JP2804100B2 - Method for producing molded article comprising liquid crystal polymer composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a molded article comprising a liquid crystal polymer composition having excellent heat resistance.

(Prior art) A liquid crystal polymer has a rigid molecular skeleton and forms an anisotropic melt when in a molten state. The liquid crystal polymer is easily oriented by the shear stress during molding, and has high strength,
It is attracting attention as a new engineering plastic that exhibits a high elastic modulus and provides molded products with excellent barrier properties, heat resistance and dimensional stability.

Although the liquid crystal polymers proposed so far are numerous, many of them have not been put to practical use because the raw materials have not been industrialized.

Currently marketed liquid crystal polymers are roughly classified into semi-aromatic liquid crystal polymers and wholly aromatic liquid crystal polymers. A semi-aromatic liquid crystal polymer is a liquid crystal polymer having an aliphatic group such as an ethylene glycol residue together with an aromatic group in the main chain, and a wholly aromatic liquid crystal polymer is a liquid crystal polymer in which the main chain is composed of only aromatic groups. It is.

Although the wholly aromatic liquid crystal polymer has excellent heat resistance, it needs to be manufactured using expensive raw materials, and has a problem that it is expensive. On the other hand, semi-aromatic liquid crystal polymers can be manufactured using mass-produced raw materials and have the advantage of being inexpensive, but they are inferior in heat resistance to wholly aromatic liquid crystal polymers and have reflow soldering resistance. However, there is a problem that the method cannot be applied to the heat-resistant field as required.

The present inventors made use of the advantages of both by making a composition obtained by melt-blending a semi-aromatic liquid crystal polymer and a wholly aromatic liquid crystal polymer to obtain a liquid crystal polymer composition having excellent heat resistance and a relatively low cost. I found out. However,
Since the wholly aromatic liquid crystal polymer has a high melting point, if the melt blending with the semi-aromatic liquid crystal polymer is performed at a temperature at which the wholly aromatic liquid crystal polymer melts, the polymer partially undergoes thermal decomposition, and the molded product is colored or bent. It has been found that there is a problem that mechanical properties such as strength and flexural modulus are reduced.

(Problems to be Solved by the Invention) The present invention relates to a method for blending a semi-aromatic liquid crystal polymer and a wholly aromatic liquid crystal polymer and subjecting the obtained liquid crystal polymer composition to injection molding to produce a molded product. An object of the present invention is to provide a method for producing a molded article made of a liquid crystal polymer composition which can prevent thermal decomposition and can provide a molded article having excellent heat resistance and mechanical properties.

(Means for Solving the Problems) The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by lowering the temperature at which both liquid crystal polymers are blended and by sufficiently increasing the temperature of injection molding. The inventors have found that this object is achieved, and have reached the present invention.

That is, the present invention relates to a semi-aromatic liquid crystal polymer and ASTM D
Blend with a wholly aromatic liquid crystal polymer whose heat distortion temperature (HDT) measured under a load of 18.6 kg / cm ² based on -648 and over 200 ° C, and injection molded the resulting liquid crystal polymer composition When manufacturing the product, blend the two liquid crystal polymers
Injection molding is performed at a temperature of 300 ° C or less and at least a temperature at which the semi-aromatic liquid crystal polymer melts, and injection molding is performed at a temperature of 380 ° C or less and at a high enough temperature to melt the wholly aromatic liquid crystal polymer. The gist of the present invention is a method for producing a molded article comprising a liquid crystal polymer composition.

The semi-aromatic liquid crystal polymer in the present invention includes aromatic components such as terephthalic acid and parahydroxybenzoic acid and adipic acid, sebacic acid, ethylene glycol, 1,3-butanediol, 1,4-butanediol and neopentyl glycol. , Cyclohexanediol and the like. Specific examples of the semi-aromatic liquid crystal polymer include the liquid crystal polymers disclosed in JP-B-56-18016 and JP-A-60-186527. From an industrial point of view, a copolymerized polyester comprising ethylene terephthalate units and parahydroxybenzoic acid residue units is most preferred, and those having a high HDT (about 150 ° C. or higher) are particularly preferred.

As the wholly aromatic liquid crystal polymer, one that can be uniformly blended with the semi-aromatic liquid crystal polymer and has an HDT of 200 ° C. or higher is used. With a wholly aromatic liquid crystal polymer having a low HDT, a large amount of an expensive wholly aromatic liquid crystal polymer must be used in order to obtain a composition having sufficiently high heat resistance, which does not meet the purpose of the present invention. Specific examples of the wholly aromatic liquid crystal polymer include a copolymerized polyester comprising a 6-hydroxy-2-naphthoic acid residue unit and a parahydroxybenzoic acid residue unit disclosed in JP-A-54-77691. Kosho 47
-47870, a copolyester comprising a residue unit of parahydroxybenzoic acid, a unit of terephthalic acid and a unit of a dihydric phenol, a terephthalic acid residue disclosed in JP-A-53-65421 And a phenylhydroquinone residue unit, and a copolymer polyester comprising a terephthalic acid residue unit, a phenylhydroquinone residue unit and a styrohydroquinone residue unit disclosed in US Pat. No. 4,600,765. Can be Above all, a wholly aromatic liquid crystal polyester having an HDT of 230 ° C. or higher disclosed in JP-B-47-47870,
The effect of improving heat resistance is particularly large and preferable.

In the present invention, first, a semi-aromatic liquid crystal polymer and a wholly aromatic liquid crystal polymer are blended to obtain a liquid crystal polymer composition. The temperature at that time is 300 ° C. or less, and at least the semi-aromatic liquid crystal polymer is melted. It is necessary that the temperature be equal to or higher than the temperature of If the temperature is too high, part of the polymer is thermally decomposed, coloring the molded product or deteriorating its mechanical properties. On the other hand, if the temperature is too low, a uniform composition cannot be obtained. Usually, the blend is formed into chips and subjected to injection molding, but if blended at least at a temperature at which the semi-aromatic liquid crystal polymer melts, it can be extruded and formed into chips. It is preferable to blend and extrude in a state where it is not completely melted, because it is easy to form chips.

The blending of the two liquid crystal polymers can be carried out by a conventional melt blending apparatus, but in the case of industrial practice, it is advantageous to use a twin-screw extruder to blend and form chips.

The liquid crystal polymer composition obtained by blending both liquid crystal polymers is injection molded into a molded product.
The temperature must be lower than 380 ° C and high enough to melt the wholly aromatic liquid crystal polymer. In the production of the heat-resistant molded article of the present invention, this temperature is usually 320 ° C.
° C or higher. When molded at a temperature at which the wholly aromatic liquid crystal polymer does not melt sufficiently, the particles of the unmelted substance hinder the molecular orientation,
A molded article having sufficient mechanical properties cannot be obtained. However, if the molding temperature is too high, even if the residence time is shortened, the effect of thermal decomposition appears, so a molding temperature of 380 ° C or lower is generally employed.

As the injection molding machine, a generally used horizontal or vertical injection molding machine can be used. However, an injection molding machine having a shaft with a high blending effect and capable of shortening the residence time is preferable. Then, in order to obtain a more uniform molded product, an appropriate back pressure may be applied as needed.

The composition according to the present invention includes a filler such as glass fiber, carbon fiber, wollastonite, mica, whisker, etc., or a material which does not significantly impair the heat resistance of the composition, as is performed with ordinary molding resins. Other resins and the like may be mixed, and it is rather preferable to mix these in terms of performance improvement and cost reduction.

The molded product obtained by the method of the present invention is widely used not only in the field of electrical and electronic devices such as connectors and switches requiring solder resistance, but also in applications requiring heat resistance such as LED cases and light reflectors. be able to.

(Examples) Next, the present invention will be specifically described with reference to examples.

Examples 1 to 7 A semi-aromatic liquid crystal polymer composed of an ethylene terephthalate unit and a parahydroxybenzoic acid residue unit and having a dissolution temperature of 280 ° C. and an HDT of 170 ° C. (Rodrun LC-50 manufactured by Unitika Ltd.)
(00) and a wholly aromatic liquid crystal polymer having a dissolution temperature of 340 ° C and an HDT of 265 ° C comprising a parahydroxybenzoic acid residue unit, a terephthalic acid residue unit and a dihydric phenol residue unit.
At a weight ratio shown in the table, using a twin screw extruder manufactured by Toyo Seiki Co., Ltd .: Labo Plastomill 20R200, the mixture was blended at a temperature of 285 ° C., extruded into strands, cooled through a water bath, and then cut into chips.

At this blending temperature, the semi-aromatic liquid crystal polymer melted, but the wholly aromatic liquid crystal polymer did not completely melt, dispersing as if it were a filler, and chipping was smooth.

After drying the obtained chips, injection molding machine: J
Using -100S, injection molding was performed at a resin temperature of 350 ° C.

Comparative Examples 1-2 The above semi-aromatic liquid crystal polymer and wholly aromatic liquid crystal polymer were molded independently under the same conditions to obtain molded articles.

Comparative Examples 3 to 9 Molded products were obtained in the same manner as in Examples 1 to 7, except that the blending temperature was 350 ° C.

Table 1 shows the characteristic values of the molded products obtained in the above Examples and Comparative Examples.

The molded products obtained in Examples 1 to 7 did not show coloring or silver due to thermal decomposition, and showed remarkable improvement in mechanical properties as compared with the molded products obtained in Comparative Examples 3 to 9.

Examples 8 to 14 and Comparative Examples 10 to 18 In the above Examples and Comparative Examples, when blending both liquid crystal polymers, 30% by weight of glass fiber was added to the composition and blended at the temperature shown in Table 2 to form chips. , To obtain a molded product.

 Table 2 shows the characteristic values of the obtained molded products.

The molded products obtained in Comparative Examples 12 to 18 were colored slightly brown, and foaming was observed in some places, but the molded products of Examples 8 to 14 showed good appearance.

(Effects of the Invention) According to the present invention, it is possible to produce a molded article having excellent heat resistance and mechanical properties at a low cost by taking advantage of the semi-aromatic liquid crystal polymer and the wholly aromatic liquid crystal polymer. Become.

Claims (1)

(57) [Claims] The heat distortion temperature measured under a load of 18.6 kg / cm ² based on a semi-aromatic liquid crystal polymer and ASTM D-648 is 200.
When blending with a wholly aromatic liquid crystal polymer having a temperature of at least 300 ° C and subjecting the resulting liquid crystal polymer composition to injection molding to produce a molded product, the blend of both liquid crystal polymers must be at a temperature of 300 ° C or less and at least a semi-aromatic liquid crystal polymer. A method for producing a molded product comprising a liquid crystal polymer composition, wherein the molding is performed at a temperature equal to or higher than the temperature at which the polymer melts, and the injection molding is performed at a temperature of 380 ° C. or lower and at a high temperature sufficient to melt the wholly aromatic liquid crystal polymer.