METHOD OF PRODUCING MODIFIED ORGANIC POLYISOCYANATE

Abstract: A modified organic polyisocyanate having isocyanurate rings is produced by adding a trimerization catalyst, an organic phosphite, a surfactant and, if desired, a ferrocene compound to an organic polyisocyanate and/or partially urethanated organic polyisocyanate, converting at most 20 % by weight of all of the isocyanate groups into isocyanurate groups, and adding, if necessary, a terminating agent to the reaction system.

Description: The present invention relates to a modified aromatic polyisocyanate having an isocyanurate ring, more particularly to a process for producing a modified aromatic polyisocyanate which is readily producible, being in a liquid state, superior in compatibility with other resins, and stable, and has an isocyanurate ring. Further, the present invention relates to a process for producing a modified polymethylenepolyphenyl-polyisocyanate, a storable resin composition and a foam prepared from the same, and more particularly to a process for producing a modified polymethylenepolyphenyl polyisocyanate having an isocyanurate ring, a storable resin composition prepared from the modified product and a polyol, and a process for producing therefrom a polyisocyananurate foam having low smoking property. Organic polyisocyanates have been utilized hitherto for various applications as foams, elastomers, paints and adhesives by reaction with active hydrogen compounds. Such organic polyisocyanates can also be used by modification to a polyisocyanate compounds having an isocyanurate ring. The products prepared by reaction of the modified polyisocyanate compound with an active hydrogen compound has heat resistance, flame resistance, rigidity and toughness which are characteristic of isocyanurates, and arcs utilized in applications where such properties are required. Accordingly, a variety of isocyanuration polymerization procedures may be conducted for the isocyanuration of organic polyisocyanates. (The term "isocyanuration" means herein the trimerization of an isocyanate compound to form an isocyanurate ring.) For example, Japanese Patent Laid-open Publications Sho. 54-32490 and Sho. 52-69497 respectively describe isocyanuration using a catalyst such as a metal salt of acetylacetone or an alkali metal salt of an organic acid. These production processes are not satisfactory, because the selectivity of the catalyst is very narrow for the organic polyisocyanate; and particularly in the isocyanuration polymerization, an organic isocyanate in which the difference between the reactivities of the first and the second isocyanate groups is small like those in diphenylmethane diisocyanate, is liable to polymerize to become viscous and to give a partially non-uniform product having a low isocyanate content and low compatibility with other resins. Further, upon inactivation of the catalyst in order to improve the stability of the modified polyisocyanate, if the reaction has been conducted without a solvent, then an insoluble precipitate tends to be formed and it is difficult to control the isocyanuration reaction, so that it is not satisfactory industrially and improvement thereof is desirable. In other words there is a desire for a modified organic polyisocyanate having an isocyanurate ring which may be prepared readily through isocyanuration of an organic polyisocyanate, and which is stable during storage, and excellent in compatibility to other resins. Hitherto, the preparation of a polyisocyanurate foam having flame resistance and a low smoking property has been carried out in the presence of a trimerization catalyst by reaction of a polyisocyanate with an active hydrogen compound. However, further improvement of the properties is desired. A polymethylenepolyphenyl-polyisocyanate (herein referred to as "polymeric MDI") exhibits heat resistance based on its characteristic feature when reacted with polyols. Polymeric MDI alone or a polyol adduct of polymeric MDI is in current use. However, polyol adducts are liable to deteriorate with heat, and are limited in use for flame-resistant foams. Polyisocyanurate foams are widely used for heat insulating materials, light-weight structural materials, and sound absorption materials because of their superior characteristics. The introduction of the isocyanurate ring into polyurethane crossliking makes heat resistance, hydrolysis resistance, and dimension stability higher. However, application is limited because of an increase in the quantity of combustion smoke on heating to a high temperature. For the improvement of this disadvantage, an additive such as ammonium polyphosphate, a phosphate ester or p-nitroaniline sulfonic acid is added to accelerate carbonization of the foam on contact with a flame, to reduce the smoke quantity. Further, in an attempt at lowering the smoking properties attributed to the control of combustibility by addition of a heat-resistant inorganic powder, for example, addition of calcium carbonate, ammonium phosphate or ammonium sulfate, it has been proposed to dilute a combustible gas generated by the foam with an inert gas (CO₂, NH₃) generated by pyrolysis of the inorganic powder and thus to lower combustibility by depression of combustion. However, since such an additive is required to be added in a large amount, these methods have the disadvantages of lowering the storage stability of reaction mixing liquid component and the mechanical properties of the foam. Further, for imparting high flame resistance to a foam, the concentration of isocyanurate rings in the formulation containing a polyisocyanate and a polyol is increased by raising the index (NCO/OH molar ratio) to make the concentration of isocyanurate linkage in the foam high so as to possess heat resistance and flame resistance derived from the isocyanurate linkage. The raising of the NCO/OH ratio, however, is limited because an excessively high ratio leads to a large amount of unreacted isocyanate groups resulting in disadvantages of increased smoking on combustion and explosive breakage upon contact with flame, and the foam thus prepared has considerable brittleness coming from the characteristic property of isocyanurate linkages. Accordingly, sufficient properties are not attained as a semi-incombustible material, and further improvement is desired. That is, it is desired to improve the modified polyisocyanate for polyisocyanurate foams, and flame resistance, smoking property, friability, heat resistance and compatibility with resins, for polyisocyanurate foam produced from the polyisocyanate, a polyol, a blowing agent and an additive, upon using them as incombustible materials. JP-A-63-96178 describes the isocyanuration of hexamethylene diisocyanate and/or an isocyanate-terminated hexamethylene diisocyanate-polyol adduct using a saturated fatty acid sodium or potassium salt catalyst, optionally an alcoholic and/or phenolic hydroxy compound co-catalyst, and a trialkylphosphate solvent and a trialkyl/phenyl phosphite colour inhibitor. The products are said to be useful as coating materials and as adhesives and as starting materials for elastomers and for plastic foams. JP-A-61-129173 describes the preparation of compounds containing an isocyanurate ring and an isocyanate group by reacting an isocyanate compound with a hydroxyalkyl quaternary ammonium compound catalyst in the presence of an organic phosphite ester co-catalyst. The product compounds are said to be useful hardening agents for polyurethane coating materials. The present invention is based on the observations that modified polyisocyanates having isocyanurate rings can be produced from aromatic polyisocyanates using amine trimerisation catalysts, organic phosphite esters and surfactants and, optionally, ferrocene compounds, and that foams prepared from such modified polyisocyanates exhibit superior properties of incombustibility, low smoking and low friability. In accordance with the invention, there is now provided a process for producing a modified aromatic polyisocyanate having an isocyanurate ring, characterised by adding an amine trimerisation catalyst, an organic phosphite ester, a surfactant, and optionally a ferrocene compound to an aromatic polyisocyanate and/or a partially urethanised aromatic polyisocyanate to cause isocyanuration of not more than 20 % by weight of entire of isocyanate groups; and, if necessary, adding a stopper to terminate isocyanuration. In accordance with the invention, there is provided also a modified polymethylene-polyphenyl-polyisocyanate prepared by adding a trimerisation catalyst and an organic phosphite ester to a polymethylene-polyphenyl-polyisocyanate or a partially urethanised polyisocyanate prepared by reacting eh polymethylene-polyphenyl-polyisocyanate with a polyol having a molecular weight from 62 to 1000. There is provided additionally a resin composition for the manufacture of a foam, which comprises such a that modified product, a polyol having a molecular weight of not less than 200, a blowing agent, a catalyst, a foam stabiliser, and if necessary a filler. There is provided too a process for producing a polyisocyanurate foam which comprises reacting together the components of that resin composition. The aromatic polyisocyanate used in the present invention is exemplified by 2,4- and 4,4'-diisocyanatodiphenyl ethers, 2,4- and 2,6-toluene diisocyanates, 4,6-dimethyl-1,3-phenylene diisocyanate, 4,4'-diisocyanatodibenzyl, 9,10-anthracene diisocyanate, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, 2,6'-dimethyl-4,4'-diisocyanatodiphenyl, xylylene diisocyanate, and 2,4'- and 4,4' -diphenylmethane diisocyanates. Particularly useful aromatic polyisocyanates are especially polymethylenepolyphenyl polyisocyanates represented by the general formula (1): where n = 0 - 8; and mixtures containing the above polyisocyanates. The partially urethanized aromatic polyisocyanate used in the present invention is a product of a urethanizing reaction of an aromatic polyisocyanate and a hydroxyl-group-containing compound, and can be prepare by adding a hydroxyl-group-containing compound to an aromatic polyisocyanate at a reaction temperature of not more than 100°C, preferably from 60 to 90°C, for approximately 2 hours in a conventional manner. If the temperature is above 100°C, a side reaction occurs which causes extremely high viscosity of the product of the trimerization reaction, sometimes resulting in formation of gel-like matter. The urethane groups thus introduced exhibit a cocatalytic effect which allows the isocyanuration reaction to proceed readily. This is considered to be due to the remarkable activation of the isocyanate group resulting from formation of hydrogen bonding between the active hydrogen in the urethane group and the oxygen atom in the isocyanate group. Thus, the cocatalytic effect of the urethane group makes it possible to decrease the amount of catalyst. Since the increase in the concentration of urethane groups reduces the characteristic heat stability of the isocyanurate ring formed later, the urethane group concentration needs to be adjusted depending on the purpose. In the present invention, the urethanizing ratio is desirably not more than 10% by weight of the entire isocyanate groups. The hydroxyl-group-containing compound to be used for urethanizing reaction preferably has a molecular weight of not higher than 2000, more preferably not higher than 1000, and has a functionality of not more than 3. Examples are primary alcohols represented by the general formula: R'OH, where R' is alkyl, arylalkyl, alkylaryl, aryl, or alkenyl: such as 2-ethylhexyl alcohol, lauryl alcohol and nonyl alcohol. Other examples are diols such as ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,6-hexane glycol, 2-ethyl-hexanediol and 2,2,4-trimethylpentanediol, and polyesterdiols and polyetherdiols. Further examples are triols including trihydric alcohols such as trimethylolethane, trimethylolpropane and glycerin, and polyester- and polyether-polyols. These are used individually or as mixtures of two or more thereof in any arbitrary ratio. The urethanizing reaction and the isocyanurating reaction may be conducted in the presence of, or in the absence of a solvent. The modified polymethyleneolphenyl-polyisocyanate according to the present invention is suitably prepared by isocyanuration of a polymethylene-polyphenyl-polyisocyanate or a polyol adduct of the polyisocyanate in the presence of a tertiary amine as the catalyst and additionally an organic phosphite ester at a temperature of not higher than 100°C, preferably from 20 to 70°C. The catalysts used for isocyanuration modification of the present invention are amine series compounds such as 2,4,6-tris(dimethylaminomethyl)phenol, 2,4-bis(dimethylaminomethyl)phenol, 2,6-di-tertiary-butyl-4-dimethylaminotrimethylsilanephenol, triethylamine, N,N',N''-tris(dimethylaminopropyl)-hexahydrotriazine and diazabicycloundecene. The organic phosphite ester per se used in the present invention does not catalyze the isocyanuration. However, the combined use thereof with a trimerization catalyst makes the control of isocyanuration reaction easy, and gives a stable modified polymethylenepolyphenyl-polyisocyanate without generating turbidity in the reaction product. The organic phosphite ester used in the present invention includes organic phosphite diesters and organic phosphite triesters. These compounds have the partial structure (in which one bond of each of the oxygen atoms is linked to a carbon atom). In the present invention, the organic phosphite triesters include tris(β-chloropropyl) phosphate. The organic phosphite diesters include the compounds represented by (RO)₂P(O)H (where R may be the same or different and is an alkyl having 1- 20 carbons or an aryl such as phenyl which may be substituted by an alkyl of 1 - 20 carbons). Such diesters are exemplified by dilauryl hydrogen phosphite and diphenyl hydrogen phosphite. The alkyl represented by the symbol R may be partially substituted by a halogen such as chlorine, for example, tris(2,3-dichloropropyl) phosphite. The oxygen atom in the phosphite may be substituted by a sulfur atom. For example, such a compound is exemplified by trilauryl trithiophosphate. The compounds represented by (R-O-)₃P (where R may be the same or different and is an alkyl having 1- 20 carbons or an aryl such as phenyl which may be substituted by an alkyl of 1 - 20 carbons) include monophosphites such as triethyl phosphite, tributyl phosphite, tris(2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, tris(tridecyl) phosphite, tristearyl phosphite, triphenyl phosphite, tris(nonylphenyl) phosphite and tris(2,4-di-t-butylphenyl) phosphite. Further, the following compounds can be exemplified: di-, tri- or tetra-phosphite derived from polyhydric alcohol, such as distearyl pentaerythrityl diphosphite, ditridecyl pentaerythritol diphosphite, dinonylphenyl pentaerythritol diphosphite, tetraphenyl tetratridecyl pentaerythrol tetraphosphite, tetraphenyl dipropylene glycol diphosphite and tripentaerythritol triphosphite; diphosphites, derived from bisphenol series compounds, such as dialkyl (1-20 carbons) bisphenol A diphosphite and 4,4'-butylidene-bis(3-methyl-6,6-butylphenyl-ditridecyl) phosphite; and polyphosphites such as hydrogenated bisphenol A phosphite polymer (molecular weight: 2400-3000). In the present invention, such an organic phosphite ester is used in combination with the catalyst, and the amount of the catalyst may then be less than the most effective amount used alone. The catalyst is used in an amount ranging from 0.005 to 0.5% by weight based on the starting isocyanate compound, depending on the activity of the catalyst. The phosphite ester is used in an amount of from approximately 1/10 to 20 times the amount of the catalyst. The reaction rate of the isocyanuration is strongly affected by the initial concentration dependency of the catalyst. In particular, upon using diphenylmethane diisocyanate, in isocyanuration in a conventional manner, gel-like matter is formed and suspends non-uniformly, and occasionally gelation occurs. Accordingly, in order to reduce the initial concentration dependency of the catalyst, it is preferable that the catalyst is added in a low initial concentration by addition of a diluent. The diluent is preferably a compound inactive to the isocyanate and incombustible to maintain the fire resistance and the heat resistance of the polymer to be produced. Examples are methylene chloride, trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane and trichlorotrifluoroethane. By using such a catalyst and conducting the partial polymerization to the extent that not more than 20% by weight of the entire isocyanate groups react, a liquid and stable polymer can be obtained. In modifying an organic polyisocyanate by isocyanuration, since the isocyanuration-modified matter does not have sufficient compatibility with the organic polyisocyanate, urethane groups are introduced for the improvement of compatibility. In the present invention, by using a surfactant, isocyanuration modification is achievable in the absence of a solvent both for organic polyisocyanates and for partially urethanized organic polyisocyanates, giving a liquid and stable isocyanuration-modified product free from turbidity and containing scarcely any polymer of high molecular weight. The use of a surfactant improves the compatibility of the resulting isocyanuration-modified product with other resins, so that the curing reaction with an active-hydrogen-containing compound will proceed smoothly, and the physical properties of the resulting cured product will be improved. In the present invention, the surfactant may be added either in the initial stage or in a later stage of the reaction. The surfactant used in the present invention is manufactured, for example, by condensing a polyglycol ether, which is derived by reacting an alkylene oxide such as ethylene oxide, propylene oxide or butylene oxide, preferably ethylene oxide, with polyethylene glycol or polypropylene glycol, with an organic compound having one reactive hydrogen atom. Such compounds having one reactive hydrogen atom include alcohols, phenols, thiols, and primary and secondary amines. The surfactant may be a nonionic surfactant prepared from a polyglycol ether and a carboxylic acid, a sulfonic acid, or an amide thereof. The surfactant may be a polyethylene glycol ether. Further, the surfactant includes polyalkylene oxide derivatives prepared from the polyglycol ether and a phenol compound having one or more alkyl substituents, including polyethylene glycol nonylphenyl ether. Further, the surfactants include those known as Pluronic type, for example. These surfactants are prepared generally by use of butylene oxide, amylene oxide, phenylethylene oxide, cyclohexene oxide, propylene oxide or a mixture thereof; for example, such surfactants can be prepared by polymerizing 1,2-alkylene oxide or a substituted alkylene oxide in the presence of an alkali catalyst to give a corresponding water-insoluble polyalkylene glycol and subsequently condensing with the required moles of ethylene oxide. Examples are Pluronic L-61, and Pluronic L-62 (made by Asahi Denka Kogyo K.K.). The surfactants further include nonionic surfactants, for example, prepared by forming an aldehyde by catalytic reaction of a polyolefin such as tripropylene, tetrapropylene, pentapropylene, diisobutylene, triisobutylene, tetrabutylene, propylene-isobutylene, and tributene with carbon monoxide and hydrogen, then reducing the resulting aldehyde into an alcohol, and reacting the alcohol with a required amount of ethylene oxide. Examples are polyoxyethylene alkyl ethers, such as polyoxyethylene lauryl ether and polyoxyethylene oleyl ether. Further, particularly effective surfactants in the present invention are those represented by the general formula (2): where R, R', and R'' are alkyl groups having 1 - 20 carbons; p, q, and r are each an integer of 1 or more; n is an integer of 2 - 4; and z is an integer of 5 or more. Examples are silicone surfactants such as L-5340 (made by U.C.C.), Toray Silicone SH193 (made by Toray Industries, Inc.) and B8404 (made by Goldschmidt Co.). Such a surfactant is used in an amount of 0.1 to 2% by weight based on the organic polyisocyanate. The modification reaction by isocyanuration according to the present invention is conducted at a reaction temperature of not higher than 100°C, preferably in the range of 15 to 70°C. In the reaction, the use of the surfactant allows the isocyanuration reaction to proceed effectively at a relatively low temperature, giving a stable and liquid isocyanuration-modified product because of uniform dispersion of the resulting isocyanuration-modified product in the reaction product and gradual progress of the reaction. An excessive amount of the catalyst or the reaction temperature exceeding 100°C tends to generate a polymer of an isocyanurate compound or a polymer of an allophanate compound, which may decrease compatibility, or cause gelation. The substance which has a linear structure containing a ferrocene skeleton in the main chain and is useful for the isocyanuration-modification of the present invention is represented by the following general formula (3) where R and R₁ may be the same or different, and are hydrogen, alkyl, alkenyl, aralkyl, or aryl, and may form a ring together with the carbon atom of -C(R) (R')-; and n is 0, or 1 or more. The position of the substitution in the ferrocene nucleus is 1,2-, 1,3-, or 1,1'-, or a mixture thereof. Otherwise, the substance may be a mixture of a linear structure having a ferrocene skeleton containing an unsubstituted ferrocene. Useful ferrocene compounds include mono- and di-lower alkyl (C₁₋₈) dicyclopentadienyl iron compounds such as ethyldicyclopentadienyl iron, n-butyldicyclopentadieneyl iron, diethyldicyclopentadieneyl iron and n-butyldicyclopentadieneyl iron; and dimer and polymeric reaction products of dicyclopentadieneyl iron or a derivative thereof, in which the substituent is a lower alkyl (C₁₋₈), with an aldehyde or a ketone, such as 2,2-di(ethyldicyclopentadienyl iron) -propane, di(butylcyclopentadienyl iron)-propane and di(cyclopentedienyl iron)-methane. The amount of the ferrocene compound to be used in the present invention is suitably in the range of from 0.05 to 0.4%, preferably 0.08 to 0.3% by weight, based on the organic polyisocyanate starting material. For producing the modified organic polyisocyanate, the reaction time, the yield and quality of the modified product may be adjusted effectively by the kind and the amount of the catalyst to be used. Accordingly, the NCO content and the viscosity of the modified organic polyisocyanate can be adjusted arbitrarily by the NCO content at the termination of the reaction since it can be measured by a known conventional titration analysis. Thus, the isocyanuration of the present invention is advantageous in using a decreased amount of catalyst, and the possibility of reaction at a low-temperature in a short time. An acidic compound may be used as a terminating agent, if necessary, in the production of the isocyanurated organic polyisocyanate according to the present invention. The acidic compound is exemplified by hydrochloric acid, phosphoric acid, dimethyl phosphate, trimethyl phosphate, triethyl phosphate, tricresyl phosphate, triphenyl phosphate, tributyl phosphate, p-toluenesulfonic acid, methyl p-toluenesulfonate, xylenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, alkylbenzenesulfonic acids, dinaphthalenedisulfonic acid, dinaphthalenemonosulfonic acid, dinonylnaphthalenedisulfonic acid, dinonylnaphthalenemonosulfonic acid, benzoyl chloride, acetyl chloride, and analogous compounds. The amount of the stopper is in the range of from 0.3 to 5 equivalents, preferably from 1.0 to 2.0 equivalents, based on the catalyst. The addition thereof during the isocyanuration reaction promotes the stabilization of the modified organic polyisocyanate without causing turbidity of the reaction liquid. The modified aromatic polyisocyanate produced according to the present invention contains a surfactant, an organic phosphite ester, and a ferrocene compound. When flames are applied to the resin obtained by the reaction of the modified aromatic polyisocyanate and an active hydrogen containing compound, it is assumed that, owing to the presence of an iron compound coming from the ferrocene compound having strong oxidizing action, the side chains of the resin are rapidly oxidized and the main chain of the resin is carbonized to form a carbon polymer, which gives to the resin superior heat resistance and oxidation resistance, and decreases the combustion velocity, thus resulting in the incombustibility and low smoking properties. Accordingly, a urethane-modified isocyanurate foam having a higher NCO/OH equivalent ratio (index) has improved heat resistance and improved flame resistance because the iron compound serves to increase carbonization yield and to decrease the amount of the decomposition gas. The modified product of the present invention has a stable quality even without a solvent, so that it is useful widely not only for plastic foams and elastomers but also as starting materials of paints and adhesives. The products derived from the reaction with an active hydrogen compound exhibit excellent performance in flame retardance, heat resistance, water resistance and toughness. Urethane linkages formed from a portion of the polymethylenepolyphenyl-polyisocyanate and a polyol facilitate isocyanuration, and improve significantly the compatibility of the resulting modified product with other resins. However, the increase in the concentration of the urethane group will prevent the generation of sufficient heat stability which is characteristic of the isocyanurate ring to be formed later, so that the concentration of the urethane group should be selected depending on the use thereof. A resin composition for polyisocyanurate foams, composed of a combination of a partially isocyanurated modified polymethylenepolyphenyl-polyisocyanate and a polyol having a molecular weight of not less than 200 and having at least two hydroxyl groups in the molecule is superior in flame retardance, heat resistance, low smoking property and low friability, when made into a foam, in comparison with conventional resin compositions for urethane foams. The partially isocyanurated modified polymethylenepolyphenyl-polyisocyanate of the present invention is a modified polymethylenepolyphenyl-polyisocyanate in which the trimerization forming the isocyanurate ring is carried out in such a way that from 1 to 10% by weight of the entire isocyanate groups are isocyanurated. There can be present other isocyanurate-group- containing polymers having higher molecular weight besides the trimer forming the isocyanurate ring of the present invention. Such a high-molecular polyisocyanurate polymer, although it may also be effective in incombustibility and heat resistance, is not preferable because a large amount of the high-molecular polymer will increase viscosity and decrease compatibility with other resins, and will impair workability. The isocyanuration reaction of the present invention is practicable at a low temperature and in a short time, and can be conducted in such a way that 1 to 10% by weight of the entire isocyanate groups turn into isocyanurate by selection of production conditions. In the present invention, virtually no high-molecular polymers are formed. However, if the reaction conditions deviate from those according to the present invention, then a high molecular isocyanurate will be formed, which is undesirable because the compatibility of the high molecular substance in particular is low. In an embodiment, the present invention can use a modified polymethylenepolyphenyl-polyisocyanate having terminal isocyanate groups, which is prepared by isocyanuration of 1% to 10% by weight of the entire isocyanate groups to form a modified product containing a trimer, and by urethanization by the reaction of the resulting modified product with a polyol to cause urethanation. The polyisocyanurate foam prepared by the reaction of a modified polymethylenepolyphenyl-polyisocyanate which is derived by selecting the ratio of the trimer forming an isocyanurate ring within the range of from 1 to 10% by weight of the entire isocyanate groups with another resin, is a foam having incombustibility, heat resistance, low smoking property, low friability, and uniform cell structure. Outside the above range, the intended characteristics is not obtainable. The polyol to be reacted with the modified polymethylenepolyphenyl-polyisocyanate or partially urethanized modified polymethylenepolyphenyl-polyisocyanate may be any polyol having a molecular weight of not less than 200, and having at least two hydroxyl groups in the molecule. Typical examples are polyesterpolyols and polyetherpolyols. These polyols may be used in combinations of two or more. The polyester polyol may be prepared in a conventional manner by reaction of one or more compounds having at least two hydroxyl groups such as ethylene glycol, diethylene glycol, trimethylene glycol, 1,2-propylene glycol, 1,3-butanediol, tetramethylene glycol, hexamenthylene glycol, decamethylene glycol, glycerin, trimethylol propane, pentaerythritol, sorbitol and bisphenol A, with one or more compounds having at least two carboxyl groups such as malonic acid, maleic acid, succinic acid, adipic acid, tartaric acid, pimelic acid, sebacic acid, oxalic acid, phthalic acid, terephthalic acid, azelaic acid, trimellitic acid, glutaconic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α,β-diethylsuccinic acid, hemimellitic acid and 1,4-cyclohexane-dicarboxylic acid. Further, polyesterpolyols derived by transesterification between a polyalkylene terephthalate polymer represented by the general formula below and a low molecular diol are useful: where R is alkyl having 1 to 10 carbons, and n is a number corresponding to a molecular weight of 1500 or more. The low molecular weight diol here includes ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, butanediol, glycerol and trimethylolpropane. The polyetherpolyols are prepared by addition-polymerizing one or more of monomers such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide, glycidyl ether, methyl glycidyl ether, t-butyl glycidyl ether and phenyl glycidyl ether, in a conventional manner by using as the initiating substance one or more compounds having at least two active hydrogen atoms such as ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, -pentane diol, 1,7-heptanediol, glycerin, trimethylolpropane, trimethylolethane, hexane-1,2,6 triol, α-methylglycoside, pentaerythritol, sorbitol, sugar type alcohols like sucrose, glucose and fructose, bisphenol A, ethylenediamine, propylenediamine, diethylenetriamine, toluenediamine, metaphenylenediamine, diphenylmethanediamine and xylenediamine. If the molecular weight of the polyol is not higher than 200, the resulting foam is extremely hard and brittle and does not give sufficiently strong foam properties, and is therefore not suitable for use as a foam. The resin composition has good storage stability and is obtained by employing a modified polymethylenepolyphenyl-polyisocyanate or a partially urethanized modified product thereof and a polyol at an NCO/OH blending ratio of not less than 2.0. Hitherto, polyisocyanurate foam had been considered not to be produced readily at a high NCO/OH ratio. The reasons for this are the difficulty of uniformly conducting the isocyanuration under the time restrictions of respective foaming reaction steps, although the urethanizing reaction proceeds rapidly in the presence of a suitable catalyst. Thus, the two different reaction mechanisms do not give satisfactory foam properties. Hence, the selection of the specific catalyst is necessary for the two different mechanisms to proceed concurrently and uniformly. According to the present invention, the urethanizing reaction and the isocyanurating reaction are conducted effectively, concurrently and uniformly even at a high NCO/OH ratio by use of a partially isocyanurated modified polymethylenepolyphenyl-polyisocyanate or a partially urethanized modified polymethylenepolyphenyl-polyisocyanate, and thus a polyisocyanurate foam intended by the present invention is produced which is low smoking, high flame retardant, high heat resistant, and low friability, useful as semi-incombustible materials. Consequently, the use of the modified polymethylenepolyphenyl-polyisocyanate or a partially urethanized modified polymethylenepolyphenyl-polyisocyanate according to the present invention allows a high concentration of isocyanurate rings, and sufficient properties of incombustibility and heat resistance which are characteristic of the isocyanurate ring. The resin composition of the present invention effects isocyanuration reaction selectively in a high yield, and smoothly even at a high NCO/OH ratio, and therefore is highly superior in workability. As the results, it gives a heat resistant foam which contains the isocyanurate ring structure in a high concentration, decreases the weight loss upon prolonged heating at a high temperature, and has heat resistance such that, even when exposed to flame, neither deformation nor cracks are found at the back face of the foam or the periphery of the portion subjected to the flame. The foam prepared from the resin composition of the present invention gives a molded product which has high heat resistance, low friability, incombustibility, and excellent physical properties of the foam in addition to the low smoking property. Such properties have not been achieved until now. In production of polyisocyanurate foam from the reaction of a modified polymethylenepolyphenyl-polyisocyanate or a partially urethanized modified polymethylenepolyphenyl-polyisocyanate with a corresponding polyol, a conventional trimerization catalyst may be used as the catalyst. Examples include alkali metal salts of carboxylic acids having 2 to 12 carbons such as potassium acetate, potassium benzoate, potassium 2-ethylhexanate and potassium naphthenate; amines such as 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, N,N',N''-tris (dimethylaminopropyl) hexa-hydrotriazine, triethylenediamine, diazabicycloundecene and tetramethylhexanediamine; and alcoholates and phenolates such as potassium phenolate and sodium methoxide. Combinations of any one or more of the above catalysts or analogous compounds may be used. The amount of the isocyanuration catalyst upon production of the polyisocyanurate foam is approximately in the range of from about 0.01 to 20% by weight based on the polymethylenepolyphenyl-polyisocyanate or partially urethanized modified polymethylenepolyphenyl-polyisonate. Any known blowing agent employed in the production of urethane foams or isocyanurate foams may be applicable in the present invention. Examples include low-boiling inert solvents such as trichloromonofluoromethane, dichlorodifluoromethane, dichloromonofluoromethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, dibromotetrafluoroethane, methylene chloride, trichloroethane, benzene, toluene, pentane and hexane ; substances which evolve carbon dioxide gas by reaction with an organic polyisocyanate, such as water, crystallisation water-containing compounds and aldoximes; and substances which evolve a decomposition gas on heating, such as sodium bicarbonate, azoisobutylonitrile and ammonium carbonate. Among them, trichloromonofluoromethane and water are preferable. The amount of the blowing agent is suitably decided depending on the kind of the blowing agent. The foam stabilizer used in the present invention may be any of conventional ones including silicone type surfactants such as organopolysiloxanes, organopolysiloxane-polyoxyalkylene copolymers and polyalkenylsiloxanes having a polyoxyalkylene side chain; and cation type, anion type, and nonion type surfactants. The amount of the foam stabilizer may be decided suitably depending on the kind and properties of the foam stabilizer. In the present invention, additives such as glass balloons, silas balloons, glass fiber, carbon fiber and other inorganic fillers, if necessary, may be additively used. Further, a flame-retarding compound such as phosphate esters may be added. Specifically the polyisocyanurate foam is readly produced from the above constituents by mixing the constituents homogeneously with any apparatus capable of homogeneous mixing the constituents, such apparatus includes a laboratory small-size mixer or a foaming machine for urethane foam production. The resin composition of the present, invention can prepare with remarkable efficiency polyisocyanurate resins excellent in heat resistance and flame retardance, by use of a two-component reaction pouring machine or an injection molding machine, so that the composition is applicable to construction materials, main exterior shells of audio apparatuses, electric appliance parts, household articles and automobile parts. The present invention can prepare a modified aromatic polyisocyanate having an isocyanurate ring readily and stably in a short time with a small amount of a catalyst. The modified product produced according to the present invention is a modified aromatic polyisocyanate which is liquid and stable, and sufficiently compatible with other resins, and has strongly active isocyanate groups at the ends of the molecules. The reaction of the modified aromatic polyisocyanate with a compound having active hydrogen reactive to the isocyanate group will give a product having flame retardance, heat resistance, and rigidity in good workability. Further, the aromatic polyisocyananurate foam produced according to the present invention has excellent flame resistance upon contact with flame. Even when subjected to forced combustion, the foam is not deformed or cracked remarkably, produces less smoke, and is superior in flame retardance, heat resistance, and mechanical properties. The present invention is described in more detail in the following Examples. In the Examples, "parts" and "%" mean "parts by weight" and "% by weight" respectively, unless otherwise mentioned. Example 1 In an 1-liter four-neck flask equipped with a thermometer, a stirrer, and a nitrogen seal tube with ground glass fitting, there were placed 500 parts of Millionate MR-200 (made by Nippon Polyurethane Industry Co., Ltd.) as an organic polyisocyanate, 4.0 parts of L-5340 as a surfactant, 1.0 part of Ankamine K-54 as a catalyst, 5.0 parts of triethyl phosphite as a cocatalyst, and 2.0 parts of R-113 as a diluent. The catalyst was fed as a mixture with the diluent. The air in the flask was replaced by nitrogen. The reaction mixture was stirred and heated to 50°C. After reaction for 3.5 hours, the NCO content was measured to be 28.6%, and the reaction liquid was found to be a transparent brown liquid. 0.5 part of phosphoric acid was added as a stopper to the reaction liquid, which was stirred at 50°C for one hour to finish the reaction. The resulting isocyanurate-modified polyisocyanate was a transparent brown liquid, having an NCO content of 28.6% and a viscosity of 850 cp/25°C, and containing a trimer as observed by infrared absorption spectra. No change was observed after 6 months. Examples 2 - 6 The reactions were conducted similarly as in Example 1 under the conditions shown in Table 1. The results are shown in Table 1 and Table 1-1. Example 7 500 parts of MR-200, and 6.1 parts of 1,3-butanediol as a polyol were placed in the same four-neck flask as used in Example 1. The air in the flask was replaced by nitrogen, and the reaction was allowed to proceed at 60°C for 2 hours. The NCO content was measured to be 29.4%. Subsequently, 4.0 parts of L-5340, 0.7 parts of Ankamine K-54 and 2.0 parts of R-113 were mixed and added thereto. 3.0 parts of triethyl phosphite was further added. The mixture was allowed to react at 50°C for 2.0 hours. The NCO content was determined to be 26.9%. To the reaction liquid, 0.35 parts of phosphoric acid was added, and the liquid was stirred at 50°C for 1.0 hour to finish the reaction. The resulting isocyanate-modified product was a transparent brown liquid, having an NCO content of 26.9% and a viscosity of 4500 cp/25°C, and containing a trimer as observed by infrared absorption spectra. No abnormality was observed after storage stability test for 6 months. Examples 8 - 15 The reactions were conducted similarly as in Example 7 under the conditions shown in Table 1. The results are shown in Table 1 and Table 1-1. Comparative examples 1 - 3 Comparative example 1 was conducted in a manner similar to that of Example 7, and Comparative examples 2 and 3 were conducted in a manner similar to that of Example 1 of the present invention. The amount of the materials, the reaction conditions and results are shown in Table 1 and Table 1-1. Example 16 In an 1-liter four-neck flask equipped with a thermometer, a stirrer, and a nitrogen seal tube with ground glass fitting, there were placed 500 parts of MR-200 as an organic polyisocyanate, 4.0 parts of L-5340 as a surfactant, 1.0 part of FE-55 as a ferrocene compound, 1.0 part of Ankamine K-54 as a catalyst, 5.0 parts of triethyl phosphite as an organic phosphite ester, and 2.0 parts of R-113 as a diluent. The catalyst was fed as a mixture with the diluent. The air in the flask was replaced by nitrogen. The reaction mixture was stirred and heated to 50 °C. After the reaction for 3.5 hours, the NCO content was measured to be 28.4 %, and the reaction liquid was found to be a transparent brown liquid. 0.5 part of phosphoric acid was added as a stopper to the reaction liquid, which was stirred at 50 °C for one hour to finish the reaction. The resulting isocyanurate-modified-polyisocyanate was a transparent brown liquid, having an NCO content of 28.4 % and a viscosity of 900 cp/25 °C, and containing a trimer as observed by infrared absorption spectra. No change was observed after 6 months. The results are shown in Table 2 and Table 2-1. Example 17 - 20 The reaction were conducted in a manner similar to that in Example 16 under the conditions shown in Table 2. The results are shown in Table 2 and Table 2-1. Example 21 500 parts of MR-200, 1.0 part of FE-55 as a ferrocene compound, 4.0 parts of L-5340 as a surfactant, and 6.9 parts of diethylene glycol as a polyol were placed in the same four-neck flask as in Example 16. The reaction was allowed to proceed at 60 °C for 2.0 hours. The NCO content was measured to be 29.5 %. Subsequently, 0.7 parts of Ankamine K-54 as a catalyst, 3.0 parts of triethyl phosphite as an organic phosphite ester, and 2.0 parts of R-113 as a diluent were added thereto. The catalyst was fed as a mixture with the diluent. The reaction mixture was allowed to react at 50 °C for 2.0 hours. The NCO content was determined to be 26.8 %. To the reaction liquid, 0.35 parts of phosphoric acid was added, and the liquid was stirred at 50 °C for 1.0 hour to finish the reaction. The resulting isocyanate-modified product was a transparent brown liquid, having an NCO content of 26.8 % and a viscosity of 4100 cp/25 °C, and containing a trimer as observed by infrared absorption spectra. No change was observed after storage test for 6 months. The results are shown in Table 2 and Table 2-1. Examples 22-25 The reactions were conducted similarly as in Example 21 under the conditions shown in Table 2. The results are shown in Table 2 and Table 2-1. Comparative example 4 This Comparative example 4 was conducted in the same manner as in Example 16 except that the ferrocene compound, FE-55, was not used. The results are shown in Table 2 and Table 2-1. Comparative example 5 This Comparative example 5 was conducted in the same manner as in Example 21 except that the ferrocene compound, FE-55, was not used. The results are shown in Table 2 and Table 2-1. Examples 26-42 The reaction mixtures A-liquid and B-liquid shown in Table 3, having been respectivley adjusted to have a liquid temperature of 20 ± 1 °C, were weighted out in 2-liter polyethylene beaker, and mixed for 3 - 5 seconds with an agitation mixer (rotation speed: 5000 rpm). The mixture was allowed to foam freely in a polyethylene bag placed in aluminum container of a size of 25 x 25 x 25 cm which had been preliminarily kept at 40 °C. All of the resulting foam samples were found to have heat resistance, low smoking property, and flame retardance by the tests. From the foams prepared as above, test specimens were prepared by cutting into a dimension of 220 mm in width and in length respectively, and 25 mm in thickness. The specimens were tested for combustion of the material according to JIS A1321 regarding a method for testing combustion of internal construction materials. The results are shown in Table 3. In Tables 3 and 5-1, "CT" means cream time, and "RT" means rise time. Example 43 (Preparation of Modified Polymethylenepolyphenyle-Polyisocyanate) In an 1-liter four-neck flask equipped with a thermometer, a stirrer, and a nitrogen seal tube with ground glass fitting, there were placed 500 parts of MR-200 as a polymeric MDI, 1.0 part of Ankamine K-54 as a trimerization catalyst, and 2.0 parts of R-113 as a diluent in a mixture. Further, 5.0 parts of triethyl phosphite was added thereto as an organic phosphite ester compound. The air in the flask was replaced by nitrogen. The isocyanuration reaction was carried out with stirring at 50 °C for 4 hours. Subsequently, 0.4 part of phosphoric acid was added, and stirred at 50 °C for one hour to finish the reaction. The resulting product was a transparent brown liquid in appearance, having an NCO content of 28.7 %, a viscosity of 950 cp/25 °C, and a trimer content of 1.8 %. Examples 44-46 Modified products were prepared from the polymethylenepolyphenyl-polyisocyanate, the catalyst, the organic phosphite ester compound and the diluent as shown in Table 4 by using the same reactor as in Example 43 in the same manner as in Example 43, under the conditions shown in Table 4-1. The NCO content, the viscosity, and the trimer, etc. are shown in Table 4-1. Example 47 (Preparation of Partially Urethanized Modified Polymethylenepolyphenyl-polyisocyanate) In an 1-liter four-neck flask equipped with a thermometer, a stirrier, and a nitrogen seal tube with ground glass fitting, there were placed 500 parts of MR-200 as a polymethylenepolyphenyl-polyisocyanate, 6.9 parts of diethylene glycol as a polyol. The air in the flask was replaced by nitrogen, and the urethanizing reaction was carried out with stirring at 60 °C for 2 hours. The NCO content after the reaction was 29.4 %. Subsequently, 0.8 part of Ankamine K-54 as a trimerization catalyst mixed with R-113 as a diluent, and 4.0 parts of triethyl phosphite as an organic phosphite ester were added, and the isocyanuration reaction was carried out with stirring at 50 °C for 1.5 hours. Then 0.4 part of phosphoric acid was added and stirred at 50 °C for 1.5 hours to finish the reaction. The resulting product was a transparent brown liquid in appearance, having an NCO content of 27.0 %, a viscosity of 4000 cp/25 °C, and a trimer content of 2.4 %. Examples 48-50 Modified products were prepared by reacting a polymethylenepolyphenyl-polyisocyanate with a polyol in a ratio as shown in Table 4 in the same reactor as in Example 43 under the conditions shown in Table 4-1, further adding the catalyst etc. as shown in Table 4-1, and conducting reaction under the conditions in Table 4-1. The NCO contents etc. are shown in Table 4-1. Examples 51 - 63 and Comparative example 6 (Preparation of Foams and Test for Properties) The A-liquid and the B-liquid for the reaction mixture shown in Table 5, having been respectively adjusted to have a liquid temperature of 20 ± 1 °C, were weighted out in 2-liter polyethylene beaker, and mixed for 3 - 5 seconds with an agitation mixer (rotation speed: 5000 rpm). The mixture was allowed to foam freely in a polyethylene bag placed in aluminum container of a size of 25 x 25 x 25 cm which had been preliminarily kept at 40 °C. All of the resulting foam samples were found to have heat resistance, low smoking property, and flame retardance by the tests. The results are shown in Table 5-1. Test for Combustion of Internal Construction Material According to JIS A1321: The foam prepared in Example was cut into a specimen of 220 mm in length, 220 mm in width, and 25 mm in thickness. The specimen is heated in a heating furnace by combinedly employing an electric heater as the main heat source and propane gas as a auxiliary heat source for the defined time length. Occurrence of crack or deformation and the level thereof, time of lingering flame after the stop of the heating, the exhaust gas temperature curve are measured. The same measurement is conducted with a perlite plate as the comparison standard. From the difference of the curves, the heating value (temperature-time area: TdA °C x min.), the smoking factor (C A ) are measured, and the combustibility of the material is evaluated according to a pierced hole test and a surface test. Heat Resistance Test: Test specimen is cut into a cube having a width, a length, and a thickness of approximately 6 cm, and is tested according to JIS A9514. Adhesiveness Test: By use of a sandwich panel prepared in Examples, the peeling adhesiveness between the panel plate and the foam is measured. Examples 64-71 and Comparative example 7 The A-liquid and the B-liquid for the reaction mixture shown in Table 6, having been respectively adjusted to have a liquid temperature of 20 ± 1 °C, were weighted out in a 2-liter polyethylene beaker, and mixed for 3 - 5 seconds with an agitation mixer (rotation speed: 5000 rpm). The mixture was poured into an aluminum mold having width, length, and depth of 46 x 46 x 25 mm with a face material of a color steel plate of 0.27 mm thick placed on the bottom, which has been previously allowed to warm to 50 °C. Immediately, another face material of color steel plate of 0.27 mm thick was set on the foam, and the cover of the mold was closed to press the foam which was kept at 50 °C for 30 minutes to cure the foam. Thereafter the product was released from the mold to give a sandwich panel. The results of the measurement of the properties are shown in Table 6.

Claims: A process for producing a modified aromatic polyisocyanate having an isocyanurate ring, characterized by adding an amine trimerization catalyst, an organic phosphite ester, a surfactant, and optionally a ferrocene compound to an aromatic polyisocyanate and/or a partially urethanized aromatic polyisocyanate to cause isocyanuration of not more than 20 % by weight of entire isocyanate. groups; and, if necessary, adding a stopper to terminate isocyanuration. A process according to Claim 1, wherein the partially urethanized aromatic polyisocyanate, is a reaction product of an aromatic polyisocyanate and a hydroxyl group-containing compound having a molecular weight of not more than 2000, preferably not more than 1000 and having a functionality of not more than 3, in which not more than 10 % by weight of the entire isocyanate groups has been reacted. A process according to Claim 1 or Claim 2, wherein the organic polyisocyanate is a polymethylene-polyphenyl-polyisocyanate. A process according to Claim 3, wherein the partially urethanized organic polyisocyanate is a reaction product of a polymethylenepolyphenyl-polyisocyanate and a polyol having a molecular weight of from 62 to 1000. A resin composition for the manufacture of a foam, which comprises the product of a process according to any one of Claims 1 to 4, a polyol having a molecular weight of not less than 200, a blowing agent, a catalyst, a foam stabilizer, and optionally a filler. A modified polymethylene-polyphenyl-polyisocyanate prepared by adding a trimerization catalyst and an organic phosphite ester to a polymethylene-polyphenyl-polyisocyanate or a partially urethanized polyisocyanate prepared by reacting the polymethylene-polyphenyl-polyisocyanate with a polyol having a molecular weight from 62 to 1000. A resin composition for the manufacture of a foam, which comprises the modified product of Claim 6, a polyol having a molecular weight of not less than 200, a blowing agent, a catalyst, a foam stabilizer, and if necessary a filler. A process for producing a polyisocyanurate foam, which comprises reacting together the components of the resin composition of Claim 5. A process for producing a polyisocyanurate foam, which comprises reacting together the components of the resin composition of Claim 7.

Inventors: MORIYA KIYOSHI, MORIYA, KIYOSHI
Applicants: NIPPON POLYURETHANE KOGYO KK, NIPPON POLYURETHANE INDUSTRY CO. LTD.
Application year: 1990
Main classification: C08G18
IPC codes: C08G18, C07D251