JPH11335518A - Polyacetal resin composition and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat stability and molding stability of a polyacetal resin to inhibit the resin from forming formaldehyde. SOLUTION: About 0.01 to 10 pts.wt. cyclic nitrogen-containing compound is added to 100 pts.wt. polyacetal resin. The cyclic nitrogen-containing compounds includes one containing -NR1 C(=NH)NR2 C(=X1 )- (wherein R1 and R2 , which may be the same or different from each other, are each hydrogen, an alkyl, or an acyl; and X1 is oxygen, sulfur or imino) as a ring constituting unit. 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 generated is remarkably suppressed and which has excellent moldability and a process 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.

[0003] The characteristics required of 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) adheres to a mold, and that long-term heating conditions (heat Aging), and that molding defects such as silver streaks and voids do not occur in the molded product. One of the important factors of these phenomena
One 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.

[0004] In order to stabilize the chemically active terminal, a homopolymer is obtained by esterifying the terminal of the polymer by acetylation or the like, and a copolymer is prepared by admixing trioxane with a cyclic ether or cyclic formal 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, and in practice, during the extrusion or the melt processing in the molding step for preparing the composition. 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.

JP-B-55-50502 and JP-A-6-73267 disclose the use of a high-molecular-weight melamine derivative obtained by the polycondensation of melamine and formaldehyde to improve the thermal stability and improve mold deposit and blooming. It has been proposed to improve the performance. However, even with the use of a high molecular weight melamine derivative, it is still difficult to significantly suppress the formation of formaldehyde.

JP-A-48-88136 discloses a stabilizer comprising a phenolic compound and a nitrogen-containing compound such as hydantoin and its derivative in order to improve the thermal stability and antioxidant properties of polyacetal. A polyacetal composition is disclosed. However, even if a hydantoin compound is added, it is difficult to maintain the amount of formaldehyde generated from the polyacetal resin at an extremely low level.

[0009]

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.

[0010] Another object of the present invention is to provide a polyacetal resin composition, a method for producing the same, and a molded article which can significantly suppress the formation of formaldehyde by adding a small amount thereof and improve the working environment.

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 the formation of a molded article. 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.

[0012]

Means for Solving the Problems In order to achieve the above object, the present inventors conducted a search for a series of nitrogen-containing compounds with respect to a polyacetal resin stabilizer, and found that nitrogen-containing compounds having a specific chemical structure were obtained. The present inventors have found that the compound has a remarkable effect as a stabilizer for polyacetal resin, particularly as a stabilizer during processing, and have completed the present invention.

That is, the polyacetal resin composition of the present invention comprises a polyacetal resin and a cyclic nitrogen-containing compound. The cyclic nitrogen-containing compound is -NR _{1
C (= NH) NR 2 C} (= X 1) - (R 1 and R _2,
Same or different, and represents a hydrogen atom, an alkyl group, or an acyl group, and X ₁ represents an oxygen atom, a sulfur atom, or an imino group. ) Is included as a structural unit of the ring. The amount of the cyclic nitrogen-containing compound 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 with a cyclic nitrogen-containing compound having a specific structure. Furthermore, the present invention also includes a molded article composed of the polyacetal resin composition.

In the present specification, the "second nitrogen-containing compound" refers to a nitrogen-containing compound other than the cyclic nitrogen-containing compound.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The resin composition of the present invention comprises a polyacetal resin and a cyclic nitrogen-containing compound.

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, trade name “Delrin” manufactured by DuPont USA, Asahi Kasei Corporation) ),
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 by adding a cyclic nitrogen-containing compound having a specific chemical structure, the thermal stability and processing stability of the polyacetal resin are improved, and the generation of formaldehyde is remarkably suppressed. . When the cyclic nitrogen-containing compound is used, a stabilizing effect far exceeding that of a conventional stabilizer is exhibited, and a polyacetal resin composition having excellent heat stability and processability can be obtained.

The cyclic nitrogen-containing compound has the formula (1) -NR ₁
It has a cyclic structural unit represented by C (= NH) NR ₂ C (= X ₁ )-. Such cyclic nitrogen-containing compounds include compounds represented by the following formulas (1a) to (1f).

[0022]

Embedded image

Where R₁, R_Two, And R_FiveAre the same or
Represents a hydrogen atom, an alkyl group, or an acyl group.
Then R_ThreeAnd R_FourAre the same or different and represent a hydrogen atom,
A alkyl group, an ester group, or an amino group;₁, X
_Two, And X_ThreeAre the same or different and represent oxygen atom, sulfur atom
Represents an imino group or an imino group. In the above formula, R₁~ R_FiveAnd an alkyl group represented by
Then, C_1-4Alkyl group, especially methyl group or ethyl group
Can be exemplified. R₁, R_TwoAnd R_FiveAcyl represented by
The base is C_1-4Acyl group, especially formyl group, acetyl
And a propionyl group. R_Threeas well as
R_FourAs the ester group represented by, an acyloxy group
(C_2-5Acyloxy group), alkoxycarbonyl group
(C_1-4Alkoxy-carbonyl group) and the like.
You. R_ThreeAnd R_FourThe amino group represented by
C such as tyl group_1-4Alkyl groups) and acyl groups (ace
C such as tyl group_1-4Such as an acyl group)
You may. Also, X₁, X_Two, And X_Three Is an oxygen atom,
A substituent selected from a sulfur atom and an imino group (NH)
And particularly preferably an oxygen atom or an imino group.

Regarding the number of nitrogen atoms constituting the ring, 2
Or more (2 to 4) is preferable, and 2 to 3 is particularly preferable. The cyclic nitrogen-containing compound may be a cyclic compound as long as it has the above-mentioned structure, and is not particularly affected by the size of the heterocyclic ring, but is preferably a 5-membered ring compound or a 6-membered ring compound. These cyclic nitrogen-containing compounds may be used alone or in combination of two or more.

The preferred nitrogen-containing compound is a 5-membered ring nitrogen-containing compound, a compound containing two nitrogen atoms in the ring skeleton as represented by the above formulas (1a) and (1b), or a compound represented by the above formula (1c) Embedded image which includes three nitrogen atoms in the ring skeleton. Examples of the compound having the structure of the formula (1a) include glycosiamidine or a derivative thereof (for example, glycosiamidine, thioglycocyanidin, creatinine, 4-methylglycocyanidin, 4,4-glycocyanidin, and the like). included. Examples of the compound having the structure of the formula (1b) include oxalylguanidine or a cyclic guanidine having a similar structure (eg, oxalylguanidine, 2,4-diiminoparabanic acid, 2,4,5-triiminoparabanic acid). Included and also the formula (1
Compounds having the structure c) include compounds in which at least one of the two oxo groups (（O) of urazole is substituted with an imino group (＝ NH) (for example, iminourazole, iminothiourazole , Guanadine, etc.).

Preferred 6-membered nitrogen-containing compounds include compounds having three nitrogen atoms as ring constitutional units as in the above formula (1d), or compounds having two nitrogen atoms as represented by the above formula (1e) or (1f). Compounds having two nitrogen atoms as ring constituent units. Examples of the compound having the structure of the formula (1d) include isocyanuric imide or a derivative thereof (for example, isoammelide, isoammeline, or an N-substituted product thereof). Examples of the compound having the structure of the formula (1e) include And cyclic guanidines such as malonylguanidine and tartronyl guanidine or derivatives thereof. Compounds having the structure of formula (1f) include cyclic guanidine compounds such as methoxalyl guanidine. These cyclic nitrogen-containing compounds can be used alone or in combination of two or more.

Among the above cyclic nitrogen-containing compounds, the compound represented by the formula (1)
The compounds represented by a) or (1d) are preferred, and glycosiamidines (especially creatinine) such as glycosiamidine or a derivative thereof, and isocyanuric imide or a derivative thereof are particularly preferred.

The amount of the cyclic nitrogen-containing compound added is, for example, 0.01 to 100 parts by weight of the polyacetal resin.
10 to 10 parts by weight (for example, 0.01 to 5 parts by weight), preferably 0.02 to 5 parts by weight, more preferably 0.03 to 5 parts by weight.
It is about 2.5 parts by weight, and even if it is about 0.03 to 1.5 parts by weight (for example, 0.1 to 1.5 parts by weight), formation of formaldehyde can be remarkably suppressed.

The above-mentioned cyclic nitrogen-containing compound can impart remarkable stability to the polyacetal resin even when used alone. However, the cyclic nitrogen-containing compound may contain an antioxidant, a second nitrogen-containing compound, an alkali or alkaline earth metal compound (particularly, , Organic carboxylic acid 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-based antioxidants include hindered amines, for example, 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 (2,2,2 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.

Examples of the phosphorus-based antioxidant 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.

The 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 second 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.), ureas (urea, ethylene urea, thiourea or derivatives thereof), polyaminotriazines (guanamines such as guanamine, acetoguanamine, benzoguanamine or derivatives thereof, melamine or Derivatives thereof), uracil or its derivatives (uracil, uridine, etc.), cytosine or its derivatives (cytosine, cytidine, etc.), and the like.

Examples of the second nitrogen-containing resin include, for example, amino resins (condensation resins such as urea resins, thiourea resins, guanamine resins, melamine resins, and guanidine resins), urea-melamine resins, and urea resins formed by the reaction with formaldehyde. Benzoguanamine resin, phenol-melamine resin, benzoguanamine-melamine resin, aromatic polyamine-melamine resin, etc.), aromatic amine-formaldehyde resin (aniline resin, etc.),
Polyamide resin (for example, nylon 3, nylon 6, nylon 66, nylon 11, nylon 12, nylon M
XD6, nylon 4-6, nylon 6-10, nylon 6-11, nylon 6-12, nylon 6-66-61
Homopolyamides such as 0, substituted polyamides having a methylol group or an alkoxymethyl group, etc.), polyesteramides, polyamideimides, polyacrylamides, polyaminothioethers and the like.

Preferred second nitrogen-containing compounds include ureas (urea or derivatives thereof), polyaminotriazines (melamine or derivatives thereof), and nitrogen-containing resins (amino resins such as urea resins and melamine resins, polyamide resins and the like). Is included. 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.

The second nitrogen-containing compound can be used alone or in combination of two or more. The amount of the second nitrogen-containing compound is, for example, 0.0 parts by weight based on 100 parts by weight of the polyacetal resin.
It can be selected from the range of about 1 to 5 parts by weight, preferably about 0.05 to 2.5 parts by weight (particularly 0.1 to 1 part by weight).

Examples of the alkali or alkaline earth metal compound include salts of an alkali metal (sodium, potassium, etc.) or an alkaline earth metal (calcium, magnesium, etc.) 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 metal carboxylate, 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.).

[0044] 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 alkali or alkaline earth metal compounds can be used alone or in combination of two or more.
For example, for 100 parts by weight of polyacetal resin,
It can be selected from the range of about 0.001 to 10 parts by weight, preferably about 0.001 to 5 parts by weight (particularly 0.001 to 2 parts by weight).

The antioxidant, the second nitrogen-containing compound, and the alkali or alkaline earth metal compound may be used in combination. Further, the ratio (weight ratio) of the cyclic nitrogen-containing compound (A) to the antioxidant and / or the second nitrogen-containing compound (B) is, for example, the former (A) / the latter (B) = 0.01 / 1 to 10/1, preferably 0.1 / 1 to 10/1 (for example, 0.2 / 1 to 10/1).
/ 1), more preferably from the range of about 0.3 / 1 to 10/1 (for example, 0.5 / 1 to 5/1).
In particular, when the proportion of the cyclic nitrogen-containing compound increases, the amount of formaldehyde generated can be greatly improved.

The total amount of the components (A) and (B) at such a ratio is generally 0.05 to 15 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 100 parts by weight of the polyacetal resin. Is 0.1 to 5 parts by weight (for example, 0.1 to 5 parts by weight).
1 to 3 parts by weight).

The polyacetal resin composition of the present invention includes:
If necessary, various additives such as a colorant containing a dye and a pigment, a release agent, a nucleating agent, an antistatic agent, a flame retardant, a surfactant, various polymers, and a combination of two or more types of fillers. May be added.

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 a polyacetal resin and a cyclic nitrogen-containing compound by a conventional method. For example, mixing each component,
After pellets are prepared by kneading and extruding with a single-screw or twin-screw extruder, a method of molding, a pellet (master batch) having a different composition is once prepared, and the pellets are mixed (diluted) in a predetermined amount and subjected to molding. A method of obtaining a molded product having a predetermined composition, a method of obtaining a molded product having a predetermined composition, and a method of obtaining a molded product having a predetermined composition by applying a scavenger to pellets of a polyacetal resin by spraying or the like can be employed. In the preparation of a composition used for a molded article, a powder of a polyacetal resin serving as a substrate (for example, a powder of a part or all of a polyacetal resin) and other components (such as a cyclic nitrogen-containing compound) are used. Is melt-kneaded to improve the dispersion of the additive.

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 products by methods such as blow molding, vacuum molding, foam molding, and rotational molding.

The polyacetal resin molded article of the present invention composed of the above polyacetal resin composition contains a specific cyclic nitrogen-containing compound, and generates a very small amount of 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,
The amount of formaldehyde generated from polyacetal resin molded products on the market is dry (under constant temperature and dry atmosphere)
Is about ^{2 to 5} μg per 1 cm ^{2 of} surface area, and in a wet method (under a constant temperature and humid atmosphere), the surface area is 1 cm 2
It is about 3 to 6 μg per ² pieces. Further, even if the molding conditions are controlled, the surface area is 1c in a dry system (under a constant temperature drying atmosphere).
m ² per 1.5μg below, wet (under constant-temperature wet atmosphere)
In this case, it is difficult to obtain a molded article 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 generation amount of 1.5 μg or less (0 to 1.5 μg / cm ² ) in a dry system.
1.5 μg), preferably 1.2 μg or less (0 to
1.2 μg), particularly about 0.01 to 1.2 μg. Further, in the wet method, the amount of formaldehyde generated is not more than 2.5 μg / cm ² (0 to 2.
About 5 μg), preferably 2 μg or less (eg, 0.0
About 1 to 1.7 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, and usually 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.

Further, 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.

In the present invention, the numerical specification of the amount of formaldehyde generated is defined as follows. As long as the polyacetal resin and the cyclic nitrogen-containing compound are contained, the molding of a polyacetal resin composition containing conventional additives (such as a usual stabilizer and a release agent) is performed. In addition to products, in the case of molded products of compositions containing inorganic fillers and other polymers, molded products in which most (for example, 50 to 100%) of the surface of the molded products are composed of polyacetal resin ( For example, a multi-color molded product or a coated molded product) can be applied.

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). 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, mechanical parts in the field of automobiles 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 product 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.

[0061]

According to the present invention, the polyacetal resin composition comprises:
Since it contains a cyclic nitrogen-containing compound having a specific chemical structure, 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 of the cyclic nitrogen-containing compound, 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 the mold (mold deposit), the leaching of decomposed products of molded products, and the thermal degradation of molded products can be suppressed. Quality and moldability can be improved.

[0062]

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 Examples and Comparative Examples, the amount of formaldehyde generated from dry and wet molded articles 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 and 2 and Comparative Examples 1 and 2 An antioxidant [pentaerythritol tetrakis [3- (3,5-di-t-) was added to 100 parts by weight of polyacetal resin.
Butyl-4-hydroxyphenyl) propionate]
0.3 parts by weight and creatinine were mixed at the ratio shown in Table 1, and then melt-mixed with a twin-screw extruder to prepare a pellet-shaped composition. Using the pellets, a test piece was molded by an injection molding machine, and the above evaluation was performed using the test piece. Table 1 shows the results.

For comparison, an example in which no nitrogen-containing compound was added and an example in which cyanoguanidine was used as the nitrogen-containing compound were evaluated in the same manner as described above. The polyacetal resin and the nitrogen-containing compound used in 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. Nitrogen-containing compound (c): creatinine (d): cyanoguanidine

[0068]

[Table 1]

As is clear from the table, compared to 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.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI C08K 5/36 C08K 5/36

Claims (12)

[Claims] 1. A polyacetal resin and a compound represented by the following formula: —NR ₁ C (＝ NH) NR ₂ C (＝ X ₁ ) — (wherein R ₁ and R ₂ are the same or different, and represent a hydrogen atom, an alkyl group, Or an acyl group, and X ₁ represents an oxygen atom, a sulfur atom, or an imino group.) As a ring constituent unit. 2. The compound of the following formula (1)
a), (1b), (1c), (1d), (1e), or (1f) (Wherein, R ₃ and R ₄ are the same or different and each represent a hydrogen atom, an alkyl group, an ester group, or an amino group;
₅ represents a hydrogen atom, an alkyl group, or an acyl group;
₂ and X ₃ are the same or different and represent an oxygen atom, a sulfur atom, or an imino group. R ₁ , R ₂ and X ₁ are the same as described above. The polyacetal resin composition according to claim 1, which is a compound represented by the formula: 3. The polyacetal resin composition according to claim 1, wherein the cyclic nitrogen-containing compound is glycosiamidine or a derivative thereof. 4. The polyacetal resin composition according to claim 1, wherein the cyclic nitrogen-containing compound is creatinine. 5. The polyacetal resin composition according to claim 1, wherein the cyclic nitrogen-containing compound is isocyanuric imide or a derivative thereof. 6. The polyacetal resin composition according to claim 1, which comprises 0.01 to 10 parts by weight of the cyclic nitrogen-containing compound based on 100 parts by weight of the polyacetal resin. 7. The polyacetal resin composition according to claim 1, further comprising an antioxidant. 8. The polyacetal resin composition according to claim 1, further comprising a second nitrogen-containing compound. 9. A method for producing a polyacetal resin composition, comprising mixing the polyacetal resin with the cyclic nitrogen-containing compound according to claim 1. 10. A polyacetal resin molded article comprising the polyacetal resin composition according to claim 1. (1) when stored in a closed space at a temperature of 80 ° C. for 24 hours, the amount of formaldehyde generated is 1.5 μg or less per 1 cm ² of surface area of the molded article;
° 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 molded article of the polyacetal resin according to claim 10, wherein the amount is not more than μg. 12. The polyacetal resin molded article according to claim 10, 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.