JP2000204210A - Styrene-based resin sheet and container using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a styrene-based resin sheet excellent in moldability in molding containers, and containers. SOLUTION: The styrene-based resin sheet contains a styrene-based resin (a) and a thermoplastic resin such as polyolefin-based resins and polyester-based resins (b) approximately in a weight ratio of 40/60 to 97/3. The styrene-based sheet is suitable for molding containers. The styrene-based resin (a) satisfies the relationships of the formulae (I) to (III), Formula (I): Δlnλn/Δε=(lnλn2-lnλn1)/(ε2-ε1)>=0.15 Formula (II): λn=λ/λ1 Formula (III): ε=ln(l/l0) (wherein λn is a nonlinear parameter; λ is an elongation viscosity in the nonlinear region; λ1 is an elongation viscosity in the linear region; ε is a Hencky's elongation strain; l0 and l are each the length of the sample at elongation time 0 and t, respectively) in an elongation viscosity measurement at 130 deg.C at an elongation rate in the range of 0.0025-0.0035 sec-1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a styrene-based resin sheet capable of suppressing drawdown by molding a container, a container using the same, and a method of manufacturing the container.

[0002]

2. Description of the Related Art In recent years, a method of cooking or processing (eg, thawing) foods in a container by using a cooking device such as a microwave oven has been widely used. Such a cooking container is required to have high heat resistance and oil resistance.

[0003] Styrene resins are inexpensive in addition to various properties such as transparency, stiffness and hygiene (no taste and odor), and are therefore inexpensive. Container). However, since styrene resins have low heat resistance and oil resistance, various methods have been proposed to improve these problems by blending other resins with styrene resins. For example, JP-A-6-25487 discloses a resin composition in which a styrene resin and a propylene resin are blended. JP-A-4-288355 discloses a resin composition in which a propylene-based polymer, a styrene-based polymer, and a propylene-styrene copolymer are blended.

On the other hand, when a resin composition (for example, a styrene-based resin composition) is molded into a container, the resin composition is melt-extruded, temporarily formed into a sheet, and the sheet is formed into a container to form a container. The method of gain is used. In such a molding method, when a blend of a styrene-based resin and a thermoplastic resin having a melting point higher than the glass transition temperature of the styrene-based resin is used, the temperature range suitable for container molding is such that the styrene-based resin and the thermoplastic resin are used. Since the sheet is different from the resin, the sheet hangs down when the sheet is heated (draw down phenomenon), and the thickness distribution in the container becomes extremely uneven, or the drawn down sheet comes into contact with an unexpected part of the molding machine and the machine itself May have to be stopped. In particular, when the difference between the glass transition temperature of the styrene resin and the melting point of the thermoplastic resin increases, it becomes difficult to heat the sheet to form a uniform container.

Further, when a non-foamed sheet is used in place of the foamed sheet, a drawdown phenomenon is likely to occur.

[0006]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a styrene-based resin sheet which suppresses drawdown during container molding and has excellent moldability, a container using the same, and a method for producing the container. Is to do.

Another object of the present invention is to provide a styrene-based resin sheet having a high level of moldability, heat resistance and oil resistance, a container using the same, and a method of manufacturing the container.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, when a sheet is formed of a styrene-based resin and a thermoplastic resin exhibiting a specific elongational viscosity behavior, container molding It has been found that the drawdown at the time can be suppressed and the moldability can be improved, and the present invention has been completed.

That is, the styrenic resin sheet of the present invention comprises a styrenic resin (a) and a thermoplastic resin (b).
° C., in measurement of extensional viscosity in the range of elongation rate 0.0025~0.0035sec ^-1, the following equation (1) ~ (3) Δlnλ n / Δε = (lnλ n2 -lnλ n1) / (ε 2 -ε 1 ) ≧ 0.15 (1) λ _n = λ / λ ₁ (2) ε = ln (1/1 ₀ ) (3) (where λ _n is a nonlinear parameter, λ is elongational viscosity in a nonlinear region, λ _l Indicates the elongational viscosity in the linear region, ε indicates the amount of Hencky elongational strain, and l ₀ and l indicate the lengths of the samples at the elongation times 0 and t, respectively.) Glass transition temperature Tg (a) ° C. of styrene resin (a) and melting point T of thermoplastic resin (b)
_m (b) ° C. may satisfy the relationship represented by the following formula (4) T _m (b) −Tg (a) ≧ 5 [° C.] (4). The ratio between the styrene-based resin (a) and the thermoplastic resin (b) is about the former / the latter = 40/60 to 97/3 (weight ratio). The melting point of the thermoplastic resin (b) may be about 120 to 300 ° C. The thermoplastic resin (b) may be a polyolefin-based resin (such as a polypropylene-based resin) or a polyester-based resin (such as a polyalkylene terephthalate or a polyalkylene naphthalate). The styrene-based resin sheet may be further composed of a compatibilizer.

The present invention also includes a container made of the styrene resin sheet and a method for producing the same. In this specification, an acrylic monomer and a methacrylic monomer are collectively referred to as a (meth) acrylic monomer.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The styrene resin sheet of the present invention comprises a specific styrene resin (a) and a thermoplastic resin (b).
It is composed of [Styrene resin (a)] The styrene resin (a) constituting the styrene resin sheet of the present invention has a temperature of 130 ° C.
In the elongational viscosity measurement in the elongation speed range of 0.0025 to 0.0035 sec- ^1, the relationship represented by the following formulas (1) to (3) is satisfied. Δlnλ _n / Δε = (lnλ _n2 −lnλ _n1 ) / (ε ₂ −ε ₁ ) ≧ 0.15 (1) λ _n = λ / λ _l (2) ε = ln (l / l ₀ ) (3) ( wherein, lambda _n nonlinear parameter, lambda any elongation viscosity at an elongation time, lambda _l is .ε showing the elongation viscosity in a linear region extending strain amount of Hencky under constant temperature and constant strain rate, l ₀ and l are the extension times 0 and t, respectively.
Shows the length of the sample at. The linear region refers to a region in which the extensional viscosity does not depend on various strain rates and shows the same time dependency (see Kiyoto Koyama, Osamu Ishizuka, Journal of the Rheological Society of Japan, 13 , 93 (1985)). ).

In the measurement of elongational viscosity, some resins have a property that the elongational viscosity in a high strain region deviates from a linear region and rises sharply (ie, strain hardening property) depending on the type of resin. In such a resin, the logarithm of λ _n (ln
λ _n ) is known to increase linearly with the Hencky elongation strain ε (see Kiyoto Koyama, Osamu Ishizuka, Journal of the Textile Society, 37 , T-258 (1981)).

[0013] When a resin having no strain hardening property for any extended distortion amount, lambda _n was plotted against 1 becomes, lambda elongation strain of Hencky log (lnλ _n) of _n epsilon linear Is 0 (= Δlnλ _n / Δε).
In the case of a resin having a strain hardening property, the slope α of the straight line plot does not become zero particularly in a high strain region.

In the present specification, the slope α of a straight line obtained by plotting the logarithm (lnλ _n ) of the nonlinear parameter λ _n with respect to the amount of elongation strain ε is defined as a parameter representing the degree of strain hardening.

The slope α of the straight line is an index indicating the fluidity and moldability of the resin. The styrene resin (a) has a temperature of 130 ° C. and an elongation rate of 0.0025 to 0.003.
When the inclination α of the straight line measured by the elongational viscosity in the range of 5 sec ⁻¹ is 0.15 or more, the sagging phenomenon (drawdown phenomenon) of the sheet during heating in the process of forming the container from the sheet can be significantly suppressed. Slope α (= Δlnλ _n / Δ
ε) is preferably from 0.2 to 2, more preferably from 0.
2 to 1.5 (e.g. 0.3 to 1.5), especially 0.35
It is about 1.0. If the inclination α of the straight line is less than 0.15, the effect of suppressing the drawdown phenomenon is insufficient, and the stretchability, low thickness unevenness, deep drawability, and the like also deteriorate.

The strain hardening property is usually exhibited by the presence of a molecular chain having a long relaxation time in the polymer. Therefore, the method for increasing the slope α of the straight line (for example, to 0.15 or more) is not particularly limited.
As a polymer chain having a long relaxation time, a method of blending a linear ultrahigh molecular weight component, a method of using a branched polymer, and the like can be given. In a preferred embodiment, the use of the styrene-based resin (a) containing a branched styrene-based polymer allows the expression of strain-hardening properties.

In the styrenic resin (a), the branching parameter (shrinkage factor) g indicating the degree of branching is not particularly limited and may be about 0.5 to 1.0. 5 or more and less than 0.99 (for example, 0.5-0.
98), preferably about 0.6 to 0.98, and more preferably about 0.7 to 0.97.

The shrinkage factor g is determined by gel permeation chromatography (GPC) for a branched styrene polymer and a linear styrene polymer synthesized by thermal polymerization.
It is the ratio of the respective intrinsic viscosities measured by the method and is represented by the following formula in this specification.

The branch parameter g (= [η] _branch / [η] _linear ) (where [η] _branch is the intrinsic viscosity of the branched polymer at 40 ° C. in chloroform, and [η] _linear is the weight of the branched polymer and weight The intrinsic viscosity of the linear polymer having the same average molecular weight in chloroform at 40 ° C. is shown.) [Η] _linear is Schultz's viscosity equation [η] = 4.
The molecular weight distribution was calculated based on 9 × 10 ⁻³ Mw ^0.794 (where Mw represents a weight average molecular weight) according to the Schultz-Zimm exponential function.

The branching parameter g, which is an index indicating the degree of branching of the styrenic resin, is also called a shrinkage factor (Kyoritsu Shuppan, edited by The Society of Polymer Science, New Polymer Experiment 1, Basic Polymer Experiment, Molecular Characteristic Analysis) , 295 (1994)), at a certain temperature, in a dilute solution of a polymer dissolved in a good solvent or a θ solvent, based on the fact that the molecular spread differs depending on the structure of the polymer molecule (BH
Zimm and WHStockmayer, J. Chem. Phys., 17,1301
(1949)). For example, when comparing a linear polymer and a branched polymer having the same molecular weight, the spread of the polymer molecule having a branched structure is smaller than that of the linear polymer molecule.
As a result, the mean square turning radius representing the intrinsic viscosity or molecular size of the branched polymer is observed to be smaller than that of the linear polymer.

The measurement of the contraction factor can be performed by using the light scattering method.
The measurement can also be performed by measuring the intrinsic viscosity. The styrene resin (a) can be composed of a styrene monomer alone or a copolymer, a copolymer of a styrene monomer and a copolymerizable vinyl monomer, or the like.

Examples of the styrene monomer include styrene, alkylstyrene (for example, vinyl toluenes such as o-, m-, p-methylstyrene and 2,4-dimethylstyrene, ethylstyrene, p-isopropylstyrene). , Alkyl-substituted styrenes such as butylstyrene and pt-butylstyrene), α-alkyl-substituted styrenes (eg, α-methylstyrene and α-methyl-p-
Methylstyrene), halogen-substituted styrene (eg, o-, m- and p-chlorostyrene, p-bromostyrene, etc.), 1,1-diphenylethylene, p-
(N, N-diethylaminoethyl) styrene, p-
(N, N-diethylaminomethyl) styrene and the like can be exemplified. These styrene monomers can be used alone or in combination of two or more. Preferred styrene monomers include styrene, vinyltoluene, α-methylstyrene and the like, and styrene is particularly preferred.

Examples of the copolymerizable vinyl monomer include, for example,
(Meth) acrylonitrile, alkyl (meth) acrylate, vinyl ester-based monomer (eg, vinyl acetate), hydroxyl group-containing monomer [hydroxy C ₁ such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, etc. _-4 alkyl (meth) acrylate, etc.], glycidyl group-containing monomer [glycidyl (meth) acrylate, etc.], carboxyl group-containing monomer [(meth) acrylic acid, maleic anhydride, fumaric acid, etc.], imide monomer Monomers (maleimide, N-methylmaleimide, N-phenylmaleimide, etc.). The alkyl (meth) acrylate includes methyl (meth) acrylate, ethyl (meth) acrylate,
Butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
_C1-20 alkyl (meth) acrylates such as lauryl (meth) acrylate are included. These vinyl monomers can be used alone or in combination of two or more. The ratio between the styrene monomer and the copolymerizable monomer is, for example, 10
0/0 to 50/50 (weight ratio), preferably 100/0
３０30/70 (weight ratio).

The styrenic resin (a) may be modified with a rubber component in order to improve moldability, impact resistance, flexibility, anti-blocking properties and the like. When a rubber-modified styrene resin is used, drawdown can be suppressed without impairing rigidity and impact strength, and moldability can be improved.

In the rubber-modified styrene resin, the rubber component includes, for example, conjugated diene rubber [polybutadiene, polyisoprene, poly (2-chloro-1-1,3-
Butadiene), poly (1-chloro-1,3-butadiene), butadiene-styrene copolymer, etc.], ethylene-propylene rubber (EPDM rubber), acrylic rubber, ethylene-vinyl acetate copolymer, chlorinated polyethylene, etc. Can be illustrated. These rubber components can be used alone or in combination of two or more. As a preferable rubber component, a conjugated diene rubber is often used.

The rubber-modified styrenic resin comprises a rubber component,
An impact-resistant styrene resin composed of an admixture with a styrene resin that is not rubber-modified may be an impact-resistant styrene resin. It is a graft copolymer (impact styrene resin) obtained by polymerizing a monomer (styrene monomer).

In the graft polymer, the aromatic vinyl monomer may be used in combination with a vinyl cyanide monomer, and if necessary, the copolymerizable vinyl monomer may be used in combination. The ratio between the aromatic vinyl monomer and the vinyl cyanide monomer is, for example, the former / the latter = 10/90 to 9
0/10 (% by weight), preferably 20/80 to 80/2
0 (% by weight), more preferably 30/70 to 70/3
0 (% by weight). The ratio between the aromatic vinyl monomer and the copolymerizable vinyl monomer is, for example, the former / the latter = 10/90 to 100/0 (% by weight), particularly 30/70.
About 70/30 (% by weight).

The styrenic resins (a) can be used alone or in combination of two or more. The branched polymer can be prepared by using at least one selected from a polyfunctional vinyl compound, a polyfunctional chain transfer agent, and a polyfunctional polymerization initiator.

The polyfunctional vinyl compound is not particularly limited as long as it has a plurality of unsaturated bonds, and various compounds can be used. Examples of the polyfunctional vinyl compound include aromatic compounds having a vinyl group or an allyl group (divinylbenzene,
-Allyl-3-vinylbenzene, etc.), alkenyl (meth) acrylates (such as allyl (meth) acrylate), di (meth) acrylate compounds of polyhydric alcohols [for example, ethylene glycol di (meth) acrylate, propylene glycol di (meth) ) Acrylate,
1,4-butanediol di (meth) acrylate, 1,
Diol (meta) such as 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (meth) acrylate ) Acrylate, dipropylene glycol di (meth)
Polyoxyalkylene glycol di () such as acrylate, tripropylene glycol di (meth) acrylate, and tetrapropylene glycol di (meth) acrylate
Bifunctional vinyl compounds such as meth) acrylates;
Trifunctional vinyl compounds such as tri (meth) acrylate (trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, etc.); tetra (meth) acrylate (tetramethylolmethane tetraacrylate, pentaerythritol tetra (meth) acrylate Etc.) and the like. These polyfunctional vinyl compounds can be used alone or in combination of two or more. Particularly, a 2- to 4-functional vinyl compound (such as divinylbenzene) is preferable.

The proportion of the polyfunctional vinyl compound is from 0 to 700 ppm, preferably from 30 to 700 ppm, based on the styrene monomer.
550 ppm, more preferably 50 to 400 ppm
(Weight basis).

When a polyfunctional vinyl compound is used, the ratio between the initiator and the polyfunctional vinyl compound is 100/100.
/ 20-20 / 100 (weight ratio), preferably 100 /
30 to 30/100 (weight ratio), for example, 1
It may be about 00/50 to 50/100 (weight ratio).

In order to control the molecular weight of the polymer, a chain transfer agent may be added, if necessary, as long as the drawdown property, heat resistance and oil resistance are not impaired. The type of the chain transfer agent is not particularly limited, and a conventional chain transfer agent can be used. For example, mercaptans (for example, polyfunctional mercaptans such as ethylene glycol bisthioglycolate, trimethylolpropane tristhioglycolate, and pentaerythritol tetrakisthioglycolate), styrene dimers (such as α-methylstyrene dimer), terpenes ( It is preferable to use terpinolene or the like.
As the terpene, for example, “NOFMER TP” (manufactured by NOF Corporation) or the like can be used. The chain transfer agents can be used alone or in combination of two or more.

The ratio of the chain transfer agent is about 10 to 2000 ppm (weight basis), preferably 50 to 1000 ppm (weight basis), more preferably about 100 to 800 ppm (weight basis), based on the styrene monomer. .

For the production of the styrenic resin (a), a polymerization initiator is not always necessary and may be thermally polymerized.
Usually, a polymerization initiator is used. As the polymerization initiator,
A monofunctional or polyfunctional initiator can be used, and may be a peroxide, an azo compound, or the like.

Examples of the monofunctional or bifunctional peroxide among the peroxides include ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide and methylcyclohexanone peroxide; -Bis (t-butylperoxy) -3,3,5-trimethylcyclohexane,
Peroxyketals such as 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valate, cumene hydroperoxide, diisopropylbenzene hydroperoxide, , 5-dimethylhexane-2,5-
Hydroperoxides such as dihydroperoxide, di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, α, α ′
Dialkyl peroxides such as -bis (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, benzoyl peroxide, decanoylperoxide Diacyl peroxides such as oxide, lauroyl peroxide and 2,4-dichlorobenzoyl peroxide; peroxycarbonates such as bis (4-t-butylcyclohexyl) peroxydicarbonate; t
-Butyl peroxybenzoate, 2,5-dimethyl-
Peroxyesters such as 2,5-di (benzoylperoxy) hexane; triazines [bis (t-alkylperoxy) triazines such as bis (t-butylperoxy) triazine; bis (di-t-butylperoxy) triazine Bistris (di-t) such as oxycyclohexyl) triazine
-Alkylperoxycycloalkyl) triazine; bis (di-t-aralkylperoxycycloalkyl) triazine such as bis (di-2-phenylpropylperoxycyclohexyl) triazine, and the like.

Examples of the trifunctional or higher polyfunctional peroxide include compounds represented by the following formulas (5) to (7).

[0037]

Embedded image

Wherein R ¹ is the same or different and represents a hydrogen atom or an alkyl group; R ² is the same or different and represents a hydrogen atom, an alkyl group or an aralkyl group;
³ is the same or different and represents an alkyl group or an aralkyl group. R ⁴ is the same or different and represents a hydrogen atom, an alkyl group or an aralkyl group. In the formulas (5) to (7), R ¹ is preferably an alkyl group, and is usually a tertiary alkyl group (t-butyl group, t-butyl group).
-Amyl group, t-hexyl group and t-C _4-10 alkyl group such as t-octyl group). Particularly, a C _4-8 alkyl group such as a t-butyl group is preferable. R ² and R
⁴ is preferably a hydrogen atom, an alkyl group (particularly, C _1-4 alkyl group such as methyl group, ethyl group), R ³
Is usually the same tertiary alkyl group or tertiary aralkyl group (such as a C _9-14 aralkyl group such as a 2-phenylpropyl group) as described above. Particularly, R ² is preferably a hydrogen atom, a methyl group or an ethyl group, and R ³ is preferably a C _4-8 alkyl group such as a t-butyl group. R ⁴ is preferably a C _4-8 alkyl group such as a t-butyl group or a C _9-14 aralkyl group such as a 2-phenylpropyl group.

The trifunctional peroxide represented by the formula (5) includes, for example, tris (t-alkylperoxy) triazine such as tris (t-butylperoxy) triazine and tris (t-amylperoxy) triazine. And the like. Also, tris (di-t-alkylperoxycycloalkyl) triazine such as tris (di-t-butylperoxycyclohexyl) triazine, tris (di-2-phenylpropylperoxycyclohexyl)
Tris (di-t-aralkylperoxycycloalkyl) triazines such as triazine can also be used.

Examples of the tetrafunctional peroxide of the formula (6) include 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane and 2,2-bis (4,4-di -T-amylperoxycyclohexyl) propane,
2,2-bis (4,4-di-t-hexylperoxycyclohexyl) propane, 2,2-bis (4,4-di-
bis (4,4-di-t-alkylperoxycyclohexyl) alkanes such as t-octylperoxycyclohexyl) propane and bis such as 2,2-bis (4,4-di-2-phenylpropylperoxycyclohexyl) propane (4,4-Di-t-aralkyl peroxycyclohexyl) C _2-8 alkane and the like can be exemplified. Preferred tetrafunctional peroxide (6) is 2,2-bis (4,4-di-
bis (4,4-di-t-C _4-10 alkylperoxycyclohexyl) alkanes such as t-butylperoxycyclohexyl) propane;

The tetrafunctional peroxide represented by the formula (7) includes, for example, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 3,3 ′,
4,4'-tetra (t-amyl peroxycarbonyl)
Benzophenone, tetra (t-alkylperoxycarbonyl) benzophenone such as 3,3 ′, 4,4′-tetra (t-hexylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra (t-2) Examples thereof include tetra (t-aralkylperoxycarbonyl) benzophenone such as -phenylpropylperoxycarbonyl) benzophenone.

These organic peroxides can be used alone or in combination of two or more. Further, an inorganic peroxide such as hydrogen peroxide or a persulfate (such as potassium persulfate or ammonium persulfate) may be used in combination.

As the azo compound, azobisnitrile [eg, 2,2'-azobisisobutyronitrile (A
2,2′-azobisbutyronitriles such as IBN) and 2,2′-azobis (2-methylbutyronitrile);
2,2′-azobisvaleronitriles such as 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) and 2,2′-azobis (2,4-dimethylvaleronitrile); 2,2'-azobispropionitrile such as 2'-azobis (2-hydroxymethylpropionitrile); 1,1'-azobiscyclohexane-1
1,1′-azobis-1-alkanenitrile such as carbonitrile, especially 1,1′-azobis-1-cycloalkanenitrile (for example, 1,1′-azobis-1)
-C _5-8 cycloalkane carbonitrile), 4,4'-azobis (4-cyanovaleric acid) and azo bis cyano carboxylic acids, such as, azonitrile [2- (carbamoylazo) Azobuchiro such isobutyronitrile Nitriles; azovaleronitriles such as 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, etc.], azobisalkanes [eg, 2,2′-azobis (2-methylpropane), 2,2 ′ - azobis (2,4,4-trimethylpentane), such as 2,2'-azobis C _3-10 alkanes, etc.], dimethyl-2,2'-azo-bis-isobutyrate and the like.

The polyfunctional organic peroxide (for example, the compound represented by the formula (6)
Has a plurality of (for example, four) functional groups in one molecule, so that the molecular weight of the polymer can be increased and the polymer has a partially branched structure. It appears to improve the flowability of the resulting polymer.

The above-mentioned polymerization initiators can be used alone or in combination of two or more. The ratio of the polymerization initiator is 2 to the polymerizable monomer containing at least the styrene monomer.
000 ppm or less (0-2000 ppm), preferably 50-1000 ppm (for example, 100-700 pp)
m) (weight basis).
It is about 0 to 500 ppm.

The ratio between the initiator and the chain transfer agent is 100 /
20-20 / 100 (weight ratio), preferably 100/3
0 to 30/100 (weight ratio), more preferably 100
/ 50 to 50/100 (weight ratio).

In order to obtain the styrenic resin, it is advantageous to carry out polymerization using at least a polyfunctional vinyl compound and a chain transfer agent, and further to use a polyfunctional polymerization initiator (polyfunctional organic compound represented by the formula (6)). It is preferable to carry out the polymerization in combination with a peroxide.

The method for producing the styrene resin is not particularly limited, and a conventional polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, or bulk-suspension polymerization can be employed.
In the bulk polymerization method (bulk polymerization method) advantageous for industrial production, a solvent may be added. The solvent is not particularly limited, and a conventional solvent such as an aromatic hydrocarbon (benzene, toluene, ethylbenzene, xylene, etc.), an alicyclic hydrocarbon (cyclohexane, etc.), an aliphatic hydrocarbon (hexane, octane, etc.) Etc.) can be exemplified.

The amount of the solvent (solvent) used is, for example, from 0 to 30% by weight, preferably from 5 to 2% by weight, based on the whole reaction mixture.
It can be selected from a range of about 0% by weight. Solvent ratio is 30
If the content exceeds% by weight, economic efficiency such as solvent recovery may be reduced.

The polymerization can be carried out at normal pressure or under pressure. The polymerization temperature depends on the type of polymerization method, the composition of the polymerization initiator system,
80 to 180 ° C., preferably 9 to 80 ° C., depending on the polymerization rate and the like.
It can be selected from the range of about 0 to 150 ° C. Polymerization temperature is 8
If the temperature is lower than 0 ° C., the productivity is reduced. If the temperature is higher than 180 ° C., the molecular weight of the resin is reduced, and the impact strength is lowered.

The polymerization may be carried out usually under an atmosphere of an inert gas such as nitrogen, helium, argon, etc., for example, under a flow of an inert gas. The polymer may be separated and purified, for example, after the polymerization reaction, if necessary, by diluting with a solvent and precipitating in a poor solvent, or removing volatile components such as monomers and solvents.

The weight average molecular weight Mw of the styrene resin is
It is about 150,000 to 700,000, preferably about 200,000 to 500,000, and more preferably about 250,000 to 350,000. If the weight average molecular weight is less than 150,000, the impact resistance of the obtained sheet and container is remarkably reduced, and if it exceeds 700,000, the viscosity at the time of melting is increased, and the moldability is significantly reduced.

In the styrene resin, the molecular weight distribution Mw
/ Mn (where Mw represents the weight average molecular weight of the styrene resin, and Mn represents the number average molecular weight of the styrene resin).
Is 10 or less (about 1 to 10), preferably 5 or less (about 1.5 to 5). If the molecular weight distribution exceeds 10, physical properties such as mechanical strength and moldability deteriorate.

The styrene-based resin (a) is another styrene-based resin not exhibiting the above-mentioned properties, for example, a styrene-based monomer alone or a copolymer, a styrene-based monomer and a copolymerizable vinyl monomer. And two or more resins selected from rubber-modified styrene resins. Further, it may include a block copolymer of a rubber block and an aromatic vinyl polymer block (such as an ABA type block copolymer). Block copolymers often form thermoplastic elastomers. The structure of the block copolymer may be linear or star (star).

As the thermoplastic resin (b), polyolefin resin, crystalline polystyrene (isotactic,
(Syndiotactic), polyester resin, polyether resin, polycarbonate resin, polyamide resin, polysulfone resin, polyphenylene ether resin, polyphenylene sulfide resin, polyetheretherketone resin, polyacetal resin (alone or in combination) Polymerized polyacetal), and thermoplastic elastomers (such as thermoplastic polyurethane elastomers and polyester elastomers). These thermoplastic resins may be used alone or in combination of two or more. Preferred thermoplastic resins (b) are polyolefin-based resins, polyester-based resins and the like.

Examples of the polyolefin resin include olefin polymers such as homo- or copolymers of olefins (polyethylene, polypropylene, poly (methyl-pentene-1), ethylene-propylene copolymer, etc.), and the above-mentioned olefins. And copolymerizable monomers (e.g., ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylate copolymer, and the like. In particular, propylene Resin containing polypropylene-based polymer (polypropylene homopolymer, ethylene-propylene copolymer, propylene-α-
Preferred are random or block copolymers such as _C4-10 olefin copolymers, especially crystalline polypropylene.

As the polyester resin, polyalkylene arylate resins such as polyalkylene terephthalate and polyalkylene naphthalate can be used. Polyalkylene terephthalate (poly C _2-4 alkylene terephthalate such as polyethylene terephthalate and polybutylene terephthalate), polyalkylene naphthalate (poly C _2-4 alkylene naphthalate such as polyethylene naphthalate and polybutylene naphthalate), poly (1, 4-cyclohexane dimethylene terephthalate)
Alternatively, in a copolymer containing these alkylene arylate units as a main component, the content of the alkylene arylate monomer is 50 to 100 mol%, preferably 8 to 100 mol%.
It is about 0 to 100 mol%.

In the copolymerized polyalkylene arylate resin, the dicarboxylic acid component of the copolymer component is a C _8-14 aromatic dicarboxylic acid such as terephthalic acid, phthalic acid, isophthalic acid, or naphthalenedicarboxylic acid; cyclohexanedicarboxylic acid or the like. _C8-14 alicyclic dicarboxylic acid; _C4-12 aliphatic dicarboxylic acid such as adipic acid), and examples of the diol component include aliphatic alkylene diols (ethylene glycol, 1,3-propanediol,
1,4-butanediol, neopentyl glycol,
C _2-12 aliphatic diols such as 1,5-pentanediol and 1,6-hexanediol, preferably linear C _2-6 alkylene glycol, particularly linear C _2-4 alkylene glycol, etc., oxyalkylene glycol ( Diethylene glycol, triethylene glycol, dipropylene glycol, etc.), alicyclic diols (cyclohexanediols such as 1,4-dihydroxycyclohexane,
4-cyclohexanedimethanol, 2,2-bis (4-
Hydroxycyclohexyl) propane, etc.), aromatic diols (eg, C _6-21 diols such as 2,2-bis (4-β-hydroxyethoxyphenyl) propane, etc.)
Can be exemplified. These copolymer components can be used alone or in combination of two or more.

The polyalkylene arylate-based resin may contain a relatively small amount of a polyhydric alcohol (glycerin,
It may have a branched structure by using trimethylolethane, trimethylolpropane, pentaerythritol and the like, or a polycarboxylic acid (trimesic acid, trimellitic acid and the like) or a derivative thereof.

The thermoplastic resins (b) can be used alone or in combination of two or more. The melting point of the thermoplastic resin (b) is, for example, 100 to 350 ° C, preferably 120 to 350 ° C.
The temperature is 300 ° C, more preferably about 150 to 200 ° C.

The thermoplastic resin (b) is used by blending with the styrene resin (a). When the preferable molding temperatures of the thermoplastic resin (b) and the styrene-based resin (a) are significantly different (such as when the melting point of the thermoplastic resin (b) is higher than the glass transition temperature of the styrene-based resin (a)), When a sheet composed of these resins is heated and further subjected to container molding, the sheet tends to draw down. In the present invention,
A glass transition temperature Tg (a) ° C. of the styrene resin (a);
The melting point T _m (b) ° C. of the thermoplastic resin (b) satisfies the relationship represented by the following formula (4) T _m (b) −Tg (a) ≧ 5 [° C.] (4) Even if the difference in suitable molding temperature is large, drawdown can be suppressed by using the styrene resin (a).

The ratio of the styrene resin (a) to the thermoplastic resin (b) is the former / the latter = 40/60 to 99/1.
(For example, 40/60 to 97/3) (weight ratio), preferably 50/50 to 98/2 (weight ratio), and more preferably about 60/40 to 97/3.

In the present invention, the styrenic resin sheet is constructed by combining the styrenic resin (a) having the above-mentioned excellent properties with the thermoplastic resin (b).
The heat resistance and oil resistance of the sheet and the container obtained by molding the sheet can be improved.

The styrenic resin sheet of the present invention is not particularly required when the styrenic resin (a) and the thermoplastic resin (b) are compatible with each other. (C) may be included. When the compatibilizer (c) is used in combination, the styrene resin (a) and the thermoplastic resin (b)
And the wettability can be improved, and the drawdown phenomenon can be greatly suppressed.

As the compatibilizer (c), various compatibilizers (low molecular weight or high molecular weight compatibilizers) can be used, and high molecular weight compatibilizers, particularly (c-1) a vinyl aromatic compound and A copolymer with a conjugated diene compound or a hydrogenated product thereof,
(c-2) an epoxidized product of a copolymer of a vinyl aromatic compound and a conjugated diene compound or a hydrogenated product thereof, (c-3) a styrene monomer constituting the styrene resin (a), and a thermoplastic resin A copolymer with a monomer constituting the resin (b), and (c-
4) A copolymer of a vinyl aromatic compound and at least one compound selected from a carboxyl group-containing compound and an acid anhydride group-containing compound is preferred. These compatibilizers can be used alone or in combination of two or more.

Examples of the vinyl aromatic compound include the same monomers as the above-mentioned styrene monomers, for example, styrene, alkylstyrene (for example, vinyltoluene, pt-butylstyrene, etc.), α-alkylstyrene (for example, , Α-
Methylstyrene), divinylbenzene, 1,1-diphenylstyrene and the like. These monomers can be used alone or in combination of two or more. Of these vinyl aromatic compounds, styrene is preferred.

Examples of the conjugated diene compound include butadiene, isoprene, 1,3-pentadiene, 2,3-
Examples thereof include dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene, and phenyl-1,3-butadiene. One or two conjugated diene compounds
More than one species can be used in combination. Preferred conjugated diene compounds include butadiene, isoprene and combinations thereof.

Examples of the carboxyl group-containing compound include (meth) acrylic acid, crotonic acid, fumaric acid and monoalkyl maleate. Examples of the acid anhydride group-containing compound include maleic anhydride.

The copolymers (c-1) to (c-4) may be any of random, block and graft copolymers, but (c-1) and (c-2) , Usually a block copolymer,
(c-3) is a graft copolymer obtained by grafting a styrene monomer to the thermoplastic resin (b). The block copolymer (C) is composed of a polymer block (A) composed of a vinyl aromatic compound (or a styrene monomer) and a polymer block (B) composed of a conjugated diene compound. ing.

The molecular structure of the block copolymer (C) may be linear, branched, radial or any combination thereof. As the block structure of the polymer block (A) and the polymer block (B), for example, AB
Type, ABA type, BAB type, ABAB type,
(A-B-) ₄ Si type, ABABA type, BA
-BAB type etc. can be illustrated.

The unsaturated bond derived from the conjugated diene compound of the block copolymer (C) may be partially or wholly hydrogenated hydrogenated copolymer (D). As the block copolymer (C), at least one selected from the above block structures can be used.

The epoxy-modified block copolymer (E) is obtained by mixing the above-mentioned block copolymer (C) and / or its partially hydrogenated product (D)
With an epoxidizing agent (hydroperoxides, peracids such as formic acid, peracetic acid, perbenzoic acid, etc.) in an inert solvent. The amount of the epoxidizing agent is not strictly limited, and the epoxy equivalent of the epoxy-modified block copolymer (E) finally obtained has an epoxy equivalent of 140 to
2700, preferably 200 to 2000 (for example, 30
It is preferable to select the amount of the epoxidizing agent so as to be about 0 to 1500).

The epoxy equivalent is calculated by the following equation: Epoxy equivalent = 1600 / X (where X represents the oxirane oxygen concentration (% by weight) in the epoxy-modified block copolymer) per mole of oxirane oxygen 1 shows the weight of the epoxy-modified block copolymer. The oxirane oxygen concentration can be measured by titration with an acetic acid solution of hydrogen bromide.

For details of the compatibilizers (c-1) and (c-2), reference can be made to JP-A-10-310694. The ratio of the compatibilizing agent (c) is determined by the ratio of the resin composition 100 containing the styrene resin (a) and the thermoplastic resin (b).
0.1 to 20 parts by weight, preferably 1 to
It is about 10 parts by weight.

The resin composition (styrene resin (a), thermoplastic resin (b) and, if necessary, compatibilizer (c)) constituting the styrenic resin sheet is required. Accordingly, various additives such as stabilizers (ultraviolet absorbers, antioxidants, heat stabilizers, etc.), lubricants, release agents (silicone oils, etc.), plasticizers (mineral oils, etc.), dispersants (higher grades) Fatty acid salts), reinforcing agents, fillers (inorganic fillers such as talc), slip agents, anti-blocking agents, nucleating agents, crosslinking agents, conductivity-imparting agents, antistatic agents, anti-fog agents, flame retardants, titanium oxide And a colorant (eg, a pigment or a dye). [Styrene-based resin sheet] The styrene-based resin sheet of the present invention is obtained by molding a resin composition containing at least the styrene-based resin (a) and the thermoplastic resin (b).

The styrene resin sheet is formed into a sheet by a conventional molding method, for example, by melt-kneading the resin composition and extruding it from a die (flat, T-shaped (T-die), cylindrical (circular die), etc.). The sheet is formed by an extrusion molding method. The sheet thus obtained may be used as an unstretched sheet, or as a stretched sheet (uniaxially or biaxially stretched sheet) stretched by a conventional stretching method, for example, a stretching method such as a tenter method or a tube method. May be used. When using a circular die,
The sheet is obtained by folding the cylindrical sheet with a pinch roll and opening it by trimming (edge cutting).

The thickness of the styrene resin sheet is in a range that does not impair the moldability of the container, for example, 0.05 to 3 mm.
Preferably 0.1 to 3 mm (for example, 0.1 to 2 m
m), more preferably 0.1 to 1.5 mm (0.3 to
1.2 mm). If the thickness is small, the mechanical strength, stiffness and heat retention of the container are reduced, and if it is too large, the moldability is reduced and the thickness of the container is liable to be uneven.

The styrene-based resin sheet may be used as a single-layer sheet or as a laminated sheet having a surface layer formed on at least one surface of the sheet. This surface layer may be a skin layer, and may be a coating layer (for example, an olefin-based resin such as polypropylene, polystyrene, polyester, or the like) laminated with or without an adhesive layer by coextrusion lamination or dry lamination. Or a stretched or unstretched film or sheet of polyamide or the like.

The styrene resin sheet further includes:
A surface modifier, an antifogging agent, a conductivity-imparting agent, an antistatic agent, a release agent (polysiloxane in the form of an emulsion, silicone oil, or the like) may be applied.

The styrene resin sheet may be a foam sheet. In a foamed sheet, residual stress due to foaming remains in the sheet, and when the container is heated, the residual stress acts as a tension in the surface direction of the sheet, so that the drawdown suppressing effect can be more effectively exerted. In the present invention, even if it is a non-foamed sheet, it is possible to greatly suppress the drawdown.

The styrene-based resin sheet thus obtained is usually wound up by a winding roll or the like. In the molding step, the sheet can be heated (heated to a temperature equal to or higher than the softening point of the base resin) and subjected to molding processing such as container molding to obtain a container. Such a sheet is useful as a container forming sheet for forming containers (trays, cups, cups, etc.).

The shape of the container is not particularly limited as long as it has an opening for accommodating the contents, and may be a square, an ellipse, a circle, or the like. Also, the size is not particularly limited. The container only needs to have a container body having an accommodation recess, and the flange portion may extend from the upper end of the side wall of the container body.

When the container has a cylindrical shape with a bottom, the degree of deep drawing can be represented by a drawing ratio represented by the following equation (8). Aperture ratio = H / (2 (A / π) ^1/2 ) (8) (where H indicates the height (mm) of the container, and A indicates the area (mm ² ) of the opening of the container. In the container of the present invention, the squeezing ratio is not particularly limited, but is, for example, 0.1 or more and less than 0.4 (for example, 0.1 to 0.1).
0.35), preferably about 0.15 to 0.3.

The heating means for molding the container is not particularly limited as long as it is suitable for molding the container. For example, the heating means may be directly heated using a hot plate contact heating molding machine or the like, or may be radiated (heated). Heater, infrared heater, etc.). The container can be formed by a conventional forming method, for example, pressure forming, vacuum forming, vacuum pressure forming, hot plate forming, or the like. In particular, vacuum forming using an indirect heating method is preferable.

[0085]

According to the present invention, since the styrene resin sheet is formed by using a specific styrene resin and a thermoplastic resin, the drawdown phenomenon at the time of molding the container can be greatly suppressed. Further, by combining the styrene resin and the thermoplastic resin, the heat resistance and oil resistance of the sheet and the container can be significantly improved.

[0086]

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

The physical properties of the styrene resin were measured by the following methods. [Inclination of straight line α] Under the following conditions, both ends of a cylindrical sample are supported by a pinch roller or a caterpillar, and the sample is rotated at a constant strain rate to apply elongation deformation to the sample, and the cross-sectional area and pinch of the sample being deformed Elongational viscosity was determined by detecting the torque applied to the roller or track. A nonlinear parameter was calculated from the obtained extensional viscosity and the extensional viscosity in a nonlinear region having the same extensional time as the extensional viscosity in accordance with the above equation (2). Further, the strain amount is calculated from the lengths of the samples at the elongation times 0 and t according to the formula (3), and the logarithm of the nonlinear parameter and the strain amount are plotted for a plurality of points having different elongation times. The slope α was calculated according to 1).

Measuring temperature: 130 ° C. Strain rate: 0.0005 to 0.1 sec ^-1 Measuring equipment: MELTEN RHEOMETER (manufactured by Toyo Seiki Co., Ltd.) [Measurement of molecular weight and branching parameter g] Chloroform at a temperature of 40 ° C. Is used as an eluent, and the polymer solution eluted by gel permeation chromatography (GPC) is detected by a differential refractive index detector and a differential pressure viscosity detector, and the molecular weight is determined from a universal calibration curve and intrinsic viscosity calibrated with standard polystyrene. Calculated. The intrinsic viscosity of the linear and branched polymers can be determined by dividing the obtained viscosity chromatogram by the polymer concentration, and by dividing the intrinsic viscosity of the branched polymer by the intrinsic viscosity of the linear polymer. The branch parameter g was calculated.

The styrene resin, thermoplastic resin (b) and compatibilizer (c) used in the examples and comparative examples are as follows. (1) Styrene resin (a) (a-1): In a reaction vessel (20 liters), an initiator [2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, Nippon Oil and Fat ( Pertetra A] 300 ppm, polyfunctional vinyl compound [divinylbenzene, Wako Pure Chemical Industries, Ltd.] 100 ppm, and chain transfer agent [pentaerythritol tetrakisthiopropionate (HSCH ₂ CH ₂ COOCH ₂ ) ₄ C, A
ldrich] 100 ppm of a styrene monomer solution was charged and, after purging with nitrogen, heated to 110 ° C. for polymerization (2 hours), then heated to 125 ° C. for polymerization (2 hours), and further heated to 140 ° C. And polymerized until the styrene monomer in the polymerization solution became 15% by weight or less. The styrene-based resin (a-1) was recovered by devolatilization of the unreacted monomer and the solvent in the reaction solution. The obtained styrenic resin (a-1) has a weight average molecular weight M
w is 320,000, Tg is 103 ° C., and strain rate is 0.
The slope α of the straight line measured at 00283 sec ⁻¹ is 0.47,
The resin had a shrinkage factor g of 0.95. (2) Thermoplastic resin (b) (b-1): Polypropylene (Tm = 137 ° C., manufactured by Sumitomo Chemical Co., Ltd., FS-8611) (b-2): Polyethylene terephthalate (Tm = 25)
5 ° C, Mitsubishi Rayon Co., Ltd., Diamond Night MA521
H) (3) Compatibilizer (c) (c-2a): Epoxy-modified styrene-butadiene copolymer (Epofriend A10 manufactured by Daicel Chemical Industries, Ltd.)
20) (c-3a): styrene-ethylene-propylene-styrene copolymer (manufactured by Kuraray Co., Ltd., Septon 2104) (c-3b): polypropylene-graft-polystyrene copolymer (manufactured by NOF Corporation) Modiper A310
0) (4) Other styrene-based resin (d-1): A styrene-based resin (d-1) similar to the styrene-based resin (a-1) without adding an initiator and a polyfunctional vinyl compound. Was prepared. The obtained styrenic resin (d-1) has a weight average molecular weight Mw of 310,
000, Tg 103 ° C, strain rate 0.00276se
The resin was found to have a slope α of 0.09 and a shrinkage factor g of 1.00 measured at c ⁻¹ .

(D-2): Rubber-modified polystyrene resin
HIPS (manufactured by Daicel Chemical Industries, Ltd., S85) Weight average molecular weight Mw: 250,000 Slope α: 0.01 (strain rate: 0.0
0281 sec ^-1 ) Shrinkage factor g: 1.00 Examples 1 to 5 and Comparative Examples 1 to 5 (Sheet molding) Styrene resin, thermoplastic resin (b) and compatibilizer (c) in proportions shown in Table 1. Was melt-kneaded with a twin screw extruder (PCM30, manufactured by Ikegai Co., Ltd.) to obtain resin pellets. An extruder (φ65 mm, L
/ D = 28), heated by an extruder, melt-kneaded, extruded into a sheet from a T-die (temperature 230 ° C.) at the tip of the extruder, and quenched to produce a sheet having a thickness of 0.4 mm. did. (Container molding) The obtained styrene resin sheet was molded into a container (opening φ90 mm, bottom φ70 mm, depth 40 mm) using a single-shot vacuum molding machine [manufactured by Asano Laboratories] under the following molding conditions. did.

Molding conditions Drawing ratio: about 0.2 Mold temperature: 40 to 70 ° C. Heating temperature: 120 to 200 ° C. The container forming process in the examples and comparative examples and the obtained containers were drawn at the time of container forming. The down property, heat resistance and oil resistance of the container were evaluated as follows. [Drawdown Property] In the above-described container forming step, four ends of the sheet (550 mm long × 550 mm wide) were fixed with clamps, and the sheet was heated under heating conditions that allowed the container to reproduce the shape of the mold. The height between the horizontal plane of the clamp and the position where the sheet sags at the center of the sheet at the maximum was measured as the maximum sagging amount dd and used as an index of the drawdown property. The drawdown property was evaluated according to the following criteria.

：: The maximum sag amount dd is less than 2 cm. X: The maximum sag amount dd is 2 cm or more. [Heat and oil resistance] In the containers obtained in Examples and Comparative Examples,
Add 100g of salad oil (Nisshin Oil Co., Ltd.) and add 50g
Heated in a 0 W microwave for 5 minutes. Deformation of the container after heating and melting marks on the container surface were visually observed, and evaluated according to the following criteria.

：: Neither deformation nor melting mark is observed. Δ: Slightly deformed or melting mark is observed. X: Result is largely deformed and melting mark is observed.

[0094]

[Table 1]

As is clear from the table, in the examples using the specific styrene resin (a-1) and the thermoplastic resin in combination, both the drawdown property and the heat resistance and oil resistance were excellent. On the other hand, the styrene resin (a-1)
In Comparative Examples 1 to 3 using styrene resins other than the above, heat resistance and oil resistance are good, but the drawdown suppressing effect is low. Further, even when the styrene resin (a-1) is used,
In Comparative Example 4 containing no thermoplastic resin, the drawdown property was good, but the heat resistance and oil resistance were poor.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 23/10 C08L 53/02 53/02 63/08 63/08 67/02 67/02 101/00 101 / 00 B65D 1/00 A F term (reference) 3E033 AA20 BA11 BA13 BA16 BA22 BB04 BB05 CA07 CA09 4F071 AA20 AA22 AA45 AA46 AA77 AA81 AA84 AA86 AH05 BB06 BC01 BC03 4J002 BB03X BB06X BB07XB BB07XB BC CF06X CF07X CF08X CF16X GG01

Claims (11)

[Claims] 1. A temperature of 130 ° C. and an elongation rate of 0.0025 to
In the measurement of elongational viscosity in the range of 0.0035 sec ^-1 ,
Formula (1) ~ (3) Δlnλ n / Δε = (lnλ n2 -lnλ n1) / (ε 2 -ε 1) ≧ 0.15 (1) λ n = λ / λ l (2) ε = ln ( l / l ₀ ) (3) (where, λ _n is a nonlinear parameter, λ is the elongational viscosity in the non-linear region, λ _l is the elongational viscosity in the linear region, ε is the Hencky elongation strain amount, and l ₀ and l are A styrene-based resin sheet composed of a styrene-based resin (a) and a thermoplastic resin (b) that satisfies the relationship represented by the following expressions: 2. The glass transition temperature Tg (a) ° C. of the styrene resin (a) and the melting point T _m (b) ° C. of the thermoplastic resin (b) are represented by the following formula (4): T _m (b) −Tg (a) ≧ 5 [° C.] The styrene resin sheet according to claim 1, which satisfies the relationship represented by (4). 3. The ratio of the styrene-based resin (a) and the thermoplastic resin (b) is 40/60 to 97/3 as the former / latter ratio.
The styrene-based resin sheet according to claim 1, which is (weight ratio). 4. The styrene resin sheet according to claim 1, wherein the styrene resin (a) has a weight average molecular weight Mw of 150,000 to 700,000. 5. A thermoplastic resin (b) having a melting point of 120 to 3
The styrene resin sheet according to claim 1, which is at a temperature of 00C. 6. The styrene resin sheet according to claim 1, wherein the thermoplastic resin (b) is at least one resin selected from a polypropylene resin, polyalkylene terephthalate and polyalkylene naphthalate. 7. The styrenic resin sheet according to claim 1, further comprising a compatibilizer. 8. A compatibilizer comprising: (c-1) a copolymer of a vinyl aromatic compound and a conjugated diene compound or a hydrogenated product thereof;
(c-2) an epoxidized product of a copolymer of a vinyl aromatic compound and a conjugated diene compound or a hydrogenated product thereof, and (c-3) a styrene monomer constituting the styrene resin according to claim 1 and heat (C-4) a copolymer of a monomer with a monomer constituting the plastic resin (b), or (c-4) a vinyl aromatic compound and at least one compound selected from a carboxyl group-containing compound and an acid anhydride group-containing compound The styrenic resin sheet according to claim 7, which is a copolymer. 9. The styrene resin sheet according to claim 1, which has a thickness of 0.1 to 3 mm. 10. A container formed of the styrene resin sheet according to claim 1. 11. A method of manufacturing a container for vacuum forming the styrene resin sheet according to claim 1.