DD148956A1 - METHOD FOR PRODUCING THERMOPLASTIC POLYURETHANES OF HIGH ELASTICITY - Google Patents

Abstract

The invention relates to a process for the preparation of high-elasticity thermoplastic polyurethanes by reacting polyether polyols with isocyanates. According to the invention, polyether polyols which are substantially free of structural defects and which are distinguished by a molecular weight range which is shifted to relatively high molar masses are preferably reacted in a two-stage process in the temperature range from 40 to 190.degree. The resulting polyurethanes are used as coating compositions, films and membranes.

Description

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Title of the invention

Process for the preparation of thermoplastic polyurethanes of high elasticity

Field of application of the invention

The invention relates to a process for the preparation of thermoplastic polyurethanes of high elasticity by reacting polyether polyols with isocyanates, which are suitable as coating compositions for fabrics or felts, for materials of high demands in terms of mechanical and hydrolytic properties and for membranes, which are used in particular in an aqueous medium.

Characteristic of the known technical solutions

Processes for the preparation of thermoplastic polyurethanes from polyesters, polycaprolactones, polytetrahydrofurans, polypropylene glycols and polypropylene polyethylene glycols or mixtures thereof by reaction with isocyanates, chain extenders and / or hardeners, optionally with the addition of catalysts and / or additives, have long been known and are used industrially.

The known PUR products have for certain applications too low elasticity and insufficient cold resistance and in some cases also poor hydrolytic stability. By mixtures of polyhydroxy compounds or additions of monoalcohols and special hardeners

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Although these properties can be improved, as known inter alia from DE-OS 2,824,641 and US Patent 4,098,772 and 4,133,943, and wherein products with elongations at break of 500 to 600 % arise, but at the same time is the Manufacturing process complicated and expensive. Thus, for example, according to W'Goyert and H * Hespe / Kunststoffe, FRG 68 (12), 819-825 (1978) / when using polyesters PUR products which age rapidly, especially in the presence of special hydrolysis protection agents, and within a short time Have changed characteristics over time »All in all, the mechanical properties are generally worse than with the polyether urethanes«

Hydrolytically somewhat more stable are polycaprolactone polyurethanes. They also have better mechanical properties, as is known from DE-OS 2,653,136.

By far the cheapest properties of the known thermoplastic polyurethanes have the PUR ~ materials prepared with polytetrahydrofuran. However, their inadequate elasticity with corresponding hardness is defective. Thus, the tetrahydrofuran polyurethanes described in DE-AS 2 059 570 have a tensile strength

of 390.6 kp / cm and a Shore A hardness of 83, an elongation at break of 340%.

The polyurethanes obtained by the reaction of polyalkylene glycols prepared by anionic processes also show a lack of elasticity. Thus, the PUR products which can be prepared from propylene oxide-ethylene oxide copolymers according to DE-OS 2 720 166 have a breaking elongation of 417 % at a tensile strength of 14.4 MPa and a Shore A hardness of 88. At somewhat lower tensile strength (10.7 FPA) is the elongation at break only slightly higher (504%) _m From the DE-OS 2623951 and 2842304 are thermoplastic polyurethanes known, the characteristics of which likewise lie in this area.

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Polyurethanes prepared in this way all have an elasticity which is too low for products used as coating material for textiles, for films or for membranes for mass separation processes.

Object of the invention

The object of the invention was therefore to find a process which provides thermoplastic polyurethane product of high elasticity, but which on the other hand can be carried out easily and without additional process steps.

Explanation of the essence of the invention

A process has now been found for the production of thermoplastic polyurethanes, with which it is possible to produce thermoplastic polyurethanes substantially improved elasticity to obtain the other good physical properties, if according to the invention as polyols prepared by catalyzed polymerization in the presence of metal salts of Hexacyanoiridium-III acid polypropylene glycols or These polyalkylene oxides are essentially free of structural defects, as evidenced by a very low ohmic number, and are characterized by a molecular weight range which is shifted to higher molar masses. These factors decisively influence the elastic properties of the PUR product.

In the case of the use of block copolymers, the water absorption and the water vapor permeability are improved; they can be set to previously calculated values ·

The polyurethanes are prepared by the usual technology in one-, two- or multistage processes, optionally in the presence of catalysts. Preference is given to a two-stage process at temperatures of from 40 to 190.degree. Processes of manufactured products can be further processed in a known manner. * In addition to their high elasticity, they are characterized by good resistance to cold and aging. · Their Shore hardness is adjustable.

As isocyanate necessary for the reaction, all isocyanates having an average functionality 2 are usable, in particular 4,4 *, 2,4'- or 2,2'-diphenylmethane diisocyanate or mixtures thereof, tolylene 2,4- or 2,6-diisocyanate or their mixtures Mixtures, 1,6-hexanediisocyanate, isophorone diisocyanate, methylenebis (4-cyclohexyl isocyanate), xylylene diisocyanate or 1,5-naphthylene diisocyanate

As a chain extender, all low molecular weight diols such as ethylene glycol, propylene glycol, 1,3-butanediol or -l _f 4 _f pentanediol-1,5, 1,6-hexanediol, di- or triethylene glycol, dipropylene glycol, neopentyl glycol and low molecular weight homopolymers or copolymers of alkylene oxides come to an average molecular weight 1000 for use.

Hardeners are generally amines, such as ethanediamine-1,2, propanediamine-1,3, butanediamine-1,4, hexanediamine-1,6, 4,4'-diphenylmethanediamine, (3,3 * dichloro-4,4 ' -diamino) -dipheny1-methane, ethylene glycol bis (aminobenzoic acid ester), butylene glycol bis (aminobenzoic acid ester) and the like.

Catalysts are the tertiary amines commonly used in polyurethane chemistry, e.g., triethylamine, tetramethylbutanediamine, dimethylcyclohexylamine, or organometallic compounds, e.g., B. Tin dioctoate, dibutyltin diacetate, dibutyltin dilaurate or copper acetylacetonate,

Additives may be, for example, plasticizers, inorganic fillers, dyes, blowing agents, pigments, flame retardants, high molecular weight polyalkylene oxides with an average molar mass> 6000, polymers such as PVC, PE, PP, rubber, polyamide, polystyrene, polyacrylonitrile, polyureas or other polyurethanes. These additives may already be present as a dispersion in the polyether polyol compound or prepared by compounding.

The process according to the invention is advantageous in that it is not only possible to prepare thermoplastic polyurethanes of high elasticity, but also to continue to use inexpensive starting materials in comparison with previously known technical solutions, such as polytetrahydrofurans or polycaprolactamides.

Tone can be implemented in an easily practicable method.

The following examples illustrate the invention,

AusführungsbeispieIe

Example 1:

From 435 g of tolylene diisocyanate (4.8 mol of a mixture of 80 % 2,4-isorneric and 20 % 2,6-isomer) and 1935 g of polypropyleneglycol 2000 (2.0 mol, average molecular weight 2000, hydroxyl value 56.4, Oxide number 0.14, molecular weight distribution see drawing, Fig, I, curve 2) is first prepared a prepolymer »For this, the isocyanate is placed in a purged with dry argon vessel, heated to 60 C and added dropwise within 30 min, the PPG 2000th It is then heated to 100 C and left for 3 hours at this temperature. The resulting prepolymer has an isocyanate equivalent of 1120 and a viscosity of 16400 cps at 20 ⁰ C.

500 g of this prepolymer are heated to 80 C and degassed for 5 min at 0.1 Torr, then 19.1 g of 1,4-butanediol (95 % ± g) , stirred for 1 min at 5000 rev / min and turn 5 degassed at 0.1 Torr. The mixture is poured into preheated PTFE molds and cured at 130 C for about 3 hours. Post-curing takes place at room temperature within one week.

The following characteristic values were determined:

Tensile strength of 18.15 MPa, elongation at break 131 · ^%, Shore A hardness of 72, glass transition temperature of -43 ⁰ C, water absorption after 4 days 2.46%,

If, instead of the specific PPG, a commercially available product (molecular weight distribution see drawing, FIG. 1, curve I) ₁ which was generally prepared using anionic catalyst, the following values are obtained with the same method: tensile strength 17.15 MPa, breaking elongation 780 % , Shore A hardness 63.

Example 2:

From 400 g of freshly distilled 4,4 * -Diphenylmethandiisocyanat (3.2 mol) and 964 g of PPG 2000 (1 mol) of the same quality as in Example 1, in turn, a prepolymer is prepared «this has an isocyanate equivalent of 675 and a viscosity of 20200 cP at 20 ⁰ C _- 500 g of this prepolymer (0.74 mol) are reacted according to Example with 31.7 g of 1,4-butanediol (0.72 mol, 95 %) and cast to 4 mm thick plates., The PUR Product has a tensile strength of 21.6 MPa, an elongation at break of 1160%, a Shore ~ A hardness of 72, a glass transition temperature of -40 C and a water absorption after 4 days of 2.62 %, A with handeJU customary PPG 2000 - as in Example 1 under identical conditions prepared comparative sample had the following characteristics: tensile strength 12.75 MPa, breaking elongation 580%, Shore A hardness 69, water absorption after 4 days 2.51 %.

Example 3:

Analogously to Example 1 (1.18 mol) and 365 g of PPG 2000 (0.38 mole) of a prepolymer is prepared from 147.5 g of 4,4 ^I ~ Diphenylmethandiisoeyanat same quality as in the above Seispielen prepared (isocyanate equivalent 600 and viscosity of 12700 cps at 20 ⁰ C).

100 g of the prepolymer (0.17 mol) is mixed with 7.2 g of butane-1, 4 (0.16 MoI ₄ 95% strength) was reacted analogously to Example 1 and cast into 4 mm thick plates "The polyurethane has a tensile strength of 24 , 0 MPa, an elongation at break of 970 % _t a Shore A hardness of 80, a water absorption after 4 days of 2.8% and a glass transition temperature of -40 ⁰ C _e

Example 4:

Analogously to Example 1 is from 400 g of 4,4'-diphenylmethane diisocyanate and 980 g of a block copolymer of propylene oxide and ethylene oxide (average molecular weight 2200, hydroxyl number 54.2, Oxide 0.26, Ethylenoxidgeha.lt 19.6 %, prim * OH groups

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76.5 %, molecular weight distribution see drawing, Fig. I _f curve 3) prepared a prepolymer having an isocyanate equivalent of 630 and a viscosity of 14800 cP at 20 C.

400 g of the prepolymer (0.635 mol) are reacted with 27.2 g of 1,4-butanediol (0.6 mol) analogously to Example 1 and cast into 4 mm thick plates. The polyurethane product had the following properties: tensile strength of 25.2 MPa, elongation at break 3.190%, Shore A 83 Huerte, water absorption after 4 days 23.6%, glass transition temperature of -42 ⁰ C,

After pressing at 135 ° C / 100 kgf / cm, a film of 0.25 mm thick is obtained after 3 minutes. The characteristic properties are: tensile strength 25.6 MPa, breaking elongation 1180 %, water absorption after 4 days 22.8 %, water vapor permeability

160 mg / 24 hrs. X 10 cm ^2,> 70000 Bully-buckling at -20 ⁰ C.

Claims (1)

-β- Invention claim: A process for the preparation of high elasticity thermoplastic polyurethanes by reacting polyether polyols with isocyanates in the presence of chain extenders, hardeners and optionally additives according to known technologies, characterized in that polyether polyols which are substantially free from structural defects and at higher molecular weight range by a higher Distinguish molar masses shifted molecular weight distribution, preferably in a two-stage process at temperatures of 40 to 190 C to be implemented. For this 1 page drawings