Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-06-18
2003-02-25
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S114000, C521S116000, C521S117000, C521S118000, C521S128000, C521S129000, C521S130000, C521S155000, C528S049000, C528S052000, C528S053000, C528S054000
Reexamination Certificate
active
06525107
ABSTRACT:
BACKGROUND OF THE INVENTION
Polyurethanes are useful in a variety of applications. For example, polyurethane elastomers are used in automotive parts, shoe soles, and other products in which toughness, flexibility, strength, abrasion resistance, and shock-absorbing properties are required. Polyurethanes are also used in coatings and in flexible and rigid foams.
Polyurethanes, in general, are produced by the reaction of a polyisocyanate and a polyol in the presence of a catalyst. The catalyst has typically been a low molecular weight tertiary amine such as triethylenediamine.
Polyurethane foams are produced through the reaction of a polyisocyanate with a polyol in the presence of various additives. One additive can be water which is used as a blowing agent. The blowing reaction produces carbon dioxide from the reaction of water with the polyisocyanate. Foams can be formed by a one-shot method or by formation of a prepolymer and subsequent reaction of the prepolymer with water in the presence of a catalyst to form the foam. Regardless of the method, a balance is needed between reaction of the isocyanate and the polyol (gelling) and the reaction of the isocyanate with water (blowing) in order to produce a polyurethane foam in which the cells are relatively uniform and the foam has specific properties depending on the anticipated application; for example, rigid foams, semi-rigid foams, and flexible foams.
The ability of the catalyst to selectively promote either gelling or blowing is an important consideration in selecting a catalyst for the production of a polyurethane foam with specific properties. If a catalyst promotes the blowing reaction to too high a degree, carbon dioxide will be evolved before sufficient reaction of isocyanate with polyol has occurred. The carbon dioxide will bubble out of the formulation, resulting in collapse of the foam and production of a poor quality foam. At the opposite extreme, if a catalyst promotes the gelling reaction too strongly, a substantial portion of the carbon dioxide will be evolved after a significant degree of polymerization has occurred. Again, a poor quality foam is produced; characterized by high density, broken or poorly defined cells, or other undesirable features. Frequently, a gelling catalyst and a blowing catalyst are used together to achieve the desired balance of gelling and blowing in the foam.
Tertiary amine catalysts are widely used in the production of polyurethanes. The tertiary amine catalysts accelerate both blowing (reaction of water with isocyanate to generate carbon dioxide) and gelling (reaction of polyol with isocyanate) and have been shown to be effective in balancing the blowing and gelling reactions to produce a desirable product. The most widely used commercial catalysts for producing polyurethanes are triethylenediamine (TEDA), also called 1,4-diazabicyclo[2.2.2]octane, and its derivatives.
Other catalysts known to be effective in the preparation of polyurethanes are those containing carboxyl functionality as well as tertiary amine groups. These catalysts are typically delayed action catalysts. Examples are described below:
U.S. Pat. No. 4,464,488 (Zimmerman et al., 1984) discloses the use of monocarboxylic acid salts of bis(aminoethyl)ether derivatives as catalysts in the preparation of polyurethanes.
DE 195 12 480 A1 (1996) disclose heat activated catalysts of the general formula:
in which R
1
and R
2
are the same or different C1 to C20 alkyl, possibly containing oxygen atoms, or together with the N atom form a 5- or 6-membered ring possibly containing oxygen atoms, X is possibly a substituted alkylene having 2-3 carbon atoms, a 1,2-substituted cyclohexyl, or an ortho-substituted phenyl group, and Y is a possibly branched C2 to C6 alkyl, possibly containing heteroatoms (O, N, S). The catalysts are useful in the production of polyurethanes.
U.S. Pat. No. 5,489,618 (Gerkin, 1996) discloses a process for preparing a polyurethane foam according to the a one-shot foaming process using a delayed action amine salt catalyst. The catalyst is formed by reaction between a tertiary amine and a carboxylic acid having hydroxyl functionality.
EP 989 146 A1 (2000) discloses a delayed action catalyst for the production of polyurethanes that is a mixture of a tertiary amine and a saturated dicarboxylic acid. The catalyst is reported to be non-corrosive.
BRIEF SUMMARY OF THE INVENTION
This invention is directed to novel acid-blocked amine catalysts and their use in the preparation of polyurethanes. The acid-blocked amine catalysts have the general structure shown below
wherein A is the residue of an organic acid anhydride; R
1
is H or C
1
to C
6
alkyl; R
2
is H or C
1
to C
6
alkyl; n is an integer of 0 to 10; and B is a compound containing a protonated amine and one or more primary amine, secondary amine, or tertiary amine groups.
The acid-blocked amine catalysts of this invention are prepared by reacting an organic acid anhydride with a mono- or poly-alcohol, such as ethylene glycol or diethylene glycol, in the presence of an amine.
This invention is also directed to the use of the new acid-blocked amine catalysts as a catalyst in the production polyurethanes, especially polyurethane foams. Use of the acid-blocked amine catalysts of this invention results in a polyurethane with improved flowability and little or no corrosion. In addition, the novel blocking catalysts are useful in both MDI (diphenylmethane diisocyanate) and TDI (toluene diisocyanate) technologies and in high and low density foam applications.
DETAILED DESCRIPTION OF THE INVENTION
This invention is directed to new acid blocked amine catalysts and their use in the preparation of polyurethanes, especially polyurethane foams. The acid-blocked amine catalysts have the general structure shown below:
wherein A is the residue of an organic acid anhydride; R
1
is H or C
1
to C
6
branched or straight chain alkyl; R
2
is H or C
1
to C
6
branched or straight chain alkyl; n is an integer of 0 to 10, preferably 1 to 2; and B is a compound containing a protonated amine and one or more primary amine, secondary amine, or tertiary amine groups.
Examples of A include a C2-C3 alkylene group which optionally may contain a double bond, such as ethyl, propyl, ethenyl, propenyl; 1,2-cyclohexylene which optionally may contain a double bond, or ortho-phenylene. Examples of R
1
, when it is an alkyl group, or R
2
are H, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, and hexyl. Examples of B
+
are protonated forms of dimethylaminopropylamine (DMAPA), triethylenediamine (TEDA), pentamethyldiethylenetriamine (PMDETA), pentamethyldipropylenetriamine (PMDPTA), bis(2-dimethylaminoethyl)ether (BDMAEE), N,N,N″,N″-tetramethyldipropylene-triamine, N,N,N′-trimethyl-N′-hydroxyethyl-bis (aminoethyl)ether, N,N-bis-(3-dimethylaminopropyl)-N-isopropanolamine, N-(3-dimethylaminopropyl)-N,N-diisopropanolamine, N-(3-dimethylaminopropyl)urea, N,N′-bis(3-dimethylaminopropyl)urea, and 2-(2-dimethylaminoethoxy)ethanol.
The acid-blocked amine catalyst of this invention is prepared by reacting an anhydride, such as phthalic anhydride, maleic anhydride, succinic anhydride, 1,2-dicyclohexanedicarboxylic acid anhydride, and 3,4-dehydrocyclohexane-1,2-dicarboxylic acid anhydride with an alcohol, such as ethyleneglycol, methyldiethyoxyalcohol, or diethyleneglycol at 60° C.-120° C. for about 2 hours, and afterwards cooling the reaction mixture down to about 50-70° C. and slowly adding, with stirring, an amine, such as the above mentioned amines. An example of this reaction is shown below in which phthalic anhydride is reacted with BDMAEE in diethyleneglycol:
The amine, acid anhydride, and alcohol are typically reacted in a 1:1:1 molar ratio, although other molar ratios can be used. The reaction is allowed to run to completion; typically, approximately 2 hours. The completion of reaction is monitored by gas chromatography (GC).
The catalyst of this invention can catalyze the reaction between an isocyanate and a comp
Fard-Aghaie Reza
Wendel Stephan Herman
Air Products and Chemicals Inc.
Bongiorno Mary E.
Sergent Rabon
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