Recycled biodegradable polyester resin, recycled biodegradable polyester resin foam sheet, and recycled biodegradable polyester resin foam molded body

Abstract

Provided is a recycled biodegradable polyester resin that can serve as a raw material for a recycled biodegradable polyester resin foam sheet having excellent foaming characteristics. Also provided are: a recycled biodegradable polyester resin foam sheet in which such a recycled biodegradable polyester resin is used as a raw material; and a recycled biodegradable polyester resin foam molded body obtained by molding such a recycled biodegradable polyester resin foam sheet.　A recycled biodegradable polyester resin according to an embodiment of the present invention is a recycled biodegradable polyester resin using a biodegradable polyester resin foam as a recycled raw material, wherein in a graph that is obtained by uniaxial extensional viscosity measurement at 160°C of the recycled biodegradable polyester resin and in which the logarithm of the strain amount ε is on the horizontal axis and the logarithm of the elongation viscosity η (Pa·s) is on the vertical axis, the gradient a2 of the graph in the direction in which the strain amount increases from an inflection point is 0.30 (Pa·s) or more.

Description

Recycled biodegradable polyester resin, recycled biodegradable polyester resin foam sheet, and recycled biodegradable polyester resin foam molded product

[0001] The present invention relates to a recycled biodegradable polyester resin, a recycled biodegradable polyester resin foam sheet, and a recycled biodegradable polyester resin foam molded article.

[0002] Resin foam sheets and resin foam molded articles are lightweight, have excellent cushioning properties, and can be easily molded into a variety of shapes, so they are used as raw materials for various molded products, including packaging materials.

[0003] In recent years, resin foam sheets and resin foam molded articles have been used in large quantities and then discarded in large quantities. This places a heavy burden on the environment and is a factor in various social problems, such as global warming, resource depletion, and waste disposal. In response to this, foam sheets and foam molded articles have been proposed that use biodegradable polyester resins, such as polylactic acid resins, which are biodegradable, have a small environmental impact, and can be produced relatively inexpensively (see, for example, Patent Document 1).

[0004] In general, in order to produce foam sheets or foam-molded articles from resins, the melt tension of the raw material resin must be relatively high. The same applies to producing foam sheets or foam-molded articles from biodegradable polyester resins; the melt tension of the raw material biodegradable polyester resin must be relatively high. Therefore, when producing foam sheets or foam-molded articles from biodegradable polyester resins, it has been proposed to use, as the raw material biodegradable polyester resin, a modified biodegradable polyester resin that has been modified to have a crosslinked or branched structure in its molecule to increase its melt tension (Patent Document 2).

[0005] On the other hand, as with ordinary resin sheets and resin molded articles, there is a strong social demand for the recycling of large quantities of discarded resin foam sheets and resin foam molded articles. Therefore, it can be said that the establishment of a recycling system for producing recycled biodegradable polyester resin foam sheets and recycled biodegradable polyester resin foam molded articles having excellent foaming properties from recovered biodegradable polyester resin foam sheets and biodegradable polyester resin foam molded articles will also become very important in the future society.

[0006] Japanese Patent No. 6971947 Japanese Patent Application Laid-Open No. 2019-183098

[0007] An object of the present invention is to provide a recycled biodegradable polyester resin that can be used as a raw material for a recycled biodegradable polyester resin foam sheet having excellent foaming properties. It is also an object of the present invention to provide a recycled biodegradable polyester resin foam sheet made from such a recycled biodegradable polyester resin. It is also an object of the present invention to provide a recycled biodegradable polyester resin foam molded article obtained by molding such a recycled biodegradable polyester resin foam sheet.

[0008] [1] A recycled biodegradable polyester resin according to an embodiment of the present invention is a recycled biodegradable polyester resin made from a biodegradable polyester resin foam as a recycled raw material, and in a graph obtained by uniaxial extensional viscosity measurement of the recycled biodegradable polyester resin at 160°C, the horizontal axis is the logarithm of the amount of strain ε and the vertical axis is the logarithm of the extensional viscosity η (Pa s), the slope a2 of the graph in the direction from the inflection point toward increasing amount of strain is 0.30 (Pa s) or more. [2] In the recycled biodegradable polyester resin according to the above [1], the biodegradable polyester resin foam may be obtained by melt-kneading a resin composition containing the biodegradable polyester resin in an extruder and extruding and foaming it. [3] In the recycled biodegradable polyester resin described in [2] above, in a graph obtained by uniaxial extensional viscosity measurement of the biodegradable polyester resin at 160°C, the ratio (a2 / a1) of the slope a2 (Pa s) of the graph to the slope a1 (Pa s) of the graph in the direction from the inflection point toward increasing strain, where the horizontal axis represents the logarithm of the strain amount ε and the vertical axis represents the logarithm of the extensional viscosity η (Pa s), may be 0.10 or more. [4] In the recycled biodegradable polyester resin described in [2] or [3] above, the biodegradable polyester resin may be a polylactic acid resin (P). [5] In the recycled biodegradable polyester resin described in [4] above, the polylactic acid resin (P) may be a modified polylactic acid resin. [6] In the recycled biodegradable polyester resin according to any one of [1] to [5] above, the biodegradable polyester resin may be obtained by melt-kneading a raw material composition containing the biodegradable polyester resin foam in an extruder, extruding the extruded mixture, and pelletizing the mixture. [7] In the recycled biodegradable polyester resin according to any one of [1] to [6] above, the recycled biodegradable polyester resin may be the biodegradable polyester resin foam. [8] In the recycled biodegradable polyester resin according to any one of [1] to [7] above, the Z-average molecular weight (M Z) may be 300,000 or more. [9] In the recycled biodegradable polyester resin according to any one of [1] to [8] above, the recycled biodegradable polyester resin may have an MFR of 15 g / 10 min or less.

[10] In the recycled biodegradable polyester resin according to any one of [1] to [9] above, the recycled biodegradable polyester resin may have a melt tension at 190°C of 1 cN or more.

[11] A recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention is obtained by foaming a recycled resin composition containing the recycled biodegradable polyester resin according to any one of [1] to

[10] above.

[12] In the recycled biodegradable polyester resin foam sheet according to

[11] above, in a graph obtained by uniaxial extensional viscosity measurement of the recycled biodegradable polyester resin foam sheet at 160°C, the horizontal axis represents the logarithm of the strain amount ε, and the vertical axis represents the logarithm of the extensional viscosity η (Pa s), the slope a3 of the graph in the direction from the inflection point toward increasing strain amount may be 0.30 (Pa s) or more.

[13] In the recycled biodegradable polyester resin foam sheet according to

[11] or

[12] above, the thickness may be 0.5 mm to 7 mm.

[14] In the recycled biodegradable polyester resin foam sheet according to any one of

[11] to

[13] above, the basis weight may be 50 g / m 2 ~600g / m 2

[15] In the recycled biodegradable polyester resin foam sheet according to any one of

[11] to

[14] above, the expansion ratio may be 4 to 20 times.

[16] In the recycled biodegradable polyester resin foam sheet according to any one of

[11] to

[15] above, the open cell ratio may be 50% or less.

[17] A recycled biodegradable polyester resin foam molded product according to an embodiment of the present invention is obtained by molding the recycled biodegradable polyester resin foam sheet according to any one of

[11] to

[16] above.

[0009] According to an embodiment of the present invention, it is possible to provide a recycled biodegradable polyester resin that can be used as a raw material for a recycled biodegradable polyester resin foam sheet having excellent foaming properties. It is also possible to provide a recycled biodegradable polyester resin foam sheet made from such a recycled biodegradable polyester resin. Furthermore, it is also possible to provide a recycled biodegradable polyester resin foam molded article obtained by molding such a recycled biodegradable polyester resin foam sheet.

[0010] 1 is a graph showing an example of a graph in which the horizontal axis represents the logarithm of the strain amount ε (unit: dimensionless) and the vertical axis represents the logarithm of the extensional viscosity η (unit: Pa s), obtained by uniaxial extensional viscosity measurement of the recycled biodegradable polyester resin according to an embodiment of the present invention at 160°C. FIG. 2 is a schematic diagram showing a preferred configuration of an extruder used in an embodiment of the present invention. FIG. 3 is a schematic diagram showing a preferred configuration of a production apparatus suitable for producing a foamed sheet in an embodiment of the present invention.

[0011] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0012] The "recycled biodegradable polyester resin" as used herein means a recycled biodegradable polyester resin made from the "biodegradable polyester resin foam" as used herein (e.g., a biodegradable polyester resin foam sheet or a biodegradable polyester resin foam molded article) as a recycled raw material.

[0013] The "recycled biodegradable polyester resin foam sheet" in the present invention means a foam sheet obtained by foaming a recycled resin composition containing the "recycled biodegradable polyester resin" in the present invention.

[0014] The "recycled biodegradable polyester resin foam molded article" in the present invention means a foam molded article obtained by molding the "recycled biodegradable polyester resin foam sheet" in the present invention.

[0015] In this specification, "polylactic acid resin" means "modified polylactic acid resin" or "unmodified polylactic acid resin." In this specification, when "polylactic acid resin" is simply stated without the term "polylactic acid resin (P)," it means unmodified polylactic acid resin. Here, "unmodified polylactic acid resin" refers to polylactic acid resin that has not been modified, typically a commonly available polylactic acid resin, and not a modified polylactic acid resin that has been modified.

[0016] In this specification, the term "substantially 100% by mass" means that the presence of a small amount of unintentionally mixed impurities (for example, less than 1% by mass) can be ignored.

[0017] <<1. Recycled Biodegradable Polyester Resin>> The recycled biodegradable polyester resin according to an embodiment of the present invention uses a biodegradable polyester resin foam as a recycled raw material. The biodegradable polyester resin foam may be of one type or two or more types.

[0018] As the biodegradable polyester resin foam as a recycled raw material, any appropriate foam can be used as long as the effects of the present invention are not impaired. Examples of such biodegradable polyester resin foam include a biodegradable polyester resin foam sheet and a biodegradable polyester resin foam molded product obtained by molding the biodegradable polyester resin foam sheet.

[0019] A representative example of a biodegradable polyester resin foam as a recycled raw material is a recovered biodegradable polyester resin foam. Such a biodegradable polyester resin foam may be a non-recycled biodegradable polyester resin foam, or may be a recycled biodegradable polyester resin foam as long as the effects of the present invention are not impaired. A representative example of such a biodegradable polyester resin foam is a biodegradable polyester resin foam obtained by melt-kneading and extrusion-foaming a resin composition containing a biodegradable polyester resin in an extruder. The above-mentioned "biodegradable polyester resin" may be a recycled biodegradable polyester resin, a non-recycled biodegradable polyester resin, or a mixture thereof, but is typically a non-recycled biodegradable polyester resin.

[0020] The biodegradable polyester resin foam as a recycled raw material can be used in any appropriate form depending on the type and scale of the apparatus used to produce the recycled biodegradable polyester resin. The form of such a biodegradable polyester resin foam may be, for example, the form itself, a pulverized product obtained by pulverizing the pulverized product, pellets made from the pulverized product, or a pulverized product of the pellets.

[0021] In a graph of the recycled biodegradable polyester resin according to an embodiment of the present invention, the horizontal axis represents the logarithm of the strain ε (unit: dimensionless) obtained by uniaxial extensional viscosity measurement at 160 ° C., and the vertical axis represents the logarithm of the extensional viscosity η (unit: Pa s). The slope a2 of the graph in the direction from the inflection point toward increasing strain is typically 0.30 (Pa s) or more, preferably 0.35 (Pa s) or more, more preferably 0.40 (Pa s) or more, and particularly preferably 0.45 (Pa s) or more. The upper limit of the slope a1 of the graph is preferably 4.00 (Pa s) or less, more preferably 3.00 (Pa s) or less, even more preferably 2.50 (Pa s) or less, particularly preferably 2.00 (Pa s) or less, and most preferably 1.50 (Pa s) or less, in order to further demonstrate the effects of the present invention. If the slope a2 of the graph is within the above range, the recycled biodegradable polyester resin according to an embodiment of the present invention can have excellent strain hardening properties. Generally, the strain hardening properties of polyester resins can be reduced by applying a thermal history using an extruder or the like, and this reduction in strain hardening properties leads to reduced foaming properties when foamed into a foam sheet. The recycled biodegradable polyester resin according to an embodiment of the present invention has excellent strain hardening properties even when subjected to a thermal history using an extruder or the like, and can therefore be used as a raw material for recycled biodegradable polyester resin foam sheets with excellent foaming properties.

[0022] FIG. 1 shows an example of a graph of a recycled biodegradable polyester resin according to an embodiment of the present invention, with the horizontal axis representing the logarithm of strain ε (unit: dimensionless) and the vertical axis representing the logarithm of extensional viscosity η (unit: Pa s) obtained by uniaxial extensional viscosity measurement at 160°C. In FIG. 1, the horizontal axis represents the logarithm of strain ε (unit: dimensionless), and the vertical axis represents the logarithm of extensional viscosity η (unit: Pa s). In FIG. 1, V represents the inflection point. In the present invention, the slope a2 of the graph in the direction from the inflection point to increasing strain is, using FIG. 1 as an example, the slope of the line obtained by linear approximation using the least squares method for the curve from inflection point V to the point where the extensional viscosity η is at its maximum in the direction of increasing strain. Note that in the case of recycled biodegradable polyester resins, the slope of the graph in the direction from the inflection point to decreasing strain may be a negative value. The same applies to the gradients a1 and a3 of the graph in the direction in which the strain amount increases from the inflection point, which will be described later.

[0023] In the recycled biodegradable polyester resin according to an embodiment of the present invention, the ratio (a2 / a1) of the slope a2 (Pa s) of the graph in the direction from the inflection point toward increasing strain, obtained by uniaxial extensional viscosity measurement at 160°C of the biodegradable polyester resin that is the raw material for the biodegradable polyester resin foam, is preferably 0.10 or more, more preferably 0.10 to 1.50, even more preferably 0.15 to 1.40, particularly preferably 0.20 to 1.35, and most preferably 0.25 to 1.30, of the slope a2 (Pa s) of the graph in the direction from the inflection point toward increasing strain, where the horizontal axis represents the logarithm of the strain ε (unit: dimensionless) and the vertical axis represents the logarithm of the extensional viscosity η (Pa s), obtained by uniaxial extensional viscosity measurement at 160°C of the biodegradable polyester resin that is the raw material for the recycled biodegradable polyester resin foam, is preferably 0.10 or more, more preferably 0.10 to 1.50, even more preferably 0.15 to 1.40, particularly preferably 0.20 to 1.35, and most preferably 0.25 to 1.30. When the ratio (a2 / a1) is within the above range, the recycled biodegradable polyester resin according to an embodiment of the present invention can be used as a raw material for a recycled biodegradable polyester resin foam sheet having better foaming properties, even when subjected to a thermal history using an extruder or the like, as the reduced strain hardening caused by the biodegradable polyester resin that is the raw material for the recycled raw material biodegradable polyester resin foam is suppressed.

[0024] The recycled biodegradable polyester resin according to an embodiment of the present invention preferably has an MFR of 15 g / 10 min or less, more preferably 0.2 g / 10 min to 15 g / 10 min or less, even more preferably 0.5 g / 10 min to 13 g / 10 min or less, particularly preferably 1.0 g / 10 min to 10 g / 10 min or less, and most preferably 1.0 g / 10 min to 8.0 g / 10 min. If the MFR is within the above range, the recycled biodegradable polyester resin according to an embodiment of the present invention can exhibit appropriate fluidity when thermally melted, have better strain hardening properties, and can be used as a raw material for a recycled biodegradable polyester resin foam sheet having better foaming properties.

[0025] The recycled biodegradable polyester resin according to an embodiment of the present invention preferably has a melt tension at 190°C of 1 cN or more, more preferably 1 cN to 100 cN, even more preferably 1 cN to 80 cN, particularly preferably 1 cN to 70 cN, and most preferably 1 cN to 60 cN. If the melt tension is within the above range, the recycled biodegradable polyester resin according to an embodiment of the present invention can be used as a raw material for a recycled biodegradable polyester resin foam sheet having superior foaming properties. In particular, even if the melt tension is low, the recycled biodegradable polyester resin according to an embodiment of the present invention has superior strain hardening properties and can be used as a raw material for a recycled biodegradable polyester resin foam sheet having superior foaming properties.

[0026] The recycled biodegradable polyester resin according to an embodiment of the present invention has a Z-average molecular weight (M Z ) is preferably 300,000 or more, more preferably 400,000 or more, even more preferably 500,000 or more, and particularly preferably 600,000 or more. Z The upper limit of the Z-average molecular weight (M) is preferably 1,800,000 or less, more preferably 1,600,000 or less, even more preferably 1,500,000 or less, and particularly preferably 1,300,000 or less. Z ) is an average molecular weight that emphasizes the contribution of high molecular weight components.Z ) is within the above range, it means that the recycled biodegradable polyester resin according to an embodiment of the present invention has a significant amount of remaining high molecular weight components even when subjected to a heat history using an extruder or the like. By having a significant amount of remaining high molecular weight components, the recycled biodegradable polyester resin according to an embodiment of the present invention has better strain hardening properties and can be used as a raw material for a recycled biodegradable polyester resin foam sheet having better foaming properties. Z ) is too small, the amount of high molecular weight components remaining in the recycled biodegradable polyester resin according to an embodiment of the present invention will be small, which may result in a decrease in strain hardening properties, and the recycled biodegradable polyester resin may not be usable as a raw material for a recycled biodegradable polyester resin foam sheet having excellent foaming properties.

[0027] The recycled biodegradable polyester resin according to an embodiment of the present invention preferably has a number average molecular weight (Mn) of 10,000 to 150,000, more preferably 20,000 to 130,000, even more preferably 30,000 to 120,000, and particularly preferably 40,000 to 110,000.

[0028] The recycled biodegradable polyester resin according to an embodiment of the present invention preferably has a weight average molecular weight (Mw) of 100,000 to 1,000,000, more preferably 130,000 to 500,000, even more preferably 150,000 to 400,000, and particularly preferably 200,000 to 350,000.

[0029] The recycled biodegradable polyester resin according to an embodiment of the present invention preferably has a melting point of 130°C to 175°C, more preferably 135°C to 170°C, and even more preferably 138°C to 168°C.

[0030] The recycled biodegradable polyester resin according to an embodiment of the present invention preferably has a crystallization temperature of 70°C to 110°C, more preferably 75°C to 105°C, and even more preferably 78°C to 103°C.

[0031] <<1-1. First embodiment of recycled biodegradable polyester resin>> A recycled biodegradable polyester resin according to a first embodiment of the present invention is produced by melt-kneading a raw material composition containing a biodegradable polyester resin foam, which is a recycled raw material, in an extruder, and pelletizing the extruded mixture. The recycled biodegradable polyester resin according to this embodiment can be typically produced by a method including: a kneading step of melt-kneading a raw material composition containing a biodegradable polyester resin foam, which is a recycled raw material, in an extruder; and a pelletizing step of pelletizing the kneaded mixture extruded from the extruder.

[0032] When producing the recycled biodegradable polyester resin according to an embodiment of the present invention, any appropriate other steps may be included in addition to the kneading step and pelletizing step, as long as the effects of the present invention are not impaired.

[0033] The recycled biodegradable polyester resin according to an embodiment of the present invention preferably further includes a drying step for adjusting the moisture content of the pellets obtained in the pelletizing step. The moisture content after adjustment in the drying step is preferably 0.30% by mass or less, more preferably 0.25% by mass or less, even more preferably 0.20% by mass or less, even more preferably 0.15% by mass or less, particularly preferably 0.10% by mass or less, and most preferably 0.05% by mass or less. The lower limit of the moisture content after adjustment in this drying step is the better, and ideally 0% by mass. By strictly adjusting the moisture content of the pellets within the above range in the drying step, excellent strain hardening properties can be imparted to the resulting recycled biodegradable polyester resin. This makes it possible to provide a recycled biodegradable polyester resin that can be used as a raw material for a recycled biodegradable polyester resin foam sheet with excellent foaming properties.

[0034] When producing a recycled biodegradable polyester resin according to an embodiment of the present invention, in order to efficiently proceed with the pelletizing process, a cooling process may be included after the kneading process and before the pelletizing process, in which the kneaded material extruded from the extruder is cooled.

[0035] It has been found that the moisture content of the pellets obtained in the pelletizing process tends to be high when a cooling step is included. As a result of investigating this tendency, it was inferred that the temperature of the high-temperature kneaded material extruded from the extruder can drop rapidly in the cooling step, making it easier for moisture to be absorbed into the kneaded material. In fact, when a recycled biodegradable polyester resin foam sheet was produced using a recycled biodegradable polyester resin obtained from pellets with a high moisture content when a cooling step was included, it was found that the foaming properties were poor. However, it has been found that by adopting the above-mentioned drying step, a recycled biodegradable polyester resin that can be used as a raw material for a recycled biodegradable polyester resin foam sheet with excellent foaming properties can be provided, even when a cooling step is included.

[0036] The recycled biodegradable polyester resin according to an embodiment of the present invention can be produced using any appropriate production apparatus as long as the effects of the present invention are not impaired. In order to further demonstrate the effects of the present invention, the recycled biodegradable polyester resin according to an embodiment of the present invention can be produced using, for example, a production apparatus such as that shown in Figure 2.

[0037] As shown in FIG. 2, typically, a raw material composition containing a biodegradable polyester resin foam as a recycled raw material (which may be a pulverized product of the foam, pellets made from the pulverized product, or pulverized pellets) is fed into a hopper 11, melt-kneaded by a twin-screw extruder 30, and the strand-like kneaded product extruded from a strand die 3 is cooled by a cooling device 6, then pelletized by a pelletizer 4, and dried by a drying device 5, thereby obtaining a recycled biodegradable polyester resin according to an embodiment of the present invention in pellet form.

[0038] <1-1-a. Kneading Step> In the kneading step, a raw material composition containing a biodegradable polyester resin foam, which is a recycled raw material, is melt-kneaded in an extruder.

[0039] The biodegradable polyester resin foam, which is a recycled raw material, will be described in detail later.

[0040] The raw material composition contains a biodegradable polyester resin foam that is a recycled raw material. The raw material composition may contain any appropriate component other than the biodegradable polyester resin foam, as long as the effect of the present invention is not impaired.

[0041] The content of the biodegradable polyester resin foam in the raw material composition is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and particularly preferably 95% by mass to 100% by mass, in order to further exhibit the effects of the present invention.

[0042] As the extruder, any appropriate extruder can be used as long as the effects of the present invention are not impaired. In terms of being able to further exhibit the effects of the present invention, a twin-screw extruder is preferred.

[0043] The twin-screw extruder may be equipped with a strand die or a T-die.

[0044] The temperature conditions for melt-kneading may vary depending on the size of extrusion, the discharge amount, etc., and any appropriate conditions may be adopted as long as the effects of the present invention are not impaired. For example, the temperature of the raw material feed section is preferably set to 100°C to 200°C.

[0045] The rotation speed of the extruder may vary depending on the size of the extrusion, the discharge rate, etc., and any appropriate condition may be adopted as long as the effects of the present invention are not impaired. For example, such a rotation speed is preferably 20 rpm to 800 rpm.

[0046] <1-1-b. Cooling Step> In the cooling step, any appropriate cooling method can be adopted as long as the effects of the present invention are not impaired. Examples of such cooling methods include a method using a cooling device, a representative example being a method in which the strand discharged from the strand die is water-cooled, and specifically a method in which the strand discharged from the strand die is water-cooled by introducing it into a water tank.

[0047] The cooling temperature is preferably 70° C. or lower, more preferably 60° C. or lower, even more preferably 50° C. or lower, particularly preferably 40° C. or lower, and most preferably 35° C. or lower. There are no particular restrictions on the lower limit of the cooling temperature, but in consideration of the cost required for cooling and the like, it is practically preferably 5° C. or higher, more preferably 10° C. or higher.

[0048] <1-1-c. Pelletizing Step> In the pelletizing step, the kneaded material extruded from the extruder in the kneading step is pelletized.

[0049] As the pelletizing method in the pelletizing step, any appropriate pelletizing method can be adopted as long as it can pelletize the kneaded material extruded from the extruder in the kneading step, as long as the effects of the present invention are not impaired. A typical pelletizing method is to cut the strand-shaped or sheet-shaped kneaded material extruded from the extruder in the kneading step into pellets using a pelletizer. In order to efficiently proceed with the pelletizing step, a cooling step may be included after the kneading step and before the pelletizing step.

[0050] As the pelletizer, any appropriate pelletizer can be used as long as it does not impair the effects of the present invention.

[0051] The extruder in the kneading step may be equipped with a pelletizing die (hot cut die). In this case, the kneaded material is pelletized immediately after being extruded, and the pelletization in the pelletizing die constitutes the pelletizing step.

[0052] <1-1-d. Drying Step> In the drying step, the moisture content of the pellets obtained in the pelletizing step is adjusted. The moisture content after adjustment in the drying step is preferably 0.30% by mass or less, more preferably 0.25% by mass or less, even more preferably 0.20% by mass or less, even more preferably 0.15% by mass or less, particularly preferably 0.10% by mass or less, and most preferably 0.05% by mass or less. The lower limit of the moisture content after adjustment in this drying step is the lower the better, and ideally 0% by mass. By strictly adjusting the moisture content of the pellets to within the above range in the drying step, excellent strain hardening properties can be imparted to the resulting recycled biodegradable polyester resin. This makes it possible to provide a recycled biodegradable polyester resin that can be used as a raw material for a recycled biodegradable polyester resin foam sheet with excellent foaming properties.

[0053] As a method for strictly adjusting the moisture content of the pellets to fall within a predetermined range in the drying step, any appropriate method can be employed as long as it does not impair the effects of the present invention. Examples of such methods include drying the pellets using a dryer such as a dehumidifying dryer, a vacuum dryer, or a hot air dryer. It is a preferred embodiment that the pellets thoroughly dried in a dryer or the like are introduced directly (without being exposed to a moist environment) into the next step. It is also a preferred embodiment that the pellets thoroughly dried in a dryer or the like are immediately sealed in an aluminum bag after drying, and the bag is opened immediately before being introduced into the next step.

[0054] 1-2. Second embodiment of recycled biodegradable polyester resin A recycled biodegradable polyester resin according to a second embodiment of the present invention is a biodegradable polyester resin foam that is a recycled raw material. The recycled biodegradable polyester resin according to this embodiment is typically the biodegradable polyester resin foam itself that is a recycled raw material, and is typically a pulverized product.

[0055] The recycled biodegradable polyester resin according to the second embodiment of the present invention is different from the recycled biodegradable polyester resin according to the first embodiment of the present invention described above, in that it is not produced by melt-kneading a biodegradable polyester resin foam, which is a recycled raw material, in an extruder and then pelletizing the kneaded material extruded from the extruder.

[0056] <1-3. Biodegradable polyester resin foam as recycled raw material> A typical example of a biodegradable polyester resin foam as recycled raw material is a biodegradable polyester resin foam obtained by melt-kneading and extrusion-foaming a resin composition containing a biodegradable polyester resin in an extruder. Accordingly, a typical embodiment of the biodegradable polyester resin foam is a biodegradable polyester resin foam sheet obtained by melt-kneading and extrusion-foaming a resin composition containing a biodegradable polyester resin in an extruder, or a biodegradable polyester resin foam molded article obtained by molding the foam sheet.

[0057] The open cell ratio of the biodegradable polyester resin foam is preferably 50% or less, more preferably 40% or less, even more preferably 30% or less, particularly preferably 20% or less, and most preferably 15% or less.

[0058] The biodegradable polyester resin foam has an average cell diameter of preferably 100 μm to 850 μm, more preferably 150 μm to 800 μm, and even more preferably 200 μm to 750 μm.

[0059] The expansion ratio of the biodegradable polyester resin foam is preferably 4 to 20 times, more preferably 4 to 15 times, even more preferably 4 to 12 times, and particularly preferably 4 to 10 times.

[0060] <1-3-a. Resin Composition> One embodiment of the biodegradable polyester resin foam is a biodegradable polyester resin foam sheet obtained by melt-kneading a resin composition containing a biodegradable polyester resin in an extruder and extrusion-foaming it, or a biodegradable polyester resin foam molded article obtained by molding the foam sheet.

[0061] The content of the biodegradable polyester resin in the resin composition is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and even more preferably 90% by mass to 100% by mass, in order to be able to exhibit the effects of the present invention.

[0062] [Biodegradable polyester resin as a raw material for biodegradable polyester resin foam] As the biodegradable polyester resin as a raw material for biodegradable polyester resin foam, any appropriate biodegradable polyester resin can be used as long as the effects of the present invention are not impaired. The biodegradable polyester resin may be one type or two or more types.

[0063] The biodegradable polyester resin used as a raw material for the biodegradable polyester resin foam preferably has an MFR of 10.0 g / 10 min or less, more preferably 0.2 g / 10 min to 6.0 g / 10 min, even more preferably 0.3 g / 10 min to 5.0 g / 10 min, particularly preferably 0.5 g / 10 min to 4.0 g / 10 min, and most preferably 0.8 g / 10 min to 3.0 g / 10 min, in order to further exhibit the effects of the present invention. When the MFR of the biodegradable polyester resin is within the above range, it can exhibit appropriate fluidity when hot-melted, and the effects of the present invention can be further exhibited.

[0064] The biodegradable polyester resin used as a raw material for the biodegradable polyester resin foam preferably has a melt tension at 190°C of 18 cN or more, more preferably 20 cN to 100 cN, even more preferably 30 cN to 80 cN, particularly preferably 40 cN to 70 cN, and most preferably more than 40 cN to 60 cN or less, in order to better exhibit the effects of the present invention.

[0065] The biodegradable polyester resin used as a raw material for the biodegradable polyester resin foam has a Z-average molecular weight (M Z ) is preferably 500,000 or more, more preferably 700,000 or more, even more preferably 900,000 or more, and particularly preferably 1,000,000 or more. ZThe upper limit of the molecular weight (Mn) is preferably 1,500,000 or less, more preferably 1,400,000 or less, even more preferably 1,300,000 or less, and particularly preferably 1,200,000 or less.

[0066] The biodegradable polyester resin used as a raw material for the biodegradable polyester resin foam preferably has a number average molecular weight (Mn) of 30,000 to 180,000, more preferably 40,000 to 150,000, even more preferably 50,000 to 130,000, and particularly preferably 60,000 to 100,000, in order to further exhibit the effects of the present invention.

[0067] The biodegradable polyester resin used as a raw material for the biodegradable polyester resin foam preferably has a weight average molecular weight (Mw) of 100,000 to 700,000, more preferably 130,000 to 550,000, even more preferably 150,000 to 500,000, and particularly preferably 200,000 to 450,000, in order to better exhibit the effects of the present invention.

[0068] The biodegradable polyester resin used as a raw material for the biodegradable polyester resin foam preferably has a melting point of 130°C to 175°C, more preferably 135°C to 170°C, and even more preferably 138°C to 168°C, in order to better exhibit the effects of the present invention.

[0069] The biodegradable polyester resin used as a raw material for the biodegradable polyester resin foam preferably has a crystallization temperature of 70°C to 110°C, more preferably 75°C to 105°C, and even more preferably 78°C to 103°C, in order to better exhibit the effects of the present invention.

[0070] In order to further demonstrate the effects of the present invention, the biodegradable polyester resin used as a raw material for the biodegradable polyester resin foam preferably has a moisture content of 0.30% by mass or less immediately before being fed into an extruder, more preferably 0.25% by mass or less, even more preferably 0.20% by mass or less, particularly preferably 0.17% by mass or less, and most preferably 0.15% by mass or less. The lower limit of the moisture content is preferably as low as possible, and is ideally 0% by mass. The moisture content immediately before being fed into the extruder can be measured, for example, using a Karl Fischer moisture content meter. In order to further demonstrate the effects of the present invention, the biodegradable polyester resin used as a raw material for the biodegradable polyester resin foam has a slope a1 (Pa s) of 0.50 (Pa s) or more, more preferably 1.00 (Pa s) or more, and particularly preferably 1.50 (Pa s) or more, in a graph obtained by uniaxial extensional viscosity measurement at 160 ° C., where the horizontal axis is the logarithm of the strain amount ε (unit: dimensionless) and the vertical axis is the logarithm of the extensional viscosity η (Pa s). The upper limit of the slope a1 of the graph is preferably 5.00 (Pa s) or less, more preferably 4.00 (Pa s) or less, even more preferably 3.00 (Pa s) or less, particularly preferably 2.70 (Pa s) or less, and most preferably 2.50 (Pa s) or less, in order to further demonstrate the effects of the present invention.

[0071] The biodegradable polyester resin is preferably a polylactic acid resin (P) in that it can more effectively exhibit the effects of the present invention.

[0072] The polylactic acid resin (P) may be a modified polylactic acid resin, an unmodified polylactic acid resin, or a mixture thereof.

[0073] The polylactic acid resin (P) typically contains a modified polylactic acid resin as a main component. The content of the modified polylactic acid resin in the polylactic acid resin (P) is preferably more than 50% by mass, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably substantially 100% by mass.

[0074] The modified polylactic acid resin is preferably obtained by melt-kneading a polylactic acid resin composition containing a polylactic acid resin and a modifier in an extruder.

[0075] The polylactic acid resin may be a homopolymer of lactic acid or a copolymer of lactic acid with other monomers, such as aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polycarboxylic acids, and polyfunctional polysaccharides.

[0076] The lactic acid constituting the polylactic acid resin may be either the L-configuration or the D-configuration, or may be both the L-configuration and the D-configuration. That is, the polylactic acid resin, which is a homopolymer of lactic acid, may be any of poly(L-lactic acid) resin, poly(D-lactic acid) resin, and poly(DL-lactic acid) resin.

[0077] Examples of hydroxycarboxylic acids other than lactic acid include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, and 6-hydroxycaproic acid.

[0078] Examples of the aliphatic polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, tetramethylene glycol, and 1,4-cyclohexanedimethanol.

[0079] Examples of the aliphatic polycarboxylic acid include oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, undecanedioic acid, and dodecanedioic acid. The aliphatic polycarboxylic acid may also be an acid anhydride.

[0080] Examples of polyfunctional polysaccharides include cellulose, cellulose nitrate, methyl cellulose, ethyl cellulose, celluloid, viscose rayon, regenerated cellulose, cellophane, cupra, cuprammonium rayon, cuprophane, Bemberg, hemicellulol, starch, acropectin, dextrin, dextran, glycogen, pectin, chitin, chitosan, gum arabic, guar gum, locust bean gum, and acacia gum.

[0081] The content of structural moieties derived from lactic acid (L- and D-forms) in the molecule of the polylactic acid resin is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more.

[0082] At least a part of the polylactic acid resin may be recycled.

[0083] The modifier exerts the effect of increasing the molecular weight of the polylactic acid resin and imparting a crosslinked structure or a long-chain branched structure to the molecular structure of the polylactic acid resin.

[0084] The modifier may be of one kind or of two or more kinds.

[0085] To increase the molecular weight of polylactic acid resin, a chain extender such as carbodiimide can be used as a modifier. Modification using a chain extender can be achieved by using a compound having one or more functional groups capable of undergoing a condensation reaction with a hydroxyl group or a carboxyl group present in the molecular structure of polylactic acid resin, such as an acrylic organic compound, an epoxy organic compound, or an isocyanate organic compound. That is, the molecular weight of polylactic acid resin can be increased by using a chain extender such as carbodiimide to bond an acrylic organic compound, an epoxy organic compound, an isocyanate organic compound, or the like to the polylactic acid resin.

[0086] To impart a crosslinked structure or a long-chain branched structure to the molecular structure of polylactic acid resin, for example, a radical initiator can be used as a modifier. In this case, polylactic acid resins are reacted with each other using the radical initiator. When polylactic acid resins are reacted with each other using a radical initiator with appropriate reactivity, for example, the decomposition starting points of the polylactic acid resin in the extruder are attacked by free radicals generated by the radical initiator, and these points become crosslinked points (branching points) and can be stabilized. By performing such modification, the thermal stability of the polylactic acid resin is increased and it becomes less susceptible to low molecular weight degradation when passing through the extruder.

[0087] Examples of the radical initiator include organic peroxides, azo compounds, and halogen molecules, with organic peroxides being preferred.

[0088] Examples of organic peroxides include peroxyesters, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxyketals, and ketone peroxides.

[0089] Examples of peroxy esters include t-butylperoxy 2-ethylhexyl carbonate, t-hexylperoxy isopropyl monocarbonate, t-hexylperoxybenzoate, t-butylperoxybenzoate, t-butylperoxy laurate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxy acetate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and t-butylperoxy isopropyl monocarbonate.

[0090] Examples of hydroperoxides include permethane hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide.

[0091] Examples of dialkyl peroxides include dicumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3.

[0092] Examples of diacyl peroxides include dibenzoyl peroxide, di(4-methylbenzoyl) peroxide, and di(3-methylbenzoyl) peroxide.

[0093] Examples of peroxydicarbonates include di(2-ethylhexyl) peroxydicarbonate and diisopropyl peroxydicarbonate.

[0094] Examples of peroxyketals include 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-t-butylperoxycyclohexane, 2,2-di(t-butylperoxy)-butane, n-butyl 4,4-di-(t-butylperoxy)valerate, and 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane.

[0095] Examples of the ketone peroxide include methyl ethyl ketone peroxide and acetylacetone peroxide.

[0096] Modification with organic peroxides may result in the modified polylactic acid resin being contaminated with components having excessively large molecular weights that gel when thermally melted, or may cause odor problems due to decomposition residues of the organic peroxide. Peroxyesters are preferred as the organic peroxides, as they can prevent such problems and easily modify the polylactic acid resin to a state suitable for foaming. Among peroxyesters, peroxycarbonate-based organic peroxides such as peroxymonocarbonate and peroxydicarbonate are preferred. Among peroxycarbonate-based organic peroxides, peroxymonocarbonate-based organic peroxides are preferred, with t-butylperoxyisopropyl monocarbonate being more preferred.

[0097] The amount of organic peroxide used depends on the molecular weight, etc., but in order to further exhibit the effects of the present invention, it is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, relative to 100 parts by mass of polylactic acid resin. The upper limit of the amount of organic peroxide used is preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, and even more preferably 1.0 part by mass or less.

[0098] The polylactic acid resin composition containing the polylactic acid resin and the modifier may contain any appropriate component other than the polylactic acid resin and the modifier, as long as the effects of the present invention are not impaired. The total content of the polylactic acid resin and the modifier in the polylactic acid resin composition containing the polylactic acid resin and the modifier is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and particularly preferably 95% by mass to 100% by mass.

[0099] The polylactic acid resin composition containing the polylactic acid resin and the modifier may be prepared by pre-mixing the polylactic acid resin, the modifier, and other components as needed. Examples of such mixing methods include mixing methods using a mixer such as a tumbler, ribbon blender, V blender, Henschel mixer, or Redige mixer.

[0100] As the extruder, any appropriate extruder can be used as long as the effects of the present invention are not impaired. In terms of being able to further exhibit the effects of the present invention, a twin-screw extruder is preferred.

[0101] The twin-screw extruder may be equipped with a strand die or a T-die. In this case, the extruded strand-shaped or sheet-shaped kneaded product may be cooled and cut into pellets using a pelletizer or the like.

[0102] The twin-screw extruder may be equipped with a pelletizing die (hot cut die), in which case the kneaded material is pelletized immediately after being extruded.

[0103] The temperature conditions for melt-kneading may vary depending on the size of the extruder, the discharge rate, etc., and any appropriate conditions may be adopted as long as the effects of the present invention are not impaired. For example, the temperature of the raw material feed section is preferably set to 100°C to 200°C.

[0104] The rotation speed of the extruder may vary depending on the size of the extruder, the discharge rate, etc., and any appropriate condition may be adopted as long as the effects of the present invention are not impaired. For example, such a rotation speed is preferably 20 rpm to 800 rpm.

[0105] The modified polylactic acid resin may be dried. Typically, the modified polylactic acid resin may be obtained by cooling a strand-shaped kneaded product extruded from a twin-screw extruder equipped with a strand die, cutting the resulting pellets with a pelletizer, or the like, and drying the pellets.

[0106] The modified polylactic acid resin can be produced using any appropriate apparatus as long as the effects of the present invention are not impaired. For example, the modified polylactic acid resin can be produced using a production apparatus such as that shown in FIG.

[0107] In Figure 2, for example, polylactic acid resin and a modifier are charged into a hopper 11 and melt-kneaded by a twin-screw extruder 30, and the strand-shaped kneaded material extruded from a strand die 3 is cooled by a cooling device 6, then pelletized by a pelletizer 4, and dried by a drying device 5 to obtain a modified polylactic acid resin.

[0108] [Foaming Agent] Examples of foaming components that can be used when producing a biodegradable polyester resin foam sheet from a resin composition include a foaming agent and a cell regulator. The resin composition typically contains a foaming agent. The foaming agent may be one type or two or more types.

[0109] Any appropriate foaming agent can be used as long as it does not impair the effects of the present invention. Examples of the foaming agent include volatile foaming agents that become gas at room temperature (23°C) and normal pressure (1 atmosphere) and decomposition type foaming agents that generate gas by thermal decomposition, and volatile foaming agents are preferred.

[0110] The volatile blowing agent is preferably an organic compound having a boiling point equal to or lower than the softening point of the polylactic acid resin and being in a gaseous or liquid state at normal pressure. Specific examples include aliphatic hydrocarbons such as propane, n-butane, isobutane, pentane (n-pentane, isopentane, neopentane), and n-hexane; alicyclic hydrocarbons such as cyclopentane and cyclopentadiene; ketones such as acetone and methyl ethyl ketone; alcohols such as methanol, ethanol, and isopropyl alcohol; low-boiling ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether; and halogen-containing hydrocarbons such as trichloromonofluoromethane and dichlorodifluoromethane. Inorganic gases such as carbon dioxide, nitrogen, and ammonia may also be used as the volatile blowing agent. Among these, the volatile blowing agent is preferably at least one selected from n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, and cyclopentadiene, and more preferably at least one selected from n-butane, isobutane, n-pentane, and isopentane, in terms of being able to further exhibit the effects of the present invention.

[0111] Examples of decomposition type foaming agents include azodicarbonamide, dinitrosopentamethylenetetramine, sodium bicarbonate, or a mixture of an organic acid such as citric acid or its salt with a bicarbonate.

[0112] The amount of the foaming agent used can be appropriately set depending on the purpose, and is preferably 0.1 to 10.0 parts by mass, more preferably 0.3 to 7.0 parts by mass, even more preferably 0.5 to 5.0 parts by mass, and particularly preferably 0.8 to 3.0 parts by mass, relative to 100 parts by mass of the biodegradable polyester resin.

[0113] [Cell Regulator] The resin composition may contain a cell regulator. The cell regulator may be one kind or two or more kinds.

[0114] Examples of foam regulators include higher fatty acid amides, partial esters of higher fatty acids and alcohols, talc, calcium carbonate, mica, citric acid, sodium bicarbonate, polytetrafluoroethylene, aluminum hydroxide, and silica. Examples of higher fatty acid amides include fatty acid monoamides such as oleic acid amide, stearic acid amide, and hydroxystearic acid amide; and fatty acid bisamides such as methylene bisstearic acid amide and ethylene bisstearic acid amide. Examples of higher fatty acids in the partial esters of higher fatty acids and alcohols include fatty acids having 15 or more carbon atoms, such as palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and behenic acid. Examples of partial esters of higher fatty acids and alcohols include stearic acid monoglyceride and stearic acid diglyceride.

[0115] The content of the cell regulator in the resin composition is preferably 0.01% by mass to 20% by mass, more preferably 0.1% by mass to 10% by mass, even more preferably 0.2% by mass to 5.0% by mass, and particularly preferably 0.3% by mass to 4.0% by mass, in order to further exhibit the effects of the present invention.

[0116] [Other Components] The resin composition may contain any appropriate other components as long as the effects of the present invention are not impaired. Such other components may be one type only or two or more types. Examples of such other components include foaming aids, other resins, pigments, radiant heat transfer suppressing components, crosslinkers, plasticizers, stabilizers, fillers, lubricants, colorants, antioxidants, antistatic agents, spreading agents, weather resistance agents, flame retardants, UV absorbers, light stabilizers, antioxidants, antifogging agents, fragrances, and antibacterial agents.

[0117] The content of other components in the resin composition may be any appropriate content as long as it does not impair the effects of the present invention, and is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, and most preferably 1% by mass or less.

[0118] <1-3-b. Production of biodegradable polyester resin foam> A biodegradable polyester resin foam is typically a biodegradable polyester resin foam sheet obtained by melt-kneading a resin composition containing a biodegradable polyester resin in an extruder and extrusion-foaming it, or a biodegradable polyester resin foam molded article obtained by molding the foam sheet. That is, the biodegradable polyester resin foam is obtained by melt-kneading a resin composition containing a biodegradable polyester resin in an extruder and extrusion-foaming it.

[0119] A biodegradable polyester resin foam molded article can be obtained by molding a biodegradable polyester resin foam sheet. Typically, the biodegradable polyester resin foam molded article can be obtained by heat-softening the biodegradable polyester resin foam sheet and subjecting it to thermoforming using a mold, such as vacuum molding and / or pressure molding, or a matched mold molding method or plug-assist molding method that are variations thereof.

[0120] Any components contained in the resin composition may be pre-mixed as necessary before feeding them into the extruder. Examples of such a mixing method include a mixing method using a mixer such as a tumbler, a ribbon blender, a V blender, a Henschel mixer, or a Redigay mixer.

[0121] As the extruder, any appropriate extruder can be used as long as the effects of the present invention are not impaired. In terms of being able to further exhibit the effects of the present invention, a tandem extruder is preferably used as the extruder.

[0122] The tip of the tandem extruder may be equipped with any appropriate die within the scope of not impairing the effects of the present invention so as to finally obtain a biodegradable polyester resin foam sheet, and preferably may further be equipped with a cooling mandrel, a take-up roller for taking up the biodegradable polyester resin foam sheet as a raw roll, and the like.

[0123] The biodegradable polyester resin foam sheet can be produced using any appropriate apparatus, for example, the production apparatus shown in FIG.

[0124] The production apparatus shown in Figure 3 includes a tandem extruder 10 and a circular die CD that extrudes the polylactic acid resin composition melt-kneaded in the tandem extruder 10 into a cylindrical shape. The production apparatus also includes a cooling device CL that air-cools the foamed sheet extruded into a cylindrical shape from the circular die CD, a mandrel MD that expands the cylindrical foamed sheet into a cylindrical shape of a predetermined size, a slitting device that slits the foamed sheet after passing through the mandrel MD to divide it into two sheets, and a take-up roller 22 that winds up the slit foamed sheet 1 after passing it through multiple rollers 21. An extruder upstream of the tandem extruder 10 (hereinafter also referred to as "first extruder 10a") includes a hopper 11 for introducing a biodegradable polyester resin, which is a raw material for the foamed sheet, and a gas inlet 12 for supplying a blowing agent into the cylinder. An extruder (hereinafter also referred to as "second extruder 10b") for melt-kneading a resin composition containing a biodegradable polyester resin and a foaming agent is provided downstream of the first extruder 10a.

[0125] The temperature conditions for melt-kneading may vary depending on the size and discharge rate of the extruder, and any appropriate conditions may be adopted as long as the effects of the present invention are not impaired. For example, the temperature of the raw material feed section of the upstream extruder 10a is preferably set to 100°C to 200°C, more preferably 140°C to 200°C, the temperature after the upstream extruder 10a is preferably set to 120°C to 300°C, more preferably 140°C to 270°C, and the temperature of the downstream extruder 10b is preferably set to 100°C to 250°C, more preferably 120°C to 220°C.

[0126] The rotation speed of the extruder may vary depending on the size of the extruder, the discharge rate, etc., and any appropriate condition may be adopted as long as the effects of the present invention are not impaired. For example, the rotation speed of the upstream extruder 10a is preferably 10 rpm to 300 rpm, and the rotation speed of the downstream extruder 10b is preferably 5 rpm to 200 rpm.

[0127] <<2. Recycled Biodegradable Polyester Resin Foam Sheet>> A recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention is obtained by foaming a recycled resin composition containing a recycled biodegradable polyester resin according to an embodiment of the present invention. A recycled biodegradable polyester resin foam sheet according to one embodiment of the present invention is obtained by melt-kneading a recycled resin composition containing a recycled biodegradable polyester resin in an extruder and extrusion-foaming it. The recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention has excellent foaming properties because it is made from a recycled resin composition containing a recycled biodegradable polyester resin according to an embodiment of the present invention.

[0128] In a graph of the recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention, the horizontal axis represents the logarithm of strain ε (unit: dimensionless) obtained by uniaxial extensional viscosity measurement at 160°C, and the vertical axis represents the logarithm of extensional viscosity η (Pa s). The slope a3 of the graph in the direction of increasing strain from the inflection point is typically 0.30 (Pa s) or more, preferably 0.35 (Pa s) or more, more preferably 0.40 (Pa s) or more, and particularly preferably 0.45 (Pa s) or more. The upper limit of the slope a1 of the graph is preferably 4.00 (Pa s) or less, more preferably 3.00 (Pa s) or less, even more preferably 2.50 (Pa s) or less, particularly preferably 2.00 (Pa s) or less, and most preferably 1.50 (Pa s) or less, in order to further exhibit the effects of the present invention. If the slope a3 of the graph is within the above range, the recycled biodegradable polyester resin foam sheet according to the embodiment of the present invention can have excellent foaming properties.

[0129] The thickness of the recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention can be appropriately set depending on the purpose. In one embodiment of the recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention, the thickness is preferably 0.5 mm to 7 mm, more preferably 0.5 mm to 5 mm, even more preferably 0.5 mm to 4 mm, and particularly preferably 0.5 mm to 3 mm.

[0130] The basis weight of the recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention can be appropriately set depending on the purpose. In one embodiment of the recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention, the basis weight is preferably 50 g / m 2 ~600g / m 2 and more preferably 100 g / m 2 ~550g / m 2 and more preferably 150 g / m 2 ~500g / m 2 and particularly preferably 200 g / m 2 ~450g / m 2 is.

[0131] The recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention has an expansion ratio of preferably 4 to 20, more preferably 4 to 15, even more preferably 4 to 12, and particularly preferably 4 to 10. The recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention can achieve such a sufficient expansion ratio despite using recycled raw materials.

[0132] The recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention has an open cell ratio of preferably 50% or less, more preferably 40% or less, even more preferably 30% or less, still more preferably 20% or less, particularly preferably 15% or less, and most preferably 12% or less. The recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention can achieve such a low open cell ratio despite using recycled raw materials.

[0133] <2-1. Recycled Resin Composition> One embodiment of the recycled biodegradable polyester resin foam sheet is obtained by melt-kneading a recycled resin composition containing a recycled biodegradable polyester resin according to an embodiment of the present invention in an extruder and extrusion-foaming the composition.

[0134] The content of the recycled biodegradable polyester resin according to an embodiment of the present invention in the recycled resin composition is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and even more preferably 90% by mass to 100% by mass, in order to be able to exhibit the effects of the present invention.

[0135] <2-1-a. Recycled biodegradable polyester resin> The recycled biodegradable polyester resin contained in the recycled resin composition is a recycled biodegradable polyester resin according to an embodiment of the present invention. For the recycled biodegradable polyester resin according to an embodiment of the present invention, the explanation in the above section <<1. Recycled biodegradable polyester resin>> can be cited.

[0136] <2-1-b. Foaming agent> The recycled resin composition typically contains a foaming agent in addition to the recycled biodegradable polyester resin. The foaming agent may be one type or two or more types. With regard to the foaming agent, the explanation in the section [Foaming agent] in the section <1-3-a. Resin composition> above may be used.

[0137] <2-1-c. Cell Regulator> The recycled resin composition may contain a cell regulator. The cell regulator may be one type or two or more types. With regard to the cell regulator, the explanation in the section [Cell Regulator] in the section <1-3-a. Resin Composition> above may be used.

[0138] <2-1-d. Other Components> The recycled resin composition may contain any appropriate other components as long as the effects of the present invention are not impaired. Such other components may be one type only, or two or more types. With regard to such other components, the explanation in the section [Other Components] in the section <1-3-a. Resin Composition> above may be used.

[0139] 2-2. Production of Recycled Biodegradable Polyester Resin Foam Sheet A recycled biodegradable polyester resin foam sheet according to one embodiment of the present invention is obtained by melt-kneading a recycled resin composition containing a recycled biodegradable polyester resin in an extruder and then extrusion-foaming the mixture.

[0140] Any components contained in the recycled resin composition may be pre-mixed as necessary before feeding them into the extruder. Examples of such a mixing method include a mixing method using a mixer such as a tumbler, a ribbon blender, a V blender, a Henschel mixer, or a Redigay mixer.

[0141] As the extruder, any appropriate extruder can be used as long as the effects of the present invention are not impaired. In terms of being able to further exhibit the effects of the present invention, a tandem extruder is preferably used as the extruder.

[0142] The tip of the tandem extruder may be equipped with any appropriate die within the scope of not impairing the effects of the present invention so as to finally obtain a biodegradable polyester resin foam sheet, and preferably may further be equipped with a cooling mandrel, a take-up roller for taking up the recycled biodegradable polyester resin foam sheet as a raw roll, and the like.

[0143] The recycled biodegradable polyester resin foam sheet can be produced using any appropriate apparatus, for example, the production apparatus shown in FIG. 3 described above as an example of the production apparatus for the biodegradable polyester resin foam sheet.

[0144] The production apparatus shown in Figure 3 includes a tandem extruder 10 and a circular die CD that extrudes the polylactic acid resin composition melt-kneaded in the tandem extruder 10 into a cylindrical shape. The production apparatus also includes a cooling device CL that air-cools the cylindrical foam sheet extruded from the circular die CD, a mandrel MD that expands the cylindrical foam sheet into a cylindrical shape of a predetermined size, a slitting device that slits the foam sheet after passing through the mandrel MD to divide it into two sheets, and a take-up roller 22 that winds up the slit foam sheet 1 after passing it through multiple rollers 21. An extruder upstream of the tandem extruder 10 (hereinafter also referred to as "first extruder 10a") is provided with a hopper 11 for introducing recycled biodegradable polyester resin, which is the raw material for the foam sheet, and a gas inlet 12 for supplying a blowing agent into the cylinder. An extruder (hereinafter also referred to as "second extruder 10b") for melt-kneading a resin composition containing recycled biodegradable polyester resin and a foaming agent is provided downstream of the first extruder 10a.

[0145] The temperature conditions for melt-kneading may vary depending on the size and discharge rate of the extruder, and any appropriate conditions may be adopted as long as the effects of the present invention are not impaired. For example, the temperature of the raw material feed section of the upstream extruder 10a is preferably set to 100°C to 200°C, more preferably 140°C to 200°C, the temperature after the upstream extruder 10a is preferably set to 120°C to 300°C, more preferably 140°C to 270°C, and the temperature of the downstream extruder 10b is preferably set to 100°C to 250°C, more preferably 120°C to 220°C.

[0146] The rotation speed of the extruder may vary depending on the size of the extruder, the discharge rate, etc., and any appropriate condition may be adopted as long as the effects of the present invention are not impaired. For example, the rotation speed of the upstream extruder 10a is preferably 10 rpm to 300 rpm, and the rotation speed of the downstream extruder 10b is preferably 5 rpm to 200 rpm.

[0147] <<3. Recycled biodegradable polyester resin foam molded body>> A recycled biodegradable polyester resin foam molded body according to an embodiment of the present invention is obtained by molding a recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention. The recycled biodegradable polyester resin foam molded body according to an embodiment of the present invention can be typically obtained by heat-softening the recycled biodegradable polyester resin foam sheet according to an embodiment of the present invention, and thermoforming it using a mold by a vacuum molding method and / or a pressure molding method, or a method based on these methods, such as a matched mold molding method or a plug-assist molding method.

[0148] The recycled biodegradable polyester resin foam molded article according to an embodiment of the present invention may be used as, for example, food containers such as trays, cups, bowls, lunch boxes, fruit containers, vegetable containers, etc.; cushioning materials such as cushioning materials for electrical appliances and cushioning materials for precision instruments; and the like.

[0149] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring and evaluating each property are as follows.

[0150] <Uniaxial Extensional Viscosity Measurement> A graph was obtained by measuring the uniaxial extensional viscosity of the resin at 160°C, with the horizontal axis representing the logarithm of the strain ε (unit: dimensionless) and the vertical axis representing the logarithm of the extensional viscosity η (unit: Pa s) as follows. Uniaxial extensional viscosity measurements were performed using a viscoelasticity measuring device "PHYSICA MCR301" (manufactured by Anton Paar) and a temperature control system "CTD450" (manufactured by Anton Paar). First, the resin to be measured (or the foam, if in the form of a foam) was pressed in a heat press at 190°C for 5 minutes to prepare a strip-shaped sample with a width of 10 mm and a thickness of approximately 0.8 mm. Next, this strip-shaped sample was cut into lengths of 20 to 25 mm to prepare test specimens. The test piece was set on a uniaxial extensional viscosity measurement jig (SER2) of a viscoelasticity measuring device heated to 160 ° C., and after waiting for 10 seconds under a nitrogen atmosphere at a temperature condition of 160 ° C. ± 0.5 ° C., the uniaxial extensional viscosity was measured at a strain rate of 1.0 / sec. The measurement point interval was set to "measurement point interval logarithmically", with the start at 0.01 sec and the end at 26 sec. The measurement points were set to 200. The obtained measurement results were plotted on a double logarithmic graph with the horizontal axis representing the common logarithmic value (log (ε)) of the strain amount ε (unit: dimensionless) and the vertical axis representing the common logarithmic value (log (η)) of the extensional viscosity η (unit: Pa s). The direction in which the strain amount increases from the inflection point, i.e., from the inflection point to the strain amount showing the maximum extensional viscosity, was linearly approximated by the least squares method, and the slope of the approximated line was determined. As a representative example, Figure 1 shows an example of a graph in which the horizontal axis represents the logarithm of the strain amount ε (unit: dimensionless) and the vertical axis represents the logarithm of the extensional viscosity η (unit: Pa s) obtained by uniaxial extensional viscosity measurement at 160°C of a recycled biodegradable polyester resin according to one embodiment of the present invention. In Figure 1, the horizontal axis represents the logarithm of the strain amount ε (unit: dimensionless) and the vertical axis represents the logarithm of the extensional viscosity η (unit: Pa s). In Figure 1, V represents the inflection point. In the present invention, the slope a2 of the graph in the direction from the inflection point to the increasing strain amount is the slope of the line obtained by linear approximation using the least squares method for the curve from the inflection point V to the point where the extensional viscosity η in the direction of increasing strain amount is shown.In the case of recycled biodegradable polyester resins, the slope of the graph from the inflection point toward the direction of decreasing strain may be a negative value. The slopes a1 and a3 of the graph from the inflection point toward the direction of increasing strain were also measured in the same manner.

[0151] <Measurement of Moisture Content> 1.0 g of sample was placed in a Karl Fischer moisture analyzer ("CA-200" manufactured by Mitsubishi Chemical Analytech Co., Ltd.) and a moisture vaporizer ("VA-236S" manufactured by Mitsubishi Chemical Analytech Co., Ltd.), and the actual moisture content was measured. Mitsubishi Chemical Corporation's Aquamicron AX and Aquamicron CXU were used as the anolyte and catholyte during the measurement, respectively. The measurement temperature was 128°C. N2 was used as the carrier gas. The carrier gas flow rate was 250 mL / min. The actual moisture content was measured three times. The moisture content was measured twice in the air atmosphere at the sample collection location, and the average value was used as the blank moisture content. Using each of the measured moisture contents obtained in the three measurements, the moisture content (% by mass) was calculated using the following formula, and the three calculation results were averaged to determine the moisture content (% by mass) of the sample. Moisture content (mass%) = [[measured moisture content (μg) - blank moisture content (μg)] ÷ 1,000,000 ÷ sample mass (g)] × 100

[0152] <Measurement of MFR (Melt Mass Flow Rate)> MFR was measured in accordance with JIS K 7210:1999. Specifically, it was measured by "b) Method of measuring the time it takes for a piston to move a predetermined distance" as described in Method B of JIS K 7210:1999. MFR was measured using a Melt Flow Index Tester (Automatic) 120-SAS (manufactured by Yasuda Seiki Seisakusho Co., Ltd.). The samples were vacuum dried at 70°C for 5 hours, then sealed and stored in a desiccator until immediately before measurement. Measurement was performed three times, and the average value was used. The measurement conditions were as follows: Sample: 3g to 8g Preheating (1): 200 seconds Preheating (2): 30 seconds Test temperature: 190°C Test load: 21.18N Piston movement distance (interval): 25mm

[0153] <Melt Tension Measurement> The melt tension was measured using a Capillograph 1D (manufactured by Toyo Seiki Seisakusho, Ltd.) and a Rheotens 71.97 (manufactured by Gottfert). The sample was previously vacuum dried at 70°C for 5 hours. The Rheotens 71.97 was installed so that the distance from the capillary die outlet of the Capillograph 1D to the measurement section was 80 mm. First, the sample was filled into a 9.55 mm diameter barrel heated to a test temperature of 190°C and then preheated for 5 minutes. Note that the measurement time must not exceed 10 minutes, including the preheating time from filling the barrel. Next, a piston was inserted from the top of the barrel, and the molten resin was extruded into a string-like shape from a capillary die (diameter 2.095 mm, length 8 mm, inlet angle 90 degrees (conical)). At this time, the piston descending speed (20 mm / min) was kept constant, and the extruded string-like material was passed through a Rheotens wheel (wheel spacing: upper 0.6 mm to 0.8 mm, lower 1.0 mm), and the take-up speed was set to an initial speed of 6.92 mm / s and an acceleration of 10 mm / s. 2 The melt tension of the sample was measured by gradually increasing the tension at this temperature. Regarding the measurement results, the average of the maximum and minimum tension values ​​immediately before the point at which the string-like material broke was taken as the melt tension of the sample. When there was only one maximum point on the tension chart, that maximum value was taken as the melt tension. Furthermore, when the string-like material became thinner and the winding became idle, that point was taken as the breaking point, and the average of the maximum and minimum tension values ​​immediately before that point was taken as the melt tension of the sample. [Measurement conditions for "Capilograph 1D"] Die: diameter 2.095 mm, length 8 mm, inlet angle 90 degrees (conical) Barrel diameter: 9.55 mm Piston speed: 20 mm / min Measurement temperature: 190°C [Measurement conditions for "Rheotens 71.97"] Wheel spacing: upper 0.6 mm to 0.8 mm, lower 1.0 mm Acceleration: 10 mm / s 2 Pull-up speed: initial speed 6.92 mm / s

[0154] <Measurement of Molecular Weight> The number average molecular weight (Mn), weight average molecular weight (Mw), and Z average molecular weight (Mz) were each determined as follows. 20 mg of a sample to be measured for molecular weight was dissolved in 6 mL of chloroform (immersion time: 6 hours ± 1.0 hour (partially insoluble)), filtered through a non-aqueous 0.45 μm syringe filter manufactured by Shimadzu GLC Corporation, and then measured using a chromatograph under the following measurement conditions. The average molecular weight of the sample was determined from a standard polystyrene calibration curve prepared in advance. The apparatus used was a gel permeation chromatograph manufactured by Tosoh Corporation ("HLC-8320GPC EcoSEC," equipped with an RI detector and a UV detector). [GPC measurement conditions] Guard column: TSK guard column HXL-H (6.0 mm x 4.0 cm) manufactured by Tosoh Corporation x 1 Measurement column: TSKgel GMHXL (7.8 mm I.D. x 30 cm) manufactured by Tosoh Corporation x 2 in series Reference side: Resistance tube (inner diameter 0.1 mm x 2 m) x 2 in series Column temperature: 40°C Mobile phase: chloroform Mobile phase flow rate of reference side pump: 0.5 mL / min Mobile phase flow rate of sample side pump: 1.0 mL / min Detector: RI detector Injection volume: 50 μL Measurement time: 25 min Sampling interval: 500 msec Standard polystyrene samples for the calibration curve were manufactured by Showa Denko K.K. under the product names "STANDARD SM-105" and "STANDARD SH-75" having mass average molecular weights of 5,620,000, 3,120,000, 1,250,000, 442,000, 151,000, 53,500, 17,000, 7,660, 2,900, and 1,320 were used. The polystyrene standards for the calibration curve were divided into groups A (5,620,000, 1,250,000, 151,000, 17,000, 2,900) and B (3,120,000, 442,000, 53,500, 7,660, 1,320). Groups A were weighed out (2 mg, 3 mg, 4 mg, 4 mg, 4 mg) and dissolved in 30 mL of chloroform. Groups B were weighed out (3 mg, 4 mg, 4 mg, 4 mg, 4 mg) and dissolved in 30 mL of chloroform. The standard polystyrene calibration curve was obtained by creating a calibration curve (cubic equation) from the retention times obtained after injecting 50 μL of each prepared solution A and solution B.The average molecular weight was calculated using the calibration curve.

[0155] <Measurement of Melting Point and Crystallization Temperature> The melting point and crystallization temperature were measured using a heat flux differential scanning calorimeter (heat flux DSC) according to the methods described in JIS K7122:1987 and JIS K7122:2012 "Method for measuring heat of transition of plastics" and JIS K7121:1987 and 2012 "Method for measuring transition temperature of plastics." The sampling method and temperature conditions were as follows. A sample was packed to the bottom of an aluminum measurement container (Hitachi High-Tech Science Corporation, product code: GAA-0065) with 5.5±0.5 mg of sample, leaving no gaps. An aluminum lid (Hitachi High-Tech Science Corporation, product code: GAA-0064) was then placed on the container. A DSC curve was then obtained using a differential scanning calorimeter (Hitachi High-Tech Science Corporation, "NEXTA DSC600") under a nitrogen gas flow rate of 20 mL / min, by heating and cooling the sample in the following steps: (Step 1) The sample was heated from 30°C to 210°C (first heating), and then held there for 10 minutes. (Step 2) The sample was removed from the measurement device, allowed to stand at room temperature for 10 minutes, and then returned to the measurement device at 30°C (rapid cooling). (Step 3) The sample was heated from 30°C to 210°C (second heating). All heating was performed at a rate of 5°C / min. Alumina was used as the reference material. (Melting point) Using the analysis software attached to the device, the top temperature of the melting peak observed during the second heating process was read and used as the melting temperature (melting point). (Crystallization temperature) The top temperature of the exothermic peak observed during the second heating process was read and used as the crystallization temperature. When multiple exothermic peaks appeared, the temperature of the peak on the lower temperature side was read.

[0156] <Measurement of Thickness of Foam Sheet> The thickness of the foam sheet in the width direction (TD direction) was measured at 9 equally spaced points in the width direction, excluding 20 mm strips at both ends, using a dial thickness gauge SM-112 (manufactured by Teclock), and the arithmetic mean of the measured values ​​was taken as the thickness of the foam sheet.

[0157] <Measurement of Basis Weight of Foam Sheet> Six 10 cm x 10 cm pieces were cut out of the foam sheet at equal intervals in the width direction (TD direction), excluding 20 mm from both ends, and the mass (g) of each piece was measured to the nearest 0.001 g. The average mass (g) of each piece was calculated as 1 m 2 The value converted into the mass per unit area is used as the basis weight (g / m) of the foam sheet. 2 )

[0158] <Measurement of apparent density> The apparent density was measured by the method described in JIS K7222:1999 "Foamed plastics and rubber - Measurement of apparent density". Specifically, it was measured by the following method. A 100 cm 3 The above samples were cut without changing the original cell structure, and the samples were conditioned for 16 hours under a grade 2 environment, JIS K7100:1999, symbol 23 / 50. After that, the dimensions and mass were measured, and the density was calculated using the following formula: Apparent density (kg / m 3 ) = mass of sample (kg) / volume of sample (m 3 The dimensions of the samples were measured using a "DIGIMATIC" CD-15 type manufactured by Mitutoyo Corporation.

[0159] <Measurement of Expansion Ratio> The expansion ratio of the biodegradable polyester resin foam sheet was determined by determining the apparent density (ρ1) of the biodegradable polyester resin foam sheet, determining the density (true density: ρ0) of the resin composition constituting the biodegradable polyester resin foam sheet, and dividing the true density (ρ0) by the apparent density (ρ1). Expansion Ratio = True Density (ρ0) / Apparent Density (ρ1). The density of the biodegradable polyester resin foam sheet can be determined by the method described in JIS-K7222:1999 "Foamed Plastics and Rubber - Measurement of Apparent Density", and specifically, was determined by the following method. (Density Measurement Method) A 100 cm 3 The above samples were cut without changing the original cell structure, and the samples were conditioned for 16 hours under a grade 2 environment, JIS K7100:1999, symbol 23 / 50. After that, the dimensions and mass were measured, and the density was calculated using the following formula: Apparent density (kg / m 3) = mass of sample (kg) / volume of sample (m 3 The dimensions of the samples were measured using a "DIGIMATIC" CD-15 type manufactured by Mitutoyo Corporation. The density of the resin composition constituting the biodegradable polyester resin foam sheet was determined by measuring a sample that had been made non-foam by, for example, heat pressing the biodegradable polyester resin foam sheet, based on the Archimedes method (a submerged weighing method in accordance with JIS-K8807:2012 "Methods for determining density and specific gravity of solids").

[0160] <Measurement of open cell ratio> A number of sheet-like samples measuring 25 mm in length and 25 mm in width were cut out from the foam sheet, and the cut-out samples were stacked together without leaving any gaps to form a measurement sample with a thickness of 25 mm. The outer dimensions of this measurement sample were measured to 1 / 100 mm using a "Digimatic Caliper" manufactured by Mitutoyo Corporation, and the apparent volume (cm 3 Next, the volume (cm) of the measurement sample was determined by the 1-1 / 2-1 atmospheric pressure method using an air comparison type hydrometer Model 1000 (manufactured by Tokyo Science Co., Ltd.). 3 ) was determined. Using these determined values ​​and the following formula, the open cell rate (%) was calculated, and the average value for five tests was determined. The measurement was carried out under the same environment as JIS K7100-1999, Code 23 / 50, Class 2, after conditioning the measurement sample for 16 hours in the environment of JIS K7100-1999, Code 23 / 50, Class 2. The air comparison hydrometer was corrected using standard balls (large 28.9 cc, small 8.5 cc). Open cell rate (%) = [(apparent volume - volume measured by air comparison hydrometer) / apparent volume] x 100 (%)

[0161] [Production Example 1] Polylactic acid resin (manufactured by Nature Works LLC, "Biopolymer Ingeo 6202D", MFR = 11.2 g / 10 min, density = 1240 kg / m 3The moisture content of the resulting polylactic acid resin was adjusted to 0.02% by mass. 100 parts by mass of this polylactic acid resin with a moisture content of 0.02% by mass and 0.5 parts by mass of t-butylperoxyisopropyl monocarbonate (manufactured by Kayaku Nouryon Co., Ltd., "Trigonox BPIC-75", 1-minute half-life temperature T1 = 158.8°C) were mixed and stirred in a ribbon blender to obtain a mixture. The resulting mixture was fed into a twin-screw extruder (L / D = 31.5) with a diameter of 57 mm. The feed section was set to a temperature of 170°C, and the subsequent temperatures were set to 200°C, and the mixture was melt-kneaded in the twin-screw extruder at a rotation speed of 100 rpm. The kneaded mixture was then extruded into strands at a discharge rate of 50 kg / hour from a die (diameter φ3 mm, number of holes 18) attached to the tip of the extruder. The extruded strand-like kneaded material was then cooled by passing it through a 2 m long cooling water tank containing water at 30 ° C. The cooled strand was cut and pelletized using a pelletizer, and then dried in a dehumidifying dryer at a drying temperature of 70 ° C. The moisture content of the pellets of the obtained modified polylactic acid resin (1) was 0.02 mass%. The physical properties of the obtained modified polylactic acid resin (1) are shown in Tables 1 and 2.

[0162] [Production Example 2] Polylactic acid resin (trade name "FY602", manufactured by Anhui Fengyuan Fort Laiju Lactic Acid Co., Ltd., MFR = 16.0 g / 10 min, D-form ratio = 2.0 ± 0.5 mol%, melting point = 164.3°C, density = 1240 kg / m 3The moisture content of the resulting polylactic acid resin was adjusted to 0.04% by mass. 100 parts by mass of this polylactic acid resin with a moisture content of 0.04% by mass and 0.5 parts by mass of t-butylperoxyisopropyl monocarbonate (manufactured by Kayaku Nouryon Co., Ltd., "Trigonox BPIC-75", 1-minute half-life temperature T1 = 158.8°C) were mixed and stirred in a ribbon blender to obtain a mixture. The resulting mixture was fed into a twin-screw extruder (L / D = 31.5) with a diameter of 57 mm. The feed section was set to a temperature of 170°C, the temperature thereafter to 200°C, and the mixture was melt-kneaded in the twin-screw extruder at a rotation speed of 100 rpm. The kneaded mixture was then extruded into strands at a discharge rate of 50 kg / hour from a die (diameter φ3 mm, number of holes 18) attached to the tip of the extruder. The extruded strand-like kneaded material was then cooled by passing it through a 2 m long cooling water tank containing water at 30 ° C. The cooled strand was cut and pelletized using a pelletizer, and then dried in a dehumidifying dryer at a drying temperature of 70 ° C. The moisture content of the pellets of the obtained modified polylactic acid resin (2) was 0.03 mass%. The physical properties of the obtained modified polylactic acid resin (2) are shown in Tables 1 and 2.

[0163]

[0164]

[0165] [Production Example 3] 100 parts by mass of the modified polylactic acid resin (1) (moisture content: 0.02% by mass) obtained in Production Example 1 and 1.0 parts by mass of a cell regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.) were dry blended to prepare a mixture. In a tandem extruder equipped with a first extruder (upstream side) having a diameter of φ50 mm and a second extruder (downstream side) having a diameter of φ65 mm, the mixture was fed through a hopper to the first extruder having a diameter of φ50 mm and heated and melted at 220 ° C. In addition, in order to confirm whether the moisture content of the modified polylactic acid resin (1) changes between the preparation of the modified polylactic acid resin (1) and the supply to the hopper, separately, when only the modified polylactic acid resin (1) was supplied to the first extruder through the hopper, the moisture content of the modified polylactic acid resin (1) collected in the hopper was confirmed to be 0.02% by mass. Subsequently, 1.2 parts by mass of butane (isobutane / normal butane = 35% by mass / 65% by mass) as a foaming agent was pressure-fed into the first extruder and melt-kneaded with the above mixture. The melt-kneaded mixture was then transferred to a second extruder with a φ65 mm diameter and cooled to 170°C. Afterwards, it was extruded through a circular die with a φ70 mm diameter at a discharge rate of 30 kg / hour to obtain a cylindrical foam. The obtained cylindrical foam was placed on a φ206 mm mandrel whose interior was cooled with water at approximately 20°C, and cooled and molded by blowing air onto its outer surface using an air ring larger than the diameter of the mandrel. The foam was then cut at one point on the circumference with a cutter to obtain a strip-shaped polylactic acid resin foam sheet (1). The physical properties of the obtained polylactic acid resin foam sheet (1) are shown in Table 3.

[0166] [Production Example 4] 100 parts by mass of the modified polylactic acid resin (2) (moisture content: 0.03% by mass) obtained in Production Example 2 and 1.0 parts by mass of a cell regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.) were dry blended to prepare a mixture. In a tandem extruder equipped with a first extruder (upstream) having a diameter of φ50 mm and a second extruder (downstream) having a diameter of φ65 mm, the mixture was fed through a hopper to the first extruder having a diameter of φ50 mm and heated to melt at 220 ° C. In addition, in order to confirm whether the moisture content of the modified polylactic acid resin (2) changes between the preparation of the modified polylactic acid resin (2) and the feeding to the hopper, separately, when only the modified polylactic acid resin (2) was fed to the first extruder through the hopper, the moisture content of the modified polylactic acid resin (2) collected in the hopper was confirmed to be 0.02% by mass. Subsequently, 1.2 parts by mass of butane (isobutane / normal butane = 35% by mass / 65% by mass) as a foaming agent was pressure-fed into the first extruder and melt-kneaded with the above mixture. The melt-kneaded mixture was then transferred to a second extruder with a φ65 mm diameter and cooled to 170°C. Afterwards, it was extruded through a circular die with a φ70 mm diameter at a discharge rate of 30 kg / hour to obtain a cylindrical foam. The obtained cylindrical foam was placed on a φ206 mm mandrel whose interior was cooled with water at approximately 20°C, and cooled and molded by blowing air onto its outer surface using an air ring larger than the diameter of the mandrel. The foam was then cut open at one point on the circumference to obtain a strip-shaped polylactic acid resin foam sheet (2). The physical properties of the obtained polylactic acid resin foam sheet (2) are shown in Table 3.

[0167] [Production Example 5] A modified polylactic acid resin was produced in the same manner as in Production Example 2, but the resulting modified polylactic acid resin (3) had a moisture content of 0.16% by mass due to insufficient drying. Using this modified polylactic acid resin (3), a polylactic acid resin foam sheet (3) was obtained in the same manner as in Production Example 4. The physical properties of the resulting polylactic acid resin foam sheet (3) are shown in Table 3.

[0168] [Production Example 6] A modified polylactic acid resin was produced in the same manner as in Production Example 2, but the resulting modified polylactic acid resin (4) had a moisture content of 0.28% by mass due to insufficient drying. Using this modified polylactic acid resin (4), a polylactic acid resin foam sheet (4) was obtained in the same manner as in Production Example 4. The physical properties of the resulting polylactic acid resin foam sheet (4) are shown in Table 3.

[0169] [Production Example 7] A modified polylactic acid resin was produced in the same manner as in Production Example 2, but the resulting modified polylactic acid resin (5) had a moisture content of 0.37% by mass due to insufficient drying. An attempt was made to obtain a polylactic acid resin foam sheet using this modified polylactic acid resin (5) in the same manner as in Production Example 4, but molten resin was discharged from the circular die, and a foam sheet could not be obtained. The results are shown in Table 3.

[0170]

[0171] [Example 1] The polylactic acid resin foam sheet (1) obtained in Production Example 3 was used as a recycled raw material. This was pulverized into a pulverized material and fed into a twin-screw extruder (L / D = 31.5) with a diameter of 57 mm. The feed section temperature was set to 170 °C, the temperature thereafter to 200 °C, and the rotation speed was 100 rpm. The pulverized material was melt-kneaded in the twin-screw extruder, and the kneaded material was extruded into strands at a throughput of 50 kg / hour from a die (diameter φ3 mm, number of holes 18) attached to the tip of the extruder. The extruded strand-like kneaded material was then passed through a 2 m long cooling water tank containing water at 30 °C and cooled. The cooled strands were cut and pelletized using a pelletizer, and subsequently dried in a dehumidifying dryer at a drying temperature of 70 °C. The moisture content of the resulting recycled polylactic acid resin (1) was 0.04% by mass. The physical properties of the resulting recycled polylactic acid resin (1) are shown in Table 4.

[0172] [Example 2] The polylactic acid resin foam sheet (2) obtained in Production Example 4 was used as a recycled raw material. This was pulverized into a pulverized material and fed into a twin-screw extruder (L / D = 31.5) with a diameter of 57 mm. The feed section temperature was set to 170°C, the temperature thereafter to 200°C, and the rotation speed was 100 rpm. The pulverized material was melt-kneaded in the twin-screw extruder, and the kneaded material was extruded into strands at a throughput of 50 kg / hour from a die (diameter φ3 mm, number of holes 18) attached to the tip of the extruder. The extruded strand-like kneaded material was then passed through a 2-m-long cooling water tank containing water at 30°C and cooled. The cooled strands were cut and pelletized using a pelletizer, and subsequently dried in a dehumidifying dryer at a drying temperature of 70°C. The moisture content of the resulting recycled polylactic acid resin (2) was 0.03% by mass. The physical properties of the resulting recycled polylactic acid resin (2) are shown in Table 4.

[0173] [Example 3] The polylactic acid resin foam sheet (3) obtained in Production Example 5 was used as a recycled raw material. This was pulverized into a pulverized material and fed into a twin-screw extruder (L / D = 31.5) with a diameter of 57 mm. The feed section temperature was set to 170°C, the temperature thereafter to 200°C, and the rotation speed was 100 rpm. The pulverized material was melt-kneaded in the twin-screw extruder, and the kneaded material was extruded into strands at a throughput of 50 kg / hour from a die (diameter φ3 mm, number of holes 18) attached to the tip of the extruder. The extruded strand-like kneaded material was then passed through a 2-m-long cooling water tank containing water at 30°C and cooled. The cooled strands were cut and pelletized using a pelletizer, and subsequently dried in a dehumidifying dryer at a drying temperature of 70°C. The moisture content of the resulting recycled polylactic acid resin (3) was 0.04% by mass. The physical properties of the resulting recycled polylactic acid resin (3) are shown in Table 4.

[0174] Comparative Example 1: The polylactic acid resin foam sheet (4) obtained in Production Example 6 was used as a recycled raw material. This was pulverized into a pulverized material and fed into a twin-screw extruder (L / D = 31.5) with a diameter of 57 mm. The feed section temperature was set to 170°C, the temperature thereafter to 200°C, and the rotation speed was 100 rpm. The pulverized material was melt-kneaded in the twin-screw extruder, and the kneaded material was extruded into strands at a throughput of 50 kg / hour from a die (diameter φ3 mm, number of holes 18) attached to the tip of the extruder. The extruded strand-like kneaded material was then cooled by passing it through a 2-m-long cooling water tank containing water at 30°C. The cooled strands were cut and pelletized using a pelletizer, and subsequently dried in a dehumidifying dryer at a drying temperature of 70°C. The moisture content of the resulting recycled polylactic acid resin (4) was 0.03% by mass. The physical properties of the obtained recycled polylactic acid resin (4) are shown in Table 4. The melt tension was below the lower limit (1 cN) of the measurable range and could not be measured.

[0175]

[0176] Example 4 A mixture was prepared by dry blending 100 parts by weight of the recycled polylactic acid resin (1) (moisture content: 0.04% by weight) obtained in Example 1 with 1.0 parts by weight of a cell regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.). A tandem extruder equipped with a first extruder (upstream) with a diameter of 50 mm and a second extruder (downstream) with a diameter of 65 mm was used. The mixture was fed through a hopper to the first extruder with a diameter of 50 mm and heated to 220°C for melting. To confirm whether the moisture content of the recycled polylactic acid resin (1) changed between the preparation and feeding to the hopper, the recycled polylactic acid resin (1) alone was separately fed to the first extruder through the hopper. The moisture content of the recycled polylactic acid resin (1) collected in the hopper was measured and found to remain at 0.04% by weight. Subsequently, 1.2 parts by mass of butane (isobutane / normal butane = 35% by mass / 65% by mass) as a foaming agent was pressure-fed into the first extruder and melt-kneaded with the above mixture. The melt-kneaded mixture was then transferred to a second extruder with a φ65 mm diameter and cooled to 170°C. Afterwards, it was extruded through a circular die with a φ70 mm diameter at a discharge rate of 30 kg / hour to obtain a cylindrical foam. The obtained cylindrical foam was placed on a φ206 mm mandrel whose interior was cooled with water at approximately 20°C, and its outer surface was cooled by blowing air through an air ring larger than the diameter of the mandrel to form a cooled foam. The foam was then cut open at one point on the circumference to obtain a strip-shaped recycled polylactic acid resin foam sheet (1). The physical properties of the obtained recycled polylactic acid resin foam sheet (1) are shown in Table 5.

[0177] Example 5: 100 parts by weight of the recycled polylactic acid resin (2) (moisture content: 0.03% by weight) obtained in Example 2 and 1.0 part by weight of a cell regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.) were dry-blended to prepare a mixture. In a tandem extruder equipped with a first extruder (upstream) with a diameter of 50 mm and a second extruder (downstream) with a diameter of 65 mm, the mixture was fed through a hopper to the first extruder with a diameter of 50 mm and heated to melt at 220°C. To confirm whether the moisture content of the recycled polylactic acid resin (2) changed between the preparation and feeding to the hopper, the recycled polylactic acid resin (2) alone was separately fed to the first extruder through the hopper. The moisture content of the recycled polylactic acid resin (2) collected in the hopper was measured and found to remain at 0.03% by weight. Subsequently, 1.2 parts by mass of butane (isobutane / normal butane = 35% by mass / 65% by mass) as a foaming agent was pressure-fed into the first extruder and melt-kneaded with the above mixture. The melt-kneaded mixture was then transferred to a second extruder with a φ65 mm diameter and cooled to 170°C. Afterwards, it was extruded through a circular die with a φ70 mm diameter at a discharge rate of 30 kg / hour to obtain a cylindrical foam. The obtained cylindrical foam was placed on a φ206 mm mandrel whose interior was cooled with water at approximately 20°C, and its outer surface was cooled and molded by blowing air through an air ring larger than the diameter of the mandrel. The foam was then cut open at one point on the circumference to obtain a strip-shaped recycled polylactic acid resin foam sheet (2). The physical properties of the obtained recycled polylactic acid resin foam sheet (2) are shown in Table 5.

[0178] Example 6 A mixture was prepared by dry blending 100 parts by weight of the recycled polylactic acid resin (3) (moisture content: 0.04% by weight) obtained in Example 3 with 1.0 part by weight of a cell regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.). A tandem extruder equipped with a first extruder (upstream) with a diameter of 50 mm and a second extruder (downstream) with a diameter of 65 mm was used. The mixture was fed through a hopper into the first extruder with a diameter of 50 mm and heated to 220°C for melting. To confirm whether the moisture content of the recycled polylactic acid resin (3) changed between its preparation and its feeding into the hopper, the recycled polylactic acid resin (3) alone was separately fed into the first extruder through the hopper. The moisture content of the recycled polylactic acid resin (3) collected in the hopper was measured and found to remain at 0.04% by weight. Subsequently, 1.2 parts by mass of butane (isobutane / normal butane = 35% by mass / 65% by mass) as a blowing agent was pressure-fed into the first extruder and melt-kneaded with the above mixture. The melt-kneaded mixture was then transferred to a second extruder with a φ65 mm diameter and cooled to 170°C. Afterwards, it was extruded through a circular die with a φ70 mm diameter at a discharge rate of 30 kg / hour to obtain a cylindrical foam. The obtained cylindrical foam was placed on a φ206 mm mandrel whose interior was cooled with water at approximately 20°C, and its outer surface was cooled and molded by blowing air through an air ring larger than the diameter of the mandrel. The foam was then cut open at one point on the circumference to obtain a strip-shaped recycled polylactic acid resin foam sheet (3). The physical properties of the obtained recycled polylactic acid resin foam sheet (3) are shown in Table 5.

[0179] Comparative Example 2: 100 parts by mass of the recycled polylactic acid resin (4) (moisture content: 0.03% by mass) obtained in Comparative Example 1 and 1.0 part by mass of a cell regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.) were dry-blended to prepare a mixture. In a tandem extruder equipped with a first extruder (upstream) with a diameter of 50 mm and a second extruder (downstream) with a diameter of 65 mm, the mixture was fed through a hopper to the first extruder with a diameter of 50 mm and heated to melt at 220°C. To confirm whether the moisture content of the recycled polylactic acid resin (4) changed between the preparation and feeding to the hopper, the recycled polylactic acid resin (4) alone was separately fed to the first extruder through the hopper. The moisture content of the recycled polylactic acid resin (4) collected in the hopper was measured and found to remain at 0.03% by mass. Then, 1.2 parts by mass of butane (isobutane / normal butane = 35% by mass / 65% by mass) was pressurized into the first extruder as a foaming agent and melt-kneaded with the above mixture. The melt-kneaded mixture was then transferred to a second extruder with a diameter of 65 mm and cooled to 170°C. An attempt was made to extrude and foam through a circular die with a diameter of 70 mm at a discharge rate of 30 kg / hour, but the molten resin was discharged from the circular die, and a foamed sheet could not be obtained. The results are shown in Table 5.

[0180]

[0181] As shown in Table 5, the recycled polylactic acid resin foam sheet (1) obtained using the recycled polylactic acid resin (1) obtained in Example 1, the recycled polylactic acid resin foam sheet (2) obtained using the recycled polylactic acid resin (2) obtained in Example 2, and the recycled polylactic acid resin foam sheet (3) obtained using the recycled polylactic acid resin (3) obtained in Example 3 all exhibited sufficient expansion ratios despite the use of recycled raw materials, and also exhibited low open cell ratios despite the use of recycled raw materials. Therefore, the recycled polylactic acid resin foam sheet (1) obtained using the recycled polylactic acid resin (1) obtained in Example 1, the recycled polylactic acid resin foam sheet (2) obtained using the recycled polylactic acid resin (2) obtained in Example 2, and the recycled polylactic acid resin foam sheet (3) obtained using the recycled polylactic acid resin (3) obtained in Example 3 all exhibited suppressed deterioration in foaming performance when made into foam sheets, despite the use of recycled raw materials, and can be said to be useful in recycling systems for producing recycled biodegradable polyester resin foam sheets and recycled biodegradable polyester resin foam molded articles with excellent foaming properties. In particular, the recycled biodegradable polyester resin according to an embodiment of the present invention has a very low melt tension as shown in Table 4, and a person skilled in the art would have conventionally determined that it would be impossible to form a foamed sheet with sufficient foaming properties. However, it has been found that the recycled biodegradable polyester resin according to an embodiment of the present invention can achieve excellent strain hardening properties, and can form a recycled biodegradable polyester resin foamed sheet with excellent foaming properties.

[0182] The recycled biodegradable polyester resin according to the embodiment of the present invention can be advantageously used in a recycling system for producing a recycled biodegradable polyester resin foam sheet or a recycled biodegradable polyester resin foam molded article having excellent foaming properties.

Claims

1. A recycled biodegradable polyester resin made from biodegradable polyester resin foam as a recycled raw material, wherein in a graph obtained by uniaxial extensional viscosity measurement of the recycled biodegradable polyester resin at 160°C, the horizontal axis represents the logarithm of the amount of strain ε and the vertical axis represents the logarithm of the extensional viscosity η (Pa·s), the slope a2 of the graph in the direction from the inflection point toward increasing amount of strain is 0.30 (Pa·s) or more.

2. The recycled biodegradable polyester resin according to claim 1, wherein the biodegradable polyester resin foam is produced by melt-kneading and extruding a resin composition containing the biodegradable polyester resin in an extruder.

3. The recycled biodegradable polyester resin according to claim 2, wherein the ratio (a2 / a1) of the slope a2 (Pa·s) of the graph in the direction from the inflection point toward increasing strain in a graph having the logarithm of the strain amount ε on the horizontal axis and the logarithm of the extensional viscosity η (Pa·s) on the vertical axis, obtained by uniaxial extensional viscosity measurement of the biodegradable polyester resin at 160°C, to the slope a1 (Pa·s) of the graph is 0.10 or more.

4. The recycled biodegradable polyester resin according to claim 2, wherein the biodegradable polyester resin is a polylactic acid resin (P).

5. The recycled biodegradable polyester resin according to claim 4, wherein the polylactic acid resin (P) is a modified polylactic acid resin.

6. The recycled biodegradable polyester resin according to claim 1, wherein the recycled biodegradable polyester resin is obtained by melt-kneading a raw material composition containing the biodegradable polyester resin foam in an extruder and pelletizing the extruded mixture.

7. The recycled biodegradable polyester resin of claim 1, wherein the recycled biodegradable polyester resin is a biodegradable polyester resin foam.

8. The Z-average molecular weight (M Z 2. The recycled biodegradable polyester resin according to claim 1, wherein the molecular weight of the polyester resin is 300,000 or more.

9. The recycled biodegradable polyester resin according to claim 1, wherein the MFR of the recycled biodegradable polyester resin is 15 g / 10 min or less.

10. The recycled biodegradable polyester resin according to claim 1, wherein the recycled biodegradable polyester resin has a melt tension of 1 cN or more at 190°C.

11. A recycled biodegradable polyester resin foam sheet obtained by foaming a recycled resin composition containing the recycled biodegradable polyester resin according to any one of claims 1 to 10.

12. The recycled biodegradable polyester resin foam sheet according to claim 11, wherein in a graph obtained by uniaxial extensional viscosity measurement of the recycled biodegradable polyester resin foam sheet at 160°C, the horizontal axis represents the logarithm of the amount of strain ε and the vertical axis represents the logarithm of the extensional viscosity η (Pa·s), the slope a3 of the graph in the direction from the inflection point toward increasing amount of strain is 0.30 (Pa·s) or more.

13. The recycled biodegradable polyester resin foam sheet according to claim 11, having a thickness of 0.5 mm to 7 mm.

14. Basis weight: 50g / m 2 Up to 600 g / m 2 The recycled biodegradable polyester resin foam sheet according to claim 11, 15. The recycled biodegradable polyester resin foam sheet according to claim 11, having an expansion ratio of 4 to 20 times.

16. The recycled biodegradable polyester resin foam sheet according to claim 11, having an open cell ratio of 50% or less.

17. A recycled biodegradable polyester resin foam molded product obtained by molding the recycled biodegradable polyester resin foam sheet according to claim 11.

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