Aqueous latex of vinylidene chloride copolymer

Abstract

An aqueous latex [latex (L)] of a vinylidene chloride copolymer [copolymer (A)], wherein the copolymer (A) consists essentially of recurring units derived from vinylidene chloride (VDC) in an amount comprised between 89.0 and 91.0 wt % of the copolymer, recurring units derived from methacrylonitrile (MAN) in an amount comprised between 2.00 and 5.50 wt % of the copolymer, recurring units derived from at least one ionic comonomer (ICO) in an amount comprised between 0.5 and 1.4 wt % of the copolymer (A), and recurring units derived from methylmethacrylate (MMA) in an amount such that the total of recurring units of VDC, MAN, ICO and MMA is 100 wt %,
and wherein the latex (L) comprises at least one surfactant [surfactant (S)] in an amount comprised between 0.09 and 1.50 wt % of the copolymer (A). Process for the manufacture of the aqueous latex (L), film made therefrom and retort pouch prepared with such film.

Claims

1. An aqueous latex (latex (L)) of a vinylidene chloride copolymer (copolymer (A)), wherein the copolymer (A) consists essentially of: recurring units derived from vinylidene chloride (VDC) in an amount comprised between 89.0 and 91.0 wt % of the copolymer (A), recurring units derived from methacrylonitrile (MAN) in an amount comprised between 2.00 and 5.50 wt % of the copolymer (A), recurring units derived from at least one ionic comonomer (ICO) in an amount comprised between 0.5 and 1.4 wt % of the copolymer (A), and recurring units derived from methylmethacrylate (MMA) in an amount such that the total of recurring units of VDC, MAN, ICO and MMA is 100 wt %, wherein the ionic comonomer is selected from the group consisting of 2-acrylamido-2-methyl-1-propane sulfonic acid sodium salt, sodium 2-sulfoethyl methacrylate, sodium 4-vinylbenzenesulfonate and mixtures thereof, and wherein the latex (L) comprises at least one surfactant (surfactant(S)) in an amount comprised between 0.09 and 1.50 wt % of the copolymer (A).

2. The aqueous latex (L) according to claim 1, wherein the recurring units derived from vinylidene chloride (VDC) are present in an amount of at least 89.2 wt % of the copolymer (A), and of at most 90.8 wt % of the copolymer (A).

3. The aqueous latex (L) according to claim 1, wherein the recurring units derived from methacrylonitrile (MAN) are present in an amount of at least 2.20 wt % of the copolymer (A), and of at most 5.25 wt % of the copolymer (A).

4. The aqueous latex (L) according to claim 1, wherein the recurring units derived from at least one ionic comonomer (ICO) are present in an amount of at least 0.6 wt % of the copolymer (A), and of at most 1.2 wt % of the copolymer (A).

5. The aqueous latex (L) according to claim 1, wherein the latex (L) comprises at least one surfactant (surfactant(S)) in an amount of at least 0.10 wt % of the copolymer (A), and in an amount of at most 1.40 wt % of the copolymer (A).

6. The aqueous latex (L) according to claim 1, wherein the copolymer (A) consists essentially of: recurring units derived from vinylidene chloride (VDC) in an amount comprised between 89.2 and 90.8 wt % of the copolymer, recurring units derived from methacrylonitrile (MAN) in an amount comprised between 2.20 and 5.25 wt % of the copolymer, recurring units derived from at least one ionic comonomer (ICO) in an amount comprised between 0.6 and 1.2 wt % of the copolymer (A), and recurring units derived from methylmethacrylate (MMA) in an amount such that the total of recurring units of VDC, MAN, ICO and MMA is 100 wt %, wherein the ionic comonomer is selected from the group consisting of 2-acrylamido-2-methyl-1-propane sulfonic acid sodium salt, sodium 2-sulfoethyl methacrylate, sodium 4-vinylbenzenesulfonate and mixtures thereof, and wherein the latex (L) comprises at least one surfactant (surfactant S in an amount comprised between 0.10 and 1.40 wt % of the copolymer (A).

7. The aqueous latex (L) according to claim 1, wherein the copolymer (A) consists essentially of recurring units derived from vinylidene chloride (VDC) in an amount of at least 89.5 wt % of the copolymer (A), and of at most 90.6 wt % of the copolymer (A).

8. The aqueous latex (L) according to claim 1, wherein the copolymer (A) consists essentially of recurring units derived from methacrylonitrile (MAN) in an amount of at least 2.50 wt % of the copolymer (A), and of at most 5.00 wt % of the copolymer (A).

9. The aqueous latex (L) according to claim 1, wherein the copolymer (A) consists essentially of recurring units derived from at least one ionic comonomer (ICO) in an amount of at least 0.7 wt % of the copolymer (A), and of at most 1.1 wt % of the copolymer (A).

10. The aqueous latex (L) according to claim 1, wherein the latex (L) comprises at least one surfactant-(surfactant(S)) in an amount of at least 0.12 wt % of the copolymer (A), and in an amount of at most 1.30 wt % of the copolymer (A).

11. The aqueous latex (L) according to claim 1, wherein the aqueous latex (L) is in the form of particles, and wherein the particles have a z-average particle diameter (D.sub.z) of at least 120 nm and of at most 300 nm.

12. The aqueous latex (L) according to claim 1, wherein the aqueous latex (L) has a pH of from 2.2 to 2.65.

13. The aqueous latex (L) according to claim 1, comprising a polymethylmethacrylate seed latex.

14. A process for the manufacture of the aqueous latex (L) according to claim 1, characterized in that vinylidene chloride (VDC), methacrylonitrile (MAN), at least one ionic comonomer (ICO) and methylmethacrylate (MMA) are polymerized by radical polymerization in aqueous emulsion in the presence of at least one surfactant(S) in order to obtain the latex (L) comprised of the copolymer (A).

15. The process according to claim 14, characterized in that the polymerization takes place in the presence of a seed latex (seed latex (SL)).

16. The process according to claim 14, characterized in that the polymerization takes place in the presence of a methyl methacrylate polymer seed latex-(PMMA seed latex).

17. A method comprising coating the aqueous latex (L) according to claim 1 on a substrate to produce a multilayer film.

18. A film comprising the aqueous latex (L) according to claim 1.

19. The film according to claim 18, characterized in that it is comprised in food packaging.

20. A retort pouch comprising the film according to claim 19.

Description

EXAMPLE 1 (ACCORDING TO THE INVENTION)PREPARATION OF A PMMA SEED LATEX

(1) An 8.7 m.sup.3 polymerization autoclave (stirred at 20 rpm), equipped with a cooling circuit, was successively charged with 3908 l of demineralized water, 14 kg (6.7 g of active material/kg of monomer) of a powdered ammonium persulfate solution and 8141 (100 g of active material/kg of monomer of the seed latex) of a sodium n-alkyl-(C.sub.10-C.sub.13) benzene sulfonate solution containing 25% of active material. The autoclave was closed then subjected to two vacuum operations at 140 mbar absolute pressure.

(2) The stirring speed was then increased to 60 rpm while bringing the mixture to 85 C. When the temperature reached 84 C., 2100 kg of methyl methacrylate was added at a constant rate over 3 h while adding 151 kg (2.87 g of active material/kg of monomer) of a 40 g/l ammonium persulfate solution at a constant rate over the same 3 h duration.

(3) After the end of the methyl methacrylate and ammonium persulfate injections, the polymerization was continued until a temperature difference of less than 5 C. was obtained between the temperature of the reaction medium and that of the cooling circuit, followed by a post-polymerization of 1 h. The stirring speed was then reduced to 20 rpm and the latex was degassed then stripped under vacuum at 65 C. for 3 h.

(4) The solid content of the PMMA seed latex thus polymerized was according to the specification i.e. 32-35%. The average diameter of the particles, determined by DLS, was according to the specification i.e. 30-38 nm.

EXAMPLE 2 (ACCORDING TO THE INVENTION)POLYMERIZATION OF VDC IN AQUEOUS EMULSION IN THE PRESENCE OF THE PMMA SEED LATEX PREPARED IN EXAMPLE 1

(5) A 65 l polymerization autoclave equipped with a cooling circuit was charged with 6.5 l of demineralized water. It was then charged with 793 ml of the PMMA seed latex (solid content of 32.75%) prepared according to the process as defined in Example 1 (corresponding to 11 g of dry matter/kg of monomers) and 135 ml of a 3.7 g/l ascorbic acid solution. The autoclave was subjected to two vacuum operations. The stirring speed of the medium was brought to 110 rpm. The autoclave was heated at 23 C.

(6) A 150 l autoclave used as premixer, equipped with a cooling circuit, was successively charged with 18.3 l of demineralized water, 109 ml of a sodium branched alkyl-(C.sub.12) diphenyloxide disulfonate solution containing 486 g/l of active material, 84 ml of a sodium n-alkyl-(C.sub.10-C.sub.13) benzene sulfonate solution containing 25% of active material. 3.49 l of a tetrasodium pyrophosphate solution at 30 g/l and 1.45 l of a 2-acrylamido-2-methylpropane sulfonic acid sodium salt solution at 180 g/l. The premixer was subjected to two vacuum operations. The stirring speed of the medium was brought to 130 rpm. A mixture of 1.45 kg of methylmethacrylate and 0.785 kg of methacrylonitrile, then 23.7 kg of vinylidene chloride were introduced in the premixer. After stirring for 30 min, the stirring rate was reduced to 90 rpm.

(7) The temperature of the reaction medium in the autoclave was raised to 60 C. At T=59 C., 340 ml of a 71.3 g/l ammonium persulfate solution were added. The introduction of ammonium persulfate was taken as the beginning of the polymerization (T.sub.o).

(8) At T.sub.o+1 min, 47.2 kg of the monomers emulsion were added from the premixer at a constant rate over 8 h. At T.sub.o+1 min, 962 ml of a 11.7 g/l ascorbic acid solution were added at a constant rate over 8 h 45 min. At T.sub.o+2 min, 823 ml of a 41.0 g/l ammonium persulfate solution were added at a constant rate over 8 h 15 min. When a temperature difference of 2 C. was obtained between the temperature of the reaction medium and that of the cooling circuit, the latex was post-polymerized for 120 min.

(9) The stirring speed was reduced to 110 rpm and the latex was then hot-degassed then stripped under vacuum at 60 C. (autoclave temperature) during two hours. Then the temperature of the cooling system was brought to 60 C.

(10) After two hours at 60 C. (cooling temperature), the stirring speed was increased to 110 rpm. After 6 h of stripping, the latex was cooled to 20 C. and then filtered through a 60 m filtration pocket. The solid content of the latex was measured and if required adjusted, by addition of water, to be between 44 wt % and 46 wt %.

(11) The properties of the PVDC latex obtained in Example 2 were measured in the manner described previously. The results are given in Table 1.

(12) Films were made with the PVDC latex obtained in Example 2. The properties measured on these films in the manner described above, are given in Table 2.

EXAMPLE 3 (ACCORDING TO THE INVENTION)POLYMERIZATION OF VDC IN AQUEOUS EMULSION IN THE PRESENCE OF THE PMMA SEED LATEX PREPARED IN EXAMPLE 1

(13) Example 2 was reproduced except that the quantity of a PMMA seed latex (solid content of 33.2%) prepared according to the process as defined in Example 1 was 781 ml (corresponding to 11 g of dry matter/kg of monomers); the quantity of demineralized water introduced into the premixer was 18.0 l; the 1.45 l of a 2-acrylamido-2-methylpropane sulfonic acid sodium salt solution at 180 g/l was replaced by 1.74 l of a styrene-4-sulfonic acid sodium salt (also called sodium 4-vinylbenzenesulfonate) solution at 150 g/l; the quantity of methylmethacrylate was 1.44 kg; and at To+1 min, 47.17 kg of the monomers emulsion were added from the premixer at a constant rate over 8 h.

(14) The properties of the PVDC latex obtained in Example 3 were measured in the manner described previously. The results are given in Table 1.

(15) Films were made with the PVDC latex obtained in Example 3. The properties measured on these films in the manner described above, are given in Table 2.

EXAMPLE 4 (ACCORDING TO THE INVENTION)POLYMERIZATION OF VDC IN AQUEOUS EMULSION IN THE PRESENCE OF THE PMMA SEED LATEX PREPARED IN EXAMPLE 1

(16) Example 2 was reproduced except that the quantity of demineralized water introduced into the polymerization autoclave was 6.6 l; the quantity of the PMMA seed latex (solid content of 34.0%) prepared according to the process as defined in Example 1 was 762 ml (corresponding to 11 g of dry matter/kg of monomers); the quantity of demineralized water introduced into the premixer was 18.5 l; the quantity of the sodium branched alkyl-(C.sub.12) diphenyloxide disulfonate solution containing 486 g/l of active material was 323 ml; no sodium n-alkyl-(C.sub.10-C.sub.13) benzene sulfonate solution containing 250 g/l of active material was added, the quantity of the 2-acrylamido-2-methylpropane sulfonic acid sodium salt solution at 180 g/l was 1.24 l; the quantity of methylmethacrylate was 1.48 kg; and at To+1 min, 47.25 kg of the monomers emulsion were added from the premixer at a constant rate over 8 h.

(17) The properties of the PVDC latex obtained in Example 4 were measured in the manner described previously. The results are given in Table 1.

(18) Films were made with the PVDC latex obtained in Example 4. The properties measured on these films in the manner described above, are given in Table 2.

EXAMPLE 5POLYMERIZATION OF VDC IN AQUEOUS EMULSION IN THE PRESENCE OF THE PMMA SEED LATEX PREPARED IN EXAMPLE 1

(19) Example 2 was reproduced except that the quantity of the PMMA seed latex (solid content of 34.0%) prepared according to the process as defined in Example 1 was 762 ml (corresponding to 11 g of dry matter/kg of monomers); the quantity of demineralized water introduced into the premixer was 18.4 l; the quantity of demineralized water introduced into the polymerization autoclave was 6.6 l; the quantity of the sodium branched alkyl-(C.sub.12) diphenyloxide disulfonate solution containing 486 g/l of active material was 484 ml; no sodium n-alkyl-(C.sub.10-C.sub.13) benzene sulfonate containing 250 g/l of active material was added, the quantity of the 2-acrylamido-2-methylpropane sulfonic acid sodium salt solution at 180 g/l was 1.24 l; the quantity of methylmethacrylate was 1.48 kg; and at To+1 min, 47.33 kg of the monomers emulsion were added from the premixer at a constant rate over 8 h.

(20) The properties of the PVDC latex obtained in Example 5 were measured in the manner described previously. The results are given in Table 1.

(21) Films were made with the PVDC latex obtained in Example 5. The properties measured on these films in the manner described above, are given in Table 2.

EXAMPLE 6(C) (COMPARATIVE)POLYMERIZATION OF VDC IN AQUEOUS EMULSION IN THE PRESENCE OF THE PMMA SEED LATEX PREPARED IN EXAMPLE 1

(22) Example 2 was reproduced except that the quantity of the PMMA seed latex (solid content of 33.2%) prepared according to the process as defined in Example 1 was 781 ml (corresponding to 11 g of dry matter/kg of monomers); the quantity of demineralized water introduced into the premixer was 17.6 l; the quantity of the sodium branched alkyl-(C.sub.12) diphenyloxide disulfonate solution containing 486 g/l of active material was 484 ml; no sodium n-alkyl-(C.sub.10-C.sub.13) benzene sulfonate solution containing 250 g/l of active material was added, the quantity of the 2-acrylamido-2-methylpropane sulfonic acid sodium salt solution at 180 g/l was 2.18 l; the quantity of methylmethacrylate was 1.31 kg; and at To+1 min, 47.33 kg of the monomers emulsion were added from the premixer at a constant rate over 8 h.

(23) The properties of the PVDC latex obtained in Example 6 were measured in the manner described previously. The results are given in Table 1.

(24) Films were made with the PVDC latex obtained in Example 6. The properties measured on these films in the manner described above, are given in Table 2.

EXAMPLE 7(C) (COMPARATIVE)POLYMERIZATION OF VDC IN AQUEOUS EMULSION IN THE PRESENCE OF THE PMMA SEED LATEX PREPARED IN EXAMPLE 1

(25) Example 2 was reproduced except that the quantity of the PMMA seed latex (solid content of 33.2%) prepared according to the process as defined in Example 1 was 781 ml (corresponding to 11 g of dry matter/kg of monomers); the quantity of demineralized water introduced into the premixer was 19.11; the quantity of the sodium branched alkyl-(C.sub.12) diphenyloxide disulfonate solution containing 486 g/l of active material was 1.08 l; no sodium n-alkyl-(C.sub.10-C.sub.13) benzene sulfonate solution containing 250 g/l of active material was added, no 2-acrylamido-2-methylpropane sulfonic acid sodium salt solution at 180 g/l was added the quantity of methylmethacrylate was 1.24 kg; the quantity of methacrylonitrile was 1.29 kg; the quantity of vinylidene chloride was 23.6 kg; the temperature of the reaction medium was raised to 65 C.; the addition of the 340 ml of the 71.3 g/l ammonium persulfate solution was made at T=64 C.; and at To+1 min, 47.60 kg of the monomers emulsion were added from the premixer at a constant rate over 8 h.

(26) The properties of the PVDC latex obtained in Example 7 were measured in the manner described previously. The results are given in Table 1.

(27) Films were made with the PVDC latex obtained in Example 7. The properties measured on these films in the manner described above, are given in Table 2.

(28) TABLE-US-00001 TABLE 1 Solid content z-average after particle diameter Surface Exam- adjustment if D.sub.z (nm)/ tension ples required (%) polydispersity (mN/m) pH 2 45.03 146/0.022 50.5 2.2 3 44.98 144/0.033 50.4 2.65 4 44.95 144/0.033 54.4 2.3 5 44.91 144/0.065 53.0 2.3 .sub.6(C) 45.09 155/0.004 51.7 2.3 .sub.7(C) 44.89 142/0.014 43.1 2.2

(29) TABLE-US-00002 TABLE 2 Treatment before Example Example Example Example Example Example measurement 2 3 4 5 6(C) 7(C) WVTr 2D40 9.2 10.5 8.9 8.2 8.5 8.1 (g .Math. m/m.sup.2 .Math. day) 2D40 + pasteurized 10.5 11.6 7.8 7.9 9.9 8.7 2D40 + sterilized 9.8 11.4 9.4 9.1 13.2 9.4 OTr 2D40 8.5 8.2 7.7 7.8 8.5 8.4 23 C., 0% HR 2D40 + pasteurized 9.5 10.8 8.1 8.1 11.3 22.2 (cm.sup.3 .Math. m/m.sup.2 .Math. day .Math. bar) 2D40 + sterilized 8.8 9.9 8.2 8.3 11.7 10.4 OTr 2D40 9.5 15.4 9.3 9.1 12.1 9.9 23 C., 85% HR 2D40 + pasteurized 11.5 21.1 9.2 9.1 16.6 20.5 (cm.sup.3 .Math. m/m.sup.2 .Math. day .Math. bar) 2D40 + sterilized 12.3 17.8 9.9 9.5 17.7 25.1 Clarity 2D40 n.d. 91.7 93.1 93.2 93.1 90.5 (%) 2D40 + pasteurized n.d. 86.6 92.8 92.5 91.4 89.8 2D40 + sterilized n.d. 90.9 92.4 92.6 90.8 78.3 Haze 2D40 n.d. 5.7 5.4 5.6 5.7 7.2 (%) 2D40 + pasteurized n.d. >30 17.1 19.5 >30 17.1 2D40 + sterilized n.d. 9.6 16.0 17.9 26.4 >30 n.d.: non determined

(30) From analysis of Table 2, it appears that the films made with latex according to the invention present less whitening after pasteurization or sterilisation and remain characterized by appropriate water vapor permeability and oxygen permeability to provide suffisant level of food protection.