Flame resistant polyetherimide resin blends

Abstract

Flame resistant polymer blends contain a polyetherimide and an impact strength-enhancing amount of a siloxane-polyetherimide copolymer. These blends exhibit high impact strengths, good blow-moldability and injection moldability, amenability to thermoforming and very low flammability. The blends are particularly suited to the manufacture of aircraft cabin interior components.

Description

BACKGROUND OF THE INVENTION

This invention relates to polymer blends which are characterized by high impact strengths, good blow-moldability, good injection moldability, amenability to thermoforming and very low flammability. The polymer blends are particularly suited for the construction of various panels and parts for aircraft interiors.

Because of their light weight, durability and strength, engineering thermoplastics are used for the construction of many components of aircraft interiors. Components such as wall panels, overhead storage lockers, serving trays, seat backs, cabin partitions and the like are conveniently and economically fabricated by extrusion, thermoforming, injection molding and blow-molding techniques. The thermoplastic resins used in these components, therefore, should be amenable to such fabrication techniques.

Recent attention to the effects of fire and smoke on survivability during aircraft mishaps has led to the promulgation of standards for the flame resistance of construction materials used for the interiors of transport category aircraft. One drawback of engineering thermoplastics conventionally used for the construction of aircraft interior components is their inability to meet the latest flammability performance standards.

Such standards are embodied in 1986 amendments to Part 25-Airworthiness Standards-Transport Category Airplanes of Title 14, Code of Federal Regulations. (See 51 Federal Register 26206, July 21, 1986 and 51 Federal Register 28322, Aug. 7, 1986.) The flammability standards are based on heat calorimetry tests developed at Ohio State University. Such tests are described in the above-cited amendments to 14 C.F.R. Part 25 and are incorporated herein by reference.

Heretofore, no conventional engineering thermoplastics, having the requisite physical properties and processing characteristics, have been able to meet the flammability standards referred to in the preceeding paragraph.

SUMMARY OF THE INVENTION

In accordance with the present invention, polymer blend compositions contain a polyetherimide and an impact strength-enhancing amount of siloxane polyetherimide copolymer.

The polymer blends of this invention have been found to possess the physical properties important for applications as aircraft cabin interior components. Moreover, these blends meet or exceed the rigorous flammability standards that have been established for such aircraft interior components.

DETAILED DESCRIPTION OF THE INVENTION

The polyetherimides employed in the blends of this invention are well-known injection moldable engineering thermoplastics. Polytherimides are characterized by high impact strengths, high temperature resistance and good processability. Unmodified polyetherimides have not, however, found widespread use in blow-molding applications.

The polyetherimides used for preparing the blends of this invention contain repeating groups of the formula ##STR1## wherein "a" is an integer greater than 1, e.g., from 10 to 10,000 or more; T is --O-- or a group of the formula

--O--Z--O-- wherein the divalent bonds of the --O-- or the --O--Z--O-- group are in the 3,3'; 3,4'; 4,3', or the 4,4'positions; Z is a member of the class consisting of (A): ##STR2## and (B) divalent organic radicals of the general formula ##STR3## where X is a member selected from the group consisting of divalent radicals of the formulas ##STR4## where y is an integer from 1 to about 5; and R is a divalent organic radical selected from the group consisting of (a) aromatic hydrocarbon radicals having from 6 to about 20 carbon atoms and halogenated derivatives thereof, (b) alkylene radicals having from 2 to about 20 carbons atoms, cycloalkylene radicals having from 3 to about 20 carbon atoms, and (c) divalent radicals of the general formula ##STR5## where Q is a member selected from the group consisting of ##STR6## and x is an integer from 1 to about 5.

In one embodiment, the polyetherimide may be a copolymer which, in addition to the etherimide units described above, further contains polyimide repeating units of the formula ##STR7## wherein R is as previously defined and M is selected from the group consisting of ##STR8## where B is --S-- or ##STR9## . These polyetherimide copolymers and their preparation are described by Williams et al. in U.S. Pat. No. 3,983,093, incorporated herein by reference.

The polyetherimides can be prepared by any of the methods well known to those skilled in the art, including the reaction of an aromatic bis(ether anhydride) of the formula ##STR10## with an organic diamine of the formula

H.sub.2 N--R--NH.sub.2 (II) wherein T and R are defined as described above.

Bis(ether anhydride)s of formula I include, for example,

1,3-bis(2,3-dicarboxyphenoxy)benzene dianhydride; 1,4-bis(2,3-dicarboxyphenoxy)benzene dianhydride; 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride; and 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride; 4,4'-bis(phthalic anhydride)ether.

A preferred class of aromatic bis(ether anhydride)s included by formula I includes compounds of formula III, IV and V, which follow: ##STR11## and mixtures thereof, where Y is selected from the group consisting of --O--, --S--, ##STR12##

Aromatic bis(ether anhydride)s of formula III include, for example:

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; 4,4'-bis(3,4-dicarboxyphenoxy)benzophenone dianhydride; 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride; and mixtures thereof.

Aromatic bis(ether anhydride)s of formula IV include, for example:

2,2-bis([4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride; 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl ether dianhydride; 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl sulfide dianhydride; 4,4'-bis(2,3-diacarboxyphenoxy)benzophenone dianhydride; 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl sulfone dianhydride; and mixtures thereof.

The aromatic bis(ether anhydride)s of formula V may be, for example,

4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy) diphenyl-2,2-propane dianhydride. 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy) diphenyl ether dianhydride; 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride; 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy) benzophenone dianhydride; 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy) diphenyl sulfone dianhydride, and mixtures thereof.

When polyetherimide/polyimide copolymers are employed, a dianhydride, such as pyromellitic anhydride, is used in combination with the bis(ether anhydride).

Some of the aromatic bis(ether anhydride)s of formula (I) are shown in U.S. Pat. No. 3,972,902 (Darrell Heath and Joseph Wirth). As described therein, the bis(ether anhydride)s can be prepared by the hydrolysis, followed by dehydration, of the reaction product of a nitrosubstituted phenyl dinitrile with a metal salt of dihydric phenol compound in the presence of a dipolar, aprotic solvent.

Additional aromatic bis(ether anhydride)s also included by formula (I) above are shown by Koton, M. M., Florinski, F. S., Bessonov, M. I. and Rudakov, A. P. (Institute of Heteroorganic Compounds, Academy of Sciences, U.S.S.R), U.S.S.R. patent 257,010, Nov. 11, 1969, Appl. May 3, 1967, and by M. M. Koton, F. S. Florinski, Zh. Org. Khin. 4(5), 774 (1968).

The organic diamines of formula (II) include, for example:

m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane (commonly named 4,4'-methylenedianiline), 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether (commonly named 4,4'-oxydianiline), 1,5-diaminonaphthalene, 3,3-diamethylbenzidine, 3,3-dimethoxybenzidine, 2,4-bis(beta-amino-t-butyl)toluene, bis(p-beta-amino-t-butylphenyl)ether, bis(p-beta-methyl-o-aminophenyl)benzene, 1,3-diamino-4-isopropylbenzene, 1,2-bis(3-aminopropoxy)ethane, benzidine, m-xylylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, bis(4-aminocyclohexyl)methane, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-dodecanediamine, 2,2-dimethylpropylenediamine, octamethylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 1,4-cyclohexanediamine, 1,12-octadecanediamine, bis(3-aminopropyl)sulfide, N-methyl-bis(3-aminopropyl)amine, hexamethylenediamine, heptamethylenediamine, nonamethylenediamine, decamethylenediamine, and mixtures of such diamines.

Preferred polyetherimides are available commercially from General Electric Company, Pittsfield, Mass. U.S.A. under the registered trademark, ULTEM.

The siloxane polyetherimide copolymers employed in the blends of this invention may be prepared in a manner similar to that used for polyetherimides, except that a portion or all of the organic diamine reactant is replaced by an amine-terminated organosiloxane of the formula ##STR13## wherein n and m independently are integers from 1 to about 10, preferably from 1 to about 5, and g is an integer from 1 to about 40, preferably from about 5 to about 25.

The organic diamine of formula II and the amine-terminated organosiloxane of formula VI may be physically mixed prior to reaction with the bis(ether anhydride)(s), thus forming a substantially random copolymer. Alternatively, block or alternating copolymers may be used.

Preferred amine-terminated organosiloxanes are those of the formula VI, in which n and m are each 3, and which have a molecular weight distribution such that g has an average value ranging from about 9 to about 20.

The diamine component of the siloxane polyetherimide copolymers generally contains from about 20 to 50 mole % of the amine-terminated organosiloxane of formula VI and from about 50 to 80 mole % of the organic diamine of formula II. In preferred copolymers, the diamine component contains from about 25 to about 40 mole %, most preferably about 30 mole % of the amine-terminated organosiloxane.

Both the polyetherimides and the siloxane polyetherimide copolymers used in the blends of this invention may be prepared by any of the procedures conventionally used for preparing polyetherimides. A presently preferred method of preparation is described in U.S. Pat. No. 4,417,044, which is incorporated herein by reference.

Blending a siloxane polyetherimide copolymer with a polyetherimide has been found to enhance various important physical properties of the polyetherimide. In particular, the impact strength of the blend is considerably better than that of the unmodified polyetherimide. In addition, the blend is easily fabricated into useful parts by sheet extrusion, thermoforming, injection molding and blow molding. Blow molding can be an efficient and economical procedure for mass production of certain types of components. The heat distortion temperatures (HDT) of the blends of this invention are unexpectedly high, especially in view of the rather low HDT's of unblended siloxane polyetherimide copolymers. Further unexpected advantages of the polyetherimide/siloxane polyetherimide copolymer blends of this invention are their greater resistance to crack propagation and enhanced retention of impact resistance after heat aging as compared to corresponding unmodified polyetherimides. The latter property can be important in applications requiring thermoforming.

In addition to the polymeric ingredients, the blends may contain other materials, such as fillers, additives, reinforcing agents, pigments and the like. These blends exhibit very low flammabilities. The blends meet or exceed the flammability standards of Part 25 of Title 14 of the Code of Federal Regulations. Moreover, in laboratory tests at 1/16" thickness, they were found to meet or satisfy UL 94 V-O requirements for flammability, as established by Underwriters Laboratories' "Flammability of Plastic Materials Bulletin" of Jan. 24, 1980.

The siloxane polyetherimide copolymer is employed in the present blends in impact strength-enhancing concentrations. Such concentations can vary over a fairly wide range, for example, from about 2% to about 90% by wt. of the blends, preferably, from about 2% to about 75% by wt. of the blends, most preferably from about 5% to about 30% by wt. of the blends.

Various blends have been prepared in accordance with this invention and tested for physical properties and flame resistance. The results of these tests are shown in the following examples, which are provided for illustration only and are not intended to be limiting.

EXAMPLES 1-18

Polymer blends described in Table I below were prepared by a conventional melt-blending procedure using a laboratory extruder. The blends were extruded into small diameter strands, which were chopped into pellets for further molding into test parts.

The polyetherimide resins employed in these experiments are commercially available resins, sold by General Electric Company, under the trademark, ULTEM.RTM.. The polyetherimide identified in Table I as type A is a homopolymer prepared by reacting 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl] propane dianhydride ("BPA-DA") and m-phenylenediamine. The polyetherimide identified as type B is a copolymer prepared by reacting BPA-DA with a 50/50 mixture of m-phenylenediamine and p-phenylenediamine. The polyetherimide identified as type C is a copolymer prepared by reacting a mixture of BPA-DA and pyromellitic dianhydride with m-phenylenediamine. The polyetherimide designated type D is a lower molecular weight form of type A. The siloxane polyetherimide copolymer is the reaction product of a mixture of m-phenylenediamine and an amine-terminated organosiloxane, with BPA-DA. The siloxane polyetherimide copolymer designated in Table I as type A is a random copolymer prepared from BPA-DA and a mixture of 70 mole % m-phenylenediamine and 30 mole % of an amine- terminated organosiloxane of formula VI wherein n and m are 3 and g has an average value of 19.4. The siloxane polyetherimide copolymer designated type B is the same as type A, except that the diamine component contains 40 mole % of the amine-terminated organosiloxane and the average value of g is 9. The siloxane polyetherimide copolymer of designated type C is the same as type B, except that it is a block, rather than random, copolymer. The siloxane polyetherimide copolymer designated type D is the same as type C except that the diamine component contains 25 mole % of the amine-terminated organosiloxane and the average value of g is 15. The siloxane polyetherimide copolymer designated type E is the same as type A, except that it is a block copolymer and the average value of g is 15.

The data provided in Table I demonstrates that the blends of the present invention have unexpectedly high heat distortion temperatures, have improved impact resistance, retain their impact resistance after heat aging, and are amenable to injection molding, blow molding, extrusion and thermoforming. Moreover, these blends have low flammability and heat release values, thus making them particularly suited to aircraft interior component applications.

TABLE 1__________________________________________________________________________ Siloxane Poly- SiloxanePoly- ether- Poly- Heat Izod Gardnerether- Poly- imide co- ether- Deflection Impact.sup.2 Impactimide ether- polymer imide co- Temperature.sup.1 (ft.-lb/in.) (in.-lb.) Sheet.sup.6Example conc. imide conc. polymer at 264 Rev As HeatNo. (wt. %) type (wt. %) type psi (.degree.c.) Notched Notched molded.sup.3 Scribed.sup.4 Sheet.sup.5 Aged__________________________________________________________________________ 1 95 A 5 A 196.5 1.24 27 250 -- -- -- 2 90 A 10 A 196.1 1.90 23.8 270 -- -- -- 3 85 A 15 A 195.8 2.40 24.7 >320 -- -- -- 4 95 A 5 B 195.1 0.71 >16 -- -- -- -- 5 90 A 10 B 193.8 1.30 >16 -- -- -- -- 6 85 A 15 B 190.9 1.70 >16 -- -- -- -- 7 90 B 10 B 195.9 1.78 >16 -- -- -- -- 8 90 C 10 B 203.5 1.16 >16 -- -- -- -- 9 85 D 15 B 193.0 1.64 >16 >320 >80>120 -- --10 85 A 15 B 194.3 2.18 >16 >320 >80 300 19511 85 A 15 C 191.5 1.6 -- >320 -- -- --12 85 A 15 D 191.5 1.6 -- >320 -- -- --13 70 A 30 C 181.6 5.2 -- >320 -- -- --14 85 A 15 E 187.3 3.5 -- -- -- -- --15 25 A 75 C 79.8 2.8 -- -- -- -- --16 25 A 75 E 98.8 12.9 -- -- -- -- --17 100 A 0 -- 200.0 0.8 25 320 16 250 10018 100.sup.11 A 0 -- 197.2 0.5 25.5 -- -- -- --__________________________________________________________________________ Dynatup .RTM. Impact.sup.7 Heat Release.sup.8 (ft.-lb.) 2 min. Max. heat 2 min. Max. Smoke Dynatup .RTM. Example As After >16 hrs. total heat release total smoke release Blow on Blow No. molded at 300.degree. F. release rate release rate moldability Molded__________________________________________________________________________ Part 1 -- -- -- -- -- -- -- -- 2 -- -- -- -- -- -- -- -- 3 45 9 -- -- -- -- -- -- 4 28 7 -- -- -- -- -- -- 5 24 14 -- -- -- -- -- -- 6 39 28 -- -- -- -- -- -- 7 34 29 -- -- -- -- -- -- 8 22 16 -- -- -- -- -- -- 9 28 12 25.2.sup.9 77.3.sup.9 43.1.sup.9 104.5.sup.9 -- -- 10 50 26 .sup. 35.7.sup.10 .sup. 67.1.sup.10 .sup. 70.2.sup.10 125.3.sup.10 -- -- 11 -- -- -- -- -- -- Good-Very 8.70 Good 12 -- -- -- -- -- -- Fair 16.7 13 -- -- -- -- -- -- Fair-Good 16.6 14 -- -- -- -- -- -- Fair 7.2 15 -- -- -- -- -- -- -- -- 16 -- -- -- -- -- -- -- -- 17 28 4 43.1.sup.9 71.3.sup.9 42.4.sup.9 67.0.sup.9 Poor -- 18 -- -- -- -- -- -- -- --__________________________________________________________________________Footnotes to Table I.sup.1 Determined by ASTM procedure D648..sup.2 Determined by ASTM procedure D256 (Rev. Notch test employs testbar with the notch on the side opposite impact)..sup.3 Gardner impact strength was determined on 21/2" .times. 21/2".times.1/8" samples supported by a 11/2" diameter support ring. A steeldart having adiameter of 1/2" and a smooth rounded tip having a radius of curvature of1/4" was positioned above the test sample with the tip of the dartin contact with the sample. An eight-pound weight was allowed to fall ameasured distance to strike the dart, forcing it into the sample.A "staircase" procedure was used to determine the work (height .times.weight) required to cause failure of the sample. The height of theweight above the impact end of the dart was changed incrementally(usually in increments of 1 inch) to find the work of failure fora given sample. Each test was replicated several times (usually 10 to 25times) to provide statistically meaningful data. The meanvalue was determined statistically as the work required to cause failureof the sample in 50% of the tests. Failure was defined asbreakage or perforation of the sample. The test was performed oninjection molded samples conditioned for 48 hours at 50% relativehumidity, room temperature..sup.4 Scribed Gardner impact strength was determined by the sameprocedure described in footnote 3, except the lower surface of the testsample was lightly scribed with a knife in an X pattern..sup.5 Test performed on extruded sheet samples..sup.6 Test performed on extruded sheet samples which had been heat agedfor more than 16 hours at 300-350.degree. F..sup.7 Dynatup .RTM. testing measures the high-speed penetrationproperties of plastics using load and displacement sensors. The testingwasperformed substantially by ASTM procedure D3763-85 using a Dynatup .RTM.instrument. Tests were performed on a 4" diameter, 1/8" thickinjection molded disc supported by a 3" diameter support ring. Five toten replicates of each sample were tested to determine the meanwork (ft.-lb.) required to cause sample failure..sup.8 Tests performed at Ohio State University according to proceduresdescribed in 14 C.F.R. Part 25..sup.9 Tests performed on 0.060 thick injection molded samples..sup.10 Tests performed on 0.060" thick extruded sheet..sup.11 Re-extruded control.

Claims

1. A polymer blend which comprises a polyetherimide component and from about 2 wt. % to about 90 wt. % of a siloxane polyetherimide copolymer component, wherein the polyetherimide component is comprised of repeating units of the formula ##STR14## and the siloxane polyetherimide copolymer component consists essentially of repeating units of the formula ##STR15## and repeating units of the formula ##STR16## and contains from about 20 to about 50 mol % of organosiloxane-containing units;

where T is --O-- or a group of the formula --O--Z--O-- wherein the divalent bonds of the --O-- or the --O--Z--O-- group are in the 3,3', 3,4', 4.3' or 4,4' positions;

Z is a member of the class consisting of (A): ##STR17## and (B) divalent organic radicals of the general formula ##STR18## where X is a member selected from the group consisting of divalent radicals of the formulas ##STR19## where y is an integer from 1 to about 5; and R is a divalent organic radical selected from the group consisting of (a) aromatic hydrocarbon radicals having from 6 to about 20 carbon atoms and halogenated derivatives thereof, (b) alkylene radicals having from 2 to about 20 carbon atoms, cycloalkylene radicals having from 3 to about 20 carbon atoms, and (c) divalent radicals of the general formula ##STR20## where Q is a member selected from the group consisting of ##STR21## and x is an integer from 1 to about 5; n and m independently are integers from 1 to about 10 and g is an integer from 5 to about 25.

2. The polymer blend of claim 1, wherein the polyetherimide further contains repeating units of the formula ##STR22## wherein R is as defined in claim 1 and M is selected from the group consisting of ##STR23## where B is --S-- or ##STR24## .

3. The polymer blend of claim 1, wherein n and m are integers from 1 to about 5.

4. The polymer blend of claim 3, wherein g has an average value from 9 to about 20.

5. The polymer blend of claim 1, wherein the organosiloxane-containing repeating unit constitutes from about 25 to about 40 mole % of the siloxane polyetherimide copolymer.

6. A polymer blend which comprises a polyetherimide and from about 2 wt. % to about 90 wt. % of a siloxane polyetherimide copolymer, wherein the polyetherimide is comprised of repeating units of the formula ##STR25## and wherein the siloxane polyetherimide copolymer consists essentially of repeating units of the formula ##STR26## and repeating units of the formula ##STR27## and repeating units of the formula ##STR28## wherein M is selected from the group consisting of ##STR29## where B is --S-- or ##STR30## and R' is R or a group of the formula ##STR31## and said siloxane polyetherimide copolymer comprises from about 20 to about 50 mol % of organosiloxane-containing units; where T is --O-- or a group of the formula

--O--Z--O--

wherein the divalent bounds of the --O-- or the --O--Z--O-- group are in the 3,3', 3,4', 4,3' or 4,4' positions; Z is a member of the class consisting of (A): ##STR32## and (B) divalent organic radicals of the general formula ##STR33## where X is a member selected from the group consisting of divalent radicals of the formulas ##STR34## where Y is an integer from 1 to about 5; and R is a divalent organic radical selected from the group consisting of (a) aromatic hydrocarbon radicals having from 6 to about 20 carbon atoms and halogenated derivatives thereof, (b) alkylene radicals having from 2 to about 20 carbon atoms, cycloalkylene radicals having from 3 to about 20 carbon atoms, and (c) divalent radicals of the general formula ##STR35## where Q is a member selected from the group consisting of ##STR36## and x is an integer from 1 to about 5; and n and m independently are integers from 1 to about 10 and g is an integer from about 5 to about 25.

7. The polymer blend of claim 6, wherein the polyetherimide further comprises repeating units of the formula ##STR37## wherein R and M are as defined in claim 6.

8. The polymer blend of claim 1, 2, 3 or 6 wherein the siloxane polyetherimide copolymer is a substantially random copolymer.

9. The polymer blend of claim 1, 2, 3 or 6 wherein the siloxane polyetherimide copolymer is a block copolymer.

10. The polymer blend of claim 1, 2, 3 or 6 wherein the siloxane polyetherimide copolymer is an alternating copolymer.

11. The polymer blend of claim 1, 2, 3 or 6 which contains from about 2% to about 75% by wt. of the siloxane polyetherimide copolymer.

12. The polymer blend of claim 1, 2, 3 or 6 which contains from about 5% to about 30% by wt. of the siloxane polyetherimide copolymer.

13. The polymer blend of claim 12, wherein the polyetherimide consists essentially of repeating units of the formula ##STR38##

14. The polymer blend of claim 6, wherein the siloxane polyetherimide copolymer consists essentially of repeating units of the formula ##STR39## wherein g has an average value of from about 9 to about 20.

15. The polymer blend of claim 12, which further contains fillers, pigments, reinforcing agents or mixtures thereof.