PROCESS FOR PRODUCING POLYAMIDE

Abstract: A process for producing a polyamide while defoaming the bubbles formed during the process comprises polymeriz­ ing at least one monomer therefor in the presence of: (1) a hydrocarbon polymer bearing at least one type of group selected from carboxyl, carboxylic acid derivative, amino and hydroxyl groups, or (2) a polymer produced by reacting a said hydrocarbon polymer with a polyamide, or polymerizing at least one poly­ amide monomer in the presence of the hydrocarbon polymer.

Description: The present invention relates to a process for producing a polyamide. In most conventional polyamide production processes, the stage in which bubbles generate determines the rate of production irrespective of polymerisation system (batch-wise or continuous), and improvement in this respect has been demanded. As a result of studies on defoaming at the stage of the generation of bubbles in producing a polyamide, the present inventors have found that an excellent defoaming effect is displayed when at least one monomer of polyamide (hereinafter referred to as "polyamide monomer material") is polymerized in the presence of a predetermined amount of a hydrocarbon polymer or a polymer of a hydrocarbon polymer with a polyamide. The present invention provides a process for producing a polyamide, which process comprises polymerizing monomer therefor (monomer A) in the presence of: (1) from 1 to less than 1,000 ppm with respect to the said monomer A of a hydrocarbon polymer bearing at least one type of group selected from carboxyl, carboxylic acid derivative, amino and hydroxyl groups, the number-average molecular weight of said hydrocarbon polymer being from 500 to 20,000 (hereinafter referred to as "modified hydrocarbon polymer"), or (2) a polyamide copolymer obtained by polymerising monomer therefor (monomer B) in the presence of a said hydrocarbon polymer or by reacting a polyamide with a said hydrocarbon polymer, the amount of the hydrocarbon polymer in said polyamide copolymer being from 1 to less than 1,000 ppm with respect to the said monomer A and the number-average molecular weight of the polyamide component in said polyamide copolymer being from 1,000 to 50,000 (hereinafter referred to as "polyamide copolymer"), to provide a defoaming effect during the polymerisation. The polyamide monomer material includes, for example, lactams having a ring of not less than 3 carbons, polymerizable ω-amino acids, dibasic acids, and diamines. Examples of lactams are ε-caprolactam, enantholactam, caprillactam, laurillactam, α-pyrrolidone and α-piperidone; examples of α-amino acids are 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid and 11-aminoundecanoic acid; examples of dibasic acids are adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, hexadecanedioic acid, hexadecenedioic acid, eicosanedioic acid, eicosandienedioic acid, diglycollic acid, 2,2,4-trimethyladipic acid, xylylene dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, terephthalic acid and isophthalic acid; and examples of diamines are hexamethylene - diamine, tetramethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4 (or 2,4,4)-trimethylhexamethylenediamine, bis-(4,4'-aminocyclohexyl) methane and methaxylylenediamine. The polymerization process of the present invention is initiated using the polyamide monomer material in the normal way. The modified hydrocarbon polymer or the polyamide copolymer may be added in an optional stage between the start of the polymerization reaction and the start of pressure release or pressure reduction. In the case of polymerization of lactams in the presence of alkali catalyst, an alkaline metal such as lithium, sodium or potassium; an alkaline earth metal such as magnesium, calcium, strontium or barium; or a hydride thereof is used as the catalyst. The reaction may be carried out either in the presence or in the absence of an organic diluent. In this case, the modified hydrocarbon polymer or the polyamide copolymer may be added in an optional stage before the start of the polymerization reaction. Example of the hydrocarbon polymer are a homopolymer or copolymer of an α-olefin such as ethylene and propylene, and a hydrogenated homopolymer or copolymer of a diene, A hydrogenated diene polymer is preferred. An example of the diene polymer is a homopolymer or a copolymer obtained by polymerizing at least one monomer selected from 1,3-butadiene, 1,3-pentadiene, chloroprene and isoprene. A polymer of a conjugated diene, in particular polybutadiene or polyisoprene, is preferred. Any method such as a radical, cation, anion or coordination polymerization may be used to polymerize the dienes. Styrene, α-methylstyrene, o- or p-vinyl toluene, vinyl xylene, or acrilonitrile may be used as a comonomer. In order to introduce a hydroxyl group into the hydrocarbon polymer ethylene oxide may, for example, be reacted with a living polymer of a diene compound, or radical polymerization may be carried out using a radical initiator containing an OH-group such as hydrogen peroxide or 4,4'-azobis (4-cyano-n-amyl alcohol). In order to introduce a carboxylic acid derivative group such as carboxylic acid, ester, acid halide or amino group into the hydrocarbon polymer carbon dioxide may, for example, be reacted with a polymer of a diene compound, or radical polymerization of a diene compound may be carried out using a radical initiator containing a carboxyl group or a carboxyl acid derivative group such as 4,4'-azobis (4-cyano-valerianic acid). Alternatively, an acid halide or anhydride may be reacted with the hydrocarbon polymer having a hydroxyl group. Additional examples of preparation include reacting ethylene oxide, for example, with a living polymer of a diene compound, and, to obtain a polymer containing a carboxyl group, reacting an acid halide or anhydride with a diene polymer containing a hydroxyl group obtained by radical polymerization using a radical initiator containing an OH-group such as hydrogen peroxide or 4,4'-azobis (4-cyano-n-amyl alcohol). Furthermore, a monomer having a carboxyl group or a carboxylic acid derivative group may be reacted with a monomer containing a diene function. Examples of monomers having a carboxyl group or a carboxylic acid derivative group are acrylic acid, methacrylic acid, maleic acid, fumaric acid, chloromaleic acid and itaconic acid, and derivatives thereof such as esters of an above-mentioned acid, for example with methanol or phenol, and anhydrides such as anhydrous maleic acid. These monomers may be added to a hydrogenated polymer of a diene compound in the form of a derivative of carboxylic acid, and may be converted into a corresponding derivative by adding carboxylic acid or an anhydride thereof thereto. An example of a method of introducing an amino group is to cyanoethylate the hydroxyl group of a polymer of a diene compound into which a hydroxyl group has been introduced, to hydrogenate the cyanoethyl group, and to aminate the halogen atom after halogenating the hydroxyl group. A polymer of a diene compound, having a carboxyl group, and a hydrogenated polymer thereof, or a polymer of a diene compound suitable for introducing a polar group selected from a carboxyl group, a carboxylic acid derivative group and an amino group are commercially available. For example the following are usable: Nisso-PB G-1000 (trade name: produced by Nippon Soda Co., Ltd.) Nisso-PB G-2000 (ditto) Nisso-PB G-3000 (ditto) Nisso-PB GI-1000 (ditto) Nisso-PB GI-2000 (ditto) Nisso-PB GI-3000 (ditto) Nisso-PB C-1000 (ditto) Nisso-PB CI-1000 (ditto) Polyter H (trade name: produced by Mitsubishi Chemical Industries, Ltd.) Polyter HA (ditto), Poly-BD (trade name: produced by Arco, Ltd.) Batarez HT (trade name: produced by Philips Ltd.) Hycar BTB (trade name: Goodrich, Ltd.) Telosen HT (trade name: General Tyre Ltd.) The number-average molecular weight of these modified hydrocarbon polymers is 500 to 20,000, preferably 1,000 to 10,000. If the number-average molecule weight is too small, the defoaming effect is disadvantageously reduced, while a too large number-average molecular weight deteriorates the dispersibility of the hydrocarbon polymers in a polyamide, which also reduces the defoaming effect. It is possible to produce a polyamide copolymer by reacting a polyamide with a modified hydrocarbon polymer by the methods disclosed in Japanese Patent Application Laying-Open (KOKAI) Nos. 57-149329/1982, 57-151622/1982, 59-213723/1984 and 59-202220/1984. For example, there is the method of mixing a polyamide monomer material with a modified hydrocarbon polymer in advance and obtaining a polyamide polymer by an ordinary polycondensation or ring opening polymerization, and the method of polymerizing a polyamide monomer material to obtain a polyamide having a number-average molecular weight of 1,000 to 50,000, preferably 5,000 to 40,000, and melt-mixing and reacting the thus obtained polyamide with a modified hydrocarbon copolymer. In this case, if the molecular weight of the polyamide is too small, no defoaming effect is expected, while too large molecular weight increases the viscosity and makes it difficult to operate the reaction with a modified hydrocarbon polymer and to handle the produced polyamide copolymer. At this time, it is possible to use dicarboxylic acid, a dicarboxylic acid derivative or a diamine as a chain restricting agent to control the average molecular weight of the polyamide. The weight ratio of the hydrocarbon polymer component to the polyamide component in the polyamide copolymer is 1 : 99 to 99 : 1, preferably 3 : 97 to 97 : 3. If the ratio of the hydrocarbon polymer component is too small, little defoaming effect is expected. On the other hand, if the ratio is too large, the hydrocarbon polymer is not well dispersed into the polyamide during polymerization, which does not produce a good defoaming effect. The molecular weight of the polyamide copolymer in variant (2) of the present invention is determined by the type, volume ratio and reaction conditions of the modified hydrocarbon polymer monomer material and the polyamide monomer material or the polymer thereof. It is ordinarily 2,000 to 60,000, preferably 5,000 to 50,000. The weight ratio of (1) the modified hydrocarbon polymer to the polyamide monomer material or (2) the modified hydrocarbon polymer of the polyamide copolymer to the polyamide monomer material, which is required in polymerizing the polyamide monomer material, is in the range of 1 to less than 1,000 ppm, preferably 2 to less than 1,000 ppm, more preferably 5 to less than 1,000 ppm. If the weight ratio is too small, no defoaming effect is obtained, while a too large weight ratio disadvantageously accelerates the foaming action even more than when nothing is added. When the polyamide monomer material is polymerized, a reinforcing agent such as glass fibers or carbon fibers; a filler such as silica, alumina, silica alumina, silica magnesia, calcium carbonate, gypsum or clay; a lubricant of a higher fatty acid or its derivative such as stearic acid, octadecyl stearate, barium stearate, calcium stearate and magnesium stearate; a flame retardant such as a melamine derivative, cyanuric acids and a triazinyl base ring; and other additives may be used together with the polyamide copolymer. According to the present invention, the use of a very small amount of modified hydrocarbon polymer or polyamide copolymer is able to reduce greatly the foaming during the production of a polyamide. In addition, the defoaming effect is prominent especially when bubbles are likely to be produced, for example, at a time of polymerization with a higher fatty acid or a derivative thereof added. Thus, it can be said that the present invention is industrially very valuable. The present invention will be explained in more detail with reference to Examples 1 to 6 below. Example of preparation of a hydrocarbon polymer having a carboxylic acid group 10ℓ of refined cyclohexane (distilled by ArF after LiAlH₄ treatment) and 1 kg of butadiene were charged into a 20ℓ reaction vessel and stirred, and 0.46 mol of n-BuLi was added to the mixture in the form of a hexane solution (2 mol/ℓ). After the reaction was continued at room temperature for 24 hours, carbon dioxide gas which had been dehydrated by molecular sieves MS-4A was introduced into the reaction solution. After the polymer solution was washed with water to remove the initiator, the solvent was distilled off under a reduced pressure to obtain 900 g of polymer. The number-average molecular weight was 2200 by VPO. The polymer obtained was dissolved in a solvent of isopropanol/n-heptane (1/1) and was hydrogenated at 120°C, under 30 atm (3040 kPa) for 6 hours in the presence of Ru/C as a catalyst. The carboxylic acid group value of the polymer obtained was 0.45 meq/g and the iodine value was 3.5. Example of preparation of a polyamide copolymer Carboxylic-acid-modified polybutadiene (1.2 unit content: 92 %) was synthesized by introducing carbon dioxide gas into the anion-polymerized butadiene in the presence of sodium as a catalyst. The thus obtained polymer was hydrogenated to obtain a modified hydrocarbon polymer of a hydrogenation rate of 90 %. The number-average molecular weight of the modified hydrocarbon polymer was 2200. 14 kg of ε-caprolactam, 129 g of hexamethylenediamine, 300 g of water and 2.4 kg of the thus obtained modified hydrocarbon polymer (the weight ratio of hydrocarbon to polyamide was 1 : 6) were charged into a 200 ℓ autoclave, which was closed in a nitrogen atmosphere, and the temperature was raised to 260°C. After the reaction was carried out for 2 hours under pressure with stirring, the pressure was gradually released and reduced to 700 Torr (93 kPa) Torr and the reaction was carried out for 5 minutes under the reduced pressure. Nitrogen was introduced and, after the pressure was restored to normal pressure, stirring was stopped. The reaction product was taken out in the form of a strand and was cut into chips. After the unreacted monomer was extracted from the reaction product using boiling water, the product was dried. The number-average molecular weight of the thus obtained polyamide copolymer was 11,300. Examples 1 to 6 and Comparative Examples 1 to 3 60 kg of ε-caprolactam; 1.2 kg of water; and a hydrocarbon polymer having a carboxylic acid group which had been produced in the "Example of preparation of a hydrocarbon polymer having a carboxylic acid group" in an amount shown in Table 1, a hydrocarbon polymer of a number-average molar weight of 2,000 having 0.9 meq/g of a hydroxyl group and an iodine value of 3.5 (trade mark: Polyter HA, produced by Mitsubishi Chemical Industries, Ltd.), or stearic acid or barium stearate together with Polyter were charged into a 200 ℓ autoclave. The temperature was raised to 260°C and the reaction was carried out for 2 hours under a pressure. The pressure was then released while maintaining the volume ratio of the bubbles to the liquid within the autoclave constantly at 0.8, and the time required for the pressure to reach normal pressure was measured. The results are shown in Table 1. After the release of the pressure, the polymerization reaction was carried out at 250°C under 500 Torr (67 kPa) for 2 hours. The pressure was restored to normal pressure and the reaction product was taken out in the form of a strand and cut into chips. The unreacted monomer was extracted and the product was dried. The relative viscosities of the polyamides obtained are shown in Table 1. For comparison, the same processes as in Examples were repeated without adding any polyamide copolymer. The results are also shown in Table 1. The relative viscosities were measured on the basis of JIS K 6810 by diluting the samples into 98 % sulfuric acid so as to have a concentration of 1 % at 25°C. Examples 7 to 10 60 kg of ε-caprolactam; 1.2 kg of water; and a polyamide copolymer which had been produced in the "Example of preparation of a polyamide copolymer" in an amount shown in Table 2, or stearic acid or barium stearate together with the polyamide copolymer were charged into a 200 ℓ autoclave and the temperature was raised to 260°C to carry out reaction under a pressure for 2 hours. The other processes were the same as in Examples 1 to 6, and the pressure release time and the relative viscosities were measured in the same way as in Examples 1 to 6. The results are shown in Table 2. Example 11 and Comparative Example 4 83 kg of 60 % saline solution was charged into a 200 ℓ autoclave. After N₂ exchange, the temperature was raised to 260°C while maintaining the pressure at 17.5 kg/cm²G, and this state was held for 1.5 hours. The pressure was gradually released down to 2.5 kg/cm²G. At this stage 5.41 meq/g of laurilamine and the hydrocarbon polymer having a carboxylic acid group which had been prepared in the "Example of preparation of a hydrocarbon polymer having a carboxylic acid group" were added to the solution and the mixture was held at the same temperature for another 1.5 hours. The pressure was then released while maintaining the volume ratio of the bubbles to the liquid within the autoclave constantly at 0.8, and the time required for the pressure to reach normal pressure was measured. The result is shown in Table 3. After the release of the pressure, the polymerization reaction was carried out at 250°C under 250 Torr (33 kPa) for 1 hour. The pressure was restored to normal pressure and the reacted product was taken out in the form of a strand, cut into chips and dried. For comparison, the same process as in Example 11 was repeated without adding any modified hydrocarbon polymer. The result is also shown in Table 3. Example 11 Comparative Example 4 Modified Hydrocarbon Polymer Kind Example of Preparation - Quantity (ppm) 10 - Additive Kind Laurilamine Laurilamine Quantity (%) 0.56 0.56 Pressure Release Time (min) 10 30 η rel 2.73 2.75 The relative viscosities were measured on the basis of JIS K 6810 by diluting the samples into 98 % sulfuric acid so as to have a concentration of 1 % at 25°C.

Claims: A process for producing a polyamide, which process comprises polymerizing monomer therefor (monomer A) in the presence of: (1) from 1 to less than 1,000 ppm with respect to the said monomer A of a hydrocarbon polymer bearing at least one type of group selected from carboxyl, carboxylic acid derivative, amino and hydroxyl groups, the number-average molecular weight of said hydrocarbon polymer being from 500 to 20,000, or (2) a polyamide copolymer obtained by polymerizing monomer therefor (monomer B) in the presence of a said hydrocarbon polymer or by reacting a polyamide with a said hydrocarbon polymer, the amount of the hydrocarbon polymer in said polyamide copolymer being from 1 to less than 1,000 ppm with respect to the said monomer A and the number-average molecular weight of the polyamide component in said polyamide copolymer being from 1,000 to 50,000, to provide a defoaming effect during the polymerisation. A process according to claim 1, wherein said hydrocarbon polymer is a hydrogenated diene polymer. A process according to claim 1 or 2, wherein the weight ratio of the hydrocarbon polymer component to the polyamide component is from 1 : 99 to 99 : 1.

Inventors: KOGA, SHINICHIRO, MIYAMOTO, MASAAKI, NAKANISHI, HIDEMI
Applicants: MITSUBISHI KASEI CORPORATION
Application year: 1986
Main classification: C08G69
IPC codes: C08L77, C08G81, C08G69