MXPA97004250A - Obtaining caprolactma mediantedespolimerizacion de policaprolactama fund - Google Patents

Abstract

The present invention relates to a process for obtaining caprolactam from mixtures containing polymers or thermoplastic molding materials having the repeating unit: - [- N (H) - (CH 2) 5-C (O) -] - a ) by decomposition at elevated temperatures in the presence of a base under reduced pressure or (b) in the presence of water, which comprises using a mixture comprising essentially 50 to 99.5% by weight of a polymer or a thermoplastic molding material having the repeating unit - [- N (H) - (CH2) 5-C (O) -] - from 0.1 to 50% by weight of additives selected from the group consisting of inorganic fillers, pigments and organic and inorganic dyes, from 0 to 10% by weight of organic or inorganic additives, from 0 to 40% by weight of polymers not containing polyamide and from 0 to 2.0% by weight of polyamides, with the exception of polycaprolactam and copolyamides prepared from caprolactam, and carry out the decomposition in the presence of a base under pressure reduced, the water content of the mixture used not being more than 0.01% by weight or carrying out the decomposition in the presence of water without the addition of acid or base at a temperature of 270§350 ° C and a weight ratio from water to polymer or thermoplastic mold material from 1: 1 to 20: 1 and in a reaction time of less than 3 hor

Description

OBTAINING CAPROLACTMA THROUGH DESPOLIMERI ZAC ION OF POLICAPRO LACTAMA FUNDIDA The present invention relates to processes for obtaining caprolactam from mixtures containing polymers or thermoplastic molding materials having the repeating unit - / -N (H) - (CH2) 5-C (0) -_ 7- (a) by depolymerization at elevated temperatures in the presence of a base under reduced pressure or (b) in the presence of water. The present invention also relates to the use of a novel process for recycling waste containing poly-prol actama. J. Appl. P. Sci 22 (1978) 361-368 describes the depolymerization of pol icaprolacta a (PA 6) in the presence of bases under reduced pressure. However, the yield of 90.5% is insufcient for industrial and economic use on a large scale. Additionally, for example, JP 50131979 and JP 551002 describe processes for despolising PA 6 that operate under reduced pressure in the presence of acids. However, in these cases too, the yields of 89 and 69%, respectively, are too much of an actor for economic use. In addition, only the depolymerization of pure polycaprolactam is described. An object of the present invention is to provide a process for obtaining caprolactam for polymers and thermoplastic molding materials that provides high yields of C Drolactam. It is also intended to provide a process that makes it possible to use wastes containing polyaproactam containing inorganic fillers to provide caproic acid, without having to accept reduced yields. We have found that this object is achieved through a process to obtain caprolactam from mixtures containing polymers or thermoplastic molding materials that have the repetitive unit / -N (H) - (CH2) 5-C (0) -_ 7- (a) by depolymerization at elevated temperatures in the presence of a base under reduced pressure or (b) in the presence of water, using a mixture comprising essentially 50 to 99.9% by weight of a polymer or a thermoplastic molding material having the repetitive unit / -M (H) - (CH2) 5-C (0) -7- from 0.1 to 50% by weight of additives selected from the group consisting of inorganic fillers, pigments and organic and inorganic dyes, from 0 to 10% by weight of organic and / or inorganic additives, 0 to 40% by weight of polymers not containing polyamide and 0 to 20% by weight of polyamides, with the exception of polycaprolactam and copolyamides prepared from - caprolactam, and carry out the depolymerization in the presence of a base under reduced pressure, the water content of the mixture used not being more than 0.0% by weight, or carry out the depolymerization in the presence of water without the addition of acid or base a of 270 to 350 [deg.] C. and a weight ratio of water to polymer or thermoplastic molding material of 1: 1 to 20: 1 and in a reaction time of less than 3 hours. We have also found that the use of the novel process to recycle wastes containing polyprolactam. According to the invention, the starting materials used are mixtures consisting essentially of 50 to 99.9, preferably 60 to 99.9% by weight of a polymer or a thermoplastic molding material having the repeating unit -rM (H) (CH2) 5- C (0) - 7- from 0.1 to 50 preferably from 0.1 to 40% by weight of additives are selected from the group consisting of inorganic fillers, pigments and organic and inorganic dyes , from 0 to 10, preferably from 0 to 5% by weight of organic and / or inorganic additives, from 0 to 40, preferably from 0 to 20% by weight of polymers that do not contain polyamide, and from 0 to 20 of Dreference of 0 to 15% by weight of polyamides, with the exception of polyprolactam and copolyamides prepared from caprol acta a. A polymer that is polycapro lactam having a relative viscosity, preferably from 1. to 5.0, is preferably used., particularly preferably from 2.0 to 4.0 (measured at a concentration of 1 g of polymer per 100 μl of resistance to 96% by weight of sulfuric acid at 25 ° C.). From time to time, it is also possible to use polyprolactam containing oiigomers in an amount of 0.01 to 10, preferably 0.05 to 0.5% by weight, based on the total amount. It is also possible to use copoiiamides obtained from caprolactam and other polyamide-forming monomers, for example salts formed from a dicarboxylic acid, such as adipic acid, sebacic acid and terephthalic acid, and a diamine, such as hexamethia lendia ina. and tetramet i lendi amine, preferably salt AH (obtained from adidic acid and hexameti lendiami na), and lactams, such as 1 aurol actama. Observations to date have shown that all the known polyprolactams can be converted to caprolactam by the novel process, for example, also a polycaprola which was prepared in the presence of mono- or di-boxic acids or amines, which act as regulators of chain, for example, acetic acid, propionic acid, benzoic acid, hexamethylbendane, C-CQ alkadicarboxylic acids, such as adipic acid, pyrilic acid, suberic acid, acelaic acid, sebacic acid, undecandioic acid, dodecandioic acid and mixtures thereof, cycloalkanediocarboxylic acids of Cc-Cg, such as cyclinic acid Dentan-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid and mixtures thereof, benzene and naphthalenedicarboxylic acids. i icos that can carry up to two sulfo groups, including the corresponding alkali metal salts, and whose carboxyl groups are not adjacent such as terephthalic acid, acid isophthalic acid and naphthalene-2,6-dicarboxylic acid, 5-sulfoisophthalic acid and its lithium sodium salts, and mixtures thereof, and 1,4-piperazindyl-Cj-α-alkanecarboxylic acids, as 1,4-piperazindiacetic acid, 1,4-piperazindipropioni -co acid, 1,4-Diperazindibuti acid, 1,4-DiDerazindipentanoic acid and 1,4-piperazindihexanoic acid. The corresponding copolyamides are known to a person skilled in the art and can be prepared by processes described, for example, in 0 93/25736, DE-A 14 95 198 and DE-A 25 58 480. Observations to The date has shown that all fillers, such as glass fibers, calcium carbonate and such, which are commonly used in the composition of polyamides can be used as inorganic fillers. Observations to date have shown that the appropriate pigments and colorants - inorganic and organic and all the pigments and dyes, such as titanium dioxide, iron oxides and carbon blacks, which are usually used to color polyamides, and the dyes of Conventional spinning such as complete chromium or copper complexes. Conventional stabilizers and antioxidants, thermal stabilizers and UV stabilizers, antistatic agents and flameproof agents can be used as organic and inorganic additives. Antioxidants and thermal stabilizers, for example, are sterically hindered phenols, hydroquinones, phosphites and derivatives and substituted members of this group and mixtures of these compounds, as well as copper compounds, such as copper iodide (I) and acetate. copper (II). Examples of UV stabilizers are substituted resorcinols, silicides, benzotriazoles, benzophenones and compounds of the HALS type (hindered amine light stabilizer), and manganese compounds (II) are also suitable for this purpose. Conventional substances, eg Dor, poly (alkylene oxide) and derivatives thereof, can be used as antistatic agents. The conventional compounds containing chlorine and ni-trogen, such as melamine cyanurate and aluminum hydroxide as well as 1,2,3,4,7,8,9,10,13,13,14,14-dodecachlor-1, 4.4a, 5,6,6a, 7 10, 10a, 11, 12,12a-dodecahydro-1, 4: 7, 10-d imetanedibenzo / _ a, e_ Ticlo-octene (product of Diels-Alder of hexac lorocyclopentadiene and 1, 5-cyclooctadiene and commercially available under the name Dichlorane ^ '), can be used as flame-proofing agents. Conventional thermoplastic engineering polymers, such as polymers based on ethylene, propylene and styrene and copolymers thereof with butadiene can be used as polymers that do not contain Doliamide. Suitable polyamides with the exception of polycaprolactam and copolyates prepared from caprolactam are, for example, polyamide 66, polyamide 610 and polyamide 46. Preferred starting materials are polyacrylate, which contains inorganic fillers, in particular fibers. of glass, and waste is disposed of in the production of polyacrylate and processing thereof to provide filaments for films or injection molded or extruded parts, and shaped utility articles, such as such as films, packaging, fabric, carpet fibers, carpeting, films and extruded parts, which are going to be discarded. According to the invention, the depolymerization in variant (a) is carried out in the presence of a base a of 0.01 to 10, preferably 0.1 to 2.5 kPa, the water content of the mixture used being not more than 0.01. % in weigh.

The temperature in the melt is selected as a ruler in the range of 240 to 350 ^ 0, preferably 250 to 310 ^ c. According to the invention, the base used is a compound selected from the group consisting of alkali metal oxide, alkali metal hydroxide, alkali metal carbonate, alkali metal alcoholate, alkaline earth metal oxide, hydroxide alkaline earth metal and alkaline earth metal carbonate, such as * sodium oxide, ptoasium oxide, magnesium oxide, calcium oxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, sodium ethylate, calcium carbonate or magnesium carbonate, preferably sodium hydroxide, potassium hydroxide or a mixture of sodium hydroxide and potassium hydroxide. The amount of base depends essentially on the basility of the base to be used and is from 0.1 to 100, preferably from 0.5 to 30 g per kg. of poly icaprol actama or polyacaprolactam donor polymer used, for example, when sodium hydroxide and potassium hydroxide are used. In the process in an autoclave, the reaction time is usually 0.25 to 6, preferably 0.5 to 3 hours. In variant (b), the mixture used is heated with up to 20 times of excess water at 270-350eC, preferably 280-330QC at 80 to 150, preferably 100 to 120 kPa, the weight ratio of water to polymer in the mixture used being selected nothing in the scale from 1: 1 to 20: 1, preferably from 7: 1 to 10: 1, and no acid or base being added. The reaction time is usually 0.25 to 5, preferably 0.75 to 1.5, hours. After depolymerization, the reaction mixture can be worked in the usual way, for example by removing by filtration or decanting the insoluble components, such as glass fibers, pigments, etc., and obtaining caproiactam from the filtrate, preferably by distillation. The caprolactam obtained according to the invention is preferably fed to a purification step for caprolactam which is used in the preparation of caprolactam. Further possibilities, if desired, for purifying the caprolactam obtained according to the invention are described, for example, in EP-A 568 882 and 570 843. The purified caprolactam is then generally available for further use, in particular for the PA preparation 6. The novel process can be used to recycle wastes containing polyaprol actama, such as used carpets, carpet cuts, plastic parts, fibers, aqueous extracts and oligomers. The advantages of the novel process over the processes of the prior art are depolymerization yields of up to 93%, short residence times and smaller amounts of waste requiring treatment and disposal.

EXAMPLES Example 1 In a 1-liter autoclave, 250 g of poia ida 6 (Ultramid (R) BS 400 (BASF), relative viscosity = 2.4 (measured at a concentration of 1 g of polymer per 100 ml of resistance of 96% by weight of sulfuric acid at 255C), which have a residual moisture content of 0.01% by weight), and 5.0 g of sodium hydroxide were heated to 280QC at 20 kPa. After a reaction time of 2 hours, 231.9 g were obtained. of caprolactam from the reaction mixture by distillation. Yield: 93%.

Examples 2 to 9 Various polymers containing PA 6 were subjected to alkaline depolymerization in a manner similar to Example 1. The mixtures used and the yields are shown in Table 1.

Table 1: Alkaline depolymerization Axis. Substance used Caprolactam Yield (g) (%) 1 Polyprolactam containing 36% by weight of glass fibers (Ultra-mid (R) B3G7 (BASF), relative viscosity = 2.7 144.3 90 (R) 2 Pol icaprolactam containing Dechlorane 'as a test agent of 137.6 79 flame and containing 30% by weight of talc (Ultra id (R) B3 UM6 (BASF), relative viscosity = 2.7) 3 Poly icaprolactam containing 30.2% by weight of glass fibers (ultra- 158.8 91 mid (R) RC 6000 (BASF), relative viscosity = 2.7) 4 Concentrate of poly icaprol actama obtained from carpeting (which contains 171.6 92 75% by weight of poly icaprol actama) (1) 5 Coooliamide 6/66 (prepared from 85% by weight of caprolactam 195.4 92 and 15% by weight of salt AH, Ultramid (R) C 35, viscosity relative = 3.25) 6 Mixture of PA 6 and PA 66 (in weight ratio of 80:20; viscosity reía- 182.2 91 tiva = 2.7 in each case) 7 Pol icaprolactam (propionic acid-regulated; UltramicPR 'BS 400 (BASF) 231.9 93 relative viscosity = 2.4) 8 Polycarbactam (propionic-regulated acid; ultramid ^ BS 700 (BASF) 232.6 93 relative viscosity = 2.7) 9 Polycaprolactam (Ultramid ^ BS 3300 (BASF) Relative viscosity = 3.3) 232.8 93 Comparison 1) The carpets were freed from polyamide-free components until the amount of polycaproiactam was 75% in weight, based on the mixture.

Example 10 In a 1 liter autoclave, 40 g were heated. from po 1J_ amide 6 (Ultramid ^ BS 400, relative viscosity = 2.4) to 3105C with 400 g of water for 1.5 hours. The caproiactam and apucaproic acid were then removed from the reaction mixture by distillation. The yield of caprolactam was 74%, that of aminocaproic acid was 8% and that of oligomers was 2%.

Examples 11 to 18 Polymers containing PA 6 were subjected to hydrolytic depolymerization in a manner similar to Example 10. The mixtures used and the yields are shown in Table 2.

Table 2: Hydrolytic depolymerization jem. Substance used Caprolactam Rend imient (g) (%) Pol icaprolactam containing 36% by weight of glass fibers 18.9 74 (Ultramid (R) B3G7 (BASF), relative viscosity = 2.7) 11 Pol icaprolactam containing Dechlorane (R) 'as a flameproof agent of 18.7 67 flame and contains 30% by weight of talc (Ultramid (R) B3 UM6 (BASF) relative viscosity = 2.7) 12 Poly icaprolactam containing 30.2% by weight of glass fibers (Ultra21.0 75 mid (R) RC 6000 (BASF), relative viscosity = 2.7) 13 Polycarboxylate concentrate obtained from carpeting (containing 75% 21.7 72 by weight of polycapol actama) (1) 14 Copolyamide 6/66 (prepared from 85% by weight of caprolactam and 25.6 75 15% by weight of salt AH, Ultramid (R) C35, relative viscosity = 3.25) 15 Mixture of PA 6 and PA 66 (in weight ratio 80:20, viscosity rela22.9 72 tiva = 2.7 in each case) 16 Poly icaprolactam (ico-regulated oro-ion acid; Ultramid (R) BS 400 (BASF) 30.2 75.5 Relative viscosity = 2-.4) 17 (R) Pol icaprolactam (pro-ionic-regulated acid; Ultramid 'BS 700 (BASF) 29.7 74 relative viscosity = 2.7). (R 1 18 Pol icaprolactam (Ultramid BS 330 (BASF), relative viscosity = 3.3) 29.9 75 mparation Note from Table 2: (1) The carpets were freed from the polyamide-free components until the amount of polycatamol was 75% by weight, based on the mixture.

Example 19 (depolymerization with phosphoric acid) In a 1 liter autoclave, 250 g of polyamide 6 (Ultra id ^ BS 700, relative viscosity = 2.7) were heated to 265 ° C with 12.5 g of 85% strength by weight of acid phosphoric. It was heated with steam at 360eC then passed through the resulting melt. A caprolactam solution of 25% strength by weight was obtained, the yield of caprolactam being 222.6 g (89%).

Claims (3)

CLAIMS:

1. - A process to obtain caprolactam from -mixes containing polymers or thermoplastic molding materials that have the repetitive undiad _ / -_ N (H) - (CH2) 5-C (0) -_ 7- (a) by depolymerization at elevated temperatures in the presence of a base under reduced pressure or (b) in the presence of water comprising using a mixture comprising essentially from 50 to 99.9% by weight of a polymer or a moldable material. thermoplastic that has the repetitive undiad - / ~ -N (H) - (CH2) 5-C (0) -7- from 0.1 to 50% by weight of additives selected from the group consisting of inorganic fillers, pigments and organic and inorganic dyes, of 0 to 10% by weight of organic or inorganic additives, from 0 to 40% by weight of polymers not containing polyamide and from 0 to 20% by weight of polyamides, with the exception of poly caprolactam and copolylates prepared from caprolactam, and carry out the depolymerization in the presence of a. base under reduced pressure, the water content of the mixture used not being more than 0.01% by weight, or carrying out the depolymerization in the presence of water without the addition of acid or base at 270 to 350 [deg.] C. and a weight ratio from water to polymer or thermoplastic-molding material from 1: 1 to 20: 1 and in a reaction time of less than 3 hours.

2. A process as claimed in Claim 1, wherein the base used is a compound selected from the group consisting of alkali metal oxide, alkali metal hydroxide, alkali metal carbonate, metal alcoholate. alkaline, alkaline earth metal oxide, earth metal hydroxide such as inothermal and alkaline earth metal carbonate.

3. The use of a process as claimed in claim 1, for recycling waste containing polycapro 1 actama. SUMMARY OF THE INVENTION: Caprolactam is obtained from mixtures containing polymers or thermoplastic molding materials having the repeating unit - / "- N (H) - (CH2) d-C (0) -_ 7- (a) by depolymerization at elevated temperatures in the presence of a base under reduced pressure or (b) in the presence of water, using a mixture comprising essentially 50 to 99.9% by weight of a polymer or a thermoplastic molding material having the repetitive unit - / -N (H) - (CH2) 5-C (0) -7- from 0.1 to 50% by weight of additives selected from the group consisting of inorganic fillers, pigments and organic and inorganic dyes, of 0 to 10% by weight of organic and / or inorganic additives, from 0 to 40% by weight of polymers not containing polyamide and from 0 to 20% by weight of poiiamides, with the exception of polycaprolactate and copolyamides prepared from - caprol actama, and carry out the depolymerization in the presence of a base under reduced pressure, the water content of the mixture used not being more than 0.01% by weight, or carry out the despolitization in the presence of water without the addition of acid or base at 270 to 350 ° C and a weight ratio of water to polymer or thermoplastic molding material from 1: 1 to 20: 1 and in a reaction time of less than 3 hours.