JP5825922B2 - Polyacetal resin composition and method for producing the same - Google Patents

Description

  The present invention relates to a polyacetal resin composition excellent in rigidity (mechanical characteristics) and appearance, and generating less formaldehyde, and a method for producing the same.

  Polyacetal resin has excellent properties in mechanical properties, thermal properties, electrical properties, slidability, moldability, etc., mainly as electrical materials, automotive parts, precision machine parts as structural materials and mechanical parts. Widely used in With the expansion of the field in which polyacetal resins are used, the required characteristics tend to become more sophisticated, complex and specialized. Among them, effective utilization of a cellulose-based material which is a renewable resource has attracted attention, and it has been studied to improve the properties as a polyacetal resin composition by blending it with a polyacetal resin.

  Patent Document 1 discloses a polyacetal resin composition in which pulp is blended with a polyacetal resin. Here, improvements such as mechanical strength, heat resistance, and flammability (resin dripping during combustion) are shown. However, in the method for preparing a resin composition described in Patent Document 1, pulp agglomeration occurs in the composition and defects tend to occur, and it is difficult to obtain a composition with little formaldehyde generation, and the appearance is poor. It is difficult to produce a molded product that is sufficient and practically excellent.

  Patent Document 2 discloses a polyacetal resin composition in which a polyacetal resin and a fibrous cellulosic material having a specific bulk density are blended. Here, since the fibrous cellulosic material is used, the result that the aggregation of the fibrous cellulosic material is relatively suppressed is obtained. However, with respect to the method for preparing the resin composition described in Patent Document 2, it is difficult to obtain a composition with little formaldehyde generation, and it is difficult to produce a practically excellent molded product with low rigidity.

JP-A-3-217447 JP 2010-150313 A

  As described above, it is difficult to obtain a resin composition that generates less formaldehyde as described above, and it is difficult to obtain a molded product having excellent rigidity (mechanical characteristics) and appearance. An object of the present invention is to solve these problems, and to provide a polyacetal resin composition excellent in rigidity (mechanical characteristics) and appearance when formed into a molded product and generating less formaldehyde, and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that (a) polyacetal resin, specific (b) woody fine powder, (c) hindered phenolic antioxidant, and specific (d It is found that a polyacetal resin composition capable of achieving the object of the present invention is obtained by blending a nitrogen-containing compound and a specific (e) processing aid, thereby completing the present invention. It came to. Specifically, the present invention provides the following.

  (1) (a) When 100 parts by weight of the polyacetal resin contains 5 to 35% by weight of lignin and sieved with a sieve having an opening of 250 μm, the sieve residue remaining on the sieve is 3% by weight or less. (B) 10 to 150 parts by weight of a woody fine powder, (c) 0.01 to 3 parts by weight of a hindered phenol antioxidant, at least one selected from aminotriazine compounds, guanamine compounds, hydrazide compounds and polyamides (D) 0.01 to 3 parts by weight of a nitrogen-containing compound, 0.01 to at least one (e) processing aid selected from long chain fatty acids, derivatives of long chain fatty acids, polyoxyalkylene glycols and silicone compounds A polyacetal resin composition comprising ~ 3 parts by weight.

  (2) The polyacetal resin composition according to (1), wherein the melt index (based on ASTM-D1238, 190 ° C., 2.16 kgf) of the (a) polyacetal resin is 10 to 50 g / 10 minutes.

(3) The polyacetal resin composition according to (1) or (2), wherein the amount of formaldehyde generated by the following method is 100 ppm or less.
(Measuring method)
Resin pellets composed of 8 g of the polyacetal resin composition were filled into a metal cylinder adjusted to 200 ° C. and held for 5 minutes in a molten state. Subsequently, the formaldehyde gas generated from the molten resin was discharged together with the nitrogen stream while flowing nitrogen through the glass absorption bottle connected to the metal cylinder, thereby allowing the distilled water in the absorption bottle to absorb the formaldehyde gas. Formaldehyde absorbed in distilled water was quantified by a method based on JIS K0102, and calculated as a ratio to the evaluation sample (resin composition).

  (4) A method for producing the polyacetal resin composition according to any one of (1) to (3), wherein a main feed port and a side feed port located on the downstream side in the extrusion direction from the main feed port And (a) a polyacetal resin, (c) a hindered phenol-based antioxidant, (d) a nitrogen-containing compound, and (e) a processing aid are supplied from the main feed port. The manufacturing method of the polyacetal resin composition which supplies the said (b) wood type fine powder from the said side feed port.

  According to the polyacetal resin composition of the present invention and the method for producing the polyacetal resin composition of the present invention, when formed into a molded article, it is excellent in rigidity (mechanical properties) and appearance, and formaldehyde is hardly generated.

  Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

<(A) Polyacetal resin>
The polyacetal resin as component (a) is a polymer compound having an oxymethylene group (—OCH ₂ —) as a main constituent unit, and includes a polyacetal homopolymer substantially consisting only of repeating oxymethylene units, in addition to oxymethylene units. Polyacetal copolymers containing other comonomer units are representative resins. Furthermore, polyacetal resins include copolymers in which a branched structure or a crosslinked structure has been introduced by copolymerizing a branch-forming component or a crosslinking-forming component, polymer units composed of repeating oxymethylene groups, and other polymer units. Also included are block copolymers, graft copolymers and the like. These polyacetal resins can be used alone or in combination of two or more.

  In general, a polyacetal homopolymer is produced by polymerization of anhydrous formaldehyde or trioxane (a cyclic trimer of formaldehyde), and is usually stabilized against thermal decomposition by esterifying its terminal.

In contrast, the polyacetal copolymer is generally a formaldehyde or a cyclic oligomer of formaldehyde represented by the general formula (CH ₂ O) n [wherein n represents an integer of 3 or more] (for example, trioxane); It is produced by copolymerizing with a comonomer such as cyclic ether or cyclic formal, and is usually stabilized against thermal decomposition by removing terminal unstable parts by hydrolysis.

  Examples of the main raw material of the polyacetal copolymer include trioxane and tetraoxane, and trioxane is usually used.

  The comonomer includes a cyclic ether, a glycidyl ether compound, a cyclic formal, a cyclic ester (for example, β-propiolactone), a vinyl compound (for example, styrene, vinyl ether, etc.), and the like.

  Examples of the cyclic ether include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, epichlorohydrin, epibromohydrin, styrene oxide, oxetane, 3,3-bis (chloromethyl) oxetane, and tetrahydrofuran.

  Examples of the glycidyl ether compound include alkyl or aryl glycidyl ethers (for example, methyl glycidyl ether, ethyl glycidyl ether, phenyl glycidyl ether, naphthyl glycidyl ether), alkylene or polyalkylene glycol diglycidyl ether (for example, ethylene glycol diglycidyl ether). , Triethylene glycol diglycidyl ether, butanediol diglycidyl ether), alkyl or aryl glycidyl alcohol, and the like.

  Examples of the cyclic formal include 1,3-dioxolane, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, and trioxepane. Etc.

  These comonomers can be used alone or in combination of two or more. Of these comonomers, cyclic ethers and / or cyclic formals are usually used, and cyclic ethers such as ethylene oxide, and cyclic formals such as 1,3-dioxolane, 1,4-butanediol formal, and diethylene glycol formal are preferred. .

  The proportion of these comonomer (for example, cyclic ether and / or cyclic formal) units is not particularly limited, but is generally in the range of 0.1 to 20% by weight with respect to the whole polyacetal resin, preferably 0.8. It is about 5 to 20% by weight, more preferably about 0.5 to 15% by weight (particularly 1 to 10% by weight).

  The polyacetal resin (a) used in the present invention preferably has an unstable terminal group content of 0.5% by weight or less. Here, the unstable terminal group amount indicates the amount of a portion which is present at the terminal portion of the polyacetal copolymer and is unstable and easily decomposed with respect to heat or a base. The amount of such unstable end groups is as follows: 1 g of polyacetal copolymer is placed in a pressure-resistant sealed container with 100 ml of 50% (volume%) aqueous methanol solution containing 0.5% (volume%) ammonium hydroxide, and at 180 ° C. for 45 minutes. The amount of formaldehyde decomposed and dissolved in the solution obtained by cooling and opening after heat treatment was quantified, and expressed in weight% with respect to the polyacetal copolymer.

  When the polyacetal resin of component (a) does not have the above-mentioned terminal characteristics and exceeds the upper limit value, it may be difficult to obtain a polyacetal resin composition having a sufficiently low formaldehyde generation amount. Therefore, the polyacetal resin as component (a) preferably has an unstable terminal group amount of 0.5% by weight or less, more preferably 0.3% by weight or less. On the other hand, the lower limit of the amount of unstable terminal groups is not particularly limited.

  The melt index of the polyacetal resin (a) is preferably in the range of 10 to 100 g / 10 minutes, and particularly preferably in the range of 10 to 50 g / 10 minutes. When the melt index is too small or too large, the effects of the present invention may not be sufficiently obtained. The melt index is a value measured under conditions of 190 ° C. and 2.16 kgf (21.2 N) according to ASTM-D1238.

<(B) Woody fine powder>
The wood-based fine powder (b) used in the present invention is made from wood as a raw material and in powder form, and contains 5 to 35% by weight of lignin. In particular, the preferred lignin content is 10 to 30% by weight. (B) When the lignin content of the woody fine powder is less than 5% by weight, the improvement for reducing the amount of formaldehyde generated from the polyacetal resin composition is insufficient, and when it exceeds 35% by weight, the polyacetal resin Since the external appearance of a composition deteriorates, it is not preferable.

  In addition, (b) the particle size of the wood-based fine powder, when sieved with a sieve having an opening of 250 μm, the sieve residue remaining on the sieve needs to be 3% by weight or less, particularly 2% by weight. Or less, more preferably 1% by weight or less. (B) When the above sieving residue of the wood-based fine powder exceeds 3% by weight, the dispersibility of the wood-based fine powder is deteriorated, and the surface of the polyacetal resin composition is rough or uneven. This is not preferable because the deterioration of toughness is observed and the toughness may be lowered. On the other hand, the lower limit of the sieve residue is not particularly limited.

  (B) The compounding quantity of a wood type fine powder is 10-150 weight part with respect to 100 weight part of polyacetal resin of (a) component, Preferably it is 15-100 weight part. (B) When the blending amount of the wood-based fine powder is less than 10 parts by weight, the improvement of the mechanical properties of the polyacetal resin composition is insufficient, and when it exceeds 150 parts by weight, (b) the dispersion of the wood-based fine powder It is not preferable because the properties deteriorate.

<(C) Hindered phenolic antioxidant>
The polyacetal resin composition of the present invention can stably improve mechanical properties by using (c) a hindered phenol compound. (C) The hindered phenol compound is a monocyclic hindered phenol compound (for example, 2,6-di-t-butyl-p-cresol), a hydrocarbon group or a group containing a sulfur atom. Polycyclic hindered phenol compounds (for example, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 4,4′-methylenebis (2,6-di-tert-butylphenol), 1,1, 3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 4,4′-butylidenebis (3-methyl-6-t-butylphenol), 1,3,5-trimethyl-2,4 , 6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 4,4′-thiobis (3-methyl-6-tert-butylphenol)), ester group or A hindered phenol compound having an amide group (for example, n-octadecyl-3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propionate, n-octadecyl-2- (4′-hydroxy-) 3 ′, 5′-di-t-butylphenyl) propionate, 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 3.9 -Bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl -2,4,8,10-tetraoxaspiro [5.5] undecane, 2-t-butyl-6- (3'-t-butyl-5'-methyl-2'-hydroxybenzyl) -4-methyl Phenyl acrylate, 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, di-n-octadecyl-3,5-di -T-butyl-4-hydroxybenzylphosphonate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-dihydrocinnamamide, N, N'-ethylenebis [3- ( 3,5-di-t-butyl-4-hydroxyphenyl) propionamide], N, N′-tetramethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide], N N′-hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide], N, N′-ethylenebis [3- (3-tert-butyl-5-methyl-) 4-hydroxyphenyl) propionamide], N, N′-hexamethylenebis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionamide], N, N′-bis [3- ( 3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine, N, N′-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionyl] hydrazine, 1, 3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) i Cyanurate, etc.) and the like.

  In this invention, (c) hindered phenolic antioxidant can be used individually or in combination of 2 or more types. The blending ratio is 0.01 to 3 parts by weight, preferably 0.02 to 1 part by weight, based on 100 parts by weight of the polyacetal resin (a).

<(D) Nitrogen-containing compound>
The polyacetal resin composition of the present invention can be stably improved in mechanical properties by using at least one (d) nitrogen-containing compound selected from aminotriazine compounds, guanamine compounds, hydrazide compounds and polyamides, Melt stability is also improved.

  Examples of aminotriazine compounds include melamine or derivatives thereof [melamine, melamine condensates (melam, melem, melon, etc.)], guanamine or derivatives thereof, and aminotriazine resins [melamine co-condensation resins (melamine-formaldehyde resin, phenol-melamine). Resin, melamine-phenol-formaldehyde resin, benzoguanamine-melamine resin, aromatic polyamine-melamine resin, etc.), co-condensation resin of guanamine, etc.].

  Guanamine compounds include aliphatic guanamine compounds (monoguanamines, alkylenebisguanamines, etc.), alicyclic guanamine compounds (monoguanamines, etc.), aromatic guanamine compounds [monoguanamines (benzoguanamine and its functional group substitution) ), Α- or β-naphthoguanamine and their functional group-substituted derivatives, polyguanamines, aralkyl or aralkylenamines, etc.], heteroatom-containing guanamine compounds [acetal group-containing guanamines, tetraoxospiro ring-containing Guanamines (CTU-guanamine, CMTU-guanamine, etc.), isocyanuric ring-containing guanamines, imidazole ring-containing guanamines, etc.]. Moreover, the compound etc. which the alkoxymethyl group of said melamine, a melamine derivative, and a guanamine type compound substituted by the amino group are also contained.

  Examples of hydrazide compounds include aliphatic carboxylic acid hydrazide compounds (such as stearic acid hydrazide, 12-hydroxystearic acid hydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and eicosanedioic acid dihydrazide), alicyclic carboxylic acid hydrazide compounds (1 , 3-bis (hydrazinocarbonoethyl) -5-isopropylhydantoin), aromatic carboxylic acid hydrazide compounds (4-hydroxy-3,5-di-t-butylphenylbenzoic acid hydrazide, 1-naphthoic acid hydrazide) 2-naphthoic acid hydrazide, isophthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, etc.), heteroatom-containing carboxylic acid hydrazide compounds, polymer-type carboxylic acid hydrazide compounds, and the like.

  As the polyamide, a polyamide derived from a diamine and a dicarboxylic acid; an aminocarboxylic acid, a polyamide obtained by using a diamine and / or a dicarboxylic acid in combination; a lactam; and a diamine and / or a dicarboxylic acid as needed Polyamide derived by the combined use of Also included are copolyamides formed from two or more different polyamide-forming components.

  Specific examples of polyamides include polyamide 3, polyamide 4, polyamide 46, polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12, and other aliphatic polyamides, aromatic dicarboxylic acids (for example, terephthalic acid). And / or polyamides obtained from isophthalic acid) and aliphatic diamines (eg hexamethylenediamine), polyamides obtained from aliphatic dicarboxylic acids (eg adipic acid) and aromatic diamines (eg metaxylylenediamine) And polyamides obtained from aromatic and aliphatic dicarboxylic acids (for example, terephthalic acid and adipic acid) and aliphatic diamines (for example, hexamethylenediamine), and copolymers thereof. It is also possible to use a polyamide block copolymer in which a polyamide hard segment and another soft segment such as a polyether component are combined.

  (D) Nitrogen-containing compounds selected from aminotriazine compounds, guanamine compounds, hydrazide compounds and polyamides can be used alone or in combination of two or more. The blending ratio is 0.01 to 3 parts by weight, preferably 0.02 to 1 part by weight, based on 100 parts by weight of the polyacetal resin (a).

<(E) Processing aid>
The polyacetal resin composition of the present invention can improve mechanical properties by using at least one (e) processing aid selected from long-chain fatty acids, derivatives of long-chain fatty acids, polyoxyalkylene glycols and silicone compounds. It can be obtained stably and melt processability is also improved.

  The long chain fatty acid may be a saturated fatty acid or an unsaturated fatty acid. Also, those in which some of the hydrogen atoms are substituted with a substituent such as a hydroxyl group can be used. Examples of such long-chain fatty acids include monovalent or divalent fatty acids having 10 or more carbon atoms, monovalent unsaturated fatty acids having 10 or more carbon atoms, and divalent fatty acids (dibasic fatty acids) having 10 or more carbon atoms. Illustrated. The fatty acids also include fatty acids having one or more hydroxyl groups in the molecule. The long chain fatty acid derivatives include fatty acid esters and fatty acid amides.

  Examples of fatty acid esters include esters of the above long-chain fatty acids with alcohols. The structure is not particularly limited, and either a linear or branched fatty acid ester can be used. Specific examples of fatty acid esters include ethylene glycol mono or dipalmitate, ethylene glycol mono or distearate, ethylene glycol mono or dibehenate, ethylene glycol mono or dimtanate, glycerin mono to tripalmitate, glycerin. Mono-tristearic acid ester, glycerol mono-tribehenic acid ester, glycerin mono-trimontanic acid ester, pentaerythritol mono-tetrapalmitic acid ester, pentaerythritol mono-tetrastearic acid ester, pentaerythritol mono-tetrabehenic acid ester, pentaerythritol mono-ester Thru tetramontanate ester, polyglycerol tristearate ester, trimethylo Propane monopalmitate, pentaerythritol monoundecylate, sorbitan monostearate, polyalkylene glycol (polyethylene glycol, polypropylene glycol, etc.) mono or dilaurate, mono or dipalmitate, mono or distearate, mono or dibehenate, mono or Dimontanate, mono or dioleate, mono or dilinoleate and the like can be mentioned.

Examples of fatty acid amides include capric acid amides, lauric acid amides, myristic acid amides, palmitic acid amides, stearic acid amides, arachidic acid amides, behenic acid amides, primary fatty acid amides, olein Primary acid amides of unsaturated fatty acids such as acid amides, secondary acid amides of saturated and / or unsaturated fatty acids and monoamines such as stearyl stearic acid amide, stearyl oleic acid amide, ethylenediamine-dipalmitic acid amide, ethylenediamine -Distearic acid amide (ethylene bisstearyl amide), hexamethylenediamine-distearic acid amide, ethylenediamine-dibehenic acid amide, ethylenediamine-dimantanoic acid amide, ethylenediamine-dioleic acid amide, ethylenediamine- Such as erucic acid amide and the like, further ethylenediamine - such as a bisamide in which different species of acyl groups to amine sites of an alkylenediamine is bound, such as (stearic acid amide) oleic acid amide can be exemplified.

  Examples of the polyoxyalkylene glycol include homopolymers or copolymers of alkylene glycols (such as alkylene glycols such as ethylene glycol, propylene glycol, and tetramethylene glycol), and derivatives thereof.

Specific examples of the polyoxyalkylene glycol include polyoxyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol, polyoxyethylene-polyoxypropylene copolymers (random or block copolymers, etc.), polyoxyethylene Examples include copolymers such as polyoxypropylene glyceryl ether and polyoxyethylene polyoxypropylene monobutyl ether. Of these, polymers having oxyethylene units, such as polyethylene glycol, polyoxyethylene polyoxypropylene copolymers, and derivatives thereof are preferable. The average molecular weight of the polyoxyalkylene glycol is about 3 × 10 ² to 1 × 10 ⁶ , preferably about 1 × 10 ³ to 1 × 10 ⁵ .

  Examples of the silicone compound include (poly) organosiloxane. Examples of the (poly) organosiloxane include monoorganosiloxanes such as dialkylsiloxanes (such as dimethylsiloxane), alkylarylsiloxanes (such as phenylmethylsiloxane), diarylsiloxanes (such as diphenylsiloxane), and homopolymers thereof (polydimethylsiloxane, poly Examples thereof include phenylmethylsiloxane) and copolymers. The polyorganosiloxane may be an oligomer.

  In addition, (poly) organosiloxane has an epoxy group, hydroxyl group, alkoxy group, carboxyl group, amino group or substituted amino group (such as dialkylamino group), ether group, vinyl group, ) Modified (poly) organosiloxane having a substituent such as acryloyl group is also included.

  At least one (e) processing aid selected from long-chain fatty acids, long-chain fatty acid derivatives, polyoxyalkylene glycols and silicone compounds can be used alone or in combination of two or more. The blending ratio is 0 to 3 parts by weight, preferably 0.01 to 1 part by weight with respect to 100 parts by weight of the polyacetal resin as the component (e).

<Other ingredients>
In the polyacetal resin composition of the present invention, a substance that improves the adhesion between (a) the polyacetal resin and (b) the woody fine powder can be blended. Here, the substances for improving the adhesion include isocyanate compounds, isothiocyanate compounds, and their modified isocyanate compounds, thermoplastic polyurethane resins, and acid anhydrides of α, β-monoolefinic unsaturated carboxylic acids. Examples thereof include a polymer, a copolymer, and a boric acid compound.

  Furthermore, various known additives can be blended in the composition of the present invention in order to improve its physical properties according to the intended use. Examples of additives include various colorants, lubricants, nucleating agents, surfactants, heterogeneous polymers, organic polymer modifiers, and inorganic, organic, metal and other fibrous, powdered, and plate-like fillers. 1 type or 2 types or more can be mixed and used.

<Preparation method of polyacetal resin composition>
In this invention, the specific aspect of the preparation method of the said polyacetal resin composition is not specifically limited, Generally a well-known installation and method can be employ | adopted as a preparation method of a synthetic resin composition or its molded article. For example, necessary components can be mixed and kneaded using an extruder or other melt kneader to prepare pellets for molding. A plurality of extruders or other melt kneaders may be used. In particular, in the present invention, the extruder is preferably a twin-screw extruder from the viewpoint of improving mechanical properties and (b) the dispersibility of the woody fine powder.

  The composition of the components constituting the polyacetal resin composition may be added to any stage, for example, once added to the polyacetal resin of component (a), or may be added at the time of preparing the resin composition. It is also possible to add and mix immediately before obtaining. In particular, improvement of mechanical properties (b) From the viewpoint of coexistence of dispersibility of the wood-based fine powder, (b) the wood-based fine powder is preferably supplied and mixed independently from other raw materials from the side of the extruder. . That is, it is preferable to use a twin-screw extruder provided with a main feed port and a side feed port located downstream of the main feed port in the extrusion direction. Using this twin-screw extruder, (a) a polyacetal resin, (c) a hindered phenol-based antioxidant, (d) a nitrogen-containing compound, (e) a processing aid is supplied from the main feed port, From (b), it is preferable to produce the polyacetal resin composition of the present invention by a method of supplying a woody fine powder.

  The polyacetal resin composition of the present invention obtained as described above has a small amount of formaldehyde generated from a molten sample. A preferred polyacetal resin composition in the present invention has a formaldehyde generation amount from a molten sample of 100 ppm or less. Here, as will be described in detail in the examples, the amount of formaldehyde generated is 5 in a state where 8 g of a pellet-shaped composition (sample) is filled in a melt indexer cylinder adjusted to 200 ° C. and melted. After holding for a minute, the amount generated from the discharged molten resin is quantified by a method according to JIS K0102.

<Method and application of polyacetal resin composition>
The polyacetal resin composition of the present invention can be molded by various known molding methods (for example, injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, etc.). The product can be molded. In particular, it is suitable for injection molding. These molded products can be used for various applications such as automobile parts, electrical / electronic parts, building materials, life-related parts, makeup-related parts, and medical-related parts.

  Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

<Use ingredients>
Details of the components used are as follows.
(A) Polyacetal resin (a-1) Polyacetal resin obtained by copolymerizing 96.5% by weight of trioxane and 3.5% by weight of 1,3-dioxolane, 0.2% by weight of unstable terminal groups, melt index = 27 g / 10 min (manufactured by Polyplastics Co., Ltd.)
(B) Woody fine powder (b-1) LIGNOCEL S150TR, sieve residue of 0.5 μm or less with an opening of 250 μm, lignin content of about 20 to 25% by weight (manufactured by Rettenmeier)
(B-2) ARBOCEL C100, sieve residue with an opening of 250 μm, 0.5% by weight or less, lignin content of about 20-25% by weight (manufactured by Rettenmeier)
(B-3) ARBOCEL HW630PU, sieve residue of 0% by weight with an opening of 250 μm, lignin content of about 20-25% by weight (manufactured by Rettenmeier)
(B-4) ARBOCEL C32-10, sieve residue having an opening of 250 μm, 5 to 20% by weight, lignin content of about 20 to 25% by weight (manufactured by Rettenmeier)
(B-5) ARBOCEL C320, sieve residue of 10 to 35% by weight with an opening of 250 μm, lignin content of about 20 to 25% by weight (manufactured by Rettenmeier)
(B ′) Other cellulosic substances (b′-6) Pulp, lignin content 1% by weight or less, α cellulose purity about 95% by weight (manufactured by Nippon Paper Group)
(C) Hindered phenol antioxidant (c-1) Pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]
(D) Nitrogen-containing compound (d-1) Melamine (e) Processing aid (e-1) Ethylene bisstearylamide (e-2) Glycerol monostearate

<Examples 1-5, Comparative Examples 1-7>
(A) polyacetal resin, (b) wood-based fine powder, (c) hindered phenol-based antioxidant, (d) nitrogen-containing compound, and (e) processing aid in the ratio shown in Table 1. And kneaded to prepare a pellet-like polyacetal resin composition. Note that (b) the woody fine powder was supplied from the feeder independently from the side of the twin-screw extruder (supplied from the side feed port), and the other components were supplied from the main feed port and mixed. In Comparative Examples 6 and 7, (b ′) other cellulosic material was used instead of (b) the woody fine powder. A predetermined test piece was molded by an injection molding machine using the obtained pellet, and the test evaluation was performed. The results are shown in Table 1.

[Extrusion conditions]
Extruder: TEX-30α (L / D = 38.5), Nippon Steel Works screw rotation: 129 rpm
Barrel temperature: C2 = 160 ° C., C3 to C11 · D = 200 ° C.
〔Molding condition〕
Molding machine: ROBOSHOT S2000i100B, screw diameter 28 mm, FANUC cylinder temperature: 200 ° C
Mold temperature: 90 ° C (water temperature control)

〔Test method〕
Details of the test method are as follows.

(1) Formaldehyde generation amount 8 g of a pellet-shaped composition (sample) prepared in Examples and Comparative Examples was filled in a metal cylinder adjusted to 200 ° C., and the resin pellets were melted to 5 Hold for a minute. Here, the used metal cylinder is connected to a glass suction bottle containing distilled water.
Subsequently, the formaldehyde gas generated from the molten resin is discharged into the distilled water in the glass suction bottle together with the nitrogen stream while flowing nitrogen into the glass absorption bottle connected to the metal cylinder. Formaldehyde gas was absorbed in the distilled water inside. Formaldehyde absorbed in distilled water was quantified by a method based on JIS K0102, and calculated as a ratio to the evaluation sample (composition).

(2) Flexural modulus Using the resin pellets of Examples and Comparative Examples, the flexural modulus (MPa) was measured according to ISO178.

(3) External appearance evaluation The external appearance of the bending test piece based on ISO178 was observed visually. A good one was indicated as “OK”, and a surface with roughness or non-uniformity was indicated as “NG”.

  From the comparison of the results in Table 1, it can be seen that the polyacetal resin compositions (Examples 1 to 5) satisfying the requirements of the present invention have a low formaldehyde generation amount and are excellent in rigidity and appearance. On the other hand, in the case of Comparative Examples 1 to 4 where (b) the woody fine powder does not satisfy the requirements of the present invention, it can be seen that the appearance is poor. Moreover, in the case of the comparative example 5 which does not mix | blend (b) wood type fine powder, it turns out that a bending elastic modulus is low. Moreover, it turns out that the amount of formaldehyde generation is high in the comparative examples 6 and 7 which mix | blended the cellulosic substance which does not satisfy the requirements of this invention.

Claims (2)

A method for producing a polyacetal resin composition comprising:
Using a twin screw extruder provided with a main feed port and a side feed port located on the downstream side in the extrusion direction from the main feed port,
From the main feed port, the (a) polyacetal resin, (c) a hindered phenol-based antioxidant, (d) a nitrogen-containing compound, and (e) a processing aid are supplied.
By supplying the wood-based fine powder (b) from the side feed port ,
(A) For 100 parts by weight of the polyacetal resin,
(B) 10 to 150 parts by weight of a woody fine powder containing 10 to 30% by weight of lignin and having a sieve residue of 3% by weight or less remaining on the sieve when sieved with a sieve having an opening of 250 μm;
(C) 0.01 to 3 parts by weight of a hindered phenol antioxidant,
0.01 to 3 parts by weight of at least one (d) nitrogen-containing compound selected from an aminotriazine compound, a guanamine compound, a hydrazide compound and a polyamide;
Containing 0.01 to 3 parts by weight of at least one (e) processing aid selected from long chain fatty acids, derivatives of long chain fatty acids, polyoxyalkylene glycols and silicone compounds;
The method to manufacture the polyacetal resin composition whose formaldehyde generation amount by the following method is 100 ppm or less .
(Measuring method)
Resin pellets composed of 8 g of the polyacetal resin composition were filled into a metal cylinder adjusted to 200 ° C. and held for 5 minutes in a molten state. Subsequently, the formaldehyde gas generated from the molten resin was discharged together with the nitrogen stream while flowing nitrogen through the glass absorption bottle connected to the metal cylinder, thereby allowing the distilled water in the absorption bottle to absorb the formaldehyde gas. Formaldehyde absorbed in distilled water was quantified by a method based on JIS K0102, and calculated as a ratio to the evaluation sample (resin composition). The manufacturing method of Claim 1 whose melt index (based on ASTM-D1238, 190 degreeC, 2.16kgf) of the said (a) polyacetal resin is 10-50 g / 10min.