POLYIMIDES, PREPARATION OF POLYIMIDES AND BLENDS OF POLYIMIDES

Abstract: Polyimides are disclosed having a particular degree of imidization and acid and/or anhydride functionality. A process for preparing polyimides, having reduced acid and/or anhydride functionality, using acid and/or anhydride blocking agent is disclosed. Blends of polyimides with other thermoplastic materials are also disclosed. When the acid and/or anhydride functionality of a poly­ imide is reduced or substantially eliminated, the resultant polyimide may exhibit altered miscibility and compatibility with the thermoplastic polymers, improved weatherability characteristics. and a lower melt viscosity thereby enhancing the processability of the polyimide.

Description: This invention is concerned with polymers comprising imide groups and optionally acid and/or anhydride functional groups, a process for the preparation of such polymers, and blends of said imide polymers with other thermoplastic materials. US-A-4246374 describes and claims polyglutarimide polymers and their preparation. This patent teaches that the degree of imidization of an acrylic polymer may vary from as low as 1% imidization up to about 100% imidization and that imidization is accomplished with anhydrous ammonia or an anhydrous primary amine. There is however no teaching as to the effect of residual acid or anhydride groups and no special steps are taken to minimise such groups in the polymer. US-A-3284425 is directed to the preparation of polymethacrylimide products. This patent discusses the possibility that acid or ester groups may become isolated between adjacent imide rings. US-A-3284425 also teaches the formation of polymethacrylimide products which "...are substantially free of carboxy or ester groups...in which the degree of imidization is at least about 95%..." Thus, while recognizing the presence of acid groups in the polyimides, US-A-3284425 teaches that their presence is minimised only as an incidental effect of a degree of imidization of at least 95% and it is therefore taught that this high degree of imidization incidentally renders the polymer more resistant to alkali. US-A-4518717 describes a process for making imide polymers by reacting a monomeric dianhydride with a lactam or oxime to form a bis-imide having an acid-group-carrying radical attached to the imide nitrogen. The bis-imide monomer is then esterified with a reactive solvent that acts as an esterifying agent; methanol is typical. In the esterification process, the aromatic imide functionality is retained. The esterified bis-imide monomer is subsequently reacted with an aromatic diamine monomer in a polycondensation reaction, to form an imide or amide-imide polymer. EP-A-0076691 describes the preparation of polyimides which are free from methyl substitution on the nitrogen atom. EP-A-0076691 teaches the preparation of imide polymers free from methyl substitution on the nitrogen atom starting from a non-cross linked polymer which contains glutaric anhydride units. The polyglutaric anhydrides are reacted with ammonia to yield the desired polyimides free from methyl substitution on the nitrogen atom. Complete imidization is taught to be preferred. Makromol. Chem., 184, pages 1705-1726 (1983) discloses an analytical technique for confirming the chemical structure of the reaction products of polymethacrylic acid and formamide. The technique encompasses treating copolymers of methacrylic acid and methacrylimide with diazomethane. There is no disclosure in the reference procedure concerning the degree of imidization. Further, the imide groups are reacted along with the acid groups. Japanese published patent application No. 60-20904 (A) describes a process for preparing a polyglutarimide by condensing a polyamide or a copolymer of a methacrylamide with a methacrylate ester. US-A-4458046 discloses blends of vinyl chloride polymers and copolymers of the styrene-maleimide type. US-A-4458046 teaches that the imide used be prepared from a dicarboxylic acid moiety and that complete conversion of the dicarboxylic acid moiety to the desired imide be obtained by using an excess of the stoichiometric amount of ammonia or amine required for such conversion. As a by-product of imidization of (meth)acrylic polymers by reaction with ammonia or primary amines, anhydride and acid groups are formed on the polymer chain. The acid and anhydride groups are intermediate in the formation of imide units. When the degree of imidization exceeds 95% and approaches 100%, the amount of acid and anhydride units present on the resultant imide product decreases and poses less of a problem. However, when the degree of imidization exceeds 95%, particularly when an autoclave process is used, then a high degree of discoloration of the resultant polymer and degradation of the polymer itself is often obtained. The degradation of the polymer may also lead to alteration of the desirable properties of the resultant imide polymer. None of the above disclosures is directed to measures to improve the processability of imide polymers. This invention however is concerned with the provision of imide polymers which exhibit altered miscibility and compatibility with other thermoplastic polymers and lower melt viscosity, thus enhancing their processability. Surprisingly we have found polymers which not only possess these advantageous properties but also have the advantage over the prior art polymers of alkali resistance without the disadvantages of discoloration and degradation associated with polymers having high degrees of imidization. Additionally the polymers of the invention avoid problems of weatherability of a molded article prepared from polymers arising from water absorption as a result of the presence of the normal amount of acid and anhydride functionality. This invention provides a polyglutarimide wherein the amount of acid and/or anhydride functionality is reduced from the amount normally present, or is substantially eliminated, a process for reducing or substantially eliminating active acid and/or anhydride functional groups existing on a polyglutarimide and blends of polyglutarimides with other thermoplastic polymers wherein the acid and/or anhydride functionality of the polyglutarimide in the blend has either been reduced from that which was originally present or has been substantially eliminated. In accordance with one aspect of the invention, a polymer comprises glutarimide groups and optionally acid and/or anhydride functional groups and has a degree of imidization of at least 1% to less than 95%, characterized in that the degree of imidization on said polymer, and the corresponding carboxylic acid, carboxylic acid salt and/or anhydride functionality on said polymer are as set forth in the Table below: the degree of imidization on said polymer the milliequivalents of acid, acid salt and/or anhydride per gram of imidizable polymer component are from 1% to 10% 0 to 0.20 above 10% to 20% 0 to 0.28 above 20% to 30% 0 to 0.32 above 30% to 40% 0 to 0.31 above 40% to 50% 0 to 0.28 above 50% to 60% 0 to 0.28 above 60% to 70% 0 to 0.27 above 70% to 80% 0 to 0.28 above 80% to 90% 0 to 0.33 and above 90% to less than 95% 0 to 0.40 In accordance with another aspect of the present invention, a process is provided for the preparation of a thermoplastic polymer comprising glutarimide groups and optionally acid and/or anhydride functional groups and having a degree of imidization of at least 1% to less than 95%, said process comprising reacting a first polymer comprising glutarimide groups and active acidic and/or anhydride functional groups with a predetermined amount of acidic and/or anhydride functional group blocking agent to reduce or substantially eliminate the active acid and/or anhydride functional groups on the polymer. Preferably the process is carried out at a temperature of from 50°C to 450°C. Preferably the process is carried out at a pressure of from 1 atmosphere (101.3 KiloPascals) to 1000 atmospheres (101300 KiloPascals). This invention also contemplates a blend of at least one other thermoplastic polymer and a second polymer, said second polymer being a polyglutarimide polymer as hereinbefore defined or a polyglutarimide polymer as prepared by the process as hereinbefore defined. It is surprising that the reduction or substantial elimination of acid and/or anhydride functionality of a polyglutarimide has the effects upon miscibility, compatibility melt viscosity and consequently processability described above. The polyglutarimide of the present invention may also possess superior thermal stability. Preferred polyglutarimides of this invention are those which have a thermal stability indicated by a 1% weight loss, by thermogravimetric analysis (TGA), at a temperature above 285°C in air and above 300°C in nitrogen. As used in the specification and claims, the term "degree of imidization" refers to the weight percentage of imide groups on a polymer in relation to the groups of the polymer capable of being reacted to form imide groups. For example, one may have a copolymer of styrene and methacrylic acid. Because the styrene is not capable of being imidized, the degree of imidization is based on the percentage of imide groups which are subsequently formed from the methacrylic acid portion of the copolymer. Any thermoplastic polyglutarimide, containing acid and/or anhydride groups, may be used in practicing the process of this invention. For example, one may use the polyglutarimides disclosed in US-A-4246374. The polyglutarimide product of this invention may be prepared from a polyglutarimide such as those derived from esters of acrylic or methacrylic acid wherein the ester moiety contains from 1 to 20 carbon atoms and which has been reacted with ammonia or a primary amine wherein the hydrocarbon portion of the amine is hydrogen or a substituted or unsubstituted alkyl or aryl group having up to 20 carbon atoms, may also be used. Such polyimides are disclosed in US-A-4246374. A preferred polyimide is derived from methyl methacrylate. Preferably the imide units are derived from a primary amine having substituted or unsubstituted alkyl or aryl groups of up to 20 carbon atoms, and more preferably are derived from methylamine, ammonia, aniline or cyclohexylamine. The composition of the thermoplastic polyglutarimide may be varied depending upon the properties desired from the final product. A preferred polyglutarimide contains up to about 50%, and preferably from about 10% to about 50%, by weight, of acrylic or methacrylic ester units, preferably wherein the ester moiety contains from 1 to 20 carbon atoms. Another preferred polyglutarimide contains from 50 to 99%, by weight, of acrylic or methacrylic ester units, with the preferred ester moiety as stated above. Among the ester moieties, a more preferred one is methyl. Among the polyglutarimides which may be used to practice the process of this invention are the polyglutarimides described above and copolymers thereof with, for example, styrenic materials such as styrene, ring substituted styrenes and/or alpha-methyl styrene, all optionally containing acrylonitrile and/or methacrylonitrile; copolymers of ethylene and propylene containing glutarimide functionality. Whichever polyglutarimide is used to practice the process of this invention, such polyimide must have residual acid and/or anhydride groups. Particularly preferred polyglutarimides are those set forth in US-A-4246374 and, even more particularly preferred, are the polyglutarimides prepared by the reaction of (1) poly(methyl methacrylate) with ammonia or methylamine and (2) a copolymer of poly(methyl methacrylate) and ethyl acrylate with ammonia or methylamine and (3) a copolymer of (methyl)styrene and methyl methacrylate with ammonia or methylamine, because these polyimides are simple to prepare and easy to work with. The first polymer may be prepared in any suitable manner and the invention is not to be construed as being limited to the method of preparation of the polyimide. For example, one may prepare a polyglutarimide, by heating, with stirring or mixing, the selected polymer such as poly(methyl methacrylate), preferably in an autoclave, in the presence of a primary amine, such as butylamine or methylamine. Other suitable amines include aniline and cyclohexylamine; ammonia is also suitable for preparing the polyimide. The reaction may be conducted in the presence of water and at an elevated pressure such as between 8 and 85 atmospheres (810.4 and 8610.5 KiloPascals). The temperature which may be used may vary from 180°C to 350°C, with the understanding that the pressure used will vary with the temperature used. One may also prepare the first polymer as described in U5-A-4246374 wherein an extruder is used in the preparation. Generally, when using an extruder, the polymer, such as poly(methacrylic acid) may be continuously fed to an extruder and ammonia or a primary amine, such as methylamine, may be introduced continuously through an injection port. Unwanted by-products and excess ammonia or primary amine are removed by progressively reducing the pressure at downstream extruder vents. The temperature in the extruder may be varied and such variation will be dependent on the nature of the starting materials, pressure being used, residence time, melt viscosity of the polymer being extruded, etc. Generally, a temperature of from about 200°C to about 450°C may be used in preparing the polyimide and a pressure may be used which is from about atmospheric to about 1000 atmospheres (101300 KiloPascals), although pressures of less than 500 atmospheres (50650 KiloPascals) are generally suitable. The reaction time of the acrylic polymer in the reaction zone of the extruder will generally vary from about 0.1 to about 1000 seconds and preferably from about 30 to about 300 seconds. The desired degree of imidization is obtained by suitable adjustment of various reaction parameters such as residence time. The extruder is generally equipped with a screw which advances the materials present through the extruder. In a particularly preferred embodiment, the extruder may be equipped with at least one pair of screws. The number of pairs of screws which is present in the extruder is dictated solely by economic and practical process conditions. In one embodiment, each screw member or each pair of screws which is present in the extruder may rotate in a direction counter to the rotational direction of the other screw member of the pair. In this manner mixing may be enhanced, as may removal of undesired materials. The first polymer may also be prepared in a tubular reaction vessel such as a baffled in-line mixer, wherein the baffles provide the necessary mixing. The baffled in-line mixer may also be equipped with various ports for the introduction of necessary reactants or materials. It is preferred that an extruder be used and that the extruder which is used for preparing the polyglutarimide, be equipped with at least one pair of screws wherein each member of the pair rotates in a direction counter to the rotational direction of the other screw member of the pair. Because the preparation of the first polymer may involve amide and/or acid intermediates which may give rise to imides or anhydrides, if an extruder apparatus is not used to prepare the polyglutarimide, the final product may contain imide, amide, acid, anhydride and ester moieties. The preference for the reaction to take place in the extruder is for the reason that the proper use of the extruder tends to cause all significant amide groups to further react to imide although some acid and anhydride groups are still present. Thus, polyglutarimides prepared using an extruder are usually substantially free of amide functionality and contain less acid and anhydride functionality than polyglutarimides prepared using other processes. Preferably, regardless of the method or apparatus used, the polyglutarimide is substantially free of amide functionality. The invention is not to be construed as limited to any particular method for preparing polyglutarimides. Regardless of which apparatus or method is used for preparing the polyglutarimides, the degree of imidization should be controlled so that the final product has a degree of imidization of less than 95%, preferably 10% to less than 95%. It is more preferred however that the degree of imidization of the polyglutarimide be from 25% to less than 95%, even more preferred that the degree of imidization be from 40% to 88%, and still more preferred that the degree of imidization be from 50% to 85%. In a preferred embodiment of the present invention, the acid and anhydride functionality of the first polymer having up to 88% degree of imidization is reduced to no more than 0.25 milliequivalents per gram of imidizable polymer component, and in a more preferred embodiment the acid and anhydride functionality of a polyglutarimide having up to 85% degree of imidization is reduced to no more than 0.25 milliequivalents per gram of imidizable polymer component. The agent which is used to block the acid and/or anhydride functional groups may be any agent which is capable of reacting with the acid and anhydride groups and incapable of reacting with the imide functionality and which will not adversely affect the properties of the polyglutarimide, either during the time the reaction with the acid and anhydride functionality is being conducted or in the final polymer. The term acid and/or anhydride functional group means any carboxylic acid, carboxylic acid salt, and/or anhydride group present on the polyglutarimide. Among the types of agents which may be used to partially or completely remove acid and anhydride functionality which is present on the polyglutarimide are alkylating agents such as orthoesters, ketals, carbonates and/or sulfoxides, preferably alkyl, aryl, alkaryl and/or aralkyl carbonate and/or dialkyl sulfoxide. Other agents, including esterification agents, may also be used such as siloxanes, silyl ethers, silylenol ethers, trialkyl phosphates, trialkyl phosphites, dialkyl sulfates, alkyl alkylsulfonates, alkyl arylsulfonates,dialkyl carbonates, diaryl carbonates, aryl isocyanates, carbodiimides, trialkylsilyl halides, enol esters, alcohols, alkyl esters, alkyl isocyanates, quaternary ammonium salts, ureas and/or guanidines. Among the specific agents which are preferably used to remove acid and anhydride functionality are one or more of dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, diethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluenesulfonate, methyl trifluoromethylsulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethyl carbodiimide, dimethyl t-butylsilyl chloride, isopropenyl acetate, dimethyl urea, tetramethylammonium hydroxide, dimethyl diethoxysilane, tetra-n-butoxysilane, dimethyl(trimethylsily) phosphite, trimethyl phosphite, trimethyl phosphate, and tricresyl phosphate. The amount of agent used to block the acid and/or anhydride functional groups will vary depending upon the amount of acid and anhydride present. This may be readily determined by the titration method described hereafter. The amount of agent used will generally be at least the stoichiometric amount of agent needed to substantially eliminate the acid and anhydride functionality if it is desired to remove substantially all acid and anhydride functionality. Generally, when substantially eliminating all acid and anhydride functionality from the polyglutarimide, it is desirable to use from 10% to 50% excess above stoichiometry of the agent. When it is desired to only partially reduce the acid and anhydride functionality, then it is preferred to use less than a stoichiometric amount of agent to avoid removing more acid and anhydride functionality than is desired. In some instances, the agent used may react with water which is associated with the first polymer. In such instances, procedures may be used to assure that the desired amount of agent is present to react with the acid and anhydride groups present on the polyglutarimide. One procedure is to dry the polyglutarimide, for example, under vacuum at a temperature of from 100°C to 135°C for 8 to 20 hours. A second procedure is to use an excess, above the amount of agent required, so that the excess amount of agent will react with the water present and the desired amount of agent will react with the acid and anhydride groups present on the polyimide. The reaction wherein the acid and anhydride functionality is removed or reduced may be conducted in a single or multi-screw extruder, in an autoclave, in a continuously recirculated pipe reactor, in a baffled in-line mixer which may be used in series with an extruder, in a wiping-film evaporator, a falling film reactor or evaporator, in a disc extruder or reactor, or other melt-mixing device. If the reaction is conducted using an extruder, then it may be conducted as a continuous process wherein a polyglutarimide is prepared in an extruder and is then passed, in the extruder, into a zone wherein the agent is introduced and the polyglutarimide is contacted with the agent for a period of time of from 15 second to 20 minutes at a temperature of from 150°C to 400°C and at a pressure of from about atmospheric to 15000 KiloPascals (2200 psi), in the absence of any solvent and/or catalyst. Alternatively, a polyglutarimide which has been previously prepared, may be introduced into an extruder at an elevated temperature so as to form a molten mass, and may then be contacted with the agent at the aforesaid temperature and pressure. If the reaction of the agent and the acid and anhydride groups is to be conducted in an autoclave, then the reaction may take place, with or without a solvent for the polyglutarimide, in the autoclave for a period of time of from 10 minutes to 8 hours at temperatures of from 100°C to 180°C and in an unpressurized vessel or a pressurized vessel at pressures up to 1000 atmospheres (101300 KiloPascals). In some instances, the agent, if a liquid, may also act as the solvent for the polyimide. In other instances a separate solvent may be used. The solvent used may vary widely depending on the nature of the polyglutarimide solute to be reacted. Generally, the solvent should be at least somewhat polar in nature and should be non-reactive with the agents to be used. If the agent is not to also act as the solvent for the polyglutarimide then the solvent should also be non-reactive with the polyglutarimide. Among the solvents which may be used are diglyme, triglyme, sulfolane, tetrahydrofuran and/or tetrahydropyran. Yet another method for conducting the reaction of the polyglutarimide with the agent is to melt the polyimide in the autoclave and to conduct the reaction between the acid and anhydride function groups of the polyglutarimide and the agent in a molten state without the addition of any solvent. Still another method is to prepare the polyglutarimide in a reaction vessel, such as an autoclave, and, as the very last step in the preparation, to add a suitable agent for the removal of the acid and anhydride groups. If one is to conduct a continuous reaction to prepare a polyglutarimide and remove or reduce acid and anhydride functionality, whether in an extruder, autoclave or other reaction vessel, then the amount of acid and anhydride groups present on the polyglutarimide may be determined by first conducting the imidization reaction under the conditions to be used in the extruder, autoclave or other reaction vessel and measuring the amount of acid and/or anhydride functional groups present on the resultant polyglutarimide. In this manner, one may predetermine the amount of agent to be added, if a continuous process is to be utilized, to reduce or substantially eliminate the desired amount of acid and anhydride groups. In some cases by-products or unreacted materials from the imidization reaction may enhance or impede the subsequent reaction of the polyglutarimide with the agent. If desired, the reaction of the agent with the polyglutarimide may be conducted in the presence of a catalyst. The catalyst preferably catalyzes the reaction of the agent with the polyglutarimide, but does not catalyze degradation of the polyglutarimide nor cause other undesirable reactions. Among the catalysts which may be used are base catalysts such as trimethylamine, triethylamine, benzyldimethylamine and/or tetramethylammonium hydroxide. One may also use acid catalysts or Lewis acid catalysts such as p-toluenesulfonic acid, tetrabutyl titanate and/or manganese tetraacetate. Optionally, the polyglutarimide may be present in the final or outermost stage of a multistage polymer and the reaction is conducted with the entire multistage polymer. Further, the polyglutarimide may be one of the elements of a block or graft copolymer, and the reaction is conducted in the presence of the entire block or graft copolymer. In another embodiment, the polyglutarimide may be in the core of a multistage polymer or in the second or other intermediate stage of a multistage polymer and the acid and anhydride functionality may be removed as aforesaid. The amount of acid and anhydride functionality on any of the polyimides of the stages of the multistage polymer may be adjusted to that which is desired. The polyglutarimides of this invention may be blended with one or more other thermoplastic polymers and may even be blended with another polyimide which may or may not have had its acid and/or anhydride functionality level reduced or substantially eliminated. The polyglutarimide according to this invention may be blended, as a multistage polymer, wherein at least one of the stages is a polyglutarimide according to this invention, with another thermoplastic polymer. When the thermoplastic polymer itself is a multistage polymer, the second polymer may also be a multistage polymer and preferably the outermost stage of the second polymer contains imide units. Generally, when blending polyglutarimides prepared according to this invention with other thermoplastic polymers, the amount of polyglutarimide present may vary widely from 1% to 99%, by weight of the entire composition. In a preferred blend, the second polymer is present in an amount of up to 50%, based on the total weight of said thermoplastic polymer plus said second polymer. In another preferred blend the second polymer is present in an amount from 50% to 99%, based on the total weight of said thermoplastic polymer plus said second polymer. The advantage of blending a polyglutarimide of this invention with at least one other thermoplastic polymer is that the resultant blends generally exhibit a better combination of properties which may include better melt viscosity, greater compatibility and/or miscibility, greater weatherability, greater impact resistance, better ductility, and better solvent resistance than the combination of properties of blends of polyimides which have not undergone diminution or substantial removal of acid and anhydride functionality. The polyglutarimides of this invention may be blended with one or more other thermoplastic polymers (as used herein "-" indicates blended polymers, "/" copolymers, and "//" graft or block polymers) such as butadiene/styrene/(meth)acrylic, styrene/(meth)acrylic, and (meth)acrylic multistage polymers; butadiene/styrene rubbers, ethylene/propylene/diene rubbers, polyamides, polyamide-multistage polymer blends, ethylene/vinyl acetate, styrene/acrylonitrile, methyl styrene/acrylonitrile, styrene/acrylonitrile-multistage polymer blends, styrene/acrylonitrileethylene/propylene/diene rubber blends, alpha -methyl-styrene/acrylonitrile, alpha -methylstyrene/styrene/acrylonitrile, alpha -methylstyrene/methyl methacrylate/ethyl acrylate, butadiene//acrylonitrile/styrene, polycarbonate, polycarbonate-multistage polymer blends, polybutylene terephthalate, polybutylene terephthalate-polycarbonate blends, polybutylene terephthalate-multistage polymer blends, polybutylene terephthalate/polytetrahydrofuran, polyvinyl chloride, polyvinyl chloride-multistage polymer blends, polyvinyl chloride-(meth)acrylate blends, chlorinated polyvinyl chloride, acrylonitrile/(meth)acrylate-multistage polymer blends, acrylonitrile/(meth)acrylate/styrene, epichlorohydrin/bisphenol-A, polyethylene terephthalate or other polyalkylene terephthalate, polyethylene terephthalateglycol modified, polyethylene terephthalate-polycarbonate blends, polycaprolactone, polyarylate, copolyester of bisphenol-A with isophthalic and/or terephthalic acids, poly(meth)acrylates, polyamide, polystyrene, polyacetal, polystyrene, high-impact polystyrene, styrene/maleic anhydride, styrene/maleimide, polyolefins, polyvinylidene fluoride, polyvinylidene fluoride-multistage polymer blends, polyvinylidene chloride, cellulosics, polyethylene oxide, polyamideimide, polyetherester, polyetheresteramide and polyetheramide. Blends having modified performance characteristics can be prepared from any other polymer systems with polyglutarimides. These include polyphenylene sulfide, polyphenylene oxide, polysulfone, polyphenylene oxidestyrene blends, polyphenylene oxide-high impact polystyrene blends, polyvinylidene chloride, polyvinylidene chloride/(meth)acrylonitrile, polyvinylidene chloride/(meth)acrylate, polyvinyl alcohol, polyvinyl acetate, polyetheretherketone, polyetherimide and thermoplastic polyimides. Random or block copolymers which combine the different functionalities can also be used, and ternary or higher blends can be made from combinations of any of these polymer types with the imide polymers. The glutarimide polymers and blends with other polymer systems can be further modified by the incorporation of glass or other fibers, or particulate fillers or reinforcing agents such as talc or other minerals, glass spheres, or metallic particles. In general, the glutarimide polymers exhibit good adhesion to glass and other inorganic fillers. Further modification of properties of the polyglutarimides and blends can be obtained by incorporating additives such as flame retardants, blowing agents, antioxidants, thermal stabilizers, pigments, flatting agents, lubricants , antistatic agents, conductive materials, toners and/or UV stabilizers. This invention is preferably concerned with a thermoplastic polymer comprising less than 95% glutarimide units of the structural formula wherein R¹, R² and R³ independently represent hydrogen or C₁ to about C₂₀ unsubstituted or substituted alkyl, aryl, or mixtures thereof, said polymer being non-crosslinked and soluble in dimethyl formamide, said polymer containing substantially no acid and/or anhydride groups. In the Examples which follow, certain tests are conducted. These tests are as follows: The Vicat is determined by ASTM Test Method 1525-65T using 40 mil (0.1 cm) penetration and heating rate B. The total acid and anhydride functionality was determined by titrating solutions of the polymers in either 1:1 methylene dichloride-methanol or 3.75:1 dimethyl sulfoxide-water. A 0.3 g sample of the polymer is dissolved in 75 ml (75 cm³) of methylene dichloride-methanol. A measured volume of 0.1 N sodium hydroxide solution, containing more than enough base to neutralize the acid and anhydride in the sample, is added to the polymer solution, and the excess base is titrated with 0.1 N hydrochloric acid. The total acid and anhydride functionality is the difference, in milliequivalents, between the added base and the acid solution used to reach neutrality, corrected by subtracting the acid titration value of a solvent blank (the blank is usually less than 5% of the total acid and anhydride functionality). If dimethylsulfoxide is used, the polymer is dissolved in 75 ml (75 cm³) of dimethylsulfoxide, and 20 ml (20 cm³) of water is added to the solution, which is then titrated as above. In the samples below, the end point of the titration was detected either colorimetrically or potentiometrically, and in some instances other solvents were used to prepare the polymer solution for titration. The total acid and anhydride functionality of a copolymer or blend containing polymer components that are imidizable is calculated as milliequivalents per gram of the imidizable polymer components. Molecular weight is determined by gel permeation chromatography using a commercial Waters instrument and a tetrahydrofuran solvent, and is a weight average molecular weight. Dynamic thermogravimetric analysis (TGA), as used herein, is a standard test conducted using a programmed temperature-increase rate of 20°C per minute and an atmosphere of either air or nitrogen, as indicated. Results given herein for TGA were either obtained using, or are consistent with those obtained using, a DuPont thermogravimetric analyzer in combination with differential thermal analyzer; specific operating instructions for the TGA instrument and for this particular test are described in E. I. DuPont de Nemours, Inc. Instrument Products Division Preliminary Product Bulletin 950-1 (A-36117). Measurements or glass transition temperature (Tg) and visual examination of polymer samples, as described below, help to quantify observations of compatibility and/or miscibility enhancement. The glass transition temperature (Tg) of polymer and blend samples is determined by differential scanning calorimetry (DSC), using a Perkin-Elmer Model DSC-2 calorimeter. The sample is heated in a nitrogen atmosphere at 20 °C per minute, and the reference material in the calorimeter is 60-80 mg aluminum. The Tg value is taken from the DSC chart as the temperature at the midpoint of the transition. All blend samples, prior to the DSC run, are preheated for one minute at a temperature 20°C higher than the higher Tg value for either component in the blend, and then cooled to a temperature below the lower Tg value of either component. The DSC values for Tg are usually sufficient to indicate whether a blend is miscible. However, If the Tg values of the two components arc similar, or if one of the components undergoes a phase change (e.g. melting or recrystallization) near the Tg of the other component, the DSC result may not be adequate to detect whether the sample is miscible. In such a case other techniques for detecting miscibility may be used. For example, domains indicating incompatibility in blend samples may be detected by transmission electron microscopy (TEM), and the sensitivity of this technique may, under some conditions, be enhanced, as by staining one of the phases. An example of this is staining phases containing carbon-carbon unsaturation using osmium tetroxide. Compatibility or miscibility of polymer blends is determined by an examination of the blend of the polyglutarimide with a specified polymer after mastication of the blend in a Brabender mixing device at a temperature of from 193 to 246°C for ten minutes in an air atmosphere. Samples of the resulting blend are removed from the melt, formed into small, flattened "buttons" and examined visually for clarity. With some blends, the refractive indices of the two polymers are similar at room temperature, and incompatibility is difficult to detect by visual examination of the button sample. In such a case the button is observed at several different temperatures; the refractive indices of two immiscible components will change at different rates if one component is heated above its glass transition temperature. In the examples which follow, the percent nitrogen of the polyglutarimides used is set forth. The degree of imidization, by weight, may be calculated from the percent nitrogen given: divide the percent of nitrogen actually present in the polyglutarimide by the theoretical amount of nitrogen at 100% imidization and multiply by 100. In order to more fully illustrate the nature of this invention and the manner of practicing the same, the following examples are presented. Examples 1 through 10 A polyglutarimide having N-methylimide groups, prepared in accordance with the procedure disclosed in US-A-4246374, is used. The imide was prepared from a feedstock of poly(methyl methacrylate) having a weight average molecular weight of 200,000. The extruder used is a 2-0 cm-diameter (0.8 inch) Welding Engineers non-intermeshing twin screw extruder. The extruder has one section about six diameters long, for introducing and plasticating the polyglutarimide followed by a closed barrel section about 6 diameters long for pumping and pressure generation, followed by the reaction zone. This zone, about 31.5 diameters long, comprises a ported barrel section for introducing blocking agents, closed barrel sections, and a venting section for removing volatile products. Another vented section, operated at substantially atmospheric pressure, follows the reaction zone, for removing additional volatiles. The extruder is purged with the polyglutarimide, to remove contaminants. The polyglutarimide is then added to the plastication zone of the extruder at a rate of 60 grams per minute. At this time the barrel temperature in the reaction zone is about 300°C, and the blocking agent pressure is about 3500 KiloPascals (500 psig). The polymer resides in the extruder for an average of about 120 seconds. The polyglutarimide used has a nitrogen content of 7.13 weight percent, as determined by micro Kjeldahl analysis, and a Vicat of 170°C. The initial, total acid and anhydride of the polyglutarimide used is 0.585 ± 0.020 milliequivalents per gram of imidizable component in the polymer. In ten separate experiments, the polyglutarimide described above was processed in the extruder. For eight of the runs, trimethyl orthoformate was used for removing anhydride and acid functionality from the polyglutarimide. The extruder screw speed was, for all examples, 400 rpm. The trimethylorthoformate (TMOF) was pumped through a port into the inlet section of the extruder where it reacted with the polyglutarimide at a temperature of from 200°C to 350°C and a pressure of 3450 ± 70 KiloPascals (500 ± 10 psig). In Table I, the letter "d" means that, prior to introduction in the extruder, the polyglutarimide is dried, under vacuum, at a temperature of 135°C. for eight to twelve hours. The letter "u" means that the polyglutarimide is not dried prior to introduction into the extruder. In Examples 3 and 4, no excess TMOF is added to the extruder. Table I sets forth the results obtained. Example 4 illustrates that when the polyglutarimide is not dried prior to reaction with the agent, there is an effect on the amount of agent available to react with acid and anhydride groups. In Example 5 (dried), a slight excess of agent, over the stoichiometric amount required, is used. The slight excess in Example 6 (undried), which is substantially the same as Example 5, results in a higher acid and anhydride content because of the reaction of water with the agent used, whereas in Example 5, the reaction is substantially quantitative. Example 8 (undried) illustrates that the effect of the reaction of water and TMOF can be overcome by using a sufficient excess of TMOF over the stoichiometric amount required. Examples 11 through 14 The procedure of Examples 1-10 was repeated except that the agent used was triethyl orthoformate (TEOF), to convert the acid and anhydride functionality to an ethyl ester; all polyglutarimides used were undried; the polyglutarimide feed rate was 3 grams/minute; the TEOF feed rate is set forth in Table II; the screw speed of the extruder was 250 rpm; the temperature in the zone for reacting TEOF with the acid and anhydride groups was 302°C. The percent nitrogen in each of the polyimides of the examples was 7.13 wt. %. The initial acid and anhydride level of polyglutarimide used was 0.585 ± 0.020 milliequivalents per gram (meq./g) determined as in Examples 1-10. The results are set forth in Table II. The pressure in the reaction zone was 2900 KiloPascals (420 psig) for Example 12; 2345 KiloPascals (340 psig) for Example 13, and 2070 KiloPascals (300 psig) for Example 14. Example No. Agent Feed rate (grams/minute) Ratio (equivs./equivs.) of agent to acid and anhydride Vicat of final product (°C.) Acid & Anhydride Content of Final Product (meq./g.) 11 none 0.00 170 0.585 12 6.3 2.11 157 0.066 13 13.8 4.62 158 0.081 14 22.4 7.50 158 0.093 Examples 13 and 14 show that the removal of acid and anhydride groups is substantially complete in Example 12 and that the additional agent used in Examples 13 and 14 has little benefit over the amount of agent used in Example 12. The amount of acid and anhydride remaining in Examples 12, 13 and 14 are substantially the same and are within the experimental error of the titration method used, which is the same as is used in Examples 1-10. Examples 15 through 20 The procedure of Examples 11 through 14 were repeated except that the agent used was trimethyl orthoformate (TMOF) and the polyglutarimide used is a 201°C-Vicat ammonia polyglutarimide which has a nitrogen content of 7.72 weight %. The polyimide used had an acid and anhydride content of 0.610 milliequivalents per gram of polyimide, as determined by titrating it in a 3.75/1.0 dimethylsulfoxide/water solution. The polyimide samples used were not dried. The polyimide feed rate was 30 grams per minute. The pressure in the reaction zone was 2205 KiloPascals (320 psig) for Example 16; 3585 KiloPascals (520 psig) for Example 17; 3655 KiloPascals (530 psig) for Example 18; 3205 KiloPascals (465 psig) for Example 19; and 3035 KiloPascals (440 psig) for Example 20. The results are set forth in Table III. Example No. Agent Feed rate (grams/minute) Ratio (equivs./equivs.) of agent to acid and anhydride Vicat of final product (°C.) Acid & Anhydride Content of Final Product (meq./g.) 15 none 0.0 201 0.610 16 1.0 0.48 198 0.432 17 1.9 0.97 198 0.311 18 2.9 1.45 192 0.000 19 3.9 1.93 190 0.000 20 7.7 3.81 192 0.000 Examples 21 through 27 The purpose of these examples is to illustrate a continuous process for making polyglutarimides and reducing or substantially eliminating acid and anhydride functionality. In this continuous process, the amount of acid and anhydride of the polyimide prior to treatment with an agent may be determined by removing a sample of polyglutarimide prior to reaction with the agent for reducing acid and anhydride functionality and titrating the amount of acid and anhydride present. A calculated amount of the agent, based on the desired acid and anhydride level, may then be added. Alternatively, prior to running the continuous process, one may determine the amount of agent to add by preparing the polyglutarimide under the same conditions to be used in the continuous process, and then measuring the acid and anhydride level. As long as the feed stock is converted to the same polyglutarimide and treated with the agent under the same conditions, the resultant final product should be substantially the same in both cases. The apparatus of examples 1-10 is used in examples 21 through 27 except that an imidization zone measuring 2.0 cm by 61 cm (0.8 inch by 24 inches) is added to the apparatus as the first zone. The imidization zone also contains a double screw. The feed which is added to the imidization zone is poly(methyl methacrylate) (PMMA) having a weight average molecular weight of 148,000. The PMMA feed rate is 45 grams per minute. To the PMMA in the imidization zone is added methylamine. The barrel temperature of the imidization zone was 302°C. ± 5°C. The gauge pressure in the imidization zone for Example 21 was 6137 KiloPascals (890 psig); for Example 22 was 6205 KiloPascals (900 psig); for Example 23 was 6275 KiloPascals (910 psig); for Example 24 was 6275 KiloPascals (910 psig); for Example 25 was 6171 KiloPascals (895 psig); and for Example 26 was 7240 KiloPascals (1050 psig). In Example 21 and 26 the polyglutarimides were not treated with any agent after preparation. The procedure of Examples 1-10 for removing acid and anhydride was then repeated. The agent used was trimethyl orthoformate (TMOF). The temperature of the TMOF/polyglutarimide reaction zone was 304°C. ± 5°C. The pressure in the TMOF/polyglutarimide reaction zone for Example 22 was 2413 KiloPascals (350 psig); for Example 23 was 3172 KiloPascals (460 psig); for Example 24 was 3103 KiloPascals (450 psig); for Example 25 was 3068 KiloPascals (445 psig); for Example 26 was atmospheric pressure (0.00 psig); and for Example 27 was 3103 KiloPascals (450 psig). Table IV sets forth the results obtained. Examples 28 to 34 The procedure of Examples 11 through 14 was repeated with the following changes. In Examples 28, 31, 33 and 34(d) the glutarimides were not treated with an agent to substantially remove or reduce acid and anhydride functionality. The agent used in Examples 29, 30 and 32 was dimethyl carbonate (DMC). Examples 30 and 32 also utilized triethylamine (TEA) as a catalyst for the reaction between the agent and the acid and anhydride groups. The TEA was added at a feed rate of 0.09 gram per minute in Example 20, and 0.11 gram per minute in Example 32. The agent used for Examples 34(a), 34(b) and 34(c) was 2,2-dimethoxypropane (DMP). The polyglutarimide used in Examples 28 through 30 was polymethylimide having a Vicat of 172 °C and a nitrogen content of 7.04 weight percent. The polyglutarimide used in Examples 31 and 32 was a polymethylimide having a Vicat of 150°C and a nitrogen content of 4.90 weight percent. The polyglutarimide used in Examples 33 and 34(a) to (c) was a polymethylimide having a Vicat of 170°C and a nitrogen content of 7.24 weight percent. The polyglutarimide used in Examples 34(d) and 34(e) was a polymethylimide having a Vicat of 162°C. and a nitrogen content of 3.08 weight percent. The pressure in the agent reaction zone was 2900 KiloPascals (420 psig) for Example 29; 2793 KiloPascals (405 psig) for Example 30; 2137 KiloPascals (310 psig) for Example 32; 2124 KiloPascals (308 psig) for Example 34(a); 2827 KiloPascals (410 psig) for Examples 34(b) and 34(c); and 2137 KiloPascals (310 psig) for Example 34(e). Examples 28-30 used polyglutarimide dried in the manner of Examples 1-10. Examples 31-34(e) used an undried polyglutarimide. The initial acid and anhydride level of the polyglutarimide of Examples 28-30 was 0.618 milliequivalents per gram (meq/g) of polyglutarimide. The polyglutarimide of Examples 33-34(c) had an initial acid and anhydride level of 0.570 meq/g. The polyglutarimide of Examples 31 and 32 was prepared from a 90/10 methyl methacrylate/styrene feedstock and contained 4.90 weight percent nitrogen and an initial acid and anhydride level of 0.689 meq/g of imidizable polymer component. The polyglutarimide of Examples 34(d) and 34(e) was prepared from a 73.5/24.5/2.0 methyl methacrylate/alpha-methylstyrene/ethyl acrylate feedstock, and had a nitrogen content of 3.08 weight percent and an initial acid and anhydride level of 0.975 meq/g of imidizable polymer component. The results are set forth in Table v. Examples 35 through 44 These examples illustrate the removal of acid and anhydride functionality from polyglutarimides using a solution reaction. The polyglutarimide for Examples 35 through 44 was the polyglutarimide of Examples 1-10. The procedure for Examples 35-44 is as follows. To a 3-neck, 500 ml round-bottom flask equipped with a magnetic stirrer and reflux condenser is added 250 ml of a solvent. A 12.5 g polyglutarimide sample is dissolved in the solvent and the agent is then added to the solution. The resulting solution is then heated to a temperature of from 160°C to 175°C, under nitrogen, for varying periods of time. The solution is then cooled to room temperature and the final product is precipitated by adding it to methanol; it is then filtered and dried. The acid and anhydride level of the final product is determined as in Examples 1-10. The results are given in Table VI. EXAMPLES 45 through 49 The purpose of these Examples is to demonstrate the change in chemical resistance for the various polyglutarimides which have been prepared. The following Examples utilize the imides prepared in earlier Examples. Example 45 utilizes the polyglutarimide prepared in Example 1 Example 46 utilizes the polyglutarimide prepared in Example 12. Example 47 utilizes the polyglutarimide prepared in Example 5. Example 48 utilizes the polyglutarimide prepared in Example 26. Example 49 utilizes the polyglutarimide prepared in Example 27. The polyglutarimides used in Examples 45 and 48 were not treated to remove acid and anhydride groups. The polyglutarimides used in Examples 48 and 49 were prepared using a continuous process for the preparation of the polyglutarimide and removal of acid and anhydride groups. The polyglutarimides used in these Examples were injection molded to form 5.1 x 1.3 x 0.32-cm (2 x 0.5 x 0.125-inch) bars. The weights of the molded bars were determined and each bar was immersed in a different solvent, which was kept at a temperature of 23°C, for seven days. The bars were then removed from the solvent and the percent weight gain or weight loss was then measured by reweighing the bars. For determining water absorption, a 0.25-mm-thick film of imide was prepared by compression molding pre-dried imide pellets. The film was dried, weighed, immersed in water for fourteen days at a temperature of 50°C, and reweighed. The results are set forth in Table VII As can be seen from Table VII, those polyglutarimides which have had acid and anhydride levels reduced or substantially eliminated absorb less water than polyglutarimides having untreated acid and anhydride levels. This indicates that weatherability would be better for those polyglutarimides having reduced acid and anhydride levels. Table VII also demonstrates that resistance to ammonium hydroxide, methanol and ethanol is better for those polyimides which have been treated to substantially remove or reduce acid and anhydride levels when compared to untreated polyglutarimides. Table VII also demonstrates that the treated polyimides are somewhat soluble in 1,1,1-trichloroethylene and toluene whereas the untreated polyglutarimides are not soluble. This indicates that the treated polyglutarimides may be dissolved, to some extent, in some solvents and may therefore be used as coating compositions whereas the untreated polyglutarimides are not soluble in those solvents. Examples 50 through 57 These examples demonstrate the effect of weathering on various polyglutarimides which have been treated with an agent to remove acid and anhydride groups. The polyglutarimides used in Examples 54 through 57 correspond to the polyglutarimides used in Examples 50 through 53 except that the procedure of Examples 1 through 10 is used to treat the polyglutarimides. The agent used in treating the polyglutarimides is, in each case, trimethyl orthoformate. Example 54 is the treated counterpart of Example 50; Example 55 is the treated counterpart of Example 51; Example 56 is the treated counterpart of Example 52; and Example 57 is the treated counterpart of Example 53. The milliequivalents of acid and anhydride per gram of imidizable group are set forth in Table VIII. The weight percent nitrogen for each of the polyglutarimides used is also set forth in Table VIII. The weathering tests employed a Xenon Arc Weater-o-meter in the modified (extreme) test mode, according to ASTM method G26-83. Test samples were molded into 5.1 x 7.6 x 0.32-cm (2 x 3 x 0.125-inch) plaques. The test conditions include a 2-hour cycle: 80 minutes dry (76.7°C black body temperature, 50% relative humidity) and 40 minutes wet (sprayed distilled water). The light level was 6500 watts throughout. Table VIII sets forth the results obtained. As can be seen from Table VIII, when a polyglutarimide is treated to substantially remove or reduce the acid and anhydride levels, the weatherability of the resultant treated polyglutarimide is much superior to that of the untreated polyglutarimides. EXAMPLES 58 through 72 A number of N-methyl polyglutarimides were prepared in accordance with the teachings of US-A-4,246,374. Some of the polyglutarimides were then treated with an agent in the manner of Examples 1 through 10, using the agent used in Examples 1 through 10. The polyglutarimides prepared in Examples 58 through 72 were then evaluated for miscibility and compatibility with other polymers. A letter designation is assigned to each example and that letter designation is utilized in later examples in which miscibility and compatibility properties are given. Table IX sets forth the polyglutarimide and its properties. The Tg was determined by differential scanning calorimetry. EXAMPLES 73 through 81 A number of 50/50 weight/weight blends were prepared with the polyglutarimides of Examples 58 through 72. The polymer blended with the various polyglutarimides was a styrene-acrylonitrile copolymer composed of 75% by weight styrene and 25% by weight acrylonitrile. The Tg for the polyglutarimide, the blend of polyglutarimide and polymer, and the polymer with which the polyglutarimide was blended, was determined. The presence of a single Tg for the blend indicates complete compatibility. The blends were prepared by melt mixing the polyglutarimide and the styrene-acrylonitrile copolymer in a Brabender melt mixer at a temperature of 232°C. Small (0.9 x 0.15-cm) buttons were formed from the melt. Table X sets forth the results obtained. Example No. Polyglutarimide Used (Table IX) Observed Tg Values °C Appearance of Blend 73 I 165/113 Opaque 74 J 165/113 Opaque 75 K 161/114 Translucent 76 L 154/119 Almost Clear 77 M 128 Clear 78 E 178/113 Opaque 79 O 131 Clear 80 E 164/112 Translucent 81 F 130 Clear 82 C 157/113 Translucent 83 D 125 Clear 84 A 125 Clear 85 B 124 Clear In Examples 73 through 77, the following should be noted. The glutarimide of Example 73 has not been treated with any agent to remove acid and anhydride functionality. The polyglutarimides of Examples 74 through 77 have been treated to remove acid and anhydride functionality but the amount of acid and anhydride remaining varies so that, as one proceeds from Example 74 through Example 77, the milliequivalents of acid and anhydride in each of these examples changes. Example 73 has 0.585 milliequivalents of acid per gram of imidizable group; Example 74 has 0.512 milliequivalents of acid; Example 75 has 0.354 milliequivalents of acid; Example 76 has 0.191 milliequivalents of acid; and Examples 77 has 0.045 milliequivalents of acid. As the amount of acid and anhydride in the polyglutarimide decreases, the compatibility of the polyglutarimide with the styreneacrylonitrile copolymer increases as is seen by the appearance or by the single Tg of the blend. In Examples 78 through 85, all of the even-number examples are of polyglutarimides which have not been treated to remove acid and anhydride functionality. The immediate following, odd-numbered example is of the same polyglutarimide treated to remove acid and anhydride functionality. It is therefore clear that compatibility of the treated polyglutarimides with styrene-acrylonitrile copolymer is enhanced. Attention is invited to Example 84, wherein the polyglutarimide is not treated and the blend is clear and shows a single Tg for the blend. It is known from US-A-4436871 that certain polyglutarimides are compatible with styrene-acrylonitrile copolymers even though no steps have been taken to remove acid and anhydride functionality. EXAMPLES 86 through 89 The procedure of Examples 73 through 85 was repeated except that the polymer with which the polyglutarimide was blended is changed. The polymer used in Examples 86 through 89 was Abson 89140 which is an ABS (acrylonitrile/butadiene/styrene terpolymer supplied by Mobay Chemical Company.) All polymer blends were opaque to translucent rather than clear, due to the fact that the initial index of refraction between the rubber and hard phases does not match. However, appearance of a single Tg for the blend indicates compatibility of the polyglutarimide with the ABS polymer (Tg values for the rubber phase are not shown). The results are set forth in Table XI. Example Number Polyglutarimide Used Observed Tg Values (°C) Appearance of Blend 86 N 168/108 Opaque 87 O 129 Semi Opaque 88 E 155/108 Translucent 89 F 128 Hazy clear As is seen from Table XI, Examples 86 and 88 utilize polyglutarimides wherein no steps have been taken to remove acid and anhydride functionality from the polyglutarimide. The results of Examples 87 and 89 show a single Tg for the blend thus demonstrating compatibility of the treated polyglutarimide with the polymer. The material in Example 87 is the material from Example 86, but treated. Similarly, the material in Example 89 is the material from Example 88, but treated. EXAMPLES 90 through 97 The procedure of Examples 73 through 85 was repeated except that the polymer used was Blendex 586, obtained from Borg-Warner Company. It is believed that Blendex 586 is a terpolymer of alpha methylstyrene/styrene/acrylonitrile. The results are expressed in Table XII. Example No. Polyglutarimide Used Observed Tg Values °C Appearance 90 N 171/129 Opaque 91 O 142 Clear 92 G 161/128 Opaque 93 H 138 Clear 94 C 140 Clear 95 D 137 Clear 96 A 136 Clear 97 B 134 Clear Attention is invited to the fact that in Examples 90 and 92, the polyglutarimide is not treated to remove acid and anhydride functionality and the blends are opaque. In Examples 94 and 96, the polyglutarimides are also not treated to remove acid and anhydride functionality and the blends are clear and exhibit only a single Tg for the blend. The difference resides in the fact that the degree of imidization for Examples 96 and 94 are 67% and 78%, respectively, and the acid and anhydride levels for Example 96 is 0.504 milliequivalents and for Example 94 is 0.452 milliequivalents. When Examples 96 and 94 are compared with Examples 90 and 92, it is seen that Examples 90 and 92 have a higher degree of imidization and a higher acid and anhydride content. The degree of imidization for Example 90 is 91% and the amount of acid and anhydride is 0.798 milliequivalents and the degree of imidization for Example 92 is 82% and the acid and anhydride content is 0.624 milliequivalents. Although the blends for certain non-treated polyglutarimides are clear and exhibit only a single Tg, other properties are altered, such as weatherability. EXAMPLES 98 to 119 Examples 98 to 119 show that polycarbonate of two different molecular weights and Phenoxy resin (a condensation polymer of epichlorohydrin and bisphenol-A) all show partial to almost complete miscibility with various imides upon melt blending. The alkylated imides uniformly show higher miscibility with these polycarbonate polymers. The similarity of imide and polycarbonate Tg's makes the DSC data in some of the below cases a less reliable indication of miscibility. In these cases the physical appearance is a more important gauge of miscibility. The results of these examples are shown in Table XIII. EXAMPLES 120 to 125 Examples 120 and 121 show that Dylark 332 (approximately 86/14 - styrene/maleic anhydride, by our analysis) is miscible with a 67% imidized alkylated methyl imide (imide from Example 59), but not with the corresponding unalkylated imide (imide from Example 58). An ammonia imide was prepared by treating Dylark 332 at 49 g/m and 260°C in an extruder with 3.9 g/m anhydrous ammonia at 2826 kPa or 410 psig. according to US-A-4246374. The resulting imide contained from 0.000 to 0.070 meq/g of acidic functionality and had a nitrogen level of 1.88 weight percent (for 14.1% maleimide, % N theoretical = 2.01%), indicating about 94 weight % imidization. The Vicat for Dylark 332 was 136°C, (Tg = 130°C) and for the ammonia imide was 151°C (Tg = 145°C). When the same unalkylated and alkylated methyl imides used in Examples 120 and 121 were melt blended with this Dylark-based ammonia imide, both blends were observed to be largely to completely miscible, indicating an inherently greater interaction between the acrylic imides and the maleimides versus the maleic anhydride polymer. When the Dylark 332 ammonia derivative was melt blended with a more highly imidized, unalkylated (Example 124) and alkylated (Example 125) acrylic imide, miscibility differences could again be observed between the alkylated and unalkylated blends. Following the previous pattern, the alkylated imide (imide F, Example 125) was completely miscible, while the unalkylated imide (imide E, Example 124) was only partially miscible. EXAMPLES 126 to 134 Examples 126 to 134 show that polyvinylidene fluoride (Kynar 720) is miscible with alkylated methyl imide but not unalkylated methyl imide (at this imidization level), thus following the same pattern as seen previously. The blends in examples 128 and 129 were prepared on a Brabender melt-mixing device, while examples 130 to 134 were extrusion blended on a 1" (25 cm) Killion extruder. Kynar polyvinylidene fluoride (PVDF) is a crystalline polymer which shows a large crystallization endotherm (CE) by DSC analysis, which obscures any nearby amorphous Tg in polyvinylidene fluoride and any nearby Tg in the blended imide polymer (Example 128). Since it is crystalline, it is also translucent to opaque. The miscibility of polyvinylidene fluoride and the imide from Example 65 (Example 129) supresses crystallization, giving an amorphous polymer blend with a single Tg. The levels of clarity and Tg's of the blends indicate that while either miscibility or mixing was not complete in all samples, the level of miscibility was quite high. The tensile properties of the imide/Kynar blends also indicate that as little as 5% Kynar polymer gives a ductile material as measured by tensile elongation. The percent elongation to break for Examples 126 and 130-134 are: 5% for Example 126, (no yield), 11% for Example 134, (greater than 6% elongation indicates yielding), 67% for Example 133, 72% for Example 132, 83% for Example 131, and 101% for Example 130. That imides may be used to provide an amorphous polyvinylidene fluoride is also clear from these results. EXAMPLES 135 to 143 The miscibility of Kynar 720 polyvinylidene fluoride (PVDF) may be exploited to provide enhanced impact resistance in glutarimide blends containing grafted rubber impact modifiers. Example 135 shows typical impact, tensile, and heat-distortion temperature data for an impact-modified blend of unalkylated, 170°C Vicat methylimide, in which the impact modifier (A) was designed to give a high notched Izod impact resistance. Example 136 shows that the same glutarimide, when alkylated, maintains good isotropic impact resistance (Gardener falling dart impact, GVHIT), but loses notched Izod impact resistance. However, when the modifier (B) is specifically designed for the difference in miscibility of the alkylated glutarimide (Example 138), an excellent notched Izod and falling dart impact resistance is maintained. These values diminish in the unalkylated glutarimide (Example 137). Examples 139 and 140 show that as small amounts of PVDF are substituted for the alkylated glutarimide in the modifier B formulation, surprisingly large increases in notched Izod impact value are observed. At 10% PVDF, the impact resistance is high enough to remove 10% rubber modifier and still maintain good impact resistance (Example 141). Fixing the PVDF level at 10% in the formulation in Example 140, and substituting modifier A again shows that lower, but good notched Izod impact values are still obtained. EXAMPLES 144 to 153 As noted in US-A-4255322, methyl imides and polyvinyl chloride (PVC) resins are miscible over a relatively wide range. However, we have found that high imidization levels, high imide acid levels, and changes in the polyvinyl chloride resins can cause immiscibility in certain instances. Examples 144-153 illustrate that reducing the acid and anhydride functionality of the glutarimide can correct such immiscibility. Example 144 shows a 50/50 glutarimide/polyvinyl chloride blend (Geon 103 PVC with a K value of 67) is only partially miscible, giving two sharply defined Tg values, while the same blend, made with alkylated glutarimide (Example 145), is completely miscible. However, when these same imides are melt blended with a lower molecular weight PVC (Example 146) (Geon 85, K value = 62), both alkylated (Example 147) and unalkylated (Example 146) glutarimides are completely miscible with the PVC. Although the Geon 85 resin appears to be more miscible with imides at lower imidization levels, only partial miscibility is observed with this resin when glutarimides having even higher imidization and acid levels are blended with the PVC resin as in Example 148. This example shows one very broad and uneven Tg by DSC, indicating partial miscibility, whereas the same glutarimide, when alkylated (Example 149), shows complete miscibility and one sharp Tg. The indices of refraction of the glutarimides having 90% imidization or greater are close enough to the PVC refractive index so that appearance is not a conclusive factor. Examples 150-153 show that the same enhanced miscibility seen with alkylated glutarimides (Examples 144 and 145) is also seen in the two formulations given below, which represent typical polyvinyl chloride siding formulations for twin-screw extruder applications, and which are based on the less-miscible Geon 103 PVC. In the blends and siding formulations, we have also observed that the alkylated imide/PVC materials of the present invention show a better combination of properties than the unalkylated PVC/glutarimide blends. A given, alkylated PVC/glutarimide blend may show less color generation, a lower initial viscosity, a slower viscosity rise (as measured by torque in Brabender melt processing experiments), high impact resistance and heat distortion resistance. Component: PVC Formulation I (PVC I) PVC Formulation II (PVC II) Geon 103 100.0 100.0 MMA/EA proc. aid 0.5 1.0 BA/S//S/MMA proc. aid 1.0 0.5 Me-Tin stabilizer 1.6 1.6 Calcium stearate 1.3 1.3 Paraffin wax 1.0 1.0 TiO₂ 10.0 10.0 Results of these Examples are given in Table XVII. EXAMPLES 154 to 207 The following examples illustrate polyimide blends having 90/10 and 10/90 weight ratios. These blends show that the enhancement of properties can occur for blends containing both small and large amounts of the glutarimides having reduced acid and anhydride functionality. The glutarimides used were prepared in the manner of Examples 52 and 56, respectively; the glutarimide sample treated according to the present invention contained 7.18 weight percent nitrogen and had a weight-average molecular weight of 129,000, and the comparative glutarimide without reduction of the acid and anhydride functionality contained 6.87 weight percent nitrogen and had a weight-average molecular weight of 145,000. Additional properties of the glutarimides, the polymers used for blending, and the blends are given in Table XVIII. EXAMPLES 208 to 219 The following examples illustrate blends of polyglutarimide copolymers with polystyrene (Sty) and polyphenylene oxide-high impact polystyrene blends (HIPS/PPO; Noryl, General Electric). The polyglutarimides having acid and anhydride functionality reduced according to the present invention were an imidized 90/10 methyl methacrylate/styrene (MMA/Sty) copolymer having a nitrogen content of 4.95 weight percent (Example 209), and an imidized, 73.5/24.5/2.0 methyl methacrylate/ alpha -methylstyrene/ethyl acrylate (MMA/AMS/EA) terpolymer having a nitrogen content of 2.93 weight percent (Example 211). The corresponding polymers not having reduced acid and anhydride functionality (Examples 208 and 210) contained 4.90 and 3.08 weight percent nitrogen, respectively. Additional properties of the polyglutarimides and blends are given in Table XIX. EXAMPLES 220 to 253 The following examples illustrate a series of 50/50 polyglutarimide/thermoplastic blends that were prepared in a Brabender mixer at the temperature indicated in the accompanying Table; an air atmosphere was used. The polyglutarimide used is the polymethylimide F (Example 63), having a Vicat value of 157°C, a Tg of 158°C, 84% imidization, by weight, and a total acid and anhydride functionality of 0.011 meq/g, reduced according to the present invention. The properties of the blends are given in Table XX. EXAMPLE 254 In a manner similar to that of Examples 242-253, a 50/50 blend of the polyglutarimide from Example 20 with alpha -methylstyrene/acrylonitrile copolymer was prepared at 246°C; the resulting clear blend had a single Tg of 138°C. EXAMPLE 255 In a manner similar to that of Example 233 a 50/50 blend of polyglutarimide (having a Vicat value of 160°C, a Tg of 158°C; 82% imidization and 0.002 meq/g total acid and anhydride functionality, reduced according to the present invention) with Noryl (polyphenylene oxide-high impact polystyrene blend) was prepared. The resulting opaque blend showed Tg values at 158°C and 138°C. Adhesion-enhanced impact resistance is expected in blends of polycarbonates with impact modifiers, and the polyglutarimides of the present invention; such blends using untreated polyglutarimides are disclosed in US-A-4254232. Improved miscibility leads to better bonding, and thus to improved impact resistance. In general, all polyglutarimides disclosed in US-A-4246374, especially those polymeric glutarimides containing up to 20% of the lower alkyl acrylates, which contain any residual acid or anhydride functionality, may be effectively treated by the methods disclosed above, such as the method described in Examples 7 and 30, to give polymeric glutarimides with reduced or substantially eliminated acid functionality. The following words are Trademarks which may be registered in some or all designated states: Blendex, Dylark, Kynan, Killion, Brabender, Geon, Barex, Kodar, Grilamid, Noryl, Trogamid, Kodar, Ardel, Udel, Zytel, Fosta, Celanex and Abson.

Claims: A thermoplastic polymer comprising glutarimide groups and optionally acid and/or anhydride functional groups and having a degree of imidization of at least 1% to less than 95% characterized in that the degree of imidization (weight percentage of imide groups on the polymer in relation to the groups on the polymer capable of being reacted to form imide groups) on said polymer and the corresponding carboxylic acid, carboxylic acid salt, and/or anhydride functionality on said polymer are as set forth in the Table below; the degree of imidization on said polymer is the milliequivalents of acid, acid salt and/or anhydride per gram of imidizable polymer component from 1% to 10% 0 to 0.20 above 10% to 20% 0 to 0.28 above 20% to 30% 0 to 0.32 above 30% to 40% 0 to 0.31 above 40% to 50% 0 to 0.28 above 50% to 60% 0 to 0.28 above 60% to 70% 0 to 0.27 above 70% to 80% 0 to 0.28 above 80% to 90% 0 to 0.33 and above 90% to less than 95% 0 to 0.40 A polymer according to claim 1 wherein the degree of imidization on said polymer is from 40% to 88%, preferably from 50% to 85%, and the milliequivalents of acid and/or anhydride present is from 0 up to 0.25, preferably less than 0.25. A polymer as claimed in claim 1 or claim 2, wherein said polymer contains up to 50%, preferably from 10% to 50%, by weight, of acrylic or methacrylic acid ester units. A polymer as claimed in claim 1 or claim 2, wherein said polymer contains from 50% to 99%, by weight, of ester units derived from acrylic or methacrylic acid. A polymer as claimed in claim 3 or claim 4, where in the ester moiety contains from 1 to 20 carbon atoms, preferably the ester moiety is methyl. A polymer according to any one of the preceding claims, wherein said polymer is a multistage polymer and either the outermost stage and/or the core and/or any other intermediate stage if present of said polymer comprises imide groups. A process for the preparation of a thermoplastic polymer comprising glutarimide groups and optionally acid and/or anhydride functional groups and having a degree of imidization (weight percentage of imide groups on the polymer in relation to the groups on the polymer capable of being reacted to form imide groups) of at least 1% to less than 95%, said process comprising reacting a first polymer comprising imide groups and active carboxylic acid, carboxylic acid salt and/or anhydride groups with a predetermined amount of blocking agent for said active groups to reduce or substantially eliminate said groups in the polymer to a level wherein the degree of imidization on said polymer and the corresponding acid, acid salt and/or anhydride functionality on said polymer are as set forth in the Table below: the degree of imidization on said polymer is the milliequivalents of acid, acid salt and/or anhydride per gram of imidizable polymer component from 1% to 10% 0 to 0.20 above 10% to 20% 0 to 0.28 above 20% to 30% 0 to 0.32 above 30% to 40% 0 to 0.31 above 40% to 50% 0 to 0.28 above 50% to 60% 0 to 0.28 above 60% to 70% 0 to 0.27 above 70% to 80% 0 to 0.28 above 80% to 90% 0 to 0.33 and above 90% to less than 95% 0 to 0.40 A process as claimed in claim 7, wherein said process is carried out at a temperature of from 50°C to 450°C. A process as claimed in claim 7 or claim 8, where in said process is carried out at a pressure of from 1 atmosphere (101.3 KiloPascals) to 1000 atmospheres (101300 KiloPascals). A process as claimed in any one of claims 7 to 9, wherein said blocking agent is an alkylating agent and/or esterification agent. A process as claimed in claim 10, wherein said blocking agent is one or more of orthoesters, ketals, carbonates, sulfoxides, siloxanes, silyl ethers, silylenol ethers, trialkyl phosfates, trialkyl phosfites, dialkyl sulfates, alkyl alkylsulfonates, alkyl arylsulfonates, carbodiimides, trialkylsilyl halides, enol esters, alcohols, alkyl esters, alkyl isocyanates, quaternary ammonium salts, ureas and/or guanidines; and is preferably one or more of dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, diethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluenesulfonate, methyl trifluoromethylsulfonate, methyl acetate, methanol, ethanol, methyl isocyanate , p-chlorophenyl isocyanate, dimethyl carbodiimide, dimethyl t-butylsilyl chloride, isopropenyl acetate, dimethyl urea, tetramethyl ammonium hydroxide, dimethyl diethoxysilane, tetra-n-butoxysilane, dimethyl(trimethylsily) phosfite, trimethyl phosfite, trimethyl phosfate, and tricresyl phosfate. A process as claimed in any one of claims 7 to 11, wherein said reaction is conducted in a single or multi-screw extruder, in an autoclave, in a continuously recirculated pipe reactor, in a baffled in-line mixer which may be used in series with an extruder, in a wiping-film evaporator, a falling film reactor or evaporator or in a disc extruder or reactor. A process as claimed in any one of claims 7 to 12 wherein said polymer has a degree of imidization of from 10% to less than 95%. A blend of at least one thermoplastic polymer and a second polymer, said second polymer being a polymer as claimed in any one of claims 1 to 6 or a polymer prepared by the process as claimed in any one of claims 7 to 13. A blend according to claim 14, wherein said second polymer is present in an amount of from about 1% to about 99%, based on the total weight of said thermoplastic polymer plus said second polymer.

Inventors: BORTNICK, NEWMAN MAYER, COHEN, LESLIE ALAN, FREED, WILLIAM THAYER, FROMUTH, HARRY CHARLES, JR., HALLDEN-ABBERTON, MICHAEL PAUL
Applicants: ROHM AND HAAS COMPANY
Application year: 1986
Main classification: C08F8
IPC codes: C08F8, C08L35, C08F20, C08L101, C08L33, C08L57