JPH08318534A - Mold assembly for molding thermoplastic resin and its cavity insert - Google Patents

Abstract

PURPOSE: To provide a mold assembly for molding a molded product based on a thermoplastic resin wherein maintenance of a cavity insert is easy; the insert is not broken in molding; no burr is generated in the molded product; and it can withstand use for a long period. CONSTITUTION: A mold assembly is composed of (1) molds 10, 20 for molding a molded product based on a thermoplastic resin, (2) a cavity insert 30 of 0.5-10mm thickness which is arranged inside the mold and constitutes a part of a cavity 40, and (3) a presser plate 32 for pressing an end part of the insert 30 which is arranged inside the mold, and constitutes a part of the cavity 40. A clearance (C) between the insert and the presser plate is at most 0.03mm, a presser margin (ΔS) of the presser plate to the nest is at least 0.1mm, and the thermal conductivity of a material constituting the insert 30 is at most 2×10<-2> cal/cm.sec.deg.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold assembly for molding a molded article based on a thermoplastic resin, and a nest used in such a mold assembly. More specifically, the invention relates to an injection molding method and an injection compression method. The present invention relates to a mold assembly that can improve a surface transferability of a molded product molded by a molding method, a blow molding method, or the like and can reliably mold a molded product having a mirror surface property, and a nest used in the mold assembly.

[0002]

2. Description of the Related Art A mold for molding a molded product based on a thermoplastic resin (hereinafter simply referred to as a mold) is usually made of a metal material such as carbon steel, stainless steel, aluminum alloy, copper alloy or the like. ing. Then, by injecting or injecting the molten resin into the cavity, which is a hollow portion formed in the mold, a molded product having a desired shape and having the mold surface of the cavity transferred is obtained.

When molding is performed using such a metal mold, it is not easy to bring the surface condition of the molded product close to the condition of the mold surface of the cavity. Usually, the mold is made of a metal material that is not deformed by high stress such as pressure caused by the injected resin, but these metal materials are also excellent in thermal conductivity. Therefore, when the molten resin injected or injected into the cavity comes into contact with the mold surface of the cavity, it immediately begins to cool. As a result, a solidified layer is formed on the portion of the molten resin that is in contact with the mold surface of the cavity, and defective appearance such as weld marks and flow marks is likely to occur in the molded product. Problems such as poor transfer also occur.

In order to solve these problems, in general, a method of injecting a molten resin at a high pressure to forcibly transfer the mold surface of the cavity to the surface of the molded article, or the mold temperature is changed. There is a method of delaying the development of the solidified layer of the molten resin at a high temperature to prevent the occurrence of weld marks and flow marks, and also to prevent the transfer failure of the mold surface of the cavity to the surface of the molded product. However, the former method leads to an increase in the size of molding equipment, an increase in the size of the mold itself, and an increase in the cost, and high-pressure filling of molten resin causes stress to remain inside the molded product. There is a problem that the quality of the product deteriorates. In the latter method, since the mold temperature is set to be slightly lower than the load deflection temperature of the resin used for molding to delay the development of the solidified layer, the cooling time of the resin in the cavity becomes longer, resulting in a molding cycle. There is a problem that it becomes longer and the productivity decreases.

[0005]

In order to solve these problems, for example, JP-A-55-55839, JP-A-61-100425, and JP-A-62-2089.
19, JP-A-5-111937, JP-A-5
-200789 gazette, Japanese Patent Publication No. 6-35134 gazette,
In Japanese Patent Laid-Open No. 6-218769, a low thermal conductive material is provided or attached to the cavity surface of a mold to delay the development of a solidified layer of resin filled in the cavity,
Methods have been proposed to prevent molding defects such as weld marks and flow marks.

When the low thermal conductive material is simply adhered to the cavity surface of the mold using an adhesive, the following problems occur. (A) When the clearance between the mold and the low thermal conductive material is small, due to the difference in linear expansion coefficient between the material forming the mold and the low thermal conductive material, the low thermal conductivity due to the temperature rise and temperature drop of the mold. The material is damaged. (B) The adhesive between the mold and the low thermal conductive material is melted by the heat of resin or the like, but if the clearance between the mold and the low thermal conductive material is large, if the molding is performed for a long time, the mold and the low thermal conductive material will not conduct. The molten resin penetrates between the material and burrs on the molded product.

Further, when minute cracks generated on the outer peripheral portion of the low thermal conductive material come into contact with the molten resin, distortion due to pressure and heat is applied to the cracked portion. There is a problem such as damage. Therefore, the durability of the mold as a whole is poor, and it is difficult to mass-produce molded products.

The low thermal conductive material may be made of heat resistant plastic in some cases. However, the low thermal conductive material has a low rigidity and further has a poor surface hardness. There is a problem that the material is easily scratched. Alternatively, there is a low thermal conductive material formed by forming a thin film of ceramic on the metal surface by chemical vapor deposition or the like, but the durability of the thin film is poor and there is a problem of peeling from the metal surface. Therefore, it is generally used only as a test mold or a simple mold, and cannot withstand long-term use.

Therefore, the object of the present invention is to maintain the insert easily, to prevent the insert made of a very brittle material such as ceramic or glass from being damaged during molding, to prevent burrs from being formed on the molded product, and to improve the long life. A mold assembly for molding a molded article based on a thermoplastic resin, which can endure use for a period of time, and can reliably transfer the state of the surface of the insert forming the cavity surface to the surface of the molded article, and such a metal mold. It is to provide a nest used or incorporated in a mold assembly.

[0010]

The nest of the present invention for achieving the above object is disposed inside a mold for molding a molded article based on a thermoplastic resin, and a part of a cavity. Which has a thermal conductivity of 2 ×
Zr of 10 ⁻² cal / cm · sec · deg or less
_{O 2, ZrO 2 -CaO, ZrO} 2 -Y 2 O 3, ZrO 2 -M
_{gO, K 2 O-TiO 2} , Al 2 O 3, Al 2 O 3 -TiC,
It is made of a ceramic selected from the group consisting of Ti ₃ N ₂ , 3Al ₂ O ₃ -2SiO ₂ or a glass selected from the group consisting of soda glass, quartz glass, heat-resistant glass and crystallized glass. Characterize.

A mold assembly for molding a thermoplastic resin according to the present invention for achieving the above object is (a) a mold for molding a molded article based on a thermoplastic resin, and (b) the mold. It is disposed inside the mold and constitutes a part of the cavity, and has a thickness of 0.5 mm to 10 mm, more preferably 1 mm to 7
mm, more preferably 2 to 5 mm nesting,
(C) A clearance plate disposed inside the mold and forming a part of the cavity for suppressing the end of the insert, and a clearance (C) between the insert and the press plate.
Is 0.03 mm or less (C ≦ 0.03 mm), and the pressing margin (ΔS) of the pressing plate with respect to the insert is 0.1 mm or more (ΔS ≧ 0.1 mm), and the heat of the material forming the insert is Conductivity is 2 × 10 ^-2 cal / cm · s
It is characterized by being less than or equal to ec · deg.

If the thickness of the insert is less than 0.5 mm, the heat insulating effect due to the insert is reduced, the molten resin filled in the cavity is rapidly cooled, and there is a possibility that appearance defects such as weld marks and flow marks occur. Get higher Also,
When fixing the insert to the inside of the mold, for example, a thermosetting adhesive may be used to adhere the insert to the inside of the mold. However, if the insert is less than 0.5 mm thick, When the film thickness becomes non-uniform, uneven stress remains in the insert, so that the surface of the molded product may undulate, or the insert may be damaged by the pressure of the injected molten resin. On the other hand, when the thickness of the insert exceeds 10 mm, the heat insulating effect of the insert becomes too large, and the molded product may be deformed after the molded product is taken out unless the cooling time of the resin in the cavity is extended. Therefore, problems such as extension of the molding cycle may occur.

The clearance (C) between the insert and the restraining plate is 0.03 mm or less, practically 0.00.
3 mm or more and 0.03 mm or less (0.003 mm ≦ C ≦
0.03 mm). The lower limit of the clearance is that when the restraint plate is attached, minute cracks are generated in the outer periphery of the insert, or the insert expands when the mold temperature rises, causing the insert to come into contact with the suppressor plate, and the outer periphery of the insert. The value may be set so as not to cause a problem that the nest is broken as a result of stress being applied to the fine cracks. Further, when the clearance (C) exceeds 0.03 mm, the molten resin enters between the nest and the restraining plate,
Cracks may occur in the nest, and burrs may occur on the molded product.

When the pressing margin (ΔS) is less than 0.1 mm,
When the minute cracks generated in the outer peripheral portion of the insert and the molten resin come into contact with each other, the crack generated in the insert may grow and the insert may be damaged.

After the insert is processed into a predetermined shape by grinding or the like, when the insert is not attached, there is no risk of the insert falling from the insert mounting portion provided inside the mold, or without using an adhesive. When the nest can be mounted on the nest mounting portion, the nest can be directly mounted on the nest mounting portion provided inside the mold without using an adhesive. Alternatively, the insert may be adhered to the insert mounting portion using a thermosetting adhesive selected from epoxy, urethane, acrylic, and the like. However, in order to prevent the nest from being distorted due to the influence of uneven thickness of the adhesive, it is desirable that the thickness of the adhesive used for the temporary fixing is as thin and uniform as possible.

The clearance (D) between the insert-mounting part of the mold and the insert may be as close as possible to 0, but practically it is preferably 0.005 mm or more. Here, the clearance (D) refers to the clearance between the nest mounting portion of the mold and the nest along the surface forming the cavity of the nest (hereinafter also referred to as the cavity surface of the nest). Although it depends on the linear expansion coefficient of the material forming the nest,
If the clearance (D) is too small, it may not be possible to prevent damage to the insert due to the difference in linear expansion coefficient between the material forming the mold and the material forming the insert. Therefore, the insert clearance (D) is The value may be set so that such a problem does not occur. Note that if the clearance (D) is made too large, there is a risk that the nest will be damaged due to the positional shift and positional stability of the nest being insufficient.
Therefore, the clearance (D) is preferably about 2 mm or less.

The thermal conductivity of the material forming the insert is 2 × 10 5 to prevent the molten resin in the cavity from being rapidly cooled.
^-2 cal / cm · sec · deg or less is required. When a nest is made using a material having a thermal conductivity exceeding this value, the molten resin in the cavity is rapidly cooled by the nest, so a mold made of ordinary carbon steel without a nest is used. Only the same appearance as the molded product can be obtained.

The nest of the present invention or the nest used in the mold assembly for molding the thermoplastic resin of the present invention is widely used, and is widely made of zirconia-based material, alumina-based material, K ₂ O-Ti.
A ceramic selected from the group consisting of O ₂ or
It can be made from a glass selected from the group consisting of soda glass, quartz glass, heat-resistant glass, and crystallized glass. Among them, ceramics composed of ZrO ₂ or ZrO ₂ —Y ₂ O ₃ or crystallized glass It is preferable to make them.

The surface roughness R of the cavity surface of the nest
It is preferable that the _max is 0.03 μm or less and the linear expansion coefficient of the material forming the insert is 12 × 10 ⁻⁶ / deg or less. Here, the linear expansion coefficient is an average value from 50 ° C to 300 ° C. The ceramic or glass forming the nest can be processed by grinding,
Depending on the application (for example, when the molten resin is brought into contact with the cavity surface of the nest in order to mold the mirror surface portion of an automobile mirror or the like), it is desirable that the surface roughness R _max of the cavity surface of the nest be 0.03 μm or less. . Surface roughness R
_{If the maximum value} exceeds 0.03 μm, the specularity may be insufficient and the properties required for the molded product may not be satisfied. The surface roughness R _max was measured according to JIS B0601.

In order to set the surface roughness R _max of the cavity surface of the insert to 0.03 μm or less, the surface roughness R _max is 0.03 μm with respect to the prepared cavity surface of the insert.
For example, diamond lapping may be performed until the temperature becomes the following, and further, if necessary, lapping with cerium oxide may be performed. Lapping can be performed using a lapping machine or the like. Compared with the usual polishing of carbon steel or the like, for example, in the case of crystallized glass, a mirror surface can be obtained at a cost of about 1/2, so that the manufacturing cost of the mold assembly can be reduced.

When molding a molded article having a matte or heller-lined surface, it is not necessary to set the surface roughness R _max of the cavity surface of the insert to 0.03 μm or less.

If the linear expansion coefficient is 12 × 10 ^-6 / deg or less, it is possible to effectively prevent the deformation and damage of the insert due to the expansion and contraction of different materials such as the mold and the insert. it can. For example, when forming a molded product by attaching a mold to a mold made of carbon steel (in some cases, a core), the mold and the mold are molded by the heat of the molten resin and the heat of water or oil of the mold temperature controller. Both thermally expand. Therefore, if the linear expansion coefficient exceeds the above value, the nest may be damaged due to the difference in linear expansion coefficient unless the clearance (D) between the nest mounting portion and the nest is considerably increased. When the insert is made of crystallized glass, the coefficient of linear expansion is 1 × 10.
It can be ^-6 / deg or less.

Alternatively, the nesting has a crystallinity of 10%.
As described above, it is preferable that the glass is made of crystallized glass having a crystallinity of 60% or more, and more preferably 70 to 90%. When the crystallinity is 10% or more, the crystals are uniformly dispersed in the entire glass, and the thermal shock strength and the interfacial peeling property are dramatically improved, so that the breakage of the nest during molding of the molded product can be significantly reduced. it can. When the crystallinity is less than 10%, the performance is almost the same as that of the amorphous glass, so that there is a drawback that interface peeling easily occurs from the surface during molding. In this case, the surface roughness R _max of the cavity surface of the insert is 0.03 μm or less, and the linear expansion coefficient of the crystallized glass forming the insert is 1 × 10 ⁻⁶ / d.
It is preferable that the heat shock strength is 400 ° C. or more and the heat resistance is not more than EG.

100 mm × 100 heated to a predetermined high temperature
The thermal shock strength is measured by measuring whether or not cracks occur in the glass when the glass of mm × 3 mm is thrown into water at 25 ° C. A thermal shock strength of 400 ° C means 100 mm x 100 heated to 400 ° C.
This means that when a glass of mm × 3 mm is thrown into water at 25 ° C., the glass does not crack. This thermal shock strength can be obtained only at a value of around 180 ° C. even in heat resistant glass. Therefore, when the resin melted at a higher temperature comes into contact with the cold insert, the insert is distorted,
The nest may be damaged. The thermal shock strength is also related to the crystallinity of the glass, and if the insert is made of crystallized glass having a crystallinity of 10% or more, it is possible to reliably prevent the insert from cracking during molding.

When the nest is made of ceramic, at least one thin film layer made of the above-mentioned material may be provided on the surface of the nest by a surface treatment technique such as ion plating, thereby filling the pores of the ceramic. Therefore, the surface characteristics of the molded product can be further improved.

When the nest is made of amorphous glass such as soda glass, heat resistant glass, and quartz glass, a thermoplastic resin excellent in affinity and adhesiveness with these materials (for example, polyamide 6 resin, polyamide 66 resin, Polyamide MX
When molding is performed using a polyamide resin such as D6 resin or a polyester resin such as polybutylene terephthalate resin (PBT resin) or polyethylene terephthalate resin (PET resin), the nest and the resin firmly adhere to each other, and At the time of releasing from the mold, there may be a problem that the insert causes interface separation from the surface. In such a case, the nest may be made of crystallized glass.
Since crystallized glass has a high strength between crystal grains, interfacial peeling does not occur from its surface, and there is no problem that the insert is broken even if molding is performed for a long time.

Here, the crystallized glass means 1600 after adding a small amount of nucleating agent of TiO ₂ and ZrO _{2 to} the raw glass.
After being melted at a high temperature of ° C or higher, it is molded by a press, blow, roll, cast method, etc., and further heat-treated for crystallization to obtain Li ₂ O-Al ₂ O ₃ -Si in the glass.
An example is a crystal in which an O ₂ type crystal is grown and a main crystal phase is a β-eucryptite type crystal and a β-spodumene crystal. Alternatively, CaO-Al ₂ O ₃ -
After melting SiO ₂ glass at 1400 to 1500 ° C,
After transferring to water and crushing to reduce the particle size, the particles are accumulated, molded into a plate on a refractory setter, and then heat-treated to give β-
The thing which the wollastonite crystal phase produced | generated can be illustrated. _{Furthermore, SiO 2 -B 2 O 3 -Al} 2 O 3 -Mg
O-K ₂ O-F-based glass heat-treating in that to produce a mica crystal and those that cordierite crystals by heat-treating MgO-Al ₂ O ₃ -SiO ₂ based glass containing nucleating agent is generated Can be illustrated.

When the insert is made of ceramic, the protruding material may be transferred to the surface of the molded product because the material of the insert is porous. However, the crystallized glass has the advantages that the crystal particles are fine, the adhesive force between the particles is excellent, and that the surface of the molded product is likely to be a mirror surface because it is not porous.

In these crystallized glasses, the ratio of crystal particles present in the glass substrate can be expressed by an index of crystallinity. The crystallinity can be measured by using an analytical instrument such as X-ray diffraction.

The material forming the insert can be easily processed into irregularities, curved surfaces, etc. by ordinary grinding, and can be manufactured into any shape other than a rather complicated shape. A nest can be produced by putting ceramic powder or molten glass in a mold, press-molding it, and then heat-treating it. Further, the nest can also be produced by naturally shaping the glass plate-like object placed in the mold in the furnace. The lapping process can be easily performed in the final step.

When molding a molded product having a three-dimensional shape or a curved surface, the mold fitting portion of the mold is fitted to the back surface of the mold (the surface opposite to the cavity surface of the mold and facing the mold). It suffices to machine and grind the restraining plate according to the curvature of the cavity surface of the nest. Also in this case, ΔS ≧ 0.1 mm, C ≦ 0.03 m
While maintaining the relationship of m, attach the insert to the insert attachment part of the mold, and hold the insert with the plate.

When the insert made by heat bending of the glass is mounted on the mold, the end of the insert is not necessarily parallel to the insert mounting part of the mold, but the insert and the insert mounting part of the mold are different from each other. The clearance (D) between them may be set to 2 mm or less, and the insert may be attached to the mold while paying attention to the occurrence of damage to the end of the insert. It is also conceivable to grind the end of the insert made of glass after heat bending to make it parallel to the insert part of the mold, but since the part with a fairly sharp angle is generated in the insert, There is a possibility that the nest will be damaged when it is attached to. Therefore, it is desirable to grind the insert mounting portion of the mold according to the angle of the end of the insert and then mount the insert to the insert mounting portion of the mold.

The mold comprises a movable mold part and a fixed mold part. At least one of the fixed mold section and / or the movable mold section is provided with a nest mounting section for mounting a nest. In the mold assembly of the present invention, the part of the mold to which the insert is attached may be configured via the core attached to the mold. In order to prevent warping of the molded product due to shrinkage of the resin after molding, consider the thermal conductivity and thickness of the fixed mold part, the movable mold part and the insert, and use the fixed metal part when taking out the molded product. It is desirable to make the temperature difference between the mold part and the movable mold part as close as possible.

Polystyrene resin, polyethylene resin, as a resin for molding using the mold assembly of the present invention,
Thermoplastic resins such as general-purpose plastics such as polypropylene resin, engineering resins such as polycarbonate resin, polyacetal resin and polyamide resin, super engineering plastics such as polyphenylene sulfide resin and liquid crystal polymer can be mentioned.

Particularly, when using plastics such as engineering plastics and super engineering plastics which have excellent heat resistance and strength but have poor moldability, molding is usually carried out at a mold temperature of 80 ° C. or higher. A lot of appearance defects occur. However, since the heat insulating effect is obtained by using the mold assembly of the present invention, it is possible to obtain a molded product having good appearance characteristics even if the mold temperature is 80 ° C. or lower. Further, a resin to which a filler is added may be used. In this case, a phenomenon in which the filler is not deposited on the surface of the molded product does not occur, and a molded product excellent in appearance characteristics such as specularity can be obtained. This is because cooling and solidification of the injected molten resin can be delayed by nesting, and as a result, the fluidity and transferability of the molten resin can be improved.

Moreover, since the fluidity of the molten resin is improved, the injection pressure of the molten resin can be set low, and the stress remaining in the molded product can be relaxed. As a result, the quality of the molded product is improved. Further, since the injection pressure can be reduced, the mold can be made thinner, the molding apparatus can be downsized, and the cost of the molded product can be reduced.

The molding method using the mold assembly of the present invention includes an injection molding method, an injection compression molding method, a multicolor molding method, a gas assist molding method, which are generally used for molding a thermoplastic resin. A blow molding method can be exemplified.

[0038]

The insert of the present invention is made of a material having a low coefficient of thermal expansion, and is made independently of the mold and disposed inside the mold, so that the insert has a large heat insulating effect. Not only that, maintenance of the nest is easy. If the nest is made of crystallized glass, the coefficient of linear expansion is low,
It is possible to manufacture a nest that is resistant to thermal shock and is less likely to be damaged or cracked.

In the mold assembly of the present invention, the heat insulation effect due to the nesting is great, quenching of the molten resin filled in the cavity can be suppressed, and appearance defects such as weld marks and flow marks occur. Can be effectively prevented. Moreover, the nesting is suppressed by the restraint plate within the predetermined clearance (C) and the restraining margin (ΔS), so that the appearance of the end of the molded product is not spoiled and burrs do not occur at the end of the molded product. Furthermore, since the fine cracks generated in the outer peripheral portion of the insert and the molten resin do not contact each other, the insert is not damaged.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings based on the embodiments.

(Embodiment 1) A specific example of the mold assembly of the present invention is shown in FIG. Also, a schematic end view of the mold assembly during assembly is shown in FIG.
(B) and (C).

The size of the cavity 40 in the mold assembly of Example 1 is 1000.00 mm × 100.00 mm.
It is × 2.00 mm, and the shape is a rectangular parallelepiped. Example 1
In the above, the insert 30 was made from quartz glass by grinding. The size of the nest 30 is 101.00 mm x
It is 101.00 mm x 3.00 mm. The cavity surface 31 of the nest 30 was polished and finished using a diamond grindstone and a cerium oxide grindstone, and the surface roughness R _max of the cavity surface 31 of the nest was set to 0.02 μm. The thermal conductivity of the quartz glass used is 0.32 × 10
^{It is −2} cal / cm · sec · deg, and the coefficient of linear expansion is 0.58 × 10 ⁻⁶ / deg.

The fixed mold part 10 was made of carbon steel S55C. Inner dimension of the nesting part 11 is 101.20mm
A cutting process was performed so that the depth was × 101.20 mm and the depth was 3.02 mm, and the fixed mold part 10 was provided with the insert mounting part 11. Next, the nest 30 was temporarily fixed in the nest mounting portion 11 by using a two-component curing type epoxy adhesive (not shown) (see FIG. 1B). After temporary fixing, the clearance (D) between the insert 30 and the insert mounting part 11 was measured using a gap gauge, and the minimum clearance was 0.
It was 05 mm.

The restraining plate 32 was made of carbon steel S55C. The inner size of the holding plate 32 is 100.00 mm
It was set to × 100.00 mm. After the pressing plate 32 was cut, it was fixed to the fixed mold part 10 using screws (not shown) (see (C) of FIG. 1). The clearance (C) between the nest 30 and the restraint plate 32 is 0.0 on average.
It was 192 mm. Further, the pressing margin (ΔS) of the pressing plate 32 with respect to the insert 30 was 1.00 mm. The gate portion is not shown in FIG. 1 (C).

On the other hand, the movable mold part 20 was made of carbon steel S55C.

After the completed mold assembly was attached to the molding apparatus, the mold assembly was heated to 130 ° C. using a mold temperature controller and then rapidly cooled to 40 ° C. No damage such as cracking occurred in the inserted nest 30.

A molding machine manufactured by Nissei Plastic Industry Co., Ltd.
The mold assembly was heated to 60 ° C using a PS-80 injection molding machine. Injection molding was performed using a glass fiber-added polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., GS2020MKR, added 20% by weight of glass fiber) as the thermoplastic resin. The molding conditions are
Mold temperature 60 ° C, resin temperature 310 ° C, injection pressure 50
It was set to 0 kgf / cm ² -G. After injecting a predetermined amount of molten resin into the cavity 40 through the gate portion 13, 20
The molded article was taken out of the mold assembly after a second.

Despite the low mold temperature, the surface of the molded product has a mirror surface property up to the end of the molded product, and the surface image clarity measuring device (manufactured by Suga Test Instruments: ICM-2DP) is used. As a result of measuring the surface characteristics of the molded product, it had a very high specularity of 90% with respect to 100% of perfect specular surface. The mold temperature without the insert is 120 to 140 ° C.
Had to be set to.

Although molding was continuously carried out for 10,000 cycles, the nest 30 did not suffer any damage such as cracking.

(Comparative Example 1) A schematic partial end view of the mold assembly used in Comparative Example 1 is shown in FIG. 200
Fixed mold part 10 made from carbon steel S55C having a mirror-finished cavity surface polished with No. 0 paper,
Also, the same thermoplastic resin as in Example 1 is used by using the mold assembly including the movable mold section 20 having the same structure as in Example 1, and the molding conditions are the same as in Example 1. Molded. However, the fluidity of the molten resin in the cavity 40 was poor, and the cavity 40 could not be completely filled with the molten resin. Therefore, the injection pressure is 200k
Gf / cm ² -G was increased, and molding was performed at 700 kgf / cm ² -G. The obtained molded product had molding defects such as flow marks and wrinkles. As a result of measuring the surface characteristics of the molded product with a surface image clarity measuring device, perfect mirror surface 1
It was 5% with respect to 00%, and the specularity was remarkably deteriorated as compared with Example 1.

Comparative Example 2 In Comparative Example 2, the same nest 30 as in Example 1 was used. In addition, the movable mold part 2
The structure of 0 was the same as in Example 1. The fixed mold part 10 was made from carbon steel S55C. Unlike the first embodiment, the inner dimensions of the nesting attachment portion 11 are 101.20 mm × 101.
Cutting processing was performed so that the depth was 20 mm and the depth was 5.02 mm, and the fixed mold part 10 was provided with the nesting part 11.
Next, the nest 30 having a thickness of 3.00 mm was temporarily fixed in the nest mounting portion 11 by using a two-component curing type epoxy adhesive. As shown in the schematic partial end view of FIG. 3B, in Comparative Example 2, unlike Example 1, the nest 30
Is not suppressed by the plate.

Then, the same thermoplastic resin as in Example 1 was used, and molding was performed under the same molding conditions as in Example 1.
As a result, the end of the molded product had an ugly appearance, and in the fifth cycle of molding, the outer periphery of the insert 30 made of quartz glass was damaged.

(Comparative Example 3) In the mold assembly of Example 1, the clearance (C) between the pressing plate 32 and the insert 30 is 0.003 mm, 0.02 mm, 0.04.
Instead of mm, the same thermoplastic resin as in Example 1 was used, and molding was performed under the same molding conditions as in Example 1. As a result, when the clearance (C) was 0.04 mm, the molten resin entered between the insert 30 and the holding plate 32, and the molded product could not be taken out from the mold assembly during mold release. When the clearance (C) was 0.003 mm and 0.02 mm, these problems did not occur at all.

(Comparative Example 4) In the mold assembly of Example 1, the pressing margin (ΔS) of the pressing plate against the insert was
It was set to 0.05 mm. Using the same thermoplastic resin as in Example 1, molding was performed under the same molding conditions as in Example 1.
As a result, cracks grew from the outer peripheral portion of the insert, and after 10 cycles of molding, cracks were generated on the entire surface of the insert.

(Example 2) In Example 2, the nest 30 was made of crystallized glass made of spodumene type crystal (Nippon Electric Glass Co., Ltd., trade name Neoceram N-11, crystallinity: 90%, density: 2). 0.50 g / cm ³ ) was used. The cavity surface 31 of the insert 30 was polished and finished with a diamond grindstone and a cerium oxide grindstone to have a surface roughness R _max of 0.02 μm. The structure of the mold assembly and the size and size of each element were the same as in the first embodiment. In addition, the measurement results of the clearance (C), the clearance (D) and the suppression margin (ΔS) were the same as in Example 1. The thermal conductivity of the crystallized glass used was 0.4 × 10 ^-2 cal / cm · sec · deg,
The linear expansion coefficient is 0.8 × 10 ⁻⁶ / deg and the thermal shock temperature is 800 ° C.

After the completed mold assembly was attached to the molding apparatus, the mold assembly was heated to 130 ° C. using a mold temperature controller and then rapidly cooled to 40 ° C. No damage such as cracking occurred in the produced nest 30.

The mold assembly was heated to 60 ° C. using Example 1 and the molding apparatus. Injection molding was performed using glass fiber-added polyamide MXD6 resin (Mitsubishi Engineering Plastics Co., Ltd., Lenny 1002F, glass fiber 30% by weight added) as the thermoplastic resin. The molding conditions were a mold temperature of 60 ° C., a resin temperature of 280 ° C., and an injection pressure of 400 kgf / cm ² -G. 20 seconds after injecting a predetermined amount of molten resin into the cavity 40, the molded product was taken out of the mold assembly.

The surface of the molded product has a mirror surface property even to the end of the molded product despite the low mold temperature, and the surface characteristics of the molded product are measured by a surface image clarity measuring device. As a result,
It had a very high specularity of 95% against 100% of the perfect specular surface. The mold temperature without the insert is
It was necessary to set the temperature to about 100 ° C.

Although molding was continuously performed for 10,000 cycles, no damage such as cracking occurred in the insert 30.

(Comparative Example 5) The same insert made of crystallized glass as in Example 2 was used, and the insert was attached to the fixed mold part having the same structure as in Comparative Example 2. The clearance (D) between the insert and the insert part is 0 mm and 0.5 mm.
And Also, the restraint plate was not attached. Then, using the same thermoplastic resin as in Example 2,
Molding was performed under the same molding conditions as. As a result, when the clearance (D) is 0 mm, cracks are generated from the outer peripheral portion of the insert during molding, and when the clearance (D) is 0.5 mm, the appearance of the end of the molded product is ugly and the molding 20
At the cycle, burrs were generated on the outer peripheral portion of the molded product.

Comparative Example 6 In the mold assembly of Example 2, the clearance (C) between the pressing plate and the insert was changed to 0.003 mm, 0.02 mm and 0.04 mm, and the same as Example 2. Example 2 using the thermoplastic resin of
Molding was performed under the same molding conditions as. As a result, when the clearance (C) was 0.04 mm, the molten resin invaded between the insert and the holding plate, and the molded product could not be taken out from the mold assembly at the time of mold release. When the clearance (C) was 0.003 mm and 0.02 mm, these problems did not occur at all.

(Comparative Example 7) The nest was replaced with quartz glass,
Clear the clearance (C) between the restraining plate and the nest to 0.
Molding was performed in the same manner as in Comparative Example 6 except that the thickness was set to 02 mm and 0.04 mm. As a result, when the clearance (C) was 0.04 mm, the molten resin invaded between the insert and the holding plate, and the molded product could not be taken out from the mold assembly at the time of mold release. Clearance (C) is 0.0
In the case of 2 mm, although molding could be performed up to 20 cycles without any problem, the interlayer strength of the quartz glass is lower than the adhesion between the quartz glass and the polyamide MXD6 resin, and therefore the quartz glass nest undergoes interfacial peeling, resulting in a nesting. Was damaged.

(Comparative Example 8) In the mold assembly of Example 2, the pressing margin (ΔS) of the pressing plate against the insert is
Molding was performed under the same molding conditions as in Example 2, using a thermoplastic resin similar to that in Example 2 with a thickness of 0.05 mm. As a result, cracks grew from the outer periphery of the insert made of crystallized glass, and cracks occurred on the entire surface of the insert after 10 cycles of molding.

(Embodiment 3) A schematic partial end view of a mold assembly according to Embodiment 3 is shown in FIG. Cavity 4
The size of 0 was 200.00 mm × 50.00 mm, the cavity thickness was 2.00 mm, and the radius of curvature of the cavity surface 31 of the insert 30 was 500 mm. The nest 30 is
Thickness 3.00 mm, size 201.00 mm × 51.
It is made of crystallized glass processed to have a radius of curvature of 00 mm and a radius of curvature of 500 mm. The cavity surface 31 of the insert 30 was surface-polished with a diamond grindstone and a cerium oxide grindstone to have a surface roughness R _max of 0.02 μm. The characteristics and physical properties of the crystallized glass used in Example 3 are the same as those of the crystallized glass used in Example 2.

The fixed mold part 10 was made of carbon steel S55C. Inner size of the nesting part 11 is 201.20 mm
The fixed mold part 10 was provided with the nesting attachment part 11 by performing cutting work so that the depth was × 51.20 mm and the depth was 3.02 mm. The radius of curvature of the bottom of the insert mounting part 11 was adjusted to the radius of curvature of the cavity surface of the insert 30 that faces the insert mounting part. Next, the nest 30 was temporarily fixed in the nest mounting portion 11 with a two-component curing type epoxy adhesive (not shown). After temporary fixing, insert 30 using a gap gauge.
When the clearance (D) of the insert mounting portion 11 was measured, the minimum clearance was 0.07 mm.

The restraining plate 32 was made of carbon steel S55C. The radius of curvature of the surface of the pressing plate 32 facing the nest 30 was set to 500 mm. After the pressing plate 32 was cut, it was fixed to the fixed mold part 10 with screws (not shown). The clearance (C) between the insert 30 and the holding plate 32 was 0.019 mm on average.
Further, the pressing margin (ΔS) of the pressing plate 32 with respect to the insert 30 was 1.00 mm.

The movable mold part 20 was made of carbon steel S55C. The radius of curvature of the surface forming the cavity is 500
mm.

After the completed mold assembly was attached to the molding apparatus, the mold assembly was heated to 130 ° C. using a mold temperature controller and then rapidly cooled to 40 ° C. No damage such as cracking occurred in the produced nest 30.

Using the same molding apparatus as in Example 1, the mold assembly was heated to 60 ° C. As a thermoplastic resin, glass fiber-added polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., Iupilon GS2020M
Injection molding was performed using R2 and 20% by weight of glass fiber). Molding conditions were a mold temperature of 60 ° C., a resin temperature of 300 ° C., and an injection pressure of 500 kgf / cm ² -G. 20 seconds after injecting a predetermined amount of molten resin into the cavity 40, the molded product was taken out of the mold assembly.

The surface of the molded product has a mirror surface property even to the end of the molded product even though the mold temperature is low, and the surface characteristics of the molded product are measured by a surface image clarity measuring machine. As a result,
It had a very high specularity of 90% against 100% of perfect specular surface.

Although molding was continuously performed for 10,000 cycles, the nesting 30 did not suffer any damage such as cracking.

The present invention has been described above based on the preferred embodiments, but the present invention is not limited to these embodiments. The conditions described in the examples and the materials used are examples, and the structure of the mold assembly is also an example, and can be appropriately changed. The shapes and sizes of the nests and the holding plates are also examples, and the design can be appropriately changed depending on the shape of the injection-molded product to be molded. The nesting plate and the restraining plate may be provided on the movable mold part or both the fixed mold part and the movable mold part, as required. Alternatively, as shown in a schematic partial end view in FIG. 2B, a portion of the fixed mold part 10 to which the insert 30 is attached is
It can also be composed of the core 12 attached to the mold.
In this case, the core 12 is provided with a nest mounting portion.

[0073]

INDUSTRIAL APPLICABILITY The insert according to the present invention not only has a large heat insulating effect, but also allows easy maintenance of the insert. Further, in the mold assembly of the present invention, it is possible to suppress the rapid cooling of the molten resin filled in the cavity, and it is possible to effectively prevent appearance defects such as weld marks and flow marks from occurring. it can. Moreover, in the mold assembly of the present invention, the nesting is suppressed even if the molding is performed for a long time by restraining the nesting by the restraining plate within the range of the predetermined clearance (C) and the restraining margin (ΔS). It is possible to easily and inexpensively manufacture a mold assembly having a mirror surface property without being damaged. In addition, the appearance of the end of the molded product is not impaired, the occurrence of burrs at the end of the molded product can be prevented, the defect rate of the molded product can be reduced, and the homogenization and high quality of the molded product can be achieved. It is possible to reduce the manufacturing cost.

By forming the insert from the crystallized glass, a molded product having excellent mirror surface property and transfer property can be easily obtained. Moreover, if the insert is made of crystallized glass, it is possible to make the insert having a low linear expansion coefficient, strong against thermal shock, and less likely to be damaged or cracked.

Further, since the fluidity of the molten resin is improved, the injection pressure of the molten resin can be set low, so that the stress remaining in the molded product can be relieved and the quality of the molded product is improved.
Further, since the injection pressure can be reduced, the mold can be made thinner, the molding apparatus can be downsized, and the cost of the molded product can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic partial end view of a preferred embodiment of a mold assembly of the present invention, and a schematic partial end view of the mold assembly during assembly.

FIG. 2 is a schematic partial end view of another preferred embodiment of the mold assembly of the present invention.

FIG. 3 is a schematic partial end view of a mold assembly according to a comparative example.

[Explanation of symbols]

 10 Fixed Mold Part 11 Nesting Mounting Part 12 Core 20 Movable Mold Part 21 Core Mounting Part 21 30 Nesting 31 Nesting Cavity Surface 32 Suppression Plate 40 Cavity

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location // B29K 101: 12 (72) Inventor Toshiaki Izumida 5-6-2 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Ryo Engineering Plastics Co., Ltd. Technical Center (72) Inventor Akira Yotsuji 2-3-11-1101 Hiranocho, Uchino-cho, Chuo-ku, Osaka-shi, Osaka Koki Engineering Co., Ltd.

Claims (13)

[Claims] 1. A nest, which is disposed inside a mold for molding a molded article based on a thermoplastic resin and constitutes a part of a cavity, having a thermal conductivity of 2 × 10 ^-2 cal. / Cm · sec · deg or less, ZrO ₂ , ZrO ₂ —CaO, ZrO ₂ —Y ₂ O
_{3, ZrO 2 -MgO, K 2} O-TiO 2, Al 2 O 3, Al
_From a ceramic selected from the group consisting of ₂ O ₃ -TiC, Ti ₃ N ₂ , 3Al ₂ O ₃ -2SiO ₂ , or a glass selected from the group consisting of soda glass, quartz glass, heat resistant glass, and crystallized glass. Nesting characterized by being made. 2. The nesting according to claim 1, wherein the nesting is made of a ceramic composed of ZrO ₂ or ZrO ₂ —Y ₂ O ₃ or crystallized glass. 3. The surface roughness R _max of the surface forming the cavity of the insert is 0.03 μm or less, and the linear expansion coefficient of the material forming the insert is 12 × 10 ⁻⁶ / deg or less. The nesting according to claim 1. 4. The nest according to claim 1, wherein the nest is made of crystallized glass having a crystallinity of 10% or more. 5. The nest according to claim 1, wherein the nest is made of crystallized glass having a crystallinity of 60% or more. 6. The surface roughness R _max of the surface forming the cavity of the insert is 0.03 μm or less, and the linear expansion coefficient of the crystallized glass forming the insert is 1 × 10 ⁻⁶ / deg or less,
The nest according to claim 4 or 5, wherein the thermal shock strength is 400 ° C or higher. 7. (a) A mold for molding a molded article based on a thermoplastic resin; and (b) a mold which is disposed inside the mold and constitutes a part of a cavity and has a thickness of 0. A mold assembly comprising: a nest of 5 mm to 10 mm; and (c) a restraining plate which is disposed inside the mold and constitutes a part of a cavity and which suppresses an end of the nest. Clearance between the restraint plate is 0.0
It is 3 mm or less, and the pressing margin of the pressing plate for the insert is 0.1 mm or more, and the thermal conductivity of the material forming the insert is 2 × 10 ^-2 cal /
A mold assembly for molding a thermoplastic resin, wherein the mold assembly has a size of not more than cm · sec · deg. 8. Nesting is ZrO ₂ , ZrO ₂ —CaO, Z
_{rO 2 -Y 2 O 3, ZrO} 2 -MgO, K 2 O-TiO 2, A
_{l 2 O 3, Al 2 O} 3 -TiC, Ti 3 N 2, 3Al 2 O 3 -2
The heat according to claim 7, which is made of a ceramic selected from the group consisting of SiO ₂ or a glass selected from the group consisting of soda glass, quartz glass, heat-resistant glass, and crystallized glass. Mold assembly for molding plastic resin. 9. The metal for molding a thermoplastic resin according to claim 8, wherein the insert is made of a ceramic composed of ZrO ₂ or ZrO ₂ —Y ₂ O ₃ or crystallized glass. Mold assembly. 10. The surface roughness R _max of the surface forming the cavity of the insert is 0.03 μm or less, and the linear expansion coefficient of the material forming the insert is 12 × 10 ⁻⁶ / deg or less. The mold assembly for molding a thermoplastic resin according to claim 8. 11. The nesting is made of crystallized glass having a crystallinity of 10% or more.
A mold assembly for molding a thermoplastic resin according to item 1. 12. The nesting is made of crystallized glass having a crystallinity of 60% or more.
A mold assembly for molding a thermoplastic resin according to item 1. 13. The surface roughness R _max of the surface forming the cavity of the insert is 0.03 μm or less, and the linear expansion coefficient of the crystallized glass forming the insert is 1 × 10 ⁻⁶ / deg or less and the thermal shock strength. Is 400 ° C. or higher, and the mold assembly for molding a thermoplastic resin according to claim 11 or 12.