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WO1996007527A1 - Procede de moulage par injection basse pression - Google Patents

Procede de moulage par injection basse pression Download PDF

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Publication number
WO1996007527A1
WO1996007527A1 PCT/JP1994/001499 JP9401499W WO9607527A1 WO 1996007527 A1 WO1996007527 A1 WO 1996007527A1 JP 9401499 W JP9401499 W JP 9401499W WO 9607527 A1 WO9607527 A1 WO 9607527A1
Authority
WO
WIPO (PCT)
Prior art keywords
resin
injection molding
low
mold
molding method
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP1994/001499
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English (en)
Japanese (ja)
Inventor
Hiroshi Kataoka
Yuo Umei
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Asahi Kasei Corp
Asahi Chemical Industry Co Ltd
Original Assignee
Asahi Chemical Industry Co Ltd
Asahi Kasei Kogyo KK
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Asahi Chemical Industry Co Ltd, Asahi Kasei Kogyo KK filed Critical Asahi Chemical Industry Co Ltd
Priority to PCT/JP1994/001499 priority Critical patent/WO1996007527A1/fr
Priority to CN94190340.0A priority patent/CN1127491A/zh
Publication of WO1996007527A1 publication Critical patent/WO1996007527A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/26—Moulds
    • B29C45/37—Mould cavity walls, i.e. the inner surface forming the mould cavity, e.g. linings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/1703—Introducing an auxiliary fluid into the mould
    • B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
    • B29C2045/1717—Temperature controlled mould parts to control the location or configuration of the hollow

Definitions

  • the present invention relates to a low-pressure injection molding method for synthetic resin.
  • the present invention relates to a synthetic resin using a metal mold obtained by coating a wall constituting a cavity of a metal mold body with a heat-resistant resin layer having a specific thickness range.
  • the present invention relates to a low-pressure injection molding method for a synthetic resin in which injection including low-speed injection in a mold cavity is performed.
  • gas assist is introduced in PI astics T echno 1 ogy, Aril, 44 (1994) or USP 4, 101, 617, etc.
  • G There is an injection molding method. This molding method involves injecting a synthetic resin into the mold cavity and then injecting a gas body, making use of the fact that the pressure loss of the gas body is small to even the end of the synthetic resin flow. This is a method of transmitting the injection pressure to the mold and performing low-pressure injection molding.
  • the assist injection molding method is a method of similarly performing low-pressure injection molding using an oligomer or a liquid.
  • the Sandwich injection molding method which has many introductions, including BP 1, 156, 217, injects the first synthetic resin first, and then the second synthetic resin.
  • a structure having a sandwich structure is formed while satisfying the mold cavity.
  • low pressure injection molding can be performed by the foaming force of the inner core resin.
  • the mold clamping plate is slightly retracted to inject the synthetic resin in a state where the mold cavity is deepened (thickened), and then the mold clamping plate is advanced to move the mold cavity to a predetermined depth.
  • Injection compression molding in which the resin thickness is reduced to a small value and the entire mold cavity is filled with synthetic resin at low pressure, has recently become widely used.
  • the Hettinger low-pressure injection molding method which performs injection at extremely low speeds with extremely low injection pressure, is introduced in Synthetic Resins, Vol. 37, N0.9, page 34 (1991), etc. It is used well depending on the shape of the molded product.
  • the molding conditions are variously changed to improve the reproducibility of the mold surface and the solvent resistance.
  • the most influential is the mold temperature. It is effective to raise the mold temperature to near the softening temperature of the synthetic resin.
  • the cooling time required for cooling and solidifying the plasticized resin increases, and the molding efficiency decreases. Therefore, there is a need for a method that does not increase the mold temperature, improves the reproducibility of the mold surface, or that does not increase the required cooling time even if the mold temperature is increased. ing.
  • gas assist injection molding liquid assist injection
  • liquid assist injection In the low-pressure injection molding method used in the present invention, such as a molding method, an oligomer assist injection molding method, an injection compression molding method, a Sandwich injection molding method, a Hettinginger low-pressure injection molding method, etc.
  • the flow velocity of the synthetic resin in the mold cavity is slow, and often the flow velocity of the resin changes rapidly during the flow. Since the flow speed of the resin is slow, the reproducibility of the mold surface is poor, and the flow speed changes suddenly.When the flow speed changes suddenly, the appearance of the resin, which is generally called a hedging mark, is poor. A roaming mark occurs.
  • the present invention has been made for the purpose of responding to this problem.
  • the present inventors have studied the relationship between low-speed flow of resin, low injection pressure, and a mold covered with an insulated eyebrow in the low-pressure injection molding method.
  • the present invention was completed by studying the relationship with SCR and the like.
  • the present invention provides a mold obtained by coating a wall of a metal mold body, which constitutes a cavity, with a heat-resistant resin layer having a thickness of more than 0.1 mm and not more than 0.5 mm.
  • the present invention relates to a low-pressure injection molding method for a synthetic resin in which a flow including a low-speed injection at a flow rate of 10 O mm Z seconds or less is performed using a synthetic resin mold cavity.
  • the present invention relates to the synthetic resin, wherein the synthetic resin contains a resin reinforced material, wherein the molded article after molding the resin has substantially no protrusion of the resin reinforced material on the surface thereof. It relates to the molding method.
  • the present invention also relates to the above-mentioned molding method, wherein the synthetic resin containing the resin-reinforced material is a rubber-reinforced synthetic resin.
  • the present invention also relates to the above-mentioned molding method, wherein the rubber-reinforced synthetic resin is a rubber-reinforced polystyrene resin.
  • the present invention relates to the above-mentioned molding method, wherein the thickness of the heat-resistant resin eyebrow is in the range of 0.15 to 0.45 mm.
  • the low-pressure injection molding method comprises the steps of: a gas-assist injection molding method, a liquid-assist injection molding method, an oligomer-assist injection molding method, an injection compression molding method, and a core resin.
  • the present invention relates to the above-mentioned molding method comprising at least one of the group consisting of a sandwich injection molding method made of foamed resin and a Hettinga low-pressure injection molding method.
  • FIGS. 1A, 1B and 1C show the low pressure injection molding method in which the present invention is carried out (gas assist injection molding method, oligomer assist injection molding method, liquid assist injection molding method).
  • FIG. 1A, 1B and 1C show the low pressure injection molding method in which the present invention is carried out (gas assist injection molding method, oligomer assist injection molding method, liquid assist injection molding method).
  • Figure 2 shows the relationship between temperature and viscosity for various synthetic resins and various fluids.
  • FIGS. 4A and 4B are views for explaining an injection compression molding method as a low-pressure injection molding method in which the present invention is carried out.
  • Figures 5, 6, 7 and 8 show the temperatures near the mold wall surface when the temperature of the mold body was 50 and the temperature of the rubber-reinforced polystyrene was 240 ° C. Indicates the distribution change (calculated value).
  • Figure 9 shows the flow pattern in a synthetic resin mold cavity.
  • Figure 10 shows the shear heating (calculated value) of a synthetic resin flowing through a mold cavity.
  • Figures 11A and 11B show that the use of a heat-insulating layer-coated mold improves SCR (stress crack resistance) even at low speed injection molding.
  • Fig. 12 shows the time-dependent change of the resin pressure applied to the mold wall surface during injection molding of synthetic resin.
  • FIG. 13 shows a method for measuring SCR.
  • FIGS. 14A and 14B show the relationship between the gloss of the molded product and the flow velocity in the mold cavity of the synthetic resin and the thickness of the polyimide as the heat-resistant resin layer, respectively.
  • FIGS. 15A and 15B show schematic views of cross sections near the surface of the injection molded article.
  • the synthetic resin used in the present invention is a thermoplastic resin that can be used for general injection molding, for example, a polyolefin such as polyethylene polypropylene, Polystyrene, styrene-acrylonitrile copolymer, styrene-based resin such as rubber-reinforced polystyrene, polyamide, polyester, polycarbonate G, methacrylic resin, and vinyl chloride resin.
  • the synthetic resin contains 1 to 60% of a resin reinforcement.
  • the resin-reinforced material include various types of rubber, glass fibers, various types of fibers such as carbon fibers, and inorganic powders such as talc, calcium carbonate, and kaolin.
  • a synthetic resin that can be used favorably is a rubber-reinforced synthetic resin, and among them, a rubber-reinforced polystyrene resin is particularly preferably used.
  • the rubber-reinforced polystyrene resin used in the present invention refers to rubber-reinforced polystyrene, ABS resin, AAS resin, MBS resin, and the like in which a rubber phase is distributed in an island shape in a resin phase.
  • Rubber-reinforced polystyrene is a resin in which a rubber phase such as polybutadiene or SBR is dispersed in an island shape in a resin phase of a polymer mainly composed of styrene.
  • ABS resin is a resin in which rubber phases such as polybutadiene and SBR are dispersed in the form of islands in a resin phase of a copolymer mainly composed of styrene and acrylonitrile.
  • AAS resin is an ATA resin in a resin phase of a copolymer mainly composed of styrene and acrylonitrile.
  • MBS resin in which the rubber phase of rubber is dispersed in the form of islands.
  • the MBS resin has islands in the resin phase consisting of a copolymer mainly composed of styrene and methyl methacrylate. It is a resin dispersed in a shape.
  • blends mainly composed of these resins can also be used in the present invention.
  • a blend with a rubber reinforced polystyrene resin blended with poly (vinylene ether) can be used favorably.
  • the injection molded products of these resins molded by the present invention have an extremely good balance between performance and economy, and are suitable as light electric appliances, housing for electronic appliances, various daily necessities, various industrial parts, and the like.
  • Used for The mold body of the mold specified in the present invention is made of iron or iron-based steel material, aluminum, or aluminum-based alloy, zinc alloy, base metal. It means a metal mold generally used for molding synthetic resins such as lithium-copper alloy. In particular, molds made of steel can be used successfully. 0
  • the heat-resistant resin used as the heat-insulating layer in the present invention has a glass transition temperature of 140 ° C or more, preferably 160 ° C or more, and / or a melting point of 230 ° C or more. Preferably, it is a heat-resistant resin of 250 ° C or higher.
  • the heat conductivity of the heat-resistant resin of the present invention is generally 0.0001 to 0.02 cal / cm'sec * ° C, which is much smaller than that of metal. Further, the heat-resistant resin has a toughness of elongation at break of 5% or more, preferably 10% or more, and more preferably 15% or more. I like it.
  • the tensile elongation at break is measured according to ASTMD 638, and the tensile speed at the time of measurement is 5 mm / min.
  • the heat-resistant resin that can be favorably used as a heat insulating layer in the present invention is used in the main chain. It is a heat-resistant polymer having an aromatic ring, and examples thereof include various amorphous heat-resistant polymers and various polyimides that are soluble in organic solvents.
  • noncrystalline heat-resistant polymer examples include polysulfone, poly-tersulfone, polyarylsulfone, polyarylate, and polyolefin Xylene ether. .
  • linear high molecular weight polyimides and partially crosslinked polyimides can be used favorably.
  • linear high molecular weight polyimide has a large tensile elongation at break, is tough, and has excellent durability, and can be used particularly well.
  • a linear high molecular weight polyimide having a repeating unit of the polymer shown in Table 1 can be used favorably.
  • heating and cooling are performed repeatedly during molding, and stress is generated between the heat-resistant resin and the mold body if the coefficients of thermal expansion differ greatly.
  • stress is generated similarly by heating and cooling. When this stress exceeds a certain value, the heat-resistant resin layer is separated from the mold body.
  • Table 2 shows examples of the thermal expansion coefficient of the low thermal expansion polyimide. Various low thermal expansion polyimides can be used successfully. In the table, Bifix and Free can freely shrink the film when the polyimide precursor is imidized to form a polyimide phenol.
  • the fixed force (Free) has the meaning that the polymer chain is fixed in a rectangular frame, the shrinkage that occurs during imidization is suppressed, and the polymer chain is oriented in-plane by the stress (Bifix). .
  • the thermal expansion coefficient of the polyimide formed by heating has an intermediate value between Free and Bifix.
  • R R, and R:
  • injection molding has economic value where a molded article having a complicated shape can be obtained in one molding.
  • a heat-resistant polymer solution or a solution of a heat-resistant polymer precursor is applied and then heated. It is most preferred to form a heat resistant polymer by heat treatment. Therefore, it is preferable that the heat-resistant polymer or the heat-resistant polymer precursor of the present invention can be dissolved in a solvent.
  • an epoxy resin, silicone resin, or melamine resin to which flexibility is imparted can also be used favorably.
  • a modified epoxy resin imparted with flexibility for example, a modified epoxy resin modified with a tough resin can be used favorably.
  • the adhesion between the heat-resistant resin layer as the heat insulating layer of the present invention and the mold body needs to be large, and is 0.5 kg Z 10 mm or more at room temperature, preferably 0.5 mm. 8 kg 10 mm width or more, more preferably 1 kg Z 10 mm width or more.
  • the above-mentioned adhesion force is expressed as a separation force when the closely adhered heat insulating layer is cut to a width of 10 mm and the cut width is pulled at a speed of 2 Om mZ in a direction perpendicular to the bonding surface. This separation varies considerably depending on the measurement location and the number of measurements, but it is important that the minimum value is large, and it is preferable that the separation be large and stable.
  • the adhesion in the present invention is the minimum value of the adhesion of the main part of the mold.
  • the thickness of the heat-resistant resin layer is approximately Another material thinner than 1/5, preferably thinner than around 1Z10, can be coated on the heat-resistant resin layer if necessary.
  • synthetic resin sheets and molds A paint generally used as a hard coat, which is used for improving scratch resistance, can be applied to the surface of the glass.
  • An example of this is a thermosetting silicone-based hardcoat, especially a hard-coated silicone-based hardcoat with an epoxy compound. Can be used well and is preferred for the present invention.
  • a thin metal layer can be coated on the heat-resistant resin layer as a heat insulating layer.
  • chrome plating or nickel plating can be coated on the heat insulating layer.
  • the thickness of the metal layer be 110 or less of the thickness of the heat-resistant resin layer.
  • the thickness of the heat-resistant resin layer as the heat insulating layer is appropriately selected within a range of more than 0.1 mm and 0.5 mm or less. Preferably it is 0.15 mm or more and 0.45 mm or less. In the low-pressure injection molding of the present invention, if the thickness of the heat insulating layer is 0.1 mm or less, the effect as the heat insulating layer cannot be sufficiently exerted. In other words, the invention relates to the flow velocity in a synthetic resin mold cavity. Temperature, the thickness of the heat-resistant resin layer as the heat insulating layer, and the reproducibility of the mold surface reproducibility of the molded product.The required thickness of the heat insulating layer was determined by the synthetic resin. There is a close relationship with the flow velocity in the mold cavity of the synthetic resin.If the flow velocity in the mold cavity of the synthetic resin is 10 Om mZ seconds or less, the thickness of the heat insulating layer exceeding 0.1 mm is required. Become.
  • the cooling time (0) is proportional to the maximum wall thickness (D) of the part and is a function of the (T x — T d) value. Covering the mold body with a heat-insulating layer acts in the same direction as increasing the thickness of the molded product and shortening the cooling time.
  • the surface of the mold body is covered with a heat-insulating layer made of a heat-resistant resin.
  • the surface of the mold receives heat from the resin and heats up.
  • the mold surface temperature is softened for at least 0.4 seconds after the injected synthetic resin comes into contact with the cooled mold surface. It is preferable that the temperature is higher than the temperature. If, for example, there is no insulating eyebrow on the mold surface, the mold surface temperature will be almost the same as the mold body temperature after 0.1 seconds.
  • the mold surface is kept at a temperature equal to or higher than the softening temperature for 0.4 seconds. be able to.
  • Changes in the mold surface temperature during injection molding can be calculated from the respective temperatures, specific heat, mature conductivity, density, latent heat of crystallization, etc. of the synthetic resin, the mold body, and the heat-resistant resin eyebrows as the heat insulating layer.
  • ADINA and ADINAT software Xa developed at the Massachusetts Institute of Technology
  • the softening temperature of the resin described here means that the synthetic resin It is the temperature at which it can be deformed.
  • the vicat softening temperature (ASTMD 1525)
  • the heat deformation temperature (ASTMD 648 load 18.6 kg / cm 2 )
  • these are the heat deformation temperatures (ASTMD 648, load 4.6 kg Z cm 2 ).
  • the hard crystalline resin include polyoxymethylene, Nylon 6, and Nylon 66.
  • the soft crystalline resin include various polyethylene and polyproylene. Pyrene and the like.
  • the low-pressure injection molding method described in the present invention is an injection molding method in which the injection pressure of a synthetic resin and a liquid or liquid injected into a mold cavity is low.
  • the injection molding method is performed at a high injection pressure of about 100 kg / cm 2
  • the low pressure injection molding method of the present invention uses a low pressure injection molding method including a low pressure injection of less than half of the injection pressure. It is.
  • the low-pressure injection molding method of the present invention includes a gas-assist injection molding method, a liquid-assist injection molding method, an oligomer-assist injection molding method, an injection compression molding method, and a sand in which the core resin is a foamed resin. It is selected from at least one of the group consisting of the injection molding method and the Hettinger low-pressure injection molding method.
  • the synthetic resin is molded by injection molding including low-speed injection in which the flow velocity in the mold cavity is 100 mmsec or less.
  • This low-speed injection includes various cases such as when the injection speed of the synthetic resin temporarily becomes low, when the flow stops momentarily, and when the injection speed is low overall. Species cases may be included.
  • the injection speed can be calculated from both the flow distance of the synthetic resin in the mold cavity and the value obtained by measuring the flow time of the synthetic resin based on the advancement time of the injection screw. .
  • Injection and molding are performed with less than half the pressure of resin, but the speed of resin flow after switching to low pressure gas is greatly reduced.
  • a high-pressure synthetic resin is switched to a low-pressure gas, a flow mark with a bad appearance is generated. This is commonly referred to as a hedging mark.
  • the resin flows at a low speed beyond the hedging mark, and the reproducibility of the mold surface generally deteriorates.
  • the synthetic resin 3 is injected into the mold cavity 2 formed by the mold body 1 (FIG. 1A), and then the gas body 5 is injected into the mold cavity 2. 2
  • the injection pressure of the gas body 5 is significantly lower than the injection pressure of the synthetic resin 3 and less than half of the injection pressure of the synthetic resin. Therefore, generally, the flow velocity of the injected synthetic resin in the mold cavity changes in conjunction with the switching of injection from synthetic resin to gas. When this flow velocity changes4, the surface of the molded product is generally referred to as a roughness mark. Bad flow marks with bad appearance remain. Also, the reproducibility of the mold surface is poor in the area between the hedging mark and the flow end. In addition, since the resin is filled at a low flow rate, the SCR of the molded product also deteriorates.
  • the present invention is a molding method which solves these problems, that is, a heat insulating layer having a thickness of more than 0.1 mm and not more than 0.5 mm is formed on the wall surface forming the mold cavity of the metal mold body.
  • Synthetic resin that is injected using a mold obtained by coating the heat-resistant resin layer as described above, including a low-speed injection with a flow velocity in the mold cavity of the synthetic resin of 10 Om mZ seconds or less. According to this method, there is substantially no protrusion of the resin-reinforced material on the surface of the molded product, the reproducibility of the mold surface is excellent, and an injection molded product with improved SCR can be obtained. This has the effect of making it possible.
  • FIG. 2 is a diagram showing the relationship between temperature and viscosity of various synthetic resins and various fluids shown in Table 3.
  • Various fluids can be used in the same manner as long as the viscosity at the time of injection is not more than 1 Z50 of the viscosity of the synthetic resin injected first.
  • the use of a liquid instead of a gas as the fluid is a liquid-assist injection molding method, and the use of a low-molecular-weight polymer is the oligomer-cast injection molding method.
  • this liquid assist injection molding method and the oligomer assist injection molding method the same results as described with reference to FIGS. 1A, 18 and 1 are obtained.
  • FIGS. 3A and 3B show another molded article formed by gas assist injection molding.
  • the molded article 7 has a thick portion 10 formed from the gate 8 to the resin flowing end 9.
  • a synthetic resin is injected from the gate 8 and then a gas body is injected, the gas body proceeds selectively in a thick portion, and a hollow part generally called a gas channel 11 is formed.
  • the pressure of the injected gas is evenly transmitted to the resin flowing end 9 by the gas pressure of the gas channel 11.
  • Figure 3B shows the cross section A-A 'of the molded product in Figure 3A.
  • FIGS. 4A and 4B show an injection compression molding method which is one of the low pressure injection molding methods described in the present invention.
  • the mold clamping plate of the injection molding machine was slightly retracted, so that the moving side of the mold 1 was retracted, and the mold cavity 2 was deepened (thickened).
  • the synthetic resin 3 is injected (FIG. 4A), and then the mold clamping plate is advanced, whereby the moving side of the mold 1 is advanced to reduce the mold cavity to a predetermined depth (thickness).
  • To fill the mold cavity with synthetic resin at low pressure (Fig. 4B).
  • the flow velocity of the synthetic resin in the mold cavity usually changes. Poor appearance Flow marks occur.
  • the depth (wall thickness) of the mold cavity is reduced, when the mold cavity is filled with a low pressure, the flow velocity of the synthetic resin in the mold cavity is low, and therefore, that portion is not sufficient.
  • the reproducibility of the mold surface of the molded product becomes poor, and the glossiness becomes poor.
  • the SCR of the molded article also deteriorates due to the slow flow rate of the synthetic resin in the mold cavity.
  • the appearance defect and the SCR are improved by using a mold covered with a heat-resistant resin layer as a selected heat-insulating layer.
  • the temperature rise on the heat-resistant resin eyebrow surface that comes into contact with the synthetic resin increases, and the temperature decreases Will also be smaller.
  • the shorter the time after the synthetic resin comes into contact with the mold wall the higher the mold surface temperature will be. The same effect can be obtained as when the mold temperature is greatly increased.
  • Figure 8 shows how the temperature of the polyimide surface of the thermal insulation layer changes with time since the resin came into contact with the surface. 0.4 seconds after the resin comes into contact with the mold surface, the mold must be coated to a thickness exceeding 0.1 mm with polyimide to keep the mold surface above the curing temperature of the synthetic resin. .
  • Heat resistance The thickness of the resin layer varies depending on the mold temperature and the softening temperature of the synthetic resin. Generally, the mold temperature is around 50 ° C and the softening temperature of the synthetic resin that is practically used is 10 ° C. The temperature is around 0 ° C or higher, which determines the thickness of the heat-resistant resin as the heat insulating eyebrows.
  • the synthetic resin reproduces the mold surface on the contact surface after the synthetic resin comes into contact with the mold wall surface. It takes time for the injection pressure to be applied to a certain degree, and the die surface temperature when the injection pressure is applied is thought to decrease.
  • the appearance tends to change suddenly due to the change in the flow rate of the resin.
  • a change in the appearance of the resin is suppressed by setting the thickness of the heat insulating member to a thickness exceeding 0.1 mm.
  • the appearance is improved by injection molding under the condition that the surface temperature is equal to or higher than the softening temperature of the synthetic resin.
  • FIG. 9 shows the flow pattern of the synthetic resin in the mold cavity
  • FIG. 10 shows that shear heat is generated by the flow of the resin.
  • Fig. 9 when the plasticized thermoplastic resin is injected into the mold cavity composed of the cooled mold 1 and 2, the injected synthetic resin contacts the cooled mold wall and solidifies immediately. Form eyebrows 13. Then, the synthetic resin that is drawn and injected advances in the solidified layer 13, reaches the flow front (F 10 w Front) 14, and then flows toward the mold wall 15, so-called Fountain F 1 ow. As shown in the velocity distribution curve 18, the flow velocity 16 of the synthetic resin is the highest at the center 17 of the mold cavity, and becomes slower as it approaches the solidified layer 13. The shear force shown in the shear rate distribution curve 19 is generated in the flowing synthetic resin, and heat is generated in proportion to the shear force.
  • This calorific value is extremely large when the injection speed is high, and is generated at a position in contact with the solidified layer, and functions to prevent the solidified layer from increasing.
  • Figure 10 shows how much heat is generated depending on the injection speed.
  • Fig. 10 shows the temperature distribution of the synthetic resin immediately after filling the mold by calculating the calorific value under the following conditions while changing the flow speed of the synthetic resin.
  • the heat generation is small, and the solidified layer is thickened during the flow by the low-speed flow, and the resin is filled in a state where the solidified eyebrows are thick.
  • injection molding is performed under extremely strict conditions in view of flow in this sense. It is estimated that thickening of the solidified layer in this way would worsen the SCR of the force-formed product.
  • the low-speed injection thickens the solidified layer and deteriorates the SCR.
  • a mold covered with a heat-resistant resin layer as a heat insulating layer is used to improve this. To use.
  • the solidified layer 20 that is formed immediately after injection is molded using a normal mold that is not covered with the heat insulating layer. It becomes thinner than.
  • the residual compressive stress of a sufficiently cooled molded article increases in proportion to C '/ S' (1 in Fig. 11.8), and the residual compressive stress is caused by the heat-resistant resin layer as a heat insulating layer. Larger than when molding with an uncoated mold.
  • a molded article molded with a mold covered with a heat-resistant resin layer as a heat insulating layer has a high resistance to soil rupture when stress is applied. It is presumed that this is the reason why the SCR of the injection molded article obtained according to the present invention becomes strong.
  • Figure 12 shows the change over time in the resin pressure applied to the mold wall during injection molding as a model difference between conventional injection molding and gas assist injection molding.
  • the pressure curves near the gate are denoted by A and a
  • the pressure curves near the flow end are denoted by Cc
  • the pressure curves near the middle of the flow are denoted by B and b.
  • the pressure applied to the vicinity of the gate rises in the curve of A and A 'and becomes the maximum in the full shot, and the pressure applied to the middle part of the resin flows increases in the curve of B and increases.
  • the pressure at the end of the flow reaches its maximum in the short shot, and the pressure applied near the flow end increases in the curve C, reaches the maximum in the full shot, and decreases with the dwell time.
  • the maximum value of each of A, B, and C is larger as the position in the molded article is closer to the gate, and the final applied pressure differs greatly depending on the position.
  • the resin is first injected at a high pressure, the injection of the resin is stopped during the injection, and a gas body with a pressure significantly lower than the resin injection pressure is injected. Satisfies the mold cavity.
  • the pressure applied near the gate first rises along the curve A, and When the resin is switched to a gas inside, the resin pressure at 24 becomes almost the same as that of the gas, and then changes at a constant pressure as shown by the a curve. After the gas is injected, the pressure in the middle of the resin flow rises as indicated by the curve b, becomes almost the same as the gas pressure at full shot, and is maintained at the pressure.
  • the pressure of the resin near the flow end is shown by curve c, which is almost the same as the gas pressure at the time of the full shot, and is almost maintained at the time of the dwell.
  • Gas assist injection molding is characterized in that the pressure near the gate, in the middle of the flow, and at the end of the flow are almost the same at full shot.
  • gas assist injection molding is widely used because the residual stress in the molded product becomes uniform and the dimensional accuracy of the molded product is improved.
  • the rise of resin pressure is slow, and the flow velocity in this part in the mold cavity is slow, and the molded product in this part It also has the drawback that the appearance and SCR are poor.
  • the present invention aims at improving the above-mentioned drawbacks by coating the surface of a mold body with a heat-resistant resin.
  • the glossiness, the sink mark and the roughness mark are improved, and an injection molded product excellent in appearance and SCR of the molded product can be obtained.
  • Die main body 1 Made of steel (S55C), the mold cavity has a side gate of 2 mm (thickness) X 100 mm x 100 mm. The mold surface is mirror-finished and chrome plated.
  • Die body 2 Made of steel (S55C), mold cavity is 3 mm (thickness) X 70 mm x 378 mm, rectangular shape, 5 mm x 5 mm The size of the rib is in the longitudinal direction and has a side gate at the corner.
  • the mold surface is mirror-like and chrome-plated.
  • Polyimide precursor and cured polyimide linear high molecular weight precursor solution “Trenice # 300” (manufactured by Toray Industries, Inc.) .
  • the performance of the cured polyimide was 300 ° C at Tg force, 0.005 ca1 / cm-sec at thermal conductivity, and the elongation at break was 60%. is there.
  • Polyimide coating mold Apply a polyimide precursor solution to each mold body, heat to 160 ° C to make partial imidization, and then apply the coating. The heating at 160 ° C. was repeated 2 to 8 times, and finally, heating was performed to 290 ° C. to make 100% imidization, and the mold surface was coated with polyimide. The surface is polished to a mirror surface, and the thickness of the polyimide is 0.025 mm, 0 mm. Make a mold covering mold of 0.5 mm, 0.075 mm, 0.1 mm, 0.15 mm, 0.16 mm, 0.175 mm.
  • Modified epoxy resin-coated mold A modified epoxy resin is applied to mold body 1, and heated to 50 ° C and then to 100 ° C to be cured. Polish the surface to make it mirror-like.
  • HIPS492 Rubber-reinforced polystyrene "Asahi Kasei Polystyrene 492" manufactured by Asahi Kasei Corporation
  • HIPS 495 Rubber reinforced polystyrene "Asahi Kasei Polystyrene 495" manufactured by Asahi Kasei Corporation
  • PMMA Metal acrylate resin "Delut 80N" manufactured by Asahi Kasei Kogyo Co., Ltd.
  • Example 1 Injection molding is performed with PMMA using the mold body 1 and a 0.175 mm thick polyimide coated mold of the mold body 1.
  • the molding conditions were as follows: the temperature of the injection cylinder was 260 ° C, the mold temperature was 60 ° C, and the injection pressure was changed to reduce the average flow velocity in the mold cavity of the synthetic resin to 13 mm ns. Molded by injection and high-speed injection of 23 Om mZ seconds. The SCR of the injection-molded product was measured by the break time, and is shown in Table 4.
  • Molded products using polyimide coated molds have improved SCR, especially at low speed injection.
  • HIPS 495 is injection-molded by using the mold body 1 and a polyimide mold having various thicknesses of the mold body 1.
  • the molding conditions were a cylinder temperature of 220 ° C and a mold temperature of 35 ° C.
  • the injection speed was changed by changing the injection pressure, and the thickness of the polyimide film was also changed.
  • the gloss of the molded article was measured and is shown in Figs. 14A and 14B.
  • the gloss of the molded article varies greatly depending on the flow velocity in the mold cavity of the synthetic resin.To obtain high gloss at low injection speeds with a flow velocity of 10 Omm ns or less
  • the thickness of the polyimide must be more than 0.1 mm, and preferably 0.15 mm or more.
  • the conventional high-speed injection molding, the conventional low-speed injection molding, and the mold body 2 and the mold body 2 covered with 0.16 mm thick polyimide are used.
  • Injection molding is performed by four types of molding methods: gas assist injection molding and oligomer assist injection molding.
  • HIPS492 is used as the synthetic resin, and the chemical foaming agent azodicarbonamide is blended with the PSST120 shown in Table 3 and Figure 2 as the oligomer. .
  • the molding is performed at a cylinder temperature of 230 ° C and a mold temperature of 40 ° C.
  • FIG. 15A and 15B A schematic diagram of a cross-section near the surface layer at the flow end of a molded product that was injection-molded using a polymide-coated mold and a Cr-mesh mold (mold body). These are shown in Figures 15A and 15B, respectively. These figures are based on transmission electron micrographs (TEM) (magnification: 500,000).
  • TEM transmission electron micrographs
  • Low-pressure injection molding methods such as gas-assist injection molding method, liquid-assist injection molding method, and oligomer-assist injection molding method of the present invention, and injection molding with a polyimide coated mold. Then, the molded product has improved gloss, sink mark, and roughness mark, and has the inherent advantages of low-pressure injection molding, such as low required mold clamp, reduced warpage of molded product, and molded product dimensional system. Can be maintained.
  • Example 2 Using the mold body 1 and the modified epoxy resin-coated molds having various thicknesses of the mold body 1, the same injection molding as in Example 2 is performed.
  • the low-pressure injection molding method of the present invention improves glossiness, sink mark, and heaviness mark, and improves the appearance and stress resistance of molded products. Injection molded products with excellent performance (SCR) can be obtained ⁇

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)

Abstract

La présente invention concerne un procédé de moulage d'une résine synthétique par injection basse pression, et faisant appel à un moule métallique, comprenant l'application d'une couche de résine thermorésistante sur une surface de paroi formant cavité, l'épaisseur de cette couche étant supérieure à 0,1 mm et inférieure ou égale à 0,5 mm. Selon ce procédé, l'injection se fait à basse vitesse, la vitesse d'écoulement dans la cavité de moulage de résine synthétique ne dépassant pas 100 mm/s. Le procédé de moulage par injection basse pression de la présente invention permet d'obtenir un produit moulé par injection présentant un meilleur brillant, sensiblement exempt de flaches et d'irrégularités, et d'un excellent aspect extérieur et d'une résistance élevée aux fendillements par contrainte.
PCT/JP1994/001499 1994-09-09 1994-09-09 Procede de moulage par injection basse pression Ceased WO1996007527A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/JP1994/001499 WO1996007527A1 (fr) 1994-09-09 1994-09-09 Procede de moulage par injection basse pression
CN94190340.0A CN1127491A (zh) 1994-09-09 1994-09-09 低压注塑方法

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
PCT/JP1994/001499 WO1996007527A1 (fr) 1994-09-09 1994-09-09 Procede de moulage par injection basse pression
CN94190340.0A CN1127491A (zh) 1994-09-09 1994-09-09 低压注塑方法

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WO1996007527A1 true WO1996007527A1 (fr) 1996-03-14

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Cited By (1)

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CN104249448A (zh) * 2013-06-27 2014-12-31 合肥杰事杰新材料股份有限公司 一种abs树脂低压注塑冰箱内胆的加工方法

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WO2011163040A1 (fr) * 2010-06-23 2011-12-29 The Procter & Gamble Company Produit moulé par injection à haute vitesse
CN104249433A (zh) * 2013-06-26 2014-12-31 合肥杰事杰新材料股份有限公司 一种用高抗冲聚苯乙烯低压注塑冰箱内胆的加工方法
CN104669643A (zh) * 2013-11-26 2015-06-03 比亚迪股份有限公司 制作纤维复合壳体的装置及方法
CN106426743A (zh) * 2016-10-07 2017-02-22 吉林省华翼汽车零部件有限公司 一种低压注塑靠背护板
CN110734291A (zh) * 2019-10-31 2020-01-31 陕西博鼎快速精铸科技有限责任公司 一种耐高温聚合物零件的陶瓷模具注塑成型的加工方法
CN112277235B (zh) * 2020-09-18 2022-05-17 中国航发北京航空材料研究院 一种超大尺寸聚合物玻璃的注射成型方法

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JPH06246797A (ja) * 1992-12-28 1994-09-06 Nippon Steel Chem Co Ltd 成形品外観へのヒケ防止方法および射出成形用金型

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CN104249448B (zh) * 2013-06-27 2018-03-02 合肥杰事杰新材料股份有限公司 一种abs树脂低压注塑冰箱内胆的加工方法

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