MXPA98009859A - Process for rigid polyurethane foams - Google Patents

Abstract

A process for preparing a rigid polyisocyanurate foam modified with urethane or polyurethane in the presence of a hydrocarbon blowing agent in which an amount of polyetherpolyol initiated with tolylenediamine which is between 10 and 40% by weight based on the isocyanate compounds is employed. total reagents

Description

PROCESS FOR RIGID FOAMS OF PO IURETANO This invention relates to processes for the production of rigid foams of urethane or polyurethane modified polyisocyanurate, with foams prepared by them and with new compositions that are useful for said process. Urethane and polyurethane modified polyisocyanurate foams are generally prepared by reacting the appropriate isocyanate- and polyisocyanate-reactant compound (usually a polyol) in the presence of a blowing agent. One of said foams constitutes a means of thermal insulation, as for example for the construction of refrigerated storage devices. The insulating properties of rigid foams depend on different factors including, for closed cell rigid foams, the cell size and the thermal conductivity of the contents of said cells. One class of materials that has been widely used as an expanding agent in the production of urethane-modified polyurethane and polyurethane polyisocyanurate foams are fully halogenated chlorofluorocarbons, and in particular trichlorofluoromethane (CFC-11). The exceptionally low thermal conductivity of these blowing agents, and in particular of CFC-11, has allowed rigid foams with very effective insulation properties to be produced. Recent concern regarding the potential capacity of chlorofluorocarbons to cause a reduction in the ozone layer of the atmosphere has led to an urgent need to develop reaction systems in which chlorofluorocarbon blowing agents are replaced by alternative materials that are acceptable from an environmental point of view and that also produce foams with the necessary properties for the many applications of the same. A class of materials that has been used as expansion agents with an ozone depletion potential equal to zero is constituted by hydrocarbons, especially alkanes and cycloalkanes such as isobutane, n-pentane, isopentane, cyclopentane and mixtures thereof. However, the insulation properties of rigid polyurethane foams expanded with hydrocarbons are not satisfactory. Another disadvantage of hydrocarbon blowing agents is their solubility in standard isocyanate-reactive compositions. One of the objects of the present invention is to provide rigid foams of urethane or polyurethane-modified polyisocyanurate expanded with hydrocarbons having improved thermal insulation properties. Another object of the present invention is to provide a process for making polyisocyanurate foams modified with urethane or polyurethane by improving the solubility of the blowing agent in the isocyanate-reactive composition. It is possible to meet these objectives by using an amount of a polyetherpolyol initiated with tolylenediamine (TDA) of 10 to 40% by weight based on the total isocyanate-reactive compounds in the process of making rigid polyisocyanurate modified urethane or polyurethane foams from of reactive isocyanate or polyisocyanate components in the presence of hydrocarbons as blowing agents. The foams prepared by the process of the present invention show a better thermal insulation than foams of the prior art that were not prepared with polyether polyols initiated with tolylenediamine (TDA). In addition, an improvement in the solubility of the blowing agents in the isocyanate-reactive composition is also achieved by the use of said polyether polyols initiated with TDA. Polyether polyols initiated with aromatic amines, such as the polyether polyols initiated with TDA, and polyether polyols initiated with polymethylene polyphenylenepolyamine or diamindiphenylmethane (D DPM) as isocyanate-reactive compounds for rigid polyurethane foams expanded with hydrocarbons (see, for example, patents EP 421269, WO 94/25514, EP 708127, US 5523333, US 5523332, US 5523334 and EP 617068). In none of these prior art documents is an improvement in thermal insulation properties or the solubility of hydrocarbons suggested by the use of polyether polyols initiated with TDA in place of the polyether polyols initiated with DADPM. In the patents WO 96/3017 and EP 747411 (both mentioned under Article 54 (3) EPC) the use of polyols initiated with TDA in rigid polyurethane foams expanded with hydrocarbons in an amount that constitutes at least 40% is described in weight based on total polyols. The polyether polyols initiated with TDA that can be used in the present invention are obtained by the addition of alkylene oxides, such as ethylene oxide and / or propylene oxide to one or more of the different isomers of tolylenediamine, such as 2, 4-, 2,6-, 2,3- and 3,4-TDA. The use of 2,3- and / or 3,4-TDA (ortho-TDA or local TDA) as initiator with 25% by weight of meta-TDA (2,4- and / or 2 6-TDA) is preferred. with respect to the total initiators. The neighborhood TDA is a pure isomer or a mixture thereof, preferably containing from 20 to 80% by weight of 2,3-TDA and from 80 to 20% by weight of 3,4-TDA. Other additional co-initiators can be used in an amount constituting up to 60% by weight of the total initiators, preferably between 5 and 10% by weight. In a preferred embodiment, aliphatic amines are not used as co-initiators.

The alkylene oxides used are preferably from 0 to 90% ethylene oxide, more preferably from 20 to 80% ethylene oxide and from 1 00 to 10%, preferably from 130 to 20%, of propylene oxide. The polyether polyols initiated with TDA that can be used in the present invention generally have OH numbers in the range of 200 to 700, preferably 250 to 550 mg of KOH / g, more preferably between 350 and 520 mg KOH / g. they have functionalities in the range from 2 to 8, preferably from 3 to 6. The molecular weight is generally between 400 and 700. The polyether polyols initiated with tolylenediamine and the methods for their preparation are described in their entirety in the prior art, for example, in US Patents 4243759, US 5141968, US 4391728, US 4421871, US 4562290, US 4469822, US 4397966, DD 272307, DD 251151, DD 290202 and DD 290201. A polyetherpolyol initiated with preferred TDA for use in the present invention is a polyetherpolyol with an OH value of 300 to 400 mg KOH / g, obtained by reaction of o-TDA (containing up to 25% by weight of m-TDA) with propylene oxide. The amount of polyol initiated with TDA is preferably between 10 and 39% by weight based on the total isocyanate-reactive compounds, more preferably between 10 and 35% by weight, more preferably still between 20 and 33% by weight. In the case of an expansion with cyclopentane only as a hydrocarbon, the amount of polyetherpolyol initiated with TDA is preferably below 35% by weight, more preferably below 30% by weight and more preferably below 25% by weight. % by weight based on total isocyanate-reactive compounds. Preferred hydrocarbon blowing agents for use in the present invention are (cyclo) alkanes, preferably containing from 3 to 8 carbon atoms, such as cyclopentane, isopentane, n-pentane, neopentane, n-butane, cyclobutane, methylcyclobutane, isobutane, propane, cyclopropane, methylcyclopropane, n-hexane, 3-methylpentane, 2-methylpentane, cyclohexane, methylcyclopentane, n-heptane, 2-methylheptane, 3-etiipentane, 2,2,3-trimethylbutane, 2,2-dimethylpentane, cycloheptane, methylcyclohexane, 2,2-dimethylbutane and 2,3-dimethylbutane. Particularly preferred hydrocarbons are the (cyclo) alkanes of C5 and C6. such as cyclopentane, n-pentane and isopentane, and any mixture thereof as well as mixtures of any of them with isobutane. A preferred blowing agent is a mixture of isopentane and n-pentane with a weight ratio between 75:25 and 25:75, more preferably with an 8/3 ratio. Another preferred blowing agent is a mixture of cyclopentane and isopentane and / or n-pentane with a weight ratio of cyclopentane: n / isopentane between 80:20 and 20:80, preferably 60:40, where the weight ratio of npentane: preferred isopentane is between 0: 100 and 50:50. Suitable isocyanate-reactive compounds which can be used in mixtures with the polyether polyols initiated with TDA include any of those known in the art for the preparation of rigid polyisocyanurate modified urethane or polyurethane foams. Of particular importance for the preparation of rigid foams are polyols and mixtures of polyols having an average hydroxyl number of 300 to 1000, especially 300 to 700 mg KOH / g, and hydroxyl functionalities of 2 to 8, especially 3. a 8. Suitable polyols are fully described in the prior art and include the reaction products of alkylene oxides, for example ethylene oxide and / or propylene oxide, with initiators containing from 2 to 8 active hydrogen atoms. per molecule. Suitable initiators include: polyols, for example glycerol, trimethylolpropane, triethanolamine, pentaerythritol, sorbitol and sucrose; polyamines, for example ethylenediamine, the various isomers of phenylenediamine, 4-chloro-o-phenylenediamine, 4-chloro-m-phenylenediamine, 4,5-dichloro-o-phenylenediamine, 4,5-dimethyl-o-phenylenediamine, 4 -methoxy-o-phenylenediamine, 2-nitro-p-phenylenediamine, 4-4 '-methylenebi (o-chloroaniline), 4,4'-methyleneb (3-nitroaniline), 3,3'-diaminbenzidine, 1, 5 diaminaphthalene, diamindiphenylmethane, polymethylenepolyphenylenepolyamines; and aminoalcohols, for example ethanolamine and diethanolamine; and mixtures of the initiators. In a preferred embodiment of the present invention, polyether polyols initiated with aliphatic amines are not used, particularly when cyclopentane is used as the blo agent. Other suitable polymer polyols comprise polyesters obtained by the condensation of appropriate proportions of glycols and polyols of higher functionality with dicarboxylic acids or polycarboxylic acids. Still other suitable polymeric polyols comprise polyether-terminated polythioethers, polyamides, polyesteramides, polycarbonates, polyacetals, polyolefins and polysiloxanes. In a preferred embodiment of the present invention the polyetherpolyol initiated with TDA is used together with other polyether polyols and up to 20% by weight (based on the total polyols) of polyester polyols. The hydroxyl value of the polyol mixture is generally between 350 and 550 mg KOH / g, preferably between 380 and 430 mg KOH / g. The polyetherpolyol initiated with TDA is preferably used together with other polyether polyols initiated with aromatic amines so that the total amount of polyether polyols initiated with aromatic amines is between 40 and 100%, preferably between 50 and 90%, more preferably between 60 and 60%. and 70% by weight based on total polyols. The polyether polyols initiated with preferred aromatic amines that will be used with the polyether polyol initiated with TDA of the present invention are the polyether polyols initiated with DADPM. Polyether polyols not initiated with preferred aromatic amines that can be used in the process of the present invention include polyether polyols initiated with sorbitol and / or sucrose. Organic polyisocyanates suitable for use in the process of the present invention include any of those known in the art for the preparation of rigid foams of urethane or polyurethane modified polyisocyanurate, and in particular aromatic polyisocyanates such as diphenylmethane diisocyanate in the form of their 2,4'-, 2,2'- and 4,4'- isomers and mixtures thereof, mixtures of diphenylmethane diisocyanates (MDI) and oligomers thereof known in the art as "crude" or polymeric MDI (polymethylene polyphenylene polyisocyanates ) having an isocyanate functionality greater than 2, toluene diisocyanate in the form of its 2,4- and 2,6-isomers and mixtures thereof, 1,5-naphthalene diisocyanate and 1,4-diisocyanatobenzene. Other organic polyisocyanates which may be mentioned include the aliphatic diisocyanates, such as isophorone diisocyanate, 1,6-diisocyanatohexane and 4,4'-diisocyanatodicyclohexylmethane. The amounts of the polyisocyanate compositions and the polyfunctional isocyanate-reactive compositions to be reacted will depend on the nature of the urethane or polyurethane modified polyisocyanurate rigid foam to be produced and will be readily determined by those skilled in the art. In addition to the hydrocarbon blo agent or agents, other blo agents may be used in amounts of up to 20 mol% at most of the total physical blo agents present in the process. Other suitable physical blo agents include those which are well described and which are well known in the art, for example dialkylethers, alkylalkanoates, aliphatic and cycloaliphatic hydrofluorocarbons, hydrochlorofluorocarbons, chlorofluorocarbons, hydrochlorocarbons and fluorine-containing ethers. In general, water and carbon dioxide donor compounds are used together with the physical expansion agents. When water is used as co-chemical expansion agent, typical amounts are in the range of 0.2 to 5%, preferably 0.5 to 3% by weight based on the isocyanate-reactive compound. The total amount of blo agent that will be used in a reaction system to produce cellular polymeric materials will be readily determined by those skilled in the art., but is typically between 2 and 25% by weight based on the total reaction system. An insoluble fluorine compound can be used in the foam forming process of the present invention in order to reduce the cell sizes of the foam and consequently improve the thermal insulation properties. Such insoluble fluorine compounds comprise any of those are described in Patents US 4981879, US 5034424, US 4792002, EP 508649 and WO 95/18176. Some of said insoluble fluorine compounds suitable for use in the process of the invention can act, themselves, as blowing agents under the conditions of the foam-forming reaction, in particular when their boiling points are lower than the temperature exothermic achieved by the reaction mixture. In addition to the polyisocyanate and isocyanate-polyfunctional reactive compositions and the blowing agent, the foam-forming reaction mixture commonly contains one or more conventional auxiliaries or additives in the formulations for the production of rigid polyurethane-polyurethane-modified polyisocyanurate foams. Such optional additives include crosslinking agents, for example low molecular weight polyols such as a triethanolamine, foam stabilizing agents or tensides, for example siloxane-oxyalkylene copolymers, urethane catalysts, for example tin compounds such as octoate tin or dibutyl tin dilaurate or tertiary amines such as dimethylcyclohexylamine or triethylene diamine, ignition retardant agent, for example halogenated alkyl phosphates such as tris chloropropyl phosphate and fillers such as carbon black. During operation of the manufacturing process of the rigid foams according to the invention, the known techniques of a single operation, of prepolymers or of semiprepolymers can be used together with the conventional mixing techniques and the rigid foam can be produced in the form of sheets, moldings, filling of cavities, atomized foams, light foams or laminates with other materials such as hardboard, plasterboard, plastics, paper or metal. In many applications it is convenient to provide the components for the production of polyurethane in pre-mixed formulations based on each of the isocyanate-reactive components and the primary polyisocyanate. Many reaction systems employ, in particular, a polyisocyanate-reactive composition containing the most important additives, such as the blowing agent and the catalyst, in addition to the polyisocyanate-reactive component (s). Accordingly, the present invention also provides a polyisocyanate-reactive composition comprising (a) one or more hydrocarbon blowing agents and a polyether polyol initiated with TDA in an amount ranging from 10 to 40% by weight based on the isocyanate compounds -total reactive. The various aspects of the invention are illustrated by means of the following examples, although they are not limited thereto. In the examples, reference is made to the following reaction and formulation components: Polyol 1: a polyetherpolyol initiated with sorbitol with an OH value of 460 mg KOH / g. Polyol 2: a polyetherpolyol initiated with sorbitol with an OH value of 420 mg KOH / g. Polyol 3: a polyetherpolyol initiated with DADPM with an OH value of 310 mg KOH / g. Polyol 4: a polyetherpolyol initiated with TDA with an OH value of 350 mg KOH / g. Surfactant: a siliconized surfactant. Catalyst: a mixture of amine catalysts. SUPRASEC DNR: a polymeric MDI that can be purchased from Imperial Chemical Industries. SUPRASEC is a trademark of Imperial Chemical Industries.

EXAMPLE 1 Rigid polyurethane foams were prepared from the ingredients listed in Table 1. The initial thermal conductivity at 10 ° C (lambda value) of the foams obtained was measured in accordance with ASTM C 518. The results are shown in Table 1.

These results show that the addition of polyether polyols initiated with TDA to expanded polyurethane foam systems with n-pentanolisopentane mixtures improves the insulation properties.

Table 1 EXAMPLE 2 Rigid polyurethane foams were prepared from the ingredients listed in Table 2. The initial thermal conductivity at 10 ° C (lambda value) of the foams obtained was measured according to ASTM C 518.

Results are shown in table 2 Table 2 The polyol mixture of the reference foam containing the hydrocarbon blowing agent, the polyetherpolyol initiated with DADPM and the polyether polyol not initiated with TDA is not stable; phase separation occurs. The replacement of the polyetherpolyol initiated with DADPM of the reference foam by polyetherpolyol initiated with TDA (Foam NO 4) improves the solubility of the hydrocarbon blowing agent in the polyol mixture; the mixture is stable. EXAMPLE 3 Mixtures of polyols were made consisting of 95 g of the basic polyol identified in Table 3 below, 1 g of amine catalyst, 2 g silicone surfactant and 2 g of water, Cyclopentane was added to these polyol mixtures until that a phase separation was detected. This amount of cyclopentane was designated as the limiting concentration for the solubility in the respective mixture of polyols. The following basic polyols were used: Polyol A is a polyetherpolyol initiated with DADPM with a hydroxyl value of 500 mg KOH / g, Polyol B is a polyetherpolyol initiated with O-TDA with a hydroxyl value of 350 mg KOH / g. The solubility (expressed in grams) of the cyclopentane in the polyol mixtures containing these specific basic polyols is shown in Table 3 below.

Table 3 These results show that the solubility of the hydrocarbon blowing agents in the polyol mixtures improved when said mixtures contained polyether polyols initiated with TDA instead of polyether polyols initiated with DADPM.

Claims (17)

1. REIVINDTC! Af? Tf.Kpi! .q 1. A process for preparing rigid foams of urethane or polyurethane-modified polyisocyanurate comprising the step of reacting an organic polyisocyanate composition with a polyfunctional isocyanate-reactive composition in the presence of an hydrocarbon expansion, characterized in that the polyfunctional isocyanate-reactive composition comprises a polyetherpolyol initiated with tolylenediamine in an amount ranging between 10 and 40% by weight based on the total isocyanate-reactive components and that the polyfunctional isocyanate-reactive composition does not comprise polyether polyols initiated with aliphatic amines.
2. 2. The process according to clause 1 wherein the amount of polyetherpolyol initiated with tolylenediamine is between 10 and 35% by weight based on the total isocyanate-reactive components.
3. 3. The process according to clause 1 or 2, wherein the polyetherpolyol initiated with tolylenediamine is obtained by the addition of ethylene and / or propylene oxides to ortho-tolylenediamine containing up to 25% by weight of total meta-tolylenediamine initiator. .
4. 4. The process according to any of the preceding clauses, wherein the polyetherpolyol initiated with tolylenediamine has an OH value in the range of 200 to 700 mg KOH / g and a functionality in the range of 2 to 8.
5. 5. The process according to any of the preceding clauses, wherein the hydrocarbon expansion agent is an alkane or a cycloalkane containing from 3 to 8 carbon atoms.
6. 6. The process according to clause 5, wherein the hydrocarbon blowing agent is isobutane, cyclopentane, n-pentane, isopentane or any mixture thereof.
7. 7. The process according to clause 6, wherein the blowing agent is a mixture of isopentane and n-pentane with a weight ratio between 3: 1 and 1: 3.
8. 8. The process according to any of the preceding clauses, wherein the hydroxyl value of the isocyanate-reactive composition is between 353 and 550 mg KOH / g.
9. 9. The process according to any of the preceding clauses, wherein the total amount of polyether polyols initiated with aromatic amines is between 40 and 100% by weight with respect to the total isocyanate-reactive components.
10. 10. The process according to any of the preceding clauses, wherein the isocyanate-reactive composition further comprises a polyetherpolyol initiated with diamindiphenylmethane or polymethylene polyphenylenepolyamine.
11. 11. Rigid polyisocyanurate modified urethane or polyurethane foams prepared by the process defined in any of the preceding clauses.
12. 12. A polyfunctional isocyanate-reactive composition, comprising from 10 to 40% by weight of polyether polyol (s) initiated with tolylenediamine.
13. 13. The composition according to clause 12, which also includes a hydrocarbon expansion agent.
14. 14. The composition according to clause 12 or 13, which has a hydroxyl value between 350 and 550 mg KOH / g.
15. 15. The composition according to any of clauses 12 to 14, wherein the amount of polyether polyols initiated with aromatic amines is between 40 and 100% by weight with respect to the isocyanate-reactive components.
16. 16. The composition according to any of clauses 12 to 15 comprising a polyetherpolyol initiated with diamindiphenylmethane or polymethylenepolyphenylenepolyamine.
17. 17. The composition according to any of clauses 13 to 16 wherein the hydrocarbon blowing agent is a mixture of n-pentane and isopentane. PTSStiMS-N A process for preparing a rigid polyisocyanurate foam modified with urethane or polyurethane in the presence of a hydrocarbon blowing agent in which an amount of polyetherpolyol initiated with tolylenediamine which is between 10 and 40% by weight based on the isocyanate compounds is employed. Total reagents.