Document 6B7LKNXmd4YrjerM5mKKJ5vkm
B.F.QOODRICH CHEMICAL COMPANY DEVELOPMENT CENTER
Project 5038*320d TOP #38
REMOVAL OF VOLATILE MONOMERS FROM GEON *50X3 LATEX IN THE
RODNEY HUNT TURBA-FILM EVAPORATOR
By E. J. Leestn
Completion Date: August 19, 1961*
Issue Date: September <-0,
Distribution Cleveland
C. H. Alexander W. F. Bixby M. W. Larson (12) 3. C. Lord W. D. Parrish E. L. Paulsen *R.D.Scott - A.Vlttone, Jr. R.E.Welch J.R.Coots I'.M.G.Zviclier Jeanne Valentine Avon Lake General Chealcal Plant *O.F.Beckmeyer - R.W.McKay Brecksvllle Research Center M. K. Frederick J. E. Jansen *V. F.. Semon Research Center Library Akron . K. Bean R.N.Rylands - R.S.Reynolds Calvert City W.E.brodine - V.D.Robb
Louisville H. E. Barrett L. G. Crunkleton S. S. Michels
Henry *C. B. Cooper
Niagara Falls *C. A. Balzersen
Avon Lake Development Center
L.F.Arnold - L.A.Bennett
R.R.Bloor - L.H.Conklin
N.G.Duke - C.E.Parks
G. E. Eilbeck R.Y.Garrett - C.H.Kctheiner
'
R.M.Kreager - J.A.TeTas
E. J. Leeson
C. H. Lufter A.L.Schultz - E.G.Schvacgvrie - A.M.IV-.r.i-
G. L. Wheelock
R. J. Wolf
..
Central.Technical Files (3)
Modified Report
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TABLE OP CONTENTS
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MAJOR OBJECTIVE........................................................................... LIMITED OBJECTIVE ....................................................................... CONCLUSIONS .................................................................................... FUTURE COURSE OF ACTION ............ DISCUSSION ......................................................................................
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MAJOR OBJECTIVE
Residual volatile monomers present In Oeon latex products after pclynerlza'lr.: represent 3 potential safety problem. Our present method for reducing the volatile monomer level In latlces In the Production plants consists of blowing tne hot latex from the polymerlzer Into an evacuated stripping vessel. The method Is neither economical or adequate. Problems associated with latex foamlr.ess, vacuum control, and high production schedules have resulted In , situation where Production stores and ships latex products containing C.2 0.5 percent residual volatile monomer. This Is well above what Is believed t. be a safe limit.
In ar. effort to reduce or completely eliminate the possibility of these monomers, vlr.yl chloride and vlr.ylldene chloride, forming a flammable or explosive mixture in the vapor space above the latex, a number of Investigations have been started to evaluate Improved stripping methods.
LIMITED OBJECTIVE
Evaluate the Rodney Hunt Turba-Pila Evaporator' as a method of removing vinyl chloride and vlnylldene chloride from Oeon 4=0X3, a soft, film-forming copolymer {46 vlr.yl chloride - 17 vlnylldene chloride - 37 ethyl hexyl acrylate) latex.
CONCLUSIONS
1. The level of volatile monomers In Oeon 450X3 latex car. be successfully reduced by the Rodney Hunt Turba-Pllm Evapcretor without adversely affecting latex properties.
2. A variety of conditions are suitable for stripping Oeon 450X3 In the
Developwit Center Rodney Hunt (Model #1, with 4 sq.ft, of heat transfer surfed^
3. The bfif&VMults, considering lstex properties and monomer removal, were achieved In a Single pass under the following conditions:
Peed Pate Vacuum Temperature on Jacket
4.0#/Minute 53 MM Kg 4f *C.
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u. Other operating conditions produced the following changes In :.r.e volatile monomer level:
a) Increasing the feed temperature nbove 50*C Improved stripping efficiency slightly. It produced two undesirable side effects * decreased latex pH and increased the outsize particle level.
b) Reducing the vacuum toward 100 MM Hg decreased stripping efficiency, but Increasing It below 50 MM Hg had little Influ ence.
c) Two passes were not necessary to obtain a satisfactory reduction In the residual monomer level.
5. Residual ethyl hexyl acrylate monomer could not be detected.
6. The length of the run was limited by the size of tne product receiver rather than the operation of the Rodney Hunt or the stability of the latex.
7. The feed rate was limited by the physical size of the pilot plant Rodney Hunt and its auxiliary condenser and vacuum system. Nothing was observed that would indicate a satisfactory rur. could not be made In a larger unit properly designed.
FUTURE COURSE OF ACTION
Additional work to remove volatile monomers from Geon <*50X3 In the Rodney Hunt Is not planned by Development. Me would strongly recommend, however, that Avon Lake General Chemical Plant arrange for an extended production run on or.e of Louisville's larger Rodney Hunt units. The Initial trial should be made under the following conditions:
Feed Temperature Vacuum Feed Rate
- 50*C. - 50 MM Hg - Maximum possible under the condlt'.cns abc-e.
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DISCUSSION
Studies at Louisville by 0. D. Schaaf and L. D. Pringle have shown that the? Rodney Hunt Turbs-Flln Evaporator can efficiently remove vinyl chloride monomer from a hsrd, resinous copolymer latex such as Geer. 351. While hard, resinous latices represent the major portion of our latex production, a substantial quan tity of softer, internally plasticized latices are also produced, principally at the Avon Lake Oeneral Chemical Plant.
Removal of monomers from softer, film forming Hycar nitrile latices in tne Rodney Hunt is usually accompanied by a greater increase in the outsize particle level than that observed with the harder Geon resin latices. Consequently, information pertaining to the behavior of the softer Geon latices in the Rodney Hunt was of considerable Importance.
Stripping studies were conducted in the Rodney Hunt unit located in Building 422 at the Development Center. This particular evaporator (Model #1) has four square feet of heat transfer surface. The unit and ita auxiliary equipment was designed primarily to strip small batches of experimental latices made In the pilot plant. It does not lend Itself well to continuous operation. This type of operation is possible, however, with close technical supervision. Por our purposes, It was felt that the unit should be used to obtain preliminary operational Information. Two objectives were established:
1. Determine if Geon 450X3 latex could be handled In a Rodney Hunt. 2. Select a favorable set of operating conditions as a starting
point for larger scale operations at a later date In a produc tion size unit. Consequently, series of short runs was made. Peed rate, vacuum, and temperature were varied.
Two lota of fresh Geon 450X3 latex were supplied by Avon Lake Oeneral Chemical Plant - one from the blend tank (20035), the other from a reactor (Charge 72). A 55-gallon drum of latex was placed on a acale, tered end sampled. The Rodney Hunt and product receiver were evacuated and checked for leaks. The vacuum was adjusted to the desired pressure and the feed was sucked from the drum Into the unit through a polyethylene hose.
Initially, the Jacket of the Rodney Hur.t was cold and the rotor waa revolving. Ar. initial 3et of readings was taken and after approximately 30 seconds, the Jacket va3 adjusted to the desired temperature with hot water. A rotometer was used to control the flow rate.
Several preliminary trials were made to establish approximate operating conditions and familiarize ourselves with the equipment. None of this data is reported. It was immediately cfcvlcus that the feed rate was limited by two factors:
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1, The general foami.iess of the letex. 2. An Inadequate foam knock-down bottle between the Rodney Hunt and
the vacuum Jets.
Above 9 pounds per minute the foam would appear as a white liquid In the barometric condenser between the Rodney Hunt and the two stage non-condenslr.g Jets. Since these same Jets are used In many othex* pilot plant operation:, e were reluctant to risk fouling them. Installation of a larger, better designed fcam trap would probably overcome most of our early operating problems and jerrlt a higher feed rate. If desired. After the preliminary trials were complete, two runs were made at 9 pound3 cf feed per minute. Foaming wa3 a problem lr. both runs er.d all subsequent runs were made at a much lower rate. After 16 minutes operation (Puns 1 ar.d 2), the rotor on the Rodney Hunt stalled. Examination of the Process log revealed that a Kycar nitrile latex had been stripped In the Rodney Hunt between the preliminary trials and Run 1. Some of this rubbery material remained firmly attached to the rotor blades despite flushing and stalled the unit. After a thorough cleaning, the unit performed satisfactorily for the remainder of the trial. In most runs, the latex was collected In the product receiver until the trial was completed and then pumped out Into 5 gallon palls. Por a number of runs, however, the product was sampled and then passed through the Rodney Hurt for a second stripping operation. The percentage of residual volatile monomers In the feed and product samples was measured at Avon Lake General Chemical Plant by the standard steam distillation method. Latex properties were measured at the Development Center. All data are summarized In the attached table.
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