EP0722475A1

EP0722475A1 - Thermoplastically processable starch-based composite materials

Info

Publication number: EP0722475A1
Application number: EP94927656A
Authority: EP
Inventors: Wolfgang Ritter; Michael Beck; Martin Schäfer
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 1993-10-05
Filing date: 1994-09-27
Publication date: 1996-07-24
Also published as: DE4333858A1; JPH09505613A; WO1995009888A1; CA2173583A1

Abstract

The description relates to a shapeable composite material based on thermomechanically hydrolyzed starch in a homogenous mixture with synthetic polymer compounds. To optimise its mechanical strength, synthetic polymer compounds with lateral and/or terminal straight-chained and saturated fatty radicals are added and homogenised with the thermoplasticised starch in selected quantity ratios. The invention also relates to the process for producing such a shape-processable composite material and its use to produce mouldings, e.g. packaging materials such as foils, bottles, jars, boxes and the like.

Description

i

'Thermoplastic composite materials based on starch'

The invention relates to a shapeable composite material based on a starch which is thermomechanically digested in a manner known per se - hereinafter also referred to as TPS - in a homogeneous mixture with selected synthetic thermoplastic polymer compounds - hereinafter also referred to as SPV. The core of the action according to the invention lies in the selection of certain structural elements of this SPV and their numerical assignment to the starch content in the composite material.

Numerous proposals in recent years have dealt with trying to make starch as a high-molecular polymer compound of natural origin accessible to an expanded range of applications. The basis of this work is to convert native starch together with limited amounts of water and / or other auxiliaries into a thermoplastic material by means of thermo-mechanical digestion, the shaping of which is possible in a conventional manner, for example by injection molding or calendering. This thermomechanical digestion using elevated temperatures and pressures is possible in particular in conventional extruders which precede the shaping processing step. From the extensive literature, reference is made here to the publication R.F.T. Stepto et al. Injection Molding of Natural Hydrophilic Polymers in the Presence of Water, CHIMIA 41 (1987) No. 3, 76-81, and the literature cited therein.

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In this context, it is known to facilitate the thermal mechanical starch digestion and to improve the product properties in the TPS by using selected low molecular weight organic additives in the starch digestion. So it is suggested the native Add starch additives that lower the melting temperature of the starch. In particular, low polyfunctional alcohols such as ethylene glycol, propylene glycol, glycerol, 1,3-butanediol, diglyceride, corresponding ethers, but also other compounds such as urea are known as additives.

Numerous proposals deal with the attempt to combine thermoplasticized starch with synthetically obtained waterproof polymer compounds in such a way that the composite material has increased resistance to water or hydrophilic solvents, but nevertheless substantial portions of the material are formed by the starch.

For example, EP-A2327505 describes polymer blend materials which are obtained from a melt of water-containing destructurized starch and at least one essentially water-insoluble synthetic thermoplastic polymer compound. Here, the starch is first converted to TPS with the addition of auxiliaries by treatment in an extruder at elevated temperatures and processed into granules. The water content in the granulate is adjusted approximately to the range of the water content of natural starch (approx. 17% by weight). These starch granules are then mixed in a predetermined mixing ratio with synthetic polymer compounds in the dry state. Further suggestions from the field concerned here of thermoplastically processable polymer mixtures based on starch can be found in EP-AI 0400531 and 0400532 and in PCT application WO 90/10671. The last-mentioned publication contains, in particular, extensive information on the mixing and the thermoplastic digestion of the polymer compounds used in the presence of water in suitable extruders, and the at least partial removal of the water from the mixture, expediently within the process step in the extruder.

DE 4038732 relates to materials and / or molded parts based on thermomechanically digested starch in admixture with synthetic thermoplastic polymer compounds. These polymer-modified materials are produced by mixing native starch with aqueous Polymer dispersions of the synthetic thermoplastic polymer compounds and, if desired, further low molecular weight plasticizers are mixed, the multicomponent mixture is subjected to starch digestion at elevated temperatures and pressures with simultaneous intensive mixing and / or kneading to form the thermoplastically processable starch and, if desired, the homogenized polymer mixture is shaped. The water content introduced via the aqueous dispersions of the synthetic polymer compounds is an integral part of the process which is used and effective in the digestion process for starch digestion. According to this proposal, suitable at least largely water-insoluble thermoplastic synthetic polymer compounds are, for example, emulsion (co) polymers such as polyvinyl esters, poly (meth) acrylates and / or corresponding copolyers. Also mentioned are polyesters, polyamides and / or polyurethane resins, it being possible to preferred thermoplastic polymer compounds which have polar groups and, where appropriate, combine oleophilic character with pronounced molecular components. DE 41 21 111 relates to materials and / or molded parts based on a correspondingly thermomechanically digested starch and synthetic thermoplastic polymer compounds, synthetic mix components now being used here which at least partly consist of raw materials based on renewable raw materials and of the class the polyester and / or polyamide are assigned.

The further development described below takes up the suggestions from the two last-mentioned documents DE 4038732 and DE 41 21 111 and modifies their teaching in the manner described below. For the purpose of completeness of the disclosure of the invention, the disclosure content of the two applications for industrial property rights named here by the applicant is expressly made the subject of the disclosure of the present invention.

This further development according to the invention in the sense of the teaching described below aims to further optimize material properties in the composite material made of thermomechanically digested starch (TPS) and the synthetic materials thus present in a homogeneous form Reach polymer compounds (SPV). The goal of this optimization aimed at according to the invention is in particular the setting of optimized mechanical strengths - determined in each case by the tensile strength according to DIN 53455. The conception of this task according to the invention is based on the following facts:

The literature describes the ability of the starch to react with fat derivatives to form so-called channel inclusion compounds. As is known, unmodified starches of natural origin contain the two main components, amylose and amylopectin. In the particularly inexpensive starch raw materials of the most varied origin, which are accessible in large quantities, the amount of amylose is the smaller amount, as a rule it is below about 30% by weight and usually in the range from about 20 to 25% by weight (% by weight). -% each based on dry matter). Typical examples of these starch raw materials are the following examples - in the brackets below, the mean values for amylose wt.% TS: potato starch (22), wheat starch (24), corn starch (21). However, starches of vegetable origin with significantly higher amounts of amylose are also known, which in particular can be at least 50% by weight, for example 70% by weight or even 90% by weight, based on dry matter.

The ability of the starch to form so-called channel inclusion compounds with fat residues is today ascribed to the amylose content in the starch. Fat residues are saturated and straight-chain hydrocarbon residues of a sufficient length. Corresponding fat residues should accordingly contain at least 6 to 8 carbon atoms, preferably 10 or more carbon atoms in the straight-chain and saturated hydrocarbon residue, in order to achieve sufficient complexation through interaction with starch components with the formation of the channel inclusion compounds.

In numerous related to the manufacture of thermoplastic starch In addition to the joint processing of starch, synthetic polymers and plasticizers, publications also mention the use of fatty derivatives. In this case, however, the function of the fat derivatives is exclusively that of a lubricant.

For example, WO 90/01043 describes the use of fats, waxes and paraffins as coating agents in the production and processing of TPS. The use of fat as a lubricant in the production of moldings based on TPS is described in DE 37 12029. Hardened fats are described in EP 404727 as processing aids of polymer materials based on destructurized starch. Further references to the combination of starch and fats can be found in US 4,016117 and in DE 1 717062. US 3,949145 describes the use of sorbitan onooleate for the production of agricultural films based on a degradable starch-based material.

Object of the invention

The teaching according to the invention also starts from the old task of providing thermoplastic materials which are largely based on natural raw materials and in particular contain natural starch as a particularly important component. These recyclable materials should be capable of being processed thermoplastically and, in the process, in the shaped body formed, should be characterized in particular by an optimization of the strength properties. In particular, the invention aims to show a way in which such optimized strength properties can be maintained in the shaped finished product over a longer period of time. Even if the known aging of such polymer composite materials based on starch with embrittlement and thus a drop in mechanical strength cannot be completely prevented, this deficiency, known per se, of the recyclable material mixtures based on TPS, which have been described to date, is to be largely alleviated can. The In particular, the teaching according to the invention aims to show a way in which shaped articles with significantly improved dimensional stability can be obtained using starch-based materials of the type described.

The teaching according to the invention wants to correspond to the above-described tasks of obtaining natural starch as the most important raw material component in the mixture of materials. In a particularly important embodiment, the teaching according to the invention aims to ensure the practically complete rotting ability or the complete degradation of the polymer material by biological processes.

The teaching according to the invention is also based on the above-described instruction to plasticize natural starch in a known manner with the use of plasticizing aids by thermomechanical digestion and, at the same time or at different times, to mix it intimately with other polymer components to be processed thermoplastically in such a way that a homogenization of the composite material takes place. In further preferred embodiments of the invention, these are at least predominantly based on raw materials based on renewable raw materials as mixture components with synthetic polymer compounds used - hereinafter also referred to as SPV.

In a further preferred embodiment, the invention wants to introduce the SPV components in the form of aqueous dispersions into the thermomechanical starch digestion, as is described in detail in DE 4038732. This enables a particularly economical 1-stage process for producing the starch-based composite materials described below.

Subject of the invention

In a first embodiment, the invention relates to a shaped bend processable composite material - hereinafter also sometimes referred to as VM - based on thermomechanical with the addition of water and / or low molecular weight plasticizers digested starch (TPS) in a homogeneous mixture with synthetic polymer compounds (SPV).

The characteristic of the teaching according to the invention is that in order to optimize the mechanical strength of the VM - determined by its tensile strength in accordance with DIN 53455 - the combination of the following parameters is observed:

Corresponding thermoplastically processable polymer compounds with lateral and / or terminal straight-chain and saturated hydrocarbon residues - hereinafter also referred to as "fat residues" - are used as the SPV component;

These SPVs substituted with fat residues are homogenized with the TPS in such proportions that the content of the fat residues in the composite material (wt.% Fat residues based on anhydrous starch) is in the range from 0.5 to 7 wt.% . Preferred ranges for the weight ratio of the fat residues to the starch are in the range from 1 to 5% by weight and in particular in the range from about 2 to 4% by weight.

In a further embodiment, the teaching according to the invention relates to the use of these thermoplastically processable composite materials based on TPS / SPV with selected and numerically determined weight ratios of the fat residues of the SPV for the production of moldings, for example for use as packaging materials such as films, bottles, cups, Boxes and the like.

Finally, the teaching of the invention relates to the process for producing polymer-modified materials based on TPS and molded articles obtained therefrom in accordance with the definitions given above. Details of the teaching according to the invention

The aim of the teaching according to the invention, in its broadest and at the same time in its most concrete conception, is based on the intention of selecting and setting a specific structural parameter for the targeted interaction between the synthetic polymer compounds (SPV) used for processing with the starch to enable the TPS and the SPV. The invention creates the possibility of optimizing the mechanical strength values of the composite material by selecting the "fat residues" which substitute the SPV in terms of type and quantity, based on the proportion of starch in the composite material. The individual SPV molecule is characterized by the presence of a plurality of the substituting fat residues in the sense of the definition according to the invention. The result of the optimization of the mechanical strength values presumably lies in the optimal allocation of the proportions of ready-to-use fat residue substituents to the amylose proportions of the starch material and the reaction of these two sub-components with one another with the formation of corresponding channel inclusion compounds. While maintaining this core to acting in the sense of the teaching according to the invention, a varied and further optimization can be carried out, in particular in the selection of the SPV components to be used in each case, in the selection of the auxiliary components for thermomechanical starch digestion and / or in the work steps for combining and homogenizing SPV / TPS can be carried out.

The SPV used together with the starch in the sense of the inventive action are polymer components which are designed in a manner known per se and have an at least predominantly linear basic structure and are to be processed thermoplastically. Their molecular weights can fluctuate over a wide range. Suitable numerical values include, for example, molar masses in the range from 1.5 × 10 ^ to 10 × 10 ^, preferred lower limit values for the molar mass of this SPV component being in the range from approximately 2 to 5 × 10 ^. These SPV components are identified in the sense of the teaching according to the invention by the presence of a sufficient number of lateral and / or terminal fat residues. The term “fat residue” is understood to mean straight-chain and saturated hydrocarbon residues with at least 6 C atoms, preferably with at least 8 C atoms. It has been shown that the strength values in the composite material can be optimized by increasing the carbon chain length in the fat residue, so that preferred fat residues have at least 10 and preferably at least 12 carbon atoms on average. The respective SPV used can contain such fat residues of the same but also of different types. Preferred chain length ranges for these straight-chain fat residues are 6 to 32 carbon atoms and in particular 10 to 24 carbon atoms. The range of about 12 to 18 carbon atoms in at least a substantial proportion of the substituting fat residues present at the SPV can be of particular importance.

In this context, reference should be made to the following peculiarity: olefinically mono- and / or polyunsaturated longer hydrocarbon residues, as they often occur in the context of natural product-based materials, can also be present as substituents on the, in particular, linear basic molecule of the SPV component. For example, olefinically unsaturated Ciss, Cig, or also higher correspondingly olefinically unsaturated hydrocarbon radicals can be suitable substituents. With regard to the mechanical strengthening effect, however, only the terminal aliphatic saturated portion of such an olefinically unsaturated substituent then obviously interacts with the starch to form the channel inclusion compounds. The strengthening effect of such substituents on the SPV and thus the adjustable increase in physical strength values is then restricted to the lower C number range of the terminally aliphatic saturated portion of such substituents. Accordingly, it can be preferred according to the invention to form at least a predominant proportion of the fat residues on the SPV in the form of aliphatic saturated fat residues of a higher carbon number. According to the invention, it is further preferred that the starch constitutes at least 40% by weight and preferably at least 50% by weight of the composite based on TPS / SVP -% by weight here based on the solid mixture free of water and low molecular weight plasticizing agents . Usually, the proportion of starch in the composite material will be approximately 50 to 80% by weight and preferably approximately 55 to 75% by weight -% by weight also calculated here as stated above.

As stated above, the starches preferred according to the invention are the inexpensively available starch materials with a limited amylose content, which here is below about 30% by weight and preferably in the range from about 15 to 25% by weight, based here on starch -Trocken¬ substance. The already mentioned starch raw materials based on potato, wheat and / or corn with the determination parameters for the aylose content given here are preferred feedstocks for the action according to the invention. However, the teaching of the invention is not restricted to these strengths. Alyose-rich starches are also suitable feedstocks. In fact, when they are used, products can be obtained which are distinguished by further improved physical properties, for example by a further improvement in the form stability of the moldings produced, for example, by injection molding. The use of starches with an amylose content of at least 50% by weight, for example about 65 to 95% by weight and in particular about 70 to 90% by weight, also falls within the scope of the teaching according to the invention.

Basically, all polymer types of this type are suitable as SPV components substituted with fat residues, but biodegradable or rotting compounds of this type are particularly preferred. In this sense, SPV of the type of fat residues containing acrylate and / or methacrylate polymers are considered, but in particular SPVs containing lateral fat residues from the range of polyesters, polyamides, polyurethanes and / or polyvinyl alcohol esters, which are at least partially in theirs Ester groupings of long-chain fat residues contain. Reference can be made here to the relevant specialist knowledge regarding the constitution and the production of corresponding polymer components with lateral and / or terminal fat residues. In a particular embodiment, in particular those types of SPV which are at least partly based on renewable raw materials are suitable. For the substance class of the polyesters, the polyamides and / or the polyurethanes, corresponding information is provided in DE 41 21 111, which is the subject of the disclosure of the invention. In the field of PVA derivatives, this element of the invention can be met by fatty acids of natural origin, for example by using corresponding esters of carboxylic acids with 10 to 24 carbon atoms, in particular with 12 to 22 carbon atoms. In an important embodiment, such ^" fat residues in a mixture with residues of shorter-chain carboxylic acids, for example C2-4-carboxylic acids, can be present in the polymer based on PVA. PVAc types modified with longer-chain fatty acid esters - copolymers of vinyl acetate and Monomers based on esters of vinyl alcohol with longer-chain fatty acids (e.g. Ci2-18 " ^fretts = '^ en) - are particularly suitable representatives here. The fat residues can be present in minor amounts - based on the sum of the acid residues.

Esters based on polyvinyl alcohol, which at least partially contain fatty residues in the sense of the definition according to the invention - in particular from the acid groups used for ester formation - can be of particular importance from the following points of view: It has been shown that appropriate mixtures of TPS / SPV in the shaping processing can have a preferred position. Thus, according to process technology known per se, both films and moldings of higher material thickness, such as bottles, cups and the like, can be produced with good product properties. At the same time, however, it is known that the quantitative microbiological degradation of SPV based on esters of PVA - shown using the example of polyvinyl acetate - takes place particularly quickly and completely, not only with regard to the ester cleavage and degradation of the acid component, but also with regard to the polyvinyl alcohol molecule formed - see the publication H. Kastien et al. "The quantitative microbiological degradation of paint resins and polymer dispersions", Farbe + Lack, 1992, 505-508. By selecting correspondingly completely microbiologically degradable components on the SPV side, the teaching according to the invention can thus be used to ensure simultaneous optimizations in the direction of the strength of the moldings and their rotting properties through natural degradation processes.

In an important embodiment, the teaching of the invention uses the elements of DE 4038732 used for the disclosure of the invention. Accordingly, the SPV substituted with fat residues in the sense of the current teaching can be used in the form of aqueous polymer dispersions which, together with this, are aqueous Phase are combined with the starch to be worked up to the thermoplastic state. If required, the required further low molecular weight plasticizers are mixed in. The finished composite materials are then produced by subjecting the multicomponent mixture at elevated temperatures and pressures with simultaneous intensive mixing and / or kneading in the starch digestion to form the composite material from TPS / SPV and, if desired, processing the homogenized polymer mixture in a shaping manner. The water content entered via the aqueous dispersion of the SPV becomes an integral part of the process which is used and effective in the digestion process for starch digestion.

According to the invention, the thermomechanical digestion of starch into the thermoplastic material also requires the use of water and / or lower organic plasticizers and / or auxiliaries in a manner known per se. In particular, lower polyfunctional alcohols such as ethylene glycol, propylene glycol, butanediol, glycerol and / or their ethers, in particular partial ethers, are suitable here. The use of urea as an auxiliary of the type concerned here is also known and can be used according to the invention. The proportion of water in the mixture of substances to be worked up can be, for example, in the range from 5 to 40% by weight, preferably 5 to 30% by weight, based on the total mixture of substances. The proportion of the low-molecular organic auxiliary components used, such as glycerol, is usually at least about 3% by weight, advantageously in the range of at least about 5-10% by weight and in particular about 10 to 50% by weight, based in turn on the total mixture.

The individual mixture components can be separated from the working device used in each case, for example the extruder, in the feed area and preferably fed continuously in the amount required in each case. When the multicomponent mixture is being transported in the extruder, the desired homogenization and mixing process takes place in the front departments. This is followed by a processing line which is kept under product temperatures and pressures which lead to the desired thermo-mechanical starch digestion. At least here the product temperatures are above 100 ° C. and preferably at or above 120 ° C., whereby working conditions in the range up to approximately 170 ° C. can be preferred at least in the final phases of the mixing and starch digestion process. The resulting working pressure usually corresponds to the intrinsic pressure of the water-containing mixture of substances at the specified working temperature. The residence times of the multicomponent mixture under the working conditions are generally not more than at most about 30 minutes, preferably at most about 20 minutes. It can be expedient to work with residence times of the multicomponent mixture at least in the range of the temperature and pressure conditions for starch digestion of about 0.5 to 10 minutes, preferably in the range of about 2 to 5 minutes.

The homogenized polymer blend can be obtained as an extrudate and, for example, be used for shaping processing at a later time. However, it is also possible to use the polymer mixed product immediately after it has been obtained for the shaping processing to supply, as described in the publication cited at the beginning in CHIMIA (1987) loc. cit. for pure thermoplasticized starch.

Typically, at least a portion of the water added to the mixing and digestion process is removed from the polyblend before its shaping processing - usually in the final stage of the digestion in the extruder. Basically, it applies to starch-based materials that the natural water contents of the starch are restored when they are stored under ambient conditions, which is known to be in the range of about 15 to 20% by weight, based here on starch.

For further details of the digestion process, reference is once again made to the protective rights according to DE 4038732 and DE 41 21 111, which have already been mentioned several times.

B e i s p i e l e

The following general information applies to the devices and raw materials used in the following examples:

a) Devices

The production of TPS (thermoplastic starch) blends requires the following process steps:

Conveying the components present as a liquid, dispersion, granulate or powder into an extruder;

Compressing the extrusion mass into a compact solid; Melting the extrusion mass; Homogenization of the melt; Pumping the melt through an extrusion tool (nozzle). In principle, various types of screw extruders are suitable for this, such as single-screw extruders or double screw extruders which run in opposite or opposite directions. Because of the advantages known from the literature (see also Handbuch der Kunststoffextrusionstechnik, Volume 1, Hanser-Verlag, 1989) such as

Self-cleaning of the screws, narrow residence time, even product stress

a co-rotating twin screw extruder with the following characteristics was used for the examples described below:

Type Continua C37, manufacturer Werner & Pfleiderer drive power 7.6 Kw length of the screws 960 mm - L / D ratio 26

Through a modular system of screws and casings, conveyor, plasticizing, homogenizing, pressure and degassing zones were realized according to the task. In addition, the screw housing was divided into two heating zones of the same length and independently controllable. The components in liquid and solid form were supplied with gravimetrically controlled dosing units (Schenck). The following extrusion parameters were generally set:

Temperature 100 - 150 ° C screw speed 100 rpm total throughput 6 - 18 kg / h

b) raw materials

The following raw materials were used to produce TPS blends based on starch / SPV: Potato starch (e.g. Südstär GmbH or Emsland-Starch) with a water content of 17-20% or wheat starch with a water content of 10-15%.

Synthetic polymer compounds (SPV) substituted with fat residues according to the specific definition given below.

Polyols with a boiling point of at least 150 ° C., such as propylene glycol or preferably glycerol and, if appropriate, further auxiliaries such as urea and / or its derivatives, have been used as plasticizers.

example 1

In the approaches designated below with experiment numbers 1 to 9, it is examined how the strength properties of TSP / SPV blends develop as a function of the content of fat residues in the sense according to the invention in the SPV component used in each case.

Homogenization with the starch in the sense of a thermomechanical digestion is subjected to 3 related types of polymer:

Experiments 1, 4 and 7:

Aqueous polyvinyl acetate dispersion which, in the sense of the teaching of DE 40 38732, is subjected to potato starch and a low-molecular plasticizer (in particular glycerol) of the common extrusion and the thermomechanical digestion associated therewith.

Experiments 2, 5 and 8:

Instead of the aqueous PVAc dispersion, the comparable dispersion of a copolymer of vinyl acetate (VAc) and vinyl laurate (VL) in a molar ratio VAc: VL of 50: 2.5 is now used. The syn- The synthetic polymer component contains the long-chain alkyl radicals of the vinyl laurate component as lateral substituents in a statistical distribution. At the same time, the biodegradability of this polymer is ensured biologically and thus its rotability.

Experiments 3, 6 and 9:

The synthetic polymer type used here for mixing with the starch and for its thermomechanical digestion corresponds to tests 2, 5 and 8, but with the modification that the molar ratio of VAc: VL is shifted to the numerical value of 47.8: 5.0.

In Table 1 below, test groups are summarized in terms of their mixture components in terms of their type and amount, each grouped into groups of three to three, four to six and seven to nine.

Table 1

Vers. Strength PVAc P (VAc-co-VL) P (VAc-co-VL) No. wt.% Wt.% VAc: VL = 50: 2.5 VAc: VL = 47.8: 5, 0

% By weight% by weight

1 40 18.3

2 40 - 18.3

3 40-18.3

4 40 20.4

5 40-20.4

6 40-20.4

7 36, 9 21, 2

8 36, 9-21.2

9 36, 9-21.2 Continuation of table 1

Vers.- urea glycerin water

No.% by weight% by weight% by weight

1 - 16.7 25

2 - 16.7 25

3 - 16.7 25

4 5.6 7.4 26.7

5 5.6 7.4 26.7

6 5.6 7.4 26.7

7 .11.5 3.9 26.5

8 11.5 3.9 26.5

9 11.5 3.9 26.5

In Table 2 below, experiment numbers 1 to 9 show the numerically calculated values for the ratios "starch: polymer" in parts by weight to the ratio of "starch: fat (in the sense of the definition according to the invention)" in parts by weight and "Fat content (in the sense of the definition according to the invention)" in the polymer in% by weight.

In the last column of Table 2 you can find the tensile strengths assigned to the respective test numbers in N / mm ² according to DIN 53455 (test speed 20 mm / min)

Table 2

Vers.- starch: polymer starch: "fat-

Polymer N / mm ²

Wt.

1 68.6 31.4 100 0 0 5.8

2 68.6 31.4 97.9 2.1 4.8 7.4

3 68.6 31.4 95.8 4.2 9.5 6.0

4 66.2 33.8 100 0 0 15.3

5 66.2 33.8 97.6 2.4 4.8 19.7

6 66.2 33.8 95.4 4.6 9.5 14.9

7 63.5 36.5 100 0 0 5.1

8 63.5 36.5 97.3 2.7 4.8 8.7

9 63.5 36.5 94.8 5.2 9.5 7.9

The optimization of the tensile strengths in test numbers 2, 5 and 8 results from the measured numerical values.

Example 2

There are 3 further lateral fat residues in the sense of the definition according to the invention containing synthetic polymer compounds - used as an aqueous dispersion - mixed with potato starch in different proportions and the thermomechanical starch digestion and homogenization in the extruder are carried out with the synthetic polymer used in each case.

The 3 polymer types examined are the following: Experiment No. 10, 11, 12:

A fat residue in the sense of the definition according to the invention containing polyurethane, commercial products "Fondoflex P202" from the applicant. The fat residues of this synthetic polymer based on PU are derived from rhicinoleic acid. For the clatrate formation with the starch, therefore, only C7 alkyl residues are available. Table 3 below shows the comparatively lowest strengths for this type of polymer, which can be explained by the lower tendency to form complexes. The proportion of steamed castor oil based on the PU melt (without water) is 12% by weight in the product used.

Experiment No. 13, 14, 15:

A Ciö / iß fatty alcohol is used here as a synthetic polymer component.

Methacrylate homopolymer used [M ^ = 166,000; M _n = 31,000).

Experiment No. 16, 17, 18:

The polymer component (acrylate polymer) is a poly (butyl-co-behenyl) acrylate with a molar ratio of butyl to behenyl acrylate of 4: 1 (MW = 74,000; Mn = 20,000)

The respective strength maxima are determined in test series with the 3 polymer types according to tests 10 to 18 - also determined here as tensile strength according to DIN 53455. In the following table 3, the weight ratios of starch: "fat" (in the sense of the definition according to the invention) "with the respective maximum strength of the test series.

Table 3

Vers. Polymer starch polymer starch "fat""fat" in strength No. wt.% Wt.% Polymer wt.% N / mm ²

10 89.2% 10.8% 98.6% 1.4% 7

11 PU 84.8% 15.2% 97.9% 2.1% 12.0 9

12 80.2% 19.8% 97.1% 2.9% 4

13 99.0% 1.0% 99.2% 0.8% 19

14 methacrylate 96.0% 4.0% 96.9% 3.1% 77.0% 23

15 93.0% 7.0% 94.5% 5.5% 10

16 98.3% 1.7% 99.4% 0.6% 11

17 Acrylate 93.3% 6.7% 97.6% 2.4% 35.0% 23

18 88.4% 11.6% 95.6% 4.4% 13

Claims

Expectations

1. Shapeable composite material based on thermomechanical with the addition of water and / or low molecular weight plasticizers digested starch (TPS) in a homogeneous mixture with synthetic polymer compounds (SPV), characterized in that to optimize its mechanical strength (determined by the tensile strength according to DIN 53455) synthetic polymer compounds with lateral and / or terminal straight-chain ^" and saturated hydrocarbon residues (fat residues) are homogenized in such proportions with the TPS that the content of the fat residues in the composite material (wt .-% fat residues based on anhydrous starch) in Range is 0.5 to 7 wt .-%.

2. Composite material according to claim 1, characterized in that the weight ratio of the fat residues to the starch is in the range from 1 to 5% by weight, preferably in the range from 2 to 4% by weight.

3. Composite material according to claims 1 and 2, characterized in that SPV with at least predominantly linear basic structure and seitenstän¬-term and optionally terminal fat residues are incorporated homogenized in the TPS.

4. Composite material according to claims 1 to 3, characterized in that the fat residues have chain lengths of at least 6 carbon atoms, preferably of at least 8 carbon atoms and in particular predominantly of at least 12 carbon atoms, the same and / or different chain lengths the fat residues can be present in the SPV material and are preferably each in the range from 6 to 32 C atoms, in particular in the range from 10 to 24 C atoms, for example in the range from 12 to 18 C atoms.

5. Composite material according to claims 1 to 4, characterized in that biodegradable or rotten SPV are processed with the TPS ho¬ mogen.

6. Composite material according to claims 1 to 5, characterized in that SPV containing lateral fat residues from the field of polyesters, polyamides, polyurethanes and / or polyvinyl alcohol esters, but optionally also polymer residues containing fat residues of the type of Poly (meth) acrylates, in admixture with the TPS.

7. Composite material according to claims 1 to 6, characterized in that the SPV are at least partially constructed on the basis of renewable raw materials.

8. Composite material according to claims 1 to 7, characterized in that its SPV content is derived from corresponding polymer dispersions which contain the polymer compounds as a disperse phase in an aqueous liquid phase and have been incorporated into the starch together with this aqueous phase.

9. Composite material according to claims 1 to 8, characterized in that it contains the starch in amounts of at least 40% by weight, preferably at least 50% by weight -% by weight here based on that of water and low-molecular plasticization free solid mixture.

10. Composite material according to claims 1 to 9, characterized in that it contains water and / or low molecular weight plasticizers in amounts of at least 3% by weight, preferably at least 5-10% by weight, based on the composite material.

11. Composite material according to claims 1 to 10, characterized in that it contains, as low molecular weight plasticizers, lower polyfunctional alcohols, in particular glycerol and / or their ethers, the proportion of which is preferably in the range from about 10 to 50% by weight, advantageously in the range from about 15 to 35% by weight, based in each case on the total mixture, can be.

12. Composite material according to claims 1 to 11, characterized in that it contains starches in the composite material of an average amylose content in the range below 30% by weight, preferably in the range of 15 to 25% by weight (based on starch dry substance) as the starch component , with potato starch or corresponding wheat and / or corn starch being preferred, but the use of starches with amylose contents of at least 50% by weight, for example 70 to 90% by weight, may also be preferred.

13. Use of the composite materials according to claims 1 to 12 for the manufacture of moldings, for example packaging materials such as foils, bottles, cups, boxes and the like.

14. A process for the production of polymer-modified materials based on TPS and the moldings obtained therefrom according to Claims 1 to 13, characterized in that native starch is mixed with the aqueous dispersions of the SPV and, if desired, other low-molecular plasticizers and / or water, which increase the multicomponent mixture Temperatures and pressures with simultaneous mixing and / or kneading are subjected to the starch digestion to form the TPS and, if desired, the homogenized polymer mixture is shaped.

15. The method according to claim 14, characterized in that with product temperatures above 100 ° C and preferably above 120 ° C, in particular in the range from about 120 to 150 ° C, at least in the final phases of the mixing and Starch digestion process works.

16. The method according to claims 14 and 15, characterized in that with residence times of the multicomponent mixture under working conditions in the range up to about 30 minutes, preferably in the range from about 0.5 to 10 minutes, and in particular in the continuous process and under which Process temperature in the system setting autoprints works.

17. The method according to claims 14 to 16, characterized in that mixing and digestion of the polymer components is carried out in heated extruders to which the starch - preferably as a starch powder - and the aqueous SPV dispersions and any other low molecular weight plasticizers used Feeders are expediently fed in separately from one another, while the homogenized and digested polymer mixture - if desired after a partial removal of excess water - is obtained as an extrudate.