KR20000034837A - Polyoxymethylene resin compostions - Google Patents

Abstract

The present invention relates to a polyoxymethylene resin composition, comprising: (a) 50 to less than 97% by weight of polyoxymethylene resin, (b) 3 to 50% by weight of a thermoplastic polyester elastomer or a mixture of this polyester elastomer and a thermoplastic polyurethane elastomer It is characterized by consisting of less than 0.1% and less than 0.1 to 10% by weight (c) maleic anhydride copolymer, the polyoxymethylene resin composition of the present invention is very excellent in toughness, thermal stability, processability and impact resistance.

Description

Polyoxymethylene resin composition {POLYOXYMETHYLENE RESIN COMPOSTIONS}

The present invention relates to a novel polyoxymethylene resin composition, in particular improved toughness, impact resistance, heat, comprising a polyoxymethylene matrix, a polyester elastomer and optionally a polyurethane elastomer and maleic anhydride copolymer The present invention relates to a polyoxymethylene resin composition having improved stability and processability.

Polyoxymethylene resins are widely used in various electrical, electronic components and machines because of their excellent mechanical, chemical, physical and electrical properties. However, conventional polyoxymethylene polymers do not provide sufficiently high impact strength for certain applications. Therefore, many efforts have been made to improve the impact strength by adding additional polymer components.

Conventional techniques for imparting impact properties and toughness enhancement to polyoxymethylene are as follows. A method of mixing a hydrocarbon rubber containing a nitrile group or a carboxylic acid ester group in a side chain (Japanese Patent Publication No. 70-12674), a method of mixing a copolymer of α-olefin / α, β-unsaturated carboxylic acid (Japan Japanese Patent Publication No. 70-18023), a method of mixing a copolymer of ethylene / vinyl or acrylic ester (Japanese Patent Publication No. 70-26231), a diolefin / nitrile copolymer, that is, an air having a nitrile group substituted in a hydrocarbon main chain Mixing the copolymer to improve impact strength and flexural modulus (US Pat. No. 3,476,832), mixing aliphatic polyether (Japanese Patent Publication No. 75-33095), α-olefin polymer and ethylene / vinyl copolymer A method of using a mixture (Japanese Patent Laid-Open No. 74-40346), a method of mixing polyolefin-based, polystyrene-based, polyester-based, and polyamide-based thermoplastic elastomers (Japanese Patent Publication 85-164116).

However, the polymer component added to the blend according to the method was not easily mixed with the polyoxymethylene resin, so that the improvement in impact resistance was limited despite attempts to homogenize the blend.

It has been suggested that agglomerated discrete particles of thermoplastic polyurethane elastomers can improve their impact resistance when dispersed in a polyoxymethylene matrix. US Pat. No. 5,286,807, for example, essentially consists of 5 to 15% by weight thermoplastic polyurethane having a soft segment glass transition temperature below 0 ° C. and 85 to 95% by weight polyoxymethylene polymer having a number average molecular weight of 20,000 to 100,000. An impact resistant polyoxymethylene composition is disclosed, wherein the thermoplastic polyurethane is dispersed in polyoxymethylene as discrete particles.

In addition, US Pat. No. 4,804,716 discloses a poly consisting essentially of 60 to 85 weight percent polyoxymethylene resin and 15 to 40 weight percent thermoplastic polyurethane dispersed in the polyoxymethylene polymer as small discrete particles of 0.01 to 0.9 μm. An oxymethylene resin composition is disclosed.

However, the polyoxymethylene composition containing polyurethane elastomer particles is problematic in the injection molding process because of low thermal stability and also in the extrusion process because of phase separation or die swelling phenomenon.

Therefore, there is an urgent need to develop a polyoxymethylene resin composition having excellent toughness, impact resistance and thermal stability as well as improved processability.

The present invention is to solve the above problems, by adding a thermoplastic polyester elastomer and optionally a thermoplastic polyurethane elastomer with a maleic anhydride copolymer as a homogenizing agent to the polyoxymethylene matrix, improved processability, thermal stability and resistance It is an object to provide a novel polyoxymethylene composition having impact properties and toughness and a molded article therefrom.

In order to achieve the above object, the present invention, based on the total amount of components A, B, C and D, (A) polyoxymethylene resin (component A) 50 to less than 97% by weight; (B) less than 3 to 50% by weight of a thermoplastic polyester elastomer (component B) or a mixture of thermoplastic polyurethane elastomer (component C) with the thermoplastic polyester elastomer; And (c) 0.1 to less than 10% by weight of maleic anhydride copolymer (component D).

The present invention also provides a molded article from the polyoxymethylene resin composition of the present invention.

Hereinafter, the present invention will be described in more detail.

The resin composition of the present invention contains a succinic anhydride group substituted with a polyoxymethylene (component A) and a mixture of a thermoplastic polyester elastomer (component B) or a thermoplastic polyurethane elastomer (component C) and a thermoplastic polyester elastomer (component B). It is characterized by homogenization by the action of the maleic anhydride copolymer (component D). In the absence of component D such homogenization of components A, B and C, which are incompatible, is believed to occur through the chemical reaction of various end-terms of the succinic anhydride of component D with the elastomer and polyoxymethylene based resins. This will be explained in more detail later.

Each component of the composition of this invention is demonstrated below.

Main ingredients and additives

(A) polyoxymethylene resin

The polyoxymethylene resin is a polymer having oxymethylene repeat units, and the polyoxymethylene resin component (component A) of the present invention may be a homopolymer having an oxymethylene repeat unit, an oxymethylene-oxyalkylene copolymer or a mixture thereof. have.

The homopolymer may be prepared by polymerizing formaldehyde or a cyclic oligomer thereof, for example trioxane, which copolymer may form formaldehyde or its cyclic oligomer with alkylene oxide or a cyclic formal such as 1,3 Produced by polymerization with dioxolane, diethylene glycol formal, 1,4-propanediol formal, 1,4-butanediol formal, 1,3-dioxepan formal, 1,3,6-trioxocane, and the like. can do.

The homopolymer or copolymer can be stabilized by capping its end groups by esterification or etherification. Polyoxymethylene copolymers can be stabilized by removing unstable terminal-oxymethylene groups to obtain stabilized copolymers having —CH ₂ CH ₂ OH end groups, for example, according to the method described in US Pat. No. 3,219,623. Which is incorporated herein by reference.

Preferred in the present invention are polyoxymethylene homopolymers or oxymethylene-oxyethylene copolymers having a melting point of about 160 ° C. or higher, a crystallinity of 65 to 85% and an average molecular weight of 10,000 to 200,000. Such homopolymers or copolymers are used in amounts of 50 to 97 weight percent (less than), preferably 65 to 95 weight percent of the composition.

(B) polyester elastomer

Component (B), the thermoplastic polyester elastomer, is a polyester block copolymer having a crystalline hard segment and an amorphous soft segment, wherein the hard segment is prepared by transesterification and polycondensation of aromatic diacids and short-chain diols, and Soft segments are prepared by reacting aromatic diacids with long chain diols.

Examples of aromatic diacids that may be used in the present invention include dimethyl terephthalate, terephthalic acid, isophthalic acid, dimethylisophthalate, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, dimethyl 2,6-naphthalate and their Mixtures are included. Of these, dimethyl terephthalate is preferred.

Typical short-chain diols that can be used in the present invention include 1,4-butanediol, 1,6-hexanediol, ethylene glycol and the like, with 1,4-butanediol being preferred. Representative long chain diols include polytetramethylene ether glycol, polyethyleneglycol, polypropylene glycol and mixtures thereof having an average molecular weight of 500 to 5,000, of which polytetramethylene ether glycol is preferred.

The terminal groups of the polyester elastomer of the present invention are a carboxyl group and a hydroxyl group.

According to the invention, the polyester elastomer preferably has a glass transition temperature of less than 0 ° C., typically about −20 ° C., and a melting point of 150 to 180 ° C., for example about 155 ° C., lower than the melting point of the polyoxymethylene based resin. It has a softening point. The polyester elastomer in the composition of the present invention serves to improve the toughness, impact resistance and thermal stability of the composition.

The thermoplastic polyester elastomer of the present invention is not completely miscible with the polyoxymethylene resin and forms a separate, different phase at high concentrations. However, in the presence of the maleic anhydride copolymer (component D) of the present invention, the polyurethane elastomer is compatible with the polyoxymethylene based resin and can be homogeneously mixed therewith.

The thermoplastic polyester elastomer is used in an amount of less than 3 to 50% by weight, preferably 5 to 35% by weight of the composition when used alone (ie, in the absence of a polyurethane elastomer).

(C) polyurethane elastomer

Polyurethane elastomers (component C) which can optionally be used in the composition of the present invention include a soft segment derived from a long chain diol having an average molecular weight in the range of 800 to 2500, having a glass transition temperature of less than 0 ° C and a softening point of 70 to 100 ° C. Hard segments derived from diisocyanates and chain extenders.

Polyurethane elastomers can be prepared by reacting long chain diols with diisocyanates to prepare polyurethane prepolymers having isocyanate end groups and then polymerizing them with diol chain extenders. Examples of the long chain diols include polyester diols such as poly (butylene adipate) diol, poly (ethylene adipate) diol and poly (ε-caprolactone) diol and poly (tetramethylene ether) glycol, poly (propylene oxide) Polyether diols such as glycols and poly (ethylene oxide) glycols.

Examples of diisocyanates include 4,4'-methylenebis (phenyl isocyanate), 2,4-toluene diisocyanate, 1,6-hexamethylene diisocyanate and 4,4'-methylenebis (cyclooxyisocyanate). Preferred are 4,4'-methylenebis (phenyl isocyanate) and 2,4-toluene diisocyanate.

Typical diol chain extenders that can be used in the present invention include aliphatic diols having 2 to 6 carbon atoms, such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol or neopentylglycol and the like.

The polyurethane elastomers of the present invention have -NCO and -OH end groups.

The polyurethane elastomers of the present invention are not completely miscible with the polyoxymethylene resin and form separate, different phases at high concentrations. However, in the presence of the maleic anhydride copolymer (component D) of the present invention, the polyurethane elastomer becomes compatible with the polyoxymethylene based resin and can be mixed homogeneously, and serves to improve the impact resistance of the composition.

In the composition of the present invention, the polyurethane elastomer is used in admixture with the polyester elastomer in a mixing ratio of 1:10 to 10: 1, typically about 1: 5.

(D) maleic anhydride copolymer

The maleic anhydride copolymer (component D) used in the composition of the present invention is a polyolefin-based elastomer containing a substituted succinic anhydride group or a copolymer of styrene and maleic anhydride. The maleic anhydride copolymer is a homogenizing agent that substantially disperses component B (with or without component C) in component A, possibly through a chemical reaction between the terminal of components A, B, and C and the succinic acid group. Act as.

That is, the hydroxy, carboxyl and / or acetyl end groups of the elastomer component and the base resin component can cause addition, transesterification and / or condensation reactions with succinic anhydride groups, for example, to form various crosslinks between the constituent components. Such chemical bonding is believed to enhance the toughness, thermal stability, impact resistance and processability of the compositions of the present invention by bonding together immiscible components.

In this regard, component D reduces the toughness and impact resistance of the polyoxymethylene resin when added alone, but when added together with the elastomer component, i.e., component B (with or without component C), tensile elongation and Izod impact strength It should be noted, for example, that the number can be increased by 6 and 15 times, respectively. It is to be understood that the compositions of the present invention with unexpected toughness and impact resistance properties are a new class of high performance polyoxymethylene resin compositions.

The maleic anhydride copolymer can be produced by polymerizing maleic anhydride with an olefin or vinyl monomer according to a conventional polymerization method. The maleic anhydride copolymer of the present invention preferably has a melting point of 110 to 150 ° C., for example about 130 ° C. and 1 to 10, for example about as measured according to ASTM D 1238 (under 2.16 kg / 230 ° C.). It has a melt flow index of 3.

The maleic anhydride copolymer may be used in an amount of 0.1 to less than 10% by weight, preferably 0.5 to 7% by weight of the composition.

(E) other optional ingredients

The resin composition of the present invention may optionally include one or more additional components, such as formaldehyde or formic acid remover, template lubricant, antioxidant, end group stabilizer, filler, colorant, adjuvant, light stabilizer, pigment and the like. The additional components can be used in a range that does not substantially adversely affect the physical properties of the composition of the present invention.

Typical mold lubricants that can be added to the compositions of the present invention include alkylene bis-stearicamide, waxes, polyether glycids and the like, with ethylene bis-stearicamide being particularly preferred. An example of an antioxidant is sterically hindered bisphenols, particularly preferably tetra-bis [methylene (3,5-di-t-butyl-4-hydrocinnamate)] methane, which is called Irganox 1010 from Ciba-Geigy. It is manufactured and sold under the brand name.

The end group stabilizer useful in the present invention serves to stabilize the unstable ends remaining after the reaction of the polyoxymethylene and the thermoplastic elastomer in the composition, and nitrogen-containing compounds may be used. Examples of the nitrogen-containing compound include at least one compound selected from the group consisting of a reactive hot melt nylon resin having an amine group at the terminal, or an unreacted hot melt nylon and a low molecular weight amine compound having no reactor at the terminal. .

As the nitrogen-containing compound, any of a hot melt nylon resin, a nylon resin, and a low molecular weight amine compound may be used, but a low molecular weight amine compound having a melting point of 230 ° C. or lower is suitable. As the low molecular weight amine compound, a compound selected from triazines, hydrazines, ureas, and dicyandiamides can be used. As hydrazines, adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, naphthalic acid dihydrazide are used, and urea is urea, thiourea, and the like. These can be used individually by 1 type or in combination of 2 or more types.

Kneading of the main ingredients

The resin composition of the present invention is blended using a conventional mixer, for example, a Brabender mixer, and then the blend is used in a temperature range higher than the melting point of the polyoxymethylene based resin using a conventional single or twin screw extruder, For example, it can manufacture by melt-kneading at 180-230 degreeC, Preferably it is 190-210 degreeC. Each component is preferably dried before the blending step. Drying may be carried out for 2 to 6 hours at a temperature of 70 to 110 ° C using dry air having a dew point of about -30 to -40 ° C. In particular, the polyurethane elastomer component (component C) is easily reacted with water at room temperature, so that the moisture content is adjusted to 0.1% or less, preferably 0.01% or less.

Example

Embodiments of the present invention are as follows, but the technical matters of the present invention are not limited thereto.

The components used in the Examples and Comparative Examples are as follows.

Component A: Oxymethylene-oxyethylene random copolymer having an internally dispersed oxyethylene group of about 2.5% by weight (trade name "KEPITAL ^R ) sold by Korea Engineering Plastics Co., Ltd., which has a tensile elongation of about 60% (ASTM) Measured according to D 638), Izod impact strength of about 6.5 kgf cm / cm (measured according to ASTM D 256), melting point of about 165 ° C, specific gravity of about 1.41 (measured according to ASTM D 792) and about 9 g / 10 minute melt flow index (measured according to ASTM D 1238 (under 2.16 kg / 190 ° C.)).

Component B: Polyester elastomer having a polybutylene terephthalate segment and a polytetramethyleneether glycol terephthalate segment in a ratio of about 50:50 (trade name SKYPEL ^R sold by SK Chemicals of Korea). This polyester has a specific gravity of about 1.16, a melting point of about 155 ° C. and a melt flow index of about 12 g / 10 min (measured according to ASTM D 1238 (under 2.16 kg / 190 ° C.)).

Component C: Polyurethane elastomer having a glass transition temperature of about -20 ° C and a softening point of about 85 ° C (trade name SKYTHANE ^R sold by SK Chemicals of Korea).

Component D: Maleic anhydride prepared by grafting on ethylene-propylene-butadiene terpolymer to about 0.86 g / cm ³ (measured according to ASTM D 792) and about 3 g / 10 min (at 190 ° C./2.16 kg) Maleic anhydride-graft copolymer with a melt flow index of.

In addition, in the Example and the comparative example, the physical characteristic and the processing characteristic of the composition were measured according to the following method.

1) Die swell

The die composition was melt-extruded at about 200 ° C. using a twin screw extruder to form pellets, and the observed die-swelling phenomena were evaluated in grades 1 (very good) to 5 (bad).

2) Tensile elongation

According to ASTM D 638, the resin composition was tested at a tensile speed of 5 mm / min unless otherwise noted.

3) Notched Izod Impact Strength

Notched Izod impact strength of the resin composition was tested according to ASTM D 256.

4) Mold deposit

In the injection molding machine, after the injection of the resin composition at the cylinder temperature of 220 ° C. using a mold deposit mold in 600 times, the degree of adherence adhered to the mold was observed through a projector to evaluate the grade from 1 (low deposit) to 5 grade. . Since the thermally labile polyoxymethylene composition tends to decompose and grow, for example, p-formaldehyde and other additives on the mold, this molddeposit data is a measure of the thermal stability of the resin composition.

Examples 1 to 3 and Comparative Examples 1 to 3

In order to demonstrate the improvement in toughness, impact strength and processability obtained in the polyoxymethylene resin composition containing components A, B and D according to the present invention, various resin compositions are prepared to contain no compatibilizer, i.e., a component D. Compared to them. The test results are shown in Table 1 below.

As the results of Table 1 show, adding maleic anhydride copolymer (component D) to the polyoxymethylene-polyester elastomer composition greatly increases toughness. More importantly, the 75:25 blend of component A and component B, which could not be extruded, possibly due to excessive die swelling caused by phase separation, has a high toughness and impact resistance due to the action of component D and die swelling It has been demonstrated that it can be converted to a polyoxymethylene resin composition.

Examples 4-1 to 7 and Comparative Examples 4 to 7

In order to demonstrate the good rheological properties of the polyoxymethylene resin composition containing components A, B, C and D according to the present invention, several resin compositions were prepared and compared with control compositions containing no component D. The test results are shown in Table 2 below.

The results in Table 2 above demonstrate that the toughness, impact resistance and die swell properties of the blend containing components A, B and C can be greatly improved by adding the appropriate amount of component D. The excellent high toughness and impact strength and satisfactory thermal stability observed in the Examples 6 and 7 compositions show that the inventive compositions containing components A, B, C and D are novel high performance polyoxymethylene resins.

Examples 8-19

Additional resin compositions containing components A, B, C and D according to the invention were prepared and tested. The results are shown in Table 3 below.

As can be seen from Table 3, the polyoxymethylene resin composition containing components A, B, C and D according to the present invention exhibits excellent toughness and impact resistance, thermal stability and processability.

As confirmed by the above examples and comparative examples, the polyoxymethylene resin composition according to the present invention not only has excellent toughness and impact strength, but also exhibits an effect of improving thermal stability and processability.

Claims (12)

Based on the total amount of components (A), (B) and (C), (A) 50-97% by weight of polyoxymethylene resin; (B) less than 3 to 50% by weight of a thermoplastic polyester elastomer or a mixture of this polyester elastomer with a thermoplastic polyurethane elastomer; And (C) less than 0.1 to 10% by weight maleic anhydride copolymer Polyoxymethylene resin composition comprising a. The method of claim 1, The composition is characterized in that the elastomer is used in an amount ranging from 5 to 35% by weight. The method of claim 1, A composition wherein the polyoxymethylene resin is a homopolymer or an oxymethylene-oxyethylene copolymer. The method of claim 1, Wherein the polyester elastomer is a polyester block copolymer having segments derived from aromatic diacids and short-chain aliphatic diols and segments derived from aromatic diacids and long-chain diols. The method of claim 4, wherein A composition wherein the aromatic diacid is dimethyl terephthalate, the short chain diol is 1,4-butanediol, and the long chain diol is polytetramethylene ether glycol. The method of claim 1, Wherein the polyurethane elastomer has soft segments derived from polyols having an average molecular weight in the range from 800 to 2,500 and hard segments derived from aromatic diisocyanates and chain extenders. The method of claim 6, The polyol is polyester diol or polyether diol, the aromatic diisocyanate is 4,4-methylenebis (phenylisocyanate) or 2,4-toluene diisocyanate, and the chain extender is ethylene glycol, 1,4-butanediol or 1,6 -Hexanediol, characterized in that the composition. The method of claim 1, The maleic anhydride copolymer is used in an amount ranging from 0.5 to 7% by weight. The method of claim 1, The maleic anhydride copolymer is a polyolefin elastomer or a copolymer of styrene and maleic anhydride. The method of claim 9, The maleic anhydride copolymer is an ethylene-propylene-butadiene terpolymer containing succinic anhydride groups. The method of claim 1, The composition further comprises a lubricant, antioxidant and / or stabilizer. An article molded from the polyoxymethylene resin composition according to any one of claims 1 to 11.