JP6290530B2 - Biaxially stretched sheet and container for vacuum / pressure forming, and methods for producing them - Google Patents

Description

  The present invention relates to a biaxially stretched sheet suitable for vacuum / pressure forming of a container and a deep-drawn container formed using the sheet.

  Styrenic resins are widely used as molding materials for household goods, electrical products and the like as inexpensive resins with excellent transparency, moldability, and rigidity. These molded products include injection molding, vacuum molding from sheets, pressure molding, and blow molding in which resin is extruded into a cylinder called a parison from an extruder, and compressed air is blown from the inside after being sandwiched between molds. It is obtained by means of Moreover, in order to obtain the molded object which has a lightweight and heat insulation performance, techniques, such as foam molding, are also used. In these molding methods, there is a high demand for a material having high strain-hardening properties at the time of melting, particularly for molding methods such as sheet molding, blow molding, and foam molding having a melt-drawing process.

  When using a resin material with low strain-hardening properties in the above molding method, the problem with sheet molding is that when the secondary processing is performed on a deep-drawn molded product such as a food container, the sagging phenomenon associated with heat melting causes the product to Thickness unevenness is likely to occur, product cracks and tears are likely to occur due to insufficient stretchability, and blow molding makes it difficult to mold due to drawdown if the distortion hardenability is low during parison formation. For example, there is a large variation in product strength due to unevenness, and in addition, foam molding makes it difficult to make the bubbles in the foam smaller and independent in order to improve the heat insulation performance.

  As a means for controlling melt viscoelasticity typified by strain hardening in a molten state, it is known that a method of incorporating an ultrahigh molecular weight component into a styrene resin composition is effective. As a styrenic resin composition containing an ultrahigh molecular weight component and excellent in melting characteristics, Patent Document 1 discloses a styrene resin containing a multi-branched ultrahigh molecular weight component and a linear component and having no gel-like substance. A composition is disclosed.

JP 2011-225866 A

  However, when a biaxially stretched sheet is molded using the styrenic resin composition disclosed in Patent Document 1, uneven thickness may occur in the sheet. In the formed deep-drawn container, the appearance and buckling strength may be insufficient.

  An object of the present invention is to provide a styrene-based biaxially stretched sheet having no thickness unevenness, and to provide a deep-drawn container excellent in appearance and buckling strength using the biaxially stretched sheet.

The biaxially stretched sheet for vacuum / pressure forming of the present invention comprises a vinyl-based monomer essentially comprising styrene and a solvent-soluble polyfunctional vinyl compound having a branched structure and having two or more vinyl groups in one molecule on average. An ultra-high molecular weight multi-branched copolymer that is a polymer with a polymer;
A linear polymer comprising the vinyl monomer, and a styrene resin composition comprising:
The solvent-soluble polyfunctional vinyl compound copolymer is 100 ppm to 3000 ppm on a mass basis with respect to the total amount of the vinyl monomer units contained in the ultrahigh molecular weight multi-branched copolymer and the linear polymer. A biaxially stretched sheet comprising a resin-based resin composition,
Uniaxial elongational viscosity represented by η2.5 / η0.5 when the elongational viscosity when the Henky strain at 130 ° C. of the styrenic resin composition is 2.5 and 0.5 is η2.5 and η0.5. The ratio is 19-28,
The maximum orientation relaxation stress (a) in the MD direction and the maximum orientation relaxation stress (b) in the TD direction of the biaxially stretched sheet are both 0.3 MPa to 2.0 MPa, and (a) and (b ) Is an absolute value of a difference of 0.5 MPa or less.
In addition, the method for producing a biaxially stretched sheet for vacuum / pressure forming according to the present invention is a solvent-soluble solvent having a branched structure and having, on average, two or more vinyl groups in one molecule in a vinyl monomer essential to styrene. A polyfunctional vinyl compound copolymer is added in an amount of 100 ppm to 3000 ppm on a mass basis, uniformly mixed, then supplied to a continuously arranged polymerization reactor to proceed a polymerization reaction, and the solvent-soluble polyfunctional vinyl compound copolymer is added. An ultra-high molecular weight multi-branched copolymer produced by polymerizing the vinyl monomer and a linear polymer produced by polymerizing the vinyl monomer;
When the elongational viscosity at 130 ° C. when the Hencky strain is 2.5 and 0.5 is η2.5 and η0.5, the uniaxial elongational viscosity ratio represented by η2.5 / η0.5 is 19 to 28. The styrenic resin composition is melt-kneaded by an extruder, extruded from a die, and then biaxially stretched.

In the container of the present invention, H / L is 0.4 to 2.0 when the depth of the container is H [mm] and the minimum inner dimension of the opening of the container is L [mm]. It is characterized by comprising the biaxially stretched sheet for vacuum / pressure forming of the present invention.
Further, in the container manufacturing method of the present invention, when the depth of the container is H [mm] and the minimum inner dimension of the opening of the container is L [mm], the squeezing ratio of the container indicated by H / L is 0. The container which is .4 to 2.0 is vacuum-pressure molded using the biaxially stretched sheet for vacuum-pressure molding of the present invention described above.

  According to the present invention, by taking the above configuration, a biaxially stretched sheet having no thickness unevenness can be obtained, and by forming the biaxially stretched sheet by vacuum / pressure forming, the depth is excellent in appearance and buckling strength. A squeeze container can be provided.

  The biaxially stretched sheet of the present invention is formed by molding a styrene resin composition containing an ultrahigh molecular weight multi-branched copolymer and a linear polymer, and the Henky strain at 130 ° C. of the styrene resin composition is When the elongational viscosity at 2.5 and 0.5 is η2.5 and η0.5, the uniaxial elongational viscosity ratio represented by η2.5 / η0.5 is 19 to 28. The styrene-based resin composition comprises a vinyl-based monomer essentially containing styrene, a solvent-soluble polyfunctional vinyl compound copolymer having an average of two or more vinyl groups in one molecule and a branched structure. It is obtained by adding 50 ppm to 5000 ppm on a mass basis, uniformly mixing, and then feeding to a continuously arranged polymerization reactor to advance the polymerization reaction.

  As a polymerization method of the styrene resin composition according to the present invention, a vinyl monomer containing styrene, a solvent-soluble polyfunctional vinyl compound copolymer, and a solvent, a polymerization catalyst, a chain transfer agent, and the like were uniformly mixed as necessary. Later, one or more reactors arranged in at least one of serial and parallel, and equipment equipped with a devolatilization process for removing unreacted monomers, etc., are continuously fed monomers, and polymerization is carried out in stages. A so-called continuous bulk polymerization method is preferably used. Examples of the reactor type include a fully mixed tank reactor, a column reactor having plug flow properties, and a loop reactor in which a part of the polymerization liquid is withdrawn while the polymerization proceeds. There are no particular restrictions on the order of arrangement of these reactors, but in order to suppress the formation of gel-like substances in continuous production, the solvent-soluble polyfunctional vinyl compound copolymer is in an unreacted state and the boundary of the reactor wall surface. It is important not to develop a state of staying in the membrane at a high concentration, and it is preferable to select a fully mixed tank reactor as the first reactor.

  In the present invention, the solvent-soluble polyfunctional vinyl compound copolymer can be added in the middle of the reactor as necessary in a state dissolved in a polymerization solvent or the like.

  100% of styrene may be sufficient as the vinyl-type monomer (henceforth a styrene-type monomer) which requires the styrene which concerns on this invention, and the mixture containing styrene and another vinyl-type monomer may be sufficient as it. Other vinyl monomers may be those having an olefinic double bond copolymerizable with styrene, aromatic vinyl monomers such as paramethylstyrene, acrylic acid monomers such as acrylic acid and methacrylic acid, Vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, acrylic monomers such as butyl acrylate and methyl methacrylate, and α, β-ethylenically unsaturated carboxylic acids such as maleic anhydride and fumaric acid, phenylmaleimide, cyclohexylmaleimide, etc. Examples include imide monomers. These other vinyl monomers can be used alone or in combination of two or more. And it is preferable in order to make use of the characteristic of a styrene resin composition that the ratio of styrene and another vinyl monomer is 50-100 mol% of styrene, and 0-50 mol% of other vinyl monomers.

  The solvent-soluble polyfunctional vinyl compound copolymer (hereinafter, also referred to as polyfunctional vinyl compound copolymer) according to the present invention is an ultrahigh molecular weight styrene-based polymer branched in various ways by being copolymerized with a styrene-based monomer. It gives resin.

  The polyfunctional vinyl compound copolymer according to the present invention can be obtained according to the methods disclosed in JP-A Nos. 2004-123873, 2005-213443, WO 2009/110453 and the like. Specifically, at least one compound selected from a divinyl compound and a monovinyl compound essentially comprising a monovinyl compound is used and copolymerized to have a reactive pendant vinyl group represented by the following formula (I). A copolymer is obtained. Furthermore, as described in the above-mentioned patent document, those having other terminal groups other than vinyl groups introduced at the terminals can also be used. Particularly, those having a phenoxymethacrylate terminal-modified other than the following formula (I) This is preferable because it can act as a crosslinking point. In this case, the terminal unsaturated bond is also handled as a mole fraction included in the following formula (I).

(In the formula, R ¹ represents an aromatic hydrocarbon group derived from a divinyl aromatic compound.)

  Here, the monovinyl compound may be 100% of a monovinyl aromatic compound such as styrene, or may be a mixture containing other vinyl monomers copolymerizable therewith. Examples of other vinyl monomers include the monomers described above. It is preferable that a monovinyl compound contains 25-100 mol% of monovinyl aromatic compounds. Moreover, when using other monovinyl compounds chosen from monofunctional ethylenically unsaturated bond containing compounds other than a monovinyl aromatic compound, it is preferable to use 50 mol% or less of all the monomers, Preferably it is 10 mol% or less.

  Preferable monovinyl compounds include monovinyl aromatic compounds such as styrene, alkylstyrene, and phenylstyrene, and more preferably styrene or C1-C2 alkylstyrene. Preferred examples of the divinyl compound include divinylbenzene and divinylbiphenyl.

  As a method for producing a polyfunctional vinyl compound copolymer, for example, two or more kinds of compounds selected from divinyl aromatic compounds, monovinyl aromatic compounds and other monovinyl compounds are used as promoters selected from Lewis acid catalysts and ester compounds. Can be obtained by cationic copolymerization in the presence of.

  The amount of divinyl compound and monovinyl compound used is determined so as to give the composition of the polyfunctional vinyl compound copolymer used in the present invention, but the divinyl compound is preferably 10 to 50 mol% of the total monomer, more preferably Is used in an amount of 30-50 mol%. The monovinyl compound is preferably used in an amount of 90 to 50 mol%, more preferably 70 to 50 mol% of the total monomers. Here, in cationic polymerization such as 2-phenoxyethyl methacrylate, what acts as a terminal modifier is not calculated as a monomer.

  The Lewis acid catalyst used in the production of the polyfunctional vinyl compound copolymer is particularly limited as long as it is a compound composed of a metal ion (acid) and a ligand (base) and can receive an electron pair. Can be used without From the viewpoints of control of molecular weight and molecular weight distribution and polymerization activity, boron trifluoride ether (diethyl ether, dimethyl ether, etc.) complexes are most preferably used. The Lewis acid catalyst is used in the range of 0.001 to 10 mol, more preferably 0.001 to 0.01 mol, per 1 mol of the monomer. An excessive amount of the Lewis acid catalyst is not preferable because the polymerization rate becomes too high and it becomes difficult to control the molecular weight distribution.

  Examples of the cocatalyst include one or more selected from ester compounds. Among them, an ester compound having 4 to 30 carbon atoms is preferably used from the viewpoint of controlling the polymerization rate and the molecular weight distribution of the copolymer. From the viewpoint of availability, ethyl acetate, propyl acetate and butyl acetate are preferably used. The cocatalyst is used in the range of 0.001 to 10 moles per mole of monomer, more preferably 0.01 to 1 mole. When the amount of the cocatalyst used is excessive, the polymerization rate decreases and the yield of the copolymer decreases. On the other hand, when the amount of the cocatalyst used is too small, the selectivity of the polymerization reaction is lowered, the molecular weight distribution is increased, the gel is generated, and the polymerization reaction is difficult to control.

  The polyfunctional vinyl compound copolymer according to the present invention can be obtained by the production method as described above, but it is necessary to leave a part of the vinyl group of the divinyl compound used as a monomer without being polymerized. Then, on average, 2 or more, preferably 3 or more vinyl groups are present in one molecule. This vinyl group exists mainly as a structural unit represented by the above formula (I). Then, by leaving a part of the vinyl group without being polymerized, the crosslinking reaction can be suppressed and solvent solubility can be imparted. Here, solvent-soluble means that it is soluble in toluene, xylene, THF, dichloroethane, or chloroform. Specifically, in 100 g of these solvents, 5 g or more dissolves at 25 ° C., and no gel is generated. Say. On the other hand, a part of the divinyl compound needs to be crosslinked or branched by the reaction of two vinyl groups, whereby a copolymer having a branched structure can be obtained. Thus, for some divinyl compounds, one of the two vinyl groups is reacted, one is left unpolymerized and the other is used in the present invention by reacting two vinyl groups. A polyfunctional vinyl compound copolymer can be obtained. The polymerization method for obtaining such a polyfunctional vinyl compound copolymer is known as described above, and can be produced as described above.

  The mass average molecular weight (Mw) of the polyfunctional vinyl compound copolymer is preferably 1,000 to 100,000, and more preferably 5,000 to 70,000. If it is less than 1000, the effect of inhibiting the progress of gelation in continuous polymerization is reduced as in the case of using an aromatic divinyl compound, and a sufficient effect cannot be obtained in continuous polymerization.

  The polyfunctional vinyl compound copolymer according to the present invention has a structural unit represented by the above formula (I) containing a vinyl group derived from a divinyl compound to be introduced, and the molar fraction of the structural unit (I) is , 0.05 to 0.50, and preferably 0.1 to 0.3. When the molar fraction is less than 0.05, it is not preferable because a high molecular weight multi-branched copolymer is difficult to obtain. On the other hand, when the molar fraction exceeds 0.50, the molecular weight of the multi-branched copolymer increases excessively and gelation tends to occur, which is not preferable.

  Further, the polyfunctional vinyl compound copolymer preferably has a ratio of the radius of inertia (nm) to the molar fraction of the structural unit (I) in the range of 1 to 100. In order to adjust the ultrahigh molecular weight multi-branched copolymer component for imparting strain hardening without gelation, the range of 5 to 70 is more preferable. When the above ratio exceeds 100, gelation does not proceed, but it is not preferable because a high molecular weight multibranched copolymer is difficult to obtain. On the other hand, when it is smaller than 1, the molecular weight of the multi-branched copolymer is excessively increased, and gelation tends to occur, which is not preferable. Here, the inertial radius is a value measured by the method described in the examples.

  The ratio of the molar fraction of the structural unit (I), which is an index representing the content of double bonds and the radius of inertia defined here, is the core of the ultrahigh molecular weight branched copolymer component. It can be said that the functional vinyl compound copolymer is an index indicating how much reaction points the spread of the functional vinyl compound copolymer has in the polymerization reaction solution. If this ratio is too small, the reaction point is in the vicinity and gelation tends to occur, and if this ratio is too large, it is difficult to increase the molecular weight of the multibranched copolymer component. In this sense, when there is a polymerizable double bond-containing group in addition to the structural unit (I), the total of the double bond-containing groups (vinyl group) is 0.05 to 0 as a molar fraction. In the range of .50, the ratio of the radius of inertia (nm) to the molar fraction is preferably in the range of 1 to 100.

  As a compounding ratio of the polyfunctional vinyl compound copolymer with respect to a styrene-type monomer, it is 50 ppm-5000 ppm on a mass basis, and 100 ppm-3000 ppm is preferable. When the blending ratio of the polyfunctional vinyl compound copolymer is less than 50 ppm, it is difficult to obtain a sufficient effect of the present invention, which is not preferable. On the other hand, when it exceeds 5000 ppm, a gel may be produced.

  By polymerizing the polyfunctional vinyl compound copolymer and a styrenic monomer, an ultrahigh molecular weight multi-branched copolymer that is a copolymer of the polyfunctional vinyl compound copolymer and the styrenic monomer, and a styrenic monomer The styrenic resin composition of the present invention which is a mixture with a linear polymer produced only from monomers is obtained. When two or more types of monomers are used as the styrenic monomer, the linear polymer becomes a copolymer.

  The Mw of the styrene resin composition according to the present invention is preferably 200,000 to 800,000. More preferably, it is 250,000 to 700,000. When the Mw is less than 200,000, the impact strength of the molded product is insufficient, and when the Mw is greater than 800,000, the viscosity increases and the moldability becomes insufficient.

  The styrenic resin composition as described above includes a multi-branched copolymer and a linear polymer. By using a styrenic resin composition exhibiting Mw as described above, a hyper-branched copolymer is obtained. Mw has an ultra high molecular weight of 1 million or more, and the linear polymer is 100,000 to 500,000. And Mw as the whole styrene-type resin composition becomes the said range. The ratio of the multi-branched copolymer having Mw of 1 million or more and the linear polymer having Mw of 100,000 to 500,000 is preferably 2.0: 98.0 to 20.0: 80.0. . These ratios can be controlled by adjusting the blending ratio of the polyfunctional vinyl compound copolymer to the styrene monomer and the polymerization conditions. Further, it contains 3.5 to 10.0% by mass of a multi-branched copolymer having an Mw of 1 million or more and 90.0 to 96.5% by mass of a linear polymer having an Mw of 150,000 to 350,000. It is more preferable.

  From the viewpoint of controlling the polymerization reaction, a polymerization initiator such as a polymerization solvent or an organic peroxide or a chain transfer agent such as an aliphatic mercaptan can be used as necessary.

  In order to lower 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 polyfunctional vinyl compound copolymer, it is preferable to use an organic solvent from the viewpoint of suppressing gelation. Thereby, the addition amount of the polyfunctional vinyl compound copolymer shown previously can be increased dramatically, and a gel is hardly generated.

  The amount of the organic solvent used is not particularly limited, but from the viewpoint of controlling gelation, it is usually preferably 1 to 50 parts by mass with respect to 100 parts by mass of the total amount of monomer components, More preferably, it is in the range of 5 to 30 parts by mass. When the amount exceeds 50 parts by mass, productivity is remarkably reduced, and the molecular weight of the linear polymer composed of the styrene monomer is excessively lowered, which is not preferable.

  As the polymerization initiator, a radical polymerization initiator is preferable. For example, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis (t-butylperoxy) butane, 2,2- Peroxyketals such as bis (4,4-di-butylperoxycyclohexyl) propane, hydroperoxides such as cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumylper Dialkyl peroxides such as oxide, di-t-hexyl peroxide, diacyl peroxides such as benzoyl peroxide, disinamoyl peroxide, t-butyl peroxybenzoate, di-t-butyl peroxyisophthalate, t -Butylperoxyisopropyl monocarbonate Peroxyesters such as N, N′-azobisisobutylnitrile, N, N′-azobis (cyclohexane-1-carbonitrile), N, N′-azobis (2-methylbutyronitrile), N, N '-Azobis (2,4-dimethylvaleronitrile), N, N'-azobis [2- (hydroxymethyl) propionitrile] and the like may be mentioned, and these may be used alone or in combination. it can.

  The chain transfer agent is added so that the molecular weight of the styrenic resin composition does not become excessively large. 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 the present invention, when the elongation viscosity when the Henky strain at 130 ° C. of the styrenic resin composition is 2.5 and 0.5 is η2.5 and η0.5, it is expressed as η2.5 / η0.5. The uniaxial elongational viscosity ratio is 19-28. When the η2.5 / η0.5 is less than 19 and exceeds 28, the thickness unevenness of the biaxially stretched sheet formed with the styrene resin composition becomes large, and the sheet is vacuum-pressure formed. Thus, the container obtained is inferior in buckling strength. Preferably it is 21-28, desirably 23-28.

  As a method for producing the biaxially stretched sheet of the present invention, the styrenic resin composition is melt-kneaded by an extruder, extruded from a die (particularly a T die), and then stretched sequentially or simultaneously in a biaxial direction. It is. Although the thickness of a biaxially stretched sheet is not specifically limited, Usually, it is 0.6 mm or more and less than 2.0 mm. Preferably it is 0.6 mm or more and less than 1.5 mm.

  When the MD (Machine Direction; sheet flow direction) stretch ratio of the biaxially stretched sheet of the present invention is A and the TD (Transverse Direction; stretch direction perpendicular to the sheet flow direction) stretch ratio is B, it is indicated by A × B. The surface magnification is preferably 4 to 10 times. In addition, as for the surface magnification which concerns, both MD draw ratio and TD draw ratio have preferable 1.5 to 3.5 times. If any of A, B, and A × B is out of the above range, thickness unevenness occurs in the sheet, and the buckling strength may decrease in a container obtained by vacuum-pressure forming the sheet, which is not preferable. . More preferably, the surface magnification is 4 to 8 times, and the MD stretching ratio and the TD stretching ratio are 2.0 to 3.0 times, respectively.

  In the biaxially stretched sheet of the present invention, when the maximum orientation relaxation stress in the MD direction is a and the maximum orientation relaxation stress in the TD direction is b, a and b are 0.3 MPa to 2.0 MPa, respectively. ab | is preferably 0.5 MPa or less. If any of a, b, and | a−b | is outside the above range, thickness unevenness occurs in the sheet, and in the container obtained by vacuum-pressure forming the sheet, the buckling strength may decrease, It is not preferable. More preferably, a and b are 0.3 MPa to 1.0 MPa and | a−b | is 0.4 MPa or less, and desirably a and b are 0.3 MPa to 0.7 MPa and | a−b | 3 MPa or less.

  The container of the present invention is obtained by vacuum-pressure forming the biaxially stretched sheet of the present invention. When the depth of the container is H [mm] and the minimum inner dimension of the opening of the container is L [mm], The squeezing ratio of the container indicated by H / L is 0.4 to 2.0. In other words, by using the biaxially stretched sheet of the present invention, the container having a drawing ratio according to the present invention can be molded with good reproducibility. More preferably, the aperture ratio is 0.6 to 2.0, and desirably 1.0 to 2.0.

  The molding method for molding the container of the present invention is a vacuum / pressure forming method. The molding method is a molding method in which a biaxially stretched sheet is softened by indirect heating and then vacuum or compressed air is applied, the biaxially stretched sheet is brought into close contact with a mold, and after cooling, air is blown to take out a molded product. . By using this molding method, a molded product having good transparency can be obtained. Further, deep drawing can be performed by plug assist.

[Solvent-soluble polyfunctional vinyl compound copolymer (α)]
160 g of divinylbenzene, 94 g of ethylvinylbenzene, 223 g of styrene, 633 g of 2-phenoxyethyl methacrylate, and 1080 g of toluene are put into a 3 L reaction vessel, and 57 g of diethyl ether complex of boron trifluoride is added at 50 ° C. for 6 hours. I let you. After the polymerization solution was stopped with an aqueous sodium hydrogen carbonate solution, the oil layer was washed three times with pure water, and the reaction mixture was poured into a large amount of methanol at room temperature to precipitate a polymer. The obtained polymer was washed with methanol, filtered, dried and weighed to obtain a solvent-soluble polyfunctional vinyl compound copolymer (α).

[Styrene resin composition]
(Resin (1))
Two tank reactors with a total mixing capacity of 40 L connected in series, a 20 L internal reactor with a built-in static mixer with plug flow, a preheater and a vacuum tank And a flash chamber type devolatilization equipment having a uniform mass polymerization equipment having 85 parts by mass of styrene, 15 parts by mass of ethylbenzene, and 0.2 parts by mass of a solvent-soluble polyfunctional vinyl compound copolymer (α). And mixed continuously at 15 L / hr. The temperature of the first tank reactor is 135 ° C., the second tank reactor is 135 ° C., the third tower reactor is 145 ° C. at the inlet, and 165 ° C. at the outlet. After the temperature is raised, it is transferred to a preheater heated to 225 ° C., and put into a vacuum tank directly under the preheater whose pressure is adjusted to 665 Pa (5 Torr) to remove unreacted monomers and solvent, and then vacuum. A styrenic resin composition (resin (1)) was obtained by cutting while removing the resin in a strand form from the tank with a gear pump.

(Resin (2))
Polymerization is carried out in the same manner as the resin (1) except that the amount of the solvent-soluble polyfunctional vinyl compound copolymer (α) added in the polymerization of the resin (1) is 0.06 parts by mass, and the styrene resin composition ( Resin (2)) was obtained.

(Resin (3))
Polymerization is carried out in the same manner as the resin (1) except that the amount of the solvent-soluble polyfunctional vinyl compound copolymer (α) in the polymerization of the resin (1) is 0.03 parts by mass, and a styrene resin composition ( Resin (3)) was obtained.

(Resin (4))
Polymerization is carried out in the same manner as the resin (1) except that the amount of the solvent-soluble polyfunctional vinyl compound copolymer (α) added in the polymerization of the resin (1) is 0.003 parts by mass, and a styrene resin composition ( Resin (4)) was obtained.

(Resin (5))
Resin (1) except that the amount of the solvent-soluble polyfunctional vinyl compound copolymer (α) in the polymerization of the resin (1) is 0.004 parts by mass, and 0.05 parts by mass of t-dodecyl mercaptan is further added. The styrene resin composition (resin (5)) was obtained by polymerization in the same manner as described above.

(Resin (6))
The amount of addition of the solvent-soluble polyfunctional vinyl compound copolymer (α) in the polymerization of the resin (1) is 0.48 parts by mass, the first tank reactor is 120 ° C., and the second tank reactor is 125 ° C, the third tower reactor was polymerized in the same manner as the resin (1) except that the temperature was increased stepwise so that the inlet portion was 130 ° C and the outlet portion was 160 ° C. A composition (resin (6)) was obtained.

(Resin (7))
Polymerization is carried out in the same manner as the resin (1) except that the amount of the solvent-soluble polyfunctional vinyl compound copolymer (α) added in the polymerization of the resin (1) is 0.8 parts by mass, and a styrene resin composition ( Resin (7)) was obtained.

(Resin (8))
“HRM61” which is general-purpose polystyrene (GPPS) manufactured by Toyo Styrene Co., Ltd. was used.

(Resin (9))
“Clearene 850L” which is a styrene / butadiene / styrene block copolymer (SBS) manufactured by Denki Kagaku Kogyo Co., Ltd. was used.

[Example 1]
Using the resin (1), an unstretched sheet having a thickness of 3.8 mm was obtained at an extrusion temperature of 230 ° C. using a sheet extruder (T-die width 500 mm, φ40 mm extruder (manufactured by Tanabe Plastic Machinery Co., Ltd.)). The sheet was preheated to 130 ° C., stretched 2.5 times in the MD direction and 2.5 times in the TD direction (surface magnification: 6.3 times) at a strain rate of 0.1 / sec, and biaxial with a thickness of 0.6 mm. A stretched sheet was obtained.

Using the resulting biaxially stretched sheet, using a vacuum / pressure forming machine, heated for 15 seconds with radiant heat at an upper and lower heater temperature of 350 ° C., and then subjected to vacuum / pressure forming, and each of the containers (1) to (4) having the following drawing ratios of 20 I got one by one.
Container (1): circular shape with opening φ100 mm, height 150 mm, taper angle 5 °, drawing ratio 1.5
Container (2): circular shape with opening φ100 mm, height 70 mm, taper angle 5 °, drawing ratio 0.7
Container (3): circular shape with opening φ100 mm, height 50 mm, taper angle 5 °, drawing ratio 0.5
Container (4): circular shape with opening φ100 mm, height 30 mm, taper angle 5 °, drawing ratio 0.3

  About the resin (1) used, the uniaxial elongation viscosity ratio was measured with the measuring method mentioned later. Further, the average thickness and thickness unevenness of the biaxially stretched sheet were measured by the method described later, and the container obtained from the biaxially stretched sheet was evaluated by the method described later. Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

[Example 2]
A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except that the resin (2) was used instead of the resin (1). Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

Example 3
A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except that the resin (3) was used instead of the resin (1). Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

Example 4
A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except that the resin (1) and the resin (8) were used in a mass ratio of 80/20 instead of the resin (1). Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

Example 5
A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except that the resin (1) and the resin (9) were used in a mass ratio of 95/5 instead of the resin (1). Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

Example 6
A biaxially stretched sheet and a biaxially stretched sheet were formed in the same manner as in Example 1 except that the thickness of the unstretched sheet was 5.8 mm and the sheet was stretched 3.1 times in the MD direction and 3.1 times in the TD direction (area magnification: 9.6 times). A container was obtained. Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

Example 7
A biaxially stretched sheet and a biaxially stretched sheet were formed in the same manner as in Example 1 except that the thickness of the unstretched sheet was 8.7 mm and the sheet was stretched 3.8 times in the MD direction and 3.8 times in the TD direction (14.4 times the surface magnification). A container was obtained. Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

Example 8
A biaxially stretched sheet and a biaxially stretched sheet were formed in the same manner as in Example 1 except that the thickness of the unstretched sheet was 1.5 mm and the sheet was stretched 1.8 times in the MD direction and 1.4 times in the TD direction (surface magnification 2.5 times). A container was obtained. Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

Example 9
Example except that the unstretched sheet was biaxially stretched 2.5 times in the MD direction at a strain rate of 0.13 / sec and 2.5 times in the TD direction (surface magnification: 6.3 times) at a strain rate of 0.07 / sec. In the same manner as in No. 1, a biaxially stretched sheet and a container were obtained. Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

Example 10
Except that the unstretched sheet was biaxially stretched at a strain rate of 0.18 / sec in the MD direction 2.5 times, and at a strain rate of 0.09 / sec in the TD direction 2.5 times (surface magnification 6.3 times). In the same manner as in No. 1, a biaxially stretched sheet and a container were obtained. Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

[ Reference Example 11]
The unstretched sheet is preheated to 120 ° C. and biaxial in the MD direction 2.5 times at a strain rate of 0.2 / sec and 2.5 times in the TD direction (surface magnification 6.3 times) at a strain rate of 0.13 / sec A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except for stretching. Table 1 shows the physical properties and evaluation results of the resin used, the biaxially stretched sheet, and the container.

[Comparative Example 1]
A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except that the resin (4) was used instead of the resin (1). Table 2 shows the physical properties and evaluation results of the resins used, biaxially stretched sheets, and containers.

[Comparative Example 2]
A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except that the resin (5) was used instead of the resin (1). Table 2 shows the physical properties and evaluation results of the resins used, biaxially stretched sheets, and containers.

[Comparative Example 3]
A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except that the resin (6) was used instead of the resin (1). Table 2 shows the physical properties and evaluation results of the resins used, biaxially stretched sheets, and containers.

[Comparative Example 4]
A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except that the resin (7) was used instead of the resin (1). Table 2 shows the physical properties and evaluation results of the resins used, biaxially stretched sheets, and containers.

[Comparative Example 5]
A biaxially stretched sheet and a container were obtained in the same manner as in Example 1 except that the resin (8) was used instead of the resin (1). Table 2 shows the physical properties and evaluation results of the resins used, biaxially stretched sheets, and containers.

[Comparative Example 6]
Biaxial stretching was performed in the same manner as in Comparative Example 1 except that the thickness of the unstretched sheet was 8.7 mm and biaxial stretching was performed 3.8 times in the MD direction and 3.8 times in the TD direction (surface magnification 14.4 times). Sheets and containers were obtained. Table 2 shows the physical properties and evaluation results of the resins used, biaxially stretched sheets, and containers.

[Comparative Example 7]
A biaxially stretched sheet and a biaxially stretched sheet were formed in the same manner as in Comparative Example 1 except that the thickness of the unstretched sheet was 1.5 mm and the film was stretched 1.8 times in the MD direction and 1.4 times in the TD direction (2.5 times the surface magnification) A container was obtained. Table 2 shows the physical properties and evaluation results of the resins used, biaxially stretched sheets, and containers.

[Comparative Example 8]
The unstretched sheet is preheated to 120 ° C. and biaxial in the MD direction 2.5 times at a strain rate of 0.2 / sec and 2.5 times in the TD direction (surface magnification 6.3 times) at a strain rate of 0.13 / sec A biaxially stretched sheet and a container were obtained in the same manner as in Comparative Example 1 except that the film was stretched. Table 2 shows the physical properties and evaluation results of the resins used, biaxially stretched sheets, and containers.

[Measurement method of uniaxial elongational viscosity ratio]
The styrene resin composition was heated and pressed at 230 ° C. to obtain a test piece of 20 mm × 10 mm × 0.7 mm. Using the test piece, the elongational viscosity (η2.5 and η0.5) was measured at a temperature of 130 ° C., a strain rate of 0.1 / sec, and a Henky strain of 2.5 and 0.5, and the ratio (η2 .5 / η0.5). In addition, “AR2000ex” manufactured by TA Instruments Co., Ltd. was used as the extension viscosity measuring device.

[Maximum orientation relaxation stress]
A test piece of 20 mm × 200 mm × 0.6 mm was obtained from the biaxially stretched sheet. Both ends of the test piece were fixed, immersed in a 130 ° C. oil bath, and then the stress value when the load reached the maximum was calculated. The stress value in the MD direction at that time was defined as the maximum orientation relaxation stress a, the stress value in the TD direction was defined as the maximum relaxation stress b, and | a−b | was determined.

[Evaluation of average thickness and thickness unevenness of biaxially oriented sheet]
The thickness is measured using a microgauge at the intersection 25 points when the biaxially stretched sheet is made into a grid shape at intervals of 50 mm in the MD direction and the TD direction, and the average thickness and its standard deviation σ are calculated. With respect to thickness unevenness, the standard deviation σ was evaluated according to the following criteria.
A: σ is less than 0.05 mm O: σ is 0.05 mm or more and less than 0.07 mm Δ: σ is 0.07 mm or more, less than 0.10 mm x: σ is 0.10 mm or more

[Evaluation of container appearance]
For containers (1) to (4), the number of containers in which tears, wrinkles, and whitening occurred were evaluated using the following indices.
◎: 0 ◯: 1 to 2 △: 3 to 5 ×: 6 or more

[Buckling strength of container]
The containers (1) to (4) were evaluated by the following indices based on the maximum load when compressed at a speed of 500 mm / min.
◎: Greater than 100N ○: 90N or more, less than 100N Δ: 80N or more, less than 90N ×: Less than 80N

〔Comprehensive evaluation〕
Evaluation of the appearance and buckling strength of the containers (1) to (4) was comprehensively evaluated according to the following criteria. The example of ◎ or ○ was accepted.
◎: When the evaluation result is ◎ only ○: There is at least one of ○ or △ in the evaluation result, △ is 1 or less and there is no x △: The evaluation result is 2 or more and there is no x ×: Evaluation If there is a cross in the result

  In Table 1, the addition amount of the polyfunctional vinyl compound copolymer of Examples 4 and 5 is the styrene resin in which the resin (1) and the resin (8) and the resin (1) and the resin (9) are mixed. The amount of the polyfunctional vinyl compound copolymer contained in the composition is shown.

Claims (5)

Ultra-high molecular weight multi-branched type, which is a polymer of a vinyl-based monomer essential to styrene and a solvent-soluble polyfunctional vinyl compound copolymer having an average of two or more vinyl groups in one molecule and having a branched structure A copolymer;
A linear polymer comprising the vinyl monomer, and a styrene resin composition comprising:
The solvent-soluble polyfunctional vinyl compound copolymer is 100 ppm to 3000 ppm on a mass basis with respect to the total amount of the vinyl monomer units contained in the ultrahigh molecular weight multi-branched copolymer and the linear polymer. A biaxially stretched sheet comprising a resin-based resin composition,
Uniaxial elongational viscosity represented by η2.5 / η0.5 when the elongational viscosity when the Henky strain at 130 ° C. of the styrenic resin composition is 2.5 and 0.5 is η2.5 and η0.5. The ratio is 19-28,
The maximum orientation relaxation stress (a) in the MD direction and the maximum orientation relaxation stress (b) in the TD direction of the biaxially stretched sheet are both 0.3 MPa to 2.0 MPa, and (a) and (b The biaxially stretched sheet for vacuum / pressure forming is characterized in that the absolute value of the difference with respect to) is 0.5 MPa or less. A solvent-soluble polyfunctional vinyl compound copolymer having two or more vinyl groups in one molecule on average and having a branched structure is added to 100% to 3000 ppm on a mass basis to a vinyl monomer essentially containing styrene, and uniform. After mixing, the mixture is fed to a continuously arranged polymerization reactor to advance the polymerization reaction, and the solvent-soluble polyfunctional vinyl compound copolymer and the vinyl monomer are polymerized to produce an ultrahigh molecular weight multi-branched copolymer. A polymer and a linear polymer produced by polymerization of the vinyl monomer,
When the elongational viscosity at 130 ° C. when the Hencky strain is 2.5 and 0.5 is η2.5 and η0.5, the uniaxial elongational viscosity ratio represented by η2.5 / η0.5 is 19 to 28. A method for producing a biaxially stretched sheet for vacuum / pressure forming , which comprises melt-kneading a styrene resin composition with an extruder, extruding from a die, and then biaxially stretching. The method for producing a biaxially stretched sheet for vacuum / pressure forming according to claim 2, wherein the biaxially stretched sheet has a surface magnification of 4 to 10 times. The vacuum / compressed air molding according to claim 1, wherein H / L is 0.4 to 2.0 when the depth of the container is H [mm] and the minimum inner dimension of the opening of the container is L [mm]. A container comprising a biaxially oriented sheet for use . When the depth of the container is H [mm] and the minimum inner dimension of the opening of the container is L [mm], a container having a squeezing ratio of 0.4 to 2.0 represented by H / L, A method for producing a container, comprising vacuum-pressure forming using the biaxially stretched sheet for vacuum-pressure forming according to claim 1.