JP5545991B2 - Polyoxymethylene resin composition and molded article - Google Patents

Description

  The present invention relates to a polyoxymethylene resin composition and a molded body.

Conventionally, a polyoxymethylene resin has been widely used as an engineering resin having both balanced mechanical characteristics and excellent heat resistance characteristics in various mechanical parts and OA equipment.
In particular, since it has excellent frictional wear characteristics, it is suitably used as a material for gears of printers and the like.
However, along with recent high precision and high functionality of equipment, reduction of vibration and noise generated by using equipment has become an important issue. Is becoming required.

Conventionally, as a material having flexibility performance, generally, a rubber-based or thermoplastic elastomer-based material, or a material in which a resin-based or rubber-based material is sandwiched between a metal plate and a metal plate, etc. It is used.
However, the rubber-based or thermoplastic elastomer-based ones have problems in heat resistance of parts due to heat generation under high temperature conditions, frictional wear characteristics with metals and resins, and chemical resistance against contact with drugs such as ink. In addition, a material in which a resin material or a rubber material is sandwiched between the metal plates has a problem in molding.

  Patent Document 1 discloses a polymer composition obtained by polymerizing formaldehyde in the presence of a block copolymer of a specific vinyl aromatic compound. Patent Document 2 includes a polyoxymethylene resin and a functional group. Mixtures with styrenic resins are each disclosed.

JP-A-8-165405 Japanese Patent Laid-Open No. 10-60224

However, although the materials disclosed in Patent Documents 1 and 2 have all been tried to improve the impact resistance, they have high flexibility performance until the vibration and noise generated by the equipment can be reduced. I can't say that.
Therefore, in the present invention, in view of the above-described problems of the prior art, a polyoxymethylene resin composition capable of producing a molded article having excellent frictional wear characteristics and further imparted with high flexibility performance, And it aims at providing the molded object which has the said characteristic.

The present inventors have conducted extensive studies to provide high flexibility performance in addition to the excellent impact resistance and frictional wear characteristics inherent to polyoxymethylene resins. It has been found that a composition in which a specific styrene-based elastomer is added to a resin can solve the above-mentioned problems, and the present invention has been completed.
That is, the present invention is as follows.

[1]
(A) Polyoxymethylene resin: 100 parts by mass;
(B) has a main dispersion peak temperature of tan δ obtained by viscoelasticity measurement at −10 ° C. or less,
Styrenic elastomer having an amount of styrene obtained by nuclear magnetic resonance (NMR) measurement of 30% by mass or less: 1 to 100 parts by mass;
Containing ,
A polyoxymethylene resin composition in which the styrenic elastomer (B) is dispersed with a dispersion average particle size of 10 μm or less .

[2]
The said (A) component is a polyoxymethylene resin composition as described in said [1] whose melt flow rate (measured on the conditions of ASTM-D1238-57T) is 1.0-80 g / 10min.

[3]
The said (A) component is a polyoxymethylene resin composition as described in said [1] containing the polyoxymethylene block copolymer of the number average molecular weight 10000-500000 represented by following General formula (1).
HR ³ —O— (CR ¹ ₂ ) _k —R ⁴ — (CR ¹ ₂ ) _k —O—R ³ —H (1)
(In General Formula (1), each R ¹ independently represents a chemical species selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aryl group, and is the same as each other. Can be different or different,
k shows the integer of 2-6 each independently.
R ³ represents a block having a plurality of oxymethylene units represented by the following general formula (2a) and oxyhydrocarbon units represented by the following general formula (2b), wherein the oxymethylene unit and the oxyhydrocarbon unit And the oxymethylene unit and the oxyhydrocarbon unit in a total amount of 100 mol%, the oxymethylene unit content is 95-99.9 mol%, the oxyhydrocarbon unit of the The content is 0.1 to 5 mol%, and the average number average molecular weight of the two R ³ is 5000 to 250,000.
In the following general formula (2b), each R ² independently represents a chemical species selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aryl group, and is the same as each other. It may be present or different, and j represents an integer of 2 to 6.
R ⁴ represents a block having a plurality of ethylene units represented by the following general formula (3a) and n-butylene units represented by the following general formula (3b), and the ethylene unit and the n-butylene unit are: Relative to each other or in blocks, the ethylene unit content is 2 to 98 mol% and the n-butylene unit content is 2 with respect to 100 mol% of the total amount of the ethylene unit and the n-butylene unit. ~ 98 mol%. R ⁴ has a number average molecular weight of 500 to 10,000, it may have the following unsaturated bond iodine value 20g-I ₂ / 100g. )
— (CH ₂ O) — (2a)
-((CR ² ₂ ) _j -O)-(2b)
_{- (CH 2 CH 2) -} ··· (3a)
_{- (CH 2 CH 2 CH 2} CH 2) - ··· (3b)

[4]
The molded object shape | molded using the polyoxymethylene resin composition as described in any one of said [1] thru | or [3].

  ADVANTAGE OF THE INVENTION According to this invention, the polyoxymethylene resin composition which can manufacture the molded object which has the outstanding frictional wear characteristic and the softness | flexibility performance, and the molded object which has the said characteristic can be provided.

Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described.
The present invention is not limited to the following description, and various modifications can be made within the scope of the gist thereof.

[Polyoxymethylene resin composition]
The polyoxymethylene resin composition of the present embodiment is
(A) Polyoxymethylene resin: 100 parts by mass;
(B) has a main dispersion peak temperature of tan δ obtained by viscoelasticity measurement at −10 ° C. or less,
Styrene elastomer having a styrene content of 30% by mass or less: 1 to 100 parts by mass;
Containing.
In the present specification, these are also referred to as (A) component and (B) component, respectively.

((A) polyoxymethylene resin)
The polyoxymethylene resin composition of the present embodiment contains (A) a polyoxymethylene resin.
Examples of (A) polyoxymethylene resins include polyoxymethylene homopolymers and polyoxymethylene copolymers.
A polyoxymethylene homopolymer is obtained by homopolymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) or tetramer (tetraoxane). Therefore, the polyoxymethylene homopolymer substantially consists of oxymethylene units.
On the other hand, the polyoxymethylene copolymer is a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) or tetramer (tetraoxane), ethylene oxide, propylene oxide, epichlorohydrin, 1,3- It is obtained by copolymerizing glycol such as dioxolane and 1,4-butanediol formal, cyclic ether such as cyclic formal of diglycol, and cyclic formal.
The polyoxymethylene copolymers include branched polyoxymethylene copolymers obtained by copolymerizing formaldehyde monomers and / or cyclic oligomers of formaldehyde with monofunctional glycidyl ethers, and formaldehyde A polyoxymethylene copolymer having a cross-linked structure obtained by copolymerizing a monomer and / or a cyclic oligomer of formaldehyde and a polyfunctional glycidyl ether can also be used.

Furthermore, (A) polyoxymethylene resin is obtained by polymerizing a formaldehyde monomer or a formaldehyde cyclic oligomer in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, such as polyalkylene glycol. It may be a polyoxymethylene homopolymer having a block component to be obtained.
Similarly, (A) polyoxymethylene resin is a formaldehyde monomer or its trimer (trioxane) in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, such as hydrogenated polybutadiene glycol. And a polyoxymethylene copolymer having a block component obtained by copolymerizing a cyclic oligomer of formaldehyde such as tetramer and tetraether or cyclic formal.
The polyoxymethylene resin (A) constituting the polyoxymethylene resin composition of the present embodiment preferably contains a polyoxymethylene copolymer having a block component.

<Method for producing polyoxymethylene copolymer>
An example of a polyoxymethylene copolymer is a copolymer of formaldehyde trimer (trioxane) and 1,3-dioxolane.
When obtaining this polyoxymethylene copolymer, the comonomer such as 1,3-dioxolane is generally 0.1 to 60 mol, preferably 0.1 to 20 mol, more preferably 0, relative to 100 mol of trioxane. Use 13 to 10 mol.
The melting point of the polyoxymethylene copolymer is preferably 162 ° C to 173 ° C, more preferably 167 ° C to 173 ° C, and further preferably 167 ° C to 171 ° C.
A polyoxymethylene 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 100 mol of trioxane.
The melting point of the polyoxymethylene copolymer is increased at a rate of 40 ° C./min from room temperature to 200 ° C. using Perkin Elmer (DSC-7) by forming the polyoxymethylene copolymer into a film using a compression press. By measuring the peak top of the endothermic curve when the temperature is raised to 200 ° C. at a rate of 2.5 ° C./min after being held at 200 ° C. for 1 minute, lowered to 40 ° C./min to 130 ° C. can get.

In the polymerization step of the polyoxymethylene copolymer, it is preferable to use a predetermined polymerization catalyst.
As a polymerization catalyst used for the polymerization of the polyoxymethylene copolymer, for example, a cationically active catalyst such as a Lewis acid, a protonic acid and an ester or an anhydride thereof is preferable.
Examples of Lewis acids include boric acid, tin, titanium, phosphorus, arsenic and antimony halides. More specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, Examples thereof include phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof.
Examples of the protonic acid, ester or anhydride thereof include perchloric acid, trifluoromethanesulfonic acid, perchloric acid-tertiary butyl ester, acetyl perchlorate, and trimethyloxonium hexafluorophosphate.
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, trifluoride is used. Boron diethyl ether and boron trifluoride di-n-butyl ether are preferred.

As a polymerization method for producing the polyoxymethylene copolymer, conventionally known methods can be applied.
For example, U.S. Pat. Nos. 3,027,352, 3,803,094, German Patents 1,161,421, 1,495,228, 1,720,358, 3,018,898, JP Polymerization can be carried out by the methods described in JP-A-58-98322 and JP-A-7-70267.

Since the polyoxymethylene copolymer obtained by the above polymerization has a thermally unstable terminal portion [-(OCH ₂ ) _n —OH group], it is difficult to put it into practical use as it is. . Therefore, it is preferable to perform the decomposition and removal treatment of the unstable terminal portion, and specifically, it is preferable to perform the decomposition and removal processing of the specific unstable terminal portion described below.
That is, in the presence of at least one quaternary ammonium compound represented by the following general formula (4), the polyoxymethylene copolymer is reacted at a temperature not lower than the melting point of the polyoxymethylene copolymer and not higher than 260 ° C. Then, a heat treatment is performed in a melted state, whereby a specific unstable terminal portion is decomposed and removed.

[R ⁵ R ⁶ R ⁷ R ⁸ N ⁺ ] _n X ⁻ⁿ (4)
In general formula (4), R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; An aralkyl group in which at least one hydrogen atom in a substituted or unsubstituted alkyl group having 1 to 30 is substituted with an aryl group having 6 to 20 carbon atoms; or at least one hydrogen in an aryl group having 6 to 20 carbon atoms An alkylaryl group in which an atom is substituted with a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms is represented, and the substituted or unsubstituted alkyl group is linear, branched, or cyclic.
The substituent in the substituted alkyl group is a halogen atom, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, or an amide group.
In the unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group, a hydrogen atom may be substituted with a halogen atom.
n shows the integer of 1-3.
X represents a hydroxyl group or an acid residue of a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than a hydrogen halide, an oxo acid, an inorganic thioacid, or an organic thioacid having 1 to 20 carbon atoms.

The quaternary ammonium compound used for decomposing and removing the thermally unstable terminal portion [— (OCH ₂ ) _n —OH group] of the polyoxymethylene copolymer is represented by the general formula (4). In general formula (4), R ⁵ , R ⁶ , R ⁷ , and R ⁸ are each independently an alkyl group having 1 to 5 carbon atoms or a carbon number. It is preferably 2 to 4 hydroxyalkyl groups, and more preferably at least one of R ⁵ , R ⁶ , R ⁷ and R ⁸ is a hydroxyethyl group.
Specific examples of the quaternary ammonium compound include 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, tripropylbenzylan Nium, tri-n-butylbenzylammonium, trimethylphenylammonium, triethylphenylammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, okdadecyltri (2-hydroxyethyl) ammonium, Hydroxides such as tetrakis (hydroxyethyl) ammonium; Hydrochloric acid salts such as hydrochloric acid, odorous acid and hydrofluoric acid; sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodic acid, silicic acid, perchloric acid, chlorine Oxoacid salts such as acid, hypochlorous acid, chlorosulfuric acid, amidosulfuric acid, disulfuric acid, and 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, benzoic acid, Shu It includes carboxylic acid salts and the like. Among these, hydroxide (OH ⁻ ), sulfuric acid (HSO ₄ ⁻ , SO ₄ ²⁻ ), carbonic acid (HCO ₃ ⁻ , CO ₃ ²⁻ ), boric acid (B (OH) ₄ ⁻ ), and carboxylic acid The salt of is preferred.
Among the carboxylic acids, formic acid, acetic acid, and propionic acid are particularly preferable.
A quaternary ammonium compound may be used individually by 1 type, and may be used in combination of 2 or more type.
Further, in addition to the quaternary ammonium compound, amines such as ammonia and triethylamine, which are known decomposition accelerators for unstable terminals, may be used in combination.

The amount of the quaternary ammonium compound used for decomposing and removing the thermally unstable terminal portion [— (OCH ₂ ) _n —OH group] of the polyoxymethylene copolymer is as follows. In terms of the amount of nitrogen derived from the quaternary ammonium compound represented by the following general formula (5) relative to the total mass of the copolymer and the quaternary ammonium compound, it is preferably 0.05 to 50 ppm by mass, more preferably Is 1-30 ppm by mass.
Amount of quaternary ammonium compound used (mass ppm) = P × 14 / Q (5)
Here, in Formula (5), P shows the density | concentration (mass ppm) with respect to the polyoxymethylene copolymer of a quaternary ammonium compound, 14 is the atomic weight of nitrogen, Q is the molecular weight of a quaternary ammonium compound. Show.

The amount of the quaternary ammonium compound used to decompose and remove the thermally unstable terminal portion [— (OCH ₂ ) _n —OH group] of the polyoxymethylene copolymer is 0.05. When it is in the range of ˜50 mass ppm, a practically sufficient decomposition / removal rate of the unstable terminal portion can be secured, and the color tone of the polyoxymethylene copolymer obtained after decomposition / removal becomes good.

As described above, the thermally unstable terminal portion [— (OCH ₂ ) _n —OH group] of the (A) polyoxymethylene resin used in the present embodiment is at a temperature not lower than the melting point and not higher than 260 ° C. A) When the polyoxymethylene resin is heat-treated in a molten state, it is decomposed and removed.
An apparatus used for the decomposition and removal treatment is not particularly limited, but an extruder, a kneader and the like are preferable.
Formaldehyde is generated by decomposition, but is usually removed under reduced pressure.
There is no particular limitation on the method for allowing the quaternary ammonium compound to be present in the polyoxymethylene copolymer when the thermally unstable terminal portion is decomposed and removed, for example, a step of deactivating the polymerization catalyst. And a method of spraying on a polyoxymethylene copolymer powder produced by polymerization.
Whichever method is used, the quaternary ammonium compound may be present in the polyoxymethylene copolymer in the step of heat-treating the polyoxymethylene copolymer.
For example, a quaternary ammonium compound may be injected into an extruder in which a polyoxymethylene copolymer is melt-kneaded and extruded. Alternatively, when a filler or pigment is added to the polyoxymethylene copolymer using the extruder or the like, a quaternary ammonium compound is first attached to the resin pellet of the polyoxymethylene copolymer, and then the filler or pigment is added. The unstable end portion may be decomposed and removed at the time of blending.

  (A) The thermally unstable terminal portion of the polyoxymethylene resin can be decomposed and removed after the polymerization catalyst coexisting with the polyoxymethylene copolymer obtained by polymerization is deactivated. It is also possible to carry out without deactivating the polymerization catalyst.

Examples of the deactivation treatment of the polymerization catalyst include a method of neutralizing and deactivating the polymerization catalyst in a basic aqueous solution such as amines.
When the polymerization catalyst is not deactivated, the copolymer is heated under an inert gas atmosphere at a temperature below the melting point of the polyoxymethylene copolymer, and the polymerization catalyst is reduced by volatilization, and then the unstable terminal. It is also an effective method to perform the disassembly and removal operation of the part.

  By decomposing and removing the unstable terminal portion as described above, (A) to obtain a polyoxymethylene copolymer suitable as a polyoxymethylene resin having very excellent unstable thermal stability and almost no unstable terminal portion. Can do.

In the present embodiment, the (A) polyoxymethylene resin includes a polyoxymethylene block copolymer having a number average molecular weight of 10,000 to 500,000, which will be described later (A-1): represented by the following general formula (1). It is preferable.
This (A-1) polyoxymethylene block copolymer can be produced by the method described in WO 01/009213.
HR ³ —O— (CR ¹ ₂ ) _k —R ⁴ — (CR ¹ ₂ ) _k —O—R ³ —H (1)
Here, in the general formula (1), each R ¹ independently represents any chemical species selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aryl group. May be the same or different from each other,
k shows the integer of 2-6 each independently.
R ³ represents a block having a plurality of oxymethylene units represented by the following general formula (2a) and oxyhydrocarbon units represented by the following general formula (2b). What are oxymethylene units and oxyhydrocarbon units? Relative to each other, the total amount of oxymethylene units and oxyhydrocarbon units is 100 mol%, the content of oxymethylene units is 95 to 99.9 mol%, and the content of oxyhydrocarbon units is 0.1. a 5 mole%, a number average molecular weight of the average of the two R ³ is from 5,000 to 250,000.
In the following general formula (2b), R ² represents any chemical species selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aryl group, and is identical to each other. May be different.
j represents an integer of 2 to 6.
The hydrogen atoms at both ends in the general formula (1) are bonded to oxygen atoms in the following general formula (2a) or (2b).
R ⁴ represents a block having a plurality of ethylene units represented by the following general formula (3a) and n-butylene units represented by the following general formula (3b), and the ethylene units and the n-butylene units are randomly selected from each other. Alternatively, the ethylene unit content is 2-98 mol% and the n-butylene unit content is 2-98 mol% with respect to 100 mol% of the total amount of ethylene units and n-butylene units present in the block. . Further, R ⁴ has a number average molecular weight thereof is 500 to 10,000, may have the following unsaturated bond iodine value 20g-I ₂ / 100g.
In the present embodiment, the number average molecular weight is a molecular weight in terms of PMMA (polymethyl methacrylate) by gel permeation chromatography.
— (CH ₂ O) — (2a)
-((CR ² ₂ ) _j -O)-(2b)
_{- (CH 2 CH 2) -} ··· (3a)
_{- (CH 2 CH 2 CH 2} CH 2) - ··· (3b)
Examples of the substituent in the substituted alkyl group and the substituted aryl group include a halogen atom, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, and an amide group.
The component (A-1) is effective in improving compatibility with a polymer containing an olefin component.

<(A) Physical properties of polyoxymethylene resin>
(A) The melt flow rate of the polyoxymethylene resin (measured under the conditions of ASTM-D1238-57T) is preferably 0.5 g / 10 min or more from the surface of molding, and 100 g / 10 min from the surface of durability. The range is preferably 1.0 to 80 g / 10 minutes, more preferably 5 to 60 g / 10 minutes, and still more preferably 7 to 50 g / 10 minutes.

<(A) Other components contained in polyoxymethylene resin>
In the polyoxymethylene resin (A) used in the present embodiment, one type of stabilizer used in conventional polyoxymethylene resins, for example, one type of thermal stabilizer is used alone or in combination of two or more types.
As the heat stabilizer, antioxidants, formaldehyde and formic acid scavengers, and combinations thereof are suitable.

The antioxidant is preferably a hindered phenol antioxidant.
Examples of the hindered phenol antioxidant include 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-t-butyl-4-hydroxyphenyl) -propionate), 1,4-butanediol-bis- (3- (3,5-di-t-butyl) -4-hydroxyphenyl) -propionate), triethylene glycol-bis- (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate).

  Examples of hindered phenol antioxidants include tetrakis- (methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate methane, 3,9-bis ( 2- (3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy) -1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro (5,5) undecane N, N′-bis-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenol) prepionylhexamethylenediamine, N, N′-tetramethylenebis-3- (3′- Methyl-5′-t-butyl-4-hydroxyphenol) propionyldiamine, N, N′-bis- (3- (3,5-di-t-butyl-4-hydroxyphenol) propionyl) hydra N-salicyloyl-N′-salicylidenehydrazine, 3- (N-salicyloyl) amino-1,2,4-triazole, N, N′-bis (2- (3- (3,5-di- Mention may also be made of butyl-4-hydroxyphenyl) propionyloxy) ethyl) oxyamide.

  Among the hindered phenol antioxidants described above, triethylene glycol-bis- (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate), tetrakis- (methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate) methane is preferred.

  Examples of the formaldehyde and formic acid scavengers include compounds and polymers containing formaldehyde-reactive nitrogen, alkali metal or alkaline earth metal hydroxides, inorganic acid salts, and carboxylate salts. Examples of compounds and polymers containing formaldehyde-reactive nitrogen include dicyandiamide, melamine, co-condensates of melamine and formaldehyde, nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12. , Nylon 12, nylon 6 / 6-6, nylon 6 / 6-6 / 6-10, nylon 6 / 6-12 and other polyamide resins, poly-β-alanine, and polyacrylamide. Among these, a co-condensate of melamine and formaldehyde, polyamide resin, poly-β-alanine and polyacrylamide are preferable, and polyamide resin and poly-β-alanine are more preferable.

Examples of the alkali metal or alkaline earth metal hydroxide, inorganic acid salt, and carboxylate include hydroxides such as sodium, potassium, magnesium, calcium or barium, carbonates and phosphates of the above metals. Silicates, borates and carboxylates.
Specifically, calcium salts are preferable, and examples include calcium hydroxide, calcium carbonate, calcium phosphate, calcium silicate, calcium borate, and fatty acid calcium salts (calcium stearate, calcium myristate, etc.), and these fatty acids are substituted with hydroxyl groups. It may be. Among these, fatty acid calcium salts (calcium stearate, calcium myristate, etc.) are more preferable.

Preferred combinations of the stabilizers are in particular triethylene glycol-bis- (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate) or tetrakis- (methylene-3- (3 ′, 5 Heavy weight containing hindered phenolic antioxidants typified by '-di-t-butyl-4'-hydroxyphenyl) propionate) methane and formaldehyde reactive nitrogen typified by polyamide resin and poly-β-alanine in particular. It is a combination of a coalescence and a fatty acid salt of an alkaline earth metal typified by a fatty acid calcium salt.
The amount of each stabilizer added is 0.1 to 2 parts by mass of a hindered phenol antioxidant and 0.1% of a polymer containing formaldehyde-reactive nitrogen with respect to 100 parts by mass of (A) polyoxymethylene resin. It is preferable that 1-3 mass parts and the fatty-acid salt of alkaline-earth metal are the range of 0.1-1 mass%.

((B) Styrenic elastomer)
The polyoxymethylene resin composition of this embodiment contains (B) a styrenic elastomer.
The styrene-based elastomer that is the component (B) will be described.
The (B) styrenic elastomer contained in the polyoxymethylene resin composition of the present embodiment is a random, block, graft or other copolymerization form, presence or absence of side chains or branches, and its degree, copolymer composition ratio The presence or absence of hydrogenation is not particularly limited, but the main dispersion peak temperature of tan δ obtained by viscoelasticity measurement is −10 ° C. or less, and the styrene content is 30% by mass or less. By setting it as this range, in the polyoxymethylene resin composition of the present embodiment, high flexibility performance can be obtained.
The main dispersion peak of tan δ in the viscoelastic spectrum is measured as follows.
First, a sheet-like sample is cut into a size of 10 mm in width and 35 mm in length, and the sample is set in a twist type geometry of a rheometer device (trade name “ARES”, manufactured by TI Instruments Inc.). .
Next, the effective measurement length is set to 25 mm, the strain is set to 0.5%, the frequency is set to 1 Hz, and the temperature is increased from −80 ° C. to 80 ° C. at a temperature increase rate of 3 ° C./min to obtain a viscoelastic spectrum.
The main dispersion peak temperature of tan δ in the obtained viscoelastic spectrum is obtained from a peak detected by automatic measurement of predetermined software (trade name “RSI Orchestrator”, manufactured by TI Instruments Inc.).
The main dispersion peak temperature of tan δ obtained by viscoelasticity measurement is preferably −20 ° C. or lower, more preferably −30 ° C.
The content of the vinyl aromatic compound in the hydrogenated block copolymer, that is, the styrene content in the styrenic elastomer is measured using, for example, a nuclear magnetic resonance apparatus (NMR) (Y. Tanaka, et al., RUBBER CHEMISTRY and TECHNOLOGY). 54, 685 (1981), and the amount of styrene is preferably 20% by mass or less, more preferably 15% by mass or less.

(B) The number average molecular weight of the styrene-based elastomer is preferably 10,000 to 500,000.
By setting it as this range, in the polyoxymethylene resin composition of the present embodiment, high flexibility performance can be obtained.
In the present embodiment, the number average molecular weight is a molecular weight in terms of polystyrene by gel permeation chromatography.

Further, among (B) styrene elastomers, preferred are copolymers of styrene monomers shown below and monomers that can be copolymerized with styrene monomers.
Examples of the styrene monomer include aromatic vinyl monomers such as styrene, α-methylstyrene, 2,4-dimethylstyrene, p-methylstyrene, t-butylstyrene, chloromethylstyrene, and ethylstyrene. Among them, styrene is preferable.
The monomer copolymerizable with the styrenic monomer includes elastomers in addition to copolymerizable unsaturated monomers.
Examples of the copolymerizable unsaturated monomer include (meth) acrylonitrile, (meth) acrylic acid ester, maleimide monomers, diene monomers (eg, butadiene, isoprene, etc.), olefins (eg, ethylene, propylene, Butene etc.).
Examples of the elastomer include polybutadiene, polyisoprene, ethylene-propylene rubber, acrylic rubber, halogenated polyolefin such as chlorinated polyethylene, and the like, and may be a hydrogenated product.

<(B) Styrenic elastomer content>
Content of (B) styrene-type elastomer in the polyoxymethylene resin composition of this embodiment is a range whose (B) component is 1-100 mass parts with respect to (A) component 100 mass parts. By being in this range, the fluidity at the time of molding and the appearance of the molded product are good, and excellent flexibility is imparted.
(B) As for content of a component, 10-80 mass parts is preferable, and 20-60 mass parts is more preferable.

<(B) Dispersion average particle diameter of styrene-based elastomer>
In the polyoxymethylene resin composition of the present embodiment, the dispersion average particle size of (B) the styrene elastomer is preferably 10 μm or less.
The dispersion average particle diameter of the component (B) was determined by using the molded body (test piece) of the polyoxymethylene resin composition of the present embodiment in the direction perpendicular to the surface layer portion (relative to the flow during molding) of 0. It can be measured by cutting into a 3 mm square 80 nm ultrathin film and observing with a transmission electron microscope (H-7500, manufactured by Hitachi, Ltd.).
When the dispersion average particle diameter is 10 μm or less, a molded article having excellent mechanical properties, excellent flexibility, and excellent frictional wear characteristics can be obtained.
The dispersion average particle diameter is preferably 8 μm or less, and more preferably 6 μm or less.

[Method for producing polyoxymethylene resin composition]
The polyoxymethylene resin composition of the present embodiment can be produced by melt-kneading the above-described component (A), component (B), and other additives as necessary.
Examples of the melt kneader include a kneader, a roll mill, a single screw extruder, a twin screw extruder, and a multi screw extruder.

[Molded body using polyoxymethylene resin composition]
The molded body of the present embodiment is formed by a predetermined molding method using the above-described polyoxymethylene resin composition.
Examples of molding methods include injection molding, hot runner injection molding, outsert molding, insert molding, gas-assisted hollow injection molding, high-frequency heat injection molding of molds, compression molding, inflation molding, and blow molding. Examples include molding methods such as molding, extrusion molding, and cutting of extruded products.

Examples of uses of the molded body include gears, cams, sliders, levers, arms, clutches, felt clutches, idler gears, pulleys, rollers, rollers, key stems, key tops, shutters, reels, shafts, joints, shafts, bearings, and the like. Examples include mechanical parts represented by guides, outsert molded resin parts, and insert molded resin parts.
Other uses of the molded body include parts for office automation equipment such as chassis, trays, side plates, printers and copiers, VTR (Video Tape Recorder), video movies, digital video cameras, cameras and digital. Camera or video equipment parts represented by cameras, cassette players, DAT, LD (Laser Disk), MD (Mini Disk), CD (CompactDisk) (CD-ROM (Read Only Memory), CD-R (Recordable), CD-RW (including Rewritable)), DVD (Digital Versatile Disk) (including DVD-ROM, DVD-R, DVD-RW, DVD-RAM (Random Access Memory), DVD-Audio), and other optical disk drives , MFD, MO, navigation system and music represented by mobile personal computer, video or Information devices, mobile phones and facsimile parts for communication equipment represented, parts for electrical equipment, and a component for electronic devices.

Other uses of the molded products include gasoline tanks, fuel pump modules, valves, fuel-related parts such as gasoline tank flanges, door locks, door handles, window regulators, and speaker grills. These include parts around doors, slip rings for seat belts, press buttons, through anchors, parts around seat belts represented by tongues, combination switch parts, switches and clips.
In addition, as other uses of the above molded products, mechanical parts such as mechanical pencil nibs and mechanical pencil cores, wash basins and drain outlets, drain plug opening / closing mechanism parts, vending machine opening / closing part locking mechanism and product discharge Mechanical parts, cord stoppers for clothing, adjusters and buttons, nozzles for sprinkling and sprinkling hose connection joints, building supplies that support stair railings and flooring materials, disposable cameras, toys, fasteners, chains, conveyors, buckles, Preferable examples include industrial parts such as sports equipment, vending machines, furniture, musical instruments, and housing equipment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to the Example mentioned later.

First, components and evaluation methods used in Examples and Comparative Examples described later are shown below.
〔component〕
((A) polyoxymethylene resin)
A twin-screw paddle type continuous polymerization machine with a jacket through which a heat medium can pass was adjusted to 80 ° C.
Boron trifluoride di-n-butyl etherate dissolved in cyclohexane as a polymerization catalyst, 40 mol / hour of trioxane containing 4 ppm of water and formic acid in combination, 40 mol / hour at the same time, 1,3-dioxolane as cyclic formal 5 × 10 ⁻⁵ mole per mole of trioxane, 1 × 10 ⁵ moles of hydroxylated hydrogenated polybutadiene (Mn = 2330) represented by the following formula (6) as a chain transfer agent per mole of trioxane Polymerization was carried out by continuously supplying the polymerizer in an amount of ^-3 mol.
The polymer discharged from the polymerization machine was put into a 1% aqueous solution of triethylamine to completely deactivate the polymerization catalyst, and then the polymer was filtered and washed.
As a quaternary ammonium compound, triethyl (2-hydroxyethyl) ammonium formate is added to 1 part by mass of the crude polyoxymethylene copolymer after filtration and washing so that the amount of nitrogen is 20 ppm by mass. They were mixed uniformly and then dried at 120 ° C.
This obtained (A) polyoxymethylene resin which is a block copolymer of following formula (7).
The flexural modulus of the resulting block copolymer (A) polyoxymethylene resin is 2550 MPa, the melt flow rate is 9.3 g / 10 min (ASTM D-1238-57T), and the number average molecular weight is 52,000.
In this example, the flexural modulus was measured based on ISO178, and the number average molecular weight was calculated in terms of PMMA (polymethyl methacrylate) using gel permeation chromatography (GPC).

((B) Styrenic elastomer)
(B-1) Styrene-polyethylene-butylene-styrene copolymer (trade name “Tuftec H1221”, manufactured by Asahi Kasei Corporation, tan δ-33 ° C., styrene content 13% by mass)
(B-2) Styrene-polyethylene-butylene-styrene copolymer (trade name “Tuftec M1913”, manufactured by Asahi Kasei Corporation, tan δ-45 ° C., styrene content 30% by mass)
(B-3) Styrene-hydrogenated vinyl polyisoprene-styrene copolymer (trade name “HIBLER 7311”, manufactured by Kuraray Co., Ltd., tan δ-17 ° C., styrene content 12% by mass)
(B-4) Styrene-hydrogenated vinyl polyisoprene-styrene copolymer (trade name “HIBLER 7125”, manufactured by Kuraray Co., Ltd., tan δ−5 ° C., styrene content 20% by mass)
(B-5) Hydrogenated styrene / butadiene copolymer (trade name “SOE L606”, manufactured by Asahi Kasei Kogyo Co., Ltd., tan δ-13 ° C., styrene content 40% by mass or more)
(B-6) Styrene-polyethylene-butylene-styrene copolymer (trade name “Tuftec H1041”, manufactured by Asahi Kasei Corporation, tan δ-45 ° C., styrene amount 32% by mass)
The main dispersion peak temperatures of tan δ in the viscoelastic spectra of (B-1) to (B-6) were measured as follows.
First, a sheet-like sample for measurement having a width of 10 mm and a length of 35 mm was set in a twist type geometry of a rheometer device (trade name “ARES”, manufactured by TI Instruments Inc.).
Next, the effective measurement length was set to 25 mm, the strain was set to 0.5%, the frequency was set to 1 Hz, and the temperature was increased from −80 ° C. to 80 ° C. at a rate of temperature increase of 3 ° C./min to obtain a viscoelastic spectrum.
The main dispersion peak temperature of tan δ in the obtained viscoelastic spectrum was determined from a peak detected by automatic measurement of predetermined software (trade name “RSI Orchestrator”, manufactured by TI Instruments Inc.).
The amount of styrene was obtained by a method described in (Y. Tanaka, et al., RUBBER CHEMISTRY and TECHNOLOGY 54, 685 (1981) using a nuclear magnetic resonance apparatus (NMR).

〔Evaluation method〕
(1) Evaluation of mechanical properties After pellets obtained in Examples and Comparative Examples were dried at 80 ° C. for 3 hours, a 5-ounce molding machine (manufactured by Toshiba Machine Co., Ltd., trade name “ IS-100GN "), an ISO dumbbell test piece for evaluating physical properties was molded under conditions of a mold temperature of 90 ° C, an injection time of 35 seconds, and a cooling time of 15 seconds.
The following tests were performed on this test piece.
(I) Tensile elongation: measured based on ISO 527-1 & -2.
(Ii) Charpy impact strength; measured based on ISO 179 / 1eA.

(2) Dispersion average particle diameter (1) Using a test piece similar to that used for the mechanical property evaluation, the thickness of the surface layer portion is 0.3 mm square in the direction perpendicular to the flow during molding. The dispersion average particle diameter (μm) of the styrene-based elastomer was determined by a method of cutting into an ultra-thin 80 nm film and observing with a transmission electron microscope (H-7500, manufactured by Hitachi, Ltd.).

[Example 1]
50 parts by mass of the component (A), 50 parts by mass of the component (B-1), and triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) as a stabilizer. Propionate] 0.3 parts by mass, 0.05 parts by mass of polyamide 66, and 0.13 parts by mass of calcium stearate were uniformly mixed with a blender to obtain a mixture.
Thereafter, the mixture was supplied to the top of a 26 mmφ twin screw extruder (trade name “TEM-26SS” manufactured by Toshiba Machine Co., Ltd.) with L / D = 48 set to 200 ° C. using a weight type feeder. They were melt-kneaded under the conditions of a screw rotation speed of 120 rpm and an extrusion speed of 11 kg / hour to obtain a resin composition.
The extruded resin composition was pelletized with a strand cutter.
Table 1 shows the evaluation results of (1) mechanical property evaluation and (2) dispersion average particle diameter.

[Example 2]
50 parts by mass of the component (A) and 50 parts by mass of the component (B-1) were uniformly mixed with a blender to obtain a mixture, and then the mixture was set to 200 ° C. L / D = 48 Of 26mmφ twin screw extruder (manufactured by Toshiba Machine Co., Ltd., trade name “TEM-26SS”) using a weight type feeder, screw rotation speed 120rpm, extrusion speed 11kg / hour Melt kneading was performed to obtain a resin composition.
The extruded resin composition was pelletized with a strand cutter.
Table 1 shows the evaluation results of (1) mechanical property evaluation and (2) dispersion average particle diameter.

[Examples 3 to 6]
The component (B) and the composition ratio (unit: parts by mass, the same applies hereinafter) were changed as shown in Table 1 below to obtain a resin composition.
Other conditions were the same as in Example 1 to obtain pellets.
Table 1 shows the evaluation results of (1) mechanical property evaluation and (2) dispersion average particle diameter.

[Comparative Examples 1-3]
The component (B) and the composition ratio (unit: parts by mass, the same applies hereinafter) were changed as shown in Table 1 below to obtain a resin composition.
Other conditions were the same as in Example 1 to obtain pellets.
Table 1 shows the evaluation results of (1) mechanical property evaluation and (2) dispersion average particle diameter.

As shown in Table 1, it was found that all of the polyoxymethylene resin compositions of Examples 1 to 6 had good mechanical properties of the molded bodies and were added with flexibility.
It was also found that the dispersed particle size of the styrene elastomer was fine and had excellent frictional wear characteristics.

The polyoxymethylene resin composition of the present invention is a mechanical component (for example, gear, cam, slider, lever, arm, clutch, joint, shaft, bearing, key stem and key) obtained by molding, cutting, or molding / cutting. At least one member selected from the group consisting of the top), at least one member selected from the group consisting of the resin component of the outsert chassis, the chassis, the tray and the side plate, and can be used for the following applications.
(1) Parts used for OA equipment represented by printers and copiers, (2) Parts used for video equipment represented by VTRs and video movies, (3) Cassette players, LD, MD, CD (including CD-ROM, CD-R, CD-RW), DVD (including DVD-ROM, DVD-R, DVD-RAM, DVD-Audio), music, video represented by navigation systems and mobile computers, or Parts used for information equipment, (4) Parts used for communication equipment represented by mobile phones and facsimiles, (5) Clips, through anchors, tongues, fuel tanks, fuel used for automobile interior and exterior parts Parts used for the tank and its peripheral parts, and (6) disposable cameras, toys, fasteners, conveyors, buckles And the parts used in industrial goods represented by housing equipment, there is a APPLICABILITY industry.

Claims (4)

(A) Polyoxymethylene resin: 100 parts by mass;
(B) has a main dispersion peak temperature of tan δ obtained by viscoelasticity measurement at −10 ° C. or less,
Styrenic elastomer having an amount of styrene obtained by nuclear magnetic resonance (NMR) measurement of 30% by mass or less: 1 to 100 parts by mass;
Containing ,
A polyoxymethylene resin composition in which the styrenic elastomer (B) is dispersed with a dispersion average particle size of 10 μm or less . The polyoxymethylene resin composition according to claim 1, wherein the component (A) has a melt flow rate (measured under the conditions of ASTM-D1238-57T) of 1.0 to 80 g / 10 minutes. The component (A) has a number average molecular weight of 10,000 to 50,000 represented by the following general formula (1).
The polyoxymethylene resin composition according to claim 1, comprising 0 polyoxymethylene block copolymer.
HR ³ —O— (CR ¹ ₂ ) _k —R ⁴ — (CR ¹ ₂ ) _k —O—R ³ —H (1)
(In General Formula (1), each R ¹ independently represents a chemical species selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aryl group, and is the same as each other. Can be different or different,
k shows the integer of 2-6 each independently.
R ³ represents a block having a plurality of oxymethylene units represented by the following general formula (2a) and oxyhydrocarbon units represented by the following general formula (2b), wherein the oxymethylene unit and the oxyhydrocarbon unit Are present at random, and the total content of the oxymethylene unit and the oxyhydrocarbon unit is 100 mol%, and the content of the oxymethylene unit is 95
-99.9 mol%, the content of the oxyhydrocarbon unit is 0.1-5 mol%, and the average number average molecular weight of the two R ³ is 5000-250,000.
In the following general formula (2b), each R ² independently represents a chemical species selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aryl group, and is the same as each other. It may be present or different, and j represents an integer of 2 to 6.
R ⁴ represents a block having a plurality of ethylene units represented by the following general formula (3a) and n-butylene units represented by the following general formula (3b), and the ethylene unit and the n-butylene unit are: Relative to each other or in a block, the ethylene unit content is 2 to 98 mol%, and the total amount of the ethylene unit and the n-butylene unit is 100 mol%.
-Content of a butylene unit is 2-98 mol%. Further, R ⁴ has a number average molecular weight of 500 to 10,000, it may have the following unsaturated bond iodine value 20g-I ₂ / 100g. )
— (CH ₂ O) — (2a)
-((CR ² ₂ ) _j -O)-(2b)
_{- (CH 2 CH 2) -} ··· (3a)
_{- (CH 2 CH 2 CH 2} CH 2) - ··· (3b)   The molded object shape | molded using the polyoxymethylene resin composition as described in any one of Claims 1 thru | or 3.