JP3422424B2 - Injection molding method, injection molded body and injection mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injection-molding a thermotropic liquid crystal polymer in which the strength and appearance of weld lines are improved.

[0002]

2. Description of the Related Art The weld strength of a thermotropic liquid crystal polymer injection-molded product is extremely weak due to the orientation of the thermotropic liquid crystal polymer, which is a serious problem in the injection molding technology of the polymer.

The weld line is a line formed on the surface of the molded product corresponding to the confluence where the molten resin of the thermotropic liquid crystal polymer injected from the gate into the cavity through the runner is branched. Say. In the case of a thermotropic liquid crystal polymer, generally, the strength in the weld line is extremely low, and a simple thermal shock easily causes breakage such as cracking in the weld line portion.

Japanese Patent Application No. 2-417780 and Japanese Patent Application No. 2-4
In patent applications such as 17781 and Japanese Patent Application No. 2-417782, improvement in weld strength of an injection molded body of thermotropic liquid crystal polymer is proposed. However, specifically, it is not always practical because a resin pool or the like is required and extra resin other than the product is lost.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for injection molding a thermotropic liquid crystal polymer which has a high weld strength and is practical.

[0006]

SUMMARY OF THE INVENTION The above object of the present invention is achieved by varying the diameter which is converted to the cross-sectional area of the plurality of inlets run Na each other.

That is, the present invention provides an injection molding method for a thermotropic liquid crystal polymer, wherein a plurality of gates and a cavity having a plurality of inlet runners connected to each of the plurality of gates are used for injection molding of a thermotropic liquid crystal polymer. inlet run Na were different from each other diameters which are converted to the cross-sectional area of the injection of the thermotropic liquid crystal polymer with a pressure difference to flow of accompanying molten resin thereto, characterized in that a molten resin is injected into the cavity It relates to a molding method. The present invention also provides a plurality of gates and the plurality of gates.
Has multiple entrance runners that connect to each of the gates
Of thermotropic liquid crystal polymer with cavities
In the injection mold, multiple inlet runners have a cross-sectional area
The converted diameters have different diameters.
Multiple inlets for injecting molten resin into the cavity
A special feature is to create a difference in molten resin inflow pressure between runners.
It may be a sign .

The present invention will be further described below with reference to the drawings. FIG. 1 shows an outline of a molding die for molding a square-shaped molded product having a hole in the center by a two-point gate mold. In the figure, the cavities are gate 1 and gate 2.
An entrance runner 1 is connected to the gate 1, and an entrance runner 2 is connected to the gate 2. Runner 1 and runner 2
Are connected to the same sprue.

Since the die shown in FIG. 1 is a single-piece die, an exit gate and an exit runner are not provided, but a plurality of exit gates and an exit runner are appropriately provided in the cavity of FIG. It is also possible to connect the cavities and form a mold having a plurality of cavities.

Molten resin composed of thermotropic liquid crystal polymer is filled in the cavities from the sprue through the runners 1 and 2 through the gates 1 and 2, respectively.

Here, for example, the diameter converted into the cross-sectional area of the runner 1 is made larger than the diameter converted into the cross-sectional area of the runner 2. Along with this, the molten resins respectively injected from the gate 1 and the gate 2 flow in with different inflow pressures, and thus a pressure difference is generated between the two branched flows which also join together in the weld portion which is the joining portion. Therefore, at the confluent portion of the molten resin, the phenomenon of the resin flowing into one resin flow of the other resin flow (in the case of FIG. 1, the resin flow from the gate 1 enters the resin flow from the gate 2). )
Occurs, and as a result, improvement of the weld line strength can be achieved.

Any method can be adopted as a method for producing a pressure difference between the molten resin flows flowing into the cavity.
For example, the runner 1 and the runner 2 or the gate 1 and the gate 2 may be separately or simultaneously made to have different diameters (cross-sectional areas) from each other. Any method can be adopted as long as it is possible to generate a pressure difference between the merging branch streams. Diameter between runners or between gates (cross-sectional area)
In the case where such a phenomenon is caused by differentiating the above, by varying the cross-sectional area of the small diameter one with the large diameter one in the range of 5 to 95%, preferably 10 to 90%, It is possible to improve the weld strength due to the phenomenon of molten resin entering.

Although FIG. 1 shows the case of a two-point gate,
It can also be a multi-point gate with three or more points. For example, in a three-point gate, naturally the entrance runners are also three separate runners corresponding to each gate. In this case, similarly, a difference in inflow pressure of the molten resin may be generated, and for example, each inlet runner and / or gate diameter may be converted into a cross-sectional area and satisfy the above relationship.

As the runner shape, any known shape can be adopted, and for example, a trapezoid, a quadrangle, a triangle, a circle, a semicircle and the like are exemplified. For example, FIGS. 2 (a) and 2 (b)
It is also possible to adopt two trapezoidal runner shapes having the sectional shape shown in FIG.

Here, when the runner shape from the gate to the sprue is substantially constant, the cross-sectional area of the inlet runner is adopted for the runner near the gate. When the shape of the runner from the gate to the sprue is changing, the cross-sectional area of the runner 3 mm away from the gate and the point 30 mm away from the gate (near the sprue when the distance from the gate to the sprue is less than 30 mm) Let the average value with the cross-sectional area of the runner be the cross-sectional area of the runner.

The runner diameter of each inlet runner is appropriately determined in consideration of the size of the molded product and its shape. For example, it is generally 0.7 to 20 mm, preferably 0.9 to 15
It is adopted from the range of mm. Of course, it is important that the diameter of the inlet runner is converted into a cross-sectional area and different from each other as described above.

Here, the runner diameter refers to the diameter of a circular runner, and in the case of other shapes such as trapezoid, square, triangle, circle, and semicircle, the runner diameter r is expressed by the following formula 1. To be done.

R = 2S / L (Equation 1) S: Cross-sectional area of runner (in this case, cross-sectional area of the runner portion) L: Perimeter of runner

As the gate, a known gate can be adopted, and for example, a submarine gate, a side gate, a pin gate, a direct gate, a jump gate and the like can be preferably used. For example, two types of rectangular gate shapes having the cross-sectional shapes shown in FIGS. 3A and 3B can also be adopted.

Gate diameter of gate 1 and gate 2 (cross-sectional area)
As described above, the pressure difference of the molten resin flowing into the cavity is caused by the difference as described above, and at the confluence portion of the molten resin, the phenomenon of resin intrusion of one resin flow into the other resin flow (gate When the cross-sectional area of 1 is large, the resin flow from the gate 1 enters the resin flow from the gate 2), and as a result, the weld line strength can be improved.

Aside from the runner, the gate diameter (cross-sectional area) can be made different and can be made different at the same time. That is, (1) the gates have the same diameter (cross-sectional area) but only the runners have different diameters (cross-sectional areas).
(2) The diameters (cross-sectional areas) of the runners may be the same, and only the gate diameter (cross-sectional area) may be different. (3) Both the runner and the gate diameter (cross-sectional area) may be different at the same time. Since the gate diameter (cross-sectional area) is generally smaller than the runner diameter (cross-sectional area), there is no effect even if the gate cross-sectional area / runner cross-sectional area is changed.

Although the present invention has been described with a mold having one cavity, that is, a mold having one cavity, the present invention is not limited to this, and a multicavity having two or more cavities, for example, up to 30 cavities. It is also possible to perform injection molding by using the mold.

The shape of the molded product molded by the method of the present invention is not particularly limited as long as the flow of the molten resin flowing into the cavity is branched, in other words, a molded product in which a weld line is generated, for example, a circular shape. It may be a molded product of any shape such as square, square or triangular. However, injection molding of a relatively large volume molded article is preferable, and a preferable molded article volume is 0.8 cc or more, and more preferably 1 to 1000 cc.

In the present invention, the thermotropic liquid crystal polymer is injection molded. The thermotropic liquid crystal polymer is a resin that exhibits optical anisotropy when heat-melted.

As described above, the polymer exhibiting optical anisotropy when melted has the property that the polymer molecular chains have a regular parallel arrangement in the melted state. The properties of the optically anisotropic molten phase can be confirmed by a usual polarization inspection method using a crossed polarizer.

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

The thermotropic liquid crystal polymer used in the present invention can be produced by subjecting the above compounds to various ester forming methods such as a melt acidolysis 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 melt phase, and the remaining part does not form an anisotropic melt phase. Also included are polymers composed of segments of thermoplastic resin. Further, it also includes a composite of a plurality of thermotropic liquid crystal polymers.

Examples of the polymer that forms the optically anisotropic molten phase as described above include wholly aromatic polyesters and polyester ethers, and the constituent component thereof is (A) an aromatic dicarboxylic acid compound. At least 1
Species, (B) at least one kind of aromatic hydroxycarboxylic acid compound, (C) at least one kind of aromatic diol compound, (D) (D1) aromatic dithiol, (D2) aromatic thiophenol, (D3) ) At least one kind of aromatic thiolcarboxylic acid compound, (E) aromatic hydroxyamine, at least one kind of aromatic diamine compound, and the like. Although these may be configured independently, 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.

As the above-mentioned (A) aromatic dicarboxylic acid type compound, 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, 1,6-naphthalenedicarboxylic acid, or chloroterephthalic acid, dichloroterephthalic acid, bromoterephthalic acid, methylterephthalic acid, dimethylterephthalic acid, ethyl Examples thereof include alkyl, alkoxy or halogen-substituted products of aromatic dicarboxylic acids represented by terephthalic acid, methoxyterephthalic acid, ethoxyterephthalic acid and the like.

(B) Aromatic hydroxycarboxylic acid compounds include aromatic hydroxy 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 substitution products of aromatic hydroxycarboxylic acids represented by dichloro-2-naphthoic acid and the like.

As the aromatic diol (C), 4,4 '
-Dihydroxydiphenyl, 3,3'-dihydroxydiphenyl, 4,4'-dihydroxytriphenyl, hydroquinone, resorcin, 2,6-naphthalenediol, 4,4'-dihydroxydiphenyl ether, bis (4-hydroxyphenoxy) ethane, 3 , 3'-dihydroxydiphenyl ether, 1,6-naphthalene diol, 2,2-bis (4-hydroxyphenyl) propane, aromatic diol such as bis (4-hydroxyphenyl) methane, chlorohydroquinone, methylhydroquinone, t- Alkyl, alkoxy, aryl and ari of aromatic diols represented by butyl hydroquinone, phenyl hydroquinone, methoxy hydroquinone, phenoxy hydroquinone, 4-chlororesorcin, 4-methylresorcin, etc. Aryloxy or halogen-substituted derivatives thereof.

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

Examples of the aromatic thiophenol (D2) include
4-mercaptophenol, 3-mercaptophenol, 6-mercaptophenol and the like can be mentioned.

As the aromatic thiolcarboxylic acid (D3), 4-mercaptobenzoic acid, mercaptobenzoic acid, 6
-Mercapto-2-naphthoic acid, 7-mercapto-2-
Naphthoic acid and the like can be mentioned.

Examples of (E) aromatic hydroxyamine and aromatic diamine compounds include 4-aminophenol and 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'-hydroxydiphenyl sulfide, 4,4'-diaminophenyl sulfide (thiodianiline), 4,4'-diaminodiphenyl sulfone,
2,5-diaminotoluene, 4,4'-ethylenedianiline, 4,4'-diaminodiphenoxyethane, 4,
4'-diaminodiphenylmethane (methylenedianiline), 4,4'-diaminodiphenyl ether (oxydianiline) and the like can be mentioned.

Of these wholly aromatic polyesters, at least the general formula

[0038]

[Chemical 1]

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

[0040]

[Chemical 2]

[0041]

[Chemical 3]

There are others.

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

The thermotropic liquid crystal polymer in the present invention has been described above, but within the scope of the object of the present invention, inorganic or organic fibers such as glass fiber and carbon fiber, conventionally known inorganic or organic fibers such as talc and titanium dioxide. One or more fillers can be included in any amount. However, in the thermotropic liquid crystal polymer, if the blending ratio of the filler is too high, the weld line strength cannot be improved even if the molding method of the present invention is used.

Therefore, a thermotropic liquid crystal polymer containing an excessively large amount of the filler is not preferable because the effect of improving the weld line strength cannot be achieved. In the case of the thermotropic liquid crystal polymer which is preferable from this viewpoint, the thermotropic liquid crystal polymer in which the filler is blended in an amount of 70 wt% or less is preferable.

As the injection molding machine used in the present invention, a usual screw in-line type or plunger type molding machine can be used. Further, the injection molding can be performed under the usual molding conditions such as the cylinder temperature, the injection pressure, the injection speed, the mold temperature, and the holding pressure suitable for the resin to be injected.

That is, the injection molding conditions in the case of the thermotropic liquid crystal polymer are not particularly limited, but the injection cylinder temperature is 200 to 4 regardless of whether the filler is filled or unfilled.
20 ° C, mold temperature 30-200 ° C, injection pressure 100-2
Injection speed (cylinder movement speed) at 000 kg / cm ^2.
It can be appropriately selected from the range of 5 to 500 mm / sec.
Since the holding pressure does not directly affect the effect of the present invention, it may be appropriately adjusted according to the resin, but usually 50 to 1200 kg / cm ^{2 is} in the range of 0.5 to 60 seconds. It can be selected appropriately.

After injection molding, the article may be cooled by an appropriate cooling time suitable for the article, for example, a cooling time of 2 to 120 seconds, and then the article may be taken out by a conventional method.

[0049]

EXAMPLES The present invention will be specifically described below with reference to Examples and the like.

<Mold used> First, the molds used in Examples and Comparative Examples will be described. Figure 1 is a vertical 140 mm, horizontal 1 1 0 mm, 100 × the central portion 8
FIG. 3 is a plan view showing a cavity and a runner portion of an injection mold that can obtain a molded product having a thickness of 2.5 mm with a hole of 0 mm.

Two sets of runners and gates are provided in the cavity, and one sprue is commonly used. One runner and gate have a nested structure and are variable. The runner shape is trapezoidal, and its dimensions are arbitrarily selected from those shown in FIGS. 2 (a) and 2 (b). The gate is a side gate, and the gate diameter is 0.8 m as shown in FIGS. 3 (a) and 3 (b).
It has a structure in which m or 1.2 mm can be arbitrarily selected.

<Measurement of Thermal Shock Strength> A molded article sample is left in a freezer with an ambient temperature of −40 ° C. for 1 hour and then left in an oven with an ambient temperature of 230 ° C. for 1 hour, and the thermal shock test is performed for 10 cycles. I did. Then, the state of destruction such as cracks in the weld line portion was observed.

The results of the evaluation evaluated the state of destruction according to the following criteria. ⊚: No cracks are seen. ◯: Very few cracks and the like. Δ: A crack is seen, but the depth of the crack is slightly large. X: A crack is seen and the depth of the crack is large.

Example 1 In the injection molding die shown in FIG. 1, the runner 1 was a runner having the shape shown in FIG. 2A, the runner 2 was the runner having the shape shown in FIG. A thermotropic liquid crystal polymer composed of a quaternary copolyester of p-hydroxybenzoic acid / terephthalic acid / biphenol / isophthalic acid (glass fiber 30 wt% filled, unfilled DSC) using the gates having the shape shown in FIG. Measured melting point 350
℃, unfilled product shows optical anisotropy when melted), using an injection molding machine SG-25 (trade name, mold clamping pressure 25 tons) manufactured by Sumitomo Heavy Industries, Ltd., a cylinder temperature of 350 ° C., a mold Temperature 100 ° C, injection pressure 600 kg / cm ² , injection speed 18
0 mm / sec, holding pressure 600 kg / cm ² , holding time 4
Seconds, cooling time was 20 seconds. The weld line was approximately generated at the position indicated by the dotted line 1 in FIG. The obtained molded product was subjected to a thermal shock test. As a result, the evaluation was ⊚.

Example 2 In the injection molding die shown in FIG. 1, the runner 1 was used.
2A, the runner 2 has the runner having the shape shown in FIG. 2B, the gate 1 has the gate having the shape shown in FIG. 3A, and the gate 2 has the gate having the shape shown in FIG. 3B. Was used under the same molding machine and molding conditions as in Example 1.
The weld line was approximately generated at the position indicated by the dotted line 2 in FIG.
The obtained molded product was subjected to a thermal shock test. As a result, the evaluation was ⊚.

Comparative Example 1 In the injection molding die shown in FIG. 1, the runners 1 and 2 have the shape of FIG. 2A, and the gates 1 and 2 have the shape of FIG. 3B. Then, the molding was performed under the same molding machine and molding conditions as in Example 1. The weld line was approximately generated at the position indicated by the dotted line 3 in FIG. The obtained molded product was subjected to a thermal shock test. The result judgment was x.

[0057]

EFFECTS OF THE INVENTION By making the diameters converted into the cross-sectional areas of a plurality of runners connected to the cavities different from each other , it is possible to effectively cause reflow of the resin and improve the weld line strength of the thermotropic liquid crystal polymer. Can be made.

[Brief description of drawings]

FIG. 1 is a plan view showing the outline of a mold for obtaining an injection molded product.

FIG. 2 is a plan view showing a runner shape.

FIG. 3 is a plan view showing a gate shape.

FIG. 4 is a plan view showing a weld line position of an injection molded product.

Claims (7)

(57) [Claims] 1. An injection molding method for a thermotropic liquid crystal polymer, comprising: a plurality of gates; and a plurality of inlet runners connected to each of the plurality of gates. br /> with different diameters to be converted to the cross-sectional area of the emission Na each other, the thermotropic liquid crystal polymer with a pressure difference to flow of accompanying molten resin thereto, characterized in that a molten resin is injected into the cavity Injection molding method. 2. Converted to cross-sectional area of inlet runner and gate
2. The method of injection molding a thermotrobic liquid crystal polymer according to claim 1, wherein different diameters are used. 3. A size is converted to the cross-sectional surface the product of one of the inlet runners, or diameter size is converted to the cross-sectional area of the inlet runner and gate, which is converted to the cross-sectional area of the other of the inlet runner,
Alternatively, the method for injection molding a thermotropic liquid crystal polymer according to any one of claims 1 and 2, wherein the cross sectional area is in the range of 10 to 90% with respect to the diameter converted into the cross sectional area of the inlet runner and the gate. 4. The injection molding according to claim 1.
Formed Thermotropic Liquid Crystal Poly
Injection molding of Ma . 5. A plurality of gates and the gates of the plurality of gates.
Cavity with multiple inlet runners connected to each
Injection molding of thermotropic liquid crystal polymer with
In the mold, multiple inlet runners are converted to cross-sectional areas
The cavities have different diameters and
Between multiple inlet runners when injecting molten resin into the tee
A service characterized by causing a difference in inflow pressure of molten resin.
-Mold for injection molding of morphotropic liquid crystal polymer. 6. Converted to cross-sectional area of inlet runner and gate
The diameter according to claim 6, which is different from each other.
Mold for injection molding of thermotropic liquid crystal polymer. 7. A method comprising a plurality of cavities.
The thermotropy according to any one of claims 6 to 7.
Mold for liquid crystal polymer injection molding.