JPH0768433B2 - Polyoxymethylene composition for molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is for molding, which is excellent in mechanical properties and hydrolysis resistance, has very little formaldehyde odor during molding, and has very few deposits on a mold. The present invention relates to a polyoxymethylene resin composition.

<Prior Art> Polyoxymethylene is known as an engineering plastic having a good balance of mechanical strength and impact resistance, and is used in a wide range of fields such as electric / electronic parts and mechanical / mechanical parts. However, polyoxymethylene is structurally poor in thermal stability, and formaldehyde gas is generated during molding to deteriorate the working environment, and precipitates composed of oligomers are formed on the mold to impair the appearance of the molded product. It has some problems to be improved.

As a method for improving the above-mentioned drawbacks, various stabilizer formulations have been devised from the past. Even if polyoxymethylene homopolymer or copolymer is added and blended with a hindered amine compound represented by the following structural formula (II), a hindered phenolic antioxidant having a molecular weight of 400 or more, and an alkaline earth metal hydroxide. A composition consisting of the above is proposed in JP-A-63-273657.

(However, n in the formula represents an integer of 0 to 20.) <Problems to be Solved by the Invention> However, the composition proposed in JP-A-63-273657 has mechanical properties and heating. Although the thermal stability represented by weight loss is extremely excellent, since the hindered amine compound used has a relatively small molecular weight, it adheres to the mold surface during continuous molding, which causes the surface of the molded product to It had a problem that the gloss was further impaired. Furthermore, there is still room for improvement in terms of hydrolysis resistance.

Therefore, as a result of intensive investigations by the present inventors to solve the above-mentioned problems, as a result, a high molecular weight type hindered amine compound having a specific structure with respect to polyoxymethylene was used as a hindered phenolic antioxidant and a carboxylic acid metal salt. The inventors have found that the above-mentioned problems can be effectively solved by adding and blending together with them, and have reached the present invention.

<Means for Solving the Problems> That is, the present invention relates to a polyoxymethylene homopolymer or copolymer, (1) a hindered amine compound represented by the following structural formula (I), and (2) a hinder having a molecular weight of 400 or more. The present invention provides a polyoxymethylene composition for molding, characterized by comprising a dephenolic antioxidant and (3) a metal salt of a carboxylic acid having 12 or more carbon atoms.

(However, R in the formula is a hydrogen atom or a formula And R'represents a hydrogen atom or a methyl group. Further, x, y and z are integers of 0 to 10 and may be different or the same. The polyoxymethylene or copolymer used in the present invention is composed of an oxymethylene homopolymer and an oxymethylene unit, and contains 15% by weight of an oxyalkylene unit having 2 to 8 adjacent carbon atoms in the main chain. It means an oxymethylene copolymer contained below.

The oxymethylene homopolymer is produced, for example, by introducing substantially anhydrous formaldehyde into an organic solvent containing a basic polymerization catalyst such as an organic amine to polymerize the compound, and then acetylating the terminal with acetic anhydride. .

The oxymethylene copolymer is prepared by, for example, dissolving or suspending a substantially anhydrous trioxane and a copolymerization component such as ethylene oxide or 1,3-dioxolane in an organic solvent such as cyclohexane.
It is produced by adding a Lewis acid catalyst such as diethyl etherate to polymerize and decomposing and removing unstable terminals.

Alternatively, it is produced by introducing trioxane, a copolymerization component and a catalyst into a self-cleaning stirrer without using any solvent to perform bulk polymerization, and further decomposing and removing unstable terminals.

Hindered amine compound (A) used in the present invention
Is a compound represented by the structural formula (I).

That is, from the above structural formula (I) and the definitions of R and R'in the formula, the hindered amine compound (A) may be a completely single compound or a mixture.

The hindered amine compound (A) preferably has a molecular weight or average molecular weight of 2,000 or more. If the molecular weight or average molecular weight is less than 2,000, it tends to adhere to the mold during continuous molding, which is not preferable.

Further, the addition amount of the hindered amine compound (A) is preferably 0.001 to 5.0 parts by weight, particularly 0.01 to 3.0 parts by weight, based on 100 parts by weight of the polyoxymethylene homopolymer or copolymer. If the addition amount is less than 0.001 part by weight, the thermal stability of the composition is insufficient, and if it is more than 5.0 parts by weight, mechanical properties are deteriorated, which is not preferable.

Next, the hindered phenolic antioxidant (B) used in the present invention has a molecular weight of 400 or more, and specific examples thereof include triethylene glycol-bis [3- (3-
t-butyl-5-methyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3
-(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate], 2,2-thio-diethylenebis [3-
(3,5-t-butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5-di-t
-Butyl-4-hydroxy-hydrocinnamide), 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], 2,4-bis-
(N-octylthio) -6- (4-hydroxy-3,5-
Di-t-butylanilino) -1,3,5-triazine, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2-thiobis (4-methyl-6-t -Butylphenol), 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-tris (4-t-butyl-3-)
Hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 1,1,3-tris (2-methyl-4-hydroxy-5)
-T-butylphenyl) butane, 1,1-bis (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 2,2'-methylene-bis (4-methyl-6-t-butylphenol) , N, N'-bis [3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionyl] hydrazine, 2-t-butyl-6- (3'-t-butyl-
5'-methyl-2'-hydroxybenzyl) -4-methylphenyl acrylate and 3,9-bis [2- [3-
(3-t-Butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl]-
2,4,8,10-tetraoxaspiro [5.5] undecane and the like can be mentioned. Among them, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-t-butyl-4-) Hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di-5-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-t- Butyl-4-hydroxy-hydrocinnamamide), 2-t-butyl-6- (3'-t-butyl-5'-methyl-2'-hydroxybenzyl) -4-
Methylphenyl acrylate and 3,9-bis [2-
The use of [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane is preferred. .

In addition, when the molecular weight of the Hinhardt phenolic antioxidant (B) is less than 400, the bleeding phenomenon is remarkable,
Not only the appearance of the resin composition is impaired, but also the heat stability decreases, making it unusable, which is not preferable.

The amount of the hindered phenolic antioxidant (B) added is 10% by weight of polyoxymethylene homopolymer or copolymer 10.
The range of 0.001 to 5.0 parts by weight, especially 0.01 to 3.0 parts by weight, relative to 0 parts by weight is preferable. If the addition amount is less than 0.001 part by weight, the heat resistance stability of polyoxymethylene is not sufficient,
If the amount is more than 5 parts by weight, the bleeding phenomenon is observed, which is not preferable.

Further, as the metal salt (C) of carboxylic acid having 12 or more carbon atoms used in the present invention, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, oleic acid, ricinol Acids, lithium salts of carboxylic acids such as 4,4'-biphenyldicarboxylic acid and 2,6-naphthalenedicarboxylic acid, sodium salts, potassium salts, magnesium salts, calcium salts, strontium salts, vatium salts and aluminum salts. However, among them, magnesium laurate, calcium laurate, calcium palmitate,
Magnesium stearate, calcium stearate,
Barium stearate and calcium ricinoleate are preferably used.

The amount of the carboxylic acid metal salt (C) added is preferably 0.001 to 5.0 parts by weight, particularly 0.01 to 3.0 parts by weight, based on 100 parts by weight of the polyoxymethylene homopolymer or copolymer, and more preferably 0.001 parts by weight. When the amount is too small, the thermal stability of polyoxymethylene is not improved, and when it is more than 5 parts by weight, the hydrolysis resistance is lowered, which is not preferable.

The hindered amine-based compound (A), the hindered phenol-based antioxidant (B), and the metal salt of a carboxylic acid (C) obtain the effect of the present invention only by using these three in combination. It is possible to achieve the object of the present invention even if any one is lacking.

Further, the composition of the present invention, calcium carbonate, barium sulfate, clay, titanium oxide, silicon oxide, mica powder, fillers such as talc, carbon fiber, glass fiber, ceramic within the range that does not impair the effects of the present invention. Fibers, reinforcing agents such as aramid fiber, pigments, dyes, conductive agents such as carbon black, plasticizers, nucleating agents, release agents, adhesion-imparting agents, flame retardants, lubricants and antistatic agents, etc. should be carefully added. You can

<Examples> Hereinafter, the present invention will be described with reference to Examples.

The mechanical properties, hydrolyzability, amount of formaldehyde attached, polymer melting point, crystallization temperature, MI (melt index) of the molded products shown in Examples and Comparative Examples, and the occurrence of mold deposits during continuous molding Was measured or observed as follows.

Molding of the composition: 1/8 inch thick x 1/2 inch wide, using an injection molding machine with 5 ounce injection capacity, setting the cylinder temperature to 200 ° C, mold temperature to 80 ° C and molding cycle to 50 seconds. And a 1/2 inch thick by 1/2 inch wide Izod impact test piece were formed.

Mechanical Properties: Using the above molded products, tensile properties were measured according to ASTM D638, and Izod impact values were measured with notches described in ASTM D256.

Polymer melting point (Tm) and crystallization temperature (Tc): Using a differential scanning calorimeter, the temperature was raised at a heating rate of 10 ° C / min in a nitrogen atmosphere, and after measuring the polymer melting point (Tm), 10 The temperature was raised at ° C / min and the crystallization temperature (Tc) was measured.

Formaldehyde content of molded product: Tensile test piece 1 immediately after molding
The book was dipped in 100 ml of pure water and left overnight at room temperature. The amount of formaldehyde in this solution was determined by a colorimetric method using chromotropic acid, and the concentration (ppm) relative to the weight of the molded product.
Expressed as

Measured at 190 ° C./2160 g according to MI: ASTM D 1238.

Hydrolysis test: Tensile test pieces which were left at room temperature for one day after molding were filled in a pressure-resistant cylinder together with pure water and kept at 120 ° C.
After a lapse of a predetermined time, the test piece was taken out, and the pH of the immersion water and the MI of the test piece were measured.

Continuous molding test: Continuous molding was performed under the above-mentioned molding conditions, and the deposits on the mold were visually observed.

In addition, in the examples, unless otherwise specified, the addition amount means parts by weight.

Reference Example Production of polyoxymethylene A-1 Production of polyoxymethylene homopolymer Formaldehyde obtained by thermally decomposing paraformaldehyde was introduced into a continuous two reaction vessel containing toluene at 0 ° C. As the polymerization initiator, an equimolar mixture of tetra (n-butyl) ammonium iodide and lauric acid dissolved in toluene was supplied. All reaction components were continuously pumped to produce a polymeric dispersion product with a residence time of 15
It was taken out at a speed that is minutes. Formaldehyde is about
The polymerization initiator was passed through the reactor at a rate of 8 g / min, and the concentration of tetra (n-butyl) iodide was 1 per reaction medium as the polymerization initiator.
1.87 mg and lauric acid concentration were fed in such a proportion that the reaction medium was 0.99 mg per reaction medium. The reaction medium was kept at 65 ° C and well stirred. Polymer was produced at a rate of 470 g / h per reaction medium. The obtained polymer was taken out by filtration, washed with acetone and methanol, and dried. A mixture of 500 g of this crude polymer, 4000 g of acetic anhydride and 1.6 g of sodium acetate was mixed and refluxed at 139 ° C. for 1 hour. After cooling, the polymer was filtered, washed with acetone and water, and dried.
This polymer (A-1) has a melting point of 179 ° C. and a crystallization temperature of 150.
It was ℃.

A-2 Preparation of polyoxymethylene copolymer 900 g of trioxane and 8.8 g of ethylene oxide were dissolved in 450 g of cyclohexane, and 60 ml of benzene containing 0.3 g of boron trifluoride / diethyl etherate was added.
Stirred at ° C. About 1 minute after the addition of boron trifluoride / diethyl etherate, the reaction solution became cloudy and a polymer was precipitated. After 30 minutes, 10% benzene solution of triethylamine
After 10 ml was added to stop the polymerization reaction, the precipitated polymer was collected by filtration, washed with acetone and then washed with water.
Further dried in vacuum. The melting point of this polymer (A-2) was 168 ° C, and the crystallization temperature was 147 ° C.

A-3 Production of polyoxymethylcopolymer Trioxane 30 in 3 kneaders with two Σ type stirring blades
00 g, 90 ml of 1,3-dioxolane and 15 ml of benzene containing 0.3 g of boron trifluoride / diethyl etherate were added, and the mixture was stirred at 65 ° C. and 40 rpm. The reaction started after about 1 minute and the internal temperature rose. Although the temperature rose to about 100 ° C., stirring was continued for 8 minutes. A powdery polymer was obtained by grinding the reaction mixture. The melting point of this polymer (A-3) was 168 ° C, and the crystallization temperature was 147 ° C.

Examples 1 to 3 For the polyoxymethylene homopolymers or copolymers produced in Reference Examples A-1 to A-3, N, N'-bis (3-aminopropylethylenediamine / 2) was prepared according to the formulation shown in Table 1. , 4-bis [N-butyl-N- (1,2,2,6,6-
Pentamethyl-4-piperidinyl) amino] -6-chloro-1,3,5-triazine condensate (hindered amine compound), triethylene glycol-bis [3- (3-t
-Butyl-5-methyl-4-hydroxyphenyl) propionate], (hindered phenolic antioxidant)
And calcium stearate (metal salt of carboxylic acid) were added, and melt-extruded at 220 to 230 ° C./5 mmHg using a biaxial 45 mmφ extruder with a vent manufactured by Ikegai Iron Works. The resulting composition was extruded as strands and pelletized by a cutter. The pellets are heated in a hot air circulation oven at 80 ° C for 5
After drying for an hour, MI measurement and molding were carried out to measure the mechanical properties, hydrolyzability, and amount of formaldehyde adhering to the molded product.

In addition, continuous molding was performed to observe the presence or absence of deposits on the mold. The results of these evaluations are summarized in Table 3.

Examples 4 to 6 N, N'-bis (3-aminopropyl) ethylenediamine /
2,4-bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidinyl) amino] -6-chloro-1,3,5
Instead of the triazine condensate, the NH form, ie
N, N'-bis (3-aminopropyl) ethylenediamine /
2,4-bis [N-butyl-N- (2,2,6,6-tetramethyl-4-piperidinyl) amino] -6-chloro-1,3,5-
A composition was produced in the same manner as in Examples 1 to 3 except that a triazine condensate was used. The evaluation results are summarized in Table 3.

Examples 7-9 In place of 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, except that Example 1 was used. A composition was produced in the same manner as 3. The evaluation results are summarized in Table 3.

Examples 10-12 Compositions were prepared as in Examples 1-3, except that magnesium stearate was used instead of calcium stearate. The evaluation results are summarized in Table 3.

Comparative Examples 1 to 3 As shown in Table 2, compositions were produced in the same manner as in Examples 1 to 3 except that no hindered amine compound was added. The evaluation results are summarized in Table 4.

Comparative Examples 4 to 6 N, N'-bis (3-aminopropyl) ethylenediamine /
2,4-bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidinylamino) amino] -6-chloro-
Instead of the 1,3,5-triazine condensate, bis (1,2,2,2,2) having a lower molecular weight than the compound represented by the general formula (I) is used.
A composition was prepared in the same manner as in Examples 1 to 3 except that 6,6-pentamethyl-4-piperidinyl) sebacate was used in the formulation shown in Table 2. The evaluation results are summarized in Table 4.

Comparative Examples 7 to 9 As shown in Table 2, compositions were produced in the same manner as in Examples 1 to 3 except that no hindered phenolic antioxidant was added. The evaluation results are summarized in Table 4.

Comparative Examples 10 to 12 As shown in Table 2, compositions were produced in the same manner as in Examples 1 to 3 except that no metal salt of carboxylic acid was added. The evaluation results are summarized in Table 4.

Comparative Examples 13 to 15 As shown in Table 2, compositions were produced in the same manner as in Examples 1 to 3 except that magnesium hydroxide was used instead of the carboxylic acid metal salt. The results are summarized in Table 4.

Comparative Examples 16 to 18 As shown in Table 2, compositions were produced in the same manner as in Examples 1 to 3 except that sodium oxalate was used instead of the carboxylic acid metal salt. The results are summarized in Table 4.

The following matters are clear from the results of Tables 1 to 4.

That is, it is understood from Examples 1 to 3 that the resin composition of the present invention is excellent in mechanical properties and hydrolysis resistance, has less formaldehyde odor during molding, and is less likely to cause mold deposit.

Further, from Examples 1 to 3 and Comparative Examples 1 to 3, when the hindered amine compound is not added, the mechanical properties of the polymer and the hydrolysis resistance are slightly lowered, and the formaldehyde odor during molding is very strong. It can be seen that mold deposit is likely to occur.

From Examples 1 to 3 and Comparative Examples 4 to 6, it can be seen that when a low molecular weight hindered amine compound is used, it adheres to the mold surface during continuous molding and impairs the surface condition of the molded product.

Furthermore, from Examples 1 to 3 and Comparative Examples 7 to 9, when no hindered phenolic compound was blended at all, mechanical properties and hydrolysis resistance were significantly reduced and formaldehyde odor during molding was extremely low. It can be seen that it is resistant to continuous molding.

Furthermore, from Examples 1 to 3 and Comparative Examples 10 to 12, hydrolysis resistance was obtained when no carboxylic acid metal salt was added,
It can be seen that the mechanical properties deteriorate and the formaldehyde odor during molding is extremely strong, and mold deposits tend to occur during continuous molding.

Similarly, from Examples 1 to 3 and Comparative Examples 13 to 18, when a metal hydroxide was used instead of the carboxylic acid metal salt and when a carboxylic acid metal salt having a small number of carbon atoms was used, hydrolysis resistance was high. It can be seen that the molded product has a strong formaldehyde odor and cannot withstand continuous molding.

In addition, Examples 4 to 6 (when the type of hindered amine compound is changed), Examples 7 to 9 (when the type of hindered phenol antioxidant is changed), and Examples 10 to 12
(When changing the type of carboxylic acid metal salt),
It is clear that excellent characteristics are exhibited as in Examples 1 to 3.

<Effects of the Invention> The polyoxymethylene composition for molding of the present invention has little formaldehyde odor during molding and has very few precipitates on the mold, which improves the working environment and makes mold maintenance very easy. Become.

Also, because it has excellent mechanical properties and hydrolysis resistance,
It can be used in a wide range of fields such as mechanical / mechanical parts and electric / electronic parts.

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Claims (1)

[Claims] 1. A polyoxymethyl homopolymer or copolymer, (1) a hindered amine compound represented by the following structural formula (I), (2) a hindered phenol antioxidant having a molecular weight of 400 or more, and (3) A polyoxymethylene composition for molding, which is obtained by adding and blending a metal salt of a carboxylic acid having 12 or more carbon atoms. (However, R in the formula is a hydrogen atom or a formula And R'represents a hydrogen atom or a methyl group. Further, x, y and z are integers of 0 to 10 and may be different or the same. )