MXPA98009623A - Rigid foams of polyurethane modified with isocianur - Google Patents

Abstract

Rigid foams of modified polyurethane with 180 to 380 isocyanurate made from a combination of aliphatic polyols and aromatic polyester

Description

RIGID FOAMS OF POLYURETHANE MODIFIED WITH ISOCIANURATE This invention relates to rigid polyurethane foams modified with isocyanurate and to the processes for their preparation. Rigid polyurethane foams with isocyanurate are generally prepared by reacting a stoichiometric excess of polyisocyanate with isocyanate-reactive compounds in the presence of blowing agents, surfactants and catalysts. One of the uses of said foams is as means of thermal insulation, for example in buildings. Polyurethane foams modified with isocyanurate show a better ignition delay than polyurethane foams in general due to the presence of the isocyanurate groups; however, these foams tend to be extremely friable which leads to deterioration of other properties such as surface curing and adhesion. To obtain good fire properties, polyester polyols are advantageously used as isocyanate-reactive compounds in the preparation of polyurethane foams modified with isocyanurate. It is common for these polyester polyols to be aromatic in nature and, in some cases, used in combination with polyether polyols. Therefore, one of the objects of the present invention is to provide rigid polyurethane foams modified with isocyanurate having a combination of desirable properties, including a suitable reaction profile and suitable friability. According to the present invention, rigid foams of isocyanurate-modified polyurethane formed by the reaction in the absence of polymer dispersions of an organic polyisocyanate composition with an isocyanate-reactive composition are provided, with an isocyanate index of 180 to 380%, preferably of 200 to 270%, more preferably 220 to 250%, wherein the isocyanate-reactive composition comprises an aliphatic polyester polyol and an aromatic polyester polyol. The isocyanurate-modified polyurethane foams of the present invention are less friable than those of the prior art made from aromatic polyester polyols only and also have improved physical properties, such as surface curing and adhesion. They are especially useful in the production of panels for buildings where the foam is applied to one or more non-combustible layers. In the patent of the U.S.A. No. 4302551 describes the use of polymer dispersions in the manufacture of rigid polyisocyanurate foams. These polymer dispersions comprise a continuous phase and a dispersed phase. The polyester polyols can be used as the continuous phase. The present invention is not made by polymer dispersions.

In the patent of the U.S.A. No. 4859523 describes the use of aromatic polyester polyols together with aliphatic polyester polyols in the manufacture of viscoelastic resins (hence they are not rigid polyisocyanurate foams). French Patent No. 1548298 relates to the use of blends of aromatic and aliphatic polyester polyols in the manufacture of thermoplastic polyester-urethanes (therefore they are not rigid polyisocyanurate foams). In the present context, the term isocyanate index means the molar ratio between the NCO groups and the hydrogen atoms present in the foam formulation with the exception of those deriving from the water present therein, expressed as a percentage. The polyester polyols which can be used advantageously in the present invention have an average functionality of 1.8 to 8, preferably of 1.8 to 5 and more preferably of 2 to 2.5. The values of the number of hydroxyls generally fall within the range of 15 to 750, preferably from 30 to 550 and more preferably from 200 to 550 mg KOH / g. Preferred polyester polyols have an acid number between 0.1 and 20 mg KOH / g, the acid number can reach, in general, values of 90 mg KOH / g. The polyester polyols of the present invention can be prepared by known processes from a polycarboxylic acid, or an acid derivative, such as an anhydride or ester of the polycarboxylic acid, and any polyol component. The polyacid and / or polyol components can be used as mixtures of two or more compounds for the preparation of said polyester polyols. The polyols can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic. Low molecular weight aliphatic polyhydric alcohols, such as aliphatic dihydric alcohols with no more than 20 carbon atoms, are highly satisfactory. The polyols may optionally include substituents which are inert in the reaction, for example chlorine and bromine substituents and / or may be unsaturated. Suitable amino alcohols, such as, for example, monoethanolamine, diethanolamine, triethanolamine or the like can also be used. A preferred polyol component is glycerol. The glycols may contain heteroatoms (for example, thiodiglycol) or may be composed only of carbon, hydrogen and oxygen. They are, conveniently, simple glycols with the general formula CnH2n (OH) 2 or polyglycols which are distinguished by comprising ether linkages in the hydrocarbon chain, represented by the general formula CnH2Ox (OH) 2. Examples of suitable polyhydric alcohols include: ethylene glycol, (1,2) - and (1,3) propylene glycol, (1,4) - and (2,3) -butylene glycol, (1,6) -hexandiol, (1,8) -octandiol, neopentyl glycol, 1,4-bihydroxymethylcyclohexane, 2-methyl-1,3-propandiol, glycerin , trimethylolethane, (1, 2, 6) -hexantriol, (1, 2,4) -butantriol, quinol, methylglucoside, triethylene glycol, tetraethylene glycol and higher polyethylene glycols, dipropylene glycol and higher polypropylene glycols, diethylene glycol, glycerol, pentaerythritol, trimethylolpropane, sorbitol, mannitol , dibutylene glycol, higher polybutylene glycols. Particularly suitable polyols are the alkylene glycols and oxyalkylene glycols, such as ethylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, tetrapropylene glycol, trimethylene glycol, tetra ethylene glycol and 1,4-cyclohexanedimethanol (1,4-bihydroxymethylcyclohexane). The polycarboxylic acid component can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic and, optionally, can be substituted, for example, by halogen atoms and / or can be unsaturated. Examples of carboxylic acids and derivatives thereof suitable for the preparation of polyester polyols include: oxalic acid, malonic acid, adipic acid, glutaric acid, succinic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid , anhydrous phthalic acid, tephthalic anhydride, phthalic isoacid, phthalic acid, trimellitic acid, anhydrous tetrahydroacid phthalic acid, pyromellitic dianhydride, anhydrous hexahydrophthalic acid, anhydrous tetrachlorophthalic acid, eridomethylenetetrahydrophthalic anhydride, anhydrous glutaric acid, maleic acid, anhydrous maleic acid, phthalic acid dimethyl ester, phthalic acid, phthalic acid, dibasic and unsaturated tribasic acids optionally mixed with unsaturated monobasic fatty acids, such as oleic acids. Polyester polyols can be prepared from substantially pure reactive materials, but more complex ingredients, such as secondary, waste or cut residues from the manufacture of phthalic acid, tetaphthalic acid, dimethyl-phthalate, polyethylene-tristalate and the like can also be employed. . These compositions can be converted to polyester polyols by reaction with polyols by conventional transesterification or esterification processes. The production of the polyester polyols is carried out by simply reacting the polycarboxylic acid or acid derivative with the polyol component in the known manner until the hydroxyl and acid values of the reaction mixture are within the desired range. After transesterification or esterification the reaction product can be reacted, optionally, with an alkylene oxide. As used in the present context, the term "Polyester polyol" includes any minor amount of unreacted polyol remaining after the preparation of the unsterified polyester and / or polyol polyol (eg, glycol) added after the preparation. The polyester polyol can include up to about 40% by weight of free glycol. The content of free glycol constitutes, preferably from 2 to 30%, more preferably from 2 to 15% by weight of the total polyester polyol component. In the aliphatic polyester polyol both the polyol and the polycarboxylic acid employed in the manufacture of said polyester polyol are aliphatic compounds. However, part of the polyol or polycarboxylic acid may be aromatic in nature; the aromaticity of the aliphatic polyester polyol (expressed as% by weight of groups containing at least one aromatic ring per molecule) is below 50%. In the aromatic polyester polyol at least one of the polyols or the polycarboxylic acid, preferably the acid, is an aromatic compound and the aromaticity is at least 50%. They are particularly useful polyester polyols whose acid component comprises at least 30% by weight of phthalic acid (or isomers thereof). The aromaticity of the polyester polyol is preferably between 70 and 90%. Preferred aromatic polyester polyoids are crude polyester polyols obtained by transesterification of the raw waste or waste of polyester resins. According to the present invention, one or more aromatic polyester polyols and one or more aliphatic polyester polyols can be used. The weight ratio of the aromatic and aliphatic polyester polyols that can be used in the present invention is preferably between 90:10 and 20:80., more preferably between 80:20 and 30:70, more preferably still between 80:20 and 40:60. For the production of the isocyanurate-modified polyurethane foams of the present invention, the described polyester polyols are newly constituted, preferably, all of the reaction mixture which is reacted with the polyisocyanate; however, it should be understood that these polyols can also be employed in the form of mixtures with other isocyanate-reactive compounds conventionally used in the art; the isocyanate-reactive composition preferably includes at least 90% by weight of the polyester polyols described above. The isocyanate-reactive compounds that can be used in combination with the polyester polyols for the preparation of the isocyanurate-modified polyurethane foams of the present invention comprise any of those known in the art for that purpose. Of particular importance in the preparation of rigid foams are polyols and blends of polyols with an average hydroxyl amount of from 300 to 1000, in particular from 300 to 700 mg KOH / g, and hydroxyl functionalities from 2 to 8, in particular from 3 to 8. Suitable polyols have been described in the prior art and include the reaction products of the 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, tolylenediamine, diaminodiphenylmethane and polyethylenepolyphenylenepolypses; and aminoalcohols, for example ethanolamine and diethanolamine; and mixtures of said initiators. Other polymeric polyols comprise polyethylene-terminated polythioethers, polyesteramides, polycarbonates, polyacetals, polyolefins and polysiloxanes. 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 polyurethane foams modified with isocyanurate, and in particular aromatic polyisocyanates, such as diphenylmethanediisocyanate in the form of their isomers. , 4'-, 2,2'- and 4,4'- and mixtures thereof, mixtures of diphenyl ethenylisocyanates (DI) and oligomers thereof known in the art as "crude" or polymeric (MDI) ( polymethylenepolyphenylenepolyisocyanates) 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 polyisocyanates which may be mentioned include the aliphatic diisocyanates, such as isophorone diisocyanate, 1,6-diisocyanatohexane and 4,4'-diisocyanato-dicyclohexylmethane. Also suitable for use in the process of the present invention are the polyisocyanates described in EP-A-0320134. Modified polyisocyanates, such as the carbodiimide or uretonimine modified polyisocyanates, can also be used. Still other useful organic polyisocyanates are the isocyanate-terminated prepolymers which are prepared by reaction of an excess of organic polyisocyanate with a minor amount of an active hydrogen-containing compound. The preferred polyisocyanates for use in the present invention are polymeric MDI's. The amounts of polyisocyanate composition and polyfunctional isocyanate-reactive composition which are reacted are such that the molar ratio between the isocyanate groups (NCO) and the groups with active hydrogen (OH) (with the exception of water) is between 180 and 380%, preferably between 200 and 270% and more preferably between 220 and 250%. The process of the present invention is carried out in the presence of any of the blowing agents known in the art for the preparation of rigid polyurethane foams modified with isocyanurate. Such blowing agents include water or other carbon dioxide donor compounds, or low boiling inert compounds whose boiling point is above -70 ° C at atmospheric pressure. When water is used as an expanding agent, the amount is selected in the known manner to obtain the foams of the desired density, typical amounts being in the range of 0.05 to 5% by weight based on the total reaction system. Suitable inert blowing agents include those well known and well described in the art, for example, hydrocarbons, dialkylethers, alkylalkanes, aliphatic and cycloaliphatic hydrofluorocarbons, hydrochlorofluorocarbons, chlorofluorocarbons, hydrochlorocarbons and fluorine-containing ethers. Examples of preferred blowing agents include: isobutane, n-pentane, isopentane, cyclopentane or mixtures thereof, 1,1-dichloro-2-fluoroethane (HCFC 14 Ib), 1,1 l-trifluor-2 -fluoroethane (HFC 134a), chlorodifluoromethane (HCFC 22), 1,1-difluoro-3,3,3-trifluoropropane (HPC 245fa) and mixtures thereof. Particular mention may be made of the mixtures of blowing agents described in WO 96/12758, the content of which is incorporated herein by reference, for the production of rigid foams of stable dimensions and low density. These mixtures of blowing agents comprise, in general, at least 3 and preferably at least 4 components, of which at least one is a (cyclo) alkane (preferably of 5 to 6 carbon atoms) and / or acetone. The blowing agents are used in sufficient amounts to give the resulting foam the desired bulk density, which is generally in the range of 15 to 70 kg / m 3, with 20 to 50 kg / m 3 being preferred and from 25 to 40 kg / m3. Typical amounts of blowing agent are in the range of 2 to 25% by weight based on the total reaction system. When the expansion agent has a boiling point equal to or below room temperature, it is kept under pressure until it is mixed with the other components. Alternatively, it is possible to keep it at temperatures below room temperature until it is mixed with the other components. In addition to the polyisocyanate and isocyanate-polyfunctional reactive and blowing agent compositions, the foam-forming reaction mixture commonly contains one or more conventional additives or auxiliaries in the rigid polyurethane foaming formulations modified with isocyanurate. Such optional additives include crosslinking agents, for example low molecular weight polyols, such as triethanolamine, process adjuvants, viscosity reducers, dispersing agents, plasticizers, mold release agents, antioxidants, fillers (for example carbon black) , cell size regulators, such as insoluble fluorine compounds (described, for example, in U.S. Patent Nos. 4,981,879, 5,034,424, 4,972,002, European Patent EP 0,508649 and EP 0498628 and in US Pat. WO 95/18176), catalysts, surfactants such as polydimethylsiloxane-polyoxyalkylene block copolymers and reactive and non-reactive ignition retardants, for example halogenated alkylphosphates, such as chloropropyl trisphosphate, triethylphosphate, diethylethylphosphonate and di ethylmethylphosphonate. The use of such additives is well known to those skilled in the art. The catalysts that can be used in the present invention include those that favor the formation of isocyanurate. Examples thereof include alkali metal or alkaline earth salts of carboxylic acids. The cation of the metal salt of the organic acid, preferably a salt of an alkali metal, is K or Na, more preferably K. The salts of Ci-Ca cartoxylates, including the potassium and sodium salts of the formic acids, are preferred, acetic, propionic and 2-ethylhexanoic. Other suitable trimerization catalysts include the triazine compounds such as Polycat 41 (available from Air Products) and the quaternary ammonium carboxylate salts. Also, combinations of catalysts such as those described in EP 228230 and GB 2288182 can be used., including combinations with urethane catalysts that facilitate the reaction between an isocyanate group and a group containing active hydrogen, such as a tertiary amine. During operation of the manufacturing process of the rigid foams according to the invention, the known one-step techniques, prepolymers or semipre-polymers can be used together with conventional mixing techniques, and the rigid foam can be produced in the form of sheets, moldings, filling of cavities, atomized foam, light foams or laminates with other materials such as hardboard, plasterboard, plastics, paper or metal. It is a common practice in the manufacture of rigid polyurethane foams to use two preformulated compositions, commonly referred to as component A and component B. Component A typically contains the polyisocyanate compound and component B contains the polyols together with the blowing agents, catalysts and others auxiliary The foams of the present invention are advantageously used in the production of laminates, in which the foam may be on one or both sides with an exposed sheet. The laminates are processed continuously by depositing the foam-forming mixture on the viewing plate that is moved along a production line, and preferably placing another plate of view on the deposited mixture. Any previously used sight iron can be used to produce building panels and can be of a rigid or flexible nature. The various aspects of the invention are illustrated by the following examples, but not limited thereto, in which the following ingredients are used: DALTOLAC P 710: an aliphatic polyester polyol (28% aromaticity) available from Imperial Chemical Industries. STEPANPOL PS 2502A: an aromatic polyester polyol (75% aromaticity) that can be purchased in Stepan. Isoexter 4537: an aliphatic polyester polyol that can be purchased from COIM. DALTOLAC R105: a polyetherioliol available from Imperial Chemical Industries. Isoexter 4565: an aliphatic polyester polyol that can be purchased from COIM. DALTOLAC P744: an aliphatic polyester polyol available from Imperial Chemical Industries. Terate 203: an aromatic polyester polyol (89% aromaticity) available from Hoechst Celanese. Terate 2541: an aromatic polyester polyol (78% aromaticity) that can be purchased from Hoechst Celanese. TCPP: tris chloropropylphosphate, an ignition delay agent that can be purchased in Courtalds. Polycat 43: a catalyst that can be purchased from Air Products. L6900: a silicone surfactant that can be purchased from OSI. Nicix Al: a catalyst that can be acquired in OSI.

LB catalyst: a catalyst that can be purchased from Imperial Chemical Industries. Polycat 8: a catalyst that can be purchased at Air Products. DMEA: a catalyst that can be acquired in Imperial Chemical Industries. SUPRASEC 2085: a polymeric MDI that can be purchased from Imperial Chemical Industries. SUPRASEC and DALTOLAC are trademarks of Imperial Chemical Industries.

EXAMPLE 1 Rigid foams were prepared from the ingredients listed below in Table 1. The reaction profile was followed in terms of cream time, yarn time and mass time. The free elevation density was determined (according to DIN 53420). The friability of the surface of the foams obtained was visually checked. The coating adhesion was measured according to ASTM D162. Adhesion by paper release was evaluated qualitatively with 100 g / m2 of paper: 1 means good (breakage of paper), 2 means medium detachment that requires some force, 3 means poor (detachment is very easy). The results are shown below in Table 1.

These results show that the use of aliphatic polyester polyols, in addition to the aromatic polyester polyols, reduces the friability of the foams obtained and improves the adhesion.

Table 1 10 fifteen fifteen

Claims (21)

1. A process for preparing rigid polyurethane foams modified with isocyanurate, characterized in that it comprises the step of reacting an organic polyisocyanate composition with an isocyanate-reactive composition, with an isocyanate index of 180 to 380%, in the presence of an expanding agent , characterized in that the isocyanate-reactive composition comprises an aliphatic polyester polyol having an aromaticity of at least 50% by weight and that the process is carried out in the absence of polymer dispersions.

2. Process according to clause 1, where the isocyanate index is between 200 and 270%.

3. The process according to clause 2, characterized in that the isocyanate index is between 200 and 250%.

4. The process according to any of the preceding clauses, characterized in that the polyester polyols have an average functionality of approximately 1.8 to 8 and a hydroxyl value of approximately 15 to 750 mg KOH / g.

5. The process according to any of the preceding clauses, characterized in that the polyester polyols are prepared from a polycarboxylic acid, or an acid derivative, and a polyol.

6. The process according to clause 5, characterized in that the polyol is a glycol or a polyglycol that is distinguished by the intervention of ether bonds in the hydrocarbon chain.

7. The process according to clause 5 or 6, characterized in that the polycarboxylic acid, or the acid derivative, is selected from the group consisting of adipic acid, glutaric acid, succinic acid, phthalic acid and its derivatives (including isophthalic and terephthalic acid) ) and waste.

8. The process according to clause 5, characterized in that the polycarboxylic acid used to make the aromatic polyester polyol is aromatic in nature.

9. The process according to any of the preceding clauses, characterized in that the weight ratio of the aromatic and aliphatic polyester polyols is between 80:20 and 40 :: 60.

10. The process according to any of the preceding clauses, characterized in that the aromatic and aliphatic polyester polyols constitute at least 90% by weight of the total isocyanate-reactive compounds.

11. The process according to any of the preceding clauses, characterized in that the organic polyisocyanate is a polymeric MDI.

12. The process according to any of the preceding clauses, characterized in that the expansion agent comprises a hydrocarbon.

13. The process according to clause 12, characterized in that the blowing agent is n-pentane, isobutane, isopentane, cyclopentane or any mixture thereof.

14. The process according to any of the preceding clauses, characterized in that the reaction is carried out in the presence of a trimerization catalyst.

15. A rigid polyurethane foam modified with isocyanurate, characterized in that it can be obtained by the process defined in any of the preceding clauses.

16. The use of the foam defined in clause 15, to make laminates.

17. An isocyanate-reactive composition, characterized in that it comprises an aromatic polyester polyol having an aromaticity of at least 50% and an aliphatic polyester polyol having an aromaticity of at least 50%.

18. The isocyanate-reactive composition according to clause 17, characterized in that the weight ratio of the aromatic polyester polyols and aliphatic is between 80:20 and 40:60.

19. The isocyanate-reactive composition according to clause 17 or 18, characterized in that the aromatic and aliphatic polyester polyols constitute at least 90% by weight of the total isocyanate-reactive compounds.

20. The isocyanate-reactive composition according to any of clauses 17 to 19, characterized in that it also comprises an expansion agent.

21. The isocyanate-reactive composition according to any of clauses 17 to 20, characterized in that it also comprises a trimerization catalyst.