JPH07228751A - Polyoxymethylene composition and its molding - Google Patents

Abstract

PURPOSE:To obtain a polyoxymethylene compsn. which is excellent in heat stability and does not allow yellow or black particles to appear in an extruder. CONSTITUTION:100 pts.wt. polyolxymethylene is compounded with 0.01-5.0 pts.wt. sterically hindered phenol antioxidant, 0.001-10 pts.wt. at least one metal-contg. compd. selected from oxides carbonate of magnesium or calcium, and 0.01-5.0 pts.wt. polyalkylene glycol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyoxymethylene composition which is excellent in thermal stability and in which generation of yellow or black particles in an extruder or the like is suppressed, and a molded article thereof.

[0002]

2. Description of the Related Art Polyoxymethylene is excellent in mechanical properties, fatigue resistance, friction and abrasion resistance, chemical resistance, heat resistance and moldability.
It is widely used in the fields of automobiles, electric and electronic devices, precision machinery, and building material piping. However, with the expansion and diversification of applications, the demand for the quality thereof is becoming more sophisticated. Required properties include reduction in mechanical strength associated with extrusion or molding, and suppression of generation of deposits (mold deposits) on dies and the like to a low level. One of the important factors of these phenomena is the decomposition of the polymer during heating. That is, due to its chemical structure, polyoxymethylene essentially has a property of being easily decomposed under acidic or alkaline conditions in a heating and oxidizing atmosphere. As one of the methods for suppressing the decomposition of polyoxymethylene and improving its thermal stability, it is known to stabilize the chemically active terminal. However,
Cleavage decomposition reaction also occurs in the main chain portion of the polymer during heating, and its prevention cannot be dealt with only by the above treatment, and it is essentially required to add an antioxidant and other stabilizers. The antioxidant added to the polyoxymethylene is a sterically hindered phenol compound or a sterically hindered amine compound, and other stabilizers are polyamide, urea derivatives, amidine compounds, alkali or alkaline earth metal hydroxides. Compounds such as organic or inorganic acid salts are used in combination, and in particular, a combination of an antioxidant and the nitrogen-containing compound as described above is preferable, and in most cases, these combinations are used. But,
In the method of using this nitrogen-containing compound in combination, during extrusion kneading, the nitrogen-containing compound adheres to the screw or barrel of the extruder and is discolored by staying for a long time, and is mixed in the composition as yellow or black particles. There is a problem, and in particular, there has been a strong demand for improvement in the fields of extrusion molding and blow molding, where the residence time in the molding machine is long.

[0003]

Means for Solving the Problems The inventors of the present invention have made diligent studies to solve the above problems and obtain a polyoxymethylene composition in which the generation of yellow or black particles is suppressed. Instead, by using a polyalkylene glycol and a specific metal-containing compound in combination, while maintaining the short-term thermal stability of the composition and the physical property life of the molded article of the composition, a polyoxy compound that does not generate yellow or black particles is obtained. They have found that a methylene composition can be obtained, and completed the present invention. That is, the present invention is based on 100 parts by weight of polyoxymethylene, (A) sterically hindered phenolic antioxidant 0.
01 to 5.0 parts by weight, (B) 0.001 to 10 parts by weight of one or more metal-containing compounds selected from magnesium or calcium oxides or carbonates, and (C) polyalkylene glycol 0.01 to 5.0 parts by weight It is an oxymethylene composition.

The present invention will be described in detail below. The polyoxymethylene used in the present invention is a polymer compound having an oxymethylene group (-CH ₂ O-) as a main constituent unit, and contains a small amount of other constituent units other than the polyoxymethylene homopolymer and the oxymethylene group. It may be a copolymer, a terpolymer or a block copolymer, 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. Further, as the polyoxymethylene used in the present invention,
As described above, it is of course preferable that the chemically active terminal is stabilized.

Next, as the sterically hindered phenolic antioxidant (A) used in the present invention, 2,2'-methylenebis (4methyl-6-t-butylphenol), 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], 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'-
Hexamethylene bis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,9-bis {2- [3
-(3-t-Butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl}
There are 2,4,8,10-tetraoxaspiro [5,5] undecane and the like, and at least one kind or two or more kinds thereof can be used. Among these, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxy-phenyl) propionate], triethylene glycol-bis- [3- (3-t-butyl-5-methyl-]- 4-Hydroxyphenyl) propionate], 3,9-
Bis {2- [3- (3-t-butyl-4-hydroxy-
5-Methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5,5
Undecane is a particularly preferred substance. The amount of the (A) sterically hindered phenolic antioxidant blended in the present invention is 0.01 to 100 parts by weight of polyoxymethylene.
5 parts by weight, preferably 0.1 to 3 parts by weight. If the amount added is less than 0.01 parts by weight, a sufficient effect cannot be obtained, and if the amount added exceeds 5 parts by weight, the effect of thermal stability reaches saturation and the discoloration tends to occur, which is not preferable.

The (B) magnesium or calcium oxide or carbonate used in the present invention is specifically magnesium oxide, calcium oxide, magnesium carbonate or calcium carbonate, with magnesium oxide and calcium oxide being particularly preferred. It is a substance. The blending amount of these components (B) is 0.001 to 10 per 100 parts by weight of polyoxymethylene.
Parts by weight, preferably 0.001 to 5 parts by weight, more preferably 0.001 to 2 parts by weight, particularly preferably 0.003 to 0.5 parts by weight.
Parts by weight. If the amount is less than 0.001 part by weight, the desired effect can hardly be obtained, and if it exceeds 10 parts by weight,
The effect of thermal stability reaches saturation, and the color tends to change, which is not preferable.

The (C) polyalkylene glycol used in the present invention can be any of homopolymers of ethylene glycol, propylene glycol and tetramethylene glycol, and copolymers and derivatives thereof. Examples thereof include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene polyoxypropylene copolymer, polyoxyethylene polyoxypropylene glyceryl ether, and polyoxyethylene polyoxypropylene monobutyl ether. The polyalkylene glycol preferably has a number average molecular weight of 2,000 to 20,000. Among these, polyethylene glycol, polyoxyethylene polyoxypropylene copolymer and their derivatives are particularly preferable substances. The blending amount of the component (C) is 0.01 to 5.0 with respect to 100 parts by weight of polyoxymethylene.
Parts by weight, particularly preferably 0.05 to 1.0 parts by weight. If the amount is less than 0.01 parts by weight, a sufficient effect cannot be obtained, and if it exceeds 5.0 parts by weight, the mechanical properties of the composition are impaired, which is not preferable. The components (A), (B), and (C) to be added to the composition of the present invention may be added to the monomer at the polymerization stage of the polymer, or may be added in the polymer stabilization step.

Further, in the present invention, for the purpose of improving the physical property life of the composition, (D) a fatty acid metal salt having 10 or more carbon atoms, particularly an alkali metal salt, an alkaline earth metal salt or a zinc salt is blended. Is preferred. As such a compound,
Magnesium stearate, calcium stearate,
Examples include zinc stearate and 12-hydroxy calcium stearate. The compounding amount of the component (D) is 0.001 to 0.5 part by weight, preferably 0.005 to 0.2 part by weight, based on 100 parts by weight of polyoxymethylene. Compounding amount
If it is less than 0.001 part by weight, the desired effect cannot be obtained, and if it exceeds 0.5 part by weight, it tends to cause discoloration, which is not preferable.

The polyoxymethylene composition of the present invention comprises
Further, various known additives such as various colorants, slidability improvers, release agents, nucleating agents, antistatic agents, weathering (light) stabilizers, other surfactants, various polymers and the like are added. obtain. Further, as long as it is within a range that does not significantly reduce the performance of the molded article targeted by the present invention, one or two known fillers such as fibrous, plate-like, and granular materials such as inorganic, organic, and metallic materials can be used.
It is also possible to mix and blend more than one species. Examples of such organic and inorganic fillers include glass fiber, aramid fiber, potassium titanate fiber, glass beads, crosslinked polystyrene beads, crosslinked melamine resin, talc, mica, white mica and wollastonite. However, it is not limited to these.

The polyoxymethylene molded article of the present invention can be easily prepared by a known method generally used as a conventional resin molded article preparation method. For example, after mixing the components, a uniaxial or biaxial extruder is kneaded and extruded to prepare pellets, and the pellets are mixed (diluted) in a predetermined amount and subjected to molding to obtain a molded product having a desired composition after molding. Any method can be used. Further, in the preparation of the composition used for such a molded article, it is possible to disperse the additives by crushing a part or all of the polyoxymethylene which is the substrate, mixing the other components with this, and then extruding. This is a preferable method for improving the properties.

The composition of the present invention can be suitably used in any molding method having a step of melting a resin, but as described above, it is particularly suitable for extrusion molding or blow molding in which the residence time in the molding machine is long. Used for. Molded products obtained by such extrusion molding or blow molding include solid extrusion products such as round rods and slabs, profile extrusion products such as tubes and rails, films, sheets, nets, bottles, tanks,
A pipe, a float, etc. are illustrated.

[0012]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited thereto. still,
The evaluation method shown in the following examples is as follows. 1) Thermal stability Pellets of the sample polyoxymethylene composition were heated to 235 ° C for 45
Determine the weight reduction rate by measuring the weight before and after leaving for a minute,
The thermal stability was evaluated. 2) Generation of yellow or black particles Using a twin-screw extruder with a barrel diameter of 30 mm, the cylinder temperature 2
After operating for 1 hour at a rate of 10 kg / Hr at 20 ° C, switch off without purging, leave for 15 hours or more, and slowly cool the cylinder to room temperature. After that, the cylinder temperature is raised to 200 ° C, and the same material is used to perform extrusion at the same ratio. This time,
First, about 500 g of the composition coming out from the die hole was sampled, pulverized, and mixed well. A disk having a thickness of 1 mm and a diameter of 100 mm was formed on the crushed product on a hot plate, and the number of yellow or black particles in the disk was measured. In this measurement, five discs were used, and the average value was evaluated. 3) Physical property life of material The polyoxymethylene composition molded into ASTM No. 1 dumbbell type tensile test piece is aged in a gear oven at 140 ° C, and after a suitable time has passed, tensile strength and elongation at room temperature are measured. It was measured. Here, the physical property life of the material was evaluated by the number of days when the tensile elongation of the material was 50% of the initial tensile elongation.

Examples 1 to 10 Polyoxymethylene copolymers (DURACON manufactured by Polyplastics Co., Ltd.), the antioxidants shown in Table 1, oxides or carbonates of magnesium or calcium, polyalkylene glycols, and Was added and mixed at a ratio shown in Table 1 (100 parts by weight of polyoxymethylene), and a pelletized composition was obtained by an extruder, and the above evaluation was performed. The results are shown in Table 1. Comparative Examples 1 to 5 For comparison, as shown in Table 1, when metal oxides and carbonates and polyalkylene glycol were not used in combination,
With respect to the case where other metal oxides and carbonates other than the definition of the present invention, a nitrogen compound, etc. were added, pelletized compositions were prepared in the same manner as in Examples 1 to 10, and the above evaluation was performed. The results are shown in Table 1. The antioxidants, metal oxides and carbonates, polyalkylene glycols, fatty acid metal salts and nitrogen compounds used are as follows. 1. Sterically hindered phenolic antioxidant a-1) Triethylene glycol-bis- [3- (3-t
-Butyl-4-hydroxy-5-methylphenyl) propionate] a-2) pentaerythritol-tetrakis [3- (3,5
-Di-t-butyl-4-hydroxyphenyl) propionate] 1. Metal oxides and carbonates b-1) Magnesium oxide b-2) Calcium oxide b-3) Magnesium carbonate b'-1) Barium oxide b'-2) Zinc oxide 3. 3. Polyalkylene glycol c-1) Polyethylene glycol: number average molecular weight 6000 c-2) Polyoxyethylene polyoxypropylene copolymer: number average molecular weight 3000 4. Fatty acid metal salt d-1) Calcium 12-hydroxystearate 5. Nitrogen compounds e-1) Melamine

[0014]

[Table 1]

[0015]

As is clear from the above description and experimental examples, the resin composition of the present invention causes the appearance of the product to be impaired while maintaining the short-term and long-term mechanical properties of the resin composition of the prior art. Alternatively, since the generation of yellow or black matter that can be the starting point of parts damage is eliminated, it is not only suitable for use in molding methods such as extrusion molding and blow molding, where the residence time in the molding machine is relatively long, but also engineering resin molding methods. Is also suitably used in general injection molding.

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Claims (6)

[Claims] 1. A sterically hindered phenolic antioxidant (A) 0.01 to 5.0 relative to 100 parts by weight of polyoxymethylene.
Parts by weight, (B) one or more metal-containing compound selected from oxides or carbonates of magnesium or calcium 0.0
01-10 parts by weight and (C) polyalkylene glycol 0.01-
A polyoxymethylene composition containing 5.0 parts by weight. 2. The polyoxymethylene composition according to claim 1, wherein the component (B) is magnesium oxide and / or calcium oxide. 3. The component (C) has a number average molecular weight of 2,000 to 20,000.
The polyoxymethylene composition according to claim 1 or 2, which is the polyalkylene glycol. 4. The polyoxymethylene composition according to claim 1, wherein the component (C) is a homopolymer of ethylene glycol, propylene glycol or tetramethylene glycol, or a copolymer or derivative thereof. . 5. The polyoxy according to any one of claims 1 to 4, which further comprises (D) 0.001 to 0.5 part by weight of a fatty acid metal salt having 10 or more carbon atoms with respect to 100 parts by weight of polyoxymethylene. Methylene composition. 6. A polyoxymethylene molded article obtained by extrusion-molding or blow-molding the polyoxymethylene composition according to any one of claims 1 to 5.