WO2014132702A1 - Insulated mold and molding manufacturing method - Google Patents

Abstract

Provided are: an insulated mold with which it is possible to improve gas extraction from the cavity and to form moldings, which have satisfactory surface mold transferability and, in the case of crystalline thermoplastic resins, satisfactory surface crystallinity, by increasing the thickness of the gas vents while holding the length of burrs generated in the gas vents to conventional levels; and a molding manufacturing method using said insulated mold. The insulated mold for forming moldings obtained from a resin composition comprising a thermoplastic resin is provided with an insulated mold body with gas vents and an insulating layer formed on the inner surface of the mold. When forming a molding under conditions in which the mold transferability of the molding surface or the crystallinity at the molding surface is in a desired range using the insulated mold or a non-insulated mold, the thickness of the gas vents of the insulated mold is greater than that of the non-insulated mold in the range in which the ratio of the lengths of burrs occurring in the gas vents for the insulated mold and the non-insulated mold is 0.9 - 1.1.

Description

Insulating mold and method for producing molded product

The present invention relates to a heat insulating mold and a method for producing a molded product.

Thermoplastic resins are used in a wide range of fields such as interior parts and housings of home appliances, exterior and interior parts of automobiles, etc. because of their excellent moldability and relatively high physical properties such as mechanical strength.

As described above, the thermoplastic resin is excellent in moldability and physical properties, but if the appearance is poor due to the gas generated during molding or the crystalline thermoplastic resin, the crystallization does not proceed sufficiently and the predetermined physical properties are not exhibited. And appearance defects due to post-shrinkage may occur. The term “post-shrinkage” means that the crystallized thermoplastic resin contained in the molded product is crystallized by heat applied to the molded product under the use environment, and the size of the molded product is changed by this crystallization.

Gas generated from the air in the mold cavity and the resin in the mold cavity in order to stably and continuously mold molded products made of thermoplastic resin with high quality such as stable appearance and physical properties. It is necessary to improve the appearance by discharging from the cavity, or by increasing the mold temperature and improving the transferability to the mold, and if it is a crystalline thermoplastic resin, it promotes crystallization There is a need to.

Here, the discharge of air and gas from the cavity will be described in detail. At the time of injection molding, when the mold is completely closed and the molten resin is injected into the cavity, the air present in the cavity is compressed. If the air and volatile components and gas components generated from the molten resin are not completely expelled from the cavity, the resin cannot be completely filled, resulting in short shots (poor filling), or high temperatures due to compression. The air and gas may cause problems such as burning, scorching, poor gloss, and poor weld strength. In addition, compressed air and gas that are heated to high temperatures damage the mold, leading to an increase in the number of times the mold is maintained. In order to prevent such problems, the mold is provided with a gas vent.

In order to exhaust the gas generated from the air and resin in the mold cavity from the cavity, it is necessary to increase the thickness of the gas vent described above to improve the exhaust efficiency. In order to promote crystallization, it is necessary to perform molding at a high mold temperature exceeding 100 ° C., for example.

However, when the mold temperature is high and the gas vent is thick, a large amount of burrs are generated in the gas vent. When molding is performed at a low mold temperature (for example, 100 ° C. or lower), not only the problem of burr generation can be solved, but also the temperature can be controlled by water without using the temperature control by oil, thereby eliminating the complexity. . For this reason, it is preferable to make the mold temperature conditions 100 ° C. or less.

On the other hand, when molding is performed under conditions of a low mold temperature, the following problems occur. That is, the transferability to the mold is inferior and the appearance of the surface of the molded product is deteriorated. In the case of a crystalline thermoplastic resin, crystallization does not proceed sufficiently, so that the surface hardness does not increase and it is difficult to protrude from the mold, and post-shrinkage increases, so it is used after molding. Problems such as surface roughness, dimensional changes, and warping occur due to environmental temperature.

For example, in polyphenylene sulfide resin which is a crystalline thermoplastic resin, a method of blending various crystallization accelerators and plasticizers to improve the crystallization speed and solve the above-mentioned problems is known (for example, Patent Document 1).

JP 2003-335945 A

As described above, generally, the gas venting effect in the cavity is improved by enlarging the gas vent of the mold (for example, increasing the thickness). On the other hand, if the thickness of the gas vent is increased, naturally, burrs are more likely to occur, and the length of the burrs becomes longer.

The present invention has been made in order to solve the above-described problems. The object of the present invention is to increase the thickness of the gas vent while suppressing the length of burrs generated in the gas vent to a conventional level, thereby increasing the gas from the cavity. A heat insulating mold that can improve the punching effect and can mold a molded article having a sufficient surface crystallization degree in the case of a surface mold transferability or a crystalline thermoplastic resin, and the above An object of the present invention is to provide a method for producing a molded article using a heat insulating mold.

The inventors of the present invention have made extensive studies to solve the above problems. As a result, the inventors have found that the above problems can be solved by a heat insulating mold provided with a heat insulating mold main body provided with a gas vent and a heat insulating layer formed on the inner surface of the mold, and have completed the present invention. More specifically, the present invention provides the following.

(1) A heat insulating mold for forming a molded article made of a resin composition containing a thermoplastic resin, wherein the heat insulating mold is formed on a heat insulating mold main body provided with a gas vent and an inner surface of the mold. A non-insulating mold that is the same as the above-described heat-insulating mold except that the heat-insulating layer is different from the thickness of the gas vent. When the molding is performed under conditions such that the mold transferability of the surface of the molded article or the crystallinity on the surface of the molded article is in a desired range, The thickness of the gas vent of the heat insulating mold is within a range where the ratio of the length of the burr generated by the gas vent of the heat insulating mold and the length of the burr generated by the gas vent of the non-insulating metal mold satisfies 0.9 to 1.1. Greater than the thickness of the gas vent of the non-insulated mold Hot mold.

(2) The heat insulation mold according to (1), wherein the thickness of the gas vent of the heat insulation mold is more than 1 time and less than 3 times the thickness of the gas vent of the non-heat insulation mold.

(3) The heat insulating mold according to (1) or (2), wherein the thermoplastic resin is a polyarylene sulfide-based resin.

(4) A method for producing a molded article comprising a resin composition containing a thermoplastic resin, comprising a step of molding the thermoplastic resin using the heat insulating mold according to any one of (1) to (3).

(5) The manufacturing method according to (4), wherein a mold temperature of the heat insulating mold is 100 ° C. or less.

According to the present invention, the degassing effect from the cavity can be improved by increasing the thickness of the gas vent while suppressing the length of the burr generated in the gas vent to the conventional level, and the surface mold transfer In the case of a crystalline thermoplastic resin, it is possible to provide a heat insulating mold capable of forming a molded article having a sufficient degree of crystallinity on the surface, and a method for producing a molded article using the heat insulating mold. it can.

It is a figure which represents typically the heat insulation metal mold | die used in the Example, (a) is a top view from the cavity side of the movement side metal mold | die of heat insulation metal mold | die, (b) is AA cross section of (a). It is sectional drawing shown, (c) is a schematic diagram of the cross section of the split mold which consists of a movement side metal mold | die and a fixed side metal mold | die. In an Example, it is a graph which shows the result of having performed the injection molding using the heat insulation metal mold | die which has specific gas vent thickness, or the non-heat insulation metal mold | die, and measuring the burr | length length produced by the gas vent.

Hereinafter, embodiments of the present invention will be described in more detail, but the present invention is not limited to the following embodiments.

The heat insulating mold of the present invention is for molding a molded article made of a resin composition containing a thermoplastic resin, and includes a heat insulating mold body provided with a gas vent, and a heat insulating layer formed on the inner surface of the mold. And comprising. The molded product is molded using the heat insulation mold and the non-heat insulation mold that is the same as the heat insulation mold except that it does not include a heat insulation layer and the thickness of the gas vent is different. When the mold transferability on the surface of the molded article or the crystallinity on the surface of the molded article is within a desired range, the variability generated by the gas vent of the heat insulating mold In the range where the ratio of the length of the burr generated by the gas vent of the non-adiabatic mold satisfies 0.9 to 1.1, the thickness of the gas vent of the adiabatic mold is that of the gas vent of the non-adiabatic mold. Greater than thickness. The thickness of the gas vent of the heat insulation mold is preferably more than 1 time and 3 times or less the thickness of the gas vent of the non-heat insulation mold.

The “inside mold surface” refers to the wall surface of the cavity. In FIG.1 (b), although the heat insulation layer is formed in the whole wall surface of a cavity, as long as the effect of this invention is acquired, you may form in a part of wall surface. In the method for producing an injection-molded product of the present invention, at least the above-mentioned heat insulating layer may be formed on all the inner surface portions of the mold that are in contact with the portions that require high transferability and high crystallinity in the obtained molded product. It is necessary and it is preferable to form a heat insulating layer on the entire inner surface of the mold.
The cavity refers to the entire space filled with resin inside the mold.

Since the heat insulating mold of the present invention is provided with a heat insulating layer formed on the inner surface of the mold, the mold transferability of the surface of the molded product to be molded or the crystallinity on the surface of the molded product to be molded The mold temperature can be set low without lowering. Generally, the burr length can be shortened by setting the mold temperature low. Therefore, when a heat insulating mold is used, if the thickness of the gas vent is the same as that of a conventional mold (non-insulating mold) that does not have a heat insulating layer, the length of the burr should be a non-insulating mold. It is shorter than if it were. This is because the non-adiabatic mold is used at a higher mold temperature in order to maintain mold transferability and crystallinity. Here, as the length of the burr, if the conventional one is allowed, the thickness of the gas vent in the heat insulating mold can be increased until the burr length is reached. As a result, the effect of degassing from the cavity is improved.
Hereafter, the manufacturing method of the metal mold | die of this invention is demonstrated in detail.

<Determination of resin materials>
First, it is necessary to select a resin material to be molded. The resin material is not particularly limited as long as it is a thermoplastic resin, and may be a crystalline thermoplastic resin or an amorphous thermoplastic resin, and conventionally known ones can be selected.
Among thermoplastic resins, polyarylene sulfide resins (particularly polyphenylene sulfide resins) which are crystalline thermoplastic resins are particularly problematic in terms of burrs and low crystallinity of the molded product surface. In other words, it is difficult to mold the polyarylene sulfide resin by setting the mold temperature to 100 ° C. or less so that the crystallinity of the surface of the molded product is sufficiently increased. However, if the mold obtained by the method of the present invention is used, even if polyarylene sulfide resin is used as the resin material, the mold temperature is set to 100 ° C. or less, and the crystallinity of the surface of the molded article is sufficiently obtained. Can be increased. Here, examples of the polyarylene sulfide resin include polyarylene sulfide resins and modified products of polyarylene sulfide resins described in JP-A-2009-178967.
In addition to polyarylene sulfide resins, polyether ether ketone resins, polyether ketone resins, polyphenylene ether resins, aromatic polyamide resins, and the like are slow to crystallize, and it is difficult to increase the degree of crystallinity on the surface of the molded product. If the heat insulation mold according to the above is used, the crystallinity of the surface of the molded product is sufficiently increased, and the gas from the cavity is increased by increasing the thickness of the gas vent while suppressing the burr length generated in the gas vent to the conventional level. Molding can be performed with improved punching effect.

The more the content of the crystalline thermoplastic resin in the resin composition containing the crystalline thermoplastic resin, the greater the problem of burrs and the lower the crystallinity of the surface of the molded product. Even in this case, the crystallinity of the surface of the molded product is sufficiently increased, and the gas venting effect from the cavity is increased by increasing the thickness of the gas vent while suppressing the burr length generated by the gas vent to the conventional level. It is possible to improve the molding. For example, even when a resin composition made of a crystalline thermoplastic resin having a low crystallization rate is used, the crystallization degree of the surface of the molded article is sufficiently increased and the length of burrs generated by the gas vent is suppressed to the conventional level. By increasing the thickness of the gas vent, molding can be performed with an improved gas venting effect from the cavity.
A resin composition containing a crystalline thermoplastic resin in which a conventionally known additive such as another resin, an antioxidant, an inorganic filler, or a stabilizer is blended with the crystalline thermoplastic resin may be used as a raw material. .

After the resin material is determined, the desired mold transferability on the surface of the molded product or the desired crystallinity on the surface of the molded product is determined. In particular, when a crystalline thermoplastic resin is used, the desired crystallinity on the surface of the molded product is determined. The desired mold transferability and crystallinity can be arbitrarily determined according to, for example, the use of the molded product. The mold transferability can be evaluated by, for example, visual observation of the surface of the obtained molded product. The crystallinity can be measured by a known method.

<Insulation layer>
The thickness of the heat insulating layer is not particularly limited, and is appropriately determined in consideration of the heat insulating effect of the material constituting the heat insulating layer, but is preferably 60 μm or more. Moreover, the thickness of the heat insulation layer may not be constant. Although the heat conductivity calculated | required by a heat insulation layer changes with uses etc., it is especially preferable that it is 2 W / m * K or less. If the heat insulating layer satisfies these conditions, the time for which the resin is held in the mold at a temperature at which the mold transferability is improved, or in the case of a crystalline thermoplastic resin, the temperature at which the crystallization speed is increased. In the case of a long mold and sufficient mold transferability or crystalline thermoplastic resin, sufficient crystallinity can be obtained.

Although the material which comprises a heat insulation layer is not specifically limited, What is necessary is just to have heat resistance of the grade which is low in heat conductivity, and does not produce a malfunction even if it contacts a high temperature resin composition. Examples of materials having a heat conductivity of 2 W / m · K or less and heat resistance sufficient to withstand high temperatures during molding include epoxy, polyimide, polybenzimidazole, and polyetheretherketone. Examples thereof include resins having high heat resistance and low thermal conductivity, and porous ceramics such as porous zirconia.

The method for forming the heat insulating layer on the inner surface of the metal part of the mold is not particularly limited. For example, it is preferable to form the heat insulating layer on the inner surface of the mold by the following method.

A polyimide precursor solution that can form a polymer heat insulation layer is applied to the inner surface of the metal part of the mold, heated to evaporate the solvent, and then heated to polymerize the polyimide. A method of forming a heat insulating layer such as a film, a method of vapor-deposition polymerization of a monomer of a heat-resistant polymer, such as pyromellitic acid anhydride and 4,4-diaminodiphenyl ether, and a piece shape in which a portion corresponding to the cavity surface is made of a heat insulating plate. There is a method of creating and mounting the piece mold to the main mold. Or about a planar shape metal mold, the method of affixing on the desired part of a metal mold | die using a polymer heat insulating film and a suitable adhesion | attachment method or an adhesive tape-like polymer heat insulating film is mentioned. The heat insulating layer may be formed by a method in which a resin for forming the heat insulating layer is electrodeposited on a mold. In addition, a metal layer can be formed in order to provide durability, such as damage prevention, to a heat insulation layer and a heat insulation board surface.

Also, a ceramic material can be used for the heat insulating layer. The ceramic is preferably porous zirconia or silicon dioxide containing bubbles inside. Among them, since the heat insulating layer made of porous zirconia is mainly made of zirconia, it has high durability against pressure applied to the heat insulating layer during injection molding. Therefore, it becomes difficult to produce the malfunction of the heat insulation layer which generate | occur | produces due to the said pressure. For this reason, the frequency | count of interrupting shaping | molding in the middle of injection molding reduces, and the productivity of an injection molded product increases.

The zirconia is not particularly limited, and may be any of stabilized zirconia, partially stabilized zirconia, and unstabilized zirconia. Stabilized zirconia is one in which cubic zirconia is stabilized even at room temperature, and is excellent in mechanical properties such as strength and toughness and wear resistance. Partially stabilized zirconia refers to a state in which tetragonal zirconia partially remains even at room temperature, and when subjected to external stress, a martensitic transformation from tetragonal to monoclinic occurs, and is particularly advanced by the action of tensile stress. Suppresses crack growth and has high fracture toughness. Unstabilized zirconia refers to zirconia that is not stabilized by a stabilizer. In addition, you may use combining at least 2 or more types selected from stabilized zirconia, partially stabilized zirconia, and unstabilized zirconia.

As the stabilizer contained in the stabilized zirconia and the partially stabilized zirconia, conventionally known general ones can be employed. For example, yttria, ceria, magnesia and the like can be mentioned. The amount of the stabilizer used is not particularly limited, and the amount used can be appropriately set according to the application, the material used, and the like.

In addition, porous ceramics other than porous zirconia can be used, but porous zirconia has higher durability than other porous ceramics. For this reason, if a mold having a heat insulating layer composed of porous zirconia is used, defects such as deformation of the heat insulating layer are unlikely to occur. Is greatly increased.

Further, conventionally known additives may be further included in addition to the above zirconia and stabilizer as long as the effects of the present invention are not impaired.

The method for forming the heat insulating layer using the above raw materials is not particularly limited, but it is preferable to employ a thermal spraying method. By adopting the thermal spraying method, the thermal conductivity of porous zirconia can be easily adjusted to a desired range. Moreover, problems such as a significant decrease in the mechanical strength of the heat insulating layer due to excessive formation of bubbles inside the porous zirconia do not occur. Thus, by forming a heat insulation layer by thermal spraying, the structure of a heat insulation layer becomes a thing suitable for the use of this invention.

Formation of the heat insulation layer by thermal spraying can be performed as follows, for example. First, the raw material for the heat insulating layer is melted to form a liquid. This liquid is accelerated and collides with the inner surface of the cavity. Finally, the material that collides with and adheres to the inner surface of the cavity is solidified. By doing so, a very thin heat insulating layer is formed on the inner surface of the mold. The thickness of the heat insulating layer can be adjusted by causing the melted raw material to collide with the very thin heat insulating layer and solidify it. As a method for solidifying the raw material, a conventionally known cooling means may be used, or the raw material may be solidified simply by leaving it to stand. The thermal spraying method is not particularly limited, and a preferable method can be appropriately selected from conventionally known methods such as arc spraying, plasma spraying, and flame spraying.

The heat insulating layer having the above multilayer structure can be manufactured by adjusting the manufacturing conditions of the heat insulating layer. For example, when forming a heat insulation layer by a thermal spraying method, it can manufacture by adjusting the conditions etc. which make the fuse | melted raw material adhere to a metal mold | die inner surface.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

In the examples, the following materials were used.
Crystalline thermoplastic resin: Polyphenylene sulfide resin (PPS resin) (manufactured by Polyplastics Co., Ltd., “DURAFIDE (registered trademark) 1140A64”)
Thermal insulation layer: A raw material mainly composed of zirconia was sprayed onto the metal surface of the mold by a thermal spraying method to form a thermal insulation layer. In addition, the thickness of the formed heat insulation layer is 0.5 mm.

As the heat insulating mold, the one shown in FIG. 1 (c) was used. In FIG. 1A, the moving-side mold has a cavity with dimensions of 50 mm width × 50 mm length × 1 mm thickness. The resin reservoir in FIG. 1A is a recess having an opening having a width of 5 mm and a length of 5 mm. The thickness of the gas vent in FIG. 1B was changed by 5 μm in the range of 5 to 30 μm.
As the non-insulating mold, the one obtained by removing the heat insulating layer from the insulating mold shown in FIG. 1 was used.

The crystalline thermoplastic resin was injection-molded into the cavity via the runner and gate under the following molding conditions, and the length of burrs generated at the gas vent was measured. In addition, by setting the mold temperature in accordance with the following molding conditions, the crystallinity degree on the surface of the molded product is in a desired range (whether using a heat insulating mold or a non-heat insulating mold) ( Specifically, it was 30 to 35%). The degree of crystallinity is the degree of crystallinity due to reflection, measured using a RINT2500HL X-ray diffractometer manufactured by Rigaku Corporation. The results are shown in Table 1 and FIG.

[Molding condition]
Molding machine: SE100D manufactured by Sumitomo Heavy Industries, Ltd. or TR100EH manufactured by Sodick Co., Ltd.
Cylinder temperature: 320 ° C
Mold temperature: 100 ° C (for heat insulation mold) or 150 ° C (for non-heat insulation mold)
Injection speed: 50mm / s
Screw rotation speed: 100rpm
Filling pressure: Minimum filling pressure (minimum pressure that can completely fill the resin reservoir in FIG. 1A)

※表中、金型温度が１５０℃の行は、非断熱金型を用いた場合の結果を表し、金型温度が１００℃の行は、断熱金型を用いた場合の結果を表す。

* In the table, the row where the mold temperature is 150 ° C. represents the result when the non-insulated mold is used, and the row where the mold temperature is 100 ° C. represents the result when the heat insulated mold is used.

As can be seen from Table 1 and FIG. 2, for example, when a non-insulated metal mold having a gas vent thickness of 5 μm is used at a mold temperature of 150 ° C., the burr length comparable to the burr length is 15 μm in thickness of the gas vent. This heat insulation mold was obtained when the mold temperature was 100 ° C. Further, when a non-insulating metal mold having a gas vent thickness of 10 μm is used at a mold temperature of 150 ° C., the burr length is approximately the same as the burr length. Obtained when used at ℃. From these facts, by using the heat insulating mold of the present invention, the thickness of the gas vent is reduced to the conventional level while the length of the burr generated in the gas vent is suppressed to the level when the conventional non-insulated metal mold is used. It was confirmed that it was possible to enlarge up to about 3 times.

Claims (5)

A heat insulating mold for forming a molded article comprising a resin composition containing a thermoplastic resin,
The heat insulating mold includes a heat insulating mold body provided with a gas vent, and a heat insulating layer formed on the inner surface of the mold,
The molded product is molded using the heat insulating mold and the non-heat insulating mold that is the same as the heat insulating mold except that the heat insulating layer is not provided and the thickness of the gas vent is different. When the mold transferability on the surface of the molded article or the crystallinity on the surface of the molded article is within a desired range, the variability generated in the gas vent of the heat insulating mold The thickness of the gas vent of the non-insulated metal mold is within the range of 0.9 to 1.1. Larger insulation mold than. The heat insulating mold according to claim 1, wherein the thickness of the gas vent of the heat insulating mold is more than 1 time and not more than 3 times the thickness of the gas vent of the non-insulating metal mold. The heat insulating mold according to claim 1 or 2, wherein the thermoplastic resin is a polyarylene sulfide-based resin. A method for producing a molded article comprising a resin composition containing a thermoplastic resin, comprising a step of molding a thermoplastic resin using the heat insulating mold according to any one of claims 1 to 3. The manufacturing method according to claim 4, wherein a mold temperature of the heat insulating mold is 100 ° C or less.

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