Blends of aromatic polvimides and aromatic sulfone polymers

CROSS-REFERENCE TO A RELATED APPLICATION

The present application claims the benefit of U.S. application serial no. 60/954821, filed August 9, 2007, the whole content of which is herein incorporated by reference. The present invention relates to blends based on aromatic polyimides and aromatic sulfone polymers. More particularly, the present invention relates to blends comprising aromatic polyimides, aromatic sulfone polymers and an additional constituent selected among aromatic polyetherimides. The invention also relates to a process for the preparation of said blends as well as to articles or parts of articles comprising those blends.

Aromatic polyimides, in particular aromatic polyamide-imide (PAI), form a class of thermoplastic polymers that offer some excellent engineering properties such as, for instance, very high heat resistance, high strength and excellent chemical resistance. They are thus well suitable for a wide variety of applications requiring strength and durability at extremely high temperatures.

Nevertheless, in certain demanding industries, the level of properties achieved by aromatic polyimides, like their impact strength and processability, are insufficient.

On the other hand, high performance amorphous thermoplastic polymers such as aromatic sulfone polymers, in particular polyphenylsulfones (PPSU), feature high strength and stiffness at high temperature ; they exhibit outstanding toughness among other polymers of same temperature class ; they possess very good chemical resistance, can be rather easily processed in the melt either for making injection molded articles or for extrusion of films and sheets, have excellent transparency and ease of colorability ; moreover sulfone polymers are inherently flame-resistant materials with low smoke emission. However, in certain demanding industries, the level of properties achieved by aromatic sulfone polymers, like their tensile and compressive strengths, should still be improved. It has already been proposed to mix certain polyamide-imides and certain polysulfones together with the aim to combine their respective advantageous properties in one sole polymeric blend. Such blends are disclosed for instance in

US-A-3658938. In this document, it is stated that the described polyamide/imides and polysulfones are not mutually soluble. This may be a serious drawback, since the multiphase behaviour of the obtained blends may be detrimental to their chemical resistance and to their thermal and optical performances.

US-A-5037902 discloses miscible blends of biphenyl-containing poly(arylsulfones) and isopropylidene -based polyimides. It is mentioned in this document that "imide groups in conjunction with isopropylidene groups ... appear to be necessary as no polyamide or amide-imide not containing an isopropylidene linkage is found to be miscible with a poly(aryl sulfone)".

Furthermore, in accordance with the teachings of this document, the biphenyl linkages in the poly(aryl sulfone) and the isopropylidene linkages in the polyamide or amide-imide must be in specific proportions for the blend to be miscible. There are thus several conditions limiting in practice the number of blends miscible according to US-A-5037902.

The present invention aims to overcome these disadvanges by improving the miscibility of these blends based on aromatic polyimides and aromatic sulfone polymers, while, in the same time, improving important properties of each of their constituents. Accordingly, in its main aspect, the present invention relates to blends (B) comprising :

■ at least one polyimide (Pl), of which more than 50 wt. % of the recurring units (Rl) comprise at least one aromatic ring, at least one imide group and 0 to 1 ether group (— O — ) ; ■ at least one aromatic sulfone polymer (P2) ;

■ at least one polyimide (P3), of which more than 50 wt. % of the recurring units (R3) comprise at least one aromatic ring, at least one imide group and at least two ether groups (— O — ).

As mentioned, the blends (B) comprise at least one polyimide (Pl), as defined above. The recurring units (Rl) of polymer (Pl) comprise at least one aromatic ring, at least one imide group and from zero to one ether group (— O — ).

The imide groups contained in the recurring units (Rl) can be imide groups as such [formula (I)] and/or in their amic acid form [formula (H)] :

formula (I) formula (II)

The imide groups, as such and/or in their corresponding amic acid form, are advantageously linked to an aromatic ring, as illustrated below :

formula (III) formula (IV) whereas Ar' denotes a moiety containing at least one aromatic ring.

The imide groups are advantageously present as condensed aromatic system, yielding a five- or six-membered heteroaromatic ring, such as, for instance, with benzene [phthalimide-type structure, formula (V)] and naphthalene [naphthalimide-type structure, formula (VI)].

formula (V) formula (VI)

For the purpose of the present description, the definition "ether group (— O -)" should be understood as having the following meaning : "ether groups which links two moieties containing each at least one aromatic ring".

In a first particular embodiment, the recurring units (Rl) of the polyimide (Pl) are further free from amide groups other than those possibly included in the amic acid form of the imide groups [recurring units (RIa)]. Recurring units (RIa) are preferably of one or more formulae (VII),

(VIII) and (IX) here below :

- A -

formula (VII) and/or formula (VIII) and/or formula (IX) where : - Ar is :

R is :

In a second particular embodiment, the polyimide (Pl) is an aromatic polyamide-imide. For the purpose of the present description, an aromatic polyamide-imide is intended to denote any polymer of which more than 50 wt. % of the recurring units (Rl) comprise at least one aromatic ring, at least one imide group, as such and/or in its amic acid form, and at least one amide group which is not included in the amic acid form of an imide group [recurring units (RIb)]. The recurring units (RIb) are preferably :

(X) and/or (XI) (imide form) (amic acid form) where : - Ar is :

with X being, in this particular embodiment,

, ^Jn with n= 1,2,3,4 or 5 ;

- R is :

with Y being, in this particular embodiment :

with n= 0,1,2,3,4 or 5.

More preferably, recurring units (RIb) are chosen from

(RIb-I)

and/or the corresponding amide-amic acid containing recurring unit

wherein the attachment of the two amide groups to the aromatic ring as shown in (XIII) will be understood to represent the 1 ,3 and the 1 ,4 polyamide-amic acid configurations ;

(Rlb-2)

and/or the corresponding amide-amic acid containing recurring unit :

wherein the attachment of the two amide groups to the aromatic ring as shown in (XV) will be understood to represent the 1,3 and the 1,4 polyamide-amic acid configurations ; and (Rlb-3)

(XVI)

and/or the corresponding amide-amic acid containing recurring unit

wherein the attachment of the two amide groups to the aromatic ring as shown in (XVII) will be understood to represent the 1,3 and the 1,4 polyamide-amic acid configurations.

Recurring units (RIb) are preferably a mix of recurring units (Rlb-2) and (Rlb-3). Polyamide-imides where essentially all, if not all, recurring units are recurring units complying with this criterion are commercialized by SOLVAY ADVANCED POLYMERS, L.L.C. as TORLON ^® polyamide-imides. The aromatic polyamide-imide can be notably manufactured by a process including the polycondensation reaction between (i) at least one acid monomer chosen from trimellitic anhydride and trimellitic anhydride monoacid halides and (ii) at least one comonomer chosen from diamines and diisocyanates.

Among the trimellitic anhydride monoacid halides, trimellitic anhydride monoacid chloride is preferred.

The comonomer comprises preferably at least one aromatic ring. Besides, it comprises preferably at most two aromatic rings. More preferably, the comonomer is a diamine. Still more preferably, the diamine is chosen from the group consisting of 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, m-phenylenediamine and mixtures thereof.

As mentioned above, the blends (B) in accordance with the present invention further comprise at least one aromatic sulfone polymer (P2).

For the purpose of the present description, the definition "aromatic sulfone polymer" is intended to denote any polymer of which more than 50 wt % of recurring units (R2) comprise at least one group of formula XVIII :

(Formula XVIII) said recurring units (R2) being free of imide groups, as such and/or in their amic acid form, as defined above in connection with the definition of polymer (Pl).

The aromatic sulfone polymer (P2) preferably contains more than 70 % wt of recurring units (R2), more preferably contains more than 90 % wt of recurring units (R2). Most preferably, it contains no recurring unit other than recurring units (R2).

In a particular embodiment, which is preferred, more than 50 % wt of the recurring units (R2) of aromatic sulfone polymer (P2) are recurring units (R2a) and/or recurring units (R2b) :

wherein :

- Q is a group chosen among the following structures :

integer from 1 to 6, or an aliphatic divalent group, linear or branched, of up to 6 carbon atoms ; and mixtures thereof ;

- Ar being, for the purpose of the definition of polymer (P2) a group chosen among the following structures :

integer from 1 to 6, or an aliphatic divalent group, linear or branched, of up to 6 carbon atoms ; and mixtures thereof ;

Ar' being, for the purpose of the definition of polymer (P2), a group chosen among the following structures :

with R _D being :

with n = integer from 1 to 6, or an aliphatic divalent group, linear or branched, of up to 6 carbon atoms ;

and mixtures thereof.

Recurring units (R2a) are preferably chosen from :

(i)

(ϋ)

(iv) and mixtures thereof.

Recurring units (R2b) are preferably chosen from :

(jjj)

Uv) and mixtures thereof.

More preferably, recurring units (R2b) are units (j) as above detailed. Still more preferably, according to the preferred embodiment, aromatic sulfone polymer (P2) contains no recurring unit other than recurring units (R2a) and/or (R2b). Good results were obtained with :

■ aromatic sulfone polymer (P2), the recurring units of which are recurring units (ii) (poly(biphenyldisulfone)) ;

■ aromatic sulfone polymer (P2), the recurring units of which are recurring units (j) (poly(phenylsulfone)) ; ■ aromatic sulfone polymer (P2), the recurring units of which are recurring units (jj) (poly(etherethersulfone)) ;

■ aromatic sulfone polymer (P2), the recurring units of which are recurring units (jjj) and, optionally in addition, recurring units (jj) (polyethersulfone) ; and ■ aromatic sulfone polymer (P2) the recurring units of which are recurring units (jv) (polysulfone, hereinafter).

Most preferably, according to the preferred embodiment, aromatic sulfone polymer (P2) contains no recurring unit other than recurring units (R2b).

Accordingly, aromatic sulfone polymer (P2) is most preferably chosen among the group consisting of polysulfone, polyphenylsulfone, polyethersulfone, copolymers and mixtures thereof and is most preferably a polyphenylsulfone, i.e. a polymer whereof the recurring units are units (j) as above detailed.

Polyphenylsulfone is notably available as RADEL ^® R from SOLVAY ADVANCED POLYMERS, L.L.C. The aromatic sulfone polymer (P2) may be prepared by any known method. Methods well known in the art are for instance those described in documents US-A-3634355 ; US-A-4008203 ; US-A-4108837 and US-A-4175175, the whole content of which is incorporated herein by reference. As mentioned above, the blends (B) in accordance with the present invention further comprise at least one polyimide (P3).

For the purpose of the present description, the definition " polyimide (P3) " is intended to denote any polymer of which more than 50 wt. % of the recurring units comprise at least one aromatic ring, at least one imide group, as such and/or in its amic acid form, and at least two ether groups [recurring units (R3)].

Recurring units (R3) may optionally further comprise at least one amide group which is not included in the amic acid form of an imide group.

A first class of polyimides (P3) consists of those wherein the recurring units (R3) are chosen from :

(R3a)

formula (XIX) and/or formula (XX) and/or formula (XXI) ; and

(R3b)

(imide form) (amic acid form)

(XXII) and/or (XXIII) where :

Ar has the same meaning as in formulae (VII - IX) ; - R being, for the purpose of the definition of polymer (P3) :

Examples belonging to this first class of polyimides (P3) are those wherein the recurring units (R3) are of formula :

and/or its two corresponding amic acid forms [see formulae (XX) and (XXI) vs. the wholly imide form of formula (XIX)].

Polyimides (P3) wherein essentially all, if not all, the recurring units are of formula (XXIV), and/or their two corresponding amic acid forms, are notably commercially available from MITSUI as AURUM ^® polyimide.

A second class of polyimides (P3) is composed of those wherein the recurring units (R3) are recurring units (R3c) of formula

(R3c)

wherein : (i) -0-Z is a member selected from

wherein R ₅ is independently hydrogen, lower alkyl or lower alkoxy ;

(i-b) (XXVII) wherein the oxygen may be attached to either ring and located ortho or para to one of the bonds of the imide carbonyl groups

and (i-c) (XXVIII) wherein the oxygen may also be attached to either ring and located ortho or para to one of the bonds of the imide carbonyl groups

(ii) Ri is selected from

(ii-a) substituted or unsubstituted aromatic radicals such as

a

(XXX) (ii-b) divalent radicals of the formula :

(XXXI) wherein R ₃ is independently Cl to C6 alkyl, aryl or halogen and R ₄ is selected from -O-, -S-, -SO ₂ -, -SO-, alkylenes of 1 to 6 carbon atoms, cycloalkylenes of 4 to 8 carbon atoms, alkylidenes of 1 to 6 carbon atoms or cycloalkylidenes of 4 to 8 carbon atoms ; (iii) R ₂ is selected from aromatic hydrocarbon radicals having from 6 to 20 carbon atoms and halogenated derivatives thereof, or alkyl substituted derivatives thereof, wherein the alkyl group contains 1 to 6 carbon atoms, alkylene and cycloalkylene radicals having from 2 to 20 carbon atoms and C2 to C8 alkylene terminated polydiorganosiloxanes or a divalent radical of the formula (XXXI) wherein R ₃ and R ₄ are as previously defined.

The recurring units (R3c) may be contained in the polyimide (P3) as such and/or in their two amic acid forms.

These polyimides are prepared by methods well known in the art as set forth in, for example, U.S. Pat. Nos. 3,833,544, 3,887,588, 4,017,511, 3,965,125 and 4,024,110.

The polyimides (P3) wherein the recurring units (R3) are recurring units (R3c) may, for example, be prepared by effecting reaction in the presence of a dipolar aprotic solvent of a mixture of ingredients comprising, for instance, (1) a bis(nitrophthalimide) of the general formula :

(XXXII) wherein R ₂ is defined as hereinabove, and (2) an alkali metal salt of an organic compound of the general formula :

MO— R j -OM

(XXXIII) wherein M is an alkali metal and Ri is defined as hereinabove.

The diamines are as described infra, when discussing the third class of aromatic polyetherimides.

The preferred nitrophthalic anhydrides useful in the present invention are 3-nitrophthalic anhydride, 4-nitrophthalic anhydride and mixtures thereof.

A third class of polyimides (P3) consists of those wherein the recurring units (R3) are recurring units (R3d)

(XXXIV) as such , and/or in their amic acid forms

and/or

(XXXVI) wherein :

- the → denotes isomerism so that in any recurring unit the groups to which the arrows point may exist as shown or in an interchanged position ;

- E is chosen from :

(E-i) ^ '°- ⁴ with the R' being, for the specific purpose of the definition of polyimide (P3) and independently from each other, alkyl radicals comprising from 1 to 6 carbon atoms, aryls or halogens ;

; and Y being, for the specific purpose of the definition of polyimide (P3), chosen from :

(Y-i) alkylenes of 1 to 6 carbon atoms, in particular

with n = integer from 1 to 6, (Y-ii) perfluoroalkylenes of 1 to 6 carbon atoms, in particular

with n = integer from 1 to 6, (Y-iii) cycloalkylenes of 4 to 8 carbon atoms ; (Y-iv) alkylidenes of 1 to 6 carbon atoms ; (Y-v) cycloalkylidenes of 4 to 8 carbon atoms ;

K

-S- -O-

(Y-vi) , (Y-vϋ) , (Y-viii)

O

(Y-ix)

- Ar" is selected from :

(Ar"-i) aromatic hydrocarbon radicals having from 6 to 20 carbon atoms and halogenated substituted thereof, or alkyl substituted derivatives thereof, wherein the alkyl substituting group contains 1 to 6 carbon atoms, such as :

and halogenated substituted thereof, or alkyl substituted derivatives thereof, wherein the alkyl substituting group contains from 1 to 6 carbon atoms ; with Y being chosen from (Y-i), (Y-ii), (Y-iii), (Y-iv), (Y-v), (Y-vi), (Y-vϋ),

(Y-viii), and (Y-ix), as above defined,

(Ar"-iii) alkylene and cycloalkylene radicals having from 2 to 20 carbon atoms, and (Ar"-iv) terminated polydiorganosiloxanes.

The polyimides (P3) wherein the recurring units (R3) are recurring units (R3d) may be prepared by any of the methods well-known to those skilled in the art including the reaction of any aromatic bis(ether anhydride)s of the formula

(XXXVII) where E is as defined hereinbefore, with a diamino compound of the formula

H ₂ N-Af-NH ₂ (XXXVIII) where Ar" is as defined hereinbefore. In general, the reactions can be advantageously carried out employing well-known solvents, e.g., o-dichlorobenzene, m-cresol/toluene, N,N-dimethylacetamide, etc., in which to

effect interaction between the dianhydrides and diamines, at temperatures of from about 20 ⁰ C to about 250 ⁰ C.

Alternatively, these polyimides can be prepared by melt polymerization of any dianhydrides of formula (XXXVII) with any diamino compound of formula (XXXVIII) while heating the mixture of the ingredients at elevated temperatures with concurrent intermixing.

The aromatic bis(ether anhydride)s of formula (XXXVII) include, for example :

■ 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride ; ■ 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl ether dianhydride ;

■ l,3-bis(2,3-dicarboxyphenoxy)benzene dianhydride ;

■ 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl sulfide dianhydride ;

■ l,4-bis(2,3-dicarboxyphenoxy)benzene dianhydride ;

■ 4,4'-bis(2,3-dicarboxyphenoxy)benzophenone dianhydride ; ■ 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl sulfone dianhydride ;

■ 2,2-bis[4 (3,4-dicarboxyphenoxy)phenyl]propane dianhydride ;

■ 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl ether dianhydride ;

■ 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride ;

■ l,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride ; ■ l,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride ;

■ 4,4'-bis(3,4-dicarboxyphenoxy)benzophenone dianhydride ;

■ 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy)diphenyl-2 ,2-propane dianhydride ; etc. and mixtures of such dianhydrides.

The organic diamines of formula (XXXVIII) include, for example, m-phenylenediamine, p-phenylenediamine, 2,2-bis(p-aminophenyl)propane, 4,4'-diaminodiphenyl-methane, 4,4'-diaminodiphenyl sulfide, 4,4'-diamino diphenyl sulfone, 4,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine,

In the recurring units (R3d), E is preferably chosen from (E-i)

with the R' having the same meaning as above ; more preferably, E is unsubstituted m-phenylene.

Besides, in the recurring units (R3d), Ar" is preferably chosen from with Y being chosen from (Y-i), (Y-ii), (Y-iii), (Y-iv), (Y-v), (Y-vi), (Y-vii), (Y-viii) and (Y-ix), as above defined. More preferably, Ar" is

Good results were obtained when the recurring units (R3c-4) were recurring units of formula (XXXIX) as such, in imide form, and/or in amic acid forms [formulae (XL) and (XLI)] :

(XXXIX) and/or

and/or

wherein in formulae (XL) and (XLI) the → denotes isomerism so that in any recurring unit the groups to which the arrows point may exist as shown or in an interchanged position.

Among all the polyimides, those belonging to this third and last class are generally preferred.

Preferably more than 75 wt. % and more preferably more than 90 wt. % of the recurring units of the polyimide (P3) are recurring units (R3). Still more

preferably, essentially all, if not all, the recurring units of the polyimide (P3) are recurring units (R3).

Excellent results were obtained when the polyimide (P3) was chosen from polyimides of which essentially all, if not all, the recurring units were of formula (XXXIX), and/or their corresponding amic acid forms (XL) and/or (XLI). Such polyimides are notably commercially available from GENERAL ELECTRIC as ULTEM ^® polyetherimides.

In blends (B) according to the present invention, the weight of the polyimide (Pl), based on the total weight of polymers (Pl), (P2) and (P3), is generally at least 10 %, preferably at least 30 %, more preferably of at least 50 % and still more preferably of at least 60 %. On the other hand, the weight of the polyimide (Pl), based on the total weight of polymers (Pl), (P2) and (P3), is generally of at most 97 %, preferably of at most 95 %, more preferably of at most 92,5 % and still more preferably of at most 85 %. Further, in blends (B) according to the present invention, the weight of the aromatic sulfone polymer (P2), based on the total weight of polymers (Pl), (P2) and (P3), is generally at least 2,5 %, preferably at least 5 %, more preferably of at least 8 % and still more preferably of at least 10 %. On the other hand, the weight of the aromatic sulfone polymer (P2), based on the total weight of polymers (Pl), (P2) and (P3), is generally of at most 89,5 %, preferably of at most 40 %, more preferably of at most 35 % and still more preferably of at most 30 %.

In the embodiments of the invention wherein the blends (B) are essentially composed of the polymers (Pl), (P2) and (P3), the combined weight of the polyimide (Pl) and the aromatic sulfone polymer (P2), based on the total weight of blend (B), is generally above 65 %, preferably above 75 %, more preferably above 80 % and still more preferably above 85 %. On the other hand, the combined weight of the polyimide (Pl) and the aromatic sulfone polymer (P2), based on the total weight of blend (B), is generally below 98 %, preferably below 95 %, more preferably below 92 % and still more preferably below 90 %. Further, the respective amounts of polyimide (Pl) and aromatic sulfone polymer (P2) in blends (B) are not actually critical. They are in a weight ratio (Pl) / (P2) generally higher than 1.5 / 1, preferably higher than 2 / 1 and more preferably higher than 5 / 1. On the other hand, the respective amounts of polyimide (Pl) and aromatic sulfone polymer (P2) in blends (B) are in a weight

ratio (Pl) / (P2) generally lower than 15 / 1, preferably lower than 12 / 1 and more preferably lower than 9 / 1.

Without wishing to be bound by any theory whatsoever, Applicants believe that the polyimide (P3), present in the blends (B) of the invention, operates as a compatibilising agent, i.e. appears to enhance the miscibility of the aromatic sulfone polymer (P2) and the polyimide (Pl). This is a reason why the amount of polyimide (P3) may be significantly lower than the combined amounts of polymers (Pl) and (P2) in said blends (B). Based on the total weight of polymers (Pl), (P2) and (P3), the weight of polyimide (P3) is generally of at least 0,5 %, preferably of at least 2 %, more preferably of at least 4 % and still more preferably of at least 5 %. On the other hand, the weight of the polyimide (P3), based on the total weight of polymers (Pl), (P2) and (P3), is generally of at most 35 %, preferably of at most 30 %, more preferably of at most 20 % and still more preferably of at most 15 %. Essentially for reasons of better processability, blending capabilities and properties of the final blends, the inherent viscosity (LV.) of the polyimide (Pl), as measured in N-methylpyrrolidone at concentrations of 0.5 % by weight at 25°C is generally higher than 0.01 dl/g, preferably higher than 0.1 dl/g, more preferably higher than 0.4 dl/g. Further, the LV. of the polyimide (Pl) is generally lower than 1.0 dl/g, preferably lower than 0.9 dl/g, more preferably lower than 0.75 dl/g.

Essentially for similar reasons, the relative melt viscosity of the of the aromatic sulfone polymer (P2), as measured by ASTM test method D 1238 at 380 ⁰ C under a load of 2.16 kg, and expressed as melt flow rate (MFR), is generally higher than 5 g /10 min, preferably higher than 8 g / 10 min, more preferably higher than 10 g / 10 min. Further, the MFR of the aromatic sulfone polymer (P2) is generally lower than 50 g / 10 min, preferably lower than 40 g / 10 min, more preferably lower than 35 g / 10 min.

Blends (B) in accordance with the invention may comprise one and only one of each of the polyimide (Pl) and of the aromatic sulfone polymer (P2). Alternately, they can comprise two, three, or even more than three polyimides (Pl), respectively aromatic sulfone polymers (P2).

Blends (B) in accordance with the present invention may further contain conventional ingredients of compositions based on polymers (Pl) and / or (P2), including reinforcing agents, lubricating agents, heat stabilizers, processing aids, anti-static agents, extenders, organic and/or inorganic pigments like TiO ₂ , carbon

black, acid scavengers, such as MgO, stabilizers, i.e., metal oxides and sulfides such as zinc oxide and zinc sulfide, antioxidants, flame retardants, smoke- suppressing agents, and particulate fillers and nucleating agents such as talc, mica, titanium dioxide, kaolin and the like. For instance, good results have been noticed by incorporating certain fluorinated polymers, e.g. poly(tetrafluor- ethylene) and the like, as processing aids in blends (B).

The weight of said optional ingredients, based on the total weight of blend (B), ranges generally from 0 to 30 %, preferably from 0 to 20 %, more preferably from 0 to 10 %, still more preferably from 0 to 5 %. The blend (B) may also be substantially free of said optional ingredients

Blends (B) in accordance with the invention may be prepared by any conventional mixing method. A certain method comprises dry mixing the ingredients of the said blends in powder or granular form, using e.g. a mechanical blender, then extruding the mixture into strands and chopping the strands into pellets. A certain other method comprises dissolving the respective polymers (Pl), (P2) and (P3) in one or more organic solvents (or dissolving the said polymers in an organic solvent, then causing the dissolved polymers to precipitate by the addition of a non solvent, and finally molding the recovered dried cake. Still another method to prepare the blends (B), which is preferred and which constitutes another aspect of the present invention comprises :

■ a step of dry mixing the aromatic sulfone polymer (P2) with the polyimide (P3), both preferably in powder or in granular form ;

■ a melt mixing step of the polymers dry mixed as above while having separately added thereto the polyimide (Pl) in powder or in granular form, alone or together with a processing aid as defined above.

The melt mixing of the polymers (Pl), (P2) and (P3) can be achieved by any appropriate means. The melt mixing is advantageously made under a sufficiently high shear, so as to achieve a high degree of mixing of the polymers in the blend (B) ("shear-mixing"). The melt mixing can notably be achieved in a desirable manner by coextruding the polymers (Pl), (P2) and (P3) and the possible processing aid, so as to obtained strands of blend (B). Very preferably, the so-obtained strands are then chopped into pellets.

Blends (B) in accordance with the invention exhibit an excellent balance of properties, including :

■ very high tensile and compressive strengths, unexpectedly higher than those of prior art neat aromatic sulfone polymers ;

■ very high impact strength, unexpectedly higher than that of prior art neat aromatic polyimides, coupled with an improved processability, compared to the latter.

Surprisingly, the presence of the polyimide (P3) in the blends (B) in accordance with the invention allows to obtain an overall unexpected improvement of their elongation at break and impact strength.

Thanks to their excellent properties, especially their mechanical properties, the blends (B) in accordance with the invention can be shaped in a large variety of articles or parts of articles usable in applications requiring high strength, especially compressive and impact strength, high temperature capability, chemical resistance, etc. Blends (B) may be shaped, for instance, in the form of thermoplastic calendar rollers for the paper industry, where these properties are required, together with another property featured by the said blends, i.e. good adhesive bonding strength with epoxy resins (which are used to bond the thermoplastic part of the rollers to the steel core thereof)

The present invention is described in greater detail below by referring to the non limitative examples. Examples IR, 2R and 3

Examples IR and 2R are given for the sake of comparison. Blends containing a polyamideimide homopolymer (Pl), commercialised by SOLVAY ADVANCED POLYMERS, L.L.C. under the trade name TORLON ^® 4000 T, and a polyphenylsulfone homopolymer (P2), commercialised by SOLVAY ADVANCED POLYMERS, L.L.C. under the trade name RADEL ^® R-5800 T, were compounded, together with a processing aid being a poly(tetrafluorethylene) polymer (PTFE) commercialized by 3M under the trade name DYNEON PA5956, as detailed hereafter.

In example 3, a polyetherimide homopolymer (P3) commercialised by GENERAL ELECTRIC under the trade name ULTEM ^® A 1000 was added to the blend.

The compositions of the blends are shown in Table 1 hereunder.

Table 1

Powder of the (Pl) polymer, preblended with PTFE powder, was fed separately from pellets of the (P2) polymer (preblended with pellets of the (P3) polymer in example 3) to a Berstorff 25 mm co-rotating twin-screw extruder using two gravimetric feeders that were adjusted for each run to achieve the target blend ratio of (Pl) to (P2).

The compounding conditions for all the blends are shown in Table 2. The set points on the extruder were the same for all the runs.

Table 2 Compounding Run Parameters Used for Compounding of Blends.

Several properties of the polymeric blends were measured, using the test methods as indicated in Table 3 below :

Table 3

Property (units) Test Method

Tensile Strength (psi) ASTM D 638

Tensile elongation (%) ASTM D 638

Tensile Modulus (psi) ASTM D 638

Compressive strength (psi) ASTM D 695

Flex Strength (psi) ASTM D 790

Flex Modulus (psi) ASTM D 790

Notched Izod (ft-lb/in) ASTM D 256

Un-notched Izod (ft-lb/in) ASTM D 4812

Heat deflection temperature (HDT), annealed ( ⁰ C) ASTM D 648

Glass transition temperature (T _g ) on pellets ( ⁰ C) DSC* 2 heats

Specific gravity (g / cm ³ ) ASTM D 792

Bulk Density (Ib / ft ^J ) -

*DSC : differential scanning calorimetry The results that were obtained are shown in table 4.

Table 4

The results of Table 4 show that the elongation at yield and impact strength (notched and un-notched Izod) of a ternary blend in accordance with the invention (example 3) are unexpectedly improved vs. binary blends not containing polymer (P3).

Further, some mechanical properties of the blend in accordance with the invention are far better than the corresponding properties of polymer (Pl) alone, compounded under the same general conditions, as shown in Table 5 hereunder.

Table 5

(*) containing 1 wt. % PTFE

Still further, some mechanical properties of the blend in accordance with the invention are far better than the corresponding properties of polymer (P2) alone, compounded under the same general conditions, as shown in Table 6 hereunder.

Table 6