Chlorosulfonated alkylene-alkyl acrylate copolymers prepared by reacting, in the absence of a solvent or diluent, a granular alkylene-alkyl acrylate copolymer with a gaseous chlorosulfonating agent. The granular, elastomeric chlorosulfonated alkylene-alkyl acrylate copolymers can be used as extrudates about wires and cables and can be formed into film material characterized by excellent optical properties.

SUMMARY OF THE INVENTION 
This invention relates to chlorosulfonated alkylene-alkyl acrylate 
copolymers prepared by reacting, in the absence of a solvent or diluent, a 
granular alkylene-alkyl acrylate copolymer with a gaseous 
chlorosulfonating agent. The granular, elastomeric chlorosulfonated 
alkylene-alkyl acrylate copolymers so produced have a tensile modulus of 
less than about 2000 psi, a crystallinity of less than about 10 percent 
and are particularly useful as flame retardant extrudates about wires and 
cables and as film material characterized by excellent optical properties. 
BACKGROUND OF THE INVENTION 
Alkylene-alkyl acrylate copolymers are known copolymers which are 
characterized by an excellent balance of properties such as relatively 
high tensile strength, resistance to moisture and resistance to common 
solvents and diluents. By reason of their excellent balance of properties, 
alkylene-alkyl acrylate copolymers have been used in many diverse 
applications including jacketing and insulation about wires and cables and 
as film to be used as packaging material. A serious drawback to the even 
wider acceptance of alkylene-alkyl acrylate copolymers in the areas of use 
described has been the poor flammability characteristics of the copolymers 
and the poor optical properties of film material prepared from these 
polymers. It has been necessary, with respect to the flammability problem, 
to compound these polymers with various flame retardant additives such as 
antimony oxide and chlorinated paraffins. The additional compounding step 
not only adds to the overall cost of the compositions but, in the case of 
chlorinated paraffins which contain labile chlorine, chlorine splits off 
as HCl which can degrade compounded compositions. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides chlorosulfonated alkylene-alkyl acrylate 
copolymers which, by their chemical structure, have a built-in flame 
retardant capability. Consequently, the chlorosulfonated alkylene-alkyl 
acrylate copolymers of this invention do not require the addition thereto 
of flame retardant additives. Furthermore, the copolymers can be formed 
into film material, by the conventional bubble technique, which is 
characterized by excellent optical properties. The chlorosulfonated 
alkylene-alkyl acrylate copolymers of this invention, therefore, are 
especially useful as flame retardant extrudates about wires and cables as 
clear film for packaging. 
The polymers of this invention are prepared by reacting, in the absence of 
a solvent or a diluent, a granular, alkylene-alkyl acrylate copolymer with 
a gaseous chlorosulfonating agent to produce a granular, elastomeric, 
chlorosulfonated alkylene-alkyl acrylate copolymer having a tensile 
modulus of less than about 2,000 psi and a crystallinity of less than 
about 10 percent, preferably a crystallinity of 0 to about 5 percent. 
These polymers generally have a total chlorine content of about 5 to about 
55 percent by weight, preferably about 15 to about 40 percent by weight 
and generally have a sulfur content of about 0.1 to about 10 percent by 
weight, preferably about 0.5 to about 5 percent by weight. 
The reaction depicting the chlorosulfonation reaction wherein chlorine and 
SO.sub.2 Cl groups replace hydrogen atoms of the polymer backbone is set 
forth below. 
##STR1## 
The chlorosulfonated polymers, prepared as shown by the reaction scheme 
above, are flexible, flame retardant polymers which can be formed into 
clear film; and are different in character from conventional 
chlorosulfonated ester polymers produced according to the process 
disclosed in U.S. Pat. No. 2,778,812. 
The reaction scheme, involving the preparation of chlorosulfonated ester 
polymers according to U.S. Pat. No. 2,778,812, can be depicted as follows: 
##STR2## 
These polymers (U.S. Pat. No. 2,778,812)are brittle and flammable. 
The alkylene-alkyl acrylate copolymers which are chlorosulfonated in 
accordance with this invention are known polymers produced by reacting an 
alkene or mixtures thereof with an alkyl acrylate or mixtures thereof. 
Suitable alkenes are ethylene, propylene, butene-1, isobutylene, pentene-1, 
2-methylbutene-1, 3-methylbutene-1, hexene-1, heptene-1, octene-1, and the 
like. 
The alkylene moiety of the alkylene-alkyl acrylate copolymer generally 
contains from 2 to 18 carbon atoms inclusive, preferably 2 to 3 carbon 
atoms inclusive. 
Suitable alkyl acrylate monomers which are copolymerized with the alkenes 
fall within the scope of the following formula: 
##STR3## 
wherein R.sup.4 is hydrogen or methyl and R.sup.5 is alkyl having one to 8 
carbon atoms inclusive. Illustrative compounds encompassed by this formula 
are: methyl acrylate, ethyl acrylate, t-butyl acrylate, methyl 
methacrylate, n-butyl acrylate, n-butylmethacrylate, 2-ethylhexyl acrylate 
and the like. 
Alkylene-alkyl acrylate copolymers generally have a density (ASTM D-1505 
with conditioning as in ASTM D-147-72) of about 0.92 to about 0.94 and a 
melt index (ASTM D-1238 of 44 psi tested pressure) of about 0.5 to about 
500 decigrams per minute and are formed by reacting about 50 to 99 and 
preferably about 80 to 98 percent by weight alkene, preferably ethylene 
and about 1 to 50 and preferably 2 to 20 percent by weight combined alkyl 
acryalte. 
For purposes of the present invention, the preferred copolymer is an 
alkylene-alkyl acrylate copolymer generally a copolymer of ethylene-ethyl 
acrylate, having about one to about 50 percent by weight combined alkyl 
acrylate, preferably having about 2 to about 20 percent by weight combined 
alkyl acrylate. 
The actual time of treatment generally varies from about 3 to about 10 
hours, depending upon the particular polymer being chlorosulfonated, the 
chlorosulfonating agent being used and the temperature and pressure being 
employed. 
Generally, suitable temperatures are in the range of about 50.degree. C. to 
about 130.degree. C., preferably about 50.degree. C. to about 100.degree. 
C. The pressure under which the reaction is conducted can range from 
atmospheric pressure to a pressure of about 1,000 psi, provided that none 
of the reactants or by-products condense under the reaction conditions 
employed. As a rule, the higher the temperature and pressure, the shorter 
the reaction time. 
In carrying out the reaction, the amount of chlorosulfonating agent used, 
e.g. a mixture of sulfur dioxide and chlorine, is about 10 to about 200 
percent by weight, preferably about 20 to about 100 percent by weight 
based on the weight of the polymer being treated. In those instances 
wherein a mixture of SO.sub.2 and Cl.sub.2 is used as the reactant or 
modifying agent, the mole ratio of Cl.sub.2 to SO.sub.2 is about 5:1 to 
10:1, preferably about 5:1. 
If desired, an inert gas such as nitrogen may be used in conjunction with 
the gaseous modifying agents, serving as a fluidizing agent, a diffusion 
aid and/or as a heat sink. 
The properties noted herein were determined by the following test methods: 
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Crystallinity 
Measured by Differential Scanning 
(percent) Calorimeter (DSC) using a duPont-990 
analyzer with a pressure DSC cell. 
Tensile Modulus 
A film, 4 inches by 4 inches by 0.020 
(psi) inch, was compression molded at a 
temperature of 130.degree. C.-150.degree. C. and its 
one percent secant modulus measured 
according to ASTM-D-638. 
Tensile Strength 
A film prepared as described for the 
(psi) Tensile Modulus test, was tested 
according to ASTM-D-638. 
Percent Elongation 
A film, prepared as described for the 
at Break Tensile Modulus test, was tested 
according to ASTM-D-638. 
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Also, the term "granular" is intended to encompass alkylene-alkyl acrylate 
copolymers which generally have a particle size of about 150 to 1000 
microns, and an average particle size of about 300 to 800 microns.

In the following Examples, which are illustrative of the present invention, 
the ethylene ethyl acrylate copolymers were chlorosulfonated in a two 
liter glass-lined stainless steel or Hastelloy (55Ni, 17Mo, 16Cr, 6Fe, 4W) 
reactor equipped with a thermocouple thermometer and a motor activated 
U-shaped Hastelloy stirrer. 
A Hastelloy dip tube (.about.2 cm in diameter) was used to feed the gaseous 
modifying agent(s) into the reactor. Unreacted modifying agent and HCl 
were vented to a collection trap containing 25 percent aqueous NaOH. The 
gaseous modifying agents were fed at the rate of 10 to 12 grams Cl.sub.2 
per hour and 2-3 g SO.sub.2 /hour under a pressure of about 15 to 450 psi. 
The polymer to be treated, about 100 to 200 grams, was charged to the 
reactor and heated therein by an external heater. No catalysts were used 
in any of these experiments. 
After the polymer was added to the reactor and heated to the desired 
reaction temperature the resin was agitated by the stirrer and the gaseous 
modifying agent was fed in. During the course of the reaction, samples of 
the modified polymer were taken from the reactor to test for S and Cl 
content, and percent crystallinity. When the modification process has 
proceeded to the point where the crystallinity of the polymer had reached 
less than about 10 percent, the flow of gaseous modifying agent was 
terminated and the product was allowed to cool in the reactor while being 
purged with nitrogen to remove SO.sub.2, Cl.sub.2 and HCl. 
Five separate runs were conducted using an ethylene-ethyl acrylate 
copolymer containing 18 percent by weight ethyl acrylate and having an 
average particle size of about 500 microns. 
Properties of the unmodified ethylene-ethyl acrylate copolymer and the 
chlorosulfonated ethylene-ethyl acrylate copolymers are set forth in Table 
1. 
TABLE 1 
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Properties of Chlorosulfonated EEA 
Starting 
Final Product 
Resin: Material 1 2 3 4 5 
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Properties: 
Cl, percent 0 16 24 28 29 30 
S, percent 0 0.85 0.45 0.15 0.9 2.2 
Crystallinity, percent 
32 6 &lt;10 5.4 3 5 
Tensile Modulus 
5,560 1,810 1,350 
1,100 
885 900 
at .about.25.degree. C., psi 
Tensile Strength, psi 
2,300 1,360 1,300 
830 850 1,210 
Elongation, percent 
919 742 660 340 527 494 
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