JP2004314511A - Injection molding method for insert-molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an insert injection-molded article having no deformation without making a heating medium contact an insert directly by an easy method. <P>SOLUTION: The insert-molded article in which the arrangement of insert members is unsymmetrical is injection-molded while a mold temperature Tn and an insert member temperature Ti at the start of the injection of the member are controlled so that the difference D(%) between the shrinkage rates of a thermoplastic resin and the insert member meets the formula: -0.01%≤D=Ai(Ti-T)×100-Sr(Tn-T)≤0.01% [Ti (°C) is an insert member temperature at the start of the injection of the member; T (°C) is an atmosphere temperature after the demolding of the molding; Ai (1/°C) is the coefficient of thermal expansion of the insert member; and Sr(Tn-T) is the molding shrinkage (%) of the thermoplastic resin when the temperature of the resin is changed from a mold temperature Tn to T]. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for molding an insert molded product having no deformation.Specifically, an insert molded product in which the arrangement of insert members is asymmetrical is determined by a specific shrinkage rate of thermoplastic resin and a coefficient of thermal expansion determined by the coefficient of thermal expansion of the insert member. The present invention relates to a method of performing injection molding without warping by controlling the temperature at the start of injection of an insert member to a value.
[0002]
[Prior art]
Generally, when performing insert injection molding by mounting an insert member in a mold, the mold temperature is made uniform. At that time, the temperature of the insert member fluctuates to near the mold temperature, and the insert member thermally expands or contracts depending on the temperature difference between before and after the mold is mounted.
On the other hand, the thermoplastic resin contracts when it is cooled and solidified from a molten state during molding, and becomes a molded product smaller than the dimensions of the mold. When the dimensional change due to the temperature difference of the insert member is different from the dimensional change due to the molding shrinkage of the thermoplastic resin, this causes a problem that the insert molded product is deformed.
[0003]
Japanese Patent Application Laid-Open No. 10-116934 discloses that the curing shrinkage of a sealing resin at the temperature (Tm (° C.)) at the time of molding the sealing resin (Tm (° C.)) is Sp, and the heat of the cured sealing resin is Sp. A sealing resin having a temperature Tm-Sp / (Kp-Kb) of −10 ° C. or more and 50 ° C. or less, where Kp (/ ° C.) is the expansion coefficient and Kb (/ ° C.) is the thermal expansion coefficient of the heat sink. A method of preventing deformation of a resin-encapsulated semiconductor device by combining it with a heat radiating plate is disclosed (for example, see Patent Document 1).
However, this technique is intended for a semiconductor device sealed with a thermosetting resin, and does not teach anything about a thermoplastic resin molded product in which metal inserts are arranged asymmetrically.
[0004]
Japanese Patent Application Laid-Open No. H11-105076 discloses that a heat medium is introduced into a mold, and the inserted heat medium is heated by the introduced heat medium to a temperature equal to or higher than the heat deformation temperature of the resin. A method for preventing stress cracking caused by a difference in molding shrinkage by a method of manufacturing an insert molded product in which a resin is injected into a mold on which a set insert is placed is disclosed. (For example, see Patent Document 2).
However, in this technique, a method of directly heating the insert with the medium is used.However, in this method, depending on the material of the insert or the material of the medium, both may be chemically sealed depending on the airtightness of the medium and the complexity of the device. There is a problem that the insert is corroded due to a reaction.
[0005]
Japanese Patent Application Laid-Open No. Hei 8-230008 discloses a method of predicting warpage of an injection molded product by a finite element method using data of a resin shrinkage and a thermal expansion coefficient. A warp deformation prediction method is disclosed (for example, see Patent Document 3).
However, this technique does not show the warpage prediction of the insert molded product.
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-116934 (Claim 1, Example)
[Patent Document 2]
Japanese Patent Application Laid-Open No. H11-105076 (Claim 5, Example)
[Patent Document 3]
JP-A-8-230008 (Claim 1)
[0007]
[Problems to be solved by the invention]
An object of the present invention is to obtain a deformable insert injection-molded article by an easy method without bringing a heating medium into direct contact with the insert.
[0008]
[Means for Solving the Problems]
The present inventor has a specific relationship between the difference in shrinkage between the thermoplastic resin and the insert member, for example, providing a temperature difference between the mold temperature on the side where the insert member is mounted and the mold temperature on the side where the insert member is not mounted, It has been found that by controlling the temperature of the insert member, it is possible to easily injection-mold an insert-shaped product in which the arrangement of the insert member is asymmetrical without warping, thereby completing the present invention.
[0009]
That is, a first aspect of the present invention is a method for injection-molding an insert molded product (20) in which the arrangement of the insert member (1) is asymmetric without warp deformation, wherein the thermoplastic resin (21) and the insert member (1) are combined. Injection molding is performed by controlling the mold temperature Tn and the injection start temperature Ti of the insert member (1) so that the difference in shrinkage D (%) represented by the following equation (i) satisfies the following equation (ii). A molding method is provided.
D = Ai (Ti−T) × 100−Sr [Tn to T] (i)
-0.01% ≦ D ≦ 0.01% (ii)
(In the formula (i), Ti is the temperature (° C.) at the start of injection of the insert member, T is the ambient temperature (° C.) after removing the molded product, Ai is the coefficient of thermal expansion (1 / ° C.) of the insert member, and Sr [ Tn to T] represent the molding shrinkage (%) of the thermoplastic resin from the mold temperature Tn (° C) to T (° C).)
A second aspect of the present invention is to control the injection start temperature Ti of the insert member by providing a temperature difference between the mold temperature on the side where the insert member (1) is mounted and the mold temperature on the side where the insert member (1) is not mounted. A molding method according to the first aspect is provided.
A third aspect of the present invention provides the molding method according to the first aspect of the present invention, wherein the temperature of a separately provided local heating device (16) is adjusted to control the injection start temperature Ti of the insert member (1). I do.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
In the insert molded product 20 according to the present invention, since the arrangement of the insert members 1 is asymmetrical, deformation such as warpage or the like is not likely to occur in a method of insert molding using a generally used mold set at a uniform temperature. appear.
FIG. 1 shows an example of an insert molding 20 in which the arrangement of the insert members 1 is asymmetric. 1 is an insert member, 2 is a resin part. Since the insert member 1 exists only on one surface of the resin portion 2, the insert member 1 is asymmetrically arranged. In accordance with the shrinkage ratio and the thickness of the resin portion 2 as compared with the insert member 1, as shown in FIG. Causes warpage.
In the above, if the insert member 1 has the same symmetrical arrangement on both surfaces of the resin portion 2, even if the expansion coefficient, the shrinkage ratio and the thickness of the resin portion 2 are different from those of the insert member 1, they cancel each other out. No warping occurs.
In the present invention, there is no particular limitation as long as it is an asymmetric arrangement that causes deformation such as warpage.
[0011]
FIG. 2 shows a schematic view of a mold for the molded article. FIG. 2 shows different cross sections of the mold on the left and right. At the time of injection molding, a molten resin 21 (not shown) is filled from the sprue 5 through the runner 4 and the gate 3 into the cavity 22 to form the resin portion 2 of the insert molded product. On the other hand, the mold is maintained at a constant temperature by a medium such as water or oil flowing into the temperature control hole 15 or a heater. After the thermoplastic resin is filled and cooled and solidified in the mold, the fixed mold plate 7 and the movable mold plate 8 are opened, and the molded product is projected from the mold by the sprue lock pin 13 and the ejector pin 14. You.
[0012]
The material and shape of the insert member 1 used in the present invention are not particularly limited. Examples of the material include metals, inorganic materials, organic materials, and the like.Specifically, steel, cast iron, stainless steel, copper, gold, silver, metals such as brass, inorganic materials such as ceramics and carbon materials, wood and the like Organic materials are mentioned. Note that the insert member may refer to not only a simple substance such as a metal and an inorganic material but also a composite including a plurality of metals, resins, and the like.
The thermal expansion coefficient (unit × 10 ⁻⁵ / ° C.) is steel 1.1 to 2.0, cast iron 1.0 to 1.1, brass 1.2 to 2.0, bronze 1.5 to 1.8, Copper is 1.5 to 1.7 or the like.
[0013]
The material of the thermoplastic resin 21 used in the present invention is not particularly limited, and may be a crystalline resin or an amorphous resin. Specifically, general-purpose thermoplastic resins include polyolefins such as polyethylene (PE), polypropylene (PP), poly-4-methyl-pentene-1, and polycyclic olefin, polystyrene (PS), AS resin, ABS resin, and polyolefin. Examples include vinyl chloride (PVC), polyacrylonitrile (PAN), (meth) acrylic resin, cellulosic resin, and elastomer, and engineering resins such as nylon 6, 6, 6, 12, and 6, 12. Various aromatic polyamide resins such as aliphatic polyamides or aromatic polyamides (PA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polycarbonate (PC), polyacetal, polyphenylene ether (PPE , Polyphenylene sulfide (PPS), polysulfone (PSu), polyimide (PI), liquid crystal polyester, liquid crystal amide. In addition, aliphatic polyesters derived from aliphatic dicarboxylic acids, aliphatic diols, aliphatic hydroxycarboxylic acids or cyclic compounds thereof, and biodegradable resins such as aliphatic polyesters whose molecular weight is increased by diisocyanate or the like. Is also good.
The thermoplastic resin 21 may be a resin alone, or may contain a filler or a reinforcing material.
The molding shrinkage in the resin flow direction during the melting and solidification of the resin depends on the resin temperature and the mold temperature, but is usually 13 to 15% for nylon, 0.2 to 1.3% for PET, 0.4% for PC, PPE 0.65%, glass fiber containing PPE 0.2 to 0.4%, PPS 1 to 2%, glass fiber containing PPS 0.04 to 1.0%, and the like.
[0014]
In the present invention, when the injection start temperature Ti of the insert member is controlled so that the difference in shrinkage ratio D between the thermoplastic resin 21 and the insert member 1 is within ± 0.01%, deformation such as warpage substantially occurs. I found that it was not a problem.
Here, the contraction rate difference D (%) is represented by the following equation (i).
D = Ai (Ti−T) × 100−Sr [Tn to T] (i)
(In the formula (i), Ti is the temperature (° C.) at the start of injection of the insert member, T is the ambient temperature (° C.) after removing the molded product, Ai is the coefficient of thermal expansion (1 / ° C.) of the insert member, and Sr [ Tn to T] represent the molding shrinkage (%) of the thermoplastic resin from the mold temperature Tn (° C) to T (° C).)
[0015]
The method of controlling the temperature Ti includes (a) a method of adjusting the temperature of the mold on the side where the insert member 1 is mounted at the time of injection molding, and (b) a method of controlling the temperature separately from the temperature control device of the mold for injection molding. There is a method in which the heating device 16 is provided to control the injection start temperature Ti of the insert member so as to be different from the mold temperature.
[0016]
In the above method (a), a temperature difference is provided between the mold temperature Ti on the side where the insert member 1 is mounted and the mold temperature Tn on the side where the insert member 1 is not mounted (referred to as the opposite side), and the temperature when the insert member is mounted on the die. Controls Ti. The mold on the side where the insert member 1 is mounted may be a movable side or a fixed side.
For example, when a copper plate is used for the insert member and PPS containing glass fiber is used for the thermoplastic resin, the movable mold temperature on the side where the insert member 1 is mounted is set to 140 ° C., and the opposite fixed side is set. The mold temperature may be set to 120 ° C. When applying the formula (i), Sr [Tn to T] represents the molding shrinkage rate (%) of the thermoplastic resin from the mold temperature Tn to T where the area where the thermoplastic resin is in contact with the mold is larger. . For this reason, it is preferable to increase the area where the resin contacts the low-temperature mold on the opposite side than the area where the resin contacts the high-temperature mold on the side where the insert member 1 is mounted.
When the fixed mold and the movable mold that have different temperatures come into contact with each other, the temperatures of both molds change, and it is necessary to open and leave the molds to return to their original temperatures. By providing the material, the temperature of both does not change, and it is not necessary to leave the material.
[0017]
In the above method (b), for example, a mold with a rod heater as shown in FIG. 4 is used. In FIG. 4, a nest 17 is provided at a portion where the insert member 1 contacts, and a bar heater 16 'for heating is provided therein.
The mold temperature is set to 120 ° C., and the bar heater 16 ′ is heated so that the temperature of the part where the insert member 1 contacts is 140 ° C.
Also in this method, a molded product that is hardly deformed in the opening direction of the mold as in the method (a) can be obtained. In this method, there is no need to provide a heat insulating material between the two dies, and there is no need to leave the dies open and left until they return to their respective temperatures during molding. Furthermore, if a part of the insert member is heated, the entire insert member is heated by heat conduction, and there is no restriction on the insert shape or the shape of the molded product. Further, when the material of each insert member is different, a local heating device may be installed at a place where it comes into contact with each insert member, and the temperature may be set for each insert member. As the local heating device 16, instead of the bar heater 16 ′, a heating means may be provided by providing a hole through which a heat medium flows, or may be heating means of another type such as heating by radiant heat instead of heat conduction.
[0018]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.
[0019]
[Comparative Example 1]
In normal molding, the mold temperature was set to 120 ° C. for both the fixed side and the movable side. Using a copper plate (thickness: 1 mm) as the insert member 1 and glass fiber-containing polyphenylene sulfide (hereinafter, simply referred to as PPS resin) as the thermoplastic resin, an insert molded product as shown in FIG. 1 was obtained. Here, the molded article has a total length of 185 mm, a maximum width of 20 mm, and a maximum thickness of 4 mm (the resin thickness of the portion where the copper plate is inserted is 3 mm).
When the copper plate is not mounted, the molded product becomes smaller than the mold cavity shape by the molding shrinkage of the thermoplastic resin, but no significant deformation occurs in the mold opening direction.
However, when the copper plate was mounted on the movable mold and integrated molding was performed, as shown in FIG. 3, the center of the molded product was deformed toward the copper plate side with a maximum of 0.12 mm as compared with both ends of the molded product.
As the deformation factor, the shrinkage deformation in the longitudinal direction of the insert molded product, that is, the molding shrinkage ratio in the flow direction of the thermoplastic resin can be considered.
From the above results, assuming that the mold temperature is 120 ° C., the ambient temperature after taking out the molded product is 23 ° C., and the molding shrinkage of the PPS resin in the resin flow direction from the mold temperature to the ambient temperature is 0.21%, the above equation (i) is obtained. The difference in shrinkage ratio D (%) is obtained as follows.
1.7 × 10 ⁻⁵ (120−23) × 100−0.21 = 0.16−0.21 = −0.05 (%)
Accordingly, it can be seen that the molding shrinkage of the thermoplastic resin was too large compared to the thermal shrinkage of the copper plate, and the convex deformation was large.
[0020]
[Comparative Example 2]
The procedure was performed in the same manner as in Comparative Example 1 except that the mold temperature was changed to 146 ° C. on both the fixed side and the movable side.
As a result, similarly to Comparative Example 1, a phenomenon in which the center of the molded product was deformed toward the copper plate side by 0.10 mm as a maximum compared to both ends of the molded product was confirmed.
From the above results, the above equation (i) was defined assuming that the mold temperature was 146 ° C., the ambient temperature was 23 ° C. after removing the molded product, and the molding shrinkage was 0.24% in the resin flow direction from the mold temperature of the PPS resin to the ambient temperature. The difference in shrinkage ratio D (%) is obtained as follows.
1.7 × 10 ⁻⁵ (146-23) × 100−0.24 = 0.21−0.24 = −0.03 (%)
Therefore, as in Comparative Example 1, the molding shrinkage of the thermoplastic resin is larger than the thermal shrinkage of the insert copper plate, but the shrinkage difference D is smaller than that of Comparative Example 1, and the convex deformation is smaller. It can be seen that it has decreased.
[0021]
[Example 1]
The insert member 1 and the thermoplastic resin are the same as in Comparative Example 1.
The fixed-side mold temperature was set to 120 ° C., and the movable-side mold temperature to which the copper plate was mounted was set to 140 ° C. The copper plate and the fixed-side cavity temperature were measured by a surface thermometer with the mold opened after the copper plate was mounted on the movable side, and when the respective temperatures reached 140 ° C. and 120 ° C., resin filling was started. . As a result, it was possible to obtain a good insert molded product having a deformation amount toward the copper plate of 0.02 mm.
From the above results, the insert member temperature was 140 ° C., the ambient temperature after removing the molded product was 23 ° C., and the molding shrinkage in the resin flow direction from the mold temperature of the PPS resin fixed side of 120 ° C. to the ambient temperature was 0.21%. When the shrinkage ratio difference D (%) is obtained using the equation (i), the following is obtained.
1.7 × 10 ⁻⁵ (140−23) × 100−0.21 = 0.20−0.21 = −0.01 (%)
Rather than empirically obtaining a good insert molded product by changing the molding conditions in various ways as in the prior art, the present invention utilizes the relationship of the above formulas (i) and (ii) to make it extremely easy. An insert-molded product without deformation can be obtained by setting appropriate conditions.
[0022]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, an insert injection molded article without a deformation | transformation can be easily obtained, without going through many empirical trial manufactures.
[Brief description of the drawings]
FIG. 1 is an example of an insert molded product according to the present invention and the prior art.
FIG. 2 is an example of a mold used for insert molding according to the present invention and the prior art.
FIG. 3 is an example showing warpage of an insert molded product according to the present invention and the prior art.
FIG. 4 is an example of an insert molding die having a local heating device according to the present invention.
[Explanation of symbols]
1: insert member 2: resin portion (of an insert molded product) 3: gate 4: runner 5: sprue 6: fixed side mounting plate 7: fixed side die plate 8: movable side die plate 9: spacer block 10: movable side mounting Plate 11: upper ejector plate 12: lower ejector plate 13: sprue lock pin 14: ejector pin 15: temperature control hole 16: local heater 16 ': rod heater 17: nest 18: lead wire 19: lead wire escape Hole 20: Insert molded product 21: Thermoplastic resin 22: Cavity

Claims (3)

In a method for injection-molding an insert molded product (20) in which the arrangement of the insert member (1) is asymmetrical without warping, the thermoplastic resin (21) and the insert member (1) are represented by the following formula (i). A molding method characterized by controlling the mold temperature Tn and the injection start temperature Ti of the insert member (1) so that the difference in shrinkage D (%) satisfies the following equation (ii).
D = Ai (Ti−T) × 100−Sr [Tn to T] (i)
-0.01% ≦ D ≦ 0.01% (ii)
(In the formula (i), Ti is the temperature (° C.) at the start of injection of the insert member, T is the ambient temperature (° C.) after removing the molded product, Ai is the coefficient of thermal expansion (1 / ° C.) of the insert member, and Sr [ Tn to T] represent the molding shrinkage (%) of the thermoplastic resin from the mold temperature Tn (° C) to T (° C).) The molding method according to claim 1, wherein a temperature difference is provided between a mold temperature on a side where the insert member (1) is mounted and a mold temperature on a side where the insert member (1) is not mounted to control the injection start temperature Ti of the insert member. The molding method according to claim 1, wherein the temperature of the injection member (1) at the start of injection is controlled by adjusting the temperature of a separately provided local heating device (16).

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