DE102004045619A1 - Thermoplastic polyurethanes containing polytetrahydrofuran - Google Patents

Abstract

Thermoplastic polyurethanes based on polytetrahydrofuran, wherein the polytetrahydrofuran is a mixture (i) having a number average molecular weight between 1200 g / mol and 1500 g / mol and wherein in the mixture, the weight fraction of polytetrahydrofurans having a degree of polymerization of less than or equal to 14 greater than 21 wt .-%, based on the total weight of the polytetrahydrofurans contained in the mixture, and in the mixture, the weight fraction of polytetrahydrofurans having a degree of polymerization greater than 40 is less than 40 wt .-%, based on the total weight of the mixture contained in the mixture polytetrahydrofurans.

Description

The The invention relates to thermoplastic polyurethanes on the Base of polytetrahydrofuran, preferably obtainable by reaction of (a) isocyanate versus (b) Isocyanate-reactive compounds having a molecular weight of 500g / mol to 10000g / mol, and optionally (c) chain extenders with a molecular weight of 50g / mol to 499g / mol optionally in the presence of (d) catalysts and / or (e) conventional excipients, wherein as (b) the polytetrahydrofuran of the invention is used. Furthermore For example, the invention relates to methods of making these transparent, soft thermoplastic polyurethanes.

thermoplastic Polyurethanes, also referred to below as TPUs, are plastics with a diverse one Of applications. For example, TPU can be found in the automotive industry, e.g. in dashboard skins, in films, in cable sheathing, in the leisure industry, as Heel stains, as a functional and design element in sports shoes, as a soft component in hard soft combinations and in a variety of other Applications.

Usually TPU have a degree of hardness from 80 Shore A to 74 Shore D up. Many of the above applications but require a degree of hardness below the 80 shore A. For this reason, it is state of the art, to add plasticizer to TPU, which lowered the Shore hardness can be. examples for common Plasticizers are benzoates, phthalates and phosphoric acid esters.

at the choice of plasticizer is preferred to ensure that the product is compatible with the TPU is. Compatible means in this context that the plasticizer during the for the TPU Production usual Procedure must mix the TPU and that the plasticizer subsequently while the whole time possible remains in the product and is not lost by exudation or evaporation goes. In addition, the mechanical properties of the TPU, e.g. the abrasion and the elastomeric properties are not getting worse.

Lots Plasticized TPUs are used in applications that also absorb sunlight are exposed, e.g. Design elements of the shoe industry. Here is it is disadvantageous if the plasticizer causes yellowing of the product contributes by UV degradation.

As well Many plasticized TPUs are exposed to environmental influences in their application, which lead to a hydrolytic Molmassenabbau. Accordingly, it is problematic if the plasticizer also enhances the hydrolysis, be it catalytically or by decomposition products of the plasticizer, e.g. by Hydrolysis of the plasticizer, e.g. Carboxylic acids the hydrolysis of an ester group-containing plasticizer.

But even if the plasticizer all the applications previously described Fulfills, this still leaves the danger of plasticizer migration out of the plasticized TPU into a medium that is softened with TPU is in contact. For seals made of plasticized TPU for fuel tanks can it be e.g. come to the migration of the plasticizer in the fuel. this leads to to an embrittlement of Poetry. Likewise, it can be a migration in food applications of the plasticizer come into the food. Plasticized TPU's are therefore generally not for Food applications suitable.

polytetrahydrofurans (Also referred to in this document as PTHF) are polyols, which by cationic polymerization can be prepared from tetrahydrofuran. Due to the production mechanism, the PTHFs are generally a low molecular weight distribution. At a PTHF 1000 lies the polydispersity, the a measure of the molecular weight distribution represents, usually 1.5. The distribution is monomodal, i. the molecular weight distribution has a maximum.

EP 1342740 A1 describes a TPU consisting of a low molecular weight polyol and a "low monool polypropyleneglykol polyol" with molecular weight 2000-12000 with at least 60% proportion of Gesamtpolylol.

The object of the present invention was therefore a soft thermoplastic polyure than to develop, which has a Shore hardness less than or equal to 80 A, more preferably between 40 A and 70 A. The soft TPU should have no migration of a plasticizer from the TPU and if possible have a very good stability to weathering. In addition, the TPU should preferably be transparent.

These Tasks could be based on thermoplastic polyurethanes of polytetrahydrofuran dissolved wherein the polytetrahydrofuran is a mixture (i) with a number average molecular weight between 1200 g / mol and 1500 g / mol and wherein in the mixture of the weight fraction of polytetrahydrofurans with a degree of polymerization of less than or equal to 14 greater than 21 wt .-%, preferably greater than 26 wt .-%, more preferably greater than 26 wt .-% and less than 40 Wt .-%, in particular greater than 26 wt .-% and less than 34 wt .-%, each based on the total weight the polytetrahydrofurans contained in the mixture, and in the Mixture of the weight fraction of polytetrahydrofurans with a degree of polymerization smaller than 40 as 40 wt .-%, preferably less than 32 wt .-%, particularly preferably less than 32% by weight and greater than 10% by weight, especially less than 32% by weight and greater than 25% by weight, respectively based on the total weight of polytetrahydrofurans contained in the mixture.

Under the term degree of polymerization is to be understood as many tetrahydrofurans in the polytetrahydrofuran. The degree of polymerization can be calculate from the molecular weight of the polymer chain, i. of polytetrahydrofuran divided by the molecular weight of the monomeric building block, i. of Tetrahydrofuran (degree of polymerization P = molecular weight polymer chain / Molecular weight of the individual building block). The term "degree of polymerization" is known to those skilled in the art common and clearly defined, in particular in the "Römpp Chemie Lexikon", Georg Thieme Verlag, 9th edition, 1992. According to the invention of Degree of polymerization for the single macromolecule used.

The Reaction product of the isocyanates (a) with the chain extenders (c) forms in a thermoplastic polyurethane the so-called Hard segment while the reaction product of the isocyanate (a) with the higher molecular weight Diols (b) the so-called soft segment of the thermoplastic polyurethane represents. For adjusting the hardness the TPU can the structural components (b) and (c) in relatively broad molar ratios be varied. For example, the molar ratio of (b) and (c) between a molar ratio of 1: 1, respectively a soft Shore hardness TPU 80 A and 1: 5.6, corresponding to a hard Shore hardness 75 D TPU, vary. Is the molar amount of (c) at a constant molar Quantity of (b) further reduced, thus reducing the hardness of TPU also continues. However, a ratio of (b) to (c) becomes clear greater than 1 selected, see above there is a hindrance to the crystallization of the hard segments. The crystallization of the TPU occurs so slowly that the cycle times for the Processing of the thermoplastic polyurethane uneconomical be long. At the same time, the TPU loses its desired thermal and mechanical properties.

By the increase the molar mass of the polyol (b) can be further reduced by the amount of (c), without the minimum ratio of (b) to (c) of approx. 1: 1 is shifted significantly. From a molecular weight of polytetrahydrofuran, Also referred to in this document as PTHF, from about 1500 g / mol it comes however, to an effect commonly known as the mother-of-pearl effect is. Hard segments of the TPU then crystallize due to their incompatibility with the soft phase and the TPU receives a nacreous non-transparent Appearance, in many cases undesirable is. In addition leads an increase the molecular weight of the soft phase polyol often to crystallization the soft phase at temperatures around the freezing point. This soft phase crystallization is undesirable, because the flexibility the TPU decreases with onset of soft phase crystallization, the Shore hardness on the other hand increases.

These negative effects of increase The molecular weight of the PTHF could by the use of the mixture according to the invention containing PTHFs of different molecular weight avoided be without the desired Lowering the hardness to dispense with the TPU.

By the use of the PTHF with the molecular weight distribution according to the invention remained the TPU despite increase the number average molecular weight of the polyol is transparent. It did not come to the above described mother-of-pearl effect. Surprisingly, showed the TPU also contains the different molecular weight PTHF no hard phase crystallization. This gives good low temperature properties ensured.

The thermoplastic according to the invention Polyurethanes preferably have a Shore hardness between 40 A and 75 A. on. Preference is given to the thermoplastic polyurethanes according to the invention transparent.

Polytetrahydrofuran is well known and available in various molecular weights from BASF Ak company commercially available. Essential to the invention is the use of polytetrahydrofurans with the molecular weight distribution according to the invention. It is preferred if the polytetrahydrofuran mixture (i) based on the mixture of at least two, preferably separately prepared Polytetrahydrofuranchargen. By the expression "at least two polytatrahydrofuran charges" it is meant that two different polytetrahydrofurans are used, which have different mean molecular weight data.Particularly preferred is if at least two of the separately prepared polytetrahydrofuran charges are at least 500 g / mol, preferably at least 800 g / mol of different number average molecular weight.

Especially preferred is when a Polytetrahydrofurancharge a number average Molecular weight between 900 g / mol and 1100 g / mol and another Polytetrahydrofurancharge a number average molecular weight between 1900 g / mol and 2100 g / mol.

to Adjustment of hardness the TPU can the synthesis components (b) and (c) are preferably in molar ratios of component (b) to total chain extenders to be used (c) between 1: 0.35 and 1: 2.0, preferably between 1: 0.50 and 1: 1, 5, in particular between 1: 0.7 and 1: 1.1 are used.

method for the production of TPU are well known. For example, the thermoplastic polyurethanes by reacting (a) isocyanates with (b) opposite Isocyanate-reactive compounds having a molecular weight of 500 to 10,000 and optionally (c) chain extenders having a molecular weight from 50 to 499, optionally in the presence of (d) catalysts and / or (e) usual Be prepared excipients.

According to the invention the production of thermoplastic polyurethanes thus by Reaction of (a) isocyanates with (b) isocyanate-reactive compounds with a molecular weight of 500g / mol to 10000g / mol, preferred 500 g / mol to 4000 g / mol and optionally (c) chain extenders with a molecular weight of 50g / mol to 499g / mol optionally in the presence of (d) catalysts and / or (e) conventional excipients, wherein one as opposite Isocyanate-reactive compound (b) a polytetrahydrofuran mixture used with a number average molecular weight between 1200 g / mol and 1500 g / mol and wherein in the mixture of the weight fraction the polytetrahydrofurans having a degree of polymerization of smaller or equal to 14 greater than 21 wt .-%, preferably greater than 26 wt .-%, more preferably greater than 26 wt .-% and less than 40 Wt .-%, in particular greater than 26 wt .-% and less than 34 wt .-%, each based on the total weight the polytetrahydrofurans contained in the mixture, and in the Mixture of the weight fraction of polytetrahydrofurans with a degree of polymerization smaller than 40 as 40 wt .-%, preferably less than 32 wt .-%, particularly preferably less than 32% by weight and greater than 10% by weight, especially less than 32% by weight and greater than 25% by weight, respectively based on the total weight of polytetrahydrofurans contained in the mixture.

Especially Preference is given to the Polytetrahydrofuranmischungen shown above containing the at least two batches.

• a) Als organische Isocyanate (a) können allgemein bekannte aromatische, aliphatische, cycloaliphatische und/oder araliphatische Isocyanate, bevorzugt Diisocyanate eingesetzt werden, beispielsweise 2,2'-, 2,4'- und/oder 4,4'-Diphenylmethandüsocyanat (MDI), 1,5-Naphthylendiisocyanat (NDI), 2,4- und/oder 2,6-Toluylendiisocyanat (TDI), Diphenylmethandiisocyanat, 3,3'-Dimethyl-diphenyldiisocyanat, 1,2-Diphenylethandiisocyanat und/oder Phenylendiisocyanat, Tri-, Tetra-, Penta-, Hexa-, Hepta- und/oder Oktamethylendiisocyanat, 2-Methylpentamethylen-diisocyanat-1,5, 2-Ethyl-butylen-diisocyanat-1,4, Pentamethylen-diisocyanat-1,5, Butylen-diisocyanat-1,4, 1-Isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexan (Isophoron-diisocyanat, IPDI), 1,4- und/oder 1,3-Bis(isocyanatomethyl)cyclohexan (HXDI), 1,4-Cyclohexan-diisocyanat, 1-Methyl-2,4- und/oder -2,6-cyclohexan-diisocyanat und/oder 4,4'-, 2,4'- und 2,2'-Dicyclohexylmethan-diisocyanat, bevorzugt 2,2'-, 2,4'- und/oder 4,4'-Diphenylmethandiisocyanat (MDI), 1,5-Naphthylendiisocyanat (NDI), 2,4- und/oder 2,6-Toluylendiisocyanat (TDI), Hexamethylendiisocyanat und/oder IPDI, insbesondere 4,4'- MDI und/oder Hexamethylendiisocyanat.
• b) Als gegenüber Isocyanaten reaktive Verbindungen (b) werden die eingangs dargestellten Polytetrahydrofuran eingesetzt. Gegebenenfalls können zusätzlich weitere allgemein bekannten gegenüber Isocyanaten reaktiven Verbindungen eingesetzt werden, beispielsweise Polyesterole, Polyetherole und/oder Polycarbonatdiole, die üblicherweise auch unter dem Begriff "Polyole" zusammengefasst werden, mit Molekulargewichten von 500 bis 12000 g/mol, bevorzugt 600 bis 6000, insbesondere 800 bis 4000, und bevorzugt einer mittleren Funktionalität von 1,8 bis 2,3, bevorzugt 1,9 bis 2,2, insbesondere 2. Bevorzugt setzt man ausschließlich die erfindungsgemäßen PTHFs als gegenüber Isocyanaten reaktive Verbindungen (b) mit Molekulargewichten von 500 bis 12000 g/mol ein.
• c) Als Kettenverlängerungsmittel (c) können allgemein bekannte aliphatische, araliphatische, aromatische und/oder cycloaliphatische Verbindungen mit einem Molekulargewicht von 50 bis 499, bevorzugt 2-funktionelle Verbindungen, eingesetzt werden, beispielsweise Diamine und/oder Alkandiole mit 2 bis 10 C-Atomen im Alkylenrest, insbesondere Butandiol-1,4, Hexandiol-1,6 und/oder Di-, Tri-, Tetra-, Penta-, Hexa-, Hepta-, Okta-, Nona- und/oder Dekaalkylenglykole mit 3 bis 8 Kohlenstoffatomen, bevorzugt entsprechende Oligo- und/oder Polypropylenglykole, wobei auch Mischungen der Kettenverlängerer eingesetzt werden können.
• d) Geeignete Katalysatoren, welche insbesondere die Reaktion zwischen den NCO-Gruppen der Diisocyanate (a) und den Hydroxylgruppen der Aufbaukomponenten (b) und (c) beschleunigen, sind die nach dem Stand der Technik bekannten und üblichen tertiären Amine, wie z.B. Triethylamin, Dimethylcyclohexylamin, N-Methylmorpholin, N,N'-Dimethylpiperazin, 2-(Dimethylaminoethoxy)-ethanol, Diazabicyclo-(2,2,2)-octan und ähnliche sowie insbesondere organische Metallverbindungen wie Titansäureester, Eisenverbindungen wie z.B. Eisen-(III)-acetylacetonat, Zinnverbindungen, z.B. Zinndiaeetat, Zinndioctoat, Zinndilaurat oder die Zinndialkylsalze aliphatischer Carbonsäuren wie Dibutylzinndiacetat, Dibutylzinndilaurat oder ähnliche. Die Katalysatoren werden üblicherweise in Mengen von 0,00001 bis 0,1 Gew.-Teilen pro 100 Gew.-Teile Polyhydroxylverbindung (b) eingesetzt.
• e) Neben Katalysatoren (d) können den Aufbaukomponenten (a) bis (c) auch übliche Hilfsmittel (e) hinzugefügt werden. Genannt seien beispielsweise oberflächenaktive Substanzen, Füllstoffe, Flammschutzmittel, Keimbildungsmittel, Oxi dationsstabilisatoren, Gleit- und Entformungshilfen, Farbstoffe und Pigmente, gegebenenfalls zusätzlich zu den erfindungsgemäßen Stabilisatoren weitere Stabilisatoren, z.B. gegen Hydrolyse, Licht, Hitze oder Verfärbung, anorganische und/oder organische Füllstoffe, Verstärkungsmittel und Weichmacher. Als Hydrolyseschutzmittel werden bevorzugt oligomere und/oder polymere aliphatische oder aromatische Carbodiimide verwendet. Um die erfindungsgemäßen TPU gegen Alterung zu stabilisieren, werden dem TPU bevorzugt Stabilisatoren zugegeben. Stabilisatoren im Sinne der vorliegenden Erfindung sind Additive, die einen Kunststoff oder eine Kunststoffmischung gegen schädliche Umwelteinflüsse schützen. Beispiele sind primäre und sekundäre Antioxidantien, Hindered Amine Light Stabilizer, UV-Absorber, Hydrolyseschutzmittel, Quencher und Flammschutzmittel. Beispiele für kommerzielle Stabilisatoren sind gegeben in Plastics Additive Handbook, 5th Edition, H. Zweifel, ed., Hanser Publishers, München, 2001 ([1]), S. 98-S. 136. Ist das erfindungsgemäße TPU während seiner Anwendung thermoxidativer Schädigung ausgesetzt, können Antioxidantien zugegeben werden. Bevorzugt werden phenolische Antioxidantien verwendet. Beispiele für phenolische Antioxidantien sind gegeben in Plastics Additive Handbook, 5th edition, H. Zweifel, ed, Hanser Publishers, München, 2001, S. 98-107 und S. 116-S. 121. Bevorzugt sind solche phenolische Antioxidantien, deren Molekulargewicht größer als 700 g/mol sind. Ein Beispiel für ein bevorzugt verwendetes phenolisches Antioxidans ist Pentaerythrityl-tetrakis (3-(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)propionate) (Irganox^® 1010). Die phenolischen Antioxidantien werden im allgemeinen in Konzentrationen zwischen 0,1 und 5 Gew.-% eingesetzt, bevorzugt zwischen 0,1 und 2 Gew.-%, insbesondere zwischen 0,5 und 1,5 Gew.-%, jeweils bezogen auf das Gesamtgewicht des TPU. Auch wenn die erfindungsgemäße TPU aufgrund ihrer bevorzugten Zusammensetzung deutlich stabiler gegen ultravioletter Strahlung sind als z.B. mit Phthalaten oder Benzoaten weichgemachte TPU, so ist eine Stabilisierung enthaltend nur phenolische Stabilisatoren oft nicht ausreichend. Aus diesem Grund werden die erfindungsgemäßen TPUs, die UV-Licht ausgesetzt werden, bevorzugt zusätzlich mit einem UV-Absorber stabilisiert. UV-Absorber sind Moleküle, die energiereiches UV-Licht absorbieren und die Energie dissipieren. Gängige UV-Absorber, welche in der Technik Verwendung finden, gehören z.B. zur Gruppe der Zimtsäureester, der Diphenylcyanacrylate, der Formamidine, der Benzylidenemalonate, der Diarylbutadiene, Triazine sowie der Benzotriazole.. Beispiele für kommerzielle UV-Absorber finden sich in Plastics Additive Handbook, 5th edition, H. Zweifel, ed, Hanser Publishers, München, 2001, Seite 116-122. In einer bevorzugten Ausführungsform weisen die UV-Absorber ein zahlenmittleres Molekulargewicht von größer als 300 g/mol, insbesondere größer als 390 g/mol, auf. Ferner sollten die bevorzugt verwendeten UV-Absorber ein Molekulargewicht von nicht größer als 5000 g/mol, besonders bevorzugt von nicht größer als 2000 g/mol aufweisen. Besonders geeignet als UV-Absorber ist die Gruppe der Benzotriazole. Beispiele für besonders geeignete Benzotriazole sind Tinuvin^® 213, Tinuvin^® 328, Tinuvin^® 571, sowie Tinuvin^® 384 und das Eversorb^® 82. Bevorzugt werden die UV-Absorber in Mengen zwischen 0,01 und 5 Gew.-%, bezogen auf die Gesamtmasse TPU zudosiert, besonders bevorzugt zwischen 0,1 und 2,0 Gew.-%, insbesondere zwischen 0,2 und 0,5 Gew.-%, jeweils bezogen auf das Gesamtgewicht des TPU. Oft ist eine oben beschriebene UV-Stabilisierung basierend auf einem Antioxidant und einem UV-Absorber noch nicht ausreichend, um eine gute Stabilität des erfindungsgemäßen TPU gegen den schädlichen Einfluss von UV-Strahlen zu gewährleisten. In diesem Falle kann zu der Komponente (e) bevorzugt zusätzlich zu dem Antioxidans und dem UV-Absorber, noch ein Hindered-Amine Light Stabiizer (HALS) zu dem erfindungsgemäßen TPU zugegeben werden. Die Aktivität der HALS-Verbindungen beruht auf ihrer Fähigkeit, Nitroxylradikale zu bilden, die in den Mechanismus der Oxidation von Polymeren eingreift. HALS gelten als hocheffiziente UV-Stabilisatoren für die meisten Polymere. HALS-Verbindungen sind allgemein bekannt und kommerziell erhältlich. Beispiele für kommerziell erhältliche HALS-Stabilisatoren finden sich in Plastics Additive Handbook, 5th edition, H. Zweifel, Hanser Publishers, München, 2001, S. 123-136. Als Hindered Amine Light Stabilizer werden bevorzugt Hindered Amine Light Stabilizer genommen, bei denen das zahlenmittlere Molekulargewicht größer als 500 g/mol sind. Ferner sollte das Molekulargewicht der bevorzugten HALS-Verbindungen bevorzugt nicht größer als 10000 g/mol, besonders bevorzugt nicht größer als 5000 g/mol sein. Besonders bevorzugte Hindered Amine Light Stabilizer sind bis-(1,2,2,6,6-pentamethylpiperidyl) sebacat (Tinuvin^® 765, Ciba Spezialitätenchemie AG) und , das Kondensationsprodukt aus 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid (Tinuvin^® 622). Insbesondere bevorzugt ist das Kondensationsprodukt aus 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid (Tinuvin^® 622), wenn der Titangehalt des Produktes < 150 ppm, bevorzugt < 50 ppm insbesondere bevorzugt < 10 ppm ist. HALS Verbindungen werden bevorzugt in einer Konzentration zwischen 0,01 und 5 Gew.-% eingesetzt, besonders bevorzugt zwischen 0,1 und 1 Gew.-%, insbesondere zwischen 0,15 und 0,3 Gew.-%, jeweils bezogen auf das Gesamtgewicht des TPU. Eine besonders bevorzugte UV Stabilisierung enthält eine Mischung aus einem phenolischen Stabilisator, einem Benzotriazol und einer HALS-Verbindung in den oben beschriebenen bevorzugten Mengen.

The thermoplastic polyurethane can be processed thermoplastically, without losing the effect of the plasticizer according to the invention. In the following, by way of example, the starting components and methods for producing the preferred TPU are shown. The components (a), (b), (c) and optionally (d) and / or (e) usually used in the preparation of the TPU are to be described by way of example below:

• a) As organic isocyanates (a) it is possible to use generally known aromatic, aliphatic, cycloaliphatic and / or araliphatic isocyanates, preferably diisocyanates, for example 2,2'-, 2,4'- and / or 4,4'-diphenylmethane diisocyanate (MDI ), 1,5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-toluene diisocyanate (TDI), diphenylmethane diisocyanate, 3,3'-dimethyl-diphenyl diisocyanate, 1,2-diphenylethane diisocyanate and / or phenylene diisocyanate, triisocyanate , Tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methylpentamethylene-diisocyanate-1,5, 2-ethyl-butylene-diisocyanate-1,4, pentamethylene-diisocyanate-1,5, butylene-diisocyanate 1, 4, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 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'-Diphenylmethandiis ocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-tolylene diisocyanate (TDI), hexamethylene diisocyanate and / or IPDI, in particular 4,4'-MDI and / or hexamethylene diisocyanate.
• b) As isocyanate-reactive compounds (b) are the Polytetrahy used drofuran. Optionally, other generally known isocyanate-reactive compounds may also be used, for example polyesterols, polyetherols and / or polycarbonatediols, which are usually also grouped under the term "polyols", with molecular weights of 500 to 12,000 g / mol, preferably 600 to 6,000, in particular 800 to 4000, and preferably an average functionality of 1.8 to 2.3, preferably 1.9 to 2.2, in particular 2. It is preferable to use exclusively the PTHFs of the invention as isocyanate-reactive compounds (b) having molecular weights of from 500 to 12000 g / mol.
• c) As chain extenders (c) it is possible to use generally known aliphatic, araliphatic, aromatic and / or cycloaliphatic compounds having a molecular weight of 50 to 499, preferably 2-functional compounds, for example diamines and / or alkanediols having 2 to 10 carbon atoms in the alkylene radical, in particular 1,4-butanediol, 1,6-hexanediol and / or di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- and / or decaalkylene glycols having 3 to 8 carbon atoms , Preferred corresponding oligo- and / or polypropylene glycols, wherein mixtures of the chain extenders can be used.
• d) Suitable catalysts which in particular accelerate the reaction between the NCO groups of the diisocyanates (a) and the hydroxyl groups of the synthesis components (b) and (c) are the tertiary amines known and customary in the prior art, such as, for example, 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 as iron (III) acetylacetonate, tin compounds, eg Zinndiaeetat, Zinndioctoat, tin dilaurate or Zinndialkylsalze aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate or the like. The catalysts are usually used in amounts of 0.00001 to 0.1 parts by weight per 100 parts by weight of polyhydroxyl compound (b).
• e) In addition to catalysts (d) can the constitutional components (a) to (c) and conventional auxiliaries (e) are added. Mention may be made, for example, of surface-active substances, fillers, flameproofing agents, nucleating agents, oxidation stabilizers, lubricants and mold release agents, dyes and pigments, optionally in addition to the stabilizers according to the invention further stabilizers, for example against hydrolysis, light, heat or discoloration, inorganic and / or organic fillers, Reinforcing agents and plasticizers. As hydrolysis protective agents it is preferred to use oligomeric and / or polymeric aliphatic or aromatic carbodiimides. In order to stabilize the TPU according to the invention against aging, stabilizers are preferably added to the TPU. 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, hindered amine light stabilizers, UV absorbers, hydrolysis protectors, quenchers and flame retardants. Examples of commercial stabilizers are given in Plastics Additive Handbook, 5th Edition, H. Zweifel, ed., Hanser Publishers, Munich, 2001 ([1]), p. 98-S. 136. If the TPU according to the invention is exposed to thermo-oxidative damage during its application, antioxidants may be added. Preferably, phenolic antioxidants are used. Examples of phenolic antioxidants are given in Plastics Additive Handbook, 5th edition, H. Zweifel, ed, Hanser Publishers, Munich, 2001, pp. 98-107 and pp. 116-S. 121. Preference is given to those phenolic antioxidants whose molecular weight is greater than 700 g / mol. An example of a preferably used phenolic antioxidant is pentaerythrityl-tetrakis (3- (3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl) propionate) (Irganox ^® 1010). The phenolic antioxidants are generally used in concentrations between 0.1 and 5 wt .-%, preferably between 0.1 and 2 wt .-%, in particular between 0.5 and 1.5 wt .-%, each based on the Total weight of the TPU. Even though the TPUs according to the invention are significantly more stable to ultraviolet radiation than, for example, TPUs softened with phthalates or benzoates, stabilization containing only phenolic stabilizers is often insufficient. For this reason, the TPUs according to the invention which are exposed to UV light are preferably additionally stabilized with a UV absorber. UV absorbers are molecules that absorb high-energy UV light and dissipate the energy. Common UV absorbers which are used in the art include, for example, the group of cinnamic acid esters, diphenylcyanoacrylates, formamidines, benzylidenemalonates, diarylbutadienes, triazines and benzotriazoles. Examples of commercial UV absorbers can be found in Plastics Additive Handbook, 5th edition, H. Zweifel, ed, Hanser Publishers, Munich, 2001, pages 116-122. In a preferred embodiment, the UV absorbers have a number average molecular weight of greater than 300 g / mol, in particular greater than 390 g / mol. Furthermore, the UV absorbers preferably used should have a molecular weight of not greater than 5000 g / mol, particularly preferably not greater than 2000 g / mol. Particularly suitable as UV absorber is the group of benzotriazoles. Examples of particularly suitable benzotriazoles are Tinuvin ^® 213, Tinuvin ^® 328, Tinuvin ^® 571 and Tinuvin ^® 384 and the Eversorb ^® 82. Preferably, the UV absorber in amounts between 0.01 and 5 wt .-%, based on Total weight TPU metered, more preferably between 0.1 and 2.0 wt .-%, in particular between 0.2 and 0.5 wt .-%, each based on the total weight of the TPU. Often a UV stabilization described above is basis rend on an antioxidant and a UV absorber is not sufficient to ensure good stability of the TPU according to the invention against the harmful influence of UV rays. In this case, to the component (e) preferably in addition to the antioxidant and the UV absorber, nor a Hindered Amine Light Stabilizer (HALS) may be added to the TPU according to the invention. The activity of the HALS compounds is based on their ability to form nitroxyl radicals, which interfere with the mechanism of the oxidation of polymers. HALS are considered to be highly efficient UV stabilizers for most polymers. HALS compounds are well known and commercially available. Examples of commercially available HALS stabilizers can be found in Plastics Additive Handbook, 5th edition, H. Zweifel, Hanser Publishers, Munich, 2001, pp. 123-136. Hindered Amine Light Stabilizers are preferably Hindered Amine Light Stabilizers in which the number average molecular weight is greater than 500 g / mol. Furthermore, the molecular weight of the preferred HALS compounds should preferably not be greater than 10,000 g / mol, more preferably not greater than 5,000 g / mol. Particularly preferred hindered amine light stabilizers are bis (1,2,2,6,6-pentamethylpiperidyl) sebacate (Tinuvin ^® 765, Ciba Specialty Chemicals Inc.), and the condensation product of 1-hydroxyethyl-2,2,6,6-tetramethyl -4-hydroxypiperidines and succinic acid (Tinuvin ^® 622). Particularly preferred is the condensation product of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidines and succinic acid (Tinuvin ^® 622) when the titanium content of the product ppm <150, preferably <50 ppm more preferably <10 ppm is. HALS compounds are preferably used in a concentration between 0.01 and 5 wt .-%, more preferably between 0.1 and 1 wt .-%, in particular between 0.15 and 0.3 wt .-%, each based on the Total weight of the TPU. A particularly preferred UV stabilization comprises a mixture of a phenolic stabilizer, a benzotriazole and a HALS compound in the preferred amounts described above.

More details about the The auxiliaries and additives mentioned above are the specialist literature see, e.g. from Plastics Additive Handbook, 5th edition, H. Zweifel, ed, Hanser Publishers, Munich, 2001. All in this The molecular weights stated have the unit [g / mol].

The Implementation can be at usual Key figures are given, preferably with a key figure between 950 and 1050, particularly preferred for a ratio between 970 and 1010, especially between 980 and 995. The key figure is defined by The relationship the total amount of isocyanate groups used in the reaction Component (a) to the opposite Isocyanate-reactive groups, i. the active hydrogens, the Components (b) and (c). With a key figure of 1000 comes to one Isocyanate group of component (a) an active hydrogen atom, i.e. one opposite Isocyanate-reactive function of components (b) and (c). at Key figures about 1000 are more isocyanate groups than OH groups. The production The TPU can be continuously, for example, according to the known methods with reaction extruders or the tape method after one-shot or the prepolymer process, or discontinuously according to the known prepolymer process respectively. In these methods can the components (a), (b) and, if appropriate, reacting (c), (d) and / or (e) successively or simultaneously with one another are mixed, the reaction starts immediately. At the Extruder processes are the structural components (a), (b) and optionally (c), (d) and / or (e) introduced individually or as a mixture into the extruder, e.g. at temperatures of 100 to 280 ° C, preferably 140 to 250 ° C The resulting TPU is extruded, cooled and granulated.

The Processing of the TPU according to the invention containing the plasticizers according to the invention, the usual as granules or in powder form, to the desired Films, molded parts, rolls, fibers, linings in automobiles, hoses, Cable plugs, bellows, Towing cables, cable sheathing, seals, belts or damping elements takes place according to usual Methods, e.g. Injection molding or extrusion. The according to the inventive method producible thermoplastic polyurethanes, preferably the films, Molded parts, soles, castors, fibers, linings in automobiles, Wiper blades, hoses, cable connectors, bellows, Tow cables, cable sheathing, seals, belts or damping elements have the advantages presented at the beginning.

example 1

1000 g of a polyol mixture consisting of PTHF 1000 (BASF Aktiengesellschaft) and PTHF 2000 (BASF Aktiengesellschaft) in a weight ratio of 1: 1 and 65.86 g of 1,4-butanediol were weighed into a 2 l tinplate bucket and heated to 90.degree. 1098 and 0.5 wt .-% Irganox ^® 1010 and 2.5 ppm was then heated with stirring 0.5 wt .-% Irganox ^® tin dioctoate were added. After heating the solution again to 90 ° C., 369 g of 4,4'-MDI (methylene diphenyl diisocyanate) were added and the mixture was stirred, until the solution was homogeneous. Subsequently, the reaction mass was poured into a shallow dish and annealed at 125 ° C on a hot plate for 10 min. Thereafter, the resulting rind was tempered in a heating cabinet for 24 h at 100 ° C. After granulating the casting plates, they were processed on an injection molding machine into 2 mm spray plates. The product had a Shore hardness of Shore 72 A.

Example 2

In a 2-L tinplate bucket 1000 of a polyol mixture consisting been g 150 g of PTHF 1000 (BASF Aktiengesellschaft) and 850g Lupranol ^® 1000 (BASF Aktiengesellschaft) and 66.37 g of 1,4-butanediol were weighed and heated to 90 ° C. 1098 and 0.5 wt .-% Irganox ^® 1010 and 5.0 ppm was then heated with stirring 0.5 wt .-% Irganox ^® tin dioctoate were added. After subsequent heating of the solution to 90 ° C again 326g 4,4'-MDI (Methylendiphenyldiisocyanat) were added and stirred until the solution was homogeneous. Subsequently, the reaction mass was poured into a shallow dish and annealed at 125 ° C on a hot plate for 10 min. Thereafter, the resulting rind was tempered in a heating cabinet for 24 h at 100 ° C. The plate did not harden. The product could not be granulated.

Of the Comparison of Examples 1 and 2 shows that it is advantageous to have a Mixture of two PTHF of different molecular weight too make and that a mixture of a PTHF and a polypropylene glycol no processable products results.

Example 3

to Measurement of opacity a TPU plate was using an UltraScan colorimeter the Company HunterLab determines the L value. This was the TPU plate once against a white one Tile and one against a light trap in reflection under exclusion of the gloss measured. The measured brightness values (L values after DIN 6174) were then in the ratio set and as opacity in%.

Example 4

Various ether TPU were prepared according to Example 1 and processed into injection plates. The recipe components of the individual products are shown in Table 1. Moreover, all the products contained 0.5 wt .-% Irganox ^® 1010 and 0.5 wt .-% Irganox ^® 1098. Table 1:

The samples were then sprayed into 2 mm test plates and mechanically tested. The test results are shown in Table 2. Table 2:

comparing one try 4.2 with 4.1, so the advantage of using a Polyols with high molecular weight significantly. The product of trial 4.2 shows significantly better mechanical properties than the comparative experiment.

comparing one experiment 4.2 with experiment 4.3, so the advantage of using a polyol mixture according to the invention compared to the use of a PTHF 2000 clearly. While the Sample 4.2 has a very low opacity, Sample 4.3 is opaque.

DSC measurements

Samples from experiment 4 were analyzed for their melting properties by DSC. The reduction of the hard segment content leads to a decrease of the melting points at constant polyol molecular weight (Tm (max) = highest measured melting temperature, Tm (peak) = temperature with maximum heat flux)). By using the inventive mixture of polyol this negative effect is traced back ( see 4.1 vs. 4.2). In comparison to the use of a higher molecular weight PTHF, the PTHF mixture according to the invention shows no soft phase crystallization. This becomes clear when comparing 4.2 and 4.3 Table 3

Example 5

Two ether TPU were prepared according to Example 1 and processed into injection plates. The recipe components of the individual products are shown in Table 4. Moreover, all the products contained 0.5 wt .-% Irganox ^® 1010 and 0.5 wt .-% Irganox ^® 1098. Table 4

DSC measurements

The samples from experiment 5 were analyzed for their melting properties by DSC. In comparison with the use of a monomodal higher molecular weight PTHF (Example 5.2), the PTHF mixture (5.1) according to the invention exhibits a higher melting temperature. This becomes clear when comparing Tm (peak) and Tm (max). Table 5

Claims (9)

Thermoplastic polyurethanes based on polytetrahydrofuran, characterized in that the polytetrahydrofuran is a mixture (i) having a number average molecular weight between 1200 g / mol and 1500 g / mol and wherein in the mixture, the weight fraction of polytetrahydrofurans having a degree of polymerization of less than or equal to 14 is greater than 21 wt .-%, based on the total weight of the polytetrahydrofurans contained in the mixture, and in the mixture, the weight fraction of polytetrahydrofurans having a degree of polymerization greater than 40 is less than 40 wt .-%, based on the total weight of in the mixture contained polytetrahydrofurans. Thermoplastic polyurethanes according to claim 1 obtainable by Reaction of (a) isocyanate with (b) isocyanate-reactive compounds having a molecular weight of from 500 g / mol to 10,000 g / mol and optionally (c) chain extenders with a molecular weight of 50 g / mol to 499 g / mol optionally in the presence of (d) catalysts and / or (e) conventional excipients in that (b) a polytetrahydrofuran mixture is used is with a number average molecular weight between 1200 g / mol and 1500 g / mol and wherein in the mixture of the weight fraction of Polytetrahydrofurans with a degree of polymerization of less or equal to 14 greater than 21 wt .-%, based on the total weight of the mixture contained polytetrahydrofurans, and in the mixture of the weight fraction the polytetrahydrofurans having a degree of polymerization greater than 40 smaller than 40% by weight, based on the total weight of the mixture in the mixture contained polytetrahydrofurans. Thermoplastic polyurethanes according to claim 1, characterized in that that the thermoplastic polyurethane has a Shore hardness between 40A and 75A. Thermoplastic polyurethanes according to claim 1, characterized in that that the thermoplastic polyurethane is transparent. Thermoplastic polyurethane according to claim 1, characterized in that that the polytetrahydrofuran mixture (i) on the mixture at least two separately prepared Polytetrahydrofuranchargen based. Thermoplastic polyurethane according to claim 5, characterized in that that at least two of the separately prepared Polytetrahydrofuranchargen at least 500 g / mol, preferably at least 800 g / mol of each other have different number average molecular weight. Thermoplastic polyurethane according to claim 5, characterized in that a polytetrahydrofuruanarge has a number average molecular weight between 900 g / mol and 1100 g / mol and another Polytetrahydrofurancharge a number average molecular weight between 1900 g / mol and 2100 g / mol. Process for the preparation of thermoplastic polyurethanes by reacting (a) isocyanates with (b) towards isocyanates reactive compounds having a molecular weight of 500 g / mol to 10,000 g / mol and optionally (c) chain extenders with a molecular weight of 50 g / mol to 499 g / mol optionally in the presence of (d) catalysts and / or (e) conventional excipients characterized in that as the isocyanate-reactive compound (b) using a polytetrahydrofuran mixture having a number average Molecular weight between 1200 g / mol and 1500 g / mol and where in the mixture of the weight fraction of polytetrahydrofurans with a Degree of polymerization of less than or equal to 14 greater than 21 wt .-%, based on the total weight of the mixture contained polytetrahydrofurans, and in the mixture of the weight fraction the polytetrahydrofurans having a degree of polymerization greater than 40 smaller than 40% by weight, based on the total weight of the mixture in the mixture contained polytetrahydrofurans. Method according to claim 8, characterized in that a polytetrahydrofuran mixture (i) according to one the claims 5, 6 and / or 7 begins.