JP2020158630A - Thermoforming sheet - Google Patents

Abstract

To provide a thermoforming sheet that is constituted of a crystalline polymer material and can form a compact having excellent morphological stability to thermal hysteresis.SOLUTION: A thermoforming sheet contains a layer made of a crystalline resin composition containing 80 mas% or larger of crystalline polypropylene, in which when thermomechanical analysis (TMA) is performed under the following condition, a dimensional shrinkage peak amount is 100 μm. <Thermomechanical Analysis (TMA) Measurement Condition> sample size: length 10 mm, width 4 mm, rate of temperature rise: 5°C/minute, load: 49.0 mN (tensile mode in a flow direction(MD)), sampling rate : 1 s-1.SELECTED DRAWING: None

Description

The present invention relates to a thermoforming sheet.

Foods, pharmaceuticals, medical instruments, etc. are generally packaged in packaging such as packaging bags and packaging containers at the time of sale. Such a package is required to have various performances for protection of the contents and the like. Therefore, in some packaging bodies, a composite (multilayered) thermoforming sheet is used.

The thermoforming sheet used for the packaging is required to have a sealing property, a gas barrier property, and the like in order to impart a function such as protection of the contents to the packaging. For example, in Patent Document 1, as a means for improving impact resistance and gas barrier properties, a multilayer film is formed by stretching a thermoforming sheet made of a multilayer film made of a crystalline polymer material such as polyethylene or polypropylene. A method of orienting the crystals inside is disclosed.

Japanese Unexamined Patent Publication No. 2007-283569

However, when the package is formed by using the multilayer film disclosed in Patent Document 1, the package made of the crystalline polymer material is thermally shrunk to generate waviness in the peripheral portion, and the lid material of the package is formed. There is a problem that the distinctiveness of the display object such as is lowered.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermoforming sheet which is made of a crystalline polymer material and can form a molded body having excellent shape stability with respect to thermal history. To do.

In order to solve the above problems, the present invention adopts the following configuration.
[1] A thermoforming sheet containing a layer made of a crystalline resin composition containing 80% by mass or more of crystalline polypropylene.
A thermoforming sheet characterized by having a dimensional shrinkage peak amount of 100 μm or less when measured by thermomechanical analysis (TMA) under the following conditions.

<Thermomechanical analysis (TMA) measurement conditions>
Sample size: length 10 mm, width 4 mm, heating rate: 5 ° C / min, load: 49.0 mN (flow direction (MD) tension mode), sampling rate: 1s ^-1
[2] The thermoforming sheet according to the above [1], wherein no dimensional shrinkage is observed when measured by thermomechanical analysis (TMA) under the above conditions.
[3] The thermoforming sheet according to the above [1] or [2], wherein the crystalline resin composition contains 1 to 20% by mass of crystalline polyethylene.

The thermoforming sheet of the present invention is made of a crystalline polymer material, and can form a molded product having excellent shape stability with respect to thermal history.

It is an example of the graph of thermomechanical analysis (TMA), and is the figure explaining the dimensional shrinkage peak amount. It is sectional drawing which shows typically the thermoforming sheet 10 of one Embodiment. It is sectional drawing which shows typically the extruder and the drawing machine. It is sectional drawing which shows typically the package body 50 of one Embodiment.

Hereinafter, a thermoforming sheet and a package using the thermoforming sheet, which is an embodiment to which the present invention is applied, will be described in detail. In addition, in the drawings used in the following description, in order to make the features easy to understand, the featured parts may be enlarged for convenience, and the dimensional ratio of each component may not be the same as the actual one. Absent.

<< Thermoforming sheet >>
The thermoforming sheet of the present embodiment is characterized in that the dimensional shrinkage peak amount is 100 μm or less when measured by thermomechanical analysis (TMA) under the following conditions. In the thermoforming sheet of the present embodiment, when the dimensional shrinkage peak amount is 100 μm or less, it is possible to form a molded body such as a package having excellent shape stability with respect to thermal history.

<Thermomechanical analysis (TMA) measurement conditions>
Sample size: length 10 mm, width 4 mm, heating rate: 5 ° C / min, load: 49.0 mN (flow direction (MD) tension mode), sampling rate: 1s ^-1

In thermomechanical analysis (TMA) measurement, the flow direction (MD) of the sample sheet is set to the length direction, and the sample is cut into strips with a length of 10 mm and a width of 4 mm to make a sample. Measure the machine analysis (TMA).

An example of a thermomechanical analysis (TMA) graph is shown in FIG. The dimensional shrinkage peak amount refers to the amount indicated by the displacement difference of the downward peak appearing due to thermal shrinkage from the displacement position at the start of shrinkage to the peak top (that is, the position of the maximum shrinkage displacement) in FIG.

The dimensional shrinkage peak amount is 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, preferably 50 μm or less, and particularly preferably 0 μm, that is, no dimensional shrinkage is observed. By setting the dimensional shrinkage peak amount to the upper limit value or less, it is possible to form a molded body such as a package having excellent shape stability with respect to heat history.

FIG. 2 is a cross-sectional view schematically showing the thermoforming sheet 10 of one embodiment. In the thermoforming sheet 10 of the present embodiment, PP transparent layers 111, 112, 113 and PP colored layers 121 are laminated. In the thermoforming sheet of the present embodiment, the PP transparent layers 111, 112, 113 and the PP colored layer 121 each include a layer made of a crystalline resin composition containing 80% by mass or more of crystalline polypropylene.

Examples of crystalline polypropylene include isotactic polypropylene. The layer made of the crystalline resin composition preferably contains 81% by mass or more of crystalline polypropylene, more preferably 82% by mass or more of crystalline polypropylene, and 83% by mass or more of crystalline polypropylene. Is particularly preferable.

The form of laminating the thermoforming sheet 10 is not limited. In the thermoforming sheet 10 of the present embodiment, both surfaces are made of the PP transparent layer 111, but only one surface may be the PP transparent layer 111, and the other surface is the PP colored layer 121. Both surfaces may be PP colored layers 121. The thermoforming sheet 10 may be composed of only the PP transparent layer 111, or may be composed of only the PP colored layer 121. It is preferable that at least one surface is the PP transparent layer 111.

The thermoforming sheet as a multilayer sheet is a layer in which at least one layer is made of a crystalline resin composition containing 80% by mass or more of crystalline polypropylene, but all the layers are crystals of 80% by mass or more. It is preferably a layer made of a crystalline resin composition containing sex polypropylene.

The crystalline resin composition preferably contains 1 to 20% by mass of crystalline polyethylene, preferably 2 to 18% by mass of crystalline polyethylene, and preferably contains 3 to 16% by mass of crystalline polyethylene. It is preferable to do so. Examples of the crystalline polyethylene include low-density polyethylene and high-density polyethylene, and high-density polyethylene is preferable.

The crystalline resin composition preferably has an MFR (melt flow rate) of 5 g / 10 min or less, more preferably 2 g / 10 min or less, and even more preferably 0.8 g / 10 min or less. The MFR is measured at 230 ° C. and a load of 2.16 kgf based on JIS K-6758.

<< Manufacturing method of thermoforming sheet >>
In the method for producing a thermoforming sheet of the present embodiment, the crystalline resin composition is extruded, the extruded molten laminate is received by a touch roll and a first cooling roll, and the first cooling roll and the second cooling roll are received. The ratio of the feed rate VR ₂ of the second cooling roll to the feed rate VR ₁ of the _first cooling roll (VR ₂ / VR ₁ ), which includes stretching between, is 0.3 to 2.0. Is.

The method for producing the thermoforming sheet of the present embodiment will be described with reference to the schematic cross-sectional view of the extruder and the drawing machine of FIG.

First, receiving the extrusion by crystalline resin composition extruder 20, the melt laminate 40 which is extruded in a touch roll R _T and the first cooling roll R _1. The extruder 20 is a coextruder capable of extruding a plurality of layers at the same time.

Then, stretched between the melt laminate 40 of the first cooling roll R ₁ and the second cooling roll R _2. The ratio of the feed rate VR ₂ of the second cooling roll to the feed rate VR ₁ of the first cooling roll (VR ₂ / VR ₁ ) is 0.3 to 2.0. The ratio (VR ₂ / VR ₁ ) is preferably 0.5 to 1.7, and more preferably 0.7 to 1.5.

Prototype when the surface temperature of the melt laminate of the first on the cooling roll _{R 1} is preferably 20 to 180 ° C., and more preferably 30 to 170 ° C.. Prototype when the surface temperature of the melt laminate of the first on the cooling roll R ₁ is measured by a radiation thermometer.

<< Packaging >>
Using the thermoforming sheet of the present invention, it is possible to form a molded body such as a package having excellent shape stability with respect to heat history.
FIG. 4 is a cross-sectional view schematically showing the package 50 of one embodiment.
The packaging body 50 of the present embodiment has a container main body 101 formed by using the thermoforming sheet, and a lid 102 heat-sealed on the peripheral edge of the container main body 101.
Since the container body 101 is molded using the thermoforming sheet, it has excellent shape stability with respect to heat history and can prevent the container body 101 or the lid 102 from wavy. The packaging body 50 of the present embodiment is suitable as a packaging container for packaging foods, pharmaceuticals, medical instruments, etc., for example.

The lid 102 can be in the form of a film, and examples of the material of the lid 102 include aluminum and the like.

<< Manufacturing method of packaging >>
A package is manufactured by molding a container body so as to form a desired storage portion using a thermoforming sheet, and attaching a lid such as another film to the peripheral edge of the container body. can do.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the examples shown below.

<Making a thermoforming sheet>
[Example 1]
A first resin made of polypropylene (“FH-1016” manufactured by Sumitomo Chemical Co., Ltd., sometimes referred to as PP) and a second resin composition made of the PP and an inorganic colorant were prepared.

Using an extruder, the first resin and the second resin composition are each melted at 250 ° C., and the PP transparent layer 111 made of the first resin and the PP colored layer 121 made of the second resin composition are formed. The PP transparent layer 112 made of the first resin, the PP transparent layer 113 made of the first resin, the PP transparent layer 112 made of the first resin, and the PP colored layer 121 made of the second resin composition. And the PP transparent layer 111 made of the first resin, and the 7-layer molten laminate made of the first resin were extruded.
Next, the extruded 7-layer molten laminate is received by the touch roll _RT and the first cooling roll R ₁ , stretched between the first cooling roll R ₁ and the second cooling roll R ₂ , and pinched roll. The thermoformed sheet 10 of Example 1 was obtained.

The ratio of the feed rate VR ₂ of the second cooling roll R ₂ to the feed rate VR ₁ of the _first cooling roll (VR ₂ / VR ₁ ) is 0.975, which is 7 on the _first cooling roll R _1. The surface temperature of the molten laminate of the layers at the time of trial production was set to about 135 ° C. Of the obtained thermoforming sheet 10 of Example 1, the thickness of the PP transparent layer 111 is 70 μm, the thickness of the PP colored layer 121 is 245 μm, and the thickness of the PP transparent layer 112 is 17.5 μm. The thickness of the PP transparent layer 113 was 35 μm, and the total thickness of the thermoforming sheet 10 of Example 1 was 0.7 mm (that is, 700 μm).

A sample sheet having a length of 10 mm and a width of 4 mm was cut out from the thermomechanical sheet 10 of Example 1 so that the flow direction (MD) was 10 mm, and TMA (manufactured by TA Instruments, Q400) was used. Thermomechanical analysis (TMA) was measured under the conditions of heating rate: 5 ° C./min, load: 49.0 mN (tensile mode in flow direction (MD)), and sampling rate: 1s- ¹ . The amount of dimensional shrinkage peak of the peak appearing around 165 ° C. was 60 μm.

[Comparative Examples 1 to 4]
Also using the first resin and the second resin composition as in Example 1, of Example 1, with respect to the feeding speed VR ₁ of the first cooling roll of the second cooling roll R ₂ of the feeding speed VR ₂ the ratio (VR 2 / _{VR 1),} except that the prototype when the surface temperature of the melt laminate of the first 7-layer on the cooling roll R ₁ of the change so that in Table 1 and Table 2, in the same manner as in example 1 Then, the thermoforming sheets of Comparative Examples 1 to 4 were prepared. However, the thickness of the thermoforming sheets of Comparative Examples 1 to 4 is 0.4 mm.

<Making a molded body>
Using the thermoforming sheets of Examples 1 and Comparative Examples 1 to 4, a molded body body having a longitudinal frontage of 200 mm, a lateral frontage of 50 mm, and a height of 35 mm was produced at a molding temperature of 170 ° C. did.

Further, an aluminum lid (thickness 50 μm) with an adhesive was prepared.
Next, using a sealing machine (multivac R535), the peripheral edge of the molded body and the peripheral edge of the lid obtained above are heat-sealed under the conditions of a sealing temperature of 180 ° C. and a sealing time of 3 seconds. , A molded body was produced.

In addition, the appearance of the printed matter on the lid after sealing was observed.
In the molded body using the thermoforming sheets of Comparative Examples 1 to 4, the shape stability of the heat seal with respect to the heat history was not sufficient, and the lid was wavy, so that the distinguishability of the displayed object was lowered. ..
In the molded body using the thermoforming sheet of Example 1, the shape stability of the heat seal against the heat history was excellent, the waviness of the lid was small, and the distinctiveness of the displayed object was ensured.

The thermoforming sheet of the present invention can be used as a material for a packaging body or the like, and the packaging body produced by using the thermoforming sheet of the present invention is for packaging foods, pharmaceuticals, medical instruments and the like. It may be used for packaging containers, etc.

10 ... Thermoforming sheet, 111, 112, 113 ... PP transparent layer, 121 ... PP colored layer, 20 ... Extruder, 30 ... Stretching machine, 40 ... Molten laminate , 50 ... Package, 101 ... Container body, 102 ... Lid, _RT ... Touch roll, R ₁ ... First cooling roll, R ₂ ... Second Cooling roll, RP ₁ , RP ₂ ... Pinch roll

Claims (3)

A thermoforming sheet containing a layer made of a crystalline resin composition containing 80% by mass or more of crystalline polypropylene.
A thermoforming sheet characterized by having a dimensional shrinkage peak amount of 100 μm or less when measured by thermomechanical analysis (TMA) under the following conditions.
<Thermomechanical analysis (TMA) measurement conditions>
Sample size: length 10 mm, width 4 mm, heating rate: 5 ° C / min, load: 49.0 mN (flow direction (MD) tension mode), sampling rate: 1s ^-1 The thermoforming sheet according to claim 1, wherein no dimensional shrinkage is observed when measured by thermomechanical analysis (TMA) under the above conditions. The thermoforming sheet according to claim 1 or 2, wherein the crystalline resin composition contains 1 to 20% by mass of crystalline polyethylene.

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