JP2004352999A - Lubricant containing phosphazene compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant for a hard disk having excellent CSS durability. <P>SOLUTION: The lubricant contains phosphazene compounds comprising a sequence in which a perfluoroxyalkylene unit selected from CF<SB>2</SB>O and CF<SB>2</SB>CF<SB>2</SB>O is randomly distributed and which contains functional terminal group A, and represented by formula (5): A-[OCH<SB>2</SB>CF<SB>2</SB>O(CF<SB>2</SB>CF<SB>2</SB>O)p(CF<SB>2</SB>O)qCF<SB>2</SB>CH<SB>2</SB>OH] [wherein, A is a group represented by formula (a); and p and q are each a real number of 1-30]. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lubricant containing a phosphazene compound. More specifically, the present invention relates to a lubricant for a recording medium such as a hard disk which is a large-capacity recording medium or a metal-deposited tape used for an 8 mm video tape recorder or a digital video cassette.

  2. Description of the Related Art With the spread of the Internet, intranets, local area networks, and the like, information can be easily retrieved simply by accessing a network. One of the things supporting such multimedia age is an external storage device. As an existing large-capacity external storage device, a recording medium layer is provided on a high-strength circular substrate (hard disk), and the hard disk is rotated at high speed to operate a recording / reproducing element (head), that is, a so-called CSS system. The hard disk includes a fixed magnetic disk, an optical disk, and a magneto-optical disk. The most popular of these is a device using a fixed magnetic disk.

  To increase the capacity without changing the size of these external storage devices, for example, it is necessary to increase the areal recording density of the recording medium layer. For this purpose, it is necessary to reduce the bit size and move the head as close to the recording medium as possible. In order to reduce the distance between the head and the disk, the irregularities on the disk surface must be reduced. For example, to reduce the distance to 100 nm or less, the irregularities must be reduced to 10 nm or less. When the smoothness of the disk surface is improved, on the other hand, the head is more easily attracted to the disk surface. Further, in order to obtain high-speed response, it is necessary to increase the bit transfer speed and, consequently, the rotation speed of the disk. For example, the maximum rotation speed of a 3.5-inch hard disk needs to be 5400 to 7200 rpm, and the head passage speed around the disk reaches 125 km / hr. However, any of the above changes greatly increases the probability of contact between the disk and the head, abrasion, etc., and lowers reliability.

  To cope with these problems and protect the disk surface and the head, the simplest method is to increase the amount of lubricant applied to the disk protective film surface. However, when the amount of the applied lubricant is increased, not only the sliding resistance of the lubricating film is increased, but also the adsorbing action of the lubricant is increased, thereby causing the spindle motor to stop and burn. If a low-viscosity lubricant is used to reduce the sliding resistance, the lubricant moves and disappears from the protective film when the disk rotates at a high speed, causing contact between the disk and the head and breakage.

  Lubricants can be formed very simply by forming a lubricant film with a uniform molecular thickness on the protective film provided on the hard disk to reduce friction and wear that occur when the hard disk rotates and when the device starts and stops. ing. To protect the disk and head, the sliding resistance is low, the bonding strength with the protective film is large, the coefficient of friction is low, the chemical stability, thermal stability, and corrosion resistance are large, and the temperature is low at -10 ° C or lower. A lubricant having a lubricating ability and capable of forming an ultra-thin film at a low vapor pressure is required. The hard disk lubricant has a CSS durability of 50,000 times or more and has no change in friction coefficient. That is, in the CSS repetition test, it is required that there is no abnormality such as burn-in of the head and scratches on the disk at least up to 50,000 times.

  For protecting the surface of the current hard disk, a diamond-like carbon (DLC) protective film is used from the viewpoints of chemical stability, strength, ultrathinness, smoothness, and the like. As is apparent from the structure, the protective film is mostly composed of carbon, and therefore has a low chemical bonding property and a small adhesive force such as hydrogen bonding with hydrogen and nitrogen atoms and van der Waals force. Nothing else depends on the interaction.

  Therefore, as a lubricant, a perfluoroalkyl polyether oligomer (hereinafter abbreviated as “PFPE”) is generally used (Monthly Tribology, No. 99, November, pp. 37-38, 1995). PFPE has low surface energy, chemical inertness, low vapor pressure, and thermal stability derived from fluorocarbons. However, there is a drawback that the particles move and disappear from the protective film. To suppress this, an additive of the second component is used (see, for example, Patent Document 1), but due to the low compatibility of PFPE derived from fluorocarbon, phase separation is caused, and a sufficient effect is obtained. There is no present. Therefore, in order to impart binding properties to PFPE, there are also those in which a functional group such as a hydroxyl group or an acylamide group is introduced at the end or the center of the PFPE main chain (Aushimont Co., Ltd., FOMBLIN Z derivative). Functional groups may reduce chemical stability due to friction with the head.

Further, a perfluoroalkoxy phosphazene compound is disclosed as a treating agent for a magnetic recording medium (for example, see Patent Document 2). However, when these compounds are used as a lubricant for a hard disk, sufficient CSS durability can be obtained. Therefore, a new lubricant is desired.
USP48771625 JP-A-63-103428

  An object of the present invention is to provide, for example, a hard disk lubricant having good CSS durability.

The present invention is _{-CF 2 O -, - CF 2} CF 2 O-, perfluorooxyalkylene units selected from is more sequences randomly distributed, further comprising a functional end group A, the following formula (5) It relates to a lubricant containing a phosphazene compound represented.
A- _{[OCH 2 CF 2 O (CF 2} CF 2 O) p (CF 2 O) qCF 2 CH 2 OH ] (5)
[In the formula, A is a group represented by the following formula (a). Here, p and q are real numbers of 1 to 30. ]

  According to the present invention, for example, a hard disk lubricant having good CSS durability can be obtained.

In the present invention, the phosphazene compound of the formula (5) can be obtained in the process of producing the phosphazene compound of the following formula (1).
A-OCH ₂ CF ₂ O (CF ₂ CF ₂ O) p (CF ₂ O) qCF ₂ CH ₂ O-A (1)
Wherein A, p and q are the same as above. ]
The phosphazene compound of the above formula (1) is a novel compound not described in the literature, and is, for example, a substance produced from an oligomer of phosphonitrile halide, a phenol and an alcohol having a hydroxyl group introduced into both ends of the PFPE main chain. Here, examples of the oligomer of the phosphonitrile halide include a cyclic trimer of phosphonitrile chloride, a cyclic tetramer of phosphonitrile chloride, and a mixture thereof. Examples of the phenols include haloalkoxyphenols such as phenol and meta-trifluoromethylphenol, and alkoxyphenols such as meta-methoxyphenol. Examples of the alcohol having hydroxyl groups introduced at both ends of the PFPE main chain include perfluoroalkyl polyether oligomers (Z derivative of Aushimont Co.) having an average molecular weight of 400 to 6000 in the following formula (b).
HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) r (CF ₂ O) sCF ₂ CH ₂ OH (b)
[r = 1-30, s = 1-30]

  The compound (1) of the present invention is produced, for example, as follows. That is, as described in JP-A-62-53996, alcohols and phenols are previously reacted with sodium or the like to form alcoholates and phenolates, and then reacted with a cyclic oligomer of phosphonitrile halide. . More specifically, phenols are dissolved in a solvent such as diethyl ether, diisopropyl ether, toluene or the like, and less than the equivalent required to convert all the phenols to phenolate, preferably 85 to 95% equivalents of metallic sodium and hydrogen. A base such as sodium chloride is reacted at the reflux temperature of the solvent until all of these bases have reacted to give the phenolate in advance. The resulting phenolate is reacted with a 15 to 25% equivalent, preferably 18 to 21% equivalent, cyclotrimer of a phosphonitrile halide to give an aryloxy-substituted tricyclophosphonitrile halide. Separately, an alcohol having a hydroxyl group introduced into both ends of PFPE (hereinafter abbreviated as “PFPE-DOH”) and a base selected from the above bases are added in the same equivalent amount, and the mixture is heated at room temperature to 120 ° C., preferably at 40 to 100 ° C. React until solid base is no longer visible.

  The above-obtained aryloxy-substituted tricyclophosphonitrile halide and PFPE-DOH that has been alcoholated are mixed with an ether solvent such as diethyl ether, diisopropyl ether, perfluorohexylmethyl ether for 1 to 10 days, preferably 2 to 10 days. The reaction is carried out at room temperature to the reflux temperature of the solvent for a period of from 5 days to 5 days. The reaction mixture obtained by this reaction is added to an ether-based solvent solution containing a phenolate separately prepared by the above method, and the mixture is heated from room temperature to the reflux temperature of the solvent, preferably at reflux temperature, and the halogenated tricyclohexane is partially substituted. The reaction is allowed to complete for 5 to 15 days until no phosphonitrile is detected. After washing the reaction mixture several times with water, it is dehydrated and dried, and the solvent used is removed by distillation under reduced pressure. When the unreacted phenol, PFPE-DOH and hexaaryloxy-substituted tricyclophosphonitrile are present from the obtained reaction mixture, these compounds are distilled off by molecular distillation to remove the above compound ( 1) is manufactured.

  In the present invention, in addition to the compound of the formula (1), compounds having a high molecular weight such as the following formulas (2) and (3) may be present in the reaction system. A small amount of such a compound may be present in the lubricant of the present invention. Here, B is a group represented by the formula (4).

_{-CH 2 CF 2 O (CF 2} CF 2 O) r (CF 2 O) sCF 2 CH 2 - (4)
[R = 1-30, s = 1-30]

Since the synthesis of the compound of the formula (1) takes time as described above, the reaction may not be completed and may be stopped at an appropriate place in consideration of economy. In this case, a compound represented by the following formula (5) occurs, for example, in an amount of 5% or more in some cases. The ratio of the compound (1) to the compound (5) can be selected from a wide range, and for example, the former / latter (weight ratio) = 5 to 95/95 to 5, preferably 20 to 80/80 to 20 can be exemplified. The compound (5) is separated from the compound (1) by, for example, extraction using supercritical carbonic acid as shown in Example 1 described later. In addition, separation can also be performed by column chromatography, molecular distillation, or solvent extraction.
A- _{[OCH 2 CF 2 O (CF 2} CF 2 O) p (CF 2 O) qCF 2 CH 2 OH ] (5)
Wherein A, p, and q are the same as above.

The compound (5) of the present invention is suitable for uses such as nonflammable lubricating oils and hydraulic oils, particularly for use as lubricants for recording media.
When the phosphazene compound (5) of the present invention is used as a lubricant, the phosphazene compound may be used as a lubricant as it is, or may be used after being dissolved in an appropriate organic solvent. Examples of the organic solvent include aromatic hydrocarbons such as toluene and xylene, methylene chloride, chloroform, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichlorotrifluoroethane (Freon 113) and perfluorohexylmethyl. Halogenated hydrocarbons such as ether (HFE-7100), ethers such as diethyl ether, dimethoxyethane, dioxane and tetrahydrofuran; esters such as ethyl acetate, butyl butyrate and amyl acetate; alicyclics such as cyclohexane, cycloheptane and cyclooctane Examples thereof include hydrocarbon, dimethylformamide, dimethyl sulfoxide, and a mixed solvent of two or more of these.

When the lubricant of the present invention is used as a lubricant for a recording medium, the concentration of the compound of the formula (5) may be 0.1% by weight or more, usually 0.1 to 100% by weight, preferably 10 to 100% by weight. And more preferably about 20 to 100% by weight.
In the present invention, a compound of the formula (5) and a perfluoroalkyl polyether oligomer having an average molecular weight of the formula (b) of 400 to 6000 can be used in combination.
HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) r (CF ₂ O) sCF ₂ CH ₂ OH (b)
[r = 1-30, s = 1-30]

In the present invention, the compound of the formula (5) and the following perfluoroalkyl polyether oligomer (c) can be used in combination.
_{X-CF 2 O (CF 2} CF 2 O) m (CF 2 O) nCF 2 -Y (c)
[X, Y is _{HO (CH 2 CH 2 O)} tCH 2 -, HOCH 2 CH (OH) CH 2 OCH 2 -, represents at least one group selected from HOOC- or piperonyl group. m = 1-80, n = 1-80, t = 1-30]
Examples of the oligomer (c) include FOMBLIN ZDol-TX, Z-TETRAOL, Z-DIAC, AM3001 (all manufactured by Asimont).

In the present invention, the compound of the formula (5) and the following perfluoroalkyl polyether oligomer (d) can be used in combination.
F [CF (CF ₃ ) CF ₂ O] uCF (CF ₃ ) COOH (d)
[u = 1-60]
Examples of the oligomer (d) include KRYTOX 157FS (DuPont).

  When the compounds (b), (c) and (d) are used in combination, the concentration of each compound is preferably at least 0.1% by weight, usually about 10 to 90% by weight. Further, at least two or more of the compounds (b), (c) and (d) can be used in combination.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto. All the reactions described below were performed in an argon gas atmosphere.

Example 1
In a 2 liter four-necked flask equipped with a reflux condenser, an argon gas inlet tube, a thermometer and a stirrer, 282.1 g (1.74 mol) of meta-trifluoromethylphenol and diisopropyl ether dried, dehydrated and purified by distillation. After adding 2 L, 36.5 g (1.59 mol) of a small piece of sodium metal was added with stirring and reacted at a temperature at which diisopropyl ether was refluxed for 2 days. After confirming that all the sodium metal had been consumed, While the reaction mixture was stirred, 107.7 g (0.31 mol) of cyclotrimer of phosphonitrile chloride was added, and the mixture was reacted at reflux temperature for 3 days to obtain about 1300 g of a reaction mixture. After the reaction mixture was washed 5 times with about 500 ml of purified water, the diisopropyl ether layer was separated, dehydrated with molecular sieves, and the diisopropyl ether was distilled off under reduced pressure using a rotary evaporator to obtain a brown transparent liquid. This is (a).

  In a flask similar to the above, PFPE-DOH｝ a diol having an average molecular weight of 2000 and an average value of r and s described in the above formula (b) of 10.8 and 9.7, respectively｝ 302 g (0. 151 mol) and 3.5 g (0.151 mol) of small pieces of metallic sodium were reacted at 50 ° C. to 100 ° C. for 12 days. After confirming that all metallic sodium was consumed in the reaction, perfluorohexyl was added. 450 g of methyl ether was added to reduce the viscosity of the reaction. A solution prepared by dissolving 150.5 g of (a) in 140 g of diisopropyl ether was gradually added dropwise thereto, and the mixture was stirred at a reflux temperature for 3 days and then allowed to cool to room temperature. The obtained reaction mixture is referred to as (b).

  Meta-trifluoromethyl separately prepared from 192.7 g (1.19 mol) of meta-trifluoromethylphenol and 24.8 g (1.08 mol) of a small piece of metallic sodium in the same manner as in the production of (a) above. To a solution containing 1.19 mol of phenolate and 700 g of diisopropyl ether, the entire amount of the above reaction mixture (b) was quantitatively added using 230 g of perfluorohexyl methyl ether, and the mixture was stirred at the reflux temperature of the solvent for 9 days. And reacted. In this reaction mixture, it was confirmed by capillary gas chromatography that the cyclotrimer of phosphonitrile in which only the meta-trifluoromethylphenoxy group and the chlorine atom were both substituted in a mixed state, that is, no reaction intermediate was present. Thereafter, the contained solvent was distilled off from the reaction mixture under reduced pressure by a rotary evaporator, and the obtained residue was dissolved in 200 g of diethyl ether. The diethyl ether solution was washed three times with 200 g of a 1% aqueous nitric acid solution and further four times with 200 g of purified water. After these operations, the diethyl ether layer was dehydrated and dried with molecular sieves, and the diethyl ether was further distilled off under reduced pressure by a rotary evaporator to obtain 350 g of a slightly turbid oily liquid.

After removing the cyclotrimer (by-product) of phosphonitrile substituted with 6 meta-trifluoromethylphenoxy groups from the reaction mixture by washing with toluene, 270 g of a yellow transparent liquid was obtained. This liquid was separated into 60 g (0.015 mol) of the compound (1-a) and 80 g (0.027 mol) of the compound (5-a) by extraction using supercritical carbonic acid.

(CF ₃ C ₆ H ₄ O) ₅ P ₃ N ₃ OCH ₂ CF ₂ (OCF ₂ CF ₂ ) _11.6 (OCF ₂ ) _10.6 OCF ₂ CH ₂ ON ₃ P ₃ (OC ₆ H ₄ CF ₃ ) ₅ [Compound (1-a)]
(CF ₃ C ₆ H ₄ O) ₅ P ₃ N ₃ OCH ₂ CF ₂ (OCF ₂ CF ₂ ) _11.6 (OCF ₂ ) _10.6 OCF ₂ CH ₂ OH [compound (5-a)]

According to 400 MHz proton NMR and F-NMR, the compound (1-a) obtained was a phosphonitrile cyclotrimer in which five meta-trifluoromethylphenoxy groups were substituted at both ends of PFPE-DOH. Compound (5-a) was a compound having a phosphonitrile cyclotrimer in which five meta-trifluoromethylphenoxy groups were substituted at only one end of PFPE-DOH. The viscosity of the compound (5-a) was 110 centipoise (40 ° C.), the density was 1.75 g / cm ³ (15 ° C.), and the surface tension was 23 dyne / cm (20 ° C.).

Comparative Example 1 (Compound described in JP-A-6-220077)
In a 1-liter four-necked flask equipped with a reflux condenser, an argon gas inlet, a thermometer and a stirrer, 41.3 g (0.083 mol) of C ₃ F ₇ O (CF ₂ CF ₂ O) ₂ CF ₂ CH ₂ OH was added. ), Dried and dehydrated, and 0.5 liter of diisopropyl ether purified by distillation, 1.73 g (0.075 mol) of a small piece of metallic sodium was added with stirring, and the mixture was reacted at 50 ° C. for 3 days. After the reaction, 6.95 g (0.02 mol) of cyclotrimer of phosphonitrile chloride and 40 ml of diisopropyl ether were added, and the mixture was reacted at 60 to 70 ° C. for 2 days. Let the obtained reaction mixture be (d).

  In the same manner as in the above (d), 18.8 g (0.198 mol) of phenol and 4.14 g (0.18 mol) of sodium metal were reacted in 250 ml of diisopropyl ether for 5 days to obtain sodium phenolate diisopropyl ether. A solution was obtained. This solution is referred to as (e).

The whole amount of the solution (e) is put into the flask containing the (d) in about 5 minutes at room temperature at a temperature of 70 ° C., and the reaction is carried out for 10 days. Then, the diisopropyl ether solution of the reaction mixture is washed with an aqueous sodium hydroxide solution. Then, it was washed four times with an aqueous nitric acid solution and further six times with purified water. The diisopropyl ether solution obtained by these washings was dehydrated and dried with molecular sieves, and the diisopropyl ether was distilled off under reduced pressure by a rotary evaporator to obtain 23.3 g of a pale yellow liquid [compound (D)].
The viscosity of the compound (D) was 740 centipoise (40 ° C.), the density was 1.51 g / cm ³ (15 ° C.), and the surface tension was 26 dyne / cm (20 ° C.).

Test example 1
Using the compound (5-a) and the compound (D) obtained in Example 1 and Comparative Example 1, a performance test of a lubricant was performed. After the hard disk was immersed in a solution of 1 g of the test compound dissolved in 1000 ml of perfluorohexyl methyl ether (HFE-7100), it was taken out and dried at 120 ° C. for 30 minutes to form a film having a thickness of 10 ° on the hard disk. . This was subjected to the following test.
The performance test of the lubricant was carried out by measuring the change in the friction coefficient by a CSS repetition test using an actual drive modified so that the friction coefficient could be measured from the force applied to the head. The CSS cycle starts with the head in contact with the disk surface, and after reaching a predetermined number of times 7200 rpm with the head floating, performs a process in 33 seconds until the head stops again with the head in contact with the disk surface, This was one cycle. The hard disk had a DLC protective film of 100 to 200 [deg.] Formed by a plasma CVD method on a recording medium prepared by 3.5-inch sputtering, and had no texture to enhance the surface smoothness. The head was a monolithic MIG (metal in gap) and the load was 7.5 g. The quality of the CSS test was determined by the number of cycles (CSS life) until the head and the disk adhere (crash), the state of the disk (whether or not worn), and the degree of contamination of the head after the test. Table 1 shows the test results.
In the head dirt shown in the table,-; no dirt ±; slightly present +; slightly present ++; solid matter attached.

Claims (5)

_{-CF 2 O -, - CF 2} CF 2 O-, perfluorooxyalkylene units selected from is more sequences randomly distributed, further comprising a functional end group A, represented by the following formula (5) A lubricant containing a phosphazene compound.
A- _{[OCH 2 CF 2 O (CF 2} CF 2 O) p (CF 2 O) qCF 2 CH 2 OH ] (5)
[In the formula, A is a group represented by the following formula (a). Here, p and q are real numbers of 1 to 30. ]

The lubricant according to claim 1, further comprising a perfluoroalkyl polyether oligomer having an average molecular weight of 400 to 6000 of the formula (b).
HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) r (CF ₂ O) sCF ₂ CH ₂ OH (b)
[R = 1-30, s = 1-30] The lubricant according to claim 1, further comprising a perfluoroalkyl polyether oligomer of the formula (c).
_{X-CF 2 O (CF 2} CF 2 O) m (CF 2 O) nCF 2 -Y (c)
[X, Y is _{HO (CH 2 CH 2 O)} tCH 2 -,
And at least one group selected from HOCH ₂ CH (OH) CH ₂ OCH ₂ —, HOOC— and piperonyl groups. m = 1-80, n = 1-80, t = 1-30] The lubricant according to claim 1, further comprising a perfluoroalkyl polyether oligomer of the formula (d).
F [CF (CF ₃ ) CF ₂ O] uCF (CF ₃ ) COOH (d)
[u = 1-60] 5. The lubricant according to claim 1, wherein the lubricant is a lubricant for a recording medium.