WO2013164855A2

WO2013164855A2 - Stable polyetherketones thermoplastic polymer

Info

Publication number: WO2013164855A2
Application number: PCT/IN2013/000207
Authority: WO
Inventors: Keki Hormusji Gharda
Original assignee: Keki Hormusji Gharda
Priority date: 2012-03-29
Filing date: 2013-03-28
Publication date: 2013-11-07
Also published as: WO2013164855A3

Abstract

The present disclosure provides a stable polyetherketones thermoplastic polymer comprising: a) a of polyetherketone of the formula - Ar-CO -, wherein Ar is a bivalent aromatic radical; and b) aryl phosphonite compound of formula I, wherein X is selected from the group consisting of CI, Br and F, the amount of said phosphonite compound being in the range of 0.01 to 4% by weight of the total composition.

Description

STABLE POLYETHERKETONES THERMOPLASTIC POLYMER

FIELD OF THE DISCLOSURE

The present disclosure relates to thermoplastic polymer.

Particularly, the present disclosure relates to a process for preparing stable thermoplastic polyetherketones polymers.

BACKGROUND

Polyetherketones have , exceptionally high heat resistance, satisfactory thermoplastic processing characteristics and have excellent resistance to the action of chemicals and to hydrolysis and also show outstanding mechanical strength, toughness as well as dimensional stability. Therefore the polyetherketones, preferably aromatic polyetherketones are among the materials preferred for technical applications. Thermoplastic polymer of aromatic polyetherketones have high softening point and are useful in applications wherein an article fabricated from the polyether ketone has to withstand high service temperatures.

The aromatic polyetherketones (PEK) comprise repeating units of the formula - Ar-CO - ,in which Ar is a bivalent aromatic radical which may vary from unit to unit in the polymer chain (so as to form copolymers of various kinds), at least some of the Ar units contain ether linkages. As the nomenclature of the class of polyetherketones (PEK), P denotes a polymer, E denotes a para-phenoxy unit and K denotes a para-phenylketp unit.

The necessary temperature for melt processing polyetherketones is in general 15 to 20°C above the respective melting points, this high processing temperature over a longer period lead to an undesired rise in the viscosity of the melts. Because of their high melting points and often high melt viscosities, the polyetherketones are difficult to melt-fabricate and tend to decompose when being melt-fabricated or on prolonged usage at elevated temperatures.

Antioxidants have been widely studied and used for preventing thermal oxidative degradation. Use of hindered phenols to improve the thermal stability of polymers is known in the art. It is known that for the improvement of the melt stability during the melt processing of polyarylether ketones, organic phosphorous compounds are used. British Patent 1446962 describes addition of aromatic phosphoric acid esters such as tris-nonyl phenyl phosphite (TNPP) to polyaryletherketone, improves melt stability. However it is seen in practice that TNPP is suitable only for lower melting polyether ketones such as PEEK, which has a melting point of 340°C. At higher temperatures, TNPP decomposes. For example at 400°C, there is only 30% of TNPP remaining as residue when evaluated on TGA. The higher melting poly ether ketones such as PEK, PEEKK and PEKEKK need to be processed at 400°C temperature and the highest melting polyether ketone, PEKK, needs an even higher temperature. TNPP decomposes quite markedly at these high temperatures of melt processing and the resultant decomposition products give dark colours to the polymers. In addition there are known toxicological dangers in the use of TNPP due to the carcinogenic effect of nonyl phenols and hence the use of TNPP is regulated in many countries such as Korea and Japan. Hence for the processing of these higher melting polyether ketones, TNPP is entirely unsuitable.

US 3925307 discloses use of amphoteric metal oxides such as oxides of aluminum, beryllium, bismuth, cadmium, cerium, gallium, germanium, lanthanum, lead, manganese, tin, titanium, zinc, zirconium, uranium and mixtures thereof, for stabilization of polyether ketones. The disadvantage is that in high quantities these oxides are frequently toxic. Besides, homogeneous processing of these metal oxides in the polymer melts is costly.

US 4593061 discloses use of molecular sieves to stabilize polyketones against thermal oxidation. However here again the homogeneous processing of these metal oxides in the polymer melts is costly. -

Therefore, there is felt a need to provide a suitable antioxidant which will be stable at processing temperatures of 400°C and above and provide thermo- oxidative stability to polyetherketones.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

It is an object of the present disclosure to provide a polyetherketone thermoplastic polymer having higher thermal stability.

Another object of the present disclosure is to provide a suitable antioxidant which is stable at processing temperatures of 400°C and above and provides homogenous processing of the molten polyetherketone polymer thereby improving stability of polyetherketone thermoplastic polymer.

SUMMARY

In accordance with the present disclosure, there is provided a stable polyetherketone thermoplastic polymer comprising: a) a polyetherketone of the formula - Ar-CO - , wherein Ar is a bivalent aromatic radical; and b) an aryl phosphonite compound of formula I, wherein X is selected from the group consisting of CI, Br and F, the amount of said phosphonite compound being in the range of 0.01 to 4% by weight of total composition.

Typically, the polyetherketone has at least one unit of the compound formula II,

II

whererin T is oxygen.

In accordance with another aspect of the present disclosure , there is provided a process for preparing a stable polyetherketone thermoplastic polymer , said process comprising:

a step of forming a blend of polyetherketone of the formula - Ar-CO - , wherein Ar is a bivalent aromatic radical and an aryl phosphonite compound of formula I,

I

wherein X is selected from the group consisting of CI, Br and F, the amount of said phosphonite compound being in the range of 0.01 by weight of total composition; and processing the blend at a temperature in the range of 350 to 500 C to form a stable polyetherketone thermoplastic polymer.

In one of the embodiment of the present disclosure, the blend is formed by stirring a mixture containing said polyetherketone and said phosphonite compound in an aprotic solvent selected from the group consisting of dimethyl sulfoxide and acetone, for a period of 30 to 120 minutes, followed by evaporating said solvent at a temperature in the range of 20 to 50°C, and thereby obtain a coating of the said phosphonite compound on said polyetherketone .

In another embodiment of the present disclosure, the blend is formed by dry mixing said polyetherketone and said phosphonite compound .

In accordance with another aspect of the present disclosure , there is provided a process for preparing an aryl phosphonite compound of formula I

wherein X is selected from the group consisting of CI, Br and F

said process comprising, reacting dichlorophenyl phosphine with an alkali metal salt of compound of formula III,

Formula III wherein X is Br, CI or F, in an aprotic solvent, at a temperature in the range of 50 to 90 C over a time period of 2 to 20 hrs.

Typically, the alkali salt metal is selected from the group consisting of Li, Na, , Cs and Ca.

Typically, the ratio of dichlorophenyl phosphine and the compound of formula III is in the range of 0.5 to 0.25.

Typically, the aprotic solvent is selected from the group consisting of dimethylsulfoxide and acetone.

DETAILED DESCRIPTION

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The description herein after, of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Phosphonite (P(OR)₂R') esters have been used on a large scale for the stabilization of polymers against degradation during processing and long-term applications. Mostly all phosphonites are hydroperoxide-decomposing secondary antioxidants. Their reactivity in hydroperoxide reduction decreases with increasing electron-acceptor ability and bulk of the groups bound to phosphorus in the order phosphonites > alkyl phosphonites > aryl phosphonites > hindered aryl phosphonites.

Aryl phosphonites, particularly derived from sterically hindered phenols, can act as chain-breaking primary antioxidants by reduction of peroxyl radicals to alkoxyl radicals. In oxidizing media at higher temperatures, however, hydrolysis of phosphonites takes place in addition to oxidation. The phenols so formed synergized by the parent phosphorus compounds and their hydrolysis products are responsible for the high antioxidative activity of aryl . phosphonites, especially the hindered compounds, in oxidations at higher temperatures.

The present disclosure provides an aryl phosphonite compound of formula I, which is found to be a highly effective thermal antioxidant and compatible with polyetherketone.

I

wherein X is Br, Cl or F .

Another aspect of the present disclosure provides a process for preparing the aryl phosphonite compound of formula I.

In accordance with the present disclosure the aryl phosphonite compound of formula I is prepared via alcoholysis reaction of the dichlorophenyl phosphine with compound of formula III, in an aprotic solvent,

Formula III wherein X is Br, Cl or F.

Compound of formula III is a haloderivative benzoyl phenol. Halo- benzoylphenol derivative is treated with an alkali metal to form an alkali metal salt of Halo- benzoylphenol derivative, which then reacts with dichlorophosphine in the presence of an aprotic solvent to yield a compound of formula I. The alkali metal is selected from the group consisting of Li, Na, , Cs and Ca . The alkali metal is preferably sodium. The reaction is carried out in an aprotic solvent, at a temperature in the range of 50 to 90°C over a time period of 2 to 20 hrs. The ratio of dichlorophenyl phosphine and the compound of formula III is in the range of 0.5 to 0.25. The aprotic solvent is selected from the group consisting of dimethylsulfoxide and acetone.

In accordance with another aspect of the present disclosure, there is provided a polyetherketone thermoplastic comprising i) aromatic polyether ketone; and ii) an aryl phosphonite compound of formula I, wherein the amount of the phosphonite compound is in the range of 0,01 to 4% by weight of the total composition.

The aromatic poly etherketones comprise repeating units of the ·.- formula, - Ar-CO - in which Ar is a bivalent aromatic radical which may vary from unit to unit in the polymer chain (so as to form copolymers of various kinds), at least some of the Ar units contain ether linkages.

The aromatic polyether ketones of the present disclosure has at least some units of the structure

in which T is oxygen .

Examples of such polyether ketones and their melting points are

PEEK, M.Pt = 34ΰ^μ€

PEK. MJPr = 37£PC

PE EKK. MPt = 383°C

PE K, M,Pt= 39l°C

In accordance with still another aspect of the present disclosure, there is provided a process for preparing a thermoplastic polymer. The process includes the step of forming a blend of aromatic polyetherketones and phosphonite compound of formula I wherein the amount of the phosphonite compound is in the range of 0.01 to 4% by weight of the total composition, and processing the blend at a temperature in the range of 350° to 500°C to form a stable polyetherketone thermoplastic polymer.

Incorporation of 0.01% to 4% by mass of the phosphonite compound reduces the tendency of the melt viscosity and/or color to increase on prolonged heating of the aromatic polyetherketone and its blends. A preferred level of inclusion is 0.1% to 0.5%. Inclusion of greater quantities appears to have little further effect and may result in the compositions having unacceptable physical properties. In one embodiment of the present disclosure the blend of aromatic polyether ketone and phosphonite compound of formula I is prepared by stirring the mixture containing the polyether ketone and the phosphonite compound in a low boiling aprotic solvent over a period of 1-2 hrs and then evaporating the entire solvent so to form a uniform coating of the antioxidant on the polyetherketone.

In another embodiment of the present disclosure aromatic polyether ketone is dry blended with the phosphonite compound of formula I.

The stable polyetherketone thermoplastic polymer after processing of the blend by coating as well as dry blending show similar results .

In preferred embodiment of the present disclosure, for phosphonite compound of formula I, preferred halogen is chlorine or bromine. It is found that the loss in weight by TGA (thermogravimetric analysis) at 400°C is only 10% when X is CI or Br and it is 16 % when X=F.

The aromatic polyetherketone and phosphonite blend/composition may be further mixed with particles of other polymeric materials having special properties, e.g. elastomeric materials and polytetrafluoroethylene. They may contain reinforcing fillers, for example glass, asbestos and carbon fibres, and other materials conferring various desired characteristics, e.g. solid lubricants (e.g. graphite or molybdenum disulphide), abrasives (e.g. carborundum), friction-conferring materials, magnetic materials (e.g. for recording tapes), photosensitizers, and any other materials for which the compositions of the disclosure make suitable vehicles. The compositions may contain dyes and pigments. The compositions may be fabricated in any desired form, such as fiber, film and moldings or extruded products of any desired shape. The disclosure is further illustrated with the help of the following examples which should not be construed to limit the disclosure in any way.

EXAMPLE 1

A) Preparation of Dichloro phenyl phosphine (DCPP)

In a 2 L Round bottomed flask fitted with condenser was charged 550 gm phosphorous trichloride PC1₃ (4m/m), 177.55 gm aluminum chloride A1C1₃ (1.33m/m) & 78 gm benzene at room temperature. The mass was maintained at 70°C for 7 hours, HC1 gas evolution was observed at the rate of 1.2 m/m. The mass was further maintained for 5 hours until no further HCL evolution was observed. 204 gm POC13 (1.33m/m) was added to the mass at 60°C over 3 hours and the mass was maintained for 3 hrs. Reaction mass was cooled and clear liquid decanted. The solids remaining were extracted with hexane. The extract was mixed with the decanted material and taken for distillation using a 6"column packed with glass helices.

Details of the fractionation:

Purity of main cut was found to be 100% by classical Analysis

Residue obtained was 9.8 gms. B) Reaction of dichlorophenyl phosphine (DCPP) using chloroderivative of benzoylphenol (NaCHBP).Batch size 0.10 mole of DCPP.

To 900 ml of DMSO was added 509gm sodium salt of para-chloro benzoyl phenol (2 moles) and the mixture was heated to 70°C to get a clear solution. 179 gm DCPP(0.1 mole) from step A was added to the solution over a period of 1.5 hr at 75-80°C, and the solution was further heated to 115-120°C and maintained for lOhr. The solution containing the product chloroaryl phosphonite compound of formula I was then filtered at room temperature to remove NaCl,. filtered NaCl cake was washed with DMSO. (DMSO fractions and the filtrate containing aryl phosphonite compound was concentrated to get 55 gm of phosphonite solid which was further purified by treating it with Methylene Chloro-benzene.

EXAMPLE 2

- Reaction of dichlorophenyl phosphine (DCPP) using fluoro derivative of benzoylphenol (NaFHBP).

Batch size 0.075 mole of DCPP

To 675 ml of DMSO was added 357 gm sodium salt para-fluoro benzoyl phenol NaFHBP (1.5 mole) and the mixture was heated to 70°C to^' get a clear solution. 134.25gm of dichlorphosphine DCPP (0.75 mole) of example 1 was added over a period of 1.5 hr at 75-80°C and the mixture was further heated to 115-120°C and maintained for lOhr. The solution containing the product chloroaryl phosphonite compound of formula I was then filtered at room temperature to remove NaF, filtered NaF was washed with DMSO.DMSO fractions and the filtrate containing aryl phosphonite compound was concentrated to get 40 gm of solid which was further purified by treating it with methylene chlorobenzene. The comparative physical properties of the antioxidant of example 1 and compared to TNPP and Doverphos S9228 are given below.

From the above table it is observed that the compound of formula I has maximum thermal stability among all.

Example 3: Thermoplastic Polymer

20 gm of polyether ketone (PEK) was taken in 200 ml acetone and to this was added 0.2-0.3% antioxidant prepared in accordance with the example 1 . The slurry was maintained for lhour and then, the entire solvent was evaporated off in a rotary evaporator so as to ensure a uniform coating of antioxidant on the polymer.

The above prepared antioxidant coated PEK powder was passed through MFI instrument @400°C and 2.16 kg load to get PEK strands. These PEK strands were used to determine melt stability by capillary rheometer, again at 400° C. Melt Viscosity (Pa.S) @

Antioxidant used in PEK 400°C, Shear Rate-1000 1/S

6 Min 60 Min % Change

1 PEK with 0.2% (NaCHBP+DCPP) 246 217 -1 1.78

2 PEK with 0.3% TNPP 254 201 -20.86

3 PEK with 0.3% Doverphos 203 132 -34.97

From above it is clear that the antioxidant, compound of formula (I) of the present disclosure made by the reaction of dichloro phenyl phospine with NaCHBP gave the best results at a level of 0.2%.

Example 4

2000 gm of PEK was uniformly coated with the compound of formula I as described in example 3, however the solvent used was acetone instead of DMSO.

For comparison purposes, 2000 gm of PEK was also coated with antioxidant Doverphos and TNPP.

The above prepared antioxidant coated PEK was extruded and the extruded polymer was cut into granular shape. These PEK granules were used to determine melt stability by capillary rheometer at 400° C.

To ensure reproducibility two different commercial lots of each polymer were tested with each antioxidant.

The results are as below -

It is seen that there is only an average of 2% drop in viscosity after 1 hour @400°C using the antioxidant made by the reaction of QCPP and NaCHBP (Compound of formula I), as compared to >10% drop for that using the standard antioxidants Doverphos and TNPP. The results were also reproducible

Example 5

To compare the effect of uniform coating of PEK with the antioxidant as against simple dry blending of PEK with the antioxidant ,2000gm each of PEK from two different commercial lots was both coated with the antioxidant, compound of formula I (made from dichlorophenyl phosphine (DCPP ) + NaCHBP) as well as dry blended with the antioxidant compound of formula I and its thermal stability determined by extruding the polymer + antioxidant mixture @400°C and the extmded^polymer was cut into granular shape. These PEK granules were used to determine melt stability by capillary rheometer at 400° C.

DRY Blend with

216 211 -2.32 0.2%DCPP(CHBP)2

Coating with 0.2%

273 263 -3.67 DCPP(CHBP)2

G-PAEK #11

DRY Blend with

273 257 -6

0.2%DCPP(CHBP)2

Coating as well as dry blending of antioxidant on G-PAEK polymer show similar results and drop in melt viscosity is about 5% during 1 hr stability test. For commercial applications dry blending of antioxidant with G-PAEK polymer is more practicable and as seen from the above example it is equally effective as coating of the anti oxidant.

Technical advantage of the antioxidant phosphonite compound of formula I

Antioxidant compound of formula I of the present disclosure is found to be stable at temperatures of over 400°C, compatible with polyether ketones and imparts improved thermal stability against oxidative degradation of the polymer.

With antioxidant known in prior-art such as TNPP, loss in weight by TGA is 70% and with antioxidant Doverphos S 92268 loss is 40%, whereas with the antioxidant (phosphonite compound of formula I) of the present disclosure loss in weight by TGA is 10 to 16%.

Moreover the phosphonite compound of formula I of the present disclosure being a fully aromatic based anti-oxidant, has increased thermal stability as compared to TNPP and Doyerphos containing large aliphatic components. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment , of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, * dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

Claims:

1. A stable polyetherketones thermoplastic polymer comprising: a) a of polyetherketone of the formula - Ar-CO - , wherein Ar is a bivalent aromatic radical; and b) an aryl phosphonite compound of formula I,

wherein X is selected from the group consisting of CI, Br and F, the amount of said phosphonite compound being in the range of 0.01 to 4% by weight of total composition.

2. The thermoplastic polymer as claimed in claim 1, wherein the polyetherketone has at least one unit of the compound of formula II,

II

whererin T is oxygen.

3. The thermoplastic polymer as claimed in claim 1, wherein X is preferably

from the group consisting, of chlorine and bromine.

4. A process for preparing a stable polyetherketone thermoplastic polymer, said process comprising:

a step of forming a blend of polyetherketone of the formula -Ar-CO- wherein Ar is a bivalent aromatic radical and an aryl phosphonite compound of formula I,

I

wherein X is selected from the group consisting of CI, Br and F, the amount of said phosphonite compound being in the range of 0.01 to 4% by weight of total composition; and

processing said blend at a temperature in the range of 350° to 500°C to form a stable polyetherketone thermoplastic polymer.

5. The process as claimed in claim 4, wherein the blend is formed by stirring a mixture containing said polyetherketone and said phosphonite compound in an aprotic solvent selected from the group consisting of dimethyl sulfoxide and acetone, for a period of 30 to 120 minutes, followed by evaporating said solvent at a temperature in the range of 20 to 50°C, and thereby obtain a coating of the said phosphonite compound on said polyetherketone.

6. The process as claimed in claim 4, wherein the blend is formed by dry mixing said polyetherketone and said phosphonite compound.

7. A process for reparing an aryl phosphonite compound of formula I

I

wherein X is selected from the group consisting of CI, Br and F said process comprising, reacting dichlorophenyl phosphine with the alkali metal salt of a compound of formula III,

Formula III wherein X is Br, CI or F. ⁷

in an aprotic solvent, , at a temperature in the range of 50 to 90°C over a time period of 2 to 20 hrs.

8. The process as claimed in claim 7, wherein the alkali metal is selected from the group consisting of Li, Na, K , Cs and Ca .

9. The process as claimed in claim 7, wherein the ratio of dichlorophenyl phosphine and the compound of formula III is in the range of 0.5 to 0.25.

10. The process as claimed in claim 7, wherein the aprotic solvent is selected from the group consisting of dimethylsulfoxide and acetone.