EPOXY RESIN MODIFIED POLYETHER POLYOLS FROM MIXED INITIATORS

Abstract: Modified polyether polyols are made by first optionally alkoxylating, subsequent reaction with epoxy resins and final alkoxylation of mixtures of initiators comprising 60 to 90 weight % of a partially alkoxylated trifunctional initiator and 10 to 40 weight % of a secondary partially alkoxylated initiator having an active hydrogen functionality of from 4 to 8. Preferably, the alkylene oxide component is a blend of ethylene oxide and propylene oxide, and the resulting modified polyol molecules have 0.25 to 2.5 weight % of internally located epoxy resin. Flexible polyurethane foams made from these polyether polyols have improved load bearing properties as compared with those made from prior art polyols.

Description: The invention relates to polyether polyols made by alkoxylating polyfunctional initiators, and more particularly relates to polyether polyols made by alkoxylating a mixture of partially alkoxylated initiators having different numbers of active hydrogens which was modified with epoxy resins. At present, polyether polyols suitable for use in the production of flexible foams, are made by the reaction of trifunctional initiators, such as glycerol with mixtures of alkylene oxides. Persons skilled in the art of making polyols can add alkylene oxides to polyhydric initiators, such as glycerol, or to an intermediate molecular weight alkylene oxide adduct of the initiator, to prepare products having hydroxyl numbers from 40 to 60. For examples of polyols made by this technique, see US-A-3 393 243; 3 535 307; 3 706 714; 3 847 992; 4 166 172 and 4 316 991. While generally satisfactory, foam prepared from the prior art polyols are not firm enough for many cushioning applications, particularly at lower foam densities. Conventional means of producing firmer (higher ILD) foams, such as the use of higher functionality initiators, short chain crosslinkers or fillers, lead to other deficiencies in foam properties, such as closed cells, poor tear and elongation properties, and increased foam density. It is, therefore, an object of this invention to increase the functionality of triols and the like, by mixing them with a minor portion of a polyol initiator having higher functionality, and modifying the mixture with epoxy resins. Several patents describe mixtures of initiators used to prepare polyols for polyurethane foams. Almost all are concerned with the preparation of polyols for rigid urethane foams. Usually, these processes involve sucrose with water, glycols, glycerol, etc. The use of lower functional polyols permit manufacture of polyols for rigid urethane foams that are easier to handle, and the resulting rigid foams have much finer cells. A recent example is disclosed in US-A-4 380 502 which employs 80 to 20 wt% of formitol (a mixture of polyhydric alcohols having an average hydroxyl functionality of at least 3) and 20 to 80 wt% of sucrose. The introductory section of this patent is a good summary of the art of mixed initiators. Also of interest is Japanese Kokai Tokkyo Koho JP 57/174,313 (82/174,313), see Chemical abstracts 98: 144401c (1983). This disclosure describes urethane foams having good post formability by hot pressing, which are prepared by reacting polyisocyanates and polyol mixtures. The polyol mixtures are 30 to 90% of polyether polyols derived from a 10:90 to 40:60 molar mixture of sucrose and glycerol, respectively, and alkylene oxides having a molecular weight between 4000 and 10,000, and 10 to 70% of polyether diols and/or triols having an average hydroxyl number between 50 and 300. Apparently, sucrose and glycerol are first mixed and then the alkylene oxides are reacted therewith (for example, a 90:10 propylene oxide/ ethylene oxide mixture) before a polyether diol is added thereto to give the polyol component for the foams described therein. This method is quite different from the present invention, particularly with regard to when the various alkoxylations take place. Other patents disclose reactions involving polyols and epoxy resins. JP-71/24,255 concerns the reaction of a glycerine-based 3,000 molecular weight triol with 2% bisphenol A epoxy resin to produce foams with increased hardness. A close examination of this patent will show that the epoxy resin is added only at the end of the triol chain. The position at which the epoxy resin is added in the polyol chain will make a substantial difference in how the modified polyol performs in producing open-celled flexible foams with improved load bearing properties. US-A-3 012 984 describes how hydroxyl terminated polyesters, epoxy resins and isocyanate terminated prepolymers may be reacted in an inert organic solvent to produce metal primers and coatings. US-A-3 010 940 discloses how phenol, epoxy resins, polyisocyanates and alphamethylbenzyldimethylamine react to produce various polyurethane coatings. US-A-3 448 046 describes how polyols containing chlorine are mixed with epoxy resins before reaction with an isocyanate. The free epoxides scavenge the HCl in the polyol, and do not contribute to the functionality of the polyol. The reaction of an epoxide with an alcoholic hydroxyl group is set out in US-A-3 317 609. Further, GB-A-968 102 describes how polyols suitable for polyurethane foams may be prepared by the reaction of a polyol and an epoxy resin, in the presence of an acidic catalyst. Further prior art polyols include those described in DE-A-2 056 080. This describes how epoxy adhesives may be made by the reaction of epoxy resins with 4-mercapto-butanol-blocked urethane prepolymers, which are made from toluene diisocyanate and various polyols. DE-A-1 905 696 discloses how polyurethane latices may be produced by chain extending a urethane prepolymer by using the reaction product of polyethylene glycols having a molecular weight of 5,000 to 10,000 and an aromatic diglycidyl ether. The modification of epoxy resins by heating them with added polyalkoxylated disaccharides is described in BE-A-785 020. Also of particular interest is U5-A-4 316 991, which describes the modification of polyether polyols by their reaction with epoxy resins and alkylene oxides such that the epoxy resin is positioned internally in the resulting modified polyol, as well as the references cited in the prosecution therein. US-A-4 309 532 concerns the modification of rigid amino polyols by their reaction with epoxy resins and alkylene oxides, while US-A-4 323 658 details a method of preparing polyether polyols having a molecular weight from 200 to 1,000 by modifying a polyol initiator with an epoxy resin and one or more alkylene oxides. EP-A-132 302 relates to a method for making polyether polyols by reacting one or more alkylene oxides with an initiator having active hydrogen, the initiator comprising a mixture of initiators comprising 1) 60 to 90 weight % of a trifunctional partially alkoxylated initiator, and 2) 10 to 40 weight % of a secondary partially alkoxylated initiator having an active hydrogen functionality of from 4 to 8, and to flexible polyurethane foam obtained by reacting an organic polyisocyanate and these polyether polyols in the presence of a polyurethane-formation catalyst. The invention concerns a modified mixed polyether polyol made by reacting a mixture of initiators with an epoxy resin and one or more alkylene oxides in such a manner that the epoxy resin is added internally along the length of the polyol chain. The mixture of initiators comprises 60 to 90 weight % of a trifunctional partially alkoxylated initiator and 10 to 40 weight % of a secondary partially alkoxylated initiator having an active hydrogen functionality of from 4 to 8. As noted above, a mixture of initiators is required. The major proportion of the mixture should comprise a trifunctional initiator; that is, a compound having three and only three active hydrogens. This initiator must be partially alkoxylated. Examples of suitable trifunctional initiators are alkylene oxide adducts of glycerol, trimethylolpropane, triethanolamine, 1,2,6-hexanetriol, monoethanolamine, diethanolamine and aminoethylpiperazine. Especially preferred triols are glycerine, glycerol, trimethylolpropane and triethanolamine. The trifunctional initiator makes up from 60 to 90 weight % of the initiator mixture, based on the total mixture weight. An unusual feature of the invention is the incorporation of a minor proportion of one other polyhydric initiator, termed a secondary initiator. The word "secondary" does not refer to the functionality of the initiator but is used to distinguish the initiator present in minor proportions as opposed to the major initiator discussed above. The secondary initiator has 4 to 8 active hydrogens and is also partially alkoxylated. Suitable secondary initiators include alkylene oxide adducts of methyl glucoside, ethylenediamine, sorbitol, sucrose, hydroxypropyl glucoside, pentaerythritol, and erythritol. Styrene-allyl alcohol copolymers may also be used. Particularly preferred are methyl glucoside, ethylenediamine, sorbitol and sucrose. The secondary initiator comprises from 10 to 40 weight % of the total initiator mixture. Both of the initiator types described above are preferably partially alkoxylated before mixing, although conceivably they could be mixed before any alkoxylation. The alkylene oxides to be used in these partial alkoxylations are preferably ethylene oxide, propylene oxide, 1,2-butylene oxide and mixtures thereof. The oxides may be added by reacting the initiators with the oxides in the presence of a catalyst at an elevated temperature in the range of 75 to 150°C. Typically this alkoxylation reaction is conducted in the presence of an alkaline catalyst, such as sodium hydroxide or potassium hydroxide. Other catalysts are also known such as cesium hydroxide, calcium hydroxide, trialkylamines and aqueous ammonia. The term "partial alkoxylation" does not refer to a specific amount or even a range of proportions. Rather, since some of the alkoxy moieties are to be placed preferably before and after the internal epoxy resin section of the ultimate molecule, the addition of alkylene oxide before reaction with epoxy resin is referred to as partial alkoxylation. The relative proportions of alkylene oxide added before and after the epoxy resin are left to the decision of the practitioner. In this way, the epoxy resin is added at selected points. Preferably, the mixed initiators are partially alkoxylated again, as a mixture, before the epoxy resin reaction step. Next, the epoxy resin is added at selected points internally along the length of the polyol chain. This tends to increase the overall funetionality of the polyol chain. Prior art techniques discussed above tend to add epoxy at the end only. It is recommended that at least two equivalents of hydroxyl functionality be present per equivalent of epoxy resin added to the reaction mixture to avoid gelling of the epoxy by crosslinking with itself. The epoxy resin may be added before, during and/or after the addition of alkylene oxide to the polyol initiator. The best results are obtained if the resin is not added only as a "cap, that is, after all of the oxide has been added, which results in the resin being attached to the end of the resulting polyol chain only. One skilled in the art who is practicing this invention may determine the best procedure with respect to when additions should be made, and at what temperature, and during which times, the reaction mixture is to be heated within the scope of this invention. A wide variety of epoxy resins is useful in practicing this invention. The vicinal polyepoxide containing compositions are organic materials having an average of at least 1.8 reactive 1,2-epoxy groups per molecule. These polyepoxide materials can be monomeric or polymeric, saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic, and may be substituted, if desired, with other substituents besides the epoxy groups; e.g., hydroxyl groups, ether radicals, and aromatic halogen atoms. Preferred polyepoxides are those of glycidyl ethers prepared by epoxidizing the corresponding allyl ethers, or reacting, by known procedures, a molar excess of epichlorohydrin and an aromatic polyhydroxy compound; i.e. isopropylidene bisphenol, a novolak, or resorcinol. The epoxy derivatives of methylene or isopropylidene bisphenols are especially preferred. The diglycidyl ether of bisphenol A (DGEBPA) is used in the examples herein. Some of these epoxy resins are known in the trade as EPON® resins and may be obtained from Shell Chemical Co. A widely used class of polyepoxides useful according to the instant invention includes the resinous epoxy polyethers obtained by reacting an epihalohydrin, such as epichlorohydrin, with either a polyhydric phenol or a polyhydric alcohol. An illustrative, but by no means exhaustive, listing of suitable dihydric phenols includes 4,4'-isopropylidene bisphenol, 2,4'-dihydroxydiphenylethylmethane, 3,3'-dihydroxydiphenyldiethylmethane, 3,4'-dihydroxydiphenylmethylpropylmethane, 2,3'-dihydroxydiphenylethylphenylmethane, 4,4'-dihydroxydiphenylpropylphenylmethane, 4,4'-dihydroxydiphenylbutylphenylmethane, 2,2'-dihydroxydiphenylditolylmethane, and 4,4'-dihydroxydiphenyltolylmethylmethane. Other polyhydric phenols which may also be co-reacted with an epihalohydrin to provide these epoxy polyethers are such compounds as resorcinol, hydroquinone, and substituted hydroquinones; e.g., methylhydroquinone. Among the polyhydric alcohols which can be coreacted with an epihalohydrin to provide these resinous epoxy polyethers are such compounds as ethylene glycol, propylene glycols, butylene glycols, pentane diols, bis(4-hydroxycyclohexyl)dimethylmethane, 1,4-dimethylolbenzene, glycerol, 1,2,6-hexanetriol, trimethylolpropane, mannitol, sorbitol, erythritol, pentaerythritol, their dimers, trimers and higher polymers, e.g., polyethylene glycols, polypropylene glycols, triglycerol and dipentaerythritol, polyallyl alcohol, polyhydric thioethers, such as 2,2'-,3,3'-tetrahydroxydipropylsulfide, mercapto alcohols such as monothioglycerol and dithioglycerol, polyhydric alcohol partial esters, such as monostearin and pentaerythritol monoacetate, and halogenated polyhydric alcohols such as the monochlorohydrins of glycerol, sorbitol and pentaerythritol. Another class of polymeric polyepoxides which can be amine cured, and used in accordance with the present invention includes the epoxy novolak resins obtained by reacting, preferably in the presence of a basic catalyst; e.g., sodium or potassium hydroxide, an epihalohydrin, such as epichlorohydrin, with the resinous condensate of an aldehyde, e.g., formaldehyde, and either a monohydric phenol, e.g., phenol itself, or a polyhydric phenol. Further details concerning the nature and preparation of these epoxy novolak resins can be obtained in Lee, H. and Neville, K., Handbook of Epoxy Resins , McGraw Hill Book Co., New York, 1967. It will be appreciated by those skilled in the art that the polyepoxide compositions which are useful according to the practice of the present invention are not limited to those containing the above described polyepoxides, but that these polyepoxides are to be considered merely as being representative of the class of polyepoxides as a whole. The reaction conditions of temperature and pressure may be selected by the practitioner of the invention to meet certain specifications required by the polyol for a particular use. The examples herein use a pressure of 0.1 to 2 MPa and a temperature of 100 to 150°C as representative conditions for the making of modified polyols that would be useful in flexible foams. The amount of epoxy resin to be added to the reaction mixture should be such that the epoxy equivalents present are less than half of the hydroxyl functionality equivalents present in the reaction mixture. Too many epoxy equivalents in relation to the hydroxyl equivalents may cause the epoxy resin to gel by crosslinking with itself. As a result a large excess of hydroxyl equivalents may be used in the reaction mixture and still be within the spirit and scope of this invention. The alkylene oxide to be added into the epoxy modified mixed alkoxylated polyhydric initiator product may be ethylene oxide, propylene oxide, 1,2-butylene oxide or mixtures thereof. It is especially preferred that the alkylene oxide component is a mixture of ethylene oxide and propylene oxide. These same alkylene oxides are the ones suitable for addition to the initiators before mixing. The amount of alkylene oxide component to be employed in each initiator will vary. Therefore, the average functionality of the initiator mixture will vary and the amount of alkylene oxide component required to alkoxylate totally the mixture of alkoxylated initiators will also vary according to the desires of the experimenter. It is preferred that first a mixture of ethylene oxide and propylene oxide be used and then the polyol should be finally capped with propylene oxide. The molecular weight and hydroxyl number of the polyol may be built up by using an excess of alkylene oxide component beyond what is necessary totally to alkoxylate the initiators. Again, the alkoxylation reaction should preferably be conducted with a catalyst at an elevated temperature in the range from 75 to 150°C. The well known way of conducting this alkoxylation reaction is again to use a catalyst, frequently an alkaline catalyst such as sodium hydroxide or potassium hydroxide. The resulting polyols may have a molecular weight in the range of 1000 to 20,000. It is preferred that the polyols have a molecular weight from 3000 to 10,000, and especially preferred that the molecular weight be 3000 to 6500. Further, it is preferred that the resulting polyols have a hydroxyl number from 20 to 60 and that the polyol contain from 0.25 to 2.5 wt% of combined epoxy resin. These polyether polyols are particularly suited for the preparation of flexible polyurethane foam. Foams made from these polyols have improved load bearing properties as compared to those made from prior art polyols. Surprisingly, the improved load bearing characteristics of these foams were not achieved at the expense of other important properties. Examples of foam preparation are presented to demonstrate the utility of the polyether polyols. It is well known that flexible and other types of foams may be made generally by reacting the polyols with polyisocyanates in the presence of a polyurethane formation catalyst, such as a tertiary amine or tin catalyst, optionally in the presence of a blowing agent and other additives. For more details on polyurethane foam preparation see US-A-3 535 307, for example. The polyether polyols of the invention are further illustrated by the following Examples, in which the DGEBPA was EPON®828 of Shell Chemical Co. EXAMPLE 1 This example will illustrate the preparation of the diglycidyl ether of Bisphenol A (DGEBPA) modified mixed initiator polyols of this invention. Propylene oxide and ethylene oxide are abbreviated PO and EO, respectively. Into a 31.5 litre reactor were charged 3.63 Kg of a 600 molecular weight PO/EO adduct of glycerol (GE-620 made by reaction of one mole of glycerol with 3 moles of EO and 6.5 moles of PO in the presence of potassium hydroxide catalyst by Texaco Chemical Co.). The GE-620 initiator had a final alkalinity of 25.88 mg KOH/g. 0.91 Kg of a 700 molecular weight PO adduct of sorbitol (ATPOL® 2410 made by ICI America) were also added. The reactor was then evacuated and purged with prepurified nitrogen. Maintaining a nitrogen purge, the reaction mixture was heated to 100°C. At this point the reaction mixture had a water content of 0.05 weight %. A mixture of 13.12 Kg of PO and 2.13 Kg of EO was then reacted at 105 to 110°C and 0.44 MPa. Approximately 3.25 hours were required for addition of the mixed PO/EO. The reaction mixture was then digested for 1.7 hours until an equilibrium pressure was reached. DGEBPA (0.27 Kg) was then charged to the kettle and reacted for 15 minutes. A mixture of 13.12 Kg of PO and 2.13 Kg of EO was then added at 105 to 110°C at 0.44 MPa over a 2.5 hour period. The reaction was terminated by reaction with 1.10 Kg of PO. After digestion to an equilibrium pressure, the alkaline product was neutralized by stirring two hours with an aqueous slurry of 560g of magnesium silicate. Octylated diphenylamine (32.7g) and 2,6-di-t-butyl phenol-4-sec-butyl phenol (109g) were then added to stabilize the product. After neutralization, the product was vacuum stripped to a minimum pressure, nitrogen stripped for 30 minutes and filtered. The finished product had the following properties: EXAMPLES 2 to 7 This example will further illustrate the preparation of the mixed initiator, DGEBPA-modified polyols of this invention. These polyols were prepared to contain 0.5 to 1.75 weight % of combined BGEBPA and had hydroxyl numbers ranging from 37.7 to 50.9 mg KOH/g. The procedure described in Example 1 was used for preparation of these products. Reaction charges, details of preparation, and properties of these polyols are shown in Table I. EXAMPLE 3 This example will illustrate the use of a mixed initiator polyol (40.6 hydroxyl number) prepared as described in Example 1 in the preparation of flexible foams. This polyol was prepared to contain 0.8 weight % of combined DGEBPA and was made using a 4:1 mixture of GE-620 and a 700 molecular weighs PO adduct of sorbitol as the initiator. The data will show that foams made from this polyol were 20% firmer than those made from a 3000 molecular weight prior art polyol (hydroxyl number: mg KOH/g 56). The prior art polyol was a 3000 molecular weight PO/EO adduct of glycerol (THANOL® F-3016 made by Texaco Chemical Co.). The data will further show that foams prepared from this polyol had properties similar to those of a prior art DGEBPA-modified polyol (THANOL F-3050 made by Texaco Chemical Co. according to the procedures of US-A-4 316 991). The higher loads were obtained without loss in tensile strength, tear elongation and compression set and the foams had good ball rebound properties. The lower isocyanate requirement for polyols of this invention (lower hydroxyl number, for equally firm foams) demonstrates the improved economics of foam manufacture using these polyols. Formulations, details of preparation and foam properties are shown in Table 2. All foams were processed on a Martin Sweets foam machine. All amounts are parts by weight.

Claims: A method for making polyether polyols by reacting one or more alkylene oxides with a mixture of initiators comprising 1) 60 to 90 weight % of a trifunctional partially alkoxylated initiator, and 2) 10 to 40 weight % of a secondary partially alkoxylated initiator having an active hydrogen functionality of from 4 to 8, characterized in that an epoxy resin is also reacted in such a manner that it is added internally along the length of the resulting polyol chain. A method according to Claim 1 characterized in that the alkylene oxide component comprises ethylene oxide, propylene oxide, 1,2-butylene oxide or a mixture thereof. A method according to Claim 1 or 2 characterized in that the alkylene oxide component comprises a mixture of ethylene oxide and propylene oxide. A method according to any of the preceding Claims characterized in that the trifunctional initiator is an alkylene oxide adduct of glycerol, trimethylolpropane or triethanolamine, and in that the secondary initiator is an alkylene oxide adduct of methyl glucoside, ethylenediamine, sorbitol or sucrose. A method according to any of the preceding Claims characterized in that the epoxy resin is the diglycidyl ether of Bisphenol A, an epoxy novolak resin, or an aliphatic epoxy resin. A method according to any of the preceding Claims characterized in that 0.25 to 2.5 weight % of epoxy resin is incorporated into the polyether polyol. A method according to any of the preceding Claims characterized in that the reaction temperature is from 100 to 150°C. A method according to any of the preceding Claims characterized in that (a) the mixture of the trifunctional partially alkoxylated initiator and the secondary partially alkoxylated initiator is reacted with one or more alkylene oxides, (b) the reaction product from step (a) is reacted with an epoxy resin, the ratio of equivalents of hydroxyl functionality to equivalents of epoxy being at least 2 to 1, and (c) the reaction product from step (b) is further reacted with one or more alkylene oxides whereby the resulting modified mixed initiator polyol has the epoxy resin added internally along the length of the polyol chain. A method for producing a flexible polyurethane foam by reacting an organic polyisocyanate and a polyol in the presence of a polyurethane-formation catalyst, characterized in that the polyol is a polyether polyol obtainable by a method according to any of the preceding Claims. A method according to Claim 9 characterized in that the polyether polyol has a molecular weight of from 1,000 to 20,000, and a hydroxyl number from 20 to 60.

Inventors: CUSCURIDA, MICHAEL, PETERSON, BRUCE WILLIAM
Applicants: ARCO CHEMICAL TECHNOLOGY INC.
Application year: 1985
Main classification: C08G65
IPC codes: C08G65, C08G59, C08G18, C08L63