WO2013124249A1

WO2013124249A1 - Method for producing blends of polyhydroxyalkanoates (pha) and thermoplastic polyurethanes (tpu)

Info

Publication number: WO2013124249A1
Application number: PCT/EP2013/053222
Authority: WO
Inventors: Klaus Hilmer; Kai BRÜNING; Rajan Hollmann
Original assignee: Basf Se; Basf Schweiz Ag
Priority date: 2012-02-21
Filing date: 2013-02-19
Publication date: 2013-08-29

Abstract

The invention relates to a method for producing blends of at least one polyhydroxyalkanoate (PHA) and at least one thermoplastic polyurethane (TPU) as main components. At least one diisocyanate or an isocyanate prepolymer, which has two isocyanate groups, or a mixture thereof is added during the production of the blend.

Description

Process for the preparation of blends of polyhydroxyalkanoates (PHA) and thermoplastic polyurethanes (TPU)

description

The invention relates to a process for the preparation of blends of polyhydroxyalkanoates (PHA) and thermoplastic polyurethanes (TPU), blends obtained in this way and the surface products and shaped articles produced from such blends. The polyhydroxyalkanoates (PHA) are thermoplastic polyesters which can be prepared by chemical synthesis, synthesized by microorganisms or plants and extracted therefrom.

Commercially available polyhydroxyalkanoates (PHA) are currently obtained primarily from microorganisms. These include, for example, the poly-3-hydroxybutyrate homopolymer or copolymer with e.g. low levels of 3-hydroxyvalerate. It is a very hard and brittle material with a modulus of elasticity (E) of approx. 3.5 GPa.

The property profiles of the polymers also show a certain range due to the commercial production in microorganisms and the resulting variability of the molecular weights and their distribution width.

For many applications of polyhydroxyalkanoates, however, one wishes for greater flexibility and ductility. This could in principle be achieved by increasing the comonomer content; However, this is associated with higher costs and lower heat resistance or lower melting point.

Polyurethanes and in particular thermoplastic polyurethanes have long been known and have found a diverse field of application. Thus, for example, polyurethanes are used in the shoe and automobile industry, for films, cable sheathing or in leisure articles, and in many different ways as a blend component.

For example, US Pat. No. 7,652,106 describes the preparation of blends of thermoplastic polyurethane (TPU) and polyhydroxybutyrate (PHB). The document discloses in addition to pure blends of TPU and PHB and those with plasticizers or inorganic fillers. This method has several disadvantages. First, there is no covalent attachment of the dispersed TPU phase to the continuous PHB phase. Second, the melting point of the TPU used must be as closely matched to the processing temperature of the PHB as possible to ensure melting and mixing by the TPU, without raising the melt temperature above the threshold of about 180 ° C, where the thermal decomposition of PHB used by intramolecular chain scission. The systems obtained in this way do not have a suitable property profile for all applications. On the one hand there are very brittle Polyhydroxyalkanoate, which are characterized by a high melting point. On the other hand, there are more ductile polyhydroxyalkanoates, which, however, then have significantly lower melting points. This often leads to moderate performance characteristics. It is therefore important for the polymer processor to be able to tailor the mechanical properties, in particular the modulus of elasticity and the ductility of the blends, precisely to the respective application.

It is an object of the present invention to provide blends of polyhydroxyalkanoates (PHA) and thermoplastic polyurethanes (TPU) which exhibit improved toughness with a reduction in brittleness, and also have increased elongation at break with sufficient strength. These properties are to be achieved without reducing the thermal stability. The blends should be particularly suitable for the production of surface products (thin films, plates, etc.), moldings and extruded semi-finished products (pipes, profiles, etc.).

In particular, a process was sought, with which the plastics processor could determine the property profile of the PHA formulation in the course of an upstream or integrated compounding process, i. a one-step process that can be optimally tuned to each end product without adversely affecting the PHA properties themselves. The compound adaptation should take place by the incorporation of a flexibilizer. The main challenge was to find an efficient compatibilization strategy or a compatibilizing concept for the two components, namely the PHA and the flexibilizer, which excludes delamination of the blend components under external stress and media effects and phase separation prevented in the course of glare processing or stressed component.

Such blends, consisting of PHA and a flexibilizer, should be distinguished in comparison to pure PHA by improved toughness, reduced brittleness and by increased elongation at break with comparable thermal stability. Compared to blends without flexibilizer, the covalent bonding of the PHA and TPU moieties should achieve improved mechanical properties.

In addition, they should have an increased notched impact strength and puncture resistance and, in addition, ensure better demoldability and shorter cycle times.

You should contact the usual plastic processing methods, such. B. extrusion, injection molding, blow molding, compression molding, rotational sintering and thermoforming to form semi-finished products and moldings.

The object is achieved according to the invention by a process for the preparation of blends from at least one polyhydroxyalkanoate (PHA) and at least one thermoplastic polymer. lyurethanen (TPU) as main components wherein in the preparation of the blend at least one diisocyanate or an isocyanate prepolymer having two isocyanate groups or a mixture thereof is added. At least one thermoplastic polyurethane (TPU) preferably has a higher melting point than at least one polyhydroxyalkanoate (PHA). Particularly preferably, the method for producing the blend comprises at least the following two steps A) and B).

Step A) Reaction of at least one thermoplastic polyurethane with at least one diisocyanate or an isocyanate prepolymer which has at least two isocyanate groups, or mixtures thereof, in the melt. This forms a thermoplastic polyurethane with an excess of isocyanate end groups. Preference is also given here to reduce the molecular weight of the thermoplastic polyurethane. Step B) introducing at least one polyhydroxyalkanoate into the melt of the product of step A) and reacting the product of step A) with the polyhydroxyalkanoate at a temperature below 190 ° C, more preferably below 185 ° C, and most preferably below 180 ° C , More preferably, the blend thus formed in a

Step C) cooled, wherein more preferably in steps A) to C) no polyols are added. The invention further provides blends consisting of at least one polyhydroxyalkanoate (PHA) and at least one thermoplastic polyurethane (TPU) which can be prepared by the abovementioned processes and furthermore contain reinforcing substances. Preferred reinforcing materials are a wide variety of fibers and / or needlelike or platelet-shaped minerals. In preferred embodiments, wollastonite, mica, talc, etc. are compounded. The PHA / TPU blends resulting from the inventive production process are two-phase materials in which the PHA is the continuous phase and the TPU is the disperse phase. Thermoplastic polyurethane (TPU) and polyhydroxyalkanoates (PHA) are addressed as main components in order to make it clear that the blends according to the invention can also contain the addition of customary auxiliaries and additives, such as reinforcing agents, dyes, stabilizers, etc. The amount of additive depends on the respective field of use and often also influences the mechanical properties of the blend.

A further subject of the invention is the use of the blends produced as described above for the production of surface products or shaped articles, including extruded semi-finished products. The invention also relates to films or molded articles from a corresponding ing blend, in which further preferred reinforcing materials are compounded, as well as surface products and molded articles produced therefrom, which also include semi-finished products.

Surprisingly, it has also been found that blends of at least one thermoplastic polyurethane (TPU) and at least one polyhydroxyalkanoate (PHA) having improved application properties can be prepared when a thermoplastic polyurethane is first treated with a diisocyanate, a prepolymer having at least two isocyanate groups, or a mixture thereof is reacted in the melt. This method is preferably used according to the invention whenever the melting temperature of at least one thermoplastic polyurethane (TPU) is higher than the decomposition temperature of at least one polyhydroxyalkanoate (PHA) present in the blend. It is preferable to reduce the molecular weight of at least one higher melting thermoplastic polyurethane (TPU), resulting in shorter fragments and thus more easily melting thermoplastic polyurethanes (TPU) as a product of step 1. At the same time, the at least one thermoplastic polyurethane (TPU) and / or its shorter chains (product of step 1) is replaced by isocyanate end groups.

An advantage of Isocyanatzugabe is that even the shorter TPU fragment that contains no isocyanate end groups by the addition of diisocyanate or the prepolymer can obtain a terminal isocyanate group with which this fragment can continue to react, especially with the PHA.

The preferably formed at least one shorter-chain thermoplastic polyurethane can then react with it after the introduction of the polyhydroxyalkanoate (PHA) and after its melting, with formation of covalent bonds with the isocyanate end groups. This results in an outstanding compatibilization of the two polymer phases, as well as an excellent morphology stability. By formulating the entire system and the type of process control, the property spectrum for the respective application can be adjusted specifically. The blends made in accordance with the present invention exhibit reduced brittleness over the non-blend polyhydroxyalkanoates (PHA), e.g. Poly-3-hydroxybutyrate or poly-4-hydroxybutyrate on. Toughness, elongation at break and impact strength are significantly increased. Compared to polyhydroxyalkanoates based on longer chain monomers such as e.g. Polyhydroxyhexanoate is achieved to increase the toughness, elongation at break and impact resistance without lowering the melting temperature. Therefore, the blends are advantageous in terms of temperature resistance.

FIG. 1 shows a preferred compounding process on a twin-screw extruder (IV), which is preferably of the Coperion ZSK 25 (L / D = 42) type from the manufacturer: Werner & Pfleiderer. TPU (I) is fed to the extruder (IV) with solid and / or liquid additives (II). In a preferred embodiment, the extruder (IV) has various temperature ranges 1 to 10, which are set in the ascending order to the following temperatures: 1: 170 ° C, 2: 190 ° C, 3: 190 ° C, 4: 190 ° C, 5: 190 ° C, 6: 170 ° C, 7: 170 ° C, 8: 170 ° C, 9: 170 ° C, 10: 170 ° C. loading Preferably, the PHA regrind (III) is fed to the extruder so that the temperature in the extruder is below 170 ° C. The compounded material (V) consisting of TPU and PHA is cooled by an air cooler (VI) before it is comminuted by a granulator (VII) into thermoplastic granules. The area of compounding (VIII) is in the region of the double arrow (VIII), the cooling takes place in the region of the double arrow (IX) and the granulation in the region of the double arrow (X).

An essential feature of the invention is that at least one thermoplastic polyurethane (TPU) is used as flexibilizers of the at least one polyhydroxyalkanoate (PHA), which in a reactive compounding process is linked via isocyanates with the at least one polyhydroxyalkanoate (PHA). The result is a two-phase material in which the PHA forms the continuous and the TPU the discontinuous or disperse phase. At least one polyhydroxyalkanoate (PHA) is covalently linked to at least one thermoplastic polyurethane (TPU).

Such a morphology is preferably obtained when the two main components PHA and TPU, which are added to 100 wt.%, Have the following mass ratios of TPU to PHA: 3 wt.% To 50 wt.%, More preferably 10 wt.% To 45 % By weight, more preferably from 20% by weight to 40% by weight, particularly preferably from 25% by weight to 35% by weight. The reactive blend process is preferably carried out in twin-screw extruders or in BUSS co-kneaders or in similar plastics processing units.

The process according to the invention for the preparation of PHA / TPU blends is preferably characterized by two, more preferably three process substeps, also designated as steps A, B, if appropriate C:

Step A) The first process step is the reaction of at least one thermoplastic polyurethane (TPU) with at least one diisocyanate or a prepolymer having at least two isocyanate end groups, or a mixture thereof. This preferably takes place in the melt, preference being given to

Molar mass of the thermoplastic polyurethane (TPU) is reduced. This product of step A has reactive isocyanate end groups.

A particularly suitable mixture consists of NCO-terminated polyesters as prepolymers and of bifunctional isocyanates (preferably MDI).

The reaction time in step A) is preferably 10 seconds to 100 seconds.

The proportion of isocyanate groups in the product of stage A) is from 0.1% by weight to 5% by weight, preferably from 0.3% by weight to 3% by weight, based on the total thermoplastic polyurethane (TPU). Step B) The second process step is the incorporation of a polyhydroxyalkanoate (PHA) in the melt of the product of process step A and the reaction of this product with the polyhydroxyalkanoate (PHA) at a temperature below the decomposition temperature of at least one preferably all polyhydroxyalkanoates (PHA) is.

The temperature is preferably kept at values in which no discoloration of the polyhydroxyalkanoate begins. However, the temperature should be well above the softening point of the polyhydroxyalkanoate and above the softening point of the product of step A). Preferably, an intensive mixing is carried out, as can be achieved for example with a reaction extruder.

Melting and softening point are determined according to European standard EN ISO 1 1357-1: 1997.

The temperature in preferred embodiments is less than 190 ° C, preferably less than 185 ° C, and more preferably less than 180 ° C. At the same time, the temperature in step B is at least 100.degree. C., more preferably at least 120.degree. C., and particularly preferably at least 140.degree. C., particularly preferably at a temperature in the range from 160.degree. C. to 175.degree.

The compatibilization of the two polymer components is carried out by linking the chain fragments formed in process step A also addressed as products of step A, with the respective one OH end-capping polyhydroxyalkanoates (PHA).

The PHA reacts with the isocyanate groups, resulting in covalent bonds in the blend. As a result, an increase in molecular weight is achieved, which in turn improves the properties. The reaction in step B) is preferably carried out within a period of 10 seconds to 180 seconds.

After the reaction, the resulting blend is cooled and granulated, for example, brought directly into shape or brought into a suitable form for further processing.

Step C) The third process substep comprises the shaping, preferably granulation, and / or the cooling of the PHA / TPU blend as the reaction product of steps A and B. In the process according to the invention, no polyols are added in steps A) to C), so that it does not come to a structure of a TPU of polyol and diisocyanate. It is furthermore preferred that in the process according to the invention the total water content in the blend is less than 1% by weight. This is based on the total blend containing all components, so in addition to the main components and the minor components such as fibers, auxiliaries and additives. Particularly preferably, the total water content is between 0.1% by weight and 0.5% by weight. The feed components are therefore preferably selected and the production conditions selected so that this water content in the production is not exceeded, since otherwise unwanted blistering occurs.

In embodiments in which a foam is to be produced, higher amounts of water are processed depending on the degree of foaming.

In the process according to the invention, suitable ratios of polyhydroxyalkanoate to thermoplastic polyurethane can be adjusted. The proportion of polyhydroxyalkanoate in the mixture of stage B) is preferably 50% by weight to 97% by weight, particularly preferably 60% by weight to 92% by weight, more preferably 65% by weight to 85% by weight. % based on the material used for the main blend components TPU and PHA.

In step A), any suitable amounts of at least one diisocyanate or at least one diisocyanate prepolymer having at least two isocyanate groups, or mixtures thereof, are introduced into the thermoplastic polyurethane. The proportion of diisocyanate, prepolymer or mixture thereof is preferably from 1% by weight to 25% by weight, particularly preferably from 1% by weight to 10% by weight, based on the product of stage A). Granules or comparable products are preferably prepared by the process according to the invention, which are processed with a further melting step to final or application products. For the production of these granules, the functionality, i. the mathematically determined proportion of analytically determined isocyanate content based on one mole of the isocyanate groups per molecule between 1, 9 and 2.1, preferably between 1, 95 and 2.05 particularly preferably at 2. If in the process according to the invention directly produced end products, so the functionality may also be higher in order to achieve higher cross-linking depending on the desired material property.

As diisocyanates or for the preparation of corresponding diisocyanate prepolymers, the iso-eyanates which are listed below for the enumerated in the production of thermoplastic polyurethane are used. Preferred isocyanates are 2,2'-, 2,4'- and / or 4,4'-diphenylmethanediisocyanate (MDI), 1-isocyanato-4 - [(4-isocyanatocyclohexyl) methyl] cyclohexane

(H12MDI), 1, 5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-tolylene diisocyanate (TDI).

If prepolymers are used, these are preferably NCO-terminated polyethers or polyesters, as described further below for the preparation of thermoplastic polyurethanes and are preferably based on MDI, H12MDI, HDI, NDI and / or TDI.

A particularly preferred mixture consists of prepolymers which are NCO-terminated polyethers, and bifunctional isocyanates, preferably MDI. The reactions in stages A), B) and optionally C) can be carried out continuously or batchwise.

Preferred is a continuous process, which is in particular a reaction extrusion. The process is carried out in an extruder, preferably in a twin-screw extruder, wherein the thermoplastic polyurethane and the diisocyanate, isocyanate prepolymer or mixture thereof are added at the inlet of the extruder while the polyhydroxyalkanoate is added downstream. By using the reaction extrusion, a favorable space-time production of the desired blend takes place.

Any suitable thermoplastic polyurethanes (TPU) which are generally obtainable from at least one diisocyanate, at least one polyol and frequently also at least one isocyanate-reactive chain extender may be used in the process according to the invention.

Thermoplastic polyurethanes TPU are understood to mean polyurethanes which are heat-softenable in a certain temperature range and solidify on cooling and repeatedly in the softened state by casting, injection molding, extrusion, blow molding, pressing and rotational sintering into semifinished products, films or molded parts, etc . are malleable. The TPUs are multiple block copolymers; these have hard and soft segments within a molecule. In a preferred embodiment, the proportion of hard phase in the total TPU is preferably 15 wt .-% to 65 wt .-%, in aliphatic TPU in particular 40 wt .-% to 65 wt .-%.

According to the invention, the preparation of the thermoplastic polyurethanes by reacting diisocyanates, which are also referred to as component a) with polydiols and optionally other isocyanate-reactive compounds, which is also referred to as component b), and chain extenders, which are also used as component c) are addressed, optionally in the presence of catalysts, which are also addressed as component d), and / or conventional excipients and / or additives, which are also addressed as component e). The components a), b), c) and optionally d) and / or e) usually used in the preparation of the polyurethanes are described below by way of example:

As organic isocyanates, component a), it is possible to use generally known aromatic, aliphatic, cycloaliphatic and / or araliphatic isocyanates, preferably diisocyanates, more preferably 2,2'-, 2,4'- and / or 4,4'-diphenylmethane diisocyanate (cf. MDI), 1,5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-tolylene diisocyanate (TDI), diphenylmethane diisocyanate, 3,3'-dimethyl-diphenyl-diisocyanate, 1, 2-diphenylethane-diisocyanate and / or Phenylene diisocyanate, tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methyl-pentamethylene diisocyanate-1, 5, 2-ethyl-butylene-diisocyanate-1, 4, pentamethylene diisocyanate-1 , 5, butylene-diisocyanate-1, 4, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate, IPDI), 1-isocyanato-4 - [(4-isocyanatocyclohexyl) me- methyl] cyclohexane (H12MDI), 2,6-diisocyanatohexanecarboxylic acid ester, 1,4- and / or 1,3-bis (isocyanatomethyl) cyclohexane (HXDI), 1,4-cyclohexane diisocyanate, 1-methyl-2,4- and or -2,6-cyclohexane diisocyanate and / or 4,4'-, 2,4'- and 2,2'-dicyclohexylmethane diisocyanate, preferably 2,2'-, 2,4'- and / or 4 , 4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-tolylene diisocyanate (TDI), hexamethylene diisocyanate, 1-isocyanato-4 - [(4-isocyanatocyclohexyl) methyl] cyclohexane, and / or IPDI.

Particularly preferred isocyanates are aliphatic isocyanates, more preferably hexamethylene endiisocyanate (HDI), 2,2'-, 2,4'- and / or 4,4'-diphenylmethane diisocyanate (MDI) and in particular 1-isocyanato-4 - [( 4-isocyanatocyclohexyl) methyl] cyclohexane (H 12MDI).

As isocyanate-reactive compounds, component b), it is possible to use the generally known isocyanate-reactive compounds, for example polyesterols, polyetherols and / or polycarbonatediols, which are usually also termed "polyols", with molecular weights (Mn), preferably by number. ren molecular weights between 500 g / mol and 8000 g / mol, preferably 600 g / mol to 6000 g / mol, in particular 800 g / mol to less than 3000 g / mol, and preferably an average functionality to isocyanates of 1, 8 to 2 , 3, preferably 1, 9 to 2.2, in particular 2.

The number average molecular weight is determined according to DIN 55672-1. Polyether polyols are preferably used as component b), for example those based on generally known starter substances and customary alkylene oxides, preferably ethylene oxide, propylene oxide and / or butylene oxide, more preferably polyetherols based on propylene oxide 1, 2 and ethylene oxide and in particular polyoxytetramethylene glycols. The advantage of the polyether polyols is u. a. in the higher hydrolytic stability.

Furthermore, it is possible to use as polyetherols preferably so-called low-unsaturated polyetherols. In the context of this invention, low-unsaturated polyols are understood as meaning, in particular, polyether alcohols having a content of unsaturated compounds of less than 0.02 meq / g, preferably less than 0.01 meq / g. Such polyether alcohols are usually prepared by addition of alkylene oxides, in particular ethylene oxide, propylene oxide and mixtures thereof, to the above-described diols or triols in the presence of highly active catalysts.

Such highly active catalysts are preferably cesium hydroxide and multimetal cyanide catalysts, also referred to as DMC catalysts. A common and preferred used

DMC catalyst is the zinc hexacyanocobaltate. The DMC catalyst can be used after conversion. tion are left in the polyether alcohol, it is usually removed, for example by sedimentation or filtration.

Instead of a polyol, it is also possible to use mixtures of different polyols as component b). The thermoplastic polyurethane according to the invention is particularly preferably based on polytetrahydrofuran having a molecular weight (Mn), preferably the number average molecular weight, between 600 g / mol and 2000 g / mol, preferably 800 g / mol and 1400 g / mol, particularly preferably 950 g / mol and 1050 g / mol as component b). As chain extenders, component c, it is possible to use generally known aliphatic, aliphatic, aromatic and / or cycloaliphatic compounds having a molecular weight, preferably average molecular weight, of from 50 g / mol to 499 g / mol, preferably 2-functional compounds. Preference is given, for example, to alkanediols having 2 to 10 C atoms in the alkylene radical, preferably butanediol-1, 4, hexanediol-1, 6 and / or di-, tri-, tetra-, penta-, hexa-, hepta-, octa -, Nona- and / or Dekaalkylenglykole having 3 to 8 carbon atoms, more preferably unbranched alkanediols, in particular propane-1, 3-diol and butane-1, 4-diol.

Suitable catalysts, component d), which in particular accelerate the reaction between the NCO groups of the diisocyanates, component a) and component b) are known and customary in the prior art tertiary amines, such as. For example, preferred triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N, N'-dimethylpiperazine, 2- (dimethylaminoethoxy) ethanol, diazabicyclo- (2,2,2) octane and the like and in particular organic metal compounds such as titanic acid esters, iron compounds such. For example, ferric (III) acetylacetonate, tin compounds, e.g. For example, preferably tin diacetate, tin dioctoate, tin dilaurate or the Zinndialkylsalze aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate or the like. The catalysts are usually used in amounts of 0.00001 parts by weight to 0.1 parts by weight per 100 parts by weight of polyhydroxyl compound, component b). In addition to catalysts, component d), customary additives and / or auxiliaries, component e) may also be added to the synthesis components a) to c) and or to the blend according to the invention. Mention may be made, for example, blowing agents, surface-active substances, flame retardants, nucleating agents, lubricants and mold release agents, dyes and pigments, stabilizers, for. As preferred against hydrolysis, light, heat or discoloration, inorganic and / or organic fillers, plasticizers and metal deactivators. As hydrolysis protective agents it is preferred to use oligomeric and / or polymeric aliphatic or aromatic carbodiimides.

Particular preference is given to TPUs based on hydrogenated MDI and at least one polyetherol having a maximum fraction of 25% by weight, preferably not more than 10% by weight, of aromatics and conjugated π-electron systems, based on the thermoplastic material - lyurethan including optionally present additives, in particular TPU excluding aromatic compounds.

The preparation of the TPU can be carried out batchwise or continuously, for example with reaction extruders or the strip process according to one-shot or the prepolymer process, preferably by the one-shot process, according to the known processes. In these processes, the components a), b) and optionally c), d) and / or e) coming into reaction can be mixed together successively or simultaneously with the reaction starting immediately. In the extruder process, the synthesis components a), b) and, if appropriate, the further components c), d) and / or e) are introduced into the extruder individually or as a mixture, for. B. preferably at temperatures of 100 to 280 ° C, more preferably reacted at 140 ° C to 250 ° C for the reaction, the resulting polyurethane is then extruded, cooled and granulated. To optimize the TPU, the polyol component, component b), and chain extender, component c) can be varied. In a preferred embodiment, a weight ratio of polyol, component b) to total chain extenders to be used, component c) from 20 to 2, in particular from 8 to 3 is set. The reaction of the isocyanate, component a) with the isocyanate-reactive components b) and optionally c) is carried out in a preferred embodiment at a ratio between 950 and 1050, particularly preferably between 970 and 1010, in particular between 980 and 1000 Code defined by the ratio of the total isocyanate groups used in the reaction of component a) to the isocyanate-reactive groups, ie in particular the groups of components b) and c). With a ratio of 1000, an isocyanate group of component a) has an active hydrogen atom. For ratios above 1000, more isocyanate groups exist than OH groups.

In order to stabilize the polyurethanes and blends made therefrom against aging, it is possible to add stabilizers to the polyurethane which are also mentioned as auxiliaries. Stabilizers in the context of the present invention are additives which protect a plastic or a plastic mixture against harmful environmental influences. Examples are primary and secondary antioxidants, thiosynergists, trivalent phosphorus organophosphorus compounds, hindered amine light stabilizers, UV absorbers, hydrolysis inhibitors, quenchers and flame retardants.

Further details on the above-mentioned auxiliary substances and additives can be found in the specialist literature, for. B. from Plastics Additive Handbook, 5th edition, H. Zweifel, ed., Hanser Publishers, Munich, 2001.

In a preferred embodiment, at least one thermoplastic polyurethane (TPU) is used which has no aromatic groups. In other preferred embodiments Forms at least one thermoplastic polyurethane (TPU) is used with aromatic groups, preferably aromatic isocyanates. Both variants can be used individually or in combination. In another preferred embodiment, the polyol olbasis of the TPU is non-aromatic and can be based on renewable raw materials.

In another preferred embodiment, the dicarboxylic acid and / or the diol of the polyester diol and / or the chain extender are of non-fossil origin, i. they are produced and isolated by plants and / or microorganisms. By reacting with the isocyanate or isocyanate prepolymer, the molecular weight of the TPU is reduced to proper processability. The number average molecular weight is preferably immediately before the reaction with the PHA 7.500 g / mol to

75,000 g / mol.

The invention also relates to a blend which can be prepared by the method described above.

The blends according to the invention can be used for any suitable applications. They are used in particular for the production of films (surface products) or moldings.

Very thin films are accessible from the blends according to the invention, so that good biodegradability can be achieved when using appropriate monomers. This can be advantageous, in particular, for garbage bags, plant bags, agricultural or mulch films, etc.

As polyhydroxyalkanoate, it is possible according to the invention to use all suitable polyhydroxyalkanoates, as known from the specialist literature, e.g. Madison & Huisman, Microbiology and Molecular Biology Reviews 63 (1): 21-53 and Sudesh et al., Prog. Polym. Be. 25: 1503-1555.

Preferred polyhydroxyalkanoates are poly (6) -hydroxyhexanoate, poly (3) -hydroxyvalerate, poly (3) -hydroxybutyrate, poly (4) -hydroxybutyrate in the form of homopolymers and / or their copolymers and / or mixtures. Poly (3) hydroxybutyrate is particularly preferred as homopolymer and / or copolymer or mixture of poly (6) -hydroxyhexanoate, poly (3) -hydroxyvalerate, poly (4) -hydroxybutyrate.

When the polyhydroxyalkanoates are made microbiologically they are often not pure homopolymers. Rather, the polyhydroxyalkanoates isolated from microorganisms or plants are present as copolymers and / or mixtures. For individual applications, the pure PHA may have advantages, for further applications the mixtures or blends are more advantageous. The blends of the invention, which are usually present as granules, can be processed by the customary injection molding and extrusion methods. The blends which can be prepared by the process of the invention are used in applications as films (surface products), preferably for the production of coatings, bellows, moldings, building and transportation floors, cables, cable plugs, cable sheathing, cushions, laminates, non-woven fabrics, gaskets, profiles, Belts, rollers, saddles, foams, hoses, shoe soles, trailing cables, solar modules, cladding in automobiles, wiper blades or fibers have the advantages presented above. Shaping into moldings / parts and semifinished products can also be carried out in direct connection with the compounding step in the form of a one-step process, eg. B. with an injection molding compounder (IMC). Further preferred production methods are calendering, powder sintering, or extrusion.

Corresponding fiber-reinforced compounds consist of the blends and fibers described.

This further advantageous property profiles can be displayed. Direct shaping (one-stage process) of the fiber-reinforced blend requires no additional processing step which damages the material and is therefore preferred. Preferred fibers are glass fibers, natural fibers (flax, hemp, cotton, sisal, bamboo, kenaf, as well as cellulose fibers, etc.). The proportion in the blend is preferably more than 1 wt .-% to 50 wt .-%, more preferably 5 wt .-% to 30 wt .-% based on the blend constituents polyhydroxyalkanoate (PHA) and thermoplastic polyurethane (TPU).

Examples:

The invention is further illustrated by the following examples. Individual components used in the Examples described below are designated Component Ki, where the letter "i" is a placeholder for a number.

Component K1: TPU1 Elastollan ^® B 85 A 15 (BASF Polyurethanes GmbH)

Aromatic polyester TPU based on butanediol adipate with a number average molecular weight 2.4 kg / mol, 1, 4-butanediol and methyl-di-phenyl-di-isocyanate. Contains hydrolysis protection and processing aids in usual concentrations. The pelletized TPU is injection molded into test plates and punched out of them. The following characteristics are measured on these test specimens. Table 1: Properties Elastollan ^® B 85 A 15

The test plates were sprayed from granules with less than 0.02% water content. The test plates were annealed at 100 ° C for 20 hours. The specimens were punched from 2 mm ^* or 6 mm ^** test plates. The test was carried out at 23 ± 2 ° C and 50 ± 6% rel. Humidity carried out. Example 2

Component K2: Polyhydroxyalkanoate 1 (PHA1)

The selected poly-3-hydroxybutyrate-co-hydroxyvalerate (PHBV) has been prepared by fermentation of Ralstonia eutropha on C5 and C6 sugars and subsequent purification of the polymer from the bacterial cells. The selected polyhydroxyalkanoate is characterized by the following properties:

Table 2: Properties PHBV

Example 3:

Component K3: Prepolymerl

Lupranat® ^® MP102; Prepolymer based on ^{4,4'-diphenylmethane} diisocyanate (MDI), dipropylene glycol, and a polyether based on ethylene oxide / propylene oxide having molecular weight 450 g / mol. The prepolymer can be metered in liquid at room temperature.

NCO content: 23.0%

Viscosity at 25 ° C 650 mPa ^* s according to DIN 53018

Density at 25 ° C 1, 21 according to DIN 51757

Example 4:

Compounding process 1 for generating the PHA / TPU blends according to the invention.

The PHA / TPU blends prepared and characterized in Examples 1 to 3 were generated by means of a co-rotating twin-screw extruder, type Coperion ZSK 25-L / D = 40, manufacturer: Werner & Pfleiderer. The compounding was performed on all Aufberei- processing procedures = operated 5.0 kg / h with a screw speed of n = 100 ^min-1 and a total mass flow rate of m. The temperature program along the extruder axis can also be taken from FIG. The cylinder temperatures set for zones 1 to 10 are: 180 °, 200 °, 200 °, 200 °, 200 °, 180 °, 180 °, 180 °, 180 °, 180 ° C. In the feed opening of the twin-screw extruder, the respective TPU type (K1 or K2 or K3) and the respective additive (K6) or the modified MDI (K5) are gravimetrically metered. brought in. In the extruder zones 2 to 5, the TPU modification takes place. The PHA granulate (K4) is metered into the feed opening of zone 6. In the subsequent zones, PHA plasticization, intensive component mixing and the coupling reaction to the covalent phase linkage occur. The emerging compound strands are cooled and then granulated.

Example 5

Test Specimens

Tension rods according to DIN-EN-ISO 527-2 and test specimens for determining the notch impact strength according to DIN-EN-ISO 179-1 were produced in a mold by injection molding. For this purpose, a screw-piston injection molding machine type Arburg 220 M 350-90 was available. The machine and process parameters are as follows:

- maximum closing force = 220 kN

- screw geometry: D = 20 mm, L / D = 25 (three-zone screw)

Flight depth ratio 2: 1

- Temperature profile Arburg 220M; constant 180 ° C

Tool temperature 30 ° C

Example 6 Test procedure

All tensile tests were carried out in accordance with DIN 53 504 at a test speed of 20 mm / min.

The test specimen for determining the notched impact strength has the following dimensions:

Example 7

Characterization of Blend 1:

PHA1 with TPU1 prepared by method 1. The base component ratio is 70% PHA1 and 30% TPU1. Tab. 3 contains the determined mechanical characteristics. Table 3: Mechanical characteristics of the PHA1 / TPU1 blends

Example 8

Characterization of Blend 2:

PHA1 with TPU1 with the addition of 5% prepolymer (K3) prepared according to method 1. The base component ratio is 70% PHA1 and 30% TPU1. Tab. 4 contains the determined mechanical characteristics. Table 4: Mechanical characteristics of the PHA1 / TPU1 blends with 5% prepolymer

Example 9 Tables 2 to 4 show the increase in tensile strength, elongation at break and elongation at break

Notched impact strength with simultaneous improvement of the Vicat softening temperature clearly. Furthermore, there is an improved property profile with the addition of the prepolymer 1 in the blend process. The task is completely solved.

Claims

claims

1 . A process for the preparation of blends of at least one polyhydroxyalkanoate (PHA) and at least one thermoplastic polyurethane (TPU) as main components, characterized in that at least one diisocyanate or an isocyanate prepolymer having two isocyanate groups, or a Mixture thereof is added.

2. The method according to claim 1, characterized in that at least one thermoplastic polyurethane (TPU) has a higher melting point than at least one polyhydroxyalkanoate (PHA).

3. The method according to any one of the preceding claims, characterized in that the blend is prepared in the following steps:

A) reacting the at least one thermoplastic polyurethane with the at least one diisocyanate or the isocyanate prepolymer having two isocyanate groups, or a mixture thereof, in the melt, B) introducing at least one polyhydroxyalkanoate (PHA) into the melt of the product of step A. ) and reaction of the product of step A) with the polyhydroxyalkanoate (PHA).

4. Method according to the preceding claim, characterized in that the

Step B) is carried out below the decomposition temperature of the polyhydroxyalkanoate (PHA).

5. The method according to any one of the preceding claims, characterized in that the water content in the blend is less than 0.1 wt.%.

6. The method according to any one of the preceding claims, characterized in that in any of the steps polyol is added.

7. The method according to any one of the preceding claims, characterized in that the proportion of polyhydroxyalkanoate (PHA) in the mixture of step B) 50 wt .-% to

97 wt .-% is.

8. The method according to any one of the preceding claims, characterized in that in

Step A), based on the product of step A), 1 wt .-% to 25 wt .-% of the diisocyanate or the isocyanate prepolymer having at least 2 isocyanate groups, or a mixture thereof are introduced.

9. The method according to any one of the preceding claims, characterized in that the proportion of isocyanate groups in the product of step A) 0.1 wt .-% to 5 wt .-%, preferably 0.3 wt .-% to 3 wt. % is.

10. The method according to any one of the preceding claims, characterized in that the reaction is carried out continuously as reaction extrusion in an extruder, wherein the thermoplastic polyurethane and the diisocyanate or the isocyanate prepolymer having at least two isocyanate groups, or a mixture thereof in the input zone are added to the extruder and the polyhydroxyalkanoate is added in a downstream zone of the extruder.

1 1. Blend of at least one polyhydroxyalkanoate (PHA) and at least one thermoplastic polyurethane (TPU), characterized in that it can be produced by a process according to one of the preceding claims.

12. blend according to claim 1 1, characterized in that it additionally contains fibers.

13. Use of a blend according to claim 1 1 or 12 for the production of surface products or moldings.

14. Surface products or molded articles produced from a blend according to claim 11

or 12.