Thermoplastic resin composition and molded article produced from same

Abstract

The present invention is characterized by including an aromatic vinyl-based copolymer, glass fiber, and zinc oxide, wherein the zinc oxide has an average particle size (D50) of about 0.5 to 3 μm as measured by a particle size analyzer, and a size ratio (B/A) of peak B, spanning the range of 450 to 600 nm, to peak A, spanning the range of 370 to 390 nm, of about 0.01 to 1.0 when measuring photoluminescence. The thermoplastic resin composition exhibits excellent rigidity, antibacterial properties, weather resistance, external appearance and the like.

Claims

1. A thermoplastic resin composition comprising: an aromatic vinyl copolymer resin; glass fibers; and zinc oxide, wherein the zinc oxide has an average particle diameter (D50) of about 0.5 μm to about 3 μm, as measured using a particle size analyzer, and a peak intensity ratio (B/A) of about 0.01 to about 1.0, where A indicates intensity of the peak in the wavelength range of 370 nm to 390 nm and B indicates intensity of the peak in the wavelength range of 450 nm to 600 nm in photoluminescence measurement, and wherein the thermoplastic resin composition has a color variation (ΔE) of about 0.1 to about 2.0, as calculated according to Equation 2 based on initial color values (L.sub.0*, a.sub.0*, b.sub.0*) measured on an injection-molded specimen having a size of 50 mm×90 mm×3 mm using a colorimeter and color values (L.sub.1*, a.sub.1*, b.sub.1*) of the specimen measured in the same manner as above after testing for 3,000 hours in accordance with ASTM D4459:
Color Variation (ΔE)=√{square root over ((ΔL*).sup.2+(Δa*).sup.2+(Δb*).sup.2)}  [Equation 2] where ΔL* is a difference (L.sub.1*−L.sub.0*) between L* values before and after testing, Δa* is a difference (a.sub.1*−a.sub.0*) between a* values before and after testing, and Δb* is a difference (b.sub.1*−b.sub.0*) between b* values before and after testing.

2. The thermoplastic resin composition according to claim 1, comprising: about 100 parts by weight of the aromatic vinyl copolymer resin; about 5 parts by weight to about 40 parts by weight of the glass fibers; and about 0.1 parts by weight to about 20 parts by weight of the zinc oxide.

3. The thermoplastic resin composition according to claim 1, wherein the aromatic vinyl copolymer resin is a polymer of an aromatic vinyl monomer and a monomer copolymerizable with the aromatic vinyl monomer.

4. The thermoplastic resin composition according to claim 1, wherein the zinc oxide has a peak position degree (2θ) in the range of about 35° to about 37° and a crystallite size of about 1,000 Å to about 2,000 Å in X-ray diffraction (XRD) analysis, as calculated by Equation 1: $\begin{array}{cc}\mathrm{Crystallite}\mathrm{size}\left(D\right)=\frac{K\lambda }{\beta \cos \theta }& \left[\mathrm{Equation}1\right]\end{array}$ where K is a shape factor, λ is an X-ray wavelength, β is an FWHM value (degree) of an X-ray diffraction peak, and θ is a peak position degree.

5. The thermoplastic resin composition according to claim 1, wherein the zinc oxide is prepared by melting zinc in a reactor, heating the molten zinc to about 850° C. to about 1,000° C. to vaporize the molten zinc, injecting oxygen gas into the reactor, cooling the reactor to about 20° C. to about 30° C., and heating the reactor to about 400° C. to about 900° C. for about 30 minutes to about 150 minutes.

6. The thermoplastic resin composition according to claim 1, wherein the zinc oxide has a BET specific surface area of about 10 m.sup.2/g or less, as measured by a nitrogen gas adsorption method using a BET analyzer.

7. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin composition has an antibacterial activity of about 2 to about 7 against Staphylococcus aureus and an antibacterial activity of about 2 to about 7 against Escherichia coli, as calculated according to Equation 3 after inoculation of 5 cm×5 cm specimens with Staphylococcus aureus and Escherichia coli, respectively, and culturing under conditions of 35° C. and 90% RH for 24 hours in accordance with JIS Z 2801:
Antibacterial activity=log(M1/M2)  [Equation 3] where M1 is the number of bacteria as measured on a blank specimen after culturing for 24 hours and M2 is the number of bacteria as measured on each of the specimens of the thermoplastic resin composition after culturing for 24 hours.

8. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin composition has a flexural modulus of about 74,000 kgf/cm.sup.2 or more, as measured on a 6.4 mm thick specimen at a strain rate of 2.8 mm/min in accordance with ASTM D790.

9. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin composition has a structure in which the glass fibers and the zinc oxide are present as a dispersed phase in the aromatic vinyl copolymer resin as a continuous phase, and a ratio of average particle diameter (D50) of the zinc oxide to diameter of the glass fibers ranges from about 1:1.7 to about 1:200.

10. A molded article formed of the thermoplastic resin composition according to claim 1.

11. The molded article according to claim 10, wherein the molded article is a cross-flow fan of an air conditioner.

Description

EXAMPLE

(1) Details of components used in Examples and Comparative Examples are as follows:

(2) (A) Aromatic Vinyl Copolymer Resin

(3) (A-1) A SAN resin (weight average molecular weight: 80,000 g/mol) obtained by polymerization of 68 wt % of styrene and 32 wt % of acrylonitrile was used.

(4) (A-2) A SAN resin (weight average molecular weight: 150,000 g/mol) obtained by polymerization of 68 wt % of styrene and 32 wt % of acrylonitrile was used.

(5) (B) Glass Fibers

(6) Circular cross-section glass fibers having a cross-sectional diameter of 13 μm and a pre-processing length of 3 mm were used.

(7) (C) Zinc Oxide

(8) (C1) Metallic zinc was melted in a reactor, followed by heating to 900° C. to vaporize the molten zinc, and then oxygen gas was injected into the reactor, followed by cooling to room temperature (25° C.) to obtain an intermediate. Then, the intermediate was subjected to heat treatment at 700° C. for 90 minutes, followed by cooling to room temperature (25° C.), thereby preparing zinc oxide (C1). For the prepared zinc oxide, average particle diameter, BET surface area, purity, peak intensity ratio (B/A) of peak B in the wavelength range of 450 nm to 600 nm to peak A in the wavelength range of 370 nm to 390 nm in photoluminescence measurement, and crystallite size were measured. Results are shown in Table 1.

(9) (C2) Zinc oxide (Manufacturer: Ristecbiz Co., Ltd., product name: RZ-950) was used.

(10) (D) Antibacterial Agent

(11) A silver (Ag) antibacterial agent (manufacturer: TOA GOSEI Co., Ltd., product name: NOVARON AGZ010) was used.

(12) TABLE-US-00001 TABLE 1 (C1) Zinc oxide (C2) Zinc oxide Average particle diameter 1.2 1.1 (μm) BET surface area (m.sup.2/g) 4 15 Purity (%) 99 97 PL peak intensity ratio 0.28 9.8 (B/A) Crystallite size (Å) 1417 503

(13) Property Evaluation

(14) (1) Average particle diameter (unit: μm): Average particle diameter (volume average) was measured using a particle size analyzer (Laser Diffraction Particle Size Analyzer LS I3 320, Beckman Coulter Co., Ltd.).

(15) (2) BET surface area (unit: m.sup.2/g): BET surface area was measured by a nitrogen gas adsorption method using a BET analyzer (Surface Area and Porosity Analyzer ASAP 2020, Micromeritics Co., Ltd.).

(16) (3) Purity (unit: %): Purity was measured by thermogravimetric analysis (TGA) based on the weight of remaining material at 800° C.

(17) (4) PL peak intensity ratio (B/A): Spectrum emitted upon irradiation of a specimen using a He-Cd laser (KIMMON, 30 mW) at a wavelength of 325 nm at room temperature was detected by a CCD detector in a photoluminescence measurement method, in which the CCD detector was maintained at −70° C. A peak intensity ratio (B/A) of peak B in the wavelength range of 450 nm to 600 nm to peak A in the wavelength range of 370 nm to 390 nm was measured. Here, an injection molded specimen was irradiated with laser beams without separate treatment upon PL analysis, and zinc oxide powder was compressed in a pelletizer having a diameter of 6 mm to prepare a flat specimen.

(18) (5) Crystallite size (unit: Å): Crystallite size was measured using a high-resolution X-ray diffractometer (PRO-MRD, X'pert Inc.) at a peak position degree (2θ) in the range of 35° to 37° and calculated by Scherrer's equation (Equation 1) with reference to a measured FWHM value (full width at half maximum of a diffraction peak). Here, both a powder form and an injection molded specimen could be measured. For more accurate analysis, the injection molded specimen was subjected to heat treatment in air at 600° C. for 2 hours to remove a polymer resin therefrom before XRD analysis.

(19) $\begin{array}{cc}\mathrm{Crystallite}\mathrm{size}\left(D\right)=\frac{K\lambda }{\beta \cos \theta }& \left[\mathrm{Equation}1\right]\end{array}$

(20) where K is a shape factor, λ is an X-ray wavelength, β is an FWHM value (degree) of an X-ray diffraction peak, and θ is a peak position degree.

Examples 1 to 2 and Comparative Examples 1 to 3

(21) The aforementioned components were mixed in amounts as listed in Tables 2 and 3, followed by extrusion at 230° C., thereby preparing a thermoplastic resin composition in pellet form. Here, extrusion was performed using a twin-screw extruder (L/D: 36, Φ: 45 mm). The prepared pellets were dried at 80° C. for 2 hours or more and then subjected to injection molding using a 6 oz. injection machine (molding temperature: 230° C., mold temperature: 60° C.), thereby preparing a specimen. The prepared specimen was evaluated as to the following properties. Results are shown in Table 2.

(22) Property Evaluation

(23) (1) Weather resistance (color variation (ΔE)): For determination of color variation, initial color values (L.sub.0*, a.sub.0*, b.sub.0*) were measured on an injection molded specimen having a size of 50 mm×90 mm×3 mm using a colorimeter (KONICA MINOLTA CM-3700A), followed by testing for 3,000 hours in accordance with ASTM D4459, and then color values (L.sub.1*, a.sub.1*, b.sub.1*) of the specimen were measured in the same manner as above. Thereafter, color variation (ΔE) was calculated according to Equation 2:
Color variation (ΔE)=√{square root over ((ΔL*).sup.2+(Δa*).sup.2+(Δb*).sup.2)}  [Equation 2]

(24) where ΔL* is a difference (L.sub.1*−L.sub.0*) between L* values before and after testing, Δa* is a difference (a.sub.1*−a.sub.0*) between a* values before and after testing, and Δb* is a difference (b.sub.1*−b.sub.0*) between b* values before and after testing.

(25) (2) Antibacterial activity: In accordance with JIS Z 2801, 5 cm×5 cm specimens were inoculated with Staphylococcus aureus and Escherichia coli, respectively, and then subjected to culturing under conditions of 35° C. and 90% RH for 24 hours, followed by calculation of antibacterial activity according to Equation 3:
Antibacterial activity=log(M1/M2)  [Equation 3]

(26) where M1 is the number of bacteria as measured on a blank specimen after culturing for 24 hours and M2 is the number of bacteria as measured on each of the specimens after culturing for 24 hours.

(27) (3) Flexural modulus (FM, unit: kgf/cm.sup.2): Flexural modulus was measured on a 6.4 mm thick specimen at a strain rate of 2.8 mm/min in accordance with ASTM D790.

(28) (4) Heat deflection temperature (HDT, unit: ° C.): Heat deflection temperature was measured at a heating rate of 120 ° C./hr under a load of 1.8 MPa in accordance with ASTM D648.

(29) (5) Appearance: A specimen having a size of 90 mm×50 mm×2.5 mm was prepared, and then the presence of flow marks was observed with the naked eye. When there are no flow marks, the corresponding thermoplastic resin composition can be evaluated as having good compatibility.

(30) (6) Creep: In accordance with ASTM D638, displacement length (unit: mm) of a tensile strength test specimen under conditions of 85° C., 100 N, and 100 hours was measured.

(31) TABLE-US-00002 TABLE 2 Example Comparative Example 1 2 1 2 3 (A) (A1) 37.5 37.5 37.5 37.5 37.5 (wt %) (A2) 62.5 62.5 62.5 62.5 62.5 (B) (parts by weight) 20 20 20 20 20 (C1) (parts by weight) 2 4 — — — (C2) (parts by weight) — — 4 — — (D) (parts by weight) — — — 4 — Color variation (ΔE) 1.0 0.5 3.0 3.5 3.5 Antibacterial activity 4 6 1.5 1 1 (Escherichia coli) Antibacterial activity 3 4 1.5 1 1 (Staphylococcus aureus) Flexural modulus 7,5000 7,6000 74,000 75,000 74,000 (kgf/cm.sup.2) Heat deflection 107 107 106 104 105 temperature (° C.) Appearance (flow mark) X X O O X Creep (mm) 0.16 0.16 0.17 0.17 0.17 * Parts by weight: relative to 100 parts by weight of the aromatic vinyl copolymer resin (A).

(32) From the results shown in Table 2, it can be seen that the thermoplastic resin composition according to the present invention had good properties in terms of rigidity (flexural modulus), antibacterial effects (antibacterial activity), weather resistance (color variation (ΔE)), heat resistance (heat deformation temperature), and appearance (flow mark, creep).

(33) Conversely, the thermoplastic resin composition of Comparative Example 1, using the zinc oxide (C2) having a PL peak intensity ratio (B/A) of 9.8 (exceeding 1.0) instead of the zinc oxide according to the present invention, and the thermoplastic resin composition of Comparative Example 2, using the silver antibacterial agent, exhibited poor properties in terms of weather resistance, appearance, and antibacterial effects. In addition, the thermoplastic resin composition of Comparative Example 3, free from zinc oxide, exhibited poor properties in terms of weather resistance and antibacterial effects.

(34) It should be understood that various modifications, changes, alterations, and equivalent embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention.