Organic compounds -- part of the class 532-570 series – Organic compounds – Carbonate esters
Reexamination Certificate
1999-11-04
2002-08-13
Chang, Ceila (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbonate esters
Reexamination Certificate
active
06433208
ABSTRACT:
BACKGROUND OF THE INVENTION
Peroxydicarbonates are important for use as free radical producing initiators in the polymerization field, and particularly in the polymerization of ethylenically unsaturated monomers, such as vinyl chloride. Peroxydicarbonates are typically made in large batches and sold in pure form either as neat or diluted products. Polymer producers must store large quantities of the peroxydicarbonates for use in their polymerization processes. Precautions must be taken with the storage and handling of these materials as they are unstable and are sensitive to both thermal and impact shock and can detonate under certain conditions. Complying with all of the safety requirements of handling these materials results in the peroxydicarbonates being very expensive to employ in the manufacture of polymers.
Various solutions to this problem have been proposed in the past. U.S. Pat. No. 4,359,427 proposes a process to continuously produce and purify the peroxydicarbonates on the polymerization site and to store them in a diluted phase until used. Another approach that has been suggested is to produce the peroxydicarbonates in the large polymerization vessel before adding the polymerizable monomer. Making the peroxydicarbonates in a large vessel has resulted in quality problems for the polymer being produced for several reasons. One such reason is that there is not adequate mixing of the small amount of reactants in a large reactor vessel. Without adequate mixing the reaction to form the peroxydicarbonates is inefficient and the yield of peroxydicarbonate produced varies, thus making the polymerization reaction using the peroxydicarbonates initiator(s) vary in reaction time. To make greater volumes, diluents are often used, such as solvents and water. With these diluents there is poor conversion of the reactants resulting in large amounts of undesirable; by-products which are formed and which remain in the large reactor to contaminate the polymer that is ultimately produced in the reactor. Solvent dilution results in solvent being present which must be recovered and contaminates the recovery system for recovering unreacted monomer. Also, by making the peroxydicarbonate in the large polymerization vessel, productivity is lowered because the polymerization vessel is occupied with the peroxydicarbonate synthesis process before each batch of polymer can be produced.
Great Britain Patent 1,484,675 proposes to solve these problems by producing the peroxydicarbonates outside of the polymerization vessel in the presence of a solvent to obtain adequate mixing of the reactants. This method is undesirable because the solvent must be removed or else it becomes a contaminant in the polymerization process and contaminates the polymerization process monomer recovery system.
WO 97/27229 patent application proposes to solve the problem by making the peroxydicarbonates outside of the polymerization reactor in a two-step process and adding a water insoluble liquid dialkyl alkanedicarboxylate . The dialkyl alkane dicarboxylate is a plasticizer for the resulting polymer and is undesirable in rigid applications of the polymer. Also, the two-step process is cumbersome and requires excess equipment.
U.S. Pat. No. 4,359,427, Great Britain patent 1,484,675 and WO 97/27229 all teach that the peroxydicarbonates can be produced by reacting a chloroformate with an alkali metal peroxide.
SUMMARY OF THE INVENTION
It has been unexpectedly found that a peroxydicarbonate initiator can be produced at a polymerization site outside of the polymerization vessel which when used in polymerizing ethylenically unsaturated monomers gives high quality polymers. The process for making the peroxydicarbonate of this invention involves first mixing an alkali metal hydroxide with a peroxide to form an alkali metal peroxide. The alkali metal peroxide is added to a mixture of haloformate, dispersant and water to form the desired peroxydicarbonate. The reaction mixture is homogenized during the reaction to give small droplets of peroxydicarbonates. The resulting peroxydicarbonates do not need to be diluted with solvents or plasticizer nor do they need to be purified. The resulting peroxydicarbonates are produced immediately prior to a polymerization reaction and charged to the polymerization vessel and the polymerization reaction is conducted to give a high quality polymer from the ethylenically unsaturated monomer.
DETAILED DESCRIPTION
Peroxydicarbonates produced by this invention have the general formula:
R and R
1
are different or identical organic radicals having from 2 to 16 carbon atoms, preferably 2 to 10 carbon atoms, and more preferably from 2 to 6 carbon atoms. The most preferred peroxydicarbonates have R and R
1
as identical radicals. Specific examples of R and R
1
are alkyl radicals such as ethyl, n-propyl, isopropyl, n-butyl, isobutyl, secondary butyl, amyl, hexyl or 2-ethylhexyl; alkenyl, aryl, alkylaryl, arylalkyl or cycloakyl radicals, or radicals derived from heterocyclic compounds and, particularly radicals such as benzyl, cyclohexyl, cinnamyl, tetrahydrofuryl, and also their substituted derivatives. The most preferred peroxydicarbonates are diethyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di-isopropyl peroxydicarbonate, di-n-butyl peroxydicarbonate, di(secondary butyl) peroxydicarbonate and di(2-ethyl hexyl) peroxydicarbonate.
The haloformates used to produce the peroxydicarbonates have the general formula:
wherein R
2
is an organic radical containing from 2 to 16 carbon atoms and R
3
is a halogen atom. R
2
is the same organic radical as described above for R and R
1
. R
3
is a halogen, such as chlorine, fluorine, iodine or bromine. Preferably R
3
is chlorine. One or more than one haloformate may be used to produce the peroxydicarbonate.
At least one dispersant is used in the synthesis of the peroxydicarbonate such as hydrolyzed polyvinyl acetates, alkyl and hydroxyalkyl cellulose ethers such as methyl cellulose, hydroxypropyl methyl cellulose, gelatin, polyvinylpyrrolidone, polyoxyethlyene sorbitan monolaurate, polyacrylic acid, and like compounds. The dispersant is preferably selected to be similar to the dispersant used in the polymerization of the ethylenically unsaturated monomer. For polymerizing vinyl chloride monomer, the preferred dispersant is hydrolyzed polyvinyl acetate having a hydrolysis in the range of about 70% to about 90%. The dispersant is preferably added as a water solution. The level of dispersant used should be sufficient to form a water emulsion of the haloformate. This level is normally from about 0.05 to 0.2 gram of dispersant per gram of haloformate, preferably from about 0.075 to about 0.1 gram of dispersant per gram of haloformate. The dispersant is added as a water solution. The solution has from about 1% to about 10% by weight of dispersant in water, preferably from about 3% to about 8% by weight of dispersant in water. Once the reaction to form the peroxydicarbonate is complete, additional dispersant may be added to stabilize the emulsion. Stabilizing the emulsion is particularly important if the peroxydicarbonate is not used shortly after being made.
Water is also used in the synthesis of peroxydicarbonates of this invention. The water is required to disperse the dispersant and other reaction ingredients. Water also assists in removal of the heat resulting from the exothermic reaction. Preferably the water used is demineralized water. The amount of water used is not critical except that the amount necessary to disperse the dispersant and dissolve the alkali metal hydroxide and peroxide must be used. The alkali metal hydroxide and peroxide are used as aqueous solutions and thus provide a portion of the required water. Preferably a minimum amount of water is used to get the required cooling. An excess of water, over that required to disperse the reactants and provide cooling, should be avoided during the reaction so as to give more intimate contact of the reactants. Once the reaction is complete, additional water may be added. Normally the amount of water
Fuerle Richard D.
Oxy Vinyls LP
Small Andrea D.
Yao Joseph D.
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