Abstract:
The 4,4&#39;-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanates) of the general formula ##STR1## are new polyisocyanates for the production of PU systems with high chemical stability and good thermal stability.

Description:
This application is a 371 of PCT/EP95/03260 filed Aug. 16, 1995. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to 4,4&#39;-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanates) of the general formula: ##STR2## in which R 1  means an alkyl group with 1 to 6 C atoms and R 2  means chlorine or an alkyl group with 1 to 6 C atoms, a process for preparing the said polyisocyanates, and the use of the said polyisocyanates in polyurethane (PU) systems. 
     PU systems are defined below as polyurethane systems that contain urethane groups and/or urea groups. 
     BACKGROUND ART 
     Toluene-2,4-diisocyanate and/or toluene-2,6-diisocyanate, abbreviated TDI, or diphenylmethane-4,4&#39;-diisocyanate, abbreviated MDI, continue to be of considerable importance as polyisocyanate components in the production of PU systems. 
     A major drawback of TDI is its high toxicity. Although the compound is handled on an industrial scale with the most stringent safety precautions possible, it carries a considerable risk potential. 
     A complete switch to the less toxic MDI is also only conditionally possible since MDI, owing to its high reactivity, can be processed with polyols, but not with aromatic polyamines. 
     In addition, the PU systems that are based on TDI and MDI are limited, in terms of their temperatures of use, to a maximum of 100° C. 
     BROAD DESCRIPTION OF THE INVENTION 
     The object of this invention was consequently to develop polyisocyanates that are not highly toxic, have lower reactivity than MDI, and can be processed with the conventional and new PU processing process. The goal of developing chemically stable PU systems that can be used at temperatures of above 100° C. was associated with the object. 
     These objects are achieved with the polyisocyanates of the above-mentioned general formula I according to the invention. 
     R 1  and R 2  mean a C 1  -C 6  -alkyl group which can be the same in meaning or different and may suitably stand for methyl, ethyl, n- or i-propyl, n-, i- or t-butyl, pentyl and its isomers and hexyl and its isomers. R 1  and R 2  are preferably the same in meaning and stand for one of the above-mentioned C 1  -C 4  -alkyl groups. 
     The preferred polyisocyanate is the 4,4&#39;-methylene-bis-(3-chloro-2,6-diethylphenylisocyanate) with the meaning of R 1  and R 2  are each ethyl. 
     The production of the polyisocyanates according to the invention is carried out in the known way by reacting the corresponding polyamine with phosgene or a phosgene-releasing compound, such as, di- or triphosgene (cf., e.g., Ullmanns Encykl. d. techn. Chemie  Ullmann&#39;s Encyclopedia of Industrial Chemistry!, 4 th  Edition, Volume 13, pp. 351 ff). 
     The corresponding polyamines are described in European Application A 0 220 641. 4,4&#39;-Methylene-bis-(3-chloro-2,6-diethylaniline) (M-CDEA) is the preferred polyamine. 
     The phosgenation is carried out suitably in the presence of an inert solvent such as, toluene or chlorobenzene at elevated temperature. The reaction generally proceeds virtually quantitatively. 
     The resulting polyisocyanates have a high purity. 
     The processing of the polyisocyanates according to the invention into PU systems is carried out basically in a known way by reaction with compounds with at least two hydrogen atoms that are active compared to polyisocyanates and optionally chain-lengthening agents and optionally in the presence of commonly used catalysts and optionally other additives (cf. Saechtling, Kunststoff Taschenbuch  Plastics Notebook!, 24 th  Edition, published in Carl Hauser Verlag, Munich 1989, pp. 429 if). 
     It is also possible to use mixtures of the polyisocyanates according to the invention with other aliphatic or aromatic polyisocyanates or prepolymers of polyisocyanates or prepolymers that are based on mixtures of polyisocyanates with aliphatic or aromatic polyisocyanates. 
     Suitable representatives of compounds with at least two hydrogen atoms that are active compared to polyisocyanates are especially polyols, such as, e.g., polyether polyols, polyester polyols, or other polyols, (e.g., polycaprolactones). Suitable representatives of chain-lengthening agents are polyamines, such as, e.g., the aromatic diamines MOCA, M-CDEA, mixtures of M-CDEA with aromatic or aliphatic diamines or polyols or isomer mixtures of dimethylthiotoluenediamine (ibid., p. 430, or European Published Patent Application No. A 220,641). 
     In addition, all commonly used catalysts, such as, tetramethylbutanediamine (TMBDA), diazabicylooctane (DABCO), dibutyltin dilaurate (DBTC) or organic heavy metal compounds, can be used individually or in combination with additives, such as, softeners, stabilizers, fireproofing agents, propellants, or fillers (ibid. p. 430). 
     A great advantage of the polyisocyanates according to the invention lies in that fact that they can be processed in the standard PU processing processes, such as, the one-shot RIM process, the two-shot prepolymer process, or the two-shot direct process. 
     In accordance with the preferred use of polyisocyanates in the PU-elastomer sector or especially in the PU-casting elastomer sector, preference is given to the prepolymer process. 
     The polyisocyanates according to the invention are suitably used in a polyurethane system that can be produced by reacting a 
     a) 4,4&#39;-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanate) of general formula I with 
     b) compounds with at least two hydrogen atoms that are active compared to isocyanates and optionally 
     c) chain-lengthening agents optionally in the presence of commonly used catalysts and optionally other additives. 
     Preferred is a polyurethane system that can be produced by reacting a 
     a) 4,4&#39;-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanate) of general formula I with 
     b) compounds with at least two hydrogen atoms that are active compared to isocyanates, preferably as described above, and 
     c) an aromatic diamine as a chain lengthener in the presence of the above-mentioned commonly used additives. 
     Especially preferably, a 4,4&#39;-methylene-bis-(3-chloro-2,6-dialkylaniline), especially the 4,4&#39;-methylene-bis-(3-chloro-2,6-diethylaniline), is used as an aromatic diamine either individually or as a component of a mixture with other aromatic or aliphatic diamines or with polyols, and 4,4&#39;-methylene-bis-(3-chloro-2,6-diethylphenyl-isocyanate) is used as component a). 
     The PU systems that are produced on the basis of new polyisocyanates according to the invention are distinguished by high chemical stability that is unexpected in comparison to known PU systems and by a temperature of use of up to 180° C.. 
     These PU systems according to the invention are therefore used mainly in the PU-elastomer sector--especially in the casting-elastomer sector--for the production of, e.g., rollers, wheels, roller coatings, insulators, seals, or sealing compounds. It is eminently possible, however, to use the PU systems for spray-coating or for PU foams. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     EXAMPLE 1a 
     Production of 4,4&#39;-methylene-bis-(3-chloro-2,6-diethylphenylisocyanate) 
     100 g (0.26 mmol) of 4,4&#39;-methylene-bis-(3-chloro-2,6-diethylaniline) was introduced into 1000 g of dichlorobenzene in an autoclave at room temperature. 57 g (0.58 mol) of phosgene was introduced into this solution over a period of 30 minutes. The reaction mixture was stirred in a sealed autoclave at 80° C. for 1 hour. Then, it was depressurized, and the hydrochloric acid that was produced, the excess phosgene, and the solvent were removed. In this case, the title product resulted in a yield of 110 g (98% of theory). Other data concerning the product is: 
     IR (KBr): 2288.1 cm -1   
       1  H-NMR (CDCl 3 , 400 MHz) in ppm: 6.69 s, 2H; 4.12 s, 2H; 2.91 q, 4H, J=7.5 Hz; 2.59 q, 4H, J=7.6 Hz; 1.20 t, 6H, J=7.6 Hz; 1.15 t, 6H, J=7.5 Hz. 
     EXAMPLE 1b 
     Analogously to Example 1a, but with the solvent toluene, the title product was obtained in a yield of 109 g. 
     Examination of 4,4&#39;-Methylene-bis-(3-chloro-2,6-diethylphenylisocyanate) in Comparison with Isocyanates from the Prior Art in PU Systems 
     1. Isocyanates Used 
     MCDE-I 4,4&#39;-Methylene-bis-(3-chloro-2,6-diethylphenylisocyanate)=compound according to the invention 
     MDE-I 4,4&#39;-methylene-bis-(2,6-diethylphenylisocyanate)=comparison substance 
     MDI 4,4&#39;-methylene-bis-phenylisocyanate=comparison substance 
     2. Production of Prepolymers (Component A) 
     Prepolymer 1 (Invention) 
     Prepolymer based on polytetramethylene ether glycol (PTMG; Tetraethane 650, Du Pont), with a molecular weight of 650 and MCDE-I 
     1850 g=4 mol of 94% MCDE-I was melted under nitrogen (N 2 ) at 80° C., introduced into a reaction flask, and intimately mixed with 1300 g of PTMG=2 mol over 30 minutes while being stirred. The PTMG is linear and was dehydrated before addition to isocyanate for 1 hour at 100° C. and under a vacuum of 2500 Pa. After the addition of PTMG was completed, it was then stirred for 2 more hours at 90° C. under N 2 . 
     A prepolymer with a content of 5.2% of free NCO groups was obtained. This prepolymer is referred to as &#34;PTMG 650-MCDE-I.&#34; 
     Prepolymer 2 (Invention) 
     Prepolymer based on polytetramethylene ether glycol (PTMG; Terathane 2000, Du Pont) with a molecular weight of 2000 and MCDE-I 
     1234 g=2.67 mol of 95% MCDE-I was melted under N 2  at 80° C., introduced into a reaction flask, and intimately mixed with 2133 g=1.066 of PTMG over 30 minutes while being stirred. The PTMG is linear and was dehydrated before addition to isocyanate for 1 hour at 100° C. and under a vacuum of 2500 Pa. After the addition of PTMG was completed, it was then stirred for 2 more hours at 90° C. under N 2 . 
     A prepolymer with a content of 3.96% of free NCO groups was obtained. This prepolymer is referred to as &#34;PTMG 2000-MCDE-I.&#34; 
     Prepolymer 3 (Invention) 
     Prepolymer based on polycaprolactone glycol (PCL; CAPA 220, Interox) with a molecular weight of 2000 and MCDE-I 
     1245 g=2.7 mol of 94% MCDE-I was melted under N 2  at 80° C., introduced into a reaction flask, and intimately mixed with 2133 g=1.066 mol of PCL over 30 minutes while being stirred. The PCL is linear and was dehydrated before addition to isocyanate for I hour at 100° C. and under a vacuum of 2500 Pa. After the addition of PCL was completed, it was then stirred for 2 more hours at 90° C. under N 2 . 
     A prepolymer with a content of 3.92% of free NCO groups was obtained. The prepolymer is referred to as &#34;PCL 2000-MCDE-I.&#34; 
     Prepolymer 4 (Comparison) 
     Prepolymer based on PTMG (Terathane 2000, Du Pont) with a molecular weight of 2000 and MDE-I 
     1158 g=3 mol of 94% MDE-I was melted under N 2  at 80° C., introduced into a reaction flask, and intimately mixed with 2400 g=1.2 mol of PTMG over 30 minutes while being stirred. The PTMG is linear and was dehydrated before addition to isocyanate for 1 hour at 100° C. and under a vacuum of 2500 Pa. After the addition of PTMG was completed, it was then stirred for 2 more hours at 90° C. under N 2 . 
     A prepolymer with a content of 4.32% of free NCO groups was obtained. We refer to this prepolymer as &#34;PTMG 2000-MDE-I.&#34; 
     Prepolymer 5 (Comparison) 
     Prepolymer based on PCL (CAPA 220, Interox) with a molecular weight of 2000 and MDE-I 
     If the PTMG in prepolymer 4 is replaced by the same amount of PCL, a prepolymer with a content of 4.23% of free NCO groups is obtained under otherwise identical conditions. This prepolymer is referred to as &#34;PCL 2000-MDE-I.&#34; 
     Prepolymer 6 
     Prepolymer based on PCL (CAPA 220, Interox) with a molecular weight of 2000 and MDI. 
     400 g=1.6 mol of MDI was melted under N 2  at 60° C., introduced into a reaction flask, heated to 80° C. and intimately mixed with 1000 g=0.5 mol of PCL over a period of 10 minutes while being stirred. The PCL is linear and was dehydrated before addition to isocyanate for 1 hour at 100° C. and under a vacuum of 2500 Pa. After the addition of PCL was completed, it was then stirred for 2 more hours at 80° C. under N 2 . 
     A prepolymer with a content of 6.6% of free NCO groups was obtained. This polymer is referred to as &#34;PCL 2000-MDI.&#34; 
     3. Component B 
     Component B is either the melted diamine* or the clear degassed solution, cooled to processing temperature (80° C.), of the diamine or diamine mixture in question in the corresponding polyol. In addition, the solutions in the polyol contain an organic bismuth compound (Coscat® 83 catalyst from the CasChem. Inc., New Jersey) relative to the overall system (components A+B). 
    
     Ethacure 300, Albemarle Inc. 
     4. Preparation of the Test Piece 
     The prepolymer (component A) and the diamines (chain lengtheners; component B) were intimately mixed at a molar ratio of 1:0.95, i.e., NCO groups to the sum of free OH and NH 2  groups, at 80° C. for 30 seconds, poured into a metal mold, preheated to 110° C., with inside dimensions of 200*200*2 (in mm), and finally pressed at the start of gelling (pot life) in a press at 200 bar and 110° C.. After setting was completed (demolding time), it was demolded and subsequently tempered at 110° C. for 16 hours. Test pieces were punched out of the hardened elastomers. 
     5. Test Parameters 
     
         ______________________________________Hardness Shore A and Shore D               DIN 53505Tear resistance  N/mm!               DIN 53515Tensile strength  N/mm.sup.2 !               DIN 53504Tension at 100% elongation               DIN 53504Elongation at break %               DIN 53504______________________________________ 
    
     
                                           TABLE I__________________________________________________________________________RESULTS WITH DIAMINE M-CDEA (I)      &#34;Proportion      by weight&#34;      of            Hardness/Room          Stress&#34;I&#34; in     comp. B       Temperature                            Hardness/                                 Tear Tensile                                           at 100%                                                ElongationPrepolymer Comp. B      per 100            Pot               Demold-                    Shore                        Shore                            175° C.                                 Resistance                                      Strength                                           Elongation                                                atNo.   in Mol %      comp. Life               ing Time                    A   D   Shore A                                  N/mm!                                       N/mm.sup.2 !                                            N/mm.sup.2 !                                                Break__________________________________________________________________________                                                %1 (Invention) 100  21.0  2&#39;00&#34;               20&#39;  99  69  99   --   --   --   --2 (Invention) 100  100   2&#39;30&#34;               20&#39;  98  45       53.3 19.7 9.2  4332 (Invention) 66   40.0  2&#39;00&#34;               45&#39;  91  33       47.7 18.3 5.2  8094 (Compar.) 100  18.2  3&#39;00&#34;               45&#39;  97  43       47.7 8.6  7.5  3884 (Compar.) 66   44.0  7&#39;30&#34;               60&#39;  91  28       35.0 15.0 4.5  8543 (Invention) 100  16.0  2&#39;30&#34;               20&#39;  98  52  97   73.5 17.7 11.4 3533 (Invention) 66   38.0  2&#39;30&#34;               45&#39;  92  37       59.4 25.7 5.7  5935 (Compar.) 100  18.7  5&#39;00&#34;               60&#39;  98  45  95   64.2 12.1 9.2  4405 (Compar.) 66   45.0  5&#39;10&#34;               60&#39;  92  32  --   50.2 22.8 5.1  7506 (Compar.) 66   72.0  19&#34;                9&#39;  88  --  --   64.0 35.1 --   --6 (Compar.) 100  30.0  20&#34;                5&#39;  98  55  --   74.0 25.6 --   --__________________________________________________________________________ 
    
     
                                           TABLE 2__________________________________________________________________________Results with the Diamino Mixture Luvocure MUT-HT from Lehmann &amp; Voss(II)Weight              Hardness/Room                            Tear       Stress atratio of            Temperature                       Hardness/                            propagation                                  Tensile                                       100% ElongationPrepolymer prepolymer:       Pot          Demold-               Shore                   Shore                       175° C.                            Resistance                                  Strength                                       Elongation                                            atNo.   comp. B       Life          ing Time               A   D   Shore A                             N/mm!                                   N/mm.sup.2 !                                        N/mm.sup.2 !                                            Break %__________________________________________________________________________2 (Invention) 100:20.5       2&#39;00&#34;          40&#39;  97  46  95   60.9  17.2 9.1  5104 (Compar.) 100:22.0       4&#39;30&#34;          45&#39;  97  40  93   50.2  13.9 7.0  7543 (Invention) 100:19.0       2&#39;40&#34;          40&#39;  98  47  95   76.8  20.7 9.7  4645 (Compar.) 100:22.5       5&#39;20&#34;          60&#39;  97  46  95   60.9  17.2 9.1  510__________________________________________________________________________ 
    
     
                                           TABLE 3__________________________________________________________________________Results with the Diamine-Isomer Mixture Ethacure 300 (2.4 and 2.6 IsomersofDimethylthiotoluenediamine) from Albemarle Inc. USAWeight              Hardness/Room                            Tear       Stress atratio of            Temperature                       Hardness/                            propagation                                  Tensile                                       100% ElongationPrepolymer prepolymer:       Pot          Demold-               Shore                   Shore                       175° C.                            Resistance                                  Strength                                       Elongation                                            atNo.   comp. B       Life          ing Time               A   D   Shore A                             N/mm!                                   N/mm.sup.2 !                                        N/mm.sup.2 !                                            Break %__________________________________________________________________________1 (Invention) 100:12.0       1&#39;30&#34;          13&#39;  99  67  95   100.5 32.0 26.1 1652 (Invention) 100:9.6       3&#39;30&#34;          20&#39;  95  41       48.8  35.4 7.4  5254 (Compar.) 100:10.2       6&#39;20&#34;          45&#39;  93  33       31.6  13.1 5.9  6583 (Invention) 100:9.0       4&#39;00&#34;          20&#39;  95  40       66.6  42.4 8.2  4795 (Compar.) 100:10.5       6&#39;20&#34;          60&#39;  94  36       45.0  18.1 6.9  571__________________________________________________________________________