US3278478A - Vinyl resins plasticized with trisubstituted nitrilotripropionates - Google Patents

Description

United States Patent F 3,278,478 VlNYL RESINS PLASTICIZED WITH TRISUBSTI- TUTED NITRILOTRIPROPIONATES James E. Masterson, Jenkintown, and David H. Clemens, Willow Grove, Pa., and Arthur W. Ritter, Jr., Haddon Heights, N.J., assignors to Rohm & Haas Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Filed Feb. 2, 1965, Ser. No. 429,887 4 Claims. (Cl. 260--31.8)

This application is a continuation-in-part of application Serial No. 296,461, filed July 22, 1963, now abandoned, which in turn is a continuation-in-part of application Serial No. 269,855, filed April 2, 1963, now abandoned.

This invention deals with trisubstituted nitrilotripropionates, processes for making these compounds, and resinous compositions. This invention also deals With disubstituted iminodipropionates and processes for making these compounds.

The trisubstituted nitrilotripropionates of the invention may be represented by the formula:

oHzoI-nooow in which R represents a non-acetylenically unsaturated hydrocarbon group. Typical thereof are ahe following: aryl, aralkyl, alkaryl, alkyl, and alkylene. Each of these groups generally has a minimum content of 6 carbon atoms and a maximum content of 18 carbon atoms;

R represents a non-acetylenically unsaturated hydrocarbon group. Typical thereof are the following: aryl, aralkyl, alkaryl, alkyl, and alkylene. Each of these groups generally has a minimum content of 6 carbon atoms and a maximum content of 18 carbon atoms;

R represents a non-acetylenically unsaturated hydrocarbon group. Typical thereof are the following: aryl, aralkyl, alkaryl, alkyl, and alkylene. Each of these groups generally has a minimum content of 6 carbon atoms and a maximum content of 18 carbon atoms.

It is preferred that the total carbon atom content of R R and R taken collectively, be no less that 20 carbon atoms and no more than carbon atoms.

The substituents R R and R need not all be the same; they may all be different or two of the three substituents may be the same; all three may be the same.

Typical of the substituents represented by R R and R are the following: 2-ethylbutyl, n-hexyl, sec-hexyl, n-octyl, isooctyl, 2-ethylhexyl, 2-ethylisohexyl, tert-octyl, isodecyl, n-decyl, stearyl, benzyl, palmityl, oleyl, monochlorobenzyl, dichlorobenzyl, nitrobenzyl, phenethyl, 6- phenylhexyl, and tetrahydrofurfuryl. Other substituents typical of R R and R include mixtures of unsaturated and saturated substituents derived from the selective reduction of vegetable and animal fats and oils, such as tallow, soybean oil, safflower oil, linseed oil, and the like. They are commonly mixtures of palmityl, stearyl, oleyl, linoleyl, and linolenyl groups in various proportions, depending on the initial composition of the fat or oil and the degree of selectivity of the reduction.

Typical of the trisubstituted nitrilotripropionates of the invention are the following: trihexyl nitrilotripropionate, tri-Z-ethylhexyl nitrilotripropionate, tri-n-octyl, nitrilotripropionate, triisooctyl nitrilotripropionate, tri-n-decyl nitrilotripropionate, diisodecyl nitrilotripropionate, tristearyl nitrilotripropionate, tripalmityl nitrilotripropionate, tribenzyl nitrilotripropionate, tritetrahydrofurfuryl nitrilotripropionate, t-riphenethyl nitrilotripropionate, dioctylmonobutyl nitrilotripropionate, distearylmonobutyl Patented Oct. 11, 1966 ice nitrilotripropionate, tripentachlorobenzyl nitrilotripropionate, trioleyl nitrilotripropionate, trioctenyl nitrilotripropionate, 11 octyl-ndecyl(1.5-1.5)nitrilotripropionate, dihexylmonoctyl nitrilotripropionate, and monohexyldioctyl nitrilotripropionate.

A particularly valuable group of the compounds of the invention is the trialkyl nitrilotripropionates in which the alkyl groups may be all the same or different.

The process for preparing the trisubstituted nitrilotripropionates of the invention comprises reacting an acrylate ester of the formula with ammonia. In the above formula, R is as defined above. When a mixture of acrylate esters is employed, the resulting trisubstituted nitrilotripropionates of the invention have R substitutents which are dissimilar. In the reaction of the invention, the molar ratio of acrylate to ammonia should be at least 3 to 1. Generally, it is preferred to use an excess of acrylate ester, preferably not exceeding 10 mole percent, over the stoichiometric amount required, although higher excesses are not detrimental.

The temperature at which the reaction proceeds may vary widely. It may range broadly from about 0 C. to the temperature at which the formation of the amide from the acrylate predominates over the addition reaction across the double bond of the acrylate to form the ester. Generally, the temperature is in the range of 5 to 150 C., and more preferably in the range of 30 to C. For best results, it is very advisable to continue heating the reaction mixture after essentially all of the ammonia has been consumed. Usually heating is carried out at a temperature higher than that at which the reaction between the ammonia and the acrylate ester proceeds. Such heating temperature ranges from 50 to 100 C. or higher. The progress of the reaction may be followed by the disappearance of any intermediate disubstituted iminodipropionates that may be formed during the reaction. Such iminodipropionates may be represented by the following formula 0 H 0 H 0 0 o R 011 01-1 0 0011 (III) wherein R and R are as defined above in conjunction with the nitrilotripropionates.

In accordance with the invention, the reaction between the acrylate ester and ammonia proceeds preferably in the presence of a solvent for the ammonia. Typical solvents are: methanol, ethanol, propanol, butanol, dimethyl sulfoxide, dimethyl formamide, tetrahydrofuran, ethylene glycol, dimethyl ether, 2-methoxyethanol, 2-butoxyethanol, and diethylene glycol.

It has also been found that for best results the reaction is carried out in the presence of a catalyst selected from the group consisting of salts of alkaline and alkaline earth metals (metals from Groups IA and IIA of the Periodic Table) and compounds of the generic formula where R R R and R are hydrogen, alkyl, aryl, or aralkyl, and X is an anion whose conjugate acid has a dissociation constant greater than 10- Examples of catalysts are the following: ammonium formate, ammonium acetate, ammonium butyrate, ammonium chloride, monomethyl ammonium chloride, monomethyl ammonium acetate, tributyl ammonium sulperiod and held at that temperature for six hours.

fate, trioctyl ammonium iodide, tetramethyl ammonium butyrate, tetrabutyl ammonium acetate, tetrabutyl ammonium chloride, lithium chloride, lithium acetate potassium chloride, sodium acetate, sodium pr-opionate, sodium dichloroace-tate, magnesium acetate, strontium trichloroacetate, and the like. Preferably, the catalyst is soluble in the reaction medium.

The catalyst is employed in catalytic amount, i.e., that amount which increases the speed of the reaction. Generally, an amount in the range of .05 to 5% of the total weight of the reactants is used.

The greatest benefits from the action of the catalyst are obtained by its presence in the reaction mixture from the time essentially all of the ammonia has been consumed. But, the catalyst may also be present during the reaction of the ammonia and the acrylate.

In a further embodiment of the invention, there is provided a transesterification process which comprises reacting trisubstituted nitrilotripropionates of the formula Ia /C HzCHzC O lower alkyl N-OH Clfl C O 0 lower alkyl CHgCHzC O 0 lower alkyl (Ia) with at least one alcohol of the formula R OH (V) In Formula Ia above, lower alkyl is taken to mean an alkyl group of 1 to 4 carbon atoms. Preferably, the lower alkyl group is an alkyl group of 1 to 2 carbon atoms. In Formula V, the R substituent may represent a nonacetylenically unsaturated aliphatic hydrocarbon group. Typical thereof are the following: aralkyl, alkyl, and alkylene. These groups generally have a minimum carbon atom content of 6 atoms and a maximum carbon atom content of 12 to 18 with a maximum of 12 carbon atoms being preferred. In this embodiment of the invention, the particular group which R represents is so selected as to be different and of substantailly higher molecular weight than the lower alkyl groups in Formula Ia.

Alcohols typical of R OH are the following: n-hexyl alcohol, Z-ethylbutyl alcohol, n-octyl alcohol, isooctyl alcohol, 2-ethylhexyl alcohol, n-decyl alcohol, 2-ethylisohexyl alcohol, isodecyl alcohol, stearyl alcohol, palmityl alcohol, benzyl alcohol, tetrahydrofurfuryl alcohol, oleyl acohol, phenethyl alcohol, and others.

This embodiment of the invention provides a process for making, in essentially quantiative yields, trisubstituted nitrilotripropionates in which the alcohol moiety of the ester is of higher molecular weight than that of the acrylate ester by reacting ammonia and the acrylate ester and then reacting the nitrilotripropionate with an appropriate alcohol.

These alcohols may be used individually or in any mixture thereof. Where the alcohols are used in a mixture, the resulting trisubstituted nitrilotripropionates have R R and R which are different, the respective ratios R R and R depending therefor on the particular ratio of alcohols used.

At the end of the reaction, the product is purified by suitable methods, as by distillation, removal of excess reactants, such as the alcohols and the acrylate.

As illustrative of the invention are the following examples. All parts are by weight unless otherwise noted.

The symbol Hg stands for mercury.

EXAMPLE 1 There are charged to a two-liter reactor parts of ammonium acetate and 75.0 parts of methanol. There are added in portions over a two-hour period 451.0 parts of methyl acrylate and 27.2 parts of ammonia. The temperature is raised gradually to 70 C. over a one-hour The product is stripped of volatile materials to a temperature of 100 C. at 0.15 mm. Hg. The product (441.8 parts) is essentially pure trimethyl nitrilotripropionate having a neutralization equivalent of 273.73.

EXAMPLE 2 The procedure of Example 1 is followed but replacing the ammonium acetate by 4.3 parts of lithium chloride. The same product is obtained.

EXAMPLE 3 The procedure of Example 1 is followed but the catalyst is omitted. The same product is obtained after a longer reaction time.

EXAMPLE 4 A stirred two-liter reactor equipped with a dropping funnel and gas inlet tube is charged with 4.30 parts of lithium chloride. The flask is evacuated to 5 mm. of Hg and 75 ml. (60 parts) of methanol is charged followed by a total of 500 parts of ethyl acrylate and 27.1 parts of ammonia which are added in portions over about a six-hour period while maintaining the temperature between 18 and 38 C. The reaction mixture is allowed to stir for 16 hours at room temperature. An additional 4.3 parts of lithium chloride is added and the reaction mixture heated at a temperature of 70 C. for 3 hours and then stripped of methanol and excess ethyl acrylate at a temperature of C. and a pressure of 0.35 mm. of Hg. There remains 480 parts of almost pure triethyl nitrolotripropionate having a neutralization equivalent of 315 compared to theory of 317.4.

EXAMPLE 5 The procedure of Example 4 is followed but omitting the lithium chloride. The same product is obtained.

EXAMPLE 6 The procedure of Example 4 is followed but 9 parts of lithium chloride are added only after all the ammonia is consumed.

EXAMPLE 7 A stirred two-liter reactor equipped with a dropping funnel and gas inlet tube is charged with 4.30 parts of lithium chloride. The flask is evacuated to 5 mm. of Hg and 75 parts of methanol charged, followed by a total of 430.1 parts of n-butyl acrylate and 21.4 parts of ammonia which are added in portions over about a 7-hour period while maintaining the temperature between 28 C. and 35 C. The reaction mixture of di-nbutyl iminodipropionate and tri-n-butyl nitrilotripropionate is allowed to stir for 13 hours at room temperature. An additional 4.30 parts of lithium chloride is added and the reaction mixture heated at a temperature of 70 to 75 C. for 3 hours and then stripped of methanol and excess butyl acrylate at a temperature of 100 C. and a pressure of 0.25 mm. of Hg. The product which is obtained is tri-n-butyl nitrilotripropionate.

EXAMPLE 8 The procedure of Example 7 is followed omitting the lithium chloride. The same product is obtained.

EXAMPLE 9 The procedure of Example 7 is followed but 9 parts of lithium chloride are added only after all the ammonia is consumed.

EXAMPLE 10 A stirred two-liter reactor equipped with a dropping funnel and gas inlet tube is charged with 4.30 parts of lithium chloride. The flask is evacuated to 5 mm. of Hg and 150 ml. parts) of methanol charged, followed by a total of 430.1 parts of 2-ethylhexyl acrylate and 13.1 parts of ammonia which are added in portions over about a 6-hour period while maintaining the temperature betwen 28 and 35 C. The reaction The procedure of Example is followed but omitting the lithium chloride. The same product is obtained.

5 EXAMPLE 14 Theprocedure of Example 13 is followed replacing the catalyst by zinc acetate. The same product is obtained.

EXAMPLE The procedure of Example 13 is followed replacing the catalyst by aluminum triisopropoxide. The same product is obtained.

Examples 16 to 27 illustrate the preparation of various higher molecular weight nitrilotripropionates from the corresponding lower ester.

Table I.-Transesterificati0n of nitrilotripropionates Alcohol Product Ester 2 Time Pressure, Exam ples Type Moles per Catalyst, Percent (Hrs) mm. N.E.

Type Mole of Yield 0 O O R (Percent) Found Caled.

16 E Isodecyl 1. STA, 1.0 1 97-110 95.13 642. 7 653 p us 17 E Mixture of n-octyl alco- 1. 50 STA, 2.0 5% -100 95. 15 603.4 007 hol, 45% n-deeyl alcohol. plus 18 M Isooetyl 2. 00 STA, 0.75 4 -100 97. 2 562. 9 569 plus 19 E Complex mixture of 1. 33 STA, .06 -103 98, 3 546. 5 549. 7

branched and straight plus chain alcohols averaging 3% 47-24 to 7 to 9 carbon atoms.

20 E A mixture 01 n-Cu, OB, and 1.33 STA, .03 8 97-120 102 589. 4 573.8

C alcohols, average conlplus position of CmHr-m. 3 17-55 21 E Benzyl 2.0 STA, 0.33 10 Atmv 80. 6

(Toluene azeotrope) 22 E Tetrahydrofurfuryl 2. 0 STA, 0.6 18% Atm. 77 480. 2 486. 6

23 E Getyl/Stearyl averaging to 1. 0 STA, 0.2 4 85400 98 979. 2 909 17.5 carbon atoms. plus 24 E 2-ethylhexyl IV 33 Aluminum triisopro- 9 95-100 98+ 554 569 poxide, 0.34. plus 25 E Z-ethylhexyl H 1. 50 ZI1(OAC)2.2HO, 0.17... 8% 95+ 550.9 569 26 M Oleyl 1. 50 STA, 0.33 10 100 97 975 983 27 M Allyl 1. 50 STA, 0.33 12 200 98 350 353 1 NE stands for neutralization equivalent. 2 E stands for triethyl nitrilotripropionate; M stands for trimethyl nitrilotripropionate.

EXAMPLE 12 The procedure of Example 10 is followed but 9 parts of lithium chloride are added only after all the ammonia is consumed.

EXAMPLE 13 There are charged to a 500 ml. reactor arranged for distillation 98.6 parts of trimethyl nitrilotripropionate, 1 86 parts of Z-ethylhexanol, and 0.5 part of a sodium hydrogen titanium mixed alkoxide. The pressure is reduced to 99-106 mm. of Hg and the reaction mixture heated to 92-116 C. After three hours, the pressure is reduced to 41 to 50 mm. of Hg and the reaction mixture maintained at 1l8120 C. for two hours. The pressure is then reduced to 24 mm. of Hg with the temperature at -117 C. The pressure is returned to atmospheric and 0.20 part of acetic acid and 0.40 part of water are added. The mixture is heated at 8095 C. for two hours and stripped of volatile materials at a temperature of 178 C. and a pressure of 0.15 mm. of Hg. The product (202.8 parts) is tri-Z-ethylhexyl nitrilotripropionate and has a refractive index of 1.4295 at 25 C.

3 STA stands for sodium hydrogen titanium alkoxide. NOTE 1.Temperature 100 0.

The esters of the invention are valuable plasticizers for polyvinyl halide resins. The term polyvinyl halide resin refers to polymers containing a predominant quantity, that is, a quantity greater than 50%, generally over 60%, by weight of the monomer as vinyl halide units. This includes the homopolymers of the vinyl halides as well as the copolymers and interpolymers of a vinyl halide and an unsaturated monomer copolymerizable therewith. Other monomers that may be copolymerized with the vinyl halide include the vinyl type monomers such as, for example, those having a single CH =C= group, such as vinylidene chloride, vinyl chloroacetate, chlorostyrene, chlorobutadienes, etc., and those copolymers of such vinyl compounds and other unsaturated materials copolymerizable therewith, for example, copolymers of a vinyl halide, such as vinyl chloride, with such materials as vinylidene chloride, vinyl esters of carboxylic acids, for example, vinyl acetate, vinyl phopionate, vinyl butyrate, vinyl benzoate; esters of unsaturated acids, for example, .al kyl acrylates, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, allyl acrylate and the corresponding esters of methacrylic acid;

vinyl aromatic compounds, for example, styrene; esters of a,/3-unsaturated carboxylic acids, for example, the methyl, ethyl, butyl, amyl, hexyl, octyl esters of maleic, crotonic, itaconic, fumarie acids and the like. Further useful copolymers are those obtained by copolymerization of vinyl chloride with an ester of an a,fl-unsaturated dicar-boxylic acid, such as diethyl maleate or other esters of maleic, fumaric, aconitric, itaconic acid, etc., in which 5 to 20 parts by weight of diethyl maleate or other analogous esters are used for every 95 to 80 parts by weight of vinyl chloride.

When the esters of the invention are employed as plasticizers for polyvinyl halide resins, they are ordinarily incorporated into the vinyl halide polymers by mixing the powdered resin with the liquid plasticizer followed by mixing and/or kneading and then by curing the mix at an elevated temperature, for example, within the range from 150 to 200 C., on hot rolls or in a heated mixer, such as a Werner-Pfieiderer or Banbury mixer. The proportion of esters that may be employed may vary over a great range since it is dependent on the particular esters of this invention which is selected, the specific polyvinyl halide resin to be plasticized, and the final degree of plasticization desired in the resin, this factor in itself being dependent on the ultimate application intended for the resin. With these facts in mind, one skilled in the art may use the esters in a plasticizing amount for most purposes, this being from about 5 to 100 parts, and more commonly from 20 to 60 parts, of esters per 100 parts of resin. In amounts from 60 to about 150 parts of ester per 100 parts of polyvinyl chloride resin, as from 60 to 90 parts, the esters of the invention are more commonly suitable for use in organosols and plastisols. One or more esters may be used in the polyvinyl halide resin.

In accordance with the invention there may be employed one or more esters of this invention in polyvinyl halide compositions; also the esters of the invention may be employed as the sole plasticizer; or they may be employed in conjunction with conventional plasticizers, such as alkyl phthalates, alkyl phosphates, monomeric or polymeric epoxides, and other plasticizers known in the art.

With the polyvinyl halide resin, there may be incorporated various stabilizers, fillers, dyes, pigments, and the like.

The value of the esters of the invention is further demonstrated by the following illustrations.

A standard resinous composition is made up from the following ingredients.

Table II.Standard formulation Parts Polyvinyl chloride 60 Plasticizer 40 Barium cadmium laurate 1.0

The resinous compositions are evaluated in accordance with tests further described hereinafter.

1 Data are for a mixture of the plastieizer with 50% of di-(2-ethylhexyD- phthalate. It is evident from the data that the polyvinyl resinous compositions are well plasticized, soft, pliable, and flexible. These properties are retained even at very low temperatures. The plasticizers also remain integrated in the resin even under high temperature conditions; they are resistant to soap extraction and highly compatible.

The above formulations are modified by replacing polyvinyl chloride by copolymers of (A) 87 parts vinyl chloride: 13 parts vinyl acetate (B) parts vinyl chloridezZO parts vinylidene chloride (C) 80 parts vinyl chloride:20 parts methyl acrylate (D) 95 parts vinyl chloride:5 parts vinyl isobutyl ether The resinous compositions are tested as described above. All compositions are supple and flexible, and they exhibit good low temperature flexibility allied with good resistance to high temperature conditions.

The plasticized polyvinyl chloride compositions of the invention are useful for many outdoor uses, such as greenhouse glazing, pond liners, ditch liners and silo covers. The compositions are well suited for many automotive applications, such as door panels, crash pad covers, and gasketing; for jacketing for electrical cables and many others.

The nitrilotripropionates of the invention are, furthermore, unique in their performance in plastisols in combining excellent gelation and fusion behavior with out standing viscosity stability.

A typical plastisol composition comprising 100 parts of finely divide-d polyvinyl chloride, 3 parts of a Ba/Cd/Zn complex stabilizer and parts of tri-2-ethylhexyl nitrilopropionate was mixed for 15 minutes in a Hobart mixer and then deaerated at 28 in. of Hg for 10 minutes. The viscosity of the plastisol was 17 poises at 60 r.p.m. after aging one day at 77 F. A comparative composition with di-(2-ethylhexyl)phthalate ('DOP) had an 18 poise/60 r.p.m. viscosity. After 21 days at 77 F., the viscosity of the composition with DOP had risen to 29. The viscosity of the nitrilotripropionate composition had decreased to 12 poise. In another experiment, at 104 F., the viscosity for the nitrilotripropionate after one day was 7 poises/60 r.p.m. The composition with DOP was 20. After 21 days at 104 F., the nitrilotripropionate composition was 5; the DOP had a viscosity which increased to 56. Thus, while the conventional DOP composition showed gradual and perceptible gelation, the plastisol of the invention showed remarkable viscosity stability. The trem plastisol is well known in the art. See Modern Plastics, vol. 29, page 87 (1951), and US. Patent No. 3,050,412, col. 3, lines 48-67, for instance.

TESTS Test 1Sh0re hardness.A Shore A durorneter, under a weight of 3 pounds, is applied to the test specimens. A recording is made at once and after 10 seconds; and the hardness is expressed by the two values, of which the first recording is the higher.

Test 2-T0rsional modulus at low temperatures.A 1%

x A1" sample is cut and mounted in a Tinius-Olsen stiffness tester, which measures the torsional modulus of plastic at various temperatures. The temperature at which a specimen has a torsional modulus of 135,000 lbs/sq. in., known as T of T is determined. This roughly corresponds to the brittle point obtained by cantilever apparatus.

Test 3Activated carbon v0latility.2" squares of weighed specimens are placed between 2-inch layers of activated carbon in sealed glass jars, which are maintained at 90 C. for 24 hours. The specimens are removed, dusted free of carbon and reweighed.

Test 4S0apy water extractio-n.3" squares of weighed specimens are immersed in a 1% aqueous solution of Ivory soap at 90 C. for 24 hours, after which they are thoroughly washed, dried, and reweighed.

Test 5-Compatibility.Weighed, conditioned duplicate samples, 4 inches by 4 inches by 0.010 inch, are placed between two sheets of cardboard, which have been conditioned at least 15 'hours. The specimens are in contact with the white, coated side of the cardboard. The cardboard-specimen sandwiches are placed between 5 inches by 5 inches by 1 inch Wood blocks under a 3- kilogram weight. After .seven days, the specimens are removed from the stack, conditioned, and reweighed.

Percent plasticizer loss is calculated. The cardboard sheets are examined qualitatively for evidence of plasticizer or plasticizing stabilizer stains.

We claim:

1. A resinous vinyl chloride composition comprising a vinyl chloride polymer selected from the group consisting of homopolymers of vinyl chloride and copolymers of 50 to 95 percent by weight vinyl chloride and from 50 to percent by weight of a monoethylenically unsaturated monomer copolymerizable therewith, said polymer being plasticized with a trisubstituted nitrilotripropionate of the formula NOH;OH OOOR OH OH COOR in which each of R R and R is an alkyl group of 8 carbon atoms.

2. The resinous composition of claim 1, wherein the 10 nitrilotripropionate is tri(2-ethyl-hexyl)nitrilotripropomate.

3. The resinous composition of claim 1, wherein the nitrilotripropionate is triisooctyl nitrilotripropionate.

4. A vinyl plastisol composition comprising a vinyl chloride resin selected from the group consisting of homopolymers of vinyl chloride and copolymers of to percent by weight vinyl chloride and from 50 to 5 percent by weight of a monoethylenically unsaturated monomer copolymerizable therewith, and tri(2-ethylheXyl)nitrilotripropionate plasticizer.

References Cited by the Examiner UNITED STATES PATENTS 9/ 1942 Bogemann et al. 260-482 OTHER REFERENCES Mellan: The Behavior of Plasticizer-s; 1961,; Pergamon Press; pages 27, 30, 31.

MORRIS LIEBMAN, Primary Examiner.

L. T. JACOBS, Assistant Examiner.

Claims (1)

1. A RESINOUS VINYL CHLORIDE COMPOSITION COMPRISING A VINYL CHLORIDE POLYMER SELECTED FROM THE GROUP CONSISTING OF HOMOPOLYMERS OF VINYL CHLORIDE AND COPOLYMERS OF 50 TO 95 PERCENT BY WEIGHT VINYL CHLORIDE AND FROM 50 TO 5 PERCENT BY WEIGHT OF A MONOETHYLENICALLY UNSATURATED MONOMER COPOLYMERIZABLE THEREWITH, SAID POLYMER BEING PLASTICIZED WITH A TRISUBSTITUTED NITRLOTRIPROPIONATE OF THE FORMULA