JP4684304B2 - Method for producing resin foam and resin foam - Google Patents

Description

  The present invention relates to a method for producing a resin foam having a high expansion ratio and an excellent surface appearance, and a resin foam obtained by the production method. The resin foam is useful, for example, as an internal insulator such as an electronic device, a cushioning material, a sound insulating material, a light shielding material, a heat insulating material, a food packaging material, a clothing material, or a building material.

  As a method for producing a thermoplastic resin foam, a chemical foaming method using a chemical foaming agent and a physical foaming method (gas foaming method) using a physical foaming agent are known. The chemical foaming method is generally a method of foam molding by mixing a raw material resin and a low molecular weight organic foaming agent that decomposes at a molding temperature to generate a gas, and heating it to a temperature higher than the decomposition temperature of the foaming agent. . This method has the advantage that the generation of gas is sharp with respect to the decomposition temperature, the decomposition temperature can be easily adjusted by adding a foaming auxiliary agent, and a foam having closed cells can be obtained. Have. However, since the chemical foaming method uses a special foaming agent, the decomposition of the foaming agent remaining in the foam causes discoloration of the foam, generation of odor, food hygiene problems, and the like. In addition, there is a problem with the molding machine contamination caused by the chemical foaming agent, and the molding failure associated therewith. In particular, in fields such as electronic component applications, there is a high demand for low contamination, and contamination with corrosive gases and impurities becomes a problem.

  In contrast, in the physical foaming method, a low boiling point organic compound such as butane, pentane or dichlorodifluoromethane is supplied to a melted resin with a molding machine, kneaded, and then released into a low pressure region. This is a molding method. The low boiling point organic compound used in this method has a characteristic of being able to obtain a high-magnification foam because it has an affinity for the resin and thus has excellent solubility and retention. Yes. However, many of the foaming agents of the physical foaming method have dangers such as flammability and toxicity, and may cause a problem of air pollution. In addition, chlorodifluoromethane and other chlorofluorocarbon gases are being abolished due to the environmental problems of ozone layer destruction.

  In order to solve such problems of the conventional method, many methods have been proposed in which an inert gas such as carbon dioxide (carbon dioxide) and nitrogen that is clean and inexpensive is used as a foaming agent. However, since the inert gas has low affinity with the resin, it has poor solubility. For this reason, since the foam has a large cell diameter, non-uniformity, and a low cell density, there are problems in appearance, mechanical strength, heat insulating properties, and expansion ratio.

  Therefore, a technology has been developed to obtain a foam having an extremely fine cell diameter and a large cell density by using a supercritical fluid as a foaming agent and impregnating it with a thermoplastic resin (see, for example, Patent Document 1). . However, even when such a supercritical fluid is used as a foaming agent, it is necessary to maintain a high pressure in order to produce a resin foam having a high expansion ratio because of its low solubility in a thermoplastic resin. .

JP-T 6-506724

  In order to maintain the high pressure in this way, it is necessary to maintain the high pressure between the die lips. For this reason, it is necessary to narrow the interval between the die lips. As a result, even if a thin plate-shaped resin foam is easily obtained, it is difficult to produce a thick plate-shaped resin foam.

  On the other hand, if the gap between the die lips is widened to produce a thick resin foam, the high pressure cannot be maintained, and the foaming agent vaporizes inside the die, which is called “in-die foaming”, and foams before discharging. The phenomenon which starts will occur, and the resin foam of high expansion ratio cannot be manufactured.

  Furthermore, in order to produce a resin foam with a high expansion ratio, it is known that innumerable “pleats” called “corrugates” occur in the width direction of the resin foam if the distance between the die lips is narrowed. Yes. Therefore, it has been very difficult to produce a high foaming ratio resin foam having an excellent surface appearance.

  Therefore, this invention is providing the manufacturing method and resin foam of the resin foam which can manufacture the resin foam which is excellent in the surface external appearance, and has a high foaming ratio easily.

  As a result of intensive investigations to achieve the above object, the present inventor can obtain a resin foam having a high expansion ratio and excellent surface appearance when a resin foam is formed using a die having a specific structure. I found out that I can do it. The present invention has been completed based on these findings.

That is, the present invention includes (I) a melting step for melting a thermoplastic resin composition by heating, (II) a gas supply step for quantitatively supplying an inert gas to the molten resin composition, and (III) an inert A resin foam comprising: a kneading step for mixing and kneading a gas and a molten resin composition; (IV) a cooling step for cooling the kneaded product; and (V) a foaming step for foaming the cooled kneaded product. In the manufacturing method, the foaming step (V) includes (Va) a cell generation step for generating a cell, and (Vb) a foam formation step for performing growth and smoothing of the surface of the generated cell. In the foaming step (V), when the cooled kneaded product is foamed, a cell generation part formed by the restriction of the resin flow path, and a foam formation for growing the generated cell and smoothing the surface And the cell generator is both in the thickness direction and the width direction. To have a continuously throttled form, foam-forming unit is used is an annular die spider-less type has the form of spread continuously in both the thickness direction and the width direction The manufacturing method of the resin foam characterized by this is provided.

In the present invention, a gap (G _A) in the cell generator, as the ratio _{(G B) / (G A} ) of the gap (G _B) in the foam forming unit is preferably from 2 to 40, the cell width in the generation unit and the (W _a), the ratio between the width (W _B) of the foam forming section _{(W B) / (W a} ) is preferably 1.5 to 10.

The present invention further relates to a die for use in manufacturing a resin foam, in which a cell generation unit formed by constricting a resin flow path, and a foam formation for growing the generated cell and smoothing the surface And the cell generation part has a form continuously squeezed in both the thickness direction and the width direction, and the foam forming part continuously spreads in both the thickness direction and the width direction. There is provided a die characterized by a spiderless type annular shape having a different shape. The present invention further provides an apparatus for producing a resin foam, the apparatus comprising the die, and the apparatus for producing a resin foam.

  According to the method for producing a resin foam of the present invention, a resin foam having an excellent surface appearance and a high expansion ratio can be easily produced.

Hereinafter, the present invention will be described in detail with reference to the drawings as necessary.
In the method for producing a resin foam of the present invention, a thermoplastic resin composition containing a thermoplastic resin and an inert gas as a foaming agent is used, and foaming using the following steps (I) to (V) The resin foam is manufactured using the apparatus. As the step (V) [foaming step (V)], (Va) a cell generation step for generating cells, (Vb) growth and surface of the generated cells It is important to have a foam forming process for smoothing.
Step (I): Melting step for melting thermoplastic resin composition by heating Step (II): Gas supplying step for quantitatively supplying an inert gas to the molten resin composition Step (III): Inactive gas and melting Kneading step for mixing and kneading the resin composition Step (IV): Cooling step for cooling the kneaded product Step (V): Foaming step for foaming the cooled kneaded product

[Thermoplastic resin]
As the thermoplastic resin, any thermoplastic resin can be used and is not particularly limited. For example, low-density polyethylene, linear polyethylene (linear polyethylene), medium-density polyethylene, and high-density polyethylene. , Copolymers of ethylene or propylene and other α-olefins, olefin resins such as polypropylene; styrene resins such as polystyrene and acrylonitrile-butadiene-styrene copolymers (ABS resins); acrylics such as polymethyl methacrylate Resins; Halogen-containing polymers such as polyvinyl chloride and polyvinyl fluoride; Alkenyl aromatic resins; Polyamides such as polyamide 6, polyamide 66, and polyamide 12; Polyesters such as polyethylene terephthalate and polybutylene terephthalate; Carbonate-based resins such as polyol A-based polycarbonates; polyacetals; polyphenylene sulfides; ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, ethylene-methacrylic acid copolymers, Ethylene copolymers such as ethylene-methacrylic acid ester copolymer, ethylene-vinyl alcohol copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, polybutene, polyisobutylene, chlorinated polyethylene, etc. Olefin-based elastomers; Styrene-based elastomers such as styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-isoprene-butadiene-styrene copolymers, and hydrogenated polymers thereof; thermoplasticity Examples thereof include polyester-based elastomers; thermoplastic polyurethane-based elastomers; and various thermoplastic elastomers such as thermoplastic acrylic elastomers. These thermoplastic resins can be used alone or in combination of two or more.

[Other ingredients]
Various additives may be contained in the thermoplastic resin composition as necessary. Examples of such additives include, but are not limited to, vulcanizing agents, pigments, dyes, surface treatment agents, anti-aging agents, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, surfactants, plasticizers. Etc. The amount of the additive used can be appropriately selected within a range that does not impair the formation of the cells.

[Foaming agent (inert gas)]
As the foaming agent (inert gas), any known or commonly used inert gas can be used without particular limitation. However, from the viewpoint of environmental protection, a foam having a small cell diameter and a high cell density can be obtained. From the point of view, an inert gas (including a supercritical fluid) such as carbon dioxide, nitrogen, and a mixed gas thereof is preferable.

[Melting step (I)]
In the melting step (I), the thermoplastic resin composition is melted by heating, whereby a composition (molten resin composition) containing a molten thermoplastic resin is prepared. An apparatus using such a melting step (I) is not particularly limited as long as it has the functions (a resin supply function for supplying a thermoplastic resin composition, a resin melting function for melting a thermoplastic resin, etc.). However, it is possible to use various types of extruders such as a twin-screw extruder, a multi-screw extruder having three or more axes, a single-type single-screw extruder, a tandem extruder, and three or more connected single-screw extruders. In particular, a tandem extruder or three or more single-screw extruders connected to each other can be preferably used.

  Therefore, the melting step (I) may be a melting step in which the thermoplastic resin composition is supplied into an extruder and the thermoplastic resin in the composition is melted by heating.

  In the melting step (I), the heating temperature at which the thermoplastic resin is melted is not particularly limited, and can be appropriately selected according to the melting temperature or glass transition temperature of the thermoplastic resin.

[Gas supply process (II)]
In the gas supply step (II), an inert gas is quantitatively supplied to the molten resin composition obtained in the melting step (I). An apparatus using such a gas supply step (II) is not particularly limited as long as it has the above function (a gas supply function for supplying an inert gas). For example, a plunger pump, a diaphragm pump, a booster A pump (gas supply pump) such as a pump is used, and it is desirable to control the pressure and flow rate in any pump.

  When an extruder is used in the melting step (I), the gas supply step (II) is a gas supply step for quantitatively supplying an inert gas to the molten resin composition in the extruder.

  In the gas supply step (II), the supply amount of the inert gas is not particularly limited, and may be appropriately selected according to the usage amount of the thermoplastic resin composition, the target expansion ratio, the bubble diameter of the foam, and the like. it can.

[Kneading process (III)]
In the kneading step (III), the inert gas supplied in the gas supply step (II) and the molten resin composition obtained in the melting step (I) are mixed and kneaded to prepare a kneaded product. Has been. An apparatus using such a kneading step (III) is not particularly limited as long as it has the above function (kneading function for mixing and kneading an inert gas and a molten resin composition). Similarly to (I), for example, various types such as a twin-screw extruder, a multi-screw extruder having three or more axes, a single-type single-screw extruder, a tandem extruder, and three or more connected single-screw extruders. An extruder can be used, and among them, a tandem extruder or a single-screw extruder in which three or more are connected can be preferably used.

  Therefore, the kneading step (III) may be a kneading step of mixing and kneading the inert gas and the molten resin composition with an extruder.

  In the kneading step (III), conditions such as temperature during kneading are not particularly limited.

[Cooling step (IV)]
In the cooling step (IV), the kneaded product obtained in the kneading step (III) is cooled to prepare a cooled kneaded product. The apparatus using such a cooling step (IV) is not particularly limited as long as it has the function (cooling function of the kneaded product), but includes a twin-screw extruder equipped with a cooling mechanism and a cooling mechanism. Various types such as a multi-screw extruder having three or more axes, a single type single-screw extruder having a cooling mechanism, a tandem extruder having a cooling mechanism, a single-screw extruder having three or more cooling mechanisms connected, etc. In particular, a tandem extruder provided with a cooling mechanism, and a single-screw extruder provided with three or more cooling mechanisms and connected together can be preferably used.

  Therefore, the cooling step (IV) may be a step of cooling the kneaded material with an extruder equipped with a cooling mechanism.

  In the cooling step (IV), the cooling temperature for cooling the kneaded product is not particularly limited, and can be appropriately selected according to the type of inert gas, the type of thermoplastic resin composition, and the like.

  Therefore, the melting step (I) to the cooling step (IV) are performed in an extruder (a twin screw extruder, a multi-screw extruder having three or more axes, a single type single screw extrusion) having a cooling mechanism and a gas supply pump. It is possible to carry out continuously by using a machine, a tandem extruder, three or more single-screw extruders connected; in particular, a tandem extruder or three or more single-screw extruders connected.

  The pressure in the extruder can be appropriately selected in consideration of the type of gas, operability, etc. For example, when the gas is carbon dioxide, it is about 5 to 100 MPa, preferably 6 to 60 MPa, more preferably. It is about 7.4-30 MPa.

  Further, the temperature in the extruder [the temperature in the extruder in the melting step (I) to the kneading step (III); that is, the temperature of the molten resin composition] varies depending on the type of gas used, the glass transition temperature of the thermoplastic resin, and the like. Although it can be selected in a wide range, it is preferably about 10 to 300 ° C. in consideration of operability and the like.

[Foaming process (V)]
In the foaming step (V), the cooled kneaded product is foamed to produce a resin foam (thermoplastic resin foam). As described above, the foaming step (V) includes (Va) a cell generation step for generating cells, and (Vb) a foam formation step for performing growth and smoothing the surface of the generated cells. This is very important.

  In the foaming step (V), a die can be suitably used when foaming the cooled kneaded product. Therefore, the foaming step (V) may be a step in which the cooled kneaded material is discharged from a die and foamed. Thus, a resin foam (thermoplastic resin foam) is produced by foaming in the foaming step (V).

  An extruder equipped with a cooling mechanism in the cooling step (IV) [particularly an extruder equipped with a cooling mechanism and equipped with a gas supply pump in the melting step (I) to the cooling step (IV)] is used. In this case, the foaming step (V) can be a foaming step in which the cooled kneaded product is discharged from a die attached to the tip of the extruder and foamed. That is, the foaming step (V) can be performed with a die attached to the tip of the extruder.

  The die may be a flat die (flat die) such as a T die, a hanger coat die, or a fish tail die, or a die having various shapes such as an annular die (cylindrical die), and an annular die is preferable. is there. Examples of the annular die include a spiderless type annular die, a spider type annular die, and a spiral type annular die. As the die, a die having a small pressure loss is preferable. From this viewpoint, a spiderless type annular die is preferable among the annular dies.

  As the die, since the foaming step (V) has a cell generation step (Va) and a foam formation step (Vb), the cell generation portion formed by the restriction of the resin flow path, and the generated cell And a foam forming part for smoothing the surface. As described above, when the die has the cell generation part and the foam formation part, the cell generation step (Va) generates the cell by the cell generation part formed by the restriction of the resin flow path in the die. The foam forming step (Vb) is a step of performing growth of the generated cells and smoothing of the surface in a foam forming portion that performs growth of the generated cells and smoothing of the surface.

  Thus, when the cell generation part formed by the restriction | limiting of the resin flow path is formed in die | dye, a high pressure state can be effectively maintained or hold | maintained to this cell generation part, and also the said cell generation | occurrence | production After passing through the section, the pressure maintained or maintained at a high pressure until then is released at once, and a cell is generated and grows (ie, foams).

  Note that cell growth (that is, foaming) is basically considered to proceed in a three-dimensional direction (that is, three directions of thickness direction, width direction, and flow direction). When it is done freely as in the case of using a die (for example, when the end of the cell generation part is an open end), the foam is formed without being sufficiently spread in the width direction. It is thought that “wrinkles” called “corrugates” occur when the (foamed sheets) interfere with each other.

  However, in the present invention, since the foam formation portion that smoothes the surface along with the growth of the cell by restraining the cell growth (that is, foaming) to some extent is provided, a smooth surface is generated without generating corrugation. It is possible to form a resin foam having. Therefore, a resin foam having a high expansion ratio and an excellent surface appearance can be easily produced.

Specifically, examples of the die having such a configuration include a die having the configuration shown in FIGS. FIG. 1 is a schematic view showing an example of a die used in the method for producing a resin foam of the present invention. 1A is a perspective view, FIG. 1B is a top view, and FIG. 1C is a side view. In FIG. 1, 11 is a die, 21 is a cell generating part, and 31 is a foam forming part. G _A1 is the gap of the cell generation part 21, G _B1 is the gap of the foam formation part 31, W _A1 is the width of the cell generation part 21, W _B1 is the width of the foam formation part 31, T is the thickness direction, W Is a width direction, L is a flow direction, and X is a resin flow path. The die 11 in FIG. 1 is a flat die (flat die), a cell generation unit 21 in a form in which the resin flow path X is narrowed, and a foam formation unit 31 that performs growth and smoothing of the surface of the generated cell. have. The foam forming unit 31 has a configuration in which the width is continuously increased from the cell generation unit 21 side, and on the open end (end opposite to the cell generation unit 21 side) side, It has a certain width. Further, the resin flows in the direction of the flow direction L.

Moreover, FIG. 2 is schematic which shows the other example of the die | dye used in the manufacturing method of the resin foam of this invention. In FIG. 2, 12 is a die, 22 is a cell generating part, and 32 is a foam forming part. G _A2 is the gap of the cell generation unit 22, G _B2 is the gap of the foam formation unit 32, D _A2 is the diameter of the cell generation unit 22 (diameter on the outer peripheral surface side), and D _B2 is the diameter of the foam formation unit 32. (Diameter on the outer peripheral surface side), and L and X are the flow direction and the resin flow path, respectively, as described above. The die 12 in FIG. 2 is an annular die, and includes a cell generation unit 22 in a form in which the resin flow path X is narrowed, and a foam formation unit 32 that performs growth and smoothing of the surface of the generated cell. ing. The foam formation part 32 has a configuration in which the width is continuously increased from the cell generation part 22 side, and the end thereof is the largest, and the open end part (relative to the cell generation part 21 side). The opposite end). Further, in the die 12 that is an annular die, the thickness direction T is a direction parallel to the direction from the outer peripheral surface to the inner peripheral surface, while the width direction W is parallel to the circumferential direction at each portion. Direction. Furthermore, the resin flows in the direction of the flow direction L.

2 is an annular die, the width W _A2 of the cell generation unit 22 can be the length of the circumference on the outer peripheral surface side of the cell generation unit 22. Further, the width _WB2 of the foam forming part 32 can be the length of the circumference on the outer peripheral surface side of the foam forming part 32. That is, W _A2 = π × D _A2 and W _B2 = π × D _B2 .

  In such a die (11, 12; may be collectively referred to as “1”), the cell generation unit (21, 22; may be collectively referred to as “2”) is provided in both the thickness direction T and the width direction W. (In other words, the lengths in both the thickness direction T and the width direction W are both continuously reduced). A high pressure state can be effectively maintained or maintained. Note that the die 1 may have a form narrowed down to only one of the thickness direction T and the width direction W (particularly, only the thickness direction T). Moreover, although it is preferable to have the form squeezed continuously, you may have the form squeezed discontinuously.

  Further, after the cell generation unit 2, a foam formation unit (31, 32; may be collectively referred to as “3”) is provided. Specifically, the foam forming unit 3 is provided after the cell generating unit 2 and continuously spreads in both the thickness direction T and the width direction W (that is, in both the thickness direction T and the width direction W). Both lengths are continuously increasing). Therefore, after the cooled kneaded material (foaming agent-containing resin composition) passes through the cell generation unit 2, the pressure that is maintained or maintained at a high pressure in the foam formation unit 3 is the thickness direction T and the width direction. W and the flow direction L are released in a three-dimensional direction (especially in the two-dimensional direction of the thickness direction T and the width direction W), so that the cell is in a three-dimensional direction (especially 2 It can grow (foam) in a dimensional direction. Thus, since the high pressure is suddenly released, it is possible to produce a resin foam having a high expansion ratio. In addition, since the foam formation part 3 is in a state in which the growth of the cells is restricted to some extent, the cells growing in the width direction W cannot be sufficiently grown in the width direction W and cannot be spread. Even if it is, the cell grows while smoothing the surface in the foam forming part 3. Therefore, a resin foam having a smooth surface can be formed without generating corrugation.

  In addition, the foam formation part 3 may have the form expanded only in one direction (especially only the thickness direction T) of the thickness direction T and the width direction W. Moreover, although it is especially preferable to have the form which spread continuously, you may have the form which spread discontinuously. It is important that the foam forming portion 3 has a flat surface or a smooth curved inner surface.

  The mechanical dimension of the foam forming part can be appropriately selected depending on the mechanical dimension of the cell generating part, the foaming ratio of the resin foam, the product dimension of the target resin foam, and the like.

For example, the gap (G _A1 , G _A2 ; sometimes collectively referred to as “G _A ”) in the cell generator 2 and the gap (G _B1 , G _B2 ; collectively referred to as “G _B ” in the foam forming part 3) (G _B ) / (G _A ) is preferably 2 to 40, more preferably 5 to 20. If (G _B) / (G _A) is less than 2, the restraint in the thickness direction (restraint when cells in the thickness direction is grown) is intensified, after leaving the foam forming section 3, the corrugated occurs May end up. On the other hand, if _{(G B) / (G A} ) is greater than 40 can not be performed sufficiently in the thickness direction restraint, in the foam forming section within 3, there is a case where the corrugated occurs.

  Note that the minimum gap of the cell generation unit can be adopted as the gap in the cell generation unit. Further, as the gap in the foam forming part, the maximum gap of the foam forming part or the gap at the open end of the foam forming part (the end opposite to the cell generation part side) may be adopted. it can.

In addition, the width (W _A1 , W _A2 (= π × D _A2 ); sometimes collectively referred to as “W _A ”) in the cell generation unit 2 and the width (W _B1 , W _B2 (= The ratio (W _B ) / (W _A ) to (π × D _B2 ); sometimes collectively referred to as “W _B ”) is preferably 1.5 to 10, more preferably 2 to 5. is there. When (W _B ) / (W _A ) is smaller than 1.5, the restraint in the width direction (restraint when the cell in the width direction grows) becomes strong, and after exiting the foam forming portion 3, the corrugate May occur. On the other hand, when (W _B ) / (W _A ) is greater than 10, the width direction cannot be sufficiently restrained, and corrugation may occur in the foam forming part 3. Dimensional variation in the width direction is caused, dimensional accuracy is lowered, and it becomes difficult to obtain a resin foam having a stable size.

  As the width of the cell generation unit, when the die is a flat die, the minimum width of the cell generation unit can be adopted. When the die is an annular die, the circumferential length on the outer peripheral surface side Can be adopted. In addition, as the width in the foam forming part, when the die is a flat die, the maximum width of the foam forming part, or the open end of the foam forming part (the end opposite to the cell generating part side) ) Can be adopted, and when the die is an annular die, the maximum circumferential length on the outer peripheral surface side of the foam forming part, or the open end part (on the cell generating part side) of the foam forming part On the other hand, the circumferential length on the outer peripheral surface side at the opposite end) can be adopted.

  In the present invention, as shown in FIG. 1, the foam forming portion has a configuration in which the width is constant on the open end portion side (the end portion side opposite to the cell generation portion side). It may have, and as shown in FIG. 2, you may have the structure which the width | variety expanded continuously from the cell production | generation part side to the open end part. In addition, nothing is provided between the cell generation part and the foam formation part, and the cell generation part and the foam formation part are directly connected, and the width is the smallest. It is preferable to have a configuration in which the foam forming portion is formed by continuously expanding the width from the cell generating portion. However, a cell growth part in which the cell grows once may be formed between the cell generation part and the foam formation part.

  As described above, the apparatus for producing a resin foam has a cell generation part formed by constricting the resin flow path, and a foam formation part for growing the generated cell and smoothing the surface. A resin foam production apparatus having a die can be used. Of course, the manufacturing apparatus of the resin foam only needs to include a foaming step (V) having a cell generation step (Va) and a foam formation step (Vb) by using the die. An apparatus for producing a resin foam comprising the melting step (I), the gas supply step (II), the kneading step (III) and the cooling step (IV) together with the foaming step (V) is suitable.

  Since the resin foam of the present invention is obtained by the above production method, it has a high expansion ratio, has a fine cell diameter and a large cell density, and has a smooth surface and an excellent surface appearance. Moreover, the resin foam which is excellent in mechanical strength, heat insulation, a softness | flexibility, etc. can also be obtained by selecting suitably as resin. Therefore, the resin foam of the present invention is useful, for example, for internal insulators such as electronic devices, cushioning materials, sound insulating materials, light shielding materials, heat insulating materials, food packaging materials, clothing materials, and building materials.

  The resin foam can be appropriately processed.

EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited at all by these Examples. The expansion ratio was calculated by the following formula.
Foaming ratio = {density before foaming (density of pellets before foaming) (g / cm ³ )} ÷ {density after foaming (density of foam) (g / cm ³ )}

Example 1
Polypropylene having a density of 0.9 g / cm ³ and a melt flow rate (230 ° C.) of 0.4 g / 10 min: 50 parts by weight, ethylene-propylene copolymer-based elastomer having a JIS-A hardness of 69: 50 parts by weight And 10 parts by weight of magnesium hydroxide having an average particle diameter of 1 μm were kneaded using a twin-screw kneading extruder and then extruded to be pelletized.

  When the obtained pellets were extruded (foamed) using a tandem extruder (φ65-φ75) equipped with an annular die (cylindrical die) shown in FIG. 2, a resin as shown in FIG. A foam was obtained. This resin foam was good with no corrugation observed when the appearance (particularly the surface appearance) was observed visually. Moreover, the foaming ratio of the resin foam was 23 times, and had a high foaming ratio. In addition, FIG. 3 is a figure which shows the photograph regarding the surface shape of the resin foam obtained in Example 1. FIG.

  Carbon dioxide was used as a foaming agent, and it was press-fitted into the first stage extruder. The operating conditions are a temperature in the extruder of 200 to 240 ° C., a pressure in the extruder of 15 to 20 MPa, a resin temperature in the die of 174 ° C., a die pressure of 10 MPa, and a throughput of 50 kg / hour.

In addition, as the shape of the annular die used, the gap (G _A ) in the cell generation part is 0.3 mm, the gap (G _B ) in the foam formation part is 4.0 mm, and the width (W _A in the cell generation part) = Π × D _A2 ) is 62 mm, and the width (W _B = π × D _B2 ) in the foam forming part is 188 mm.

(Example 2)
Polypropylene having a density of 0.9 g / cm ³ and a melt flow rate (230 ° C.) of 0.5 g / 10 min: 50 parts by weight, ethylene-propylene copolymer-based elastomer having a JIS-A hardness of 69: 50 parts by weight And 50 parts by weight of magnesium hydroxide having an average particle diameter of 1 μm were kneaded using a twin-screw kneading extruder and then extruded to be pelletized.

  The obtained pellets were extruded (foamed) using a tandem extruder (φ65-φ75) equipped with an annular die (cylindrical die) shown in FIG. 2 to obtain a resin foam. This resin foam was good with no corrugation observed when the appearance (particularly the surface appearance) was observed visually. Moreover, the foaming ratio of the resin foam was 17 times, and had a high foaming ratio.

  Carbon dioxide was used as a foaming agent, and it was press-fitted into the first stage extruder. The operating conditions are a temperature in the extruder of 200 to 240 ° C., a pressure in the extruder of 15 to 20 MPa, a resin temperature in the die of 174 ° C., a die pressure of 10 MPa, and a throughput of 50 kg / hour.

In addition, as the shape of the annular die used, the gap (G _A ) in the cell generation part is 0.3 mm, the gap (G _B ) in the foam formation part is 2.5 mm, and the width (W _A in the cell generation part) = Π × D _A2 ) is 62 mm, and the width (W _B = π × D _B2 ) in the foam forming part is 188 mm.

(Comparative Example 1)
Instead of the tandem extruder provided with the annular die shown in FIG. 2, a tandem extruder provided with a conventional annular die as shown in FIG. 4 was used, in the same manner as in Example 1, When the resin foam was formed, as shown in FIG. 5, a resin foam in which a large number of corrugates was obtained was obtained. Therefore, the surface appearance of the resin foam was poor. Further, the expansion ratio of the resin foam was 11 times. In addition, FIG. 5 is a figure which shows the photograph regarding the surface shape of the resin foam obtained by the comparative example 1. FIG.

  FIG. 4 is a schematic view partially showing an example of a conventional annular die. The conventional annular die shown in FIG. 4 does not have a foam forming part. Specifically, the conventional die 4 shown in FIG. 4 has a configuration in which the cell generator 41 is opened after the cell generator 41 (the end of the cell generator 41 is an open end). . In the conventional annular die shown in FIG. 4, the gap in the cell generation unit 41 is 0.3 mm, and the width (circumference length on the outer peripheral surface side) in the cell generation unit is 188 mm (diameter 60 mm on the outer peripheral surface side). ).

(Comparative Example 2)
A resin foam was formed in the same manner as in Comparative Example 1 except that an annular die having a gap of 0.5 mm in the cell generator 41 in FIG. 4 was used, and foamed inside the die. No foaming occurred after the cell generation unit 41, and the surface appearance of the resin foam was poor. Furthermore, the expansion ratio of the resin foam was as small as 1.5 times.

  In addition, it shows in Table 1 about the shape of the die | dye used in Examples 1-2 and Comparative Examples 1-2, and the resin foam obtained in Examples 1-2 and Comparative Examples 1-2.

  From Table 1, in the resin foam manufacturing method according to the examples, as a die, a cell generation part formed by constricting the resin flow path, and a foam formation part that performs growth and smoothing of the surface of the generated cell Since the die having the same is used, it is possible to obtain a resin foam having a smooth surface with a high foaming ratio and no corrugation, which is safe and less burdened on the environment.

It is the schematic which shows an example of the die | dye used in the manufacturing method of the resin foam of this invention. It is the schematic which shows the other example of the die | dye used in the manufacturing method of the resin foam of this invention. It is a figure which shows the photograph regarding the surface shape of the resin foam obtained in Example 1. FIG. It is the schematic which shows an example of the conventional annular die partially. It is a figure which shows the photograph regarding the surface shape of the resin foam obtained by the comparative example 1. FIG.

Explanation of symbols

11, 12 dies
21, 22 Cell generator
31, 32 Foam formation part
G _A1 , G _A2 cell generator (21, 22) gap
G _B1 , G _B2 foam formation part (31, 32) gap
W _A1 cell generator 21 width
W _B1 Foam forming part 31 width
D Diameter of outer peripheral surface of _A2 cell generator 22
D Diameter of outer peripheral surface side of _B2 foam forming part 32 T thickness direction W width direction L flow direction X resin flow path

Claims (5)

(I) a melting step for melting the thermoplastic resin composition by heating, (II) a gas supply step for quantitatively supplying an inert gas to the molten resin composition, (III) an inert gas, and a molten resin composition A method of producing a resin foam comprising a kneading step of mixing and kneading a product, (IV) a cooling step of cooling the kneaded product, and (V) a foaming step of foaming the cooled kneaded product, The foaming step (V) includes (Va) a cell generation step for generating cells, and (Vb) a foam formation step for performing growth and smoothing of the generated cells. V), when the cooled kneaded product is foamed, it has a cell generation part formed by constricting the resin flow path, and a foam formation part for growing the generated cell and smoothing the surface. The cell generator was continuously squeezed in both the thickness and width directions. A resin foam characterized in that a spiderless type annular die having a form and having a form in which a foam forming part continuously spreads in both the thickness direction and the width direction is used. Body manufacturing method. A gap (G _A) in the cell generator, the ratio between the gap (G _B) in the foam forming section _{(G B) / (G A} ) is the production of resin foam of claim 1, wherein 2 to 40 Method. The resin according to claim 1 or 2, wherein a ratio (W _B ) / (W _A ) of a width (W _A ) in the cell generation part and a width (W _B ) in the foam forming part is 1.5 to 10. A method for producing a foam. A die for use in producing a resin foam by the method for producing a resin foam according to any one of claims 1 to 3, comprising a cell generation part formed by a restriction of a resin flow path, and a generation A foam formation part that performs cell growth and surface smoothing, and the cell generation part has a form that is continuously squeezed in both the thickness direction and the width direction. A die having a spiderless type annular shape in which a portion has a form continuously expanding in both the thickness direction and the width direction. An apparatus for producing a resin foam, comprising the die according to claim 4.

Images