JP4620374B2 - Method for producing resin foam molded body and resin foam molded body - Google Patents

Description

  The present invention relates to a method for producing a resin foam molded article, and more particularly to a method for producing a resin foam molded article useful as a functional material, a structural material, and the like, and a resin foam molded article obtained by the production method. .

Conventionally, foamed moldings made of thermoplastic resins typified by polyolefin resins and polystyrene resins have been widely used in the fields of food containers and building materials due to their excellent heat insulating properties, buffer properties, sealing properties, etc. Has been.
As a typical method for producing a thermoplastic resin foam, there are a chemical foaming method and a physical foaming method. The chemical foaming method is a method in which a low molecular weight chemical foaming agent is mixed and foamed by heating to a temperature higher than the decomposition temperature of the foaming agent. However, the chemical foaming agent is expensive, and due to the decomposition residue of the foaming agent, problems such as discoloration of the obtained foam and food hygiene arise. In addition, since the chemical foaming agent itself has a particle size distribution, there is a problem that when the resin is melted and extruded, the thickness and density of the resulting resin molded product become non-uniform.

On the other hand, the physical foaming method is a method in which a low-boiling organic compound such as butane is supplied and kneaded, and then subjected to foam molding by extrusion into a low pressure region. This method has a feature that various foams from a low magnification to a high magnification can be easily produced by adjusting the amount of the foaming agent added to the resin. However, since a foaming agent such as butane has dangers such as flammability and toxicity, there is a problem that it must be cured until the concentration of the foaming agent remaining in the foamed molding body is lowered.
In order to solve such problems of the conventional physical foaming method, a method using an inert gas such as carbon dioxide or nitrogen has been proposed. Since the inert gas is harmless and has no concern about environmental load, it has an economic effect such as no need for a curing period after the molded body is manufactured. However, it is difficult to stably add an inert gas into the molding machine, and it is difficult to produce a high-quality foam molded article.

In addition, in order to expand the performance range of the foam material, a microphase separation structure obtained by compatibilizing two or more incompatible polymers with a supercritical fluid (for example, see Patent Document 1), syndiotactic polypropylene A foam manufactured from a blend of a thermoplastic resin and a thermoplastic resin (see, for example, Patent Document 2), a continuous manufacturing method in which extrusion is performed by controlling temperature and blowing agent concentration in order to adjust the small bubble diameter and bubble diameter distribution ( For example, see Patent Document 3).
The methods of Patent Documents 1 to 3 are methods using a supercritical fluid in the kneading process by an extruder or an injection molding machine. In these methods, since the contact time between the supercritical fluid and the polymer in the mechanical kneading field is short, it is difficult to control the cell structure and the foam cell diameter of the foam molded article. In addition, even if the droplets can be subdivided once, re-aggregation occurs in the molding process, and the subdivided droplet diameter may return to the original value. Therefore, there is a problem that the foamed cell diameter cannot be controlled.

Japanese Patent Laid-Open No. 10-330493 JP-T-2002-523587 Special Table 2002-542208 gazette

  Under such circumstances, an object of the present invention is to provide a method for advantageously producing a resin foam molded article that is easy to control the structure of a foam cell and that is useful as a functional material, a structural material, or the like.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention manufactured in advance a molded body composed of two types of resins that have different solubility and diffusion coefficient of carbon dioxide and are incompatible with each other. It has been found that the above object can be achieved by impregnation with carbon dioxide at low temperature and foaming.
That is, the present invention
(1) Resin (A) and Resin (B) having different solubility and diffusion coefficient of carbon dioxide and incompatible with each other (however, solubility and diffusion coefficient of carbon dioxide are resin (A) <resin (B)) The resin (A) and the resin (B) have a mass ratio of (A) / (B) of 50/50 to 95/5 , and the resin (A) becomes a matrix phase. Obtained by impregnating carbon dioxide at a temperature equal to or lower than the melting point, followed by foaming, and (2) a method for producing a resin foam molded article according to (1) above. A resin foam molded article is provided.

According to the production method of the present invention, a molded body made of a resin having different solubility and diffusion coefficient of carbon dioxide is produced in advance, and then impregnated with carbon dioxide at a temperature equal to or lower than the melting point of the resin and foamed. Therefore, the cell structure of the matrix (sea) phase and island phase of the foamed molded product, the expansion ratio, etc. can be easily controlled. Therefore, it is possible to produce a resin foam molded article having a structure in which resin particles are encapsulated in pores formed by foaming, or a resin foam molded article having a structure having a uniform particle diameter.
Further, since the impregnation conditions (temperature of carbon dioxide, pressure, impregnation time) can be set in a wide range and can be appropriately controlled within the ranges, resin foam molded articles having various cell structures can be produced. In addition, the obtained resin foam is used in the medical field such as a drug delivery system (DDS) for the purpose of optimizing drug administration, and in the field of regenerative medical engineering such as a scaffold for replacing hard tissue (substrate serving as a cell scaffold). It can be effectively used in the field of materials requiring high strength porous materials, optical properties, heat insulation (low thermal conductivity), and low dielectric properties.

The method for producing a resin foam molded article of the present invention comprises a resin (A) and a resin (B) that are different in solubility and diffusion coefficient of carbon dioxide and incompatible with each other, and have a mass ratio of (A) / (B). It is a great feature that a resin molded body having a 1 to 99/99 to 1 is impregnated with carbon dioxide at a temperature not higher than the melting points of the resin (A) and the resin (B).
Here, the solubility of carbon dioxide indicates the amount of carbon dioxide dissolved in the resin, and the diffusion coefficient of carbon dioxide indicates the diffusion rate of carbon dioxide in the resin. In the present invention, the effect of the present invention is exhibited by using two types of resins having different solubility and diffusion coefficient of carbon dioxide.

In general, the solubility of carbon dioxide in a thermoplastic resin decreases as the free volume increases and the molecular mobility increases with increasing temperature. On the other hand, the diffusion coefficient of carbon dioxide with respect to the thermoplastic resin increases with increasing temperature. In the resin (A) and the resin (B), the solubility and diffusion coefficient of carbon dioxide are preferably 1.1 times or more different from room temperature to the melting temperature of the resin, more preferably 1.2 times or more. Most preferably, the difference is 1.4 times to 20 times.
The solubility and diffusion coefficient of the carbon dioxide of the resin (A) or the resin (B) can be increased at a predetermined temperature (for example, 70 ° C. to 330 ° C.) using a molding machine (for example, Imoto Seisakusho, desktop molding press). A test piece without bubbles (for example, 20 mmφ, thickness 1 mm to 3 mm) is prepared by pressure and decompression, and 5 MPa to 20 MPa using a magnetic levitation balance measuring apparatus (BEL P / O 152, manufactured by RUBOTHERM, Germany). It can obtain | require by measuring the weight change at the time of the carbon dioxide atmosphere of the pressure range of this when a sample contains a carbon dioxide.
The solubility (g-gas / g-polymer) and diffusion coefficient (m ² / s) of carbon dioxide at a predetermined temperature (° C.) and a predetermined pressure (MPa) of a typical thermoplastic resin are as follows.

Polystyrene (Idemitsu Petrochemical Co., Ltd., HH32, Mw: 321,000)
Temperature (° C) Pressure (MPa) Solubility Diffusion coefficient
110 10.0 0.0576 1.77 × 10 ^-9
200 11.0 0.0426 2.9 × 10 ^-9

Polypropylene (Idemitsu Petrochemical Co., Ltd. F-704NP, Mw: 294,000)
Temperature (° C) Pressure (MPa) Solubility Diffusion coefficient
200 11.0 0.0833 8.07 × 10 ^-9

Polycarbonate (Idemitsu Petrochemical Co., Ltd. A2200, Mw: 27,100)
Temperature (° C) Pressure (MPa) Solubility Diffusion coefficient
260 9.0 0.0259 5.66 × 10 ⁻⁹

Polyethylene glycol (Wako Pure Chemical Industries, Ltd.)
Temperature (° C.) Pressure (MPa) Solubility Diffusion coefficient Mw = 2,000 100 11.1 0.1271 2.35 × 10 ⁻⁹
Mw = 4 million 110 10.0 0.0859 1.49 × 10 ⁻⁸
Mw = 4 million 200 11.0 0.0656 2.35 × 10 ⁻⁸

Polylactic acid (Cargill Dow, PLA-D, Mw: 196,000)
200 6.0 0.0325 3.29 × 10 ^-9
200 11.0 0.0581 4.32 × 10 ^-9

  The resin (A) and the resin (B) in the present invention can be used without particular limitation as long as they have different carbon dioxide solubility and diffusion coefficient and are incompatible with each other. Preferably, the resin (A) is an amorphous thermoplastic resin and / or a biodegradable resin, and the resin (B) is selected from an amorphous thermoplastic resin, a crystalline thermoplastic resin, and a biodegradable resin. Or one or more of them. For example, when an amorphous thermoplastic resin is used as the resin (A) and the resin (B), those that are incompatible with each other may be selected.

Amorphous thermoplastic resin is a thermoplastic resin that has the characteristics that it softens when heated and exhibits plasticity and solidifies when cooled. A thermoplastic resin and a thermoplastic resin whose main component is the amorphous resin.
Examples of the amorphous thermoplastic resin include polystyrene resin, polycarbonate resin, methacrylic resin, vinyl chloride resin, and thermoplastic elastomer.

Polystyrene resins include general-purpose polystyrene (GPPS), rubber-reinforced polystyrene (HIPS), acrylonitrile / styrene copolymer (AS resin), acrylonitrile / butadiene / styrene copolymer (ABS resin), and styrene-methyl methacrylate copolymer. And styrene-methyl methacrylate-butadiene copolymer. The weight average molecular weight (Mw) of the polystyrene resin is preferably 50,000 to 400,000.
Polycarbonate resins include bis (4-hydroxyphenyl), bis (3,5-dialkyl-4-hydroxyphenyl), or hydrocarbon derivatives having bis (3,5-dihalo-4-hydroxyphenyl) substitution. Polycarbonate is preferred, and polycarbonate having 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) is particularly preferred. The weight-average molecular weight (Mw) of the polycarbonate resin is preferably 10,000 to 50,000.
Examples of the methacrylic resin include polymethyl acrylate, polymethyl methacrylate (PMMA), and a methyl methacrylate-styrene copolymer. The weight average molecular weight (Mw) of the methacrylic resin is preferably 50,000 to 600,000.

Examples of the vinyl chloride resin include polyvinyl chloride, vinyl chloride-ethylene copolymer, vinyl chloride-vinyl acetate copolymer, and the like. The vinyl chloride resin preferably has a weight average molecular weight (Mw) of 40,000 to 200,000.
Thermoplastic elastomers include styrene block copolymers such as acrylonitrile-butadiene-styrene (ABS), styrene-isoprene-styrene (SIS), styrene-ethylene / butylene-styrene block co-thermoplastic resin (SEBS), Examples include polybutadiene, polyisoprene, polychloroprene, styrene-butadiene rubber (SBR), ethylene-propylene-diene monomer rubber, ethylene-propylene rubber, and polyethylene-terephthalate (PETG).

  Specific examples of other amorphous thermoplastic resins include cyclic olefin resins (Nippon ZEON Co., Ltd .: cycloolefin polymer “ZEONOR”, Mitsui Chemicals, Inc .: ethylene / tetracyclododecene copolymer “APEL”, etc.) , Polysulfone, polyethersulfone (PES), polyphenylene oxide (PPO), polyimide, polyetherimide, polyamideimide, polyarylate, polyphenylene oxide, polytetrafluoroethylene, polytetrafluoroethylene, polyvinyl acetate, polyvinylidene chloride, liquid crystal Examples thereof include a thermoplastic resin and a hydrophilic amorphous resin.

  Examples of the amorphous resin having hydrophilicity include polyethylene glycol (PEG), polyethylene oxide, polybutyl succinate (PBS), the above polylactic acid resin, and polyvinyl alcohol. Among these, polyethylene glycol (PEG) having a weight average molecular weight (Mw) of polyethylene glycol of 200 to 4,000,000 is preferable.

The biodegradable resin used in the present invention is not particularly limited as long as it is a biodegradable resin, and is preferably thermoplastic considering moldability. Any resin such as a chemically synthesized resin, a microbial resin, or a natural product utilizing resin may be used. For example, aliphatic polyester, polyvinyl alcohol, a cellulose derivative, etc. can be mentioned.
More specifically, the aliphatic polyester includes polylactic acid (PLA) resin and derivatives thereof, polyhydroxybutyrate (PHB) and derivatives thereof, polycaprolactone (PCL), polyethylene adipate (PEA), polytetramethylene adipate, Examples of celluloses such as polyglycolic acid (PGA), a condensate of diol and dicarboxylic acid, and the like include acetyl cellulose, methyl cellulose, and ethyl cellulose. Of these, polylactic acid resin is preferred.
The polylactic acid resin is a polycondensate of lactic acid or lactide. The polylactic acid resin includes optical isomers of D-form, L-form, and DL-form, and includes a single substance or a mixture thereof. The weight average molecular weight (Mw) of the polylactic acid resin is preferably 100,000 to 400,000.

Among the above resins, polystyrene resins, polycarbonate resins, methacrylic resins, cyclic olefin resins, polyethersulfone, polylactic acid resins, and polyethylene glycol are particularly preferable.
Said amorphous resin can be used individually by 1 type or in mixture of 2 or more types.

  On the other hand, as crystalline thermoplastic resins, polyolefin resins, special polystyrene resins, polyamide resins, saturated polyester resins, polyacetal resins, polyphenylene sulfide (PPS), polyphenylene ether (PPE), PPE and other resins (polypropylene, nylon, And modified PPE resin modified by blending or graft polymerization with ABS or the like.

Polyolefin resins include high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-α-olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylate copolymer, and other polyethylene. Examples thereof include polypropylene resins such as polypropylene resins, polypropylene, and propylene-ethylene copolymers, ionomers, polybutenes, and special polyolefin resins.
Special polyolefin resins include ultra high molecular weight polyethylene, ultra high molecular weight polypropylene, syndiotactic polypropylene (polypropylene homopolymer, propylene-ethylene copolymer, propylene-1-butene copolymer, etc.), poly-4-methyl-pentene. -1, cyclic polyolefin resin and the like.
Among these, a polypropylene resin having a weight average molecular weight (Mw) of 30,000 to 600,000 and a syndiotactic polypropylene having a syndiotacticity of 70% or more, particularly 80% or more are preferable.

Examples of the special polystyrene resin include syndiotactic polystyrene (SPS) and α-methylstyrene copolymer.
Examples of the polyamide-based resin include nylon 6, nylon 66, aromatic polyamide, and aromatic / aliphatic polyamide copolymer.
Examples of the saturated polyester resin include polyethylene terephthalate and polybutylene terephthalate.
Examples of the polyacetal resin include homopolyoxymethylene and polyoxymethylene copolymers.

Other crystalline thermoplastic resins include polyketone, polyetherketone, polyetheretherketone, polyethernitrile, thermotropic liquid crystalline resin (paraoxybenzoic acid, aromatic diol, aromatic dicarboxylic acid, naphthalene in the main chain skeleton) And those containing a molecular structure such as a ring).
Among the above crystalline thermoplastic resins, particularly preferred are polyolefin resins such as polypropylene resin and syndiotactic polypropylene, polyamide resins, and saturated polyester resins.
Said crystalline thermoplastic resin can be used individually by 1 type or in mixture of 2 or more types. In addition, an inorganic or organic filler may be added to the amorphous thermoplastic resin, the crystalline thermoplastic resin, and the biodegradable resin for the purpose of imparting strength and improving dimensional accuracy. it can.

  When using the resin foam molding in the medical field, from the viewpoint of biocompatibility, (A) polylactic acid (PLA) resin or the like as the resin, and (B) polyethylene glycol (PEG) or the like may be combined. preferable. When used in the automotive field, it is preferable to combine (A) a polyamide resin, a polypropylene resin or the like as the resin, and (B) a thermoplastic elastomer or the like from the viewpoint of improving heat insulation and strength. Further, when used in the construction field, it is preferable to combine a polycarbonate (PC) resin or the like as the (A) resin and a polystyrene (PS) resin or the like as the (B) resin from the viewpoint of sound insulation.

The mass ratio of the resin (A) and the resin (B) is (A) / (B) = 1 to 99 / 99-1. The weight ratio of (A) / (B) is preferably 5 to 95/9 5-5, more preferably 10 to 90/9 0 - 10.

  In the case of producing a resin molded body, a predetermined amount of the resin (A) and the resin (B) and various additives to be added as necessary are mixed, and then uniaxial or multiaxial extrusion with sufficient kneading ability. After melt-kneading using a machine, a kneader, a mixing roll, etc., it can be molded by a conventional method to obtain a resin molded body. Here, the molded body includes not only a structure having a three-dimensional structure but also a structure having a planar shape such as a sheet or a film. The molding method is not particularly limited, and a known molding method such as injection molding, extrusion molding, blow molding, calendar molding, compression molding, transfer molding, laminate molding, cast molding, inflation molding, or the like can be employed. . Further, the shape of the molded product is not particularly limited, and may be a complicated shape.

Next, carbon dioxide is introduced into the system in which the resin molding is present and impregnated. The impregnation condition depends on the resin constituting the molded body, but is not particularly limited as long as carbon dioxide can be impregnated. Also, there is no particular limitation on the method of impregnating the resin molded body with carbon dioxide, for example, a method of placing the resin molded body in a pressure vessel, introducing carbon dioxide into a supercritical state, and processing in a batch system, For example, a method of continuously treating the resin molded body by introducing it into the carbon dioxide treatment zone can be employed.
Although nitrogen can be used instead of carbon dioxide, carbon dioxide is more preferable than nitrogen because it has a larger amount of dissolution in the resin and more swelling of the thermoplastic resin constituting the molded body.

The resin molded body is impregnated with carbon dioxide, and after the carbon dioxide is saturated in the resin molded body, foaming is performed. The foaming method is not particularly limited, and any one of a reduced pressure foaming method in which foaming is performed by rapid decompression and a temperature rising foaming method in which foaming is performed by raising the temperature can be employed.
In the case of the reduced pressure foaming method, from the viewpoint of efficiently impregnating and foaming carbon dioxide, the temperature is 15 to 250 ° C., preferably 25 to 200 ° C., preferably 1 to 50 MPa, preferably 2 to 2 at the time of carbon dioxide impregnation. 30 MPa, contact time 5 minutes to 30 hours, preferably 10 minutes to 20 hours. From the viewpoint of performing carbon dioxide impregnation particularly efficiently, it is preferable to set the carbon dioxide to a subcritical state or a supercritical state. The subcritical state refers to a state below the critical temperature (31 ° C.) of carbon dioxide (for example, 27 to 31 ° C.) and equal to or higher than the critical pressure (7.38 MPa), and the supercritical state refers to the critical temperature of carbon dioxide. It means a state of (31 ° C.) or more and a critical pressure or more.
In the foaming under reduced pressure, foaming is performed by suddenly reducing the pressure, and the rate of pressure reduction is preferably 0.5 to 10 MPa / second, more preferably 1 to 8 MPa / second. When supercritical carbon dioxide is used, the solubility of carbon dioxide in the resin is drastically lowered when the pressure is lowered. Therefore, carbon dioxide can be removed from the resin molded body only by a decompression operation.

In addition, the temperature, pressure, and contact time in the case of the temperature rising foaming method depend on the physical properties of the target resin, the properties required for the target foam, etc., but the viewpoint of efficiently performing carbon dioxide impregnation and foaming From the time of impregnation with carbon dioxide, the temperature is −10 to 60 ° C., preferably 15 to 50 ° C., the pressure is 1 to 40 MPa, preferably 2 to 30 MPa, the contact time is 5 minutes to 30 hours, preferably 10 minutes to 30 hours. is there. From the viewpoint of performing carbon dioxide impregnation particularly efficiently, carbon dioxide is preferably in a subcritical state or a supercritical state.
Moreover, the temperature at the time of foaming in a temperature rising foaming method should just be a temperature at which a resin molding foams, and there is no restriction | limiting in particular. Usually, it is 20 to 150 ° C., preferably 30 to 100 ° C. higher than the temperature at the time of carbon dioxide impregnation.

According to the present invention, it is possible to produce a foamed molded product in which particles are present in bubbles or a resin foamed molded product having a structure with a uniform particle diameter. For example, when an amorphous thermoplastic resin is used as the resin (A) and a crystalline thermoplastic resin is used as the resin (B), the matrix phase becomes an amorphous thermoplastic resin, and the crystalline heat exists as particles. It becomes a plastic resin. In addition, when (A) an amorphous thermoplastic resin is used as the resin and a biodegradable resin is used as (B), the matrix phase becomes an amorphous thermoplastic resin, and the particles present in the bubbles are biodegradable. It becomes resin. In addition, when (A) an amorphous thermoplastic resin is used as the resin and an amorphous thermoplastic resin is used as (B), a resin foam molded body having a structure with a uniform particle diameter, or particles in the bubbles As a structure in which an amorphous thermoplastic resin is present.
Next, a typical resin blend system will be described in detail.

In a blend system of polystyrene / polyethylene glycol-based polystyrene (Mw: 100,000 to 400,000) and polyethylene glycol (20,000 to 4,000,000), polystyrene / polyethylene glycol (mass ratio) = 50/50 to 95/5, After impregnation with carbon dioxide (impregnation conditions: temperature 50 to 150 ° C., pressure 2 to 40 MPa, time 10 minutes to 30 hours), and sufficient impregnation to the inside of the resin, depressurization (pressure reduction rate: 1 to 1) 10 MPa / second), a foamed molded article having polyethylene glycol particles in the bubbles can be obtained.
This mechanism is considered as follows. As an initial morphology, polyethylene glycol exists as a dispersed phase (island phase) in polystyrene which is a matrix phase (sea phase). When carbon dioxide is impregnated to a saturated state and rapidly decompressed, the polyethylene glycol phase foams first, and a polyethylene glycol phase having a high solubility of carbon dioxide produces more bubbles than the polystyrene phase. Subsequently, in the polyethylene glycol phase having a large diffusion coefficient, bubbles grow faster than the polystyrene phase. And since the viscosity of the polyethylene glycol phase is low, the bubbles are united and the polyethylene glycol / polystyrene interface moves in the direction in which the volume of polyethylene glycol increases. Thereafter, since the foaming temperature is 110 ° C., which is sufficiently higher than the melting point of polyethylene glycol (68 ° C.), the polyethylene glycol melts and remains in the large pores, and a bimodal foam cell structure including the polyethylene glycol particles is formed. .

In the blend system of polylactic acid / polyethylene glycol polylactic acid (Mw: 100,000 to 400,000) and polyethylene glycol (1 to 50,000), the range of polylactic acid / polyethylene glycol (mass ratio) = 50/50 to 95/5 Then, carbon dioxide is impregnated (impregnation conditions: temperature 15 to 50 ° C., pressure 2 to 30 MPa, time 10 minutes to 30 hours), and after the impregnation is sufficiently achieved to the inside of the resin, the water is heated to 60 to 80 ° C. By dipping and heating and foaming, it is possible to obtain a foamed molded article in which polyethylene glycol particles are included in the bubbles of the polylactic acid matrix phase.

In the blend system of polycarbonate / polypropylene polycarbonate (Mw: 10,000 to 50,000) and polypropylene (Mw: 100,000 to 600,000), polycarbonate / polypropylene (mass ratio) = 50/50 to 95/5, Carbon is impregnated (impregnation conditions: temperature 80 to 200 ° C., pressure 2 to 30 MPa, time 10 minutes to 30 hours), and after the impregnation is sufficiently achieved to the inside of the resin, depressurization at a stretch (decompression rate: 1 to 10 MPa) ), The polycarbonate that is the matrix phase is foamed, but the foamed molded product that is present without foaming the polypropylene of the island phase can be obtained.

In a blend system of polycarbonate / polystyrene polycarbonate (Mw: 10,000 to 50,000) and polystyrene (Mw: 100,000 to 400,000), polycarbonate / polystyrene (mass ratio) = 50/50 to 95/5, Carbon is impregnated (impregnation conditions: temperature 80 to 200 ° C., pressure 2 to 30 MPa, time 10 minutes to 30 hours), and after the impregnation is sufficiently achieved to the inside of the resin, depressurization at a stretch (decompression rate: 1 to 10 MPa) / Second), both the polycarbonate as the matrix phase and the polystyrene as the island phase are foamed, and a foamed molded product having a structure with a uniform foamed particle diameter can be obtained.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this.
Example 1
Polystyrene (hereinafter referred to as PS) (Idemitsu Petrochemical Co., Ltd., HH32, Mw: 321,000, Mw / Mn: 2.3) and polyethylene glycol (hereinafter referred to as PEG) (Wako Pure Chemical Industries, Ltd., Mw: 4,000,000) and kneading using a small twin screw extruder (PRISM, TSE16TC) at a temperature of 210 ° C. and a screw rotation speed of 300 rpm at a ratio of PS / PEG (mass ratio) = 90/10. Thereafter, using a desktop press molding machine (manufactured by Kimoto Seisakusho), the temperature was 220 ° C. for 10 minutes and the pressure was applied to obtain a cylindrical molded body (20 mmφ, thickness 2 mm). This compact was put in an autoclave having an internal volume of 50 mL and impregnated with carbon dioxide in a supercritical state at 110 ° C. and 10 MPa for 2.5 hours. Thereafter, the valve attached to the autoclave was opened, and the pressure was reduced rapidly (pressure reduction rate: 5 MPa / second) to cause foaming to obtain a foam molded article.
The solubility (g-gas / g-polymer) of PS at 110 ° C. and 10 MPa as measured using a magnetic levitation balance measuring apparatus (BEL P / O 152, manufactured by RUBOTHERM, Germany) is 0.0576. The diffusion coefficient (m ² / s) is 1.77 × 10 ⁻⁹ . Further, the solubility (g-gas / g-polymer) of PEG at 110 ° C. and 10 MPa is 0.0859, and the diffusion coefficient (m ² / s) is 1.49 × 10 ⁻⁸ .
The photograph which image | photographed the cross section of the obtained foaming molding body with the scanning electron microscope (made by SEM: TECNIC company) is shown in FIG. 1 (magnification: 400 times). From FIG. 1, it can be seen that the structure has PEG particles in the bubbles of the PS matrix phase. This is because, when PEG is foamed, PEG expands by expanding the interface (interface area) of PS and remains as a sphere.

Example 2
In Example 1, PS / PEG (mass ratio) = 75/25, and a foamed molded article was obtained in the same manner as in Example 1 except that carbon dioxide in a supercritical state was impregnated at 90 ° C. for 3 hours. It was. As a result of observing the cross section of the obtained foamed molded article with SEM, it was a structure in which PEG particles were present in PS bubbles as in FIG.

Example 3
In Example 1, PS / PEG (mass ratio) = 60/40, and a foamed molded article was obtained in the same manner as in Example 1 except that carbon dioxide in a supercritical state was impregnated at 70 ° C. for 3 hours. . As a result of observing the cross section of the obtained foamed molded article with SEM, it was a structure in which PEG particles were present in PS bubbles as in FIG.

Comparative Example 1
The same polystyrene and alumina particles (particle diameter: 30 μm) as used in Example 1 were prepared, kneaded at a ratio of PS / Al ₂ O ₃ (mass ratio) = 80/20, and then obtained using a desktop press molding machine. The cylindrical molded body (20 mmφ, thickness 2 mm) was placed in an autoclave and impregnated with carbon dioxide in a supercritical state at 110 ° C. under 10 MPa for 3 hours. Thereafter, the pressure was reduced rapidly to obtain a foamed molded product.
In the observation of the foam cross section of this system, the structure in which the particles are not present in the foam as shown in FIG. 1 was not obtained, and the particle diameter could not be controlled, resulting in a non-uniform structure. And the alumina particle became the structure which exists in the resin layer between the walls between a foam cell and a foam cell.
From this, it can be seen that the solubility of carbon dioxide in the dispersed phase and the diffusion coefficient are important factors for the formation of a foam structure in which particles are present.

Example 4
The same polystyrene and PEG (Wako Pure Chemical Industries, Ltd., Mw: 20,000) used in Example 1 were prepared, kneaded at a ratio of PS / PEG (mass ratio) = 75/25, and then a desktop press molding machine A cylindrical molded body (20 mmφ, thickness 2 mm) obtained by molding using was put in an autoclave and impregnated with supercritical carbon dioxide at 35 ° C. under 10 MPa for 10 hours. Then, it heated up at 70 degreeC and made it foam (temperature rising foaming), and obtained the foaming molding. As a result of observing the cross section of the obtained foamed molded article with SEM, it was a structure in which PEG particles were present in PS bubbles as in FIG.

Example 5
Polylactic acid (Cargill Dow, PLA-D, Mw: 196,000) and PEG (Wako Pure Chemical Industries, Ltd., Mw: 20,000) were prepared, using a small twin screw extruder, After kneading at a screw rotation speed of 300 rpm and a ratio of polylactic acid / PEG (mass ratio) = 75/25, using a desktop press molding machine, heating and pressurizing at 200 ° C. for 10 minutes to form a cylindrical molded body (20 mmφ, Thickness 2 mm) was obtained. This molded body was put in an autoclave and impregnated with supercritical carbon dioxide at 35 ° C. under 10 MPa for 10 hours. Then, it heated up at 70 degreeC and made it foam and obtained the foaming molding. As a result of observing the cross section of the obtained foamed molded article with SEM, it was a structure in which PEG particles were present in the bubbles of polylactic acid, as in FIG.
The polylactic acid used had a solubility (g-gas / g-polymer) at 200 ° C. and 11 MPa of 0.0581, and a diffusion coefficient (m ² / s) of 4.32 × 10 ⁻⁹ .

Example 6
Polycarbonate (Idemitsu Petrochemical Co., Ltd. A2200, Mw: 27,100, Mw / Mn: 3.53) and polypropylene (Idemitsu Petrochemical Co., Ltd., F704NP, Mw: 294,000, Mw / Mn: 4.5, MFR7.0) is prepared, kneaded at a ratio of polycarbonate / polypropylene = 80/20 (mass ratio) at 280 ° C. and screw rotation speed of 50 rpm using a small twin screw extruder, and then using a desktop press molding machine. And heated and pressurized at 280 ° C. for 10 minutes to obtain a cylindrical molded body (20 mmφ × 2 mm). This molded body was put in an autoclave, impregnated with supercritical carbon dioxide at 140 ° C. under 10 MPa for 2 hours, and then foamed under reduced pressure.
In addition, the solubility (g-gas / g-polymer) in 260 degreeC and 9 MPa of a polycarbonate measured using the said magnetic suspension balance measuring apparatus is 0.0259, and a diffusion coefficient (m < ² > / s) is 5. FIG. 66 × 10 ⁻⁹ . Moreover, the solubility (g-gas / g-polymer) in polypropylene 200 degreeC and 11 Mpa is 0.0833, and a diffusion coefficient (m < ² > / s) is 8.07 * 10 < ^-9 >.
The photograph which image | photographed the cross section of the obtained foaming molding with the scanning electron microscope (made by SEM: TECNIC company) is shown in FIG. 2 (magnification: 1000 times). From FIG. 2, it can be seen that the matrix polycarbonate is foamed but the island phase polypropylene is not foamed.

Example 7
Polycarbonate (Idemitsu Petrochemical Co., Ltd. A2200, Mw: 27,100, Mw / Mn: 3.53) and PS (Idemitsu Petrochemical Co., Ltd., HH32, Mw: 321,000, Mw / Mn: 2.3) Prepared at 280 ° C. using a small twin screw extruder at a screw rotation speed of 50 rpm and a ratio of polycarbonate / PS (mass ratio) = 80/20, and then 280 ° C. using a desktop press molding machine. Heated and pressurized for 10 minutes to form a cylindrical shaped body (20mmφ
Thickness 2 mm) was obtained. This molded body was put in an autoclave, impregnated with supercritical carbon dioxide at 140 ° C. under 10 MPa for 2 hours, and then foamed under reduced pressure.
The photograph which image | photographed the cross section of the obtained foaming molding with a scanning electron microscope (made by SEM: TECNIC company) is shown in FIG. 3 (magnification: 300 times). From FIG. 3, it can be seen that the polycarbonate and PS have a fired diameter of approximately the same diameter and a uniform particle diameter. As described above, the cell structure can be controlled by changing the solubility / diffusion coefficient of the thermoplastic resin which becomes the matrix phase and the island phase.

Comparative Example 2
In Example 1, a foamed molded article was obtained in the same manner as Example 1 except that only PS was used.
When the cross section of the obtained foamed molded product was observed, in Comparative Example 2, a closed cell structure (average cell size was 50 μm) with non-uniform particle size was obtained.

The method for producing a resin foam molded article of the present invention makes it easy to control the structure of the foam cell, and can advantageously produce a resin foam molded article useful as a functional material and a structural material. The obtained resin foam is used in the medical field such as a drug delivery system (DDS) for the purpose of optimizing drug administration, and in the field of regenerative medical engineering such as a scaffold for replacing hard tissue (substrate serving as a cell scaffold). It can be effectively used in the field of materials that require high-strength porous materials, optical properties, heat insulation (low thermal conductivity), and low dielectric properties.

2 is a scanning electron micrograph (magnification: 400 times) showing a cross section of the resin foam molded article obtained in Example 1. FIG. It is a scanning electron micrograph (magnification: 1000 times) which shows the cross section of the resin foam molding obtained in Example 6. It is a scanning electron micrograph (magnification: 300 times) showing a cross section of the resin foam molded article obtained in Example 7.

Claims (12)

The solubility and diffusion coefficient of carbon dioxide are different, and they are incompatible resin (A) and resin (B) (however, the solubility and diffusion coefficient of carbon dioxide is resin (A) <resin (B)) The resin (A) / (B) mass ratio is 50/50 to 95/5 , and the resin (A) becomes a matrix phase, and the resin (A) and the resin (B) have a melting point or less. A method for producing a resin foam molded article, wherein the foamed foam is impregnated with carbon dioxide at a temperature.   The resin foam molded article according to claim 1, wherein the solubility of the carbon dioxide and / or the diffusion coefficient in the resin (A) and the resin (B) differ from each other by 1.1 times or more from the room temperature to the melting temperature of the resin. Manufacturing method.   The resin (A) is an amorphous thermoplastic resin and / or a biodegradable resin, and the resin (B) is a kind selected from an amorphous thermoplastic resin, a crystalline thermoplastic resin and a biodegradable resin or The method for producing a resin foam molded article according to claim 1 or 2, wherein the resin foam molded article is of two or more kinds.   The amorphous thermoplastic resin is one or more selected from polystyrene resins, polycarbonate resins, methacrylic resins, cyclic olefin resins, polyethersulfones, polylactic acid resins, and polyethylene glycols. The manufacturing method of the resin foam molding in any one of 1-3.   The method for producing a resin foam molded article according to any one of claims 1 to 4, wherein the crystalline thermoplastic resin is one or two or more selected from polyolefin resins, polyamide resins, and saturated polyester resins.   The method for producing a resin foam molded article according to any one of claims 1 to 5, wherein the biodegradable resin is one or more selected from polylactic acid.   The resin according to any one of claims 1 to 6, wherein the resin (A) is one or more selected from polystyrene, polymethyl methacrylate, and polylactic acid, and the resin (B) is polyethylene glycol. A method for producing a foam molded article.   The method for producing a resin foam molded article according to any one of claims 1 to 7, wherein foaming is performed by reduced pressure foaming or temperature rising foaming.   The method for producing a resin foam molded article according to claim 8, wherein the carbon dioxide impregnation is performed at a temperature of 15 to 250 ° C and a pressure of 1 to 50 MPa, and foamed under reduced pressure at a pressure reduction rate of 0.5 to 10 MPa / second.   The resin foam molded article according to claim 8, wherein the carbon dioxide impregnation is performed at a temperature of -10 to 60 ° C and a pressure of 1 to 40 MPa, and foamed at a temperature higher by 20 to 150 ° C than the temperature at the time of carbon dioxide impregnation. Method.   A resin foam molded article obtained by the method for producing a resin foam molded article according to claim 1.   The resin foam molding according to claim 11, wherein the resin particles are encapsulated in the pores of the foam molding.

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