The styrene-based biaxially stretched sheet according to any one of (1) to (5), wherein the arithmetic mean roughness of the arithmetic mean roughness Ra as defined in JIS B0601 is 0.002 to 0.020, and the fluctuation parameter Wa is 0.005. ~0.050.

(7) A biaxially stretched sheet with an antifogging agent layer, comprising the styrene biaxially stretched sheet according to any one of (1) to (6), and a styrene biaxially stretched sheet. At least one of the materials The antifogging agent layer on the surface, and the surface contact angle of the surface of the antifogging agent layer is 5 to 25°.

(8) A packaging container formed of the styrene biaxially stretched sheet of any one of (1) to (6) or the biaxially stretched sheet of the antifogging agent layer of (7) .

(9) A packaging container formed of a biaxially stretched sheet having an antifogging agent layer as in (7), and a surface on the side of the antifogging agent layer is a content contact surface.

(10) A heat conditioning method which heat-treats a foodstuff filled in a packaging container such as (8) or (9) by a microwave oven.

According to the present invention, it is possible to provide a styrene-based biaxially stretched sheet, a biaxially stretched sheet with an antifogging agent layer, and a packaging container which are all excellent in transparency, slipperiness, and antifogging property. Further, the biaxially stretched sheet with the antifogging agent layer of the present invention can maintain good antifogging performance, especially when the sheet is formed into a roll after film formation, and the antifogging agent is less transferred.

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

The styrene-based biaxially stretched sheet of the present embodiment contains a resin containing 97.0 to 99.9% by mass of a styrene resin and 0.1 to 3.0% by mass of a diene rubber-modified polystyrene based on the total amount of the resin composition. The composition is biaxially stretched. In other words, the styrene-based biaxially stretched sheet of the present embodiment contains 97.0 to 99.9% by mass of the styrene resin and 0.1 to 3.0% by mass of the diene rubber-modified polystyrene based on the total amount of the biaxially stretched sheet. .

The styrene resin is a resin containing a styrene monomer unit, and may be a homopolymer or a copolymer. However, the styrene resin is different from the resin of the diene rubber modified polystyrene (described later in detail). Examples of the styrene-based resin include an acrylonitrile-styrene copolymer.

The acrylonitrile-based monomer unit constituting the acrylonitrile-styrene copolymer may, for example, be acrylonitrile or methacrylonitrile, but is preferably an acrylonitrile unit. These acrylonitrile-based monomer units may be used singly or in combination of two or more.

The styrene monomer unit constituting the acrylonitrile-styrene copolymer may be styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, For units such as t-butyl styrene, a styrene unit is preferred. These styrene monomer units may be used singly or in combination of two or more.

In the acrylonitrile-styrene copolymer, the content of the acrylonitrile monomer unit is preferably from 12 to 36% by mass, more preferably from 16 to 33% by mass based on the total of the monomer units. When the acrylonitrile monomer unit is 36% by mass or less, the moldability and the hue are excellent. When the acrylonitrile monomer unit is 12% by mass or more, the oil resistance and the microwave resistance are excellent.

In the acrylonitrile-styrene copolymer, the content of the styrene monomer unit is preferably from 64 to 88% by mass, more preferably from 67 to 84% by mass based on the total of the monomer units. When the styrene monomer unit is 88% by mass or less, the oil resistance and the microwave resistance are excellent. When the styrene monomer unit is 12% by mass or more, the moldability and the hue are excellent.

The acrylonitrile-styrene copolymer may optionally contain other vinyl monomer units capable of copolymerization. Examples of the other vinyl monomer unit include acrylic acid, methacrylic acid, maleic anhydride, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate. Dicyclopentyl methacrylate, methacrylic acid A unit such as a methacrylate such as a acrylate, a methyl acrylate, an ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate or decyl acrylate. The content of the other vinyl monomer unit may be, for example, less than 10 parts by mass based on 100 parts by mass of the total of the styrene monomer unit and the acrylonitrile monomer unit.

The acrylonitrile-styrene copolymer is obtained by polymerizing an acrylonitrile-based monomer and a styrene-based monomer. The polymerization method is not particularly limited, but from the viewpoint of reducing odor, it is preferably a continuous polymerization in a block form.

As the bulk continuous polymerization method, a known example can be employed, but it is preferred to use a method of adding ethylbenzene, toluene, methyl ethyl group to 100 parts by mass of the total of the styrene monomer and the acrylonitrile monomer. The solvent such as a ketone is 10 to 40 parts by mass and polymerized.

When polymerizing, tert-butyl peroxybenzoate, tributyl phthalate (2-ethylhexanoate), 1,1-bis(t-butylperoxy)-3,3,5-three may be added. Methylcyclohexane, 1,1-bis(t-butylperoxy)-cyclohexane, 2,2-bis(4,4-di-butylperoxycyclohexyl)propane, isopropyl peroxide Known organic peroxides such as tert-butyl carbonate, dibutyl butyl peroxide, dicumyl peroxide, and 3,3-di-(t-butylperoxy)butyric acid ethyl ester may also be used. A known molecular weight modifier such as 4-methyl-2,4-diphenylpentene-1, tert-dodecylmercaptan or n-dodecylmer is added.

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

The polystyrene-equivalent weight average molecular weight measured by the SEC (Size Exclusion Chromatography) method of the acrylonitrile-styrene copolymer is not particularly limited, but is preferably from 100,000 to 250,000, more preferably 15~200,000. When the weight average molecular weight is 100,000 or more, the strength of the resin can be maintained, and the sheet strength and the folding endurance are excellent. When the weight average molecular weight is 250,000 or less, the viscosity rise can be suppressed, and the sheet formability and the container formability are excellent.

Further, the SEC measurement was carried out under the following conditions.

Device: Shodex "SYSTEM-21" manufactured by Showa Denko

Column: PLgel MIXED-B

Temperature: 40 ° C

Solvent: tetrahydrofuran

Flow rate: 1.0ml/min

Detection: RI (Refractive Index, refractive index)

Concentration: 0.2% by mass

Injection volume: 100μl

Calibration curve: The relationship between the dissolution time and the elution amount was converted into a molecular weight using standard polystyrene (manufactured by Polymer Laboratories), and various average molecular weights were determined.

The content of the styrene resin in the resin composition is from 97.0 to 99.9% by mass based on the total amount of the resin composition, preferably from 98.5 to 99.9% by mass, more preferably from 99.0 to 99.9% by mass, still more preferably from 99.3 to 9%. 99.7 mass%. In other words, the content of the styrene resin in the biaxially stretched sheet is from 97.0 to 99.9% by mass, preferably from 98.5 to 99.9% by mass, more preferably from 99.0 to 99.9% by mass, based on the total amount of the biaxially stretched sheet. Further, it is preferably 99.3 to 99.7 mass%. When the content is at least the above lower limit, it is excellent in transparency. When the content is at most the above upper limit, it is excellent in terms of slip properties and antifogging properties.

The diene rubber modified polystyrene (hereinafter also referred to as "rubber-modified impact styrene resin") is obtained by dissolving a rubbery polymer in a styrene monomer and polymerizing it (preferably, Branch obtained).

Examples of the monomer which is a raw material of the rubber-modified impact-resistant styrene-based resin include styrene and alkylstyrene (for example, methylstyrene, ethylstyrene, isopropylstyrene, and butylstyrene). And the third-stage butyl styrene and the like, or the respective isomers thereof, α-alkylstyrene (for example, α-methylstyrene, α-ethylstyrene, etc.), monohalogenated styrene ( For example, chlorostyrene, bromostyrene, and fluorostyrene, etc., or dihalogenated styrene (such as dichlorostyrene, dibromostyrene, difluorostyrene, and chlorobromide) Trinuclear styrenes such as styrene, etc., trihalogenated styrene (eg, trichlorostyrene, tribromostyrene, trifluorostyrene, dichlorobromostyrene, dibromochlorostyrene, and difluorochlorostyrene) Such as nuclear replacement of isomers), tetrahalogenated styrene (such as tetrachlorostyrene, tetrabromostyrene, tetrafluorostyrene and dichlorodibromostyrene, etc.), pentahalogenated benzene Ethylene (eg, nuclear substituted isomers such as pentachlorostyrene, pentabromostyrene, trichlorodibromostyrene, and trifluorodichlorostyrene) alpha] and [beta] a halogen-substituted styrene (e.g. alpha] chloro styrene, α- bromostyrene, β- [beta] bromostyrene and chlorostyrene, etc.) and the like. These monomers may be used alone or in combination of two or more.

As the rubbery polymer which is a raw material of the rubber-modified impact-resistant styrene-based resin, for example, one or two or more kinds of conjugated 1,3-dienes (for example, butadiene, isoprene, and 2) can be used. -Chloro-1,3-butadiene, 1-chloro-1,3-butadiene, pentadiene, etc.), butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, butadiene a styrene-acrylonitrile copolymer, an isobutylene-acrylate copolymer, a butyl rubber, and an ethylene propylene terpolymer (EPDM).

The content of the diene rubber-modified polystyrene is 0.1 to 3.0% by mass, preferably 0.2 to 2.0% by mass, more preferably 0.3 to 1.5% by mass, still more preferably 0.4%, based on the total amount of the resin composition. 1.2% by mass. In other words, the content of the diene rubber-modified polystyrene is 0.1 to 3.0% by mass, preferably 0.2 to 2.0% by mass, more preferably 0.3 to 1.5% by mass, based on the total amount of the biaxially stretched sheet, and further Good is 0.4~1.2% by mass. When the content is at least the above lower limit value, it is excellent in terms of slip properties and antifogging properties. When the content is at most the above upper limit value, it is excellent in transparency.

The content of the diene rubber component (hereinafter simply referred to as "rubber component") in the rubber-modified impact-resistant styrene resin is preferably 5 based on the total amount of the rubber-modified impact-resistant styrene resin. ~12% by mass, more preferably 8 to 10% by mass. When the content is at least the above lower limit value, it is more excellent in terms of slip properties and antifogging properties. When the content is at most the above upper limit value, the transparency is further excellent.

The content of the rubber component in the styrene-based biaxially stretched sheet is preferably 0.005 to 0.36% by mass, and more preferably 0.008 to 0.3% by mass based on the total amount of the styrene-based biaxially stretched sheet. When the content is at least the above lower limit value, it is more excellent in terms of slip properties and antifogging properties. When the content is at most the above upper limit value, the transparency is further excellent.

The resin composition may further contain one or more selected from the group consisting of an ultraviolet absorber, a light stabilizer, and an antioxidant.

Examples of the ultraviolet absorber include 2-(5'-methyl-2'-hydroxyphenyl)benzotriazole and 2-(5'-tert-butyl-2'-hydroxyphenyl)benzotriene. Azole, 2-[2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]benzotriazole, 2-(3',5'-di-third Base-2'-hydroxyphenyl)benzotrien Oxazole, 2-(3'-tert-butyl-5'-methyl-2'-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3',5'-di-t-butyl -2'-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3',5'-di-third-pentyl-2'-hydroxyphenyl)benzotriazole, 2-[3' -(3",4",5",6"-tetrahydro-phthalimidomethyl)-5'-methyl-2'-hydroxyphenyl]benzotriazole, 2,2' a benzotriazole-based ultraviolet absorber such as methylene bis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol]; 2-ethoxy-2'-ethyl bis-oxalic acid bis-aniline, 2-ethoxy-5-tert-butyl-2'-ethyl bis-oxalic acid anilide and 2-ethoxy-4'- Oxalyl oxalic acid anilide-based ultraviolet absorber such as isodecylphenyl oxalic acid bis-anilide; 2-hydroxy-4-n-octyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy- 4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2 a benzophenone-based ultraviolet absorber such as '-dihydroxy-4,4'-dimethoxybenzophenone or 2-hydroxy-4-methoxy-2'-carboxybenzophenone; salicylic acid Phenyl ester, salicylic acid, p-butyl phenyl ester, salicylic acid p-octyl phenyl ester, etc. Salicylic acid ultraviolet absorber; 2-ethylhexyl 2-cyano-3,3'-diphenylacrylate, cyanoacrylate such as 2-cyano-3,3'-diphenylacrylate Ultraviolet absorber; rutile-type titanium oxide, anatase-type titanium oxide, and titanium oxide-based ultraviolet stabilizer such as titanium oxide treated with a surface treatment agent such as alumina, ceria, a decane coupling agent, or a titanium coupling agent .

As the light stabilizer, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate and bis (1,2,2,6,6-penta-a) Base-4-piperidinyl) ester, dimethyl succinate. 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly[[6,(1,1,3,3-tetramethylbutyl)) Amino-1,3,5-three -2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imido]hexamethylene[(2,2,6,6-tetramethyl- 4-piperidinyl)imido]] and 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propanoxy]ethyl]-4-[ 3-(3,5-Di-t-butyl-4-hydroxyphenyl)propanyloxy]-2,2,6,6-tetramethylpiperidine, and the like.

Examples of the antioxidant include triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] and 2,4-bis(n-octylthio). )-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-three , pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 3-(3,5-di-t-butyl-4-hydroxyphenyl) Octadecyl propionate, 2,2-thiobis(4-methyl-6-tert-butylphenol) and 1,3,5-trimethyl-2,4,6-tris (3, Phenolic antioxidants such as 5-di-t-butyl-4-hydroxybenzyl)benzene; di(tridecyl) 3,3'-thiodipropionate, 3,3'-thiodipropane Dilauryl acid ester, di(tetradecyl) 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, 3,3'-thiodipropionic acid A sulfur-based antioxidant such as octyl ester; tris(nonylphenyl) phosphite, 4,4'-butylene-bis(3-methyl-6-tert-butylphenyl-di-tridecane) Ester, (tridecyl) pentaerythritol diphosphite, bis(octadecyl)pentaerythritol diphosphite, bis(di-tert-butylphenyl)pentaerythritol diphosphite, bis(di- Tert-butyl-4-methylphenyl)pentaerythritol diphosphite, dinonylphenyloctyl phosphite, tetrakis(2,4-di-t-butylphenyl)1,4-phenylene Base-di-phosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4'-extended biphenyl-diphosphite, 10-decyloxy-9,10- 9-oxa-10-phosphaphenanthrene hydrogen phenanthrene phosphorus antioxidants and the like.

The resin composition containing the acrylonitrile-styrene copolymer may also contain a lubricant, a plasticizer, a colorant, an antistatic agent, a flame retardant, and the like, without depending on the properties of the biaxially stretched sheet. Additives such as mineral oil; reinforcing fibers such as glass fiber, carbon fiber and aromatic polyamide fiber, talc, cerium oxide, mica, calcium carbonate and the like.

The content of the optional component such as the additive or the filler described above is, for example, 1.0% by mass or less based on the total amount of the resin composition. In other words, the content of the optional component such as the additive or the filler described above is, for example, 1.0% by mass or less based on the total amount of the biaxially stretched sheet.

As a method for producing the biaxially stretched sheet, a resin composition containing an acrylonitrile-styrene copolymer is melt-kneaded by an extruder and extruded from a die (particularly a T-die), and then A manufacturing method in which the axial direction is extended sequentially or simultaneously. The thickness of the biaxially stretched sheet is not particularly limited and is, for example, 0.05 mm or more and less than 0.6 mm, preferably 0.1 mm or more and less than 0.5 mm.

In the production of the biaxially stretched sheet, it is also possible to further remove the antioxidant, the lubricant, and the like, if necessary, in the melt-kneading of the resin composition, without damaging the object of the present invention. A known additive such as a molding agent, a plasticizer, a pigment, a dye, a foaming agent, a foaming nucleating agent, an inorganic filler, an antistatic agent, or the like is added to the resin composition.

The average rubber particle diameter (R _o ) in the biaxially stretched sheet is preferably from 1.0 to 9.0 μm, more preferably from 1.5 to 7.0 μm, still more preferably from 2.0 to 5.0 μm. When R _o is 1.0 μm or more, the sliding property and the antifogging property are more excellent. When R _o is 9.0 or less, the decrease in transmitted light and the increase in scattered light are suppressed, and the transparency is further excellent.

The average rubber particle diameter (R _o ) in the present invention is cut by an ultrathin sectioning method so that the observation surface becomes parallel to the main surface of the biaxially stretched sheet, and the rubber is made of osmium tetroxide (OsO ₄ ). After the components were dyed, the particle diameters of 100 particles were measured by a transmission microscope, and were calculated according to the following formula (1).

(wherein ni represents the number of measurements, and Di represents the particle size of the rubber particles measured)

When the MD (Machine Direction) stretching ratio of the biaxially stretched sheet is set to A, TD (Transverse Direction; direction perpendicular to the sheet flow direction), the stretching ratio is B, and A×B is expressed. The face magnification is preferably 4 to 11 times. At this surface magnification, the MD stretching ratio and the TD stretching ratio are preferably 1.5 to 3.5 times, respectively. When any of A, B, and A × B is in the above range, the thickness unevenness of the sheet can be suppressed, and the buckling strength can be secured in the container obtained by hot-plate forming the sheet. The above surface magnification is preferably 4 to 9 times, and the MD stretching ratio and the TD stretching ratio are preferably 2.0 to 3.0 times, respectively.

In the present invention, the stretch ratio is a ratio at which the test piece of the biaxially stretched sheet changes before and after heating, and specifically means a value calculated by the following formula, that is, the stretch ratio = Y/Z (unit [times]). . In the formula, Y represents the test piece of the biaxially stretched sheet along the MD before heating and The length of the straight line [mm] drawn by the TD, and Z represents the straight line after the test piece is allowed to stand for 60 minutes in an oven which is 30 ° C higher than the Vickers softening point temperature of the sheet measured in accordance with JIS K7206. The length [mm].

In the biaxially stretched sheet, when the maximum directional relaxation stress in the MD direction is a and the maximum directional relaxation stress in the TD direction is b, a and b are preferably 0.2 to 0.8 MPa, more preferably 0.3 MPa. 0.7 MPa, |ab|(absolute value of ab) is preferably 0.2 MPa or less, more preferably 0.10 MPa or less. When a and b are 0.2 MPa or more, the sheet strength can be ensured and the folding endurance is excellent. When a and b are 0.8 MPa or less, the increase in shrinkage force can be suppressed, and whitening (oil resistance) and moldability at the time of oil adhesion are excellent. When |a-b| is 0.2 MPa or less, it is possible to suppress the poor formability due to the difference in the contraction force in the MD and TD directions and the strain of the molded article.

The roughness parameter Ra of the arithmetic mean roughness prescribed by JIS B0601 of the biaxially stretched sheet is preferably from 0.002 to 0.020 μm, and the undulation parameter Wa is preferably from 0.005 to 0.050 μm. When the roughness parameter Ra is 0.002 μm or more and the undulation parameter Wa is 0.005 μm or more, the adhesion between the sheets can be maintained, and the slipperiness and the antifogging agent after long-term storage can be suppressed. When Ra is 0.02 μm or less and Wa is 0.050 μm or less, the unevenness of the surface of the sheet can be suppressed, and the appearance and moldability are excellent.

The biaxially stretched sheet (hereinafter also referred to as "laminated sheet") with the antifogging agent layer of the present embodiment includes a styrene biaxially stretched sheet and an antifogging layer. The antifogging agent layer is disposed on at least one surface of the laminated sheet. Thereby, the oil resistance of the laminated sheet can be improved.

Examples of the antifogging agent include nonionic surfactants such as sucrose fatty acid ester, sorbitan monostearate, sorbitan monopalmitate, sorbitan monobehenate, and sorbitan. A sorbitan fatty acid ester surfactant such as montanic acid ester, glycerol monolaurate, glyceryl monopalmitate, glyceryl monostearate, diglyceryl distearate, triglyceride monostearate, A glycerol fatty acid ester-based surfactant such as tetraglycerol mono-montanate, a polyethylene glycol-based interface such as polyethylene glycol monopalmitate or polyethylene glycol monostearate Agent, alkylene oxide adduct of alkanol, ester of sorbitan/glycerol condensate with organic acid; polyoxyethylene (2 mol) stearylamine, polyoxyethylene (2 mol) laurylamine, poly Polyoxyethylene alkylamine compound such as oxyethylene (4 mol) stearylamine, polyoxyethylene (2 mol) stearylamine monostearate, polyoxyethylene (2 mol) stearylamine distearate Ester, polyoxyethylene (4 mol) stearylamine monostearate, polyoxyethylene (4 mol) stearylamine distearate, polyoxyethylene (8 mol) stearylamine monostearyl Fatty acid ester of polyoxyethylene alkylamine compound such as acid ester, polyoxyethylene (2 mol) stearylamine monobehenate, polyoxyethylene (2 mol), laurylamine stearate, polyoxyethylene (polyoxyethylene) 2 mol) an amine-based surfactant such as a fatty acid guanamine such as a polyoxyethylene alkylamine compound such as stearylamine. Further, a water-soluble polymer represented by, for example, polyvinyl alcohol and a copolymer thereof (for example, a copolymer with acrylamide, polyvinylpyrrolidone), polyvinylpyrrolidone, and a copolymer thereof may be mentioned. (for example, a copolymer with vinyl acetate), a cellulose derivative (hydroxymethylcellulose, hydroxyethylcellulose, etc.), a starch derivative, gelatin, gum arabic, casein, sanmon gum, glycogen, Chitin, chitosan, agarose, carrageenan, heparin, hyaluronic acid, pectin, xyloglucan/polyethylene oxide, polypropylene oxide, water-soluble alkyd resin, water-soluble epoxy resin , water-soluble phenol resin, water-soluble urea resin, water-soluble melamine resin, water-soluble amine-based resin, water-soluble polyamide resin, water-soluble acrylic resin, water-soluble polycarboxylate, water-soluble polyester resin, water-soluble A polyurethane resin, a water-soluble polyol resin, or a chemical modification of the polymer.

The method of applying the antifogging agent to the biaxially stretched sheet is not particularly limited, and a method of applying it by a roll coater, a knife coater, a gravure roll coater or the like can be mentioned. The antifogging agent layer can also be formed by spraying, dipping, or the like.

The water contact angle after application of the antifogging agent (i.e., the surface of the antifogging agent layer) is preferably 5 to 25°. When the water contact angle is 5° or more, it is possible to suppress the appearance of the surface from being adhered, resulting in poor appearance or adhesion of dirt during molding, and also suppressing slipperiness due to stickiness. When the water contact angle is 25 or less, the preferred lipophilicity is ensured, the content is excellent in visibility, and the antifogging property is more excellent.

The styrene biaxially stretched sheet of the present embodiment and the biaxially stretched sheet with the antifogging agent layer can be used for molding products such as packaging containers by molding. In the case of a packaging container formed of a biaxially stretched sheet with an antifogging agent layer, it is preferred that the surface of the antifogging agent layer side of the sheet is a content contact surface. The molded article is preferably a food packaging container (that is, a packaging container containing food as a content) or a lid material for a food packaging container, and particularly preferably in the case where the food is a fat-containing food. Moreover, the lid of the food packaging container and the food packaging container can be used for heating and refrigerating in a microwave oven. When the styrene biaxially stretched sheet and the biaxially stretched sheet with the antifogging agent layer are used for the lid of a food packaging container or a food packaging container, the styrene biaxially stretched sheet and The raw material of the biaxially stretched sheet with the antifogging agent layer is preferably a material which is publicly approved for hygienicity and stability registered in the forward list of the food additive or the polyolefin hygiene agreement.

As a method of obtaining a molded article from a biaxially stretched sheet of a styrene-based biaxially stretched sheet and an antifogging agent layer, a commercially available ordinary hot plate forming machine can be cited. The molding machine to be used is preferably one that can set the time during which the sheet is pressed against the hot plate or the time of forming by pressure, the time difference from the sheet pressure to the time difference of the pressure forming, the molding cycle, and the like. These methods are described, for example, in the Journal of Plastic Processing Technology, "The Handbook of Plastic Processing Technology", Nikkan Kogyo Shimbun (1995).

The heating conditioning method of the present embodiment includes a step of heating and conditioning a food filled in the packaging container by a microwave oven.

[Examples]

The production example of the acrylonitrile-styrene copolymer used is shown below.

{Experimental Example 1: Manufacture of acrylonitrile-styrene copolymer (AS-1)}

The first reactor as a completely mixed type agitation tank having a volume of about 20 L is connected in series with the second reactor of a tower plug flow type reactor as a mixer having a volume of about 40 L, and then two preheaters are connected in series. It is constructed by removing the groove. As shown in Table 1, ethylbenzene was mixed with 85 parts by mass of a monomer solution containing 12% by mass of acrylonitrile and 88% by mass of styrene. 15 parts by mass, 0.01 parts by mass of butyl tricarbonate monoperoxide, and 0.25 parts by mass of third-dodecyl mercaptan were used to prepare a raw material solution. The raw material solution was introduced at 6.0 kg per hour to a first reactor controlled at 125 °C. The reaction liquid was continuously withdrawn from the first reactor, and the reaction liquid was introduced into a second reactor adjusted to have a gradient of from 125 ° C to 160 ° C in the direction of flow. Next, it is introduced into a first devolatilization tank which is heated to 160 ° C by a preheater and then reduced to 67 kPa, and further introduced into a second devolatilization tank which is heated to 230 ° C by a preheater and then depressurized to 1.3 kPa. Thereby, the residual monomer and solvent are removed. This was extruded into a rope shape and cut, whereby a pellet-shaped acrylonitrile-styrene copolymer (AS-1) was obtained.

{Experimental Example 2 to 7: Manufacture of acrylonitrile-styrene copolymer (AS-2~7)}

An acrylonitrile-styrene resin (AS-2 to 7) was obtained in the same manner as in Production Example 1, except that the amounts of acrylonitrile and styrene were changed as shown in Table 1.

{Experimental Example 8: Manufacture of impact-resistant polystyrene (HS-1)}

3.4% by mass of a low-butadiene butadiene rubber (manufactured by Asahi Kasei Co., Ltd., trade name: Diene 55AS) and 91.6% by mass of styrene as a rubbery polymer were dissolved in 5.0% by mass of ethylbenzene. Further, 0.1 part by mass of a rubber antioxidant (manufactured by Ciba Gaki, trade name Irganox 1076) was added. The polymerization raw material was supplied to a reactor of 14 liters of a cannula having an anchor type stirring blade having a blade diameter d = 0.285 [m] at 12.5 [kg/hr] (R-01, see Fig. 2) in. The reaction temperature was 140 ° C, N3d2 was 0.83 [m 2 /S 3 ], and the resin ratio was 25%. The obtained resin liquid was introduced into a plug flow type reactor in which two internal volumes of a casing having a volume of 21 liters were placed. In the first plug flow type reactor (R-02), the casing temperature is adjusted so that the reaction temperature has a gradient of 120 ° C to 140 ° C in the flow direction of the resin liquid, and the second plug flow type reactor is used. In (R-03), the jacket temperature is adjusted so that the reaction temperature has a gradient of 130 ° C to 160 ° C in the flow direction of the resin liquid. The resin ratio at the exit of R-02 is 50%, and the resin ratio at the exit of R-03 is 70%. After the obtained resin liquid is heated to 230 ° C, it is sent to a devolatilization tank having a degree of vacuum of 5 [torr], and the unreacted monomer and solvent are separated and recovered, and then extracted by a gear pump from the devolatilization tank, and formed by a template. After the rope is formed, it is granulated by a water tank and recovered as a product. The obtained resin had a diene rubber component content of 5.0%.

{Experimental Examples 9 to 13: Manufacture of diene rubber modified polystyrene (HS-1)}

The amount of each raw material added in Experimental Example 8 was adjusted to obtain a diene rubber-modified polystyrene containing the diene rubber component described in Table 2.

<Example 1>

Acrylonitrile-styrene copolymer (A) and rubber-modified impact-resistant styrene resin (B) using a sheet extruder (T die width 500 mm, Φ 40 mm extruder (Extruder) (Tanabe Plastic Machinery Co., Ltd. Manufactured)) An unstretched sheet having a thickness of 1.2 mm was obtained at an extrusion temperature of 230 °C. The unstretched sheet was preheated to 140 ° C by a batch type biaxial stretching machine (Toyo Seiki) to a strain rate of 0.1 / sec, extended to 2.4 times in the MD direction, and extended in the TD direction. Up to 2.4 times (face magnification 5.8 times), a biaxially stretched sheet having a thickness of 0.21 mm was obtained.

Further, 1% sucrose oleate (Ryoto Sugar Ester O-1570 (manufactured by Mitsubishi Chemical Corporation)) was applied at 5 g/m ² by a bar coater, and dried in an oven at 105 ° C for 1 minute. The physical properties of the obtained laminated sheet were measured and evaluated by the following methods. The results are shown in Table 3.

[Extension ratio]

For the test piece of the laminated sheet, a straight line Y of 100 mm was taken along MD and TD, and the test piece was allowed to stand in an oven 30 ° C higher than the Vickers softening point temperature of the sheet measured in accordance with JIS K7206 for 60 minutes. The length Z [mm] of the straight line after the contraction was calculated, and the MD stretching ratio, the TD stretching ratio, and the surface magnification were calculated according to the following formula, that is, the stretching ratio = Y/Z and the unit [times].

[Maximum alignment relaxation stress]

A test piece of 20 mm × 200 mm × 0.2 mm was obtained from the laminated sheet. The both ends of the test piece were fixed, immersed in an oil bath of 130 ° C, and the stress value at the time of the maximum load was calculated. The stress value in the MD direction at this time is set as the maximum alignment relaxation stress (a), and the stress value in the TD direction is set as the maximum relaxation stress (b), and |(a)-(b)| is obtained.

[water contact angle]

According to JIS R3257, the contact angle meter DM-701 (Xiehe Interface Chemistry) was used, and the test liquid was distilled water, and the contact angle after 30 seconds from the dropwise addition amount to the laminated sheet was measured.

[transparency]

The haze was measured by a fog meter NDH5000 (Nippon Denshoku Co., Ltd.) in accordance with JIS K-7361-1. The biaxially stretched sheet produced as described above was used to have a thickness of 0.21 mm. Further, if the haze is less than 2.0%, it is excellent in transparency.

A: Less than 1.0%

B: 1.0% or more and less than 2.0%

C: 2.0% or more

[slip property]

When the food contact surface of the laminated sheet cut from the top surface of the container overlaps with the non-contact surface of the food, the friction angle (the angle at which the sliding starts) is determined by the method according to JISP8147 paper and paperboard-static and dynamic friction coefficient measurement method. . Further, if the rubbing angle is less than 30, the slip property is excellent.

A: Less than 15°

B: 15° or more and less than 30°

C: 30° or more

[Anti-fog property after storage]

The laminated sheet was taken up and left to stand at 23 ° C for 6 months in a roll state, and then subjected to a hot plate forming machine HPT-400A (manufactured by WAKISAKA ENGINEERING) at a hot plate temperature of 135 ° C and a heating time of 2.0 seconds. A molded lid (size 241 x width 193 x height 28 mm). 50 g of water at 95 ° C was poured into the obtained container body, and the lid was placed and allowed to stand at 23 ° C. Confirm the content of the contents after 10 minutes. In addition, when it evaluates as A or B, it can be said that it is excellent in anti-fogging property after storage.

A: The contents can be clearly confirmed.

B: It is difficult to see the contents due to condensation on the lid.

C: There is a large amount of condensation on the lid portion, and it is impossible to discriminate the contents.

<Examples 2 to 48, Comparative Examples 1 to 4>

In the same manner as in Example 1, a laminated sheet was produced under the composition and elongation conditions described in Tables 3 to 10, and evaluated. The results are shown in Tables 3 to 10.

Further, the following evaluations were performed on the laminated sheets of the respective examples and comparative examples. The results are shown in Tables 11 to 16.

[Folding resistance]

The bending strength of the laminated sheet in the extrusion direction (longitudinal direction) and the direction perpendicular thereto (lateral direction) was measured in accordance with ASTM D2176. The average of the vertical and horizontal directions was obtained and evaluated.

A: 10 or more times

B: 5 times or more and less than 10 times

C: less than 5 times

[formability]

Using a hot plate forming machine HPT-400A (manufactured by WAKISAKA ENGINEERING), The appearance of the toilet lid (size 241 × width 193 × height 28 mm) formed of the laminated sheet was evaluated under the conditions of a hot plate temperature of 135 ° C and a heating time of 2.0 seconds.

A: Good

B: slight whitening, water droplets, and poor shape caused by the roughness of the surface

C: Significant whitening, water droplets, and poor shape caused by rough surface (unproductive)

[container strength]

A 500 g weight was placed in the container body formed of the laminated sheet, and the lid of the lid was overlapped by the lid 5, and the deformed state of the lid member after standing for 24 hours was confirmed.

A: No shape change.

B: Deformation occurred.

C: Cracking occurred.

[hue]

Ten sheets of a laminated sheet having a thickness of 0.21 mm were superposed, and the b value obtained by SCI measurement (including specular reflection light) of the spectrophotometer CM-2500d (Konica Minolta) was evaluated.

A: not up to 3

B: 3 or more and less than 5

C: 5 or more

[Oil resistance]

In the center of the toilet lid formed by the laminated sheet, a gauze 10* is infiltrated with a test liquid of a salad oil (manufactured by Nisshin Oil Co., Ltd.), mayonnaise (manufactured by Ajinomoto Co., Ltd.), and COCONARD ML (manufactured by Kao Corporation). 10 mm, allowed to stand in an oven at 60 ° C for 24 hours, and the surface of the attached portion was observed.

A: No change

B: slightly whitened

C: Significantly whitened and cracked

[microwave oven tolerance]

The mayonnaise was placed at 2 x 2 cm in the center of the lid of the laminated sheet formed by the laminated sheet, 300 g of water was added to the container body, and the lid container was placed, and the mixture was heated in a microwave oven of 1500 W for 1 minute, and then the condition of the portion to be attached to the mayonnaise was visually evaluated.

A: No change

B: The container is slightly deformed

C: whitening, opening, and the container is significantly deformed (cannot be produced)

Claims (9)

A styrene-based biaxially stretched sheet comprising a resin composition containing 97.0 to 99.9% by mass of a styrene resin and 0.1 to 3.0% by mass of a diene rubber-modified polystyrene based on the total amount of the resin composition. The styrene resin is a copolymer comprising styrene and acrylonitrile as a monomer unit, and the content of the styrene is 64 to 88% by mass based on the total amount of the monomer units. The content of acrylonitrile is 12 to 36% by mass, and the styrene-based biaxially stretched sheet contains diene rubber particles having an average rubber particle diameter of 1.5 μm or more as the diene rubber, and the diene rubber modified poly The content of the diene rubber component in the styrene is 8 to 12% by mass based on the total amount of the diene rubber-modified polystyrene. The styrene-based biaxially stretched sheet of claim 1, which contains diene rubber particles having an average rubber particle diameter of 1.5 to 9.0 μm as the diene rubber. The styrene biaxially stretched sheet according to claim 1 or 2, wherein the content of the diene rubber component is 0.005 to 0.36 mass% based on the total amount of the styrene biaxially stretched sheet. The styrene biaxially stretched sheet of claim 1 or 2, wherein the biaxially extending surface ratio is 4 to 11 times, the maximum alignment relaxation stress is 0.2 to 0.8 MPa, and the maximum alignment relaxation stress in the MD direction is in the TD direction. The absolute value of the difference between the maximum alignment relaxation stresses is 0.2 MPa or less. The styrene biaxially stretched sheet according to claim 1 or 2, wherein the roughness parameter Ra of the arithmetic mean roughness specified in JIS B0601 is 0.002 to 0.020, and the undulation parameter Wa is 0.005 to 0.050. A biaxially stretched sheet with an antifogging agent layer, comprising: The styrene biaxially stretched sheet according to any one of claims 1 to 5, and an antifogging agent layer provided on at least one surface of the styrene biaxially stretched sheet, and a surface of the antifogging agent layer The water contact angle is 5~25°. A packaging container formed by the styrene biaxially stretched sheet of any one of claims 1 to 5 or the biaxially stretched sheet of the antifogging agent layer of claim 6. A packaging container formed of a biaxially stretched sheet of the antifogging agent layer as claimed in claim 6, and the surface of the antifogging agent layer side is a content contact surface. A heat conditioning method for heating and conditioning a foodstuff filled in a packaging container according to claim 7 or 8 by a microwave oven.