PL151681B1 - An agent for imparting photodegradability to ethylene polymers - Google Patents

Description

PATENT DESCRIPTION

151 681

REPUBLIC

POLAND

Additional patent to patent No.--Int.Cl. ⁵ C08K 5/39

Reported: 87 05 13 (P. 265675) ^{C08K 5/49}

C08L 23/00

Priority --- OFFICE

PATENT

RP

Application announced: 88 11 24

Patent description published: 1991 04 30 δΖΥΤΕΠίί

GENERAL

Inventor: - Patent holder: The Dow Chemical Company,

Midland (United States of America)

An agent for imparting photodegradability to ethylene polymers

The present invention relates to an agent for rendering ethylene polymers photodegradable when exposed to ultraviolet light.

Films and other products made of ethylene polymers are widely used, for example, due to their excellent flexibility and chemical inertness to hydrated and non-aqueous liquids.

As a result of its widespread use, e.g. as packaging material, disposal has become a serious problem, especially in recreational areas, on roadsides and similar locations.

Hence, many efforts have been devoted by those skilled in the art to develop ethylene polymer articles which, without substantially affecting their good physical properties, disintegrate faster on exposure to light or ultraviolet radiation than known ethylene polymer articles.

For many years, e.g., Belgian Patent No. 809,568 and U.S. Patent No. US No. 3,676,401 it is known that ethylene copolymers containing carbonyl groups, such as ethylene carbon monoxide copolymers, degrade when exposed to ultraviolet light, however, films made from these copolymers do not have sufficient strength required for many end-use applications. In French Patent No. 2,179,245 / corresponding to US Pat. US No. 3,860,538, it is stated that compositions consisting of polyethylene and ethylene carbon monoxide copolymers are photodegradable.

Chemical Abstract, Vol. 83, No. 12, 1975, p. 38, Abstract 98475v describes photodegradable polyolefin compositions.

Those skilled in the art recommend various photosensitizing additives to render the ethylene polymers photodegradable. In Canadian Patent No. 1,073,581 it is suggested that ethylene homo or copolymers, such as ethylene vinyl acetate or ethylene ethyl acrylate copolymers, be added to the films produced therefrom to be photodegradable.

151 681 titanium dioxide in the form of anatase. However, it is known that the photodegradability of polymers increases progressively with the concentration of the photosensitizing material only up to a certain level of this concentration. Besides this value, the addition of more photosensitizing material does not significantly increase the degradation rate of the ethylene polymers.

In U.S. Patent No. US In US 3,676,401, it is suggested to increase the photodegradability of ethylene-carbon monoxide copolymers by adding thereto organometallic compounds containing carboxyl groups. Due to the aforementioned low mechanical strength, films made of such copolymers are unsuitable for many applications and therefore have not found wider acceptance in the market.

In U.S. Patent No. Eat. No. 3,825,627 suggests that in order to increase the degradation rate of the polymer compositions, a small amount of polypropylene as well as the maximum effective amount of photosensitizing material should be incorporated into the polyethylene polymer composition. Although a significant increase in the degradation rate is achieved by the addition of polypropylene, an increase in the degradation rate of the ethylene polymer compositions is nevertheless still desirable.

It has been surprisingly found that the incorporation of both an ethylene-carbon monoxide copolymer and a photosensitizing material into the ethylene polymer composition significantly increases the degradation rate of the composition. It has surprisingly been found that the blend of photosensitizing material and ethylene-carbon monoxide copolymer increases the photodegradability of the ethylene polymer composition much more than the photosensitizing material or ethylene-carbon monoxide copolymer each used separately.

The photodegrading agent of the invention comprises a photosensitizing material and an ethylene carbon monoxide copolymer, the photosensitizing material being a heavy metal dithiocarbamate or dithiophosphate with an atomic number greater than 21 excluding metals from Groups 1A, 2A, and 3B of the Periodic Table.

The photodegradation agent of the invention is used as an additive to ethylene polymers. By adding this photodegrading agent, a predictable period of degradation of the ethylene polymer composition and articles made therefrom can be achieved.

Degradable ethylene polymer compositions containing an agent of the invention and articles made therefrom substantially retain the physical properties of the ethylene polymer when making articles, such as film, therefrom and during normal use of the articles, and when exposed to sunlight or other sources. Ultraviolet light compositions and articles made therefrom degrade at a faster rate than ethylene polymer compositions containing comparable amounts of photosensitizing material alone or ethylene-carbon monoxide copolymer alone.

The novel degradable ethylene polymer compositions containing the agent of the present invention are particularly useful as compression molding and extrusion compositions which are discarded after use as waste typically made of polyethylene and other ethylene polymers. Examples of such articles are containers such as boxes, cups, pouches, folding boxes, tubes, bowls, kettles and baskets; agricultural films and films for wrapping and packaging.

The ethylene-carbon monoxide copolymers used in the photodegradant of the invention and in the photodegradable ethylene polymer compositions preferably have a melt index of 0.1-100 dg / min, especially 1-20 dg / min. The amount of carbon monoxide in the copolymer is usually 0.2-25% by weight, preferably 1-20% by weight, especially 5-15% by weight, based on the total weight of the ethylene-carbon monoxide copolymer. Ethylene carbon monoxide copolymers are known. Processes for the preparation of such ethylene carbon monoxide copolymers are described, for example, in US Pat. Eat. No. 2,641,590 and in French Patent No. 2,388,842.

The choice of the most appropriate ethylene carbon monoxide copolymer to be included in the photodegradation agent of the invention depends on various factors, e.g., the desired rate of photodegradation and the nature of the ethylene polymer to which the photodegradant is added. One skilled in the art can readily select the physical properties of the ethylene carbon monoxide copolymer, e.g. its melt index, such that the ethylene carbon monoxide copolymer is homogeneously dispersed in the ethylene polymer and easy to process with it.

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Further additives, such as known antioxidants, may be incorporated into the ethylene-carbon monoxide copolymer.

The term "photosensitizing material" means any material known to fc activates to become a photodegradation catalyst in the presence of ultraviolet light and accelerates the degradation of ethylene polymers containing it when exposed to external weather conditions. A material of this type without adversely affecting other desirable properties of the ethylene polymer composition is suitable. Such materials include agents that accelerate the oxidation of hydrocarbons and / or which, when activated by ultraviolet light, tend to depolymerize or degrade the ethylene polymers containing them.

Photosensitizing materials are known, e.g., from US Pat. US No. 3,676,401 and published German Patent Application No. 2,136,704. Some of these, namely those described in U.S. Patent No. 2,136,704. US No. 3,676,401 is known to enhance the photodegradability of ethylene carbon monoxide copolymers, however, they are not known to be used in conjunction with ethylene carbon monoxide copolymers to increase the photodegradability of other ethylene polymers such as linear low molecular weight polyethylene.

. Preferred photosensitizing materials are, for example, photosensitive aromatic ketones with 8-40 carbon atoms such as 1,5-dihydroxyanthraquinone, anthraquinone, phenolphthalein, benzophenone, anthranone, m-hydroxybenzophenone and p-hydroxybenzophenone; photosensitive aromatic ammonium compounds such as methylene blue and alizarin cyanide green; photosensitive aliphatic ketones with 6-40 carbon atoms such as hexanone, octane and dodecanone; photosensitive aliphatic aromatic aldehydes such as heptanal, caproaldehyde, benzaldehyde and salicylaldehyde; and photosensitive heavy metal stearates and acetylacetonates. Heavy metals are defined below. The preferred heavy metals are iron, cobalt, nickel, copper and zinc. The most preferred heavy metal stearate is iron stearate. Particularly preferred photosensitizing materials are non-ionic photosensitive organic complexes of heavy metals, i.e. metals with an atomic number greater than 21, excluding metals belonging to groups ΙΑ, 2A and 3B of the Periodic Table of the Elements, as given in the Handbook of Chemistry and Physios, 48th Edition. , The Chemical Rubber Co. (1967-1968), which are just used in the environment of the invention. The term "photosensitive complex" is understood to mean a complex which activates under the influence of ultraviolet light to form a photo-oxidative active form of said metal, which thus catalyzes the degradation of the polymer. The metals present in the complex are preferably iron, zinc, copper, lead and tellurium. Other metals are also suitable, such as, for example, cobalt, nickel, manganese, silver, palladium, molybdenum, chromium, tungsten and cerium. The organic group making up the remainder of the complex is a dithiocarbamate group or a dithiophosphate group.

Representatives of preferred complexes are heavy metal dithiocarbamates of the general formula in which R 1 and R 2 are independently a hydrocarbon radical, preferably an alkyl of 1-18 carbon atoms, or are linked together to form a heterocyclic ring with the nitrogen atom, preferably a saturated or unsaturated ring with 4-6 carbon atoms, especially 4-5 carbon atoms, a is an integer corresponding to the valency of M and M is a heavy metal as defined above.

Hydrocarbon radicals are, for example, alkyl, aralkyl, aryl or cycloalkyl. It is possible that there may be as many as 8 different hydrocarbon radicals in a single complex containing 4 dithiocarbamate groups. Preferred heavy metal dithiocarbamates are tris (N, N-di-n-butyl dithiocarbamate / -iron / III, / III), tris / N, N-dimethyldithiocarbamate / bismuth / III /, bis / N, N-dimethyldicatiocarbamate / -copper 1 /, bis- (N, N-dimethyldithiocarbamate / lead / II /, tetrabis / N, N-diethyldithiocarbamate / tellurium / IV /, bis / dimethyldithiocarbamate / zinc / 11 /, bis / N, N-dipropyldithiocarbamate / -nicel / II /, bis / N, N-dihexyldithiocarbamate / cobalt / 11 /, tris / dioctyldithiocarbamate / chromium / 111 /, tris / N, N-dilauryldithiocarbamate / iron / III /, tris- / N, N-distearyldithiocarbamate / iron III /, tris- (N, N-dibenzyldithiocarbamate / iron / 111), tris (N, N-diphenyldithiocarbamate) / iron (111), tris (N, N-dinaphthyl dithiocarbamate / iron / 111), bis (N-phenyl-N-benzyldithiocarbamate) / N -methyl-N-ethyl-dithiocarbamate / iron / 111 /, tris / dicyclohexyldithiocarbamate / iron / 111 / and other dithio4

151 681 carbamates of other heavy metals. The most preferred photosensitizing material is tris (N, N-di-n-butyldithiocarbamate (iron) (111).

Preferred useful dithiophosphates are of the general formula wherein R 1, R ₂ , N and a are as defined above.

The photodegradation agent according to the invention usually comprises 30-250,000 ppm, preferably 100-100,000 ppm, especially 1,000-50,000 ppm and most preferably 2,500-15,000 ppm of photosensitizing material, based on the weight of the ethylene-carbon monoxide copolymer.

To prepare the photodegrading agent of the invention, said ethylene carbon monoxide copolymer and photosensitizing material may be blended in any known manner such as dry blending or melt blending of the components. Mixtures of various ethylene-carbon monoxide copolymers with photosensitizing materials can also be used.

Prior to mixing the photosensitizing material with the ethylene carbon monoxide copolymer, the photosensitizing agent may be dispersed in a polyolefin such as an ethylene or propylene polymer. The polyolefm may be different or the same as the ethylene polymer in the photodegradable polymer composition. Such polyolefins may be used in any amount as long as they are sufficiently compatible with the ethylene polymer composition and do not significantly affect the properties of the composition.

The term "ethylene polymer" refers to normal solid ethylene polymers, suitable for extrusion, casting, molding or similar processing and includes ethylene homo- and copolymers with the exception of ethylene carbon monoxide polymers. The most preferred ethylene polymers are ethylene homopolymers and ethylene copolymers with minor amounts (usually up to 20%, preferably 5-20% by weight) of other copolymerizable aliphatic σ-olefins with

3-18 carbon atoms, high, medium and low density, and mixtures thereof and compositions made therefrom. Such ethylene polymers preferably have a melt index according to ASTM D-1238-65T (E) in the range 0.1-50 dg / min and a density in the range 0.89-0.99 g / cm ³ . Methods of making such ethylene polymers are well known in the art, e.g. from Schildknecht, Polymer Processes, Vol. X (1956) or Chem. Eng. News December 5, 1977

Preferred ethylene polymers are linear low density polyethylenes in which the ethylene has been polymerized with a small amount of [alpha], [beta] ethylenically unsaturated alkenes having 3-12, and preferably 4-8 carbon atoms per alkene molecule.

The linear low density ethylene copolymers with which the agent of the invention is preferably used are copolymers, e.g. made using coordination catalysts, e.g. the well known Ziegler, Natta or Philips catalysts. This applies to high, medium and low pressure polymers. Such ethylene polymers contain a minor amount (usually up to 20% by weight, preferably 5-20% by weight) of at least one alpha-olefin comonomer selected from propylene, butene-1, isobutene-1,4-methylpentene-1, pentene-1, isopentene-1, hexene-1, isohexene-1, heptene-1, isoheptene-1, octene-1, iso-octene-1, nonene-1, isononene-1, decene-1, and isodecene-1. The most preferred comonomers are octene-1, hexene-1, 4-methylpentene-1 and butene-1. The amount of comonomers used should generally be sufficient to result in a polymer having a density in the range of 0.90-0.94 g / cm ³ . Typically, the copolymers have a high molecular weight and have a melt index (melt index) in the range of 0.1-30 dg / min as determined by ASTM-D-1238 (E).

Further suitable ethylene copolymers are the terpolymers described in European Patent Application No. 010428. Preferred ethylene terpolymers are ethylene with butene-1 and octene-1 or ethylene with propylene and octene-1.

The ethylene polymer can also be a copolymer of ethylene and a small amount, e.g. up to 20% by weight, preferably 5-20% by weight of a diene; a cycloaliphatic olefin, e.g. cyclopentene or 1,5-cyclooctadiene; a substituted olefin, e.g., a monoethylenically unsaturated carboxylic acid or one of its alkyl esters; a conjugated olefin such as butadiene; or an alkenyl aromatic monomer such as styrene or its derivatives.

The photodegrading agent may be incorporated into the ethylene polymer in any order by any known method known for mixing solids, a liquid, or polymeric material with the polymer and the solid or liquid component prior to converting the composition into shaped articles. For example, the desired amount of photodegradation agent can be dry blended with the ethylene polymer and, if desired, further blended in a high temperature blender. It is also possible to mix the components of the photodegradation agent separately, i.e. the photosensitizing material, the ethylene carbon monoxide polymer and optional additives, with the ethylene polymer. Alternatively, the photosensitizing material with the ethylene polymer may be premixed and the ethylene carbon monoxide copolymer and optional additives incorporated into the premix. The aforementioned ingredients may also be in the form of a solution and / or dispersion and mixed with a solution or dispersion of the ethylene polymer in a suitable solvent. The temperature of the mixture of the aforementioned components with the ethylene polymer is not particularly critical as long as it does not reach the temperature of thermal degradation of the ethylene polymer or ethylene carbon monoxide copolymer. Moreover, it is understood that the mixing should not be carried out under conditions in which the photosensitizing material significantly loses its photosensitizing properties.

In addition to the previously mentioned necessary ingredients, optional additives such as plasticizers, stabilizers, antioxidants, antistatic agents, anti-molding agents, lubricants or fillers can also be added.

The preferred concentration of the sensitizing material and the ethylene carbon monoxide copolymer depends on various factors, e.g., the nature of the ethylene polymer, photosensitizing material and ethylene carbon monoxide copolymer used in the particular polymer composition. In general, the photodegradable compositions contain from 20, preferably from 50, most preferably from 70 and up to 99, preferably up to 98 and most preferably up to 95% by weight of the ethylene polymer, based on the total weight of the polymers. The amount of ethylene carbon monoxide copolymer is usually from 1, preferably from 2, most preferably from 5% by weight and usually up to 80, preferably up to 50, most preferably up to 30% by weight based on the total weight of the polymers. The photodegradable composition further comprises typically from 25 ppm, preferably from 50 ppm, most preferably from 100 ppm, and usually up to 25,000 ppm, preferably up to 15,000 ppm, most preferably up to 2,500 ppm of photosensitizing material, based on the total weight of the polymers.

Polymers containing a high amount of photosensitizing material, e.g. 25,000 ppm and more, can be used in combination with polymers lacking photosensitizing material to produce a photodegradable composition with an optimal concentration of photosensitizing material.

The photodegradable ethylene polymer compositions can be processed by molding, extrusion, casting, blowing and other known processing methods to a wide variety of shaped articles such as agricultural films, e.g. so-called mulch films; discarded after use collapsible boxes and containers for packaging e.g. beverages and other liquids, packaging films and other articles of ethylene polymers where the disposal of polymeric material after the end of the product remains a problem.

The processed ethylene polymer compositions exhibit relatively poor resistance to ultraviolet light, and they degrade in the prescribed time under the influence of sunlight to such an extent that shaped articles made of these compositions become hard and brittle, and finally crack and / or crumble into small amounts. particles.

The following examples illustrate the invention. In these examples, all parts and percentages are by weight, unless otherwise indicated. The melt numbers of the ethylene polymers and ethylene carbon monoxide copolymers were determined according to ASTM D-1238-65T / E /. The ingredients used in the examples are described in Table 1.

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Table 1

Ingredient Characteristic LLDPE Linear copolymer of ethylene and nominally 6-9% octene-1 based on the weight of the polymer, low density, characterized by an average density of 0.920 g / cm ³ and a melt number of 1 dg / min ECO-1 Ethylene-carbon monoxide copolymer, melt index 1.5 dg / min, containing 1.1% carbon monoxide copolymerized with 98.9% ethylene, based on the total weight of the polymer ECO-2 Ethylene carbon monoxide copolymer, melt index 1.5 dg / min, containing 10% carbon monoxide copolymerized with 90% ethylene, based on the total weight of the polymer ECO-3 Ethylene-carbon monoxide copolymer, melt index 10 dg / min, containing 10% carbon monoxide, copolymerized with 90% ethylene, based on the total weight of the polymer

Standard phenolic antioxidant was added to all ethylene-carbon monoxide copolymers.

Tris (N, N-di-n-butyl dithiocarbamate (iron) (111) was used as the photosensitizing material.

Example Photodegradable ethylene polymer compositions were prepared by dry blending the desired amounts of LLDPE, ECO and photosensitizing material. All parts by weight are based on the total weight of the linear low density polyethylene (LLPDE) and the ethylene carbon monoxide copolymer (ECO). The obtained materials, after dry blending of the ingredients, were then extruded at a temperature of 220 ° C, producing 12 µm thick films on an extrusion blown film processing line. The obtained film samples were tested for degradability in a Sairem Sepap UV chamber. The Sairem Sepap UV chamber emits radiation from the HBO 500W lamp, which gives an intense beam of UV photons with a wavelength of 300-400 mm.

The composition according to the invention was prepared with the following composition: 90% LLDPE, 10% ECO-3,400 ppm photosensitizing material; and three comparative compositions: (A) consisting of LLDPE alone, converted to film, (B) consisting of 100% LLDPE and 400 ppm of photosensitizing material, and (C) consisting of 90% LLDPE and 10% ECO-3.

Film samples made from the composition of the invention and from comparative compositions (A), (B) and (C) were tested as follows.

Ultimate elongation at break was tested on 20 film samples prepared from the composition of the invention and each of the comparative compositions (A), (B) and (C). Of these 20 samples, 4 were not exposed to UV radiation prior to the elongation determination, 4 were exposed to UV radiation for 14 hours, 4 samples for 20 hours, 4 samples for 25 hours and 4 samples for 30 hours. The results of the determinations are summarized in Table 2, and they are the mean value of the determinations for 4 samples.

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Table 2

Ultimate elongation at break /% / after exposure of the film samples to UV radiation for the specified number of hours

A sample Exposure time / in hours / 0 14 twenty 25 thirty 35 45 65 75 Comparative composition / A / 485 . -. • - ' - - 450 480 460 32 Comparative composition / B / 515 - - - - 490 460 380 60 Comparative composition / C / 485 480 475 450 430 296 50 - - Composition according to the invention 570 570 565 350 34 - - - -

The results presented in Table 2 show that the film containing the photosensitizing agent according to the invention degrades much faster than the films made from the comparative compositions / A /, / B / and / C /. The faster degradation is evidenced by the time required for the film to become brittle (i.e. its ultimate elongation at break <100%).

Example 1 illustrates the unexpected effect that the combination of photosensitizing material and ethylene carbon monoxide copolymer increases the photodegradability of the polyethylene film much more than the photosensitizing material or ethylene carbon monoxide copolymer used separately.

Examples II-XV. In these examples, Table III provides further exemplary compositions of the photodegradable agent and the degradable ethylene polymer compositions of the invention.

Table 3

Example no % LLDPE %/type ECO Amount of photosensitizing material / ppm / II 90 10 / ECO-l 400 III 90 10 / ECO-2 400 IV 80 20 / ECO-l 400 V 80 20 / ECO-2 400 VI 80 20 / ECO-3 400 VII 95 5 / ECO-l 400 VIII 95 5 / ECO-2 400 IX 95 5 / ECO-3 400 X 97 3 / ECO-3 400 XI 93 7 / ECO-3 400 XII 94 6 / ECO-3 400 XIII 95 5 / ECO-3 200 XIV 90 10 / ECO-3 600 XV 94 6 / ECO-3 500

Examples xvi-xxxiv. Example 1 was repeated using different photosensitizing materials and polymers of ethylene and carbon monoxide with different monomer proportions. The ingredients used are listed below:

ECO-4: copolymer of ethylene and carbon monoxide containing 0.2% of carbon monoxide copolymerized with 99.8% of ethylene calculated on the total weight of the polymer,

ECO-5: copolymer of ethylene and carbon monoxide containing 14% of carbon monoxide copolymerized with 86% of ethylene calculated on the total weight of the polymer,

ECO-6: ethylene carbon monoxide copolymer containing 25% carbon monoxide copolymerized with 75% ethylene based on the total weight of the polymer.

Photosensitizing material: PSM-1: tris (N, N-di-n-butyldithiocarbamate) iron / III /; PSM-2: tris (N, N-dimethyldithiocarbamate / bismuth / III /; PSM-3: bis (N, N-dimethyldithiocarbamate) copper (II); PSM-4: tetrabis (Ν, Ν-diethyldithiocarbamate) tellurium (IV) PSM-5: bis (N, N-dipropyldithiocarbamate) nickel (II); PSM-6: tris (dioctyldithiocarbamate) chromium (II);

151 681

PSM-7: tris (N, N-distearyl-dithiocarbamate) iron (III); PSM-8: tris (N, N-diphenyldithiocarbamate) iron (III); PSM-9: tris (dicyclohexyldithiocarbamate) iron (III); PSM-10: iron (III) tris (dimethyldithiophosphate); PSM-11: cobalt (II) bis (dihexyldithiophosphate).

The composition of the film produced with the above ingredients is shown in Table 4.

Table 4

Example Percent LLDPE Percentage of ECO type PSM quantity / type XVI 50 50 / ECO-4 25 OOOppm / PSM- 1 XVII twenty 80 / ECO-4 15 OOOppm / PSM- 1 XVIII 70 30 / ECO-l 1 OOOppm / PSM- 2 XIX 80 20 / ECO-l 600ppm / PSM- 3 XX 90 10 / ECO-5 400ppm / PSM- 3 XXI 90 10 / ECO-5 400ppm / PSM- 4 XXII 95 5 / ECO-6 400ppm / PSM- 4 Xxiii 95 5 / ECO-6 400ppm / PSM- 5 Xxiv 90 10 / ECO-6 200ppm / PSM- 6 Xxv 90 10 / ECO-2 600ppm / PSM ·· 7 XXVI 90 10 / ECO-5 600ppm / PSM- 8 XXVII 80 20 / ECO-5 200ppm / PSM- 9 Xxviii 70 30 / ECO-l 800ppm / PSM-10 XXIX 80 20 / ECO-2 600ppm / PSM-10 XXX 90 10 / ECO-5 300ppm / PSM-10 XXXI 95 5 / ECO-6 200ppm / PSM-l 1 XXXII 95 5 / ECO-5 400ppm / PSM-l 1 XXXIII 90 10 / ECO-3 600ppm / PSM-l 1 XXXIV 50 50 / ECO-4 25 OOOppm / PSM-i 1

Claims (4)

Patent claims 1. An agent for rendering ethylene polymers photodegradable, containing a photosensitizing material, characterized in that it comprises a photosensitizing material and an ethylene-carbon monoxide copolymer, the photosensitizing material being a dithiocarbamate or a heavy metal dithiophosphate with an atomic number greater than 21, excluding metals from the group ΙΑ, 2A and 3B of the periodic table. 2. The agent according to claim The process of claim 1, wherein the photosensitizing material is a heavy metal dithiocarbamate of formula I, wherein R 1 and R 2 are independently a hydrocarbon radical or are linked together to form a heterocyclic ring with the nitrogen atom, and is an integer corresponding to the valency of M, and M is Heavy metal with an atomic number greater than 21, with the exception of metals of groups ΙΑ, 2A and 3B of the periodic table of the elements. 3. The agent according to claim The process of claim 1 or 2, characterized in that the photosensitizing material is tris / N, N-di-n-butyl-dithiocarbamate / iron (III). 4. The agent according to claim 1 The method of claim 1, wherein the copolymer of ethylene with carbon monoxide comprises a copolymer of 1-20% by weight of carbon monoxide, copolymerized with 80-99% by weight of ethylene. M (S- C- Ν) _a R. MODEL 1 S. II M [S-P - ORJa I or ₂ PATTERN 2