Novel soluble polymidesiloxanes and methods for their preparation and use

Abstract: Fully imidized polyimidisiloxanes which are based on oxydiphthalic anhydride are soluble in diglyme which gives them particular utility in the micro-electronics industry. The polymers are prepared from oxydiphthalic anhydride, a difunctional siloxane monomer and an organic diamine that provides an assymetrical structure in the polyimidesiloxane polymer chain. The polyimide­ siloxane can be prepared with functional groups which render them directly curable. The polyimides can also be prepared with functional groups which when reacted with an unsaturated compound renders the polymers curable. The products of the invention can be used in the form of solutions in the micro-electronic industry. The polymers can also be used in wire and cable coating and to prepare films, fibers, and molded and extruded articles.

Description: Background of the Invention and Information Disclosure Statement A class of polymers known as polyimides has become known for its combination of good heat stability and high upper use temperatures, as measured by glass transition temperature. A particularly useful type of such polyimides is known as polyimidesiloxanes. Because of their combination of properties, polyimidesiloxanes have been used in electronic applications, particularly in micro-electronic components in the computer industry. Because the previously known polyimidesiloxanes are insoluble or difficultly soluble in solvents, when used in the micro-electronics industry, there is a great need for polyimidesiloxanes having improved solubility characteristics, as well as a better balance of heat resistance and upper use temperature. The chemistry for making polyimides has been well-known since about 1960. A structurally simple polyimide can be prepared by reacting a diamine with a dianhydride. The first step, or the polycondensation reaction, generates polyamide acids which are hydrolytically unstable even at room temperature. The second step, or the imidization reaction, produces the stable polyimides desired for various applications. Polyimidesiloxanes can be prepared by reactions employing siloxane diamines or siloxane dianhydrides with organic comonomers. Polyimidesiloxanes can also be prepared from siloxane diamines and siloxane dianhydrides without an organic comonomer. Only a few polyimides are soluble, even in high boiling and relatively toxic solvents, such as 1-methyl-2-pyrrolidinone (NMP), despite the fact that most of their polyamide acids are soluble. The usage of polyamide acids in coating applications has many drawbacks. First, a subsequent imidization reaction on substrates produces water. Therefore, it can only be used in very thin film coatings and where void-free property is not critical to performance. Second, the removal of high boiling, polar solvents, such as NMP, requires temperatures as high as 350°C for about 30 minutes even for films of a micron thickness. This drying process is not only energy intensive, but also unacceptable to some heat sensitive electronic devices or substrates. In addition, the polyamide acids solution has to be stored at refrigeration temperature (< 4°C) and it still has a very short shelf life (about 3 months). Finally, only the fully imidized polyimides are thermally stable for melt processing such as extrusion and injection molding. A soluble polyimidesiloxane can be fully imidized at temperatures of about 160 to 170°C in a solvent, whereas imidization for insoluble polyimides in the solid state may require temperatures 50°C above their glass transition temperatures which can be as high as 200 to 250°C. Shaping not fully imidized polyimides by the melt processing method produces voids in the products and often is not desirable. Therefore, one object of the present invention is to prepare fully imidized polyimides. Polyimides derived from reactions of 4,4'-oxydiphthalic anhydride (4,4'-ODPA) and organic diamines have been studied by Frank W. Harris and Lyn H. Lanier (in F. W. Harris & R. Seymour Edt., "Structure - Property Relationship in Polymers", Academic Press, 1977, pp. 182-198) and also by T. L. St. Clair et al, (Ibide. pp. 199-213). These polyimides, as well as other BTDA containing polyimides based on benzophenone tetracarboxylic dianhydride (BTDA), are very insoluble. For instance, out of 12 polyimides prepared in T. L. St. Clair's report, there are only two polyimides that are soluble in NMP and none are soluble in diglyme or methyl ethyl ketone (MEK). Diglyme is diethylene glycol dimethy ether, also known as 2-methoxyethyl ether. Polyimides prepared from oxydiphthalic anhydride and complex diamines are disclosed in U.S. Patents 3,705,809 and 3,705,870. U.S. Patent No. 4,048,142 discloses the use of 3,3'-oxydiphthalic anhydride in making polyimides. The first polyimidesiloxane was prepared by reacting pyromellitic dianhydride (PMDA) with 1,3-bis-(aminopropyl)-1,1,3,3-tetramethyl disiloxane in 1966 (see V. H. Kuckertz, Macromol. Chem. 98 , 1966, pp. 101-108). This polyimidesiloxane is a crystalline material and cannot be cast into flexible films from solvent. Polyimidesiloxanes derived from reactions of benzophenone tetracarboxylic dianhydride (BTDA) and α,w-diamino organo-polysiloxanes were disclosed by General Electric in 1967 in U.S. Patent No. 3,325,450. Polyimidesiloxanes containing an α,w-diamino organo-polysiloxane and a diether dianhydride (DEDA) have also been disclosed in U.S. Patent No. 3,847,867. All these BTDA and DEDA containing polyimides are amorphous materials. They have a glass transition temperature of no more than 100°C and, therefore, have very limited upper use temperatures, despite the excellent thermal stability of these polymers up to about 200°C. Polyimidesiloxanes containing both organic and siloxane monomers have been reported for PMDA containing copolymers (see Japan Kokai Tokkyo Koho 83/7473 and 83/13631); for BTDA containing copolymers (U.S. Patent Nos. 3,553,282 and 4,404,350) and for diether dianhydride containing copolymers (U.S. Patent No. 3,847,867). These PMDA containing polyimides are not soluble in any solvent. The BTDA containing polyimides are only soluble in high boiling or toxic solvents such as N-methyl pyrrolidone (NMP), phenol or cresol, and the like. The diether dianhydride containing polyimidesiloxane, in addition, are also soluble in chlorinated solvents such as dichlorobenzene and dichloromethane. Since these phenol and chlorinated compounds are both corrosive and highly toxic, the polyimides have limited application in coating applications, especially in heat sensitive electronic devices. This is also due to the fact that a NMP soluble polyimidesiloxane normally has to be heated to 350°C for at least half an hour to remove all the residual solvent in a film having a micron-thickness film. Some diether dianhydride containing polyimides are soluble in diglyme (T b = 162°C) and may be sparingly soluble in tetrahydrofuran (T b = 60°C); but none of these polyimides are soluble in solvents such as methyl ethyl ketone (T b = 80°C) which is one of the most used solvents in the coating industries. However, all these polyimides have relative low glass transition temperatures (below about 125°C to 150°C) and limited thermal stability (350°C/0.5 hour with retention of film flexibility and integrity). Thermally stable polyimides which are soluble in non-toxic and low boiling solvents such as diglyme or methyl ethyl ketone, are not readily available. U.S. Patent No. 4,395,527 to Berger discloses a large number of various components as useful in manufacturing polyimides. While the use of oxydiphthalic anhydride is disclosed in the patent there is no recognition that this compound would provide particularly useful properties. Moreover, the tolylene diamine used in the present invention is not even disclosed in the cited patent. U.S. Patent No. 4,586,997 teaches the utility of making polyimides based on diether dianhydrides, diamines and α,w-diaminosiloxanes. Cross-linked polymers are also disclosed. There is no recognition that the use of oxydiphthalic anhydride, which is a monoether dianhydride, as the sole essential organic dianhydride in the polymer produces a polymer with exceptional properties. Another object of the invention is to provide fully imidized polyimides which are soluble not only in high boiling solvents, such as NMP, but also in low boiling, low toxic, less polar solvents such as diglyme, tetrahydrofuran (THF) or methyl ethyl ketone (MEK). A further object of the invention is to provide polyimides that have a good balance of heat resistance and high upper use temperatures, as measured by glass transition temperatures. Another object of this invention is to produce curable and cross-linked polyimides. Summary of the Invention Fully imidized polyimides which are based on oxydiphthalic anhydride are soluble in diglyme which gives them particular utility in the micro-electronics industry. The polymers are prepared from oxydiphthalic anhydride, a difunctional siloxane monomer which is an α,ω-siloxane diamine and an organic diamine as defined in claim 1 that provides an assymetrical structure in the polyimidesiloxane polymer chain. The polyimidesiloxane can be prepared with functional groups which render them directly curable. The polyimides can also be prepared with functional groups which when reacted with an unsaturated compound renders the polymers curable. The products of the invention can be used in the form of solutions in the micro-electronic industry. The polymers can also be used in wire and cable coating and to prepare films, fibers, and molded and extruded articles. Detailed Description of the Invention The Organic Anhydrides The present invention is based on the discovery that the use of oxydiphthalic anhydrides (ODPA), particularly 4,4'-oxydiphthalic anhydride (4,4'-ODPA), provides polyiminesiloxanes which have a unique combination of properties. Other oxydiphthalic anhydrides that can be used in the practice of the invention are 3,3'-oxydiphthalic anhydride and 3,4'-oxydiphthalic anhydride. Other organic dianhydrides can be employed in small proportions, up to 5 to 20 weight percent of the oxydiphthalic anhydride. The other organic dianhydrides include compounds having the following general formula: wherein Ar is wherein Y is -O-, -S-, C n H 2n , C(CF 3 ) 2 , and m' = 0 or 1, wherein M is phenylene or wherein m' and Y have the same values as before. Specific examples are diether dianhydrides which have the formulas: Other examples of such other dianhydrides are disclosed in U.S. Patents Nos. 4,395,527 and 4,586,997. However, even though the incorporation of these dianhydrides may alter only slightly the solubility of the resulting polyimides in NMP or diglyme, these modified polyimides may become insoluble in solvents, such as MEK or THF. This limits their applications where a very low boiling, non-toxic solvent such as MEK is required. In addition, the incorporation of the diether dianhydrides (DEDA) also reduces the glass transition temperature and thermal stability of ODPA-containing polyimides and limit their upper use temperatures. Thus only up to about 5 weight percent of PMDA, and only up to about 20 weight percent of BTDA or the diether dianhydrides (DEDA) can be employed in the composition of the invention. The Organic Diamines It has been found that diamines that provide assymetrical structure in the polyimidesiloxane chains are especially useful in combination with the oxydiphthalic anhydrides in making polyimides with the desirable and superior properties of this invention. The diamines that provide assymetrical structure in the polyimidesiloxane chain either have the following formula: where x, y and z are independently selected from hydrogen, halogen, alkyl or halogenated alkyl of 1 to 12 carbon atoms or aryl or halogenated aryl of 6 to 12 carbon atoms. Examples are: 2,4-tolyldiamine 2,5-tolyldiamine 2,6-tolyldiamine m-xylyldiamine 2,4-diamine-5-chloro toluene 2,4-diamine-6-chloro toluene trifluoromethyl-2,4-diaminobenzene 2,4,6-trimethyl 1,3-diaminobenzene The other diamine compounds that are assymetrical in the polymer chain are compounds with the formula: wherein x' is -CH 2 -, Examples are: m,m-methylene dianiline m,m-sulfone dianiline o,m-sulfone dianiline. Another suitable diamine that is assymetrical in the polyimidesiloxane is diaminoanthraquinone. An especially preferred diamine is a mixture of 80 weight percent 2,4-tolyldiamine and 20 weight percent 2,6-tolyldiamine. Small amounts up to about 25 weight percent of diamines that are not assymetrical in the polymer chain can be employed in the polyimidesiloxane compositions. Such other diamines are disclosed in U.S. Patents Nos. 4,395,527 and 4,586,997. Such auxiliary diamines have the formula wherein x 2 is preferably for retaining solubility in diglyme, THF or MEK. In addition, the x 2 can also be -O-, -S- and -CH 2 - for achieving only solubility in NMP. The Siloxane Monomers Siloxane diamino compounds that can be used for the present invention have the following formula: wherein R 1 , R 2 , R 3 , and R 4 are independently selected from a substituted or unsubstituted aliphatic mono-radical of 1 to 12 carbon atoms or substituted or unsubstituted aromatic mono-radical of 6 to 10 carbon atoms. Suitable radicals include -CH 3 , -CF 3 , -(CH 2 ) n CF 3 , -C 6 H 5 , -CF 2 -CHF-CF 3 and R' is a di-radical of the foregoing type. Suitable di-radicals include (CH 2 ) n , (CF 2 ) n , -(CH 2 ) n CF 2 - and -C 6 H 4 -, wherein n = 1 to 10. R' is independently selected from substituted or unsubstituted aliphatic difunctional radicals of 1 to 12 carbon atoms or substituted or unsubstituted aromatic difunctional radicals of 6 to 10 carbon atoms, m is an integer of from 5 to 200. The employment of an α,w-diaminosiloxane is important for achieving the desired solubility in diglyme, THF or MEK in the present invention when the essential dianhydride employed in the invention is ODPA. The siloxane diamine also provides the flexibility or resilience of the polyimidedisiloxanes at low temperatures, especially when the m is an integer of more than 5, or preferably more than 7. When the m is more than 50, the incorporation of diaminosiloxane into the polyimidesiloxane becomes difficult even though it is not impossible; and a dual solvent system (one polar and one non-polar solvent) for copolymerization may have to be employed. In general, the employment of the α,w-diaminosiloxane and α,w-dianhydride siloxane are interchangeable in the present invention. However, for making polyimides of high glass transition temperature, the mole percent of the ODPA in the total dianhydride should be maximized; and therefore, it is more desirable to employ the combination of an ODPA with an organic diamine and an α,w-diaminosiloxane. Siloxane dianhydrides which can be incorporated in addition to the siloxane diamines for the practice of the present invention can have the formula: wherein R 1 , R 2 , R 3 and R 4 are independently selected from a substituted or unsubstituted aliphatic mono-radical of 1 to 12 carbon atoms substituted or unsubstituted aromatic mono-radical of 6 to 10 carbon atoms and m is 5 to 50. Suitable radicals include -CH 3 , -CF 3 , -(CH 2 ) n CF 3 , -CF 2 -CHF-CF 3 , and -C 6 H 5 . R is a tri-radical of the foregoing type. Suitable tri-radicals include -CH , When a dianhydride other than the ODPA is employed, their solubility in various solvents, glass transition temperatures and thermal stability changes depending on the chemical nature of these co-monomers. For instance, when a siloxane dianhydride is incorporated in the presence of ODPA, the solubility of the polymer increases, while the glass transition temperature and thermal stability will be lowered. Therefore, depending on the requirements for applications, the incorporation of siloxane dianhydride may become unfavorable. On the other hand, when an organic dianhydride such as PMDA is added in small proportions of less than 5 mole percent, the resulting ODPA-containing polyimides still has the desirable solubility in, for instance, NMP. The incorporation of PMDA can increase the glass transition temperature and thermal stability of the resulting ODPA-containing polyimides, and, therefore, can provide more favorable products for extrusion or injection molding applications. However, one may also find that even with a small amount of PMDA or BTDA in the ODPA-containing polyimides, the resulting copolymers may become insoluble in solvents, such as diglyme, THF or MEK, and their applications as coating materials will be limited, for instance, in heat sensitive electronic devices or substrates. The polyimides of the invention which utilize fluorine substituted substituents have improved thermal stability and chemical resistance. They also have a lower dielectric constant. The Process For Soluble Polyimidesiloxanes Although the chemistry for reactions of organic diamines with organic dianhydrides has become well-known, the preparation of polyimides in the presence of the siloxane comonomers may sometimes require special techniques. For instance, when the repeating unit m, of the siloxane monomer is larger (i.e., > 20 to 40), it may be desirable to use a dual solvent system: i.e., a solvent system consisting not only of a polar solvent, but also a less polar solvent. (See, for instance, McGrath et al, Polymer Preprints, 27 (2), 1986, pp. 403). In the practice of making soluble polyimides, if a polyimide is soluble in a given solvent, in which the polyamide acid is not soluble, one can prepare the polyimide directly in a one step polymerization process, that is, by a simultaneous imidization and polycondensation process, referred to as the one-step process. This procedure can be advantageous, especially when a desirable polymer solution for coating applications has to be made out of a given solvent in which the polyamide acids are not soluble. The problem with the simultaneous imidization and polycondensation is that the depolymerization of the polyamide acid in the presence of the water which is produced during the imidization step, can be very severe. Theoretically, the depolymerization can become an irreversible process, since it produces a dicarboxylic acid and an amino compound. The carboxylic acid reacts with amino compounds at much higher temperatures as compared to the almost instantaneous reaction of the dianhydrides with the amino compounds at room temperature. The depolymerization of polyamide acids can become very severe at high temperatures. This one-step process often produces polyimides with much lower molecular weight as compared to those produced in a good solvent, in which the polyamide acid and the imidized polymers are both soluble, and one employs a two-step process. The two-step process employs a low temperature polycondensation step which generates very high molecular weight polyamide acid and then a very fast heating step to imidize and remove water generated from imidization. The two-step process produces higher molecular weight materials which have higher thermal stability and mechanical strength, especially higher elongation at break. The polycondensation temperature for the two-step process should be below 60°C, preferably below room temperature. The imidization can be carried out at temperatures from 90°C to 180°C, or the refluxing temperature of the solvents. When the boiling temperature of the desirable solvent for imidization is below 160°C, the use of dehydrating agents and/or a base catalyst is desirable. A suitable dehydrating agent is acetic anhydride. The catalyst is a tertiary amine, such as pyridine. When the acetic anhydride is employed, lower imidization temperatures can be employed to complete the imidization. In addition, an azeotropic agent with water can also be added to the reactor. The use of an azeotropic agent such as toluene can facilitate the removal of water presented in the reactor and minimize the depolymerization of the polyamide acids. When an azeotropic agent is employed, a continuous recovery of fresh azeotropic agent can be achieved by using also a Dean Stark trap under the condenser. The degree of polycondensation is important for obtaining good thermal and mechanical properties in making polyimides. The reaction time for making high molecular weight polyimides is normally several times longer than that required for making polyimides due to the fact that the reactivity of the α,w-diamino or dianhydride siloxanes is normally lower than organic monomers. In general, the high molecular weight siloxane monomers react much slower than the organic monomers in a polar solvent. Accordingly, one can also expect that the microstructure of the polyimidesiloxane depends not only on the molar ratio of the organic to siloxane monomers (or the composition of the monomers), but also on the additional sequence of these monomers during polycondensation. For instance, when a high molecular weight α,w-diamino siloxane is employed, one sometimes finds that it is advantageous to first react the organic dianhydride without the presence of the organic diamine. This procedure not only can overcome the need of using a dual solvent system, but also can result in a much more uniform and controllable polyimide block size and distribution. Compared to a polyimidesiloxane with identical chemical make-up, but prepared with a different addition sequence (i.e., add all monomer together into a solvent at once) the polyimidesiloxane with more uniform and controlled imide size and distribution have a more soluble characteristic toward siloxane-like solvent or non-polar solvent. On the other hand, polyimides have the identical number average molecular weight of imide-block but having a broad molecular weight distribution will be less soluble in the diglyme or THF. Depending on the property requirements for various applications, one can therefore design polyimides by their composition, but also control their microstructures through monomer addition sequence for one's advantage. The solvents that can be used for the polymerization of the present invention are the phenol solvents; N,N-dialkylated carboxylamide solvents and monoalkylated or dialkylated ether type solvents. The examples of phenol solvents are phenol, o-cresol, m-cresol, o-chlorophenol, m-chlorophenol, p-fluorophenol, 2,4,6-tribromophenol; examples of N,N-dialkylated carboxylamide solvents are N,N-dimethylformamide, N,N-dimethylacetamide, NMP; ether type solvents are tetrahydrofuran (THF), diglyme or triglyme . Other solvents such as methyl ethyl ketone sulfolane, dimethylsulfoxide and chlorinated benzenes such as p-dichloro benzene which are commonly mentioned in various polyimide patents can also be used. Polyimidesiloxane can also be prepared in a melt polymerization process; especially when the glass transition temperature of the imide block is lower than say about 200°C; or a large proportion (>25%) of the siloxane comonomers is employed. In practice, the melt polycondensation can be done in an extruder in which imidization can be achieved using a vented zone situated close to the outlet nozzle. To achieve high molecular weight polyimides, the total moles of dianhydride component(s) should equal the total moles of diamine component(s). To reduce the molecular weight an excess of dianhydride, diamine components or small amounts of monofunctional compounds can be employed. When the siloxane monomer is a diamine, for every 1 mole of siloxane diamine employed, assume that n moles of organic diamine is employed. Then n + 1 moles of organic dianhydride is employed. When the siloxane monomer is a dianhydride, for every 1 mole of siloxane dianhydride employed, assume that n moles of organic dianhydride is employed. Then n + 1 moles of organic diamine must be employed. In the foregoing cases, n has a value of greater than 0.01 but no more than 40, preferably 20. When 0.01≤n≤0.1, the polyimidesiloxane exhibit elastomeric or rubber properties and are useful for potting, encapsulation, and sealing applications. Especially, a cross-linking elastomeric polyimidesiloxane will have great value in the above-mentioned applications. When 0.1≤n≤10, polyimides with thermoplastic elastomeric properties are obtained. These materials are useful for wire, cable, injection molding and protective coating applications. When 10≤n≤40, very high strength and rigid thermoplastics are produced which are useful for molding and coating applications. The Curable Polyimidesiloxanes The soluble polyimides described above have many valuable properties and uses. However, limitations are found in their applications, especially in areas where higher chemical or creep resistance are desirable or even critical. For instance, most of the polyimides show limited hydraulic fluid or jet fuel resistance when their siloxane content is over 30 to 40%. Even though this weakness can be largely reduced by incorporating fluorinated compound into their backbone structure, in particular, into their siloxane blocks, it is still more desirable to convert these fluorinated polyimides into thermosets in order to achieve higher solvent and creep resistance. In general, when a cross-linkable polyimidesiloxane carries an acrylic functionally, it can be cured by either thermal or photo-method. A photosensitive or photocurable polyimidesiloxane is especially valuable for patterning applications in microchips or integrated circuit industries. Furthermore, these novel curable polyimides, as well as the soluble polyimidesiloxanes, can also find applications in passivation layer, alpha particle barrier, electron beam patterning, ion implant mask or interlayer dielectric in electronics and micro-electronic industries. The polyimidesiloxanes of the invention can be made curable by the inclusion of reactants that have functionalities that are capable of being cross-linked, or that have intermediate functionalities that can be suitably modified with cross-linkable moieties after formation of the polymer. The required functionalities can be incorporated into the polymer of the invention by use of suitable diamines and/or siloxane compounds. The diamine compounds have the characteristic described for the soluble polymers of a diamine that provide assymetrical structure in the polyimidesiloxane chains. The diamines further have the following general formula: wherein Ar is aromatic, R" is a hydroxyl, hydrothiol or carboxylic radical, preferably a hydroxyl or carboxylic radical. The typical examples of these compounds are, for instance, 3,5-diaminobenzoic acid and 3,5-di-aminophenol. The functionalized siloxane diamines or dianhydrides have the following general structure: wherein D is either an amino or anhydride group and the R 1 is a diradical R' or a triradical R, such as described hereinbefore. Radicals R 1 , R 2 , R 3 and R 4 are described hereinbefore, except that one or more of R 1 , R 2 , R 3 and R 4 can be a halogen, hydride (H), vinyl or a hydroxyl group, when D is an anhydride group; or vinyl or hydroxyl when D is an amino group. Examples of the functionalized siloxane α,w-diamino compounds can be the following: or wherein n is an inteaer from 2 to 6, preferably 3 and 4; and R"' is a vinyl or hydroxyl group, and x + y = 1 to 100, preferably 4-40 and y is an integer of 1 to 15, preferably 1 to 5. The examples of the functionalized dianhydride are: where R 1 is and R"" is selected from hydride (H), hydroxyl, halogen and vinyl groups, preferably the H and vinyl groups. The x and y have the same meanings as above. The Process For Making Curable Polyimidesiloxanes The procedures for making soluble polyimidesiloxanes are generally followed. The comonomers are generally copolymerized in an appropriate solvent such as NMP or diglyme. The fully imidized, polyimidesiloxane which carries at least one kind of the functionalities described above, can then be further reacted or grafted with an acetylinic, ethylenic or acrylic-bearing compound to provide the final products desired for this invention. The grafting reaction is preferably conducted in a non-reactive solvent, preferably in diglyme, THF or MEK. Since there are many different functional groups that can be selected for the functionalized polyimidesiloxane, the grafting reaction desired for this invention has to be varied accordingly. For instance, when a carboxylic or hydroxyl-containing polyimidesiloxane is first prepared, the grafting of an acrylic group can be achieved by using either an epoxy-bearing acrylate such as the or an isocyanate-bearing acrylate such as When the functional group of the polyimidesiloxane is located in the siloxane blocks, the grafting reaction can be achieved using either an hydrosilylation reaction or a condensation reaction. For instance, when a group is present in a polyimidesiloxane, the grafting can be achieved via hydrosilylation: i.e., reaction of a vinyl group with a Si-H group in the presence of a catalyst, such as a Pt catalyst. Therefore grafting of a compound results in an acrylate-bearing polyimidesiloxane. When a -OH or epoxy group is present in the polyimidesiloxane, on the other hand, the grafting can be achieved via a condensation reaction. For instance, the reactions of an isocyanate-bearing acrylate or an acrylic acid or methylacrylic acid with the hydroxyl or epoxy group on the polyimidesiloxane can result in an acrylic- bearing polyimidesiloxane desired for the present invention. When an acetylenic-bearing compound also bears a carboxylic, an epoxy or isocyanato functionality, it is clear that the compounds can be grafted onto a polyimidesiloxane which carries an -OH or, a carboxylic group, respectively. When an ethylenic group is present in the siloxane block of the polyimidesiloxane, it can be used as such, and further be cured thermally via free radical cross-linking reactions or can be further changed into polyimides which carry either an acrylic or an acetylinic group. The grafting reaction of this kind is difficult to achieve, however, due to the lack of appropriate chemicals. To prepare the functionalized polyimidesiloxanes with a functional group presented in the imide block, it is preferred to start with an OH or -COOH-bearing diamino compound. On the other hand, this kind of siloxane monomer is usually not readily available. The incorporation of epoxy, silicone hydride or silicone hydroxyl group can be achieved via equillibration of the α,w-diamino or α,w- dianhydride siloxane with cyclic silicone epoxy, silicone hydride or silicone hydroxy compounds. In any event, it is preferred to graft the acrylic or ethylenic or acetylenic group rather than using an acrylic, ethylenic or acetylenic diamino or dianhydride compound for making the desired polyimidesiloxane. This is to avoid thermally cross-linking reactions of these functionalities during imidization of the polyimidesiloxane at high temperatures (about 160 to 170°C/2 hrs in solvent). A grafting reaction of a fully imidized polyimidesiloxane with the above described functionalities can be, in general, carried out at much lower temperatures. For instance, the hydrosilylation can be carried out at temperatures as low as 25°C in the presence of a platinum catalyst. The condensation between the -OH or carboxylic group with the epoxy group can be achieved at temperatures of no more than 120°C, within hours with the presence of a tertiary amine as a catalyst, while the reaction of an OH or carboxylic group with an isocyanate group needs even lower temperatures (RT to 80°C). To avoid the need for isolation of the reaction product from solvent, it is desirable to conduct the grafting reaction in the solvent which is acceptable for coating operations. The desirable solvents of these kinds are solvents with low flammability and/or toxicity, such as diglyme or MEK. The latter has been widely employed in coating industries due to its low boiling temperature. In this specification and claims halogen shall refer to fluorine, chlorine, bromine and iodine, but preferably to fluorine and chlorine. Aromatic generally refers to hydrocarbon aromatic. In the following Examples and throughout the specification and claims, parts are by weight and temperatures are in degrees Celsius, unless indicated otherwise. In the following Examples, the following test procedures were used: Solubility Tests Into a 5 ml small vial, 0.2-0.3 mg of polymer specimens were added with 2-3 ml of solvent. The observations for solubility was conducted normally after ≥ 16 hours, at temperatures from 25°C to the boiling temperature of the solvent. Glass Transition Temperatures The glass transition temperatures were measured by both differential scanning Calorimeter (DSC) and also by dynamic mechanical analysis (DMA) methods. Examples Example 1 (Comparative) Into a 125 ml Erlenmeyer flask was loaded 1.55 g of 4,4'- oxydiphthalic anhydride (4,4'-ODPA) and 10 ml of anhydrous N-methyl pyrrolidone (NMP). The ODPA was dissolved with rigorous mixing using a magnet stirrer. Then 0.61 g of 2,4-tolyldiamine (2,4-TDA) was added. The reaction was continued at room temperature for 2 hours. The solution was cast in a Teflon mold at temperatures about 160-165°C for 4 hours, then at 250°C for 30 minutes. A flexible film was obtained. The polyimide is designated as the [(OT)]. Example 2 (Comparative) Example 1 was repeated by reacting 1.55 g of 4,4'-ODPA with 0.54 g of p-diaminobenzene. The product was a powder-like material which is designated as [(OA p )]. Example 3 (Comparative) Example 1 was repeated by reacting 1.55 g of 4,4'-ODPA with 1.00 g of 4,4'-oxydianiline. The product was a flexible film with its structure being designated as [(OO p )]. Examples 4 to 6 and 8 to 21 Example 1 was repeated except for reactants, amounts of reactants and reaction times. The nature of the polymer product was as indicated in Table 1. The products were tested for solubility in various solvents and the results are also shown in Table 1. The glass transition temperatures for some of the products were tested and the results are shown in Table 1. In the foregoing examples, G m has the formula: where m indicates the number of repeating units, as shown in Table 1, for example, G 1 , G 7.5 , G 9 , G 11 and G 12 . Example 7 Into a 125 ml Erlenmeyer flask was loaded 4.93 g of 4,4'-ODPA with 30 ml of anhydrous NMP. After the 4,4'-ODPA was dissolved, 3.82 g of G 9 was added. The solution was stirred with a magnetic stirrer for another hour at room temperature. Then 1.39 g of TDA was added and the reaction was continued overnight (≥16 hours). The solution was cast into a 12.7cm x 12.7cm x 0.08cm (5" X 5" X 1/32") Teflon plate a temperatures about 160-165°C for 4.5 hours, then at 250°C for 30 minutes. The product was a flexible film. The designated structure is (OT) 2.5 G 9 . The product properties are shown in Table 1. The solubility and some glass transition temperatures were measured for the products of Examples 1 to 21. The results are given in Table 1. As seen from the results of Examples 1 to 21, the solubility of the polyimidesiloxanes of the invention in low boiling, non-polar solvents, such as THF or diglyme is a function of the proportions of siloxane and block size of the siloxane. The results of Examples 1 to 21, would form a phase diagram to show the effect of structural differences in the siloxane monomer. Thus, polyimidesiloxane consisting of 25% of siloxane with one repeating unit is soluble in both THF and diglyme. A polyimidesiloxane consisting of a similar 25% siloxane, but with 3 repeating units is only soluble in THF but not soluble in diglyme. A polyimidesiloxane consisting of a similar 25% siloxane but with 8 repeating units will neither solubilize in THF nor in diglyme. Therefore the solubility of a given polyimidesiloxane is dependent on both the proportion of the siloxane component in the polyimidesiloxane and also the siloxane block size. Comparative Examples Example 22 Example 1 was repeated by reacting 4.02 g of 1,4-(3,4-dicarboxyphenoxy)benzene dianhydride with 1.22 g of TDA. The product is designated as (HT). Example 23 Example 6 was repeated by reacting 4.02 g of 1,4-(3,4-dicarboxyphenoxy)benzene dianhydride with 0.81 g of TDA and 2.80 g of G 9 . The product is flexible films with a designated structure as (HT) 2 G 9 . Example 24 Example 1 was repeated by reacting 3.22 g BTDA with 1.22 g TDA. The product is flexible film designated as (BT). Example 25 Example 10 was repeated by reacting 4.83 g of BTDA, 1.22 g TDA and 4.20 g of G 9 . The product is flexible film designated as (BT) 2 G 9 . The solubility data for Comparative Examples 1 and 22 to 25 were determined and compared with the solubility obtained in accord with the invention in Example 8. These data are also compared with data obtained for the polymers disclosed in Examples 1b and 3b in U.S. Patent No. 4,586,997. The solubility data are shown in Table 2. The data in Table 2 show the lack of predictability that a given dianhydride will give a glyme soluble polymer. Thus, even though all (BT), (HT) and (UT) are soluble in NMP, only (UT) 2 G 9 is soluble in diglyme. Considering the fact that (OT) is not soluble in NMP, the discovery that the polyimidesiloxane (OT) 2 G 9 is soluble, was totally unexpected. In Table 3, the thermal properties for polyimides shown in Table 2 are compared. Comparative Solubility of Various Polyimides and Polyimide Siloxanes Solubility [10g/254mm(100 mil)] Example No. Designated Composition NMP Diglyme THF MEK 24 (BT) n + - - - 1 (OT) n - - - - 22 (HT) n + - - - (a) (UT) n + - - - 25 (BT) 2 G 9 + - - - 8 (OT) 2 G 9 + + +* ± 23 (HT) 2 G 9 + - ± - (b) (UT) 2 G 9 + + - - Comparative Thermal Properties of Polyimidesiloxanes Oxygen Index Glass Transition Temperature, °C Example No. Designated Composition 25.4mm (10 mil)Film 0.08cm (1/32") 0.16cm (1/16") Tg 1 Tg 2 25 (BT) 2 G 9 40-41 - - -80 205 8 (OT) 2 G 9 40-41 42 44 -80 196 23 (HT) 2 G 9 36-37 - - -80 170 (b) (UT) 2 G 9 30-31 - - -80 145 The thermal stability of the polymer of the invention disclosed in Example 7 was compared with the thermal stability of the polymer composition identified in U.S. Patent No. 4,586,997, Example 3b. The data are shown in Table 4. Example No. 8 Polymer Structure (OT) 2.5 G 9 [(UT) 2 G 9 ] Tensile Strength (psi) 5200 4500 % Elongation at Break 15 10 Tensile Strength (psi) After 350°C/0.5 hour 5600 5200 350°C/1 hour 2900 450 % Elongation at Break After 350°C/0.5 hour 12 4 350°C/1 hour 10 1 Tg (°C) 205 145 Curable Polyimidesiloxanes Example 26 Into a 150 ml flask was loaded 3.1 grams of 4,4'-ODPA, 0.75 gram of 3,5-diamino benzoic acid, 4.20 grams of G 9 and 20 ml of NMP. The reaction was carried out at room temperature for about 6 hours. Then the solution was cast into two Teflon cavities (12.7 x 12.7 x 0.08cm) (5 X 5 X 1/32 inches), and dried at temperatures of about 160°C for 4 hours. The imidized polyimidesiloxane was designated as [(OA 1 ) 1 G 9 ]. The product contained 40.5 weight percent of G 9 siloxane. The product was tested and found soluble in NMP, diglyme and THF but not in MEK. Example 27 The above example was repeated to provide 3.40 grams of [(OA 1 ) 1 G 9 ], which was dissolved in 20 ml of diglyme. Then into the solution, 0.25 gram of acrylic acid epoxy propyl ester was loaded. The solution was heated to about 90°C in the presence of about 0.005 gram of hydroquinone as free radical inhibitor and 0.02 gram of diazo-[2,2,z]-bicyclic octane as catalyst. The reaction was conducted under a blanket of nitrogen atmosphere for about one hour. Then into the solution was added 2 drops of t-butyl perbenzoate, and the solution then was cast into a Teflon cavity at temperatures of about 120 to 140°C for two hours. The cured polyimidesiloxane is designated as [(OA") 1 G 9 ]. The cured product was insoluble in NMP, diglyme, THF and MEK. The solubility of all the products of Examples 26 and 27 were tested as follows: About 0.4 mg of the film for each material was placed into a 5 ml vial and then 2-3 ml of NMP, diglyme, THF or MEK was loaded. The vials were left at room temperatures for at least 24 hours with occasional stirring and shaking to promote the dissolution of the materials. The polyimides of the invention are useful in a variety of applications in the micro-electronic industry. Such applications include use in the form of coatings as dielectrics and/or for passivations for semiconductors and thin film hybrids. Coatings of the polyimides can be used in the fabrication of semiconductor devices in the following areas: a) as a protective overcoat, b) as an interlayer dielectric for multi-level devices, c) as an alpha particle barrier, and d) as a non-implant mask. These uses are described in detail by Lee and Craig in Polymer Materials for Electronic Applications, ACS Symposium, Ser. 184, page 108. Other uses for the polyimides of the invention include wire and cable coatings, in fibers and films, and molded and extruded articles.

Claims: A fully imidized polyimidesiloxane soluble in diglyme for use in the microelectronics industry, which comprises the reaction product of an organic dianhydride, an organic diamine and a difunctional siloxane monomer, wherein (a) said organic dianhydride is an oxydiphthalic anhydride containin up to 20 weight percent of other organic dianhydrides, b) said organic diamine is a diamine providing an asymmetrical structure in the polyimidesiloxane chain selected from (b1) a diamine having the following formula where x, y and z are independently selected from hydrogen, halogen, alkyl or halogenated alkyl of 1 to 12 carbon atoms or aryl or halogenated aryl of 6 to 12 carbon atoms, (b2) a diamine having the following formula wherein x 1 is -CH 2 -, (b3) diaminoanthraquinone and (b4) a diamine having the following Formula : wherein Ar is aromatic and R" is a hydroxyl, hydrothiol or carboxylic acid radical, and may contain up to 25 weight percent of an organic diamine having the following formula that is not asymmetrical in the polymer chain wherein x 2 is -CH 2 -, and (c) said difunctional siloxane monomer is an α,w-siloxane diamine. The polyimidesiloxane of Claim 1 wherein the oxydiphthalic anhydride is 4,4'-oxydiphthalic anhydride, 3,3'-oxydiphthalic anhydride or 3,4'-oxydiphthalic anhydride. The polyimidesiloxane of Claim 1 comprising at least one radical selected from hydride (H), hydroxyl, halogen, carboxyl, hydrothiol, and vinyl, wherein said radical is located in the siloxane blocks and/or in the imide blocks. The polyimidesiloxane of Claim 3 comprising a carboxyl radical. The polyimidesiloxane of Claim 1 comprising at least one radical selected from an acrylic radical, an ethylenic radical and an acetylenic radical, wherein said radical is located in the siloxane blocks and/or in the imide blocks. The polyimidesiloxane of Claim 5 comprising an acrylic radical. A polyimidesiloxane of Claim 1 comprising the reaction product of 4,4'-oxydiphthalic anhydride, the difunctional siloxane monomer, and an organic diamine selected from 2,4-tolyldiamine, 2,5-tolyldiamize, 2,6-tolyldiamine and a mixture of 2,4-tolyldiamine and 2,6-tolyldiamine. A polyimidesiloxane of Claim 1 comprising the reaction product of 4,4'-oxydiphthalic anhydride, a difunctional siloxane monomer and an organic diamine selected from m-xylyldiamine, 2,4-diamino-5-chloro toluene, 2,4-diamino-6-chloro toluene, 2,4,6-trimethyl-1,3-diaminobenzene, m,m-methylene dianiline, m,m-sulfone dianiline, o,m-sulfone dianiline and diaminoanthroquinone. The polyimidesiloxane of Claim 1 wherein the siloxane diamine (a) has the formula wherein R' is independently selected from substituted or unsubstituted aliphatic difunctional radicals of 1 to 12 carbon atoms, or substituted or unsubstituted aromatic difunctional radicals of 6 to 10 carbon atoms, R 1 , R 2 , R 3 , and R 4 are indepedently selected from a substituted or unsubstituted aliphatic monofunctional radical of 1 to 12 carbon atoms, or substituted or unsubstituted aromatic monofunctional radicals of 6 to 10 carbon atoms, and m is a number from 5 to 200. The polyimidesiloxane according to Claim 9 wherein R 1 , R 2 , R 3 , and R 4 are methyl groups. The polyimidesiloxane of Claim 9 wherein at least a portion of the siloxane diamine of the formula comprises a diamine wherein at least one of R 1 , R 2 , R 3 , and R 4 is a radical selected from hydroxyl and vinyl. The polyimidesiloxane according to Claim 9 wherein at least one of R 1 , R 2 , R 3 , and R 4 is vinyl and the remainder are methyl groups. The polyimidesiloxane according to Claim 10 or 12 wherein the R' is (CH 2 ) 3 . The polyimidesiloxane of Claim 9 wherein at least a portion of the siloxane diamine of the formula comprises a siloxane diamine component wherein at least one of R 1 , R 2, R 3 , and R 4 is a radical selected from acrylic-, ethylenic-and acetylenic-bearing radicals. The polyimidesiloxane of Claim 14 comprising an acrylic-bearing radical. A process for producing a fully imidized polyimidesiloxane soluble in diglyme for use in the microelectronics industry, which comprises reacting an organic dianhydride, an organic diamine and a difunctional siloxane monomer, wherein (a) said organic dianhydride is an oxydiphthalic anhydride containi up to 20 weight percent of other organic dianhydrides, b) said organic diamine is a diamine providing an asymmetrical structure in the polyimidesiloxane chain selected from (b1) a diamine having the following formula where x, y and z are independently selected from hydrogen, halogen, alkyl or halogenated alkyl of 1 to 12 carbon atoms or aryl or halogenated aryl of 6 to 12 carbon atoms, (b2) a diamine having the following formula wherein x 1 is -CH 2 -, (b3) diaminoanthraquinone and (b4) a diamide having the following Formula : wherein Ar is aromatic and R" is a hydroxyl, hydrothiol or carboxylic acid radical, and may contain up to 25 weight percent of an organic diamine having the following formula that is not asymmetrical in the polymer chain wherein x 2 is -CH 2 - , and (c) said difunctional siloxane monomer is an α,w-siloxane diamine. The process of Claim 16 wherein the reaction is conducted in a solvent for the polyimidesiloxane. The process of Claim 16 wherein the solvent is selected from diglyme, triglyme, 1-methyl-2-pyrrolidinone, tetrahydrofuran, methyl ethyl ketone, phenols or mixtures thereof. The process of Claim 16 wherein the siloxane monomer is a siloxane diamine (a) having the formula wherein R' is independently selected from substituted or unsubstituted aliphatic difunctional radicals of 1 to 12 carbon atoms or substituted or unsubstituted aromatic difunctional radicals of 6 to 10 carbon atoms, R 1 , R 2 , R 3 , and R 4 are independently selected from a substituted or unsubstituted aliphatic monofunctional radical of 1 to 12 carbon atoms or substituted or unsubstituted aromatic monofunctional radicals of 6 to 10 carbon atoms, and m is an integer from 5 to 200. The process of Claim 19 wherein R 1 , R 2 , R 3 , and R 4 , are methyl groups. The process of Claim 19 wherein at least a portion of the siloxane diamine of the formula comprises a diamine wherein at least one of R 1 , R 2 , R 3 , and R 4 is a radical selected from hydroxyl and vinyl. The process according to Claim 21 wherein at least one of R 1 , R 2 , R 3 , and R 4 is vinyl radical, and the remainder are methyl groups. The process according to Claim 20 or 22 where the R' is (CH 2 ) 3 . The process of Claim 21 wherein the product of the process is reacted with a compound comprising at least one of an acrylic-, an ethylenic- and an acetylenic-bearing radical. A solution comprising the polyimidesiloxane of Claim 1 dissolved in a solvent for the polyimidesiloxane. The solution of Claim 25 wherein the solvent is selected from diglyme, triglyme, 1-methyl-2-pyrrolidinone tetrahydrofuran, methyl ethyl ketone, phenols and chlorinated solvents. An article comprising a substrate coated with a polyimidesiloxane according to Claim 1. The article cf Claim 27 wherein the substrate is a wire or cable. An article prepared from the polyimidesiloxane according to Claim 1 wherein said article is a film, a fiber, a molded article or an extruded article. A cured composition of Claim 5, or Claim 15.

Inventors: LEE CHUNG J, LEE, CHUNG J.
Applicants: OCCIDENTAL CHEM CO, OCCIDENTAL CHEMICAL CORPORATION
Application year: 1988
Main classification: C08G77
IPC codes: C08G73, C08G77