Process for the manufacture of bisphenol-A

Details Process for the manufacture of bisphenol-A Process for the manufacture of bisphenol-A

1998-12-15

2001-02-06

Jordan, Charles T. (Department: 3641)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

Statutory Invention Registration

active

H0001943

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a novel process for producing bisphenol-A in a fully integrated commercial process. The process comprises five major steps with several optional minor steps. The fully integrated process provides a balance between process economics, environmental performance and product quality.
BACKGROUND OF THE INVENTION
Bisphenol-A has been an extremely useful chemical for many decades. As a difunctional monomer, it has been used in the preparation of numerous polymers. For example bisphenol-A [2,2-bis(4-hydroxyphenyl)-propane] has been utilized in preparing such materials as epoxy resins, polyetherimides, polyarylates and, in particular, polycarbonates. In certain of these polymer systems, particularly the epoxy systems, the purity of the bisphenol-A (hereinafter sometimes referred to as BPA) employed in the polymer reaction need not be that high. Epoxy resins only need BPA of approximately 95% purity. The impurity which is present in the greatest amount in such systems is generally orthopara BPA. However, with other polymer systems, particularly polycarbonates, the purity of the BPA must be substantially higher. Purities of BPA of about 99.50% or higher preferably 99.80 or 99.90% or higher are desirable and in many cases necessary for the preparation of BPA polycarbonates. The need for high purity BPA is particularly critical when it is used as a raw material in the melt process for the manufacture of polycarbonate. Not only is highly pure BPA required for use in this melt process, but also the differing types of impurities can have differing effects on the efficiency of the melt process and the performance characteristics of the polycarbonate made by the melt process. Therefore, there has been substantial attention directed to the preparation and purification of BPA.
The art is replete with references directed to the preparation of BPA. Usually this is done by the condensation of phenol with acetone in the presence of a catalyst system. Generally the catalyst is an acidic catalyst. For many years, one of the particularly useful catalyst systems in the patent art and employed commercially was hydrochloric acid. Although the economics of the process are initially good with respect to the conversion of the reactants to BPA, the maintenance of the apparatus is costly. The hydrochloric acid is extremely corrosive and ordinary metallic reactors and piping must be changed on a frequent basis. Obviously glass lined reactors or certain alloyed metals can be employed, however, these are quite expensive. In later years there seems to be the tendency to use a heterogeneous acidic catalyst system wherein the acidic catalyzation occurs at the catalyst surface and is actually bound to the catalyst. In this manner the “acid” does not flow with the unused reactants and BPA. Such catalyst systems are generally sulfonated polystyrenes which are substantially crosslinked such as the Amberlites and like materials.
After the BPA is prepared, various isolation and purification procedures are known. Many of these appear in the relatively voluminous patent art. Generally phenol is distilled off to a great extent and/or the initial purification by crystallization of a bisphenol-A phenol adduct. Distillation of the bisphenol-A itself can also be employed. The purification of the bisphenol-A phenol adduct can then be further accomplished through the addition of various organic solvents such as toluene or methylene chloride so as to remove the BPA from various impurities. Additionally water and various glycols such as ethylene glycol and glycerin have been used alone or together to separate and thus purify the BPA from its impurities.
SUMMARY OF THE INVENTION
In accordance with this invention, the novel process comprises five major steps to be utilized in a fully integrated commercial process for producing dihydric phenol, preferably Bisphenol-A. The process comprises the steps of (1) formulating of ingredients for reacting to form a product mixture comprising dihydric phenol, (2) reacting the ingredients forming a mixture comprising dihydric phenol, (3) subjecting the mixture to crystallization wherein a solid phase and a liquid phase are formed said solid phase is a crystal adduct of dihydric phenol and phenol, (4) removing phenol from the crystal dihydric phenol and phenol adduct, and (5) fractional melt crystallizing the product of step 4 to obtain highly purified dihydric phenol. Several optional minor steps may also be included in preferred embodiments of the process of this invention. These preferred embodiments additionally comprise some or all of the minor steps comprising (a) dehydrating the liquid phase from the crystallization step, which liquid phase is referred to as the mother liquor, (b) recovering phenol from a waste product of dehydration which is comprised of water and phenol wherein the phenol is recycled to the reaction step, (c) disposing of waste water from step (b) in accordance with environmental requirements and (d) recovering phenol from a purged portion of the dehydrated residue by way of catalytic tar cracking which purged portion comprises BPA, phenol and by-products.


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patent: 3621664 (1971-11-01), Saxer
patent: 4374283 (1983-02-01), Aneja
patent: 4400553 (1983-08-01), Aneja
patent: 5198591 (1993-03-01), Kiedik
patent: 5214073 (1993-05-01), Fukawa
patent: 5243093 (1993-09-01), Kissinger et al.
patent: 5315042 (1994-05-01), Cipullo et al.
patent: 5783733 (1998-07-01), Kissinger
patent: 5786522 (1998-07-01), Cipullo
patent: 246681 (1987-10-01), None

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