JP2660896B2 - shutter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shutter made of a polyacetal resin, having excellent antistatic properties and having little change over time in antistatic properties.

[0002]

2. Description of the Related Art Polyacetal resins are plastics widely used in various fields as engineering resins, particularly in the fields of automobiles and home appliances, because of their excellent mechanical properties and moldability. However, in applications such as parts with friction, static electricity is easily generated and often causes various obstacles. That is, dusts are easily formed, electric discharge occurs, and problems such as generation of electric noise occur. Therefore, a material having less of these problems and having excellent antistatic properties has been desired.

The following methods are known as methods for improving the antistatic property. Japanese Patent Publication No. 56-22341 discloses a method of uniformly dispersing a polyoxyalkylene-polysiloxane block copolymer in a polyacetal. Japanese Patent Publication No. 52940/1981 discloses a method of blending a polyacetal with a polyhydric alcohol fatty acid ester having a hydroxyl group and polyethylene glycol.

In addition, Japanese Patent Publication No. 57-16616 discloses a method in which a borate ester of glycerin monofatty acid ester is blended with polyacetal. In addition, 2-57
No. 583 discloses that an antistatic agent is added to a composition comprising an acetal resin and a polyetheresteramide copolymer.
There is a method of blending 5 to 5 parts by weight.

In addition, Japanese Patent Publication No. 14709/1991 discloses a method in which 0.01 to 3% by weight of a hindered amine compound and an effective amount of an antistatic agent are added to a polyacetal resin. However, these conventionally known antistatic techniques do not always show satisfactory antistatic properties, and at present, there is little improvement in antistatic properties over time.

Japanese Patent Publication No. 3-80819 discloses a polyoxymethylene resin having a conductive carbon black of 0.5 to 0.5.
There is a method in which 30% by weight, 0.05 to 10% by weight of an epoxy compound and 0.1 to 10% by weight of an organic phosphorus compound are blended to improve antistatic properties. However, this technique has the disadvantage that the color of the resin is limited to black because of blending the conductive carbon black, and that the lubricity and thermal stability of the polyoxymethylene resin are greatly impaired. I have.

Japanese Patent Application Laid-Open No. 61-41583 discloses a method of penetrating and printing a polyacetal resin molded article having a depth up to a complete spherulite layer of 200 μm or less in order to perform clear penetrating printing on a polyacetal resin. Although disclosed, the polyacetal resin molded articles in the references have too large maximum spherulite diameters, and the antistatic properties with time have hardly been improved.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a shutter made of a polyacetal resin which has a sufficient initial antistatic property and an antistatic property with little change over time.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to a high and low molecular weight compound having a water absorption of 0.3% or more based on 100 parts by weight of a polyacetal resin.
That has been molded with an antistatic agent 0.01-5 parts by weight of a material obtained by blending, with the thickness of the skin layer 15μm or less, and the maximum spherulites size provides a shutter of the disk or tape cartridge is 40μm or less It is.

Hereinafter, the present invention will be described in detail. The polyacetal resin in the present invention is an oxymethylene homopolymer substantially composed of oxymethylene units produced from a cyclic oligomer such as a formaldehyde monomer or a trimer (trioxane) or tetramer (tetraoxane) thereof, And the above raw materials and ethylene oxide, propylene oxide, epichlorohydrin, 1,
An oxymethylene copolymer containing 0.1 to 20% by weight of an oxyalkylene unit having 2 to 8 carbon atoms produced from a cyclic ether such as 3-dioxolan, glycol formal and diglycol formal. Also included are oxymethylene copolymers having branched molecular chains, and oxymethylene block copolymers containing 50% by weight or more of oxymethylene repeating units and less than 50% by weight of heterogeneous polymer units. Further, in the present invention, two or more selected from oxymethylene homopolymer, oxymethylene copolymer, branched polymer and oxymethylene block copolymer can be used by blending.

The polyacetal resin used in the present invention has an FR (ASTM D1238-57E condition) of 20 to 20.
100 g / 10 min is preferred. When the FR is less than 20 g / 10 minutes, it is difficult to obtain a shutter having a skin layer thickness of 15 μm or less. When the FR exceeds 100 g / 10 minutes, the antistatic property is undesirably reduced. The antistatic agent used in the present invention is a high / low molecular weight compound having a water absorption of 0.3% or more, and is an ethylene oxide adduct of an amine compound represented by the general formula (I).

[0012]

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(Wherein R ₁ is an alkyl or alkenyl group having 10 to 22 carbon atoms, m ₁ and n ₁ each represent an integer of 1 to 10), and represented by the general formula (II): Amide compounds

[0014]

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(Wherein R ₂ is a carboxylic acid residue, x and y are each an integer of 0 or 1 or more, and n ₂ is an integer of 1 or more), ethylene oxide-propylene represented by the general formula (III) Oxide copolymer

[0016]

HO (C ₂ H ₄ O) _n3 (C ₃ H ₆ O) _m3 (C ₂ H ₄ O) _n3 H (III)

(Wherein m ₃ and n ₃ are integers from 1 to 99;
₃ + n ₃ represents an integer of 10 to 100. ), The general formula (I
Polyethylene glycol alkyl ether represented by V)

[0018]

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(Wherein R ₄ is an integer of 10 to 32 carbon atoms, and n ₄ is an integer of 6 to 30), a polyoxyalkylene-polysiloxane block copolymer, a polyhydric alcohol fatty acid ester having a hydroxyl group, Glycerin monofatty acid ester borate, polyethylene glycol, ethylene bisstearylamide, etc., among which polyethylene glycol stearyl ether, glycerin monostearate borate, polyethylene glycol (molecular weight 1,000 to 10,000), ethylene bisstearylamide Is more preferred.

The above antistatic agents may be used alone or in combination of two or more. The molecular weight of the antistatic agent is preferably from 200 to 20,000,
0 to 10000 is more preferable. The compounding amount of the antistatic agent in the present invention is 0.01 to 5 parts by weight, preferably 0.03 to 5 parts by weight, based on 100 parts by weight of the polyacetal resin.
It is selected in the range of 3.0 parts by weight. This compounding amount is 0.01
If the amount is less than parts by weight, sufficient antistatic properties cannot be obtained.
If it exceeds 5 parts by weight, the thermal stability decreases, silver streaks (silver strips) occur due to decomposition gas at the time of molding, and the appearance of the shutter is remarkably deteriorated.

The materials for forming the shutter of the present invention may further include additives commonly used in polyacetal resins, for example, β-alanine polymer described in JP-A-3-234729, -6, 6-6
10 Copolymer nylon, polyamide such as nylon-6,6, heat stabilizer such as melamine, 2,2′-methylene-bis (4-methyl-6-t-butylphenol), triethylene glycol-bis [3- ( 3-t-butyl-5-
Methyl-4-hydroxyphenyl) propionate],
Antioxidants such as pentaerythritol-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], lubricants, glass fibers, carbon fibers,
Potassium titanate fibers, reinforcing materials such as organic fibers, glass beads, talc, inorganic fillers such as calcium carbonate, nucleating agents, release agents, plasticizers, carbon black, pigments, etc., to such an extent that the object of the present invention is not impaired. Can be blended.

The thickness of the skin layer on the shutter surface of the present invention must be 15 μm or less. The thickness of the skin layer in the present invention is defined as when a resin molded body constituting a shutter is sliced into a thin section with a microtome to a thickness of 10 μm in a thickness direction and observed at 340 × by a transmission polarization microscope using crossed Nicols. Refers to the thickness of the layer on the outer surface of the molded body that does not receive polarized light. If the thickness of the skin layer can be reduced, the change with time of the antistatic property can be extremely reduced. The thickness of the skin layer is 15 μm
When it exceeds, the change with time of the antistatic property becomes large.

The thickness of the skin layer of the molded article constituting the shutter of the present invention can be obtained by (1) a method of controlling the crystallization time of the resin, (2) a method of selecting an appropriate molding method, or the like. These methods may be used alone or in combination. As a method of controlling the crystallization time of the resin, there is a method of setting the crystallization time to 20 to 100 seconds.

The crystallization time in the present invention means that a sample of 5 mg of a polyacetal resin is measured at 320 ° C. by DSC.
When the temperature of the sample holder was raised to 150 ° C. when the temperature was raised to 200 ° C. at 200 ° C., held at 200 ° C. for 2 minutes, and lowered at 150 ° C. at 80 ° C./min. This is the time (seconds) until the peak top is detected.

The method of controlling the crystallization time to 20 to 100 seconds is performed by using a generally known crystal nucleating agent such as silicate (inorganic filler) powder such as talc or wollastonite, hydrotalcite, calcium carbonate, etc. And / or an organic nucleating agent such as a branched polyacetal copolymer. Other additives for controlling the crystallization time include amine compounds such as melamine and dicyandiamine; nitrides such as boron nitride; oxides such as zinc oxide, titanium oxide, calcium oxide and magnesium oxide; acetylene black; Examples include, but are not limited to, carbon powder such as conductive carbon black, amide resin powder such as ionic polymer of nylon 6,6 and acrylamide, and powder of vinyl polymer such as radical polymer of acrylamide. However, among them, preferred crystal nucleating agents are nitrides such as boron nitride and powders of amide resins such as ionic polymers of nylon 6,6 and acrylamide, and boron nitride is more preferred. Preferred boron nitride has an average particle size of 1 to 10 μm, preferably 2 to 7 μm.
It has a diboron trioxide content of 0.05 to 0.7% by weight, preferably 0.1 to 0.6% by weight, and the addition amount thereof is 5 to 200 ppm, preferably 20 to 200 ppm.
ppm is good. However, strictly speaking, a shutter made of a polyacetal resin has other properties besides the antistatic property (for example, heat aging property, hot water resistance, weather resistance, slidability, mold release property, heat stability during molding and heat stability). Decomposability, etc.) in many cases, it is necessary to select an appropriate nucleating agent in consideration of the compatibility between the nucleating agent and an additive other than the nucleating agent added at the same time.

As a method of controlling by selecting an appropriate molding method, there is the following method. First,
The mold temperature should be 100 ° C or higher and 150 ° C or lower, preferably 110
A method in which the temperature is set to not less than 140 ° C. and molded. Next, the surface (cavity) of the mold for injection molding is induced by induction heating with high frequency as disclosed in Japanese Patent Publication No. 58-40804.
And injection molding by selective heating. Next, compression molding with a hot press followed by slow cooling. A method of cutting, polishing, and sandblasting extruded round bars. Next, this is a method in which a molded article injection-molded at a mold temperature of 10 ° C. or more and less than 100 ° C. is thermally annealed at a temperature of 150 ° C. or more and less than the melting point of the polyacetal resin. Considering the productivity among these molding methods, the above method is preferable.

The maximum spherulite size of the crystal of the resin constituting the shutter of the present invention must be 40 μm or less. The maximum spherulite size in the present invention means that the cross section of
When sliced into thin sections with a microtome to a thickness of μm and observed at 340 times with a transmission polarization microscope using crossed Nicols, if the spherulite diameter can be clearly identified, the largest spherulite among those spherulites When the spherulite diameter cannot be clearly discriminated, the same polarization part (same color part) is twice as large as the particle having the maximum length among particles that were confirmed as particles without being connected to other polarization parts ( The same maximum polarization length is regarded as み な of the diameter of the spherulite).

When the maximum spherulite size of the crystal of the resin constituting the shutter exceeds 40 μm, the spherulite state of the molded body is liable to change, and the amount of the antistatic agent on the surface changes with time. The preferred maximum spherulite size is 6 to 30 μm, more preferably 10 to 20 μm, in view of dimensional stability and antistatic stability.
m. The application of the present invention is a shutter of a disk or a tape cartridge having a thickness of 1 mm or less, and a floppy disk shutter is more preferable.

The disk or tape cartridge shutter in the present invention relates to a disk or tape cartridge incorporating a magnetic disk or magnetic tape, and is a shutter provided on the outer surface of the case for opening and closing a head insertion window.

[0030]

【Example】

[0031]

[Reference example]

<Production of polyacetal resin> Ethylene oxide
Polyacetal copolymerized at 8% was prepared according to US Pat.
352 by a known method. This had an intrinsic viscosity of 1.0. (The intrinsic viscosity was measured at 60 ° C. by dissolving 0.1% by weight of the polymer in a p-chlorophenol solution containing 2% by weight of alpha pinene.)
The melt index according to STM D1238-57T (E condition) was 30.0 g / 10 minutes. This polyacetal is designated as P-1.

A double-acetylated polyacetal homopolymer powder was prepared by a known method described in US Pat. No. 2,998,409. This had an intrinsic viscosity of 1.2. (Intrinsic viscosity was measured at 60 ° C. by dissolving 0.1% by weight of the polymer in a p-chlorophenol solution containing 2% by weight of alpha pinene.) ASTM D1238
The melt index at -57T (E condition) is 40.0.
g / 10 minutes. This polyacetal is designated as P-2.

[0033]

Examples 1 to 18 and Comparative Examples 1 to 14 Triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4
-Hydroxyphenyl) propionate] and 0.2 parts by weight of the polyacetal, antistatic agent and nucleating agent shown in Tables 1 and 2 were blended in a nitrogen atmosphere at the compounding ratio shown in the table.
Extruder with a single-screw vent of L / D = 25 set to 00 ° C. (conditions: screw rotation speed; 100 rpm, discharge 6 kg /
The pellets obtained by melt-kneading in (hr) were dried, and a 3.5-inch floppy disk shutter was molded with a 5 oz molding machine (conditions: mold temperature 100 ° C., cooling time 10 seconds). After leaving the shutter in a constant temperature and humidity room at a temperature of 20 ° C. and a humidity of 50% for 1 hour and 500 hours to obtain a sample, a voltage of 10 KV is applied to the sample, and a half-life of the charged voltage after stopping the application ( S) was measured with a Statec Honestometer.

The results are shown in Tables 1 and 2. The symbols in the table indicate the following. (T) Antistatic agent : T-1: Polyethylene glycol stearyl ether T-2: Boric acid ester of glycerin monostearate T-3: Polyethylene glycol (molecular weight 6000) (K) Nucleating agent : K-1: Boron nitride ( K-2: boron nitride (average particle size 5 μm) K-3: talc (average particle size 5 μm)

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

According to the present invention, it is possible to provide a shutter which is excellent in antistatic property and has little change with time in antistatic property.

Claims (6)

(57) [Claims] 1. A high / low molecular weight compound having a water absorption of 0.3% or more based on 100 parts by weight of a polyacetal resin.
A disk or tape cartridge formed from a material containing 0.01 to 5 parts by weight of an antistatic agent, having a skin layer thickness of 15 μm or less and a maximum spherulite size of 40 μm or less. 2. The polyacetal resin having an FR of 20 to 1
2. The shutter according to claim 1, wherein the shutter speed is 00 g / 10 minutes. 3. An amine compound represented by the general formula (I):
Do adduct [Formula 1] (Wherein R ₁ is alkyl or alk having 10 to 22 carbon atoms)
M ₁ and n ₁ are both 1 to 10
Indicates a number. ), An amide compound represented by the general formula (II) : Wherein R ₂ is a carboxylic acid residue, x and y are each 0 or less.
Other is an integer of 1 or more, n ₂ is an integer of 1 or more. ), Ethylene oxide-propylene represented by the general formula (III)
Ren'okishido copolymer embedded image _{HO (C 2 H 4 O)} n3 (C 3 H 6 O) m3 (C 2 H 4 O) n3 H (III) ( wherein _m 3, _{n 3} is 1 to 99 Where m ₃ + n ₃ is
Shows the integer of 10 to 100. ), Polyethylene glycol alcohols represented by the general formula (IV)
Kill ether [4] (Wherein R ₄ is an integer having 10 to 32 carbon atoms, and n ₄ is
Shows an integer of 6 to 30. ), According to claim 1 or 2, wherein at least one compound selected from
Shutter. 4. The method according to claim 1, wherein the antistatic agent is a polyoxyalkylene-
Polysiloxane block copolymer, hydroxyl-containing poly
Polyhydric alcohol fatty acid ester, glycerin mono fatty acid ester
Stele borate, polyethylene glycol, d
One of the compounds selected from Tylenebisstearylamide
The shutter according to claim 1, which is the above. 5. The method according to claim 1, wherein the antistatic agent is polyethylene glycol.
Of stearyl ether and glycerin monostearate
Uric acid ester, polyethylene glycol (molecular weight 100
0-10000), 1 of ethylenebisstearylamide
The shutter according to claim 1, wherein the number of the shutters is at least one. 6. The amount of the antistatic agent added to the polyacetal
0.03 to 3.0 parts by weight based on 100 parts by weight of resin
The shutter according to claim 1. "