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Abstract

To provide a lid which is formed of biodegradable resin and has superior shape stability against heat and attaching / detaching operation.SOLUTION: There is provided a lid to be put on a tumbler-shaped beverage container, wherein resin forming the lid is biodegradable resin, and while 50 mass% or more of the biodegradable resin has a load deflection temperature of 80°C or higher, 5 mass% or more of the biodegradable resin has a flexural modulus of 3,000 MPa or larger.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a lid for covering a cup-shaped drinking container.

Background Art

[0002] When taking home a beverage placed in a cup-shaped drinking container from a store, a lid is put on the drinking container so that the beverage does not spill or dust and dirt in the air do not mix in. For example, Patent Document 1 discloses improving the shape of such a lid to prevent the beverage from spilling even during and before and after ingestion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional lids for covering cup-shaped drinking containers are formed from non-biodegradable resins such as high impact polystyrene (HIPS), as also described in Patent Document 1. The inventors of the present invention have worked on developing a lid formed from a biodegradable resin from the viewpoint of environmental protection, but when using a biodegradable resin, it has been difficult to simultaneously satisfy a plurality of qualities required for such a lid.

[0005] As an important quality required for such a lid, first, shape stability against hot beverages such as hot coffee and black tea is required. In addition, as an important quality, it is required that the lid does not deform even when the lid is attached and detached for the purpose of adding milk or sugar to the beverage. Therefore, an object of the present invention is to provide a lid formed from a biodegradable resin and having excellent shape stability against heat and attachment / detachment operations.

Means for Solving the Problems

[0006] According to one aspect of the present invention, a lid is provided for a cup-shaped drinking container, wherein the resin constituting the lid is a biodegradable resin, and 50% by mass or more of the biodegradable resin has a load deflection temperature of 80°C or higher, and 5% by mass or more of the biodegradable resin has a flexural modulus of 3000 MPa or higher. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a lid made from a biodegradable resin that has excellent shape stability against heat and attachment / detachment operations. [Brief explanation of the drawing]

[0008] [Figure 1] A side view showing a lid according to one embodiment of the present invention placed over a cup-shaped container body. [Figure 2] A plan view showing the structure of the lid. [Figure 3] A cross-sectional view showing a magnified view of the fitting portion between the lid and the container body. [Figure 4] A flowchart showing an example of a manufacturing method for the lid. [Modes for carrying out the invention]

[0009] The present invention will be described below, but the following description is intended to explain the present invention in detail and is not intended to limit it.

[0010] 1. Lid material The lid is a lid that can be placed over a cup-shaped drinking container, and may be used as a lid for a container of hot beverages or as a lid for a container of cold beverages.

[0011] The lid is characterized by being made of biodegradable resin. That is, the lid mainly contains biodegradable resin and may contain additives as needed.

[0012] At least 50% by mass of the biodegradable resin has a load deflection temperature of 80°C or higher, and at least 5% by mass of the biodegradable resin has a flexural modulus of 3000 MPa or higher. Here, the upper limit of the load deflection temperature is, for example, 120°C. The upper limit of the flexural modulus is, for example, 6000 MPa.

[0013] If 50% or more by mass of the biodegradable resin has a load deflection temperature of 80°C or higher, the lid will be less likely to deform even when exposed to high temperatures, thereby improving its thermal dimensional stability. If 5% or more by mass of the biodegradable resin has a flexural modulus of 3000 MPa or higher, the rigidity of the lid will increase, improving its dimensional stability during attachment and detachment operations. The dimensional stability of the lid is an important quality required for lids because it relates to preventing leakage of beverages from the joint between the lid and the container body when carrying or consuming beverages in the container.

[0014] At least 50% by mass of the biodegradable resin constituting the lid consists of a resin having a load deflection temperature of 80°C or higher, and such resin preferably accounts for 55% by mass or higher, more preferably 60% by mass or higher, and even more preferably 65% ​​by mass or higher of the biodegradable resin. Furthermore, at least 5% by mass of the biodegradable resin constituting the lid consists of a resin having a flexural modulus of 3000 MPa or higher, and such resin preferably accounts for 10% by mass or higher of the biodegradable resin.

[0015] While biodegradable resins may be composed of a single type of resin, it is preferable that they be composed of multiple types of resins, given that the types and properties of commercially available biodegradable resins are more limited compared to non-biodegradable resins.

[0016] When a biodegradable resin is composed of one type of resin, that one type of resin possesses both a temperature deflection of 80°C or higher and a flexural modulus of 3000 MPa or higher. On the other hand, when a biodegradable resin is composed of multiple types of resins, one of the multiple resins has a temperature deflection of 80°C or higher, and another resin has a flexural modulus of 3000 MPa or higher. Examples of resins with a temperature deflection of 80°C or higher include polybutylene succinate (PBS). Examples of PBS that can be used include FZ91PM (PTT MCC Biochem Co., Ltd.). Examples of resins with a flexural modulus of 3000 MPa or higher include polylactic acid (PLA). Examples of PLA that can be used include Ingeo 2003D (NatureWorks), Luminy L175 (Total Corbion PLA), REVODE101 (Zhejiang Haizheng Biomaterials), and Terramac TP-4000 (Unitika Ltd.).

[0017] It is preferable that the biodegradable resin is composed of multiple types of resins, for example, two or three types of resins. When the biodegradable resin is composed of multiple types of resins, it is possible to easily obtain a resin that satisfies the intended physical properties (i.e., temperature of deflection under load and flexural modulus), and it has the advantage of making it easier to design the resin composition.

[0018] In other words, in a preferred embodiment, the biodegradable resin comprises a first resin having a load deflection temperature of 80°C or higher and a second resin having a flexural modulus of 3000 MPa or higher, wherein the proportion of the first resin in the biodegradable resin is in the range of 50 to 95% by mass, and the proportion of the second resin in the biodegradable resin is in the range of 5 to 50% by mass. Here, the first resin and the second resin are different types of resins. In this embodiment, the biodegradable resin may consist only of the first resin and the second resin, or it may further contain a different type of biodegradable resin than the first resin and the second resin.

[0019] In a more preferred embodiment, the biodegradable resin includes a first resin having a heat deflection temperature of 80°C or higher and a flexural modulus of less than 3000 MPa, and a second resin having a flexural modulus of 3000 MPa or higher and a heat deflection temperature of less than 80°C. The proportion of the first resin in the biodegradable resin is within the range of 50 to 95% by mass, and the proportion of the second resin in the biodegradable resin is within the range of 5 to 50% by mass. Here, the first resin and the second resin are different types of resins. In this embodiment, the biodegradable resin may be composed only of the first resin and the second resin, or may further include a biodegradable resin of a different type from the first resin and the second resin.

[0020] It is more preferable that the biodegradable resin is composed of two types of resins. That is, in a more preferred embodiment, the biodegradable resin is composed of two types of resins, a first resin having a heat deflection temperature of 80°C or higher and a second resin having a flexural modulus of 3000 MPa or higher. The proportion of the first resin in the biodegradable resin is within the range of 50 to 95% by mass, and the proportion of the second resin in the biodegradable resin is within the range of 5 to 50% by mass. Here, the first resin and the second resin are different types of resins. In a more preferred embodiment, it is composed of two types of resins, a first resin having a heat deflection temperature of 80°C or higher and a flexural modulus of less than 3000 MPa, and a second resin having a flexural modulus of 3000 MPa or higher and a heat deflection temperature of less than 80°C. The proportion of the first resin in the biodegradable resin is within the range of 50 to 95% by mass, and the proportion of the second resin in the biodegradable resin is within the range of 5 to 50% by mass. Here, the first resin and the second resin are different types of resins.

[0021] In all of the above preferred embodiments, the upper limit of the heat deflection temperature of the first resin is, for example, 120°C, and the heat deflection temperature of the first resin is preferably 80 to 120°C, more preferably 90 to 120°C, still more preferably 90 to 110°C, and even more preferably 90 to 100°C. In all of the above preferred embodiments, the flexural modulus of the first resin is, for example, 400 MPa or more and less than 3000 MPa. Also, in all of the above preferred embodiments, the upper limit of the flexural modulus of the second resin is, for example, 6000 MPa, and the flexural modulus of the second resin is preferably 3000 to 6000 MPa, more preferably 3000 to 5000 MPa, and still more preferably 3000 to 4000 MPa. The heat deflection temperature of the second resin is, for example, 40°C or more and less than 80°C.

[0022] In all of the above preferred embodiments, it is more preferable that the proportion of the first resin in the biodegradable resin is 55 to 95% by mass and the proportion of the second resin in the biodegradable resin is 5 to 45% by mass. Also, it is more preferable that the proportion of the first resin in the biodegradable resin is 60 to 95% by mass and the proportion of the second resin in the biodegradable resin is 5 to 40% by mass. Also, it is more preferable that the proportion of the first resin in the biodegradable resin is 65 to 95% by mass and the proportion of the second resin in the biodegradable resin is 5 to 35% by mass.

[0023] In all of the above preferred embodiments, it is more preferable that the proportion of the first resin in the biodegradable resin is 50 to 90% by mass and the proportion of the second resin in the biodegradable resin is 10 to 50% by mass. Also, it is more preferable that the proportion of the first resin in the biodegradable resin is 55 to 90% by mass and the proportion of the second resin in the biodegradable resin is 10 to 45% by mass. Also, it is more preferable that the proportion of the first resin in the biodegradable resin is 60 to 90% by mass and the proportion of the second resin in the biodegradable resin is 10 to 40% by mass. Also, it is more preferable that the proportion of the first resin in the biodegradable resin is 65 to 90% by mass and the proportion of the second resin in the biodegradable resin is 10 to 35% by mass.

[0024] As described above, the first resin has a load deflection temperature of 80°C or higher, and preferably a load deflection temperature of 80°C or higher and a flexural modulus of less than 3000 MPa. Examples of such a first resin (i.e., a resin having a load deflection temperature of 80°C or higher and a flexural modulus of less than 3000 MPa) include polybutylene succinate (PBS) and poly(hydroxybutyrate / hydroxyhexanoate) (PHBH). For PBS, for example, BioPBS FZ91PM (PTT MCC Biochem Co., Ltd.) can be used. For PHBH, for example, Aonirex X131A (Kaneka Corporation) and Aonirex X151A (Kaneka Corporation) can be used. The first resin is preferably polybutylene succinate (PBS).

[0025] As described above, the second resin has a flexural modulus of 3000 MPa or more, preferably a flexural modulus of 3000 MPa or more and a load deflection temperature of less than 80°C. Examples of such a second resin (i.e., a resin having a flexural modulus of 3000 MPa or more and a load deflection temperature of less than 80°C) include polylactic acid (PLA). Examples of PLA that can be used include Ingeo 2003D (NatureWorks), Luminy L175 (Total Corbion PLA), REVODE101 (Zhejiang Haizheng Biomaterials), and Terramac TP-4000 (Unitika Ltd.). The second resin is preferably polylactic acid (PLA).

[0026] The first resin preferably has a tensile elongation at break of 20% or more. That is, the first resin preferably has a load deflection temperature of 80°C or higher and a tensile elongation at break of 20% or more. The upper limit of the tensile elongation at break of the first resin is, for example, 1000%. If the first resin has a tensile elongation at break of 20% or more, the bending resistance of the hinge portion that constitutes a repeatedly openable and closable drinking spout can be increased, thereby improving the durability of the hinge portion. Examples of such a first resin (i.e., a resin having a load deflection temperature of 80°C or higher and a tensile elongation at break of 20% or more) include polybutylene succinate (PBS) and poly(hydroxybutyrate / hydroxyhexanoate) (PHBH).

[0027] The tensile elongation at break of the first resin is more preferably 50% or more, even more preferably 100% or more, even more preferably 150% or more, even more preferably 200% or more, even more preferably 300% or more, even more preferably 400% or more, and even more preferably 500% or more. That is, the tensile elongation at break of the first resin is more preferably 50-1000%, even more preferably 100-1000%, even more preferably 150-1000%, even more preferably 200-1000%, even more preferably 300-1000%, even more preferably 400-1000%, and even more preferably 500-1000%. Examples of resins having a load deflection temperature of 80°C or higher and a tensile elongation at break of 50% or higher include polybutylene succinate (PBS) and poly(hydroxybutyrate / hydroxyhexanoate) (PHBH). Examples of resins having a load deflection temperature of 80°C or higher and a tensile elongation at break of 100% or higher include polybutylene succinate (PBS). Examples of resins having a load deflection temperature of 80°C or higher and a tensile elongation at break of 500% or higher include polybutylene succinate (PBS). The tensile elongation at break of the second resin is not particularly limited and may be 20% or more or less than 20%.

[0028] The physical properties of a resin, namely its temperature of deflection under load, flexural modulus, and tensile elongation at break, can be adjusted by changing the molecular weight of the resin, by using branching agents or chain extenders, or by changing the proportion of optical isomers if they are present.

[0029] "Load deflection temperature" refers to the temperature at which the deflection of a sample becomes constant when the temperature of the sample is raised while a load of 0.45 MPa is applied. The load deflection temperature refers to the value measured according to JIS K7191-1:2015. "Flexural modulus" refers to the load at which the sample breaks when a bending load is applied to it. The flexural modulus refers to the value measured according to JIS K7171:2016. "Tensile elongation at break" refers to the tensile elongation at which the sample breaks when it is pulled. The tensile elongation at break refers to the value measured according to JIS K7161-1:2014.

[0030] The tensile elongation at fracture is calculated using the following formula. Tensile elongation at break (%) = {(L - L0) / L0} × 100 L = Length of the sample at the time of fracture L0 = Length of the sample before testing

[0031] The lid may contain additives in addition to the biodegradable resin, as needed. Various additives known as resin additives can be used. Examples of additives include antioxidants, UV stabilizers, weathering agents, antistatic agents, fillers, nucleating agents, lubricants, mold release agents, coloring pigments, matting agents, color inhibitors, antifogging agents, and flame retardants. These additives can be used individually or in combination of two or more.

[0032] Additives can be added in amounts that do not impair the effects of the present invention. The total amount of additives can be, for example, less than 50% by mass of the final product (lid), preferably 1% by mass or more and less than 50% by mass. The total amount of organic additives can be, for example, less than 5% by mass of the final product (lid). The amount of each organic additive can be, for example, less than 1% by mass of the final product (lid).

[0033] Among the additives, it is preferable to use fillers. Preferably, inorganic fillers such as calcium carbonate, talc, and silica can be used as fillers, and more preferably, talc can be used. The particle size of the filler is not particularly limited, but for example, the average particle size is 0.1 to 50 μm. Here, the average particle size refers to the value measured by laser diffraction and scattering. Using fillers can improve the heat resistance and strength of the lid and suppress drawdown during molding.

[0034] The total amount of filler can be, for example, less than 40% by mass of the final product (lid), preferably 1% by mass or more and less than 40% by mass. Additionally, the lid may contain recycled materials.

[0035] The lid is used by being detachably fitted onto the container body. The container body can be a known type that is detachably fitted onto the lid. The container body may be made of, for example, a paper substrate or a resin such as a biodegradable resin, and is preferably made of a paper substrate.

[0036] 2. Lid configuration The lid typically consists of a disc-shaped top plate and a cylindrical portion that is continuous with the outer edge of the top plate. One end of the cylindrical portion is continuous with the top plate, and the other end forms a circular opening. The lid may have the following dimensions, for example: the inner diameter of the opening is, for example, 60 to 100 mm, the diameter of the top plate is, for example, 60 to 100 mm, and the height of the cylindrical portion is, for example, 5 to 50 mm.

[0037] The lid preferably has a thickness of 0.03 mm or more in all parts. That is, the lid preferably has a thickness of at least 0.03 mm in the thinnest part. Having a thickness of 0.03 mm or more in all parts of the lid is preferable from the viewpoint of strength, i.e., shape stability. The lid more preferably has a thickness of 0.03 to 0.50 mm in all parts. The lid even more preferably has a thickness of 0.03 to 0.45 mm in all parts.

[0038] The lid preferably has a mechanism that allows it to be repeatedly opened and closed by a hinge provided on the top plate. The repeatedly openable and closed mechanism forms the drinking spout. Therefore, the repeatedly openable and closed mechanism has a size suitable for a drinking spout. An example of the repeatedly openable and closed mechanism is shown in Figure 2 as score 41 and hinge portion 42 and is described below.

[0039] Below, a lid according to one embodiment of the present invention will be described together with the container body using Figures 1 to 3. Figure 1 is a side view showing the lid 12 according to one embodiment of the present invention placed over a cup-shaped container body 11. However, Figure 1 shows the structure of the lid 12 and the container body 11 partially cut open. Figure 2 is a plan view showing the structure of the lid 12. Figure 3 is an enlarged cross-sectional view showing the fitting portion between the lid 12 and the container body 11.

[0040] As shown in Figure 1, the lid 12 is placed over the container body 11 to form the container 1. The container 1 holds contents such as beverages. Here, the contents may be hot beverages such as hot coffee, or cold beverages such as iced coffee. The container 1 is used, for example, in stores such as convenience stores and coffee shops to provide beverages.

[0041] As shown in Figure 1, the container body 11 is a cup-shaped drinking container. The container body 11 is formed from, for example, a resin material such as a biodegradable resin or a paper substrate. In this embodiment, the container body 11 will be described using the example of a paper cup formed from a paper substrate. As shown in Figure 1, the container body 11 comprises a body portion 21 and a bottom portion 22.

[0042] The body portion 21 is formed in a cylindrical shape with a bottom portion 22 at one end and an open end at the other. The body portion 21 gradually widens in diameter from one end towards the open end. The body portion 21 is formed, for example, by forming a rectangular or fan-shaped paper substrate into a cylindrical shape and overlapping and bonding the two ends together. Therefore, the body portion 21 has a double overlapping seam portion 21a formed by bonding the two ends of the paper substrate together.

[0043] Furthermore, the body portion 21 has a curled portion 21b that forms the mouth at the opening end (the other end). The curled portion 21b is called a top curl and is formed by curling the end of the body portion 21. The curled portion 21b is formed in an annular shape. The curled portion 21b protrudes outward from the outer circumferential surface of the end of the body portion 21. The curled portion 21b is wound multiple times, and its cross-section is formed to be approximately circular.

[0044] The bottom portion 22 is provided on one end of the body portion 21. The bottom portion 22 is located slightly inside the body portion 21 from one end and is integrally bonded to the body portion 21. The bottom portion 22 closes off one end of the body portion 21.

[0045] The lid 12 is what is commonly called a lid. As shown in Figure 1, the lid 12 is detachably fitted onto the curled portion 21b of the container body 11. As shown in Figures 1 to 3, the lid 12 comprises a top plate portion 31, a peripheral wall portion 32, a fitting portion 33, and a skirt portion 34. The lid 12 is formed by integrally molding the top plate portion 31, the peripheral wall portion 32, the fitting portion 33, and the skirt portion 34 from a sheet of resin material. The resin material forming the lid 12 consists of a biodegradable resin having a specific composition, as described above. The resin material is prepared in the form of a roll sheet in which a sheet is wound, and the lid 12 is formed by molding this roll sheet.

[0046] As shown in Figure 2, the top plate portion 31 is appropriately configured according to design and usability, such as ease of drinking, with a surface shape such as flat or uneven. The top plate portion 31 includes, for example, a score 41, a hinge portion 42, a small hole 43, a locking portion 44, and a locked portion 45.

[0047] The score 41 is provided along a portion of the area of ​​the beverage passage through which the contents are discharged. The score 41 is located on a portion of the peripheral wall portion 32 side of the top plate portion 31. The score 41 is a notch provided in the top plate portion 31. The score 41 forms a beverage passage that serves as a drinking spout on the top plate portion 31 by rotating the area enclosed by the score 41 around the hinge portion 42 in a direction away from the outer surface of the other areas of the top plate portion 31. The shape of the score 41 can be set as appropriate, as long as it is possible to form a beverage passage. For example, in the example of this embodiment, as shown in Figure 2, the score 41, together with the hinge portion 42, encloses a trapezoidal area, with the score 41 forming the short side and the inclined side, and the hinge portion 42 forming the long side.

[0048] The hinge portion 42 is provided linearly between the two ends of the score 41. The hinge portion 42 is formed, for example, by a recess or step provided in the top plate portion 31. The hinge portion 42 forms the axis of rotation of the portion enclosed by the score 41.

[0049] The small hole 43 is a through-hole provided in the top plate portion 31. The small hole 43 has an opening area that allows air inside the container 1 to escape in order to reduce the internal pressure that rises due to the heating of the air inside the container 1 when a hot contents such as hot coffee are placed in the container body 11 and the lid 12 is attached.

[0050] As shown in Figure 2, the locking portion 44 is a projection provided in the area enclosed by the score 41. As shown in Figure 2, the locked portion 45 is a recess provided symmetrically to the locking portion 44 with respect to the hinge portion 42. The locked portion 45 is formed in a shape that allows the locking portion 44 to be fitted into it.

[0051] As shown in Figures 1 to 3, the peripheral wall portion 32 has one end continuous with the outer edge of the top plate portion 31 and the other end continuous with the fitting portion 33. For example, the peripheral wall portion 32 is formed in a cylindrical shape that gradually decreases in diameter from the fitting portion 33 side toward the top plate portion 31 side. The peripheral wall portion 32 also has an annular plate portion 32a at the other end that extends in a direction perpendicular to the axial direction and is continuous with the fitting portion 33.

[0052] As shown in Figures 1 to 3, the fitting portion 33 is formed in an annular shape, and its inner surface shape is formed to be substantially the same as the outer surface shape of the curled portion 21b of the container body 11. The fitting portion 33 fits into the curled portion 21b of the container body 11.

[0053] The skirt portion 34 is integrally provided with the outer end of the fitting portion 33. The skirt portion 34 is formed in a cylindrical shape that expands in diameter from top to bottom. The skirt portion 34 also has a plurality of projections 34a provided along the circumferential direction. The plurality of projections 34a are provided on the skirt portion 34 at equal intervals with predetermined spacings along the circumferential direction of the skirt portion 34. The projections 34a extend along the circumferential direction of the skirt portion 34.

[0054] 3. Method for manufacturing the lid Next, the manufacturing method of the lid 12 will be explained using Figure 4. First, a roll sheet made of biodegradable resin is fed along a conveyor path by a dispensing device (Step ST1). Next, the conveyed sheet is heated by a heater in a pressure molding device (Step ST2).

[0055] Next, the upper mold and pressure box (lower mold) of the pressure forming apparatus are moved to the forming position and the sheet is clamped (step ST3). Then, the sheet is evacuated through the upper mold by the vacuum pump of the pressure forming apparatus, and compressed air is blown onto the sheet through the pressure box (lower mold) by the compressor of the pressure forming apparatus, thereby vacuum pressure forming the sheet (step ST4). As a result, multiple shapes of the lid 12 are formed on the sheet, excluding the score 41 and small holes 43.

[0056] Next, the upper mold and the compressed air box (lower mold) are moved to the standby position and the molds are opened (step ST5). Next, the multiple score cutters and multiple pilot punches are pressed into the sheet, which has the shape of the multiple lids 12 formed on it, by a predetermined amount of pressure to perform punching (step ST6). Punching here means forming the scores 41 and the small holes 43. As a result, the scores 41 and small holes 43 are formed in the predetermined parts of the sheet where the shape of the multiple lids 12 is formed.

[0057] Next, the pair of cutting blades are moved to the punching position to perform a trimming process that cuts out multiple lids 12 from the sheet in which the shapes of multiple lids 12 are formed (step ST7). As a result, each lid 12 is cut from the sheet at the end shape of the skirt portion 34 and collected. Next, the collected multiple lids 12 undergo post-processing such as inspection and packaging (step ST8). [Examples]

[0058] (Lid manufacturing) The lids shown in Figures 1-3 were manufactured using resin mixtures in which the ratio (mass ratio) of polybutylene succinate (PBS) and polylactic acid (PLA) was varied as follows. Example 1 PBS:PLA=100:0 Example 2 PBS:PLA=90:10 Example 3 PBS:PLA=70:30 Example 4 PBS:PLA=0:100

[0059] The PBS used has a deflection temperature of 90-100°C, a tensile elongation at break of 500-700%, and a flexural modulus of 500-700 MPa. The PLA used has a flexural modulus of 3000-4000 MPa, a deflection temperature of 50-60°C, and a tensile elongation at break of 15% or less.

[0060] As described above, the lid was manufactured by forming the outer shape of the lid using vacuum pressure forming, and then creating the drinking spout and air vent by forming scores and small holes.

[0061] (Evaluation method) We evaluated the "shape stability against heat," "shape stability against attachment and detachment operations," and "hinge suitability." The container body used was a container body made from a paper substrate (GDNC09AR manufactured by Nippon Dixie).

[0062] The "thermal dimensional stability" was evaluated as follows: First, 195±3g of the test solution (hot coffee liquid) at 95°C was poured into the container body, and the lid was attached to prepare the container with the test solution. The container with the test solution was held at a 45° angle relative to the direction of gravity for 15 seconds. After that, it was visually inspected to see if the shape of the lid was damaged and if the test solution was leaking. If the shape of the lid was damaged or the test solution leaked, the evaluation result was marked as ×. If no such defects were observed, the evaluation result was marked as ○.

[0063] The "shape stability during attachment and detachment operations" was evaluated as follows. The evaluation was conducted by five randomly selected panelists. Each panelist performed the attachment and detachment operation twice on one sample. Each operation consisted of fitting the lid onto the container body and then removing the lid from the container body. After the two operations, the lid was visually inspected for any deformation such as buckling. If deformation such as buckling occurred in the lid, the evaluation result was marked as ×. If no such defects were observed, the evaluation result was marked as ○.

[0064] The "hinge suitability" was evaluated as follows: A lid was fitted onto an empty container body and left overnight in a constant temperature room at 5°C. Afterwards, the hinge mechanism was opened and closed five times in the constant temperature room at 5°C. Each opening and closing operation consisted of rotating the hinge approximately 180°C around its axis to open it, and then closing it back to its original position. After the five opening and closing operations, the hinge was visually inspected for any cracks or damage. If cracks or damage were found in the hinge, the evaluation result was marked as ×. If no such defects were observed, the evaluation result was marked as ○.

[0065] (Evaluation results) The evaluation results are shown in Table 1.

[0066] [Table 1]

[0067] The results in Table 1 show that a lid with excellent shape stability against heat and attachment / detachment operations, as well as bending resistance of the hinge portion, can be manufactured by combining 50% or more by mass of PBS and 5% or more by mass of PLA. In this embodiment, a lid with a mechanism that allows repeated opening and closing by the hinge portion was manufactured, but even when manufacturing a lid without such a mechanism, a lid with excellent shape stability against heat and attachment / detachment operations can be manufactured by combining 50% or more by mass of PBS and 5% or more by mass of PLA.

[0068] Furthermore, the results in Table 1 show that PBS contributes to the property of being resistant to deformation due to heat (i.e., heat resistance) and the property of being resistant to breakage during bending of the hinge (i.e., flexural resistance), while PLA contributes to the property of being resistant to deformation during attachment and detachment operations (i.e., strength). The heat resistance of a resin can be expressed by an index called "temperature of deflection under load," the flexural resistance of a resin can be expressed by an index called "tensile elongation at break," and the strength of a resin can be expressed by an index called "elastic modulus." "Flexural modulus" is known as a stable index for representing the strength of a resin.

[0069] Therefore, these results show that if 50% by mass or more of the biodegradable resin has a load deflection temperature of 80°C or higher, and 5% by mass or more of the biodegradable resin has a flexural modulus of 3000 MPa or higher, it is possible to manufacture a lid with excellent shape stability against heat and attachment / detachment operations, as well as excellent bending resistance of the hinge portion. In this embodiment, a lid with a mechanism that allows repeated opening and closing by the hinge portion was manufactured, but if a lid without such a mechanism is manufactured, a lid with excellent shape stability against heat and attachment / detachment operations can be manufactured if 50% by mass or more of the biodegradable resin has a load deflection temperature of 80°C or higher, and 5% by mass or more of the biodegradable resin has a flexural modulus of 3000 MPa or higher. The following are the embodiments of the claims originally filed for this application. [1] A lid that can be placed over a cup-shaped drinking container, wherein the resin constituting the lid is a biodegradable resin, and 50% by mass or more of the biodegradable resin has a load deflection temperature of 80°C or higher, and 5% by mass or more of the biodegradable resin has a flexural modulus of 3000 MPa or higher. [2] The lid according to [1], wherein the biodegradable resin comprises a first resin having a load deflection temperature of 80°C or higher and a second resin having a flexural modulus of 3000 MPa or higher, the proportion of the first resin in the biodegradable resin is in the range of 50 to 95% by mass, and the proportion of the second resin in the biodegradable resin is in the range of 5 to 50% by mass. [3] The lid according to [2], wherein the first resin has a tensile elongation at break of 20% or more. [4] The lid according to [2] or [3], wherein the first resin is polybutylene succinate. [5] The lid according to any one of [2] to [4], wherein the second resin is polylactic acid. [6] The lid is the lid according to any one of [1] to [5], having a thickness of 0.03 mm or more in all parts. [7] The lid according to any one of [1] to [6], wherein the lid has a mechanism that allows it to be repeatedly opened and closed by a hinge provided on the top plate. [Explanation of Symbols]

[0070] 1...Container, 11...Container body, 12...Lid, 21...Body, 21a...Seam, 21b...Curl, 22...Bottom, 31...Top plate, 32...Peripheral wall, 32a...Ring plate, 33...Fitting part, 34...Skirt, 34a...Protrusion, 41...Score, 42...Hinge, 43...Small hole, 44...Locking part, 45...Locking part.

Claims

1. A lid that is detachably fitted to a cup-shaped drinking container, wherein the resin constituting the lid is a biodegradable resin, the biodegradable resin is a mixture containing polybutylene succinate and polylactic acid, the proportion of polybutylene succinate in the biodegradable resin is in the range of 65 to 95% by mass, and the proportion of polylactic acid in the biodegradable resin is in the range of 5 to 35% by mass.

2. The lid according to claim 1, wherein the lid has a thickness of 0.03 mm or more in all parts.

3. The lid according to claim 1 or 2, wherein the lid has a mechanism that allows it to be repeatedly opened and closed by a hinge provided on the top plate.

Images