DK146222B - PROCEDURE FOR THE PREPARATION OF BREAKABLE OLEPHINE POLYMERIZATES - Google Patents

Description

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(19) DENMARK V

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DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Patent Application No: 0114/74 (51) Int.CI.3: C 08 G 67/02 (22) Filing Date: 09 Jan 1974 (41) Aim. available: 17 Jul 1974 (44) Submitted: 01 Aug 1983 (86) International Application No: - (30) Priority: 16 Jan 1973 DE 2301889 15 Nov 1973 DE 2357035 (71) Applicant: 'RUHRCHEMIE AKTIENGESELLSCHAFT; 42 Oberhausen 13, DE.

(72) Inventor: Hans-Walter 'Birnkraut; DE, Werner * Kluy; DE, Rudolf 'Stelner; DE, Werner 'Wicke; THE.

(74) Plenipotentiary: Chas. Hude_ (54) Process for Preparation of Degradable Olefin Polymericates

The present invention relates to a process for the preparation of degradable olefin polymers of ethylene, carbon monoxide and an olefinic unsaturated compound containing a non-paraffinic substituent.

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Plastics are increasingly used in the various application areas in industry, crafts and trade. Especially as packaging material, they have proven to be extremely good. The many advantages that plastics have in relation to other materials 2 must be compared with the disadvantage that most of them are only degraded very slowly, i.e. remains unchanged over a long period of time before they are weathered. Among the few plastics that are noticeably attacked by storage in the open, in depots or by composting processes by the resulting biological, chemical, thermal or light effects, for example. some semi-synthetic cellulose esters and certain aliphatic polyesters. However, precisely the most commonly used pulp plastics, polyethylene, polystyrene and polyvinyl chloride, to a great extent resist all such attacks and decay only very slowly. They therefore pose a significant burden to the outside world.

It has not been lacking in attempts to develop plastic which decomposes under external conditions. According to German publication no. 2,136,704, degradable thermoplastic masses are obtained by admixture of suitable metal complexes in the polymers. However, it cannot be ruled out that such additives are later sweated or excluded so that the use of such modified plastics may be contrary to e.g. food law provisions.

Furthermore, it is known that the polymer chains can be cleaved from C = O group-containing polymerisates by light effects. When exposed to UV light, substances of lower degree of polymerization occur, resulting in the starting material becoming brittle. Such polymerisates can e.g. is prepared by the process described in British Patent No. I.129,793 by copolymerization of ethylene with CO or, as disclosed in German Publication No.

I.745.33I, by copolymerization of olefins with vinyl ketone.

Furthermore, it is known in the art concerned that only such paraffinic materials can be biologically degraded if chains are unbranched and do not consist of more than ca. 30 carbon atoms, while branched paraffins already have a content of approx. 10 carbon atoms are no longer attacked. Medium and high molecular weight polyolefins resist any biological attack, even when some percent CO or a C = O group-containing compound or a non-paraffinic side chain compound such as e.g. a vinyl = ester or an acrylic acid derivative.

Therefore, it is the case that olefin homopolymers (such as polyethylene, polypropylene or polystyrene) and olefin copolymers with monomers bearing non-paraffinic side chains (such as, for example, ethylene / vinyl acetate, ethylene / acrylic ester copolymers or ethylene / acrylic acid / acrylic acid / acrylic acid terpolymers) are not appreciably attacked by light or by bio-influences. Olefin copolymers containing carbon monoclonal or C = O group-containing compounds (such as, for example, ethylene / cartanecarbon or ethylene / methylvinyl ketone copolymers) are readily degradable and become brittle under the influence of UV radiation.

However, the resulting degradation product does not return or only very limited to the biological circuit, i.e. that the polymercates decay only very slowly.

The present invention therefore relates to a process for the preparation of such polymerisates which, after use due to biological, chemical or thermal stresses occurring by composting, weather in a relatively short time. By means of appropriate control of such a process, it can be achieved that the plastic thereby not only degrades mechanically, but at least partially returns to the biological circuit. In this way, substances can even be synthesized, which in turn can be utilized for the plant or animal nutrition (such as peat crush or feed materials).

The process of the invention is characterized in that polymer is isolated under such conditions as to obtain polymerisates consisting of 70 - 99 mole% ethylene units 0.5-20 mole% carbon monoxide units and 0.1-10 mole% units. of an olefinically unsaturated compound selected from: vinyl acetate, vinyl stearate, vinyl benzoate, vinyl thioacetate, ethyl vinyl ether, acrylic acid, acrylonitrile, methacrylic acid, methacrylonitrile, alkyl acrylate, alkyl methacrylate, diethyl maleate, dimethyl fumarate, N-methyl fumarate, N

Surprisingly, it has been found that degradable olefin polymerates of ethylene, carbon monoxide and a further olefinically unsaturated compound can be prepared in the presence of usual initiators and using usual polymerization conditions.

These polymers are degraded under the biological, chemical and thermal conditions of composting, the attack being significantly more potent than olefin homopolymer or olefin copolymer which, in addition to the olefin, contains only one of the mentioned comonomers.

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Further, from German Publication No. 2,119,855, a process is known for preparing a degradable polymer material consisting of a polymer of an unsaturated monomer which is mixed polymerized with an unsaturated ketone to form vinyl ketone-containing copolymers.

Such copolymers have a greater number of side chains than the olefin polymerates produced by the process of the invention, and their density is therefore noticeably less than the density of the carbon monoxide-containing copolymers which can be prepared by the process of the invention. In addition, vinyl ketones as a blend polymeric ingredient = increase the brittleness, which is particularly evident from the low tear strength and impact strength. The usefulness of the vinyl ketone-containing copolymers for producing films - which manufacture represents the main field of application of the ethylene blend polymers produced according to the invention - is therefore very limited.

Two terpolymericates have been compared, which terpolymericates have approximately the same proportional composition of ethylene and vinyl acetate and equal molecular weight, although differing in their composition in that one terpolymer as third monomer component contains vinyl methyl ketone, while the other terpolymer as third terpolymer. monoinergic component contains carbon monoxide.

Comparison between E / VA / CO copolymer and E / VA / VMK copolymer.

Density Thrust stress Tear strength Impact -____ (g / cm3) __ (kp / cm2) (kp / cm2) (¾¾¾ É / VA / VMKK ^ 0.916 55 105 850 93.2 / 5 / 1.8 E / VA / CO 0.928 58 130 1280 94.3 / 3.8 / 1.9

Si. t, - »- '» -----' I ».

For both samples MFI 190 / 2.16 = 3-4. x) Vinyl methyl ketone.

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It can be seen from this that the olefin polymerisates produced by the process according to the invention not only result in films which are degraded under biological conditions, but can also be processed into packaging material which has high mechanical stability and thus represents a technical advance over the polymer material which can be produced. by the method of German Publication No. 2,119,855.

Polymer isates having the residual seal 85 to 98.5 mol% ethylene units, 1-10 mol% carbon monoxide units and 0.5 to 5 mol% units of one of the above-mentioned olefinically unsaturated compounds containing a non-paraffinic substituent , has proven to be particularly excellent.

By virtue of their qualitative and quantitative composition, the polymeric agents prepared by the process of the invention exhibit optimum chemical, optical and dielectric properties. In the case of high molecular weight polymerisates, to obtain sufficient degradability, higher content of the co-components contained in addition to the olefin is required than in the case of polymerisates with lower degree of polymerization.

The polymerization of the present invention can be made by the usual methods such as mass, e, solution, precipitation, suspension or emulsion polymerization. Nor are any limitations subject to the choice of the polymerization initiator as well as the reaction conditions. It should be borne in mind that, depending on the copolymerization parameters and the reaction system in question, it may be required to give the reaction mixture a different molar composition than is desired in the final product prepared by the process of the invention. Thus, in the preparation of ethylene-carbon monoxide-vinyl acetate terpolymers, substantially less CO may be contained in the starting mixture than corresponding to the molar amount in the final polymer.

Polymerisates of the kind in question are not only decomposed under the influence of light, but are also decomposed under the conditions of composting already within a relatively short time.

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An irradiation of the polymeric material with a certain amount of light before or after its use can thereby further degrade, but is by no means an imperative necessity.

The invention is further illustrated in the following examples. Terpolymers and comparative copolymers consisting of two monomers as well as ethylene homopolymers which had been prepared in a manner known per se in the high pressure process were used. To test the degradability by light, the polymerisates were formed into foils and pressed sheets, irradiated with different amounts of light, and the spraying was examined visually and also by measurement by means of a penetration test. The testing of the polymeric seeds for their degradability under composting conditions took place by placing illuminated and unlit films in an experimental waste container in which a composting process was carried out in a mixture of dewatered, clear sludge and metal-free household waste at temperatures between 70 and 80 ° C.

Examples.

The preparation of the blend polymerisates takes place in a continuously functioning laboratory autoclave whose core is a magnetic stirrer and electric heating equipped with an autoclave with a capacity of 550 cm3. To the ethylene, prior to introduction into this auto-claw is added initially with gaseous additives (e.g., O 2 as the initiator and CO as a comonomer), whereupon the pressure of two successively injected compressors via an intermediate pressure of approx. 300 bar is increased from the vapor pressure (about 5 bar) to the reaction pressure. Via a preheater, the reaction mixture then enters the autoclave, in which the polymerization takes place at temperatures between 170 and 280 ° C. At the same time, liquid additives (such as, for example, vinyl acetate as a comonomer) can be fed into the reactor with two high pressure metering pumps of different supply capacities. The polymer-monomer mixture coming out of the reactor is expanded by means of a control valve from the operating pressure to a lower pressure (about 5 bar), whereby the resulting polymeric material is mostly excreted in flocculated state and intercepted in alternate form.

Table 1 lists the polymerized preparations and their physical properties. It will be seen that the mechanical property values of the terpolymers do not change much in relation to the values of the homo- and copolymers. Due to the incorporation of 7 146222 CO, the tensile strength leaves something to be desired, while vinyl acetate improves impact resistance. Furthermore, a high carbon monoxide content increases the density of the material and the dielectric constant. Taken together, however, the terpolymerisates still exhibit the characteristic feature of high-pressure polyethylene, and they exist as colorless polymeric compositions which are easily thermoplastic, especially for films.

To test the light degradability, foils (of about 100 μπι'β thickness, applied to aluminum foils) and pressed sheets (of approx.

1 mm thickness) subjected to UV radiation (xenotest, reversal). For the foils, the time needed for spraying was ascertained by means of an indentation test. The results of these tests are listed in Table 2. The pressed plates were each irradiated for 1000 hours and then visually inspected for their brittleness condition. Thereby, it was found that the homopolymers and the ethylene / vinyl acetate copolymers still showed no external changes. By contrast, for ethylene / CO and ethylene / vinyl acetate / CO terpolymerisates with 6-7 mol% CO could already be observed noticeably and in those with approx. 10 mol% CO even a strong formation of fine cracks in the plates. These results show that the spraying time under UV influence depends unequivocally on the carbonyl group content of the polymerisates, thus confirming the known fact that olefin polymerisates incorporated in C = 0 groups promote light decomposition.

For testing for degradability due to biological, chemical and thermal stresses that prevail during a composting process, pressed films of approx. 330 to 350 μΐη'ε thickness, which is partly unlit and partly after a pre-illumination time of 10 hours. (UV irradiation at an intensity of about 145 μ ¥ / οπι at 220 to 280 nm, about 240 μ ¥ / οιη ^ at 280 to 315 nm, and about 310 μ ¥ / οιη ^ at 315 to 400 nm). The pre-illumination time was adjusted so that the radiation dose is far from sufficient to disperse the material. The foils were then placed for 20 days in a test waste container containing a mixture of dewatered, clear sludge and sieved, metal-free household waste (about 1: 1 ratio) under intermittent forced aeration (alternately 2 minutes of aeration and about 10 minutes of standstill). ) at temperatures of 70 to 80 ° C, subjecting them to a composting process. At the end of this test time 8 146222, initially, colorless and almost equally thick foils showed significant changes in color, thickness and external appearance (Table 3).

It can be seen that the ethylene homopolymers and the ethylene / vinyl acetate copolymers have practically not been subjected to degradation. Also, all ethylene / carbon monoxide copolymers were still well preserved, but both the irradiated and the unirradiated samples showed appreciable staining. Particularly noteworthy, however, is the fact that ethylene / vinyl acetate / carbon monoxide terpolymers have been subjected to a much stronger degradation than the homo- and copolymerized agents tested. This is reflected in the fact that all samples could no longer be transferred out of the test storage container as foil, but only in the form of smaller foil residues, and in addition, the thickness of the foils was clearly reduced. This shows that the films are not only degraded due to very strong spraying, but that they were also attacked chemically and biochemically. The strong degradation under the composting conditions also occurred already at relatively low CO content in the polymer, such as e.g. sample 54/1 with approx. 2 mol% CO and approx.

2 mole% vinyl acetate shows. It is also recognized that a pre-illumination of the samples is not necessary for this biological attack. Nevertheless, it is conceivable that the degradation times can be somewhat influenced by a different illumination of the polymerisates, which can be technically utilized to set a desired degradation time by a UV irradiation of the polymerisate before composting or deposition. but possibly even before the polymerization's use as packaging material.

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