KR20170039040A - Polyoxymethylene Resin Composition and Molding Product Including the Same - Google Patents

Abstract

The present invention relates to a polyoxymethylene resin composition and a molded article formed by using the resin composition. To this end, the polyoxymethylene resin composition comprises: a base resin including polyoxymethylene; 1.0-3.0 parts by weight of an aluminum pigment; 0.1-0.5 parts by weight of polyvalent alcohol fatty acid ester; 0.5-3.0 parts by weight of an acrylate-styrene copolymer; and 0.05-0.5 parts by weight of an alkali earth metal silicate compound, with respect to 100 parts by weight of the base resin. According to the present invention, the polyoxymethylene resin composition reduces formation of flow marks during an injection process, and also creates metallic texture.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyoxymethylene resin composition and a molded article comprising the same,

The present invention relates to a polyoxymethylene resin composition and a molded article produced using the same.

BACKGROUND ART Polyoxymethylene resin is known as a high-performance plastic having a balance of mechanical strength and impact resistance, and has been used in a wide range of fields such as electronic appliances and automobile parts. However, in the case of polyoxymethylene (polyoxy methylene) resin, pyrolysis reaction proceeds due to heat and frictional heat during extrusion or injection molding, and there is a problem that formaldehyde is generated although it is extremely small. In particular, polyoxymethylene (polyoxy methylene) resin may be used in combination with a pigment containing metal particles such as aluminum for the appearance of a luxurious metal feel of the final molded product. When such a metallic pigment is used, Decomposition is further promoted, and the generation of formaldehyde is remarkably increased.

Formaldehyde generated during polyoxymethylene resin molding is closely related not only to the environmental hormone problem but also to the increase of the defective rate due to the contamination of the mold or the molding operation. It is therefore urgent to reduce the amount of formaldehyde generated in the production of molded articles using polyoxymethylene It is a challenge. Thus, as an additive for inhibiting formaldehyde generated from a polyoxymethylene resin, a nitrogen-based compound such as a melamine compound, a hydrazine compound, a urea compound, an amine compound or an amide compound has been conventionally examined.

In the prior art related to the inhibition of formaldehyde generation, Japanese Patent Laid-Open Publication No. 2012-92185 discloses a polyaluminum compound which improves the metallic feeling and weatherability and inhibits the formation of formaldehyde by containing aluminum particles, hindered amine light stabilizers, ultraviolet absorbers and formaldehyde- A polyoxy methylene resin composition is disclosed. Japanese Patent Application Laid-Open No. 2009-155418 discloses a polyoxy methylene resin composition which inhibits the generation of formaldehyde by specifying the amount of terminal groups of a polyacetal copolymer including a hemiformal terminal group And International Publication No. 2011-129445 discloses a polyoxy methylene resin composition that achieves formaldehyde reduction and injection moldability improvement by using a formaldehyde capturing agent

However, there is a problem that it is difficult to say that the formation of formaldehyde is sufficient to suppress the generation of formaldehyde, and the flowability and the dispersibility can be lowered simultaneously with the reduction of formaldehyde. In addition, when a large amount of aluminum particles is added, the flowability is deteriorated and the resin can only stay. As a result, pyrolysis due to frictional heat during extrusion processing and the effect of suppressing gas generation due to this heat may not be substantial.

Above all, the gas generated by pyrolysis during injection molding contaminates the surface of the mold and affects the melt flow of the aluminum pigment, thereby lowering the surface gloss of the molded article or forming a flow mark etc. do. This problem tends to become more prominent as the size of the molded article increases. As the need for a painted molded article gradually increases, the generation of gas during polyoxymethylene processing is suppressed to reduce the contamination of the mold It is an important task to keep the flow of the aluminum pigment constant so as to be able to provide an excellent surface appearance.

Accordingly, research and development of a polyoxy methylene resin composition having a metal texture and exhibiting excellent formaldehyde generation and excellent melt flowability and pigment dispersibility have been steadily required.

Thus, the present invention can improve the thermal stability, flowability and dispersibility while maintaining the physical properties such as excellent mechanical strength and impact resistance, thereby reducing the flow mark generated at the time of injection, And a molded article produced using the same.

A first preferred embodiment of the present invention for solving the above problems is a base resin comprising polyoxymethylene; 1.0 to 3.0 parts by weight of an aluminum pigment relative to 100 parts by weight of the base resin; 0.1 to 0.5 parts by weight of a polyhydric alcohol fatty acid ester; 0.5 to 3.0 parts by weight of an acrylate-styrene copolymer; And 0.05 to 0.5 parts by weight of an alkaline earth metal silicate compound.

The aluminum pigment according to the first embodiment may include a flaky or spherical aluminum flake having an average diameter of 5 to 30 mu m.

The polyhydric alcohol fatty acid ester according to the first embodiment may be at least one selected from the group consisting of glycerol monostearate, glycerol monobehenate and glycerol monomontane.

The acrylate-styrene copolymer according to the first embodiment may have a weight average molecular weight of 2000 to 4000.

The alkaline earth metal silicate compound according to the first embodiment may have a KOH adsorption amount of 180 mg or more per g, wherein the alkaline earth metal silicate compound may be calcium silicate or magnesium silicate.

The resin composition according to the first embodiment has a time required to reach 240 占 폚 at a heating rate of 20 占 폚 / min in an air atmosphere and a weight loss The sum of the time taken to become 10% may be more than 45 minutes.

A second preferred embodiment of the present invention is a molded article formed from the polyoxymethylene resin composition of the first embodiment.

According to the present invention, it is possible to reduce the decomposition of resin and the generation of formaldehyde due to the retention during injection molding while maintaining the physical properties such as excellent mechanical strength and impact resistance, and also to reduce the flow mark It is possible to manufacture a molded article having excellent appearance. Above all, resin decomposition (formaldehyde generation) phenomenon due to frictional heat during molding is reduced, and excellent surface luster and metallic feeling can be realized. Accordingly, it is possible to provide a feeling of metal more like a surface without painting, Can be produced.

Fig. 1 is a graph showing the results of a comparison between a molded article (a) of a conventional polyoxymethylene resin and a molded article of a polyoxymethylene resin (b) produced according to an embodiment of the present invention in which a flow mark is generated due to poor flowability during injection molding, FIG.

The present invention relates to a base resin comprising polyoxymethylene; 1.0 to 3.0 parts by weight of an aluminum pigment relative to 100 parts by weight of the base resin; 0.1 to 0.5 parts by weight of a polyhydric alcohol fatty acid ester; 0.5 to 3.0 parts by weight of an acrylate-styrene copolymer; And 0.05 to 0.5 parts by weight of an alkaline earth metal silicate compound, and a polyoxymethylene resin molded article formed from the composition.

Hereinafter, the present invention will be described more specifically.

[Base resin: Polyoxymethylene ]

The base resin of the present invention contains polyoxymethylene as a main component, wherein the polyoxymethylene is an oxymethylene homopolymer in which both ends of the polymer are blocked by an ester or an ether group, or in the polymer chain composed of oxymethylene monomer units, May be an oxymethylene copolymer in which an oxyalkylene unit having 2 to 8 carbon atoms is randomly inserted and both ends of the polymer are blocked with an ester or an ether group. In the present invention, the polyoxymethylene is not particularly limited as long as it is a commonly used polyoxymethylene, but it has a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 150000 to 300000 and a melting point of 165 to 172 Lt; 0 > C.

In the present invention, the oxyethylene homopolymer and the oxymethylene-based copolymer may be prepared by the following method. First, the oxyethylene homopolymer is polymerized by introducing anhydrous formaldehyde into an organic solvent containing a basic polymerization catalyst such as organic amine, organic or inorganic tin compound or metal hydroxide, filtering the polymer, By heating in acetic anhydride in the presence of sodium to acetylate the end.

Further, the oxymethylene-based copolymer can be produced, for example, by reacting a cyclic oligomer of formaldehyde such as anhydrous trioxane or tetraoxane with a cyclic oligomer of ethylene oxide, propylene oxide, 1,3-dioxolane, , 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, diethyleneglycol formal, 1,3,5-trioxepan, Is dissolved or suspended in an organic solvent such as cyclohexane or benzene and then added with a Lewis acid catalyst such as boron triflate diethyl etherate to polymerize and decompose to remove the unstable terminal .

Alternatively, an oxymethylene copolymer may be prepared by mass-polymerizing trioxane with a pre-mixture of a copolymerization component and a catalyst in a self-cleaning type agitator without using any solvent at all. As the deactivation agent for the polymerization catalyst, hindered amine compounds having a molecular weight of 400 or more can be used. In particular, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) have.

In the present invention, it may be preferable to select an oxymethylene copolymer from the viewpoint of balance of heat resistance, mechanical strength and impact resistance. Here, the content of the oxyalkylene comonomer unit in the oxymethylene-based copolymer is preferably 0.1 to 10 moles per 100 moles of the oxymethylene monomer unit, more preferably 0.1 to 10 moles per 100 moles of the oxymethylene monomer unit from the viewpoints of improving the thermal stability of the oxymethylene- May be 0.1 to 7 mol, and more preferably 0.1 to 5 mol.

The polyoxymethylene resin in the present invention is not necessarily limited to this, but the polyoxymethylene resin can be produced by a method described in JP-A-62-257922, for example, a method in which trioxane and a cyclic ether or a cyclic formaldehyde are reacted with boron triflate diethyl Polymerized in the presence of a Lewis acid catalyst such as tetraethoxysilane, then added with a hindered amine compound to terminate the polymerization reaction, and further decompose and remove the unstable terminal to obtain a stabilized polymer.

[Aluminum Pigment]

In the present invention, an aluminum pigment is added for the purpose of color and gloss-like expression of a metal without being subjected to a painting process including painting and coating. However, in the extrusion and injection molding of a resin, It is preferable to control the degree of dispersion and the particle size and content of the flakes.

Accordingly, the aluminum pigment in the present invention preferably includes a flaky or spherical aluminum flake having an average diameter of 5 to 30 mu m. If the particle size is less than 5 탆, the particle size is too small and the gloss effect is insignificant. If the particle size is more than 30 탆, the dispersibility is lowered and the aluminum flake tends to sag, so that the metal feeling and gloss can not be evenly distributed throughout the resin moldings. There may be side effects in which different metallic senses and gloss appear at each site.

If the content of the aluminum flakes contained in the flakes is in the range of 5 to 30 mu m, the amount of the aluminum flakes is less than 1.0 part by weight, and the metal texture and gloss are insignificant. If the amount is more than 3.0 parts by weight, The resin composition of the present invention can not be applied to parts requiring durability and the manufacturing cost of the resin composition is increased.

[Polyhydric alcohol fatty acid ester]

In the present invention, the polyhydric alcohol fatty acid ester improves the fluidity of the resin during extrusion, thereby reducing pyrolysis due to frictional heat, and consequently contributing to the reduction of formaldehyde. However, if the molecular weight is excessively increased, the compatibility may be lowered, the fluidity may be improved, and the lubricant improving effect may be insignificant. Therefore, the polyhydric alcohol fatty acid ester may have a molecular weight of 300 to 1000 in consideration of extrudability.

In the present invention, the polyhydric alcohol fatty acid ester may be one or more selected from the group consisting of glycerol monostearate, glycerol monobehenate, and glycerol monomontanate, 0.5 part by weight. If the content of the polyhydric alcohol fatty acid ester is less than 0.1 parts by weight, flowability upon melting may be lowered. If the content is more than 0.5 parts by weight, mold contamination due to reaction with formaldehyde may be increased.

[ Acrylate - Styrene  Copolymer]

In the present invention, the acrylate-styrene copolymer plays a role of improving the flowability at the time of injection and the dispersibility of the aluminum pigment, thereby reducing the occurrence of flow marks in the articles and improving the appearance of metal texture and surface gloss Contributing. If the molecular weight is excessively low, it is difficult to add because of the liquid phase, and if the molecular weight is excessively large, the effect of improving the dispersibility may be insignificant. Therefore, the acrylate-styrene copolymer preferably has a weight average molecular weight of 2000 to 4000 .

The content of the acrylate-styrene copolymer in the present invention is preferably 0.5 to 3.0 parts by weight based on 100 parts by weight of the base resin. If the content in the acrylate-styrene copolymerization is less than 0.5 part by weight, flowability and dispersibility deteriorate during injection molding, and if it exceeds 3.0 parts by weight, miscibility may be deteriorated and appearance quality may be deteriorated.

[Alkaline earth metal Silicate (silicate)]

In the present invention, in order to minimize the generation of gas which can be generated by the retention of the molten resin during the extrusion or injection molding, the alkaline earth metal silicate compound is added in an amount of 0.05 to 10 parts by weight based on 100 parts by weight of the polyoxymethylene resin. 0.5 part by weight. The alkaline earth metal silicate can be prepared by a conventional method, and the synthesized alkaline earth metal silicate has an amorphous porous structure and exhibits excellent adsorption ability to hydroxyl. Accordingly, the alkaline earth metal silicate is present as a part of the resin and captures the hydroxyl of the gas generated as the end in the polyoxymethylene is decomposed, thereby reducing gas generation occurring in the secondary processing and enhancing thermal stability . Particularly, in the alkaline earth metal silicate, the silicate group captures a low molecular substance and captures a substance that decomposes the polymer such as formic acid, thereby contributing to the inhibition of formaldehyde generation.

If the content of the alkaline earth metal silicate compound is less than 0.05 part by weight, the efficiency of removing the gas generated during the processing may be lowered, so that the decomposition of the polyoxymethylene resin may occur due to gas retention. When the content of the alkaline earth metal silicate compound exceeds 0.5 parts by weight , Pyrolysis due to frictional heat occurs in the manufacturing process, so that a substance contaminating the injection mold due to the reaction with the gas during extrusion and injection is generated, the surface of the injection-molded article due to such contaminants is deteriorated, The quality may be deteriorated.

In the present invention, the alkaline earth metal silicate compound may have an adsorption amount of KOH of 180 mg or more per 1 g of the silicate compound. As the amount of adsorption increases, the generation of gas is suppressed. Therefore, there is no restriction on the upper limit, , It is not sufficient to prevent the problem that the hydrolysis of hydroxyl, especially formic acid, in the polymer is reduced and the metastable and unstable terminals of the polymer are attacked by the gas to cause decomposition.

In the present invention, the alkaline earth metal silicate compound is preferably an alkaline earth metal silicate such as calcium silicate (CaO: XSiO ₂ ) or magnesium silicate (MgO: XSiO ₂ ) in view of preventing secondary decomposition of polyoxymethylene Do.

On the other hand, the resin composition of the present invention having such a composition has a time required to reach 240 占 폚 at a temperature raising rate of 20 占 폚 / min in an air atmosphere and a time to reach 240 占 폚 The sum of the time taken for the weight loss to become 10% may be more than 45 minutes. If the measured time is fast, it means that the decomposition of the polymer occurs quickly due to lack of heat resistance. It is not a problem that the measured time is long, but if it is less than 45 minutes, The flow mark (see the left side of Fig. 1) is generated on the surface, which is undesirable.

Accordingly, it is an object of the present invention to provide a process for producing a resin molded article excellent in metal texture of an injection-molded article itself, without requiring a painting process including painting, coating and the like, on the surface of the resin using the polyoxy methylene resin composition And the excellent flowability of the polyoxymethylene resin and excellent dispersibility to the pigment can significantly reduce the flow mark in the molded product, thereby realizing excellent surface gloss and appearance.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for the purpose of illustrating the present invention more specifically, and the present invention is not limited thereto.

The components used in the examples of the present invention are as follows.

- Base resin: K900 (polyoxymethylene, Kolon plastics)

- Aluminum pigment: NME020T2 (Toyo Aluminum)

- polyhydric alcohol fatty acid ester: Glycerol mono-behenate (GM-B, Kao Corporation)

-Acrylate-styrene copolymer: ADF1350 (BASF, Mw 2000-4000)

- Magnesium silicate: Ambosol (PQ Corporation)

Example  One

2.1 parts by weight of an aluminum pigment (NME020T2, TOYO aluminum), 0.2 part by weight of a polyhydric alcohol fatty acid ester (GM-B, Kao Corporation), and 1.0 part by weight of an acrylate-styrene copolymer (ADF1350, BASF) based on 100 parts by weight of a base resin (K900) And 0.1 part by weight of magnesium silicate (Ambosol, PQ Corporation) were melted and mixed through a twin-screw extruder having an extruder temperature of 180 to 200 ° C, and then extruded into chips. The polyoxymethylene resin prepared in a chip form was dried in a hot air drier at 130 ° C for 4 hours. A portion of the chip thus prepared was put into a heated screw extruder and heated to a temperature of 4 cm x 8 cm 0.3 cm injection specimen.

Example  2 to 9

The same procedure as in Example 1 was applied except that aluminum flakes, polyhydric alcohol fatty acid esters, acrylate-styrene copolymers, and magnesium silicate were blended in the ratios shown in Table 1 to 100 parts by weight of the base resin, And chips and injection specimens were prepared.

Comparative Example  1 to 8

The same procedure as in Example 1 was applied except that aluminum flakes, polyhydric alcohol fatty acid esters, acrylate-styrene copolymers, and magnesium silicate were blended in the ratios shown in Table 1 to 100 parts by weight of the base resin, And chips and injection specimens were prepared.

Property evaluation

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

(1) Evaluation of metal texture : The metal texture and the surface gloss of the surface appearing in the injection specimen were divided into excellent (◯), normal (Δ) and poor (ⅹ).

(2) Evaluation of flow mark : The flow mark at the gate part of the injection specimen was divided into ◯, △, and ⅹ.

(3) TGA ( Thermogravimetric analysis) : The time required to reach 240 ° C at a heating rate of 20 ° C / minute in an air atmosphere and the time required for the weight to decrease by 10% The total time was confirmed.

(4) extruder residence formaldehyde (FA, Formaldehyde): the one after the injection temperature was 195 ℃, filling the resin into the injection molding machine to stay for 10 minutes and then injected to generated formaldehyde (Fomaldehyde) were measured in the VDA 275 method .

(5) Izod Impact Strength : The Izod Notched impact strength was measured using an impact tester after leaving the specimen at room temperature (23 ° C) and relative humidity of 50% for one day according to ASTM D256.

division
(Parts by weight) K900 NME020T2 GM-B ADF 1350 Ambosol Example 1 100 2.1 0.2 1.0 0.1 Example 2 100 1.0 0.2 1.0 0.1 Example 3 100 2.1 0.2 1.0 0.1 Example 4 100 2.1 0.1 1.0 0.1 Example 5 100 2.1 0.5 1.0 0.1 Example 6 100 2.1 0.2 0.5 0.1 Example 7 100 2.1 0.2 1.5 0.1 Example 8 100 2.1 0.2 1.0 0.05 Example 9 100 2.1 0.2 1.0 0.5 Comparative Example 1 100 0.8 0.2 1.0 0.1 Comparative Example 2 100 4.0 0.2 1.0 0.1 Comparative Example 3 100 2.1 0.05 1.0 0.1 Comparative Example 4 100 2.1 0.6 1.0 0.1 Comparative Example 5 100 2.1 0.2 0.3 0.1 Comparative Example 6 100 2.1 0.2 4.0 0.1 Comparative Example 7 100 2.1 0.2 1.0 0.03 Comparative Example 8 100 2.1 0.2 1.0 0.6

division Metal texture
(Visual evaluation) Flow mark
(Visual evaluation) TGA
(minute) Injection stay FA
(ppm) Impact strength
(Kg 占 ㎝ m / cm) Example 1 О О 47.8 10.2 7.5 Example 2 О О 52.6 9.5 7.6 Example 3 О О 48.7 9.3 7.0 Example 4 О О 49.1 11.5 7.7 Example 5 О О 50.8 7.6 7.3 Example 6 О О 49.9 12.8 7.6 Example 7 О О 53.2 6.5 7.4 Example 8 О О 46.6 9.6 7.7 Example 9 О О 48.9 14.3 7.6 Comparative Example 1 X О 49.6 8.7 7.7 Comparative Example 2 О Δ 42.1 24.5 5.7 Comparative Example 3 О О 43.2 20.9 7.5 Comparative Example 4 Δ Δ 51.2 8.7 7.6 Comparative Example 5 О X 46.3 13.2 7.7 Comparative Example 6 Δ Δ 52.4 10.5 7.8 Comparative Example 7 О О 38.8 29.4 7.6 Comparative Example 8 Δ X 35.6 35.7 7.6

As shown in Table 2, Comparative Example 1, which had a low content of aluminum pigment, was poorly evaluated in terms of metal texture, and Comparative Example 2, which was too high, had flow problems and caused flow marks, . In addition, as in Comparative Examples 3, 4, 7 and 8, when the polyalcohol fatty acid ester or the alkaline earth silicate content is low or high, the TGA weight loss time is fast, the formaldehyde content is high during the injection stay, appear. Further, as in Comparative Examples 5 and 6, it was found that the dispersibility was lowered depending on the difference in content of the acrylate / styrene copolymer, and flow marks were generated.

On the other hand, in Examples 1 to 9, the polyoxymethylene resin composition exhibited excellent metal texture, no flow mark, and excellent impact strength. However, in the case of Example 8 in which the content of the alkaline earth metal silicate was low, the TAG weight loss time was relatively shorter than those in Comparative Examples 1, 4 and 6, but Comparative Examples 1, 4, The appearance of the surface was not better than that of Example 8. In other words, it was confirmed that Examples 1 to 9 exhibited excellent overall surface appearance and reduced amount of formaldehyde generation during injection retention.

Claims (8)

A base resin comprising polyoxymethylene;
1.0 to 3.0 parts by weight of an aluminum pigment relative to 100 parts by weight of the base resin; 0.1 to 0.5 parts by weight of a polyhydric alcohol fatty acid ester; 0.5 to 3.0 parts by weight of an acrylate-styrene copolymer; And 0.05 to 0.5 parts by weight of an alkaline earth metal silicate compound.
The polyoxymethylene resin composition according to claim 1, wherein the aluminum pigment comprises an aluminum flake having a plate shape or a spherical shape with an average diameter of 5 to 30 占 퐉.
The polyoxymethylene resin composition according to claim 1, wherein the polyhydric alcohol fatty acid ester is at least one selected from the group consisting of glycerol monostearate, glycerol monobehenate, and glycerol monomontanate.
The polyoxymethylene resin composition according to claim 1, wherein the acrylate-styrene copolymer has a weight-average molecular weight of 2000 to 4000.
The method of claim 1, wherein the alkaline earth metal silicate compound Wherein the KOH adsorption amount per 1 g of the polyoxymethylene resin composition is 180 mg or more.
6. The polyoxymethylene resin composition according to claim 5, wherein the alkaline earth metal silicate compound is calcium silicate or magnesium silicate.
The resin composition according to claim 1, wherein the resin composition has a time required to reach 240 占 폚 at a temperature raising rate of 20 占 폚 / min in an air atmosphere and a weight loss when maintained at 240 占 폚 according to a heat loss (TGA) And the time required for the polyoxyalkylene resin to become 10% is 45 minutes or more.
A molded article formed from the polyoxymethylene resin composition according to any one of claims 1 to 7.

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