CZ2011848A3 - Modified starch-based biologically degradable composition and process for preparing thereof - Google Patents

Abstract

The essence of the solution is a biodegradable composition based on chemically modified starch and maltodextrin acetate, which forms a homogeneous thermoplastic mixture. The composition consists of acetylated maltodextrin (A), a chemically modified starch (B) with an A / B weight ratio of at least 1/20 and a maximum of 20/1, acetylated maltodextrin (A) being the product of hydrolytically or enzymatically degraded starch with dextrose equivalent of 10 to 25 with acetic anhydride and the degree of substitution of the resulting acetylated maltodextrin is at least 2.0 and at most 3.0, and the chemically modified starch (B) is a starch acetate having a degree of substitution of 0.6 to 3.0, or a benzyl ether starch acetate of 0 , 6 to 3.0 and a molar ratio of benzyl and acetate groups of 1:30 to 1: 1, or is a mixture of starch acetate and benzyl acetate acetate in any ratio.

Description

Technical field

The invention relates to a modified starch composition and a process for its preparation.

BACKGROUND OF THE INVENTION

Biodegradable plastics find practical application especially as packaging materials for foodstuffs, carrying bags for goods, foam fillings of solid packaging for the transport of impact sensitive goods, mulch foils for agriculture, sanitary products and other products with short lifetime. Since its inception, the development of biodegradable plastics has been closely linked to the development of polymers based on renewable raw materials. Polysaccharides, especially cellulose and starch, are particularly suitable for the manufacture and biodegradable plastics of their availability and properties.

The starch can be plasticized to a thermoplastic material by applying pressure and shear stress at a higher temperature (about 150-180 ° C). Two-screw co-rotating screw extruders in which the material to be processed is kneaded at high fraction are suitable for this starch plasticization process. The starch plasticization can be accelerated and the properties of the resulting thermoplastic material modified by the addition of various plasticizers, such as glycerol, urea, polyvinyl alcohol. The main disadvantage of such a prepared thermoplastic starch is its low mechanical strength and its high hydrophilicity, which excludes it from a number of applications. A number of inventions have been addressed to overcome these drawbacks. For example, a process for plasticizing starch with glycerol by adding glycerol monostearate to increase the water resistance of the material under specified conditions in an extruder is described in German Patent No. 43 17 696 and U.S. Patent No. 6,136,097. As in the case of synthetic plastics, a well-established process based on blending with suitable cf polymers is used to modify the plasticized starch. For example, US Patent Nos. 6,821,590 and 7,005,168 disclose mixtures of starch with vinyl alcohol copolymers with vinyl acetate or methyl methacrylate and low molecular weight plasticizers and lubricants as packaging film materials. The thermoplastic material based on a blend of destructurized starch with polyesters and graft copolymers of polysaccharides is described in Italian Patent No. (Α92Α0672 and related US Patent 6,277,899). A similar material but with a high proportion of fillers and additive with fluidizing agents is i

disclosed in Italian Patent No. T092-A-000672 and related US 5,874,486. A composition in which a destructuralized or complexed starch is dispersed in a matrix consisting of a plasticized polysaccharide ester is the subject of Italian patent WO98A0735 (US Patent i> 6,730 _r 724). A thermoplastic based on a heterogeneous blend of a starch complex dispersed in a polyester matrix is the subject of Italian patent WO98A0800 (US Patent '6,962,950), similar materials to another matrix (copolyesters, polyester amides, polyester-ether-amides,. Polyurethanes are described in Italian patent publications T096A0996, T096A0890, T098A0524, and US 6,348,524 and US 7,176,251 derived therefrom. Another variant is a thermoplastic blend of starch, modified starch, plasticizer and aliphatic polyester reinforced with exfoliated silicate mineral described in U.S. Patent No. 7,094,817.

Chemical modification of starch, which is relatively reactive due to its hydroxyl groups, can also be used to formulate biodegradable materials containing starch as the main constituent. The simplest way of chemical modification of starch is its esterification. Chemically modified plasticized starch prepared by a reactive extrusion process is the subject of U.S. Patent & 7,153,354. In this case, the starch in the mixture with the plasticizer and the clay nanofiller is esterified with dicarboxylic acids or their anhydrides. Starch esterified with dicarboxylic acids or their anhydrides in admixture with polyvinyl acetate or polyvinyl alcohol, polyol plasticizer and fatty acids or their salts forms a thermoplastic biodegradable material for extrusion of flat packaging materials according to US Patent No. 7,384,993. Material on a similar basis is also protected by US Patent No. 7,495,044 a year earlier.

Another method of chemical modification of starch is by grafting it with suitable polymers, e.g. polyesters. This method of modifying starch is the subject of the invention according to U.S. Pat. ; _ř 1

7,629,405. According to the invention, starch is grafted with an aliphatic-aromatic polyester by a continuous extrusion process with a twin-screw extruder with co-rotating screws. Polymer starch based polymer graft foam and process for its preparation by reactive extrusion are described in U.S. Patent 7,638,560.

The method of chemical modification of starch for the production of biodegradable plastics is described in Slovak patent & 279 600. In this case the starch is modified by etherification with ethylene oxide or propylene oxide and subsequent reaction with polysiloxane.

The technology for producing the materials described above has one common feature that is

- 3 their common shortcoming. This is an energy-intensive preparation of plasticized starch melt materials, which is the case both of mixing various starch mixtures with polymers and of chemical modification of starch by reactive extrusion. However, the material prepared in this way has to be processed again in the melt to form the final product, whereby the total energy consumption for the final product is significantly increased.

SUMMARY OF THE INVENTION

The present invention provides a biodegradable composition based on chemically modified starch and maltodextrin acetate which forms a homogeneous thermoplastic composition. The composition is resistant to water, weak acid and alkali solutions, mineral and vegetable oils, aliphatic solvents, but decomposes rapidly and completely in the soil or compost by the action of soil microorganisms.

The biodegradable composition is prepared from a heterogeneous mixture of maltodextrin acetate (A) and starch acetate and / or starch benzyl ether (B) with a weight ratio of A / B 20/1 to 1/20 that is heated above 110 ° C to form a homogeneous thermoplastic mixture.

Maltodextrin is a mixture of oligosaccharides and polysaccharides, which is formed by partial hydrolysis of native starch with a mineral acid or by the action of an α-amylase enzyme. Acetylated maltodextrin (A) is the product of the reaction of maltodextrin with a dextrose equivalent (DE) of 10 to 25 with acetic anhydride at a temperature of 90 to 140 ° C. The reaction is catalyzed by an aqueous solution of NaOH or KOH or NaClCl or K2CO3 or pyridine at concentrations of 40% to 60% and the degree of substitution (DS) of the resulting acetylated maltodextrin is at least 2.0. The acetylated maltodextrin may be used in the form of a liquid reaction mixture containing 30 to 45% unreacted acetic anhydride or in powder form for the preparation of the composition, where it is precipitated from the reaction mixture with water and subsequently dried.

Acetylated starch (B) is the product of a starch reaction with an amylose content of at least 15% by weight. with acetic anhydride at temperatures ranging from 90 ° C to 140 ° C and catalysed with a solution of 40% to 60% NaOH, KOH, Na 2 CO 3, K 2 CO 3 or pyridine. The degree of substitution (DS) of the resulting acetylated starch is 0.6 to 3.0.

The acetylated starch may contain any amount of starch benzyl ether (B) acetate, which is produced by a process customary for the preparation of acetylated starch also up to a degree of substitution of 0.6 to 3.0, starting with a benzylated starch of DS 0.05 to 1.0 Obtained, for example, by reacting starch with benzylchloride in an alkaline aqueous medium at temperatures of 20 to 90 ° C and a molar ratio of benzyl and acetate groups of starch benzyl ether acetate is 1:30 to 1: 1.

The preparation of a modified starch-based biodegradable composition consisting of a homogeneous mixture of acetylated maltodextrin (A) and acetylated starch and / or starch benzyl ether acetate (B) is based on two basic technological steps, in which a heterogeneous mixture is prepared in a first step. In this step, the mixture is heated to a temperature of 110 ° C to 180 ° C, whereby components (A) and (B) produce a homogeneous single-phase compound material.

In addition to the acetylated maltodextrin (A) and the acetylated starch or the starch benzyl ether acetate (B), the blend prepared in the first material preparation may also contain a filler (C) containing as main constituent oxides or hydroxides of aluminum, silicon or magnesium or calcium carbonate or magnesium carbonate or minerals with a composition corresponding to the chemical formula Mg3Si40io (OH) 2 or ALi (OH) 8S4C10 or cellulose or starch in a weight ratio (A + B) / C not more than 1/4. Heating in the second material preparation step then results in a matrix composite filler consisting of a single phase mixture of acetylated maltodextrin and acetylated starch and / or starch benzyl ether acetate. The heterogeneous mixture prepared in step 1 of the process may be in the form of a paste or a powder mixture.

The homogeneous mixture of acetylated maltodextrin (A) and acetylated starch or starch benzyl ether acetate (B) is hard and brittle. By adding 10% to 50% of a plasticizer which is triethyl citrate or acetyl triethyl citrate or acetyl tributyl citrate in the first preparation step, a soft and pliable material is obtained after heating in the second step.

Preferably, the overall reduction in energy costs is a heterogeneous mixture of acetylated maltodextrin (A) and acetylated starch (B) in the form of a semi-finished or finished product heated to 110 ° C to 180 ° C by electromagnetic radiation at a frequency in the 1 MHz to 10 GHz range.

An advantage of the biodegradable composition of the invention is that its biodegradation rate can be controlled by the degree of substitution of the acetylated maltodextrin (A) and the acetylated starch or acetate of the starch benzyl ether (B) and their content in the composition.

r t »«

* T · t4 t * t

DETAILED DESCRIPTION OF THE INVENTION

Example 1

A solution of acetylated maltodextrin with a degree of substitution DS = 2.8 was prepared from 150 g of maltodextrin having a D2 = 2.0, obtained by enzymatic degradation of wheat starch, by reaction with 390 ml of acetic anhydride at 120 DEG C. The reaction was catalyzed by 15.0 mL of 50% NaOH. and run for 2.5 hours. The obtained reaction product of the acetylated maltodextrin contained 30% of unreacted acetic anhydride.

Two types of acetylated starch of varying degrees of substitution were prepared from dried fine-grain wheat B-starch with a dry matter content of 91.3% and an amylose content of 25.5% by reaction with acetic anhydride: sample 1 o DS = 0.8 and sample 2 o DS = 3, 0. A suspension of 490 ml of acetic anhydride and 170 g of starch was tempered to 115 ° C, followed by 15.5 ml of 50% NaOH. The reaction time was 0.5 h (sample 1, DS = 0.8), respectively. 12 h (sample 2, DS = 3.0). Acetylated starch was precipitated from the reaction mixture in excess of water, which was further mechanically wet-disintegrated and washed several times to a constant pH of 3.6. Subsequently, the obtained product was dried and finely ground to a grain size of less than 0.08 mm.

Pasty mixtures were prepared from acetatlated maltodextrin and both acetylated starches at room temperature by stirring in a planetary mixer at a stirrer speed of 60 min ¹ for 10 minutes. The viscosity of the mixtures was adjusted by the addition of turpentine oil.

Composition of mixture I:

V ¹ Acetylated maltodextrin solution (reaction product containing 30% hmi unreacted acetic anhydride) - 80% pour ·

Acetylated starch vz. 1 (DS = 0.8) - 20% hxr ^ ' ^v ·

Composition of mixture II:

FN ·

Acetylated maltodextrin solution (reaction product containing 30% unreacted acetic anhydride) - 80% w / w Acetylated starch vz. 2 (DS = 3.0) - 20% w / w

Composition of mixture III:

.- • i '

Acetylated maltodextrin solution (reaction product containing 30% unreacted acetic anhydride HMI ^J) - 45% hmrNU · '<5 * t <I tf

I!

«I« · t t 1 · t «í«! 9 '«t« ««

Acetylated starch vz. l (DS = 0.8) - 45% hniX ^ ·

Turpentine oil - 10% hmcX ™ '

Composition IV:

.v ⁷¹⁷ ·

Acetylated maltodextrin solution (reaction product containing 30% hmi unreacted acetic anhydride) - 45%

Acetylated starch vz. 2 (DS = 3.0) - 45%

Turpentine oil - 10%

Mixtures I to IV were then applied on both sides with a squeegee of paper weighing 80 g / m ² . For comparison, acetylated maltodextrin alone was applied to the same type of paper in the form of a reaction product containing 30 wt. unreacted acetic anhydride.

The laminated paper was then exposed to a temperature of 120 ° C for 2 hours in a hot air oven, followed by a temperature of 140 ° C for a further 2 hours. After cooling the samples, their basis weight was determined. The basis weight of the individual coatings was between 58 and 90 g / m ² .

Laminated paper samples were found to be biodegradable according to ASTM D5338-93. The laminated papers were placed in the matured compost in the compost so that they were evenly covered by the compost and the smallest layer of compost above the samples and was approximately 10 cm between the samples. Three test specimens of 20x20 cm were exposed from each material, i.e. paper backed with mixtures I-IV and acetylated maltodextrin alone. After 19 days of exposure, the samples were removed and their weight loss was determined. The weight loss was determined as the arithmetic mean of the observed weight loss of 3 specimens. The temperature in the compost during the exposure period ranged from 12.7 to 15.8 ° C. The results of the weight loss determination after composting are given in Table 1.

• t

Table 1: Weight loss of paper laminated with compositions I to IV after 19 days of exposure to compost

Paint material Weight ratio acetyl. maltodextrin / acetyl. starch Degree of substitution of starch Surface weight of paint, g / m ² Weight loss,% acetylated maltodextrin - - 58.0 89.3 mixture I 4/1 0.8 59.8 83.3 mixture II 4/1 3.0 60.2 67.7 mixture III 1/1 0.8 78.3 76.8 mixture IV 1/1 3.0 89.7 47.6

Example 2

A solution of acetylated maltodextrin in acetic anhydride was prepared as follows: From 160 g of DE4.0 maltodextrin obtained by enzymatic degradation of wheat starch, a solution of DSI substitution degree of acetylated maltodextrin was prepared for 3.5 hours at 120 ° C with acetic anhydride. = .alpha.0 containing 30% unreacted acetic anhydride. The reaction was catalyzed by 50% NaOH.

ΐ »

Starch acetate was prepared from dried fine-grain wheat B-starch with a dry matter content of 91.3% and an amylose content of 25.5% by reaction with acetic anhydride. A suspension of 490 ml of acetic anhydride and 170 g of starch was tempered to 115 ° C, followed by 15.5 ml of 50% KOH. The reaction time was 5 h. Acetylated starch was precipitated from the reaction mixture with excess water, which was further mechanically wet-disintegrated and washed several times to a constant pH of 3.6. The obtained dried product was a micronized to a particle size of less than 0.08 ^{<f! V} 'mm. The degree of substitution (DS) of the thus prepared acetylated starch was 2.4.

From a solution of maltodextrin acetylated degree of substitution DS = 3.0, and acetylated starch B on DS = 2.4 was a laboratory planetary mixer at room temperature and at an impeller speed of 30 min ^-1 for 8 minutes stirring the mixture prepared in the weight ratio 1 : 1. This mixture was placed in a mold for 4 minutes and pressed at 140 ° C into a 4.0 mm plate. The pressed plate was transparent and light brown in color. The specimen was machined from the plate by machining to determine ·

Charpy impact strength according to EN ISO 179-1, Shore D hardness according to EN ISO 868 and water absorption according to EN ISO 62. The water absorption was determined as the relative weight gain after 24 hours of immersion of the plate-shaped test specimen in water at 23 o ·

The biodegradability of the material was determined by the procedure of ASTM D5338-93 as the weight loss of plate-shaped specimens after 19 days of exposure in compost at an average temperature of 17.3 ° C.

Table 2: Properties of the composition of Example 2 2! Charpy impact strength; kJ.m ' 6 Shore D hardness; ° Sh _; 48 1 Water absorption; % and 2.5 Weight loss after 19 days in compost,% i 33

Example 3 /

From 160 g of maltodextrin having DI = 0.0.0 obtained by enzymatic degradation of wheat starch, a solution of acetylated maltodextrin containing 30% of unreacted acetic anhydride was prepared by reaction with 560 ml of acetic anhydride at 120 ° C for 3.5 hours. The reaction was catalyzed by 50% NaOH. Maltodextrin acetate of DS = 3.0 was precipitated from the liquid reaction product of acetyl hydride acetyl hydride by pouring into 3000 ml of water. After filtration, the maltodextrin acetate was made into powder form by drying and milling.

Acetate maltodextrin powder was in a laboratory planetary mixer at room temperature and at an impeller speed of 60 min ^-1 for 5 minutes mixed with the acetylated starch with DS = 3.0 (prepared as described in Example 1) in a weight ratio of 1: 1 . This composition was then pressed at 160 ° C for 4 minutes to form a 4.0 mm thick plate. The pressed plate was transparent and light brown in color. Test specimens were made from the slab by chip machining for determination of Charpy impact strength according to EN ISO 179-1, Shore D hardness according to EN ISO 868 and water absorption according to EN ISO 62. Water absorption was determined as relative weight gain after 24 hours immersion plate-shaped test specimen into water at 23 ° C. The biodegradability of the material was determined by weight according to ASTM D5338-93

plate-shaped test specimens after 19 days of exposure in compost at an average temperature of 17.3 ° C. The results of the assays are given in Table 3.

Table 3: Properties of the Composition of Example 3 i Charpy Impact Toughness; kJ.m ²

Shore D hardness; ° Sh

Water absorption; %

Weight loss after 18 days in compost,%

2.7

Example 4

Maltodextrin acetate powder of DS = 3.0, prepared as described in Example 3, was mixed in a laboratory planetary mixer with a DS = 3.0 powdered acetylated starch prepared as described in Example 1, and a filler in a 1: 1 weight ratio: 2. The filler used in the composition was (1) micronized limestone with an average particle size of 12 µm, (2) dried saturation sludge from sugar production with an average particle size of 6 µm, (3) micronised talc with an average particle size of 16 µm, (4) kaolin with an average particle size of 8 µm, (5) wheat starch B, (6) beech cellulose with an average fiber length of 40 µm and (7) aspen wood flour of an average particle size of 30 µm. Plates of 4 mm thickness were pressed from the powder mixture at 160 ° C. The test specimens for determination of Charpy impact strength according to EN ISO 179-1, Shore D hardness according to ENISO 868 and water absorption according to EN ISO 62 were prepared from these plates by machining. plate-shaped bodies into water at 23 ° C. The biodegradability of the material was determined by the procedure of ASTM D5338-93 as the weight loss of plate-shaped test specimens after 19 days of exposure to compost at an average temperature of 17.3 ° C. The results of the assays are shown in Table 4.

Table 4: Properties of maltodextrin acetate / starch acetate / filler composition (1/1/2) according to

Example 4

Filler Charpy impact strength; kJ.m ² Shore D hardness; ° ShD Water absorption; % Weight decrease after 19 days in compost,% (1) micronized limestone 12 57 2.2 37 (2) saturating sludge 16 61 2.5 47 (3) talc 14 59 2.1 27 Mar: (4) kaolin 8 55 2.3 25 (5) starch B 10 48 7.5 100 ALIGN! (6) cellulose 15 Dec 46 8.0 32 (7) wood flour 8 46 8.5 38

Example 5

From a maltodextrin acetate powder of DS = 3.0 prepared according to the procedure described in Example 3 or a mixture thereof with a starch acetate of DS = 3.0 prepared according to the procedure described in Example 'f', suspensions in water were prepared in a solids / water ratio by weight of 1: 2 . Polyoxyethylene sorbitan monolaurate was added to the water at a concentration of 1.0 wt.

Composition of the solid component of suspension I: maltodextrin acetate 100% Composition of the solid component of suspension II: maltodextrin acetate 75% starch acetate 25% Composition of the solid component of suspension III: maltodextrin acetate 50% starch acetate 50%

The suspensions were applied with a squeegee on paper weighing 80 g / m ² . The coated paper was then dried in a microwave oven at 90 ° C for 20 minutes, and after the coating had dried, the slurry was applied and dried on the other side of the paper in the same manner. The double-sided paper was then heated in a microwave oven at 130 ° C for 5 min to form a transparent, homogeneous layer laminated on both sides with paper. The test specimens were punched out of the laminated papers and the impact bodies were measured on them with a &quot; 4 ' 5 &quot; Tensile strength according to EN ISO 8256. Biodegradability of the laminated paper samples was further determined according to ASTM D5338-93 described in Example 1.

The results of the determination of toughness and weight loss after composting are given in Table 5.

Material paint Composition of the laminated layer Surface weight of paint, g / m ² Tensile impact strength; kJ.m ² Weight loss after 9 days exp.,% Weight loss after 19 days exp.,% suspension I maltodextrin acetate 100% 60.8 19.3 100 ALIGN! - suspension II Maltodextrin acetate 75% Starch acetate 25% 80.2 17.3 17.8 39.0 suspension III Maltodextrin acetate 50% Starch acetate 50% 78.3 10.8 13.2 27.7

Example 6

The reaction product of the acetylated maltodextrin with a degree of substitution DS = 2.8 prepared according to Example 1 was mixed with an acetylated starch of DS 3.0 in a weight ratio of 10: 1 in a laboratory planetary mixer. The liquid composition prepared in this way was then mixed with the dust fraction of construction debris (so-called "demolition dust", waste from the recycling of construction debris) in a weight ratio of 1: 3 in an arm mixer. A 1 cm thick slab was formed in the mold from the resulting mixture of the appearance and consistency of the mortar, which was further heated in a microwave oven at 150 ° C for 20 minutes. The resulting composite was similar in appearance to fine-grain concrete. Test specimens of dimensions 120x15x10 mm were determined from the slab by cutting to determine Charpy impact strength and 120x50x10 slab-shaped bodies to determine biodegradability.

Charpy impact strength was determined as an arithmetic mean of 10 measurements and was 10 kJ.m2.

The specimens for determining biodegradability were placed in the matured compost under the conditions described in Example 1. After 19 days of exposure, the specimens were removed.

The exposed bodies showed an advanced degree of disintegration, the weight loss could not be determined because the mass of the bodies was no longer cohesive.

»·

Example 7

From 40 g of fine-grain wheat B-starch with a dry matter content of 91.3%, by reaction in an aqueous medium (400 ml of water) with 10 g of benzyl chloride and the addition of 6 ml of 35% NaOH solution was prepared at 100 ° C. The reaction lasted 36 hours. Subsequently, the dried starch benzyl ether was acetylated by reaction with acetic anhydride. A suspension of 320 mL of acetic anhydride and benzylated starch (42 g) was placed in a flask and tempered to 115 ° C, followed by the addition of 10 mL of 50% NaOH. The acetylation time was 1 h. After isolation and washing, the product of DS = 1.2 was dried and milled to a powder with an average grain diameter of 0.08 µw. mm?

Powder mixtures of triethyl citrate, acetyl triethyl citrate and acetyl tributyl citrate were prepared from powdered acetylated starch benzyl ether, maltodextrin powder of DS = 3.0 and starch powder of DS = 2.4 by mixing in a laboratory planetary mixer:

Mixture I:

Starch acetate 45%

Maltodextrin acetate 15%

Triethyl citrate 40%

Mixture II:

Starch acetate 45%

Maltodextrin acetate 15%

Acetyltriethylcitrate 40%

Mix III:

Starch acetate 45%

Maltodextrin acetate 15%

Acetyltributyl citrate 40%

Mix IV:

Starch acetate

55%? ·

Maltodextrin acetate 5%

Triethyl citrate 40%

Mixture V:

Benzyl ether starch acetate 55%

Maltodextrin acetate 5%

Triethyl citrate 40%

Mix VI:

Benzyl ether starch acetate 25%

Starch acetate

30%

Maltodextrin acetate 5%

Triethyl citrate

40%

Films of 0.5 mm thickness were extruded from the powder blends on a 19 mm diameter single screw auger equipped with a worm compression compression for PVC processing with a compression ratio of 1: 3 and a flat film head of 100 mm width. Mechanical tensile properties were determined on foils according to ČSN EN ISO 527-3. In addition, weight loss was determined after 19 days of exposure to foils in an average temperature of 17.3 ° C. The results of the assays are summarized in Table 6 for each mixture.

• · · · ·

»· · · · · · · · · · · · · · · · ·

Table 6: Mechanical properties and weight loss after 19 days of films prepared from mixtures I to V

Foil material ; Strength tensile modulus v Stretch at Weight decrease after MPa thrust, GPa _: tear,% i 19 days exp.,% Mixture I 15 Dec 0.16 200 34 Mixture II 13 0.16 150 33 Mixture III i ¹² 0.15 100 ALIGN! 1 31 Mixture IV 16 0.18 200 30 Mixture V 11 and 0.10 1 ⁷ i 150 18 Mixture VI 14 0.12 120 24 . ....._. . ......... ............. .......... ........ _________________________________________ ........... ......... ...................

Industrial applicability

The composition according to the invention is particularly useful as a biodegradable material for the production of short-lived packages and articles, in particular as a binder of biodegradable composites, for waterproofing paper by coating or lamination, and making films for use as compostable packages and mulch films in agriculture.

Claims (6)

PATENT CLAIMS A modified starch biodegradable composition comprising a homogeneous thermoplastic mixture of acetylated maltodextrin (A) having a dextrose equivalent of 10 to 25 and an acetylation degree of 2.0 to 3.0 and an acetylated starch (B) having an amylose content of at least 15 % wt. and an acetylation degree of 0.6 to 3.0 with an A / B weight ratio of 1/20 to 20/1, wherein the acetylated components (A) and (B) are the product of acetylation performed with acetic anhydride in an alkaline medium at 90 to 140 2. The modified starch biodegradable composition of claim 1, wherein the acetylated starch comprises acetylated benzylated starch, wherein the molar ratio of benzyl and acetate groups is from 1:30 to 1: 1. A modified starch biodegradable composition according to claim 1 or 2, characterized in that it further comprises a filler (C) in a weight ratio to the acetylated maltodextrin (A) and the acetylated starch (B) (A + B) / C at most. , l / j, wherein the filler consists of oxides or hydroxides of aluminum or silicon or magnesium or calcium carbonate or magnesium carbonate or minerals of a composition corresponding to the chemical formula Mg 3 Si 4 O 10 (OH) 2 or Al 2 OH 3 SiO 10 or cellulose or starch. A modified starch biodegradable composition according to claim 1 or 2 or 3, characterized in that it contains 10 to 50% by weight, based on the total weight of the biodegradable composition, of a plasticizer selected from the group consisting of triethyl citrate, acetyltriethyl citrate and acetyltributyl citrate. Process for preparing a modified starch biodegradable composition according to claims 1 to 4, characterized in that the acetylated maltodextrin (A) and the acetylated starch (B) are prepared by acetylation with acetic anhydride in an alkaline medium at 90 to 140 ° C, and subsequently mixed in a weight ratio A / B of 1/20 to 20/1, and the prepared heterogeneous mixture is heated to a temperature of 110 ° C to 180 ° C until a homogeneous single-phase thermoplastic mixture is formed. A method for preparing a modified starch biodegradable composition according to claim 5, wherein the prepared heterogeneous mixture is heated by the action of electromagnetic radiation at a frequency in the region of 1 MHz to 10 GHz.