JP5530150B2 - container - Google Patents

Description

  The present invention relates to a container made of an injection molded product of polylactic acid resin.

  In recent years, biodegradable resins that are decomposed by the action of microorganisms such as bacteria in the soil after disposal, such as polylactic acid resins, have been proposed in order to reduce the burden on the environment caused by wastes made of synthetic resins. . The polylactic acid resin can be formed into a molded body having various shapes by, for example, injection molding.

  Conventionally, an injection-molded product of the above-mentioned polylactic acid resin, which is a food container made of a hollow molded body such as a cup or tray, and contains polylactic acid and a powder having an average particle diameter of 1 to 150 nm as a filler An injection-molded product of the composition has been proposed (see, for example, Patent Document 1).

  However, since the food container is solid as a whole, the food container has high heat conductivity, so that it is difficult to maintain the temperature of the contained food and drink.

  Moreover, since the color of the food container is governed by the color of the powder, the food container has to be monotonous as a decoration. Therefore, it is conceivable to give decorativeness by coating the surface of the food container.

  However, the food container having the surface coated has a disadvantage that the biodegradability of the polylactic acid resin is hindered depending on the type of coating.

JP 2004-204143 A

  An object of the present invention is to provide a container having a decorative property without impairing the biodegradability of a polylactic acid resin, while eliminating such disadvantages and providing a cold retaining property for the contents.

In order to achieve such an object, the present invention includes a non-filler-containing polylactic acid resin containing carbon dioxide in a supercritical state that is non-reactive with the polylactic acid resin, and injecting the polylactic acid resin. A container having a foam layer formed therein and a non-foam layer formed integrally with the foam layer on a surface thereof, wherein the foam layer has a bubble formed therein , It was formed by integrating while moving with the flow of lactic acid resin, and it was injected by having an average diameter in the range of 0.1 to 10 mm gradually increasing from the upstream side to the downstream side in the injection direction . The non-foamed layer shows traces of flow of the polylactic acid resin, and the non-foamed layer is colorless and transparent, and is provided with a decoration made of the bubbles seen through the non-foamed layer. The “supercritical state” means a state having both gas diffusibility and liquid solubility exceeding a temperature and pressure (critical point) determined by the type of gas.

The container of the present invention is formed by containing the supercritical carbon dioxide in a polylactic acid resin not containing a filler, and injection-molding the polylactic acid resin from a cylinder toward a mold. At this time, the injected polylactic acid resin is cooled by the mold and solidifies from the surface region in contact with the mold toward the inside. In addition, since the inside of the mold is at a lower pressure than the inside of the cylinder, the supercritical carbon dioxide in the injected polylactic acid resin becomes non-supercritical in the internal region where the polylactic acid resin is not solidified. Become bubbles. As a result, a container having a foam layer inside and a non-foam layer formed integrally with the foam layer on the surface is formed. A foam layer is comprised by the bubble which is mutually independent, and the non-foaming part which surrounds this bubble.

  Therefore, the container of the present invention has a foam layer inside, thereby lowering the thermal conductivity as compared with the conventional solid container, and obtaining cold insulation for maintaining the temperature of the contents. Can do.

  In addition, bubbles generated in the injected polylactic acid resin cannot be moved to the surface region because the polylactic acid resin is solidified from the surface region toward the inside, and the solidified inside The region moves from the upstream side in the injection direction toward the downstream side as the polylactic acid resin flows. And the said bubble will show the trace which the polylactic acid resin flowed while forming the said foam layer with solidification of the internal area | region of the injected polylactic acid resin.

  The non-foamed layer is formed to be colorless and transparent because the polylactic acid resin does not contain a filler.

  Therefore, the container of this invention can see through the said bubble through the non-foamed layer which is colorless and transparent, and can obtain decoration property by this bubble.

  Moreover, since the said decoration is obtained by the said trace which the said bubble shows, and is not obtained using anything other than biodegradable resin, the container of this invention ensures biodegradability. Can do.

The container of the present invention has a large diameter because the polylactic acid resin contains carbon dioxide in a supercritical state, and a plurality of bubbles generated in the injected polylactic acid resin are integrated. There is a tendency to generate bubbles.

In the container of the present invention, the plurality of bubbles generated in the injected polylactic acid resin are integrated while moving from the upstream side to the downstream side in the injection direction along with the flow of the polylactic acid resin. Thus, bubbles having an average diameter in the range of 0.1 to 10 mm that gradually increases from the upstream side in the injection direction toward the downstream side in the above range are formed.

  Since the bubbles have an average diameter in the above range, they can be seen with the naked eye and do not diffusely reflect light. As a result, the entire container becomes transparent. In addition, the bubbles have an average diameter that gradually increases from the upstream side to the downstream side in the injection direction, so that the soot has an impression that the bubbles are rising from the bottom of the water into the water.

  Therefore, according to the container of this invention, the bubble which exhibits the said impression can be seen through a colorless and transparent non-foamed layer, and the decorativeness provided with a cool feeling can be obtained.

In the container of the present invention, when the air bubbles comprise a mean diameter of less than 0.1mm, it is that you can not be seen bubbles with the naked eye. In the container of the present invention, when the bubbles exceed the average diameter of 10 mm, the bubbles may not be maintained due to bubble breakage.

In order to achieve the above object, the present invention includes a non-filler-containing polylactic acid resin containing nitrogen in a supercritical state that is non-reactive with the polylactic acid resin. A container comprising a foam layer inside and a non-foam layer formed integrally with the foam layer on a surface thereof, wherein the bubbles in the foam layer are injected. It is formed by moving with the flow of the polylactic acid resin, has an average diameter in the range of 0.5 to 50 μm, diffuses light irregularly, and shines in white stripes from the upstream side to the downstream side in the emission direction. The non-foamed layer is colorless and transparent, and includes a decoration made of the bubbles seen through the non-foamed layer.
The container of the present invention is formed by containing supercritical nitrogen in a polylactic acid resin not containing a filler, and injection-molding the polylactic acid resin from a cylinder toward a mold. At this time, the injected polylactic acid resin is cooled by the mold and solidifies from the surface region in contact with the mold toward the inside. Further, since the inside of the mold is at a lower pressure than the inside of the cylinder, the nitrogen in the supercritical state in the injected polylactic acid resin becomes a non-supercritical state in the internal region where the polylactic acid resin is not solidified. To produce bubbles. As a result, a container having a foam layer inside and a non-foam layer formed integrally with the foam layer on the surface is formed. A foam layer is comprised by the bubble which is mutually independent, and the non-foaming part which surrounds this bubble.
Therefore, the container of the present invention has a foam layer inside, thereby lowering the thermal conductivity as compared with the conventional solid container, and obtaining cold insulation for maintaining the temperature of the contents. Can do.
In addition, bubbles generated in the injected polylactic acid resin cannot be moved to the surface region because the polylactic acid resin is solidified from the surface region toward the inside, and the solidified inside The region moves from the upstream side in the injection direction toward the downstream side as the polylactic acid resin flows. And the said bubble will show the trace which the polylactic acid resin flowed while forming the said foam layer with solidification of the internal area | region of the injected polylactic acid resin.
The non-foamed layer is formed to be colorless and transparent because the polylactic acid resin does not contain a filler.
Therefore, the container of this invention can see through the said bubble through the non-foamed layer which is colorless and transparent, and can obtain decoration property by this bubble.
Moreover, since the said decoration is obtained by the said trace which the said bubble shows, and is not obtained using anything other than biodegradable resin, the container of this invention ensures biodegradability. Can do. In the container of the present invention, since the polylactic acid resin contains carbon dioxide in a supercritical state, a plurality of bubbles generated in the injected polylactic acid resin tend to have a small diameter.

In the container of the present invention, a plurality of bubbles generated by the injected the polylactic acid resin is moved toward the downstream side from the upstream side of the injection direction with the flow of the polylactic acid resin, 0.5 Bubbles with an average diameter in the range of 50 μm are formed.

  Since the bubbles have an average diameter in the above range, they cannot be seen with the naked eye and diffusely reflect light. As a result, the entire container of the present invention is recognized as white. In addition, the bubbles are arranged along the injection direction by moving from the upstream side to the downstream side in the injection direction of the injected polylactic acid resin. And the said bubble shows the trace which shines white in the shape of a streak along the injection direction of a polylactic acid resin by irregularly reflecting light.

  Therefore, according to the container of the present invention, it is possible to see the bubbles that appear to shine white in a streaky manner through the colorless and transparent non-foamed layer, and it is possible to obtain a decorative property with a cool feeling.

  In the container of the present invention in which the fluid is nitrogen, when the bubbles have an average diameter of less than 0.5 μm, the bubbles show traces of white streaks along the injection direction of the polylactic acid resin. There may not be. Further, in the container of the present invention in which the fluid is nitrogen, when the bubbles exceed an average diameter of 50 μm, the bubbles approach a region where they can be seen with the naked eye, and light is not diffusely reflected. You may not be able to see the white glowing bubbles.

The perspective view which shows the food container of 1st Embodiment. Sectional drawing of the food container shown in FIG. Explanatory sectional drawing of the injection molding apparatus used for manufacture of the food container shown in FIG. The perspective view which shows the food container of 2nd Embodiment. Sectional drawing of the food container shown in FIG.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a perspective view showing the food container of the first embodiment, and FIG. 2 is a cross-sectional view of the food container shown in FIG. FIG. 3 is an explanatory sectional view of an injection molding apparatus used for manufacturing the food container shown in FIG. FIG. 4 is a perspective view showing the food container of the second embodiment, and FIG. 5 is a cross-sectional view of the food container shown in FIG.

  The food container 1 according to the first embodiment, which is an injection molded product of polylactic acid resin, contains food and drink such as cooled juice and ice cream. For example, as shown in FIG. It consists of a bottom cylindrical body.

  The food container 1 of the present embodiment contains carbon dioxide as a supercritical fluid that is non-reactive with the polylactic acid resin in a polylactic acid resin that does not contain a filler, and injects the polylactic acid resin. This is an injection-molded product formed by molding, and as shown in FIG. 2, it has a foam layer 2 inside and a non-foam layer 3 on the surface. Both the foam layer 2 and the non-foam layer 3 are made of polylactic acid resin, and the non-foam layer 3 is formed integrally with the foam layer 2. The non-foamed layer 3 is amorphous.

  The foam layer 2 is composed of irregularly shaped bubbles 4 and non-foamed portions 5 surrounding the bubbles 4. As shown in FIG. 1, the bubbles 4 have an average diameter that gradually increases from the upstream side in the injection direction to the downstream side (from the bottom to the top in FIG. 1) in the range of 0.1 to 10 mm.

  The food container 1 according to the present embodiment has the foam layer 2 inside, so that the thermal conductivity is lower than that of a conventional food container made of a solid substance, and the contents are maintained at a temperature suitable for the taste. Cold insulation can be obtained.

  Moreover, in the food container 1 of this embodiment, since the bubbles 4 have the average diameter in the above range, they can be seen with the naked eye and do not diffusely reflect light. As a result, the entire food container 1 becomes transparent. In addition, the bubbles 4 have an average diameter that gradually increases from the upstream side to the downstream side in the injection direction, so that the soot has an impression that the bubbles are rising from the bottom of the water into the water.

  Therefore, according to the food container 1 of the present embodiment, the bubbles 4 exhibiting the impression can be seen through the colorless and transparent non-foamed layer 3, and a decorative property with a cool feeling can be obtained.

  Moreover, since the foam layer 2 and the non-foam layer 3 are both made of a polylactic acid resin, the food container 1 of this embodiment is not easily decomposed during use, and is easily biodegraded after disposal. Can be played. Moreover, since the said decoration was obtained by the said trace which the bubble 4 shows, and was not obtained using things other than biodegradable resin, the food container 1 can ensure biodegradability. it can.

  The food container 1 of this embodiment can be manufactured, for example with the injection molding apparatus 11 shown in FIG. The injection molding apparatus 11 includes a cylinder 13 that conveys the polylactic acid resin toward the mold 12, a rotating shaft portion 14 disposed in the cylinder 13, and a motor 15 that rotationally drives the rotating shaft portion 14. Yes. The cylinder 13 includes a hopper 16 that supplies polylactic acid resin into the cylinder 13 near the end opposite to the mold 12, and supercritical fluid is supplied near the center of the cylinder 13 on the downstream side of the hopper 16. A supercritical fluid supply unit 17 for supplying the cylinder 13 is provided. The supercritical fluid supply unit 17 generates a supercritical fluid generator 18 that generates a supercritical fluid, and a fluid conduit 19 that transports the supercritical fluid generated by the supercritical fluid generator 18 toward the cylinder 13. And a metering device 20 interposed in the middle of the fluid conduit 19. The fluid conduit 19 is connected to the cylinder 13 via a shut-off valve 21.

  The cylinder 13 includes a nozzle 22 at the tip on the mold 12 side and a plurality of heating devices 23a on the outer peripheral surface. The nozzle 22 includes a heating device 23 b on the outer peripheral surface, and is connected to the mold 12 through a shut-off valve 24.

The rotating shaft portion 14 is connected to the motor 15 at the end opposite to the mold 12, and has a helical screw 25 provided on the outer peripheral surface, and a screw provided at the most distal portion on the mold 12 side. And a head 26. The screw 25 includes a base-end-side continuous screw 25 a provided from the end on the motor 15 side to the front of the lower part of the supercritical fluid supply unit 17 through the lower part of the hopper 16, and the supercritical fluid supply unit 17. Is formed of a discontinuous screw 25b provided in a lower portion of the screw and a distal-side continuous screw 25c provided between the screw head 26 and the discontinuous screw 25b . The discontinuous screw 25 b includes a plurality of discontinuous portions along the circumferential direction of the rotating shaft portion 14.

  The mold 12 includes a fixed mold 12a having a concave portion 27 having a shape along the outer shape of the food container 1 and a movable mold 12b having a convex portion 28 having a shape along the inner shape of the food container 1. A cavity portion 29 is formed between the portion 28. The cavity part 29 is connected to the nozzle 22 of the injection molding apparatus 11 through a sprue 30 provided in the fixed mold 12a.

Next, a method for manufacturing the food container 1 of the present embodiment using the injection molding apparatus 11 will be described. In the injection molding apparatus 11, first, a polylactic acid resin containing no filler is introduced into the cylinder 13 from the hopper 16. An example of the filler-free polylactic acid resin is Terramac (registered trademark) TE-2000 manufactured by Unitika Ltd.

  The polylactic acid resin is melted by being stirred by the continuous screw 25 a while being heated by the heating device 23 a in the cylinder 13, and the formed molten resin is conveyed in the direction of the mold 12.

  Next, carbon dioxide as a supercritical fluid that is non-reactive with respect to the polylactic acid resin is supplied from the supercritical fluid supply unit 17 to the molten resin. At this time, since the discontinuous screw 25b is provided in the lower part of the supercritical fluid supply unit 17, the supercritical carbon dioxide is stirred by the discontinuous screw 25b and sufficiently mixed with the molten resin. . As a result, in the cylinder 13 between the screw head 26 and the nozzle 22, a polylactic acid resin is formed as a single-phase solution in which the molten resin is mixed and impregnated with the supercritical carbon dioxide. However, the single-phase solution is in a state where nuclei for foaming are not formed. At this time, the impregnation amount of the carbon dioxide in the supercritical state with respect to the polylactic acid resin can be, for example, in the range of 0.01 to 0.3% by weight.

  Next, the polylactic acid resin in which the molten resin is impregnated with the carbon dioxide in the supercritical state is injected from the nozzle 22 into the cavity portion 29 of the mold 12 through the sprue 30. At this time, the inside of the nozzle 22 is a region where the pressure drops as compared with the inside of the cylinder 13, and a nucleus for foaming is formed in the polylactic acid resin while passing through this region.

  The injection of the polylactic acid resin can be, for example, a cylinder temperature of 190 to 230 ° C., an injection pressure of 120 MPa, an injection speed of 20 mm / second, a filling time for the cavity 29 of 3 seconds, and a pressure holding time of 12 seconds.

  The surface temperature of the cavity portion 29 of the mold 12 can be set to 30 ° C. Usually, in order to obtain an injection-molded product having a crystallized surface, a polylactic acid resin containing a filler that acts as a crystallization nucleus is placed in the cavity 29 having a surface temperature equal to or higher than the crystallization temperature (110 ° C.). Even when the polylactic acid resin is impregnated with a supercritical fluid, the surface temperature can only be lowered slightly. However, in this embodiment, since the injected polylactic acid resin does not contain a filler and it is not necessary to crystallize the non-foamed layer 3 on the surface, the surface temperature can be lowered to 30 ° C., and the molding cycle Can be shortened.

  Next, the polylactic acid resin injected into the cavity 29 is filled up to the tip of the cavity 29 and cooled by the mold 12. The cooling time can be set to 70 seconds, for example.

At this time, the polylactic acid resin injected into the cavity 29 is solidified from the surface region in contact with the mold 12 toward the inside. Further, since the cavity portion 29 has a lower pressure than the inside of the cylinder 13 , the supercritical carbon dioxide in the injected polylactic acid resin is in a non-supercritical state in the internal region where the polylactic acid resin is not solidified. To produce bubbles.

  The bubbles generated in the polylactic acid resin cannot be moved to the surface region because the polylactic acid resin is solidified from the surface region, and the polylactic acid resin is not solidified in the inner region. It moves from the upstream side in the injection direction toward the downstream side with the flow. The plurality of bubbles are integrated while moving to become bubbles 4 having an average diameter that gradually increases from the upstream side to the downstream side in the injection direction within a range of 0.1 to 10 mm. The bubbles 4 form the foam layer 2 as the internal region of the injected polylactic acid resin is solidified, and the average diameter gradually increases from the upstream side in the injection direction toward the downstream side in the range. As a result, the kite also gives the impression that bubbles are rising from the bottom of the water into the water. In addition, bubbles generated on the downstream side in the injection direction in the polylactic acid resin become bubbles 4 having a small diameter when the polylactic acid resin is solidified before being integrated with other bubbles.

  In addition, a non-foam layer 3 is formed on the surface area of the injected polylactic acid resin, and the non-foam layer 3 is formed colorless and transparent because the polylactic acid resin does not contain a filler. The

  As described above, the foam layer 2 is provided inside, the surface is provided with the non-foam layer 3 formed integrally with the foam layer 2, and the impression is exhibited through the colorless and transparent non-foam layer 3. The bubble 4 can be seen, and the injection molded product provided with the decorativeness with a cool feeling can be obtained.

  The injection molded product can be taken out as a food container 1 as a product by opening the mold 12 and removing the mold.

  Next, the food container 41 made of an injection molded product of the polylactic acid resin of the second embodiment will be described. The food container 41 is similar to the food container 1 and contains food and drink such as cooled juice and ice cream. For example, as shown in FIG. 4, the food container 41 is a bowl-shaped bottomed cylindrical body.

  The food container 41 according to the present embodiment is an injection-molded product obtained by containing nitrogen as the fluid in the supercritical state in a polylactic acid resin not containing a filler and injection-molding the polylactic acid resin. As shown in FIG. 2, the foam layer 42 is provided inside, and the non-foam layer 43 is provided on the surface. The foam layer 42 and the non-foam layer 43 are both made of polylactic acid resin, and the non-foam layer 43 is formed integrally with the foam layer 42. Similar to the food container 1, the food container 41 is provided with a foam layer 42 in the interior thereof, so that the food container 41 has a cold insulation property that maintains a temperature suitable for the taste.

  The foam layer 42 includes a true spherical bubble 44 and a non-foam portion 45 surrounding the bubble 44. As shown in FIG. 4, the bubbles 44 have an average diameter that is in the range of 0.5 to 50 μm.

  Moreover, in the food container 41 of the present embodiment, the bubbles 44 have an average diameter in the above range, so that they cannot be seen with the naked eye and diffusely reflect light. As a result, the entire food container 41 is recognized as white. Moreover, the bubble 44 shows the trace which shines in stripe shape white along the injection direction of a polylactic acid resin.

  Therefore, according to the food container 41 of the present embodiment, it is possible to see the bubbles 44 that appear to shine in a streaky manner through the colorless and transparent non-foamed layer 43, and to obtain decorativeness with a cool feeling. . Moreover, since the said decoration was obtained by the said trace which the bubble 44 shows, and was not obtained using things other than biodegradable resin, the food container 41 can ensure biodegradability. it can.

  The food container 41 of this embodiment can be manufactured by the injection molding apparatus 11 shown in FIG. At this time, the injection condition and the cooling condition of the polylactic acid resin can be the same as the food container 1 except that nitrogen is used instead of carbon dioxide as a fluid in a supercritical state. The amount of impregnation of the supercritical nitrogen into the polylactic acid resin can be, for example, in the range of 0.01 to 0.3% by weight.

  When the polylactic acid resin injected into the cavity portion 29 is cooled by the mold 12, the polylactic acid resin is solidified from the surface region in contact with the mold 12 toward the inside, and the polylactic acid resin in the polylactic acid resin Nitrogen in a supercritical state becomes a non-supercritical state in the inner region where the polylactic acid resin is not solidified, and generates bubbles.

  The bubbles generated in the polylactic acid resin are solidified from the surface region in the inner region where the polylactic acid resin is solidified, and downstream from the upstream side in the injection direction as the polylactic acid resin flows. It moves to the side and becomes a bubble 44 with an average diameter in the range of 0.5-50 μm. The bubbles 44 are arranged along the injection direction of the injected polylactic acid resin, and form a foam layer 42 as the internal region of the polylactic acid resin is solidified.

  As described above, the food container 41 having the foam layer 42 inside and the non-foam layer 43 formed integrally with the foam layer 42 on the surface can be obtained. Further, in the food container 41, the bubbles 44 have an average diameter in the above range, so that they cannot be seen with the naked eye and diffusely reflect light. As a result, the whole food container 41 of this embodiment is recognized as white. In addition, the air bubbles 44 are arranged along the injection direction of the polylactic acid resin, thereby showing traces that appear as white stripes along the injection direction of the polylactic acid resin, and the food container of this embodiment 41 can obtain a decoration with a cool feeling.

  As described above, the food containers 1 and 41 according to the present embodiment have been described as having a bowl-shaped bottomed cylindrical body, but are not limited to a bowl-shaped bottomed cylindrical body, such as a mug. In addition, the bottomed cylindrical body may be provided with a handle.

  In the present embodiment, the food containers 1 and 41 have been described. However, the container is not limited to a food container, and may be a decorative container such as a vase, for example.

  DESCRIPTION OF SYMBOLS 1 ... Food container, 2 ... Foam layer, 3 ... Non-foam layer, 4 ... Bubble, 41 ... Food container, 42 ... Foam layer, 43 ... Non-foam layer, 44 ... Bubble.

Claims (2)

A polylactic acid resin containing no filler contains carbon dioxide in a supercritical state that is non-reactive with the polylactic acid resin, and the polylactic acid resin is injection-molded, and has a foam layer inside. And a container having a non-foam layer formed integrally with the foam layer on the surface,
Bubble foam layer is formed by integrating while moving along with the flow of the injected the polylactic acid resin, gradually increases toward the downstream side from the upstream side of the injection direction 0.1~10mm By showing an average diameter in the range of, the flow trace of the injected polylactic acid resin,
The container is characterized in that the non-foamed layer is colorless and transparent, and includes a decoration made of the bubbles seen through the non-foamed layer.   A non-filler-containing polylactic acid resin contains nitrogen in a supercritical state that is non-reactive with the polylactic acid resin, the polylactic acid resin is injection-molded, and has a foam layer inside. A container comprising a non-foam layer formed integrally with the foam layer on the surface,
  The bubbles in the foam layer are formed by moving along with the flow of the injected polylactic acid resin, and have an average diameter in the range of 0.5 to 50 μm and diffusely reflect light to the upstream side in the injection direction. By showing the traces of the flow of the injected polylactic acid resin by shining in white stripes along the downstream side,
  The container is characterized in that the non-foamed layer is colorless and transparent, and includes a decoration made of the bubbles seen through the non-foamed layer.