JP2007118578A - Polylactic acid resin foamed sheet molded article and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid resin foamed sheet molded article which is be manufactured by a shortened molding cycle time, and which has practical heat resistance, excellent appearance, and excellent environmental suitability, and to provide the manufacturing method of the molded article in which the thermoforming of a polylactic acid resin is carried out by pinching it with a pair of molds, the deformation of a foamed sheet molded article is inhibited when releasing in carrying out the crystallization treatment, and too long shaping cycle time can be shortened. <P>SOLUTION: This polylactic acid resin foamed sheet molded article is obtained by carrying out the thermoforming of a crystalline polylactic acid resin foamed sheet, wherein the difference of the degrees of crystallinity between one split body and the other split body which are obtained by partitioning the molded article in the center section of the thickness of the molded article is 5% or more, the degree of crystallinity of one split body is ≥25% and ≤70% and the degree of crystallinity of the other split body is ≥0% and <25%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polylactic acid resin foam sheet molded article having excellent heat resistance and appearance, and a production method thereof by thermoforming.

  In recent years, awareness of the global environment has increased, and environmental problems such as depletion of petroleum resources have been highlighted. Plant-derived polylactic acid resins have been replaced by conventional resins such as polystyrene resins that use petroleum resources as raw materials. Attention has been paid. Among them, the polylactic acid resin foam sheet is expected to be widely used in the future because it is lighter and has higher heat insulation than a non-foamed polylactic acid resin sheet.

  However, the polylactic acid resin foam sheet has low heat resistance and cannot withstand practical use. For example, when an industrial component tray is formed from a polylactic acid resin foam sheet by thermoforming, and the component tray is transported by ship, the temperature rises to around 60 ° C in a container on the ocean. There is a problem that happens. Moreover, when a hot foodstuff is accommodated using a polylactic acid resin foamed sheet molding as a food container, there is a problem that the container is greatly deformed.

  For example, Patent Literature 1 and Patent Literature 2 disclose a technique for improving the heat resistance problem of a polylactic acid resin foam sheet molded body. The foam sheet disclosed in Patent Document 1 or Patent Document 2 is a foam sheet formed by extrusion foaming a crystalline polylactic acid resin or a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin. Thus, by adjusting the crystal state of the polylactic acid resin, both thermoformability and heat resistance are achieved. That is, a polylactic acid resin foam sheet having a low crystallinity is excellent in moldability but inferior in heat resistance. On the other hand, a polylactic acid resin foamed sheet having a high degree of crystallinity is excellent in heat resistance. Based on this knowledge, in Patent Document 1 and Patent Document 2, by adjusting the foamed sheet in a state in which the degree of crystallinity of the polylactic acid resin is kept low, it is adjusted to one excellent in thermoformability, During or after thermoforming of the foamed sheet, the crystallized degree of the polylactic acid resin is promoted by maintaining the temperature within the range of the glass transition temperature of the polylactic acid resin and below the melting point to increase the degree of crystallinity. A method for improving the heat resistance of the molded body is described.

  However, the methods disclosed in Patent Document 1 and Patent Document 2 have problems to be improved. Usually, in order to obtain a foamed sheet molded body from a thermoplastic resin foamed sheet, so-called matched mold molding is employed in which a softened thermoplastic resin foamed sheet is sandwiched between a pair of molds. However, when a polylactic acid resin foam sheet is thermoformed by matched molding, the mold that has been adjusted to a high set temperature for crystallization treatment and the foam sheet molded body that has been heat-treated at a high temperature are sufficiently cooled. Otherwise, the foamed sheet molded body cannot be taken out from the mold, so that the molding cycle time becomes long and the productivity is not improved. Dare to open the mold before the foam sheet molded body is sufficiently cooled, if you try to take out the foam sheet molded body, the molded body sticks to the mold and can not be released smoothly, if you forcibly release The molded body is greatly deformed.

  Thus, in the matched mold molding of the polylactic acid resin foamed sheet, it was necessary to repeat heating and cooling of the mold, so that the molding cycle time took about 30 minutes. Accordingly, in view of the fact that the molding cycle time of a normal thermoplastic resin sheet is within 30 seconds, it is desired to shorten the molding cycle time in performing matched mold molding of a polylactic acid resin foamed sheet.

  Furthermore, the polylactic acid resin foamed sheet molded body heat-treated and thermoformed by the molding method described above was inferior in appearance because the surface of the molded body became uneven.

JP 2005-145058 A Examples of JP 2004-217288 A

  The present invention has been made in view of the above problems, and can be produced with a shortened molding cycle time, has practical heat resistance, has an excellent appearance, and is excellent in environmental suitability. It aims at providing the resin foam sheet molding. In addition, the present invention is to thermoform a polylactic acid resin foam sheet sandwiched between a pair of molds and prevent deformation of the foamed sheet molded body at the time of mold release, and an excessively long molding cycle. It aims at providing the manufacturing method of this molded object which can shorten time.

According to the present invention, the following polylactic acid resin foamed sheet molded body and a thermoforming method thereof are provided.
[1] A molded body obtained by thermoforming a crystalline polylactic acid resin foamed sheet, wherein one divided body and the other divided body obtained by dividing the molded body at the center of the molded body thickness The difference in crystallinity between the two divided bodies is 5% or more, the degree of crystallinity of one divided body is 25% or more and 70% or less, and the degree of crystallinity of the other divided body is 0% or more and less than 25%. Polylactic acid resin foam sheet molded product.
[2] The difference in crystallinity between the one divided body and the other divided body is 6% to 20%, the crystallinity of the one divided body is 25% to 35%, and the other The polylactic acid resin foamed sheet molded article according to [1] above, wherein the crystallinity of the divided product is 15% or more and less than 25%.
[3] In a method for producing a molded body in which a crystalline polylactic acid resin foam sheet is sandwiched between a pair of molds and thermoformed, the temperature of one mold is equal to or higher than the glass transition temperature of the foam sheet + 20 ° C. The glass transition temperature of the foamed sheet + 70 ° C. or lower is set, and the other mold is set to [glass transition temperature of the foamed sheet−40 ° C.] or higher and lower than the glass transition temperature of the foamed sheet. Thermoforming with a foam sheet sandwiched between molds, performing crystallization treatment, and then releasing the molded body from the one mold while holding the molded body on the other mold, then molding A method for producing a molded body of a polylactic acid resin foamed sheet, wherein the body is released from the other mold.
[4] The production of a polylactic acid resin foam sheet according to [3], wherein the crystalline polylactic acid resin foam sheet used for thermoforming has a crystallinity of 0% or more and 20% or less. Method.

The polylactic acid resin foamed sheet molded body of the present invention is excellent in heat resistance because one of the divided bodies has a high degree of crystallinity even though it can be produced with a shortened molding cycle time. It is. In addition, the polylactic acid resin foamed sheet molded body of the present invention has a crystallinity difference between one divided body and the other divided body within a specific range, and the other divided body has a low crystallinity. The molded body surface on the other divided body side having a low degree of crystallinity is excellent in appearance such as surface smoothness.
On the other hand, according to the method for producing a polylactic acid resin foamed sheet molding of the present invention, the crystalline polylactic acid resin foamed sheet has one mold set at a specific high temperature and the other set at a specific low temperature. A foamed sheet molded article having excellent heat resistance is obtained by performing thermocrystallization while sandwiching between the molds of the mold and releasing the foamed sheet molded article obtained from the one mold first. It can be taken out from the mold without being deformed. Further, according to the method of the present invention, the molding cycle time can be remarkably shortened.

Hereinafter, the thermoforming method of the polylactic acid resin foamed sheet molding of the present invention will be described.
In the method for producing a polylactic acid resin foamed sheet molded body (hereinafter also simply referred to as a molded body) of the present invention, a polylactic acid resin foamed sheet (hereinafter also simply referred to as a foamed sheet) made of a crystalline polylactic acid resin is appropriate. The polylactic acid resin foamed sheet is molded by a thermoforming method in which a molded body is manufactured by being heated between various temperatures and softened and then sandwiched between a pair of molds. Usually, the pair of molds are arranged one above the other, with the upper mold being a convex mold and the lower mold being a concave mold. However, the method of the present invention is not limited to this, and the upper mold may be a concave mold, the lower mold may be a convex mold, and a pair of molds may be arranged horizontally.
In the following description, one mold is an upper mold having a convex shape, and the other mold is a lower mold having a concave shape. However, as described above, the present invention is not limited to this. For example, one mold may be a concave upper mold and the other mold may be a convex lower mold.

  Matched molding as described above is a conventionally known thermoforming method, but the feature of the method of the present invention is that, as will be described later, one mold set at a high temperature and the other mold set at a low temperature Using a pair of molds, and releasing a molded body from one mold, and then releasing the molded body from the other mold after releasing from one mold. By thermoforming the foam sheet in this way, the molded body after the crystallization treatment can be released without sticking to the mold, so that it can be thermoformed in a short cycle time without deforming the molded body. become.

First, each step of the method of the present invention will be described in detail.
In the method of the present invention, the foamed sheet is heated before thermoforming by sandwiching the foamed sheet between molds. The temperature at which the foamed sheet is heated is usually [Tg-10 ° C.] or more and [Tg + 10 ° C.] or less based on the glass transition temperature of the foam sheet (hereinafter also simply referred to as Tg). Preferably, the surface temperature of the foamed sheet is in the range of [Tg−5 ° C.] or more and [Tg + 5 ° C.] or less.

  Next, the heated foamed sheet is guided between one mold and the other mold, and then sandwiched between the two molds to be thermoformed and subjected to a crystallization treatment. At this time, in the method of the present invention, the temperature of one mold set to a high temperature is set to [Tg + 20 ° C. of the foam sheet] or more and [Tg + 70 ° C. of the foam sheet] or less and the other mold set to a low temperature is set. [Tg of foamed sheet −40 ° C.] is set to be equal to or higher than the Tg of the foamed sheet. Thus, by setting one mold to the above temperature range, the foam sheet is molded and the polylactic acid resin foam sheet molded body is crystallized, and the other mold is set to the above temperature range. As a result, the solidification of the foamed polylactic acid resin foamed sheet is promoted by cooling and solidifying the foamed sheet.

  In addition, the concave mold and the convex mold in the matched mold molding of the foam sheet are designed so that they can be completely adhered to both surfaces of the foam sheet, and the clearance (interval) between the concave mold and the convex mold is set to the desired thickness of the molded body. Is set.

  As described above, the temperature of one mold is set to [Tg + 20 ° C. of foam sheet] or more and [Tg + 70 ° C. of foam sheet] or less. By setting to such a temperature range, crystallization of the molded body can proceed from one mold side of the foamed sheet molded body, and the resulting molded body has good heat resistance. If the set temperature of one mold is less than “Tg of the foamed sheet + 20 ° C.”, the crystallization of the polylactic acid resin is difficult to proceed. The upper limit of the set temperature of one mold is [fusing sheet melting temperature−10 ° C.] as a guide, and is as described above in the present invention. When the set temperature of one mold is too high, depending on the apparent density of the foamed sheet, the appearance of the molded body is inferior, for example, the surface of the resulting molded body is melted. From this viewpoint, the set temperature of one mold is preferably “Tg of foamed sheet + 25 ° C.” or more and “Tg of foamed sheet + 60 ° C.” or less, more preferably “Tg of foamed sheet + 35 ° C.” or more and “Tg of foamed sheet + 50 ° C.” It is as follows.

The temperature of the other mold is set to [Tg of foamed sheet −40 ° C.] or more and Tg of the foamed sheet or less. By setting such a temperature, cooling and solidification of the molded body is promoted from the other mold side of the foamed sheet molded body, which leads to a reduction in molding cycle time.
When the set temperature of the other mold exceeds Tg, cooling and solidification of the molded body is not promoted, so it takes a long time to release the molded body from one mold, and the purpose of shortening the molding cycle time is It will not be achieved. If the set temperature of the other mold is too low, crystallization of the molded body by one mold is hindered, and the heat resistance of the molded body is lowered. From this viewpoint, the set temperature of the other mold is preferably [Tg-30 ° C. of foam sheet] or more and [Tg-5 ° C. of foam sheet] or less, more preferably [Tg-25 ° C. of foam sheet] or more [ It is below Tg-10 degreeC of a foam sheet.

In this specification, the glass transition temperature of the foamed sheet is the midpoint glass transition of the DSC curve obtained by heat flux differential scanning calorimetry according to JIS K7121-1987 for 1 to 4 mg test pieces cut out from the foamed sheet. The value obtained as temperature.
As a test piece for obtaining the glass transition temperature, JIS K7121-1987 3. Use the test piece conforming to “When measuring the glass transition temperature after performing a certain heat treatment” described in (3) Conditioning of test piece. That is, 1 to 4 mg of a test piece cut out from a foamed sheet was put in a container of a DSC apparatus, heated to 200 ° C. at a rate of 10 ° C./minute, heated and melted, and kept at this temperature for 10 minutes. Use the one that has been conditioned to be rapidly cooled to ° C. In this case, the rapid cooling is performed by cooling at a speed of 40 ° C./min from 200 ° C. to 50 ° C. and at a speed of 30 ° C./min from 50 ° C. to 0 ° C. To be implemented.

  Moreover, the melting temperature of a foam sheet is a value calculated | required by heat flux differential scanning calorimetry based on JISK7121-1987 about the test piece of 1-4 mg cut out from the foam sheet. The measurement conditions are the same as the glass transition temperature described above, and the temperature at the top of the obtained melting peak is taken as the melting temperature. However, the heating rate in the condition adjustment of the test piece is 10 ° C./min, the cooling rate is 10 ° C./min, the heating rate at the time of measuring the melting temperature is 10 ° C./min, and when two or more melting peaks appear, The temperature at the top of the melting peak with the largest area is taken as the melting temperature.

In the method of the present invention, the molded body which has been molded and crystallized as described above is held in the other mold set to [Tg of the foamed sheet −40 ° C.] or more and Tg of the foamed sheet or less. The mold is released from one mold set to [Tg + 20 ° C. of foam sheet] or more and [Tg + 70 ° C. of foam sheet] or less, and then the molded body is released from the other mold.
In this way, by holding the molded body in the other mold set at a low temperature, the molded body can be released from the one mold set at a high temperature without deforming. In this case, the mold release is usually performed by moving one mold away from the molded body while holding the molded body fixed to the other mold by holding the molded body in the other mold. Is done. At this time, it is preferable to release the molded body by ejecting a gas such as air or nitrogen from one mold toward the molded body so as not to adversely affect the molded body. If it does in this way, mold release from one metal mold | die can be performed easily, and cooling of the one metal mold | die surface side of a molded object can be accelerated | stimulated.

  In addition, even if it tries to release the molded body first from the other mold set to [Tg−40 ° C. of foam sheet] or more and Tg or less of the foam sheet, or one mold and the other mold are separated. At the same time, even if trying to release the mold, the molded body sticks to the one mold, and if the molded body is forcibly released, the resulting molded body is deformed.

  The holding time from the start of mold forming from one mold after thermoforming and crystallization treatment with the foam sheet sandwiched between the molds is the thickness of the molded body to be obtained, Depending on the temperature of one mold set at a high temperature and the degree of crystallinity of the molded body on the side in contact with the inner surface of one mold, practical heat resistance and molding cycle time are required. From the viewpoint of shortening, it is usually 10 seconds or longer and 150 seconds or shorter, preferably 15 seconds or longer and 100 seconds or shorter, and more preferably 15 seconds or longer and 45 seconds or shorter.

In addition, the holding time from when the molded body is released from one mold to when the molded body starts to be released from the other mold set at a low temperature is sufficient for cooling the molded body and the molding cycle. From the viewpoint of time reduction, it is usually 0.5 seconds or more and 50 seconds or less, preferably 1 second or more and 40 seconds or less, more preferably 2 seconds or more and 30 seconds or less, and particularly preferably 5 seconds or more and 25 seconds or less. It is.
Next, in order to release the molded body from the other mold, gas such as air or nitrogen is jetted from the other mold toward the molded body to such an extent that the molded body is not adversely affected. The other mold may be moved away from the molded body.

Next, the foam sheet used in the method of the present invention will be described.
The crystalline polylactic acid resin foamed sheet of the present invention has an endothermic amount (ΔH _{endo: raw} ) of 10 J / g or more and 65 J / g or less, or an endothermic amount (ΔH _{endo: raw} ) of 10 J / g. It is composed of a mixture of a crystalline polylactic acid resin of 65 J / g or less and an amorphous polylactic acid resin having an endotherm (ΔH _{endo: raw} ) of 0 J / g or more and 2 J / g or less, and the following heat flux differential scanning calorific value It is a foamed sheet made of a polylactic acid resin having an endothermic amount (ΔH _{endo: raw} ) determined by measurement exceeding 10 J / g.

Furthermore, as the crystalline polylactic acid resin constituting the foamed sheet used in the method of the present invention, the endothermic amount (ΔH _{endo: raw} ) is preferably 20 J / g or more and 65 J / g or less, more preferably 30 J / g or more and 65 J / g. It is as follows.

Moreover, the polylactic acid resin in this specification is a lactic acid homopolymer or a copolymer having a lactic acid component ratio of 50% by weight or more. Specifically, (1) a polymer of lactic acid, (2) a copolymer of lactic acid and another aliphatic hydroxycarboxylic acid, (3) a copolymer of lactic acid, an aliphatic polyhydric alcohol, and an aliphatic polycarboxylic acid, (4) Copolymer of lactic acid and aliphatic polyhydric carboxylic acid, (5) Copolymer of lactic acid and aliphatic polyhydric alcohol, (6) Mixture of two or more combinations of (1) to (5) Is included.
Specific examples of the lactic acid include L-lactic acid; D-lactic acid; DL-lactic acid; or their cyclic dimer L-lactide, D-lactide, DL-lactide; or a mixture thereof. Can do.

The endothermic amount (ΔH _{endo: raw} ) of the polylactic acid resin is JIS K7122, except that the polylactic acid resin is 1 to 4 mg as a test piece, and the condition adjustment of the test piece and the measurement of the calorific value in the DSC curve are performed according to the following procedure. The value obtained according to the heat flux differential scanning calorimetry described in -1987.
Conditioning of the test piece and measurement of heat quantity in the DSC curve are carried out as follows. The test piece is put in a container of a DSC apparatus and heated and melted to 200 ° C. The temperature is maintained for 10 minutes and then cooled to 125 ° C. at a cooling rate of 2 ° C./min. After maintaining at that temperature for 120 minutes, after heat treatment to cool down to 40 ° C. at a cooling rate of 2 ° C./minute, heat and melt again at a heating rate of 2 ° C./minute to a temperature about 30 ° C. higher than the end of the melting peak. To obtain a DSC curve. As shown in FIG. 1, a point where the endothermic peak departs from the low temperature side baseline of the endothermic peak of the DSC curve is a point a, and a point where the endothermic peak returns to the high temperature side baseline is a point b. The endothermic amount (ΔH _{endo: raw} ) of the polylactic acid resin is a value obtained from the straight line connecting the points a and b and the area of the portion surrounded by the DSC curve. The device should be adjusted so that the baseline is as straight as possible. If the baseline is inevitably curved, as shown in FIG. 2, the point where the endothermic peak is separated from the curved low-temperature base line is point a, and the point where the endothermic peak is returned to the curved high-temperature base line. Let it be point b.

The reason for adopting the 120-minute holding at 125 ° C., the cooling rate of 2 ° C./min, and the heating rate of 2 ° C./min as the condition adjustment of the test piece and the measurement condition of the DSC curve is as follows. This is because the crystallinity of the test piece is increased as much as possible, and the endothermic amount (ΔH _{endo: raw} ) of a completely crystallized state or a state close to that is determined by this measurement. .

In the present invention, the above-mentioned polylactic acid resin constituting the foamed sheet was mixed or copolymerized with a thermoplastic resin other than polylactic acid resin in a proportion of 50% by weight or less within a range where the object and effect of the present invention can be achieved. Things can also be used.
Examples of the thermoplastic resin other than the polylactic acid resin include polyethylene resin; polypropylene resin; polystyrene resin; polyester resin. Of these, aliphatic polyester resins containing at least 35 mol% of aliphatic ester component units are preferred. Examples of the aliphatic polyester resin include hydroxy acid polycondensates other than the above polylactic acid resins; ring-opening polymerization products of lactones such as polycaprolactone; fats such as polybutylene succinate, polybutylene adipate, and polybutylene succinate adipate. Aliphatic polyesters and aliphatic copolyesters; and aliphatic aromatic copolyesters such as polybutylene adipate terephthalate.

The foamed sheet of the present invention is excellent in thermoformability before crystallization treatment, and heat resistance is improved by performing crystallization treatment. Specifically, an endothermic amount (ΔH _{endo: 2 ° C./min} ) and a calorific value (ΔH _{exo: 2 ° C./min} ) determined by heat flux differential scanning calorimetry (heating rate 2 ° C./min) for the foamed sheet Difference (ΔH _{endo: 2 °} C./min−ΔH _{exo: 2 ° C./min} ) is less than 40 J / g, the endotherm (ΔH _{endo: 2 ° C./min} ) is 10 J / g or more, and the calorific value ( A foamed sheet having a ΔH _{exo (2 ° C./min} ) of 3 J / g or more is preferable.
Such a foam sheet can be produced by a conventionally known extrusion foaming method.

For example, the polylactic acid resin and an air conditioner such as talc are supplied to an extruder, heated and melt-kneaded, and then a physical foaming agent such as normal butane, isobutane, carbon dioxide or the like is injected into the extruder and kneaded. Next, the resin temperature is adjusted to an appropriate foaming temperature and extruded from an annular die for foaming. A foamed sheet can be obtained by taking up the obtained foam along the side surface of the cylindrical cooling device and cutting it with a blade in the extrusion direction. The adjustment of the crystal state can be performed by rapidly cooling the surface of the cylindrical foamed sheet immediately after being extruded, for example, by blowing air or mist.
However, the manufacturing method of the foam sheet used by this invention method is not limited to this method.

The calorific value of the foam sheet (ΔH _{exo: 2 ° C./min} ) is the amount of heat released along with the accelerated crystallization of the test piece by heat flux differential scanning calorimetry at a heating rate of 2 ° C./min. _Yes , the larger the value of the calorific value (ΔH _{exo: 2 ° C./min} ), the more the foamed sheet from which the test piece was cut out means that crystallization has not progressed. Further, the endothermic amount of the foam sheet (ΔH _{endo: 2 ° C./min} ) is the amount of heat of fusion when the crystal of the test piece is melted by the heat flux differential scanning calorimetry at the heating rate of 2 ° C./min. A larger value of (ΔH _{endo: 2 ° C./min} ) means that a foamed sheet from which a test piece has been cut out has a higher crystallinity by heat treatment. The difference between the endothermic amount and the exothermic amount (ΔH _{endo: 2 °} C./min−ΔH _{exo: 2 ° C./min} ) is determined by setting a test piece used for heat flux differential scanning calorimetry in the measuring device. This corresponds to the amount of heat of fusion required for melting the amount of crystals that had been present at the time, and the smaller the value, the less the crystallization of the foam sheet.
Accordingly, the foamed sheet having (ΔH _{endo: 2 °} C./min−ΔH _{exo: 2 ° C./min} ) of less than 40 J / g does not significantly progress in crystallization of the foamed sheet, and secondary processability such as thermoformability. The (ΔH _{endo: 2 ° C./min} ) is 10 J / g or more. If the crystallization degree of the foamed sheet is increased by a heat treatment in the subsequent process, the foamed sheet becomes rigid. It means that the heat resistance is excellent.

In the foamed sheet, the value of (ΔH _{endo: 2 °} C./min-ΔH _{exo: 2 ° C./min} ) is preferably 0 J / g or more and 40 J / g or less, more preferably 0 J / g or more and 30 J / g or less. More preferably, they are 0 J / g or more and 20 J / g or less, More preferably, they are 1 J / g or more and 20 J / g or less, Especially preferably, they are 2 J / g or more and 19 J / g or less. When the value of the difference (ΔH _{endo: 2 °} C./min−ΔH _{exo: 2 ° C./min} ) is too large, the thermoformability of the foamed sheet is deteriorated. ) And the ratio of (B) to (A) when the area of the molded article after molding of the part corresponding to the foamed sheet area (A) of the molded part is (B): (B) / (A) ) Is 1.5 or more, particularly 2.0 or more, deep drawing thermoformability is deteriorated.

Further, in the foamed sheet, the endothermic amount (ΔH _{endo: 2 ° C./min} ) is preferably 10 J / g or more, more preferably 20 J / g or more, still more preferably 25 J / g or more, particularly preferably. Is 30 J / g or more. When the endothermic amount (ΔH _{endo: 2 ° C./min} ) of the foamed sheet is too small, preferable rigidity and heat resistance cannot be obtained even if the obtained molded body is crystallized by heat treatment. The upper limit of the endothermic amount (ΔH _{endo: 2 ° C./min} ) of the foam sheet is not particularly limited, but is generally 65 J / g.

Further, in the foamed sheet used in the method of the present invention, the calorific value (ΔH _{exo: 2 ° C./min} ) is preferably 3 J / g or more, more preferably 5 J / g or more, and further preferably 15 J / g. As described above, it is particularly preferably 20 J / g or more. When the calorific value (ΔH _{exo: 2 ° C./min} ) of the foamed sheet is too small, even if an attempt is made to crystallize the resulting molded body by heat treatment, crystallization does not proceed sufficiently, and preferable rigidity and heat resistance cannot be obtained. In addition, although the upper limit of the calorific value (ΔH _{exo: 2 ° C./min} ) of the foam sheet is not particularly limited, it is approximately 65 J / g. Naturally, the heat generation amount of the foam sheet (ΔH _{exo: 2 ° C./min} ) does not exceed the heat absorption amount of the foam sheet (ΔH _{endo: 2 ° C./min} ).

  The degree of crystallinity of the foamed sheet before thermoforming used in the method of the present invention is preferably 20% or less, more preferably 18% or less, and still more preferably 16% or less. If the degree of crystallinity of the sheet before thermoforming is too high, the elongation is lowered during forming, which causes deterioration of formability. If the crystallinity of the foamed sheet is 20% or less, the elongation during molding will not be too low. On the other hand, the degree of crystallinity of the foamed sheet is preferably 2% or more, more preferably 10% or more, from the viewpoint of shortening the heat treatment time for crystallization during the subsequent thermoforming. In addition, since the crystallinity of the foamed sheet may be low, the lower limit is 0%. Examples of a method for controlling the crystallinity of the foamed sheet include a method in which the sheet is rapidly cooled when the sheet is brought into contact with a mandrel during extrusion foaming.

In the present invention, the degree of crystallinity of the foam sheet refers to the heat generation amount of the foam sheet (ΔH _{exo: 2 ° C./min} ) by the heat flux differential scanning calorimetry at the heating rate of 2 ° C./min and the heat absorption amount of the foam sheet ( It is a value obtained by the following equation (1) from the difference between the endothermic amount determined by ΔH _{endo: 2 ° C./min} and the exothermic amount (ΔH _{endo: 2 °} C./min−ΔH _{exo: 2 ° C./min} ).

Crystallinity (%) = [(ΔH _{endo: 2 °} C./min−ΔH _{exo: 2 °} C./min)/93]×100 (1)
In the above formula (1), “93” means the heat of crystal melting (93 J / g) when the polylactic acid resin shown in the known literature is crystallized 100%.

The measurement of the calorific value (ΔH _{exo: 2 ° C./min} ) and the endothermic amount (ΔH _{endo: 2 ° C./min} ) of the foamed sheet is performed on a cylinder or prism with the one surface and the other surface of the foam sheet as upper and lower surfaces. The heat flux differential scanning calorific value described in JIS K7122-1987, except that 1 to 4 mg of the foam piece cut out was used as a test piece, and the condition adjustment of the test piece and the measurement of the calorific value in the DSC curve were performed according to the following procedure. The value obtained according to the measurement.
The test piece condition adjustment and the calorific value in the DSC curve were measured by placing the test piece in a DSC apparatus container and not performing heat treatment (as described in JIS K7122-1987, as the condition adjustment of the test piece “adjusted in the standard state and measured the transition temperature. This is carried out by obtaining a DSC curve when heating and melting to a temperature about 30 ° C. higher than the end of the melting peak at a heating rate of 2 ° C./min.

Note that the point at which the exothermic peak departs from the low-temperature base line of the DSC curve's exothermic peak is designated as point c, and the point at which the exothermic peak returns to the high-temperature base line is designated as point d, where ΔH _{exo: (2 ° C./min} ) is a value obtained from the area of the portion surrounded by the straight line connecting the points c and d and the DSC curve. The endothermic amount of the foam sheet (ΔH _{endo: 2 ° C./min} ) is defined as a point e where the endothermic peak departs from the low-temperature base line of the endothermic peak of the DSC curve, and the endothermic peak reaches the high-temperature base line. The return point is defined as a point f, and a value obtained from the area of the portion surrounded by the straight line connecting the point e and the point f and the DSC curve. Note that the apparatus is adjusted so that the baseline in the DSC curve is as straight as possible. If the baseline is inevitably curved, a point where the exothermic peak is separated from the curved low-temperature side baseline is point c, and a point where the exothermic peak returns to the curved high-temperature side baseline is point d, or A point where the endothermic peak departs from the curved low temperature side baseline is a point e, and a point where the endothermic peak returns to the curved high temperature side baseline is a point f.

For example, in the case shown in FIG. 3, the heat generation amount of the foamed sheet (ΔH _{exo: 2 ° C./min} ) from the area surrounded by the straight line connecting the points c and d defined as described above and the DSC curve. The endothermic amount (ΔH _{endo: 2 ° C./min} ) of the foam sheet is determined from the area surrounded by the straight line connecting the points e and f and the DSC curve defined as described above. In the case shown in FIG. 4, since it is difficult to determine the point d and the point e by the above method, the intersection of the line connecting the point c and the point f determined as described above and the DSC curve. _Is determined as a point d (point e) to determine the calorific value (ΔH _{exo: 2 ° C./min} ) and the endothermic amount (ΔH _{endo: 2 ° C./min} ) of the foam sheet. Also, as shown in FIG. 5, when a small exothermic peak occurs on the low temperature side of the endothermic peak, the heat generation amount of the foam sheet (ΔH _{exo: 2 ° C./min} ) is the first exothermic in FIG. It is obtained from the sum of the area A of the peak and the area B of the second exothermic peak. That is, the area A is defined as a point c where the exothermic peak moves away from the low temperature side baseline of the first exothermic peak, and a point d where the first exothermic peak returns to the high temperature side baseline. It is assumed that the area A is a portion surrounded by a straight line connecting the point d and the DSC curve. The area B is defined as a point g where the second exothermic peak is separated from the low temperature side baseline of the second exothermic peak, a point f where the endothermic peak returns to the high temperature side baseline, and a point g. The intersection of the straight line connecting the point f and the DSC curve is defined as a point e, and the area B of the portion surrounded by the straight line connecting the point g and the point e and the DSC curve is defined. On the other hand, in FIG. 5, the endothermic amount (ΔH _{endo: 2 ° C./min} ) of the foamed sheet is a value obtained from the area of the portion surrounded by the straight line connecting point e and point f and the DSC curve.

In addition, in the measurement of the calorific value (ΔH _{exo: 2 ° C./min} ) and the endothermic amount (ΔH _{endo: 2 ° C./min} ), the reason for adopting the heating rate of 2 ° C./min as the measurement condition of the DSC curve is as follows: When the exothermic peak and the endothermic peak are separated as much as possible, and an accurate exothermic amount (ΔH _{exo: 2 ° C./min} ) and an accurate endothermic amount (ΔH _{endo: 2 ° C./min} ) are obtained by heat flux differential scanning calorimetry. This is based on the finding that a heating rate of 2 ° C./min is suitable.

In the foam sheet used in the method of the present invention, the calorific value (ΔH _{exo: 10 ° C./min} ) determined by heat flux differential scanning calorimetry at a cooling rate of 10 ° C./min of the foam sheet is 20 J / g or more and 45 J / g. g is preferably 25 J / g or more and 40 J / g or less, and more preferably 30 J / g or more and 38 J / g or less.

When the heat generation amount (ΔH _{exo: 10 ° C./min} ) of the foamed sheet is 20 J / g or more and 45 J / g or less, the crystallization rate is neither too fast nor too slow. Accordingly, it is easy to produce a foam sheet having a low crystallinity, and it is easy to produce a molded body having a high degree of crystallinity by heat treatment during thermoforming. It means that the foam sheet has an optimum crystallization speed suitable for both of them. In heat flux differential scanning calorimetry under conditions where the cooling rate is slow, such as 2 ° C./min, crystallization is accelerated by the measurement even for foamed sheets made of polylactic acid resin with a slow crystallization rate. A clear exothermic peak is confirmed. On the other hand, in the heat flux differential scanning calorimetry under the fast cooling rate of 10 ° C./min, the foamed sheet made of polylactic acid resin having a low crystallization rate accelerates the crystallization almost or not at all. And little or no exothermic peak is observed. Thus, in the heat flux differential scanning calorimetry of the foam sheet, crystallization proceeds at a cooling rate of 2 ° C./min. However, when the cooling rate is 10 ° C./min, the foamed sheet that does not progress crystallization little or not can be easily thermoformed, but the time required for heat treatment to promote crystallization becomes longer. There is a possibility that the productivity of a molded article having excellent properties and the like may be lowered. Therefore, a foam sheet having a calorific value (ΔH _{exo: 10 ° C./min} ) of 20 J / g or more and 45 J / g or less in heat flux differential scanning calorimetry under a cooling rate of 10 ° C./min is a heat treatment during thermoforming. Since it can be said that crystallization proceeds at a high speed, it is suitable for thermoforming a molded article having excellent heat resistance with high productivity.

In addition, the calorific value (ΔH _{exo: 10 ° C./min} ) of the foamed sheet was measured using 1 to 4 mg foam pieces cut out from the foamed sheet as test pieces, and adjusting the state of the test pieces and the calorific value in the DSC curve. The measurement is performed according to the heat flux differential scanning calorimetry described in JIS K7122-1987 except that the measurement is performed according to the following procedure.
Conditioning of the test piece and measurement of the amount of heat in the DSC curve were carried out by placing the test piece in a DSC apparatus container, heating to 200 ° C. to melt and keeping at that temperature for 10 minutes, then 10 ° C./min to 10 ° C. This is done by obtaining a DSC curve when cooling at the cooling rate. The heating value of the foamed sheet (ΔH _{exo: 10 ° C./min} ) is not particularly shown, but the point at which the exothermic peak departs from the high temperature side base line of the exothermic peak of the DSC curve is point h, and the exothermic peak is A point returning to the low-temperature base line is a point i, and a value obtained from a straight line connecting the point h and the point i and an area of a portion surrounded by the DSC curve. It should be noted that the apparatus should be adjusted so that the baseline is as straight as possible, and if the baseline is inevitably curved, the point where the exothermic peak leaves the curved base line on the high temperature side is point h, and the curved low temperature The point where the exothermic peak returns to the base line on the side is defined as point i.

  In the molding method of the present invention, it is preferable to use a foam sheet having a thickness of 0.5 mm or more. If the thickness is 0.5 mm or more, it is easy to control the crystallinity of the front surface and the back surface by sandwiching the obtained molded body between molds. Furthermore, the obtained molded article has excellent mechanical strength such as bending and compression. From this viewpoint, the thickness of the foamed sheet is preferably 0.6 mm or more, and more preferably 0.7 mm or more. On the other hand, if the foamed sheet is too thick, it is difficult to thermoform, and therefore it is preferably 6 mm or less, more preferably 4 mm or less, although it depends on the mold to be molded. In addition, the upper limit of the thickness of a foam sheet is about 8 mm in general.

The apparent density of the foamed sheet is preferably 63 kg / m ³ or more and 630 kg / m ³ or less. If the apparent density is too small, the resulting molded article may lack mechanical strength such as bending and compression. On the other hand, when the apparent density is too large, the heat insulating property and buffering property of the molded body are insufficient, and the lightness may be insufficient.

  In the present invention, a thermoplastic resin layer (hereinafter also simply referred to as a resin layer) can be formed on one side or both sides of a foamed sheet made of polylactic acid resin as long as the object of the present invention is not impaired. Although there is no restriction | limiting in particular in the thickness of the said resin layer, 0.5 to 500 micrometers is preferable, 3 to 300 micrometers is more preferable, 10 to 180 micrometers is still more preferable. In addition, the thickness of the said resin layer is taken as the total thickness of an adhesive layer and a resin layer, when the resin layer is laminated | stacked on the foamed sheet via the adhesive layer. Moreover, when the resin layer of a multilayer structure is formed in the foamed sheet, it is set as the total thickness of each resin layer, ie, the thickness of a multilayer resin layer. Furthermore, when the multilayer resin layer is laminated | stacked on the foamed sheet via the contact bonding layer, let the total thickness of a multilayer resin layer and a resin layer be the thickness of the said resin layer.

  Synthetic resins constituting the resin layer include polylactic acid resin; polyolefin resin; polyester resin; polystyrene resin; polyamide resin such as nylon-6 and nylon-6, 6; polyacrylic resin such as polymethyl methacrylate and polyacrylate; Polycarbonate resins and the like; and further mixtures thereof.

Hereinafter, the polylactic acid resin foamed sheet molding of the present invention will be described.
The molded article of the present invention is preferably a molded article obtained from a polylactic acid resin foam sheet having a thickness of 0.5 mm or more. If the thickness of the foamed sheet is 0.5 mm or more, as described above, mechanical strength such as bending and compression of the obtained molded body is particularly excellent.
In addition, the molded body of the present invention preferably has a thickness of 0.5 mm or more, more preferably 0.7 mm or more, because the molded body has excellent mechanical strength and the like.

  Note that the thickness of the molded body is 0.5 mm or more, when the molded body has a flange, that part is excluded from the thickness measurement object, and the surface area of the molded body is determined for other parts other than the flange. The part where 60% or more is 0.5 mm or more. The thickness of the molded body is such that the portion other than the flange is 60% or more of the surface area of the molded body (preferably 70% or more, more preferably 80% or more, particularly preferably 90% or more) of the surface area. It is preferably 5 mm or more and 7 mm or less, and more preferably 0.7 mm or more and 3 mm or less.

In the molded body of the present invention, the difference in crystallinity between one divided body obtained by dividing the molded body at the central portion of the molded body and the other divided body is 5% or more, and crystallization The degree of crystallinity of one divided body having a high degree is 25% or more and 70% or less, and the degree of crystallinity of the other divided body having a low degree of crystallinity is 0% or more and less than 25%. In the molded body of the present invention, the crystallinity of one of the divided bodies is 25% or more and 70% or less, and the crystallization of this portion is sufficiently promoted, so that the heat resistance is improved, bending, compression, etc. This is a molded article with improved mechanical strength. On the other hand, if the degree of crystallinity of one divided body is less than 25%, it means that the crystallization of this portion is insufficient, and such a molded body has insufficient heat resistance and is not bent. Also, the mechanical strength such as compression becomes insufficient. Further, when the crystallinity of one of the divided bodies exceeds 70%, the crystallization of this part is sufficient and excellent in the heat resistance of the molded body, but the molding cycle for obtaining the molded body It has a productivity problem of long time.
Further, the crystallinity of the other divided body is 0% or more and less than 25%, and the crystallization of this portion is hardly promoted, so that the molded body has excellent surface smoothness and good appearance. That is, if the degree of crystallinity of the other divided body is less than 25%, the surface of the other divided body is hardly uneven, so that the surface of the other divided body side of the molded body is excellent in appearance.

  The difference in crystallinity between the one divided body and the other divided body is 5% or more. Accordingly, since the crystallinity of the other divided body is lower than the crystallinity of one of the divided bodies, the heat resistance of one of the divided bodies is improved, and at the same time, irregularities are generated on the surface of the other divided body. It becomes easy to suppress the phenomenon and becomes a molded article having an excellent appearance. In addition, since the molded body is excellent in appearance, it is possible to give clear marking or printing to the molded body. From this viewpoint, the difference in crystallinity between one divided body and the other divided body is preferably 5% or more and 70% or less, more preferably 6% or more and 20% or less, and particularly preferably 9% or more and 15% or less. .

  In addition, as described above, when one mold is a convex-shaped high-temperature upper mold and the other mold is a concave-shaped low-temperature lower mold, one divided body is in contact with the upper mold, The other divided body is preferably in contact with the lower mold. Furthermore, if the molded body to be obtained is a tray, it is preferable that the surface of one divided body is the inner surface of the tray and the surface of the other divided body is the outer surface of the tray. In this case, a tray having an inner surface having heat resistance and an outer surface having an excellent appearance can be obtained. However, the present invention is not limited to such an embodiment, and the surface of one divided body may be the outer surface of the molded body, and the surface of the other divided body may be the inner surface of the molded body.

Furthermore, the crystallinity of one of the divided bodies is preferably 25% or more and 35% or less.
If the crystallinity of one of the divided bodies is 25% or more, crystallization is sufficiently promoted, and thus a molded body having excellent heat resistance and excellent mechanical strength can be obtained. Moreover, if the target value of the crystallinity of one divided body is set to 35% or less, the heat treatment for crystallization at the time of thermoforming can be completed in a short time. From this viewpoint, the crystallinity of one of the divided bodies is more preferably 26% or more and 34% or less, and further preferably 27% or more and 33% or less.

And it is preferable that the crystallinity of the other divided body is 15% or more and less than 25%.
If the crystallinity of the other divided body is 15% or more, it contributes to the improvement of the heat resistance of the molded body. Moreover, if the crystallinity of the other divided body is less than 25%, the surface of the other divided body is excellent in appearance. From such a viewpoint, the crystallinity of the other divided body is more preferably 15% or more and 24% or less, and further preferably 16% or more and 23% or less.

A method for measuring the degree of crystallinity between one divided body and the other divided body obtained by dividing the molded body at the center of the molded body thickness is as follows.
A relatively flat portion of the bottom of the molded body is selected and cut into a cylinder or prism having upper and lower inner and outer surfaces of the bottom of the molded body. By cutting at the center position of the thickness of the cut molded body, it is divided into one divided body and the other divided body (the weight of each divided body is 1 mg or more and 4 mg or less). Each obtained divided body is used as a test piece, and the degree of crystallinity between one divided body and the other divided body is determined by measuring in the same manner as measuring the crystallinity of the foam sheet.

  When the thickness of the molded body exceeds 2 mm, the thickness of each divided body cut at the central position of the thickness exceeds 1 mm. When the thickness of each divided body becomes too thick, there is a tendency that many portions having a low degree of crystallinity in the central portion in the thickness direction of the molded body are included, and the crystallinity of one divided body tends to be relatively small. Therefore, when the thickness of the molded body exceeds 2 mm, each divided body for measuring the degree of crystallinity has a thickness of each divided body of about 1 mm (by cutting the central portion in the thickness direction of the molded body). It is preferable to adjust to 0.95 mm or more and 1.05 mm or less.

  In addition, in this specification, all DSC measurement is a value measured using "DSC Q1000" of TA Instruments, USA. The DSC Q1000 data analysis program used is “Windows 2000 / XP version Universal Analysis 2000 Version 4.0C Build 4.0.0.103”.

  The molded body of the polylactic acid resin foamed sheet of the present invention is excellent in heat resistance and appearance, and can be used as an industrial component tray, a food container or the like. Moreover, according to the manufacturing method of the polylactic acid resin foamed sheet molding of the present invention, a polylactic acid resin foamed sheet molded article having good heat resistance and appearance can be produced in a short molding cycle time.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the examples.

Production of Foam Sheet A product name “HV-6200” of Unitika Ltd. having a glass transition temperature of 60 ° C. was used as a polylactic acid resin. Talc as a nucleating agent is mixed with polylactic acid resin at a ratio of 1.3 parts by weight per 100 parts by weight of the polylactic acid resin, supplied to an extruder having an inner diameter of 90 mm, the extruder is heated to 200 ° C., and they are kneaded. did. Subsequently, butane as a blowing agent was pressed into the extruder from a blowing agent injection port provided on the downstream side of the extruder at a ratio of 0.8 part by weight per 100 parts by weight of the polylactic acid resin, and further kneaded. The kneaded product obtained as described above was supplied to a second extruder having an inner diameter of 120 mm connected to the tip of the extruder and cooled to produce a foamable molten resin. Subsequently, the foamable molten resin whose cooling temperature is adjusted to 171 ° C. when passing through the breaker plate portion is supplied to an annular die attached to the tip of the second extruder, the lip diameter at the die outlet is 90 mm, and the lip gap The foamable molten resin was extruded into a cylindrical shape from an annular die having a thickness of 0.5 mm to form a cylindrical foam. The cylindrical foam was rapidly cooled by blowing cooling air onto both the inner and outer surfaces of the cylindrical foam immediately after extrusion foaming. Next, the tubular foam was taken up while contacting the inner surface of the cylindrical cooling device, and then one end of the tubular foam was cut in the extrusion direction with a cutter to produce a polylactic acid resin foam sheet. The obtained polylactic acid resin foamed sheet had a width of 720 mm, a thickness of 1.7 mm, a basis weight of 450 g / m ² , and an apparent density of 266 kg / m ³ (expanding ratio of 4.7 times). The heat generation amount (ΔH _{exo: 2 ° C./min} ) of the obtained foamed sheet was 22 J / g, the heat absorption amount (ΔH _{endo: 2 ° C./min} ) was 38 J / g, the crystallinity was 17%, and the heat generation amount (ΔH _{exo : 10 ° C / min} ) was 35 J / g, and the glass transition temperature (Tg) was 60 ° C. The endothermic amount (ΔH _{endo: raw} ) of the polylactic acid resin used in this example was 38 J / g.

Examples 1 to 4 and Comparative Examples 1 to 5
The obtained foamed sheet was thermoformed with a continuous molding machine to obtain a pasta tray having a circular shape in plan view. The inner diameter of the opening of the tray was 180 mm, the outer diameter of the bottom was 135 mm, the height was 29 mm, the thickness of the bottom was 2 mm ± 0.1 mm, and the thickness of the side wall was 2 mm ± 0.1 mm. The mold used in the continuous molding machine consists of an upper mold (concave mold) and a lower mold (convex mold), 12 in total, 3 in the width direction of the foam sheet and 4 in the longitudinal direction of the foam sheet at a time. A mold capable of obtaining a tray was used.

The thermoforming procedure is as follows.
After the foam sheet is softened with a heater and the surface temperature of the foam sheet is adjusted to around 60 ° C., the foam sheet is transported between the upper mold and the lower mold of the mold and then sandwiched between the upper mold and the lower mold. Then, thermoforming and crystallization treatment were performed. Next, the lower mold was released from the molded body while maintaining the state where the molded body was adhered to the upper mold while being sucked. The state in which the molded body is sucked into the upper mold (lower mold in Comparative Example 4) is maintained for the time shown in Table 1 (indicated as “one-side mold holding” in Table 1), thereby promoting cooling of the molded body. The molded body was released from the upper mold (lower mold in Comparative Example 4). For Comparative Example 1, after the upper mold and the lower mold were clamped, the mold was cooled in the mold clamped state until the mold temperature reached 50 ° C., and the upper mold and the lower mold were released at the same time. In order to thermoform the foamed sheet, the temperature of the upper mold and the lower mold was raised to 95 ° C. In Comparative Example 5, after the crystallization treatment, the upper mold and the lower mold were released at the same time.

  Table 1 shows the thermoforming procedure, the time for each step, and the molding cycle time. Since the molding cycle time takes 2 seconds to convey the foam sheet, the molding cycle time is 2 seconds longer than the total number of seconds described in the column of thermoforming procedure in Table 1. Table 1 also shows the temperature of the upper mold, the lower mold, and the respective molding dies, the deformation of the molded body at the time of mold release, the crystallinity of each of the one divided body and the other divided body, It shows the difference in crystallinity of the body, the heat resistance of the molded body, and the smoothness of the other surface of the molded body.

Evaluation criteria for deformation at the time of mold release ○ ・ ・ ・ No deformation or substantial deformation × ・ ・ ・ There is large deformation

Crystallinity of the divided body The molded body is divided at the center of the thickness, and one of the divided bodies (the inner surface side of the tray) and the other divided body (the outer surface side of the tray) are collected. The calorific value (ΔH _{exo: 2 ° C./min} ) and endothermic amount (ΔH _{endo: 2 ° C./min} ) were measured at a heating rate of 2 ° C./min using a DSC apparatus in the same manner as the measurement method, and the measurement The crystallinity of each divided body was determined by substituting the value into the equation (1).

Evaluation Criteria for Heat Resistance of Molded Body Hot water at 90 ° C. was put into the molded body so that the inner volume was 80%, and the hot water was taken out after 3 minutes, and changes in appearance were observed. The following are the evaluation criteria.
◎ ・ ・ ・ ・ No deformation ○ ・ ・ ・ ・ No deformation × ・ ・ ・ ・ With deformation

Evaluation criteria of surface smoothness on the other divided body side of the molded product The surface on the other divided body side was visually observed and evaluated as follows: ◎ ... very smooth ○ ... Smooth × ··· Large irregularities

FIG. 1 is an explanatory diagram of a DSC curve showing ΔH _{endo: raw} of a polylactic acid resin determined by heat flux differential scanning calorimetry. FIG. 2 is another explanatory diagram of a DSC curve showing ΔH _{endo: raw} of the polylactic acid resin obtained by heat flux differential scanning calorimetry. FIG. 3 is an explanatory diagram of a DSC curve showing ΔH _{exo: 2 ° C./min} and ΔH _{endo: 2 ° C./min} of the foamed sheet obtained by heat flux differential scanning calorimetry. FIG. 4 is another explanatory diagram of a DSC curve showing ΔH _{exo: 2 ° C./min} and ΔH _{endo: 2 ° C./min} of the foam sheet obtained by heat flux differential scanning calorimetry. FIG. 5 is still another explanatory diagram of a DSC curve showing ΔH _{exo: 2 ° C./min} and ΔH _{endo: 2 ° C./min} of the foam sheet obtained by heat flux differential scanning calorimetry.

Claims (4)

  A molded body obtained by thermoforming a crystalline polylactic acid resin foamed sheet, wherein the molded body is crystallized from one divided body and the other divided body obtained by dividing the molded body at the center of the molded body thickness. The degree difference is 5% or more, the crystallinity of one divided body is 25% or more and 70% or less, and the crystallinity of the other divided body is 0% or more and less than 25%. Lactic acid resin foam sheet molding.   The difference in crystallinity between the one divided body and the other divided body is 6% or more and 20% or less, and the degree of crystallinity of the one divided body is 25% or more and 35% or less, and the other divided body. 2. The polylactic acid resin foamed sheet molded article according to claim 1, wherein the degree of crystallinity is 15% or more and less than 25%.   In a method for producing a molded body in which a crystalline polylactic acid resin foam sheet is sandwiched between a pair of molds and thermoformed, the temperature of one mold is equal to or higher than the glass transition temperature of the foam sheet + 20 ° C. [Glass transition temperature + 70 ° C.] or lower, and the other mold is set to [Glass transition temperature of foamed sheet −40 ° C.] or higher and lower than the glass transition temperature of the foamed sheet, between one mold and the other mold In the state where the foamed sheet is sandwiched between the mold and thermoformed, and then the molded body is held in the other mold, the molded body is released from the one mold, and then the molded body is A method for producing a molded body of a polylactic acid resin foam sheet, wherein the mold is released from the other mold.   The method for producing a polylactic acid resin foam sheet molded article according to claim 3, wherein the crystallinity of the crystalline polylactic acid resin foam sheet used for thermoforming is 0% or more and 20% or less.

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