JPH09143379A - Vibration-proofing injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an injection molding having high specific rigidity, excellent dimensional stability and excellent vibration-damping properties. SOLUTION: A composite resin material comprising 99-50wt.% thermoplastic resin which does not form an anisotropic molten phase and 1-50wt.% liquid crystal polymer which can form an anisotropic molten phase is injection molded into a product in which the liquid crystal polymer which can form an anisotropic molten phase in the matrix phase of a thermoplastic resin which does not form an anisotropic molten phase in the form of fibers of an aspect ratio of 6 or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molded article having a high specific rigidity, excellent dimensional stability and vibration damping characteristics by using a specific composite resin material.

[0002]

2. Description of the Related Art In recent years, attention has been paid to measures against vibration sources in various devices, and materials having vibration suppressing (vibration suppressing) performance have been required. AV (audiovisual) mechanical parts such as digital disks, speaker parts, body parts around the engine of the car such as gearbox,
Structural parts such as door mirror stays and other rearview mirrors and fender mirrors do not sustain vibration due to their performance.
Further, it is often desired that the vibration does not propagate. For example, with the development of optical technology, mini discs and compact discs that read and write digitized information with light, which are widely used as information media for music devices, home game devices, computer peripherals, etc. A chassis used for a drive device for a digital disk such as a CD-ROM, a laser disk, a phase change disk, or a magneto-optical disk that reads and writes by light and magnetism has not only vibration absorption characteristics but also high dimensional accuracy and use. It is required that the coefficient of linear expansion be low so that the dimensions do not change in response to environmental changes, and that the specific rigidity is high so that deformation due to load and vibration is small. This is because the chassis used for the drive device of the digital disc is required to have high dimensional accuracy because it is necessary to improve the positioning accuracy of the optical reading device (pickup). For this reason, such a chassis for a digital disk drive generally uses a metal or a thermoplastic resin mainly reinforced with glass fiber. However, it is difficult to process complicated shapes with metallic materials, and with thermoplastic resins mainly reinforced with glass fibers, mechanical strength such as rigidity improves as the glass fiber content increases, but material specific gravity also increases. It is difficult to increase the specific rigidity of the chassis. From this situation,
An injection molded product such as a chassis for a digital disk drive device having a high specific rigidity and an excellent dimensional accuracy is industrially desired.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The dimensional accuracy and rigidity required for injection molded products such as chassis for digital disk drive, gearbox, door mirror stay, etc. are relatively close to each other, and the injection molding is still possible. Aromatic polycarbonate resins and modified polyphenylene ether resins are known as relatively easy thermoplastic resin materials. Therefore, these resins are mixed with an inorganic filler composed mainly of glass fiber to improve dimensional accuracy and rigidity, and to make injection molded products such as chassis for digital disk drive devices, gear boxes, and door mirror stays industrial. It is considered to be produced in the market and is used in some products with low required performance. However, even if an aromatic polycarbonate-based resin or a modified polyphenylene ether-based resin is mixed with an inorganic filler such as glass fiber, the rigidity is not sufficiently high. On the other hand, due to the addition of an inorganic filler such as glass fiber, Since the specific gravity of the material increases, it is very difficult to increase the specific rigidity of the chassis. Carbon fiber is known as a filler having a relatively small specific gravity and a high reinforcing effect, but since it is very expensive, a thermoplastic resin material containing such a reinforcing material is required to be inexpensive. It cannot be practically used for injection molded articles. Therefore, it has been the actual situation that an inexpensive injection-molded product having high dimensional accuracy and specific rigidity and adapted to the recent trend toward lighter, thinner, shorter, and smaller products has not yet been obtained industrially.

[0004]

In view of the above situation, the present inventor has made earnest studies to obtain an inexpensive injection-molded article having high dimensional accuracy and specific rigidity, and as a result, formed an anisotropic molten phase. It has been found that this can be solved by injection molding a composite resin material of a non-thermoplastic resin and a liquid crystalline polymer capable of forming an anisotropic molten phase. Even more surprisingly, for example, in the case of a digital disk drive chassis, it is an important physical property to reduce the vibration of the internal mechanism of the device in a digital disk drive which handles information pits of micron unit formed on the digital disk. The inventors of the present invention have found that the injection-molded article (1) exhibits extremely excellent vibration damping properties, that is, vibration damping characteristics, and have reached the present invention. That is, the present invention comprises injection-molding a composite resin material of 99 to 50% by weight of a thermoplastic resin that does not form an anisotropic melt phase and 1 to 50% by weight of a liquid crystalline polymer that can form an anisotropic melt phase. , A liquid crystal polymer capable of forming an anisotropic molten phase is dispersed in a matrix phase of a thermoplastic resin which does not form an anisotropic molten phase in the form of fibers having an aspect ratio of 6 or more. It is an injection molded product.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The specific constitution of the present invention will be described below. The injection-molded product in the present invention means injection of AV mechanical parts such as digital disks, speaker parts, body parts around the engine of automobiles such as gearboxes, room mirrors such as door mirror stays and structural parts such as fender mirrors. Suitable for molded products, especially mini disc players, compact disc players, C
A chassis used in a digital disk drive such as a D-ROM drive, a laser disk player, or a magneto-optical (MO) disk drive, that is, a plate-like or box-like shape as a base on which internal structural parts of the digital disk drive are mounted. A general term for parts, which is a plate or box shape in which various drive parts, motors, printed circuit boards, optical parts, etc. can be mechanically attached by bolts or snap fits, or chemically using an adhesive or the like. Parts are a preferred application in the properties of the injection molded articles of the present invention.

Examples of the thermoplastic resin which does not form an anisotropic molten phase in the present invention include polyolefin (co) polymers such as polyethylene, polypropylene and poly-4-methyl-1-pentene, polyethylene terephthalate resin, polybutylene terephthalate. Resin, polyester resin such as polycarbonate resin, polyamide polymer,
Examples thereof include ABS resins, polyarylene sulfide resins, polyacrylates, polyacetals, and resins mainly containing these. Among these, polyester resins such as polycarbonate resin, polybutylene terephthalate resin and polyethylene terephthalate resin are preferable, and polycarbonate resin having a relatively low molding shrinkage coefficient and linear expansion coefficient is particularly preferable.

The liquid crystalline polymer used in the present invention is
It has molecular orientation in the molten state and exhibits optical anisotropy. In the molecular orientation in this case, the molecules are arranged as a whole in the long axis direction of the molecule and the parallel direction thereof, and this axis and the inclination of the molecule do not necessarily have to match. The anisotropy observation in the molten state can be performed by a conventional polarization inspection method using a crossed polarizer. More specifically, the anisotropic molten phase can be confirmed by using a Leitz polarizing microscope and observing the molten sample placed on a Leitz hot stage under a nitrogen atmosphere at a magnification of 40 times. 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 peculiar to the liquid crystal phase in a certain temperature range when gradually heated. Also, a phase-specific diffraction pattern can be observed in X-ray diffraction. In thermal analysis, a differential scanning calorimeter is generally used to measure entropy change and transition temperature of various phase transitions. Liquid crystalline polymers suitable for use in the present invention tend to be substantially insoluble in common solvents and are therefore unsuitable for solution processing. However, as already mentioned, these polymers can be easily processed by conventional melt processing methods. The liquid crystalline polymer used in the present invention is preferably an aromatic polyester and an aromatic polyesteramide, and a preferable example is also an aromatic polyester and a polyester partially containing the aromatic polyesteramide in the same molecular chain. Particularly preferred are liquid crystalline aromatic polyesters and liquid crystalline aromatic polyesteramides having at least one compound selected from the group consisting of aromatic hydroxylcarboxylic acid, aromatic hydroxylamine and aromatic diamine as a constituent component. 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, if necessary, a molecular weight modifier may be used in combination with the above constituent components. Preferred examples of specific compounds constituting the liquid crystalline polyester of the present invention are 2,6-naphthalenedicarboxylic acid, 2,6-dihydroxynaphthalene,
4-dihydroxynaphthalene and 6-hydroxy-2-
Naphthalene compounds such as naphthoic acid, 4,4′-diphenyldicarboxylic acid, biphenyl compounds such as 4,4′-dihydroxybiphenyl, p-hydroxybenzoic acid, terephthalic acid,
Para-substituted benzene compounds such as hydroquinone, p-aminophenol and p-phenylenediamine and their nucleus-substituted benzene compounds (substituents are selected from chlorine, bromine, methyl, phenyl and 1-phenylethyl), isophthalic acid, Meta-substituted benzene compounds such as resorcinol. Preferred examples of the specific compound include naphthalene compounds such as 2,6-naphthalenedicarboxylic acid, 2,6-dihydroxynaphthalene, 1,4-dihydroxynaphthalene and 6-hydroxy-2-naphthoic acid, and 4,4′-diphenyl Dicarboxylic acids, biphenyl compounds such as 4,4'-dihydroxybiphenyl, and compounds represented by the following general formulas (I), (II) or (III):

[0008]

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(However, X: a group selected from alkylene (C ₁ -C ₄ ), alkylidene, -O-, -SO-, -SO _2- , -S-, -CO-, Y :-( CH ₂ ). _n- (n = 1 to 4), —O (CH ₂ ) _n O— (n = 1 to 4)) Further, the liquid crystalline polyester used in the present invention may have the above-mentioned constitutional components. Further, polyalkylene terephthalate which does not partially show an anisotropic melt phase in the same molecular chain may be used. 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 above aromatic polyesters and polyesteramides also have an inherent viscosity (IV) of at least about 2.0 dl / g, for example about 2.0-10.0 dl / g, when dissolved in pentafluorophenol at a concentration of 0.1% by weight at 60 ° C. Generally indicated.

The composite resin material constituting the chassis for a digital disk drive according to the present invention comprises the thermoplastic resin which does not form the anisotropic molten phase and the liquid crystalline polymer which can form the anisotropic molten phase. It is necessary that the liquid crystalline polymer capable of forming the anisotropic molten phase is microdispersed in a fibrous state in the matrix phase of the thermoplastic resin not forming the anisotropic molten phase, preferably with an average aspect ratio of 6 or more. . As a result, the liquid crystalline polymer serves as a fiber reinforcing material, and the thermoplastic resin can be reinforced. The term “fiberization” means that the liquid crystalline polymer has a fibrous or needle-like structure, and includes one having a branched fiber structure with respect to the fibrous stem fiber. The composite resin material in which a liquid crystalline polymer capable of forming an anisotropic molten phase is microdispersed in a fibrous state in a matrix phase of a thermoplastic resin which does not form an anisotropic molten phase is kneaded by an ordinary extruder, Obtained by shearing force during injection molding, but if the composition ratio of the liquid crystalline polymer is higher than the composition ratio of the thermoplastic resin, the matrix phase may be inverted,
The composition ratio of the liquid crystalline polymer in the composite resin material is 1 to
It is preferably in the range of 50% by weight.

Further, in order to make the liquid crystalline polymer into fibers at the time of molding, it is preferable to add a phosphorus compound. In particular, when the thermoplastic resin that does not form an anisotropic molten phase is a polycarbonate resin, the liquid crystalline polymer and the polycarbonate resin do not disperse in an island shape and may not be fiberized even by injection molding. Is. Examples of the phosphorus compound include phosphides, phosphoric acid compounds, and phosphorous acid compounds. Examples thereof include tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphonite and bis ( 2,6-Di-t-butyl-4-methylphenyl) pentaerythritol-diphosphite, bis (2,4,6-di-t-butylphenyl) pentaerythritol-diphosphite, tris (2,4- Di-t-butylphenyl)
Phosphite and the like are exemplified, but phosphorous acid compounds are preferable, and pentaerythritol type phosphorous acid compounds are particularly preferable. In the present invention, the addition of the phosphorus compound allows the liquid crystalline polymer, which is one of the resin components, to easily become fibrous even in the low shear rate region. A fibrous layer of a liquid crystalline polymer is formed from the surface layer of the flesh portion to a considerable interior, and high strength and high elastic modulus can be exhibited. That is, the specific rigidity of the component can be increased. The specific rigidity should be 50,000 or more when used for chassis etc. The compounding amount of the phosphorus compound is 0.01 to 0 with respect to 100 parts by weight as a total of 100 parts by weight of a thermoplastic resin that does not form an anisotropic melt phase and a liquid crystalline polymer that can form an anisotropic melt phase.
The amount is preferably 5 parts by weight, particularly preferably 0.05 to 0.3 parts by weight. If the blending amount is less than 0.01 part by weight, it is difficult to fiberize the liquid crystalline polymer by ordinary molding, and
If the compounding amount exceeds 5 parts by weight, a large amount of the compound of the phosphorus compound gas is generated, which rather impairs the mechanical strength and moldability. When the ratio of the phosphorus compound is within this range, the liquid crystalline polymer can be easily formed into fibers, and can be formed into fibers regardless of the molding conditions and the shape of the molded product.

Further, in the composite resin material according to the present invention, a known fibrous, powdery, plate-like, or hollow filler or a difficult filler may be added to the composite resin material within a range that does not impair the effects of the present invention. A flame retardant, a flame retardant aid, various stabilizers, etc. may be added.

The present invention is an injection-molded article having excellent vibration damping characteristics, and the characteristics can be expressed by a vibration damping rate. The larger the value, the better the vibration damping characteristics, and 2.0 (1 / sec)
The above is preferable, and 3.5 (1 / sec) or more is particularly preferable.

[0014]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples unless it departs from the gist thereof. The evaluation method and the like are as follows. (Specific gravity) A chassis type molded product for a digital disk drive device as shown in Fig. 1 is molded, a part of it is cut out, and AST
The specific gravity was measured according to MD792. (Flexural Modulus) A chassis type molded product for a digital disk drive device as shown in FIG. 1 was molded, and a shaded portion was cut out to obtain a test piece, and the flexural modulus (kg) was measured according to ASTM D790.
/ Cm ² ) was measured. (Specific rigidity) It is a value obtained by dividing the bending elastic modulus by the specific gravity. (Coefficient of linear expansion) A chassis type molded product for a digital disk drive device as shown in FIG. 1 was molded, and a shaded portion was cut out to make a test piece, which was performed according to ASTM D696, and an average coefficient of linear expansion from 0 ° C. to 100 ° C. Displayed in. (Vibration damping characteristics) A chassis type molded product for a digital disk drive device as shown in Fig. 1 was molded, the shaded portion was cut out to make a test piece, and the damping free vibration of the test piece was examined using the device as shown in Fig. 2. It was An example of the measurement result is shown in FIG. Next, in the obtained damping free vibration waveform, an arbitrary time t
When the vibration at 1 is defined as 1, and the damping ratio R of the vibration after a certain time has elapsed is expressed for each elapsed time, and the amplitude is converted into a logarithm and expressed in a graph, a straight line descending to the right (logarithmic attenuation straight line) is obtained. From the slope of this straight line, the attenuation rate per second (1 /
Second) was calculated as the vibration damping rate. Therefore, the larger this value is, the better the vibration damping characteristic is. [Average aspect ratio of liquid crystalline polymer (length / thickness)]
The test piece used for measuring the flexural modulus was cut so that a plane parallel to the flow direction was exposed, the cross section was mirror-polished, and the surface was observed by an electron microscope for evaluation. That is, the length / thickness of 50 arbitrarily selected fibrous liquid crystalline polymers were measured and the average value was calculated. Regarding the length, the length that can be observed on the surface was measured. The evaluation criteria were as follows. Average aspect ratio 6 or more ○ Average aspect ratio less than 6 × Example 1 Polycarbonate resin (Mitsubishi Gas Chemical Co., Inc., Upilon S3000) and liquid crystalline polyester [p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (mol A liquid crystal polyester having a melting point of 280 ° C. and a logarithmic viscosity of 5.7 (dl / g) as a constituent monomer of 70:30).
100 parts by weight of 80:20 resin component, bis (2,6-di-t-butyl-4-methylphenyl) as phosphite
Pentaerythritol-diphosphite (0.2 parts by weight) was blended, melt-kneaded at a resin temperature of 300 ° C. in a 30 mm twin-screw extruder, and pelletized. Then, the mold clamping force of the pellet is 150
Using an injection molding machine of t, molding the chassis for the digital disk drive device shown in FIG. 1 at a molding temperature of 300 ° C. (indicating a cylinder set temperature), specific gravity, flexural modulus, specific rigidity, linear expansion coefficient, vibration damping characteristics, The average aspect ratio of the liquid crystalline polyester was evaluated. Table 1 shows the results. The molding conditions are as follows. Mold temperature: 80 ° C. Injection speed: 3 m / min Injection pressure: 600 kg / cm ² Example 2 Mixing ratio of polycarbonate resin (Mitsubishi Gas Chemical Co., Inc., Iupilon S3000) and the liquid crystalline polyester used in Example 1 Of 70:30 to 100 parts by weight of a resin component, bis (2,6-di-t-butyl-4-
Methylphenyl) pentaerythritol-diphosphite (0.3 parts by weight) was blended, pelletized in the same manner as in Example 1, and a chassis for a digital disk drive was molded and evaluated. Table 1 shows the results.

Comparative Example 1 A molding machine similar to that of Example 1 was prepared by using a composition of 80% by weight of a polycarbonate resin (Panlite GN-3120 manufactured by Teijin Chemicals Ltd.) and 20% by weight of glass fiber (GF). A chassis for a digital disk drive was molded at a molding temperature of 300 ° C and evaluated. Table 1 shows the results. The molding conditions are as follows. Mold temperature: 80 ° C. Injection speed: 3 m / min Injection pressure: 1000 kg / cm ² Comparative example 2 Modified PPO (Asahi Kasei Co., Ltd., Zylon G703V) 70
Using a composition of 1% by weight and 30% by weight of glass fiber (GF), a chassis for digital disk drive was molded and evaluated at the molding temperature of 300 ° C. in the same molding machine as in Example 1.
Table 1 shows the results. The molding conditions are as follows. Mold temperature: 80 ° C. Injection speed: 6 m / min Injection pressure: 1200 kg / cm ² Comparative example 3 Polycarbonate resin (Mitsubishi Gas Chemical Co., Inc., Upilon S3000) and liquid crystal polyester used in Example 1 The 80:20 resin mixture was pelletized in the same manner as in Example 1 to mold a chassis for a digital disk drive and evaluate the same. Table 1 shows the results. The molding conditions are as follows. Mold temperature: 80 ℃ Injection speed: 3m / min Injection pressure: 1000kg / cm ²

[0016]

[Table 1]

[0017]

As described above in detail, the injection-molded product of the present invention obtained by injection molding using a specific composite resin material has high specific rigidity and excellent dimensional stability. In addition, since it has an extremely excellent vibration damping characteristic, it is preferably used for a chassis of a digital disk drive device for a high density information medium such as a CD-ROM which requires high precision.

[Brief description of the drawings]

FIG. 1 is a view showing a chassis type molded product for a digital disk drive device manufactured in an example, (a) is a top view,
(b) is a side view.

FIG. 2 is a diagram showing a measurement situation of damping free vibration performed in an example.

FIG. 3 is a graph showing measurement results of damping free vibration performed in an example.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08L 69/00 LPQ C08L 69/00 LPQ F16F 15/02 8917-3J F16F 15/02 Q // G10K 11/16 G11B 33/12 302Z 11/162 G10K 11/16 J G11B 33/12 302 A B29K 69:00 105: 12 B29L 31:34

Claims (7)

[Claims] 1. A thermoplastic resin which does not form an anisotropic molten phase
Injection molding a composite resin material of 99 to 50% by weight and 1 to 50% by weight of a liquid crystalline polymer capable of forming an anisotropic molten phase,
Vibration-damping injection characterized in that a liquid crystalline polymer capable of forming an anisotropic melt phase is dispersed in the matrix phase of a thermoplastic resin not forming an anisotropic melt phase in the form of fibers having an aspect ratio of 6 or more. Molding. 2. The vibration-damping injection-molded article according to claim 1, wherein the thermoplastic resin is a polyester resin. 3. The vibration-damping injection-molded article according to claim 2, wherein the thermoplastic resin is a polycarbonate resin. 4. A composite resin material comprising a polycarbonate resin and 0.01 to 0.5 part by weight of 100 parts by weight of a liquid crystalline polymer capable of forming an anisotropic molten phase together with a polycarbonate resin, and injection molding the composite resin material. The vibration-damping injection-molded article according to claim 3. 5. The vibration-damping injection-molded article according to claim 1, which is a chassis for a digital disk drive. 6. The vibration-damping injection-molded article according to claim 1, which is a gear box. 7. The vibration-damping injection-molded article according to claim 1, which is a door mirror stay.