FLAME RESISTANCE POLYAMIDE RESIN COMPOSITION

Abstract: A polyamide resin composition containing a polyamide copolymer made from 1) an aromatic dicarboxylic acid component, which is terephthalic acid or a mixture of terephthalic acid and isophthalic acid, and an aliphatic diamine component, which is a mixture of hexamethylene diamine and 2-methylpentamethylene diamine, 2) a polytribromostyrene and/or polyphenylene ether flame retardant, and 3) an antimony oxide and/or sodium antimonate flame retardant coagent, said composition being high melting, having good flame resistance, and yielding molded articles having good appearance.

Description: TITLE FLAME RESISTANT POLYAMIDE RESIN COMPOSITION BACKGROUND OF THE INVENTION The present invention relates to a highly heat resistant and flame resistant polyamide resin composition. Polyamide resins, which have excellent mechanical properties, moldability, and chemical resistance, are used in a variety of fields, such as in automotive parts, electrical and electronic parts, mechanical parts, and the like. In particular, electrical and electronic parts require resistance to soldering and flame resistance. High melting resins, such as aromatic polyamides, 4,6-nylon, polyphenylene sulfide, or the like, have been developed for applications in soldering-resistant molded goods. However, 4,6-nylon, fails to provide a molded article with good dimensional stability due to the fact that it absorbs much water. Polyphenylene sulfide mainly has moldability problems in that it generates extensive flash with molded products and requires a high molding temperature. Aromatic polyamides are superior in moldability to the other resins. However, there is no product known to the present inventors that can fully meet market requirements. Resins are rendered flame resistant by an extensively-used procedure which involves incorporating a considerable amount of a flame retardant. In particular, a combination of a halide and an antimony compound is excellent in terms of flame resistance and raw material cost. Many compositions use such a flame retardant system. Similar compositions are known for high melting resins, but these compositions lack sufficient stability, failing to provide a flame resistant resin composition which is satisfactory with respect to the appearance of the molded articles and safety during molding or pellet production. The present invention aims to provide a high melting flame resistant polyamide resin composition having excellent heat resistance, mold safety, and good appearance of the molded articles. In order to solve the above problems, the present invention comprises incorporating a specific flame retardant and a flame retardant coagent into a high melting aromatic polyamide copolymer obtained by copolymerizing terephthalic acid, or a mixture of terephthalic acid and isophthalic acid, with a mixture of hexamethylene diamine and 2- ethylpentamethylene diamine. This polyamide copolymer, which is excellent in heat resistance and mechanical strength, has a melting point in the range of 280-330°C. Such a melting point range allows one to set the resin temperature during production so as not to cause the flame retardant to decompose or degrade, thereby permitting one to obtain a composition which is excellent in moldability and work safety. DETAILED DESCRIPTION OF THE INVENTION The present invention is a flame retardant polyamide resin composition comprising (A) 100 parts by weight of a polyamide copolymer, having a melting point of 280-330°C, which is comprised of (1) an aromatic dicarboxylic acid component, which is terephthalic acid or a mixture of terephthalic acid and isophthalic acid, with the content of isophthalic acid being not more than 40 mole % of said mixture, and (2) an aliphatic diamine component, which is a mixture of hexamethylene diamine and 2- methylpentamethylene diamine, with hexamethylene diamine being at least 40 mole % of the mixture; (B) 10-100 parts by weight, based upon 100 parts by weight of (A), of polytribromostyrene and/or polybromophenylene ether; and (C) 0.5-40 parts by weight, based upon 100 parts by weight of (A), of antimony oxide and/or sodium antimonate. The polyamide copolymers of this invention have melting points of 280-330°C, preferably 285-305°C. Component (B) is a flame retardant. The flame retardant used in this invention is polytribromostyrene or polybromophenylene ether, which may be used alone or in combination. Said flame retardant is used in an amount of 10-100 parts by weight, preferably 20-50 parts by weight, based upon 100 parts by weight of (A). The amount of incorporation of the above flame retardant is selected at 10-100 parts by weight because a level less than 10 parts by weight may cause a problem with heat resistance, while adding more than 100 parts by weight may cause problems with respect to mechanical strength. Component (C) is a flame retardant coagent. The flame retardant coagent used in this invention is antimony oxide or sodium antimonate, which may be used alone or in combination. The amount of the flame retardant coagent is 0.5-40 parts by weight, preferably 5-20 parts by weight, based upon 100 parts by weight of (A). The flame retardant coagent is added in an amount of 0.5-40 parts by weight because a level less than 0.5 parts by weight may fail to provide a flame retardation effect, while a level greater than 20 parts by weight may cause a problem in mechanical strength. Antimony oxides include, for example, antimony trioxide, antimony tetroxide, antimony pentoxide, or the like. The flame retardant coagent in this invention is preferably antimony pentoxide or sodium antimonate. The polyamide resin of this invention may also contain up to 200 parts by weight, based upon 100 parts by weight of (A), of an inorganic reinforcing agent, depending upon the application for the molded article. Inorganic reinforcing agents include glass fibers, carbon fibers, potassium titanate, whiskers, talc, mica, and the like. The flame resistant polyamide resin composition of this invention may also contain, in addition to the above components, additives such as heat stabilizers, plasticizers, antioxidants, nucleating agents, dyes, pigments, mold release agents, and the like, to the extent they do not significantly adversely affect the properties thereof. EXAMPLES The present invention is now specifically described by the examples below, which in no way limit the scope of the present invention. For the samples show below, "6T", "6l", and "2MPT" are as follows: 6T: 2MPT: — NH-C H 2 — C (C H 3 )H — (C H 2 ) 3 — NH-CO- P— Ph-)-C 0 where T represents terephthalic acid; I represents isophthalic acid; p-PH is p-phenylene; m-Ph is m-phenylene; 6 in 6T and 6l is hexamethylene diamine; and 2MP is 2-methylpentamethylene diamine. A polyamide copolymer, with a 50:50 of 6T:2MPT, or a polyamide copolymer from 6T, 6l, and 2MPT, at a ratio of 45:5:50 or 40:10:50, polytribromostyrene (Nissan Fero Company's Pyrochek 68PB), polybromophenylene ether (Great Lakes Company, P064), crosslinked brominated polystyrene (Nanac Company EVR370-FK), sodium antimonate (Nissan Kagaku K.K., NA1070L), antimony trioxide (Campine Company, White Star N), antimony tetroxide (Nissan Kagaku K.K., NA5050), and microglass chopped strands (Nippon Itagarasu Company TP64) were mixed at the weight ratios given in Table 1 and Table 2, below, kneaded in a twin screw extruder (Toshiba TEM35) at a set temperature of 320°C, and pelletized. A polyamide copolymer with a ratio of 6T:2MPT of 50:50 and a polyamide copolymer of 6T, 6l, and 2MPT at a ratio of 45:5:50, brominated aromatic amide (Nanac Company EB905), brominated phenylene oxide (Ethyl Corporation, Saytex 120), and brominated i ide (Ethyl Corporation, Saytex BT93) were mixed at the weight ratios given in Tables 1 and 2, below, and were pelletized in a manner similar to the above example. TESTS Heat Resistance The heat resistance of the resultant pellets was evaluated by measuring a thermogravimetric change in a stream of nitrogen in a DuPont Instrument Thermal Analysis (sic) 2,000 TGA2950. The pellets were heated at a heating rate of 10°C/min and the temperature at which a 5% weight loss occurred was defined as Tg. Samples were rated satisfactory if the Tg was equal to or higher than 345°C, which corresponds to the resin temperature at the time of extrusion. An example with a Tg less than 345°C was rated unsatisfactory. The results are shown in Table 1, below. Combustion Test Pellets rated satisfactory according to the above heat resistance test were then injection molded in an injection molding machine (Toshiba 170F111-5A) to give a 1/32 inch thick UI ^ 94 combustion test piece. In order to evaluate these samples for combustibility, state of extrusion, and moldability, use was made (as a comparative example) of a composition obtained by incorporating a flame retardant to yield a composition with Tg value of 345°C as an example for the heat resistance test. The combustion test was carried out on these test pieces according to the UL class specification described below. UL Specification Regulation The top end of a test piece was held by a clamp so as to set the test piece vertically: A defined flame was allowed to make contact with the bottom end of the test piece for 10 seconds and then the flame was kept away from the sample to measure the duration of combustion (from the first ignition of the test piece). When burning extinguished, the flame was immediately allowed to come into contact with the bottom end of the test piece for 10 seconds to measure the combustion time (second ignition) of the test piece. The same measurement was repeated for five test pieces, five times each for the first ignition combustion time and second ignition combustion time, to yield a total of 10 data points. The total of the 10 data points was designated S; the largest value among the 10 data points was called M. A rating of V-O equivalent was given if S was not more than 50 seconds and M was not more than 10 seconds with no continued burning which reached the clamp and there was no drip of the flame melt, causing the ignition of cotton placed 12 inches below the sample. A rating of V-2 equivalent was given if S was not greater than 250 seconds and M was not greater than 30 seconds, where the flame melt dripped to cause the ignition of the cotton located 12 inches below the sample. State of Extrusion and Rating of Moldability The state of extrusion was rated poor based on the difficulty of pulling out resin strands, on any resin decomposition at high temperatures, on gas formation, and the like, and in regard to problems in pellet productivity and work safety. A rating of satisfactory was given if no problems occurred in these aspects. Moldability time was rated poor if there were any problems, such as resin decomposition, gas formation, flash formation, poor appearance of the molded article, and the like, as well as any problems in molded article productivity and work safety. Those without any problems were rated satisfactory. The results for state of extrusion, color, moldability time, average combustion, and UL-94 are shown in Table 3, below. Table 1; Heat Resistance Test Examples FR-1: Brominated aromatic amide (Nanac Company, EB905) FR-2: Brominated epoxy resin (Dainippon Ink K.K., EP500) FR-3: Brominated epoxy resin (Dainippon Ink K.K., EP100) FR-4: Brominated epoxy resin (Dainippon Ink K.K., EC30) FR-5: Brominated phenylene oxide (Ethyl Corporation, Saytex 120) FR-6: Brominated imide (Ethyl Corporation, Saytex BT93) FR-7: Polybromophenylene ether (Great Lakes Company, PO-64) FR-8: Crosslinked brominated polystyrene (Nanac Company, EBR370-FK) FR-9: Polytribromostyrene (Nissan Fero Company's Pyrochek 68PB) Sy-1: Sodium antimonate (Nissan Kagaku K.K., Sunepoch NA1070L) Table 2: Combustion Test. State of Extrusion, and Moldability Examples PA-2: 6T/6I/2MPT = 45/5/50 PA-3: 6T/6I/2MPT = 40/10/50 FR-1: Brominated phenylene oxide (Ethyl Corporation, Saytex 120) FR-2: Polybromophenylene ether (Great Lakes Company, PO-64) FR-3: Crosslinked brominated polystyrene (Nanac Company, EBR370-FK) FR-4: Polytribromostyrene (Nissan Fero Company, Pyrochek 68PB) Sy-1: Antimony trioxide (Campine Company, White Star N) Sy-2: Antimony tetroxide (Nissan Kagaku, Sunepoch NA5050) Sy-3: Antimony pentoxide (Nissan Kagaku, Sunepoch NA1030) Sy-4: Sodium antimonate (Nissan Kagaku) GR: Microglass Chopped Strand (TP64, Nippon Sheet Glass Co., Ltd.) Table 1 Parts by Weight Based on ' 100 Parts by Weight of PA-1 Ex. PA-1 FR-1 FR-2 FR-3 FR-4 FR-5 FR-6 FR-7 FR-8 FR-9 S -1 T Rating Cl 100 35 7 338 U C2 100 - 35 - - - - - - - 7 342 u C3 100 - - 35 - - - - - - 7 333 u C4 100 - - - 35 - - - ~ - 7 331 u C5 100 - - - - 35 - - - - 7 344 u C6 100 - - - - - 35 - - " 7 335 u 1 100 w -. „ _ -. 35 _ _ 7 352 s 2 100 - - - - - - - 35 " 7 349 s 3 100 - - - - - - - - 35 7 348 s U = Unsatisfactory S = Satisfactory Table 2 Table 3 State Moldability of Time Average Example Extrusion Color* (sec) Combustion UL-94 C7 Poor Grey Poor 8.4 V-2 C8 Poor Grey Poor 0.6 V-0 C9 Poor Grey Poor 1.1 V-0 CIO Poor Grey Poor 4.9 V-0 σ 4 Satisfactory Grey Satisfactory 0.6 V-0 I 5 Satisfactory Grey Satisfactory 2.8 V-0 6 Satisfactory Grey Satisfactory 3.5 V-0 7 Satisfactory Grey Satisfactory 3.9 V-0 8 Satisfactory Whitish YeUow Satisfactory 1.5 V-0 9 Satisfactory Whitish YeUow Satisfactory 2.1 V-0 10 Satisfactory Whitish YeUow Satisfactory 1.9 V-0 11 Satisfactory Whitish YeUow Satisfactory 17 V-0 *as determined by the naked eye

Claims: CLAIMS 1. A polyamide resin composition comprised of (A) 100 parts by weight of a polyamide copolymer having a melting point of 280-330°C and made from (1) an aromatic dicarboxylic acid component selected from terephthalic acid or a mixture of terephthalic acid and isophthalic acid, with the content of isophthalic acid in the mixture being not more than 40 mole % of said mixture and (2) an aliphatic diamine component made from a mixture of hexamethylene diamine and 2- ethylpentamethylene diamine, with the hexamethylene diamine being at least 40 mole % of the mixture; (B) 10-100 parts by weight, per 100 parts by weight of (A), of a flame retardant selected from the group consisting of polytribromostyrene, polybromophenylene ether, and mixtures thereof; and (C) 0.5-40 parts by weight, per 100 parts by weight of (A), of a flame retardant coagent selected from the group consisting of antimony oxides, sodium antimonate, and mixtures thereof. 2. The composition of Claim 1 further containing at least one of inorganic reinforcing agents, heat stabilizers, plasticizers, antioxidants, nucleating agents, dyes, pigments, and mold release agents.

Inventors: HAYASHI RYUICHI, MATSUDA TOYOHARU, HAYASHI, RYUICHI, MATSUDA, TOYOHARU
Applicants: DU PONT, HAYASHI RYUICHI, MATSUDA TOYOHARU, E. I. DU PONT DE NEMOURS AND COMPANY, HAYASHI, RYUICHI, MATSUDA, TOYOHARU
Application year: 1993
Main classification: C08K3
IPC codes: C08J5, C08K3, C08L25, C08L71, C08L77