A Composite Material and a Method of Preparing the Same

Abstract

There is provided a composite material comprising a porous silica particle, a plurality of metal particles disposed within the pores of said silica particle and a polymeric coating that at least partially encapsulates said silica particle. There is also provided a method of preparing a composite material, comprising the step of mixing a solution containing a plurality of activated metal and silica particles with a polymer solution to thereby form said composite material, wherein said composite material comprises a porous silica particle, a plurality of metal particles disposed within the pores of said silica particle and a polymeric coating that at least partially encapsulates said silica particle.

Claims

1. A composite material comprising a porous silica particle, a plurality of metal particles disposed within the pores of said silica particle and a polymeric coating that at least partially encapsulates said silica particle.

2. The composite material according to claim 1, wherein the silica particle is modified with a silane compound.

3. The composite material according to claim 2, wherein the silane compound is functionalised with an amino group or a carboxylic group.

4. The composite material according to any one of the preceding claims, wherein the metal of the metal particle is selected from Group 8 of the Periodic Table.

5. The composite material according to any one of the preceding claims, wherein the metal of the metal particle is iron.

6. The composite material according to any one of the preceding claims, wherein the size of the metal particle is less than 100 nm.

7. The composite material according to any one of the preceding claims, wherein the size of the porous silica particle is in the range of 20 nm to 1 μm.

8. The composite material according to any one of the preceding claims, wherein the pore size of the porous silica particle is in the range of 5 to 50 nm.

9. The composite material according to any one of the preceding claims, wherein the weight of the metal particles in the composite material is in the range of 1 to 80 wt % based on the dry weight of the porous silica particle.

10. The composite material according to any one of the preceding claims, further comprising an activator.

11. The composite material according to claim 10, wherein the activator is a halide salt.

12. The composite material according to any one of the preceding claims, wherein the polymeric coating comprises a polymer having a monomer selected from the group consisting of urethane, acrylate, methacrylate, epoxy, ethylene, vinyl alcohol and mixtures thereof.

13. The composite material according to any one of the preceding claims, wherein the thickness of the polymer coating is in the range of 0.5 to 15 nm.

14. The composite material according to any one of the preceding claims, wherein the composite material has an oxygen scavenging performance in the range of 210 to 230 cm.sup.3/g.

15. A method of preparing a composite material, comprising the step of mixing a solution containing a plurality of activated metal and silica particles with a polymer solution to thereby form said composite material, wherein said composite material comprises a porous silica particle, a plurality of metal particles disposed within the pores of said silica particle and a polymeric coating that at least partially encapsulates said silica particle.

16. The method according to claim 15, further comprising a step of annealing or chemical etching to enlarge the pore size of the silica particle.

17. The method according to claim 16, wherein the annealing step is undertaken at a temperature range of 100 to 700° C.

18. The method according to claim 16, wherein the chemical etching step comprises the use of an alkali salt solution.

19. The method according to claim 18, wherein the amount of alkali salt in said solution is in the range of 0.01% to 5 wt % of the silica particle.

20. The method according to any one of claims 15 to 19, further comprising the step of modifying the silica particles with a silane compound.

21. The method according to claim 20, wherein the silane compound is functionalised with an amino group or a carboxylic group

22. The method according to any one of claims 15 to 21, wherein the polymer of the polymer solution is dissolved in a mixture of alcohol and water.

23. The method according to any one of claims 15 to 22, wherein the concentration of the polymer in the polymer solution is in the range of 0.01 to 10 wt %.

24. The method according to any one of claims 15 to 23, further comprising the step of activating a metal particle with a salt to form said activated metal.

25. Use of the composite material of any one of claims 1 to 14 as an oxygen scavenger material.

26. A method of forming an oxygen scavenging or oxygen barrier film comprising the step of compounding or coating a substrate with a composite material as defined in any one of claims 1 to 14.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0058] The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

[0059] FIG. 1 is a schematic diagram showing the process 2 of forming a composite material as defined herein.

[0060] FIG. 2 shows a number of transmission electron microscopy (TEM) images of iron/silica nanoparticles with and without polymeric coating. FIG. 2(a) is a TEM image of iron/silica nanoparticles without polymeric coating. FIG. 2(b) is a TEM image of ethylene vinyl alcohol copolymer (EVOH) coated iron/silica nanoparticles prepared by using 0.1 wt % EVOH solution. FIG. 2(c) is a TEM image of EVOH coated iron/silica nanoparticles prepared by using 0.15 wt % EVOH solution. FIG. 2(d) is a TEM image of EVOH coated iron/silica nanoparticles prepared by using 0.3 wt % EVOH solution.

[0061] FIG. 3 shows a number of optical images of compressed EVOH pellets. FIG. 3(a) is an optical image of compressed EVOH pellets which were made from of 5 wt % iron/silica nanoparticles. The inset here is a photograph of the corresponding compressed EVOH pellets. FIG. 3(b) is an optical image of compressed EVOH pellets which were made from of 5 wt % EVOH coated Iron/silica nanoparticles. The inset here is a photograph of the corresponding compressed EVOH pellets.

DETAILED DESCRIPTION OF FIGURES

[0062] As shown in FIG. 1, there is provided a process 2 of forming a composite material 500 comprising a porous silica particle 200, a plurality of metal particles 300 disposed within the pores 100 of the silica particle 200 and a polymeric coating 400 that at least partially encapsulates the silica particle 200. Initially, a silica particle 200 having pores 100 is provided, which is then subjected to a pore enlargement step 4 to increase the size of the pores 100 in order to allow the metal particles 300 to be disposed within the pores 100. As the size of the pores 100 increased, more metal particles 300 can be present within the silica particle 200. This is then subjected to a polymeric coating step 6 whereby the metal/silica particle is added to a polymer solution which forms a polymeric coating 400 on the metal/silica particle to form the resultant composite material 500.

EXAMPLES

[0063] Non-limiting examples of the invention will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Materials and Methods

[0064] Cetyl trimethylammonium bromide (CTAB), ferric chloride (FeCl3), sodium chloride (NaCl), ethylene vinyl alcohol copolymer (EVOH), aminopropyltriethoxysilane (APTES), tetraethyl orthosilicate (TEOS), ethanol, ethyl ester and sodium borohydride were purchased from Sigma Aldrich Singapore. Ammonia (30%) was purchased from Honey well Singapore. Sodium hydroxide (NaOH) was purchased from Merck Singapore.

Example 1: Preparation of Porous Iron/Silica from Mesoporous Silica Nanoparticles

[0065] 0.6 g of CTAB was dissolved in 70 mL of water and mixed with 0.6 mL of ammonia solution (30%) and 20 mL ethyl ester. The resulting solution was stirred at 500 rpm at 30° C. for 30 minutes. With vigorous stirring, 3.5 mL TEOS was added into the solution dropwisely in 10 minutes. After the addition of TEOS, the mixture was stirred for 12 hours at 30° C. The resulting mesoporous silica nanoparticles were purified through centrifugation at 9000 rpm for 10 minutes and washed with ethanol twice. The silica nanoparticles were re-dispersed in ethanol solution with 1M hydrochloric acid. The suspension was stirred at 500 rpm at 60° C. for 5 hours and then purified by centrifugation at 9000 rpm for 10 minutes to remove excess CTAB molecules in the silica particles. The step for the removal of CTAB was repeated to ensure most of the CTAB was eliminated from the silica nanoparticles. The particles were air dried and then vacuum dried at room temperature.

[0066] For the preparation of iron/silica nanoparticles, 1 g of mesoporous silica nanoparticles were dispersed in 25 mL of water. Then, another solution of ferric chloride (0.25 g) was added into the suspension in a dropwise manner. The suspension was stirred for 12 hours to ensure the adsorption of Fe ions in the channels of mesoporous silica. With vigorous stirring, 2 mL solution of sodium borohydride (0.2 g) was added into the silica suspension in a dropwise manner. The final product was purified via centrifugation and re-dispersed in mixture of ethanol and water with volume ratio of 7:3.

Example 2: Preparation and Oxygen Scavenging Test of Porous Iron/Silica Composite Nanoparticles with Enlarged Pore Size

[0067] To prepare mesoporous silica etched by 0.1 wt % NaOH and treated with 10 wt % APTES, porous silica nanoparticles were prepared according to the steps in Example 1. 1 g of porous silica nanoparticles were dispersed in 500 mL ethanol. 10 mL sodium hydroxide (NaOH) solution (0.1 wt %) was added into the suspension and stirred for 3 hours at room temperature. After purified by centrifugation, porous silica nanoparticles were re-dispersed in ethanol solution with 0.1 g APTES. The mixture was kept stirring for 1 hour at room temperature and then the nanoparticles were collected through centrifugation.

[0068] To prepare mesoporous silica annealed at 300° C. and treated with 10 wt % APTES, porous silica nanoparticles were prepared according to the steps in Example 1. 1 g of porous silica nanoparticles were annealed in oven 300° C. for 1 hr. Then, porous silica nanoparticles were re-dispersed in ethanol solution with 0.1 g APTES. The mixture was kept stirring for 1 hour at room temperature and then the nanoparticles were collected through centrifugation.

[0069] Table 1 shows the pore size, iron loading and oxygen scavenging performance of the iron/silica composite without treatment, with chemical etching and silane treatment, and with annealing and silane treatment.

TABLE-US-00001 Iron Oxygen Pore loading of Oxygen scavenging size of iron/silica scavenging capacity of Mesoporous meso- based on capacity of iron/silica silica with 60 wt % porous ICP charac- iron/silica based on of iron based on silica terization (cc/g of ICP result feeding ratio (nm) (wt %) scavenger) (cc/g Fe) Mesoporous silica 8.2 51.1 73.5 143.8 without treatment Mesoporous silica 25.0 55.2 91.7 166.1 etched by 0.1 wt % NaOH and treated with 10 wt % APTES Mesoporous silica 15.1 48.2 80.5 167.1 annealed at 300° C. and treated with 10 wt % APTES

Example 3: Preparation of Polymer Coated Iron/Silica Nanoparticles

[0070] EVOH pellets were dissolved in a mixture of isopropanol and water with volume ratio of 7 to 3 at 65° C. 100 mL of the EVOH solution was placed in a reagent bottle and stirred at 65° C., bubbled with nitrogen gas for 20 minutes to fully remove the residue oxygen in the solution. Sodium chloride water solution was added into the iron/silica ethanol/water mixture with mass content of 10 wt % of the iron/silica nanoparticles. Then, 50 mL ethanol/water solution with 0.5 g iron/silica nanoparticles was added dropwisely into the EVOH solution. The suspension was cooled to room temperature, bubbled with nitrogen. 20 mL of water that had been bubbled with nitrogen for 10 minutes was added into the suspension in a dropwise manner. The EVOH coated iron/silica nanoparticles was purified by centrifugation and dried at 50° C. in vacuum oven. The TEM images of (a) iron/silica nanoparticles, and ethylene vinyl alcohol copolymer (EVOH) coated iron/silica nanoparticles prepared by using EVOH solution with (b) 0.1 wt %, (c) 0.15 wt % and (d) 0.3 wt % EVOH are shown in FIG. 2. As shown in FIG. 2(b), ethylene vinyl alcohol copolymer (EVOH) coating was not observed. As shown in FIG. 2(c), the EVOH polymeric layer had a thickness of 5 nm. As shown in FIG. 2(d), the EVOH polymeric layer had a thickness of 10 nm.

Example 4: Oxygen Scavenging Test of EVOH Coated Iron/Silica Nanoparticles

[0071] To evaluate the oxygen scavenging performance of EVOH coated iron/silica nanoparticles, 0.1 g of each sample obtained from Example 3 was placed into a 25 ml glass conical flask. A vial containing 1 ml of water was placed inside the flask to adjust the room humidity (RH) to 100%. Then, the flask was sealed by a gas-tight rubber septum stopper and placed at room temperature for the duration of the oxygen scavenging experiment. The oxygen scavenging performance of the EVOH coated iron/silica nanoparticles are listed in Table 2. The polymer coating thickness of the iron/silica sample with 0.1 wt % EVOH was about 1 nm. The polymer coating thickness of the sample with 0.15% EVOH was about 5 nm and the polymer coating thickness of the sample with 0.3% EVOH was about 10 nm. For reference, the (non-polymeric coated) iron/silica nanoparticles showed scavenging capacity of 193.1 cc/g Fe. The EVOH coated iron/silica nanoparticles prepared by EVOH solution with 0.15 wt % EVOH gave higher oxygen scavenging capacity (211 cc/g Fe).

[0072] Table 2 shows the oxygen scavenging performance of iron/silica and EVOH coated iron/silica nanoparticles prepared using different EVOH solution.

TABLE-US-00002 Oxygen scavenging Test at room temperature and 100% humidity capacity (cc/g Fe) Iron/Silica 193.1 (ICP of Fe: 34.7 wt %) EVOH EVOH solution with 0.1 116.7 coated wt % EVOH Iron/silica (ICP of Fe: 30.1 wt %) EVOH solution with 211 0.15 wt % EVOH (ICP of Fe: 29.7 wt %) EVOH solution with 0.3 164 wt % EVOH (ICP of Fe: 20.1 wt %)

[0073] Oxygen scavenger with thicker EVOH coating took longer time to achieve saturated oxygen scavenging capacity. The saturated scavenging capacity of the sample with 0.3 wt % EVOH could be higher than 164. The sample with 0.15 wt % EVOH had better performance as compared to the sample with 0.3 wt % EVOH, mainly because of the barrier property of EVOH against oxygen to reduce oxygen diffused into silica to be consumed. Little amount of EVOH cannot block oxygen effectively, while too high amount of EVOH hinder the diffusion of oxygen significantly. The optimized range of EVOH concentration should be 0.15 to 0.25 wt %.

Example 5: Preparation of Polymer Composites with EVOH Coated Iron/Silica Nanoparticles

[0074] Iron/silica nanoparticles and EVOH coated Iron/silica nanoparticles (prepared by using 0.15 wt % EVOH solution) were mixed with EVOH pellets and compounded through twin screw extruder, flushed with nitrogen gas. The mass content of Iron/silica and EVOH coated Iron/silica nanoparticles were kept at 5 wt %. The resulting polymer pellets were compressed to form thin films via hot press. As shown in FIG. 2, much less aggregation of nanoparticles were observed in the sample with EVOH coated iron/silica, resulting in more transparent films. Furthermore, the EVOH pellets with EVOH coated iron/silica possessed higher oxygen scavenging capacity (1.14 cc/g of pellet) than the sample compounded with iron/silica (0.52 cc/g of pellet). The optical images of the compressed EVOH pellets with (a) 5 wt % iron/silica nanoparticles and (b) 5 wt % EVOH coated Iron/silica nanoparticles and the photographs of the corresponding compressed EVOH pellets are shown in FIG. 3. Much less aggregation of iron/silica nanoparticles were observed in the sample with EVOH coated iron/silica nanoparticles as shown in the optical images, resulting in more transparent films as shown in the inlets. The film shown in inlet of FIG. 3a had a thickness of 140 μm. The film shown in inlet of FIG. 3a had a thickness of 70 μm

[0075] Table 3 shows the oxygen scavenging performance of EVOH pellets compounded with iron/silica and EVOH coated iron/silica nanoparticles

TABLE-US-00003 Oxygen Scavenging Capacity (cc/ Test at 100° C. with 100% humidity gram of pellet) 5 wt % Iron/silica compounded with EVOH 0.52 5 wt % polymer protected Iron/Silica 1.14 (0.15 wt % EVOH) compounded with EVOH

INDUSTRIAL APPLICABILITY

[0076] In the present disclosure, the composite material may be used as oxygen scavenger to be placed in containers such as laminated sheets, sachets, and permeable bags. The composite material may also be used as oxygen scavenger to be integrated into polymer matrix via compounding or coating to form an oxygen scavenging or oxygen barrier plastic film.

[0077] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.