Water-based 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: -repeating units derived from vinylidene chloride (VDC) in an amount comprised between 89.0 and 91.0 wt% of the copolymer, -repeating units derived from methacrylonitrile (MAN) in an amount comprised between 2.00 and 5.50 wt% of the copolymer, -repeating 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 -repeating units derived from methyl methacrylate (MMA) in an amount such that the total amount of the recurring units of VDC, MAN, ICO and MMA is 100 wt%; and wherein the latex (L) contains at least one surfactant [surfactant (S)] in an amount comprised between 0.09 and 1.50 wt% of the copolymer (A). A method for making the aqueous latex (L), a film made therefrom and a retort pouch made with such a film.

Description

[0001] This application claims priority from application No. 19315171.9 filed in Europe on December 20, 2019, the entire contents of which are incorporated by reference into the present application for all purposes.

[0002] The present invention relates to an aqueous latex of a vinylidene chloride copolymer, a method for preparing the latex, a film made therefrom, and a retort bag prepared using the film.

[0003] One of the main applications of aqueous latexes of vinylidene chloride copolymers (PVDC) is the preparation of films for food packaging, due to which appropriate water vapor permeability and oxygen permeability are achieved.

[0004] Pasteurization and sterilization are commonly used to enhance food preservation. These methods involve the use of water or steam and often result in disappointingly observed whitening during pasteurization or sterilization of packages containing PVDC films.

[0005] Therefore, there remains a need to provide aqueous PVDC latexes that can lead to the preparation of films that exhibit less whitening after pasteurization or sterilization. It is also important that these films remain characterized by appropriate water vapor permeability and oxygen permeability to provide adequate food protection levels.

[0006] A subject of the present invention is therefore an aqueous latex of a vinylidene chloride copolymer which does not suffer from the disadvantages of the latexes of the prior art while retaining their advantages.

[0007] Firstly, a subject of the present invention is an aqueous latex [latex (L)] of a vinylidene chloride copolymer [copolymer (A)], wherein the copolymer (A) consists essentially of:

[0008] - repeating units derived from vinylidene chloride (VDC) in an amount comprised between 89.0 and 91.0 wt% of the copolymer,

[0009] - recurring units derived from methacrylonitrile (MAN) in an amount comprised between 2.00 and 5.50 wt % of the copolymer,

[0010] - 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

[0011] - repeating units derived from methyl methacrylate (MMA) in an amount such that the total amount of repeating units of VDC, MAN, ICO and MMA is 100 wt %;

[0012] 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).

[0013] For the purposes of the present invention, the expression “aqueous latex [latex (L)] of a vinylidene chloride copolymer [copolymer (A)]” is understood to mean an aqueous dispersion of this copolymer (A) in water.

[0014] For the purposes of the present invention, the term "essentially consisting of the above-mentioned recurring units" is understood to mean that any further recurring units different from the recurring units detailed above may be present in the copolymer (A) in an amount of advantageously up to 1 mol %, preferably up to 0.5 mol % and most preferably up to 0.25 mol %, relative to the total number of moles of recurring units in the copolymer (A) and so as not to substantially alter the advantageous properties of the copolymer (A).

[0015] When present in copolymer (A), these additional repeating units may be repeating units of (meth)acrylic monomers other than MAN and MMA, these (meth)acrylic monomers corresponding to the following general formula:

[0016] CH2=CR1R2

[0017] wherein R1 is chosen from hydrogen and methyl, and R2 is chosen from a -CN group and a -CO-R3 group, wherein R3 is chosen from an -OH group, an -O-R4 group, wherein R4 is chosen from a linear or branched alkyl group containing from 2 to 18 carbon atoms, optionally with one or more -OH groups, an oxirane group containing from 2 to 10 carbon atoms and an alkoxyalkyl group containing a total of 2 to 10 carbon atoms, and finally R3 is also chosen from a -NR5R6 group, wherein R5 and R6 are identical or different and are chosen from hydrogen and an alkyl group containing from 1 to 10 carbon atoms, optionally with one or more -OH groups.

[0018] Preferably, when present in copolymer (A), the additional repeating units are repeating units of methyl acrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, acrylonitrile, acrylic acid, methacrylic acid, acrylamide and N-hydroxymethyl acrylamide.

[0019] More preferably, when present in copolymer (A), the further repeating units are repeating units of acrylonitrile, acrylic acid or n-butyl acrylate.

[0020] Copolymer (A) consists essentially of recurring units derived from vinylidene chloride (VDC), in particular in an amount comprised between 89.0 wt% and 91.0 wt% of copolymer (A).

[0021] Copolymer (A) consists essentially of repeating units derived from vinylidene chloride (VDC), especially in an amount of at least 89.0 wt% of copolymer (A); preferably at least 89.2 wt%, more preferably at least 89.5 wt% and most preferably at least 90.0 wt%.

[0022] The copolymer (A) consists essentially of recurring units derived from vinylidene chloride (VDC), especially in an amount of up to 91.0 wt%, preferably up to 90.8 wt% and more preferably up to 90.6 wt% of the copolymer (A).

[0023] The copolymer (A) consists essentially of recurring units derived from methacrylonitrile (MAN), in particular in an amount comprised between 2.00 and 5.50 wt % of the copolymer of the copolymer (A).

[0024] Copolymer (A) consists essentially of repeating units derived from methacrylonitrile (MAN), especially in an amount of at least 2.00 wt%; preferably at least 2.20 wt%, more preferably at least 2.50 wt% and most preferably at least 2.80 wt% of the copolymer (A).

[0025] Copolymer (A) consists essentially of recurring units derived from methacrylonitrile (MAN), especially in an amount of up to 5.50 wt%, preferably up to 5.25 wt%, more preferably up to 5.00 wt% of the copolymer (A).

[0026] The copolymer (A) consists essentially of recurring units which are derived, inter alia, from at least one ionic comonomer (ICO).

[0027] According to the invention, "at least" means that copolymer (A) consists essentially of recurring units derived especially from one or more than one ionic comonomer (ICO). Preferably, copolymer (A) consists essentially of recurring units derived especially from one ionic comonomer (ICO).

[0028] The ionic comonomer (ICO) is advantageously selected from 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt, sodium 2-sulfoethyl methacrylate, sodium 4-vinylbenzenesulfonate (also known as styrene-4-sulfonic acid sodium salt), and mixtures thereof.

[0029] The ionic comonomer (ICO) is preferably selected from 2-acrylamido-2-methylpropane sulfonic acid sodium salt, sodium 4-vinylbenzene sulfonate (also known as styrene-4-sulfonic acid sodium salt), and mixtures thereof.

[0030] The ionic comonomer (ICO) is more preferably selected from 2-acrylamido-2-methylpropane sulfonic acid sodium salt and sodium 4-vinylbenzene sulfonate (also known as styrene-4-sulfonic acid sodium salt).

[0031] When the latex (L) is used for preparing films or retort bags for food packaging subjected to pasteurization, latex (L) of a copolymer (A) consisting essentially of repeating units derived especially from 2-acrylamido-2-methylpropanesulfonic acid sodium salt is more particularly preferred.

[0032] When the latex (L) is used for the preparation of packaging or retort bags for foods subjected to sterilization, more particular preference is given to latex (L) of a copolymer (A) consisting essentially of repeating units derived in particular from ionic comonomers selected from the group consisting of 2-acrylamido-2-methylpropanesulfonic acid sodium salt and sodium 4-vinylbenzenesulfonate (also known as styrene-4-sulfonic acid sodium salt).

[0033] The copolymer (A) consists essentially of recurring units derived from at least one ionic comonomer (ICO), especially in an amount comprised between 0.5 and 1.4 wt % of the copolymer (A).

[0034] Copolymer (A) consists essentially of repeating units derived from at least one ionic comonomer (ICO), especially in an amount of at least 0.5 wt%; preferably at least 0.6 wt%, more preferably at least 0.7 wt%, most preferably at most 0.8 wt% of copolymer (A).

[0035] Copolymer (A) consists essentially of repeating units derived from at least one ionic comonomer (ICO), especially in an amount of up to 1.4 wt%, preferably up to 1.2 wt% and more preferably up to 1.1 wt% of copolymer (A).

[0036] The copolymer (A) consists essentially of recurring units derived from methyl methacrylate (MMA), in particular in such an amount that the total amount of recurring units of VDC, MAN, ICO and MMA is 100 wt%.

[0037] The latex (L) comprises at least one surfactant [surfactant (S)] in an amount comprised between 0.09 wt % and 1.50 wt % of the copolymer (A).

[0038] "At least one surfactant (S)" means that the latex may contain one or more than one surfactant (S).

[0039] In the remainder of the text, the expression "surfactant (S)" used in the singular or plural should be understood to mean one or more than one surfactant (S), unless otherwise stated.

[0040] The surfactant (S) may be an anionic surfactant or a nonionic surfactant.

[0041] Among the anionic surfactants, mention may be made, without limitation, of the alkyl sulfates, such as sodium lauryl sulfate; C 2-H 2 O 2 in pure form or in the form of what are sometimes called paraffin sulfonates; 12 -C 20 Alkyl sulfonates in the form of mixtures of alkyl sulfonates, such as n-alkyl-(C 10 -C 13 ) sodium benzene sulfonate and sodium 1-hexadecane sulfonate; alkyl aryl monosulfonates or disulfonates; alkyl aryl oxide disulfonates, such as branched alkyl-(C 12 ) sodium diphenyl oxide disulfonate; and dialkyl sulfosuccinates, such as sodium diethylhexyl sulfosuccinate and sodium dihexyl sulfosuccinate.

[0042] Among the nonionic surfactants, mention may be made, without limitation, of the alkyl ethoxylated or alkyl aryl ethoxylated derivatives, the alkyl propoxylated or alkyl aryl propoxylated derivatives and sugar esters or ethers.

[0043] The surfactant (S) is preferably an anionic surfactant, optionally as a mixture with one or more nonionic surfactants. Particularly preferred are anionic surfactants.

[0044] The latex (L) comprises at least one surfactant [surfactant (S)] in an amount of at least 0.09 wt % of the copolymer (A); preferably at least 0.10 wt %, more preferably at least 0.12 wt %, particularly more preferably at least 0.15 wt %, most preferably at least 0.17 wt % and particularly most preferably at least 0.20 wt %.

[0045] The latex (L) comprises at least one surfactant [surfactant (S)] in an amount of at most 1.50 wt% of the copolymer (A); preferably at most 1.40 wt%, more preferably at most 1.30 wt%, particularly more preferably at most 1.20 wt%, most preferably at most 1.10 wt% and particularly most preferably at most 1.00 wt%.

[0046] The latex (L) advantageously comprises two surfactants, preferably two anionic surfactants, more preferably an alkyl sulfonate and an alkyl aryl ether disulfonate, most preferably an n-alkyl-(C 10 -C 13 ) benzenesulfonate sodium and branched alkyl-(C12 )Sodium diphenyl oxide disulfonate.

[0047] Firstly, a subject of the present invention is an aqueous latex [latex (L)] of a vinylidene chloride copolymer [copolymer (A)], wherein the copolymer (A) consists essentially of:

[0048] - repeating units derived from vinylidene chloride (VDC), in an amount comprised between 89.2 and 90.8 wt% of the copolymer,

[0049] - recurring units derived from methacrylonitrile (MAN), in an amount comprised between 2.20 and 5.25 wt % of the copolymer,

[0050] - 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

[0051] - repeating units derived from methyl methacrylate (MMA) in an amount such that the total amount of repeating units of VDC, MAN, ICO and MMA is 100 wt %;

[0052] 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).

[0053] The aqueous latex [latex (L)] of the vinylidene chloride copolymer [copolymer (A)] according to the present invention is advantageously such that the copolymer (A) is composed of

[0054] - repeating units derived from vinylidene chloride (VDC) in an amount comprised between 89.0 and 91.0 wt% of the copolymer,

[0055] - recurring units derived from methacrylonitrile (MAN) in an amount comprised between 2.00 and 5.50 wt % of the copolymer,

[0056] - 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

[0057] - repeating units derived from methyl methacrylate (MMA) in an amount such that the total amount of repeating units of VDC, MAN, ICO and MMA is 100 wt %;

[0058] 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).

[0059] For the purposes of the present invention, the term "consisting of the above-mentioned repeating units" is understood to mean that no further repeating units other than the repeating units detailed above may be present in the copolymer (A).

[0060] The preferences defined above when copolymer (A) consists essentially of recurring units defined above also apply when copolymer (A) consists of recurring units defined above.

[0061] The aqueous latex [latex (L)] according to the invention is characterized by a solid content of advantageously at least 40 wt% and preferably at least 42 wt%. The aqueous latex [latex (L)] is characterized by a solid content of advantageously at most 50 wt% and preferably at most 48 wt%. The aqueous latex [latex (L)] according to the invention is characterized by a solid content of more preferably between 44 and 46 wt%.

[0062] The individual polymer particles in the aqueous latex [latex (L)] have a z-average particle size (D ) of advantageously at least 120 nm, preferably at least 130 nm and more preferably at least 140 nm, measured by dynamic light scattering (DLS) as described in the experimental part. z ). They have an average diameter of advantageously at most 300 nm, preferably at most 200 nm and more preferably at most 160 nm.

[0063] The aqueous latexes [latex (L)] according to the invention are characterized by a surface tension of advantageously at least 48 mN / m, preferably at least 49 mN / M and more preferably at least 50 mN / m measured by the Wilhelmy plate method as described in the experimental part. They have a surface tension of advantageously at most 65 mN / m, preferably at most 63 mN / m, more preferably at most 60 mN / m and most preferably at most 55 mN / m.

[0064] Secondly, a subject of the present invention is a process for producing an aqueous latex [latex (L)] of a vinylidene chloride copolymer [copolymer (A)] according to the invention, characterized in that VDC, MAN, at least one ICO and MMA are polymerized by free radical polymerization in an aqueous emulsion in the presence of at least one surfactant (S) to obtain a latex (L) of copolymer (A).

[0065] According to the invention, the expression "free radical polymerization in aqueous emulsion" is understood to mean any free radical polymerization process carried out in an aqueous medium in the presence of at least one surfactant and at least one free radical generator. This definition includes in particular the so-called "conventional" polymerization in aqueous emulsion, in which water-soluble free radical generators are used, and also polymerization in microsuspension, also called polymerization in homogeneous aqueous dispersion, in which oil-soluble free radical generators are used and an emulsion of monomer droplets is prepared by intensive mechanical stirring and in the presence of a surfactant.

[0066] The present invention is particularly suitable for so-called "conventional" polymerizations in aqueous emulsion, which are carried out under conditions known to those skilled in the art, ie, in the presence of surfactants and water-soluble free-radical generators.

[0067] The process according to the invention for producing a latex (L) advantageously uses at least one free radical generator and at least one surfactant (S).

[0068] According to the present invention, the expression "at least one free radical generator" is understood to mean that the process for producing the latex (L) may use one or more than one free radical generator.

[0069] In the remainder of the text, the expression "free radical generator" used in the singular or in the plural should be understood to mean one or more than one free radical generator, unless otherwise specified.

[0070] These free radical generators are advantageously water-soluble. According to the invention, the expression "water-soluble free radical generator" is understood to mean a free radical generator which is soluble in water.

[0071] These free radical generators are advantageously chosen from water-soluble diazo compounds, water-soluble peroxides and redox systems combining water-soluble peroxides and reducing agents.

[0072] As examples of water-soluble diazo compounds, mention may be made of:

[0073] -2-(Carbamoyl azo)isobutyronitrile;

[0074] -4,4'-azobis(4-cyanovaleric acid);

[0075] -4,4'-azobis(4-cyanovaleric acid)ammonium;

[0076] -4,4'-azobis(4-cyanovaleric acid)sodium;

[0077] -4,4'-azobis(4-cyanovaleric acid)potassium;

[0078] -2,2'-azobis(N,N'-dimethyleneisobutylamidine);

[0079] -2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride;

[0080] -2,2'-azobis(2-amidinopropane) dihydrochloride;

[0081] -2,2'-azobis[2-methyl-N-(1,1-bis(hydroxymethyl)-2-hydroxyethyl)propionamide];

[0082] -2,2'-azobis[2-methyl-N-(1,1-bis(hydroxymethyl)ethyl)propionamide];

[0083] -2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide]; and

[0084] -2,2'-Azobis(isobutylamide) dihydrate.

[0085] Preferred are 4,4'-azobis(4-cyanovaleric acid), ammonium 4,4'-azobis(4-cyanovaleric acid), sodium 4,4'-azobis(4-cyanovaleric acid) and potassium 4,4'-azobis(4-cyanovaleric acid).

[0086] As examples of water-soluble peroxides, mention may be made of:

[0087] - Inorganic peroxides such as sodium persulfate, potassium persulfate and ammonium persulfate;

[0088] - tert-butyl hydroperoxide;

[0089] - Hydrogen peroxide; and

[0090] -Perborates.

[0091] Preferred are water-soluble peroxides. Among these water-soluble peroxides, particularly preferred are alkali metal persulfates (such as sodium persulfate and potassium persulfate), ammonium persulfate and also hydrogen peroxide. More particularly preferred are alkali metal persulfates and ammonium persulfate.

[0092] As examples of water-soluble peroxides constituting the redox system, mention may be made of the water-soluble peroxides mentioned above. As reducing agents constituting the redox system, mention may be made of alkali metal sulfites, alkali metal metabisulfites, sodium salts of ascorbic acid and organic sulfinic acid derivatives, such as the disodium salt of 2-hydroxy-2-sulfinyl-acetic acid or mixtures containing it (such as, for example, the product FF7 and FF6M).

[0093] Preferred redox systems are alkali metal persulfates or ammonium persulfates / alkali metal sulfites, alkali metal persulfates or ammonium persulfates / alkali metal metabisulfites, alkali metal persulfates or ammonium persulfates / ascorbic acid, alkali metal persulfates or ammonium persulfates / 2-hydroxy-2-sulfinyl-acetic acid disodium salt, hydrogen peroxide / ascorbic acid, hydrogen peroxide / ferrous sulfate, hydrogen peroxide / 2-hydroxy-2-sulfinyl-acetic acid disodium salt and tert-butyl hydroperoxide / sulfoxylate system. Among these alkali metal sulfites and metabisulfites, sodium sulfite and sodium metabisulfite are particularly preferred, respectively.

[0094] Particularly preferably, the method for producing latex (L) according to the invention uses a single water-soluble free radical generator. The single water-soluble free radical generator is more particularly preferably selected from alkali metal persulfates, ammonium persulfate, hydrogen peroxide and alkali metal persulfates or ammonium persulfate / sodium sulfite, alkali metal persulfates or ammonium persulfate / sodium metabisulfite, alkali metal persulfates or ammonium persulfate / ascorbic acid, alkali metal persulfates or ammonium persulfate / 2-hydroxy-2-sulfinyl-acetic acid disodium salt, hydrogen peroxide / 2-hydroxy-2-sulfinyl-acetic acid disodium salt and hydrogen peroxide / ascorbic acid redox system.

[0095] Furthermore, at the end of the polymerization, an oil-soluble free radical generator (soluble in one or more of the monomers) may optionally be added.

[0096] Preferably a portion of the one or more free radical generators is introduced at the beginning and another portion is introduced at a later time.

[0097] When such introduction occurs at a later time, the introduction may be done continuously or in a single injection.

[0098] According to the invention, the expression "continuous introduction" is understood to mean that the introduction is carried out over a certain period of time and not as a single injection at a given time. It is preferably carried out at a certain rate, which is particularly preferably constant.

[0099] The method for producing an aqueous latex [latex (L)] according to the present invention is characterized by polymerizing VDC, MAN, at least one ICO and MMA by free radical polymerization in an aqueous emulsion in the presence of at least one surfactant (S).

[0100] According to the present invention, the expression "at least one surfactant (S)" is understood to mean that the process for producing the latex (L) may use one or more than one surfactant (S).

[0101] Preferably a portion of the one or more surfactants (S) is introduced at the beginning and another portion at a later time.

[0102] When this introduction takes place at a later time, it is preferably carried out continuously according to a continuous introduction as defined above.

[0103] According to the process for making the latex (L) according to the invention, these monomers, namely VDC, MAN, ICO and MMA, can be introduced into the polymerization medium in several different ways and in different forms.

[0104] Thus, according to a first variant, some monomers are introduced all at once at the beginning and other monomers are introduced at a later time all at once or continuously.

[0105] According to a second variant, all the monomers are introduced at once at the beginning.

[0106] According to a third variant, all the monomers are introduced continuously at a later time.

[0107] According to a fourth variant, a portion of the total monomers is introduced at the beginning and the remainder is introduced at a later time all at once or continuously.

[0108] These monomers can be introduced individually (in the pure state or in the form of an emulsion) or after having been blended (the blend is introduced as such or in the form of an emulsion).

[0109] After reaction of the contents of the reactor, preferably by heating the contents of the reactor until the conversion of the monomers is advantageously at least 82%, and preferably at most 100%, a latex (L) of the copolymer (A) is advantageously obtained.

[0110] The temperature at which the contents of the reactor are reacted is advantageously at least 30° C. and preferably at least 40° C. Furthermore, the temperature is advantageously at most 200° C. and preferably at most 120° C.

[0111] The latex obtained is then advantageously subjected to stripping of residual monomers before its subsequent use. Stripping can be carried out by stripping under vacuum or by stripping under vacuum and simultaneously injecting steam into the latex. Preferably, stripping is carried out by stripping under vacuum and simultaneously injecting steam into the latex.

[0112] In the process according to the invention, the polymerization is advantageously carried out in the presence of a seed latex [seed latex (SL)].

[0113] According to the invention, the term "seed latex (SL)" is understood to mean a latex characterized in that it can be used as a base component for the manufacture of at least one other latex. In particular, its advantageous characteristics are that it absorbs organic phases very well and that it prevents the formation of parasitic particle groups.

[0114] In the process according to the invention, the polymerization is preferably carried out in a methyl methacrylate polymer seed latex.

[0115] The process was carried out in the presence of [PMMA seed latex].

[0116] According to the invention, the expression "in the presence of..." is understood to mean that the seed latex (SL), preferably PMMA seed latex, is in the polymerization medium when such polymerization is carried out. Although it is not excluded that a small amount of seed latex (SL), preferably PMMA seed latex, may be added at a later time, it is preferred that all of the seed latex (SL), preferably all of the PMMA seed latex, is present when the contents of the reactor react. Particularly preferably, all of the seed latex (SL), preferably PMMA seed latex, is introduced at the beginning and therefore all of the seed latex (SL), preferably PMMA seed latex, is present when the contents of the reactor react.

[0117] The expression "at the beginning" is understood to mean the initial charge.

[0118] The expression "at a later time" is understood to mean that the introduction starts after the initial charge has been introduced and the polymerization reaction has been initiated.

[0119] According to the process for manufacturing the latex (L) according to the invention, the polymerization is carried out in the presence of advantageously up to 3 wt %, preferably up to 2.5 wt %, particularly preferably up to 2 wt %, more particularly preferably up to 1.5 wt % and most particularly preferably up to 1.3 wt % of dry matter of seed latex (SL), preferably PMMA seed latex, expressed relative to the total weight of the monomers (VDC, MAN, MMA and ICO).

[0120] The seed latex (SL), preferably PMMA seed latex, can be prepared by any method.

[0121] Advantageously, the PMMA seed latex is prepared by free radical polymerization in an aqueous emulsion of (a) methyl methacrylate (MMA) and optionally at least one comonomer in the presence of (b) at least one free radical generator, (c) at least one surfactant [surfactant (S')] in a total amount of at least 4 wt% relative to the total weight of (a) and (d) water, the free radical polymerization comprising the steps according to:

[0122] (1) introducing at least a portion of (b), at least 2.5 wt% of (c), at least a portion of (d), and optionally at least a portion of (a) into a reactor; then

[0123] (2) reacting the contents of the reactor while continuously introducing therein the remainder of (a), (b), (c) and (d); and

[0124] (3) Obtain and separate PMMA seed latex.

[0125] The expression "free radical polymerization in aqueous emulsion" is as defined above, and the preferences defined above also apply to the process for preparing the PMMA seed latex.

[0126] The polymerization is preferably carried out by introducing at least a portion of (b), at least 2.5 wt% of (c) relative to the total weight of (a), at least a portion of (d) and optionally at least a portion of (a) into a reactor, and then reacting the contents of the reactor while continuously introducing the remainder of (a), (b), (c) and (d) therein, and then obtaining and isolating the PMMA seed latex.

[0127] The PMMA seed latex is characterized by a solids content of advantageously at least 25 wt%, preferably at least 30 wt% and more preferably at least 32 wt%.The PMMA seed latex is characterized by a solids content of advantageously at most 40 wt% and preferably at most 35 wt%.

[0128] The PMMA seed latex is characterized by a solids content more preferably between 32 and 35 wt%.

[0129] The individual polymer particles in the PMMA seed latex have a z-average particle size (D ) of advantageously at least 25 nm, preferably at least 28 nm and more preferably at least 30 nm as measured by dynamic light scattering (DLS) as described in the experimental part. z ). They have an average diameter of advantageously at most 42 nm, preferably at most 40 nm and more preferably at most 38 nm.

[0130] The expression "methyl methacrylate polymer or PMMA" is understood to mean both homopolymers of methyl methacrylate (MMA) and copolymers of methyl methacrylate as main monomer with at least one comonomer copolymerizable with MMA.

[0131] The expression "main monomer" of the MMA polymer is understood to mean a monomer which is present in an amount of at least 100 / n wt% of the monomer blend and will give rise to at least 100 / n wt% of the monomer units of the resulting polymer, n being the number of monomers of the monomer blend.

[0132] Particularly preferred MMA copolymers are MMA copolymers containing MMA in an amount of at least 100 / n wt % and, as copolymerizable monomers, vinyl chloride, vinylidene chloride and / or a (meth)acrylic acid monomer corresponding to the following general formula:

[0133] CH2=CR1R2

[0134] wherein R1 is chosen from hydrogen and methyl, and R2 is chosen from a -CN group and a -CO-R3 group, wherein R3 is chosen from an -OH group, an -O-R4 group, wherein R4 is chosen from a linear or branched alkyl group containing from 2 to 18 carbon atoms, optionally with one or more -OH groups, an oxirane group containing from 2 to 10 carbon atoms and an alkoxyalkyl group containing a total of 2 to 10 carbon atoms, and finally R3 is also chosen from a -NR5R6 group, wherein R5 and R6 are identical or different and are chosen from hydrogen and an alkyl group containing from 1 to 10 carbon atoms, optionally with one or more -OH groups.

[0135] More particularly preferred MMA copolymers are those containing vinyl chloride, vinylidene chloride and / or (meth)acrylic acid monomers as copolymerizable monomers, such as methyl acrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylamide and N-hydroxymethyl acrylamide.

[0136] Preferably, no comonomer copolymerizable with MMA is used. Therefore, the method for preparing PMMA by free radical polymerization in aqueous emulsion is preferably such a method using (a) methyl methacrylate. Therefore, the PMMA seed latex is preferably a seed latex of an MMA homopolymer.

[0137] According to step (1) of the method for preparing a PMMA seed latex, at least a portion of (a) is optionally introduced into a reactor.

[0138] When at least a portion of (a) is introduced in step (1), preferably at least 1%, particularly preferably at least 2.5%, more particularly preferably at least 5% and most particularly preferably at least 8% by weight of the total (a) introduced in step (1).

[0139] When at least a portion of (a) is introduced in step (1), preferably at most 30%, particularly preferably at most 25%, more particularly preferably at most 20% and most particularly preferably at most 15% by weight of the total (a) introduced in step (1).

[0140] Good results have been obtained by not introducing a portion of (a) in step (1), but by introducing all of (a) continuously in step (2), or by introducing about 10% by weight of all of (a) in step (1) and the remainder in step (2).

[0141] The process for preparing the PMMA seed latex advantageously uses at least one free radical generator.

[0142] The expression "at least one free radical generator" is understood to mean that the process for preparing the PMMA seed latex may use one or more than one free radical generator.

[0143] Preferably, a single free radical generator is used. In the remainder of the text, the expression "free radical generator" used in the singular or plural is to be understood as meaning one or more free radical generators, unless otherwise stated.

[0144] These free radical generators are advantageously water-soluble, as defined above.

[0145] These free radical generators are advantageously chosen from water-soluble diazo compounds and water-soluble peroxides. Examples of water-soluble diazo compounds and water-soluble peroxides are given above.

[0146] Preferred are water-soluble peroxides. Among these water-soluble peroxides, particularly preferred are alkali metal persulfates (such as sodium persulfate and potassium persulfate), ammonium persulfate and also hydrogen peroxide. More particularly preferred are alkali metal persulfates and ammonium persulfate.

[0147] In a particularly preferred manner, the process for preparing a PMMA seed latex by free radical polymerization in an aqueous emulsion uses a single free radical generator (b), and the free radical generator is selected from alkali metal persulfates and ammonium persulfate.

[0148] According to step (1) of the method for preparing a PMMA seed latex, at least a portion of (b) is introduced into a reactor.

[0149] In step (1), preferably at least 50%, particularly preferably at least 60%, more particularly preferably at least 65% and most particularly preferably at least 70% by weight of the total (b) is introduced.

[0150] The process for preparing a PMMA seed latex advantageously uses (c) at least one surfactant (S') in a total amount of at least 4 wt % relative to the total weight of (a).

[0151] The expression "at least one surfactant (S')" is understood to mean that the process for preparing the PMMA seed latex may use one or more than one surfactant (S').

[0152] Preferably a single surfactant (S') is used. In the remainder of the text, the expression "surfactant (S')" used in the singular or plural is understood to mean one or more than one surfactant (S'), unless otherwise stated.

[0153] The surfactant (S') may be an anionic surfactant or a nonionic surfactant. Examples of the anionic surfactant and the nonionic surfactant are the same as those given above for the surfactant (S).

[0154] The surfactant (S') is preferably an anionic surfactant, optionally as a mixture with one or more than one nonionic surfactant. The surfactant (S') is more preferably an anionic surfactant.

[0155] The method for preparing a PMMA seed latex uses at least one surfactant (S'), preferably a single surfactant (S'), in a total amount of advantageously at least 4 wt%, preferably at least 5 wt%, more preferably at least 7 wt% and most preferably at least 8 wt% relative to the total weight of (a).

[0156] The process for preparing a PMMA seed latex uses at least one surfactant (S'), preferably a single surfactant (S'), in a total amount of advantageously up to 20 wt%, preferably up to 15 wt% and most preferably up to 12 wt% relative to the total weight of (a).

[0157] According to step (1) of the method for preparing a PMMA seed latex, at least 2.5 wt% of (c) relative to the total weight of (a) is introduced into a reactor.

[0158] Preferably at least 3 wt%, more preferably at least 5 wt% and most preferably at least 7 wt% of (c) relative to the total weight of (a) is introduced in step (1).

[0159] Preferably at most 20 wt%, more preferably at most 15 wt% and most preferably at most 12 wt% of (c) is introduced in step (1 ), relative to the total weight of (a).

[0160] Preferably at most 5 wt % and more preferably at most 2.5 wt % of (c) is introduced in step (2) relative to the total weight of (a).

[0161] Good results have been obtained by introducing all of (c) in step (1), preferably about 10 wt% of (c) relative to the total weight of (a), or by introducing about 8 wt% of (c) relative to the total weight of (a) in step (1) and about 2 wt% of (c) relative to the total weight of (a) in step (2).

[0162] According to step (1) of the method for preparing a PMMA seed latex, at least a portion of (d) is introduced into a reactor.

[0163] In step (1), preferably at least 70% by weight of all (d), more preferably at least 75% by weight of all (d) and most preferably at least 80% by weight of all (d) are introduced.

[0164] Therefore, during step (1), advantageously no reaction occurs.

[0165] According to step (2) of the method for preparing a PMMA seed latex, the contents of the reactor are reacted.

[0166] The expression "reacting the contents of the reactor" is understood to mean that the polymerization reaction is initiated in step (2).

[0167] In order to react the contents of the reactor according to step (2), a device is used in which free radicals are generated. For this purpose, it is especially possible to heat the contents of the reactor or to expose them to strong light radiation such as, for example, UV or visible light. Preferably, the contents of the reactor are heated.

[0168] The temperature at which the contents of the reactor are reacted is advantageously at least 30° C. and preferably at least 40° C. Furthermore, the temperature is advantageously at most 200° C. and preferably at most 120° C.

[0169] The method for preparing PMMA seed latex is advantageously a continuous method. The expression "continuous method" is understood to mean that at least a portion of one of (a), (b), (c) or (d) is introduced during step (2), which is contrary to a batch or discontinuous method, according to which all (a), (b), (c) and (d) are introduced in step (1).

[0170] According to step (2), the contents of the reactor are reacted while continuously introducing therein the remaining amounts of (a), (b), (c) and (d). The expression "continuously introducing" is as defined above.

[0171] The balance of (a), (b), (c) and (d) can be introduced independently or as a mixture. Preferably, the balance of (a), (c) and (d) are introduced as a mixture, and the balance of (b) is introduced separately from the mixture.

[0172] The process for preparing the PMMA seed latex is preferably carried out in the absence of a viscosity reducing agent such as, for example, an ionic electrolyte.

[0173] Advantageously, step (2) is continued until MMA and optionally one or more other comonomers have reacted to a certain extent. Preferably, step (2) is continued until the conversion of MMA and optionally one or more other comonomers is at least 82% and at most 100%.

[0174] According to step (3) of the method for preparing a PMMA seed latex, a methyl methacrylate polymer seed latex is obtained and separated.

[0175] According to step (3), the PMMA seed latex is thus separated from the reactor in which it was prepared. Therefore, the method for preparing the PMMA seed latex is advantageously an ex-situ method, i.e. a method in which the seed latex is separated at the end of the method, in contrast to an in-situ method, according to which the seed latex is synthesized in a reactor and then used therein for subsequent polymerization.

[0176] Then PMMA seed latex may or may not be subjected to the stripping of residual monomers before its subsequent use. In the case of stripping, it can be by stripping under vacuum or by stripping under vacuum and simultaneously injecting steam in this latex. Preferably, when carrying out it, it is to strip under vacuum.

[0177] According to a particularly preferred variant, the method for preparing a PMMA seed latex is characterized in that it comprises the following steps:

[0178] (1) introducing into a reactor at least a portion of (b), at least 7 wt% of (c) relative to the total weight of (a), at least 80 wt% of all (d) and at most 15 wt% of all (a); then

[0179] (2) reacting the contents of the reactor while continuously introducing therein the remainder of (a), (b), (c) and (d); and

[0180] (3) Obtain and separate PMMA seed latex.

[0181] The aqueous latex [latex (L)] of the vinylidene chloride copolymer [copolymer (A)] according to the present invention is advantageously applied as a coating on a substrate to produce a multilayer film.

[0182] Another object of the present invention is therefore the use of an aqueous latex [latex (L)] of a vinylidene chloride copolymer [copolymer (A)] according to the invention as a coating on a substrate to produce a multilayer film preferably for food packaging.

[0183] Any method can be used to coat the aqueous latex (L) on the substrate. Non-limiting examples of coating methods are air knife coating and engraved roll coating.

[0184] The substrate may be a polymer substrate, a paper substrate or a regenerated cellulose substrate. The substrate is preferably a polymer substrate.

[0185] Polymer substrates which can be coated with the latex (L) according to the invention are, for example, polyvinyl chloride, polyesters (preferably polyethylene terephthalate), polyamides and polypropylene. Polyethylene terephthalate is particularly preferred as polymer substrate.

[0186] Another object of the present invention is a film prepared with an aqueous latex [latex (L)] of the vinylidene chloride copolymer [copolymer (A)] according to the present invention, preferably a film for packaging, more preferably a film for food packaging, and most preferably a flexible film for food packaging.

[0187] The film according to the invention is preferably used for food packaging, more preferably for retortable food packaging.The film according to the invention is most preferably used for the preparation of retort pouches.

[0188] Another object of the invention is a retort bag made with the film according to the invention.

[0189] According to the present invention, a "retort bag" (also referred to as a "retortable bag") means a type of food packaging that allows aseptic packaging of various foods and beverages processed by aseptic processing and is used as an alternative to traditional industrial canning methods.

[0190] When the films according to the invention are used for producing retort pouches, polyethylene terephthalate is particularly preferred as polymer substrate.

[0191] Retort bags are typically subjected to pasteurization or sterilization.

[0192] Should the disclosure of any patents, patent applications, and publications incorporated by reference into this application conflict with the description of this application to the extent that a term may be unclear, this description shall take precedence.

[0193] The present invention will now be described in more detail with reference to the following examples, which are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0194] Measurement of particle size distribution

[0195] The z-average particle size (D z ) and polydispersity were measured by dynamic light scattering (DLS) using a ZetasizerNano ZS (Malvern Instruments) at 20° C. The samples taken from the PMMA seed latex and from the PVDC latex for DLS measurement were highly diluted with deionized water (diluted approximately to 1000 times) in order to avoid interference between particles that may occur at high concentrations.

[0196] Surface tension

[0197] The surface tension of the PVDC latex was measured at 20° C. by the platinum plate method (Krüss device).

[0198] pH Measurement

[0199] The pH of PVDC latex was measured with a pH meter.

[0200] Film production with PVDC latex

[0201] Films were produced using PVDC latex. For this purpose, the PET film was first subjected to a corona treatment. A PVDC layer of about 5 μm thick was applied thereto and, after drying, the film was rewound.

[0202] The coating is carried out on a Kroenert production line with the following features:

[0203] -Line speed: 100m / min;

[0204] -Corona treatment: 1.5kW;

[0205] - "Reverse" rotation of the etching roller (110%);

[0206] - Drying temperature = 110°C.

[0207] The thickness of the layer M of the film is measured before the water vapor transmission rate and oxygen transmission rate measurements are made.

[0208] After coating, the films were placed in a refrigerator.

[0209] Membrane treatment before measurement

[0210] The films were subjected to accelerated aging for 2 days at 40°C and then sterilized or pasteurized under the conditions defined below which are standard conditions in the art.

[0211] The membranes were sterilized by placing them in a container containing steam at 120°C for 30 min.

[0212] The membranes were pasteurized by placing them in a container and immersing them in water heated at 95° C. for 2 h.

[0213] After these treatments, the films were placed in a refrigerator until measurement.

[0214] Before measurement, the films were removed from the refrigerator and placed at 23° C. and 50% relative humidity for 24 h.

[0215] Measurement of water vapor transmission rate of films

[0216] The water vapor transmission rate (WVTr) of the films prepared as described above was measured according to standard ASTM F-1249 on a Permatran W 3 / 31 machine from Mocon at 38° C. and 90% relative humidity.

[0217] Water vapor transmission rate is expressed in g.μm / m 2 .Day indicates.

[0218] The water vapor transmission rate was measured on films that had been subjected to accelerated aging at 40° C. for 2 days (2D40) and then further subjected to sterilization (Sterilized) or pasteurization (Pasteurized) before measurement.

[0219] Measurement of oxygen transmission rate of membranes

[0220] The principle of the method consists in determining, for defined temperature and relative humidity, the amount of oxygen that passes through a membrane made of vinylidene chloride copolymer latex per unit time and unit area.

[0221] The machine used was an OX-TRAN 1000-H HUMIDICON (Mountain Con) machine, conditioned at 23° C. and 0% relative humidity or at 23° C. and 85% relative humidity.

[0222] Oxygen transmission rate (OTr) in cm 3 .μm / m 2 .Tian.Ba said.

[0223] Oxygen transmission rate was measured on films that had been subjected to accelerated aging at 40° C. for 2 days (2D40) and then further subjected to sterilization (Sterilized) or pasteurization (Pasteurized) before measurement.

[0224] Transparency and haze measurement

[0225] Transparency and haze were measured in accordance with standard ASTM D 1003 applied to transparent samples having a haze value of 30% or less.

[0226] The principle is strength I O The light beam passes through the sample to be analyzed which has a flat surface and then enters the integrating sphere. The light evenly distributed by the matte white coating of the sphere wall is measured by the detector.

[0227] Haze (H) is a measure of the dispersion of light at large angles and is defined as the intensity of light transmitted by a sample outside a solid angle of 5° (I H ) and the total light intensity transmitted by the entity (I T ) between them.

[0228] Transparency is a measure of the dispersion of light at small angles and is defined as the ratio between:

[0229] The light intensity at the center of the ring sensor (I 圆环 ) minus the light intensity of the ring sensor (placed in the exit hole) (I 中心 );and

[0230] The light intensity of the ring sensor ring (I 中心 ) is the light intensity (I 圆环 ).

[0231] The device used was the device HAZE-GARD PLUS 4725 (illuminant type C) from BYK GARDNER. This device complies with standard ASTM D 1003.

[0232] Example 1 (according to the present invention) - Preparation of PMMA seed latex

[0233] To the 8.7m equipped with cooling circuit 3 The polymerization autoclave (stirred at 20 rpm) was charged in sequence with 3908 l of demineralized water, 14 kg (6.7 g active material / kg monomer) of powdered ammonium persulfate solution and 814 l (100 g active material / kg monomer of seed latex) of n-alkyl-(C 10 -C 13 ) sodium benzenesulfonate solution. The autoclave was closed and then subjected to two vacuum operations at 140 mbar absolute pressure.

[0234] The stirring speed was then increased to 60 rpm while the mixture was brought to 85° C. When the temperature reached 84° C., 2100 kg of methyl methacrylate were added at a constant rate over 3 h while 151 kg (2.87 g active material / kg monomer) of a 40 g / l ammonium persulfate solution were added at a constant rate over the same 3 h duration.

[0235] After the end of the injection of methyl methacrylate and ammonium persulfate, the polymerization was continued until a temperature difference of less than 5° C. was obtained between the temperature of the reaction medium and the temperature of the cooling circuit, followed by 1 h of postpolymerization. The stirring speed was then reduced to 20 rpm and the latex was degassed and then stripped under vacuum at 65° C. for 3 h.

[0236] The solid content of the PMMA seed latex thus polymerized meets the specification, i.e., 32%-35%. The average diameter of the particles measured by DLS meets the specification, i.e., 30nm-38nm.

[0237] Example 2 (according to the invention) - Preparation of a PMMA seed latex in an aqueous emulsion in the presence of VDC Aggregation

[0238] A 65 l polymerization autoclave equipped with a cooling circuit was charged with 6.5 l of demineralized water. Then 793 ml of a PMMA seed latex (32.75% solids content) prepared according to the method defined in Example 1 (corresponding to 11 g dry matter / kg monomer) and 135 ml of a 3.7 g / l ascorbic acid solution were charged thereto. 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.

[0239] A 150 l autoclave used as a premixer and equipped with a cooling circuit was charged successively with 18.3 l of demineralized water, 109 ml of branched alkyl-(C 12 ) sodium diphenyl ether disulfonate solution, 84 ml of n-alkyl-(C 10 -C 13 ) sodium benzenesulfonate solution. 3.49 1 of 30 g / l tetrasodium pyrophosphate solution and 1.45 1 of 180 g / l 2-acrylamido-2-methylpropanesulfonic acid sodium salt solution. The premixer is subjected to two vacuum operations. The stirring speed of the medium is brought to 130 rpm. A mixture of 1.45 kg of methyl methacrylate and 0.785 kg of methacrylonitrile and then 23.7 kg of vinylidene chloride are introduced into the premixer. After stirring for 30 min, the stirring rate is reduced to 90 rpm.

[0240] 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 regarded as the start of the polymerization (T o ).

[0241] In T o At T + 1 min, 47.2 kg of monomer emulsion was added from the premixer at a constant rate over 8 h. o At T + 1 min, 962 ml of 11.7 g / l ascorbic acid solution was added at a constant rate over 8 h 45 min. o At +2 min, 823 ml of a 41.0 g / l ammonium persulfate solution were added at a constant rate within 8 h 15 min. When a temperature difference of 2° C. was obtained between the temperature of the reaction medium and the temperature of the cooling circuit, the latex was postpolymerized for 120 min.

[0242] The stirring speed is reduced to 110rpm, and the latex is then thermally degassed and then stripped under vacuum at 60°C (autoclave temperature) for two hours. The temperature of the cooling system is then brought to 60°C. After two hours at 60°C (cooling temperature), the stirring speed is increased to 110rpm. After stripping for 6h, the latex is cooled to 20°C and then filtered through a 60μm filter bag. The solid content of the latex is measured and, if necessary, adjusted to between 44wt% and 46wt% by adding water.

[0243] The properties of the PVDC latex obtained in Example 2 were measured in the manner previously described. The results are given in Table 1.

[0244] Films were produced using the PVDC latex obtained in Example 2. The properties measured on these films in the manner described above are given in Table 2.

[0245] Example 3 (according to the invention) - Preparation of a PMMA seed latex in an aqueous emulsion in the presence of VDC Aggregation

[0246] Repeat Example 2, except as follows:

[0247] The amount of PMMA seed latex (33.2% solids content) prepared according to the method defined in Example 1 is 781 ml (corresponding to 11 g dry matter / kg monomer);

[0248] The amount of demineralized water introduced into the premixer was 18.0 l;

[0249] 1.45 l of a 180 g / l solution of 2-acrylamido-2-methylpropanesulfonic acid sodium salt were replaced by 1.74 l of a 150 g / l solution of styrene-4-sulfonic acid sodium salt (also known as sodium 4-vinylbenzenesulfonate);

[0250] The amount of methyl methacrylate is 1.44 kg; and

[0251] At To + 1 min, 47.17 kg of monomer emulsion was added from the premixer at a constant rate within 8 h.

[0252] The properties of the PVDC latex obtained in Example 3 were measured in the manner previously described. The results are given in Table 1.

[0253] Films were produced using the PVDC latex obtained in Example 3. The properties measured on these films in the manner described above are given in Table 2.

[0254] Example 4 (according to the invention) - Preparation of a PMMA latex in aqueous emulsion in the presence of the PMMA seed latex prepared in Example 1 VDC Aggregation

[0255] Repeat Example 2, except as follows:

[0256] The amount of demineralized water introduced into the polymerization autoclave was 6.6 l;

[0257] The amount of PMMA seed latex (34.0% solids content) prepared according to the method defined in Example 1 is 762 ml (corresponding to 11 g dry matter / kg monomer);

[0258] The amount of demineralized water introduced into the premixer was 18.5 l;

[0259] Contains 486 g / l of active material branched alkyl-(C 12 ) The amount of sodium diphenyl oxide disulfonate solution is 323 ml;

[0260] · No addition of n-alkyl-(C 10 -C 13 ) sodium benzenesulfonate solution,

[0261] The amount of 180 g / l 2-acrylamido-2-methylpropanesulfonic acid sodium salt solution is 1.24 l;

[0262] The amount of methyl methacrylate is 1.48 kg; and

[0263] At To + 1 min, 47.25 kg of monomer emulsion was added from the premixer at a constant rate within 8 h.

[0264] The properties of the PVDC latex obtained in Example 4 were measured in the manner previously described. The results are given in Table 1.

[0265] Films were produced using the PVDC latex obtained in Example 4. The properties measured on these films in the manner described above are given in Table 2.

[0266] Example 5 - Polymerization of VDC in aqueous emulsion in the presence of PMMA seed latex prepared in Example 1

[0267] Repeat Example 2, except as follows:

[0268] The amount of PMMA seed latex (34.0% solids content) prepared according to the method defined in Example 1 is 762 ml (corresponding to 11 g dry matter / kg monomer);

[0269] The amount of demineralized water introduced into the premixer was 18.4 l;

[0270] The amount of demineralized water introduced into the polymerization autoclave was 6.6 l;

[0271] Contains 486 g / l of active material branched alkyl-(C 12 ) The amount of sodium diphenyl oxide disulfonate solution is 484 ml;

[0272] · No addition of n-alkyl-(C 10 -C 13 ) sodium benzenesulfonate,

[0273] The amount of 180 g / l 2-acrylamido-2-methylpropanesulfonic acid sodium salt solution is 1.24 l;

[0274] The amount of methyl methacrylate is 1.48 kg; and

[0275] At To + 1 min, 47.33 kg of monomer emulsion was added from the premixer at a constant rate within 8 h.

[0276] The properties of the PVDC latex obtained in Example 5 were measured in the manner previously described. The results are given in Table 1.

[0277] Films were produced using the PVDC latex obtained in Example 5. The properties measured on these films in the manner described above are given in Table 2.

[0278] Example 6 (C) (Comparative) - VDC in aqueous emulsion in the presence of PMMA seed latex prepared in Example 1 polymerization

[0279] Repeat Example 2, except as follows:

[0280] The amount of PMMA seed latex (33.2% solids content) prepared according to the method defined in Example 1 is 781 ml (corresponding to 11 g dry matter / kg monomer);

[0281] The amount of demineralized water introduced into the premixer was 17.6 l;

[0282] Contains 486 g / l of active material branched alkyl-(C 12 ) The amount of sodium diphenyl oxide disulfonate solution is 484 ml;

[0283] · No addition of n-alkyl-(C 10 -C 13 ) sodium benzenesulfonate solution,

[0284] The amount of 180 g / l 2-acrylamido-2-methylpropanesulfonic acid sodium salt solution is 2.18 l;

[0285] The amount of methyl methacrylate is 1.31 kg; and

[0286] At To + 1 min, 47.33 kg of monomer emulsion was added from the premixer at a constant rate within 8 h.

[0287] The properties of the PVDC latex obtained in Example 6 were measured in the manner previously described. The results are given in Table 1.

[0288] Films were produced using the PVDC latex obtained in Example 6. The properties measured on these films in the manner described above are given in Table 2.

[0289] Example 7 (C) (Comparative) - VDC in aqueous emulsion in the presence of PMMA seed latex prepared in Example 1 polymerization

[0290] Repeat Example 2, except as follows:

[0291] The amount of PMMA seed latex (33.2% solids content) prepared according to the method defined in Example 1 is 781 ml (corresponding to 11 g dry matter / kg monomer);

[0292] The amount of demineralized water introduced into the premixer was 19.1 l;

[0293] Contains 486 g / l of active material branched alkyl-(C 12 ) The amount of sodium diphenyl oxide disulfonate solution is 1.08 l;

[0294] · No addition of n-alkyl-(C 10 -C 13 ) sodium benzenesulfonate solution,

[0295] · No addition of 180g / l 2-acrylamido-2-methylpropanesulfonic acid sodium salt solution

[0296] The amount of methyl methacrylate is 1.24 kg;

[0297] The amount of methacrylonitrile is 1.29 kg;

[0298] The amount of vinylidene chloride is 23.6 kg;

[0299] Raise the temperature of the reaction medium to 65°C;

[0300] · the addition of 340 ml of a 71.3 g / l ammonium persulfate solution was carried out at T = 64°C; and

[0301] At To + 1 min, 47.60 kg of monomer emulsion was added from the premixer at a constant rate within 8 h.

[0302] The properties of the PVDC latex obtained in Example 7 were measured in the manner previously described. The results are given in Table 1.

[0303] Films were produced using the PVDC latex obtained in Example 7. The properties measured on these films in the manner described above are given in Table 2.

[0304] Table 1

[0305]

[0306]

Claims

1. An aqueous latex [latex (L)] of a vinylidene chloride copolymer [copolymer (A)], in, The copolymer (A) consists essentially of: - repeating 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, - repeating units derived from at least one ionic comonomer (ICO) chosen from 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt, sodium 2-sulfoethyl methacrylate, sodium 4-vinylbenzenesulfonate and mixtures thereof, in an amount comprised between 0.5 and 1.4 wt% of the copolymer (A), and - repeating units derived from methyl methacrylate (MMA) in an amount such that the total amount of repeating 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).

2. 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 89.2 wt% of the copolymer (A) and at most 90.8 wt% of the copolymer (A).

3. The aqueous latex (L) according to claim 2, 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).

4. The aqueous latex (L) according to claim 2, wherein The copolymer (A) consists essentially of recurring units derived from vinylidene chloride (VDC) in an amount of at least 90.0 wt% of the copolymer (A).

5. The aqueous latex (L) according to claim 2, wherein The copolymer (A) consists essentially of recurring units derived from vinylidene chloride (VDC) in an amount of up to 90.6 wt% of the copolymer (A).

6. The aqueous latex (L) according to claim 1 or 2, wherein The copolymer (A) consists essentially of recurring units derived from methacrylonitrile (MAN) in an amount of at least 2.20 wt% of the copolymer (A) and at most 5.25 wt% of the copolymer (A).

7. The aqueous latex (L) according to claim 6, 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).

8. The aqueous latex (L) according to claim 6, wherein The copolymer (A) consists essentially of recurring units derived from methacrylonitrile (MAN) in an amount of at least 2.80 wt% of the copolymer (A).

9. The aqueous latex (L) according to claim 6, wherein The copolymer (A) consists essentially of recurring units derived from methacrylonitrile (MAN) in an amount of up to 5.00 wt% of the copolymer (A).

10. The aqueous latex (L) according to claim 1 or 2, wherein The copolymer (A) consists essentially of recurring units derived from at least one ionic comonomer (ICO) in an amount of at least 0.6 wt% of the copolymer (A) and at most 1.2 wt% of the copolymer (A).

11. The aqueous latex (L) according to claim 10, 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).

12. The aqueous latex (L) according to claim 10, wherein The copolymer (A) consists essentially of recurring units derived from at least one ionic comonomer (ICO) in an amount of at most 0.8 wt.-% of the copolymer (A).

13. The aqueous latex (L) according to claim 10, wherein The copolymer (A) consists essentially of recurring units derived from at least one ionic comonomer (ICO) in an amount of at most 1.1 % by weight of the copolymer (A).

14. The aqueous latex (L) according to any one of claims 1 or 2, 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).

15. The aqueous latex (L) according to claim 14, 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).

16. The aqueous latex (L) according to claim 14, wherein The latex (L) comprises at least one surfactant [surfactant (S)] in an amount of at least 0.15 wt% of the copolymer (A) and in an amount of at most 1.20 wt% of the copolymer (A).

17. The aqueous latex (L) according to claim 14, wherein The latex (L) comprises at least one surfactant [surfactant (S)] in an amount of at least 0.17 wt% of the copolymer (A) and in an amount of at most 1.10 wt% of the copolymer (A).

18. The aqueous latex (L) according to claim 14, wherein The latex (L) comprises at least one surfactant [surfactant (S)] in an amount of at least 0.20 wt% of the copolymer (A) and in an amount of at most 1.00 wt% of the copolymer (A).

19. The aqueous latex (L) according to any one of claims 1 or 2, wherein The copolymer (A) consists essentially of: - repeating 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 - repeating units derived from methyl methacrylate (MMA) in an amount such that the total amount of repeating 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 0.10 and 1.40 wt % of the copolymer (A).

20. The aqueous latex (L) according to any one of claims 1 or 2, wherein The ionic comonomer is selected from the group consisting of 2-acrylamido-2-methylpropane sulfonic acid sodium salt and sodium 4-vinylbenzene sulfonate.

21. A method for producing an aqueous latex (L) according to any one of claims 1 to 20, characterized in that Vinylidene chloride (VDC), methacrylonitrile (MAN), at least one ionic comonomer (ICO) selected from the group consisting of 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt, sodium 2-sulfoethyl methacrylate, sodium 4-vinylbenzenesulfonate and mixtures thereof, and methyl methacrylate (MMA) are polymerized by free radical polymerization in an aqueous emulsion in the presence of at least one surfactant (S) to obtain the latex (L) of the copolymer (A).

22. The method according to claim 21, characterized in that The polymerization is carried out in the presence of a seed latex [seed latex (SL)].

23. The method according to claim 21 or 22, characterized in that The polymerization is carried out in the presence of a methyl methacrylate polymer seed latex [PMMA seed latex].

24. Use of an aqueous latex (L) according to any one of claims 1 to 20 as a coating on a substrate for producing a multilayer film.

25. The use according to claim 24, wherein the multilayer film is used for food packaging.

26. A film prepared using the aqueous latex (L) according to any one of claims 1 to 20.

27. The film of claim 26, wherein the film is used for packaging.

28. The membrane according to claim 26, characterized in that The film is used for food packaging.

29. The membrane according to claim 28, characterized in that The film is used to prepare retort pouches.

30. A retort bag prepared using the film according to claim 28.

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