JPH06136234A - Polyoxymethylene composition - Google Patents

Abstract

PURPOSE:To obtain a polyoxymethylene composition having excellent weather resistance, excellent heat stability and improved occurrence of attached material to a mold. CONSTITUTION:A composition containing 0.01-5wt.% antioxidant and 0.01-5wt.% weather (light) stabilizer based on polyoxymethylene is blended with 0.01-10wt.% melamine-formaldehyde polycondensate which is mainly prepared by reacting melamine with formaldehyde, is insoluble in warm water and soluble in dimethylsulfoxide.

Description

Detailed Description of the Invention

[0001]

The present invention has excellent weather resistance,
The present invention also relates to a polyoxymethylene composition having excellent heat resistance stability and improved generation of mold deposits.

[0002]

2. Description of the Related Art Polyoxymethylene resins are excellent in physical and chemical properties such as mechanical, electrical and thermal properties and chemical resistance.
Engineering plastics for automobiles, electricity,
It is widely used in the fields of electronic equipment and precision machinery. However, with the expansion and diversification of the uses of polyoxymethylene resins, the peculiarities of the materials have been further required. One of such peculiarities is further improvement in weather resistance (light) stability. That is, interior and exterior parts such as automobiles and parts such as electric devices may be discolored or lose surface smoothness depending on the atmosphere in which they are used when exposed to sunlight, fluorescent lamps, rain, and other atmospheres for a long period of time. As a result, the gloss may be lost, and cracks may occur on the surface of the component, which may impair the external appearance. So far, in order to improve such defects, for example, a benzophenone-based or benzotriazole-based UV absorber, or a combination of this UV absorber and a hindered amine-based light stabilizer, or such weather resistance improvement Additives are used in combination with coloring agents such as dyes or pigments. However, in the case of adding an ultraviolet absorber or a hindered amine light stabilizer, if a large amount of these additives is added in an attempt to obtain sufficient weather resistance, heat stability, moldability, etc. are reduced, and polyoxymethylene originally It is inevitable that the characteristics of will be impaired. Also, the blending of a coloring component such as carbon black has a drawback that the thermal stability is significantly reduced. As a means for improving the thermal stability of polyoxymethylene during the molding process, a method is known in which a sterically hindered phenol compound and a polyamide, an amidine compound, a hydroxide of an alkali or alkaline earth metal, or the like is used in combination. There is.

Although a slight improvement is recognized by these methods, it is still insufficient. Particularly, when molding is carried out for a long time, the working environment is deteriorated due to the generation of formaldehyde, or fine powdery matter or tar-like matter is applied to the mold surface. There are various drawbacks such as adhesion (mold deposit), deterioration of work efficiency, and deterioration of the surface condition of the molded product, and improvement thereof has been demanded.

[0004]

Means for Solving the Problems The present inventors have made detailed studies on various stabilizers in order to solve the above-mentioned problems with polyoxymethylene resins containing a weathering (light) stabilizer. As a result, it was found that blending a specific melamine-formaldehyde polycondensate into a polyoxymethylene composition is effective in achieving the intended purpose,
The present invention has been completed. That is, the present invention relates to 0.01 to 5% by weight of an antioxidant, based on polyoxymethylene,
0.01 to 5% by weight of a weathering (light) stabilizer, and 0.01 to 10% by weight of a melamine-formaldehyde polycondensate which is insoluble in warm water and is soluble in dimethyl sulfoxide, which is obtained by reacting mainly melamine and formaldehyde. , A thermally stabilized, weathering (light) resistant polyoxymethylene composition.

The constituent components of the composition of the present invention will be described in detail below. The feature of the composition of the present invention is to blend a melamine-formaldehyde polycondensate which is insoluble in warm water and soluble in dimethyl sulfoxide. The melamine-formaldehyde polycondensate itself used in the present invention is a known method, preferably, the melamine: formaldehyde molar ratio is 1: 0.8 to 1: 5, particularly preferably 1: 1.0 to.
It can be produced by reacting 1: 2.0 in an aqueous solution or dispersion. For example, melamine is added to a formaldehyde aqueous solution adjusted to pH 8 to 9, the temperature is maintained at 60 to 90 ° C, and the mixture is dissolved and reacted with stirring. Since the solution becomes cloudy as the reaction proceeds, the condensation reaction is stopped by cooling for an appropriate time. This is dried by a method such as spray drying to obtain a crude melamine-formaldehyde polycondensate powder.
The crude melamine-formaldehyde polycondensate is washed with warm water (50 to 70 ° C.) for 30 minutes to 1 hour, filtered, and the residue is dissolved in dimethyl sulfoxide. After filtering and removing the insoluble solid matter remaining at this time, a white powder of a purified melamine-formaldehyde polycondensate can be obtained by adding a large excess of acetone to cause precipitation and filtering and drying. It is an object of the present invention to combine the melamine-formaldehyde polycondensate subjected to such a treatment and an antioxidant described below in combination with polyoxymethylene,
The amount of decomposition gas generated during molding is small, and the generated decomposition gas is also prevented from adhering to the mold. Furthermore, since it itself has almost no sublimation or decomposability, it does not generate mold deposits. Methylene can be obtained. Here, if the melamine-formaldehyde polycondensate produced by the conventional method is used as it is, it contains a sublimable monomer component, or the condensation that promotes the generation of decomposition gas at the time of molding is excessively advanced. Since it contains the components, it is difficult to obtain a thermally stable polyoxymethylene composition.
The specific melamine-formaldehyde polycondensate defined in the present invention further comprises an alkanol having 1 to 4 carbon atoms and a melamine: ether group molar ratio of 1: 2.0 or less, preferably 1: 1.0 or less. It may be etherified. Furthermore, up to 50 mol% of melamine can be replaced with other condensable substances. Other condensable substances used in the melamine-formaldehyde polycondensate defined in the present invention include guanamine compounds represented by acetoguanamine, adipoguanamine, and benzoguanamine, dicyandiamide, and 2,5-diamino-1. Amidine compounds such as 3,3,4-triazole, urea derivatives such as urea and ethylene urea, amides such as malonamide and isophthalic acid diamide, and aliphatic compounds such as monoethanolamine and diethanolamine. Aromatic amines typified by amines, o-toluidine, p-toluidine, p-phenylenediamine, aminoamides typified by p-aminobenzamide, and sterically hindered phenols typified by 2,4-t-butylphenol. ,
Examples thereof include hydrazine and hydrazine represented by N, N-bis- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) -propionylhydrazine. The blending amount of the melamine-formaldehyde polycondensate to be added and blended in the present invention is 0.01 to 10% by weight, preferably 0.02 to 3% by weight, particularly 0.05 to 1% by weight, based on polyoxymethylene.
Is preferred. If the amount is less than 0.01% by weight, it is not sufficient to improve the thermal stability of the polyoxymethylene resin composition, and if it exceeds 10% by weight, the mechanical properties of the material are significantly impaired and the composition becomes brittle. .

Next, as the antioxidant used in the present invention, 2,2'-methylenebis (4methyl-6-t-butylphenol) and 1,6-hexanediol-bis [3
-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis [3
-(3,5-di-t-butyl-4-hydroxy-phenyl)
Propionate], triethylene glycol-bis-
[3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,
4,6-Tris (3,5-di-t-butyl-4-hydroxy-benzyl) benzene, n-octadecyl-3- (4'-
Hydroxy-3 ', 5'-di-t-butylphenol) propionate, 4,4'-methylenebis (2,6-di-t-butylphenol), 4,4'-butylidene-bis- (6-t-
Butyl-3-methyl-phenol), di-stearyl-
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)
Are listed as hindered phenolic antioxidants,
Also, triphenylphosphite, trisnonylphenylphosphite, 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, tris (2-t-phenylphenyl) phosphite, tris (2- (1,1-dimethylpropyl) -phenyl) phosphite, tris (2,4- (1,1-dimethylpropyl) -phenyl) Phosphite, tris (2-cyclohexylphenyl) phosphite, tris (2-t-butyl-4-phenylphenyl) phosphite and the like can be mentioned as the phosphorus antioxidant. In addition, any antioxidant such as hindered amine type and sulfur type can be used, and at least one kind or two or more kinds thereof can be used. Among these, 1,6-hexanediol-
Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene Glycol
Bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide ) Is a particularly preferred substance. The amount of the antioxidant added and blended in the present invention is 0.01 to 5% by weight, preferably 0.0 to 5% by weight, based on polyoxymethylene.
5 to 2% by weight, particularly 0.10 to 1% by weight are preferred. If the amount is less than 0.01% by weight, it is not sufficient to improve the thermal stability of the polyoxymethylene composition, and if it exceeds 5% by weight, the effect of thermal stability reaches saturation and rather a discoloration tendency occurs. Absent.

Next, the weather resistance (light) used in the present invention
Among the stabilizers, those preferably used are selected from the group consisting of benzotriazole-based substances, benzophenone-based substances, aromatic benzoate-based substances, cyanoacrylate-based substances, oxalic acid anilide-based substances and hindered amine-based substances. There are two or more species.

Examples of these substances include the following. That is, as a benzotriazole-based substance, 2- (2 '
-Hydroxy-5'-methyl-phenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-butyl-phenyl) benzotriazole, 2- (3,5-di-
t-amyl-2-hydroxyphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-isoamyl-phenyl) benzotriazole, 2- [2-hydroxy-3,5-bis- ( α, α-Dimethylbenzyl) phenyl] benzotriazole, 2- (2′-hydroxy-4 ′
Examples of the benzophenone-based substance such as -octoxyphenyl) benzotriazole include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxy. Benzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-4-oxybenzyl Benzophenone, etc. As aromatic benzoate-based substances, pt-butylphenyl salicylate, p-octylphenyl salicylate, etc., As cyanoacrylate-based substances, 2-ethylhexyl-2-cyano-3,3'-diphenyl Acrylate, ethyl-2- Examples of oxalic acid anilide-based substances such as ano-3,3′-diphenyl acrylate include N- (2-ethyl-phenyl) -N ′-(2-ethoxy-5-t-butylphenyl) oxalic acid diamide and N- (2 -Ethyl-phenyl) -N'-
A hindered amine-based substance such as (2-ethoxy-phenyl) oxalic acid diamide is a piperidine derivative having a sterically hindering group. For example, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4 -Stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, 4 -Benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4 -Benzyloxy-2,2,6,6-
Tetramethylpiperidine, 4- (phenylcarbamoyloxy) -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, bis (2,2,6,6-tetra Methyl-
4-piperidyl) hexamethylene-1,6-dicarbamate, bis (1-methyl-2,2,6,6-tetramethyl-4-
Piperidyl) adipate, tris (2,2,6,6-tetramethyl-4-piperidyl) benzene-1,3,5-tricarboxylate and the like. Further, a high molecular weight piperidine derivative polycondensate such as dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate of succinate is also effective. These weather resistance (light) stabilizers are at least one kind or two kinds.
It is preferable to mix one or more kinds, and it is particularly preferable to use the above-mentioned weather resistance stabilizer and a hindered amine-based substance in combination.
The amount of the weathering (light) stabilizer used here is appropriately 0.01 to 5% by weight, particularly preferably 0.02 to 3% by weight, based on polyoxymethylene. If these components are too small, no effect can be expected, and even if they are added unnecessarily excessively, not only the economical disadvantage but also the problems such as the deterioration of mechanical properties and the contamination of molds are brought about. .

The composition of the present invention preferably contains a coloring component, although it is not essential. A dye or a pigment is used as the coloring component. There are no particular restrictions on the types of dyes and pigments used, and any of those conventionally used for polyoxymethylene compositions can be selected and used. The dye is preferably, for example, anthraquinone dye, and the pigment includes carbon black, azo dye, phthalocyanine dye,
Perylene type, quinacridone type, anthraquinone type, indoline type, titanium type, iron oxide type, cobalt type and the like are preferable. These coloring components may be used alone or 2
You may use it in combination of 2 or more types. In particular, when carbon black is added as a coloring component, it has the effect of further improving weather resistance stability. As the carbon black, those usually used for coloring plastics, for example, Micronex, acetylene black, Ketjen black and the like can be used. In the composition of the present invention, the content of the coloring component is preferably in the range of 0.1 to 5% by weight based on polyoxymethylene. Particularly, 0.3 to 3% by weight is preferable. If the blending amount is less than 0.1% by weight, the coloring effect is not sufficiently exerted, and
It is not necessary to compound more than 5% by weight, and too much compounding rather lowers the physical properties and thermal stability of the composition.

The polyoxymethylene to which the above-mentioned additives are added is a polymer compound having an oxymethylene group (--CH ₂ O--) as a main constituent unit, and other than polyoxymethylene homopolymer and oxymethylene group. It may be any of copolymers, terpolymers and block copolymers containing a small amount of other constitutional units, and the molecule may have not only a linear structure but also a branched or crosslinked structure. Further, there is no particular limitation on the degree of polymerization or the like.

The composition of the present invention is not essential, but depending on the purpose thereof, a nitrogen-containing compound other than the melamine-formaldehyde polycondensate of the present application, a hydroxide of an alkali or alkaline earth metal, an inorganic acid salt, It is also possible to use one or more metal-containing compounds such as carboxylates or alkoxides in combination. In order to further impart desired properties to the composition of the present invention depending on its purpose, conventionally known additives such as lubricants, nucleating agents, release agents and other surfactants, or organic polymer materials, inorganic or It is also possible to add one or more kinds of organic fibrous, powdery or plate-like fillers.

The method for preparing the composition of the present invention is not particularly limited, and can be easily prepared by the known equipment and method generally used as a conventional method for preparing a resin composition. For example,
i) After mixing each component, kneading and extruding with an extruder to prepare pellets, and then molding, ii) Once preparing pellets with different compositions, mixing the pellets in a prescribed amount and molding A method of later obtaining a molded article of the target composition,
iii) Any method such as directly charging one or more of each component into a molding machine can be used. In addition, mixing a part of the resin component in the form of fine powder with the other components and adding the powder is a preferable method for uniformly blending these components.
Further, the resin composition according to the present invention can be molded by any of extrusion molding, injection molding, compression molding, vacuum molding, blow molding, and foam molding.

[0013]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. still,
The evaluation method shown in the following examples is as follows. 1) Amount of formaldehyde gas generated from the melt A pellet of 5 g is accurately weighed (Ag) and kept in a metal container at 200 ° C for 5 minutes. Then, the atmosphere in the container is absorbed in deionized water. The amount of formaldehyde in this water was quantified according to JIS K0102, 2L formaldehyde (B μg) and calculated as the amount of formaldehyde gas generated (C ppm) per 1 g of the material. Bμg / Ag = C ppm 2) Moldability (amount of deposit on the mold) A sample polyoxymethylene composition is continuously molded into a molded product of a specific shape under the following conditions using an injection molding machine (about 24 hours).
Then, the amount of the deposit on the mold was evaluated. That is, the stains on the mold during continuous molding were evaluated by visual observation in five levels. (Molding conditions) Injection molding machine: Toshiba IS30EPN (manufactured by Toshiba Machine Co., Ltd.) Cylinder temperature: 210 ° C Injection pressure: 750kg / cm ² Injection time: 4sec Cooling time: 3sec Mold temperature: 30 ° C ABCDE E ← ─────────────── → Extremely small amount (there are deposits on the entire surface) 3) Crack occurrence time A test piece was prepared by injection molding and a UV fade meter (Suga Test Instruments ), FAL-AU ・ H ・ B ・_Em type), and irradiate with ultraviolet rays at a black panel temperature of 83 ° C, and observe the presence or absence of cracks on the surface of the test piece with a magnifier 10 times,
The time when the crack was first generated was defined as the crack occurrence time. The larger this value is, the better the weather resistance is.

Examples 1 to 6 Polyoxymethylene copolymers (DURACON, manufactured by Polyplastics Co., Ltd.) were added with the antioxidants shown in Table 1.
The weather resistance (light) stabilizer and a specific purified melamine-formaldehyde polycondensate were added and mixed in the proportions shown in Table 1 to obtain a pelletized composition with an extruder, and the above evaluation was carried out. The results are shown in Table 1.

Example 7 A pellet composition was obtained in the same manner as in Example 3 except that 1.0% by weight of a coloring component (acetylene black) was further added to and mixed with the composition of Example 1, and the above evaluation was carried out. The results are shown in Table 1.

Comparative Examples 1 to 6 As shown in Table 1, when the purified melamine-formaldehyde polycondensate is not blended, when the crude melamine-formaldehyde polycondensate is blended, melamine is blended in place of the melamine-formaldehyde polycondensate. If you do
The pellet composition was obtained and the above evaluation was performed in the same manner as in Examples 1 to 7. The results are shown in Table 1.

[0017]

[Table 1]

Note-1) Antioxidant a-1 Triethylene glycol-bis [3- (3-t-
Butyl-5-methyl-4-hydroxyphenyl) propionate] Note-2) b-1 2- [2-hydroxy-3,5-bis- (α, α)
-Dimethylbenzyl) phenyl] -benzotriazol b-2 2-hydroxy-4-oxybenzylbenzophenone Note-3) b-3 Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate b-4 Dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate Note-4) Melamine-formaldehyde polycondensate c-1 Formaldehyde / melamine molar ratio Is 1.0 / 1
After preparation with the composition as described above, the mixture was filtered with warm water at 60 ° C for 30 minutes, washed with acetone, dried at room temperature, dissolved in dimethylsulfoxide at a concentration of 0.5% by weight for 2 hours, filtered to remove insolubles, and the solution was diluted 20 times. Melamine-formaldehyde polycondensate c-2 purified by adding acetone to acetone to precipitate, then filtering this and drying at room temperature. The molar ratio of formaldehyde / melamine is 1.5 / 1.
A melamine-formaldehyde polycondensate purified by the same treatment as that for c-1 after the preparation with the composition of c-1 and the molar ratio of c'-1 formaldehyde / melamine is 1.0 / 1.
Crude melamine-formaldehyde polycondensate prepared by the following composition (polycondensate before treatment to obtain purified melamine-formaldehyde of c-1) Note-5) d-1 acetylene black

[0019]

As is apparent from the above description and the examples, the present invention significantly improves the thermal stability without impairing the original weather resistance (light) of the polyoxymethylene resin composition containing the weather resistance (light) stabilizer. It is possible to obtain a polyoxymethylene composition which is very preferable in view of occupational environmental hygiene, because the mold is less contaminated even during continuous molding for a long time, and the generation of formaldehyde odor during molding is significantly suppressed. .

Claims (4)

[Claims] 1. 0.01 based on polyoxymethylene
~ 5 wt% antioxidant, 0.01-5 wt% weather resistance (light)
Stabilizer and melamine-formaldehyde polycondensate 0.01 to 10 which is made by reacting mainly melamine and formaldehyde and is insoluble in warm water and soluble in dimethyl sulfoxide.
Thermally-stabilized weather resistance (light) blended with wt%
Polyoxymethylene composition. 2. A melamine: formaldehyde molar ratio of the melamine-formaldehyde polycondensate of 1: 0.8 to 1: 1.
The polyoxymethylene composition according to claim 1, which is 5. 3. The weather resistance (light) stabilizer is one or two selected from the group consisting of benzotriazole-based substances, benzophenone-based substances, aromatic benzoate-based substances, cyanoacrylate-based substances and oxalic acid anilide-based substances. The polyoxymethylene composition according to claim 1 or 2, which comprises a combination of at least one of these and a hindered amine-based substance. 4. The polyoxymethylene composition according to claim 1, further comprising 0.1 to 5% by weight of a coloring component.