Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-05-08
2002-03-26
Vollano, Jean F. (Department: 1621)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S155000
Reexamination Certificate
active
06362247
ABSTRACT:
This invention relates to a method of improving the stability of aromatic polycarbodiimides. More particularly, this invention relates to a method of improving the stability of aromatic polycarbodiimides using catalyst poisons.
Aromatic polycarbodiimides (hereinafter referred to as “ar-pCDI”) are used as crosslinkers in a variety of applications, including coatings, adhesives, caulks, mastics, and the like. Generally, ar-pCDI are made by heating aromatic isocyanates in the presence of phosphorous oxides, usually phospholene oxides such as 3-methyl-1-phenyl-2-phospholene-1-oxide (hereinafter referred to as “MPPO”). The phosphorus oxides catalyze the reaction between 2—NCO groups to make a carbodiimide (hereinafter referred to as “CDI”) and CO
2
:
2R-NCO→R—N═C═N—R+CO
2
The catalyst reacts with —NCO to form a phosphinimide and carbon dioxide:
R′NCO+R
3
P═O→R
3
P═NR′+CO
2
that then reacts with another R′NCO to regenerate the catalyst and make CDI:
R
3
P═NR′+R′NCO→R′N═C═NR′+R
3
P═O.
After they are made, the ar-pCDI molecules begin to slowly build viscosity until they gel. While not wishing to be bound by theory, it is believed that the residual phosphorous oxide present in ar-pCDI solutions catalyze the reaction between the ar-pCDI and any compounds containing active hydrogens such as water, alcohols, amines, and other materials bearing active hydrogens that may contaminate the ar-pCDI solutions:
N═C═N+ROH→N═C(OR)NH
Over time, the accumulation of N═C(OR)NH causes the ar-pCDI to build viscosity and eventually gel.
This instability limits the usefulness of ar-pCDI because the shelf life is too short, i.e., less than six months, to be commercially viable. Aliphatic pCDI do not suffer the same stability problems as ar-pCDI, but, inter alia, are too reactive to make good crosslinkers for water-borne coatings when compared with ar-pCDI. Thus, ar-pCDI would be preferred if the shelf-life stability problems could be solved.
I have discovered that the stability or gel time of ar-pCDI is dependent on the level of phosphorous oxide used to make it and that remains in the ar-pCDI after manufacture; the more phosphorous oxide, the shorter the gel time. I have further discovered a way to deactivate these catalysts. Certain chemicals, hereinafter referred to as “catalyst poisons,” may be added to the ar-pCDI after it is made that will react with the catalyst to deactivate it, thus greatly extending the storage stability or shelf-life of the ar-pCDI.
These catalyst poisons are not novel. For example in U.S. Pat. No. 5,202,358, U.S. Pat. No. 4,014,935, and U.S. Pat. No. 4,614,785, organic isocyanates containing carbodiimides and/or uretone imine groups are prepared by the partial polymerization of the —NCO groups using phosphorous oxide .catalysts. When only partial conversion takes place, the carbodiimides react with further isocyanate groups to give uretone imine groups. To ensure only a partial polymerization of the —NCO groups, U.S. Pat. No. 5,202,358 discloses the addition of silylated acid compounds of the formula X—[Si(CH
3
)
3
]
n
to the reaction to terminate the formation of carbodiimide groups. To ensure only a partial polymerization of the —NCO groups, U.S. Pat. No. 4,014,935 discloses that the phosphorous oxide catalyst is absorbed onto a substrate or deactivated by halides of hydrogen, tin, or phosphorus, or the oxyhalide of phosphorus or sulfur. To ensure only a partial polymerization of the —NCO groups, U.S. Pat. No. 4,614,785 discloses that the phosphorus oxide catalyst is deactivated with sulfonyl isocyanates.
In each of the above-referenced patents, the starting material is an isocyanate catalyzed by a phosphorous oxide. Only a partial reaction is desired so that the final product is a mixture. However, the presence of the residual phosphorous oxide leads to an undesired, complete reaction. The deactivation of the catalyst, either by adsorption onto a substrate or by the addition of a catalyst poison, prevents complete conversion to the pCDI. The present invention utilizes the deactivation steps but their purpose is to prevent the residual phosphorous oxide in the completed reaction from gelling the system rather from preventing the completed reaction.
STATEMENT OF THE INVENTION
The invention is directed to a method of improving the stability of ar-pCDI formed using a phosphorous oxide catalyst including the step of deactivating the catalyst.
Preparation of ar-pCDI using phosphorous oxide catalysts may be by conventional means such as those methods disclosed in U.S. Pat. No. 2,853,473, U.S. Pat. No. 2,941,966, U.S. Pat. No. 2,941,983, U.S. Pat. No. 4,487,964 and U.S. Pat. No. 5,574,083. On completion of the preparation of ar-pCDI, the phosphorous oxide catalysts is deactivated by addition to the ar-pCDI of at least one catalyst poison.
Deactivation may be carried out by addition to the ar-pCDI of at least one catalyst poison. The catalyst poisons useful in the method of invention include sulfonyl isocyanates and silylated acids of the formula X—[Si(CH
3
)
3
]
n
where X represents the neutral acid residue obtained by removal of the acidic hydrogen atoms from an n-basic acid having a pKa value of at most 3, other than a hydrohalic acid, and n is an integer of 1 to 3.
Examples of suitable sulfonyl isocyanates include any inorganic or organic compounds which contain at least one structural unit corresponding to the following formula —SO
2
—NCO. Organic sulfonyl isocyanates are preferably used, while those containing aromatically-bound isocyanatosulfonyl residues are particularly preferred. Processes for producing organic sulfonyl isocyanates of the type suitable for use in accordance with the invention and also their chemical behavior are comprehensively described by H. Ulrich in
Chem. Rev
. 65, pages 369-376, 1965. In addition, the production of aryl sulfonyl isocyanates is described in U.S. Pat. No. 2,666,787 and U.S. Pat. No. 3,484,466. According to the invention, it is possible to use aliphatic, cycloaliphatic and also aromatic mono- or polysulfonyl isocyanates, of which the following are mentioned by way of example: methyl sulfonyl isocyanate, butyl sulfonyl isocyanate, cyclohexyl sulfonyl isocyanate, chlorosulfone isocyanate, perfluorooctyl sulfonyl isocyanate, phenyl sulfonyl isocyanate, p-toluene sulfonyl isocyanate, benzyl sulfonyl isocyanate, p-chlorophenyl sulfonyl isocyanate, m-nitrophenylsulfonyl isocyanate, 2,5-dimethyl phenyl sulfonyl isocyanate, p-fluorophenyl sulfonyl isocyanate, 2,5-dichlorophenyl sulfonyl isocyanate, 3,4-dichlorophenyl sulfonyl isocyanate, p-bromophenyl sulfonyl isocyanate, p-methoxyphenyl sulfonyl isocyanate, p-nitrophenyl sulfonyl isocyanate and o-nitrophenyl sulfonyl isocyanate; m-phenylene disulfonyl diisocyanate, p-phenylene disulfonyl diisocyanate, 4-methyl-m-phenylene disulfonyl diisocyanate, 2-chloro-p-phenylene disulfonyl diisocyanate, 5-chloro-m-phenylene disulfonyl diisocyanate, 1,5-naphthylene disulfonyl diisocyanate, 3-nitro-p-phenylene disulfonyl diisocyanate, 4-methoxy-m-phenylene disulfonyl diisocyanate, 2,5-furandiyl-bis-(methylene-sulfonyl)-diisocyanate, 4,4′-bis-phenylene disulfonyl diisocyanate, 2,2′-dichloro-4,4′-biphenylylene-disulfonyl diisocyanate, 3,3′-dimethoxy-4,4′-biphenylylene-disulfonyl diisocyanate, (methylene-di-p-phenylene)-disulfonyl diisocyanate, (methylene-di-3,3′-dimethoxy-p-phenylene)-disulfonyl diisocyanate, (methylene-di-3,3′-dimethyl-p-phenylene)-disulfonyl diisocyanate and 2-methyl-p-phenylene disulfonyl diisocyanate; also sulfonyl isocyanates containing free NCO-groups such as m-isocyanatophenyl sulfonyl isocyanate, p-isocyanatophenyl sulfonyl isocyanate, 3-isocyanato-p-tolyl sulfonyl isocyanate, 5-isocyanato-o-tolyl sulfonyl isocyanate, 3-isocyanato-4-methoxyphenyl sulfonyl isocyanate, 4-isocyanato-3-chlorophenyl sulfonyl isocyanate, 4′-isocyanato-4-biphenylyl sulfonyl isocyanate, 4&pri
Rohm and Haas Company
Vollano Jean F.
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