CONDUCTIVE, LOW WARP POLYETHERIMIDE RESIN COMPOSITIONS

Abstract: Polyetherimide compositions having low warp and conductive properties are provided. The compositions are prepared by combining a polyetherimide resin or polyetherimide-copolymer resin and a filler wherein the filler comprises a plate-like filler and a conductive filler.

Description: CONDUCTIVE, LOW WARP POLYETHERIMIDE RESIN COMPOSITIONS FIELD OF THE INVENTION The present invention relates to conductive, low aφ polyetherimide resin compositions. BACKGROUND OF THE INVENTION Polyetherimide resin compositions have been used to fabricate parts for numerous applications. Each application requires particular tensile and flexural properties, impact strength, heat distortion temperature, and resistance to waφ. For example, U.S. Patent 4,455,410 provides a polyetherimide-polyphenylenesulfide blend having good flexural strength characteristics. U.S. Patent 3,983,093 provides polyetherimide compositions having improved solvent resistance and suitable for use in preparing films, molding compounds, coatings, and the like. When fabricating certain components, a combination of low waφ and low surface resistance (i.e., high electrical conductivity) are required. The waφ of a given product is dependent upon composition, the geometry of the product and processing conditions such as molding temperature and pressure. For a material to be useful in computer chip tray applications, the material must provide low waφ properties and must possess a surface resisit y of less than about 10 6 ohms per square centimeter (ohms/cm 2 ). This is difficult to achieve because the Dolyetherimide is non-conductive and high levels of conductive materials, such as carbon fiber, added to achieve the desired low surface resistance may contribute to an increase in waφ. There remains a need, therefore, for conductive polyethermide compositions having low waφ and low surface resistance. SUMMARY OF THE INVENTION The present invention provides a polyetherimide composition having low waφ and conductive properties prepared by combining a polyetherimide resin or polyetherimide-copolymer resin and a filler composition wherein the filler composition comprises a plate-like filler and a conductive filler. DETAILED DESCRIPTION OF THE INVENTION The present invention provides a polyetherimide composition having low waφ and conductive properties prepared by combining a polyetherimide resin or polyetherimide-copolymer resin and a filler composition wherein the filler composition comprises a plate-like filler and a conductive filler. The polyetherimide compositions comprise a polyetherimide resin or polyetherimide-copolymer resin and a filler composition comprising a platelike filler material present in an amount sufficient to impart dimensional stability, in particular, low waφ, to the composition and a conductive filler present in an amount sufficient to impart conductive properties to the composition. Polyetherimide Resins The polyetherimide resins useful in the compositions of the present invention are known compounds whose preparation and properties are described in U.S. Patent Nos. 3,803,085 and 3,905,942, each of which is incoφorated herein by reference. Typically, the polyetherimide used for preparing the compositions of this invention comprise about 10 to about 1000 or more, and more preferably about 10 to about 500 structural units, of the formula (I): wherein T is -0-, carbonyl, sulfur, sulfoxide or a residue of a bisphenol group of the formula -0-Z-O- wherein the divalent bonds of the -0- or the -0-Z-O- group are in the 3,3', 3,4', 4,3', or the 4,4' positions; Z includes, but is not limited to, a divalent radical of formulae (II): (10 X includes, but is not limited to, divalent radicals of the formulae (III): -4- O O — -CyH2y— , — C— , — S— . , — O— and — S— O (III) wherein y is an integer from 1 to about 5, and q is 0 or 1 ; R includes, but is not limited to, a divalent organic radical: (a) aromatic hydrocarbon radicals having from 6 to about 20 carbon atoms and halogenated derivatives thereof, (b) alkyiene radicals having about 2 to about 20 carbon atoms, (c) cycioalkylene radicals having about 3 to about 20 carbon atoms, and (d) divalent radicals of the general formula (IV): where Q includes, but is not limited to, the formulae (V): O O — CyH2y — , — <ϋ — , — & — , — O— and — S — (V) * wherein y is an integer about 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 structural units of the formula (VI): O O II II c c — Nf' s / \ / V N-R — c c I! II (VI) ° ° wherein R is as previously defined for formula (I) and M includes, but is not limited to, formula (VII): The polyetherimide 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 (VIII): with an organic diamine of the formula (IX): (IX) H 2 N-R-NH 2 wherein T and R are defined as described above in formula (I). In general the reactions can be carried out employing well-known solvents, e.g., o- dichlorobenzene, m-cresol/toluene and the like to effect interaction between the anhydride of formula (VIII) and the diamine of formula (IX), at temperatures of about 100°C to about 250°C. Alternatively, the polyetherimide can be prepared by melt polymerization of aromatic bis(ether anhydrides) and diamines accomplished by heating a mixture of the ingredients to elevated temperatures with concurrent stirring. Generally melt polymerizations employ temperatures of about 200°C to about 400°C. Chain stoppers and branching agents may also be employed in the reaction. Examples of specific aromatic bis(ether anhydrides) and organic diamines are disclosed, for example, in -U.S. Patent Nos. 3,972,902 and 4,455,410, which are incorporated herein by reference. Illustrative examples of aromatic bis(etheranhydride)s of formula (VIII) include: 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; 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- dicarboxyphenoxy)benzophenone dianhydride; 4,4'-bis(2,3- dicarboxyphenoxy)diphenyl sulfone dianhydride; 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 and 4-(2,3-dicarboxyphenoxy)- 4'-(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride, as wefl as various mixtures thereof. A preferred class of aromatic bis (etheranhydride)s included by formula (VIII) above includes, but is not limited to, compounds wherein T is of the formula (X): (X) - o -D>- γ -C^ 0 - and the ether linkages, for example, are preferably in the 3,3', 3,4', 4,3', or 4,4' positions, and mixtures thereof, and where Y includes, but is not limited to the formulae (XI): O O — C H2y — . — C— , — £ — . , — O— and — S — (XI) When polyetherimide/polyimide copolymers are employed, a dianhydride, such as pyromellitic dianhydride, is used in combination with the bis (ether anhydride). The bis(ether anhydride)s can be prepared by the hydrolysis, followed by dehydration, of the reaction product of a nitro substituted phenyi dinrtrile with a metal salt of dihydric phenol compound in the presence of a dipolar, aprotic solvent. Suitable organic diamines of formula (IX) 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-diamiπonaphthalene; 3,3- dimethylbenzidine; 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-aminocyciohexyl)methane; 3- methylheptamethylenediamine; 4,4-dimethylheptamethylenediamine; 2,11- dodecanediamine; 2,2-dimethylpropylenediamine; 1,18- octamethylenediamine; 3-methoxyhexamethylenediamine; 2,5- dimethylhexamethylenediamine; 2,5-dimethylheptamethyienediamine; 3- methylheptamethylenediamine; 5-methylnonamethylenediamine; 1-4- cyclohexanediamine; 1,18-octadecanediamine; bis(3-aminopropyl)sulfιde; N- methyl-bis(3-aminopropyl)amine; hexamethylenediamine; heptamethylenediamine; nonamethylenediamine; decamethylenediamine and mixtures of such diamines. Generally, useful polyetherimides have a melt index of between 0.1 and 10 grams per minute ("g/min"), as measured by American Society for Testing Materials ("ASTM") D1238 at 295°C, using a 6.6 kilogram ("kg") weight. In a preferred embodiment, the polyetherimide resin of the present invention has a weight average molecular weight of from 10,000 to 150,000 grams per mole ("g/mole"). as measured by gel permeation chromatography, using a polystyrene standard. Such polyetherimide resins typically have an intrinsic viscosity [η] greater than about 0.2 deciliters per gram, preferably about 0.35 to about 0.7 deciliters per gram measured in m-cresol at 25 β C. In a preferred embodiment, the polyetherimide resin comprises structural units according to formula (I) wherein each R is independently paraphenylene or metaphenylene and T is a divalent radical of the formula (XII): Polyetherimide and polyetherimide-copolymers are suitable for the present invention, such as those disclosed in U.S. Patent 3,983,093, commonly assigned, which is hereby incoφorated herein in its entirety. Particularly preferred for compositions of the present invention are polyetherimide-pyromellitic dianhydride copolymer resins and polyetherimide resins available from General Electric. The polyetherimide resins and copolymers of this invention can be further blended with other high temperature thermoplastics. Especially preferred are other amoφhous high glass transition temperature polymers such as polycarbonates, polyarylates, polyester carbonates, polysulfones, polyether sulfones, and polyphenylene ethers. Plate-jike Filler The plate-like filler may be any plate-like filler selected to impart dimensional stability, and in particular low waφ characteristics, to the composition, such as mica or flaked glass. Preferable mica fillers are the naturally occurring mica fillers such as phlogophite mica of the formula (XIII): KAI 2 (AISi 3 O 10 )(OH) 2 (XIII) and muscovite mica of the formula (XIV): KMg 3 (AISi 3 O 10 )(OH) 2 (XIV). A preferred plate-like flaked glass filler is borosilicate E glass. The particle size of the plate-like filler may range from a maximum dimension of from 5 to about 1000 microns, with about 20 to about 300 microns most preferred. The thickness of the plate-like filler is about 0.5 to about 300 microns. The plate-like fillers of the present invention may be treated to enhance performance as dimensional stabilizers. Suitable surface treatment agents include functionalized siianes such as amino, mercaptOi or epoxy functionaiized alkoxy siianes. Gamma-aminopropyltriethoxysilane is particularly preferred as a surface treatment agent. The plate-like filler and conductive filler are employed in relative amounts sufficient to impart the desired combination of low waφ and low surface resistivity to the composition Preferably, the plate-like filler comprises about 1% to about 50% by weight based upon the total weight of the composition. More preferably tne Diate-like filler comprises about 5% to about 30% by weight based on the tctai weight of the composition. Most preferably, the plate-like filler comprises about 10% to about 20% by weight based on the total weight of the composition. Conductive Filler The conductive filler may comprise any electrically conductive material capable of imparting sufficient electrical conductivity to the polyetherimide composition and which is compatible with polyetherimide. Suitable conductive materials include, but are not limited to, carbon fibers, carbon fibrils, conductive carbon powder, metal fibers, metal coated carbon fibers, especially nickel coated carbon fibers, metal flake, metal powder, or mixtures thereof and others, with materials exhibiting surface resistivities below about 10 6 ohms/cm 2 preferred. Most preferably, the conductive filler is a fibrous conductive filler such as carbon fiber, preferably having a diameter of about 1 to about 20 microns. The conductive filler material can be surface treated, preferably with a polyetherimide coating, to enhance performance. In a preferred embodiment, the conductive filler comprises about 9% to about 45% by weight of the total weight of the composition. In a most preferred embodiment, the conductive filler material comprises about 9% to about 15% by weight of the total weight of the composition. Other additives Additionally, the thermoplastic resin composition of the present invention may optionally also contain various additives, such as antioxidants, such as, for example, organophosphites, for example, tris(nonyl- phenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4-di-t- butylphenyl)pentaerythritol diphosphite or distearyi pentaerythritol diphosphite, alkylated monophenols. polyphenols and alkylated reaction products of polyphenols with dienes. such as, for example, tetra- cis(methylene)-3,5-di-t-butyl-4-hydroxycιnnamate, butylated reaction products of para-cresol and dicyclopentadiene. alkylated hydroquinones, hydroxylated thiodiphenyl ethers, alkylidene-bisphenols, benzyl compounds, acylaminophenols, esters of beta-(3,5-di-tert-butyl-4-hydroxyphenol)-propionic acid with monohydric or polyhydric alcohols, esters of beta-(5-tert-butyl-4- hydroxy-3-methylphenyl)-propionic acid with monohydric or polyhydric alcohols, esters of beta-(5-tert-butyl-4-hydroxy-3-methylphenyl) propionic acid with mono-or polyhydric alcohols, esters of thioalkyl or thioaryl compounds, such as, for example, distearylthiopropionate, dilaurylthiopropionate, ditridecylthiodipropionate, and amides of beta-(3,5-di-tert-butyl-4- hydroxyphenol)-propionic acid. Other optional additives include mold release agents, UV absorbers, stabilizers such as light stabilizers, lubricants, plasticizers, pigments, dyes, colorants, blowing agents, and flame retardants, among others. The preferred lubricants (i.e., mold release agents) for these compositions are polyolefin materials such as polyethylene. As a mold release/processing aid, the polyolefin can be added at about 0.1% to about 5% by weight, preferably about 0.2% to about 1 % by weight based on the total weight of the composition. The total amount of all filler, including plate-like filler, conductive filler, and any other additives, present in the inventive composition is preferably about 50% and most preferably about 15% to about 30% by weight based on the total weight of the composition. The compositions of the present invention exhibit a surface resistance of less than about 10 6 ohms/cm 2 , preferably less than about 10 4 ohms/cm 2 , and most preferably less than about 10 3 ohms/cm 2 . While the compositions of the present invention have application in a wide variety of physical shapes and forms, including use as films, molding compounds, and the like, the surface resistivities achieved render the compositions particularly useful as electrostatic discharge materials for fabricating components such as computer chip trays. The compositions of the present invention possess good dimensional stability, i.e., exhibit low warp. While waφ will partially depend on the geometry of the part and material processing, parts produced with the compositions of the present invention will exhibit less waφ than parts produced with resin compositions comprising only conductive filler or resin compositions comprising a blend of conductive filler with a non-platelike filler. An edge-gated 4 inch by 1/16 inch disk, for example, would exhibit a waφ on molding of about 0 millimeters (mm) to about 8 mm. Included among the many methods of making the polyetherimide are those disclosed in U. S. Patent Nos. 3,847,867, 3,850,885, 3,852,242, 3,855,178, and 3,983,093. These patents are incorporated herein by reference for the purpose of teaching, by way of illustration, general and specific methods for preparing polyetherimide for use in the compositions of this invention. The preparation of the compositions of the present invention is normally achieved by blending the ingredients under conditions for the formation of an intimate blend. Such conditions often include solution blending or melt mixing in single or twin screw type extruders, mixing bowl, roll, kneader, or similar mixing devices that can apply a shear to the components. Twin screw extruders are often preferred due to their more intensive mixing capability over single screw extruders. However, severe compounding or mixing conditions should be avoided as such processing can break the plate-like filler and conductive filler down resulting in reduced performance. It is often advantageous to apply a vacuum to the blend through at least one vent port in the extruder to remove volatile impurities in the composition. Examples 1-9 were prepared as set forth in Table 1, in order to illustrate specific polyetherimide resin compositions comprising plate-like filler and conductive filler in accordance with the present invention. Comparative Examples A-H were prepared as set forth in Table 2. It should be understood that the examples and comparative examples are given for the puφose of illustration and do not limit the invention. In the examples and comparative examples, all parts and percentages are by weight. Computer chip trays and disk-shaped sample parts were prepared from the compositions of the present invention (Examples 1-9) and from comparative compositions (Examples A-H). Processing conditions were as set forth in the Tables. After forming the compositions into computer chip trays or sample disks, waφ on molding and waφ on annealing was determined Waφ on molding and waφ on annealing was measured using a "waφ test," which is performed by placing a sample on a flat surface and measuring the maximum height of the bottom surface both after molding and after annealing. Surface resistivity was determined using ASTM Test Method D157 using the 803B Surface Resistivity meter commercially available from ETS Coφoration. TABLE I 'Polyetherimide-coated carbon fiber available from Akzo; Diameter 7 micron; length 1/8pj. 2 Carbon Fiber coated with water-based coating available from Akzo; Diameter 7 micron; length 1/8RJ. 3 Mica 1 = phlogophite available from Suzorite Corporation as 150S. 'Mica 2 = phlogophite available from Suzorite Corporation as 150 NY. 5 Polyetherimide-pyromellitic dianhydride copolymer available from General Electric. "Polyetherimide polymer available from General Electric. 7 PE = polyethylene 8 "Molding condition for chip tray is 740-^F; 600 psi hold pressure, 30 s cycle time, mold temp 400-»F 8 9 Std. Molding condition for 1/16fb x 4fb disk is 750 * F; 500 psi hold pressure, 20 s cycle time, mold temp 350' The results in Tables 1 and 2 show that disk-shaped parts formed with the poiyetherimide-pyromellitic dianhydride copolymer compositions of the present invention comprising about 20% mica filler and about 10% carbon fiber filler had the minimum (undetectable) waφ on molding and the minimum warp on annealing at temperatures of 350°F, as illustrated in Examples 7, 8, and 9, with surface resistivities of less than 10 β ohms/cm 2 . In contrast, disk-shaped parts formed with compositions that were outside the scope of the present invention did not possess the advantageous combination of low warp and conductive (i.e., low surface resistivity) properties obtained with the compositions of the present invention. As shown in Comparative Example H, a disk-shape part was formed from a poiyetherimide-pyromellitic dianhydride copolymer composition comprising about 20% mica filler with about 8% carbon fiber filler. The part prepared with the composition of Comparative Example H exhibited adequate waφ properties but provided a surface resistivity of 10 12 ohms/cm 2 , which does not provide a conductivity suitable for many applications. The results further show that computer chip trays formed from the compositions of the present invention, Examples 1 and 2, provided a combination of low warp and conductive properties not achieved with computer chip trays formed from compositions outside the scope of the present invention, as shown in Comparative Examples A and B. The present inventors have shown that conductive filler and plate-like filler have significant effects on warp. Increasing the amount of conductive filler increases waφ while increasing the amount of plate-like filler material decreases warp. At the same time, however, a minimum amount of conductive filler material is necessary to impart the desired electrical conductivity to the compositions. The polyetherimide and polyetherimide- copolymer compositions of the present invention provide a balance of low waφ and low surface resistivity that render the compositions useful for applications requiring both dimensional stability and conductivity. Compositions of the present invention are particularly suitable for forming computer chip trays and printed circuit board carriers, which much be dimensionaliy stable (i.e., exhibit low waφ) and provide a surface resisitivy of less than about 10 6 ohms/cm 2 .

Claims: CLAIMS We claim: CLAIM 1. A polyetherimide composition, prepared by combining: a polyetherimide resin or polyetherimide-copolymer resin; and a filler comprising a plate-like filler present in an amount sufficient to impart low waφ properties to the composition; and a conductive filler present in an amount sufficient to impart a surface resistivity to the composition of less than or equal to about 10 6 ohms/cm 2 . CLAIM 2. The composition of claim 1 , wherein said surface resistivity is about 10 3 to about 10 β ohms/cm 2 . CLAIM 3. The composition of claim 1 , wherein said plate-like filler is mica, flaked glass, or a mixture thereof. CLAIM 4. The composition of claim 3, wherein said mica filler is phlogophite mica, muscovite mica, or a mixture thereof. CLAIM 5. The composition of claim 3, wherein said flaked-glass filler is borosilicate E glass. CLAIM 6. The composition of claim 1 , wherein said plate-like filler has a maximum dimension in the range of about 20 to about 300 microns. CLAIM 7. The composition of claim 1 , wherein said plate-like filler is present in an amount of about 5 to about 30% by weight based on the total weight of the composition; and said conductive filler is present in an amount of about 9% to about 40% by weight based on the total weight of the composition. CLAIM 8. The composition of claim 7, wherein said plate-like filler is present in an amount of about 10 to about 20% by weight based on the total weight of the composition; and said conductive filler is present in an amount of about 9 to about 15 % by weight based on the total weight of the composition. CLAIM 9. The composition of claim 1 , wherein said filler is present in an amount of about 50% by weight based on the total weight of the composition CLAIM 10. The composition of claim 9, wherein said filler is present in an amount of about 15% to about 30% by weight based on the total weight of the composition. CLAIM 11. The composition of claim 1 , wherein said conductive filler is carbon fibers, carbon fibrils, conductive carbon powder, metal- fibers, metal coated carbon fibers, metal flakes, metal powders, or mixtures thereof. CLAIM 12. The composition of claim 11, wherein said metal coated carbon fiber is nickel coated carbon fiber. CLAIM 13. The composition of claim 11 , wherein said conductive filler is carbon fiber. CLAIM 14. The composition of claim 1, wherein said conductive filler is coated with polyetherimide resin or polyetherimide copolymer resin. CLAIM 15. The composition of claim 1, wherein said conductive filler is a carbon fiber having a diameter in the range of about 1 to about 20 microns. CLAIM 16. A computer chip tray comprising the polyetherimide composition of claim 1. CLAIM 17. The computer chip tray of claim 16, wherein said plate-like filler is present in an amount of about 5 to about 30% by weight; and said conductive filler is present in an amount of about 9 to about 40% by weight. CLAIM 18. The computer chip tray of claim 17, wherein: said filler composition is present in an amount of about 50% by weight based on the total weight of the composition. 00/34381 -20- CLAIM 19. The computer chip tray of claim 18, wherein: said filler composition is present in an amount of about 15% to about 30% by weight based on the total weight of the composition. CLAIM 20. The composition of claim 1 , wherein said polyetherimide resin is of the formula where T is selected from the group consisting of oxygen, carbonyl, sulfur, sulfoxide, and bisphenol residue, and R is selected from the group consisting of aromatic hydrocarbon radicals having from 6 to 20 carbon atoms and halogenated derivatives thereof. CLAIM 21. The composition of claim 20, wherein said bisphenol residue is derived form bisphenol A and R is phenyl. CLAIM 22. The composition of claim 1, further comprising: a polyolefin. CLAIM 23. The composition of claim 22, wherein: said polyolefin is polyethylene. CLAIM 24. The composition of claim 23, wherein: said polyethylene is present in an amount of about 0.1% to about 5% by weight based on the total weight of the composition.

Inventors: GALLUCCI ROBERT RUSSELL, SUNDARARAJ UTTANDARAMAN, GALLUCCI, ROBERT, RUSSELL, SUNDARARAJ, UTTANDARAMAN
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1999
Main classification: C08K13
IPC codes: B65D1, C08K3, C08K7, C08L79, H01L21