Process for preparing water-stable thermoplastic composition

Abstract

The present invention relates to a process for the preparation of a thermoplastic composition comprising an aromatic polycarbonate, a polyester, a hydrolysis stabilizer composition, optionally an impact modifier and optionally further components, comprising the steps of: a) combining the polyester with the hydrolysis stabilizer composition in a first melt mixing device to form a stabilized polyester, b) combining the stabilized polyester with an aromatic polycarbonate and optionally an impact modifier in a second melt mixing device, wherein the hydrolytic stabilizer composition comprises at least one compound containing diimide and / or epoxy functional groups.

Description

[0001] The present invention relates to a process for preparing a water-stable thermoplastic composition comprising polycarbonate and polyester, and to the composition so prepared per se. The present invention also relates to articles comprising or made from such a composition.

[0002] Compositions comprising polycarbonate and polyester have excellent appearance, mechanical properties, dimensional stability and chemical resistance, and are widely used in various fields. In particular, compositions consisting of polycarbonate and poly(butylene terephthalate) (PBT) impart excellent mechanical properties (e.g., impact, ductility and dimensional stability) and chemical resistance to polycarbonate. These compositions are particularly useful in the field of interior and exterior parts such as in automobiles.

[0003] However, polyesters such as PBT having a relatively large number of -COOH end groups can affect the stability of polycarbonates in polyester-polycarbonate blends. It is believed that the -COOH end groups of the polyester can cause the polycarbonate to lose molecular weight, resulting in changes in the properties of the polycarbonate. This effect can be enhanced by the presence of catalysts or catalyst residues that may be applied during the manufacture of the polycarbonate.

[0004] The impact properties of compositions comprising polycarbonate and polyester can be enhanced by adding suitable impact modifiers. Such impact modifiers can be prepared by means of an emulsion polymerization process including the use of processing aids such as emulsifiers and coagulants. Such processing aids, if part of the impact modifier, may also cause the decomposition of the polycarbonate, i.e. promote hydrolysis.

[0005] In addition to the above, a quencher is usually added to the composition comprising polycarbonate and polyester in order to prevent transesterification of the polyester and the polycarbonate. Such quenchers are usually moderately acidic. In order to maintain a certain level of hydrolytic stability of the composition, it is necessary to select the quencher so that its acidity is sufficient to quench the residual catalyst in the polyester, but at the same time it does not significantly cause hydrolysis of the polycarbonate.

[0006]

[0006] It would therefore be desirable to provide compositions comprising polycarbonates and polyesters which have improved hydrolytic stability in demanding applications, particularly where the compositions may be exposed to moisture at elevated temperatures.

[0007] Hydrolysis stabilizers are added to such PC / PBT compositions to improve the hydrolysis stability of the compositions. However, the use of such hydrolysis stabilizers in PC / PBT compositions prepared by the methods described in the prior art (such as blending all components in a high-speed mixer or by hand mixing) often results in disadvantages such as unsatisfactory mechanical and thermal properties.

[0008] It is an object of the present invention to provide a suitable process for preparing thermoplastic compositions which have good initial mechanical properties and are suitable for use in applications in which the compositions may be exposed to moisture at elevated temperatures.

[0009] It is a further object of the present invention to provide a thermoplastic composition comprising polycarbonate and polyester, wherein the composition has a good combination of water stability, impact properties and thermal stability.

[0010] These objects are at least partially met according to the present invention, which relates to a process for preparing a thermoplastic composition comprising an aromatic polycarbonate, a polyester, a hydrolysis stabilizer composition, optionally an impact modifier and optionally other components, comprising the following steps:

[0011] a) combining the polyester with a hydrolysis stabilizer composition and optionally other components in a first melt mixing device to form a stabilized polyester,

[0012] b) combining the stabilized polyester with an aromatic polycarbonate and optionally an impact modifier in a second melt mixing device,

[0013] The hydrolysis stabilizer composition comprises at least one compound containing imide and / or epoxy functional groups.

[0014] Without wishing to be bound by it, the inventors believe that combining the polyester with the hydrolysis stabilizer composition helps capping the acid end groups of the polyester, thereby forming a stabilized polyester. It is well known that the higher the acid end groups in the polyester, the higher the rate of the hydrolysis reaction. Therefore, acid end group capping helps to improve the hydrolytic stability of the polyester. Surprisingly, the inventors have found that by making a masterbatch of the polyester with a hydrolysis stabilizer composition before combining the thus stabilized polyester with an aromatic polycarbonate in a two-step process according to the present invention, the hydrolytic stability of the thermoplastic composition is improved. It is believed that, through this two-step process, the residence time of the hydrolysis stabilizer composition to react with the acid end groups of the polyester is longer, thereby allowing the hydrolysis stabilizer to cap the acid end groups of the PBT to a higher degree. The reduction of the acid end groups of the polyester reduces the hydrolysis kinetics, thereby improving the hydrolytic stability of the composition.

[0015] The present invention will now be described in more detail.

[0016] Aromatic polycarbonate

[0017] In the context of the present invention, the term polycarbonate is understood to mean aromatic polycarbonate. The terms "polycarbonate" and "aromatic polycarbonate" both therefore have the same meaning and can be used interchangeably. As known to the skilled person, aromatic polycarbonates are polycarbonates containing aromatic groups.

[0018] Aromatic polycarbonates are generally manufactured using two different technologies. In the first technology, which is called the interfacial technology or interfacial process, phosgene reacts with bisphenol, usually bisphenol A (BPA), in the liquid phase. Another well-known technology is the so-called melt technology, sometimes also called melt transesterification or melt polycondensation technology. In the melt technology or melt process, a bisphenol, usually BPA, reacts with a carbonate, usually diphenyl carbonate (DPC), in the melt phase. Aromatic polycarbonates obtained by the melt transesterification process are known to be structurally different from aromatic polycarbonates obtained by the interfacial process. In this regard, it should be particularly noted that the so-called "melt polycarbonate" usually has the least amount of Fries branches, and Fries branches are generally absent in "interfacial polycarbonates". In addition, melt polycarbonates usually have a greater number of phenolic hydroxyl end groups, while polycarbonates obtained by the interfacial process are usually end-capped and have phenolic hydroxyl end groups of up to 150 ppm, preferably up to 50 ppm, and more preferably up to 10 ppm. Usually, the amount of phenolic hydroxyl end groups is below the detection limit.

[0019] Preferably, the aromatic polycarbonate comprises or consists of a mixture of bisphenol A polycarbonate or bisphenol A polycarbonate. Preferably, the aromatic polycarbonate of the invention disclosed herein comprises at least 75% by weight, preferably at least 95% by weight, of bisphenol A polycarbonate based on the total amount of aromatic polycarbonate. More preferably, the aromatic polycarbonate in the composition consists essentially of or consists of bisphenol A polycarbonate. Preferably, the aromatic polycarbonate has a weight average molecular weight (Mw) of 15,000 to 60,000 g / mol measured using gel permeation chromatography with polystyrene standards. Preferably, the Mw of the aromatic polycarbonate is 20,000 to 45,000 g / mol. If the polycarbonate is a mixture of two or more aromatic polycarbonates, the Mw should be determined based on the mixture, wherein each of the aromatic polycarbonates that preferably constitute the mixture has an Mw of 20,000 to 45,000 g / mol.

[0020] In one aspect, the aromatic polycarbonate is an interfacial polycarbonate.

[0021] In another aspect, the aromatic polycarbonate is a melt polycarbonate.

[0022] In yet another aspect, the aromatic polycarbonate is a mixture of 20-80 wt % or 40-60 wt % interfacial polycarbonate and 80-20 wt % or 60-40 wt % molten polycarbonate, based on the weight of the aromatic polycarbonate.

[0023] Preferably, the aromatic polycarbonate in the composition according to the present invention is composed of interfacial polycarbonate, with an end-capping level of at least 90 mol %. On the other hand, the aromatic polycarbonate in the composition according to the present invention is composed of molten polycarbonate, with an end-capping level of at least 75 mol %, preferably at least 80 mol %, more preferably at least 85 mol %. End-capping level can be at most 95 mol %, for example at most 90 mol %. In this respect, end-capping level is regarded as a measured value of the aromatic polycarbonate in the composition. In yet another aspect, the aromatic polycarbonate can be a mixture of molten polycarbonate and a polycarbonate that is not made using a melting method (such as an interfacial method), as long as end-capping level is at least 75 mol %.

[0024] The aromatic polycarbonate may have a melt volume rate (MVR) of 1 to 50 cc / 10 min, specifically 2 to 30 cc / 10 min, for example 10 to 15 cc / 10 min, measured according to ISO 1133 (300° C., 1.2 kg). The aromatic polycarbonate may include two or more aromatic polycarbonates having different melt volume rates (i.e., molecular weights). The aromatic polycarbonates in the mixture may all be bisphenol A polycarbonate homopolymers. On the other hand, the aromatic polycarbonate may include a polycarbonate copolymer containing a structural unit of bisphenol A and a structural unit of another bisphenol.

[0025] Polyester

[0026] The polyester in the composition disclosed herein comprises at least 80 wt %, preferably at least 90 wt %, of polybutylene terephthalate (PBT), based on the weight of the polyester. More preferably, the polyester in the composition disclosed herein consists essentially of or consists of polybutylene terephthalate. The PBT can be a mixture of two or more different polybutylene terephthalates, for example a mixture of PBTs having mutually different intrinsic viscosities. The polyester can also include mechanically recycled PBT or PBT obtained from (chemically) recycled poly(ethylene terephthalate) (PET). Polyesters such as PBT and PET are themselves well known to the skilled person.

[0027] The PBT can be a single polymer, or can be a combination of two or more, preferably two, PBTs having different properties from each other. For example, the PBT can include a first PBT and a second PBT, each of which has a different intrinsic viscosity. Therefore, the PBT in the composition of the present invention can be a blend of such a first PBT and a second (or more) PBT. In this regard, the first PBT can have an intrinsic viscosity of 1.1 to 1.4 dl / g, and the second PBT can have an intrinsic viscosity of 0.6 to 0.8 dl / g.

[0028] According to the present invention, the polyester may have an intrinsic viscosity of 0.4 to about 2.0 dl / g measured in a 60:40 phenol / tetrachloroethane mixture at 23° C. In aspects where the polyester is a mixture, this preferred feature applies to the mixture.

[0029] Preferably the polyester comprises at least 50 wt%, preferably at least 75 wt%, more preferably at least 95 wt% PBT based on the weight of the polyester. Preferably the polyester consists of PBT. Preferably PBT is the only polyester in the composition.

[0030] In one aspect, the polyester may further include an additional polyester miscible with PBT. Such polyesters include poly(ethylene terephthalate), poly(ethylene naphthalate) (PEN), poly(butylene naphthalate) (PBN), poly(trimethylene terephthalate) (PPT), poly(cyclohexanedimethylene terephthalate) (PCT), poly(cyclohexane-1,4-dimethylenecyclohexane-1,4-dicarboxylate) (also known as poly(1,4-cyclohexane-dimethanol-1,4-dicarboxylate) (PCCD) and copolyesters PCTG and PETG, preferably PET. According to this aspect of the invention, the composition preferably comprises 99 to 80 wt% PBT and 1 to 20 wt% of one or more of the additional polyesters, based on the weight of the polyester. Preferably, the additional polyester is PET.

[0031] The polyester may also include mechanically recycled PBT or PBT obtained from renewable resources. Polyesters such as PBT are well known to the skilled person per se. The PBT used in the composition of the present invention may, for example, be a polymer comprising polymerized units derived from terephthalic acid or its diester, such as dimethyl terephthalate, and polymerized units derived from butanediol, such as 1,4-butanediol.

[0032] In any aspect where the polyester comprises PBT, a mixture of PBT and a non-PBT polyester, the intrinsic viscosity of the polyester is preferably 0.6 to 1.4 dl / g. The PBT may have a carboxyl end group content of 10-80 mmol / kg, preferably 20-60 mmol / kg, more preferably 20-40 mmol / kg, as determined according to ASTM D7409-15.

[0033] Hydrolysis Stabilizer

[0034] The hydrolysis stabilizer composition preferably comprises at least one compound containing imide and / or epoxy functional groups. Preferably, the hydrolysis stabilizer essentially comprises at least 80% by weight, preferably at least 90% by weight, more preferably at least 95% by weight of the at least one compound containing imide and / or epoxy functional groups, based on the weight of the hydrolysis stabilizer composition. More preferably, the hydrolysis stabilizer essentially consists of or consists of the at least one compound containing imide and / or epoxy functional groups.

[0035] The thermoplastic composition with improved hydrolysis stability obtainable by the process of the invention preferably comprises from 0.1 to 10% by weight, preferably from 0.5 to 3% by weight, based on the weight of the composition, of a hydrolysis stabilizer composition comprising at least one compound containing imide and / or epoxy functional groups.

[0036] The epoxy compound may have one or more epoxy functional groups. The term "multifunctional epoxy compound" is defined to include compounds having at least two epoxy functional groups. A preferred difunctional epoxy compound is 3,4-epoxycyclohexyl-3,4-epoxycyclohexyl carboxylate, which is commercially available as ERL-4221 epoxy resin from Union Carbide. Other preferred examples of difunctional epoxy compounds are bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene diepoxide, bisphenol diglycidyl ether, diglycidyl adducts of amides, diglycidyl adducts of carboxylic acids, and the like.

[0037] Other hydrolysis stabilizers containing epoxy functional groups can be ethylene and / or styrene copolymers, which contain repeating units derived from ethylene and epoxy comonomers, and the epoxy comonomers include, for example, glycidyl acrylate, glycidyl methacrylate, glycidyl butyl acrylate, glycidyl vinyl ether, or a combination of two or more thereof. Frequently used ethylene and / or styrene copolymers may further contain repeating units derived from esters of unsaturated carboxylic acids (including (meth) acrylates or (meth) acrylic acid C1-C8 alkyl esters, or a combination of two or more thereof). "(Meth) acrylate" refers to acrylate, alkyl acrylate, methacrylate, or a combination of two or more thereof. Examples of alkyl acrylates include methyl acrylate, ethyl acrylate and butyl acrylate.

[0038] The ethylene and / or styrene copolymers may also comprise, consist essentially of, or consist of repeating units derived from ethylene and / or styrene and an epoxy comonomer (including, for example, glycidyl esters of acrylic acid or methacrylic acid, glycidyl vinyl ether, or combinations thereof) and an additional comonomer (e.g., carbon monoxide). Such epoxy compounds are commercially available or may be prepared by techniques well known to those skilled in the art.

[0039] On the other hand, the hydrolysis stabilizer composition comprises at least one compound containing an imide functional group. The compound preferably contains at least one carbodiimide group. These compounds are known and commercially available, for example, Stabaxol P is a product of Rhein Chemie Corporation, which can be prepared by known methods (e.g. European Patent No. 582983; Japanese Patent Publication No. 33279 / 1972; Journal of Organic Chemistry, 28, 2069-207591963); Chemical Review, 1981, Vol. 81, No. 4, 619-621; Journal of Applied Polymer Science, 1977, Vol. 21, 1999-2008, all incorporated herein by reference).

[0040] Impact modifiers

[0041] The thermoplastic composition of the present invention optionally comprises an impact modifier. The amount of the impact modifier may be 0 to 15 wt % based on the weight of the composition. Preferably, the impact modifier is included in the composition in an amount of 2 to 12 wt %, more preferably 4 to 8 wt %.

[0042] Suitable impact modifiers are typically high molecular weight elastomeric materials derived from olefins, monovinyl aromatic monomers, acrylic and methacrylic acids and their ester derivatives, and conjugated dienes. The polymers formed from the conjugated dienes can be fully or partially hydrogenated. The elastomeric material can be in the form of a homopolymer or copolymer, including random, block, radial block, grafted, and core-shell copolymers. Combinations of impact modifiers are also used.

[0043] The impact modifier preferably comprises or consists of at least one of an acrylonitrile-butadiene-styrene (ABS) polymer and / or a methyl methacrylate-butadiene-styrene (MBS) polymer.

[0044] Other components

[0045] The thermoplastic composition disclosed herein comprises 0 to 5% by weight of other components, which are preferably selected from reinforcing fillers or non-reinforcing fillers, such as talc, calcium carbonate, glass flakes, glass fibers, etc., antifogging agents, plasticizers, flow enhancing additives, lubricants, pigments, dyes, flame retardants, nucleating agents, heat stabilizers, UV absorbers, UV stabilizers, dispersants, surfactants, antistatic agents, slip agents, or a combination of two or more thereof. Such additional components are known per se to the skilled person.

[0046] Preferably, the other components according to the present invention comprise 0.01 to 1 wt. % of a compound selected from Group IB metal phosphates and Group IIB metal phosphates, based on the weight of the composition. Preferably, the compound is selected from Group IB and / or Group IIB metal acid phosphates, metal acid pyrophosphates and metal polyphosphates, more preferably the catalyst quencher is zinc phosphate. The compound is used as a quencher of the catalyst or catalyst residues in the polyester.

[0047] Preferably, the other components comprise 0.01 to 1 wt %, preferably 0.03 to 0.5 wt %, based on the weight of the composition, of a compound containing at least one of an alkali metal cation or an alkaline earth metal cation and a halogen anion, the compound preferably being selected from one or more of lithium fluoride, lithium iodide, potassium bromide, potassium iodide, sodium dihydrogen phosphate, sodium acetate, sodium benzoate, sodium hexanoate, sodium stearate, sodium ascorbate and magnesium hexanoate.

[0048] Composition

[0049] According to the present invention, the thermoplastic composition comprises:

[0050] (A) 40 to 70 wt% aromatic polycarbonate

[0051] (B) 20 to 40% by weight of polyester

[0052] (C) 0.1 to 10 wt% hydrolysis stabilizer composition

[0053] (D) 0 to 15 wt% impact modifier

[0054] (E) 0 to 5 wt% of other components

[0055] wherein the total amount of (A) to (E) is 100% by weight, and

[0056] The hydrolysis stabilizer composition comprises at least one compound containing imide and / or epoxy functional groups.

[0057] The amount of component (A) may be 50 to 70% by weight.

[0058] The amount of component (B) may be 25-35% by weight.

[0059] The amount of component (C) may be 0.5-3% by weight.

[0060] The amount of component (D) may be 2-12% by weight.

[0061] The amount of component (E) may be from 0.01 to 3% by weight.

[0062] Preferably, component (B) comprises or consists of poly(butylene terephthalate).

[0063] For the avoidance of doubt, the skilled person will appreciate that the total weight of the composition will be 100 wt % and that any combination of materials that does not add up to 100 wt % is impractical and not in accordance with the present invention.

[0064] Preferred ranges for the amounts of the components can be combined with preferred ranges for the properties of the composition without limitation, provided that they certainly fall within the scope of the invention as defined herein in its broadest form. That is, preferred ranges for one or more of the amounts and / or types of the components making up the thermoplastic composition can be combined with preferred ranges for one or more properties of the thermoplastic composition, and all such combinations are considered to be disclosed herein.

[0065] Method for making thermoplastic composition

[0066] According to the present invention, the thermoplastic composition is prepared by a method comprising the following steps:

[0067] a) combining the polyester with a hydrolysis stabilizer composition and optionally some or all of the other components in a first melt mixing device to form a stabilized polyester,

[0068] b) combining the stabilized polyester with an aromatic polycarbonate and optionally an impact modifier and / or some or all of the other components in a second melt mixing device.

[0069] Addition of the hydrolysis stabilizer composition in step (a) may occur before the polyester is melted or after the polyester is melted or both before and after the polyester is melted.

[0070] The residence time in step a) is preferably at most 90 seconds, more preferably at most 60 seconds or at most 30 seconds. The residence time may be at least 2, 10 or 20 seconds. The residence time should be appropriately selected so that the polyester and the hydrolysis stabilizer have sufficient time to react, thereby providing a stabilized polyester. In order to determine whether a stabilization reaction has occurred, the amount of hydrolysis stabilizer in the polyester obtained in step a) can be measured. If this amount is less than the feed amount of the first melt mixing device, a stabilization reaction has occurred. Alternatively, the effect can also be determined based on measuring the properties of the thermoplastic composition finally obtained.

[0071] It is essential to the present invention that the polyester is stabilized before it is combined with the polycarbonate. The stabilized polyester is preferably combined with the polycarbonate directly after the stabilization step a), wherein the stabilized polyester is still in molten form. In this case, the term "directly" means that the stabilized polyester does not undergo any further specific process steps and / or is not combined with any other materials in additional equipment before it is combined with the polycarbonate in the second melt-mixing device.

[0072] Alternatively, although less preferred, the stabilized polyester may be pelletized and combined with the polycarbonate in step b) by feeding such pellets to the feed section of the melt mixing apparatus of step b). This alternative allows large quantities of stabilized polyester to be prepared and stored for repeated use when convenient. However, it is important that the pelletized and stabilized polyester is subsequently stored under dry conditions, i.e., at a relative humidity of no more than 20% at 25°C.

[0073] The residence time in step b) is less critical and may be the same as or different from the residence time in step a).The melt mixing temperature in the first and second melt mixing devices is preferably from 230°C to 350°C.

[0074] The melt mixing device used in step a) and / or b) is preferably an extruder.

[0075] The stabilized polyester from the first melt-mixing device is fed into the second melt-mixing device. The extrudate from the second melt-mixing device can be cooled, for example in a water bath, and pelletized. The pellets so prepared can be 0.6 cm long or shorter as desired. Such pellets can be used for subsequent molding, shaping or forming into semi-finished or finished products.

[0076] According to the present invention, the thermoplastic composition obtained or obtainable by the process described above has or is selected to have the following combination:

[0077] - At least 50 kJ / m 2 Initial notched Izod impact measured at 23°C according to ISO180-1A,

[0078] - a notched Izod impact retention of at least 80% measured according to the method described in the specification,

[0079] A heat deformation temperature of at least 90°C, preferably 90°C to 120°C, measured under a load of 0.45 MPa according to ISO 75A flat method.

[0080] In a preferred aspect, the thermoplastic composition prepared by the process of the present invention exhibits a notched Izod impact retention that is at least about 5%, preferably at least about 10%, more preferably at least about 20% greater than the same composition without component (C).

[0081] Also provided are shaped, formed or molded articles comprising the composition. The composition can be molded into articles by various methods such as injection molding, extrusion and thermoforming. Some examples of articles include automotive and vehicle body panels such as bumper covers and bumpers or housings for electrical equipment.

[0082] Thus, the present invention relates to an article comprising or consisting of a thermoplastic composition or a thermoplastic composition obtainable by the process disclosed herein, wherein preferably the article is an automotive interior article or a housing for an electrical device.

[0083] More specifically, the present invention relates to a vehicle body part or a housing of an electrical device comprising or consisting of the thermoplastic composition disclosed herein. Likewise, the present invention relates to an article comprising or constituting any one or more selected from the group consisting of an instrument panel, a cup holder, a glove box, an instrument panel, an instrument panel carrier, a door covering, a door fixing, an armrest, a pillar covering, a seat covering, a trunk covering, and a component used in a heating, ventilation and / or air conditioning device. In addition, the present invention relates to a vehicle or an electrical device comprising the vehicle body part or the housing. The present invention relates to the use of a thermoplastic composition or a thermoplastic composition obtainable by the method disclosed herein in the manufacture of an article (preferably an automotive part, more preferably an interior automotive part).

[0084] The invention will now be further elucidated based on the following non-limiting examples.The examples and comparative examples disclosed herein provide the skilled person with material that does and does not fall within the scope of the invention, respectively, and thus constitute a basis for developing further embodiments according to the invention without undue burden.

[0085] The invention disclosed herein is based on the discovery that compositions comprising a polyester, an aromatic polycarbonate, and a hydrolysis stabilizer are preferably prepared such that the hydrolysis stabilizer is combined with the polyester before the polyester is combined with the aromatic polycarbonate.

[0086] Thus, in one aspect, the present invention relates to a process for preparing a thermoplastic composition comprising the step of combining a stabilized polyester and an aromatic polycarbonate, wherein the stabilized polyester is obtained by reacting the polyester and a hydrolysis stabilizer composition in the melt.

[0087] A hydrolysis stabilizer is a compound that is capable of reacting with the acidic groups of the polyester so that these groups can no longer interact with the (aromatic) polycarbonate, resulting in a decrease in the mechanical properties of the polyester-aromatic polycarbonate composition. In principle, any hydrolysis-stabilizing compound that is capable of such a reaction with the polyester can be considered suitable for the purposes of the present invention. Despite the above provisions, although there are in principle no strict restrictions on the type of stabilizer, the hydrolysis stabilizer composition preferably comprises, essentially consists of or consists of a compound containing imide or epoxy functional groups. Such compounds are disclosed in more detail above. The amount of the hydrolysis stabilizer composition may be 0.1 to 25% by weight, for example 1 to 20% by weight, based on the weight of the stabilized polyester.

[0088] Preferably, the polyester comprises at least 50 wt. %, preferably at least 75 wt. %, more preferably at least 95 wt. % PBT, based on the weight of the polyester. The polyester may consist essentially of or consist of a mixture of PBT and PET. The weight ratio between PET and PBT may be from 0.1 to 10 and may be suitably selected to adjust the final properties of the thermoplastic composition. Advantageously, at least part of the PET is mechanically recycled PET, such as marine or ocean derived recycled PET. All further preferred aspects of the thermoplastic composition and its method of preparation are as described herein.

[0089] Test methods

[0090] Example

[0091] Table 1 lists the components of the composition and their sources.

[0092] Table 1: Components of the composition and their sources

[0093]

[0094] In the examples, PBT was combined with a hydrolysis stabilizer composition, an impact modifier, and other components (i.e., an antioxidant) using a dry blender to form a dry blend. In the examples where the hydrolysis stabilizer composition contained at least one compound containing an epoxy functional group (i.e., ERL, JCR, or ELV, see Table 1), 0.1 parts of sodium stearate were also added, which catalyzed the ring opening of the epoxy resin and promoted the end-capping of the acid end groups of the PBT. The dry blend was melt mixed in an intermeshing twin-screw extruder (model ZSK-25) manufactured by Coperion at a temperature range of 150°C to 260°C. The screw diameter was 25 mm, the L / D ratio was 41, and the screw rotation was maintained at 300 rpm during the melt mixing process. The observed residence time was approximately 40 seconds. This formed a stabilized polyester (masterbatch). The stabilized polyester thus formed was then fed to a second melt-mixing device (another intermeshing twin-screw extruder manufactured by Coperion (Model ZSK-25)) by a gravimetric feeder, whereupon it was combined with PC and further melt-mixed under the same conditions as the previous one, with a residence time of about 40 seconds, and extruded. The extruded pellets were thoroughly dried in a hot air circulating oven at 100°C for a minimum of four hours. The samples were molded by injection molding at 260°C on an L&T ASWA 100T injection molding machine, with the mold temperature of all compositions being maintained at 100°C.

[0095]

[0096]

[0097] The amounts in Table 2 are weight percent based on the total weight of the composition. In all examples, the total amount of the components is equal to 100 weight percent. Table 2 shows that thermoplastic compositions comprising PC / PBT and an impact modifier, i.e., ABS or MBS, in the absence of the hydrolysis stabilizer of the present invention (CE1 and CE2) do not show the desired hydrodynamic aging properties in terms of notched Izod impact retention as determined according to the method described above. For samples CE3 to CE9, thermoplastic compositions comprising the desired hydrolysis stabilizer composition were prepared by simply blending all the components together in a high-speed mixer. Such compositions show lower hydrolytic stability (in terms of NII(Ret)) than similar compositions prepared according to the method described in the present invention (E1 to E9).

Claims

1. A method for preparing a thermoplastic composition comprising an aromatic polycarbonate, a polyester, a hydrolysis stabilizer composition, an optional impact modifier and optional other components, comprising the following steps: a) combining the polyester and the hydrolysis stabilizer composition in a first melt mixing device to form a stabilized polyester, b) combining the stabilized polyester with an aromatic polycarbonate and optionally an impact modifier in a second melt mixing device, The hydrolysis stabilizer composition comprises at least one compound containing imide and / or epoxy functional groups.

2. The method of claim 1, wherein the addition of the hydrolysis stabilizer composition in step (a) occurs before the polyester is melted, after the polyester is melted, or both before and after the polyester is melted.

3. The process according to claim 1 or 2, wherein the stabilized polyester from the first melt mixing device is fed into the second melt mixing device.

4. The process according to any one or more of claims 1 to 3, wherein the melt mixing temperature in step a) is from 230°C to 350°C.

5. The process according to any one or more of claims 1 to 4, wherein the residence time in step (a) is at most 90 seconds, preferably at most 60 seconds, more preferably at most 30 seconds.

6. The method according to any one or more of claims 1 to 5, wherein the thermoplastic composition comprises: (A) 40 to 70% by weight of an aromatic polycarbonate, (B) 20 to 40% by weight of said polyester, (C) 0.1 to 10% by weight of the hydrolysis stabilizer composition, (D) 0 to 15 wt. % of said impact modifier, (E) 0 to 5% by weight of the other components, in, The total amount of (A) to (E) is 100% by weight.

7. The process according to any one or more of claims 1 to 6, wherein the polyester comprises at least 80% by weight, preferably at least 90% by weight, based on the weight of the polyester, of poly(butylene terephthalate), wherein preferably the polyester consists of poly(butylene terephthalate).

8. The method according to any one or more of claims 1 to 7, wherein the impact modifier comprises or consists of at least one of an acrylonitrile-butadiene-styrene (ABS) polymer and / or a methyl methacrylate-butadiene-styrene (MBS) polymer.

9. The process of any one or more of claims 1 to 8, wherein the aromatic polycarbonate has a weight average molecular weight of 15,000 to 60,000 g / mol as determined using gel permeation chromatography with polystyrene standards and / or wherein the polyester has an intrinsic viscosity of 0.4 to about 2.0 dl / g as determined in a 60:40 phenol / tetrachloroethane mixture at 23°C.

10. The method of any one or more of claims 1-9, wherein the other components comprise 0.01 to 1 wt. %, based on the weight of the composition, of a compound selected from Group IB metal phosphates and Group IIB metal phosphates.

11. The method according to any one or more of claims 1 to 10, wherein the other components comprise 0.01 to 1% by weight, based on the weight of the composition, of a compound containing at least one of an alkali metal cation or an alkaline earth metal cation and a halogen anion, the compound preferably being selected from one or more of lithium fluoride, lithium iodide, potassium bromide, potassium iodide, sodium dihydrogen phosphate, sodium acetate, sodium benzoate, sodium hexanoate, sodium stearate, sodium ascorbate and magnesium hexanoate.

12. The method according to any one or more of claims 1 to 10, wherein the composition has the following combination: - At least 50 kJ / m 2 Initial notched Izod impact measured at 23°C according to ISO180-1A, - a notched Izod impact retention of at least 80% measured according to the method described in the specification, - A heat distortion temperature of at least 90°C measured in accordance with ISO 75A flat method under a load of 1.8 MPa.

13. Thermoplastic composition obtained or obtainable by a process according to any one or more of claims 1 to 12.

14. An article comprising or consisting of the thermoplastic composition according to claim 13, wherein preferably the article is an automotive interior article or a housing for an electrical device.

15. Use of a thermoplastic composition obtainable by the process according to any one or more of claims 1 to 12 for the manufacture of articles, preferably automotive parts, more preferably interior automotive parts.

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