Process for making polyvinyl chloride using phenothiazine oligomer

A microsuspension polymerization process for polymerizing vinyl chloride and optional comonomers to polyvinyl chloride and optional copolymers is disclosed which comprises conducting the polymerization in a tubular reaction zone without agitation in the presence of a compound having the formula ##STR1##

BACKGROUND OF INVENTION AND INFORMATION DISCLOSURE STATEMENT 
U.S. Pat. Nos. 4,853,446 and 4,855,424 disclose and claim novel compounds 
and compositions which have been found to inhibit the build-up of scale on 
the walls of vinyl chloride polymerization reactors. Such reactor scale 
interferes with heat transfer, and consumes valuable monomer which is lost 
to the final products, and results in the increase in waste product that 
must be disposed of safely. 
The above listed patents disclose the use of the additive of the invention 
in various polymerization reactions for making polyvinyl chloride 
including emulsion polymerization, bulk or mass polymerization, suspension 
polymerization and microsuspension polymerization. 
It is the purpose of this invention to provide an improved microsuspension 
process to demonstrate reduced reactor wall fouling or scale deposits, as 
well as flocculated material, during polymerization of vinyl chloride and 
other monomers. The microsuspension process of the invention is 
characterized in that the polymerization is conducted in a tubular 
reaction zone without agitation. The microsuspension process used in the 
process of this invention is disclosed in U.S. Pat. Nos. 2,981,722; 
4,377,672, and 4,528,337, the disclosures of which are incorporated herein 
by reference. 
SUMMARY OF THE INVENTION 
The purposes of this invention are accomplished by providing a 
microsuspension polymerization process for polymerizing vinyl chloride and 
co-monomers to polyvinyl chloride and co-polymers, which comprises 
conducting the polymerization in a tubular reaction zone without 
agitation, in the presence of a compound having the formula 
##STR2## 
wherein n has an average value of about one to about five. 
The purposes of this invention are accomplished by providing a 
microsuspension polymerization process for polymerizing vinyl chloride and 
co-monomers to polyvinyl chloride and co-polymers which comprises 
conducting the polymerization in a tubular reaction zone without 
agitation, in the presence of a composition having the formula 
##STR3## 
wherein n has an average value of about one to about five.

PREFERRED EMBODIMENTS OF THE INVENTION 
The compounds (dimers) and compositions (dimer together with higher 
oligomers) that form the basis of the invention are disclosed and claimed 
in U.S. Pat. Nos. 4,853,446 and 4,855,424, the disclosures of which are 
incorporated herein by reference. The processes for manufacturing the 
compounds and compositions are also disclosed in these patents. Processes 
suitable for use in preparing the compounds and compositions are disclosed 
in copending application Ser. No. 07/424,415, filed on even date herewith, 
the disclosure of which is incorporated herein by reference. 
The microsuspension process employed in the process of the invention is 
disclosed in U.S. Pat. Nos. 2,981,722; 4,377,672, and 4,528,337, the 
disclosures of which are incorporated herein by reference. In this 
process, the tubular reactor is preferentially vertically elongated and 
preferably has a substantially circular cross-section. 
The foregoing compounds (dimers) and compositions of the invention (dimer 
together with higher oligomers) are utilized as disclosed as follows in 
the reduction or elimination of scale and flocculated material in a 
reaction vessel and reactor components such as an agitator, used for the 
polymerization of vinyl chloride. The compositions of the invention are 
also useful in the polymerization of vinyl chloride with 
.alpha.-olefinically, more specifically ethylenically unsaturated 
comonomers in a proportion of up to about 80 mole percent comonomers, more 
specifically, up to about 40 mole percent comonomers. Such comonomers 
include vinyl acetate, and other ethylenically unsaturated monomers that 
are well known in the art. 
The dimer alone or together with higher oligomers is dissolved in a 
suitable solvent such as tetrahydrofuran (THF) in a proportion of about 
0.3 to about 1 weight percent. The resulting solutions are then brushed or 
sprayed on the reactor walls, on the reactor agitator, and inside the 
reactor head. The polymerization reaction mixture is inhibited from 
forming undesirable scale on the reactor components. Other solvents that 
can be employed in the application of the solutions to the reactor 
components include dimethylformamide (DMF), cyclohexanone and 
dimethylsulfoxide (DMSO). 
The compounds and compositions of the invention can also be added directly 
to the polymerization reaction mixture, generally in a proportion of about 
0.0001 to about 0.01 weight percent solids, preferably about 0.001 weight 
percent solids based on the weight of vinyl chloride and comonomers. The 
compounds and compositions of the invention can be added to the 
polymerization zone as dry solid or in solution in the foregoing solvents. 
The compounds and compositions can also be added in the wet cake form 
after filtering, but before drying in the manufacturing process. 
The compounds and compositions of the invention are also useful in 
inhibiting the polymerization of monomers such as vinyl chloride or in 
shortstopping the polymerization of such monomers. 
EXAMPLES 
In the following examples and throughout the specification and claims, 
parts are by weight and temperatures are in degrees Celsius, unless 
indicated otherwise. 
PREATION EXAMPLE A (ADDITIVE COMPOSITION) 
200 grams of phenothiazine were dissolved in 500 cc of tetrahydrofuran with 
stirring at room temperature. A solution of 98 cc of 96 percent sulfuric 
acid and 50 cc of 37 weight percent formaldehyde solution in 500 cc of 
methanol was added slowly to the phenothiazine solution with continued 
stirring. The mixture was refluxed with stirring for 11/2 hours. The 
sulfuric acid was neutralized by the addition of 87 grams of sodium 
hydroxide in 250 cc of water. The slurry was filtered, washed three times 
with 500 cc portions of a 50/50 by volume mixture of tetrahydrofuran and 
methanol to remove unreacted phenothiazine. The solvent wetcake was then 
washed 4 times with 1 liter portions of 70.degree. C. water to remove 
salts and solvents. This wetcake was dried for 16 hours at 60.degree. C. 
in an oven. The dried material was ready for use for reactor wall coating. 
EXAMPLE 1 (Control) 
2320 grams of vinyl chloride together with 2680 grams of deionized water, 
7.3 grams of tridecyl alcohol, 46.4 grams of ammonium salt of dihydroxy 
stearic acid, 2.28 grams of lauroyl peroxide and 3.2 grams of 25% 
bis(2-ethyl hexyl) peroxydicarbonate were mixed for 30 minutes in a premix 
tank, then homogenized for 15 minutes through a high shear Ross mixer. The 
monomer emulsion was introduced into an evacuated tubular autoclave (H=45 
inches, D=3 inches) and heated to 50.degree. C. 16 hours after the 
reaction temperature had been reached, polymerization was complete which 
could be detected by the drop in pressure. The pressure was released and 
the polyvinyl chloride latex was drained off. The latex was stable and had 
a solids content of 44 percent. The autoclave wall was uniformly coated 
with polyvinyl chloride polymer residue which was collected and found to 
weigh 20.9 grams. 
EXAMPLE 2 
In this example, the internal wall of a tubular autoclave was coated with a 
solution containing 0.1 gram of the composition prepared as in Example A, 
0.2 gram of phytic acid, 5.0 grams of THF and 5.0 grams of DMF. The 
coating material was air dried for 2 hours with air blowing on the coating 
surface. Then a batch of polyvinyl chloride was prepared as in Example 1. 
The latex obtained was stable and had a solids content of 44 percent. 
There was only 2 grams of scale built up on the autoclave wall. 
EXAMPLE 3 (Control) 
2320 grams of vinyl chloride together with 2680 grams of deionized water, 
55 grams of 30% sodium lauryl sulfate, 4.5 ml. of calcium versene, 2.28 
grams of lauroyl peroxide and 3.2 grams of 25 percent bis (2-ethyl hexyl) 
peroxydicarbonate were mixed for 30 minutes in a premix tank, then 
homogenized for 15 minutes through a high shear Ross mixer. The monomer 
emulsion was polymerized as in Example 1. The latex was stable and had a 
solids content of 45 percent. The autoclave wall was uniformly coated with 
polyvinyl chloride polymer residue which was collected and found to weigh 
23.0 grams. 
EXAMPLE 4 
In this example, the internal wall of a tubular autoclave was coated with a 
solution containing 0.1 gram of the composition prepared as in Example A, 
0.2 gram of phytic acid, 5.0 grams of THF and 5.0 grams of DMF. The 
coating material was air dried for 2 hours with air blowing through the 
tube. Then a batch of polyvinyl chloride was prepared as in Example 3. The 
latex obtained was stable and had a solids content of 44 percent. There 
were only trace amounts of scale buildup on the autoclave wall.