Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1999-11-23
2001-04-24
Trinh, Ba K. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S516000
Reexamination Certificate
active
06222054
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a novolak-type epoxy resin used for a encapsulating material and the like in the electric and electronic industries.
2. Description of the Related Art
In normal production of an o-cresol novolak-type epoxy resin, first, o-cresol is reacted with formalin to obtain an o-cresol novolak resin as an intermediate material. Then, the o-cresol novolak resin is fed into an epoxidation reactor together with epichlorohydrin and, if necessary, a solvent also, to allow for epoxidation. One of major factors for determining the properties or quality of the thus-produced epoxy resin is the molecular structure, in particular, skeleton structure of the novolak resin.
Whether or not a novolak resin has a desired molecular structure is normally determined by measuring the softening point of the resin. In other words, a novolak resin having a specific softening point is used for epoxidation so that an epoxy resin having a desired molecular structure or desired properties such as softening point, etc., can be produced.
Therefore, in order to produce an epoxy resin suitable for a desired usage, it is required to prepare a novolak resin having a predetermined softening point.
In a conventional production process of a novolak resin, a novolak resin produced in a reactor is once solidified by cooling into flakes to avoid possible quality degradation and the like. The resin flakes are stored in an appropriate container so that a required amount of the resin can be fed into a reactor when an epoxy resin is to be produced.
The above process has following problems. The operations of putting the novolak resin in a container and taking a predetermined amount of the resin out from the container to feed it into a reactor are mostly performed manually. Dust of the novolak resin generated during these operations may worsen the working environment.
Another problem is that the resultant epoxy resin is colored. In particular, when the novolak resin is stored at higher temperature than normal temperature as in summer, it may degrade by oxidation, causing quality degradation of the resultant epoxy resin such as significant coloring, an increase in epoxy equivalent weight, and a change in softening point.
The inventors have intensively studied for solving the above problems and found that the novolak resin can be prevented from quality degradation by storing it in a molten state in an inert gas atmosphere, and that this storage in a molten state allows for in-line handling of the resin, improving operability and the working environment.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method for producing an epoxy resin where no manual operation is necessary in handling a novolak resin, no dust is generated, and the quality of the epoxy resin is stabilized.
Another object of the present invention is to provide a method for producing an epoxy resin capable of easily producing an epoxy resin having desired properties.
The present invention provides the method for producing an epoxy resin comprising the steps of: reacting at least one phenol compound with at least one aldehyde compound to obtain a novolak resin; storing the novolak resin in a molten state in an inert gas atmosphere; feeding the stored novolak resin into an epoxidation reactor; and reacting the novolak resin with an epihalohydrin compound.
The present invention also provides the method for producing an epoxy resin comprising the steps of: reacting separately at least one phenol compound with at least one aldehyde compound to obtain separately at least two novolak resins having different softening points; storing separately at least two novolak resins in the molten state in an inert gas atmosphere; feeding at least two stored novolak resins into an epoxidation reactor and mixing thereof; and reacting the mixed novolak resins with an epihalohydrin compound.
According to the method of the present invention, the novolak resin as an intermediate material is stored in a molten state in an inert gas atmosphere, without once being moved outside of vessels as solid flakes as in the conventional case, to allow for in-line feeding for epoxidation. This eliminates the necessity of manual operations such as transportation and feeding of the novolak resin, prevents generation of dust, and suppresses quality degradation of the epoxy resin caused by the novolak resin being exposed to the air in a high-temperature environment.
According to the present invention, it is preferable to store the plural novolak resins having different softening points separately in a molten state in an inert gas atmosphere. Further, the plural novolak resins having different softening points may be mixed, to react the mixture with an epihalohydrin compound for epoxidation.
This makes it possible to easily respond to production of various kinds of epoxy resins which are different in properties such as the softening point.
The reason why the softening point is used for separating a kind of novolak resin from another is that the softening point can be an index for the molecular structure of the novolak resin such as the molecular weight and the molecular weight distribution as previously described. Besides the softening point, other properties which can be such an index, such as the viscosity and the melting point, may also be used.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the step of reacting at least one phenol compound with at least one aldehyde compound to obtain a novolak resin, at least one phenol compound and an acid catalyst are fed into a reactor, and at least one aldehyde compound is added dropwise while heating to a predetermined temperature and stirring, for polymerization.
After the reaction is completed, the resultant solution is subjected to neutralization and other processing such as separation of an aqueous solution, and heated under atmospheric pressure or reduced pressure removing water and unreacted substances to obtain a novolak resin.
Examples of the phenol compound include phenol, o-cresol, m-cresol, p-cresol, resorcinol, brominated phenol, brominated cresol, brominated resorcinol, naphthol and the like.
Examples of the acid catalyst include p-toluene sulfonic acid, oxalic acid, sulfuric acid, hydrochloric acid and the like.
Examples of the aldehyde compound include formaldehyde, acetaldehyde, butyraldehyde, benzaldehyde and the like.
The degree of polymerization of the resultant novolak resin is normally 2 to about 20. The molecular structure [skeleton structure expressed with the average molecular weight (degree of condensation polymerization), the molecular weight distribution, the bonding form and the like] of the novolak resin can be controlled by adjusting the reaction conditions such as the molar ratio of at least one aldehyde compound to at least one phenol compound fed into the reactor, the drop rate of at least one aldehyde compound, the reaction time, the reaction temperature, and the amount of catalyst. The molar ratio of at least one aldehyde compound to at least one phenol compound is normally selected in the range of about 0.4 to 0.9.
In general, the softening point is used as an index for the molecular structure of the novolak resin. By adjusting the production conditions described above, various kinds of novolak resins having softening points normally in the range of room temperature to about 200° C. can be produced.
The resultant novolak resin is stored as it is in the same reactor or in a separate storage vessel in a molt
Morimoto Takashi
Sakamoto Hideshi
Takahashi Masakazu
Sughrue Mion Zinn Macpeak & Seas, PLLC
Sumitomo Chemical Company Limited
Trinh Ba K.
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