Recycling process for elastomer toughened thermoplastic polymers

Abstract

Toughened thermoplastic polymers, such as acrylonitrile butadiene styrene-containing polymers (ABS), can be recycled by the following process, the method comprises dissolving the toughened thermoplastic polymer in an aprotic solvent in the presence of a separation powder comprising smectite minerals of small size (desirably submicron) and separating the insoluble additive, elastomer particles, and the separation powder by applying a force, which may be gravity, and recovering the separated thermoplastic polymer. The recovered elastomer and thermoplastic polymer may then be reused in the same type, similar or different plastics, thereby avoiding degradation that would otherwise occur when recycling the toughened thermoplastic polymer.

Description

Technical Field

[0001] This invention relates to the recycling of thermoplastic polymers toughened with elastomeric domains / parts. In particular, this invention relates to the recycling and separation of elastomers and insoluble additives (e.g., inorganic pigment particles) from elastomeric toughened thermoplastics such as styrene-butadiene polymers (HIPS) and acrylonitrile-butadiene-styrene polymers (ABS). Background Technology

[0002] Recycling of thermoplastic polymers is typically achieved by mechanically pulverizing and incorporating insoluble materials (e.g., fillers, insoluble polymers, pigments, etc.) into the composite material, or by dissolving and physically separating insoluble materials (e.g., fillers, insoluble polymers, pigments, etc.). Examples of such recycling include selectively dissolving the polymer in solvents and supercritical fluids with or without heating, and removing insoluble particles (including polymer precipitates) by filtration or other means (such as centrifugal decantation), as described in the following patents and patent publications: US5233021, US5278282, US8138232, US8338563, US20030191202, WO2001072900, WO2005026244, and WO2015076868.

[0003] Elastomer domain / particle-reinforced thermoplastic polymers (e.g., HIPS and ABS) are widely used in various devices, such as electrical appliances (e.g., refrigerators) and electronic devices (e.g., televisions and computers), due to their impact strength and chemical resistance. It is well known that recycling these types of plastics is problematic because recycled plastics do not achieve the same properties and introduce substantial changes, even when mixed with the virgin polymer, as described in the following Japanese patent applications: JP2003231119 and JP2004323825A.

[0004] Therefore, there is a need for an improved recycling method that allows for greater use of thermoplastic polymers toughened with elastomeric domains / particles, such as HIPS and ABS polymers. Summary of the Invention

[0005] The applicant unexpectedly discovered that certain toughened thermoplastic polymers (such as ABS or HIPS polymers) in which elastomeric domains / particles are dispersed can be selectively dissolved, and that the thermoplastic polymers can be substantially separated from the elastomers and inorganic particles even under gravity. This makes it possible to use each of these individually in subsequent applications (such as initial applications by blending with other components (e.g., the original polymer or original rubber particles) to restore the characteristics of the recycled polymer). Alternatively, the recycled polymers can be used in other applications that do not require the same characteristics (e.g., applications of polystyrene "PS" or styrene-acrylonitrile "SAN" type polymers), where the recycled material can be used for reinforcing properties due to the presence of a small amount of elastomer within the recycled PS or SAN.

[0006] A first example of the present invention is a method for recycling a toughened thermoplastic polymer (TTP), said toughened thermoplastic polymer having a thermoplastic polymer in which an elastomeric polymer exists in the form of dispersed elastomeric domains, the method comprising, (a) Dissolving the thermoplastic polymer of the TPP in a solvent containing an aprotic solvent to form a solution in which insoluble additive particles and elastomer particles are suspended; (b) mixing therein with a separated powder containing smectite minerals having an average particle size of up to 2 micrometers; (c) applying force to the solution to separate the elastomer particles and insoluble additive particles from the solution to form a separated system; and (c) removing one or more of the thermoplastic polymer, elastomer particles and insoluble additive particles from the separated system to form one or more of the recycled thermoplastic polymer, recycled elastomer particles and recycled insoluble additive particles.

[0007] Other examples include: (1) a method of forming a thermoplastic polymer comprising a recycled thermoplastic polymer of the first example and an original impact modifier dispersed therein; (2) in this respect, for example, blending an original monomeric thermoplastic polymer with a recycled thermoplastic polymer by melt blending (e.g., to form a SAN thermoplastic polymer).

[0008] A third aspect of the invention is an impact-modified thermoplastic polymer comprising the recycled thermoplastic polymer of the first aspect and the original impact modifier dispersed therein. In this aspect, it has been found that the recycled thermoplastic polymer can be compounded in the same manner as the original thermoplastic polymer to achieve an impact-modified thermoplastic polymer having substantially the same characteristics and properties as such polymers made from the original thermoplastic polymer.

[0009] A fourth aspect of the invention is an impact-modified thermoplastic polymer comprising a thermoplastic polymer blended with a recycled elastomer of the first aspect. In one embodiment of this aspect, an elastomer containing an insoluble, higher-density component (e.g., filler, etc.) separated from a toughened thermoplastic polymer can be used in applications requiring some toughness improvement but not to the extent provided by the original elastomer when blended with the thermoplastic polymer. Attached Figure Description

[0010] Figure 1 This illustrates the time-dependent separation in an embodiment of the present invention.

[0011] Figure 2 Articles made from recycled thermoplastic polymers of the present invention and those not of the present invention are shown. Detailed Implementation

[0012] The method involves dissolving a thermoplastic polymer toughened by an elastomeric domain / particle. The elastomeric domain / particle-toughened thermoplastic polymer (“toughened thermoplastic polymer”) comprises a vinyl aromatic monomer polymerized in the presence of a conjugated diene (elastomer) dissolved in an aromatic vinyl monomer and any solvent used for polymerizing the aromatic vinyl monomer and comonomer. The vinyl aromatic monomer is typically a monomer of the following formula: Ar-C(R 1 )=C(R 1 )2 Each R 1 Each time it appears, it is either independently hydrogen or alkyl, or with another R. 1 The forming ring, Ar, is phenyl, halophenyl, alkylphenyl, alkylhalophenyl, naphthyl, pyridyl, or anthracene, wherein any alkyl group contains 1 to 6 carbon atoms, and the alkyl group may optionally be monosubstituted or polysubstituted by functional groups such as halogenated, nitro, amino, hydroxyl, cyano, carbonyl, and carboxyl. Typically, vinyl aromatic monomers have less than or equal to 20 carbons and a single vinyl group. In one embodiment, Ar is phenyl or alkylphenyl, and is typically phenyl. Typical vinyl aromatic monomers include styrene (including conditions that can be used to produce syndiotactic polystyrene blocks), α-methylstyrene, all isomers of vinyltoluene (especially p-vinyltoluene), all isomers of ethylstyrene, propylstyrene, butylstyrene, vinylbiphenyl, vinylnaphthalene, vinylanthracene, and mixtures thereof. Typically, vinyl aromatic monomers are styrene. Further examples of vinyl aromatic monomers include those described in U.S. Patent Nos. 4,666,987, 4,572,819, and 4,585,825, which are incorporated herein by reference.

[0013] Vinyl aromatic monomers can be copolymerized with other addition-polymerizable monomers, such as unsaturated nitrile and (meth)acrylate. Unsaturated nitrile includes, but is not limited to, acrylonitrile, methacrylonitrile, ethyl acrylonitrile, fumaric acid, and mixtures thereof. An unsaturated nitrile may be acrylonitrile.

[0014] As used herein, (meth)acrylates refer to compounds having a vinyl group or vinylidene bonded to the carbonyl moiety of an alkyl ester, wherein the carbon atom of the vinylidene group bonded to the carbonyl group also has a hydrogen or methyl group bonded thereto. Exemplary (meth)acrylates available include those corresponding to the following formula:

[0015] Where R a Each occurrence is either H or -CH3; and Rb can be C1 to C2. 30 alkyl groups or C 1-10 Alkyl group. Examples of one or more (meth)acrylates include lower (meth)acrylate alkyl esters, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, and hexyl (meth)acrylate.

[0016] Other addable monomers may include ethylene halooxides, such as vinyl chloride and vinyl bromide; vinylidene chloride and vinylidene bromide; vinyl esters, such as vinyl acetate and vinyl propionate; olefinic unsaturated dicarboxylic acids and their anhydrides and derivatives, such as maleic acid, fumaric acid, maleic anhydride, dialkyl maleate or dialkyl fumarate, such as dimethyl maleate, diethyl maleate, dibutyl maleate, the corresponding fumarates, N-phenylmaleimide, etc.

[0017] The copolymer may contain suitable amounts of other addition-polymerizable monomers, and typically may be greater than 0.1% by weight or more, about 1% by weight or more, or about 2% by weight or more of the copolymer. The copolymer may contain one or more unsaturated nitriles in amounts of about 40% by weight or less, about 35% by weight or less, about 30% by weight or less, or about 20% by weight or less of the copolymer.

[0018] The elastomeric domains within the thermoplastic polymer can be any elastomeric polymer that separates into domains during the formation of the toughened thermoplastic polymer. Surprisingly, in one embodiment, the elastomer can be crosslinked, grafted onto the thermoplastic polymer, or retained within the thermoplastic polymer and still separate. Crosslinking can be caused by intra- and inter-chain crosslinking of the conjugated diene, or crosslinking formed between the chains of the polybutadiene and the thermoplastic polymer, or combinations thereof. When the elastomer is fully crosslinked, the domains remain as particles upon dissolution, but they may undergo some swelling due to solvation by the solvent. However, the particles can withstand centrifugal forces and can be separated.

[0019] In another embodiment, the polymer may have insufficient crosslinking (e.g., it is a linear elastomer polymer), which can undergo phase separation in a solvent to form droplets, which can then be separated by the methods described herein. This can be achieved even if the elastomer may have been grafted or adsorbed within the thermoplastic polymer.

[0020] Illustratively, the elastomer can be a polymerized conjugated olefin (e.g., diene) that forms elastomeric domains or particles within the thermoplastic polymer and can be any olefin suitable for toughening the thermoplastic polymer. Typically, conjugated olefin monomers have the following formula: R2C=CR-CR=CR2 Each R group, when appearing independently, is either hydrogen or an alkyl group having one to four carbons, wherein any two R groups can form a ring. Ideally, the conjugated olefin is a conjugated diene monomer having at least four carbons and no more than about 20 carbons. The conjugated olefin monomer may have two or more conjugated double bonds. Examples include 1,3-butadiene (butadiene), 2-methyl-1,3-butadiene (isoprene), 2-methyl-1,3-pentadiene, and similar compounds and mixtures thereof. Ideally, the monomer is butadiene, isoprene, or a combination thereof.

[0021] The elastomer can be any thermoplastic elastomer (TPE) known in the art that undergoes phase separation during the formation of a toughened thermoplastic elastomer. Illustratively, a TPE can be a block copolymer comprising at least two distinct blocks of a polymerized vinyl aromatic monomer and at least one block of a polymerized conjugated olefin monomer. Each block copolymer has at least two blocks of a vinyl aromatic monomer having up to 20 carbon atoms, as previously described herein, and a conjugated diene, as previously described herein. The block copolymer may contain more than one specific polymerized conjugated olefin monomer. In other words, the block copolymer may contain, for example, polymethylpentadiene blocks and polyisoprene blocks, or one or more mixed blocks. Generally, block copolymers contain long stretches of two or more monomer units linked together. Suitable block copolymers typically have a total weight ratio of about 30:70 to about 95:5, 40:60 to about 90:10, or 50:50 to 65:35 for the conjugated olefin monomer units and vinyl aromatic monomer units. Block copolymer TPEs may contain more than one polymerizable vinyl aromatic monomer. In other words, block copolymers may contain pure polystyrene blocks and pure polyα-methylstyrene blocks, or any blocks may consist of a mixture of such monomers. It is desirable that block A contains styrene, and block B contains butadiene, isoprene, or a mixture thereof. In one embodiment, the remaining double bonds of the conjugated diene monomer may be hydrogenated.

[0022] Examples of such TPEs may include styrene-(butadiene)-styrene (SBS), styrene-(ethylene-butene)-styrene (SEBS), or combinations thereof. In one embodiment, the STPE comprises SEBS in which substantially all unsaturated bonds of the source SBS have been hydrogenated. Such TPEs are generally available from Kuraray (Houston, TX) under trade names such as SEPTON and HYBRAR. Potentially suitable STPEs may also be available from Audia Elastomers (Washington, PA) under the trade name TPE. Other suitable STPEs may include those purchased from Dynasol under the trade name CALPRENE, those purchased from Kraton Corporation (Houston, TX) under the trade names KRATON F and G, those purchased from Mexpolimeros (Mexico), and those purchased from Asahi Kasei Corporation (Japan) under the trade names ASAPRENE and TUFPRENE.

[0023] The elastomer can also be a core-shell rubber. A core-shell rubber comprises particles having an elastomer material core and a protective material shell. Typically, the core contains an elastomer with a low Tg (such as about 0°C or lower, about -25°C or lower, or about -40°C or lower) to achieve toughening of the toughened thermoplastic polymer. Exemplary core materials include polymers of siloxanes, silicones, ethylene, propylene, butadiene, acrylates, methacrylates, etc.

[0024] The shell is a relatively rigid polymer and may contain reactive groups that react with the polyester. Exemplary reactive groups on the shell surface of the core-shell rubber may include glycidyl groups, maleic anhydride, etc. The shell may also contain polymer chains derived from one or more monomers that form rigid polymer chains. Any monomer that forms rigid polymer chains can be used. The monomers can be polymerized by free radical polymerization. The monomers may be capable of polymerization during emulsion polymerization. Exemplary monomer classes are alkyl (meth)acrylates, styrene, acrylonitrile, etc. Exemplary alkyl (meth)acrylates include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and alkyl methacrylates such as hexyl methacrylate, 2-ethylhexyl methacrylate, n-dodecyl methacrylate, with n-butyl acrylate being preferred. The shell may be made of alkyl (meth)acrylates, crosslinking agents, and grafted active monomer units. Multifunctional compounds can be used as crosslinking agents. Examples include ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, and 1,4-butanediol dimethacrylate. The following compounds can be used alone or in mixtures to insert the grafting active site: allyl methacrylate, triallyl cyanurate, triallyl isocyanurate, and allyl methacrylate. Allyl methacrylate can also act as a crosslinking agent. These compounds can be used in amounts from about 0.1% to about 20% by weight of the core-shell rubber. Preferred graft shells comprise one or more (C1-C8) alkyl esters of (meth)acrylate, particularly methyl methacrylate copolymerized with glycidyl methacrylate.

[0025] The core may have grafting sites on its outer surface to facilitate bonding between the shell and the core. The core is a particle of sufficient size to positively influence the impact resistance and environmental stress cracking resistance of the compositions of the present invention. The particle size may be a median particle size (d50 value) of about 0.05 micrometers or larger, or about 0.1 micrometers or larger. The particle size may be a median particle size (d50 value) of about 5.0 micrometers or smaller, about 2.0 micrometers or smaller, or about 1.0 micrometers or smaller. The core-to-shell weight ratio may be any weight ratio commonly used in the art, such as about 1:99 or larger, about 2:98 or larger, or about 3:97 or larger. The core-to-shell weight ratio may be about 95:5 or smaller, about 90:10 or smaller, or about 80:20 or smaller.

[0026] The amount of elastomer in a toughened thermoplastic polymer can be any amount, such as the amount typically used in the art to prepare such polymers. Illustratively, when the toughened thermoplastic polymer is ABS or HIPS, the amount of conjugated olefin (e.g., butadiene) is typically in the range of about 1% by weight, or 5% by weight, to about 40% by weight, 35% by weight, or 30% by weight of the ABS or HIPS polymer (i.e., excluding any other additives, such as fillers, etc.). Typically, the particle size / domain size of the elastomer within the thermoplastic polymer is from about 0.1 micrometers to about 10 micrometers of equivalent sphere diameter, which can be determined by known photomicrographic techniques. This level of elastomer can certainly be applied to any elastomer used to form the toughened thermoplastic polymer.

[0027] Toughened thermoplastic polymers may contain other additives commonly used in such polymers. Exemplary additives include flame retardants, stabilizers, colorants, antioxidants, antistatic agents, silicone oils, flow enhancers, mold release agents, etc. Exemplary flame retardants include halogenated hydrocarbons, halogenated carbonate oligomers, halogenated diglycidyl ethers, organophosphorus compounds, fluorinated olefins, antimony oxides, and metal salts of aromatic sulfur, or mixtures thereof. Compounds may be used to stabilize bulk-polymerized, rubber-modified, vinylene-substituted aromatic copolymer compositions to prevent degradation caused by, but not limited to, heat, light, and oxygen, or mixtures thereof.

[0028] Insoluble additive particles include fillers / pigments and reinforcing materials. Exemplary fillers / pigments include oxides (CaO and TiO2), talc, clay, wollastonite, mica, carbon black, glass, or mixtures thereof. Fillers typically have a particle size of 1 to 500 micrometers.

[0029] Based on the weight of the composition, such insoluble additive particles may be present in the toughened thermoplastic polymer in amounts of about 0.01% by weight or more, about 0.1% by weight or more, about 1% by weight or more, about 2% by weight or more, or about 3% by weight or more. Based on the weight of the composition, additives and / or fillers may be present in amounts of about 40% by weight or less, about 30% by weight or less, about 20% by weight or less, about 15% by weight or less, about 10% by weight or less, or about 5% by weight or less. Based on the weight of the toughened thermoplastic polymer, additives may be present in amounts of up to 5% by weight, while fillers may be present in amounts of up to 40% by weight.

[0030] These insoluble additives can advantageously be separated simultaneously in the methods of the invention as described herein. They can be further separated in series or in parallel by other techniques such as those known in the art, including, for example, filtration, sedimentation, precipitation, preferential dissolution, flotation, or combinations thereof. Similarly, it should be understood that the toughened thermoplastic polymer can be present in the recycling device as a blend with other polymers commonly used in the art (e.g., polycarbonate-ABS or polycarbonate-HIPS blends). Alternatively, the toughened thermoplastic polymer can be present in the device with other polymers such as in the form of laminates, coatings, or individual polymer components (individual polymers), wherein dissolution may include the dissolution of both the blend and the individual polymers, which can be separated by the methods described herein and can be further separated from the thermoplastic polymer also present in solution by any method available to achieve this purpose.

[0031] To perform dissolution, any known method or combination of methods can be employed to promote or accelerate the dissolution of the toughened thermoplastic polymer. For example, the waste polymer may be in the form of an apparatus that can be mechanically shredded, crushed, pulverized, or disassembled and separated prior to dissolution, or it may be present during dissolution and simultaneously separable by any known method for separating insoluble or soluble components of such an apparatus. Generally, the size of the toughened thermoplastic can be any size that can be used to dissolve to a commercially viable solution concentration for separation by the method of the present invention within a given time. Illustratively, the size of the residue of the toughened thermoplastic polymer or apparatus can range from a few millimeters to 10 or 20 centimeters.

[0032] Dissolution can be performed intermittently or continuously by known methods (which may include the use of agitation, heating, etc.) and can be carried out in a closed or open system. Ideally, the system is closed, in which the solvent is contained and recycled, and heat can be applied to minimize solvent loss to the atmosphere. Overpressure may contain an inert gas, including but not limited to nitrogen or rare gases. The increased pressure can be any pressure that can be used to perform the method and minimize solvent vapor loss. For example, the pressure can be from 1.1, 2, 5, or 10 bar to about 100 bar.

[0033] Upon dissolution, the toughened thermoplastic polymer dissolves in a specific solvent, and the elastomeric polymer forms particles or droplets (collectively referred to as particles) that are immiscible in the solvent solution and suspended in both the thermoplastic polymer and the solvent solution. It should be understood that the solution may contain some elastomeric polymer, but this amount is small. For example, the amount of residual elastomeric polymer in the thermoplastic polymer recovered from the method is typically at most about 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, or 0.3 wt% or less, and the reduction of the elastomeric polymer is at least about 80%, 90%, or 95% of the amount in the recycled toughened thermoplastic polymer.

[0034] To enable the separation of elastomeric polymers from thermoplastic polymers, the solvent-thermoplastic polymer solution has a different density than the elastomeric polymer particles (elastomeric particles), which may or may not be used for solvation in the solvent to dissolve the thermoplastic polymer. This density difference allows the elastomeric polymer to separate from the solvent-thermoplastic polymer solution upon application of force, thereby allowing the recovery of both the thermoplastic and elastomeric polymers. Generally, this means that the density difference allows for commercially viable separation using centrifugal forces readily available in commercially available centrifuges for separating larger volumes. Typically, the density difference is at least about 1%, 2%, 5%, or 10%.

[0035] The solvent can be any solvent that sufficiently dissolves the thermoplastic polymer, thereby allowing the separation of elastomer particles and insoluble additive particles. The solvent can be any solvent suitable for dissolving the toughened thermoplastic polymer, including, for example, aprotic solvents and polar aprotic solvents. Illustratively, the first solvent may include one or more of linear aliphatic ketones, linear acetates, linear aldehydes, linear carbonates, and linear ethers. It is desirable that the solvent comprises a polar aprotic solvent with a dielectric constant of at least 10, 15, or 20, particularly when the thermoplastic polymer is a copolymer of a nitrile monomer and a vinyl aromatic monomer, such as ABS. Examples of such polar aprotic solvents are aliphatic ketones having 1 to 6 carbon atoms, such as acetone, methyl ethyl ketone, methyl propyl ketone, and methyl propyl ketone. The solvent can be any polar aprotic solvent with a dielectric constant greater than 10. The solvent may comprise a mixture of solvents. Illustratively, the solvent may comprise one or more of ketones, nitriles, amides, sulfoxides, formamides, cyclic ethers, cyclic carbonates, and cyclic esters. Ideally, when the thermoplastic polymer is a copolymer such as ABS, nitrile (e.g., aliphatic nitrile) and ketone are used. Illustratively, the solvent may comprise ketones and aliphatic nitrile having 1 to 7 carbon atoms. In addition to the aliphatic ketones described above, exemplary solvents may also include N-methylpyrrolidone, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetonitrile, and propylene carbonate.

[0036] Generally, in embodiments where the density of the solvent-thermoplastic polymer is less than the density of the elastomeric polymer suspended in the solution and has a suitable viscosity, the concentration of the thermoplastic polymer in the solvent is from about 5% to 25%, 20%, or 15% by weight. It is desirable that the viscosity of the solvent be as low as possible to facilitate the separation of the elastomeric polymer from the solvent-thermoplastic polymer solution. To facilitate separation, the solvent has a low viscosity. For example, under ambient conditions (about 20°C), the viscosity (kinematic) is less than 10, 5, 1, or even 0.5 mPa·s. seconds (mPa s). In one embodiment, the viscosity of the solvent-thermoplastic solution can be reduced by heating during or at any part of the method. Typically, heating is to a temperature below the solvent boiling point and is carried out in a closed system under the previously described high pressure. Illustratively, the heating temperature can be from about 25°C or 30°C to about 50°C or 40°C. It should be understood that cooling of the solution or any component thereof is not excluded herein if necessary, but cooling is not required. However, it is contemplated that the method can be performed at reduced temperatures (e.g., below about 20°C to about -40°C, -20°C, or 0°C). Similarly, it should be understood that some cooling may be required to maintain the temperature during the method, for example, to extract frictional heat generated by the rotating equipment.

[0037] Each solvent present in the solvent typically has a density of up to 1.2 g / cc. It is desirable that each solvent has a density of up to 1.1 g / cc, 1.0 g / cc, 0.9 g / cc, or 0.8 g / cc. Each solvent also typically has a molecular weight of up to about 100 g / mol or 90 g / mol.

[0038] It has been unexpectedly found that adding a separating powder containing montmorillonite minerals and having an average particle size of up to 2 micrometers can allow the separation of elastomeric particles with small domain elastomers, such as toughened thermoplastic polymers from emulsion polymerization (e.g., ABS). The separating powders typically have average sizes ranging from 1.5 micrometers, 1 micrometer, 0.75 micrometers, 0.5 micrometers, 0.250 micrometers to 50 nanometers. It is desirable that all particles be smaller than 1 micrometer, 0.75 micrometers, 0.5 micrometers, or 0.25 micrometers. Typically, the separating powders have a specific surface area comparable to submicron powders (ISO 9277:2010), where it is generally advantageous to have a specific surface area of ​​at least 10 m². 2 / g、25m 2 / g or 50 m 2 / g, 100 m 2 / g to any actual value, including 1000, 750, 500 or 300 m 2 / g.

[0039] It is believed, but not limited to, that such small-sized separating powders can cause insoluble additives and elastomer particles suspended in solution to aggregate, thereby allowing them to be separated by applying much lower forces (including gravity separation alone) in commercially viable timeframes and at much higher throughputs than commercially available continuous centrifugation methods described herein. Agglomeration can be attributed, but is not limited to, to a plate-like structure and the possibility of having different charged surfaces that may bridge the surfaces of elastomer particles, insoluble particles, or combinations thereof, leading to their aggregation. Plate-like means having two larger, somewhat equivalent dimensions (typically width and length) and one smaller dimension (typically height). Aspect ratios are typically 3, 4, 5, or 10 to 1000, 500, or 100. The average aspect ratio can be determined by measuring the longest and shortest dimensions of a randomly representative particle sample (e.g., 100 to 200 particles) using photomicrography techniques.

[0040] The separated powder may contain any suitable montmorillonite mineral, such as those known in the art. As used herein, the term "montmorillonite mineral" refers to a general category of clay minerals having an expanded lattice, excluding vermiculite. This includes dioctahedral montmorillonite composed of montmorillonite, bedesite, and chlorodiazepine, as well as trioctahedral montmorillonite comprising soapstone, lithium montmorillonite, and zinc montmorillonite. Also covered are montmorillonite-clay synthesized, for example, by hydrothermal methods disclosed in U.S. Patent Nos. 3,252,757; 3,666,407; 3,671,190; 3,844,978; 3,844,979; and 3,855,147, wherein synthetic montmorillonite is generally preferred, and particularly synthetic montmorillonite of high purity. High purity may be desirable to enhance the aggregation of insoluble additives and elastomer particles suspended in solution, wherein the purity of montmorillonite is desired to be at least 95% or 99% pure (i.e., essentially montmorillonite mineral, which may be, for example, montmorillonite). It may also be desirable for the separating powder to be a stripped montmorillonite mineral as described in U.S. Patent 6,730,719. Exemplary separating powders may be those commercially available from Intelligent Materials Pvt. Ltd. (montmorillonite K10 powder) under CAS: 1318-93-0.

[0041] The amount of separating powder can be any amount that can facilitate the separation of elastomer particles and insoluble additive particles. Generally, the amount of separating powder can be, for example, any amount from 0.05 wt%, 0.1 wt%, 0.25 wt%, or 0.5 wt% to 20 wt%, 15 wt%, or 10 wt% of the toughened thermoplastic polymer comprising any insoluble additive, solvent, and separating powder. When the separating force is solely gravity (sedimentation), it may be desirable for the amount of separating powder to be at least about 2 wt% to any feasible amount up to 20 wt%, as just described.

[0042] To separate elastomer particles or droplets and insoluble additives suspended together with a solvent-thermoplastic polymer solution, sufficient force is applied. The desired force is one that achieves the separation of at least about 80% of the particles in the toughened thermoplastic polymer within a reasonable time (e.g., about 1 minute to about 30 minutes, 20 minutes, 15 minutes, or 10 minutes). Generally, the force is at least about 1 g, 10 g, 50 g, 100 g, 200 g, or 500 g up to 20,000 g, 10,000 g, 5,000 g, or 2,500 g.

[0043] In one embodiment, other additives dissolved in the solvent (“soluble additives”) can be removed from the solvent by an adsorption column after separation by applied force (including centrifugal force). Exemplary soluble additives may be flame retardants, light stabilizers (e.g., hindered amines), and colorants. The adsorption column can be any suitable adsorption column, such as those known in the art. Typically, the adsorption column contains activated carbon black.

[0044] The separated system formed after the application of force typically contains other insoluble additives that separate simultaneously with the elastomer particles. These insoluble additives can be any of those known in the art (such as fillers, fibers, flame retardants, etc.) and can be recovered by any suitable method, such as those known in the art (including, for example, screening, filtration, etc.).

[0045] The force can be gravity alone or generated by any suitable rotating device, such as a commercial-scale centrifuge / rotary separator. Examples can include tubular rotary centrifuges, chamber rotary centrifuges, disc separators, non-porous basket centrifuges, decanter centrifuges, or combinations thereof. The application can be continuous, intermittent, semi-continuous, or a combination thereof. Several centrifuges can also be used in series. For example, a combination of continuous centrifuges can be combined with an intermittent centrifuge such as a rotary centrifuge, where one centrifuge performs coarse separation and a second centrifuge performs finer separation.

[0046] In one embodiment, a decanting centrifuge is used, wherein the elastomer, along with other insoluble additives (if present), is removed from the decanting centrifuge in one stream, and the solvent-thermoplastic polymer solution is decanted in a second stream. The thermoplastic polymer is then recovered from the second stream. Each stream can be subjected to suitable methods for separating or altering any component of the stream, such as those known in the art (e.g., solvent decomposition or pyrolysis, or separation as previously described). For example, thermoplastics can be further separated and recovered by suitable methods, such as precipitating the polymer from the solvent and recovering the polymer by filtering or decanting off the solvent or by removing the solvent by evaporation or any other known method described in any of the following patents: US5233021, US5278282, US8138232, US8338563, US20030191202, WO2001072900, WO2005026244, and WO2015076868, each of which is incorporated herein by reference. In another embodiment, there may be three streams comprising a separated system generated by applied force, the first and second streams as described above, and the third stream comprising insoluble material. In this embodiment, a decanter centrifuge can be configured to extract the three streams.

[0047] After recycling the thermoplastic polymers and granules, each of these polymers and granules can be reused in the same type of toughened thermoplastic polymer or in different polymers. In one embodiment, the recycled elastomeric polymer, with or without any original elastomeric polymer, can be dissolved in a thermoplastic monomer (such as styrene or styrene-acrylonitrile) and optionally a solvent, and then the thermoplastic monomer can be polymerized by a suitable polymerization method (e.g., bulk or solution polymerization) to form a toughened thermoplastic polymer comprising an elastomeric domain, wherein at least some portions (i.e., at least 10 wt%, 25 wt%, 50 wt%, 75 wt%, or 90 wt%) or all of the domain comprise the recycled elastomeric polymer.

[0048] In another embodiment, the recycled elastomer can be blended with the original thermoplastic polymer (such as those described herein) by melt blending, as is common in the art, to form a toughened thermoplastic polymer. When the recycled elastomer is reused, it can be further separated from other components (e.g., fillers, etc.) entrained in the recycled elastomer or used in their presence, which is desirable when property improvement is desired but not to the extent required by the original elastomer. In one embodiment, the recycled elastomer, with or without other entrained components, can be used to modify the properties of a thermosetting polymer (e.g., added to a subsequently cured thermosetting resin).

[0049] In another embodiment, the recycled thermoplastic polymer may be blended with the virgin thermoplastic polymer. The virgin thermoplastic polymer is defined as a polymer that does not contain any recycled or reclaimed polymer. In this embodiment, the virgin thermoplastic polymer may contain thermoplastic monomers, such as those described above, and may be the same as one or more monomers of the recycled thermoplastic polymer. For example, the recycled thermoplastic polymer may be a styrene-acrylonitrile (SAN) copolymer or polystyrene (PS) with trace amounts of an elastomeric polymer (e.g., polybutadiene or polyisoprene as described above) blended with SAN copolymers or PS, depending on the situation. Alternatively, the recycled thermoplastic polymer may be blended with different compatible thermoplastic polymers, such as thermoplastic polymers with different monomers. For example, the recycled thermoplastic polymer may be a SAN copolymer, and the virgin polymer may be PS or SAN with different styrene / acrylonitrile ratios, or a copolymer of α-methylstyrene and methacrylonitrile. Blending can be performed by any suitable method, such as those known in the art (including, but not limited to, melt blending and extrusion).

[0050] In another embodiment, the recycled thermoplastic polymer can be combined with the virgin elastomer (e.g., those described herein) in any suitable manner (such as those known in the art) to prepare the toughened thermoplastic polymer as described herein. Illustratively, the virgin elastomer and the recycled thermoplastic polymer can be melt-blended and compounded using an extruder as commonly practiced in the art. The level of the elastomer and the dispersion of the elastomer can be any level as previously described herein. In this embodiment, it has been unexpectedly found that such toughened thermoplastic polymers can have substantially the same properties and characteristics as such toughened thermoplastic polymers prepared using the virgin thermoplastic polymer in the same manner and concentration.

[0051] Example

[0052] Example 1. A method for recycling a toughened thermoplastic polymer having an elastomeric polymer present in the form of dispersed elastomeric domains, the method comprising, (a) Dissolving the thermoplastic polymer in an aprotic solvent containing an aprotic solvent to form a solution in which insoluble additive particles and elastomer particles are suspended. (b) Therein, a separated powder containing montmorillonite minerals having an average particle size of up to 2 micrometers is mixed. (b) Applying force to the solution to separate the elastomer particles and insoluble additive particles from the solution to form a separated system. (c) Removing one or more of the thermoplastic polymer, elastomer particles and insoluble additive particles from the separated system to form one or more of the recycled thermoplastic polymer, recycled elastomer particles and recycled insoluble additive particles.

[0053] Example 2. The method as described in Example 1, wherein the separated powder contains at least 95% of the montmorillonite mineral.

[0054] Example 3. The method as described in Example 2, wherein the separated powder comprises at least 99% by weight of the montmorillonite mineral.

[0055] Example 4. The method as described in Example 3, wherein the montmorillonite mineral comprises montmorillonite.

[0056] Example 5. The method described in Example 4, wherein the montmorillonite mineral is essentially montmorillonite.

[0057] Example 6. The method of any one of Examples 1 to 5, wherein the separated powder has an average particle size of up to 1 micrometer.

[0058] Example 7. The method as described in any of the preceding examples, wherein the separated powder has a maximum particle size of less than 1 micrometer.

[0059] Example 8. The method of any one of Examples 1 to 7, wherein the separated powder has a particle size of at least 50 μm. 2 Specific surface area per g.

[0060] Example 9. The method as described in Example 8, wherein the specific surface area is at least 100 m². 2 / g.

[0061] Example 10. The method as described in Example 9, wherein the specific surface area is at least 200 m². 2 / g.

[0062] Example 11. The method as described in any of the preceding examples, wherein the aprotic solvent comprises a first solvent having a dielectric constant of 2 to 25 and a second polar aprotic solvent having a dielectric constant greater than 25.

[0063] Example 12. The method of Example 11, wherein the first solvent comprises one or more of linear aliphatic ketones, linear acetates, linear aldehydes, linear carbonates, and linear ethers.

[0064] Example 13. The method as described in Example 12, wherein the first solvent comprises a linear ketone.

[0065] Example 14. The method as described in Example 11 or 12, wherein the density of the first solvent is at most 0.8 g / cc.

[0066] Example 15. The method of any one of Examples 11 to 14, wherein the ketone comprises acetone or methyl ethyl ketone.

[0067] Example 16. The method of any one of Examples 11 to 15, wherein the second solvent has a density of at most 1 g / cc.

[0068] Example 17. The method of any one of Examples 11 to 16, wherein the second solvent comprises one or more of nitriles, amides, sulfoxides, formamides, cyclic ethers, cyclic carbonates, and cyclic esters.

[0069] Example 18. The method of Example 17, wherein the second solvent comprises one or more of acetonitrile, propionitrile, butyronitrile, valerate, and hexanonitrile.

[0070] Example 19. The method as described in any of the preceding examples, wherein the toughened thermoplastic polymer is an acrylonitrile-butadiene-styrene copolymer.

[0071] Example 20. The method as described in any of the preceding examples, wherein centrifugal force is applied by a centrifuge, wherein the separation produces at least two streams, one stream containing the thermoplastic polymer in the solution, and the other stream containing the elastomer and insoluble additives.

[0072] Example 21. A method of forming a thermoplastic polymer comprising, as described in any one of Examples 1 to 20 above, a recycled thermoplastic polymer and an original impact modifier dispersed therein.

[0073] Example 22. A method of forming a thermoplastic polymer, the method comprising blending a virgin thermoplastic polymer with a recycled thermoplastic polymer as described in any one of Examples 1 to 20 above.

[0074] Example 23. A method for forming an impact-modified thermoplastic polymer, said impact-modified thermoplastic polymer comprising a thermoplastic polymer blended with the recycled elastomers described in Examples 1 to 20.

[0075] Example 24. The method of any one of Examples 1 to 20, wherein an inorganic particulate matter insoluble in the solvent is added to the thermoplastic polymer.

[0076] Example 25. The method of any one of Examples 1 to 20, wherein the solution is passed through an adsorption column.

[0077] Example 26. The method as described in Example 25, wherein the solution is passed through the adsorption column after the force is applied.

[0078] Example 27. The method as described in any of the preceding examples, wherein the dielectric constant of the second solvent is at least 10.

[0079] Example 28. An article comprising one or more of the recycled thermoplastic polymer, recycled elastomer particles, and recycled insoluble additive particles as described in any of the preceding examples.

[0080] Example 29. An article as described in Example 28, wherein the recycled polymer article is a consumer product.

[0081] Example 30. The article of manufacture as described in Example 29, wherein the consumer product is an electrical appliance, electronic device, or toy.

[0082] Example

[0083] Examples 1-9

[0084] ABS waste collected from discarded toys was dissolved in a 200 L drum container at a 10 wt% ABS waste load in a solvent containing a mixture of 90 wt% acetone and 10 wt% acetonitrile, with montmorillonite clay (K10, CAS: 1318-93-0) added in varying amounts (1% to 9% by weight of ABS waste). After 2 hours of kneading / stirring, each mixture was subjected to gravity sedimentation. A significant increase in separation efficiency with varying montmorillonite concentration was observed within less than 20 minutes. Improvements in separation with more than 2 wt% clay under gravity were observed. Figure 1 It is obvious.

[0085] Comparing Example 1 and Example 10

[0086] Example 10: The above process was repeated using 5% wt% montmorillonite and 4 hours of settling. The supernatant was extracted and passed through a carbon adsorption column to remove soluble dyes. The remaining thermoplastic polymer was removed from the solvent and compounded into recycled emulsion-polymerized ABS, and the resulting polymer was injection molded as follows: Figure 2 The substrate shown.

[0087] Comparative Example 1 underwent the same dissolution process as Example 10, but without montmorillonite. Gravity separation was not feasible within 4 hours, therefore centrifugal force was applied using a continuous flow centrifuge (centrifugal force = 2400 g, flow rate 300 L / h). In a similar manner to Example 10, the remaining thermoplastic polymer was removed from the solvent and compounded into recycled emulsion-polymerized ABS, and the resulting polymer was formed as shown in Example 10. Figure 2The tiles shown. From Figure 2 It is evident that gravity settling in Example 10 is more effective than separation without montmorillonite in removing unwanted additives, even when using much higher separation forces as in Comparative Example 1.

Claims

1. A method for recycling a toughened thermoplastic polymer, said toughened thermoplastic polymer having a thermoplastic polymer and an elastomeric polymer dispersed therein in the form of dispersed elastomer domains, said method comprising, (a) Dissolving the thermoplastic polymer in a solvent containing an aprotic solvent to form a solution of the thermoplastic polymer in which insoluble additive particles and elastomer particles are suspended. (b) Therein, a separated powder containing montmorillonite minerals having an average particle size of up to 2 micrometers is mixed. (c) Applying force to the solution to separate the elastomer particles and the insoluble additive particles from the solution, to form a separated system, and (d) Removing one or more of the thermoplastic polymer, the elastomer particles, and the insoluble additive particles from the separated system to form one or more of the recycled thermoplastic polymer, recycled elastomer particles, and recycled insoluble additive particles.

2. The method of claim 1, wherein the separated powder has a particle size of at least 100 m 2 / g of surface area.

3. The method of claim 2, wherein the separated powder comprises at least 99% by weight of the montmorillonite mineral.

4. The method of claim 3, wherein the montmorillonite mineral comprises synthetic montmorillonite.

5. The method of any of the preceding claims, wherein the separated powder has a maximum particle size of less than 1 micrometer.

6. The method of any of the preceding claims, wherein the aprotic solvent comprises a first solvent having a dielectric constant of 2 to 25 and a second polar aprotic solvent having a dielectric constant greater than 25.

7. The method of claim 6, wherein the first solvent comprises one or more linear aliphatic ketones, linear acetates, linear aldehydes, linear carbonates, and linear ethers.

8. The method of any one of claims 7, wherein the ketone comprises acetone or methyl ethyl ketone.

9. The method of any one of claims 6 to 9, wherein the second solvent comprises one or more of nitriles, amides, sulfoxides, formamides, cyclic ethers, cyclic carbonates, and cyclic esters.

10. The method of claim 9, wherein the second solvent comprises one or more of acetonitrile, propionitrile, butyronitrile, valerate, and hexanonitrile.

11. The method of any one of claims 6 to 10, wherein the second solvent comprises acetonitrile and the first solvent comprises acetone.

12. The method of any of the preceding claims, wherein the toughened thermoplastic polymer is an acrylonitrile-butadiene-styrene copolymer.

13. The method of any of the preceding claims, wherein the force is applied by a centrifuge, wherein the separation produces at least two streams, one stream containing the thermoplastic polymer in the solution, and the other stream containing the elastomer particles and the insoluble additive particles.

14. An article comprising one or more of the recycled thermoplastic polymer, recycled elastomer particles, and recycled insoluble additive particles as described in any of the preceding claims.

15. The article of claim 14, wherein the article of claim 14 is an electrical appliance, an electronic device, or a toy.

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