DK173567B1 - Thermoplastic processable starch and its process - Google Patents

Abstract

In the manufacture of thermoplastically processable starch, an additive is essentially mixed with native or natural starch and the mixture is caused to melt by the application of heat and mechanical energy. The additive is a substance which lowers the melting point of the starch so that the melting point of the starch together with this additive lies below the decomposition temperature of the starch while, in addition, the additive has a solubility parameter of over 15 cal<1/2>cm<-3/2>. Once the starch-additive mixture has melted, the molten substance is mixed until it is at least virtually homogenous. In the melting range of the starch-additive mixture, the vapour pressure of the additive should be lower than 1 bar.

Description

in DK 173567 B1

The present invention relates to thermoplastic processable starch and to a process for producing thermoplastic processable starch, to a process for producing granules, scales or chips, etc., and to 5 molds, extruded bodies, foils, etc. of starch as well as molds, fillers, etc. and carriers consisting mainly of starch.

Natural or so-called native starch, which can be recovered by washing and drying from raw starch, such as from 10 potatoes, grains, corn, etc., exhibits a distinct macromolecular structure in which the macromolecules are not at all or only partially permeable. These structures cause native starch to be highly inhomogeneous and these inhomogeneities are preserved at least in part even by melting of the starch.

In the course of using so-called hydrophilic polymers, which also include starch, as so-called natural resins for a wide range of applications, it is also attempted to process starch using known processing techniques used in processing mold 20, such as . injection molding and extrusion.

However, due to the properties of native starch described above, no common starch bodies are capable of exhibiting satisfactory mechanical properties such as e.g. firmness. By using the techniques known today in the processing of so-called hydrophilic polymers, such as gelatin or cellulose, it has been attempted to subject starch to which a certain water content has been added, in the order of 10 to 20%. , homogenization, and subsequent processing in a worm extrusion device of an injection molding machine, for example.

English Patent No. 1,014,801 discloses a process according to which a cooled mixture of □ native starch with 12% to 15% water, or with a not substantially less water content, and with a gelatinizing agent is processed into a resin. similar product.

2 DK 173567 B1

It is essential, according to this described method, that the starch exhibit a sufficient water content.

German Publication No. 3,712,029 discloses a process for pressurizing mold bodies 5 of starch, wherein a mixture of native starch with, inter alia, 0.5% of a lubricant and 10% to 20% of water in an injection molding machine is subjected to melting in a temperature range of 90 ° C to 240 ° C and then processed. To this end, it is essential that the water content is maintained throughout the process.

It has been found that these processing techniques only improve the mechanical properties of the starch mold bodies and thus the homogenization effect in the starch melt when the water in the worm piston withdrawal zone is not driven out by heat as steam. from the starch, but on the whole the length of the piston remains in the starch. It is also a prerequisite for this to be a marked mixing, such as this. is the case in a kneading mechanism or in a two-shaft extruder having a correspondingly long piston length. In this case, the shaft piston, or the knob piston, forms a quasi-closed space where the length of the piston and the temperature course along the piston are critical to obtain a sufficiently homogenizing effect.

This process of producing more homogeneous starch or of better thermoplastic processable starch is apparently complicated and critical, having to adhere strictly to various processing parameters, such as adherence to a sufficient water content, of temperature, of process, of machine type, length of screw, etc. It is therefore not strange that according to the process known from European Patent Specification No. 0304,401 it is recommended to separate the so-called homogenization or also destructive process step from the subsequent processing of the starch melt in order to obtaining satisfactory properties of the starch molding bodies. According to the said process, it is essential that the first process step takes place in a so-called closed system, so that the water e.g. cannot dodge in the form of steam.

5 The high water content of 10% to 20% required by said process is, as is generally known in the art of plastics machining, not necessarily advantageous in the processing nor for the properties of the mold bodies to be manufactured. Eg.

In particular, 10 prevents a water content of the order of 17% or more from a reasonable extrusion of the starch by e.g. manufacture of foils, profiles or hoses. In general, it can be stated that the water content makes it impossible to open processing, as is the case with extrusion, due to the high vapor pressure of water clearly above 1 bar. However, if the water content is at least 25% by weight, the mixture can be processed in "open" system at 108 ° C. However, the extruded is sticky at 20 ° C and not stable.

It is therefore the object of the present invention to provide thermoplastic processable starch as well as to a process for its preparation where the above disadvantages are not present and where a simpler process process is permitted and where trouble-free thermoplastic processing of the starch is possible. according to the known 25 polymer processing techniques.

This is achieved according to the invention by means of starch according to one of claims 22-25 and by a method according to one of claims 1-19.

The thermoplastic processable starch may be in the form of granules, peel or shavings, pellets, tablets or as powders or in the form of fibers.

The solubility parameter § is, as is well known, mainly composed of three parts, namely a polar proportion δρ »one proportion of hydrogen bridging bonds and a proportion of gH and a dispersion proportion 5a / respectively, it is a function of these three sizes. According to the invention it is proposed that the proportion of gp corresponding to the polar interactions corresponding to the proportion of g of the solubility parameter § of the solubility parameter § is greater than the proportion of gp of the solubility parameter g of at least 5 one additive. Preferably, gp and gH are twice the dispersion proportion of gd.

Preferably, the admixture of starch with additive takes place substantially anhydrous, respectively, at least almost present moisture is extracted from the mixture of starch and additive.

Preferably, the solubility parameter of the additive in a temperature range from 100 ° C to 300 ° C is on the order of 15 - 25 calxcm 3/2.

In particular, if melting and mixing of the starch with at least one additive takes place in an open environment, ie. not under pressure, the vapor pressure of the additive in the melting region of the additive and starch, in which the mixing or processing of the thermoplastic processable starch takes place, must be less than one atmosphere so that the additive does not evade or controllably avoid from the mixture with starch.

Furthermore, it is proposed that at least one additive be selected such that the interface energy between the additive and starch is not greater than 20% of the individual interface energies relative to air. If the additive meets this requirement, it is ensured that the interaction between additive and starch is satisfactory.

Preferably, 5 - 35% of additive is added to the starch, based on the total weight of the mixture.

It is suggested that the mixing of the starch melt with additive takes place in a temperature range between 100 and 300 ° C, preferably between 120 and 220 ° C, respectively, between 150 and 170 ° C.

5 DK 173567 B1

Mixing of natural or native starch with additive can take place by adding the mixture to a plastic processing machine such as e.g. a single- or two-shaft extruder, or a kneading apparatus, and 5 herein, e.g. in the shaft piston or the knead piston, the mixture is blended to a at least nearly homogeneous thermoplastic mass. In particular, if the vapor pressure of the additive in the temperature range in which the mixture takes place is less than one atmosphere, the mixing operation may take place in some open or closed container means. Only if the vapor pressure of the additive in the temperature range of the mixing operation is greater than one atmosphere, the container means must be closed so that the additive does not escape from the mixture.

It is further proposed as an additive to use at least one of the following substances: 1,3-butanediol, glycerine, ethylene glycol, propylene glycol, diglyceride, diglycol ether, formamide and / or n-methylformamide.

However, as an additive, at least one substance of the following formula is also suitable:

WE

I - [(- O-CH-CH-) - (CH) - {CH)] -R

R n m k z R11 R111 S Ϊ 30

1 II VI

with R = -H or -alkyl; R -R = -OH, -NH2, where in it 35. (ii-vi) at least one R = -OH, and n = 1.2, ... 5; m, k = 0, 1, 2 ... 5 and n »0 if m, k = 0 and z = 1, 2. . . . (+) 40 or Rx C = O with Ra, R2 = -H, -alkyl, r2 r3

-N

R 4 6 with R 3, R 4 = -H, -alkyl; however, without r 2 = r 2 = -H; RL = R2 = alkyl; R 1 = R 2 = -NH 2; and R 1 = -H 2 R 2 = alkyl; at the same time 10 and R 2 = -H R 1 = -alkyl.

At the same time, the above-mentioned preferred examples for theorems mainly exhibit a solubility parameter § <which is either approximately equal to 15 cal * cm³ 3/2 or also, as required, is greater than this value. Thus, for example, the solubility parameter for ethylene glycol 16 , 3 20 cal * cm3 / 2, for formamide 17.8, for glycerine 21.1, for n-methylformamide 16.1, for diglyceride 15.8, etc.

For the determination of the solubility parameter, reference is also made to the following literature: J. Brandrup, E. H. Immergut, Polymer Handbook, Second Edition, 1975, John 25 Wiley, 5. IV - 337 et seq., And in particular Table 3.

In this literature reference, reference is made to Table 3.3, in which both the total solubility parameter § as well as the proportions §p 'δκ ° 9 5d are individually listed.

It is further proposed to add the mixture of starch and additive at least one additional additive, such as e.g. a filler, a lubricant, a plasticizer, a plasticizer, a pigmentant, or unspecified dye and / or a molding agent.

35 The following materials are particularly suitable as fillers: 7 DK 173567 B1

Gelatin, protein, polysaccharide, a cellulose derivative, a synthetic polymer which is at least almost soluble in a starch additive, and / or a gelatin phthalate.

It is proposed to add 0-50 wt% of filler material, preferably 3-10 wt%, based on the total weight of the mixture of starch and additive material.

It is further proposed to add at least one inorganic filler, such as e.g. magnesium oxide, aluminum, silicon, titanium, etc., at a concentration of 0.02 to 3% by weight, preferably 0.02 to 1% by weight, based on the total weight.

Particularly suitable as plasticizers are polyalkylene oxide, glycerine, glycerine mono-, di- or triacetate, sorbitol and a citrate which is added at a concentration in the range 0.5 - 15% by weight, preferably 0.5-5% by weight. %, relative to the total weight of the mixture of starch and additive.

In particular, for coloring the mixture of starch and additive material, organic or inorganic pigments having a concentration in the range of from 0.001 to 10% by weight, preferably 0.5 to 3% by weight, are suitable.

In order to improve the yield strength properties, animal or plant fats and / or · are particularly suitable; 25 lecithins which are preferably used in hydrogenated form and wherein these fats and other fatty acid derivatives preferably have a melting point greater than 50 ° C.

In addition, in order to reduce the water uptake capacity and thus the thermoplastic processable starch's resistance to water during and after processing, it is also proposed to add a wetting agent or agent for the chemical modification of the starch, such as alkyl siloxanes, to the mixture of starch and additive material. .

35 As a wetting agent, the substances listed below are particularly suitable: 8 DK 173567 B1

Two- and multi-valent carbonic acids and their anhydrides, acid halides and / or acid amides of two- and multi-valent carbonic acids, derivatives of two or more valent inorganic acids, epoxides, formaldehyde and / or urea derivatives, divinylsulfones , isocyanates, oxo compounds, such as acetone formaldehyde or multi-valent oxo compounds and / or cyanamide. When using acid amides of carboxylic acids, an acid group should be present as a free carboxyl group.

The processes proposed above are suitable for the production of thermoplastic processable starch and in particular for the production of granules, scales or chips, pills, powders, tablets, fibers, etc. of thermoplastic processable starch.

The thermoplastic starch prepared according to the above-described processes can be directly processed according to the prior art plastics processing methods. However, it must be particularly observed, when extruding hoses, foils and the like, that the additive material at the processing temperature exhibits a vapor pressure less than one atmosphere to prevent foaming of the starch. For example, in case of excessive water content, manufacture of blowing films, hoses, etc., not possible. By adding a sufficient amount of additives, at least in part the natural uptake of water into the starch is prevented.

The thermoplastic starch prepared according to the processes described above is particularly suitable as a filler, or as a formulation auxiliary material, for addition to thermoplastic or duroplastic polymers. The suitability as a filler material or as a formulation auxiliary material, in particular, is evident from the fact that the properties of the thermoplastic processable starch are controllable by means of the mole amount of the pathway and the mole amount distribution which is relatively narrow.

9 DK 173567 B1

Further, the thermoplastic processable starch is suitable, e.g. as a carrier material for working materials, such as e.g. pharmaceutical materials, and as reagent material, e.g. floatant for drains.

Also thermoplastic processable starch is suitable for bonding water in water-poor environments and / or on a water-permeable substrate. The starch is extruded e.g. for films or networks which exhibit large surface area and are applied to the substrate, e.g. consists of TO sand or gravel. Because of the water absorption ability, the starch binds water, so that e.g. in desert-like areas artificial irrigation of the soil can take place more effectively.

The method according to the invention is described in greater detail below with the aid of principle experimental results 15 and with reference to tables which provide further information and of which:

Table I shows the effect of additive materials on the melting temperature of native starch, Table II shows homogenization operation at different batches and different homogenization conditions, and their effect on starch's mole amount and crystal state, Table III shows selected mechanical values for homogenized and insufficient homogenized, Table IV shear viscosity dependence on homogenization temperature and starch composition.

In order to investigate the influence of additive materials on native starch, it is necessary to remove the naturally occurring content of water of approx. 17%. This takes place, on the one hand, by the addition of additives, in particular by melting operation and by mixing, and on the other hand by the usual drying methods known. In dependence on the properties required by the mold bodies to be manufactured, such as in particular thermal and mechanical properties, preferably approx. 10-25% of additive to the native starch, thereby reducing the water content of the starch by the addition of additives. Hereby the melting temperature of the starch can also be substantially influenced, which on the one hand affects the processing of the starch and on the other hand affects the heat resistance of the molded articles produced.

This effect has been further investigated by the addition of five preferred additives. First, the native starch was completely dried so that the influence of water could be excluded. Then, in the 15 dried starch, 10% of the additive material was mixed and the mixture was slowly heated, with the application of heat being closely followed. Hereby the thermal transformation of the mixture could be closely followed, and it could be concluded at the temperature range where the mixture was completely melted. As additives, DMSO, glycerine, ethyl glycol, propylene glycol and butylene glycol were used. The measured thermal transformation ranges and thus the effect of the additives on the starch melt temperature are summarized in Table I. To this end, it should be noted that the lower beginning of a "tip" is associated with glass transformation while a melt occurs in the "tip" upper end.

Of the additives used, ethylene glycol greatly reduced the starch's melting point, while the use of butylene glycol caused a relatively high melting range of approx. 200 ° C. Also, an addition of propylene carbonate was investigated with which the starch was decomposed before the onset of melting. Decrease in melting temperature seems to be related to the influence of the molecular structure in the native starch, but this effect was not investigated further.

11 DK 173567 B1

If the mixture of starch and feedstock is now further processed, the homogenization operation, ie. by mixing the melt of starch and additive, the resulting melting temperature is observed.

Thus, e.g. mixtures of propylene glycol and native starch with proportions of propylene glycol in the range of between 10 and 20% a kneading apparatus and mixing was then done at 175 ° C. Depending on the amount of additive, the residence time of the mixture in the kneading apparatus was 40 - 100 seconds, and by the addition of more additive the processing temperature could be lowered to obtain satisfactory melting homogeneity. In another example, glycerine was added and correspondingly the processing temperature of the kneading apparatus could be lowered.

Experience has shown that the addition of 1% additive causes a reduction in the melting range of about 10 ° C, or at the same shear rate, but achieves the same viscosity of the mixture with 1% more additive already at a temperature of 10 ° C lower.

The average performance of the kneading apparatus in the above tests was approx. 10 kW per 100 kg of mixture of starch and additive. The homogeneity of the melt was tested by making test bodies and performing tensile / expansion tests. In the area where the measured mechanical properties, ie. Accordingly, if tensile strength or tear strength were no longer significantly improved, a satisfactory homogeneity of the melt could be concluded. On the basis of these tensile / expansion experiments, satisfactory reference data were compiled so that a certain composition of the melt of starch and additive material could be concluded for similar residence times in the extrusion device or in the kneading apparatus.

1 2 DK 173567 B1 Table II shows homogenisation of starch and with the homogenisation made under different homogenisation conditions as well as their effect on the homogeneity of the resulting thermoplastic starch.

Potato starch has been used, with potato starch together with 15% additive including a melting range of approx. 180 ° C, as well as potato starch P1, which together with 15% additive includes a melting range of approx. 195 ° C.

Column A specifies the composition of the starch additive mixture, wherein value A indicates grams of additive per gram. (grams of starch + grams of additive).

Thus, a value A = 0.15 indicates 15 grams of additive per 100 grams of the starch mixture plus additive in 15 rials. As a filler, a mixture of the aforementioned, preferably used, filler materials having a solubility parameter at 150 ° C of 20 cal1 / 2cm_3 / 2 has been used.

Temperatures - Tg denotes the reference temperatures 20 at the controlled temperatures in the individual zones of the homogenizer. As a homogenizer, a kneading apparatus is used.

TE is equal to the temperature of the mass upon withdrawal from the kneading apparatus.

25 B is equal to the kneading device shaft speed (revolutions U per minute).

C is equal to the input energy into the mass in the form of mechanical work in kW.

D is equal to the mass flow in the kneading apparatus, i.

30 melting passes through the kneading apparatus (kg / h).

E is equal to the intrinsic viscosity of the thermoplastic starch after leaving the kneading apparatus measured in the solution in 0.1nKOH at 60 ° C after a dissolution time 35 of one hour at 110 ° C in Ubelhode capillary viscosity. gram). At E, it is a measure of the mole amount (M) of thermoplastic starch in (g / mole). The associated correlation is: 0 4 E = 0.2 * '(M0 = mean weight of mole amount).

Kj \ J

5 E for nativ / untreated starch is 260, of which for M_ for the native, untreated starch G 7 results in a value of 6 * 10.

F denotes the crystalline proportion in%. Thus, by means of the starch crystal condition, it can be determined whether homogenization has been satisfactorily achieved and thus whether the starch is thermoplastic processable. Native starch is highly crystalline, whereas thermoplastic processable starch no longer comprises 15 crystalline proportions.

Measurement of the crystalline proportion: Measurement method: X-ray diffraction in powder, size of measurement: Intensity of the scattering radiation as a function of the scattering angle.

20 Native potato starch: Sharp reflexes at scattering angles (degrees): 6, 14, 17, 20, 22, 24, 26.

Targets for crystalline state:

Eg = The surface content of scattering intensity - 25 scattering angle function for sharp reflections from the treated starch,

Fn = Surface content as above for native, untreated starch.

For example, F = = 5 * 100 (%) n The 30 F value for treated starch in homogeneous thermoplastic state is less than 5%.

Discussion of Table II:

The assessment criterion for whether or not good or poor homogenization of the starch has taken place indicates the value F of the crystalline shares. Values between 0 and 5 are optimum values, while values greater than 5% already suggest unsatisfactory homogeneity for the thermoplastic starch.

5 The values found for E, ie. for the boundary viscosity, is within reasonable limits, and even the lowest value found for E corresponds to a mean molar range M of 1.5 M.

The different values of A are compared, ie. for the 10 compositions of the starch mixtures with P3 and with P4, it appears that the values in an area between 0.25 and 0.3 go through an optimum. Thus, e.g. mixtures of starch P1 with A values of 0.35 and 0.4 after homogenization continue to have high crystalline proportions, with its values of A of 0.3 and 0.25 practically no further crystalline proportions. The same also applies to starch mixtures consisting of potato starch and additive. Of course, these indications cannot be generalized, but the hogogenization effect depends not least on the composition, or the properties, of the additive or additive materials, respectively.

An important criterion for homogenization is the energy supplied, as it is clear from the experiments that the greater the energy supplied to the kneading apparatus, the better homogenization of the starch is achieved.

This is stated, for example. of samples 3a, 3b and 3c where the homogenization took place in practically the same temperature range and where the composition of the starch mixture was similar, namely with a value of A = 0.35. The same effect can be deduced by comparison with samples 9 and 10, where sample 10 with a greater energy supply to the kneading apparatus achieved a satisfactory homogeneity, while sample 9 showed a crystalline proportion of 25%.

1 5 DK 173567 B1

In order to obtain a satisfactory homogeneity in the thermoplastic starch, the selection of temperatures in the homogenizer is also important, as can be seen, for example, in a comparison of samples 5a and 5b. Thus, e.g. sample 5b has a better homogeneity, although less energy has been added to the kneading apparatus. The better homogeneity is to a large extent here due to the selected higher temperatures in the kneading apparatus.

However, the measurement values given in Table II clearly show that a statement of composition, selected temperatures in the kneading apparatus and energy supplied cannot be generalized. Therefore, in any selected starch / additive mixture, the task is to optimize the process to obtain a thermoplastic starch. Finally, it is also an important question whether a high or a low mole amount should be set. However, this question is ultimately dependent on requirements, namely whether the thermoplastic starch should be used for injection molding or also for extrusion. As is well known, high viscosity polymers are rather suitable for extrusion, whereas low viscosity polymers are more suitable for injection molding.

To return to the starch homogenization, it must also be stated that, of course, the homogeneity of the material can be affected by the residence time of the material in the homogenizer and the kneading apparatus, respectively.

Comments on Table III; Table III shows the effect of the thermoplastic starch homogeneity, or crystal state, on mechanical properties by means of the exemplary indication of the effect on the starch's expansion and fracture behavior.

In Sample I, these are sample bodies of thermoplastic starch material which are satisfactorily or almost ideally homogenized and are similarly thermoplastic processable. In test II it is a starch sample that is insufficiently homogenized and correspondingly exhibits a too high crystalline content.

The column module indicates the modulus of elasticity for both materials, which interestingly is practically the same for the two materials. Column A indicates the composition of the samples, column E as in Table II the intrinsic viscosity of the samples, and column F the value of the crystalline proportion.

G indicates the relative expansion of the material by fracture in (%), and H indicates the amount of energy applied to the material to obtain material breakage. The dimension for H is (kJ / m2).

In line I, the values of various measurements for sample I are summarized, which contain a crystalline proportion of the order of 0 to max 5%. This is thus about materials that are almost completely homogenized. "And are similarly thermoplastic flawless processable.

Similarly, in line II, various measurements are summarized for the materials II which are insufficiently homogenized.

From Column G, it is clearly deduced that the starch materials of Line II are substantially more easily broken than the materials of Line I. Also, the starch materials of Line I must be supplied with substantially more energy according to Column H to impart expansion of the 25 materials to breakage. them.

Due to these tensile / expansion experiments, listed by numbers in Table III, the improvement in the mechanical properties of the thermoplastic processable starch is clearly evident. Due to the reduction of the crystalline content of the material to below 5%, starch materials having satisfactory to good mechanical properties are obtained. Of course, these mechanical properties can be further improved by the amount of additive and by the appropriate choice of additives.

17 DK 173567 B1

Since apparent shear forces in the melt containing the mixture of starch and additive material are responsible for the homogenization effect and thus lead to a material with less crystalline proportion, the relationship between the shear viscosity of the melt and the shear effect of the homogenizer must be further described. For this, the structure-viscosity of the starch melt, i.e. shear viscosity dependence on shear rate in a capillary rheometer.

10 As a correlation between the two sizes, the following equation is found: n = K * γ * 1_πι * where η denotes the shear viscosity of the melt in (Pa * sec), _ i and the γ shear rate in (sec). K is a material-15 constant that is also occasionally referred to as consistency.

K can be calculated by the following equation:

E

K - exp [-! <! - - a (A-Ao)] 4 for the term E 1 / R, the value 5.52 * 10 (degree Kelvin) is found, with R = the gas constant and EA = the thermal activation energy of the molecules at space-shifting. the operation of flowing the melt.

T indicates the temperature of the melt (in degrees Kelvin), and Two indicates a reference temperature of 458 degrees Kelvin.

2a is also a constant with the value of 2.76 * 10, and 25A is, as is known, related to the composition of the starch / additive mixture. AQ, with the value A = 0.1, indicates the composition of a reference mixture.

From this it appears that the term m is a function of the temperature of the melt and the composition of the starch / additive mixture 30.

Table IV lists values of m in dependence of T (degree Kelvin) and of A, whereby these values were obtained, since, at predicted Y, indicating the shear rate, the shear viscosity of the measuring device has adjusted accordingly. For m, there is thus a function according to the general formula: 5 m = (g <T) + f (A) + r (T, A)).

The values of Table IV emphasize the already presumed fact that, at elevated temperature of the melt, the shear rate can be reduced to obtain the same shear viscosity in the melt, and at elevated additive proportion, the temperature of the melt can be reduced to obtain the same. shear viscosity in the melt.

The thus homogenized starch or better thermoplastic starch can subsequently be directly processed according to the usual known plastics processing methods, such as by injection molding, extrusion, foil blasting, spray blasting, deep drawing, etc. foil blasting, spray blasting, etc., it is observed that the additive material exhibits a vapor pressure that is clearly below 1 bar at the temperature at which the melt leaves the nozzle of the extruder. The same applies to the water content of the melt, which must not be too high. Furthermore, it should be noted that there is sufficient additive material in the melt to displace or replace the water, respectively. If the water content is too high or when using an additive material with too high vapor pressure, the material foams at the exit of the nozzle.

By further adding additives as described above, the properties of the molding and extrusion products can be further significantly affected. Thus, e.g. by the addition of inorganic fillers such as magnesium oxide, aluminum, silicon, etc. the transparency is reduced or completely removed. Additions of plant or animal fats improve the flow properties of the melt, respectively, and serve to improve the forming ability. However, the property influence is not a primary object of the present invention, so that a more detailed description of this subject is waived.

A further and more important aspect consists in the addition of wetting agents to the starch, since mold bodies and pure starch extrusion products are not water resistant due to the starch's water absorption capacity. With the addition of wetting agents and not specific chemical modifiers, parts of the starch become at least partially or almost completely water-resistant and thus can be used practically without problems. The choice and addition of one of the aforementioned wetting agents 15 depends mainly on the additive material and its amount of addition to the native starch, since the additives may also play a role. Temperature and residence time in extruder, ie. Therefore, in melting, homogenizing and processing, the essential criteria that exist in the choice of wetting agent type are. In principle, when processing the starch, the moisturisation should not set in such force that the thermoplasticity is affected so that processing becomes problematic. However, this problem is well known in practice in the processing of partially wettable thermoplastic materials, in the manufacture of powder coatings, and so this question does not need further description here.

The additives and processing conditions used above, for example, have served only 30 for a more detailed description of the invention and may vary according to the requirements of any application and other materials and processing conditions. However, it is essential that by adding an additive to native starch and by mixing these materials in the melt, thermoplastic starch can be provided. Furthermore, it is essential that the additives exhibit a cohesive energy density which allows them to influence the molecular starch's molecular structure in such a way that the thermoplastic processability of it can be achieved. Finally, a further requirement is that the vapor pressure of the additives, at least in the case of open processing, in the processing temperature range is less than 1 bar.

1 0

Claims (29)

A process for preparing thermoplastic, homogeneous starch having a crystalline proportion of the starch of less than 5%, characterized in that native or natural starch, optionally dried, is mixed with at least 10% by weight of an additive, determined as a weight percent value in ratio to the total weight of the mixture, and this is brought to melt by the application of heat, after which the melt is homogenized where the additive used has a solubility parameter greater than 30.7 (MPa) * (= 15 (cal (Cm3 / 2)), and when mixed with the starch lowers its melting point such that the melting temperature of the mixture falls below the decomposition temperature of the starch and where the vapor pressure of the additive (s) in the mixture in its melting temperature range is less than 1 bar , to obtain the desired homogeneous starch having a water content of less than 5%. Process according to Claim 1, characterized in that the naturally occurring water content of the native or natural starch is approx. 17% is removed by the addition of the at least one additive. Process according to claim 1, characterized in that the starch prior to mixing with the at least one additive is completely dried. Process according to claim 1, 2 or 3, characterized in that at least one of the following substances is used as an additive: Glycerin, formamide or N-methylformamide. Process according to claims 1, 2, 3 or 4 characterized in that the starch is mixed with at least 10 to 35% by weight of additive, after which the mixture is brought to melt and the melt is homogenized. Process according to claim 1, 2, 3, 4 or 5, characterized in that the mixing and homogenisation takes place in a temperature range between 120 and 220 ° C. DK 173567 B1 Process according to claims 1, 2, 3, 4, 5 or 6, characterized in that the starch is mixed with at least 10 to 35% by weight of glycerine, determined as a percentage by weight of the total weight of the mixture, and the mixture is brought to melt. Process according to claim 1, 2, 3, 4, 5, 6 or 7, characterized in that the additive in a temperature range between 100 and 300 ° C has a solubility parameter between 30.7 and 51.0 (MPa) K ( = between 15 and 25 (cal * »ίο cm" 3''2)) and where its interface energy against starch is not greater than 20% of the individual interface energies for starch and additive in relation to air. Process according to claims 1, 2, 3, 4, 5, G, 7 or 8, characterized in that the mixture and ice homogenisation are carried out in a plastic processing machine, such as a single or two-shaft extruder or a kneading machine. Process according to claim 1, 2, 3, 6, 8 or 9, characterized in that, as an additive 20, a plasticizer selected from polyalkylene oxide, glycerine, glycerine mono or diacetate, sorbitol and a citrate having a concentration in the range from 0.5 to 15% by weight, determined relative to the total weight. 11. A process according to any one of claims 1-10 characterized in that at least one of the following materials is added as a filler to the starch / additive mixture: - Another polysaccharide - a cellulose derivative 30. A polymer soluble in the additive - A gelatin phthalate, adding more than between 0 and 50% by weight of filler, determined as a weight percentage value relative to the total weight of the total mixture. DK 173567 B1 Process according to claim 11, characterized in that between 3 and 10% by weight of filling material is added. A process according to any one of claims 1 to 12 characterized in that at least one inorganic filler material is mixed in the starch additive mixture at a concentration of 0.02 to 3% by weight, determined relative to the total weight. Process according to any one of claims 1 to 13 characterized in that in the starch mixture is added 0.02 to 3% by weight of magnesium oxide as filler determined relative to the total weight. The process according to any one of claims 1 to 14 characterized in that an organic or inorganic pigment having a concentration in the range of 0.001 to 10% by weight, determined relative to the total weight, is further admixed. The method according to any one of claims 1 to 15 characterized in that the pigment is used in a concentration in the order of 0.5 to 3% by weight determined relative to the total weight. Process according to one of Claims 1 to 16, characterized in that a further flow-enhancing agent in the form of an animal or plant fat is preferably added, preferably in hydrogenated form, these substances having a melting point which is greater than 50 ° C. A process according to any one of claims 1 to 17 characterized in that a wetting agent is further admixed. Process according to one of Claims 1 to 18, characterized in that at least one of the following substances is used as a wetting agent: - a two- or multi-valent carbonic acid and / or an anhydride thereof 35. a halide and / or an acid amide of a two- or multi-valent carbonic acid - a derivative of a two- or multi-valent inorganic acid - an epoxide, such as a multi-valent glycide ether - formaldehyde and / or a urea derivative 5. an isocyanate - an oxo compound, such as an acetone formaldehyde or a multi-valent oxo compound, - cyanamide. in Island A process for preparing granules, scales, pills, powders, tablets or fibers of the thermoplastic, homogeneous starch obtained by the practice of any one of claims 1 to 19 characterized in that the starch is formed into these desired ice products. A process for preparing mold bodies, extrusion products or films of the thermoplastic, homogeneous starch obtained by the practice of any one of claims 1 to 20, characterized in that the homogeneous starch melt is processed directly. A thermoplastic, homogeneous starch having a crystalline proportion in the starch of less than 5% provided by the practice of any one of claims 1-19, Thermoplastic processable starch according to claim 22, characterized in that the molecular viscosity interfacial agent of the starch is in the range 3 million to 10 million. Thermoplastic processable starch according to claim 22 or 23, characterized in that it is in the form of granules, scales, pills and / or tablets or as powder or in the form of fibers. Thermoplastic processable starch according to claim 35, 22, 23 or 24, characterized in that the proportion corresponding to the polar interactions <£ p and the proportion corresponding to <17> of the solubility parameter £ for the at least one additive is greater than that of the dispersion forces corresponding to D of the solubility parameter <5 for the at least one additive. A thermoplastic, homogeneous starch mold body according to claims 22, 23, 24 or 25. Use of thermoplastic processable starch according to claim 22, 23, 24 or 25 as a filler material for filling in and / or formulation of thermoplastic or io-duroplastic polymers. Use of thermoplastic processable homogeneous starch according to claims 22, 23, 24 or 25 as a carrier material for uptake of active materials and / or reactants. ice Use of thermoplastic processable homogeneous starch according to claim 23, 24 or 25 for bonding water in a water-poor environment and / or on a water-permeable substrate, the starch being used in the form of a foil, a network or a net. indicated extrusion product.