DE19729272A1 - Thermoplastic mixture based on starch for the production of biodegradable moldings with improved properties, preferably improved mechanical properties, production of the mixture and use - Google Patents

Abstract

The invention relates to a thermoplastic mixture with a starch base, for producing biodegradable moulded bodies with improved properties, preferably improved mechanical properties. The inventive thermoplastic mixture can be obtained by providing and mixing; A) 100 weight parts of any native, chemically modified, fermentative starch which is recombinant and/or produced by biotransformation and corrected to a water content of zero per cent by calculation, and/or derivatives of said starches, B) optionally up to 100 weight parts of a physiologically harmless, biodegradable, thermoplastically processable polymeric material which is different from A), C) 1 to 100 weight parts of water, D) at least one plasticiser in a quantity of between 10 weight parts to half of the sum of the weight parts of A) and B), E) at least one phosphate, preferably a phosphoric acid salt, in a quantity of between 0.01 weight parts and (A)+B))/10 weight parts, and F) optionally, up to (A)+B)) weight parts of other usual additives. At least the mixing of constituents A and A) is carried out with the introduction of heat and mechanical energy, preferably at a high temperature with shearing forces being applied to the thermoplastic mixture simultaneously.

Description

The invention relates to thermoplastic starch-based mixtures which Production of such mixtures and the use of these mixtures for Production of biodegradable moldings, preferably with improved mechanical properties, such as molded parts or foils.

Starch as a biocompatible material has the major advantage of one good biodegradability. In the course of the increased use of so-called hydrophilic polymers as natural and thus physiologically compatible and degradable plastics for a wide variety of applications, too made considerable efforts to use the known strength To process plastics processing techniques, d. H. for example by means of Injection molding and extrusion. However, products made from it are lacking, such as Moldings or foils, often with sufficient mechanical properties, such as for example, sufficient strength or sufficient Dimensional stability.

This can be remedied by chemical modification of the starch. Reactions used to modify starch are legion. Underneath fall oxidative processes, polymer-analogous reactions with organic  Chemicals, cross-linking reactions or graft polymerizations in which Monomers based on starch are coupled to the backbone as initiators.

When processing starch mixtures using conventional Polymer process technology is in most cases a meltdown of the Polymer mixture of interest (e.g. injection molding, blow molding, extrusion, Coextrusion). This is due to a thermoplastic behavior of the molding compounds Starch base required.

Trying to crosslink the thermoplastic behavior of starch improve, often bifunctional molecules based on aldehydes play an important role, such as glyoxal, glutardialdehyde, dialdehyde starch, but also based on diisocyanates, epoxies, epichlorohydrin, diesters, etc., can if the crosslinker content is too high, the extent of the Crosslinking reaction the desired effect, which in a better Plasticization of the starch exists, counteracts. In particular, one results stronger networking in an insoluble but swellable product.

The publications become closer state of the art
WO 90/05161 (PCT / CH89 / 00185) = D1,
DE-A 39 31 363 = D2,
US 2,801,242 = D3,
US 2,938,901 = D4,
US 2,328,537 = D5,
WO 94/21236 = D6,
EP-A 0 143 643 = D7,
DE-A 23 08 886 = D8,
EP-A 0 391 853 = D9,
EP-A 0 298 920 = D10 and
Solarek, DB, in "Modified Starches": Properties and Uses, 1986, p. 97-112, ed. Otto B. Publisher, Boca Raton, Florida = D11. called.

D1 describes the production of thermoplastically processable starch Addition of an aggregate to essentially native or natural Starch and melt the mixture by adding heat and mechanical energy. The aggregate is a substance which lowers the melting temperature of the starch so that the melting temperature the strength together with this aggregate below the The decomposition temperature of the starch lies. Specifically, it is the aggregate for example DMSO, 1,3-butanediol, glycerin, ethylene glycol, propylene glycol, Butylene glycol, diglyceride, diglycol ether, formamide, N, N-dimethylformamide, N-methylformamide, N, N'-dimethylurea, dimethylacetamide, N-methylacetamide. The D1 also suggests the addition of a crosslinking agent from the group of dibasic or polyvalent carboxylic acids and / or anhydrides, the halides and / or acid amides of di- or polyvalent carboxylic acids, the derivatives of dibasic or polyvalent inorganic acids, the epoxides, formaldehyde, the Urea derivatives, divinyl sulfones, isocyanates, mono- or polyvalent Oxo compounds and cyanamide.

D2 refers to a process to reduce the swellability of starch through Modification such that the cross-linking reagent is pure or in encapsulated form is added, and the crosslinking reaction by subsequent annealing is reached at elevated temperature. The crosslinking agents used are u. a. Urea derivatives, urotropin, trioxane, di- or polyepoxides, di- or Polychlorohydrins, di- or polyisocyanates, carbonic acid derivatives, di-esters or also inorganic polyacids, such as phosphoric acids or boric acids. The described Mixtures are characterized in that very high weight ratios Crosslinkers are used (between 10 and 100 wt .-%) to pass through the  subsequent thermal treatment a corresponding increase in to achieve mechanical stability.

From the D3 is a process for the production of distarch phosphates Sodium phosphates known. Here two molecules are attached to one phosphate different chains of starch connected and bridged in this way. Here However, if the starch is not plasticized, the starch grain is retained.

Similar to the D3, the D4 discloses a method in which the unsolved and Unswollen starch granules in suspension with phosphoric acids and their salts is modified to be non-dusting powder for use in the surgical sector to manufacture.

According to the D5, inorganic chlorides are used to modify starch grains used in aqueous suspension. These starch mixtures are also before or not thermoplasticized during processing with these chemicals.

D6 describes the use of crosslinking agents, in particular epichlorohydrin, in such a way that a mixture of starch and crosslinker is pressed directly. Such Starch mixtures are claimed as binders in tablets.

The use of difunctional carboxylic acids, esp. Adipic acid as Networkers are also discussed in more detail in the D7.

D8 describes a process in which a phosphate-containing solution is based on starch is sprayed on. The subsequent kneading results in a crumbly mass get the following over times of several hours at temperatures of is heated to at least 140 ° C. The product can be very cool after cooling dissolve easily in water. The disadvantage is the good low-viscosity properties compared to the heterogeneous implementation.  

The use of starch with phosphate groups is known from D9 Manufacture of thermoplastic starches. This is done using native vegetable starch used. The properties become predominant through different additions modified divalent cations.

D10 describes the provision of native starch with phosphate groups, which is modified in that the free electrolytes are first washed out by a washing process with demineralized water. Subsequently, the acidic protons of the phosphate groups are replaced by predominantly bivalent ions, such as Mg ²⁺ or Ca ²⁺ , and the starch is modified in this way.

The D11 reflects the state of the art in the modification of starch Phosphates, mostly in suspension.

In view of the prior art indicated and discussed herein, it was hence the object of the invention, a thermoplastic mixture based on starch to provide which are the production of biodegradable Shaped bodies with improved properties, for example improved mechanical properties, allowed.

The object of the invention was also a method for producing a thermoplastic mixture for extrudates or granules as well as use the thermoplastic mixture.

These tasks are solved by a mixture with the characteristics of Claim 1. Preferred embodiments are the subject of the dependent Product claims. In procedural terms, the subject of the Claim 8 the problems existing until the invention. Beneficial Modifications of the method according to the invention are in the on  independent procedural claim related claims under protection posed. An inventive use specifies claim 12.

The fact that a thermoplastic mixture based on starch is available by providing and mixing
100 parts by weight of any native, chemically modified, fermentative, recombinant and / or biotransformation-corrected arithmetically corrected to a water content of zero percent and / or derivatives of said starch; optionally up to 100 parts by weight of a physiologically acceptable, biodegradable, thermoplastically processable polymer material different from A); 1 to 100 parts by weight;
at least one plasticizer in an amount in the range from 10 parts by weight to half the sum of parts by weight A) and B);
at least one phosphate in an amount ranging from 0.01 part by weight to (A) + B)) / 10 parts by weight;
optionally up to (A) + B)) parts by weight of other customary additives;
whereby at least the mixing of component E) with component A) takes place with the introduction of thermal and mechanical energy into the thermoplastic mixture, it is not readily possible to create thermoplastically processable starch-based mixtures which have excellent thermoplastic processability which can be processed into molded parts which have excellent mechanical properties and which are nonetheless easily biodegradable, for example rot or compostable.

In addition, the products, such as moldings or films, are essentially biocompatible and possibly edible, which leads to edible packaging, in particular food packaging.  

Food packaging is understood to mean both outer packaging, who have only temporary contact with the food, as well as packaging, such as hoses, sleeves or coatings that are on their inner surface Have contact with the food and therefore also with the Food intake can be taken with you. The packing are therefore suitable for fruit, eggs, cheese, candy, cakes, Cookies or effervescent tablets, drinks, meat, sausages or meat.

The use of the thermoplastic molding compositions according to the invention available molded body is not for use in combination with temporary products limited, but can also be for temporary use to protect commodities and capital goods during transport or Storage can be applied. In particular, here is the protection from to think of climatic influences, such as when transporting overseas Automobiles occur.

In particular, it has now surprisingly been found that when using special, defined additives, such as phosphates, preferably about Polyphosphates, metaphosphates and / or polymetaphosphates, among others Conditions effects are achieved which on the one hand modify the strength, on the other hand, however, further processing of the starch with conventional ones Allow thermoplastic processing techniques.

Under the special conditions according to the invention, the Carry out modification reaction during processing. The practice Additives according to the invention even in low concentrations positive influence on the properties and processability of thermoplastic starch mixtures.

Component A) of the starch mixture according to the invention

Component A) is an essential component in the invention Mixture.

Component A) is one or more starches, one or several of their derivatives or mixtures of starch and starch derivatives.

An important group of starches includes those from vegetable raw materials strengths gained. These include starches from tubers, such as Potatoes, cassava, maranta, batata, from seeds such as wheat, corn, rye, rice, Barley, millet, oats, sorghum, from fruits such as chestnuts, acorns, beans, Peas, u. a. Legumes, bananas, and from vegetable pulp, e.g. B. the Sago palm.

The starches which can be used in the context of the invention essentially consist of Amylose and amylopectin, in varying amounts.

Particularly good results can be achieved with starches made from potatoes (e.g. ®Toffena from South Starch) and maize (e.g. Maize Starch from National Starch) or polyglucans, which are characterized by a perfectly linear structure of the Mark up polymers.

The molecular weights of the starches useful according to the invention can vary over a wide range. Starches which essentially consist of a mixture of amylose and amylopectin and have molecular weights M _w in the range between 5 × 10 ⁴ and 1 × 10 ⁷ can be used as the basis of the thermoplastic mixture according to the invention. Longer-chain polymers with molecular weights M _w between 1 × 10 ⁶ and 5 × 10 ⁶ are preferred.

Linear polysaccharides, preferably polyglucans, in particular 1,4-aD-polyglucan, with molecular weights M _w in the range between 5 × 10 ² and 1 × 10 ⁵ , preferably with molecular weights M _w between 1 × 10 ³ and 5 × 10, are also preferred ^4th

In addition to molding compounds based on starches of native plant origin to the invention also such thermoplastic mixtures or molding compositions Starches that are chemically modified, obtained by fermentation, are of recombinant origin or through biotransformation (also: biocatalysis) were manufactured.

The invention understands "chemically modified starches" to mean such starches which are chemically compared to their natural properties Properties were changed. This is essentially due to polymer analogs Achievements achieved where strength with mono-, bi- or polyfunctional Reagents or oxidizing agents is treated. The are preferably Hydroxy groups of the starch polyglucans by etherification, esterification or selective oxidation or modification is based on a radical initiated graft copolymerization of copolymerizable unsaturated monomers on the starch backbone.

Special chemically modified starches include starch esters, such as xanthates, acetates, phosphates, sulfates, nitrates, starch ethers, such as. B. nonionic, anionic or cationic starch ethers, oxidized starches such as Dialdehyde starch, carboxy starch, persulfate-degraded starches and the like Substances.

"Fermentative starches" are, in the parlance of the invention, starches which are produced by fermentative processes using organisms found in nature, such as fungi, algae or bacteria are obtained or with the help of Can be obtained using fermentative processes. examples for Starches from fermentative processes include Gum Arabicum and others  related polysaccharides (Gellan Gum, Gum Ghatti, Gum Karaya, Gum Tragacauth), Xanthan, Emulsan, Rhamsan, Wellan, Schizophyllan, Polygalacturonates, laminarin, amylose, amylopectin and pectins.

"Strengths of recombinant origin" or "recombinant strengths" means in individual strengths by using fermentative processes in nature non-occurring organisms, but with the help of genetic engineering Methods modified natural organisms such as fungi, algae or bacteria be obtained or with the involvement and with the help of fermentative Processes can be won. Examples of starches from fermentative, Genetically modified processes include amylose, amylopectin and other polyglucans.

In the context of the invention, “starches produced by biotransformation” means that starches, amylose, amylopectin or polyglucans by catalytic reaction of monomeric building blocks, generally oligomeric saccharides, in particular mono- and disaccharides, are produced by a Biocatalyst (also: enzyme) is used under special conditions. Examples of starches from biocatalytic processes include others Polyglucan and modified polyglucans, polyfructan and modified polyfructans.

Finally, the individual can also be used using derivatives strengths mentioned advantageous thermoplastic mixtures. Here the terms "derivatives of starches" or "starch derivatives" mean in general modified starches, d. H. such strengths in which to change their Properties the natural amylose / amylopectin ratio was changed, one Pre-gelatinization was carried out, the partial hydrolytic degradation have been subjected to or which have been chemically derivatized.  

Special derivatives of starches include oxidized starches, e.g. B. Dialdehyde starch or other oxidation products with carboxyl functions, or native ionic starches (e.g. with phosphate groups) or further ionically modified ones Strengths, with both ionic and cationic modifications among them Term fall.

Particularly cheap thermoplastic mixtures are obtained if starches are used that only a small proportion of other compounds that are not saccharides (e.g. proteins, fats, oils) (for example and especially potato starch), or ionic starches as Base material or used as an admixture and / or through their Uniformity in structure, molecular weight and purity outstanding polyglucans, e.g. B. manufactured by biotransformation 1,4-a-D-polyglucan, can be used as a starch base.

The thermoplastic mixture according to the invention is calculated in terms of Component A) or a mixture of components A) on one Corrected water content of zero percent. That is, the water content of the component A) is determined and accordingly when dimensioning 100 parts by weight subtracted, but taken into account when dimensioning component C).

Component B) of the thermoplastic mixture according to the invention Starch base

Component B) of the thermoplastically processable according to the invention Mixing is an optional component.

It is more precisely a physiologically harmless, essentially also biodegradable, thermoplastically processable, other than A) polymeric material, which in amounts up to 100 parts by weight in the mixture  can be included. Mixtures of two or more such compounds are considered as component B).

A group of materials that meet these requirements is the group of the proteins. Components B) which can be used successfully in the context of the invention include gelatin, vegetable proteins such as sunflower protein, Soy protein, cottonseed protein, peanut protein, rapeseed protein, Plasma proteins, egg whites, egg yolks and the like.

Favorable mixtures also result in additions of zein, gluten (corn, potatoes), Albumin, casein, creatine, collagen, elastin, fibroin and / or whey protein.

Also of interest as component B) are polysaccharides which are different from those under A) strengths mentioned are different.

Water-soluble polysaccharides such as alginic acid and its salts, Carrageenans, Furcellaran, Guar Gum, Agar-Agar, Gum Arabicum and related Polysaccharides (Gum Ghatti, Gum Karaya, Gum Tragacauth), Tamarind Gum, Xanthan gum, aralia gum, locust bean gum, locust bean gum, Arabinogalactan, pullulan, chitosan, dextrins, cellulose are used.

Additions of lentinan, laminarin, chitin, heparin, inulin, Agarose, galactans, hyaloronic acid, dextrans, dextrins and / or glycogen impact.

Component C) of the starch mixture according to the invention

Component C) of the mixture according to the invention is an essential one Component.  

Water is in the amount of 1 part by weight to 100 parts by weight in the mixture of the invention included. If the amount of water is below one part by weight, the destructuring and homogenization of the mixture is inadequate. Is the water content is greater than 100 parts by weight, there is a risk that the The viscosity of the mixture is too low. Favorable ranges are between about 10 and 75 parts by weight of water. The area between is of particular interest 20 and 60 parts by weight.

If significant proportions of the optional component B) in the mixture of Invention are present, this can be done separately when defining the amount of water be taken into account. In this case, the water content is preferably between one and to). The water content is about half of the total of parts by weight A) and B) is the thermoplasticization of the entire mixture particularly good. Preferred water contents are also between about 5 and (A) + B)) / 2 parts by weight, water parts between 10 and (A) + B)) / 3 parts by weight.

In these preferred areas, the mixture is optimally plasticized, d. H. Destructuring the starch, homogenizing the mixture and its Thermoplastification instead.

The amount of water C) includes actually added water as well computational water content of other components, in particular the amount of bound or contained in component A) Water or optionally bound or contained in the compounds E) Water.

The nature of component C) is essentially not critical. One can Demineralized water, deionized water but also tap water or Use water of other origin if the water contains salts  or other foreign substances are tolerable with regard to the intended use is.

Component D) of the starch mixture according to the invention

Component D) is essentially contained in the mixture according to the invention.

The amount of component D) is of particular importance, i. H. only inside defined limits freely selectable. One or more plasticizers are in the Composition of the invention in an amount ranging from 10 parts by weight to Half of the sum of the parts by weight A) and B) included. Is the content at softening compounds below 10 parts by weight, that is Plasticization insufficient, even at higher mechanical and / or thermal energies. If the plasticizer content exceeds that of the Half of the sum of the parts by weight A) and B) corresponds, none is worth mentioning better plasticization of the mixture was observed.

Plasticizer quantities in the range from 12.5 to (A) + B)) / 2 are favorable Parts by weight are particularly useful in the range of plasticizers from 15 to (A) + B)) / 4 parts by weight.

In the context of the invention, the terms plasticizing, Plasticizers, plasticizers, or elasticizers synonymous with Plasticizers.

All indifferent, preferably organic, substances with im general low vapor pressure, which has no chemical reaction, preferably by their ability to dissolve and swell, and, but also without, with the components A) and optionally B) in physical interaction kick and form a homogeneous system with them.  

Component D) to be used according to the invention imparts the mixture preferably a reduced freezing temperature, elevated Shape change, increased elastic properties, reduced hardness and possibly increased adhesiveness.

Preferred plasticizers according to the invention are odorless, colorless, light, cold and heat resistant, low hygroscopic, water resistant, not harmful to health, flame retardant and as little volatile as possible, neutral reactive, miscible with polymers and auxiliaries and have a good Gelling behavior. In particular, they should be compared to components A) and optionally B) compatibility, gelling power and plasticizing Show effectiveness.

Furthermore, those to be used according to the invention as component D) are to be used Connections have low migration, which is especially true for Applications of the moldings according to the invention in the food sector of Meaning is.

Particularly preferred plasticizing components D) include other dimethyl sulfoxide, 1,3-butanediol, glycerin, ethylene glycol, propylene glycol, Diglyceride, diglycol ether, formamide, N, N-dimethylformamide, N-methylformamide, Dimethylacetamide, N-methylacetamide and / or N, N'-dimethylurea.

Polyalkylene oxide, glycerol mono-, di- or are also particularly useful -triacetate, sorbitol, or other sugar alcohols, such as erythritol, sugar acids, such as Gluconic acid, polyhydroxycarboxylic acids, saccharides such as glucose, fructose or Sucrose, as well as citric acid and its derivatives.

Component E) of the thermoplastic mixture according to the invention Starch base

Component E) is essential for the mixture according to the invention.

The amount with which component E) in the mixture according to the invention is of particular importance. Component E) is in quantities between 0.01 parts by weight and (A) + B)) / 10 parts by weight in the mixture according to of the invention included. At least 0.1 part by weight is expediently preferred 0.1- (A) + B)) / 20 parts by weight.

If the amount of component E) is too small, the mechanical Properties of the moldings obtainable from the mixture according to the invention bad. If the amount exceeds the value of (A) + B)) / 10 parts by weight, then comes it affects the plasticization of the molding compound.

According to the invention, component E) is phosphates. In the context of the invention, this includes salts and esters of the various Understand phosphoric acids. However, are far preferred for the invention the salts of the various phosphoric acids. According to the invention as Component E) one or more salts and / or esters of the different Phosphoric acids, therefore one or more phosphates, component E) form.

As component E), ortho-phosphates of the general formulas M ^I H ₂ PO ₄ (eg NaH ₂ PO ₄ ) and M ^II (H ₂ PO ₄ ) ₂ [z. B. Ca (H ₂ PO ₄ ) ₂ ], secondary orthophosphates of the general formulas M ^I ₂ HPO ₄ or M ^II HPO ₄ (e.g. K ₂ HPO ₄ , CaHPO ₄ ) or tertiary orthophosphates of the general formulas M ^I ₃ PO ₄ or M ^II ₃ (PO ₄ ) ₂ [e.g. B. Na ₃ PO ₄ , Ca ₃ (PO ₄ ) ₂ ], where M ^I for a monovalent cation such as ⁺NRR'R''R ''', where R, R', R '' and R ''' independently of one another, identically or differently, represent hydrogen, (C ₁ -C ₈ ) -alkyl, linear or branched, (C ₄ -C ₈ ) -aryl, preferably phenyl, alkali metal ion, preferably Na⁺ or K⁺, M ^II for a divalent Cation, preferably alkaline earth metal ion, particularly preferably Ca ^2+, is used.

Of particular interest as component E) is also that of the acidic Salting of the orthophosphoric acid-dissipating group when heated Condensed phosphates are formed, which in turn Metaphosphates (systematic name: cyclo-polyphosphates) and Subdivide polyphosphates (systematic name: catena polyphosphates) to let.

Among the preferred representatives are Graham's salt, Kurrolsche To count salt and Maddrell salt as well as melting or annealing phosphates.

Particularly useful modifiers E) include metaphosphates of the general formula M ^I _n [P _n O _3n ], in which M ^{I is} a monovalent cation, preferably metal ion, suitably alkali metal ion, preferably Na⁺ or K⁺, or ⁺NRR'R''R "", where R, R ', R "" and R "" independently of one another are identical or different for hydrogen, (C ₁ -C ₈ ) -alkyl, linear or branched, (C ₄ -C ₈ ) -aryl, preferably phenyl, and n is a whole natural positive number, preferably in the range between 3 and 10. Of these in turn, those metaphosphates are preferred in which n is 3, 4 or 5 and M ^{I is} sodium or potassium. Most preferred are sodium trimetaphosphate, sodium tetrametaphosphate and sodium pentametaphosphate.

Advantageous mixtures also result with polyphosphates of the general formula M ^I _{n + 2} [P _n O _{3n + 1} ] or M ^I _n [H _2n PnO _{3n + 1} ], where M ^{I is} a monovalent cation, preferably a metal ion, preferably an alkali metal ion, preferably Na⁺ or K⁺, or ⁺NRR'R''R ''', in which R, R', R '' and R '''are, independently of one another, the same or different for hydrogen, (C ₁ -C ₈ ) -alkyl, is linear or branched, (C ₄ -C ₈ ) aryl, preferably phenyl, and n is a whole natural positive number greater than 2. Of these, sodium and potassium polyphosphates in which n is <10 are preferred.

Mixtures with favorable properties can also be obtained if polyphosphates of the general formula M ^I _{n + 2} [P _n O _{3n + 1} ] are used as component E), in which M is a monovalent cation, preferably metal ion, advantageously alkali metal ion, preferably Na bevorzugt or K⁺, or ⁺NRR'R''R ''', in which R, R', R '' and R '''are, independently of one another, identical or different for hydrogen, (C ₁ -C ₈ ) -alkyl, linear or branched , (C ₄ -C ₈ ) aryl, preferably phenyl, and n is a whole natural positive number in the range between 3 and 10. Among others, pentasodium tripolyphosphate is preferred.

Furthermore, the thermoplastic mixture according to the invention is special Embodiment characterized in that component E) is an alkali salt a metaphosphate or polyphosphate.

Another favorable modification of the thermoplastic according to the invention Mixture results from the fact that component E) sodium trimetaphosphate, Sodium metaphosphate, sodium polyphosphate and / or sodium hexametaphosphate, preferably sodium polyphosphate.

The phosphates mentioned can have a different degree of hydration exhibit. Due to the relatively small proportions of component E) in the thermoplastic mixture is this water content when determining the parts by weight to E) usually irrelevant and due to the essential component C) not harmful.

Component F) of the starch mixture according to the invention

Component F) of the mixture according to the invention is optional, i. H. she must not be contained in the mixture according to the invention.

It can be one or more substances that collectively as Component F) in amounts up to 200 parts by weight, preferably not more than 100 parts by weight, can be used.

Common additives or additives include fillers, Lubricants that differ from the plasticizers mentioned under D), Flexibilizers, pigmentants, dyes, mold release agents and other.

Suitable fillers are, for example, synthetic polymers that are almost in the Mixture are soluble, such as lactic acid based polymers such as ®Lacea from Mitsui, ®Resomer from Boehringer Ingelheim, and others Polymers based on lactic acid and related polymers of lactic acid, of Wako Pure Chemical Industries Ltd., Medisorb Co., Birmingham Polymers, Inc., Polysciences Inc., Purac Biochem BV, Ethicon, Cargill or Chronopo, although it is clear that this list is not an absolute one Completeness can correspond.

Furthermore, other polyesters made from preferably physiologically harmless hydroxycarboxylic acids can also be used, for example polyhydroxybutter co-valeric acids, in particular polyester of the ®Biopol brand and others
It is also proposed to add at least one inorganic filler, such as magnesium oxide, aluminum oxide, SiO ₂ , TiO ₂ , etc.

Organic or. Are particularly suitable for coloring the mixture inorganic pigments, especially also biocompatible, i.e. harmless to  so-called pearlescent pigments based on living organisms Silicate structures, which in principle can be classified as edible and in quantities between 0.001 and 10 parts by weight can be used.

Animal or are particularly suitable for improving the flow properties vegetable fats and / or lecithins, preferably in hydrogenated form are used, these fats and other fatty acid derivatives preferably have a melting point of greater than 50 ° C.

To the hydrophilicity and thus the water resistance of the thermoplastic can reduce workable mixture during and after processing a crosslinking agent is added to the mixture in minor amounts, to chemically modify the starch. Alkyl siloxanes are preferred for this purpose used in quantities of up to 5 parts by weight.

Also suitable as crosslinking agents are, inter alia, divalent or polyvalent Carboxylic acids and their anhydrides, acid halides of di- or polyvalent Carboxylic acids, acid amides of dibasic or polyvalent carboxylic acids, derivatives of dibasic or polyvalent inorganic acids derived from component E) are different, epoxides, formaldehyde and / or urea derivatives, divinyl sulfones, Isocyanates, oxo compounds and / cyanamide, these compounds also especially for chemical modification following the thermoplastic Suitable processing and thus for further improvement in particular mechanical properties can contribute.

Components A) to F) of the mixture according to the invention become such mixed together that at least the mixing of component E) with the Component A) with the introduction of thermal and mechanical energy into the thermoplastic mixture takes place.  

The mechanical and thermal ones are preferably introduced Energy at the same time, e.g. B. by working at elevated temperatures and simultaneous application of shear forces on the plasticized thermoplastic mixture based on starch.

In general, the better the homogeneity of the mixtures at higher Temperatures result. However, the temperatures should not be too high to to avoid unnecessary discoloration or decomposition of the molding compounds.

In this connection, the thermoplastic mixture of the invention is in preferred modification obtainable by mixing at temperatures in the range of <60 ° C to 200 ° C.

In principle, the homogenization of the mixture increases with the introduced one Performance. That is, the higher the power introduced into the mixing unit, in order to the homogenization of the thermoplastic starch mixture is thus better. Another modification of the invention therefore sees one by mixing Exposure to high shear mixing units available thermoplastic Mixing before, the energy introduced into the mixture in particular at the Performance of the processing machines used can be derived. So is processing is possible, above all with equipment, its plasticizing element are equipped with torques in the range from 5 to 300 Nm (1 Newton Meters). Processing at a torque in the Proven range from 10 to 100 Nm. Processing in one is preferred Torque range from 20 to 40 Nm.

A particularly favorable absorption of thermal and / or mechanical Energy through the mixture is achieved when you look at the components of the mixture according to the invention in a plastics processing machine, such as mixed and homogenized in an extruder, kneader or similar units.  

The process can preferably be carried out on single or twin screw extruders be performed. These are preferably made of individual housings composed, which have temperature-controlled coats. The design of the Snails are not subject to any restrictions, conveyor elements (with or without shear edges), kneading elements and / or mixing elements. In addition, it is possible and often advantageous partially, i. H. in sections jamming or returning elements to be used in the extruder to increase residence time and to influence and control mixing properties.

The order in which ingredients A) to F) are mixed can also be special Have meaning.

The invention thus also relates to a process for producing a thermoplastic mixture based on starch, in which

• A) 100 parts by weight arithmetically for a water content of zero percent corrected any native, chemically modified, fermentative, recombinant and / or starch produced by biotransformation and / or derivatives of the named strengths;
• B) optionally up to 100 parts by weight of a physiologically different from A) harmless, biodegradable, thermoplastically processable, polymeric material;
• C) 1 to 100 parts by weight of water;
• D) at least one plasticizer in an amount in the range of 10 parts by weight up to half the sum of parts by weight A) and B);
• E) at least one phosphate, preferably phosphoric acid salt, in an amount in the range of 0.01 parts by weight to (A) + B)) / 10 parts by weight;
• F) optionally up to (A) + B)) parts by weight of other customary additives; prepared and mixed together,

where component E) to components A) to D) and optionally F) is added, at least mixing component E) with the rest Components incorporating thermal and mechanical energy into, preferably under the influence of elevated temperature and simultaneous exercise of shear forces, the thermoplastic mixture takes place.

This procedure differs significantly in terms of type and effect known prior art.

So far, phosphoric acids or their salts or esters have been used as modifiers used in the production of thermoplastic mixtures based on starch, the starch grain was modified exclusively and always directly or else it was caused by a high addition of parts by weight of the phosphate and subsequent thermal treatment brings about a crosslinking that leads to Molding compounds, which no longer a thermoplastic processing are accessible.

In contrast to this, the procedure according to the invention ensures that not only the surface of the starch grain, but the starch in all of their molecules are preferably modified on the starch backbone. This leads to different types of products whose improved properties do not were readily predictable.

An addition of component E) during processing in the homogenization or Mixing unit, such as in a kneader or extruder, under alkaline to acidic Conditions leads to the reaction with starch, starch derivatives or else mixed proteins to a minor extent of crosslinking equals. I.e. the focus is on the modification of the polymer backbone.  

This difference to known starch phosphates from the prior art can, for example, also be reflected in the degree of substitution.

The number of hydroxyl groups per glucose unit of starch by another functional group (phosphates) is replaced as a degree of substitution DS ("degree of substitution ").

There are three free hydroxyl groups per glucose unit. Thus, the Degree of substitution vary from 0.0 to 3.0.

The degree of substitution DS is therefore a purely statistical variable. A degree of substitution DS of 1.0 only means that on average at each grucose unit a hydroxyl group is replaced by a substituent. That is, a DS of 1.0 does not necessarily mean that there is a substituent on exactly each glucose unit in addition to two unsubstituted remaining hydroxyl groups.

For example, it is known that native starch contains phosphate groups per se can. The degree of substitution is in the range of about 0.001. That means, that statistically about every 300 glucose units a phosphate group in the Polymer is present.

Now it is the case with the known methods which show the starch as grain and Modify as far as possible only on the surface so that from Degrees of substitution DS in the range from about 0.001 to 0.01 can be assumed.

According to the invention, however, by modification with phosphates (Component E)) achieved a significantly higher DS during plastication. This is approximately between <0.01 and 1.0. Preferably the DS is for the Component A) modified according to the invention approximately in the range from 0.05 to 0.5. The DS is particularly useful from 0.1 to 0.3.  

In addition, the addition of plasticizers, which are high per se Ratio of hydroxyl groups or other hydrogen bonds Have groups to carbon atoms, with appropriate reaction over the reaction of the phosphate also coupled the plasticizer to the Strength backbone can be achieved, which ultimately - especially during processing - leads to a reduction in the migration of the plasticizer from the mixture. At the same time, however, the plasticizing effect of the plasticizer does not excluded, causing the destructuring of strength, in the sense of a Disruption of the starch grain is only possible. This possibility of Interpretation of the reactions taking place that lead to the surprisingly found Results lead, but also exclude other interpretations not from.

The thermoplastic molding composition according to the invention can be according to the known Processing methods to produce products. So it can e.g. B. in a first Step granulated or pelletized.

The invention thus also relates to granules obtained by extrusion and Pelletization available from the thermoplastic mixture according to the invention is.

In addition, either directly or through renewed thermoplastic Process a thermoplastic granulate biologically well degradable moldings or films with improved properties, preferably improved mechanical properties can be obtained.

Finally, the invention also includes the use of thermoplastic mixtures for the production of molded parts or films.  

Thereby, the thermoplastic molding compounds, as well as the Further processing obtained moldings and films from that by Mixing of the essential component E) both an increased Temperature resistance as well as an improvement in flame resistance is achieved.

Overall, the products according to the invention thus cover a large number of Possible applications. These include, among other things Adhesive adhesives for paper and corrugated cardboard, molded articles by injection molding are produced, especially rods, tubes, bottles, capsules, granules, Food additives, films, as coatings or free-standing films, also as Laminates, especially foils, packaging materials, bags, slow release materials for controlled release of active substances in general, in particular pharmaceuticals, Pesticides or other active ingredients, fertilizers, flavorings used in agro-culture etc. The release of the active substance from films, foils, compacts, Particles, microparticles, rods or other extrudates or others Shaped bodies are made.

Other preferred applications include food packaging, in particular sausage or cheese casings, absorbers, powder and the like.

In a special embodiment, the thermoplastic mixtures according to the invention for the production of moldings for controlled release of active ingredients, such as tablets or coated tablets.

Another convenient and particularly inexpensive use of the thermoplastic mixture according to the invention relates to the production of Shaped bodies that are used for the production of solid shaped bodies, hollow bodies or Combinations of these are suitable.  

Another outstanding use of the thermoplastic according to the invention Mixture is in the manufacture of films for use in agriculture located.

The invention sees the use of the in a further particular modification thermoplastic mixture for the production of films for use in the Food application.

Another special use of the thermoplastic according to the invention Mixture lies in the manufacture of films for use as Food packaging.

Another extremely favorable use of the thermoplastic Mixture according to the invention results in the production of films for Use as food packaging with full surface contact to the Food.

Finally, a use of the thermoplastic mixture according to the Invention particularly advantageous in the use of flat or tubular films are produced as food casings for sausage and cheese.

It is also preferred within the scope of the invention to use the thermoplastic as temporary protective films for technical Utensils.

The following examples illustrate the subject matter of the invention.

example 1

Production of a thermoplastic processable blend of potato starch with sodium polyphosphate, gum arabic and glycerin:
The compounds are provided in a commercially available kneading unit (Brabender kneader). The kneading unit is heated to 100 ° C. 30 g of potato starch (®Toffena from SüdStar) are added while the kneading unit is in operation. 0.9 g of NaCO ₃ are dissolved in 10 g of water and added to the potato starch in the kneader. The mixture is homogenized. The process takes about 3 minutes. Then 9 g of gum arabic are added at once. It is homogenized again. Then 9 g of glycerin are added in portions (about 3 portions of equal size, each with a 2-minute kneading interval between the additions). After a further 2 minutes, 1.2 g of sodium polyphosphate (Riedel de Haen) dissolved in 5 ml of water are added. The entire mixture is kneaded again for a further 2 minutes. The mass is removed while the device is still heated. The product is a homogeneous mass that is slightly yellow in color. It is a non-transparent product. After cooling, the thermoplastic mass can be processed further.

The films obtained from thermoplastic processing of the product are transparent and show good mechanical strength.

Comparative Example 2

Production of a thermoplastic blend mixture from potato starch with sodium polyphosphate and gum arabic:
The preparation of this mixture is identical to the description in Example 1. The only difference in the recipe is that glycerol is not used as a plasticizer.

After homogenization is complete, the mass is still in heated state is removed. The product is a homogeneous mass that is slightly brownish in color. It is a non-transparent product, which tends to be brittle. Further processing, in particular into foils or Filming can only be achieved after the molding compound has been washed.

Example 3

Production of a thermoplastically processable blend of casein and potato starch with sodium polyphosphate:
The connections are made in a commercially available kneading unit (Brabender kneader). The kneading unit is heated to 100 ° C. 20 g of casein and 10 g of potato starch (Toffena from SüdStar) are added in the operating state of the kneading unit. 1.2 g of sodium polyphosphate (Riedel de Haen) dissolved in 5 ml of water are immediately added. It is homogenized for 3 minutes. 6 g of glycerin are then added in portions (about 3 portions of equal size, each with a 2-minute kneading interval between the additions). It is homogenized for a further 2 minutes. The product is a slightly yellowish, thermoplastically deformable mass, which can be further processed immediately after being removed from the kneading unit while it is still heated or after it has cooled.

The films obtained from thermoplastic processing are transparent and show good mechanical properties in terms of elongation at break and Tensile strength.  

Example 4

Production of a thermoplastically processable blend of potato starch with sodium polyphosphate:
The procedure is analogous to that described in Example 1. The kneading unit (Brabender) is heated to 100 ° C. 30 g of potato starch (Toffena from SüdStar) are added while the kneading unit is in operation. 0.9 g of Na ₂ CO ₃ dissolved in 10 ml of water are immediately added. It is homogenized for 3 minutes. 15 g of glycerin are then added in portions (about 3 portions of equal size, each with a 2-minute kneading interval between the additions). It is homogenized for a further 2 minutes and then 0.15 g of sodium polyphosphate (Riedel de Haen) in 5 ml is added. The experiment is ended after a further homogenization phase. The product is a slightly yellowish, thermoplastically deformable mass that can be processed further after cooling.

The films obtained from thermoplastic processing are transparent and show very high mechanical strength. The film thicknesses are in Range from 100 to 150 mm. The flexibility of the foils allows further processing, for example a filling with food.

Example 5

Production of a thermoplastic processable blend of potato starch and casein with sodium polyphosphate:
The procedure is analogous to that described in Example 1. The kneading unit is heated to 120 ° C. 21 g of potato starch (Toffena from SüdStar) and 9 g of casein are added in the operating state of the kneading unit (Brabender). 0.9 g of NaCO ₃ are dissolved in 10 g of water and added to the mixture of casein and potato starch in the kneader. The mixture is homogenized. The process takes about 3 minutes. Then 1.5 g of Pluronic F 68 in 10 ml of water and 6 g of glycerin are added in succession. It is homogenized again. After about 2 minutes, 1.2 g of sodium polyphosphate (Riedel de Haen) dissolved in 5 ml of water are added. The entire mixture is kneaded again for a further 2 minutes. The mass is removed while the device is still heated. The product is a very white, homogeneous mass. After cooling, the thermoplastic mass can be processed further.

The films obtained from thermoplastic processing are opaque. The Film thickness is approximately 160 to 200 mm. The mechanical strength together with the film thickness obtained from processing by pressing results in a certain brittleness. For further processing regarding an application In the food sector, watering is therefore necessary.

Example 6

Production of a thermoplastically processable blend of casein and corn starch with sodium polyphosphate:
The procedure is analogous to that described in Example 1. The kneading unit (Brabender) is heated to 100 ° C. 24 g casein and 6 g corn starch are added when the kneading unit is in the operating state. After a short time, 10 ml of water and 4 g of glycerin are added. After a further brief homogenization phase, 0.8 g of sodium polyphosphate (Riedel de Haen) in 2 ml of water are added. The experiment is ended after a further homogenization phase. The product is a slightly yellowish, thermoplastically deformable mass that can be processed after cooling.

The films obtained from thermoplastic processing (press technology) are slightly opaque and show high mechanical strength. The film thicknesses are in the range of 170 to 190 mm. The flexibility of the foils leaves one Further processing, for example a filling with food.

Example 7

Production of a thermoplastically processable blend of casein and potato starch with sodium polyphosphate:
The procedure is analogous to that described in Example 1. The kneading unit (Brabender) is heated to 100 ° C. 15 g of casein and 15 g of potato starch (e.g. Toffena from SüdStar) are added in the operating state of the kneading unit. After a short time, 1.5 g of citric acid in 10 ml of water and 6 g of glycerin are added. After a further brief homogenization phase, 1.2 g of sodium polyphosphate (Riedel de Haen) in 5 ml of water are added. The experiment is ended after further homogenization. The product is a yellowish, homogeneous, solid mass that can be processed after cooling.

The films obtained from thermoplastic processing (press technology) are yellowish, as well as transparent to slightly opaque. The foils are very thin and lie in the range of 80 to 100 mm.

Example 8

Production of foils by means of pressing technology from the thermoplastic molding compositions produced in Examples 1 to 7:
The procedure for processing a thermoplastic molding composition as described is as follows. A commercially available press from Schwabenthan (Polystat 300 S) is used for this. The press is preheated to 100 ° C. The sample preparation takes place in a "sandwich technique" between two fabric-reinforced polytetrafluoroethylene (PTFE, ®Teflon), which are kept at a distance with an approximately 100 mm thick metallic frame. About 2 g of the mass produced in the kneader are placed in the middle of the lower film during the preparation. The sample is tempered for 5 minutes at 100 ° C and a pressure of 1 t. The sample is then pressed at 100 ° C for minutes and a pressure of 10 t. This corresponds to a pressure of 200 bar. The press is relieved and the sample is transferred to another press for cooling. This is a water-cooled press from Robert Fuchs Hydraulische Maschinen und Werkzeuge. A pressure of 50 bar is applied during the cooling process over a period of 2 minutes. The sample can then be taken to be used for further investigations. It should be noted that storage in air, depending on the hydrophilicity of the materials used, shows signs of aging, which can be attributed to fluctuating water contents.

Example 9

Production of a thermoplastically processable blend mixture from corn starch with a high content of sodium polyphosphate:
The connections are made in a commercially available kneading unit (IKA duplex kneader). The kneading unit is heated to 100 ° C. 150 g of potato starch (maize starch from National Starch) and 45 g of glycerin are added in the operating state of the kneading unit. 5.0 g of NaCO ₃ are dissolved in 50 g of water and added to the corn starch in the kneader. The mixture is homogenized. The process takes about 5 to 10 minutes, during which time the mixture becomes glassy. 15 g of sodium triphosphate (Riedel de Haen) are then dissolved in 25 ml and added. The entire mixture is kneaded for a further 5 minutes. The mass is removed while the device is still heated.

Comparative Example 10

Production of a thermoplastically processable blend mixture from corn starch without sodium polyphosphate:
The connections are made in a commercially available kneading unit (IKA duplex kneader). The kneading unit is heated to 100 ° C. 150 g of potato starch (maize starch from National Starch) and 45 g of glycerin are added in the operating state of the kneading unit. 5.0 g of NaCO ₃ are dissolved in 50 g of water and added to the corn starch in the kneader. The mixture is homogenized. The process takes about 5 to 10 minutes, during which time the mixture becomes glassy. The entire mixture is kneaded for a further 5 minutes. The mass is removed while the device is still heated.

Example 11

Production of foils using press technology from thermoplastic materials based on starch:
The thermoplastic molding compositions are further processed into films using the pressing technique described here. A commercially available press from Schwabenthan (Polystat 300 S) is used for this. The press is preheated to 100 ° C. The sample preparation takes place in a "sandwich technique" between two tissue-reinforced Teflon foils, which are kept at a distance with an approximately 100 mm thick metallic frame. About 2 g of the mass produced in the kneader are placed in the middle of the lower film during the preparation.

The sample is tempered for 5 minutes at 100 ° C and a pressure of 1 t. Then the sample is at 100 ° C for 5 minutes and a pressure of 10 t pressed. This corresponds to a pressure of 200 bar. The press is relieved and the Sample is transferred to another press for cooling. This is what it is about a water-cooled press from Robert Fuchs Hydraulische Maschinen and tools. During the cooling process over a period of 2 minutes a pressure of 50 bar is applied.

Example 12

Investigation of the temperature stability of films produced according to Example 11 from the thermoplastic molding compositions from Example 9 and Comparative Example 10:
A film measuring 5 cm by 5 cm is placed on a ring with an inner diameter of 3 cm. Fixation is achieved with metal clips so that slight air movements on the fixation of the foils do not change anything. The ring is fixed in a horizontal arrangement by means of a holding rod attached to the ring in such a way that the foil is in a parallel arrangement at a height of 20 cm above the laboratory bench. An open flame is arranged below the ring, which provides identical energies per time for all examinations and has a height of 1-2 cm. The upper limit of the open flame is 5 cm +/- 0.5 cm from the film. The times are measured with a stopwatch which are necessary to achieve a charring of the film which comprises more than 50% of the ring area covered by the thermoplastic film. Averages of ten measurements each are formed.

Film from Example 9 with sodium triphosphate: 25 sec. +/- 3 sec.

Film from comparative example 10 without sodium triphosphate: 16 sec. +/- 3 sec.  

Further advantages and embodiments of the invention result from the subsequent claims.

Claims (19)

1. Thermoplastic mixture based on starch for the production of biodegradable moldings with improved mechanical properties, obtainable by providing and mixing

• A) 100 parts by weight of any native, chemically modified, fermentative, recombinant and / or biotransformation-corrected arithmetically corrected to a water content of zero percent and / or derivatives of said starches;
• B) optionally up to 100 parts by weight of a physiologically acceptable, biodegradable, thermoplastically processable polymer material different from A);
• C) 1 to 100 parts by weight of water;
• D) at least one plasticizer in an amount in the range from 10 parts by weight to half the sum of parts by weight A) and B);
• E) at least one phosphate in an amount in the range of 0.01 parts by weight to (A) + B)) / 10 parts by weight;
• F) optionally up to (A) + B)) parts by weight of other customary additives;

wherein at least the mixing of component E) with component A) takes place with the introduction of thermal and mechanical energy into the thermoplastic mixture. 2. Thermoplastic mixture according to claim 1, characterized in that contain component E) in an amount of at least 0.1 part by weight is.   3. Thermoplastic mixture according to claim 1 or 2, characterized in that that component E) in an amount up to (A) + B)) / 20 parts by weight is included. 4. Thermoplastic mixture according to one or more of the preceding Claims, characterized in that component E) is an alkali salt a metaphosphate or polyphosphate. 5. Thermoplastic mixture according to claim 4, characterized in that component E) sodium trimetaphosphate, sodium metaphosphate, Sodium polyphosphate and / or sodium hexametaphosphate, preferably Sodium polyphosphate. 6. Thermoplastic mixture according to one or more of the preceding Claims, characterized in that they are mixed at temperatures is available in the range from <60 ° C to 200 ° C. 7. Thermoplastic mixture according to one or more of the preceding Claims, characterized in that they are mixed by exposure of mixing units with strong shear plasticizing elements is available, with the plasticizing elements torques in the range from 10 to 100 Nm, preferably 20 to 40 Nm, can be achieved. 8. A process for the preparation of a thermoplastic starch-based mixture, in which

• A) 100 parts by weight of any native, chemically modified, fermentative, recombinant and / or biotransformation-corrected arithmetically corrected to a water content of zero percent and / or derivatives of said starches;
• B) optionally up to 100 parts by weight of a physiologically acceptable, biodegradable, thermoplastically processable, polymeric material different from A);
• C) 1 to 100 parts by weight of water;
• D) at least one plasticizer in an amount in the range from 10 parts by weight to half the sum of parts by weight A) and B);
• E) at least one phosphate, preferably phosphoric acid salt, in an amount in the range from 0.01 part by weight to (A) + B)) / 10 parts by weight;
• F) optionally up to (A) + B)) parts by weight of other customary additives;

provides and mixed together, characterized in that component E) is added to components A) to D) and optionally F), at least the mixing of component E) with the remaining components with the introduction of thermal and mechanical energy in, preferably under the influence of elevated temperature and simultaneous exertion of shear forces, the thermoplastic mixture takes place. 9. Granules available from the thermoplastic mixture according to the Claims 1 to 7 by extrusion and pelletization. 10. Biodegradable molded part or film with improved mechanical Properties showing the thermoplastic mixture according to the Claims 1 to 7. 11. Use of the thermoplastic mixture according to claims 1 to 7 for the production of molded parts or foils. 12. Use of the thermoplastic mixture according to claims 1 to 7 for the production of moldings for the controlled release of active substances.   13. Use of the thermoplastic mixture according to claims 1 to 7 for the production of moldings for the production of massive moldings, Hollow bodies or combinations thereof. 14. Use of the thermoplastic mixture according to claims 1 to 7 for the production of films for use in agriculture. 15. Use of the thermoplastic mixture according to claims 1 to 7 for the production of films for use in food applications. 16. Use of the thermoplastic mixture according to claims 1 to 7 for the production of films for use as food packaging. 17. Use of the thermoplastic mixture according to claims 1 to 7 for the production of films for use as food packaging with full surface contact with the food. 18. Use of the thermoplastic mixture according to claims 1 to 7 for the production of flat or tubular films for use as Food casings for sausage and cheese. 19. Use of the thermoplastic mixture according to claims 1 to 7 for use as temporary protective films for technical Utensils.