JP7084822B2 - Polyacetal resin composition and molded product - Google Patents

Description

The present invention relates to a polyacetal resin composition and a molded product comprising the polyacetal resin composition.

Since polyacetal resin has excellent mechanical strength, chemical resistance, slidability, etc., it is widely used as a typical engineering plastic mainly for molded bodies such as electrical and electronic parts, automobile parts, and mechanical parts of other precision equipment. There is. In particular, for parts that require rigidity, a method of blending an inorganic filler with a polyacetal resin has been used for a long time as a general method. As the inorganic filler, in addition to the fibrous inorganic filler such as glass fiber, carbon fiber and wollastonite, a plate-shaped or granular inorganic filler such as talc and calcium carbonate is blended to improve rigidity and improve shrinkage anisotropy. Techniques for reducing the amount are disclosed (see, for example, Patent Document 1).

As an example of a technique for applying calcium carbonate to a polyacetal resin, calcium carbonate is added to the polyacetal resin for the purpose of improving the stability of the resin during molding, suppressing the coloring of the molded product, and suppressing contamination of the mold. And a technique for blending a fatty acid and a nitrogen compound are disclosed (see, for example, Patent Document 2).

Further, a technique for blending a polyacetal resin, a polylactic acid resin, and a reinforcing material for improving mechanical properties, reducing warpage of a molded product, and improving the appearance of a molded product is disclosed (for example, Patent Document 3).

International Publication No. 2005/071011 Japanese Unexamined Patent Publication No. 2013-124364 Japanese Patent Application Laid-Open No. 2003-286402

However, in the system containing calcium carbonate, while the rigidity is improved, even higher sliding characteristics are required.

Further, also in the technique disclosed in the examples of Patent Document 3, the rigidity is improved, but the toughness and heat resistance are lowered, so that it is required to suppress these declines. Further, even higher sliding characteristics are required.

Therefore, in the market, there is a need for a polyacetal resin material whose rigidity is increased by an inorganic filler and which has higher slidability while maintaining strength, toughness, and heat resistance.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyacetal resin composition having higher rigidity and slidability while maintaining strength, toughness, and heat resistance.

The present inventors have repeated studies to solve the above problems, and as a result, have found that a resin composition containing a specific amount of polyacetal resin, polylactic acid resin and calcium carbonate can solve the above problems, and completed the present invention. I came to do.

That is, the present invention is as follows.
[1]
(A-1) 50 to 99 parts by mass of polyacetal resin, and (A-2) 100 parts by mass of component (A) consisting of 1 to 50 parts by mass of polylactic acid resin.
(B) 10 to 65 parts by mass of calcium carbonate and
A polyacetal resin composition comprising.
[2]
The above [1], wherein the ratio ((A-1) / (B)) of the content of the (A-1) polyacetal resin to the content of the (B) calcium carbonate is 4 or less on a mass basis. Polyacetal resin composition.
[3]
The ratio ((A-1) / (B)) of the content of the (A-1) polyacetal resin to the content of the (B) calcium carbonate is 2 or more on a mass basis, the above [1] or [ 2] The polyacetal resin composition according to.
[4]
The polyacetal resin composition according to any one of the above [1] to [3], further comprising (C) a fatty acid in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the component (A).
[5]
The polyacetal resin composition according to any one of the above [1] to [4], further comprising (D) a nitrogen compound in an amount of 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the component (A). ..
[6]
The above-mentioned [4] or [5], wherein the ratio ((C) / (D)) of the content of the (C) fatty acid to the content of the (D) nitrogen compound is 8 to 30 on a mass basis. Polyacetal resin composition.
[7]
The polyacetal resin composition according to any one of [1] to [6] above, wherein the calcium carbonate (B) is a light calcium carbonate having a number average particle diameter of 1 μm or less.
[8]
The polyacetal resin composition according to any one of [4] to [7] above, wherein the fatty acid (C) is a saturated fatty acid having a total number of carbon atoms in the molecule of 12 or more and less than 30.
[9]
The polyacetal resin composition according to any one of [4] to [8], wherein the (C) fatty acid is contained in an amount of 2 to 6 parts by mass with respect to 100 parts by mass of the calcium carbonate (B).
[10]
The polyacetal resin composition according to any one of [1] to [9] above, wherein the nitrogen compound (D) is melamine or a reaction product of melamine and formaldehyde.
[11]
A molded product comprising the polyacetal resin composition according to any one of [1] to [10].

According to the present invention, it is possible to provide a polyacetal resin composition having even higher rigidity and slidability while maintaining the strength, toughness and heat resistance of the polyacetal resin.

Hereinafter, embodiments for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.
In the embodiment of the present invention, A (numerical value) to B (numerical value) mean A or more and B or less.

The polyacetal resin composition of the present embodiment (hereinafter, also simply referred to as “resin composition”) is (A-1) 50 to 99 parts by mass of polyacetal resin and (A-2) 1 to 50 parts by mass of polylactic acid resin. It is a polyacetal resin composition containing 10 to 65 parts by mass of (B) calcium carbonate with respect to 100 parts by mass of the component (A) comprising.

Examples of the (A-1) polyacetal resin according to the present embodiment include polyacetal homopolymers and polyacetal copolymers, and known ones may be used.

The polyacetal homopolymer is obtained by homopolymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) and a tetramer (tetraoxane) thereof. Therefore, polyacetal homopolymers consist substantially of oximethylene units.

Polyacetal copolymers are formaldehyde monomers or formaldehyde cyclic oligomers such as triomers (trioxane) and tetramers (tetraoxane) thereof, and ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, 1,4-. It is obtained by copolymerizing with cyclic ether or cyclic formal such as glycol such as butanediol formal or cyclic formal of diglycol. Further, as the polyacetal copolymer, a polyacetal copolymer having a branch obtained by copolymerizing a formaldehyde monomer and / or a cyclic oligomer of formaldehyde with a monofunctional glycidyl ether, and a polyfunctional glycidyl ether are copolymerized. A polyacetal copolymer having a obtained crosslinked structure can also be used.

Further, the (A-1) polyacetal resin is polymerized with 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, for example, polyalkylene glycol. It may be a polyacetal homopolymer having a obtained blocking component.

Similarly, the (A-1) polyacetal resin is a formaldehyde monomer or a trimer thereof (trioxane) in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, for example, hydrogenated polybutadiene glycol. It may be a polyacetal copolymer having a block component obtained by copolymerizing a cyclic oligomer of formaldehyde such as a tetramer (tetraoxane) with a cyclic ether or cyclic formal.

As described above, as the (A-1) polyacetal resin according to the present embodiment, either a polyacetal homopolymer or a polyacetal copolymer can be used. Moreover, these (A-1) polyacetal resins are used individually by 1 type or in combination of 2 or more types. In this case, the (A-1) polyacetal resin preferably contains 50% by mass or more of the polyacetal copolymer, more preferably 80% by mass or more, and substantially all (95% by mass or more) are polyacetal copolymers. Is most preferable.
The percentage here is based on the total amount of the (A-1) polyacetal resin set to 100% by mass.

The method for obtaining a polyacetal copolymer will be described in detail below.

When a polyacetal copolymer is obtained using trioxane, the commonomer such as 1,3-dioxolane is generally 0.1 to 60 mol%, preferably 0.1 to 20 mol%, more preferably 0.1 to 20 mol% with respect to 100 mol% of trioxane. Is used in an amount of 0.13 to 10 mol%. In the present embodiment, the preferred melting point of the polyacetal copolymer is 162 ° C to 173 ° C, more preferably 167 ° C to 173 ° C, still more preferably 167 ° C to 171 ° C. The 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 100 mol% of trioxane.

As the polymerization catalyst used for the polymerization of the polyacetal copolymer, a cationically active catalyst such as Lewis acid, a protonic acid and an ester thereof or an anhydrate is preferable. Examples of the Lewis acid include halides of boric acid, tin, titanium, phosphorus, arsenic and antimony, and more specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, and the like. Examples thereof include phosphorus pentachloride, antimony pentafluoride and complex compounds or salts thereof. Specific examples of the protonic acid, its ester or anhydrate include perchloric acid, trifluoromethanesulfonic acid, perchlorolic acid-quaternary butyl ester, acetylparklorate 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, and specifically, trifluoride is preferable. Boron diethyl ether and boron trifluoride di-n-butyl ether are preferred examples.

Further, when obtaining the polyacetal copolymer, a polymerization chain agent (chain transfer agent) such as methylal may be appropriately used in addition to the polymerization catalyst. Further, when using methylal, it is preferable that the content of water is 100 ppm or less and the amount of methanol contained is 1% by mass or less, and more preferably, the amount of water contained is 50 ppm or less and the amount of methanol contained is 0.7% by mass or less. ..

Polyacetal copolymers can be prepared by conventionally known methods, for example, US Pat. No. 3,027,352, No. 3803094, German Patent Invention No. 1161421, No. 1495228, No. 1720358, etc. The polymerization can be carried out by the methods described in Japanese Patent Application Laid-Open No. 3018898, Japanese Patent Application Laid-Open No. 58-98322 and Japanese Patent Application Laid-Open No. 7-70267. Since the polyacetal copolymer obtained by the above polymerization has a thermally unstable terminal portion (-(OCH ₂ ) _n -OH group; hereinafter referred to as "unstable terminal portion"), it is practical as it is. It is difficult to provide to. Therefore, it is preferable to carry out the decomposition / removal treatment of the unstable end portion, and specifically, it is preferable to carry out the decomposition / removal treatment of the specific unstable end portion shown below. That is, in the decomposition removal treatment of the specific unstable end portion, in the presence of at least one quaternary ammonium compound represented by the following general formula (1), at a temperature equal to or higher than the melting point of the polyacetal copolymer and lower than 260 ° C. , The polyacetal copolymer is heat-treated in a molten state.
[R ¹ R ² R ³ R ⁴ N ⁺ ] _n X ^n- (1)
Here, in the formula (1), R ¹ , R ² , R ³ and R ⁴ are independently substituted or unsubstituted alkyl groups having 1 to 30 carbon atoms; and aryl groups 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 carbon atoms is substituted with an aryl group having 6 to 20 carbon atoms; or at least one in an aryl group having 6 to 20 carbon atoms. Represents an alkylaryl group in which the hydrogen atom of 1 to 30 is substituted with a substituted or unsubstituted alkyl group, and the substituted or unsubstituted alkyl group is linear, branched, or cyclic. The substituent in the substituted alkyl group is preferably a halogen atom, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, or an amide group. Further, in the above-mentioned unsubstituted alkyl group, aryl group, aralkyl group and alkylaryl group, the hydrogen atom may be substituted with a halogen atom. n represents an integer of 1 to 3. X indicates a hydroxyl group, a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than hydrogen halide, an oxo acid, an inorganic thioic acid, or an acid residue of an organic thioic acid having 1 to 20 carbon atoms.

The quaternary ammonium compound is not particularly limited as long as it is represented by the above general formula (1), but from the viewpoint of more effectively and surely exerting the above effect according to the present invention, R ¹ in the general formula (1). It is preferable that R ² , R ³ and R ⁴ are independently an alkyl group having 1 to 5 carbon atoms or a hydroxyalkyl group having 2 to 4 carbon atoms. Specifically, hydroxides such as tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetra-n-butylammonium, cetyltrimethylammonium and tetradecyltrimethylammonium; Hydrochloride; those ammonium sulfates, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodine acid, silicic acid, perchloric acid, chloric acid, hypochlorite, chlorosulfuric acid, amidosulfate, disulfate. , Oxoates such as tripolyphosphoric acid; those ammonium thioates such as thiosulfate; those ammonium formic acid, acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, caproic acid, capric acid, capric acid, Examples thereof include carboxylates such as benzoic acid and oxalic acid. Among these, ammonium hydroxide (OH- ⁾ , sulfuric acid (HSO _{4-, SO 4 2-} ⁾ , carbonic acid (HCO _3- , CO ₃ ^2- ), boric acid ₍ B (OH) ^{4- ) .} , And salts of carboxylic acids are preferred. Of the carboxylic acids, formic acid, acetic acid and propionic acid are particularly preferred. The quaternary ammonium compound may be used alone or in combination of two or more. Further, in addition to the above-mentioned quaternary ammonium compound, amines such as ammonia and triethylamine, which are known decomposing agents at the unstable terminal portion, may be used in combination.

The amount of the quaternary ammonium compound used is preferably 0.05 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. It is ~ 50% by mass, more preferably 1 to 30% by mass.
P × 14 / Q (2)
Here, in the formula (2), P indicates the concentration (mass ppm) of the quaternary ammonium compound with respect to the polyacetal copolymer, 14 is the atomic weight of nitrogen, and Q indicates the molecular weight of the quaternary ammonium compound.

When the amount of the quaternary ammonium compound used is 0.05 mass ppm or more, it becomes easy to suppress the decrease in the decomposition / removal rate of the unstable end portion, and when it is 50 mass ppm or less, after the decomposition / removal of the unstable end portion is performed. It becomes easy to suppress the deterioration of the color tone of the polyacetal copolymer.

The unstable end portion of the (A-1) polyacetal resin according to the present embodiment is preferably decomposed and removed by heat treatment in a state where the polyacetal copolymer is melted at a temperature of melting point or higher and 260 ° C. or lower. The apparatus used for this decomposition removal treatment is not particularly limited, but an extruder, a kneader, or the like is suitable. Formaldehyde generated by decomposition is usually removed under reduced pressure. The method for allowing the quaternary ammonium compound to be present in the polyacetal copolymer is not particularly limited, and examples thereof include a method of adding the quaternary ammonium compound as an aqueous solution in the step of deactivating the polymerization catalyst and a method of spraying the polyacetal copolymer powder produced by the polymerization. Regardless of which method is used, it is sufficient that the quaternary ammonium compound is present in the copolymer in the step of heat-treating the polyacetal copolymer. For example, the quaternary ammonium compound may be injected into an extruder in which the polyacetal copolymer is melt-kneaded and extruded. Alternatively, when a filler or pigment is blended into the polyacetal copolymer using the extruder or the like, the quaternary ammonium compound is first adhered to the resin pellet containing the polyacetal copolymer, and then unstable when the filler or pigment is blended. The end portion may be decomposed and removed.

The decomposition and removal treatment of the unstable terminal portion can be performed after deactivating the polymerization catalyst coexisting with the polyacetal copolymer obtained by the polymerization, or can be performed 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 (for example, triethylamine). If the polymerization catalyst is not deactivated, the copolymer is heated in an inert gas atmosphere at a temperature below the melting point of the polyacetal copolymer, the polymerization catalyst is reduced by volatilization, and then the unstable end portion is decomposed and removed. Doing so is also an effective method.

By the decomposition and removal treatment of the unstable end portion as described above, it is possible to obtain a polyacetal copolymer having very excellent thermal stability with almost no unstable end portion.

The melt flow rate (hereinafter, also referred to as “MFR”) of the polyacetal resin (A-1) is preferably 0.1 to 100 g / 10 minutes, more preferably 1 to 50 g / 10 minutes, and 3 to 3 to. It is more preferably 30 g / 10 minutes, and even more preferably 10 to 20 g / 10 minutes.
In addition, in this specification, MFR is a value measured at 190 degreeC in accordance with ISO 1131-1: 2011 (JIS K7210-1: 2014).

The (A-2) polylactic acid resin according to the present embodiment is polymerized with a lactic acid monomer as a main component and contains more than 50 mol% of structural units derived from lactic acid. For example, poly L-lactic acid whose structural unit is L-lactic acid, poly D-lactic acid whose structural unit is D-lactic acid, poly DL-lactic acid whose structural units are L-lactic acid and D-lactic acid, and a mixture thereof. Can be a polymer containing lactic acid as a main component.

The composition of the optical isomer in the (A-2) polylactic acid resin is that the molar ratio is D-lactic acid: L-lactic acid = 100: 0 to 85:15 or 0: 100 to 15:85. It is more preferably 100: 0 to 90:10 or 0: 100 to 10:90, and even more preferably 100: 0 to 95: 5 or 0: 100 to 5:95. It is also possible to blend other polylactic acids having different composition ratios of D-lactic acid and L-lactic acid.

When the D / L ratio is 0/100 or 100/0, it is preferable because it exhibits extremely high crystallinity, has a high melting point, and is excellent in heat resistance and mechanical properties.

In the present invention, in order to more easily adjust the D / L ratio of (A-2) polylactic acid resin, it is also possible to blend polylactic acid resins having different copolymerization ratios of D-lactic acid and L-lactic acid. Is. In this case, the average value of the D / L ratios of the plurality of polylactic acid resins may be within the above range.

Further, the (A-2) polylactic acid resin is a polymer of D-lactic acid and / or L-lactic acid and at least one selected from α-hydroxycarboxylic acid, aliphatic diol, and aliphatic dicarboxylic acid. It may contain a small amount of chain extender residue.

Examples of the α-hydroxycarboxylic acid include optical isomers of lactic acid (referring to D-lactic acid for L-lactic acid and L-lactic acid for D-lactic acid), glycolic acid, 3-hydroxyfatty acid, and 4 Bifunctional aliphatic hydroxy-carboxylic acid such as -hydroxybuty acid, 2-hydroxyn-buty acid, 2-hydroxy-3,3-dimethylbuty acid, 2-hirodoxy 3-methylbuty acid, 2-methylbuty acid, 2-hydroxycaprolactoic acid , Caprolactone, butyl lactone, valero lactone and other lactones.

Examples of the aliphatic diol include ethylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Further, examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid and dodecanedioic acid.

The copolymerization ratio of the copolymer of lactic acid and at least one selected from α-hydroxycarboxylic acid, aliphatic diol, and aliphatic dicarboxylic acid is lactic acid vs. α-hydroxycarboxylic acid, aliphatic diol, and aliphatic. The mass ratio of at least one selected from the dicarboxylic acid is preferably 95: 5 to 10:90, more preferably 90:10 to 20:80, and even more preferably 80:20 to 30:70.

(A-2) As the method for polymerizing the polylactic acid resin, any known method such as a condensation polymerization method or a ring-opening polymerization method can be adopted. For example, in the case of a condensation polymerization method, D-lactic acid, L-lactic acid, or a mixture thereof can be directly dehydrated and condensed to obtain a polylactic acid resin having an arbitrary composition. Further, in the ring-opening polymerization method, a poly having an arbitrary composition is obtained by ring-opening polymerization of lactide, which is a cyclic dimer of lactic acid, in the presence of a predetermined catalyst while using a polymerization modifier or the like, if necessary. Lactide resin can be obtained. The lactide includes DL-lactide, which is a dimer of L-lactic acid, and by mixing and polymerizing these as necessary, a polylactic acid resin having an arbitrary composition and crystallinity can be obtained. .. Furthermore, a small amount of chain extender, for example, a diisocyanate compound, a diepoxy compound, an acid anhydride, an acid chloride, or the like may be used for the purpose of increasing the molecular weight.

The mass average molecular weight of the (A-2) polylactic acid resin is preferably 20,000 or more, more preferably 50,000 or more, still more preferably 100,000 or more, and preferably 400,000 or less, more preferably. Is 350,000 or less, more preferably 300,000 or less. When the mass average molecular weight is 20,000 or more, appropriate strength and toughness tend to be obtained. On the other hand, when the mass average molecular weight is 400,000 or less, the melt viscosity is not too high, so that an appropriate melt processability tends to be obtained, which is preferable from the viewpoint of manufacturing and productivity improvement. The mass average molecular weight can generally be measured by GPC (gel permeation chromatograph) or a viscosity method.

In the polyacetal resin composition of the present embodiment, the (A-1) polyacetal resin is 50 to 99 with respect to 100 parts by mass of the (A) component composed of (A-1) polyacetal resin and (A-2) polylactic acid resin. It is a part by mass, and the (A-2) polylactic acid resin is the balance, that is, 1 to 50 parts by mass.
The lower limit of the mass part of the (A-1) polyacetal resin is 50 parts by mass with respect to 100 parts by mass of the (A) component composed of the (A-1) polyacetal resin and the (A-2) polylactic acid resin. The heat resistance is improved by increasing the amount to a mass part or more. It is preferably 60 parts by mass, more preferably 70 parts by mass, and even more preferably 75 parts by mass.
On the other hand, the upper limit of the mass part of the (A-1) polyacetal resin is 99 parts by mass with respect to 100 parts by mass of the (A) component composed of the (A-1) polyacetal resin and the (A-2) polylactic acid resin. By setting the content to 99 parts by mass or less, the rigidity (flexural modulus) and slidability can be improved. It is preferably 97 parts by mass, more preferably 95 parts by mass, and even more preferably 90 parts by mass.

Calcium carbonate (B) according to the present embodiment refers to a component represented by the composition formula of CaCO ₃ , which may contain impurities, and is obtained by crushing and classifying a natural calcium carbonate to an appropriate size as it is, or light carbonic acid. Also included are artificially synthesized calcium carbonate, such as what is called calcium, ie precipitated calcium carbonate. Among these, artificially synthesized light calcium carbonate is suitable for the present embodiment because its particle shape is uniform and its particle size distribution is relatively sharp.

(B) Calcium carbonate is in the form of particles, but its shape is not particularly limited. Specific examples of the shape include a spherical shape, a cubic shape, a spinning shape, a flaky shape, an amorphous shape, and the like.
Of these, a cube is preferable from the viewpoint of reducing anisotropy and improving mechanical strength when a molded product, particularly an injection molded product, is used, and the average major axis (L) and average minor axis (D) of the particles are used. It is more preferable that the aspect ratio (L / D), which is the ratio of the above, is 3 or less. The crystal morphology may be any of the generally known calcite type, aragonite type and patelite type, and among these, interfacial adhesion with the polyacetal resin and mechanical of the polyacetal resin composition. From the viewpoint of improving the balance of physical properties, the calcite type is preferable.

As the artificially synthesized (B) calcium carbonate, those called colloidal calcium carbonate, light calcium carbonate or active calcium carbonate are preferable. Among these, those produced by reacting carbon dioxide with slurry-like calcium hydroxide are particularly preferable.

The number average particle size of (B) calcium carbonate before blending into the resin composition is not particularly limited, but the upper limit of the number average particle size is preferably 1 μm, more preferably 800 nm, and further. It is preferably 700 nm, most preferably 500 nm. In order not to reduce the whiteness of the molded piece when it is not colored, it is recommended to set the upper limit to 1 μm or less. The lower limit is not particularly limited, but is preferably 50 nm from the viewpoint of ease of supply to the extruder. From the viewpoint of suppressing the soaring during the mixing operation, the lower limit is more preferably 100 nm.

Further, the number average particle size of (B) calcium carbonate in the resin composition is not particularly limited, but the upper limit of the number average particle size is preferably 1 μm, more preferably 800 nm, and further preferably. It is 700 nm. From the viewpoint of suppressing deterioration of the mechanical properties (particularly tensile elongation and impact strength) of the resin composition, the upper limit is preferably 1 μm. The lower limit of the number average particle size of (B) calcium carbonate in the resin composition is not particularly limited, but is preferably 100 nm or more in order to suppress a decrease in fluidity of the resin composition.

The number average particle size here means that (B) calcium carbonate is dispersed in purified water in an amount of 0.01 to 0.2% by volume, a known surfactant is added, and a laser is applied while applying ultrasonic vibration. It is a 50% median diameter measured by a diffraction / scattering type particle size meter. At this time, the refractive index of calcium carbonate is 1.59 to 1.60, and the refractive index of the dispersion medium (water) is 1.33. Specific examples of commercially available laser diffraction / scattering particle size meters include SALD-2000J manufactured by Shimadzu Corporation and LMS-2000e manufactured by Seishin Corporation.

Further, since it is not easy to confirm the number average particle size of (B) calcium carbonate in the resin composition as it is, in the present embodiment, the residue obtained by incinerating the resin composition or the molded body in an electric furnace or the like is measured. It can be used as a target and used as a substitute. A specific incineration method is to incinerate a resin composition (for example, pellets) or a molded product at 450 ° C. for 2 hours in an oxygen-presence atmosphere. The number average particle size of the residue can be obtained by similarly measuring using the above-mentioned laser diffraction scattering type particle size meter.

The calcium carbonate (B) according to the present embodiment is desirable from the viewpoint that the calcium carbonate which has not been surface-treated can maintain higher dimensional stability. The term "surface treatment" as used herein means that at least one of a known surface treatment agent, adhesive or complexing agent, and anti-aggregation agent is added for the purpose of preventing the aggregation of particles in the calcium carbonate manufacturing process. As a result, it means that the surface of calcium carbonate is covered with the substance.

Here, the surfactants, adhesives or complexing agents, and antiaggregating agents are, for example, 232 to "Elucidation of dispersion / aggregation and applied technology, 1992" (supervised by Fumio Kitahara, published by Techno System Co., Ltd.). Examples thereof include anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants as described on page 237. Further, silane-based coupling agents such as aminosilane and epoxysilane, titanate-based coupling agents, fatty acids (saturated fatty acids and unsaturated fatty acids), aliphatic carboxylic acids, resin acids and metal soaps are exemplified.

In the present embodiment, (B) calcium carbonate may be used alone having a specific particle shape, particle size, and crystal form, and at least one of the particle shape, particle size, and crystal form is different. 2 Calcium carbonate of more than one kind may be used in combination.

In the polyacetal resin composition of the present embodiment, the lower limit of the blending amount of (B) calcium carbonate is based on 100 parts by mass of the (A) component composed of (A-1) polyacetal resin and (A-2) polylactic acid resin. It is 10 parts by mass or more. If it is less than 10 parts by mass, the improvement of rigidity is not sufficient.
(B) The lower limit of the blending amount of calcium carbonate is preferably 15 parts by mass, more preferably 20 parts by mass, and further preferably 25 parts by mass. Further, the upper limit of the blending amount of (B) calcium carbonate is 65 parts by mass with respect to 100 parts by mass of the component (A). If it exceeds 65 parts by mass, the fluidity decreases and the melt processability becomes insufficient. It is preferably 50 parts by mass, more preferably 40 parts by mass, and even more preferably 35 parts by mass.

In the polyacetal resin composition of the present embodiment, the content ratio ((A-1) / (B)) of the (A-1) polyacetal resin to (B) calcium carbonate is preferably 4 or less on a mass basis. It is more preferably 3.5 or less, and even more preferably 3.0 or less. When the content ratio ((A-1) / (B)) of the (A-1) polyacetal resin to (B) calcium carbonate is within the above range, the rigidity can be further improved.

In the polyacetal resin composition of the present embodiment, the content ratio ((A-1) / (B)) of the (A-1) polyacetal resin to (B) calcium carbonate is preferably 2 or more on a mass basis. It is more preferably 2.2 or more, and even more preferably 2.4 or more. When the content ratio ((A-1) / (B)) of the (A-1) polyacetal resin to (B) calcium carbonate is within the above range, the slidability can be further improved.

The resin composition of the present embodiment may further contain (C) fatty acid as an optional component. The fatty acid (C) according to the present embodiment, which is an optional component, has a structure in which a carboxyl group is bonded to a hydrocarbon group. Examples thereof include saturated fatty acids having only carbon-carbon single bonds (carbon-carbon saturated bonds) and unsaturated fatty acids having carbon-carbon double bonds and triple bonds (carbon-carbon unsaturated bonds). Of these, saturated fatty acids having high heat aging properties are preferable.

The saturated fatty acid that can be used as the (C) fatty acid of the present embodiment is a fatty acid having a structure in which a carboxyl group is bonded to a linear or branched aliphatic hydrocarbon group that does not have a carbon-carbon unsaturated bond in the molecular structure. be. Preferably, it is a saturated fatty acid having a total number of carbon atoms in the molecule (hereinafter, may be simply abbreviated as "carbon number") of 12 to 30. Specific examples of saturated fatty acids include dodecanoic acid (lauric acid), tridecic acid, tetradecanoic acid (myristic acid), pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid (margaric acid), octadecanoic acid (stearic acid), and nonadecan. Examples thereof include acid (tubercrostearic acid), icosanoic acid (arachidic acid), docosanoic acid (bechenic acid), tetradocosanoic acid (lignoseric acid), hexadokosanoic acid (serotinic acid), octadocosic acid (montanoic acid) and melicic acid. Of these, fatty acids having 14 to 22 carbon atoms are preferable. Specifically, tetradecanoic acid (myristic acid), pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid (margaric acid), octadecanoic acid (stearic acid), nonadecanic acid (tubercrostearic acid), icosanoic acid (arachidic acid). ) And docosanoic acid (bechenic acid). Furthermore, among these, tetradecanoic acid (myristic acid), octadecanoic acid (stearic acid) and docosanoic acid (behenic acid) are more preferable.

The resin composition of the present embodiment is a linear or branched aliphatic hydrocarbon having a carbon-carbon unsaturated bond in the molecular structure as long as it does not hinder the solution of the problem according to the present invention when saturated fatty acids are added. A fatty acid having a structure in which a carboxyl group is bonded to a group (hereinafter, simply referred to as “unsaturated fatty acid”) may be contained, and such a fatty acid may be contained as an impurity. Examples of unsaturated fatty acids include undecylenic acid, oleic acid, elaidic acid, setreic acid, erucic acid, brushzic acid, linoleic acid, linolenic acid, arachidonic acid and stearolic acid.

The (C) fatty acid in the present embodiment may be natural or synthesized. When fatty acids made from natural fats and oils and animal and vegetable oils are used, they may be a mixture of a plurality of fatty acids having different carbon atoms.

Further, the fatty acid (C) may be partially substituted with a functional group such as a hydroxy group. In the resin composition of the present embodiment, the content of the fatty acid substituted with the functional group is preferably less than 10 parts by mass with respect to 100 parts by mass of the total amount of (C) fatty acid.

In the present embodiment, the (C) fatty acid may be used alone or in combination of two or more having different carbon atoms. Usually, fatty acids made from natural fats and oils or animal and vegetable oils usually contain a small amount of structures having different carbon atoms, and such fatty acids may be used.

The content of the (C) fatty acid in the resin composition of the present embodiment is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the component (A). The lower limit is more preferably 0.5 parts by mass, further preferably 0.8 parts by mass, and particularly preferably 1.0 part by mass. The upper limit thereof is more preferably 3 parts by mass, further preferably 2 parts by mass, and particularly preferably 1.5 parts by mass. By setting the lower limit to 0.5 parts by mass, it is possible to suppress the occurrence of bleeding (bleed-out) on the surface of the molded body, and by setting the upper limit to 3 parts by mass, it is possible to suppress the deterioration of dimensional stability.

Further, in the resin composition of the present embodiment, the content of (C) fatty acid is within the above range, and further, it is within the range of 2 to 6 parts by mass with respect to 100 parts by mass of (B) calcium carbonate. The more preferable lower limit is 2.5 parts by mass, and the more preferable upper limit is 5.5 parts by mass. When the content of (C) fatty acid with respect to (B) 100 parts by mass of calcium carbonate is 2 parts by mass or more, mold contamination can be further suppressed, and when it is 6 parts by mass or less, it is applied to the surface of the molded body. Bleed generation (bleed out) can be further suppressed.

The resin composition of the present embodiment may further contain (D) a nitrogen compound as an optional component. Hereinafter, the (D) nitrogen compound in this embodiment will be described in detail. The nitrogen compound (D) in the present embodiment has the ability to react with formaldehyde generated during thermal processing of the polyacetal resin and capture formaldehyde. For example, a polymer-reactive nitrogen compound and a non-polymer-reactive nitrogen compound can be mentioned. Further, it excludes a high molecular weight reactive nitrogen compound, and may be a compound conventionally known as a reactive nitrogen compound having such performance.

In the present embodiment, the reactive nitrogen compound can be used not only as a formaldehyde scavenger but also for the purpose of improving the thermal stability of the resin composition during melt processing and exhibiting the dimensional stability effect during molding. .. Generally, the reactive nitrogen compound also includes a high molecular weight reactive nitrogen compound, but in the present embodiment, if it is desired to emphasize dimensional stability, it may be preferable to exclude it. The non-polymer reactive nitrogen compound preferably does not have a repeating unit, but may have one, and in that case, the number of repetitions is preferably 3 or less.

Examples of the polymer reactive nitrogen compound include a polyamide resin having an amide bond in its molecular structure. Specific examples thereof include polyamides 4, 6, polyamide 6, polyamide 6, 6, polyamide 6, 10, polyamide 6, 12, polyamide 12, and copolymers thereof.

Examples of the non-polymer reactive nitrogen compound include guanamine compounds, melamines, hydrazide compounds, and reaction products of these with formaldehyde.

Examples of the guanamine compound include an aliphatic guanamine compound, an alicyclic guanamine compound, an aromatic guanamine compound, and a heteroatom-containing guanamine compound.
Examples of aliphatic guanamine compounds are monoguanamines such as valerognamine, caproganamin, heptanoganamin, capriloganamin and stealoganamin; as well as succinoguanamine, glutaloganamin, adipoguanamine, pimero. Examples thereof include alkylene bisguanamines such as guanamine, sveloganamin, azero guanamine and sebacoganamin.
Examples of alicyclic guanamine compounds include monoguanamines such as cyclohexanecarboguanamine, norbornencarboguanamine, cyclohexenecarboguanamine and norbornancarboguanamine; as well as functional groups on their cycloalkhan residues, such as alkyl groups and hydroxys. 1 to 3 functional groups selected from the group consisting of a group, an amino group, an acetamino group, a nitrile group, a carboxy group, an alkoxycarbonyl group, a carbamoyl group, an alkoxy group, a phenyl group, a cumyl group and a hydroxyphenyl group. Examples thereof include the substituted derivatives.

Examples of aromatic guanamine compounds include benzoguanamine, a functional group on the phenyl residue of benzoguanamine, for example, an alkyl group, a hydroxy group, an amino group, an acetamino group, a nitrile group, a carboxy group, an alkoxycarbonyl group, a carbamoyl group, and an alkoxy group. , A derivative substituted with 1 to 5 of one or more functional groups selected from the group consisting of a phenyl group, a cumyl group and a hydroxyphenyl group (for example, toluguanamine, xyloganamin, phenylbenzoguanamine, hydroxybenzoguanamine, 4- (4). '-Hydroxyphenyl) benzoguanamine, nitrile benzoguanamine, 3,5-dimethyl-4-hydroxybenzoguanamine and 3,5-di-t-butyl-4-hydroxybenzoguanamine), naphthoguanamine, and naphthyl residues of naphthoguanamine. Monoguanamines such as derivatives substituted with 1 to 7 groups, eg, the above-mentioned functional groups; polyguanamines such as phthaloganamin, isophthaloganamin, terephthalologanamin, naphthalenediguanamine and biphenylenediguanamine; and phenylacet. Examples thereof include aralkyls such as guanamine, β-phenylpropioguanamine and xylylenebisguanamine, or aralkylanamins.

Examples of heteroatom-containing guanamine compounds include acetal group-containing guanamines such as 2,4-diamino-6- (3,3-dimethoxypropyl) -s-triazine; [2- (4'-6'-diamino). -S-Triazine-2'-yl) ethyl] -1,3-dioxane, and [2- (4'-6'-diamino-s-triazine-2'-yl) ethyl] -4-ethyl-4- Dioxane ring-containing guanamines such as hydroxymethyl-1,3-dioxane; tetraoxospiro ring-containing guanamines such as CTU-guanamine and CMTU-guanamine; and 1,3,5-tris [2- (4', 6', 6'. '-Diamino-s-triazine-2'-yl) ethyl] isocyanurate and 1,3,5-tris [3- (4', 6'-diamino-s-triazine-2'-yl) propyl] isocyanurate Examples thereof include guanamines containing an isocyanul ring such as.

Examples of the hydrazide compound include aliphatic or alicyclic carboxylic acid hydrazide and aromatic carboxylic acid hydrazide.

Examples of aliphatic or alicyclic carboxylic acid hydrazides include lauric acid hydrazide, palmitate hydrazide, stearate hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, eikosan diacid hydrazide, sorbic acid hydrazide and the like. Or unsaturated fatty acid hydrazide; oxyfatty acid hydrazide such as α-oxybutyric acid hydrazide, glyceric acid hydrazide; 7,11-octadecazien-1,18-dicarbohydrazide, 1,3-bis (hydrazinocarbonoethyl)- 5-Isopropylhydrantin), tris (hydrazinocarbonylethyl) isocyanurate and the like.

Examples of aromatic carboxylic acid hydrazides include 1-naphthoic acid hydrazide, 2-naphthoic acid hydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide and 2,6-naphthoic acid dihydrazide.

Among these non-polymer reactive nitrogen compounds, preferable ones are selected from the group consisting of melamine, benzoguanamine, stearate hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and reaction products of these with formaldehyde. One or more of them, more preferably melamine, and a reaction product of melamine and formaldehyde.

In the resin composition of the present embodiment, the lower limit of the content of the nitrogen compound (D) is set with respect to 100 parts by mass of the component (A) from the viewpoint of higher dimensional stability and thermal stability during melt processing. It is preferably 0.01 part by mass, more preferably 0.03 part by mass, and even more preferably 0.05 part by mass. On the other hand, from the viewpoint of further preventing bleeding out to the surface of the molded product, the upper limit of the content is preferably 0.5 parts by mass, more preferably 0.18 parts by mass, and further preferably 0.15 parts by mass. Is.

In the resin composition of the present embodiment, a preferable content ratio of (C) saturated fatty acid to (D) nitrogen compound, that is, (C) saturated fatty acid / (D) non-polymer reactive nitrogen compound ratio (hereinafter, "(C)" ) / (D) ratio ”) is preferably 8 to 30 on a mass basis. The lower limit is preferably 10, more preferably 12, and even more preferably 15. The upper limit is preferably 28, more preferably 25.

In the resin composition of the present embodiment, various resins and additives which have been conventionally considered to be added to the polyacetal resin composition may be contained as other components of each of the above components. Specifically, for example, fatty acid metal salt compounds, antioxidants, weather-resistant (light) stabilizers, mold release agents, colorants such as pigments and dyes (including coloring masterbatches), lubricants, fluorescent bleaching agents, and plasticization. Examples include agents, antistatic agents, fluidity improvers, other fillers, reinforcing materials, spreading agents, rubbers, reinforcing agents and other polymers. These may be added individually by 1 type or in combination of 2 or more types as long as the achievement of the object of this invention is not impaired.

As the fatty acid in the fatty acid metal salt compound, the fatty acid mentioned in (C) saturated fatty acid in the present embodiment is preferably used, and more preferable fatty acids include palmitic acid, stearic acid, behenic acid and the like. Further, as the metal element forming the salt of the fatty acid metal salt compound, an alkali metal element or a second group element of the periodic table is preferable, among them, sodium, potassium, magnesium and calcium are more preferable, and calcium is particularly preferable. Specific examples of the fatty acid metal salt compound include calcium palmitate, calcium stearate, calcium behenate and the like. These may be used alone or in combination of two or more.

Preferred antioxidants in this embodiment include hindered phenolic antioxidants. Specific examples of the hindered phenolic antioxidant include n-octadecyl-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) -propionate and 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-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] and pentaerythritol tetrakis [methylene-3- (3) ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane and the like. Of these, more preferably triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] and pentaerythritol tetrakis [methylene-3- (3', 3',). 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane. These may be used alone or in combination of two or more.

Preferred weather resistant (light) stabilizers in the present embodiment include one or more selected from the group consisting of benzotriazole-based and oxalic acid anilides-based ultraviolet absorbers, and hindered amine-based light stabilizers.

Specific examples of the benzotriazole-based ultraviolet absorber include 2- (2'-hydroxy-5'-methyl-phenyl) benzotriazole and 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'- Examples thereof include bis- (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole and 2- (2'-hydroxy-4'-octoxyphenyl) benzotriazole. These benzotriazole-based ultraviolet absorbers may be used alone or in combination of two or more.

Specific examples of the oxalic acid anilides-based UV absorber include 2-ethoxy-2'-ethyloxalic acid bisanilide, 2-ethoxy-5-t-butyl-2'-ethyloxalic acid bisanilide and 2-. Ethoxy-3'-dodecyl oxalic acid bisanilide and the like can be mentioned. These oxalic acid arinide-based ultraviolet absorbers may be used alone or in combination of two or more.

Specific examples of the hindered amine-based light stabilizer include N, N', N'', N'''-tetrakis- (4,6-bis (butyl- (N-methyl-2,2,6,6-tetra)). Methylpiperidin-4-yl) amino) -triazine-2-yl) -4,7-diazadecan-1,10-diamine, dibutylamine 1,3,5-triazine N, N'-bis (2,2) , 6,6-Tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate, 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) imino}], a condensate of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol, decane Reaction product of bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl) ester with 1,1-dimethylethylhydroperoxide and octane, bis (1,2,2) , 6,6-Pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] Butylmalonate, Methyl-1,2,2,6,6- Pentamethyl-4-piperidyl sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, And 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β', β'-tetramethyl-3,9- [2 , 4,8,10-Tetraoxaspiro (5,5) undecane] Condensates with diethanol and the like. The hindered amine-based photostabilizer is 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 1,2,2,6,6 -A condensate of 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 are 1 The seeds may be used alone or in combination of two or more.

Examples of the release agent that can be used in the present embodiment include alcohols, fatty acids and fatty acid esters thereof, polyoxyalkylene glycols, and olefin compounds having an average degree of polymerization of 10 to 500. Of these, polyoxyalkylene glycols are preferred.

The polyacetal resin composition of the present embodiment may further contain a known additive, if necessary, as long as the achievement of the object of the present invention is not impaired. Specific examples of such additives include inorganic fillers, crystal nucleating agents, conductive agents, other thermoplastic resins, thermoplastic elastomers and pigments.

As the inorganic filler, for example, fibrous, powdery particle, plate and hollow ones are used. Examples of the fibrous inorganic filler 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, and titanium. , Inorganic fibers typified by metal fibers such as copper and brass. Further, as the inorganic filler, whiskers such as potassium titanate whiskers and zinc oxide whiskers having short fiber lengths may be used. The polyacetal resin composition of the present embodiment may contain a refractory organic fibrous substance such as an aromatic polyamide resin, a fluororesin and an acrylic resin.

Examples of the powdery inorganic filler include silicates such as carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth and wollastonite. , Metal oxides such as iron oxide, titanium oxide and alumina, metal sulfates such as calcium sulfate and barium sulfate, carbonates such as magnesium carbonate and dolomite, and other metals such as silicon carbide, silicon nitride, boron nitride and various metals. Examples include powder.
Examples of the plate-shaped inorganic filler include mica, glass flakes, and various metal foils.
Examples of the hollow inorganic filler include glass balloons, silica balloons, shirasu balloons and metal balloons.

These inorganic fillers may be used alone or in combination of two or more. These inorganic fillers may be either surface-treated or unsurface-treated, but surface-treated ones may be preferable from the viewpoint of smoothness and mechanical properties of the molded surface. .. As the surface treatment agent, conventionally known ones can be used. As the surface treatment agent, for example, various coupling treatment agents such as silane-based, titanate-based, aluminum-based, and zirconium-based can be used. Specifically, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltristearoyl titanate, diisopropoxyammonium ethyl acetate, n-butylzirconate and the like. Can be mentioned.

The crystal nucleating agent is not particularly limited, and examples thereof include boron nitride. The crystal nucleating agent may be used alone or in combination of two or more.

Examples of the conductive agent include conductive carbon black, metal powder and metal fiber. Carbon fibers are also included if they are blended for the purpose of conductivity.

Examples of the thermoplastic resin include polyolefin resin, acrylic resin, styrene resin, polycarbonate resin, polyester resin (excluding polylactic acid resin) and uncured epoxy resin. Further, modified products of these resins may be used as the thermoplastic resin. Examples of the thermoplastic elastomer include polyurethane-based elastomers, polyester-based elastomers, polystyrene-based elastomers, and polyamide-based elastomers.

Examples of the pigment include inorganic pigments and organic pigments, metallic pigments and fluorescent pigments. Here, examples of the inorganic pigment include those generally used for coloring a resin, such as zinc sulfide, titanium oxide, zinc oxide, barium sulfate, titanium yellow, cobalt blue, fuel pigment, and carbonate. , Phosphate, acetate, carbon black, acetylene black and lamp black are exemplified. Examples of organic pigments include condensed zo-based, inon-based, phthalocyanine-based, monoazo-based, diazo-based, polyazo-based, anthracinone-based, heterocyclic, pennon-based, quinacridone-based, thioindico-based, verylene-based, and dioxazine. Examples include system-based and phthalocyanine-based pigments. In the polyacetal resin composition of the present embodiment, it is difficult to clearly specify the content of the pigment because it varies greatly depending on the required color tone, but in general, 100 mass of the (A-1) polyacetal resin is used. It is in the range of 0.005 to 5 parts by mass with respect to the part.

Next, a suitable method for producing the polyacetal resin composition of the present embodiment will be described. As an apparatus that can be used for producing the resin composition, for example, a commonly used kneader may be applied. Examples of the apparatus include a uniaxial or multiaxial kneading extruder, a roll and a Banbury mixer and the like. From the viewpoint of workability and productivity, a uniaxial or multiaxial kneading extruder is more preferably used. Among them, a twin-screw extruder is particularly preferably used.

As a twin-screw extruder, a twin-screw extruder having an L / D (screw length / screw diameter) of 40 or more and having one or more supply ports other than the upstream supply port (top feed port) is available. More preferably used.

Further, the screw diameter of the twin-screw extruder is preferably 40 mm or more for the twin-screw extruder from the viewpoint of mass productivity and supply stability in consideration of productivity.

When a twin-screw extruder having a supply port other than the upstream side is used, the raw materials of the polyacetal resin composition can be separately supplied to the extruder. As an example of the combination, a method of supplying a polyacetal resin (A-1) from an upstream supply port and supplying all the remaining components from a supply port other than the upstream side, a polyacetal resin (A-1) and other desired ones. (For example, a method of supplying a part or all of the components (for example, calcium carbonate (B) and fatty acid (C)) from the upstream supply port and the rest from other than the upstream supply port can be mentioned. Of course, the raw material supply method can be adopted without particular limitation as long as it is a known supply method.

Even when using an extruder having only an upstream supply port, a feeder in which a mixture other than the polyacetal resin (A-1) is mixed in advance is prepared and used to supply the polyacetal resin (A-1). It is preferable to supply the resin composition to the extruder by a different feeder from the viewpoint of suppressing fluctuations in the composition of the resin composition.

When the resin composition of the present embodiment is processed by an extruder or the like, it is preferable to set a part of the barrel in a reduced pressure environment at the time of processing to remove unnecessary volatile components. The degree of decompression at that time is not particularly limited, but it is preferably 0.07 MPa or more.

The resin pellet of the present embodiment is a pellet made of the polyacetal resin composition, and the molded body of the present embodiment is a molded body made of the polyacetal resin composition.

The resin pellets are generally obtained by processing with the above-mentioned extruder. The shape of the pellet is not particularly limited, but when extruded into a strand shape and pelletized, a columnar pellet can be obtained, and a spherical pellet can be obtained as a pellet obtained by a hot cut method, an underwater cut method, or the like. Be done. The size of the pellet is also not particularly limited, but the upper limit of the particle size of the preferable pellet is 3 mm. The preferred lower limit is 1 mm. The preferred upper limit of the dimensions of the columnar pellets is 3 mm in diameter and 4 mm in length, and the preferred lower limit is 1 mm in diameter and 2 mm in length. From the viewpoint of biting property during the subsequent molding process, the upper limit is preferably the above dimensions, and the lower limit is preferably the above dimensions in order to prevent clogging during transport of the pellets.

The molded product of the present embodiment includes any molded product having a shape within the composition range of the polyacetal resin composition of the present embodiment. Examples of the molded body of the present embodiment include extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, molding of other materials, gas-assisted injection molding, foam injection molding, low-pressure molding, and ultra-thin wall molding. Examples thereof include articles made of the polyacetal resin composition of the present embodiment obtained by injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, outsert molding) and the like.

The articles obtained by the above-mentioned manufacturing method include, for example, fibers, sheet films, and deformed extruded products, in addition to ordinary injection-molded products. The article may be a part, and specific parts include, for example, a gear, a cam, a slider, a lever, an arm, a clutch, a felt clutch, an idler gear, a pulley, a roller, a roller, a key stem, a key top, and a shutter. , Mechanical parts such as reels, shafts, joints, shafts, bearings and guides, resin parts for outsert molding, resin parts for insert molding, chassis, trays, side plates, printers and office automation equipment such as copying machines. Parts for parts, VTRs, video movies, digital video cameras, cameras and parts for cameras or video equipment represented by digital cameras, cassette players, DATs, LDs, MDs, CDs [CD-ROM, CD-R, CD-RW Including], DVD [including DVD-ROM, DVD-R, DVD + R, DVD-RW, DVD + RW, DVD-R DL, DVD + R DL, DVD-RAM, DVD-Audio], Blu-ray® Disc, HD -For DVDs, other optical disk drives, MFDs, MOs, navigation systems and music, video or information devices such as mobile personal computers, communication equipment parts such as mobile phones and facsimiles, electrical equipment parts, and electronic equipment. Parts and the like can be mentioned.

The molded body can also be used as parts for automobiles, for example, fuel tanks, fuel pump modules, valves, fuel parts such as gasoline tank flanges, door locks, door handles, etc. , Window regulators, door parts such as speaker grills, seatbelt slip rings, seatbelt peripheral parts such as press buttons, combination switch parts, switches and the like. In addition, clip parts, sharp pencil pen tips, mechanical parts for inserting and removing the sharp pencil core, washbasins and drain outlets and drain plug opening and closing mechanical parts, cord stoppers for clothing, adjusters and buttons, for sprinkling Nozzle and sprinkler hose connection joints, building supplies that support stair railings and flooring, disposable cameras, toys, fasteners, chains, conveyors, buckles, sporting goods, vending machines (eg vending machine opening / closing lock mechanism) It is also suitably used as an industrial part of equipment represented by (and product discharge mechanism parts), furniture, musical instruments and housing equipment.

Although the embodiment for carrying out the present invention has been described above, the present invention is not limited to the above-described embodiment. The present invention can be modified in various ways without departing from the gist thereof.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
The following raw materials were used for producing the polyacetal resin compositions of Examples and Comparative Examples.

(A-1) Polyacetal Resin As the polyacetal resin (POM), one prepared by the following production method was used.
A twin-screw self-cleaning type polymerizer (L / D = 8) with a jacket capable of passing a heat medium was adjusted to 80 ° C., and trioxane and 1,3-dioxolane (trioxane 100 mol%) as a comonomer were prepared therein. 1.5 mol%), and methylal as a chain transfer agent was added in an amount such that the melt flow rate at 190 ° C. (same below) based on JIS K7210 of the polyacetal resin after polymerization was 14 g / 10 minutes. .. Further, as a polymerization catalyst, boron trifluoride di-n-butyl ether was continuously added to the polymerization machine in an amount of 1.5 × 10 ^-5 mol with respect to 1 mol of trioxane to carry out the polymerization.
The polyacetal copolymer discharged from the polymerization machine was put into a 0.1% aqueous solution of triethylamine to inactivate the polymerization catalyst. The deactivated polyacetal copolymer of the polymerization catalyst is filtered by a centrifuge and dried under nitrogen at 120 ° C. for 3 hours, and then the polyacetal copolymer is supplied to a twin-screw extruder with a vent and melted in the extruder. 5 parts by mass of an aqueous solution of triethylamine (2% by mass) was added to 100 parts by mass of the polyacetal copolymer, and the unstable end portion was decomposed and removed at an extruder set temperature of 200 ° C. and a residence time of 7 minutes in the extruder. Then, it was devolatile from the vent provided at the rear stage of the extruder at −0.07 MPa, extruded as a strand from the die portion of the extruder, and pelletized. Triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] 0 as an antioxidant under certain conditions with respect to 100 parts by mass of pelletized polyacetal copolymer (polyacetal resin) .3 parts by mass was added and melt-kneaded with a twin-screw extruder with a vent to obtain resin pellets of polyacetal resin.
The melting point of the polyacetal resin thus obtained was 169 ° C. and MFR 14 g / 10 minutes.
In the table, the polyacetal resin is referred to as "POM".

(A-2) Polylactic acid resin Polylactic acid resin (denoted as PLA) (manufactured by NatureWorks, trade name "Ingeo2003D"
MFR; 2.5 g / 10 minutes, Mw = 210,000, 100% lactic acid monomer, D-lactic acid: L-lactic acid = 4: 96 (molar ratio))

(B) Calcium carbonate Calcium carbonate (CaCO ₃ ) (Product name "Brilliant 1500" manufactured by Shiraishi Kogyo Co., Ltd., primary particle size: 150 nm, no surface treatment.)
Tarku used as a comparative example of calcium carbonate (manufactured by Nippon Tarku Co., Ltd., trade name D-600, average particle diameter 0.6 μm, no surface treatment)

(C) Fatty acid stearic acid (manufactured by Kawaken Fine Chemical Co., Ltd., trade name "F-3")

(D) Nitrogen compound Melamine (manufactured by Nissan Chemical Industries, Ltd., trade name "melamine")

[Manufacturing method of polyacetal resin composition]
Set the cylinder temperature of the same-direction rotary twin-screw extruder (trade name "TEM26SS", manufactured by Toshiba Machine Co., Ltd.), which has one supply port on the upstream side, to 210 ° C, and set the discharge rate to 14 kg / hour. The feeder was adjusted, and the raw material was extruded into a strand shape under the condition of a screw rotation speed of 150 rpm, cooled, and pelletized to obtain a resin pellet made of a polyacetal resin composition. At this time, the polyacetal resin and the polylactic acid resin were mixed in advance so as to be uniform and supplied to the extruder from one feeder. The remaining components other than the polyacetal resin and the polylactic acid resin were also uniformly mixed in advance and then supplied to the extruder from another feeder different from the previous one (supplied to the same supply port). In addition, volatile matter and water were removed from the vacuum suction port installed on the downstream side.

[Various evaluation methods]
Details of various evaluation methods are described below.

(1) Extrudability In the method for producing a polyacetal resin composition, a stable productivity in production was evaluated using an extruder. Specifically, if additives (calcium carbonate, talc, etc.) are blocked at the supply port of the extruder and stable supply is interrupted, or strands are cut and stable pelletization is interrupted, it is continuous. It was evaluated as Δ because of its low stable productivity. It was evaluated as ◯ when the interruption of additive supply and the interruption of stable pelletization did not occur. It was evaluated as ◯>Δ> × in the order of good stable productivity, that is, in the order of excellent extrudability.
When the interruption occurred many times, it was evaluated as x, and the subsequent evaluation items (2) to (6) were not carried out.

(2) Tensile strength Using an injection molding machine (EC-75NII, manufactured by Toshiba Machine Co., Ltd.), the mold temperature was adjusted to 90 ° C, the cylinder temperature was set to 205 ° C, the injection time was 35 seconds, and the cooling time. By molding under injection conditions of 15 seconds, a molded piece of a multipurpose test piece (A type) compliant with ISO294-1 was molded.
Using the molded piece obtained above, a tensile test was performed at a tensile speed of 50 mm / min in accordance with ISO527-1, and the tensile strength (MPa) was measured.
The larger the tensile strength value, the better the strength.

(3) Tensile elongation (%)
The ratio of the displacement amount (breaking displacement amount) between the chucks (test piece fittings) at the time when the test piece is broken in the tensile test of (2) to the initial chuck distance before the tensile test is the tensile elongation. It was set to (%). Specifically, it is calculated by the following formula.
Tensile elongation (%) = (displacement at break / initial chuck distance) x 100
The larger the tensile elongation value, the better the toughness.

(4) Bending elastic modulus Using the molded piece obtained in (2) above, a bending test was performed in accordance with ISO178, and the bending elastic modulus (Gpa) was measured.
The higher the flexural modulus, the better the rigidity.

(5) Friction coefficient Using the molded piece obtained in (2) above, the SUS304 ball dynamic friction coefficient was measured by a ball-on-disk type reciprocating friction and wear tester (AFT-15MS type, manufactured by Toyo Seimitsu Co., Ltd.). .. A sliding test was conducted under the conditions of a load of 19.6 N, a linear speed of 30 mm / sec, a reciprocating distance of 20 mm, and a reciprocating frequency of 4,000 times in an environment of 23 ° C. and a humidity of 50%. As the ball material, a SUS304 ball (a ball having a diameter of 5 mm) was used. The slidability was evaluated from the dynamic friction coefficient of each molded body at the time of reciprocating 4,000 times.
The smaller the value of the coefficient of friction, the better the slidability.

(6) Deflection temperature under load (1.8 MPa)
Using the molded body obtained in (2) above, the deflection temperature under load at 1.8 MPa was measured in accordance with ISO75.
The higher the deflection temperature under load, the better the heat resistance.

(Examples 1 to 9 and Comparative Examples 1 to 8)
A polyacetal resin composition was produced as described above so that each component had the composition shown in Table 1, and was evaluated by the above-mentioned various evaluation methods. The results are shown in Table 1.

As can be seen from Table 1, the polyacetal resin compositions of Examples exhibited excellent rigidity and slidability while maintaining excellent strength, toughness, and heat resistance. On the other hand, the polyacetal resin composition of the comparative example could not exhibit excellent rigidity and slidability while maintaining excellent strength, toughness, and heat resistance.

As described above, the polyacetal resin composition and the molded product of the present invention can impart even higher rigidity and slidability while maintaining strength, toughness, and heat resistance, and thus can be used in automobiles, electrical and electronic equipment, and other industries. It can be suitably used for parts that require rigidity and slidability in the field.

Claims (11)

(A-1) 50 to 99 parts by mass of polyacetal resin, and (A-2) 100 parts by mass of component (A) consisting of 1 to 50 parts by mass of polylactic acid resin.
(B) 10 to 65 parts by mass of calcium carbonate and
A polyacetal resin composition comprising. The first aspect of claim 1, wherein the ratio ((A-1) / (B)) of the content of the (A-1) polyacetal resin to the content of the (B) calcium carbonate is 4 or less on a mass basis. Polyacetal resin composition. The ratio of the content of the (A-1) polyacetal resin to the content of the (B) calcium carbonate ((A-1) / (B)) is 2 or more on a mass basis, according to claim 1 or 2. The polyacetal resin composition according to the above. The polyacetal resin composition according to any one of claims 1 to 3, further comprising (C) a fatty acid in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the component (A). The polyacetal resin composition according to any one of claims 1 to 4, further comprising (D) a nitrogen compound in an amount of 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the component (A). The polyacetal resin according to claim 4 or 5, wherein the ratio ((C) / (D)) of the content of the (C) fatty acid to the content of the (D) nitrogen compound is 8 to 30 on a mass basis. Composition. The polyacetal resin composition according to any one of claims 1 to 6, wherein the calcium carbonate (B) is a light calcium carbonate having a number average particle diameter of 1 μm or less. The polyacetal resin composition according to any one of claims 4 to 7, wherein the fatty acid (C) is a saturated fatty acid having a total number of carbon atoms in the molecule of 12 or more and less than 30. The polyacetal resin composition according to any one of claims 4 to 8, wherein the (C) fatty acid is contained in an amount of 2 to 6 parts by mass with respect to 100 parts by mass of the calcium carbonate (B). The polyacetal resin composition according to any one of claims 5 to 9, wherein the nitrogen compound (D) is melamine or a reaction product of melamine and formaldehyde. A molded product comprising the polyacetal resin composition according to any one of claims 1 to 10.