The present invention provides a method for manufacturing a molded foam product which can reduce blisters on the surface and foaming failure in injection molding of a molten resin containing a fluid in a supercritical state even in the case of manufacturing a molded product designed to have a small thickness, thereby giving a molded foam product having excellent heat insulation. The method of the present invention is a method for manufacturing a molded foam product through injection molding of a molten resin containing a fluid in a supercritical state, the method including a step of injecting the molten resin into a cavity formed in a mold and moving a portion of the mold to increase the volume of the cavity before the molten resin injected into the cavity completely solidifies, the cavity being communicated only with a single resin injection port, the mold having a dimple which has a substantially hemispherical shape and is situated to face the resin injection port, the mold having a minimum gap size of 0.2 mm or greater in the cavity during injection of the molten resin.

There is provided a method which includes: plasticizing and melting a thermoplastic resin to provide a molten resin in a plasticization zone of a plasticizing cylinder; allowing the molten resin to be in a starved state in a starvation zone of the plasticizing cylinder; introducing a pressurized fluid containing a physical foaming agent having a fixed pressure into the starvation zone to retain the starvation zone at the fixed pressure; bringing the molten resin in the starved state in contact with the pressurized fluid containing the physical foaming agent having the fixed pressure in the starvation zone in a state in which the starvation zone is retained at the fixed pressure; and molding the molten resin having been brought in contact with the pressurized fluid containing the physical foaming agent into the foam-molded product.

The interior of a heating cylinder (2) is divided into a first stage (5) and a second stage (7) due to the shape of a screw (3). A first compression zone in which a resin is compressed is formed in the first stage (5). A starvation zone (7a) in which an inert gas is injected and a second compression zone in which the resin is compressed are formed in the second stage (7). A barrier flight (13) that is obtained by combining a main flight (14) and a sub-flight (15) having a greater lead angle than the main flight is provided to a section of the screw (3), said section corresponding to the first compression zone. A multiple flight is provided to another section of the screw (3), said section corresponding to the second stage (7).

A method for producing a foamed molded product includes: using a molding apparatus including a plasticizing cylinder having a high pressure kneading zone and a pressure reduction zone; and a screw; controlling a pressure of the pressure reduction zone to be a first pressure in a state that communication between the high pressure kneading zone and the pressure reduction zone is shut off, the first pressure being not less than an atmospheric pressure and not more than a maximum pressure of the high pressure kneading zone which is reached in a case that a molten resin is brought in contact and kneaded with a physical foaming agent; controlling back pressure of the screw to be a second pressure which is not less than the first pressure; and measuring a predetermined amount of the molten resin from which the gasified physical foaming agent has been separated.

A molded foam manufacturing apparatus 1 includes a cylinder 2 in which a plasticization zone 21 where a thermoplastic resin is plasticized and melted, a starvation zone 22 where the molten resin is put into a starvation state and an injected physical foaming agent is dissolved in the molten resin, and a feeding zone 23 where the molten resin in which the physical foaming agent is dissolved is compressed and metered are provided in this order from an upstream side, and a screw 3 that is installed inside the cylinder 2 so as to be freely rotatable around an axis of the cylinder and has flights formed in a spiral shape on an outer circumference of a shaft 31, wherein a lead angle R of the flights of the screw 3 corresponding to the feeding zone 23 is set smaller than a lead angle of the flight corresponding to the starvation zone 22, and the number of pieces of the flight of the screw 3 corresponding to the feeding zone 23 is set smaller than the number of pieces of the flight corresponding to the starvation zone 22. In this way, it is possible to prevent a decrease in the flow rate of the molten resin transported in the starvation zone and the feeding sone and manufacture high-quality molded foams with high production efficiency.

An injection device includes a heating cylinder having a gas injection port, a screw, a gas supply device and a control unit. The interior of the heating cylinder is divided into a plasticization zone on an upstream side, a starvation zone on a downstream side of the plasticization zone, and a compression zone on the downstream side of the starvation zone. The gas injection port is provided with an injection valve, and gas is supplied into the heating cylinder in the starvation zone. The heating cylinder includes a pressure sensor. The control unit is configured to control the injection valve based on a resin pressure detected by the pressure sensor.

A process for injection molded microcellular foaming various flexible foam compositions from biodegradable and industrially compostable bio-derived thermoplastic resins for use in, for example, footwear components, seating components, protective gear components, and watersport accessories wherein a process of manufacturing includes the steps of: producing a suitable thermoplastic biopolymer or biopolymer blend; injection molding the thermoplastic biopolymer or biopolymer blend into a suitable mold shape with inert nitrogen gas; controlling the polymer melt, pressure, temperature, and time such that a desirable flexible foam is formed; and utilizing gas counterpressure in the injection molding process to ensure the optimal foam structure with the least amount of cosmetic defects and little to no plastic skin on the outside of the foamed structure.

A process for injection molded microcellular foaming various flexible foam compositions from biodegradable and industrially compostable bio-derived thermoplastic resins for use in, for example, footwear components, seating components, protective gear components, and watersport accessories wherein a process of manufacturing includes the steps of: producing a suitable thermoplastic biopolymer or biopolymer blend; injection molding the thermoplastic biopolymer or biopolymer blend into a suitable mold shape with inert nitrogen gas; controlling the polymer melt, pressure, temperature, and time such that a desirable flexible foam is formed; and utilizing gas counterpressure in the injection molding process to ensure the optimal foam structure with the least amount of cosmetic defects and little to no plastic skin on the outside of the foamed structure.

Molded polymer foam articles are described as having a novel a foam structure. The polymer foam articles include a continuous polymer matrix defining a plurality of pneumatoceles therein which is present throughout the entirety of the article, including in the surface region extending 500 microns beneath the surface of the article. The surface region is further characterized as having compressed pneumatoceles. The novel foam structure is achieved even when molding polymer foam articles comprising a thickness of more than 2 cm, a volume of more than 1000 cm.sup.3; or both a volume of more than 1000 cm.sup.3 and a thickness of more than 2 cm. Methods of making the molded polymer foam articles are also described.

System and method for physical foaming injection suitable for manufacturing low-density member are provided. The method for physical foaming injection includes i) heating an inside of a barrel that is elongated in one direction; ii) providing resin beads in the barrel; iii) manufacturing a melt by rotating and heating the resin beads with a first screw provided in the barrel; iv) directly providing a gas for physical foaming in the barrel along a transferring direction of the resin beads by spacing the resin beads; v) providing a gas for physical foaming in the barrel and forming a supercritical fluid by agitating a second screw placed in front of a first screw, the first screw to be spaced apart the second screw along a transferring direction; vi) providing a mixture in which the supercritical fluid is incorporated into the melt while the melt passes through the supercritical fluid; vii) pressurizing a cavity formed by the combination of a upper mold part and a lower mold part by injecting gas into the cavity; viii) foaming the mixture in the cavity while injecting the mixture into the cavity; ix) reducing pressure of the cavity in multiple stages after the injection of the mixture, and x) separating the upper mold part and the lower mold part from each other to remove the foamed member with a low density of 0.1 g/cc to 0.5 g/cc.