JP2010201719A - Resin sheet for packaging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly transparent resin sheet for packaging of high grade feeling, excellent in an easy-tearing property. <P>SOLUTION: This resin sheet for the packaging is laminated with polycarbonate resin layers on both faces of an acrylic resin layer by coextrusion. The resin sheet is used favorably, for example, as a packing material for a lunch, a cake, a condiment and the like, and also for packaging and packing materials for various products of a toy, miscellaneous goods, clothes or the like. The resin sheet is usable as a bag-like form, for example, by reducing a thickness to enhance flexibility, and is usable in a box-like form, by thickening the thickness to enhance rigidity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a resin sheet for packaging having easy tearability.

  Conventionally, for example, packaging materials in food-related fields such as lunch boxes, food seasonings, and confectionery are required to be easily tearable by hand. As a material having easy tearability, sheet materials mainly made of polyolefin resin have been used so far. As a polyolefin material having easy tearability, Patent Document 1 describes one using a predetermined ethylene (co) polymer.

  However, the conventional polyolefin material as described in Patent Document 1 is not sufficiently easy to tear. Therefore, when using a polyolefin material, it was necessary to cut the portion to be cut in advance or make a small hole called a perforation to make it easy to tear when manually opened. .

  On the other hand, in recent years, high-grade orientation has become strong also in the food-related field, and the packaging material is required to have transparency and a high-class feeling. This tendency is becoming stronger in packaging materials such as sundries and toys.

  However, the polyolefin material has poor transparency and low rigidity, so that a high-class feeling cannot be obtained. In order to give a sense of quality, if a polycarbonate resin, polystyrene resin, acrylic resin, or the like made into a film by extrusion molding or stretch molding is used, it cannot be torn by hand or easily broken. there were.

JP 2005-53997 A

  An object of the present invention is to provide a resin sheet for packaging which has high transparency and a high-class feeling and is excellent in easy tearability.

The packaging resin sheet of the present invention comprises a polycarbonate resin layer laminated on both sides of an acrylic resin layer by coextrusion molding.
The “packaging” in the present invention is a concept including packaging as long as the effects of the present invention are not impaired.
In addition, the “sheet” is not limited to a sheet shape, and is a concept including a sheet shape or a film shape as long as the effects of the present invention are not impaired.

  The packaging resin sheet of the present invention is excellent in transparency, has an appropriate rigidity and flexibility, has a high-class feeling, and can be easily torn by hand from any part. In addition to packaging materials such as seasonings, it can be suitably used as packaging and packaging materials for various products such as toys, sundries, and costumes. Moreover, this resin sheet can be used in a bag-like form by increasing the flexibility by reducing the thickness, for example, or it can be used in a box-like form by increasing the thickness to increase rigidity. it can.

It is a schematic explanatory drawing which shows the manufacturing method of the resin sheet for packaging concerning one Embodiment of this invention. It is a schematic sectional explanatory drawing which shows the metal roll and elastic roll concerning one Embodiment of this invention. It is a schematic cross-section explanatory drawing which shows the elastic roll concerning other embodiment of this invention.

  The resin sheet of the present invention has a polycarbonate resin layer laminated on both sides of an acrylic resin layer by coextrusion molding, and is used for packaging. As the acrylic resin constituting the acrylic resin layer, methacrylic resin is generally used. The methacrylic resin is mainly composed of a methyl methacrylate unit, specifically, a methyl methacrylate resin containing usually 50% by weight or more, preferably 70% by weight or more of a methyl methacrylate unit. It may be a methyl methacrylate homopolymer having 100% by weight of methyl units, or may be a copolymer of methyl methacrylate and another monomer copolymerizable with the methyl methacrylate.

  Examples of the other monomer that can be copolymerized with methyl methacrylate include, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate. Methacrylic acid esters other than methyl methacrylate such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc. Of the acrylic acid esters. Moreover, styrene and substituted styrenes, for example, halogenated styrenes such as chlorostyrene and bromostyrene, and alkylstyrenes such as vinyltoluene and α-methylstyrene are also included. Furthermore, unsaturated acids such as methacrylic acid and acrylic acid, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like can also be mentioned. These other monomers that can be copolymerized with methyl methacrylate may be used alone or in combination of two or more.

The acrylic resin preferably has a Charpy impact strength (notched) of 1 to 2.5 kJ / m ² . If the Charpy impact strength is too small, cracks are likely to occur when the obtained resin sheet is bent, and if it is too large, the obtained resin sheet is difficult to tear. The Charpy impact strength (notched) of the acrylic resin is measured according to JIS K7111 ISO 179 / 1eA method.

  On the other hand, the polycarbonate resin constituting the polycarbonate resin layer is preferably an aromatic polycarbonate resin, for example, obtained by reacting a dihydric phenol and a carbonylating agent by an interfacial polycondensation method or a melt transesterification method. In addition to those obtained, there may be mentioned those obtained by polymerizing a carbonate prepolymer by a solid phase transesterification method or the like, and those obtained by polymerizing a cyclic carbonate compound by a ring opening polymerization method.

  Examples of the dihydric phenol include hydroquinone, resorcinol, 4,4′-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl) phenyl} methane, 1,1- Bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 2,2-bis { (4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dibromo) ) Phenyl} propane, 2,2-bis {(3-isopropyl-4-hydroxy) phenyl} propane, 2,2-bis {( -Hydroxy-3-phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4-hydroxyphenyl) ) -3,3-dimethylbutane, 2,4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl)- 4-methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3 , 5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis {(4-hydroxy -3-methyl) phenyl} fluorene, α, α′-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, α, α′- Bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfoxide, 4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenyl ketone, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl ester, and the like, and two or more of them are used as necessary. You can also.

  Among them, bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3 -Methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) It is preferable to use a dihydric phenol selected from −3,3,5-trimethylcyclohexane and α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene alone or in combination of two or more. Single use, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and bisphenol A , 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane and α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene and one or more dihydric phenols in combination Is preferred.

  Examples of the carbonylating agent include carbonyl halides such as phosgene, carbonate esters such as diphenyl carbonate, and haloformates such as dihaloformates of dihydric phenols, and two or more of them can be used as necessary.

  Note that the composition of one polycarbonate resin layer and the composition of the other polycarbonate resin layer may be the same or different, and may be different from each other. In addition, for the acrylic resin layer and the polycarbonate resin layer, if necessary, for example, a light diffusing agent, a matting agent, a dye, a light stabilizer, an ultraviolet absorber, an antioxidant, a release agent, a flame retardant, an antistatic agent. One or more additives such as an agent may be added.

  The resin sheet of the present invention is preferably produced by laminating and integrating an acrylic resin layer and a polycarbonate resin layer by coextrusion molding. In this coextrusion molding, the above-mentioned acrylic resin layer material and polycarbonate resin layer material are melt-kneaded using two or three uniaxial or biaxial extruders, respectively, and then fed block die or multi-manifold. This can be done by stacking through a die or the like. Then, the sheet-like or film-like molten resin laminated and integrated is cooled and solidified using, for example, a roll unit to obtain the resin sheet of the present invention. Hereinafter, an embodiment of a method for producing a resin sheet according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic explanatory view showing a method for producing a resin sheet according to the present embodiment. FIG. 2 is a schematic cross-sectional explanatory view showing a metal roll and an elastic roll according to the present embodiment. As shown in FIG. 1, first, an acrylic resin and a polycarbonate resin are extruded from a die 3 for coextrusion molding while being melted and kneaded by separate extruders 1 and 2, respectively, and laminated and integrated.

  Next, the sheet-shaped or film-shaped molten resin 4 coextruded from the die 3 is sandwiched between two cooling rolls 5 arranged to oppose each other in a substantially horizontal direction to cool the resin sheet 11 for packaging.

  As shown in FIG. 2, the cooling roll 5 includes a highly rigid metal roll 6 and an elastic roll having a metal thin film 9 on the outer peripheral portion, that is, a metal elastic roll 7. At least one of the metal roll 6 and the metal elastic roll 7 is connected to a rotation driving means such as a motor, and both rolls are configured to rotate at a predetermined peripheral speed.

  The highly rigid metal roll 6 is a winding roll around which the resin sheet 11 after being sandwiched between the metal roll 6 and the metal elastic roll 7 is wound. The metal roll 6 is not particularly limited, and a normal metal roll conventionally used in extrusion molding can be employed. Specific examples include a drilled roll and a spiral roll. The surface state of the metal roll 6 may be, for example, a mirror surface, or may have a pattern or unevenness.

  The metal elastic roll 7 includes a substantially cylindrical shaft roll 8 that is rotatably provided, and a cylindrical metal thin film 9 that is disposed so as to cover the outer peripheral surface of the shaft roll 8 and that contacts the molten resin 4. The fluid 10 is enclosed between the shaft roll 8 and the metal thin film 9, so that the metal elastic roll 7 can exhibit elasticity. The shaft roll 8 is not particularly limited, and is made of, for example, stainless steel.

  The metal thin film 9 is made of, for example, stainless steel, and the thickness is preferably about 2 to 5 mm. The metal thin film 9 preferably has flexibility, flexibility, etc., and preferably has a seamless structure without a welded joint. The metal elastic roll 7 provided with such a metal thin film 9 is excellent in durability, and if the metal thin film 9 is mirror-finished, it can be handled in the same manner as a normal mirror roll, and the metal thin film 9 has a pattern or unevenness. If it is given, it becomes a roll that can transfer the shape, so it is easy to use.

  The metal thin film 9 is fixed at both ends of the shaft roll 8, and a fluid 10 is sealed between the shaft roll 8 and the metal thin film 9. Examples of the fluid 10 include water and oil. By controlling the temperature of the fluid 10, the temperature of the metal elastic roll 7 can be controlled. For the temperature control, a known control method such as PID control or ON-OFF control can be employed. Note that a gas such as air may be used in place of the fluid 10.

  When the molten resin 4 is sandwiched between the metal roll 6 and the metal elastic roll 7, the metal elastic roll 7 is elastically deformed into a concave shape along the outer peripheral surface of the metal roll 6 via the molten resin 4, and the metal elastic roll 7. And the metal roll 6 are brought into contact with each other with a predetermined contact length L via the molten resin 4.

  The contact length L is 1 to 20 mm, preferably 1 to 10 mm, more preferably 1 to 7 mm. The contact length L can be arbitrarily set, for example, by adjusting the thickness of the metal thin film 9 and the amount of fluid 10 enclosed. The contact length L means a length of a straight line connecting a point where the metal elastic roll 7 and the metal roll 6 start to contact via the molten resin 4 and a point where the contact ends.

  When the metal elastic roll 7 and the metal roll 6 come into contact with each other through the molten resin 4 with the contact length L, the metal roll 6 and the metal elastic roll 7 come to be pressed against the molten resin 4 by surface contact. The molten resin 4 sandwiched between the rolls is formed into a film while being uniformly pressed into a planar shape. When the film is formed in this manner, the anisotropy of the material tends to be reduced, and in the obtained resin sheet 11, the difference between the tearing property in the extrusion direction and the tearing property in the width direction tends to be reduced.

  Moreover, when it forms into a film as mentioned above, there also exists a tendency for the heat contraction characteristic of the resin sheet 11 to become small. Specifically, the shrinkage rate S1 (%) in the extrusion direction and the shrinkage rate S2 (%) in the width direction of the resin sheet 11 are both 0 when the resin sheet 11 is left in a thermal atmosphere at 160 ° C. for 30 minutes. There is a tendency to be ~ 5%. If the shrinkage ratios S1 and S2 are negative, that is, less than 0%, the resin sheet will expand when heated. When the resin sheet is coated with a coating film, for example, the coating film is cracked. There is a risk of cracking. On the other hand, when the shrinkage rates S1 and S2 exceed 5%, the shrinkage increases when the resin sheet is heated, and the yield of the product obtained decreases. A method for calculating the shrinkage rates S1 and S2 will be described later.

  When the molten resin 4 is sandwiched and formed between the metal roll 6 and the metal elastic roll 7 in order to reduce the heat shrinkage characteristics of the resin sheet 11, both the rolls are used in the process of cooling and solidifying the molten resin 4 before or after cooling. It is good to hold. Specifically, the surface temperature (Tr) of the metal roll 6 and the metal elastic roll 7 is (Th−20 ° C.) ≦ Tr ≦ (Th + 20 ° C.) with respect to the thermal deformation temperature (Th) of the acrylic resin or polycarbonate resin. Preferably, (Th-15 ° C.) ≦ Tr ≦ (Th + 10 ° C.), more preferably (Th−10 ° C.) ≦ Tr ≦ (Th + 5 ° C.).

  On the other hand, when the surface temperature (Tr) is lower than (Th-20 ° C.), the shrinkage rate S2 tends to decrease. Further, when the surface temperature (Tr) is higher than (Th + 20 ° C.), the shrinkage rate S1 tends to increase. Moreover, the peeling trace from a roll remains on a resin sheet, and there exists a tendency for the external appearance to be impaired.

  The surface temperature (Tr) is based on a resin having a higher thermal deformation temperature (Th) among acrylic resin and polycarbonate resin. Although it does not specifically limit as heat deformation temperature (Th), Usually, it is about 60-200 degreeC. The heat distortion temperature (Th) is a temperature measured according to ASTM D-648.

  The resin sheet 11 after being sandwiched between the metal roll 6 and the metal elastic roll 7 is wound around the metal roll 6 and then taken up while being cooled on the transport roll by a take-up roll (not shown). 11 is obtained.

  Next, another embodiment of the method for producing a resin sheet according to the present invention will be described. FIG. 3 is a schematic cross-sectional explanatory view showing the elastic roll according to the present embodiment. In FIG. 3, the same components as those in FIGS. 1 and 2 described above are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 3, the metal elastic roll 15 according to the present embodiment is obtained by coating the outer peripheral surface of a substantially cylindrical shaft roll 16 with a cylindrical metal thin film 17.

  The shaft roll 16 is a rubber roll made of rubber such as silicon rubber, and the metal elastic roll 15 can exhibit elasticity. The contact length L can be set to a predetermined value also by adjusting the hardness of the rubber.

  The metal thin film 17 is made of, for example, stainless steel, and its thickness is preferably about 0.2 to 1 mm.

  In order to configure the metal elastic roll 15 so that the temperature can be controlled, for example, a backup cooling roll may be attached to the metal elastic roll 15. Other configurations are the same as those of the above-described embodiment, and thus description thereof is omitted.

  The thickness of the resin sheet of this invention is 50-700 micrometers normally, Preferably it is 70-600 micrometers, More preferably, it is 100-500 micrometers. When the thickness of the resin sheet is too small, the rigidity of the resin sheet is lowered, and when it is too large, the easy tearability is lowered.

  In the resin sheet of the present invention, the thickness of the acrylic resin layer is 10 to 90% of the total thickness, preferably 20 to 80%, more preferably 30 to 70%. Thereby, the tearing property by hand can be made favorable, maintaining transparency.

  When importance is attached to the rigidity of the resin sheet, the thickness of the polycarbonate resin layer is 10 μm or more, preferably 10 to 150 μm. The thickness of one polycarbonate resin layer and the thickness of the other polycarbonate resin layer may be the same and may be different from each other. The thickness of the resin sheet can be adjusted by the thickness of the molten resin 4 extruded from the die 3 described above, the distance between the two cooling rolls 5 and the like.

  The resin sheet of the present invention thus obtained is excellent in transparency, has an appropriate rigidity and flexibility, and is excellent in easy tearability. The reason for this is presumed as follows. That is, the acrylic resin layer having the above-described composition is excellent in transparency and easily cracked appropriately. On the other hand, the polycarbonate resin layer having the above-described composition has rigidity and flexibility. A resin sheet having a three-layer structure in which a polycarbonate resin layer is laminated on both surfaces of such an acrylic resin layer by coextrusion molding has high transparency and appropriate rigidity and flexibility.

  Here, a resin sheet having moderate rigidity and flexibility is usually difficult to tear. When an external force is applied to the resin sheet of the present invention in the direction of tearing by hand, the acrylic resin layer of the intermediate layer is first cracked. Next, cracks generated by the cracking of the acrylic resin layer are propagated to the polycarbonate resin layers on both surface layers, and the polycarbonate resin layer is easily broken. Therefore, it is surmised that the resin sheet of the present invention can be easily torn by hand despite having appropriate rigidity and flexibility.

  The resin sheet of the present invention can be suitably used as a packaging material and packaging material for various products that require easy tearability such as toys, sundries, and costumes, as well as packaging materials such as lunch boxes, confectionery, and seasonings. It is.

  Examples of the present invention will be described below, but the present invention is not limited thereto. The structure of the extrusion apparatus used in the following examples and comparative examples is as follows.

Extruder 1: Screw diameter 65 mm, uniaxial, with vent (manufactured by Toshiba Machine Co., Ltd.).
Extruder 2: Screw diameter 45 mm, uniaxial, with vent (manufactured by Hitachi Zosen).
Feed block: 2-type, 3-layer distribution (manufactured by Hitachi Zosen Corporation).
Die 3: T die, lip width 1400 mm, lip interval 1 mm (manufactured by Hitachi Zosen Corporation).
Roll: Horizontal type, two cooling rolls having a surface length of 1400 mm and a diameter of 300 mmφ.

  The extruders 1 and 2 and the die 3 were arranged as shown in FIG. 1, and the feed block was arranged at a predetermined position. Next, of the two cooling rolls, the roll closest to the extruders 1 and 2 was designated as the first roll, the winding roll as the second roll, and each roll was configured as follows.

<Roll configuration 1>
The configuration shown in FIG. Specifically, the first roll and the second roll were configured as follows.
(Roll 1)
The metal thin film 9 is disposed so as to cover the outer peripheral surface of the shaft roll 8, and the metal elastic roll 7 in which the fluid 10 is sealed between the shaft roll 8 and the metal thin film 9 is used as the first roll. The shaft roll 8, the metal thin film 9, and the fluid 10 are as follows.
Shaft roll 8: Stainless steel metal thin film 9: Stainless steel mirror surface metal sleeve fluid 10: oil with a thickness of 2 mm. By controlling the temperature of this oil, the temperature of the metal elastic roll 7 can be controlled. More specifically, the oil was heated and cooled by ON / OFF control of a temperature controller so that the temperature could be controlled and circulated between the shaft roll 8 and the metal thin film 9.
(2nd roll)
A stainless steel spiral roll having a mirror-finished surface was used as a highly rigid metal roll 6, which was designated as No. 2 roll.
In addition, the contact length L with which the metal elastic roll 7 and the metal roll 6 contact via the molten resin 4 was 4 mm.

<Roll configuration 2>
The first roll and the second roll were both high-rigidity metal rolls (stainless steel spiral rolls having a mirror surface surface).

Resins used in the following examples and comparative examples are as follows.
Resin 1: Aromatic polycarbonate ("Caliber 301-10" manufactured by Sumitomo Dow Co., Ltd.). The heat distortion temperature (Th) is 140 ° C.
Resin 2: Copolymer of methyl methacrylate / methyl acrylate = 98/2 (weight ratio). The heat distortion temperature (Th) is 100 ° C. As a result of the Charpy impact test (based on ISO 179 / 1eA method of JIS K7111), the Charpy impact strength was 1.4 kJ / m ² .

[Examples 1 to 7 and Comparative Example 3]
<Production of resin sheet>
As the resin layer A, the types of resins shown in Table 1 were melt-kneaded by the extruder 1 and supplied to the feed block. On the other hand, as the resin layer B, the types of resins shown in Table 1 were melt-kneaded by the extruder 2 and supplied to the feed block. Co-extrusion molding was performed so that the resin layer A supplied from the extruder 1 to the feed block became an intermediate layer, and the resin layer B supplied from the extruder 2 to the feed block became both surface layers.

  Then, the molten resin 4 extruded from the die 3 is formed while being sandwiched between the first roll and the second roll having the roll configuration shown in Table 1, and a resin sheet having a three-layer structure having a thickness shown in Table 1 is formed. Obtained. In addition, the surface temperature of the 1st roll was 120 degreeC, and the surface temperature of the 2nd roll was 130 degreeC. These temperatures are values obtained by actually measuring the surface temperature of each roll. In Table 1, “thickness” in the extruders 1 and 2 indicates the thickness of each of the resin layers A and B, and “total thickness” indicates the total thickness of the obtained resin sheet.

[Comparative Examples 1 and 2]
The types of resins shown in Table 1 were melted and kneaded in the extruder 1 and fed in the order of the feed block and the die 3. Then, the molten resin 4 extruded from the die 3 is formed while being sandwiched between the first roll and the second roll having the roll configuration shown in Table 1, and a resin sheet having a single-layer structure having a thickness shown in Table 1 is obtained. Obtained. In Comparative Example 1, the surface temperature of the first roll was 130 ° C., and the surface temperature of the second roll was 140 ° C. Moreover, in the comparative example 2, the surface temperature of the 1st roll was 90 degreeC, and the surface temperature of the 2nd roll was 93 degreeC.

<Evaluation>
About each obtained resin sheet (Examples 1-7 and Comparative Examples 1-3), shrinkage rate and tearability were evaluated. Each evaluation method is shown below, and the results are also shown in Table 1.

(Shrinkage factor)
First, a test piece having a size of about 10 cm square was cut out from the obtained resin sheet, and the dimension in the extrusion direction (MD0) and the dimension in the width direction (TD0) of the test piece were measured. Next, a baby powder (“Shicaroll High” manufactured by Wakodo Co., Ltd.) was laid on a metal bat, and the test piece was placed thereon and placed in an oven at 160 ° C. for 30 minutes.

  Thereafter, the dimension (MD) in the extrusion direction and the dimension (TD) in the width direction of the naturally cooled test piece were measured, and the obtained dimensions were expressed by the formula: shrinkage ratio S1 = {1- (MD / MD0)} × 100, Formula: Shrinkage rate S2 = {1− (TD / TD0)} × 100 was applied to calculate shrinkage rates S1 and S2. Further, the ratio (S1 / S2) was calculated from the calculated shrinkage rates S1 and S2. In the shrinkage ratios S1 and S2 in Table 1, the result of + indicates that it has contracted, and the result of-indicates that it has expanded.

(Tearability)
A test piece was cut out from the obtained resin sheet with a size of 20 cm square, and it was evaluated whether the test piece was torn by hand. The following criteria were used.
○: easily torn by hand ×: could not be torn by hand

  As can be seen from Table 1, the resin sheets of Examples 1 to 7 are excellent in easy tearability. Moreover, the transparency of these resin sheets was visually evaluated, and the rigidity and flexibility were evaluated by lightly bending by hand. As a result, the resin sheets of Examples 1 to 7 all had high transparency and appropriate rigidity and flexibility. In particular, the resin sheets of Examples 1 and 3 to 6 adopting the roll configuration 1 had a small shrinkage rate.

  On the other hand, the resin sheet of Comparative Example 1 having a single layer structure of the polycarbonate resin layer could not be torn by hand. Further, the resin sheet of Comparative Example 2 having a single layer structure of an acrylic resin layer was broken when trying to tear by hand. When the resin sheet of Comparative Example 3 in which the acrylic resin layers are laminated on both sides of the polycarbonate resin layer is torn by hand, the acrylic resin layers on both surface layers are broken to expose the intermediate polycarbonate resin layer. However, even if external force was applied, it could not be torn.

DESCRIPTION OF SYMBOLS 1, 2 Extruder 3 Die 4 Molten resin 5 Cooling roll 6 Metal roll 7,15 Metal elastic roll 8,16 Axis roll 9,17 Metal thin film 10 Fluid 11 Packaging resin sheet

Claims (1)

  A packaging resin sheet comprising a polycarbonate resin layer laminated on both sides of an acrylic resin layer by coextrusion molding.

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