Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Ion implantation of dopant into semiconductor region
Reexamination Certificate
2002-03-04
2004-04-06
Lovering, Richard D. (Department: 1712)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Ion implantation of dopant into semiconductor region
C252S182240, C252S182250, C427S411000, C528S155000, C568S724000
Reexamination Certificate
active
06716729
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of manufacturing a stable solution containing bisphenolic stillbottoms. This invention also relates to phenolic compositions that are manufactured using solutions of bisphenolic stillbottoms. This invention further relates to phenolic compositions that are useful in the manufacture of laminates and paper products.
BACKGROUND OF THE INVENTION
Bisphenol A stillbottoms, as one example of bisphenolic stillbottoms known in the art, are produced by dehydrocondensing phenol and acetone in the presence of a strong acid catalyst. When bisphenol A is separated from the reaction mixture by distillation, for example, or by other purification methods, there is a material remaining that has been generally described in the art as a bisphenol stillbottom. Consistent with the use of the term in the art, hereinafter, the term bisphenol stillbottoms refers to that material separated during the preparation of bisphenol that is not purified bisphenol. Thus, bisphenol A stillbottoms may contain some bisphenol A. The bisphenol A stillbottom typically contains, in predominant proportions, other phenol-acetone reaction products. Dihydroxydiphenylpropane isomers and chromane compounds are typically present in lesser amounts.
The reuse of bisphenolic stillbottoms is generally quite limited. Bisphenolic stillbottoms are a solid at room temperature and typically must be kept in a molten state, or processed into a small particle such as a flake or powder, if the stillbottoms are to be further used in most manufacturing processes. Molten stillbottoms are subject to degrading oxidation Therefore, the chemical composition of the stillbottoms will change as function of the length of storage time in the molten state. As a result of this changing chemical composition, products made using molten stillbottoms may have unpredictable properties. The processing of stillbottoms into an intermediate form, such as a flake or powder, adds significant cost to products made using this intermediate form and a flake or powder may sinter. Therefore, typically, bisphenolic stillbottoms are incinerated for disposal.
The use of bisphenolic stillbottoms in phenolic resin compositions has until now been limited. Not surprisingly, because phenolic resins are typically condensed from aqueous solutions, the insolubility of bisphenoic stillbottoms generally makes their use prone to problems. In one prior art process, for example, bisphenol A stillbottoms must be further refined before they are useable in the synthesis of a novolac resin. In this process, bisphenol A stillbottom are further processed, at extreme temperatures, reduced pressures and in the presence of an alkaline catalyst, to recover phenol and isopropenyl phenol. A residue remains after such processing and this residue is said to be useful in the manufacture of novolac resins.
The use of bisphenols in phenolic resin synthesis in the prior art is surprisingly limited. As described above with respect to bisphenol stillbottoms, the relative insolubility of bisphenolic compounds generally makes their use prone to problems. For example, in one prior art composition, alkylidenepolyphenols, together with a trifunctional phenol and formaldehyde, are used in the synthesis of resoles. However, as the prior art provides, the timing of the addition of the alkylidenepolyphenol is critical. The alkylidenepolyphenol can be added neither at the start of the synthesis nor near the end of the synthesis, but must be added at some mid-point in the reaction sequence. One prior art process describes a resin that is the reaction of product of formaldehyde and bisphenol A. However, as the prior art teaches, it is essential to maintain a very narrow mole ratio of formaldehyde to bisphenol A. Resins of this type have limited application as leveling compounds or metal coating compounds.
The preparation of aqueous solutions of bisphenolic stillbottoms, let alone the use of these aqueous solutions in the manufacture of resins, until now has been unknown in the art. It has been generally concluded in the prior art that bisphenolic stillbottoms do not form stable aqueous solutions. It has been taught in the prior art that bisphenol A, for example, forms a two-phase system with hot water. It is known that molten bisphenol A forms a two-phase system with water at temperatures even as high as 85° C. to 100° C. In fact, it has long been known in the art that water washing of phenolic mixtures is one means to recover a relatively pure phenol product. The water will dissolve inorganic salts and acid impurities, while the phenolic product readily separates from the aqueous solution.
The development of methods that would allow reuse of bisphenolic stillbottoms have understandably been the object of few prior art attempts. One prior art process provides an aqueous suspension of ultrafine bisphenol particles. Strongly alkaline compounds are used in the preparation of such a suspension. This suspension is used in the preparation of polycarbonates. Yet another prior art process uses strongly alkaline compounds, such as sodium hydroxide, to provide for the dissolution of bisphenol A in hot water. In this prior art process, purified bisphenol A may be recovered from a bisphenolic mixture. Fractions of the bisphenolic mixture will dissolve in the hot water in increasing amounts as the amount of sodium hydroxide is increased. Purified insoluble bisphenol A is recovered by separation from the liquid portion that contains the soluble fractions. Still another prior art process employs a co-solvent, such as an alcohol, to provide for the dissolution of diphenols in water. In this prior art process bisphenol A is said to dissolve in a water/alcohol solution that has been heated to reflux. This process is said to be useful in the purification of bisphenol A.
Each of the prior art processes has disadvantages. A heterogeneous two-phase system of bisphenolic stillbottoms and water is an impractical composition both for the storage of bisphenolic stillbottoms and the use of the stillbottoms in the synthesis of resins. Likewise, the use of strongly alkaline materials or co-solvents adulterates the bisphenolic stillbottoms thus limiting the further use of the modified stillbottoms. The use of molten bisphenolic stillbottoms can result in degradation of the bisphenolic stillbottoms thus affecting the properties of resins made using such stillbottoms. Pre-processing the bisphenolic stillbottoms into a flake or powder is costly. Furthermore, flakes or powders must be re-dissolved during the synthesis of a resin in order for the flake or resin to participate in the synthesis. The re-dissolution presents yet an additional energy requirement. Purification of the bisphenolic stillbottoms to another form is an energy intensive process that changes the chemical composition of the bisphenolic stillbottoms, thus further limiting the utility of the modified form.
It would therefore be advantageous to have a stable aqueous solution of bisphenolic stillbottoms thus obviating the need to store bisphenolic stillbottoms in a molten state or to further process bisphenolic stillbottoms into a flake or powder form. It would also be an advantage to have a phenolic resin composition that included in the manufacture of the phenolic resin the use of a stable aqueous solution of bisphenolic stillbottoms. It would be a further advantage to have a process for using bisphenolic stillbottoms in the synthesis of phenolic resins that did not require refinement of the bisphenolic stillbottoms into another chemical form.
The preparation of laminates and resin-impregnated papers using phenolic resins is also known in the art. The resins used in such preparations range from low molecular weight resins having a high tolerance for water to high molecular weight resins having a low tolerance for water.
The preparation of laminates and resin saturated papers using phenolic resins based on the prior art has attendant disadvantages. Low molecular weight resins are typically prepared by using a high phenol to f
Arbuckle Stephen Wayne
Juras, Jr. John George
Malhotra Vinay
Borden Chemical, Inc.
Cantor & Colburn LLP
Lovering Richard D.
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