JPH1148278A - Method for injection molding of liquid crystal polymer and injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for injection molding of liquid crystal polymer to suppress generation of a blister suitable to a molding which requires high temperature heat treating step (for about 3 to 5 min at 200 to 240 deg.C) such as solder welding or infrared reflowing. SOLUTION: In the case of injection molding of the liquid crystal polymer, the polymer is injection molded by using an injection molding machine using a screw having a screw compression ratio of 1.90 or less. And, in the case of injection molding the polymer, the polymer is injection molded with a set temperature of a rear part of a cylinder in a temperature range of (melting point -20 deg.C) to (melting point +10 deg.C) of used resin and with resin temperature injected from a nozzle in a temperature range of melting point to (melting point +25 deg.C).

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 liquid crystal polymer and an injection molded article. More specifically, the present invention relates to an injection molding method and an injection molded product of a liquid crystalline polymer suitable as a molded product requiring a high-temperature heat treatment step (200 to 240 ° C. for about 3 to 5 minutes) such as solder welding and infrared reflow.

[0002]

2. Description of the Related Art Liquid crystal polymers are often used for materials requiring high-temperature heat treatment (solder welding, infrared reflow, etc.) because of their good high-temperature thermal stability. However, if the injection-molded product is left in a high-temperature environment of 200 ° C. or more, fine blisters called blisters may be formed on the surface of the molded product, resulting in defective shape. This not only impairs the appearance of the molded product, but also causes a problem that the function as a product does not work due to a change to a shape or dimension that greatly deviates from the originally designed shape. As an example where such high-temperature heating treatment is practically used, when soldering a connector molded product or the like to a substrate, solder is applied in advance on the substrate, the connector molded product is placed thereon, and the solder is melted. By placing these prepared samples in a heated furnace capable of causing
There is a method of bonding the connector and the board by melting the solder, but the blisters described above occur on the molded product, causing problems such as poor fitting in the processing after the heat treatment, greatly hindering automation in the product processing process , Greatly reducing productivity. It is considered that such blisters are generated because a gas component held in the injection-molded product expands inside the molded product by the heat treatment, thereby exerting an effect of pressing and expanding the surface layer. If it is a general thermoplastic resin molded product, blisters are rarely generated because the gas component inside the molded product during heating easily transmits from the molded product surface to the outside,
The liquid crystal polymer has a prominent gas barrier property, and blisters are easily generated because the gas component can be suppressed from transmitting to the outside. At present, as a method of improving blister generation, a method of suppressing the cylinder temperature to be as low as possible in order to suppress gas components generated during injection molding has been taken.However, when an effective effect cannot be obtained, There are problems such as deterioration of appearance. In addition, a method of improving the blister by gradually allowing the internal gas to permeate to the outside by leaving it heated and left for a certain period of time in a high temperature environment lower than the temperature at which the blister occurs,
There is a disadvantage that secondary processing costs are required. Therefore,
There is a need for a method for improving the fundamental blistering, that is, for improving the blistering temperature.

[0003]

The inventors of the present invention have conducted intensive studies with the aim of solving the above problems and obtaining molded articles with improved blister generation. As a result, the screw compression ratio was 1.90.
Using an injection molding machine using the following screws,
Alternatively, the present inventors have found that by forming a cylinder at a specific temperature range, it is possible to efficiently improve the blister generation temperature of a molded product, and arrived at the present invention. That is, in the present invention, when the liquid crystal polymer is injection-molded, 1) Injection molding using an injection molding machine using a screw having a screw compression ratio of 1.90 or less expressed by an area ratio of a screw supply section and a measuring section. 2) The cylinder set temperature condition is defined as: (melting point −20 ° C.) to (melting point +10)
C) and the temperature of the resin injected from the nozzle is in the range of the melting point of the resin to (melting point + 25 ° C.). 3) Injection molding is performed by combining the above methods 1) and 2). Accordingly, the present invention relates to an injection molding method of a liquid crystal polymer and an injection molded product characterized by improving a blister generation temperature.

[0004]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The concrete constitution of the present invention will be described below. The liquid crystalline polymer used in the present invention has a molecular orientation in a molten state and exhibits optical anisotropy. Observation of anisotropy in a molten state can be performed by a conventional polarization inspection method using a crossed polarizer. More specifically, the confirmation of the anisotropic molten phase was performed using a Leitz polarizing microscope and Leit.
z Place the molten sample on the hot stage in a nitrogen atmosphere for 40 minutes.
It can be carried out by observing at double magnification. When tested between crossed polarizers, the polymers of the present invention transmit polarized light and exhibit optical anisotropy, even in the melt-static state. This can be observed as an optical pattern specific to the liquid crystal phase in a certain temperature range when gradually heated. Also, in X-ray diffraction, a phase-specific diffraction pattern can be observed. In thermal analysis, a differential scanning calorimeter is generally used, and entropy changes and transition temperatures of various phase transitions can be measured.
The liquid crystalline polymer used in the present invention is preferably an aromatic polyester or an aromatic polyesteramide, and a polyester containing an aromatic polyester and an aromatic polyesteramide partially in the same molecular chain is also a preferable example.
Particularly preferred are a liquid crystalline aromatic polyester and a liquid crystalline aromatic polyesteramide having at least one compound selected from the group consisting of aromatic hydroxyl carboxylic acid, aromatic hydroxylamine and aromatic diamine as a constituent. More specifically, 1) a polyester mainly comprising one or more aromatic hydroxycarboxylic acids and derivatives thereof 2) mainly a) one or more aromatic hydroxycarboxylic acids and derivatives thereof and b) Polyester comprising one or more aromatic dicarboxylic acids, alicyclic dicarboxylic acids and derivatives thereof and c) at least one or two or more aromatic diols, alicyclic diols, aliphatic diols and derivatives thereof 3) Mainly a) one or more aromatic hydroxycarboxylic acids and derivatives thereof and b) one or more aromatic hydroxyamines, aromatic diamines and derivatives thereof and c) aromatic dicarboxylic acids and fats Polyesteramide comprising one or more cyclic dicarboxylic acids and derivatives thereof 4) Mainly a) aromatic hydroxycarboxylic acids and And b) one or more aromatic hydroxyamines, aromatic diamines and derivatives thereof and c) one or more aromatic dicarboxylic acids, alicyclic dicarboxylic acids and derivatives thereof. Polyester amides comprising two or more and d) at least one or two or more of aromatic diols, alicyclic diols, aliphatic diols and derivatives thereof. Further, a molecular weight modifier may be used in combination with the above constituents as necessary. Preferred examples of specific compounds constituting the liquid crystalline polyester of the present invention include naphthalene such as 2,6-naphthalenedicarboxylic acid, 2,6-dihydroxynaphthalene, 1,4-dihydroxynaphthalene and 6-hydroxy-2-naphthoic acid. Compounds, biphenyl compounds such as 4,4'-diphenyldicarboxylic acid and 4,4'-dihydroxybiphenyl, para-substituted benzenes such as p-hydroxybenzoic acid, terephthalic acid, hydroquinone, p-aminophenol and p-phenylenediamine Compounds and their nucleus-substituted benzene compounds (substituents are selected from chlorine, bromine, methyl, phenyl and 1-phenylethyl), and meta-substituted benzene compounds such as isophthalic acid and resorcinol. Preferred examples of the specific compound include 2,6-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid.
Dihydroxynaphthalene, naphthalene compounds such as 1,4-dihydroxynaphthalene and 6-hydroxy-2-naphthoic acid, biphenyl compounds such as 4,4′-diphenyldicarboxylic acid and 4,4′-dihydroxybiphenyl, the following general formula
Compound represented by (I), (II) or (III):

[0005]

Embedded image

(Where X is a group selected from alkylene (C ₁ -C ₄ ), alkylidene, —O—, —SO—, —SO ₂ —, —S— and —CO— Y :—( CH ₂ ) _{n - (n = 1~4),} - a _{O (CH 2) n O- (} n = 1~4) from the group selected).

The liquid crystalline polyester used in the present invention may be a polyalkylene terephthalate which does not show an anisotropic molten phase partially in the same molecular chain, in addition to the above-mentioned constituents. In this case, the alkyl group has 2 to 4 carbon atoms. Among the above-mentioned components, those containing one or more compounds selected from a naphthalene compound, a biphenyl compound and a para-substituted benzene compound as essential components are more preferable examples. Among the p-substituted benzene compounds, p-hydroxybenzoic acid, methylhydroquinone and 1-phenylethylhydroquinone are particularly preferred examples. Specific examples of the compound having an ester-forming functional group serving as a constituent component and specific examples of a polyester forming an anisotropic molten phase preferable for use in the present invention are described in JP-B-63-36633. I have. The aromatic polyesters and polyesteramides described above also exhibit a logarithmic viscosity (IV) of at least about 2.0 dl / g, such as about 2.0-10.0 dl / g, when dissolved in pentafluorophenol at 0.1% by weight at 60 ° C. Generally shown.

[0008] The thermotropic liquid crystal polymer of the present invention is polymerized by a direct polymerization method or a transesterification method. As the polymerization method, a melt polymerization method, a solvent polymerization method, a slurry polymerization method or the like is used. In these polymerization methods, various catalysts can be used, and typical examples are dialkyltin oxide, diaryltin oxide, titanium dioxide, alkoxytitanium silicates, titanium alcoholate,
Alkali and alkaline earth metal salts of carboxylic acids, B
A Lewis acid such as salts of F ₃ and the like. The amount of catalyst used is generally from about 0.001 to 1% by weight, particularly preferably from about 0.01 to 0.2% by weight, based on the total weight of the monomers. Polymers produced by these polymerization methods can be further increased in molecular weight by solid phase polymerization in which heating is performed under reduced pressure or in an inert gas. Further, as the thermotropic liquid crystal polymer of the present invention, it is preferable that the number of monomer components is small, and it is desirable that the number of components be three or less, particularly two or less.

Next, the injection molding method of the present invention will be specifically described. Generally, when performing injection molding of a polymer, a standard screw manufactured by an injection molding machine manufacturer is mostly used. However, detailed information on the shape of the screw is not generally disclosed by the know-how of each manufacturer. When actually performing molding work, it is empirically confirmed that there is no blistering due to molding machine differences and the difference in frequency, but in addition to screws, injection capacity, temperature sensor position, heater capacity, etc. are different,
He left many unclear points about the cause. The present inventors have clarified the effect on blister generation,
It has been found that among the elements of the injection molding machine, setting the screw compression ratio to 1.90 or less is particularly effective in improving blister generation. FIG. 1 shows a schematic shape of a screw including a measuring section, a compression section, and a supply section used for injection molding. FIG. 2 is a cross-sectional view of the measuring section of the screw,
FIG. 3 shows the cross-sectional shape of the screw supply section. The screw compression ratio may be expressed by the ratio of the depth of the supply section and the depth of the metering section. In the present invention, the screw compression ratio is defined by the area b of the screw supply section shown by the hatched portion in FIG. Is the ratio (b / a) divided by the area a of the measuring part of the screw indicated by the hatched part. The screw compression ratio of standard commercially available thermoplastic resin injection molding machines excluding special material specifications varies depending on the manufacturer and screw diameter, but on average it seems that many are in the range of 2 to 2.5. is there. In injection molding, when using a screw with a large compression ratio, in order to supply the material from the supply side to the measurement side, the direction in which the volume space in the cylinder becomes narrower than when using a screw with a small compression ratio, The material is then in a state of melting the resin while applying greater compression. On the other hand, regarding the melting of the resin, it is originally melted by screw shear insulation or cylinder heater heat.However, when the molding cycle is short and the cylinder heater heat on the supply side is low, preheating and heat transfer from the cylinder heater heat are The point at which the resin melts due to the shortage tends to move more toward the metering side at the screw position. In such a case, since the resin pellets are not sufficiently melted and are strongly melted in the vicinity of the screw compression portion, they are indented in an unmelted state, so that the resin pellets are wound around the screw outer periphery. Due to this phenomenon, the residence time of the wrapped resin in the cylinder becomes longer, gas is more likely to be generated, and the resin feed path from the supply side to the measurement side is partially squeezed. A void is formed at the position immediately after, so that the gas component is easily stored. As a result, the gas component and the molten resin are mixed and mixed into the molded product in a large amount. Since the gas component has a large expansion pressure, blisters are generated at a low temperature. Therefore, in order to improve the blister generation temperature of the liquid crystal polymer, it is effective to reduce the screw compression ratio to 1.90 or less, which is smaller than a commonly used compression ratio, in order to prevent winding due to indentations.

[0010] In addition, by injection molding with an injection molding machine equipped with the above-described low compression screw, a molded article with improved blister generation can be obtained. It has been found that performing under molding conditions is also an effective method for improving the blister generation temperature. That is, the cylinder set temperature condition is set such that the rear temperature is (melting point −20 ° C.) to (melting point +
In other words, injection molding is performed at a temperature of the resin injected from the nozzle in a temperature range of 10 ° C.) and a temperature range of the melting point to (melting point + 25 ° C.). Conventionally, as a method of improving the blister generation temperature from the molding method, a method of lowering the resin temperature as much as possible in order to suppress the decomposition of the resin has been recommended, and molding at a temperature lower than the melting point of the liquid crystal polymer has been observed. . In addition, it has been considered that a method in which the temperature at the rear portion of the cylinder is suppressed to a low temperature in order to reduce the residence time in the cylinder is reduced. In the present invention, the temperature of the resin using the cylinder rear set point (melting point -20 ° C)
~ (Melting point + 10 ° C) by setting the temperature range to sufficiently promote resin preheating for melting into resin pellets,
Screw wrapping due to indentation of the resin pellets at the time of measurement was prevented, and the phenomenon of gas component wrapping was suppressed. on the other hand,
The temperature of the resin injected from the nozzle is from melting point to (melting point + 25
C), and preferably within a temperature range of (melting point + 5 ° C) to (melting point + 25 ° C), the resin itself secures a sufficient molten state, and exhibits sufficient strength and physical properties inherent to the resin, Even if there is some entrainment of gas, the high-temperature rigidity of the liquid crystal polymer surface layer makes it possible to obtain rigidity that can resist surface deformation due to the expansion pressure of the gas component. Prevent it. Further, by setting the injection molding conditions in which the temperature is raised stepwise or horizontally from the rear temperature to the front temperature, the balance between supply and melting in the cylinder can be maintained in a good state, and the melt residence time of the resin can be reduced. This is more preferable because it can be shortened and suppresses the generation of gas components. If the temperature set at the rear of the cylinder is lower than the melting point of the resin by at least 20 ° C, preheating of the resin will be insufficient, the screw wrapping phenomenon of the resin pellet will easily occur, the amount of gas components will increase, and the expansion pressure in the molded product will increase. And blisters are generated even at low temperatures. Conversely, if the temperature set at the rear of the cylinder is set to a temperature higher than the melting point of the resin used by more than 10 ° C., the decomposition of the resin is promoted and a large amount of gas components are generated, which is not preferable. Further, if the temperature of the resin injected from the nozzle is lower than the melting point, physical properties are reduced due to the presence of unmelted components, and in particular, the blister generation temperature is reduced due to a reduction in high-temperature rigidity.
Therefore, in the injection molding of the liquid crystal polymer, as the molding conditions for more effectively improving the blister temperature,
Cylinder rear set temperature is used for resin (melting point -20
It is necessary to perform injection molding in a temperature range of (° C.) to (melting point + 10 ° C.) and in a temperature range of the melting point to (melting point + 20 ° C.) of the resin injected from the nozzle.

[0011]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
The evaluation method and the like are as follows. (Blister temperature) The molded product obtained by injection molding is
The product was immersed in silicone oil stabilized at a constant temperature by heating and stirring for 5 minutes, and after cooling, the appearance of the molded product was visually checked for blisters. The temperature interval of the silicon oil is in increments of 10 ° C.
The upper limit temperature at which no blister occurred was set as the blister temperature. Example 1 Vectra E130i (manufactured by Polyplastics Co., Ltd., melting point: 335 ° C.) using an injection molding machine PS60E manufactured by Nissei Plastic Industry Co., Ltd.
Was subjected to injection molding under the conditions shown in Table 1 to obtain a molded product. The injection pressure was 50 MPa, and the injection speed was 33 mm / s. Table 1 shows the results. Examples 2 to 6 A molded product was obtained and evaluated in the same manner as in Example 1 except that the screw compression ratio and the resin temperature were changed. Table 1 shows the results
Shown in Example 7 A molded product was obtained and evaluated in the same manner as in Example 1 except that an injection molding machine M70B-DM manufactured by Meiki Seisakusho was used. Table 1 shows the results. Comparative Examples 1-3 Injection molding machine PS60E manufactured by Nissei Plastic Industry Co., Ltd., compression ratio 2.39
Vectra E130i (manufactured by Polyplastics Co., Ltd., melting point: 335 ° C.) was injection-molded under the conditions shown in Table 2 to obtain a molded product. The injection pressure was 50 MPa, and the injection speed was 33 mm / s. Table 1 shows the results.

[0012]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a view showing a schematic shape of a screw used for injection molding, comprising a measuring section, a compression section, and a supply section.

FIG. 2 shows the cross-sectional shape of the measuring section of the screw, FIG.
3 is a sectional view taken along line AA of FIG.

FIG. 3 shows a cross-sectional shape of a screw supply section,
FIG. 7 is a sectional view taken along line BB of FIG.

Claims (4)

[Claims] 1. In injection molding a liquid crystal polymer,
An injection molding method for a liquid crystal polymer, which comprises performing injection molding using an injection molding machine using a screw having a screw compression ratio of 1.90 or less. 2. Injection molding of a liquid crystal polymer,
The set temperature at the rear of the cylinder is used for the resin (melting point-
Injection molding of a liquid crystal polymer, wherein the temperature is in the range of 20 ° C. to (melting point + 10 ° C.) and the temperature of the resin injected from the nozzle is in the range of the melting point of the resin to (melting point + 25 ° C.). . 3. In injection molding a liquid crystal polymer,
Using an injection molding machine using a screw with a screw compression ratio of 1.90 or less, set the temperature at the rear of the cylinder to the temperature range of (melting point -20 ° C) to (melting point + 10 ° C) of the resin to be used, and inject from the nozzle. Injection molding, wherein the temperature of the resin to be used is in a temperature range from the melting point of the resin to (melting point + 25 ° C.). 4. An injection molded article of a liquid crystal polymer formed by the injection molding method according to claim 1.