JP2007291366A - Resin composition for biaxially oriented styrenic resin sheet, and sheet and formed article using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented styrenic resin sheet improved in deep drawing properties and prevented from extraction breakage at the time of trimming without causing sheet defects in appearance at the time of sheet forming, and further excellent in low temperature formability at the time of postforming and applicability of antifogging agents, a formed article using the sheet and a resin composition constituting them. <P>SOLUTION: This resin composition for the biaxially oriented styrenic resin sheet is characterized by comprising a copolymer resin made by copolymerizing a styrenic monomer with an acrylic acid ester and in that the number of branching per one molecule for an absolute molecular weight of 734,000 obtained by GPC-MALLS method is 0.04-0.35, the weight-average molecular weight (Mw) obtained by GPC-MALLS method is 250,000-450,000, the ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) is 2.20-3.00, and the ratio (Mw/Mp) of the weight-average molecular weight (Mw) obtained by GPC method to the peak molecular weight (Mp) is 1.05-1.28. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a biaxially stretched styrene-based resin sheet, a molded article using the same, and a resin composition constituting them.

  Biaxially stretched styrene resin sheets are often used for food packaging containers and other packaging containers for reasons such as environmental hygiene, waist strength, sheet appearance (transparency, image clarity, etc.) and excellent moldability. It is used. As the secondary forming method, a contact heating type pressure forming method, an indirect heating type vacuum forming method, a pressure forming method, and the like are known. Among them, a sheet and a hot plate are contact-heated, and a softened sheet is removed from the hot plate. In general, a so-called contact heating type pressure forming method is used in which pressing is applied to a mold by pressurization. Molded articles obtained by these methods are used by being punched by various methods. However, there is a case where the molded product is broken when the molded product is punched in piles, and this improvement is demanded. In addition to this, in recent years, in order to maintain the appearance of the sheet and improve the production efficiency, in particular, shortening of the molding cycle (low temperature moldability and deep drawability) and further improvement of the antifogging agent coating property are required.

  Therefore, as a biaxially stretched styrene resin sheet that has improved deep-drawing formability during secondary molding and improved cracking prevention, there is a technology that contains 0.8 to 2.5 wt% of an internal lubricant. It is disclosed (for example, see Patent Document 1).

  Although this method can improve the deep drawability, a satisfactory effect cannot be obtained with respect to the anti-cracking property. Furthermore, since it contains a lot of internal lubricant, the volatile matter of the internal lubricant generated in the melt-extrusion process at the time of forming the sheet is agglomerated and adhered to the sheet manufacturing apparatus, and this is transferred to the sheet to cause poor appearance. There is. Furthermore, the internal lubricant bleeds out on the sheet surface, and the coating property of the antifogging agent is lowered.

  Further, in order to improve the cracking prevention property, a method of adding a styrene-butadiene block copolymer (hereinafter referred to as SB block copolymer) to a styrene resin to the styrene resin (for example, see Patent Document 2), A method of adding an SB block copolymer and an impact-resistant polystyrene resin to the resin (for example, see Patent Document 3) is disclosed.

  In these methods, a decrease in transparency and image clarity becomes a problem. Further, the SB block copolymer is inferior in thermal stability, and a gel-like substance is likely to be generated at the time of melt extrusion, which may cause a problem in the sheet appearance and the productivity in sheet forming.

Furthermore, a resin composition comprising a styrene resin and a plasticizer, in which the ratio (Mw / Mp) of the weight average molecular weight (Mw) and the peak molecular weight (Mp) determined by the GPC method is 1.3 to 1.8. The foam sheet used has been proposed (see Patent Document 4). However, since the Mw / Mp of the main component styrene resin is large, the ratio of the high molecular weight styrene resin is increased. When the resin composition is used to form a biaxially stretched sheet, image clarity and flexibility are improved. For example, it is not suitable for applications such as food packs where the appearance and strength are important.
JP-A-1-185333 JP 49-98857 A Japanese Patent Laid-Open No. 58-129038 JP 2003-49033 A

  The problem to be solved by the present invention is to improve the deep drawability and prevention of cracking at the time of trimming without causing poor sheet appearance when forming a biaxially stretched styrene resin sheet, and further, secondary molding Another object of the present invention is to provide a biaxially stretched styrene resin sheet excellent in low temperature moldability and antifogging agent coating property, a molded product using the same, and a resin composition constituting them.

  The present inventors diligently studied to solve the above-mentioned problems. As a result, the number of branches per molecule at an absolute molecular weight of 734,000 determined by the GPC-MALLS method, the weight average molecular weight (Mw determined by the GPC-MALLS method) ), By using a styrene resin composition in which the ratio (Mw / Mp) of the weight average molecular weight (Mw) to the peak molecular weight (Mp) determined by the GPC method is in a specific range, a biaxially stretched styrene resin It has been found that the sheet appearance defect does not occur when the sheet is formed, and that the deep drawability and the cracking property during trimming can be improved. Furthermore, the present inventors use a copolymer resin obtained by polymerizing a styrene monomer and an acrylate ester as a resin constituting the styrene resin composition. The present inventors have found that the low temperature moldability and the antifogging agent coating property at the time can be improved, and the present invention has been completed.

  That is, the present invention has a weight average molecular weight (Mw) determined by the GPC-MALLS method in which the number of branches per molecule is 0.04 to 0.35 at an absolute molecular weight of 734,000 determined by the GPC-MALLS method. ) Is 25 to 450,000, and the ratio (Mw / Mp) of the weight average molecular weight (Mw) to the peak molecular weight (Mp) determined by the GPC method is 1.05 to 1.28, and the styrenic monomer The present invention provides a resin composition for a biaxially stretched styrene-based resin sheet, comprising a copolymer resin obtained by polymerizing a polymer and an acrylic ester.

  The present invention also provides a biaxially stretched styrene resin sheet formed from the above-described resin composition for a biaxially stretched styrene resin sheet and a molded product obtained by thermoforming the sheet.

  The styrenic resin composition of the present invention does not cause poor sheet appearance when a biaxially stretched styrene resin sheet is formed, and the sheet appearance (transparent) is a characteristic of the biaxially stretched styrene resin sheet during secondary molding. Performance, image sharpness, smoothness, etc.), and deep drawability and anti-cracking properties, as well as low temperature moldability and antifogging agent coating properties. It is useful as a food packaging container, a packaging container for other articles, or a member thereof.

The present invention is described in detail below.
The styrene monomer and acrylate copolymer forming the biaxially stretched styrene resin sheet of the present invention have a number of branches per molecule of 0. 340,000 as determined by the GPC-MALLS method. 04 to 0.35, the weight average molecular weight (Mw) determined by the GPC-MALLS method is 25 to 450,000, and the ratio of the weight average molecular weight (Mw) to the peak molecular weight (Mp) (Mw / Mp ) Is 1.05-1.28.

Here, as the styrene monomer and the acrylate ester copolymer, the number of branches per molecule at an absolute molecular weight of 734,000 obtained by the GPC-MALLS method is important. The number of branches obtained from this GPC-MALS is calculated by the following method, for example.
(i) High-performance liquid chromatography (HPLC manufactured by Shodex, detector: DAWN EOS manufactured by Wyatt Technology, RI-101 manufactured by Shodex, column: KF-806L × 2, manufactured by Shodex, solvent: THF, flow rate: 1.0 ml / Min), the absolute molecular weight was measured, and the weight average inertial radius was determined with analysis software ASTRA manufactured by Wyatt Technology.
(ii) Weight average inertia radius (RwB) of branched styrene monomer and acrylate copolymer, and Weight average inertia radius (RwL) of linear styrene monomer and acrylate copolymer ) Is substituted into equation (1) to calculate g, and then the number of branches per molecule (n) is calculated according to equation (2).
Formula (1) g = (RwB) ² / (RwL) ²
Formula (2) g = (1 / n) × ln (1 + n)

  And the number of branches per molecule in the absolute molecular weight of 734,000 calculated | required by GPC-MALLS method of the copolymer of a styrene-type monomer and acrylic acid ester is 0.04-0.35 piece, Preferably it is 0 0.06 to 0.32, more preferably 0.08 to 0.30. When the number of branches is less than 0.04, the moldability and the strength of the biaxially stretched styrene resin sheet and the molded product using the same are insufficient, and the biaxially stretched styrene resin sheet and the molded product using the same Appearance deteriorates. Moreover, when the number of branches exceeds 0.35, a gel-like substance is produced and the appearance is impaired.

  Moreover, as a copolymer of a styrene monomer and an acrylic ester, the weight average molecular weight (Mw) and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) determined by the GPC-MALLS method A certain molecular weight distribution (Mw / Mn) is important. The weight average molecular weight and molecular weight distribution according to the GPC-MALLS method can be measured under the same conditions using, for example, the equipment used when determining the number of branches, and can be analyzed by analysis software manufactured by Wyatt. The weight average molecular weight and molecular weight distribution of the copolymer of styrene monomer and acrylate ester are 250,000 to 450,000 and 2.20 to 3.00, preferably 270,000 to 430,000 and 2.00. ~ 2.80. When the weight average molecular weight is less than 250,000, the strength of the biaxially stretched styrene resin sheet or a molded product using the biaxially stretched styrene resin sheet is insufficient. Inferior in deep-drawing formability during secondary molding to be molded into a container. Further, if the molecular weight distribution is less than 2.20, the stretchability at the time of forming a biaxially stretched styrene resin sheet and the deep drawability at the time of secondary molding to form into a container are inferior, and the molecular weight distribution exceeds 3.00. In addition, the strength of the biaxially stretched styrene resin sheet and a molded product using the same is insufficient.

  Furthermore, as a copolymer of a styrene monomer and an acrylate ester, the ratio between the weight average molecular weight and the peak molecular weight by the GPC method is important. The ratio between the weight average molecular weight and the peak molecular weight by the GPC method can be determined, for example, by the following measurement. High-performance liquid chromatography (HLC-8220 GPC manufactured by Tosoh Corporation, detector: RI detector, column: TSKgel G6000H × 1 + G5000H × 1 + G4000H × 1 + G3000H × 1 + TSKguard column H × 1-H, solvent: THF, flow rate: 1.0 ml / min, temperature 40 ° C.), a standard calibration curve is prepared with standard polystyrene, and the weight average molecular weight (Mw) is obtained from the weight fraction and molecular weight in the elution volume. On the other hand, the peak molecular weight is determined as a linear styrene equivalent molecular weight corresponding to the peak of the chromatogram. The ratio of the weight average molecular weight and the peak molecular weight of the copolymer of the styrene monomer and acrylate ester of the present invention is 1.05 to 1.28, preferably 1.08 to 1.24. . When the ratio between the weight average molecular weight and the peak molecular weight is less than 1.05, the stretchability during biaxially stretched styrene resin sheet formation and the deep drawability during secondary molding to be molded into a container are inferior and biaxially stretched. The strength of the styrene resin sheet or a molded product using the styrene resin sheet decreases, and if it exceeds 1.28, the image clarity of the biaxially stretched styrene resin sheet or a molded product using the same becomes insufficient.

In the copolymer of styrene monomer and acrylate ester used in the present invention, the number average inertia radius (Rn), the number average inertia radius and the weight average inertia radius (by the GPC-MALLS method) ( The ratio of Rw) (Rw / Rn) can also be examined if necessary. The number average inertia radius by the GPC-MALLS method and the ratio of the number average inertia radius to the weight average inertia radius can be measured under the same conditions using, for example, the equipment used for obtaining the number of branches, and are analyzed by Wyatt. Can be analyzed by software. The number average inertia radius of the copolymer of the styrene monomer and the acrylate ester is preferably 10 to 30 nm, more preferably 13 to 25.
nm. The ratio (Rw / Rn) of the number average inertia radius to the weight average inertia radius is 1.0 to 2.0, more preferably 1.0 to 1.8. If the number average inertia radius of the copolymer of the styrene monomer and the acrylate ester is within the above range, the strength of the biaxially stretched styrene resin sheet and the molded product using the same will be higher, and the biaxially stretched styrene It is excellent in stretchability at the time of forming a resin sheet and deep drawability at the time of secondary molding to be molded into a container. Further, when the ratio of the number average inertia radius to the weight average inertia radius (Rw / Rn) is in the above range, the stretchability at the time of forming a biaxially stretched styrene resin sheet and the deep drawing at the time of secondary molding to be molded into a container The strength of the biaxially stretched styrene resin sheet and a molded product using the same is further improved.

  The copolymer of styrene monomer and acrylate ester is a copolymer of styrene monomer and acrylate ester, styrene monomer and acrylate ester, and copolymerizable with these monomers. And a copolymer with a copolymerizable vinyl monomer. Examples of the styrene monomer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, isobutylstyrene, tertiary butylstyrene, o-bromostyrene, m. -Bromostyrene, p-bromostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene and the like. Preferred styrenic monomers include styrene, α-methylstyrene, etc., with styrene being particularly preferred. Examples of the acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, pentyl acrylate, and lauryl acrylate. Of these, butyl acrylate is preferably used.

  Examples of styrene monomers and acrylate esters and copolymerizable vinyl monomers copolymerizable with these monomers include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, and n-ester of methacrylic acid. Esters; Vinyl and cyanide compounds such as (meth) acrylonitrile; Polymerizable unsaturated fatty acids such as methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and cinnamic acid; N-methylmaleimide, N-ethylmaleimide, N -Maleimides such as butylmaleimide, N-octylmaleimide, N-isopropylmaleimide, N-phenylmaleimide, Np-bromophenylmaleimide, N-o-chlorophenylmaleimide, N-cyclohexylmaleimide; maleic anhydride, itaconic anhydride Acid, citraconic anhydride, etc. Sum carboxylic acid anhydrides; allylamine, (meth) aminoethyl acrylate, (meth) acrylic acid - the amino group-containing unsaturated compounds such as aminopropyl; acrylamide, N- methyl acrylamide acrylamide compounds. These copolymerizable vinyl monomers may be copolymerized alone or in combination of two or more with a styrene monomer.

  In order to achieve the above-mentioned specific branch number and molecular weight distribution in the copolymer of styrene monomer and acrylate ester used in the present invention, there is no particular limitation, and a polyfunctional polymerization initiator, polyfunctional chain A transfer agent, a polyfunctional monomer, and a multibranched macromonomer can be used. Among them, it is preferable to use a polyfunctional polymerization initiator and a multibranched macromonomer. Furthermore, it is preferable to use a hyperbranched macromonomer from the viewpoint of gelation. In the polyfunctional polymerization initiator, a tetrafunctional polymerization initiator is preferable. For example, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-hexylperoxycyclohexyl) propane, 2,2-bis ( 4,4-di-t-octylperoxycyclohexyl) propane and the like can be mentioned, among which 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane is preferable.

The multi-branched macromonomer has a plurality of branches and a plurality of polymerizable double bonds at the tip. Moreover, the mass mean molecular weight (Mw) by GPC becomes like this. Preferably it is 1000-30000, More preferably, it is 2000-10000, More preferably, it is 2000-5000. The content of the polymerizable double bond in the molecule is preferably 1.0 to 5.0 mmol / g, more preferably 1.5 to 3.5 mmol / g.
In the present invention, the hyperbranched macromonomer is preferably used in a ratio of 50 ppm to 3000 ppm, more preferably 100 ppm to 1500 ppm, based on the styrene monomer and the acrylate ester. With such a ratio, it is easy to produce hyperbranched polystyrene and it is easy to suppress gelation.

  The branched structure of the multi-branched polystyrene contained in the styrene resin composition of the present invention is not particularly limited, but all three bonds other than the electron-withdrawing group and the bond bonded to the electron-withdrawing group are carbon atoms. Those containing a branched structure composed of a saturated carbon atom bonded thereto and those containing a branched structure composed of repeating structural units selected from an ether bond, an ester bond and an amide bond are preferred.

The branched structure of the hyperbranched polystyrene is derived from a hyperbranched macromonomer that is a copolymer of a styrene monomer and an acrylate ester. The electron-withdrawing group content of the branched structure of the multi-branched styrene monomer and acrylate copolymer contained in the styrene resin composition of the present invention is the multi-branched styrene monomer and acrylate copolymer It is 2.5 × 10 ⁻⁴ mmol to 5.0 × 10 ⁻¹ mmol, preferably 5.0 × 10 ⁻⁴ mmol to 5.0 × 10 ⁻² mmol per gram.

The multi-branched macromonomer used in the present invention is not particularly limited except that it is a monomer having a multi-branched chain. However, as one of the preferred ones, an electron-withdrawing group and one electron-withdrawing group are contained in one molecule. There are multi-branched macromonomers containing a branched structure consisting of a saturated carbon atom in which all three bonds other than the bonding bond are bonded to a carbon atom, and a double bond directly bonded to the aromatic ring. This hyperbranched macromonomer is a hyperbranched macromonomer derived from an AB type ₂ monomer and has a branched structure as schematically shown in FIG.

Such a branched structure can be easily obtained by a nucleophilic substitution reaction of an active methylene group to which an electron withdrawing group is bonded. Examples of the electron withdrawing group include —CN, —NO ₂ , —CONH ₂ , —CON (R) ₂ , —SO ₂ CH ₃ , —P (═O) (OR) ₂ , and the like. When the methylene group to which the electron withdrawing group is bonded is directly bonded to the aromatic ring or the carbonyl group, the activity of the methylene group is further increased.

As a multibranched macromonomer used for this invention, the multibranched macromonomer which has a branched chain containing the repeating unit represented by following General formula (1) is mentioned, for example.
General formula (1)

［式中、Ｙ_１は−ＣＮ、−ＮＯ_２、−ＣＯＮＨ_２、−ＣＯＮ（Ｒ）_２、−ＳＯ_２ＣＨ_３、−Ｐ（＝Ｏ）（ＯＲ）_２（ここでＲはアルキル基またはアリール基を表す）から成る群から選ばれる電子吸引基であり、Ｙ_２はアリーレン基、−Ｏ−ＣＯ−または−ＮＨ−ＣＯ−であり、Ｚは−（ＣＨ_２）_ｎＯ−、−（ＣＨ_２ＣＨ_２Ｏ）_ｎ−、−（ＣＨ_２ＣＨ_２ＣＨ_２Ｏ）_ｎ−から成る群から選ばれる基であり、かつＹ_２が−Ｏ−ＣＯ−または−ＮＨ−ＣＯ−である場合はＺは−（ＣＨ_２）_ｎ−、−（ＣＨ_２）_ｎＡｒ−、−（ＣＨ_２）_ｎＯ−Ａｒ−、−（ＣＨ_２ＣＨ_２Ｏ）_ｎ−Ａｒ−、または−（ＣＨ_２ＣＨ_２ＣＨ_２Ｏ）_ｎ−Ａｒ−（ここでＡｒはアリール基である）を表す］
ここで、Ｙ_２は例えば、

[Wherein Y ₁ represents —CN, —NO ₂ , —CONH ₂ , —CON (R) ₂ , —SO ₂ CH ₃ , —P (═O) (OR) ₂ (where R represents an alkyl group or aryl Y ₂ is an arylene group, —O—CO— or —NH—CO—, and Z is — (CH ₂ ) _n O—, — (CH ₂ CH ₂ O) _n —, a group selected from the group consisting of — (CH ₂ CH ₂ CH ₂ O) _n —, and when Y ₂ is —O—CO— or —NH—CO—, Z is _{- (CH 2) n -,} - (CH 2) n Ar -, - (CH 2) n O-Ar -, - (CH 2 CH 2 O) n -Ar-, or _- (CH 2 _CH 2 CH ₂ O) _n -Ar- (wherein Ar represents an aryl group)]
Here, Y ₂ is, for example,

から成る群から選ばれるアリーレン基である。なかでもＹ_１は−ＣＮ、Ｙ_２はフェニレン基が好適である。Ｙ_２がフェニレン基である場合は、Ｚの結合位置はｏ−位、ｍ−位又はｐ−位のいずれであってもよく特に制限されるものではないが、ｐ−位が好ましい。またＺの繰り返し数ｎは特に制限されるものではないが、スチレンへの溶解性の点から１〜１２が好ましく、更に好ましくは２〜１０が好ましい。

An arylene group selected from the group consisting of Among these, Y ₁ is preferably —CN, and Y ₂ is preferably a phenylene group. When Y ₂ is a phenylene group, the bonding position of Z may be any of the o-position, m-position and p-position, and is not particularly limited, but the p-position is preferred. The number n of repeating Z is not particularly limited, but is preferably 1 to 12, more preferably 2 to 10 from the viewpoint of solubility in styrene.

The hyperbranched macromonomer having the above branched structure is, in the presence of a basic compound, (1) AB ₂ type having an active methylene group and a leaving group in a nucleophilic substitution reaction of an active methylene group in one molecule. A precursor of a multi-branched self-condensation polycondensate obtained by subjecting a monomer to a nucleophilic substitution reaction,
(2) A double bond in which an unreacted active methylene group or methine group remaining in the polycondensate is directly bonded to an aromatic ring in one molecule and a leaving group in a nucleophilic substitution reaction of the active methylene group. It is obtained by carrying out a nucleophilic substitution reaction with a compound having it.

Here, the leaving group in the nucleophilic substitution reaction of the active methylene group is any halogen bonded to a saturated carbon atom, —OS (═O) ₂ R (R represents an alkyl group or an aryl group), and the like. Specific examples include bromine, chlorine, methylsulfonyloxy group, tosyloxy group and the like.
The basic compound is preferably a strong alkali such as sodium hydroxide or potassium hydroxide, and used as an aqueous solution in the reaction.

Examples of the AB type ₂ monomer having an active methylene group and a leaving group in the nucleophilic substitution reaction of the active methylene group in one molecule include alkoxy halides such as bromoethoxy-phenylacetonitrile and chloromethylbenzyloxy-phenylacetonitrile. Examples include phenylacetonitriles having a tosyloxy group, such as phenylacetonitriles, tosyloxy- (ethyleneoxy) -phenylacetonitrile, tosyloxy-di (ethyleneoxy) -phenylacetonitrile.

  Representative compounds having a double bond directly bonded to an aromatic ring in one molecule and a leaving group in the nucleophilic substitution reaction of an active methylene group include, for example, chloromethylstyrene and bromomethylstyrene. .

  The above (1) is a reaction for synthesizing a polycondensate as a precursor, and (2) is a reaction for synthesizing a multi-branched macromonomer by introducing a double bond directly bonded to an aromatic ring to the precursor. . The reactions (1) and (2) can be performed sequentially, but can also be performed simultaneously in the same reaction system. The molecular weight of the hyperbranched macromonomer can be controlled by changing the compounding ratio of the monomer and the basic compound.

  As other preferable ones of the multi-branched macromonomer used in the present invention, preferably a branched structure composed of repeating structural units selected from an ester bond, an ether bond and an amide bond, and an ethylenic double bond at the branch end The multibranched macromonomer to contain can be mentioned.

In the multi-branched macromonomer having an ester bond as a repeating structural unit, the carbon atom adjacent to the carbonyl group of the ester bond forming the molecular chain is a saturated carbon atom, and all the hydrogen atoms on the carbon atom are substituted. An ethylenic double bond such as a vinyl group or an isopropenyl group is introduced into a multi-branched polyester polyol having a molecular chain. When an ethylenic double bond is introduced into a multi-branched polyester polyol, it can be carried out by an esterification reaction or an addition reaction.
As the above-mentioned multi-branched polyester polyol, “Boltorn H20, H30, H40” manufactured by Perstorp is commercially available.

In the above multi-branched polyester polyol, 1 g of the hydroxy group may have a substituent introduced beforehand by an ether bond or other bond, and 1 g of the hydroxy group is modified by an oxidation reaction or other reaction. May be.
Further, in the multi-branched polyester polyol, 1 g of the hydroxy group may be esterified in advance.

  A typical example of such a multi-branched macromonomer is a compound having one or more hydroxyl groups, in which the carbon atom adjacent to the carboxyl group is a saturated carbon atom, and all the hydrogen atoms on the carbon atom are substituted. In addition, a monobranched polymer having two or more hydroxyl groups is reacted to form a multi-branched polymer, and then the hydroxyl group which is a terminal group of the polymer is unsaturated acid such as acrylic acid or methacrylic acid, isocyanate group-containing acrylic compound, etc. Can be obtained by reacting. The multi-branched polymer having an ester bond as a repeating structural unit is also described in “Angew. Chem. Int. Ed. Engl. 29” p138-177 (1990) by Tamalia et al.

  Examples of the compound having one or more hydroxyl groups include: a) aliphatic diol, alicyclic diol, or aromatic diol, b) triol, c) tetraol, d) sugar alcohols such as sorbitol and mannitol, e) anhydro Ennea-heptitol or dipentaerythritol, f) α-alkyl glucosides such as α-methyl glycoside, g) monofunctional alcohols such as ethanol and hexanol, h) a molecular weight of at most 8000, and alkylene oxides or derivatives thereof And a hydroxyl group-containing polymer produced by reacting with one or more hydroxyl groups of an alcohol selected from any of the above-mentioned a) to g).

Examples of the aliphatic diol, alicyclic diol and aromatic diol include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, Polytetrahydrofuran, dimethylolpropane, neopentylpropane, 2-propyl-2-ethyl-1,3-propanediol, 1,2-propanediol, 1,3-butanediol, diethylene glycol, triethylene glycol, polyethylene glycol, di- Examples include propylene glycol, tripropylene glycol, polypropylene glycol; cyclohexanedimethanol, 1,3-dioxane-5,5-dimethanol; 1,4-xylylenediethanol, 1-phenyl-1,2-ethanediol and the like.
Examples of the triol include trimethylolpropane, trimethylolethane, trimethylolbutane, glycerol, 1,2,5-hexanetriol and the like.
Examples of tetraols include pentaerythritol, ditrimethylolpropane, diglycerol, and ditrimethylolethane.
Examples of the aromatic compound having two or more hydroxyl groups bonded to the aromatic ring include 1,3,5-trihydroxybenzene, 1,4-xylylenediethanol, 1-phenyl-1,2-ethanediol and the like. it can.
Examples of the monocarboxylic acid in which the carbon atom adjacent to the carboxyl group is a saturated carbon atom and all the hydrogen atoms on the carbon atom are substituted and which has two or more hydroxyl groups include dimethylolpropionic acid, α, α-bis Examples include (hydroxymethyl) butyric acid, α, α, α-tris (hydroxymethyl) acetic acid, α, α-bis (hydroxymethyl) valeric acid, α, α-bis (hydroxymethyl) propionic acid. By using such a monocarboxylic acid, the ester decomposition reaction is suppressed and a multi-branched polyester polyol can be formed.
Further, when producing such a multi-branched polymer, it is preferable to use a catalyst, such as a dialkyl tin oxide, a dialkyl tin halide, a dialkyl tin biscarboxylate, or an organic tin compound such as stannoxane, Examples thereof include titanates such as tetrabutyl titanate, organic sulfonic acids such as Lewis acid, and paratoluenesulfonic acid.

  The multi-branched macromonomer having an ether bond as a repeating structural unit is, for example, made into a multi-branched polymer by reacting a compound having one or more hydroxyl groups with a cyclic ether compound having one or more hydroxyl groups, and then terminal groups of the polymer And those obtained by reacting an unsaturated acid such as acrylic acid or methacrylic acid, an isocyanate group-containing acrylic compound, or halogenated methylstyrene such as 4-chloromethylstyrene with the hydroxyl group. As a method for producing a multi-branched polymer, a compound having one or more hydroxyl groups and a compound containing two or more hydroxyl groups and a halogen atom, -OSO2OCH3 or -OSO2CH3 are reacted based on Williamson's ether synthesis method. It is also useful to do so.

As the compound having one or more hydroxyl groups, those described above can be used.
As cyclic ether compounds having one or more hydroxyl groups, 3-ethyl-3- (hydroxymethyl) oxetane, 2,3-epoxy-1-propanol, 2,3-epoxy-1-butanol, 3,4-epoxy- Examples include 1-butanol.
As the compound having one or more hydroxyl groups used in Williamson's ether synthesis method, those described above may be used, but aromatic compounds having two or more hydroxyl groups bonded to an aromatic ring are preferred. Typical examples of such compounds include 1,3,5-trihydroxybenzene, 1,4-xylylenediethanol, 1-phenyl-1,2-ethanediol and the like.
Examples of the compound containing two or more hydroxyl groups and a halogen atom, -OSO2OCH3 or -OSO2CH3 include 5- (bromomethyl) -1,3-dihydroxybenzene, 2-ethyl-2- (bromomethyl) -1,3- Examples include propanediol, 2-methyl-2- (bromomethyl) -1,3-propanediol, and 2- (bromomethyl) -2- (hydroxymethyl) -1,3-propanediol.
In producing the above-mentioned multibranched polymer, it is preferable to use a normal catalyst. Examples of such a catalyst include BF3 diethyl ether, FSO3H, CLSO3H, HCLO4 and the like.

  In addition, as the multi-branched macromonomer having an amide bond as a repeating structural unit, for example, there are those in which a amide bond has a repeating structure through a nitrogen atom in the molecule, and a generation 2.0 (PAMAM) manufactured by Dentortech. Dentrimer) is a typical one.

  The larger the number of double bonds bonded to the molecular terminals introduced into the multibranched macromonomer, the more the multibranched styrene monomer and acrylic that are a copolymer of a styrene monomer and an acrylate ester. The degree of branching of the acid ester is increased. The degree of branching (DB) of the multibranched macromonomer used in the present invention is defined by the following formula (3), and the range of the degree of branching (DB) is preferably 0.3 to 0.8.

Formula (3) DB = (D + L) / (D + T + L)
(In the formula, D represents the number of dendritic units, L represents the number of linear units, and T represents the number of terminal units)

In addition, said D, L, and T can be calculated | required by the 2nd, 3rd, 4th carbon atom number derived from the active methylene group and its reaction which can be measured by < ¹³ > C-NMR, D is the 4th carbon atom number. In addition, L corresponds to the number of third carbon atoms, and T corresponds to the number of second carbon atoms.

  The content of the double bond directly bonded to the aromatic ring introduced into the multibranched macromonomer is preferably 0.1 mmol to 5.5 mmol per 1 g of the multibranched macromonomer, 3.5 mmol is still preferred. When the amount is less than 0.1 mmol, it is difficult to obtain a copolymer of a high molecular weight hyperbranched styrene monomer and an acrylate ester. The molecular weight of the monomer and acrylate ester copolymer is excessively increased.

  In order to reduce the viscosity of the reaction product in the polymerization reaction, an organic solvent may be added to the reaction system, and the organic solvent is toluene, ethylbenzene, xylene, acetonitrile, benzene, chlorobenzene, dichlorobenzene, anisole, cyanobenzene. , Dimethylformamide, N, N-dimethylacetamide, methyl ethyl ketone and the like.

  In particular, when it is desired to increase the amount of the hyperbranched macromonomer, it is preferable to use an organic solvent from the viewpoint of suppressing gelation. Thereby, the addition amount of the multibranched macromonomer shown previously can be increased dramatically, and gelation does not occur.

  Further, a chain transfer agent may be added so that the molecular weight of the styrene resin composition does not become excessively large. As the chain transfer agent, a monofunctional chain transfer agent having one chain transfer group or a polyfunctional chain transfer agent having a plurality of chain transfer agents can be used. Examples of the monofunctional chain transfer agent include alkyl mercaptans and thioglycolic acid esters.

  Polyfunctional chain transfer agents such as ethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, sorbitol, etc. are esterified with thioglycolic acid or 3-mercaptopropionic acid. The thing which was done is mentioned.

  In order to produce the styrenic resin composition used in the present invention, in addition to the method of polymerizing a multi-branched macromonomer, a styrenic monomer, and an acrylate ester in a single stage as described above, they are synthesized separately in advance. A linear styrene monomer / acrylic acid ester copolymer and a multi-branched styrene monomer / acrylic acid ester copolymer are mixed, and the styrene type has an arbitrary mixing ratio. A resin composition may be produced.

  As a copolymer of a styrene monomer and an acrylate ester used in the present invention, stretchability at the time of forming a biaxially stretched styrene resin sheet and deep drawability at the time of secondary molding to be molded into a container In order to improve the low-temperature moldability and the anti-fogging agent coating property, the styrene monomer and the acrylate ester are styrene monomer / acrylate ester = 95/5 to 99.7 / 0.3. A resin polymerized at a mass ratio is preferred. More preferably, 96/3 to 99.6 / 0.4 is preferable, and still more preferably 97.5 / 2.5 to 99.5 / 0.5. If the acrylic ester is less than 0.3%, the number of branches is low, the deep drawability and the low temperature moldability are inferior, and the antifogging agent coatability is also inferior. If it exceeds 5%, the heat resistance is poor. Become. By setting the mass ratio of the styrene monomer and the acrylate to the above range, the low-temperature moldability and antifogging agent coatability of the composition of the present invention are improved. In particular, for anti-fogging agent coating properties, for example, a silicon emulsion is applied to the surface of a biaxially stretched styrene resin sheet formed by the resin composition for a biaxially stretched styrene resin sheet of the present invention with a coater, and then dried. After that, when the sheet surface is magnified and observed with a microscope, it can be confirmed that the antifogging agent is uniformly applied. Therefore, when a food is packaged using the biaxially stretched styrene resin sheet formed by the resin composition for a biaxially stretched styrene resin sheet of the present invention, the sheet surface is clouded by water vapor evaporated from the food, and the contents are visually recognized. It won't be difficult.

Furthermore, low molecular weight components extracted as methanol-soluble components improve the stretchability during biaxially oriented styrene resin sheet formation, deep drawability during secondary molding to be molded into containers, and low temperature moldability. And a certain amount of plasticizer can be contained. For example, the methanol-soluble content is determined by the following method.
1 g of a sample is dissolved in 100 ml of toluene for 24 hours, dropped into 800 ml of methanol under stirring, left standing, settled, filtered through a glass filter, and dried in a vacuum dryer for 24 hours. The methanol-soluble component can be calculated from the sample weight, the weight after drying, and the following formula.

Methanol-soluble content (%) = ((sample weight−weight after drying) / sample weight) × 100

  It is preferable that the methanol soluble part measured by this contains 0.5-2.0 mass%, and it is more preferable that it is 0.5-1.5 mass%. More preferably, it is 0.5 to 1.0% by mass. When it is less than 0.5% by mass, it is inferior in deep drawability and low-temperature moldability, and when it exceeds 2.0% by mass, it prevents oil stains when forming a biaxially stretched styrene resin sheet or molding into a container. Uneven coating of the clouding agent is likely to occur, resulting in poor productivity.

  As a method for producing a copolymer of a styrene monomer and an acrylate ester used in the present invention, a known and commonly used styrene polymerization method can be used. The polymerization method is not particularly limited, but bulk polymerization, suspension polymerization, or solution polymerization is preferable. Moreover, the usual thing used for manufacture of a normal polystyrene can be used for polymerization adjuvants, such as a suspending agent and an emulsifier required for superposition | polymerization.

  Although the thickness of the biaxially-stretched styrene resin sheet of this invention is not specifically limited, 0.01-0.5 mm from which heat moldability becomes favorable is preferable.

  Various fine particles can be added to the biaxially stretched styrene resin sheet of the present invention in order to impart an antiblocking effect. Examples of the fine particles include resin crosslinked particles such as styrene resin crosslinked particles, (meth) acrylic ester resin crosslinked particles, polyurethane resin crosslinked particles; silica, hydrophobized silica, spherical silica, light calcium carbonate, oxidized Examples thereof include inorganic fine particles such as titanium and talc, and rubber fine particles such as styrene grafted diene rubber. In particular, styrene-grafted diene rubber is particularly preferred because it improves the strength, anti-blocking property, and peelability of the biaxially stretched styrene resin sheet and a molded product using the same. Here, as the styrene graft diene rubber, a biaxially stretched styrene-based resin sheet and a molded article using the same can be obtained with an excellent balance between strength and appearance, so that the average particle size is 0.1 to 5. What is contained in the biaxially-stretched styrene-based resin sheet so that the diene component is in the range of 0.05 to 3.0% by mass at 0 μm is preferable. In order to obtain higher transparency, it is preferable to contain 0.05-0.5 mass%.

  As a method for containing the styrene-grafted diene rubber, a method in which the diene rubber is dissolved and polymerized during the production of the copolymer of the styrene monomer and the acrylate ester, and a graft-type rubber containing 5 to 12% by mass of the diene rubber. Copolymer of modified polystyrene resin, styrene monomer and acrylate ester, copolymer of styrene monomer and copolymerizable vinyl monomer copolymerizable with acrylate ester, etc. Any of the methods in which a copolymer of a styrene monomer and an acrylate ester composed of When the graft type rubber-modified polystyrene resin is mixed, if the average particle size is 0.1 to 5.0 μm and the diene component is in the range of 0.05 to 3.0% by mass, 1 is added. Two or more species can be used.

  Further, mineral oil may be contained in order to improve stretchability at the time of forming a biaxially stretched styrene-based resin sheet, deep drawability at the time of secondary molding to be molded into a container, and low temperature moldability. However, the volatile matter of mineral oil generated at the time of melt extrusion is aggregated and adhered to the sheet manufacturing apparatus, and this is transferred to the sheet to prevent the appearance failure of the biaxially oriented styrene resin sheet. It is preferable to do.

  The mineral oil used in the present invention is a mixture of saturated hydrocarbon compounds also called liquid paraffin or mineral oil, and has a 2.5% distillation temperature by ASTM D1160 of 260 ° C. or higher, More preferably, it is 280 degreeC or more.

  The method for producing the biaxially stretched styrene resin sheet of the present invention is not particularly limited, and may be performed by a method commonly used in the production of conventional stretched sheets. One example is a method in which a resin is supplied to an extruder, melted and kneaded, and then continuously extruded with a T die or a circular die, and the sheet is continuously or simultaneously biaxially stretched by a tenter method, a bubble method, or the like. It is.

  The stretching ratio of these sheets is 1.2 to 7 times, preferably 1.5 to 7 times, and more preferably 1.8 to 5 times in both the machine direction and the transverse direction. The stretching temperature is the Vicat softening point of the resin constituting the sheet +5 to 50 ° C., preferably +10 to 35 ° C. When the draw ratio is less than 1.2 times and / or the draw temperature is higher than the Vicat softening point + 50 ° C., the stretch orientation degree becomes low, and the strength of the biaxially stretched styrene resin sheet and the container using the same is not sufficient. . In addition, when the draw ratio exceeds 8 times and / or the draw temperature is lower than the Vicat softening point + 5 ° C., the sheet may be cut at the time of drawing or the deep drawability at the time of secondary forming to be molded into a container may be reduced. A problem occurs.

  The degree of orientation of the biaxially stretched styrene resin sheet of the present invention is such that the orientation relaxation stress measured in accordance with ASTM D-1504 is preferably 0.3 to 1.2 MPa, preferably 0 in both the longitudinal direction and the transverse direction. It should be in the range of 4 to 1.0 MPa. When the orientation relaxation stress is less than 0.3 MPa, it is inferior in preventing cracking at the time of trimming, and when it exceeds 1.2 MPa, the deep drawability is inferior.

  Moreover, the biaxially-stretched styrene resin sheet of this invention can apply | coat an antifogging agent or a mold release agent to at least one surface or both surfaces. You may use an antifogging agent and a mold release agent together. Examples of the antifogging agent include nonionic surfactants such as sorbitan fatty acid ester, sucrose fatty acid ester, polyglycerin fatty acid ester, and polyoxyethylene derivative, and these can be used alone or in a mixture. Examples of the release agent include silicone oil and emulsion thereof. Various nonionic surfactants, cationic surfactants, anionic surfactants, and the like may be applied as an antistatic agent. Examples of these coating methods include spray coaters, roll coaters, gravure roll coaters, knife coaters, air knife coaters, rotor dampening coaters, and applicator systems.

  The biaxially stretched styrenic resin sheet of the present invention provides design, functionality, etc. within a range that does not impair the effects of the present invention, so printing on the surface of the sheet, barrier properties, antibacterial properties, heat A resin having functionality such as a sealing property may be laminated. Moreover, you may use as a part of container, such as laminating the biaxially-stretched styrene resin sheet of this invention on a foam sheet.

  The biaxially stretched styrene resin sheet of the present invention can be heated and molded by a direct heating method or an indirect heating method to obtain the molded product of the present invention. The method of heat forming is not particularly limited, and can be performed by a usual method using a vacuum forming machine, a pressure forming machine, a hot plate pressure forming machine, a pressure forming machine, or the like.

  EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples and is not intended to be limited thereto.

Each characteristic value was measured and evaluated by the following method.
(1) Number of branches High-performance liquid chromatography (HPLC manufactured by Shodex, detector: DAWN EOS manufactured by Wyatt Technology, RI-101 manufactured by Shodex, column: KF-806L × 2, manufactured by Shodex, solvent: THF, flow rate: 1 0.0 ml / min), the absolute molecular weight was measured, the weight average inertia radius was determined by analysis software ASTRA manufactured by Wyatt Technology, and then the weight average inertia radius of the copolymer of the branched styrene monomer and the acrylate ester (RwB), the weight average inertia radius (RwL) of the copolymer of the linear styrene monomer and the acrylate ester is substituted into the formula (1) to calculate g, and one molecule according to the formula (2). The number of branches per n (n) was calculated.
Formula (1) g = (RwB) ² / (RwL) ²
Formula (2) g = (1 / n) × ln (1 + n)

(2) Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)
The equipment used for obtaining the number of branches was measured under the same conditions, and analyzed with analysis software manufactured by Wyatt.

(3) Ratio (Mw / Mp) of weight average molecular weight (Mw) and peak molecular weight (Mp)
High-performance liquid chromatography (HLC-8220 GPC manufactured by Tosoh Corporation, detector: RI detector, column: TSKgel G6000H × 1 + G5000H × 1 + G4000H × 1 + G3000H × 1 + TSKguard column H × 1-H, solvent: THF, flow rate: 1.0 ml / min, temperature 40 ° C.), a standard calibration curve was prepared with standard polystyrene, and the weight average molecular weight (Mw) was determined from the weight fraction and molecular weight in the elution volume. On the other hand, the peak molecular weight was determined as a linear styrene equivalent molecular weight corresponding to the peak of the chromatogram.

(4) Methanol-soluble component 1 g of a sample was dissolved in 100 ml of toluene for 24 hours, dropped into 800 ml of methanol under stirring, allowed to stand, settled, filtered through a glass filter, and dried in a vacuum dryer for 24 hours. The methanol soluble content was calculated by the following formula.

Methanol-soluble content (%) = ((sample weight−weight after drying) / sample weight) × 100

(5) Alignment relaxation stress Measured according to ASTM D-1504.

(6) Transparency The haze value was measured according to JIS K-7105.

(7) Image sharpness Image sharpness was measured according to JIS K-7105 with a comb spacing of 0.5 mm.

(8) Cracking prevention property Using a biaxially stretched styrene resin sheet for evaluation, with a single hot plate pressure forming machine (manufactured by Kansai Automatic Molding Machine Co., Ltd.), a heating temperature of 123 ° C., a heating pressure of 0.1 MPa, heating A food pack is molded under the conditions of time 2.0 seconds, molding pressure 0.4 MPa, molding time 2 seconds, mold temperature 60 ° C., 50 sheets are stacked and punched with a press punching machine, and cracks occur in the molded product The cracking prevention property was evaluated based on the proportion of the cracks.
◎: 0% cracking rate
○: Ratio of cracking is less than 2% Δ: Ratio of cracking is 2% or more and less than 10% ×: Ratio of cracking is 10% or more

(9) Deep-drawing formability Using a biaxially stretched styrene resin sheet for evaluation, with a single hot plate pressure forming machine (manufactured by Kansai Automatic Molding Machine Co., Ltd.), heating temperature 117 ° C., heating pressure 0.1 MPa, heating Molding was performed under the conditions of a time of 2.0 seconds, a molding pressure of 0.4 MPa, a molding time of 2 seconds, and a mold temperature of 60 ° C., and the deep drawability was evaluated by the ratio of the diameter and depth of the molded product (drawing ratio) . The higher the drawing ratio, the better the deep drawability.

(10) Low temperature moldability Using a biaxially stretched styrene resin sheet for evaluation, with a single hot plate pressure forming machine (manufactured by Kansai Automatic Molding Machine Co., Ltd.), heating pressure 0.1 MPa, heating time 2.0 seconds, Molded under the conditions of a molding pressure of 0.4 MPa, a molding time of 2 seconds, and a mold temperature of 60 ° C., and R of the fitting part of the molded product (container lid: vertical × horizontal × depth = 100 × 100 × 30 mm) The heating temperature at which the value was 1.5 mm (R value of the fitting part of the mold: 125% with respect to 1.2 mm) was measured. The lower the heating temperature, the better the deep drawability.

(11) Anti-fogging agent coating property After coating a silicon emulsion having a solid content concentration of 0.2% by mass with a coater, a drying treatment is performed to obtain a biaxially stretched sheet having a silicon coating amount of 25 mg / m ^{2 on} both sides. The surface was magnified and observed with a microscope to observe the state of application of the antifogging agent. Uniform application: ○, non-uniform application: ×

[Example 1]
In this example, an apparatus arranged as shown in FIG. 1 was used. A mixed solution containing styrene, butyl acrylate, a solvent, and the like was supplied to a stirring reactor (2) by a plunger pump (1). Then, it supplied to the circulation polymerization line (I) with the gear pump (3). The circulation polymerization line (I) is used to circulate the 2.5 inch inner diameter tubular reactor (SMX static mixer manufactured by Gebrüu Sulzer, Switzerland) (4), (5), (6) and the mixed solution in order from the inlet. Gear pump (7). The reaction volume of (4) to (6) is about 20L. Between the tubular reactor (6) and the gear pump (7), there is an outlet that leads to the non-circulating polymerization line (II). Tubular reactors (8), (9) and (10) similar to the above and a gear pump (11) are connected in series to the non-circulation polymerization line (II) in order from the inlet. The reaction volume of (8) to (10) is about 16L.
99.5 parts of styrene, 0.5 part of butyl acrylate, 8 parts of ethylbenzene, a polymerization initiator (2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane) were added to styrene and butyl acrylate. A mixed solution consisting of 150 ppm with respect to a total of 100 parts was prepared and polymerized continuously under the following conditions using the apparatus shown in FIG.
Feed rate of mixed solution: 9.0 liter / hour Reaction temperature in stirred reactor: 130 ° C
Reaction temperature in circulating polymerization line (I): 130 ° C
Reaction temperature in non-circulation polymerization line (II): 155 to 165 ° C
The mixed solution obtained by polymerization was heated with a heat exchanger at 260 ° C., and after removing volatile components under a reduced pressure of 5 kPa, the mixture was pelletized to obtain the styrenic resin composition 1 of the present invention.
The obtained styrene resin 1 has a branch number of 0.23, a weight average molecular weight of 255,000 by GPC-MALLS method, a molecular weight distribution (Mw / Mn) of 2.32, a number average inertia radius of 16.0 nm, and an inertia radius distribution. (Rw / Rn) was 1.48, the ratio of the average weight average molecular weight to the peak molecular weight by GPC method was 1.07, and the methanol soluble content was 1.1%.
Styrene resin 1 was supplied to an extruder, and after melt kneading, a melt-extruded sheet was obtained in a sheet form from a T-die. This sheet was stretched 2.5 times in the longitudinal and lateral directions by a single stretcher. The stretching temperature was set so that the orientation relaxation stress was 0.6 MPa in both the vertical and horizontal directions.

[Comparative Example 1]
Using the same reaction apparatus as in Example 1, polymerization was continuously carried out under the following composition and polymerization conditions.
A mixed solution of 88 parts of styrene, 12 parts of ethylbenzene, and 150 ppm of a polymerization initiator (2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane) with respect to a total of 100 parts of styrene and butyl acrylate. Was continuously polymerized under the following conditions using the apparatus shown in FIG.
Feed rate of mixed solution: 6.52 liters / hour Reaction temperature in a stirred reactor: Reaction temperature in a room temperature circulation polymerization line (I): 125 ° C.
Reaction temperature in non-circulation polymerization line (II): 150 to 160 ° C
The mixed solution obtained by polymerization was heated with a heat exchanger at 250 ° C., and after removing volatile components under a reduced pressure of 5 kPa, pelletized to obtain a styrene resin composition 2 of the present invention.
The obtained styrene resin 2 has a branch number of 0.07, a weight average molecular weight of 292,000 according to GPC-MALLS method, a molecular weight distribution (Mw / Mn) of 2.37, a number average inertia radius of 14.5 nm, and an inertia radius distribution. (Rw / Rn) was 1.57, the ratio of the average weight average molecular weight to the peak molecular weight by the GPC method was 1.10, and the methanol soluble content was 1.1%.
After obtaining a sheet using the same extruder as in Example 1, this sheet was stretched 2.5 times in both the longitudinal and transverse directions by a single stretcher. The stretching temperature was set so that the orientation relaxation stress was 0.6 MPa in both the vertical and horizontal directions.

[Comparative Example 2]
Prepare a mixture of 150 parts of styrene, 97 parts of styrene, 3 parts of butyl acrylate, 8 parts of ethylbenzene, and a polymerization initiator (2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane) with respect to styrene. Then, it was continuously polymerized using the apparatus shown in FIG.
Feed rate of mixed solution: 6.52 liters / hour Reaction temperature in a stirred reactor: Reaction temperature in a room temperature circulation polymerization line (I): 112 ° C.
Reaction temperature in noncircular polymerization line (II): 146 to 156 ° C
The mixed solution obtained by polymerization was heated with a heat exchanger at 250 ° C., volatile components were removed under a reduced pressure of 5 kPa, and then pelletized to obtain a styrene resin composition 9 of the present invention.
The obtained styrene resin 9 has a branching number of 0.76, a weight average molecular weight of 46,000, GPC-MALLS method, a molecular weight distribution (Mw / Mn) of 3.2, a number average inertia radius of 25.9 nm, and an inertia radius distribution. (Rw / Rn) was 1.20, the ratio of average weight average molecular weight to peak molecular weight by GPC method was 1.38, and methanol soluble matter was 1.0%.
After obtaining a sheet using the same extruder as in Example 1, this sheet was stretched 2.5 times in both the longitudinal and transverse directions by a single stretcher. The stretching temperature was set so that the orientation relaxation stress was 0.6 MPa in both the vertical and horizontal directions.

[Comparative Example 3]
Prepare a mixture of 250 parts of styrene with 97 parts of styrene, 3 parts of butyl acrylate, 6 parts of ethylbenzene, and a polymerization initiator (2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane) with respect to styrene. Then, it was continuously polymerized using the apparatus shown in FIG.
Feed rate of mixed solution: 6.52 liters / hour Reaction temperature in a stirred reactor: Room temperature Reaction temperature in circulation polymerization line (I): 109 ° C.
Reaction temperature in non-circulation polymerization line (II): 115 to 130 ° C
The mixed solution obtained by polymerization was heated with a heat exchanger at 250 ° C., volatile components were removed under a reduced pressure of 5 kPa, and then pelletized to obtain a styrene resin composition 9 of the present invention.
The obtained styrene resin 9 has a branching number of 0.80, a weight average molecular weight of 476,000 by GPC-MALLS method, a molecular weight distribution (Mw / Mn) of 3.0, a number average inertia radius of 26.3 nm, and an inertia radius distribution. (Rw / Rn) was 1.40, the ratio of the average weight average molecular weight to the peak molecular weight by the GPC method was 1.29, and the methanol soluble matter was 1.0%.
After obtaining a sheet using the same extruder as in Example 1, this sheet was stretched 2.5 times in both the longitudinal and transverse directions by a single stretcher. The stretching temperature was set so that the orientation relaxation stress was 0.6 MPa in both the vertical and horizontal directions.

[Comparative Example 4]
Prepare a mixed solution consisting of 700 parts of styrene with 97 parts of styrene, 3 parts of butyl acrylate, 6 parts of ethylbenzene, and a polymerization initiator (2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane) with respect to styrene. The gas phase was purged with nitrogen in a 25 ml ampoule, and then sealed and polymerized. The polymerization conditions were as follows, and gelled when polymerized.
After polymerization at 110 ° C. for 3 hours, polymerization was performed at 115 ° C. for 1 hour and 130 ° C. for 1.3 hours.

  Comparative Example 1 was excellent in transparency and image sharpness, but was inferior in punching prevention property, deep-drawing formability, low-temperature formability, and antifogging agent coatability. In Comparative Example 2, the transparency was relatively good, but the image clarity was insufficient and the cracking prevention property was inferior. Comparative Example 3 was excellent in transparency and image clarity, but was inferior in cracking prevention. In Comparative Example 4, in order to increase the amount of the branching agent, the polymerization initiator was increased, but gelation was not obtained for use in the molding process.

  The resin composition for a biaxially stretched styrene-based resin sheet of the present invention has an excellent appearance and transparency, and is excellent in processability such as low-temperature moldability, deep-drawn moldability, and anti-cracking property, so that it is a food packaging container. It is useful as a raw material for sheets for packaging and other packaging containers.

The schematic diagram of the manufacturing apparatus of copolymer resin.

Explanation of symbols

(1): The plunger pump
(2): Stirred reactor
(3): Gear pump
(4): Tubular reactor with static mixing elements
(5): Tubular reactor with static mixing elements
(6): Tubular reactor with static mixing elements
(7): Gear pump
(8): Tubular reactor with static mixing elements
(9): Tubular reactor with static mixing elements
(10): Tubular reactor with static mixing elements
(11): Gear pump
(I): Circulation polymerization line
(II): Acyclic polymerization line

Claims (10)

  The number of branches per molecule in the absolute molecular weight of 734,000 obtained by the GPC-MALLS method is 0.04 to 0.35, and the weight average molecular weight (Mw) obtained by the GPC-MALLS method is 250,000 to 45. A styrene monomer having a ratio (Mw / Mp) of 1.05 to 1.28 between the weight average molecular weight (Mw) and the peak molecular weight (Mp) determined by the GPC method is 1.05 to 1.28. A resin composition for a biaxially oriented styrenic resin sheet, comprising a copolymerized resin.   The copolymer resin is a resin obtained by polymerizing a styrene monomer and an acrylate at a mass ratio of styrene monomer / acrylate = 95/5 to 99.7 / 0.3. Item 2. The resin composition for a biaxially stretched styrene-based resin sheet according to Item 1.   The resin composition for a biaxially stretched styrene-based resin sheet according to claim 1 or 2, wherein the copolymer resin contains 0.5 to 2.0 mass% of a methanol-soluble component.   The copolymer resin has a number average inertia radius (Rn) of 10 to 30 nm, and a ratio (Rw / Rn) of the number average inertia radius to the weight average inertia radius (Rw) of 1.3 to 2.0. The resin composition for biaxially-stretched styrene resin sheets according to any one of claims 1 to 3.   The resin composition for a biaxially stretched styrene resin sheet according to any one of claims 1 to 4, wherein the acrylic ester is butyl acrylate.   6. The resin composition for a biaxially oriented styrene resin sheet according to claim 1, further comprising 0.05 to 3.0% by mass of a styrene graft diene rubber having an average particle size of 0.1 to 5.0 μm as a diene component. .   Furthermore, the resin composition for biaxially-stretched styrene-type resin sheets in any one of the Claims 1 thru | or 6 which contain a mineral oil 0.5 mass% or less.   A biaxially stretched styrene resin sheet formed from the resin composition for a biaxially stretched styrene resin sheet according to any one of claims 1 to 7. The biaxially-stretched styrene resin sheet according to claim 8, wherein an antifogging agent and / or a release agent is applied to one side or both sides.   A molded product obtained by thermoforming the biaxially stretched styrene resin sheet according to claim 8 or 9.

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