JP2945147B2 - Injection molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for improving a weld strength suitable for a thermotropic liquid crystal polymer.

[0002]

2. Description of the Related Art Thermotropic liquid crystal polymer has an extremely low weld strength due to the characteristics of the resin itself and is extremely low in weld strength, which is a major problem in the injection molding technology of the polymer. . For example, the low weld strength is also observed due to a phenomenon such as breakage from a weld portion of a molded product due to thermal shock.

Here, in general, a weld line in injection molding is inevitably generated in the case of a multipoint gate, and even in the case of a single point gate, an injection molded product having a large thickness deviation ratio or an injection molded product provided with a push-off pin is used. As in the case of injection molding, the flow of the molten resin injected from the gate into the mold cavity is branched, and this is generated on the surface of the molded body corresponding to the junction where the molten resin flows further. That is, the weld line indicates a joining portion where a joining interface formed by joining the molten resin flows is exposed on the surface of the molded body. Here, the term “weld strength” means the strength of the molded body at the weld line.

Here, the present inventors have considered the reason why the molded article formed by injection-molding a thermotropic liquid crystal polymer has a low weld strength. It was considered that the molecules themselves were extremely easy to orient, and the flowing tip resin was molecularly oriented parallel to the weld interface by the fountain flow effect when proceeding inside the mold cavity.

However, in the case of merely changing the molding conditions such as increasing the resin temperature, the mold temperature or increasing the injection pressure and the holding pressure as conventionally performed for improving the weld strength, especially the thermotropic liquid crystal polymer is required. In the case of (1), an injection molded article having almost improved weld strength cannot be obtained.

It is presumed that this is because the mere change in the injection molding conditions does not change the molecular orientation of the molten molecules of the flowing tip resin in parallel to the weld interface.

On the other hand, in an injection mold having at least two plasticizers and a sprue connected to an injection device as disclosed in Japanese Patent Application Laid-Open No. 1-299015, plasticization is performed by two plasticizers and injection devices after filling a cavity. The method by reciprocating the converted resin is a method for obtaining a molded body having essentially no weld interface. Therefore, it requires special equipment and is not a method suitable for a general injection molding method.

[0008] Furthermore, the reduction in weld strength causes the gas generated from the air or the molten resin in the mold to be drawn into the molten resin confluence, so that the V notch formed on the surface or the slag entrained by the low-temperature resin is generated. In consideration of this, it has been proposed to provide an air vent or a resin reservoir in the cavity.

[0009] Since these improved methods are essentially intended to prevent entrapment of foreign substances into the molten resin junction, for example, the position of the air vent or the resin reservoir is necessarily located near the weld line. Will be. However, the present inventors have found that such a position does not sufficiently improve the weld strength.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for injection molding a thermotropic liquid crystal polymer having a high weld strength. To complete the present invention.

[0011]

That is, according to the present invention, a molten resin is injected into a mold cavity from a plurality of gates via a runner, and a plurality of molten resin flows merge in the mold cavity. In the method of injection molding of a thermotropic liquid crystal polymer in which a weld line is formed on the surface of a molded article correspondingly, one of the molten resin streams to be merged can be reflowed after substantially merging at the junction. A cavity having a large volume and being provided separately from the mold cavity in a runner portion near one of the plurality of gates, wherein the weld strength is improved. The present invention relates to a liquid crystal polymer injection molding method.

Hereinafter, the present invention will be described in more detail.

[0013] In the case of a multipoint gate in which a plurality of gates are injected into one cavity in injection molding, the resin is branched into a plurality of resin flows without branching, and in each case, a plurality of resin flows are filled into the cavity. Go. The plurality of resin streams join at a junction located at an appropriate position in the mold cavity, and after cooling and solidification, a linear weld line appears on the surface of the molded body. A plurality of mold cavities can be provided in one mold.

In the molding method of the present invention, in the case of a multipoint gate, it is necessary to provide a cavity separate from the mold cavity in the runner portion.

Since the separate cavity exists in the runner portion near one of the plurality of gates, the cavity is provided in the plurality of molten resin flows flowing from the plurality of gates in the mold cavity. The resin flow that has flowed through the runner that has flowed into the cavity continues to flow into the cavity even after the merger, so that reflow occurs.

That is, if two molten resin flows A and B flow into the mold cavity from the plurality of gates a and b respectively via the runners and merge at the junction, one molten resin flow A is It also merges with the molten resin flow B toward the junction at the junction. When no separate cavity is provided in the runner portion, the two resin streams merge and immediately form a merge interface, which is cooled and fixed as it is.

However, if one of the two resin streams has a separate cavity in the runner portion near the gate a of the resin stream A, for example, after the resin streams A and B have joined, the separate The molten resin flows into the inside, and as a result, the pressure on the resin flow A side decreases. As a result, the resin flow B
And the resin flow continues to flow. on the other hand,
The resin stream A flows backward and reflows.

It is therefore necessary that the filling volume of the separate cavity has sufficient volume to cause this reflow. The filling volume includes the volume of the runner portion connected to the cavity. That is,
The larger the volume of the runner part, the less the volume of the separate cavity needs to be increased.

If the separate cavities are filled with the molten resin before joining the junction, reflow cannot occur naturally. Therefore, in order to prevent the filling of the separate cavities from being completed before merging, the gate diameter for the separate cavities is made smaller than that of the plurality of gates a and b, and so on. It is preferable to provide inflow resistance to the cavity. The separate cavity is usually a so-called resin reservoir, and after molding, the molded body from the cavity is appropriately removed. A molded product from can be used as a product.

The separate cavities are not preferable if they are located in the runner portions equidistant from any of the gate positions, because a pressure difference due to the two resin flows at the confluence portion hardly occurs. Normally, a cavity may be provided in a runner portion sufficiently close to any gate position.

Here, the reflow of the resin flow can be easily observed by cutting the obtained molded article and closely inspecting the cut surface.

That is, by cutting the obtained injection molded body and inspecting the cut surface, the position of the tip of the reflowed resin is obtained, and the distance from this position to the weld line exposed on the surface of the molded body is obtained. This is the reflow length Y. In addition, even if the resin reflows, the position of the weld line exposed on the surface of the molded body usually indicates a position generated by the first merger and does not particularly move.

Here, in the conventional injection-molded article of a liquid crystal polymer, since the resin does not reflow, the resin confluence interface substantially forms a simple plane or curved surface, and a weld line exposed on the surface of the molded article is formed. Construct the plane that includes.

In the present invention, the reflow length Y measured by a measuring method described later is calculated by the following formula (I) to obtain a molded product thickness X
The volume of the cavity is determined so as to take a value equal to or greater than the value calculated from.

Y ≧ (2.69) ^X · 0.26 (I) (However, the thickness X is 0.5 mm or more)

If the measured reflow length is lower than the value calculated from the thickness, the weld strength is remarkably reduced, and it cannot be a practical injection molded product. The length of the reflow length is
The value may be a value greater than the value calculated by the above formula, and may be a considerably large value depending on the shape of the molding die and the molding conditions. As described above, this value is the length of the reflow of the molten resin, so that it cannot be so large as long as it follows the usual injection molding machine and injection conditions, and is usually at most about 100 mm at most. .

The molded body thickness X refers to the thickness of the molded body at the weld line. In the case of a flat cross-sectional shape such as a rectangular cross-section of a molded body, the thickness means the length of a thinner side, whereas in the case of a circular or polygonal shape, the thickness indicates the diameter. This thickness needs to be 0.5 mm or more. 0.5
It is not preferable to use a thin molded body having a thickness of less than 1 mm because the effect of the present invention is not exhibited. Therefore, the preferred molding method of the present invention is such that the thickness at the weld line in the molded body is 0.5 m
This method is applied to a molded product of m or more.

Here, a multilayer structure of a skin layer and a core layer is usually observed in an injection molded article of a liquid crystal polymer. It is said that the liquid crystal polymer exhibits strong mechanical strength and other excellent physical properties due to such a multilayer structure. This skin layer is a layer obtained by cooling and solidifying a molten resin layer strongly oriented along the inner wall of the mold. The reflow of the molten resin mainly occurs in the resin flow portion corresponding to the core layer. The length of the reflow portion (reflow length) can be easily measured by cutting the obtained injection molded body, inspecting the cut surface thereof, and determining the tip flow portion.

That is, the obtained injection molded article is cut,
The position of the tip of the molten resin is determined by inspecting the cut surface, and the distance from this position to the weld line exposed on the surface of the molded product is determined as the reflow length. Here, since the conventional liquid crystal polymer injection molded body does not cause the resin to reflow, the resin confluence interface substantially constitutes a simple plane, and is a plane including a weld line exposed on the molded body surface. I have.

The molded body thickness X (mm) refers to the minimum thickness of the molded body at the weld line. That is, when the weld line is exposed over portions having different thicknesses of the compact, the smallest value among the different thicknesses is adopted as the thickness X of the compact in the present invention, and the calculation is performed according to the above formula.

In the case of a flat cross-sectional shape such as a rectangular cross-section, the thickness means the length of the thinner side, while in the case of a circular or polygonal shape, the thickness indicates the diameter. The thickness needs to be 0.5 mm or more. It is not preferable to use a thin molded body having a thickness of less than 0.5 mm because the effect of the present invention is not exhibited. Thickness X
Is not particularly limited as long as it can be injection-molded.

In the present invention, the measured reflow length is
It is necessary that the value satisfies the expression (I). That is, it is important to take a value equal to or greater than the value calculated from the thickness X (mm) of the molded body. If the value is lower than the calculated value, the weld strength is remarkably reduced, and it cannot be a practical injection molded product.

(Method for measuring the length Y of the reflow length) The obtained injection molded body is cut perpendicular to the weld line and parallel to the injection flow. The cutting is preferably performed by notching appropriately and mechanically splitting than cutting by a saw, a rotary blade, or the like because the flow pattern described below is easily exposed on the cut surface.

A large number of so-called flow patterns forming a mountain shape in the flow direction are continuously observed in the cross section of the molded body cut in this way, as schematically shown in FIG. In FIG. 3, reference numerals 4 and 5 indicate the positions of the weld lines.

As shown in the drawing, the flow pattern has a mountain shape at the position of the weld line, but after passing the position of the weld line along the flow direction, the flow pattern is gradually deformed, and the position of the flow line 6 is changed. Is also observed to be substantially parallel to the flow pattern from the opposite direction that is also gradually deformed. In the present invention, the length from the weld lines 4, 5 to the point where the flow pattern becomes substantially parallel to the flow pattern from a substantially opposite direction is measured, and this is measured as the reflow length Y ( mm). In the figure, when the flow patterns are non-similar mountain shapes and the lengths from the points of the weld lines 4 and 5 are different, the longest length is Y.

Since the molten resin flow usually flows in a three-dimensionally similar flow pattern, the above-described cutting is performed at a substantially central point in the width direction of the molded body, and the reflow at the cut surface is performed. The length may be measured.

However, there are often cases where the flow pattern does not have a three-dimensionally similar flow pattern. In such a case, the injection molded body is cut at a plurality of points of the molded body perpendicularly to the weld line and parallel to the injection flow, and all cut surfaces are observed to determine a reflow length,
The longest one is the reflow length Y in the present invention.
(Mm).

Note that a normal injection molding machine can be used for the injection molding machine itself, and there is no need to use any special molding machine. Injection molding conditions such as cylinder temperature, mold temperature, mold pressure and the like can be performed under ordinary conditions suitable for the thermoplastic resin to be injected.

The thermotropic liquid crystal polymer in the present invention is a resin having optical anisotropy when melted.

As described above, the polymer having optical anisotropy at the time of melting has the property that the polymer molecular chains take a regular parallel arrangement in the molten state. The properties of the optically anisotropic molten phase can be confirmed by a normal polarization inspection method using an orthogonal polarizer.

A thermotropic liquid crystal polymer generally has an elongated, flat molecular structure, has high rigidity along the long chain of the molecule, and has a plurality of chain-extended bonds in either a coaxial or parallel relationship. Manufactured from such monomers.

The thermotropic liquid crystal polymer used in the present invention can be produced from the above compound by various ester forming methods such as a melt acidilysis method and a slurry polymerization method.

In the thermotropic liquid crystal polymer used in the present invention, a part of one polymer chain is composed of a polymer segment forming an anisotropic molten phase, and the remaining part does not form an anisotropic molten phase. Also included are polymers composed of thermoplastic resin segments. Further, a composite of a plurality of thermotropic liquid crystal polymers is also included.

Examples of the polymer forming the optically anisotropic molten phase as described above include, for example, wholly aromatic polyesters and polyester ethers, and the constituent components thereof include (A) an aromatic dicarboxylic acid compound. At least one
Species, (B) at least one aromatic hydroxycarboxylic acid compound, (C) at least one aromatic diol compound, (D) (D1) aromatic dithiol, (D2) aromatic thiophenol, (D3 At least one kind of aromatic thiol carboxylic acid-based compound, and at least one kind of (E) aromatic hydroxyamine and aromatic diamine-based compound. These may be constituted by themselves, but in many cases (A) and (C); (A) and (D); (A),
(B) and (C); (A), (B) and (E); or (A), (B), (C) and (E), and the like.

The aromatic dicarboxylic acid compound (A) includes terephthalic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-triphenyldicarboxylic acid, 2,6-
Naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, diphenoxybutane-4,
4'-dicarboxylic acid, diphenylethane-4,4'-dicarboxylic acid, isophthalic acid, diphenyl ether-3,
3'-dicarboxylic acid, diphenoxyethane-3,3'-
Aromatic dicarboxylic acids such as dicarboxylic acid, diphenylethane-3,3'-dicarboxylic acid and 1,6-naphthalenedicarboxylic acid, or chloroterephthalic acid, dichloroterephthalic acid, bromoterephthalic acid, methylterephthalic acid, dimethylterephthalic acid, and ethyl Alkyl, alkoxy or halogen-substituted aromatic dicarboxylic acids represented by terephthalic acid, methoxyterephthalic acid, ethoxyterephthalic acid and the like can be mentioned.

(B) Examples of the aromatic hydroxycarboxylic acid-based compound include aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 6-hydroxy-1-naphthoic acid. Carboxylic acid, or 3-methyl-4-hydroxybenzoic acid, 3,
5-dimethyl-4-hydroxybenzoic acid, 2,6-dimethyl-4-hydroxybenzoic acid, 3-methoxy-4-hydroxybenzoic acid, 3,5-dimethoxy-4-hydroxybenzoic acid, 6-hydroxy-5 Methyl-2-naphthoic acid, 6-hydroxy-5-methoxy-2-naphthoic acid, 2-chloro-4-hydroxybenzoic acid, 3-chloro-4-hydroxybenzoic acid, 2,3-dichloro-4-hydroxybenzoic acid Acid, 3,5-dichloro-4-hydroxybenzoic acid, 2,5-dichloro-4-hydroxybenzoic acid, 3-bromo-4-hydroxybenzoic acid, 6-hydroxy-5-chloro-2-naphthoic acid, 6 -Hydroxy-
7-chloro-2-naphthoic acid, 6-hydroxy-5,7
Alkyl-, alkoxy-, or halogen-substituted aromatic hydroxycarboxylic acids represented by -dichloro-2-naphthoic acid and the like.

(C) As the aromatic diol, 4,4 '
-Dihydroxydiphenyl, 3,3'-dihydroxydiphenyl, 4,4'-dihydroxytriphenyl, hydroquinone, resorcinol, 2,6-naphthalenediol, 4,4'-dihydroxydiphenyl ether, bis (4-hydroxyphenoxy) ethane, Aromatic diols such as 3,3'-dihydroxydiphenyl ether, 1,6-naphthalenediol, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, chlorohydroquinone, methylhydroquinone, t- Alkyl, alkoxy, aryl and aryl of aromatic diols represented by butylhydroquinone, phenylhydroquinone, methoxyhydroquinone, phenoxyhydroquinone, 4-chlororesorcin, 4-methylresorcin and the like Aryloxy or halogen-substituted derivatives thereof.

(D1) Examples of the aromatic dithiol include benzene-1,4-dithiol, benzene-1,3-dithiol, and 2,6-naphthalene-dithiol.

(D2) As the aromatic thiophenol,
4-mercaptophenol, 3-mercaptophenol, 6-mercaptophenol and the like.

(D3) Examples of the aromatic thiolcarboxylic acid include 4-mercaptobenzoic acid, 3-mercaptobenzoic acid, 6-mercapto-2-naphthoic acid, and 7-mercapto-2-naphthoic acid.

(E) As aromatic hydroxyamine and aromatic diamine compounds, 4-aminophenol, N-
Methyl-4-aminophenol, 1,4-phenylenediamine, N, N'-methyl-1,4-phenylenediamine, N, N'-dimethyl-1,4-phenylenediamine, 3-aminophenol, 3-methyl -4-aminophenol, 2-chloro-4-aminophenol, 4-amino-1-naphthol, 4-amino-4'-hydroxydiphenyl, 4-amino-4'-hydroxydiphenyl ether, 4-amino-4'- Hydroxydiphenylmethane, 4-amino-4'-hydroxydiphenylsulfide, 4,4'-diaminophenylsulfide (thiodianiline), 4,4'-diaminodiphenylsulfone,
2,5-diaminotoluene, 4,4'-ethylenedianiline, 4,4'-diaminodiphenoxyethane, 4,
4'-diaminodiphenylmethane (methylenedianiline), 4,4'-diaminodiphenylether (oxydianiline) and the like.

Among these wholly aromatic polyesters, at least a compound represented by the general formula:

[0053]

Embedded image

A (co) polymer containing a repeating unit represented by the formula:

[0055]

Embedded image

[0056]

Embedded image

And the like.

That is, a particularly preferred wholly aromatic copolyester of the present invention is a copolyester having a repeating unit derived respectively from three compounds of p-hydroxybenzoic acid, phthalic acid and biphenol, or p-hydroxybenzoic acid And a copolyester having a repeating unit each derived from two compounds of hydroxynaphthoic acid.

This thermotropic liquid crystal polymer is not limited to the fibrous material filler, but the more the filler is compounded, the lower the degree of orientation thereof becomes. Further, if the compounding ratio of the filler is too high, even if the molding method of the present invention is employed, improvement in weld strength cannot be achieved. Therefore, a thermotropic liquid crystal polymer containing too much filler is not preferable. A preferred thermotropic liquid crystal polymer is 70w
It is a liquid crystal polymer containing a filler in an amount of t% or less.

The injection molding conditions in the case of the thermotropic liquid crystal polymer are not particularly limited, but the cylinder temperature of the extruder is 200 to 420 ° C., the mold temperature is 30 to 200 ° C., and the injection pressure is 100 to 100. 2000kg
/ Cm ² , injection speed (cylinder moving speed) 5 to 500
mm / sec and an injection molding cycle of 5 to 120 seconds.

In the present invention, it is not necessary to apply a holding pressure for re-fluidization.
2,000 kg / cm ² holding pressure and holding time of 2-12
The pressure can be maintained under the condition of 0 second. The holding pressure indicates the pressure applied to the mold after substantially all of the molten resin has filled the inside of the mold cavity and the time required for the pressure.

After injection molding, an appropriate cooling time, for example, 2
Cooling is performed for a cooling time of up to 120 seconds and the mold is released to obtain a desired molded product.

[0063]

By providing a separate cavity in the runner part, an improvement in weld strength is achieved. In addition, the injection molding conditions such as cylinder temperature, mold temperature, mold pressure and the like can be performed in accordance with ordinary injection molding conditions suitable for each thermoplastic resin to be injected.

[0064]

【Example】

Hereinafter, the present invention will be further described with reference to examples and the like.

The mold used first will be described.

FIG. 1 shows a gate a, for obtaining a rectangular product.
FIG. 3 is a plan view showing a multipoint gate type injection mold having respective b. In the mold shown in the figure, a cavity 3 separate from the cavity 2 is provided in a runner portion 1 near the gate a of the mold cavity 2. In this embodiment,
The length and length of the separate cavity 3 are not changed.
A mold was used in which only a predetermined length was changed.

The mold of FIG. 2 is a mold corresponding to the mold of FIG. 1 from which the separate cavity 3 and the runner attached thereto are omitted.

The measurement of the molded article thickness X and the reflow length is as follows.
The thickness at the weld line of the molded product obtained as described above was measured, and the calculated value was obtained by calculating according to the above formula. The molded product was cut, and the reflow length was measured from observation of the cut surface.

The molded article of this embodiment has a cross section of width 13
Since it is a rectangular molded body of mm, the length of the thinner side was defined as the molded body thickness X (mm). The thickness of the molded body at any part of the weld line was the same. Further, the molded body was cut at substantially the center of the molded body, and the length Y (mm) of the reflow length was obtained from observation of the cut surface. As a precautionary measure, the reflow lengths at a plurality of locations were measured in parallel with the flow in the width direction of the molded body, but it was confirmed that all of them were almost the same value.

Example 1 An injection molding die having the shape and dimensions shown in the plan view of FIG. 1 was used. In addition, the length L of the separate cavity 3 in FIG. 1 is variable, and the length is separately described in Table 1. Using this mold, a thermotropic liquid crystal polymer composed of a quaternary copolyester of p-hydroxybenzoic acid / terephthalic acid / biphenol / isophthalic acid (filled with 30 wt% of glass fiber, DSC measurement melting point of unfilled product)
10 ° C, unfilled products show optical anisotropy when melted)
The cylinder temperature shown in Table 1 was measured using an injection molding machine IS-80 (trade name, mold clamping pressure 80 tons) manufactured by Toshiba Machine Co., Ltd.
Molding was performed under molding conditions such as mold temperature, injection pressure, holding pressure, and injection cycle time. Injection speed is 100mm / sec
Met.

Table 1 shows the measurement results of the bending strength and the tensile strength of the plate-like molded product obtained from the cavity 2.

Example 2 A thermotropic liquid crystal polymer comprising a quaternary copolyester of p-hydroxybenzoic acid / terephthalic acid / biphenol / isophthalic acid (unfilled product, DSC melting point: 410 ° C., optical anisotropy upon melting) (Shown), and molded under the molding conditions shown in Table 1 in the same manner as in Example 1.

Table 1 shows the measurement results of the bending strength and the tensile strength of the plate-like molded product obtained from the cavity 2.

Comparative Example Using the mold shown in FIG. 2, the thermotropic liquid crystal polymer of Example 1 was injection molded.

Table 1 shows the measurement results of the bending strength and the tensile strength of the plate-like molded product obtained from the cavity 2. In this comparative example, from the observation of the cut surface, the flow pattern was almost linear at the weld line, and the reflow length was zero according to the measurement method described above.

[Brief description of the drawings]

FIG. 1 is a plan view showing an injection molding die for obtaining a rectangular product of the same shape used in the present invention.

FIG. 2 is a plan view showing an injection mold used in a comparative example.

FIG. 3 is a schematic view of a cut surface at a weld line of the injection molded article of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Runner 2 Cavity 3 Separate cavity L Length of cavity 2 4,5 Weld line 6 Dotted line where flow pattern became linear Dotted line Weld line exposed on the surface of molded product Arrow Sprue

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-29859 (JP, A) JP-A-52-68260 (JP, A) JP-A-63-221023 (JP, A) 310924 (JP, A) JP-A-3-159713 (JP, A) JP-A-3-288609 (JP, A) JP-A-4-16320 (JP, A) JP-A-1-299015 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/00-45/84

Claims (3)

(57) [Claims] 1. A molten resin is injected from a plurality of gates into a mold cavity through a runner, and welded to the surface of the molded body corresponding to a junction where the plurality of molten resin flows merge in the mold cavity. In the method of injection molding of a thermotropic liquid crystal polymer in which a line is formed, a cavity having such a volume that one of the merging resin streams that merges can reflow after substantially merging at the merging section. A method for injection molding a thermotropic liquid crystal polymer having improved weld strength, wherein a cavity separate from the mold cavity is provided in a runner portion near one of the plurality of gates. 2. The molding method according to claim 1, wherein the liquid crystal polymer is a wholly aromatic copolyester. 3. The molding method according to claim 1, wherein the liquid crystal polymer contains 70% by weight or less of a filler.