HU207096B - Process for producing photosensitizer based on basic iron(iii)-carboxylate, suitable for photosensitizing polyolefin or polystyrene based plastics, as well as composition and master mixtures comprising same - Google Patents

Abstract

Basic Fe(III) carboxylate cpd. for photosensitising polyolefin and polystyrene polymers is prepd. from a water sol. Fe(III) salt and an R-COOH carboxylic acid, where R = 5-20C alkyl gp., 20-24C alkenyl gp., 2-5C alkyl or alkenyl gp. substd. by a phenyl gp. or a phenyl gp. substd. with 1-4C alkoxy gp., A 1-8 wt.% alkali hydroxide soln. is prepd. up to an equimolar quantity of the R-COOH acid is added to the hydroxide. Based on 1 mol. of the carboxylic acid, 0.4-0.6 mol. Fe(III) salt is added in an aq. soln. at 70-90 deg.C. A buffer is added when the pH falls to pH 9 during addn. of Fe(III) salt. Finally pH values are allowed to fall to 8-5 on completion of the reaction and the pptd. prod. is isolated. - The invention also applies to polymer master batches and compsns. contg. photosensitisers of this type.(Dwg.0/1)

Description

The present invention relates to a process for the preparation of basic iron (III) carboxylate-based photosensitizers for the photosensitization of polyolefin or polystyrene-based plastics. The invention further relates to polyolefin or polystyrene based polymer compositions and masterbatches containing such photosensitizers.

With the advancement of packaging technology, the use of disposable packaging for single use, including the proportion of plastic materials, is increasing. Plastic waste scattered in the open environment is increasingly accumulating because it cannot return to the natural cycle of the material within a reasonable amount of time. In addition to the aesthetic aspects, this has a detrimental effect on the quality and machinability of the soil.

In order to prevent the accumulation of non-collectible plastic waste, which has been scattered outdoors, sunlight-degradable plastics have been developed primarily for packaging applications, which have proved to be advantageous in early vegetable production.

As is known, photooxidative degradation of traditionally manufactured polymers by sunlight is a suitable additive, so-called. using a photosensitizer. One group of additives can only initiate the process (initiator), while the other type can increase the rate of degradation (accelerator, propagator). The latter are more important for practice.

A common feature of accelerator-type photosensitizers is that they contain transition metal, mostly iron, in organic bonding. Typical examples of such additives are iron (III) acetylacetonate (German Patent Publication No. 2,353,089), iron (III) dialkyldithiocarbamates (British Patent No. 1,356,107). , ferrocene and its derivatives, and iron (III) carboxylates, such as iron (III) stearate (British Patent No. 1382062) and basic iron (III) stearate (German Patent Publication No. 2244801). document).

When these different organic ligand iron compounds are tested under the same conditions in the same polymer and at the same concentration, their effects on the time course of photooxidative degradation are found to be very different. Thus, of the exemplary types, iron (III) -acetylacetonate is very fast acting, ferrocene and its derivatives, iron (III) carboxylates are medium, while iron (III) dialkyl dithiocarbamates are highly delayed photosensitizers. Depending on their different photochemical activity, each type can be advantageously used only within a limited climate area and within a narrow range of applications. Their production technology, equipment and material requirements also differ significantly from one type to another.

One of the basic requirements for products made of plastic that is degraded by sunlight is that they should not be damaged during their intended use, and should not be degraded until their function has ceased. The desired life span varies greatly between applications; This is the need for lifetime controllability.

As a means of controlling lifespan, most communications refer to changes in the amount of photosensitizer additive. However, this method cannot be considered as a control in itself, since a small change in the amount of additive can result in a large shift in the service life. Thus, in places where the life span needs to be timed very precisely, such as when used in crop production, this method of regulation is unsatisfactory.

Some methods attempt to help this by adding a photoinitiator (U. S. Patent No. 2244801) or a UV stabilizer (U.S. Patent No. 4,461,853) in addition to the photosensitizing iron compound. The disadvantage of such solutions is that they work in one direction only, that is, depending on the type of additive used - they only reduce or increase the life span, and thus do not allow for a wide range of control. Another possibility is that photosensitizers and other additives - accelerating or slowing down the degradation - often do not coexist with each other in the polymer matrix, even in the most careful dispersion, thus exerting their effects locally and independently of each other, which also undermines the accuracy of life control. going.

The problems arising from the heterogeneous distribution of additives are described in U.S. Patent Nos. 2,347,318 and 2,319,533. According to the method described in the German Federal Patent Application, the additives are concentrated by concentrating the additives on the surface of the pigment. Concentration is performed using a polar solvent in which the additives are soluble and this solution binds by sorption to the surface of the pigment. However, it has not been demonstrated that this solution ensures the coexistence of the additives at the melting phase of the polymer. On the other hand, the pigment greatly reduces the light transmission of the plastic, which in many cases, such as flat films for crop production, precludes its use.

In our experiments, it has been found that, when the basic iron (III) carboxylates are already known and used as photosensitizers, the reaction mixture is appropriately buffered, resulting in products having a better photochemical activity than basic iron (III) carboxylates prepared without the use of a buffer. It has also been found that occasionally, the appropriate choice of buffer or buffer system may alter the photochemical activity of the resulting product so that products of different photochemical activity can be obtained using the same starting material and reagent, but only by varying the buffer or buffer system.

It has also been found that the photosensitizers produced by the process of the present invention are different Akt2

Applying variations in the composition within a composition and adjusting their amount relative to each other and the polymer matrix can provide a fine control over a wide range of polymer life and photochemical degradation.

The present invention relates to a process for the preparation of a basic iron (III) carboxylate-based photosensitizer for the photosensitization of polyolefin or polystyrene-based plastics by reaction of a water-soluble iron (III) salt and an alkali metal salt of a carboxylic acid of formula R-COOH alkyl, C 20 -C 24 alkenyl, phenyl-monosubstituted C 2 -C 5 alkyl or alkenyl, or C 1 -C 4 alkoxy-substituted phenyl. According to the invention, a carboxylic acid of the formula R-COOH, equimolar to the alkali metal hydroxide, is added to a 1 to 8% by weight aqueous solution of an alkali metal hydroxide, and then at a temperature of 70-90 ° C, 0.40, 6 M water-soluble iron (III) salt is added to the reaction mixture, optionally in the form of an aqueous solution, when the water-soluble iron (III) salt is added when the pH of the reaction mixture is reduced to 9, the reaction mixture is continued. The pH is allowed to drop to 5 to 8 and the precipitated product is isolated.

Examples of buffers used in the process of the invention are acetate / acetic acid, ammonium acetate / acetic acid, ammonium hydrogen phosphate / hydrochloric acid, hydrogen phosphate / dihydrogen phosphate buffer systems or hexamethylene tetramine.

Generally, 40-80% of the water-soluble iron (III) salt or aqueous solution of the alkali metal salt of the carboxylic acid R-COOH is added, followed by the addition of the buffer or buffer system, and the addition of iron. The remainder of the (III) salt or aqueous solution and finally the precipitated product are isolated.

The physical characteristics of the products prepared from the same starting materials and reagents of the present invention, but with different buffers or buffer systems, such as their melting point, infrared spectrum and DSC data, are different. The exact cause of this discrepancy is unknown. Occasionally, depending on the material quality of the buffer or buffer system used, the photosensitizing activity of the products may vary.

Figure 1 shows the infrared spectrum, Figure 2 shows the DSC curves, where the solid line is for non-buffered medium (m.p. 92-94 ° C), the dashed line for ammonium acetate / acetic acid buffered medium (m.p. 99-101 ° C) and the dotted line refers to hexamethylenetetramine buffered medium (mp 106-108 ° C).

The invention further relates to masterbatches which can be used in the production of sunlight-degradable plastic products. The masterbatches of the invention

- a polymer of polystyrene or polyolefin type,

- from 5 to 30% by weight, based on the amount of polymer, of one or more basic iron (III) carboxylate-based photosensitizers prepared as above, and

optionally containing one or more known, conventional plastic additives and / or excipients used in the masterbatches, such as plasticizer, pigment, filler, heat stabilizer and the like.

Finally, the present invention relates to polymeric compositions suitable for the production of sunlight-degradable plastic products. These are polymeric compositions

- a polymer of polystyrene or polyolefin type,

- from 0.1 to 5% by weight, based on the amount of polymer, of one or more basic iron (UI) -carboxylate-based photosensitizers prepared as described above, and

- optionally containing one or more known customary additives and / or excipients used in the manufacture of plastic products. These compositions, which are directly applicable to the production of plastic products, are conveniently prepared by diluting the masterbatch of the above composition with the polymer and, if necessary, admixing other additives and / or excipients.

In view of the compatibility conditions, the photosensitizers are suitably added to the polyolefins, in which the R groups in the carboxylic acids of the formula R-COOH are aliphatic hydrocarbon groups, while in the case of basic polymers containing aromatic groups, photosensitizers containing an aromatic group are preferred.

The sunlight-degradable polymer composition is formed in a known manner by mixing the raw materials and processing the mixture by conventional techniques (extrusion, rolling, pressing, injection molding, etc.). The photosensitizer may be directly added to the other components, but is preferably added as a pre-formulated masterbatch.

Compositions which contain photosensitizers prepared in the presence of at least two different buffer systems have proven particularly advantageous. These photosensitizers, when used together in a composition, do not separate because they are incorporated into each other's crystal lattice to form a mixture of crystals. The ability to work together provides a more balanced and accurate lifetime control than any known solution. In the presence of two (or more) different buffers, the concentration dependence of the photosensitizer of the present invention relative to each other and to the parent polymer can be approximately linearly plotted over a given concentration range. A further advantage of this solution is that the leap in quality change is minimized by inaccurate dosing of the photosensitizer or by fluctuations in other manufacturing parameters (which is almost inevitable in large-scale production).

EN 207 096 B can be reduced and polymer products of various degradation rates can be manufactured in a reliable standard quality.

In addition to the base polymer and one or more photosensitizers prepared according to the invention, the compositions of the present invention may optionally include plastic additives and / or auxiliaries known in the art, such as heat stabilizers, antistatic agents, lubricants, plasticizers, fillers, pigments and the like. may also be included. The amount, proportion and type of these may be conventionally used in the manufacture of a given plastics product (such as a film).

The compositions and products of the present invention have the same mechanical, optical and other properties as the non-photosensitized plastic compositions and products; the only difference is that the compositions according to the invention and the plastic products made therefrom are photooxidatively degradable. Photooxidative degradation starts and takes place only when exposed to sunlight (or artificial UV). The mechanical and other properties do not change significantly over the lifetime of the additive system; the product remains usable until it becomes fragile. Life expectancy in domestic climate ranges from 5-6 weeks to 10-12 months and can be very finely regulated. These extreme values may be extended below the lower limit in areas south of Hungary and above the upper limit in areas to the north.

Within a short time from the onset of fragility, which varies from 10 to 12 days to a few weeks, depending on the season and the number of hours of sunshine, the photosensitized plastic breaks down into small, invisible pieces due to accelerated photooxidative degradation. This debris no longer mocks the environment, nor does it hinder the cultivation of the soil. When decomposed into soil, it continues to decompose in a non-polluting manner.

Further degradation of the photodegraded plastic debris in the soil is essentially biological. In the process of photooxidative degradation, the plastic disintegrates into a mixture of low molecular weight oligomers with a large number of hydrophilic groups, which are available to soil microorganisms and can be used as a nutrient source.

The invention is further illustrated by the following non-limiting Examples.

Example 1

Preparation of basic iron (1ll) stearate-based photosensitizer

To a four-necked 250 ml flask with stirring, addition funnel, thermometer and reflux was added a solution of sodium hydroxide (0.06 mol) in water (150 ml) and stearic acid (0.4 mol) was added. After stirring for 2 hours at 83 ± 2 ° C, a solution of 0.02 mol of ferric chloride in 30 ml of water heated to 50 ° C was added. After the addition of half the aqueous iron (III) chloride solution at pH 9, 5 ml of ammonium acetate / acetic acid buffer was added and the aqueous iron (III) chloride solution continued to be added. After the addition of the reagent, the mixture was stirred at 83 + 2 ° C for an additional 20 minutes and then cooled to room temperature with stirring. The precipitated solid was filtered through a G2 glass filter and dried to constant weight under an infrared lamp. The basic iron (III) stearate-based photosensitizer is obtained in 95% yield. The aqueous solution remaining after removal of the product has a pH of 5.5.

The above procedure is repeated except that 0.5 g of hexamethylene tetramine and 7 ml of ammonium hydrogen phosphate / hydrochloric acid buffer are used as buffers.

The product was prepared in the presence of the ammonium acetate / acetic acid buffer system at 99-101 ° C, the product prepared in the presence of the hexamethylenetetramine buffer at 106108 ° C, the product prepared in the presence of the ammonium hydrogen phosphate / hydrochloric acid buffer at 103-105 ° C. are good. By way of comparison, basic iron (III) stearate prepared in non-buffered medium has a melting point of 92-94 ° C. The infrared spectrum and DSC curve of the basic iron (III) stearate-based photosensitizer obtained in the presence of ammonium acetate / acetic acid buffer and hexamethylenetetramine buffer are shown in Figures 1 and 2; for comparison, the corresponding curves of the compound prepared in unbuffered medium are also shown.

From the data it can be seen that the physical constants of the products obtained in the presence of different buffers are different, which indicates the fine structure differences.

Example 2

TIPOEEN FB 2223 S1 TVK Low Density Polyethylene was mixed with 0.64 g (10 ^-3 mol) / 100 g polyethylene of the basic iron (III) stearate-based photosensitizer prepared in Example 1 and blended from the mixture. 0.1 mm thick 20x40 mm specimens were produced by pressing.

The specimens were aged in an Xenotest 450 accelerated weatherproofing apparatus at 45 ± 0.5 ° C and 70 ± 10% relative humidity. From time to time, samples were subjected to a bending test to determine the fragility of the samples and the time needed to do so. The results are reported in Table 1.

/. spreadsheet

Fragmentation time of polyethylene specimens containing basic iron (III) stearate-based photosensitizer produced in the presence of various buffers

The buffer system used for production Time for fragility, hour Ammonium hidiOgén- phosphate / hydrochloric 490 Ammonium acetate / acetic acid 570 Hexamethylenetetramine 770 Without buffering 1300 Additive-free polyethylene > 4000

HU 207 096 B

By way of comparison, Table 2 shows the results of experiments performed with known photosensitizers doped with polyethylene specimens prepared as described above. The known photosensitizer was used in each case in an amount of 10 ^-3 mol / 100 g polyethylene.

Table 2

Fragmentation time of polyethylene specimens containing a known photosensitizer

photosensitizer Time for fragility Iron (IH) acetylacetonate 300 Iron (III) tristearate 690 ferrocene 800 Iron (III) diethyl-dithiocarbamate 1200

From the data in Table 1, it can be seen that the iron (III) stearate-based photosensitizers produced according to the invention in the presence of different buffer systems have different photochemical activities. Comparison of the data in Tables 1 and 2 also shows that the iron (III) stearate-based photosensitizers of the present invention are capable of sensitizing polyethylene in the same range and with similar differences as the previously known photosensitizers of different chemical structures. Thus, iron (III) stearate-based photosensitizers of different photochemical activities produced by the process of the present invention are useful as substitutes for known photosensitizers.

Example 3

TIPOLEN FB 2223 into low-density polyethylene type SI, using the amounts of photosensitizer A in Table 3 (product based on basic iron (III) stearate prepared as described in Example 1 in the presence of ammonium hydrogen phosphate / hydrochloric acid buffer system) and " Photosensitizer B (basic iron (III) stearate-based product prepared as in Example 1 in the presence of hexamethylenetetramine buffer) was mixed and the test specimens prepared as described in Example 2 and determined as in Example 2. the time the fragments became fragile. To characterize lifetime controllability,

Y _ dt_ hours but 10 ⁴ moles of adjustability coefficient were introduced, which gives the change in the time of fracture to the change in health concentration. It is good (almost linear) to control the lifetime as a function of the concentration of the photosensitizer, if the Y value is nearly constant in the test row.

The results are shown in Table 3.

Table 3

Amount of additive (IO ^-4 mol / 100 g PE) Altogether Time for fragility, hour Y "THE "B" 2.5 - 2.5 900 - 3.0 1.0 4.0 820 53 3.0 2.0 5.0 760 60 5.2 2.3 7.5 620 56 10.0 - 10.0 490 52

From Table 3 it can be stated that the control coefficient Y, apart from a minor variance, is constant over the studied interval with good approximation, ie the use of basic iron (III) stearate based products produced in the presence of two different buffers has become very finely controllable.

Example 4

The procedure described in Example 1 was followed except that the compounds listed in Table 4 were used as carboxylic acids of the formula R-COOH. In each case, the reaction was carried out in the presence of hexamethylenetetramine buffer; the pH of the aqueous mixture was 5 to 7 at the end of the reaction. The melting point of the products is shown in Table 4.

The basic iron (III) -caboxylate-based photosensitizers thus obtained were mixed with low density polyethylene of the type TIPOLEN FB 2223 Si 10 to ³ mol / 100 g polyethylene, and the mixtures were prepared as described in Example 2 and determined as in Example 2. the time the fragments became fragile. The results are shown in Table 4. For comparison, results from the use of appropriate basic iron (III) carboxylate additives in buffered medium are also provided.

Table 4

R-COOH Product op. C Time for fragility, hour Bowl. of A comparison parative 2-Ethyl-hexanoic acid oil 430 720 isostearic oil 380 430 erucic 73-74 2100 2280 3,4,5-petrol benzoic acid 145-146 2400 2800 3-phenyl-propionic acid 70-72 2580 2900 3-Phenyl-acrylic acid 99-100 2800 3250 Additive-free polyethylene > 4000

The data in Table 4 show the different photosensitizing effects of basic iron (III) carboxylates with different ligands and the photosensitizing effect on polyethylene.

EN 207 096 függ both the nature of the R group and the use of the buffer are illustrated.

Example 5

In this example, the photosensitizing effect of a basic iron (III) stearate-based product prepared in the presence of hexamethylenetetramine buffer as in Example 1 was investigated in various polymers. The photosensitizer was used in an amount equivalent to 1CV'mol (0.64 g) / 100 g of polymer. The specimens were prepared as described in Example 2 and the fracture time was determined as in Example 2.

The following polymers were tested:

TIPOLEN FB 2223 SKI (TVK made low density polyethylene, fine film type)

TIPELIN FS (340-02 (TVK linear ethylene / hexene-1 copolymer, heavy duty bag type)

TIPPLEN H 631 F (Type TVK Polypropylene Fine Film)

GEDEX 4200 (CdF Chimie polystyrene)

The results are reported in Table 5.

Table 5

Polymer Time for fragility, hour Additive grows Foloszenzibili- pivalate TIPOLEN FB 2223 SÍ > 4000 770 70% by weight TIPOLEN FB2223 SKI + 30% by weight TIPELIN FS 340-02 > 4000 500 TIPPLEN H 631 F 800 100 GEDEX 4200 400 200

Example 6

This example illustrates the stepwise production of the type of photosensitizer of the present invention as well as the master blend and film utilized therein, as well as the degradation of the photosensitized film under agricultural use. At the same time, the effect of the cover on crop yields is also described.

For the semi-scale production of the photosensitizer we used a 2 m ³ steam-heated enameled duplicator with an anchor stirrer. The measured quantities were as follows:

15.85 kg (390 moles) of technical sodium hydroxide dissolved in 1150 liters of tap water,

72.0 kg (260 moles) of technical stearic-palmitic acid mixture,

35.2 kg (130 mol) of technical ferric chloride (FeCl ₃ X ₆ H ₂ O) dissolved in 220 liters of tap water,

3.2 kg (22.8 mol) of hexamethylenetetramine dissolved in 30 liters of tap water.

The reaction was carried out under the same conditions as in Example 1. The product was separated from the mother liquor by centrifugation and dried in a container vacuum evaporator at 7580 ° C and 0.1 bar pressure to constant weight. 77.14 g (95%) of a light pink powder were obtained; 105-106 ° C. Iron content (average molecular weight 624.66): 8.94% found: 8.87%.

The product was blended into a low-density polyethylene (FB 2223 Si) type FB 2223 Si blend with 15% by weight of a photosensitizer, using the same feedstock as a 1 x 2x10 ³ mol (0.75 g) / 100 g polyethylene photosensitizer. The 04mm flat film was extruded with a wide slot die, chill-roll technology.

The foil was tested at three different times for growing three types of vegetables, cultivated with earthworms, fixed on both sides by digging. For film ventilation and perforation, 400x010 mm / m ² perforation was used.

Table 6 shows the degradation data for the films and the yields of the vegetables grown under them.

Note that the periods from the beginning of the fragility to the complete fragility were sufficient for the plants to survive the microclimate change resulting from the loss of cover, without shock. At the time of total fragility, the cover was virtually eliminated, and the film debris was no longer visible to the naked eye in a few days.

Table 6

Potato Tomato Green pepper Date of posting March 24 April 17 May 7 Fragility onset, time May 6 May 19 June 5 Sun 43 32 29 Total fragility, time May 14 May 25 June 12 Sun 51 38 36 Energy absorbed, kJ / cm ² 89.3 72.45 75.08 Yield, kg / m ² covered plants 2.15 4.87 3.39 Uncovered control 1.53 4.09 2.99

When the film is made of low density polyethylene AE 1716 from TVK, the above procedure is followed, except that in the first step a master blend containing 25% by weight of a photosensitizer is prepared.

Claims (8)

PATENT CLAIMS 1. A process for the preparation of a basic iron (III) carboxylate-based photosensitizer for the photosensitization of polyolefin or polystyrene-based plastics in water6. By reaction of an alkali metal salt of a soluble iron (III) salt and a carboxylic acid of the formula R-COOH in an aqueous medium, wherein R is a C 5-20 alkyl group, a C 20-24 alkenyl group, a C 2 -C 5 alkyl or alkenyl monosubstituted phenyl group; C 1-4 alkoxy substituted phenyl, characterized in that to a 1-8 wt% aqueous solution of an alkali metal hydroxide is added an equimolar amount of the carboxylic acid R-COOH equimolar to the alkali metal hydroxide, followed by 70-90 ° C. 0.4-0.6 mole of water soluble iron (III) salt per mole of carboxylic acid, optionally in the form of an aqueous solution, is added during the addition of the water soluble iron (III) salt when the pH of the reaction mixture is reduced to 9 buffer is added, the reaction is carried out while allowing the pH to drop to 5 to 8, and the precipitated product is isolated. 2. A process according to claim 1, wherein the buffer is selected from the group consisting of hexamethylenetetramine or acetate / acetic acid, ammonium acetate / acetic acid, ammonium hydrogen phosphate / hydrochloric acid, or hydrogen phosphate / dihydrogen phosphate. The process according to claim 1 or 2, wherein the buffer or buffer system is added to the reaction mixture after the addition of 40-80% of the water-soluble iron (III) salt. 4. Masterbatch for use in the manufacture of plastic products which are decomposed by sunlight, which: - a polymer of polystyrene or polyolefin type, a photosensitising additive, and optionally containing one or more known, conventional plastic additives and / or excipients for use in the masterbatch, characterized in that the photosensitising additive comprises one or more products obtained by the process of claim 1, based on the polymer present. quantities. 5. A polymeric composition suitable for the production of plastic products which are degradable by sunlight - a polymer of polystyrene or polyolefin type, a photosensitising additive, and optionally containing one or more known conventional additives and / or auxiliaries for the plastics industry for use in the manufacture of plastic products, characterized in that they contain, as a photosensitising additive, one or more products obtained by the process according to claim 1 5% by weight, optionally in the form of a masterbatch according to claim 4. Composition according to claim 5, characterized in that the basic iron (III) carboxylate, preferably basic iron (III) stearate, isostearate produced as a photosensitising additive in the presence of an ammonium acetate / acetic acid buffer system according to claim 1. or a product based on -2-ethylhexanoate. Composition according to claim 5, characterized in that it contains a basic iron (III) carboxylate based product, preferably a basic iron (III) stearate, produced as a photosensitising additive in the presence of hexamethylenetetramine buffer according to the method of claim 1. 8. The composition of claim 5, wherein said photosensitizing additive is a basic iron (III) carboxylate-based product prepared by the process of claim 1 and a basic iron (III) carboxylate prepared in the presence of a hexamethylene-tetramine buffer. III) contains a carboxylate-based product together.