DE2336724A1 - METHOD FOR RECOVERING WASTE POLYESTER FILM - Google Patents

Description

AGIA-GE V- AEEiB AKTIEETGESEILSCHU ¹ T

Process for the recovery of polyester film waste.

Priority: Great Britain, July 27, 1972 Note Ur. 35 228/72

This invention relates to a method of recovery of scrap polyester film, in particular to a method of making adhesive layers of scrap polyester film and especially of Remove polyethylene terephthalate film waste.

In the production of photographic films, it is common to to cover a support formed from polyester film with anchoring substrates to ensure the adhesion of photosensitive and other hydrophilic layers on the hydrophobic polyester film base.

In the manufacture of photographic films that have a Have a carrier which is formed from a high molecular weight linear polyester, in particular from polyethylene terephthalate, there is a considerable amount of pilm waste, so it would be very interesting to have a simple method of recovery of polyester film waste and the removal of the various layers attached to it. The full Removal especially of the primer layers attached to the polyester film is difficult and naturally hangs on the chemical nature of the polymers that make up the binders of the primer coats.

In British Patent 1,234,755 a polyester film described, which carries a primer layer with a copolymer that is 4-5 to 99.5 wt .-% of vinylidene

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chloride and / or vinyl chloride, 0.5 to 10 wt .-% of one Ethylenically unsaturated, hydrophilic monomers made from ethylenically unsaturated mono- or dicarboxylic acids or N-vinyl! pyrrolidone consists, and from 0 to 54.5% by weight of at least one other copolymerizable, ethylenic unsaturated monomers such as acrylic amides, methacrylamides, Acrylic, methacrylic and maleic acid esters and N-alkyl maleimides is formed. Examples of such copolymers are:

- Copolymers of vinyl chloride, vinylidene chloride, N-tert-butyl acrylamide and itaconic acid (50: 30: 18: 2% by weight),

- Copolymers of vinyl chloride, vinylidene chloride, n-butyl acrylate and itaconic acid (63: 30: 5: 2% by weight),

- copolymers of vinylidene chloride, N-tert-butyl acrylamide, n-butyl acrylate and N-vinylpyrrolidone (70: 23: 3: 4% by weight),

- Copolymers of vinylidene chloride, N-1 er t. -Bu ty! Acrylamide, Vinyl versatate and itaconic acid (75: 12: 10: 3% by weight);

the vinyl versatate is sold by Shell Chemical Co. under the trade name VEOVA 10 and is a branched-chain vinyl carboxylic acid ester which has a molecular weight of 198 and the formula CH ₂ = CH-O-CO-CR ^, where R ₁ , Rp and R ^ $ e represent an alkyl group having 3 together 7 to 9 carbon atoms and wherein only one of R ^, R ^ and R- is a methyl group

Other primer coats are described in the UK patents 1 014 344, 1 020 054, and 1 030 753. Polyesters are used as binders for these primer layers used, which are soluble in chlorinated, aliphatic hydrocarbons. These polyesters are made by the polycondensation at least one phthalic acid and at least one aliphatic diol, e.g. by polycondensation of at least one aliphatic diol with a diacid component, the az 55-100 Mo 1-% from isophthalic acid, 0-25 Mo 1-% from terephthalic acid and 0-20 mol% from an aliphatic, saturated dicarboxylic acid.

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In the above-mentioned British Patent Specification 1,234,755 a second layer is applied onto the primer layer, which is composed of a mixture of gelatin and a butadiene copolymer latex. The usual gelatin silver halide emulsion layers can then be coated thereon.

In Belgian patent 7 ^ 2 769 the second layer from the above-mentioned adhesive layer combination, which consists of a primer layer of vinyl chloride and / or vinylidene chloride copolymer and an adhesive layer made of gelatine / butadiene mixed polymer is omitted.

This second layer is made by a corona discharge treatment replaced in order to prevent the adhesion of one or more hydrophilic, light-sensitive emulsion layers on the vinyl chloride and / or vinylidene chloride copolymer layer and so on the polyester film carrier.

In British patents 688 528 and 718 422, the primer layer on the polyester film is composed of a copolymer of vinylidene chloride, an acrylic acid ester including acrylonitrile and itaconic acid. In the second of these patents, the primer layer is applied prior to the orientation of the film at an elevated temperature, ¹ .

There are several methods of removing these primer layers of polyester film has been suggested.

In British Patent Specification 870 639 it has been proposed 2u treat waste polyester film with an adhesive layer of the above-described macromolecular hydrophobic polymers with an aqueous solution of an alkali metal or alkaline earth metal hydroxide at a temperature of 40-130 ⁰ C for at least one minute. The alkali is then washed away from the resulting polyester film with water or another aqueous medium. "■

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In British Patent 134-967, scrap polyester film subbed on at least one side with at least one copolymeric vinylidene halide casting composition is contacted with alkaline glycol obtained by adding a sufficient amount of a strong base to the glycol to alkalize the mixture. Suitable strong bases are alkali metal oxides, hydroxides and carbonates, alkaline earth metal oxides and hydroxides, quaternary ammonium hydroxides and pyridine. Sodium hydroxide and potassium hydroxide are preferred. This mixture is used to treat the film waste at a temperature comprised between 90 ⁰ C and the temperature can be at which 5 wt .-% of the polyester wearer i _m Glycol dissolved, and for a time sufficient that: at least part of the adhesive layer flakes off the polyester carrier. In a separate process step, the polyester carrier is removed from the glycol fraction which contains the adhesive layer flakes.

This process involves a simple peeling of the primer layer realized by polyester film. A complete separation of the small film particles from the aqueous suspension, the film particles and primer layer containing flakes is very difficult. However, it is of paramount importance that Keeping polyester particles in a perfectly pure state because of the presence of the smallest amounts of impurities makes recovered polyester film particles worthless as a raw material for extrusion of new photographic film base.

It is an object of the present invention to develop a method for recovering polyester film starting material, especially for the recovery of polyethylene terephthalate feedstock -from photographic film waste, in which the primer layers attached to the polyester film supports are removed from the film, resulting in a completely pure polyester that is useful in the manufacture of photographic Film carriers or other objects such as films and foils can be reused.

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According to the invention a method for the recovery of pure Polyester film is presented from polyester film waste, which is at least carrying a primer layer of macromolecular, hydrophobic polymer, the method comprising washing the polyester film waste with a halogenated, aliphatic hydrocarbon solvent, separating the pure polyester film from the halogenated, aliphatic hydrocarbon solvent, after dissolving or dispersing therein the layer or layers attached to the polyester film, and drying the pure polyester film.

The macromolecular, hydrophobic polymer that forms the binder for the primer layer can contain halogen Be a mixed polymer, e.g. a vinyl chloride and / or vinylidene chloride mixed polymer, as described above, or it can be a polyester which is chlorinated, aliphatic Hydrocarbons is soluble and through the polycondensation of at least one phthalic acid and at least one aliphatic Mol is formed, for example a polyester, which is obtained by polycondensation of at least one aliphatic diol with a diacid component, which is 55-100 Mo1-% from isophthalic acid, 0-25 mol% from terephthalic acid and 0-20 mol% from an aliphatic, saturated dicarboxylic acid consists.

The polyester film waste can be washed with halogenated aliphatic hydrocarbon solvents without being subjected to any special pretreatment. Most advantageously, however, the film waste is chopped into small particles so that its transport to the various washing steps is greatly facilitated, for example in a knife mill equipped with a sieve with small holes, for example from 8 to 16 mm. Of course, when the scrap has been chopped into small particles, the latter are constantly agitated during the treatment with the hydrocarbon solvent.

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Suitable halogenated, aliphatic hydrocarbon solvents are methylene chloride, dichloroethane, 1,1,1-trichloroethane, Dichlorethylene, trichlorethylene, sthylenechlorohydrin or Mixtures thereof. The halogenated, aliphatic hydrocarbon solvents can with smaller amounts of other solvents such as methanol, ethanol, toluene, morpholine and dimethyl sulfoxide be mixed.

The washing of the polyester film waste with the halogenated, aliphatic hydrocarbon solvent can take place within a wide temperature range, which varies between ⁰ ° C. or even below and a temperature below the boiling point of the hydrocarbon solvent used. Temperatures above the boiling point of the solvent can even be used, but in this case the film waste must be washed in a closed pressure vessel.

There is of course a relationship between the temperature of the washing bath, the duration of the washing treatment and the amount the halogenated aliphatic hydrocarbon solvent used. The larger the amount of solvent present and the higher the washing temperature, the shorter is the time it takes to remove any adhesive layer from the polyester film base.

The recovery "of the polyester film from the treatment bath, wherein the primer layer or layers of polyester film waste are dissolved away can be carried out by known means will. The scrap polyester film that has been previously chopped into small particles can be put in, for example, a classification column are treated, in which the particles are constantly agitated against an ascending stream of liquid be moved. The particles slowly sink to the bottom of the column, taking them through the rising liquid

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and the constant agitation freed from the primer layer, which is in the halogenated, aliphatic hydrocarbon solvent solves. The cleaned particles are collected on the floor and the treatment liquid and hydrocarbon solvent with the loosened primer layer on top Part of the column discharged.

In the production of photographic film, the polyester film carrier is not only covered with primer layers, the vinylidene chloride and / or contain vinyl chloride copolymers, or with the above-described soluble polyesters, but also with hydrophilic layers such as light-sensitive emulsion layers. It is the job of the primer layers to anchor to improve hydrophilic layers on the hydrophobic film carrier or even to enable it in the first place. It's clear, that a large amount of film waste not only has at least one primer layer, but also one or more, hydrophilic Will wear layers that must also be removed from the polyester film. In this case it is preferred these hydrophilic layers by special pretreatments before the actual washing with the halogenated, aliphatic Remove hydrocarbon solvents.

This can be done very conveniently by washing with hot water to which a part of sulfuric acid has been added. The sulfuric acid shortens the washing time required. If sulfuric acid is used, its concentration in the aqueous bath can vary widely. It depends largely on the temperature of the water bath. At about 90 ⁰ C, the addition of. 5% by volume of sulfuric acid (6O ⁰ Be) are sufficient. It can be interesting to add a small amount of copper (II) sulfate to the sulfuric acid bath in order to protect the stainless steel vessels in which the washing takes place against the corrosive effects of the acid. For a wash bath containing 5% by volume of sulfuric acid, 0.2 g of copper (II) sulfate per liter is usually sufficient.

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As with the treatment of the primer layers with the halogenated one aliphatic hydrocarbon solvents there is also a dependency between the temperature of the wash bath, the concentration of sulfuric acid and the duration of the washing treatment. It is clear that with increasing temperature the Concentration of sulfuric acid and the washing time are reduced, as well as the temperature as the concentration decreases and the washing time can be reduced.

After the Pilmabfall in large amounts of water is repeatedly washed and the temperature of the laundry, preferably at the beginning of the process at about 90 ⁰ C is maintained, the washing is continued until the pH of the wash water is neutral, so that all traces of sulfuric acid actually have been removed.

During the acidified hot water washing, the portions of the silver halide emulsion layers are dissolved away by the waste film.

To be sure that all traces of silver have been removed, the pilma waste is washed in an aqueous bath, containing up to about 50 grams per liter of sodium thiosulfate; the waste is then rinsed with clear water. Treatment with sodium thiosulfate can even be done at room temperature happen.

To be sure that all hydrophilic layers based on hydrophilic binders such as gelatin have been removed, the waste is finally ^{washed in an aqueous bath at about 90 °} C., sodium hydroxide in a concentration of a few grams to about 50 g per Liters have been added. Washing is followed by rinsing with clear water.

After these various washes, the entire thing is hydrophilic Material removed from the film waste. It remains only the toothy primer layers on the waste. These

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are washed away, xfie previously described, by waste is made up of halogenated, aliphatic hydrocarbon solvents "treated.

It has already been said that the film waste can be treated as it is; however, it is usually in advance in chopped up in a knife mill to obtain transportable particles, which have a size of, for example, 8 to 16 mm » The waste particles are treated in large vessels, in which the particles are stirred into the washing liquid Movement are kept.

The method according to the invention has the advantage that the recycled polyester waste, especially if it has previously been chopped into small particles, can be used directly after drying for the extrusion of films ₉ whose properties match those of films made from fresh Polyesters are made, comply with the utmost hatred, so that they can be used as photographic film supports * The dried polyester waste can also be mixed with fresh polyester granulate and processed in the extruder to produce photographic film supports. Additions of up to 50% by weight of the extruder content are common.

Furthermore, the purified polyester waste can be used alone or mixed with fresh polyester to be formed into articles by the usual methods of spinning and casting, such as Films, tapes, fibers, brushes and the like. It can be used in the production of yarns, woven or non-woven products, Papers, leather and other structures can be used by well known methods.

Up until now it has been of the utmost importance to carefully sort the film waste prior to the recovery treatment to remove everything Exclude foreign film material, e.g. material consisting of cellulose triacetate. The presence of the smallest GV.638

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Amount of cellulose triacetate in the recovered films makes it wholly unsuitable for use as a raw material for the production of new films. With the inventive Procedure, this careful sorting is unnecessary. Even if a photographic film base made of cellulose triacetate is randomly mixed with the polyester film waste, this cellulose triacetate would be in the chlorinated, aliphatic Hydrocarbons are dissolved and finally removed with the processing liquid. So finally in each. Case of completely purified polyester film waste obtained.

The present invention is not only for the recovery of polyester from photographic manufacturing waste Materials applicable, but also for the recovery of polyester from old and exposed as well as developed, photographic Films with polyester carriers.

During the recovery of polyester film from scrap film on which photographic layers have been applied, the silver can be removed from the first washing liquids by known methods. First, the solids, which contain approximately 99% of the silver, separated from the washing liquids in a centrifuge, during the The remainder of the silver can be recovered from the washing liquids according to other known recovery methods. The halogenated, aliphatic hydrocarbons can be produced by simple evaporation and cooling in a closed circuit recovered from the contaminated liquids.

The examples given below relate in particular to the recovery of pure polyethylene terephthalate film Polyethylene terephthalate film waste. However, the invention is not limited to film recovery from the reaction of terephthalic acid or dimethyl terephthalate with Ethylene glycol is derived. In this reaction it can Ethylene glycol partly or wholly with other glycols er-GV.638

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e.g. heopentyl glycol and% 4-di (hydroxymethyl) cyclohexane. Terephthalic acid or its diesters can also be partially or completely replaced by other dibasic acids, such as isophthalic acid, Sebacic acid and adipic acid, or can be replaced by their di-esters.

The following examples illustrate the invention.

example 1

Samples of polyethylene terephthalate film, each one containing chlorine Carrying primer coat are chopped in a knife mill to form 'particles that are a diameter of approximately 10 mm. The primer layer in the different patterns is as follows:

Pattern 1

A layer consisting essentially of a copolymer of vinyl chloride, vinylidene chloride, n-butyl acrylate and itaconic acid (63: 30: 5: 2 wt%).

Pattern 2

A layer consisting essentially of a copolymer of vinylidene chloride, H-tert-butyl acrylamide, n-butyl acrylate and N-vinyl pyrrolidone (70: 23: 3: 4% by weight).

Pattern 3

A layer consisting essentially of a copolymer Vinylidene chloride, F-tert-butyl acrylamide, vinyl versatate and itaconic acid (75ϊ12: 10: 3% by weight); the vinyl acetate is marked as mentioned above.

Pattern 4 - ■

A copolymer of vinyl chloride, vinylidene chloride, N-tert-butyl acrylamide and itaconic acid (50: 30: 18: 2% by weight)

The pilm waste is stored for 2 to 5 minutes at room temperature in stirred in one of the following baths:

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1. A mixture of methylene chloride and methanol (90:10% by volume)

2. methylene chloride

3-ethylene chlorohydrin

4-. A mixture of equal parts by volume of methylene chloride and

Dimethyl sulfoxide
5- A mixture of equal parts by volume of methylene chloride and ethylene chlorohydrin.

After these treatments, the film waste is checked for its purity examined.

1 - melt test :

A film pattern of approximately 3mm 3mm will be at about 285 ° C melted between two glasses on a melting point microscope .. when the chlorine-containing primer layer is completely removed the crystallized polymer is completely colorless after cooling. If any containing chlorine Polymer remains, a clearly visible, brown stain appears.

2. Pyridine test :

A reagent tube will be up to 3/4 of its height with chopped film debris and pure pyridine filled. The chlorine-containing polymers that may be present dissolve at room temperature in pyridine very quickly. After 5 minutes, the pyridine is decanted into another reagent tube, including 10 ml of a saturated one Solution of methanol and sodium hydroxide can be added without stirring. If it does not contain any chlorine-containing polymer, the solution remains white, in the other! "all it turns brown. In In this case, the waste must be washed again or several times with methylene chloride.

All remains of the primer coat have completely disappeared, and the polyester film waste is completely pure, so that the dry waste immediately alone or mixed with fresh polyester grains can be used for the purpose of extruding high quality polyester film.

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If by chance cellulose triacetate film waste with the polyester film waste has been mixed, you get pure polyester particles in each pail, since the cellulose triacetate is in the halogenated, aliphatic hydrocarbon solvents.

Example 2

Photographic film waste with a carrier made of polyalkylene terephthalate, one primer layer of a copolymer of vinyl chloride, vinylidene chloride, tert-butyl acrylamide and itaconic acid (50: 30: 18: 2% by weight) and the usual hydrophilic Gelatin, which has a silver halide emulsion layer, is chopped up in a knife mill so that particles form that form a Have a diameter of no more than 10 mm.

The chopped up film waste (almost 200 kg) is passed through a sieve into a vessel with a capacity of approximately 1000 Liters and then treated with vigorous stirring in various baths according to the procedure given below. Almost 800 liters of liquid are needed per bath. The contaminated liquid is through after each treatment the sieve removed. The different baths are the following:

1. A ten-minute treatment at 90 ^° C. in an aqueous bath which contains 5% by volume of sulfuric acid (60 Be) and 0.2 g of copper (II) sulfate per liter. The light-sensitive silver halide layers are washed away as a result.

2. A treatment with water at 90 ° C in successive Process steps until the wash water has become completely neutral, so one proves that the sulfuric acid is completely was removed.

3 · A five minute treatment at 90 ⁰ C in.einer aqueous solution of 50 g sodium thiosulfate / liter to the last

Solve silver traces.
4. Rinse with water at 20 ° C.
5 · Wash away all other hydrophilic gelatin-containing layers with an aqueous solution at 90 ^° C. which contains 50 g sodium hydroxide / liter.

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6. Rinsing twice with water at 90 ⁰ G.

7- Repeated treatment of the film waste (2 minutes each time with methylene chloride baths) to loosen the primer layer.

To determine whether all primer layers of the film waste have been dissolved in the methylene chloride, the waste can dem Melt test or the pyridine test as described in Example 1.

The waste is then placed in a drying device dried. It is then immediately available for the production of high quality photographic film supports.

Example 5

A photographic film comprising a support made of polyethylene terephthalate, a primer layer of a polyester Ethylene glycol and isophthalic acid, made up a second layer Gelatin-cellulose nitrate, and a gelatin-silver halide emulsion layer has been described in Example 8 of U.S. Patent 3,495,985.

Film scrap of the above photographic material is chopped into particles in a knife mill, which is a knife-edge of no more than 10 mm. These particles are treated according to the 7 process steps described in Example 2 became.

To check whether the primer layer of polyethylene terephthalate has been completely washed away after treatment with the last bath of methylene chloride, the waste is examined in a melt microscope, the temperature of which is gradually increased. If the waste has been fully released from the primer layer, it remains unchanged even above 200 ⁰ C. If something Polyäthylenisophthalat is still contained, which melts at approximately 100 ⁰ C, the film waste at this temperature is sticky, which can very easily be observed under the microscope melting. Γη in this case GV.638

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carried out one or more washing treatments with methylene chloride to pure polyethylene terephthalate film waste obtain.

After drying, the Pilmahfall is ready to be made available on high quality photographic film carriers.

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Claims (11)

Claims 1. Process for the recovery of pure polyester film ais Polyester film waste comprising at least one primer layer of a macromolecular, hydrophobic polymer, characterized in that it is the washing of the polyester fiber waste with at least one halogenated, aliphatic hydrocarbon solvent, separating the pure polyester film from the halogenated, aliphatic hydrocarbon solvent in which the layer or layers containing attached, dissolved or dispersed on the polyester film, and drying the pure polyester film contains. 2. The method according to claim 1, characterized in that the macromolecular, hydrophobic polymer that forms the primer layer is a halogen-containing copolymer. 3 · Process according to claims 1 and 2, characterized in that that the halogen-containing copolymer is a copolymer is that of 45 to 99.5 wt .-% of vinylidene chloride and / or vinyl chloride of 0.5 to 10 wt .-% an ethylenically unsaturated, hydrophilic monomer consisting of ethylenically unsaturated mono- and dicarboxylic acids or N-Viny! Pyrrolidon, and from 0 to 54.5% by weight at least one other copolymerizable, unsaturated monomer. 4. The method according to claims 1 and 2, characterized in that that the halogen-containing copolymer is a copolymer of vinyl chloride, vinylidene chloride, N-tert-butyl acrylamide and · is itaconic acid. 5. The method according to claim 1, characterized in that the macromolecular, hydrophobic polymer that the primer rail is a polyester that is found in chlorinated, alx- 309886/1165 phatic hydrocarbons is soluble, and by the Polycondensation of at least one phthalic acid and at least one aliphatic diol is formed. 6: Process according to claims 1 and 5, characterized in that the polyester soluble in chlorinated, aliphatic hydrocarbons by the polycondensation, ■ is formed from at least one aliphatic diol with a diacid component, 55-100 Mo 1-% of isophthalic acid, consists of 0-25 mol% of terephthalic acid and 0-20 mol% of an aliphatic, saturated dicarboxylic acid. 7. The method according to any one of claims 1 to 6, characterized in that that the film waste before treatment with the halogenated, aliphatic hydrocarbon solvent is chopped into small particles. 8. The method according to any one of claims 1 to 7 »characterized in that that the halogenated, aliphatic hydrocarbon solvents methylene chloride, dichloroethane, 1,1,1-trichloroethane, dichloroethylene, trichlorethylene, Is ethylene chlorohydrin or a mixture thereof. 9- method according to any one of claims 1 to 8, characterized in that that the halogenated, aliphatic hydrocarbon is mixed with another solvent, that from methanol, ethanol, toluene, morpholine and dimethyl sulfoxide is chosen. 10. The method according to each of claims 1 to 9? characterized, that the polyester film waste, the photographic one Wears emulsion layers before it goes with the halogenated, aliphatic hydrocarbon solvents, successively prewashed with the following agents will : 309886/1165 "7336724 (a) Water at about 90 ° C which contains a small amount of sulfuric acid contains, (b) large amounts of water until the pH of the wash water has become neutral (c) water containing sodium thiosulphate, (d) pure water, (e) water containing sodium hydroxide, (f) pure water. 11. The method according to any one of claims 1 to 10, characterized in that that the polyester is polyethylene terephthalate. 309886/1165