Abstract:
A polycarbodiimide-polyisocyanurate foam is prepared by reacting 
     (A) mixture of a polyol blend comprising 
     (a) 25 to 100% of an aromatic polyester polyol having the following structure: ##STR1## where n=1, 2, or 3 and having hydroxyl number 150 to 330, (b) 0 to 35% of a flexible polyether polyol with hydroxyl number 20 to 70, 
     (c) 0 to 25% of a toluene diamine ethoxylated polyol, optionally with some propoxylate, and having hydroxyl number 330 to 480, 
     (d) 0 to 25% of a nonyl phenol ethoxylate and having hydroxyl number 70 to9 150, and 
      with surfactant, catalyst, and water; and reacting with 
     (B) a polyphenyl polymethylene polyisocyanate such that the mixture of A is reacted with B at a 1:1 by volume mix ratio.

Description:
BACKGROUND OF THE INVENTION 
     Chloroflurocarbons (CFCs) apparently act to deplete the ozone layer in the stratosphere, yielding ecological damage. The amount of CFCs and ozone depletion potential can be reduced by using some water or CO 2  as blowing agents, and the amount of CFC can be eliminated by using all water or CO 2  blowing agents. Water reacts with isocyanate to yield substituted urea and gaseous CO 2  : 
     
         H.sub.2 O+2RNCO→RN(H)--CO--N(H)R+CO.sub.2 
    
     The isocyanate reaction to carbodiimide also generates gaseous CO 2  : 
     
         2RNCO→RN═C═NR+CO.sub.2 
    
     However, it is known that the CO 2  -blown foams shrink. In an article entitled &#34;Novel Polyols for CFC Reduction&#34; (M. Aoyagi et al., SPI ANTC (1980), pages 95-100), CO 2  -blown foam which had passable dimensional stability in low temperature or high temperature accelerated aging tests showed large deformations after a certain passage of time when left at room temperature. 
     In another article entitled &#34;Low Density Rigid Foam Without the Use of CFCs&#34; (D. C. Krueger et al., SPI ANTC (1990), pages 90-94), a number of all water (CO 2 ) blown urethane foams gave good room temperature dimensional stability but poor stability at elevated temperature. Shrinkage was especially pronounced at 158° F./100% R.H. 
     In U.S Pat. No. 4,945,119, rigid closed cell urethane foams produced using 5 to 70 mole percent CO 2  blowing gave cold shrinkage (-22° F.) unless co-expanded with a low boiling cylindered gas (e.g., CFC-142b having a boiling point of 10° C. or 263.8° K.). A low boiling gas must be included so as to withstand the negative internal pressure from the departing CO 2 , otherwise shrinkage occurs. The use of low boiling gases will require that current foam producers purchase very expensive processing equipment. Most of the low boiling gases being considered, such as CFC-142b, are HCFCs. The Clean Air Act of 1990 moved up to the end of 1995 the deadline for the U.S. to cease production of CFCs and other ozone depleting chemicals. The HCFCs, such as CFC-142b, will be phased out in the 2015-2030 time frame, with current impetus to move this up. CFC-142b, for example, still has an ozone depletion level of 0.025, though this is lower than CFCl 3  with an ozone depletion level of 1.0. 
     The three references cited above, whereby CO 2  -blown foams are shown to shrink at room temperature, elevated temperature, and low temperature, show that shrinkage is a problem with CO 2  -blown foams. Shrinkage is a problem because a freshly made foam containing CO 2  in the cells rapidly loses this gas by outward diffusion, leaving a negative internal pressure and possible shrinkage. Conversely, the rate of diffusion of CFCl 3  from a foam is almost negligible with much less chance of shrinkage. 
     In addition, water blowing yields high exotherm or heat of reaction. In the typical CFCl 3  expanded urethane foam, the hydroxyl groups react with isocyanate in an exotherm reaction to give a peak exotherm temperature in the 280°-320° F. range. But in an all water blown foam, the water reaction with isocyanate is also exothermic, and adds to the heat generated and now liquids such as CFCl 3  cannot be utilized to volatilize and dissipate some of the heat. So all water blown foams give much higher exotherm (e.g., in the 350°-380° F. range). At these high temperatures, foams can thermally split or scorch and char or even burst into flames, and some foams are even deformed and collapse at too high a temperature. 
     SUMMARY OF THE INVENTION 
     The present invention discloses the use of novel catalysts and polyol systems for carbodiimide formation. For example, potassium acetate or potassium octoate (the same catalysts used to effect isocyanurate formation) have been found to yield carbodiimide formation at relatively high concentration. Further, the all water-blown, CFC free, carbodiimide-isocyanurate foam is produced using existing foam process equipment so as to mix at 1:1 by volume mix ratios, although the foam could be produced at other mix ratios if desired. 
     A polycarbodiimide-polyisocyanurate foam is prepared by reacting 
     (A) a mixture of a polyol blend comprising 
     (1) an aromatic polyester polyol having the following structure: ##STR2##  where n=1, 2 or 3 and having hydroxyl number 150 to 330,  (2) a polyether polyol with hydroxyl number 20-70 generally used to make flexible foam and containing over half primary hydroxyl, 
     (3) optionally a toluene diamine (TDA) ethoxylate or ethoxylate/propoxylate polyol having hydroxyl number 330-480, 
     (4) optionally a nonyl phenol ethoxylate, hydroxyl number 70-150, 
      so as to give a miscible polyol blend composition with hydroxyl number 90-240 range, with surfactant, catalyst, and water; and reacting with 
     (B) a polyphenyl polymethylene polyisocyanate, such that the mixture of A is reacted with B at a 1:1 by volume mix ratio, although other ratios could be utilized. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An all water-blown, CFC free, carbodiimide-isocyanurate-urethane foam is generated at typically 1:1 by volume mix ratio, although other mix ratios may be utilized. The open-celled foam can be generated at relatively low density (e.g., 1.3-1.6 pcf) without shrinkage at 77° F., -40° F., or 158° F./100% R.H. The foam is useful for general purpose void filling and insulation. 
     The polyol blend comprises: 
     1. An aromatic polyester polyol made using mostly diethylene glycol or polyethylene glycols; said aromatic polyester polyol having hydroxyl number 150-330, preferably OH#200-300, and most preferably hydroxyl number 220-260. 
     The aromatic polyester polyols utilized in the present invention can be any of several available, such as Terate 254, Chardol 170, Stepan Pol PS-2502A, Terol 250, Chardol 196, etc. (as described in U.S. Pat. No. 4,981,879 which is incorporated by reference in its entirety). The aromatic polyester polyol generally contains predominantly primary OH groups. Predominantly primary OH groups mean that approximately 100% of the OH groups are primary (e.g., Ter-254, Chardol 170, Stepan PS-2502A); in addition, Chardol 196 (estimated 55-60% primary OH) may also be utilized. 
     2 A flexible polyether polyol with hydroxyl number 20-70 range. 
     3. A toluene diamine (TDA) ethoxylate polyol, with optionally some propoxylate, and having hydroxyl number 360-470. 
     4. A nonyl phenol ethoxylate, hydroxyl number 80-130. 
     The present invention is directed in one respect to a miscible polyol blend composition useful in the preparation of carbodiimide-isocyanurate-urethane foams. In another respect, the polyol blend composition is such that foams can be generated at 1:1 by volume mix ratios in existing process equipment, although other mix ratios could be utilized if so desired. 
     The polyol composition of the present invention is as follows: 
     
         ______________________________________          % by weight                          most          range  preferred                          preferred______________________________________1. aromatic polyester polyol            25-100   25-70    30-502. flexible polyether polyol            0-50     10-35    15-253. TDA ethoxylate            0-30     10-30    15-254. nonyl phenol ethoxylate            0-30     10-30    15-25______________________________________ 
    
     The polyol composition can contain component 1 by itself, with only one of components 2-4, or only two of components 2-4, or all three of components 2-4. 
     The term &#34;polyol&#34; as used herein has reference to a molecule containing two or more hydroxyl groups. In any given such polyol blend composition, the above indicated components are selected so as to result in a product polyol blend composition having a hydroxyl number in the range from about 90 to 240. 
     The foams are generated preferably with methylene bis diisocyanate (MDI) having functionability of 2.3 to 2.8,  preferably 2.6 to 2.7, with viscosity at 25° C. of about 200 cps. 
     The foams are generated at a 1:1 by volume mix ratio of A:B; where A is the premix or blend of polyols, surfactant, catalyst and water, and any organic acid adulterant, and B is the isocyanate. The isocyanate index is 80 to 270 based on ROH (and any COOH adulterant), plus additional isocyanate for the water reaction to substituted urea. The isocyanate index is preferably 100 to 140 on ROH, plus additional isocyanate for the water reaction to substituted urea. 
     The amount of water used to blow the carbodiimide isocyanurate foams is about 2.7 to 5.5, preferably 3 to 4, parts per hundred parts (php) of polyol. The water-isocyanate reaction yields urea groups that give a friable foam structure. The carbodiimide structure, being linear, gives a more rubbery foam structure. In fact the carbodiimide-isocyanurate foam of the present invention are very resilient. 
     All php refer to parts per hundred parts of the polyol blend (A). 
     The foam are generated at component temperatures 75° to 140° F., preferably 120° to 140° F. 
     Relatively high concentrations of potassium acetate or potassium octoate are required in order to effect carbodiimide formation (e.g., about 3-6 (php) Polycat-46 which is a solution of potassium acetate in glycol sold by Air Products). But then foam speed may be too fast and cause splits and scorch in the foam. The use of about 0.5-2.5 (php) of an organic acid such as formic acid, acetic acid, 2-ethyl hexoic acid, etc. proved useful in buffering the system to give slower foam speed without splits and scorch. Other acids such as isobutyric acid, n-caprylic acid, caproic acid, 3-methyl valeric acid, propionic acid, etc. can also be utilized. 
     The use of a good water-blowing catalyst (for example 0.2 to 0.5 (php) pentamethyldiethylene triamine) gave faster initial foaming reaction and finer cells. Some other good blowing catalysts are Texaco Chemical Company Texacat ZR-70, ZF-10, etc. 
     Another means to generate the carbodiimide foams of the present invention is to use a polyol or polyols that promote carbodiimide formation Particularly effective polyols in promoting carbodiimide formation have been found to be the toluene diamine (TDA) ethoxylates, optionally with some propoxylate (e.g., toluene diamine alkoxylated with 3-8 moles ethylene oxide and 0-4 moles propylene oxide; preferably 3.5 moles ethylene oxide and 4 moles propylene oxide). Particularly effective polyols of this nature are listed as follows: Pluracol 735, Pluracol 824, Multranol 4063, Multranol 9166, Dow XAS-10797.00, etc. The TDA ethoxylated polyol is used in the range of 10 to 30% of the polyol blend, and preferably 15 to 25% of the polyol blend. A catalyst level of about 0.4 to 1.0 php K-977 or K-15 potassium octoate was used. The K-977 or K-15 is a solution of potassium octoate in glycol. 
     Carbodiimide catalysts are numerous, but only cyclic phospholene oxides, such as 1-phenyl-3-methyl-2-phospholene-1-oxide, 1-methyl-3-phospholene-1-oxide, and 1-ethyl-3-methyl-3-phospholene oxide have the high degree of reactivity necessary to cause rapid formation of cellular products. Catalysts of the present invention are far less costly and more readily available. 
     EXAMPLES 
     The following are examples of polycarbodiimide-polyisocyanurate foams according to the present invention. All parts are given by weight. 
     EXAMPLE 1 
     Forty parts Ter-254, 20 pts. GP-3010, 20 pts. Pluracol 735, 20 pts. B-315, 2.0 pts. L-5420 surfactant, 0.4 pts. K-977 potassium octoate and 0.2 pts. Polycat 5 (pentamethyldiethylene triamine) and 4 pts. water were blended to give 106.6 pts. premix or A component. The Viscosity of A was 1200 cps at 77° F. The A component was mixed with 119.3 pts. Lupranate M-20 or B component that gave 1:1 by volume mix ratio A:B. 
     Components were metered through an E.R. Carpenter Co. 1100 series pump at the 1:1 by volume mix ratio through an EZ-500 gun used in packaging foam at 120°-140° F. component temperatures. The calculated index on ROH was 117. 
     Foam times follow: cream 2 sec, gel 18 sec, tack-free 41 sec, rise 58 sec. A fine celled foam was produced with the following properties: 
     
         ______________________________________density, pcf.       1.35% open cell         94compressive strength, psiparallel            9perpendicular       7tensile strength, psiparallel            20perpendicular       9K-factor, 2 weeks   0.276Shrinkage, % change74° F., 2 weeks               0.0158° F./95% R.H., 16 hrs.               0.0-40° F., 16 hrs.               0.0______________________________________ 
    
     EXAMPLES 2-6 
     were prepared analogously to example 1: 
     
         ______________________________________pbw        2       3       4     5      6______________________________________Terate 254 25.0    55.0    32.5  32.5   35.0GP-3010    35.0    25.0    27.5  27.5   35.0Pluracol 735      20.0    20.0    20.0  20.0   20.0B-315      20.0    --      20.0  20.0   10.0L-5420     2.2     2.2     2.0   2.0    2.2K-977      0.8     0.8     0.8   0.2    0.8Desmorapid PV      0.2     0.2     0.2   0.2    0.2water      4.0     3.8     4.0   4.0    3.8Total &#34;A&#34;  107.2   107.0   107.0 106.4  107.0Lupranate M-20 S      121.2   118.7   120.3 120.3  118.7index on ROH      134     88      125   125    102B/A temp., ° F.      120/    120/    120/  120/120                                   120/120      120     120     120cream, sec 4       4       5     5      4gel, sec   18      21      16    32     21tack-free, sec      --      35      28    80     37rise, sec  --      55      72    70     60density, pcf      1.47    1.58    1.46  1.99   1.58shrinkage77° F., 1 day      none    none    none  very   none                            slight158° F., 95% RH,      none    none    none  none   none1 day______________________________________ 
    
     EXAMPLES 7-11 
     were prepared analogously to example 1: 
     
         ______________________________________pbw        7       8       9     10     11______________________________________Chardol-196      50.0    60.0    100.0 --     --Terate-254 --      --      --    50.0   50.0GP-6500    50.0    25.0    --    50.0   50.0Voranol 360      --      15.0    --    --     --Formic Acid      1.0     1.0     1.0   --     --L-5420     2.0     2.0     2.0   2.0    2.0PC-46, KOAc      4.8     5.0     5.0   2.5    2.5PC-5       --      --      --    --     0.5water      3.1     3.4     3.1   4.0    4.0total &#34;A&#34;  110.9   111.4   111.1 108.5  109.0Lupranate M-20      122.5   125.9   125.2 123.0  123.0index on ROH &amp;      260     191     147   172    172COOHB/A temp,°F.      77/77   77/77   77/77 120/120                                   120/120cream, sec 13      14      28    14     5gel, sec   36      30      53    27     17tack-free, sec      44      33      57    36     25rise, sec  --      64      80    70     40density, pcf.       1.41   1.29    1.37  1.62   1.63shrinkage  0       0       0     0      077° F., 2 weeks% open cell      95      74      94    --     --______________________________________ 
    
     EXAMPLES 12-14 
     were prepared analogously to example 1: 
     
         ______________________________________pbw            12         13       14______________________________________Terate 254     100.0      --       100.0Chardol 196    --         100.0    --formic acid    1.0        --       --L-5420         2.0        2.0      2.0PC-46, KOAc    3.5        3.5      2.5water          3.1        3.1      3.1total &#34;A&#34;      109.6      108.6    107.6Lupranate M-20 117.3      113.6    115.3index on ROH and COOH          104        127      109B/A temp., ° F.          120/120    120/120  120/120Cream, sec     11         8        15Gel, sec       25         14       22Tack-free, sec 29         16       24Rise, sec      50         34       48density, pcf   1.36       1.32     1.61shrinkage      0          0        077° F., 2 weeks______________________________________ 
    
     Further variations and modifications of the invention will become apparent to those skilled in the art from the foregoing and are intended to be encompassed by the claims appended hereto.