Published April 2019
Polyurethanes (PU) constitute one of the most versatile sets of materials known. PU are widely used in both industry and everyday life. The wide range of polyols available to react with isocyanates gives rise to a broad spectrum of polyurethane materials, with applications ranging from cushioning and insulation to coatings, clothing, and electronics.
In addition to structural components, the properties of PU depend on the molecular weight (MW) of the starting polyol and the degree of cross-linking. While highly branched polyols result in rigid PU with good heat and chemical resistance, less branched polyols give PU with good flexibility (at low temperature) and low chemical resistance. Similarly, low-MW polyols produce rigid PU, and high-MW long-chain polyols yield flexible PU.
This report describes alternative processes for production of singular products for two types of polyols for polyurethanes—polyether polyols and polyester polyether polyols.
We first develop the design and cost for construction of a semicontinuous, multiproduct batch polyether polyols plant that campaigns production of a single polyether polyol-based product in a single-train facility. One set of conditions is evaluated herein to make a polyol of 3,000 Daltons (Da) molecular weight, although the amounts of glycerin, KOH catalyst, and propylene oxide (PO) used per batch, as well as the reaction time and PO addition rate, can be varied to enable separate, campaigned production of multiple grades of polyether polyol products in the same equipment (after cleaning between batches).
We next describe the use of a special catalyst to produce polyether polyols in a continuous process, and present the process requirements and economics for operating a continuous polyether polyols plant at the same production capacity as the aforementioned batch plant. Two versions of a process using double metal cyanide (DMC) catalysis are developed and evaluated—one making a 3,000 Da MW polymer and the other making a 707 Da MW polymer. The 707 Da polymer is used as a starter for the larger polyol and is similar to a polyol sold by Covestro.
Shell, BASF, and Covestro may opt to use this innovative technology to offer long-chain polyether polyols to the flexible slabstock polyurethanes product market, and one product of this type is selected herein for detailed economic analysis.
Polyester polyols for polyurethanes are prepared by the condensation reaction between glycols—such as ethylene glycols, propylene glycols, 1,4 butanediol, or 1,6 hexane diol—and a dicarboxylic acid. Polyesters are a class of polymers that allows for enormous variation of structural and property design.
Hundreds of polyesters exist due to combinations of diols and diacids, although only about a dozen are of commercial significance. Although the process of combining polyacids and polyalcohols to form polyesters is generically similar in every case, the individual monomers may be obtained from vastly different building blocks and sources. Each building block may be obtained by multiple routes, each having its own pros, cons, and economic sensitivities.
In this report, we develop the design and cost for construction of a partly batch, partly continuous multiproduct polyester polyether polyol plant that campaigns production of polyether polyol-based products in a single-train facility. In contrast to polyether manufacturers, which are generally backintegrated into the building blocks (ethylene oxide, propylene oxide, and tetrahydrofuran), polyester polyol manufacturers purchase building blocks from several sources, and may qualify multiple sources as primary suppliers using contracts and futures strategies. This also results in polyester manufacturers being “middleman” manufacturers and primarily suppliers to other businesses.
The three largest manufacturers of polyesters in the world are Stepan Corporation, CIOM Corporation, and Huafeng Group. BASF is also a major chemical manufacturer and has extensive back-integration into polyester building blocks and forward-integration into products that use polyester polyols. BASF produces only about one-sixth the volume of either of the two largest polyester polyol producers
Relative regional consumption of polyester polyols to polyether polyols ranges from 1:1 to 2:1. Polyester polyols based on esters are primarily consumed in production of rigid polyurethane foams. Major global producers of polyester polyols include Stepan, Invista, Covestro, BASF, CIOM, Huada Chemical Group, Hyafeng Group Co., Xuchuan Chemical Co., and Stepan (Nanjing) Chemical Co. China is the largest consumer of polyester polyols in the world, and most Chinese production is used to fulfill domestic consumption.
The three broad technologies described above and some other technologies for production of polyether polyols and polyester polyols are reviewed herein, with a bibliography and abstracts for the most relevant patents over the past few decades. The industry status of polyether polyols is also described. Three representative processes for production of polyether polyols using semicontinuous, continuous, and a combination of batch and continuous process technologies are described and compared in terms of technical features, process design, and process economics. Economics are also presented for a fourth process, which makes a lower-MW, 707 Da, commercial polyol using the DMC catalyst technology.
The iPEP Navigator polyether polyols tool is attached to the electronic version of this report. The iPEP Navigator interactive module provides an economic snapshot for each process, allowing the user to select and compare the processes, units, and regions of interest.