COMPOSITE MATERIAL AND A METHOD FOR PREPARING THE SAME

Abstract

The present invention generally relates to a composite material. In particular, the present invention relates to a composite material comprising a mixture of a plurality of metal particles and a porous silica particle, wherein said metal particles are disposed within the pores of the porous silica particle. The present invention also provides a method for preparing the composite material used as an oxygen scavenger.

Claims

1. A composite material comprising a mixture of a plurality of metal particles and a porous silica particle, wherein said plurality of metal particles is disposed within pores of said porous silica particle, wherein said composite material is a nanostructured composite material having a cavity in a range of 40 nm to 80 nm.

2. The composite material according to claim 1, wherein said porous silica particle comprises a nanosized channel.

3. The composite material according to claim 1, wherein said metal particle is a metal nanoparticle.

4. The composite material according to claim 3, wherein the metal of said metal nanoparticle is selected from Group 8 of the Periodic Table.

5. The composite material according to claim 1, wherein the particle size of the metal particle is in the range of 1 nm to 50 nm.

6. The composite material according to claim 1, wherein said porous silica particle is a porous silica nanoparticle.

7. The composite material according to claim 6, wherein a particle size of said porous silica nanoparticle is in a range of 20 nm to 1000 nm.

8. The composite material according to claim 6, wherein said porous silica nanoparticle is selected from the group consisting of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate, tetrapropyl orthosilicate tetrabutyl orthosilicate, and tetraisopropyl orthosilicate.

9. The composite material according to claim 1, wherein said nanostructured composite material having a cavity has an oxygen scavenging performance in a range of 190 cm.sup.3/g to 210 cm.sup.3/g of metal.

10. A method of preparing a composite material comprising a mixture of a plurality of metal particles and a porous silica particle material, comprising the steps of: a) dissolving a surfactant in water, followed by mixing surfactant solution with a base and a reactant, wherein a resulting solution is stirred at a suitable temperature; b) adding a solution of silicate precursor into the solution of step a), wherein a resulting mixture is stirred at a suitable temperature to thereby form a suspension of silica particle; c) immersing a purified and air-dried silica particle having a porous structure into a solution of metal ions to allow the metal ions to impregnate into pores of the silica particle, wherein a resulting suspension is stirred for a period of time; d) adding a solution of a reducing agent into the suspension of step c) to form a solution of impregnated silica particle; and e) purifying and drying the solution of impregnated silica particle under inert gas flow to thereby form said composite material; wherein said composite material is a nanostructured composite material having a cavity in a range of 40 nm to 80 nm.

11. The method according to claim 10, wherein said metal ions are iron ions derived from an iron salt selected from the group consisting of iron chloride, iron bromide, iron fluoride, iron iodide, iron sulfate, iron nitrate, iron oxalate, iron gluconate, iron acetylacetonate, iron fumarate, and iron phosphate.

12. The method according to claim 10, wherein said reducing agent is selected from the group consisting of sodium borohydride, lithium aluminum hydride, diisobutylaluminium hydride (DIBAL-H), and sodium cyanoborohydride.

13. The method according to claim 10, wherein said reactant is an alkyl ester.

14. A composition comprising: a) a composite material comprising a mixture of a plurality of metal particles and a porous silica particle material, wherein said plurality of metal particles is disposed within pores of said porous silica particle, and wherein said composite material is a nanostructured composite material having a cavity in the range of 40 nm to 80 nm; and b) a polymeric matrix.

15. The composition according to claim 14, wherein said polymeric matrix is selected from the group consisting of montmorillonite, bentonite, laponite, kaolinite, saponite, vermiculite, and mixtures thereof.

16. A method of preparing a composition comprising: a) a composite material comprising a mixture of a plurality of metal particles and a porous silica particle material; and b) a polymeric matrix, wherein said plurality of metal particles is disposed within pores of said porous silica particle, wherein said composite material is a nanostructured composite material having a cavity in the range of 40 nm to 80 nm, and wherein said method comprises the steps of dispersing said composite material in a solution of alkyl alcohol and adding an amount of polymeric matrix.

17. An article containing a composition comprising a composite material and a polymeric matrix according to claim 14.

18. The article according to claim 17, wherein said article is a transparent coated film.

19. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0120] 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.

[0121] FIG. 1 shows two methods for preparing the composite material Fe/S1 and Fe/S2, described in Examples 1 and 2, respectively.

[0122] FIG. 2 is a number of transmission electron microscope (TEM) images of the mesoporous silica nanoparticles and of the Fe/silica nanoparticles (Fe/S1) synthesized from mesoporous silica nanoparticles as described in Example 1. FIG. 2A shows TEM image of mesoporous silica nanoparticles at low magnification (with a scale bar of 100 nm); FIG. 2B shows TEM image of mesoporous silica nanoparticles at high magnification (with a scale bar of 20 nm); FIG. 2C depicts TEM image of Fe/S1 nanoparticles at low magnification (with a scale bar of 100 nm); FIG. 2D describes TEM image of Fe/S1 nanoparticles at high magnification (with a scale bar of 20 nm).

[0123] FIG. 3 is a number of transmission electron microscope (TEM) images of the mesoporous silica nanoparticles and of the Fe/silica nanoparticles with large cavity (Fe/S2) synthesized from mesoporous silica nanoparticles as described in Example 2. FIG. 3A shows TEM image of mesoporous silica nanoparticles at low magnification (with a scale bar of 100 nm); FIG. 3B shows TEM image of mesoporous silica nanoparticles at high magnification (with a scale bar of 50 nm); FIG. 3C depicts TEM image of Fe/S2 nanoparticles at low magnification (with a scale bar of 100 nm); FIG. 3D describes TEM image of Fe/S2 nanoparticles at high magnification (with a scale bar of 20 nm).

[0124] FIG. 4 is a graph obtained from an X-ray diffraction (XRD) analysis of the Fe/silica nanoparticles with large cavity (Fe/S2) obtained in Example 2.

[0125] FIG. 5 is a number of graphs summarizing the results obtained from the oxygen scavenging test as described in Example 3.

[0126] FIG. 6 is a photograph of a transparent Fe/S2 nanoparticles coating on polyethylene terephthalate (PET) film as described in Example 4.

DETAILED DESCRIPTION OF DRAWINGS

[0127] Referring to FIG. 1, this figure describes two methods for preparing the composite material of the present disclosure. FIG. 1A depicts a method for synthesizing the composite material Fe/S1 as described in Example 1. In FIG. 1A, it can be seen that nanosized channels (101) are found within the mesoporous silica particle (100). After addition of the iron solution (102), composite material Fe/S1 (103) is formed having iron nanoparticles (104) adsorbed in said nanosized channels (101) of mesoporous silica particle (100).

[0128] On the other hand, FIG. 1B depicts a method for synthesizing the composite material Fe/S2 as described in Example 2. In FIG. 1B, it can be observed that nanosized channels (101) are found within the mesoporous silica particle (100) with a large cavity (105). After addition of the iron solution (102) via wet impregnation process, composite material Fe/S2 (106) is formed having iron nanoparticles (104) adsorbed in said nanosized channels (101) of mesoporous silica particle (100) having a large cavity (105). The iron nanoparticles (104) may be also adsorbed and attached to the inner walls in said large cavity (105).

EXAMPLES

[0129] Non-limiting examples of the invention and a comparative example 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.

Example 1: Preparation of Porous Fe/Silica from Mesoporous Silica Nanoparticles (Fe/S1)

[0130] Schematic diagram of the mesoporous silica nanoparticles and composite material Fe/S1 is depicted in FIG. 1A.

[0131] a) Preparation of Mesoporous Silica Nanoparticles

[0132] 2 g of cetyl trimethylammonium bromide (CTAB) (98%, purchased from Alfa Aesar of Lancashire of the United Kingdom) was dissolved in water and mixed with 10 mL of ammonia solution (28-30%, purchased from Honeywell of New Jersey of the United States of America). The resulting mixture (i.e. a first mixture) was stirred at 500 rpm under room temperature for about 30 minutes. With vigorous stirring, 40 mL of hexane solution of tetraethyl orthosilicate (TEOS, purchased from Sigma Aldrich of St. Louis, Mo. of the United States of America) was added dropwise into the first mixture for about 30 minutes. Upon completion of the addition of TEOS solution, a second mixture was obtained and further stirred for about 12 hours under room temperature to form mesoporous silica nanoparticles. The resulting mesoporous silica nanoparticles were recovered via centrifugation at 9000 rpm for about 10 minutes and washed with ethanol twice.

[0133] The purified nanoparticles were re-dispersed in ethanol solution (purchased from Green Tropic Products Pte Ltd of Singapore) with 1 M hydrochloric acid (purchased from Sigma Aldrich of St. Louis, Mo. of the United States of America). The resulting suspension was stirred at 500 rpm at about 60 C. for approximately 5 hours and the nanoparticles were then purified using centrifugation at 900 rpm for about 10 minutes to remove the excess of CTAB molecules in the silica particles. This removal step was repeated to ensure that most of the CTAB molecules were eliminated from the silica nanoparticles. Following this, the nanoparticles were air dried and vacuum dried at room temperature. The transmission electron microscope (TEM) images of the mesoporous silica nanoparticles using low and high magnification are depicted in FIGS. 2A and 2B, respectively.

[0134] b) Preparation of Fe/S1

[0135] 2 g of mesoporous silica nanoparticles obtained in step a) were dispersed in 50 mL of water to form a first suspension. Following this, 5 mL of a solution of ferric chloride (0.5 g, purchased from Sigma Aldrich of St. Louis, Mo. of the United States of America) was added into the first suspension dropwise. The resulting suspension was stirred for about 12 hours to ensure the adsorption of Fe.sup.3+ ions in the channels of mesoporous silica. With vigorous stirring, 4 mL solution of sodium borohydride (0.35 g, purchased from Honeywell Fluka of New Jersey of the United States of America) was added into silica suspension dropwise. The final product was purified via centrifugation followed by drying in oven or furnace with inert gas flow. The TEM images of the Fe/S1 nanoparticles using low and high magnification are depicted in FIGS. 2C and 2D.

[0136] As shown in FIG. 2, transmission electron microscope (TEM) images revealed that the synthesized porous silica nanoparticles obtained via emulsion reaction method have the particle size in a range from about 20 nm to about 200 nm. The size and structure of the porous silica nanoparticles may be easily tuned by changing the ratio of precursors.

[0137] The mesoporous silica nanoparticles are embedded with ordered nanoscale empty channels after the surfactant CTAB was removed. Upon analysis of FIG. 2B, the size of such empty channels is estimated to be about 5 nm and appears to be fairly uniform along individual channel in the mesoporous silica nanoparticles. The TEM image in FIG. 2D revealed that the Fe nanoparticles having a size of about 5 nm are uniformly distributed in silica nanoparticles. The actual content of iron in the Fe/Si was determined to be about 30 wt % by inductively coupled mass spectrometry (ICP-MS).

Example 2: Preparation of Porous Fe/Silica from Mesoporous Silica Nanoparticles with Large Cavity (Fe/S2)

[0138] Schematic diagram of the mesoporous silica nanoparticles and composite material with large cavity Fe/S2 is depicted in FIG. 1B.

[0139] a) Preparation of Mesoporous Silica Nanoparticles

[0140] 0.6 g of CTAB (98%, purchased from Alfa Aesar of Lancashire of the United Kingdom) was dissolved in 70 mL of water and mixed with 0.6 mL of ammonia solution (28-30%, purchased from Honeywell of New Jersey of the United States of America), and 20 mL of anhydrous ethyl ester (purchased from TEDIA of Ohio of the United States of America). The resulting solution was stirred at 500 rpm at 30 C. for about 30 minutes. With vigorous stirring, 3.5 mL of TEOS was added dropwise into the solution for about 10 minutes. Upon complete addition of TEOS, the mixture was further stirred for about 12 hours at 30 C. to produce the mesoporous silica nanoparticles. The products were purified via centrifugation at 9000 rpm for 10 minutes and washed two times with ethanol.

[0141] The silica nanoparticles were re-dispersed in ethanol solution with 1 M hydrochloric acid. The resulting suspension was stirred at 500 rpm for 5 hours at about 60 C. and was then purified by centrifugation at 9000 rpm for about 10 minutes to remove excess CTAB molecules in the silica particles. The step of removing CTAB was repeated to ensure that most of the CTAB was eliminated from the silica nanoparticles. Finally, the particles were air dried followed by vacuum drying at room temperature.

[0142] The TEM images of the mesoporous silica nanoparticles with large cavity using low and high magnification are depicted in FIGS. 3A and 3B.

[0143] b) Preparation of Fe/S2

[0144] 1 g of mesoporous silica nanoparticles was dispersed in 25 mL of water to form a suspension. A solution of ferric chloride (0.25 g, 2.5 mL) was added dropwise into the suspension to form a second suspension. The resulting suspension was stirred for about 12 hours to ensure the adsorption of Fe ions in the channels of the mesoporous silica.

[0145] With vigorous stirring, 2 mL of sodium borohydride (0.2 g) solution was added dropwise into the suspension. The final product was purified via centrifugation and dried in a furnace with inert gas flow. The TEM images of the Fe/silica nanoparticles synthesized from mesoporous silica nanoparticles with large cavity using low and high magnification are shown in FIGS. 3C and 3D.

[0146] As can be seen from FIG. 3, mesoporous silica nanoparticles with a size of approximately 80 nm were observed. In each mesoporous silica nanoparticle, a relatively large cavity was formed with a size of about 60 nm.

[0147] After the growth of Fe nanoparticles, there was no significant change in the shape of silica nanoparticles. Fe nanoparticles with a size of less than 2 nm were uniformly distributed in silica nanoparticles.

[0148] X-ray diffraction (XRD) analysis shown in FIG. 4 revealed that most of the iron particles in the mesoporous silica nanoparticles are of zero valent and only minor amount of iron oxide was present. The actual content of Fe in the Fe/S2 determined by ICP-MS was found to be about 34.7 wt %.

Example 3: Oxygen Scavenging Test of Fe/S1 and Fe/S2

[0149] To evaluate the oxygen scavenging performance of sample Fe/S1 and Fe/S2, 0.1 g of each sample with 7.5 wt % of NaCl 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%. The flask was then sealed with a glass-tight rubber septum stopper and placed at room temperature for the duration of the oxygen scavenging experiment. As can be seen from Table 1, both Fe/S1 and Fe/S2 are capable of removing most of the oxygen from the model packaging after three days. Fe/S2 displayed higher scavenging capacity (193 cm3 vs. 177 cm3) and faster scavenging rate than Fe/S1.

TABLE-US-00001 TABLE 1 Oxygen scavenging performance of Fe/S1, Fe/S2 and Fe/C Oxygen Capacity Oxygen Capacity Oxygen Capacity Time of Fe/S1 of Fe/S2 of Fe/C with 40 wt % Fe (hours) (cm.sup.3/g Fe) (cm.sup.3/g Fe) (cm.sup.3/g Fe) 0 0 0 0 2 6.7 11.5 16.6 4 28.3 47.6 40.5 6 63.3 82.1 51.2 8 81.7 125.4 82.1 24 175.0 193.5 219.4 48 177.0 193.5 230.2 72 177.0 193.1 229.5

[0150] As can be observed in FIG. 5, the oxygen scavenging performance of Fe/S2 is comparable to Fe/C nanocomposites (with 40 wt % Fe). It is noteworthy that the preparation of the Fe/Si oxygen scavenger in the present invention is more cost-effective than that of Fe/C nanocomposites.

Example 4: Preparation of Polymer Composites Film with Fe/Si Nanoparticles

[0151] Fe/S2 was dispersed in EVOH solution by adding small amount of clay (about 5 wt % based on the weight of Fe/S2). The dispersion of Fe/S2 in EVOH solution was achieved by homogenization at 10000 rpm for one minute, flushed with Argon gas. The suspension was then coated on PET film with coating thickness of about 20 m. The coated film was then dried in vacuum oven at 60 C.

[0152] As can be seen from FIG. 6, transparent coated film was obtained with the content of Fe/S2 up to 20 wt %. These transparent films with Fe/Silica oxygen scavengers could be used as oxygen scavenging packaging films to prolong the shelf life of food and incorporated with barrier polymer films to further improve the oxygen barrier.

INDUSTRIAL APPLICABILITY

[0153] As can be seen from the detailed description and examples provided, the composite material of the present disclosure exhibits promising oxygen scavenging performance and therefore may be potentially used for the food, beverage and pharmaceutical applications. Specifically, the composite material of the present disclosure may be used for food, beverage or pharmaceutical packaging.

[0154] The composite material of the present disclosure such as Fe/silica nanoparticles may be directly used as sachets to scavenge oxygen. Further, Fe/silica nanoparticles may also be integrated into a polymeric matrix to form coated or laminated films. Alternatively, Fe/silica nanoparticles may be integrated in extruded/blown polymer films or bottles.

[0155] In addition to the above, the composite material may also be used as a metallic based oxygen scavenger that is non-detectable by industrial metal detector commonly used in the food and pharmaceutical processing and packaging industries. The composite material may also be used in biological application including bio-imaging and drug delivery.

[0156] 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.