KR950006148B1 - Process of recovering lactam from polyamide waste yarn containing spinning oil - Google Patents

Abstract

(1) treating the aqueous solution of salvaging lactam in an organic solvent separator having a separating membrane so as to physically separate and remove non-aqueous organic component; (2) adding polyacrylamide high molecular coagulating agent to the solution so as to separate and remove the aqueous organic component as a coagulate; and (3) treating with potassium permanganate and active carbon and distillation so as to obtain salvaging lactam.

Description

Process for recovering lactam from emulsion-containing polyamide

1 is a schematic process diagram of a fluid separator employed in the present invention.

The present invention relates to a method for purifying an aqueous solution of a recovered lactam obtained by depolymerization of polyamide, and more particularly, a purification of a recovered lactam obtained by depolymerizing an oil-containing polyamide waste sand.

There are various methods of purifying caprolactam obtained by depolymerization with a phosphate catalyst. For example, a multi-stage distillation method (US Pat. No. 3,855,080), a method of purifying by adding alkali and a peroxide before distillation (Japanese Patent Application No. 47-4190), after oxidation treatment Purification using ion exchange resin (German Patent 2,156,075), organic solvent extraction, recrystallization from an aqueous sulfuric acid solution, and the like.

However, these patents generally relate to a method for purifying depolymerization of an oil-free polyamide, and a method for purifying recovery lactam obtained by depolymerization of an oil-containing polyamide is still unknown.

The recovery lactam obtained by depolymerization of polyamide waste containing an oil agent is difficult to purify, and is difficult to separate by normal treatment, which adversely affects the quality of the final lactam. Until now, polyamide wastes containing an oil agent have been discarded as wastes without being recovered, or when recovered with lactam, it has been difficult to industrially perform the process of washing the sands in advance to remove the oils and then depolymerizing them.

MEANS TO SOLVE THE PROBLEM The present inventors earnestly researched about the refinement | purification method of the recovery lactam obtained by depolymerizing the polyamide waste containing an oil as it is, and after separating the aqueous solution of recovery lactam by the physical method by the oil separator first, and then polyacryl By treating as an amide polymer coagulant, a method of easily removing impurities including an oil agent has been found. That is, the present invention is characterized in that in the purification of the recovery lactam obtained by depolymerizing the polyamide waste containing the oil, the oil is separated by performing physical purification by an emulsion separator and chemical purification using a polyacrylamide polymer coagulant. .

In general, emulsions used during spinning consist of a mixture of water-insoluble components of natural oils and water-soluble components such as emulsifiers and antistatic agents.They are water-soluble during spinning, but carbonized when depolymerized in the presence of phosphoric acid and superheated steam. It is transformed into two components, water insoluble and water soluble.

Since these two components are present in the recovery lactam obtained by depolymerization of the polyamide containing an oil agent, it cannot be removed by normal oxidation, activated carbon treatment and distillation, which causes a significant reduction in the quality of the final lactam. The primary and secondary physical and chemical treatments can effectively remove the emulsion. The method of the present invention is described in detail as follows.

Polyamide containing an emulsion is heated and depolymerized at 250 to 350 ° C. in the presence of phosphoric acid and superheated steam by a conventional method to give lactam in the form of water vapor to form an aqueous solution of 10 to 60%. The water-insoluble emulsion component is separated and removed by using the principle of layer separation between oil and oil, and the pH of the aqueous solution is adjusted to about neutral, and then a polyacrylamide-based polymer coagulant is added to generate aggregates of mainly water-soluble emulsion components. Filter off. Since the aggregates float on the surface of the aqueous solution, they can be easily separated and removed by the perlite coated nonwoven filter. The separated filtrate can be obtained with a high quality recovery lactam by a conventional purification method which is oxidized with potassium permanganate and activated carbon treatment.

The emulsion separator used in the present invention has a simple process structure as shown in FIG. 1, and thus, detailed description thereof is omitted, but it is preferable to have three or more separators. In the present invention, the amount of the polyacrylamide polymer coagulant added is preferably 0.05 to 10% by weight, more preferably 0.1 to 5.0% by weight based on the recovery lactam. If it is added less than 0.05% by weight, the removal effect of the emulsion component is insufficient, and in excess of 10% by weight, the polymer coagulant acts as an impurity, making purification difficult. At this time, the pH of the aqueous solution is preferably neutral or weak acidity, the treatment temperature is 30 to 80 ℃, the treatment time is good 0.5 to 3 hours.

According to the present invention, it is possible to effectively purify the polyamide waste containing the oil agent generated in the production site to recover caprolactam, thereby providing a very beneficial advantage in the utilization of resources and environmental protection. .

An Example is given to the following and this invention is demonstrated to it further in detail.

[Examples 1-3], [Comparative Examples 1-2]

After dissolving the medical polyamide waste containing about 1% by weight of the spinning emulsion, it was depolymerized with superheated steam at 350 ° C. under a phosphate catalyst to obtain about 8 L of an aqueous solution of recovery lactam at a concentration of 11%. The recovered lactam aqueous solution was concentrated by evaporation to 40% by weight, and the water-insoluble emulsion was separated and removed through an emulsion separator having five separation membranes. 2 liters of 40 wt% lactam aqueous solution was added to ca. 4.5 g of caustic soda to pH 7.5 and left for about 1 hour (until this time the emulsion was not completely removed, which was a yellow opaque liquid).

Next, 0.5 to 5.0% by weight of the polyacrylamide polymer coagulant was added to the recovery lactam as shown in Table 1, and after standing for 1 hour, the aggregates floating on the surface of the aqueous solution were separated and removed using a perlite coated nonwoven fabric filter. 0.75% by weight of potassium permanganate was added to the obtained clear filtrate and stirred for about 2 hours, and 0.5% by weight of activated carbon was then stirred for about 2 hours. After that, the aqueous solution was filtered using a nonwoven fabric filter, and about 2.5 g of a small amount of caustic soda was added and distilled to obtain a recovery lactam. The physical properties thereof are shown in Table-1.

Comparative Examples 3 to 5

In the same manner as in the above example, the medical polyamide waste containing about 1% by weight of the spinning emulsion was melted, and then depolymerized with superheated steam at 350 ° C. under a phosphate catalyst to obtain about 8 L of an aqueous recovery lactam solution having a concentration of 11%. The obtained recovery lactam aqueous solution was concentrated, and the emulsion recovery treatment and the polyacrylamide-based polymer coagulant treatment were carried out in 2 L of 40 wt% aqueous solution, respectively, as shown in Table 1, and the general purification without the recovery lactam and the emulsion removal treatment obtained through the purification process. Table 1 shows the physical properties of the recovered lactam obtained by treatment only.

Comparative Example 6

In the same manner as in Examples and Comparative Examples, 8 L of medical polyamide waste containing about 1% by weight of a spinning emulsion was melted, and then depolymerized with superheated steam at 350 ° C. under a phosphate catalyst to obtain about 8 L of a recovery solution of 11% concentration. Got it. The recovered lactam solution was concentrated to a concentration of 40% by weight, and the physical properties of the recovered lactam obtained by distillation without a conventional purification treatment after the emulsion removal treatment in the same manner as in Example are shown in Table-1.

Comparative Example 7

After dissolving 8 l of medical polyamide yarn containing about 1% by weight of a spinning emulsion, it was depolymerized with superheated steam at 350 ° C. under a phosphate catalyst to obtain about 8 l of recovered lactam solution at a concentration of 11%. The recovery lactam solution obtained was concentrated to a concentration of 40% by weight, and then passed through an emulsion separator having two separation membranes, followed by addition of a polyacrylamide polymer coagulant and a conventional purification treatment in the same manner as in Example. Physical properties are shown in Table-1.

TABLE 1

No. * PM is a 1 / 100N potassium permanganate (KMnO ₄₎ solution 1㎖ this two-color standard solution was added to 1% aqueous solution of lactam 100㎖ (CoCl ₂ and 6H ₂ O, CuSO ₄ 5H ₂ O 2g and water 1ℓ The time in seconds until the same color as the dissolved solution).

Claims (3)

In the method for purifying a recovery lactam obtained by depolymerizing a polyamide waste containing a spinning oil under a phosphate catalyst, (1) an aqueous solution of the recovery lactam is treated in an emulsion separator having a membrane to physically separate and remove the water-insoluble emulsion component, and (2 3) The polyacrylamide polymer coagulation system is added to the aqueous solution to separate and remove the water-soluble oil component as an agglomerate, and (3) recovery lactam is obtained by ordinary potassium permanganate, activated carbon treatment and distillation treatment. A method for recovering lactam from the polyamide contained. The method according to claim 1, wherein the amount of the polyacrylamide-based polymer coagulant added is 0.05 to 10.0 wt% based on the lactam. The method of claim 1 wherein the emulsion separator has at least three separators.