Coating formulation, an article and methods to prepare the same

Abstract

There is provided a coating formulation comprising an inorganic oxygen scavenger, a surfactant, an activator, a hydrophilic agent, optionally an additive and a plurality of monomers capable of forming a polymeric matrix, and a method to prepare the same. There is also provided an article comprising an inorganic scavenger, a surfactant, an activator, a hydrophilic agent and optionally an additive dispersed within a polymeric matrix, and a method to prepare the same.

Claims

1. A coating suspension formulation comprising: a) an inorganic oxygen scavenger which is a composite of an inorganic metal material and a carbon material, wherein the composite comprises a plurality of the inorganic metal in particulate form disposed within the carbon material; b) a surfactant comprising natural clay, synthetic clay, or modified clay; c) an activator solution which is a halide salt or an acidifying agent; d) a hydrophilic agent selected from a polymer comprising monomers selected from an alkylene oxide, a carboxylic acid, and combinations thereof; e) an additive being ascorbic acid; and f) a polymeric matrix, wherein an amount of the additive in the coating suspension formulation is in a range of 0.1 wt % to 2.5 wt %.

2. The coating suspension formulation of claim 1, wherein the inorganic metal material has a particle size of less than 500 nm.

3. The coating suspension formulation of claim 1, wherein an amount of inorganic oxygen scavenger in the coating suspension formulation is in a range 1 wt % to 20 wt %.

4. The coating suspension formulation of claim 1, wherein an amount of surfactant in the coating suspension formulation is in a range of 0.5 wt % to 10 wt %.

5. The coating suspension formulation of claim 1, wherein an amount of the hydrophilic agent in the coating suspension formulation is in a range of 0.5 wt % to 10 wt %.

6. The coating suspension formulation of claim 1, wherein the polymeric matrix is selected from a polyurethane, a polyacrylate, a poly(meth)acrylate, a polyepoxide, or an ethylene vinyl alcohol copolymer.

7. The coating suspension formulation of claim 1, wherein the carbon material has a porous structure with a pore size in a range of 10 nm to 700 nm.

8. The coating suspension formulation of claim 1, wherein the inorganic material is iron.

9. A method to prepare the coating suspension formulation of claim 1, comprising the steps of a) mixing the inorganic oxygen scavenger, the surfactant, the activator solution, the hydrophilic agent, and the additive to form a mixture, and b) mixing the mixture from step a) with the polymeric matrix or monomers of said polymeric matrix.

10. The method of claim 9, further comprising a degassing step.

11. The method of claim 9, further comprising a crosslinking step wherein the polymeric matrix is formed by a plurality of monomers capable of forming the polymeric matrix with the addition of a polymerization crosslinker.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) 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.

(2) FIG. 1 shows the transmittance of the prepared films with PAA or PEO as the hydrophilic agent and PET film as a control.

(3) FIG. 2 shows the transmittance of the prepared films with different amount of Fe/C composite and PET film as a control.

(4) FIG. 3 shows the comparison of film formation without (A) and with (B) clay as the surfactant.

(5) FIG. 4 shows the appearance of the film formed by Iron/Carbon oxygen scavenger in EVOH.

(6) FIG. 5 shows the oxygen scavenging performance of the film with and without ascorbic acid.

EXAMPLES

(7) 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.

Materials and Methods

Example 1: Preparation of Coating Formulation Using Thinky Mixer

(8) 0.015 g of NaCl (99.5-100.5%, ACS Reagant Grade from VWR Chemicals) was first dissolved with 2 ml of H.sub.2O. The Iron/Carbon scavenger was prepared according to the method disclosed in PCT/SG2018/050235, which is hereby incorporated by reference. Briefly, the Iron/Carbon scavenger has a carbon sphere size of about 300 nm and was synthesized using 40 wt % iron and 20 wt % glucosamine. Different amount of Iron/Carbon oxygen scavenger [as described in Table 1 and 2], were added to the solution and mixed by vortex. 1 ml of PAA (Mw 450 k from Polyscience) was added to the suspension and mixed again. 1 ml of MMT clay (Nanocor) solution (4 wt %) was added to the suspension and mixed using vortex mixer again.

(9) The prepared suspension was now added into PU monomer (Aqueous polycarbonate based polyurethane from STAHL), sealed in a container and flushed with N.sub.2, and mixed for 5 minutes using Thinky mixer. PU crosslinker (Melamine based crosslinker for aqueous coating from STAHL) was added and mixed for another 2 minutes, followed by 2 minutes deforming. The coating suspension was coated onto PET film and dried in a vacuum oven at the curing temperature (110 C.).

(10) The same procedure was used to prepare the film with PEO (Mw 400 k from Stigma Aldrich) by replacing the PAA in the above sequence. The transparency of the films using PEO and PAA as hydrophilic agent is shown in FIG. 1 in comparison with PET film alone. The film using PEO as hydrophilic agent showed higher transparent as compared to the film using PAA as hydrophilic agent. Both films using PAA and PEO as hydrophilic agents showed transmittance of more than 70% in the visible range.

(11) Table 1 shows the composition of the coating formulation and the attained oxygen scavenging capacity after 1 week.

(12) TABLE-US-00001 Iron/ PU Scavenging PU PAA PEO Clay Carbon cross- Capacity/ (g) (g) (g) (g) (g) linker (g) 100 cm.sup.2 PAA 3.5 0.06 0 0.04 0.1 0.52 1.1 composition PEO 3.5 0 0.06 0.04 0.1 0.52 0.92 composition

(13) The transparency of the films using different amount of iron/carbon oxygen scavengers is shown in FIG. 2 in comparison with PET film alone. The transmittance slight decreased with higher content of the iron/carbon oxygen scavengers. The logos under the film are clearly visible.

(14) Table 2 shows the different amount of Iron/Carbon scavenger to prepare different wt % of coating formulation. The oxygen scavenging capacity is calculated based on 1 week at 60 C. (20 m coating thickness).

(15) TABLE-US-00002 Iron/ PU Scavenging PU PEO Clay Carbon NaCl cross- Capacity/ (g) (g) (g) (g) (g) linker (g) 100 cm.sup.2 4.6 3.6 0 0 0.2 0.015 0.52 0.0 wt % 2.4 3.5 0.06 0.04 0.1 0.015 0.52 0.92 wt % 3.5 3.5 0.06 0.04 0.15 0.015 0.52 1.42 wt % 4.6 3.5 0.06 0.04 0.2 0.015 0.52 1.89 wt %

(16) Without coating formulation (4.6 wt % Iron/Carbon in PU), no oxygen scavenging was observed for the film prepared. With proper formulation, oxygen scavenging can be achieved for the films which increased oxygen scavenging performance with the increase of Iron/Carbon weight percentage.

Example 2: Coating Formulation with NaCl for Polymer that Cannot Dissolve NaCl

(17) 0.015 g of NaCl was first dissolved with 2 ml of H.sub.2O. 1 ml of MMT clay solution (4 wt %) was added to the suspension and mixed using vortex mixer again. 0.2 g of Iron/Carbon oxygen scavenger was added to the solution and mixed by vortex The prepared suspension was now added into 10 g of polyurethane (Aqueous polycarbonate based polyurethane from Mitsui Chemicals), sealed in a container and flushed with N2, and mixed for 5 min using Thinky mixer, and degassed for 5 min. The coating suspension was coated onto PET film and dried in a vacuum oven at the curing temperature.

(18) Strips of 8 cm12 cm of the dried film was cut and placed into a placed into a 50 ml flask and sealed with a rubber septa. The oxygen concentration is measured using a SYSTECH Headspace Gas Analyser. The results are shows below.

(19) Table 3 shows the oxygen scavenging performance of the coating formulation with and without NaCl, and at room temperature and 60 C. (20 m coating thickness)

(20) TABLE-US-00003 Oxygen Concentration in 50 ml flask (%) Oxygen Concentration (At room temperature) in 50 ml flask (%) 4.6 wt % (60 C.) Iron/Carbon 4.6 wt % Iron/Carbon coating in 4.6 wt % Iron/Carbon coating in Time polyurethane coating in polyurethane Time polyurethane (Days) (No NaCl) (with NaCl and clay) (Days) (with NaCl and clay) 0 20.9% 20.9% 0 20.9% 5 20.9% 16.7% 1 15.9% 12 20.9% 15.4% 3 7.63% 20 20.9% 12.6% 7 0.107% Scavenging 0 4.32 Scavenging 10.8 Capacity/ Capacity/ 100 cm.sup.2 100 cm.sup.2

(21) The film with clay as the surfactant showed much smoother surface as compared to the film without clay surfactant, as shown in FIG. 3. Poor dispersion was observed by dispersing 4.6 wt % Iron/Carbon in polyurethane only (FIG. 3A). With clay addition, good dispersion was achieved (FIG. 3B).

Example 3: Iron/Carbon Oxygen Scavenger in EVOH

(22) 10 wt % EVOH solution was prepared by dissolving EVOH pellets in n-propanol/water (65:35), and stirred at 65 C. overnight (around 18 hours). 0.2 g of Iron/Carbon oxygen scavenger was added to 10 g of 10 wt % EVOH solution to achieve 20 wt % coating (the weight of Iron/Carbon to EVOH). The appearance of the film with Iron/Carbon oxygen scavenger in EVOH is shown in FIG. 4. A good transparency was also observed similar to the film prepared in polyurethane.

(23) Table 4 shows the oxygen scavenging capacity of the film and its appearance

(24) TABLE-US-00004 Oxygen Scavenging (cc/(100 cm.sup.2 of coated film)) 60 C. 20 wt % of Iron/Carbon in EVOH 1.32

Example 4: Iron/Carbon Oxygen Scavenger with Clay in EVOH

(25) To prepare clay in propanol/H.sub.2O, 0.2 g of MMT clay has to be dispersed into 5 ml of H.sub.2O followed by adding 5 ml of propanol to obtain 2 wt % in propanol/H.sub.2O. Otherwise, the MMT clay will precipitate. Iron/Carbon, clay, EVOH coating formulation can be prepared according to the above examples.

Example 5: Improvement of Scavenging Capacity of Iron/Carbon Coating with the Addition of Ascorbic Acid

(26) 0.015 g of NaCl was first dissolved with 2 ml of H.sub.2O. 0.2 g of Iron/Carbon oxygen scavenger was added to the solution and mixed by vortex. 50 mg of ascorbic acid (AA) (L-(+)-Ascorbic acid, 99+% from Alfa Aesar) was added. 1 ml of PAA was added to the suspension and mixed again. 1 ml of MMT clay solution (4 wt %) was added to the suspension and mixed using vortex mixer again.

(27) The prepared suspension was now added into PU monomer (Aqueous polycarbonate based polyurethane from STAHL), sealed in a container and flushed with N.sub.2, and mixed for 5 minutes using Thinky mixer. PU crosslinker (Melamine based crosslinker for aqueous coating from STAHL) was added and mixed for another 2 minutes, followed by 2 minutes deforming. The coating suspension was coated onto PET film using 40 m thickness and dried in a vacuum oven at the curing temperature. 4.6 wt % Iron/Carbon coating formulation was achieved.

(28) The same procedure was used to prepare the film at 3.5 wt % Iron/Carbon.

(29) Table 5 show the improvement of scavenging capacity of film with ascorbic acid (AA) (40 m coating thickness)

(30) TABLE-US-00005 Scavenging Capacity/100 cm.sup.2 No AA With AA 3.5 wt % of Iron/Carbon in 2.4 3.64 formulation 4.6 wt % of Iron/Carbon in 2.3 5.62 formulation

Example 6: Improvement of Scavenging Capacity of Iron/Carbon Material with the Addition of Ascorbic Acid

(31) The oxygen scavenging capacity and performance of the prepared Iron/Carbon powder were compared with the addition of ascorbic acid. 0.05 g of Iron/Carbon oxygen scavenger powder was mixed with 0.0035 g of NaCl and 0.03 g of Ascorbic acid and the mixture was placed in a 50 ml conical flask, sealed with a rubber septum. The percentage of oxygen was monitored over a period of time. With the addition of ascorbic acid, there was an observed synergistic effect. The oxygen scavenging capacity and duration increased due to the regenerative effect of the ascorbic acid to reduce Fe(III) to Fe(II) cycle.

(32) The oxygen scavenging property of the Iron/Carbon oxygen scavenger material with and without ascorbic acid is shown in FIG. 5. With addition of ascorbic acid, further oxygen scavenging performance can be achieved.

(33) Table 6 shows the improvement of scavenging capacity of Iron/Carbon oxygen scavenger material with the addition of ascorbic acid.

(34) TABLE-US-00006 0.05 g Fe/C 0.05 g Fe/C with NaCl with NaCl and Time (Hrs) (control) ascorbic acid 0 20.9% 20.9% 8 15.8% 16.6% 24 11.1% 11.1% 72 10.7% 5.10% 168 10.6% 2.6% 240 10.6% 2.4% Max scavenging capacity per 103 185 gram of scavenger

Example 7: Improvement of Scavenging Capacity of Iron/Carbon Coating with the Addition of Ascorbic Acid

(35) 3 ml of 1.33 wt % of MMT clay solution was bubbled with argon (Ar) for 10 minutes to remove the oxygen in the solution. 0.05 g of Iron/Carbon oxygen scavenger powder was added to the clay solution and homogenized for 10 minutes, while bubbling with Ar. 0.005 g of NaCl and 0.03 g of Ascorbic acid, previously dissolved in 1 ml of water was added to the above Iron/Carbon suspension. 10 g of polyurethane was also added, and homogenized for another 10 minutes. The mixture was then degassed using Thinky Mixer for 2 minutes. The coating suspension was coated onto PET film using 20 m thickness coating bar and dried in a vacuum oven at the curing temperature. 1.41 wt % Iron/Carbon coating formulation was achieved.

(36) The same procedure was used to prepare the film at 1.41 wt % Iron/Carbon coating on PET film without ascorbic acid. 55 cm film size was cut and placed in a 20 ml vial, tested under 100% humidity for 60 C. The addition of ascorbic acid in the coating increased the scavenging speed and capacity.

(37) Table 7 shows improvement of scavenging capacity of Iron/Carbon coating with the addition of ascorbic acid.

(38) TABLE-US-00007 0.05 g Fe/C 0.05 g Fe/C with NaCl with NaCl and Time (Hrs) (control) ascorbic acid 0 20.9% 20.9% 8 15.8% 16.6% 24 11.1% 11.1% 72 10.7% 5.10% 168 10.6% 2.6% 240 10.6% 2.4% Max scavenging capacity per 103 185 gram of scavenger

(39) The data comparison clearly showed that the combination of Iron/Carbon oxygen scavenger and ascorbic acid is not a mere addition of the individual effect. Even though ascorbic acid is known to be an oxygen scavenger, the oxygen scavenging reaction is slow on its own and a large amount of ascorbic acid is required. In the control experiment, there is no oxygen scavenging detected using ascorbic acid alone. This example shows that the ascorbic acid can form a regenerative effect for the Fe(III) to Fe(II) cycle with the Iron/Carbon oxygen scavenger, leading to a synergistic effect between the ascorbic acid and the iron.

INDUSTRIAL APPLICABILITY

(40) In the present disclosure, the article may be used as a packaging film for food or beverage packaging for scavenging oxygen efficiently. The packaging film may be used as oxygen scavengers and may have low permeability to the flow of oxygen through the article. The use of the article for food or beverage packaging may prolong the shelf life of the food or beverage.

(41) 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.