Polymer latex and elastomeric film produced therefrom having self-healing properties

Abstract

The present invention relates to aqueous dispersions, methods for making the aqueous dispersions, elastomeric films made from the aqueous dispersions, articles comprising the elastomeric films, and methods for making free-standing elastomeric films from the aqueous dispersions. The aqueous dispersions include core-shell polymer latex particles, the shell of which has ethylenically unsaturated groups retained from the polymer backbone of the shell of the latex particle, the ethylenic unsaturation being separated from the polymer backbone by at least three chemical bonds, the shell of the core-shell particle being crosslinked, and the core of the core-shell particle being uncrosslinked.

Description

[Technical Field]

[0001] The present invention particularly relates to, but is not limited to, aqueous dispersions comprising core-shell polymer latex particles that are particularly suitable for preparing elastomeric films, methods for making such aqueous dispersions, elastomeric films made from the aqueous dispersions, and methods for making free-standing elastomeric films using the aqueous dispersions. [Background technology]

[0002] According to current industry standards, elastomeric films, particularly for dip-molding applications such as surgical gloves, are manufactured from compounds containing carboxylated acrylonitrile butadiene latex (XNBR). To obtain the mechanical strength required for the intended use of these elastomeric films, some crosslinking of the film must be achieved during the manufacture of the elastomeric film.

[0003] Several different concepts for obtaining such crosslinked elastomeric films are available in the prior art. One possibility is that the compound for producing the elastomeric film contains a conventional sulfur vulcanization system, such as sulfur, in combination with accelerators such as thiurams and carbamates and zinc oxide.

[0004] Because sulfur-vulcanized systems can cause allergic reactions, alternative concepts have been developed to make latex films curable. Another possibility is to include a crosslinker component in the compound, such as a polyvalent cation (e.g., zinc oxide) or other polyfunctional organic compound suitable for reacting with functional groups on the latex particles, to achieve chemical crosslinking. Furthermore, if the polymer latex has a sufficient amount of self-crosslinking groups, such as N-methylol amide groups, sulfur-vulcanized systems and / or crosslinkers can be completely avoided.

[0005] Systems using specific additives such as sulfur or crosslinking agents are summarized in WO 2018 / 111087 and WO 2017 / 164726.

[0006] WO 2017 / 209596 discloses a polymer latex for dip molding applications that includes two different types of latex particles: one type of latex particle is carboxylated, while the second type of latex particle contains oxirane functionality.

[0007] All of these different concepts result in crosslinked elastomeric films, where the crosslinking is essentially irreversible. As a result, these elastomeric films cannot be easily recycled and do not exhibit self-healing properties. For example, due to the lack of self-healing properties of the film, if any type of defect, such as a pinhole, occurs during the production of the elastomeric film, these products must be discarded, resulting in waste that cannot be reused. Furthermore, if such an elastomeric film tears during its use, this cannot be repaired, resulting in irreversible disposal of the elastomeric film and, in turn, failure of the article containing such an elastomeric film.

[0008] Therefore, there is a need in the industry for elastomeric films that have inherent self-healing properties and can potentially be recycled to reduce unusable waste and prevent the eventual failure of articles containing such films. This would also lead to more environmentally friendly techniques for producing elastomeric films. Furthermore, such a system would avoid the need to use materials that can cause so-called Type IV allergic reactions.

[0009] US 4,244,850, JPS 6,069,178 and US 5,306,744 disclose polymer latex compositions for use in coating compositions or adhesives, including polymer latex particles having ethylenically unsaturated groups that can be introduced by reacting functional groups present on the latex particles with ethylenically unsaturated compounds having functional groups reactive with the functional groups on the latex particles. US 5,306,744 and JPS 6,069,178 disclose core-shell particles obtained by two-stage emulsion polymerization, but the core in these particles is crosslinked and the outer shell is not crosslinked. None of these documents relate to elastomer films or the self-healing properties of elastomer films.

[0010] Accordingly, the present invention seeks to provide a polymer latex composition suitable for preparing an elastomeric film having self-healing properties. Summary of the Invention

[0011] According to a first aspect of the present invention, there is provided an aqueous dispersion comprising core-shell polymer latex particles, wherein the shell of the core-shell polymer latex particles is formed from a polymer backbone of the shell of the latex particles. Pending An aqueous dispersion is provided having ethylenically unsaturated groups, the ethylenic unsaturation being separated from the polymer backbone by at least three chemical bonds, the shell of the core-shell particles being crosslinked, and the core of the core-shell particles being uncrosslinked.

[0012] Furthermore, according to a further aspect, the present invention also relates to a method for producing an aqueous dispersion comprising core-shell polymer latex particles, wherein the shell of the core-shell polymer latex particles is formed from the polymer backbone of the shell of the latex particles. Pending The shell of the core-shell particle is crosslinked, and the core of the core-shell particle is not crosslinked, by aqueous emulsion polymerization having ethylenically unsaturated groups and comprising at least the following two steps: (I) polymerizing ethylenically unsaturated monomers that do not contain monomers containing two or more non-conjugated ethylenically unsaturated groups in the process of producing the core of the core-shell particle; and (II) in the step of preparing the shell, polymerizing a monomer mixture comprising: (a) a monomer selected from conjugated dienes, monoethylenically unsaturated monomers that do not have a functional group that can be subsequently reacted after formation of the latex particles to introduce an ethylenically unsaturated group, and combinations thereof; and (bi) a monomer having at least two non-conjugated ethylenically unsaturated groups that exhibit different reactivities in aqueous emulsion polymerization, wherein at least a portion of the ethylenically unsaturated groups having the lower reactivity remain unreacted after completion of the aqueous emulsion polymerization; and / or (bii) a monoethylenically unsaturated monomer having a functional group that can be subsequently reacted after formation of the latex particles to introduce an ethylenically unsaturated group; and (c) a monomer having at least two non-conjugated ethylenically unsaturated groups different from (bi); Here, when the monomer (bi) is not present, at least a portion of the functional groups of the monomer (bii) reacts after the aqueous emulsion polymerization is completed to introduce ethylenically unsaturated groups.

[0013] Furthermore, according to a further aspect, the present invention relates to an elastomeric film made from the aqueous dispersion of the present invention, which film is preferably free-standing, substantially free of sulfur crosslinks, and substantially free of ionomeric crosslinks.

[0014] Another aspect of the present invention relates to a method for making a free-standing elastomeric film, comprising: (a) providing a composition comprising the aqueous dispersion defined above; (b) applying the composition to a substrate to form a wet film; (c) drying and / or curing the wet film to form an elastomeric film; and (d) separating the elastomeric film from the substrate; (e) optionally heat treating the elastomeric film before or after step (d) at a temperature between 20°C and 160°C, preferably between 250°C and 100°C, more preferably between 75°C and 100°C.

[0015] Furthermore, in a further aspect, the present invention also relates to an article comprising an elastomeric film according to the present invention.

[0016] Furthermore, the inventors have surprisingly discovered that in addition to self-healing properties, elastomeric films obtained from the aqueous dispersions of the present invention exhibit shape-retaining properties when the elastomeric films are subjected to moderate temperatures, as shown in more detail in the examples. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a graph of dz values ​​for nanoparticles as a function of pH. [Figure 2A] Figure 2A shows (a) before cutting, (b) the dumbbell cut into two pieces and marked on the top of the dumbbell, (c) pressed together for 60 seconds to reconnect, and (d) after annealing at 40°C for 24 hours. [Figure 2B] FIG. 2B shows the stress-strain data. [Figure 3] FIG. 3 shows the shape memory behavior of a cast film made from a latex of the present invention. [Figure 4] Figure 4 shows the relaxation of both the folded and spring-like samples. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will now be described in more detail.

[0019]

[0003] Aqueous dispersions containing core-shell latex particles are provided. The shells of the core-shell particles are crosslinked, and the cores of the core-shell particles are not crosslinked. In particular, core-shell polymer latex particles are formed by polymeric backbones of the shells of the latex particles. Pending It carries an ethylenically unsaturated group, where the ethylenic unsaturation is separated from the polymer backbone by at least three chemical bonds.

[0020] Polymer latex particles are thereby distinct from core-shell particles in which a crosslinked shell is formed by polymerization of a monomer mixture containing a conjugated diene, such as butadiene, because the remaining double bond resulting from polymerization of one double bond of the conjugated diene in a free radical emulsion polymerization process is separated from the polymer backbone of the shell by fewer than three chemical bonds.

[0021] In particular, the shell of the core-shell polymer particles may comprise structural units represented by formula (1). -L-CR 1 =CR 2 R 3 (1) In the formula, L is -CR 1 =CR 2 R 3 and the polymer backbone of the shell of the latex particle, R is a linear or branched divalent group, or a divalent group containing a cyclic group, which provides at least two atoms in the chain between R 1 , R 2 and R 3 are independently selected from hydrogen and monovalent organic groups, preferably C1-C4-alkyl groups.

[0022] In formula (1), -L- represents a divalent hydrocarbon group, and -CR- is attached to the polymer backbone. 1 =CR 2 R 3 and preferably, -L- is selected from groups containing at least one heteroatom in the chain connecting -CR 1=CR 2 R 3 The chain connecting the groups includes a group selected from an ester, an ether, a urethane, a thiourethane, a urea, an amide group, and a combination thereof.

[0023] Therefore, there are two different synthetic routes that can be used to prepare polymer latex particles. According to one route, the monomer mixture for polymerizing the shell portion of the core-shell particle may contain, in addition to the monomer having at least two unconjugated ethylenically unsaturated groups that cause crosslinking of the shell portion of the polymer latex particle, a monomer having at least two unconjugated ethylenically unsaturated groups that exhibit different reactivity in aqueous emulsion polymerization, so that at least a portion of these ethylenically unsaturated groups with lower reactivity remain unreacted after the end of aqueous emulsion polymerization. Therefore, the ethylenically unsaturated groups that have the necessary separation from the polymer backbone of the shell polymer remain present on the surface of the polymer latex particle according to the present invention.

[0024] Alternatively, the polymeric latex particles can be prepared by polymerizing a monomer mixture for the shell portion of the core-shell particles that includes a monoethylenically unsaturated monomer having a functional group that can be subsequently reacted to introduce an ethylenically unsaturated group after the formation of the latex particles and then reacted after completion of the aqueous emulsion polymerization to introduce an ethylenically unsaturated group.

[0025] Thus, the core-shell latex particles can be prepared by aqueous emulsion polymerization comprising at least two steps: (I) polymerizing ethylenically unsaturated monomers that do not contain a monomer containing a plurality of non-conjugated ethylenically unsaturated groups in the step of producing the core of the core-shell particle; and (II) in the step of preparing the shell, polymerizing a monomer mixture comprising: (a) a monomer selected from conjugated dienes, monoethylenically unsaturated monomers that do not have a functional group that can be subsequently reacted after formation of the latex particles to introduce an ethylenically unsaturated group, and combinations thereof; and (b)(i) a monomer having at least two non-conjugated ethylenically unsaturated groups that exhibit different reactivities in aqueous emulsion polymerization, wherein at least a portion of the ethylenically unsaturated groups having the lower reactivity remain unreacted after completion of the aqueous emulsion polymerization; and / or (b)(ii) a monoethylenically unsaturated monomer having a functional group that can be subsequently reacted after formation of the latex particles to introduce an ethylenically unsaturated group; and (c) a monomer having at least two non-conjugated ethylenically unsaturated groups different from (bi); Here, when the monomer (bi) is not present, at least a portion of the functional groups of the monomer (bii) reacts to introduce ethylenically unsaturated groups after the aqueous emulsion polymerization is completed.

[0026] Monomer (a) The monomer (a) for polymerization of the shell portion of the core-shell particle of the present invention may be suitably selected from conjugated dienes, aromatic vinyl compounds, linear alkyl esters of ethylenically unsaturated acids, branched alkyl esters of ethylenically unsaturated acids, linear alkyl amides of ethylenically unsaturated acids, branched alkyl amides of ethylenically unsaturated acids, ethylenically unsaturated nitriles, vinyl esters of carboxylic acids, diesters of ethylenically unsaturated acids, vinyl ethers, ethylenically unsaturated silanes, alkenes, and any combination thereof.

[0027] Suitable conjugated dienes include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, 1,3-octadiene, 2-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 3,4-dimethyl-1,3-hexadiene, 2,3-diethyl-1,3-butadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, 3,7-dimethyl-1,3,6-octatriene, 2-methyl-6-methylene-1,7-octadiene, 7 ...2,3-dimethyl-1,3-pentadiene, 3,4-dimethyl-1,3-hexadiene, 2,3-diethyl-1,3-butadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, 3,7-dimethyl-1,3,6-octatriene, 2-methyl-6-methylene-1,7-octadiene, 7-methyl-1,3- It may be selected from methyl-3-methylene-1,6-octadiene, 1,3,7-octatriene, 2-ethyl-1,3-butadiene, 2-amyl-1,3-butadiene, 3,7-dimethyl-1,3,7-octatriene, 3,7-dimethyl-1,3,6-octatriene, 3,7,11-trimethyl-1,3,6,10-dodecatetraene, 7,11-dimethyl-3-methylene-1,6,10-dodecatriene, 2,6-dimethyl-2,4,6-octatriene, 2-phenyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, and 1,3-cyclohexadiene. 1,3-butadiene, isoprene, and combinations thereof are preferred conjugated dienes, with 1,3-butadiene being especially preferred.

[0028] Representative examples of vinyl aromatic monomers include, for example, styrene, α-methylstyrene, vinyltoluene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 4-bromostyrene, 2-methyl-4,6-dichlorostyrene, 2,4-dibromostyrene, vinylnaphthalene, vinyltoluene, vinylxylene, 2-vinylpyridine, 4-vinylpyridine, as well as 1,1-diphenylethylene and substituted 1,1-diphenylethylene, 1,2-diphenylethene and substituted 1,2-diphenylethylene. Mixtures of one or more vinyl aromatic compounds can also be used. Preferred monomers are styrene and α-methylstyrene.

[0029] The alkyl ester of an ethylenically unsaturated acid may be selected from n-, iso- or tertiary alkyl esters of (meth)acrylic acid, in which the alkyl group has 1 to 20 carbon atoms, reaction products of (meth)acrylic acid with glycidyl esters of neo acids (preferably versatic acid, neodecanoic acid or pivalic acid), and alkoxyalkyl (meth)acrylate monomers.

[0030] Generally, preferred alkyl esters of (meth)acrylic acid are C1-C 20 Alkyl (meth)acrylate, preferably C1-C 10The acrylate monomer may be selected from alkyl (meth)acrylates. Examples of such acrylate monomers include n-butyl acrylate, sec-butyl acrylate, methyl acrylate, ethyl acrylate, hexyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, 4-methyl-2-pentyl acrylate, 2-methylbutyl acrylate, methyl methacrylate, butyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, ethyl methacrylate, isopropyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, and cetyl methacrylate. It is particularly preferred to select (meth)acrylic acid esters from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and combinations thereof.

[0031] Alkoxyalkyl (meth)acrylate monomers that can be used as monomer (a) include methoxyethyl methacrylate, ethoxyethyl methacrylate, methoxybutyl methacrylate, ethoxyethyl acrylate, butoxyethyl methacrylate, methoxybutyl acrylate, and methoxyethoxyethyl acrylate. Preferred alkoxyalkyl (meth)acrylate monomers are ethoxyethyl acrylate and methoxyethyl acrylate.

[0032] The amides of ethylenically unsaturated acids can be selected from (meth)acrylamide, N-methylol (meth)acrylamide and diacetone acrylamide. The preferred amide monomer is (meth)acrylamide.

[0033] Examples of ethylenically unsaturated nitrile monomers that can be used for monomer (a) for preparing the shell of the core-shell latex particles according to the present invention include polymerizable unsaturated aliphatic nitrile monomers containing 2 to 4 carbon atoms in a linear or branched arrangement, which may be substituted with either an acetyl or additional nitrile group. Such nitrile monomers include acrylonitrile, methacrylonitrile, α-cyanoethyl acrylonitrile, fumaronitrile, and combinations thereof, with acrylonitrile being most preferred.

[0034] Suitable vinyl esters of ethylenically unsaturated acids may be selected from vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl 2-ethylhexanoate, vinyl stearate, and vinyl esters of versatic acid. The most preferred vinyl ester is vinyl acetate.

[0035] Suitable diesters of ethylenically unsaturated acids may be selected from dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dihexyl maleate, di(2-ethylhexyl) maleate, di-n-octyl maleate, di(6-methylheptyl) maleate, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, dibutyl fumarate, dihexyl fumarate, di(2-ethylhexyl) fumarate, di-n-octyl fumarate, di(6-methylheptyl) fumarate. The most preferred diester is dibutyl maleate.

[0036] The ethylenically unsaturated silane can be selected from trialkoxy vinyl esters (e.g., trimethoxyvinylsilane, triethoxyvinylsilane), trialkoxy (meth)acrylates (e.g., trimethylsilyl (meth)acrylate, triethylsilyl (meth)acrylate, 3-(trimethoxysilyl)propyl (meth)acrylate and 3-(trimethoxysilyl)propyl (meth)acrylate), 3-methacrylamidopropyltriethoxysilane, and combinations thereof; and / or the vinyl ether is selected from alkyl vinyl ethers, such as methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, ethylhexyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, and cyclohexyl vinyl ether.

[0037] Monomer (bi) Suitable monomers (bi) are selected from allyl (meth)acrylate, allyl crotonate, N,N diallyl (meth)acrylamide, 2-allyloxyethyl (meth)acrylate, 2-allyloxyethoxyethyl (meth)acrylate, vinyloxybutyl (meth)acrylate, and butenyl (meth)acrylate.

[0038] Monomer (bii) Suitable monomers (bii) for the preparation of the shell of the core-shell particles according to the invention may be selected from carboxylic acid functional ethylenically unsaturated monomers, oxirane functional ethylenically unsaturated monomers, hydroxyl functional ethylenically unsaturated monomers, isocyanate functional monomers and amino functional ethylenically unsaturated monomers.

[0039] Ethylenically unsaturated carboxylic acid monomers suitable as monomer (bii) according to the present invention include monocarboxylic and dicarboxylic acid monomers, and monoesters of dicarboxylic acids. In the practice of the present invention, it is preferred to use ethylenically unsaturated aliphatic mono- or dicarboxylic acids or anhydrides containing 3 to 5 carbon atoms. Examples of monocarboxylic acid monomers include acrylic acid, acrylic anhydride, methacrylic acid, 4-vinylbenzoic acid, trichloroacrylic acid, crotonic acid, 2-carboxyethyl acrylate, monoesters of maleic acid or fumaric acid (e.g., monomethyl maleate, monoethyl maleate, monobutyl maleate, monohexyl maleate, mono(2-ethylhexyl) maleate, monolauryl maleate, monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monohexyl fumarate, mono(2-ethylhexyl) fumarate, monolauryl fumarate); and examples of dicarboxylic acid monomers include fumaric acid, itaconic acid, 4-methacryloxyethyltrimellitic anhydride, maleic acid, and maleic anhydride. Examples of other suitable ethylenically unsaturated acids include vinyl acetate, vinyl lactate, vinyl sulfonic acid, 2-methyl-2-propene-1-sulfonic acid, styrene sulfonic acid, acrylamidomethylpropane sulfonic acid, and salts thereof. Preferably, the ethylenically unsaturated carboxylic acid monomer is selected from (meth)acrylic acid, crotonic acid, 2-carboxyethyl acrylate, itaconic acid, maleic acid, fumaric acid, and combinations thereof.

[0040] Suitable oxirane-functional ethylenically unsaturated monomers include glycidyl (meth)acrylate, allyl glycidyl ether, vinyl glycidyl ether, vinylcyclohexene oxide, limonene oxide, 2-ethylglycidyl acrylate, 2-ethylglycidyl methacrylate, 2-(n-propyl)glycidyl acrylate, 2-(n-propyl)glycidyl methacrylate, 2-(n-butyl)glycidyl acrylate, 2-(n-butyl)glycidyl methacrylate, dimethylglycidyl methacrylate, glycidyl methyl methacrylate, glycidyl acrylate, 2,3-epoxybutyl methacrylate, (3',4'-epoxyheptyl)-2-ethyl acrylate, (3',4'-epoxyheptyl)-2-ethyl methacrylate, (6',7'-epoxy The epoxy group may be selected from the group consisting of (6',7'-epoxyheptyl)acrylate, (6',7'-epoxyheptyl)methacrylate, allyl-3,4-epoxyheptyl ether, 6,7-epoxyheptyl allyl ether, vinyl-3,4-epoxyheptyl ether, 3,4-epoxyheptyl vinyl ether, 6,7-epoxyheptyl vinyl ether, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, 3-vinylcyclohexene oxide, α-methylglycidyl methacrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, (3-methyloxiran-2-yl)methyl-2-methacrylate, styrene glycidyl ether, 2,4-vinylphenyl glycidyl ether, and combinations thereof. Glycidyl (meth)acrylate is particularly preferred.

[0041] Hydroxyalkyl (meth)acrylic monomers include hydroxyalkyl acrylates and methacrylates based on ethylene oxide, propylene oxide, and higher alkylene oxides or mixtures thereof. Examples include 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, glycerol monomethacrylate, N-hydroxyethyl acrylamide, N-(2-hydroxypropyl)methacrylamide, 3-phenoxy-2-hydroxypropyl methacrylate, hydroxypolyethoxy (10) allyl ether, (meth)acrylates derived from polyethylene glycol or polypropylene glycol (e.g., polypropylene glycol monomethacrylate containing an average of 6 propylene glycol units). Preferably, the hydroxyalkyl (meth)acrylate monomer is selected from 2-hydroxyethyl (meth)acrylate. Additionally or alternatively, the hydroxy monomer may include phenol (meth)acrylate, dopamine methacrylamide, or 4-vinylphenol.

[0042] Examples of isocyanate monomers include 2-(acryloyloxy)ethyl isocyanate and 2-(methacryloyloxy)ethyl isocyanate.

[0043] The amino-functional ethylenically unsaturated compound can be selected from 2-aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, aminobutyl (meth)acrylate, N-(2-aminoethyl) methacrylamide, N-(3-aminopropyl) methacrylamide, and salts thereof.

[0044] Monomer (c) Monomer (c) suitable for achieving crosslinking of the shell of the core-shell latex particles of the present invention can be selected from monomers containing two ethylenically unsaturated groups (preferably selected from divinylbenzene, (meth)acrylates of polyols, and allyl ethers of polycarboxylic acids), monomers containing three ethylenically unsaturated groups (preferably selected from diallyl maleate or trimethylolpropane tri(meth)acrylate), monomers containing four ethylenically unsaturated groups (preferably selected from pentaerythritol tetra(meth)acrylate), and any combination thereof. Examples of (meth)acrylates of polyols include ethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and dipropylene glycol di(meth)acrylate. Further examples of suitable monomers are those cited in EP 3119815. The monomer having at least two ethylenically unsaturated groups is preferably selected from divinylbenzene, 1,2 ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate and 1,6-hexanediol di(meth)acrylate.

[0045] According to the present invention, the shell of the core-shell particles is preferably prepared by aqueous emulsion polymerization of a mixture of ethylenically unsaturated monomers comprising monomer (a), monomer (bii) and monomer (c), and optionally monomer (bi), thereby forming polymeric latex particles having a shell bearing a first functional group derived from the functional group of monomer (bii), and subsequently reacting the polymeric latex particles bearing the first functional group with an ethylenically unsaturated compound having, in addition to the ethylenic unsaturation, a second functional group reactive with the first functional group.

[0046] Therefore, according to the present invention, monomer (bii) may be present and may comprise an ethylenically unsaturated carboxylic acid. As a result, the ethylenically unsaturated compound having a first functional group that is a carboxyl group and a second functional group that reacts with the polymer latex particles is selected from epoxy-functional ethylenically unsaturated compounds. These epoxy-functional ethylenically unsaturated compounds may be selected from the epoxy compounds as defined above as monomer (bii) for preparing the shell of the core-shell particles.

[0047] Alternatively, monomer (bii) can comprise an epoxy-functional ethylenically unsaturated compound as defined above, wherein the first functional group is an epoxy group and the ethylenically unsaturated compound having the second functional group is selected from ethylenically unsaturated carboxylic acids, which can be selected from the carboxylic acid-functional monomers as defined above used to make the shell of the core-shell particles.

[0048] Alternatively, monomer (bii) may comprise a hydroxy and / or amino functional ethylenically unsaturated compound which may be selected from the monomers as defined above which provide a first functional group selected from hydroxy and amino groups, and the ethylenically unsaturated compound having a second functional group which is reacted with the polymer latex particles is selected from carboxylic acid, isocyanate- or thioisocyanate-functional ethylenically unsaturated compounds.

[0049] Suitable carboxylic acids are listed above, and suitable isocyanate- or thioisocyanate-functional ethylenically unsaturated compounds may be selected from allyl isocyanate, 2-isocyanatoethyl (meth)acrylate, 3-isopropenyl-α,α′-dimethylbenzyl isocyanate, 2-isocyanatoethyl methacrylate, allyl isothiocyanate, 4-vinylbenzyl isothiocyanate.

[0050] According to the present invention, it is preferred to use only monomer (bii) and not monomer (bi) to prepare the shell of the core-shell particles. It is particularly preferred that monomer (bii) comprises an ethylenically unsaturated carboxylic acid, and that the ethylenically unsaturated compound having a second functional group that is reacted with the polymer latex particles is selected from epoxy-functional ethylenically unsaturated compounds, preferably as defined above.

[0051] The relative amounts of monomers used to prepare the shell of the core-shell particles of the present invention are not particularly important so long as monomers (b) and (c), as defined above, are present in sufficient amounts to provide a crosslinked shell and to provide ethylenic unsaturation in the shell, either initially by using monomer (bi) or by subsequent reaction with a functional ethylenically unsaturated compound, if monomer (bii) is present, even in their preferred embodiments. Therefore, the monomer mixture for producing the shell of the core-shell particle of the present invention can contain 78 to 99.8% by weight of monomer (a). Preferably, the monomer composition for producing the shell of the core-shell particle can contain 78 to 99% by weight of monomer (a), 0.5 to 16% by weight of monomer (b), and 0.5 to 6% by weight of monomer (c). More preferably, the monomer composition for producing the shell of the core-shell particle can contain 80 to 98% by weight of monomer (a), 1 to 15% by weight of monomer (b), and 0.1 to 5% by weight of monomer (c). Even more preferably, the monomer mixture for producing the shell of the core-shell particle can contain 85 to 98% by weight of monomer (a), 1 to 10% by weight of monomer (b), and 1 to 5% by weight of monomer (c). Even more preferably, the monomer mixture for producing the shell of the core-shell particle can contain 88 to 96% by weight of monomer (a), 3 to 8% by weight of monomer (b), and 0.1 to 4% by weight of monomer (c). Most preferably, the monomer mixture for producing the shell of the core-shell particle can contain 90 to 97% by weight of monomer (a), 2 to 7% by weight of monomer (b), and 0.5 to 3% by weight of monomer (c).

[0052] Monomer (a), which typically constitutes the majority of the monomers in the monomer mixture for producing the shell of the core-shell particles according to the present invention, and their relative amounts are selected to tailor the desired properties of the polymer latex composition and elastomeric films prepared therefrom.

[0053] Thus, monomer (a) may include: - 15 to 99% by weight of alkyl (meth)acrylates including alkoxyalkyl (meth)acrylates - 1 to 80% by weight of ethylenically unsaturated nitrile compounds - Vinyl aromatic monomer 0-50% by weight - Conjugated diene 0-90% by weight - 0 to 18% by weight of vinyl esters and / or vinyl ethers of carboxylic acid esters - 0 to 10% by weight of an ethylenically unsaturated compound having a silane, and - 0 to 18% by weight of an ethylenically unsaturated compound having an amide group, Here, the weight percentages are based on the total weight of monomer (a).

[0054] According to the invention, the amounts of the above mentioned monomers for the monomer mixture (a) for the preparation of the shell of the core-shell particles of the invention may total up to 100% by weight.

[0055] Typically, the amount of alkyl (meth)acrylate, including alkoxyalkyl (meth)acrylate monomers, ranges from 15 to 99 weight percent, preferably 20 to 90 weight percent, more preferably 40 to 80 weight percent, and most preferably 50 to 75 weight percent, based on the total weight of the monomers. Thus, the conjugated diene may be present in an amount of at least 15 weight percent, at least 20 weight percent, at least 22 weight percent, at least 24 weight percent, at least 26 weight percent, at least 28 weight percent, at least 30 weight percent, at least 32 weight percent, at least 34 weight percent, at least 36 weight percent, at least 38 weight percent, or at least 40 weight percent, based on the total weight of the ethylenically unsaturated monomers (a).

[0056] Accordingly, alkyl (meth)acrylates, including alkoxyalkyl (meth)acrylate monomers, can be used in amounts of 95% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, 78% by weight or less, 76% by weight or less, 74% by weight or less, 72% by weight or less, 70% by weight or less, 68% by weight or less, 66% by weight or less, 64% by weight or less, 62% by weight or less, 60% by weight or less, 58% by weight or less, or 56% by weight or less. One of ordinary skill in the art would understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein.

[0057] The nitrile monomer may be contained in an amount of 1 to 80% by weight, preferably 10 to 70% by weight, or 1 to 60% by weight, more preferably 15 to 50% by weight, even more preferably 20 to 50% by weight, and most preferably 20 to 40% by weight, based on the total weight of the ethylenically unsaturated monomer (a).

[0058] Thus, the unsaturated nitrile may be present in an amount of at least 1 weight percent, 5 weight percent, at least 10 weight percent, at least 12 weight percent, at least 14 weight percent, at least 16 weight percent, at least 18 weight percent, at least 20 weight percent, at least 22 weight percent, at least 24 weight percent, at least 26 weight percent, at least 28 weight percent, at least 30 weight percent, at least 32 weight percent, at least 34 weight percent, at least 36 weight percent, at least 38 weight percent, or at least 40 weight percent based on the total weight of the ethylenically unsaturated monomers (a).

[0059] Accordingly, the unsaturated nitrile monomer can be used in an amount of 80% by weight or less, 75% by weight or less, 73% by weight or less, 70% by weight or less, 68% by weight or less, 66% by weight or less, 64% by weight or less, 62% by weight or less, 60% by weight or less, 58% by weight or less, 56% by weight or less, 54% by weight or less, 52% by weight or less, 50% by weight or less, 48% by weight or less, 46% by weight or less, or 44% by weight or less. One of ordinary skill in the art would understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein.

[0060] The vinyl aromatic compound can be used in an amount of 0 to 50% by weight, preferably 0 to 40% by weight, more preferably 0 to 25% by weight, even more preferably 0 to 15% by weight, and most preferably 0 to 10% by weight, based on the total weight of the ethylenically unsaturated monomer (a). Therefore, the vinyl aromatic compound can be present in an amount of 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 18% by weight or less, 16% by weight or less, 14% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, 2% by weight or less, or 1% by weight or less, based on the total weight of the ethylenically unsaturated monomer (a). The vinyl aromatic compound may also be completely absent.

[0061] Typically, the conjugated diene monomer can be present in an amount of 90% by weight or less, 85% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, 2% by weight or less, or 1% by weight or less, based on the total weight of the ethylenically unsaturated monomers (a).

[0062] Typically, the vinyl ester and / or vinyl ether monomers can be present in an amount of 18% by weight or less, 16% by weight or less, 14% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, 2% by weight or less, or 1% by weight or less, based on the total weight of the ethylenically unsaturated monomers (a).

[0063] The ethylenically unsaturated silane compound may be present in an amount of 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, 2% by weight or less, or 1% by weight or less, based on the total weight of the ethylenically unsaturated monomer (a). In particular, the ethylenically unsaturated silane compound may be present in an amount of 0.05 to 5.0% by weight, preferably 0.3 to 2.0% by weight, and more preferably 0.3 to 1.0% by weight, based on the total weight of the ethylenically unsaturated monomer (a).

[0064] Typically, the amide of the ethylenically unsaturated acid may be present in an amount of 18% by weight or less, 16% by weight or less, 14% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, 2% by weight or less, or 1% by weight or less, based on the total weight of the ethylenically unsaturated monomers (a).

[0065] Furthermore, the monomer (c) having at least two non-conjugated ethylenically unsaturated groups can be present in the monomer mixture for preparing the shell of the core-shell polymer latex particle of the present invention in an amount of 0.1 to 6.0 wt %, preferably 0.1 to 3.5 wt %, based on the total weight of the ethylenically unsaturated monomers. Typically, these monomers can be present in the monomer mixture for preparing the shell of the core-shell polymer latex particle of the present invention in an amount of 6 wt % or less, 4 wt % or less, 2 wt % or less, or 1 wt % or less, based on the total weight of the ethylenically unsaturated monomers.

[0066] In the monomer mixture for preparing the shell of the core-shell particle of the present invention, monomer (b) is typically present in an amount of 0.1 to 16% by weight, based on the total weight of monomers in the mixture. Monomer (bi) may be present in an amount of 15% by weight or less, 14% by weight or less, 13% by weight or less, 12% by weight or less, 11% by weight or less, 10% by weight or less, 9% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less. As mentioned above, preferably, monomer (bi) is not present in the monomer mixture for preparing the shell of the core-shell particle of the present invention.

[0067] When monomer (bii) is selected from ethylenically unsaturated carboxylic acids and oxirane-functional ethylenically unsaturated compounds, preferably as defined above, these compounds are present in an amount of preferably 0.05 to 10 wt%, in particular 0.1 to 10 wt%, or 0.05 to 7 wt%, preferably 0.1 to 9 wt%, more preferably 0.1 to 8 wt%, even more preferably 1 to 7 wt%, and most preferably 2 to 7 wt%, based on the total weight of monomers for preparing the shell of the core-shell particle. Thus, the ethylenically unsaturated carboxylic acid monomer or the oxirane-functional ethylenically unsaturated monomer may be present in an amount of at least 0.01 wt%, at least 0.05 wt%, at least 0.1 wt%, at least 0.3 wt%, at least 0.5 wt%, at least 0.7 wt%, at least 0.9 wt%, at least 1 wt%, at least 1.2 wt%, at least 1.4 wt%, at least 1.6 wt%, at least 1.8 wt%, at least 2 wt%, at least 2.5 wt%, or at least 3 wt%, based on the total weight of monomers for preparing the shell of the core-shell particle. Similarly, the ethylenically unsaturated acid monomer or oxirane-functional ethylenically unsaturated monomer may be present in an amount of 10% by weight or less, 9.5% by weight or less, 9% by weight or less, 8.5% by weight or less, 8% by weight or less, 7.5% by weight or less, 7% by weight or less, 6.5% by weight or less, 6% by weight or less, 5.5% by weight or less, or 5% by weight or less, based on the total weight of ethylenically unsaturated monomers for preparation of the shell of a core-shell particle according to the present invention. One of ordinary skill in the art will understand that any range defined by an explicitly disclosed lower limit and an explicitly disclosed upper limit is herein disclosed.

[0068] When monomer (bii) is selected from hydroxyl- and / or amino-functional ethylenically unsaturated monomers, these monomers may be present in an amount of 0.05 to 18 wt%, in particular 0.1 to 15 wt% or 0.05 to 10 wt%, preferably 0.1 to 12 wt%, more preferably 1 to 10 wt%, and even more preferably 2 to 8 wt%. Thus, the hydroxyl- and / or amino-functional ethylenically unsaturated monomers may be present in an amount of at least 0.01 wt%, at least 0.05 wt%, at least 0.1 wt%, at least 0.3 wt%, at least 0.5 wt%, at least 0.7 wt%, at least 0.9 wt%, at least 1 wt%, at least 1.2 wt%, at least 1.4 wt%, at least 1.6 wt%, at least 1.8 wt%, at least 2 wt%, at least 2.5 wt%, or at least 3 wt%. Similarly, the hydroxy-functional and / or amino-functional ethylenically unsaturated monomer may be present in an amount of 18% by weight or less, 16% by weight or less, 15% by weight or less, 14% by weight or less, 13% by weight or less, 12% by weight or less, 11% by weight or less, 10% by weight or less, 9.5% by weight or less, 9% by weight or less, 8.5% by weight or less, 8% by weight or less, 7.5% by weight or less, 7% by weight or less, 6.5% by weight or less, 6% by weight or less, 5.5% by weight or less, or 5% by weight or less, based on the total weight of the ethylenically unsaturated monomers for producing the shell for the core-shell particle according to the present invention. One of ordinary skill in the art will understand that any range defined by an explicitly disclosed lower limit and an explicitly disclosed upper limit is herein disclosed.

[0069] The monomer composition for producing the core of the core-shell particle according to the present invention is not particularly limited, as long as the monomer is selected so as not to cause internal crosslinking of the core. Therefore, the monomer mixture for producing the core does not contain a monomer having multiple non-conjugated ethylenically unsaturated groups in the molecule. Conjugated dienes may be present, but in that case, the polymerization conditions are preferably selected to avoid gelation of the core portion, preferably by using a molecular weight regulator, such as an alkyl mercaptan, during the emulsion polymerization process.

[0070] In particular, the monomers for preparing the core of the core-shell particles according to the present invention can be selected from the monomers (a) described above for the monomer mixture for producing the shell of the core-shell particles according to the present invention. The monomer mixture for producing the core preferably contains 50 to 100% by weight of alkyl (meth)acrylate monomers, based on the total weight of the monomers for producing the core of the core-shell particles according to the present invention. Preferably, the alkyl group contains 1 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, even more preferably 3 to 10 carbon atoms, and most preferably 4 to 8 carbon atoms. Thus, the alkyl (meth)acrylate monomers may be present in the mixture for polymerizing the core of the core-shell particles according to the present invention in an amount of at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 82%, at least 85%, at least 87%, or at least 90% by weight, based on the total weight of the monomers for producing the core of the core-shell particles according to the present invention. The remaining monomers may be selected in particular from conjugated dienes, vinyl aromatic monomers, ethylenically unsaturated amides, ethylenically unsaturated nitriles, alkoxyalkyl (meth)acrylates, vinyl esters and vinyl ethers, as described above for monomer (a) for preparing the shell of the core-shell particles of the present invention.

[0071] In particular, the conjugated diene may be present in an amount of 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, 2% by weight or less, based on the total weight of the monomers for producing the core of the core-shell particle according to the invention. In particular, the conjugated diene may be absent.

[0072] In particular, the vinyl aromatic compound may be present in an amount of 20% by weight or less, 18% by weight or less, 16% by weight or less, 14% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, or 2% by weight or less, based on the total weight of the monomers for producing the core of the core-shell particle according to the invention. In particular, the vinyl aromatic compound may be absent.

[0073] In particular, the ethylenically unsaturated amide may be present in an amount of 20% by weight or less, 18% by weight or less, 16% by weight or less, 14% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, 2% by weight or less, based on the total weight of the monomers for producing the core of the core-shell particle according to the invention. In particular, the ethylenically unsaturated amide may be absent.

[0074] In particular, the vinyl ester or ether may be present in an amount of 20% by weight or less, 18% by weight or less, 16% by weight or less, 14% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, 2% by weight or less, based on the total weight of the monomers for producing the core of the core-shell particle according to the invention. In particular, the vinyl ester or ether may be absent.

[0075] In particular, the alkoxyalkyl(meth)acrylate may be present in an amount of 20% by weight or less, 18% by weight or less, 16% by weight or less, 14% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, 2% by weight or less, based on the total weight of the monomers for producing the core of the core-shell particle according to the invention. In particular, the alkoxyalkyl(meth)acrylate may be absent.

[0076] In addition, the monomer mixture for producing the core of the core-shell particle according to the present invention may contain a small amount of ethylenically unsaturated acid, suitably selected from the ethylenically unsaturated acids described above for the monomer mixture for producing the shell of the core-shell particle. Thus, such ethylenically unsaturated carboxylic acid may be present in an amount of up to 20% by weight, up to 16% by weight, up to 12% by weight, up to 8% by weight, up to 6% by weight, up to 4% by weight, up to 3% by weight, up to 2% by weight, or up to 1% by weight, based on the total weight of the monomers for producing the core of the core-shell particle according to the present invention. The ethylenically unsaturated acid may also be completely absent.

[0077] The core of the core-shell particles according to the present invention may be formed from a separately prepared seed latex, so long as the above requirements set forth for the core are met for the seed latex. Alternatively, such a seed latex may be prepared in situ at the start of the emulsion polymerization before the polymerization of the core monomers. Alternatively, such a seed latex may be prepared in situ at the start of the emulsion polymerization before the polymerization of the shell monomers.

[0078] The core-shell polymerization according to the present invention can also be carried out as a seeded core-shell polymerization, whereby a seed latex may be preformed or formed in situ at the start of the core-shell emulsion polymerization.

[0079] In the core-shell particles of the present invention, the shell can comprise 10 to 90 wt.%, preferably 20 to 80 wt.%, more preferably 20 to 50 wt.%, and most preferably 25 to 45 wt.% of the total weight of the core-shell particle, and the core can comprise 90 to 10 wt.%, preferably 80 to 20 wt.%, more preferably 80 to 50 wt.%, and most preferably 75 to 55 wt.%. When the core is formed by preformed or in-situ seeds, or when the core-shell polymerization is carried out in the presence of preformed or in-situ seeds, the seeds are counted as part of the core of the core-shell particle when specifying the relative amounts of the core and shell of the core-shell particles of the present invention. The seeds can comprise 0 to 100 wt.%, preferably 5 to 30 wt.%, more preferably 10 to 30 wt.%, even more preferably 15 to 30 wt.%, and most preferably 20 to 30 wt.% of the total weight of the core.

[0080] The monomers for producing the core and the shell should have a glass transition temperature T g wherein the core preferably has a T as measured by dynamic mechanical thermal analysis at a fixed frequency of 1 Hz and a heating rate of 3°C / min. g is below 0°C, preferably below -20°C, and the T g is above 0°C, preferably above 20°C.

[0081] When the monomers for producing the shell of the core-shell particle according to the present invention include monomer (bii), the core-shell particle according to the present invention after the completion of emulsion polymerization is reacted with an ethylenically unsaturated compound having a second functional group reactive with the first functional group of monomer (bii) to construct a part of the shell of the core-shell particle according to the present invention.

[0082] The amount of the ethylenically unsaturated compound having a second functional group is selected to constitute at least 20 mol%, based on the total moles of the first functional groups introduced into the core-shell particles of the core-shell particles according to the present invention that are reacted with the ethylenically unsaturated compound having a second functional group. Preferably, this amount is selected to constitute at least 25 mol%, at least 30 mol%, at least 35 mol%, at least 40 mol%, at least 42 mol%, at least 45 mol%, at least 47 mol%, at least 50 mol%, at least 52 mol%, at least 55 mol%, at least 57 mol%, or at least 60 mol%, based on the total moles of the first functional groups in the shell of the core-shell particles that have reacted with the ethylenically unsaturated compound having a second functional group. Similarly, the ethylenically unsaturated compound having a second functional group reacts in an amount that constitutes 100 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 77 mol% or less, 75 mol% or less, 72 mol% or less, 70 mol% or less, 68 mol% or less, 65 mol% or less, or 62 mol% or less of the total moles of first functional groups present in the shell of the core-shell particle that reacts with the ethylenically unsaturated compound having a second functional group. One skilled in the art will understand that all ranges defined by either the lower or upper limits defined above are disclosed herein.

[0083] Surprisingly, it has been found that it is possible to prepare free-standing elastomeric films by modifying the core-shell latex of the present invention by subsequent reaction with a difunctional monomer. One functional group can react with a suitable reactive group on the core-shell latex of the present invention, and the other functional group can react, for example, by polymerization, in the presence of, for example, oxygen, or a free radical initiator, or a suitable controlled radical initiator system known in the art (e.g., RAFT, ATRP, MADIX, or NMP). Such a reaction can be exemplified by selecting a core-shell latex of the present invention having a carboxylic acid functional group, preferably, but not necessarily, located on the surface of the latex particle, which can be reacted with a suitable monomer, for example, glycidyl methacrylate. Furthermore, it has been found that this esterification reaction can be carried out either at a pH above 8 or preferably below 8, preferably at a pH of 7 or below, more preferably at a pH of 6 or below, and most preferably at a pH of 5 or below. Furthermore, this esterification reaction may or may not be carried out in the presence of a catalyst known in the art. The catalyst may be, for example, a metal ion, preferably a polyvalent metal ion, such as zinc acetate; or a quaternary phosphonium or ammonium salt, particularly useful are cetyldimethylbenzylammonium chloride, tetrabutylammonium hydroxide, or tetramethylguanidine. Furthermore, the difunctional monomer may or may not react with another monomer in the core-shell latex of the present invention.

[0084] The amount of monomer added to functionalize the core-shell latex may be less than the stoichiometric amount required to react with all of the available groups on the core-shell latex, or it may be more than the stoichiometric amount required to react with all of the available groups on the core-shell latex. Preferably, an excess of functional monomer is used, and this excess can be up to two, three, or even four times the available groups. If an excess of functional monomer is present, efforts should be made to minimize this excess unreacted monomer in the final latex. This can be accomplished by washing the latex with a solvent in which the functionalizing monomer is soluble but the latex particles are not (such a solvent is chloroform). Alternatively, unreacted difunctional monomer may remain in the latex.

[0085] The core-shell particles according to the invention can be produced by standard seeded or unseeded core-shell emulsion polymerization processes. Methods such as those described in WO2017164726A1 are particularly suitable for producing seeds.

[0086] Emulsion (or latex) polymerization may or may not be carried out under an inert atmosphere, such as provided by nitrogen or argon. A delayed monomer charge (typically including a chain transfer agent) defining the core, as described above, is added to the dispersion of seed particles, and after the completion of this monomer feed and post-heating period, a monomer mixture defining the shell, as described above, is added using continuous monomer addition, also known as delayed addition. Alternatively, the shell may be produced by the addition of a single portion of the desired monomer mixture, or multiple portions of the desired monomer mixture. Preferably, the components comprising the delayed monomer mixture are not altered during the addition.

[0087] The core does not contain a crosslinked structure. The shell may or may not form a continuous layer around the core, preferably the shell forms a continuous layer around the core. The shell contains a crosslinked structure. Alternatively, emulsion (or latex) polymerization can be carried out with in situ formation of seeds, typically created by the addition of an aliquot of polymerizable core monomer, and then a delay monomer is added upon detection of this polymerization exotherm. A preferred option is to carry out the core-shell latex polymerization in a single vessel in a continuous manner.

[0088] The above-mentioned process for preparing the polymer latex can be carried out in the presence or absence of one or more emulsifiers, in the presence or absence of one or more colloids, and in the presence of one or more initiators at temperatures of 0 to 130° C., preferably 0 to 100° C., particularly preferably 5 to 70° C., and very particularly preferably 5 to 60° C., including all values ​​and subvalues ​​therebetween, in particular 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, and 125° C.

[0089] Initiators that can be used in the practice of the present invention include water-soluble and / or oil-soluble initiators that are effective for polymerization purposes. Alternative initiators are well known in the art and include, for example, azo compounds (e.g., AIBN, AMBN, and cyanovaleric acid) and inorganic peroxy compounds (e.g., hydrogen peroxide, sodium, potassium, and ammonium peroxodisulfates, peroxycarbonates, and peroxyborates), as well as organic peroxy compounds (e.g., alkyl hydroperoxides, dialkyl peroxides, acyl hydroperoxides, and diacyl peroxides), and esters (e.g., tert-butyl perbenzoate), and combinations of inorganic and organic initiators.

[0090] The initiator is used in an amount sufficient to initiate the polymerization reaction at the desired rate. Generally, an amount of initiator of 0.01 to 5 wt. %, preferably 0.1 to 4 wt. %, based on the weight of the total polymer, is sufficient. Most preferably, the amount of initiator is 0.01 to 2 wt. %, based on the total weight of the polymer. The amount of initiator includes all values ​​and subvalues ​​therebetween, particularly 0.01, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 4, and 4.5 wt. %, based on the total weight of the polymer.

[0091] The inorganic and organic peroxy compounds mentioned above can also be used alone or in combination with one or more suitable reducing agents, as is well known in the art. Examples of such reducing agents that may be mentioned include sulfur dioxide, alkali metal disulfites, alkali metal and hydrogen ammonium sulfites, thiosulfates, hyposulfites, and formaldehyde sulfoxylate, as well as hydroxylamine hydrochloride, hydrazine sulfate, iron(II) sulfate, copper naphthanate, glucose, sulfonic acid compounds (e.g., sodium methanesulfonate), amine compounds (e.g., dimethylaniline), and ascorbic acid. The amount of reducing agent is preferably 0.03 to 10 parts by weight per part by weight of the polymerization initiator.

[0092] The initiator is present during the polymerization of the initial monomer charge used to form the seeds, either external seeds or in situ seeds, the latter approach being preferred as it has been found that this does not require additional initiator to be added to the core-shell latex polymerization reaction. Alternatively, additional aliquots of initiator may be added during the polymerization process or after completion of the delayed monomer to reduce the final level of free monomer in the core-shell latex.

[0093] Suitable surfactants or emulsifiers for stabilizing latex particles include conventional surfactants for polymerization processes. Surfactants can be added to the aqueous phase and / or the monomer phase. In seeded processes, an effective amount of surfactant is an amount selected to support colloidal stabilization of the particles, minimize interparticle contact, and prevent coagulation. In non-seeded processes, an effective amount of surfactant is an amount selected to affect particle size.

[0094] An effective amount of surfactant is that amount selected for any process that creates the appropriate particle size for the seed latex, whether exogenous or formed in situ, and further, a portion of the surfactant is also required to create a pre-emulsion for both the monomers used to create the core and / or the monomers used to create the shell, the total amount of surfactant being such that it maintains a stable latex and minimizes the nucleation of any new particles during the production of both the core and shell, as well as during functionalization of the latex.

[0095] Representative surfactants include saturated and ethylenically unsaturated sulfonic acids or their salts (e.g., unsaturated hydrocarbon sulfonic acids, vinyl sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, and their salts); aromatic hydrocarbon acids (e.g., p-styrene sulfonic acid, isopropenyl benzene sulfonic acid, and vinyloxybenzene sulfonic acid, and their salts); sulfoalkyl esters of acrylic acid and methacrylic acid (e.g., sulfoethyl methacrylate and sulfopropyl methacrylate, and their salts, and 2-acrylamido-2-methylpropane sulfonic acid and its salts); alkylated diphenyloxide disulfonates, sodium dodecylbenzene sulfonate, and dihexyl ester of sodium sulfosuccinate, sodium alkyl esters of sulfonic acid, sodium alkyl ethoxy esters of sulfonic acid, ethoxylated alkylphenols, and ethoxylated alcohols; fatty alcohol (poly)ether sulfates.

[0096] The type and amount of surfactant typically depend on the number of particles, their size, and their composition. Typically, surfactants are used in amounts of 0 to 20, preferably 0 to 10, and more preferably 0 to 5 weight percent based on the total weight of the monomers. The amount of surfactant includes all values ​​and subvalues ​​therebetween, particularly 0, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, and 19 weight percent based on the total weight of the monomers. According to one embodiment of the present invention, the polymerization is carried out without the use of a surfactant.

[0097] Various protective colloids can be used instead of, or in addition to, the surfactants listed above. Suitable colloids include polyhydroxy compounds (e.g., partially acetylated polyvinyl alcohol, casein, hydroxyethyl starch, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polysaccharides, and degraded polysaccharides), polyethylene glycol, and gum arabic. Preferred protective colloids are carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. Generally, these protective colloids are used in amounts of 0 to 10, preferably 0 to 5, and more preferably 0 to 2 parts by weight based on the total weight of the monomers. The amount of protective colloid includes all values ​​and subvalues ​​therebetween, particularly 1, 2, 3, 4, 5, 6, 7, 8, and 9% by weight based on the total weight of the monomers.

[0098] When the polymer latex composition is used in dip molding applications, it is preferred that the polymer latex composition have a certain maximum electrolyte stability, determined as a critical coagulation concentration (determined for a total solids content of the composition of 0.1% at pH 10 and 23°C) of calcium chloride of less than 30 mmol / L, preferably less than 25 mmol / L, more preferably less than 20 mmol / L, and most preferably less than 10 mmol / L.

[0099] It is often recommended to further carry out the emulsion polymerization in the presence of buffer substances and chelating agents. Suitable substances are, for example, alkali metal phosphates and pyrophosphates (buffer substances) and alkali metal salts of ethylenediaminetetraacetic acid (EDTA) or hydroxyl-2-ethylenediaminetriacetic acid (HEEDTA) as chelating agents. The amount of buffer substances and chelating agents is usually 0.001 to 1.0% by weight, based on the total amount of monomers.

[0100] In the examples of the present invention, it was found that the presence of a buffer was not necessary to produce a stable latex, and therefore the final pH of the core-shell latex was typically less than 5, and typically about 3.

[0101] Furthermore, it may be advantageous to use chain transfer agents (regulators) in the emulsion polymerization. Typical additives include, for example, organic sulfur compounds (e.g., thioesters, 2-mercaptoethanol, 3-mercaptopropionic acid, and C1-C 12 The chain transfer agent is preferably n-dodecyl mercaptan or t-dodecyl mercaptan, and the amount of the chain transfer agent, if present, is usually 0.05 to 3.0% by weight, preferably 0.2 to 2.0% by weight, based on the total weight of the monomers used.

[0102] Additionally, it may be beneficial to introduce partial neutralization into the polymerization process. Those skilled in the art will appreciate that by appropriate selection of this parameter the necessary control can be achieved.

[0103] Various other additives and ingredients can be added to prepare the latex composition of the present invention. Such additives include, for example, defoamers, wetting agents, thickeners, plasticizers, fillers, pigments, dispersants, optical brighteners, crosslinkers, accelerators, antioxidants, biocides, and metal chelating agents. Known defoamers include silicone oil and acetylene glycol. Commonly known wetting agents include alkylphenol ethoxylates, alkali metal dialkyl sulfosuccinates, acetylene glycol, and alkali metal alkyl sulfates. Typical thickeners include polyacrylates, polyacrylamides, xanthan gum, modified cellulose, or granular thickeners (e.g., silica and clay). Typical plasticizers include mineral oil, liquid polybutene, liquid polyacrylate, and lanolin. Zinc oxide is a suitable ionic crosslinker. Titanium dioxide (TiO2), calcium carbonate, and clay are typically used fillers. Known accelerators and secondary accelerators include dithiocarbamates (e.g., zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc pentamethylenedithiocarbamate (ZPD)), xanthates, thiurams (e.g., tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), dipentamethylenethiuram hexasulfide (DPTT)), and amines (e.g., diphenylguanidine (DPG), di-o-tolylguanidine (DOTG), o-tolylbiguanidine (OTBG)).

[0104] As mentioned above, the present invention also relates to elastomeric films prepared from the aqueous dispersions according to the present invention.

[0105] One advantage of the present invention is that the core-shell polymer latex particles according to the present invention allow for the preparation of elastomeric films without the use of conventional sulfur vulcanization, in that elemental sulfur and a suitable accelerator are added to the compound containing the polymer latex particles, and there is no need to add multivalent cations, such as zinc compounds, to the compounded latex to produce the elastomeric film.

[0106] Thus, in the process for producing a free-standing elastomeric film as defined above in the Summary of the Invention, providing step (a) does not include the addition of elemental sulfur and an accelerator for sulfur vulcanization to the composition, nor the addition of a zinc compound to the composition, whereby preferably the composition in step (a) has a pH of at most 8.5, preferably at most 8.0, preferably at most 7.5, more preferably at most 7.

[0107] Elastomeric films can be obtained by casting, dip molding, spraying or knife coating.

[0108] The elastomeric film may be heat treated, before or after separating the elastomeric film from the substrate, at a temperature of 40° C. to 180° C., preferably 60° C. to 100° C., more preferably 75° C. to 100° C. Thus, according to the present invention, the elastomeric film is preferably self-supporting, substantially free of sulfur crosslinks, and substantially free of ionomeric crosslinks.

[0109] The present invention also relates to an article comprising the above-defined elastomeric film, wherein the elastomeric film may have first and second outer surfaces and an inner core between the first and second outer surfaces, and the degree of cross-linking between the polymer particles at the first and second outer surfaces is higher than the degree of cross-linking at the inner core of the film.

[0110] The article according to the invention may be selected from surgical gloves, examination gloves, industrial gloves, household gloves, disposable gloves including fabric-supported gloves, medical devices such as catheters, condoms and femidoms, or the article comprises a binder component for an energy cell (preferably a battery containing lithium ions).

[0111] The present invention will now be further described with reference to the following examples. [Example]

[0112] Measurement of physical parameters: The latexes (also known as emulsions or dispersions) were characterized by determining the total solids content (TSC), pH, and z-average particle size. Additionally, the final films were tested for tensile properties both before and after cutting and rejoining. A film was deemed self-healing if it exhibited tensile strength when cut in two, the two films were then placed together, and the two films so joined were subsequently separated.

[0113] Determination of Total Solids Content (TSC): The TSC of the dispersed samples was determined by weight. The latex was gently stirred by manually swirling the contents. Three aliquots of latex (~2.0 g) were pipetted into pre-weighed aluminum pans, weighed, and then dried in a preheated oven set at 80 °C for 24 hours. After cooling to room temperature, the final weight was determined. The TSC is calculated as follows: TSC(%)=(m o / m i )x100 (1) where m o and m i are the weights of the dry and latex samples, respectively. The average values ​​of the three samples tested were used.

[0114] Determination of pH value: The pH of the dispersion was measured using a CyberScan model pH meter.

[0115] Particle size (PS) determination: Dynamic Light Scattering Dynamic light scattering (DLS) was performed using a Malvern Zetasizer Nano ZS90 (Malvern Instruments Ltd.) equipped with a 20 mW He-Ne laser. Typically, samples had a final concentration of 0.01 wt% to ensure that the photon count rate was maintained between 100 and 200 kcps (kilocounts per second). Measurements were performed at 25°C. The z-average particle size (d z ) was recorded. transmission electron microscope Transmission electron microscopy was performed using a Philips CM200 instrument operating at 200 kV. For a typical preparation, 0.4 mL of 0.2 wt% latex was dissolved in 1.6 mL of 2 wt% phosphotungstic acid (HO). 40 P.W. 12 ) and mixed at room temperature for at least 15-20 minutes. Phosphotungstic acid was used as a negative stain for the particle samples. The final mixture concentration used was approximately 0.04 wt%. One drop (μL) of the mixture was pipetted onto a 300-mesh copper holey carbon grid (Agar Scientific Ltd.) and left for 2 minutes, after which excess liquid was drained (a tissue was used to absorb the excess liquid). The sample was dried overnight in a desiccator. At least 100 particles were analyzed and the number-average diameter (d) was calculated using the following formula: TEM ) was calculated. d TEM =Σn i d i / Σn i (2) where d i is the diameter of the particle in group i, n i is the number of particles in group i. The coefficient of variation (CV) was calculated from the standard deviation (SD) using equation (3). CV=(100xSD) / d TEM (3) In the examples below, the CV is given in parentheses after the average particle number.

[0116] Potentiometric titration of latex samples The carboxylic acid content of the samples was determined using a Mettler Toledo DL15 titrator. For a typical preparation, a 1 wt. % (0.88 g of 45 wt. %) dispersion was mixed in 40 mL of 0.1 M aqueous NaCl solution. The diluted latex was mechanically stirred for 15 seconds at room temperature and then titrated against a standardized NaOH (1.0 M) solution.

[0117] Zeta potential measurement Zeta potential was measured using a Malvern Zetasizer NanoZS90 (Malvern Instruments). A latex concentration of 0.01 wt% containing NaNO3 (0.001 wt%) was prepared. The diluted mixture was transferred to the measurement cell using a 1 mL plastic syringe. The average zeta potential and electrophoretic mobility derived from the software were then averaged from three measurements. The measurement temperature was set at 25°C.

[0118] Determination of dynamic mechanical properties The viscoelastic behavior of the studied materials was measured using a TA-Q800 dynamic mechanical thermal analyzer in tension mode. Film specimens were in the form of rectangular strips with dimensions of 15 mm x 5.5 mm x 0.5 mm. Measurements were performed at temperatures from -110 °C to 200 °C, with a heating rate of 3 °C / min and a frequency of 1 Hz. The data obtained measured the storage modulus (E'), loss modulus (E"), and tangent delta (E" / E') values ​​as a function of temperature from -110 to 200 °C.

[0119] Determination of tensile properties: Tensile properties of the specimens were measured using a Hounsfield H10KS tensile apparatus (2000 N load cell load) equipped with a laser extensometer. Films were cut into dumbbell shapes using a steel die measuring 75.0 mm in length and 4.0 mm in width at its narrowest point and stretched over a length of 25 mm. The films were conditioned in a climate-controlled room at 25°C (±2°C) and 50% (±5%) relative humidity for 24 hours prior to measurement. The stretching rate was determined at a constant crosshead speed of 500 mm per minute. Measurements were performed at 25°C and 50% RH. Reported results are averages of 3 to 5 measurements.

[0120] Polymerization equipment A 2 L five-neck glass reactor was immersed in a water bath equipped with a temperature controller, and the reactor lid contained a mechanical stirrer, a condenser for the cooling system, and appropriate inlet points for argon gas and reactant feed inlets. The stirring speed indicator was kept constant at 250 rpm. The polymerization temperature was maintained at 75 °C. A Watson-Marlow Model 505S peristaltic pump was used to feed the reactants for the emulsion polymerization at rates of 5.50 g / min (for the core growth stage) and 3.21 g / min (for the shell growth stage).

[0121] BA = n-butyl acrylate ACN = acrylonitrile BDDA = 1,4-butanediol diacrylate MAA = methacrylic acid t-ddm = tert-dodecyl mercaptan GMA = glycidyl methacrylate KPS = potassium persulfate TSC = Total Solids PS = particle size DLS = Dynamic Light Scattering TEM = Transmission Electron Microscope DMTA=Dynamic Mechanical Thermal Analysis

[0122] In the following, the use of the term "latex" is interchangeable with "dispersion," "emulsion," or "heterogenous."

[0123] Below, all parts and percentages are by weight unless otherwise stated.

[0124] Example 1: Preparation of seed latex In the apparatus detailed above, deionized water (300 g) was added to a reaction vessel and purged with argon for 20 minutes. An aqueous solution of the surfactant Aerosol MA-80® (dihexylsulfosuccinate sodium) from Solvay (14 g of Aerosol MA-80® dissolved in 76 g of deionized water) was then added. After 5 minutes of constant stirring at 250 rpm under argon flow, butyl acrylate monomer (54.0 g, 0.42 mol) was added and stirred for 5 minutes. Finally, an initiator solution containing potassium persulfate (1.37 g dissolved in 54 g of deionized water) was added (time = 0). After 60 minutes of polymerization at 75 °C, seed particles with average particle sizes of 45 nm (by DLS) and 43(15) nm (by TEM) were obtained. It was found that controlling the target seed particle size to ~50 nm was important to obtain monodisperse final core-shell particles with diameters of ~100 nm. The seed particle results are shown in Table 1.

[0125] Example 2: Preparation of core latex Core nanoparticles were prepared using the seed latex of Example 1. Immediately after completion of the seed stage, a pre-emulsion mixture of surfactant (Aerosol MA-80), butyl acrylate, tert-dodecyl mercaptan, and potassium persulfate dissolved in deionized water was continuously added using a metering pump at a feed rate of 5.50 g / min. Polymerization was continued for 135 minutes after the pre-emulsion was added to the reactor to obtain the core latex. The pre-emulsion contained the following: deionized water (171.45 g), tert-dodecyl mercaptan (0.085 g), Aerosol MA-80 (2.97 g), and butyl acrylate (237.50 g, 2.13 mol), which were combined and stirred for 30 minutes before the start of the delayed addition. The core particles obtained had an average particle size of 79 nm (by DLS) and 80(28) nm (by TEM). The results for the core particles are shown in Table 1.

[0126] Example 3: Preparation of core-shell particles containing a crosslinked shell To the repeat latex of Example 2, a pre-emulsion containing Aerosol MA-80 (2.97 g), tert-dodecyl mercaptan (0.085 g), and a shell comonomer solution (237.51 g, containing butyl acrylate (64 wt%, 152.00 g), acrylonitrile (30 wt%, 71.25 g), methacrylic acid (5 wt%, 11.88 g), and 1,4-butanediol diacrylate (1 wt%, 2.38 g)) was added using a metering pump set at a feed rate of 3.21 g / min. After the reaction was complete (total 4 hours at 75 °C), the latex was immediately cooled in an ice bath. It was then filtered through a 28 μm sieve to separate the coagulum. The average particle size of the resulting core-shell particles was 76 nm by DLS and 63 (16) nm by TEM. The results for the core-shell particles are shown in Table 1.

[0127] Example 4: (Comparative) Preparation of Core-Shell Particles Without Shell Crosslinking To the latex of Example 2, a pre-emulsion containing Aerosol MA-80 (2.97 g), tert-dodecyl mercaptan (0.085 g), and a shell comonomer solution (237.51 g, containing butyl acrylate (65 wt %, 154.38 g), acrylonitrile (30 wt %, 71.25 g), and methacrylic acid (5 wt %, 11.88 g)) was added using a metering pump set at a feed rate of 3.21 g / min. After the reaction was complete (total 4 hours at 75°C), the latex was immediately cooled in an ice container. It was filtered through a 28 μm sieve to separate the coagulum. The average particle size of the resulting core-shell particles was 97 nm (by DLS) and 93 (20) nm (by TEM). The core-shell particle results are shown in Table 1.

[0128] Example 5: Preparation of core-shell particles containing a crosslinked shell To the repeat latex of Example 2, Aerosol MA-80 (2.97 g), tert-dodecyl mercaptan (0.085 g), and a pre-emulsion containing shell comonomer solution (237.51 g, containing butyl acrylate (64 wt%, 154.38 g), acrylonitrile (30 wt%, 71.25 g), methacrylic acid (5 wt%, 11.88 g), and 1,4-butanediol diacrylate (1 wt%, 2.38 g)) were added using a metering pump with a feed rate of 3.21 g / min. After the reaction was completed (total 4 hours at 75 °C), the latex was immediately cooled in an ice bath. It was filtered through a 28 μm sieve to separate the coagulum. The average particle size of the resulting core-shell particles was 95 nm (by DLS) and 91 (15) nm (by TEM). The results for the core-shell particles are shown in Table 1.

[0129] Example 6: Preparation of core-shell particles containing a crosslinked shell To the repeat latex of Example 2, Aerosol MA-80 (2.97 g), tert-dodecyl mercaptan (0.085 g), and a pre-emulsion containing shell comonomer solution (237.51 g, containing butyl acrylate (66 wt%, 156.75 g), acrylonitrile (28 wt%, 66.5 g), methacrylic acid (5 wt%, 11.88 g), and 1,4-butanediol diacrylate (1 wt%, 2.38 g)) were added using a metering pump with a feed rate of 3.21 g / min. After the reaction was completed (total 4 hours at 75 °C), the latex was immediately cooled in an ice bath. It was filtered through a 28 μm sieve to separate the coagulum. The average particle size of the resulting core-shell particles was 96 nm (by DLS) and 84 (14) nm (by TEM). The results for the core-shell particles are shown in Table 1.

[0130] Example 7: Preparation of core-shell particles containing a crosslinked shell To the repeat latex of Example 2, Aerosol MA-80 (2.97 g), tert-dodecyl mercaptan (0.085 g), and a pre-emulsion containing shell comonomer solution (237.51 g, containing butyl acrylate (71 wt%, 168.63 g), acrylonitrile (23 wt%, 54.63 g), methacrylic acid (5 wt%, 11.88 g), and 1,4-butanediol diacrylate (1 wt%, 2.38 g)) were added using a metering pump with a feed rate of 3.21 g / min. After the reaction was completed (total 4 hours at 75 °C), the latex was immediately cooled in an ice bath. It was filtered through a 28 μm sieve to separate the coagulum. The average particle size of the resulting core-shell particles was 93 nm by DLS and 82 (24) nm by TEM. The results for the core-shell particles are shown in Table 1.

[0131] Example 8: Preparation of core-shell particles containing a crosslinked shell To the repeat latex of Example 2, Aerosol MA-80 (2.97 g), tert-dodecyl mercaptan (0.085 g), and a pre-emulsion containing shell comonomer solution (237.51 g, containing butyl acrylate (74 wt%, 175.75 g), acrylonitrile (20 wt%, 44.5 g), methacrylic acid (5 wt%, 11.88 g), and 1,4-butanediol diacrylate (1 wt%, 2.38 g)) were added using a metering pump with a feed rate of 3.21 g / min. The latex was then maintained at 75°C for an additional 55 minutes to complete the polymerization. After the reaction was complete, the latex was immediately cooled in an ice container and then filtered through a 28 μm sieve to separate any coagulum. The average particle size of the obtained core-shell particles was 90 nm (by DLS) and 83(20) nm (by TEM). The results of the core-shell particles are shown in Table 1.

[0132] Table 1. Latex properties [Table 1]

[0133] a = nominal volume fraction of cores present based on 100% conversion. b = z-average diameter measured using DLS at pH 5.0. c = number-average diameter of particles measured using TEM (number in parentheses is coefficient of variation). d = shell thickness, calculated from DLS data using: (dz (cs) -dz (c) ) / twenty four) where dz (cs) and dz (c) are the z-average diameters of the final core-shell and core nanoparticles, respectively. NA = Not Applicable

[0134] Example 9: pH response of the examples and the effect of cross-linking the shell of core-shell polymer particles During the preparation of coated and dipped films prepared from the polymers of the present invention, it may be necessary to increase the pH of the latex to enhance storage stability, or to incorporate a metal, preferably a polyvalent metal, such as zinc ions (in the form of zinc oxide), to form ionomeric crosslinks to form free-standing nitrile latex films, as is known in the art (see, for example, "Crosslinking in carboxylated nitrile rubber dipped films," Kells A. and Groves B., Latex 2006: Frankfurt, Germany, January 24-25, 2006). Furthermore, the viscosity-pH response of the latex is important to the quality of films cast or dipped from such carboxylated latexes. d for nanoparticles z The values ​​were measured as a function of pH by dynamic light scattering, and the results are shown in FIG.

[0135] FIG. 1 demonstrates that the presence of a crosslinked shell negates any pH response of the latex, and visual inspection shows that while all of the examples were free-flowing liquids at pH 3, Example 4 formed a gel at pH 8, while one example, Example 5, remained a free-flowing latex.

[0136] Example 10: Estimation of available methacrylic acid by potentiometric titration Measured methacrylic acid (MAA) (wt%) values ​​were determined from the titration data by applying the following equation: MAA(weight%)=((V KOH xC KOH ) / (m dispersion xTSC(wt%) dispersion )xMw (MAA) (3) MAA (wt%) = (neutralized MAA mass) / solid polymer mass × 100 (4) where V KOH and C KOHare the volume of KOH at the neutralization point (from the point of maximum slope on the graph of pH versus added KOH) and the concentration of the KOH solution, respectively. dispersion is the mass of the polymer dispersion used for titration (mass % of the solid content of the polymer dispersion used). (MAA) is the molecular weight of MAA, which is 86.09 g / mol.

[0137] Table 2. Potentiometric titration data [Table 2]

[0138] a = nominal concentration of MAA in whole particles based on composition. b = measured MAA concentration value calculated from titration data.

[0139] Apparatus for functionalizing the shell of core-shell latex One-third of a 1 L round-bottom conical glass vessel was placed in a paraffin oil bath at 40 °C. The reaction mixture was magnetically stirred, and the stirring rate was controlled by setting the magnetic stir plate at a constant speed of 250 rpm. The nanoparticle dispersion was functionalized with glycidyl methacrylate. The amount (g) of glycidyl methacrylate added to the latex to be functionalized is shown in Table 3.

[0140] Acid-base potentiometric titration was used to detect the degree of glycidyl methacrylate functionalization achieved through the reduction in the weight percent of detectable methacrylic acid in the resulting functionalized core-shell latex. That is, the amount of methacrylic acid that did not undergo esterification with the glycidyl methacrylate functionalization was detected. The titration data (Table 3) show the resulting reduction in methacrylic acid content.

[0141] Example 11: Functionalization of Example 3 Example 3 (300 g, 10 wt %) was adjusted to pH 5.0 using 0.5 M aqueous KOH solution. The mixture was first stirred at 250 rpm for 15 minutes and then added to a 1 L flask. Next, an aliquot of glycidyl methacrylate (5.94 g, 4.18 mol %) was added to the flask, and the mixture was heated at 40°C and 250 rpm for 8 hours. Unreacted glycidyl methacrylate was removed using a separatory funnel. The nanoparticle dispersion was washed twice with 200 ml of chloroform. Residual chloroform in the glycidyl methacrylate-functionalized latex was removed by evaporation using a rotary evaporator at a temperature of 25°C. The latex thus purified was then concentrated to 12 wt % using a rotary evaporator. The characterization data obtained for the functionalized core-shell Example 9 are shown in Table 3 and are compared with the unfunctionalized core-shell precursor latex, Example 3. It can be seen that the weight percent of methacrylic acid detected after functionalization decreased from 3.8 weight percent to 1.7 weight percent, respectively. This difference is then used to calculate the mole percent of glycidyl methacrylate now present on the latex particles after the reaction between the carboxylic acid groups on the latex particles and the oxirane groups on the glycidyl methacrylate, which in the case of Example 9 is 2.5 mole percent.

[0142] Example 12: Functionalization of Example 5 Example 5 (300 g, 10 wt %) was adjusted to pH 5.0 using 0.5 M aqueous KOH solution. The mixture was first stirred at 250 rpm for 15 minutes and then added to a 1 L flask. Next, an aliquot of glycidyl methacrylate (53.42 g, 2.41 mol %) was added to the flask, and the mixture was heated at 250 rpm and 40° C. for 8 hours. Unreacted glycidyl methacrylate was removed using a separatory funnel. The nanoparticle dispersion was washed twice with 200 ml of chloroform. The thus purified latex was then concentrated to 12 wt % using a rotary evaporator. Residual chloroform in the glycidyl methacrylate-functionalized latex was removed by evaporation using a rotary evaporator at a temperature of 25° C. The property data obtained for Example 10 before (i.e., Example 5) and after functionalization with glycidyl methacrylate are shown in Table 3. The mole % of glycidyl methacrylate currently present on the latex particles is 1.5 mole %.

[0143] Example 13 This is a repeat of Example 12, except that the latex of Example 8 replaces the latex of Example 5.

[0144] Table 3. Titration data of nanoparticles before and after functionalization [Table 3]

[0145] a = pH of the final dispersion. b = MAA content based on potentiometric titration data. c = GMA added to the latex particles (mol %).

[0146] The stability of the thus functionalized latex particles was then evaluated by measuring the z-average diameter (d z ), zeta potential (ζ) and number average diameter (d TEM) was evaluated. Without wishing to be bound by theory, it is believed that the consistency of these parameters is important to enable the preparation of similar films. Table 4 shows the characterization data of the latex particles before and after functionalization with glycidyl methacrylate, respectively.

[0147] Table 4. Latex property data before and after functionalization [Table 4]

[0148] a = value determined from DLS. b = number-average diameter (at least 100 particles) measured by TEM (number in parentheses is coefficient of variation). c = Zeta potential value measured at pH 5.0. Sample concentration is 0.01 wt% in the presence of 0.001 M sodium nitrate, NaNO3. d = value determined from DLS. e = Zeta potential value measured at pH 6.0. Sample concentration is 0.01 wt% in the presence of 0.001 M sodium nitrate, NaNO3.

[0149] Table 4 shows the z and d TEM Both the polydispersity and zeta potential values ​​increased minimally after functionalization, which, without wishing to be bound by theory, is believed to reflect the functionalization of surface carboxylic acid groups. Low polydispersity values ​​were observed for all functionalized dispersions, and the zeta potential values ​​were not significantly different before and after functionalization. TEM micrographs of core-shell latex samples deposited on carbon mesh (note that some deformation may have occurred as the particles dried) and subsequently stained with phosphotungstic acid demonstrate that the functionalization procedure did not significantly change the morphology of the latex particles.

[0150] Example 14: Preparation of cast films and measurement of their glass transition temperatures The dispersion (12 wt. %, 60 g) was stirred at 200 rpm for 15 minutes and then poured into a glass mold (100 x 125 mm) surrounded by a removable stainless steel wall (5 mm high). The mold surface was pre-cleaned and then sprayed with Ambersil Dry PTFE Film Anti-Stick Aerosol Spray (CRC) to prevent the dried film from adhering to the mold surface. The mold surface was then dried to prevent Ambersil from contaminating the latex. The cast latex film was then placed in a circulating air oven at 25°C for 3 days. The film was dried at atmospheric pressure in a humidity-controlled environment (50% RH). The dried film typically had an average thickness of 550-600 μm, as measured with a pair of calipers. To anneal the films, they were further dried in a circulating air oven at 90° C. for 24 hours. Dynamic mechanical thermal analysis (DMTA) experiments were performed on the cast films using an ATA-Q800 Instrument dynamic mechanical thermal analyzer operating in tension mode. Samples were in the form of rectangular strips with dimensions of 15 mm x 5.5 mm x 0.5 mm, and measurements were performed over a temperature gradient from -110 °C to 200 °C at a heating rate of 3 °C / min and a frequency of 1 Hz. The data obtained measured the storage modulus (E'), loss modulus (E"), and tan δ (= E" / E') as a function of temperature.

[0151] The Tg values ​​obtained for the core-shell polymers are shown in Table 5.

[0152] Table 5. Characterization data of latex films [Table 5]

[0153] a = latex pH at which the film was cast b = film annealing temperature c = Tg (c) and Tg (s)are the measured glass transition temperatures of the GMA-functionalized films for the core and shell, respectively, determined from the maximum values ​​of tan d. d = Young's modulus e = stress at break f = strain at break ND = Not Detected, NM = Not Measured

[0154] Example 15: Self-healing properties of films of the present invention Careful observation revealed that if a sample of the cast film was cut into two pieces, the interfaces of the two halves could be held together and rejoined, a self-healing process that took only a few minutes at room temperature. To improve the self-healing process and therefore enhance the physical properties of the self-healing film, the cut samples were analyzed by the Tg (s) Figure 2A shows the results obtained when dumbbell films of unfunctionalized Example 3 and functionalized Example 11 were cut in half with a blade, immediately marked with two dots on the top surface of the cut dumbbell with a pen, and then rejoined by pressing the two halves together at room temperature for 60 seconds and then annealing the samples in a circulating air oven at 40°C for 24 hours.

[0155] Figure 2A shows (a) before cutting, (b) cutting the dumbbell into two pieces and marking the top of the dumbbell, (c) pressing to reconnect for 60 seconds, and (d) after annealing for 24 hours at 40° C. Note that Example 3 (unfunctionalized film) failed after reconnecting at room temperature.

[0156] The stress-strain data shown in Figure 2B was obtained for an example dumbbell film cut and rebonded according to the protocol above using a Hounsfield H10KS (200 N load cell).

[0157] Therefore, it is believed that using annealing temperatures above 40°C further accelerates the re-healing process of the film. The observation of the self-healing properties of these films is expected to enable healing of pinhole defects in elastomeric film products, such as gloves and catheters; or in films with cavitation, such as elastomeric films used to bind active components in lithium-ion batteries, which, if left unhealed, can lead to the formation of dendrites and short-circuit the battery.

[0158] Example 16: Shape memory properties of the film of the present invention Upon careful observation, it was also found that cast films made from the latex of the present invention exhibit shape memory behavior. To further illustrate this observation, strips of film cast from Examples 3 and 11 were immersed in hot (60°C) water for 30 minutes (i.e., T > Tg (S) ), removed, immediately wrapped around a cylinder, and cooled in cold (15°C) water (i.e., T <Tg (S) ) before forming a rolled spring-like shape. Note that the strip of film cast from Example 11 is decorated with ink stripes to aid in recognition.

[0159] The thus-formed samples were then placed in a water bath held at 60°C for 1 minute, and it was observed that they returned to their original shape (see Figure 3(e)). This process was repeated, but this time the sample was wound into a coil shape before cooling (Figure 3(c)) and relaxation. Further experiments were performed using the same protocol (Figure 3(d)), in which the relaxed film was placed in a zigzag configuration and then relaxed at 60°C.

[0160] Shape memory relaxation of formed films prepared from Examples 3 and 11 was also evident when stored at room temperature; Figure 4 shows the relaxation of both folded and spring-like samples prepared according to the temperature profile described above, but then allowed to relax at 25°C depending on the storage period, initially warmed from storage at 15°C for 1 minute following shape creation.

Claims

1. 1. An aqueous dispersion comprising core-shell polymer latex particles, wherein the shell of the core-shell polymer latex particles has ethylenically unsaturated groups pending from a polymer backbone of the shell of the latex particles, the ethylenically unsaturated bonds in the ethylenically unsaturated groups being separated from the polymer backbone by at least three chemical bonds, the shell of the core-shell particles being crosslinked, and the core of the core-shell particles being uncrosslinked.

2. The aqueous dispersion of claim 1, wherein the shell of the core-shell polymer latex particles comprises a structural unit represented by formula (1): -L-CR 1 =CR 2 R 3 (1) In the formula, L is -CR 1 =CR 2 R 3 and the polymer backbone of the latex particle shell, R 1 , R 2 and R 3 are independently hydrogen or a monovalent organic group.

3. -L- is a divalent hydrocarbon group, and the polymer backbone is -CR 1 =CR 2 R 3 3. The aqueous dispersion according to claim 1, wherein the heteroatom is selected from the group consisting of a group containing at least one heteroatom in the chain connecting the

4. The aqueous dispersion of any one of claims 1 to 3, wherein the core-shell polymer latex particles are prepared by aqueous emulsion polymerization comprising at least two steps: (I) polymerizing ethylenically unsaturated monomers that do not contain a monomer containing a plurality of non-conjugated ethylenically unsaturated groups in the step of producing the core of the core-shell particle; and (II) polymerizing a monomer mixture comprising: (a) a monomer selected from conjugated dienes, monoethylenically unsaturated monomers that do not have a functional group that can be subsequently reacted after formation of the latex particles to introduce an ethylenically unsaturated group, and combinations thereof; and (bi) a monomer having at least two non-conjugated ethylenically unsaturated groups that exhibit different reactivities in aqueous emulsion polymerization, wherein at least a portion of the ethylenically unsaturated groups having the lower reactivity remain unreacted after completion of the aqueous emulsion polymerization; and / or (bii) a monoethylenically unsaturated monomer having a functional group that can be subsequently reacted after formation of the latex particles to introduce an ethylenically unsaturated group; and (c) a monomer having at least two non-conjugated ethylenically unsaturated groups different from (bi); Here, when the monomer (bi) is not present, at least a portion of the functional groups of the monomer (bii) reacts to introduce ethylenically unsaturated groups after the aqueous emulsion polymerization is completed.

5. Monomer (a) is selected from conjugated dienes, aromatic vinyl compounds, linear alkyl esters of ethylenically unsaturated acids, branched alkyl esters of ethylenically unsaturated acids, linear alkyl amides of ethylenically unsaturated acids, branched alkyl amides of ethylenically unsaturated acids, ethylenically unsaturated nitriles, vinyl esters of carboxylic acids, vinyl ethers, ethylenically unsaturated silanes, alkenes and any combination thereof; and / or the monomers (bi) are selected from allyl (meth)acrylate and allyl crotonate; and / or - monomer (bii) is selected from ethylenically unsaturated carboxylic acids, epoxy-functional ethylenically unsaturated compounds, hydroxyl-functional ethylenically unsaturated compounds, amino-functional ethylenically unsaturated compounds and any combination thereof; and / or - the monomer (c) is selected from a monomer containing two ethylenically unsaturated groups, a monomer containing three ethylenically unsaturated groups, a monomer containing four ethylenically unsaturated groups, and any combination thereof; and The monomers for step (I) are selected from monomers (a), (bii), and combinations thereof. The aqueous dispersion of claim 4.

6. the conjugated dienes are selected from 1,3-butadiene, isoprene and 2,3-dimethyl-1,3-butadiene; and / or the aromatic vinyl compound is selected from styrene, α-methylstyrene, p-methylstyrene, t-butylstyrene and vinyltoluene; and / or the linear alkyl esters of ethylenically unsaturated acids and the branched alkyl esters of ethylenically unsaturated acids are selected from n-, iso- or tert-alkyl esters of (meth)acrylic acid, in which the alkyl group has 1 to 20 carbon atoms, reaction products of (meth)acrylic acid with glycidyl esters of neo-acids, and alkoxyalkyl (meth)acrylate monomers; and / or the linear alkylamides of ethylenically unsaturated acids and the branched alkylamides of ethylenically unsaturated acids are selected from (meth)acrylamide, N-methylol (meth)acrylamide and diacetone acrylamide; and / or the ethylenically unsaturated nitrile is selected from (meth)acrylonitrile and fumaronitrile; and / or the vinyl esters of carboxylic acids are chosen from vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl 2-ethylhexanoate, vinyl stearate and vinyl esters of versatic acid; and / or the ethylenically unsaturated silanes are selected from trimethoxyvinylsilane, triethoxyvinylsilane, trimethylsilyl(meth)acrylate and triethylsilyl(meth)acrylate, 3-(trimethoxysilyl)propyl(meth)acrylate and 3-(trimethoxysilyl)propyl(meth)acrylate, and / or the vinyl ethers are selected from alkyl vinyl ethers; and / or the alkene is selected from ethene, propene, butene, hexene and cyclohexene; and / or the ethylenically unsaturated carboxylic acid is chosen from monofunctional and / or difunctional acids; and / or the hydroxyl-functional ethylenically unsaturated compound is selected from hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and hydroxybutyl (meth)acrylate; and / or the amino-functional ethylenically unsaturated compound is selected from aminoethyl (meth)acrylate, aminopropyl (meth)acrylate and aminobutyl (meth)acrylate; and / or - Epoxy-functional ethylenically unsaturated compounds include glycidyl (meth)acrylate, allyl glycidyl ether, vinyl glycidyl ether, vinylcyclohexene oxide, limonene oxide, 2-ethylglycidyl acrylate, 2-ethylglycidyl methacrylate, 2-(n-propyl)glycidyl acrylate, 2-(n-propyl)glycidyl methacrylate, 2-(n-butyl)glycidyl acrylate, 2-(n-butyl)glycidyl methacrylate, glycidyl methyl methacrylate, glycidyl acrylate, (3',4'-epoxyheptyl)-2-ethyl acrylate, (3',4'-epoxyheptyl)-2-ethyl methacrylate. acrylate, (6',7'-epoxyheptyl)acrylate, (6',7'-epoxyheptyl)methacrylate, allyl-3,4-epoxyheptyl ether, 6,7-epoxyheptyl allyl ether, vinyl-3,4-epoxyheptyl ether, 3,4-epoxyheptyl vinyl ether, 6,7-epoxyheptyl vinyl ether, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, 3-vinylcyclohexene oxide, α-methylglycidyl methacrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and combinations thereof; The aqueous dispersion of claim 5.

7. 7. The aqueous dispersion of any one of claims 4 to 6, wherein the shell of the core-shell particles is prepared by: - forming polymeric latex particles having a shell bearing first functional groups derived from the functional groups of monomer (bii) by aqueous emulsion polymerization of a mixture of ethylenically unsaturated monomers comprising monomer (a), monomer (bii) and monomer (c) and optionally monomer (bi); and subsequently reacting said polymer latex particles carrying a first functional group with an ethylenically unsaturated compound which, in addition to the ethylenically unsaturated group, has a second functional group which is reactive with the first functional group.

8. (A) monomer (bii) comprises an ethylenically unsaturated carboxylic acid, the first functional group is a carboxyl group, and the ethylenically unsaturated compound having the second functional group is selected from epoxy-functional ethylenically unsaturated compounds; or (B) monomer (bii) comprises an epoxy-functional ethylenically unsaturated compound, wherein the first functional group is an epoxy group and the ethylenically unsaturated compound having a second functional group is selected from an ethylenically unsaturated carboxylic acid; or (C) Monomer (bii) comprises a hydroxy- and / or amino-functional ethylenically unsaturated compound, resulting in a first functional group selected from a hydroxy group and an amino group, and the ethylenically unsaturated compound having a second functional group is selected from an isocyanate- or thioisocyanate-functional ethylenically unsaturated compound; The aqueous dispersion of claim 7.

9. the core is constructed by a seed latex, which is either pre-prepared or prepared in situ at the start of the free-radical emulsion polymerization, or the core is formed by seeded free radical emulsion polymerization in the presence of a pre-made or in situ prepared seed latex, or - the core is formed by unseeded free radical emulsion polymerization; The aqueous dispersion according to any one of claims 4 to 8.

10. the monomer mixture for polymerizing the core comprises an alkyl ester of (meth)acrylic acid; The monomer mixture for polymerizing the shell comprises: - alkyl esters of (meth)acrylic acid, - ethylenically unsaturated nitrile compounds, - ethylenically unsaturated acids, and - containing a non-conjugated diene, and The core-shell particles are reacted with an ethylenically unsaturated epoxy compound after the aqueous emulsion polymerization is completed. The aqueous dispersion according to any one of claims 4 to 9.

11. The core has a lower glass transition temperature T than the shell as measured by dynamic mechanical thermal analysis at a fixed frequency of 1 Hz and a heating rate of 3°C / min. g The aqueous dispersion according to any one of claims 1 to 10, having

12. 1. A method for producing an aqueous dispersion comprising core-shell polymer latex particles, comprising: the shell of the core-shell polymer latex particle has ethylenically unsaturated groups pending from the polymer backbone of the shell of the latex particle; A method according to any one of claims 4 to 10, wherein the shell of the core-shell particle is crosslinked and the core of the core-shell particle is not crosslinked by the aqueous emulsion polymerization.

13. An elastomeric film prepared from the aqueous dispersion of any one of claims 1 to 11.

14. 14. The elastomeric film of claim 13, wherein the film is free-standing, substantially free of sulfur crosslinks and substantially free of ionomeric crosslinks.

15. 14. The elastomeric film of claim 13, wherein the elastomeric film has first and second outer surfaces and an inner core between the first and second outer surfaces, and wherein the degree of cross-linking between polymer particles at the first and second outer surfaces is higher than that at the inner core of the elastomeric film.

16. An article comprising the elastomeric film of any one of claims 13 to 15.

17. 17. The article of claim 16, selected from surgical gloves, examination gloves, industrial gloves, household gloves, disposable gloves including fabric-supported gloves, medical devices, or comprising a binder for an active ingredient for an energy cell.

18. 1. A method for producing a free-standing elastomeric film, comprising: (a) providing a composition comprising the aqueous dispersion of any one of claims 1 to 11; (b) applying the composition to a substrate to form a wet film; (c) drying and / or curing the wet film to form an elastomeric film; and (d) separating the elastomeric film from the substrate; (e) optionally heat treating the elastomeric film at a temperature between 20°C and 160°C before or after step (d).

19. 20. The method of claim 18, wherein the providing step (a) does not include adding sulfur and accelerators for sulfur vulcanization to the composition, and does not include adding a zinc compound to the composition.

20. 20. The method of claim 18 or 19, wherein the applying step (b) comprises casting, dip-molding, spraying or knife coating.

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