Water-recoverable composite material and preparation and recovery methods thereof

Abstract

The invention discloses a water-recoverable composite material as well as a preparation method and a recovery method thereof. The composite material comprises a polysaccharide-based macromolecular thermoplastic material and a non-woven fabric composite material, wherein the water-recoverable polysaccharide-based thermoplastic material is used as a heat bonding layer and is compounded with paper or a non-woven fabric to prepare the non-woven fabric composite material; the paper-plastic-aluminum composite material is prepared by taking a water-recoverable polysaccharide-based thermoplastic material as a heat bonding layer and a hydrophobic layer and thermally bonding the heat bonding layer and the hydrophobic layer with paper and aluminum foil. According to the non-woven fabric / paper-plastic-aluminum composite material, complete separation of multiple components in the paper-plastic composite material can be achieved through a dilute-concentration aqueous alkali solution, specifically, the dilute-concentration aqueous alkali solution is adopted for soaking, washing and separation, finally, a small amount of an acid solution is dropwise added into the recycled dilute-concentration aqueous alkali solution, the polysaccharide-based thermoplastic material is settled, and the polysaccharide-based thermoplastic composite material is obtained. According to the method, the recovery process is simple, and industrialization of practical application and recovery of the paper-plastic composite material is easy to realize.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite materials, and in particular, relates to a water-recyclable non-woven fabric or paper-plastic-aluminum composite material and a preparation and recycling method thereof. BACKGROUND

[0002] Paper-plastic composite materials have become popular packaging materials in the field of disposable packaging materials for modern food, medicine, chemicals and daily necessities due to their excellent barrier properties, biological safety, convenience of use and low cost. With the rapid development of economy, the demand for disposable paper-plastic composite materials is increasing year by year. The paper-plastic composite material waste contains non-degradable petroleum-based plastics, and improper disposal will exacerbate plastic pollution and waste resources. Liquid milk packaging material is a typical representative of paper-plastic composite materials, which is a multi-layer paper-plastic material composed of paper (75%), plastic (PE, 20%) and aluminum foil (5%). Recycling of waste milk packaging materials or other paper-plastic composite materials can not only solve the environmental pollution problem caused by waste plastics, but also realize the recycling of resources.

[0003] There are mainly two methods for recycling paper-plastic-aluminum composite materials: 1. Directly crushing to form new raw materials, such as using extrusion plastic-wood technology to prepare floor, garbage can and seat, and using cold pressing and hot pressing technology to prepare color plates; 2. Separating paper, plastic and aluminum foil for separate reuse, which can maximize the use of paper, plastic and aluminum foil. However, the harsh recycling conditions, complicated washing and separation process make the recycling rate of paper-plastic-aluminum packaging materials low.

[0004] Therefore, it is of great significance to develop a simple, efficient and mild paper-plastic-aluminum packaging material and recycling method to maximize the recycling efficiency of waste resources. SUMMARY

[0005] In order to solve the above problems, the present application provides a water-recyclable composite material and a preparation and recycling method thereof, especially a paper-plastic-aluminum or non-woven fabric composite material. The paper-plastic-aluminum composite material has high barrier properties, and the mechanical properties of the non-woven fabric composite material can be adjusted in a wide range, and it can be recycled by using low-concentration alkaline water, realizing simple and efficient recycling and reuse of non-woven fabric / paper-plastic-aluminum composite materials.

[0006] In order to achieve the above purpose, the present application provides a water-recyclable composite material, which comprises a polysaccharide-based high molecular thermoplastic material; the polysaccharide-based high molecular thermoplastic material is a polysaccharide derivative with switch-type water solubility and thermoplastic processing dual functional characteristics.

[0007] In an embodiment of the present application, the polysaccharide is selected from one or more of cellulose, starch, chitosan and xylan, preferably one or more of cellulose, starch and xylan.

[0008] In one embodiment of the present application, the switch of water-solubility is an acid switch or a base switch; the reaction of the acid switch is the reaction of the base switch is

[0009]

[0010] In one embodiment of the present application, in order to increase the adhesion of the polysaccharide-based thermoplastic material to paper and aluminum foil, part of the hydroxyl groups in the polysaccharide-based thermoplastic material should be retained or introduced, and at the same time, the polysaccharide-based thermoplastic material should be introduced with a group capable of coordinating with aluminum, such as a functional group containing a carboxyl group, exemplarily or -CH2COOH.

[0011] In one embodiment of the present application, the polysaccharide-based thermoplastic material is a polysaccharide derivative with a glass transition temperature of 100-140℃. Preferably, the polysaccharide derivative has a glass transition temperature of 105-130℃, for example, 110℃, 120℃.

[0012] In one embodiment of the present application, the composite material is a non-woven fabric composite material or a paper-plastic-aluminum composite material, and the non-woven fabric composite material is prepared by compounding paper or non-woven fabric with a water-recoverable polysaccharide-based thermoplastic material as a thermal adhesive layer;

[0013] The paper-plastic-aluminum composite material is prepared by thermal adhesion of paper and aluminum foil with a water-recoverable polysaccharide-based thermoplastic material as a thermal adhesive layer and a hydrophobic layer.

[0014] In the present application, the water in "water-recoverable" is a low-concentration alkaline aqueous solution, and the concentration thereof is preferably 0.005-0.03 mol / L, exemplarily 0.008 mol / L, 0.01 mol / L and 0.02 mol / L.

[0015] In one embodiment of the present application, the hydrophobic layer is the same material as or different from the thermal adhesive layer.

[0016] Preferably, the water contact angle of the hydrophobic layer is not less than 90°, preferably 90°-98°, and the water absorption rate thereof is not more than 15% in 24 hours at room temperature, preferably 8%-12%.

[0017] Preferably, the glass transition temperature of the hydrophobic layer is the same as or similar to that of the thermal adhesive layer, and is preferably 100-120℃, for example, 100℃, 110℃ and 120℃.

[0018] Preferably, the thickness of the polysaccharide-based thermoplastic plastic film is not more than 40μm, preferably 5-35μm, exemplarily 8μm, 10μm, 15μm, 20μm, 25μm and 30μm.

[0019] In one embodiment of the present application, the paper-plastic-aluminum composite material is prepared by stacking and hot-pressing polysaccharide-based thermoplastic film, paper and aluminum foil layer by layer; or paper-plastic and plastic-aluminum materials are prepared by casting and emulsion method respectively, and then hot-pressed to obtain the final product. The polysaccharide-based thermoplastic material in the non-woven fabric composite material can form a dense coating on the surface of the paper or non-woven fabric, and the coating has certain water, oil and oxygen resistance.

[0020] In one embodiment of the present application, the non-woven fabric composite material is prepared by stacking and hot-pressing polysaccharide-based thermoplastic film and non-woven fabric or paper layer by layer.

[0021] The non-woven fabric can be unused or recycled bio-based non-woven fabric (cellulose, PLA, PBAT and PHA), petroleum-based non-woven fabric (PET, PA66, PU, PE and PP) and blended non-woven fabric of the two;

[0022] The ratio of non-woven fabric and polysaccharide-based thermoplastic material can be adjusted according to specific needs. For example, if the desired non-woven fabric / polysaccharide composite material has mechanical characteristics similar to ordinary engineering plastics, the proportion of non-woven fabric is 55-80wt%, preferably 65wt% and 75wt%.

[0023] If the desired composite material has mechanical characteristics similar to engineering plastics, the proportion of non-woven fabric should be ≤50wt%, preferably 40wt% and 45wt%.

[0024] Preferably, the paper-plastic-aluminum composite material is obtained by hot-pressing at least 7 layers of plastic, paper, plastic, aluminum foil, plastic, paper and plastic.

[0025] In one embodiment of the present application, the molding temperature during hot-pressing is not higher than the thermal flow temperature of the plastic; preferably, the hot-pressing temperature is 130-160℃, for example, 130℃, 135℃, 140℃, 145℃, 150℃.

[0026] In one embodiment of the present application, when the plastic-aluminum material is prepared by emulsion method, the polysaccharide-based thermoplastic material emulsion is an ethanol dispersion solution, and the concentration of the ethanol dispersion solution is 0.1-0.5wt%. Preferably, 0.2-0.3wt%.

[0027] In one embodiment of the present application, the non-woven fabric / paper-plastic-aluminum composite material has good gas and water vapor barrier properties. The oxygen transmission rate of the non-woven fabric / paper-plastic-aluminum composite material is not higher than 0.03cm 3 / m 2 ·24h·0.1MPa, preferably 0.01-0.02cm 3 / m 2• 24h • 0.1MPa; Carbon dioxide permeability not exceeding 0.1cm 3 / m 2 • Days, preferably 0.04-0.08cm 3 / m 2 • Day; water vapor transmission rate not exceeding 0.2 g / m 2 • 24h, preferably 0.1-0.18g / m 2 ·24h.

[0028] The paper-plastic-aluminum composite material of the present invention has good hydrophobicity and gas barrier properties, and can be applied to the packaging of food (milk and juice, etc.), pharmaceuticals and cosmetics.

[0029] The nonwoven composite material of the present invention can be applied to food packaging (packaging for fast food, coffee and straws, etc.), pharmaceutical packaging, electronic product packaging and daily necessities packaging.

[0030] The present invention also provides a method for recycling the above-mentioned composite material, comprising the following steps:

[0031] The non-woven fabric / paper-plastic-aluminum composite material to be recycled is soaked, washed, and separated in a dilute alkaline aqueous solution. After the alkaline aqueous solution containing polysaccharide-based thermoplastic material is separated from other materials, a small amount of acid solution is added dropwise to the recycled dilute alkaline aqueous solution to cause the polysaccharide-based polymer thermoplastic material to settle. After filtration, washing, and drying, the recycled polysaccharide-based polymer thermoplastic material is obtained.

[0032] Polysaccharide-based thermoplastic materials exhibit high water stability during service. After service, the materials can be dissolved and recovered in water by triggering a water-soluble switch with a dilute alkaline solution.

[0033] In one embodiment of the present invention, the dilute alkaline aqueous solution is selected from one or more of NaNO3, NaCO3, NaHCO3, CH3COONa, Na2HPO4 and NaH2PO4 aqueous solutions.

[0034] Preferably, the concentration of the dilute alkaline aqueous solution is not less than 0.005 mol / L, more preferably 0.005-0.03 mol / L.

[0035] For example, 0.008mol / L, 0.010mol / L, 0.012mol / L, 0.014mol / L, 0.016mol / L, 0.018mol / L, 0.020mol / L, 0.022mol / L, 0.024mol / L, 0.026mol / L, 0.028mol / L, 0.030mol / L.

[0036] This invention uses a water-recyclable polysaccharide-based polymer thermoplastic material as a thermal adhesive layer and a hydrophobic layer, and thermally bonds it with paper and aluminum foil to prepare a paper-plastic-aluminum composite material. After use, the paper, plastic and aluminum foil can be completely separated by simply soaking and washing with water.

[0037] This invention uses a water-recyclable polysaccharide-based polymer material as a thermal adhesive layer, and combines it with paper or non-woven fabric to prepare paper-plastic or non-woven fabric composite materials. The recycled composite material can be completely separated from the plastic and paper / non-woven fabric by soaking it in water.

[0038] Among them, a paper-plastic-aluminum composite material with high barrier properties is prepared by using water-recyclable polysaccharide-based thermoplastic material as the thermal adhesive layer and hydrophobic layer, and combining it with cardboard and aluminum foil; a non-woven composite material (paper-plastic composite material) with a wide range of adjustable mechanical properties is prepared by using water-recyclable sugar-based thermoplastic material as the thermal adhesive layer, and combining it with non-woven fabric and paper. The recycling solutions used in the two composite materials may be the same or different. The same means that both can be recycled using a low concentration of alkaline aqueous solution. The different means that the concentration of the alkaline aqueous solution needs to be adjusted within a small range according to the different polysaccharide-based thermoplastic materials.

[0039] The beneficial effects of this invention are:

[0040] 1) The preparation method of the present invention uses water-recyclable polysaccharide-based thermoplastic material as a thermal adhesive layer and a hydrophobic layer, and combines it with cardboard and aluminum foil to prepare a paper-plastic-aluminum composite material with high barrier properties, which can be applied to the packaging fields of food (milk, juice and fast food, etc.), pharmaceuticals and cosmetics.

[0041] 2) The preparation method of the present invention can also use water-recyclable sugar-based thermoplastic material as a thermal adhesive layer to prepare a non-woven composite material with a wide range of adjustable mechanical properties by combining it with non-woven fabric and paper. It can be applied to highway maintenance (crash barriers), public transportation (seats and luggage racks of high-speed rail, automobiles and airplanes, etc.) and daily necessities (furniture).

[0042] 3) The nonwoven composite material and paper-plastic-aluminum composite material prepared by this invention have a simple and efficient recycling process, and the complete separation of multiple components in the composite material can be achieved using a dilute alkaline aqueous solution. Specifically, the process involves soaking, washing, and separating the components in a dilute alkaline aqueous solution, and finally adding a small amount of acid solution dropwise to the recycled dilute alkaline aqueous solution to cause the polysaccharide-based thermoplastic material to settle. After filtration and drying, the recycled polysaccharide-based thermoplastic polymer material is obtained. This recycling process is simple and easy to realize for the practical application and industrialization of paper-plastic composite materials recycling. Attached Figure Description

[0043] Figure 1 This is a photograph of the paper-plastic-aluminum composite material prepared in Example 1;

[0044] Figure 2 This is a flowchart illustrating the recycling process of the paper-plastic-aluminum composite material prepared in Example 1.

[0045] Figure 3 This is a photograph of the nonwoven composite material prepared in Example 3.

[0046] Figure 4 This is a flowchart illustrating the recycling process of the nonwoven composite material prepared in Example 3. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0049] Example 1

[0050] 1) Using microcrystalline cellulose with DP=220 as raw material, a structure was prepared as follows: The cellulose-based thermoplastic material has a glass transition temperature of 105℃. The cellulose-based thermoplastic film is prepared by hot pressing at 150℃, with a film thickness of 15–30 μm. This thermoplastic film serves as both the thermal adhesive layer and the hydrophobic layer. The water contact angle of the hydrophobic layer is 90°, and the water absorption rate is 8% at room temperature over 24 hours.

[0051] Cellulose-based thermoplastic films exhibit switchable water solubility, with the switching mechanism being an alkaline switch.

[0052]

[0053] A paper-plastic-aluminum composite material with high gas barrier properties was prepared by layering cellulose-based thermoplastic, cardboard, and aluminum foil in the following order: plastic, cardboard, plastic, aluminum foil, plastic, cardboard, and plastic. The layers were then hot-pressed at 150°C for 1-3 minutes. Its oxygen permeability was 0.016 cm⁻¹. 3 / m 2 • 24h • 0.1MPa, carbon dioxide permeability 0.063cm 3 / m 2 • Day, water vapor permeability 0.15 g / m 2 ·24h.

[0054] Figure 1 This is a photograph of the paper-plastic-aluminum composite material prepared in Example 1. (From...) Figure 1As can be seen, the cellulose-based thermoplastic material is firmly bonded to the cardboard and aluminum foil.

[0055] 2) The paper-plastic-aluminum composite material prepared above can be recycled and reused using a dilute alkaline solution. The recycling process is detailed below. Figure 2 The specific recycling process is as follows:

[0056] The paper-plastic-aluminum composite material was immersed in a 0.05 mol / L dilute NaHCO3 alkaline solution for 3 hours. As the polysaccharide-based thermoplastic dissolved in the solution, the cardboard and aluminum foil gradually peeled off. The water-absorbing cardboard sank to the bottom of the solution, while the aluminum foil remained suspended. Filtration separated the paper, aluminum, and the alkaline solution containing the polysaccharide-based thermoplastic from the mixture. Subsequently, a small amount of acid (HCl) was added to the alkaline solution for precipitation, followed by filtration, washing, and drying to obtain the regenerated cellulose-based thermoplastic polymer material.

[0057] Example 2

[0058] The structure is A 0.2wt% ethanol dispersion of cellulose-based polymer thermoplastic material was prepared. This dispersion was sprayed onto the top and bottom surfaces of cardboard and aluminum foil respectively. After the emulsion formed a dry and dense film on the surface of cardboard and aluminum foil, cardboard, aluminum foil and cardboard were stacked layer by layer and hot-pressed at 160℃ for 1-3 minutes to obtain paper-plastic-aluminum composite material.

[0059] Tests showed that the oxygen permeability of the paper-plastic-aluminum composite material was 0.021 cm⁻¹. 3 / m 2 • 24h • 0.1MPa, carbon dioxide permeation rate 0.082 cm 3 / m 2 •day, water vapor permeability 0.16 g / m 2 ·24h.

[0060] The recycling process of the paper-plastic-aluminum composite material obtained in Example 2 is the same as that in Example 1.

[0061] Example 3

[0062] Taking the preparation of nonwoven composite materials with mechanical properties comparable to engineering plastics as an example, 4g of nonwoven fabric and 6g of the structure of... Starch-based thermoplastic film (glass transition temperature 110℃) is pre-bonded layer by layer on a hot plate at 150℃, and then hot-pressed at 125℃ and 3MPa for 3-5 minutes to obtain a non-woven composite material with high mechanical strength, with a flexural strength as high as 120MPa (the flexural strength of PA66 is 105MPa).

[0063] Figure 3This is a photograph of the nonwoven composite material prepared in Example 3. (From...) Figure 3 As can be seen, starch-based thermoplastics and non-woven fabrics are combined to form a uniform composite plastic sheet.

[0064] The recycling process of the nonwoven composite material obtained in Example 3 is the same as that in Examples 1 and 2. The dissolution and recycling process is described in [link to example]. Figure 4 As can be seen from the figure, the nonwoven composite material gradually peels off as the starch-based thermoplastic material dissolves in the low-concentration alkaline aqueous solution.

[0065] Example 4

[0066] Using the starch-based thermoplastic material from Example 3 as the thermal adhesive layer and hydrophobic layer, the starch-based thermoplastic material was melted in a casting machine (casting machine temperatures: zone 1 140°C, zone 2 160°C, zone 3 165°C, zone 4 175°C; screw speed 160 r / min). The molten film obtained by casting was then rolled and laminated with cardboard. During this process, the cardboard needed to be cast on both sides. Finally, the cardboard with starch-based thermoplastic cast film on both sides was stacked layer by layer with aluminum foil and hot-pressed at 150°C to obtain a paper-plastic-aluminum composite material.

[0067] Testing showed that the oxygen permeability of the prepared paper-plastic-aluminum composite material was 0.035 cm⁻¹. 3 / m 2 • 24h • 0.1MPa, carbon dioxide permeation rate 0.089 cm 3 / m 2 • Day, water vapor permeability 0.27 g / m 2 ·24h.

[0068] The recycling process of the paper-plastic-aluminum composite material obtained in Example 4 is the same as that in the above examples.

[0069] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A water-recyclable composite material, characterized in that, Including polysaccharide-based polymer thermoplastic materials; the polysaccharide-based polymer thermoplastic materials are polysaccharide derivatives with dual functional characteristics of switchable water solubility and thermoplastic processability.

2. The composite material according to claim 1, characterized in that, The composite material is a non-woven fabric composite material or a paper-plastic-aluminum composite material. The non-woven fabric composite material is prepared by using a water-recyclable polysaccharide-based polymer thermoplastic material as a thermal adhesive layer and combining it with paper or non-woven fabric. The paper-plastic-aluminum composite material is prepared by thermally bonding paper and aluminum foil with a water-recyclable polysaccharide-based polymer thermoplastic material as the thermal adhesive layer and hydrophobic layer.

3. The composite material according to claim 1, characterized in that, The switch-type water-soluble switch is an acid switch or a base switch; the reaction of the acid switch is... The reaction of the alkaline switch is 4. The composite material according to claim 3, characterized in that, The polysaccharide-based thermoplastic polymer retains or introduces some hydroxyl groups; the polysaccharide-based thermoplastic polymer also introduces carboxyl-containing functional groups that coordinate with metallic aluminum, preferably... Or -CH2COOH.

5. The composite material according to claim 3, characterized in that, The polysaccharide-based polymer thermoplastic material is a polysaccharide derivative with a glass transition temperature of 100-140℃. Preferred polysaccharide derivatives have a glass transition temperature of 105-130°C, for example, 110°C and 120°C.

6. The composite material according to claim 2, characterized in that, The hydrophobic layer may be made of the same or different material as the thermal adhesive layer. Preferably, the water contact angle of the hydrophobic layer is not less than 90°, preferably 90°-98°, and the water absorption rate at room temperature for 24 hours does not exceed 15%, preferably 8%-12%. Preferably, the hydrophobic layer and the thermal adhesive layer have the same or similar glass transition temperatures, preferably 100-120°C, for example, 100°C, 110°C, or 120°C. Preferably, the thickness of the polysaccharide-based polymer plastic film is not higher than 40 μm, and more preferably 5–35 μm. For example, 8μm, 10μm, 15μm, 20μm, 25μm and 30μm.

7. The composite material according to any one of claims 1 to 6, characterized in that, The polysaccharide is selected from one or more of cellulose, starch, chitosan and xylan, preferably one or more of cellulose, starch and xylan.

8. The composite material according to any one of claims 1 to 6, characterized in that, The paper-plastic-aluminum composite material is prepared by hot-pressing polysaccharide-based thermoplastic film, paper, and aluminum foil layer by layer; or by preparing paper-plastic and aluminum-plastic materials respectively using casting and emulsion methods, and then hot-pressing the two together. Preferably, the paper-plastic composite material is obtained by hot pressing polysaccharide-based thermoplastic film and non-woven fabric or paper layer by layer. Preferably, the paper-plastic-aluminum composite material is obtained by hot pressing at least seven layers of plastic, paper, plastic, aluminum foil, plastic, paper and plastic. Preferably, the molding temperature during hot pressing is not higher than the heat flow temperature of the plastic; preferably, the hot pressing temperature is 130-160℃, for example, 130℃, 135℃, 140℃, 145℃, 150℃. Preferably, when preparing aluminum-plastic materials using the emulsion method, the polysaccharide-based polymer thermoplastic material emulsion is an ethanol dispersion with a concentration of 0.1-0.5 wt%, preferably 0.2-0.3 wt%. Preferably, the oxygen permeability of the nonwoven fabric or paper-plastic-aluminum composite material is not higher than 0.03 cm. 3 / m 2 • 24h • 0.1MPa, preferably 0.01-0.02cm 3 / m 2 • 24h • 0.1MPa; Carbon dioxide permeability not exceeding 0.1cm 3 / m 2 • Days, preferably 0.04-0.08cm 3 / m 2 • Day; water vapor transmission rate not exceeding 0.2 g / m 2 • 24h, preferably 0.1-0.18g / m 2 ·24h.

9. A method for recycling the composite material according to any one of claims 1 to 8, characterized in that, Includes the following steps: The non-woven fabric / paper-plastic-aluminum composite material to be recycled is soaked, washed, and separated in a dilute alkaline aqueous solution. Finally, a small amount of acid solution is added dropwise to the recycled dilute alkaline aqueous solution to cause the polysaccharide-based thermoplastic material to settle. After filtration and drying, the recycled polysaccharide-based thermoplastic material is obtained. The dilute alkaline aqueous solution is selected from one or more of the following: NaNO3, NaCO3, NaHCO3, CH3COONa, Na2HPO4, and NaH2PO4 aqueous solutions. Preferably, the concentration of the dilute alkaline aqueous solution is not less than 0.005 mol / L, more preferably 0.005-0.03 mol / L.

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