MXPA03008624A

MXPA03008624A - Process for the preparation fo polyurethane foams.

Info

Publication number: MXPA03008624A
Application number: MXPA03008624A
Authority: MX
Inventors: Fava Flavio
Original assignee: Dow Global Technologies Inc
Priority date: 2001-03-23
Filing date: 2002-03-22
Publication date: 2004-06-30
Also published as: BR0208607A; CN1498235A; CN1229413C; ITMI20010619A1; WO2002077056A1; EP1373351A1; ITMI20010619A0; KR20030085039A; CA2441694A1; JP2004523632A

Abstract

A process for the preparation of a visco-elastic foam having a density from 50 to 100 kg/m3 involving reacting an isocyanate component having a functionality from 2.1 to 2.7 of general formula (I): wherein PHgr; represents a phenyl group and n is an integer greater than or equal to 1 with a polyol component comprising 80 to 100 % by weight of a bifunctional polyol polyether having an average molecular weight from 1000 to 4000, 0 to 5 % by weight of a monofunctional alcohol, 0 to 20 % by weight of a polyol having a functionality equal to or greater than three and an average molecular weight from 92 to 4000.

Description

PROCESS FOR THE PREPARATION OF POLYURETHANE FOAMS The present invention relates to a process for the preparation of a polyurethane foam. In particular, the present invention relates to a process for preparing a viscoelastic polyurethane foam, using an isocyanate component based on diphenylmethane diisocyanate (MDI). The term "viscoelastic polyurethane foam", when used herein, refers in particular to materials or expanded or block and molding polyurethane foams (hot and cold), with a substantial density of 50 to 100 kg / m3, and that they have an adequate elasticity value, measured according to the test method UNI 6357-68 (Urethane flexible cellular material - Determination of elasticity (ball bounce)), less than 30 percent; and a permanent deformation value at 50 percent compression, at 23 ° C, measured in accordance with ISO 1857-80 test method, less than 4 percent, preferably less than 3 percent. These foams have the characteristic of slowly returning to their original shape, after being compressed. Materials that have these characteristics are used in the preparation of impact absorbing articles, in the furniture industry, for the preparation of mattresses and cushions and, more generally, in applications in which an object capable of moving without bouncing or bouncing, it has to be supported; and in the furniture market for health care, for example, in the production of seats and beds that do not produce sores. Viscoelastic polyurethane foams can be prepared by reacting toluene diisocyanate (TDI) with a polyol compound, comprising a polyether or polyol polyester, as well as conventional additives for this type of reaction. However, the use of TDI can cause problems of a hygienic-environmental nature, both in the preparation phase of the foam and during its use, due to the possible presence of unreacted monomer, which can be released from the final product after its preparation. The use of alternative isocyanates, such as MDI, typically requires the use of certain materials, polyethers, polyesters or additives, to ensure the desired viscoelastic properties. The use of MDI with conventional raw materials typically produces traditional flexible foams (elasticity is greater than 30 percent) or non-expanded materials (crushed products), since it is difficult to process the MDI. It has now been discovered, surprisingly, that viscoelastic polyurethane foams can be prepared from an isocyanate component based on MDI and certain types of conventional polyether polyols, and that the drawbacks of, for example, the foam of the polyurethane can be reduced or avoided. great elasticity and foam that is crushed, typical of art. In a first aspect, the present invention provides a process for preparing a viscoelastic foam having a density of 50 to 100 kg / m3, which comprises reacting: a) an isocyanate component, with a functionality of 2.1 to 2.7, having the general formula (I): F - CH2 - [- F - CH2 -] ni- FIII NCO NCO NCO wherein F represents a phenyl group and n is an integer greater than or equal to 1; b) a polyol component comprising: i) from 80 to 100 percent, and preferably from 85 to 95 percent by weight, based on the total polyol component, of a bifunctional polyol polyether, having an average molecular weight from 1,000 to 4,000, preferably from 1,500 to 3,000; ii) from 0 to 5 percent, and preferably from 1 to 5 percent by weight, based on the total polyol component, of a monofunctional alcohol R-OH, where R is selected from an alkyl or isoalkyl radical of 1 to 20 carbon atoms, and preferably an alkyl and / or isoalkyl radical of 1 to 12 carbon atoms (hereinafter referred to as an (iso) alkyl radical), and a group obtained by condensation of an olefinic oxide of 2 to 6 carbon atoms, in an alkyl and / or isoalkyl radical of 1 to 20 carbon atoms; iii) from 0 to 20 percent, and preferably from 5 to 15 percent by weight, based on the total polyol component, of a polyol having a functionality equal to or greater than three, and an average molecular weight of 92 to 4,000; and c) water. The amount of water present is selected so as to ensure that the desired density of the polyurethane foam can be ensured. The isocyanate component having the general formula (!) Is suitably obtained by phosgenation of formaldehyde-aniline condensates, and is generally referred to as crude MDI or polymeric MDI. To obtain the desired isocyanate functionality from 2.1 to 2.7, if necessary, the isocyanate component having the formula (I) can be diluted with 4,4'-diphenylmethane diisocyanate, optionally mixed with 2,4'-diphenylmethane diisocyanate. . The bifunctional polyol polyether (i) used in the preparation of expanded viscoelastic materials, according to the process, is suitably selected from polyol polyethers, obtained by condensation of an olefinic oxide of 2 to 8 carbon atoms, in a compound which it has two active hydrogen atoms (referred to herein as "initiator"), for example, diethylene glycol and dipropylene glycol, or water. Ethylene oxide, propylene oxide or mixtures thereof are the preferred olefinic oxides. The monofunctional alcohol ii) suitably has a molecular weight of 200 to 1,500 and, in particular, of 250 to 1,200. When the alcohol i) is a group obtained by condensation of an olefin oxide in an alkyl and / or isoalkyl radical of 1 to 20 carbon atoms, the olefin oxide preferably comprises ethylene oxide and / or propylene oxide. In a preferred embodiment R is a group obtained by condensation of ethylene oxide and, optionally, propylene oxide, in an alkyl and / or isoalkyl radical of 1 to 12 carbon atoms and, especially an alkyl and / or isoalkyl radical of 2 to 8 carbon atoms. Examples of suitable polyols, having a functionality of three or more, include: polyol polyethers based on ethylene oxide and / or propylene oxide, and wherein the initiator is a triol, such as glycerin or trimethylolpropane; a tetrol, such as pentaerythritol; an alkanolamine, such as triethanolamine, or a polyfunctional hydroxyalkane, such as xylitol, arabitol, sorbitol, mannitol and the like. These polyols can be used as they are, or they can contain, in dispersion or partially grafted in the polyol chains, solid particles, preferably polymeric, which suitably have dimensions of less than 20 microns. Polymers suitable for this purpose include: polyacrylonitrile, polystyrene, polyvinyl chloride, polyurea, mixtures thereof, copolymers thereof and the like. These solid particles can be prepared by in situ polymerization in the polyol or, when desired, they can be prepared separately and subsequently added to the polyol. The polyol composition may also comprise other additives commonly used in the preparation of expanded polyurethane products, such as: amine catalysts, for example, triethylene diamine, and / or metal catalysts, such as stannous octoate; interleavers, cell regulators, anti-oxidation stabilizers, pigments, flame retardants, etc. Details have been given about the polymerization of polyurethanes in the work "Saunders &Frisch - Polyurethanes, Chemistry and Technology, Interscience, New York, 1964, and in Polyurethane Handbook, edited by G. Oertel, Hanser Publishers, Munich, New York , 1993. In the production of viscoelastic polyurethane foams according to the invention, the blowing agent suitably consists of water and an auxiliary blowing agent, for example C02, in liquid or gaseous form, and preferably consists of water. has a critical function, since it causes the formation of urea ligatures, associated with the release of carbon dioxide, which causes the expansion process of the polyurethane polymer, obtaining the viscoelasticity. Water amounts of 1 to 3 parts by weight, based on 100 parts of polyol component, are suitably used. In a preferred embodiment, suitably the elasticity of the foam is less than 30 percent, and more conveniently, less than 10 percent. Suitably, the polyol component comprises at least some of a monoalcohol of the formula R-OH, as defined herein, since it helps provide less elasticity. It is suitable that the process of the invention uses an isocyanate index of at least 70, and preferably at least 90. Some illustrative examples have been given below, but they do not impose limitations.

EXAMPLE 1 42.7 parts by weight of an isocyanate component having the general formula (I), and an isocyanate functionality of 2.2 (TEDIMON 4420, from Enichem S. p.A) are reacted according to the "free lift" technique with a polyol formulation consisting of 95 parts by weight of a bifunctional polyether polyol, having an average molecular weight of 2,000 (TERCAROL VD 2000, Enichem S. p.A.); 5 parts by weight of trifunctional polyether, having an average molecular weight of 300 (TERCAROL G 310, Enichem S. p.A); 1.5 parts by weight of water; 0.7 parts of a silicone-based surfactant (TEGOSTAB B 8002 from Goldschmidt); 0.05 parts by weight of tertiary aliphatic amine (NIAX A-1, Crompton Corporation); 0.23 parts by weight of a solution of dibutyltin dilaurate and 0.5 parts by weight of diethanolamine. The reaction index is equal to 100.

At the end of the reaction a viscoelastic foam is obtained, which has a density of 65 kg / m3, a permanent deformation by compression of 2.35 percent, and elasticity of 24 percent.

EXAMPLE 2 (COMPARATIVE) The same procedure described in Example 1 is adopted, except for the use of 39.2 parts of 4,4'-diphenyl methane diisocyanate, having a functionality of 2, instead of TEDIMON 4420, and 0.25 parts by weight of a amine catalyst (NIAX A 107 from Witco Corporation). At the end of the reaction a crushed product is obtained.

EXAMPLE 3 43.3 parts by weight of TEDIMON 4420 is reacted, according to the "free lift" technique, with a polyol formulation consisting of 93 parts by weight of a bifunctional polyol polyether having an average molecular weight of 2,000 ( TERCAROL VD 2000); 7 parts by weight of trifunctional polyether having an average molecular weight of 300 (TERCAROL G 310); 1.5 parts by weight of water; 0.7 parts of a silicone-based surfactant (TEGOSTAB B 8002); 0.3 parts by weight of a solution of dibutyltin dilaurate; 0.05 parts by weight of NIAX A 107 and 0.01 part by weight of dimethylethanolamine (DABCO DMEA from Air Products). The reaction index is equal to 98. At the end of the reaction, a viscoelastic foam having a density of 55 kg / m3, a compression set of 3.5 percent and an elasticity of 29 percent is obtained.

EXAMPLE 4 43.75 parts by weight of TEDIMON 4420 is reacted, according to the "free lift" technique, with a polyol formulation consisting of 95 parts by weight of a bifunctional polyol polyether, having an average molecular weight of 2,000. (TERCARON VD 2000); 5 parts by weight of trifunctional polyether having an average molecular weight of 300 (TERCAROL G 310); 1 part by weight of trifunctional polyol polyether having an average molecular weight of 4,000 and containing a high level of ethylene oxide (TERCAROL 241 of Enichem S.P.A.), which acts as a cell opener; 1.6 parts by weight of water; 0.8 part of a silicone surfactant (TEGOSTAB B 8002); 0.23 part by weight of a solution of dibutyltin dilaurate and 0.5 part by weight of dimethylethanolamine. The reaction index is equal to 100. At the end of the reaction, a viscoelastic foam having a density of 77 kg / m3, a permanent compression deformation of 2.70 percent and an elasticity of 28 percent is obtained.

EXAMPLE 5 (COMPARATIVE) 60.5 parts by weight of TEDIMON 4420 is reacted, according to the "free lift" technique, with a polyol formulation consisting of 90 parts by weight of a trifunctional polyol polyether, having an average molecular weight of 6,000. (TERCAROL 427 by Enichem, S. p. A.); 10 parts by weight of trifunctional polyol polyether having an average molecular weight of 4,000 (TERCAROL 241); 3.1 parts by weight of water; 3.5 parts by weight of diethanolamine; 0.15 parts by weight of tertiary aliphatic amine (DABCO 33 LV); 0.6 part of a silicone surfactant (TEGOSTAB B 8636); 0.15 parts of a dibutyltin dilaurate solution (DABCO T-12 from Air Products). The reaction index is equal to 100. At the end of the reaction, a highly elastic foam is obtained, which has a density of 36 kg / m3, a permanent compression deformation of 11.5% and an elasticity of 51%.

EXAMPLE 6 After pre-mixing, 37.6 parts of TEDIMON 4420 and a polyol formulation consisting of 90 parts by weight of a bifunctional polyol polyether having an average molecular weight of 2000 (TERCAROL VD) are fed to a cube-shaped mold. 2000); 10 parts by weight of a hexafunctional polyether, having an average molecular weight of 2700 (GLEDION PS 1504 of Enichem S. p.A); 1.6 parts by weight of water; 0.3 parts of a silicone-based surfactant (TEGOSTAB B 8002); 0.3 part by weight of amine catalyst (NIAX A-1) and 0.6 part by weight of diethanolamine. The reaction rate is equal to 95. At the end of the reaction, a viscoelastic foam having a density of 100 kg / m3, a compression set of 2.1 percent, and an elasticity of 18 percent is obtained.

Claims

1. - A process for the preparation of a viscoelastic foam having a density of 50 to 100 kg / m3, characterized in that it comprises reacting: a) an isocyanate component, with a functionality of 2.1 to 2.7, having the general formula (I) : f _ CH2 - [- F - CH2 -] ni- F

I I NCO NCO NCO where F represents a phenyl group and n is an integer greater than or equal to 1; b) a polyol component comprising: i) from 80 to 100 percent, and preferably from 85 to 95 percent by weight, based on the total polyol component, of a bifunctional polyol polyether, having an average molecular weight from 1,000 to 4,000, preferably from 1,500 to 3,000; ii) from 0 to 5 percent, and preferably from 1 to 5 percent by weight, based on the total polyol component, of a monofunctional alcohol R-OH, where R is selected from an alkyl or isoalkyl radical of 1 to 20 carbon atoms, and preferably an alkyl and / or isoalkyl radical of 1 to 12 carbon atoms (hereinafter referred to as an (iso) alkyl radical), and a group obtained by condensation of an olefinic oxide of 2 to 6 carbon atoms, in an alkyl and / or isoalkyl radical of 1 to 20 carbon atoms; iii) from 0 to 20 percent, and preferably from 5 to 15 percent by weight, based on the total polyol component, of a polyol having a functionality equal to or greater than three, and an average molecular weight of 92 to 4,000; and c) water. 2. - A process according to claim 1, further characterized in that the isocyanate component having the general formula (I) is obtained by phosgenation of a formaldehyde-aniline condensate and, optionally, 4,4'-diphenylmethane diisocyanate; optionally, the 4,4 'isomer is mixed with its 2,4' isomer.

3. - A process according to any of claims 1 or 2, further characterized in that the bifunctional polyol polyether comprises a polyol polyether obtained from the condensation of an olefinic oxide of 2 to 8 carbon atoms, in a compound (initiator) that has two active hydrogen atoms.

4. - A process according to any of the preceding claims, further characterized in that the polyol having a functionality equal to or greater than three, and an average molecular weight of 92 to 4,000, is present at a level of 5 to 15 percent in weigh.

5. - A process according to any of the preceding claims, further characterized in that the polyol having a functionality equal to or greater than three, comprises a polyol polyether, based on ethylene oxide and / or propylene oxide, condensed on a triol, a tetrol, an alkanolamine or a polyfunctional hydroxyalkane.

6. - A process according to any of the preceding claims, further characterized in that water is present at a level of 1 to 3 parts by weight, with respect to 100 parts of polyol component.

7. - A viscoelastic polyurethane foam, characterized in that it has a density of 50 to 100 kg / m3, a value of permanent deformation by compression, at 23 ° C, measured in accordance with ISO 1856-80, less than 4 per hundred; and an elasticity of less than 30 percent, measured in accordance with rule UNI 6357-68, which is obtained by a process as defined by any of claims 1 to 6.