DD289279A5 - PROCESS FOR PREPARING HYDROPHILIC PUR ELASTOMERS - Google Patents

Abstract

The invention relates to a process for the preparation of hydrophilic polyurethane elastomers, which are suitable for applications in the field of PUR synthetic leather, in biology and medicine as well as for processing PUR films as membrane materials for mass transfer and separation processes. According to the invention, new polyurethane systems having good physico-mechanical properties are obtained from a, v-OH-functional * of the general formula * with n130 and m125, chain extenders and diisocyanates. {PUR elastomers; * Diisocyanate; chain; Wasserkettenverlaengerung; Membrane material}

Description

The process of the invention is characterized in that it proceeds without phase separation during the reaction. The present invention as the starting material serving α, ω-OH-functional Ollgotetramethylenoxid-1,3,6-trioxocane-diols can be obtained by reacting α, ω-Tetrahydrofurandlole having an average molecular weight of 300-2 OOOg / mol and a functionality> 1 , 8 in a ratio of 1: 1 to 10: 1 with ISe trioxocancopolymerized such that they are first mixed well with about the tenth to twentieth part of the total amount of the 1,3,6-trioxocane at temperatures between 30 and 50 ° C, by Gintragen from 0.05 to 0.1 mol of a protonic or low acid as initiator per mol of OH groups introduced the block copolymer formation within 5 to 30 minutes, then quickly added dropwise the residual monomer so that the actual monomer concentration at the reaction centers approaching remains constant, and after 15 to 60 minutes alkali hydroxide solution is added to the neutral point.

Suitable chain extenders are the compounds customary in polyurethane chemistry. Preferably, the use of 1,4-butanediol. As Diisoyanat preferably diphenylmethane diisocyanate is used. To determine the excess of water, the NCO equivalent is determined after the prepolymer formation process step. The water content of the aqueous dimethylformamide solution is determined so that, based on the determined NCO equivalent, an excess of 100 to 200%. The amount of solvent is chosen so that the solids content of the solution is between 10 and 20%. The PUR solutions obtained according to the invention can then be further processed according to their field of application without their properties changing over time. The advantage of this procedure is that the molecular weights of the polyurethanes are precisely controlled, reproducible viscosities of the PU solutions are obtained, the use of water-containing solvents is possible, crosslinking reactions are largely avoided and the last synthesis step can be carried out at room temperature.

From the PUR solution obtained in accordance with the invention, it is possible to prepare clear gel particle-free sheet-like polyurethanes. In them, the hydrophilic and hydrophobic properties of the individual polyol components are combined to form a polyurethane with good physico-mechanical properties. They have a good stress-strain behavior, whereby the elongation of the PTHF / TO-PUR pattern exceeds both the We ¹ Ie of the oligotetrahydrofurandiol PUR and the Homo-TO-PUR produced pattern, and are distinguished by a high gas permeation (in particular O ₂ ).

embodiments example 1

First, 97.5 g (OH equivalent 801.65) blocks of iodol based on Oligotetrahydrofuran with a Moimasse of 1000g / mol and 1,3,6-trioxocane in the ratio T ^ iOH «2: 1 and 2.5g (OH Equivalent 45.06) of 1,4-butanediol. This mixture is added via a dropping funnel to 44.285 g of molten diphenylmethane diisocyanate (NCO equivalent of 125) at a NCO / OH ratio of 2: 1. The conversion to the pre-adduct runs over several hours. The NCO equivalent weight of 840 is determined by titration. 40 g of the preadduct are dissolved in 100 ml of DMF and further 100 ml of DMF, which were previously provided with 0.86 ml (200% equivalent) of water added. When mixed at room temperature and stored for at least 24 hours, a PUR solution having a solids content of 20% is obtained. Property of the PUR solution

- Viscosity at 20 "C in Pas 2600 Properties of PUR

Tensile strength in N / mm ² 16.66

- Elongation at break 945.7%

- Water absorption in% "5.9

- water vapor permeability

in mg dm " ² (24 h) 307

Example 2

97.5 g of a PTHF / TO block codiol based on polytetrahydrofuran having a molecular weight of 1OCOg / mol and 1,3,6-trioxocane (TO: OH = 7: 1) having an OH equivalent of 1270 are given as 2.5 g 1,4-butanediol mixed and added via a dropping funnel to 33.05 g Diphenylmethandiisocyant. The NCO / OH ratio is 2: 1. The titration of the NCO equivalent weight after several hours gave a value of 922.40 g of the preadduct thus prepared are dissolved in 100 ml of DMF and another 200 ml of DMF added with 0.4485 ml (150% equivalent) of water are added. The PUR solution has a solids content of 15% after appropriate storage.

Property of the PUR solution

- Viscosity at 20 ⁰ C in Pas 2200 Properties of PUR

Tensile strength in N / mm ² 14.3

- Elongation at break in% 1010

- Water absorption in% 7.1

- Water permeability

in mg dm " ² (24 h) 334

Comparison of the physico-mechanical values of the PTHF / TO-PUR with those of the PTHF-PUR and Homo-TO-PUR (Neumann, Rübner in Piasto and Kautschuk 33/4 [1986])

PTHF / TO PUn PTHF PUR Homo-TO-PUR Recipe in equivalents 1,4-butanediol 0,025 1 - FTHF _ 1 _ Homo-TO - _ 1 PTHF / TO 0,975 _ _ MDI · 2 2 1 Tensile strength in N / mm ' 16,66 45 8.6 Elongation at break in% 945.70 520 745 Water absorption in% 5.90 3.9 26 Water vapor permeability in mg dm " ² (24 h) 307 170 510

Claims (1)

Process for the preparation of hydrophilic polyurethane elastomers, characterized in that a mixture of 90 to 99 parts by weight of an α, ω-OH-functional oligotetramethylene oxide-1 ₍ 3,6-trioxocane diol of the general formula! - [(CH 2) 2 O (CH ₂ ) 2O (CH ₂ ) O] _n - [(CH ₂ ) 4 O] _m - [(CH ₂ ) 1 O (CH ₂ ) ₂ OCH ₂ O] n-mitn = 1-30 and m = 1-25 and 1 to 10 parts by weight of one Chain extender is reacted with a diisocyanate in a molar ratio of OH: NCO groups of 1: 1.5 to 1: 2.2 at a temperature of 40 to 6O ⁰ C to form an NCO prepolymer and its free NCO groups then with an excess Water, in the form of an aqueous dimethylformamide solution, are reacted Field of application of the invention The invention relates to a process for the preparation of hydrophilic polyurethane elastomers, which are suitable for applications in the field of PUR synthetic leather, in biology and medicine as well as for processing to thin PUR folion as membrane materials for mass transfer and separation processes. Characteristic of the known state of the art Polyurethanes with high elasticity and a demanding level of their general physico-mechanical properties are advantageously obtained from polytetramethylene ether glycols (PTMG), diisocyanates (preferably diphenylmethane diisocyanate) and butondiol. For such materials in particular high values for the elongation at break, favorable rebound behavior and low glass transition temperature ranges are given. Specifically, these properties depend significantly on the chain length of the PTMG used. A comprehensive description of the property pictures of PTMG-PUR is given by E. Pechold and G. Pruckmayr in: Rubber Chemistry and Technology 55 (1982), p. 76, whereby the dependencies of the PUR properties on the molecular weight range between 600 and 5000 g / mol have been studied becomes. Optimum elasticity is achieved for corresponding polyurethanes, if the molecular weights of PTMG at 1800g / mo! lie. Low "" values are already found with the use of PTMG with molecular weights of 10OOg / mol.The temperature range of the glass transition is also dependent on the ratio of the hard and soft Segmentaüteile.The disadvantage of this PTMG-PUR their basically hydrophobic nature is considered is caused _(CH2) 4-O-segment However, for certain applications it is useful to have highly elastic polyurethane materials with hydrophilic properties Thus, such demands are made in the field of polyurethane synthesis leather, for applications - from present in the polyol.. in biology and medicine as well as for the use of thin PUR foils as membrane materials for mass transfer and separation processes in which polar substrates and above all water are included as permeants.These hydrophilic-equipped PTMG-PUR are obtained when, as polyols a, ω-OH-functional copolymers of tetrahydrofuran and ethylene oxide (Y. Ikeda et al., J. Chem. Soc., Jpri (1986), 699-705). The importance of a property modification of polyoxyalkylene polyols by ter- or copolymerization of suitable monomers such as propylene oxide or epichlorohydrin with ethylene oxide in terms of hydrophilization has long been known (GB-PS 1120223). Initially, these syntheses serve to obtain variants of the polyether polyol products having an increased proportion of primary OH end groups to ensure high reactivity of the polyol component in PUR formation. This is associated with the fact that the ethylene-modified polyols have a much higher solubility for water. While a propylene oxide polyol contains 5% primary hydroxyl groups and can be absorbed by 100ml polyol at 25 ° C 3.5g water, the water uptake capacity at 4,6,8 and 10% ethylene oxide content (terminal or chain) increases to 4,5,5, 4,6,2 and 6,5g water per 100ml polyol. If, on the other hand, 11% of ethylene oxide are introduced into the copolyol terminal, the water absorption achieves a new quality of 100 g of water per 10 μmol of polyol. The increased water absorption capacity is advantageous, for example, for processing during foaming with water. Too high a hydrophilicity, however, leads to a drop in quality of PUR foams with respect to the resistance under hydrolytic aging conditions (DE-OS 2035134). Object of the invention The object of the invention is to produce hydrophilic PU elastomers having good physico-mechanical properties and high hydrophilicity. Explanation of the essence of the invention The object of the invention is to develop a novel reaction system for the production of hydrophilic polyurethane elastomers. The object is achieved in that a mixture of 90 to 99 parts by weight of an α, ω-OH-functional oligotetramethylene oxide-1,3,6-trioxocane diol of the general formula - [(CH ₂ ) ₂ O (CH ₂ ) ₂ O (CH ₂₎ O) _n - [(CH ₂₎ 4O] _m - [(CHj) ₂ O (CHj) ₂ OCH ₂ Ol _n -with η = 1-30undm = 1-25und1 to 10 parts by mass of a chain extender with a Diisocyanate is reacted in a molar ratio of OH: NCO groups of 1: 1.5 to 1: 2.2 at a temperature of 40 to 60 ⁰ C to an NCO prepolymer and its free NCO groups then with an excess of water in the form of an aqueous dimethylformamide solution, are reacted.