PROCESS FOR PRODUCING BLOCK COPOLYAMIDE

Abstract: A block copolyamide having effectively improved impact strength is obtained by polymerizing a mixture comprising substantially from about 50 to about 95 parts by weight of lactam and from about 50 to about 5 parts by weight of polyol in the presence of a catalyst for an anionic polymeriza­ tion and an activator represented by the following formula (I); wherein A denotes a bifunctional organic residue having at least one kind of heteroatom selected from the group consisting of N, O, S, F, Cl, Br and I, Y and Y′ denote an acyl group selected from the group consisting of -- , -- and -- and n and n′ denote an integer of 3 to 11 or by polymerizing, in the presence of a catalyst for anionic polymerization, a mixture comprising substantially from about 50 to about 95 parts by weight of lactam and from about 5 to about 50 parts by weight of prepolymer obtained by a reaction of polyol and an activator represented by the above formula (I), wherein A denotes a bifunctional aromatic residue having at least one halogen atom attached to the aromatic ring.

Description: The present invention relates to a process for producing a block copolyamide having effectively improved impact strength by means of anionic polymerization. It is well known that lactam can be anionically polymerized in the presence of an anionic polymerization catalyst and some kinds of activators. Many kinds of molded polyamide articles are obtained by anionic polymerization procedures. In general, these anionically polymerized polyamide articles possess high mechanical strength, good abrasion resistance and good fatigue resistance due to the high degrees of crystallinity. However, impact strength of these articles is fairly low and this disadvantage causes the application of anionic polymerization to be restricted. In order to improve impact strength, it is proposed to employ processes for producing a block copolyamide from lactam and polyols such as polyalkylene glycols, polylactonediols and polyolefin polyols by anionic polymerization. One of the important advantages of anionic polymerization is that final products can be directly obtained by polymerizing raw materials such as lactam and polyol in a mold. Therefore a high polymerization rate is demanded for the effective production of molded products. In general, the polymerization rate in the anionic polymerization of lactam is mainly governed by the structure of employed activators. There has been presented no activators which enable one not only to achieve completion of polymerization of a mixture of lactam and polyol in a short time but also to give molded articles having good surface appearance and mechanical properties. It has been long desired to make appearance of activators which can satisfy all of the above-described requirements. For example, when isocyanate compounds were employed as activators (United States Patent Specification No. 3704280), it took a very long time to complete the polymerization reaction because of the low activity of the activators. For another example,when polyacyllactams such as adipyl biscaprolactam, terephthaloyl-bis-caprolactam or isophthaloyl-bis-caprolactam were used (United States Patent Specification No. 3862262), molded products could not be demolded easily and, therefore, had poor surface appearance. Surface appearance can be improved to some extent by increasing the amount of activators, but then, decrease in molecular weight and impact strength of the produced polymer occurs simultaneously. The object of the present invention is to provide a process for producing block copolyamide moldings having good surface appearance and good impact strength rapidly and effectively by means of anionic polymerization. The object of the invention can be achieved by polymerizing a mixture comprising substantially from 50 to 95 parts by weight of lactam and from 50 to 5 parts by weight of polyol in the presence of a catalyst for an anionic polymerization and an activator represented by the following formula (I); wherein A denotes a bifunctional aromatic residue having on an aromatic ring at least one heteroatom selected from the group consisting of F, Cl, Br, and I (hereinafter referred to as halogens) and Y and Y' each independently denotes an acyl group selected from the group consisting of and n and n' each independently denotes an integer of 3 to 11, or by polymerizing, in the presence of catalyst for anionic polymerization, a mixture comprising substantially from 50 to 95 parts by weight of lactam and from 5 to 50 parts by weight of prepolymer obtained by a reaction of polyol and activator (I). Generally, in anionic polymerization of a mixture of lactam and polyol, the rate of polymerization and moldability are influenced by reactivity and the amount of activators. The polymerization is accomplished in a short time by use of activators having high reactivity. The more amount of activators is used, the more the polymerization rate is enhanced and the mold-release property and surface appearance of molded articles become to be excellent. Activators employed in the present invention are represented by the above described general formula (I). Activators of the present invention are characterized to be at least bifunctional compounds comprising that two lactams are combined with the bifunctional organic residue A having specific heteroatoms through acyl groups represented by Y and Y'. Y and Y' are selected from preferably The role of heteroatoms introduced to the residue A is important. The heteroatom can bring about the effects to elevate the solubility of activators to a mixture of lactam and polyol, and to enhance the reactivity of activators in anionic polymerization. As a result, it can be effectively achieved by use of activators having specific heteroatoms in the residue A that molded articles having excellent surface appearance and mechanical properties can be obtained very rapidly in anionic polymerization of a mixture of lactam and polyol . Representative examples of the group A in formula (I) include, monochlorophenylenes such as 2-chloro-1,3-phenylene, 2-chloro-1,4-phenylene; dichlorophenylenes such as 2,5-dichloro-1,3-phenylene, 4,6-dichloro-1,3-phenylene, 2,3-dichloro-1,4-phenylene, 2,5-dichloro-1,4-phenylene, 2,6-dichloro-1,4-phenylene; trichlorophenylenes such as 2,3,5-trichloro-1,4-phenylene; tetrachlorophenylenes such as 2,3,5,6-tetrachloro-1,4-phenylene; monobromophenylenes such as 2-bromo-1,3-phenylene, 5-bromo-1,3-phenylene, 2-bromo-1,4-phenylene; dibromophenylenes such as 2,5-dibromo-1,3-phenylene, 2,5-dibromo-1,4-phenylene; tetrabromophenylenes such as 2,3,5,6-tetrabromo-1,4-phenylene; monofluorophenylenes such as 2-fluoro-1,3-phenylene, 2-fluoro-1,4-phenylene; difluorophenylenes such as 2,5-difluoro-1,3-phenylene, 2,5-difluoro-1,4-phenylene; monoiodophenylenes such as 2-iodo-1,3-phenylene, 2-iodo-1,4-phenylene; diiodophenylenes such as 2,5-diiodo-1,3-phenylene, 2,5-diiodo-1,4-phenylene; monochloronaphthylenes such as 1-chloro-2,6-naphthylene, 1-chloro-2,5-naphthylene; dichloronaphthylenes such as 1,5-dichloro-2,6-naphthylene; tetrachloronaphthylenes such as 1,4,5,8-tetrachloro-2,6-naphthylene; monobromonaphthylenes such as 1-bromo-2,6-naphthylene; monochlorobiphenylenes such as 2-chloro-4,4'-biphenylene, 4-chloro-2,2'-biphenylene; dichlorobiphenylenes such as 2,2'-dichloro-4,4'-biphenylene; tetrachlorobiphenylenes such as 2,2' 6,6'-tetrachloro-4,4'-biphenylene; monobromobiphenylenes such as 2-bromo-4,4'-biphenylene; Preferably, monochlorophenylenes, dichlorophenylenes, tetrachlorophenylenes, and monobromophenylenes are employed. Most preferably, 2-chloro-1,4-phenylene and 2,5-dichloro-1,4-phenylene are employed. Activators (I) having at least one halogen atom attached to an aromatic ring of the residue A, have favourable characteristic features compared with known activators in which the residue A comprises hydrocarbon. That is, activators (I) can bring about high polymerizability because of the electron-withdrawing effect of the halogen atom positioned at near to acyl groups represented by Y and Y' and much solubility to a mixture of lactam and polyol owing to the high polarity of the halogen atom . Thus the molded articles having excellent surface appearance can be obtained by use of activators (I). Activators (I) of the present invention are generally synthesized by addition of lactams such as α-pyrrolidone, ε-caprolactam, ω-lauryllactam to acid halides of dicarboxylic acid having at least one halogen atom attached to the aromatic ring. Acid halides are represented by the following formula; wherein A denotes the same aromatic residue in said formula (I) and X denotes halogen atom. Representative examples of the said acid halides include 2-chloroisophthaloyldichloride, 2,5-dichloroisophthaloyldichloride, 4,6-dichloroisophthaloyldichloride, 2-bromoisophthaloyldichloride, 5-bromoisophthaloyldichloride, 2,5-dibromoisophthaloyldichloride, 2-bromoisophthaloyldibromide, 5-bromoisophthaloyldibromide, 2-chloroterephthaloyldichloride, 2,3-dichloroterephthaloyldichloride, 2,5-dichloroterephthaloyldichloride, 2,6-dichloroterephthaloyldichloride, 2,3,5,6-tetrachloroterephthaloyldichloride, 2-bromoterephthaloyldichloride, 2,5-dibromoterephthaloyldichloride, 2-chloroterephthaloyldibromide, 1-chloronaphthalene-2,6-dicarboxylic acid dichloride, 1,5-dichloronaphthalene-2,6-dicarboxylic acid dichloride, 1-bromonaphthalene-2,6-dicarboxylic acid dichloride, 1-chloronaphthalene-2,5-dicarboxylic acid dichloride, 2-chlorobiphenyl-4,4'-dicarboxylic acid dichloride, 2,2'-dichlorobiphenyl-4,4'-dicarboxylic acid dichloride, 4-chlorobiphenyl-2,2'-dicarboxylic acid dichloride, 2-bromobiphenyl-4,4'-dicarboxylic acid dichloride, 2-chlorodiphenylmethane-4,4'-dicarboxylic acid dichloride, 2,2'-dichlorodiphenylmethane-4,4'-dicarboxylic acid dichloride, 1,2-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid dichloride, 1,2-bis (3-chlorophenoxy)ethane-4,4'-dicarboxylic acid dichloride, 1,2-bis (2,6-dichlorophenoxy)ethane-4,4'-dicarboxylic acid dichloride, 1,2-bis (2-bromophenoxy) ethane-4,4'-dicarboxylic acid dichloride. In the present invention, it is also possible to form the prepolymer represented by the following formula (II) by reaction of activator (I) and polyol . The block copolyamide is obtained by subsequently polymerizing a mixture of prepolymer and lactam in the presence of catalyst for anionic polymerization. wherein D denotes the polyol residue and A denotes the bifunctional aromatic residue having at least one halogen atom attached to an aromatic ring and Y and Y' denote an acyl group selected from the group consisting of and n denotes an integer of 3 to 11, m denotes an integer of 2 or 3. Prepolymers can also be synthesized by preliminary reaction of diacid halide and polyol and succeeding addition of lactam . A mixture of prepolymer thus obtained and lactam is polymerized in the presence of catalyst for anionic polymerization. The rate of anionic polymerization of prepolymer and lactam can also be enhanced by at least one halogen atom attached to an aromatic ring in the residue A. The above-described activators can be employed in the form of mixtures or alone in the amount of about 0.0005 -- 0.6 times, preferably about 0.001 -- 0.25 times by mole based on lactam. Lactams of the present invention are cyclic amide compounds usually having 4 to 12 carbon atoms. Representative examples of lactams include α-pyrrolidone, valerolactam, caprolactam, enantholactam, capryllactam and lauryllactam. Preferably ε-caprolactam is employed. Polyols of the present invention have at least two hydroxyl groups and normally a molecular weight of about 200 to 10,000, preferably about 300 -- 5,000. Representative examples of polyol include polyethylene glycol, polypropylene glycol, poly (oxyethylene / oxypropylene) diol, polyoxyethylene triol, polyoxypropylene triol, poly (oxyethylene / oxypropylene) triol, polytetramethylene glycol, polyoxybutylene triol, polyetherpolyols obtained by addition of ethyleneoxide and / or propyleneoxide to glycerine, trimethylolpropane, pentaerythritol and so on, polyesterpolyols such as poly-ε-caprolactonediol, polybutadienediol and poly (butadiene / styrene) copolymer diol. Preferably polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (oxyethylene / oxypropylene) glycol, polyoxyethylene triol, polyoxypropylene triol, poly (oxyethylene / oxypropylene) triol, polyoxybutylene triol and more preferably polypropylene glycol, poly (oxyethylene / oxypropylene) glycol, polyoxypropylene triol, poly (oxyethylene / oxypropylene) triol are employed. Polyols can be employed in one kind or more than two kinds in the amount of about 0.05 -- 0.5 times by weight based on the total mixture of lactam and polyol. Where the amount of polyols is less than 0.05 times by weight, toughness of blockcopolyamide obtained is insufficient. On the other hand, where the amount of polyols is greater than 0.5 times by weight based on the total mixture of lactam and polyol, rigidity and heat resistance of the blockcopolyamide are deteriorated remarkably. Catalysts for anionic polymerization of the present invention are not defined and well known compounds can be employed. Representative examples of catalysts include salts of alkali metals and alkaline earth metals and lactams such as sodium lactamate, potassium lactamate and calcium lactamate and basic compounds which are able to form lactamate anion by reaction of lactam in situ such as alkali metals, alkaline earth metals, their hydrides, hydroxides, oxides, carbonates, alkoxides, alkyl compounds and aryl compounds, trialkylaluminium compounds and Grignard reagents. Catalysts can be employed in one kind or more than two kinds usually, in the amount of about 0.001 -- 0.1 times, preferably 0.003 -- 0.05 times by mole based on lactam. Polymerization of a block copolyamide of the present invention can be carried out using an equipment which is conventionally employed for an anionic polymerization of lactams under usual processing conditions. For example, a so-called one-component method or two-component method can be used. In the former case, lactam , polyol , catalyst and activator are mixed in a molten state in one reactor and then the resultant mixture is poured into molds to undergo subsequent polymerization therein. In the latter case, lactam is melted in two separate containers, one portion being mixed with catalysts and the other with activators. Polyols are added into one of the two lactam solutions and it is not important whether polyols are introduced into catalyst-side or activator-side. Then exactly measured quantities of the two components are fed to a mixing head and the mixture is poured into molds in which polymerization takes place. Polymerization can be carried out in the temperature range between the melting point of the lactam monomer and the melting point of the resultant polymer, preferably in the range of 100 -- 200 °C. Conventional molding methods such as rotational casting or centrifugal casting can also be applied. The block copolyamide of the present invention may optionally contain inorganic or organic fibrous reinforcing agents such as glass fibers, carbon fibers, asbestos fibers and fibers consisting of wholly aromatic polymers. Polyamides and polyesters whose melting temperatures are higher than the anionic polymerization temperature can also be contained as reinforcing agents. The block copolyamide of the present invention may also optionally contain powdery or beaded fillers such as talc, wollastonite, calcium carbonate, magnesium oxide, aluminium oxide, mica, glass beads, and potassium titanate whiskers. Fibrous reinforcing agents can be used in any normally available form, milled, chopped, roved and so on. Other additives may be contained in the block copolyamide of the present invention without preventing the polymerizability and moldability. Representative examples of additives include pigments, dyes, flame retarding agents, heat stabilizers, antioxidants, light stabilizers, lubricants, mold-releasing agents, antistatic agents, plasticizers, nucleating agents, forming agents and other polymer materials. Molded articles obtained by molding the block copolyamide of the present invenition are useful for a variety of parts, especially for machinery parts and automobile parts. The present invention will be more clearly understood with reference to the following examples. Properties of polyamides described in examples were measured by the following methods. (1) Tensile properties: ASTM D638 (2) Flexural properties: ASTM D790 (3) Izod impact strength: ASTM D256 (4) Heat distortion temperature: ASTM D648 (5) Surface appearance: Observation with the naked eye Example 1 (Preparation of activator) 300 g of anhydrous ε-caprolactam and 77 g of pyridine as acid capturing agent were mixed at 50 -- 60 °C in a flask equipped with a stirrer and nitrogen inlet. 88 g of 2,5-dichloroterephthaloyl chloride was added to the mixture gradually under stirring in the stream of nitrogen. The solution was heated at 130 °C for 1 hr and then the reaction mixture was poured into 10 l of cold water under vigorous stirring to give white precipitates. The precipitates were washed three times with water and dried in vacuo to yield white powder whose melting point was 187 °C. The product was determined as 2,5-dichloroterephthaloyl-bis-caprolactam by IR (1710 and 1690 cm⁻¹, and elemental analysis (calcd. C: 56.5%, H: 5.2%, N: 6.6%, Cl: 16.7%, found C: 56.7%, H: 5.1%, N: 6.8%, Cl: 17.0%). (Anionic polymerization) 50 g of anhydrous ε-caprolactam and 14.2 m mol of ethylmagnesium bromide (ether solution) were mixed in a nitrogen atmosphere at 90 -- 100 °C and then ether was distilled off under a slight vacuum to give a solution (A component solution). 30 g of anhydrous ε-caprolactam, 20 g of polypropylene glycol (number average molecular weight Mn : 2,000) and 7.5 g of 2,5-dichloroterephthaloyl-biscaprolactam were mixed in a nitrogen atmosphere at 90 °C for about 20 minutes to give a clear solution (B component solution). A and B component solutions were mixed well and the mixture was quickly poured into a metal mold which was kept at 140 °C. After about 5 minutes, the mold was opened. Anionic polymerization of ε-caprolactam and polypropylene glycol was completed within about 5 minutes to give a block copolyamide and the molded test-pieces designated by ASTM could be taken from the mold. Mechanical properties and characteristics of these test-pieces were measured and the results were summarized in Table 1. This block copolyamide proved to give molded articles having excellent surface appearance and excellent mechanical properties. Comparative Example 1 The same procedure as Example 1 was repeated except that terephthaloyl-biscaprolactam instead of 2,5-dichloroterephthaloyl-biscaprolactam as activator was employed. A mixture of A component solution consisting of ε-caprolactam and catalyst and B component solution consisting of ε-caproalctam, polypropylene glycol and activator was poured into a mold which was kept at 140 °C. After about 5 minutes, the mold was opened. However anionic polymerization was not completed yet and surface appearance of the molded articles was not sufficiently excellent for practical use. Example 2 (Preparation of prepolymer) A reaction of 1 mol of polypropylene glycol ( Mn : 2,000) and 2 mol of 2,5-dichloroterephthaloyl-biscaprolactam as activator was carried out in the presence of 0.05 mol of sodium ethylate at 120 -- 140 °C to yield a slightly brown-colored product. This product proved to be a prepolymer having a structure represented by the following formula by IR and ¹³C-NMR spectra. Assignments of peaks in each spectra are as follows. IR: no signals in 3,300 -- 3,500 cm⁻¹ region (ν OH ), 1730 cm⁻¹: ν C=O of ester group, 1670 cm⁻¹: ν C=O of imino group. ¹³C-NMR: chemical shifts are presented in ppm referred to tetramethylsilane a: 177.0, b: 173.0; c: 133.6, d: 131.4, e: 131.0, f: 142.7, g: 145.3, h: 128.8, i: 166.1, j: 75.1 -- 75.3, k: 72.9 -- 73.3, 1: 17.3 (Anionic polymerization) 50 g of anhydrous ε-caprolactam and 14.2 m mol of ethylmagnesium bromide (ether solution) were mixed in a nitrogen atmosphere at 90 -- 100 °C and then ether was distilled off under a slight vacuum to give a solution (A component solution). 30 g of anhydrous ε-caprolactam and 20 g of prepolymer were mixed in a nitrogen atmosphere at 90 °C to give a solution (B' component solution). A mixture of A and B' component solution was quickly poured into a metal mold which was kept at 150 °C. After about 5 minutes, the mold was opened and the molded test-pieces were taken from the mold. Mechanical properties of these test-pieces were measured and the results were summarized in Table 1. Examples 3 to 9. By the method described in Example 1 -- 2, but varying the kind and amount of lactam, polyol, catalyst and activator, the block copolyamides were prepared and test-pieces were molded. The characteristics of the molded test-pieces were summarized in Table 1. In each case, test-pieces showed excellent mechanical properties. Example 10 30 % by weight of milled glass fibers (diameter: 10 µm and length: 150 µm were added to A and B component solutions employed in Example 1. Then the mixture of A and B component solutions containing milled glass fibers was poured into a mold which was kept at 160 °C. After about 4 minutes, the mold was opened and the molded test-pieces were taken from the mold. Mechanical properties of these test-pieces were measured and the following results were obtained. Tensile strength: 730 kg/cm² Flexural strength: 930 kg/cm² Flexural modulus: 32,500 kg/cm² Izod impact strength: 14 kg·cm/cm notch Heat distortion temperature: 210 °C (4.64 kg/cm² load) 1) CL: ε-caprolactam, PY: α-pyrrolidone 2) PPG: polypropylene glycol, PPT: polyoxypropylene triol, PTMG: polytetramethylene glycol, PEG-PPG: poly (oxyethylene / oxypropylene) diol, PEG: polyethylene glycol Affix number represents number average molecular weight of polyols.

Claims: A process for producing a block copolyamide which comprises polymerizing a mixture comprising substantially from 50 to 95 parts by weight of lactam and from 50 to 5 parts by weight of polyol in the presence of a catalyst for anionic polymerization and an activator represented by the following formula (I): wherein A denotes a bifunctional aromatic residue having on an aromatic ring at least one heteroatom selected from the group consisting of F, Cl, Br and I (referred to herein as "halogens"), Y and Y' each independently denotes an acyl group selected from and n and n' each independently denotes an integer of 3 to 11. A process for producing a block copolyamide which comprises polymerizing, in the presence of a catalyst for anionic polymerization, a mixture comprising substantially from 50 to 95 parts by weight of lactam and from 5 to 50 parts by weight of a prepolymer obtained by a reaction of polyol and activator (I). A process according to claim 2, wherein said prepolymer is represented by the following formula (II); wherein D denotes a polyol residue, m denotes an integer of 2 or 3, and B, Y, and n denote the same as in claim 1. A process according to any preceding claim, wherein A denotes a bifunctional group having at least one group selected from monochlorophenylene, dichlorophenylene, tetrachlorophenylene and monobromophenylene. A process according to any one of claims 1 to 3, wherein A is selected from 2 chloro-1,4-phenylene or 2,5-dichloro-1,4-phenylene. A process according to any preceding claim, wherein Y and Y' denote A process according to any preceding claim, wherein the activator is used in the amount of 0.001 -- 0.25 times by mole based on the lactam to be polymerized. A process according to any preceding claim, wherein the lactam is selected from pyrrolidone, valerolactam, caprolactam, enantholactam, capryllactam and lauryllactam. A process according to claim 8, wherein the lactam is ε-caprolactam. A process according to any preceding claim, wherein the number average molecular weight of the polyol is in the range of 300 to 5,000. A process according to any preceding claim, wherein the polyol is selected from polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (oxyethylene / oxypropylene) diol, polyoxyethylene triol, polyoxypropylene triol, poly(oxyethylene / oxypropylene) triol and polyoxybutylene triol. A process according to any one of claims 1 to 10, wherein the polyol is selected from polypropylene glycol, poly (oxyethylene / oxypropylene) diol, polyoxypropylene triol and poly (oxyethylene / oxypropylene) triol. A process according to any preceding claim, wherein the catalyst for anionic polymerization is selected from alkali metals and alkaline earth metals and their lactamate salts, hydrides, alkoxides and alkylides, trialkylaluminium compounds and Grignard reagents. A process according to claim 13, wherein the alkali metal is selected from sodium and potassium. A process according to any preceding claim, wherein the catalyst for an anionic polymerization is used in the amount of 0.001 -- 0.1 times by mole based on the lactam to be polymerized.

Inventors: CHIBA, KAZUMASA, KOBAYASHI, KAZUHIKO, SUSUKI, TOSAKU
Applicants: TORAY INDUSTRIES, INC.
Application year: 1983
Main classification: C08G69
IPC codes: C08G69