JP2010179560A - Foam-molding mold and method of manufacturing thermoplastic resin-made foamed body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foam-molding mold for manufacturing a thermoplastic resin foam-molded body having a desired molded shape and a good appearance, and to provide a method of manufacturing the thermoplastic resin-made foam-molded body. <P>SOLUTION: The foam-molding mold 10 for molding the thermoplastic resin-made foam-molded body by foaming a foamable sheet 3 by decompressing the inside of a vacuum chamber 2 with the heat-softened thermoplastic resin-made foamable sheet 3 arranged in the vacuum chamber 2 includes: the first mold member 11 arranged in the vacuum chamber 2 and having the first molding surface 11a on which the foamable sheet 3 is arranged; and the second mold member 12 arranged in the vacuum chamber 2 and having the second molding surface 12a facing the first molding surface 11a wherein at least one of the first mold member 11 and the second mold member 12 is separated from the inner walls 4a and 5a of the vacuum chamber 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a foam molding die used for producing a thermoplastic resin foam molded article and a method for producing a thermoplastic resin foam molded article.

  Conventionally, in the production of a thermoplastic resin foam molded article in which a foamed sheet is made by foaming a foamed sheet by placing the foamed sheet made of thermoplastic resin inside the vacuum chamber and then depressurizing the inside of the vacuum chamber, the vacuum chamber itself is used as a mold. It is known to use. However, when the vacuum chamber itself is used as a mold, a depression is generated in the vacuum chamber due to the influence of external air pressure during decompression, and it has been difficult to shape the foamed molded product into a desired shape due to the depression.

  Patent Document 1 discloses a vacuum chamber in which a reinforcing rib is bolted to a main body portion. According to this vacuum chamber, the rigidity is increased by the reinforcing rib, so that it is possible to prevent the vacuum chamber from being depressed during decompression.

JP 2004-89872 A

  However, the conventional vacuum chamber described above has the following problems. That is, if the vacuum chamber is slightly recessed during decompression, the in-plane thickness distribution of the foamed molded product may be deteriorated by the recess. Further, if a large number of highly rigid reinforcing ribs are provided in order to reduce the dent, there is a problem that the vacuum chamber is increased in weight and size.

  The present invention has been made in view of such circumstances, and a foam molding die and a thermoplastic that can form a thermoplastic resin foam sheet into a thermoplastic resin foam molded body having a desired shape. It aims at providing the manufacturing method of a resin-made foaming molding.

  The mold for foam molding according to the present invention is a thermoplastic resin in which a foamed sheet is foamed by depressurizing the inside of the vacuum chamber in a state where the foamed sheet made of a heat-softened thermoplastic resin is disposed inside the vacuum chamber. A foam molding die for molding a foamed molded article, which is disposed inside a vacuum chamber, has a first molding member having a first molding surface on which a foam sheet is disposed, and a vacuum chamber. A second mold member disposed and having a second molding surface opposite to the first molding surface, wherein at least one of the first mold member and the second mold member is formed from an inner wall of the vacuum chamber. It is separated.

  The method for producing a thermoplastic resin foam-molded article according to the present invention is a method for producing a thermoplastic resin foam-molded article from a thermoplastic resin foam sheet using the above-described foam-molding mold. Is placed inside the vacuum chamber, and the foamed sheet heated and softened is placed in the mold, and after the placing step, the inside of the vacuum chamber is depressurized to form the first molding surface. Foaming step for foaming the foamed sheet between the first molding surface and the second molding surface, and after the foaming step, opening the vacuum chamber with the inside at normal pressure and taking out the thermoplastic resin foam molding from the mold And including.

  According to the present invention, when the inside of the vacuum chamber is depressurized to form a foamed sheet made of a thermoplastic resin by foaming the foamed sheet, even if a dent is generated in the wall of the vacuum chamber due to the influence of external pressure. Since the foam sheet is disposed in the foam molding die, a thermoplastic resin foam molded body having a desired shape can be formed. Specifically, even if a dent is generated in the wall of the vacuum chamber, at least one of the first and second mold members included in the foam molding die is separated from the inner wall of the vacuum chamber. It is possible to suppress the pressure due to the dent from being absorbed by the gap between the foam molding die and the foam molding die, and the deformation of the foam molding die by being pressed by the concave wall. This leads to a uniform thickness distribution of the thermoplastic resin foam molded article, so that it is possible to produce a thermoplastic resin molded article having a good appearance shaped into a desired shape.

  In addition, it is preferable that at least one of the first molding surface and the second molding surface is formed with a gas vent for releasing gas. According to such a configuration, when the foam sheet foamed on the first molding surface expands until it contacts the second molding surface, the gas at the interface between the first molding surface and the foam sheet (air in the vacuum chamber). And the residual gas at the time of manufacturing the foam sheet can be removed, so that the thickness distribution can be prevented from becoming non-uniform, thereby producing a thermoplastic resin molded article having a good appearance. It becomes possible.

  Moreover, it is preferable that the degassing part is formed of a porous member having air permeability. According to such a configuration, the gas can be efficiently released to the outside with a simple configuration.

Moreover, it is preferable that the air permeability of a porous member is 900-2000 cm < ³ > / cm < ² > / s. In this case, gas can be suitably released through the porous member.

  Moreover, it is preferable that the hole diameter of a porous member is 600 micrometers or less. In this case, since the pore shape of the porous member is suitably suppressed from being transferred to the surface of the thermoplastic resin foam molded article, a thermoplastic resin molded article having a good appearance can be manufactured.

  Moreover, it is preferable to further comprise temperature adjusting means for adjusting the temperature of at least one of the first molding surface and the second molding surface. When the foamed sheet expanded in the foam-molding mold is cooled and solidified, if the temperature difference in the foamed sheet becomes large, the crystallinity of the resin may vary depending on the location, resulting in poor appearance such as warpage. Therefore, by providing the temperature adjusting means described above and adjusting the temperature of the molding surface so as to reduce the temperature difference in the foamed sheet, it is possible to produce a thermoplastic resin molded body having a good appearance.

  ADVANTAGE OF THE INVENTION According to this invention, the foaming body made from a thermoplastic resin of the favorable external appearance shape | molded by the desired shape can be manufactured.

It is sectional drawing which shows 1st Embodiment of the mold for foam molding which concerns on this invention. It is sectional drawing which shows the heating method of the foam sheet of FIG. It is sectional drawing which shows the other example of the heating method of the foam sheet of FIG. It is sectional drawing which shows the pressure reduction state of the vacuum chamber of FIG. It is sectional drawing which shows 2nd Embodiment of the mold for foam molding which concerns on this invention. It is a top view which shows a thermoplastic resin foaming molding.

  Hereinafter, preferred embodiments of a foam molding die according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

(First embodiment)
As shown in FIG. 1, a foam molding apparatus 1 provided with a foam molding die 10 according to the first embodiment of the present invention produces a thermoplastic resin foam molded body from a thermoplastic resin foam sheet 3. And a vacuum chamber 2 connected to a vacuum pump (not shown). In the foam molding apparatus 1, the pressure inside the vacuum chamber 2 is reduced in a state where the foam molding die 10 is arranged inside the vacuum chamber 2 and the foam sheet 3 is arranged inside the foam molding die 10. As a result, the foamed sheet 3 is expanded and expanded, and a thermoplastic resin foam molded body having a shape corresponding to the foam molding die 10 is manufactured.

  First, the foamed sheet 3 made of a thermoplastic resin will be described. The thermoplastic resin which comprises the foam sheet 3 is not specifically limited, A well-known thermoplastic resin can be used. Examples of such a thermoplastic resin include ethylene resins such as low density polyethylene, medium density polyethylene, high density polyethylene and linear low density polyethylene, and olefin resins including propylene resins. The foam sheet 3 may be composed of one type of resin, or may be composed of two or more types of thermoplastic resins.

  From the viewpoint of heat resistance and rigidity, it is preferable that 50% by weight or more of the thermoplastic resin constituting the foamed sheet 3 is made of a propylene resin. Examples of the propylene-based resin used for the foam sheet 3 include a propylene homopolymer, a copolymer of propylene and ethylene, a copolymer of propylene and α-olefin, and a copolymer of propylene, ethylene and α-olefin. Or a polymer in which an amorphous ethylene / α-olefin copolymer is dispersed.

The thermoplastic resin constituting the foamed sheet 3 is more preferably a propylene-based resin in which 5% by weight or more satisfies the following formula (1) from the viewpoint of foamability. In Formula (1), MT (190) adopts a melt tension tester MT-501D3 type manufactured by Toyo Seiki Co., Ltd. as a melt tension tester, a sample amount of 5 g, a heating temperature of 190 ° C., and a heating time of For 5 minutes, the piston descending speed was set to 5.7 mm / min, and a resin strand was extruded from a rectangular orifice having a length of 8 mm and a width of 2 mm, and the extruded strand was wound by a winding roller having a diameter of 50 mm at a winding speed of 100 rpm. It shows the tension when removed. MFR (230) indicates a melt flow rate value measured in accordance with JIS standard K7210 under conditions of a temperature of 230 ° C. and a load of 2.16 kgf.

  Examples of the propylene resin satisfying the formula (1) include a branched propylene resin and a linear propylene resin containing a high molecular weight component. Examples of such branched propylene resins include resins obtained by irradiating a linear propylene resin disclosed in JP-A-62-1121704 with radiation. ) PF814 and SD632 manufactured by the company) are exemplified. Examples of the linear propylene-based resin include propylene-based resins introduced with an ultrahigh molecular weight component disclosed in JP-A-11-228629. Such a propylene resin includes a step of producing a crystalline propylene polymer portion having an intrinsic viscosity of 5 dl / g or more and a step of producing a crystalline propylene polymer portion having an intrinsic viscosity of less than 3 d1 / g. It is preferably obtained by a polymerization method, the intrinsic viscosity is less than 3 dl / g, and the proportion of the crystalline propylene polymer portion is preferably 0.05% by weight or more and less than 35% by weight. The intrinsic viscosity is the viscosity of a polymer solution having a concentration of 0 obtained by obtaining the viscosity of several polymer solutions having different concentrations and extrapolating the viscosity to 0.

  The expansion ratio and closed cell ratio of the foam sheet 3 are not particularly limited, but the expansion ratio is preferably 1.2 to 5.0 times, and the closed cell ratio is 80 to 100%. preferable. Here, the expansion ratio is a value indicating how many times the volume of the foam sheet becomes the volume of the material before foaming, and the closed cell rate is the closed cell (the whole is surrounded by the resin) in the sample volume. The ratio of the volume of bubbles that are not connected to other bubbles). Moreover, foaming gas is not specifically limited, Various gas can be used according to the kind of foaming agent mentioned later.

  The foamed sheet 3 that satisfies the conditions as described above is less likely to burst when foamed further by the reduced pressure inside the vacuum chamber 2, so that the foaming molding made of a thermoplastic resin having a high foaming ratio and a closed cell ratio is high. You can get a body. In particular, it is composed of a propylene-based resin containing 5 to 20% by weight of a propylene polymer satisfying the formula (1), having a foaming ratio of 1.5 to 2.5 times and a closed cell ratio of 90 to 100%. It is preferable to use as the foam sheet 3.

  Moreover, although the thickness of the foam sheet 3 is not specifically limited, It is preferable that it is 1-10 mm. The foam sheet 3 may be a single layer or may be composed of a plurality of layers. Examples of the layer structure of the foamed sheet 3 include 2 types 2 layers (non-foamed layer / foamed layer), 2 types 3 layers (non-foamed layer / foamed layer / non-foamed eyebrows), and 3 types 5 layers (non-foamed layer / non-foamed layer). Examples are foamed layer / foamed layer / non-foamed eyebrow / non-foamed layer). Here, the foam layer is a thermoplastic resin layer mixed with a foaming agent, and the non-foam layer is a layer made of a material that does not contain a foaming agent.

  Various layers of low molecular weight type or high molecular type additives may be blended in each layer of the foam sheet having a multi-layer structure, if necessary. Examples of such additives include conductive agents, antistatic agents, flame retardants, fillers, antioxidants, copper damage inhibitors, antifungal agents, ultraviolet absorbers, lubricants, pigments, adhesion improvers, and the like. It is done.

  The production method of the foamed sheet 3 is not particularly limited, and a known production method such as an extrusion foaming method, a batch foaming method, a bead type foaming method or the like can be adopted. Is preferred. In the extrusion foaming method, first, a thermoplastic resin and a foaming agent are melt-kneaded in an extruder to obtain a molten resin composition, and this molten resin composition is sent into a die connected to the extruder. The molten resin composition sent to the die is extruded into the atmosphere from the die outlet and foamed, then cooled to be formed into a sheet shape, and the foamed sheet is cut into a desired size by a cutting machine. Manufactured. Here, as a shape of the die used in the extrusion foaming method, a T die or a circular die can be used. The foamed sheet 3 produced in this manner is further softened by heating and then decompressed in the vacuum chamber 2 to further foam and expand in the thickness direction. At this time, the foam sheet 3 hardly expands in the length direction and the width direction. The foamed sheet 3 may have a multi-layer structure by pasting a non-foamed layer or the like by a known pasting technique. From the viewpoint of productivity, the foam sheet 3 may be multilayered by a multilayer coextrusion foaming method using a known multilayer die. It is preferable to manufacture the foam sheet 3 having the configuration.

  Moreover, the foaming agent used for manufacture of the foam sheet 3 is not specifically limited, A well-known physical foaming agent and a chemical foaming agent can be used individually or in combination. Examples of such physical foaming agents include carbon dioxide gas, nitrogen gas, air, propane, pentane, pentane, hexane, dichloroethane, dichlorodifluoromethane, dichloromonofluoromethane, and trichloromonofluoromethane. It is preferable to use an inorganic gas such as nitrogen gas, carbon dioxide gas or air. In addition, when the resin which comprises the foam sheet 3 is a propylene-type resin, it is more preferable to use a carbon dioxide gas as a foaming agent from a viewpoint of safety | security and the solubility to a propylene-type resin. When carbon dioxide gas is used as a foaming agent, it is injected into the resin in a supercritical state where the pressure is 7.4 MPa or more and the temperature is 31 ° C. or more from the viewpoint of diffusion and solubility in the resin. Is preferred.

  When a physical foaming agent is used, a cell nucleating agent may be used in combination. Bubble nucleating agents include talc, silica, diatomaceous earth, calcium carbonate, magnesium carbonate, barium sulfate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium silicate, zeolite, mica, clay, wollastonite, hydrotalcite , Magnesium oxide, zinc oxide, zinc stearate, calcium stearate, polymer peas such as polymethyl methacrylate resin, synthetic aluminosilicate and the above chemical foaming agents.

  Chemical foaming agents include organic acids such as citric acid, sodium citrate and stearic acid, baking soda, azodicarponamide, tolylene diisocyanate, isocyanate compounds such as 4,4′diphenylmethane diisocyanate, azopisoptilo Azo such as nitrile, barium azodicarboxylate, diazoaminobenzene, trihydrazinotriazine, diazo compound, benzene sulfonyl hydrazide, P, P'-oxypis (Pensen sulfonyl hydrazide), toluene sulfonyl hydrazide, etc. Hydrazine derivatives, nitroso compounds such as N, N'-dinitroso-pentamethylene-tetramine, N, N'-dimethyl-N, N'-dinitroso-terephthalamide, P-toluenesulfonyl semicarbazide, 4.4 'oxypisbene Semicarbazide compounds such emissions sulfonyl semi Scarpa disilazide, azide compounds, and triazole compounds. In particular, it is preferable to use any of sodium bicarbonate, citric acid, and azodicarponamide.

  When a chemical foaming agent is used, a foaming aid may be used in combination to adjust the decomposition temperature and decomposition rate. For example, since the decomposition temperature of azodicarbonamide alone is as high as about 200 ° C., zinc oxide, zinc stearate, urea or the like can be added and used as a foaming aid when processing at low temperatures.

  Next, the foam molding apparatus 1 will be described. The foam molding apparatus 1 includes a vacuum chamber 2 and a foam molding die 10 disposed inside the vacuum chamber 2. The vacuum chamber 2 is a substantially rectangular parallelepiped member that forms a sealed space inside. The material of the vacuum chamber 2 is not particularly limited, but is preferably made of metal from the viewpoint of durability and thermal conductivity, and particularly preferably made of aluminum from the viewpoint of cost and weight reduction.

  The vacuum chamber 2 includes a box-shaped storage unit 4 opened upward and a lid unit 5 disposed on the storage unit 4. In the vacuum chamber 2, a suction pipe 6 connected to a vacuum pump (not shown) and a purge pipe 7 for releasing the vacuum chamber 2 to the atmosphere are connected. The suction pipe 6 is provided with a suction valve 6 a for switching the open / close state of the suction pipe 6, and the purge pipe 7 is provided with a purge valve 7 a for switching the open / close state of the purge pipe 7.

  The foam molding die 10 is a die for expanding the foam sheet 3 to form a foamed product made of a thermoplastic resin, and is disposed inside the vacuum chamber 2. The material of the foam molding die 10 is not particularly limited, but is preferably made of metal from the viewpoint of durability and thermal conductivity, and particularly preferably aluminum from the viewpoint of cost and weight reduction. The foam molding die 10 includes a rectangular plate-shaped first mold member 11 having a first molding surface 11a on which the foam sheet 3 is disposed, and a second molding surface 12a facing the first molding surface 11a. It has a rectangular plate-like second mold member 12 and a plurality of columnar connecting portions 13 provided between the first mold member 11 and the second mold member 12.

The 1st type | mold member 11 has the gas vent part 11c comprised from a porous member. The gas vent 11c forms the inner surface of the first mold member 11, that is, the first molding surface 11a, and the foam sheet 3 is disposed on the gas vent 11c. Gases (such as air in the vacuum chamber and residual gas at the time of manufacturing the foam sheet) existing at the interface between the molding surface 11a and the foam sheet 3 are released to the outside through the gas vent 11c. Examples of the porous member constituting the gas vent portion 11c include a wire mesh, a punching sheet, a nonwoven fabric, and ceramic. The porous member preferably has a permeability of 900 to 2000 cm ³ / cm ² / s measured along the Frazier method (A method) defined in JIS standard L1096. In this case, gas can be efficiently released through the porous member. The porous member preferably has a pore diameter of 600 μm or less. In this case, since the hole shape of the porous member is preferably suppressed from being transferred to the surface of the foamed molded body made of thermoplastic resin, a thermoplastic resin molded body having a good appearance is manufactured. The porous member may be used by superposing porous members having the same air permeability or by superposing porous members having different air permeability. When the same type or different types of porous members are used in an overlapping manner, the air permeability of the porous members when they are overlapped is preferably in the above-mentioned numerical range. The pore diameter of the porous member can be obtained, for example, by analyzing an image obtained by SEM (Scanning Electron Microscope). In a wire mesh or the like, the hole diameter can be calculated from the number of meshes and the wire diameter.

  The first mold member 11 is disposed on the bottom surface of the vacuum chamber 2 via a block-shaped foot portion 11b. The foot portions 11b are respectively provided at the four corners of the lower surface of the first mold member 11 (the surface opposite to the first molding surface 11a), and support the first mold member 11. The second mold member 12 is supported by the first mold member 11 via the connecting portion 13. The second mold member 12 is disposed so as to be separated from the inner walls 4 a and 5 a of the vacuum chamber 2, and there is a gap between the outer peripheral surface of the second mold member 12 and the inner walls 4 a and 5 a of the vacuum chamber 2. Is formed.

  The connecting portion 13 is a columnar member extending in the vertical direction, and is provided at each of the four corners of the first molding surface 11a. The lower end of the connecting portion 13 is connected to the first molding surface 11a, and the upper end is connected to the second molding surface 12a. The length in the vertical direction of the connecting portion 13 corresponds to the distance between the first molding surface 11a and the second molding surface 12a. The distance between the first molding surface 11a and the second molding surface 12a is larger than the thickness of the foamed sheet 3 that is the molding target. In addition, when the space | interval of the 2nd molding surface 12a and the foam sheet 3 is too large, since the closed cell rate of the foaming molding obtained tends to fall, the 1st molding surface 11a and the 2nd molding surface 12a Is preferably 1.1 to 5.0 times the thickness of the foamed sheet 3. Further, the surface of the first molding surface 11a of the first mold member 11 and the second molding surface 12a of the second mold member 12 are made of Teflon (registered trademark) or anodized from the viewpoint of the peelability of the foam molded product. It is preferable that surface treatment by (registered trademark) is performed.

  Then, the manufacturing method of the thermoplastic resin foam molded object using the foam molding apparatus 1 which has the above structure is demonstrated. As shown in FIG. 2, first, the foamed sheet 3 made of thermoplastic resin is put into a heating device 8 and heated. Examples of the heating method in the heating device 8 include those using a hot plate, oven, hot air, infrared heater, microwave, etc., but avoiding the drawdown of the foamed sheet 3 during heating, and the appearance of the molded product is poor. From the viewpoint of suppressing the generation of heat, a heating method using a hot plate or an oven is preferable. In order to heat the foamed sheet 3 made of thermoplastic resin, the foamed sheet 3 is previously disposed on the first molding surface 11 a of the foam-molding mold 10, and then the foam-molding mold 10 in the heating device 8. The foamed sheet 3 may be heated together (see FIG. 3).

  Moreover, the heating temperature in the heating apparatus 8 is not specifically limited, What is necessary is just to set suitably according to the thermoplastic resin which comprises a foam sheet. For example, when the thermoplastic resin constituting the foamed sheet 3 is a crystalline resin, it is preferable to set the heating temperature in the vicinity of the melting point of the thermoplastic resin. Moreover, when the foamed sheet 3 is comprised from 2 or more types of thermoplastic resins, it is preferable to set heating temperature in the vicinity of melting | fusing point of the thermoplastic resin contained mainly.

  The heating time by the heating device 8 is such that the temperature at the center of the foamed sheet 3 in the thickness direction reaches the heating temperature in accordance with the type of the thermoplastic resin constituting the foamed sheet 3, the foaming ratio, the thickness of the sheet, and the like. What is necessary is just to set suitably. For example, it is possible to attach temperature sensors to the central portion and the upper and lower surfaces in the thickness direction of the foamed sheet 3, measure the time change of each temperature, and set the heating temperature and the heating time according to the measurement results. Further, the foamed sheet 3 may be preheated for shortening the heating time.

  Subsequently, the foam sheet 3 heated and softened by the heating device 8 is disposed on the first molding surface 11 a of the foam molding die 10, and the foam molding die 10 is placed inside the accommodating portion 4 of the vacuum chamber 2. Be placed. At this time, the foam sheet 3 is disposed in the foam molding die 10 in a state of being separated from the second molding surface 12a.

  Thereafter, as shown in FIG. 1, the lid 5 is closed to make the inside of the vacuum chamber 2 sealed. Then, the vacuum pump is operated in a state where the suction valve 6a is opened and the purge valve 7a is closed, and the inside of the vacuum chamber 2 is decompressed. At this time, a depression is generated in the vacuum chamber 2 due to the influence of the external air pressure (see FIG. 4). Although not shown in the drawing, not only the inner wall 5a of the lid portion 5 of the vacuum chamber 2 but also the inner wall 4a of the housing portion 4 has a dent. Then, the foam sheet 3 is foamed by the reduced pressure in the vacuum chamber 2 and expands in the thickness direction. The foam sheet 3 expands until it comes into contact with the second molding surface 12a. At this time, in order to improve the expansion ratio of the foamed sheet 3, the pressure in the vacuum chamber 2 is preferably as close to vacuum as possible. Specifically, the pressure in the vacuum chamber 2 during decompression is preferably 0.01 MPa or less, and the decompression speed by the vacuum pump is preferably 0.01 MPa / s or more. Further, if necessary, a vacuum tank may be provided to facilitate exhaust.

  Thereafter, the foamed sheet 3 is cooled in a state where the vacuum pump is stopped and the atmospheric pressure in the vacuum chamber 2 is maintained. Then, the expanded foam sheet 3 is solidified to produce a foamed thermoplastic resin molded article that is molded to a desired thickness (ie, the distance between the first molding surface 11a and the second molding surface 12a). . Thereafter, the purge valve 7a is opened to bring the inside of the vacuum chamber 2 to normal pressure. Subsequently, the vacuum chamber 2 is opened, the foam molding die 10 is taken out, and the thermoplastic resin foam molding is taken out from the foam molding die 10.

  The thermoplastic resin foam molded article thus obtained is used for packaging, boxing, partition plates, food containers, stationery, building materials, automobile interior materials, and the like.

  Further, the surface of the thermoplastic resin foamed molded article may be subjected to corona treatment, ozone treatment, application of an antistatic agent, or the like. These surface treatments may be performed in advance on the foamed sheet 3 before heating, or may be performed on the thermoplastic resin foamed molded body.

  Further, a skin material such as a sheet or a film may be bonded to the surface of the foamed molded body made of thermoplastic resin depending on the application. A well-known thing can be used for a skin material according to a use. Examples of the skin material include a thin plate made of a metal such as aluminum or iron, a resin, paper, synthetic paper, or the like. You may laminate the nonwoven fabric and woven fabric which consist of plant materials, such as a thermoplastic resin or hemp, and inorganic materials, such as glass. Moreover, decorations, such as embossing and printing, may be given to the thin-plate surface to be used, and you may carry out lamination | stacking lamination | stacking by making a foaming molding into a skin material.

  Lamination lamination of these skin materials may be performed on the thermoplastic resin foam molded body obtained in the present invention, or may be performed on the foam sheet 3 in advance. Also, the method of laminating the skin material is not particularly limited, for example, a method of applying and laminating an adhesive on the surface of the foamed molded product or the foamed sheet 3, using a skin material laminated with an adhesive resin film, A method of laminating the adhesive resin film surface by heating and melting and laminating the foam molded body or the foamed sheet 3, and laminating by laminating the laminating surface of the skin material and the foam molded body or the foamed sheet 3 using a heater, hot air or the like. Examples thereof include a method, a method in which a molten resin is laminated by extrusion lamination between a skin material and a foamed molded product or a foamed sheet 3.

  The thermoplastic resin foam molded article obtained in the present invention can be further subjected to thermoforming such as vacuum molding. Examples of thermoforming include known methods such as vacuum forming and heat ruled line processing.

  As described above, according to the foam molding die 10 according to the present embodiment and the method for producing a foam molded body made of a thermoplastic resin using the foam molding die 10, foaming is performed by reducing the pressure inside the vacuum chamber 2. When foaming the sheet 3 to form a thermoplastic resin foam molded body, even if a dent is generated in the wall of the vacuum chamber 2 due to the influence of external air pressure as shown in FIG. Since it is arrange | positioned in 10, the foamed molded object made from a thermoplastic resin of a desired shape can be shaped. Specifically, even if a recess is generated in the wall of the vacuum chamber 2, the second mold member 12 included in the foam molding die 10 is separated from the inner walls 4 a and 5 a of the vacuum chamber 2. The pressure between the recesses is absorbed by the gaps between 4a, 5a and the foam molding die 10, and the foam molding die 10 can be prevented from being deformed by being pressed against the recessed wall. This makes it possible to produce a thermoplastic resin molded article having a good appearance molded into a desired shape in order to make the thickness distribution of the thermoplastic resin foam molded article uniform.

  Further, according to the foam molding die 10, when the foamed sheet 3 foamed on the first molding surface 11 a expands until it comes into contact with the second molding surface 12 a, it is between the molding surface 11 a and the foamed sheet 3. It is possible to suppress appearance defects such as non-uniform thickness distribution of the molded body due to air bleeding present at the interface, thereby making it possible to produce a thermoplastic resin molded body having a good appearance. . Furthermore, by configuring the gas vent 11c with a porous member having air permeability, the gas can be released to the outside with a simple configuration. In addition, the gas vent part 11c is not limited to the case where the gas vent part 11c is formed of a porous member, and may be configured to release gas by forming minute irregularities on the molding surface, for example. Such irregularities are formed by, for example, sand paper or sand blasting. Alternatively, the venting part 11c may be formed by providing a vent hole in a part of the molding surface, and the venting part 11c is formed by forming the whole or part of the molding surface in a mesh shape such as a wire mesh. May be.

(Second Embodiment)
As shown in FIG. 5, the foam molding apparatus 21 according to the second embodiment of the present invention is different from the first embodiment only in that the foam molding die 22 has a temperature adjusting unit (temperature adjusting means) 26. . Other configurations are the same as those of the first embodiment.

  The temperature adjusting unit 26 is embedded in the second mold member 24 of the foam molding die 22 and adjusts the temperature of the second molding surface 24a. The temperature adjusting unit 26 is a circulation pipe through which a fluid such as heated or cooled oil circulates, and adjusts the temperature of the second molding surface 24a by controlling the temperature of the fluid. The temperature adjustment unit 26 is not limited to the circulation pipe, and may be a heating wire, for example. It is preferable that the temperature adjustment part 26 can adjust the temperature of the 2nd molding surface 24a in the range of about 10-90 degreeC. The temperature adjustment unit 26 may be provided in the first mold member 23 instead of the second mold member 24, or may be provided in both the first mold member 23 and the second mold member 24. .

  Then, the manufacturing method of the thermoplastic resin foam molded object using the foam molding apparatus 21 which has the above structure is demonstrated. As shown in FIG. 2, first, the foamed sheet 3 made of thermoplastic resin is put into a heating device 8 and heated. Thereafter, the foam sheet 3 heated and softened by the heating device 8 is disposed on the first molding surface 23 a of the foam molding die 22, and the foam molding die 22 is disposed inside the accommodating portion 4 of the vacuum chamber 2. Is done. At this time, the foam sheet 3 is disposed in the foam molding die 22 in a state of being separated from the second molding surface 24a. Subsequently, as shown in FIG. 5, the lid 5 is closed to make the inside of the vacuum chamber 2 sealed. Then, the vacuum pump is operated in a state where the suction valve 6a is opened and the purge valve 7a is closed, and the inside of the vacuum chamber 2 is decompressed. The foam sheet 3 is foamed by the reduced pressure in the vacuum chamber 2 and expands in the thickness direction. The foam sheet 3 expands until it comes into contact with the second molding surface 24a.

  Thereafter, the foamed sheet 3 is cooled in a state where the vacuum pump is stopped and the atmospheric pressure in the vacuum chamber 2 is maintained. At this time, the temperature adjusting unit 26 adjusts the temperature of the second molding surface 24a so that the temperature difference in the foamed sheet 3 is reduced. And the expanded foam sheet 3 in an expanded state is solidified, and a foamed molded body made of a thermoplastic resin molded to a desired thickness is manufactured. Thereafter, the purge valve 7a is opened to bring the inside of the vacuum chamber 2 to normal pressure. Subsequently, the vacuum chamber 2 is opened, the foam molding die 22 is taken out, and the thermoplastic resin foam molding is taken out from the foam molding die 22.

  As described above, in the foam molding die 21 according to the second embodiment, when the foam sheet 3 expanded in the foam molding die 21 is cooled and solidified, a temperature difference in the foam sheet 3 is caused by the temperature adjusting unit 26. By adjusting the temperature of the second molding surface 24a so as to be small, uniform cooling and solidification in the foamed sheet 3 can be achieved, and thereby a thermoplastic resin molded body having a good appearance can be manufactured. .

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples relating to a method for producing a thermoplastic resin foam molded article.

  First, the foam sheet 3 used in Examples and Comparative Examples will be described. This foam sheet 3 was produced using a propylene polymer P1, a propylene resin P2, and a linear low density polyethylene P3. These resins P1 to P3 will be described.

  The propylene polymer P1 was produced by the method disclosed in JP-A-11-228629. The propylene polymer P1 powder had a crystalline propylene polymer portion A having an intrinsic viscosity of 7.7 dl / g and a crystalline propylene polymer portion B having an intrinsic viscosity of 1.2 d1 / g. The weight ratio of the crystalline propylene polymer portion A having an intrinsic viscosity of 7.7 dl / g and the crystalline propylene polymer portion B having an intrinsic viscosity of 1.2 dl / g is 11:89, The intrinsic viscosity was 1,9 dl / g. 0.05 parts by weight of Irganox 1010 (registered trademark) manufactured by Ciba Geigy Co., Ltd., and 0,000,000 of Sumilizer BHT (registered trademark) manufactured by Sumitomo Chemical Co., Ltd. with respect to 100 parts by weight of the propylene polymer P1 powder. 2 parts by weight was added and melt kneaded at 230 ° C. This propylene-based polymer P1 satisfied the formula (1) because the melt flow rate MFR (230) in the formula (1) was 12 g / 10 min and the melt tension MT (190) was 4.7 g.

  As the propylene-based resin P2, Nobrene AW161C (registered trademark) manufactured by Sumitomo Chemical Co., Ltd. was employed. This propylene-based resin P2 did not satisfy the formula (1) because the melt flow rate MFR (230) in the formula (1) was 11 g / 10 min and the melt tension MT (190) was 0.9 g.

  As the linear low density polyethylene P3, Exelen FX and CX3502 manufactured by Sumitomo Chemical Co., Ltd. were employed. The linear low density polyethylene P3 had a melt flow rate MFR (230) of 4 g / 10 min.

  25% by weight of the above-mentioned propylene-based polymer P1, 60% by weight of propylene-based resin P2, and 15% by weight of linear low-density polyethylene P3 were blended and used to produce the foam sheet 3.

In addition, as a cell nucleating agent master batch for producing the foam sheet 3, azodicarponamide having an average particle diameter of 4.48 μm and a density of 1.65 g / cm ³ is used. A master batch having a concentration of 30% by weight was used. Moreover, the same direction rotation biaxial extruder with a diameter of 104 mm was employ | adopted as an extruder for foaming layers. The ratio of the effective screw length to the screw diameter in this extruder was 32: 1.

  With respect to 100% by weight of the thermoplastic resin obtained by blending the resins P1 to P3, 0.3 PHR of the cell nucleating agent master batch was blended. The resin blended with the cell nucleating agent master batch was fed into the hopper of the extruder through a quantitative feeder. Melting and kneading were performed in an extruder, and liquefied carbon dioxide gas 0.35 PHR was injected at a high pressure with a diaphragm metering pump at the timing when melting progressed. The molten resin and carbon dioxide gas were sufficiently melted and kneaded, and then introduced into the T die by a gear pump at a discharge rate of 200 kg / h. And it cooled-molded by conveying the flat molten sheet extruded from the die | dye of T-die with the roll with a diameter of 210 mm adjusted to about 60 degreeC. Thereafter, the sheet was taken up with a take-up machine equipped with a nip roll, and cut into predetermined dimensions (length 260 mm, width 200 mm) with a cutting machine to obtain a foamed sheet 3. The obtained foam sheet 3 had a foam layer magnification of 3 times and a thickness of 3 mm.

[Example 1]
The above-described foamed sheet 3 was placed in a foam-molding mold 10 and heated for 20 minutes in an oven-type heating device 8 set at 173 ° C. (see FIG. 3). The desired thickness of the thermoplastic resin foam molded article, that is, the distance between the first molding surface 11a and the second molding surface 12a in the foam molding die 10 was 6.0 mm. Thereafter, the foam molding die 10 and the foam sheet 3 were taken out from the heating device 8 and placed in the vacuum chamber 2. Subsequently, the suction valve 6a of the suction pipe 6 connected to the vacuum pump is opened, the pressure reduction rate in the vacuum chamber 2 is set to 0.018 MPa / s, and the pressure is reduced to a vacuum state of 0 Pa to expand the foam sheet 3. I let you. Thereafter, the expanded foam sheet 3 was cooled and solidified to produce a thermoplastic resin foam molded article. Subsequently, the suction valve 6a was closed and the purge valve 7a was opened to bring the inside of the vacuum chamber 2 to normal pressure, and the vacuum chamber 2 was opened to obtain a thermoplastic resin foam molded article.

[Comparative Example 1]
Example 1 except that the vacuum chamber 2 itself is used as a mold without using a foam molding die, and the distance between the bottom surface of the accommodating portion 4 and the inner surface 5a of the lid portion 5 in the vacuum chamber 2 is 6.0 mm. The same was done.

These results are shown in Table 1. Positions A to D in Table 1 indicate positions that are 10 mm in the longitudinal direction from the four corners of the foamed sheet 3 in a plan view of the foamed sheet 3 and 10 mm in the direction orthogonal to the longitudinal direction, and the position E is the foamed sheet. 3 shows the center position (see FIG. 6).

  As shown in Table 1, when the vacuum chamber 2 itself was used as a mold, the thickness of the thermoplastic resin foamed molded article was 3 mm or more thicker than the desired thickness (6.0 mm). The thickness of the thermoplastic resin foam molded body molded using the foam molding die 10 was a more uniform value than when the vacuum chamber 2 itself was used as a mold.

  DESCRIPTION OF SYMBOLS 1,21 ... Foam molding apparatus, 2 ... Vacuum chamber, 3 ... Foam sheet, 4 ... Accommodating part, 4a ... Inner wall, 5 ... Cover part, 5a ... Inner wall, 6 ... Suction pipe, 7 ... Purge pipe, 8 ... Heating apparatus DESCRIPTION OF SYMBOLS 10,22 ... Mold for foam molding, 11, 23 ... 1st mold member, 11a, 23a ... 1st molding surface, 12, 24 ... 2nd mold member, 12a, 24a ... 2nd molding surface, Reference numerals 13 and 25 are connecting parts, and 26 are temperature adjusting parts (temperature adjusting means).

Claims (7)

In order to form a foamed product made of a thermoplastic resin by foaming the foamed sheet by reducing the pressure in the vacuum chamber while the foamed sheet made of a heat-softened thermoplastic resin is placed inside the vacuum chamber Foam molding mold,
A first mold member disposed within the vacuum chamber and having a first molding surface on which the foam sheet is disposed;
A second mold member disposed inside the vacuum chamber and having a second molding surface facing the first molding surface;
With
At least one of the first mold member and the second mold member is a foam molding mold separated from an inner wall of the vacuum chamber.   2. The foam molding die according to claim 1, wherein a gas vent for releasing gas is formed on at least one of the first molding surface and the second molding surface.   The foaming mold according to claim 2, wherein the gas vent part is formed of a porous member having air permeability. The air permeability of the porous member, a foam molding mold according to claim 3 which is 900~2000cm ³ / ^cm 2 / s.   The foaming mold according to claim 3 or 4, wherein the pore diameter of the porous member is 600 µm or less.   The mold for foam molding according to any one of claims 1 to 5, further comprising temperature adjusting means for adjusting a temperature of at least one of the first molding surface and the second molding surface. . A method for producing a thermoplastic resin foam molded article from a thermoplastic resin foam sheet using the foam molding die according to any one of claims 1 to 6,
An arrangement step in which the mold is arranged in a vacuum chamber, and the foamed sheet heated and softened is arranged in the mold;
A foaming step of foaming the foamed sheet between the first molding surface and the second molding surface by reducing the pressure inside the vacuum chamber after the arranging step;
After the foaming step, opening the vacuum chamber with the inside at normal pressure, and taking out the thermoplastic resin foam molded product from the mold; and
A method for producing a foamed molded article made of a thermoplastic resin.

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