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Thursday, July 31, 2008

Bisphenol A Product Yield

The yield of monomeric diglycidyl ether can be increased by conducting the reaction in two stages, the first being the reaction between epichlorohydrin and bisphenol A in the presence of a catalityc amount of a lithium compund to form the chlorohydrin ether, and the second the reaction wherein dehydrochlorination of this is effected, giving a product consisting of up to 87% of the monomeric of this is effected, giving a product consisting of up to 87% of the monomeric diglycidyl ether when using three moles epichlorohydrin per phenolic hydroxyl group.

It will be seen from the molecular structures shown that whereas the pure monomeric diglycidyl ether contains no hydroxyl groups, as the value of n increases the percentage of hydroxyl groups, as the value of n increases the percentage of hydroxyl content, epoxide content, physical state (liquid or solid) is shown in the table below.

These properties are important in considering adhesives use: for example De Bruyne has shown that there is a correlation between hydroxyl concentration and adhesion (as measured by the joint strength of oxide coated aluminum joints), although recognizing the influence of hydroxyl groups on properties that can indirectly affect adhesion, for example, shrinkage.

Mole/ratio of

combined

epichloro-

hydrin to

bisphenol A

Value of

n (2)

Epoxy

Content

(eq/kg)

Hydroxyl

content

(eq/kg)

Viscocity

at 21 oC

Softening point

(ASTM)

2:1

0

5.88

0

Crystalline

solid at R.T

1.95:1

0.05

5.65

not det.

118 P (3)

1.84:1

0.2

5.05

0.86

318 P

1.32:1

2.15

2.10

2.62

70 OC

1.24:1

3.12

1.63

3.09

75 OC

1.16:1

5.44

1.06

3.36

90 OC

Notes:

1. Calculated from n by using the formula: ratio = (n+2)/(n+1)

2. Calculated from the epoxy content by using the formula n = (2000/284.4E) – 340.4/284.4

Where E = epoxy content in eq/kg

(In this calculation the assumption is made that each molecule is terminated by two epoxy group)

3. Determinates on the super cooled liquid.