Process for recycling polymers and polyols obtained therefrom

Abstract

Disclosed are a method for recycling polymer waste, a polymer polyol prepared by the method, and a polyurethane prepared from the polymer polyol and a polyisocyanate.

Description

Background Technology

[0001] As society faces climate change, sustainability has become an increasingly urgent issue. Among the many sustainable solutions aimed at carbon neutrality or resource efficiency, the circularity of plastics has attracted the interest of the chemical industry.

[0002] Many polymer materials, such as polyethylene terephthalate (PET), have been incorporated into the circular economy through existing physical recycling processes. These processes typically involve melting thermoplastics and then manufacturing products. Physical recycling processes generally produce lower-grade products than those made from virgin polymers. Recycled polymers are often permitted for use in applications requiring lower-quality polymers. Furthermore, many polymer wastes cannot be reused through conventional physical recycling methods due to thermosetting or other reasons.

[0003] On the other hand, chemical recycling is often accompanied by high construction costs for facilities and extremely high temperatures, corrosiveness, or other hazardous conditions. Furthermore, some chemical recycling methods (such as transesterification) are selective in terms of the chemical properties of the polymer. Notable examples of chemical recycling include pyrolysis, transesterification, and depolymerization. Some polyols obtained through chemical recycling may contain high levels of volatile organic compounds (VOCs), which are harmful to the environment and health.

[0004] Therefore, what is desired is a method for recycling polymer waste under mild operating conditions and with broad polymer versatility. Summary of the Invention

[0005] One object of this disclosure is to provide a method in which polymer waste can be converted into polymer polyols.

[0006] According to one aspect of this disclosure, a method for recycling polymer waste is provided, the method comprising: mixing polymer waste and a dispersion medium to form a mixture; shearing the mixture at a temperature of 160°C to 250°C to form a dispersion of droplets of the polymer waste in a liquid phase; and cooling the dispersion at a temperature of 0°C to 100°C to obtain a polymer polyol, wherein the dispersion medium comprises a polyhydroxy oligomer or polymer selected from polyester polyols, polyether polyols, polycarbonate polyols, and any combination thereof.

[0007] According to another aspect of this disclosure, a polymeric polyol prepared by this method is provided.

[0008] According to another aspect of this disclosure, a polyurethane prepared from the polymeric polyol and polyisocyanate is provided.

[0009] This method is simple and does not involve pressurized operation or highly corrosive media. It can be applied to a wide range of polymer wastes, thus reducing the complexity associated with sorting and collecting different types of polymers from composites or end products. Furthermore, this method does not exhibit selectivity for certain types of polymers. The polymeric polyols obtained by this method have relatively small average particle sizes, accompanied by a uniform particle size distribution, and show very little or no phase separation after storage for a period of time, such as six months. The polyurethanes according to this disclosure have properties comparable to those of polyurethanes prepared from petrochemical polyols. Attached Figure Description

[0010] To facilitate identification of any particular element or action being discussed, one or more of the most significant bits in the reference numerals refer to the figure number in which the element is first introduced.

[0011] Figure 1 One aspect of the subject matter according to one embodiment is illustrated;

[0012] Figure 2 A schematic diagram of a melt emulsification pilot plant according to one embodiment is shown;

[0013] Figure 3 A photograph of the prepared polymer polyol is shown; and

[0014] Figure 4 It shows Figure 3 A photograph of the polymer polyol after it has been prepared and stored at room temperature for six months. Detailed Implementation

[0015] The term "bimodal" refers to a particle size distribution with two maximum values.

[0016] The term "multimodal" refers to a granular distribution with three or more maximum values.

[0017] Diameter D10 (x 10,3 This defines a particle size at which 10% of the dispersed phase volume consists of particles smaller than that size. More detailed specifications are available in DIN ISO 9276-2, 2009.

[0018] Diameter D50 (x 50,3 This defines a particle size at which 50% of the dispersed phase volume consists of particles smaller than that size. More detailed specifications are available in DIN ISO 9276-2, 2009.

[0019] Diameter D90 (x 90,3This defines a particle size at which 90% of the dispersed phase volume consists of particles smaller than that size. More detailed specifications are available in DIN ISO 9276-2, 2009.

[0020] The “index” of a polyurethane forming composition refers to the ratio of the number of NCO groups present in the polyurethane system to the number of reactive hydrogen atoms in the isocyanate, given as a percentage.

[0021]

[0022] [NCO] represents the number of NCO groups.

[0023] [Isocyanate reactive hydrogen] is the number of isocyanate reactive hydrogen atoms.

[0024] In other words, the index represents the percentage of isocyanate actually used in a formulation relative to the amount of isocyanate theoretically required (for reacting with the reactive hydrogen of the isocyanate used in the formulation).

[0025] The term “cream time (CT)” is defined as the time elapsed between the start of the mixing process and the moment when foam begins to rise.

[0026] The term "gel time" is defined as the time elapsed between the start of the mixing process of the mixture and the moment when polymer filaments can be pulled from the foam surface (by means of a rod (or observation rod) applied to the foam surface).

[0027] The term "rise time (RT)" is defined as the time it takes for the foam height to reach 98% of the maximum height reached by the foam during the foaming process in an open cup.

[0028] The term "free rise density (FRD)" is defined as the density of a non-surface cut test specimen taken from the reaction profile test sample.

[0029] The term "isocyanate content" refers to the amount of isocyanate groups in a preparation, calculated as the ratio of the mass of isocyanate groups (NCO) to the mass of the preparation. Isocyanate content is determined according to ISO 14896 Method A and is expressed in wt.%.

[0030] The "functionality" of a polyol refers to the number of hydroxyl groups in each polyol molecule.

[0031] The "OH value" (also known as the "hydroxyl value") refers to the mass (in milligrams) of potassium hydroxide (KOH) required to neutralize one gram of acetic acid absorbed during the acetylation of a polyol or a blend of polyols. The hydroxyl value is determined according to DIN 53240 (German Institute for Standardization) 2012 and is expressed as mg KOH / g.

[0032] The term "meltable emulsifiable" refers to the ability of a polymer to be dispersed in a dispersion medium at the operating temperature. Meltability at a certain temperature does not necessarily mean that the polymer will melt at that temperature.

[0033] The term "polymer polyol" refers to a polyol having a continuous liquid phase consisting of a polyhydroxy polymer (also known as a "carrier polyol") and solid particles of another polymer dispersed in that continuous liquid phase.

[0034] The term "sterically hindered phenol" refers to a phenol in which at least one, preferably two, position adjacent to the phenolic hydroxyl group is substituted with an alkyl and / or aryl group.

[0035] Figure 1 Example routines illustrating methods for recycling polymer waste are provided. While the example routines depict a specific sequence of operations, this sequence can be changed without departing from the scope of this disclosure. For example, some of the depicted operations may be performed in parallel or in a different sequence that does not substantially affect the functionality of the routine. In other instances, different components of the example apparatus or system implementing the routine may perform their functions simultaneously or in a specific order.

[0036] According to some examples, the method includes, in step 110, mixing polymer waste and dispersion medium to form a mixture.

[0037] In step 110, the preferred weight ratio of polymer waste to dispersion medium is 1:(0.6-19). When the polymer waste is in excess relative to the dispersion medium, the raw materials may be difficult to mix, and the dispersion may be highly heterogeneous. When the polymer waste is too little relative to the dispersion medium, the recycling process will consume a large amount of dispersion medium.

[0038] Preferably, the polymer waste and the dispersion medium are mixed using an extruder. The advantage of using an extruder is that it can perform both heating and mixing functions, which helps soften or even melt the polymer waste and facilitates the mixing process.

[0039] According to some examples, the method includes, in step 120, shearing the mixture at a temperature of 160°C to 250°C to form a dispersion of polymer waste droplets in the liquid phase.

[0040] In step 120, the mixture is preferably sheared for a period of 0.5 to 10 hours. Under temperatures and shear conditions of 160°C to 250°C, the polymer waste can melt or soften and form droplets. The shear force can further help reduce the size of the droplets and disperse them in the liquid phase.

[0041] Preferably, by having a time range of 10 to 80 s -1 A rotating device with a circumferential speed within a certain range shears the mixture. More preferably, the rotating device is selected from a group consisting of a stirrer, a rotor-stator, and any combination thereof.

[0042] Optionally, the method includes, before step 130, removing at least one impurity from the dispersion in step 125. This impurity may include volatile chemicals, insoluble solids, or any other impurities. Removal of volatile chemicals can be carried out by first stripping, thin-film evaporation, or vacuum evaporation followed by condensation. This additional step of removing volatile chemicals from the mixture helps reduce the content of volatile organic compounds (VOCs), particularly aldehydes or other chemicals, formed during the previous steps. Insoluble solids can be removed by filtration. Preferably, the filtration is membrane filtration or nanofiltration.

[0043] According to some examples, the method includes, in step 130, cooling the dispersion at a temperature of 0°C to 100°C to obtain a polymeric polyol.

[0044] The cooling in step 130 can cause the dispersed droplets in the liquid phase to solidify and form microparticles.

[0045] Unlike conventional steps of pulverizing polymer materials and dispersing the pulverized polymer materials in a liquid phase, these steps (steps 110 to 130) can produce polymer polyols with a more uniform particle size distribution and higher storage stability.

[0046] Polymer waste can be derived from post-consumer or post-industrial waste as a raw material for recycling methods.

[0047] Industrial post-use polymer waste includes, but is not limited to, polymer waste generated during the manufacturing process or detected through quality control processes, such as waste generated at the start or end of production; waste disposed of through finishing, cutting, grinding, or refining products; by-products; or non-conforming articles identified through quality control procedures. Consumer post-use polymer waste includes, but is not limited to, polymer waste generated by end users of synthetic leather products that can no longer be used for their intended purpose, such as used bags, discarded sofas, etc.

[0048] Although the term “polymer waste” is used in this article, the articles referred to therein may include materials other than polymers, such as metals, ceramics, water, or any other non-polymer substances.

[0049] Preferably, the polymer waste is selected from the group consisting of polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(methyl methacrylate) (PMMA), polyurethane (PU), polyurea, poly(lactic acid) (PLA), polybutylene terephthalate (PBT), polybutylene adipate (PBAT), and any combination thereof. More preferably, the polymer waste is selected from polyurethane, polyurea, poly(lactic acid), polybutylene terephthalate, polybutylene adipate, or any combination thereof. More preferably, the polymer waste is polyurethane.

[0050] Advantageously, the polymer waste is polyurethane, polyurea, poly(lactic acid), polybutylene terephthalate, polybutylene adipate, or any combination thereof. These polymers exhibit good compatibility with the dispersion medium, at least because they can react with the dispersion medium or because they possess relatively polar structures or domains. As an example, polyurethanes based on polyester polyols or polycarbonate polyols can react with polyhydroxy oligomers or polymers in transesterification reactions and undergo a degree of bond cleavage, resulting in polyurethanes with smaller molecular weights and / or simpler structures. As another example, polyurethanes based on polyether polyols possess relatively polar domains and therefore exhibit good compatibility with the dispersion medium. The use of additional surfactants, stabilizers, or other auxiliaries in the dispersion medium can be avoided. Therefore, the dispersion medium and the resulting polymer polyol can have a simple composition.

[0051] Preferably, the polymer waste is melt-emulsifiable in the dispersion medium at temperatures below 250°C. For example, the polymer waste may have a melting point below 250°C. Alternatively, when present independently, the polymer waste may have a melting point equal to or higher than 250°C. However, when present in a dispersion medium, the polymer waste is emulsifiable at temperatures below 250°C due to its interaction with the dispersion medium.

[0052] This dispersion medium is another input material for the recycling process.

[0053] According to this disclosure, the dispersion medium comprises a polyhydroxy oligomer or polymer selected from polyester polyols, polyether polyols, polycarbonate polyols, and any combination thereof. Generally, due to the presence of hydroxyl groups, the dispersion medium is an isocyanate reactive medium and can be used to produce polymers (e.g., polyurethanes).

[0054] Preferably, the dispersion medium has a total OH value of 20 to 1,000 mg KOH / g.

[0055] Preferably, the polyhydroxy oligomer or polymer has an average functionality of 1.5 to 6.

[0056] Polyester polyols, polyether polyols, and polycarbonate polyols are known in the art and have been commercially available for decades. They are typically used extensively in the production of polyurethane-based polymer materials, which are applied in a variety of scenarios.

[0057] Preferably, the dispersion medium further comprises an antioxidant selected from the group consisting of sterically hindered phenols and their esters. More preferably, the antioxidant is a sterically hindered phenol, a carboxylic acid ester of a sterically hindered phenol, or a phosphite ester of a sterically hindered phenol. Known examples of antioxidants include, but are not limited to, primary antioxidants, such as octadecyl β-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, N,N'-(hexane-1,6-diyl)bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), and thiodi-2,1-ethylenedimethyl 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionate; and secondary antioxidants, such as tris(2,4-di-tert-butylphenyl) phosphite and bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, which are commercially available from BASF as stabilizers in the Irgafos series.

[0058] More preferably, the weight ratio of antioxidant to polymer waste is 1:(20-1000).

[0059] Preferably, the dispersion medium is substantially free of any solvent selected from the group consisting of: water, C1-C4 alcohols, acetone, methyl ethyl ketone, acetonitrile, 1,4-dioxane, pyridine, and tetrahydrofuran. The advantage of a dispersion medium free of these solvents is that when the polymer polyol is used as a hydroxyl-containing reactant in polymer production, there is no need to remove such solvents, and the reaction remains simple. Water and simple alcohols can react with isocyanate components and lead to side reactions or byproducts. The absence of water and other solvents in the dispersion medium also reduces or avoids the tendency for side reactions to occur between the polyurethane and the dispersion medium, which could release harmful diamines. Furthermore, it is desirable to avoid the presence of non-reactive and volatile solvents in the subsequent synthesis of polymer products, as the final product will have low volatile organic compound (VOC) emissions.

[0060] According to this disclosure, a polymeric polyol is provided, which is prepared by the method of recycling polymer waste.

[0061] Preferably, the polymeric polyol further comprises additives selected from the group consisting of antioxidants, catalysts, deamination agents, rheology modifiers, fillers, and pigments.

[0062] Antioxidants or deamination agents can reduce or eliminate unwanted byproducts or side-products formed during or after the melt emulsification process, such as carbonyl compounds (ketones or aldehydes) or amines, which are often foul-smelling or contribute to indoor air pollution. Carbonyl compounds and / or amines may be generated during the melt emulsification process. Rheology modifiers or inorganic fillers can adjust the viscosity or rheological properties of the dispersion medium. Fillers can further modulate the mechanical, thermal, or electrical properties of articles made from polymeric polyols. Pigments can help achieve uniform or consistent coloring of polymeric polyols and subsequently improve the color properties of the final articles made from polymeric polyols.

[0063] Exemplary antioxidants are those selected from the group consisting of sterically hindered phenols and their esters. In some embodiments, the antioxidant is a sterically hindered phenol, a carboxylic acid ester of a sterically hindered phenol, or a phosphite ester of a sterically hindered phenol. Known examples of antioxidants include, but are not limited to, primary antioxidants such as octadecyl β-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, N,N'-(hexane-1,6-diyl)bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), and thiodi-2,1-ethylenedimethyl 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionate; and secondary antioxidants such as tris(2,4-di-tert-butylphenyl) phosphite and bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, which are commercially available from BASF as stabilizers in the Irgafos series.

[0064] Exemplary deamination agents include monoglycidyl ethers, such as, in particular, phenylglycidyl ether, tolylglycidyl ether, tert-butylphenylglycidyl ether, cashew phenol glycidyl ether, 2-ethylhexylglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, bisphenol A diglycidyl ether, and bisphenol F diglycidyl ether.

[0065] Exemplary rheology modifiers include cellulose, triethyl citrate, tributyl citrate, and o-acetyltributyl citrate.

[0066] Exemplary fillers include calcium carbonate, zinc oxide, titanium dioxide, silica, alumina, aluminosilicate, magnesium stearate, carbon fiber, glass fiber, clay, diatomaceous earth, and perlite.

[0067] Exemplary pigments include carbon black, zinc oxide, titanium oxide, and iron oxide.

[0068] Preferably, the polymeric polyol has an average particle size D50 of less than 50 μm, preferably less than 20 μm, as measured by static laser diffraction according to DIN ISO 9276-2:2018.

[0069] Preferably, the polymeric polyol has a viscosity in the range of 2,000 to 200,000 mPa s at 25°C, as measured according to DIN EN ISO 3219.

[0070] The average particle size and / or viscosity of polymeric polyols can be adjusted by regulating the processing conditions during their preparation. For example, the duration of shearing, the circumferential speed of the rotating device, and the temperature at which shearing occurs can independently or jointly affect the particle size distribution and / or viscosity. As another example, the weight ratio of polymer waste to the dispersion medium can influence the particle size distribution and / or viscosity.

[0071] In some embodiments, polymeric polyols are obtained by blending different polymeric polyol products prepared under different processing conditions. In this way, the particle size distribution of the final polymeric polyol can be adjusted or even designed to, for example, exhibit a bimodal or multimodal distribution. Furthermore, the viscosity and / or rheological properties of the final polymeric polyol can be adjusted by blending different polymeric polyol products.

[0072] The polymeric polyols disclosed herein can be reacted with polyisocyanates to prepare polyurethanes. The polyisocyanates can be selected from the group consisting of aliphatic, alicyclic, aryl-aliphatic, and aromatic isocyanates. Each polyisocyanate molecule can have more than one isocyanate group. Optionally, a foaming agent can also be used.

[0073] Polymer polyols can be used in a variety of applications, especially in PU foam, PU elastomers, thermoplastic polyurethane (TPU), PU coatings, PU sealants, PU adhesives, surfactants, lubricants, dispersants, and concrete liquefaction agents.

[0074] In one embodiment, the polymeric polyol obtained by this method is used to produce flexible polyurethane foam. Specific applications of polyurethane foam include footwear and vehicle components.

[0075] The following examples illustrate this disclosure.

[0076] The contents of methylene diphenylamine (MDA) and toluene diamine (TDA) were determined by gas chromatography using a Thermofisher TRACE 1300 gas chromatography system. Column: R-1; Carrier gas: Helium; Injection temperature: 200°C; Injection volume: 1 μl; Flow rate: 1 ml / min; Split ratio: 1:5; Flame ionization detector temperature: 290°C.

[0077] Test standard samples (MDA or TDA) (as a baseline), and then test and compare the analytes to determine the content of MDA or TDA.

[0078] VOC emissions were tested using the 10 L bag method as described in Ford FLTM BZ 108-01: 2018.

[0079] The average density is calculated as the mass of the polyurethane material relative to the volume of the mold.

[0080] The particle size distribution of the polymer polyol dispersion was determined by laser diffraction using a Beckman LS 13 320 XR particle size analyzer after diluting the sample with isopropanol to obtain a suitable concentration for measurement. The particle size distribution was calculated using Fraunhofer theory on the Beckman LS 13 320 XR.

[0081] The vertical rebound rate was determined as the ratio of the rebound height of the metal plunger allowed to fall onto the specimen to the drop height.

[0082] Use the following materials:

[0083] Polyether polyol 1: based on glycerol and propylene oxide, end-capped with ethylene oxide; functionality 2.5; OH value, 35 mg KOH / g; viscosity at 25°C, 850 mPa s.

[0084] Polyether polyol 2: based on glycerol and propylene oxide, end-capped with ethylene oxide; functionality 2.29; OH value, 28 mg KOH / g; viscosity at 25°C, 1,100 mPa s.

[0085] Polyether polyol 3: based on glycerol and propylene oxide, end-capped with ethylene oxide; functionality 2.88; OH value, 42 mg KOH / g; viscosity at 25°C, 950 mPa s.

[0086] Polyether polyol 4: based on propylene glycol and propylene oxide, with ethylene oxide end capping; functionality 1.76; OH value, 29 mg KOH / g; viscosity at 25°C, 778 mPa s.

[0087] CHE-628: OH value, 28 mg KOH / g; viscosity at 25°C, 1,300-1,900 mPa s; a polyether polyol based on ethylene oxide and propylene oxide from Changhua Chemical Technology Co., Ltd.

[0088] CHP-H45: Solid content, 41%; OH value, 19-23 mg KOH / g; viscosity at 25°C, 4,500-7,500 mPa s; a styrene-acrylonitrile (SAN) based polymer polyol synthesized by free radical graft polymerization from Changhua Chemical Technology Co., Ltd.

[0089] GPOP-H45Y: Solid content, 40%-45%; OH value, 19-23 mg KOH / g; a polymer polyol based on trifunctional polyether polyol from Sinopec Shanghai Gaoqiao Company.

[0090] NJ-3645D: OH value, ≤ 24 mg KOH / g; viscosity at 25°C, ≤ 10,000 mPa s; trifunctional polymer polyol from Jurong Ningwu New Material Development Co., Ltd.

[0091] Isocyanate 1: An isocyanate prepolymer prepared from diphenylmethane-4,4-diisocyanate, difunctional polyether polyol and trifunctional polyether polyol; isocyanate content 22.3 wt.%.

[0092] Isocyanate 2: Isocyanate content, 29.5%; Functionality, 2.2; Carbodiimide-modified diphenylmethane-4,4-diisocyanate.

[0093] Isocyanate 3: Isocyanate content, 33.5%; Functionality, 2; Diphenylmethane-4,4-diisocyanate.

[0094] Isocyanate 4: An isocyanate prepolymer prepared from diphenylmethane-4,4-diisocyanate and a difunctional polyether polyol; isocyanate content 27.85 wt.%.

[0095] Irganox 1035 is a sulfur-containing phenolic primary antioxidant and heat stabilizer from BASF.

[0096] Catalyst: A 1:1 (w:w) mixture of DABCO 33 LV and DABCO BL 11 (both from Evonik).

[0097] Monoethylene glycol (MEG), diethylene glycol (DEG), butylene glycol (BDO), and glycerin were all sourced from BASF.

[0098] Surfactants: Tegostab B 8734 and Tegostab B 8715, both from Evonik.

[0099] Six recycling examples (RE 1 to RE 6) were conducted to produce polymer polyols from polymer waste.

[0100] Recycling Examples

[0101] RE 1

[0102] Before feeding the material into the reactor, the PU shoe sole with a density of 400 g / L is shredded.

[0103] 560 g of polyether polyol 1 and 140 g of shredded PU were charged into a 1-L glass reactor. The shredded PU and the dispersion medium had a weight ratio of 1:4.

[0104] The mixture was heated to 200°C and discharged at 600 rpm (circumferential speed 62.8 s) under a nitrogen atmosphere. -1 Stir for 1 h to form a dispersion. After heating and stirring, cool the dispersion to 60°C for 30 minutes. Obtain an emulsion-like viscous liquid polymer polyol (“POP”) and designate it as POP 1.

[0105] RE 2

[0106] Before feeding the material into the reactor, the PU shoe insole with a density of 140 g / L is shredded.

[0107] 490 g of polyether polyol 1 and 210 g of shredded PU were charged into a 1-L glass reactor. The shredded PU and the dispersion medium had a weight ratio of 1:2.33.

[0108] The reaction mixture was heated to 200°C and subjected to a nitrogen atmosphere at 200 rpm (circumferential speed 20.9 s). -1 Stir for 3 hours to form a dispersion. After heating and stirring, cool the dispersion to 60°C for 30 minutes. A viscous emulsion solution is obtained and designated as POP 2.

[0109] RE 3

[0110] Before being fed into the reactor, PU tires with a density of 450 g / L are shredded.

[0111] 560 g of polyether polyol 1 and 140 g of shredded PU were charged into a 1-L glass reactor. The shredded PU and the dispersion medium had a weight ratio of 1:4.

[0112] The reaction mixture was heated to 200°C and subjected to a nitrogen atmosphere at 400 rpm (circumferential speed 41.9 s). -1 Stir for 3 hours to form a dispersion. After heating and stirring, cool the dispersion to 60°C for 30 minutes. A viscous emulsion solution is obtained and designated POP 3.

[0113] RE 4 and RE 5

[0114] Shred the PU steering wheel with a density of 350 g / L.

[0115] RE 4 and RE 5 were carried out using a melt emulsification pilot plant with an extruder and rotor / stator setup. The extruder setup used is schematically shown in [illustration missing]. Figure 2 middle.

[0116] exist Figure 2 The schematic design of a melt emulsification pilot plant 200 is shown, which includes an extruder 210, a rotor / stator 230, and three inlets 252, 254, and 256. The pilot plant 200 is fluidly connected to a storage tank 270 for shredded polyurethane foam via inlet 252. The pilot plant 200 is fluidly connected to a storage tank 290 for polyols via inlets 254 and 256. The extruder 210 is a twin-screw extruder. The rotor / stator 230 has eleven zones... Figure 2 The extruder is designated by Z1 to Z11. Z1 to Z10 represent ten extruder barrels (processing areas), and Z11 represents the extruder head. The extruder 210 has an L / D (length to diameter ratio) of 42 and is divided into multiple processing areas, each corresponding to one barrel.

[0117] Under a nitrogen atmosphere, the material is fed via a weightless metering unit ( Figure 2(Not shown in the image) Shredded PU foam in granular form from tank 270 is fed into Z1 through inlet 252. Polyether polyol 1 from tank 290 is separately metered in liquid form using a gear pump. Both the PU granules and polyether polyol 1 are preheated at 180°C and injected into the extruder. The metering rate of the PU granules is 18 kg / h. Polyether polyol 1 is metered into Z3 through inlet 254 at a rate of 6 kg / h and into Z7 through inlet 256 at a rate of 36 kg / h. The polyol and shredded polyurethane are fed at a weight ratio of 7:3. The temperatures of zones Z1 to Z10 are listed in Table 1.

[0118] Table 1

[0119]

[0120] Shearing and heat transfer within the barrel facilitate the melting of the PU foam and the emulsification of the PU material in the polyol. The extruder outlet is connected to the rotor / stator unit via a heated pipe. The rotor / stator unit is used to obtain small and uniform particles. An emulsion-like viscous solution is obtained, designated POP 4.

[0121] To evaluate the recycled polymeric polyol prepared from an antioxidant-containing dispersion medium, recycling example RE 5 was conducted under the same scheme as recycling example RE 4, except that the antioxidant Irganox 1035 was incorporated into polyether polyol 1 at a concentration of 0.71 wt.%. The weight ratio of Irganox 1035 to polyurethane foam was 1:60. An emulsion-like viscous solution was obtained and designated POP 5.

[0122] All polymer polyol samples were tested for their properties, which are listed in Table 2.

[0123] Table 2

[0124]

[0125] In Table 2, "Bi" indicates a bimodal size distribution, and "Multi" indicates a multimodal size distribution. The solids content of the polymer polyol is calculated based on the weight of the polymer waste used and the total weight of the polymer polyol.

[0126] Application Examples

[0127] To evaluate the availability of polymeric polyols in polyurethane forming compositions and the performance of the final products, a series of application examples (AE 1 to AE 5) and comparative application examples (CAE 1 to CAE 4) based on commercially available polymeric polyols or other types of polyols were conducted. Another comparative application example, CAE 1*, was also conducted. In CAE 1*, the polyol component comprised its separate liquid component and polyurethane sole fragments used in RE 1. The polyurethane soles were processed using a Junnuo JN-600 plastic pulverizer to produce microparticles. Solid weights were calculated based on the solid content of the polymeric polyols CHP-H45, GPOP-H45Y, or POP 1 to POP 5, or based on the weight of the polyurethane fragments used in CAE 1*. The solid content in CAE 1* remained approximately the same as that in CAE 1 or AE 1.

[0128] To further evaluate and compare application examples, the composition was fabricated into foam, and the foam's properties were tested. To prepare the foam, the components of each composition were mixed for 5 seconds at 1820 rpm using a stirrer. 250 g of the mixture was immediately transferred to a 1.6 L mold. The mold was then closed. After 5 minutes, the mold was opened, and the foam was removed. Its physical properties were then tested.

[0129] Comparative foam 1 (abbreviated as "CF 1") refers to the foam prepared by comparative application example CAE 1, while foam 1 (abbreviated as "F 1") refers to the foam prepared by application example AE 1, and so on. Foams CF 1, CF 1*, CF 2, CF 3, CF 4, F 1, F 2, F 3, F 4, and F 5 were prepared.

[0130] Details of the composition and reactivity of CAE 1, CAE 1* and AE 1 are listed in Table 3-1.

[0131] The performance of foams CF 1, CF 1*, and F 1 has been tested and is listed in Table 3-2. All foams are particularly suitable for shoe insole applications.

[0132] Table 3-1

[0133]

[0134] Table 3-2

[0135]

[0136] According to Table 3-2, polyurethane foams prepared from polyol components containing pulverized polyurethane foam dispersed in the liquid phase exhibit the worst physical properties, such as the lowest tensile strength, tear strength, and elongation at break. These are likely due to the inhomogeneity of the polyol components. Typically, the particles in polymer polyols prepared by pulverizing and dispersing polymer waste in a carrier polyol are found to be much larger than those formed in the melt-dispersion-solidification process disclosed herein. Large particle size negatively impacts the properties of the final product prepared from it.

[0137] Details of the composition and reactivity of CAE 2 and AE 2 are listed in Table 4-1.

[0138] The properties of foams CF2 and F2, prepared by CAE2 and AE2 respectively, have been tested and are listed in Table 4-2. Foams CF2 and F2 can be used in footwear, especially as insoles.

[0139] Details of the composition and reactivity of CAE 3 and AE 3 are listed in Table 5-1.

[0140] The properties of foams CF3 and F3, prepared by CAE 3 and AE 3 respectively, have been tested and are listed in Table 5-2. Foams CF3 and F3 can be used in footwear, especially as insoles.

[0141] Details of the composition and reactivity of CAE 4, AE 4 and AE 5 are listed in Table 6-1.

[0142] The properties of foams CF4, F4, and F5 prepared by CAE 4, AE 4, and AE 5 have been tested and are listed in Table 6-2. Foams CF4, F4, and F5 can be used in steering wheels.

[0143] Table 4-1

[0144]

[0145] Table 4-2

[0146]

[0147] Table 5-1

[0148]

[0149] Table 5-2

[0150]

[0151] Table 6-1

[0152]

[0153] Table 6-2

[0154]

[0155] In contrast, polyurethane foam prepared from polymeric polyols with antioxidant-containing dispersion media emits fewer VOCs (such as the listed aldehydes) than polyurethane foam prepared from polymeric polyols with antioxidant-free dispersion media.

[0156] It was found that adding antioxidants to the dispersion medium during the recycling process reduced the VOC content in polyurethane produced from polymeric polyols, as indicated by a comparison of recycling examples RE 4 and RE 5.

[0157] The recycled polymeric polyols indicated by these examples exhibit reactivity comparable to commercial products. Application examples made from polymeric polyols from recycled sources described in this disclosure generally have comparable performance to those made from commercial polymeric polyol products. Therefore, the polymeric polyols provided in this disclosure can be introduced into existing polyurethane forming formulations as alternatives to currently available polymeric polyols for a variety of applications without sacrificing the reactivity or performance of the final product. The polymeric polyols in this disclosure can be used alone as a polyol component in two-component polyurethane formulations. Alternatively, the polymeric polyols in this disclosure can be used in combination with another polyol (polyether polyol, polyester polyol, or polycarbonate polyol) to form a polyol component for the production of polyurethane.

[0158] Compared to polyol components incorporating ground or fine particles / waste of polyurethane waste, the polymeric polyols disclosed herein can be homogeneous and stable during storage. Products prepared from these polymeric polyols exhibit superior mechanical properties, as indicated by the data shown in Tables 3-1 and 3-2.

[0159] The polymeric polyols disclosed herein are less dependent on fossil sources because they are derived from recycled sources, and can provide a method for recycling polyurethane materials.

[0160] Figure 3 A photograph of a sample of the prepared polymer polyol 1 (“POP 1”) is shown.

[0161] Figure 4 A photograph of a POP 1 sample after it has been stored at room temperature for six months following its preparation is shown.

[0162] from Figure 3 and Figure 4The polymeric polyol exhibited good storage stability and showed almost no segregation or agglomeration. This polymeric polyol can be used as a raw material for polyurethane applications.

Claims

1. A method for recycling polymer waste, the method comprising: (a) Mixing polymer waste and dispersion media to form a mixture; (b) Shearing the mixture at a temperature of 160°C to 250°C to form a dispersion of the polymer waste droplets in the liquid phase; (c) Cool the dispersion at a temperature of 0°C to 100°C to obtain a polymeric polyol. The dispersion medium comprises polyhydroxy oligomers or polymers selected from polyester polyols, polyether polyols, polycarbonate polyols, and any combination thereof.

2. The method as described in claim 1, wherein, The polymer waste is selected from the group consisting of polyethylene, polypropylene, polystyrene, poly(methyl methacrylate), polyurethane, polyurea, poly(lactic acid), polybutylene terephthalate, polybutylene adipate, and any combination thereof. Preferably, the polymer waste is selected from the group consisting of polyurethane, polyurea, poly(lactic acid), polybutylene terephthalate, polybutylene adipate, and any combination thereof. More preferably, the polymer waste is polyurethane.

3. The method as described in claim 1, wherein, The dispersion medium has a total OH value of 20 to 1,000 mg KOH / g.

4. The method of claim 1, wherein, The polyhydroxy oligomer or polymer has an average functionality of 1.5 to 6.

5. The method of claim 1, wherein, The dispersion medium further contains an antioxidant selected from the group consisting of sterically hindered phenols and their esters.

6. The method of claim 5, wherein, The weight ratio of the antioxidant to the polymer waste is 1:(20-1000).

7. The method of claim 1, wherein, The dispersion medium is substantially free of any of the following groups: water, C1-C4 alcohols, acetone, methyl ethyl ketone, acetonitrile, 1,4-dioxane, pyridine, and tetrahydrofuran.

8. The method of claim 1, wherein, The weight ratio of the polymer waste to the dispersion medium is 1:(0.6-19).

9. The method of claim 1, wherein, The polymer waste and the dispersion medium are mixed by an extruder.

10. The method of claim 1, wherein, The mixture was sheared for a period of 0.5 to 10 hours.

11. The method of claim 1, wherein, By having a range of 10 to 80 s -1 A rotating device with a circumferential speed within a certain range shears the mixture.

12. The method of claim 11, wherein, The rotating device is selected from a combination of a stirrer, a rotor-stator, and any combination thereof.

13. The method of claim 1, further comprising removing at least one impurity from the dispersion prior to step (c).

14. A polymeric polyol prepared by the method according to any one of claims 1 to 13.

15. The polymer polyol of claim 14, wherein, The polymeric polyol has an average particle size D50 of less than 50 μm, preferably less than 20 μm, as measured by static laser diffraction according to DIN ISO9276-2:2018.

16. The polymer polyol of claim 14, wherein, The polymeric polyol has a viscosity in the range of 2,000 to 200,000 mPa·s at 25°C, as measured according to DIN EN ISO 3219.

17. A polyurethane prepared from a polymeric polyol and a polyisocyanate as described in any one of claims 14 to 16.

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