JP4550646B2 - Method for producing foamed molded article made of thermoplastic resin or mixture thereof - Google Patents

Description

  The present invention supplies a solid state extrusion material made of a thermoplastic resin or a mixture thereof added with a nucleating agent to the upstream side of a heating cylinder of a twin-screw extruder and melts by rotating the screw. Injecting supercritical inert fluid and continuously extruding molten extruded material in which the inert fluid is dissolved and dispersed from the die provided at the downstream end of the heating cylinder to obtain a foam molded product. The present invention relates to a method for producing a foam-molded article made of a thermoplastic resin or a mixture thereof.

A screw extruder is known as an apparatus for continuously plasticizing a thermoplastic resin. As is well known, the screw extruder includes a heating cylinder having a predetermined length in the axial direction and a screw that is rotationally driven in the heating cylinder. Such screw extruders can be broadly classified into a single screw extruder having one screw and two twin screw extruders, all of which are directed from the material supply side to the product extrusion side. , Outline, material supply unit, compression unit, melting unit and the like. In the case of a single screw extruder, when the axial length of the screw is L and the diameter of the heating cylinder is D, the thermoplastic resin supplied to the heating cylinder starts to melt from 3 to 7 L / D, and 15 Finish at ~ 20 L / D. That is, a long screw is required for melting. On the other hand, the melting region, that is, the compression portion of the twin screw extruder is only 1 to 3 L / D under normal molding process conditions, and has a feature that it melts quickly and efficiently.
On the other hand, the melting region of the screw that generates the greatest shear stress plays a major role in the kneading effect of the screw extruder, in particular, dispersion mixing. However, the single-screw extruder has a long melting region, and the generation of shear stress is much slower than a twin-screw extruder having a short melting region, and is considerably low. Therefore, the twin screw extruder is superior in the dispersion and mixing action with respect to the thermoplastic resin and the mixture thereof, and the twin screw extruder is frequently used for molding processing that requires high kneading such as a compounding operation.

  By the way, most of the enthalpy required for molding a thermoplastic resin is consumed for plasticizing or melting the thermoplastic resin material. Such energy consumption can also be reduced by injecting a supercritical inert fluid. In addition, the viscosity of the molten resin material also decreases.

JP-A-10-230528 JP 2001-150504 A JP 2002-322288 A

  Many foam molded product manufacturing apparatuses using an extruder having such properties have been proposed, for example, in Patent Document 1. Japanese Patent Application Laid-Open No. H10-228561 includes a cylinder barrel, a kneading screw rotatably provided in the cylinder barrel, a supercritical carbon dioxide fluid supply device, an accumulator, an injection device having an injection cylinder, a foam made of a mold and the like. An apparatus for manufacturing a molded article is shown. Therefore, when the kneading screw is rotationally driven to supply the pellet-shaped resin material, the resin material is melted as conventionally known. At this time, when the carbon dioxide liquid is supplied from the carbon dioxide fluid supply device, the carbon dioxide liquid penetrates into the molten resin material. The molten resin infiltrated with the carbon dioxide liquid is supplied to the injection plunger via the accumulator, and when the plunger is driven by the injection device, counter pressure is applied to the mold cavities from the gas cylinder. A thermoplastic resin foam molding having a skin layer on the surface is obtained.

  Patent Document 2 discloses a method for molding the following foamed molded product. That is, a plurality of injection plungers are used for the injection plunger device, and a plurality of molds are used for the molding device, and a plurality of molten resins obtained by a plasticizing device for molding a thermoplastic resin foam molded product are injected. Sequentially supplied to the plunger, and sequentially injected into the mold cavity from the injection plunger to which the molten resin was supplied, to obtain a foam molded product, which is continuously obtained by a plasticizer for molding a thermoplastic resin foam molded product. There is shown a molding method characterized in that a molten resin to be used is used for molding a foam molded product without interruption. Patent Document 2 also discloses a production method in which talc, calcium carbonate, titanium oxide, carbon black and the like are added as a nucleating agent when producing a foam molded article as described above.

  On the other hand, for example, Patent Document 3 proposes an extrusion molding method in which an inert fluid is injected into a heating cylinder when a thermoplastic resin is molded using the above-described extruder. In Patent Document 3, when a thermoplastic resin composition is produced by mixing two or more kinds of thermoplastic resins in a molten state, for example, carbon dioxide in a supercritical state with respect to a total amount of 100 parts by weight of the thermoplastic resin. The manufacturing method of the thermoplastic resin composition which adds 2-20 weight part in the ratio is shown.

  According to the molding method described in Patent Literature 1, it is possible to obtain a foam molded product, but it is expected that a foam molded product composed of fine cells is difficult to obtain. On the other hand, according to the invention described in Patent Document 2, since an inert fluid such as a carbon dioxide fluid can be continuously supplied, the supply amount can be easily controlled, and the mixing ratio of the molten resin material and the carbon dioxide fluid Since the plasticizing device for molding the thermoplastic resin foam molded product does not stop, separation of the carbon dioxide fluid that has penetrated into the molten resin material can be prevented. The effect that a high-quality foam-molded article is obtained is recognized. Furthermore, by dissolving the carbon dioxide fluid in the molten resin, the fluidity is increased, low temperature injection becomes possible, and the effect of shortening the cooling time of the molded product can be obtained. However, according to the invention using a nucleating agent, since no special consideration is given to the type, size, shape, etc. of the nucleating agent, it is expected that a foam molded product having fine cells is not necessarily obtained. The For example, conventionally used synthetic clay, that is, smectite, is a layered compound, so that the average cell diameter of the foamed molded product may be 10 μm or more.

  Further, according to the invention described in Patent Document 3, since an inert fluid in a supercritical state is injected, it is possible to continuously mold difficult-to-mold resins without being restricted by the type of thermoplastic resin. Certain benefits are recognized. Further, for example, the thermoplastic resin is melted before reaching the supply portion of the inert fluid, so that the melted thermoplastic resin is located on the upstream side and exerts a sealing action, such as a seal ring, a gate, etc. Even if the backflow prevention device is not specially provided, there is an advantage that the backflow of the injected inert fluid can be prevented. However, the energy saving effect of the injected inert gas is not fully utilized. This is because it is injected not into the melted region of the screw that generates the greatest shear stress but into the region after being melted. The injection rate of carbon dioxide has been selected, but the carbon dioxide metering pump is controlled while checking the liquid carbon dioxide with a mass flow meter so that the flow rate becomes a predetermined flow rate. There is a possibility that excess or deficiency will occur, and there is a risk that the quality of the product will vary. Furthermore, the invention described in Patent Document 3 does not use a nucleating agent, nor is it intended to obtain a foam molded article having fine cells.

  An object of the present invention is to provide a method for producing a foam molded product, which obtains a foam molded product from a thermoplastic resin or a mixture thereof, which has solved the conventional problems as described above, and specifically, at a low temperature. Foam molding that can melt thermoplastic resin, can greatly reduce the enthalpy required for melting, improve the dispersion and mixing action, and also has a thermoplastic resin having a fine uniform foam cell or a mixture thereof. It aims at providing the manufacturing method of goods.

  In order to achieve the object of the present invention, the present invention is applied with a twin screw extruder excellent in dispersion and mixing action for thermoplastic resins and mixtures thereof. Then, a supercritical inert fluid is injected into the heating cylinder of the twin screw extruder. The screw is a first transport section, a kneading section, and a second transport section from the upstream side of the material supply side, and a solid plug is formed in the vicinity of the material from a solid to a melt in the kneading section. Is configured to be injected downstream of the solid plug, that is, into the molten region where the thermoplastic resin and mixture thereof exist in a solid state and a semi-molten state. If the amount of the inert fluid to be injected is small, effects such as sufficient low-temperature molding, energy saving, kneading improvement of the mixture, and production of a foam molded product of fine cells cannot be obtained. On the other hand, when the injection amount is too large, phase separation occurs and the gas phase and the liquid phase are separated. As a result, for example, mixing / kneading failure occurs, and when the foamed molded product is obtained, the bubble cells are uneven. Therefore, in the present invention, the injection amount of the inert fluid is controlled below its saturation solubility. The viscosity of the molten thermoplastic resin or mixture thereof is proportional to the amount of inert gas injected until the saturation point is reached. Therefore, the present invention continuously measures the viscosity of a molten thermoplastic resin or a mixture thereof with a viscometer that can be continuously measured, for example, PCR620 manufactured by Rheometric Co., and is controlled below the saturation solubility.

In the present invention, a nucleating agent is applied. Conventionally, talc and the like that are frequently used as a nucleating agent have various particle sizes, but the effect of suppressing the growth of bubbles as shown in the present invention is not recognized. Thus, the cell diameter of the foam-molded article obtained by using talc or the like having various particle diameters is large, and the average cell diameter is 10 μm or more. Therefore, in the present invention, spherical silicate is used as the nucleating agent. The particle diameter of the silicic acid also affects the cell diameter. When the particle diameter of the silicic acid is increased, the cell diameter of the foam-molded product becomes 1 to 10 μm or more and becomes irregular, and the average cell diameter becomes about 15 μm. Therefore, in the present invention, the diameter of the spherical silicic acid nucleating agent is selected to be 1 μm or less. Further, when the addition amount is 0.1% by mass or less with respect to the thermoplastic resin and the mixture thereof, the effect as a foaming inhibitor is lost, and a cell diameter larger than 10 μm and a smaller one of several μm are mixed. It becomes like this. That is, a uniform foam molded product cannot be obtained. On the other hand, if it exceeds 5% by mass , the agglomeration of particles becomes severe, the effect as a foam nucleating agent and the effect of suppressing the foam diameter are too strong, and a foam molded product having an appropriate foam diameter cannot be molded. Therefore, in the present invention, 0.1 to 5% by mass of spherical silicic acid of 1 μm or less is added to the thermoplastic resin or a mixture thereof.

Thus, in order to achieve the above-mentioned object, the invention according to claim 1 is a method in which a solid-state extruded material made of a thermoplastic resin or a mixture thereof added with a nucleating agent is placed upstream of a heating cylinder of a twin screw extruder. The supercritical state inert fluid is supplied from the inert fluid inlet provided to inject the supercritical state inert fluid into the heating cylinder. Injecting and continuously extruding a molten extruded material in which an inert fluid is dissolved / dispersed from a die provided at the downstream end of the heating cylinder to obtain a foam molded product, a supercritical state of inert material fluid, downstream of the solid plug formed between a position extruded material is 100% solid in the heating cylinder of the twin screw extruder, a position that is 100% melting of the downstream , Is injected into the melted region coexist in the solid state and a semi-molten state to lower the melt viscosity, while suppressing the temperature rise in the heating cylinder, a nucleating agent, 0.1 to 5 mass% relative to the extruded material The spherical silicic acid having a spherical diameter of 1 μm or less is added.
According to the second aspect of the present invention, the screw is rotated by supplying a solid state extrusion material made of a thermoplastic resin or a mixture thereof added with a nucleating agent to the upstream side of the heating cylinder of the twin screw extruder. In addition, the supercritical inert fluid is injected from the inert fluid inlet provided to inject the supercritical inert fluid into the heating cylinder, and the inert fluid is dissolved and dispersed. When the molten extruded material is continuously extruded from the die provided at the downstream end of the heating cylinder to obtain a foamed molded product, the supercritical inert fluid is heated by the twin screw extruder. and position the extrusion material in the cylinder is 100% solid, melting territory the solid plug formed between the 100% melted to have a position on the downstream side of the downstream side, mixed in the solid state and a semi-molten state Injected to reduce the melt viscosity, reduce the temperature rise in the heating cylinder, the viscosity of the extruded material in a molten state measured by the viscometer that the injection volume is provided on the downstream end side of the said heating cylinder , Controlled to be in the range below the saturated solubility of the inert fluid, and configured to add 0.1 to 5% by mass of spherical silicic acid having a sphere diameter of 1 μm or less with respect to the extruded material as a nucleating agent Is done.
According to a third aspect of the present invention, a solid-state extruded material made of a thermoplastic resin to which a nucleating agent is added or a mixture thereof is supplied to the upstream side of a heating cylinder of a twin-screw extruder to rotate the screw. In addition, the supercritical inert fluid is injected from the inert fluid inlet provided to inject the supercritical inert fluid into the heating cylinder, and the inert fluid is dissolved and dispersed. The molten extruded material is supplied to a screw extruder arranged in series on the downstream side, and continuously extruded from a die provided at the downstream end of the cylinder barrel of the screw extruder, and foamed. when to obtain a molded article, an inert fluid in a supercritical state is set to the position extruded material in the heating cylinder of the twin screw extruder is 100% solid, and 100% melted downstream thereof Downstream of the solid plug formed between the location and injected into the melted region coexist in the solid state and a semi-molten state to lower the melt viscosity, while suppressing the temperature rise in the heating cylinder, nucleating As described above, 0.1 to 5% by mass of a spherical silicic acid having a spherical diameter of 1 μm or less is added to the extruded material.
According to a fourth aspect of the present invention, a solid-state extruded material made of a thermoplastic resin to which a nucleating agent is added or a mixture thereof is supplied to the upstream side of a heating cylinder of a twin screw extruder to rotate the screw. In addition, the supercritical inert fluid is injected from the inert fluid inlet provided to inject the supercritical inert fluid into the heating cylinder, and the inert fluid is dissolved and dispersed. The molten extruded material is supplied to a screw extruder arranged in series on the downstream side, and continuously extruded from a die provided at the downstream end of the cylinder barrel of the screw extruder, and foamed. when to obtain a molded article, an inert fluid in a supercritical state is set to the position extruded material in the heating cylinder of the twin screw extruder is 100% solid, and 100% melted downstream thereof Downstream of the solid plug formed between the location and injected into the melted region coexist in the solid state and a semi-molten state to lower the melt viscosity, suppress the temperature rise in the heating cylinder, the injection volume The saturated solubility of the inert fluid is determined by the viscosity of the extruded material in a molten state measured by a viscometer provided near the downstream end of the heating cylinder or a viscometer provided near the downstream end of the cylinder barrel. It controls so that it may become the following ranges, and is comprised so that 0.1-5 mass% of spherical silicic acids with a spherical diameter of 1 micrometer or less may be added with respect to an extrusion material as a nucleating agent. The invention according to claim 5 is the production method according to any one of claims 1 to 4, wherein the mixing container is made of an extruded material, and 0.1 to 5% by mass of the nucleating material based on the extruded material. It is configured to continuously feed and mix the agent, and to feed continuously from the mixing vessel to the twin screw extruder.

As described above, according to the present invention, an inert fluid in a supercritical state is melted at a position where the extruded material in the heating cylinder of the twin screw extruder is 100% solid, and 100% melted downstream thereof. Since it is injected into the melting region mixed with the solid state and the semi-molten state downstream of the solid plug formed between the melted position and the melt, the melt viscosity of the melt is lowered, and thus high kneading is performed at low temperature molding. Can be molded. Further, since the molding temperature is low, the cooling time is shortened. Since the temperature is low even if the cooling time is short, the foam molded product becomes a fine foam molded product. Furthermore, since the temperature is low, thermal decomposition and thermal deterioration do not occur. Further, since the viscosity is lowered, the screw driving force is small, energy-saving molding can be performed, and mixing and kneading of the fine particles are promoted.
In particular, according to the present invention, 0.1 to 5% by mass of spherical silicic acid having a spherical diameter of 1 μm or less is added to the extruded material as a nucleating agent, so that bubble growth is suppressed and a fine foam cell is formed. The effect peculiar to this invention that the foamed product which can be obtained can be obtained is acquired.

According to the second aspect of the present invention, the supercritical inert fluid is melted at a position where the extruded material in the heating cylinder of the twin-screw extruder is 100% solid and 100% downstream thereof. It is injected into the melting region mixed in the solid state and semi-molten state downstream of the solid plug formed between it and the melted position to reduce the melt viscosity, suppress the temperature rise in the heating cylinder , and the injection amount is Since the viscosity measured by the viscometer provided near the downstream end of the heating cylinder is controlled so that it is within the saturation solubility of the inert fluid, in addition to the above effects, in the supercritical state Inert fluid is injected without excessive flow without backflow, avoiding problems of phase separation between liquid and gas phase due to excessive injection, irregularity of foamed cells, problems of mixing / kneading failure due to insufficient injection, etc. did Effect is further obtained that the goods can be obtained.
According to the third aspect of the present invention, the screw is rotated by supplying a solid state extrusion material made of a thermoplastic resin or a mixture thereof added with a nucleating agent to the upstream side of the heating cylinder of the twin screw extruder. And then injecting a supercritical inert fluid and supplying the molten extruded material in which the inert fluid is dissolved and dispersed to a screw extruder arranged in series downstream thereof, When continuously extruding from a die provided at the downstream end of the cylinder barrel of the screw extruder to obtain a foamed molded product, the supercritical inert fluid is extruded in the heating cylinder of the twin screw extruder. infusion but the position is 100% solid, the downstream side of the solid plug formed between a position that is 100% melting of the downstream side, the melted region coexist in the solid state and a semi-molten state Lowering the melt viscosity Te, suppresses the temperature rise of the heating cylinder, a nucleating agent, 0.1 to 5 wt% with respect to the extrusion material, the sphere diameter is added to the following spherical silicate 1 [mu] m, wherein In addition to the effect obtained by the invention according to Item 1, the molten extruded material is cooled by a screw extruder, and an effect of obtaining a foamed molded article having finer cells is obtained.
According to the invention described in claim 4, the screw is rotated by supplying a solid state extrusion material made of a thermoplastic resin to which a nucleating agent is added or a mixture thereof to the upstream side of the heating cylinder of the twin screw extruder. While being driven to melt, supercritical inert fluid is injected, and molten extruded material in which the inert fluid is dissolved / dispersed is supplied to a screw extruder arranged in series downstream thereof, When continuously extruding from a die provided at the downstream end of the cylinder barrel of the screw extruder to obtain a foam molded product, the supercritical state inert fluid is in the heating cylinder of the twin screw extruder. and position extruded material is 100% solid, melting region where the solid plug formed between the 100% melted to have a position on the downstream side of the downstream side, mixed in the solid state and a semi-molten state Injected to lower the melt viscosity, reduce the temperature rise of the heating cylinder, the injection quantity is provided in the downstream end side of the viscometer or the cylinder barrel are provided on the downstream end side of the said heating cylinder The viscosity of the extruded material in a molten state measured by a viscometer is controlled so as to be in the range below the saturated solubility of the inert fluid, and as a nucleating agent, 0.1 to 5% by mass with respect to the extruded material In addition to the effect obtained by the invention according to claim 3, since the spherical silicate having a sphere diameter of 1 μm or less is added, the supercritical inert fluid is injected without excess and deficiency, and the liquid phase and gas due to excess injection are injected. The problem of phase separation of phases, the problem of unevenness of foamed cells, the problem of mixing / kneading failure due to insufficient injection, etc. are avoided, and the effect of obtaining a stable product can be further obtained. According to the invention described in claim 5, the extruded material and 0.1 to 5% by mass of the nucleating agent are continuously fed to the mixing container and mixed, and then continuously mixed. Since it supplies to an axial screw extruder, in addition to the above effects, the effect which can adjust addition amount with a foaming state in the manufacturing field is further acquired.

  The first and second embodiments of the present invention will be described with reference to FIGS. A manufacturing apparatus 1 according to the first embodiment shown in FIG. 1 is composed of a twin screw extruder 3 supported on a gantry 2. The twin-screw extruder 3 includes a twin-bore type heating cylinder 4 as is well known in the art, a pair of bores are formed in the heating cylinder 4 in the axial direction, and the heat generation temperature is individually controlled on the outer peripheral portion. Are provided in the axial direction.

  A material supply chute 6 that reaches the bore of the heating cylinder 4 is attached to the upstream side of the heating cylinder 4 thus configured on the right side in FIG. According to the present embodiment, two types of thermoplastic resins to which a nucleating agent has been added and mixed in advance, such as polyethylene and polystyrene, are applied. Therefore, a screw or a rotary is associated with the material supply chute 6. There are provided first and second two hoppers 7 ', 7' provided with a mechanical metering feeder such as a feeder. The downstream ends of the hoppers 7 ′ and 7 ′ face the material supply chute 6. Near the downstream end of the heating cylinder 4, a viscometer 10 for continuously measuring the viscosity of the molten extruded material in which the inert fluid has been melted and diffused is attached. A die 12 is attached to the downstream end as is well known in the art.

  In the twin cylinder type heating cylinder 4, two screws 7 are rotatably provided in different directions or in the same direction. The screw 7 has a length corresponding to the length of the heating cylinder 4, and FIG. 2 (a) is a diagram schematically showing the screw 7 taken out. As shown in FIG. Forward lead full flight screw a, kneading disc (forward shift, 90 ° shift, reverse shift) b, forward lead full flight screw c, forward shift kneading disc d, 90 ° shift kneading disc e It is configured as follows. A material supply chute 6 is provided at a position corresponding to the upstream side of the forward lead full flight screw a.

  The results of analysis of the twin screw extruder provided with the screw 7 configured as described above with the analysis software TEX-FAN of Nippon Steel Co., Ltd. are shown in (b) to (e) of FIG. Yes. In the drawing, the extrusion molding material is 100% solid at the position S downstream of the forward lead full flight screw a of the screw 7, but at the downstream position F, the extrusion molding material is 100% molten. A solid plug is formed near the position P between the S position and the F position. According to the present embodiment, the inert fluid inlet 15 for injecting the supercritical inert fluid into the heating cylinder 4 near the downstream side of the position P where the solid plug is formed is provided. More specifically, an inert fluid inlet 15 is provided at a melting position or a melting region P where the extrusion forming material exists in a solid state and a semi-molten state. According to the present embodiment, a plurality of the inert fluid inlets 15 are provided at predetermined intervals in the axial direction as shown in FIG. These inert fluid inlets 15 are connected to an inert fluid production apparatus 18 through a fluid supply pipe 17 in which a flow control valve 16 is interposed. The inert fluid production apparatus 18 is composed of a compressor for pressurizing an inert gas, a heater for heating, and the like. When the inert gas is, for example, carbon dioxide, the critical temperature is 31.1 ° C., and the critical pressure is 7.38 MPa. In the case of nitrogen gas, since the critical temperature is −147 ° C. and the critical pressure is 3.4 MPa, a supercritical inert fluid is produced by pressurizing and heating above these values.

  According to the present embodiment, the control device 30 is also provided. The control device 30 includes various functions such as an analog / digital conversion function, a calculation function, a storage function, and a comparison function, and also includes setting means for setting various values necessary for extrusion molding. According to the embodiment shown in FIG. 1, the viscometer 10 is connected to the signal line x and the flow control valve 16 is connected to the signal line y. FIG. 3 (a) is a diagram showing the relationship between the viscosity of the melt-extruded material into which the inert fluid is injected and the injection amount of the inert fluid. As shown in FIG. 3, the injection amount is increased. The viscosity decreases with time, but when the injection amount reaches point A, the viscosity does not decrease even if the injection amount is further increased. This point A is the saturation dissolution point, and this saturation dissolution point A or saturation solubility is stored in the storage means of the control device 30. And according to this Embodiment, the injection quantity of an inert fluid is controlled so that it may be settled in the predetermined range below saturation solubility.

Next, the operation of the above embodiment will be described. Molding materials such as polyethylene and polystyrene, each containing 0.1 to 5% by mass of spherical silicic acid having a spherical diameter of 1 μm or less, are stored in the first and second hoppers 7 ′ and 7 ′, respectively. Then, a predetermined amount is supplied to the heating cylinder 4. On the other hand, the heating cylinder 4 is heated to a set temperature by the heaters 5, 5,. Further, an inert fluid is supplied from the inert fluid production device 18. The molding material supplied to the heating cylinder 4 forms a solid plug in the vicinity P where the solid is melted on the downstream side of the forward lead full flight screw a of the screw. The inert fluid is injected in multiple stages from the inert fluid inlets 15, 15,... Into the molten region P where the solid state molding material and the semi-molten molding material are mixed.

Since the inert fluid is injected, the melting temperature of the molding material decreases , the solid molding material melts rapidly, and the supercritical inert fluid dissolves and diffuses in the molding material. Further, the dispersion / mixing action in the melting region is accelerated, the kneading of the mixture is improved, and many chemical reaction rates that are diffusion-limited are improved. Further, since the inert fluid is dissolved, the viscosity is lowered, and it is melted and kneaded with a relatively low shearing force.

At this time, according to the present embodiment, 0.1 to 5% by mass of spherical silicic acid having a sphere diameter of 1 μm or less is added to the molding material, that is, the extruded material. Viscosity increases and bubble growth is suppressed. The state where the viscosity has increased is shown in FIG. Thereby, a fine cell is obtained. In this way, the molding material in which the supercritical inert fluid is dissolved and diffused is extruded from the die 12 into the atmosphere and foamed. At this time, since the melting temperature is relatively low, a foam molded product composed of fine foam cells is obtained. In FIG. 3B, the arrow between PP and HDPE means that the material has been changed from polypropylene to high-density polyethylene. The same applies to the following arrows.

  As described above, the viscosity of the molten extruded material in which the inert fluid is dissolved and diffused is continuously measured by the viscometer 10 and input to the controller 30. In the control device 30, the measured viscosity is compared with the stored viscosity, the injection amount is calculated so as to be within a predetermined range below the saturation solubility, and the flow control valve 16 is controlled. As a result, it is injected without excess or deficiency and does not cause gas-liquid phase separation. Therefore, effective mixing and kneading are performed, and a foam molded product having a uniform cell diameter is obtained.

  A second embodiment of the present invention will be described with reference to FIG. An apparatus 1 ′ for producing a foam molded article made of a thermoplastic resin according to the second embodiment or a mixture thereof is roughly arranged downstream of the twin screw extruder 3 according to the first embodiment. The single screw extruder 33 is connected in series. Therefore, the same reference numerals are given to the same elements as the constituent elements of the manufacturing apparatus 1 according to the first embodiment, and the same reference numerals are given the same reference numerals with a dash “′”, and a duplicate description will not be given. do not do.

  The single-screw extruder 33 is for increasing the cooling effect of the extruded material in the molten state. As is conventionally known, the single-screw extruder 33 includes a cylinder barrel and a screw that is rotationally driven by a geared motor 34 in the cylinder barrel. Has been. The upstream side of such a conventionally known single-screw extruder 33 is connected by a twin-screw extruder 3 and a transport pipe 35. A viscometer 10 is provided near the downstream end, and a die 12 is provided at the downstream end. Furthermore, a pressure gauge 36 is attached to the downstream end of the single screw extruder 33, and a pressure gauge 37 and a thermometer 38 are attached to the die 12, respectively. Various values measured by the measuring instruments 10, 36, 37, and 38 are converted into digital signals by the analog-digital converter 40 and input to the computer PC. The manufacturing apparatus 1 ′ according to the present embodiment also includes a display TV, and the foamed state photographed by the video camera 41 and the cell size of the foamed molded product inspected by the microscope 42 are displayed on the display TV. It is like that.

  The manufacturing apparatus 1 'according to the second embodiment operates in substantially the same manner. That is, as described above, the supercritical state inert fluid is injected by the twin screw extruder 3 and the supercritical state inert fluid is dissolved and diffused from the transport pipe 35. It is supplied to the single screw extruder 33. Since the single screw extruder 33 is rotationally driven by the geared motor 34, the molten extruded material in which the supercritical inert fluid is dissolved and diffused is continuously extruded from the die 12 and foamed. Thereby, the foam molded product HS is obtained continuously. At this time, the viscosity of the molten extruded material in which the inert fluid is dissolved and diffused is continuously measured by the viscometer 10 and input to the computer PC via the analog-digital converter 40. In the computer PC, as described above, the measured viscosity is compared with the stored viscosity, the injection amount is calculated so as to be within a predetermined range below the saturation solubility, and the flow control valve 16 is controlled. . As a result, it is injected without excess or deficiency and does not cause gas-liquid phase separation. Therefore, effective mixing and kneading are performed, and a foam-molded product having a uniform cell diameter is obtained. The expanded state and the cell size of the expanded molded product HP are displayed on the display TV.

  According to the present embodiment, the single-screw extruder 33 cools the molten extruded material in which the supercritical inert fluid is dissolved and diffused, so that a foam molded article having fine cells is obtained. It is done. That is, when the temperature of the extrusion molding material is high, the cell diameter increases, but a foam molded product having a small cell diameter can be obtained by lowering the temperature.

  According to the second embodiment, since the viscometer 10 is provided toward the single screw extruder 33, there may be a delay in controlling the injection amount of the supercritical inert fluid. Therefore, it can also be provided in the direction of the twin screw extruder 3. It should be noted that the present invention can be implemented by a twin screw extruder instead of the single screw extruder 33.

  An embodiment of a supply device 50 for continuously supplying the extrusion material from the mixing container to the twin screw extruder 3 is shown in FIG. That is, the supply device 50 includes a mixing container 51, a mixing blade 53, an extruded material supply device 56, a nucleating agent supply device 60, and the like. A mixing blade 53 is provided inside the mixing container 51 so as to be rotated by a motor 52. The mixing container 51 has a funnel shape, and a rotary metering feeder 54 is provided at the lower end thereof. Therefore, the extrusion material to which a predetermined amount of nucleating agent has been added and mixed by the fixed amount feeder 54 is supplied to the twin screw extruder 3.

  The extruded material supply device 56 includes a hopper 57. One or more types of thermoplastic resins are supplied to the hopper 57, and a rotary metering feeder 58 is provided at the lower end of the hopper 57 and connected to the mixing container 51. In the embodiment shown in the figure, the nucleating agent supply device 60 is composed of a screw-type quantitative supply device 61. The fixed amount feeder 61 is rotationally driven at a speed controlled by a motor 62.

The extruded material is supplied to the mixing container 51 from the rotary-type quantitative feeder 58 and the nucleating agent is supplied from the screw-type quantitative feeder 61. At this time, these quantitative feeders 58, 61 are supplied to the extruded material. The amount of nucleating agent is controlled to be 0.1 to 5% by mass . As a result, an extruded material in which a predetermined amount of the nucleating agent is uniformly mixed in the mixing container 51 is obtained and supplied to the twin screw extruder 3. According to the present embodiment, there is an advantage that the addition amount of the nucleating agent can be adjusted while inspecting the foam molded product at the molding site.

As described above, according to the present embodiment, since the injection amount is controlled so that the inert fluid falls within a predetermined range below the saturation solubility, it is injected without excess and deficiency, causing gas-liquid phase separation. However, just by injecting an inert fluid into the molten region where the extruded material exists in a solid state and a semi-molten state, the melt viscosity of the melt is lowered. Obviously we can do it. Further, since the molding temperature is low, the cooling time is shortened and a fine foam molded product is obtained. Further, since the temperature is low, thermal decomposition and thermal deterioration do not occur, and the viscosity is lowered, so that it is clear that the screw driving force is small and energy saving molding can be performed. Further, according to the present embodiment, 0.1 to 5% by mass of spherical silicic acid having a sphere diameter of 1 μm or less is added to the extruded material as a nucleating agent, so that bubble growth is suppressed and fine foaming is performed. A foamed product having cells can be obtained.

  Analysis results, examples, etc .: The analysis results of the Nippon Steel Corporation's analysis software TEX-FAN for the Nippon Steel Works' twin screw extruder equipped with the screw 7 shown in FIG. 2. From FIG. 5C, it is understood that the power for driving the screw 7 increases when the extrusion material starts to melt, but can be suppressed by injecting an inert fluid. Similarly, when the inert fluid is injected from (d) and (e) of FIG. 2, it is understood that the temperature and pressure rise in the heating cylinder 4 are suppressed and stabilized.

Using the production apparatus as shown in FIG. 4 (a), supercritical carbon dioxide is injected below the saturation solubility, and the foamed state due to the spherical diameter of the spherical silicic acid and the addition amount is small. The test was conducted in Examples 1 and 2 and Comparative Examples 1 to 3.
In addition, the manufacturing apparatus used in the following Examples and Comparative Examples used TEX30 made by Nippon Steel Works for a twin screw extruder, and PCR620 made by Rheometric Co. for a viscometer.

Example 1:
Extruded material: Polypropylene (PP, trade name: PF814)
Nucleating agent: spherical silicic acid (trade name: DI-5000), the average particle size was 0.9 μm, and the amount added was 2% by mass relative to polypropylene 100.
Molding conditions: 0.2 kg / h of carbon dioxide fluid was injected into 7.0 kg / h of the extruded material. That is, the amount of supercritical carbon dioxide fluid injected was 2.9% by mass .
Results: FIG. 5 shows a scanning electron micrograph or SEM photograph of the obtained foamed molded article. As shown in this photograph, the cell size of the obtained foamed molded article was 1 to 5 μm.

Example 2:
Extruded material: High density polyethylene (HDPE)
Nucleator: The same spherical silicic acid as in Example 1, the average particle size was smaller 0.1 μm, and the addition amount was 1 to 2% by mass relative to the high-density polyethylene 100.
Molding conditions: The amount of supercritical carbon dioxide fluid injected was 0.1 to 0.2% by mass . The temperature of the heating cylinder was 190 ° C., and the extrusion rate was 7.0 kg / h.
Results: An SEM photograph of the obtained foamed molded article is shown in FIG. As shown in this photograph, the average cell diameter of the obtained foamed molded product was 0.1 μm or less.

Comparative Example 1:
Extruded material: the same polypropylene as in Example 1 Nucleating agent: spherical silicic acid, the average particle size was 2 μm, and the amount added was 1% by mass with respect to polypropylene 100.
Molding conditions: The amount of supercritical carbon dioxide fluid injected was 2% by mass .
Result: FIG. 7 shows a transmission electron micrograph, that is, a TEM photograph (magnification depends on the scale in the photograph) of the obtained foamed molded article. As shown in this photograph, the cell diameter was 1-10 μm, irregular, and the average diameter was about 3-4 μm.

Comparative Example 2:
The test was performed under the same conditions as in Example 1 except that the amount of nucleating agent added was 0.05 mass % (0.1 or less). An SEM photograph of the obtained foamed molded product is shown in FIG.

Comparative Example 3: The amount of nucleating agent added was 6% by mass , and the others were tested under the same conditions as in Example 1. A TEM photograph of the obtained foamed molded product is shown in FIG.

Comparative Example 4:
The layered compound smectite was used as the nucleating agent, and the extruded material was tested using the same polypropylene (trade name: PF814) as in Example 1. The result is shown in FIG.

From Examples 1 and 2 and Comparative Examples 1 to 4 described above, when the amount of the nucleating agent is extremely reduced, the effect as a foaming inhibitor is lost, the cell diameter is larger than 10 μm, and about several μm. A small thing comes to be mixed. That is, a uniform foam molded product cannot be obtained. On the other hand, if it exceeds 5% by mass , the agglomeration of particles becomes severe, the effect as a foam nucleating agent and the effect of suppressing the foam diameter are too strong, and a foam molded product having an appropriate foam diameter cannot be molded.

From the above, it has been found that when 0.1 to 5% by mass of spherical silicic acid having a size of 1 μm or less is added, a foam molded product having fine cells can be obtained.

It is a side view which shows typically the manufacturing apparatus of the foaming molded article which consists of a thermoplastic resin concerning the 1st Embodiment of this invention, or its mixture. (A) is a side view schematically showing the screw, (b) is the state of the extruded material at the position corresponding to the screw, (c) is the pressure of the extruded material, and (d) is the extrusion It is a figure which shows roughly the temperature of a molding material, respectively. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows embodiment of this invention, The (a) is a figure which shows the relationship between the injection amount of the inert fluid of a supercritical state, and the viscosity of the extrusion molding material of a molten state, The (b) is the inorganic fine particle It is a figure which shows the relationship between addition and a viscosity. (A) is a front view schematically showing the entire production apparatus for a foam molded article made of a thermoplastic resin or a mixture thereof according to the second embodiment of the present invention, and (b) is an implementation of the mixing apparatus. It is a front view which shows a form typically. It is a SEM photograph of the foaming molded product manufactured in Example 1 of this invention. It is a SEM photograph of the foaming molded product manufactured in Example 2 of this invention. 2 is a SEM photograph of a foam molded product obtained in Comparative Example 1. 4 is a SEM photograph of a foam molded product obtained in Comparative Example 2. 4 is a TEM photograph of a foam molded product obtained in Comparative Example 3. 4 is a SEM photograph of a foam molded product obtained in Comparative Example 4.

Explanation of symbols

1, 1 'Production apparatus for foam molded product 3 Twin screw extruder 10 Viscometer 12 Die
15 Inert fluid inlet 33 Single screw extruder 51 Mixing container 53 Mixing blade
56 Extruded material supply device 60 Nucleating agent supply device

Claims (5)

A solid-state extruded material made of a thermoplastic resin or a mixture thereof added with a nucleating agent is supplied to the upstream side of the heating cylinder of the twin-screw extruder and melted by rotating the screw. An inert fluid is injected from an inert fluid inlet provided to inject the supercritical inert fluid into the heating cylinder, and the molten extruded material in which the inert fluid is dissolved and dispersed is heated. When continuously extruding from a die provided at the downstream end of the cylinder to obtain a foam molded product,
The inert fluid in the supercritical state is a solid formed between a position where the extruded material in the heating cylinder of the twin screw extruder is 100% solid and a position where it is 100% molten on the downstream side. Injecting into the melting region mixed in the solid state and the semi-molten state downstream of the plug to lower the melt viscosity, and suppress the temperature rise in the heating cylinder ,
A method for producing a foam-molded product, comprising adding 0.1 to 5% by mass of a spherical silicic acid having a spherical diameter of 1 μm or less as a nucleating agent. A solid-state extruded material made of a thermoplastic resin or a mixture thereof added with a nucleating agent is supplied to the upstream side of the heating cylinder of the twin-screw extruder and melted by rotating the screw. An inert fluid is injected from an inert fluid inlet provided for injecting a supercritical inert fluid into the heating cylinder, and a molten extruded material in which the inert fluid is dissolved and dispersed is heated to the heating cylinder. When extruding continuously from the die provided at the downstream end of the to obtain a foam molded product,
The inert fluid in the supercritical state is a solid formed between a position where the extruded material in the heating cylinder of the twin screw extruder is 100% solid and a position where it is 100% molten on the downstream side. Injecting into the melted region mixed in the solid state and semi-molten state downstream of the plug to lower the melt viscosity, suppress the temperature rise in the heating cylinder , the injection amount is provided near the downstream end of the heating cylinder By controlling the viscosity of the extruded material in the molten state as measured by a viscometer, it is controlled to be in the range below the saturation solubility of the inert fluid,
A method for producing a foam-molded product, comprising adding 0.1 to 5% by mass of a spherical silicic acid having a spherical diameter of 1 μm or less as a nucleating agent. A solid-state extruded material made of a thermoplastic resin or a mixture thereof added with a nucleating agent is supplied to the upstream side of the heating cylinder of the twin-screw extruder and melted by rotating the screw. An inert fluid is injected from an inert fluid inlet provided to inject the supercritical inert fluid into the heating cylinder, and a molten extruded material in which the inert fluid is dissolved and dispersed is downstream. When supplied to a screw extruder arranged in series on the side, continuously extruded from the die provided at the downstream end of the cylinder barrel of the screw extruder to obtain a foam molded product,
The inert fluid in the supercritical state is a solid formed between a position where the extruded material in the heating cylinder of the twin screw extruder is 100% solid and a position where it is 100% molten on the downstream side. Injecting into the melting region mixed in the solid state and the semi-molten state downstream of the plug to lower the melt viscosity, and suppress the temperature rise in the heating cylinder ,
A method for producing a foam-molded product, comprising adding 0.1 to 5% by mass of a spherical silicic acid having a spherical diameter of 1 μm or less as a nucleating agent. A solid-state extruded material made of a thermoplastic resin or a mixture thereof added with a nucleating agent is supplied to the upstream side of the heating cylinder of the twin-screw extruder and melted by rotating the screw. An inert fluid is injected from an inert fluid inlet provided to inject the supercritical inert fluid into the heating cylinder, and a molten extruded material in which the inert fluid is dissolved and dispersed is downstream. When supplied to a screw extruder arranged in series on the side, continuously extruded from the die provided at the downstream end of the cylinder barrel of the screw extruder to obtain a foam molded product,
The inert fluid in the supercritical state is a solid formed between a position where the extruded material in the heating cylinder of the twin screw extruder is 100% solid and a position where it is 100% molten on the downstream side. It is injected into the melted region mixed in the solid state and semi-molten state downstream of the plug to lower the melt viscosity, suppress the temperature rise in the heating cylinder, and the injection amount is close to the downstream end of the heating cylinder. The viscosity of the extruded material in a molten state measured by a provided viscometer or a viscometer provided near the downstream end of the cylinder barrel is controlled so as to be in the range below the saturation solubility of the inert fluid. ,
A method for producing a foam-molded product, comprising adding 0.1 to 5% by mass of a spherical silicic acid having a spherical diameter of 1 μm or less as a nucleating agent.   The manufacturing method according to any one of claims 1 to 4, wherein an extruded material and 0.1 to 5% by mass of a nucleating agent are continuously supplied to the mixing container and mixed. And the manufacturing method of the foaming molded article supplied to a twin screw extruder continuously from the said mixing container.

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