Aliphatic polyester resin foam board and folding box

Abstract

To provide a folding box which improves brittleness and dimensional stability of an aliphatic polyester-based resin foamed plate, and facilitates manufacture while using the aliphatic polyester-based resin foamed plate.SOLUTION: An aliphatic polyester-based resin foamed plate includes at least one foam layer, wherein the foam layer is composed of an aliphatic polyester-based resin composition containing an aliphatic polyester-based resin, the aliphatic polyester-based resin composition further contains a butadiene rubber, contains 0.3 pts.mass or more and 4.0 pts.mass or less of the butadiene rubber with respect to 100 pts.mass of the aliphatic polyester-based resin, and a degree of crystallinity of the aliphatic polyester-based resin in the foam layer is 25% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aliphatic polyester resin foam board and a folding box. [Background technology]

[0002] Traditionally, folding boxes made of cedar, cypress, or other wood bent into a square shape and attached to a peripheral frame with a bottom plate have been widely used as containers for sweets, lunch boxes, etc. In recent years, the use of folding boxes made of resin foam boards as an alternative to such wooden folding boxes has been considered (see Patent Document 1 below).

[0003] In recent years, with the rise in environmental awareness, the use of aliphatic polyester resins such as polylactic acid resin, which are easily decomposed in nature, as materials for various products has been considered. Patent Document 1 below describes the use of foam boards made of polylactic acid resin as a material for forming folding boxes (see paragraph 0082 of Patent Document 1 below, etc.).

[0004] As described in Patent Document 2 below, efforts are being made to improve the brittleness of aliphatic polyester resins, but attempts to improve brittleness may result in insufficient dimensional stability being exhibited. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-158608 [Patent Document 2] Patent Publication No. 2021-155651 Summary of the Invention [Problem to be solved by the invention]

[0006] When forming the folding box described above, a V-groove is formed in the resin foam board, and the resin foam board is folded using the V-groove. However, aliphatic polyester resins are inferior to other resins in terms of brittleness, and aliphatic polyester resin foam boards are prone to cracking and dust generation when cut into wood veneers or ground to form the V-groove. Therefore, while there is a demand for ways to prevent such problems, no fully established countermeasures have been established. Furthermore, as described above, aliphatic polyester resin foam boards sometimes lack sufficient dimensional stability, and improvements are needed.

[0007] Improving the brittleness of aliphatic polyester resin foam boards to make them easier to process and improving their dimensional stability are not only required when aliphatic polyester resin foam boards are used for folding boxes, but are also required for aliphatic polyester resin foam boards used for a variety of purposes. Therefore, an object of the present invention is to improve the brittleness and dimensional stability of aliphatic polyester resin foam boards and provide folding boxes that are easy to manufacture even when using aliphatic polyester resin foam boards. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, it was found that by adding butadiene rubber in a predetermined ratio and adjusting the crystallinity of the aliphatic polyester resin, both improvement in brittleness and dimensional stability of the aliphatic polyester resin foam board could be achieved, leading to the completion of the present invention.

[0009] To solve the above problems, the present invention provides: An aliphatic polyester-based resin foam board having at least one foam layer, the foam layer being made of an aliphatic polyester-based resin composition containing an aliphatic polyester-based resin, the aliphatic polyester-based resin composition further contains a butadiene rubber, and the butadiene rubber is contained in an amount of 0.3 parts by mass or more and 4.0 parts by mass or less per 100 parts by mass of the aliphatic polyester-based resin, The aliphatic polyester resin foam board is provided, wherein the aliphatic polyester resin in the foam layer has a crystallinity of 25% or more.

[0010] To solve the above problems, the present invention provides: A folding box having a peripheral side frame made of a resin foam board having at least one foam layer, the foam layer is made of an aliphatic polyester-based resin composition containing an aliphatic polyester-based resin, the aliphatic polyester-based resin composition further contains a butadiene rubber in a ratio of 0.3 parts by mass or more to 4.0 parts by mass or less per 100 parts by mass of the aliphatic polyester-based resin, The foamed layer of the aliphatic polyester resin has a crystallinity of 25% or more. [Effects of the Invention]

[0011] According to the present invention, the brittleness of the aliphatic polyester resin foam board is improved, and a folding box having excellent dimensional stability and being easy to manufacture can be provided even though it uses an aliphatic polyester resin foam board. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 shows a foam board (aliphatic polyester resin foam board) for forming folding boxes. [Figure 2] FIG. 2 is a schematic perspective view showing a folding box (food container). [Figure 3] FIG. 3 is a schematic perspective view illustrating a foam board (aliphatic polyester resin foam board) used for the peripheral side frame of one embodiment of the folding box. [Figure 4] FIG. 4 is a schematic perspective view illustrating a folding box according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described. The aliphatic polyester resin foam board of this embodiment has a foam layer. The aliphatic polyester resin foam board of this embodiment may have a single-layer structure consisting of only a foam layer, or a laminate structure consisting of a foam layer and another layer (for example, a non-foam layer). The aliphatic polyester resin foam board of this embodiment has a foam layer made of an aliphatic polyester resin composition containing an aliphatic polyester resin.

[0014] First, the aliphatic polyester resin composition that is the main raw material for the aliphatic polyester resin foam board will be described below. The aliphatic polyester resin composition of this embodiment contains an aliphatic polyester resin and a butadiene rubber. The aliphatic polyester resin composition is prepared so that the proportion of the butadiene rubber is 0.3 parts by mass or more and 4.0 parts by mass or less per 100 parts by mass of the aliphatic polyester resin. The proportion of the butadiene rubber may be 0.4 parts by mass or more, or 0.7 parts by mass or more. The proportion of the butadiene rubber may be 3.5 parts by mass or less, 3.0 parts by mass or less, or 2.5 parts by mass or less.

[0015] The butadiene rubber may be contained in the aliphatic polyester-based resin composition in the form of a butadiene homopolymer, or may be contained in the form of a copolymer rubber containing a butadiene rubber component composed of butadiene and a copolymer component composed of a monomer copolymerizable with butadiene. The copolymer rubber may be a block polymer having a polybutadiene block and a copolymer block composed of a monomer other than butadiene, a graft copolymer of polybutadiene and another polymer, or a random copolymer of butadiene and another monomer. When the butadiene rubber is contained in the aliphatic polyester-based resin composition in the form of a copolymer rubber containing such a butadiene rubber component and a copolymer component, the proportion of the butadiene rubber is calculated based on only the butadiene rubber component.

[0016] The butadiene rubber of this embodiment is preferably contained in the aliphatic polyester resin composition in the form of a copolymer rubber, and more preferably in the form of a graft copolymer rubber. The copolymer rubber may be a copolymer rubber of butadiene and styrene (styrene-butadiene rubber). The copolymer rubber may also be a multicomponent copolymer rubber composed of three or more types of monomers. Examples of copolymerizable monomers other than styrene include acrylic monomers such as methyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate.

[0017] The copolymer rubber is preferably a core-shell rubber. The core-shell rubber preferably includes a core and a shell layer covering the core, the core being composed of a polymer having butadiene as a structural unit, and the shell layer being composed of a polymer having methyl methacrylate as a structural unit.

[0018] The copolymer rubber preferably contains 35% by mass or more of butadiene units, more preferably 40% by mass or more, and even more preferably 45% by mass or more of butadiene units.

[0019] As the copolymer rubber, it is preferable to use a multi-component copolymer rubber containing styrene and an acrylic monomer in addition to butadiene. The styrene (St) and the acrylic monomer (Aa) are preferably contained in the multi-component copolymer rubber in a molar ratio of 0.8:1 to 1:0.8 (St:Aa). Methyl methacrylate is suitable as the acrylic monomer. That is, MBS polymer (methyl methacrylate-butadiene-styrene copolymer) is suitable as the copolymer rubber. The MBS polymer may further contain a small amount of butyl acrylate (e.g., 0.5% by mass to 2% by mass).

[0020] The aliphatic polyester resin of this embodiment may be a condensation polymer of an aliphatic polycarboxylic acid and an aliphatic polyol, or a ring-opening polymer of a cyclic ester.

[0021] Examples of the aliphatic polycarboxylic acid include aliphatic polycarboxylic acids having 2 to 30 carbon atoms. Examples of the aliphatic polycarboxylic acid include oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, phenylsuccinic acid, and 1,4-phenylenediacetic acid.

[0022] Examples of the aliphatic polyol include aliphatic polyols having 2 to 30 carbon atoms. Examples of the aliphatic polyol include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, polytetramethylene glycol, 1,4-cyclohexanedimethanol, and 1,4-benzenedimethanol.

[0023] The aliphatic polyester resin may contain a polyol such as a monosaccharide or polysaccharide as a constituent unit in place of a portion of the aliphatic polyol.

[0024] The cyclic ester may be, for example, a dimeric cyclic ester of an α-hydroxycarboxylic acid, a lactone, a cyclic ether ester, a cyclic carbonate, etc. Examples of α-hydroxycarboxylic acids that form dimeric cyclic esters include glycolic acid, L-lactic acid, D-lactic acid, α-hydroxybutyric acid, α-hydroxyisobutyric acid, α-hydroxyvaleric acid, α-hydroxycaproic acid, α-hydroxyisocaproic acid, α-hydroxyheptanoic acid, α-hydroxyoctanoic acid, α-hydroxydecanoic acid, α-hydroxymyristic acid, α-hydroxystearic acid, and alkyl-substituted derivatives thereof.

[0025] Examples of the lactone include β-propiolactone, β-butyrolactone, pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, and ε-caprolactone.

[0026] Examples of the cyclic ether ester include dioxanones such as 1,4-dioxan-2-one (p-dioxanone).

[0027] The cyclic carbonate includes 1,3-dioxane-2-one (trimethylene carbonate).

[0028] Specific examples of aliphatic polyesters include polylactic acid, polybutylene sebacate, polybutylene succinate, polybutylene succinate / adipate, polypropylene sebacate, polypropylene succinate, polypropylene succinate / adipate, and polyglycolic acid.

[0029] The aliphatic polyester resin contained in the aliphatic polyester resin composition is preferably a polylactic acid resin. The polylactic acid resin contained in the aliphatic polyester resin composition may be a homopolymer of lactic acid or a copolymer of lactic acid and another monomer. Examples of other monomers in the copolymer include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, and aliphatic polycarboxylic acids. The monomer may be, for example, a polyfunctional polysaccharide.

[0030] The lactic acid constituting the polylactic acid resin may be either or both of the L- and D-forms. The polylactic acid resin may be any of poly(L-lactic acid) resin, poly(D-lactic acid) resin, and poly(DL-lactic acid) resin. The polylactic acid resin preferably contains a higher proportion of the L-form than the D-form in order to provide excellent strength to the foamed layer. However, poly(L-lactic acid) resins containing essentially 100% L-form by mass have excellent mechanical strength but tend to cause the foamed layer to become brittle. Therefore, the polylactic acid resin of this embodiment preferably has a proportion (mass proportion) of the D-form of the total of the D- and L-forms of 0.1% by mass or more. This mass proportion is more preferably 0.2% by mass or more, and particularly preferably 0.3% by mass or more. A high proportion of the D-form may result in the foamed layer not providing excellent strength. Therefore, the proportion of the D-isomer in the total of the D- and L-isomers is preferably 4% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less. That is, the mass ratio of the D- to L-isomer (D- / L-isomer) is preferably within the range of 0.1 / 99.9 to 4 / 96. This preferable mass ratio of the D- to L-isomer also applies to copolymers.

[0031] The aliphatic polyester resin composition preferably contains a polylactic acid resin (modified polylactic acid resin) that is a resin modified with an organic peroxide, and more preferably contains a modified polylactic acid resin in which the homopolymers are crosslinked with an organic peroxide. By making at least a portion of the polylactic acid resin contained in the aliphatic polyester resin composition a modified polylactic acid resin crosslinked with an organic peroxide, toughness can be imparted to the foam layer.

[0032] Examples of organic peroxides for crosslinking the polylactic acid resin include peroxyesters, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxyketals, and ketone peroxides.

[0033] Examples of the peroxy ester 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.

[0034] Examples of the hydroperoxide include permethane hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide.

[0035] Examples of the dialkyl peroxide include dicumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3.

[0036] Examples of the diacyl peroxide include dibenzoyl peroxide, di(4-methylbenzoyl) peroxide, and di(3-methylbenzoyl) peroxide.

[0037] Examples of the peroxydicarbonate include di(2-ethylhexyl) peroxydicarbonate and diisopropyl peroxydicarbonate.

[0038] Examples of the 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, etc. Examples of the ketone peroxides include methyl ethyl ketone peroxide, acetylacetone peroxide, etc.

[0039] The organic peroxide is preferably a peroxyester, since it is easy to make the aliphatic polyester resin composition suitable for foaming. Furthermore, among peroxyesters, the organic peroxide used for crosslinking the aliphatic polyester resin such as polylactic acid resin is preferably a peroxycarbonate-based organic peroxide such as peroxymonocarbonate or peroxydicarbonate. In this embodiment, the organic peroxide used for crosslinking the aliphatic polyester resin is preferably a peroxymonocarbonate-based organic peroxide among peroxycarbonate-based organic peroxides, and particularly preferably t-butylperoxyisopropyl monocarbonate.

[0040] When modifying polylactic acid resin, the organic peroxide is typically used in a proportion of 0.1 parts by mass or more per 100 parts by mass of the polylactic acid resin to be crosslinked. By using an amount of 0.1 parts by mass or more of the organic peroxide, the crosslinking effect on the modified polylactic acid resin can be more reliably achieved. The amount of organic peroxide used is preferably 0.2 parts by mass or more, and particularly preferably 0.3 parts by mass or more. The amount of organic peroxide used is preferably 2.0 parts by mass or less. By using an amount of organic peroxide used of 2.0 parts by mass or less, the presence of gel in the modified polylactic acid resin after crosslinking can be suppressed. The amount of organic peroxide used is more preferably 1.5 parts by mass or less, and particularly preferably 1.0 part by mass or less per 100 parts by mass of the polylactic acid resin. Crosslinking the polylactic acid resin using an organic peroxide in such a proportion can make the modified polylactic acid resin suitable for foaming.

[0041] By incorporating a modified polylactic acid resin into an aliphatic polyester resin composition, the viscosity of the aliphatic polyester resin composition when melted is improved, making it easier to ensure the thickness of the bubble membrane that forms the cells during foaming. Furthermore, improving the viscosity of the aliphatic polyester resin composition when melted makes it easier to apply shear force to the butadiene rubber during kneading, which can also be expected to have the effect of finely dispersing the butadiene rubber. Therefore, modifying the polylactic acid resin not only improves the brittleness of the resin itself, but also has the effect of improving the brittleness of the foam board in terms of its microstructure.

[0042] The aliphatic polyester resin, such as modified polylactic acid resin, contained in the aliphatic polyester resin composition preferably has a melt mass-flow rate (MFR) of 0.1 g / 10 min or more. The melt mass-flow rate of the aliphatic polyester resin is more preferably 0.5 g / 10 min or more, and even more preferably 1 g / 10 min or more. The melt mass-flow rate of the aliphatic polyester resin is preferably 10 g / 10 min or less, more preferably 8 g / 10 min or less, and even more preferably 5 g / 10 min or less.

[0043] The melt mass flow rate (MFR) of the aliphatic polyester resin or the aliphatic polyester resin composition can be determined, for example, as follows.

[0044] (How to calculate the melt mass-flow rate (MFR)) The melt mass flow rate of an aliphatic polyester resin or an aliphatic polyester resin composition can be measured using, for example, a "Semi-Auto Melt Indexer 2A" manufactured by Toyo Seiki Seisakusho, Ltd. The MFR can be measured by measuring the time it takes for a piston to move a predetermined distance as described in JIS K7210-1:2014 "Plastics - Determination of melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastic plastics - Part 1" Method B. In principle, the measurement conditions are as follows: Sample: 3 to 8 g The sample to be measured is vacuum dried at 70°C for 4 hours, and after drying, it is placed in a nylon plastic bag for vacuum packing, vacuum packed, and stored in a desiccator until immediately before measurement. Preheat: 270 seconds Load hold: 30 seconds Test temperature: 190℃ Test load: 2.16 kg (21.18 N) Piston travel distance (interval): 25mm The test is carried out for each sample three times, and the average of the three tests is taken as the melt mass-flow rate (g / 10 min).

[0045] The resins contained in the aliphatic polyester resin composition may consist solely of an aliphatic polyester resin and a butadiene rubber, or may contain other resins. The proportion of the aliphatic polyester resin in all resins contained in the aliphatic polyester resin composition can be 80% by mass or more. This proportion may be 85% by mass or more, or even 90% by mass or more. When the butadiene rubber is a butadiene homopolymer, it is contained in an amount of 0.3 parts by mass or more and 4.0 parts by mass or less per 100 parts by mass of the aliphatic polyester resin, as described above. On the other hand, a copolymer rubber containing a butadiene component can be contained in the aliphatic polyester resin composition so that its proportion in all resins is 8% by mass or less. This proportion may be 7% by mass or less, or may be 6% by mass or less. The proportion of the butadiene homopolymer or the copolymer rubber containing a butadiene component in all resins contained in the aliphatic polyester resin composition is, for example, 1% by mass or more. This proportion may be 1.5% by mass or more, or may be 2% by mass or more.

[0046] The aliphatic polyester resin contained in the aliphatic polyester resin composition may be polylactic acid resin alone or a combination of polylactic acid resin and other aliphatic polyester resins. The proportion of the polylactic acid resin in all the aliphatic polyester resins contained in the aliphatic polyester resin composition may be 80% by mass or more. This proportion may be 85% by mass or more, or 90% by mass or more. 95% by mass or more of the aliphatic polyester resin contained in the aliphatic polyester resin composition may be polylactic acid resin.

[0047] The polylactic acid resin contained in the aliphatic polyester resin composition may be a modified resin alone, or a combination of a modified polylactic acid resin and an unmodified polylactic acid resin (unmodified resin). The proportion of the modified polylactic acid resin in the total polylactic acid resin contained in the aliphatic polyester resin composition may be 80% by mass or more. This proportion may be 85% by mass or more, or 90% by mass or more. 95% by mass or more of the polylactic acid resin contained in the aliphatic polyester resin composition may be modified polylactic acid resin.

[0048] The aliphatic polyester resin composition may further contain various additives such as polymers other than the aliphatic polyester resin, pigments, and additives for adjusting the foaming state such as a cell adjusting agent.

[0049] The aliphatic polyester resin composition may contain additives such as glycerin fatty acid esters. Examples of glycerin fatty acid esters include monoglycerides such as glycerin monostearate, glycerin monobehenate, glycerin mono-12-hydroxystearate, glycerin monooleate, glycerin monocaprylate, glycerin monocaprate, and glycerin monolaurate; and mono- and diglycerides such as glycerin monodistearate, glycerin monodibehenate, and glycerin monodiolate. The aliphatic polyester resin composition may be incorporated into an aliphatic polyester resin foam board by being applied to the surface.

[0050] The aliphatic polyester resin foam board of this embodiment is a plate-like body having a thickness of 1 mm or more and including only a foam layer composed of the above-described aliphatic polyester resin composition. The thickness of the aliphatic polyester resin foam board (hereinafter simply referred to as "foam board") may be 2 mm or more. The thickness of the foam board is, for example, 10 mm or less. The thickness of the foam board may be 8 mm or less, or may be 6 mm or less. When the foam board of this embodiment includes other layers such as a non-foamed layer rather than a foam layer alone, the overall thickness can also be set to the above value. The thickness of the foam board of this embodiment is calculated as the arithmetic average of thickness measurements at multiple randomly selected locations (e.g., 10 locations), and is calculated as the arithmetic average of measurements using a thickness gauge.

[0051] The foam board of this embodiment may be an extruded foam sheet produced by an extrusion foaming method. The foam board of this embodiment has an apparent density of the foam layer of 300 kg / m 3 The apparent density of the foam layer is preferably 250 kg / m or less. 3 may be less than 200 kg / m 3 The apparent density of the foam layer may be, for example, 70 kg / m or less. 3 It can be more than that.

[0052] In the foam board of this embodiment, the aliphatic polyester resin in the foam layer has a crystallinity of 25% or more. The crystallinity may be 30% or more, or even 35% or more. The foam board of this embodiment, in which the aliphatic polyester resin is contained in the foam layer in a state of high crystallinity, has excellent strength and toughness. The crystallinity is, for example, 60% or less.

[0053] In the case of extruded foam sheets, the aliphatic polyester resin composition typically cools and solidifies before the aliphatic polyester resin is sufficiently crystallized. In particular, when a crosslinked modified polylactic acid resin is included, sufficient crystallization is difficult because the molecular motion of the polylactic acid resin is restricted by the crosslinking. Therefore, in this embodiment, it is preferable to extrude and foam the aliphatic polyester resin composition into a molten state by melt-kneading it in an extruder or the like into the atmosphere to produce an extruded foam sheet with a crystallinity of less than 25%, and then heat the extruded foam sheet to increase the crystallinity to the above-mentioned value, thereby producing a foam plate.

[0054] A foamed board with improved crystallinity in this way not only has excellent strength and toughness, but also is less susceptible to distortion due to heat (excellent dimensional stability). The foamed board of this embodiment, which is less susceptible to distortion due to heat, is suitable, for example, as a peripheral frame for a folding lunch box that contains freshly cooked rice or side dishes immediately after cooking. The foamed board preferably exhibits a dimensional change of 5% or less when heated at a temperature of 90°C. The dimensional change is more preferably 4% or less, and particularly preferably 3% or less.

[0055] The foam board of this embodiment can be used as a component of the following folding box. The folding box of this embodiment has a peripheral frame that rises in the shape of a square tube. The peripheral frame is composed of a plurality of flat side walls. The peripheral frame has corners between adjacent side walls in the circumferential direction. The peripheral frame may be a square frame formed by bonding the ends of four strip-shaped foam boards that form each side wall. The peripheral frame may be a hexagonal frame formed by bonding the ends of six strip-shaped foam boards. The shape of the peripheral frame when viewed from above may be other than square or hexagonal.

[0056] The folding box may have a peripheral frame in which the side walls constituting the peripheral frame do not have to be made of independent individual members, but may have a peripheral frame in which a strip-shaped foam board having a length corresponding to the side walls is bent at the corners. The folding box may be made by bending a single foam board in which the side walls constituting the peripheral frame are connected to a bottom plate.

[0057] The folding box BX shown in Figures 1 and 2 includes a bottom plate BW, a cylindrical peripheral frame FB rising from the outer periphery of the bottom plate BW, and a cover plate CW closing the upper opening FBa of the peripheral frame FB. The bottom plate BW of the folding box BX illustrated in these figures has a polygonal shape in plan view, specifically a square, and more specifically a rectangle. The peripheral frame FB of the folding box BX is composed of four side walls SW, forming a rectangular frame (square tube). The cover plate CW has a shape common to the bottom plate BW and is arranged opposite the bottom plate BW at a distance in the vertical direction. The bottom plate BW, side walls SW, and cover plate CW are each flat, and the folding box BX of this embodiment is a rectangular parallelepiped with six faces formed by six flat plate portions FP.

[0058] In the folding box BX of this embodiment (shown in Figures 1 and 2), adjacent flat plate portions FP are connected to each other at at least one of the corner portions CP on the 12 sides of the rectangular parallelepiped (four sides at the boundaries between the outer edge of the cover plate CW and the four side walls SW, four sides at the boundaries between the side walls SW, and four sides at the boundaries between the outer edge of the bottom plate BW and the four side walls SW). As shown in Figure 1, a V-groove VC is formed at the location where the flat plate portions FP are connected to each other. The folding box BX of this embodiment is formed by folding a foam plate 10 in a direction that narrows the groove width of the V-groove VC, and has a corner portion CP formed by a mountain fold on the side opposite the V-groove VC. In the folding box BX of this embodiment, V-grooves VC are formed at the boundaries between the four sides of the bottom plate BW and the four side walls SW, and at the boundary between one of the four side walls SW and the cover plate CW, and a total of five corner portions CP are formed by bending the V-grooves VC.

[0059] A folding box may be made of foam board alone, or may be made of a combination of foam board and a material other than foam board. For example, the folding box shown in Figures 3 and 4 has a bottomed, cylindrical container body CB for containing contents made of a material such as cardboard, and a cylindrical peripheral frame FB surrounding the container body CB made of foam board 10. The container body CB has a bottomed, cylindrical main body portion CH that is slightly smaller than the peripheral frame FB and can be accommodated within the peripheral frame FB, and a flange portion FR that extends outward from the upper opening edge of the main body portion CH. The container body CB is configured so that the flange portion FR is larger than the inner shape of the peripheral frame FB, and the flange portion FR is supported from below by the peripheral frame FB when the main body portion CH is accommodated in the peripheral frame FB.

[0060] The peripheral frame FB of this embodiment (shown in FIGS. 3 and 4 ) has an octagonal cylindrical shape. The peripheral frame FB of this embodiment has four side walls SW that are relatively long in the circumferential direction and four side walls SW that are shorter than the four side walls SW. The peripheral frame FB of this embodiment has eight side surfaces, with long and short side walls SW arranged alternately in the circumferential direction. The peripheral frame FB is used as a folding box BX by combining with a container body CB. As shown in the figures, the peripheral frame FB is formed of a strip-shaped foam board 10 with multiple V-shaped grooves VC on one side. The foam board 10 has a first direction that is the circumferential direction of the peripheral frame FB and a second direction that is perpendicular to the first direction and is the up-down direction of the peripheral frame FB. The multiple V-shaped grooves VC are provided at multiple locations spaced apart in the first direction and extend in the second direction. The peripheral side frame FB of this embodiment is formed by bending a foamed plate 10 in the direction in which the groove width of the V-groove VC narrows, and includes a corner portion CP that is a mountain fold on the side opposite the V-groove VC, and a flat plate portion FP that forms between the two corner portions CP.

[0061] The folding box BX of this embodiment is made of a foamed plate 10 with excellent toughness, which suppresses dust generation from the cut end surface. Furthermore, the folding box BX illustrated in the figures suppresses dust generation and chipping during the cutting process for forming the V-grooves VC. Furthermore, the folding box BX is also suppressed from cracking in the foamed plate 10 during bending at the V-grooves VC. The foamed plate 10x of this embodiment is useful for forming a folding box BX in which two V-grooves VC are formed in such a short section and then bent.

[0062] Although folding boxes are an example of a preferred application of the foam board of this embodiment because it can be cut and folded, the foam board can also be used for various applications other than folding boxes. The above examples are merely specific examples, and the foam board of the present invention is not limited to the above examples. [Example]

[0063] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0064] Example 1 The aliphatic polyester resin foam board was made from modified polylactic acid resin. The modified polylactic acid resin was prepared as follows.

[0065] (Preparation of modified polylactic acid resin) Polylactic acid resin (Nature Works Biopolymer Ingeo 6202D, MFR = 10.1 g / 10 min, density = 1.24 g / cm 3 100 parts by mass of tert-butylperoxyisopropyl monocarbonate (KAYACARBON BIC-75 manufactured by Kayaku Akzo Co., Ltd., 1-minute half-life temperature T1: 158.8°C) and 0.5 parts by mass of tert-butylperoxyisopropyl monocarbonate (KAYACARBON BIC-75 manufactured by Kayaku Akzo Co., Ltd., 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 temperature of the feed section was set to 170°C, and the temperature thereafter to 230°C. The mixture was melt-kneaded in a twin-screw extruder at a rotation speed of 150 rpm, and the kneaded material was extruded in the form of strands at a discharge rate of 50 kg / h from a die with a diameter of 3 mm and 18 holes attached to the tip of the extruder. Next, the extruded strand-like kneaded product was passed through a 2 m long cooling water tank containing water at 30°C to cool it. The cooled strand was cut with a pelletizer to obtain pellets of the modified polylactic acid resin.

[0066] (Preparation of primary foam sheet) A mixture was prepared by dry blending 100 parts by mass of the modified polylactic acid resin obtained by the method described above, 1.0 part by mass of a cell regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.), and 3 parts by mass of copolymer rubber ("Metablen C-223A" (MBS polymer) manufactured by Mitsubishi Chemical Corporation). In a tandem extruder equipped with a first extruder (upstream) with a bore diameter of φ50 mm and a second extruder (downstream) with a bore diameter of φ65 mm, the obtained mixture was supplied to the first extruder with a bore diameter of φ50 mm through a hopper and heated to melt. Thereafter, butane (isobutane / normal butane=70 / 30) as a foaming agent was pressure-fed into the first extruder and melt-mixed with the mixture. Next, this molten mixture was transferred to a second extruder with a diameter of 65 mm and uniformly cooled to a temperature suitable for extrusion foaming, and then extrusion foaming was carried out through a circular die with a diameter of 70 mm at a discharge rate of 30 kg / h to obtain a cylindrical foam. The obtained cylindrical foam was placed on a φ206 mm mandrel whose inside was cooled with water at about 20°C, and its outer surface was cooled and molded by blowing air onto it using an air ring larger in diameter than the mandrel. The foam was then cut open at one point on the circumference using a cutter to obtain a strip-shaped primary foamed sheet. The crystallinity of the primary foamed sheet at this time was 8.8%.

[0067] The primary foamed sheet obtained by the above method was passed through a conveyor heater (heating zone temperature 120°C, length 3.0 m) at a moving speed of 2 m / min to be heated and cooled, and then cut into foam boards by a cutter. The crystallinity of the foam plate at this stage was 42%. The crystallinity of the foam board and the primary foam sheet was measured as follows.

[0068] (Measurement of crystallinity) The crystallinity was measured based on JIS K7121:1987 and JIS K7121:2012, but the temperature rise rate was 5°C / min. However, the sampling method and temperature conditions were as follows: 5.5±0.5 mg of sample was packed into the bottom of an aluminum measurement container so that there were no gaps, and then the aluminum lid was placed on it. Next, differential scanning calorimetry was performed using a Hitachi High-Tech Science DSC7000X, AS-3 differential scanning calorimeter. The DSC curve was obtained by heating in the following steps under a nitrogen gas flow rate of 20 mL / min. (Step 1) Hold at 30°C for 2 minutes. (Step 2) The temperature is increased from 30°C to 210°C at a rate of 5°C / min. Alumina was used as the reference material. The difference between the heat of fusion (J / g) determined from the area of ​​the melting peak and the heat of crystallization (J / g) determined from the area of ​​the crystallization peak was calculated. The degree of crystallinity was calculated by dividing this difference by the theoretical heat of fusion of perfectly crystalline polylactic acid (93 J / g). The heat of fusion and the heat of crystallization were calculated using the analysis software provided with the apparatus. Specifically, the heat of fusion was calculated from the area enclosed by the line connecting the point where the DSC curve departs from the low-temperature baseline and the point where the DSC curve returns to the high-temperature baseline, and the area enclosed by the line connecting the point where the DSC curve departs from the low-temperature baseline and the point where the DSC curve returns to the high-temperature baseline. The heat of crystallization was calculated from the area enclosed by the line connecting the point where the DSC curve departs from the low-temperature baseline and the point where the DSC curve returns to the high-temperature baseline, and the area enclosed by the line connecting the point where the DSC curve departs from the low-temperature baseline and the point where the DSC curve returns to the high-temperature baseline. That is, the crystallinity was calculated using the following formula: Crystallinity (%) = (Heat of fusion (J / g) - Heat of crystallization (J / g)) / 93(J / g)×100(%)

[0069] The amount of the butadiene rubber component in the foam plate of Example 1 was 1.4 parts by mass.

[0070] The butadiene rubber content was measured as follows. Approximately 0.1 g of the foam sample was dissolved in approximately 20 mL of chloroform, and a film was prepared on a hot plate. Approximately 0.1 to 0.5 mg of the filmed sample was precisely weighed. A test specimen was prepared by wrapping the sample in a ferromagnetic metal body called "Pyrofoil" manufactured by Japan Analytical Industry Co., Ltd., which has a Curie point of 590°C. The test specimen was prepared so that the ferromagnetic metal body was pressed onto the sample. The test specimen was heated in a Japan Analytical Industry Co., Ltd. "JPS-700" Curie Point Pyrolyzer to decompose the sample. The 4-vinylcyclohexene produced by decomposition was measured using an Agilent Technologies GC7820 gas chromatograph (detector: FID) and the peak area was calculated. The amount of butadiene contained in the sample was calculated from a calibration curve prepared in advance. (Pyrolysis conditions) Measuring device: Japan Analytical Industry Co., Ltd. "JPS-700" Pyrofoil Sampler Heating temperature=590℃ Heating time=5sec Oven temperature = 300°C Needle temperature = 300℃ (GC measurement conditions) Measurement equipment: Agilent Technologies "7820A" gas chromatograph Detector = FID Column: Agilent Technologies "DB-5" capillary column (0.25 μm x 0.25 mm φ x 30 m) (GC oven temperature rise conditions) Initial temperature = 50℃ (held for 0.5min) First stage heating rate = 10°C / min (up to 200°C, hold for 0 min) Second stage heating rate = 20℃ / min (up to 320℃) Final temperature = 320℃ (held for 0.5min) Carrier gas = He He flow rate=63.736mL / min Inlet pressure = 100 kPa Column inlet pressure = 100 kPa Inlet temperature=300℃ Detector temperature = 300°C Split ratio = 1 / 50 The standard sample used for preparing the calibration curve was Metablen C-223A manufactured by Mitsubishi Chemical Corporation.

[0071] Furthermore, the foam board of Example 1 was evaluated as follows.

[0072] (Measurement of apparent density) The apparent density of the foam board was measured by the method described in JIS K7222:1999 "Foamed plastics and rubber - Measurement of apparent density", specifically, by the following method. From foam sheet, 100cm 3 The above samples were cut without changing the original cell structure, and the samples were conditioned for 16 hours in a JIS K7100:1999, 23 / 50, Class 2 environment. Thereafter, the dimensions and mass were measured, and the apparent 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.

[0073] (Measurement of dimensional change rate due to heating) Five flat square test pieces, each about 10 cm on a side, were cut out from the foam plate so that each side was parallel to the extrusion direction (MD) or transverse direction (TD) of the foam plate. Next, two straight lines were drawn on the surface of each test piece, connecting the centers of the opposing sides in the shape of a cross. At this time, the lengths of the straight lines in each direction before heating were defined as MD1 and TD1. Next, each test piece was placed on a platform in an oven set to 90°C without humidity control, heated for 150 seconds, then removed from the oven and cooled at room temperature for 30 minutes. Thereafter, the lengths of the straight lines drawn in each direction before heating were measured, and the arithmetic mean value of the measured lengths of each test piece was taken as the length after heating. From the obtained lengths MD2 and TD2 after heating and the lengths MD1 and TD1 before heating, the ratio of the length before heating (MD1) to the length after heating (MD2) in the extrusion direction (MD ratio = MD2 / MD1) and the ratio of the length before heating (TD1) to the length after heating (TD2) in the width direction (TD ratio = TD2 / TD1) were calculated. In this case, the ratio of the larger change was judged as "◎" if it was "0.99 or more and 1.01 or less" (dimensional change rate 1% or less), "〇" if it was "0.97 or more and less than 0.99 or more than 1.01 and 1.03" (dimensional change rate more than 1% and 3% or less), "△" if it was "0.95 or more and less than 0.97 or more than 1.03 and 1.05" (dimensional change rate more than 3% and 5% or less), and "×" if it was "less than 0.95 or more than 1.05" (dimensional change rate more than 5%).

[0074] (Evaluation of foam board workability) Machinability was evaluated based on the occurrence of chipping and chips during V-groove machining. A V-groove spanning the entire width of the foam board in the width direction perpendicular to the extrusion direction was formed by cutting, and the board was then cut into 35 mm wide strips that were long in the extrusion direction perpendicular to the V-groove direction.Then, an evaluation was conducted to see how chips and chips would occur. At this time, if "chipping" or "chips" occurred in the cut area, it was judged as a poor "x", and if no "chipping" or "chips" occurred, it was judged as a good "o".

[0075] <Overall rating> Dimensional change rate after heating: ◎: 5 ​​points, 〇: 3 points, △: 1 point, ×: 0 points Workability...◎: 5 points, ×: 0 points According to the above scores, the rate of dimensional change during heating (dimensional stability) and processability were evaluated, and an overall evaluation was carried out by adding up the scores of both, with 10 points being rated as A, 8 points as B, 6 points as C, and 5 points or less as D. The results are shown in Table 1 below.

[0076] Example 2 A foam plate was produced and evaluated in the same manner as in Example 1, except that the moving speed in the conveyor heater was set to 5 m / min. The foamed plate had a crystallinity of 26% and contained 1.4 parts by mass of butadiene rubber.

[0077] Example 3 A foam plate was produced and evaluated in the same manner as in Example 1, except that the moving speed in the conveyor heater was set to 3 m / min. The foamed plate had a crystallinity of 36% and contained 1.4 parts by mass of butadiene rubber.

[0078] Example 4 A foam plate was prepared and evaluated in the same manner as in Example 1, except that the amount of copolymer rubber containing a butadiene component added was 1 part by mass. The foamed plate had a crystallinity of 45% and contained 0.5 parts by mass of butadiene rubber.

[0079] Example 5 A foam plate was prepared in the same manner as in Example 1, except that the amount of copolymer rubber containing a butadiene component added was 5 parts by mass, and evaluation was carried out. The foamed plate had a crystallinity of 43% and contained 2.4 parts by mass of butadiene rubber.

[0080] Example 6 A foam plate was prepared and evaluated in the same manner as in Example 1, except that the amount of copolymer rubber containing a butadiene component added was 8 parts by mass. The foamed plate had a crystallinity of 43% and contained 3.8 parts by mass of butadiene rubber.

[0081] Example 7 The primary foamed sheet was prepared in the following manner (the polylactic acid resin was also modified in the extruder that extrudes the primary foamed sheet), and the crystallinity of the foamed sheet was adjusted and evaluated under the same heating conditions as in Example 1. The crystallinity of the foamed plate at this time was 41%.

[0082] (Preparation of primary foamed sheet in Example 7) A mixture was prepared by dry blending 100 parts by mass of polylactic acid resin, 0.3 parts by mass of t-butylperoxyisopropyl monocarbonate ("Kayacarvone BIC-75" manufactured by Kayaku Akzo Co., Ltd., 1-minute half-life temperature T1: 158.8°C), 1.0 part by mass of a cell regulator ("Crown Talc" manufactured by Matsumura Sangyo Co., Ltd.), and 3 parts by mass of copolymer rubber ("Metablen C-223A" manufactured by Mitsubishi Chemical Corporation). In a tandem extruder equipped with a first extruder (upstream) with a bore diameter of φ50 mm and a second extruder (downstream) with a bore diameter of φ65 mm, the obtained mixture was supplied to the first extruder with a bore diameter of φ50 mm through a hopper and heated to melt. Thereafter, butane (isobutane / normal butane=70 / 30) as a foaming agent was pressure-fed into the first extruder and melt-mixed with the mixture. Next, this molten mixture was transferred to a second extruder with a diameter of 65 mm and uniformly cooled to a temperature suitable for extrusion foaming, and then extrusion foaming was carried out through a circular die with a diameter of 70 mm at a discharge rate of 30 kg / h to obtain a cylindrical foam. The obtained cylindrical foam was placed on a φ206 mm mandrel whose inside was cooled with water at about 20°C, and its outer surface was cooled and molded by blowing air onto it using an air ring larger in diameter than the mandrel. The foam was then cut open at one point on the circumference using a cutter to obtain a strip-shaped primary foamed sheet. The primary foamed sheet had a crystallinity of 9.1%, and the foamed plate had a crystallinity of 41%, with the amount of butadiene rubber being 1.4 parts by mass.

[0083] Example 8 The primary foamed sheet was prepared in the following manner (the polylactic acid resin was also modified in the extruder that extrudes the primary foamed sheet), and the crystallinity of the foamed sheet was adjusted and evaluated under the same heating conditions as in Example 1. The crystallinity at this time was 42%.

[0084] (Preparation of primary foamed sheet in Example 8) Polylactic acid resin (Nature Works Biopolymer Ingeo 6202D, MFR = 10.1 g / 10 min, density = 1.24 g / cm) was fed into a mixing screw installed in a twin-screw extruder with a bore of 41 mm. 3 100 parts by mass of tert-butylperoxyisopropyl monocarbonate (KAYACARBON BIC-75 manufactured by Kayaku Akzo Co., Ltd., 1-minute half-life temperature T1: 158.8°C), 0.4 parts by mass of a cell regulator (CROWN TALC manufactured by Matsumura Sangyo Co., Ltd.), and 3 parts by mass of copolymer rubber (METABLEN C-223A manufactured by Mitsubishi Chemical Corporation) were fed and mixed, and then fed into an extruder to be heated and melted. Thereafter, butane (isobutane / normal butane = 70 / 30) as a foaming agent was pressure-fed into the extruder and melt-mixed with the mixture. The mixture was then extruded through a circular die with a diameter of 70 mm at a discharge rate of 30 kg / h to obtain a cylindrical foam. The obtained cylindrical foam was placed on a φ206 mm mandrel whose inside was cooled with water at about 20°C, and its outer surface was cooled and molded by blowing air onto it using an air ring larger in diameter than the mandrel. The foam was then cut open at one point on the circumference using a cutter to obtain a strip-shaped primary foamed sheet. The primary foamed sheet had a crystallinity of 7.8%, and the foamed plate had a crystallinity of 42%, with the amount of butadiene rubber being 1.4 parts by mass.

[0085] (Comparative Example 1) The primary foamed sheet of Example 1 (crystallinity: 8.8%, amount of butadiene rubber: 1.4 parts by mass) was used as a foamed plate without being heated by a conveyor heater, and was evaluated in the same manner as in Example 1.

[0086] (Comparative Example 2) A foam plate was produced and evaluated in the same manner as in Example 1, except that the amount of copolymer rubber containing a butadiene component added was 0 parts by mass (no copolymer rubber was included). At this time, the crystallinity of the foam board was 41%.

[0087] (Comparative Example 3) A foam plate was prepared in the same manner as in Example 1, except that the amount of copolymer rubber containing a butadiene component added was 10 parts by mass, and evaluation was carried out. At this time, the foam plate had a crystallinity of 41% and an amount of butadiene rubber of 4.9 parts by mass.

[0088] Comparative Example 4 A foam plate was produced without heating in the same manner as in Comparative Example 1, except that 10 parts by mass of an acrylic resin was added instead of the copolymer rubber containing a butadiene component, and evaluation was carried out. At this time, the crystallinity was 9.4%.

[0089] The above evaluation results are shown in Table 1 below.

[0090] [Table 1]

[0091] From the above results, it is clear that the present invention improves the brittleness of aliphatic polyester resin foam boards, making it possible to provide folding boxes that are excellent in dimensional stability and easy to manufacture.

Claims

1. An aliphatic polyester-based resin foam board having at least one foam layer, the foam layer being made of an aliphatic polyester-based resin composition containing an aliphatic polyester-based resin, the aliphatic polyester-based resin composition further contains a methyl methacrylate-butadiene-styrene copolymer, which is a copolymer rubber containing a butadiene rubber component, and the butadiene rubber component is contained in a proportion of 0.3 parts by mass or more and 4.0 parts by mass or less per 100 parts by mass of the aliphatic polyester-based resin; The aliphatic polyester-based resin foam board has a crystallinity of 25% or more in the foam layer.

2. 2. The aliphatic polyester resin foam board according to claim 1, which has a dimensional change of 5% or less when heated at 90°C.

3. 3. The aliphatic polyester resin foam board according to claim 1, wherein the aliphatic polyester resin composition contains a polylactic acid resin as the aliphatic polyester resin.

4. 4. The aliphatic polyester resin foam board according to claim 3, wherein said polylactic acid resin is a resin modified with an organic peroxide.

5. A folding box having a peripheral side frame made of a resin foam board having at least one foam layer, the foam layer is made of an aliphatic polyester-based resin composition containing an aliphatic polyester-based resin, the aliphatic polyester-based resin composition further contains a methyl methacrylate-butadiene-styrene copolymer, which is a copolymer rubber containing a butadiene rubber component, and the butadiene rubber component is contained in a proportion of 0.3 parts by mass or more and 4.0 parts by mass or less per 100 parts by mass of the aliphatic polyester-based resin; The folding box has a crystallinity of 25% or more for the aliphatic polyester resin in the foam layer.

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