Continuous process for producing poly(esterimide) polymer

Abstract

A continuous, solvent free, process for producing poly(esterimide) comprising the steps of: a. Providing a polyester, a hydroxyl-functional compound, a diimide compound, and a catalyst through one or more feeding ports into an extruder; b. Mixing and melting the composition inside the extruder at a temperature in the range of 80 – 120 °C; c. Reacting the composition inside the extruder at a temperature in the range of 250 – 400 °C; d. Collecting the reacting mixture at the exit of the extruder; and e. Cooling the reacting mixture.

Description

[0001] CONTINUOUS PROCESS FOR PRODUCING POLY(ESTERIMIDE) POLYMER

[0002] The present invention relates to a continuous, solventless process for producing poly(esterimide) polymer.

[0003] A poly(esterimide) polymer (PEI) can be used as a magnet wire for coatings. Currently such polymers are synthesized in batch conditions using a stirred vessel with an overhead condenser system to remove water. Typically, ethylene glycol or another diol is reacted with terephthalic acid and a diimide diacid (DIDA) to form a hydroxyl rich poly(esterimide). Synthesis in a batch process requires between 10-30% solvent to promote reaction conditions in a stirred reactor. Most common solvents for PEI are cresylic acid or phenol solvents, which are classified as toxic and hazardous to the environment. Without the solvent the reactor is prone to produce char on the heated wall, what is difficult to remove from the final product. The diimide diacid is normally also very insoluble and does not allow efficient stirring resulting in slow reaction rates and agitator damage. Normally, during the synthesis a small amount of TNBT is added typically (0.1 -0.3% on total resin solids).

[0004] US 4,605,710 discloses a powder composition suitable for providing a thermally stable electrically insulative coating on wire when said composition is fused and cured thereon, the composition comprising a blend of a carboxyl-terminated polyester resin derived from at least one aromatic diacid and at least one aliphatic glycol; at least about 5 percent by weight of at least one diimide diacid derived from the reaction product of at least one tricarboxylic acid anhydride and at least one diamine; and at least one triglycidyl isocyanurate, said isocyanurate being present at a mol ratio of epoxide functionality to total acid functionality of from about 0.8 to about 1 .5.

[0005] US 4,233,435 relates to a process for preparing a poly(esterimide) resin having increased stability against gelation and wherein during the process, sublimation of the lower dialkyl ester of a phthalic acid component is substantially reduced, which process comprises reacting under ester imide resin forming conditions a reaction mixture composition consisting essentially of: (I) an imide-group-contributing component selected from the group consisting of (A) both (1 ) a diamine component and (2) an anhydride component including at least one (a) aromatic carboxylic acid anhydride containing at least one additional carboxylic group, said additional group being esterifiable and substantially non-imidizable, or (b) the corresponding acid thereof containing two-imide-forming vicinal carboxylic groups in lieu of the anhydride group. (B) the carboxy functional polyimide reaction product of said diamine component and said anhydride component, and (C) mixtures of (A) above and (B) above; (II) an ester- group-contributing component comprising (D) at least one dihydric alcohol containing two esterifiable hydroxy groups, (E) at least one polyhydric alcohol containing at least three esterifiable hydroxyl groups, (F) at least one lower dialkyl ester of a phthalic acid component selected from the group consisting of terephthalic acid, isophthalic acid, and mixtures of said acids; and (G) a saturated aliphatic monohydric alcohol selected from the class consisting of n-hexanol, 2-ethylhexanol, n-nonanol n-decanol, n- dodecanol, 2-butyloctanol, tetradecanol, 2,6,8-trimethylnonane-4-ol, and mixtures thereof, wherein said reaction mixture comprises (a) from about 0.035 to 0.25 mole of the dihydric alcohol, (b) from about 0.025 to 0.15 mole of the polyhydric alcohol, (c) from about 0.03 to 0.18 mole of the lower dialkyl ester, (d) from about 0.1 to 0.2 mole of the aromatic carboxylic acid anhydride containing at least one additional carboxylic group, (e) from 0.05 to 0.10 mole of the diamine component, and from about 1.0 to 20.0 parts of the monohydric alcohol, said amounts being per 100 parts, by weight, of the total weight of the five components (a) through (e) recited therein.

[0006] US 4,795,790 discusses a polyetherimide ester polymer comprised of the reaction products of: (i) a diol component comprising at least one low molecular weight diol and at least one high molecular weight diol; (ii) at least one dicarboxylic acid or an ester forming reactive derivative thereof; and (iii) a set of reactants selected from (a) (1 ) at least one high molecular weight poly(oxy alkylene)diamine, and (2) at least one tricarboxylic acid or its derivative, or (b) at least one high molecular weight polyoxyalkylene diimide diacid. The polymer of this disclosure is reported to exhibit improved flexibility; and the diol component (i) contains an amount of high molecular weight diol at least effective to improve the flexibility of the polymer. CN 1252137 A relates to a method for continuously extruding reactants using a twin- screw reactor to prepare polyetherimide, and more specifically to a twin-screw reactor for continuous extrusion based on bisphenol A diether anhydride and aromatic diamine.

[0007] CN 102471466 A provides a method for preparing polyimide molding powder through solid-phase polymerization. The method comprises the following steps that aromatic binary primary amine, aromatic binaryanhydride and a toughening plasticizer maleic anhydride ester are smashed and evenly mixed in a high-speed mixer; the mixed material is subjected to continuous feeding in continuous rotation-screw-type conveying equipment, and polyimide is generated through a reaction; generated polyimide is subjected to rotation, extrusion and temperature control of the equipment, and polyimide particles are formed and smashed to obtain the polyimide molding powder. It is stated that: an organic solvent is not used, the environment-friendly production route is achieved, the prepared polyimide plate is high in strength and resistant to impact, and the mechanical property of polyimide is superior to that of polyimide prepared through a solvent method.

[0008] US 4,073,773 discloses an extrusion melt polymerization method for continuously making polyetherimides, wherein a mixture of an organic diamine and an aromatic bis(ether anhydride) is continuously fed through an inlet opening into a screw extruder having a second opening downstream from the inlet opening. The mixture is passed through a first extruder zone maintained at a low temperature to a zone where the mixture is melted, and water of reaction is continuously removed through the second opening. A melt seal may be employed between the second opening and a third opening through which water of reaction may be removed under vacuum.

[0009] PEI polymers are applied to a conductor typically at 30-50% solids content. The solvents are then traditionally burned as a source of high-cost fuel which adds to additional environmental emissions. Also due to the low solids content, it is costly to ship a hazardous material around the world where 50-70% of the material is not adding value to the final product. What is desired is a coating that can be applied without solvent yet duplicate the performance of the solvent based coating. This would eliminate the hazardous solvent component and reduce shipping volume by potentially 50-70%.

[0010] The process according to the present invention allows for the manufacture of PEI polymers without the use of any toxic or hazardous solvents and allows for the direct application of the fresh prepared PEI on a conductor wire.

[0011] The present invention therefore relates to a continuous, solvent free, process for producing poly(esterimide) polymer, the process comprising the steps of a. Providing a polyester, a hydroxyl-functional compound, a diimide compound, and a catalyst through one or more feeding ports into an extruder, wherein the polyester is selected from polyethylene terephthalate), poly(butylene terephthalate), polyethylene naphthalate) or poly(propylene furanate); wherein the hydroxyl-functional compound is selected from monoethylene glycol, diethylene glycol, 1 ,4-butane diol, propylene glycol, dipropylene glycol, 1 ,4-cyclohexanedimethanol, glycerine, trimethylolpropane, bisphenols or tris-(2-hydroxy ethyl) isocyanurate; wherein the diimide compound is an at least difunctional compound with respect to functional groups which are capable of reacting in an esterification and / or transesterification reaction; wherein the catalyst is present in an amount of 1 - 5 wt.% based on the total content of the composition provided in the extruder; b. Mixing and melting the composition inside the extruder at a temperature in the range of 80 - 120 °C; c. Reacting the composition inside the extruder at a temperature in the range of 250 - 400 °C; d. Collecting the reacting mixture at the exit of the extruder; and e. Cooling the reacting mixture.

[0012] Preferred is that no additional material apart from polyester, hydroxyl-functional compound, diimide compound and catalyst is provided in the extruder. Technically unavoidable impurities are not considered to violate this condition.

[0013] In the event that additional material is to be introduced it is preferred that the amounts of the polyester, the hydroxyl-functional compound, the diimide compound and the catalyst which are provided in the extruder are 95 to <100 weight-% of the total amount of material provided in the extruder. More preferred are 99 to <100 weight-%.

[0014] Typically, a polyester material is synthesized by reacting a diol or triol compound with a diacid or triacid compound. For examples, polyesters can be formed by reacting ethylene glycol or glycerine or other aliphatic triols, such as trimethylolpropane (TMP) with an aromatic diacid, such as phthalic acid, isophthalic acid or terephthalic acid. This synthesis is well known in the art and is generally achieved by a polycondensation reaction in conjunction with an azeotropic distillation to remove the water formed by the reaction of the diol or triol compound with the acid compound. Suitable commercially available polyester compounds according to the invention are PET (polyethylene terephthalate)), PBT (poly(butylene terephthalate)) and PEN (polyethylene naphthalate)). Preferred molecular weight ranges for the polyesters include 20 kDa to 40 kDa, corresponding to bottle grade or textile grade polyesters, and 60 kDa to 80 kDa, corresponding to film grade polyesters.

[0015] Alternatively, biobased polyester compounds can be used, such as polypropylene furanate). As understood herein, a bio-based material is a material intentionally made, either wholly or partially, from substances derived from living (or once-living) organisms, such as plants, animals, enzymes, and microorganisms, including bacteria, fungi and yeast.

[0016] The hydroxyl-functional compound that is used in the process according to the present invention can be a diol compound or a triol compound. Examples of suitable diol compounds include monoethylene glycol, diethylene glycol, 1 ,4-butane diol, propylene glycol, dipropylene glycol, and 1 ,4-cyclohexanedimethanol. Examples of suitable triol compounds include glycerine, trimethylolpropane, bisphenols or tris-(2-hydroxy ethyl) isocyanurate. Triol compounds are preferred in view of the thermal stability of the obtained poly(esterimide) polymer, tris-(2-hydroxy ethyl) isocyanurate is the most preferred compound for the process according to the present invention in view of the good electrical insulation properties of a magnet wire coated with the thus obtained poly(esterimide) polymer.

[0017] The diimide compound that is used in the process according to the present invention can be characterized by having the following general structure:

[0018] (R1CO)2 - N - R2- N - (R3CO)2 wherein each R1, R2, and R3, can be the same or different and represent aliphatic or aromatic organic moieties. Diimide-diesters of carboxylic anhydrides have been disclosed in US3,461 ,136. In this reference various methods are mentioned for the manufacture of this material. Diimide-diacid compounds can be formed by reacting a diamine with trimellitic anhydride.

[0019] It is further provided that the diimide compound is at least difunctional with respect to functional groups which are capable of reacting in an esterification and / or transesterification. Such functional groups include carboxylic groups, hydroxyl groups and carboxylic ester groups. The difunctionality criterion ensures that the diimide compound can act as a chain extender and not a chain terminator. For example, while a compound with only one moiety R-C(=O)-O-CH2-CH2-OH has two (trans)esterification-accessible functional groups, it is still considered monofunctional on account of the lack of reactive sites at other parts of the molecule.

[0020] Preferred diimide compounds are based on trimellitic anhydride as the carboxylic monomer. Regarding the diamino component, any aromatic dianiline with either ether or single-carbon linkages may be employed, with preference given to methylene dianiline, oxydianiline, and m- or p-phenylenediamine, 2,2-bis[4-(4- aminophenoxy)phenyl]propane or 1 ,3-bis(4-aminophenoxy)benzene. The resulting diimide of any of these combinations may then be reacted with any diol to make a useful diimide. 1 ,2-diols are preferred in this respect. Particularly preferred is the diimide denoted “DIDE” as used in the experimental section of this disclosure.

[0021] The reaction can be catalyzed by using different kinds of catalysts. Metal salts, such as acetates or octoates of metals such as zinc, tin or manganese can be used. Alternatively, titanates can be used as catalyst, such a tetrabutyl titanate monomer, tetraisopropyl titanate or tetrabutyl titanate polymer. Normally, the catalyst is present in an amount of 1 - 5 wt.% based on the total content of the composition.

[0022] The reaction mixture typically comprises:

[0023] • From 8 to 12 pbw (parts by weight) of the polyester,

[0024] • From 8 to 12 pbw of a hydroxyl-functional compound

[0025] • From 15 to 25 pbw of a diimide compound

[0026] • From 1 ,4 to 1 ,9 pbw of catalyst

[0027] In this embodiment it is also preferred that the amounts of the polyester, the hydroxyl- functional compound, the diimide compound and the catalyst which are provided in the extruder are 95 - 100 weight-% of the total amount of the reaction mixture. More preferred are 99 to 100 weight-%. Particularly preferred is the absence of any additional material apart from polyester, hydroxyl-functional compound, diimide compound and catalyst with the exception of technically unavoidable impurities.

[0028] The molten material that is collected at the exit of the extruder can be used in various ways. Either it is left to solidify for later use, or it is kept in a molten state and directly used, for example to coat a wire, for example through a wire coating technique, as disclosed in WO 2016 / 038335. However, it is also possible to solve the solidified material in a suitable solvent, for example cresylic acid or phenol solvents.

[0029] Using techniques known to the person skilled in the art, such solution can also be used to coat a wire in a more traditional process. The extruder that is used in the process according to the present invention can be any type of extruder. Good results have been obtained by using a twin-screw extruder or a planetary extruder.

[0030] EXAMPLES

[0031] All polymer synthesis experiments were performed using a Brabender Co-Rotating Clamshell Twin-screw Extruder Model 20 / 40D. The extruder contained 4 heating zones, a die adapter heating zone and a die heating zone. The screw design contained forward and reverse conveying elements, forward and reverse kneading blocks, and teeth elements. Polyethylene terephthalate (PET) was fed through a single spiral screw volumetric feeder. Tris (2-hydroxyethyl) isocyanurate (THEIC) and a diimidediethylene glycol ester (DIDE) were fed through either a twin concave screw volumetric feeder or a single auger screw volumetric feeder. The catalyst was premixed with THEIC. All materials were dosed through a 3L stainless steel hopper. No additional equipment was used unless otherwise specified.

[0032] The structure of DIDE is given below:

[0033] Example 1

[0034] PEI was synthesized using 1 pbw (part by weight) of THEIC, 1 pbw of PET, and 1 ,8 pbw of DIDE. 4 wt.% (wt.% based on the total content of the composition) of tetra-n- butyl titanate was used as catalyst.

[0035] Prep Steps: Break up DIDE solid into chunks and grind into a fine powder using Jaw Crusher Machine. Mix DIDE powder with THEIC powder and TNBT in a gallon can (leaving ~1 / 3rd of free space in the can to allow proper mixing) and shake on paint shaker for 15 minutes. TNBT will form small clumps / balls with the powders. Break up the clumps and shake the mixture for an additional 10 minutes. Extruder Conditions:

[0036] Screw Design - V3 (multiple sections of kneading blocks)

[0037] Screw Speed - 250 rpm

[0038] Extruder Temperatures Setpoints: 100, 300, 300, 300, 300, 300, 300°C

[0039] PET Feed Rate — 20 g / min

[0040] DIDE / THEIC / TNBT Mixture Feed Rate - ~59 g / min

[0041] Procedure: Heat extruder to the appropriate temperatures and turn on the drive. Feed PET pellets using single screw feeder and DIDE / THEIC / TNBT mixture using twin- screw feeder. Allow for material to come out of the extruder for 2 - 3 minutes to allow for equilibrium to be reached within the extruder. Collect synthesized PEI in unlined metal cans and allow to cool to room temperature before handling. The solid was characterized by parallel plate rheometer and at 180°C a complex viscosity of 550 Pa-s was observed. A melt flow index (MFI) of 14g / 1 Omin at 160°C and 3.8 kg of weight was recorded.

[0042] The resulting polymer was dissolved in a solvent and applied to 1 .0 mm copper wire. Oven temperatures of 380-450°C were used to complete the final wire cure. The properties are identical to the results from conventionally prepared PEI wire enamel.

[0043] FIG. 1 shows GPC curves of a poly(esterimide) prepared in accordance with example 1 (“extruded”, dashed curve) and a typical poly(esterimide) prepared via a solventbased process for the purpose of benchmarking (“std”, solid curve). The intensity scale of the y axis refers to the output signal of a refractive index sensor. The eluent was a 70 / 30 mixture of THF and DMF and polystyrene standards were used for calibration. The molecular weights determined were: Example 2 (Comparative)

[0044] PEI was synthesized using 1 pbw (part by weight) of THEIC, 1 pbw of PET, and 1 ,8 pbw of DIDE. 0,2 wt.% (wt.% based on the total content of the composition) of tetra-n- butyl titanate was used as catalyst.

[0045] Prep Steps: Break up DIDE solid into chunks and grind into a fine powder using Jaw Crusher Machine. Mix DIDE powder with THEIC powder and TNBT in a gallon can (leaving ~1 / 3rd of free space in the can to allow proper mixing) and shake on paint shaker for 15 minutes. TNBT will form small clumps / balls with the powders. Break up the clumps and shake the mixture for an additional 10 minutes.

[0046] Extruder Conditions:

[0047] Screw Design - V3 (multiple sections of kneading blocks)

[0048] Screw Speed - 250 rpm

[0049] Extruder Temperatures Setpoints: 100, 250, 250, 250, 250, 250, 250°C

[0050] PET Feed Rate — 20 g / min

[0051] DIDE / THEIC / TNBT Mixture Feed Rate - ~59 g / min

[0052] Procedure: Heat extruder to the appropriate temperatures and turn on the drive. Feed PET pellets using single screw feeder and DIDE / THEIC / TNBT mixture using twin- screw feeder. Allow for material to come out of the extruder for 2 - 3 minutes to allow for equilibrium to be reached within the extruder. Collect synthesized PEI in unlined metal cans and allow to cool to room temperature before handling. The solid collected was of a broad distribution of molecular weights including unreacted PET still present. The material was not completely soluble in THF confirming the mixture of materials present.

[0053] The resulting polymer could not be applied to copper wire due to the poor physical properties of the mixture.

Claims

CLAIMS1 . A continuous, solvent free, process for producing poly(esterimide) polymer, the process comprising the steps of a. Providing a polyester, a hydroxyl-functional compound, a diimide compound, and a catalyst in an extruder, wherein the polyester is selected from polyethylene terephthalate), poly(butylene terephthalate), polyethylene naphthalate) or poly(propylene furanate); wherein the hydroxyl-functional compound is selected from monoethylene glycol, diethylene glycol, 1 ,4-butane diol, propylene glycol, dipropylene glycol, 1 ,4-cyclohexanedimethanol, glycerine, trimethylolpropane, bisphenols or tris-(2-hydroxy ethyl) isocyanurate; wherein the diimide compound is an at least difunctional compound with respect to functional groups which are capable of reacting in an esterification and / or transesterification reaction; wherein the catalyst is present in an amount of 1 - 5 wt.% based on the total content of the composition provided in the extruder; b. Mixing and melting the composition inside the extruder at a temperature in the range of 80 - 120°C; c. Reacting the composition inside the extruder at a temperature in the range of 250 - 400°C, thereby obtaining a reacting mixture; d. Collecting the reacting mixture at the exit of the extruder; and e. Cooling the reacting mixture.

2. The process of claim 1 wherein no additional material apart from polyester, hydroxyl-functional compound, diimide compound and catalyst is provided in the extruder.

3. The process of claim 1 wherein in step a. it is provided in the extruder:• From 8 to 12 pbw (parts by weight) of the polyester,• From 8 to 12 pbw of a hydroxyl-functional compound• From 15 to 25 pbw of a diimide compound• From 1 ,4 to 1 ,9 pbw of catalyst4. The process according to any one of the preceding claims, wherein the extruder is a twin-screw extruder.

5. The process according to any of the preceding claims wherein the polyester is polyethylene terephthalate or polybutylene terephthalate.

6. The process according to any of the preceding claims wherein the hydroxyl- functional compound is tris-(2-hydroxy ethyl) isocyanurate.

7. The process according to any of the preceding claims wherein the diimide compound has the following structure:

8. The process according to any of the preceding claims wherein the catalysts is present in an amount of 1 - 5 wt.% based on the total content of the composition.

9. The process according to claim 8 wherein the catalyst is a titanate compound.

10. Poly(esterimide) polymer obtainable by the process of claim 1 .

11. A process for applying a poly(esterimide) polymer on a wire wherein the reaction mixture that is collected from the extruder according to the process of claim 1 is applied on a wire.

12. The process of claim 11 , wherein the poly(esterimide) polymer is solved in a solvent prior to application to the wire.

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