Internally plasticized vinyl chloride copolymer
This application is a continuation-in-part of U.S. Serial No. 801,957, filed May 31, 1977, which in turn was a continuation-in-part of U.S. Ser. No. 763,185, filed Jan. 27, 1977, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an internally plasticized copolymer of vinyl chloride, an alkyl acrylate and a bis (hydrocarbyl)vinylphosphonate. 
     2. Description of the Prior Art 
     External plasticizers in vinyl chloride homo- and copolymers are commonly employed today to form products having the required degree of flexibility for a given purpose. Such external plasticization, however, it not entirely satisfactory since the plasticizer tends to migrate to the surface and eventually is lost either by volatilization or extraction. This loss gives rise to such problems as surface stickiness, automotive windshield fogging and embrittlement of vinyl films containing the polymer which are used in such applications as shower curtains, baby pants, vinyl seat covers, and the like. Hence, various proposals for &#34;internal plasticization&#34; of vinyl chloride polymers have been made wherein the plasticizing action is supplied by one or more comonomers for vinyl chloride which are polymerized with the vinyl chloride to form the polymer. 
     The use of copolymers of a vinyl monomer and a polymerizable polyester, for example, an acrylate or a vinyl ester of a polyester of an aliphatic hydroxycarboxylic acid, was proposed in U.S. Pat. No. 3,640,927 to C. S. Marvel et al. An internally plasticized, two component vinyl chloride copolymer containing from about 75% to about 95% vinyl chloride and about 25% to about 5% of an ester of an unsaturated mono- or polycarboxylic acid, e.g., a C 6  -C 12  alkyl maleate, fumarate or acrylate, was proposed in U.S. Pat. No. 3,544,661 to A. Oth et al. A four component polymer composition vinyl chloride, a dialkyl maleate or fumarate, an alkyl ester of acrylic or methacrylic acid and a monohydrogen, monoalkyl maleate or fumarate was proposed in U.S. Pat. No. 3,196,133 to R. A. Piloni et al. for use as a solvent-based coating having both good adhesiveness and flexibility. In copending U.S. Ser. No. 795,990 filed May 11, 1977, by R. E. Gallagher et al. an internally plasticized copolymer of vinyl chloride, a C 1  -C 10  alkyl acrylate and a C 8  -C 22  dialkyl maleate or fumarate is disclosed. 
     Two component copolymers of vinyl chloride and such acrylates as 2-ethylhexyl acrylate, as seemingly suggested by certain portions of the Oth et al. patent produce heterogeneous resin compositions which do not show the desirable performance properties of flexible vinyl films of the present invention. 
     A variety of two component vinyl chloride/vinylphosphonate copolymers are known which cannot be classified as internally plasticized copolymers (U.S. Pat. Nos. 3,691,127, 3,792,113 and 3,819,770) since copolymerizing just vinyl chloride and a bis(hydrocarbyl)vinylphosphonate, e.g., bis(beta chloroethyl) vinylphosphonate, leads to production of a resin which gives a hard, relatively unflexible film requiring external plasticization. It does not appear to have been hitherto appreciated that a vinyl chloride/acrylate/vinylphosphonate copolymer, as described and claimed herein, would have flexibility characteristics as well as performance properties equivalent in many respects to externally platicized polyvinyl chloride without having to add a substantial amount of external plasticizer. Unexpectedly, the bis(hydrocarbyl)vinylphosphonate monomer aids in rendering the terpolymer less heterogeneous in appearance and resulting properties than if only vinyl chloride and an alkyl acrylate were used as comomers as suggested by certain prior art patents. The copolymers also has reduced smoke generation characteristics. 
     SUMMARY OF THE PRESENT INVENTION 
     The copolymer of the present invention is an internally plasticized vinyl chloride copolymer of from about 50% to about 85%, by weight, vinyl chloride, from about 3% to about 47%, by weight, of a C 6  -C 10  alkyl acrylate, e.g., 2-ethylhexyl acrylate, and from about 3% to about 47%, by weight, of a bis(hydrocarbyl) vinylphosphonate, e.g., bis(beta-chloroethyl)vinylphosphonate. The copolymer is formed using conventional suspension, emulsion, bulk and solution polymerization techniques and can be used in those applications where externally plasticized polyvinyl chloride is used, e.g., as a vinyl film or sheeting material, in vinyl wire and cable insulation, as vinyl flooring, and as bag and tubing for blood transfusion equipment. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It has been unexpectedly found that a flexible vinyl film prepared from an internally plasticized vinyl chloride polymer without any external plasticization exhibits a Clash-Berg value of about 0° C. or below, preferably about -15° C. or below, and a tensile strength at break of at least about 60 kg./cm. 2  or higher, preferably about 85 kg./cm. 2  or greater. Such an internally plasticized polymer can be formed with conventional emulsion, suspension, bulk and solution polymerization procedures by using a basic three component monomer charge which contains certain amounts of vinyl chloride, a C 6  -C 10  alkyl acrylate, and a bis(hydrocarbyl) vinylphosphonate, e.g., bis(beta-chloroethyl)vinylphosphonate. The invention is, more particularly, an internally plasticized copolymer which contains from about 50% to about 85%, by weight, of vinyl chloride, from about 3% to about 47%, by weight, of a C 6  -C 10  alkyl acrylate, and from about 3% to about 47%, by weight, of a bis(hydrocarbyl)vinylphosphonate copolymerized therein. 
     The terminology &#34;bis(hydrocarbyl)vinylphosphonate&#34; as used in the present application is meant to encompass vinylphosphonates having the formula: ##STR1## wherein X is selected from the group consisting of hydrogen, halogen, cyano, aryl, such as phenyl, C 1  -C 18  alkyl and ##STR2## wherein R and R&#39; are hydrocarbyl and substituted hydrocarbyl groups consisting essentially of hydrogen and carbon, and containing up to about 18 carbon atoms inclusive, with the proviso that R and R&#39; may be the same, different or conjoint, i.e., R and R&#39; may combine to form one single radical. 
     The use, in this disclosure, of the expression &#34;hydrocarbyl&#34; and &#34;substituted hydrocarbyl groups&#34; in the definition of the suitable bis(hydrocarbyl)vinylphosphonates given hereinabove refers to the radicals obtained upon the removal of a hydrogen from a hydrocarbon or substituted hydrocarbon group which may be either an aliphatic or aromatic group. These hydrocarbyl groups may be substituted with any non-interferring groups, i.e., with any group which does not interfere with the polymerization of the bis(hydrocarbyl)vinylphosphonate. Such substituent groups include, for example, chloro, bromo, fluoro, nitro, hydroxy, sulfone, ethoxy, methoxy, nitrile, ether, ester and keto groups and the like. 
     Illustrative of the aliphatic and aromatic groups as represented by R and R&#39; in the structure of the bis(hydrocarbyl) vinylphosphonate given hereinabove are alkyl groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, nonyl, and the like; alkenyl groups, such as pentenyl and hexenyl groups and all of their respective isomers; cycloalkyl groups, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like; cycloalkenyl groups, such as cyclohexenyl and the like; typical aryl groups include phenyl, benzyl, phenethyl, tolyl, naphthyl and the like. 
     Representative of the above-defined bis(hydrocarbyl)vinylphosphonates are: 
     Bis(beta-chloroethyl)vinylphosphonate; 
     Bis(2-ethylhexyl)vinylphosphonate; 
     Bis(beta-chloropropyl)vinylphosphonate; 
     Bis(beta-chloroethyl) 1-methylvinylphosphonate; 
     Bis(beta-chloroethyl) 1-cyanovinylphosphonate; 
     Bis(beta-chloroethyl) 1-chlorovinylphosphonate; 
     Bis(beta-chloroethyl) 1-phenylvinylphosphonate; 
     Dimethyl vinylphosphonate 
     Diethyl vinylphosphonate; 
     Bis(omega-chlorobutyl)vinylphosphonate; 
     Di-n-butyl vinylphosphonate; 
     Di-isobutyl vinylphosphonate; 
     Bis(2-chloroisopropyl) 1-methylvinylphosphonate 
     Diphenyl vinylphosphonate; and 
     Bis(2,3-dibromopropyl)vinylphosphonate 
     From the above group of bis(hydrocarbyl)vinylphosphonate monomers, it is preferred to employ bis(beta-chloroethyl) vinylphosphonate in preparing the novel polymers of this invention since this monomer is a commercially available material, lower in cost than any of the other bis(hydrocarbyl)vinylphosphonates. Bis(2-ethylhexyl)vinylphosphonate is also a preferred monomer since it gives a product having very desirable physical properties such as good low temperature flexibility. 
     Representative C 6  -C 10  alkyl acrylates which can be used in the practice of the present invention include n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and mixtures of the foregoing acrylates. The C 8  -C 10  alkyl acrylates are preferred for use, especially the branched alkyl groups, for example, 2-ethylhexyl acrylate, since such branched alkyl groups give better physical properties to the resulting resin. 
     Mixtures of the respective alkyl acrylates and of the vinylphosphonates can be used, if desired. 
     One preferred copolymer from the standpoint of cost and performance is a terpolymer containing from about 55% to about 80%, by weight, vinyl chloride, from about 10% to about 35%, by weight of the C 6  -C 10  alkyl acrylate, and from about 5% to about 25%, by weight, of a bis(C 2  -C 8  alkyl) or (C 1  -C 8  haloalkyl)vinylphosphonate copolymerized therein. One terpolymer which can be used to form films having a Shore &#34;A&#34; hardness of about 60 to about 72 contains about 56%, by weight, of vinyl chloride, about 29% to about 31%, by eight, 2-ethylhexyl acrylate and about 11% to about 13%, by weight, of the vinylphosphonate, e.g., of bis(beta-chloroethyl)vinylphosphonate or of bis (2-ethylhexyl)vinylphosphonate. For a harder film having a Shore &#34;A&#34; hardness of about 80 to about 90, a higher vinyl chloride content is needed. This is easily accomplished by raising the vinyl chloride content and correspondingly reducing the acrylate and vinylphosphonate content. For example a terpolymer having a Shore &#34;A&#34; hardness of about 85 to about 95 can contain about 73% to about 75%, by weight, vinyl chloride, about 17% to about 19%, by weight, of the C 6  -C 10  alkyl acrylate, e.g., 2-ethylhexyl acrylate and about 7% to about 9%, by weight of the bis(hydrocarbyl)vinylphosphonate, e.g., bis(beta chloroethyl)vinylphosphonate. 
     The copolymer of the present invention can be formed using conventional bulk, emulsion, suspension and solution polymerization procedures. Suspension polymerization is preferred since it avoids the problems of isolation of the product from a latex that can be encountered using emulsion polymerization techniques, the heat of reaction is more readily removed as compared to bulk polymerization procedures, and no solvent recovery is needed as in solution polymerization. 
     Suspension polymerization reaction mixtures comprise from about 20% to about 45%, by weight, based on the amount of water, of the above-enumerated monomers in an aqueous reaction medium. Also included will be from about 0.05% to about 5%, by weight, based on the weight of monomers, of a suspending agent, such as methyl cellulose, hydroxypropyl methyl cellulose, gelatine, and the like; from about 0.005% to about 1%, by weight, based on the amount of monomer, of at least one-monomer-soluble initiator, such as azobisisobutyronitrile, lauroyl peroxide, benzoyl peroxide or isopropyl peroxydicarbonate. The polymerization reaction is conducted by heating the suspension containing the above components to a temperature of from about 35° C. to about 75° C. for about 2 to about 12 hours with agitation being applied throughout the course of the reaction. As is well known in the art, the use of the more active of the above mentioned initiators will require use of either a lower temperature or shorter reaction time, or both, whereas use of the less active initiators may require more vigorous reaction conditions. If desired the molecular weight of the polymers can be regulated by adding an effective amount of a chain transfer agent during the polymerization. Generally from about 0.01 to about 0.1%, by weight of the monomers, will be effective. Representative chain transfer agents include the chlorinated hydrocarbons, e.g., tetrachloroethane, trichloroethane and carbon tetrachloride, and mercaptans of the formula RSH, where R is an alkyl group, e.g., a C 1  -C 12  alkyl group, such as butyl or dodecyl. 
     If emulsion polymerization is to be employed, the above described suspending agent is replaced with from about 0.2% to about 2%, by weight, of an emulsifying agent, such as sodium lauryl sulfate, potassium stearate, an alkyl benzene sulfonate, an ammonium dialkyl sulfosuccinate, and the like, and the monomer soluble initiator is replaced by from about 0.1% to about 1% of a water-soluble initiator, such as an alkali metal persulfate, perborate or peracetate, ammonium persulfate, perborate or peracetate, the urea peroxides, hydrogen peroxide, tertiary butyl hydroperoxide, and the like. If desired, a redox initiator system such as ammonium persulfate and sodium bisulfite or hydrogen peroxide and ascorbic acid can also be used as the initiator. Polymerization is carried out at similar temperatures and over similar times as those used in suspension polymerization. 
     If bulk polymerization is employed, the monomers are polymerized in the presence of the above-described amounts of the monomer-soluble catalysts under the same temperature and time conditions described above in connection with suspension and emulsion polymerization. 
     If solution polymerization is employed, the monomers are polymerized in the presence of at least one inert organic solvent, such as butane, pentane, octane, benzene, toluene, cyclohexanone, acetone, isopropanol, tetrahydrofuran or the like. The selected initiator should be soluble in the reaction medium. The copolymer can either remain dissolved in the solvent at the end of the polymerization or can precipitate from the liquid phase during the polymerization. In the former case, the product can be recovered by evaporation of the solvent or by precipitation of the polymer solution by combining it with a non-solvent for the product. The same reaction conditions used in suspension and emulsion polymerization can be used. 
     The final product of the present invention can contain, if desired, various optional additives which are compatible with the copolymer product and which do not adversely affect the properties of said product. Included within this class of additives are those heat and light stabilizers, ultraviolet stabilizers, pigments, fillers, dyes, and other additives known to persons of ordinary skill in the art. A suitable listing of possible additives which a person of ordinary skill in the art may use to select appropriate additives, if desired, is given in Modern Plastics Encyclopedia, Vol. 51, No. 10A, e.g., at pp. 735-754. 
     The following Examples illustrate certain preferred embodiments of the present invention: 
    
    
     EXAMPLE 1 
     This Example illustrates the generalized procedure which was used to form an internally plasticized resin in accordance with the present invention by suspension polymerization. 
     The following ingredients were used. All amounts are given in parts by weight: 
     
         ______________________________________                                    
Ingredient               Amount                                           
______________________________________                                    
Vinyl chloride monomer   100                                              
2-ethylhexyl acrylate    46.5                                             
Bis(beta-chloroethyl)                                                     
vinylphosphonate         19.95                                            
Hydroxypropylmethylcellulose sus-                                         
pending agent (&#34;Methocel&#34; K-35                                            
from The Dow Chemical Co.)                                                
                         0.23                                             
20 wt. % isopropylperoxydi-                                               
carbonate in heptane     0.54                                             
Deionized water          423                                              
______________________________________                                    
 
    
     The following procedure was used to polymerize the vinyl chloride, acrylate and vinylphosphonate monomers: 
     1. The suspending agent was dissolved in a portion of the deionized water and was charged into the reactor along with the remainder of the deionized water. The mixture was stirred briefly and the perioxydicarbonate/heptane initiator mixture was added; 
     2. The acrylate and vinylphosphonate monomers were added; 
     3. The reactor was closed, vacuum was applied (approx. 584.2-635 mm. of Hg. pressure) for 10 minutes to remove air from the reactor, and vinyl chloride monomer vapor was added to break the vacuum. This operation was repeated once and the vinyl chloride was charged into the reactor; 
     4. The agitator was set at 496 revolutions per minute and the reactor was heated to 50° C. until the pressure in the reactor dropped 4.2 kg./cm 2  from the maximum pressure noted near the beginning of the reaction; 
     5. The reactor was vented and sparged with nitrogen at a rate of 70.7 cubic cm./sec. for a 44 liter reactor for a period of 1 hour to remove residual monomer from the product; 
     6. The reactor was allowed to cool and the polymer particles were recovered by centrifuging. The particles were dried in a fluid bed drier using air at 30° C.; 
     7. The dried polymer was milled through a Fitz mill and was sieved through a 30 mesh screen. 
     Three repeats of the above procedure were conducted. The polymers which were obtained contained from about 57.4 to about 57.7%, by weight, vinyl chloride from about 29.7 to about 31.5%, by weight, 2-ethylhexyl acrylate and from about 11.1 to about 12.6%, by weight, bis(beta-chloroethyl)vinylphosphonate and had a relative viscosity of from about 2.74 to about 3.07 when measured as a 1%, by weight, solution of the copolymer in cyclohexanone. The feed composition in each case was a 60/28/12 weight percent composition of each of the respective monomers. The differences were due to minor uncontrollable variations in the above described reaction conditions. 
     EXAMPLE 2 
     This Example illustrates the physical properties of a series of film formulations made from the copolymer of the present invention. The following procedures were used to make each test sample: 
     Samples 1-3: 
     A compressible film formulation was made for each sample by mixing together the following ingredients in the following amounts:______________________________________                     (Amount in Grams)Ingredient             1       2      3______________________________________Copolymer of this Invention*                       255     255    255Chlorinated Polyethylene                       45      45     45Epoxidized octyl tallate                       15      15     15Barium Cadmium liquid Stabilizer                       9       9      9Calcium stearate lubricant                       3       3      3Stearic acid lubricant 3       3      3Calcium Carbonate filler                       90      90     90Titanium dioxide pigment                       12      12     12Acrylic Processing Aid (&#34;K-175&#34; soldby Rohm and Haas Co.)  15      --     --Ethylene bisstearamide lubricant(&#34;Lubrol EA&#34; sold by I.C.I.Organics, Inc.)        3       3      --Bisstearamide lubricant (&#34;Advawax 240&#34;sold by Cincinnati Milacron)                       --      --     3______________________________________ *Sample 1 used a 57.4/31.5/11.1 copolymer of vinyl chloride (VC)/2-ethylhexyl acrylate (EHA)/bis(beta-chloroethyl)vinylphosphonate (BB) having a relative viscosity of 2.78. Sample 2 used a 57.6/30.9/11.5 copolymer having a relative viscosity of 3.07. Sample 3 used a 57.7/29.7/12.6 copolymer with a relative viscosity of about 2.8. 
     The ingredients mentioned in the above formulations were handmixed and were then milled on a 2 roll having the rolls at 310° F. (154° C.) and 315° F. (157° C.), respectively, for Sample 1 and 157° F. (160° C.) for Samples 2 and 3. After fluxing in the 2 roll mill for about 7 min., the milled stocks were compression molded at 320° F. (160° C.) to produce films having a thickness of from about 0.038 in. (0.09 cm.) to about 0.048 in. (0.12 cm.) for measurement of the physical properties according to various standard testing procedures. 
     Samples 4-7: 
     Compressible film formulations were formed from the following ingredients:______________________________________                  (Amount in Grams)Ingredient          4       5      6    7______________________________________Copolymer of this Invention*                    300     300    300  300Epoxidized soybean oil                    15      --     15   --Epoxidized octyl tallate                    --      15     --   15Barium cadmium stabilizer (liq.)                    9       9      9    9Calcium stearate    3       3      3    3Stearic acid        3       3      3    3Bisstearamide lubricant                    3       --     --   --Ethylene bisstearamide lubricant                    --      3      3    3______________________________________ *the copolymer used in Samples 4 and 5 was the same copolymer used in Sample 1, whereas the copolymer used in Samples 6 and 7 was the same as that used in Sample 2. 
     The mill conditions for Samples 4 and 5 were the same as for Sample 1, and the conditions for Samples 6 and 7 were the same as for Samples 2 and 3. 
     Samples 8-11: 
     Compressible film formulations were formed from the following ingredients:______________________________________                  (Amount in Grams)Ingredient          8       9      10   11______________________________________Copolymer of this Invention*                    255     255    225  150Chlorinated polyethylene                    45      45     75   150Epoxidized octyl tallate                    15      15     15   15Barium cadmium stabilizer (liq.)                    9       9      9    9Calcium stearate    3       3      3    3Stearic acid        3       3      3    3Calcium Carbonate   90      90     90   90Titanium Dioxide    12      12     12   12Fused silica (Cab-O-Sil)                    3       --     3    3Ethylene bisstearamide lubricant                    3       3      --   --Bisstearamide lubricant                    --      --     3    3______________________________________ *the copolymer used in Sample No. 8 was the same as that used in Sample No. 1; the copolymers in Samples Nos. 9-11, the same as in Sample No. 2. 
     Sample No. 8 was milled using the same procedure as that used with Sample No. 1. Samples Nos. 9-11 were milled using the procedure for Samples Nos. 2 and 3. 
     Samples 12-13: 
     Compressible film formulations were formed from the following ingredients:______________________________________                  (Amount in Grams)Ingredient          12         13______________________________________Copolymer of this Invention*                    150        150Epoxidized soybean oil                    7.5        7.5Calcium carbonate   45         45Titanium Dioxide    6          6Calcium stearate    1.5        1.5Stearic acid        1.5        1.5Bisstearamide lubricant                    1.5        1.5______________________________________ *this consisted of 150 grams of a blend formed by admixing 1970 g. of the copolymer used in Sample No. 1, 3988 grams of the copolymer used in Sampl No. 2 and 5080 grams of the copolymer used in Sample No. 3. 
     The samples were milled in accordance to the procedure used to mill Sample No. 1 with the rolls for Sample 12 being at (154°/157° C.) and those for Sample 13 at (138°/140.5° C.). 
     Table 1 which follows sets forth the physical properties for these thirteen samples. 
     
                                           TABLE 1                                 
__________________________________________________________________________
                 SAMPLE NO.                                               
PROPERTY         1    2    3    4    5    6    7                          
__________________________________________________________________________
Clash-Berg Temperature (° C.).sup.1                                
                 -27  -30  -28  -23  -28  -28  -37                        
Shore &#34;A&#34; Hardness.sup.2                                                  
                 67   69   64   65   61   68   58                         
Tensile Strength, Break (kg./cm..sup.2).sup.3                             
                 72.1 80.8 63.4 115.6                                     
                                     97.7 106.4                           
                                               91.5                       
100% Modulus (kg./cm..sup.2).sup.4                                        
                 44.5 48.0 37.8 65.4 46.6 55.6 49.3                       
Elongation at Break (%).sup.5                                             
                 269  257  279  229  271  231  219                        
Graves Tear Strength (kg./cm.).sup.6                                      
                 20.3 23.7 20.1 24.4 19.6 24.8 18.3                       
Flexural Modulus of Elasticity                                            
(kg./cm..sup.2).sup.7                                                     
                 54.1 81.5 49.9 54.8 44.2 84.3 37.9                       
Hexane Permanence.sup.8                                                   
                 --   4.6  5.5  --6.9                                     
                                     6.8  6.6                             
Perchloroethylene Permanence.sup.9                                        
                 --   4.5  7.3  --   8.6  5.0  6.4                        
% Volatile Weight Loss.sup.10                                             
                 --   1.0  1.7  1.5  1.8  1.8  1.6                        
                 8     9     10    11    12    13                         
__________________________________________________________________________
Clash-Berg Temperature (° C.).sup.1                                
                 -30   -30   -29   -31   --    --                         
Shore &#34; A&#34; Hardness.sup.2                                                 
                 58    69    65    62    76    76                         
Tensile Strength, Break (kg./cm..sup.2).sup.3                             
                 80.2  80.8  62.5  62.0  105.5 106.1                      
100% Modulus (kg./cm..sup.2).sup.4                                        
                 36.2  48.0  35.8  26.4  70.0  72.3                       
Elongation at Break (%).sup.5                                             
                 311   257   309   523   203   201                        
Graves Tear Strength (kg./cm.).sup.6                                      
                 19.8  23.7  23.0  28.3  26.4  24.6                       
Flexural Modulus of Elasticity                                            
(kg./cm..sup.2).sup.7                                                     
                 40.0  81.5  78.7  74.5  147.6 140.6                      
Hexane Permanence.sup.8                                                   
                 --    4.6   6.0   6.0   --    --                         
Perchloroethylene Permanence.sup.9                                        
                 --    4.5   9.3   8.6   --    --                         
% Volatile Weight Loss.sup.10                                             
                 --    1.0   1.6   1.3   --    --                         
__________________________________________________________________________
 Footnotes:                                                               
 .sup.1 This is the temperature at which the apparent modulus of elasticit
 of a specimen is 9491.4 kg./cm..sup.2. It is the end of flexibility of th
 sample as defined by Clash and Berg in their studies of low temperature  
 flexibility. This point can be determined by ASTM D 1043, which is       
 incorporated herein by reference.                                        
 .sup.2 This is a measure of indentation hardness and is measured on the  
 Shore A durometer after 10 seconds ASTM Test Method No. D-2240). This    
 instrument comprises a spring loaded indentor point with a load of 822   
 grams projecting through a hole in a presser foot. The device has a scale
 which indicates the degree of penetration into the plastic beyond the fac
 of the foot. The scale ranges from 0 (for 0.254 cm. penetration) to 100  
 (for zero penetration).                                                  
 .sup.3 This is the maximum tensile stress sustained by a specimen of the 
 resin during a tension test (ASTM D-882). The result is expressed in     
 kilograms per Cm..sup.2, the area being that of the original specimen at 
 the point of rupture rather than the reduced area after break.           
 .sup.4 This is the tensile strength needed to elongate a specimen to 100%
 of its original length (ASTM D-822).                                     
 .sup.5 In tensile testing elongation is the increase in length of a      
 specimen at the instant before rupture occurs (ASTM D-882). Percent      
 elongation is expressed as the increase in distance between two gauge    
 marks at rupture divided by the original distance between the marks, the 
 quotient being multiplied by 100.                                        
 .sup.6 The Graves test (ASTM) was used to determine the tear strengths   
 using specimens 0.10- 0.127 cm. in thickness.                            
 .sup.7 The ratio of stress (nominal) to corresponding strain below the   
 proportional limit of a material (ASTM-790). It is expressed in force per
 unit area.                                                               
 .sup.8 Measured at room temperature after 24 hours. The films were kept i
 hexane at room temperature for 24 hours, followed by oven drying in a    
 forced air oven at 50° C. for three to four hours. The numbers giv
 the percent weight loss of extractibles in the film. Lower numbers are   
 desired.                                                                 
 .sup.9 Measured at room temperature after 1 hour. The films were kept in 
 perchloroethylene for 1 hour, followed by drying in a forced air oven at 
 50° C. for five hours. The numbers give the percent weight loss of
 extractibles in the film. Lower numbers are desired.                     
 .sup.10 The films were placed in a container containing activated carbon 
 and were heated at 90° C. for 24 hours. The volatile materials wer
 absorbed by the carbon. The numbers represent the percent volatile weight
 loss from the film. Lower numbers are desired.                           
 
    
     Samples 1-3 which are the internally plasticized resins of the present invention are all fairly alike in physical properties. Resin No. 3 is slightly softer than the first two resins. 
     Samples 4-7 show the effects that the addition of two epoxy stabilizers has on Resin Nos. 1 and 2. The epoxidized octyl tallate reduces the low temperature flexibility by about 5° to 7° C. at a concentration of 5 parts per hundred (based on 100 parts of resin) as compared to the epoxidized soybean oil. However, the use of the tallate additive effects the physical properties, e.g., lowers the hardness of the films as well as the tensile and tear strengths. The presence of these epoxy stabilizers increases both the light and heat stability of the resin. 
     Samples 8-11 show the effect of addition of chlorinated polyethylene to the resin and should be compared to Sample 5 as a control. In general, addition of as low as 15% by weight of chlorniated polyethylene improves the elongation with only a slight reduction of other desired characteristics. 
     Samples 12 and 13 illustrate the physical property data for the internally plasticized resin of the present invention processed at two different temperatures. The properties are essentially the same, which would allow a person of ordinary skill in the art to use the lower temperature. 
     EXAMPLE 3 
     This Example illustrates the mill heat stability of various internally plasticized resins made in accordance with the present invention. 
     Compressible film formulations were formed from the following ingredients for each of the enumerated samples:______________________________________                (Amount in Grams)Ingredient        1      2      3    4    5______________________________________Copolymer of the Invention*                  170    85     85   170  170Chlorinated polyethylene                  30     15     15   30   30Epoxidized octyl tallate                  10     5      5    10   10Barium cadmium stabilizer (liq.)                  6      --     --   6    6Calcium stearate  2      1      1    2    2Stearate acid     2      1      1    2    2Calcium carbonate 60     30     30   60   60Titanium dioxide  8      4      4    8    8Bisstearamide lubricant                  2      1      1    2    2Barium-cadmium-zinc-stabilizer                  --     3      3    --   --Phosphite chelator (&#34;Mark C&#34;sold by Argus Chemical)                  --     1      1    --   2______________________________________ *the copolymer used in Samples 1--3 is the same as that used in Samples Nos. 12 and 13 from Example 2. The copolymer used in Sample No. 4 was the same as that used in Sample No. 1 from Example 2. The copolymer used in Sample No. 5 was a 59 VC/28 EHA/12 BB copolymer having a relative viscosity of about 2.86. 
     Table 2 which is set forth below gives the processing temperatures in the 2 roll mill, the type of stabilizer system that was used and comments on the appearance of the film. 
     
                                           TABLE 2                                 
__________________________________________________________________________
      Processing.sup.1                                                    
Sample No.                                                                
      Temperature                                                         
             Stabilizer System.sup.2                                      
                       Comments                                           
__________________________________________________________________________
             Ba-Cd: 3phr                                                  
                       After 160 minutes of processing, there was         
1     121/124° C.                                                  
             Epoxy Stab.:                                                 
                    5phr                                                  
                       substantially no film color development com-       
                       pared to the initial film color after 10           
                       minutes.                                           
             Ba-Cd-Zn:                                                    
                    3phr                                                  
                       After 160 minutes of processing, there was         
2     138/141° C.                                                  
             Epoxy Stab.:                                                 
                    5phr                                                  
                       substantially no film color development com-       
             Phosphite pared to the initial film color after 10           
             Chelator:                                                    
                    1phr                                                  
                       minutes                                            
             Ba-Cd-Zn:                                                    
                    3phr                                                  
                       At about 90 minutes, the film surface be-          
3     157/160° C.                                                  
             Epoxy Stab.:                                                 
                    5phr                                                  
                       came rough and a very slight yellow color          
             Phosphite developed.                                         
             Chelator:                                                    
                    1phr                                                  
             Ba-Cd: 3phr                                                  
                       At about 80 minutes, the film surface be-          
4     157/160° C.                                                  
             Epoxy Stab.:                                                 
                    5phr                                                  
                       came rough with a slight development of            
                       yellow color                                       
             Ba-Cd: 3phr                                                  
                       At about 90 minutes, the film surface be-          
5     157/160° C.                                                  
             Epoxy Stab.:                                                 
                    5phr                                                  
                       came rough with slight development of              
             Phosphite yellow color                                       
             Chelator:                                                    
                    1phr                                                  
__________________________________________________________________________
 Footnotes:                                                               
 .sup.1 The milling was carried out on a two roll mill operated at the    
 temperature values set forth in Table 2. The temperature before the slash
 refers to the front roll, whereas the one after the slash the back roll. 
 .sup.2 Ba-Cd and Ba-Cd-Zn stand for barium-cadmium and barium-cadmium-zin
 heat stabilizers, respectively. The epoxy stabilizers used were epoxidize
 soybean oil and epoxidized octyl tallate. The phosphite chelator is      
 available commercially as &#34;Mark C&#34; from the Argus Chemical Co. All parts 
 per hundred (phr) are based on the resin as 100 parts by weight.         
 
    
     EXAMPLE 4 
     This Example gives the results of smoke measurement tests conducted in a commercial smoke density chamber modeled after one developed at the National Bureau of Standards by the Fire Research Group (See D. Gross, J. J. Loftus and A. F. Robertson, ASTM Special Technical Publication 422, pages 166-204, 1969). This chamber contains a radiant heater producing 2.5 W/cm. 2  of heat at the surface of a 7.62 cm. × 7.62 cm. sample, a propane-air pilot burner and a vertical beam of light with a photomultiplier tube detector and microphotometer to record the attenuation of light by smoke developing in the chamber. During smoke testing, the chamber is sealed to enclose the combustion products and smoke. The tests were conducted under the smoldering mode (Table 3) as well as the flaming mode (Table 4). The values shown in parenthesis are from duplicate runs. 
     
                                           TABLE 3                                 
__________________________________________________________________________
                                                 Dm/Gm.sup.6              
              FR               Dm = MAXIMUM.sup.4                         
                                          Dm/Gm of.sup.5                  
                                                 OF                       
              ADDITIVE                                                    
                     WEIGHT OF SPECIFIC OPT.                              
                                          ORIGINAL                        
                                                 MASS                     
SAMPLE DESCRIPTION                                                        
              (PHR)  SAMPLE (grams)                                       
                               DENSITY    SAMPLE LOSS LOI.sup.7           
__________________________________________________________________________
PVC + 55 phr dioctyl                                                      
phthalate.sup.1                                                           
              None   2.1       126        60     140  21.4                
PVC + 55 phr dioctyl                                                      
phthalate.sup.1                                                           
              Sb.sub.2 O.sub.3                                            
                     2.5       140        56     128  27.1                
              (5)              (142)                                      
Internally Plasticized                                                    
Resin.sup.2   None   2.7       53         19     50   22.2                
                     (2.9)     (52)       (18)   (36)                     
Internally Plasticized                                                    
Resin.sup.2   Sb.sub.2 O.sub.3                                            
                     3.0       37         12     29   28.4                
              (5)    (3.4)     (53)       (15)   (34)                     
Internally Plasticized                                                    
Resin.sup.3   None   2.4       51         21     43   23.3                
                     (2.7)     (52)       (19)   (41)                     
Internally Plasticized                                                    
Resin.sup.3   Sb.sub.2 O.sub.3                                            
                     2.5       40         16     32   28.6                
              (5)    (2.8)     (45)       (16)   (32)                     
__________________________________________________________________________
 
    
     
                                           TABLE 4                                 
__________________________________________________________________________
                                                Dm/Gm                     
              FR               Dm = MAXIMUM                               
                                         Dm/Gm OF                         
                                                OF                        
              ADDITIVE                                                    
                     WEIGHT OF SPECIFIC OPT.                              
                                         ORIGINAL                         
                                                MASS                      
SAMPLE DESCRIPTION                                                        
              (phr)  SAMPLE (grams)                                       
                               DENSITY   SAMPLE LOSS                      
__________________________________________________________________________
PVC + 55 phr dioctyl                                                      
phthalate.sup.1                                                           
              None   1.9       117       61     105                       
                     (2.0)     (117)     (58)   (94)                      
PVC + 55 phr dioctyl                                                      
phthalate.sup.1                                                           
              Sb.sub.2 O.sub.3                                            
                     2.5       195       78     135                       
              (5)    (2.5)     (168)     (67)   (110)                     
Internally Plasticized                                                    
Resin.sup.2   None   3.2       125       39     78                        
                     (2.7)     (124)     (46)   (83)                      
Internally Plasticized                                                    
Resin.sup.2   Sb.sub.2 O.sub.3                                            
                     3.4       138       40     73                        
              (5)    (3.4)     (144)     (42)   (78)                      
Internally Plasticized                                                    
Resin.sup.3   None   2.5        88       35     68                        
                     (2.2)     (99)      (45)   (82)                      
Internally Plasticized                                                    
Resin.sup.3   Sb.sub.2 O.sub.3                                            
                     2.9       110       37     81                        
              (5)    (2.6)     (114)     (43)   (77)                      
__________________________________________________________________________
 Footnotes:-                                                              
 .sup.1 The polyvinyl chloride (PVC) resin is a high molecular weight PVC 
 resin developed for calendered goods applications and is available       
 commercially as SCC-686 from Stauffer Chemical Company, Plastics Division
 The dioctyl phthalate (an external plasticizer) is available under the   
 tradename &#34;6-10 Phthalate&#34; from Hatco Chemicals.                         
 .sup.2 The copolymer of the present invention. This particular sample    
 contained the same copolymer that was used in Example 2, Sample Nos. 12  
 and 13.                                                                  
 .sup.3 Another embodiment of the present invention. This particular sampl
 contained a 63.4 VC/ 27.4 EHA/ 9.2 BB copolymer having a relative        
 viscosity of 2.89.                                                       
 .sup.4 The maximum specific optical density gives a measure of the smoke 
 buildup during the test. Lower numbers indicate less obstruction of light
 due to smoke and are preferred. Dm=25, light smoke; 25-75 moderate smoke;
 100-400, dense smoke; 400, very dense smoke.                             
 .sup.5 This gives a corrected value for the maximum smoke generation per 
 unit weight of sample. Lower numbers are desired.                        
 .sup.6 This value represents the smoke generation per unit weight of     
 material consumed during the burning process. Lower numbers are again    
 desired.                                                                 
 .sup.7 This is an abbreviation for the Limiting Oxygen Index and is      
 defined as the minimum mole percent O.sub.2 content required in an       
 oxygen/nitrogen mixture to maintain combustion of a vertical, top-lighted
 test specimen. Higher numbers are indicative of a more fire retardant    
 material.                                                                
 
    
     Analysis of the data presented in Tables 7 and 8 show that under smoldering conditions, a film of the internally plasticized resin of the present invention containing no fire retardant additives produces approximately 65-68% less smoke compared to a similar externally plasticized film whether or not these data are based on unit mass of the original sample tested or unit mass of the original sample consumed during the testing process. Similarly, again under smoldering test conditions, a similar film containing a fire retardant-additive produces even better smoke reduction (e.g., 78% reduction) compared to an externally plasticized film containing a similar fire retardant additive. Under flaming modes of burning, the internally plasticized films of the present invention again show less smoke generation as compared to externally plasticized film, i.e., approximately 30% less for films containing no fire retardant additives and approximately 50% for films containing fire retardant additives. 
     EXAMPLE 5 
     This Example illustrates the generalized procedure which was used to form an internally plasticized resin having a higher vinyl chloride content than the copolymer formed in Example 1 and to blends of this copolymer with another internally plasticized polymer. 
     The following ingredients were used. All amounts are given in parts by weight:______________________________________Ingredient             Amount______________________________________Vinyl chloride monomer (VCM)                       50 lbs. 131/2 oz.2-ethylhexyl acrylate (2-EHA)                       11 lbs. 9 oz.Bis-(beta-chloroethyl)vinyl-phosphonate (BB)       4 lbs. 12 oz.Methylcellulose suspendingagent (&#34;Methocel&#34; 1242from The Dow Chemical Co.)                       30 grams20 wt. % isopropylperoxydi-carbonate in heptane   85 gramsDeionized water        74.85 kg.______________________________________ 
     The following procedure was used to polymerize the vinyl chloride, acrylate and vinylphosphonate monomers: 
     1. The suspending agent was dissolved in a portion of the deionized water and was charged into the reactor along with the remainder of the deionized water. The mixture was stirred briefly and the peroxydicarbonate/heptane initiator mixture was added; 
     2. The acrylate and vinylphosphonate monomers were added; 
     3. The reactor was closed, vacuum was applied (approx. 584.2-635 mm. of Hg. pressure) for 10 minutes to remove air from the reactor, and vinyl chloride monomer vapor was added to break the vacuum. This operation was repeated once and the vinyl chloride monomer was charged into the reactor; 
     4. The agitator was set at 351 revolutions per minute and the reactor was heated to 50° C. until the pressure in the reactor dropped 4.2 kg./cm. 2  from the maximum pressure noted near the beginning of the reaction: 
     5. The reactor was vented and sparged with nitrogen at a rate of 70.7 cubic cm./sec. for a 44 liter reactor for a period of 1 hour to remove residual monomer from the product; 
     6. The reactor was allowed to cool and the polymer particles were recovered by centrifuging. The particles were dried in a fluid bed drier using air at 30° C.; 
     7. The dried polymer was milled through a Fitz mill and was sieved through a 30 mesh screen. 
     The resin that was produced from the 76% VC/17.3% 2-EHA/6.7% BB feed composition had a 73.6% VC/18.2% 2-EHA/8.2% BB composition and a relative viscosity of 2.72 when measured at 25° C. as a 1% by weight solution of the copolymer in cyclohexanone. 
     This resin and combinations of the resin with the 57.4% VC/31.5% 2-EHA/11.1% BB resin from Example 2 (Samples 12-13) were fabricated into film forming compositions by mixing together the following ingredients in the following amounts:______________________________________                   (Amount of Grams)Ingredient           1       2       3______________________________________Copolymer of Example 2 (Samples12-13)               --      70      60Copolymer of Example 5                     100     30      40Epoxidized Soybean Oil                     5       5       5Barium Cadmium liquid stabilizer                     3       3       3Phosphite chelator (&#34;Mark C&#34;, soldby Argus Chemical Corp.)                     1       1       1Calcium stearate     1       1       1Stearic acid         1       1       1Bisstearamide lubricant                     1       1       1Calcium carbonate filler                     30      30      30Titanium dioxide pigment                     4       4       4______________________________________ 
     The above formulations were calendered into a film on a 2 roll mill, 310°/315° F. (154°/157° C.) for all samples, at 30/42 rpm after all ingredients had been mixed and fluxed for about 7 minutes. The samples were compression molded at 320° F. (160° C.) to produce films with a thickness of about 0.09 to 0.12 cm. The Table which follows sets forth the physical properties of the samples that were tested.______________________________________                 SAMPLE NO.                 1*     2**      3***______________________________________Clash Berg Temperature (° C.)                   -4       -19      -16Shore &#34;A&#34; Hardness 95       84       86Tensile Str. at Break (kg/cm 2 )                   155.6    108.9    106.2100% Modulus (kg./cm. 2 )                   148.4    94.4     98.1Elongation of Break (%)                   135      153      135Graves Tear Strength (kg/cm.)                   52.2     29.5     32.4Flexural Modulus of Elasticity                   630.6    261.8    197.5(kg./cm. 2 )______________________________________ *The copolymer used in this example is a copolymer formed in accordance with Example 5. **The copolymer used in this sample is a blend of 70%, by weight, of the copolymer from Example 2 (Samples 12-13) and 30%, by weight, of the copolymer from Example 5. ***The copolymer used in this sample is a blend of 60% of the copolymer from Example 2 (Samples 12-13) and 40% of the copolymer from Example 5. 
     The data presented in the preceding Table illustrates that a variation of the physical properties and hardness of the flexible vinyl films can be achieved by incorporating the &#34;hard&#34; and &#34;soft&#34; embodiments of the present copolymer films in varying ratios in the formulations. 
     EXAMPLE 6 
     This Example illustrates that use of alkyl acrylate comonomers having alkyl groups that contain less carbon atoms than specified for the acrylates used herein do not function as internally plasticized resins as that term is used herein. 
     The terpolymers listed on the Table which follows were formed by suspension polymerizing the ingredients also listed in the Table for 13 hours at about 46° C. All amounts are given in parts by weight using as the initiator 10% by weight of isopropylperoxydicarbonate in heptane and hydroxypropylmethylcellulose (1% by weight solution) as the suspending agent. 
     
                                           TABLE                                   
__________________________________________________________________________
               INGREDIENTS* (parts by weight)                             
                               Chain                                      
                  Suspend.     Trans.**                                   
TERPOLYMER*    H.sub.2 O                                                  
                  Agent                                                   
                       BB                                                 
                         BA EA Agent                                      
                                    Initiator                             
                                         VCM                              
__________________________________________________________________________
1. 65% VC/20% BA/15% BB                                                   
               350                                                        
                  45   15                                                 
                         20 -- 0.05 2.5  65                               
2. 81% VC/5% BA/14% BB                                                    
               350                                                        
                  45   14                                                 
                          5 -- --   2.5  81                               
3. 40% VC/20% EA/40% BB                                                   
               350                                                        
                  45   40                                                 
                         -- 20 --   2.5  40                               
4. 60% VC/20% EA/20% BB                                                   
               350                                                        
                  45   20                                                 
                         -- 20 --   2.5  60                               
5. 60% VC/30% EA/10% BB                                                   
               350                                                        
                  45   10                                                 
                         -- 30 --   2.5  60                               
6. 75% VC/10% EA/15% BB                                                   
               350                                                        
                  45   15                                                 
                         -- 10 --   2.5  75                               
__________________________________________________________________________
 *the abbreviations are as follows: BB =                                  
 bis(beta-chloroethyl)vinylphosphonate; BA = butyl acrylate; VCM = vinyl  
 chloride monomer; EA = ethyl acrylate. The weight amounts of reactants fo
 terpolymer Nos. 1 and 2 were reacted in each of four bottles and the     
 product from each was combined. The weight amounts for the remaining     
 terpolymers were each reacted in a single bottle.                        
 **the chain transfer agent was 0.05 ml. of t-dodecyl mercaptan.          
 
    
     Each of the terpolymers set forth on the preceding Table was then formed into compressible film formulations using the procedures described in Example 2 using the following ingredients. All amounts are given in parts by weight.______________________________________Ingredient                Amount______________________________________Terpolymer resin          100Epoxidized soybean oil (&#34;G-62&#34;,sold by Rohm and Haas Co.)                          5Barium cadmium powder stabilizer(&#34;V-1541&#34;, sold by Tenneco Chem-icals, Inc., Intermediates Div.)                          1.5Phosphite chelator stabilizer(&#34;V-1542&#34;, sold by Tenneco Chem-icals, Inc., Intermediates Div.)                          1.5Calcium stearate lubricant                          0.5Stearic acid lubricant    0.5______________________________________ 
     Each product was then tested for the various physical properties reported on the Table which follows: 
     
                                           TABLE                                   
__________________________________________________________________________
               SAMPLE NO.                                                 
               1    2      3   4    5    6                                
__________________________________________________________________________
Clash-Berg Temperature (° C.)                                      
               NA   NA     O   NA   NA   NA                               
Shore &#34;A&#34; Hardness                                                        
               98   96     72.5                                           
                               90   99   96                               
Tangent Modulus of                                                        
Elasticity (kg/cm.sup.2)                                                  
               1212.4                                                     
                    11,139.9                                              
                           23.0                                           
                               1328.2                                     
                                    1722.2                                
                                         9431.1                           
Tensile St., Break                                                        
(kg/cm.sup.2)  182.3                                                      
                    14.1   108.1                                          
                               242.0                                      
                                    237.7                                 
                                         60.3                             
% Elongation, Break                                                       
               103  0      215 67   83   0                                
Secant Modulus at 100%                                                    
Elongation (kg/cm.sup.2)                                                  
               NA   NA     92.2                                           
                               NA   NA   NA                               
__________________________________________________________________________
 Note:                                                                    
 For those films for which &#34;NA&#34; appears for the Clash-Berg value, they wer
 judged to be physically more rigid than Sample No. 3 and hence would have
 a Clash-Berg value above 0° C. This value was not experimentally  
 determined for these samples. Of all the samples tested, only Sample No. 
 shows some degree of flexibility.                                        
 Secant modulus is the ratio of total stress to corresponding strain at a 
 specified point in the stress-strain curve. It is expressed as force per 
 unit area with higher numbers generally indicating more rigid materials. 
 Tangent modulus is the slope of the line at any point on a static        
 stress-strain curve expressed as force per unit area. Where &#34;NA&#34; appears,
 it indicates that the value could not be obtained since the sample broke 
 before 100% elongation was reached, or in the case of Sample No. 1, the  
 value was not measured. Higher values also generally indicate a more rigi
 sample.                                                                  
 
    
     The data which is presented in the preceding Table illustrates that use of the lower alkyl acrylates (for example, the C 2  or C 4  alkyl acrylates) in a terpolymer of vinyl chloride and a bis(hydrocarbyl)vinylphosphonate does not yield an internally plasticized resin, as does use of the higher alkyl acrylates (for example, the C 8  alkyl acrylates), as contemplated by the present invention. 
     The foregoing Examples illustrate certain preferred embodiments of the present invention but should not be construed in a limiting sense. The scope of protection which is sought is given in the claims which follow.