Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-09-16
2001-07-17
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S480000, C525S509000, C528S089000, C528S093000, C528S102000, C528S112000
Reexamination Certificate
active
06262189
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the preparation of an advanced resin.
BACKGROUND OF THE INVENTION
Epoxy resins are well known in the art. In combination with a suitable curing agent, they result in thermosetting products showing superior toughness, chemical resistance, heat resistance, adhesion and electrical properties.
The most common types of epoxy resins are those which are based on bisphenol-A and which contain 1,2-epoxy groups. These compounds can be made by reaction of bisphenol-A with epichlorohydrin. The reaction is often carried out in such a way that liquid reaction products are obtained, but higher molecular weight semi-solid and solid products are also produced in this way. Another process to produce higher molecular weight semi-solid and solid resinous polyepoxides is a process known as “upgrading” or “advancement”. In such an upgrading or advancement process, usually an initially liquid resinous polyepoxide is reacted with a dihydric phenol in the presence of a catalyst until the required amount of the dihydric phenol is incorporated in the epoxy chain to increase the molecular weight to the desired level.
It will be appreciated that said upgrading or advancement process as described hereinbefore with reference to dihydric phenol, can also be carried out using carboxyl compound or other hydroxyl compounds.
Such upgrading processes have been described in the past both on a batch basis and on a continuous basis, see e.g. U.S. Pat. Nos. 3,547,881, 3,919,169 and 4,105,634. In such known batch and continuous processes, the dihydric phenol and liquid epoxy resin are mixed together at a relatively low temperature and then heated up to the reaction temperature and held at elevated temperature for the time sufficient to produce the resinous epoxy compound of the higher molecular weight. The catalyst is usually added either to the starting reaction mixture at the relatively low temperature or after heating of the reacting mixture to the reaction temperature.
In such known batch and continuous upgrading processes, however, cycle times, including dumping, are typically relatively lengthy. For example, batch processes involving bisphenol-A and a liquid polyepoxide consisting essentially of the diglycidyl ether of bisphenol-A can take from 4 to 20 hours for the reaction to be completed. Further, the homogeneity of temperature in a large kettle reactor is complicated by heat transfer, i.e. the heat of reaction is more difficult to control and localized high heats will cause adverse reactions to occur, e.g. crosslinking and/or gelling. Furthermore, the reaction may continue during dumping when the conditions are less controlled, resulting in different conditions for different batches and thus in different product properties for each batch. The continuous process using a pipe reactor described in U.S. Pat. No. 3,919,169 involves a shorter reaction time in the order of about two hours, but in a continuous process it would be highly advantageous if the reaction time could be significantly lower. Also, due to the flow profile in a pipe, the use of pipe reactors often results in a rather broad molecular weight distribution and in a fouling of the reactor wall, ultimately resulting in a thick layer of deposited material which needs regular cleaning.
In addition to economies of time, long reaction times can lead to a relatively wide molecular weight distribution which may in their turn lead to end use disadvantages. For example, surface coating imperfections due to gel particles (MEK-insolubles, MEK is methyl ethyl ketone) have been observed when molecular weight distribution and concomitant viscosity characteristics are not properly controlled.
Another possibility to produce advanced epoxy resin is the use of an extruder process. However, there are numerous disadvantages to such a process. The investment costs are relatively high, the more because high performance extruders are needed (to avoid any stagnant zones). Further, a relatively high effort is needed to operate the extruder, maintenance is cumbersome and the product quality is not optimal, especially due to gel formation (gel particles which do not dissolve in MEK). These gel particles may result in a low quality cured product. Another disadvantage is the relatively short residence time in an extruder (typically up to five minutes). This short residence time results in the need to use relatively high catalyst concentration to complete the reaction, as illustrated in U.S. Pat. No. 4,612,156.
In addition it is observed that, depending on the intended use of the advanced resin, in some cases the upgrading process is preferably carried out in the absence of a solvent in order to avoid solvent stripping and vacuum devolatilization since even then the final product contains significant amounts of undesirable solvents. These residual solvents may cause numerous problems when the product is fabricated into a usable product, such as films, by coextrusion or moulding. The residual solvents require extensive vacuum drying to prevent voids in the film and moulded articles. The hazard of solvents being released from a product during fabrication could cause a problem unless proper venting is employed. Solvents may have an adverse effect on polymer properties such as stability, colour, haze etc.
It will be appreciated that depending on the relative amounts of epoxy compound and the compound having at least one hydroxyl compound or carboxyl compound, the end product is epoxy compound or a hydroxyl or carboxyl compound. The above described problems, however, hold for all end products.
SUMMARY OF THE INVENTION
The process of the present invention solves the above described problems. Short reaction times are sufficient (reaction times are usually in the order of up to 1 hour at most), relatively low capital requirements are necessary and a constant product consistency is obtained. Operational costs are low when compared with the known processes. These advantages are obtained by mixing the reactants, transferring the mixture to a moving surface at a suitable temperature to form a reacting layer and allowing the components to react on the moving surface. Optionally further heating and/or cooling may be applied to the reaction mixture on the moving surface to create the desired temperature profile. It will be appreciated that an ideal plug flow is obtained in this way, resulting in the high product quality.
Thus, the present invention relates to a process for the preparation of an advanced resin by reaction of a compound having on average more than one epoxy group per molecule and a compound having on average at least one hydroxyl group or carboxyl group per molecule, in the presence of a catalyst at elevated temperature, the process comprising (1) mixing the epoxy compound with the compound having at least one hydroxyl compound or carboxyl compound and the catalyst, and (2) transferring the mixture as a feedstream to a surface which is at least intermittently moving with respect to the feedstream.
DETAILED DESCRIPTION OF THE INVENTION
It will be clear that the above described process has numerous advantages over the prior art processes. The process is a continuous process using short reaction times only. The necessary equipment is relatively cheap. No back mixing is possible. No continuous fouling of the equipment occurs. High quality advanced resin can be made of equally consistent quality.
It will be appreciated that reaction between components to be transferred on moving surface may alternatively have partially taken place. However, according to preferred embodiments, substantial reaction between the components before transferring to the moving surface, is avoided.
In the above process the mixing of the epoxy compound and the hydroxyl compound (preferably phenolic compound) or carboxyl compound is preferably carried out as a continuous process. The two components are preferably mixed as liquid components. Mixing may be carried out by methods well known in the art, e.g. in one or more simple mixing chamber
Beerepoot Johannes Petrus JozeF
Blom Johannes Jozias
De Jong Feike
Raas Paulus Egidius
Sjardijn Willem
Sellers Robert E. L.
Shell Oil Company
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