KR820000554B1 - Method of recovering polxester film from waste magnetic record tape - Google Patents

Abstract

The method of recovering polyester film from self-recording tape used for video tape and audio tape using organic solvent was described. Self recording tape was stirred and heated to 60-180oC in alliphatic ketone or aromatic solvent or the mixture of alliphatic ketone and aromatic solvent having solubility parameter 8-10, b.p. 80-160oC, and then cured and filtered to give base polyester film. As a result of the above process, polyester film was separated from the self-recording coating materials.

Description

Method of recovering polyester film from magnetic recording tape

The present invention relates to a method for recovering a polyester film from a magnetic recording tape used as a video tape and an audio tape.

In more detail, the present invention is a base film is a polyester film, by applying a coating agent (magnetic coating) for the magnetic recording tape used as a video tape and audio tape on the magnetic film by the method described below The present invention relates to a method of removing the recording coating and recovering only the polyester base film in its original state.

The magnetic recording tape is a magnetic powder such as iron oxide or chromium oxide coated on a base film made of polyester, cellulose acetate, or the like. Cellulose films have been used as the original base film, but recently, polyester films are mainly used because of excellent wear resistance, and polyethylene terephthalate-based polyester films are most frequently used.

Since the magnetic powder, which is an inorganic material, does not show any adhesive force to the polyester base film which is an organic material, when the magnetic powder is applied to the base film, a powder containing the magnetic powder as a pigment is prepared and applied. Such magnetic paints are composed of organic solvents, binder resins, magnetic powder pigments and other additives like other ordinary solvent paints.

The solvent used for the magnetic paint is different depending on the type of binder resin and additives. Generally, toluene, methyl ethyl ketone, tetrahydrofuran, ethyl acetate or the like or a mixture thereof is used.

As the binder resin, vinyl chloride copolymers such as vinyl chloride / vinyl acetate copolymer, vinyl chloride / vinyl acetate / vinyl alcohol copolymer, or vinyl chloride / vinyl acetate / acrylic acid copolymer are most frequently used. Polyester co-polymers and polyurethane resins are also used.

Other additives include small amounts of plasticizers, crosslinkers, stabilizers, dispersants, antistatic agents and the like.

In the process of manufacturing the magnetic recording tape, the magnetic paint is applied to the base film by a suitable coating method such as spray coating or knife coating, and then the solvent is first volatilized to form a coating film and then heated to a high temperature to cure the coating film. Rolling with a roller makes the surface of the coating film uniform. The magnetic recording tape produced through such a process may swell in any solvent because the coating layer containing the magnetic powder is cured, but does not melt.

The wide magnetic recording tape produced in this way is cut into small pieces and wound on a reel of a cassette to produce a finished product that can be shipped to the market. In the process of manufacturing magnetic recording tape, scrap film may occur due to poor coating of magnetic paint, poor post-treatment, or poor cutting. Also, since the wide ends of the wide film are not coated when coated with a wide width, scrap may occur. Cause.

Recycling or recycling such magnetic recording tape scraps is a very difficult problem. The base film is polyester, and the magnetic powder layer is not polyester and is cured, and thus, the two polymer film layers have very different physical properties, so refilming and molding are impossible. Even at the melting point, the polyethylenterephthalate resin melts above 260 ° C. The vinyl chloride or vinylidene chloride copolymer-based binder resins are all decomposed at 260 ° C to generate toxic gas, hydrogen chloride.

A fundamental object of the present invention is to separate, recover and recycle the polyester base film in the magnetic recording tape scrap as described above.

Known methods for recovering a polyester base film or polyester resin from a magnetic recording tape (see Japanese Patent Application Laid-Open No. 78-112, 78-92,879,78-94,381), firstly, scraps are crushed and sodium hydroxide 0.01- After dipping the wrap film in the ethylene glycol solution containing 5% and heated to about 150 ℃ to remove the magnetic powder layer, the magnetic material was separated by magnetic, the polyester substrate film obtained was washed with water sufficiently and dried.

These methods have some drawbacks. First, since the polyester base film is made of an ester bond, it may react with ethylene glycol when immersed in ethylene glycol and heated. When such a reaction occurs, the molecular weight of the polyethylene terephthalate resin, which is a base film material, becomes low, and thus physical properties are significantly different from that of the polyester resin for film. In addition, the reaction rate of the ester compound is accelerated by acid or alkali. Treatment with an ethylene glycol solvent containing sodium hydroxide may cause a large change in the physical properties of the base polyester film. In addition, since the base film from which the magnetic layer is separated has a large amount of sodium hydroxide, it must be washed with water, which can be a pollutant as basic. In addition, in order to treat such chemicals, the magnetic recording tape must be pulverized first, and a large amount of work and energy are consumed in the pulverization, and a refrigerator is required to absorb the heat generated during the pulverization. There was a disadvantage to harm.

It is an object of the present invention, in particular, when recovering a polyester base film from scraps and magnetic recording tapes, the process of separating the magnetic coating film is simple and completely flawless, without affecting the physical properties of the polyester resin. It is recovered and recycled in the same condition as before the paint is applied.

Still another object of the present invention is to provide an economical polyester film scrap recovery method while simplifying an energy intensive pretreatment process such as crushing or powdering scrap tape.

The inventors have studied various methods of separating the magnetic coating layer from the polyester base film in order to achieve the above object. As a result, aromatic solvents and aliphatic ketones having a solubility parameter of 8 to 10 and a boiling point of 80 to 160 ° C It has been invented that the method of using a solvent is very simple and excellent.

The method of the present invention is described in detail as follows.

Cut the magnetic recording tape scrap into a single or mixture of aliphatic ketone solvents and aromatic solvents with a solubility parameter of 8 to 10 and a boiling point of 80 to 160 ° C. to a width of about 0.1 to 10 cm, immerse and vigorously stir 60 When heated to 140 DEG C, the magnetic coating layer of the magnetic recording tape is separated from the polyester base film and becomes particles having a maximum size of about 3 mm, and there is no change in the polyester base film. After cooling to room temperature, the entire contents are shaken with a sieve (U.S. sieve, 3-150mesh), and the polyester film remains on the body, and the magnetic coating layer turned into particles passes through the sieve together with the solvent. The polyester film thus separated is colorless and transparent when dried under reduced pressure at room temperature.

The solubility parameters used in the method of the present invention are 8 to 10 and an aliphatic ketone solvent having an boiling point of 80 to 160 ° C and aromatic examples are as follows.

Aliphatic ketone solvents such as methyl ethyl ketone, cyclohexanone, diisopropyl ketone, methine butyl ketone, ethyl amyl ketone, diethyl ketone, and metal isobutyl ketone; and benzene, p-xyline, o-xylene, and xylene And aromatic compounds such as toluene, ethylbenzene, and xylene mixtures. These solvents may be used alone or in admixture at any ratio.

In the method of the present invention, the use of aliphatic ketone solvents and aromatic solvents having a solubility parameter of 8 to 10 is performed by swelling a very small amount without dissolving the magnetic coating layer coated on the magnetic recording tape. Contribute to being a particle. In addition, the boiling point should be 80 to 160 ° C because desorption of the coating does not occur at too low a temperature and heating to 160 ° C or more causes damage to the polyester base film.

The method of the present invention has the advantage of saving a lot of work and energy because there is no need to grind or powder the scrap film. However, a wide scrap film of 20 inches or more generated due to a coating defect during magnetic recording coating may be cut into a width of 0.1 to 10 cm regardless of length. In addition, according to the application of the method of the present invention, the magnetic coating layer has a particle size of the maximum diameter of about 3mm when the heat treatment is easy to separate the polyester base film, it has the advantage of easy to dry the organic solvent in use. In addition, the organic solvents used do not dissolve the magnetic coating layer at all, and are used to granulate by detaching from the base film. Therefore, the filtration of these particles facilitates the recovery of the solvent, so that the solvent can be reused without the need for distillation and purification. It has the advantage of preventing loss.

The present invention is explained in detail by the following examples, which do not limit the present invention.

[Example 1-11]

A 20-inch wide magnetic recording tape scrap generated by a poor coating is cut into 20 to 60 cm long and 0.1 to 10 cm wide. Next, put 1.5 l of the solvent shown in Table 1 into a 2 l three-necked flask equipped with a stirrer, a cooler, and a thermometer, and immerse the cut tape 20-.

Allow the stirrer blade to be immersed in the solvent, but adjust the position so that it does not touch the shredded tape, and then stir at a speed of 100 revolutions / minute and heat it until the temperature reaches 60 to 140 ° C and continue for 3 to 20 minutes. Keep at temperature. After the heat treatment, remove the heater, leave it to cool to room temperature, and shake the sieve while pouring the entire contents over a sieve (U.S. Sieve, 4mesh). The coating layer transformed into particles passes through a sieve and the polyester film remains on the sieve. The film was placed in a vacuum dryer and dried under reduced pressure at room temperature for 30 minutes to recover a transparent film with a tensile strength comparable to that of the original film before the magnetic paint coating.

The conditions and results of each experiment are shown in Table 1 below.

TABLE 1

Example 12-18

In the same manner as in 1-11, when the magnetic recording tape having a width of 3cm and a length of 2cm is treated, the appearance is colorless and transparent, and the tensile strength is recovered from the original film before the magnetic paint coating, as shown in Table 2 below. do.

TABLE 2

Example 19-20

In this embodiment, the results of a polyester base film recovery experiment are presented from the magnetic recording tape discarded during normal home use. Irregularly unwound audio film (width = evil 3.0mm) and video film (width = about 6.5mm) that are discarded while in use at home will result in a hunched reel state. This was cut five times with scissors and treated in the same manner as in Example 1 to obtain a polyester substrate film having a colorless appearance. Each experimental condition and result are shown in Table 3.

TABLE 3

[Control Example 1-2]

This embodiment is independent of the claims of the present invention, but is an experiment to show that the solvent used once in the present invention can be recovered and used again.

In Example 4 and Example 9, 1470 ml of solvent was recovered by filtration using filter paper to separate the solvent passed through the sieve and the granulated magnetic film layer from each other. Therefore, the recovery rate of the solvent was 98%.

The magnetic recording tape was treated in the same manner as in Example 1 using 1470 ml of the recovered solvent to obtain a colorless and transparent polyester film. The recovery solvent remains colorless and transparent even after continuing to use it up to three times, but becomes slightly cloudy after five times. At this time, the solvent can be purified by atmospheric distillation.

Claims (1)

Solubility parameter 8 to 10, boiling point of 80 to 160 ℃ aliphatic ketone-based and aromatic solvent alone or a mixture of magnetic recording tape heated to 60 to 180 ℃ stirring, cooling to room temperature and filtered to a polyester substrate film Recovering the polyester base film from the magnetic recording coating and drying.