Preparation of poly (arylene ether ketones) |
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| 申请号 | EP87200609.3 | 申请日 | 1984-03-30 | 公开(公告)号 | EP0243997A1 | 公开(公告)日 | 1987-11-04 |
| 申请人 | RAYCHEM CORPORATION (a Delaware corporation); | 发明人 | Jansons, Viktors; Gors, Heinrich Carl; | ||||
| 摘要 | A process for producing an aromatic polyketone which comprises polymerizing an appropriate monomer or monomers by a Friedel-Crafts polymerization reaction using a Lewis acid catalyst . The reaction is conducted under specified conditions depending on the monomer system to control the reaction to obtain melt-processable, high molecular weight, substantially linear polymers, for example poly(carbonyl-p-phenylene-oxy-p-phenylene), poly(carbonyl-p-phenylene-oxy-p-phenylene-oxy-p-phenylene), and the like. Copolymers containing up to 30% by weight of an aromatic sulfonyl halide comonomer can also advantageously be produced by this process. |
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| 权利要求 | |||||||
| 说明书全文 | This invention relates to a method of preparing poly(arylene ketones) and in particular to an electrophilic polymerization process for preparing such polymers. Poly(arylene ether ketones), in particular all para-linked poly(arylene ether ketones), possess many desirable properties, for example, high temperature stability, mechanical strength, and resistance towards common solvents. The preparation of poly(arylene ether ketones) by two different approaches has been described in the literature. The first approach is an electrophilic synthesis in which an aryl ketone linkage is formed. The second is a nucleophilic synthesis in which an aryl ether linkage is formed. This invention is directed to an improved electrophilic synthesis for preparing poly(arylene ether ketones), in particular para-linked poly(aryl ether ketones). In such an electrophilic synthesis, the polymerization step involves the formation of an aryl ketone group from a carboxylic acid or acid derivative group and an aromatic compound containing an aromatic carbon bearing an activated hydrogen atom, i.e., a hydrogen atom displaceable under the electrophilic reaction conditions. The monomer system employed in the polymerization can be, for example, (a) a single aromatic compound containing both a carboxylic acid or acid derivative group as well as an activated hydrogen atom on an aromatic carbon for example, p-phenoxybenzoyl chloride; or (b) a two-component system of a dicarboxylic acid or acid derivative and an aromatic compound containing two activated hydrogen atoms, for example, 1,4-diphenoxybenzene and terephthaloyl chloride. Electrophilic polymerization of this type is often referred to as Friedel-Crafts polymerization. Typically, such polymerizations are carried out in a reaction medium comprising the reactant(s), a catalyst, such as anhydrous aluminum trichloride, and solvent such as methylene chloride, carbon disulfide, nitromethane, nitrobenzene, or orthodichlorobenzene. Because the carbonyl groups of the reactant(s) and products complex with aluminum trichloride and thereby deactivate it, the aluminum trichloride catalyst is generally employed in an amount greater than one equivalent for each equivalent of carbonyl groups in the reaction medium. Other inorganic halides such as ferric chloride may be employed as the catalyst. Such Friedel-Crafts polymerizations generally have produced an intractable reaction product difficult to remove from the reaction vessel and purify. Further, such processes have tended to produce polymer of undesirably low molecular weight and/or of poor thermal stability. The all para-linked poly(arylene ether ketones) have been particularly difficult to prepare under such Friedel-Crafts conditions. One factor that appears to contribute to the unsatisfactory results reported in the literature is that the para-linked polymers are more highly crystalline than the ortho, meta or mixed isomeric members of this polymer family and are therefore generally more insoluble in the reaction media typically used in such Friedel-Crafts reactions. This tends to result in the premature precipitation of the polymer in low molecular weight form. Another factor that may lead to these poor results is deactivation of the terminal aryloxy groups by complexation with aluminum chloride or alkylation of the terminal group which prevents further growth of the polymer chain. Also, side reactions, particularly at the ortho position of activated aromatic rings can result in a polymer that is branched and/or is more likely to cross-link at elevated temperatures such as those required for melt processing the polymer. It is generally recognized that in Friedel-Crafts reactions, ortho substitution of the polymer is more likely to occur if the reaction is conducted at elevated temperatures and/or for a relatively long reaction time. U.S. Patents No. 3,065,205 to Bonner , U.S. Patent No.3,767,620 to Angelo et al , 3,516,966 to Berr, 3,791,890 to Gander et al, 4,008,203 to Jones and U.K. Patents No. 971,227 and 1,086,021 both to Imperial Chemical Industries, Limited, disclose the preparation of poly(arylene ketones) by Friedel-Crafts polymerization and generally acknowledge some of the difficulties in producing tractable, melt-stable polymers. For example, Gander et al provide a method of producing the polymers in granular form by special treatment of the reaction mixture before gellation can occur and Angelo et al provide a method of treating the polymer to reduce undesired end groups which result from side reactions during polymerization and which cause thermal instability of the polymer. To overcome the disadvantages encountered in producing poly(arylene ketones) by the above described Friedel-Crafts polymerization, it has been proposed to use boron trifluoride catalyst in anhydrous hydrogen fluoride. as described for example, in U.S. Patents 3,44l,538 to Marks, 3,442,857 to Thornton, 3,953,400 to Dahl, and 3,956,240 to Dahl et al. This general process has been used commercially to produce polymer of the desired high molecular weight and thermal stability. However, the use of boron trifluoride and hydrogen fluoride requires special techniques and equipment making this process difficult to practice on a commercial scale. We have now discovered an improved method for the production of poly(arylene ether ketones) by an electrophilic synthesis which results in high molecular weight, thermally stable polymers using reaction media that are readily handled on a commercial scale. In the method of this invention, the Friedel-Crafts polymerization of appropriate monomer systems, as defined more fully hereinafter, is controlled to suppress side reactions including ortho substitution, alkylation and chain branching and/or to solubilize or swell the polymer, by conducting the reaction under select reaction conditions and proportions of reactants. By this method, a thermally stable, linear poly(arylene ether ketone) substantially free of pendant groups resulting from ortho substitution of para-linked aromatic rings in the polymer backbone can be obtained. The invention accordingly provides a method of producing a poly(arylene ether ketone) which comprises polymerizing a monomer system comprising:
The method of this invention provides a high reaction rate which enables the reaction to be carried out at relatively low temperatures over a relatively short period of time. Further, the polymer is maintained in the reaction medium, for example in solution or in a reactive gel state, until high molecular weight polymer is obtained. Further, the polymer pro duced is essentially linear with little, if any, ortho substitution process of this invention maintains the polymer in solution or in a more tractable state, recovery and purification of the polymer is greatly facilitated. The polymers produced by the process of the invention have repeat units of the general formula -Ar-O-Ar-CO- wherein each Ar is independently selected from substituted and unsubstituted phenylene and substituted and unsubstituted polynuclear aromatic moieties. The term polynuclear aromatic moieties is used to mean aromatic moieties containing at least two aromatic rings. The rings can be fused, joined by a direct bond or by a linking group. In certain of the monomers, e.g. the polynuclear aromatic comonomers, the acid halide monomes and certain diacid dihalides, at least two of the aromatic rings are linked by an ether oxygen linkage. Other linking groups which can join aromatic rings in the aromatic moieties include, for example, carbonyl, sulfone, sulfide, amide, imide, azo, alkylene, perfluoroalkylene and the like. The phenylene and polynuclear aromatic moieties can contain substitutents on the aromatic rings. These substituents should not inhibit or otherwise interfere with the polymerization reaction to any significant extent. Such acceptable substituents include, for example, phenyl, halogen, nitro, cyano, alkyl, 2-aralkenyl, alkynyl and the like. These polymers are prepared in accordance with this invention by polymerising an appropriate monomer system from those defined above. Aromatic diacid dihalide employed is preferably a dichloride or dibromide. Illustrative diacid dihalides which can be used include, for example Illustrated polynuclear aromatic comonomers which can be used with such diacid halides are:
Monomer systems II and III comprise an acid halide. (The term acid halide is used herein to refer to a monoacid monohalide.) In monomer system II, the acid halide is of the formula H-Ar-O-[(Ar-CO)p-(Ar-O) Such monomers include for example, where k = O In monomer system III, the acid halide is of the formula H-(Ar-O)n-Ar-Y Examples of such acid halides include It is to be understood that combinations of monomers which fall within the same proviso clause, as set forth above, can be employed. For example, one or more diacid dihalides can be used with one or more polynuclear aromatic comonomers as long as the correct stoichiometry is maintained. Further, one or more acid halides can be included. In addition monomers which do not contain an ether linkage can be employed as long as one or more of the comonomers used contains at least one ether oxygen linkage. Such comonomers include for example: The term "Lewis acid" is used herein to refer to a substance which can accept an unshared electron pair from another molecule. Lewis acids which can be used in the practice of this invention include, for example, aluminum trichloride, aluminum tribromide, antimony pentachloride antimony pentafluoride, indium trichloride, gallium trichloride, boron trichloride, boron trifluoride, zinc chloride, ferric chloride, stannic chloride, titanium tetrachloride, and molybdenum pentachloride. The use of substantially anhydrous aluminum trichloride as the Lewis acid is preferred. The amount of Lewis acid used in the practice of this invention varies depending on the particular monomers and reaction medium selected. In all instances at least about one equivalent of Lewis acid per equivalent of carbonyl groups present in the monomer system is used plus an amount effective to act as a catalyst for the polymerization (also referred to herein as a catalytic amount). Generally a catalytic amount added is from about 0.05 to about 0.3 equivalents of Lewis acid per equivalent of acid halide in the reaction mixture. Additional amounts of Lewis acid are also required depending on the nature of the monomers and the reaction conditions in a manner as set forth below. Further, if a comonomer containing other basic species, such as sulfone groups, is used, additional Lewis acid may be required. In this invention, suppression of side reactions results in a polymer that is thermally stable, that is it does not degrade or cross-link when subjected to elevated temperatures, e.g. temperatures above the melting point of the polymer, for a period of time. For a polymer of this type to be suitable for melt processing, it must be able to withstand the processing temperatures for the required processing time. Typically these conditions require that the polymer can withstand temperatures up to about 30°C above the melting or softening point of the polymer for periods of at least 30 minutes, preferably at least 60 minutes and most preferably at least 90 minutes, without undesired gel formation or substantial change in inherent viscosity. The temperature at which the reaction is conducted can be form about -50°C to about +l50°C. It is preferred to start the reaction at lower temperatures, for example at about -50 to about -l0°C particularly if the monomer system contains highly reactive monomers. After polymerisation has commenced, the temperature can be raised if desired, for example, to increase the rate of reaction. It is generally preferred to carry out the reaction at temperatures in the range of between about -30°C and +25°C (room temperature). It is believed that the aromatic rings which are particularly susceptible to ortho substitution are active aryloxy groups. Such groups are referred to herein as undeactivated aryloxy groups. By "undeactivated aryloxy group" is meant an aryloxy group which is in a molecule in which there are no deactivating groups or is located at least two aromatic moieties (i.e. Ar as defined above) away from a deactivating group such as a carbonyl. Conversely a "deactivated aryloxy group" is an aryloxy group separated from a deactivating group usually carbonyl, by an aromatic group containing one aromatic ring, fused aromatic rings or aromatic rings linked by direct bonds. A non-protic diluent can also be employed, if desired. Advantageously, the diluent should dissolve the Lewis acid/Lewis base complex and the resulting polymer/Lewis acid complex. It should also be relatively inert toward Friedel-Crafts reactions. The diluent is preferably somewhat polar as measured by its dielectric constant and solubility parameter. Preferably the dielectric constant of the diluent is at least about 2.5 at 24°C, and preferably in the range of from about 4.0 to about 25 at 24°C. The Hildebrand solubility parameter of the diluent is preferably at least about 7.2 [cal/cm³]1/2 and is preferably in the range of from about 9.2 to about 15 [cal/cm³]1/2. Preferred diluents include, for example, methylene chloride, carbon disulfide, o-dichlorobenzene, 1,2,4-trichlorobenzene, o-difluorobenzene, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane and mixtures thereof. The diluent is used in an amount from 0 to about 93% by weight, based on the weight of the total reaction mixture. As is known in polymerizations of this type, the reactions can be run neat, that is without the presence of a diluent. As discussed in more detail below, it has been found that the monomer to diluent molar ratio can contribute to control of the polymerization reaction to yield the desired product. Typically the diluent is used in an amount of at least about l0%, preferably at least about 20% by weight based on the weight of the reaction mixtures. Use of an alkylating or acylating diluent can lead to undesired side reactions as mentioned above. When such solvents are employed control of the polymerization by techniques taught in this specification suppresses such alkylation or arylation. The result is a thermally stable, melt processable, essentially linear polymer. The term substantial absence of Lewis base is used herein to refer to reaction mixtures to which no Lewis base is added as a controlling agent. Minor amounts of Lewis base may be generated in situ during the polymerization reaction, but such amounts are inadequate to control the reaction. The reaction conditions required depend on the reactivity of the monomers used. Two general classes of monomers need to be considered - those containing undeactivated aryloxy groups as defined above and those which do not. If any monomer in the monomer system contains an undeactivated aryloxy group, the amount of Lewis acid used generally should not exceed a certain amount. Monomer systems which can be used in the practice of this invention have been defined above with consideration of the reactivity of the aryloxy groups present. The conditions under which the polymerization will be controlled to produce the desired product can then be set forth, with further requirements provided where the relative activity of the acid halide groups make this necessary. Monomer systems that contain undeactivated aryloxy groups are I wherein the comonomer is as defined in I(ii)(a), I(ii)(b), I(ii)(d) and III. In general, when monomers of this type are used the amount of Lewis acid present in addition to the above noted one equivalent per equivalent of carbonyl groups present plus an amount effective to act as a catalyst for the polymerization, should be up to 0.8 equivalents per equivalent of undeactivated aryloxy groups. Preferably even less than that should be used, for example less than about 0.6 equivalents and most perferably less than about 0.4 equivalents per equivalent of undeactivated aryloxy groups present. However, because of the reactivity of certain polynuclear diacid dihalides such as diphenyl ether dicarbonyl dichloride, it has been found desirable to employ a different amount of Lewis acid when such diacid dihalides are used in the monomer system. When such polynuclear diacid dihalides are used in monomer system I with a comonomer defined in I(ii)(a), I(ii)(b) and I(II)(d) it is often desirable to add further Lewis acid up to about 0.5 equivalents per equivalent of acid halide groups. Preferably the further amount added is between about 0.03 and 0.5 equivalents per equivalent of acid halide groups. we have found that meta-benzene dicarbonyl dichloride is sufficiently reactive and the product suffieciently soluble in the reaction medium that it is not necessary to limit the maximum excess of Lewis acid to obtain high molecular weight polymer. However, to prepare polymers which are at least partly crystalline from monomer systems including substantial amounts of less reactive para benzene dicarbonyl dichlorides, it is very beneficial to use an amount of Lewis acid in excess of that defined in A) above by an amount of up to about 0.8 equivalents per equivalent of undeactivated aryloxy groups in the monomers. Crystallinity of the polymers may be measured by standard techniques such as differential scanning calorimetry or X-ray diffraction. It has also been found to be necessary when the monomer system used is I with the comonomer being that defined in I(ii)(a), I(ii)(b) or I(ii)(d) that the concentration of monomers in the reaction mixture be at least about 7%, preferably at least about 10%, and most preferably at least about 15%, by weight based on the total weight of the reaction mixture. When the monomer system employed is III, it is also desirable to conduct the reaction at similar monomer concentrations. The second general class of monomers are monomer systems which contain no undeactivated aryloxy groups. Monomers of this type are set forth in monomer system I wherein the comonomer is as defined in I(ii)(c) and II. With this class of polymers it is preferred to use a large excess of Lewis acid, the excess depending on the particular monomer to diluent molar ratio (D). Generally, it is preferred to have a relatively high monomer to diluent ratio and a relatively large excess of Lewis acid. The amount of excess Lewis acid (in addition to the above noted equivalent per equivalent of carbonyl groups plus a catalytic amount) is at least about 0.6 + (0.25 × tanh [50(0.1-D)]) equivalents per equivalent of acid halide groups. The amount of excess Lewis acid is preferably at least about 0.8 + (0.25 × tanh [50(0.1-D)]) and most preferably is at least about 1.0 + (0.25 × tanh [50(0.1-D)]) equivalents per equivalent of acid halide groups. When the monomer to diluent molar ratio is greater than about 0.15, the amount of Lewis acid in excess of the standard amount is at least about 0.3 equivalents per equivalent of acid halide groups. In general, it is preferred to add Lewis acid in a substantial excess of the minimum amounts specified. Generally, at least about 0.5 equivalent and preferably at least about 1.0 equivalents of additional Lewis acid, per equivalent of acid halide groups are used. The reaction conditions found to be necessary to prepare melt-processable, high molecular weight, substantially linear poly(arylene ether ketones) are not taught or suggested by the prior art and in fact are contrary to the generally held beliefs of Friedel-Crafts chemistry. Conventionally, a moderate excess of Lewis acid usually about 0.4 equivalents per equivalent of carbonyl groups in the monomer system is used in Friedel-Crafts reactions. Applicant has found that when all aryloxy groups present in the monomer system are deactivated by carbonyl groups as defined above, a large excess of Lewis acid must be used. This is illustrated in Figure 1, by a graph showing the relationship between the amount of Lewis acid used and the molecular weight of the polymer as measured by inherent viscosity as described below. Prior art Friedel-Crafts polymerization reactions of this type were conducted using a Lewis acid to monomer ratio well below that needed for the production of polymer having the desired inherent viscosity or used monomer to diluent molar ratios below that required. This is illustrated in Figure 1, where it is shown that at least 2 equivalents of aluminum chloride per equivalent of monomer are required when preparing poly(carbonyl-p-phenylene-oxy-p-phenylene). Prior art processes used aluminum chloride to monomer ratio shown to produce polymer of lower inherent viscosity, as shown on the graph, or where there are undeactivated aryloxy groups present in the monomer system, it has been found to be necessary to add a smaller excess of Lewis acid than taught in the prior art but to maintain a relatively high monomer concentration in the reaction mixture. As mentioned above, this results in suppression of side reactions, particularly in the ortho position of para-linked aromatic rings in the polymer chain. Traditional Friedel-Crafts chemistry suggests the use of a moderate excess of Lewis acid and a more dilute reaction mixture to achieve these results. Applicants have found the opposite to be necessary in the preparation of poly(arylene ether ketones). As mentioned above, one of the important features of this invention is that poly(arylene ketones) of high molecular weight can be obtained. By "high molecular weight" is meant polymer having an inherent viscosity greater than about 0.6. Preferably the polymer prepared by the process of this invention has an inherent viscosity in the range of about 0.6 to about 2.0. Polymers having an inherent viscosity below about 0.6 are generally not useful because they have poor mechanical properties, such as tensile strength and elongation. They also tend to be brittle while polymers having an inherent viscosity above about 2.0 are very difficult to melt process. Throughout this application, inherent viscosity refers to the mean inherent viscosity determined according to the method of Sorenson et al, "Preparative Methods of Polymer Chemistry" Interscience (1968), at page 44 [0.1g polymer dissolved in 100 ml of concentrated sulfuric acid at 25°C]. If desired, the molecular weight of the polymer, the degree of branching and amount of gelation can be controlled by the use of, for example, capping agents as described in U.S. Patent No. 4,247,682 to Dahl. The molecular weight of the polymer can also be controlled by a polymerization reaction utilizing a two-monomer system as described above, by employing a slight excess of one of the monomers. Capping agents, when employed, are added to the polymerization reaction medium to cap the polymer on at least one end of the polymer chain. This terminates continued growth of that chain and controls the resulting molecular weight of the polymer, as shown by the inherent viscosity of the polymer. Judicious use of the capping agents results in a polymer within a selected narrow molecular weight range, decreased gel formation during polymerization, and decreased branching of the polymer chains and increases melt stability. Both nucleophilic and electrophilic capping agents are used to cap the polymer at each end of the chain. Preferred nucleophlic capping agents are 4-chlorobiphenyl, 4-phenoxybenzophenone, 4-(4-phenoxyphenoxy)benzophenone, biphenyl 4-benzenesulfonylphenyl phenyl ether, and the like. Typical electrophilic capping agents are compounds of the formula Arʺ-CO-E or Arʺ-SO₂-E wherein Arʺ is phenyl, 3-chlorophenyl, 4-chlorophenyl, 4-cyanophenyl, 4-methylphenyl or an aromatic group substituted with an electron withdrawing substituent and E is halogen or other leaving group. Preferred electrophilic capping agents include benzoyl chloride, benzenesulfonyl chloride and the like. As mentioned above, Lewis acid is present in the reaction medium as the catalyst for the Friedel-Crafts polymerization reaction. The resulting polymer contains Lewis acid complexed to the carbonyl groups of the polymer. For many polymerizations, the Lewis acid is complexed to substantially all the carbonyl groups in the polymer. As is well known with polymers of this type, the catalyst residue must be removed, i.e. the Lewis acid must be decomplexed from the polymer and removed. A method for removing the catalyst residue is described in U.S. Patent No. 4,237,884 to Dahl. Decomplexation can be accomplished by treating the polymerization reaction mixture with a decomplexing base after completion of polymerization. The base can be added to the reaction medium or the reaction medium can be added to the base. The decomplexing base must be at least as basic towards the Lewis acid as the basic groups on the polymer chain. Such decomplexation should be effected before isolation of the polymer from the reaction mixture. The amount of decomplexing base used should be in excess of the total amount of bound (complexed) and unbound Lewis acid present in the reaction mixture and is preferably twice the total amount of Lewis acid. Typical decomplexing bases which can be used include water, dilute aqueous hydrochloric acid, methanol, ethanol, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, pyridine, dimethyl ether, diethyl ether, tetrahydrofuran, trimethylamine, trimethylamine hydrochloride, dimethyl sulfide, tetramethylenesulfone, benzophenone, tetramethylammonium chloride, isopropanol and the like. The decomplexed polymer can then be removed by conventional techniques such as adding a nonsolvent for the polymer which is a solvent for or miscible with the Lewis acid/Lewis base complex and the Lewis acid; spraying the reaction medium into a non-solvent for the polymer; separating the polymer by filtration; or evaporating the volatiles from the reaction medium and then washing with an appropriate solvent to remove any remaining base/catalyst complex and diluent from the polymer. |
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