JP2020169931A - Method for measuring formaldehyde discharged from polyacetal resin product - Google Patents

Abstract

To provide a method for easily measuring the amount of formaldehyde discharged from a polyacetal resin product.SOLUTION: The method for measuring formaldehyde discharged from a polyacetal resin product according to the present invention is characterized by measuring the amount of formaldehyde discharged from a polyacetal resin product on the basis of the maximum weak emission amount measured from the polyacetal resin product.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for measuring formaldehyde emitted from a polyacetal resin molded product.

Polyacetal resin is a crystalline resin and is a resin material having excellent rigidity, strength, toughness, slidability, and creep property. Therefore, it has been conventionally used for mechanical parts such as automobile parts, electrical / electronic parts, and industrial parts. It is widely used as a material.
In recent years, there has been an increasing demand for low VOC in polyacetal resins mainly in the field of automobiles, and there is an increasing demand for polyacetal resins having a small amount of formaldehyde emitted from parts as resins used for automobile interior parts.
As a method for measuring the amount of formaldehyde emitted from a molded product, the VDA275 method (see, for example, Patent Document 1), the sampling bag method (see, for example, Patent Document 2) and the like are known, and both methods are used for automobiles and houses. This is a measurement method that is widely used in fields and the like.

Japanese Patent No. 4827435 Japanese Patent No. 4980986

However, in the conventionally known method, the work process for obtaining the measured value is complicated and takes time, so that the number of points that can be measured in one day is currently limited. Therefore, a method that can be easily measured has been urgently desired.

Therefore, an object of the present invention is to provide a method for simply measuring the amount of formaldehyde emitted from a polyacetal resin molded product.

As a result of diligent research to solve the above-mentioned problems of the conventional method, the present inventors have a relationship between the maximum weak emission amount detected from the polyacetal resin molded product and the formaldehyde emission amount emitted from the molded product. We have found that there is, and found that the amount of formaldehyde emitted from a molded product can be easily measured, and have completed the present invention.

That is, the present invention is as follows.
[1]
A method for measuring formaldehyde emitted from a polyacetal resin molded product, which comprises measuring the amount of formaldehyde emitted from the polyacetal resin molded product based on the maximum weak light emission amount measured from the polyacetal resin molded product.
[2]
The method for measuring formaldehyde according to the above [1], wherein the measurement temperature of the maximum weak light emission amount is 150 to 180 ° C.
[3]
The method for measuring formaldehyde according to the above [1] or [2], wherein the measurement environment for the maximum weak light emission amount is a nitrogen atmosphere.

According to the present invention, the amount of formaldehyde emission from a polyacetal resin molded product can be easily measured without requiring a complicated process and time as in the conventional method.

This is an example showing the relationship between the maximum weak emission amount and the formaldehyde emission amount measured by the VDA275 method.

Hereinafter, embodiments for carrying out the present invention (hereinafter, 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.

The maximum weak emission amount refers to the maximum amount of light energy released when excited carbonyls and singlet oxygen generated in the process of decomposition of organic peroxides return to the ground state. Here, the weak light emission in the polyacetal resin molded product is mainly derived from the organic peroxide. The maximum weak luminescence amount is preferably the maximum weak luminescence amount derived from an organic peroxide.
In addition, in this specification, a polyacetal resin molded article may be simply referred to as a "molded article".

Examples of the measurement method in the present embodiment include the following methods.
First, the amount of formaldehyde emission by the VDA275 method is measured from a plurality of polyacetal resin molded products as reference samples. Other methods may be used for measuring the amount of formaldehyde emission. Subsequently, the maximum weak luminescence amount is measured using the plurality of polyacetal resin molded products, and the relational expression between the formaldehyde emission amount of the reference sample by the VDA275 method and the maximum weak luminescence amount is obtained in advance (see FIG. 1). ). Next, the maximum amount of weak light emitted from the molded product as a measurement sample is measured and applied to the relational expression to obtain the amount of formaldehyde emission.
Further, a relative formaldehyde concentration relationship can be obtained by measuring the maximum weak light emission amount of a plurality of molded products as measurement samples and comparing the maximum weak light emission amount of each measurement sample. At that time, the maximum weak emission amount is measured with a sample without a sample or a sample containing no organic peroxide or the like to obtain a background value, and the maximum weak emission amount corrected by the background value is used to obtain a more accurate concentration. You can get a relationship.

The following is estimated as to the relationship between the maximum weak emission amount and the formaldehyde emission amount from the molded product.
Generally, when the polyacetal resin is extruded or molded, the polyacetal resin is decomposed and a small amount of decomposed formaldehyde is generated in the process of thermal oxidative deterioration due to the influence of heat history and oxygen. At that time, it is considered that an organic peroxide is generated and remains in the molded product. That is, the present inventors have found that the amount of organic peroxide remaining in the molded product correlates with the amount of formaldehyde released from the molded product, leading to the present invention.

There are various theories about the mechanism by which weak light emission is generated from the molded product. For example, it is necessary to detect the light energy released when excited carbonyls and singlet oxygen generated in the process of decomposition of organic peroxides return to the ground state. The amount of weak light emission can be measured with.

The means for detecting the amount of weak light emission is not particularly limited, and for example, a means using a device having a photomultiplier tube inside a container that blocks light is used.
Weak light emission refers to light emission of about 50 Photos / cm ² / sec. For example, it refers to light emission having a "maximum weak light emission amount per 1 g of molded product" measured by the method of Examples described later of about 10,000 or less.
The temperature at which the maximum weak light emission amount is measured is preferably 150 to 180 ° C, more preferably 150 to 170 ° C, and even more preferably 155 to 165 ° C.
The environment for measuring the maximum weak light emission amount is not particularly limited, but a nitrogen atmosphere is preferable from the viewpoint of stably detecting the weak light emission amount.
The maximum weak light emission amount is the highest intensity light emission amount among the weak light emission amounts amplified by a photomultiplier tube after measuring light emission at a wavelength of 300 to 350 nm and about 50 Photos / cm ² / sec for 1 to 1800 seconds. May be. Further, the obtained luminescence amount may be divided by the mass of the sample to obtain the luminescence amount per gram. Above all, it is preferable that the value is measured by the method described in Examples described later.
Examples of the organic peroxide include hydroperoxides, ketone peroxides, dialkyl peroxides, and alkyl peroxides.

[Polyacetal resin molded product]
Hereinafter, the components necessary for obtaining the above-mentioned polyacetal resin molded product will be described.
The polyacetal resin molded product may be a molded product obtained by molding a polyacetal resin composition containing a polyacetal resin. The polyacetal resin composition may further contain an additive.

(Polyacetal resin)
The polyacetal resin contained in the above-mentioned polyacetal resin molded product refers to a polymer having an oxymethylene group in the main chain, and is, for example, a formaldehyde monomer or a formaldehyde such as a trimer (trioxane) or a tetramer (tetraoxane) thereof. A polyacetal homopolymer obtained by homopolymerizing a cyclic oligomer, which is substantially composed of only oximethylene units; a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimeric (trioxane) or tetramer (tetraoxane) thereof. Polyacetal copolymer obtained by copolymerizing with glycol such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, 1,4-butanediolformal, cyclic ether such as cyclic formal of diglycol, or cyclic formal; formaldehyde. A polyacetal copolymer having a branch obtained by copolymerizing a cyclic oligomer of formaldehyde such as a monomer or a trimeric (trioxane) or a tetrameric (tetraoxane) thereof with a monofunctional glycidyl ether; a polyacetal copolymer having a branch; Alternatively, a polyacetal copolymer having a crosslinked structure obtained by copolymerizing a cyclic oligomer of formaldehyde such as a trimeric (trioxane) or a tetrameric (tetraoxane) with a polyfunctional glycidyl ether; and the like can be mentioned.
Further, as the polyacetal resin, a compound having a functional group such as a hydroxyl group at both ends or one end, for example, a formaldehyde monomer or its trimer (trioxane) or tetramer (tetraoxane) in the presence of polyalkylene glycol. Polyacetal homopolymer having a blocking component obtained by polymerizing a cyclic oligomer of formaldehyde such as; formaldehyde monomer 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. Alternatively, a polyacetal copolymer having a blocking component obtained by copolymerizing a cyclic oligomer of formaldehyde such as a trimeric (trioxane) or a tetrameric (tetraoxane) with a cyclic ether or a cyclic formal can also be used.
The polyacetal resin may be used alone or in combination of two or more.

-Polyacetal homopolymer-
The polyacetal homopolymer is obtained by, for example, feeding a monomer such as formaldehyde, a chain transfer agent (molecular weight modifier) and a polymerization catalyst to a polymerization reactor into which a hydrocarbon-based polymerization solvent is introduced, and polymerizing by a slurry polymerization method. Can be manufactured.
At this time, since the raw material monomer, the chain transfer agent, and the polymerization catalyst may contain chain transferable components (components that generate unstable terminal groups) such as water, methanol, and formic acid, these chain transferable components are possible first. It is preferable to adjust the content of various components.
The content of these chain transferable components is preferably in the range of 1 to 1000 mass ppm, more preferably 1 to 500 mass ppm, and further preferably 1 to 300 mass ppm with respect to the total mass of formaldehyde. ..
By adjusting the content of the chain-transferable component within the above range, a polyacetal homopolymer having excellent thermal stability can be obtained.

The molecular weight of the polyacetal homopolymer can be adjusted by chain transfer using a molecular weight modifier such as carboxylic acid anhydride or carboxylic acid.
As the molecular weight modifier, propionic anhydride and acetic anhydride are particularly preferable, and acetic anhydride is more preferable.

The amount of the molecular weight modifier introduced is adjusted and determined according to the characteristics (particularly melt flow rate) of the target polyacetal homopolymer. For example, polyacetal homopolymers preferably have a melt flow rate (MFR value (based on ISO1133)) in the range of 0.1 to 100 g / 10 min, 1.0 g / 10 min to 70 g / 10. It is more preferable to keep it in the range of minutes.
By setting the MFR value of the polyacetal homopolymer in the above range, a polyacetal homopolymer having excellent mechanical strength can be obtained.

As the polymerization catalyst, an anionic polymerization catalyst is preferable, and an onium salt-based polymerization catalyst represented by the following general formula (I) is more preferable.
_{[R 1 R 2 R 3 R} 4 M] + X - ··· (I)
In formula (I), R ₁ , R ₂ , R ₃ and R ₄ each independently represent an alkyl group, M represents an element having a lone electron pair, and X represents a nucleophilic group. )
Only one type of polymerization catalyst may be used alone, or two or more types may be mixed and used.

Among the onium salt-based polymerization catalysts, quaternary phosphonium salt-based compounds such as tetraethylphosphonium iodide and tributylethylphosphonium iodide, and quaternary ammonium salt-based compounds such as tetramethylammonium bromide and dimethyl distearylammonium acetate. Compounds are preferred.
The amount of the onium salt-based polymerization catalyst such as the quaternary phosphonium salt-based compound and the quaternary ammonium salt-based compound added is preferably 0.0003 to 0.01 mol with respect to 1 mol of formaldehyde, more preferably. Is 0.0008 to 0.005 mol, more preferably 0.001 to 0.003 mol.

The hydrocarbon-based polymerization solvent may be any solvent that does not react with formaldehyde, and is not particularly limited. For example, a solvent such as pentane, isopentane, hexane, cyclohexane, heptane, octane, nonane, decane, and benzene. However, hexane is particularly preferable.
Only one of these hydrocarbon solvents may be used alone, or two or more of them may be mixed and used.

In the production of polyacetal homopolymers, it is preferable to first obtain crude polyacetal homopolymers by polymerization, and then to perform stabilization treatment on unstable end groups as described later.

The polymerization reactor for producing a crude polyacetal homopolymer is particularly limited as long as it can simultaneously supply the monomers formaldehyde, chain transfer agent (molecular weight modifier) and polymerization catalyst, and a hydrocarbon-based polymerization solvent. However, from the viewpoint of productivity, a continuous polymerization reactor is preferable.

The crude polyacetal homopolymer obtained by polymerization has a thermally unstable terminal group. Therefore, it is preferable to seal the unstable terminal group with an esterifying agent, an etherifying agent or the like to stabilize the group.

In the stabilization treatment of the terminal groups of the crude polyacetal homopolymer by esterification, for example, the crude polyacetal homopolymer and the esterifying agent and / or the esterification catalyst are put into a terminal stabilizing reactor into which a hydrocarbon solvent is introduced. It can be done by charging and reacting.
The reaction temperature and reaction time at this time are preferably 130 to 155 ° C. and preferably 1 to 100 minutes, and the reaction temperature is 135 to 155 ° C. and the reaction time is 5 to 100. More preferably, the reaction temperature is 140 to 155 ° C., and the reaction time is more preferably 10 to 100 minutes.

As the esterifying agent that seals and stabilizes the terminal group of the crude polyacetal homopolymer, an acid anhydride represented by the following general formula (II) can be used.
R ₅ COOCOR ₆ ... (II)
(In formula (II), R ₅ and R ₆ each independently represent an alkyl group. R ₅ and R ₆ may be the same or different from each other.)

Examples of the esterifying agent include benzoic anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, propionic anhydride, and acetic anhydride, and acetic anhydride is preferable. Only one of these esterifying agents may be used alone, or two or more thereof may be mixed and used.

As the esterification catalyst, an alkali metal salt of a carboxylic acid having 1 to 18 carbon atoms is preferable, and the addition amount thereof can be appropriately selected in the range of 1 to 1000 mass ppm with respect to the mass of the polyacetal homopolymer. .. Examples of alkali metal salts of carboxylic acids having 1 to 18 carbon atoms include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caprylic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, and myristic acid. Examples thereof include alkali metal salts of carboxylic acids such as palmitic acid, margaric acid and stearic acid, and examples of the alkali metals include lithium, sodium, potassium, rubidium and cesium. Among the alkali metal salts of these carboxylic acids, alkali metal salts of lithium acetate, sodium acetate, and potassium acetate are preferable.

It is also possible to seal and stabilize the terminal groups of the crude polyacetal homopolymer by etherification.
As the etherifying agent, an orthoester of an aliphatic or aromatic acid and an aliphatic, alicyclic or aromatic alcohol, for example, methyl orthoformate or ethyl orthoformate, methyl orthoacetate or ethyl ortho. You can choose from acetate, methyl orthobenzoate or ethyl orthobenzoate, and orthocarbonates, specifically ethyl orthocarbonates, medium strength organic acids such as p-toluenesulfonic acid, acetic acid and oxalic acid, dimethylsulfate and It can be stabilized with a Lewis acid type catalyst such as medium strength mineral acid such as diethylsulfate.

When the terminal group of the crude polyacetal homopolymer is sealed and stabilized by etherification, the solvent used for the etherification reaction is, for example, a low boiling aliphatic organic solvent such as pentane, hexane, cyclohexane and benzene; alicyclic. Formulas and aromatic hydrocarbon-based organic solvents; organic solvents such as halogenated lower aliphatics such as methylene chloride, chloroform and carbon tetrachloride; and the like can be mentioned.

The polyacetal homopolymer whose end groups have been stabilized by the above method is sealed with air or nitrogen gas adjusted to 100 to 150 ° C. using a dryer such as a hot air dryer or a vacuum dryer to remove water. And drying to obtain the desired polyacetal homopolymer.

-Polyacetal copolymer-
The polyacetal copolymer uses, for example, a glycol such as 1,3-dioxolane or 1,4-butanediolformal, a cyclic ether such as cyclic formal of diglycol, or a cyclic formal as a comonomer, and these and a monomer such as trioxane are used. It can be produced by copolymerizing or the like.

The proportion of the comonomer to be copolymerized is preferably 0.03 to 20 mol%, more preferably 0.03 to 15 mol%, and further preferably 0.04 to 5 mol% with respect to 1 mol of the trioxane. preferable.
When the proportion of comonomer is in the above range, polyacetal resin pellets having more excellent mechanical strength can be obtained.

Examples of the polymerization catalyst in the polymerization of the polyacetal copolymer include cationically active catalysts such as Lewis acid, protonic acid and its ester or anhydride.
Examples of the Lewis acid include halides of boric acid, tin, titanium, phosphorus, arsenic and antimony, and specific examples thereof include boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride and pentafluoride. Examples thereof include phosphorus chloride, antimony pentafluoride and its complex compounds or salts.
Examples of the protonic acid and its ester or anhydride include perchloric acid, trifluoromethanesulfonic acid, percarolic acid-quaternary butyl ester, acetylparklorate, trimethyloxonium hexafluorophosphate and the like.
Among these, boron trifluoride; boron trifluoride hydrate; and a coordination complex compound of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride; are preferable, for example, boron trifluoride diethyl ether. , Boron trifluoride di-n-butyl ether is preferred.

The amount of boron trifluoride added is preferably 0.10 × 10 ^-4 mol or less, more preferably 0.07 × 10 ^-4 mol or less, still more preferably 0.03, based on 1 mol of the trioxane. ~ 0.05 × 10 ^-4 mol.
When the amount of boron trifluoride added is in the above range, a polyacetal resin composition having excellent thermal stability can be provided.

As the polymerization method of the polyacetal copolymer exemplified above, in addition to the slurry polymerization method, for example, a massive polymerization method may be used, and either a batch method or a continuous method can be applied.
Examples of the polymerization apparatus include a self-cleaning type extrusion kneader such as a conider, a twin-screw type continuous extrusion kneader, and a twin-screw paddle type continuous mixer.
The melted monomer is supplied to the above-mentioned polymerization apparatus, and as the polymerization progresses, a solid massive polyacetal copolymer is obtained.

Since the polyacetal copolymer obtained by the above polymerization may have a thermally unstable end portion [-(OCH ₂ ) _n- OH group], this unstable end portion is decomposed and removed. It is preferable to carry out. As a method for decomposing and removing the unstable end portion, a known method can be used.

As described above, in the present embodiment, the (A) polyacetal resin is not limited, and both the polyacetal homopolymer and the polyacetal copolymer can be used.
Of these, polyacetal comopolymer is preferable.

(Additive)
The polyacetal resin composition includes known additives such as antioxidants, heat stabilizers, stabilizers such as formic acid traps, weather stabilizers, mold release agents, lubricants, conductive agents, thermoplastic resins, and heat. Plastic elastomers, dyes and pigments, pigments, inorganic fillers, organic fillers and the like may be added. These additives may be used alone or in combination of two or more.

As the antioxidant, a hindered phenolic antioxidant is preferable. 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- Hexandiol-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], pentaerythritol tetrakis [methylene-3- (3') , 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, 1,2-bis [3- (4-hydroxy-3,5-di-t-butylphenyl) propionyl] hydrazine, N, N'-hexamethylene bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propanamide], 1,3,5-tris [[3,5-bis (1,1-dimethylethyl) ) -4-Hydroxyphenyl] methyl] -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 4-[[4,6-bis (octylthio) -1,3, 5-Triazin-2-yl] amino] -2,6-di-t-butylphenol and the like can be mentioned. Preferably, triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] and pentaerythritol tetrakis [methylene-3- (3', 5'-di-t). -Butyl-4'-hydroxyphenyl) propionate] methane, 1,2-bis [3- (4-hydroxy-3,5-di-t-butylphenyl) propionyl] hydrazine, N, N'-hexamethylenebis [ 3- (3,5-di-t-butyl-4-hydroxyphenyl) propanamide]. These antioxidants may be used alone or in combination of two or more.

Examples of the heat stabilizer include polyamide resins such as nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, and nylon 12, and polymers thereof, for example, nylon 6/6. -6 / 6-10, nylon 6 / 6-12 and the like can be mentioned. Other examples include amide compounds, amino-substituted triazine compounds, additions of amino-substituted triazine compounds and formaldehyde, condensates of amino-substituted triazine compounds and formaldehyde, urea, urea derivatives, hydrazine derivatives, imidazole compounds and imide compounds.
Specific examples of the amide compound include polyvalent carboxylic acid amides such as isophthalic acid diamide, anthranyl amides, and polyacrylamide copolymers.
Specific examples of the amino-substituted triazine compound include 2,4-diamino-sim-triazine, 2,4,6-triamino-sim-triazine, N-butylmelamine, N-phenylmelamine, N, N-diphenylmelamine, N. , N-diallyl melamine, benzoguanamine (2,4-diamino-6-phenyl-sim-triazine), acetoguanamine (2,4-diamino-6-methyl-sim-triazine), 2,4-diamino-6-butyl -Sym-triazine and the like.
Specific examples of the adduct of the amino-substituted triazine compound and formaldehyde include N-methylol melamine, N, N'-dimethylol melamine, N, N', N "-trimethylol melamine.
Specific examples of the condensate of the amino-substituted triazine compound and formaldehyde include a melamine-formaldehyde condensate.
Examples of urea derivatives include N-substituted ureas, urea condensates, ethylene ureas, hydantoin compounds, and ureido compounds.
Specific examples of the N-substituted urea include methyl urea, alkylene bisurea, and aryl-substituted urea substituted with a substituent such as an alkyl group.
Specific examples of the urea condensate include a condensate of urea and formaldehyde.
Specific examples of the hydantoin compound include hydantoin, 5,5-dimethylhydantoin, 5,5-diphenylhydantoin and the like.
Specific examples of the ureido compound include allantoin and the like.
Examples of the hydrazine derivative include a hydrazide compound. Specific examples of the hydrazide compound include dicarboxylic acid dihydrazide, and more specifically, dihydrazide malonate, dihydrazide succinic acid, dihydrazide glutarate, dihydrazide adipic acid, dihydrazide pymeric acid, dihydrazide speric acid, and dihydrazide azelaide. , Sebatic acid dihydrazide, dodecanodiic acid dihydrazide, isophthalic acid dihydrazide, phthalic acid dihydrazide, 2,6-naphthalenedibo dihydrazide and the like. Specific examples of the imide compound include succinimide, glutarimide, and phthalimide.
Among these heat stabilizers, polyamide resins and acrylamide polymers are preferable.

Examples of the formic acid trapping agent include the above-mentioned amino-substituted triazine compound and a condensate of an amino-substituted triazine compound and formaldehyde, for example, a melamine-formaldehyde condensate. Other formic acid traps include hydroxides, inorganic acid salts, carboxylates or alkoxides of alkali metals or alkaline earth metals. For example, hydroxides such as sodium, potassium, magnesium, calcium or barium, carbonates, phosphates, silicates, borates, carboxylates and layered double hydroxides of the above metals can be mentioned. ..
The carboxylic acid of the above carboxylic acid salt is preferably a saturated or unsaturated aliphatic carboxylic acid having 10 to 36 carbon atoms, and these carboxylic acids may be substituted with a hydroxyl group. Specific examples of saturated or unsaturated aliphatic carboxylates include calcium dimyristate, calcium dipalmitate, calcium distearate, calcium (myristic acid-palmitate), calcium (myristic acid-stearate), ( Calcium palmitate-stearate) and calcium 12-hydroxystearate are mentioned, with calcium dipalmitate, calcium distearate and calcium 12-hydroxydistearate being preferred.
The formic acid trapping agent may be used alone or in combination of two or more.

As the light-resistant stabilizer, as the weather-resistant stabilizer, at least one selected from the group consisting of benzotriazole-based compounds, oxalic acid anilide-based compounds, and hindered amine-based light stabilizers is preferable.

The benzotriazole-based compound is not particularly limited, but is, for example, 2- (2'-hydroxy-5'-methyl-phenyl) benzotriazole, 2- (2'-hydroxy-3,5-di-t-butyl-. Phenyl) benzotriazole, 2- [2'-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] benzotriazole, 2- (2'-hydroxy-3,5-di-t-amylphenyl] Benzotriazole, 2- (2'-hydroxy-3,5-di-isoamyl-phenyl) benzotriazole, 2- [2'-hydroxy-3,5-bis- (α, α-dimethylbenzyl) phenyl] -2H -Benzotriazole, 2- (2'-hydroxy-4'-octoxyphenyl) benzotriazole and the like can be mentioned. These compounds may be used alone or in combination of two or more.

Examples of the oxalic acid arinide compound 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. Each of these compounds may be used alone, or two or more kinds may be used in combination.

Examples of hindered amine light stabilizers include 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2, 2,6,6-tetramethylpiperidine, 4- (phenylatoxi) -2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy -2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-benzyl Oxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4- (ethylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (Cyclohexylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (phenylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, bis (2,2,6,6- Tetramethyl-4-piperidyl) -carbonate, bis (2,2,6,6-tetramethyl-4-piperidyl) -oxalate, bis (2,2,6,6-tetramethyl-4-piperidyl) -malonate, Bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis- (N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (2,2) 6,6-Tetramethyl-4-piperidyl) -sevacate, bis (2,2,6,6-tetramethyl-4-piperidyl) -adipate, bis (2,2,6,6-tetramethyl-4-piperidyl) ) -Telephthalate, 1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) -ethane, α, α'-bis (2,2,6,6-tetramethyl-4-piperidyloxy) Oxy) -p-xylene, bis (2,2,6,6-tetramethyl-4-piperidyltrilen) -2,4-dicarbamate, bis (2,2,6,6-tetramethyl-4-piperidyl) ) -Hexamethylene-1,6-dicarbamate, tris (2,2,6,6-tetramethyl-4-piperidyl) -benzene-1,3,5-tricarboxylate, tris (2,2,6) 6-Tetramethyl-4-piperidyl) -benzene-1,3,4-tricarboxylate, 1- [2- {3- (3,5) -Di-t-butyl-4-hydroxyphenyl) propionyloxy} butyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] 2,2,6,6- Tetramethylpiperidin, 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β', β'-tetramethyl-3,9- [2,4,8,10-Tetraoxaspiro (5,5) undecane] A condensate with diethanol, and the like. The above-mentioned hindered amine-based light stabilizers may be used alone or in combination of two or more.
Among them, preferred weather-resistant stabilizers are 2- [2'-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] benzotriazole and 2- (2'-hydroxy-3,5-di-t-butyl). Phenyl) benzotriazole, 2- (2'-hydroxy-3,5-di-t-amylphenyl] benzotriazole, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis- ( N-Methyl-2,2,6,6-tetramethyl-4-piperidinyl) sevacate, bis (2,2,6,6-tetramethyl-4-piperidinyl) sevacate, 1,2,3,4-butanetetra Carboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β', β', -tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (2,4,8,10-tetraoxaspiro) 5,5) Undecane] A condensate with diethanol.

As the release agent and the lubricant, alcohols, fatty acids and fatty acid esters thereof, olefin compounds having an average degree of polymerization of 10 to 500, and silicones are preferably used. The release agent and the lubricant may be used alone or in combination of two or more.

Examples of the conductive agent include conductive carbon black, metal powder and fibers. The conductive agent may be used alone or in combination of two or more.

Examples of the thermoplastic resin include polyolefin resin, acrylic resin, styrene resin, polycarbonate resin, uncured epoxy resin and the like. The thermoplastic resin may be used alone or in combination of two or more.
It also includes these modified products. Examples of the thermoplastic elastomer include polyurethane-based elastomers, polyester-based elastomers, polystyrene-based elastomers, and polyamide-based elastomers. The thermoplastic elastomer may be used alone or in combination of two or more.

Examples of dyeing pigments include inorganic pigments, organic pigments, metallic pigments, fluorescent pigments and the like. Inorganic pigments are those commonly used for coloring resins, for example, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, fuel pigments, carbonates, phosphates, acetic acid. Examples include salt, carbon black, acetylene black, and lamp black. Organic pigments include condensed zo-based, inon-based, flotasianin-based, monoazo-based, diazo-based, polyazo-based, anthracinone-based, heterocyclic, pennon-based, quinacridone-based, thioindico-based, berylene-based, dioxazine-based, phthalocyanine-based, etc. Pigments such as the pigment of. The dyeing pigment may be used alone or in combination of two or more.

Examples of the pigment include inorganic pigments, organic pigments, metallic pigments, fluorescent pigments and the like. Inorganic pigments are pigments commonly used for coloring resins, such as zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, fuel pigments, carbonates, phosphates, etc. Examples thereof include acetate, carbon black, acetylene black, and lamp black. Organic pigments include condensed ouzo, inon, flotasianin, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennon, quinacridone, thioindico, berylene, dioxazine, and phthalocyanine. Etc. are pigments. It is difficult to clarify the addition ratio of the pigment because it varies greatly depending on the color tone, but it is generally used in the range of 0.05 to 5 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. One kind of pigment may be used, or two or more kinds of pigments may be used in combination.

Examples of other resins include polyolefin resins, acrylic resins, styrene resins, polycarbonate resins, uncured epoxy resins and the like. Other resins may be used alone or in combination of two or more.

As the inorganic filler, for example, fibrous, powdery, plate-like, hollow-shaped fillers and the like are used.

Examples of fibrous fillers include glass fibers, carbon fibers, silicone fibers, silica / alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, potassium titanate fibers, and stainless steel, aluminum, titanium, and copper. , Inorganic fibers such as metal fibers such as brass and the like. In addition, whiskers such as potassium titanate whiskers and zinc oxide whiskers having short fiber lengths are also included.

Examples of the powder particle filler include silicates such as carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, magnesium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, and wollastonite; iron oxide, Metal oxides such as titanium oxide and alumina; metal sulfates such as calcium sulfate and barium sulfate; carbonates such as magnesium carbonate and dolomite; other examples include silicon carbide, silicon nitride, boron nitride, and various metal powders.

Examples of the plate-shaped filler include mica, glass flakes, various metal foils, and the like.

Examples of the hollow filler include glass balloons, silica balloons, shirasu balloons, metal balloons and the like.

Examples of the organic filler include refractory organic fibrous fillers such as aromatic polyamide resin, fluororesin, and acrylic resin.
These fillers can be used alone or in combination of two or more.

Both of these fillers can be used as surface-treated fillers or unsurface-treated fillers, but in terms of the smoothness and mechanical properties of the molded surface, the use of surface-treated fillers is used. May be preferable. The surface treatment agent is not particularly limited, and conventionally known surface treatment agents can be used. As the surface treatment agent, for example, various coupling treatment agents such as silane type, titanate type, aluminum type and zirconium type, and surfactants such as resin acids, organic carboxylic acids and salts of organic carboxylic acids can be used. Specific examples of the surface treatment agent include N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltristearoyl titanate, and diisopropoxyammonium ethyl. Examples thereof include acetate and n-butylzirconeate.

The method for producing the polyacetal resin composition, which is a raw material for the polyacetal resin molded product, is not particularly limited.
In general, a polyacetal resin and a known additive are mixed with, if necessary, the above-mentioned predetermined components with, for example, a Henschel mixer, a tumbler, a V-shaped blender, or the like, and then uniaxial or poly. It can be obtained by kneading using a kneader such as a shaft extruder, a heating roll, a kneader, or a tumbler mixer. Above all, kneading with an extruder equipped with a vent decompression device is preferable from the viewpoint of productivity. Further, in order to stably produce a polyacetal resin composition in a large amount, a single-screw or twin-screw extruder is preferably used.
Further, each component can be continuously fed to the extruder individually or in groups of several types by a quantitative feeder or the like without mixing in advance.
It is also possible to prepare a high-concentration masterbatch composed of each component in advance and dilute it with a polyacetal resin at the time of extrusion melt kneading.
The kneading temperature may be in accordance with the preferable processing temperature of the polyacetal resin to be used, and is generally in the range of 140 to 260 ° C, preferably in the range of 180 to 230 ° C.

[Molding method]
The method for obtaining the polyacetal resin molded product is not particularly limited, and known molding methods such as extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, molding of other materials, and gas-assisted injection. It can be molded by any of molding methods such as molding, foam injection molding, low pressure molding, ultra-thin wall injection molding (ultra-high speed injection molding), and in-mold composite molding (insert molding, outsert molding).
Among these, the injection molding method is preferable from the viewpoint of stable productivity.

Hereinafter, the present embodiment will be described with reference to specific examples, but the present embodiment is not limited to the following examples.
The measurement method applied in the examples is shown below.

〔Measuring method〕
<Amount of formaldehyde released from molded products>
Using an IS-100GN injection molding machine manufactured by Toshiba Corporation, a test piece was molded at a cylinder temperature of 220 ° C., a mold temperature of 80 ° C., an injection pressure of 60 MPa, an injection time of 30 seconds, and a cooling time of 15 seconds. The molded product from the start of molding to the 5th shot was discarded, and the amount of formaldehyde released from the molded product was measured for the 6th shot molded product under the conditions shown below (VDA275 method).
-VDA275 method-
50 mL of distilled water and a test piece of the specified size (length 100 mm x width 40 mm x thickness 3 mm) are placed in a polyethylene container, sealed, and formaldehyde is extracted into the distilled water while heating at 60 ° C. for 3 hours, and then at room temperature. Cooled to.
After cooling, 5 mL of a 0.4% by mass aqueous solution of acetylacetone and 5 mL of a 20% by mass aqueous solution of ammonium acetate are added to 5 mL of distilled water that has absorbed formaldehyde to prepare a mixed solution, which is heated at 40 ° C. for 15 minutes to formaldehyde and acetylacetone. Reaction was performed.
Further, after cooling the mixed solution to room temperature, the amount of formaldehyde in the distilled water was quantified from the absorption peak at 412 nm using a UV spectrophotometer.
The amount of formaldehyde released from the molded product (mg / kg) was calculated by the following formula.
Formaldehyde emission amount from molded product (mg / kg) = Formaldehyde amount in distilled water (mg) / Mass of polyacetal resin molded product used for measurement (kg)

<Maximum weak light emission per 1 g of molded product>
Using an IS-100GN injection molding machine manufactured by Toshiba Corporation, a test piece was molded at a cylinder temperature of 220 ° C., a mold temperature of 80 ° C., an injection pressure of 60 MPa, an injection time of 30 seconds, and a cooling time of 15 seconds. Discard the molded product from the start of molding to 5 shots, cut the molded product on the 6th shot into a length of 30 mm, a width of 30 mm, and a thickness of 3 mm, and measure the maximum weak light emission amount per 1 g of the molded product by the method shown below. did.
For the measurement, a very weak emission detection spectroscopic system Chemylluminescence analyzer CLA-FS4 manufactured by Tohoku Denshi Sangyo Co., Ltd. was used. In a sample chamber heated to 160 ° C., the above-mentioned molded piece cut into a length of 30 mm and a width of 30 mm is placed on an aluminum cell having a diameter of 50 mm, held at a nitrogen flow rate of 100 ml / min, and a weak luminescence amount amplified by a photomultiplier tube. Read the numerical value at the time when the maximum value was reached. The maximum weak light emission amount read was divided by the mass of the molded piece previously weighed to calculate the maximum weak light emission amount per 1 g of the molded product.
The raw material components used in the examples are shown below.

<(A) Polyacetal resin>
A twin-screw paddle type continuous polymerization reactor with a jacket (manufactured by Kurimoto, Ltd., diameter 2B, L / D = 14.8) was adjusted to 80 ° C., and the raw material was subjected to the polymerization conditions (supply rate) shown below. Etc. were supplied to polymerize the crude polyacetal copolymer.
The crude polyacetal copolymer discharged from the polymerization reactor is immersed in an aqueous triethylamine solution (0.5% by mass), then stirred at room temperature for 1 hr, filtered through a centrifuge, and 120 ° C. × under nitrogen. It was dried for 3 hours to obtain a polyacetal copolymer before end stabilization.
The obtained polyacetal copolymer before end stabilization was supplied from the top hood port of a 30 mm twin-screw extruder having an end stabilization zone and a vacuum devolatilization zone set at 200 ° C. In the twin-screw extruder, while the supplied polyacetal copolymer before end stabilization is heated and melted in the end stabilization zone, 3.0 parts by mass of a 0.8% aqueous solution of triethylamine as an end stabilizer is fed, and the polyacetal is fed. End stabilization of the copolymer was performed. In the next decompression devolatilization zone, formaldehyde and the like generated during terminal stabilization were removed from the system by decompression operation to obtain a polyacetal resin.

[Polymerization conditions]
The raw materials were supplied to the reactor at the supply rates shown below.
-Trioxane (main monomer): 3500 g / hr
-1,3-Dioxolane (comonomer): 120.9 g / hr
-Methylal (molecular weight regulator): 4.7 g / hr
-Cyclohexane (organic solvent): 6.5 g / hr
-Boron trifluoride-di-n-butyl etherate (polymerization catalyst) :: 0.15 g / hr
(The supply rate was set so that boron trifluoride was 0.2 × 10 ^-4 mol with respect to 1 mol of trioxane.)
Only the polymerization catalyst was fed on a separate line from the above other components.

<(B) Additive>
B-1: Triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] (Irganox 245)
B-2: 1,2-bis [3- (4-hydroxy-3,5-di-t-butylphenyl) propionyl] hydrazine (Irganox MD1024)
B-3: Dihydrazide sebacate B-4: Melamine B-5: Polyamide 6,6

[Manufacturing Example 1]
To 100 mass of (A) polyacetal resin, 0.1 part by mass of (B-1) triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] was added to a Henschel mixer. Was mixed uniformly using the above to obtain a mixture.
This mixture was fed from the top feed port of a twin-screw extruder with a 30 mm vent set at 200 ° C., and melt-kneaded and pelletized at a screw rotation speed of 80 rpm, a vent pressure reduction degree of −0.09 MPa, and a discharge rate of 5 kg / hr. Then, the pellet was dried at a product temperature of 100 ° C. for 6 hours to obtain a polyacetal resin pellet.

[Production Examples 2 to 5]
The same operation as in Production Example 1 was carried out except that the composition was as shown in Table 1, to obtain polyacetal resin pellets.

[Manufacturing Examples 6 to 8]
The same operation as in Production Example 1 was carried out except that the composition was as shown in Table 2, to obtain polyacetal resin pellets.

(Example 1)
Using the polyacetal resin pellets obtained in Production Examples 1 to 5, the maximum weak light emission amount per 1 g of the molded product and the formaldehyde emission amount from the molded product were measured by the above-mentioned method to obtain the values in Table 1.
Based on this result, a relational expression (FIG. 1) was created between the maximum weak light emission amount per 1 g of the molded product and the formaldehyde emission amount from the molded product, and the relational expression: y = 0.0014x-1.804 was calculated. .. The relational expression was obtained by using the linear approximation method.

(Example 2)
Using the polyacetal resin pellets obtained in Production Examples 6 to 8, first, the maximum weak light emission amount per 1 g of the molded product was measured by the above method. Next, the numerical value was substituted into the relational expression obtained in Example 1 to obtain the formaldehyde emission amount (calculated value) from the molded product. In addition, as a result of measuring the amount of formaldehyde emission (measured value) from the molded product by the above-mentioned VDA275 method and verifying the consistency with the numerical value obtained by the simple method, it was confirmed that the calculated value and the measured value are almost in agreement. did. The results of the verification are shown in Table 2.

Claims (3)

A method for measuring formaldehyde emitted from a polyacetal resin molded product, which comprises measuring the amount of formaldehyde emitted from the polyacetal resin molded product based on the maximum weak light emission amount measured from the polyacetal resin molded product. The method for measuring formaldehyde according to claim 1, wherein the measurement temperature of the maximum weak light emission amount is 150 to 180 ° C. The method for measuring formaldehyde according to claim 1 or 2, wherein the measurement environment for the maximum weak light emission amount is a nitrogen atmosphere.

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