Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Ethylenically unsaturated reactant admixed with either...
Reexamination Certificate
2002-05-22
2003-02-04
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Ethylenically unsaturated reactant admixed with either...
C528S271000, C528S298000, C528S306000, C528S392000, C525S445000
Reexamination Certificate
active
06515071
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY FUNDED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
The present invention relates to a process of preparing polyester resins. More particularly the invention relates to a method of preparing polyester resins using dicyclopentadiene (DCPD) where the resins have reduced levels of gel particles or which are free of gel particles. DCPD is commonly obtained as a complex mixture of various components derived from a cracking operation. The predominant component of the mixture is the dimer of cyclopentadiene (CPD) dicyclopentadiene. Commercially DCPD is available in a number of grades. Present in most grades are adducts of CPD with isoprene referred to as C-10 co-dimers in addition to other co-dimers and low molecular weight materials. The lower purity grades contain various and increasing amounts of C-15 isomers (trimers) of CPD. The trimer component is important because it is believed that the higher the trimer content the greater the amount of gel particles formed during standard resin processes. Lower grade DCPD can have as much as 2% by weight trimer while typical “polyester grade” DCPD has less than 0.1% trimer content. Trimer content is not the sole cause of gel particle formation. On occasions where lower grade DCPD has been diluted with “polyester grade DCPD to contain less than 0.1% by weight trimer, gel particles can still be a problem.
DCPD modified polyester resins are known. See for example U.S. Pat. Nos. 3,347,806, 4,029,848, 4,148,765 and 4,233,432. Typically, resins are prepared using the higher purity or “polyester grade” DCPD. A general method of preparing DCPD modified polyester resins includes the steps of preparing the half ester by reacting a carboxylic acid or anhydride with polyester grade DCPD in the presence of water. The reaction is normally carried out at atmospheric pressure and a temperature high enough to ensure that the DCPD reacts with the acid or anhydride but is not high enough to cause the DCPD to decompose. The reaction is carried out to a predetermined end point for the half ester formation. This point can be conveniently determined by measuring the acid value of the reaction mixture. Once the predetermined end point of the half ester reaction mixture is reached, multivalent alcohols are added and allowed to react to a predetermined end point. This end point can also be determined by monitoring the acid value. Economically it would be desirable to use the less expensive lower grade DCPD, but the use of the lower grade DCPD tends to yield polyester resin that contain gel particles. Gel particles are undesirable in part because they are a contaminant in the resin and tend to plug spraying equipment and filters. In order to remove the gel particles the resin must be filtered. Although resins may be filtered to remove minor amounts of particulates the presence of gel particles causes increased problems due to filter fouling. The gel particles also represent a reduction in the percent yield of resin in a batch. So while it would be desirable to use low grade DCPD in polyester production the costs associated with dealing with gel particle formation offsets the lower material cost. Efforts have been made to prepare gel particle free polyester resins using low grade DCPD. U.S. Pat. No 4,360,634 discloses polyester resins made using diene oligomers. According to the patent the product can be prepared using standard methods of preparation for DCPD modified polyester resins. The stated advantage of the invention is the use of oligomers of crude DCPD prepared by heating the crude diene under a pressure of from 100 to 200 psig at a temperature of from 150° C. to 200° C. for a period of from 30 minutes to 4 hours prior to adding to the ester reaction. Korean Patent No. 98-026116 discloses a method of preparing DCPD modified polyester resins using low purity DCPD where the formation of gel particles is reduced. The method discloses the reaction of 70% to 80% pure DCPD with multivalent unsaturated acids in the presence of an oxidation preventing reagent and/or a polymerization preventing agent. It is stated that although the half ester method can be used the invention is not limited to any one method. U.S. Pat. No. 5,777,065 discloses a method of making polyester alkyd resins having reduced gel particle content where prior to adding a low purity DCPD, from 10 to 300 ppm of an aromatic inhibitor is added to reaction mixture.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a process for preparing polyester resins free of or substantially free of gel particles even when low purity DCPD is used. The process comprises forming the half ester and then raising the temperature of the half ester reaction mixture to from 165° C. to 220° C. and holding the reaction mixture at the desired temperature for up to 120 minutes while optionally removing volatiles.
The formation of the half ester can be carried out using process parameters typically used in the preparation of DCPD modified esters. In practice it is preferable to perform the half ester reaction step at atmospheric pressure and a maximum temperature of 150° C. After the half ester step is complete but before addition of the multivalent alcohol the half ester reaction mixture is heated to a temperature of 165° C. to 220° C. for up to 120 minutes while optionally removing volatiles. Subsequent to the heating step a multivalent alcohol is added to the reaction mixture. The multivalent alcohol can be added in a single addition step or over time. Preferably the alcohol is added at a rate such that the temperature of the reaction mixture is maintained in the 165° C. to 220° C. range. Most preferably the alcohol is pumped into the reaction mixture at a rate so that the temperature of the reaction mixture is maintained in the desired range. The condensation reaction of the alcohol and half ester is carried out with removal of volatiles. The condensation reaction is carried out to a predetermined acid value generally between 5 and 45. When prepared according to the invention the formation of gel particles is reduced or the gel particles are completely eliminated. No prereaction of the DCPD is needed. No additional oxidation or polymerization preventing agents or inhibitors other than those present in the commercially available raw materials need be added during the preparation of the half ester.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
Not Applicable
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a process of preparing polyester resins preferably using low grade DCPD. The resins prepared according to the process of the invention have reduced levels of gel particles. In a process of the invention where the reactor is sealed during heating prior to addition of the glycols the resin product contains about 10% by weight or less of the amount of gel particles based on the total weight of the undiluted resin, typically produced in resins prepared using low grade DCPD by known methods of preparation. In a preferred version of the process where volatiles are removed during the heating step that is performed after the half ester reaction step and prior to addition of glycols gel particle content is reduced to less than 0.01% by weight in filtration residue based on the total weight of the undiluted resin. In many instances gel particles are not detectable in the filter residue.
In the first step of the process DCPD preferably low grade DCPD and a carboxylic acid having at least two carboxy functional groups or the corresponding anhydride are reacted in the presence of water. From 1% to 100% by weight of the carboxylic acid or corresponding anhydride contain ethylenic unsaturation. The reaction can be carried out at any temperature at which the formation of the half ester proceeds. Generally a temperature between 50° C. and 150° C. is used. A preferred temperature range is from 70° C. to 140° C. In a more preferred embodiment the temperature of the half ester reaction mixture i
Loza Roman
Riley Daniel J.
Acquah Samuel A.
Ashland Inc.
Connaughton Martin
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