JPH0757838B2 - Polyoxymethylene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a polyoxymethylene resin composition which has a very low formaldehyde odor at the time of molding and an extremely low amount of deposits on a mold.

<Prior Art> Polyoxymethylene resin is known as an engineering plastic with a good balance of mechanical strength and impact resistance, and is used in a wide range of fields such as electrical / electronic parts and mechanical / mechanical parts. . However,
Polyoxymethylene resin is structurally poor in thermal stability, and formaldehyde gas is generated at the time of molding to deteriorate the working environment, and oligomers are generated on the mold to impair the appearance of the molded product. It leaves some points.

As a method for improving the above-mentioned drawbacks, various stabilizer formulations have been devised from the past. For example, a resin composition obtained by adding a polyamide and a fatty acid metal salt having 12 to 35 carbon atoms to polyoxymethylene is blended.
-4422 publication.

However, in the resin composition proposed in JP-B-62-4422, polyamide 12 or polyamide 6/66 is used.
Polyamides such as the / 610 terpolymer are used as heat stabilizers, but these polyamides still do not sufficiently stabilize the polyoxymethylene resin, resulting in mold deposits due to formaldehyde odor and precipitates during thermoforming. However, there is a molding problem that the occurrence cannot be avoided.

Therefore, as a result of intensive investigations by the present inventors to solve the above problems, a polyamide copolymer having a specific quaternary copolymer composition was added and blended together with a hindered phenolic antioxidant and a fatty acid metal salt. By doing
The present invention has been accomplished by finding that a polyoxymethylene resin composition having extremely high thermal stability and good moldability can be obtained.

<Means for Solving the Problems> That is, the present invention relates to a polyoxymethylene homopolymer or copolymer, (1) a hindered phenol antioxidant having a molecular weight of 400 or more, and (2) a carboxylic acid having 12 or more carbon atoms. It is intended to provide a polyoxymethylene resin composition obtained by adding and blending a metal salt and (3) polyamide 6/66/610/12 quaternary copolymer.

The polyoxymethylene resin used in the present invention comprises an oxymethylene homopolymer and mainly oxymethylene units, and contains 15% by weight or less of oxyalkylene units having 2 to 8 adjacent carbon atoms in the main chain. It means an oxymethylene copolymer.

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, and then acetylating the terminal with acetic anhydride. It

The oxymethylene copolymer is obtained 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, and then adding boron trifluoride.・
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 a solvent at all, performing bulk polymerization, and further decomposing and removing unstable terminals.

Next, the hindered phenolic antioxidant 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-
Di-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] -2,4,8,1
0-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-t-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- [3- (3
-T-butyl-4-hydroxy-5-methylphenyl)
Propionyloxy] -1,1-dimethylethyl] -2,4,
The use of 8,10-tetraoxaspiro [5.5] undecane is preferred.

The molecular weight of the hindered phenolic antioxidant is 40
If it is less than 0, not only the bleeding phenomenon is remarkable, the appearance of the resin composition is impaired, but also the heat stability is lowered and the resin composition becomes unusable, which is not preferable.

Further, the addition amount of the hindered phenolic antioxidant 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 resin. If the addition amount is less than 0.001 part by weight, the heat resistance stability of the polyoxymethylene resin is insufficient, and if it is more than 5 parts by weight, the bleeding phenomenon is observed, which is not preferable.

Further, as the metal salt of a 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, ricinoleic acid, 4 ,
4'-biphenyldicarboxylic acid and 2,6-naphthalenedicarboxylic acid, and other lithium salts, sodium salts, potassium salts, magnesium salts, calcium salts, strontium salts, barium salts, aluminum salts, and the like, among which magnesium laurate , Calcium laurate, calcium palmitate, magnesium stearate, calcium stearate, barium stearate, calcium ricinoleate can be preferably used. The addition amount of these carboxylic acid metal salts is 0.001 to 5.0 parts by weight, especially 0.01 to 5.0 parts by weight based on 100 parts by weight of the polyoxymethylene resin.
The range of 3.0 parts by weight is suitable, and if it is less than 0.001 parts by weight, the effect of improving the heat resistance stability of the polyoxymethylene resin is not seen, and if it is more than 5 parts by weight, mechanical properties are deteriorated, which is not preferable.

Further, the polyamide 6/66/610/12 quaternary copolymer used in the present invention is a copolymer obtained by copolymerization of a salt of dicarboxylic acid and diamine and ω-aminocarboxylic acid or lactam. Thus, it means a copolyamide having a constitutional unit composed of four components of polyamide 6, polyamide 66, polyamide 610 and polyamide 12.

In this copolyamide, it is possible to copolymerize each structural unit in various proportions, and in the present invention, if any of the above four structural units are present, any copolyamide having any copolymerization composition should be used. You can

The addition amount of the polyamide 6/66/610/12 quaternary copolymer to the polyoxymethylene resin is 0.001 to 5.0 parts by weight, particularly 0.01
A range of from 3.0 to 3.0 parts by weight is preferable, and if it is less than 0.001 parts by weight, the effect of addition is not seen, and if it is more than 5.0 parts by weight, the rigidity of the polyoxymethylene resin decreases, which is not preferable.

The hindered phenolic antioxidant, the carboxylic acid metal salt and the polyamide 6/66/610/12 quaternary copolymer can be added only by adding and blending these three components to the polyoxymethylene resin. The desired effects of the present invention can be obtained, and the object of the present invention cannot be achieved without any one of them.

In addition, other heat stabilizers are added to the resin composition of the present invention.
Incorporation may further improve the thermal stability. As such a heat stabilizer, a urethane compound,
Examples thereof include pyridine derivatives, pyrrolidone derivatives, urea derivatives, triazine derivatives, hydrazine derivatives and amidine compounds. Specific examples include toluene diisocyanate, diphenylmethane diisocyanate and other diisocyanates, and 1,4-butanediol and other glycols and poly (tetramethylene). Oxide) glycol, polybutylene adipate, polyurethane derived from high molecular glycol such as polycaprolactone, melamine, benzoguanamine, acetoguanamine, N-butylmelamine, N-phenylmelamine, N, N'-diphenylmelamine, N, N ' , N "-triphenylmelamine, N-methylolmelamine, N, N'-dimethylolmelamine, N, N ', N"
-Trimethylolmelamine, 2,4-diamino-6-benzyloxytriazine, 2,4-diamino-6-butoxytriazine, 2,4-diamino-6-cyclohexyltriazine, triazine derivatives such as melem and melam, N-
Phenylurea, N, N'-diphenylurea, thiourea, N
-Phenylthiourea, N, N'-diphenylthiourea, urea derivatives such as nonamethylene polyurea, phenylhydrazine, diphenylhydrazine, benzaldehyde hydrazone, benzaldehyde semicarbazone, benzaldehyde 1-methyl-1-phenylhydrazone, thiosemicarba Zone, hydrazine derivatives such as hydrazone of 4- (dialkylamino) benzaldehyde, dicyandiamide, guanzine, guanidine, aminoguanidine, guanine, guanacrine, guanochlor, guanoxane, guanosine, amiloride, N-amidino-3-.
Amidine compounds such as amino-6-chloropyrazinecarboxamide, poly (2-vinylpyridine), poly (2
-Methyl-5-vinylpyridine), poly (2-ethyl-)
5-vinylpyridine), 2-vinylpyridine-2-methyl-5-vinylpyridine copolymer, 2-vinylpyridine-styrene copolymer, and other pyridine derivatives. Among them, melamine, benzoguanamine, and acetoguanamine can be mentioned. , N-methylolmelamine, N, N'-dimethylolmelamine and N, N ', N "-trimethylolmelamine, dicyandiamide are preferred.

The addition amount of the heat stabilizer other than the above-mentioned polyamide is 0.001 to 5.0 parts by weight with respect to 100 parts by weight of the polyoxymethylene resin,
Particularly, the range of 0.01 to 3.0 parts by weight is preferable, and the addition amount is
If it is less than 0.001 part by weight, the effect of addition is small, and if it is more than 5.0 parts by weight, the tendency of the bleeding phenomenon appears, which is not preferable.

Further, the composition of the present invention, calcium carbonate, barium sulfate, clay, titanium oxide, silicon oxide, mica powder, filler such as talc, carbon fiber, glass fiber, within the range that does not impair the effects of the present invention, Ceramic fibers, reinforcing materials such as aramid fibers, pigments, dyes, conductive agents such as carbon black, plasticizers, nucleating agents, release agents, tackifiers, flame retardants, lubricants and antistatic agents may be optionally contained. be able to.

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

The mechanical properties of the molded products, the amount of formaldehyde deposited, the polymer melting point, the crystallization temperature, the MI (melt index), and the occurrence of mold deposit during continuous molding as shown in Examples and Comparative Examples are as follows. Measured or observed.

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 molded.

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 lowered 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 was determined.
Expressed as

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

Occurrence of mold deposit in continuous molding: Continuous molding was performed under the above-described molding conditions, and the occurrence of mold deposit was visually observed.

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

Reference Example Production of Polyoxymethylene Resin A-1 Production of Polyoxymethylene Homopolymer Formaldehyde obtained by thermal decomposition of paraformaldehyde was introduced into a continuous 2 liter 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 in and the polymeric dispersion product was withdrawn at a rate such that the residence time was 15 minutes. Formaldehyde is about 8g
The polymerization initiator was tetra (n
-Butyl) iodide concentration of 1.87 per reaction medium
mg, lauric acid concentration was supplied in such a ratio 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. This crude polymer 50
A mixture of 0 g, acetic anhydride 4000 g and sodium acetate 1.6 g was mixed and refluxed at 139 ° C. for 1 hour.

After cooling, the polymer was filtered, washed with acetone and water, and dried. The melting point of this polymer (A-1) was 179 ° C, and the crystallization temperature was 150 ° C.

A-2 Production of polyoxymethylene copolymer 900 g of trioxane and 8.8 g of ethylene oxide were dissolved in 450 g of cyclohexane, 60 ml of benzene containing 0.3 g of boron trifluoride / diethyl etherate was added, and the temperature was changed to 60 ° C.
It was stirred at. 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 10
After stopping the polymerization reaction by adding ml, 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) is
The temperature was 168 ° C and the crystallization temperature was 147 ° C.

A-3 Manufacture of polyoxymethylene copolymer Trioxane 3000 in 3L kneader with two Σ type stirring blades
g, 1,3-dioxolane 90 ml and 15 ml of benzene containing 0.3 g of boron trifluoride diethyl etherate,
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, the mixture was stirred for 8 minutes as it was. A powdery polymer was obtained by grinding the reaction mixture. The melting point of this polymer (A-3) is
The temperature was 168 ° C and the crystallization temperature was 147 ° C.

As the polyamide 6/66/610/12 quaternary copolymer, one having the copolymer composition shown in Table 1 was used.

Examples 1 to 3 Triethylene glycol-bis [3- (3-t-butyl-5-methyl) at a ratio shown in Table 2 with respect to the polyoxymethylene resins produced in Reference Examples A-1 to A-3. -4-Hydroxyphenyl) propionate], calcium stearate and polyamide quaternary copolymer B-1 were added, and a biaxial 45 mmφ extruder with a vent manufactured by Ikegai Iron Works was used.
The mixture was melt-extruded and kneaded at 0 to 230 ° C / 10 mmtorr.

The resulting composition was extruded as strands and pelletized by a cutter. After drying the pellets at 80 ° C. for 5 hours in a hot air circulation oven, MI measurement and molding were performed, and the amount of formaldehyde adhering to the molded product and mechanical properties were measured. Further, continuous molding was performed, and the time until a whitish "cloudy" was observed on the mold was measured. The results are summarized in Table 4.

Examples 4 to 6 Melamine was further added to the compositions of Examples 1 to 3 in the ratio shown in Table 2, and compositions were obtained in the same manner as in Examples 1 to 3. The same measurement as in Examples 1 to 3 was performed, and the results are summarized in Table 4.

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 as in Examples 1-3 To produce a composition.

In addition, the same measurement as in Examples 1 to 3 was performed, and the results are shown in Table 4.
Summarized in.

Examples 10 to 12 Compositions were prepared in the same manner as in Examples 1 to 3 except that magnesium stearate was used instead of calcium stearate. In addition, the same measurement as in Examples 1 to 3 is performed,
The results are summarized in Table 4.

Examples 13 to 14 Compositions were prepared in the same manner as in Example 3 except that B-2 or B-3 was used instead of the polyamide quaternary copolymer B-1. The same measurement as in Example 3 was performed, and the results are summarized in Table 4.

Comparative Examples 1 to 3 In the same manner as in Examples 1 to 3 except that triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] was not used, Table 3 A composition ratio composition was produced. Moreover, Example 1
The same measurement as in Example 3 was performed, and the results are summarized in Table 5.

Comparative Examples 4 to 6 Compositions having the compounding ratios shown in Table 3 were produced in the same manner as in Examples 1 to 3 except that calcium stearate was not used. Further, the same measurement as in Examples 1 to 3 was performed, and the results are summarized in Table 5.

Comparative Examples 7 to 9 Compositions having the compounding ratios shown in Table 3 were produced in the same manner as in Examples 1 to 3 except that the polyamide quaternary copolymer was not used. Further, the same measurement as in Examples 1 to 3 was performed, and the results are summarized in Table 5.

Comparative Examples 10 to 12 Compositions having the compounding ratios shown in Table 3 were produced in the same manner as in Examples 1 to 3 except that sodium acetate was used instead of calcium stearate. Further, the same measurement as in Examples 1 to 3 was performed, and the results are summarized in Table 5.

Comparative Examples 13 to 15 Compositions having the compounding ratios shown in Table 3 were produced in the same manner as in Examples 1 to 3 except that the polyamide terpolymer was used instead of the polyamide terpolymer. Moreover, Example 1
The same measurement as in Example 3 was performed, and the results are summarized in Table 5.

Comparative Examples 16 to 18 Compositions having the compounding ratios shown in Table 3 were produced in the same manner as in Examples 1 to 3 except that polyamide 66 was used instead of the polyamide quaternary copolymer. Further, the same measurement as in Examples 1 to 3 was performed, and the results are summarized in Table 5.

Comparative Examples 19 to 21 Compositions having the compounding ratios shown in Table 3 were produced in the same manner as in Examples 1 to 3 except that polyamide 12 was used instead of the polyamide quaternary copolymer. Further, the same measurement as in Examples 1 to 3 was performed, and the results are summarized in Table 5.

The following matters are clear from the results of Tables 2 to 5.

The composition of the present invention has excellent mechanical properties, has little formaldehyde odor during molding, and does not generate mold deposit (Examples 1 to 3).

When another heat stabilizer (melamine) was added (Examples 4 to 6), the kind of hindered phenolic antioxidant was changed (Examples 7 to 9), the kind of fatty acid metal salt was changed. Even in the cases (Examples 10 to 12) and the types of the polyamide quaternary copolymers (Examples 13 to 14), excellent characteristics equivalent to or higher than those of Examples 1 to 3 are exhibited.

On the other hand, when the hindered phenolic antioxidant is not added, not only the mechanical properties are deteriorated, but also the formaldehyde odor during molding becomes strong and continuous molding becomes difficult (Comparative Examples 1 to 3).

Even when the metal salt of carboxylic acid is not added, the same tendency as described above is obtained (Comparative Examples 4 to 6).

The same tendency as described above is obtained when a lower carboxylic acid metal salt having a small number of carbon atoms is used (Comparative Examples 10 to 12).

When the polyamide quaternary copolymer is not added, not only the mechanical properties are slightly lowered, but also the formaldehyde odor during molding is strong and the deposition of mold deposits during continuous molding becomes faster (Comparative Examples 7 to 9).

When a polyamide terpolymer, polyamide 66 or polyamide 12 is used instead of the polyamide quaternary copolymer, the formaldehyde odor during molding is strong, and the deposition of mold deposits during continuous molding becomes faster (comparative). Examples 13-21).

<Effects of the Invention> The polyoxymethylene resin composition of the present invention has an extremely low formaldehyde odor during molding and extremely low deposits on the mold.

Therefore, the working environment is extremely good, and the mold maintenance becomes easy, so that a long-term continuous production of molded products is possible.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08L 77:00)

Claims (1)

[Claims] 1. A polyoxymethylene homopolymer or copolymer, (1) a hindered phenolic antioxidant having a molecular weight of 400 or more, (2) a metal salt of a carboxylic acid having 12 or more carbon atoms, and (3) polyamide 6 / 66/610/12 A polyoxymethylene resin composition obtained by adding and blending a quaternary copolymer.