Packaging sheet for PTP and manufacturing method thereof

Abstract

To provide a packaging sheet for PTP provided with a heat-resistant coating layer containing a predetermined amount of biomass resin, having sufficient practicality, and being ease of manufacture, and a manufacturing method thereof.SOLUTION: A heat-resistant coating agent preparation process KK1 is provided in which a petroleum-derived resin blended with biomass resin is used as a main ingredient to prepare a heat-resistant coating agent 30x liquefied by mixing a volatile solvent with a solid component in which the blending ratio of biomass resin is set in the range of 10 to 25 mass%. A heat-resistant coating agent application process KK2 is provided in which a predetermined amount of heat-resistant coating agent 30x is coated on a first side 22a of aluminum foil 22 so that the thickness of the finished state of a heat-resistant coating layer 30 becomes a specified value. A heat-resistant coating agent heating process KK3 is provided in which the heat-resistant coating agent 30x is heated to volatilize the volatile solvent and thermally cure the solid component to form the heat-resistant coating layer 30. The heating conditions in the heat-resistant coating agent heating process KK3 are set to the same conditions as when a conventional heat-resistant coating agent 42x is used.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a packaging sheet for PTPs that is thermally bonded to a container sheet to become a lid material for PTP packages, and a method for producing the same. [Background technology]

[0002] Conventionally, PTPs (press through packages) are a type of packaging in which a small solid object 14 is placed in a storage section 12a formed in a resin container sheet 12, as in the PTP packaging body 10 shown in Figure 7, and the storage section 12a is closed by adhering a packaging sheet 16 to the flat section 12b of the container sheet 12, and are widely used for packaging solid objects such as medicinal tablets and capsules.

[0003] When opening the package, the contained solid material 14 is pressed strongly from the outside of the containing portion 12a against the inner surface of the packaging sheet 16, so that it can be broken through and removed. In order to do this, a thin aluminum foil is generally used as the base material of the packaging sheet 16. When attaching the packaging sheet 16 to the container sheet 12, a method is used in which a heat seal layer provided on one side of the packaging sheet 16 is brought into contact with the flat portion 12b of the container sheet 12, and heat and pressure are applied from the side of the heat-resistant coating layer provided on the other side of the packaging sheet 16 to fuse them together.

[0004] For example, as disclosed in FIG. 3 of Patent Document 1 by the present applicants, there is a PTP packaging sheet (laminate 1') that includes an aluminum foil substrate (aluminum substrate 2) and a heat-resistant coating layer (heat-resistant coating layer 4') located on the first surface of the aluminum foil, and the second surface of the aluminum foil is thermally bonded to a mating container sheet (container 12) to form a lid for the PTP package. In this packaging sheet, the heat-resistant coating layer is formed using an ink composition for a heat-resistant coating layer that contains an epoxy resin and a blocked isocyanate curing agent. In other words, the use of the blocked isocyanate curing agent prevents the generation of formaldehyde during thermal curing in the process of forming the packaging sheet and when the packaging sheet is thermally bonded to the container sheet, thereby eliminating the effects of formaldehyde on solids (e.g., pharmaceuticals) in the PTP package.

[0005] Furthermore, in recent years, reducing plastic waste and carbon dioxide emissions has become a major issue, and attempts are being made in various industrial fields to replace petroleum-derived resins with biomass resins derived from living organisms such as plants. The use of biomass resins is also being considered in the field of PTP packaging sheets, and for example, Patent Document 2 (paragraph 0020, etc.) describes the application of bio-polyurethane resins to laminated products such as PTP sheets, which are packaging materials for pharmaceuticals. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-2922 [Patent Document 2] Japanese Patent Application Publication No. 2019-172977 Summary of the Invention [Problem to be solved by the invention]

[0007] The inventors considered replacing part of the petroleum-derived resin used in the heat-resistant coating layer of PTP packaging sheets with biomass resin. However, simply increasing the blending ratio of biomass resin was expected to reduce certain performance characteristics of the heat-resistant coating layer, and it was unclear how high the blending ratio of biomass resin could be. It was also unclear whether increasing the blending ratio of biomass resin would require changes to manufacturing conditions or equipment.

[0008] The packaging sheet for PTP in Patent Document 1 does not take into consideration the inclusion of biomass resin in the heat-resistant coating layer. Furthermore, Patent Document 2 only suggests that biomass resin can be used in packaging sheets for PTP, but does not describe at all the performance when used in packaging sheets or the manufacturing method.

[0009] The present invention has been made in view of the above-mentioned background art, and aims to provide a packaging sheet for PTP that has a heat-resistant coating layer containing a predetermined amount of biomass resin, has sufficient practicality, and is easy to produce, and a method for producing the same. [Means for solving the problem]

[0010] The present invention provides a method for manufacturing a packaging sheet for PTP, which comprises an aluminum foil as a base material and a heat-resistant coating layer located on the surface of a first surface side of the aluminum foil, and in which the second surface side of the aluminum foil is thermally bonded to a counterpart container sheet to become a lid material of a PTP package, a heat-resistant coating agent preparation step of preparing a heat-resistant coating agent by mixing a volatile solvent with a solid component containing a petroleum-derived resin blended with a biomass resin in a range of 10 to 25 mass % as a main component, to thereby prepare a liquid heat-resistant coating agent; A heat-resistant coating agent application process in which a predetermined amount of the heat-resistant coating agent is applied to the first surface side of the aluminum foil so that the thickness of the heat-resistant coating layer in a finished state becomes a specified value; a heat-resistant coating agent heating step of heating the heat-resistant coating agent to volatilize the volatile solvent and thermally cure the solid component to form the heat-resistant coating layer, Heat-resistant coating agent heating step A continuous furnace with three zones was used in Heating temperature and heating time, The first zone is set to 170±10°C and 2.3±0.3 seconds, the second zone to 220±10°C and 2.2±0.3 seconds, and the third zone to 240±10°C and 2.2±0.3 seconds, in the order of the first zone, the second zone, and the third zone. The heat-resistant coating layer is formed by heating in this method for producing a packaging sheet for PTP.

[0011] The petroleum-derived resin contains at least an epoxy resin and a blocked isocyanate curing agent. It does not contain melamine resin.

[0012] The present invention also provides a packaging sheet for PTPs, which comprises an aluminum foil as a base material and a heat-resistant coating layer located on the surface of a first surface side of the aluminum foil, and in which the second surface side of the aluminum foil is thermally bonded to a counterpart container sheet to form a lid material for a PTP package, The heat-resistant coating layer is a packaging sheet for PTP, the main component of which is a petroleum-derived resin blended with a biomass resin, and the blending ratio of the biomass resin is set in the range of 10 to 25 mass %.

[0013] moreover, The petroleum-derived resin contains at least an epoxy resin and a blocked isocyanate curing agent. and does not contain melamine resin. . [Effects of the Invention]

[0014] According to the PTP packaging sheet and its manufacturing method of the present invention, it is possible to replace a portion of the petroleum-derived resin used as the base resin of a conventional heat-resistant coating layer with a biomass resin, while still satisfying the performance required of the heat-resistant coating layer. Moreover, the heat-resistant coating layer containing biomass resin can be formed under the same manufacturing conditions as for a conventional heat-resistant coating layer, making it possible to easily obtain a PTP packaging sheet that can contribute to reducing the environmental load. [Brief explanation of the drawings]

[0015] [Figure 1] 1A is an enlarged cross-sectional view showing the structure of one embodiment of a packaging sheet for PTP of the present invention, and FIG. 1B is an enlarged cross-sectional view showing the structure of the packaging sheet during production. [Figure 2]1(a) is a flowchart showing the relationship between the flow of a general method for manufacturing the packaging sheet of FIG. 1(a) and one embodiment of the method for manufacturing a packaging sheet for PTP of the present invention. [Figure 3] FIG. 1 is a schematic diagram illustrating an example of a packaging sheet manufacturing apparatus. [Figure 4] 10 is a graph showing the results of a heat resistance test conducted on a heat-resistant coating layer of a prototype packaging sheet. [Figure 5] 10 is a graph showing the results of a solvent resistance test conducted on a heat-resistant coating layer of a prototype packaging sheet. [Figure 6] 10 is a graph showing the results of an abrasion resistance test conducted on the heat-resistant coating layer of the prototype packaging sheet. [Figure 7] FIG. 1 is a cross-sectional view showing the structure of a typical PTP package. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of a packaging sheet for PTPs and a manufacturing method thereof according to the present invention will be described below with reference to the drawings. First, the structure of the packaging sheet 18 of this embodiment, the manufacturing flow of the packaging sheet 18 (steps K11, K12(1) to K19(1), K12(2), K13(2), K18(2), K19(2)), and the configuration of a packaging sheet manufacturing apparatus 20 that sequentially executes the steps in the manufacturing flow other than step K11 will be briefly described with reference to FIGS.

[0017] The packaging sheet 18 is manufactured as a single continuous sheet and shipped to a PTP package assembly plant in a rolled state. As shown in FIG. 1( a), the packaging sheet 18 has an aluminum foil 22 as a base material. On a first surface 22a of the aluminum foil 22, a milky white printed layer 24 covering the first surface 22a, first and second printed layers 26, 28 for displaying information provided on the outer surface of the milky white printed layer 24, and a heat-resistant coating layer 30 covering the outer surfaces of the milky white printed layer 24, the first printed layer 24, and the second printed layer 28 are laminated in this order. On a second surface 22b of the aluminum foil 22, a third printed layer 32 for displaying information and a heat-seal layer 34 covering the outer surfaces of the second surface 22b and the third printed layer 32 are laminated in this order.

[0018] The aluminum foil 22 is made of a hard or soft aluminum material having a thickness of about 10 to 30 μm so that it can be easily torn when removing the solid matter 14 from the storage section 12a. The aluminum foil 22 is prepared in a member preparation step K11 in Fig. 2, and is set in a rolled state in the unwinder 34 of the packaging sheet manufacturing apparatus 20 as shown in Fig. 3.

[0019] The opaque white printing layer 24 is formed by preparing a liquid opaque white printing agent 24x, which is a coating resin made by mixing a medium with an ink containing a white pigment (component preparation step K11). This is then applied to the first surface 22a of the aluminum foil 22 using an applicator Ts12 of the packaging sheet manufacturing apparatus 20 (opaque white printing agent application step K12(1)). This is then pre-dried in a heating furnace Kr13 (pre-heating step K13(1)), and subsequently dried and cured in a subsequent heating furnace Kr19 (main heating step K19(1)). The medium is, for example, a solid mixture of vinyl chloride resin as the base resin and an amino resin for promoting molecular cross-linking, diluted with an appropriate amount of solvent such as thinner. The white pigment-containing ink is prepared by diluting a solid mixture of titanium oxide, which serves as a white pigment, with the same composition as the solid mixture of the medium, with an appropriate amount of solvent such as thinner.

[0020] The first printing layer 26 is formed by preparing a first printing ink 26x by blending a pigment of an appropriate color with a base material such as vinyl chloride resin and mixing it with an appropriate amount of volatile solvent to form a liquid (component preparation process K11), applying it to the outer surface of the opaque white printing agent 24x using an application device Ts14 of the packaging sheet manufacturing apparatus 20 (first printing ink application process K14(1)), heating it in a heating furnace Kr15 to pre-dry it (pre-heating process K15(1)), and heating it in a subsequent heating furnace Kr19 to dry and harden it (main heating process K19(1)).

[0021] The second printing layer 28 is formed by preparing a second printing ink 28x, which is made by blending a pigment of a different color with a base material similar to that of the first printing ink 26x and mixing it with an appropriate amount of volatile solvent to form a liquid (component preparation process K11), applying it to the outer surface of the opaque white printing agent 24x using an application device Ts16 of the packaging sheet manufacturing apparatus 20 (second printing ink application process K16(1)), heating it in a heating furnace Kr17 to temporarily dry it (temporary heating process K17(1)), and heating it in a subsequent heating furnace Kr19 to dry and harden it (main heating process K19(1)).

[0022] The heat-resistant coating layer 30 is formed by preparing a heat-resistant coating agent 30x (component preparation step K11) by mixing a volatile solvent with a solid component mainly composed of a predetermined petroleum-derived resin blended with a predetermined amount of biomass resin to form a liquid, applying the liquid to the outer surfaces of the opaque printing agent 24x, the first printing ink 26x, and the second printing ink 28x using an application device Ts18 of the packaging sheet manufacturing apparatus 20 (heat-resistant coating agent application step K18(1)), and then heating and drying / curing the liquid in a heating furnace Kr19 (main heating step K19(1)). The solid component of the heat-resistant coating agent 30x will be described in detail later.

[0023] The heat-resistant coating layer 30 is transparent or translucent, allowing the information displayed on the first and second printed layers 26, 28 to be visible from the outside. The opaque white printed layer 24 is a layer that suppresses reflection from the glossy surface of the aluminum foil 22 when the first and second printed layers 26, 28 are viewed, thereby improving the visibility of the first and second printed layers 26, 28, and may be opaque white or pure white.

[0024] After the main heating step K19(1) is performed, the semi-finished packaging sheet 18h is carried out from the heating furnace Kr19, inspected by an appearance inspection device 38, and then wound up by a winding machine 36. The structure of the packaging sheet 18h is as shown in FIG. 1(b), and the step of providing the third printed layer 32 and the heat seal layer 34 on the second surface 22b of the aluminum foil 22 is performed by setting the wound packaging sheet 18h on the unwinding machine 34 again.

[0025] The third printing layer 32 is formed by preparing a third printing ink 32x, which is a liquid made by blending a predetermined pigment with a base material similar to that of the first and second printing inks 26x, 28x and mixing it with an appropriate amount of volatile solvent (component preparation process K11), applying it to the second surface 22b of the aluminum foil 22 using an application device Ts12 of the packaging sheet manufacturing apparatus 20 (third printing ink application process K12(2)), heating it in a heating furnace Kr13 to pre-dry it (pre-heating process K13(2)), and heating it in a subsequent heating furnace Kr19 to dry and harden it (main heating process K19(2)).

[0026] The heat seal layer 34 is formed by preparing a liquid heat seal agent 34x that is primarily made of a mixture of polyvinyl chloride resin and polyester resin, a mixture of polyvinyl chloride resin and acrylic resin, or polypropylene resin (component preparation step K11), applying it to the second surface 22b of the aluminum foil 22 and the outer surface of the third printing ink 32x using an application device Ts18 of the packaging sheet manufacturing apparatus 20 (heat seal agent application step K18(2)), and then heating it in a subsequent heating furnace Kr19 to dry and harden it (main heating step K19(2)).

[0027] After the main heating step K19(2) is performed, the finished packaging sheet 18 is carried out from the heating furnace Kr19, inspected by the appearance inspection device 38, and then wound up by the winding machine 36. The packaging sheet 18 is manufactured according to the above process, and is shipped in a rolled state to a packaging factory for PTP packages 10, etc.

[0028] Next, one embodiment of the manufacturing method for the PTP packaging sheet of the present invention will be described in comparison with the manufacturing flow of the packaging sheet 18 described above (steps K11, K12(1) to K19(1), K12(2), K13(2), K18(2), K19(2)).

[0029] As shown in the right column of FIG. 2, the manufacturing method of the packaging sheet of this embodiment comprises a heat-resistant coating agent preparing step KK1, a heat-resistant coating agent applying step KK2, and a heat-resistant coating agent heating step KK3.

[0030] The heat-resistant coating agent preparation process KK1 is a process of preparing a heat-resistant coating agent 30x by mixing a volatile solvent with a solid component whose main component is a predetermined petroleum-derived resin blended with a predetermined amount of biomass resin to form a liquid, and is performed as part of the component preparation process K11 described above. The heat-resistant coating agent 30x may be produced and prepared in the manufacturing plant of the packaging sheet 18, or may be purchased and prepared from a heat-resistant coating agent manufacturer.

[0031] The petroleum-derived resin used is a resin containing a general-purpose epoxy resin and a blocked isocyanate curing agent. Generally, a mixture of epoxy resin and melamine resin is widely used, but melamine resin can generate formaldehyde when heated later, which can be problematic, so the composition used here does not contain melamine resin.

[0032] Regarding the amount of biomass resin, it is important that the blending ratio of biomass resin to the total solid components is in the range of 10 to 25 mass %. The meaning of this numerical range will be explained later.

[0033] The heat-resistant coating agent application step KK2 corresponds to the previously described heat-resistant coating agent application step K18(1), which is a step of applying a heat-resistant coating agent 30x to the first surface 22a of the aluminum foil 22. The amount of the heat-resistant coating agent 30x to be applied in the heat-resistant coating agent application step K18(1) is determined according to the amount of volatile solvent mixed in, and is adjusted so that the thickness of the heat-resistant coating layer 30 in its finished state is a specified value.

[0034] The heat-resistant coating agent heating step KK3 is a step of heating the heat-resistant coating agent 30x to volatilize the volatile solvent and thermally curing the solid components to form the heat-resistant coating layer 30, and corresponds to the main heating step K19(1) described above. The heating furnace Kr19 used in this step is a continuous furnace with three zones, and the preferred heating conditions will be described later.

[0035] Next, the meaning of the numerical range (10 to 25 mass %) of the blending ratio of biomass resin in the heat-resistant coating agent 30x prepared in the heat-resistant coating agent preparation step KK1 and the heating conditions in the heat-resistant coating agent heating step KK3 will be explained.

[0036] First, we will explain the performance tests conducted by the inventors in the process of developing the packaging sheet and its manufacturing method of the present invention. The inventors believed that if the heating conditions for the heat-resistant coating agent 30x in the heat-resistant coating agent heating step KK3 could be made the same as those used when using conventional heat-resistant coating agents 40x and 42x (which do not contain biomass resin), mass production would be much easier. Therefore, three types of heat-resistant coating agents 30x, 40x, and 42x were prepared, and the heat-resistant coating layers 30, 40, and 42 were prototyped under the same conditions for the heat-resistant coating agent application step KK2 and the heating step KK3. The heat resistance, solvent resistance, and abrasion resistance of the heat-resistant coating layers 30, 40, and 42 were evaluated in the state of the packaging sheet 18h shown in Figure 1(b).

[0037] Conventional heat-resistant coating agent 40x is a liquid (general product) made by mixing a volatile solvent with a petroleum-derived resin (a mixture of epoxy resin and melamine resin) as the main ingredient and a solid component that does not contain biomass resin. Conventional heat-resistant coating agent 42x is a liquid (formaldehyde-resistant product) made by mixing a volatile solvent with a petroleum-derived resin (including epoxy resin and blocked isocyanate) as the main ingredient and a solid component that does not contain biomass resin. Furthermore, for heat-resistant coating agent 30x, to evaluate the relationship between the amount of biomass resin and performance, several samples were prepared in which the biomass resin content relative to the total solid component was varied between 5 and 30% by mass.

[0038] When producing the heat-resistant coating layers 30, 40, and 42, a three-zone continuous furnace was used as the heating furnace Kr19 for the heat-resistant coating agent heating step KK3, with the first zone set to 170±10°C for 2.3±0.3 seconds, the second zone set to 220±10°C for 2.2±0.3 seconds, and the third zone set to 240±10°C for 2.2±0.3 seconds. These heating conditions were suitable for the conventional heat-resistant coating agents 40x and 42x, and the heat-resistant coating agent 30x (blending ratio 5 to 30% by mass) could also be cured under the same conditions.

[0039] Figure 4 shows the results of a heat resistance test on the prototype heat-resistant coating layers 30, 40, and 42. In the heat resistance test, stress equivalent to the heat and pressure applied by a heat seal bar when welding a packaging sheet to a mating container sheet was applied to each heat-resistant coating layer, and the heat-resistant coating layer was observed for changes in appearance such as discoloration and deformation, and a pass / fail judgment was made. The pass / fail judgment was classified into three levels: significant abnormality (×), slight abnormality (△), and almost no change (○).

[0040] The upper graph in Figure 4 shows the change in heat resistance when the pressure is fixed at 0.294 MPa, the pressure time is fixed at 2 seconds, and the heating temperature is changed. The lower graph in Figure 4 shows the change in heat resistance when the pressure is fixed at 0.294 MPa, the heating temperature is fixed at 260°C, and the heating time is changed. These two graphs show that the heat resistance of the heat-resistant coating layer 30 changes little within a blending ratio range of 5 to 30 mass%. It also shows that the heat resistance of the heat-resistant coating layer 30 is higher than that of the conventional heat-resistant coating agent 40x and is equivalent to that of the conventional heat-resistant coating layer 42. Since the conventional heat-resistant coating layer 40 has a proven track record in the market, if the heat resistance of the heat-resistant coating layer 40 is considered to be acceptable, the heat resistance of the heat-resistant coating layer 30 can be said to be acceptable within a blending ratio range of 5 to 30 mass%.

[0041] Figure 5 shows the results of a solvent resistance test on the prototype heat-resistant coating layers 30, 40, and 42. For the solvent resistance test, the prototype sample and paper impregnated with MEK (methyl ethyl ketone) were placed in a Gakushin-type friction tester. The paper was placed in contact with the surface of the heat-resistant coating layer at a predetermined pressure, and the sample or paper was rubbed by moving back and forth. The limit number of rubbings Rk(limit) required to remove the heat-resistant coating layer was evaluated. The graph in Figure 5 shows that the higher the biomass resin content of the heat-resistant coating layer 30, the lower the limit number of rubbings Rk(limit), indicating a decrease in solvent resistance. Furthermore, the conventional heat-resistant coating layer 40 was not removed even after 50 rubbings. Empirically, it has been determined that a limit number of rubbings of 10 or more is practical for PTP packaging sheets. Therefore, the solvent resistance of the heat-resistant coating layer 30 can be considered acceptable when the content of the biomass resin is in the range of 5 to 30% by mass.

[0042] Figure 6 shows the results of a friction resistance test on the prototype heat-resistant coating layers 30, 40, and 42. The friction resistance test involved placing two identical samples in a Gakushin-type friction tester, and then rubbing one sample back and forth 150 times while the heat-resistant coating layers were pressed together at a predetermined pressure. The percentage change Ha in surface roughness (peak density Spd) before and after rubbing was evaluated. This graph shows that the percentage change Ha for the heat-resistant coating layer 30 increases with the biomass resin blend ratio, resulting in a decrease in friction resistance. It was also found that the percentage change Ha for the conventional heat-resistant coating layer 40 was only 0.8%, which is very small.

[0043] In addition, when a heat-resistant coating layer 40 was intentionally produced by underheating (underheated product), the change rate Ha was 12.4% (plotted with triangles). Further evaluation was performed using this underheated product, and it was confirmed that there is no problem in terms of practicality if the change rate Ha is ≦12.4%. Therefore, if the change rate Ha = 12.4% is set as the pass mark for abrasion resistance, the abrasion resistance of the heat-resistant coating layer 30 can be said to pass when the compounding ratio is in the range of 5 to 25% by mass.

[0044] From the three performance test results shown in Figures 4 to 6, it was found that the heat-resistant coating layer 30 passed all performance tests when the biomass resin blending ratio relative to the total solid components was in the range of 25 mass% or less. In other words, it was found that by preparing a heat-resistant coating agent 30x with a biomass resin blending ratio set to 5 to 25 mass% or less in the heat-resistant coating agent preparation step KK1 and then performing the heat-resistant coating agent heating step KK3, a heat-resistant coating layer 30 with sufficient practicality (a heat-resistant coating layer with a biomass resin blending ratio of 5 to 25 mass%) can be obtained. However, since the main purpose of the present invention is to significantly contribute to reducing the environmental load, and a blending ratio of less than 10 mass% is not sufficient, the heat-resistant coating agent 30x prepared in the heat-resistant coating agent preparation step KK1 described above has a biomass resin blending ratio of 10 to 25 mass%.

[0045] Furthermore, after the above-mentioned prototyping and performance tests, similar prototyping was performed by changing the heating conditions of the heat-resistant coating agent heating step KK3. It was confirmed that the heat-resistant coating agents 30x, 40x, 42x could be well cured under specific heating conditions within the range of 150 to 250°C and 5.8 to 7.6 seconds, and that heat-resistant coating layers 30, 40, 42 with similar performance could be obtained. It was also confirmed that heat-resistant coating layers 30, 40, 42 with similar performance could be obtained even if the type of biomass resin was changed appropriately.

[0046] As described above, the PTP packaging sheet 18 and its manufacturing method can satisfy the performance required of a heat-resistant coating layer while replacing a portion of the petroleum-derived resin (petroleum-derived resin containing epoxy resin and blocked isocyanate) used as the main component of the conventional heat-resistant coating layer 42 with biomass resin. Moreover, the heat-resistant coating layer 30 containing biomass resin can be formed under the same manufacturing conditions as the conventional heat-resistant coating layers 40, 42, making it possible to easily obtain a PTP packaging sheet 18 that can contribute to reducing the environmental impact.

[0047] Next, a modified example of the packaging sheet 18 for PTP and its manufacturing method will be described. The modified packaging sheet 18 has the same basic structure as the modified example, except that the heat-resistant coating layer 30 is replaced with a heat-resistant coating layer 44, as shown in Fig. 1(a). In addition, in the heat-resistant coating agent preparation step KK1 (member preparation step K11), a heat-resistant coating agent 44x is prepared instead of the heat-resistant coating agent 30x, as shown in Fig. 2.

[0048] Heat-resistant coating agent 44x, like heat-resistant coating agent 30x, is a liquid made by mixing a volatile solvent with a solid component whose main ingredient is a petroleum-derived resin blended with a specified amount of biomass resin.However, what differs from heat-resistant coating agent 30x is that the petroleum-derived resin is a mixture of epoxy resin and melamine resin.

[0049] Heat-resistant coating agent 44x contains melamine resin, so a small amount of formaldehyde is generated when it is heat-cured during the process of forming the packaging sheet, but it is widely used in applications where formaldehyde is not a major problem.

[0050] The heat-resistant coating layer 44 using the heat-resistant coating agent 44x can be formed by carrying out the heat-resistant coating agent application step KK2 and the heat-resistant coating agent heating step KK3 under the same conditions as when the above-mentioned heat-resistant coating agents 30x, 40x, and 42x are used.

[0051] The graph of heat resistance test results in Figure 4 does not include test results for the heat-resistant coating layer 44. However, the conventional heat-resistant coating layer 40 (which is based on a petroleum-derived resin that is a mixture of epoxy resin and melamine resin and does not contain biomass resin) has acceptable heat resistance. Also, the heat-resistant coating layer 30 (in which a portion of the petroleum-derived resin containing epoxy resin and a blocked isocyanate curing agent is replaced with biomass resin) shows almost no change in heat resistance even when the blending ratio of biomass resin is increased.

[0052] From this, it can be naturally predicted that the heat-resistant coating layer 44 (a mixture of epoxy resin and melamine resin in which part of the petroleum-derived resin has been replaced with biomass resin) will have almost no change in heat resistance even if the blending ratio of biomass resin increases, and will have heat resistance equivalent to that of the heat-resistant coating layer 40. Therefore, it can be said that the heat resistance of the heat-resistant coating layer 44 is acceptable at least when the blending ratio of biomass resin is in the range of 5 to 25% by mass.

[0053] The graph of solvent resistance test results in Figure 5 does not include test results for the heat-resistant coating layer 44. However, the conventional heat-resistant coating layer 40 (based on a petroleum-derived resin that is a mixture of epoxy resin and melamine resin and does not contain biomass resin) has significantly better solvent resistance than the conventional heat-resistant coating layer 42 (based on a petroleum-derived resin that contains epoxy resin and a blocked isocyanate curing agent and does not contain biomass resin). Furthermore, the heat-resistant coating layer 30 (in which a portion of the petroleum-derived resin that contains epoxy resin and a blocked isocyanate curing agent is replaced with biomass resin) passed the test within a blending ratio range of 5 to 25% by mass, although its solvent resistance gradually decreased as the blending ratio of biomass resin increased.

[0054] Based on this trend, it is expected that the heat-resistant coating layer 44 (in which a portion of the petroleum-derived resin mixed with epoxy resin and melamine resin is replaced with biomass resin) will gradually lose solvent resistance as the blending ratio of biomass resin increases, just like the heat-resistant coating layer 30. However, it is empirically known that the rate of decline will be the same as that of the heat-resistant coating layer 30, or even gentler, so it can be said that the solvent resistance of the heat-resistant coating layer 44 is acceptable at least when the blending ratio of biomass resin is in the range of 5 to 25% by mass.

[0055] The graph of abrasion resistance test results in Figure 6 does not include test results for the heat-resistant coating layer 44. However, the conventional heat-resistant coating layer 40 (based on a petroleum-derived resin that is a mixture of epoxy resin and melamine resin and does not contain biomass resin) has almost the same excellent abrasion resistance as the conventional heat-resistant coating layer 42 (based on a petroleum-derived resin that contains epoxy resin and a blocked isocyanate curing agent and does not contain biomass resin). Furthermore, the heat-resistant coating layer 30 (in which a portion of the petroleum-derived resin that contains epoxy resin and a blocked isocyanate curing agent is replaced with biomass resin) passed the test when the blending ratio of biomass resin was in the range of 5 to 25% by mass, although the abrasion resistance gradually decreased as the blending ratio of biomass resin increased.

[0056] The heat-resistant coating layer 44 (a mixture of epoxy resin and melamine resin in which part of the petroleum-derived resin has been replaced with biomass resin) is expected to gradually decrease in abrasion resistance as the blending ratio of biomass resin increases, similar to the heat-resistant coating layer 30. However, it has been empirically found that the slope of the decrease is the same as that of the heat-resistant coating layer 30, or even gentler, so it can be said that the abrasion resistance of the heat-resistant coating layer 44 is acceptable at least when the blending ratio of biomass resin is in the range of 5 to 25% by mass.

[0057] In this way, the packaging sheet 18 (heat-resistant coating layer 44) of the modified example and its manufacturing method also provide the same excellent effects as those described above.

[0058] The packaging sheet for PTP of the present invention and its manufacturing method are not limited to the above-mentioned embodiment. For example, the packaging sheet 18 described above has the opaque white printed layer 24 and the first and second printed layers 26, 28 between the aluminum foil 22 and the heat-resistant coating layers 30, 44, but if not necessary, some or all of these may be omitted. Conversely, it is also possible to add another printed layer between the aluminum foil 22 and the heat-resistant coating layers 30, 44.

[0059] 2 corresponds to the configuration of the packaging sheet 18 shown in FIG. 1(a), and if a portion of the configuration of the packaging sheet 18 is changed, only some of the steps need to be changed accordingly. For example, when manufacturing a packaging sheet 18 that does not include the opaque white printed layer 24 or the first and second printed layers 26, 28, the steps related to the opaque white printed layer 24 and the first and second printed layers 26, 28 (steps K12(1) to K17(1)) in the flowchart of FIG. 2 can be simply omitted, and the other steps (steps K11, K18(1), K19(1), K12(2) to K19(2) / steps KK1 to KK3) need not be changed much. The same applies to manufacturing a packaging sheet 18 that does not include the third printed layer 32. [Explanation of symbols]

[0060] 10 PTP packaging 12 Container sheet Packaging sheet for 16,18 PTP 20 Packaging sheet manufacturing equipment 22 Aluminum foil 22a Front page 22b Second side 30,44 Heat-resistant coating layer 30x, 44x heat-resistant coating agent KK1 Heat-resistant coating agent preparation process KK2 heat-resistant coating process KK3 Heat-resistant coating agent heating process

Claims

[Claim 1] A method for manufacturing a packaging sheet for a PTP, comprising: an aluminum foil as a base material; and a heat-resistant coating layer located on the surface of a first surface side of the aluminum foil; and the second surface side of the aluminum foil is thermally bonded to a mating container sheet to form a lid material for a PTP package, a heat-resistant coating agent preparation process in which a petroleum-derived resin is blended with a biomass resin as a main component, and a volatile solvent is mixed with a solid component in which the blending ratio of the biomass resin is set to a range of 10 to 25 mass% to prepare a heat-resistant coating agent in a liquid form; A heat-resistant coating agent application process in which a predetermined amount of the heat-resistant coating agent is applied to the first surface side of the aluminum foil so that the thickness of the heat-resistant coating layer in a finished state becomes a specified value; a heat-resistant coating agent heating step of heating the heat-resistant coating agent to volatilize the volatile solvent and thermally cure the solid component to form the heat-resistant coating layer, the petroleum-derived resin contains at least an epoxy resin and a blocked isocyanate curing agent, and does not contain a melamine resin; A method for manufacturing a packaging sheet for PTP, characterized in that in the heat-resistant coating agent heating step, a continuous furnace having three zones is used, the heating temperature and heating time are set to 170±10°C and 2.3±0.3 seconds in the first zone, 220±10°C and 2.2±0.3 seconds in the second zone, and 240±10°C and 2.2±0.3 seconds in the third zone, and the heat-resistant coating layer is formed by heating in the first zone, second zone, and third zone in that order.

Images