NO116819B - - Google Patents

Description

Process for the production of rigid polyurethane foam with good fire safety.

The present invention relates to a method for the production of rigid polyurethane foams which are resistant to combustion.

Polyurethane foam is produced by reacting

in the presence of a blowing agent, a polyfunctional active hydrogen-containing polyester polyesteramide or polyether (hereinafter collectively

net a "polyol") with an organic polyisocyanate. Such polyurethane materials are usually not i

themselves fireproof, i.e. they will ignite on contact with a flame, and once ignited they will continue to burn, until they are essentially two-

spoken burnt out. It is known to give such polyurethane combinations fire safety by incorporating agents containing halogen or phosphorus or both. Such agents can be those that do not react with the polyisocyanate, such as e.g.

e.g. chlorinated hydrocarbons, tris (chloro ethyl) phos-

fat and tris (2,3-dibromopropyl) phosphate, or those that enter into the polymeric reaction, such as e.g.

polyesters and polyethers containing halogen or phosphorus or both. The degree of fire safety achieved is roughly proportional to the amount of halogen and/or phosphorus present,

i.e. the more halogen and/or phosphorus that is added, the greater degree of fire safety is achieved. It has been found, however, that in order to achieve an effect

tive degree of fire safety, so much of the agent must be used that the physical properties of the resulting structure, such as dimensional stability, tensile strength and resistance to shock, are degraded to an undesirable degree. This effect occurs in particular when non-reactive flame retardants are used.

It is known that polyurethane foam can be produced by converting phosphorus generation products

of an aromatic diamine either by distilling off the isocyanates that are formed and reacting the distillate with a polyol or by reacting the reaction mixture as it is with a polyol. Such

methods are disclosed in U.S. Pat. patent no. 2,902,703. It has now been found that polyurethane foams with improved dimensional stability can be obtained if the aryl diisocyanate is partially removed from the phosgeneration product reaction mixture and the residue is reacted with the polyol. The exact conditions and degree of removal of the aryl diisocyanate, and the particular phosgenation product used are regulated to give a mixture which has certain critical properties. When a mixture having these properties is reacted with a polyol (in the presence of a blowing agent), improved polyurethane foams are obtained.

In one respect, the invention therefore consists in a method for producing rigid polyurethane foams with good fire safety by reacting together in the presence of a blowing agent and optionally in the presence of a fire retardant (A) a polyol containing at least two hydroxyl groups and (B) a mixture consisting of the phosgenation product of an aromatic diamine comprising non-volatile hexane-insoluble polyisocyanate dissolved in a volatile aromatic diisocyanate which has been removed from the phosgenation product, and the method is characterized in that the mixture (B) contains from 40 to 90 wt. volatile aromatic diisocyanate, preferably 55 to 85% by weight, preferably toluene diisocyanate or p,p'-diamine diphenylmethane diisocyanate which can be separated from the phosgenation product by molecular distillation at a pressure of approx. 1 mm Hg or by separation in a gas chromatograph and that an amount of the mixture containing 1 to 1.2, preferably 1.03 to 1.05 equivalents of isocyanate groups per equivalent active hydrogen atom in the polyol and where the mixture (B) used consists of 20 to 55 wt. nonvolatile hexane-insoluble polyisocyanate, the infrared spectrum for the mixture includes an absorption maximum in each of the ranges 4.3 to 4.5 microns, 5.8 to 5.9 microns, and 5.95 to 6.05 microns, the molar concentration of the volatile aromatic diisocyanate in the mixture is such that it gives said spectrum at the absorption maximum between 5.8 and 5.9 microns, an absorbency between 0.2 and 0.5, the viscosity of the mixture is between 20 and 10,000 eps, preferably between 50 and 70 eps at 25°C, the amine equivalent of the mixture is between 98 and 120, preferably between 102 and 108, and the density of the mixture is between 1.23 and 1.29 at 25°C.

As already indicated, the term "volatile aromatic diisocyanate", as used herein, means aromatic diisocyanate which can be separated from the product of phosgenation of an aromatic diamine in a molecular distillation apparatus at a pressure of approx. 1 mm Hg or by separation in a gas chromatograph. Preferred volatile aromatic diisocyanate components in said products are phosgenation products of a tolylenediamine or p,p'-diamino-diphenylmethane, e.g. m-tolylenediisocyanates (especially the 2,4- and 2,6-isomers or mixtures thereof) and methylene bis (4-phenylisocyanate). Other suitable volatile aromatic diisocyanates include meta- and para-phenyl diisocyanates, chlorophenylene diisocyanates,

1,5-naphthalene diisocyanate and 3,3'-dimethyl-4,4'-

diphenylmethane diisocyanate, which is produced by phosgenation of the corresponding diamines.

The aromatic diamine phos generation product, e.g. a tolylene diamine phosgenation product, prepared by phosgenerating tolylene diamine in the presence of a solvent more volatile than the tolylene diisocyanate corresponding to the tolylene diisocyanate and then distilling the crude reaction product to remove the solvent and tolylene diisocyanate until the remaining concentrated distillate has a volatile tolylene diisocyanate content of between 50 and 90 wt., may be used as such or alternatively mixed with one or more volatile aromatic diisocyanates obtained from a separate source as long as the total volatile aromatic diisocyanate amounts to from 40 to 90 wt. of the total mixture. For example, a concentrated tolylene diisocyanate can be diluted with distilled tolylene diisocyanate or methylene bis(4-phenyl isocyanate) until the volatile aromatic diisocyanate content of the mixture is 80 percent. Similarly, a concentrated phosgenation product prepared from p,p'-diaminodiphenylmethane can be diluted with distilled methylene bis(4-phenyl isocyanate) or tolylene diisocyanate.

The aromatic diamine phosgenation products prepared by mixing aromatic diamine and phosgene in the presence of a solvent, which is more volatile than the aromatic diisocyanate structurally corresponding to the aromatic diamine, heat the reaction mixture until the phosgenation reaction is essentially complete, as evidenced by the reaction bipro -ducted hydrogen chloride is no longer formed in significant quantity, separate from phosgene and hydrogen chloride from the resulting solution of the phosgene and distill the solvent and aromatic diisocyanate from the solution of the phosgenation product until the concentrated distillate has a volatile, aromatic diisocyanate content between 40 and 90 per cent, end the distillation and recover the concentrated distillate.

When working in batches, it is appropriate to mix the reactants by adding a solution of diamine, e.g. tolylenediamine to a solution of phosgene under essentially atmospheric pressure conditions. Cooling is used during the mixing operation to prevent excess phosgene from boiling away. Generally, the mixing temperature must be kept below approx. 30°C. Mixing temperatures below -20°C are undesirable because excess amounts of the diamine tend to precipitate as solid masses which are encapsulated with a protective coating of amine hydrochloride. Such solid encapsulated amines would melt and react at higher process temperatures under conditions of high local amine concentration and which promote the formation of excess amounts of byproduct urea.

During the mixing treatment, approx. in 50 per cent of the total phosgene consumed by the process to form an intermediate reaction product. In this product, the amine groups in the tolylenediamine reaction component have preferably been converted into approximately equal numbers of amine hydrochloride groups and carbamyl chloride groups. At higher

temperatures, the carbamyl chloride groups are thermally split into isocyanate groups and HC1, and amine

the hydrochloride groups react with phosgene to give the same products. The isocyanate groups can react with the diamine and form urea-type by-products.

If the method according to the present invention is carried out continuously, the mixing temperature can be far higher than what is possible in a batch process, carried out as described above under the same conditions for batch comparison, pressure etc. In batch work, a diami solution is added to a solution of phosgene which contains at least 2.2 mol of phosgene per moles of diamine used. (The reverse mixing method, adding phosgene solution to diamine solution should be avoided because it (1) promotes urea formation and (2) the diamine is relatively insoluble in most solvents, except when the solution is warm). The mixing temperature must therefore be low enough to allow the solvent to retain the necessary 2.2 mol of phosgene per moles of added diamine. Separate streams of diamine solution and phosgene or phosgene solution are introduced into a mixing reactor where they mix with an already formed quantity of intermediate product containing excess phosgene dissolved in the solvent intermediate phase. However, 1 mol of phosgene is consumed per moles of diamine introduced immediately upon the formation of the intermediate reaction product (diamine hydrochloride carbamyl chloride mixture), so that the mixing temperature is not limited by the requirement that the solvent should contain the total phosgene consumed in the process. Thus, if the molar ratio between phosgene and diamine is 2.2, the mixing temperature in a batch process is limited by the ability of the solvent and contains 2.2 mol of phosgene per mol introduced diamine, while the mixing temperature in an analogous continuous process is only limited by the ability of the solvent to contain 1.2 mol phosgene per moles of introduced diamine. However, the mixing temperature must be kept below 100 °C because mixing at higher temperatures results in cleavage of carbamyl chloride groups.

After the mixing operation is completed, the reaction mixture is further heated under superatmospheric pressure until the phosgenation reaction is complete and the maximum temperature is between 100 and 200°C. Heating causes (1) cleavage of carbamyl chloride groups into isocyanate groups and HC1 at temperatures above approx. 40—45°C, and (2) phosgenation of amine hydrochloride groups to isocyanate groups and HC1 at temperatures above 80—85°C. The progress of the reaction can be followed by measuring the amount of hydrogen chloride that develops from the reaction mixture. Such measurements indicate that 60-70 percent of the free amino groups in a tolylenediamine batch are converted to isocyanate groups at temperatures below 100°C.

The pressure under which the reaction mass is heated must be sufficient to maintain a stoichiometric excess of phosgene in the reaction medium during the reaction, i.e. an amount of phosgene in excess of that which is chemically equivalent to the incompletely converted intermediate reaction product, which is present in the reaction mass at all times . In other words, at the end of the phosgenation, the reaction mass will contain parts of the excess phosgene added to the reactor at the end of the phosgenation.

In practice, the pressure required to achieve the phosgenation will depend on the composition of the reaction component charge and the type of reactor used. In a closed reactor, the pressure will rise as the reaction progresses due to hydrogen chloride which _ is developed during the reaction at a reaction temperature higher than the critical temperature (51.4°C) for hydrogen chloride. The size of this pressure increase will largely depend on the relative volume of free space in the reactor, i.e. on the percentage of the reactor capacity that is taken up by the reaction mixture. The pressure which develops during the development of hydrogen chloride can thus be kept to a suitable minimum by providing sufficient free space. Optionally, the total pressure can be kept low by using an aeration system at the reactor, which allows evolved hydrogen chloride to pass to a scrubber system, but retains the phosgene and solvent. For example the pressure vessel may be surrounded by a reflux condenser which carries a solution phosgene condensate back to the reactor, and allows hydrogen chloride to pass to an off-gas line leading to a scrubber system. The pressure on the system is controlled by a valve in the gas line down from the return condenser. If the valve pressure is higher than the sum of the partial pressures for the solvent, phosgene and isocyanate in the reactor, none of these components will leave the reaction system. The actual reaction pressure will depend in part on the volatility of the chosen solvent. Thus, to obtain results comparable to those obtained with a reaction pressure of 3 atmospheres and a relatively non-volatile solvent, such as dichlorobenzene, 6 to 8 atmospheres are required with benzene or a similar solvent of relatively high volatility. Generally, the method according to the present invention can be carried out efficiently at total pressures above 3 atmospheres. Maximum pressure is determined by the safety of the available equipment.

If a closed system is used, the pressure in it at constant temperature will no longer increase when the evolution of hydrogen chloride ceases. In the case of an air autoclave, it will be necessary to close the relief valve to maintain the pressure in the autoclave when development ceases. When the reaction is complete, the autoclave is vented to atmosphereThick. The reaction mass is then purified to remove dissolved phosgene and hydrogen chloride, e.g. by passing inert gas (nitrogen or carbon dioxide) through the mass or by a distillation purification which removes hydrogen chloride and phosgene together with solvent.

A solvent less volatile than the aromatic diisocyanate must not be used because the concentrated distillation residue would then contain large amounts of solvent.

The relative volatility of the solvent in comparison with the tolylene diisocyanate product corresponding to the tolylene diamine charge should be between 4 and 100 at 140°C. The relative volatilities at 140 °C for dichlorobenzene, monochlorobenzene and benzene in comparison with a tolylene diisocyanate mixture containing 80% of the 2,4-isomer and 20% of the 2,6-isomer are approx. 11.43, 87 respectively. Solvents having a relative volatility below 4 are undesirable because their distillation from the phosgenate involves an excess amount of heat which has an undesirable effect on the concentrated distillate. Solvents having a relative volatility higher than 100 are undesirable because extra high pressures are required to keep them in the reaction system. By "relative volatility" is understood the ratio VjLj/VjL,,, where Vs and V, mean mole fractions of the solvent and the isocyanate in the vapor phase, and LB and L; means mole fractions of the solvent and isocyanate in the liquid phase under equilibrium conditions.

Preferably, the crude phosgenation product is distilled under vacuum. Solvent must be removed essentially completely together with other low-boiling components, such as traces of monoisocyanates. Traces of the solvent (e.g. concentration of dichlorobenzene above 0.02 per cent) in the phosgenation product can impart an undesirable odor to urethane foam produced from it. Some diisocyanate is distilled off with removal of the solvent and low-boiling impurities. If the concentration of non-volatile solvent in the diamine phosgenation product is higher, this may be all the distillation that is necessary. However, if the method and equipment are also to be used to produce a significant amount of the diisocyanate, e.g. pure tolylene diisocyanate, the yield thereof will be low if the process conditions are chosen to give a high concentration of non-volatile solvent. It is preferred to use process conditions which give a lower concentration of non-volatile solvent in the phosgenation product and to distill off a significant amount of tolylene diisocyanate from the phosgenate to obtain a concentrated distillate with desired properties. Tolylene diisocyanate distillate which can amount to as much as 50% by weight. of the total phosgenation product, is a valuable by-product. The comparison and properties of the concentrated distillate will be affected to some extent by the distillation conditions. The solvent concentration can be increased, if desired, by extending the duration of the distillation and/or raising the distillation temperature. Such an increase in the solvent concentration can be reduced by using a lower temperature and/or shorter distillation duration, which can be achieved by distilling at a lower absolute pressure.

The aromatic diamine phosgenation products are mixtures of volatile aromatic diisocyanates and congeneric relatively non-volatile dissolved polyisocyanates with higher molecular weight and functionality than the volatile aromatic diisocyanates. Components of the congeneric non-volatile dissolved fraction are not only fire-retardant synergistic substances, but also chain-extending and cross-linking agents that impart desired properties (especially stiffness) to the foams. Such components also make the aromatic polyisocyanate blends superior to distilled aromatic diisocyanates as reaction components in foam compositions, because (1) the higher viscosity level makes it easier to mix the formulation and hold blowing agent in it during foaming, (2) the lower heat of reaction developed during foaming allows the production of larger foaming masses and improves other properties of the foam, and (3) the lower vapor pressure reduces the dangers arising from the toxicity of the diisocyanate vapors. Although current knowledge of the molecular structure of the dissolved substances is incomplete and undetermined, it appears that the structures include isocyanate-substituted tolylene groups connected by bonds that include amido-substituted carbonyl groups that absorb infrared rays with wavelengths between 5.8 and 5.9 microns. However, data for the isocyanate equivalent weights of the dissolved substances and their fractions establish that the substances do not consist of such simple polyurea polyisocyanates as bis(isocyanatotolyl urea), bis(isocyanatotolyl)-uretidinedione, tris-isocyanatocyanurates or tris-isocyanatotolyl biuret or similar linear polyurethanes.

The non-volatile solutes present in the aromatic amine phosgenation products can be thermally decomposed at elevated temperatures releasing aromatic diisocyanate vapors and forming tarry or solid residues. For example, solid solutes isolated from tolylene diamine phosgenation products by extracting the tolylene diisocyanate therefrom with n-hexane will release as much as 30 percent tolylene diisocyanate when heated at 225°C and 1 mm Hg in a molecular distillation apparatus. Thus, the volatile aromatic diisocyanate content in the aromatic polyisocyanate mixtures used in the method according to the present invention, as determined by distillation in a molecular distillation apparatus at 1 mm Hg or by separation in a gas chromatograph, will include volatile aromatic diisocyanate present as such in the polyisocyanate mixture. The non-volatile dissolved polyisocyanates present in the amine phosgenation products usually do not correspond to the distillation residues used in previously known methods for the production of aromatic diisocyanates, because such distillation residues are formed by pyrolytic cleavage of the non-volatile dissolved polyisocyanates. Accordingly, in the preparation of aromatic amine phosgenation products it is desired to avoid concentrating the distillate too strongly because temperature and concentration conditions prevailing during the later stages of the product distillation result in undesirable side reactions and decomposition of non-volatile solutes.

The concentration of non-volatile solutes present in the aromatic diamine phosgenation product can be increased or decreased by increasing or decreasing, respectively, one or more of the following variables in the phosgenation process: the amine/solvent ratio, the amine/phosgene ratio, the temperature and the duration of heating during reaction and distillation, and the amount of volatile, aromatic diisocyanate, which is distilled off from the phosgenation product. If the aromatic diamine is mononuclear, the concentration of non-volatile solutes in the phosgenation product can be increased or decreased by increasing or decreasing the orthoisomer content of the aromatic diamine reaction component. If the concentration of non-volatile, dissolved polyisocyanates in the crude reaction mixture is adequate, it will be sufficient to distill the phosgenation product sufficiently to remove all solvent together with such aromatic diisocyanate as is incidentally removed at the same time. However, it will often be found necessary to remove additional aromatic diisocyanate to obtain an aromatic amine phosgenation product having the desired concentration of solutes.

Fire-retardant, synergistic agents, which are present in the aromatic diamine phosgenation product used according to the method according to the invention, greatly reduce the amount of fire-retardant agents necessary to make the foam self-extinguishing upon ignition. This is surprising, because the fire retardants, synergistic agents are not very effective by themselves as fire retardants in the absence of fire retardants. The chemistry involved in this fireproofing synergism is unknown.

The method according to the present invention makes it possible to produce rigid polyurethane foam with exceptional fire safety, i.e. foam that does not flare up or is self-extinguishing after ignition without using excess amounts of fire retardants that would otherwise be necessary, and which would affect other properties of the foam unfortunate. The resulting foams are superior to comparable foams made from distilled aromatic diisocyanates in the following respects: Higher melting point (which itself is a factor in improved fire safety), lower thermal conductivity, higher compressive strength and higher dimensional stability.

Rigid polyether polyurethane foams are produced by this method which have a combination of excellent properties, e.g. low thermal conductivity, high compressive strength and dimensional stability, which make them excellently suited for industrial thermal insulation. This is particularly surprising because when polyesters are used instead of polyether, foams with less brittleness are obtained which collapse before rising and have a non-uniform cell structure. Tolylene diisocyanate alone is also not suitable for use in the production of rigid foams of the polyether type, apart from the intermediate conversion of the diisocyanate into a prepolymer or quasi-prepolymer.

Preferably, the solution contains 10 to 40% by weight. non-volatile polyisocyanate which precipitates from solution when diluted with a hexane-toluene mixture according to the particular method described below, and the precipitate has a thermal stability below 130°C, an average molecular weight above 640, and an average amine equivalent above 180.

The tolylenediamine phosgenation product which can be used as a reactant in the above process can be produced by a method which consists in the steps (1) mixing tolylenediamine, phosgene and solvent at between approx. -20 and 100°C in such amounts that the molar ratio between phosgene and tolylenediamine is at least 2.2 (preferably between 2.3 and 6) and the weight ratio between tolylenediamine and solvent is between approx. 0.05 and 0.50 (preferably between 0.1 and 0.3), which solvent has a relative volatility at 140°C compared to the tolylene diisocyanate of between 4 and 100, and preferably between 8 and 50, (2) heating the reaction mixture under pressure sufficient to maintain a stoichiometric excess of phosgene in the reaction medium, to a temperature between 100 and 200°C until the phosgenation reaction is substantially complete, (3) separating the phosgene and hydrogen chloride from the resulting solution, (4) distilling the solvent and tolylene diisocyanate from the solution until the remaining concentrated distillate consists of a tolylene diisocyanate solution that meets the above requirements with respect to infrared spectrum, hexane-soluble solute concentrations, amine equivalent, recoverable tolylene diisocyanate content, viscosity and density and (5) terminate the distillation and recover it concentrated distillate.

The infrared spectrum characteristics for some of the phosgenation products according to the present invention are conveniently carried out in chloroform solution containing approx. 5 percent of the sample using a chloroform reference in a tuned cell. It is essential that chloroform or another solvent used is essentially free of alcohol or other additives or contaminants that react with the isocyanate groups in the sample,

The absorption maximum at 4.3 to 4.5 microns is characteristic of NCO groups and occurs in the spectra of pure tolylene diisocyanate, mixtures used according to the present invention and solute fractions isolated from these.

Absorption maxima at 5.8 to 5.9 and 5.95 to 6.05 microns do not appear in the spectrum for pure tolylene diisocyanates or tolylene diisocyanates prepared by various prior processes, but appear in the spectra for mixtures used in the present invention and fractions of dissolved substance isolated from these.

The phosgenation products characterized by their infrared spectra show an absorbance between 0.2 and 0.5 at 5.85 microns when measured by the following special process: (1) the spectrum for the chloroform solvent is recorded using a 0.1 mm path length cell in range 5.0 to 6.5 microns, (2) a chloroform solution of the sample having a concentration of 5 g of sample per 100 ml of chloroform is prepared, (3) the resulting curve obtained by applying the sample and a chloroform reference standard in an adjusted cell pair, having a cell length of 0.1 mm is recorded on the sheet containing the previously recorded curve for the solvent in the region 5 .0 to 6.5 microns at the same instrument parts used to plot the curve for the solvent. A Barid infrared spectrophotometer, mo-de! 455, which is used NaCl optics or a similar instrument is used. The absorbency at approx.

5.85 microns is proportional to the molar concentration of solute in the sample and is thus in accordance with Baird's law.

Isocyanate equivalent weights are measured by an analytical method which includes reacting the isocyanate groups in the sample with n-dibutylamine to give corresponding urea groups and back titrating excess amine with hydrogen chloride solution. The procedure is as follows: 6 to 8 g of sample is weighed out and diluted with 35-50 cc. toluene (analytical grade), 20 ems of a 2n solution of n-dibutylamine in commercial grade toluene is added, and the resulting mixture is heated for 5 to 10 minutes without boiling and cooled, 100 cm.3 of methanol is added, and the resulting solution is titrated with ln hydrogen chloride solution to an end point pH 4.2 to 4.5 using a pH meter, and finally a blank test is performed. The results can be calculated either as a weight percentage of NCO groups in the sample or as so-called "amine equivalent", i.e. the weight of the sample that contains in equivalent weight (42 g) of the NCO groups. The equation is: where AE = amine equivalent, WS = weight of sample in grams, TB = titration of blank in ml of HC1, TS = titration of sample in ml of HCL, and N = normality of HC1.

The range of amine equivalents for products according to the present invention is preferably 98 to 120, especially 102 to 108. The amine equivalent

for pure tolylene diisocyanate is 87. The polyisocyanate substance that is isolated from the product can have an equivalent weight of over 200.

Gas chromatograph data reproduced here was recorded in a Perkin Eimer Model 188 Triple Stage Vapor Fractometer which uses an evaporation temperature of 250°C. "Fluoropak 80" column packing coated with silicone grease as distribution agent, and helium gas as eluent. The analysis was carried out using trichlorobenzene as an internal standard. Chromatograph plots are obtained for two samples: (1) a reference mixture of tolylene diisocyanate and trichlorobenzene of unknown (i.e., the solution for which the free tolylene diisocyanate content is to be determined) and trichlorobenzene having a known trichlorobenzene content. The samples are introduced into the evaporation chamber with a syringe, and have a volume (which does not need to be measured) of one microliter or less. The ratio or quantity of the sample size A introduced into the fractometer is determined from chromatographs by the expression:

The phosgenation products used in the method according to the present invention have a recoverable tolylene diisocyanate content of between 40 and 90 per cent, normally between 55 and 85 per cent when measured by this or similar methods.

The non-volatile substance fraction of the phosgenation products can be isolated as a filterable solid by the following method: A 6 gram sample in a large bottle is covered with 360 ml of n-hexane (e.g. "SkellysolveB"), the bottle is shaken in 10 minutes in a shaking machine, such as is used to homogenize the contents of paint cans, the dispersed solids are allowed to separate, the extract is decanted and the decantate is centrifuged to separate from the solids which are returned to the bottle and the extraction is repeated as it is used about. 250 ml of hexane, and the resulting suspension is filtered to isolate the solute, which is then dried in a vacuum oven at 50°C. This treatment prevents the excretion of solute as a tar containing occluded tolylene diisocyanate, which adheres to surfaces, and which cannot be filtered or processed with satisfactory results.

A fraction of the total dissolved substance that has a higher molecular weight and melting point than the rest of the phosgenation products can be separated with a hexantholylene mixture as follows: A 2 gram sample is diluted with a mixture of 6 ml of tolylene and 50 ml of n-hexane (e.g. . "Skellysolve B") and stirred, the resulting precipitate is isolated on a sintered glass filter, washed with n-hexane and dried in a vacuum oven at 50 °C.

The phosgenation products according to the present invention contain from 20 to 50 wt. total of hexane-soluble polyisocyanates of which 10 to 40 percent can be isolated by the method described above. Solid residues remaining after the pyrolysis are granular in nature in the case of hexanetoluene-insoluble polyisocyanates and of a fused topless character in the case of hexane solubility. The following table sets forth data for the solute isolated from the phosgenation product described in Example 1 below:

Knowledge of the molecular structure of the dissolved substance is not necessary to enable the invention to be put into practice with all its advantages. The combination of infrared absorption spectral characteristics, wt. hexane-soluble constituents, amine equivalent, recoverable tolylene diisocyanate content, viscosity and density indicated above, define the mixtures that provide the stated advantages and distinguish them from phosgenation products that have too high or too low a concentration of solute or are produced by different phosgenation processes. A particularly desirable property for phosgenation products with this combination of characteristics is that their freezing points are lower than the freezing point of tolylene diisocyanate, which facilitates storage and processing during winter. The viscosity of these phosgenation products is from 20 to 10,000 eps, at 25°C, and is preferably approx. 50-70 eps., while the viscosity for pure tolylene diisocyanate is approx. 3 eps. The higher viscosity makes it easier to mix the phosgenation products with the polyether reactants and forms a higher viscosity reactant mixture which holds the blowing agent back during foaming. The high viscosity also reduces spattering.

The foaming reactions between these phosgenation products and polyether polyols develop less heat of reaction than comparable reactions between polyether polyols and tolylene diisocyanate do, so that the reaction temperature is 20 to 30°C lower. This enables the production of larger foamed masses and for-

improves the properties of the foam.

Foam is advantageously produced by mixing the aromatic polyisocyanate mixture with a "premix", which contains polyol mixed with the blowing agent, the fire retardant, and any other component, e.g. catalyst, dispersant, or cross-linking agent. Appropriately, the "premix" and aromatic polyisocyanate mixture are mixed in a conventional mixing device designed for foam formulations which discharges the mixture into a mold or a cavity to be filled. The foam expands on standing and can be hardened by heating, if necessary.

The amount of aromatic polyisocyanate mixture used for reaction with the polyol can be varied from 1 to 1.2 equivalents of isocyanate groups per equivalent active hydrogen, and the exact volume depends on the nature and properties of the rigid polyurethane foam desired. Thus, foams that use fluorocarbon blowing agents will require less of the isocyanate component than those in which carbon dioxide developed by the reaction of water and isocyanate groups is used. Preferably, approx. 1.03 more

1.05 isocyanate equivalents for each equivalent of active hydrogen.

The polyol can be selected from a wide class of polyfunctional derivatives, which in particular include the following: a) Polyfunctional polyesters, such as the reaction product of adipic acid, phthalic anhydride and trimethylolpropane which have a low acid number (below 10) and a high hydroxyl number (above 400) , and which is essentially water-free. Comparable polyesters, such as are obtained by the known methods from polyhydric acids, such as sebacic, glutaric, phthalic, halogenated phthalic, hydrogenated phthalic, succinic, fumaric and maleic acids, with polyols such as ethylene glycol, sorbitol and polypropylene glycol can also be used. b) Polyfunctional polyester amides where part or essentially all of the polyol component in the polyesters described above has been replaced by an amino derivative, such as tetraethylenediamine or ethanolamine. Such polyesteramides should, of course, be hydroxy terminated. c) Polyfunctional polyethers containing several hydroxyl groups and which are assumed to have

the general formula:

in which R is the residue of a polyol as defined below, R<1>is hydrogen, methyl or phenyl, X is a number from 1 to 5, Y is a number from 1 to 10 and Z is a number from 1 to 9 or O. Preferably, such polyethers have from three to ten hydroxyl groups capable of reacting with isocyanate groups and have a hydroxyl number from 200 to 750, preferably from 370 to 620. Such polyethers can be obtained by condensation of an alkylene oxide, such as ethylene oxide, propylene oxide, styrene oxide or mixtures of these alkylene oxides with polyhydric alcohols and/or polyhydric phenols in the presence of suitable basic catalysts, such as tri-alkylamines, e.g. trimethylamine or inorganic bases, such as potassium hydroxide. The polyhydric alcohols or phenols suitable for the preparation of polyfunctional polyethers include glycerol, trimethylolpropane, hexanetriol, fructose, hexitol, sorbitol, maltose, sucrose, triphenylolethane, triphenylolpropane, resorcinol, pyrogallol, bisphenyl A, chlorinated diphenol, and mixtures thereof compounds with or without water. In the method according to the present invention, these polyethers can be used in admixture with a fireproofing agent, which may or may not contain groups that react with the isocyanate groups, e.g. diallyl styrene phosphate, diallyl phenyl phosphonate, alkyl esters of halogenated organic acids, e.g. tetrachlorophthalic acid, dibromophthalic acid and dibromosuccinic acid, tris(2,3-di-bromopropyl) phosphate, tris (2,3)-dichloropropyl) phosphate, tris (chloroethyl) phosphate, bis-beta-chloroethylvinylphosphonate, «Phosgard» B- 52-R (a product of Monsanto Chemical Co.), in which the principal component is the compound whose formula is:

"Vircol" 82 (a product of Virginia Carolina Chemical) which is a phosphorus-containing diol which

has a hydroxyl number of 212; chlorinated diphenol (Monsanto Chemical Co.), and "Salowax" 1014 (a chlorinated naphthene, product of the Koppers Company).

The preferred polyethers for use in the present invention are those in which the fireproofing properties are built into the molecule, i.e. the polyfunctional polyethers which contain halogen and/or phosphorus as an essential part of the polyether molecule. Examples of such preferred polyethers are the reaction products of epichlorohydrin and a polyol, such as glycerin or sorbitol. These polyethers, either alone or in admixture with a non-reactive, fire-retardant agent, are highly effective in the production of fire-resistant, rigid polyurethane foam by the method according to the present invention.

The above described fire retardants vary with respect to effectiveness, i.e. they vary in potency and ability to impart resistance to fire and self-extinguishing character to the mixtures containing them. Some have the ability to provide a useful degree of fire safety when used in quantities as small as approx. 5 parts per 100 parts resin mixture, while others require the use of 25 or more parts per hundred parts resin mixture to impart an acceptable degree of fire safety. However, incorporation of large amounts of non-reactive fire retardants is detrimental to the isocyanate (foaming) reaction, as well as to many of the important properties of the polyurethane structure, particularly dimensional stability, crushing strength and heat resistance. The fire retardant tends to migrate into the foam and cause gradual shrinkage and destruction of the mold, which is greatly accelerated when the foam is exposed to elevated temperatures.

In accordance with what is now common practice for producing rigid polyurethane foams, the aromatic polyisocyanate and polyol are reacted in the presence of various auxiliaries, which, in addition to blowing agents, contain activators or catalysts and acidic dispersants or emulsifiers.

Examples of suitable blowing agents for use in the method according to the present invention are carbon dioxide (produced by the in situ reaction of water and polyisocyanate) and preferably fluorinated saturated aliphatic hydrocarbons. Mixtures of these can sometimes be used. The preferred blowing agents are liquids or gases at normal temperatures and pressures, poor solvents for the organic polymer, and which boil at temperatures below that developed in the polyurethane formation reaction. They preferably have a considerable solubility in the mixtures of the aromatic polyisocyanate distillation residue, and in the gaseous state they have a molecular size so that they do not diffuse through the spaces in the polyurethane molecules at ambient temperature. Such fluorocarbons are e.g. the following special compounds: monofluorotrichloromethane, dichlorodifluoromethane, monochlorotrifluoromethane, trichlorotrifluoroethane, dichlorobetafluoroethane, tetrachlorodifluoroethane, 1,1-difluoroethane, 1,1,1-dichlorofluoroethane. Mixtures of these and equivalent fluorocarbons can also be used.

Suitable activators or catalysts for use in the present invention include: 1) tertiary amine catalysts, such as tri-ethylamine, N-methylmorpholine, triethylenediamine, N,N,N'N'-tetramethyl-1,3-butanediamine, 2) tertiary amines such as contains hydroxyl groups and with the ability to cross-link the polyurethane. There are compounds such as those represented in the following general formula:

where X], X2, X3 and X4 may be the same or different and means the group H-(0-alkylene)z, where z is a number from 1 to 4, alkylene means a divalent aliphatic saturated hydrocarbon radical containing from 1 to 10 carbon atoms, with the limitation that one of X1, X2, X3 and X4 can be an alkyl group containing up to 20 carbon atoms, n is a number from 1 to 10, preferably 2 or 3, m is 0 or a number from 1 to 3, and Y is a number from 1 to 10. Representative of such a class of compounds are: tetra(hydroxyethyl)ethylenediamine, tetra(hydroxypropyl)ethylenediamine, the condensation product of propylene oxide and di(ethylenediamine), and N-Coco-(N,N'N '-tri-hydroxyethyl) ethylenediamine. 3) Organotin compounds with the general formula:

where CHgX means a hydrocarbonalkane radical of from 1 to 18 carbon atoms, R, R2 and R3 each means a hydrocarbonalkane radical of from 1 to 18 carbon atoms, hydrogen, halogen or a hydrocarbonacyl group, R1; Rg and R3 are the same or different, with the additional possibility that two members of this group R,, Rg and Rg together can be oxygen or sulphur. Representative members of this group of organotin compounds include the following special compounds: tetramethyltin, tetra-n-butyltin, tetraoctyltin, dimethyldioctyltin, triethyltin chloride, dioctyltin dichloride, di-n-butyltin dichloride, dilauryltin difluoride, 2-ethylhexyltin triiodide , di-n-octyltin oxide, di-n-butyltin dilaurate, di-n-butyltin diacetate, di-n-octyltin bis(monobutyl maleate), di-2-ethylhexyltin bis-(2-ethylhexanoate), tri-n- butyltin acetonate and dibutyltin diacetate. 4) Organic tin salts, such as stannous octoate and stannous oleate.

These catalysts and/or accelerators and/or activators can be used alone or in mixtures comprising one or more of the three types of substances.

Examples of dispersants or emulsifiers commonly used in the field include polyethylene phenol ethers, mixtures of polyalcohol carboxylic acid esters, oil-soluble sulphonates and siloxane-oxyalkylene block copolymers. The preferred emulsifiers for the purposes of the present invention are the siloxane-oxyalkylene block copolymers of the general formula:

where R, R' and R" are alkyl radicals with 1 to 18 carbon atoms, p, q and r are numbers from 2 to 15 and -(CnHgnO)2- is a polyoxyalkylene block which is preferably a polyoxyethylene-polyoxypropylene block containing from 10 to 50 of each type of oxyalkylene units. Products of this kind are described in U.S. Patent No. 2,834,748 and their use in polyurethane foam manufacture is the subject of Belgian Patents Nos. 582,362 and 582,363.. Such siloxane-oxyalkylene block copolymers are commercially available, and such a product is offered under the trade name "Silicon" L-520 by Union Carbide Chemical Co., in which, in accordance with the above formula, R = CH 3 , R' = C 2 H 5 , R" = C 4 H!); p = q = n = 7, and the block (^H^O).^- is a polyoxyethylene-polyoxypropylene block, containing approx. 50 units of each oxyalkylene moiety.

In addition to the aforementioned commonly used aids, the rigid polyurethane foams that are now known can and do also contain cross-linking agents, auxiliary blowing agents and pigments. Methods for composition, curing and carrying out treatment of the mixtures of the kind produced in accordance with the present invention are well known to those skilled in the art and are therefore not discussed in detail here.

The invention is illustrated by the following examples, where parts and percentages are by weight unless otherwise stated. Examples 1-4 describe the production of foam that does not contain any added fire retardant, examples 5-11 illustrate the production of foam with an added fire retardant.

Example 1.

A. Preparation of phosgenation product

The apparatus used in this example consisted of an autoclave surrounded by a reflux condenser, which is connected to an exhaust gas manifold leading to an absorber. It was equipped with a supply line for reaction components, a stirrer, a jacket for circulation of heating and cooling media and instruments for measuring pressure and temperature. A pressure relief valve was placed in the outlet gas line downwards from the reflux condenser.

The tolylenediamine reaction component used in this example contained approx. 77.2% of 2,4-isomer, 19.3% of 2,6-isomer, 1.0% of 3,4-isomer, 0.9% of 2,3-isomer and 0.6% .of the 2.5-isomer.

Phosgene (560 parts) and monochlorobenzene (120 parts) were introduced into the autoclave and cooled to -10°C. A warm (90°) solution of metathol-ylenediamine (244 parts) in 880 parts monochlorobenzene was prepared in a mixer and added to the autoclave at such a rate that the mixing temperature did not exceed 20°C. The charge composition in the reactor was: amine/solvent weight ratio 0.244, phosgene/amine molar ratio 2.8.

The autoclave was closed and heated slowly. The phosgenation became violent at approx. 45°C, which resulted from a pressure surge from the evolution of hydrogen chloride. After the temperature had risen to 80°C, the pressure valve was opened and treated so that hydrogen chloride is vented at a rate sufficient to keep the pressure below approx. 7 atmospheres. Heating continued at a controlled rate to avoid overvoltage during evolution of hydrogen chloride. As the reaction neared completion (as indicated by a drop in hydrogen chloride evolution), the temperature was raised to 136°C to complete the phosgenation of small amounts of unreacted amine hydrochloride. When the phosgenation was complete, the discharge of hydrogen chloride stopped, and it was necessary to close the valve to maintain the pressure in the autoclave. Heating was discontinued and the autoclave vented to atmospheric pressure.

The reaction mass was distilled at atmospheric pressure. Hydrogen chloride and phosgene were combined with approx. 100 parts of the solvent removed. The solvent was distilled off under 25 mm Hg pressure and at boiler temperature up to 165°C. The distillate was cooled to 120°C and then distilled at 10-12 mm Hg to separate from approx. 70 parts tolylene diisocyanate from 280 parts concentrated distillate.

B. Properties of the phosgenation product

The concentrated distillate had the following

properties:

Data for the composition of the fraction of polyisocyanates for this product are given above.

C. Preparation and characteristics of foam

A premix was prepared by mixing together 100 parts of "Actol 52-460" (a polyoxypropyl enpolyol having a hydroxyl number of about 460, an acid number of less than 0.1 and a water content of less than 0.1 percent by weight), 0.37 parts of dibutyltin dilaurate, 1.0 part dimethylethanolamine, 1.5 parts "Dow-Corning 113" (a silicone-glycol copolymer used to stabilize the foam) and 38 parts trichloromonofluoromethane as blowing agent.

The foaming machine was equipped with a Martin-Sweets mixing head operating at 5500 rpm. minute rotor speed and was continuously fed separate streams of (1) premix, flow rate of approx. 5.45 kg/minute at a temperature of 23°C, and (2) phosgenation product described above, flow rate of approx. 3.6 kg/minute at a temperature of 22°C. The batch contained 83.2 parts of phosgenation product per 100 parts polyether polyol corresponding to an average NCO/OH ratio of 1.03.

A sample of the foam mixture was collected in a tube and remained liquid for 18 seconds, turned to gel after 68 seconds, expanded to maximum volume after 2 minutes 23 seconds, and hardened after 6y2 minutes. It had a density of 29 kg/m<3>.

Another sample of the foam mixture was dispensed into a heated (41°C) aluminum mold to produce a sample of dimensions 60 x 60 x 4.4 cm. The resulting foam had a density of 32 kg/m<3>, a cell structure of approx. 96.9 percent closed cells, a compressive strength of 1.3 kg/cm<2> at yield point and 1.85 kg/cmf at 10 percent deflection, and a thermal conductivity ("K factor") determined by thermal conductivity mea- toden (Pittsburgh Corning), at 27°C and 0.250 K,cal/hr/m2/°C. The K-factor increased slightly to 0.265 after aging for 10 days at 60°C.

The results of the dimensional stability tests are given in the following table:

Example 2. . The phosgenation product used in this example was prepared in one way. similar to that in Example 1, except that the phosgene-amine ratio in the reactor batch was 2.3, and the final distillate-| lation treatment was terminated when the concen-; tert distillate had an amine equivalent of; 103.5 and a volatile tolylene diisocyanate content of approx. 75 percent

A premix was prepared by mixing 160 parts of Niax Triol LK-380 (a mixture of polyether triols having a hydroxyl number of 375-380, an acid number of less than 1 and a water content of less than 1 percent), 1.5 parts of "silicone emulsifier", 1.2 parts dibutyltin dilaurate, 15 parts tetra(hydroxypropyl) ethylenediamine and 47 parts of the blowing agent trichloromonofluoromethane.

The phosgenation product (137 parts) was cooled to 15°C and added to the cold (20°C) premix. The mixture was stirred for 35 seconds, allowed to expand to maximum volume and allowed to stand at room temperature for 16 hours.

The resulting foam had a density of 27.2 kg/m<3>, a cell structure of approx. 90 percent closed cells, a compressive strength of 1.65 kg/cm<3> at the yield point and a thermal conductivity (K-factor) at 24°C of approx. 0.21 K.cal/hour/mV°C. The dimensional stability tests gave the following results:

For comparison, another foam was prepared by the same procedure except that a tolylene diisocyanate mixture containing 80% 2,4-isomer and 20% 2,6-isomer was substituted for the polyisocyanate mixture. The resulting foam. had unsatisfactory dimensional stability.

Example 3.

The phosgenation product used in this example is similar to that used in Example 2, but had an amine equivalent of 105.

A premix containing three different polyether-polyol components was prepared by mixing together 90 parts of Voranol RN-600 (a polyether obtained by condensing propylene oxide with sucrose and having a hydroxyl number of about 600 and a water content of less than 1 percent), 20 parts E.T. 390 (a polyether obtained by

to condense propylene oxide with a polyolini-tiator and which has a hydroxyl number of approx. 405 and water content below 1 percent), 1 part "Silicone emulsifier", 1 part dimethylethanolamine, 10 parts Niax Pentol LA-700 (a basic polyether obtained by condensing propylene oxide with diethylenediamine) and which has a hydroxyl number of approx. 700), 1 part dibutyltin dilaurate and 50 parts of the blowing agent trichloromonofluoromethane.

The phosgenation product (137 parts) was cooled to 15°C and added to the cold (20°C) premix. The reaction mixture was stirred for 35 seconds. The foam expanded to full volume in another 36 seconds and was allowed to settle for 16 hours.

The foam had a density of 25.6 kg/m<3>.

Dimensional stability tests gave the following results:

Example 4.

The phosgenation product used in this example is essentially the same as in example 3. A premix was prepared by mixing together 100 parts of polyether hexitol ("G-2410", a condensation product of propylene oxide with sorbitol and which has a hydroxyl number of 500 and a water content below 1 percent), 1 part "Silicon emulsifier", 1.2 parts dibutyltin dilaurate, 0.5 part dimethylethanolamine, and 35 parts of the blowing agent trichloromonofluoromethane.

The premix was cooled to 20°C before adding 95 parts of cold (15°C) phosgenation product. The foam was allowed to stand for 16 hours after expansion to full volume. The density was 27.2 kg/m<3>. Dimensional stability data were as follows:

Example 5.

Rigid polyurethane foams were prepared as follows: a) A premix consisting of the following components was prepared: 100 parts of a polyether (Solvay Gr 450-EP-14,

prepared by the reaction of epichlorohydrin with a mixture of glycerin and sorbitol, and

which has a hydroxyl number of approx. 450), 0.4 parts dimethylethanolamine,

0.4 parts dibutyltin dilaurate,

1.0 parts of a siloxane-oxyalkylene block copolymer (Silicone DC-113, a product of Dow-Corning),

8.33 parts pentakis (Hydroxypropyl)diethylenetriamine, and

30.0 parts trichloromonofluoromethane (Allied Chemical Corp., General Chemical Div. "Gene-tron 11").

This premix was thoroughly mixed at ambient temperature and to it was added 81.7 parts of a distilled mixture of 20% 2,6- and 80% 2,4-tolylene diisocyanates. The reaction mass was vigorously stirred for 15 to 30 seconds and then poured into a suitable form. It was allowed to foam in this and then allowed to stand for approx. 16 to 24 hours at ambient temperature.

b) A premix composed exactly as described in part a) above was traded with 100 parts

of a tolylenediamine phosgenation product having an isocyanate equivalent weight of 106.1 and containing approx. 70 to 75% volatile tolylene diisocyanate.

c) The procedure according to parts a) and b) was repeated using, as aromatic

polyisocyanate components, 123.4 parts of a p,p'-

diaminodiphenylmethane phosgenation product having an isocyanate equivalent weight of 131.4 and containing approx. 80 percent volatile methylenebis(4-phenylisocyanate). d) A rigid foam was prepared according to the procedure described in c), except that it

p,p'-diaminodiphenylmethanephos generation product used had an isocyanate equivalent weight of approx. 143 and contained approx. 70 percent volatile aromatic diisocyanate.

Samples of all four foams were tested for fire safety according to AS TM Flammability Test C-1692. The results are reproduced in

the table below:

These results show that rigid polyurethane foams made from a polyether containing chlorine and pure aromatic diisocyanate are not fireproof. Similar foams made from the same chlorine-containing polyether and an aromatic diamine phos generation product are not only fireproof but also self-extinguishing. This surprising improvement is attributable to the presence of a compound or compounds of unknown constitution present in the aromatic diamine phos generation products used to prepare the foams B, C and D.

Example 6.

A rigid polyurethane foam was prepared by mixing: 100 parts of a polyether containing a reaction product of sucrose and propylene oxide, having a hydroxyl number of 600, and a viscosity of 16,000 eps, at 25°C ("Voranol" RN 600- Dow Chemical), 2 parts "Silicone" DC-113 (see example 5). 1.5 parts dibutyltin dilaurate,

1.5 parts distilled dimethyl-hexadecylamine, 20 parts tri(chloroethyl)phosphate ("Celluflex" CEF, from the Celanese Corp.),

45 parts trichloromonofluoromethane,

until a homogeneous emulsion resulted. Then 116 parts of a tolylenediamine phosgenation product, which has an isocyanate equivalent weight of 105.3 and which contains approx. 75 percent volatile tolylene diisocyanate, added. The resulting mass was stirred vigorously for 15 to 30 seconds, then poured into a suitable mold and allowed to rise to its full height and set aside to stand at ambient temperature for 16 to 24 hours. A sample of the resulting foam, when tested according to the ASTM D-1692 test, had a burn rate of 5.0 cm/min, and was self-extinguishing.

A similar foam made from 96 parts of distilled tolylene diisocyanate was prepared and tested for fire resistance. This foam had a burning rate of 6.9 cm/min. and was not self-extinguishing.

Example 7.

A series of rigid polyurethane foams were prepared in a manner analogous to that of Example 6 using distilled tolylene diisocyanate, but the amount of flame retardant was varied (TDI foam). These foams were compared for fire resistance (according to ASTM-D-1692) with a sample of the foam prepared according to Example 6 using the tolylenediamine phosgenation product. A similarly prepared foam with 40 parts tri-(chloroethyl)phosphate was also included in this comparison. The results are shown in the table below:

These results show that TDI foams containing 20 parts flame retardant burned completely when ignited, while PP foams containing the same amount of flame retardant were self-extinguishing. It also shows that in order to obtain a self-extinguishing foam with a comparable extinguishing time using TDI, twice the amount of fire retardant is needed compared to the amount required in the PP mixture.

Example 8.

A crude tolylenediamine phosgenation product containing approx. 75% volatile tolylene diisocyanate (80% 2,4-isomer and 20% 2,6-isomer) was prepared by phosgenation of a tolylene-diamine mixture in the presence of monochlorobenzene and distillation of the crude reaction product at atmospheric pressure to remove the solvent. The resulting phosgenation product was concentrated by distilling 39 wt. of tolylene diisocyanate from this at a pressure of approx. 3.2 mm Hg. The concentrated distillate had an isocyanate equivalent weight of 139 and contained approx.

59 percent volatile tolylene diisocyanate.

Two mixtures of concentrated distillate (CD) and pure tolylene diisocyanate (TDI) were prepared.

Three polyether premixes were prepared as in example 6 and one premix was reacted with 96 parts of tolylene diisocyanate, and another premix was reacted with 106 parts of mixture A and the third premix was reacted with 102 parts of mixture B.

The foams thus prepared were tested for fire safety according to ATM Test D-1692 with the following results: (1) Foams prepared with pure tolylene diisocyanate burned completely within 95 seconds. (2) Foam prepared from mixture A: extinguishing time 58 seconds, sample burned 6.8 cm from the 2.54 cm mark. (3) Foam prepared from mixture B: extinguishing time 25 seconds, sample burned 2.1 cm from the 2.54 cm mark.

Example 9.

The production of fireproof rigid polyurethane foams, which make use of a fireproofing agent containing groups which react with polyisocyanate, is illustrated in the following compositions. The way to shape the rigid polyurethane foams was as described above. The tolylenediamine phosgenation product used in this example had an isocyanate equivalent weight of approx. 106.3 and a volatile tolylene diisocyanate content of approx. 75 wt.

Explanation:

<*>"Vircol" 82, a product of Virginia Carolina Chemical Corp. is a phosphorus-containing polyol having a hydroxyl number of 212, an acid number of 1, a water content of 0.1, and a functionality of 2, a phosphorus content of 12 percent and a viscosity of 2,500 eps at 25°C;xx Sample burned completely when ignited. ;These results show that the toluene diamine fusion product imparts to a non-flammable rigid polyurethane foam a surprising fire-retardant character. ;Example 10. ;Rigid polyurethane foams were prepared as described above using the following compositions. The tolylenediamine phosgenation product used was essentially the same as that of Example 9; <*>N,N,N',N,-tetra-(2-hydroxypropyl)-ethylenediamine.

Foam A gave 1 to 2 percent shrinkage, was easy to crumble, had good cell structure and did not melt when ignited. Its fire safety was good.

Foam B gave 3 pst's shrinkage, had good cell structure, was easy to crumble, and melted when ignited. Its fire resistance was only fair and worse than that of foam A.

Example 11.

In a similar manner to that described above, rigid foams were prepared using the following formulation. The tolylenediamine phosgenation product used in this example was essentially the same as in Example 9.

Foam A, prepared using pure tolylene diisocyanate, melted when ignited and had poor fire safety.

Foam B, prepared using tolylenediamine phosgenation product, did not melt when ignited and had good fire resistance.

It can thus be seen that the fire safety of rigid polyurethane foams can be improved to a surprising extent by using the phosgenation products of aromatic diamines as opposed to distilled aromatic diisocyanates.

Claims (2)

1. Process for the production of rigid polyurethane foam with good fire safety by reacting together in the presence of a blowing agent and possibly in the presence of a fire retardant, (A) a polyol having at least two hydroxyl groups, and (B) a mixture comprising the phosgenation product of an aromatic amine consisting of a non-liquid hexane-insoluble polyisocyanate dissolved in a volatile aromatic diisocyanate, where the aromatic diisocyanate has been partially removed from the phosgenation product, characterized in that a mixture (B) is used which contains from 40 to 90 wt. volatile aromatic diisocyanate, preferably 55 to 85% by weight, preferably tolylene diisocyanate or p,p'-diaminephenylmethane diisocyanate which can be separated from the phosgenation product by molecular distillation at a pressure of approx. 1 mm Hg or by separation in a gas chromatograph, and that an amount of the mixture containing from 1 to 1.2, preferably 1.03 to 1.05 equivalents of isocyanate groups per equivalent active hydrogen atom in the polyol, and where the mixture (B) used consists of 20 to 55 wt. non-volatile hexane soluble polyisocyanate, the infrared spectrum of the mixture includes an absorption maximum in each of the ranges 4.3 to 4.5 microns, 5.8 to 5.9 microns and 5.95 to 6.05 microns, the molar concentration of the non-volatile aromatic diisocyanate in the mixture is such that it gives said spectrum at an absorption maximum between 5.8 and 5.9 microns, an absorbency between 0.2 and 0.5, the viscosity of the mixture is between 20 and 10,000 eps, preferably 50 and 70 cps„ at 25°C, the amine equivalent of the mixture is between 98 and 120, preferably between 102 and 108, and the density of the mixture is between 1.23 and 1.29 at 25°C. 2. Method according to claim 1, characterized in that a mixture (B) is used which contains 10 to 40 wt. non-volatile hexane-insoluble polyisocyanate which precipitates when the mixture is diluted with hexane-toluene mixture to give a precipitate having a thermal stability below 130°C, an average molecular weight above 640 g and an average amine equivalent above 180.