JP3082010B2 - Packing material for magnetic disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust-proof cover for a magnetic disk drive and a packing material for hermetically sealing a container body for accommodating a magnetic disk.

[0002]

2. Description of the Related Art A magnetic disk drive is referred to as a hard disk drive (hereinafter abbreviated as HDD) and rotates a hard disk-shaped magnetic disk housed in an airtight container in a range of 0.1 to 0. Information is recorded / reproduced from a magnetic head through a gap of 0.5 μm. However, in this apparatus, the gap between the disk and the head is extremely small, such as about 0.1 to 0.5 μm. When dust enters, the head and the disk are damaged, and a trouble that important data cannot be read easily occurs. In order to prevent such troubles, a packing material for sealing the closed container body and the dustproof cover has been used. In recent years, dusts and oils such as silicon-based substances generated from the packing material have been removed from the head or disk. There has also been a problem that reading and erroneous operations may occur due to adhesion and contamination of the image. For this reason, attention is paid to use of a clean material free from generation of dust and oil from the packing material interposed between the container main body and the dustproof cover while improving the hermeticity of the container main body.

Conventionally, chloroprene sponge, urethane sponge, silicone rubber and the like have been used as packing materials. However, the chloroprene sponge has a large set, there is no long-term reliability in the sealing property, and when the cover is opened for adjustment of the apparatus, the seal is set, and it takes time to replace it. Urethane sponge has high air permeability, cannot achieve the purpose of dustproof and moistureproof, and the silicon compound used as a foam stabilizer vaporizes, adheres to magnetic heads and magnetic disks, and contaminates, causing malfunctions in reading. Silicon rubber has good resilience and dust resistance, but unreacted low-molecular-weight silicon compounds in the rubber contaminate the magnetic head and magnetic disk, causing read errors and causing reliability problems. However, there was a disadvantage that it was lacking. Furthermore, in the past, there was a case in which chlorofluorocarbon cleaning was performed in order to increase the cleanliness of the sealing material itself.
There has been a demand for a seal material that is hardly absorbed by water and easy to dry.

[0004]

SUMMARY OF THE INVENTION The present inventor has made various studies to eliminate the above-mentioned disadvantages and to obtain a packing material which does not easily absorb water even when washed with water. As a result, the present invention has been completed. An object of the present invention is to provide a packing material for a magnetic disk drive which has a small compression set (small set), no oil such as silicon or dust, and does not cause a malfunction of the magnetic disk drive.

[0005]

The gist of the present invention is that an average cell diameter obtained from a polyol, an isocyanate, a foaming agent, a reactive silicone foam stabilizer and other auxiliaries is 150 μm.
This is a packing material for a magnetic disk drive made of flexible microcell urethane of m or less. That is, in the present invention, when obtaining a packing material comprising a polyurethane-based foam material, a reactive silicon foam stabilizer was used as a foam stabilizer, and the average pore diameter of the cells was 150 μm or less to form a flexible microcell urethane. , Was able to achieve its purpose.

The present invention will be described in more detail. The microcell urethane in the present invention has an average pore size of 150 μm or less. The cell diameter of a general urethane is 400 to 500 μm, and even if it is used as a seal material, it is 250 to 300 μm, whereas the microcell urethane of the present invention has an average pore diameter of the cell. It is 150 μm or less, and the cell diameter is smaller than the conventional one. If the cell diameter is larger than 150 μm, air permeability is increased, dust resistance is deteriorated, and water absorption is increased, which is not preferable. The density of the microcell urethane is 0.1 to 0.7.
g / cm ³ is preferable. When the density is low, the air permeability from the interface of the packing material is high, and there is a risk of intrusion of dust. On the other hand, when the density is high, the compressive stress increases, and when compressed, it spreads laterally, and There is a risk of protruding.

The polyol in the present invention may be any of polyether polyol, polyester polyol and the like generally used in the urethane industry, and is not particularly limited. As for isocyanate, tolylene diisocyanate, diphenylmethane diisocyanate (MD
I) and crude MDI are not particularly limited. Examples of the foaming agent include water, methylene chloride, nitrogen, air, and chlorofluorocarbon. The reactive silicone foam stabilizer which is one of the features of the present invention is a foam stabilizer having a reactive group which reacts with a polyol, an isocyanate, a foaming agent and the like used for producing the microcell urethane of the present invention. Such reactive groups include OH groups, NH groups, NH ₂ groups, SH groups,
COOH group, Si-OCH ₃ group (methoxy group) and the like. The structure of the silicone foam stabilizer is typically a polydimethylsiloxane-polyalkylene ether block copolymer shown below.

[0008]

Embedded image

In the formula, m and n are integers of 1 or more, R 'is an organic group, POA is an alkylene ether group A is a reactive group (for example, OH group). By using a reactive silicone foam stabilizer, the air permeability of the packing material of the present invention is reduced, and as a result,
There is a feature that a reading malfunction does not occur because the dust proof effect is enhanced and the divergence of silicon is small at the same time. Furthermore, when a reactive type silicone foam stabilizer is used, the water absorption becomes significantly lower than that of a normal addition type (non-reactive type) silicone foam stabilizer, and washing with water becomes possible. The cleanliness of the packing material is at the same level as the CFC cleaning, and can contribute to the elimination of CFCs. Other auxiliary agents include conventional auxiliary agents used in the production of polyurethane.

The method for producing microcell urethane by using the above-mentioned polyol, isocyanate, foaming agent, reactive silicone foam stabilizer and other auxiliaries includes a water foaming method which is usually carried out, Either a foaming method with a solvent or a method of bubbling air or the like may be used. However, if a microcell is used, the thermal conductivity is reduced, and the former two methods are preferable because the curing time is shorter than the latter method. As a method of adjusting the cell diameter of the obtained microcell urethane, for example, the number of added parts of the silicone foam stabilizer or the amount of the catalyst is increased, or the number of functional groups of the crosslinking agent is increased by increasing the number of functional groups of the polyol to three from two. The cell diameter can be made smaller by such means as increasing the pressure at the time of foaming, or increasing the amount of the tin catalyst compared to the amine catalyst.

[0011] In any of these foaming methods, after producing into a block, it is sliced to a predetermined thickness to obtain an original fabric, a method to obtain a product having a predetermined thickness by a mold, There are methods such as applying foaming material and foaming. According to the latter two methods, a product with a self-skin on the front and back of the product is obtained, and the adhesiveness with the adhesive is good and the adhesiveness with the cover And the air permeability from the interface decreases, so that the degree of sealing and the degree of dust prevention are increased, which is preferable.

[0012]

The effects of the present invention are listed below. (1) A microcell urethane using a reactive silicon foam stabilizer provided a highly clean packing material with less generation of silicon compounds causing malfunction of the HDD. (2) Microcell urethane having a cell diameter of 150 μm or less makes it easy to close the cell hole with only a slight compression, so that low air permeability can be achieved. (3) Microcell urethane having a cell diameter of 150 μm or less using a reactive silicon foam stabilizer, has extremely low water absorption, can be washed with water, and can provide a clean packing material regardless of Freon washing.

(4) Since a reactive silicone foam stabilizer is used: the adhesiveness to the adhesive tape is good, and in the case of a packing material having a self-skin layer, the adhesiveness is further improved.
For this reason, there is no problem that the packing material comes off in the HDD assembling operation, and the reliability is high. H
There is a merit that it is easy to cope even when the cover shape of the DD becomes complicated. (5) Since it is a microcell urethane, it does not contain a plasticizer unlike chloroprene sponge and has little settling.

[0014]

Next, the present invention will be described more specifically with reference to examples and comparative examples. Example 1 Polyoxypropylene triol 10 having a molecular weight of 3000
0 parts, 1,4 butanediol 6 parts, amine catalyst (Dabco 33LV) 0.1 part, dibutyltin dilaurate (DBTDL) 0.1 part as a catalyst, reaction of terminal OH group as a silicone foam stabilizer Type silicone foam stabilizer (F-3
42, Shin-Etsu Chemical Co., Ltd.).
The mixture was mixed and stirred with 40 parts of MDI, foamed in a block shape, heated at 100 ° C. for 10 minutes, and sliced into 1 mm to obtain a sheet-like product.

Example 2 In the same manner as in Example 1, 2 parts of an NH group-containing reactive silicon foam stabilizer (X22-3939A Shin-Etsu Chemical Co., Ltd.) was used as a silicone foam stabilizer, foamed into a block, and heated at 100 ° C. for 10 minutes. It heated and sliced to 1 mm, and obtained the sheet-shaped product. Example 3 Coating was performed on release paper in the same manner as in Example 1 to obtain a foam with skin.

Comparative Example 1 In the same manner as in Example 1, 2 parts of non-reactive silicon (F-304 Shin-Etsu Chemical) having a butoxy end group was used as a silicone foam stabilizer, foamed into a block, and heated at 100 ° C. for 10 minutes. And sliced to 1 mm to obtain a sheet-like product. Comparative Example 2 In the same manner as in Example 1, a sheet-like foam was obtained by reducing the amount of nitrogen in order to produce urethane having a large cell diameter.

Table 1 shows the results of the evaluation of these foams by the following evaluation methods. Evaluation method: Cell diameter The number of cells within a 0.5 mm square of the cross section perpendicular to the foaming direction was measured.

[0018]

(Equation 1)

## EQU1 ## Outgassing content 125 ° C 10 ~ ⁶ torr 24H in vacuum
The rate of weight loss is measured. Silicon extraction Extracted with acetone, and the amount of Si in the extract was measured by atomic absorption. After 48 hours under a water pressure of 10 cm, the weight of the sample was measured and expressed as a percentage of the increased weight relative to the original weight. 90 ° Peel A packing material was adhered to a fixed panel, and a tape laminated with a film was pressed, and the 90 ° peel strength was measured. 50% compression residual strain The test piece was fixed at 50% compression, and 70 ± 1
After heating at 22.degree. C. for 22 hours, the compression is removed, the thickness is measured for 30 minutes after standing at room temperature, and then the thickness is calculated by a calculation method. Strain = original thickness-thickness after test / original thickness x 100%

[0020]

[Table 1]

According to Table 1, in Example 1, the cell diameter was 60 μm, the generated gas was 0.11%, the silicon extraction was 15 ppm, and the water absorption was 3 wt.
%, 50% compression residual strain 1.3%, 90 ° peel, material destruction, hardly absorbs water when washed with water, has good drying properties, does not cause erroneous reading, and has good adhesive properties, and thus is suitable as a packing for HDD. In the second embodiment, a gas having a cell diameter of 60 μm and a gas pressure of 0.1 μm is used.
12% silicon extraction 15ppm water absorption 2.5wt%,
50% compression residual strain 2.0%, 90 ° peel, material destruction, hardly absorbs water during washing, good dryness, no erroneous reading, good adhesion, suitable for HDD packing. In the third embodiment, the cell diameter is 60 μm and the generated gas is 0.10.
% Silicon extractables 14 ppm Water absorption 2.6 wt%, 50
% Compression residual strain 1.0%, 90 ° peel material, broken, hardly absorbs water when washed with water, has good drying properties, does not malfunction in reading, has good adhesion, and has improved airtightness, and is suitable as a packing for HDD. Was something.

In Comparative Example 1, a gas having a cell diameter of 80 μm and a gas generation of 1.4 were used.
5% silicon extractables 280 ppm water absorption 20 wt%, 5
0% compression set 1.8%, 90 ° peel 500g / 25
mm, the target of silicon extraction is 50-100 ppm
As described above, there is a possibility that a reading error may occur, which is unsuitable for packing for HDDs. In Comparative Example 2, the cell diameter was 160
μm generated gas 0.11% silicon extraction 15ppm water absorption 18wt%, 50% compression residual strain 2.4%, 90 ° peel 400g / 25mm, silicon extraction is small,
It has a high water absorption, is not suitable for washing with water, and has poor adhesiveness to a tape, which is not preferable in terms of assembly and is unsuitable for packing for HDDs.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Noboru Murata 3-10-10, Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Japan Hakko Co., Ltd. (56) References JP-A-63-211182 (JP, A) JP-A-2 -24890 (JP, A) Japanese Utility Model 62-98098 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 33/14 G11B 25/04

Claims (1)

(57) [Claims] 1. A packing material for a magnetic disk drive comprising a flexible microcell urethane having an average cell diameter of 150 μm or less obtained from a polyol, an isocyanate, a foaming agent, a reactive silicone foam stabilizer and other auxiliaries. .