Wholly aromatic polyamide copolymer

Abstract: A wholly aromatic polyamide copolymer having excellent heat, flame and chemical resistances, solubility in organic solvents and shaping property and useful for shaped articles having a high mechanical strength and modulus of elasticity, comprising the repeating units of the formulae: and wherein X = a halogen atom, n, or m = 1 to 4 and n + m = 1 to 8.

Description: BACKGROUND OF THE INVENTION (1) Field of the Invention The present invention relates to a wholly aromatic polyamide copolymer. More particularly, the present invention relates to a wholly aromatic polyamide copolymer containing, as a portion of the aromatic diamine moiety, a chloro-benzidine structure and having an excellent heat, flame and chemical resistance, solubility in organic solvents and shaping property, and useful for shaped articles having a superior mechanical strength and modulus of elasticity. (2) Description of the Related Arts It is known that wholly aromatic polyamide (aramid) resins have a superior mechanical strength and modulus of elasticity and an excellent heat resistance, and thus are useful for fibers, films and other shaped articles. Especially, a para type aramide resin, namely poly-p-phenylene terephthalamide (PPTA) resin, is a typical aramide resin useful for industrial materials and protecting devices in which the specific properties of the aramide resins are effectively utilized. Nevertheless, the PPTA resin poses problems in the polymerization thereof and has an unsatisfactory spinnability and formability due to a high rigidity or stiffness of the PPTA molecules. For example, in the production process of the PPTA resin, hexamethylphosphortriamide, which has a high toxity for the human body and other life-forms, must be used as a polymerization medium. Also, in the production of PPTA fibers, films or other shaped articles, a concentrated sulfuric acid must be employed to prepare a liquid crystalline dope solution of the PPTA resin and a liquid crystal spinning or shaping procedure must be carried out. After this procedure, the sulfuric acid in the resultant product must be neutralized with a large amount of a neutralizing agent. Also, the resultant product (fibers or other shaped articles) contains inorganic ions derived from the sulfuric acid and the the neutralizing agent, and these inorganic ions cause a lowering of the quality of the product. Further, removal of the inorganic ions raises the cost of the resultant product. To eliminate the above-mentioned disadvantages, attempts have been made to employ a popular organic polar solvent for the dope solution of the PPTA resin, to prepare an isotropic dope solution and to simplify the spinning or shaping procedure. Particularly, Japanese Unexamined Patent Publication Nos. 51-76,386, 51-134,743, 51-136,916, 61-252,229, 62-27,431, 62-225,530, 62-177,022 and 62-177,023 disclose methods for enhancing the solubility of the aramide resins, to introduce ether bonds into the aramide molecules by copolymerization. In one such attempt, wholly aromatic polyamide copolymers prepared by the copolymerization of an aromatic diamine component comprising p-phenylene diamine (PPDA) and 3,4'-diaminodiphenylether (3,4'-DAPE) with an aromatic dicarboxylic component comprising terephthalic acid, have a high mechanical strength, modulus of rigidity and chemical resistance, and can be prepared by using a popular polar solvent, for example, N-methylpyrrolidone, as the polymerization medium. Also, the resultant polymer solution can be directly utilized as a dope solution for spinning or other shaping processes. Therefore, the above-mentioned ether-bond-containing wholly aromatic polyamide copolymers provide a greatly improved process for producing shaped aramide resin-articles. Nevertheless, the introduction of the ether bonds usually causes the resultant wholly aromatic polyamide copolymer resins to exhibit an unsatisfactory heat resistance and modulus of rigidity, which can be assumed from the primary structure of the resultant aramide copolymer molecules. DE-A-3007063 discloses aromatic copolyamide fibres or films comprising recurring units of aromatic polyamides, and having good solubility in organic solvents, the copolyamides including 3, 4'-diaminodiphenyl ether residues, meta -substituted diamines and para -substituted diamines. EP-A-0199090 discloses copolyamides for processing into shaped structures and having recurring structural units of terephthalic acid residues, phenylene diamines, substituted benzidines and various defined diamines. However, there is still a strong demand for a new type of wholly aromatic polyamide resins having a satisfactory mechanical strength, heat resistance and modulus of rigidity, and capable of being produced by an easy polymerization process and of being shaped by an easy shaping process. SUMMARY OF THE INVENTION An object of the present invention is to provide a wholly aromatic polyamide copolymer soluble in an organic solvent having less toxity to the human body and other life-forms, and having a spinning and shaping stability. Another object of the present invention is to provide a wholly aromatic polyamide copolymer having a high mechanical strength and heat resistance, and a satisfactory modulus of rigidity. The above-mentioned objects can be attained by the wholly aromatic polyamide copolymer of the present invention which comprises: an aromatic dicarbonyl moiety consisting of repeating units of the formula: and an aromatic diamine moiety comprising: (A) repeating units of the formula: where X represents a halogen atom, m and n represent, respectively and independently from each other, zero or an integer of 1 to 4, and the sum of m and n is 1 to 8, (B) repeating units of the formula: and (C) repeating units of the formula: in which the molar proportions of (A), (B) and (C) are as defined in Claim 1. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a triangular coordinate diagram showing preferable molar proportions of three different types of repeating units in the aromatic diamine moiety in an embodiment of the wholly aromatic polyamide copolymer of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The wholly aromatic polyamide copolymer of the present invention is based on the finding that the mechanical strength, chemical resistance, and heat resistance of the conventional PPTA copolymer comprising a polymerization product of an aromatic dicarboxylic acid component comprising terephthalic acid chloride (TPC) with an aromatic diamine component comprising p-phenylenediamine (PPDA) and 3,4'-diaminodiphenyl ether (3,4'-DAPE), and having a high solubility in a widely-used polymerization medium, can be significantly enhanced by copolymerizing, as a third aromatic diamine ingredient, a member selected from halogenated benzidines, which have a rigid molecular structure, with the above-mentioned components. In the copolymer of the present invention, the aromatic dicarboxylic acid moiety comprises the repeating units of the formula: which are derived from terephthalic acid chloride (TPC). The aromatic diamine moiety in the copolymer of the present invention comprises: (A) repeating units of the formula: wherein X represents a halogen atom, preferably a chlorine or bromine atom, and m and n represent, respectively and independently from each other, zero or an integer of 1 to 4, preferably 1 to 2, and the sum of m and n is 1 to 8, preferably 2 to 4. (B) repeating units of the formula: which are derived from p-phenylene diamine, and (C) repeating units of the formula which are derived from 3,4'-DAPE. In the copolymer of the present invention, the total equivalent number of the carbonyl radicals (-CO-) in the aromatic dicarboxylic acid moiety is substantially equal to the total equivalent number of the secondary amine radicals (-NH-) in the aromatic diamine moiety, so that substantially all of the carbonyl radicals and the secondary amine radicals are formed into an amide group -CONH-. Furthermore, the molar proportions of the repeating units (A), (B) and (C) fall on or within a polygonal diagram defined by the coordinates C D E F G H as shown in Fig. 1, except for the lines defined by the coordinates C and D and the coordinates C and H. These coordinates are defined as follows. Coordinate Molar% of repeating units (A) (B) (C) C 0 0 100 D 65 0 35 E 65 30 5 F 45 50 5 G 15 65 20 H 0 60 40 The molecular proportions of the repeating units (A), (B), and (C) as indicated above cause the resultant copolymer to exhibit a very high solubility in widely-used polymerization mediums, and the resultant shaped articles from the copolymer to exhibit an excellent mechanical strength and chemical and heat resistances. Especially, when the content of halogen in the copolymer is 0.5% by weight or more, preferably 1.0% by weight or more, the copolymer exhibits an excellent flame resistance or flame retardant property. The wholly aromatic polyamide copolymer of the present invention is prepared by copolymerizing an aromatic dicarboxylic component comprising terephthalic acid chloride (TPC) with an aromatic diamine component comprising p-phenylene diamine (PPDA), 3, 4'-diamino-diphenylether (3, 4'-DAPE) and a member selected from chlorobenzidine compounds from which the repeating units (A) are derived, in widely-used polymerization polar mediums by a conventional melt polymerization method, solid phase polymerization method, interface polymerization method or solution polymerization method. The halogenated benzidine compound usable for the present invention is preferably selected from 3-chlorobenzidine, 3-bromobenzidine, 3,3'-dichlorobenzidine, 3,3'-dibromobenzidine, 3,3'-difluorobenzidine, 2,2'-dichlorobenzidine, 2,2-dibromobenzidine, 2,2'-difluorobenzidine, 3,3',5,5'-tetrafluorobenzidine, 3,3',5,5'-tetrabromobenzidine, and 3,3',5,5,-tetrachlorobenzidine. The most preferable halogenated benzidine is 3,3'-dichlorobenzidine. The widely-used polymerization mediums preferably comprise, as a principal component, at least one member selected from, for example, dimethyl formamide, dimethyl acetamide, N-methylpyrrolidone, N-methyl caprolactam, dimethylsulfone or tetramethyl urea. In the polymerization process, to increase the dissolving activity of the polymerization medium for the resultant polyamide copolymer, before, during or after the copolymerization is carried out, an inorganic salt may be added in an amount of less than 10% by weight to the polymerization medium. The inorganic salt can be selected from those usable for the above-mentioned purpose, for example, lithium chloride and calcium chloride. As mentioned above, the aromatic dicarboxylic acid component is reacted in a equivalent molar ratio of the -CO- radicals to the -NH- radicals of substantially 1:1, but at least one member of the polymerization components may be employed in an excessive amount to control the degree of polymerization of the resultant copolymer. Also, a monofunctional acid compound or amino compound may be added, as a terminating agent, to the copolymerization system, to control the degree of polymerization of the resultant copolymer. Also, the copolymerization system may contain an aliphatic or aromatic amine compound or quaternary ammonium compound to catch and neutralize an acid substance, for example, hydrogen chloride, produced as a by-product of the polymerization. After the polymerization procedure is completed, if necessary, the polymerization mixture is neutralized by adding a basic inorganic substance, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide and calcium oxide, to the polymerization mixture. In the polymerization procedures for the polyamide copolymer of the present invention, the concentration of the resultant copolymer in the polymerization medium is important, to ensure that the resultant copolymer resin has a uniform degree of polymerization. That is, the concentration of the resultant copolymer in the polymerization medium is preferably 20% by weight or less, more preferably, 10% by weight or less, which effectively stabilizes the polymerization system and produces a polymer having a uniform quality. Also, the copolymer of the present invention preferably exhibits an intrinsic viscosity of 1.5 to 10, more preferably 2 to 8, determined in a concentration of 0.5 g/100 ml in a solvent consisting of a 98% by weight concentrated sulfuric acid at a temperature of 30°C. There is no specific restriction on the polymerization conditions, and usually, since the reaction of the aromatic dicarboxylic acid component, for example, aromatic dicarboxylic acid halide, with the aromatic diamine component is carried out at a high reaction rate, the polymerization system is preferably maintained at a polymerization temperature of -25°C to 100°C, more preferably -10°C to 80°C. Note, the polymerization system must be protected from undesirable contamination with water or other substances which may hinder the polymerization. Since the copolymer of the present invention has a very high solubility in the polymerization medium, the polymerization can be stably carried out without deposition of the resultant copolymer from the polymerization medium. The resultant polymerization product, namely an aromatic polyamide copolymer resin, may be deposited in a pulp-like form by mixing the resultant polymerization system with a non-solvent, for example, methyl alcohol or water. The pulp-like copolymer is separated and collected from the polymerization system. The collected resin can be used for forming shaped articles by conversion to a copolymer solution in a solvent, shaping the dope solution into a desired form, and solidifying the shaped dope solution by drying or coagulating. Preferably, the resultant polymerization solution containing the resultant copolymer is directly employed for producing a shaped article. When directly employed, the polymerization solution may be supplemented with an inorganic salt, for example, calcium chloride, which effectively prevents a deposition of the copolymer, and a whitening of the resultant shaped article caused by the deposition of the copolymer. Also, the polymerization solution should be employed under conditions whereby the undesirable whitening of the resultant shaped article is prevented. The pulp-like copolymer resin can be directly converted to a shaped article by a compression molding method. Also, the solution of the copolymer in an organic solvent can be converted, into a shaped article, for example, film, by a solution-spreading method, casting method, or wet film-forming method, or into filaments by a wet-spinning method. In the wet spinning or film-forming method, the dope solution of the copolymer in a solvent is formed into filaments or a film, the shaped dope-solution is brought into contact with a coagulating liquid preferably comprising a mixture of water, which is a non-solvent for the copolymer, and an organic solvent compatible with the copolymer, to provide a coagulated copolymer filament or film. The resultant filament or film is washed with water, and if necessary, drawn at a predetermined draw ratio, of, for example, 1.5 to 30, and heat-treated at a temperature of, for example, 250°C to 600°C for 1/20 second to 5 seconds. The wholly aromatic polyamide copolymer of the present invention exhibits a high solubility in a widely-used polymerization medium causing no or little harm to the human body, and thus can be easily produced in the medium. Also, the wholly aromatic polyamide copolymer of the present invention is useful for forming filaments, films sheet, and other articles having a high mechanical strength, a proper modulus of rigidity, and enhanced chemical and heat resistances. The copolymer shaped articles are useful as reinforcing materials for rubber articles, ropes cords, and resin-reinforcing materials. EXAMPLES The present invention will be further illustrated by way of specific examples, which are merely representative and do not restrict the scope of the present invention in any way. In the examples, the logarithmic viscosity number (inherent viscosity number, h inh ) of the polymer was determined in a concentration of 0.5 g/100 ml in a solvent consisting of a 98% by weight concentrated sulfuric acid at a temperature of 30°C. Also, the solubility of the copolymer in a polymerization medium was evaluated into the following three classes. Class Item 3 No deposition of copolymer found throughout polymerization procedure 2 Copolymer deposition found only at final stage of polymerization procedure 1 Copolymer deposition found at initial or middle stage of polymerization procedure. Example 1 In Example 1, a completely dried three-necked flask equipped with a stirrer was charged with a mixture consisting of 1888.5 parts by weight of N-methyl pyrrolidone (NMP), 33.534 parts by weight (30 molar%) of 3,3'-dichlorobenzidine (DCB), 23.687 parts by weight (50 molar%) of PPDA, and 17.545 parts by weight (20 molar%) of 3,4'-DAPE at room temperature. After the DCB, PPD and 3,4'-DAPE were dissolved in NMP in a nitrogen gas atmosphere, 88.945 parts by weight of terephthalic acid chloride (TPC) were further mixed to the solution at room temperature while stirring the mixture to copolymerize the TPC with the DCB, PPD and 3,4'-DAPE. With the lapse of the polymerization time, the viscosity of the polymerization mixture was increased. After the polymerization procedure was carried out at a temperature of 80°C for 60 minutes, a highly viscous copolymer solution having a very high transparency was obtained. The polymerization solution was neutralized by adding 143.824 parts by weight of a neutralizing slurry of 22.5% by weight of a calcium hydroxide in NMP. The resultant copolymer was collected by deposition from the copolymer solution, and this copolymer had a logarithmic viscosity number (h inh ) of 3.59. The copolymer (aramid) solution was charged into a spinning cylinder having a cap with 25 spinning holes each having a diameter of 0.17 mm, and extruded from the spinning cap located 10 mm above the liquid surface of a coagulating liquid through the spinning holes into the coagulating liquid consisting of an aqueous solution containing 30% by weight of NMP, by a dry-jet spinning method. The resultant copolymer filaments were washed with water and dried, and the dried filaments were drawn in two steps on a first heating plate at a temperature of 300°C and then on a second heating plate at a temperature of 460°C, at a total draw ratio of 9.5. The resultant drawn filament yarn had a total denier of 37. The filament yarn had a tensile strength of 23.8 g/d, an ultimate elongation of 2.6%, and a modulus of rigidity of 910 g/d. A filament yarn bundle consisting of 100 filament yarns was placed at a center portion of a copper coil having a diameter of 100 mm and maintained at an angle of 45 degrees from the horizontal level. Then, a flame was brought into contact with the filament yarn bundle. The combustion of the filament yarn bundle was observed by the naked eye, and it was found that the filament yarn bundle was not burnt by the above-mentioned ignition operation. The content of chlorine in the filaments was 7.3% by weight. For comparison, a filament yarn bundle consisting of poly-p-phenylene terephthalamide (PPTA) filaments was subjected to the same flame test as mentioned above. It was found that the filament yarn bundle having a length of 10 cm was burnt by four ignition operations, and flame was transmitted along the filament yarn bundles. Example 2 The same procedures as in Example 1 were carried out with the following exceptions. The aromatic diamine component consisted of 33.811 parts by weight (50 molar%) of DCB, 11.449 parts by weight (40 molar%) of PPDA and 5.300 parts by weight (10 molar%) of 3,4'-DAPE, and was dissolved in 1932.7 parts by weight of NMP, and mixed with 53.737 parts by weight of TPC. The resultant polymerization solution was neutralized with 86.892 parts by weight of the NMP slurry containing 22.5% by weight of calcium hydroxide. The resultant copolymer had a logarithmic viscosity number (h inh ) of 3.36. The total draw ratio was 3.3. The resultant copolymer filament yarn had a total denier of 73, exhibited a tensile strength of 14.3 g/d, an ultimate elongation of 1.8%, a modulus of rigidity of 890 g/d, and an excellent flame resistance, and contained 11.17% by weight of chlorine. Example 3 The same procedures as in Example 1 were carried out with the following exceptions. The aromatic diamine component consisted of 48.633 parts by weight (40 molar%) of DCB, 12.022 parts by weight (30 molar%) of PPDA and 22.262 parts by weight (30 molar%) of 3,4'-PAPE, was dissolved in 1905.6 parts by weight of NMP and mixed with 75.289 parts by weight of TPC. The resultant viscous, transparent polymerization solution was neutralized with 121.73 parts by weight of the NMP slurry containing 22.5% by weight of calcium hydroxide. The resultant copolymer had a logarithmic viscosity number of 2.30. The total draw ratio was 22.0. The resultant copolymer filament yarn had a total denier of 29 and a chlorine content of 8.9% by weight and exhibited a tensile strength of 12.5 g/d, an ultimate elongation of 2.0%, a modulus of rigidity of 790 g/d, and an excellent flame-retardant property. Example 4 The same procedures as in Example 1 were carried out with the following exceptions. An aromatic diamine component consisting of 37.709 parts by weight (60 molar%) of DCB, 5.320 parts by weight (20 molar%) of PPDA and 9.852 parts by weight (20 molar%) of 3,4-DAPE was dissolved in a mixed polymerization medium consisting of 1937.4 parts by weight of NMP and 19.374 parts by weight of a solubility-enhancing agent consisting of calcium chloride and dissolved in the NMP, and then mixed with 49.944 parts by weight of TPC. With a lapse of the polymerization time, the viscosity of the polymerization solution was increased and the resultant polymerization solution was slightly muddy and colored light yellow. The resultant polymerization solution was neutralized with 80.759 parts by weight of the NMP slurry containing 22.5% by weight of calcium hydroxide. The resultant copolymer had a logarithmic viscosity number of 3.83. The two step drawing operation was carried out at a temperature of 300°C and then at a temperature of 440°C, at a total draw ratio of 2.50. The resultant copolymer filament yarn had a total denier of 90 and a chlorine content of 11.2% by weight and exhibited a tensile strength of 17.3 g/d, an ultimate elongation of 1.8%, a modulus of rigidity of 830 g/d, and an excellent flame retardant property. Example 5 The same procedures as in Example 1 were carried out with the following exceptions. The aromatic diamine component consisted of 5 molar% of DCB, 45 molar% of PPDA, and 50 molar% of 3,4'-DPAE. The resultant copolymer had a logarithmic viscosity number of 3.56. The two step drawing operation was carried out at a temperature of 300°C and then at a temperature of 490°C, at a total draw ratio of 20.0. The resultant copolymer filament yarn had a total denier of 33 and a chlorine content of 1.3% by weight, and exhibited a tensile strength of 23.5 g/d, an ultimate elongation of 3.9%, a modulus of rigidity of 780 g/d and a satisfactory flame retardant property such that, to burn the filament yarn bundle having a length of 10 cm, 12 ignition operations were necessary. Examples 6 to 12 and Comparative Example 1 and Referential Examples 1 to 4 In each of Examples 6 to 12, Comparative Example 1 and Referential Examples 1 to 4, the same procedures as in Example 1 were carried out except that DCB, PPDA and 3,4'-DAPE were employed in the molar proportions as indicated in Table 1. The solubility and logarithmic viscosity number of the resultant copolymer are shown in Table 1. In Comparative Example 1, the polymer did not contain any PPDA and in Referential Examples 1 to 4, the molar proportions of DCB, PPDA and 3, 4'-DAPE fell outside of the polygonal diagram C D E F G H as indicated in Fig. 1.

Claims: A wholly aromatic polyamide copolymer comprising: an aromatic dicarbonyl moiety consisting of repeating units of the formula: and an aromatic diamine moiety comprising: (A) repeating units of the formula: where X represents a halogen atom, m and n represent, respectively and independently from each other, zero or an integer of 1 to 4, and the sum of m and n is 1 to 8; (B) repeating units of the formula: and (C) repeating units of the formula: characterised in that when indicated in a triangular coordinate, the molar proportions of the repeating units (A), (B) and (C) in the aromatic diamine moiety are on or within a polygonal diagram defined by the coordinates C, D, E, F, G and H, except for lines defined by the coordinates C and D and the coordinates C and H, which coordinates are defined as follows: Coordinate Molar% of repeating units (A) (B) (C) C 0 0 100 D 65 0 35 E 65 30 5 F 45 50 5 G 15 65 20 H 0 60 40 The polymer according to Claim 1, characterised in that the repeating units (A) have a chlorobenzidine structure. The copolymer according to Claim 1 or Claim 2, characterised in that the repeating units (A) have a 3,3'-dichlorobenzidine structure. A shaped article comprising the wholly aromatic polyamide copolymer as claimed in any preceding claim.

Inventors: KIRIYAMA TSUTOMU, SANTA TOSHIHIRO, KIRIYAMA, TSUTOMU, SANTA, TOSHIHIRO
Applicants: TEIJIN LTD, TEIJIN LIMITED
Application year: 1989
Main classification: C08G69
IPC codes: C08G69