RU2570905C1 - Method of obtaining biodegradable thermoplastic composition - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: polyethylene, starch and technological additives are mixed, with hydroxypropylmethylcellulose and glycerol being used as the latter.

EFFECT: combination of components in specified ratio provides high biodegradability of composition, possessing high deformation-strength characteristics and thermostabilisation properties, high water resistance and decreased migration of plasticiser from product in the process of exploitation.

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Description

The invention relates to biodegradable compositions designed to create films and various packaging products capable of biodegradation under the influence of natural factors.

Due to the current environmental situation in the world, the production of biodegradable polymer compositions is one of the main ways to reduce the amount of municipal solid waste due to their ability to collapse under the influence of moisture, heat, light and soil microflora.

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.

Currently, natural biodegradable polymers such as starch, cellulose, chitosan, gelatin, polypeptides, etc. are widely used as active components. Of particular interest is starch as the cheapest type of raw material, the main source of industrial production of which is potato, wheat, corn, rice, maize and some other plants.

Currently, 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.

For example, the Dutch company Rodenburg Polymers already produces starch-based Solanyl biopolymers [1]. By its physical and mechanical characteristics, the biopolymer is close to polypropylene (PP) and polystyrene (PS). In compost, it decomposes in less than 12 weeks, and the time for its complete decomposition depends on the composition and technology of production, as well as on environmental conditions. By extrusion of mixtures of corn starch, microcrystalline cellulose and methyl cellulose with or without additives of plasticizers (polyols), edible films are prepared to protect food from weight loss (by reducing the rate of evaporation of moisture). Such films, creating a certain barrier to the penetration of oxygen and other substances from the outside, slow down the spoilage of food products.

Another well-known and large-capacity synthetic product containing starch as an active biodegradable filler is Mater-Bi material (grades AT 05Н, AF 05Н, А 105Н, АВ 05Н, АВ ОН, AF UN). Its industrial production is carried out by the Italian company Novamont S.p.A [2]. A unique property of the materials of the Mater-Bi family, such as the ability to absorb and pass some liquids, is currently used in the production of so-called breathable films. Such polymers produce trays for food products, disposable tableware for fast-food fast-food systems, etc .; film materials with low oxygen permeability (brand AF10H).

Among commercial products made on the basis of polyethylene-starch compositions, we can name the PolycleanTM concentrate developed by the American company Archer Daniels Midland [3] for the production of biodegradable films. In addition to starch (40%), it contains an oxidizing additive that acts as a catalyst for biodegradation of starch not only in the light but also in the dark.

Firm "St. Sawrence ”(USA) offers EcostarplusTM concentrate. It contains a self-oxidizing agent and photodegradant (organometallic salts), which synergistically interacts with a biodegradable component - starch. The material is used as an additive in the manufacture of compost bags.

There is a method (see US Pat. RF No. RU 2180670 (C2), application form 06.01.2000, publ. March 20, 2002) for producing a biodegradable thermoplastic composition comprising starch, a polymer, a mixture of plasticizers, the composition containing a polymer binder as a polymer - the copolycondensation product of caprolactam, adipic acid and hexamethylenediamine - copolyamide, as a mixture of plasticizers - glycerin and water and additional titanium dioxide and ultramarine in the following ratio of components, parts by weight: starch 100, glycerin 20, water 20, copolyconde product sensations of caprolactam, adipic acid and hexamethylenediamine 1-10, titanium dioxide 3, ultramarine 0.008 [4]. The disadvantage of this method is the presence in the finished polymer of significant quantities of low molecular weight substances, which may impair its performance.

A method has been developed (see US Pat. RF No. RU 2404205 (C1), application form 04/09/2009, publ. 11/20/2010) for producing a biodegradable thermoplastic composition that contains cellulose diacetate with a content of acetate groups of 56.4%, in an amount of 25 wt. . including biodegradable filler - starch in an amount of 40-45 wt. hours, hydrolysis lignin in an amount of 5-10 wt. hours and a plasticizer in an amount of 25 wt. h. As a plasticizer, the composition contains a mixture of dioxane alcohols and their high boiling esters, obtained by distillation from flotoreagentoxal light fraction with a boiling point of 115-160 ° C at a pressure of 5-10 mm RT. Art. in the amount of 25 wt. Part [5]. EFFECT: composition has high operational characteristics, products obtained from it are biologically destroyed under the influence of natural factors. This method is characterized by a disadvantage: the presence in the composition of toxic substances that pollute the environment both during processing of the material, and during its operation and disposal.

A known method of obtaining (see US Pat. RF No. RU 2073037 (C1), application. May 29, 1990, publ. 02/10/1997) biodegradable extruded polymer composition, which consists of a copolymer of ethylene and vinyl alcohol (ethylene content of 19-50 mol.% ), degraded starch in a mass ratio of from 1:19 to 4: 1 and water in an amount of 1.5-6.0% of the composition [6]. The composition may further include glycerol in an amount of 12.2-28.4% of starch, urea in an amount of 10.0-17.6% and polyvinyl alcohol or a copolymer of ethylene and acrylic acid in an amount of 7.1-12.8% per 100 % starch. The mixing of the components is carried out in an extruder. The main disadvantage of this method is that synthetic polymers are used as the polymer base.

The closest in technical essence to the claimed invention - the prototype - is a method (see US Pat. RF No. RU 2418014 (C1), application. September 30, 2009, publ. May 10, 2011) to obtain a biodegradable thermoplastic composition that contains polyethylene, ethylene copolymer and vinyl acetate, a biodegradable filler, which uses starch, and processing aids, which use a nonionic surfactant, shungite [7]. 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. The main disadvantage of the prototype is the insufficiently high thermal stabilization properties, which leads to the need for processing at temperatures not exceeding 170 ° C.

The objective of the invention is the creation of a biodegradable thermoplastic composition with high deformation and strength characteristics and thermal stabilization properties, high water resistance, reduced migration of plasticizer from products during operation.

The technical problem is solved in that the thermoplastic composition contains a mixture of polyethylene, starch, hydroxypropyl methylcellulose, glycerin is used as a plasticizer.

Polyethylene plays the role of a dispersion medium. As the polyethylene used high pressure polyethylene grade 11503-070, with the following characteristics:

- density - 0.9180 ± 0.001 g / cm ³ ;

- melt flow rate - 7.0 ± 15 g / 10 min;

- yield strength under tension - not less than 93 · 10 ⁵ PA;

- tensile strength - not less than 98 · 10 ⁵ Pa;

elongation at break - not less than 450%.

Starch is eaten by soil microorganisms and contributes to the mechanical destruction of the product. In the invention, starch of various nature can be used: potato, wheat, rice, corn, etc. Potato starch is preferred. Potato starch is a loose powder of white or slightly yellowish color. Potato starch grains are oval in shape and have a diameter of 15 to 100 microns. According to physical and chemical parameters, potato starch meets the requirements of:

- mass fraction of moisture - 17-20%;

- mass fraction of total ash in terms of dry matter - not more than 0.3%;

- acidity - the volume of a solution of sodium hydroxide with a concentration of 0.1 mol / dm ³ to neutralize acids and acid salts contained in 100 g of dry matter of starch - not more than 10.0 cm ³ .

Glycerin is responsible for the plasticity and flexibility of the films. In the claimed invention uses glycerin brand "pure" with the following characteristics:

- density - 1.256-1.261 g / cm ³ ;

- mass fraction of glycerin - not less than 98.5%;

- refractive index - 1.4710-1.4744;

- mass fraction of the residue after calcination in the form of sulfates - not more than 0.002%.

Hydroxypropyl methylcellulose (HPMC) is a film-forming polymer. HPMC used in this invention is characterized by the following properties:

- degree of substitution (OCH ₃ ) - 1.10-1.55;

- the content of methoxy groups - 19-24%;

- humidity - not more than 5.0%;

- mass fraction of ash in the form of sulfates - not more than 1.0%.

According to the invention, the biodegradable thermoplastic composition contains, by weight. %:

polyethylene - 35-45;

biodegradable filler starch - 25-35;

GPMC - 10-20;

glycerin - 15-25.

In order to obtain a material with high deformation and strength characteristics compared with the materials described in the prior art, the claimed invention uses certain mass ratios of components and processing in an extruder or other apparatus capable of providing temperature and shear conditions that make it possible to reduce the dispersed phases to very small particles.

The invention is illustrated by the following examples.

Example 1

40 wt. % polyethylene is mixed with 25 wt. % starch and 15 wt. % HPMC in a high-speed turbo mixer for 5 minutes, then a plasticizer, glycerin, in the amount of 20 wt. % The resulting mixture enters the extruder for homogenization. The temperature of the melt at the exit of the extruder 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 extrusion at a temperature of 130-135 ° C.

Example 2

Preparation of the composition according to example 1. The amount of polyethylene 45 wt. %, the amount of starch 30 wt. %, the amount of HPMC 10 wt. %, the amount of glycerol 15 wt. %

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

Example 3

Preparation of the composition according to example 1. The amount of polyethylene 35 wt. %, the amount of starch 35 wt. %, the amount of HPMC 20 wt. %, the amount of glycerol 25 wt. %

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

The compositions of the examples are shown in table 1.

Technological and operational properties of biodegradable thermoplastic polymers are presented in table 2.

Thus, the use of a method for producing biodegradable thermoplastic compositions, including high-pressure polyethylene, starch, hydroxypropyl methylcellulose and glycerin, allows you to:

- simplify the technology for the production of biodegradable polymers;

- reduce the heterogeneity of the composition;

- provide high biodegradability of the polymer;

- improve thermostabilization properties;

- increase the temperature of processing of biodegradable compositions to 200 ° C, which provides improved rheological properties of polymers;

- reduce the cost of biodegradable polymers.

Bibliography

1. Electronic resource: http://biopolymers.nl/.

2. Electronic resource: http://www.novamont.com/.

3. Electronic resource: http://www.adm.com/en-US/company/Pages/default.aspx.

4. Pat. 2180670 Russian Federation, IPC ⁷ C08L 77/02, C08L 77/06. Biologically degradable thermoplastic composition based on starch / Lukin ND, Kraus S.V., Kalugina N.A., Peshekhonova A.L., Samoilova L.G., Sdobnikova O.A .; Applicant and patent holder All-Russian Research Institute of Starch Products. - No.2000100058 / 04; declared 01/06/2000; publ. 10/20/2001.

5. Pat. 2404205 Russian Federation, IPC ⁷ C08L 1/12. Biologically destructible thermoplastic composition / Gottlib E.M., Garaeva M.R., Halilullin R.N., Kostochko A.V .; applicant and patent holder State Educational Institution of Higher Professional Education “Kazan State Technological University”. - No. 2009113403/04; declared 04/09/2009; publ. 11/20/2010.

6. Pat. 2073037 Russian Federation, IPC ⁶ C08L 23/08, C08L 3/02. Biologically extruded polymer composition and method for its preparation / Bastioli K., Bellotti V., Del Giudice L., Lombi R.; Applicant and patent holder Novamont S.p.A. - No. 4830150/04; declared 05/29/1990; publ. 02/10/1997.

7. Pat. 2418014 Russian Federation, IPC ⁶ C08L 23/06, C08L 23/08. Biologically degradable thermoplastic composition using a natural filler / Sdobnikova OA, Samoilova LG, Aksenova TI, Ivanova TV, Kraus CB, Lukin ND, Pankratov VA, Ananyev V .V., In Thi Hoai Thu; Applicant and patent holder State educational institution of higher professional education “Moscow State University of Applied Biotechnology”. - No. 2009136075/05; declared 09/30/2009; publ. 05/10/2011.

Claims (1)

A method of producing a biodegradable thermoplastic composition, comprising mixing polyethylene, a biodegradable filler, which uses starch, and processing aids, characterized in that hydroxypropyl methylcellulose and glycerin are used as processing aids responsible for the plasticity and flexibility of the films in the following ratios of components:
polyethylene 35-45 biodegradable filler starch 25-35 GPMC 10-20 glycerol 15-25