Abstract:
Moisture-hardening varnishes which have an isocyanate resin base of adducts of a mixture of diisocyanates, wherein the diisocyanate mixture has 88 to 99% by weight of 2-methyl-1,5-diisocyanatopentane and 12 to 1% by weight of 2-ethyl-1,4-diisocyanatobutane. 
     These varnishes exhibit excellent thermal and oxidative stability and have excellent storage stability. They also exhibit excellent compatibility with solvents, pigments and other auxiliary materials.

Description:
BACKGROUNDS OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to moisture-hardening varnishes based on derivatives of aliphatic diisocyanate mixtures. 
     2. Description of the Prior Art 
     Moisture-hardening resins based on aromatic polyisocyanates are known and can be produced in several manners. Unfortunately, these resins have a tendency to yellow upon exposure to sunlight. 
     Cyclic polyisocyanates, such as e.g. isophoronediisocyanate or methylene-bis-(4-cyclohexylisocyanate) are used for more demanding applications. However, the isocyanurate or the propanetriol prepolymer of these cyclic diisocyanates merely form hard, brittle films following moisture hardenings. 
     Based on cyclic polyisocyanates and, e.g., higher molecular polyols, NCO terminated adducts can be produced that provide hard or soft films, in each case elastic films, following moisture hardening. But the resins are inactive and must be activated with additions of, e.g., 0.1 to 0.2% tin catalysts, which limits the weathering resistance of the hardened films. The hardened films have excellent thermal and oxidative stability, but have no outstanding solvent stability. 
     Aliphatic polyisocyanates through their floating, NCO end groups introduce highly reactive moisture-hardening resins in the form of their isocyanurate or their propanetriol prepolymers, which, following hardening, form hard, elastic weather and solvent resistant films. However, their thermal and oxidative stability and compatibility with other products are problematical, as e.g., also with solvents and pigments which are present especially in cyclic polyisocyanate resins. 
     Hence, a need clearly continues to exist for moisture-hardening varnishes with both excellent thermal and oxidative stability, and resistance to solvent attack. Also, it is necessary for these moisture-hardening varnishes to have excellent storage stability. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a moisture-hardening varnish which has excellent thermal and oxidative stability, and which also has excellent solvent stability. 
     It is also an object of this invention to provide a moisture-hardening varnish which has excellent compatibility with solvents, pigments, reactants or auxiliary products. 
     According to the present invention, the foregoing and other objects are attained by providing a moisture-hardening varnish with an isocyanate resin base of adducts of a mixture of diisocyanates, wherein said diisocyanate mixture has about 88 to 99% by weight of 2-methyl-1,5-diisocyanatopentane and about 12 to 1% by weight 2-ethyl-1,4-diisocyanatobutane. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     According to the present invention, it has now been surprisingly found that resin derivatives of the 2-methyl-1,5-diisocyanatopentane (MPDI)/2-ethyl-1,4-diisocyanatobutane (EBDI) mixture possess quality properties which considerably surpass those of the conventionally used aliphatic isocyanate resins. 
     The moisture-hardening varnishes with an isocyanate resin base according to this invention contain adducts of a diisocyanate mixture having the composition of about 88 to 99% by weight of 2-methyl-1,5-diisocyanatopentane (MPDI) and about 12 to 1% by weight of 2-ethyl-1,4-diisocyanatobutane (EBDI), according to the following formulas: ##STR1## 
     The resins are produced by trimerization of the MPDI/EBDI mixture to the corresponding isocyanattoisocyanurate or by reaction of the MPDI/EBDI mixture with propanetriols in NCO:OH equivalents of about 2:1. 
     These resins are chemically hardened through the effects of atmospheric moisture and provide films and coatings of superior quality. 
     The isocyanate mixture is the result of phosgenation of the corresponding diamine mixture, whereby the latter is formed by hydrogenation of the corresponding dinitrile mixture. The mixture is obtained, e.g., as a by-product in the adipodinitrile production through reaction of butadiene with HCN or by dimerization of acrylonitrile. 
     The isocyanurate or the propanetriol prepolymers here are understood to be adducts. 
     The moisture-hardening varnishes according to the invention have the following qualities: 
     1. Thermooxidation stability 
     2. Storage stability of pigmented systems 
     3. Compatibility with solvents, pigments, reactants or auxiliary products 
     4. Solvent resistance 
     The present invention will be further illustrated by certain examples and references which are provided for purposes of illustration only and are not intended to limit the present invention. 
     The thermooxidation stability of the resins applied according to the invention, as shown in Table 1, is not typical of aliphatic isocyanate resins and comparable with that shown by the indicator diagram of cyclic isocyanate resins. 
     
                       TABLE 1______________________________________Thermooxidation Test with Moisture-hardened Films withAliphatic Isocyanurate BaseConditions: 10 min., 240° C.Evaluation: Color value 1 to 10, according to Gardner              Color ValueInitial Resins     According to GardnerIsocyanurates Based on              Before Test                        After Test______________________________________1,6-Diisocyanato-hexane (HDI)              1         7-82,2,4/2,4,4-Trimethyl-1,6-              1         4diisocyanato-hexane (TMDI)5-Methyl-1,9-diisocyanato-              1         10nonane (MNMDI)2-Methyl-1,5-diisocyanato-              1         2pentane (MPDI)2-Ethyl-1,4-diisocyanato-butane (EBDI)Isophoronediisocyanate (IPDI)              1         1-2______________________________________ 
    
     The storage stability especially of white pigmented resins, which require a high pigment volume concentration, is extraordinary considering the high reactivity of the resins used according to the invention (Table 2). 
     The results of the severe storage test at 60° C. permit the empirical conclusion of an over 10 times greater shelf life at 25° C. 
     
                       TABLE 2______________________________________Basic Resins Trimethylopropane Prepolymers (TMP)of the following Isocyanates, reacted in OH:NCOequivalents as 1:2      (a) Storage               (b) Gloss Values      Stability               Acc to GardnerIsocyanate Component        60° C.                   20° C.                            60° C.                                  85° C.______________________________________HDI-Prepolymer        3-4     days   40     71    78TMDI-Prepolymer        &gt;30     days   82     88    97MNMDI-Prepolymer        20-25   days   76     91    96(MPDI + EBDI)-        &gt;30     days   80     85    95Prepolymer______________________________________ (a) Storage stability of moisturehardening resins following pigmentation with TiO.sub.2 (Kronos Cl 310) PVK 15 (b) Gloss Values of the Hardened Films 
    
     The very limited storage life of the HDI prepolymers as well as their low gloss value at 20° C. Gardner indicate clear incompatibility of this system with pigments, reaction products and solvents. This incompatibility of HDI prepolymers or additives becomes evident when such prepolymers are to be modified by partial oxyester additives. 
     Thus, e.g., not only hard substrates, such as metal, concrete and parquet flooring have to be coated but also softer substrates, such as PVC floor coverings and the like. Softer resin adjustments can be made very advantageously if the resin systems according to the invention are chemically reacted with small amounts of oxyester additives and moisture-hardening of the coating takes place only thereafter. Surprisingly, the resins used according to the invention permit such a modification while standard types of aliphatic isocyanates, such as HDI derivatives, coagulate after a few hours&#39; storage at room temperature. 
     
                                           TABLE 3__________________________________________________________________________Oxyester Partially Modified Adducts and Prepolymers ofAliphatic Isocyanates for Coating of PVC. Film andFoil Data as Well as Storage Stability. Basic Resin:Isocyanurate and Propanetriol Prepolymers. To modifyOxyester Polycaprolactone 210 (PCP) used.           Film Data                      Abrasion           Pendulum   acc to    Foil Data            Storage           Hardness                 Erichsen                      Taber mg  Tear                 Life           Acc to                 Test H 2 Roll  Resistance                                      Elongation                                            Solvent  25° C.Resin Component Koenig                 [mm] 100 U 500 g Bel.                                N/mm.sup.2                                      %     Resistance                                                     (Days)__________________________________________________________________________  HDI--TMP adducts           177   8.5  23.8      78.7  8     resistant                                                      &lt;2  modified with 127   10   31.3      45.7  10    to EGA,  PCP 210                                        xylene, MEK,  NCO:OH = 11:1                                  acetone  (MPDI + EBDI)--TMP           187   9.5  35.1      78.2  7              &gt;100  modified with 130   &gt;10  32.2      48.4  9  PCP 210  NCO:OH = 9:1  Hdi--Isocyanurate           190   8.0  33        53.4  9     Resistant                                                       40  modified with 140   9.6  28        35.2 ± 1.4                                      13    to EGA,  PCP 210                                        xylene, MEK,  NCO:OH = 20:1                                  acetone  (MPDI EBDI) - 184   10.0 43.1      57.3  8               &gt;40  modified with 130   10.00                      32.2      43.2  10  PCP 210  NCO:OH = 9:1__________________________________________________________________________ 
    
     In view of the good compatibility of the resins used according to the invention, their excellent solvent resistance is surprising compared with the premium gasoline sensitivity of the well compatible 5-methyl-1,4-dicyanatononane (MMDI) (Table 4). 
     
                                           TABLE 4__________________________________________________________________________Solvent Resistance of Moisture-hardened Films of theTrimethylol Prepolymers of the following Isocyanates,reacted in OH:NCO equivalents = 1:2.                            Premium gasoline test 1 h, 50°                            C.          EGA.sup.+  MEK.sup.+  Acetone Xylene                            Pendulum Hardness acc to Koenig          Abrasion Test     (sec)Isocyanate Component          100 Cyclene       Before Test                                    After Test__________________________________________________________________________HDI-prepolymer no effect whatsoever                            167     158TMDI-prepolymer          no effect whatsoever                            172     169MNMDI-prepolymer          no effect whatsoever                            178      52*(MPDI + EBDI)-prepolymer          no effect whatsoever                            177     167__________________________________________________________________________ *Solvent absorption and softening of film .sup.+ EGA = ethylene glycol acetate .sup.+ MEK = methyl ethyl ketone 
    
     The resins used according to the invention provide directly applied reactive, cold-hardening, hard but elastic coatings. If necessary, hardening can also take place in the presence of heat. 
    
    
     EXAMPLE 1 
     134 g of trimethylolpropane (1 mol) and 504 g of a mixture of MPDI and EBDI (3 mol) in 343 g of ethyl glycol acetate are reacted for 6 hours at 80° C. 
     Yield: 978 g of prepolymer, NCO content: 12.79% (theoretical 12.84%), of a highly viscous, practically colorless resin. 
     
         ______________________________________Resin Preparation:           65 parts by weight of resin           35 parts by weight of ethyl           glycol acetate           0.01 part by weight of           dibutyltinlaurate (DBTL)           0.2 parts by weight of           diazabicyclooctane (DABCO)______________________________________ 
    
     The following data were obtained following moisture hardening: 
     
         ______________________________________Sheet Steel Data       Foil Data______________________________________PendulumHardness Accto Koenig  Erich-  Taber Abrasion                          Tear[sec]      sen     Test-H 22 Roll                          Resis-1st  3rd    7th    test  100 Cyclene                              tance   Elonga-Day  Day    Day    [mm]  500 g Bel. [mg]                              [N/mm.sup.2 ]                                      tion %______________________________________160  180    193    9.8   35        78.2    ?______________________________________Solvent resistance to MEK, EGA, xylene, acetone, premiumgasoline (1 h, 50° C.)Sheet steel data resin example 1, however pigmentedwith TiO.sub.2 (kronos Cl 310) PVK 15______________________________________PendulumHardnessto Koenig  Erich-[sec]      sen     Gloss Values According to1st  3rd    7th    Test  GardnerDay  Day    Day    [mm]  20° C.                              60° C.                                      85° C.______________________________________157  159    171    9.0   84        93      95______________________________________ 
    
     EXAMPLE 2 
     Triisocyanatoisocyanurate of MPDI and EBDI mixture. 
     Resin Preparation: 65 parts by weight of isocyanurate (MPDI+EBDI) 
     NCO content: 16.2% 
     35 parts by weight of ethyl glycol acetate 
     0.01 part by weight of DBTL 
     0.2 parts by weight of DABCO 
     The following data were obtained following moisture-hardening: 
     
         ______________________________________Sheet Steel DataPendulumHardness Acc       Abrasion Acc                          Foil Datato Koenig  Erich-  to Taber-H 22                          Tear[sec]      sen     Roll 100    Resis- Elonga-1st  3rd    7th    Test  Cyclene 500                              tance  tionDay  Day    Day    [mm]  g Bel. [mg]                              [N/mm.sup.2 ]                                     %______________________________________129  195    200    7.1   43.1      57.3   8______________________________________ 
    
     Solvent resistant to EGA, xylene, MEK, acetone, premium gasoline. 
     By reaction of the monomer diisocyanate mixture consisting of MPDI and EBDI with linear oxyesters, preferably those of molecular weights of about 1000 in NCO:OH equivalents=2:1, resins are obtained that, following moisture-hardening, form soft, tacky films and are not particularly suitable for immediate use. But these NCO end prepolymers are excellently suited for modification according to examples 1 and 2 to obtain less hard films on flexible substrates: 
     EXAMPLE 3 
     1,016.9 g of resin (produced by reaction of PCP 210 with (MPDI+EBDI) in the equivalence ratio OH:NCO=1:2) NCO content: 4.13%; and 2,616.8 of resin according to example 1 are homogenized and provide the following data after moisture-hardening: 
     
         ______________________________________Sheet Steel DataPendulumHardness Acc                   Foil Datato Koenig         Abrasion Acc to                          Tear[sec]    Erichsen T H 22 Roll  Resis- Elonga-15 min   Test     100 Cyclene  tance  tion150° C.    [mm]     500 g Bel. [mg]                          [N/mm.sup.2 ]                                 %______________________________________148      &gt;12      32           48.8   13______________________________________ Solvent resistant to EGA, MEK, acetone, xylene. 
    
     EXAMPLE 4 
     Analogously to example 3, both resins are mixed but in a 1:1 ratio. 
     The following data are obtained following moisture-hardening: 
     
         ______________________________________         2 -Sheet Steel DataPendulumHardness Accto Koenig              Foil Data[sec]      Erichsen    Tear15 min     Test        Resistance                            Elongation150° C.      [mm]        [N/mm.sup.2 ]                            %______________________________________77         &gt;12         19.1      35______________________________________ 
    
     EXAMPLE 5 
     Analogous mixtures according to examples 3 and 4 of the isocyanurate (MPDI+EBDI) and of the linear prepolymer (produced by reactions of PCP 210 with MPDI/EBDI mixtures in OH:HCO equivalents 1:2) following moisture-hardening provide numerically analogously equivalent sheet steel and foil data. 
     The outstanding performance of the adducts of the MPDI/EBDI mixture used according to the invention result from the fact that oxyester prepolymers as shown in example 6 provide high reactivity, good compatibility, and remarkable mechanical film data but are inadequate as regards storage stability and solvent resistance. 
     EXAMPLE 9 
     Prepolymer produced from 
     210 g of oxyester (1 mol of TMP, 2 mol of PS, 2 mol of HMG) 
     OHZ=266.7 
     168 g of MPDI/EBDI 
     378 g of ethyl glycol acetate (PA=phthalic acid; HMG=hexamethylene glycol) 
     Colorless resin, NCO content: 5.55% 
     Following catalytic activation with 0.02% DBTL and 0.2% DABCO and moisture-hardening, the following film data and properties have been determined. 
     
         ______________________________________PendulumHardness Accto Koenig[sec]      Erichsen            Storage Stability1st  3rd    7th    Test   Solvent  at RoomDay  Day    Day    [mm]   Resistance                              Temperature______________________________________113  133    170    &gt;10.0  Resistant                              Clear varnish about                     to       6 months;                     EGA, xylene                              pigmented systems                     susceptible                              about 4 weeks                     to MEK,                     acetone and                     premium                     gasoline______________________________________ 
    
     Having now fully described this invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein.