JP4801781B2 - Method for producing heat-resistant hollow body made of polylactic acid-containing resin - Google Patents

Description

  The present invention relates to a method for producing a hollow body comprising a polylactic acid-containing resin composition and having heat resistance.

  In recent years, the use of food containers made of biodegradable resins, such as jars, cups, jars, trays, etc., has been studied in restaurants and the like. Since the food container made of the biodegradable resin is decomposed by the action of microorganisms such as bacteria in the soil after disposal, the burden on the environment can be reduced.

  Conventionally, a polylactic acid resin is known as the biodegradable resin. However, since the polylactic acid resin has low heat resistance, when it is used as the food container, it is injected with hot water, heated with a microwave oven, used once, then recovered with an alkaline detergent for reuse. There is a problem that it cannot withstand cleaning, rinsing (rinsing) at a temperature of about 0 ° C., high temperature drying at a temperature of about 80 ° C., and sterilization.

  In order to solve the above problem, a biodegradable resin composition containing a polylactic acid resin in an amount of 50% by mass or more and nanocompositing an inorganic filler is known (for example, see Patent Document 1). The biodegradable resin composition can give excellent heat resistance regardless of stretching by crystallizing at a temperature around 110 ° C., and the food container can be formed by injection molding.

  When a hollow body such as the food container is formed by injection molding of the biodegradable resin composition, for example, a female mold having a concave portion having a shape along the outer surface shape of the hollow body, and facing the concave portion The biodegradation is performed in a molten state in a cavity surrounded by the concave portion and the convex portion by heating, for example, a mold including a male die having a convex portion having a shape along the inner surface shape of the hollow body. The functional resin composition. Then, after the injected biodegradable resin composition is solidified to form the hollow body, the hollow body is taken out by opening the mold.

  However, the injection molded body made of the biodegradable resin composition has a problem that if it is taken out from the mold before being sufficiently cooled, it may be deformed and its shape may be damaged due to insufficient rigidity. . In addition, the injection-molded body made of the biodegradable resin composition tends to shrink and closely adhere to the male mold when it is excessively cooled during solidification, and when the mold is opened, the female The mold is easily released from the mold, but there is a problem that the mold cannot be released from the male mold. In particular, when a hollow body such as a bag is injection-molded, it is very difficult to release the molded body when it is completely solidified.

  Because of the above problems, only injection-molded bodies made of the biodegradable resin composition have been produced as products with shallow irregularities such as spoons and forks. Moreover, most of the polylactic acid-containing resin compositions currently distributed on the market also serve as a polymer alloy (for example, 40% by mass of polylactic acid, Polycarbonate 60% by mass, or polylactic acid 50% by mass, ABS 50% by mass). However, the polymer-alloyed polylactic acid-containing resin composition has a disadvantage that it is inferior in biodegradability and has a large environmental load because the residual amount of petroleum-derived synthetic resin that is not biodegradable is very large.

  Therefore, in order to solve the above problems, the inventors have determined that the temperature of the biodegradable resin composition injected into the mold cannot be released from the temperature at which the hollow body exhibits heat resistance. A technique for opening the mold when the temperature is in a range up to a certain temperature is proposed (see Patent Document 2).

JP 2004-204143 A International Publication No. 2006/080125

  However, in the biodegradable resin composition injected into the mold, the temperature corresponding to the time when the mold is opened, that is, the range from the temperature at which the heat resistance is exhibited in the hollow body to the temperature at which release is impossible. There is a disadvantage that the temperature of fluctuates according to the manufacturing conditions. The manufacturing conditions include the thickness of the hollow body, the filling pressure and the injection start temperature of the biodegradable resin composition to the mold, the temperature control capability of the mold by the heat balance capacity of the heater and heat retaining fluid, The compounding quantity etc. of the inorganic filler with respect to a biodegradable resin composition can be mentioned.

  Therefore, the present invention determines when to open a mold regardless of manufacturing conditions when obtaining a hollow body by injection molding of a biodegradable resin composition obtained by nanocompositing an inorganic filler with a polylactic acid-containing resin. It aims at providing the manufacturing method of the heat resistant hollow body which can be manufactured.

  In order to determine when to open the mold without being affected by manufacturing conditions, the present inventors solidify the surface temperature of the mold and the biodegradable resin composition, and release the mold from the mold. Experiments were repeatedly conducted to investigate the relationship with the temperature of the biodegradable resin composition when possible. As a result, the temperature of the biodegradable resin composition is based on a temperature obtained by adding a predetermined numerical value to the surface temperature of the mold, and becomes a temperature in a predetermined range centered on a reference temperature. It has been found that the biodegradable resin composition is solidified and can be released from the mold regardless of the production conditions.

  The present invention has been completed based on the above findings, and in order to achieve the above object, the present invention is a method for producing a heat-resistant hollow body that is molded by injecting a polylactic acid-containing resin composition into a mold. The polylactic acid-containing resin composition is a biodegradable resin composition containing 50% by mass or more of polylactic acid, 1 to 28% by mass of an inorganic filler, and nanocompositing the inorganic filler. A female mold having a concave portion having a shape along the outer surface shape of the hollow body, a male mold having a convex portion having a shape along the inner surface shape of the hollow body facing the concave portion, and the male mold A stripper plate provided along the outer periphery and provided with an edge forming portion having a shape along the edge of the hollow body, and forming a cavity surrounded by the concave portion, the convex portion, and the edge forming portion. The surface of the mold facing the cavity is A step of heating to a temperature in the range of 110 to 120 ° C. corresponding to the crystallization temperature of the conductive resin composition, and the mold being heated to the temperature, and disposed in the mold The step of injecting the biodegradable resin composition in a molten state through the gate portion and the temperature T (° C.) of the biodegradable resin composition injected into the cavity are expressed by the equation T = (t + 3.5 ) ± 1.5 (t (° C.) is the surface temperature of the mold facing the cavity) When the temperature is in the range indicated by Moves the male mold and the stripper plate away from the female mold when detected by an infrared temperature sensor housed in a concave portion of the mold and provided at a position facing the cavity. The male mold and the strike The compressed air is jetted between the solidified inner surface of the hollow body and the male mold convex portion from the compressed air introduction path formed between the ripper plate and the inner surface of the hollow body and the convex portion. And a step of releasing the inner surface of the hollow body from the convex portion of the male mold, and advancing the stripper plate in the direction of the hollow body, And a step of removing from the mold.

  The mold used in the manufacturing method of the present invention is a male mold provided with a female mold provided with a concave portion that conforms to the outer surface shape of the hollow body, and a convex portion formed along the inner surface shape of the hollow body so as to face the concave portion. A mold, and a stripper plate provided along the outer periphery of the male mold and provided with an edge forming portion having a shape along the edge of the hollow body. In the mold, a cavity surrounded by the concave portion, the convex portion, and the edge forming portion is formed.

  In the present specification, the term “hollow body” means an injection-molded body including a bottom portion and a peripheral wall portion that is connected to the bottom portion and rises from the bottom portion. Examples of such hollow bodies include tableware such as bowls, bowls and cups, cosmetic containers such as lipstick containers, chemical containers, container caps, beverage bottles (excluding PET bottles formed by blow molding), and tupperware. Sealable containers such as (registered trademark), food packaging containers for microwave ovens, containers for heat-resistant electronic devices, and the like can be given.

  In the production method of the present invention, the biodegradable resin composition contains polylactic acid in an amount of 50% by mass or more, 1 to 28% by mass of an inorganic filler, and a polylactic acid obtained by nanocompositing the inorganic filler. The containing resin composition is used. The inorganic filler is preferably a layered silicate having an average layer thickness of 1 to 100 nm and a major axis of 150 nm or less. The layered silicate is originally a clay, and if the polylactic acid as a matrix is biodegraded, it is reduced to the environment as it is, so that the environmental load is small. Specifically, the biodegradable resin composition contains 1 to 28% by mass of the inorganic filler, and the balance is substantially composed of polylactic acid and a minor component for component adjustment.

  In the production method of the present invention, first, the mold is heated, and the surface of the mold facing the cavity is in the range of 110 to 120 ° C. corresponding to the crystallization temperature of the biodegradable resin composition. To heat. The biodegradable resin composition starts to crystallize at a temperature around 125 ° C., and the peak temperature of crystallization is 110 ° C.

  Next, the biodegradable resin composition in a molten state is injected into the cavity heated so that the surface becomes the crystallization temperature. The biodegradable resin composition is cooled and solidified in the cavity to form the hollow body. At this time, the biodegradable resin composition is crystallized by being maintained at the surface temperature of the mold, and heat resistance is imparted.

  Next, when the injected biodegradable resin composition is solidified to form the hollow body, the male mold and the stripper plate are moved away from the female mold, open. Here, as described above, the present inventor uses, as a reference, the temperature of the biodegradable resin composition injected into the mold as a reference to a temperature obtained by adding a predetermined numerical value to the surface temperature of the mold. It has been found that the biodegradable resin composition is solidified and can be released from the mold when the temperature reaches a temperature within a predetermined range centering on the temperature.

  That is, in the manufacturing method of the present invention, the temperature T (° C.) of the biodegradable resin composition in the cavity is expressed by the formula T = (t + 3.5) ± 1.5 (t (° C.) faces the cavity. The surface temperature of the mold), the biodegradable resin composition is solidified to form the hollow body and can be released from the mold. to decide. Specifically, the temperature T of the biodegradable resin composition serving as the criterion is 123.5 ± 1.5 ° C. when the surface temperature of the mold is 120 ° C. When the surface temperature is 110 ° C., it is 113.5 ± 1.5 ° C. Therefore, the temperature T of the biodegradable resin composition when the biodegradable resin composition is solidified to form the hollow body and can be released from the mold is in the range of 125 to 112 ° C. Temperature.

  Here, since the crystallization of the biodegradable resin composition starts from a temperature around 125 ° C. as described above, when the temperature T of the biodegradable resin composition is higher than 125 ° C., the biodegradable resin composition The object is not solidified and does not form the hollow body. In addition, since the biodegradable resin composition has a crystallization peak temperature of 110 ° C. as described above, crystallization proceeds excessively when the temperature T of the biodegradable resin composition is lower than 112 ° C. Release from the male mold becomes difficult.

  Moreover, in the manufacturing method of this invention, it is preferable that the surface temperature of the said metal mold | die is 110 degreeC which is the peak temperature of crystallization of the said biodegradable resin composition. In this case, the temperature T of the biodegradable resin composition serving as the determination criterion is in the range of 113.5 ± 1.5 ° C., ie, 115 to 112 ° C. as described above.

  In the production method of the present invention, the determination of solidification of the biodegradable resin composition and formation of the hollow body is performed by the polylactic acid injected into the cavity by an infrared temperature sensor provided at a position facing the cavity. This is done by measuring the temperature of the resin contained.

  In the production method of the present invention, the mold is opened when the temperature T of the biodegradable resin composition falls within the aforementioned range. At this time, the hollow body is not inseparable, but is in close contact with the male mold due to shrinkage accompanying solidification of the biodegradable resin composition, and is easily released from the female mold. However, it is difficult to release from the male mold. Therefore, after moving the male mold and the stripper plate in a direction away from the female mold, and opening the mold, from the compressed air introduction path formed between the male mold and the stripper plate Compressed air is injected between the solidified inner surface of the hollow body and the convex portion of the male mold. As a result, compressed air is introduced between the surface of the hollow body and the convex portion, and the inner surface of the hollow body can be released from the convex portion of the male mold.

  Next, when the hollow body is released from the convex portion of the male mold, the stripper plate is advanced in the direction of the hollow body, and the hollow body is taken out from the mold.

  According to the manufacturing method of the present invention, the biodegradable resin composition injected into the cavity using the infrared temperature sensor to determine the solidification of the biodegradable resin composition and the formation of the hollow body. This is done by directly measuring the temperature. Therefore, the temperature of the biodegradable resin composition can be detected with high accuracy without being affected by the environment such as the outside air temperature, and the temperature of the biodegradable resin composition is derived from the above equation. The mold can be opened within a narrow temperature range where T is 125 to 112 ° C.

  As a result, according to the manufacturing method of the present invention, when the hollow body is taken out from the mold, the hollow body is produced without being deformed or being unable to be taken out from the mold. Can do. The hollow body obtained as described above is composed of the biodegradable resin composition crystallized by being heated to the crystallization temperature, and thus has excellent heat resistance, injection of hot water, microwave oven It can be suitably used for applications that require heating by heat treatment, heat treatment for repeated use, and the like.

  In addition, the biodegradable resin composition requires a long time until it is cooled and solidified to obtain a molded product, as compared with general resins such as polyethylene, and therefore generally has a long cycle time for injection molding. However, according to the production method of the present invention, the biodegradable resin composition exhibits heat resistance by crystallization and is released when solidified to some extent, so that the cycle time can be shortened.

  In the manufacturing method of the present invention, the infrared temperature sensor receives an infrared ray generated by the biodegradable resin composition injected into the cavity with an infrared receiving device via an optical fiber, and an amount of energy of the infrared ray. It can be suitably used to detect the temperature of the resin.

  Since the inside of the cavity is dark and there is no source of infrared rays other than the biodegradable resin composition, the temperature of the biodegradable resin composition in the cavity is highly accurate according to the infrared temperature sensor. Can be detected.

  The infrared temperature sensor is preferably provided at a position facing the cavity at a portion where the temperature of the biodegradable resin composition located at the gate portion can be detected. The biodegradable resin composition has the highest temperature at the exit of the gate portion. Therefore, the infrared temperature sensor is a portion where the temperature of the biodegradable resin composition located at the gate portion can be detected, and is provided at a position facing the cavity, whereby the temperature T of the biodegradable resin composition is achieved. Can be reliably detected within the aforementioned range, and the timing for opening the mold can be reliably determined.

(A) is a perspective view of the hollow body in one Embodiment of this invention, (b) is the II sectional view taken on the line of (a). Explanatory sectional drawing which shows the manufacturing process of the hollow body in one Embodiment of this invention. Explanatory sectional drawing which shows the manufacturing process of the hollow body in one Embodiment of this invention. The graph which shows the endothermic property of the biodegradable resin composition used for this invention. The system block diagram which shows the structure of an infrared temperature sensor. The graph which shows the time-dependent change of the temperature of the biodegradable resin composition in the cavity measured by the infrared temperature sensor shown in FIG. Explanatory sectional drawing which shows the manufacturing process of the food container in one Embodiment of this invention. Explanatory sectional drawing which shows the manufacturing process of the food container in one Embodiment of this invention.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

  In the present embodiment, a case where the bag A shown in FIG. 1 is manufactured as a heat-resistant hollow body by injection molding of a polylactic acid-containing resin will be described as an example. As shown in FIGS. 1A and 1B, the ridge A includes a bottom part a and a peripheral wall part b that stands up from the bottom part a and continues to the bottom part a. In addition, the heel A includes an annular landing portion c that protrudes outward at the bottom portion a.

  The ridge A is manufactured using the mold 1 shown in FIG. As shown in FIG. 2, the mold 1 used in the manufacturing method of the present embodiment includes a female mold 3 including a recess 2 having a shape along the outer surface shape of the ridge A, and an inner surface of the ridge A facing the recess 2. A male die 5 having a convex portion 4 having a shape along the shape, and a stripper plate 7 having an edge forming portion 6 arranged along the outer periphery of the male die 5 and having a shape along the edge of the flange A. Prepare. In the mold 1, a cavity 8 surrounded by the concave portion 2, the convex portion 4, and the edge portion forming portion 6 is formed. Reference numeral 2a denotes a recess for forming an annular protrusion that is provided at the bottom of the ridge A and serves as a landing portion c.

  In the mold 1, the female mold 3 is a fixed mold, the male mold 5 and the stripper plate 7 are movable molds, and the female mold 3 includes a runner 10 that communicates with a cavity 8 through a gate 9. Further, a compressed air introduction path 11 is formed between the male mold 5 and the stripper plate 7 to eject compressed air along the outer periphery of the male mold 5. An infrared temperature sensor 12 is disposed at a position facing the cavity 8 facing the gate 9.

  In the manufacturing method of this embodiment, first, the female die 3, the male die 5, and the stripper plate 7 are heated by a heating means (not shown) to form the concave portion 2, the convex portion 4, and the edge portion forming portion 6 that form the cavity 8. The surface of the substrate is set to a temperature of 100 to 120 ° C., for example, 110 ° C. Then, as shown in FIG. 3, a molten biodegradable resin composition R is injected into the cavity 8 through the runner 10.

  As the biodegradable resin composition R, a resin composition containing 1 to 28% by mass of an inorganic filler, the balance being substantially made of polylactic acid, and a nanocomposite of the inorganic filler is used. The inorganic filler is preferably a layered silicate having an average layer thickness of 1 to 100 nm and a major axis of 150 nm or less as observed with a transmission electron microscope. Further, the biodegradable resin composition R may contain other resins than polylactic acid for moldability adjustment, but the content of the other resins must be within a range not impairing the biodegradability. There is. An example of such a biodegradable resin composition R is Terramac TE-8210 (trade name) manufactured by Unitika Ltd.

  As shown in FIG. 4, the biodegradable resin composition R exhibits endothermic properties in the range of 95 to 125 ° C., and its peak is 110 ° C. Therefore, when the biodegradable resin composition R is cooled and solidified in the cavity 8, the biodegradable resin composition R is maintained at a temperature in the above range, for example, a temperature in the range of 110 to 120 ° C. in the vicinity of 110 ° C. which is the peak temperature of crystallization. To crystallize.

  Thus, the polylactic acid-containing resin that draws a curve that rapidly crystallizes (endothermic) near 110 ° C. when cooled and solidified in the mold 1 is the biodegradable material obtained by nanocompositing the inorganic filler. It is limited to the resin composition R. A polylactic acid-containing resin or a normal polylactic acid-containing resin in which an inorganic filler is normally composited does not have a temperature range that causes rapid crystallization when cooled and solidified in a mold.

  Since the biodegradable resin composition R in which the inorganic filler is nanocomposited rapidly crystallizes in the vicinity of 110 ° C., if it is cooled for a long time in the vicinity of 110 ° C., the shrinkage proceeds too much and the mold It is difficult to release the molded product by firmly adhering to 1.

  Next, when the injected biodegradable resin composition R is solidified to form the ridge A, the mold is moved by moving the male mold 5 and the stripper plate 7 away from the female mold 3. Open 1 At this time, according to the study of the present inventors, when the temperature T (° C.) of the biodegradable resin composition R becomes a temperature in the range represented by the following formula, the biodegradable resin composition R is It solidifies to form the heel A, and it can be determined that the heel A can be released from the male mold 5.

T = (t + 3.5) ± 1.5
(T (° C.) is the surface temperature of the concave portion 2, the convex portion 4, and the edge forming portion 6 facing the cavity 8.)
Specifically, the temperature T of the biodegradable resin composition R serving as the determination criterion is specifically abbreviated as the surface temperature of the concave portion 2, the convex portion 4, and the edge portion forming portion 6 (hereinafter referred to as “mold surface temperature”). ) Is 120 ° C., it is 123.5 ± 1.5 ° C., and when the surface temperature of the mold is 110 ° C., it is 113.5 ± 1.5 ° C. Therefore, when the surface temperature of the mold is in the range of 110 to 120 ° C., the temperature T of the biodegradable resin composition R serving as the determination criterion is in the range of 125 to 112 ° C.

  Here, since the crystallization of the biodegradable resin composition R starts from a temperature around 125 ° C. as described above, when the temperature T of the biodegradable resin composition R is higher than 125 ° C., the biodegradable resin composition R R is not solidified, and no soot A is formed. In addition, since the biodegradable resin composition R has a crystallization peak temperature of 110 ° C. as described above, when the temperature T of the biodegradable resin composition R is lower than 112 ° C., crystallization proceeds excessively. , It becomes difficult to release the bag A from the male mold 5.

  In this embodiment, the surface temperature of the mold is preferably set to 110 ° C. In this case, the temperature T of the biodegradable resin composition R serving as the determination criterion is 113.5 ± 1.5 from the above formula. ° C, that is, a range of 115 to 112 ° C.

  In the present embodiment, the temperature of the biodegradable resin composition R in the cavity 8 is traced over time by the infrared temperature sensor 12, thereby solidifying the biodegradable resin composition R and forming the soot A. Judgment. As a result, the mold 1 can be opened as described above when the temperature of the biodegradable resin composition R reaches an appropriate range.

  As shown in FIG. 5, the infrared temperature sensor 12 includes an optical fiber 14 disposed in a steel sleeve 13 made of hardened steel, and the optical fiber 14 exposes one end thereof in the cavity 8, and An infrared transmission / reception device 15 is connected to the other end. The infrared transmitter / receiver 15 is connected to a temperature detector 16, and the temperature detector 16 is further connected to display means 17 such as a personal computer.

  The infrared temperature sensor 12 receives the infrared rays generated by the biodegradable resin composition R injected into the cavity 8 by the infrared transmission / reception device 15 via the optical fiber 14 and performs a predetermined calculation by the temperature detector 16. By performing the treatment, the temperature of the biodegradable resin composition R is detected from the energy amount of the infrared rays. The temperature of the biodegradable resin composition R detected by the temperature detector 16 is displayed by the display means 17. An example of the change over time of the temperature of the biodegradable resin composition R in the cavity 8 measured by the infrared temperature sensor 12 is shown in FIG.

  As shown in FIG. 6, the temperature of the biodegradable resin composition R in the cavity 8 is the highest temperature immediately after injection (214 ° C. in one embodiment), from the filling-holding pressure switching to the pressure-holding completion. Slowly falls (in one embodiment, 193 ° C. when pressure holding is complete). Then, immediately after completion of the pressure holding, it once falls steeply, but after that, it gradually falls again. FIG. 6 shows the temperature T1 (125 ° C.) at which the temperature of the biodegradable resin composition R in the cavity 8 exhibits heat resistance in the biodegradable resin composition R, and the biodegradable resin composition R in the cavity 8. The temperature T2 (112 ° C.) at which の A becomes unmoldable due to a further decrease in the temperature of. From FIG. 6, the temperatures T <b> 1 and T <b> 2 are very close, and when measured indirectly from the temperature of the mold 1, it is difficult to properly grasp a suitable temperature range for opening the mold 1. Is clear.

  In this embodiment, since the infrared temperature sensor 12 is used, the temperature of the biodegradable resin composition R in the cavity 8 is in the range of 125 to 112 ° C. corresponding to the temperature T1 and the temperature T2, more preferably 115 to 112. In the range of 0 ° C., the biodegradable resin composition R is solidified to some extent, so that a ridge A is formed, and it can be determined that the mold can be released from the male mold 5, and the mold 1 can be opened as described above. .

  Here, the temperature reduction control of the biodegradable resin composition R can be performed by any one of an electric heater, hot water, oil, or a combination thereof.

  In the present embodiment, the mold 1 is opened when the temperature of the biodegradable resin composition R in the cavity 8 reaches 112 ° C. The fact that the temperature of the biodegradable resin composition R in the cavity 8 has reached 112 ° C. means that the average temperature in the predetermined minute time (for example, 0.05 seconds) of the temperature measured by the infrared temperature sensor 12 is 112 first. Judgment is made when the temperature reaches ° C.

  When the male mold 5 and the stripper plate 7 are moved away from the female mold 3 and the mold 1 is opened, the biodegradable resin composition R shrinks as it solidifies. Although A is not inseparable, it is in close contact with the male mold 5. As a result, as shown in FIG. 7, the heel A is easily released from the female mold 3, but is not easily released from the male mold 5, and remains in close contact with the male mold 5. 3 is released.

  If the heel A remains in close contact with the male mold 5, it will be in close contact with the male mold 5 more and more firmly as the contraction proceeds. Therefore, next, compressed air is introduced between the inner surface of the flange A solidified from the compressed air introduction path 11 and the convex portion 4 of the male mold 5, and the inner surface of the flange A is released from the convex portion 4. The compressed air introduction path 11 may be opened to the entire periphery along the outer peripheral edge of the male mold, or may be partially opened to several places. As a result, a clearance Z is formed between the ridge A and the convex portion 4, and the ridge A is slightly lifted from the convex portion 4, but is not removed from the convex portion 4. The pressure of the compressed air to be introduced may be appropriately determined according to the weight, thickness, etc. of the heel A as long as deformation or balloon-like swelling does not occur on the heel A, for example, 0.05 MPa to 1.0 MPa. It is.

  Then, next, as shown in FIG. 8, the stripper plate 7 is advanced in the heel A direction, and the heel A is removed from the mold 1. As described above, the ridge A is released from the convex portion 4, and the stripper plate 7 is lifted by the edge forming portion 6 that is in contact with the edge of the ridge A. It can be easily removed from the mold 5.

  The bag A obtained by the production method of the present embodiment is heat resistant because it is made of the crystallized biodegradable resin composition R, and is used as a container for food heated by hot water injection or a microwave oven. be able to. In addition, the bag A can be used as a so-called returnable container that can be washed, dried, and sterilized at a high temperature because it has heat resistance, and can be collected and reused after use.

  In addition, since the biodegradable resin composition R requires a long time until it is cooled and solidified to obtain a molded product, compared with a general resin such as polyethylene, the cycle time of injection molding is generally long. However, according to the manufacturing method of the present embodiment, when the biodegradable resin composition R develops heat resistance and solidifies to such an extent that deformation is not caused by an external force due to protrusion by the stripper plate 7 while jetting compressed air. Thus, since the bag A is released, the cycle time can be shortened.

  When the mold 1 is opened as described above when the temperature T of the biodegradable resin composition R in the cavity 8 is, for example, 130 ° C., which is higher than 125 ° C., the ridge A is caused by the compressive stress of the stripper plate 7. It deforms step by step like a bellows. Moreover, when the pressure of compressed air is high, the bag A swells like a balloon. These are considered to be because the surface layer portion of 丼 A does not exhibit sufficient crystallization and lacks rigidity.

  On the other hand, when the mold 1 is opened as described above when the temperature T of the biodegradable resin composition R in the cavity 8 is lower than 112 ° C., for example, 110 ° C., the heel A contracts into the male mold 5 due to contraction. It is firmly adhered, and the heel A cannot be released or is deformed when released.

  In the present embodiment, the case where the candy A is produced as the hollow body is described as an example, but the hollow body includes tableware such as a candy, candy, a cup, a cosmetic container such as a lipstick container, a chemical container, Caps for containers, bottles for beverages (excluding PET bottles formed by blow molding), sealable containers such as Tupperware (registered trademark), food packaging containers for microwave ovens, containers for heat-resistant electronic devices, etc. by injection molding Any hollow body that can be molded may be used.

  Further, in the present embodiment, the heel A including the annular landing portion c is described, but the heel A may not include the landing portion c.

  In this embodiment, the infrared temperature sensor 12 is disposed on the convex portion 4 of the male mold 5, but the infrared temperature sensor 12 has a temperature of the biodegradable resin composition R at the outlet of the gate 9. As long as it is a detectable position, it may be disposed at any position, and may be disposed in the recess 2 of the female die 3.

  DESCRIPTION OF SYMBOLS 1 ... Metal mold | die, 2 ... Recessed part, 3 ... Female metal mold, 4 ... Convex part, 5 ... Male metal mold, 6 ... Edge part formation part, 7 ... Stripper plate, 8 ... Cavity, 12 ... Infrared temperature sensor, 13 ... Optical fiber, 14 ... Infrared receiver, A ... Hollow body, R ... Biodegradable resin composition, Z ... Clearance.

Claims (6)

A method for producing a heat-resistant hollow body molded by injecting a polylactic acid-containing resin composition into a mold,
The polylactic acid-containing resin composition is a biodegradable resin composition containing polylactic acid in an amount of 50% by mass or more, containing 1 to 28% by mass of an inorganic filler, and nanocompositing the inorganic filler.
A female mold having a concave portion that conforms to the outer surface shape of the hollow body, a male mold that has a convex portion that conforms to the inner surface shape of the hollow body and faces the concave portion, and an outer periphery of the male mold. And a stripper plate provided with an edge forming portion arranged along the edge of the hollow body, and forming a cavity surrounded by the concave portion, the convex portion, and the edge forming portion Heating the surface of the mold facing the cavity to a temperature in the range of 110 to 120 ° C. corresponding to the crystallization temperature of the biodegradable resin composition,
Injecting the molten biodegradable resin composition into the cavity of the mold heated to the temperature via a gate portion disposed in the mold; and
The temperature T (° C.) of the biodegradable resin composition injected into the cavity is expressed by the equation T = (t + 3.5) ± 1.5 (t (° C.) is the surface temperature of the mold facing the cavity. The infrared ray provided at a position facing the cavity accommodated in the part forming the convex part of the male mold or the part forming the concave part of the female mold. Moving the male mold and the stripper plate in a direction away from the female mold when detected by a temperature sensor;
From the compressed air introduction path formed between the male mold and the stripper plate, compressed air is injected between the solidified inner surface of the hollow body and the convex part of the male mold, and the hollow body Introducing compressed air between the inner surface of the hollow body and the convex portion to release the inner surface of the hollow body from the convex portion of the male mold,
And a step of advancing the stripper plate in the direction of the hollow body and taking out the hollow body from the mold. A method for producing a heat-resistant hollow body made of polylactic acid-containing resin.   The method for producing a heat-resistant hollow body made of polylactic acid-containing resin according to claim 1, wherein the inorganic filler is a layered silicate having an average layer thickness of 1 to 100 nm and a major axis of 150 nm or less.   In the step of moving the male mold and the stripper plate away from the female mold, the temperature T of the biodegradable resin composition measured by the infrared sensor is in the range of 125 to 112 ° C. The method for producing a heat-resistant hollow body made of polylactic acid-containing resin according to claim 1, wherein the male mold and the stripper plate are moved in a direction away from the female mold.   In the step of moving the male mold and the stripper plate away from the female mold, the temperature T of the biodegradable resin composition measured by the infrared sensor is in the range of 115 to 112 ° C. The method for producing a heat-resistant hollow body made of polylactic acid-containing resin according to claim 1, wherein the male mold and the stripper plate are moved in a direction away from the female mold.   The infrared temperature sensor receives infrared rays generated by the biodegradable resin composition injected into the cavity through an optical fiber by an infrared receiver, and detects the temperature of the resin from the energy amount of the infrared rays. The method for producing a heat-resistant hollow body made of polylactic acid-containing resin according to claim 1.   The method for producing a heat resistant hollow body made of polylactic acid-containing resin according to claim 1, wherein the infrared temperature sensor is provided at a position facing the cavity facing the gate portion.

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