JP4144808B2 - Non-foamed molded body manufacturing method and non-foamed molded body - Google Patents

Description

  The present invention relates to a method for producing a non-foamed molded body and a non-foamed molded body, and more specifically, a non-foamed molded body by injection molding an amorphous thermoplastic resin impregnated with a small amount of carbon dioxide and / or nitrogen. The present invention relates to a method for efficiently producing a non-foamed molded article.

In injection molding of optical plastic parts, etc., in addition to improving moldability (fluidity), improve mold surface transferability, suppress orientation distortion, suppress warpage, and prevent coloration due to thermal degradation (improved transparency) ) Etc. are demanded.
In general, one of the indexes representing the fluidity of thermoplastic resin is melt viscosity. Thermoplastic resins have a high melt viscosity and are poor in fluidity as a molding material, and therefore thin-walled parts often cannot be completely filled with resin, and transferability is often insufficient.
As a method for improving the fluidity by lowering the viscosity of the molten resin, there is a method of raising the molding temperature. However, when the molding temperature is raised, depending on the resin composition, thermal decomposition of the resin itself and thermal decomposition of additives, etc. occur, and not only the strength of the molded body but also the generation of foreign matter due to resin degradation products, mold contamination, coloring ( Problems such as discoloration). In addition, there is a problem that the cooling rate of the resin in the mold becomes slow and the molding cycle time becomes long.
As other methods for improving the fluidity, there are methods of lowering the molecular weight of the resin and adding a plasticizer to the resin material, but there arises a problem that the mechanical strength of the resin is lowered.

Therefore, as a method of improving the fluidity of the molten resin without increasing the molding temperature or decreasing the molecular weight of the resin, the resin is plasticized by impregnating the resin with carbon dioxide or nitrogen, and the melt viscosity or glass transition temperature ( A method for reducing Tg) is known (see Non-Patent Document 1 and Patent Documents 1 to 3).
In Patent Document 1, a compound that becomes a gas body at 40 ° C. is directly introduced into a cylinder of an injection molding machine, the gas body is contained in a thermoplastic resin, and the mold cavity is opened to the atmosphere or reduced in pressure. An injection molding method is disclosed in which a thermoplastic resin is injected into a mold cavity and boosted with a pressing force equal to or higher than the pressure at which bubbles are generated. However, this method requires special equipment such as a pressure-resistant cylinder and a carbon dioxide supply device and has a problem that stable injection molding is difficult.

Further, in Patent Document 2, foaming of a molten resin in which 0.2 to 10% by weight of carbon dioxide is dissolved to lower the melt viscosity is caused at the flow front (the front end of the molten resin flow in the mold). An injection molding method is disclosed in which a mold cavity is filled while being pressed, and then pressed to a pressure higher than the pressure at which foaming does not occur. However, this method has a problem that a foam pattern remains on the surface of the obtained molded body.
In Patent Document 3, carbon dioxide is added to an alloy resin obtained by mixing a crystalline thermoplastic resin such as syndiotactic polystyrene and a non-crystalline thermoplastic resin such as a styrene resin, so that the crystalline property is increased. An injection molding method characterized by molding at a temperature lower than the melting point of a single resin is disclosed. However, this method cannot be applied to a resin composition composed only of an amorphous resin.
As a technique to which the above method is applied, a technique “AMOTEC” (registered trademark) is known in which carbon dioxide is dissolved in a molten resin in an injection molding machine, and carbon dioxide is filled in a mold in advance before the resin is injected. ing. However, this technique requires a special gas supply device, a molding machine and a mold.
Under such circumstances, there has been a demand for development of a method for producing a non-foamed molded article by simpler and more efficient injection molding using carbon dioxide, nitrogen, or the like.

Hisao Hachisuka, Polymer Journal, vol.22, No.1, pp77-79 (1990) Japanese Patent Laid-Open No. 5-318541 International Publication No. 01/96084 Pamphlet JP 2003-211483 A

  In view of the above situation, the present invention uses a normal injection molding machine to injection-mold an amorphous thermoplastic resin impregnated with a small amount of carbon dioxide and / or nitrogen, thereby forming a non-foamed molded article. It aims at providing the method of manufacturing efficiently, and its non-foaming molding.

As a result of intensive investigations to achieve the above object, the present inventors have previously impregnated carbon dioxide and / or nitrogen in an amount capable of suppressing foaming in the mold, and performed injection molding, thereby achieving the above-described problem. I found that it could be solved.
That is, the present invention provides the following (1) and (2).
(1) polystyrene resin, polycarbonate resin, methacrylic resin, and the powdery grains of one or more amorphous thermoplastic resin selected from the cycloolefin resin, carbon dioxide and / or nitrogen put into a pressure vessel And impregnating at 100 ° C. to room temperature to give a carbon dioxide impregnation amount of 3 to 10% by mass and / or a nitrogen impregnation amount of 0.05 to 1.0% by mass. Unimpregnated amorphous thermoplastic resin granules are mixed, so that the carbon dioxide impregnation amount is 0.3 to 3.0 mass% and / or the nitrogen impregnation amount is 0.05 to 1.0 mass%. After the adjustment, the carbon dioxide and / or nitrogen impregnated resin obtained is supplied to a raw material supply port at the most upstream part of a cylinder of an injection molding machine and molded, and a non-foamed molded body manufacturing method .
(2) A non-foamed molded article obtained by the method described in (1) above.

According to the method of the present invention, since the fluidity of the resin is improved, the torque load during the molding process can be reduced (energy reduction), and the resin flow length in the mold can be increased by about 5 to 25%. it can. Moreover, since the decomposition reaction rate of the resin can be slowed and the molding temperature can be lowered by about 10 ° C. from the normal temperature range, coloring of the molded product due to heating can be suppressed, and the non-foamed molded product with excellent appearance Can be efficiently manufactured. Furthermore, the transferability of the mold surface can be improved, and orientation distortion and warpage can be reduced even with a thin molded body.
Further, according to the method of the present invention, an injection molded body can be produced using a normal injection molding machine equipped with a shut-off nozzle, and there is no need to use special equipment.

The method for producing a non-foamed molded article according to the present invention comprises (i) impregnating an amorphous thermoplastic resin with 0.3 to 3.0% by mass of carbon dioxide and / or 0.05 to 1.0% by mass of nitrogen. And (ii) supplying the nitrogen-impregnated resin to the most upstream part of the cylinder of the injection molding machine and performing injection molding.
In the present invention, the amorphous thermoplastic resin constituting the non-foamed molded body is a resin that is generally used as various molded body materials such as films, sheets, and substrates, and can be impregnated with carbon dioxide and / or nitrogen. There is no particular limitation. Examples of such amorphous thermoplastic resins include polystyrene resins, polycarbonate resins, polymethacrylic resins, cycloolefin resins, and polyvinyl chloride resins.

Polystyrene resins include general-purpose polystyrene (GPPS), rubber-reinforced polystyrene (HIPS), acrylonitrile-styrene copolymer (AS), acrylonitrile-butadiene-styrene copolymer (ABS), styrene-isoprene-styrene copolymer ( SIS), styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-methyl methacrylate copolymer, styrene-methyl methacrylate-butadiene copolymer, styrene-butadiene rubber (SBR), and the like. The mass average molecular weight (Mw) of the polystyrene-based 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 bisphenol A type polycarbonate having 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) is particularly preferred. The mass average molecular weight (Mw) of the polycarbonate resin is preferably 10,000 to 50,000.
Examples of the polymethacrylic resin include polymethyl acrylate, polymethyl methacrylate (PMMA), and a methyl methacrylate-styrene copolymer. The weight average molecular weight (Mw) of the polymethacrylic resin is preferably 50,000 to 600,000.
Cyclo (cyclic) olefin resin includes cycloolefin polymer manufactured by Nippon Zeon Co., Ltd., trade names “ZEONOR”, “ZEONEX”, ethylene tetracyclododecene copolymer manufactured by Mitsui Chemicals, Ltd., trade name “Apel” ", A cycloolefin copolymer manufactured by Topas Advanced Polymers GmbH, the trade name" TOPAS "and the like are preferable.

Examples of the polyvinyl chloride resin include polyvinyl chloride (PVC), vinyl chloride-ethylene copolymer, vinyl chloride-vinyl acetate copolymer, and the like. The weight average molecular weight (Mw) of the polyvinyl chloride resin is preferably 40,000 to 200,000.
Other amorphous thermoplastic resins include polysulfone, polyethersulfone (PES), polyphenylene oxide (PPO), polyarylate (PAR), polyimide (PI), polyetherimide (PEI), polyamideimide, polytetrafluoro Examples thereof include ethylene, polytetrafluoroethylene, polyvinyl acetate, polyvinylidene chloride, liquid crystal thermoplastic resin, and biodegradable resin.

Examples of the biodegradable resin include aliphatic polyester, polyvinyl alcohol (PVA), and cellulose derivatives. Aliphatic polyesters include polylactic acid (PLA) resin and derivatives thereof, polyhydroxybutyrate (PHB) and derivatives thereof, polycaprolactone (PCL), polyethylene adipate (PEA), polytetramethylene adipate, polyglycolic acid (PGA) , Diol and dicarboxylic acid condensates and the like, and celluloses include acetyl cellulose, methyl cellulose, ethyl cellulose and the like.
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 mass average molecular weight (Mw) of the polylactic acid resin is preferably 100,000 to 400,000.

Among the amorphous thermoplastic resins, polystyrene resins, polycarbonate resins, polymethacrylic resins, and cycloolefin resins are particularly preferable.
The amorphous thermoplastic resins can be used singly or in combination of two or more. In addition, for the purpose of imparting strength and heat resistance, improving dimensional accuracy, and the like, an inorganic or organic filler can be blended. Furthermore, flame retardants, antioxidants, ultraviolet absorbers, antistatic agents, plasticizers, lubricants, colorants and the like can be blended as additives.

Before supplying the amorphous thermoplastic resin to the injection molding machine, carbon dioxide is 0.3 to 3.0% by mass, preferably 0.5 to 3.0% by mass, more preferably 0.5 to 3.0% by mass. It is important to impregnate 1.9% by mass and / or nitrogen 0.05-1.0% by mass, preferably 0.08-0.9, more preferably 0.1-0.8% by mass. .
There is no particular limitation on the impregnation method of carbon dioxide and / or nitrogen. For example, an amorphous thermoplastic resin granule is placed in a pressure vessel, carbon dioxide and / or nitrogen is supplied into the pressure vessel, and is kept under heating or pressure for a predetermined time to form a resin granule. Carbon dioxide and / or nitrogen can be impregnated.

The pressure of carbon dioxide impregnation is preferably 1 to 40 MPa, more preferably 2 to 20 MPa, still more preferably 2 to 15 MPa, and the pressure of nitrogen impregnation is preferably 1 to 30 MPa, more preferably 2 to 20 MPa. More preferably, it is 3-10 MPa.
The temperature of carbon dioxide and / or nitrogen impregnation is preferably not higher than the glass transition temperature (Tg) of the amorphous thermoplastic resin, and varies depending on the resin, but more preferably 230 ° C. to −30 ° C., still more preferably 100. C. to room temperature. The impregnation time varies depending on the pressure, temperature, type of resin, etc., but is usually 1 minute to 100 hours, preferably 0.5 to 30 hours, more preferably 1 to 30 hours.
As the impregnation treatment method, a batch method, a method in which resin particles are introduced into a nitrogen treatment zone and continuously treated, or the like can be adopted. Here, the resin powder is not particularly limited as long as it refers to powder such as resin powder, granules, pellets, tablets, and the like and can be supplied as a raw material for injection molding.

In impregnation with carbon dioxide, an organic solvent can be added as an auxiliary agent in an amount of about 0.05 to 1% by mass of the plasticizer.
The organic solvent that can be used is not particularly limited, and examples thereof include alcohol solvents, ketone solvents, ether solvents, benzene, toluene, polyols, and the like.
Examples of alcohol solvents include methanol, ethanol, n-propanol, isopropanol, n-butanol, tertiary butanol, isobutanol, diacetone alcohol, and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane, and cyclic ether. Among these, alcohol solvents such as ethanol and propanol, and ketone solvents such as methyl ethyl ketone are particularly preferable.

Carbon dioxide and / or nitrogen supplied to the pressure vessel may be in a normal cylinder pressure state at the time of supply, or in a subcritical state or a supercritical state. Moreover, it is good also as a subcritical state or a supercritical state after supplying in a pressure vessel.
The conditions for impregnating the resin particles with carbon dioxide and / or nitrogen can be appropriately determined according to the characteristics of the resin itself, the shape of the intended molded body, the application, and the like. For example, carbon dioxide is supplied into the pressure vessel at room temperature under a cylinder pressure (about 5 MPa) and / or nitrogen is under room temperature under a cylinder pressure (about 10 MPa), and the resin powder is appropriately stirred as necessary. By holding for 0.5 to 24 hours, the amount of carbon dioxide impregnation is about 3 to 10% by mass and / or the amount of nitrogen impregnation is about 0.05 to 1.0% by mass. From the viewpoint of equipment, it is preferable to adjust the amount of carbon dioxide and / or nitrogen impregnation by mixing unimpregnated resin particles.
However, the impregnation property of carbon dioxide and / or nitrogen varies depending on the resin, and there are resin materials that require a long time for impregnation of carbon dioxide and / or nitrogen at a cylinder pressure at room temperature. Therefore, in order to shorten the impregnation time of carbon dioxide and / or nitrogen, it is preferable to impregnate at a glass transition temperature or lower under a subcritical state or a supercritical state.

Here, the “subcritical state” of carbon dioxide or nitrogen means that (i) the pressure is not less than the critical pressure of carbon dioxide (7.38 MPa) or not less than the critical pressure of nitrogen (3.4 MPa), and the temperature is dioxide. A liquid state that is less than the critical temperature of carbon (31.1 ° C.) or less than the critical temperature of nitrogen (−147 ° C.), (ii) the pressure is less than the critical pressure of carbon dioxide or nitrogen, and the temperature is above the critical temperature A liquid state, or (iii) a state in which both temperature and pressure are less than the critical point of carbon dioxide or nitrogen, but close to this.
More specifically, in the case of carbon dioxide, a temperature of 20 ° C. to 31 ° C. and a pressure of 5 MPa or more are preferable, and in the case of nitrogen, a temperature of room temperature to 100 ° C. and a pressure of 1 to 3.4 MPa are preferable. .

The “supercritical state” refers to a state where the pressure is higher than the critical pressure of carbon dioxide and / or nitrogen, and the temperature is higher than the critical temperature. In order to bring carbon dioxide into a supercritical state, it is preferable to set the temperature to 40 to 50 ° C. and pressure 7.38 to 30 MPa, particularly 8 to 20 MP. It is preferable that the temperature is 100 ° C. and the pressure is 3.4 to 30 MPa, particularly 5 to 20 MPa.
When carbon dioxide in the subcritical state or supercritical state is used, it is generally maintained for 1 minute to 30 hours, preferably 5 minutes to 5 hours. When nitrogen in the subcritical state or supercritical state is used, What is necessary is just to hold | maintain for 10 minutes-30 hours, Preferably it is 1 to 10 hours.

The amount of carbon dioxide impregnated as described above is 0.3 to 3.0% by mass, preferably 0.5 to 1.9% by mass, or the amount of nitrogen impregnated is resin particles. 0.05 to 1.0% by mass of the body, preferably 0.08 to 0.9%, more preferably 0.1 to 0.8% by mass.
Next, the pressure in the pressure vessel is released, and the resin particles inside are taken out. A part of carbon dioxide and / or nitrogen impregnated in the resin granules by this pressure release and the organic solvent added as needed are diffused from the resin granules as a gas. If it is within 5 hours, about 50 mass% of the impregnated carbon dioxide or about 60 mass% of nitrogen remains inside the resin powder. When impregnated with carbon dioxide and / or nitrogen in a subcritical state or a supercritical state, it is preferable to reduce the pressure slowly so as to suppress foaming of the resin particles.
Also, the obtained carbon dioxide and / or nitrogen impregnated resin and non-impregnated resin are mixed in an appropriate ratio to adjust the amount of carbon dioxide and / or nitrogen impregnated into the resin, and the resin powder raw material for injection molding It can be.

Next, the resin particles are promptly supplied to the most upstream part of the cylinder of the injection molding machine, and injection molding is performed under molding conditions corresponding to the type of amorphous thermoplastic resin forming the resin particles. , Non-foamed molded articles having various shapes can be obtained. The amorphous thermoplastic resin can be supplied to the injection molding machine by feeding it into a normal raw material supply port of the injection molding machine. At the time of injection molding, the pressure and temperature in the cylinder of the injection molding machine are usually higher than the pressure and temperature in the supercritical state of carbon dioxide and / or nitrogen. And / or nitrogen is not released.
However, when the molten resin is filled in the mold, the impregnated 0.3 to 3.0% by mass of carbon dioxide and / or 0.05 to 1.0% by mass of nitrogen is a bonding surface between the mold and the mold. The carbon dioxide that does not dissolve in the amorphous thermoplastic resin is injected by back pressure or injected when it is diffused from the gas venting part or injected into the mold from the injection molding machine or during plasticization in the injection molding machine. Since it dissipates by controlling the molding conditions such as pressure and holding pressure, it does not remain in the molded body, and foaming does not leave a foam pattern on the surface of the molded body.

According to the method of the present invention, a normal injection molding machine can be used as it is, and the molding conditions are normal conditions, so that molding efficiency is not lowered. Further, the obtained non-foamed molded article is excellent in appearance without coloring. Furthermore, it is possible to efficiently produce a molded article having excellent mold transferability and less orientation strain.
The method of the present invention is particularly suitable for the production of thin molded articles such as substrates, sheets and films having a thickness of 2 mm or less, particularly 1 mm or less.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this.

Example 1
A pellet of commercially available polycarbonate (made by Idemitsu Kosan Co., Ltd., trade name: A2200, Mw: 27,100, Tg = 145 ° C.) was dried at 90 ° C. for 5 hours, and then this pellet (hereinafter referred to as “PC pellet-1”). ) Put 100g into a cylindrical rod made of stainless steel wire mesh (45mmφ, length 135mm), install in a 300mL capacity autoclave (manufactured by Kogyo Kogyo Co., Ltd.), and then treat with carbon dioxide at bomb pressure of 5.4MPa at room temperature for 5 hours. Went. Thereafter, the carbon dioxide in the autoclave was depressurized over 10 minutes. The amount of carbon dioxide (CO ₂ ) impregnation of PC pellet-1 calculated from the mass method shown below was 7.41% by mass.
Dissolved amount of CO ₂ (mass%) = {[mass of cylindrical rod after impregnation of CO ₂ (g) + mass of pellet after impregnation of CO ₂ (g)] − [mass of cylindrical rod before impregnation of CO ₂ (g) + CO ₂ Pellet mass before impregnation (g)]} / pellet mass before impregnation (g) × 100
500 g of a mixture of 100 g of the obtained carbon dioxide-impregnated PC pellet-1 and 400 g of non-carbon dioxide-impregnated PC pellet-1 was used as a raw material supply port for an injection molding machine (trade name: J35ELIII-F, manufactured by Nippon Steel Works). It was directly charged into the most upstream part of the cylinder). In addition, the carbon dioxide impregnation amount of the pellet mixture was 1.48% by mass.
Cylinder diameter: 25 mm, screw rotation speed: 50 rpm
Injection conditions: Speed 30 mm / second, pressure 130 MPa, time 1.3 seconds, mold clamping 20 tons Holding pressure condition: pressure 25 MPa, time 1.5 seconds Back pressure: 5 MPa
Molding temperature: raw material supply port 280 ° C, nozzle 320 ° C
Mold temperature: 80 ℃
Using the bar flow mold (spiral flow mold: width 5 mm, thickness: 1 mm) under the above injection molding conditions, the influence of the resin flow length in the mold due to the carbon dioxide impregnation treatment was evaluated. As a result, the resin flow length in the mold was 57 mm, the molded body mass was 1.4540 g, and the resin biting stability was also good.
Moreover, the sprue runner part of the obtained molded body was heated and pressurized at a temperature of 260 ° C. for 10 minutes using a desktop press molding machine (manufactured by Imoto Seisakusho Co., Ltd.) to produce a 2 cm square sheet having a thickness of 500 μm.
As a result of measuring the transmittance of the produced sheet using an ultraviolet-visible spectrophotometer (trade name: V-550, manufactured by JASCO Corporation), the transmittance in the visible light region (400 nm) was 82.5%, ultraviolet. The transmittance in the region (300 nm) was 31.2%.
In addition, the image of the molded product was taken into a computer, and the color degree was compared with a chromaticity diagram using a color luminance meter (2K LCD COLOR ANALYZER, CD-1500, manufactured by Konica Minolta Holdings Co., Ltd.). As a result, chromaticity Δx = 0 .377 and chromaticity Δy = 0.398, and coloring (yellowing change) of the molded product was not observed.

Comparative Example 1
The PC pellet-1 used in Example 1 was injection molded under the same conditions as in Example 1. As a result, the resin flow length in the mold was 46 mm, and the molded body weight was 1.4205 g.
Further, the transmittance was measured in the same manner as in Example 1. As a result, the transmittance in the visible light region (400 nm) was 81.1%, and in the ultraviolet region (300 nm), it was 26.2%. Moreover, as a result of evaluating the coloring degree of a molded object, it was chromaticity (DELTA) x = 0.399 and chromaticity (DELTA) y = 0.417, and the molded object was colored yellow.
Comparing Example 1 and Comparative Example 1, in Example 1, the resin flow length in the mold increased 24% from 46 mm (Comparative Example 1) to 57 mm (Example 1), and the rotational force (torque) ) Decreased from 100% to 70%. In the untreated PC pellet-1 of Comparative Example 1, the low molecular weight component at the hydroxyl end was structurally changed by heat, and the transmittance in the ultraviolet region was particularly lowered. Is reflected.

Example 2
In Example 1, it carried out like Example 1 except having hold | maintained carbon dioxide as a supercritical state (10 MPa, 40 degreeC) for 3 hours, and impregnating the carbon pellet to PC pellet-1.
As a result, the carbon dioxide impregnation amount of the obtained PC pellet-1 was 9.0% by mass.
500 g of a mixture of 100 g of this carbon dioxide impregnated PC pellet-1 and 400 g of PC pellet-1 not impregnated with carbon dioxide was added to a raw material supply port (cylinder of J35ELIII-F, manufactured by Nippon Steel Works, Ltd.). The most upstream part was directly charged. In addition, the carbon dioxide impregnation amount of the pellet mixture was 1.8% by mass.
Hereinafter, as a result of performing the same operation as in Example 1, the flow length in the mold was 60 mm, and the molded body mass was 1.4580 g.
When Example 2 and Comparative Example 1 are compared, the flow length in the mold increases by 30% from 46 mm (Comparative Example 1) to 60 mm (Example 2), and the rotational force (torque) increases from 100% to 70%. Declined. Furthermore, the resin biting stability was also improved. Further, coloring (yellowing change) of the molded body was not recognized.

Example 3
A pellet of a commercially available polycarbonate (manufactured by Mitsubishi Engineering Plastics, trade name: Iupilon HL-4000, Mw: 12,000, Tg = 145 ° C.) was dried at 90 ° C. for 5 hours, and then the pellet (hereinafter referred to as “PC Pellet-2 ”(100 g) is placed in a stainless steel wire mesh cylindrical rod (45 mmφ, length 135 mm), placed in an autoclave with a capacity of 300 mL (manufactured by Pressure Industrial Co., Ltd.), and at a room temperature and a cylinder pressure of 5.4 MPa. Carbon dioxide treatment was performed for 4 hours. Thereafter, the carbon dioxide in the autoclave was depressurized over 10 minutes.
As a result of calculating the carbon dioxide impregnation amount of the PC pellet-2 in the same manner as in Example 1, it was 6.61% by mass.
400 g of a mixture of 40 g of the obtained carbon dioxide-impregnated PC pellet-2 and 360 g of carbon pellet-unimpregnated PC pellet-2 was fed into a raw material supply port of an injection molding machine (product name: J35ELIII-F, manufactured by Nippon Steel Works, Ltd.) It was directly charged into the most upstream part of the cylinder). In addition, the carbon dioxide impregnation amount of the pellet mixture was 0.66% by mass.
Cylinder diameter: 25 mm, screw rotation speed: 50 rpm
Injection conditions: speed 20 mm / second, pressure 100 MPa, time 1.5 seconds, mold clamping 20 tons Holding pressure condition: pressure 25 MPa, time 1.5 seconds Back pressure: 5 MPa
Molding temperature: raw material supply port 250 ° C, nozzle 280 ° C
Mold temperature: 80 ℃
Using the bar flow mold (spiral flow mold: width 5 mm, thickness: 1 mm) under the above injection molding conditions, the influence of the resin flow length in the mold due to the carbon dioxide impregnation treatment was evaluated. As a result, the resin flow length in the mold was 42 mm, the molded body mass was 1.413 g, and the resin biting stability was also good.

Comparative Example 2
The PC pellet-2 used in Example 3 was directly injection molded under the same conditions as in Example 3. As a result, the resin flow length in the mold was 40 mm, and the molded body weight was 1.408 g.
When Example 3 and Comparative Example 2 were compared, the flow length increased by 5% from 40 mm (Comparative Example 2) to 42 mm (Example 3), and the rotational force (torque) decreased from 17% to 15%.

Example 4
A pellet of commercially available polymethyl methacrylate (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumipex LG, Mw = 100,000, Tg = 100 ° C.) was dried at 90 ° C. for 5 hours, and then the pellet (hereinafter “PMMA pellet”). 100 g in a cylindrical rod made of stainless wire mesh (45 mmφ, length 135 mm), placed in an autoclave with a capacity of 300 mL (made by Kogyo Kogyo Co., Ltd.), and then carbon dioxide at room temperature and a cylinder pressure of 5.7 MPa for 20 minutes. Processed. Thereafter, the carbon dioxide in the autoclave was depressurized over 10 minutes.
As a result of calculating the carbon dioxide impregnation amount of the PMMA pellets in the same manner as in Example 1, it was 7.5% by mass.
500 g of a mixture of 100 g of the carbon dioxide-impregnated PMMA pellets obtained and 400 g of carbon dioxide-unimpregnated PMMA pellets is supplied to the raw material supply port (the most upstream of the cylinder) of an injection molding machine (manufactured by Nippon Steel Works, Ltd., trade name: J35ELIII-F). Part). In addition, the carbon dioxide impregnation amount of the pellet mixture was 1.5% by mass.
Cylinder diameter: 25 mm, screw rotation speed: 50 rpm
Injection conditions: speed 20 mm / second, pressure 100 MPa, time 1.3 seconds, mold clamping 20 tons Holding pressure condition: pressure 25 MPa, time 1.5 seconds Back pressure: 5 MPa
Molding temperature: raw material supply port 200 ° C, nozzle 250 ° C
Mold temperature: 60 ℃
Using a bar flow mold (spiral flow mold) under the above injection molding conditions, the influence of the resin flow length in the mold due to the carbon dioxide impregnation treatment was evaluated (n = 10). As a result, the resin flow length in the mold was 106 mm, the molded body mass was 1.7912 g, and the resin biting stability was also good. Further, coloring (yellowing change) of the molded body was not recognized.

Comparative Example 3
The PMMA pellets used in Example 4 were injection molded under the same conditions as in Example 3. As a result, the flow length in the mold was 89 mm, the molded body weight was 1.7218 g, and the molded body was colored yellow.
When Example 4 was compared with Comparative Example 3, the flow length increased 19% from 89 mm (Comparative Example 3) to 106 mm (Example 4), and the rotational force (torque) decreased from 50% to 40%. Further, in the untreated PMMA pellet of Comparative Example 2, it is considered that the low molecular weight component at the hydroxyl group terminal was structurally changed by heat, and the transmittance in the ultraviolet region in particular was lowered, and the degree of yellowing change of the molded product reflected this. is doing.

Example 5
100 g of commercially available polystyrene (made by Idemitsu Kosan Co., Ltd., trade name: HH32, Mw = 321,000, Mw / Mn = 2.3, Tg = 105 ° C.) (this pellet (hereinafter referred to as “PS pellet”)) It was placed in a stainless steel wire mesh cylindrical rod (45 mmφ, length 135 mm) and placed in a 300 mL autoclave (manufactured by Pressure Industrial Co., Ltd.), and then subjected to carbon dioxide treatment at room temperature and a cylinder pressure of 4.0 MPa for 24 hours. Thereafter, the carbon dioxide in the autoclave was depressurized over 10 minutes.
As a result of calculating the carbon dioxide impregnation amount of PS pellets in the same manner as in Example 1, it was 6.8% by mass.
500 g of a mixture of 100 g of the carbon dioxide-impregnated PS pellets obtained and 400 g of carbon dioxide-unimpregnated PS pellets is used as a raw material supply port (the most upstream of the cylinder) of an injection molding machine (product name: J35ELIII-F, manufactured by Nippon Steel Works). Part). In addition, the carbon dioxide impregnation amount of the pellet mixture was 1.36% by mass.
Cylinder diameter: 25 mm, screw rotation speed: 50 rpm
Injection conditions: Speed 20 mm / second, pressure 100 MPa, time 1.5 seconds, mold clamping 20 tons Holding pressure condition: 25 MPa, time 1.5 seconds Back pressure: 5 MPa
Molding temperature: raw material supply port 200 ° C, nozzle 250 ° C
Mold temperature: 60 ℃
Using a bar flow mold (spiral flow mold) under the above injection molding conditions, the influence of the resin flow length in the mold due to the carbon dioxide impregnation treatment was evaluated (n = 10). As a result, the resin flow length in the mold was 160 mm, the molded body mass was 1.730 g, and the resin biting stability was also good. Further, coloring (yellowing change) of the molded body was not recognized.

Comparative Example 4
The PS pellets used in Example 5 were directly injection molded under the same conditions as in Example 5. As a result, the flow length in the mold was 150 mm, the molded body weight was 1.700 g, and the molded body was slightly colored yellow.
When Example 5 was compared with Comparative Example 4, the flow length increased 7% from 150 mm (Comparative Example 4) to 160 mm (Example 5), and the rotational force (torque) decreased from 17% to 15%.

Example 6
A pellet of a commercially available polycarbonate (manufactured by Mitsubishi Engineering Plastics, trade name: Iupilon HL-4000, Mw: 12,000, Tg = 145 ° C.) was dried at 100 ° C. for 5 hours, and then the pellet (hereinafter referred to as “PC 1000 g) (referred to as “Pellet-3”) is placed in a stainless steel wire mesh cylindrical rod (100 mmφ, length 200 mm), placed in an autoclave with a capacity of 2 L (manufactured by Kogyo Kogyo Co., Ltd.), and at a cylinder pressure of 5.6 MPa at room temperature. Carbon dioxide treatment was performed for 24 hours. Thereafter, the carbon dioxide in the autoclave was depressurized over 7 minutes.
As a result of calculating the carbon dioxide impregnation amount of PC pellet-3 in the same manner as in Example 1, it was 9.6% by mass.
600 g of a mixture of the obtained carbon dioxide impregnated PC pellets-3, 60 g and carbon dioxide non-impregnated PC pellets-3, 540 g is supplied to an injection molding machine (trade name: J35ELIII-F, manufactured by Nippon Steel Works). It was directly put into the mouth (the most upstream part of the cylinder). In addition, the carbon dioxide impregnation amount of the pellet mixture was 0.96% by mass.
Cylinder diameter: 25 mm, screw rotation speed: 50 rpm
Injection conditions: speed 100 mm / second, pressure 150 MPa, 1.3 seconds, mold clamping 20 tons Holding pressure condition: pressure 100 MPa, time 1.5 seconds, back pressure: 5 MPa
Molding temperature: raw material supply port 240 ° C, nozzle 295 ° C
Mold temperature: 100 ° C
Mold for evaluation of transferability under the above-mentioned injection molding conditions (mold size; length: 39 mm, width: 28 mm, thickness: 0.5 mm, surface pattern; pitch-to-pitch crest height interval: 26 μm, Using a prism shape having a pitch height of 5.2 μm and a pitch width of 18 μm, the transferability of the mold to the resin and the orientation strain by the carbon dioxide impregnation treatment were evaluated.
Here, the transferability was evaluated by the mold transfer rate (%) calculated by the following formula.
Mold transfer rate (%) = [Pitch height of molded body (μm) / Pitch height of mold (μm)] × 100
In addition, the pitch height of the molded body was measured using an ultra-deep color 3D shape measurement microscope (manufactured by Keyence Corporation, trade name: VK-9500).
The orientation strain is determined by first determining the flow pattern of the entire molded body using a polarization strain meter, and then measuring the phase difference (retardation: Re) using a spectrophotometer and a polarization microscope based on the obtained flow pattern. And evaluated.
The pitch height and orientation strain were measured at the center of the injection-molded molded body (length from the gate: 20 mm, width: 14 mm). As a result, the pitch height of the molded body was 4.79 μm, the mold transfer rate was 92.1%, and Re was 469 nm.

Example 7
The same operation as in Example 6 was performed using 100 g of a mixture of PC pellet-3 treated with carbon dioxide obtained in Example 6 and 500 g of PC pellet-3 not impregnated with carbon dioxide. As a result, the amount of carbon dioxide impregnated in the pellet mixture was 1.59% by mass, the pitch height of the molded body was 4.85 μm, the mold transfer rate was 93.3%, and Re was 650 nm.

Example 8
The same operation as in Example 6 was performed using 660 g of a mixture of 460 g of PC pellet-3 treated with carbon dioxide obtained in Example 6 and 460 g of PC pellet-3 not impregnated with carbon dioxide. As a result, the amount of carbon dioxide impregnated in the pellet mixture was 2.91% by mass, the pitch height of the molded body was 5.03 μm, the mold transfer rate was 96.7%, and Re was 473 nm.

Comparative Example 5
The same operation as in Example 6 was performed using 200 g of the PC pellet-3 treated with carbon dioxide obtained in Example 6 and 200 g of 400 g of PC pellet-3 not impregnated with carbon dioxide. As a result, the carbon dioxide impregnation amount of the pellet mixture was 3.19% by mass. Moreover, since bubbles entered the molded body and the pitch height of the molded body could not be evaluated, the mold transfer rate could not be obtained. The orientation strain was 837 nm.
In Comparative Example 5, the amount of carbon dioxide impregnated in the pellet mixture was high and a foam pattern remained on the surface of the molded body, whereas in Example 6, Re was changed from 837 nm (Comparative Example 5) to 469 nm (Example 6). 44% decrease. In Example 7, Re decreased by 22% from 837 nm (Comparative Example 5) to 650 nm (Example 7). In Example 8, Re decreased by 43.5% from 837 nm (Comparative Example 5) to 473 nm (Example 8).

Comparative Example 6
The PC pellet-3 used in Example 6 was injection molded under the same conditions as in Example 1. As a result, the pitch height of the obtained molded body was 4.65 μm, the mold transfer rate was 89.4%, and Re was 846 nm.
Comparing Example 6 and Comparative Example 6, the mold transfer rate was improved from 89.4% (Comparative Example 6) to 92.1% (Example 6), and Re was 846 nm (Comparative Example 5). It decreased by 45% to 469 nm (Example 6). Further, when Example 7 and Comparative Example 6 are compared, the mold transfer rate is improved from 89.4% (Comparative Example 6) to 93.3% (Example 7), and Re is 846 nm (Comparative Example 6). ) To 650 nm (Example 7), a 23% decrease. When Example 8 and Comparative Example 6 are compared, the mold transfer rate is improved from 89.4% (Comparative Example 6) to 96.7% (Example 8), and Re is 846 nm (Comparative Example 6). ) To 473 nm (Example 8).
From these results, it can be seen that impregnation with 0.3 to 3.0% by mass of carbon dioxide improves fluidity, improves the mold transfer rate, and reduces orientation strain.

Example 9
A pellet of a commercially available polycarbonate (manufactured by Mitsubishi Engineering Plastics, trade name: Iupilon HL-4000, Mw: 12,000, Tg: 145 ° C.) was dried at 100 ° C. for 5 hours, and then the pellet (hereinafter referred to as “PC 1000 g (referred to as “pellet”) is placed in a stainless steel wire mesh cylindrical rod (100 mmφ, length 200 mm), placed in an autoclave with a capacity of 2 liters (manufactured by Pressure Industrial Co., Ltd.), and then at room temperature (22 ° C.) at a cylinder pressure of 10 MPa. Nitrogen treatment was performed for 24 hours. Thereafter, the nitrogen in the autoclave was depressurized over 7 minutes. The amount of nitrogen (N ₂ ) impregnation of the PC pellet calculated from the mass method shown below was 0.8% by mass.
N ₂ dissolution amount (mass%) = {[cylindrical rod mass after impregnation with N ₂ (g) + pellet mass after impregnation with N ₂ (g)] − [cylindrical rod mass before impregnation with N ₂ (g) + N ₂ Pellet mass before impregnation (g)]} / pellet mass before impregnation (g) × 100
600 g of the mixture of 300 g of the obtained nitrogen-impregnated PC pellets and 300 g of non-nitrogen-impregnated PC pellets was supplied to the raw material supply port (the most upstream part of the cylinder) of an injection molding machine (product name: J35ELIII-F). Directly into In addition, the nitrogen impregnation amount of the pellet mixture was 0.4 mass%.
Cylinder diameter: 25 mm, screw rotation speed: 50 rpm
Injection conditions: speed 125 mm / second, pressure 170 MPa, time 1.3 seconds, mold clamping 20 tons Holding pressure condition: pressure 140 MPa, time 1.5 seconds, back pressure: 10 MPa
Molding temperature: Raw material supply port 240 ° C, 300 ° C in injection molding machine, nozzle 300 ° C
Mold temperature: 100 ° C
Mold for evaluation of transferability under the above-mentioned injection molding conditions (mold size; length: 39 mm, width: 28 mm, thickness: 0.5 mm, surface pattern; pitch-to-pitch crest height interval: 26 μm, Using a prism shape having a pitch height of 5.2 μm and a pitch width of 18 μm, the transferability of the mold to the resin and the orientation strain by the carbon dioxide impregnation treatment were evaluated.
Here, the transferability was evaluated by the mold transfer rate (%) calculated by the following formula.
Mold transfer rate (%) = [Pitch height of molded body (μm) / Pitch height of mold (μm)] × 100
In addition, the pitch height of the molded body was measured using an ultra-deep color 3D shape measurement microscope (manufactured by Keyence Corporation, trade name: VK-9500).
The orientation strain is determined by first determining the flow pattern of the entire molded body using a polarization strain meter, and then measuring the phase difference (retardation: Re) using a spectrophotometer and a polarization microscope based on the obtained flow pattern. And evaluated.
The pitch height and orientation strain were measured at the center of the injection-molded molded body (length from the gate: 20 mm, width: 14 mm). As a result, the pitch height of the molded body was 4.85 μm, the mold transfer rate was 93.3%, and Re was 515 nm.
Further, coloring (yellowing change) of the molded body was not recognized.

Example 10
600 g of nitrogen-treated PC pellets in the same manner as in Example 9 were directly charged into the raw material supply port (the most upstream part of the cylinder) of an injection molding machine (trade name: J35ELIII-F, manufactured by Nippon Steel Works, Ltd.). In addition, the nitrogen impregnation amount of PC pellets was 0.8 mass%.
Thereafter, the same operation as in Example 9 was performed. As a result, the pitch height of the molded body was 4.73 μm, the mold transfer rate was 91.0%, and Re was 660 nm.
Further, coloring (yellowing change) of the molded product was not recognized.

Comparative Example 7
The dried PC pellets used in Example 9 were directly injection molded under the same conditions as in Example 1. As a result, the obtained molded product had a pitch height of 4.65 μm, a mold transfer rate of 89.4%, and Re of 846 nm.
Comparing Example 9 and Comparative Example 7, the mold transfer rate was improved from 89.4% (Comparative Example 7) to 93.3% (Example 9), and Re was 846 nm (Comparative Example 7). It decreased by 39% to 515 nm (Example 9). Further, when Example 10 and Comparative Example 7 are compared, the mold transfer rate is improved from 89.4% (Comparative Example 7) to 91.0% (Example 10), and Re is 846 nm (Comparative Example 7). ) To 660 nm (Example 10).
From these results, it is understood that by impregnating with 0.05 to 1.0 mass% of nitrogen, the fluidity is improved, the mold transfer rate is improved, and the orientation strain is reduced.

Example 11
A pellet of commercially available cycloolefin (manufactured by Nippon Zeon Co., Ltd., trade name: ZEONEX, 480R, Tg: 140 ° C.) is dried at 100 ° C. for 5 hours, and then 1000 g of this pellet (hereinafter referred to as “COP pellet”) is made of stainless steel wire mesh. The sample was placed in a cylindrical rod (100 mmφ, length 200 mm) and placed in a 2 L capacity autoclave (manufactured by Pressure Industrial Co., Ltd.), and then subjected to nitrogen treatment at room temperature (22 ° C.) and a cylinder pressure of 10 MPa for 24 hours. Thereafter, the nitrogen in the autoclave was depressurized over 8 minutes.
The amount of COP pellets impregnated with nitrogen (N ₂ ) was calculated in the same manner as in Example 9, and as a result, it was 0.33 mass%.
600 g of the obtained nitrogen-impregnated COP pellets were directly charged into a raw material supply port (the most upstream part of the cylinder) of an injection molding machine (manufactured by Nippon Steel Works, Inc., trade name: J35ELIII-F).
Cylinder diameter: 25 mm, screw rotation speed: 50 rpm
Injection conditions: speed 140 mm / second, pressure 175 MPa, time 1.3 seconds, mold clamping 20 tons Holding pressure condition: pressure 120 MPa, time 1.5 seconds, back pressure: 10 MPa
Molding temperature: Raw material supply port 220 ° C, injection molding machine 320 ° C, nozzle 315 ° C
Mold temperature: 100 ° C
Thereafter, the same operation as in Example 9 was performed. As a result, the pitch height of the molded body was 4.80 μm, the mold transfer rate was 92.3%, and Re was 323 nm.
Further, coloring (yellowing change) of the molded product was not recognized.

Comparative Example 8
The dry COP pellets used in Example 11 were injection molded under the same conditions as in Example 3. As a result, the obtained molded article had a pitch height of 4.65 μm, a mold transfer rate of 89.4%, and Re of 456 nm.
When Example 11 and Comparative Example 8 are compared, the mold transfer rate is improved from 89.4% (Comparative Example 8) to 92.3% (Example 11), and Re is from 456 nm (Comparative Example 8). It decreased by 29% to 323 nm (Example 11).

According to the production method of the present invention, a non-foamed molded article having improved resin fluidity, no coloration, excellent appearance, good mold surface transferability, and less molding distortion and warpage of the molded article. It can be manufactured efficiently. Therefore, the production method of the present invention can be suitably used in the field of micro-molding such as a light guide plate, diffraction grating, micropattern, and microlens, and the field of optical molding such as a lens and prism.
In addition, the production method of the present invention can be applied to resins that are difficult to mold, for example, thermoplastic resins having a molecular weight that is too high for injection molding, resins that are poor in thermal stability and susceptible to thermal decomposition, and high softening temperatures. It is suitable for injection molding using resins that need to be molded (for example, engineering plastics), resins that contain additives such as flame retardants that are easily pyrolyzed, and the like.

Claims (5)

Polystyrene resin, polycarbonate resin, methacrylic resin, and the powdery grains of one or more amorphous thermoplastic resin selected from the cycloolefin resin, supplying carbon dioxide and / or nitrogen put into a pressure vessel Impregnation at 100 ° C. to room temperature to obtain a carbon dioxide impregnation amount of 3 to 10% by mass and / or a nitrogen impregnation amount of 0.05 to 1.0% by mass, which is impregnated with carbon dioxide and / or nitrogen After mixing amorphous thermoplastic resin particles and adjusting the impregnation amount of carbon dioxide to 0.3-3.0 mass% and / or the impregnation amount of nitrogen to 0.05-1.0 mass% A method for producing a non-foamed molded article, wherein the carbon dioxide and / or nitrogen impregnated resin obtained is supplied to a raw material supply port at the most upstream part of a cylinder of an injection molding machine and molded. The impregnation of the carbon dioxide, the production method of the non-foamed molded article according to claim 1 carried out at a temperature below the glass transition temperature of the pressure 1~40MPa and amorphous thermoplastic resins. The method for producing a non-foamed molded article according to claim 1 or 2 , wherein the impregnation with nitrogen is performed at a pressure of 1 to 30 MPa and a temperature not higher than a glass transition temperature of the amorphous thermoplastic resin. The non-foaming molded object obtained by the method in any one of Claims 1-3 . The non-foamed molded article according to claim 4 , wherein the molded article has a thickness of 2 mm or less.