Starter feed stream acidification in DMC-catalyzed process

Abstract

The process of the present invention provides for the manufacture of lower molecular weight DMC-catalyzed polyols than is possible using non-acidified continuous addition of starter (CAOS) feeds, by adding excess acid to a starter feed stream over that required for mere neutralization of the basicity of the starter. The benefits of the invention also extend to starters which do not contain basicity. Polyether polyols made by the inventive process may be used to produce improved polyurethane products such as coatings, adhesives, sealants, elastomers, foams and the like.

Description

FIELD OF THE INVENTION [0001] The present invention relates in general to catalysis, and more specifically, to the acidification of starter feed stream(s) in a continuous addition of starter (CAOS) polyether polyol production process to improve double metal cyanide (“DMC”) catalyst activity. BACKGROUND OF THE INVENTION [0002] Base-catalyzed oxyalkylation has been used to prepare polyoxyalkylene polyols for many years. In such a process, a suitably hydric low molecular weight starter molecule, such as propylene glycol or glycerine, is oxyalkylated with one or more alkylene oxides, such as ethylene oxide or propylene oxide, to form a polyoxyalkylene polyether polyol product. Because it is possible to employ a low molecular weight starter, the build ratio (polyol weight / starter weight) is relatively high, and thus the process effectively utilizes reactor capacity. Strongly basic catalysts such as sodium hydroxide or potassium hydroxide are typically used in such oxyalkylations. [0003] ...

AI Technical Summary

Benefits of technology

[0014] Accordingly, the present invention provides a process for the manufacture of lower molecular weight DMC-catalyzed polyols than was heretofore possible using non-acidified continuous addition of starter (CAOS) feeds. An excess of acid over that required for neutralization of the basicity of a low molecular weight starter is added to a CAOS feed stream. The inventive process may permit the use of less catalyst for a given process than was heretofore required. The polyether polyols provided by the process of the present invention may allow for the production of improved polyurethane products, such as coatings, adhesives, elastomers, sealants, foams and the like.

Problems solved by technology

In addition to broadening the molecular weight distribution of the product, the continuous generation of monols lowers the product functionality.

As the oxypropylation proceeds further, the functionality continues to decrease, and the molecular weight growth rate slows.

Even at those modest equivalent weights, the products are characterized by low actual functionality and broad molecular weight distribution.

Numerous attempts have been made to lower unsaturation, and hence monol content, but few have been successful.

However, the catalyst activity, coupled with catalyst cost and the difficulty of removing catalyst residues from the polyol product, prevented commercialization of the products.

However, the economics of the process were marginal, and in many cases, improvements expected in polymer products due to higher functionality and higher polyol molecular weight did not materialize.

As those skilled in the art appreciate, one drawback of DMC-catalyzed oxyalkylation is the difficulty of using low molecular weight starters in polyether synthesis.

Polyoxyalkylation of low molecular weight starters is generally sluggish, and often accompanied by catalyst deactivation.

The additional steps associated with catalyst removal from the oligomeric starter can add significant process time, and thus cost, to the overall process.

Furthermore, the higher molecular weight of the starter lowers the build ratio of the process significantly, thereby decreasing reactor utilization.

Another drawback associated with oxyalkylation with DMC catalysts is that a very high molecular weight component is generally observed.

Unfortunately, when glycerine, a widely used trifunctional starter, is employed in either the batch-type continuous addition of starter process, or the continuous-type continuous addition of starter process, the DMC catalyst gradually deactivates, and often a polyether of the desired molecular weight cannot be obtained, or when obtained, product characteristics such as amount of high molecular weight tail, polydispersity, etc., are less than optimal.

Because glycerine is derived from plant or animal matter by base-dependent processes, it contains one or more basic contaminants which may cause a loss of DMC catalyst activity.

McDaniel et al. fail to provide any teaching or suggestion to add greater amounts of acid than that needed to neutralize basic contaminants of the glycerine.

However, these objectives cannot be met if catalyst deactivation occurs.