Method for producing polycarbonate

Abstract

The invention relates to a method for producing a polycarbonate, comprising the steps of:-subjecting a dihydroxy compound and a carbonate to a melt reaction, optionally in the presence of a transesterification catalyst, thereby forming a molten polycarbonate stream, and-combining the molten polycarbonate stream with 5 to 5000 ppm of water and 50 to 10000 ppm of a siloxane compound, based on the weight of the polycarbonate.

Description

[0001] This invention relates to a method for manufacturing polycarbonate using a melt transesterification process.

[0002] Polycarbonate is a well-known material and generally exhibits good mechanical and optical properties. Typical applications include optical media carriers, glass windows, extruded sheets, lenses, and water bottles. Polycarbonate is typically manufactured using two different technologies. In the first technology, known as interfacial technology or interfacial process, phosgene is reacted with one or more bisphenols, such as bisphenol A (BPA), in the liquid phase. The other well-known technology used to manufacture polycarbonate is the so-called melt technology, sometimes also called melt transesterification or melt polycondensation. In melt technology or melt process, a dihydroxy compound (typically bisphenol, more typically BPA) is reacted with a carbonate (typically diaryl carbonate, more typically diphenyl carbonate (DPC)) in the molten phase. Transesterification catalysts are typically used to achieve the desired molecular weight and to facilitate the polycondensation reaction.

[0003] In interfacial processes, polycarbonate is dissolved in a solvent such as dichloromethane, chlorobenzene, or a mixture of both, and the process includes several purification steps before the polycarbonate is separated and provided in powder or granule form. This means that interfacial polycarbonate is typically free of catalyst or catalyst residues and contains only small amounts of other impurities.

[0004] In melt processes, polycarbonate is obtained directly from the final reactor, and purifying the polycarbonate is impossible or at least economically infeasible. This means that any contaminants present in the feedstock or generated during polymerization, as well as further catalysts or catalyst residues, remain in the obtained polycarbonate. Furthermore, it is known that polycarbonates obtained via melt transesterification processes differ structurally from interfacial polycarbonates. First, melt polycarbonates typically have minimal branching due to the Fries and / or Kolbe-Schmidt rearrangement mechanism, which is generally absent in interfacial polycarbonates. Second, melt polycarbonates typically have a much higher number of phenolic hydroxyl end groups, while polycarbonates obtained via interfacial processes are typically capped and have up to 150 ppm, preferably up to 50 ppm, more preferably up to 10 ppm of phenolic hydroxyl end groups.

[0005] For the reasons mentioned above, molten polycarbonate is often found to exhibit less favorable initial color and / or color stability compared to interfacial polycarbonate.

[0006] US 5514767 discloses a method for improving the thermal and color stability of molten polycarbonate, which discloses a method for manufacturing a polycarbonate composition comprising: thermally melting polycondensation of an aromatic dihydroxy compound and a dicarbonate in the presence of an alkaline catalyst; adding (B) 0.1-10 ppm of a sulfur-containing acid compound or a derivative thereof with a pKa value less than 3; and (C) 5-1000 ppm of water for the polycarbonate, while the reaction product polycarbonate (A) is still in a molten state; and kneading material.

[0007] However, there is a need to further improve the quality of molten polycarbonate, therefore, one object of the present invention is to provide a molten transesterification process that produces polycarbonate with improved color properties. There is also a need for a polycarbonate containing a small amount of a starting material dihydroxy compound, such as bisphenol, for example bisphenol A (BPA).

[0008] According to the present invention, at least part of the aforementioned objectives are satisfied. The present invention relates to a method for manufacturing polycarbonate, comprising the steps of:

[0009] -Optionally, in the presence of a transesterification catalyst, the dihydroxy compound and the carbonate are melt-reacted to form a molten polycarbonate stream, and

[0010] - Combine the molten polycarbonate stream with 5-5000 ppm of water and 50-10000 ppm of siloxane compounds based on the weight of the polycarbonate.

[0011] It has been surprisingly discovered that polycarbonates obtained by the method according to the invention combine improved color properties with relatively low amounts of dihydroxy compounds.

[0012] It has been found that adding water improves the color properties of polycarbonate. However, it has also been observed that adding water leads to higher levels of residual dihydroxy compounds in the resulting polycarbonate. According to the present invention, it has been found that adding siloxane compounds reduces this increase in the amount of residual dihydroxy compounds in polycarbonate.

[0013] The method according to the invention includes combining a stream of molten polycarbonate formed by a melt reaction with water and a siloxane compound. Therefore, it should be understood that the method according to the invention does not include an intermediate step of solidifying the molten polycarbonate (e.g., granulating the molten polycarbonate) between the step of forming the molten polycarbonate stream by a melt reaction and the step of combining the stream with water and a siloxane compound. It should also be understood that the method follows the steps sequentially.

[0014] Add water

[0015] Although the exact mechanism is unknown, the inventors have surprisingly discovered that if a small amount of water is added and mixed with the polycarbonate melt from the final reactor, the color properties (especially those determined by parameter b) are improved. The yellowing (representation) has been improved.

[0016] Therefore, according to the present invention, during the polymerization process, water is added to the molten polycarbonate stream after the molten polycarbonate stream has reached the desired molecular weight (i.e., after the dihydroxy compound reacts with the carbonate and forms a polycarbonate polymer).

[0017] To ensure that water achieves the desired color properties, it is important to thoroughly mix the water with the molten polycarbonate. Therefore, mixing is preferably carried out in a static mixer or a melt mixing device, such as, in particular, an extruder.

[0018] For the purposes of this invention, the water needs to be as pure as possible. Specifically, its pH should be neutral, meaning a pH of 6.0-8.0, preferably 6.5-7.5, and more preferably 6.9-7.1. Preferably, the total dissolved solids (TDS) content of the water at 25°C is at most 3.0 ppm. The water may have one or more of the following: an iron ion content of at most 0.05 ppm, a copper ion content of at most 0.01 ppm, a carbon dioxide content of at most 2.0 ppm, and a silica content of at most 0.1 ppm. The water may have a bicarbonate content of at most 1.0 ppm.

[0019] Preferably, the conductivity of water at 25°C is at most 5.0 μS / cm. More preferably, the conductivity of water at 25°C is at most 3.0 μS / cm, more preferably at most 1.0 μS / cm, more preferably at most 0.5 μS / cm, and even more preferably 0.05 μS / cm. Methods for measuring the conductivity of water are known to those skilled in the art. Therefore, the conductivity of water is measured using a conductivity meter by determining its resistance between two flat or cylindrical electrodes with a fixed spacing. An alternating voltage is typically applied to avoid electrolysis. The conductivity is determined according to ISO 7888:1985.

[0020] The amount of water to be added and mixed is 5-5000 ppm based on the weight of polycarbonate. The inventors have found that if the amount of water is too high, it leads to undesirable degradation of the polycarbonate, particularly an undesirable decrease in molecular weight. For this reason as well, the inventors have found it important to add water online before the polycarbonate is converted into flakes, powder, or granules. Too low a amount will generally not have the desired effect or at least show only a very small improvement in the color properties of the polycarbonate.

[0021] Preferably, the amount of water is 10-4000 ppm, 30-3000 ppm, 50-2500 ppm, 75-1000 ppm, 100-800 ppm, or 150-500 ppm, most preferably 200-400 ppm, wherein the amount in ppm is based on the weight of polycarbonate. In one specific embodiment, the amount of water is 5-800 ppm, wherein the amount in ppm is based on the weight of polycarbonate.

[0022] To avoid any ambiguity, it should be understood that the water added to the polycarbonate stream is essentially water-free, which means that the amount of water in the polycarbonate stream prior to treatment is at most 10 ppm, preferably at most 1 ppm.

[0023] Preferably, the method according to the invention is carried out such that the molecular weight loss of the molten polycarbonate caused by the addition of water is limited. This is achieved, for example, by appropriately selecting the amount of water incorporated with the molten polycarbonate stream.

[0024] Preferably, the molten polycarbonate formed by the melt reaction has a first weight-average molecular weight determined using GPC based on polystyrene standards, and

[0025] After being combined with 5-5000 ppm of water, molten polycarbonate has a second weight-average molecular weight, determined using GPC based on polystyrene standards.

[0026] The second average molecular weight is at least 90%, preferably at least 95%, and more preferably at least 99% of the first average molecular weight.

[0027] Siloxane compounds

[0028] The siloxane compound is combined with the molten polycarbonate stream. The amount of the siloxane compound can be 50-10000 ppm, for example 50-5000 ppm or 100-1000 ppm, depending on the weight of the polycarbonate.

[0029] Siloxane compounds can be represented by general formula (I):

[0030]

[0031] in

[0032] Each occurrence of R1 can be the same or different, and is selected from hydrogen, methyl, ethyl, phenyl, and vinyl.

[0033] Each occurrence of R2 can be the same or different, and is selected from hydrogen, methyl, ethyl, phenyl, and vinyl.

[0034] R3 and R6 are each selected from hydrogen, hydroxyl, vinyl, methyl, methoxy, and ethoxy.

[0035] R4, R5, R7, and R8 are each selected from methyl, methoxy, ethyl, ethoxy, and phenyl.

[0036] x is an integer between 1 and 500.

[0037] Preferably, x is an integer from 2 to 400, 3 to 300, 4 to 200, 5 to 100, or 10 to 50. Higher x values ​​result in lower volatility of the siloxane compound, reducing losses in the discharge port of melt mixing devices such as extruders. Lower x values ​​result in lower viscosity of the siloxane compound, allowing for better mixing with polycarbonate. These preferred ranges of x provide a good balance of volatility and viscosity for use in this invention.

[0038] Preferably, R4, R5, R7 and R8 are each selected from methyl and phenyl.

[0039] Preferably, at least one of R3 and R6 is methyl. In some embodiments, each of R3 and R6 is methyl. In some embodiments, one of R3 and R6 is methyl, and the other of R3 and R6 is hydrogen, hydroxyl, or vinyl. In some embodiments, each of R3 and R6 is selected from hydrogen, hydroxyl, and vinyl.

[0040] Preferably, at least one of R4, R5, R7, and R8 is methyl. More preferably, at least two or at least three of R4, R5, R7, and R8 are methyl. Most preferably, each of R4, R5, R7, and R8 is methyl.

[0041] In some preferred embodiments, R3, R6, R4, R5, R7 and R8 are each methyl.

[0042] In some preferred embodiments, the siloxane compound (I) comprises or is a compound represented by the following formula:

[0043] (II)

[0044] Each occurrence of R1 can be the same or different, and is selected from hydrogen and phenyl, and y is an integer, z is an integer, and y+z=x.

[0045] y / (y+z) can be from 0.0 (i.e., y is 0) to 1.0 (i.e., z is 0). y / (y+z) can be at least 0.1-0.9, for example, 0.4-0.6. y / (y+z) can be at most 0.1, at most 0.05, or at most 0.01. y / (y+z) can be at least 0.9, at least 0.95, or at least 0.99.

[0046] In some preferred embodiments, the siloxane compound (I) comprises or is a compound represented by the following formula:

[0047] (III)

[0048] In some preferred embodiments, the siloxane compound (I) comprises or is a compound represented by the following formula:

[0049] (IV)

[0050] Where y and z are integers, and y + z = x. This has the advantage that the resulting polycarbonate has good haze properties. Preferably, y / (y + z) is at least 0.1, for example, 0.4-0.6, and may be at least 0.9, at least 0.95, or at least 0.99. In some embodiments, z is 0.

[0051] In some preferred embodiments, the siloxane compound (I) is as follows:

[0052] (V)

[0053] Where y and z are integers, and y + z = x. This has the advantage that the resulting polycarbonate has good haze properties and a particularly large reduction in the amount of bisphenol in the polycarbonate. Preferably, y / (y + z) is at least 0.1, for example 0.4-0.6, and may be at least 0.9, at least 0.95, or at least 0.99. In some embodiments, z is 0.

[0054] In some preferred embodiments, the siloxane compound (I) is as follows:

[0055] (VI)

[0056] Where y and z are integers, and y + z = x. This has the advantage of a particularly large reduction in the amount of bisphenol in the polycarbonate. Preferably, y / (y + z) is at least 0.1, for example, 0.4-0.6, and may be at least 0.9, at least 0.95, or at least 0.99. In some embodiments, z is 0.

[0057] The siloxane compound used in this invention may consist of a siloxane compound of one type as shown in formula (I), or a mixture of siloxane compounds of different types as shown in formula (I), for example, a mixture of siloxane compounds of formulas (II)-(VI).

[0058] Preferably, the siloxane compound comprises or is selected from the following compounds: phenylmethylsiloxane, methylhydrosiloxane, methylmethylsiloxane and phenylhydrosiloxane and combinations thereof, with methylhydrosiloxane being the most preferred.

[0059] While the inventors have found that the aforementioned siloxane compounds having mainly R2Si-O2 repeating units are advantageous, other siloxane compounds having any combination of R2Si-O2 repeating units, R3Si-O repeating units and / or RSi-O3 repeating units and / or Si-O4 repeating units (“R” groups correspond to any one of R1-R8 above) may also be used.

[0060] raw material

[0061] Commercially available melt polycarbonates are typically manufactured based on a dihydroxy compound and a carbonate. The dihydroxy compound can be, for example, a dihydroxy compound having a triphenylamine structure, as described in EP 0610912, but is usually a bisphenol. The carbonate can be a diaryl carbonate or a dialkyl carbonate, but is usually a diaryl carbonate.

[0062] Specifically, the dihydroxy compound is BPA, and the carbonate is DPC. However, the invention is not limited to these starting materials, and other bisphenols or carbonates can be used as is or in combination. For example, the invention also relates to a process in which the dihydroxy compound comprises BPA and another type of bisphenol. The carbonate is preferably DPC, but so-called activated carbonates, such as ester-substituted diaryl carbonates disclosed in US 2008 / 0004417, can also be used. Preferably, the polycarbonate produced according to the invention is obtained by reacting BPA and DPC as the sole monomers.

[0063] Therefore, preferably, the dihydroxy compound comprises or is composed of bisphenol, and / or the carbonate comprises or is composed of diaryl carbonate. More preferably, the dihydroxy compound comprises or is composed of bisphenol A (BPA), and / or the carbonate comprises or is composed of diphenyl carbonate (DPC). Most preferably, the dihydroxy compound is composed of bisphenol A (BPA), and the carbonate is composed of diphenyl carbonate (DPC).

[0064] Melt transesterification processes typically do not include a purification step for the resulting polycarbonate, similar to the purification steps performed in interfacial processes. Therefore, the purity of the raw material affects the quality level of the obtained polycarbonate.

[0065] One advantage of this invention is that it allows the use of slightly lower quality BPA and / or DPC while still obtaining polycarbonate with acceptable hue and bisphenol content.

[0066] Preferably, the bisphenol (especially BPA) has a purity of at least 99.3% by weight, preferably at least 99.5% by weight or at least 99.9% by weight. In some embodiments, the bisphenol (especially BPA) has a purity of up to 99.7% by weight.

[0067] Furthermore, the diaryl carbonate (especially DPC) has a purity of at least 98.5% by weight, preferably at least 98.6% by weight or at least 99.0% by weight. In some embodiments, the carbonate (especially DPC) has a purity of up to 98.7% by weight.

[0068] catalyst

[0069] The catalyst used in the method according to the invention is not limited, and any catalyst commonly known for transesterification reactions to produce polycarbonates can be used. Therefore, the catalyst can be a so-called α-catalyst, a so-called β-catalyst, or a combination of both.

[0070] Suitable examples of α-catalysts and β-catalysts are described on page 15, lines 1-28 and on page 13, lines 11 to 14, lines 34 of WO 2020074983A1, respectively, the description of which is incorporated herein by reference.

[0071] Catalyst quencher

[0072] Alpha catalysts are transesterification catalysts, which are generally more thermally stable than β catalysts. Therefore, almost all α catalysts (e.g., greater than 80% by weight, especially greater than 90% by weight) persist in the polymerization process. Consequently, such catalysts can be used to catalyze additional and generally undesirable reactions downstream of the polymerization process, such as in extruders or even in any downstream processing step such as injection molding. Therefore, catalyst deactivators or quenchers are typically added at the desired stage of the polymerization process.

[0073] Preferably, the process includes combining a molten polycarbonate stream with a quencher to at least partially deactivate the transesterification catalyst, wherein the combination with the quencher occurs upstream of the combination with water.

[0074] The quencher preferably contains a sulfonate, such as formula R 8 SO3R 9 Alkyl sulfonates, wherein R 8 It is hydrogen, C1-C 12 Alkyl, C6-C 18 Aryl or C7-C 19 alkylaryl, and R 9 It is C1-C 12 Alkyl, C6-C 18 Aryl or C7-C19 Alkyl aryl groups. Examples of alkyl sulfonates include benzene sulfonates, p-toluene sulfonates, methyl benzene sulfonates, ethyl benzene sulfonates, n-butyl benzene sulfonates, octyl benzene sulfonates and phenyl benzene sulfonates, methyl p-toluene sulfonate, ethyl p-toluene sulfonate, n-butyl p-toluene sulfonate, octyl p-toluene sulfonate and phenyl p-toluene sulfonate. Sulfonates may contain alkyl toluene sulfonates, such as n-butyl toluene sulfonate.

[0075] The amount of quencher added can be 1-10 ppm based on the total weight of polycarbonate. The exact amount of quencher depends on the amount of α-catalyst added during the process and should be sufficient to deactivate at least 90% of the remaining catalyst. To this extent, the amount of quencher added corresponds to 0.1-75 times, specifically 0.5-30 times, more specifically 1-20 times, or even more specifically 1.5-10 times, the neutralization equivalent of the catalyst used. The quencher can be part of a quencher composition that further comprises a liquid carrier such as a solvent, or a solid carrier such as a polymer, preferably polycarbonate.

[0076] A preferred quencher is butyl toluenesulfonate.

[0077] Process / facilities

[0078] Melt transesterification reaction

[0079] This invention is not limited to how the melt transesterification reaction is carried out or how the facilities for polymerization are configured. Typically, the process includes a monomer mixing stage, an oligomerization stage, and a polymerization stage. During polymerization, the temperature is typically increased, the pressure is typically decreased, and the molecular weight of the polycarbonate increases.

[0080] Given the increased viscosity of the polymer in formation, it is necessary to raise the temperature and lower the pressure to advance the polymerization reaction and effectively remove the byproducts of the condensation reaction, typically phenols.

[0081] The facility for manufacturing polycarbonate can be part of an integrated base, and BPA and DPC and / or other raw materials can be directly sourced from other facilities or units on-site, producing the monomers in solid or molten form. However, the invention is not limited to such embodiments, and raw materials such as BPA and DPC can also be obtained from external sources and added to the facility during the monomer mixing stage using suitable feeding devices and by any optional pretreatment such as melting, filtration, purification, solvent removal, etc. For example, BPA and DPC can be provided in tanks or bulk containers and fed directly or indirectly to the monomer mixing unit.

[0082] In the monomer mixing stage, the feedstocks (typically BPA and DPC) are mixed in a molten state. Optionally, a certain amount of β-catalyst may be added during this stage. The monomer mixing stage is preferably carried out at a temperature of 100-250°C, particularly 150-200°C, and even more particularly 160-185°C. The pressure during the monomer mixing stage is preferably substantially atmospheric pressure, for example, 900-1100 mbar.

[0083] The α catalyst is preferably added downstream of the monomer mixing unit, but can also be added upstream and / or directly to one or more oligomerization and / or polymerization reactors, for example.

[0084] The oligomerization stage is preferably carried out in two steps, wherein in the first step, the temperature is 230-260°C and the pressure is 140-250 mbar, and wherein in the second step, the temperature is higher than that in the first step, at 260-290°C, and the pressure is 10-50 mbar. However, the invention is not limited to two steps, and any number between 1 and 6, such as 2, 3, 4, or 5 oligomerization steps, can be used.

[0085] The weight-average molecular weight of the oligomers formed from the oligomerization stage is preferably up to 20,000, more preferably 8,000-12,000 Daltons, determined based on polystyrene standards.

[0086] The polymerization stage is preferably carried out in two steps, wherein in the first step, the temperature is 280-315°C and the pressure is 1-5 mbar, and wherein in the second step, the temperature is 280-315°C and the pressure is 0.3-5.0 mbar. However, the invention is not limited to two steps, and any number between 1 and 6, such as 2, 3, 4 or 5 polymerization steps, can be used.

[0087] Combination of molten polycarbonate with water and siloxane

[0088] After the final polymerization reactor, molten polycarbonate (which has essentially the same temperature as the final reactor) can be conveyed to a unit in which water, siloxane compounds and other optional components can be added, such as a static mixer and / or a melt mixing device, preferably an extruder.

[0089] Preferably, molten polycarbonate from the final polymerization reactor is fed directly and in molten form into such a unit.

[0090] Preferably, the method of the present invention is a continuous method for manufacturing polycarbonate.

[0091] Water can be added to the melt-mixing apparatus, for example, in the feed section of the melt-mixing apparatus, corresponding to the section where the melt from the final polymerization reactor is fed into the extruder. However, water can also be added after the final polymerization reactor and before the melt-mixing apparatus, for example, in the feed line connecting the final polymerization reactor and the melt-mixing apparatus. Water can be added at a single location or at different locations, such as in different sections of the extruder or in the feed section and feed line of the melt-mixing apparatus.

[0092] Preferably, water is not added to the final polymerization reactor. When the quencher is added to the polymer melt, it is preferable to add water after the polycarbonate has been at least partially quenched. Therefore, it is preferable to add water downstream of the addition of the catalyst quencher. The inventors have found that this configuration is preferred for maintaining the molecular weight at the desired level.

[0093] Siloxane compounds can be added to the melt mixing apparatus before, during, and / or after the addition of water.

[0094] Alternatively or alternatively to adding water and siloxane compounds to the melt mixing apparatus, water and / or siloxane compounds may be added to a static mixer. For example, water and / or siloxane compounds may be added to a static mixer that receives molten polycarbonate from a final reactor, from which the mixture can then be conveyed to an extruder. In another example, water (or siloxane) may be added to a delivery line between the final reactor and the first static mixer, and the mixture from the first static mixer may be conveyed to a second static mixer to which a siloxane compound (or water) is added.

[0095] Additives may optionally be added to, for example, melt mixing devices and / or static mixers. Suitable examples of optional additives include one or more of the following: impact modifiers, flow modifiers, fillers, reinforcing agents (e.g., glass fiber or talc), antioxidants, heat stabilizers, light stabilizers, UV light stabilizers and / or UV absorbing additives, plasticizers, lubricants, mold release agents, particularly glyceryl monostearate, pentaerythritol tetrastearate, glyceryl tristearate, stearyl stearate, antistatic agents, antifogging agents, antimicrobial agents, colorants (e.g., dyes or pigments), and flame retardants (in combination with or without anti-drip agents such as polytetrafluoroethylene (PTFE) or PTFE-encapsulated styrene-acrylonitrile copolymers). The invention is not limited in the type and amount of additives, and embodiments in which none of the additives listed above are added are feasible.

[0096] In some embodiments, the method according to the invention includes combining a molten polycarbonate stream with tris(2,4-di-tert-butylphenyl) phosphite (e.g., commercially available from BASF as Irgafos® 168). The amount of tris(2,4-di-tert-butylphenyl) phosphite relative to the amount of polycarbonate can be, for example, 10-500 ppm, such as 10-100 ppm or 100-500 ppm. It has been observed that when higher amounts of tris(2,4-di-tert-butylphenyl) phosphite are combined with the molten polycarbonate stream, the effect of the siloxane compound on reducing the amount of dihydroxy compounds, such as bisphenol, in the polycarbonate is greater.

[0097] melt filter

[0098] Preferably, the molten polycarbonate stream is passed through a melt filter after being combined with the water. The melt filter is designed to remove any particulate matter or gel from the stream.

[0099] Melt filters can have pore sizes ranging from, for example, 2.5 to 60 micrometers.

[0100] Alternatively or concurrently, the molten polycarbonate stream is passed through a melt filter before being combined with the water. It has been observed that the amount of dihydroxy compounds, such as BPA, in the final polycarbonate increases due to the presence of water in the polycarbonate stream before it passes through the melt filter. Therefore, in some embodiments, the molten polycarbonate stream is passed through a melt filter before being combined with the water, rather than after it has been combined with the water. Since the stream before passing through the melt filter does not contain water, an increase in the amount of dihydroxy compounds in the final polycarbonate due to water is avoided.

[0101] In some embodiments, the molten polycarbonate stream is subjected to a vacuum after being combined with the water. This can be done using a vacuum device provided in the melt mixing apparatus. This reduces the amount of water in the molten polycarbonate stream supplied from the melt mixing apparatus. The vacuum can be, for example, 1-800 mbar, such as 100-700 mbar. This is particularly advantageous in embodiments where the molten polycarbonate stream is passed through a melt filter after being combined with the water.

[0102] In some embodiments, the molten polycarbonate stream fed into the melt mixing apparatus includes an exhaust port for subjecting the stream to a vacuum after it has been combined with the water.

[0103] Finally, the molten polycarbonate stream is passed through a die to become one or more streams, which are then cooled and cut into pellets.

[0104] Figure 1This is an illustrative and non-limiting example of a facility for manufacturing polycarbonate according to the present invention;

[0105] Figure 2 This is another illustrative and non-limiting example of a facility for manufacturing polycarbonate according to the present invention; and

[0106] Figure 3 This is another illustrative and non-limiting example of a facility for manufacturing polycarbonate according to the present invention.

[0107] BPA and DPC are added to monomer mixing unit 10 as feed streams A and B1, respectively. The DPC to BPA ratio in monomer mixing unit is kept constant. β-catalyst is added to monomer mixing unit 10 via feed stream C. Monomer mixing unit 10 is equipped with a suitable stirrer to ensure a homogeneous mixture within the unit. Monomer mixing unit 10 is typically maintained at a temperature of 160-185°C and essentially atmospheric pressure. The feed stream exiting monomer mixing unit 10 is fed to the first oligomerization reactor 20. For process flexibility, an additional amount of DPC can be added as feed stream B2. α-catalyst is added as feed stream D. This monomer mixture is then fed into the oligomerization reactor 20 at the oligomerization stage.

[0108] The oligomerization reactor 20 operates at a temperature of 230-260°C and a pressure of 140-250 mbar. The overhead stream containing phenolic byproducts and optionally monomers or other low molecular weight reaction products is removed via stream 70 and fed to column 50, which separates the phenol from this stream. The phenol is then removed via top stream E for further purification and / or use, while the bottom stream is fed back to reactor 20 as stream 71. In an alternative embodiment, stream 70 is purified elsewhere, and no material is recycled to oligomerization reactors 20, 21.

[0109] The mixture exiting reactor 20 is fed into a second oligomerization reactor 21 for further reaction. The second oligomerization reactor 21 operates at a temperature of 260-290°C and a pressure of 10-50 mbar. Phenolic byproducts are removed from the second reactor 21 as feed stream E.

[0110] Oligopolymer reactors 20 and 21 constitute the oligopolymerization stage, generating a polycarbonate oligomer feed stream, which is fed into the first polymerization reactor 30 and then into the second polymerization reactor 31. Reactor 30 operates at a temperature of 280-315°C and a pressure of 1-5 mbar. The feed stream from the first polymerization reactor 30 is then fed into the second polymerization reactor 31, which operates at a temperature of 280-315°C and a pressure of 0.3-5.0 mbar. The temperature in reactor 31 is typically higher than that in reactor 30, and the pressure in reactor 31 is typically lower than that in reactor 30. Similar to the oligopolymerization stage, phenolic byproducts are removed from reactors 30 and 31. Together, polymerization reactors 30 and 31 constitute the polymerization stage.

[0111] The polymer leaving the second polymerization reactor 31 is fed into the extruder 40.

[0112] According to the invention, a certain amount of water is added to the feed section of the extruder 40 via feed 16a. Alternatively, water may be injected into the melt stream from the reactor 31 in a delivery line and near the feed section of the extruder (denoted as feed 16b).

[0113] According to the present invention, a certain amount of a siloxane compound and other optional additives, denoted by I, are added. The siloxane compound may alternatively be added in the feed section of the extruder, denoted by feed 16a.

[0114] A catalyst quencher is also added to the extruder to deactivate the catalyst in the molten polycarbonate. For the avoidance of doubt, it should be noted that there are no restrictions on the location of the catalyst quencher addition, and it can be added, for example, concurrently with feed 16a or 16b, or at other locations before or after either feed 16a or 16b.

[0115] The material stream extruded from the extruder 40 is passed through the melt filter 60, then extruded into strands, cooled, and cut into granules denoted by J.

[0116] It should be noted that, although Figure 1 The polymerization reactors 30 and 31 are shown as horizontal polymerization units, but these reactors can also be vertical reactors independently, such as wire wetting fall polymerization units.

[0117] Figure 1The method shown is presented as a single production line. However, at any point in the process, this production line can be split into two or more parallel production lines, each operating under the same or different conditions, including monomer mixture composition, temperature, pressure, residence time, etc. For example, the stream exiting oligomer reactor 21 can be split into two or more distinct streams, each subsequently polymerized in one or more polymerization reactors under different conditions, thereby producing different grades of polycarbonate in parallel. Another possibility is to split the stream exiting final polymerization reactor 31 and then feed the polycarbonate streams to different extruders. Figure 1 The parallel operation of the production line (partially) shown is known to those skilled in the art.

[0118] Apart from Figure 1 In addition to the specific construction shown, polycarbonate can be manufactured under one or more of the following preferred conditions.

[0119] Preferably, the monomer mixing stage includes the addition of a β catalyst, wherein the β catalyst is a quaternary ammonium or quaternary phosphorus compound or a mixture thereof.

[0120] Preferably, the oligomerization stage consists of producing polycarbonate oligomers in two oligomerization reactors, and the polymerization stage consists of producing polycarbonate in two polymerization reactors.

[0121] In a preferred embodiment of the method of the present invention, the bisphenol is BPA, the diaryl carbonate is DPC, a β catalyst is added during the monomer mixing stage, and an α catalyst is added before the monomer mixture prepared in the monomer mixing device is fed into the first oligomerization reactor. In another preferred embodiment, the bisphenol is BPA, the diaryl carbonate is DPC, the α catalyst is NaKHPO4, and the β catalyst is tetrabutylphosphonium acetate.

[0122] The method of the present invention is preferably a continuous method.

[0123] Figure 2 This is another illustrative and non-limiting example of a facility for manufacturing polycarbonate according to the present invention, and related to Figure 1 The same, except that the melt filter 61 is located between the reactor 31 and the extruder 40, rather than... Figure 1 The downstream melt filter 60 of the extruder 40.

[0124] According to this embodiment, the molten polycarbonate stream is passed through the melt filter 61 before water is added at feed 16a and / or feed 16b. This prevents any negative impact caused by the presence of water in the melt passing through the melt filter 61. Therefore, a further reduction in the amount of dihydroxy compounds in the polycarbonate is achieved.

[0125] Figure 3 and Figure 1 Similarly, except that the extruder 40 has a vacuum device 40c, the melt stream that has been mixed with water is subjected to a vacuum by the vacuum device 40c.

[0126] According to this embodiment, water is removed by vacuum before the molten polycarbonate stream passes through the melt filter 60. This reduces any negative impact caused by the presence of water in the melt passing through the melt filter 60. Therefore, a further reduction in the amount of dihydroxy compounds in the polycarbonate is achieved.

[0127] polycarbonate

[0128] The present invention further relates to a polycarbonate that can be obtained or acquired by the method according to the present invention.

[0129] The polycarbonate produced according to the present invention has an improved color compared to other polycarbonates produced under otherwise identical conditions without the addition of water to the melt mixing apparatus.

[0130] The weight-average molecular weight of polycarbonate can be, for example, 30,000-70,000 g / mol, such as 30,000-50,000 g / mol or 50,000-70,000 g / mol, which is determined using GPC based on polystyrene standards.

[0131] Preferably, the polycarbonate has an end-capping level of at least 60%, more preferably 65-95%, and even more preferably 70-95%, where the end-capping level is defined as the percentage of non-hydroxyl polycarbonate chain ends. Thus, a polycarbonate with a 60% end-capping level means that the polycarbonate has 40% of its chain ends with phenolic OH groups, typically derived from bisphenol A monomers. The other 60% of the end groups do not contain OH end groups and can be phenolic (typically derived from diphenyl carbonate) or correspond to end-capping agent molecules. The amount of chain ends capped with the end-capping agent is preferably at least 40% based on the total amount of end groups.

[0132] The end cap level is calculated using the following formula:

[0133]

[0134] Where %EC is the end-capping level, ppmOH is the amount of hydroxyl end groups (parts per million weight), and Mn is the number-average molecular weight of polycarbonate based on polycarbonate standards.

[0135] Therefore, the end-capping level is defined as the molar percentage of terminal groups in non-hydroxyl polycarbonates, and can be calculated from the amount of terminal OH groups and number-average molecular weight (Mn) in the polycarbonate.

[0136] Polycarbonates can have a degree of branching of 200–4000 ppm, for example 500–2000 ppm, resulting from the Fries (or Kolbe-Schmidt) rearrangement reaction. The degree of branching is commonly referred to as the amount of Fries branching. Methods for determining the amount of Fries branching are known to those skilled in the art and typically involve the methanol decomposition of the polycarbonate followed by HPLC chromatography to identify the total amount of Fries structure. Furthermore, NMR techniques can be used to determine the type and amount of branched structures, such as the corresponding amounts of straight-chain and branched Fries structures.

[0137] Polycarbonate can have, for example, a thickness of 1.0-100.0 cm³, as determined according to ISO 1133-1:2022 at 1.2 kg and 300 °C. 3 / 10min, preferably 2.0-50.0 cm 3 / 10min, more preferably 3.0-30.0 cm 3 Melt volumetric flow rate per 10 min. For example, polycarbonate can have a melt volumetric flow rate of 1.0–7.5 cm⁻¹, determined according to ISO 1133-1:2022 at 1.2 kg and 300 °C. 3 / 10min, 7.5-12.5 cm 3 / 10min or 12.5-30.0 cm 3 / 10min melt volume flow rate.

[0138] Preferably, the polycarbonate has a b content of up to 7.0, more preferably up to 6.5, more preferably up to 6.0, more preferably up to 5.5, and more preferably up to 4.5. The value is determined according to ClELAB (ASTM D6290-05) and ASTM E313, using a 45 / 0 geometry, a D65 light source, a 10° viewing angle, and a 32mm measuring area.

[0139] It will be understood that some amount of residual material used during the process of manufacturing polycarbonate can remain in the polycarbonate obtained by that process. Therefore, as used herein, the term "polycarbonate" should be understood to mean not only the polycarbonate molecule but also the residual material.

[0140] Preferably, the amount of residual dihydroxy compound in the polycarbonate is at most 100 ppm, at most 80 ppm, at most 70 ppm, at most 60 ppm, at most 50 ppm, at most 40 ppm, at most 30 ppm, at most 20 ppm or at most 10 ppm based on the weight of the polycarbonate.

[0141] In some embodiments, the dihydroxy compound is bisphenol A, and the amount of residual bisphenol A in the polycarbonate is at most 100 ppm, at most 80 ppm, at most 70 ppm, at most 60 ppm, at most 50 ppm, at most 40 ppm, at most 30 ppm, at most 20 ppm, or at most 10 ppm based on the weight of the polycarbonate.

[0142] The amount of residual dihydroxy compounds in polycarbonate can be determined by the following methods.

[0143] Sample preparation:

[0144] Dissolve 0.5 g of polycarbonate in 5 ml of dichloromethane (DCM) and precipitate the polycarbonate with 10 ml of methanol. Filter the solution into an LC sampler vial.

[0145] Analytical techniques:

[0146] High-performance liquid chromatography-diode array detector (HPLC-DAD).

[0147] Column: Zorbax Eclipse XDB-C18 4.6×75 mm 3.5um.

[0148] Column temperature: 35℃.

[0149] Wavelength: 280 nm (BPA)

[0150] polycarbonate composition

[0151] The present invention further provides a polycarbonate composition comprising polycarbonate and additives.

[0152] Suitable examples of additives include one or more of the following: impact modifiers, flow modifiers, fillers, reinforcing agents (e.g., glass fiber or talc), antioxidants (primary and / or secondary antioxidants), heat stabilizers, light stabilizers, UV light stabilizers and / or UV absorbing additives, plasticizers, lubricants, mold release agents, particularly glyceryl monostearate, pentaerythritol tetrastearate, glyceryl tristearate, stearyl stearate, antistatic agents, antifogging agents, antimicrobial agents, colorants (e.g., dyes or pigments), and flame retardants (in combination with or without anti-drip agents such as polytetrafluoroethylene (PTFE) or PTFE-encapsulated styrene-acrylonitrile copolymers). The invention does not limit the type and amount of additives.

[0153] In some embodiments, the polycarbonate composition comprises at least one of a primary antioxidant and a secondary antioxidant.

[0154] In some embodiments, the polycarbonate composition comprises the polycarbonate according to the invention and at least one of a primary antioxidant and a secondary antioxidant.

[0155] In some embodiments, the polycarbonate composition comprises tris(2,4-di-tert-butylphenyl) phosphite (e.g., commercially available from BASF as Irgafos® 168). The amount of tris(2,4-di-tert-butylphenyl) phosphite may be, for example, 10-800 ppm based on the amount of polycarbonate, such as 10-100 ppm or 100-800 ppm.

[0156] In some embodiments, the polycarbonate composition comprises, for example, 50-1000 ppm of a siloxane compound and tris(2,4-di-tert-butylphenyl) phosphite (e.g., commercially available from BASF as Irgafos® 168), wherein the amount of tris(2,4-di-tert-butylphenyl) phosphite is 10-800 ppm based on the amount of polycarbonate, for example, 10-100 ppm or 100-800 ppm. It has been observed that when the polycarbonate composition contains a higher amount of tris(2,4-di-tert-butylphenyl) phosphite, the siloxane compound has a greater effect on reducing the amount of bisphenol in the polycarbonate.

[0157] The present invention further provides a thermoplastic composition comprising the polycarbonate according to the invention or a polycarbonate composition according to the invention and at least one additional polymer, wherein the additional polymer is preferably selected from polycarbonate-polysiloxane copolymers, polycarbonate-polyester copolymers, polyesters, polyolefins, acrylonitrile / butadiene / styrene copolymers, methyl methacrylate / butadiene / styrene copolymers, styrene / butadiene / styrene copolymers (SBS), styrene / ethylene-butene / styrene copolymers (SEBS), styrene / ethylene-propylene / styrene copolymers (SEPS), styrene / acrylonitrile copolymers (SAN), acrylonitrile / styrene / acrylonitrile copolymers (ASA), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), unsaturated polyesters (UPES), polyamides (PA), thermoplastic polyurethanes (TPU), polystyrene (PS), high-impact polystyrene (HIPS), and polyvinyl chloride (PVC). The amount of polycarbonate may be, for example, 5-95 wt%, 50-95 wt%, or 55-95 wt% relative to the thermoplastic composition.

[0158] The thermoplastic composition according to the invention can be manufactured, for example, by melt-blending the polycarbonate according to the invention or the polycarbonate composition according to the invention with at least one other polymer.

[0159] The present invention further provides a molded article comprising, or consisting of, a polycarbonate according to the invention, a polycarbonate composition according to the invention, or a thermoplastic composition according to the invention.

[0160] The present invention further provides a method for manufacturing molded articles, the method comprising molding a polycarbonate according to the invention, a polycarbonate composition according to the invention, or a thermoplastic composition according to the invention.

[0161] The invention will now be further illustrated based on the following non-limiting embodiments.

[0162] use Figure 1 The schematic diagram shows the equipment used for the continuous production of polycarbonate.

[0163] BPA and DPC were introduced into a monomer mixing unit maintained at a temperature of 170°C and a pressure of approximately 1050 mbar. Based on each mole of BPA, 50 μmol of tetrabutylphosphonium acetate (TBPA) was also added as a β-catalyst.

[0164] The monomer mixture was then introduced into a first oligomerization reactor operating at 257°C and 180 mbar. The initial DPC / BPA ratio (molar ratio) was adjusted to 1.040 with additional DPC, and a certain amount of NaKHPO4 was added as an α catalyst. The carbonate oligomer formed in the first oligomerization reactor was fed into a second oligomerization reactor operating at 280°C and 37 mbar.

[0165] The resulting carbonate oligomers were then introduced into first and second polymerization reactors, operating at 300 and 302 °C, respectively. The pressure was selected to accommodate the formation of the desired molecular weight.

[0166] The residence time in the oligomerization stage is 1.8 hours (1.1 hours in the first oligomerization reactor and 0.7 hours in the second polymerization reactor), and the residence time in the polymerization stage is 1.0 hour (0.5 hours in each polymerization reactor).

[0167] After polymerization, the polymer is fed into an extruder, where a catalyst quencher (2 ppm butyl toluenesulfonate) is added to deactivate the catalyst. Water (conductivity <5 uS / cm, bicarbonate <1 ppm, pH 6-8) and siloxane compounds are also fed into the extruder in the amounts shown in Tables 1 and 2. Additives (200 ppm Irgafos 168, 300 ppm Irganox 1076, and 800 ppm Tinuvin 360) are also added.

[0168] The extruded material from the extruder is passed through a melt filter, then extruded into strands and cut into pellets.

[0169] b is measured in the following manner Granule color. Color measurement was performed using a BYK Gardner ColorView 9000, employing a 45 / 0 geometry, a D65 light source, a 10° viewing angle, and a 32 mm measurement area to measure L. a b The color values ​​(CIE), yellowness index (YI), and whiteness index (WI) were measured. Color measurements were performed according to CIELAB (ASTM D6290-05) and ASTM E313. The following examples disclose b. Granular color value.

[0170] The amount of residual BPA is measured using the following method.

[0171] Sample preparation:

[0172] Dissolve 0.5 g of polycarbonate in 5 ml of dichloromethane (DCM) and precipitate the polycarbonate with 10 ml of methanol. Filter the solution into an LC sampler vial.

[0173] Analytical techniques:

[0174] High-performance liquid chromatography-diode array detector (HPLC-DAD).

[0175] Column: Zorbax Eclipse XDB-C18 4.6×75 mm 3.5um.

[0176] Column temperature: 35℃.

[0177] Wavelength: 280 nm (BPA).

[0178] MW was determined using GPC based on polystyrene standards.

[0179] The following measures the end cap level %EC

[0180]

[0181] Where %EC is the end-capping level, ppmOH is the amount of hydroxyl end groups (parts per million weight), and Mn is the number-average molecular weight of polycarbonate based on polycarbonate standards.

[0182] Fries branching was determined using an Agilent 1100 series HPLC system equipped with an MWD G1365B detector. The column was an Agilent Zorbax Eclipse XDB-C18 4.6 × 75 mm. The injection volume was 50 mL. The oven temperature was 35 °C, and the data acquisition wavelength was 320.16 nm. For sample preparation, 0.3 g of sample was dissolved in 7.5 mL of a solvent mixture (based on 5 mL of tetrahydrofuran and 2.5 mL of a 10% potassium hydroxide methanol solution), heated at 40 °C for 20 min, and then 1.4 mL of acetic acid was added. Fries branching shown below is the total amount of straight-chain and branched Fries units expressed as ppm by weight.

[0183] Table 1: Effects of water and water and siloxane on pellet color and residual BPA for different types of siloxane compounds.

[0184]

[0185] As can be seen from the comparison between Comparative Example 1 and Comparative Example 2, adding water achieves less coloring than not adding water. However, adding water alone produces more residual BPA. Adding water and siloxane (Examples 3-11) achieves less coloring than without water (Comparative Example 1), and less residual BPA than adding water without siloxane (Comparative Example 2).

[0186] Increasing the amount of siloxane added further reduces the amount of residual BPA. The amount of siloxane added affects the amount of BPA in the b... The color of the granules has no substantial impact.

[0187] When the amounts of siloxane compounds are equal, the reduction in residual BPA is greatest with methylhydrosiloxane, followed by phenylmethylsiloxane, and then methylmethylsiloxane.

Claims

1. A method for manufacturing polycarbonate, comprising the steps of: -Optionally, in the presence of a transesterification catalyst, the dihydroxy compound and the carbonate are melt-reacted to form a molten polycarbonate stream, and - The molten polycarbonate stream is combined with 5-5000 ppm of water and 50-10000 ppm of siloxane compound by weight based on the polycarbonate.

2. The method of claim 1, wherein the water and the molten polycarbonate stream are combined in a melt mixing apparatus, preferably an extruder.

3. The method according to claim 1 or 2, further comprising combining the molten polycarbonate stream with a quencher to at least partially deactivate the transesterification catalyst, wherein the combination with the quencher occurs upstream of the combination with water.

4. The method according to claim 2 or 3, wherein the melt mixing apparatus comprises a vacuum device by which the molten polycarbonate stream containing the water and optionally the quencher is subjected at least partially to a vacuum of 1-800 mbar, for example 100-700 mbar, to at least partially remove water from the molten polycarbonate stream.

5. The method of claim 4, wherein after being subjected to the vacuum, the obtained molten polycarbonate stream is passed through a melt filter.

6. The method according to any one or more of claims 1-5, wherein the molten polycarbonate stream is passed through the melt filter before being combined with the water, and preferably before the molten polycarbonate stream is introduced into the melt mixing apparatus.

7. The method according to any one or more of claims 1-6, further comprising, downstream of the said combination with water and siloxane compound, cooling the molten polycarbonate stream and cutting the cooled polycarbonate into pellets.

8. The method according to any one or more of claims 1-7, wherein The dihydroxy compound contains or is composed of bisphenols, and / or the carbonate contains or is composed of diaryl carbonates. Preferably, the dihydroxy compound comprises or consists of bisphenol A (BPA), and / or the decarbonate comprises or consists of diphenyl carbonate (DPC). More preferably, the dihydroxy compound is composed of bisphenol A (BPA), and the decarbonate is composed of diphenyl carbonate (DPC).

9. The method according to any one or more of claims 1-8, wherein the siloxane compound has the general formula (I): in Each occurrence of R1 can be the same or different, and is selected from hydrogen, methyl, ethyl, phenyl, and vinyl. Each occurrence of R2 can be the same or different, and is selected from hydrogen, methyl, ethyl, phenyl, and vinyl. R3 and R6 are each selected from hydrogen, hydroxyl, vinyl, methyl, methoxy, and ethoxy. R4, R5, R7, and R8 are each selected from methyl, methoxy, ethyl, ethoxy, and phenyl. x is an integer between 1 and 500.

10. The method according to claim 9, wherein the siloxane compound of formula (I) comprises or is represented by the following formula: (II) in Each occurrence of R1 can be the same or different, and is selected from hydrogen and phenyl. y is an integer, z is an integer, and y + z = x.

11. The method according to claim 9 or 10, wherein the siloxane compound of formula (I) comprises or is represented by the following formula: (III), (IV), (V) or (WE) Where y / (y+z) is at least 0.1, for example 0.4-0.6, or at least 0.9, at least 0.95, or at least 0.99, or z is 0.

12. The method according to any one or more of claims 1-11, wherein the siloxane compound comprises or is selected from compounds including phenylmethylsiloxane, methylhydrosiloxane, methylmethylsiloxane and phenylhydrosiloxane and combinations thereof, preferably the siloxane compound comprises or is methylhydrosiloxane.

13. The method according to any one or more of claims 1-12, wherein the amount of water is 10-4000 ppm, 30-3000 ppm, 50-2500 ppm, 75-1000 ppm, or 150-500 ppm or 200-400 ppm, and / or wherein the conductivity of the water is at most 5 μS / cm, which is measured at 25°C according to ISO 7888:1985.

14. A polycarbonate that can be obtained or acquired by any one or more of the methods according to claims 1-13, preferably wherein the amount of residual dihydroxy compound or residual bisphenol A in the polycarbonate is at most 100 ppm, at most 80 ppm, at most 70 ppm, at most 60 ppm, at most 50 ppm, at most 40 ppm, at most 30 ppm, at most 20 ppm or at most 10 ppm based on the weight of the polycarbonate.

15. A method for manufacturing a molded article, the method comprising molding the polycarbonate according to claim 14.

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