Polymer Complex

Abstract

The present disclosure relates to a polymer complex comprising microcellulose fibers comprising nanofibrils and fine particles; and a polymer matrix. According to the present disclosure, there is provided a polymer complex capable of exhibiting excellent mechanical properties while being environmentally friendly by including cellulose fibers as a reinforcing material.

Claims

1. A polymer complex comprising microcellulose fibers; and a polymer matrix, wherein the microcellulose fibers comprise nanofibrils and fine particles.

2. The polymer complex of claim 1, wherein the nanofibrils are bonded to a surface of the microcellulose fibers, and the fine particles are bonded to the nanofibrils or bonded to a surface or inside of the microcellulose fibers.

3. The polymer complex of claim 1, wherein the fine particles comprise one or more metal particles selected from the group consisting of copper, zinc, calcium, aluminum, iron, silver, platinum, palladium, ruthenium, iridium, rhodium, osmium, chromium, cobalt, nickel, manganese, vanadium, molybdenum, magnesium, strontium, titanium, zirconium, hafnium, and gallium, or silicon oxide particles.

4. The polymer complex of claim 1, wherein the fine particles are included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the microcellulose fibers.

5. The polymer complex of claim 1, wherein the fine particles comprise spherical fine particles having a diameter of 0.01 μm to 10 μm, columnar particles having a diameter of 0.01 μm to 10 μm on one axis and a diameter of 0.02 μm to 30 μm on another axis, or a mixture thereof.

6. The polymer complex of claim 1, wherein the microcellulose fibers have a minor axis diameter of 1 μm to 30 μm, and the nanofibrils have a minor axis diameter of 10 nm to 400 nm.

7. The polymer complex of claim 1, wherein the polymer matrix is a thermoplastic resin.

8. The polymer complex of claim 1, wherein the polymer matrix comprises at least one selected from the group consisting of polyolefin, polyamide, styrenic polymer, and polycarbonate.

9. The polymer complex of claim 1, further comprising a compatibilizer.

10. The polymer complex of claim 9, wherein the compatibilizer comprises a modified polyolefin.

11. The polymer complex of claim 9, wherein the polymer complex comprises 50 to 90 wt % of the polymer matrix; 5 to 40 wt % of the microcellulose fibers comprising nanofibrils and fine particles; and 0.1 to 15 wt % of the compatibilizer.

12. The polymer complex of claim 1, Wherein a flexural strength measured according to ISO 178 for a specimen having a size of 80 mm×10 mm×4 mm prepared from the polymer complex is 30 MPa to 70 MPa.

13. The polymer complex of claim 1, wherein a flexural modulus measured according to ISO 178 for a specimen having a size of 80 mm×10 mm×4 mm prepared from the polymer complex is 1.0 GPa to 3.0 GPa.

14. The polymer complex of claim 1, which has a tensile strength measured according to ASTM D638-5 of 20 MPa to 50 MPa.

15. The polymer complex of claim 9, wherein the modified polyolefin is polypropylene or polyethylene in which 0.1 to 10 wt % thereof is grafted with maleic anhydride.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] FIG. 1A is an enlarged schematic view of microcellulose fibers, and FIG. 1B is an enlarged schematic view of microcellulose fibers including nanofibrils and fine particles.

[0074] FIG. 2 is a scanning electron microscope (SEM) image of pulp fibers used in Example 1.

[0075] FIG. 3 is a SEM image of microcellulose fibers including nanofibrils and fine particles obtained in Example 1.

[0076] FIG. 4 is a SEM image of microcellulose fibers including nanofibrils and fine particles obtained in Example 2.

[0077] FIG. 5A shows a comparison of SEM images of fibrillated microcellulose fibers according to Example 1, FIG. 5B shows a comparison of SEM images of miniaturized cellulose complexed with fine particles according to Comparative Example 4.

[0078] FIG. 6A is a comparison of SEM images of FIG. 5A taken at a higher magnification, and FIG. 6B is a comparison of SEM images of FIG. 5B taken at a higher magnification.

[0079] FIG. 7 shows specifications of a dog-bone-shaped specimen (or a dumbbell-shaped specimen) for measuring tensile strength according to Type V of ASTM D638 (unit: mm).

DESCRIPTION OF SYMBOLS

[0080] 100, 100′: microcellulose fiber
11: nanofibril
20: fine particle

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0081] Hereinafter, the function and effect of the present invention will be described in more detail through specific examples. However, these examples are for illustrative purposes only, and the invention is not intended to be limited by these examples.

Example 1

[0082] 1) Preparation of Microcellulose Fibers Including Nanofibrils and Fine Particles

[0083] Softwood kraft pulp fibers (cellulose fibers) were prepared as cellulose raw materials. Then, the shape of the pulp was observed using a scanning electron microscope (SEM image of FIG. 2).

[0084] 20 g of the above pulp fibers were added to an aqueous solution in which 20 g of zinc acetate was dissolved in 1000 g of distilled water, and stirred at 500 rpm for 2 hours to prepare a mixture. In this mixture, zinc acetate was attached to the swollen pulp fibers through hydrogen bonding or ionic bonding.

[0085] 3.6 g of sodium hydroxide (NaOH) was added to the mixture at room temperature, and stirred at 500 rpm for 2 hours to grow fine particles on the pulp fibers. As shown in FIG. 3, FIG. 5A and FIG. 6A, it was confirmed using a scanning electron microscope that fibrillation occurred in the pulp fiber portion on which particles (ZnO) were grown.

[0086] By the above method, microcellulose fibers including nanofibrils and fine particles were obtained.

[0087] 2) Preparation of Polymer Complex

[0088] 10 wt % of microcellulose fibers including nanofibrils and fine particles, 85 wt % of polypropylene, and 5 wt % of compatibilizer were added to a batch mixer, and mixed at 170° C. for 20 minutes to prepare a master batch in the form of pellets. As the compatibilizer, maleic anhydride-grafted polypropylene was used.

[0089] The master batch was put into a twin-screw extruder to perform a compounding process, and then extruded. The polymer complex thus obtained was put back into an injection machine and injected, and a specimen having a size of 80 mm×10 mm×4 mm according to ISO 178 and a dog-bone-shaped specimen according to Type V of ASTM D638 (see FIG. 7) were prepared.

Example 2

[0090] 1) Preparation of Microcellulose Fibers Including Nanofibrils and Fine Particles

[0091] 20 g of the same pulp fibers as in Example 1 were added to 1 L of a 0.05 M aqueous solution in which 9.08 g (0.05 mol) of copper acetate was dissolved in distilled water, and stirred at 500 rpm for 2 hours to prepare a mixture. In this mixture, copper acetate was attached to the swollen pulp fibers through hydrogen bonding or ionic bonding.

[0092] 0.05 mol of benzene-1,3,5-tricarboxylate (BTC) was added to the mixture at room temperature, and stirred at 500 rpm for 2 hours to grow fine particles on the pulp fibers. As shown in FIG. 4, it was confirmed using a scanning electron microscope that fibrillation occurred in the pulp fiber portion on which particles (HKUST-1: Cu-BTC) were grown.

[0093] By the above method, microcellulose fibers including nanofibrils and fine particles were obtained.

[0094] 2) Preparation of Polymer Complex

[0095] 10 wt % of microcellulose fibers including nanofibrils and fine particles, 85 wt % of polypropylene, and 5 wt % of compatibilizer were added to a batch mixer, and mixed at 170° C. for 20 minutes to prepare a master batch in the form of pellets. As the compatibilizer, maleic anhydride-grafted polypropylene was used.

[0096] The master batch was put into a twin-screw extruder to perform a compounding process, and then extruded. The polymer complex thus obtained was put back into an injection machine and injected, and a specimen having a size of 80 mm×10 mm×4 mm according to ISO 178 and a dog-bone-shaped specimen according to Type V of ASTM D638 (see FIG. 7) were prepared.

Example 3

[0097] A polymer complex and specimens were prepared in the same manner as in Example 1, except that the content ratio of the microcellulose fibers including nanofibrils and fine particles, the polypropylene, and the compatibilizer was changed to 30:55:15 (wt %).

Comparative Example 1

[0098] Specimens were prepared in the same manner as in Example 1 using polypropylene, except that the microcellulose fibers including nanofibrils and fine particles and the compatibilizer were not added. The specimen is a neat polymer specimen.

Comparative Example 2

[0099] A polymer complex and specimens were prepared in the same manner as in Example 1, except that the same pulp fibers as in Example 1 soaked in water to swell were used instead of the microcellulose fibers including nanofibrils and fine particles.

Comparative Example 3

[0100] A polymer complex and specimens were prepared in the same manner as in Example 1, except that the microcellulose fibers including nanofibrils and fine particles were not added.

Comparative Example 4

[0101] 1) Preparation of Miniaturized Cellulose Fibers Including Fine Particles

[0102] The same softwood kraft pulp fibers as in Example 1 were prepared as cellulose raw materials. A surface of the pulp fibers was oxidized using 2,2,6,6-tetramethylpiperidinyl-1-oxyradical (TEMPO) as a catalyst to obtain oxidized pulp.

[0103] 1 g of the oxidized pulp was dispersed in 99 g of distilled water and miniaturized (defibrated) with a mixer for 30 minutes to obtain an aqueous dispersion of miniaturized cellulose at a concentration of 1%.

[0104] A zinc acetate aqueous solution was prepared by dissolving 20 g of zinc acetate in 1000 g of distilled water. 3.6 g of sodium hydroxide (NaOH) was dissolved in 10 ml of distilled water to prepare a sodium hydroxide solution.

[0105] While stirring 100 g of the aqueous dispersion of miniaturized cellulose at 15° C., 50 ml of the zinc acetate aqueous solution and 10 ml of the sodium hydroxide solution were added thereto, followed by stirring at 500 rpm for 2 hours to prepare a complex of zinc oxide (ZnO) particles and miniaturized cellulose.

[0106] As shown in FIG. 5B and FIG. 6B, it was confirmed using a scanning electron microscope that the complex of zinc oxide particles and miniaturized cellulose according to Comparative Example 4 had strong bonding strength and aggregation between the miniaturized celluloses, so that nanofibers were aggregated and the dispersion degree of particles was low.

[0107] 2) Preparation of Polymer Complex

[0108] A polymer complex and specimens were prepared in the same manner as in Example 1, except that a complex of zinc oxide (ZnO) particles and miniaturized cellulose was used instead of the microcellulose fibers including nanofibrils and fine particles.

Test Examples

[0109] The physical properties of the specimens prepared in Examples and Comparative Examples were evaluated by the following method, and the results are shown in Table 2 below.

[0110] 1) Minor Axis Diameter of Fiber

[0111] The minor axis diameter of the microcellulose fibers (the shortest diameter in the cross section of fiber) prepared in Examples was measured using a scanning electron microscope.

[0112] Specifically, in the case of microcellulose fibers, the minor axis diameters of 10 microfibers per each sample were measured and displayed in a range excluding the maximum and minimum values. In the case of nanofibrils, the minor axis diameters of 20 nanofibrils per each sample were measured, and displayed in a range excluding the maximum and minimum values.

[0113] In addition, in Comparative Example 4, the pulp fibers were miniaturized (defibrated), and then complexed with particles unlike Examples. The minor axis diameter of nanofibrils of Comparative Example 4 in Table 2 below means the minor axis diameter of the miniaturized cellulose after complexing with particles.

[0114] 2) Flexural Strength and Flexural Modulus

[0115] A specimen having a size of 80 mm×10 mm×4 mm was prepared according to ISO 178. The specimen was left for 24 hours in a constant temperature and humidity room adjusted to a temperature of 23° C. and a relative humidity of 50%, and then subjected to a flexural test.

[0116] The flexural strength and flexural modulus of the specimen were measured according to ISO 178 using a universal testing machine (UTM) manufactured by Instron. In accordance with ISO 178, a supports span was set to 46 mm using a three-point flexural test jig, and flexural strength and flexural modulus were obtained by performing a flexural test under a crosshead speed of 5 mm/min.

[0117] 3) Tensile Strength

[0118] The following specimen (FIG. 7) was prepared according to the standard of specimen Type V of ASTM D638. The specimen was left for 24 hours in a constant temperature and humidity room adjusted to a temperature of 23° C. and a relative humidity of 50%, and then subjected to a tensile test.

[0119] The tensile strength of the specimen was measured according to ASTM D638 using a universal testing machine (UTM) manufactured by Instron. In accordance with ASTM D638, a gap between the grips holding the specimen at both ends was set to 25.4 mm, and the test was performed at a constant tensile rate with a crosshead speed of 5 mm/min.

[0120] 4) Antibacterial Property

[0121] Colonies of E. coli cultured in a solid medium were collected using a loop, inoculated in 5 mL of LB (Luria Bertani) liquid medium, and suspension-cultured at 37° C. for about 16 hours while stirring at 160 rpm. After centrifuging the cultured bacteria at 3000 rpm for 1 min and discarding the supernatant, an OD (optical density) value was measured at a wavelength of 600 nm using 5 mL 1×PBS. Thereafter, it was finally adjusted to OD 600=0.01 using 1×PBS solution.

[0122] 50 of bacteria adjusted to OD 600=0.01 was dropped into the center of a circular polymer complex having a diameter of about 2.5 cm sterilized with 70 wt % ethanol. After covering it with a round PET film having a diameter of about 2 cm, it was placed in a small petri-dish having a diameter of 6 cm, and then placed in an airtight container again. A filter paper moistened with water was placed in the airtight container to prevent the bacteria from drying out during culture. The sealed box was cultured for one day in an incubator at 37° C.

[0123] The cultured polymer complex was placed in a 50 mL tube containing 10 mL 1×PBS, and stirred at 180 rpm for 1 hour to disperse the bacteria in the liquid phase. 100 of the culture solution and 100 of the 10-fold diluted culture solution were taken. Then, they were smeared on LB agar medium until absorbed into the medium using glass beads, and cultured at 37° C. in an incubator for one day. After 24 hours, the number of colonies was counted and the number of bacteria reduced compared to the control group (PP) was calculated to calculate the antibacterial rate.

TABLE-US-00001 TABLE 1 (a) (b) (b′) (c) Example 1 85 10 0 5 Example 2 85 10 0 5 Example 3 55 30 0 15 Comparative Example 1 100 0 0 0 Comparative Example 2 90 0 10 0 Comparative Example 3 95 0 0 5 (a) polymer matrix (b) microcellulose fibers containing nanofibrils and fine particles (b′) unmodified pulp (c) compatibilizer

TABLE-US-00002 TABLE 2 Minor axis diameter Size of Flexural Flexural Tensile Microcellulose Nanofibrils fine strength modulus strength Antibacterial fibers (μm) (nm) particles (μm) (MPa) (GPa) (MPa) property (%) Example 1 1~10 50~100 0.1~1 48 1.7 35 30 Example 2 1~10 50~100  0.05~0.1 47 1.8 35 90 Example 3 1~10 50~100 0.1~1 62 1.9 38 99 Comparative None None None 40 1.2 30 0 Example 1 Comparative 1~10 100~500  None 46 1.7 31 0 Example 2 Comparative None None None 42 1.3 31 0 Example 3 Comparative None 10~100 0.1~1 45 1.7 31 30 Example 4

[0124] Referring to Table 2, it was confirmed that the specimens of Examples could exhibit equivalent or higher mechanical properties compared to the specimens of Comparative Examples, and in particular, could also have antibacterial property as additional physical properties depending on the type of fine particles grown on the cellulose fibers.

[0125] As the specimen of Comparative Example 2 contained unmodified cellulose fibers, the improvement in tensile strength was very insignificant compared to that of the specimen of Comparative Example 1. As the specimen of Comparative Example 3 contained only the compatibilizer, it was confirmed that the improvement in mechanical properties was insignificant.

[0126] In the cellulose fibers prepared in Comparative Example 4, although the particles were grown on the miniaturized cellulose, re-aggregation of the miniaturized cellulose and the particles occurred excessively when complexed with the polymer matrix. The specimen of Comparative Example 4, which showed low dispersibility due to the re-aggregation, exhibited poor physical properties similar to those of Comparative Example 2.