Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2002-06-27
2004-03-09
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S052000, C528S045000, C528S073000, C252S182200, C544S193000, C544S222000
Reexamination Certificate
active
06703471
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing a low-odor, and storage-stable, monomer-containing polyisocyanurate based on isophorone diisocyanate.
2. Discussion of the Background
As polyisocyanate adducts, polyisocyanurates are valuable components in the production of high-grade coatings having good mechanical properties and also good light stability and weather resistance. Polyisocyanurates based on isophorone diisocyanate (IPDI) are also used as raw materials for PU-based elastomer applications. It may be desirable for the IPDI-based polyisocyanurate, also referred to as IPDI trimer, to be used in a form which still includes monomer.
Polyisocyanurates are basically obtained by catalytic trimerization of appropriate isocyanates. Examples of appropriate isocyanates are aromatic, cycloaliphatic, and aliphatic diisocyanates and higher polyisocyanates. Examples of suitable catalysts include tertiary amines (U.S. Pat. No. 3,996,223), alkali metal salts of carboxylic acids (CA 2113890; EP 56159), quaternary ammonium salts (EP 798299; EP 524501; U.S. Pat. Nos. 4,186,255; 5,258,482; 4,503,226; 5,221,743), aminosilanes (EP 197864; U.S. Pat. No. 4,697,014), and quaternary hydroxyalkylammonium salts (EP 17998; U.S. Pat. No. 4,324,879). Depending on the catalyst it is also possible to use various cocatalysts, for example, OH-functionalized compounds or Mannich bases composed of secondary amines and aldehydes and/or ketones.
For trimerization, the polyisocyanates are reacted in the presence of the catalyst, where appropriate using solvents and/or auxiliaries, until the desired conversion has been achieved. In this context, one also speaks of partial trimerization, since the target conversion is generally well below 100%. The reaction is then terminated by deactivating the catalyst. This is done by adding a catalyst inhibitor such as, for example, p-toluenesulfonic acid, hydrogen chloride or dibutyl phosphate, and results unavoidably in a possibly unwanted contamination of the polyisocyanate containing isocyanurate groups that are formed. Of particular advantage in respect of the trimerization of isocyanates on the industrial scale is the use of quaternary hydroxyalkylammonium carboxylates as oligomerization catalysts. This type of catalyst is thermally labile and is amenable to targeted thermal deactivation, so that it is unnecessary to stop the trimerization by adding potentially quality-reducing inhibitors when the desired conversion has been reached.
Monomer-containing IPDI trimer, which is suitable, for example, for the abovementioned PU injection applications, has an NCO content of 28-32% by weight. The polyisocyanurate is prepared by partial trimerization of IPDI in the presence of one or more appropriate catalysts. Afterward, the catalyst must either be removed fully from the reaction solution—this can be done by short-path or thin-film distillation—or deactivated, because the trimer lacks storage stability in the presence of active catalyst residues. Where the NCO content of the IPDI polyisocyanurate obtained is below the desired level, it can be adjusted as desired without problems by diluting the solution with monomeric IPDI.
Alkali metal salts of carboxylic acids are not very suitable as catalysts for preparing monomer-containing IPDI trimer, because they are difficult, if not impossible, to remove from the reaction product. With regard to the amine catalysts available, it has been found that the resulting IPDI trimer solutions are fundamentally hampered by a clearly perceptible odor, which is sufficiently pronounced to remain detectable in the end application and to manifest itself unpleasantly. In order to eliminate the odor nuisance, it is technical practice to free the reaction solution, following partial trimerization and catalyst deactivation, from excess IPDI, from odoriferous components, and, where appropriate, from unwanted catalyst inhibitors. This is generally done by means of short-path or thin-film distillation. Subsequently, the monomer-freed solid resin is converted into the desired, low-odor and monomer-containing IPDI polyisocyanurate by adding fresh IPDI.
The sequence of partial trimerization/deactivation, demonomerization/purification, and, finally, dissolution of the solid resin in the monomer is very cumbersome. The step of separating off the monomer in the existing process consumes a lot of time, adds a lot of costs, and, moreover, represents a capacity-limiting bottleneck.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a more economical process for preparing a low-odor and storage-stable monomer-containing polyisocyanurate based on isophorone diisocyanate, in which demonomerization is avoided. It has surprisingly been found that this step can in fact be omitted and, moreover, that the use of possibly quality-reducing inhibitors can be avoided if the trimerization of IPDI is conducted in the presence of specific catalysts.
Accordingly, the present invention provides for a process for preparing a low-odor, storage-stable monomer-containing polyisocyanurate, comprising:
partially trimerizing isophorone diisocyanate at a temperature of 0-160° C. for 3 minutes to 3 hours in the presence of 0.05-2% by weight of a catalyst, based on the weight of the isophorone diisocyanate;
wherein said catalyst is represented by the following formula
[R—NX
3
]
m⊕
mY
⊖
wherein
Y
⊖
is a carboxylic acid anion having 4-8 carbons;
R is a &bgr;-hydroxyalkyl group having 2-6 carbons;
X is an alkylene group having 2-3 carbons; and
m is a number from 1.0 to 2.0;
wherein the three radicals X form a ring with the quaternary nitrogen by way of a common nitrogen atom; and
wherein said process proceeds at a temperature of from 0 to 160° C.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for preparing a low-odor, storage-stable monomer-containing polyisocyanurate from isophorone diisocyanate. The process comprises conducting a partial trimerization of isophorone diisocyanate over a period of 3 minutes to 3 hours in the presence of 0.05-2% by weight of a catalyst, based on the weight of the diisocyanate, the catalyst having the general formula
[R—NX
3
]
m⊕
mY
⊖
wherein Y
⊖
is a carboxylic acid anion of 4-8 carbons,
R is a &bgr;-hydroxyalkyl group of 2-6 carbons,
X is an alkylene group of 2-3 carbons, and
m is a number from 1.0 to 2.0. The three radicals X form a ring with the quaternary nitrogen by way of a common nitrogen atom, which may be partly &bgr;-hydroxyalkylated, said ring possibly having an OH group positioned &agr;, &bgr; or &ggr; to the nitrogen. The process proceeds at a temperature of 0-160° C., preferably 40-120° C., and most preferably 55-95° C. In this it is possible to dispense with separating off the monomer and chemically deactivating the trimerization catalyst. The reaction temperature includes all values and subvalues therebetween, especially including 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140 and 150° C. The reaction time of the partial trimerization includes all values and subvalues therebetween, especially including 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160 and 170 min. The amount of catalyst includes all values and subvalues therebetween, especially including 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 and 1.9%.
In principle, isocyanates appropriate for trimerization can be prepared by different kinds of processes (Annalen der Chemie 562 (1949) 75 ff.). Particularly well established in the industry is their preparation by phosgenating organic polyamines to the corresponding polycarbamoyl chlorides and cleaving these chlorides thermally into organic polyisocyanates and hydrogen chloride. Alternatively, organic polyisocyanates can also be prepared without using phosgene, i.e., by phosgene-free processes. According to EP-A-126 299 (U.S. Pat. No. 4,596,678), EP-A-126 300 (U.S. Pat. No. 4,
Kohlstruk Stephan
Kreczinski Manfred
Lomölder Rainer
Degussa - AG
Gorr Rachel
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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