A process for preparing monomers

Abstract: A process for preparing monomers useful in a wide range of polymers is disclosed.

Description: This invention relates to a process for preparing synthetic wax monomers, in particular to a process suitable for preparing monomers useful in a wide range of polymers. High molecular weight (C 20 -C 300 ) alcohols are known as synthetic wax alcohols, and have been in commercial production for several years. Whereas synthetic wax alcohols have limited use in candle wax, synthetic wax monomers are quite useful in a wide range of polymers. The use of synthetic wax alcohols would increase significantly if there was a process to convert them into synthetic wax monomers. There is an ongoing need for a process for preparing synthetic wax monomers from synthetic wax alcohols. Japanese Patent Application J 6-329720 discloses polyethylene macromonomers with a (meth)acryloyl terminal group and a method for preparation of these monomers. According to the disclosed method, a polyethylene derivative is reacted with specific carbonyl compounds, or is oxidized with oxygen to produce polyethylene alkoxide, and subsequently reacted with (meth)acrylic acid halide to yield the desired product. Another method known in the art is the use of transesterification to produce short chain acrylate esters. This method has routinely been performed utilizing catalysts selected from Group IVA elements such as, for example Sn, Ge, and Pb; Group IVB elements such as, for example, Ti and Hf; Group VA elements such as, for example, As and Sb; and Group VIII element Fe, see for example U.S. Pat. No. 5,037,948. These catalysts require relatively high use levels to be effective, and can be difficult to remove from the final product. Strong acids such as, for example, methane sulfonic acid and strong alkalies such as, for example, lithium hydroxide are also known to catalyze transesterifications. These catalysts also are undesirable because of their corrosive nature. If not removed from the product, these catalysts may interfere with subsequent polymerizations and end uses. Removal of the catalyst from the product is also difficult. FR-A-2602229 discloses a transesterification process using a catalyst which is a chelate of zirconium in which at least one chelating group is a (poly)glycol ether, one or two chelating groups are acetylacetonate groups and the other chelating groups are alkoxy groups. DE-A-2805702 discloses the use of zirconium acetylacetonate as a transesterification catalyst in relation to the reaction of certain alcohols and e.g. methyl methacrylate. The alcohols are generally described as containing 3 to 20 carbon atoms but steric alcohol (C18) is the highest listed and, in the Examples using only a zirconium catalyst (Examples 1- 6), lauryl alcohol contains the largest number of carbon atoms. Despite the disclosure of the prior art, there is a continuing need for a process for preparing synthetic wax monomers from synthetic wax alcohols. We have surprisingly found that certain zirconium compounds are extremely effective at catalyzing the transesterification reactions which produce synthetic wax monomers from synthetic wax alcohols. Very low levels of zirconium compounds can be used effectively. An advantage of the present invention is that the zirconium compound does not need to be removed from the final product, due to its low usage level and benign character in downstream applications. The present invention provides a process for preparing synthetic wax monomers comprising: admixing 1) a synthetic wax acohol, 2) a (meth)acrylate ester selected from the group consisting of methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, n-butyl(meth)acrylate, isopropyl methacrylate, isobutyl methacrylate, and t-butyl methacrylate, 3) a zirconium compound selected from zirconium butoxide, zirconium tert-butoxide, zirconium chloride, zirconium citrate ammonium complex, zirconium ethoxide, zirconium fluoride, zirconium hydride, zirconium isopropoxide isopropanol complex, zirconium oxide, zirconium propoxide, zirconium sulfate hydrate, zirconium tetrachloride, and zirconium silicate, and 4) an inhibitor selected from the group consisting of nitroxyl radical containing compounds, hydroquinone, methoxy hydroquinone, phenothiazine, and copper compounds heating the mixture to 100-165 degrees C. to provide the synthetic wax monomer; and removing the lower alcohol formed from the reaction of the synthetic wax alcohol and the (meth)acrylate ester from the synthetic wax alcohol and the methacrylate ester. The lower alcohol formed from reaction of the synthetic wax alcohol and the (meth)acrylate ester may be removed by fractional distillation. The excess (meth)acrylate ester may be stripped from the product. Synthetic wax alcohols are commercially available as Unilin™ or Unithox™ products sold through Petrolite Inc. Suitable synthetic wax alcohols for use in this invention include (C 20 - C 50 ) linear alcohols and ethoxylates thereof. (Meth)acrylate esters are commercially available from Rohm and Haas Company. The (meth)acrylate esters used in this invention are methyl acrylate, ethyl acrylate, propyl acrylate, and n-butyl acrylate; and methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, and t-butyl methacrylate. Typically, the (meth)acrylate ester and synthetic wax alcohol are reacted on a molar basis of from 2 (meth)acrylate ester to 1 synthetic wax alcohol to 10 (meth)acrylate ester to 1 synthetic wax alcohol. More preferred is a ratio of from 3 (meth)acrylate ester to 1 synthetic wax alcohol to 9 (meth)acrylate ester to 1 synthetic wax alcohol. Most preferred is a ratio of from 4 (meth)acrylate ester to 1 synthetic wax alcohol to 8 (meth)acrylate ester to 1 synthetic wax alcohol. Zirconium compounds are commercially available through Aldrich Chemical Company. Zirconium compounds used in this invention are zirconium butoxide, zirconium tert-butoxide, zirconium chloride, zirconium citrate ammonium complex, zirconium ethoxide, zirconium fluoride, zirconium hydride, zirconium isopropoxide isopropanol complex, zirconium oxide, zirconium propoxide, zirconium sulfate hydrate, zirconium tetrachloride, and zirconium silicate. Zirconium acetylacetonate is preferred. The zirconium compound may be added at from 0.1% to 10% based on the moles of synthetic wax alcohol. More preferred is from 0.5% to 7.5% zirconium compound based on the moles of synthetic wax alcohol. Most preferred is from 1% to 4% zirconium compound based on the moles of synthetic wax alcohol. Inhibitors used in this invention are nitroxyl radical containing compounds, hydroquinone, methoxy hydroquinone, phenothiazine, and copper compounds. The inhibitors are commercially available through Aldrich Chemical Company. Suitable copper compounds include cupric acetate, cupric bromide, cupric chloride, cupric 2-ethylhexanoate, cupric fluoride, cupric gluconate, cupric nitrate, cupric methoxide, cupric sulfate, and cupric dibutyl dithio carbamate. Cupric dibutyl dithio carbamate is preferred. Suitable nitroxyl radical containing compounds include 2,2,6,6-tetramethyl-1-piperidinyloxy, free radical ("4-hydroxy-TEMPO"), 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy, free radical ("4-oxo-TEMPO"), and di-tertiary butyl nitroxyl (DtBN)(available through Nova Molecular Technologies, Lake Geneva, Wisconsin). The inhibitor may be added at from 100 ppm to 4,000 ppm based on the total weight of the synthetic wax alcohol and (meth)acrylate ester to be reacted. More preferred is from 500 ppm to 3,000 ppm inhibitor based on the total weight of the synthetic wax alcohol and (meth)acrylate ester to be reacted. Most preferred is from 1,000 ppm to 2,000 ppm inhibitor based on the total weight of the synthetic wax alcohol and (meth)acrylate ester to be reacted. The following examples are intended to illustrate the process for making synthetic wax monomers from synthetic wax alcohols wherein a catalyst from the prior art is used. All percentages are on a weight basis. Abbreviations used are: g = grams, mm = millimeters, l = liter, % = percent, N 2 = nitrogen, O 2 = oxygen, n = normal, and °C = degrees Centigrade. Example 1 - Acrylate Of C 40 Alcohol (comparative) A 5 l flask equipped with an overhead stirrer, a 10 plate - 2 inch Oldershaw column, a thermocouple and controller,a graduated receiver, a magnetically controlled reflux head, and an 8% O 2 /92% N 2 sparge at 19.5 cubic centimeters per minute was charged with 2,000 g of Unilin™ 550 (a primary, linear synthetic wax alcohol). To this was added 1,164 g n-butyl acrylate and 1.4 g 4-hydroxy-TEMPO. While agitating and sparging, the batch was heated to 100°C. When a homogenous solution was obtained, 20.0 g zirconium acetylacetonate was added. The vacuum was increased to 200 mm and the temperature was increased to 120°C - 125°C. The vacuum and temperature were held constant until the vapor temperature reached 97°C. At this point, transesterification was complete. The total time from zirconium acetyl acetonate addition to completion of the reaction was 2.45 hours. The vacuum and temperature were lowered. The column was removed and a straight-lead take-off head was installed. The vacuum was then increased to 25 mm and the temperature was increased to 125°C. The temperature and vacuum were held until distillation stopped. The molten product was dropped out at 125°C. Conversion of the Unilin™ 550 alcohol to the acrylate ester was quantitative as measured by Nuclear Magnetic Resonance ("NMR"). The product contained 0.12% residual butyl acrylate as measured by Gas Chromatography ("GC").

Claims: A process for preparing synthetic wax monomers comprising: admixing 1) a synthetic wax alcohol, 2) a (meth)acrylate ester selected from the group consisting of methyl (meth)acrylate, ethyl(meth)acrylate, propyl (meth)acrylate, n-butyl(meth)acrylate, isopropyl methacrylate, isobutyl methacrylate, and t-butyl methacrylate, 3) a zirconium compound selected from zirconium butoxide, zirconium tert-butoxide, zirconium chloride, zirconium citrate ammonium complex, zirconium ethoxide, zirconium fluoride, zirconium hydride, zirconium isopropoxide isopropanol complex, zirconium oxide, zirconium propoxide, zirconium sulfate hydrate, zirconium tetrachloride, and zirconium silicate, and 4) an inhibitor selected from the group consisting of nitroxyl radical containing compounds, hydroquinone, methoxy hydroquinone, phenothiazine, and copper compounds heating the mixture to 100-165 degrees C. to provide the synthetic wax monomer; and removing the lower alcohol formed from the reaction of the synthetic wax alcohol and the (meth)acrylate ester from the synthetic wax alcohol and the methacrylate ester. The process according to Claim 1 wherein the synthetic wax alcohol is selected from the group consisting of (C 20 - C 50 ) linear alcohols and ethoxylates thereof. The process according to Claim 1 further comprising the additional step of stripping off the excess (meth)acrylate ester.

Inventors: GROSS ANDREW WILLIAM, SCHLAEFER FRANCIS WILLIAM, GROSS, ANDREW WILLIAM, SCHLAEFER, FRANCIS WILLIAM
Applicants: ROHM & HAAS, ROHM AND HAAS COMPANY
Application year: 1997
Main classification: C07C67
IPC codes: B01J31, C08F20, C07C67, C07B61, C07C69