RU2658415C2 - Method for producing a polymer biodegradable material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to development of a method for creating a biodegradable material based on a primary or secondary polymeric feedstock and can be used to produce polymer materials capable of accelerated photo-oxidative aging. Process for producing a polymer biodegradable material, characterized in that the sodium form of montmorillonite is suspended in an aqueous solution of an organic solvent, taken in a weight ratio of montmorillonite to the solvent, not more than 15% per unit weight of the solvent, and left until completely swollen to form a gelatinous mass into which a salt of a variable valence metal is added under vigorous stirring in an amount calculated from the cation exchange capacity of the clay necessary to completely replace the exchange cations with variable valence metals, after stirring, the resulting mass is left to settle before precipitation, the resulting precipitate is first washed with distilled water, and then with an aqueous solution of an organic solvent until the products of the cation exchange reaction are completely removed, the resulting precipitate is dried in a freeze-dried to constant weight, then the resulting semifinished product containing the extrusion decomposition activator is introduced into the melt of polyethylene or ethylene/vinyl acetate copolymer at a rate of 2 to 5% by weight to form a biodegradable material.

EFFECT: technical result is increase in the rate of photooxidative decomposition of LDPE as the primary act of polymer biodegradation.

11 cl, 3 tbl, 1 dwg

Description

Technical field

The invention relates to the development of a method of creating a biodegradable material based on primary or secondary polymer raw materials and can be used to produce polymer materials capable of accelerated photo-oxidative aging.

State of the art

Known methods for producing composite materials based on a polymer with added clay additives, however, they all differ from that proposed by the absence of the introduction of decomposition activators (patents RU No. 2577359, PH No. 22015000398, PH No. 22015000397, CN No. 201510336823, CN No. 201510265440, CN No. 104231319, CN No. 105199489).

The disadvantage of these methods is the impossibility of using the proposed nanofillers as an activator of decomposition, since the authors of the patents did not set their goals on obtaining biodegradable material, but on creating composites with enhanced mechanical properties.

A number of patents have been identified where montmorillonite used is pre-modified with surfactants to increase the degree of affinity between the nanoclay and the polymer base in order to ensure the intercalation of the filler in the polymer material (RU 2344066, RU 2344067, RU 2380316, RU 2424797, RU 2440392).

A number of patents have been identified that describe a method for preparing a nanofiller for incorporation into a polymer matrix (RU 2344066, RU 2344067, RU 2380316, RU 2424797, RU 2440392).

However, no patents have been identified where the finely dispersed clay material, montmorillonite, modified with active substances, is used as a nanofiller capable of activating polymer decomposition processes.

Closest to the claimed is a method of obtaining a breakdown inhibitor, which consists in the fact that the layered mineral based on montmorillonite (bentonite - Na + forms) is enriched with sodium ions (Na +) by treatment and exposure to 5-20% aqueous solution of sodium chloride, followed by washing deionized water, with drying to obtain a semi-finished product. The resulting semi-finished product is subjected to intercalation using 0.3-20% aqueous solutions of inorganic salts of the metals magnesium, scandium, chromium, manganese, iron, cobalt, nickel, copper, zinc, silver, tin, lead, cerium, or combinations thereof. After enrichment and intercalation, drying is carried out at a temperature of not more than 110 ° C (RU 2440392).

In the proposed method, the modification of polymeric materials is carried out by mixing the obtained nanofiller with liquid thermosets or liquid polyvinyl chloride plastisols. The process of mixing the polymer material and the inhibitor is carried out using ultrasound at a power of 20-75 W / cm ² , a frequency of 20-50 kHz, for 3-10 minutes, and before curing the polymer composition, it is evacuated until the gaseous products are completely removed, using 0 5-5.0 wt. % inhibitor of destruction on the weight of the polymer material. In the obtained composite materials, a nanofiller based on nanodispersion of montmorillonite intercalated by metal ions acts as a destruction inhibitor. It is impossible to obtain a biodegradable polymer material by the described method.

Disclosure of invention

The objective of the invention is to obtain biodegradable polymeric materials capable of photo-oxidative aging. The technical result is the production of polymeric materials capable of accelerated photo-oxidative aging (the first stage of biodegradation of polymers), compared with the original polymers.

The specified technical result is achieved by the claimed method for producing a polymer biodegradable material, by introducing a nanofiller with a decomposition activator into the polymer, in which montmorillonite is used as the decomposition activator, with cations of metals of variable valency embedded in the interplanar spaces of the clay.

The inventive method for producing a polymer biodegradable material is that the sodium form of montmorillonite is suspended in an aqueous solution of an organic solvent, taken in a mass ratio of montmorillonite to a solvent of not more than 15% per unit mass of solvent, and left until complete swelling with the formation of a gel-like mass into which with vigorous stirring, add a salt of a metal of variable valency in an amount calculated on the basis of the cationic exchange capacity of clay necessary for complete replacement After exchanging the cations with metals of variable valency, after stirring the resulting mass is left to settle until a precipitate precipitates, the precipitate is first washed with distilled water and then with an aqueous solution of an organic solvent until the cation exchange reaction products are completely removed. The resulting precipitate is dried in a freeze dryer to constant weight, then the resulting the semi-finished product containing the decomposition activator by extrusion is introduced into the polymer melt (thermoplastic elastomer) from 2 to 10% wt. . with the formation of biodegradable material.

As an aqueous solution of an organic solvent, it is preferable to use a water-alcohol mixture or a water-acetone mixture with a water content in the mixture of 0.2 to 0.8 volume fractions, while acetone, diethyl ketone, ethyl and isopropyl alcohols are used as an organic solvent.

The addition of a metal salt of variable valency to the gel-like mass formed is carried out with vigorous stirring, which is continued for at least 3 hours. After mixing, the resulting mass is defended for at least 3 hours.

The resulting precipitate is washed with distilled water at the rate of at least 100 ml of water per 2 g of montmorillonite, and an aqueous solution of an organic solvent is taken in a volume ratio of no more than 1: 1 to the precipitate.

Preferably, metal chlorides, acetylacetonates or metal sulfates are used as the metal salt of variable valency.

Preferably, Mn, Ni, Co, Fe, Cu are used as metals of variable valency.

It is preferable to use thermoplastic elastomers as polymers, namely polyethylene, copolymers of vinyl acetate and ethylene.

Additionally, additives are added to the melt to uniformly disperse the decomposition activator in the polymer, for which it is preferable to use copolymers of vinyl acetate with ethylene, maleized ethylene with a maleic acid content of 0.3 to 1.5 wt%.

The advantage of the proposed method is that it allows you to increase the content of metal with a catalytic effect in the filler compared with other methods of introducing metal ions of variable valency. Thus, the total amount of filler in the polymer required to achieve the desired effect will be reduced.

In addition, interplanar cations can be replaced directly when clay is extracted from natural raw materials, which greatly simplifies the preparation of a filler, a biodestructor. For the introduction and uniform dispersion of the decomposition activator in the polymer into the polymer melt, specially selected additives are used as compatibilizers.

The present invention is aimed at imparting bioresorbability to a polymer nanocomposite and, thus, reducing the decomposition time of such a material in nature under the influence of external factors such as oxidation, ultraviolet radiation and the influence of microorganisms.

In addition, it is possible to increase the mechanical properties due to the introduction of clay nanoparticles with a decomposition activator. It is known that the introduction of a small (about 5-15%) amount of organically modified clay leads to an increase in the strength of the material.

The method is implemented by obtaining a specially prepared nanofiller with a decomposition activator deposited on its surface and introducing this nanofiller by extrusion into the polymer melt using specially selected additives as compatibilizers.

Brief Description of the Drawings

- Na-MMT;

- Ni-MMT;

- Со-ММТ;

- Mn-ММТ; -

- Fe-MMT;

- NiAcAc-MMT;

- Cu-MMT.In FIG. 1 presents the diffraction patterns of Na-MMT and synthesized samples, where

- Na-MMT;

- Ni-MMT;

- Co-MMT;

- Mn-MMT; -

- Fe-MMT;

- NiAcAc-MMT;

- Cu-MMT.

The implementation of the invention

The ability of sodium montmorillonite (Na-MMT) to swell and disperse into single layers in polar media is used to obtain decomposition activators. A suspension of sodium montmorillonite with vigorous stirring is mixed with salts of variable valency, while the process of replacing sodium cations with metals of variable valence. For the processing of sodium montmorillonite into an activator of decomposition of a salt of metals of variable valency, they are taken in an amount that allows the clay mineral to be converted from the sodium form into a form containing the corresponding metal of variable valency. As salts of metals of variable valency, NiCl ₂ × 6H ₂ O, CoCl ₂ , FeCl ₂ × 6H ₂ O, MnCl ₂ , CuSO ₄ , and Ni (C ₅ H ₇ O ₂ ) ₂ (Ni (AcAc) ₂ ) are used.

To give a complex filler - modified montmorillonite, in which sodium cations are replaced by cations of other metals with thermodynamic compatibility with high-pressure polyethylene (LDPE), technological additives are used - polymer co-modifiers with hydrophilic functional groups that have photosensitizing properties. Technological additives are introduced into the composition directly at the stage of mixing the decomposition activator with the polymer, immediately before the extrusion process by mixing in the hopper for at least half an hour. As technological additives, an ethylene-octene copolymer with grafted anhydride and carboxyl functional groups, a copolymer of ethylene and vinyl acetate are used.

The proposed method is implemented as follows.

A certain amount of aluminosilicate is suspended in a water-alcohol solvent taken before swelling for 4-6 hours (1 mol per kg of clay and a salt solution concentration of 2 / 0.05 = 40 mm). Particles of Na-MMT dispersed in a water-alcohol solution during the interaction with a metal salt form a gel. With vigorous stirring, a solution of the calculated amount of metal salt is loaded so that the metal concentration is 1 mol per kg of clay (Table 1). During the reaction, delamination and precipitation are observed in a water-alcohol solvent (time 3 hours). After settling the mixture, the mother liquor is drained, the residue is repeatedly washed first with distilled water and then with a solvent (ethyl alcohol: water 1: 1) until Na + is absent in the wash water, filtered through filter paper and dried to constant weight under vacuum (deviations of the mass from constant value of not more than 0.1% during conditioning).

The following examples of a specific embodiment of the invention are provided to provide those skilled in the art with a complete description of the method of the invention, and it is intended that the examples do not limit the scope of the invention that is intended by the authors.

Example 1

2 g of Cloisite Na aluminosilicate was suspended in 150 ml of a water-alcohol solution (the volume ratio of water to ethyl alcohol was 1: 1). Left for 5 hours to swell. Into the resulting gel with vigorous stirring, 50 ml of an aqueous-alcoholic solution of MnCl _{2 was} loaded (Table 1 shows the mass content of the transition metal salt, sample 3) and stirring was continued for 3 hours.

Next, the resulting mixture was left for 3 hours. After settling the mixture, the mother liquor was drained, the residue was washed with distilled water 3 times in 50 ml portions, then with a mixture of ethyl alcohol and water (50 ml), filtered through a standard paper filter and the resulting precipitate was dried at a temperature of -50 ° С to constant weight under a vacuum. The resulting sample was analyzed. The results are presented in table. 2.

The polyethylene and the resulting additive were mixed using a Haake minilab laboratory twin screw extruder at a temperature of 170 ° C for 15 minutes.

Example 2. Carried out analogously to example 1, but instead of alcohol, acetone was used (water-acetone solvent with a volume ratio of 1: 1 was used).

Example 3-5. Examples 3-5 were carried out analogously to example 1, but instead of a water-alcohol solution of MnCl ₂ used solutions of the salts of the corresponding metals shown in table 1, see sample numbers No. 1, 2, 4-6.

In the diffraction patterns of modified clays (Fig. 1), the reflex at 7 ° degrees is shifted to small angles or greatly flattened as a result of intercalation of exchange cations in the interlayer space of clay.

The elemental composition of the modified filler obtained using x-ray fluorescence analysis is shown in (table 2).

From those given in table 2 and FIG. 1 results should be:

- the ratio of Si / Al / Mg / Fe elements in the aluminosilicate layers of modified clays practically does not differ from their composition of sodium MMT. This indicates the invariability of the composition of the aluminosilicate layer under the selected conditions of the modification process;

- as a result of modification, cations of metals of variable valency are introduced into the interlayer spaces of clay. At the same time, various cations during modification of sodium montmorillonite displace sodium and calcium cations in different ways (Table 1):

- Ni almost completely replaces Na cations and almost 70% of Ca cations, and its complex - only 33% and does not displace Ca;

- Co displaces about 80% of Na cations and only 40% of Ca;

- Mn and Cu replace 75-77% of Na cations and only 19-22% of Ca;

To analyze the destruction of polyethylene (PE), we analyzed the IR spectra of polymer – filler composites obtained by melt mixing before and after ultraviolet irradiation.

During the oxidation of polyethylene, a complex mixture of oxygen-containing groups, both hydroxides and peroxides, and various carbonyl groups having strong bands in the range of 1660-1850 cm ^{-1 is} mainly formed. In this regard, to describe the content of oxidized groups in LDPE, the carbonyl index (CI) was used - the integral intensity of the bands of 1660-1850 cm ^-1 entirely in LDPE during oxidation, attributed to the 2020 cm ^-1 band, characteristic of both crystalline and amorphous phases of LDPE and not requiring separation.

During the oxidation of PE, trans-vinylene and terminal vinyl groups are also formed. An undistorted baseline for the integral description of the content of unsaturated groups formed during oxidation in LDPE (Vinyl Index, VI) was selected when integrating bands 910 and 890 in the aggregate:

From the results shown in table 3, it follows that, compared with PE-158 + SEVA:

- In the presence of activators in the polymer, with the exception of Fe-MMT, the rate of formation of vinyl groups increases significantly.

- For samples with Na, Ni, Co and Mn-MMT, the characteristic oxidation time decreases, which indicates an increase in the oxidation rate of the polymer chain.

- The composite PE-158 + SEVA + Fe-MMT gains KI an order of magnitude faster, loses its mechanical properties even after 150 hours of irradiation, compares KI faster than VIs compared to other samples: Fe-MMT catalyzes the oxidation processes in the polymer without affecting reactions of the formation of vinyl groups.

The proposed invention can be implemented to obtain polymeric materials with increased ability to oxodestruction and further biodegradation.

Claims (11)

1. A method of producing a polymer biodegradable material, characterized in that the sodium form of montmorillonite is suspended in an aqueous solution of an organic solvent taken in a mass ratio of montmorillonite to a solvent of not more than 15% per unit mass of solvent, and left until complete swelling with the formation of a gel-like mass into which with vigorous stirring, a metal salt of variable valency is added in an amount calculated on the basis of the cation exchange capacity of the clay necessary for complete replacement I exchange cations with metals of variable valency, after stirring, the resulting mass is left to settle until a precipitate precipitates, the precipitate is first washed with distilled water and then with an aqueous solution of an organic solvent until the cation exchange reaction products are completely removed, the obtained precipitate is dried in a freeze dryer to constant weight, then the resulting the semi-finished product containing the decomposition activator by extrusion is introduced into the melt of polyethylene or a copolymer of ethylene with vinyl acetate from p counting from 2 to 5 wt.% to form a biodegradable material. 2. The method according to p. 1, characterized in that as an aqueous solution of an organic solvent using a water-alcohol mixture or a water-acetone mixture with a water content in the mixture from 0.2 to 0.8 volume fractions. 3. The method according to p. 1, characterized in that the organic solvent used is acetone, diethyl ketone, ethyl and isopropyl alcohols. 4. The method according to p. 1, characterized in that the stirring is continued for at least 3 hours. 5. The method according to p. 1, characterized in that the sedimentation is carried out for at least 3 hours. 6. The method according to p. 1, characterized in that the washing with distilled water is carried out at the rate of at least 100 ml of water per 2 g of montmorillonite. 7. The method according to p. 1, characterized in that the amount of solvent for washing the precipitate is taken in a volume ratio to the precipitate of not more than 1: 1. 8. The method according to claim 1, characterized in that metal chlorides, acetylacetonates or metal sulfates are used as a metal salt of variable valency. 9. The method according to p. 1, characterized in that the metals of variable valency are Mn, Ni, Co, Fe, Cu. 10. The method according to p. 1, characterized in that additives are added to the thermoplastic elastomer melt to ensure uniform dispersion of the decomposition activator in the polymer. 11. The method according to p. 10, characterized in that as additives use copolymers of ethylene with vinyl acetate.

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