KR20230044814A - Polyoxymethylene resin composition and molded article prepared therefrom - Google Patents

Abstract

The purpose of the present invention is to provide a polyoxymethylene resin composition which is excellent in low-temperature impact resistance and weld strength retention and has low formaldehyde emissions even at high temperatures. To this end, provided is a polyoxymethylene resin composition comprising 100 parts by weight of a polyoxymethylene resin, 15 to 30 parts by weight of methyl methacrylate-butadiene-styrene rubber particles, 0.01 to 1 part by weight of a dihydrazide compound, 0.01 to 0.5 parts by weight of a hindered phenol-based antioxidant, 0.01 to 0.5 parts by weight of a hindered amine-based stabilizer, and 0.01 to 0.5 parts by weight of a metal salt phosphate-based compound.

Description

Polyoxymethylene resin composition and molded article manufactured therefrom

The present invention relates to a polyoxymethylene resin composition and a molded product manufactured therefrom, and more particularly, to a polyoxymethylene resin composition having excellent low-temperature impact resistance and weld strength retention and low formaldehyde emission even at high temperatures, and thereby It relates to molded articles manufactured from

Conventionally, thermoplastic polyurethane is applied to modify the impact resistance of polyoxymethylene.

In this case, it is possible to modify the impact resistance, but the compatibility between thermoplastic polyurethane and polyoxymethylene is poor, and due to the linear chemical structure of thermoplastic polyurethane, strength and elongation decrease at the weld part where the resin meets during injection molding of the product. appears very large. For this reason, a cracking phenomenon occurs in a complex part with many weld parts or a thin weld part.

In addition, thermoplastic polyurethane is known to have a glass transition temperature of about -15 ° C, so there is a problem of low impact resistance at a low temperature of -30 ° C or less.

An object of the present invention is to provide a polyoxymethylene resin composition having excellent low-temperature impact resistance and weld strength retention and low formaldehyde emission even at high temperatures.

According to one embodiment, 100 parts by weight of polyoxymethylene resin, 15 parts by weight to 30 parts by weight of methyl methacrylate-butadiene-styrene rubber particles, 0.01 part by weight to 1 part by weight of a dihydrazide compound, hindered phenol-based oxidation Provided is a polyoxymethylene resin composition comprising 0.01 to 0.5 parts by weight of an inhibitor, 0.01 to 0.5 parts by weight of a hindered amine stabilizer, and 0.01 to 0.5 parts by weight of a metal salt phosphate compound.

The residual acid concentration of the methyl methacrylate-butadiene-styrene rubber particles may be 300 ppm or less.

Dihydrazide compounds include sebacic acid dihydrazide, adipic acid dihydrazide, 1,12-dodecanedicarboxylic acid dihydrazide, isophthalic acid acid dihydrazide (isophthalic acid dihydrazide), or a combination thereof.

The metal salt phosphate-based compound may be an ester-based compound containing zinc.

The polyoxymethylene resin composition may have a formaldehyde emission of 5 mg/kg or less at 220° C. based on VDA275 measurement.

According to another embodiment, a molded article manufactured from the polyoxymethylene resin composition described above is provided.

The molded article may have a Charpy Notched low temperature impact strength (-30 °C) of 11 kJ/m ² or more, and a Weld tensile strength retention of 90% or more.

The polyoxymethylene resin composition of the present invention has excellent low-temperature impact resistance and weld strength retention, and has low formaldehyde emission even at high temperatures.

Advantages and features of the techniques described hereinafter, and methods of achieving them, will become clear with reference to the implementations described below in detail. However, the form to be implemented is not limited to the implementation examples disclosed below. Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with meanings commonly understood by those skilled in the art. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless explicitly specifically defined.

When it is said that a certain part "includes" a certain component throughout this specification, it means that it may further include other components, not excluding other components unless otherwise stated. In addition, singular forms also include plural forms unless specifically stated otherwise in a phrase.

The polyoxymethylene resin composition according to one embodiment includes a polyoxymethylene resin, methyl methacrylate-butadiene-styrene rubber particles, a dihydrazide compound, a hindered phenol-based antioxidant, a hindered amine-based stabilizer, and a metal salt phosphate-based contains a compound

The polyoxymethylene resin serves as a base resin of a resin composition, serves to secure basic mechanical and chemical properties of the resin, and performs an important function in impact resistance performance in particular.

Polyoxymethylene can be used without particular limitation as long as it is a commercially used normal polyoxymethylene. For example, polyoxymethylene may have a melting point (T _m ) of 160 °C to 180 °C as measured by differential scanning calorimetry (DSC).

Polyoxymethylene is an oxymethylene homopolymer containing an oxymethylene -(OCH ₂ ) _n - group as a repeating unit, both ends of which are blocked by ester or ether groups, or a polymer having 2 to 8 carbon atoms in a polymer main chain composed of oxymethylene monomer units. It may be an oxymethylene-based copolymer or terpolymer in which oxyalkylene units are randomly inserted and both ends of the polymer are blocked by ester or ether groups.

For example, the oxymethylene homopolymer and the oxymethylene-based copolymer may be prepared by the following method. First, the oxymethylene homopolymer is polymerized by introducing anhydrous formaldehyde in an organic solvent containing a basic polymerization catalyst such as, for example, an organic amine, an organic or inorganic tin compound, or a metal hydroxide, and the polymer is filtered, followed by acetic acid It can be prepared by acetylating the ends by heating in acetic anhydride in the presence of sodium.

In addition, the oxymethylene-based copolymer is, for example, anhydrous trioxane or formaldehyde cyclic oligomer such as tetraoxane and ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3-flopanedioformal , 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, diethylene glycol formal, 1,3,5-trioxepane, or 1,3,6- It can be prepared by dissolving or suspending a cyclic ether such as trioxocane in an organic solvent such as cyclohexane or benzene, polymerizing it by adding a Lewis acid catalyst such as boron trifluoride diethyl etherate, and decomposing and removing unstable terminals. there is.

For example, an oxymethylene-based copolymer may be selected from the viewpoint of balance of heat resistance, mechanical strength, and impact resistance. At this time, the structure of the polyoxymethylene copolymer may be a linear structure, a branched structure, or a crosslinked structure.

Comonomers other than the main chain oxymethylene group include oxyethylene (-(OCH ₂ CH ₂ ) _n -), oxypropylene (-(OCH ₂ CH ₂ CH ₂ ) _n -), oxybutylene (-( OCH ₂ CH ₂ CH ₂ CH ₂ ) _n -) containing a branched oxyalkylene group having 2 to 10 carbon atoms, especially a branched oxyalkylene group having 2 to 4 carbon atoms, especially an oxyethylene group It is preferable from the viewpoint of improving the thermal stability of the polymer and improving the crystallinity of moldability.

In addition, the comonomer is ethylene oxide, 1,3-dioxolane (1,3-dioxolane), 1,3-dioxepane (1,3-dioxepane), or 1,3,5-trioxepane (1,3,5-trioxepane), for example, 1,3-dioxolane.

Methyl methacrylate-butadiene-styrene rubber particles are added as impact modifiers.

Methyl methacrylate-butadiene-styrene rubber particles have a spherical chemical structure and a core-shell structure. For example, the rubber core of the methyl methacrylate-butadiene-styrene rubber particles is polybutadiene or poly(butadiene/styrene) and the polymethyl methacrylate or poly(methyl methacrylate/styrene) hard shell is the rubber core grafted onto it. Methyl methacrylate-butadiene-styrene rubber particles can be produced by emulsion polymerization.

Since the glass transition temperature of butadiene constituting the methyl methacrylate-butadiene-styrene core is -80 °C or less, the low-temperature impact resistance of the polyoxymethylene resin composition can be improved.

The methyl methacrylate-butadiene-styrene rubber particles may be included in an amount of 15 parts by weight to 30 parts by weight based on 100 parts by weight of the polyoxymethylene resin. When the content of the methyl methacrylate-butadiene-styrene rubber particles is less than 15 parts by weight, the Charpy Notched low-temperature impact strength (-30 ℃) may drop to 11 kJ/m ² or less, and exceed 30 parts by weight In this case, the weld tensile strength retention rate is lowered to 90% or less, and formaldehyde emission may be increased at high temperatures.

Meanwhile, since the polyoxymethylene resin composition having modified impact resistance is mainly applied to automobile interior materials such as fasteners and clips, it is essential to reduce the amount of formaldehyde emission. However, methyl methacrylate-butadiene-styrene rubber particles are prepared by graft polymerization through emulsion polymerization and then using an acid such as sulfuric acid or hydrochloric acid or a coagulant such as a salt.

In this process, the residual coagulant contained in the methyl methacrylate-butadiene-styrene rubber particles mainly causes decomposition of polyoxymethylene with sulfuric acid and hydrochloric acid, and formaldehyde is released as polyoxymethylene is decomposed.

Therefore, in order to reduce formaldehyde emission of the polyoxymethylene resin composition, the residual acid concentration of the methyl methacrylate-butadiene-styrene rubber particles may be 300 ppm or less, for example, 200 ppm or less.

Additionally, the methyl methacrylate-butadiene-styrene rubber particles include a dihydrazide compound to reduce the amount of formaldehyde emitted due to the residual acid. The amine group of the dihydrazide compound can effectively capture formaldehyde.

For example, the dihydrazide compound may be a compound represented by Formula 1 below.

[Formula 1]

In Formula 1, R ₁ may be an alkylene group or an arylene group having 4 to 10 carbon atoms.

For example, the dihydrazide compound is sebacic acid dihydrazide, adipic acid dihydrazide, 1,12-dodecanedicarboxylic acid dihydrazide ), isophthalic acid dihydrazide, or a combination thereof.

The dihydrazide compound may be included in an amount of 0.01 part by weight to 1 part by weight, for example, 0.1 part by weight to 0.5 part by weight, based on 100 parts by weight of the polyoxymethylene resin. If the content of the dihydrazide compound is less than 0.01 part by weight, the formaldehyde trapping effect may not be sufficient, and formaldehyde emitted from molded products may not be effectively reduced. frequency of occurrence may increase.

The hindered phenol-based antioxidant serves to trap radicals generated in the polyoxymethylene resin whose bond is broken by heat. That is, radicals generated by breaking polymer bonds due to heat must be captured because they continuously destroy the bonds of surrounding polymers, and hindered phenolic antioxidants play this role.

The hindered phenolic antioxidant may have a weight average molecular weight of 500 g/mol to 1,500 g/mol and a melting point of 45 °C to 200 °C.

For example, hindered phenolic antioxidants include tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] methane, octadecyl-3-(3,5 -di-tert-butyl-4-hydroxyphenyl) propionate, triethylene glycol-bis-3(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, tris(3,5- Di-tert-butyl-4-hydroxylbenzyl)isocyanurate, thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexa Methylenebis(3,5-di-tert-butyl-4-hydroxyhydrocyamide), 1,3,5-tris(2,6,-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurates, or combinations thereof.

The hindered phenol-based antioxidant may be included in an amount of 0.01 part by weight to 0.5 part by weight based on 100 parts by weight of the polyoxymethylene resin. When the content of the hindered phenolic antioxidant is less than 0.01 parts by weight, the antioxidant effect may be insignificant, and when it exceeds 0.5 parts by weight, the effect of impurities may be increased, and thus mechanical properties may be deteriorated.

The hindered amine-based stabilizer protects the resin from being decomposed by exposure to ultraviolet rays and serves as a free radical scavenger to prevent decomposition of the polyoxymethylene resin.

Hindered amine stabilizers include, for example, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4 -Acryloylox-2,2,6,6-tetramethylpiperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6, 6-Tetramethylpiperidine, 4-cyclohexoxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4- Benzyloxy-2,2,6,6-tetramethylpiperidine, 4-(phenylcarboxy)-2,2,6,6-tetramethylpiperidine, bis(2,2,6,6- Tetramethyl-4-piperidyl)oxalate, 1,2-bis(2,2,6,6-tetramethyl-4-piperidyloxy)ethane, bis(2,2,6,6-tetramethyl -4-piperidyl) hexamethylene-1,6-dicarbomate, bis(1-methyl-2,2,6,6-tetramethyl-4-piperidyl) adipate, bis(2,2, 6,6-tetramethyl-4-piperidyl)sebacate, tris(2,2,6,6-tetramethyl-4-piperidyl)benzene-1,3,5-tricarboxylate, dimethyl polymers of succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol, or mixtures thereof.

The hindered amine-based stabilizer may be included in an amount of 0.01 part by weight to 0.5 part by weight based on 100 parts by weight of the polyoxymethylene resin. If the content of the hindered amine-based stabilizer is less than 0.01, the anti-oxidation performance is insufficient, and the formaldehyde reduction effect at high temperature may decrease. If the content exceeds 1 part by weight, the effect of impurities may be increased, and polyoxymethylene after injection The color of the molded article may be yellowed.

The metal salt phosphate-based compound can prevent thermal decomposition of the polyoxymethylene resin composition by enhancing heat resistance of the polyoxymethylene resin, thereby further reducing formaldehyde emission. In particular, the phosphate of the metal salt phosphate-based compound increases the heat resistance of the polyoxymethylene resin so that decomposition does not occur easily even at a high temperature of 220 °C.

The metal salt phosphate-based compound may be, for example, an ester-based compound containing zinc, and specifically may be a zinc phosphate ester-based compound.

The zinc phosphate ester-based compound is, for example, a compound represented by Formula 2 or Formula 3 below, and may be a fatty acid ester-based compound having 16 to 22 carbon atoms.

[Formula 2]

In Formula 2, R ₂ is a C16 to C24 alkyl group.

[Formula 3]

In Formula 3, R ₂ is a C16 to C24 alkyl group.

The zinc phosphate ester-based compound represented by Formula 2 or Formula 3 is, for example, zinc stearyl phosphate, zinc behenic phosphate, zinc arachidonic phosphate, zinc palmitic Phosphate (Zine palmitic phosphate), or a mixture thereof.

The metal salt phosphate compound may be included in an amount of 0.01 part by weight to 0.5 part by weight, for example, 0.1 part by weight to 0.3 part by weight, based on 100 parts by weight of the polyoxymethylene resin. If the content of the metal salt phosphate-based compound is less than 0.01, the thermal stability effect may be insufficient and the formaldehyde reduction effect may be reduced, and if it exceeds 0.5 parts by weight, the effect of impurities may be greater, and thus mold deposits occur frequency may increase.

On the other hand, the polyoxymethylene resin composition is a filler such as calcium carbonate, clay, silicon oxide, mica powder, glass fiber, carbon fiber, polyamide fiber and Additives such as reinforcing agents, coloring agents, nucleating agents, plasticizers, release agents such as ethylene bis stir and polyethylene wax, and lubricants may be additionally included.

As described above, the polyoxymethylene resin composition includes methyl methacrylate-butadiene-styrene rubber particles as an impact modifier, and is free from residual coagulants such as sulfuric acid and hydrochloric acid included in the methyl methacrylate-butadiene-styrene rubber particles. In order to reduce the decomposition of polyoxymethylene and consequent formaldehyde emission, a dihydrazide compound is included, and a hindered phenolic antioxidant is included to improve the heat resistance of the polyoxymethylene resin, especially at a high temperature of 220 ° C. As the hindered amine-based stabilizer and the metal salt phosphate-based compound are included to improve heat resistance, the polyoxymethylene resin composition may have a formaldehyde emission of 5 mg/kg or less at 220° C. based on VDA275.

A molded article according to another embodiment is prepared from the polyoxymethylene resin composition described above.

The molded article contains methyl methacrylate-butadiene-styrene rubber particles as an impact modifier, and decomposition of polyoxymethylene from residual coagulants such as sulfuric acid and hydrochloric acid contained in methyl methacrylate-butadiene-styrene rubber particles and resulting form A dihydrazide compound is included to reduce aldehyde emission, a hindered phenolic antioxidant is included to improve heat resistance of polyoxymethylene resin, and a hindered amine stabilizer is included to improve heat resistance at 220 ° C. As prepared from a polyoxymethylene resin composition containing a metal salt phosphate compound, the molded article has a Charpy Notched low temperature impact strength (-30 ℃) of 11 kJ/m ² or more, and a weld tensile strength The retention rate may be 90% or more.

Hereinafter, specific embodiments of the invention are presented. However, the embodiments described below are only intended to specifically illustrate or explain the invention, and the scope of the invention should not be limited thereto.

[Production Example: Preparation of polyoxymethylene resin composition]

(Examples and comparative examples)

A polyoxymethylene resin composition was prepared by mixing the contents of each component in the ratio shown in Table 1 based on 100 parts by weight of the polyoxymethylene resin.

division go me all la mind bar buy ah ruler Example 1 100 18 0.4 - 0.2 0.2 0.1 0.1 - Example 2 100 25 0.5 - 0.3 0.3 0.1 0.1 - Example 3 100 18 - 0.6 0.2 0.2 0.1 0.1 - Comparative Example 1 100 - 0.1 - 0.1 - 0.1 0.1 18 Comparative Example 2 100 18 - - 0.2 0.2 0.1 0.1 - Comparative Example 3 100 18 0.4 - 0.2 - 0.1 0.1 - Comparative Example 4 100 18 0.4 - - 0.2 0.1 0.1 - Comparative Example 5 100 18 1.8 - 0.2 0.2 0.1 0.1 - Comparative Example 6 100 18 0.4 - 1.8 0.2 0.1 0.1 - Comparative Example 7 100 18 0.4 - 0.2 1.2 0.1 0.1 -

A) Polyoxymethylene resin (made by Kolon Plastics): melting point 167 ℃

B) Methyl methacrylate-butadiene-styrene rubber particles (made by LG): residual acid concentration 150 ppm

C) Adipic acid dihydrazide (product of Japan finechem)

D) Sebacic acid dihydrazide (product of Japan finechem)

E) Zinc stearyl phosphate (product of Sakai chemical)

F) Hindered amine stabilizer (product of Songwon)

G) Hindered phenolic antioxidant (product of Songwon)

H) Release agent (Shinwon Chemical Co.)

I) Thermoplastic polyurethane (product of Songwon)

[Experimental Example: Measurement of Physical Properties of Polyoxymethylene Resin Composition]

The physical properties of the polyoxymethylene resin compositions prepared in Examples and Comparative Examples were measured by the following method, and the results are shown in Table 2.

1) Impact strength (-30℃) (kJ/m ² ): Measured based on ISO179/1eA.

2) Weld strength retention rate (%): Tensile specimens without a weld part and specimens with a weld part in the middle of the specimen were prepared and the tensile strength was measured based on ISO 527. Weld strength retention is the value obtained by dividing the tensile strength measured with a weld tensile specimen by the tensile strength measured with a tensile specimen.

3) Formaldehyde gas emission (FA GAS 200 ℃) (mg/kg): Measured according to VDA275.

4) Formaldehyde gas emission (FA GAS 220 ℃) (mg/kg): Measured according to VDA275.

division Impact strength (-30℃) Weld strength retention rate (%) FA GAS 200℃ FA GAS 220℃ Example 1 11.5 95 0.6 2.2 Example 2 12.2 93 1.4 4.0 Example 3 11.0 93 1.8 4.5 Comparative Example 1 10.0 75 0.3 0.8 Comparative Example 2 12.0 95 71.3 98.9 Comparative Example 3 10.6 94 2.6 6.5 Comparative Example 4 10.3 94 1.9 12.8 Comparative Example 5 9.4 92 0.2 1.5 Comparative Example 6 10.7 93 0.8 1.3 Comparative Example 7 10.5 93 1.0 1.8

Referring to Table 2, it can be seen that in Comparative Example 1, as 18 parts by weight of thermoplastic polyurethane was used instead of the methyl methacrylate-butadiene-styrene rubber particles, the low-temperature impact resistance was slightly reduced and the weld strength retention rate was very low.

In the case of Comparative Example 2, it can be seen that the amount of formaldehyde emission cannot be controlled because the dihydrazide-based material is not included.

In the case of Comparative Example 3, since the hindered amine-based stabilizer was not included, it was difficult to control the amount of formaldehyde emission at a high temperature (220° C.).

In the case of Comparative Example 4, since zinc stearyl phosphate was not included, it can be seen that it is difficult to control the amount of formaldehyde emission at a high temperature (220 ° C.).

In the case of Comparative Example 5, as the dihydrazide-based material was excessively included, the low-temperature impact was greatly reduced, and it was confirmed that the amount of mold deposit in the mold during injection increased.

In the case of Comparative Example 6, as the zinc stearyl phosphate was included in an excessive amount, the low-temperature impact was slightly reduced, and it could be seen that the amount of mold deposit in the mold increased during injection.

In the case of Comparative Example 7, as the hindered amine-based stabilizer was included in an excessive amount, the low-temperature impact properties were slightly decreased, and the color after chipping and injection was very yellow.

On the other hand, the polyoxymethylene resin compositions of Examples 1 to 3 include methyl methacrylate-butadiene-styrene rubber particles as an impact modifier, and contain sulfuric acid and hydrochloric acid contained in methyl methacrylate-butadiene-styrene rubber particles. A dihydrazide compound is included to reduce the decomposition of polyoxymethylene from the residual coagulant and consequently the release of formaldehyde, and a hindered phenolic antioxidant is included to improve the heat resistance of the polyoxymethylene resin, especially at 220 ° C. As it contains a hindered amine-based stabilizer and a metal salt phosphate-based compound to improve heat resistance, the polyoxymethylene resin composition has a formaldehyde emission of 5 mg/kg or less at 220 ° C. based on VDA275, and is prepared therefrom It can be seen that the molded article has a Charpy Notched low temperature impact strength (-30 °C) of 11 kJ/m ² or more and a Weld tensile strength retention of 90% or more.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It falls within the scope of the right of invention.

Claims (7)

100 parts by weight of polyoxymethylene resin;
15 parts by weight to 30 parts by weight of methyl methacrylate-butadiene-styrene rubber particles,
0.01 part by weight to 1 part by weight of a dihydrazide compound,
0.01 part by weight to 0.5 part by weight of a hindered phenolic antioxidant,
0.01 part by weight to 0.5 part by weight of a hindered amine stabilizer, and
A polyoxymethylene resin composition comprising 0.01 part by weight to 0.5 part by weight of a metal salt phosphate compound. In paragraph 1,
The residual acid concentration of the methyl methacrylate-butadiene-styrene rubber particles is 300 ppm or less of the polyoxymethylene resin composition. In paragraph 1,
The dihydrazide compound is sebacic acid dihydrazide, adipic acid dihydrazide, 1,12-dodecanedicarboxylic acid dihydrazide, isof A polyoxymethylene resin composition comprising isophthalic acid dihydrazide or a combination thereof. In paragraph 1,
The metal salt phosphate-based compound is a polyoxymethylene resin composition of an ester-based compound containing zinc. In paragraph 1,
The polyoxymethylene resin composition is a polyoxymethylene resin composition having a formaldehyde emission of 5 mg / kg or less at 220 ° C based on VDA275 measurement. A molded article manufactured from the polyoxymethylene resin composition according to any one of claims 1 to 5. In paragraph 1,
The molded article has a Charpy Notched low temperature impact strength (-30 ° C) of 11 kJ / m ² or more, and a weld tensile strength retention of 90% or more.