JP2007320082A - Method for producing resin-integrated molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a resin-integrated molding in which parts such as a container barrel part are foamed selectively to form a foamed region, and parts required for characteristics such as strength and dimensional stability are not foamed selectively to form a non-foamed region. <P>SOLUTION: The integrated molding of a thermoplastic resin is molded, and the integrated molding is impregnated with gas. By heating the obtained gas-impregnated molding partially and selectively, foaming by the generation of bubbles by the incorporated gas is carried out selectively. In this way, the resin-integrated molding having the foamed region and the non-foamed region is produced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for producing a resin integrated molded body, and more specifically, using a microcellular technique, a resin integrated molded body having a foamed region and a non-foamed region at a desired position, particularly for containers. The present invention relates to a preform manufacturing method.

  Currently, polyester containers represented by polyethylene terephthalate (PET) are excellent in properties such as transparency, heat resistance and gas barrier properties, and are widely used in various applications.

  On the other hand, in recent years, the reuse of resources has been strongly demanded, and with respect to the polyester container as described above, a used container is collected and reused for various purposes as a recycled resin. By the way, as for the contents stored in the packaging container, those that are easily altered by light, for example, certain beverages, pharmaceuticals, cosmetics, etc., are molded using a resin composition in which a colorant such as a pigment is blended in a resin. Provided in a sealed opaque container. However, from the viewpoint of resource reuse, it is not desirable to add a colorant (it would be difficult to ensure transparency in the recycled resin). For this reason, the use of a transparent container is required. Therefore, it is necessary to improve recyclability of opaque containers suitable for accommodating photo-altered contents.

  In order to impart light-shielding properties (opacity) without blending a colorant, it is conceivable to form the container wall from a resin foam. For example, in Patent Document 1, it is molded from a crystalline polyester resin foam. A method of manufacturing a body is disclosed.

  However, when the container is formed of a resin foam as in Patent Document 1, there is a problem that inconvenience due to foaming also occurs. That is, in a container typified by a bottle, a screw part is usually formed in the mouth part, and a cap is attached by screw fastening. However, when such a container mouth portion is formed of a foam, due to a decrease in strength due to foaming, the dimensional stability at the container mouth portion is reduced, and in particular, the dimensional stability at the screw portion is reduced. , Causing a decrease in sealing performance when the cap is attached.

In order to avoid the above problems, for example, Patent Document 2 contains a foaming agent such as a decomposable foaming agent such as azo-based dicarbonimide or baking soda, or a fluorocarbon-based or hydrocarbon-based organic solvent-based foaming agent. The resin composition to be injection-molded to form a preform (parison), the portion corresponding to the container mouth of the preform is heated to cause foaming, and in this state, stretch blow molding is performed. It has been proposed to obtain a container whose mouth is not foamed. In Patent Document 3, various foaming agents and a thermoplastic resin are melt-kneaded, directly blow-molded while being melt-extruded, and cooled to form a foamed preform. The bottle is manufactured by reheating to temperature and blow molding with a predetermined blowing air pressure. In this method, the bottle is manufactured by two-stage blow combining direct blow and cold parison blow, and the portion corresponding to the container mouth portion does not expand during foam preform molding. In the mouth, no foaming occurs.
Further, Patent Document 4 discloses a multi-layered foam having a low strength reduction and having a light shielding property, a heat shielding property, and a heat insulating property.
JP-A-60-87043 JP 61-53021 A JP-A-10-329203 JP-A-2005-246822

  In both Patent Documents 2 and 3, a container in which the body and bottom of the container are formed of foam and no foaming is obtained at the container mouth is obtained. Since remodeling is performed, foaming at the container mouth cannot be completely suppressed, and the container mouth becomes a low foaming region where the degree of foaming is low compared to the body and bottom. Therefore, improvement is still required in terms of suppressing a decrease in strength and a decrease in dimensional stability of the container mouth portion (screw portion). Moreover, in patent document 4, since a mouth part is not selectively made non-heating, a mouth part also foams at the time of the surface heating of the parison before blow molding, and there exists a problem which mouth part dimension stability falls. .

  It is also known that a portion corresponding to the body and bottom and a portion corresponding to the mouth are separately formed, and the two are joined after the formation. A part and a bottom part are selectively foamed, and a container mouth part can be made non-foamed. However, in this method, the body portion, the bottom portion, and the mouth portion must be formed separately, which results in low productivity and high manufacturing cost, and cannot be employed from an industrial standpoint.

Accordingly, an object of the present invention is an integrally molded body of a resin having a foaming portion, and a portion such as a container body is selectively foamed to form a foamed region, and the container mouth portion. It is an object of the present invention to provide a method for producing a resin-integrated molded body in which a portion requiring characteristics such as strength and dimensional stability is a non-foamed region that is not selectively foamed.
Another object of the present invention is to provide a container obtained by secondary molding of the resin integrated molded body.

  According to the present invention, an integral molded body of a thermoplastic resin is molded, and then the integral molded body is impregnated with gas, and the resulting gas-impregnated molded body is impregnated by partially selectively heating. There is provided a method for producing a resin-integrated molded body having foaming regions and non-foaming regions by selectively performing foaming by generating bubbles with gas.

In the production method of the present invention,
(1) The integral resin molded body of the thermoplastic resin is a container preform, and by selectively heating a region excluding the container mouth portion of the preform and a portion corresponding to the vicinity thereof, the container mouth A portion corresponding to the portion and the vicinity thereof as a non-foaming region,
(2) The container preform has a test tube shape with a closed bottom portion, and has a neck portion provided with a support ring and a screw portion positioned above the support ring on the outer surface of the upper portion. And by selectively heating the area excluding the neck, the neck becomes a non-foamed area,
Is preferred.

  Moreover, according to this invention, the container obtained by carrying out secondary shaping | molding of the preform for containers obtained by said method is provided.

  The manufacturing method of the present invention is to manufacture a resin integrated molded body having a foamed region and a non-foamed region by utilizing a so-called microcellular technique. Then, the molded body is heated to expand the gas impregnated in the molded body. As a result, foaming occurs and a foamed region is formed. After that, it is impregnated with gas, and then the part that should be the foaming area is selectively heated to perform foaming, so foaming does not occur during molding of the integrally molded body, and foaming in the non-foaming area is reliably prevented. Thus, the foamed region and the non-foamed region can be clearly distinguished. Therefore, the present invention is very effectively applied to the production of an integrally molded body having a portion (that is, a screw portion) that requires local strength or dimensional stability, such as a container preform. A container such as a bottle obtained by secondary reforming, the body part is a foamed region, and since light shielding is imparted by foaming, it is suitable as a packaging container for contents that cause alteration due to light, Since the colorant is not blended, it is suitable for recycling, and further, since the screw part is not foamed and becomes a non-foamed region, the decrease in strength and dimensional stability due to foaming is effectively suppressed, Excellent sealing performance.

  Furthermore, the manufacturing method of the present invention does not join the separately formed non-foamed part and the foamed part, but selectively forms the part that becomes the non-foamed area and the part that becomes the foamed area, Since the foamed region is formed by gentle heating, the manufacturing cost is low.

<Raw resin>
In the present invention, the resin used for the production of the resin foam is not particularly limited as long as it can be impregnated with an inert gas, and a thermoplastic resin known per se can be used. Random or block copolymers of polyethylene, high density polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene or α-olefins such as ethylene, propylene, 1-butene, 4-methyl-1-pentene Olefin resins such as cyclic olefin copolymers; ethylene / vinyl acetate copolymers, ethylene / vinyl alcohol copolymers, ethylene / vinyl chloride copolymers and other ethylene / vinyl copolymers; polystyrene, acrylonitrile / styrene Copolymers, ABS, styrene-based trees such as α-methylstyrene / styrene copolymers Fat; Vinyl-based resins such as polyvinyl chloride, polyvinylidene chloride, vinyl chloride / vinylidene chloride copolymer, polymethyl acrylate, polymethyl methacrylate; nylon 6, nylon 6-6, nylon 6-10, nylon 11, Examples include polyamide resins such as nylon 12; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and copolyesters thereof; polycarbonate resins; polyphenylene oxide resins; biodegradable resins such as polylactic acid; In particular, olefin-based resins and polyester resins that are preferably used in the field of containers are suitable, and among these, polyester resins are most suitable for maximizing the advantages of the present invention.

<Manufacture of resin integrated molded body>
Hereinafter, the manufacturing method of the resin integrated molded body of the present invention will be described taking a container preform as an example.

  FIG. 1 shows the basic concept of the manufacturing process of the present invention. That is, referring to FIG. 1, this manufacturing process includes a gas impregnation step [FIG. 1 (a)], a foaming step [FIG. 1 (b)], and a foaming stop step [FIG. 1 (c)]. Hereinafter, each process will be described in sequence.

Gas impregnation step [FIG. 1 (a)]:
First, the non-foamed preform 1 molded using the above-described raw material resin is prepared. The non-foamed preform 1 has a test tube shape as a whole, and has a body portion 2 and a bottom portion 3. A neck portion 5 is formed on the body portion 2. A screw portion 7 and a support ring 9 are formed on the outer surface. Such a non-foamed preform 1 is molded by a known molding method such as injection molding or compression molding.

  By the way, the screw portion 7 is a portion that is screw-engaged with the cap when the preform 1 is secondarily formed into a container (for example, a bottle), and is required to have strength and dimensional stability. Further, the support ring 9 is a part used for gripping the container when the formed container is supported and transported, and mechanical strength is required. Therefore, it is necessary for the neck portion 5 including the screw portion 7 and the support ring 9 to avoid a decrease in strength and a decrease in dimensional stability due to foaming. For this reason, the neck portion 5 (particularly, the screw portion 7) Through the following steps, it becomes a non-foaming region, and the body 2 and the bottom 3 become a foaming region.

  In the present invention, first, the non-foamed preform 1 as described above is impregnated with an inert gas such as carbon dioxide gas or nitrogen gas. Such an inert gas functions as a foaming agent, and foams when the inert gas impregnated in the preform 1 expands in a foaming process described later.

  That is, in this step, the non-foamed preform 1 is held by a jig such as a pole fixed in a sealed chamber 10, an inert gas is supplied from a gas supply pipe 11, and the inside of the chamber is pressurized. The non-foamed preform 1 is impregnated with the inert gas.

  The impregnation while holding the non-foamed preform 1 under high pressure as described above is a sufficient amount of gas to obtain desired characteristics (for example, light-shielding properties) in the molded body (container) finally obtained by foaming. As long as it dissolves, it may be carried out without heating or under heating. That is, the higher the temperature of the non-foamed preform 1, the smaller the amount of gas dissolved, but the faster the impregnation speed. The lower the temperature, the larger the amount of dissolved gas, but the longer the impregnation takes.

Foaming process [FIG. 1 (b)]:
In the present invention, foam molding is performed on the non-foamed preform 1 impregnated with the inert gas as described above. In such foam molding, when the non-foamed preform 1 is heated, the impregnated inert gas expands to cause foaming. That is, a rapid change in the internal energy (free energy) of the gas dissolved in the resin is brought about, which causes phase separation, and the dissolved gas separates from the resin as bubbles, and the resin is plasticized. In combination with this, bubbles grow and foaming occurs. Although heating for such foaming is not limited to this, it can be performed using an oil bath, an infrared heater, etc. as shown in the figure. The heating temperature is a glass transition point (Tg) or higher and lower than the melting point, preferably 200 ° C. or lower. If the heating temperature is too high, the cell diameter is difficult to control because of the rapid foaming after the heating, the appearance is deteriorated, and further, the crystallization of the body portion proceeds and the secondary formability is lowered.

  By the way, in the present invention, as described above, it is necessary to make the neck portion 5 a non-foaming region. For this reason, the foaming molding as described above involves the body portion 2 and the bottom portion 3 to be the foaming region. This is done by selective heating. For example, as shown in the drawing, the neck 5 of the non-foamed preform 1 is held by a holding mold 17 having a cooling water pipe 15 and the neck 5 is cooled while an oil bath, an infrared heater such as a quartz heater, or the like. Then, the body 2 and the bottom 3 may be heated. By such selective heating, foaming can be selectively generated at the body portion 2 and the bottom portion 3, and foaming of the neck portion 5 can be surely avoided.

The foaming conditions such as temperature and treatment time are usually such that the average diameter of the foamed cells produced by foaming is about 5 to 50 μm and the density of the foamed cells in the foamed region, depending on the amount of the inert gas dissolved. Is adjusted to be about 1 × 10 ^{6 to} 1 × 10 ⁹ cells / cm ³ to ensure a desired light-shielding property and avoid a decrease in strength and gas barrier property due to foaming more than necessary. Preferred above. That is, the larger the dissolved amount of the inert gas, the smaller the diameter of the foamed cell and the larger the cell density. On the other hand, as the dissolved amount of gas increases, the glass transition point of the resin decreases linearly or exponentially. Further, the viscoelasticity of the resin also changes due to the dissolution of the gas. For example, the viscosity of the resin decreases due to an increase in the amount of dissolved gas. Therefore, depending on the intended function, foaming conditions such as the amount of dissolved gas, gas pressure, temperature, etc. are adjusted so that an appropriate cell diameter and cell density can be obtained and the foamed cells are uniformly distributed in the foamed region. It may be set for each resin.

Foam stop process [FIG. 1 (c)]:
After foaming is performed as described above, the foaming is stopped by cooling, and a container preform 20 having a foamed region and a non-foamed region can be obtained. That is, the trunk | drum 2 and the bottom part 3 of this container preform 20 become a foaming area | region, and the neck part 5 becomes a non-foaming area | region.

Container preform:
That is, in the container preform 20 that is a resin integrated molded body obtained as described above, the body portion 2 and the bottom portion 3 that are foamed regions have characteristics such as light shielding properties and heat insulation properties, and non- In the neck part 5 which is a foaming region, the screw part 7 and the support ring 9 located in the neck part 5 effectively avoid a decrease in strength and a decrease in dimensional stability due to foaming. Furthermore, the preform 20 is advantageous in terms of weight reduction by foaming.

  Such a preform 20 is attached to secondary molding such as known blow molding, and is formed into a bottle-shaped container. In such a container, the body portion and the bottom portion are foamed regions to provide light shielding properties. It is effectively applied to contain contents that are altered by light. In addition, the neck portion provided with the screw portion and the support ring is a non-foaming region, and a decrease in strength and a decrease in dimensional stability due to foaming can be effectively avoided. Therefore, an excellent seal can be obtained by attaching a cap to the screw, for example. A structure can be formed. Furthermore, since the light-shielding property is imparted without blending the colorant, it is also suitable for recycling.

  Further, in the container preform 20 shown in FIG. 1 (c), the body portion 2 and the bottom portion 3 serving as the foaming region have a structure in which foam cells are distributed over the entire thickness direction of the wall portion. There is no need, and for example, a layered structure having a foamed layer in which foamed cells are distributed in layers and a non-foamed layer in which no foamed cells are present can be used.

  Specifically, referring to FIG. 2 and FIG. 3 showing a suitable layered structure in the foam region, the skin layers 25 and 25 where no foam cell exists are present on the outer surface side and the inner surface side. A three-layer structure (skin layer 25 / foam layer 27 / skin layer 25) in which a foam layer 27 in which foam cells (indicated by A in FIGS. 2 and 3) are distributed in layers is formed below the skin layer 25 (See FIG. 2) Further, a five-layer structure (skin) in which a skin layer 25 as described above is formed and a core layer 29 in which a foam cell is not present in the central portion of the lower foam layer 27 is formed. Layer 25 / foam layer 27 / core layer 29 / foam layer 27 / skin layer 25) (see FIG. 3).

  In the layered structure as described above, for example, in the foaming step of FIG. 1B, a heating mold or the like is inserted into the preform 1, and heating is performed from the inner surface side simultaneously with the outer surface of the non-foamed preform 1. The foamed cells can be formed by utilizing the sequential growth from the surface side to the center side.

  For example, after the above-described gas impregnation step is completed, the preform 1 impregnated with the gas is released under normal pressure (atmospheric pressure) for a predetermined time in a state where the resin is cooled and solidified, whereby the surface of the preform 1 ( An inert gas is discharged from the body 2 and the bottom 3) which are the foaming regions. As a result, a surface layer in which the inert gas is not dissolved or a surface layer with a low inert gas concentration is formed on the outer surface and the inner surface of the body portion 2 and the bottom portion 3 which are foamed regions of the preform 1. .

  Next, when the preform 1 having such a surface layer is subjected to foam molding by the foaming process of FIG. 1B described above by heating from the outer surface side and the inner surface side of the preform 1, the surface layer is inactive. Since the gas is not present or its concentration is low, the foam is not substantially foamed to such an extent that bubbles cannot be confirmed unless it is observed carefully so that it does not foam even when heated. That is, the skin layers 25 and 25 in FIGS. 2 and 3 are formed by this heating. In this case, for example, when the gas is released prior to foaming, the relationship between the open time under atmospheric pressure and the amount of dissolved gas is measured, and the retention time under normal pressure (released) is determined based on the measurement result. By adjusting (time), the thickness of the surface layer where the inert gas is not dissolved or the surface layer where the inert gas concentration is lowered can be adjusted, and thereby the thickness of the skin layer 25 can be adjusted.

  On the other hand, in the inside where a sufficient amount of inert gas is dissolved, foaming is performed sequentially from the surface layer side, and foamed cells A are formed. Therefore, when this foam molding is performed for a long time, the foam layer 27 in which the foam cells A are distributed is formed in the entire interior of the preform 1 except for the surface layer, and the foam region of the three-layer structure shown in FIG. 3) is formed. On the other hand, when heating is stopped at an appropriate point and foaming is stopped by cooling, a core layer 29 in which the foamed cells A do not exist is formed inside the foamed layer 27, and the foamed region having the five-layer structure shown in FIG. (The trunk | drum 2 and the bottom part 3) will be formed. The formation of the core layer 29 does not depend on the foaming time. For example, in the above-described impregnation step of FIG. The core layer 29 can also be formed by stopping the impregnation at a stage before spreading, and performing foaming in this state.

  In the present invention, when the foamed region having the layered structure as described above is formed, the scratch resistance of the container preform 20 can be improved by forming the skin layers 25 and 25. Further, in the finally obtained container, not only the scratch resistance but also the printing characteristics and label sticking property of the container can be improved. The thickness of the skin layer 25 formed in the foam region of the preform 20 is preferably about 20 to 200 μm. Further, the formation of the core layer 29 in the foamed region of the preform 20 is useful for avoiding a decrease in gas barrier properties due to foaming, and further improving secondary moldability such as blow molding. From the viewpoint, it is preferable to set various conditions so that the thickness of the core layer 29 is 100 μm or more.

  As mentioned above, the resin integrated molded body of the present invention and the manufacturing method thereof have been described by taking the test tube shape container preform as an example. However, the present invention is not limited to such a test tube shape container preform or the preform. It is not limited to bottles obtained by secondary molding.

  For example, the container preform may be in the form of a sheet as shown in FIG. 4, and in this case, the non-foamed preform 1 described above is formed into a sheet by extrusion molding, injection molding, compression molding, or the like. The sheet-shaped container preform 30 shown in FIG. 4 can be manufactured by performing each step in accordance with the method described in FIGS. 1A to 1C described above. In this preform 30, the peripheral portion corresponding to the portion that becomes the container mouth portion is the non-foaming region X, and the central portion corresponding to the trunk portion and the bottom portion is the foaming region Y.

  Such a sheet-shaped preform 30 is subjected to secondary molding such as vacuum molding typified by plug-assist molding and molded into a cup-shaped container 31 as shown in FIG. The container 31 includes a trunk portion 33 and a bottom portion 35, and a flange 37 is formed at an opening at the upper end of the trunk portion 33, the flange 37 becomes a non-foaming region X, and the trunk portion 33 and the bottom portion 35 are foamed regions. Y. That is, by making the flange 37 the non-foaming region X, it is possible to avoid a decrease in strength of the flange 37 and to improve the heat sealability by making the surface of the flange 37 a smooth surface. Furthermore, since the trunk | drum 33 and the bottom part 35 become the foaming area | region Y, light-shielding property and lightness are provided. Of course, also in such a cup-shaped container 31, the foamed region Y of the preform 30 has the above-described three-layer structure or five-layer structure, so that characteristics such as scratch resistance, label sticking property, gas barrier property, etc. Can be increased.

  The present invention is not limited to the container preforms and containers as described above, and can be applied to, for example, films, sheets, and other resin integrated molded products of various shapes. By forming the region and the non-foaming region, the light-shielding property, heat insulating property, lightness, etc. due to foaming are imparted to the molded product, and at the same time, the non-foaming region is formed at a desired position, thereby improving, for example, printability You can also.

Example 1
A non-foamed preform for a test tube-shaped container having a barrel portion, a bottom portion and a neck portion by injection molding using polyethylene terephthalate resin (PET) having an intrinsic viscosity of 0.84 (neck inner diameter: 21.6 mm, barrel thickness) : 3 mm, internal volume: 25.4 ml).

  The non-foamed preform was placed in a pressure resistant container maintained at 30 ° C., and maintained at a pressure of 15 MPa for 2 hours to impregnate with carbon dioxide. Thereafter, the non-foamed preform is taken out from the pressure vessel, the neck is held by a mold equipped with a cooling pipe, and the body and the bottom are immersed in an oil bath at 90 ° C. for 10 seconds while the neck is cooled. Foamed. After foaming, the preform was cooled to room temperature, then cut in the axial direction, and the cross section of the part from the neck to the trunk was observed. Foaming was observed.

  For comparison, the preform taken out from the pressure vessel is held by a mold not equipped with a cooling pipe, and the neck and bottom are placed in an oil bath in the same manner as in the above example without cooling the neck. It was immersed in and foamed. After cooling this preform to room temperature, it was cut in the axial direction, and when a cross section of the portion from the neck portion to the trunk portion was observed, foaming was recognized at the trunk side portion, and at the same time, some foaming was also observed at the neck portion. Was recognized.

The figure which shows the manufacturing process of the resin integrated molding of this invention for the preform for containers. The figure which shows an example of the layered structure in a foaming area | region. The figure which shows the other example of the layered structure in a foaming area | region. The figure which shows the sheet-shaped preform manufactured by this invention. The figure which shows the cup-shaped container shape | molded from the preform of FIG.

Explanation of symbols

1: Non-foamed preform 5: Neck part 7: Screw part 9: Support ring

Claims (4)

  Formation of a bubble by the impregnated gas by molding an integrally molded body of thermoplastic resin, then impregnating the integral molded body with gas, and partially heating the resulting gas-impregnated molded body A method for producing a resin-integrated molded body having a foaming region and a non-foaming region by selectively performing foaming.   The integral resin molded body of the thermoplastic resin is a preform for a container, and by selectively heating a region excluding the container mouth portion of the preform and a portion corresponding to the vicinity thereof, the container mouth portion and its The manufacturing method according to claim 1, wherein a portion corresponding to the vicinity portion is a non-foaming region.   The container preform has a test tube shape with a closed bottom, and has a neck portion provided with a support ring and a screw portion positioned above the support ring on the outer surface of the upper portion. The manufacturing method according to claim 2, wherein the region other than the neck portion is selectively heated to make the neck portion a non-foaming region.   A container obtained by secondary molding of a resin integrated molded body obtained by the production method according to claim 2.

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