Method and system for recycling polyvinylidene chloride-containing composites

Abstract

A method for recovering a polyolefin and polyvinylidene chloride composite material. The composite material is subjected to a polar aprotic solvent to dissolve the polyvinylidene chloride from the composite material into a solution of the polar aprotic solvent. Undissolved composite material from the solution can be collected and rinsed. The collected undissolved composite material is substantially free of polyvinylidene chloride. Polyvinylidene chloride can be precipitated from the solution. The precipitated polyvinylidene chloride is substantially pure polyvinylidene chloride.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 114,035, filed November 16, 2020, entitled “Method and System for Recycling Composite Materials Containing Polyvinylidene Chloride,” the entire contents of which are incorporated herein by reference. Background Technology

[0003] The subject matter disclosed herein relates to a method for recovering polyvinylidene chloride (PVDC) from composite materials. More specifically, it relates to a method for recovering PVDC from a composite material containing PVDC and at least one polyolefin.

[0004] Plastic recycling is a solution to reduce the demand for virgin materials. Recycling and reusing plastics diverts potential waste from landfills and reduces the need for virgin plastics.

[0005] Many plastics are made from blends of polymers. Multilayer packaging materials typically contain blends of polymers or different polymers contained in different layers. These different polymers are used to achieve different performance properties. For example, many foods require high oxygen and / or vapor barrier protection to ensure a longer shelf life and enhanced flavor. Polyvinylidene chloride (PVDC) is frequently used in multilayer structures due to its excellent barrier properties. However, plastics containing both polyolefins and PVDC are difficult to recycle. PVDC-containing membranes cannot be mechanically recycled because this material has a low thermal degradation temperature. Even small amounts of PVDC impurities in polyolefins can lead to high levels of black carbon formation, which contaminates other polymers. Therefore, PVDC-containing membranes are often sent to landfills.

[0006] To recycle plastic materials, such as membranes containing multiple resins, it is necessary to separate the resins. A useful method for separating resins is through mechanical recycling, such as sedimentation separation, which can be used to separate different compounds. For example, in blends containing polyolefins and polyvinylidene chloride, since the polyolefin has a concentration of less than 1.0 g / cm³... 3 Their density is such that they float in water (or have a density of 1.0 g / cm³). 3 In other liquids (or higher), polyvinylidene chloride has a concentration greater than 1.6 g / cm³. 3The density of polyvinylidene chloride (PVDC) is high, and therefore it sinks in water. This allows PVDC and polyolefins to be collected as separate streams. Further separation can be achieved by changing the specific gravity of the solutions used in flotation separation, thereby altering the mixing ratio of the solutions. Other plastic recycling methods are described in SMA1-Salem, P. Lettieri, J. Baeyens, “Recycling and recovery routes of plastic solid waste (PSW): A review,” Waste Management, Vol. 29, No. 10, October 2009, pp. 2625-2643, ISSN 0956-053X. While mechanical separation is useful for separating plastic materials, it does have limitations when it comes to composite materials.

[0007] Composite materials, such as blends of plastic materials or multilayered composites with different compositions, cannot be mechanically separated on their own. Normal crushing and grinding processes merely break the material into smaller fragments. Because the layers do not separate, this does not adequately separate the resin. While some separation may occur (especially in the case of grinding), both streams separated by sedimentation and flotation remain contaminated with components from the other stream. Therefore, even after mechanical recovery and sedimentation / flotation, the collected polyolefin stream contains a certain amount of polyvinylidene chloride (PVDC), typically about 5% by weight or more. Even trace amounts of PVDC in the polyolefin stream are problematic when attempting to recycle polyolefins. PVDC has a low thermal degradation temperature and turns brown or black when polyolefins are heated and converted into pellets. This prevents the collected polyolefins from being reused or processed as virgin-like materials.

[0008] Similarly, polyvinylidene chloride (PVDC) contains a certain amount of polyolefins. Even small amounts of polyolefins negatively impact the barrier properties of PVDC. This prevents the collected PVDC from being reused as a barrier resin.

[0009] The above discussion is provided for general background information only and is not intended to help determine the scope of the subject matter for which protection is claimed.

[0010] Brief description

[0011] A method for recovering polyolefin and polyvinylidene chloride (PVDC) composites. The composite is subjected to a polar aprotic solvent to dissolve the PVDC from the composite into a solution of the polar aprotic solvent. Undissolved composite material from the solution can be collected and rinsed. The collected undissolved composite material is substantially free of PVDC. PVDC can be precipitated from the solution. The precipitated PVDC is substantially pure PVDC.

[0012] One advantage that can be achieved in some publicly disclosed implementations of the practical approach is that the composite material containing polyolefins and polyvinylidene chloride can be recycled into a usable stream.

[0013] In one exemplary embodiment, a method for recycling a composite material is disclosed. The method includes the steps of: a) providing a composite material having a polyolefin and polyvinylidene chloride; b) subjecting the composite material to a polar aprotic solvent to dissolve at least a portion of the composite material in a solution having the polar aprotic solvent; c) separating undissolved composite material from the solution, the solution containing dissolved polyvinylidene chloride; and d) collecting the undissolved composite material. The collected undissolved composite material contains less than any of the following amounts of polyvinylidene chloride: 1.0 wt%, 0.9 wt%, 0.8 wt%, 0.7 wt%, 0.6 wt%, 0.5 wt%, 0.4 wt%, 0.3 wt%, 0.2 wt%, or 0.1 wt%.

[0014] In another exemplary embodiment, a method for recycling a composite material is disclosed. The method includes the steps of: a) providing a composite material having a polyolefin and polyvinylidene chloride; b) subjecting the composite material to a polar aprotic solvent to dissolve at least a portion of the composite material in a solution having the polar aprotic solvent; c) separating undissolved composite material from the solution, the solution containing dissolved polyvinylidene chloride; and d) precipitating polyvinylidene chloride from the solution. The precipitated polyvinylidene chloride has a content of at least 99.0 wt%, 99.1 wt%, 99.2 wt%, and...

[0015] 99.3% by weight, 99.4% by weight, 99.5% by weight, 99.6% by weight, 99.7% by weight

[0016] Purity of 99.8% by weight or 99.9% by weight.

[0017] In another exemplary embodiment, a system for recovering a composite material is disclosed. The system includes a pulverizer or mill to reduce the size of the composite material, which comprises at least a polyolefin and polyvinylidene chloride. A solvent bath having a polar aprotic solvent to dissolve at least some of the composite material into the solution. A filter or sieve for separating undissolved composite material from the solution containing dissolved polyvinylidene chloride. A collector for precipitating and collecting polyvinylidene chloride from the solution. The precipitated polyvinylidene chloride has a purity of at least 99.0 wt%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt%, 99.5 wt%, 99.6 wt%, 99.7 wt%, 99.8 wt%, or 99.9 wt%.

[0018] This brief description of the invention is intended only to provide a concise overview of the subject matter disclosed herein based on one or more illustrative embodiments, and is not intended to be used as guidance for interpreting the claims or to limit or restrict the scope of the invention, which is defined only by the appended claims. This brief description is provided to present, in a simplified form, an illustrative choice of concepts that will be further described in the detailed description below. This brief description is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter. The claimed subject matter is not limited to embodiments that address any or all of the disadvantages mentioned in the background art. Attached Figure Description

[0019] The invention can be described in detail with reference to certain embodiments, some of which are shown in the accompanying drawings, so that its features can be understood. However, it should be noted that the drawings illustrate only certain embodiments of the invention and should not be considered as limiting its scope, as the scope of the invention covers other equivalent embodiments. The drawings are not necessarily to scale, and the emphasis is generally placed on illustrating the features of certain embodiments of the invention. In the drawings, the same reference numerals are used to denote the same parts in the various views. Therefore, for a further understanding of the invention, reference can be made to the following detailed description, taken in conjunction with the accompanying drawings, wherein:

[0020] Figure 1 This is an exemplary flowchart illustrating a method for recycling composite materials containing polyvinylidene chloride.

[0021] Figure 2 This is an exemplary flowchart illustrating a method for recycling composite materials containing polyvinylidene chloride.

[0022] Figure 3 This is an exemplary flowchart illustrating a method for recycling composite materials containing polyvinylidene chloride.

[0023] Figure 4 The following image shows the resulting product: the ground barrier bag was heated at 350°F for 2 minutes in a hydraulic press to become a pressed product.

[0024] Figure 5 The following image shows the product obtained after the ground barrier was subjected to cyclohexanone at 50°C for 2 hours, and then the resulting solid was pressed in a hydraulic press at 350°F for 2 minutes.

[0025] Figure 6 The following image shows the product obtained after the ground barrier was subjected to cyclohexanone at 80°C for 6 hours, and then the resulting solid was pressed in a hydraulic press at 350°F for 2 minutes.

[0026] Figure 7The following image shows the result of exposing the ground barrier to dimethyl sulfoxide at 80°C for 2 hours, followed by pressing the resulting solid in a hydraulic press at 350°F for 2 minutes.

[0027] Figure 8 The following image shows the result of exposing the ground barrier to dimethyl sulfoxide at 80°C for 6 hours, followed by pressing the resulting solid in a hydraulic press at 350°F for 2 minutes.

[0028] Figure 9 The following image shows the product obtained after the ground barrier was subjected to N-methyl-2-pyrrolidone at 80°C for 2 hours, followed by pressing the resulting solid in a hydraulic press at 3500°F for 2 minutes.

[0029] Figure 10 The following image shows the product obtained after the ground barrier was subjected to N-methyl-2-pyrrolidone at room temperature for 3 hours, followed by pressing the resulting solid in a hydraulic press at 3500°F for 2 minutes.

[0030] Figure 11 The following image shows the product obtained after the ground barrier was subjected to dihydro-L-glucanone at 50°C for 5 hours, and then the resulting solid was pressed in a hydraulic press at 350°F for 2 minutes.

[0031] Figure 12 The following image shows the product obtained after the ground barrier was subjected to dihydro-L-glucanone at 90°C for 5 hours, followed by pressing the resulting solid in a hydraulic press at 350°F for 2 minutes.

[0032] Figure 13 The following image shows the product obtained after the ground barrier was subjected to triethyl phosphate at 90°C for 1 hour, followed by pressing the resulting solid in a hydraulic press at 350°F for 2 minutes.

[0033] Figure 14 The following image shows the product obtained after the ground barrier was subjected to tetrahydrofuran for 1.5 hours at room temperature, followed by pressing the resulting solid in a hydraulic press at 350°F for 2 minutes.

[0034] Figure 15 This is the FTIR spectrum of the powder precipitated from dimethyl sulfoxide solvent.

[0035] Figure 16 This is the FTIR spectrum of a powder precipitated from an N-methyl-2-pyrrolidone solvent.

[0036] Figure 17 This is the FTIR spectrum of the powder precipitated from dihydro-L-glucosamine solvent.

[0037] Figure 18This is the FTIR spectrum of the powder precipitated from triethyl phosphate solvent.

[0038] Figure 19 This is the FTIR spectrum of the powder precipitated from tetrahydrofuran solvent.

[0039] Figure 20 It is an image of cut strips of a multilayer film.

[0040] Figure 21 yes Figure 20 Image of the cut strip in tetrahydrofuran solution.

[0041] Figure 22 From Figure 21 The solution shown is separated into layers after being taken out. Figure 20 The image of the stripes.

[0042] Detailed description

[0043] Composite materials, such as multilayer films, are typically made of layers of different resins. Each layer may be a single resin compound or a blend of resins. Examples include, but are not limited to, the following resins, including but not limited to, polyolefins, polyesters, polypropylene, methacrylic acid copolymers, ionomers, ethylene-methacrylic acid copolymers, ethylene-vinyl acetate, methylene-vinyl acetate, ethylene vinyl alcohol, and polyvinylidene chloride. As used herein, the term "film" includes plastic mesh, whether it is a membrane or a sheet. The membrane may have a thickness of 0.25 mm or less, or the following thicknesses: 0.5 to 30 mils, or 0.5 to 15 mils, or 1 to 10 mils, or 1 to 8 mils, or 1.1 to 7 mils, or 1.2 to 6 mils, or 1.3 to 5 mils, or 1.5 to 4 mils, or 1.6 to 3.5 mils, or 1.8 to 3.3 mils, or 2 to 3 mils, or 1.5 to 4 mils, or 0.5 to 1.5 mils, or 1 to 1.5 mils, or 0.7 to 1.3 mils, or 0.8 to 1.2 mils, or 0.9 to 1.1 mils.

[0044] The multilayer membranes described herein may include at least and / or at most any of the following numbers of layers: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15. As used herein, the term "layer" refers to a discrete membrane assembly that extends substantially co-exists with the membrane and has a substantially uniform composition. Where two or more directly adjacent layers have substantially the same composition, these two or more adjacent layers may be considered a single layer for the purposes of this application. In one embodiment, the multilayer membrane utilizes microlayers. Each microlayer portion may include 10 to 1,000 microlayers.

[0045] As used herein, the term "polyolefin" refers to olefin polymers and copolymers, particularly ethylene and propylene polymers and copolymers, as well as polymeric materials having at least one olefin comonomer. Polyolefins can be linear, branched, cyclic, aliphatic, aromatic, substituted, or unsubstituted. The term polyolefin includes olefin homopolymers, olefin copolymers, copolymers of olefins and non-olefin comonomers that can copolymerize with olefins (such as vinyl monomers), and the aforementioned modified polymers. Modified polyolefins include modified polymers prepared by copolymerizing or grafting olefin homopolymers or copolymers thereof with unsaturated carboxylic acids such as maleic acid, fumaric acid, etc., or their derivatives such as acid anhydrides, ester metal salts, etc. It can also be obtained by introducing unsaturated carboxylic acids such as maleic acid, fumaric acid, etc., or their derivatives such as acid anhydrides, ester metal salts, etc., into olefin homopolymers or copolymers. In one embodiment, the heat-sealing layer is primarily composed of polyolefin.

[0046] Ethylene homopolymers or copolymers refer to ethylene homopolymers, such as low-density polyethylene; ethylene / α-olefin copolymers, such as those defined below; and other ethylene copolymers, such as ethylene / vinyl acetate copolymers; ethylene / alkyl acrylate copolymers; or ethylene / (meth)acrylic acid copolymers. Ethylene / α-olefin copolymers as used herein refer to copolymers of ethylene with one or more comonomers selected from C4-C10 α-olefins such as butene-1, hexene-1, octene-1, etc., wherein the copolymer molecules comprise long polymer chains having relatively few side chains from the α-olefins reacting with ethylene. This molecular structure contrasts with conventional high-density or medium-density polyethylene, which is highly branched relative to ethylene / α-olefin copolymers and contains both long-chain and short-chain branches. Ethylene / α-olefin copolymers include one or more of the following: 1) high-density polyethylene, for example having a density greater than 0.94 g / cm³. 3 2) Medium-density polyethylene, for example, with a density of 0.93-0.94 g / cm³. 3 3) Linear medium-density polyethylene, for example, with a density of 0.926-0.94 g / cm³. 3 4) Low-density polyethylene, for example, with a density of 0.915-0.939 g / cm³. 3 5) Linear low-density polyethylene, for example, with a density of 0.915-0.935 g / cm³. 3 6) Extremely low or ultra-low density polyethylene, for example, having a density of less than 0.915 g / cm³. 3 The density and uniformity of the ethylene / α-olefin copolymer. Uniform ethylene / α-olefin copolymers include those having a density less than approximately any of the following: 0.925, 0.922, 0.92, 0.917, 0.915, 0.912, 0.91, 0.907, 0.905, 0.903, 0.90, and 0.86 g / cm³.3 Unless otherwise specified, all densities mentioned herein are measured according to ASTM D1505.

[0047] Polyvinylidene chloride (PVDC) refers to homopolymers or copolymers of vinylidene chloride. PVDC copolymers contain a major amount of vinylidene chloride and minor amounts of one or more comonomers. A major amount is defined as one that comprises more than 50%.

[0048] To recycle composite materials, such as membranes containing multiple resins, resin separation is necessary. While mechanical recycling techniques can be used to separate different components, these techniques are not sufficient to completely separate composite materials. As used herein, composite materials are materials containing multiple layers bonded together by lamination, coating, or co-extrusion, said layers having different compositions, or containing a single layer of a blend of two or more different kinds of compounds. For example, a multilayer membrane with a barrier layer, wherein the barrier layer is polyvinylidene chloride (PVDC), and the other layers of the membrane comprise polyolefins. Another example of composite material articles includes a single-layer structure, which is a blend of PVDC and polyolefins. Other composite materials include blends or layers of PVDC and polyolefins plus one or more of the following additional resins: polyamides, polyesters, polypropylenes, ionomers, and vinyl alcohol.

[0049] Polyamides refer to polymers having amide bonds along their molecular chains, and include synthetic polyamides such as nylon. Furthermore, the term includes two other types: polymers comprising repeating units derived from monomers such as caprolactam, which are polymerized to form polyamides; polymers of diamines and diacids; and copolymers of two or more amide monomers, including nylon terpolymers, sometimes referred to in the art as "copolyamides". Polyamides include those of the type that can be formed by the condensation polymerization of one or more diamines with one or more diacids and / or those of the type that can be formed by the condensation polymerization of one or more amino acids. Polyamides also include amorphous, crystalline or partially crystalline, aromatic or partially aromatic polyamides.

[0050] Polyesters include polymers prepared by: 1) condensation of polyfunctional carboxylic acids and polyfunctional alcohols, 2) polycondensation of hydroxycarboxylic acids, and 3) polymerization of cyclic esters (e.g., lactones). Polyesters may be selected from random polymers or block polymers. Polyesters may be thermoplastic. Polyesters may be substantially amorphous or partially crystalline (semi-crystalline).

[0051] In some embodiments, the size of the composite material is reduced without applying any additional mechanical recycling techniques. Size reduction is achieved by pulverizing or grinding the composite material. Commercial pulverizers and grinders are used to reduce the size of plastic materials. When pulverized, the average size of the material is 0.1 cm to 5 cm, 0.3 cm to 3 cm, or 0.5 cm to 2 cm in one or both directions. While other sizes are anticipated, it should be understood that smaller sizes can facilitate a faster dissolution rate of polyvinylidene chloride in subsequent processing steps. When ground, the particle size is typically reduced to less than 1.6 cm, 1.4 cm, 1.2 cm, 1.0 cm, 0.8 cm, or 0.6 cm. In some embodiments, mechanical recycling techniques are used to separate at least some material from the composite material. For example, flotation separation can be used to separate the floating stream from the sinking stream. In blends containing polyolefins and polyvinylidene chloride, due to the polyolefin having a size of less than 1.0 g / cm³, the particle size is reduced to less than 1.0 g / cm³. 3 Their density is such that they float in water (or have a density of 1.0 g / cm³). 3 In other liquids (or higher), polyvinylidene chloride has a concentration greater than 1.6 g / cm³. 3 The density of polyvinylidene chloride (PVDC) is high, and therefore it sinks in water. Thus, PVDC and polyolefins are allowed to be collected as separate streams. Further separation can be achieved by changing the mixing ratio of the solutions used in flotation separation, thereby altering the specific gravity of the solutions. As mentioned above, even after sedimentation-flotation separation, both the sinking and floating streams tend to be contaminated by material from the other stream.

[0052] To remove polyvinylidene chloride (PVDC) from the composite material, the composite material is subjected to a polar aprotic solvent. The polar aprotic solvent attracts PVDC to the solvent, while the other components of the composite material remain in solid form. The remaining solids are collected from the polar aprotic solvent. In one embodiment, the collected solids are then rinsed and dried. The solids after rinsing and drying contain less than one of the following PVDC concentrations: 1.0 wt%, 0.9 wt%, 0.8 wt%, 0.7 wt%, 0.6 wt%, 0.5 wt%, 0.4 wt%, 0.3 wt%, 0.2 wt%, or 0.1 wt%. In embodiments where the composite material comprises only polyvinylidene chloride and polyolefin, the washed and dried solids have a polyolefin purity of at least 99.0 wt%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt%, 99.5 wt%, 99.6 wt%, 99.7 wt%, 99.8 wt%, or 99.9 wt%. In some embodiments, the remaining solid material is also melted and granulated.

[0053] In the embodiments, the polar aprotic solvent is at least 90%, 95%, 99%, or substantially all of a substance selected from N-methyl-2-pyrrolidone, cellulose-derived dipolar aprotic solvents such as dihydro-L-glucanone, triethyl phosphate, tetrahydrofuran, and blends thereof. In the embodiments, the treatment of the polyolefin and polyvinylidene chloride with the polar aprotic solvent is a solvent decomposition reaction. The ratio of the polar aprotic solvent to the solid material is at least any one of the following: 30:70, 40:60, 50:50, 60:40, 70:30, or 80:20, measured as a weight percentage.

[0054] The method of subjecting polyolefin and polyvinylidene chloride materials to a polar aprotic solvent is carried out at lower temperatures and pressures to reduce energy requirements. In one embodiment, the method is carried out at standard atmospheric pressure. In other embodiments, the method is carried out at elevated pressures, such as 200 kPa–1000 kPa. In one embodiment, the polar aprotic solvent has a temperature below any of the following: 160°C, 150°C, 140°C or 130°C, 120°C, 110°C, 100°C, 90°C, 80°C, 70°C, or 60°C. In some embodiments, the polar aprotic solvent is at room temperature. In one embodiment, the pressure and temperature are adjusted such that at least 99% by weight of the polyvinylidene chloride is drawn into the solution in less than 5, 4, 3, 2, or 1 hour.

[0055] In one embodiment, after removing the solid material from the solvent, polyvinylidene chloride (PVDC) is precipitated from the solvent and collected. PVDC can be precipitated from the solution using any suitable non-solvent such as water and / or alcohol. In one embodiment, the precipitated PVDC has a purity of at least 99.0 wt%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt%, 99.5 wt%, 99.6 wt%, 99.7 wt%, 99.8 wt%, or 99.9 wt%. In another embodiment, the collected PVDC can be stabilized and prepared for reuse in PVDC operations.

[0056] It should be understood that additional sieving or filtration can be used to collect the solid material and precipitated polyvinylidene chloride from the polar aprotic solvent. Sieving and filtration equipment is known to those skilled in the art. To improve the efficiency of the method, the solvent can be recycled in steady-state operation or purified by any suitable technique and reused in batch methods.

[0057] Turn now Figure 1This document shows an exemplary flow chart of a system and method for recycling composite materials containing polyvinylidene chloride and polyolefins according to an embodiment. The composite material is provided and pulverized into smaller particle sizes. Although not shown, optional mechanical recycling techniques may be used. The pulverized composite material contains polyolefins and polyvinylidene chloride. In an embodiment, the composite material contains at least 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, or 75 wt% polyolefins. In an embodiment, the composite material contains at least 5 wt%, 10 wt%, 15 wt%, 20 wt%, or 25 wt% polyvinylidene chloride. In an embodiment, the composite material is a multilayer film.

[0058] The composite material is subjected to a polar aprotic solvent to attract at least some of the composite material into the solution. In an embodiment, the polar aprotic solvent is used at a low operating temperature and at standard or low pressure. The lower operating temperature allows for reduced energy costs. In an embodiment, the polar aprotic solvent has a temperature below any of the following: 160°C, 150°C, 140°C or 130°C, 120°C, 110°C, 100°C, 90°C, 80°C, 70°C, or 60°C. In an embodiment, the composite material is subjected to the polar aprotic solvent at a standard pressure ±50 kPa. Polyvinylidene chloride is attracted into the solution, while the remaining resin of the composite material remains solid. In an embodiment, the polyvinylidene chloride is attracted into the solution via a solvent decomposition reaction.

[0059] Solids are removed from the solvent. In some embodiments, solids are removed from the solvent by sieving or filtration. The collected solids, which are undissolved composite materials, are then rinsed, resulting in a material having less than 1.0 wt%, 0.9 wt%, 0.8 wt%, 0.7 wt%, 0.6 wt%, 0.5 wt%, 0.4 wt%, 0.3 wt%, 0.2 wt%, or 0.1 wt% of polyvinylidene chloride.

[0060] In some embodiments, the undissolved composite material collected from the rinsing is then melted and granulated using methods known to those skilled in the art. For example, a granulation method for a polymer as described in U.S. Patent 6,339,109 to Day et al. The resulting granules are essentially pure polyolefins.

[0061] After removing the solid from the solution, polyvinylidene chloride (PVDC) is precipitated from the solution. The precipitated PVDC can be filtered, washed, dried, and collected. In some embodiments, the collected PVDC is then stabilized by known methods and reused as a barrier material. The collected PVDC has a purity of at least 99.0 wt%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt%, 99.5 wt%, 99.6 wt%, 99.7 wt%, 99.8 wt%, or 99.9 wt%.

[0062] In some implementations, the solvent is reused, making the method more efficient and less wasteful. In some implementations, the method is part of a recycling system.

[0063] Turn now Figure 2 This is another exemplary flow diagram of a system and method for recycling composite materials containing polyvinylidene chloride and polyolefins according to an implementation scheme. The method is similar to that described herein. Figure 1 The method described involves grinding the material instead of pulverizing it. Grinding the material typically results in a smaller particle size and can partially separate some layers from a multilayered structure.

[0064] Turn now Figure 3 This is another exemplary flow diagram of a system and method for recycling composite materials containing polyvinylidene chloride and polyolefins according to an implementation scheme. The method is consistent with the description herein. Figure 3 The method is similar, wherein additional mechanical separation is performed after grinding the composite material and before exposing the material to a solvent. In an embodiment, incompatible materials can be removed from the method before exposing the material to a solvent. Example:

[0065] A multilayer membrane B2690 containing 16% by weight of polyvinylidene chloride, commercially available from Sealed Air, was used in the following examples. 10 g of the milled membrane was mixed with 50 mL of the listed solvent and stirred with a magnetic stirrer at the indicated temperature and time. The mixture was then filtered to separate undissolved material. The solids were washed with an additional 10–15 mL of solvent and dried overnight in a vacuum oven.

[0066] The solids are analyzed by heating the sample in a hydraulic press at 350°F for 2 minutes to form a pressed film. In this test, pure polyolefins will remain colorless, while polyvinylidene chloride will turn dark brown / black. Any brown / black discoloration on each test sample indicates whether polyvinylidene chloride has not been completely removed.

[0067] The solvent-soluble component containing dissolved polyvinylidene chloride (PVDC) is treated with water or alcohol such as methanol, ethanol, or isopropanol to precipitate PVDC from the solution. The solid material is filtered and dried in a vacuum oven. The precipitated dried powder is analyzed by FTIR to confirm its purity.

[0068] control material

[0069] 10g of the milled membrane was not subjected to any solvent. Figure 4 The image shows a polished film after hot pressing as a control to illustrate the discoloration of polyvinylidene chloride in the material due to thermal degradation of polyvinylidene chloride.

[0070] Comparison - Cyclohexanone

[0071] As described above, 10g of the milled membrane was placed in 50mL of cyclohexanone at 50°C for 2 hours. Figure 5 As shown, the pressed solid exhibits discoloration due to the thermal degradation of polyvinylidene chloride.

[0072] To test for additional solvent exposure, as described above, 10 g of the milled membrane was placed in 50 mL of cyclohexanone at 80°C for 6 hours. Figure 6 As shown, the pressed solid exhibits discoloration due to the thermal degradation of polyvinylidene chloride.

[0073] dimethyl sulfoxide

[0074] 10g of the ground membrane was placed in 50mL of dimethyl sulfoxide at 80°C for 2 hours. Figure 7 As shown, the pressed solid exhibits discoloration due to the thermal degradation of polyvinylidene chloride.

[0075] To test for further solvent exposure, as described above, 10 g of the milled membrane was placed in 50 mL of dimethyl sulfoxide at 80°C for 6 hours. The resulting pressed product appeared cleaner. However, as... Figure 8 As shown, some discoloration still exists due to the thermal degradation of polyvinylidene chloride.

[0076] N-Methyl-2-pyrrolidone

[0077] As described above, 10g of the milled membrane was placed in 50mL of N-methyl-2-pyrrolidone at 80°C for 2 hours. Figure 9 As shown, the pressed solid did not show any color change, indicating that the sample lacked polyvinylidene chloride.

[0078] As described above, 10g of the milled membrane was placed in 50mL of N-methyl-2-pyrrolidone at room temperature for 3 hours. Figure 10As shown, the pressed solid did not show any color change, indicating that the sample lacked polyvinylidene chloride.

[0079] dihydro-L-glucanone

[0080] As described above, 10g of the milled membrane was placed in 50mL of dihydro-L-glucosamine at 50°C for 5 hours. Figure 11 As shown, the pressed solid exhibits discoloration due to the thermal degradation of polyvinylidene chloride.

[0081] As described above, 10g of the milled membrane was placed in 50mL of dihydro-L-glucosamine at 90°C for 5 hours. Figure 12 As shown, the pressed solid did not show any color change, indicating that the sample lacked polyvinylidene chloride.

[0082] Triethyl phosphate

[0083] As described above, 10g of the milled membrane was placed in 50mL of triethyl phosphate at 90°C for 1 hour. Figure 13 As shown, the pressed solid did not show any color change, indicating that the sample lacked polyvinylidene chloride.

[0084] Tetrahydrofuran

[0085] As described above, 10 g of the ground membrane was placed in 50 mL of tetrahydrofuran at room temperature for 1.5 hours. While polyvinylidene chloride (PVDC) was effectively extracted, filtering PVDC from the tetrahydrofuran was difficult due to its volatility, which caused PVDC to solidify in the filter and rapidly evaporate from the suction flask. The resulting pressed solid was as follows: Figure 14 As shown.

[0086] Recovery of polyvinylidene chloride from solvent

[0087] like Figure 8 As shown, polyvinylidene chloride is precipitated from dimethyl sulfoxide used in the examples. After filtration and drying as described above, as... Figure 15 The FTIR spectra shown indicate that the sample matches the polyvinylidene chloride (PVDC) reference, suggesting that the precipitate is relatively pure PVDC.

[0088] like Figure 9 As shown, polyvinylidene chloride is precipitated from N-methyl-2-pyrrolidone used in the examples. After filtration and drying as described above, as... Figure 16 The FTIR spectra shown indicate that the sample matches the polyvinylidene chloride reference to some extent, but also show additional peaks for the N-methyl-2-pyrrolidone solvent.

[0089] like Figure 12As shown, polyvinylidene chloride is precipitated from dihydro-L-glucanone used in the examples. After filtration and drying as described above, as... Figure 18 The FTIR spectra shown indicate that the sample matches the polyvinylidene chloride (PVDC) reference, suggesting that the precipitate is relatively pure PVDC.

[0090] like Figure 13 As shown, polyvinylidene chloride is precipitated from triethyl phosphate used in the examples. After filtration and drying as described above, Figure 18 The FTIR spectra shown indicate that the sample matches the polyvinylidene chloride reference to some extent, but also show additional peaks for the triethyl phosphate solvent.

[0091] Tetrahydrofuran

[0092] like Figure 14 As shown, polyvinylidene chloride is precipitated from the tetrahydrofuran used in the examples. After filtration and drying as described above, as... Figure 19 The FTIR spectra shown indicate that the sample matches the polyvinylidene chloride reference to some extent, but also show additional peaks for the triethyl phosphate solvent.

[0093] Cut four pieces of B2690 film into strips approximately 1cm x 2cm using scissors. Figure 20 ), and placed it in an Erlenmeyer flask containing approximately 30 mL of tetrahydrofuran. Figure 21 Gently stir the contents with a magnetic stirrer for about 1 hour at room temperature. The B2690 membrane has a polyvinylidene chloride layer sandwiched between the other membrane layers. Tetrahydrofuran effectively dissolves the polyvinylidene chloride layer in the membrane, resulting in... Figure 22 The complete stratification is shown. By achieving separation of the shear membrane (the most difficult to separate), tetrahydrofuran solvent can also successfully separate polyvinylidene chloride from pulverized or ground materials.

[0094] This written description uses examples to disclose the invention, including the best mode, and also enables those skilled in the art to practice the invention, including making and using any device or system and performing any combination of methods. The patentable scope of the invention is defined by the claims and may include other examples that would occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that are not indistinguishable from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A method for recycling a composite material comprising polyolefin and polyvinylidene chloride, comprising the following steps: a. Provide composite materials containing polyolefins and polyvinylidene chloride; b. Exposing the composite material to a polar aprotic solvent to dissolve at least some of the composite material in a solution containing a polar aprotic solvent; c. Separating the composite material from a solution that remains undissolved, the solution containing dissolved polyvinylidene chloride; as well as d. Collect undissolved composite materials; The collected undissolved composite material contained less than 1.0% by weight of polyvinylidene chloride. The polar aprotic solvent is at least 90% selected from dihydro-L-glucanone, triethyl phosphate, and blends thereof.

2. The method according to claim 1, wherein the polar aprotic solvent is at least 95% selected from dihydro-L-glucosamine, triethyl phosphate, and blends thereof.

3. The method according to claim 2, wherein the polar aprotic solvent is at least 99% selected from dihydro-L-glucanone, triethyl phosphate, and blends thereof.

4. The method according to claim 2, wherein the polar aprotic solvent is composed of one of dihydro-L-glucosamine or triethyl phosphate.

5. The method according to any one of claims 1-4, further comprising a step of mechanically grinding or pulverizing the composite material prior to the step of subjecting the composite material to a polar aprotic solvent.

6. The method according to any one of claims 1-4, wherein the composite material is a multilayer barrier film.

7. The method according to any one of claims 1-4, further comprising the step of precipitating the polyvinylidene chloride from the solution.

8. The method of claim 7, wherein the precipitated polyvinylidene chloride has a purity of at least 99.0% by weight.

9. The method according to any one of claims 1-4, wherein the polar aprotic solvent has a concentration of less than 160. 0 The temperature of C.

10. The method according to any one of claims 1-4, wherein the composite material comprises at least 50% by weight of polyolefin.

11. The method according to any one of claims 1-4, wherein the composite material comprises at least 1% by weight of polyvinylidene chloride.

12. The method according to any one of claims 1-4, wherein the step of subjecting the composite material to a polar aprotic solvent lasts for less than 3 hours.

13. The method according to any one of claims 1-4, wherein the step of subjecting the composite material to a polar aprotic solvent is performed at a pressure of 0.1 atm to 1.5 atm.

14. The method according to any one of claims 1-4, wherein the ratio of polar aprotic solvent to solid material is at least 30:70, measured as a weight percentage.

15. The method according to any one of claims 1-4, wherein the polar aprotic solvent is composed of dihydro-L-glucosamine or triethyl phosphate.

16. The method according to any one of claims 1-4, wherein the polar aprotic solvent is dihydro-L-glucosamine and has a temperature of less than 120°C.

17. The method according to any one of claims 1-4, wherein the polar aprotic solvent is triethyl phosphate and has a temperature of less than 120°C.

18. The method according to any one of claims 1-4, wherein the polyolefin is an ethylene homopolymer or copolymer.

19. The method according to any one of claims 1-4, wherein the composite material does not contain metal.

20. The method according to any one of claims 1-4, further comprising the following step: a. Rinse the collected undissolved composite material; b. Melt the collected undissolved composite material after rinsing; as well as c. Granulate the molten, undissolved composite material.

21. A method for recycling a composite material comprising polyolefin and polyvinylidene chloride, comprising the following steps: a. Provide composite materials containing polyolefins and polyvinylidene chloride; b. Exposing the composite material to a polar aprotic solvent to dissolve at least some of the composite material in a solution containing a polar aprotic solvent; c. Separate the composite material that remains undissolved from the solution containing dissolved polyvinylidene chloride; as well as d. Precipitate polyvinylidene chloride from the solution; The precipitated polyvinylidene chloride has a purity of at least 99.0% by weight. The polar aprotic solvent is at least 90% selected from dihydro-L-glucanone, triethyl phosphate, and blends thereof.

22. The method of claim 21, further comprising the step of: a. Rinse the precipitated polyvinylidene chloride; b. Melt the rinsed polyvinylidene chloride; and c. Granulate the molten polyvinylidene chloride.

23. The method of claim 21, wherein the polar aprotic solvent is at least 95% selected from dihydro-L-glucosamine, triethyl phosphate, and blends thereof.

24. The method of claim 23, wherein the polar aprotic solvent is at least 99% selected from dihydro-L-glucanone, triethyl phosphate, and blends thereof.

25. The method of claim 23, wherein the polar aprotic solvent is composed of one of dihydro-L-glucosamine or triethyl phosphate.

26. The method according to any one of claims 21-25, further comprising the step of mechanically grinding or pulverizing the composite material prior to the step of subjecting the composite material to a polar aprotic solvent.

27. The method according to any one of claims 21-25, wherein the composite material is a multilayer barrier film.

28. The method according to any one of claims 21-25, wherein the polyolefin is an ethylene homopolymer or copolymer.

29. The method according to any one of claims 21-25, wherein the composite material further comprises at least one selected from polyamide, polyester, polypropylene, ionomer or ethylene vinyl alcohol.

30. A system for recycling a composite material comprising polyolefin and polyvinylidene chloride, the system comprising: a. A pulverizer or mill for reducing the size of a composite material comprising a polyolefin and polyvinylidene chloride; b. A solvent bath comprising a polar aprotic solvent to dissolve at least some of the composite material in a solution having said polar aprotic solvent; c. A filter or sieve to separate undissolved composite material from the solution containing dissolved polyvinylidene chloride; as well as d. A collector for precipitating and collecting polyvinylidene chloride from solution; The precipitated polyvinylidene chloride has a purity of at least 99.0% by weight. The polar aprotic solvent is at least 90% selected from dihydro-L-glucanone, triethyl phosphate, and blends thereof.

31. The system of claim 30 further includes a collector for collecting the undissolved composite material, the undissolved composite material comprising less than 1.0% by weight of polyvinylidene chloride.

32. The system of claim 30, wherein the polar aprotic solvent is at least 95% selected from dihydro-L-glucosamine, triethyl phosphate, and blends thereof.

33. The system of claim 32, wherein the polar aprotic solvent is at least 99% selected from dihydro-L-glucanone, triethyl phosphate, and blends thereof.

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