JPH11335519A - Polyacetal resin composition and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the stability of a polyacetal resin to inhibit the resin from forming formaldehyde. SOLUTION: About 0.01-10 pts.wt. specified urea derivative is added to 100 pts.wt. polyacetal resin. The specified urea derivative includes a mono-N- substituted urea (e.g. N-methylurea or N-ethylurea) or a urea condensate (e.g. urea/aldehyde condensate). An antioxidant may be added to the polyacetal resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyacetal resin composition in which the amount of formaldehyde generation is remarkably suppressed and which is excellent in moldability, a method for producing the same, and a polyacetal resin molded article molded from the resin composition.

[0002]

2. Description of the Related Art Polyacetal resins are excellent in mechanical properties, fatigue resistance, friction and abrasion resistance, chemical resistance and moldability, and are therefore used in automobile parts, electric and electronic equipment parts, other precision mechanical parts, It is widely used in the fields of building materials and piping parts, living and cosmetic parts, medical parts, and the like. However, with the expansion and diversification of applications, the demand for the quality thereof has been increasing. The characteristics required for the polyacetal resin include that the mechanical strength does not decrease in a processing step such as an extrusion or molding step, that no deposit (mold deposit) is generated on a mold,
The mechanical properties under long-term heating conditions (heat aging) do not decrease, and molding defects such as silver streaks and voids do not occur in molded products.
One of the important factors of these phenomena is decomposition of the polymer upon heating. In particular, the polyacetal resin is liable to be easily decomposed in a heated oxidizing atmosphere under acidic or alkaline conditions due to its chemical structure. Therefore, an essential problem of the polyacetal resin is that it has high thermal stability and suppresses the generation of formaldehyde from a molding process or a molded product. Formaldehyde is chemically active and becomes formic acid by oxidation, which adversely affects heat resistance.When used for parts of electric and electronic equipment, metal contact parts are corroded or discolored by the attachment of organic compounds, resulting in poor contact. Is generated. Furthermore, formaldehyde itself pollutes the working environment in the parts assembling process and the living environment around the use of the final product.

[0003] In order to stabilize the chemically active terminal, a homopolymer is obtained by esterifying the terminal of the polymer by acetylation or the like. For a copolymer, trioxane and a cyclic ether or cyclic formal are used during polymerization. After copolymerizing with a monomer having a carbon bond,
There is known a method of decomposing and removing an unstable terminal to make an inactive stable terminal. However, at the time of heating, cleavage and decomposition of the main chain portion of the polymer also occur, and the prevention cannot be dealt with only by the above treatment, and the addition of an antioxidant and other stabilizers is practically essential. .

However, even if these stabilizers are blended, it is difficult to completely suppress the decomposition of the polyacetal resin. In addition, under the action of heat or oxygen in the cylinder of an extruder or a molding machine, the main chain is decomposed or formaldehyde is generated from a terminal that is not sufficiently stabilized, thereby deteriorating the working environment during extrusion molding. In addition, when molding is performed for a long time, fine powders and tars adhere to the mold (mold deposit), which reduces the work efficiency and is one of the biggest factors in lowering the surface condition of the molded product. I have. Further, degradation of the polymer causes a decrease in mechanical strength and discoloration of the resin. From such a point, great efforts have been made for polyacetal resins in search of more effective stabilizing formulations.

As antioxidants added to polyacetal resin, sterically hindered phenol compounds (hindered phenols) and sterically hindered amine compounds (hindered amines) are known. As other stabilizers, melamine derivatives , Amidine compounds, alkali metal hydroxides and alkaline earth metal hydroxides, and organic or inorganic acid salts. Usually, antioxidants are used in combination with other stabilizers. However, even if such an additive is used, it is difficult to impart high stability to the polyacetal resin.

Japanese Patent Application Laid-Open No. 52-59646 discloses a polyacetal resin which is free from coloring by adding an antioxidant, an alkylene urethane, and urea to a polyacetal copolymer to improve the stability against heat and oxidizing atmosphere. A composition is disclosed. However, it is still difficult to significantly suppress the generation of formaldehyde only by adding an antioxidant and urea.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a resin composition capable of improving the thermal stability of a polyacetal resin, particularly the melt stability during molding, a method for producing the same, and a molded article. It is in.

It is another object of the present invention to provide a polyacetal resin composition which can significantly suppress the formation of formaldehyde by adding a small amount thereof and improve the working environment, a method for producing the same, and a molded article.

Still another object of the present invention is to suppress the formation of formaldehyde even under severe conditions, to adhere decomposed substances to a mold, to exude decomposed substances from a molded article, and to prevent An object of the present invention is to provide a polyacetal resin composition, a method for producing the same, and a molded article, which can suppress thermal deterioration, improve the quality of the molded article, and improve moldability.

[0010]

Means for Solving the Problems In order to achieve the above object, the present inventors conducted a search for a series of urea derivatives with respect to a polyacetal resin stabilizer, and as a result, it was found that a urea derivative having a specific chemical structure was obtained. The present inventors have found that the polyacetal resin has a remarkable effect as a stabilizer, particularly as a stabilizer at the time of processing, and have completed the present invention.

That is, the polyacetal resin composition of the present invention comprises a polyacetal resin and at least one urea derivative selected from a mono-N-substituted urea and a urea condensate having at least one amino group. . The amount of the urea derivative used is, for example, about 0.01 to 10 parts by weight based on 100 parts by weight of the polyacetal resin. The composition may further include an antioxidant.

In the method of the present invention, a polyacetal resin composition having improved thermal stability and processing stability is produced by mixing a polyacetal resin and a urea derivative. Furthermore, the present invention also includes a molded article composed of the polyacetal resin composition.

In the present specification, in addition to mono-N-substituted urea, a condensate of urea may be collectively referred to as "urea derivative".

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The resin composition of the present invention comprises a polyacetal resin and a urea derivative.

The polyacetal resin is a high molecular compound having an oxymethylene group (—CH ₂ O—) as a main constituent unit, and is a polyacetal homopolymer (for example, “Delrin” (trade name, manufactured by DuPont, USA); ),
And a polyacetal copolymer containing another comonomer unit in addition to the oxymethylene group (for example, trade name “Duracon” manufactured by Polyplastics Co., Ltd.). In the copolymer, the comonomer unit includes an oxyalkylene unit having about 2 to 6 carbon atoms (preferably about 2 to 4 carbon atoms) (for example, an oxyethylene group (—CH ₂ CH ₂ O—), an oxypropylene group, Methylene group, etc.). The content of the comonomer unit is small, for example, 0.01 to 20 mol%, preferably 0.03 to 10 mol% (for example, 0.05 to 5 mol%) based on the whole polyacetal resin.
Mol%), and more preferably from the range of about 0.1 to 5 mol%.

The polyacetal copolymer may be a copolymer composed of two components, a terpolymer composed of three components, or the like. The polyacetal copolymer may be a random copolymer, a block copolymer, a graft copolymer, or the like. Further, the polyacetal resin may have a branched structure as well as a linear structure, and may have a crosslinked structure. Further, the terminal of the polyacetal resin may be stabilized, for example, by esterification with a carboxylic acid such as acetic acid or propionic acid or an anhydride thereof. The degree of polymerization, the degree of branching and the degree of crosslinking of the polyacetal are not particularly limited as long as they can be melt-molded.

The polyacetal resin includes, for example, aldehydes such as formaldehyde, paraformaldehyde and acetaldehyde, trioxane, ethylene oxide, propylene oxide, 1,3-dioxolan,
It can be produced by polymerizing a cyclic ether such as diethylene glycol formal and 1,4-butanediol formal or a cyclic formal.

A feature of the present invention is that the addition of a specific urea derivative significantly improves the processing stability of the polyacetal resin and significantly suppresses the generation of formaldehyde. When the urea derivative is used, a stabilizing effect far exceeding the conventional stabilizer is exhibited, and a polyacetal resin composition having excellent processability can be obtained.

The urea derivative only needs to have at least one amino group (particularly at least two amino groups), and such a urea derivative includes a mono-N-substituted urea, a urea condensate and the like. As mono N-substituted ureas,
For example, mono-N-alkyl-substituted ureas (for example, mono-NC _1-6 alkyl-substituted ureas such as N-methyl and N-ethyl), alkylenebisureas (for example, ethylene, propylene, butylene, hexamethylene and the like) C _2-8 bis urea alkylene group), mono N- cycloalkyl-substituted urea (e.g., N- cyclobutyl body, mono- N-C _3-10 cycloalkyl substituted ureas, such as N- cyclohexyl body),
Mono-N-aryl-substituted ureas (eg, mono-N-C _6-12 aryl-substituted ureas such as phenyl-substituted urea)
Examples include hydrocarbon group-substituted urea. Examples of the urea condensate include a cyclic or acyclic condensate of urea and an aldehyde such as formaldehyde, acetaldehyde, and isobutyraldehyde.

Examples of these urea condensates include a multimer having a plurality of urea units (or urea residues) (for example, a dimer of urea (for example, biuret, biurea, etc.)) and a non-polymer of urea and isobutyraldehyde. Cyclic condensates (for example, isobutylidene diurea), condensates of urea and acetaldehyde [for example, 2-oxo-4-methyl-6-ureidohexahydropyrimidine (clotilidene diurea) and the like], and urea and formaldehyde Acyclic condensates (e.g., ureaform, form nitrogen, etc.) and urea resins (urea-formaldehyde resins) can be exemplified. In the acyclic condensate of urea and formaldehyde, one or more urea units may be condensed, and (n + 1) urea units (n is 1) via n methylene chains.
(The above integers) may be condensed. The urea derivatives can be used alone or in combination of two or more. The urea resin may be soluble or insoluble in warm water at about 40 to 100 ° C (particularly 50 to 80 ° C). The urea resin can be obtained by reacting at least urea, thiourea, and, if necessary, a co-condensation component (a phenol compound, melamine, guanamine, etc.) with formaldehyde. Good.
It may also be a methylol urea resins having a methylol group, at least a portion of the methylol groups, alcohols (e.g., methanol, ethanol, propanol, isopropanol, C _1-6 alcohol such as butanol) has been etherified with It may be an alkoxymethylurea resin. The urea resin may be a water-soluble urea resin, but is preferably a water-insoluble urea resin.

The amount of the urea derivative to be added is, for example, 0.01 to 10 parts by weight, preferably about 0.02 to 5 parts by weight, based on 100 parts by weight of the polyacetal resin.
Even at 3 to 2.5 parts by weight, the formation of formaldehyde can be significantly suppressed. If the amount of the urea derivative is less than 0.01 part by weight, it is difficult to effectively reduce the amount of formaldehyde generated, and if it exceeds 10 parts by weight, the moldability and the mechanical strength decrease.

The urea derivative alone can impart remarkable stability to the polyacetal resin even when used alone. However, the urea derivative may be an antioxidant, a basic nitrogen-containing compound, an alkali or alkaline earth metal compound (particularly, an organic carboxylate metal). Salts, metal oxides, metal carbonates, metal inorganic acid salts) and the like.

Examples of the antioxidant include phenol-based (such as hindered phenols), amine-based, phosphorus-based,
Examples include sulfur-based, hydroquinone-based, and quinoline-based antioxidants.

The phenolic antioxidants include hindered phenols such as 2,2'-methylenebis (4-
Methyl-6-t-butylphenol), 4,4'-methylenebis (2,6-di-t-butylphenol), 4,
4'-butylidenebis (3-methyl-6-t-butylphenol), 2,6-di-t-butyl-p-cresol, 1,3,5-trimethyl-2,4,6-tris (3,5- Di-t-butyl-4-hydroxybenzyl)
Benzene, 1,6-hexanediol-bis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate], pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxy) Phenyl) propionate], n-octadecyl-3
-(4 ', 5'-di-t-butylphenol) propionate, n-octadecyl-3- (4'-hydroxy-
3 ', 5'-di-tert-butylphenol) propionate, stearyl-2- (3,5-di-tert-butyl-4-)
(Hydroxyphenol) propionate, distearyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate, 2-t-butyl-6- (3-t-butyl-
5-methyl-2-hydroxybenzyl) -4-methylphenyl acrylate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4.
8,10-tetraoxaspiro [5,5] undecane,
4,4'-thiobis (3-methyl-6-t-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenol) butane and the like are included.

The amine antioxidants include hindered amines such as 4-methoxy-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,2.
6,6-tetramethylpiperidine, 4-phenoxy-
2,2,6,6-tetramethylpiperidine, bis-
(2,2,6,6-tetramethyl-4-piperidyl) oxalate, bis- (2,2,6,6-tetramethyl-
4-piperidyl) malonate, bis- (2,2,6,6)
-Tetramethyl-4-piperidyl) adipate, bis-
(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis- (1,, 2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (2,2,6)
6-tetramethyl-4-piperidyl) terephthalate,
1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) ethane, phenyl-1-naphthylamine, phenyl-2-naphthylamine, N, N′-diphenyl-1,4-phenylenediamine, N-phenyl-
N'-cyclohexyl-1,4-phenylenediamine and the like are included.

Examples of the phosphorus antioxidants include triisodecyl phosphite, triphenyl phosphite, trisnonyl phenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite,
2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite, 4,4'-butylidenebis (3-methyl-6-t-butylphenyl) ditridecyl phosphite, tris (2,4- Di-t-butylphenyl) phosphite, tris (2-t-butyl-4-methylphenyl) phosphite, tris (2,4-di-t-
Amylphenyl) phosphite, tris (2-t-butylphenyl) phosphite, bis (2-t-butylphenyl) phenylphosphite, tris [2- (1,1-
Dimethylpropyl) -phenyl] phosphite, tris [2,4- (1,1-dimethylpropyl) -phenyl]
Phosphite, tris (2-cyclohexylphenyl)
Phosphite compounds such as phosphite and tris (2-t-butyl-4-phenylphenyl) phosphite; and triethylphosphine, tripropylphosphine, tributylphosphine, tricyclohexylphosphine,
Diphenylvinylphosphine, allyldiphenylphosphine, triphenylphosphine, methylphenyl-p-
Anisylphosphine, p-anisyldiphenylphosphine, p-tolyldiphenylphosphine, di-p-anisylphenylphosphine, di-p-tolylphenylphosphine, tri-m-aminophenylphosphine, tri-
2,4-dimethylphenylphosphine, tri-2,4
6-trimethylphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-
Examples include phosphine compounds such as tolylphosphine, tri-o-anisylphosphine, tri-p-anisylphosphine, and 1,4-bis (diphenylphosphino) butane.

Hydroquinone-based antioxidants include, for example,
2,5-di-t-butylhydroquinone and the like, and quinoline-based antioxidants include, for example, 6-ethoxy-2,
2,4-trimethyl-1,2-dihydroquinoline and the like, and the sulfur-based antioxidants include, for example, dilauryl thiodipropionate, distearyl thiodipropionate and the like.

These antioxidants can be used alone or in combination of two or more. Preferred antioxidants include phenolic antioxidants (particularly, hindered phenols). Among the hindered phenols, particularly, for example, 1,6-hexanediol-bis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
C _2-10 alkylenediol-bis [3- (3,5-di-branched C _3-6 alkyl-4-hydroxyphenyl) propionate] such as propionate]; for example, triethylene glycol-bis [3- (3- t- butyl-5-methyl-4-hydroxyphenyl) propionate] di- or Toriokishi C _2-4 alkylene diol such as - bis [3- (3,5-di - branched C _3-6 alkyl-4-hydroxyphenyl) propionate]; for example, glycerol tris [3- (3,5-di -t- butyl-4-hydroxyphenyl) propionate] C _3-8 alkylene triol such as - bis [3- (3,5-di - branched C _3-6 alkyl-4-hydroxyphenyl) propionate]; for example, pentaerythritol tetrakis [3- (3,5
-Di-t-butyl-4-hydroxyphenyl) propionate] and the like; and C _4-8 alkylenetetraol tetrakis [3- (3,5-di-branched C _3-6 alkyl-4-hydroxyphenyl) propionate]. preferable.

These antioxidants can be used alone or in combination of two or more. The content of the antioxidant is, for example, from 0.01 to 5 parts by weight, preferably from 0.05 to 2.5 parts by weight, particularly from 0.1 to 5 parts by weight, based on 100 parts by weight of the polyacetal resin.
It can be selected from a range of about 1 part by weight.

The basic nitrogen-containing compound includes a low-molecular compound and a high-molecular compound (nitrogen-containing resin). Examples of the nitrogen-containing low molecular weight compound include aliphatic amines such as monoethanolamine and diethanolamine, and aromatic amines (eg, aromatic secondary amines such as o-toluidine, p-toluidine, and p-phenylenediamine, and tertiary amines). Amines), amide compounds (polycarboxylic amides such as malonamide and isophthalic diamide, p-aminobenzamide and the like), hydrazine or derivatives thereof (hydrazine,
Hydrazones, hydrazides such as polycarboxylic hydrazides, etc.), polyaminotriazines (guanamines such as guanamine, acetoguanamine, benzoguanamine or derivatives thereof, melamine or derivatives thereof), uracil or derivatives thereof (uracil, uridine etc.), cytosine Or derivatives thereof (cytosine, cytidine, etc.).

Examples of the nitrogen-containing resin include amino resins (condensation resins such as guanamine resin, melamine resin and guanidine resin, phenol-melamine resin, benzoguanamine-melamine resin, and aromatic polyamine-melamine resin) formed by reaction with formaldehyde. , Aromatic amine-formaldehyde resin (aniline resin, etc.), polyamide resin (eg, nylon 3, nylon 6, nylon 66, nylon 11, nylon 12, nylon MXD6, nylon 4-6, nylon 6) -10, nylon 6-11, nylon 6-12,
Homogenized or copolymerized polyamides such as nylon 6-66-610, substituted polyamides having a methylol group or an alkoxymethyl group), polyesteramides, polyamideimides, polyacrylamides, polyaminothioethers, and the like.

Preferred nitrogen-containing compounds include polyaminotriazines (melamine or a derivative thereof) and nitrogen-containing resins (amino resins such as melamine resins, polyamide resins, etc.). In particular, melamine, amino resin (such as melamine resin), and polyamide resin are preferable.
Among them, a crosslinked amino resin is preferable. Further, a melamine resin (melamine-formaldehyde resin), particularly a crosslinked melamine resin, is preferred.

These nitrogen-containing compounds can be used alone or in combination of two or more. The amount of the nitrogen-containing compound used is, for example, 0.01 to 5 parts by weight per 100 parts by weight of the polyacetal resin.
Parts by weight, preferably 0.05 to 2.5 parts by weight (especially 0.
1 to 1 part by weight).

Examples of the alkali or alkaline earth metal compound include salts of an alkali metal (such as sodium and potassium) or an alkaline earth metal (such as calcium and magnesium) with an organic carboxylic acid; metal oxides such as CaO and MgO; ₃ , metal carbonates such as MgCO ₃ ; metal inorganic acid salts such as salts of alkali metals (such as sodium and potassium) or alkaline earth metals (such as calcium and magnesium) with boric acid and phosphoric acid.

As the carboxylic acid constituting the carboxylic acid metal salt, a saturated or unsaturated aliphatic carboxylic acid having about 1 to 36 carbon atoms can be used. Further, these aliphatic carboxylic acids may have a hydroxyl group.

The saturated aliphatic carboxylic acids include acetic acid, propionic acid, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid,
Saturated C _1-36 monocarboxylic acid such as stearic acid, arachidic acid, behenic acid, lignoceric acid, cellotic acid, montanic acid, melicic acid, celloplastic acid, and saturated C such as oxalic acid, malonic acid, succinic acid, adipic acid _3-36
Polycarboxylic acids such as saturated C _6-36 tricarboxylic acids such as dicarboxylic acid, tricarballylic acid and butanetricarboxylic acid, or oxy acids thereof (eg, lactic acid, hydroxybutyric acid, hydroxylauric acid, hydroxypalmitic acid, hydroxystearic acid) , Malic acid, citric acid, etc.).

[0037] Examples of the unsaturated aliphatic carboxylic acid, undecylenic acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, brassidic acid, sorbic acid, linoleic acid, linolenic acid, unsaturated C such as arachidonic acid _3-36 Examples thereof include carboxylic acids and their oxy acids (for example, propiolic acid, stearolic acid, and the like).

The above-mentioned alkali or alkaline earth metal compounds can be used alone or in combination of two or more, and the proportion thereof is 0.0 to 100 parts by weight of the polyacetal resin.
It can be selected from the range of about 01 to 10 parts by weight, preferably about 0.001 to 5 parts by weight (particularly 0.001 to 2 parts by weight).

The antioxidant, nitrogen-containing compound, and alkali or alkaline earth metal compound may be used in combination. Further, the ratio (weight ratio) of the urea derivative (A) to the antioxidant and / or the nitrogen-containing compound (B) is, for example, the former (A) / the latter (B) = 0.1 /
1 to 10/1, preferably 0.2 / 1 to 10/1, more preferably 0.3 / 1 to 10/1 (for example, 0.5 /
1 to 5/1). In particular, when the ratio of the urea derivative increases, the amount of formaldehyde generated can be greatly improved.

The components (A) and (B) in such proportions
Is usually 0.05 to 15 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.1 to 5 parts by weight (e.g., 100 parts by weight of polyacetal resin)
0.1 to 3 parts by weight), especially about 0.3 to 3 parts by weight.

The resin composition of the present invention may contain, if necessary, various additives such as a heat stabilizer, a coloring agent containing a dye and a pigment, a release agent, a nucleating agent, an antistatic agent, a flame retardant, and a surfactant. Agent,
Various polymers, fillers and the like may be added alone or in combination of two or more.

The polyacetal resin composition of the present invention may be a powdery or granular mixture or a molten mixture, and can be prepared by mixing the polyacetal resin, the urea derivative, and if necessary, other additives with a conventional method. . For example,
After mixing each component, kneading and extruding with a single-screw or twin-screw extruder to prepare pellets, a method of molding, once preparing pellets having different compositions (master batch),
A method of mixing (diluting) the pellets in a predetermined amount and subjecting the mixture to molding to obtain a molded product of a predetermined composition, after adhering a urea derivative to the polyacetal resin pellets by spraying or the like,
A method of molding and obtaining a molded product having a predetermined composition can be employed. In the preparation of the composition used for the molded article,
Dispersion of additives is improved by mixing and melting and kneading a powder of a polyacetal resin as a substrate (for example, a powder obtained by crushing a part or all of the polyacetal resin) with another component (a urea derivative or the like). It is advantageous to have

The polyacetal resin composition of the present invention can remarkably suppress the formation of formaldehyde due to oxidation or thermal decomposition of the polyacetal resin in the molding (particularly, melt molding) process, and can improve the working environment. Further, adhesion of a decomposed product or the like to a mold (mold deposit) and leaching of the decomposed product from a molded product are remarkably suppressed, heat aging properties can be largely improved, and problems during molding can be improved. Therefore, the resin composition of the present invention, a conventional molding method, for example, injection molding, extrusion molding, compression molding,
It is useful for molding various molded articles by methods such as blow molding, vacuum molding, foam molding, rotational molding, and gas injection molding.

The polyacetal resin molded article of the present invention composed of the polyacetal resin composition contains a urea derivative, and generates very little formaldehyde.
That is, a molded article made of the conventional polyacetal resin containing a stabilizer such as an antioxidant generates a relatively large amount of formaldehyde, and contaminates a living environment and a working environment in addition to corrosion and discoloration. For example, generally the formaldehyde emission from the polyacetal resin molded article as it is marketed, in a dry (under constant-temperature dry atmosphere), the surface area 1 cm ² per 2~5μg about, in the wet (under constant-temperature wet atmosphere), surface area 1 cm ² 3-6 μg per
It is about. Even if the molding conditions are controlled, it is difficult to obtain a molded product having a dry surface of 2.0 μg or less per 1 cm ² of surface area and a wet process having a molded product of 2.5 μg or less per 1 cm ^{2 of} surface area.

On the other hand, the polyacetal resin molded article of the present invention has a formaldehyde emission of 2.0 μg or less per 1 cm ² surface area (0 to
2.0 μg), preferably 1.7 μg or less (0 to
1.7 μg), more preferably 1.5 μg or less (0 to 1.5 μg), particularly 1.2 μg or less (0 to
1.2 μg). In the wet method, the amount of formaldehyde generated was 2.C / cm ² of the surface area of the molded article.
5 μg or less (about 0 to 2.5 μg), preferably 2.2
μg or less (about 0 to 2.2 μg), more preferably 2 μg or less.
μg or less (about 0 to 2 μg).

The polyacetal resin molded article of the present invention only needs to have the above-mentioned formaldehyde generation amount in either the dry type or the wet type. Usually, it has the formaldehyde generation amount in both the dry type and the wet type. I have.

The amount of formaldehyde generated in a dry system can be measured as follows. After the polyacetal resin molded product is cut as necessary to measure the surface area, an appropriate amount of the molded product (for example, about 10 to 50 cm ² in surface area) is placed in a closed container (capacity: 20 ml), and the temperature is adjusted to 80 ° C.
Leave at 24 ° C. for 24 hours. Thereafter, 5 ml of water was poured into the closed container, and the amount of formalin in the aqueous solution was measured according to JIS K
Quantification is carried out according to 0102, 29 (formaldehyde) to determine the amount of formaldehyde generated (μg / cm ² ) per surface area of the molded article.

The amount of formaldehyde generated in a wet system can be measured as follows. After measuring the surface area by cutting the polyacetal resin molded product as necessary, an appropriate amount of the molded product (for example, about 10 to 100 cm ² in surface area) is placed in a closed container containing 50 ml of distilled water (capacity 1).
L), hang it on the lid and seal it tightly.
Leave for a time. Then, the mixture was left at room temperature for 1 hour, and the amount of formalin in the aqueous solution in the closed container was measured according to JIS K0102, 29.
(Formaldehyde), the amount of formaldehyde generated per surface area of the molded article (μg / cm ² )
Ask for. The numerical specification of the formaldehyde generation amount in the present invention is not limited to the molded product of the polyacetal resin composition containing a conventional additive (such as a normal stabilizer or a release agent) as long as the polyacetal resin and the urea derivative are included. , Inorganic fillers, and other polymer-containing compositions, most of the surface of the molded article (for example, 50 to 100%) is composed of polyacetal resin (for example, multicolor molding). Products and coated molded products).

The molded article of the present invention can be used in any application where formaldehyde is detrimental (for example, knobs and levers as bicycle parts), but it can be used for mechanical parts (active parts) in the field of automobiles and electric / electronic fields. Parts, passive parts, etc.), construction materials and plumbing, daily necessities (life), cosmetics,
And it is suitably used as a part / member in the medical field (medical / treatment field).

More specifically, the mechanical parts in the automobile field include inner handles, fuel trunk openers, seat belt buckles, assist wraps, interior parts such as various switches, knobs, levers, clips, and electric parts such as meters and connectors. System parts, in-vehicle electric and electronic parts such as audio equipment and car navigation equipment,
Parts that come into contact with metal typified by a carrier plate of a window regulator, door lock actuator parts, mirror parts, wiper motor system parts, and fuel system parts can be exemplified.

As mechanical parts in the electric and electronic fields, parts or members of equipment made of a polyacetal resin molded article and having many metal contacts [for example, audio equipment such as a cassette tape recorder, VTR (video tape recorder)] OA (Office Automation) equipment such as copiers, facsimile machines, word processors, computers, etc., as well as toys, telephones, computers, etc. that are driven by driving power such as motors and splicers. Keyboard etc.]. Specific examples include a chassis (base), gears, levers, cams, pulleys, bearings, and the like. Further, optical and magnetic media components at least partially composed of a polyacetal resin molded product (for example, a metal thin film magnetic tape cassette, a magnetic disk cartridge, a magneto-optical disk cartridge, etc.),
More specifically, the present invention can be applied to a metal tape cassette for music, a digital audio tape cassette, an 8 mm video tape cassette, a floppy disk cartridge, a mini disk cartridge, and the like. Specific examples of optical and magnetic media components include tape cassette components (tape cassette main body, reel, hub, guide, roller, stopper, lid, etc.), disk cartridge components (disk cartridge main body (case), shutter, clamping) Plate and the like).

Further, the polyacetal resin molded article of the present invention can be used for building materials and piping parts such as lighting fixtures, fittings, piping, cocks, faucets, toilet peripheral parts, stationery, lip cream / lipstick containers, washing machines, water purifiers, It is suitably used for a wide range of living-related parts, cosmetic-related parts, and medical-related parts such as spray nozzles, spray containers, aerosol containers, general containers, and injection needle holders.

[0053]

According to the present invention, the polyacetal resin composition comprises:
Since the polyacetal resin contains a specific urea derivative, the thermal stability of the polyacetal resin (particularly, the melt stability during molding) can be greatly improved. Further, the amount of formaldehyde generated can be suppressed to an extremely low level by adding a small amount, and the working environment can be greatly improved. Furthermore, even under severe conditions, the formation of formaldehyde can be suppressed, the adhesion of decomposed products to molds (mold deposit), the leaching of decomposed products from molded products, and the thermal degradation of molded products can be suppressed. Product quality and moldability can be improved.

[0054]

EXAMPLES The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples.

In the examples and comparative examples, the amount of formaldehyde generated from the dry and wet molded products was evaluated as follows. [Amount of formaldehyde generated from molded product in dry process] 10 test pieces (2 mm x 2 mm x 50 mm) (total surface area of about 4
0cm ² ) Resin sample in closed container (capacity 20ml)
After heating in a thermostat at a temperature of 80 ° C. for 24 hours, the mixture was air-cooled to room temperature, and 5 ml of distilled water was injected with a syringe. The amount of formalin in this aqueous solution was determined according to JIS K010
2,29 (formaldehyde), formaldehyde gas generation per surface area (μg / cm
² ) was calculated.

[Amount of Formaldehyde Generated from Wet Molded Article] Flat molded article (120 mm × 120 mm × 2 m
m) to obtain a test piece (100 mm × 40
mm × 2 mm; total surface area 85.6 cm ² ) with distilled water 50
ml of polyethylene bottle (capacity: 1 L), which was hung on a lid and hermetically sealed, and left in a thermostat at a temperature of 60 ° C. for 3 hours.
It was left at room temperature for 1 hour. The amount of formalin in the aqueous solution in the polyethylene bottle was determined in accordance with JIS K0102, 29 (formaldehyde), and the amount of formaldehyde generated (μg / cm ² ) per surface area of the molded article was calculated.

Examples 1 to 8 and Comparative Examples 1 to 3 An antioxidant [pentaerythritol tetrakis [3- (3,5-di-t-)] was added to 100 parts by weight of polyacetal resin.
Butyl-4-hydroxyphenyl) propionate]
After 0.3 parts by weight and the urea derivative were mixed at the ratio shown in Table 1, the mixture was melt-mixed with a twin-screw extruder to prepare a pellet-shaped composition. Using the pellets, a test piece was formed by an injection molding machine, and the above evaluation was performed using the test piece. Table 1 shows the results.

For comparison, examples in which no urea derivative was added, and examples in which 1,1-dimethylurea and 1,3-dimethylurea were used as stabilizers other than the urea derivative of the present invention were used in the same manner as described above. evaluated.

The polyacetal resins, antioxidants, urea derivatives and other stabilizers used in the examples and comparative examples are as follows. 1. 1. Polyacetal resin (a): polyacetal resin copolymer (manufactured by Polyplastics Co., Ltd., “Duracon”) Antioxidant (b): pentaerythritol tetrakis [3- (3,
5-di-t-butyl-4-hydroxyphenyl) propionate] 3. Urea derivative (c): N-methyl urea (d): biuret (e): urea heat condensate (160 ° C./5 hour heating reaction product insoluble in hot water) (f): biurea (g): IB nitrogen ( (H): CDU (2-oxo-4-methyl-6-ureidohexahydropyrimidine: Chisso Asahi Fertilizer Co., Ltd.) (i): 2 moles of form nitrogen ( (J): 3 mol powder of form nitrogen (manufactured by Mitsui Chemicals, Inc.) Other stabilizers (k): 1,1-dimethylurea (l): 1,3-dimethylurea

[0060]

[Table 1]

As is clear from the table, compared with the comparative example,
Since the amount of formaldehyde generated in the resin compositions of the examples is extremely small, the working environment can be greatly improved, and the quality and moldability of molded products can be improved.

Claims (10)

[Claims] 1. A polyacetal resin composition comprising a polyacetal resin and at least one urea derivative selected from a mono N-substituted urea and a urea condensate having at least one amino group. 2. The urea derivative is biuret, biurea,
The polyacetal resin composition according to claim 1, which is isobutylidene diurea, clotilidene diurea, or a condensate of urea and formaldehyde. 3. The polyacetal resin composition according to claim 1, wherein the amount of the urea derivative used is 0.01 to 10 parts by weight based on 100 parts by weight of the polyacetal resin. 4. The polyacetal resin composition according to claim 1, further comprising an antioxidant. 5. The polyacetal resin composition according to claim 4, wherein the ratio (weight ratio) of the urea derivative to the antioxidant is 0.1 / l to 10/1. 6. The method according to claim 1, further comprising a nitrogen-containing compound.
The polyacetal resin composition according to the above. 7. A method for producing a polyacetal resin composition, comprising mixing a polyacetal resin and at least one urea derivative selected from a mono N-substituted urea and a urea condensate having at least one amino group. 8. A polyacetal resin molded product comprising the polyacetal resin composition according to claim 1. 9. An amount of formaldehyde generated is 2.0 μg or less per 1 cm ² of surface area of a molded article when stored in a closed space at a temperature of 80 ° C. for 24 hours, or (2) a temperature of 60 ° C.
° C., when stored for 3 hours in enclosed spaces saturated humidity, the amount of generated formaldehyde surface area 1 cm ² per shaped article 2.5
The polyacetal resin molded product according to claim 8, wherein the amount is not more than μg. 10. The polyacetal resin molded article according to claim 8, wherein the molded article is at least one selected from an automobile part, an electric / electronic part, a building material / piping part, a living / cosmetic part, and a medical part.