Polyurethane curatives

Abstract

A class of alkanol amine ligands reacted with bismuth carboxylates lends unique curability properties to isocyanate and polyols for production of polyurethane for CASE applications, including growing demand for polyurethane spray-foam. The amino-alcohol ligand, when associated with bismuth neodecanoate, offers improved moisture and solvent resistance during B-side (polyol) storage, cure rates analogous to tin-based curatives, and overall good final physical properties of the cured polyurethane.

Claims

1. A spray-foam polyurethane catalyst produced by the reaction between a bismuth carboxylate with an alkanolamine and a polyol, wherein polyol is selected from polyethylene glycols, polypropylene glycols and polybutylene ether glycols, wherein the bismuth carboxylate is bismuth neodecanoate, and wherein the alkanolamine is tetrakis(2-hydroxyethyl)ethylenediamine.

2. A polyurethane catalyst produced by the reaction between a bismuth carboxylate with an alkanolamine and a polyol, wherein polyol is selected from polyethylene glycols, polypropylene glycols and polybutylene ether glycols, wherein the bismuth carboxylate is bismuth neodecanoate, and wherein the alkanolamine is ethylenedinitrilo-tetra-2-propanol.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is the FTIR spectrum for Curative 8840 in Example 1.

(2) FIG. 2 is the .sup.1H NMR spectrum for Curative 8840 in Example 1.

(3) FIG. 3 is the FTIR spectrum for Curative 8842 in Example 2.

(4) FIG. 4 is the .sup.1H NMR spectrum for Curative 8842 in Example 2.

DETAILED DESCRIPTION

(5) Bismuth carboxylates have been used as catalysts for polyurethane formation. Bismuth carboxylates are attractive catalysts as these compounds have low toxicity and a rapid cure rate. Yet, with conventional bismuth carboxylate catalysts, the window of reactivity may be too short, or the backend cure may result in a tacky finish. Accordingly, it would be desirable to have an improved bismuth catalyst with a longer reactivity period resulting in a smoother finished product with no tack.

(6) The catalysts of the instant application are prepared by the reaction of a bismuth carboxylate salt with an alkanolamine. The carboxylate salt may have 2 to 20 carbon atoms in the molecule, preferably 8 to 12 carbon atoms in the molecule. The useful carboxylic acids are represented by the formula RCOOH wherein R is a hydrocarbon radical containing 1 to about 19 carbon atoms. R can be alkyl, cycloalkyl aryl, alkaryl such as methyl, ethyl, propyl, isopropyl, neopentyl, octyl, neononyl, cyclohexyl, phenyl, tolyl or napthyl. More specifically, the bismuth carboxylate is bismuth neodecanoate which is reacted with an alkanolamine to form the desired catalyst.

(7) The catalysts of the present technology can be employed in a wide range of elastomer formulation systems where reduced catalyst toxicity is desirable. The catalyst provides an alternative to the use of catalysts based on lead, tin or mercury. The catalyst of this technology provides optimum performance based on tailored gel times, provides rapid release or remold times, and will not contribute to embrittlement of the cured elastomer. The catalyst of the instant technology, as a polymerization catalyst, has minimal effect on the water/isocyanate reaction with moisture levels normally found in a wet/undried formulated urethane system. Most importantly, the catalyst has an excellent acute toxicity profile. No occupational exposure limit standard must be met when using the catalyst.

(8) In contrast to many conventional catalysts, bismuth may be considered a green metal which is safe for human consumption. It can found in applications such as bismuth subsalicylate (for nausea, heartburn, etc.), bismuth subgallate (internal deodorant), bismuth subnitrate/subsulfate (radiochemicals), bismuth oxychloride (in make-up), and bismuth brocathol (for eye infections).

(9) The use of coordination or complexation ligands such as alkanolamines, when added to a conventional bismuth carboxylate has been found to mediate and control the initial and/or backend cure properties of bismuth-catalysts. Alkanloamines may include, but are not limited to N-methyldiethanolamine, N-methylethanolamine, Diethanolamine

(10) Diisopropanolamine, N,N-diethylethanolamine, N,N-dimethylethanolamine, 2-(2-aminoethoxy)ethanol, 2-amino-2-methyl-1-propanol, 1-dimethylamino-2-propanol 2-(((2-dimethylamino)ethyl)methylamine)ethanol, 2-(butylamino)ethanol, 2-(ethylamino)ethanol, 2-(methylamino)ethanol, 1-amino-2-propanol, 3-amino-1-propanol.

(11) Additional examples of alkanolamine ligands are shown in FIG. 1:

(12) ##STR00001##

(13) The bismuth diaminotetraol complexes BiCAT 8840 and BiCAT 8842, (where BiCAT 8840 is bismuth, 1,1,1,1-(1,2-ethanediyldinitrilo)tetrakis[2-propanol] neodecanoate complexes; and BiCAT 8842 is bismuth, 2,2,2,2-(1,2-ethanediyldinitrilo)tetrakis[ethanol] neodecanoate complexes) may be used as catalysts in polymerization reactions, including use as polyurethane catalysts. A benefit of the use of these compounds is thought to be the combination of the bismuth carboxylate with the diaminotetraol ligands for use in the formation of polyurethane foam and CASE applications.

(14) The ratio of alkanolamine to metal may be varied from 2.0: to 0.1 mole ratio to produce the desired cure profile, which is also based on selection of isocyanate (MDI and polyol (polyester, polyether, etc.)) to form the polyurethane. Temperature can also be varied in the polymerization process (temperature ranges of ambient temperature to 90 C.) to obtain the desired cure rate.

(15) All catalysts used prior to this technology had the capability of promoting reaction between a hydroxyl group and isocyanates to produce urethane linkages and, ultimately, polyurethane products. The major disadvantage of these catalysts is that they contain metals including mercury and as such, must be handled with extreme caution due to their classification as poisons and the shipping containers must be labeled accordingly. Organolead catalysts must also be handled with a great deal of caution due to their toxicity classification as a hazardous substance. Primarily due to these questions regarding toxicity and handling, the use of tin catalysts in non-cellular urethane systems has become popular. As a class, tin compounds do not provide the same type of catalytic performance as mercury and lead compounds, since the tin compounds also promote the reaction between moisture and isocyanates in addition to the hydroxyl group-isocyanate reaction. The non-specific nature of the tin catalysts makes them difficult to use, with the processor required to go to extreme measures to reduce the presence of moisture in order to eliminate bubbling or pinhole formation in the elastomers obtained.

(16) The hydroxy containing reactants used in the preparation of the polyurethane elastomers of the present technology comprise primary and secondary hydroxy terminated polyalkylene ethers and polyesters having from 2 to 4 hydroxyl groups and a molecular weight of from about 1000 to 10,000. They are liquids, or are capable of being dissolved or melted for handling.

(17) Examples of polyalkylene polyols include linear and branched polyethers having a plurality of ether linkages and containing at least 2 hydroxyl groups and being substantially free from functional groups other than hydroxyl groups. Typical examples of the polyalkylene polyols which are useful in the practice of the technology are the polyethylene glycols, polypropylene glycols and polybutylene ether glycols. Linear and branched copolyethers of ethylene oxide and propylene oxide are also useful in preparing the elastomers of this technology. Those having molecular weights of from 2000 to 5000 are preferred. Polyethers having a branch chain network are also useful. Such branched chain polyethers are readily prepared from alkylene oxides and initiators having a functionality greater than 2.

(18) Any organic di- or tri-isocyanate can be used in the practice of the present technology. Diisocyanates are preferred. Examples of suitable organic polyisocyanates are isophorone diisocyanate (weatherability), polyisocyanates, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate and hexamethylene diisocyanate. Examples of aromatic diisocyanates include 2,4-tolylene diisocyanate, and 2,6-tolylene diisocyanate. In addition, methylene diphenyldiisocyanates and polymeric isocyanates based on methylene diphenyldiisocyanates can be employed.

(19) The amount of polyisocyanate employed ranges from about 0.7 to 1.3 mole of NCO in the polyisocyanate per mole of active hydrogen in the polyols.

(20) In certain instances it may be desirable to add a chain extender to complete the formulation of polyurethane polymers by reacting isocyanate groups of adducts or prepolymers. Examples of some types of polyol chain extenders include 1, 4-butanediol, diethylene glycol, trimethylol propane and hydroquinone di(beta hydroxyethyl ether).

(21) The chain extender when present is added as 1 to 20 weight percent, preferably 3 to 6 weight percent based on the weight of the reactants. The technology is illustrated by the following specific but non-limiting examples.

(22) Another aspect of this technology is the combination of alkanolamine ligands per metal center through substitution of the initial ligand, and/or displacement, with complexation. It is believed that unique polyurethane curative properties can be obtained either as synergistic or additive in nature.

(23) In another aspect of the technology, when a bismuth-based catalyst such as BiCAT 8840 or BiCAT 8842 is used in the same formulation as the stannous octanoate at the same use level, the VOC's are the same for both BiCAT systems, confirming the catalysts of the present disclosure may be used as a suitable substitute for tin-based catalysts. This PU formulation is for interior automotive applications. Accordingly, in an industrial evaluation designed to analyze both VOC's and the interior fogging, the foam produced using the bismuth catalysts of the present technology have a cellular structure, comparable to the stannous octanoate catalyst. Importantly, measurement of VOC (fogging) under standardized automotive conditions showed that a PU formulation cured with TEDA had a VOC content of 208 ug/g, relative to the use of BiCAT 8840 which yielded a VOC content of 94 ug/g.

EXAMPLES

Example 1

Preparation of Curative 8840

(24) To a 500 mL reaction flask with a nitrogen blanket, overhead stirrer, and temperature probe, is added 100 grams of BiCAT 8106, (bismuth neodecanoic acid, 20 wt % Bi). Begin agitation and warm to 35 C. After temperature is reached, charge 60 grams N,N,N,N-tetrakis(2-hydroxypropyl)ethylenediamine. After adding, a small exotherm is observed along with a color change from yellow to orange. After exotherm subsides, 40 g of diethylene glycol monoethyl ether is charged. Agitate at medium speed for one hour. Raise the temperature to 45 C. and hold for one hour. The material is then poured into a sample cup with lid. Characterization, or fingerprinting, of the 8840 is conducted by FTIR, .sup.1H NMR, and metal concentration determination. Analytical measurement of the bismuth concentration was 10.1 wt %, with a quantitative yield.

Example 2

Preparation of Curative 8842

(25) To a 500 mL reaction flask with a nitrogen blanket, overhead stirrer, temperature probe, is added 50 grams of BiCAT 8106, (bismuth NDA, 20 wt % Bi). Begin agitation and warm to 35 C. After temperature is reached, charge 50 grams N,N,N,N-tetrakis(2-hydroxyethyl)ethylenediamine. After adding, a small exotherm is observed along with a color change from yellow to orange. Using medium agitation speed, continue to mix for one hour. Raise the temperature to 45 C. and hold for one hour. The material is then poured into a sample cup with lid. Characterization, or fingerprinting, of the 8842 is conducted by FTIR, NMR, and metal concentration determination. Analytical measurement of the bismuth concentration was 10.7 wt %, with a quantitative yield.

Example 3

Spray Foam Formulation of Two-Component PU System Using Curative 8842

(26) BiCAT 8842 was used in a two-part polyurethane system (TDI) for spray-foam applications. The BiCAT 8842 was added at 0.125 wt % to the polyol side (B-part). In addition, the polyol side contained 2.5 wt % water. It has been demonstrated that the 8842 remained stable for many weeks in the presence of moisture, while a control formulation using bismuth neodecanoate at the same use level began to turn white after 14 min, sign of bismuth hydrolysis to the hydroxide. The same dosage of stannous octoate curative was added to the TDI-tin-based control formulation. The cure rate and gel time were similar to that of the stannous octoate.

Example 4

Foam Kinetics and Density of Two-Component PU System Using Curative 8842

(27) A polyurethane formulation representative of typical foam compositions was tested with weight percent equivalent stannous octoate and BiCAT 8842 added with the other catalysts to the B side. The following composition was used:

(28) A Side: Isocyanate TDI 80-20

(29) B side: Polyester polyol OH number 60, F=2 Water (3.5 w/w) Silicon surfactant (varied)

(30) Catalyst: TEDA (Dabco) crystal (0.16% w/w) BDMAEE (0.12% w/w) BICAT 8842 (0.02% w/w) or stannous octoate (0.02% w/w)

(31) The test showed the following reaction times and foam densities:

(32) TABLE-US-00001 8842 Stannous Octoate Cream time (min) 14 15 Tack free time (min) 89 88 Foam Density (kg/m.sup.3) 35.4 35.1

Example 5

Slabstock Foam Application of Two-Component PU System Using Curative 8842

(33) During an industrial test, 13 meters of polyurethane slabstock foam matrix in continuous mode was produced and, from visual analysis, the foam matrix retains the same properties as did the stannous octoate formulation.

(34) The following composition was used:

(35) A Side:

(36) TABLE-US-00002 TDI 80-20 80% w/w TDI 65 20% w/w

(37) B Side:

(38) TABLE-US-00003 Polyether polyol (OH = 28) 90% w/w Polymeric polyol: 10% w/w Water 2.75% w/w TEDA in DPG 0.125% w/w BDMAEE in DPG 0.125% w/w Siliconic copolymer 2.05% w/w Flame retardant 6.0% w/w Stannous octoate or BiCAT 8842 0.16% w/w

Example 6

Accelerated Aging of Curatives

(39) Accelerated aging of curatives 8840 and 8842 (2.0 pphp) in the presence of water (2.5 pphp) and temperature, as indicated in the Table below:

(40) [Note: polyols supplied to Shepherd as their 4-component polyol systems by Huntsman.] BiCAT 8108 is bismuth neodecanoate, 20 wt % bismuth.

(41) TABLE-US-00004 Component Use level Terate 4020 60 parts Voranol 470x 30 parts Jeffol SG 360 10 parts TMCP 20 parts DI Water 2.5 parts/4.0 parts Curative 2.0 parts DI Water Oven temperature Curative Stability DAY 2.5 parts 130 F. POLYOL MIX - CONTROL transparent 1 BiCAT 8108 - CONTROL transparent 1 8842 transparent 1 8840 transparent 1 2.5 parts 130 F. POLYOL MIX - CONTROL transparent 2 BiCAT 8108 - CONTROL transparent 2 8842 transparent 2 8840 transparent 2 2.5 parts 130 F. POLYOL MIX - CONTROL transparent 3 BiCAT 8108 - CONTROL transparent 3 8842 transparent 3 8840 transparent 3 2.5 parts 160 F. POLYOL MIX - CONTROL transparent 4 BiCAT 8108 - CONTROL transparent 4 8842 transparent 4 8840 transparent 4 4.0 parts 160 F. POLYOL MIX - CONTROL transparent 5 BiCAT 8108 - CONTROL very sl. hazy 5 8842 transparent 5 8840 transparent 5 POLYOL MIX - CONTROL transparent 6 BiCAT 8108 - CONTROL opaque; ppt formation 6 8842 transparent 6 8840 transparent 6