Dispersant system for making polyvinyl chloride which produces low color chlorinated polyvinyl chloride

Chlorinated polyvinyl chloride (CPVC) is prepared from polyvinyl chloride (PVC). When PVC is made utilizing polyvinyl alcohol, the low molecular weight CPVC compound so prepared is colored. A low molecular weight CPVC compound prepared from PVC that was made in the presence of a cellulose ether instead of polyvinyl alcohol resulted in a very low color compound having a DE of O by definition. However, a CPVC compound prepared from PVC made in the presence of polyvinyl alcohol resulted in a relatively high color (DE 18.51). During the polymerization of vinyl chloride, polyvinyl alcohol is replaced with the hydroxypropylmethyl cellulose ether having a methoxyl substitution of 15-35 percent and a hydroxypropoxyl substitution of from 4-35 percent.

FIELD OF THE INVENTION 
This invention relates to a low color chlorinated polyvinyl chloride (CPVC) 
composition as well as the preparation thereof. The low color is due to 
the type of polymerization additive employed in the polymerization of 
vinyl chloride to obtain polyvinyl chloride (PVC). The typical 
polymerization additives used in the making of PVC were found to cause 
discolorated CPVC products. It has been found that polyvinyl alcohol in 
general and especially low to medium hydrolysis polyvinyl alcohol are the 
major contributors to the discoloration of CPVC. 
BACKGROUND 
U.S. Pat. No. 4,612,345 (Hess, Sept. 16, 1986) relates to suspending agents 
of the hydroxypropyl methyl cellulose type and to a process for preparing 
vinyl chloride polymers by suspension polymerization of vinyl chloride 
wherein hydroxypropyl methyl cellulose ethers are used as suspending 
agents. 
This patent provides new suspending agents of the hydroxypropyl methyl 
cellulose type for suspension polymerization of vinyl chloride which do 
not have the deficiencies of the known suspending agents of this type. 
This reference also provides new suspending agents of the hydroxypropyl 
methyl cellulose type for suspension polymerization of vinyl chloride 
which suspending agents are useful for increasing or controlling the 
porosity of the produced polyvinyl chloride particles. 
U.S. Pat. No. 4,797,458 (Sharaby, Jan. 10, 1989) relates to polymers of 
vinyl halides having low molecular weight, good particle characteristics 
and improved melt flow. The polymers are made by aqueous polymerization 
utilizing an effective amount of a mercaptan as a chain transfer agent, 
wherein the mercaptan chain transfer agent is mixed with at least one 
material which is non-polymerizable with vinyl chloride and wherein 
non-polymerizable material is substantially insoluble in water and is 
miscible with said mercaptan to form a chain transfer composition. The 
chain transfer composition is added before the start of the polymerization 
while maintaining colloidal stability. 
U.S. Pat. No. 4,471,096 (Sharaby et al, Sept. 11, 1984) relates to a 
process for the production of vinyl chloride polymers. It has been found 
that mercapto organic compounds having at least one beta-ether linkage are 
highly efficient chain-transfer agents in the production of vinyl chloride 
polymers that do not have the disadvantages of the previously known 
chain-transfer agents. These chain-transfer agents do not affect the 
color, odor, and other physical properties of the polymers and do not 
cause pollution problems. 
SUMMARY OF THE INVENTION 
This invention is directed to a composition of a chlorinated polyvinyl 
chloride polymer having improved color that does not utilize polyvinyl 
alcohol as well as a method for its preparation. A polymer so prepared by 
this process has utility as pipe and pipe fittings, molding around 
windows, doors and at baseboards, electrical equipment housings as well as 
products made by extension sheet blow injection molding and injection 
molding for home appliances. The composition and method involve 
polymerizing parts by weight of vinyl chloride optionally with a vinyl 
component monomer other than vinyl chloride in the from about 0.02 to 
about 0.5 parts by weight of a surfactant characterized in that the 
surfactant is a hydroxypropyl methyl cellulose ether having a methoxyl 
substitution of from 15 percent to 35 percent and a hydroxypropoxyl 
substitution of from 4 percent to 35 percent to form an intermediate, and 
(C) chlorinating said intermediate to obtain a chlorinated vinyl chloride 
polymer.

DESCRIPTION OF THE INVENTION 
According to the present invention, chlorinated polymer compositions are 
provided wherein the polymerization of the monomer or comonomers occurs in 
the presence of at least one surfactant of hydroxypropyl methyl cellulose 
ether to yield a product having improved color as well as high Tg. 
The hydroxypropyl methyl cellulose ethers used in the process of the 
present invention are commercially available and are defined primarily by 
their methoxyl substitution and hydroxypropoxyl substitution. The methoxyl 
and hydroxypropoxyl substitution are measured and calculated according to 
ASTM-D 2363. All the percentages of substitution are by weight of the 
finally substituted material. 
The methoxyl substitution of the hydroxypropyl methyl cellulose ethers 
ranges from 15 percent to 35 percent and preferably from I9 to 25 percent. 
The hydroxypropoxyl substitution of the hydroxypropyl methyl cellulose 
ethers ranges from 4 percent to 35 percent and preferably from 4 percent 
to 12 percent. 
The molecular weight of hydroxypropyl methyl cellulose can be expressed as 
the viscosity of the solution thereof in a solvent therefor. Unless 
otherwise stated, the molecular weight of hydroxypropyl methyl cellulose 
is given herein as the viscosity of a 2 weight percent solution of 
hydroxypropyl methyl cellulose in water as measured using a UBBELOHDE 
viscosimeter at 20.degree. C. 
The viscosity is generally about 5 to about 200,000 mPa's. The 
hydroxypropyl methyl cellulose ethers which are used as suspending agents 
for the suspension polymerization of ethylenically unsaturated monomers 
have preferably a viscosity of from about 5 mPa's, most preferably from 
about 10 mPa's, to about 400 mPa's, most preferably to about 100 mPa's. 
The viscosities of 5, 10, 100 and 400 mPa's correspond to number average 
molecular weights (M.sub.n) of 10,000, 13,000, 26,000, and 41,000 
respectively. 
The hydroxypropyl methyl cellulose ethers of the present invention have the 
above-mentioned methoxyl and hydroxypropoxyl substitution provided that 
the average molecular weight is less than 50,000. By average molecular 
weight the number average molecular weight (M.sub.n) is meant. The 
preferred average molecular weight is from 5000, most preferably from 
10,000, to 40,000, most preferably to 30,000. A particularly preferred 
range of the molecular weight is from 13,000 to 26,000 which corresponds 
to a viscosity of 10 mPa's to 100 mPa's. Provided that when the average 
molecular weight is more than or equal to 50,000, the methyoxyl 
substitution is more than 24 percent, preferably from 24.5 percent, most 
preferably from 25 percent, to 35 percent, preferably to 33 percent, and 
most preferably to 31 percent. 
The hydroxypropyl methyl cellulose ethers of the present invention are, for 
example, useful as suspending agents for the suspension polymerization of 
vinyl chloride and a vinyl component monomer other than vinyl chloride. 
The hydroxypropyl methyl cellulose ethers used for the purpose of the 
present invention can be produced according to known methods, for example, 
as described in U.S. Pat. Nos. 2,949,452, and 3,388,082, the teachings of 
which are included herein by reference. The levels of substitution of the 
hydroxypropyl methyl cellulose ethers of the present invention can be 
achieved by increasing the amounts of propylene oxide and methyl chloride 
and reaction times until the desired substitution level has been reached. 
The hydroxypropyl methyl cellulose ethers described herein are used as 
suspending agents for the suspension polymerization of vinyl chloride and 
a vinyl component monomer other than vinyl chloride. Preferably, these 
hydroxypropyl methyl cellulose ethers are used as secondary or 
co-suspending agents, i.e. together with other suspending agents, for 
suspension polymerization of vinyl chloride. 
The polymerization is done on 100 parts of vinyl chloride or a total of 100 
parts of vinyl chloride and vinyl component monomer. 
By the term "vinyl component," it is meant a vinyl type monomer other than 
vinyl chloride. Such monomers are well known to the art and to the 
literature and include esters of acrylic acid wherein the ester portion 
has from 1 to 12 carbon atoms, for example, methyl acrylate, ethyl 
acrylate, butyl acrylate, octyl acrylate, cyanoethyl acrylate, and the 
like; vinyl acetate; and vinyl aliphatic esters containing from 3 to 18 
carbon atoms; esters of methacrylic acid wherein the ester portion has 
from to I2 carbon atoms, such as methyl methacrylate, ethyl methacrylate, 
butyl methacrylate, and the like; styrene and styrene derivatives having a 
total of from 8 to 15 carbon atoms such as alpha-methylstyrene, vinyl 
toluene, chlorostyrene; vinyl naphthalene; diolefins having a total of 
from 4 to 8 carbon atoms such as butadiene, isoprene, and including 
halogenated diolefins such as chloroprene; monoolefins having from 2 to 10 
carbon atoms and preferably 2 to 4 carbon atoms such as ethylene, 
propylene and isobutylene; and mixtures of any of the above types of 
monomers and other vinyl monomers copolymerizable therewith known to the 
art and to the literature. An amount of vinyl chloride monomer is utilized 
to produce a copolymer containing from about 70 to about 95 percent by 
weight, and preferably from about 80 to about 93 percent by weight of 
vinyl chloride repeating units therein. The remainder of the copolymer is 
made up of the one or more above-noted vinyl component monomers, for 
example, vinyl acetate. Thus, an amount of vinyl component monomer when 
utilized to produce a copolymer is from about 5 to about 30 percent and 
preferably from about 7 to about 20 percent by weight of vinyl component 
repeating units therein. 
For the production of some goods, vinyl chloride polymers or copolymers 
must be able to absorb plasticizers. Accordingly, particle porosity is an 
important property of these resins since it determines the ability of the 
resin to absorb liquid plasticizers. The porosity of the polymer particles 
can be easily controlled or increased by using suspending agents such as 
hydroxypropyl methyl cellulose ethers. The suspending agents are generally 
used in the amount of 0.02 to 0.5, preferably of 0.05 to 0.3, most 
preferably 0.05 to 0.20 parts by weight per 100 parts of vinyl chloride or 
vinyl chloride and vinyl component monomer. 
Methods for preparing polyvinyl chloride by suspension polymerization of 
vinyl chloride are known in the art. Such polymerization processes are for 
example described in DE 2153727-B and in DD patent specification 160354, 
the teachings of which are included herein by reference. This procedure 
generally relates to the utilization of an aqueous system wherein the 
monomer is in a dispersed phase, an initiator is dissolved in a monomer 
phase, and the formed polymer is a dispersed solid. 
The process of this invention may be used in the production of polyvinyl 
chloride as well as copolymers that are formed by the copolymerization of 
vinyl chloride with a water-insoluble vinyl component monomer that is 
copolymerizable therewith. Suitable comonomers are disclosed above as 
"vinyl component." 
The molecular weight of PVC may be related to its inherent viscosity which 
is determined herein by dissolving 0.24 gram of the resin in 50 ml of 
cyclohexane while mildly heating and agitating according to ASTM procedure 
D-1243 (1966). The PVC resin starting material useful in the process of 
this invention preferably has a molecular weight such that it possesses an 
n.sub.1 (inherent viscosity) in the range from about 0.2 to about 1.4, the 
most commonly used PVC resins having an n.sub.1 in the range from about 
0.4 to about 1.1. 
The PVC can be prepared with at least one mercaptan or a non-mercaptan 
chain transfer agent composition. The mercaptan chain transfer agent 
composition comprises (a) at least one mercaptan chain transfer agent and 
(b) at least one non-polymerizable material which is miscible with the 
mercaptan chain transfer agent Suitable mercaptans include water soluble 
mercaptans such as 2-mercaptoethanol, 3-mercaptopropanol, 
thiopropyleneglycol, thioglycerine, thioglycolic acid, thiohydracrylic 
acid, thiolactic acid, and thiomalic acid, and the like. Suitable 
non-water soluble mercaptans include isooctyl thioglycolate, n-butyl 
3-mercaptopropionate, n-butyl thioglycolate, glycol dimercaptoacetate, 
trimethylolpropane trithioglycolate, alkyl mercaptans, and the like. The 
preferred mercaptan is 2-mercaptoethanol, however, any chain transfer 
agent having a mercapto (--SH) group would be acceptable. 
The chain transfer composition comprises, in addition to the mercaptan, at 
least one non-polymerizable material which is miscible with the mercaptan 
and is substantially insoluble in water. The term non-polymerizable as 
used herein means that the material does not form a part of the vinyl 
chloride polymer chain in the sense that a traditional comonomer would 
form. The nonpolymerizable material may, in some cases, graft polymerize 
onto the vinyl chloride polymer chain but this is not normally considered 
a copolymer. The term substantially insoluble in water as used in this 
specification means that the material has less than 5 percent solubility 
in water. The non-polymerizable material may be a monomer, oligomer or a 
polymer. Suitable non-polymerizable materials include dioctyl phthalate, 
low molecular weight poly(caprolactone), polysilicones, esters of 
glycerols, polyesters, water insoluble esters of fatty acids with OH 
terminated polyoxyethylene and polyoxypropylene, esters of polyols, esters 
of monoacids and polyacids, esters of organic polyphosphates, phenyl 
ethers, ethoxylated alkylphenols, sorbitan monostearate and sorbitan 
monooleate and other sorbitol esters of fatty acids. The choice of 
material is not critical as long as the material is non-polymerizable with 
the vinyl chloride monomer and is substantially insoluble in water. 
The chain transfer composition must contain at least enough 
non-polymerizable material to encapsulate the mercaptan chain transfer 
agent. This amount varies according to the type and amount of chain 
transfer agent used. Usually, the chain transfer composition must contain 
at least an equal amount in weight of nonpolymerizable material as chain 
transfer agent in order to encapsulate or host the chain transfer agent. 
Preferably, the composition contains at least twice as much weight of 
non-polymerizable material as chain transfer agent. Other non-essential 
ingredients may be used in the chain transfer compositions of this 
invention but are not preferred. 
The chain transfer compositions are formed by mixing the two essential 
ingredients together. The method used to mix the ingredients is not 
critical and may be any of the known methods used by those skilled in the 
art. The ingredients may even be charged to the polymerization reactor and 
mixed before adding the other polymerization ingredients but is preferably 
mixed outside the reactor. 
Because of the detrimental effects that mercaptans, such as 
2-mercaptoethanol have on colloidal stability, it is necessary to mix the 
2-mercaptoethanol with the non-polymerizable material before adding it to 
the reaction medium. The non-polymerizable material serves as a host 
material for the chain transfer agent. This procedure surprisingly 
eliminates the adverse effects of 2-mercaptoethanol on colloidal 
stability. It is believed that the non-polymerizable material averts the 
adverse effect of 2-mercaptoethanol on colloidal stability via 
encapsulation, complexation or interaction and, thus, allows relatively 
high levels of 2-mercaptoethanol to be introduced to the reaction medium 
prior to the start of polymerization. The term "encapsulation" as used 
herein is not intended as the traditional meaning of encapsulation which 
is to coat or contain and the result is a heterogeneous system. The chain 
transfer composition of this invention is homogeneous. 
The level of chain transfer composition used to make the low molecular 
weight polymers will be described in terms of the level of mercaptan in 
the composition. The level of mercaptan used is greater than 0.03 part by 
weight per 100 parts by weight of vinyl chloride or vinyl component 
monomer. The preferred levels of mercaptan range from about 0.03 to about 
5.00 parts by weight per 100 parts of monomer or comonomers, and, most 
preferably, from 0.10 to 1.50 parts. 
When high amounts of mercaptan, such as 2-mercaptoethanol, are used, it is 
desirable to not charge the entire amount of chain transfer agent at the 
beginning of polymerization since 2-mercaptoethanol has a diminishing 
effect on molecular weight above about the 1.5 parts level. Therefore, if, 
for example, 3.0 parts were used, it would be advisable to add only up to 
1.5 parts at the beginning of polymerization and to gradually add the 
remainder during polymerization. Amounts added at the beginning which are 
greater than 1.5 parts do not result in colloidal instability. However, 
for the most efficient use of chain transfer agent, it is preferred to not 
add more than 1.5 parts before the beginning of polymerization. This 
preferred initial level could, of course, be different for different 
mercaptans. The above described preferred procedure is for 
2-mercaptoethanol. 
If less than 0.25 part by weight of chain transfer agent is used, then all 
of the chain transfer agent will be added in the form of the chain 
transfer composition before the beginning of polymerization. If more than 
0.25 part is used, then at least 0.25 part will be added in the form of 
the chain transfer composition before the beginning of polymerization and 
the remainder may be added later. To gain the most efficiency of the chain 
transfer agent, no more than 1.5 parts by weight should be added before 
the start of polymerization. For best results, at least 50 percent of the 
chain transfer agent, preferably 100 percent, is added to the 
polymerization medium prior to the start of polymerization. Any amount not 
added at the start and not encapsulated should be added after the 
polymerization has reached about 10 percent conversion to maintain 
colloidal stability. Except for the use of the chain transfer composition, 
the polymerization is much the same as in the conventional polymerization 
of vinyl chloride in an aqueous medium. 
Another class of chain-transfer agents that are used in the process of this 
invention are mercapto organic compounds having at least one beta-ether 
linkage that have the structural formula 
EQU X--(CH.sub.2).sub.m --(OY).sub.n --SH 
wherein X represents hydrogen or --SH, Y represents an alkylene group 
having 1 to 6 carbon atoms, and m and n each represents a number in the 
range of 1 to 10. 
A preferred group of beta-ether linkage chaintransfer agents includes 
mercapto organic compounds that have the structural formula 
EQU X--CH.sub.2).sub.m '--(OY').sub.n '--SH 
wherein X represents hydrogen or --SH, Y' represents an alkylene group 
having 2 to 4 carbon atoms, and m' and n' each represents a number in the 
range of 2 to 4. 
Illustrative of the beta-ether linkage chaintransfer agents that can be 
used in the practice of this invention are the following compounds: 
mercaptomethyl ethyl ether, 
2-mercaptoethyl ethyl ether, 
2-mercaptoethyl propyl ether, 
2-mercaptoethyl butyl ether, 
3-mercaptopropyl methyl ether, 
3-mercaptopropyl ethyl ether, 
3-mercaptopropyl butyl ether, 
2-mercaptopropyl isopropyl ether, 
4-mercaptobutyl ethyl ether, 
bis-(2-mercaptoethyl) ether, 
bis-(3-mercaptopropyl) ether, 
bis-(4-mercaptobutyl) ether, 
(2-mercaptoethyl) (3-mercaptopropyl) ether, 
(2-mercaptoethyl) (4-mercaptobutyl) ether, 
ethoxypolypropylene glycol mercaptan, 
methoxypolyethylene glycol mercaptan, 
and the like and mixtures thereof. 
Among the preferred beta-ether linkage chaintransfer agents are 
2-mercaptoethyl ethyl ether and bis(2-mercaptoethyl) ether. 
The amount of the beta-ether linkage chaintransfer agent that is used in 
the polymerization reaction is that which will provide a polymer having 
the desired molecular weight or degree of polymerization. In most cases 
from 0.01 percent to 5 percent by weight, based on the weight of the 
monomer component, is used. When a low molecular weight product that has a 
viscosity, n.sub.1, in the range of 0.20 to 0.60 is desired, the amount of 
chain transfer agent used is preferably in the range of 0.1 percent to 2.0 
percent by weight, based on the weight of the monomer. 
The non-mercaptan chain transfer agents that can be utilized in the 
practice of this invention are monoolefins containing from 2 to about 18 
carbon atoms. The olefinic double bond may be terminal (alpha) or 
internal. Also functioning as non-mercaptan chain transfer agents are 
chlorinated hydrocarbons containing from 1 to about 10 carbon atoms. These 
chlorinated hydrocarbons may be mono-, di-, or tri-chlorinated. A 
representative chlorinated chain transfer agent is 1,1,2-trichloroethane. 
Other non-mercaptans chain transfer agents are aldehydes containing from 2 
to -8 carbon atoms and ethers containing from 2 to 18 carbon atoms, as 
well as cyclic ethers such as furan and tetrahydrofuran. 
The level of non-mercaptan chain transfer agent used to make the low 
molecular weight polymers will be described in terms of the level of 
non-mercaptain chain transfer agent in the composition. This level is 
generally greater than 0.1 up to about 10 parts by weight per 100 parts by 
weight of vinyl chloride or vinyl chloride and vinyl component monomer. 
The preferred levels range from 0.5 to about 10 parts by weight per 100 
parts of monomer or comonomers, and, most preferably from 0.5 to 5 parts. 
The process of this invention uses polymerization initiators. The 
polymerization initiators used in this process are known in the art and 
are selected from the conventional free radical initiators such as organic 
peroxides and azo compounds. The particular free radical initiator 
employed will depend upon the monomeric material(s) being polymerized, the 
molecular weight and color requirements of the polymer, the temperature of 
polymerization, and the type of process such as suspension or emulsion 
process, etc. Insofar as the amount of initiator employed is concerned, it 
has been found that an amount in the range of about 0.005 part by weight 
to about 1.00 part by weight, based on 100 parts by weight of the monomer 
or monomers being polymerized, is satisfactory. However, it is preferred 
to employ an amount of initiator in the range of about 0.01 part by weight 
to about 0.20 part by weight based on 100 parts by weight of monomer(s). 
For the process as described herein, examples of suitable initiators 
include lauryl peroxide, azobisisobutylonitrile, benzoyl peroxide, 
isopropyldicarbonate, acetyl cyclohexyl sulfonyl peroxide, t-butyl 
peroxypivalate, t-butyl peroxyactoate, and alpha-cumyl peroxyneodecanoate, 
the choice depending on the reaction temperature. The preferred initiator 
is a dual system comprising t-butyl peroxypivalate and alpha-cumyl 
peroxyneodecanoate. This initiator system results in a reduced residual 
initiator level in the final product and a shorter high temperature 
history due to faster reactions. 
The suspension polymerization process may be carried out at any temperature 
which is normal for the monomeric material to be polymerized. Preferably, 
a temperature in the range of from 0.degree. C. to about 100.degree. C., 
more preferably from about 40.degree. C. to about 85.degree. C. is 
employed. In order to facilitate temperature control during the 
polymerization process, the reaction medium is kept in contact with 
cooling surfaces cooled by water, brine, evaporation, etc. This is 
accomplished by employing a jacketed polymerization reactor wherein the 
cooling material is circulated through the jacket throughout the 
polymerization reaction. This cooling is necessary since most all of the 
polymerization reactions are exothermic in nature. It is understood, of 
course, that a heating medium can be circulated through the jacket, if 
necessary. 
The above vinyl chloride polymer can be chlorinated in any conventional 
manner as known to the art and to the literature to contain high amounts 
of chlorine therein, as for example from about 57 percent by weight up to 
about 74 percent by weight based upon the total weight of the polymer, 
preferably from about 61 percent to about 74 percent by weight, and most 
preferably from about 63 percent to 72 percent by weight based upon the 
total weight of the copolymer. 
To produce CPVC commercially, and preferably economically, it has been 
found that a relatively concentrated aqueous suspension of PVC must be 
chlorinated. But such a relatively concentrated suspension cannot be 
routinely uniformly chlorinated to get high quality. By "uniformly 
chlorinated" we describe a CPVC resin having a density which does not 
deviate more than 20 percent from the mean density, and a surface area 
which does not deviate more than 30 percent from the mean surface area. By 
"relatively concentrated" we refer to a concentration of about 15 to about 
35 percent by weight of PVC solids in the suspension. Since the physical 
characteristics of such a relatively concentrated suspension of PVC in 
water are quire different from those having relatively low concentrations, 
the problems of chlorination in each are quire different, such factors as 
viscosity of the suspension, clumping of macrogranules, penetration of 
ultraviolet light, diffusion of gases into and out of the liquid and solid 
phases present, inter alia, not lending themselves to extrapolation by 
known methods. It has been found that a concentration of PVC higher than 
the specified range results in non-uniform product, while concentrations 
below 15 percent yield uniform product, but is not economical. By "aqueous 
suspension" of PVC we refer to a slurry-like mixture of PVC macrogranules 
suspended in water. Though, initially the water is not deliberately 
acidified by the addition of acid, HCl acid is formed during the course of 
the chlorination and is absorbed in the water. The above-specified 
concentration of PVC in the suspension is found to yield high output of 
CPVC for a given reactor volume, without sacrificing the quality of the 
product, which quality cannot be compromised. This process is particularly 
directed to a batch process since wholly different considerations enure to 
the operation of a continuous process. 
It is essential for the purpose of obtaining the desired CPVC product that 
oxygen be removed from the aqueous suspension before chlorination is 
initiated. This may be effected in any convenient manner. For example, a 
hot suspension at a temperature in the range from about 60.degree. C. to 
about 75.degree. C. and containing about 30 percent PVC may be introduced 
into a batch reactor and subjected to a vacuum at that temperature so that 
it boils. Lower temperatures as low as about 20.degree. C. may be 
employed, but removal of oxygen at such low temperatures is impractical, 
particularly since the temperature of the suspension is to be raised if it 
is to be chlorinated by the process of this invention. Removal of oxygen 
is assisted by agitation of the suspension. After several minutes, 
depending upon the size of the charge to the reactor, the temperature and 
the initial oxygen content of the suspension, it is found that essentially 
all the oxygen has been removed. The same result may be obtained by 
sparging an inert gas such as nitrogen through the suspension, again 
preferably, when the suspension is hot, that is, in the range from 
60.degree. C. to 75.degree. C. Any conventional test to determine the 
concentration of oxygen may be used, and it is preferred to have less than 
100 ppm of oxygen remaining in the slurry, the less the better. 
During the period when oxygen is removed, the temperature of the suspension 
may be lowered sufficiently to require heating it to return to a 
temperature within the range from about 60.degree. to about 75.degree. C. 
which is the preferred starting temperature range in which the 
photochlorinated reaction is to be initiated. Such heating as may be 
required is preferably done after Cl.sub.2 is sparged into the suspension 
from a liquid Cl.sub.2 cylinder until the pressure in the reactor reaches 
about 25 psig, at which point the suspension is saturated with Cl.sub.2. 
It is preferred that this pressure be somewhat higher, that is in the 
range from about 35 psig to about 100 psig, to get the optimum results, 
though a pressure as low as 10 psig gives acceptable results. Pressures 
higher than 100 psig may be employed, though it will be recognized that 
the cost of equipment for operation at such higher pressures adversely 
affects the economics of the process. The amount of Cl.sub.2 charged to 
the reactor is determined by the weight loss in the Cl.sub.2 cylinder. 
After the reactor is pressurized with chlorine, the reactor is preferably 
brought up to a "soak" temperature in the range from about 60.degree. C. 
to about 75.degree. C. at which soak temperature the suspension is 
maintained for a soak period in the range from about minute to about 45 
minutes. The soak period appears to have an unexpectedly beneficial 
function. It provides Cl.sub.2 the opportunity to diffuse into the 
macrogranules where it will do the most good. 
A longer soak period, under pressure, may be used if the soak temperature 
is lower than 60.degree. C., but a soak period longer than 45 minutes is 
undesirable. An unnecessarily long soak period only defeats a primary 
object to this water chlorination process, namely to speed up the 
production of high quality CPVC. 
It must be recognized that the relatively high pressure in the reactor, 
which pressure is preferably maintained constant also retards the removal 
of HCl and HOCl from within the macrogranules, and if too high, adversely 
affects the porosity of the macrogranules to the detriment of the 
stability of the CPVC product. Again, it is preferred to maintain 
agitation of the suspension during soaking, though the intensity of 
agitation may be substantially lower than that preferred during the 
photo-chlorination step to follow. In fact, the aqueous suspension is 
preferably kept agitated from the time the preheated PVC suspension is 
charged to the reactor, until the end, when the CPVC slurry is ready to be 
dumped. 
Irrespective of the length of the soak period and the temperature at which 
the suspension is maintained during the soak period, it is essential to 
complete the chlorination reaction under photo-illumination, preferably 
with ultraviolet light, or the desired conversion of PVC to CPVC product 
does not occur. 
It is feasible to carry out the process of this invention without a soaking 
step, but such a process is economically impractical. For example, after 
removing oxygen from an aqueous PVC suspension charged to the reactor, the 
lights may be turned on prior to introducing the chlorine. Chlorination 
proceeds at a rate which depends upon the pressure and temperature within 
the reactor, higher rates being favored at higher temperature and 
pressure. When pressure and temperature are raised to a level sufficient 
to give a favorable rate without a soaking step, the uniformity of the 
CPVC product suffers. 
After the "soak" period, the suspension is photo-illuminated with a bank of 
ultraviolet lights in the manner described in U.S. Pat. No. 2,996,489, 
except that it has been found that a relatively high and constant 
intensity of light should be used, preferably in the range from about 5 
watts to about 50 watts per gallon of suspension, if high rates of 
chlorination with a relatively concentrated suspension are to be obtained. 
With a preferred high level of photo-illumination, it has been found that 
reaction rates far greater than in prior art aqueous suspension 
chlorination processes may be obtained. Most important, the reaction rates 
may be achieved without a sacrifice in product quality. For example, in 
contrast with the process disclosed in U.S. Pat. No. 3,100,762, for 
chlorinating a non-photo-illuminated suspension, the chlorination of an 
aqueous suspension of PVC at 60.degree. C. and 40 psig by the instant 
process, with a soak period, photo-illumination and "temperature ramping" 
as will be described hereinbelow, produces a reaction rate of from 
0.01-0.04 min.sup.-1 and a HDT of a test recipe of from 100.degree. C. to 
130.degree. C. The reaction rate is computed on the basis of it being a 
first order reaction, using the formula 
EQU k=-2.303 [1.sub.n (1-x)]/t 
where, x is fractional conversion to one chlorine atom per carbon atom, 
and, t is time (in minutes). 
It has been found that carrying out a chlorination reaction under widely 
fluctuating elevated temperature and pressure while photo-illuminating the 
suspension does not produce CPVC of adequate quality and stability. It is 
essential, at elevated pressure, to commence the chlorination reaction at 
a temperature in the range from about 60.degree. C. to about 75.degree. 
C., and then to finish the reaction at an even higher temperature 
generated because of the reaction. No additional heat is required to be 
added to the reactor because the self-generated heat is sufficient to 
produce the desired increase in temperature, until it reaches a finishing 
temperature in the preferred range of from about 80.degree. C. to about 
100.degree. C. A finishing temperature as high as 120.degree. C. may be 
employed if the pressure is high enough. The "finishing temperature" is so 
termed because it is the temperature at which the chlorination reaction is 
"finished," that is a preselected chlorine content in the CPVC has been 
attained. The precise finishing temperature at which the autogenously 
ramped temperature levels off, will depend on several factors. It is most 
preferred to adjust the soak temperature, the mass of resin, and the level 
of photo-illumination so that the temperature is "ramped" by the 
self-produced heat of reaction until it levels off at a finishing 
temperature of about 110.degree. C. 
It will now be evident to one skilled in the art that the temperature at 
which the chlorination occurs should, at all times be below the Tg of the 
resin in the suspension, whether the resin is a mass polymerized PVC, a 
suspension polymerized PVC, or a mixture of PVC and CPVC. For example, 
chlorination of a Geon .sup.R 103EP or 30 PVC resin having a Tg of about 
84.degree. C., must be commenced at a temperature below 84.degree. C., 
though as the reaction progresses, the reaction temperature maybe 
permitted to rise because the Tg of the resin rises as the reaction 
proceeds to completion. In other words, as the reaction proceeds, the Tg 
of the mixture of remaining PVC and the CPVC formed, continuously 
increases. This process requires that the autogenously ramped temperature 
be maintained at all times below the effective Tg of the solid resins. It 
will also be evident to one skilled in the art, that the problem of 
maintaining the finishing temperature of the reaction substantially 
constant at about 90.degree. C. (say) during the exothermic chlorination 
reaction in a batch reactor requires highly effective heat transfer 
control or the resin will "burn." This problem is exacerbated as the size 
of the reactor increases, and is especially onerous in a 2500 gallon, or 
larger, reactor. 
The progress of the chlorination reaction depletes the free chlorine in the 
reactor and the additional Cl.sub.2 is introduced into the reactor to 
maintain the pressure, and to make sure that the desired level of 
conversion of PVC to produce CPVC is attained. The level of conversion is 
estimated by the amount of Cl.sub.2 fed from the Cl.sub.2 feed cylinder. 
It is not desirable to permit the pressure in the reactor to fluctuate 
more than 20 percent as the effects of wide fluctuations are reflected in 
poorer quality CPVC. 
When sufficient chlorine is added to the reactor to result in the desired 
conversion of about 50 percent conversion (say) of PVC, that is, about 50 
percent of all the vinyl chloride (monomeric.sub.-- units have been 
chlorinated with at least one atom of chlorine, or, to result in a desired 
density of CPVC in the range from about 1.50 to about 1.65 g/cc, more 
preferably from about 1.536 to about 1.656 g/cc, the flow of chlorine to 
the reactor is stopped. The suspension is not cooled but dumped to be 
centrifuged and the CPVC freed from the aqueous phase, after which HCl 
acid is removed from the CPVC, preferably by neutralizing the CPVC with an 
aqueous solution of an alkali. The CPVC product is then washed with water 
to free the CPVC of residual alkali, and dried, all in a conventional 
manner, except that the temperatures at which the operations are carried 
out may be in the range from about 60.degree. C. to about 100.degree. C., 
which are higher than conventionally used. 
The chlorinated products of this invention have densities in the range from 
about 1.5 to about 1.7 g/cc at 25.degree. C., and a HDT in the range from 
about 128.degree. C. (for 65 percent Cl content) to about 170.degree. C. 
(for 72 percent Cl content). The increase in HDT over conventionally 
prepared CPVC is ascribed to the probability that there are more 
1,1,2-trichloroethylene units in a CPVC molecule than generally present, 
and which units are not otherwise obtained, at least in an amount 
significant enough to increase HDT so markedly, even if a conventional 
photo-illumination is carried out at about atmospheric pressure, with or 
without a swelling agent, for an extended period of time. 
The CPVC is useful in the rigid vinyl field for the manufacture of pipe, 
ductwork, tanks, appliance parts, etc., especially where the products will 
handle or contact hot water and other hot, corrosive liquids. It has found 
particular utility in the production of hot waterpiping for industrial and 
domestic use. Ordinarily, a small amount of another resin or rubber, e.g., 
chlorinated polyethylene, styrene-acrylonitrile copolymer, or chlorinated 
isobutylene is blended with the chlorinated PVC resin to improve its shock 
resistance and mechanical processability. The pigments, lubricants and 
stabilizers well known in the vinyl art also can be incorporated therein. 
To further illustrate the present invention, the following specific 
examples are given, it being understood this is merely intended in an 
illustrative and not a limitative sense. In the examples, all parts and 
percentages are by weight unless otherwise indicated. 
The below table shows the preparation of a polyvinyl chloride homopolymer 
utilizing 100 parts vinyl chloride, 150 parts water, and 0.1 part of 
cellulose ether having a methoxyl substitution of 22 percent and a 
hydroxyl substitution of 8 percent. Examples and 2 are control examples 
utilizing polyvinyl alcohol. Examples 3 through 12 are prepared utilizing 
additional hydroxypropylmethyl cellulose ether, hereinafter referred to as 
cellulose ether. This cellulose ether has a viscosity of about 15.5 mPa's 
and is commercially available from Dow Chemical under the trade name XZ 
87310. Numbers in parentheses indicate parts by weight of additive, chain 
transfer agent and initiators. Where a mercaptan chain transfer agent is 
used, there is also employed a nonpolymerizable material of a 500 
molecular weight polycaprolactone (0.34 parts). The inherent viscosity is 
n.sub.1, APS is average particle size in microns, PSD is particle size 
distribution, and Hg Por is mercury porosity. For the initiators 
TBP=t-butyl peroxyactoate, TBPP=t-butyl peroxypivalate, ACPND=alpha-cumyl 
peroxyneodecanoate, TAPND=t-amyl peroxyneodecanoate, TAPP=t-amyl 
peroxypivalate, and TBPNB=t-butyl peroxyneodecanoate. 
TABLE I 
__________________________________________________________________________ 
Additional 
Dispersant Chain 
Polyvinyl 
Cellulose 
Transfer Reaction 
Example 
Alcohol 
Ether 
Agent Initiators 
Temp .degree.C. 
__________________________________________________________________________ 
1* (0.10) -- None TBP/TBPP 81.7 
(.046/0093) 
2* (0.10) -- 2-Mercapto- 
ACPND/TBPP 
70 
ethanol (.17) 
(.04/.065) 
3 -- (.12) 
None TBP/TBPP 81.7 
(.02/.019) 
4 -- (.10) 
2-Mercapto- 
ACPND/TBPP 
70 
ethanol (.17) 
(.035/.065) 
5 -- (.15) 
2-Mercapto- 
ACPND/TBPP 
70 
ethanol (.17) 
(.04/.065) 
6 -- (.15) 
2-Mercapto- 
ACPND/TBPP 
70 
ethanol (.15) 
(.035/.060) 
7 -- (.15) 
2-Mercapto- 
ACPND/TBPP 
70 
ethanol (.15) 
(.04/.09) 
8 -- (.15) 
Isobutylene 
TAPND/TAPP 
70 
(2.5) (.02/.085) 
9 -- (.15) 
Isobutylene 
ACPND/TBPND 
53 
(7.0) (.08/.14) 
10 -- (.15) 
Propylene 
ACPND/TAPND 
65 
(10.0) (.09/.12) 
11 -- (.09) 
2-Mercapto- 
ACPND/TBPP 
70 
ethanol (.14) 
(.035/.65) 
12 -- (.09) 
2-Mercapto- 
ACPND/TBPP 
70 
ethanol (.14) 
(.035/.65) 
__________________________________________________________________________ 
Reaction 
Example 
Time (Min.) 
n.sub.1 
APS PSD Hg Por 
__________________________________________________________________________ 
1 274 .520 98 56 .159 
2 211 .440 166 36 .154 
3 246 .552 102 40 &lt;.02 
4 255 .479 78 45 .093 
5 272 .4436 
174 62 .119 
6 240 .47 192 68 .112 
7 241 .316 134 69 .111 
8 400 .433 198 62 .086 
9 600 .442 124 99 .140 
10 418 .455 105 55 .120 
11 278 .467 77 47 .077 
12 235 .467 76 46 .087 
__________________________________________________________________________ 
*Control Examples 
Examples 13 and 14 deal with the preparation of chlorinated polyvinyl 
chloride from polyvinyl chloride that was made using polyvinyl alcohol. 
EXAMPLE 13 
An externally jacketed glass-lined vessel equipped with a mercury vapor 
light and an agitator was charged with slurry to about 75 percent of 
capacity. The slurry consisted of 82 percent deionized water and 18 
percent polyvinyl chloride (PVC). The PVC was produced using the standard 
polyvinyl alcohol surfactant system as prepared in Example 1. This slurry 
was then heated to 60.degree. C. and the reactor was sealed. A vacuum was 
pulled on the reactor to remove oxygen and other gasses. The vacuum was 
broken with chlorine which was also used to pressurize the reactor to 35 
psig. This slurry was allowed to agitate for about 15 minutes to allow the 
chlorine to diffuse into the PVC particles. The reaction was initiated by 
turning on the mercury vapor light. As the reaction proceeded, chlorine 
was added to maintain the pressure until the chlorine to PVC ratio of 
0.4:1.0 was reached. During the reaction, the temperature of the slurry 
was allowed to increase to 90.degree. C., from the heated reaction, and 
then was controlled at this temperature. After all the chlorine was in, 
the reaction continued until the reactor was under vacuum, indicating that 
all of the chlorine had been reacted. The slurry was then neutralized and 
dried. The reaction took 270 minutes and the final percent chlorine level 
on the polymer was 64.1 percent. 
EXAMPLE 14 
The same equipment and procedures as in Example 13 were used for this 
example as well. This example employs the PVC of Example 2 that was made 
using polyvinyl alcohol and a nonpolymerizable material for the chain 
transfer agent. 
The remaining examples, 15 and 16, both prepared as per Example 13, employ 
a PVC that was made using a cellulose ether rather than polyvinyl alcohol. 
Table II summarizes all the chlorinated polyvinyl chloride products of 
Examples 13-16. Color properties were measured on injected molded 
compounds of Examples 13, 14 and 16 using Example 15 as a reference (DE of 
zero by definition). Color properties were measured with the ACS 1400 
spectrophotometer, using the CIE test procedure and color differentiating 
formula. DE is a qualitative measurement of the total color difference 
between a color standard (Example 15 in this instance) and a sample. This 
difference includes the lightness and chromaticity differences. The lower 
the DE value, the closer the colors will appear to each other when 
examined visually. 
Table II also summarizes Dynamic Thermal stability (DTS) on control Example 
13 and present invention Examples 15 and 16. Control Example 13 has a 
lower time to the onset of the degradation (and induced crosslinking). 
Inventive Examples 15 and 16 exhibit much longer times to the onset of 
degradation (and induced crosslinking) indicating a more stable resin. 
TABLE II 
__________________________________________________________________________ 
Properties of Chlorinated 
Polyvinyl 
Chloride 
Cl.sub.2 
Polyvinyl Chloride 
Example 
Example 
n.sub.1 
Time (Min) 
% Cl 
DE Time (min.) 
__________________________________________________________________________ 
13 (Control) 
1 .520 270 64.1 
18.5 
22 
14 (Control) 
2 .440 198 65.2 
22.9 
27 
15 3 .552 140 63.4 
0 35 
16 12 .467 131 63.6 
5.4 
28 
__________________________________________________________________________ 
Table III is directed to HCl elimination at 170.degree. C. This test is a 
measure of the stability of the CPVC resins. CPVC prepared from a 
polyvinyl alcohol PVC exhibit a higher mole percent HCl evolution versus 
CPVC prepared from a cellulose ether PVC. CPVC prepared from a cellulose 
ether PVC is more stable than CPVC prepared from a polyvinyl alcohol PVC. 
TABLE III 
______________________________________ 
Comparison of CPVC Samples (n.sub.1 = 0.54) 
Mole % HCl Mole % HCl 
Evolved Evolved Mole % HCl 
Ex. 13 Ex. 15 Evolved 
PVC Made From PVC Made From 
Ex. 15 
Minutes 
Polyvinyl Alcohol 
Cellulose Ether 
(repeat) 
______________________________________ 
0 0.0000 0.0000 0.0000 
10 0.026 0.014 0.019 
20 0.058 0.033 0.039 
30 0.088 0.053 0.058 
40 0.118 0.068 0.078 
50 0.146 0.087 0.097 
60 0.175 0.106 0.118 
______________________________________ 
While in accordance with the Patent Statutes, the best mode and preferred 
embodiment has been set forth, the scope of the invention is not limited 
thereto, but rather by the scope of the attached claims.