JP2001288241A - Urethane resin composition for electronic part, and electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a urethane resin composition for electronic parts which dispenses with the steps of ultrasonic wave cleaning, heating under vacuum, etc., and is free of a problem of outgassing from electronic parts and provide an electronic part used for hard disks and produced form the urethane resin. SOLUTION: This urethane resin composition comprises (A) a lactone polyol of which the sum of contents of cyclic lactone oligomers and a lactone monomer is 0.5 wt.% or lower, (B) a polyisocyanate, and (C) a low-mol.-wt. glycol as a chain extender. An electronic part obtained from the composition is also provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a urethane resin composition for electronic parts in which the occurrence of outgas which causes a functional failure of a hard disk device or the like in a thermal environment is reduced, and a hard disk device manufactured by using the resin composition. Electronic components for electronic devices.

[0002]

2. Description of the Related Art A hard disk drive is composed of a hard disk in which a magnetic material is fixed on a disk made of aluminum alloy or ceramics, and a magnetic head. The magnetic head is about 0.1 ~
It is mounted with a gap of 0.5 μm, and records information to and reads information from the hard disk. Therefore, if dust adheres to the magnetic surface of the hard disk or the magnetic head, the function is impaired, and recording and reading of information becomes impossible.

The hard disk and the magnetic head are housed in a closed container formed by a cover and a container body, and a packing is arranged in a gap between the cover and the container body to block dust from entering from outside. . Furthermore, an air purifier having a high-performance filter is mounted in the closed container to collect dust from inside and outside to keep the inside air clean. However, in recent years, as the access time has been shortened, the hard disk drive has been downsized, and the storage capacity has been increased, a very small amount of contamination due to outgas generated from electronic components in a sealed container has easily caused malfunction of the hard disk drive. Is starting to happen.

Since some heat is generated inside the hard disk drive during operation, the electronic components are exposed to a thermal environment. Therefore, as the electronic components used in the hard disk drive, ester-based polyurethanes which have been given priority to heat resistance, are less likely to deteriorate in physical properties under a thermal environment and are not easily deteriorated by heat have been used. Among them, a lactone-based polyurethane resin having good hydrolysis resistance is often used.
However, conventional urethane resin electronic components using general-purpose polyester polyols or general-purpose polylactone polyols are exposed to a thermal environment during the operation of a hard disk drive, so that additives such as BHT contained in the resin are volatilized or volatilized. Because of sublimation and generation of a large amount of outgas, the inside of the hard disk drive was contaminated and caused a malfunction.

As a countermeasure against this outgassing, an ultrasonic cleaning process or a heating / vacuum process is introduced as a post-processing step of the formed electronic component to remove outgas components in advance. However, although an additive such as BHT contained in the urethane resin has a removing effect, it has not yet reached a drastic solution.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a urethane resin composition for electronic parts which does not require an ultrasonic cleaning treatment of a molded part, a heating vacuum treatment step, etc., and which does not cause outgassing of electronic parts. An object of the present invention is to provide an electronic component for a hard disk manufactured from a urethane resin.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies on the outgassing problem of a lactone-based urethane resin, and as a result, the monomer contained in the lactone polyol (A),
The present inventors have found that oligomers have the cause, and have proceeded with the development of urethane resins containing few such monomers and oligomers. As a result, the present invention has been completed.

That is, the present invention relates to a lactone polyol (A) containing a total of 0.5% by weight or less of a cyclic lactone oligomer and a lactone monomer, and a polyisocyanate.
(B) A low molecular weight glycol (C) as a chain extender provides a urethane resin composition for electronic components, and an electronic component for a hard disk drive using the same.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A lactone polyol (A) containing the cyclic lactone oligomer and the cyclic lactone monomer of the present invention in a total amount of 0.5% by weight or less is a low molecular weight glycol initiator (A-1). When the lactone (A-2) is addition-polymerized, the lactone (A-2) is obtained by using a specific catalyst (A-3) and producing by a specific production method.

The lactone polyol (A) of the present invention contains a total amount of the cyclic lactone oligomer and the cyclic lactone monomer of 0.5% by weight or less, preferably of 0.01 to 0.1% by weight. %, Dimer: 0.02
-0.08% by weight, trimer: 0.05-0.12% by weight, tetramer: 0.02-0.08% by weight, pentamer: 0.
02 to 0.05% by weight. The total amount of the cyclic lactone oligomer in the lactone polyol obtained by the specific operation does not exceed 0.5% by weight, but if it exceeds 0.5% by weight, these problems can be overcome. In order to reduce the amount of cyclic lactone oligomers and momers, a post-treatment is required, resulting in a very inefficient operation.

The method for measuring the content of the cyclic lactone oligomer and lactone monomer is as follows: <gas chromatography conditions> Model Shimadzu GC-7A Conditions Column glass: 5% SE-30 1.1 m Carrier Uniport HP 80-100 mesh Column temperature : 150 ° C → 320 ° C Hold time: 1min Heating rate: 15 ° C / min Inlet temperature: 300 ° C Carry gas: Helium 50ml / min Combustion gas: Air 0.5Kg / cm2 H2 0.6Kg / cm2 Detector: FID It is performed by a gas chromatograph measuring device according to the analysis method. In particular, when the molecular weight is relatively large such that the molecular weight exceeds 1,000, it is desirable to perform the following pretreatment. The lactone polyol is dissolved in a solvent containing the lactone polyol as an internal standard and extracted with hexane to precipitate the lactone polyol, and the hexane layer is extracted with the cyclic ester compound. This is measured by gas chromatography, and the amount of the cyclic lactone oligomer and monomer contained in the lactone polyol can be calculated from the internal standard. The cyclic lactone oligomer of the present invention refers to the lactone monomer 2
The term "mer, trimer, tetramer, pentamer, etc."

Examples of the low molecular weight glycol initiator (A-1) include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, Methyl-
1,3-propanediol, 1,4-butanediol,
Neopentyl glycol, 1,5-pentanediol,
3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, diethylene glycol, dipropylene glycol, etc. And these can be used alone or in combination.

As the lactone (A-2), ε-caprolactone is mainly used, but other lactones can be used in combination as long as the effects of the present invention are not impaired. Valerolactone, β-methyl-δ-valerolactone, β-methyl-ε-caprolactone, γ-methyl-ε-caprolactone, β, δ-dimethyl-ε-caprolactone, 3,3,5-trimethyl-ε-caprolactone, Examples include compounds such as enantholactone and dodecanolactone, but are not limited thereto.

As the specific catalyst (A-3), tin-based organic compounds such as stannous octylate, dibutyltin oxide, dibutyltin dilaurate, n-butyltin hydroxyoxide, stannous chloride, stannous bromide, etc. Stannous halides such as stannous iodide are mentioned.

The amount of the catalyst used is 0.000
It can be used in the range of 1% by weight to 0.001% by weight. When the amount of the catalyst is less than 0.0001% by weight, the reaction rate is extremely slow and the reaction end point is not reached, so that a large amount of the cyclic lactone monomer remains in the lactone polyol.
On the other hand, when the content exceeds 0.001% by weight, the lactone polyol polymer and the urethane deteriorate in color stability and heat stability, including hydrolysis resistance.

The reaction proceeds in the range of 150 ° C. to 180 ° C., preferably 160 ° C. to 170 ° C.
If the reaction temperature is lower than 150 ° C., the reaction rate becomes extremely slow, and a long time is required to reach the reaction end point. Conversely, if the reaction temperature is higher than 180 ° C., it may cause coloration due to the oxidation reaction, or the reaction is too fast to promote the formation of a cyclic lactone oligomer.

The reaction time depends on the type of catalyst used, the amount of catalyst,
Since the reaction rate varies depending on the reaction temperature, the end point of the reaction is determined by tracking the amount of the remaining monomer. When the amount of the residual monomer becomes 0.1% by weight or less, the reaction does not decrease further even if the reaction is continued and becomes almost constant. After reaching the end point of the reaction, the temperature must be immediately lowered to 120 ° C. or lower to terminate the reaction.

When a catalyst other than the above, for example, a titanium-based catalyst such as tetraisopropyl titanate is used in the addition polymerization of the lactone monomer, the formation rate of the cyclic lactone oligomer is high, and 0.5% is contained in the formed lactone polyol. By weight more than cyclic lactone oligomers,
Since the lactone monomer is present, an electronic component formed by urethane-forming the lactone monomer cannot achieve the object of the present invention.
Further, even when a tin-based catalyst is used, if the reaction is not terminated when the reaction end point is reached and heating is continued excessively, the amount of the cyclic lactone oligomer increases and is present in the lactone polyol in an amount of more than 0.5% by weight. Therefore, an electronic component obtained by urethane-forming the molded product cannot achieve the object of the present invention.

The polyisocyanate (B) is, for example, 2,
4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, tolidine diisocyanate, paraphenylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, Compounds such as hydrogenated diphenylmethane diisocyanate can be mentioned, but not limited thereto.

As the chain extender (C), a low molecular weight glycol is used, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,
1,2-butanediol, 1,3-butanediol, 2
-Methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol,
1,6-hexanediol, diethylene glycol, dipropylene glycol and the like can be used.

The urethane resin composition for electronic parts composed of the above components is produced in the form of pellets as a thermoplastic polyurethane resin by a known production method, and can be molded into an electronic part by a molding machine. The method for producing a thermoplastic polyurethane resin is, for example, a method in which a lactone polyol (A) containing a total amount of a cyclic lactone oligomer and a lactone monomer of 0.5% by weight or less is added to an excess polyisocyanate.
(B) a pre-terminated isocyanate prepolymer which has been previously reacted at a temperature of 120 ° C. or lower, and a chain extender
A prepolymer method in which two liquids of (C) are weighed and mixed and stirred, respectively, and two liquids of a polyol compound obtained by mixing a lactone polyol (A) and a chain extender (C) and a polyisocyanate (B) are weighed. Or one-shot method of mixing and stirring, or after the above-mentioned raw materials are measured with a metering pump and stirred vigorously, then poured onto a vat, and further, for example, 80 to 80%
A method of reacting at a temperature of 200 ° C., preferably 120 to 160 ° C., and then pulverizing,
Any method may be used, in which the above-mentioned raw materials are supplied to an extruder preferably set to 120 to 250 ° C, and the raw materials are kneaded and polymerized while being conveyed in the extruder to extrude a thermoplastic polyurethane from a die.

In the above production, the reaction equivalence ratio between the isocyanate group and the active hydrogen is not particularly limited, but is usually 0.9%.
5 to 1.05, preferably 0.97 to 1.03. The active hydrogen-containing compounds of the lactone polyol (A) and the chain extender (C) having a low molecular weight glycol as an initiator in which the total amount of the cyclic lactone oligomer and the lactone monomer is 0.5% by weight or less absorb moisture. In such a case, the strength of the polyurethane obtained by foaming becomes low. In this case, it is preferable to previously dehydrate and defoam under reduced pressure at a temperature of about 100 ° C.

Although a catalyst need not be used, the use of a catalyst often gives better results. As the catalyst, any commonly used urethanization catalyst can be used, for example, bismuth, lead, tin, iron, antimony, uranium,
Organic compounds such as cadmium, cobalt, thorium, aluminum, mercury, zinc, nickel, cerium, molybdenum, vanadium, copper, manganese, zirconium, and calcium, and inorganic compounds are exemplified. Preferred catalysts are organometallic compounds, especially dialkyltin compounds.
Representative organotin catalysts include, for example, stannous octylate, stannous octoate, stannous oleate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, dibutyltin mercaptopropionate, dibutyltin dodecyl mercaptide, etc. Is mentioned. The amount of the catalyst to be used is not particularly limited because it is determined by the properties of the other raw materials, the reaction conditions, the desired reaction time, and the like. However, the catalyst is generally used in an amount of 0.1% of the total weight of the reaction mixture. It is mixed with the active hydrogen-containing compound in the range of 0001 to about 5% by weight, preferably about 0.001 to 2% by weight.

The thermoplastic polyurethane resin obtained by the above-mentioned production method further comprises, as auxiliary materials, an antioxidant, an ultraviolet ray inhibitor, a flame retardant, a filler, an antistatic agent, a coloring agent, and the like. Can be added in a range that does not adversely affect the water content. The thermoplastic polyurethane resin obtained by the above-mentioned production method can be easily formed into a urethane molded product for electronic parts by a commonly used injection molding machine, extrusion molding machine or the like.

The electronic component of the present invention is an electronic component for a hard disk drive, and is particularly preferably a stopper. The present invention can also be used as electronic components requiring other heat resistance.

[0026]

EXAMPLES Next, the present invention will be described specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. Parts in Examples and Comparative Examples represent parts by weight unless otherwise specified.

<Synthesis of Lactone Polyol> 451 parts of diethylene glycol, 8049 parts of ε-caprolactone, and 0.0425 parts of a catalyst were charged into a 10 L four-necked flask, and the temperature was raised to 170 ° C. while blowing nitrogen from a nitrogen inlet tube. Let it go. During the reaction, the amount of the remaining lactone monomer was traced every two hours, and when the amount of the remaining lactone monomer became 0.1% by weight or less of the total charged amount, 1
The temperature was lowered to 20 ° C. or lower to complete the reaction.

[0028] dissolving the solvent extraction process the synthesized lactone polyols about 1 g <quantification method of cyclic lactone> in tetrahydrofuran 0.5 ml. At this time, 10 mg of diisobutyl phthalate is added as an internal standard substance. 2.5 ml of n-hexane is added to this solution to extract the cyclic lactone oligomer and the cyclic lactone monomer in the hexane layer. 2 μl of the extract was injected into the gas chromatography, and the detected amount of the cyclic lactone oligomer and the amount of the detected cyclic lactone monomer were calculated from a calibration curve.

<Method of Evaluating Outgas from Urethane Resin> ( Heat Extraction Method) A thermoplastic urethane resin sample is exposed to a thermal environment in a closed chamber. The generated outgas is adsorbed on activated carbon, and the outgas component is thermally extracted from the activated carbon in another chamber and concentrated into glass wool. The concentrated outgas component was qualitatively and quantitatively determined by gas chromatography / mass spectrometry. (Evaluation) ：: The total amount of the detected monomers and oligomers is 50
It is less than ppm. ×: The total amount of the detected monomers and oligomers is 50
More than ppm.

<Evaluation of mechanical strength> Using a test piece obtained by injection molding, hardness, tensile strength and elongation were measured in accordance with JIS-K-7311.

(Synthesis Example 1) Lactone polyol was obtained by the above polymerization method using stannous octylate as a catalyst.
The cyclic lactone oligomer and the cyclic lactone monomer in the lactone polyol were quantified by a solvent extraction method.

Synthesis Example 2 Lactone polyol was obtained by the above polymerization method using dibutyltin dilaurate as a catalyst. The cyclic lactone oligomer and the cyclic lactone monomer in the lactone polyol were quantified by a solvent extraction method.

(Synthesis Example 3) Lactone polyol was obtained by the above polymerization method using tetraisopropyl titanate as a catalyst. The cyclic lactone oligomer and the cyclic lactone monomer in the lactone polyol were quantified by a solvent extraction method.

(Synthesis Example 4) Lactone polyol was synthesized by the above polymerization method using stannous octylate as a catalyst.
After the completion of the reaction end point, the mixture was excessively heated at 170 ° C. for 20 hours. The cyclic lactone oligomer and the cyclic lactone monomer in the lactone polyol were quantified by a solvent extraction method.

Table 1 shows the quantitative results of the cyclic lactone oligomer and the cyclic lactone monomer in the lactone polyols obtained in (Synthesis Examples 1 to 4).

[0036]

[Table 1]

Example 1 MDI 72 was added to 998 parts of the lactone polyol (hydroxyl value = 56.3) obtained in Synthesis Example 1.
3 parts were added and reacted at 80 ° C. to obtain a prepolymer (NCO
eq = 360.4). 1,4-
215 parts of butanediol were added, mixed with high-speed stirring, cast into a vat, and reacted at 180 ° C. for 1 hour. After pulverizing this reaction product, it was pelletized by an extruder to obtain a thermoplastic polyurethane resin.

Example 2 To 998 parts of the lactone polyol (hydroxyl value = 56.3) obtained in Synthesis Example 1, 215 parts of 1,4-butanediol was added and mixed with stirring.
Was added to the mixture, and the mixture was stirred and mixed at a high speed and cast into a vat.
A thermoplastic polyurethane resin was obtained in the same manner as in Example 1.

Example 3 TODI7 was added to 998 parts of the lactone polyol (hydroxyl value = 56.3) obtained in Synthesis Example 1.
92 parts were added and reacted at 80 ° C. to obtain a prepolymer (NC
Oeq = 360.2). 1,4
-223 parts of butanediol and stannous octoate.
2 parts were added, mixed at a high speed under stirring and cast into a vat, and a thermoplastic polyurethane resin was obtained in the same manner as in Example 1.

Example 4 MDI 7 was added to 1003 parts of the lactone polyol (hydroxyl value = 55.9) obtained in Synthesis Example 2.
27 parts were added and reacted at 80 ° C. to obtain a prepolymer (NC
Oeq = 359.6). 1,4
216 parts of butanediol were added, mixed at a high speed with stirring, and cast into a vat to obtain a thermoplastic polyurethane resin in the same manner as in Example 1.

Comparative Example 1 MDI 7 was added to 1006 parts of the lactone polyol (hydroxyl value = 55.4) obtained in Synthesis Example 3.
26 parts were added and reacted at 80 ° C. to obtain a prepolymer (NC
Oeq = 360.3). 1,4
216 parts of butanediol were added, mixed at a high speed with stirring, and cast into a vat to obtain a thermoplastic polyurethane resin in the same manner as in Example 1.

Comparative Example 2 MDI 72 was added to 998 parts of the lactone polyol (hydroxyl value = 56.3) obtained in Synthesis Example 4.
3 parts were added and reacted at 80 ° C. to obtain a prepolymer (NCO
eq = 360.5). 1,4-
215 parts of butanediol were added, mixed with high-speed stirring and cast into a vat, and a thermoplastic polyurethane resin was obtained in the same manner as in Example 1.

(Examples 1 to 4) The thermoplastic polyurethane resins obtained in (Comparative Examples 1 and 2) were evaluated for mechanical strength by the above-described methods and for outgas components by the heat extraction method. The results are shown in Table 2.

[0044]

[Table 2]

The compounds used are indicated using abbreviations, but the relationship between the abbreviations and the compounds is as follows. [Abbreviation] MDI: 4,4'-diphenylmethane diisocyanate TODI: tri-diisocyanate

[0046]

The urethane resin composition of the present invention is used as an electronic component as a urethane molded product, and is used in electronic equipment, especially in a hard disk drive, etc., even when exposed to a thermal environment during use.
Since the outgas amount of the cyclic lactone oligomer, lactone monomer and the like generated inside the device is extremely low, the probability of causing a malfunction of the hard disk device is very low. As described above, the present invention can provide an electronic component that can make a great contribution to reducing the amount of outgas generated from the electronic component.

Claims (2)

[Claims] 1. A lactone polyol (A) having a total amount of a cyclic lactone oligomer and a lactone monomer of 0.5% by weight or less, a polyisocyanate (B), and a low molecular weight glycol (C) as a chain extender. A urethane resin composition for an electronic component, comprising: 2. An electronic component for a hard disk drive using the urethane resin composition for an electronic component according to claim 1.