Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2001-10-09
2003-09-16
Lovering, Richard D. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C525S527000, C525S930000, C528S488000, C528S489000, C528S492000
Reexamination Certificate
active
06620907
ABSTRACT:
FIELD OF INVENTION
This invention relates to a process for the elimination of undesirable materials from epihalohydrin-derived epoxy resins. More particularly, this invention relates to a process for eliminating materials containing hydrolyzable halides and other high molecular weight materials including those containing hydroxyl functionality from epihalohydrin derived epoxy resins.
BACKGROUND
Epihalohydrins are often used as an ingredient to prepare epoxy resins. Particularly useful in the preparation of epoxy resins is epichlorohydrin. For example, a dihydric phenol (or other active-hydrogen containing material) is often reacted with epichlorohydrin in the presence of a catalyst. The resulting products include the desired epoxy, high molecular weight materials including oligomers, residual epichlorohydrin, and other contaminants containing hydrolyzable chloride, etc. The preparation of pure epoxies is desirable. High molecular weight materials, such as, for example, oligomers or materials containing hydroxyl functionality, may interfere with the epoxy's performance.
One use for epihalohydrin-derived epoxies is in the electronics area. Some electronic applications where these epoxies are used include, but are not limited to, conformal coatings, high pressure laminations, castings, die attach adhesives, electrical pottings, encapsulations, and underfills. Hydrolyzable halide is a source of free halide in the presence of moisture. Thus, corrosion caused by a halide is a critical issue in the manufacture of electronic devices. Therefore, elimination of hydrolyzable halides is desirable.
Several methods or processes are known for purifying or isolating epoxies. One of these methods is using one or more separation processes such as stripping or distillation. Another method is reacting an alkali metal hydroxide solution or other solvent-based system and water-washing to remove the free chloride or phenolic salts.
Additionally, various methods or processes are known that reduce the amount of hydrolyzable halide in the epoxy product. For example, many methods have been described for the preparation of resins with low levels of hydrolyzable chloride. (See for example, U.S. Pat. No. 4,485,221). However, most of these methods involve extraction with an aqueous base and require organic solvents, which add expense and decrease process efficiency.
Therefore, the need exists for a process of eliminating hydrolyzable halides and other high molecular weight materials from epihalohydrin-derived epoxies that is safe, environmentally-friendly, versatile, efficient, and solventless.
SUMMARY OF INVENTION
The present invention provides a process for eliminating hydrolyzable halides and high molecular weight materials from epihalohydrin-derived epoxies. This process can be conducted by the epoxy manufacturer, or can be conducted on a commercially sold epoxy to reduce the level of or to eliminate hydrolyzable halide and high molecular weight materials present. The present invention comprises a process for eliminating hydrolyzable halides and high molecular weight materials from epihalohydrin-derived epoxy resins comprising the steps of: a) reacting an epoxy resin comprising materials containing hydrolyzable halides with a base wherein said base is present in a quantity that exceeds the molar equivalent based on the materials containing hydrolyzable halide; b) heating the mixture while agitating; c) neutralizing said heated mixture with carbon dioxide to form a crude product; and d) distilling said crude product using molecular distillation to yield a product.
Another embodiment of the present invention is a process for eliminating hydrolyzable halides and high molecular weight materials from epihalohydrin-derived epoxy resins comprising the steps of: a) distilling an epoxy resin comprising materials containing hydrolyzable halide using molecular distillation to yield an epoxy distillate; and b) reacting said epoxy distillate with a base wherein said base is present in a quantity that exceeds the molar equivalent based on the materials containing hydrolyzable halide.
Another embodiment of the present invention is an epoxy product formed using said contaminant elimination process. The epoxy product formed advantageously has low hydrolyzable halide content. Additionally, the epoxy product can have an epoxide equivalent weight at or near the theoretical value.
Yet another embodiment of the present invention is an epoxy derived from epihalohydrin that has low hydrolyzable halide content and that does not contain high molecular weight material.
The process of the present invention is solvent-free, relatively inexpensive, versatile, and environmentally-friendly. Moreover, the process of the present invention can be carried out using standard manufacturing equipment and in high volume.
The process of the present invention can be done in batch or as a continuous process.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The present invention provides a process for eliminating undesirable materials from epoxy resins that are derived from epihalohydrin. These undesirable materials or by-products are defined herein as including materials comprising hydrolyzable halides (such as, for example, hydrolyzable chloride, hydrolyzable bromide, or hydrolyzable iodide) and in some epoxy resins high molecular weight materials. Hydrolyzable halides are halide releasing materials. High molecular weight materials are defined herein as dimers and other materials having a molecular weight greater than the dimer. These high molecular weight materials can be oligomers that can contain hydroxyl groups. Other high molecular weight materials include, but are not limited to, reaction by-products, polymerized epoxies, phenolic salts, etc., and mixtures thereof. Examples of some high molecular weight materials that may be eliminated from some epoxy resins include, but are not limited to:
The process of the present invention has many advantages. For example, this process is a relatively inexpensive procedure for preparing epoxy resins that contain low levels (i.e., preferably 0.1 ppm to 100 ppm, more preferably less than 10 ppm, and most preferably less than 1 ppm) of hydrolyzable halide.
The epoxies of the present invention have an epoxide equivalent weight at or near the theoretical value expected for the specific monomer. Prior to the present invention, low molecular weight halide epoxies such as EPON™ Resin 828 (and its high purity version EPON™ Resin 825), available from Shell Chemical Company, Houston, Tex., is disclosed as having an epoxide equivalent weight of 185-192 (175-180 for EPON™ Resin 825) whereas the theoretical epoxide equivalent weight is 170. (See Shell Resins, SC:235-96.828, October 1996 and Technical Bulletin, Shell Chemical Company SC:235-88.825 January 1992). Whereas, using the present invention, starting with EPON™ Resin 828, an epoxide equivalent weight of 170 is obtained. The method used to obtain the epoxide equivalent weight is set forth in Example 1.
Additionally, the process is non-extractive and thus can be and is solventless. The process is run at 100 percent solids with only a small amount of base being added. Thus, the process is more environmentally-friendly than processes requiring solvents. There are no residual solvents in the epoxy product and therefore no outgassing. Further, this process is a non-solvent and chemical reagent waste generating process. If the high molecular weight materials that are eliminated are used, then the process of the present invention can be non-waste generating.
The process of the present invention is versatile. To purify different epoxy resins, one only needs to change the base in light of the starting epoxy resin. Therefore, the equipment, etc., can remain the same that helps to reduce cost. Further, the required equipment is readily available in the chemical industry.
The process advantageously eliminates oligomers and other high molecular weight materials including those high molecular weight materials containing hydroxyl groups that may not be desirable. Sid
3M Innovative Properties Company
Fagan Lisa M.
Lovering Richard D.
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