CA1139037A - Isocyanurate products and polyurethanes therefrom - Google Patents

Abstract

ABSTRACT

Potassium salt of 2-pyrrolldinone is used as a catalyst to cyclotrimerize an organic diisocyanate, yielding a mixture of mono-meric cyclotrimerized product (isocyanurate) and oligomers thereof, soluble in common organic solvents and vinyl monomers. The cata-lyst can be used to make one-shot isocyanurate-crosslinked polyure-thanes. Prepolymers and moisture-curing coating compositions can also be prepared.

Description

ISOCYANURATE PRODUCTS AND
POLYURETHANES THEREFPcOM

This invention relates to a method of cyclotrimerizing an or-ganic diisocyanate to form an isocyanurate product, and to the isocyanurate product thus formed. The invention also relates to isocyanurate-containing polyurethanes and methods OI making ~ame.
In one aspect the invention is directed to the use of the potassium salt of 2-pyrrolidinone as a catalyst for cyclo~rimerizing an organic diisocyanate, to form a product containing a mixture of monomeric and oligomeric isocyanurates.
In another aspect the invention relates to the use of the potassium salt of 2-pyrrolidinone as a catalyst for making an iso-, cyanurate-crosslinked polyurethane from a diol and an organic diisocyanate, especially a non-cellular polyurethane.
The invention is also concerned with a so]ution of cyclotri-merized organic diisocyanate in a liquid ~7inyl monomer, and to a thermoset polymer made by treating such solution with a diol, a peroxide catalyst and an amine or tin catalyst.
The invention is further concerned with making a urethane prepolymer by reacting a diol with the described cyclotrimerized organic diisocyanate product, anA with the preparation of cured polyurethane elastomer by reaction of such prepolymer with a poly-urethane curative.
Additionally the inven tion involves coating compositions com-prising cyclotrimerized organic diisocyanate, a diol, and a poly-urethane cata]yst, dissolved in an inert organic solvent.
As indicated, the invention is directed to the use of the potas-sium salt OI 2-pyrrolidinone as a catalyst to cyclotr~merize an or-ganic diisocyanate. The organic diisocyanate employed may be any organic diisocyanate of the kind usually employed in the manu-facture o polyurethanes and may be aromatic, aliphatic or cyclo-aliphatic. Examples are toluene diisocyanate, methylene diphenyl~
isocyanate and isophorone diisocyanate. Only a small, catalytic amount of the potassium salt of 2-pyrrolidinone is required, e . g ., l3 from about 0.0û1% or less to about 1% or more based on the weight of the diisocyanate. To carry out the reaction the organic diisocya-nate and potassium salt of 2-pyrrolidinone are s~mply mixed together and allowed to react. It is frequently more convenient to dissolve 5 the potassium salt of 2-pyrrolidinone in any suitable inert solvent or in excess 2-pyrrolidinone. Such solution may contain for example from about 3% or less to about 30% or more, by weight, of the potassium salt of 2-pyrrolidinone.
The catalyst employed in the present invention has many 10 interesting features. Although the potassillm salt of 2-pyrrolidinone has been utilized as a catalyst for the polymerization oE 2-pyrroli-dinone to nylon-4, it has not been used as an isocyanate trimeriza-tion catalyst, as far as the present inventor is aware. The typical procedure utilized in the preparation of this catalyst is quite simple:
Solid potassium hydroxide is dissolved in 2-pyrrolidinone to form a 10% by weight solution which is heated at 100C for 3 to 4 hours (until homogeneous). This catalyst is quite active as will appear from the data below.
The cyclotrimerization may be carried out in bulk or in the presence of an inert organic solvent. The reaction proceeds at ambient temperatures but is faster at elevated temperatures. Some-times the reaction is exothermic in which case it may be desirable to cool the reaction mixture externally; in other cases it may be desir-able to apply external heat. Depending upon the particular diiso-cyanate and the duration of the reaction, a reaction temperature within the range of from about 20C or less to about 150C or more is ordinarily suitable.
The cyclotrimerization reac~ion is best carried out under an inert atmosphere (e.g., nitrogen), whether a~ atmospheric pressure or superatmospheric pressure.
Th~ catalyst oan be neutralized by an acylating agent, thus quenching the cyclotr~merization reaction at any stage desired. The activities of the acylating agents follow the pattern~ acetyl chloride ~enzoyl chloride ,~ allyl choride ~ benzyl chloride,~ methyl iodide.
Usually the reaction is allowed to proceed until insoluble mate-rial begins ~o form, whereupon the reaction may be substantially stopped by cooling and/or addition oE an acylating agent.

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Usually the reaction time ranges from about ~ hour or less to about 24 hours or more. It is desirable to agitate the reaction rnixture especially in the initial stages.
The cyclotrimerized product is a mixture of isocyanurates, 5 containing the trimer and low molecular weight oligomers of the trimer. The product is soluble in many common solvents such as tetrahydrofuran, ethyl acetate, chlorinated hydrocarbons (e. g., chloroform, chlsrobenzene), including the common v~nyl monomers (e.g., styrene, acrylonitrile, alkyl acrylates, etc.~.
In another aspect of the invention the potassium salt of

2-pyrrolidinone is used as a catalyst for the reaction of an organic diisocyanate with at least one diol to form an isocyanurate-cross-linked polyurethane. This reaction may be carried out under the conditions previously specified or unàer conditions conven~ionally 15 used in making "one-shot" polyurethane articles. Any diol of the kind conventionally employed in making "one-shot" polyurethanes may be employed, including for example polyester glycols, polyether glycols, mixed polyester-ether glycols, poly(butadiene-co-acryloni-trile)diol, etc . Polymeric or high molecular weight diols (e . g ., 20 molecular weight of from about 200 or less to about 4000 or more) may be employed, or monomeric low molecular weight diols (e . g ., 1,4-butanediol or cyclohexanedimethanol may be used. Mixture~; of diols are frequently advantageous . I he diisocyanate and diol may be employed in molar ratios conventionally used to make polyure-25 thanes. Frequently the ratio of isocyanate groups to hydroxylgroups is from abou t 0 . 8 :1 or less to abou t 2 . 5 :1 or more . The final products consist of isocyanurate crosslinked polyurethanes having physical properties that render them useful for making shaped articles of all sorts. Particularly noteworthy are non-30 cellular products prepared in this way, as distinguished from rigidfoams based on isocyanurate structures.
Unexpectedly, the present catalys~ has been found to promote the alcohol/isocyanate reaction at a rate faster than that of ~he isocyanate tr~merization reaction. Thus, to demonstrate this, a 35 mixture of toluene diisocyanate and a polypropylene glycol of mole-cular weight 425, in NCO:OH ratio of 2:1, may be allowed to react at 80~C in the presence as well as in the abserice of potassium salt

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of 2-pyrrolidinone catalyst. The loss of isocyanate absorption at 2250 cm 1 and the appearance of urethane carbonyl absorption at 1720 to 1750 cm 1, and of isocyanurate ring absorption at 1420 cm, may be followed by infrared spectroscopy. The catalyst 5 promotes urethane formation at a faster rate than the appearance of isocyanurate rings. The uncatalyzed reaction proceeds only slowly.
The catalyzed material becomes non-tacky in 15-20 minutes whereas the uncatalyzed mixture is tacky even a~er 1. 5 hours at 80C .
This behavior is especially useful in the preparation of "one-shot"
10 po]yurethane compositions, lightly crosslinked through isocyanurate units .
A particularly valuable form of the invention comprises a solution o:E the oligomeric cyclotrimerized organic diisocyanate com-position in at least one liquid vinyl monomer, that is, a liquid 15 ethylenically unsaturated (usually monoethylenically unsaturated) polymerizable monomer such as a v~nyl aromatic compound, especially styrene, alpha-methylstyrene, methylstyrene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclo-hexylstyrene, benzylstyrene and the like, substituted styrenes such 20 as chlorostyrene, 2, 5-dichlorostyrene, bromostyrene, fluorostyrene, trifluoromethylstyrene, iodostyrene, cyanostyrene, nitrostyrene, N,N-dimethylaminostyrene, acetoxystyrene, methyl 4-vinyl-ben20ate, phenoxystyrene, p-vinyl diphenyl sulfide, p-vinylphenyl phenyl oxide, vinyl naphthalene, and the like; the acrylic and substituted 25 acrylic monomers such as acrylic acid, me thacrylic acid, methyl acrylate, methyl methacryla-te, cyclohexyl methacrylate, benzyl methacrylate, isopropyl methacrylate, octyl methacrylate, methacrylo-nitrile, methyl alpha-chloroacrylate, ethyl alpha-ethoxyacrylate, methyl alpha-acetaminoacrylate, butyl acrylate, 2-ethylhexyl acry-30 late, phenyl acrylate, phenyl methacrylate, alpha-chloroacrylonitrile, N,N-dimethylacrylamide, N,N-dibenzylacrylam~de, N-butylacrylamide, methacrylyl formamide, and the like; vinyl ketones, such as v~nyl methyl ketone, vinyl ethyl ketone, v;nyl phenyl ketone, N-vinyl-pyrrolidone, vinyl ~midazole, N-vinyl pyrrole, and the like; di~
35 methylaminoethyl methacrylate, glycidyl acrylate, dichlorobutadiene, vinyl pyridine, and the like. Preferred materials are the vinyl aryl monomers (especially styrene and alpha methyl styrene), the acrylic nitriles (especially acrylonitrile and methacrylonitrile), and the alkyl alkenoate esters (especially methyl and ethyl acrylate and metha-crylate). Mixtur~;of vinyl aryl monomer with acrylic nitrile or alkyl alkenoate ester are especially preferred. The amount of such vinyl monomer in ~he composition may range from about 5% or less to about 95% or more, based on the combined weight of the vinyl monomer and oligomeric composition. If desired, the solution may be stabilized by the addition of small amounts of acylating agen t and/or free radical polymerization inhibitor. The composition may be cured quite readily by reacting with a diol (for example a poly-meric diol of the kind conventionally used for reaction with isocya-nates to make polyurethanes) especially in the presence of a cata-lyst of the kind usually used to promote polyurethane-forming reaction between -NCO and -OH yroups, such as a tertiary amine or tin catalyst, and a free radical polymerization catalyst such as a peroxide catalyst. Useful cast articles of all sorts may be prepared in this way from the described solution.
Thus, for example, the soluble nature of the oligomeric prod-ucts in the isocyanurate mixture from toluene diisocyanate permits ready solubilization in vinyl monomers such as styrene. At about 50% by weight, the solution viscosity is comparable to that of some resins. The isocyanurate/vinyl mixture is found to be stable for at least four mon ths when 1~ 2% ace tyl chloride and 0 . 03% naphtho-quinone are added as stabilizers.
The reactive mixture ob ~ained by dissolving the isocyanurate composition prepared from toluene diisocyanate in styrene, is cured quite readily by polymeric diols in the presence of a tertiary amine catalyst such as triethylene diamine or N-ethylmorpholine or tin catalyst and a peroxide catalyst such as benzoyl peroxide. If the peroxide catalyst is not used, a solid casting is still obtained. In this situation, styrene then acts as a filler and the casting gradu-ally loses weight due to the vola~ility of styrene. Peroxide catalyst polymerizes ~e styrene. The casting then does not lose weight when kept at room temperature or heated to 100C. Good physical properties are obtained after a room temperature cure Eor 1 week and no post curing at higher temperatures is necessary. These products can be classified as ~mpact resistant styrene polymers and 3~ 1 ~s such they have properties close to ABS polymers, w~th the added advantage of processibility from the liquid state, requiring less costly processing machines.
In the form of the invention wherein the oligomeric isocyan-5 urate preparation is used to make a polyurethane prepolymer, it w~llbe understood that the oligomeric cyclotrimerized product is reacted wi th any diol of the kind conventionally employed in making poly-urethane propolymers (such as a diol of the kind described above), suitably in the absence of moisture. Subsequently, the resulting 10 prepolymer may be mixed with additional diol and a polyurethane curative ~e.g., a diamine or the like), with or without a polyure-thane catalyst (e . g . a tertiary amine or a tin catalyst) to form a cured polyurethane elastomer or plastic of ~he desired shape.
An excess of the organic diisocyanate may also be used as a 15 solvent for the cyclotrimeri2ed oligomeric product. Thus, the isocyanurate mixture obtained from toluene diisocyanate is soluble in monomeric toluene diisocyanate. The solution of oligomer in diiso-cyanate may be used to prepare a prepolymer (by reaction with a diol as in conventional polyurethane prepolymer practice) and cured 20 elastomers and plastics may then be prepared from these prepoly-mers in the usual manner. For example, various amounts of the isocyanurate mixture obtained from toluene diisocyanate were dis-solved in toluene diisocyanate and these mixtures used to prepare prepolymers. Cured elastomers were prepared in the usual manner.
25 The isocyanurate units did not substantially alter the physical properties of unmodified elastomers, when present at lower concen~
trations . Changes were more noticeable in percent elonga tion and tear strength than in other proper~ies, showing that the isocy-anurate units impart more rigidity ~o the polyurethane elastomers 30 and plastics.
The product obtained from TDI (toluene diisocyanate) by the action oE ~he potassium salt of 2-pyrrolidinone appears to be a complex mixture of various isocyanurate materials. The composition depends upon whether TDI is trimerized in bulk or in solution.
35 The best way to analyze the mixture is to separate each component quantitatively. However, for commercial applications of the above mixtures, it is not necessary to know the composition exactly, as ~3~7 long as the amine equivalent is known. Based on this information, one equivalent amount of curative can be employed to react w~th the composition .
An empirical estimate of the amount of various components 5 present in the above mixture can be made based on certain assump-tions and a very simple fractionation experiment. Thus, 100 g of the isocyanurate mixture (amine equivalent 160) is dissolved in 250 ml of ethyl acetate and the solution is poured slowly into excess n-hexane with vigorous stirring. The precipitated material is fil-10 tered and freed o~ solvent by drying in a vacuum oven at 80~C/6hours. The residue weighs 82 g (amine equivalent 206). The following equation describes the different products. From infra-red spectra it is established that only isocyanurate and isocyanate structures are present and neither carbodiimide nor diazetanedione 15 structures can be found.

NCO / CO NCO NCO ~ NCO NCO NCO NCO
catalys ~ + ~ + ~ ~

NCO NCO NCO NCO NCO NCO NCO

TDI Unreacted TDI TDI-trimer TDI-pentamer* TDI-heptamer*
Isocyanate groups 2 3 4 5 No.of TDI units 1 3 5 7 Molecular weight174 522 870 1218 OCN NCO ,NCO ~ NCO
OCN ~ O ~ ~ et~
TDI-nonamer*
Isocyanate groups 6 * isocyanurate oligomers No~of TDI units 9 Molecular weight1566 ~
~ = lsocyanurate ring.
It is difficult to estimate the exact amount and nature of each oligomer present but it is apparent that these oligomers are of low molecular weight since they are soluble in common solvents. The ~32~

following calculatiorls may be made wi~h respect to a product in which the average number of isocyanate groups in the oligomer is 5 and the average molecular weight is 1218, based on the TDI-hepta-mer. If 100 g of the original mixture has x moles of unreacted TDI, y moles of TDI-trimer and z moles of TDI-oligomer, then 522Y ~ 1218Z = 206 orY = 188 z 3Y + 5Z 96 Because 522Y ~ 1218Z - 82,Z(522 x 188 + 1218) = 8Z
Therefore Y = .072 mole = 38 g.
Z = .037 mole = 44 g.
Thus, in such a product, 100 g of the mixture has 18 g of unreacted TDI, 38 g of TDI trimer and 44 g TDI-oligomer. Thus a considerable amount of oligomer is present in such a m~xture.
The following examples will serve to illustrate the practice of the inven~ion in more detail.

Example 1 One kilogram commercial TDI (a mixture of 80% 2,4-isomer and 20% 2,6-isomer of toluene diisocyanate) is placed in a two liter container which is equipped with a mechanical stirrer and a thermo-meter. The contents are kept under a nitrogen atrnosphere and a catalyst solution prepared from 200 mg potassium hydroxide in 2 g 2-pyrrolidinone (this catalyst preparation is hereinafter referred to as "K2P" ) is added with thorough mixing . Ten to fifteen minutes after the addition, an exothermic reaction starts. The temperature of the reaction mixture is kept below 70C by cooling with a water bath. The reaction mixture becomes increasingly viscous. As the mixtwre begins to solidify, the stirrer and the thermometer are removed. The container is sealed under nitrogen and the reaction allowed to continue to completion overnight. The amine equivalent of the product ranges from 150 to 165, showing that most of TDI
has undergone trimerization. The product is soluble in tetrahydro-furan, chloroform, ethyl acetate, excess TDI and common vinyl monomers. The infra-red spectrum shows the presence of isocyan-urate rings w~th strong absorp~ons at 2250 cm~l (-NCO), 1720 cm 1 (carbonyl) ~nd 1420 cm 1 (isocyanura~e).

Example 2 In a 500 ml, round bottom, three-necked flask equipped with a magnetic stirrer and a thermometer is placed a mixture of 50 g TDI
and 50 ml purified chlorobenzene. The contents of flask are kept 5 under nitrogen and 50 mg of the catalyst solution of potassium salt of 2-pyrrolidinone in 2-pyrrolidinone (K2P catalyst so]ution prepared as in Example 1) added. The reac~ion mixture is heated at 60-70C
for three hours during which time the solution becomes viscous.
The solution is cooled to room temperature and poured into 300 ml 10 diethyl ether with vigorous stirring. The solid material obtained is filtered under suction and washed several times with ether, then dried free of residual ether and chlorobenzene at 80C/vacuum for 6 hours to a constant weight. Yield 43 g (86%). Amine equivalent, 255. Theoretical amine equivalent for the trimer, 174.

15 Example 3 In a 500 ml, round bottom, ~hree-necked flask, fitted with a magnetic stirrer and a thermometer is placed a mixture of 60 g methylene diphenylisocyanate (MDI) and 100 ml purified chloroben-zene. The mixture is kept under nitrogen and 20 mg of K2P cata-20 lyst mixture (prepared an in Example 1) is added. Insoluble mater-ial starts to form after the reaction mixture has been heated at 80-~5 for 45 minutes. The mixture is then quickly cooled to room temperature and the contents of the flask poured in~o 300 ml diethyl ether with vigorous stirring. The solid material obtained is filtered 25 under suction and washed several times with ether, and freed of - solvents by drying at 80C/6 hours in a vacuum oven. Yield 20 g (33%). Amine equivalent, 330. Theoretical amine equivalent for the trimer, 250. The product is soluble in common solvents such as tetrahydrofuran and chloroform. The infra-red spec~rum shows the 30 presence of isocyanurate groups.

Example 4 One hundred g isophorone diisocyanate is tr~merized at 110C
for 18 hours using 50 mg of the K2P catalyst mixture. A ~Tlassy solid is obtained with an amine equivalent of 200. Theoretical amine 35 equivalent for the trimer, 222. The infra-red spectrum shows the presence of the isocyanurate ring struc~ure.

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Example 5 In a 500 ml, round bottom flask equipped with a magnetic stirrer, a thermometer and a nitrogen inlet tube is placed a mixture of 34.8 g TDI (0.2 mole), 11.9 g phenylisocyanate (0.10 mole~ and 5 50 ml purified chlorobenzene. The mixture is kept under nitrogen and 30 mg of the K2P catalyst mixture added with vigorous stir-ring. The mixture is heated at 60-70C for three hours. The solution is cooled to room temperature, then poured into 300 ml diethyl ether with vigorous stirring. The solid material obtained is 10 filtered, washed several times with ether and dried until free of solvents at 80C/6 hours in a vacuum oven. The material is sub-stantially difunctional~ Yield 45 g (95%). Amine equivalent, 450.

Exam~le 6 In a 500 ml resin ket~le, fitted with a stirrer, a thermometer and nitrogen inlet, 20 g (0.022 mole) of isocyanurate material from , Example 5 is dissolvecl in 100 ml purified dimethyl sulfoxide. Two g1,4-butanediol (0.022 mole) is added and the mixture heated to 90C
and stirred for three hours. The progress of the reaction is followed by the disappearance of the isocyanate absorption at 2250 20 cm 1 in infra-red spectrum. When all the isocyanate group has reacted, there is no siyn of gelation. The polymer thus prepared is precipitatPd by pouring the solution in~o 1000 ml water. The solid is filtered under suction, washed several times with water and dried in a vacuum oven at 100C to constan~ weight. Yield 18 g 25 (81%). The fact that the product is a linear polyurethane indicates that the isocyanurate material obtained in Example 5 is substantially a difunctional material.

Example 7 This Example shows that the isocyanurate m~xture from TDI
30 consists of some unreacted TDI, monomeric isocyanura~e and oligo-meric isocyanurate. Isocyanurate mixture (100 g), prepared as in ~xample 1, is dissolved in 250 ml ethyl acetate . The solu ~ion is poured into 10 times its volume of n-hexane with vigorous s ~irring and the precipitated rnaterial is fil~ered and dried. Weight re-35 covered 82 g. Amine equivalent, 206. The theoretical amine 31Y,~3~

equivalent of monomeric isocyanurate is ï74. Thus higher molecularweight oligomeric isocyanurates must be present in this m~xture which has an am~ne equivalent of 206. Each of the solution-prepared isocyanurates, precipitated as described in Ex~nples 2, 3, 5 and 5, has an amine equiva~ent higher ~an that expected for the monomeric trimer struc~ures. This indicates tha~ soluble oli~omeric isocyanurates are obtained by the action of the present catalyst system.

Example 8 ~larious diols indicated in TABLE I are reacted with TDI in the presence of the K2P catalyst system to make one-shot polyurethanes.
Thus, in a one liter container 38 g of polypropylene glycol (about 0.09 mole) is mixed with 100 mg of the K2P catalyst. The m~xture is warmed to 60C and evacuated to remove dissolved air bubbles.
After half an hour, 21 g TDI (about 0.12 mole) [NCO:OH, 1.3:1.0]
is added, mixed well and further evacuated to remove bubbles.
The mixture is then poured onto a flat glass plate mold and kept at room temperature for 15 minutes, followed by post-curing at 100C/2 hours. A clear casting is obtained. TABLE I summarizes the physical properties of various compositions made in this way using polypropylene glycols (PPG) of molecular weights 425~ 710 and 1010, poly(tetramethylene ether glycol) (PTMG) of 1000 molecular weight, N,N'-bis(2-hydroxypropyl)aniline (BHPA), and 1,4-butanediol, in the molar proportions shown. The physical properties are measured by the following ASTM procedures: tensile properties, D-638-63T;
~ear strength D-624-54; hardness, D-1484-59.
TABLE I
Properties of Isocyanurate Crosslinked Polyurethanes Prepared by 'One~Shot' Method, Using K2P Catalyst Tear Molar ratios Tensile % Elon- Strength of the com- Strength gation at (Die G) Hardness Composition ponents Psi break Pli Shore A
PPG-425+TDI 1. 0 :1. 3 2140 200 380 62 PPG-425+TDI 1. 0 :1. 4 2600 200 460 72 PPG-710+TDI 1. 0 :1. 5 430 150 120 48 3Q~

TABLE 1 Cont'd.
Tear Molar ratios Tensile % Elon- Strength of the com- Strength gation at (Die C) Hardness Com~osi~ion ponents Psi break Pli Shore A
PPG-710+TDI 1.0:1.6 720 150 110 61 PPG-710+TDI 1.0:2.0 1200 150 150 77 PPG-1010~TDI 1.0:2.0 400 150 90 45 PTMG-1000+
BHPAtTDI 1.0:1.0:3.0 2500 100 280 83 PTMG-1000~
BHPA+TDI 1. 0: 2 . 0: 4 . 54400 100 770 85 PTMG-1000+
1, 4-butanediol +T:DI 1 . 0: 2 . 0: 4 . 5 6800 50 - - - - -PPG-1010+
BHPA+TDI 1. 0: 2 . 0: 4 . 54400 50 --- --Example 9 In a three-liter resin kettle fitted with a stirrer, a thermo-20 meter and a nitrogen inlet tube is placed 1, 500 g TDI . Whilestirring under nitrogen, 3 . 3 g K2P catalyst mixture is rapidly added. An exothermic reaction starts in a few minutes. After 30 minutes, the temperature reaches 65C and the reaction mixture is cooled using a water bath. At this stage the reaction mixture is 25 quite viscous and 250 ml styrene is added to reduce viscosity. A
total of 1500 ml (1350 g) styrene is added in 250 ml portions at suitable intervals so that a workable viscosity is always maintained.
In three hours, the temperature has fallen to 38C. To stabilize the mixture, 750 mg naphthoquinone and 5.8 g acetyl chloride are 30 added and mixed thoroughly. Amine equivalent is 306.

Example 10 Using the same method as described in Example 9, various mixtures are prepared by replacing styrene with equivalent amounts of other v;inyl monomers such as acrylonitrile, methyl acrylate, 35 ethyl acrylate and n-butyl acrylate.

ExamE~le_ The above mixtures from Examples 9 and 10 are compatibl~
with polyethylene glycols and polypropylene glycols of various molecular weights. They are also compatible with poly(butadiene-5 co-acrylonitrile)diol, cyclohexanedimethanol, etc. The curing of these compositions is accomplished as shown below.
The composition (67 g) from Example 9 is mixed with 40 g polyethylene glycol 400 [NCO:OH, 1.1:1.0]. A clear solution is obtained. Benzoyl peroxide paste (50%, 1 g) is added and n~ixed 10 thoroughly. The mixture is quite stable. However, when 0.25 ml N-ethylmorpholine is added and mixed, an exothermic reac~ion starts. The resin m~xture is poured onto a glass mold and allowed to set. Gel time is 15 to 20 minutes. The casting is removed from the mold after 3 hours. The physical properties are determined 15 a~ter allowing the casting to cure at room temperature for 7 days.
TP.BLE II summarizes the physical properties of the casting obtained from the compositions indicated. ~lexural properties are obtained according to ASTM D-790-66; heat deflection by ASTM
D-648-56 and Izod notched impact strength by ASTM D-256-70.

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~ o u~ O In Exanlple 12 In this Example, instead of a single monomer, mixtures of monomers are used (styrene: ethyl acrylate in 1:1 ratio by volume, and styrene:n-butyl methacrylate in 1:1 ratio by volume) to 5 prepare isocyanurate resins following the procedure of Example 9 ~isocyanurate 52%, vinyl monomers 48%, by weight). The resins are employed to make castings accordiny to the procedure of Example 11, using polyethylene glycol (PEG) of molecular weight 400 or 600, at an NCO:OH ratio of 1.1:1.0, in the presence of 1% by weight of 10 benzoyl peroxide paste and 0 . 25% by volume of N-ethyLmorpholine catalyst. After cure at room temperature for seven days the physical properties are as shown in TABLE III.
T A B L E III
Properties of Castings Prepared from Isocyanurate Resins Containing Mixtures of Vinyl Monomers Tensile Properties ear Properties Hardrless Tensile Elonga-Strength tion Composition (Psi) (%)_ Die C (Pli) Shore A
Isocyanurate + lethylacrylate:
styrene]

Isocyanurate + ¦n-butyl ~ethacrylate:
styrene]

TABLES II and III show that the final products have a higher elongation when they are prepared from a mixture o:E styrene and an acrylate monomer, rather than from a single monomer. Other physical properties show less significant variations. In these 35 systems, the vinyl monomers undergo polymerization during cure of ~3 -17~

the resins. The above results indicate that ~he contributions of homopolymers and of copolymers to properties such as elongation are different.

Example 13 In this example, styrenated isocyanurate resin prepared as in Example 9 is blended with two diols, namely, polyethylene glycol (PE~a) of 600 molecular weight and 1, 4-butanediol, in the ratios indicated in TABLE IV, and castings are made using benzoyl perox-ide and M-ethylmorpholine as in Example 11. Physical properties after cure at room temperature for seven days are shown in TABLE
IV .
T A B L E IV
Properties of Produc~s from S~yrenated Isocyanurate Resins Cured with a Mixture of Diols Tensile Properties ~ Flexural Modulus ~ensile Elonga-Strength tion Composition (Psi) (%) Die C(Pli) (K Psi) Resin: PEG
600: 1,4-Butanediol (ratio in equivalents)

4:3:1 4100 150 650 30 ! 25 3:2:1 3800 100 830 50 2:1:1 4100 125 840 60 3:1:2 5200 30 570 160 ~:1:3 5000 5 230 180 Resin: PEG
600: 1,4 - Buta-nediol (ratio in equivalents) 4:3:1 3900 175 600 30 3:2:1 4000 100 970 50 2:1:1 6100 75 ~90 ---3:1:2 4700 10 390 190 Thus, products with medium to hiyh flexural moduli with good elongation characteristics can be prepared readily by choice of a suitable mixture of diols instead of a single diol.

Example 14 IJrethane prepolymer resin based on a polyether diol is pre-pared as follows:
Poly(tetramethylene ether glycol) of 1000 molecular weight (750 g) is maintained under a nitrogen atmosphere in a 1-liter resin kettle equipped with a mechanical stirrer, thermometer and nitrogen inlet, heated to 95C, then placed under vacuum for 1 hour to remove traces of moisture. The diol is then cooled to 40C, TDI
~268 g), (NCO:OH, 2.05:1.0) is quickly added and the mixture maintained at 80C Eor 1 hour after the initial exotherm is over.
The prepolymer ~hus obtained is degassed under vacuum for 15 minutes with stirring and 15 minutes without stirring and stored in a metal can after being sealed under nitrogen. Amine equivalent, 645 .
Differen~ weight percentages of isocyanurate products from TDI (indicated as "ICU A" in Table V) or isocyanurate products from a mixture of 2 moles TDI and 1 mole phenyl isocyanate (indi-cated as "ICU B" in Table V) are dissolved in TDI and the appro-priate isocyanate values determined. Prepolymers are prepared following the procedure in the previous paragraph using these isocyanate mixtures and keeping NCO:OH at 2.05:1Ø

Example lS
The urethane prepolymer resin prepared as in Example 14 (100 g) is heated in a vacuum oven at 80C and evacuated for 1 hour until all the dissolved gases are removed . Methylene bis (o~chloro-aniline) (18.5 g) (NCO:NH2 1.1:1.0) is melted and mixed with the degassed prepolymer. The mixture is fur~er degassed and then poured on~o a flat mold and cured at 100C~16 hours to form an elastorner. The isocyanurate-containing prepolymers of Example 14 are similarly cured with methylene bis~o-chloroaniline) to form elas-tomers keeping N~:O:NH2 at 1.1:1Ø TABLE V summarizes physical properties of these castings.

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Example 16 In a 500 1l-1, round bottom, three-necked flask, fitted with a magnetic stirrer, reflux condenser, thermometer and ni~rogen inlet tube, 52 g solid isocyanurate mixture prepared from toluene diiso-

5 cyanate using K2P catalyst is dissolved in 100 ~nl ethyl acetate w~thstirring under nitrogen. The mixture is warmed to 60C, then a mixture of poly(tetramethylene ether glycol) 1000 molecular weight ~63 g~ and di-n-butylamine (16 g) dissolved in ethyl acetate (50 ml) is added to the above solution duriny 5 ~o lO minutes. The mixture 10 is heated at 6û-70C for 30 minutes and the contents of the flask coated onto a flat glass plate. The solvent is allowed to evaporate and the coating cured by moisture in the atmosphere. After two days, most of the solvent has evaporated and the coating is post-cured at 100C/2 hours. TABLE VI lists some of the physical 15 properties of such coatings.
TABLE VI
Physical Properties of Moisture-cured, Solvent-cast Isooyanurate Polymer Coatings Tear Ratio Tensile Elonga- Strength NCO/Active Strength tion Die C, C:omposition Solvent hydrogen Psi _ % Pli Isocyanurate+ Ethyl 1. 7 :1. 0 1600 300 260 PTMG 1000+ acetate 25 di-n-butyl-am~ne Isocyanurate+ Chloroform 1. 7 :1. 0 2400 250 330 PTMG 1000+
di-n-butyl-30 amine Isocyanurate+ Chloroform 1. 6 :1. 0 2300 200 360 PTMG lOOOt n-bu~anol

Claims (13)

Div.
The embodiments of the inveniton in which an exclusive property or privilege is claimed are defined as follows:

1. A method of making an isocyanurate-crosslinked polyurethane comprising mixing a diol, an organic diisocyanate and a catalytic amount of potassium salt of 2-pyrrolidinone.

2. The product of the method of claim 1.

3. A non-cellular product as in claim 2.

4. A method of making a thermoset polymer comprising mixing (a) a solution of the product obtained by cyclo-trimerizing an organic diisocyanate by contacting the organic diisocyanate with a small but effective amount of potassium salt of 2-pyrrolidinone as a cyclotrimerization catalyst, in a vinyl monomer, (b) a diol, (c) a peroxide curative, and (d) a catalyst for the reaction between -NCO and -OH to form polyurethane, and thereafter subjecting the mixture to curing conditions.

5. The product of the method of claim 4.

6. A non-cellular product as in claim 5.

7. A method of making a urethane prepolymer comprising mixing a polymeric diol with the product obtained by cyclo-trimerizing an organic diisocyanate by contacting the organic diisocyanate with a small but effective amount of potassium salt of 2-pyrrolidinone as a cyclotrimization catalyst, in the absence of moisture.

Div.

8. A prepolymer produced by the method of claim 7.

9. A method of making a cured polyurethane elastomer comprising providing a prepolymer as in claim 8, mixing the prepolymer with a polyurethane curative, and subjecting the mixture to curing conditions.

10. The product of the method of claim 9.

11. A non-cellular product as in claim 10.

12. A coating composition comprising the product obtained by cyclotrimerizing an organic diisocyanate by contacting the organic diisocyanate with a small but effective amount of potassium salt of 2-pyrrolidinone as a cyclotrimerization catalyst, a diol, and a polyurethane catalyst, dissolved in an inert organic solvent.

13. A method of coating a substrate comprising providing the coating composition of claim 12, applying said composition to the substrate, volatilizing the solvent, and curing the thus-deposited coating by the action of atmospheric moisture.

14. The coated substrate resulting from method of

claim 13.