Method for making specialty polyesters and copolyesters from recycled bis(2-hydroxyethyl) terephthalate (rBHET) and products thereof

Abstract

The present invention relates to a process for producing specialty polyesters and copolyesters from recycled bis-2-hydroxyethyl terephthalate (rBHET), which is derived from polyethylene terephthalate (PET) recovered from PET scrap or waste. The polyesters / copolyesters thus obtained are clean and high-quality and can be used in all applications, including but not limited to textiles, packaging, engineering, and industry.

Description

Technical Field

[0001] The present invention relates to a method for recycling polyethylene terephthalate (PET). More specifically, the present invention relates to a method for producing environmentally friendly specialty polyesters and copolyesters from recycled bis-2-hydroxyethyl terephthalate (rBHET), which is derived from polyethylene terephthalate (PET) recovered from PET scrap or waste. Background Art

[0002] Polyethylene terephthalate (PET) is a member of the polyester family of thermoplastic polymers with a wide range of applications in engineering, textiles, and packaging (both rigid and flexible). In its native state, PET is a highly flexible, colorless, semi-crystalline resin. The rigidity of PET depends on its processing. The polymer is processed by extrusion and spinning, molding (injection stretch blow molding, extrusion blow molding, injection blow molding), coating, and lamination to produce a variety of articles, such as fibers, filament yarns for apparel and industrial applications, nonwovens, carpets, containers, films, and sheets.

[0003]

[0004] PET is produced by the polymerization of ethylene glycol and terephthalic acid (PTA) in the presence of a catalyst.

[0005]

[0006] The traditional method for producing PET polyester and other similar polyesters such as polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), and various copolyesters currently uses purified terephthalic acid or its derivatives and diols as the primary raw materials. Derivatives of terephthalic acid include, but are not limited to, dimethyl terephthalate (DMT). PTA is a preferred raw material. Diols used herein include, but are not limited to, monoethylene glycol (MEG), 1,4-butanediol (BDO), and 1,3-propylene glycol (PDO).

[0007] The reaction of PTA or its derivatives with diols is a two-step reaction: esterification followed by polycondensation. In the esterification reaction, a diacid such as purified terephthalic acid (PTA) is first reacted with a diol such as monoethylene glycol (MEG), 1,4-butanediol (BDO), or 1,3-propylene glycol (PDO) to produce a monomer / prepolymer such as bis-hydroxyethylene terephthalate (BHET), bis(4-hydroxybutyl) terephthalate (BHBT), or bis(2-hydroxypropyl) terephthalate (BHPT), with water being released as a byproduct.

[0008] In a polycondensation reaction, the monomers / prepolymers thus obtained are then reacted under polymerization to obtain polymers, including but not limited to polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypropylene terephthalate (PTT), with byproducts being released as related diols, such as monoethylene glycol (MEG), 1,4-butanediol (BDO), 1,3-propylene glycol (PDO), respectively.

[0009] PET's poor biodegradability makes waste removal difficult. Waste PET can be removed through combustion or recycling. However, since combustion releases toxic fumes into the atmosphere, posing health risks and environmental pollution, recycling PET is a more viable solution.

[0010] Nowadays, recycling PET has become very important for protecting the environment and achieving sustainability. Therefore, waste PET in the form of fabrics / yarns / containers / films / polymer blocks has become an important source of recycling. Chemical recycling and mechanical recycling methods have been developed. It is difficult to obtain a clean product through mechanical recycling because the collected waste PET contains a large amount of polymer and non-polymer contaminants, which makes it difficult to obtain the resulting recycled polyethylene terephthalate (PET). In addition, due to the residual presence of contaminants, it is difficult to process the recycled polyethylene terephthalate (PET). Chemical recovery methods through glycolysis cannot completely remove the presence of polymer and non-polymer contaminants. Other chemical recovery methods, such as methanolysis (to obtain DMT) and hydrolysis (to obtain PTA) are quite expensive.

[0011] Bis-2-hydroxyethyl terephthalate (BHET) is a product obtained from the glycolysis of PET waste and is further purified by various techniques such as fermentation, multi-stage purification steps, use of microwave technology, ionic liquids, etc. BHET can be further used to obtain recycled PET by a polycondensation process, in which monoethylene glycol (MEG) is a by-product.

[0012] Until now, purified, clean bis-2-hydroxyethyl terephthalate (BHET) has not been commercially available. However, it is now available, as many companies have developed purification methods to remove color, residual catalysts, polymer contaminants (particularly for use in multilayer bottles, sheets, films, conjugate fibers, carpets, etc.), and various comonomers used. However, none of the existing PET recycling methods known, including mechanical recovery and chemical recovery (methanolysis, glycolysis, hydrolysis) purification methods, can produce a high-quality recycled product (polyester) with the same purity as the synthetic product originally made from virgin raw materials.

[0013] Therefore, the problem with existing methods is that earlier technologies or methods do not produce clean products and are not economically viable.

[0014] Therefore, instead of using virgin raw materials, namely PTA and MEG or RPET waste itself, or using existing chemical recycling methods that use RPET as the starting material, rBHET is used as the starting material. It is a monomer that exists in molten form or powder form, which is advantageous in many aspects. This can be used as a raw material for making rPET polyester. In addition, by feeding other diols with BHET, the MEG molecules in BHET can be replaced with other diols such as 1,4-butanediol (BDO) or 1,3-propylene glycol (PDO), and recycled polybutylene terephthalate (PBT) or recycled polypropylene terephthalate (PTT) can be produced from rBHET.

[0015] By adding various comonomers and additives, specialty polymers, copolymers, or polymer blends can be produced with modified properties required / desired for various applications. Summary of the Invention

[0016] In order to address the difficulties prevalent in existing recycling methods and obtain high-quality rPET, the present invention aims to produce high-quality, clean polyester / copolyester from BHET derived from PET waste, which can be used in various applications including but not limited to textiles, packaging, engineering and industry.

[0017] Another object of the present invention is to purify BHET from recycled BHET obtained from chemical recycling of PET.

[0018] Yet another object of the present invention is to produce high quality chemically recycled PET polyester from recycled BHET.

[0019] Yet another object of the present invention is to produce specialty chemical recycled PET by adding various additives / comonomers such as different alkylene / aromatic diols, aliphatic / aromatic diacids or their esters; polyalkylene glycols (such as polyethylene glycols, polypropylene glycols, etc.); esters of various diacids and diols; comonomers such as DMSIP / SIPA, etc.; or their esters to the recycled BHET to improve specific properties / characteristics required in various applications.

[0020] Yet another object of the present invention is to improve the dyeability, flame retardancy and stain resistance of existing polymers by blending recycled PET to form blended polyesters / copolyesters.

[0021] Another object of the present invention is to produce pure product for packaging applications at competitive costs.

[0022] Another object of the present invention is to reduce investment and conversion costs.

[0023] Another object of the present invention is to enable the convenient use of a wide variety of comonomers.

[0024] Yet another object of the present invention is to produce a masterbatch having various functions.

[0025] Yet another object of the present invention is to produce green PBT, green PTT and other green copolyesters.

[0026] Yet another object of the present invention is to produce flame retardant (FR) polyesters and copolyesters. DETAILED DESCRIPTION

[0027] It should be noted that the specific description and embodiment set forth in the following specification are only examples of the wide variety and arrangement of reactions that the present invention can adopt. Without departing from the spirit or essential characteristics of the present invention, the present invention can be embodied in other specific forms. Therefore, unless otherwise clearly stated, all embodiments are within the scope of the present invention. Without departing from the scope or spirit of the present invention, various modifications or replacements are also possible. Therefore, it should be understood that this specification has been described by the most preferred embodiments and is for illustrative and non-restrictive purposes.

[0028] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but are merely used to enable a clear and consistent understanding of the present invention. Therefore, it should be clear to those skilled in the art that the following description of exemplary embodiments of the present invention is provided for illustrative purposes only and not for the purpose of limiting the present invention.

[0029] It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0030] It should be emphasized that, when used in this specification, the term "comprises / comprising" is used to specify the presence of stated features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or combinations thereof.

[0031] As used herein, the term "degree of polymerization" (DP) refers to the number of monomer units in a polymer.

[0032] The present invention discloses a purification method for BHET obtained from chemical recycling of PET polyester waste.After glycolysis (chemical recycling), bis-2-hydroxyethyl terephthalate (BHET) is subjected to various purification methods to obtain clean rBHET.

[0033] Clean BHET is then used as a starting material to replace PTA and MEG to make polyester. BHET is a monomer and is available in molten or powder form. It can be used as a raw material for making PET polyester.

[0034] Recovered BHET can be provided in molten or powder form. The melting point of recovered BHET is approximately 110°C. The recovered BHET is charged into a reactor equipped with a heating coil and a stirrer. The reactor temperature is gradually raised to a maximum of 300°C while stirring, and high pressure is applied for a specified period of time. The required amount of catalyst and / or additives is added as a solution in diol. The reactor pressure is then gradually reduced to 0.1 mbar while the product temperature is gradually raised to approximately 280°C. A polycondensation reaction occurs, and diol is distilled off as a by-product.

[0035]

[0036] After reaching the desired degree of polymerization based on monitoring of the agitator motor power consumption, the reaction is terminated and the polymer is extruded using an underwater pelletizer or any other type of pelletizer / granulator.

[0037] The degree of polymerization is determined in the laboratory by solution viscosity measurements using intrinsic viscosity (IV), and other chemical and rheological properties are also examined in order to adjust the process to obtain optimal properties.

[0038] The copolyester can be further subjected to solid-state polymerization (SSP). SSP results in an increase in the molecular weight and / or intrinsic viscosity of the copolyester product and a decrease in the oligomer content. If necessary, the polymer particles are crystallized and further upgraded to the desired IV by solid-state polymerization (SSP) in a batch reactor or a continuous reactor. Finally, the granular product is packaged.

[0039] Optional additives used to make specialty polyesters include:

[0040] a) Aromatic sulfonated salts in an amount of 2 wt% to 50 wt% Na, wherein the metal can be Li, Na, K, Mg, Ni, Ca and Fe in the desired form, such as SIPA / DMSIP5-dimethyl sulfoisophthalate sodium salt) or its esters.

[0041] b) other basic dicarboxylic acids / esters thereof, such as adipic acid, sebacic acid, NDA (naphthalene dicarboxylic acid), etc. and aromatic diacids;

[0042] c) alkylene and aromatic diols;

[0043] d) isosorbide, polyalkylene glycol;

[0044] e) other polyesters, such as PBT, PTT and copolyesters;

[0045] f) Active phosphorus-based additives, compatibilizers, antioxidants, and nucleating agents.

[0046] g) Special masterbatch of branching agent including chain extender, heat stabilizer, antioxidant and functional additive.

[0047] In an embodiment of the present invention, the additive:

[0048] - isosorbide, polyalkylene glycols, such as polyethylene glycol (PEG) and polypropylene glycol, having a molecular weight of up to 10,000;

[0049] - Incorporation of up to 8000 ppm of heat stabilizers and antioxidants during the polymerization process.

[0050] - Addition of up to 8000 ppm of branching agent / chain extender.

[0051] - Add up to 2000 ppm of nucleating agent;

[0052] - Rapidly crystallizing polyesters such as PBT and PTT are incorporated in an amount of up to 20% by weight;

[0053] - other aliphatic and aromatic dicarboxylic acids or esters of these acids, such as succinic acid, adipic acid, isophthalic acid, naphthalene dicarboxylic acid, in an amount of 20%; and

[0054] - 2 to 50% by weight of an aromatic metal sulfonate.

[0055] The comonomer is selected from the group consisting of aliphatic and aromatic diacids selected from dicarboxylic acids / acids / esters including but not limited to succinic acid, adipic acid, isophthalic acid, sebacic acid, IPA, NDC, naphthoic acid NDA (naphthalene dicarboxylic acid), hydroxyphenylphosphinylpropionic acid (UKANOL FR 50) and aromatic diacids.

[0056] The polyalkylene glycol may be selected from, but is not limited to, glycols such as polyethylene glycol (PEG) and polypropylene glycol having a molecular weight of up to 10,000.

[0057] The amount of heat stabilizers and antioxidants incorporated during the polymerization process may be up to 8000 ppm. The antioxidant may be selected from but not limited to 1010, 1076, 126 and 168. The heat stabilizer is selected from, but not limited to, flame retardants such as decabromodiphenyl ether and triaryl phosphates such as triphenyl phosphate.

[0058] The catalyst may be selected from the oxides / acetates of antimony (Sb), titanium (Ti), germanium (Ge), manganese (Mn), cobalt (Co), tin (Sn), and Ca (calcium), and the amount used is not more than 800 ppm of the element. The catalyst used herein is a compound containing a metal selected from, but not limited to, antimony (Sb), titanium (Ti), and germanium (Ge). The metal compound is selected from compounds including, but not limited to, antimony trioxide / antimony triacetate, tetraisopropyl titanate, tetrabutyl titanate, potassium titanium oxalate, germanium dioxide, and mixtures thereof.

[0059] Branching agents / chain extenders may optionally be added up to 8000 ppm. The branching agent may be selected from, but is not limited to, 1,2,4-benzenetricarboxylic acid (trimellitic acid); 1,2,4-benzenetricarboxylic acid trimethyl ester; 1,2,4-benzenetricarboxylic anhydride (trimellitic anhydride); 1,3,5-benzenetricarboxylic acid; 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid); 1,2,4,5-benzenetetracarboxylic dianhydride (pyromellitic anhydride); 3,3′,4,4′-benzophenonetetracarboxylic dianhydride; 1,4,5,8-naphthalenetetracarboxylic dianhydride; citric acid; tetrahydrofuran-2,3,4,5-tetracarboxylic acid; 1,3,5-cyclohexanetricarboxylic acid; pentaerythritol, 2-(hydroxymethyl)-1,3-propanediol; 2,2-bis(hydroxymethyl)propionic acid; sorbitol; glycerol; or combinations of any two or more thereof. Specifically, the branching agent may include pentaerythritol, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, and sorbitol.

[0060] A nucleating agent may optionally be added in an amount up to 2000 ppm. The nucleating agent may be organic or inorganic. Examples of inorganic nucleating agents include, but are not limited to, calcium silicate, nanosilica powder, talc, microtalc, aclyn, kaolinite, montmorillonite, synthetic mica, calcium sulfide, boron nitride, barium sulfate, aluminum oxide, neodymium oxide, or metal salts of phenylphosphonic acid. The inorganic nucleating agent may be modified with an organic material to improve its dispersibility in the polyester product of the present disclosure. Examples of organic nucleating agents include, but are not limited to, metal salts of carboxylates such as sodium benzoate, potassium benzoate, lithium benzoate, calcium benzoate, magnesium benzoate, barium benzoate, lithium terephthalate, sodium terephthalate, potassium terephthalate, calcium oxalate, sodium laurate, potassium laurate, sodium myristate, potassium myristate, calcium myristate, sodium octacocarbonate, calcium octacocarbonate, sodium stearate, potassium stearate, lithium stearate, calcium stearate, magnesium stearate, barium stearate, sodium montanate, calcium montanate, sodium toluate, sodium salicylate, potassium salicylate, zinc salicylate, aluminum dibenzoate, diphenyl benzoate, Potassium formate, lithium dibenzoate, sodium β-naphthalene dicarboxylate and sodium cyclohexanecarboxylate; organic sulfonates, such as sodium p-toluenesulfonate and sodium sulfoisophthalate; carboxylic acid amides, such as stearic acid amide, ethylenebislauric acid amide, palmitic acid amide, hydroxystearic acid amide, erucic acid amide and tris(tert-butylamide) trimellitate; metal salts of phosphoric acid compounds, such as benzylidene sorbitol and its derivatives, sodium 2,2′-methylenebis(4,6-di-tert-butylphenyl) phosphate and sodium 2,2-methylbis(4,6-di-tert-butylphenyl), etc., or a combination of any two or more thereof.

[0061] Fast crystallizing polyesters such as polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polybutylene naphthalate (PBN), fast crystallizing polyesters, polytrimethylene naphthalate (PTN), or combinations thereof can optionally be incorporated up to 20 weight percent of the total weight of the copolyester composition.

[0062] Aliphatic and aromatic dicarboxylic acids or acid esters, such as succinic acid, adipic acid, isophthalic acid, naphthalene dicarboxylic acid, may also be incorporated in amounts up to 20% by weight.

[0063] The recovered products have the following notable characteristics:

[0064] * Melt flow rate of 5 to 60 g / 10 min at 270 degrees Celsius under 2.16 kg weight

[0065] *Intrinsic viscosity greater than 0.250 dl / g and up to 1.60 dl / g

[0066] *Sulfonate content up to 50% by weight, i.e. S content up to 50,000 ppm

[0067] *P content up to 60000ppm

[0068] Furthermore, various products can be obtained by adding BHET to other diols. For example, the MEG (monoethylene glycol) molecule in BHET can be replaced with other diols such as 1,4-butanediol (BDO) or 1,3-propylene glycol (PDO), hexanediol, cyclohexanedimethanol, etc., and specialty polyesters such as polybutylene terephthalate (PBT) or polypropylene terephthalate (PTT) can be manufactured from BHET.

[0069] The glycol may also include suitable glycols known in the art. For example, the alkylene glycol may include glycols having 2 to 20 carbon atoms. The glycol may be unsubstituted or substituted; a linear, branched, cyclic aliphatic glycol, an aliphatic-aromatic glycol, an aromatic glycol, or a combination of any two or more thereof. The glycol may also be a poly(alkylene ether) glycol having a molecular weight of about 250 to about 4,000. Examples of glycols include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, and poly(ethylene ether) glycols. Branched glycols include C4-C 16 Aliphatic branched glycols. The branched glycols may have 4 to 12 carbon atoms. In some embodiments, the branched glycols may have 4 to 10 carbon atoms. In other embodiments, the branched glycols may have 4 to 8 carbon atoms.

[0070] Furthermore, by adding various comonomers and additives, specialized polyesters with modified properties required / desired for various applications can be produced. Additives can be selected from isosorbide, polyalkylene glycols, thermal stabilizers, antioxidants, catalysts, branching agents / chain extenders, nucleating agents, crystalline polyesters, aliphatic or aromatic dicarboxylic acids or esters, and the like.

[0071] In addition, the above-mentioned copolyesters and / or copolyester blends can be used in textile applications together with other polyesters, nylons, polyethylene and polypropylene polymers to obtain easier and more superior dyeability with cationic dyes and disperse dyes than non-blended polymers. For example, copolyesters and / or copolyesters blended with polyester and nylon demonstrate flame retardant properties (FR properties). Due to the P molecules of the reaction, the FR properties are permanent and can not be reduced because of washing. In addition, the copolyesters made according to the present invention are blended with nylon to have permanent stain resistance.

[0072] The resulting recycled products can be used in textiles, packaging and engineering applications.

[0073] Purified and recovered BHET

[0074] Recycled BHET (rBHET) is made from recycled polyester waste produced by glycolysis of polyester waste. Polyester waste is heated with monoethylene glycol (MEG) at a nitrogen pressure of 2.5 bar at a temperature of about 200 to 240 degrees Celsius with stirring. After complete depolymerization in the presence of MEG, rBHET is purified through a multi-stage purification process to obtain pure BHET free of any polymer and non-polymer impurities. rBHET can be provided in a molten form or in a powder form. Since BHET is already a monomer, an esterification reaction is not required.

[0075] BHET was purified by using the following steps known to those skilled in the art:

[0076] Multi-stage purification method

[0077] Use microwave reactor

[0078] Use of ionic fluids

[0079] Use special filtration and crystallization technology

[0080] Using fermentation technology

[0081] Preparation of polyester from recycled BHET

[0082] I. Heating the recovered BHET powder in a reactor by raising the temperature to 120 degrees Celsius with stirring to melt the rBHET;

[0083] II. Preparation of a mixture of catalyst and diol.

[0084] III. adding the mixture of step II and at least one comonomer and additives to the molten rBHET powder of step I;

[0085] IV. gradually increasing the temperature of the mixture in step III in the range of 120 to 240;

[0086] V. adding the diol and / or comonomer to the mixture of step IV and applying an absolute pressure of 2.5 to 3.5 bar to the mixture for a period of 30 to 40 minutes, then depressurizing the reactor over 10 minutes and gradually venting the reactor to a pressure of 100 mb over 30 minutes to distill the by-products;

[0087] VI. Raising the temperature of the product to 290°C and reducing the reactor pressure to 0.20 mb to 0.1 mb to obtain a polymer product having a degree of polymerization (DP)> 50;

[0088] VII. Terminating the reaction and pelletizing the polymer;

[0089] VIII. optionally upgrading the particles by a solid state polymerization (SSP) process in a continuous SSP process operating in a batch reactor under vacuum or under a nitrogen purge in a temperature range of 160 to 220°C;

[0090] IX. Cooling and packaging the polyester or copolyester obtained as the final product.

[0091] Step I: The BHET powder obtained from waste polyester waste is recovered in a reactor equipped with a heating coil and an agitator. Heat transfer oil circulates in the heating coil. The temperature of the rBHET is gradually increased to above its melting point, which is 110 degrees Celsius. The required catalyst solution and additives are added to the reactants. The product temperature is gradually increased to 240 degrees Celsius. Thereafter, the required glycol and / or comonomer are added and the reactor is pressurized to an absolute pressure of 2.5 bar with nitrogen. After 30 minutes, the reactor is decompressed within 10 minutes and gradually emptied to a pressure of 100 mb within 30 minutes. The methyl ethylene (MEG) / glycol by-product is distilled. Once the by-product distillation is complete, heating is continued gradually to increase the product temperature to 290 degrees Celsius, and the reactor pressure is gradually reduced to 0.20 mb, and polymerization is continued. After reaching a desired degree of polymerization (DP) of >50, the reaction is terminated and the polymer is granulated. The resulting particles can be further upgraded in a solid-state polymerization (SSP) process at temperatures between 160 and 220 degrees Celsius, either in a batch SSP process operated under vacuum or in a continuous SSP process operated under nitrogen purge. The final product is then cooled and packaged.

[0092] The ratio of rBHET ranges from 20 to 100 wt %, the amount of diol ranges from 0 to 40 wt %, the amount of catalyst ranges from 0.02 to 0.09 wt %, and the amount of additives ranges from 0 to 40 wt %.

[0093] The method according to the present invention can produce copolyesters with a melting point in the range of 110 degrees Celsius to 230 degrees Celsius for various applications in extrusion, coating and spinning, and by replacing MEG with other glycols, such as DEG, a variety of polyesters and copolyesters can be produced. For example, recycled polybutylene terephthalate (rPBT) and recycled polypropylene terephthalate (rPTT) can be prepared by replacing MEG in BHET with 1,4-butanediol and 1,3-propylene glycol. Optionally, these heavier glycols can be obtained from biological sources. This enables the production of green PBT and green PTT.

[0094] The following examples illustrate various embodiments of the invention and should not be construed as limiting the scope of the invention.

[0095] Examples

[0096] The following exemplary embodiments are intended only to illustrate the process for producing polyesters and copolyesters starting with rBHET. These examples are for a pilot batch reactor with a batch size of 10 kg. The reactor is equipped with a heating coil, a stirrer, a condenser, and a vacuum system. At the bottom of the reactor is an extrusion dye with a cooling trough and a granulator. Similarly, there is a pilot batch drum dryer with a vacuum system, heating and cooling systems. Both reactors are equipped with a circulating heat transfer oil circulation system.

[0097] Example-1

[0098] Using BHET to make polyester

[0099] 1. First, add 13.50 kg of rBHET to the reactor and begin heating at a circulating heat transfer medium temperature set point of 120 degrees Celsius. Above 110 degrees Celsius, the rBHET powder will melt. At a batch temperature of 110 degrees Celsius, start the agitator.

[0100] 2. Add required amount of catalyst at batch temperature of 110 degrees C. Add antimony trioxide solution in MEG to give 280 ppm Sb in the final product.

[0101] 3. The product temperature gradually increased to 240° C. At 220° C., MEG began to distill.

[0102] 4. At 240°C, reactor venting was initiated and the reactor pressure was reduced to 500 mb over 30 minutes.

[0103] 5. After holding the batch at 240°C and 500 mb pressure for 15 minutes, the reactor pressure is further gradually reduced to 0.2 mb over 25 minutes, and the batch temperature is gradually increased to 290°C. Polymerization will continue with the release of MEG byproduct. The increase in degree of polymerization is evident as the agitator motor current power requirement increases. At the desired IV, the polymerization reaction is terminated and the polymer is pelletized into chips / granules.

[0104] *The particles have the following properties:

[0105] IV: 0.640dl / g

[0106] Carboxyl end group: 32mEQ / Kg

[0107] Melting temperature: 254 degrees Celsius

[0108] DEG: 0.80wt%

[0109] Color value L*: 58%

[0110] Color value b*: +1.0.

[0111] The above products are suitable for films and textiles (PFY / PSF)

[0112] For application in BCF, IV is increased to >1.0 by upgrading amorphous fragments in solid state polymerization (SSP)

[0113] Example-2

[0114] Using BHET to make polyester / copolyester

[0115] 1. Add 11.50 kg of rBHET to the reactor and begin heating with the circulating heat transfer medium temperature set point at 120 degrees Celsius. Above 110 degrees Celsius, the rBHET will melt. At a batch temperature of 110 degrees Celsius, start the agitator.

[0116] 2. Add the required amount of catalyst at a batch temperature of 110 degrees Celsius. A solution of antimony trioxide in MEG was added to yield 280 ppm Sb in the final product. 2.0 kg of bishydroxyethylene isophthalate (BHEI) was added to the reactor. BHEI was prepared by reacting isophthalic acid (IPA) with MEG at 240 degrees Celsius. Approximately 0.50% DEG was also added to the reactor.

[0117] 3. The product temperature is gradually increased to 240 degrees Celsius. MEG will begin to distill at 220 degrees Celsius.

[0118] 4. Start venting the reactor at 240 degrees C. Reduce the reactor pressure to 500 mb over 30 minutes.

[0119] 5. After maintaining the batch at 240°C and 500 mb pressure for 15 minutes, the reactor pressure is further gradually reduced to 0.2 mb over 25 minutes, and the batch temperature is gradually increased to 290°C. Polymerization will continue with the release of MEG byproduct. The increase in degree of polymerization is evident as the agitator motor current power requirement increases. At the desired IV, the polymerization reaction is terminated and the polymer is pelletized into chips / granules.

[0120] *Properties of amorphous particles:

[0121] IV: 0.600dl / g

[0122] Carboxyl end group: 35mEQ / Kg

[0123] Melting temperature: 247 degrees Celsius

[0124] DEG: 1.20wt%

[0125] Color value L*: 58%

[0126] Color value b*; -2.0

[0127] *The amorphous particles are then upgraded in solid state polymerization to the required IV > 0.80 for rigid packaging. Properties of SSP particles:

[0128] IV: 0.80

[0129] Carboxyl end group: 25

[0130] DEG: 1.20wt%

[0131] IPA: 1.90wt%

[0132] Color value L*: 78.0%

[0133] Color value b*: 0.0

[0134] Example-3

[0135] Using BHET to make sulfonated copolyesters

[0136] 1) Add 0.950 kg of rBHET to the reactor and begin heating with the circulating heat transfer medium temperature set point at 120 degrees Celsius. Above 110 degrees Celsius, the rBHET will melt. Start the agitator at a batch temperature of 110 degrees Celsius.

[0137] 2) Add the required amount of catalyst at a batch temperature of 110 degrees Celsius. Add antimony trioxide solution in MEG to give 280 ppm Sb in the final product. Also add 10 ppm of Ti catalyst, for which TiBT (isobutyl titanate) or TiPT (isopropyl titanate) can be used.

[0138] 3) 3.0 kg of DMSIP (1,5-dimethylsulfoisophthalate) was reacted separately with 1,4-butanediol at a molar ratio of 1:6 in the presence of calcium acetate (1.0 wt%) at 250 degrees Celsius, and the resulting ester solution was added to the reactor.

[0139] 4) 800 ppm of pentaerythritol and 300 ppm of pyromellitic dianhydride were also added to the reactor.

[0140] 5) The product temperature is gradually increased to 240 degrees Celsius. MEG will begin to distill at 220 degrees Celsius.

[0141] 6) At a product temperature of 240 degrees Celsius, 4 kg of 1,4-butanediol and 2 kg of PEG (polyethylene glycol) were added and the reactor was pressurized to a pressure of 2.5 kg / cm2. The batch was maintained under these conditions for 20 minutes and then depressurized.

[0142] 7) The reactor was then vented and the reactor pressure was reduced to 500 mb within 30 minutes.

[0143] 8) After holding the batch at 240°C and 500 mb pressure for 15 minutes, the reactor pressure is further gradually reduced to 0.2 mb over 25 minutes, and the batch temperature is gradually increased to 290°C. Polymerization will continue with the release of MEG by-product. The increase in degree of polymerization is evident with the increase in agitator motor current power requirement. At the desired IV, the polymerization reaction is terminated and the polymer is pelletized into chips / granules.

[0144] *The particles have the following properties:

[0145] IV: 0.280dl / g

[0146] Carboxyl end group: 32mEQ / Kg

[0147] Melting temperature: 220 degrees Celsius

[0148] DEG: 2.5wt%

[0149] Color value L*:>58%

[0150] Color value b*: +1.0.

[0151] S content: 30000ppm.

[0152] *The amorphous particles were then crystallized in a batch SSP reactor at a pressure of 0.20 mb at a temperature of 210 degrees Celsius and upgraded to an IV of 0.340.

[0153] The resulting sulfonated polyester is used as a masterbatch to impart stain resistance to nylon and cationic dyeability to polyester, PP, PE, and nylon.

[0154] Example-4

[0155] Using rBHET to make rPBT

[0156] 1. Add 13.50 kg of rBHET to the reactor and begin heating at a circulating heat transfer medium temperature set point of 120 degrees Celsius. Above 110 degrees Celsius, the rBHET will melt. Start the agitator at a batch temperature of 110 degrees Celsius.

[0157] 2. Add the required amount of catalyst at a batch temperature of 110 degrees C. Add 150 ppm of Ti catalyst in the form of TiBT or TiPT and 4 Kg of 1,4-butanediol to the reactor.

[0158] 3. The product temperature is gradually increased to 240 degrees Celsius. MEG will begin to distill at 190 degrees Celsius.

[0159] 4. Start venting the reactor at 240 degrees C. Reduce the reactor pressure to 500 mb over 30 minutes.

[0160] 5. After maintaining the batch at 240°C and 500 mb pressure for 15 minutes, the reactor pressure is further gradually reduced to 0.2 mb over 25 minutes, and the batch temperature is gradually increased to 260°C. Polymerization continues with the release of MEG byproduct. Each MEG molecule in the BHET is replaced by butanediol. The increase in degree of polymerization is evident as the agitator motor current power requirement increases. At the desired IV, the polymerization reaction is terminated and the polymer is pelletized into chips / pellets.

[0161] *The particles have the following properties:

[0162] IV: 0.820dl / g

[0163] Carboxyl end group: 32mEQ / Kg

[0164] Melting temperature: 228 degrees Celsius

[0165] Color value L*:>58%

[0166] Color value b*: +1.0.

[0167] The above rPBT is suitable for extrusion and injection molding.

[0168] Example-5

[0169] Production of rPTT using BHET

[0170] 1. Add 13.50 kg of rBHET to the reactor and begin heating with the circulating heat transfer medium temperature set point at 120 degrees Celsius. Above 110 degrees Celsius, the rBHET will melt. At a batch temperature of 110 degrees Celsius, start the agitator.

[0171] 2. Add the required amount of catalyst at a batch temperature of 110 degrees C. 150 ppm of Ti catalyst was used in the form of TiBT or TiPT, and 3.8 kg of 1,3-propylene glycol was added to the reactor.

[0172] 3. The product temperature is gradually increased to 240 degrees Celsius. MEG will begin to distill at 220 degrees Celsius.

[0173] 4. Start venting the reactor at 240 degrees C. Reduce the reactor pressure to 500 mb over 30 minutes.

[0174] 5. After maintaining the batch at 240°C and 500 mb pressure for 15 minutes, the reactor pressure is further gradually reduced to 0.2 mb over 25 minutes, and the batch temperature is gradually increased to 290°C. Polymerization will continue with the release of MEG byproduct. Each MEG molecule in the BHET is replaced by propylene glycol. The increase in degree of polymerization is evident as the agitator motor current power requirement increases. At the desired IV, the polymerization reaction is terminated and the polymer is pelletized into chips / pellets.

[0175] *The particles have the following properties:

[0176] IV: 0.920dl / g

[0177] Carboxyl end group: 32mEQ / Kg

[0178] Melting temperature: 225 degrees Celsius

[0179] Color value L*:>58%

[0180] Color value b*: +1.0.

[0181] 6. Amorphous particles were crystallized in a SSP process at a temperature of 200 degrees Celsius under a vacuum of <2mb and upgraded to an IV level of 1.1.

[0182] The above rPTT is suitable for filament yarn spinning, BCF and molding applications.

[0183] Example-6

[0184] Making low-melting-point polyester from rBHET

[0185] 1. Add 13.50 kg of rBHET to the reactor and begin heating with the circulating heat transfer medium temperature set point at 120 degrees Celsius. Above 110 degrees Celsius, the rBHET will melt. Start the agitator at a batch temperature of 110 degrees Celsius.

[0186] 2. Add required amount of catalyst at batch temperature of 110 degrees C. Antimony trioxide solution in MEG was added to give 280 ppm Sb in the final product.

[0187] 3. Add 4 kg of DEG to the reactor.

[0188] 4. The product temperature is gradually increased to 220 degrees Celsius. At 220 degrees Celsius, MEG will begin to distill.

[0189] 5. Start venting the reactor at 240 degrees C. Reduce the reactor pressure to 500 mb over 30 minutes.

[0190] 6. After maintaining the batch at 240°C and 500 mb pressure for 15 minutes, the reactor pressure is further gradually reduced to 0.2 mb over 25 minutes, and the batch temperature is gradually increased to 290°C. Polymerization will continue with the release of MEG byproduct. The increase in degree of polymerization is evident as the agitator motor current power requirement increases. At the desired IV, the polymerization reaction is terminated and the polymer is pelletized into chips / granules.

[0191] *The particles have the following properties:

[0192] IV: 0.640dl / g

[0193] Carboxyl end group: 32mEQ / Kg

[0194] Melting temperature: 140 degrees Celsius

[0195] Color value L*: 58%

[0196] Color value b*: +1.0.

[0197] The above products are suitable for spinning and coating applications. IV is adjusted as needed.

[0198] Example-7

[0199] Create masterbatches for easy dyeing in polyester, polypropylene (PP) and polyethylene (PE)

[0200] 1. Add 8.5 kg of rBHET to the reactor and begin heating with the circulating heat transfer medium temperature set point at 120 degrees Celsius. Above 110 degrees Celsius, the rBHET will melt. Start the agitator at a batch temperature of 110 degrees Celsius.

[0201] 2. Add required amount of catalyst at batch temperature of 110 degrees C. Add antimony trioxide solution in MEG to give 280 ppm Sb in the final product.

[0202] 3. 0.2 kg of DMSIP was reacted with 1,4-butanediol, and the resulting ester solution was added to the reactor along with 1 kg of DEG. 800 ppm of pentaerythritol and 500 ppm of pyromellitic dianhydride were also added to the reactor.

[0203] 4. The product temperature is gradually increased to 240 degrees Celsius. MEG will begin to distill at 220 degrees Celsius.

[0204] 5. Start venting the reactor at 240 degrees C. Reduce the reactor pressure to 500 mb over 30 minutes.

[0205] 6. The reactor was then depressurized and 4 kg of PEG (polyethylene glycol, molecular weight 400) was added to the reactor.

[0206] 7. After maintaining the batch at 240°C and 500 mb pressure for 15 minutes, the reactor pressure is further gradually reduced to 0.2 mb over 25 minutes, and the batch temperature is gradually increased to 290°C. Polymerization will continue with the release of MEG byproduct. The increase in degree of polymerization is evident as the agitator motor current power requirement increases. At the desired IV, the polymerization reaction is terminated and the polymer is pelletized into chips / granules.

[0207] *The particles have the following properties:

[0208] IV: 0.880dl / g

[0209] Carboxyl end group: 32mEQ / Kg

[0210] Color value L*: 58%

[0211] Color value b*: +1.0.

[0212] The resulting amorphous particles were upgraded in SSP to an IV of 1.60 dl / g

[0213] The above product is suitable for textile applications, and its mixing ratio is up to 12 wt%, and can impart dyeability to polyester, PP and PE.

[0214] Example-8

[0215] Using BHET to make polyester

[0216] 1. First, add 10 kg of rBHET to the reactor and begin heating at a circulating heat transfer medium temperature set point of 120 degrees Celsius. Above 110 degrees Celsius, the rBHET powder will melt. At a batch temperature of 110 degrees Celsius, start the agitator.

[0217] 2. Add required amount of catalyst at batch temperature of 110 degrees C. Add antimony trioxide solution in MEG to give 280 ppm Sb in the final product.

[0218] 3. The product temperature was gradually increased to 240° C. MEG distillation began at 220° C. 3.3 kg of Ukanol FR (hydroxyphenylphosphamidonopropionic acid) were added. Additives were added. The batch was kept under a nitrogen pressure of 3.0 bar for 30 minutes and then decompressed.

[0219] 4. Start venting the reactor at 240°C and reduce the reactor pressure to 500 mb over 30 minutes.

[0220] 5. After maintaining the batch at a temperature of 240°C and a pressure of 500 mb for 15 minutes, the reactor pressure is further gradually reduced to 0.2 mb over 25 minutes, and the batch temperature is gradually increased to 290°C. Polymerization will continue with the release of MEG byproduct. The increase in degree of polymerization is evident as the agitator motor current power requirement increases. At the desired IV, the polymerization reaction is terminated and the polymer is pelletized into chips / pellets.

[0221] *The particles have the following properties:

[0222] IV: 0.640dl / g

[0223] Carboxyl end group: 32mEQ / Kg

[0224] Melting temperature: 254 degrees Celsius

[0225] DEG: 0.80wt%

[0226] Color value L*: 55%

[0227] b*: +2.0

[0228] P content: 18000ppm

[0229] The above products are suitable for films and textiles (PFY / PSF)

[0230] Advantages of the present invention

[0231] The advantage of this method is that the chemically recycled PET product produced by using recycled BHET is absolutely pollution-free and can therefore be used to make specialty products to a 100% degree without any processing issues. It is as good as products made from virgin raw materials such as PTA and MEG / other diols, and is particularly suitable for applications in textiles and packaging. Secondly, the product is green and supports environmental protection and sustainability.

[0232] Because the recycled BHET has very low acid end groups, no esterification reaction is required, so high-quality chemically recycled PET can be produced compared to the virgin raw material method, and the conversion cost is lower than the traditional method using virgin raw materials.

[0233] Since the recovered BHET also does not contain antimony (Sb) catalyst, a heavy metal-free final product can be manufactured or prepared.

[0234] Since recycled BHET is free of diethylene glycol (DEG) and purified isophthalic acid (IPA), it can be used to manufacture high-quality textile PET / CoPET grades with superior stiffness and toughness.

[0235] Copolyesters and / or copolyester blends have flame retardancy, high dyeability and permanent stain resistance. Product of the present invention can be used / melt blended with other polyesters, nylon, polyethylene and polypropylene polymers in textile applications to obtain easier and more excellent dyeability with cationic dyes and disperse dyes than non-blended polymers. For example, copolyesters and / or copolyesters blended with polyester and nylon demonstrate flame retardancy (FR performance). Due to the P molecules of the reaction, FR performance is permanent and can not be reduced because of washing. In addition, copolyesters made according to the present invention are blended with nylon to have permanent stain resistance.

[0236] Polyesters are obtained from rBHET, where 99% of the MEG in rBHET is partially replaced by an aliphatic or aromatic diol selected from 1,4-butanediol (BDO) or 1,3-propylene glycol (PDO), diethylene glycol (DEG), hexanediol, cyclohexanedimethanol, or mixtures thereof, to obtain recycled polyesters such as rPBT and rPTT. Thus, green PBT and green PTT are prepared by replacing the MEG in BHET with 1,4-butanediol and 1,3-propylene glycol, which are derived from bio- or petroleum-based sources.

[0237] Although the embodiments herein are described with reference to various specific embodiments, it will be apparent to those skilled in the art that modifications can be made to implement the present invention. However, all such modifications are considered to be within the scope of the present invention.

Claims

1. A method for preparing an environmentally friendly specialty polyester or copolyester from recycled bis(2-hydroxyethyl) terephthalate, comprising the following steps: I. melting recovered bis-2-hydroxyethyl terephthalate powder in a reactor by raising the temperature to 120 degrees Celsius, wherein the recovered bis-2-hydroxyethyl terephthalate powder is pure bis-2-hydroxyethyl terephthalate free of any polymeric and non-polymeric impurities; II. Preparation of a mixture of catalyst and diol; III. adding the mixture of step II and at least one comonomer and additives to the melt-recovered 2-hydroxyethyl terephthalate powder of step I; IV. gradually increasing the temperature of the mixture of step III in the range of 120 ℃ to 240 ℃; V. adding a diol or comonomer to the mixture of step IV and applying an absolute pressure of 2.5 bar to 3.5 bar to the mixture of step IV for a period of 30 to 40 minutes, then depressurizing the reactor over 10 minutes and gradually venting the reactor to a pressure of 100 mb over 30 minutes to distill by-products, wherein the diol is selected from the group consisting of monoethylene glycol, diethylene glycol, 1,3-propylene glycol, and 1,4-butanediol; VI. The temperature of the product was raised to 290 ° C and the reactor pressure was reduced to 0.20 mb to obtain a polymer product having a degree of polymerization> 50; VII. terminating the reaction and pelletizing the polymer; VIII. Cooling and packaging the polyester or copolyester obtained as the final product, wherein the polyester or copolyester has the following characteristics: - a melt flow rate of 5 to 60 g / 10 minutes at 270 degrees Celsius under a 2.16 kg weight; - an intrinsic viscosity greater than 0.250 dl / g and at most 1.60 dl / g; - a sulfonate content of at most 50% by weight, i.e. an S content of at most 50,000 ppm; -P content is up to 60000 ppm.

2. The method according to claim 1, wherein the proportion of the recovered bis-2-hydroxyethyl terephthalate is in the range of 20 to 100 wt%, the amount of the diol is in the range of 0 to 40 wt%, the amount of the catalyst is in the range of 0.02 to 0.09 wt%, and the amount of the additive is in the range of 0 to 40 wt%.

3. The method according to claim 1, wherein the comonomer is selected from the group consisting of aliphatic and aromatic diacids selected from succinic acid, adipic acid, isophthalic acid, sebacic acid, naphthalene dicarboxylic acid, hydroxyphenylphosphinylpropionic acid, dimethyl 2,6-naphthalene dicarboxylate, naphthoic acid and their esters.

4. The process as claimed in claim 1, wherein the catalyst is selected from the group consisting of oxide / acetate compounds of metals including antimony, titanium, germanium, manganese, cobalt, tin, calcium and is used in an amount of up to 800 ppm of the element.

5. The method of claim 4, wherein the metal oxide / acetate compound is selected from the group consisting of antimony trioxide, antimony triacetate, tetraisopropyl titanate, tetrabutyl titanate, isopropyl titanate, potassium titanium oxalate, and germanium dioxide.

6. The method of claim 1 , wherein the additive is selected from 2 to 50 wt % of a catalyst, a branching agent / chain extender, isosorbide, a polyalkylene glycol, a thermal stabilizer, an antioxidant, a nucleating agent, a fast crystallizing polyester, an aliphatic or aromatic dicarboxylic acid or ester, and an aromatic metal sulfonate, wherein the metal is selected from Li, Na, K, Mg, Ca, Ni, or Fe.

7. The method according to claim 6, wherein the additive is selected from the group consisting of: - isosorbide, polyalkylene glycol selected from the group consisting of polyethylene glycol and polypropylene glycol having a molecular weight of up to 10,000; - up to 8000 ppm of heat stabilizers and antioxidants incorporated during the polymerization process; - Up to 8000 ppm of branching agents / chain extenders added; - Up to 2000 ppm of nucleating agent added; - rapidly crystallizing polyesters selected from the group consisting of polybutylene terephthalate and polytrimethylene terephthalate incorporated in an amount of up to 20% by weight; - aliphatic and aromatic dicarboxylic acids or esters of these acids, chosen from the group consisting of succinic acid, adipic acid, isophthalic acid, naphthalene dicarboxylic acid, incorporated in an amount of 20%; and - 2 to 50% by weight of an aromatic metal sulfonate.

8. The method of claim 6, wherein the branching agent / chain extender is selected from the group consisting of 1,2,4-benzenetricarboxylic acid; trimethyl 1,2,4-benzenetricarboxylate; 1,2,4-benzenetricarboxylic anhydride; 1,3,5-benzenetricarboxylic acid; 1,2,4,5-benzenetetracarboxylic acid; 1,2,4,5-benzenetetracarboxylic dianhydride; 3,3',4,4'-benzophenonetetracarboxylic dianhydride; 1,4,5,8-naphthalenetetracarboxylic dianhydride; citric acid; tetrahydrofuran-2,3,4,5-tetracarboxylic acid; 1,3,5-cyclohexanetricarboxylic acid; pentaerythritol, 2-(hydroxymethyl)-1,3-propanediol; 2,2-bis(hydroxymethyl)propionic acid; sorbitol; glycerol; and the branching agent comprises pentaerythritol, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic dianhydride, and sorbitol.

9. The method according to claim 6, wherein the polyalkylene glycol is selected from the group of glycols comprising polyethylene glycol and polypropylene glycol having a molecular weight of at most 10,000; fast crystallizing polyesters, and the heat stabilizer is selected from the group of flame retardants selected from the group of decabromodiphenyl ether and triaryl phosphates, the triaryl phosphates including triphenyl phosphate.

10. The method according to claim 6, wherein the aromatic metal sulfonate salt is selected from 5-sulfoisophthalic acid monosodium salt and 5-sulfoisophthalic acid dimethyl ester sodium salt or esters thereof.

11. The method of claim 6, wherein the fast crystallizing polyester is selected from the group consisting of polybutylene terephthalate, polytrimethylene terephthalate, polybutylene naphthalate, fast crystallizing polyester, and polytrimethylene naphthalate.

12. The method according to claim 6, wherein the nucleating agent is selected from the group consisting of: a carboxylic acid metal salt selected from the group consisting of sodium benzoate, potassium benzoate, lithium benzoate, calcium benzoate, magnesium benzoate, barium benzoate, lithium terephthalate, sodium terephthalate, potassium terephthalate, calcium oxalate, sodium laurate, potassium laurate, sodium myristate, potassium myristate, calcium myristate, sodium octacocarbonate, calcium octacocarbonate, sodium stearate, potassium stearate, lithium stearate, calcium stearate, magnesium stearate, barium stearate, sodium montanate, calcium montanate, sodium toluate, sodium salicylate , potassium salicylate, zinc salicylate, aluminum dibenzoate, potassium dibenzoate, lithium dibenzoate, sodium β-naphthalene dicarboxylate and sodium cyclohexanecarboxylate; organic sulfonates, including sodium p-toluenesulfonate and sodium sulfoisophthalate; carboxylic acid amides, including stearic acid amide, ethylenebislauric acid amide, palmitic acid amide, hydroxystearic acid amide, erucic acid amide and tris(tert-butylamide) trimellitic acid ester; metal salts of phosphate compounds, including benzyl sorbitol and its derivatives, sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate and sodium 2,2-methylbis(4,6-di-tert-butylphenyl).

13. A polyester or copolyester obtained by the method according to claim 1, characterized in that: - a melt flow rate of 5 to 60 g / 10 minutes at 270° C. under a 2.16 kg weight; - an intrinsic viscosity greater than 0.250 dl / g and at most 1.60 dl / g; - a sulfonated salt content of up to 50% by weight, i.e. a sulfur content of up to 50,000 ppm; - As a reactive flame retardant additive, the phosphorus content is up to 60,000 ppm.

14. The polyester or copolyester according to claim 13, wherein the copolyester is selected from green polybutylene terephthalate and green polypropylene terephthalate prepared by substituting monoethylene glycol in bis-2-hydroxyethyl terephthalate with 1,4-butanediol or 1,3-propylene glycol obtained from petroleum or bio-sources.

15. The polyester or copolyester of claim 13, wherein the polyester is a copolyester or a copolyester blend.

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