Polylactic acid resin foam sheet and polylactic acid resin foam molded body

Abstract

The present invention provides a polylactic acid resin foam sheet with excellent foaming and moldability properties, and also provides a polylactic acid resin foam molded article obtained by molding such a polylactic acid resin foam sheet. [Solution] The polylactic acid resin foam sheet according to an embodiment of the present invention is a polylactic acid resin foam sheet obtained by foaming a polylactic acid resin composition containing polylactic acid resin (P), wherein the breaking point velocity is 45.0 m / min or more and 170.0 m / min or less.

Description

[Technical Field]

[0001] This invention relates to polylactic acid resin foam sheets and polylactic acid resin foam molded articles. [Background technology]

[0002] Because resin foam sheets are lightweight, have excellent cushioning properties, and are easy to mold into various shapes, they are used as raw materials for various molded products, including packaging materials.

[0003] In recent years, foamed resin sheets have been used in large quantities and then discarded in large quantities, placing a significant burden on the environment and contributing to various social problems such as global warming, resource depletion, and waste disposal. Therefore, foamed sheets and foamed molded articles using biodegradable polyester resins such as polylactic acid resin, which are biodegradable, have a low environmental impact, and can be manufactured relatively inexpensively, have been proposed (for example, Patent Document 1).

[0004] Conventional polylactic acid resin foam sheets undergo resin modification using organic peroxides or other substances to impart foaming properties to the polylactic acid resin. However, this modification increases the resin viscosity, resulting in poor resin elongation, making the air bubbles more prone to bursting during foaming, and leading to a decrease in the open-cell ratio. Additionally, moldability tends to deteriorate. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6971947 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a polylactic acid resin foam sheet with excellent foaming properties and moldability. Furthermore, it is also to provide a polylactic acid resin foam molded article obtained by molding such a polylactic acid resin foam sheet. [Means for solving the problem]

[0007] [1] The polylactic acid resin foam sheet according to the embodiment of the present invention is A foamed polylactic acid resin sheet obtained by foaming a polylactic acid resin composition containing polylactic acid resin (P), The fracture velocity is between 45.0 m / min and 170.0 m / min. [2] The polylactic acid resin foam sheet described in [1] above may contain modified polylactic acid resin and unmodified polylactic acid resin. [3] In the polylactic acid resin foam sheet described in [2] above, when the total amount of the unmodified polylactic acid resin and the modified polylactic acid resin is 100 parts by mass, the content of the unmodified polylactic acid resin may be 15 to 85 parts by mass. [4] The polylactic acid resin foam sheet described in any one of the above items [1] to [3] may have a melt mass flow rate (MFR) of 4.5 g / 10 min or more. [5] The polylactic acid resin foam sheet described in any one of the above items [1] to [4] may have a melt tension of 12.0 cN or less. [6] The polylactic acid resin foam sheet described in any one of the above items [1] to [5] may have an open-cell ratio of 35% or less. [7] The polylactic acid resin foam sheet described in any one of the above items [1] to [6] may have a foaming ratio of 5.0 times or more. [8] A polylactic acid resin foam molded article according to an embodiment of the present invention is obtained by molding a polylactic acid resin foam sheet described in any one of the above [1] to [7]. [9] A method for producing a polylactic acid resin foam sheet according to an embodiment of the present invention is a method for producing a polylactic acid resin foam sheet by melt-kneading polylactic acid resin (P) with a foaming agent in an extruder and extruding foam, The above-mentioned polylactic acid resin (P) contains a modified polylactic acid resin and an unmodified polylactic acid resin, when the total amount of the above-mentioned unmodified polylactic acid resin and the above-mentioned modified polylactic acid resin is 100 parts by mass, the content of the above-mentioned unmodified polylactic acid resin is 15 parts by mass to 85 parts by mass.

Effect of the Invention

[0008] According to an embodiment of the present invention, a polylactic acid resin foam sheet excellent in foaming properties and moldability can be provided. Further, a polylactic acid resin foam molded body obtained by molding such a polylactic acid resin foam sheet can be provided.

Brief Description of the Drawings

[0009] [Figure 1] It is a schematic diagram showing one preferred configuration of an extruder used in a method for producing a modified polylactic acid resin. [Figure 2] It is a schematic diagram showing one preferred configuration of a manufacturing apparatus suitable for manufacturing a polylactic acid resin foam sheet according to an embodiment of the present invention. [Figure 3] It is a photograph of a molded product of one test piece in the evaluation of the moldability of the polylactic acid resin foam sheet of Example 4. [Figure 4] It is a photograph of a molded product of one test piece in the evaluation of the moldability of the polylactic acid resin foam sheet of Comparative Example 1.

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0011] ≪≪Polylactic Acid Resin Foam Sheet≫≫ The polylactic acid resin foam sheet according to an embodiment of the present invention is a polylactic acid resin foam sheet formed by foaming a polylactic acid resin composition containing a polylactic acid resin (P), and the breaking point speed is 45.0 m / min or more and 170.0 m / min or less.

[0012] The polylactic acid resin foam sheet according to the embodiment of the present invention achieves both excellent foaming properties and moldability because the breaking point velocity is within the above range. Here, excellent foaming properties in the present invention refer to, for example, a high foaming ratio and resistance to bubble bursting during foaming. Therefore, the polylactic acid resin foam sheet according to the embodiment of the present invention does not easily have a high open-cell ratio due to its excellent foaming properties. Consequently, the polylactic acid resin foam sheet according to the embodiment of the present invention can have a significantly more beautiful appearance than conventional polylactic acid resin foam molded articles because the breaking point velocity is within the above range.

[0013] If the breaking point velocity of the polylactic acid resin foam sheet is too low and outside the above range, the sheet may not expand well when heated, potentially resulting in poor moldability. Furthermore, the open-cell ratio may increase, potentially leading to a poor appearance of the molded product. If the breaking point velocity of the polylactic acid resin foam sheet is too high and outside the above range, the foaming ratio may decrease. Furthermore, the open-cell ratio may increase, potentially leading to a poor appearance of the molded product. The method for measuring the breaking point velocity of the polylactic acid resin foam sheet will be described later.

[0014] As a result of extensive research, the inventors of the present invention have found that polylactic acid resin foam sheets exhibit excellent moldability because their breaking point velocity falls within the above range, and furthermore, that polylactic acid resin foam sheets with a breaking point velocity within the above range can be obtained by foaming a polylactic acid resin composition having a resin viscosity suitable for preventing air bubbles from bursting during foaming and for achieving a sufficient foaming ratio, i.e., they also exhibit excellent foaming properties, thus completing the present invention.

[0015] The polylactic acid resin foam sheet according to the embodiment of the present invention exhibits the effects of the present invention more effectively, and its breaking point velocity is preferably 48.0 m / min to 170.0 m / min, more preferably 50.0 m / min to 165.0 m / min, even more preferably 53.0 m / min to 165.0 m / min, particularly preferably 55.0 m / min to 160.0 m / min, and most preferably 58.0 m / min to 155.0 m / min.

[0016] The polylactic acid resin foam sheet according to the embodiments of the present invention exhibits the effects of the present invention more effectively when its melt mass flow rate (MFR) is preferably 4.5 g / 10 min or more, more preferably 5.0 g / 10 min or more, even more preferably 5.5 g / 10 min or more, particularly preferably 6.0 g / 10 min or more, and most preferably 6.5 g / 10 min or more. The upper limit of the MFR of the polylactic acid resin foam sheet according to the embodiments of the present invention is not particularly limited, but is, for example, 25.0 g / 10 min or less, and preferably 20.0 g / 10 min or less. The method for measuring the MFR of the polylactic acid resin foam sheet will be described later.

[0017] The polylactic acid resin foam sheet according to the embodiment of the present invention preferably has a melt tension of 12.0 cN or less, more preferably 10.0 cN or less, even more preferably 9.0 cN or less, even more preferably 8.5 cN or less, particularly preferably 8.0 cN or less, and most preferably 7.0 cN or less, in order to better exhibit the effects of the present invention. The lower limit of the melt tension of the polylactic acid resin foam sheet according to the embodiment of the present invention is not particularly limited, but is, for example, 0.5 cN or more, preferably 1.0 cN or more, and more preferably 1.5 cN or more. The method for measuring the melt tension of the polylactic acid resin foam sheet will be described later.

[0018] The open-cell ratio of the polylactic acid resin foam sheet according to the embodiment of the present invention is preferably 35% or less, more preferably 33% or less, even more preferably 30% or less, even more preferably 27% or less, particularly preferably 25% or less, and most preferably 20% or less. The lower limit of the open-cell ratio is better the lower it is, preferably 0% or more. If the open-cell ratio of the polylactic acid resin foam sheet according to the embodiment of the present invention is within the above range, the effects of the present invention can be more fully realized. Furthermore, a polylactic acid resin foam molded article with a beautiful appearance can be obtained. The method for measuring the open-cell ratio will be described later.

[0019] The foaming ratio of the polylactic acid resin foam sheet according to the embodiments of the present invention is preferably 5.0 times or more, more preferably 5.0 to 20.0 times, even more preferably 6.0 to 15.0 times, particularly preferably 6.5 to 12.0 times, and most preferably 7.0 to 10.0 times, in order to better exhibit the effects of the present invention. The method for measuring the foaming ratio will be described later.

[0020] The thickness of the polylactic acid resin foam sheet according to the embodiment of the present invention is preferably 1.00 mm to 10.00 mm, more preferably 1.20 mm to 7.00 mm, even more preferably 1.30 mm to 5.00 mm, particularly preferably 1.40 mm to 3.00 mm, and most preferably 1.50 mm to 2.50 mm, in order to better exhibit the effects of the present invention. The method for measuring the thickness will be described later.

[0021] The basis weight of the polylactic acid resin foam sheet according to the embodiments of the present invention is preferably 100 g / m², in order to better exhibit the effects of the present invention. 2 ~500g / m 2 More preferably 150 g / m² 2 ~450g / m 2 And more preferably 200 g / m² 2 ~400g / m 2 The most preferred amount is 250 g / m². 2 ~350g / m 2 The method for measuring basis weight will be described later.

[0022] In order to better demonstrate the effects of the present invention, in the polylactic acid resin foam sheet according to the embodiment of the present invention, it is preferable that the polylactic acid resin (P) contains both modified polylactic acid resin and unmodified polylactic acid resin. In this case, the content of unmodified polylactic acid resin is preferably 15 to 85 parts by mass, and more preferably 20 to 80 parts by mass, when the total amount of unmodified polylactic acid resin and modified polylactic acid resin is 100 parts by mass.

[0023] In other words, the polylactic acid resin foam sheet according to the embodiment of the present invention may be manufactured by a preferred embodiment of the method for manufacturing the polylactic acid resin foam sheet described below, in that it can better exhibit the effects of the present invention.

[0024] Manufacturing of polylactic acid resin foam sheets Polylactic acid resin foam sheets according to embodiments of the present invention can be manufactured by any suitable method without impairing the effects of the present invention. Such polylactic acid resin foam sheets can preferably be manufactured by foaming a polylactic acid resin composition containing a polylactic acid resin (P) which includes a modified polylactic acid resin and an unmodified polylactic acid resin. The polylactic acid resin (P) is preferably a mixture of a modified polylactic acid resin and an unmodified polylactic acid resin. More specifically, polylactic acid resin foam sheets can be manufactured by melt-kneading the polylactic acid resin (P) with a foaming agent in an extruder and then extruding and foaming it.

[0025] "Modified polylactic acid resin" refers to polylactic acid resin that has undergone modification treatment, typically the polylactic acid resin that has undergone the modification treatment described in the first step below. "Unmodified polylactic acid resin" refers to polylactic acid resin that has not undergone modification treatment, typically the polylactic acid resin that is generally available and has not undergone the modification treatment described in the first step below. In this specification, when "polylactic acid resin (P)" is not mentioned and only "polylactic acid resin" is mentioned, it means unmodified polylactic acid resin.

[0026] The following describes a method for producing polylactic acid resin foam sheets (sometimes referred to as the two-stage method) in which a polylactic acid resin (P) containing modified and unmodified polylactic acid resin is melt-kneaded with a foaming agent in an extruder and then extruded to foam it.

[0027] In the method for producing a polylactic acid resin foam sheet according to an embodiment of the present invention, a polylactic acid resin (P) containing a modified polylactic acid resin and an unmodified polylactic acid resin is melt-kneaded with a foaming agent in an extruder and then extruded to foam it.

[0028] The polylactic acid resin (P) is a mixture of modified polylactic acid resin and unmodified polylactic acid resin, and the content of the unmodified polylactic acid resin is preferably 15 to 85 parts by mass, more preferably 15 to 80 parts by mass, even more preferably 20 to 80 parts by mass, even more preferably 30 to 80 parts by mass, particularly preferably 30 to 75 parts by mass, and most preferably 30 to 70 parts by mass, when the total amount of unmodified polylactic acid resin and modified polylactic acid resin is 100 parts by mass. Therefore, the modified polylactic acid resin in the polylactic acid resin (P) is preferably 15 to 85 parts by mass, more preferably 20 to 85 parts by mass, even more preferably 20 to 80 parts by mass, even more preferably 20 to 70 parts by mass, particularly preferably 25 to 70 parts by mass, and most preferably 30 to 70 parts by mass.

[0029] The polylactic acid resin (P) is preferably a mixture obtained by mixing a modified polylactic acid resin and an unmodified polylactic acid resin, and more preferably a dry blend of a modified polylactic acid resin and an unmodified polylactic acid resin. Here, the modified polylactic acid resin is preferably obtained by melt-kneading composition C containing the polylactic acid resin and a modifier in an extruder.

[0030] Therefore, the method for producing a polylactic acid resin foam sheet according to an embodiment of the present invention preferably includes a first step of producing a modified polylactic acid resin by melt-kneading a composition C containing a polylactic acid resin and a modifier in an extruder; a second step of obtaining a polylactic acid resin (P) by mixing the modified polylactic acid resin and an unmodified polylactic acid resin; and a third step of producing a polylactic acid resin foam sheet by melt-kneading the polylactic acid resin (P) with a foaming agent in an extruder and extruding foaming it.

[0031] <1st process> In the first step, a composition C containing polylactic acid resin and a modifier is melt-kneaded in an extruder to produce a modified polylactic acid resin. The polylactic acid resin used as a raw material in the first step here preferably means an unmodified polylactic acid resin.

[0032] Polylactic acid resin may be a homopolymer of lactic acid or a copolymer of lactic acid and other monomers. Examples of other monomers include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polyhydric acids, and polyfunctional polysaccharides.

[0033] The lactic acid constituting the polylactic acid resin may be either the L-form or the D-form, or both. In other words, the polylactic acid resin, which is a homopolymer of lactic acid, may be poly(L-lactic acid) resin, poly(D-lactic acid) resin, or poly(DL-lactic acid) resin.

[0034] 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.

[0035] Examples of aliphatic polyhydric alcohols 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.

[0036] Examples of aliphatic polycarboxylic acids include oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, undecanediic acid, and dodecanediic acid. Furthermore, the aliphatic polycarboxylic acid may also be an acid anhydride.

[0037] Examples of polyfunctional polysaccharides include cellulose, cellulose nitrate, methylcellulose, ethylcellulose, celluloid, viscose rayon, regenerated cellulose, cellophane, cuprazole, copper ammonia rayon, cuprophane, Bemberg, hemicellol, starch, acropectin, dextrin, dextran, glycogen, pectin, chitin, chitosan, gum arabic, guar gum, locust bean gum, and acacia gum.

[0038] In polylactic acid resin, the content of structural parts derived from lactic acid (L- and D-forms) in the molecule 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.

[0039] The polylactic acid resin used as a raw material may be recycled in some respects.

[0040] In the first step, a modified polylactic acid resin is produced by using a modifier to increase the molecular weight of the polylactic acid resin or to give the polylactic acid resin crosslinked structures or long-chain branched structures in its molecular structure.

[0041] The modifier may be one type or two or more types. The amount of modifier used is preferably 0.1 to 2.0 parts by mass, more preferably 0.2 to 1.5 parts by mass, and even more preferably 0.3 to 1.0 parts by mass, per 100 parts by mass of polylactic acid resin, in order to better exhibit the effects of the present invention.

[0042] Radical initiators can be used as modifiers. By using radical initiators as modifiers, crosslinked structures and long-chain branched structures can be introduced into the molecular structure of the polylactic acid resin. In this case, the radical initiator is used to react the polylactic acid resins with each other. When polylactic acid resins are reacted with a radical initiator having appropriate reactivity, for example, the decomposition starting point of the polylactic acid resin in the extruder can be attacked by free radicals generated by the radical initiator, and that site can become a crosslinking point (branching point) and be stabilized. With such modification, the thermal stability of the polylactic acid resin increases and it becomes less likely to be reduced in molecular weight when passing through the extruder.

[0043] Examples of radical initiators include organic peroxides, azo compounds, and halogen molecules, with organic peroxides being preferred.

[0044] Examples of organic peroxides include peroxyesters, hydroperoxides, dialkylperoxides, diacylperoxides, peroxydicarbonates, peroxyketals, and ketoneperoxides.

[0045] Examples of peroxyesters include t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl carbonate, t-hexyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, t-hexyl peroxybenzoate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxyacetate, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane.

[0046] Examples of hydroperoxides include permethane hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide.

[0047] Examples of dialkyl peroxides include α,α-bis(t-butylperoxy)diisopropylbenzene, dicumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3.

[0048] Examples of diacyl peroxides include dibenzoyl peroxide, di(4-methylbenzoyl) peroxide, and di(3-methylbenzoyl) peroxide.

[0049] Examples of peroxydicarbonates include di(2-ethylhexyl)peroxydicarbonate and diisopropylperoxydicarbonate.

[0050] 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.

[0051] Examples of ketone peroxides include methyl ethyl ketone peroxide and acetylacetone peroxide.

[0052] Modification with organic peroxides may result in undesirable problems. For example, it may cause the modified polylactic acid resin to contain components with excessively high molecular weights that form a gel when heated and melted, or it may cause odor problems due to the decomposition residue of the organic peroxides. These issues may adversely affect the effectiveness of the present invention.

[0053] In order to suppress the occurrence of problems associated with modification by organic peroxides as described above, to easily modify the polylactic acid resin to a state suitable for foaming, and to provide a polylactic acid resin foam molded article that can better exhibit the effects of the present invention, one preferred embodiment of the organic peroxide is at least one selected from the group consisting of peroxyesters and dialkyl peroxides. In order to provide a polylactic acid resin foam molded article that can further exhibit the effects of the present invention, the peroxyester is more preferably a peroxycarbonate-based organic peroxide such as t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl carbonate, or t-hexyl peroxyisopropyl carbonate, and even more preferably t-butyl peroxyisopropyl carbonate. The dialkyl peroxide is more preferably α,α-bis(t-butylperoxy)diisopropylbenzene.

[0054] The above-mentioned organic peroxides can provide a polylactic acid resin foam molded article that can further exhibit the effects of the present invention, and the 1-minute half-life temperature is preferably 140°C to 190°C, more preferably 145°C to 185°C, even more preferably 150°C to 180°C, and particularly preferably 152°C to 178°C. In one preferred embodiment, the above 1-minute half-life temperature is preferably 140°C to 180°C, more preferably 145°C to 170°C, even more preferably 150°C to 160°C, and particularly preferably 150°C to 158°C.

[0055] The organic peroxides described above may be in liquid or solid (powder) form. However, from the viewpoint of uniform reactivity in the extruder and ease of handling, a liquid form is preferred.

[0056] The amount of organic peroxide used depends on its molecular weight and other factors, but in order to better exhibit the effects of the present invention, it is preferably 0.1 to 2.0 parts by mass, more preferably 0.2 to 1.5 parts by mass, and even more preferably 0.3 to 1.0 parts by mass, per 100 parts by mass of polylactic acid resin.

[0057] Chain extenders may be used as modifiers. In modification using chain extenders, compounds having one or more functional groups that can react with hydroxyl groups and carboxyl groups present in the molecular structure of polylactic acid resin, such as acrylic organic compounds, epoxy organic compounds, and isocyanate organic compounds, can be used.

[0058] Examples of chain elongators include Joncryl® ADR 4368 (manufactured by BASF), Joncryl® ADR 4468 (manufactured by BASF), Cardura® E10 (manufactured by Shell), and long-chain acrylates described in EP application No. 08166596.0.

[0059] When a chain extender is used as a modifier, the amount of chain extender used is preferably 0.1 to 2.0 parts by mass, more preferably 0.2 to 1.5 parts by mass, and even more preferably 0.3 to 1.0 parts by mass, per 100 parts by mass of polylactic acid resin, in order to better exhibit the effects of the present invention.

[0060] In the first step, composition C, which contains the polylactic acid resin and the modifier, may contain any suitable other components besides the polylactic acid resin and the modifier, as long as they do not impair the effects of the present invention. The total amount of the polylactic acid resin and the modifier in composition C is preferably 50% to 100% by mass, more preferably 70% to 100% by mass, even more preferably 90% to 100% by mass, and particularly preferably 95% to 100% by mass.

[0061] In the first step, composition C, which contains polylactic acid resin and a modifier, may be pre-mixed with the polylactic acid resin, modifier, and other components as needed. Examples of such mixing methods include using a mixer such as a tumbler, ribbon blender, V-blender, Henschel mixer, or Readygay mixer.

[0062] In the first step, composition C, which contains polylactic acid resin and a modifier, is melt-kneaded in an extruder.

[0063] Any suitable extruder can be used as the extruder, as long as it does not impair the effects of the present invention. A twin-screw extruder is preferred as the extruder in terms of being able to better express the effects of the present invention.

[0064] Twin-screw extruders may be equipped with strand dies or T-dies. In this case, the extruded strand-like or sheet-like mixture may be cooled and cut with a pelletizer or the like to form pellets.

[0065] A twin-screw extruder may be equipped with a granulation die (hot-cut die). In this case, the mixture is pelletized immediately after being extruded.

[0066] The temperature conditions for melt mixing can vary depending on the size and discharge rate of the extrusion, so any appropriate conditions can be adopted within a range that does not impair the effects of the present invention. For example, the temperature of the raw material feed section is preferably set to 100°C to 200°C.

[0067] The rotational speed of the extruder can vary depending on the size of the extrusion and the discharge volume, so any appropriate conditions can be adopted within a range that does not impair the effects of the present invention. For example, a preferred rotational speed is 20 rpm to 800 rpm.

[0068] The modified polylactic acid resin obtained in the first step may be dried by, for example, subjecting it to a drying process. Typically, the modified polylactic acid resin obtained in the first step may be obtained by cooling a strand-shaped mixture extruded from a twin-screw extruder equipped with a strand die, cutting the resulting pellets with a pelletizer, and then subjecting them to a drying process.

[0069] In the drying process, drying can be carried out using a dryer such as a dehumidifying dryer, a vacuum dryer, or a hot air dryer. The modified polylactic acid resin, which has been thoroughly dried using such a dryer, may be used as is in the subsequent second step (without being exposed to a moisture-containing environment), or the modified polylactic acid resin, which has been thoroughly dried using such a dryer, may be sealed in an aluminum bag or the like immediately after drying, and then opened and used just before the subsequent second step.

[0070] The first step can be carried out using any suitable apparatus as long as it does not impair the effects of the present invention. In terms of more effectively exhibiting the effects of the present invention, the first step can be carried out using, for example, a manufacturing apparatus as shown in Figure 1.

[0071] As shown in Figure 1, in the first step, typically, polylactic acid resin as raw material is put into the hopper 11 and melted and kneaded by a twin-screw extruder 30, the strand-shaped kneaded material extruded from the strand die 3 is cooled by a cooling device 6, then pelletized by a pelletizer 4, and dried by a drying device 5, and the resulting modified polylactic acid resin is supplied to the second step.

[0072] The modified polylactic acid resin obtained in the first step has a moisture content of preferably 0.30% by mass or less, 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 above moisture content is better the less it is, and ideally it is 0% by mass.

[0073] The MFR of the modified polylactic acid resin obtained in the first step is preferably 0.20 g / 10 min to 20.0 g / 10 min, more preferably 0.50 g / 10 min to 10.0 g / 10 min, even more preferably 1.0 g / 10 min to 5.0 g / 10 min, particularly preferably 1.1 g / 10 min to 4.0 g / 10 min, and most preferably 1.2 g / 10 min to 3.0 g / 10 min.

[0074] The melt tension of the modified polylactic acid resin obtained in the first step is preferably 5.0 cN to 100.0 cN, more preferably 10.0 cN to 80.0 cN, even more preferably 20.0 cN to 70.0 cN, particularly preferably 25.0 cN to 60.0 cN, and most preferably 30.0 cN to 50.0 cN.

[0075] <Second process> In the second step, the modified polylactic acid resin obtained in the first step is mixed with the unmodified polylactic acid resin to obtain polylactic acid resin (P). The second step is typically a dry blending step of the modified polylactic acid resin and the unmodified polylactic acid resin. That is, in the second step, polylactic acid resin (P), which is a dry blend of the modified polylactic acid resin and the unmodified polylactic acid resin, is obtained. In the second step, it is preferable not to melt-knead the modified polylactic acid resin and the unmodified polylactic acid resin.

[0076] The moisture content of the unmodified polylactic acid resin to be mixed with the modified polylactic acid resin is preferably 0.30% by weight or less, more preferably 0.25% by weight or less, even more preferably 0.20% by weight or less, particularly preferably 0.17% by weight or less, and most preferably 0.15% by weight or less. The lower limit of the above moisture content is better the less it is, and ideally it is 0% by weight.

[0077] Unmodified polylactic acid resin may be dried using a dryer such as a dehumidifying dryer, vacuum dryer, or hot air dryer before being mixed with modified polylactic acid resin. Alternatively, the polylactic acid resin that has been thoroughly dried using such a dryer may be mixed directly with the modified polylactic acid resin (without being exposed to a moisture-containing environment), or the polylactic acid resin that has been thoroughly dried using such a dryer may be sealed in an aluminum bag or similar immediately after drying, and then opened and used immediately before mixing.

[0078] The MFR of the unmodified polylactic acid resin to be mixed with the modified polylactic acid resin is preferably 1.5 g / 10 min to 50.0 g / 10 min, more preferably 3.0 g / 10 min to 40.0 g / 10 min, even more preferably 4.0 g / 10 min to 30.0 g / 10 min, particularly preferably 5.0 g / 10 min to 25.0 g / 10 min, and most preferably 6.0 g / 10 min to 20.0 g / 10 min.

[0079] The number-average molecular weight (Mn) of the unmodified polylactic acid resin to be mixed with the modified polylactic acid resin is preferably 20,000 to 150,000, more preferably 40,000 to 130,000, even more preferably 60,000 to 120,000, and particularly preferably 80,000 to 110,000.

[0080] The weight-average molecular weight (Mw) of the unmodified polylactic acid resin to be mixed with the modified polylactic acid resin is preferably 100,000 to 500,000, more preferably 130,000 to 400,000, even more preferably 160,000 to 350,000, and particularly preferably 180,000 to 300,000.

[0081] The Z-average molecular weight (Mz) of the unmodified polylactic acid resin to be mixed with the modified polylactic acid resin is preferably 100,000 to 800,000, more preferably 200,000 to 700,000, even more preferably 250,000 to 600,000, and particularly preferably 300,000 to 500,000.

[0082] The polylactic acid resin (P) is preferably measured by melting, kneading, and extruding the polylactic acid resin (P) in an extruder, and the MFR of the measurement sample obtained is preferably 3.0 g / 10 min or more, more preferably 4.0 g / 10 min or more, even more preferably 5.0 g / 10 min or more, particularly preferably 6.0 g / 10 min or more, and most preferably 6.5 g / 10 min or more. The upper limit of the above MFR is not particularly limited, but for example it is 25.0 g / 10 min or less, and preferably 20.0 g / 10 min or less. The method for preparing the measurement sample and the method for measuring the MFR will be described later. Hereinafter, "MFR of the measurement sample obtained by melting, kneading, and extruding the polylactic acid resin (P) in an extruder" may be referred to as "MFR of polylactic acid resin (P)".

[0083] The melt tension of the measurement sample obtained by melting, kneading, and extruding the polylactic acid resin (P) in an extruder is preferably 15.0 cN or less, more preferably 13.0 cN or less, even more preferably 12.0 cN or less, particularly preferably 10.0 cN or less, and most preferably 9.0 cN or less. The lower limit of the melt tension of the polylactic acid resin (P) is not particularly limited, but is, for example, 1.0 cN or more, and preferably 1.5 cN or more. The method for preparing the measurement sample and the method for measuring the melt tension will be described later. Hereinafter, "melt tension of the measurement sample obtained by melting, kneading, and extruding the polylactic acid resin (P) in an extruder" may be referred to as "melt tension of the polylactic acid resin (P)".

[0084] The fracture velocity of the measurement sample obtained by melting, kneading, and extruding the polylactic acid resin (P) in an extruder is preferably 45.0 m / min to 170.0 m / min, more preferably 50.0 m / min to 165.0 m / min, even more preferably 53.0 m / min to 165.0 m / min, particularly preferably 55.0 m / min to 160.0 m / min, and most preferably 58.0 m / min to 155.0 m / min. The method for preparing the measurement sample and the method for measuring the fracture velocity will be described later. Hereinafter, "the fracture velocity of the measurement sample obtained by melting, kneading, and extruding the polylactic acid resin (P) in an extruder" may be referred to as "the fracture velocity of the polylactic acid resin (P)".

[0085] In the second step, when mixing the modified polylactic acid resin and the unmodified polylactic acid resin to obtain polylactic acid resin (P), other components described in the third step, which will be described later, may be further mixed in addition to the modified and unmodified polylactic acid resins. That is, in the second step, the modified polylactic acid resin obtained in the first step, the unmodified polylactic acid resin, and the other components may be mixed to obtain a composition containing polylactic acid resin (P) containing the modified and unmodified polylactic acid resins, and the other components. In this case, the above composition is put into an extruder in the subsequent third step. In the second step, it is preferable that a foam regulator is mixed as the other component along with the modified and unmodified polylactic acid resins. The foam regulator will be described later.

[0086] Methods for mixing modified polylactic acid resin, unmodified polylactic acid resin, and other components as needed include, for example, mixing methods using mixers such as tumblers, ribbon blenders, V-blenders, Henschel mixers, and Readygae mixers.

[0087] <3rd process> In the third step, the polylactic acid resin (P) obtained in the second step is melt-kneaded with a foaming agent in an extruder and extruded to produce a polylactic acid resin foam sheet.

[0088] Here, the second and third steps may be performed simultaneously. That is, the modified polylactic acid resin and the unmodified polylactic acid resin obtained in the first step may be fed into an extruder without mixing, and melt-kneaded with a foaming agent in the extruder to obtain a melt-kneaded product of polylactic acid resin (P), which is a mixture of the modified and unmodified polylactic acid resins, and a foaming agent, and then extruded to foam. In the method for producing a polylactic acid resin foam sheet according to the embodiment of the present invention, it is preferable to perform the third step after the second step. Therefore, it is preferable to mix the modified polylactic acid resin and the unmodified polylactic acid resin obtained in the first step to obtain a mixture, then feed the mixture into an extruder, melt-knead it with a foaming agent in the extruder, and extrude to foam and produce a polylactic acid resin foam sheet. This allows the effects of the present invention to be more fully realized.

[0089] The foaming agent may be one type or two or more types.

[0090] As a blowing agent, any suitable blowing agent can be used as long as it does not impair the effects of the present invention. Examples of blowing agents include volatile blowing agents that become a gas at room temperature (23°C) and atmospheric pressure (1 atm), and decomposition-type blowing agents that generate gas by thermal decomposition, and preferably, volatile blowing agents.

[0091] Preferably, the volatile blowing agent is an organic compound whose boiling point is below the softening point of the polylactic acid resin and which is gaseous or liquid at atmospheric 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 point 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 volatile blowing agents. Among these, the volatile foaming 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 better express the effects of the present invention.

[0092] 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.

[0093] The amount of foaming agent used can be appropriately set depending on the purpose. The amount of foaming agent used 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, when the amount of polylactic acid resin (P) is 100 parts by mass.

[0094] In the third step, the extruder may contain any other suitable components other than polylactic acid resin (P) and the blowing agent, to the extent that it does not impair the effects of the present invention. That is, in the third step, the extruder may contain any other suitable components other than modified polylactic acid resin, unmodified polylactic acid resin, and the blowing agent, to the extent that it does not impair the effects of the present invention. In the third step, the total content of polylactic acid resin (P) and the blowing agent in the total of polylactic acid resin (P), the blowing agent, and other components as needed in the extruder is preferably 50% to 100% by mass, more preferably 70% to 100% by mass, even more preferably 90% to 100% by mass, and particularly preferably 95% to 100% by mass.

[0095] In the third step, the extruder may contain foaming agents as other components. There may be only one type of foaming agent, or two or more types. Examples of foaming agents include diisobutyl adipate, toluene, cyclohexane, ethylbenzene, liquid paraffin, and coconut oil.

[0096] In the third step, the extruder may contain a foam regulator as another component. There may be only one type of foam regulator or two or more types. 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 oleamide, stearamide, and hydroxystearamide; and fatty acid bisamides such as methylenebisstearamide and ethylenebisstearamide. Examples of higher fatty acids in partial esters of higher fatty acids and alcohols include fatty acids with 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 monoglyceride stearate and diglyceride stearate.

[0097] The amount of foam regulator used can be appropriately set depending on the purpose. The amount of foam regulator used is preferably 10.0 parts by mass or less, more preferably 0.1 to 10.0 parts by mass, 0.3 to 9.0 parts by mass, 0.5 to 8.0 parts by mass, 0.8 to 7.0 parts by mass, even more preferably 1.0 to 6.0 parts by mass, particularly preferably 1.5 to 5.0 parts by mass, and most preferably 2.0 to 4.0 parts by mass, when the amount of polylactic acid resin (P) is 100 parts by mass.

[0098] Other components not listed above include, for example, other resins, pigments, radiant heat transfer inhibitors, crosslinking agents, plasticizers, stabilizers, fillers, lubricants, colorants, antioxidants, antistatic agents, spreading agents, weathering agents, flame retardants, UV absorbers, light stabilizers, anti-aging agents, anti-fogging agents, fragrances, and antibacterial agents.

[0099] As mentioned above, the polylactic acid resin (P) and other components may be mixed in advance. For example, the foam regulator included in the extruder in the third step may be the same one that was mixed together when the polylactic acid resin (P) was produced in the second step. That is, in the second step, the modified polylactic acid resin, the unmodified polylactic acid resin, and the foam regulator may be mixed to obtain a composition containing the polylactic acid resin (P) and the foam regulator, and then in the third step, this composition may be put into an extruder, melt-kneaded with a foaming agent in the extruder, and then extruded to foam it.

[0100] Any suitable extruder can be used as the extruder, as long as it does not impair the effects of the present invention. In terms of being able to better express the effects of the present invention, a tandem extruder is preferably used as the extruder.

[0101] The tip of the tandem extruder is equipped with any suitable die, within the limits that do not impair the effects of the present invention, so that a polylactic acid resin foam sheet is ultimately obtained. Preferably, it may also be equipped with a cooling mandrel, a winding roller for winding the polylactic acid resin foam sheet as a raw material roll, and so on.

[0102] The third step can be carried out using any suitable apparatus, provided that it does not impair the effects of the present invention. In terms of more effectively exhibiting the effects of the present invention, the third step can be carried out using, for example, a manufacturing apparatus as shown in Figure 2.

[0103] The manufacturing apparatus illustrated in Figure 2 includes a tandem extruder 10 and a circular die CD that extrudes the polylactic acid resin composition melted and kneaded in the tandem extruder 10 in a cylindrical shape. Furthermore, this manufacturing apparatus includes a cooling device CL for air-cooling the foamed sheet extruded in a cylindrical shape from the circular die CD, a mandrel MD for expanding the diameter of the cylindrical foamed sheet to form a cylinder of a predetermined size, a slitting device for slitting the foamed sheet after it has passed through the mandrel MD to divide it into two sheets, and a winding roller 22 for winding the slit foamed sheet 1 after it has passed through a plurality of rollers 21. The extruder upstream of the tandem extruder 10 (hereinafter also referred to as "first extruder 10a") is provided with a hopper 11 for feeding in the polylactic acid resin (P), which is the raw material for the foamed sheet, and a gas introduction section 12 for supplying a foaming agent into the cylinder. Downstream of the first extruder 10a, there is an extruder (hereinafter also referred to as "second extruder 10b") for melt-kneading a polylactic acid resin composition containing polylactic acid resin (P) and a foaming agent.

[0104] The temperature conditions for melt mixing can vary depending on the size of the extrusion and the discharge rate, so any appropriate conditions can be adopted within a range that does not impair the effects of the present invention. For example, the temperature of the raw material feed section of the first extruder 10a is preferably set to 100°C to 200°C, more preferably to 140°C to 200°C, the temperature of the subsequent sections of the first extruder 10a is preferably set to 120°C to 300°C, more preferably to 140°C to 270°C, and the temperature of the second extruder 10b is preferably set to 100°C to 250°C, more preferably to 120°C to 220°C.

[0105] The rotational speed of the extruder can vary depending on the size of the extrusion and the discharge volume, so any appropriate conditions can be adopted within a range that does not impair the effects of the present invention. For example, such rotational speeds are preferably 10 rpm to 300 rpm for the first extruder 10a and preferably 5 rpm to 200 rpm for the second extruder 10b.

[0106] Through the above third step, a polylactic acid resin foam sheet is obtained.

[0107] <<<Polylactic acid resin foam molded product>>> A polylactic acid resin foamed molded article according to an embodiment of the present invention is obtained by molding a polylactic acid resin foamed sheet according to an embodiment of the present invention.

[0108] A polylactic acid resin foam molded article according to an embodiment of the present invention can typically be obtained by heating and softening a polylactic acid resin foam sheet according to an embodiment of the present invention, and then thermoforming it using a mold by vacuum forming and / or pressure forming, or by a matched mold forming method or plug-assisted molding method that applies these methods.

[0109] The polylactic acid resin foam molded articles according to embodiments of the present invention can be used as food containers such as trays, cups, bowls, lunch boxes, fruit containers, and vegetable containers; cushioning materials such as cushioning materials for electrical products and cushioning materials for precision equipment; and so on. [Examples]

[0110] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement and evaluation methods for each characteristic are as follows.

[0111] <Molecular weight measurement of unmodified polylactic acid resin> The number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) of the unmodified polylactic acid resin were determined as follows. 20 mg of the sample to be measured 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 pre-prepared standard polystyrene calibration curve. The apparatus used was a gel permeation chromatograph manufactured by Tosoh Corporation ("HLC-8320GPC EcoSEC," with built-in RI detector and UV detector). [GPC measurement conditions] Guard column: TSK guardcolumn HXL-H (6.0mm x 4.0cm) x 1, manufactured by Tosoh Corporation. Measurement column: Two TSKgel GMHXL (7.8mm I.D. × 30cm) manufactured by Tosoh Corporation, in series. Reference side: Two resistor tubes (0.1mm inner diameter x 2m) in series. Column temperature: 40℃ Mobile phase: Chloroform Reference pump mobile phase flow rate: 0.5 mL / min Mobile phase flow rate of sample-side pump: 1.0 mL / min Detector: RI detector Injection volume: 50μL Measurement time: 25 min Sampling pitch: 500 msec Standard polystyrene samples for the calibration curve were "STANDARD SM-105" and "STANDARD SH-75" manufactured by Showa Denko K.K., with 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. The above calibration curve standard polystyrene was grouped into 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). After grouping, A was weighed into (2mg, 3mg, 4mg, 4mg, 4mg), dissolved in 30 mL of chloroform, B was weighed into (3mg, 4mg, 4mg, 4mg, 4mg), 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 A solution and each B solution for measurement. The average molecular weight was calculated using this calibration curve.

[0112] <Measurement of the Thickness of the Polylactic Acid Resin Foamed Sheet> Regarding the part excluding 20 mm at both ends in the width direction (TD direction) of the polylactic acid resin foamed sheet obtained in the examples and comparative examples, the thicknesses at 9 equally spaced points in the width direction were measured using a dial thickness gauge SM-112 (manufactured by Teclock), and the value obtained by adding and averaging the measured values was taken as the thickness of the polylactic acid resin foamed sheet.

[0113] <Measurement of the Basis Weight of the Polylactic Acid Resin Foamed Sheet> Excluding 20 mm at both ends in the width direction (TD direction) of the polylactic acid resin foamed sheet obtained in the examples and comparative examples, 6 slices of 10 cm × 10 cm were cut out at equal intervals in the width direction, and the mass (g) of each slice was measured to the nearest 0.001 g. The average value of the mass (g) of each slice was converted to the mass per 1 m 2 The value obtained by conversion was taken as the basis weight (g / m 2 ) of the polylactic acid resin foamed sheet. Basis weight (g / m 2 ) = (average value of the mass of the slices (g) / (10 (cm) × 10 (cm))) × 10000 (cm 2 / m 2 )

[0114] <Measurement of the Foaming Ratio of the Polylactic Acid Resin Foamed Sheet> The foaming ratio of the polylactic acid resin foam sheets obtained in the examples and comparative examples was determined by calculating the apparent density (ρ1) of the polylactic acid resin foam sheet, calculating the density (true density: ρ0) of the resin composition constituting the polylactic acid resin foam sheet, and then dividing the true density (ρ0) by the apparent density (ρ1). Expansion ratio = True density (ρ0) / Apparent density (ρ1) The apparent density of polylactic acid resin foam sheets can be determined by the method described in JIS-K7222:1999 "Foamed plastics and rubber - Measurement of apparent density," and specifically, it was determined by the following method. (Method for measuring apparent density) From polylactic acid resin foam sheet, 100cm 3 The above samples were cut without altering their original cell structure, and these samples were conditioned for 16 hours under JIS K7100:1999 symbol 23 / 50, Class 2 environment. After that, their dimensions and mass were measured, and their density (apparent density: ρ1) was calculated using the following formula. Apparent density (kg / m³) 3 ) = Mass of sample (kg) / Volume of sample (m³) 3 ) For measuring the dimensions of the samples, a Mitutoyo Corporation "DIGIMATIC" CD-15 type was used. (True density measurement method) The density (true density: ρ0) of the resin composition constituting the polylactic acid resin foam sheet was determined by performing measurements based on the Archimedes method (liquid weighing method according to JIS-K8807:2012 "Method for measuring the density and specific gravity of solids") on samples that had been made non-foamed by methods such as heat pressing of the polylactic acid resin foam sheet.

[0115] <Measurement of the open-cell ratio of polylactic acid resin foam sheets> Multiple sheet-like samples measuring 25 mm in length and 25 mm in width were cut from the polylactic acid resin foam sheets obtained in the examples and comparative examples. The cut samples were stacked without gaps to form a 20 mm thick measurement sample. 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 (cm³) was determined. 3 ) was sought. Next, using a dry automatic densimeter (Shimadzu Corporation, "AccuPic II 1340-100cc"), the volume (cm³) of the sample to be measured was measured under the following conditions. 3 The following measurements were taken: Gas used: Nitrogen Container used: 35cc Filling pressure: 0.005 psig Pressure equilibrium completion rate: 0.005 psig / min Number of repetitions: 1 The percentage of open cells (%) was calculated using these values ​​and the following formula, and the average value of 5 tests was taken as the percentage of open cells for the polylactic acid resin foam sheet. Open cell percentage (%) = [(Apparent volume - Volume measured by dry automatic densimeter) / Apparent volume] × 100 The measurements were performed after conditioning the sample for 16 hours under JIS K7100-1999 symbol 23 / 50, Class 2 conditions.

[0116] <Measurement of MFR of polylactic acid foam sheet> The MFR of the polylactic acid resin foam sheets obtained in the examples and comparative examples was measured in accordance with the JIS K 7210:1999 standard. Specifically, the measurement was performed according to "b) Method for measuring the time it takes for a piston to travel a predetermined distance" as described in Method B of the JIS K 7210:1999 standard. The MFR was measured using a Melt Flow Index Tester (Automatic) 120-SAS (manufactured by Yasuda Seiki Seisakusho Co., Ltd.). The sample was prepared by pressing a polylactic acid resin foam sheet in a hot press at 190°C for 5 minutes to create a plate with a width of 150 mm and a thickness of approximately 3.8 mm, and then crushing the plate to a size of approximately 1 mm to 2 mm using a pulverizer. For measurement, the obtained sample was vacuum dried at 90°C for 5 hours, then sealed and stored in a desiccator until immediately before measurement. Three measurements were taken, and the average value was used. The measurement conditions were as follows: Sample: 3g~8g Preheating (1): 200 seconds Preheating (2): 30 seconds Test temperature: 190℃ Test load: 21.18N Piston travel distance (interval): 25mm

[0117] <Measurement of MFR of polylactic acid resin (P)> The modified polylactic acid resin and the unmodified polylactic acid resin were stirred and mixed in a ribbon blender at the mixing ratios specified in each example and comparative example to obtain a mixture. The resulting mixture was fed into a twin-screw extruder with a bore diameter of 57 mm (L / D = 31.5). The feed section temperature was set to 170°C, and the temperature thereafter was set to 200°C. Under these conditions, the mixture was melted and kneaded in the twin-screw extruder at a rotation speed of 100 rpm. The kneaded material was then extruded in strand form from a die (diameter φ3 mm, 18 holes) attached to the tip of the extruder at a discharge rate of 50 kg / hour. Next, the extruded strand-shaped mixture was cooled by passing it through a 2-meter-long cooling water tank containing 30°C water. The cooled strands were cut in a pelletizer to produce pellets. The MFR of polylactic acid resin (P) was measured in the same manner as in <Measurement of MFR of polylactic acid resin foam sheet>, except that the obtained pellets were used as the measurement sample. For the measurement, the obtained sample was vacuum-dried at 90°C for 5 hours, then sealed and stored in a desiccator until immediately before measurement.

[0118] <Measurement of melt tension of polylactic acid resin foam sheet> The melt tension of the polylactic acid resin foam sheets obtained in the examples and comparative examples was measured using a Capillograph 1D (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and a Rheotens (manufactured by Gottfert, Rheotens 71.97) as measuring devices. The samples were prepared by pressing a polylactic acid resin foam sheet in a hot press at 190°C for 5 minutes to create a plate with a width of 15 mm and a thickness of approximately 0.8 mm, and then crushing the plate to a size of approximately 1 mm to 2 mm using a pulverizer. For measurement, the samples were pre-dried under vacuum at 90°C for more than 5 hours, and after drying, they were vacuum-packed in nylon poly bags for vacuum sealing and stored in a desiccator until immediately before measurement. First, the sample to be measured was filled into a 9.55 mm diameter barrel heated to a test temperature of 190°C and preheated for 5 minutes. The molten resin was extruded in a string-like form from the capillary die (2.095 mm diameter, 8 mm length, 90-degree inlet angle (conical)) of the measuring device while maintaining a constant piston descent speed (20 mm / min). This string-like material was then passed through a wheel (wheel spacing: 0.6 mm to 0.8 mm at the top, 1.0 mm at the bottom) positioned so that the distance from the outlet of the capillary die to the measuring section (rheotense) was 80 mm. The take-up speed was set to an initial velocity of 6.92 mm / s and an acceleration of 10 mm / s. 2 The tension was gradually increased as the sample passed through, and the average value of the maximum and minimum tension values ​​immediately before the point where the string-like material broke was taken as the melt tension of the sample. If interference prevented the rheotens from being brought within 80 mm, measures were taken to avoid interference and set the rheotens in the designated location. If there was only one maximum point on the tension chart, that maximum value was taken as the melt tension. When the string-like material became thinner and the pull mechanism became free-spinning, the point at which it became free-spinning was considered the break point, and the average value of the maximum and minimum tension values ​​immediately before that point was taken as the melt tension of the sample. The measurement time, including the preheating time, must not exceed 10 minutes from the time the sample is filled into the barrel. [Measurement conditions for "Capillograph 1D"] Die: Diameter 2.095mm, length 8mm, inlet angle 90 degrees (conical) Barrel diameter: 9.55mm Piston speed: 20 mm / min Measurement temperature: 190℃ [Measurement conditions for "Rheotens71.97"] Wheel spacing: Top 0.6mm~0.8mm, Bottom 1.0mm Acceleration: 10mm / s2 Retrieval speed: Initial velocity 6.92mm / s The lower limit of the measurable melt tension was 1.0 cN.

[0119] <Measurement of melt tension of polylactic acid resin (P)> The modified polylactic acid resin and the unmodified polylactic acid resin were stirred and mixed in a ribbon blender at the mixing ratios specified in each example and comparative example to obtain a mixture. The resulting mixture was fed into a twin-screw extruder with a bore diameter of 57 mm (L / D = 31.5). The feed section temperature was set to 170°C, and the temperature thereafter was set to 200°C. Under these conditions, the mixture was melted and kneaded in the twin-screw extruder at a rotation speed of 100 rpm. The kneaded material was then extruded in strand form from a die (diameter φ3 mm, 18 holes) attached to the tip of the extruder at a discharge rate of 50 kg / hour. Next, the extruded strand-shaped mixture was cooled by passing it through a 2-meter-long cooling water tank containing 30°C water. The cooled strands were cut in a pelletizer to produce pellets. The melt tension of polylactic acid resin (P) was measured in the same manner as in <Measurement of Melt Tension of Polylactic Acid Resin Foam Sheet>, except that the obtained pellets were used as the measurement sample. For the measurement, the sample was pre-dried under vacuum at 90°C for more than 5 hours, and after drying, it was vacuum-packed in a nylon poly bag for vacuum packing until immediately before measurement and then stored in a desiccator.

[0120] <Measurement of the breaking point velocity of polylactic acid resin foam sheets> The breaking point velocities of the polylactic acid resin foam sheets obtained in the examples and comparative examples were measured using a capillary rheometer ("Capillograph F-1" manufactured by Toyo Seiki Seisakusho Co., Ltd.). The sample was prepared by pressing a polylactic acid resin foam sheet in a hot press at 190°C for 5 minutes to create a plate with a width of 15 mm and a thickness of approximately 0.8 mm, and then crushing the plate to a size of approximately 1 mm to 2 mm using a pulverizer. For measurement, the sample was vacuum-dried at 90°C for 5 hours, then sealed and stored in a desiccator until immediately before measurement. The fracture velocity was measured using a tension-sensing pulley located 34 cm below a capillary die with a diameter of 2.095 mm, a length of 8 mm, and an inlet angle of 90 degrees (conical), which was set in the above measuring device. First, the sample was filled into a 9.55 mm diameter barrel heated to a test temperature of 170°C. The filled sample was preheated for 5 minutes to melt. The molten material was extruded from the capillary die in a string-like form while maintaining a constant piston descent speed of 10 mm / min. This string-like material was passed through the heat-insulating cover attached to the apparatus, then through a pulley for tension detection, and finally wound up using a winding roll. The winding speed was set to an initial velocity of 5 m / min. 2 The winding speed was gradually increased. The winding speed immediately before the string-like material broke was defined as the "breaking point velocity." The measurement was performed 10 times, and the arithmetic mean was taken as the breaking point velocity of the polylactic acid foam sheet. The maximum winding speed in the measuring device was 200 m / min. That is, the upper limit of the measurable breaking point velocity was 200.0 m / min.

[0121] <Measurement of the breaking point rate of polylactic acid resin (P)> The modified polylactic acid resin and unmodified polylactic acid resin used in each example and comparative example were stirred and mixed in a ribbon blender at the mixing ratio used in each example and comparative example to obtain a mixture. The resulting mixture was fed into a twin-screw extruder with a bore diameter of 57 mm (L / D = 31.5). The feed section temperature was set to 170°C, and the temperature thereafter was set to 200°C. Under these conditions, the mixture was melted and kneaded in the twin-screw extruder at a rotation speed of 100 rpm. The kneaded material was then extruded in strand form from a die (diameter φ3 mm, 18 holes) attached to the tip of the extruder at a discharge rate of 50 kg / hour. Next, the extruded strand-shaped mixture was cooled by passing it through a 2-meter-long cooling water tank containing 30°C water. The cooled strands were cut in a pelletizer to produce pellets. The fracture point velocity of polylactic acid resin (P) was measured in the same manner as in <Measurement of Fracture Point Velocity of Polylactic Acid Resin Foam Sheet>, except that the obtained pellets were used as the measurement sample. For the measurement, the sample was vacuum-dried at 90°C for 5 hours, then sealed and stored in a desiccator until immediately before measurement.

[0122] <Moldability Evaluation> A rectangular test piece measuring 700 mm in length and 640 mm in width was cut from the polylactic acid resin foam sheet obtained in the examples and comparative examples. Next, a single-shot molding machine (manufactured by Tosei Sangyo Co., Ltd., product name "Unic Automatic Molding Machine FM-3A") was prepared, and the average temperature of the upper heater of this single-shot molding machine was set to 272°C, the average temperature of the lower heater to 228°C, the upper ambient temperature to 196°C, and the lower ambient temperature to 191°C. Next, the above test specimen was introduced into a single-shot molding machine and heated for 5 seconds. Then, using a mold equipped with 22 frustums of different heights, each with a diameter of 10 mm (top) x 35 mm (bottom), the mold surface temperature was controlled to 50°C, and heat molding was performed. The heights of the 22 frustums of cones are shown in Table 1. The mold was equipped with a total of 24 frustums: one each of heights No. 1 to 20, and two each of heights No. 21 and No. 22. Subsequently, the molded products were visually inspected, and the score for that molding was determined by the number of the tallest frustum of cone (the value of "No." shown in Table 1) among those whose shape was molded according to the mold and which were free of tears in each cone shape. Here, "tear" refers to a condition in which cracks or holes are visually observed in the molded product. The test was conducted three times, and the average score was used as the value for elongation. The moldability was evaluated according to the following criteria. ◎: The growth value is 22 or higher. ○: The growth value is 20 or more but less than 22. △: The growth rate is between 18 and 20. ×: The growth rate is less than 18.

[0123] [Table 1]

[0124] [Manufacturing Example 1] Polylactic acid resin (manufactured by Anhui Fengyuan Futai Lai Polylactic Acid Co., Ltd., product name "FY602", MFR = 15.0 g / 10 min, D-isomer ratio = 2.0 ± 0.5 ml%, melting point = 164.3 °C, density = 1240 kg / m³) 3 ): 100 parts by mass and t-butyl peroxyisopropyl monocarbonate (manufactured by Kayaku Nurion Co., Ltd., "Triganox BPIC-75", half-life temperature T1 = 158.8°C) were stirred and mixed in a ribbon blender to obtain a mixture. The resulting mixture was fed into a twin-screw extruder with a bore diameter of 57 mm (L / D = 31.5). The feed section temperature was set to 170°C, and the temperature thereafter was set to 200°C. Under these conditions, the mixture was melted and kneaded in the twin-screw extruder at a rotation speed of 100 rpm. The kneaded material was then extruded in strand form from a die (diameter φ3 mm, 18 holes) attached to the tip of the extruder at a discharge rate of 50 kg / hour. Next, the extruded strand-shaped mixture was cooled by passing it through a 2-meter-long cooling water tank containing 30°C water. The cooled strands were cut in a pelletizer to form pellets, and then dried in a dehumidifying dryer at a drying temperature of 70°C. In this way, the modified polylactic acid resin of Production Example 1 was obtained.

[0125] [Manufacturing Example 2] The modified polylactic acid resin of Production Example 2 was obtained by the same method as in Production Example 1, except that the amount of t-butyl peroxyisopropyl monocarbonate was 0.7 parts by mass.

[0126] [Manufacturing Example 3] The polylactic acid resin used is manufactured by Anhui Fengyuan Futai Lai Polylactic Acid Co., Ltd., product name "FY802" (MFR = 7.8g / 10min, D-isomer ratio = 2.0±0.5mol%, melting point = 164.4℃, density = 1240kg / m³). 3 The modified polylactic acid resin of Production Example 3 was obtained in the same manner as in Production Example 1, except that the ) was used.

[0127] [Manufacturing Example 4] The modified polylactic acid resin of Production Example 4 was obtained by the same method as in Production Example 3, except that the amount of t-butylperoxyisopropyl monocarbonate was 0.6 parts by mass.

[0128] [Manufacturing Example 5] The polylactic acid resin is manufactured by Anhui Fengyuan Futai Lai Polylactic Acid Co., Ltd., and its product name is "FY202" (MFR = 35.0 g / 10 min, D-isomer ratio = 2.0 ± 0.5 ml%, melting point = 164.3 °C, density = 1240 kg / m³). 3 The modified polylactic acid resin of Production Example 5 was obtained in the same manner as in Production Example 1, except that the ) was used.

[0129] [Manufacturing Example 6] The modified polylactic acid resin of Production Example 6 was obtained by the same method as in Production Example 5, except that the amount of t-butyl peroxyisopropyl monocarbonate was 0.8 parts by mass.

[0130] [Example 1] A mixture was prepared by dry blending 80 parts by mass of the modified polylactic acid resin from Production Example 1, 20 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). A tandem extruder was prepared, consisting of a first extruder with a diameter of φ50 mm (upstream) and a second extruder with a diameter of φ65 mm (downstream). The resulting mixture was supplied to the first extruder through a hopper and heated and melted at 220°C. Subsequently, 1.5 parts by mass of butane (isobutane / n-butane = 35% by mass / 65% by mass) was injected into the first extruder under pressure as a blowing agent and melt-kneaded together with the above mixture to obtain a molten mixture. Next, the molten mixture was transferred to a second extruder with a diameter of φ65 mm and cooled to 170°C. Then, it was extruded and foamed through a circular die with a diameter of φ70 mm at a discharge rate of 30 kg / hour to obtain a cylindrical foam. The obtained cylindrical foam was placed along 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 its diameter. A strip-shaped polylactic acid resin foam sheet was then obtained by cutting it at a point on the circumference with a cutter. In this way, the polylactic acid resin foam sheet of Example 1 was produced. Table 2 shows the measurement results for the number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) of unmodified polylactic acid resin FY602. Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 1, the MFR of the polylactic acid resin (P) was 3.8 g / 10 min. The melt tension of the polylactic acid resin (P) was 13.0 cN. The breaking point velocity of the polylactic acid resin (P) was 49.2 m / min.

[0131] [Example 2] In preparing the mixture, the polylactic acid resin foam sheet of Example 2 was prepared in the same manner as in Example 1, except that the mixing ratio was changed to 70 parts by mass of the modified polylactic acid resin from Production Example 1, 30 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of the foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 2, the MFR of the polylactic acid resin (P) was 4.8 g / 10 min. The melt tension of the polylactic acid resin (P) was 12.0 cN. The breaking point velocity of the polylactic acid resin (P) was 54.2 m / min.

[0132] [Example 3] In preparing the mixture, the polylactic acid resin foam sheet of Example 3 was prepared in the same manner as in Example 1, except that the mixing ratio was changed to 50 parts by mass of the modified polylactic acid resin from Production Example 1, 50 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 3, the MFR of the polylactic acid resin (P) was 6.8 g / 10 min. The melt tension of the polylactic acid resin (P) was 8.6 cN. The breaking point velocity of the polylactic acid resin (P) was 59.8 m / min.

[0133] [Example 4] In preparing the mixture, the polylactic acid resin foam sheet of Example 4 was prepared in the same manner as in Example 1, except that the mixing ratio was changed to 30 parts by mass of the modified polylactic acid resin from Production Example 1, 70 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of the foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. Figure 3 is a photograph of a molded product of one test piece in the moldability evaluation of the polylactic acid resin foam sheet of Example 4. The numbers assigned to each cone shape in Figure 3 are the corresponding frustocone numbers (No.) of the mold used to form each cone shape. No tears were observed in the molded product shown in Figure 3, even in the cone No. 22. In Example 4, the MFR of the polylactic acid resin (P) was 11.0 g / 10 min. The melt tension of the polylactic acid resin (P) was 3.4 cN. The breaking point velocity of the polylactic acid resin (P) was 69.0 m / min.

[0134] [Example 5] In preparing the mixture, the polylactic acid resin foam sheet of Example 5 was prepared in the same manner as in Example 1, except that the mixing ratio was changed to 20 parts by mass of the modified polylactic acid resin from Production Example 1, 80 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of the foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 5, the MFR of the polylactic acid resin (P) was 10.0 g / 10 min. The melt tension of the polylactic acid resin (P) was 2.5 cN. The breaking point velocity of the polylactic acid resin (P) was 95.0 m / min.

[0135] [Example 6] The polylactic acid resin foam sheet of Example 6 was prepared in the same manner as in Example 1, except that the mixture was prepared by dry blending 50 parts by mass of the modified polylactic acid resin of Production Example 2, 50 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 6, the MFR of the polylactic acid resin (P) was 6.2 g / 10 min. The melt tension of the polylactic acid resin (P) was 10.1 cN. The breaking point velocity of the polylactic acid resin (P) was 50.1 m / min.

[0136] [Example 7] In preparing the mixture, the polylactic acid resin foam sheet of Example 7 was prepared in the same manner as in Example 6, except that the mixing ratio was changed to 30 parts by mass of the modified polylactic acid resin from Production Example 2, 70 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 7, the MFR of the polylactic acid resin (P) was 8.8 g / 10 min. The melt tension of the polylactic acid resin (P) was 5.9 cN. The breaking point velocity of the polylactic acid resin (P) was 58.8 m / min.

[0137] [Example 8] The polylactic acid resin foam sheet of Example 8 was prepared in the same manner as in Example 1, except that the mixture was prepared by dry blending 50 parts by mass of the modified polylactic acid resin of Production Example 5, 50 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 8, the MFR of the polylactic acid resin (P) was 17.4 g / 10 min. The melt tension of the polylactic acid resin (P) was 1.7 cN. The breaking point velocity of the polylactic acid resin (P) was 150.8 m / min.

[0138] [Example 9] The polylactic acid resin foam sheet of Example 9 was prepared in the same manner as in Example 1, except that the mixture was prepared by dry blending 50 parts by mass of the modified polylactic acid resin of Production Example 6, 50 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 9, the MFR of the polylactic acid resin (P) was 12.5 g / 10 min. The melt tension of the polylactic acid resin (P) was 5.1 cN. The breaking point velocity of the polylactic acid resin (P) was 79.4 m / min.

[0139] [Example 10] In preparing the mixture, the polylactic acid resin foam sheet of Example 10 was prepared in the same manner as in Example 1, except that the mixture was prepared by dry blending 50 parts by mass of the modified polylactic acid resin of Production Example 1, 50 parts by mass of polylactic acid resin FY802, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 2 shows the measurement results for the number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) of unmodified polylactic acid resin FY802. Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 10, the MFR of the polylactic acid resin (P) was 7.8 g / 10 min. The melt tension of the polylactic acid resin (P) was 6.4 cN. The breaking point velocity of the polylactic acid resin (P) was 104.0 m / min.

[0140] [Example 11] The polylactic acid resin foam sheet of Example 11 was prepared in the same manner as in Example 1, except that the mixture was prepared by dry blending 50 parts by mass of the modified polylactic acid resin from Production Example 2, 50 parts by mass of polylactic acid resin FY202, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 2 shows the measurement results for the number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) of unmodified polylactic acid resin FY202. Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Example 11, the MFR of the polylactic acid resin (P) was 13.4 g / 10 min. The melt tension of the polylactic acid resin (P) was 2.8 cN. The breaking point velocity of the polylactic acid resin (P) was 89.6 m / min.

[0141] [Comparative Example 1] A polylactic acid resin foam sheet of Comparative Example 1 was prepared in the same manner as in Example 1, except that the mixture was prepared by dry blending 100 parts by mass of the modified polylactic acid resin of Production Example 1 with 2.5 parts by mass of a foam regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. Figure 4 is a photograph of a molded product of one test piece in the moldability evaluation of the polylactic acid resin foam sheet of Comparative Example 1. The numbers assigned to each cone shape in Figure 4 are the corresponding frustum numbers (No.) of the mold used to form each cone shape. In the molded products shown in Figure 4, there were no cone shapes that were taller than No. 17 and free from cracks. In Comparative Example 1, the MFR of polylactic acid resin (P) was 2.8 g / 10 min. The melt tension of polylactic acid resin (P) was 22.0 cN. The breaking point velocity of polylactic acid resin (P) was 35.6 m / min.

[0142] [Comparative Example 2] In preparing the mixture, the polylactic acid resin foam sheet of Comparative Example 2 was prepared in the same manner as in Example 1, except that the mixing ratio was changed to 90 parts by mass of the modified polylactic acid resin from Production Example 1, 10 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of the foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Comparative Example 2, the MFR of polylactic acid resin (P) was 3.3 g / 10 min. The melt tension of polylactic acid resin (P) was 15.0 cN. The breaking point velocity of polylactic acid resin (P) was 40.7 m / min.

[0143] [Comparative Example 3] In preparing the mixture, the polylactic acid resin foam sheet of Comparative Example 3 was prepared in the same manner as in Example 1, except that the mixing ratio was changed to 10 parts by mass of the modified polylactic acid resin from Production Example 1, 90 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of the foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Comparative Example 3, the MFR of polylactic acid resin (P) was 11.0 g / 10 min. The melt tension of polylactic acid resin (P) was 1.2 cN. The breaking point velocity of polylactic acid resin (P) was 176.0 m / min.

[0144] [Comparative Example 4] A polylactic acid resin foam sheet of Comparative Example 4 was prepared in the same manner as in Example 1, except that the mixture was prepared by dry blending 100 parts by mass of the modified polylactic acid resin from Production Example 3 with 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Comparative Example 4, the MFR of polylactic acid resin (P) was 2.1 g / 10 min. The melt tension of polylactic acid resin (P) was 45.6 cN. The breaking point velocity of polylactic acid resin (P) was 4.25 m / min.

[0145] [Comparative Example 5] A polylactic acid resin foam sheet of Comparative Example 5 was prepared in the same manner as in Example 1, except that the mixture was prepared by dry blending 50 parts by mass of the modified polylactic acid resin from Production Example 3, 50 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Comparative Example 5, the MFR of polylactic acid resin (P) was 3.0 g / 10 min. The melt tension of polylactic acid resin (P) was 20.6 cN. The breaking point velocity of polylactic acid resin (P) was 28.5 m / min.

[0146] [Comparative Example 6] In preparing the mixture, the polylactic acid resin foam sheet of Comparative Example 6 was prepared in the same manner as in Comparative Example 5, except that the mixing ratio was changed to 30 parts by mass of the modified polylactic acid resin from Production Example 3, 70 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Comparative Example 6, the MFR of polylactic acid resin (P) was 7.8 g / 10 min. The melt tension of polylactic acid resin (P) was 13.5 cN. The breaking point velocity of polylactic acid resin (P) was 38.9 m / min.

[0147] [Comparative Example 7] A polylactic acid resin foam sheet of Comparative Example 7 was prepared in the same manner as in Example 1, except that the mixture was prepared by dry blending 50 parts by mass of the modified polylactic acid resin from Production Example 4, 50 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Comparative Example 7, the MFR of polylactic acid resin (P) was 2.8 g / 10 min. The melt tension of polylactic acid resin (P) was 23.7 cN. The breaking point velocity of polylactic acid resin (P) was 20.8 m / min.

[0148] [Comparative Example 8] In preparing the mixture, the polylactic acid resin foam sheet of Comparative Example 8 was prepared in the same manner as in Comparative Example 7, except that the mixing ratio was changed to 30 parts by mass of the modified polylactic acid resin from Production Example 4, 70 parts by mass of polylactic acid resin FY602, and 2.5 parts by mass of a foam regulator (Crown Talc, manufactured by Matsumura Sangyo Co., Ltd.). Table 3 shows the results of various measurements and moldability evaluations of the polylactic acid resin foam sheet. In Comparative Example 8, the MFR of polylactic acid resin (P) was 6.6 g / 10 min. The melt tension of polylactic acid resin (P) was 12.1 cN. The breaking point velocity of polylactic acid resin (P) was 31.7 m / min.

[0149] [Table 2]

[0150] [Table 3]

[0151] In Table 3, "<1.0" in the Melt Tension column means that the melt tension was below the lower limit of the measurable melt tension and therefore could not be measured. ">200.0" in the Breaking Point Velocity column means that the material did not break even when the winding speed reached the upper limit and therefore could not be measured. [Industrial applicability]

[0152] Because the polylactic acid resin foam sheet of the present invention can be easily molded into various shapes, it can be used as a raw material for various molded products, including packaging materials. [Explanation of Symbols]

[0153] 1. Foam sheet 3 Strand Die 4 Pelletizer 5 Drying equipment 6 Cooling device 10 Tandem extruders 10a First extruder 10b Second extruder 11 Hopper 12 Gas inlet 21 Laura 22 Rewinding roller 30 Twin-screw extruder

Claims

1. A foamed polylactic acid resin sheet obtained by foaming a polylactic acid resin composition containing polylactic acid resin (P), The fracture velocity is between 45.0 m / min and 170.0 m / min. Polylactic acid resin foam sheet.

2. The polylactic acid resin foam sheet according to claim 1, wherein the polylactic acid resin (P) comprises a modified polylactic acid resin and an unmodified polylactic acid resin.

3. The polylactic acid resin foam sheet according to claim 2, wherein when the total amount of the unmodified polylactic acid resin and the modified polylactic acid resin is 100 parts by mass, the content of the unmodified polylactic acid resin is 15 parts by mass to 85 parts by mass.

4. The polylactic acid resin foam sheet according to claim 1, wherein the melt mass flow rate (MFR) is 4.5 g / 10 min or more.

5. The polylactic acid resin foam sheet according to claim 1, wherein the melt tension is 12.0 cN or less.

6. The polylactic acid resin foam sheet according to claim 1, wherein the open-cell ratio is 35% or less.

7. A polylactic acid resin foam sheet according to claim 1, wherein the foaming ratio is 5.0 times or more.

8. A polylactic acid resin foamed molded article obtained by molding a polylactic acid resin foamed sheet according to any one of claims 1 to 7.

9. A method for producing a polylactic acid resin foam sheet by melt-kneading polylactic acid resin (P) with a foaming agent in an extruder and then extruding and foaming it, The polylactic acid resin (P) comprises a modified polylactic acid resin and an unmodified polylactic acid resin. When the total amount of the unmodified polylactic acid resin and the modified polylactic acid resin is 100 parts by mass, the content of the unmodified polylactic acid resin is 15 to 85 parts by mass. A method for manufacturing polylactic acid resin foam sheets.

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