RU2717032C1 - Method of producing organic-mineral composite for thermoplastic oxo-biodegradation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of elastomer compositions with high content of mineral filler and can be used in production of organic-mineral biodegradable additive. Method of producing an organic mineral composite for oxo-biodegradation of thermoplastics includes steps of preparing an aqueous dispersion of a mineral filler, liquid phase alignment of the aqueous dispersion of the filler with latex, separating the filled elastomer system, dehydration and drying of the obtained composite, wherein preparation of the aqueous dispersion of the modified filler, wt%: water – 92.92–92.96; natural calcium carbonate – 7.00 and PolyDADMAC 0.04–0.08 is performed by mixing components at ultrasonic effect from 2.0 to 6.0 min, liquid-phase combination of natural latex is carried out by diluting to dry rubber content of 5.0 to 15.0 wt%, followed by introduction of an aqueous dispersion of calcium carbonate, with the following ratio of components, pts.wt: natural rubber : modified calcium carbonate is 100:(250÷400) with constant stirring and subjected to ultrasound action for 3–10 minutes, extraction of the filled elastomer composition is carried out on a filtering surface from a capron micro-mesh with subsequent mechanical-thermal dehydration in a twin-screw unit with a vacuum zone with a granulating device, where at 160–190 °C the composite is dehydrated to moisture content of not more than 2.0 wt%; the obtained granulate is mixed with a synthetic thermoplastic in terms of dry calcium carbonate, pts.wt. – polymer : calcium carbonate = 100:(5÷30).

EFFECT: technical result is production of organomineral composite promoting biodegradation of thermoplastics, as well as obtaining a highly filled master batch, low consumption of coagulating substances, efficient distribution of filler over the polymer phase, obtaining a highly disperse system, wider field of use of the obtained masterbatches, low cost of the obtained products.

1 cl, 5 tbl

Description

The invention relates to the production of elastomeric compositions with a high content of mineral filler and can be used to obtain organo-mineral biodegradable additives.

The essence of the invention lies in the liquid-phase filling of latex (an aqueous polymer dispersion) with mineral fillers, which are capable of causing premature coagulation of the system and, as a result, do not ensure uniform distribution of components throughout the polymer composition. Liquid-phase filling with ligated (modified) finely dispersed materials at the latex stage, unlike traditional “dry” mixing on rollers or in a rubber mixer, ensures maximum introduction into the polymer matrix, even when using partially crosslinked polymer.

The use of the invention in the preparation of an organo-mineral additive is aimed at improving the manufacturability of the production of oxobiodegradable polymer compositions, including when using secondary raw materials as a polymer matrix, to reduce costs, and most importantly, to create packaging materials and products for short-term household use.

There is a known method (RF Patent No. 2210576 dated 05/14/2001) for producing a powdered mineral polymer material, which consists in adding a non-ionic surfactant OP-10, a stabilizing additive, to the initial component — SKS-65GP, which is taken in the amount of 2 wt. % based on rubber, mix. Additionally add mineral filler - chalk and mix again to obtain a curd mass. It is kept at a temperature of 18-20 ° C and ambient humidity W = 40-50% for 1-2 hours until a polymer film appears on the surface of the agglomerates, crushed to a fineness, grinding through a 008 sieve of at least 95% and dried. The components are maintained in a ratio of 20 wt. % - latex SKS-65GP, 8 0 wt. % - mineral filler - chalk.

The disadvantage of this method is the length of the process, the insufficient degree of dispersion and distribution of chalk, and the main use is as a polymer phase of the structured commodity latex SKS-65GP with a high content of aromatic monomer unit .. This organo-mineral composition cannot be used as an additive in the manufacture biodegradable polymer composition. It should be noted that the use of non-ionic surfactant OP-10 as a stabilizing additive of a mineral filler requires its increased consumption in obtaining highly filled polymer compositions and, as a result, contributes to the additional emulsification of the latex system, which complicates the process of coagulation with mineral fillers, in particular, natural calcium carbonate.

It should be noted that the interaction with hydrophilic mineral fillers of high molecular weight cationic surfactants with amine salts in aqueous or organic media promotes the formation of organic complexes with hydrophobic properties [Pat. No. 3755127 United States. Elastomrs compounded by sprey drying. / Hedberg J.G. - 1965].

A known method for producing emulsion rubbers in powder form by coagulating a mixture of carboxylate and non-carboxylate latexes with a weight ratio of 80: 20-20: 80, alkaline earth metal compounds in the presence of anti-agglomerates - calcium stearate and zinc stearate, amine type antioxidants and fillers (calcium carbonate, talc , silicon dioxide, etc.), the amount of which is 3-10% per dry matter, followed by the removal of moisture from the separated crumbs and drying them (RF Patent No. 2201422 of 03/27/2003).

The disadvantage of this method of producing filled polymers at the latex stage is the strict procedure for introducing the components of the coagulating system at a certain ratio. The lack of intensive dispersion of mineral fillers is often associated with certain difficulties, which consist in their uniform distribution over the volume of the polymer phase. The difficulty in the distribution of the filler is associated either with the hydrophobicity of the organic filler, due to poor wettability of the aqueous dispersion of the polymer, which requires the use of effective mixing equipment or additional introduction of surfactants, or with the difficulty of isolating the polymer and filler from the dispersion phase. At the same time, inorganic substances can cause premature coagulation, and substances of organic origin are difficult to disperse in the aqueous phase.

The known method [RF Patent No. 2689750 of 05/28/2019] to obtain an elastomeric composite, which includes providing a continuous stream under pressure of the first fluid containing dispersed particles and a destabilized dispersion of the filler having a zeta potential of less than 30 mV, and a continuous stream a second fluid containing elastomeric latex. The patent describes various schemes for the preparation and mixing of two fillers, the dispersion of which is carried out using mechanical processing, which includes grinding, grinding, grinding, impact grinding or processing of a fluid with high shear, or any combination thereof. In this case, the combination of latex and filler occurs in the reaction zone at high feed rates.

The disadvantages of this method are the high energy consumption for mechanical dispersion, the complexity of the hardware design of the processes of dispersion and liquid-phase combination, as well as the observance of high metering accuracy and media transportation speeds.

The closest in technical essence and the achieved effect is the method [RF Patent No. 2563013 dated 09/10/2015] for production, which involves doping silicon oxide with aluminum, preparing a dispersion of doped silicon oxide in water, bringing into contact and mixing plantation rubber natural rubber and water latex a dispersion of doped silicon oxide to obtain a coagulate, extraction of coagulate, drying of the extracted coagulate to obtain a masterbatch. In this case, one of the conditions is satisfied: the pH in the range of 3.5 ÷ 6.0; 6.0 ÷ 8.0 or higher 8. The pH measurement is carried out immediately after the contact of two dispersions. The invention improves the efficiency and obtaining the masterbatch with a mineral filler content of at least 80% (wt.). The dispersion of the filler is processed using a 1,500-watt vibracell ultrasonic unit manufactured by sonics et materials inc with a piezoelectric transducer.

The method has the following disadvantages:

- the use of doped silicon oxide as a biodegradable additive will not allow to obtain an biodegradable polymer composition using synthetic thermoplastics, because silicon oxide is not capable of leaching from polymer composites in aqueous media;

- the need to maintain the value of the hydrogen index during coagulation of the filled polymer system in strict intervals;

- the formation of wastewater with a high content of aluminum compounds;

- the introduction of a stabilizing agent in the form of aluminum compounds into the composition of the polymer composition promotes thermo-oxidative degradation of the elastomeric phase with unsaturated bonds during drying in air of atmospheric oxygen;

- during the drying process, emissions containing aluminum compounds are not excluded;

- obtaining a shapeless crumb composition containing mineral filler.

An object of the invention is to provide a method for producing an organo-mineral composite for the biodegradation of thermoplastics in the form of a masterbatch by liquid-phase combination of natural latex with modified calcium carbonate in a ratio of components, wt.% Rubber: filler = 100: (250 ÷ 400) wt. h without the use of coagulating agents, but with the use of effective external energy exposure to violate the aggregate stability of the latex system, to ensure a high degree of dispersion of the filler and its uniform distribution over the volume of the polymer composition, followed by mechanical-thermal dehydration, eliminating thermal oxidative processes in the polymer phase with unsaturated compounds.

The technical task of the invention is achieved by the fact that in the method for producing an organo-mineral composite for the hydrobiodegradation of thermoplastics, which includes the steps of preparing a dispersion of a mineral filler with water, combining a liquid-phase aqueous dispersion of a filler with latex, isolating a filled elastomeric system, dewatering and drying the resulting composite, it is new that preparation of an aqueous dispersion of a modified filler of the following composition, wt. %: water - 92.92 ÷ 92.96; natural calcium carbonate - 7.00 and PolyDADMAC 0.04 ÷ 0.08 is carried out by mixing the components under ultrasonic action from 2.0 to 6.0 minutes, the liquid-phase combination of natural latex is carried out by dilution to dry rubber content from 5.0 to 15.0 wt. % after which an aqueous dispersion of calcium carbonate is introduced in the following ratio of components, wt. h: natural rubber: modified calcium carbonate from 250 to 400 with constant stirring and is subjected to ultrasound for 3 ÷ 10 min., the filling of the filled elastomeric is performed on the filter surface from a nylon microgrid with subsequent mechanothermal dehydration in a twin-screw unit with a vacuum zone with a granulating device where at a temperature of 160-190 ° C the composite is dehydrated to a moisture content of not more than 2.0%, the obtained granulate is mixed with synthetic thermoplastic in terms of dry to calcium carbonate, wt. hours - polymer: calcium carbonate = 100: (5 ÷ 30).

The technical result of the invention is to obtain an organo-mineral composite by liquid-phase combination of natural rubber with the maximum introduction of calcium carbonate using ultrasonic treatment and mechano-thermal dehydration in sealed high-performance equipment. Oxobiodegradable additive has the ability to limited leaching of the mineral filler in the aquatic environment, and most importantly obtained using natural rubber with a high content of unsaturated bonds, as well as naturally occurring impurities that contribute to biodegradation when exposed to external factors.

In the method of producing a composite that promotes the biodegradation of thermoplastics, use:

- low ammonia natural latex produced in Vietnam.

Table 1 - Properties and chemical composition of natural latex

Options Value Rubber,% (wt.) 55.0 ÷ 60.0 Water,% (wt.) 45.0 ÷ 40.0 Proteins,% (wt.) 2.0 ÷ 2.7 Resins,% (wt.) 1.65 ÷ 3.40 Sugar,% (wt.) 1,5 ÷ 4,2 Ash,% (wt.) 0.2 ÷ 0.7 The pollution determined on a sieve of 45 microns, wt. %, no more 0.05 Initial plasticity, not less thirty Nitrogen content,% (wt.), No more 0.6 Ash content,% (wt.), No more 0.6 Mooney viscosity MB 1 + 4 (100 ° C) 55 ÷ 60

As a filler, calcium carbonate was used, the quality indicators of which are presented in table 2.

Table 2 - Quality indicators used calcium carbonate

The name of indicators GOST 4530-76 requirements Analysis result Mass fraction of calcium carbonate,%, not less than 99.0 99.0 Mass fraction of substances insoluble in hydrochloric acid,%, no more 0.010 0.009 Mass fraction of soluble alkalis and carbonates (in the form of OH),%, no more 0.0030 0.0010 Mass fraction of total nitrogen,%, no more 0,020 No more than 0,020 Mass fraction of sulfates,%, no more 0.01 0.01 Mass fraction of phosphates,%, no more not standardized - Mass fraction of chlorides,%, no more 0.002 Less than 0.002 Mass fraction of iron,%, no more 0.005 Less than 0.005 Mass fraction of potassium and sodium,%, no more 0.04 - Mass fraction of magnesium,%, no more 0.02 Less than 0.02 Mass fraction of heavy metals,%, no more 0.002 No more than 0,002

PolyDADMAC polyelectrolyte was used as a stabilizer, which is an effective coagulant (in minimum dosages) for latex and a stabilization agent in the preparation of dispersions (TU 2227-184-00203312-98).

A method of obtaining an organo-mineral composite for the oxobiodegradation of thermoplastics is as follows.

In a capacitive apparatus with a volume of 10.0 dm ³ , equipped with a mixing device and ultrasonic emitters, an aqueous dispersion of calcium carbonate is prepared at a ratio of components, wt.% - water: calcium carbonate: stabilizer = 92.96: 7.00: 0.04, t. e. water is poured in an amount of 4610 g with the stirring device turned on, and then natural calcium carbonate in an amount of 350 g is filled in. After preliminary mixing of a suspension of calcium carbonate, an aqueous solution of the PolyDADMAC stabilizer is added in an amount of 40 g with a content of 5.0 wt% on a dry matter basis.

Dispersion is carried out with stirring and ultrasonic treatment for 2 ÷ 6 minutes to an average equivalent particle size of calcium carbonate of less than 15 microns. The stabilized dispersion of calcium carbonate is sent to the stage of liquid-phase combination with latex in a coagulator equipped with ultrasonic emitters, a mixing device and a jacket to maintain the temperature at 30 ÷ 55 ° C. Before mixing with a stabilized dispersion of calcium carbonate, natural latex is diluted to a concentration of 5-15 wt.% On a dry matter basis. After mixing natural latex with an aqueous dispersion of calcium carbonate, increase the number of revolutions of the mixing device to maximum values without disabling ultrasonic scoring. The process of combining and coagulation is carried out for 3 ÷ 10 minutes. The resulting water pulp of the filled rubber is sent for separation into an inclined filter surface from a nylon microgrid with a mesh size of not more than 80 μm and is subjected to mechanical dewatering in a laboratory single-screw machine. The pre-dehydrated crumb of rubber to a moisture content of not more than 20% (wt.) Is sent for final dehydration to a twin-screw unit with a vacuum degassing zone, where at the temperature of 160 ÷ 190 ° С and shear rates γ = 100-200 s ^{-1 the} free and most part bound moisture. In a twin-screw unit equipped with a granulating device, dehydration is carried out to a moisture content of not more than 2.0 wt.%.

Upon receipt of an aqueous dispersion of calcium carbonate, a strict ratio of components is maintained, wt.%: Water: calcium carbonate: stabilizer - (92.92 ÷ 92.96): 7.00: (0.04 ÷ 0.08) depending on the degree of filling organo-mineral composite.

Using a granulate of an organic-mineral composite, a biodegradable thermoplastic of synthetic origin is obtained.

The method is illustrated by the following examples.

Examples No. 1 - No. 4 explain the effect of the duration of ultrasonic treatment on the dispersion composition in the manufacture of modified calcium carbonate by the ratio of components, wt.%: Water: calcium carbonate: stabilizer - 92.96: 7.00: 0.04.

The results are presented in table 3.

Example No. 1.

4610 g of water is poured into the tank apparatus, equipped with a mixing device and ultrasonic emitters, when the mixing device is turned on, natural calcium carbonate is added in an amount of 350 g. After preliminary mixing of a suspension of calcium carbonate, an aqueous solution of PolyDADMAC stabilizer is added in an amount of 40 g with a content of 5, 0% wt. by dry matter.

Dispersion was carried out with stirring and ultrasonic treatment for 1 minute. The dispersion composition of the calcium carbonate suspension after ultrasonic treatment was determined using a Zetatrac laser particle size analyzer.

The average particle size of the resulting dispersion of calcium carbonate is more than 20 μm, which will complicate the mechanochemical activation of the process of dispersing the organo-mineral composite used as a biodegradable additive when modifying a synthetic thermoplastic.

Example No. 2.

The process was carried out analogously to example 1, however, dispersion with stirring and ultrasonic treatment was carried out for 2 minutes.

The particle size of the dispersion of calcium carbonate after ultrasonic exposure for more than 2 minutes was less than 14 microns, which is acceptable when receiving biodegradable polymer products with a thickness of more than 200 microns.

Example No. 3.

The process was carried out analogously to example 1, however, dispersion with stirring and ultrasonic treatment was carried out for 6 minutes.

Processing during this time allowed to obtain a micro-sized mineral filler with a maximum diameter of not more than 11.0 μm, which is effective for mechanochemical activation of the process of dispersing a biodegradable additive in a synthetic thermoplastic.

Example No. 4.

The process was carried out analogously to example 1, however, dispersion with stirring and ultrasonic treatment was carried out for 7 minutes.

The results obtained are identical to the experimental data of example 3. However, processing over 7 minutes contributes to the production of micro-sized mineral filler with a maximum diameter of about 11.1 μm, which indicates the inappropriateness of increasing the duration of ultrasonic exposure, because increasing energy consumption.

Table 3 - the Effect of ultrasonic treatment time on the dispersion characteristics of the suspension

Example Number Duration of ultrasonic exposure, min. The average particle diameter, microns Width of distribution, nm Energy of ultrasonic impact, J / g 1 1,0 22.9 483 720 2 2.0 13.8 497 860 3 6.0 11.0 562 2480 4 7.0 11.1 689 3770

Thus, during ultrasonic treatment of an aqueous dispersion of calcium carbonate prepared according to the recipe presented in the examples, a decrease in the average equivalent particle diameter from 22 μm to 11 μm is observed for 1 to 7 minutes, which indicates the feasibility of the proposed technological solutions.

Examples No. 5 - No. 10 allow us to determine the optimal content of the stabilizer PolyDADMAC in an aqueous dispersion of calcium carbonate upon receipt of a highly filled organic-mineral composite and to ensure the completeness of coagulation and uniformity of the filled coagulation system.

Upon receipt of an aqueous dispersion of calcium carbonate, a strict ratio of components is maintained, wt.%: Water: calcium carbonate: stabilizer - (92.92 ÷ 92.96): 7.00: (0.04 ÷ 0.08) depending on the degree of filling organo-mineral composite.

The effect of the degree of filling of the composition with modified calcium carbonate on the coagulation process is shown in table 4.

Example No. 5

In a coagulator — a capacitive apparatus with a volume of 10 dm ³ , equipped with a mixing device and ultrasonic emitters, latex is poured in an amount of 2 kg with a content of 5.0 wt% on a dry matter basis, and then a stirrer is added and an aqueous dispersion of modified calcium carbonate with a content of 7 is added, 0% wt. in the amount of 3.7 kg with a ratio of components, wt.%: water: calcium carbonate: stabilizer - 92.96: 7.00: 0.04, after which it is subjected to ultrasonic treatment for 10 minutes. In the process of combining (coagulation), the supply of components in the ratio, wt. hours - rubber: modified calcium carbonate = 100: 250.

The resulting filled rubber pulp is sent to separation on an inclined filter surface from a nylon microgrid with a mesh size of not more than 80 μm and subjected to mechanical dehydration in a laboratory single-screw machine, followed by final dehydration in a twin-screw unit with a vacuum zone.

With this ratio, almost complete coagulation is observed under ultrasonic exposure for 6 minutes, and crumbs with a size of 5–7 mm are formed with calcium carbonate evenly distributed over the polymer phase. The resulting effluent does not contain uncoagulated latex and calcium carbonate.

Example No. 6

The process was carried out analogously to example No. 5, with the ratio of components, wt. hours - natural rubber: modified calcium carbonate = 100: 200, respectively.

The process of liquid-phase combination of natural latex with dispersions of calcium carbonate stabilized with PolyDADMAX solution (0.04 wt.%) Does not allow complete coagulation, while the resulting effluents contain uncoagulated latex and calcium carbonate.

Example No. 7

The process was carried out analogously to example No. 5, with the ratio of components, wt. hours - natural rubber: modified calcium carbonate = 100: 400, respectively.

With this ratio, complete coagulation with ultrasonic exposure for 4 minutes is noted, crumbs with a size of 3 to 5 mm are formed with calcium carbonate unevenly distributed over the polymer phase. Reducing the duration of ultrasonic exposure less than 4 minutes does not ensure the completeness of coagulation. The resulting effluent does not contain calcium carbonate.

Example No. 8

The process was carried out analogously to example No. 5, with the ratio of components, wt. hours - natural rubber: modified calcium carbonate = 100: 450, respectively.

With this ratio, incomplete coagulation with ultrasonic exposure for 10 minutes is noted, and crumbs with a size of 3 to 7 mm are formed with calcium carbonate unevenly distributed over the polymer phase. The resulting effluent contains calcium carbonate.

Example No. 9

The process was carried out analogously to example No. 7, but the ratio of the components was kept in an aqueous dispersion of calcium carbonate, wt.% - water: calcium carbonate: PolyDADMACh solution = 2.97 ÷ 7.00 ÷ 0.03.

The decrease in the content of PolyDADMAC solution is less than 0.04 wt.%, With an increase in the degree of filling of natural rubber: calcium carbonate to 100: 400 wt. h, with ultrasound exposure, it is possible to isolate the crumb of the organo-mineral composition within 15 minutes, but at the same time incomplete combination of components is noted, and the resulting effluents contain calcium carbonate.

Example No. 10

The process was carried out analogously to example No. 7, but the ratio of the components was kept in an aqueous dispersion of calcium carbonate, wt. % - water: calcium carbonate: PolyDADMACh solution = 92.91: 7.00: 0.09.

The increase in the content of the stabilizer PolyDADMAC in the aqueous dispersion of calcium carbonate in excess of 0.08 wt.% With liquid-phase combination of natural rubber: modified calcium carbonate at a ratio of 100: 400 wt. hours is not effective, as there is lumpy coagulation with a maximum extraction of the organo-mineral composite of less than 80%. The data in example 10 are presented in table 4.

Table 4 - The effect of the degree of filling of the composition of natural rubber - calcium carbonate on the dynamics of the coagulation process

Example Number The degree of filling of the composition per 100 wt. including elastomer pH stage isolation Allocation time
min The completeness of coagulation,% Equivalent size of crumbs formed, mm The content of PolyDADMAC in the dispersion = 0.04 wt. % 5 250 11.6 ± 0.1 6 99 ± 1 5 - 7 6 200 11.3 ± 0.2 4-6 92 ± 2 More than 7 7 400 12.0 ± 0.2 3-4 99.9 3.5 - 5 8 450 12.0 ± 0.2 8-10 94 3-7 The content of PolyDADMAC in the dispersion = 0.03 wt. % 9 400 12.0 ± 0.2 fifteen 94 ± 2 3.5 - 7  The content of PolyDADMAC in the dispersion = 0.09 wt. % 10 400 12.0 ± 0.2  1 80 ± 2 Lump coagulation

Examples No. 11 to No. 14 explain the effect of the degree of dilution of natural latex on the aggregative stability of a filled coagulation system and the completeness of its coagulation.

The process was carried out analogously to example No. 5, followed by liquid-phase combination of the obtained dispersion with natural diluted latex with a dry matter content of rubber from 5.0 to 15.0%.

Example No. 11

In the coagulator - a capacitive apparatus with a volume of 10 dm ³ , equipped with a mixing device and ultrasonic emitters, latex is poured in an amount of 0.67 kg with a content of 15.0% wt. dry matter, and then include a stirrer and poured an aqueous dispersion of modified calcium carbonate with a content of 7.0 wt. % in the amount of 3.7 kg with a ratio of components,% wt .: water: calcium carbonate: stabilizer - 92.96: 7.00: 0.04, after which it is subjected to ultrasonic treatment for 10 minutes. In the process of combining (coagulation), the supply of components in the ratio, wt. hours - rubber: modified calcium carbonate = 100: 250.

With this ratio, complete coagulation is noted, and a large crumb with a size of 5–7 mm is formed, while the resulting effluents do not contain uncoagulated latex and calcium carbonate.

Example No. 12.

The process was carried out analogously to example No. 11, but the dilution of the latex was 20.0 wt. %

At this ratio, incomplete coagulation is noted, while crumbs with a size of more than 7 mm are formed, and the drains contain uncoagulated latex.

Example No. 13

The process was carried out analogously to example No. 11, but the dilution of the latex was 5.0 wt. %

With this ratio, complete coagulation is noted, with this crumb with a size of 3 ÷ 7 mm is formed, and uncoagulated latex is absent in the drains.

Example No. 14

The process was carried out analogously to example No. 11, but the dilution of the latex was 4.0 wt. %

In this ratio, incomplete coagulation is noted after a 10-minute ultrasound exposure, and crumbs with a size of 3–7 mm are formed, and uncoagulated latex is present in the drains.

The aqueous pulp of highly filled rubber obtained by liquid-phase combination of natural rubber and modified calcium carbonate is sent to mechanothermal dehydration, followed by granulation. Preliminary separation of the aqueous phase from the rubber filled with calcium carbonate is carried out on an inclined filter surface from a nylon microgrid with a mesh size of not more than 80 μm, and then subjected to mechanical dehydration in a laboratory single-screw machine. Pre-dehydrated crumb rubber to a moisture content of not more than 20 wt. % is sent for final dehydration to a twin-screw unit with a vacuum degassing zone, where free and most of the bound moisture is separated at a temperature of 160-190 ° С and shear rates γ = 100 - 200 s ^-1 . In a twin-screw unit equipped with a granulating device, dehydration is carried out to a moisture content of not more than 2.0 wt.%.

Examples No. 15 - No. 18 illustrates the temperature range of mechanical-thermal dehydration in a twin-screw unit.

Example No. 15

The pre-dehydrated rubber crumb to a moisture content of not more than 20 wt.% Is sent for final dehydration to a twin-screw unit with a vacuum degassing zone, where free and most of the bound moisture is removed at a temperature of 160 ° C.

As a result of dehydration, a moisture content of not more than 2.0 wt.% Is achieved in the granulate of the organo-mineral composite.

Example No. 16

The process was carried out analogously to example No. 15, but mechano-thermal dehydration was carried out at a temperature of 150 ° C.

As a result of dehydration in the granulate of the organic-mineral composite, a moisture content of more than 3.0 wt.% Is achieved, which complicates its use in the preparation of biodegradable films and molding products from thermoplastics.

Example No. 17

The process was carried out analogously to example No. 15, but mechano-thermal dehydration was carried out at a temperature of 190 ° C.

As a result of dehydration in the granulate of the organo-mineral composite, a moisture content of less than 2.0 wt.% Is achieved.

Example No. 18

The process was carried out analogously to example No. 15, but mechano-thermal dehydration was carried out at a temperature of 200 ° C.

As a result of dehydration in the granulate of the organic-mineral composite, a moisture content of less than 2.0 wt.% Is achieved, but thermomechanical destruction of natural rubber filled with calcium carbonate is observed, which is accompanied by darkening and gas inclusions in the granules.

Example No. 19.

In a centrifugal mixer, 1000 g of LDPE polyethylene 10803-020 and 62.5 g of granulate of an organo-mineral composite were loaded in a ratio of natural rubber: calcium carbonate components of 100: 400 wt. h, which corresponds in terms of dry calcium carbonate, wt. hours - polymer: calcium carbonate = 100: 5. Then it was mixed for 1.0 minute in a twin-screw extruder at a temperature of 190 ° C to obtain a granulate filled with an organo-mineral composite polyethylene. Next, the granules were sent to a blown film extruder, where at a temperature of 150 + 10 ° C a sleeve film of a thickness of 40 μm was obtained.

Samples of the obtained films were subjected to accelerated aging under the influence of UV radiation at a temperature of 60 ºС for 150 hours (GOST 34281-2017). The following parameters were selected as indicators of the effectiveness of oxobiodegradation: maximum tensile strength in the longitudinal direction and elongation at break; tests were performed according to GOST 11262-80. The results are presented in table 5.

Example No. 20.

Samples of polyethylene films were obtained according to example 19, however, the ratio of polyethylene ÷ calcium carbonate was 100 ÷ 4 wt. h. The results are presented in table 5.

Example No. 21.

Samples of polyethylene films were obtained according to example 20, however, the ratio of polyethylene ÷ calcium carbonate was 100 ÷ 30 wt. h. The results are presented in table 5.

Example No. 22.

Samples of polyethylene films were obtained according to example 21, however, the ratio of polyethylene ÷ calcium carbonate was 100 ÷ 31 wt. h. The results are presented in table 5.

Table 5 - Test results of films containing organo-mineral filler

Example Number Ratio
Polyethylene: calcium carbonate, wt. h Tensile Strength, MPa Elongation at break,% Before exposure After 150 hours of exposure Before exposure After 150 hours of exposure 19 100: 5 9.8 ± 0.2 8.8 ± 0.2 385 ± 10 346 ± 10 20 100: 4 9.9 ± 0.2 9.8 ± 0.2 380 ± 10 385 ± 10 21 100: 30 6.6 ± 0.2 5.3 ± 0.2 238 ± 10 192 ± 10 22 100: 31 6.3 ± 0.2 4.3 ± 0.2 238 ± 10 172 ± 10

As can be seen from table 5, the use of an organo-mineral filler contributes to the initiation of oxidation degradation processes and makes it possible for films containing the claimed additive to accelerate oxidative decomposition, while in compositions with an organic-mineral filler (in terms of calcium carbonate) less than 100: 5 wt. . hours, destruction processes are not observed, but with a content of more than 100: 30 wt. including low values of physical and mechanical properties of the resulting products.

The proposed method for producing an organo-mineral composite that promotes biodegradation of thermoplastics allows:

- get a highly filled masterbatch;

- reduce the consumption of coagulating substances;

- effectively distribute the filler in the polymer phase;

- get a highly dispersed system;

- expand the scope of the resulting masterbatch;

- reduce the cost of products received.

Claims (1)

A method of producing an organo-mineral composite for biodegradation of thermoplastics, comprising the steps of preparing an aqueous dispersion of a mineral filler, liquid-phase combining an aqueous dispersion of a filler with latex, isolating a filled elastomeric system, dehydrating and drying the resulting composite, characterized in that the preparation of an aqueous dispersion of a modified filler of the following composition, wt. .%: water - 92.92 ÷ 92.96; natural calcium carbonate - 7.00; and PolyDADMACh 0.04 ÷ 0.08 is carried out by mixing the components under ultrasonic action from 2.0 to 6.0 minutes, the liquid-phase combination of natural latex is carried out by dilution to the rubber content of dry matter from 5.0 to 15.0 wt.%, after which is introduced an aqueous dispersion of calcium carbonate in the following ratio of components, parts by weight: natural rubber: modified calcium carbonate is 100: (250 ÷ 400) with constant stirring and is subjected to ultrasound for 3 ÷ 10 min, the allocation of filled elastomeric the composition is produced on a filtering surface from a nylon microgrid followed by mechanothermal dehydration in a twin-screw unit with a vacuum zone with a granulating device, where at a temperature of 160 - 190 ° C the composite is dehydrated to a moisture content of not more than 2.0 wt.%, the granules obtained are mixed with a synthetic thermoplastic in in terms of dry calcium carbonate, parts by weight - polymer: calcium carbonate = 100: (5 ÷ 30).