This patent application relates to novel high molecular weight alkylene oxide based polyether polyols and a process for their preparation. This application further relates to the use of such high molecular weight alkylene oxide based polyether polyols to prepare prepolymers useful in high performance adhesives and elastomers. This invention further relates to high viscosity polyether polyols useful as lubricants. The invention further relates to high molecular weight polyether polyols useful as thickening agents in hydraulic fluids.
Polyether polyols used in preparing polyurethane adhesives and elastomers are usually prepared by reacting an initiator compound having a plurality of active hydrogen atoms with an alkylene oxide in the presence of basic catalysts such as tertiary amines, sodium and potassium hydroxides and sodium where a sodium derivative such as the alkylate of alkoxide is formed in situ. However, these catalysts must usually be removed by filtration and/or neutralization or other catalyst removal methods prior to use, particularly when prepolymers are to be prepared from such polyether polyols.
Olstowski and Nafziger, U.S. Pat. No. 4,282,387, issued Aug. 4, 1981, incorporated herein by reference, disclosed preparing polyols by reacting alkylene oxides with hydroxyl initiator compounds in the presence of catalysts of calcium, strontium, or barium salts of organic acids. These catalysts do not need to be removed before the resultant product is used in the preparation of polyurethanes. Such catalysts are generally available in a mineral spirit solvent which further contains monoether glycols. Such monoether glycols contain active hydrogen atoms and act as initiators. This results in the preparation of a mixture of polyols wherein some of the polyols are mono functional with respect to the hydroxyl group. The presence of mono functional polyether polyols decrease the physical properties of the elastomers that are made from them. They also form polyether polyols which have low molecular weight species and result in a high polydispersity. Polydispersity is defined as the weight average molecular weight divided by the number average molecular weight. A high polydispersity indicates that the polyether polyol prepared is a mixture of polyether polyols having a wide range of molecular weights. A high polydispersity and low molecular weight renders such polyether polyols unsuitable for high performance applications such as high performance elastomers and adhesives. Many of the polyether polyols prepared using such a catalyst system are initiated with a monofunctional glycol ether and are monofunctional, and therefore are not useful in high performance applications.
Yates et al. U.S. Pat. No. 4,326,047 discloses a process for preparing polyols using the catalysts described in Olstowski, wherein the catalyst is precipitated from the mineral spirits carrier and the glycol ether coupling agent. The resulting catalyst is solid. To be effective this catalyst must be redissolved in the reaction medium. This extra step takes time and negatively affects the productivity of the reaction and the polydispersity of the product prepared.
Hydraulic fluids are generally thickened with polyether polyols. In order to achieve the desired viscosity of such hydraulic fluids, it is often necessary to use a high concentration of polyether polyols in the water based hydraulic fluids. A common hydraulic fluid is ISO VG 46 hydraulic fluid which has a viscosity of 46 centistokes at 40.degree. C. Most polyether polyols used in this application have a relatively low molecular weight. In order to prepare a hydraulic fluid meeting this requirement with these low molecular weight polyethers a concentration of from about 30 to about 70 percent by weight of polyether polyol is required. This formulation is expensive due to the need for such a high concentration of polyether polyols. There are known high molecular weight polyethylene oxide based polyethers used as thickening agents in hydraulic fluid available from Union Carbide under the tradename POLYOX WSRN-10.TM.. These generally have a molecular weight of 100,000 or greater. These can be used at a low concentration but exhibit poor shear stability and the fluid containing these polyethers is not shear stable and suffers from a reduction in viscosity during use. It would be desirable to have a high molecular weight polyether polyol which could thicken hydraulic fluid to the desired level at a significantly lower concentration and which is shear stable.
Some lubricants are designed to have a certain viscosities at 40.degree. C., ISO VG 1000 lubricants demonstrate a viscosity of 1000 centistokes at 40.degree. C. ISO VG 2000 lubricants demonstrate a viscosity of 2000 centistokes at 40.degree. C. Polyether polyols made with basic catalysts generally do not have sufficient molecular weight to achieve the desired viscosities. High molecular weight polyether polyols which have sufficient viscosity to function as these lubricants are desired.
What is needed are high molecular weight polyether polyols which are useful in high performance applications. What is further needed is a process for the preparation of such high performance polyether polyols. What is also needed is a prepolymer useful in preparing high performance elastomers and adhesives prepared from such high molecular weight polyether polyols. What is further needed are high molecular weight polyether polyols which can be used as a thickener in water based hydraulic fluids and which are shear stable under lubricating conditions. What is needed is a high viscosity polyether polyol which can achieve the desired ISO VG 1000 and ISO VG 2000 viscosities.