JPH05112714A - Polyamide resin composition, molded object, and housing for electronic device - Google Patents

Abstract

PURPOSE:To provide a polyamide resin composition which is injection-moldable and suited for producing a thin-wall molding and has high strength, low moisture absorption, and good dimensional stability even after moisture absorption. CONSTITUTION:The title composition comprises 100 pts.wt. amorphous polyamide and 10-100 pts.wt. liquid-crystal polyester. It may further contain 3-40 pts.wt. reinforcing filler per 100 pts.wt. the sum of the two components. Moldings produced from this composition and each constituting the bottom of a housing for an electronic device are shown in Figs. (A) to (C), in which numeral 1 refers to a pin gate and numeral 2 to a weld.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide resin composition, a molded article, and a housing for electronic equipment. More specifically, the polyamide resin composition can be injection-molded, and the resin composition can be obtained by injection molding. The present invention relates to a plastic molded product and a plastic housing for electronic equipment such as office automation equipment and telephones.

[0002]

2. Description of the Related Art Polyamide resins are generally high in strength, high in rigidity, excellent in impact resistance and solvent resistance, and are useful as a metal substitute material. Polyamide resin is particularly suitable for structural parts that require strong force, and is used in various fields such as parts of transportation equipment such as automobiles, general machinery, precision machinery, electric and electronic equipment parts, leisure sports equipment, civil engineering and construction materials, etc. ing. In particular, the amorphous polyamide resin is suitable for a housing material because it has less warp because it does not have a rapid volume change near its glass transition temperature (Tg) and has high impact resistance. However, since polyamide resin has an amide bond (-CONH-) in its molecule, it generally has high hygroscopicity, and the mechanical and electrical characteristics of the molded product are significantly reduced under high temperature and high humidity. There is a problem that the dimensional stability is also poor.

It has been described above that the polyamide resin is used in electronic equipment parts. In recent years, in particular, OA devices, telephones, and the like have been reduced in size and weight, and along with this, improvements in the housing of electronic devices have been desired. In other words, recently, personal computers, word processors, mobile phones, etc. that can be carried in a bag or pocket are on the market, but along with this, not only the internal electronic components but also the housing have become thinner and lighter. However, higher strength is required. In particular, since the housing portion occupies about 20 to 50% of the weight of the entire device, if the housing can be made thin and lightweight, it can greatly contribute to the weight reduction of the entire electronic device. However, a plastic material such as ABS resin is usually used for the housing of the electronic device, and the wall thickness is required to be about 3 mm in view of strength and the like. In fact, if the wall thickness is less than 1 mm in order to make the equipment smaller, lighter, and thinner, the fluidity will be extremely reduced depending on the resin when the projected area is relatively large (for example, A4 size, 620 cm ² ). , Cannot be molded. Further, even if it becomes possible to mold it, the strength and rigidity are lowered, so there is a problem that it is not suitable as a housing. The "projected area" is a scale indicating the size (size) of the article,
When an article has a complicated shape or the like, its dimension can be converted into a projected area and displayed.

Liquid crystal polyester resins, which are excellent in fluidity and thin-wall moldability, and have high strength and rigidity, can be used as substitutes for plastic materials such as ABS resin for housings of electronic devices. At this time, when the resin is cooled while flowing in the mold, the fluidity in the weld portion is lowered, and the resin is less mixed due to the characteristic that the orientation is particularly high. For this reason, the strength of the weld portion is extremely reduced, and the strength is only about 10 to 20% of the strength of the portion other than the weld portion. Usually, since the casing of an OA device or the like has a rib for reinforcement, a boss hole at the time of assembly, an opening, etc., there is at least one weld portion regardless of the type of gate, Weld strength is required to be at least 40% of the value other than weld strength. Therefore, the liquid crystal polyester resin cannot be used alone in the casing of electronic equipment such as office automation equipment and telephones.

Further, in the case of a thin-walled case, in particular, warpage is likely to occur due to stress applied during molding, stress generated due to contraction during cooling, and the like. If this warp is greater than about 1 mm, it becomes unfavorable as a housing due to problems in mounting inside the housing and external appearance. This tendency becomes more remarkable as the wall thickness becomes thinner and the area becomes larger, and it is difficult to suppress the warpage to less than 1 mm when a molded product having a wall thickness of less than 1 mm and a projected area of about A4 size is obtained.

[0006]

SUMMARY OF THE INVENTION The first object of the present invention is to:
Another object of the present invention is to provide a polyamide resin composition having excellent thin-wall moldability, high strength, low hygroscopicity, and good moisture-absorption dimensional stability. Secondly, an object of the present invention is to provide a plastic molded product mainly composed of an amorphous polyamide resin and excellent in various characteristics.

Thirdly, an object of the present invention is to provide a plastic housing for electronic equipment, which is thin and relatively large, has excellent characteristics such as weld strength, and does not warp. .. The fourth, fifth, ... Objects of the present invention will be easily understood from the following description.

[0008]

The present invention, in one aspect thereof, comprises an amorphous polyamide and about 10 to 100 parts by weight of liquid crystalline polyester per 100 parts by weight of the polyamide. And an injection-moldable polyamide resin composition. The polyamide resin composition of the present invention preferably comprises, in addition to the blend of the amorphous polyamide and the liquid crystal polyester, about 3 to 40 parts by weight of a reinforcing filler with respect to 100 parts by weight of the polyamide resin composition, Above all, carbon fibers can be further contained.

In another of its aspects, the present invention relates to an amorphous polyamide and about 100 parts by weight of the polyamide.
A reinforcing filler (for example, glass fiber, mica, titanium) containing 10 to 100 parts by weight of the liquid crystal polyester, and optionally about 3 to 40 parts by weight with respect to 100 parts by weight of the polyamide resin composition. A molded product obtained by injection molding a polyamide resin composition further containing calcium acid, zinc oxide having a three-dimensional structure, and the like).

In yet another of its aspects, the present invention comprises an amorphous polyamide and about 10 to 100 parts by weight of liquid crystal polyester per 100 parts by weight of said polyamide, and optionally polyamide. An injection-molded article of a polyamide resin composition further containing about 3 to 40 parts by weight of a reinforcing filler with respect to 100 parts by weight of the resin composition, and having a size of 2000 cm ² or less in terms of a projected area. In addition, the thickness of 70% or more of the surface of the molded product is 2 mm or less, and the strength of the weld part is 40% or more of the strength of the non-weld part.

[0011]

Function: Polyamide resin has high strength, high rigidity, and excellent impact resistance and solvent resistance. However, such a resin
Due to the presence of the amide bond, it has high hygroscopicity and poor hygroscopic dimensional stability. In the present invention, by using the polyamide resin as a blend with the liquid crystal polyester resin, the hygroscopicity is reduced and the hygroscopic dimensional stability is improved by the synergistic effect of both effects. The liquid crystal polyester resin has a unique flow characteristic in that even rigid polymer molecules flow with almost no entanglement and are oriented in the direction of shear stress applied during injection molding.
It has advantages such as high fluidity for filling thin parts, excellent dimensional stability due to low molding shrinkage and low thermal expansion coefficient, high strength, high rigidity, low hygroscopicity, and good releasability. ing. Although this liquid crystal polyester resin has drawbacks such as strength, elastic modulus, molding shrinkage, thermal expansion coefficient being anisotropic, and weak weld strength,
All of these drawbacks can be covered by the advantages of polyamide resins.

[0012]

EXAMPLES In the practice of the present invention, polyamide is used as the main ingredient of the resin composition. The polyamides preferably used in the present invention are synthetic linear polyamides, above all nylons with a high amorphous content (for example CX-30.
00, Unitika; X-21, Mitsubishi Kasei) has characteristics such as high strength, high rigidity, low molding shrinkage and high impact strength compared to other nylons, making it a thin, large-area molded product. It is also effective in solving the problem of warpage that tends to occur. In this specification, polyamides such as nylon having a large amount of amorphous components are referred to as amorphous polyamides.

In the present invention, the polyamide is used as a blend with a liquid crystal polyester. The liquid crystal polyester blended with the polyamide is typically a polymer of parahydroxybenzoic acid, biphenol and terephthalic acid (for example, Zaider, Nippon Petrochemical), parahydroxybenzoic acid and 6-hydroxy-2-naphthalenecarboxylic acid. And polymers of terephthalic acid (for example,
Vectra, Polyplastics), polymers of para-hydroxybenzoic acid and polyethylene terephthalate (eg,
Rodran, Unitika) and the like, but Rodlan LC-5000 manufactured by Unitika, which can improve the compatibility by utilizing a reactive group at the terminal, is particularly preferable.

The reason why the liquid crystal polyester is blended with the amorphous polyamide is that the defect of the polyamide having high hygroscopicity is compensated by the liquid crystal polyester, the strength and the rigidity are improved by the self-reinforcing effect of the liquid crystal polyester, and the weld strength is improved. This is because the drawback of liquid crystal polyester, which is low, is compensated by blending with a polyamide. Therefore, in the polyamide resin composition of the present invention, the liquid crystal polyester is amorphous polyamide 1
It is mixed in a ratio of about 10 to 100 parts by weight with respect to 00 parts by weight. If it is less than 10 parts by weight, the effect of blending liquid crystal polyester, that is, the reduction of water absorption, improvement of releasability, improvement of strength and rigidity, etc. does not appear, and if it exceeds 100 parts by weight, the weld strength is lowered and it is anisotropic. This is because the disadvantage of the liquid crystal polyester that the property becomes large appears remarkably.

The polyamide resin composition of the present invention further comprises, if necessary and preferably, about 3 to 40 parts by weight of carbon fiber or other reinforcing filler with respect to 100 parts by weight of the polyamide resin composition. Can be included. The presence of the reinforcing filler is effective in preventing a marked decrease in strength, the occurrence of defects such as warpage and sink marks, and the like. In particular, carbon fiber is lightweight and has high strength among the reinforcing fillers, and is particularly effective for making the housing material thin, lightweight and high-strength.
The carbon fiber used in the present invention is not limited as long as it can be used as a reinforcing material for the resin, and may be either roving or chopped strands, but usually, the fiber length is 0.1 to 10 mm, the average fiber diameter. Is preferably 4 to 10 μm. If the fiber length is too long, the warpage deformation of the molded product will be large, and if it is too short, the reinforcing effect on the strength and rigidity will be poor. The carbon fiber may be surface-untreated, or may be surface-treated with a coupling agent such as a silane coupling agent or a titanate coupling agent, but it may be subjected to coupling treatment. One is preferable. As the type of carbon fiber, either PAN type or pitch type can be used. Other reinforcing fillers suitable in the present invention include, but are not limited to, those listed below, a member selected from the group consisting of glass fibers, mica, calcium titanate and zinc oxide whiskers of three-dimensional structure, or a member thereof. A mixture can be given. The type of reinforcing filler used depends on factors such as the resulting molded article and the intended use of the housing. For example, carbon fibers are effective in applications that require lighter weight, higher strength, and higher rigidity than glass fibers. Also, mica, calcium titanate,
The zinc oxide whisker having a three-dimensional structure is used particularly for the purpose of preventing warpage of a molded product, and is effective for a molded product having a thin wall and a relatively large area. It is also recommended to use carbon fiber in combination with mica and / or zinc oxide whiskers having a three-dimensional structure.

The above-mentioned reinforcing filler is, as described above,
It is used in an amount of about 3 to 40 parts by weight based on 100 parts by weight of the polyamide resin composition. This is because when the addition amount is less than 3 parts by weight, the effect of adding the reinforcing filler does not appear, and when the addition amount exceeds 40 parts by weight, the specific gravity and the melt viscosity of the resin are increased and the molding failure occurs. This is because there is a risk.

The polyamide resin composition of the present invention is, for example, a coloring material, a pigment, a compatibilizing agent, an inorganic filler other than the above, a flame retardant material, or any other conventional material, as is commonly used in this technical field. If desired, the additive may be contained in any amount. The resin composition of the present invention can be easily prepared by blending its constituents using a conventional kneading means or the like. An example of a suitable kneading means is an intermediate feed type melt kneading extruder.

The plastic molded articles and plastic housings from the polyamide resin composition of the present invention are preferably
It can be produced by molding the resin composition with a conventional injection molding machine. However, a molding method other than injection molding may be used for carrying out the present invention, if necessary. The size of the plastic housing of the present invention is preferably 2000 cm ² or less in terms of projected area.
This is because if the housing is larger, a long flow length is needed at the time of molding, and there are unfilled parts.
In addition, the warpage of the whole becomes large and it becomes unsuitable as a housing.

Next, the present invention will be described with reference to its examples and comparative examples. In the following examples, in order to measure the warpage of each molded product, the temperature-humidity cycle conditions shown in FIG. 1 were applied and a temperature-humidity cycle test was performed using a coordinate measuring machine. Example 1 100 parts by weight of amorphous polyamide (CX-3000, Unitika), 20 parts by weight of liquid crystal polyester (Rod Run LC-5000, Unitika), and 20 parts by weight of carbon fiber were blended by a kneading extruder, and an injection molding machine was used. To form a flat plate of 300 × 200 × 1 mm. The molding conditions were a resin temperature of 280 ° C., a mold temperature of 80 ° C., and an injection pressure of 1200 kgf / cm ² . This molded product was examined for releasability, weld strength, water absorption and warpage. To measure the warpage, a temperature and humidity cycle test (10
The warp before and after was measured. The results obtained are shown in Table 1. Example 2 100 parts by weight of amorphous polyamide (X-21, Mitsubishi Kasei), 25 parts by weight of liquid crystal polyester (Rod Run LC-5000, Unitika), 15 parts by weight of carbon fiber and 10 parts by weight of mica are blended,
Molding evaluation was performed in the same manner as in Example 1. The results obtained are shown in Table 1. Example 3 100 parts by weight of amorphous polyamide (CX-3000, Unitika), 30 parts by weight of liquid crystal polyester (Rod Run LC-5000, Unitika), 15 parts by weight of carbon fiber, and 10 parts by weight of zinc oxide whiskers having a three-dimensional structure are blended. Then, the molding evaluation was performed in the same manner as in Example 1. The results obtained are shown in Table 1. Comparative Example 1 Blending was performed in the same manner as in Example 1 except that 6 parts by weight of liquid crystal polyester was used, and molding evaluation was performed. The results obtained are shown in Table 1. Comparative Example 2 Blending was carried out in the same manner as in Example 1 except that the liquid crystal polyester was changed to 120 parts by weight, and molding evaluation was performed. The results obtained are shown in Table 1. Comparative Example 3 Blending was carried out in the same manner as in Example 1 except that the carbon fibers were 60 parts by weight and the zinc oxide whiskers were 70 parts by weight, and molding evaluation was performed. The results obtained are shown in Table 1.

[0020]

[Table 1]

In the following examples, the resin composition of each example was injection-molded at a molding temperature of 280 ° C. to obtain three types of casing bottom molded products I, II and III having different dimensions (see FIG. 2 ( A),
(See (B) and (C)). Obtained molded articles I, II and I
The dimensions of II are shown below: As shown in the drawing, each molded product was provided with pin gates 1 at 6 locations and a weld portion 2 for evaluating weld strength. Example 4 100 parts by weight of amorphous polyamide (CX-3000, Unitika) and 30 parts by weight of liquid crystal polyester (Rod Run LC-5000, Unitika) were blended by a kneading extruder and shown in FIG. 2 using an injection molding machine. The bottom of each type of casing was molded at a molding temperature of 280 ° C. With respect to each of the molded products I, II and III, the mold releasability, the bending strength of the weld portion, the bending elastic modulus, the bending strength other than the weld portion, the bending elastic modulus, the water absorption rate, the warp and the weight were examined. Bending strength and flexural modulus of the molded product is 10 mm x 50 mm x 0.8 mm
Cut out 5 pieces each on the weld part and other parts,
The tensile tester was used. The water absorption rate was evaluated using a pressure cooker tester at 121 ° C, 2 atm, 100%.
It was conducted under conditions of RH and 24 hours. The warpage was measured by using a three-dimensional measuring machine before and after the temperature-humidity cycle test (10 days). The measurement results of each molded product are shown in the following table. Molded products I (projected area 630 cm ² ) and II (projected area 1980 cm ² ) had a warp of less than 1 mm, good mold releasability and moldability, and bending strength and bending elastic modulus of the weld part Other than 40%, the overall evaluation was ◯, but since the warpage of the molded product III (projected area 2250 cm ² ) was 1 mm or more, the overall evaluation was x.

[0022]

[Table 2]

Example 5 100 parts by weight of amorphous polyamide (X-21, Mitsubishi Kasei), 30 parts by weight of liquid crystal polyester (Rod Run LC-5000, Unitika) and 20 parts by weight of carbon fiber were blended by a kneading extruder,
Molding evaluation was performed in the same manner as in Example 4. The results are shown in the table below. Similar to Example 4, the overall evaluation of the molded products I and II was ◯, but the overall evaluation of the molded product III was × because the warpage was 1 mm or more and no filling was performed.

[0024]

[Table 3]

Example 6 100 parts by weight of amorphous nylon (CX-3000, Unitika), 40 parts by weight of liquid crystalline polyester (Rod Run LC-5000, Unitika), 20 parts by weight of carbon fiber, and 15 parts by weight of mica were blended together to prepare Example 4 Molding evaluation was carried out in the same manner as in.
The results are shown in the table below. Similar to Example 4, the overall evaluation of the molded products I and II was ◯, but the overall evaluation of the molded product III was x because the product was unfilled.

[0026]

[Table 4]

Example 7 100 parts by weight of amorphous nylon (X-21, Mitsubishi Kasei), 30 parts by weight of liquid crystal polyester (Rod Run LC-5000, Unitika), 20 parts by weight of carbon fiber, 10 parts by weight of mica, calcium titanate 10 parts by weight were blended, and molding evaluation was performed in the same manner as in Example 4. The results are shown in the table below. As in Example 4, the molded products I and II gave a comprehensive evaluation of O, but the molded product II.
I was unfilled with a warp of 1 mm or more, so the overall evaluation was ×
Met.

[0028]

[Table 5]

Comparative Example 4 Blending was carried out in the same manner as in Example 4 except that 5 parts by weight of liquid crystal polyester was used, and molding evaluation was carried out. The results obtained are shown in the following table. The molded products I and II both had a higher water absorption rate and a lower releasability than those of Example 4, and thus the overall evaluation was x.

[0030]

[Table 6]

Comparative Example 5 Blending was carried out in the same manner as in Example 4 except that 120 parts by weight of liquid crystal polyester was blended, and molding evaluation was carried out. The results obtained are shown in the following table. For molded products I, II, and III, the bending strength and flexural modulus of the weld were 50
Since it was below%, the overall evaluation was all x.

[0032]

[Table 7]

Comparative Example 6 Blending was carried out in the same manner as in Example 5 except that 2 parts by weight of carbon fiber was used, and molding evaluation was carried out. The results obtained are shown in the following table. Similar to Example 4, the overall evaluation of the molded products I and II was ◯, but the overall evaluation of the molded product III was × because the warpage was 1 mm or more and no filling was performed. However, when the carbon fiber is about 2 parts by weight, the reinforcing effect by the carbon fiber is not seen.

[0034]

[Table 8]

Comparative Example 7 Blending was carried out in the same manner as in Example 6 except that 70 parts by weight of carbon fiber and 70 parts by weight of mica were used for molding evaluation. The results obtained are shown in the following table. Since the molded articles I, II, and III were all unfilled and could not be molded, the overall evaluation was x.

[0036]

[Table 9]

Comparative Example 8 Blending was carried out in the same manner as in Example 7 except that 2 parts by weight of carbon fiber, 2 parts by weight of mica, and 2 parts by weight of calcium titanate were used, and molding evaluation was carried out. The results obtained are shown in the following table. Similar to Example 4, the overall evaluation of the molded products I and II was ◯, but the overall evaluation of the molded product III was × because the warpage was 1 mm or more and no filling was performed. However, when the reinforcing filler is about 2 parts by weight, the reinforcing effect and the warp are not reduced.

[0038]

[Table 10]

Comparative Example 9 Blending was carried out in the same manner as in Example 7 except for using 60 parts by weight of carbon fiber, 65 parts by weight of mica, and 65 parts by weight of calcium titanate, and molding evaluation was carried out. The results obtained are shown in the following table. Since the molded articles I, II, and III were all unfilled and could not be molded, the overall evaluation was x.

[0040]

[Table 11]

[0041]

EFFECT OF THE INVENTION By using the polyamide resin composition according to the present invention, the strength, rigidity, hygroscopicity, and dimensional stability of hygroscopicity of the obtained polyamide molded product are improved, and the mold releasability from the mold is facilitated. It becomes possible. Further, the plastic housing of the present invention is thin (less than 1 mm) and can mold a large area (projected area of 2000 cm ² or less), and the obtained molded product has a warp of 1 mm or less and a high weld strength. In addition, strength and rigidity are high, hygroscopicity is low, and releasability is good. Therefore, this plastic housing is very effective as a housing for electronic equipment such as office automation equipment and telephones for the purpose of small size and light weight.

[Brief description of drawings]

FIG. 1 is a graph showing temperature / humidity cycle conditions used for measuring warpage of a molded article of the present invention.

2 (A), (B) and (C) are perspective views showing the shapes of case bottom molded products I, II and III, respectively, manufactured in Examples.

[Explanation of symbols]

 1 ... Pin gate 2 ... Weld section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location // B29K 105: 06 B29L 22:00 4F (72) Inventor Makoto Usui Nakahara-ku, Kawasaki-shi, Kanagawa Kamiodanaka 1015, within Fujitsu Limited (72) Inventor Takashi Muratani, Kamagawada, Nakahara-ku, Kawasaki, Kanagawa 1015, within Fujitsu Limited (72) Inventor, Koichi Kimura 1015, Kamiodanaka, Nakahara-ku, Kawasaki, Kanagawa Within Fujitsu Limited (72) Inventor Katsura Adachi 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Within Fujitsu Limited (72) Inventor Jun-ichi Suenaga 9-2 Yamada, Nagara, Seika-cho, Soraku-gun, Kyoto Prefecture 2-37-1 Minamirokugo, Ota-ku, Tokyo Riken Vinyl Industry Co., Ltd.

Claims (11)

[Claims] 1. An amorphous polyamide and the polyamide 100
An injection-moldable polyamide resin composition comprising 10 to 100 parts by weight of liquid crystal polyester with respect to parts by weight. 2. The polyamide resin composition according to claim 1, further comprising 3 to 40 parts by weight of a reinforcing filler with respect to 100 parts by weight of the polyamide resin composition. 3. The reinforcing filler is a member selected from the group consisting of glass fiber, carbon fiber, mica, calcium titanate, and zinc oxide whiskers having a three-dimensional structure, or a mixture thereof. Item 3. The polyamide resin composition according to item 2. 4. A molded article obtained by injection molding the polyamide resin composition according to claim 1. 5. A molded article obtained by injection molding the polyamide resin composition according to claim 2. 6. An injection-molded article of the polyamide resin composition according to claim 1, wherein the dimension is 2000 cm when converted into a projected area.
² or less and 70% or more of the surface of the molded product has a plate thickness of 2 mm
The following is a housing for an electronic device. 7. The electronic device according to claim 6, wherein the polyamide resin composition further contains 3 to 40 parts by weight of a reinforcing filler with respect to 100 parts by weight of the polyamide resin composition. Case. 8. The reinforcing filler is a member selected from the group consisting of glass fibers, carbon fibers, mica, calcium titanate, and zinc oxide whiskers having a three-dimensional structure, or a mixture thereof. Item 7. An electronic device casing according to item 7. 9. The electronic device casing according to claim 6, further comprising 3 to 40 parts by weight of carbon fiber as a reinforcing filler with respect to 100 parts by weight of the polyamide resin composition. An electronic device housing. 10. The electronic device casing according to claim 9, wherein carbon fibers having an average fiber diameter of 4 to 10 μm and a fiber length of 0.1 to 10 mm are used. .. 11. The electronic device casing according to claim 6, wherein the strength of the weld portion is 40% or more of the strength of the non-weld portion.