JP2009256498A - Ramp molded body of hard disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ramp molded body of a hard disk having a mechanical physical balance that a polyacetal resin has and excellent heat stability and excellent in heat stability after washing, dimensional stability after washing and an abrasion loss after washing which are peculiar to the ramp molded body. <P>SOLUTION: The ramp molded body of the hard disk is composed of a polyacetal resin composition containing 0.001 to 0.03 pts.mass talc (B) having >10 μm and <20 μm average particle diameter to 100 pts.mass polyacetal resin (A). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention has a balance of mechanical properties possessed by polyacetal resin, and is excellent in thermal stability, and is excellent in thermal stability after washing, dimensional stability after washing, and wear amount after washing, which are characteristic of lamp molded bodies. The present invention relates to a lamp molded body of a hard disk.

Polyacetal resin has excellent balance of mechanical strength, chemical resistance and slidability, and its processability is easy. Therefore, as typical engineering plastics, electrical equipment, mechanical parts of electrical equipment, automotive parts and others It is used over a wide range centering on these mechanical parts. The polyacetal resin is often used in an environment in which deterioration is accelerated depending on the use environment, and further, the required performance is becoming higher due to the expansion of the field of use.
Polyacetal resin is used as a lamp molded body of a hard disk, but when used for a hard disk part, there is a cleaning step of cleaning oil and fat so as not to cause defects due to outgas or the like before assembly. However, the properties of polyacetal resin may change before and after the washing process.

As the characteristics, for example, the thermal stability, dimensional accuracy, wear amount, etc. inherent in the polyacetal resin can be mentioned. Particularly in this application, the characteristics after cleaning are becoming important because they are used after being cleaned.
When the lamp molded body is cleaned, the oil and fat components coming from the surface lubricant, additives, and the like are cleaned, so the frictional wear performance before and after cleaning changes. In addition, since the crystal state of the polyacetal resin is usually changed by washing at a temperature higher than normal temperature, the dimensional accuracy before and after the washing also changes. Thus, the physical properties after cleaning are often unpredictable from the physical properties before cleaning.

  In response to these requirements, a method of adding boron nitride as a crystallization nucleating agent (for example, Patent Document 1) is generally mentioned. However, depending on the amount of addition or the dispersion state of boron nitride, the toughness may be lowered. Therefore, the physical property balance is not sufficient. In addition, there is a method of adding talc in an amount exceeding the scope of the present application as a crystal nucleating agent (eg, Patent Documents 2, 3, and 4). However, these methods have certain effects in improving mechanical properties and dimensional stability, but have not yet improved the thermal stability after washing and the amount of wear after washing. Further, as a combination of talc and another crystallization nucleating agent, a method of adding talc and a polyalkylene / unsaturated carboxylic acid lower alkyl ester polymer nucleating substance (for example, Patent Document 5), adding talc and a melamine-formaldehyde condensate Examples include a method (for example, Patent Document 6) and a method for adding talc and a terpolymer (for example, Patent Document 7), but these methods are also effective in improving mechanical properties and dimensional stability. The thermal stability and the amount of wear after washing have not been improved. Further, Patent Document 7 also describes that the use of talc alone is disadvantageous for thermal stability. Further, as a method not adding a crystallization nucleating agent such as talc other than those described above, there is a method using a polyoxymethylene copolymer having a high melting point range (for example, Patent Document 8).

However, this method is effective in improving mechanical properties, but has not yet improved the thermal stability after washing, dimensional accuracy, and the amount of wear after washing. Furthermore, Patent Document 9 describes a hard disk lamp whose sliding performance does not deteriorate even after solvent cleaning, but has not yet improved the dimensional accuracy after cleaning.
As described above, the conventional technology maintains the balance of mechanical strength, chemical resistance and slidability, which are the characteristics of polyacetal resin, and has a good balance of thermal stability after washing, dimensional accuracy and wear after washing. It was difficult.
JP 47-11136 A Japanese Patent Publication No. 45-37672 JP-A-62-187751 Japanese Patent Laid-Open No. 2001-2887 Special Table 2002-200266 gazette Japanese translation of PCT publication No. 2002-506107 JP-T-2004-512411 International Publication No. 00/17247 Pamphlet International Publication No. 03/055945 Pamphlet

  The present invention provides a hard disk comprising a polyacetal resin composition having a balance of mechanical properties possessed by a polyacetal resin, excellent in thermal stability, excellent in thermal stability after cleaning, dimensional accuracy after cleaning, and wear after cleaning. An object of the present invention is to provide a lamp molded body.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that polyacetal containing 0.001 to 0.03 parts by mass of talc (B) having a specific particle diameter with respect to 100 parts by mass of polyacetal resin (A). The present inventors have found that a lamp molded body of a hard disk made of a resin composition can solve the above problems, and have completed the present invention.
That is, the present invention is as follows.
1. Polyacetal resin composition comprising 0.001 to 0.03 parts by mass of talc (B) having an average particle diameter of more than 10 μm and less than 20 μm with respect to 100 parts by mass of polyacetal resin (A) Lamp molded body of hard disk made of materials.
2. The polyacetal resin composition comprises (C) a polymer lubricant obtained by polymerizing (c-1) a polyolefin resin and / or (c-2) an isocyanate compound and a polyalkylene oxide. 2. The lamp molded body of hard disk according to 1, wherein 0.1 to 10 parts by mass is contained per 100 parts by mass.

3. The lamp molded body of the hard disk according to 1 or 2, wherein the talc (B) is not surface-treated.
4). The hard disk lamp according to any one of claims 1 to 3, wherein the polyacetal resin composition is manufactured by adding talc (B) to a melted state of the polyacetal resin (A). Molded body.
5. The melting point of the polyacetal resin composition is 167 ° C. or more and 173 ° C. or less, wherein the lamp molded body of the hard disk according to any one of claims 1 to 4.
6). The MFR of the polyacetal resin composition is 20 to 40 g / 10 min, and the lamp molded body of the hard disk according to any one of 1 to 5, wherein:
7). The polyacetal resin composition comprises at least one selected from (D) an antioxidant, a polymer or compound containing formaldehyde-reactive nitrogen, a formic acid scavenger, a weathering (light) stabilizer, a release agent, and a lubricant. (A) 0.01-10 mass parts is contained with respect to 100 mass parts, The lamp molded object of the hard disk as described in any one of 1-6 characterized by the above-mentioned.

  According to the present invention, there is provided a lamp molded body of a hard disk having a balance of mechanical properties possessed by a polyacetal resin, excellent in thermal stability, excellent in thermal stability after cleaning, dimensional accuracy after cleaning, and wear after cleaning. Became possible.

Hereinafter, the present invention will be described in detail.
The polyacetal resin (A) used in the present invention is substantially only an oxymethylene unit obtained by homopolymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) or a tetramer (tetraoxane). A polyacetal homopolymer consisting of formaldehyde monomers or cyclic oligomers of formaldehyde such as trimer (trioxane) and tetramer (tetraoxane), ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane and 1,4 -Representative examples include polyacetal copolymers obtained by copolymerizing glycols such as butanediol formal, cyclic ethers such as cyclic formal of diglycol, and cyclic formal.

  Moreover, the polyacetal copolymer which has a branch obtained by copolymerizing monofunctional glycidyl ether, and the polyacetal copolymer which has a crosslinked structure obtained by copolymerizing polyfunctional glycidyl ether can also be used. Furthermore, a polyacetal homopolymer having a block component obtained by polymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, for example, polyalkylene glycol, A compound having a functional group such as a hydroxyl group at both ends or one end, for example, a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) or tetramer (tetraoxane) in the presence of hydrogenated polybutadiene glycol; A polyacetal copolymer having a block component obtained by copolymerizing cyclic ether or cyclic formal can also be used.

As described above, in the present invention, both a polyacetal homopolymer and a copolymer can be used. Preference is given to polyacetal copolymers.
A comonomer such as 1,3-dioxolane is generally used in an amount of 0.1 to 60 mol%, preferably 0.1 to 20 mol%, more preferably 0.13 to 10 mol%, relative to 1 mol of trioxane.
The melting point of the polyacetal copolymer particularly suitable in the present invention is 162 ° C to 173 ° C, preferably 167 ° C to 173 ° C, more preferably 167 ° C to 171 ° C. A polyacetal copolymer having a melting point of 167 ° C. to 171 ° C. can be obtained by using a comonomer of about 1.3 to 3.5 mol% with respect to trioxane.

  As the polymerization catalyst in the polymerization of the polyacetal copolymer, cationically active catalysts such as Lewis acids, proton acids and esters or anhydrides thereof are preferable. Examples of the Lewis acid include boric acid, tin, titanium, phosphorus, arsenic and antimony halides. Specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, pentachloride. Examples thereof include phosphorus, antimony pentafluoride, and complex compounds or salts thereof. Specific examples of the protonic acid, its ester or anhydride include perchloric acid, trifluoromethanesulfonic acid, perchloric acid-tertiary butyl ester, acetyl perchlorate, trimethyloxonium hexafluorophosphate, and the like. Among these, boron trifluoride; boron trifluoride hydrate; and a coordination complex compound of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride are preferable. Specifically, boron trifluoride diethyl ether is used. Boron trifluoride di-n-butyl ether can be mentioned as a preferred example.

The polymerization method may be a conventionally known method, for example, US-A-3027352, US-A-3803094, DE-C-1161421, DE-C-1495228, DE-C-1720358, DE-C-3018898 and JP-A No. 3018898. 58-98322 and JP-A-7-70267 can be employed.
As a polymerization method of the polyacetal copolymer, it is generally carried out by bulk polymerization, and both batch type and continuous type are possible. As a polymerization apparatus to be used, a self-cleaning type extrusion kneader such as a kneader, a twin-screw continuous extrusion kneader, or a twin-screw paddle type continuous mixer is used, and a molten monomer is supplied to the polymerization machine. A solid agglomerated polyacetal copolymer is obtained as the polymerization proceeds.

Since the polyacetal copolymer obtained by the above polymerization has a thermally unstable terminal portion [— (OCH ₂ ) _n —OH group], it cannot be put into practical use as it is. Therefore, it is necessary to carry out decomposition / removal processing of the unstable terminal portion, but it is preferable to perform the following specific decomposition / removal processing of the unstable terminal portion. The decomposing / removing treatment of the specific unstable terminal is a polyacetal copolymer at a temperature not lower than the melting point of the polyacetal copolymer and not higher than 260 ° C. in the presence of at least one quaternary ammonium compound represented by the following general formula (1). Is heat-treated in a melted state.

^{[R 1 R 2 R 3 R} 4 N +] n X -n formula (1)

(In the formula, R ¹ , R ² , R ³ , and R ⁴ each independently represent an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; An aralkyl group having 30 unsubstituted alkyl groups or substituted alkyl groups substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms having at least one carbon atom having 1 to 30 carbon atoms Represents an unsubstituted alkyl group or an alkylaryl group substituted with a substituted alkyl group, wherein the unsubstituted alkyl group or substituted alkyl group is linear, branched, or cyclic. An aldehyde group, a carboxyl group, an amino group, or an amide group, and the above-mentioned unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group have a hydrogen atom as a halogen atom. N represents an integer of 1 to 3. X is a hydroxyl group, a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than hydrogen halide, an oxo acid, an inorganic thioacid, or a carbon number of 1. Represents an acid residue of ˜20 organic thioacids.)

The quaternary ammonium compound is not particularly limited as long as it is represented by the general formula (1), but R ¹ , R ² , R ³ , and R ⁴ in the general formula (1) are each independently , An alkyl group having 1 to 5 carbon atoms or a hydroxyalkyl group having 2 to 4 carbon atoms, and among them, at least one of R ¹ , R ² , R ³ , and R ⁴ is a hydroxyethyl group. Some are particularly preferred. Specifically, tetramethylammonium, tetoethylammonium, tetrapropylammonium, tetra-n-butylammonium, cetyltrimethylammonium, tetradecyltrimethylammonium, 1,6-hexamethylenebis (trimethylammonium), decamethylene-bis- ( Trimethylammonium), trimethyl-3-chloro-2-hydroxypropylammonium, trimethyl (2-hydroxyethyl) ammonium, triethyl (2-hydroxyethyl) ammonium, tripropyl (2-hydroxyethyl) ammonium, tri-n-butyl ( 2-hydroxyethyl) ammonium, trimethylbenzylammonium, triethylbenzylammonium, tripropylbenzylammonium, tri-n-butylbenzene Zirammonium, trimethylphenylammonium, triethylphenylammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, okdadecyltri (2-hydroxyethyl) ammonium, tetrakis (hydroxyethyl) ammonium, etc. Hydroxides of hydrochloric acid, odorous acid, hydrofluoric acid, etc .; sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodic acid, silicic acid, perchloric acid, chlorous acid, hypochlorous acid Oxo acid salts such as chlorosulfuric acid, amidosulfuric acid, disulfuric acid, tripolyphosphoric acid; thioic acid salts such as thiosulfuric acid; formic acid, acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, caproic acid, caprylic acid, capric acid Carboxylic acid salts such as benzoic acid and oxalic acid. It is.

Among them, hydroxide (OH ⁻ ), sulfuric acid (HSO ₄ ⁻ , SO ₄ ²⁻ ), carbonic acid (HCO ₃ ⁻ , CO ₃ ²⁻ ), boric acid (B (OH) ₄ ⁻ ), and carboxylic acid salts are included. preferable. Of the carboxylic acids, formic acid, acetic acid, and propionic acid are particularly preferred. These quaternary ammonium compounds may be used alone or in combination of two or more. Further, in addition to the quaternary ammonium compound, there may be used any known amines such as ammonia and triethylamine which are known decomposition accelerators for unstable terminals.
The amount of the quaternary ammonium compound used is 0.05 to 50 mass in terms of the amount of nitrogen derived from the quaternary ammonium compound represented by the following formula (2) with respect to the total mass of the polyacetal copolymer and the quaternary ammonium compound. ppm, preferably 1 to 30 ppm by mass.

                          P × 14 / Q Formula (2)

(In the formula, P represents the concentration (mass ppm) of the quaternary ammonium compound relative to the polyacetal copolymer, 14 represents the atomic weight of nitrogen, and Q represents the molecular weight of the quaternary ammonium compound.)

If the amount of the quaternary ammonium compound added is less than 0.05 ppm by mass, the rate of decomposition and removal of the unstable end decreases, and if it exceeds 50 ppm by mass, the color tone of the polyacetal copolymer after the decomposition and removal of the unstable end is degraded. To do.
The decomposition and removal treatment of the unstable terminal portion of the polyacetal resin used in the present invention is achieved by heat-treating the polyacetal copolymer in a molten state at a temperature of not lower than the melting point and not higher than 260 ° C. Although there is no restriction | limiting in particular in the apparatus to be used, It is suitable to heat-process using an extruder, a kneader, etc. In addition, formaldehyde generated by decomposition is removed under reduced pressure. There are no particular restrictions on the method of adding the quaternary ammonium compound, and there are a method of adding it as an aqueous solution in the step of deactivating the polymerization catalyst, a method of spraying the polyacetal copolymer powder produced by the polymerization, and the like. Any addition method may be used as long as it is added in the step of heat-treating the polyacetal copolymer, as long as it is a variety that is injected into an extruder or blends fillers and pigments using an extruder or the like. The compound may be attached to the resin pellet, and the unstable terminal removal operation may be performed in the subsequent blending step.

The unstable terminal removal operation can be performed after the polymerization catalyst in the polyacetal copolymer obtained by polymerization is deactivated, or can be performed without deactivating the polymerization catalyst. A typical example of the deactivation operation of the polymerization catalyst is a method of neutralizing and deactivating the polymerization catalyst in a basic aqueous solution such as amines. It is also effective to perform this unstable terminal removal operation after heating in an inert gas atmosphere at a temperature below the melting point without deactivating the polymerization catalyst to reduce the volatilization of the polymerization catalyst. .
By the above-mentioned specific unstable terminal decomposition and removal treatment, it is possible to obtain a polyacetal copolymer with very few unstable terminals and excellent in thermal stability.
The MFR of the polyacetal resin (A) in the lamp molded body of the hard disk used in the present invention is 1-110 g / 10 min, which is the range in which the lamp molded body can be molded, but in order to improve the dimensional accuracy after washing, it is 6-80 g / 10 min. Preferably there is. More preferably, it is 20-40 g / 10min.

Next, talc (B) used in the present invention will be described.
The chemical name of talc used in the present invention (B) is a hydrated magnesium silicate, typically SiO ₂ about 60%, MgO 30% and 4.8% crystal water as a main component. The true specific gravity is 2.7 to 2.8, the whiteness is 93% or more according to JIS K-8123, and the pH is 9.0 to 10 according to JIS K-5101. A range is preferred. The 45 μm sieve residue has a value measured according to JIS K-5101 of 0.2% or less, preferably 0.1% or less, more preferably 0.08% or less. The average particle size in the resin composition of talc (B) is 10 μm from the viewpoint of improvement in thermal stability after cleaning, dimensional accuracy after cleaning, and improvement in wear after cleaning. And less than 20 μm, preferably 11 to 19 μm, more preferably 12 to 18 μm.

In the present invention, the average particle diameter of talc in the resin composition can be measured by microscopy. Specifically, for example, a pellet of the polyacetal resin composition of the present invention is formed into a thin film with a press machine that can be heated to, for example, a melting point of polyacetal or higher, and a particle image is observed and photographed using a polarizing microscope. The average particle size can be determined by measuring the maximum particle size and the number of at least 100 talcs selected in the above.
For the talc (B) used in the present invention, a known surface treating agent can be used in order to improve the affinity with the resin. Examples of the surface treatment agent include silane coupling agents such as amino silane and epoxy silane, titanate coupling agents, fatty acids (saturated fatty acids and unsaturated fatty acids), alicyclic carboxylic acids, resin acids and metal soaps. Can do. The addition amount of the surface treatment agent in talc (B) is preferably 3% by mass or less, more preferably 2% by mass or less, and most preferably no surface treatment is performed.

The content of talc (B) in the lamp molded body of the hard disk comprising the polyacetal resin composition of the present invention is 0.001 to 0.03 parts by mass with respect to 100 parts by mass of the polyacetal resin (A), and after washing. From the viewpoint of thermal stability, dimensional accuracy after cleaning, and improvement of the amount of wear after cleaning, it is necessary to be 0.001 part by mass or more and 0.03 part by mass or less. Preferably it is 0.002-0.03 mass part, More preferably, it is 0.005-0.02 mass part, Most preferably, it is 0.005-0.015 mass part.
In order to quantify the talc content in the lamp molded body of the hard disk comprising the polyacetal resin composition of the present invention, for example, a method of hydrolyzing the lamp molded body of the hard disk with hydrochloric acid or the like to quantify talc, or high-frequency inductive coupling There is a method of quantifying metal components (Si, Mg) caused by talc by plasma (ICP) emission analysis.

The MFR of the polyacetal resin composition used in the present invention is 1-110 g / 10 min in the range in which the lamp molded body can be molded, but is preferably 6-80 g / 10 min in order to improve the dimensional accuracy after washing. More preferably, it is 20-40 g / 10min.
The suitable melting point of the polyacetal resin composition is 162 ° C. to 173 ° C., preferably 167 ° C. to 173 ° C., more preferably 167 ° C. to 171 ° C. from the viewpoints of dimensional accuracy after washing and improvement of the wear amount after washing. It is.

Next, the polymer lubricant (C) used in the present invention will be described.
In the present invention, as the polymer lubricant (C), it is possible to use a polymer obtained by polymerizing (c-1) a polyolefin resin and / or (c-2) an isocyanate compound and a polyalkylene oxide. This is preferable from the viewpoint of improving the amount of wear after cleaning, which is characteristic of a lamp molded body.
(C-1) The polyolefin resin is a homopolymer, copolymer, or modified product of the olefin compound represented by the general formula (3).

[Wherein R5 is a hydrogen atom or a methyl group, R6 is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a carboxyl group, an alkylcarboxyl group containing 2 to 5 carbon atoms, or 2 to 5 carbon atoms. An acyloxy group having an atom or a vinyl group is meant. ]

  (C-1) Polyolefin resin specifically includes polyethylene (high density polyethylene, medium density polyethylene, high pressure method low density polyethylene, linear low density polyethylene, ultra low density polyethylene) as a homopolymer and a copolymer. , Polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, polypropylene-butene copolymer, polybutene, polybutadiene hydrogenated product, ethylene-acrylate copolymer, ethylene- Examples thereof include a methacrylic acid ester copolymer, an ethylene-acrylic acid copolymer, and an ethylene-vinyl acetate copolymer. As a modified body, a graft copolymer obtained by grafting one or more of other vinyl compounds; α, β-unsaturated carboxylic acid (acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid Etc.) or an acid anhydride thereof (modified with a peroxide if necessary); a copolymer obtained by copolymerizing an olefinic compound and an acid anhydride.

Among these, polyethylene (high pressure method low density polyethylene, linear low density polyethylene, ultra low density polyethylene), ethylene-propylene copolymer, ethylene-butene copolymer, and ethylene-octene copolymer are preferable.
These (c-1) polyolefin resins are not particularly limited, but the melt flow rate (ASTM-D1238-57T) is preferably in the range of 0.5 to 150 g / 10 minutes, more preferably 3 to 120 g / The range is 10 minutes, most preferably 5 to 100 g / 10 minutes. When the melt flow rate is 0.5 g / 10 min or more, the sliding performance is good, and when it is 150 g / 10 min or less, the level of peeling is good.

  (C-2) A polymer obtained by polymerizing an isocyanate compound and a polyalkylene oxide is obtained by melt-kneading the isocyanate compound and the polyalkylene oxide using a reactor such as an extruder, a kneader, or a Banbury mixer. can get. In addition, you may add a low molecular diol compound in the case of melt-kneading an isocyanate compound and a polyalkylene oxide as needed. It is also possible to use a solvent such as dimethylformamide, methyl ethyl ketone, and toluene, an organometallic compound such as dibutyltin laurate and dioctyltin laurate, and a urethanization catalyst such as amines such as triethylamine and diazabicycloundecene. Details are described in JP-A-7-316421 and JP-A-8-92476.

  Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenylmethane disocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, cyclohexylene diisocyanate, diisocyanate methylhexane, hexamethylene diisocyanate, triphenylmethane triisocyanate, tris ( At least one selected from the group consisting of (isocyanatophenyl) thiophosphate and a cyclic trimer of hexamethylene didiisocyanate, among which tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenylmethane disocyanate Are preferred, and tolylene Isocyanate, diphenylmethane Socia sulfonates are more preferred.

Examples of the polyalkylene oxide include polyethylene glycol, ethylene oxide propylene oxide copolymer, polypropylene glycol, poly-1,4-butanediol, and polytetraethylene having a degree of polymerization of 4 to 1000, preferably 10 to 500. There may be mentioned at least one selected from methylene glycol.
Examples of the low molecular diol compound used as necessary include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, polyalkylene oxide having a polymerization degree of 4 or less (copolymer of polyethylene glycol and ethylene oxide propylene oxide). Polymer, polypropylene glycol, poly 1,4-butanediol, polytetramethylene glycol, etc.), among which ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexane Diols are preferred.

The weight average molecular weight of a polymer obtained by polymerizing an isocyanate compound and a polyalkylene oxide (and a low molecular diol compound as required) is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography using chloroform as a solvent. The range of 10,000 to 500,000 is preferable, and the range of 20,000 to 300,000 is more preferable. When the weight average molecular weight is 10,000 or more, the peeling of the molded article is good, and when the weight average molecular weight is 500,000 or less, the slidability and the surface appearance are good.
The blending ratio of these (C) polymer lubricants is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 7 parts by mass, and more preferably 100 parts by mass of (A) polyacetal resin. Preferably it is 0.5-5 mass parts. When the addition amount is 0.1 parts by mass or more, sufficient slidability can be imparted. When the addition amount is within 10 parts by mass, the wear amount is small and the peeling is good.

  The polyacetal resin composition used in the present invention can obtain a lamp molded body of a hard disk made of a polyacetal resin composition excellent in thermal stability by blending an appropriate additive depending on the application. Preferred examples include (D) an antioxidant, a polymer or compound containing formaldehyde-reactive nitrogen, a formic acid scavenger, a weathering (light) stabilizer, a mold release agent, and a lubricant with respect to 100 parts by mass of the polyacetal resin. A lamp molded body of a hard disk made of a polyacetal resin composition containing 0.01 to 10 parts by mass of at least one selected from an agent can be mentioned.

  As the antioxidant, a hindered phenol antioxidant is preferable. Specifically, for example, n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) -propionate, n-octadecyl-3- (3′-methyl-5′-t -Butyl-4'-hydroxyphenyl) -propionate, n-tetradecyl-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) -propionate, 1,6-hexanediol-bis- [ 3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate], 1,4-butanediol-bis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) -Propionate], triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate], pentaerythritol tetrakis Methylene-3- (3 ', 5'-di -t- butyl-4'-hydroxyphenyl) propionate] methane, and the like. Preferably, triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] and pentaerythritol tetrakis [methylene-3- (3 ′, 5′-di-t -Butyl-4'-hydroxyphenyl) propionate] methane. These antioxidants may be used alone or in combination of two or more.

  Examples of polymers or compounds containing formaldehyde-reactive nitrogen include nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 12 and other polyamide resins, and polymers thereof Examples thereof include nylon 6 / 6-6 / 6-10 and nylon 6 / 6-12. Other examples include acrylamide and its derivatives, and copolymers of acrylamide and its derivatives and other vinyl monomers, such as those obtained by polymerizing acrylamide and its derivatives and other vinyl monomers in the presence of a metal alcoholate. And poly-β-alanine copolymer. Other examples include amide compounds, amino-substituted triazine compounds, adducts of amino-substituted triazine compounds and formaldehyde, condensates of amino-substituted triazine compounds and formaldehyde, urea, urea derivatives, hydrazine derivatives, imidazole compounds, and imide compounds.

  Specific examples of the amide compound include polycarboxylic acid amides such as isophthalic acid diamide and anthranilamides. Specific examples of the amino-substituted triazine compound include 2,4-diamino-sym-triazine, 2,4,6-triamino-sym-triazine, N-butylmelamine, N-phenylmelamine, N, N-diphenylmelamine, N , N-diallylmelamine, benzoguanamine (2,4-diamino-6-phenyl-sym-triazine), acetoguanamine (2,4-diamino-6-methyl-sym-triazine), 2,4-diamino-6-butyl -Sym-triazine and the like. Specific examples of the adduct of an amino-substituted triazine compound and formaldehyde include N-methylol melamine, N, N′-dimethylol melamine, and N, N ′, N ″ -trimethylol melamine.

  Specific examples of condensates of amino-substituted triazine compounds and formaldehyde include melamine / formaldehyde condensates. Examples of the urea derivative include N-substituted urea, urea condensate, ethylene urea, hydantoin compound, and ureido compound. Specific examples of the N-substituted urea include methylurea, alkylenebisurea, and aryl substituted urea substituted with a substituent such as an alkyl group. Specific examples of the urea condensate include urea and formaldehyde condensates. Specific examples of the hydantoin compound include hydantoin, 5,5-dimethylhydantoin, 5,5-diphenylhydantoin and the like.

Specific examples of the ureido compound include allantoin. Examples of hydrazine derivatives include hydrazide compounds. Specific examples of the hydrazide compound include dicarboxylic acid dihydrazide. More specifically, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, superic acid dihydrazide, and azelaic acid dihydrazide. And sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, phthalic acid dihydrazide, 2,6-naphthalenedicarbodihydrazide and the like. Specific examples of the imide compound include succinimide, glutarimide, and phthalimide.
These polymers or compounds containing formaldehyde-reactive nitrogen atoms may be used alone or in combination of two or more.

Examples of the formic acid scavenger include condensates of the above amino-substituted triazine compounds and amino-substituted triazine compounds with formaldehyde, such as melamine / formaldehyde condensates. Other formic acid scavengers include alkali metal or alkaline earth metal hydroxides, inorganic acid salts, carboxylate salts or alkoxides. For example, hydroxides such as sodium, potassium, magnesium, calcium or barium, carbonates, phosphates, silicates, borates, carboxylates, and layered double hydroxides of the above metals can be used. .
The carboxylic acid of the carboxylate is preferably a saturated or unsaturated aliphatic carboxylic acid having 10 to 36 carbon atoms, and these carboxylic acids may be substituted with a hydroxyl group. Specific examples of saturated or unsaturated aliphatic carboxylates include calcium dimyristate, calcium dipalmitate, calcium distearate, (myristic acid-palmitic acid) calcium, (myristic acid-stearic acid) calcium, ( (Palmitic acid-stearic acid) calcium is mentioned, and among them, calcium dipalmitate and calcium distearate are preferable.
Examples of the layered double hydroxide include hydrotalcites represented by the following general formula.

[(M ²⁺ ) _1-X (M ³⁺ ) _X (OH) ₂ ] _X ⁺ [(A ⁿ⁻ ) _{x / n} · mH ₂ O] _X ⁻

[ ^Wherein , M ²⁺ represents a divalent metal, M ³⁺ represents a trivalent metal, An ⁻ represents an n-valent anion (n is an integer of 1 or more), and X is in a range of 0 <X ≦ 0.33, m is a positive number. ]

In the general formula (1), examples of M ²⁺ include Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ^2+, etc. Examples of M ³⁺ include Al ³⁺ , Fe ³⁺ , Cr ³⁺ , ^Co 3+, ^{an in 3+, etc.,} as an example of ^{a n- is, OH -, F -, Cl} -, Br -, NO 3 -, CO 3 2-, SO 4 2-, Fe (CN) 6 3-, CH ₃ COO ⁻ , oxalate ion, salicylate ion and the like can be mentioned. Particularly preferred examples include CO ₃ ²⁻ and OH ⁻ . As a specific example, natural hydrotalcite represented by Mg _0.75 Al _0.25 (OH) ₂ (CO ₃ ) _0.125 · 0.5H ₂ O, Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ · 3.5 H _{2 O,} may be mentioned synthetic hydrotalcite represented by _{Mg 4.3 Al 2 (OH) 12.6} CO 3 or the like.
These formic acid scavengers may be used alone or in combination of two or more.

The weather resistance (light) stabilizer referred to in the present invention is preferably one or more selected from benzotriazole-based, oxalic anilide-based UV absorbers, and hindered amine-based light stabilizers.
Examples of benzotriazole ultraviolet absorbers include 2- (2′-hydroxy-5′-methyl-phenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butyl-phenyl). ) Benzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis -(Α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole and the like. Examples of oxalic acid alinide ultraviolet absorbers include 2-ethoxy-2′-ethyloxalic acid bisanilide, 2-ethoxy-5-tert-butyl-2′-ethyloxalic acid bisanilide, and 2-ethoxy. -3'-dodecyl oxalic acid bisanilide and the like. Preferably 2- [2′-hydroxy-3 ′, 5′-bis- (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di- t-butyl-phenyl) benzotriazole. These benzotriazole-based UV absorbers may be used alone or in combination of two or more.

Examples of hindered amine light stabilizers include N, N ′, N ″, N ′ ″-tetrakis- (4,6-bis- (butyl- (N-methyl-2,2,6,6-tetramethyl). Piperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10-diamine, dibutylamine, 1,3,5-triazine, N, N′-bis (2,2,2) A polycondensate of 6,6, tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6, tetramethyl-4-piperidyl) butylamine, poly [{6- (1 , 1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6, tetramethyl-4-piperidyl) imino} hexamethylene {( 2,2,6,6-tetramethyl-4-piperidyl) Mino}], a condensate of dimethyl succinate and 4-hydroxy-2,2,6,6, tetramethyl-1-piperidineethanol, bis (2,2,6,6-tetramethyl-1 (octyl) decanoate Oxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and octane reaction product, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis ( 1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate, bis (2,2,6,6-tetramethyl) -4-piperidyl) -sebacate, 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β ′, β ′,-tetra Examples thereof include condensates with methyl-3,9- [2,4,8,10-tetraoxaspiro (5,5) undecane] diethanol, etc. Preferably, bis (2,2,6,6-tetramethyl- 4-piperidyl) -sebacate, bis- (N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 1,2,3,4-butanetetracarboxylic acid and 1,2,2, Between 6,6-pentamethyl-4-piperidinol and β, β, β ′, β ′,-tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (5,5) undecane] diethanol These hindered amine light stabilizers may be used alone or in combination of two or more.
As the release agent and lubricant, alcohol, fatty acid and fatty acid ester thereof, polyoxyalkylene glycol, olefin compound having an average polymerization degree of 10 to 500, and silicone are preferably used.

In the present invention, a suitable known additive can be further blended as necessary within a range not impairing the object of the present invention. Specific examples include inorganic fillers, crystal nucleating agents, conductive materials, thermoplastic resins, thermoplastic elastomers, and pigments.
As the inorganic filler, fibrous, powdery, plate-like and hollow fillers are used. Fiber fillers include glass fiber, carbon fiber, silicone fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and stainless steel, aluminum, titanium, copper, brass. And inorganic fibers such as metal fibers. In addition, whiskers such as potassium titanate whisker and zinc oxide whisker having a short fiber length are included. A high melting point organic fibrous material such as an aromatic polyamide resin, a fluororesin, or an acrylic resin can also be used.

Examples of powder particulate fillers include carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, wollastonite, iron oxide, titanium oxide, and alumina. Examples thereof include metal oxides such as these, metal sulfates such as calcium sulfate and barium sulfate, carbonates such as magnesium carbonate and dolomite, silicon carbide, silicon nitride, boron nitride, and various metal powders.
Examples of the plate-like filler include mica, glass flakes, and various metal foils. Examples of the hollow filler include glass balloons, silica balloons, shirasu balloons, and metal balloons. These fillers can be used alone or in combination of two or more. These fillers can be used either surface-treated or unsurface-treated, but in some cases it is preferable to use a surface-treated one in terms of smoothness of the molding surface and mechanical properties. is there. A conventionally well-known thing can be used as a surface treating agent. For example, various coupling treatment agents such as silane, titanate, aluminum, and zirconium can be used. Specifically, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyl trisstearoyl titanate, diisopropoxyammonium ethyl acetate, n-butyl zirconate, etc. Can be mentioned.
Examples of the conductive agent include conductive carbon black, graphite, carbon nanotube, metal powder, or fiber.

Examples of the thermoplastic resin include polyolefin resin, acrylic resin, styrene resin, polycarbonate resin, and uncured epoxy resin. These modified products are also included. Examples of the thermoplastic elastomer include polyurethane elastomers, polyester elastomers, polystyrene elastomers, and polyamide elastomers.
As the pigment, known pigments that are usually used for polyacetal resins can be used as long as they do not interfere with the purpose of the present application. Inorganic pigments and organic pigments, metallic pigments, fluorescent pigments and the like can be mentioned. Inorganic pigments are those commonly used for resin coloring, such as zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, combustion pigments, carbonates, phosphates, acetic acid. Salt, carbon black, acetylene black, lamp black, chlorinated carbon lead, basic lead sulfate, basic lead silicate, metal sulfide, etc. Organic pigments are condensed azo, inon, furothocyanin, monoazo, diazo, polyazo, azomethine, methine, indanthrone, pyranthrone, flavanthrone, benzenethrone, perinone, iso There are pigments such as indoline, isoindolinone, pyrrole pyrrole, quinophthalone, anthraquinone, heterocyclic, pennon, quinacridone, thioindico, berylene, dioxazine, and phthalocyanine.

In the present invention, one or two or more of these pigments can be used in combination. Usually, two or more pigments are used in combination in order to obtain the required color tone.
The total addition amount of the pigment is preferably 0.005 to 5.0 parts by mass with respect to 100 parts by mass of the polyacetal resin. From the viewpoint of the thermal stability of the polyacetal resin, it is preferably 5.0 parts by mass or less.
The method for producing the polyacetal resin composition used for the lamp molded body of the present invention can be produced using a general extruder. Examples of the extruder include a single-screw or multi-screw kneading extruder, and a twin-screw extruder equipped with a pressure reducing device is particularly preferable. Examples of the method for producing the polyacetal resin composition include a method of feeding the polyacetal resin (A) and talc (B) from the top of the extruder and a method of adding talc (B) from the side feed, and talc (B). A side feed method is preferred.

Moreover, as a manufacturing method at the time of adding (D) component, specifically,
<1> Polyacetal resins (A) and (D) are mixed with a Henschel mixer, tumbler, V-shaped blender, etc., then fed from the top of the extruder, and talc (B) is fed from a side feed with a quantitative feeder or the like. A method of adding and melt-kneading,
<2> A method in which the polyacetal resin (A) is fed from the top of the extruder, and the talc (B) and (D) components are added from the side feed with a quantitative feeder or the like and melt-kneaded.
<3> After mixing the polyacetal resins (A) and (D) with a Henschel mixer, tumbler, V-shaped blender, etc., feed from the top of the extruder, and further talc (B) into a master batch with polyacetal resin , A method of melt kneading by adding from a side feed with a quantitative feeder,

<4> Feeding the polyacetal resin (A) from the top of the extruder, further adding a talc (B), (D) component into a master batch with a polyacetal resin, etc., adding from a side feed with a quantitative feeder, etc., and melt-kneading,
<5> Polyacetal resin (A), talc (B), (D) component are mixed with a Henschel mixer, tumbler, V-shaped blender, etc., and then melt-kneaded using an extruder,
<6> Part of polyacetal resin (A) and component (D) are fed from the top of the extruder, and the remainder of polyacetal resin (A) and talc (B) are added from the side feed with a quantitative feeder or the like and once melted. A kneading method.
Of these, the polyacetal resin melts talc (B) from the viewpoints of thermal stability after cleaning of the lamp molded body of the hard disk made of the polyacetal resin composition obtained, dimensional accuracy after cleaning, and improvement of wear after cleaning. The method <1>, <2>, <3>, <4>, <6> added to the prepared state is preferred, and the production method <6> is particularly preferred.
Also, a high-density master batch consisting of (A), (B), and (D) is prepared in advance and diluted with a polyacetal resin during injection molding to form a lamp molded body of a hard disk made of the polyacetal resin composition of the present invention. You can also get
When component (C) is added, it may be fed either top or side in the methods <1> to <6>.

<7> Polyacetal resin (A) is fed from the top of the extruder, talc (B) and component (D) are added from the side feed with a quantitative feeder, etc., once melt-kneaded, and the resulting pellets and polymer lubrication A method of further melt-kneading the agent (C) is also included.
There is no particular limitation on the method of molding the lamp molded body of the hard disk comprising the polyacetal resin composition of the present invention, and known molding methods such as extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, Molding methods such as decorative molding, molding of other materials, gas-assisted injection molding, firing injection molding, low pressure molding, ultra-thin injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, outsert molding) It can shape | mold by either.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention more concretely, this invention is not limited at all by these.
[Measuring method]
<Measuring method of average particle diameter>
Using a SH-75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., a lamp molded body of a hard disk was produced at a cylinder temperature of 200 ° C., an injection pressure of 60 MPa, an injection time of 15 seconds, a cooling time of 25 seconds, and a mold temperature of 120 ° C. Produced. A thin film was prepared with a press machine in which the lamp molded body was set at 200 ° C., and a particle image was observed and photographed at a magnification of 400 times using a polarizing microscope (Nikon ECLIPSE E600WPOL). The maximum particle diameter (maximum major axis) of talc was measured one by one, and the average value of the 100 maximum particle diameters was taken as the average particle diameter.

<Measurement method of talc content>
Using a SH-75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., a lamp molded body of a hard disk was produced at a cylinder temperature of 200 ° C., an injection pressure of 60 MPa, an injection time of 15 seconds, a cooling time of 25 seconds, and a mold temperature of 120 ° C. Produced. 200 batches of lamp molded bodies were mixed with 300 ml of 0.1N hydrochloric acid aqueous solution, and 10 batches were prepared in a state of being charged in a glass pressure-resistant bottle. After these were decomposed under pressure in a sterilizer at 130 ° C. for 6 to 10 hours, talc in the decomposition solution for 10 batches was filtered, and the filter residue was further washed and filtered with chloroform, etc. Additives other than were removed. The remaining talc was dried under reduced pressure and then weighed to determine the talc content in the lamp molded body.

<Measurement method of MFR>
Melt flow rate: Measured based on ASTM D-1238-57T. The conditions are a load of 2.16 kgf and a temperature of 190 ° C.
<Measuring method of melting point>
In the process of using a differential calorimeter (DSC-2C, manufactured by Perkin Elmer Co., Ltd.), once the sample was heated to 200 ° C. and melted, cooled to 100 ° C. and then heated again at a rate of 2.5 ° C./min. The temperature of the peak of the generated exothermic spectrum was taken as the melting point.

<Measurement method of formaldehyde gas generation rate after cleaning>
Using a SH-75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., a lamp molded body of a hard disk was produced at a cylinder temperature of 200 ° C., an injection pressure of 60 MPa, an injection time of 15 seconds, a cooling time of 25 seconds, and a mold temperature of 120 ° C. Produced. This lamp molded body was immersed in a chloroform / methanol mixed solution (70/30 volume ratio) heated to 50 ° C. for 4 hours, and then the surface was washed with the same solvent and dried for 2 hours with a hot air dryer at 60 ° C. Further, a drying treatment was performed at 140 ° C. for 1 hour in advance. The obtained lamp molded body was heated and melted at 240 ° C. in a nitrogen stream (50 NL / hr) to absorb formaldehyde gas generated from the lamp molded body in water, and then titrated by a sodium sulfite method. At that time, when the formaldehyde generation amount (ppm) from the start of heating to 10 minutes later is Y ₁₀ and the 90 minutes is Y ₉₀ ,
Generation rate for 10 to 90 minutes (Y ₉₀ -Y ₁₀ ) / 80 (ppm / min.)
Calculated as The formaldehyde generation rate was the average of the values measured at n = 5. A small value indicates excellent thermal stability after washing.

<Measurement of dimensional accuracy after cleaning>
Using a SH-75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., a lamp molded body of a hard disk was produced at a cylinder temperature of 200 ° C., an injection pressure of 60 MPa, an injection time of 15 seconds, a cooling time of 25 seconds, and a mold temperature of 120 ° C. Produced. Further, these lamp molded bodies were immersed in a chloroform / methanol mixed solution (70/30 volume ratio) heated to 50 ° C. for 4 hours, and then the surface was washed with the same solvent, and then heated with a hot air dryer at 60 ° C. for 2 hours. Drying was performed. About the obtained molded object, the space | interval of the dimension measurement position of the lamp | ramp shown in FIG. 2 was measured similarly. Differences from the design dimensions are shown in Table 1. The smaller this difference, the better the dimensional accuracy.

<Measurement of amount of wear after cleaning>
Using a SH-75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., a lamp molded body of a hard disk was produced at a cylinder temperature of 200 ° C., an injection pressure of 60 MPa, an injection time of 15 seconds, a cooling time of 25 seconds, and a mold temperature of 120 ° C. Produced. These molded bodies were immersed in a chloroform / methanol mixed solution (70/30 volume ratio) heated to 50 ° C. for 4 hours, then the surface was washed with the same solvent, and dried with a hot air dryer at 60 ° C. for 2 hours. Went. About the upper end surface of the obtained molded body, using a reciprocating friction and wear tester (AFT-15MS type manufactured by Toyo Seimitsu Co., Ltd.), load 19.6 N, linear velocity 30 mm / sec, reciprocation distance 6 mm, reciprocation number 5, After sliding for 000 times and at an environmental temperature of 23 ° C., the depth of wear of the lamp molded body was measured. As the counterpart material, a SUS304 test piece (sphere having a diameter of 5 mm) was used.

[raw materials]
<Polyacetal resin a-1>
A biaxial self-cleaning type polymerization machine (L / D = 8) with a jacket capable of passing a heat medium is adjusted to 80 ° C., 4 kg / hr of trioxane, 42.8 g / liter of 1,3-dioxolane as a comonomer h (1.3 mol% with respect to 1 mol of trioxane) and 2.35 × 10 ⁻³ mol of methylal as a chain transfer agent were continuously added to 1 mol of trioxane. Further, boron trifluoride di-n-butyl etherate was continuously added as a polymerization catalyst at 1.5 × 10 ⁻⁵ mol with respect to 1 mol of trioxane to carry out polymerization. The polyacetal copolymer discharged from the polymerization machine was put into a 0.1% aqueous solution of triethylamine to deactivate the polymerization catalyst. After the deactivated polyacetal copolymer was filtered with a centrifugal separator, choline hydroxide formate (triethyl-2-hydroxyethylammonium formate (b-1) as a quaternary ammonium compound was added to 100 parts by mass of the polyacetal copolymer. 1 part by weight of an aqueous solution containing) was added, mixed uniformly, and dried at 120 ° C. The addition amount of the hydroxycholine formate was adjusted by adjusting the concentration of the hydroxycholine formate in the aqueous solution containing the added choline formate, and was 20 mass ppm in terms of the amount of nitrogen. The dried polyacetal copolymer is supplied to a vented twin screw extruder, and 0.5 parts by mass of water is added to 100 parts by mass of the melted polyacetal copolymer in the extruder, and the extruder set temperature is 200 ° C. The unstable terminal portion was decomposed and removed in a residence time of 7 minutes in the extruder. The polyacetal copolymer whose unstable terminal portion was decomposed was devolatilized under a condition of a vent vacuum of 20 Torr, extruded as a strand from the extruder die, and pelletized. The polyacetal resin (a-1) thus obtained had a melting point of 169.5 ° C. and an MFR of 30 g / 10 min.

<Polyacetal resin a-2>
When polymerizing the polyacetal resin, the same operation as in the production of the polyacetal resin (a-1) except that the continuous addition amount of 1,3 dioxolane was 128.3 g / h (3.9 mol% with respect to 1 mol of trioxane). To obtain a polyacetal resin (a-2). The polyacetal resin (a-2) thus obtained had a melting point of 164.5 ° C. and an MFR of 30 g / 10 min.
<Polyacetal resin a-3>
4 kg / hr of trioxane, 42.8 g / h of 1,3-dioxolane as a comonomer (1.3 mol% with respect to 1 mol of trioxane), and 1.52 × 10 ⁻³ of methylal as a chain transfer agent with respect to 1 mol of trioxane. A polyacetal resin (a-3) was obtained in the same manner as in the production of the polyacetal resin (a-1) except that mol was continuously added. The polyacetal resin (a-3) thus obtained had a melting point of 169.1 ° C. and an MFR of 8 g / 10 min.

<Talc (b)>
b-1: MS manufactured by Nippon Talc Co., Ltd. (untreated surface)
b-2: (b-1) MS manufactured by Nippon Talc Co., Ltd. surface-treated with 1% aminopropyltriethoxysilane b-3: P-3 manufactured by Nihon Talc Co., Ltd. (untreated surface)
b-4: K-1 manufactured by Nippon Talc Co., Ltd. (untreated surface)
b-5: Nippon Talc Co., Ltd. MS-KY (untreated surface)
b-6: Boron nitride

[Examples 1 to 3]
To 100 parts by mass of the polyacetal resin (a-1), 0.3 parts by mass of triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant and Then, 0.15 parts by mass of calcium distearate as a formic acid scavenger and a Henschel mixer were mixed uniformly. This mixture was fed from the main feed port of a 30 mm vented twin-screw extruder with L / D = 30 set to 200 ° C., and the amount shown in Table 1 from the side feed port installed downstream of the main feed port. Talc (b-1) was fed and melt-kneaded at a screw rotation speed of 100 rpm to produce polyacetal resin composition pellets. The obtained polyacetal resin composition pellets were evaluated for the average particle diameter, talc content, melting point, MFR, formaldehyde gas generation rate after cleaning, dimensional accuracy after cleaning, and wear amount after cleaning by the above-described measurement methods. It was.

[Examples 4 to 6]
Polyacetal resin pellets were produced in the same manner as in Example 1 except that talc (b-2) shown in Table 1 was fed from the side feed port. The obtained polyacetal resin composition pellets were evaluated for the average particle diameter, talc content, melting point, MFR, formaldehyde gas generation rate after cleaning, dimensional accuracy after cleaning, and wear amount after cleaning by the above-described measurement methods. It was.

[Examples 7 to 9]
Except having used polyacetal resin (a-2), it operated similarly to Example 1 and manufactured the polyacetal resin composition pellet. The obtained polyacetal resin pellets were evaluated for the average particle size, talc content, melting point, MFR, formaldehyde gas generation rate after washing, dimensional accuracy after washing, and wear after washing by the above-described measurement methods.

[Examples 10 to 12]
Polyacetal composition resin pellets were produced in the same manner as in Example 7 except that talc (b-2) shown in Table 1 was fed from the side feed port. The obtained polyacetal resin pellets were evaluated for the average particle size, talc content, melting point, MFR, formaldehyde gas generation rate after washing, dimensional accuracy after washing, and wear after washing by the above-described measurement methods.

[Example 13]
To 100 parts by mass of the polyacetal resin (a-1), 0.3 parts by mass of triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant, As a formic acid scavenger, 0.15 parts by mass of calcium distearate and 0.01 parts by mass of talc (b-1) were uniformly mixed using a Henschel mixer. This mixture was fed from the main feed port of a 30 mm vented twin screw extruder of L / D = 30 set at 200 ° C., and melt kneaded at a screw rotation speed of 100 rpm to produce polyacetal resin composition pellets. The obtained polyacetal resin pellets were evaluated for the average particle size, talc content, melting point, MFR, formaldehyde gas generation rate after washing, dimensional accuracy after washing, and wear after washing by the above-described measurement methods.

[Example 14]
To 95 parts by mass of the polyacetal resin (a-1), 0.3 parts by mass of triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant and Then, 0.15 parts by mass of calcium distearate as a formic acid scavenger and a Henschel mixer were mixed uniformly. This mixture was fed from the main feed port of a 30 mm vented twin screw extruder of L / D = 30 set at 200 ° C., and the polyacetal resin (a-1) from the side feed port installed downstream of the main feed port 5 parts by mass and 0.01 parts by mass of talc (b-1) were fed and melt-kneaded at a screw rotation speed of 100 rpm to produce polyacetal resin composition pellets. The obtained polyacetal resin pellets were evaluated for the average particle size, talc content, melting point, MFR, formaldehyde gas generation rate after washing, dimensional accuracy after washing, and wear after washing by the above-described measurement methods.

[Example 15]
Except having used polyacetal resin (a-3), it operated similarly to Example 1 and manufactured the polyacetal resin composition pellet. The obtained polyacetal resin composition pellets were evaluated for the average particle diameter, talc content, melting point, MFR, formaldehyde gas generation rate after cleaning, dimensional accuracy after cleaning, and wear amount after cleaning by the above-described measurement methods. It was.

[Example 16]
To 100 parts by mass of the polyacetal resin (a-1), 0.3 parts by mass of triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant and Then, 0.15 parts by mass of calcium distearate as a formic acid scavenger and a Henschel mixer were mixed uniformly. This mixture was fed from the main feed port of a 30 mm vented twin-screw extruder with L / D = 30 set to 200 ° C., and the amount shown in Table 1 from the side feed port installed downstream of the main feed port. Talc (b-1) and (C) polymeric lubricant “(c-1) as polyolefin resin, ethylene-butene copolymer (butene content 10 mol%, melt flow rate 70 g / 10 min (ASTM D-1238- 57T)), and (c-2) as a polymer obtained by polymerizing an isocyanate compound and polyalkylene oxide, 3 parts by mass of 89 parts by mass of polyethylene glycol having an average molecular weight of 2,000 and 11 parts by mass of diphenylmethane diisocyanate were fed. , Polyacetal resin composition pellets by melt kneading at a screw speed of 100 rpm Manufactured. In addition, the polystyrene conversion weight average molecular weight of the obtained resin measured using a gel permeation chromatograph (chloroform solvent) of (C) a polymer lubricant was 200,000 (measuring device pump HITACHI 510).
The obtained polyacetal resin composition pellets were evaluated for the average particle diameter, talc content, melting point, MFR, formaldehyde gas generation rate after cleaning, dimensional accuracy after cleaning, and wear amount after cleaning by the above-described measurement methods. It was.

[Comparative Example 1]
To 100 parts by mass of the polyacetal resin (a-1), 0.3 parts by mass of triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant and Then, 0.15 parts by mass of calcium distearate as a formic acid scavenger and a Henschel mixer were mixed uniformly. This mixture was fed from the main feed port of a 30 mm vented twin screw extruder of L / D = 30 set at 200 ° C., and melt kneaded at a screw rotation speed of 100 rpm to produce polyacetal resin composition pellets. The obtained polyacetal resin composition pellets were evaluated for the average particle diameter, talc content, melting point, MFR, formaldehyde gas generation rate after cleaning, dimensional accuracy after cleaning, and wear amount after cleaning by the above-described measurement methods. It was.

[Comparative Examples 2-6]
To 100 parts by mass of the polyacetal resin (a-1), 0.3 parts by mass of triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant and Then, 0.15 parts by mass of calcium distearate as a formic acid scavenger and a Henschel mixer were mixed uniformly. This mixture was fed from the main feed port of a 30 mm vented twin-screw extruder with L / D = 30 set to 200 ° C., and the amount shown in Table 1 from the side feed port installed downstream of the main feed port. Various talcs were fed and melt-kneaded at a screw rotation speed of 100 rpm to produce polyacetal resin composition pellets. The obtained polyacetal resin composition pellets were evaluated for the average particle diameter, talc content, melting point, MFR, formaldehyde gas generation rate after cleaning, dimensional accuracy after cleaning, and wear amount after cleaning by the above-described measurement methods. It was.

[Comparative Example 7]
Except having used polyacetal resin (a-2), it operated similarly to the comparative example 1 and manufactured the polyacetal resin composition pellet. The obtained polyacetal resin composition pellets were evaluated for the average particle diameter, talc content, melting point, MFR, formaldehyde gas generation rate after cleaning, dimensional accuracy after cleaning, and wear amount after cleaning by the above-described measurement methods. It was.

[Comparative Example 8]
Except having used polyacetal resin (a-2), it operated like the comparative example 2 and manufactured the polyacetal resin composition pellet. The obtained polyacetal resin composition pellets were evaluated for the average particle diameter, talc content, melting point, MFR, formaldehyde gas generation rate after cleaning, dimensional accuracy after cleaning, and wear amount after cleaning by the above-described measurement methods. It was.

[Comparative Example 9]
A polyacetal resin composition pellet was produced in the same manner as in Comparative Example 2 except that 0.01 parts by mass of boron nitride (b-6) was fed from the side feed port. Evaluation of average particle diameter, boron nitride content, melting point, MFR, formaldehyde gas generation rate after cleaning, dimensional accuracy after cleaning, and amount of wear after cleaning of the obtained polyacetal resin composition pellets by the measurement methods described above Went.

  As described above, the present invention has a balance of mechanical properties possessed by polyacetal resin, has excellent thermal stability, thermal stability after washing, dimensional stability after washing, and wear after washing, which are characteristic of lamp molded bodies Since it is excellent in quantity, it can be suitably used in the field of hard disk lamp moldings.

Hard disk internal mechanism diagram Figure and dimension measurement position from the horizontal direction of hard disk lamp molded body

Claims (7)

  The polyacetal resin (A) is composed of a polyacetal resin composition containing 0.001 to 0.03 parts by mass of talc (B) having an average particle diameter of more than 10 μm and less than 20 μm with respect to 100 parts by mass of the polyacetal resin (A). Hard disk lamp molded body.   The polyacetal resin composition comprises (C) a polymer lubricant obtained by polymerizing (c-1) a polyolefin resin and / or (c-2) an isocyanate compound and a polyalkylene oxide. 2. The lamp molded body of a hard disk according to claim 1, comprising 0.1 to 10 parts by mass with respect to 100 parts by mass.   The lamp molded body of the hard disk according to claim 1 or 2, wherein the talc (B) is not surface-treated.   The hard disk according to any one of claims 1 to 3, wherein the polyacetal resin composition is manufactured by adding talc (B) to a melted state of the polyacetal resin (A). Lamp molded body.   The melting point of the polyacetal resin composition is 167 ° C. or higher and 173 ° C. or lower, and the lamp molded body of the hard disk according to any one of claims 1 to 4.   The MFR of the polyacetal resin composition is 20 to 40 g / 10 min, and the lamp molded body of the hard disk according to any one of claims 1 to 5.   The polyacetal resin composition comprises at least one selected from (D) an antioxidant, a polymer or compound containing formaldehyde-reactive nitrogen, a formic acid scavenger, a weathering (light) stabilizer, a release agent, and a lubricant. (A) 0.01-10 mass parts is contained with respect to 100 mass parts, The lamp molded object of the hard disk as described in any one of Claims 1-6 characterized by the above-mentioned.

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