RU2418014C1 - Biodegradable thermoplastic composition using natural filler - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to a biodegradable thermoplastic composition used in making films and various hot-moulded articles in form of consumer packaging. The composition contains polyethylene, a copolymer of ethylene and vinylacetate, starch, nonionic surfactant and schungite. ^ EFFECT: composition has good rheological characteristics and is biodegradable under the effect of light, moisture and soil microflora. ^ 2 tbl, 4 ex

Description

The invention relates to the production of plastics based on polyethylene, used in the manufacture of films, thermoformed products (consumer packaging, utensils, etc.), operated both in contact with food and for technical purposes for the manufacture of packaging of goods for economic purposes.

In a difficult global environmental situation, the use of biodegradable polymeric materials to obtain consumer goods is the main direction of reducing the amount of solid waste, as it will ensure their rapid decomposition under the influence of climatic factors and microorganisms.

One of the possible directions for the production of biodegradable materials is the modification of traditional polymers. The combination of a synthetic polymer with a natural active filler can give the material a new set of properties.

Such materials are filled systems where starch is used as an active filler. The most important quality of these compositions is their ability to decompose under the influence of natural environmental factors: light, heat, microorganisms. Known biodegradable packaging material based on starch (France, 2691467, CL 5 C08J 5/18, B65D 1/10, 65/46, C08L 3/20).

Recently, a significant number of patents and scientific publications have appeared containing information on the use of starches as fillers for imparting biodegradability to polymer compositions (US Pat. No. 5,248,702, C08J 9/12, publ. Vol. 1,154, No. 4; US Pat. No. 5,298,267, C08J 9 / 02, 9/12, publ. 03.05.2004, vol. 1150, No. 1; patent RU 2095379, publ. 06/30/98; patent RU 2180670, publ. 06.01.2000; patent RU 2174132, publ. 23.06.2000; EP patent 1338405, MLK ВСС 67/24, C08J 5/06, publ. 08/27/2003; US patent 6054510, IPC 7 C08L 63/00, publ. 25.04.2000).

Archer Daniels Midland, USA has developed a Poly Clean brand concentrate based on polyethylene to produce biodegradable films. The concentrate contains 40% starch and an oxidizable additive, the amount of starch in the final product is 5-6%. The disadvantage of this composition is that only the starch component undergoes biological destruction in it.

The closest in technical essence and the achieved result to the proposed invention is a composition according to the patent of the Russian Federation No. 2349612:

Ethylene Vinyl Acetate Copolymer 59.5-79.5 wt.% Cocoa shell 20.0-40.0 wt.% Surface-active substance 0.2-0.5 wt.%

The objective of the invention is the creation of a thermoplastic composition using a biodegradable starch (potato) filler, products from which are destroyed by the action of light, moisture and soil microflora.

This is achieved by the fact that the biodegradable thermoplastic composition according to the invention contains polyethylene (63.5-86.4 wt.%), A copolymer of ethylene and vinyl acetate (3.0-5.0 wt.%), A biodegradable filler, the quality of which use starch (10.0-30.0 wt.%) and technological additives, which use shungite (0.5-1.0 wt.%), and nonionic surfactant lauryl myristyl (0.1-0, 5 wt.%).

According to the invention, starch in an amount of (10-30) wt.% Is used as a biodegradable filler, stimulating the biological destruction process of final products made from a mixture of polyethylene and a copolymer of ethylene and vinyl acetate.

The potato starch used for filling has the following physical characteristics:

Moisture content, % 17-20 Mass fraction of total ash in terms of dry matter,%, no more 0.3-1.0 Acidity - consumption 0.1 n NaOH solution to neutralize 100 g of dry matter, ml, not more than 6.0-20.0

For filling, you can use starch of various nature: corn, potato, rice, wheat, etc. However, preference is given to potato starch. Potato starch grains are oval, their size varies from 15 to 100 microns, the grain structure is mainly amorphous, such starch is easier to process.

According to the invention, shungite is used as a processing aid.

Shungite consists of an aluminosilicate microporous framework and carbon filling this framework. Shungite carbon has an amorphous structure, is characterized by high reactivity in thermal processes, has high sorption and catalytic properties, and electrical conductivity. Due to its composition and structure, shungite is characterized by a large internal surface and, accordingly, high sorption ability.

The mineral composition of shungite material is characterized by the following indicators: carbon - 25%; silicon - 65%; the rest is 10%.

Physicochemical properties:

- carbon content from 20 to 30% - mechanical abrasion resistance 90% - iodine adsorption activity 11.6 mg / l - heterogeneity coefficient 1.4 - total pore volume in water 0.087 cm ³ / g

Shungite can be used as a filler for rubbers, plastics, mastics, and other composite materials to replace carbon black and soot and give materials new properties. In agriculture, shungites are used as top dressing in the form of a shungite-dolomite mixture, which contains calcium and magnesium, necessary for plant growth, trace elements - potassium, phosphorus, vanadium, cobalt, copper, nickel, zinc, accelerating plant growth.

The black color of shungite grains regulates the thermal regime of the soil: accumulation, long-term preservation and slow release of solar heat absorbed per day. Top dressing loosens the soil due to the presence in it of grains of shungite with a diameter of 1 ... 3 mm.

Biodegradable material containing shungite, when composted, can be a kind of soil top dressing.

The surfactant was selected according to the principle of the need to create a heterogeneous system with specified values of its effective viscosity in the selected processing temperature range. The surfactant is lauryl myristyl (ALM-7), the general formula is RO (CH ₂ CH ₂ O) _n H, where n = 7; R is an alkyl residue containing mainly (12 ... 14) carbon atoms. This surfactant was used in the composition to improve the compatibility of the ingredients and achieve homogenization, and also as an initiator of biodegradation.

LDPE 15803-020 polyethylene with the following characteristics was used as a polymer that acts as a dispersion medium.

density, kg / m ³ - 919.0

PTR, g / 10 min at a load of 2.16 kg - 2.0

As a polymer acting as a modifier, a copolymer of ethylene and vinyl acetate (SEVA) was used, which has the following characteristics:

the content of vinyl acetate from 5 to 30 wt.%

density 0.928-0.945 g / cm ³

elongation in tension (600-800)%

breaking stress at break of 9-12 MPa

The proposed copolymer of ethylene and vinyl acetate has a sufficient water absorption (1-3)%, which contributes to the biodegradation of finished products during disposal. In addition, SEVA has a rather high compatibility with starch, and as a result of technological processing of the composition, the starch is better distributed over the matrix of polyethylene.

Such a composition has rheological characteristics that correspond to the requirements for materials for processing on traditional equipment for plastics (extruder, injection molding machine).

Products from the proposed composition have the desired performance characteristics.

The choice of optimal ratios of polymer, filler, technological additives is determined by the theoretical filling limit, which is determined by the strength of interaction at the phase boundary.

The proposed composition is made as follows.

Example 1. 10 wt.% Starch is mixed with 86.4 wt.% Polyethylene, 3.0 wt.% Copolymer of ethylene and vinyl acetate, 0.5 wt.% Schungite, 0.1 wt.% Surfactant in a high-speed turbo mixer for 5 min The resulting mixture enters the extruder for homogenization. The melt temperature at the outlet of the extruder head is (140-150) ° C.

The obtained bundles are cooled by a stream of cold air and cut into granules of 3-5 mm in size. A film is made from the obtained granules by blown extrusion at a temperature of 130-135 ° C.

Example 2. Preparation of the composition according to example 1. The amount of starch 30 wt.%, The amount of polyethylene 63.5 wt.%, The amount of ethylene vinyl acetate copolymer 5.0 wt.%, The amount of schungite 1.0 wt.%, The amount of surfactant 0, 5 wt.%.

The granules obtained from this composition are used for the manufacture of a sheet from which consumer packaging of various configurations and sizes is formed.

Example 3. Preparation of the composition according to example 1. The amount of starch 20.0 wt.%, The amount of polyethylene 75.0 wt.%, The amount of copolymer of ethylene and vinyl acetate 4.0 wt.%, The amount of schungite 0.7 wt.%, The amount of surfactant 0.3 wt.%.

The granules obtained from this composition are used to make the film by extrusion.

The compositions of the compositions of the examples are shown in table 1. In the examples, their optimum amounts are given.

Table 2 shows the methods for determining the properties that provide the objective of the invention.

table 2 No. p / p Name of indications Test methods one. The processing temperature of the composition, ° C GOST 11645-73 2. The melt flow rate of the composition (MFR) at a temperature of 190 ° C and a load of 2.16 kg, g / 10 min GOST 11645-73 3. Determination of physical and mechanical properties (elongation,%; tensile strength, n / m ² ) GOST 14236-81 four. Method for determination of resistance to chemical media GOST 12020-72 5. Microbiological resistance GOST 9.053-75 GOST 9.049-91

Claims (1)

A biodegradable thermoplastic composition for products, characterized in that it contains polyethylene, a copolymer of ethylene and vinyl acetate, a biodegradable filler, which uses starch, and processing aids, which use a nonionic surfactant, shungite, in the following ratio of components, wt .%:
Polyethylene 63.5-86.4 Ethylene Vinyl Acetate Copolymer 3-5 Starch 10-30 Surfactant 0.1-0.5 Shungite 0.5-1.0