COPOLYMERS OF CYCLICAL KETENACETAL MONOMERS

Description

[0001] The invention relates to copolymers of cyclic ketene acetal monomers, in particular in the form of solid resins or aqueous dispersions or water-redispersible powders, processes for their production by means of radically initiated polymerization and their use, for example, in adhesives or coating materials, in particular for the production of textile fabrics.

[0002] For environmental reasons, there is a growing need to improve the biodegradability of polymers based on ethylene-unsaturated monomers, such as acrylic esters, vinyl esters, vinyl halides, or vinyl aromatics. One approach to this is the incorporation of comonomers that are unstable under natural conditions. US 5541275 describes the copolymerization of vinyl esters and cyclic ketene acetals, specifically 2-methylene-1,3-dioxo hydrocarbon cycles such as 2-methylene-1,3-dioxepane (MDO). Such cyclic ketene acetal monomers can be incorporated into the polymer chains via ring-opening polymerization, thereby introducing ester bonds as predetermined breaking points into the polymer backbone and improving the biodegradability of the polymers, as illustrated, for example, in US 11111328.

[0003] However, such labile monomers can already be unstable under polymerization conditions and tend towards side or degradation reactions, making it challenging to selectively and as completely as possible polymerize these labile monomers into the polymers. For example, cyclic ketene acetals tend to hydrolyze even under aqueous emulsion polymerization conditions and are then no longer polymerizable, as US5541275 and US11111329 emphasize. For instance, MDO hydrolyzes instantaneously in water to the corresponding 4-hydroxybutyl acetate of the following formula:

[0004] C.U. Pittman, Journal of Organic Chemistry, 1995, 60, pages 5729 to 5731, and B. Capon, Journal of American Chemical Society, Vol. 103, No. 7, 1981, pages 1765 to 1768, also report rapid hydrolysis of 2-methylene-1,3-dioxo-carbon-hydrogen cycles, such as 2-methylene-1,3-dioxolane or 2-methylene-1,3-dioxepane. While the literature discusses the emulsion polymerization of MDO or other cyclic ketene acetal monomers, our own attempts to replicate such reactions showed no significant incorporation of the hydrolysis-labile monomers into the polymers, but instead primarily the formation of the respective hydrolysis products, as demonstrated by Comparative Example 9 of the present application. Our own experiments on the hydrolysis kinetics of cyclic ketene acetals also explain these problems in emulsion polymerization.

[0005] Even acidic vinyl comonomers, such as acrylic acid, can hydrolyze cyclic ketene acetals, making the synthesis of copolymers between these monomers particularly challenging. Furthermore, cyclic ketene acetals can exhibit unfavorable copolymerization properties, preventing the formation of copolymers. In summary, producing copolymers of cyclic ketene acetals and acidic vinyl monomers, especially in aqueous dispersions, presents significant difficulties.

[0006] US10287380 BB describes the preparation of copolymers of 80 to 98 wt% methacrylic esters and 2 to 10 wt% cyclic ketene acetals by bulk or solution polymerization processes. JP2017210503 relates to bulk or solution polymers of methacrylic esters (a1) and cyclic ketene acetals (a2) with a weight ratio (a2) / (a1) of 1 / 99 to 20 / 80. US11111328 and US11111329 describe emulsion polymerizations using vinyl esters, cyclic ketene acetals, and ethylene unsaturated acid monomers.

[0007] Against this background, the task was to provide copolymers of cyclic ketene acetal monomers and acid-group-bearing ethylene-unsaturated monomers, especially in the form of aqueous dispersions.

[0008] Surprisingly, the problem was solved by first producing copolymers via multi-step, radical-initiated bulk or solution polymerization of a) cyclic ketene acetal monomers and other ethylene-unsaturated monomers and b) ethylene-unsaturated, acid-group-bearing monomers, and then converting the resulting copolymers into aqueous dispersions. For this to work, it proved essential that, in the multi-step polymerization, a) the cyclic ketene acetal monomers be polymerized with the other ethylene-unsaturated monomers in a first step, and then b) the ethylene-unsaturated, acid-group-bearing monomers be polymerized in a further step.

[0009] An object of the invention is multi-stage copolymers, in particular in the form of solid resins, obtainable by means of multi-stage, radically initiated bulk or solution polymerization, characterized in that a) in a first step, one or more cyclic ketene acetal monomers a1) and one or more monomers a2) selected from the group comprising vinyl esters of carboxylic acids with 1 to 15 C atoms, methacrylic acid esters or acrylic acid esters of carboxylic acids with unbranched or branched alcohols with 1 to 15 C atoms, olefins, dienes, vinyl aromatics and vinyl halides are copolymerized, and b) in a further step, in the presence of the copolymer from the first step a), one or more ethylene-unsaturated, acid-group-bearing monomers b1) are polymerized.

[0010] The multi-stage copolymers are preferably in the form of solid resins, aqueous dispersions, or water-dispersible powders.

[0011] Another object of the invention is multi-stage copolymers in the form of aqueous dispersions, obtainable by dispersing one or more of the multi-stage copolymers according to the invention, for example in the form of solid resins, in water.

[0012] Another object of the invention is multi-stage copolymers in the form of water-redispersible powders, obtainable by drying aqueous dispersions of the multi-stage copolymers according to the invention.

[0013] The multi-stage copolymers according to the invention necessarily differ structurally from polymerization products from single-stage polymerization processes due to their production by means of multi-stage polymerization. This can manifest itself, for example, in different dispersibilities in water or in different glass transition temperatures (Tg) of the multi-stage copolymers according to the invention and conventional single-stage polymers despite the same monomer composition. Thus, the process characteristic of multi-stage polymerization is reflected in the structural characteristics of the multi-stage copolymers.

[0014] Cyclic ketene acetal monomers a1) of general formula 1 are preferred. where n = 0, 1, 2 or 3; R represents a hydrogen atom or a C1-C6 alkyl group; R1< and R2< each independently represent a hydrogen atom, a C1-C12 alkyl, phenyl, vinyl or halogen group; or R1< and R2< together with the carbon atoms to which they are bonded form a fused benzene ring or a fused C3-C7 cycloaliphatic ring; and R1<' and R2<' each independently represent a hydrogen atom, a C1-C12 alkyl, phenyl, vinyl or halogen group; or R1< and R1<' and / or R2< and R2<' form an exocyclic double bond; and R 3< and R 3< ' each independently represent a hydrogen atom, a C 1 -C 12 -alkyl, phenyl, vinyl or halogen residue; or R 3< and R 3< ' form an exocyclic double bond or a spirocycloaliphatic group or a spiro-2-methylene-1,3-dioxepane group;or R3< and R3<' with the carbon atoms to which they are bonded, form an internal double bond, a fused benzene ring, or a fused C3-C7 cycloaliphatic ring; wherein optionally one or more preferably non-adjacent -(CR3<R3<') groups, particularly preferably one -(CR3<R3<') group, are replaced by an oxygen atom.

[0015] Preferably, when n = 1, R 3< and R 3< ' each independently represent a hydrogen atom, a C 1 -C 12 -alkyl, phenyl, vinyl or halogen residue; or R 3< and R 3< ' form an exocyclic double bond or a spirocycloaliphatic group or a spiro-2-methylene-1,3-dioxepane group.

[0016] Preferably, when n = 2, R 3< and R 3< ' each independently represent a hydrogen atom, a C 1 -C 12 alkyl, phenyl, vinyl or halogen group; or R 3< and R 3< ' form an internal double bond, a fused benzene ring or a fused C 3 -C 7 cycloaliphatic ring with the carbon atoms to which they are bonded.

[0017] In the general formula (1) for the cyclic ketene acetal monomers a1), n ​​preferably takes the value 2.

[0018] The substituents R, R 1< , R 1< , R 2< , R 2< ', R 3< and R 3< ' each represent, independently of one another, preferably a hydrogen atom or a methyl, ethyl, propyl, butyl, phenyl or benzyl, chlorine substituent; particularly preferably a hydrogen atom or a methyl, phenyl or benzyl substituent; and most preferably a hydrogen atom or a methyl substituent.

[0019] In a preferred embodiment of formula (1) n = 2 and R, R 1< , R 1< ', R 2< , R 2< ', R 3< and R 3< ' each represent a hydrogen atom.

[0020] Examples of cyclic ketene acetal monomers include 2-methylene-1,3-dioxolane, 2-methylene-4-methyl-1,3-dioxolane, 2-methylene-4,5-dimethyl-1,3-dioxolane, 8-methylene-7,9-dioxabicyclo[4.3.0]nonane, 2-methylene-1,3-dioxane, 2-methylene-5-methyl-1,3-dioxane, 2-methylene-5,5-dimethyl-1,3-dioxane, 2-methylene-1,3-dioxolane-5-spirocyclopentane, 2-methylene-1,3-dioxolane-5-spirocyclopentane, 2-methylene-1,3-dioxepane, 2-methylene-1,3-dioxocan, 2-Methylene-4-phenyl-1,3-dioxolane, 4,7-Dimethyl-2-methylene-1,3-dioxepane, 5,6-Benzo-2-methylene-1,3-dioxepane, 2-Methylene-1,3,6-trioxocan and 2-Methylene-1,3,5-trioxane.

[0021] The most preferred option is 2-Methylene-1,3-dioxepane (MDO).

[0022] The synthesis of cyclic ketene acetal monomers (a1) is known from the literature and is described in detail in JP2017210503. Cyclic ketene acetal monomers are also commercially available.

[0023] The multi-stage copolymers are based preferably 5 to 99 wt.%, more preferably 15 to 95 wt.%, even more preferably 20 to 70 wt.%, particularly preferably 22 to 50 wt.% and most preferably 25 to 40 wt.% on cyclic ketene acetal monomers a1), based on the total weight of the monomers of stage a) or of the monomers a1), a2) and optionally a3).

[0024] The multi-stage copolymers are based preferably 5 to 99 wt.%, more preferably 15 to 95 wt.%, even more preferably 20 to 70 wt.%, particularly preferably 22 to 50 wt.% and most preferably 25 to 40 wt.% on cyclic ketene acetal monomers a1), based on the total weight of the multi-stage copolymers.

[0025] The ring-opening polymerization of the cyclic ketene acetal monomers a1) generally leads to monomer units a1) of the following formula (2):

[0026] The monomer units a1) preferably contain an ester group and are particularly preferably an aliphatic residue with an ester group which most preferably does not bear any further functional group.

[0027] The monomers a2) of the first stage a) are selected from the group comprising vinyl esters of carboxylic acids with 1 to 15 C atoms, methacrylic acid esters or acrylic acid esters of carboxylic acids with unbranched or branched alcohols with 1 to 15 C atoms, olefins, dienes, vinyl aromatics and vinyl halides.

[0028] Preferred vinyl esters are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, vinyl stearate, 1-methyl vinyl acetate, vinyl pivalate, and vinyl esters of branched or unbranched monocarboxylic acids with 5 to 20 carbon atoms, such as vinyl esters of alpha-branched monocarboxylic acids with 5 to 13 carbon atoms, for example VeoVa9R or VeoVa10R (trade names of Hexion). Vinyl acetate is particularly preferred.

[0029] Preferred methacrylic acid esters or acrylic acid esters are esters of unbranched or branched alcohols with 1 to 15 carbon atoms, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, and norbornyl acrylate. Methyl acrylate, methyl methacrylate, n-butyl acrylate, n-butyl methacrylate, and 2-ethylhexyl acrylate are particularly preferred.

[0030] Preferred olefins or dienes are ethylene, propylene, and 1,3-butadiene. Preferred vinyl aromatics are styrene and vinyltoluene. A preferred vinyl halide is vinyl chloride.

[0031] Preferred monomers a2) are methacrylic acid esters or acrylic acid esters and in particular vinyl esters, such as vinyl acetate.

[0032] The use of several monomers a2) (monomer mixture a2)) is also particularly preferred.

[0033] Examples of monomer mixtures a2) are vinyl acetate with ethylene, monomer mixtures a2) of vinyl acetate with ethylene and one or more other vinyl esters, monomer mixtures a2) of vinyl acetate with ethylene and acrylic esters, monomer mixtures a2) of vinyl acetate with ethylene and vinyl chloride, monomer mixtures a2) of styrene and (meth)acrylic esters and monomer mixtures a2) of styrene with 1,3-butadiene.

[0034] Preferred are monomer mixtures a2) of vinyl acetate with 1 to 40 wt.% ethylene; monomer mixtures a2) of vinyl acetate with 1 to 40 wt.% ethylene and 1 to 50 wt.% of one or more further comonomers from the group of vinyl esters with 1 to 12 C atoms in the carboxylic acid residue such as vinyl propionate, vinyl laurate, vinyl esters of alpha-branched carboxylic acids with 5 to 13 C atoms such as VeoVa9R, VeoVa10R, VeoVa11R; monomer mixtures a2) of vinyl acetate, 1 to 40 wt.% ethylene and preferably 1 to 60 wt.% (meth)acrylic acid esters of unbranched or branched alcohols with 1 to 15 C atoms, in particular n-butyl acrylate or 2-ethylhexyl acrylate; and monomer mixtures a2) with 30 to 75 wt.% vinyl acetate, 1 to 30 wt.% vinyl laurate or vinyl ester of an alpha-branched carboxylic acid with 5 to 13 C atoms, and 1 to 30 wt.%-% (Meth)acrylic acid esters of unbranched or branched alcohols with 1 to 15 carbon atoms, in particular n-butyl acrylate or 2-ethylhexyl acrylate, which may also contain 1 to 40 wt.% ethylene; monomer mixtures a2) with vinyl acetate, 1 to 40 wt.% ethylene and 1 to 60 wt.% vinyl chloride; wherein the values ​​in wt.% are added up to 100 wt.%, based on the total weight of the monomer mixtures a2).

[0035] Also preferred are monomer mixtures a2) of methyl methacrylate with n-butyl acrylate and / or 2-ethylhexyl acrylate and optionally ethylene; monomer mixtures a2) of styrene and one or more monomers from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate; monomer mixtures a2) of vinyl acetate with one or more monomers from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate and optionally ethylene; monomer mixtures a2) of styrene with 1,3-butadiene; wherein the values ​​in wt.% are added up to 100 wt.%, based on the total weight of the monomer mixtures a2).

[0036] The multi-stage copolymers are based preferably 1 to 95 wt.%, more preferably 5 to 85 wt.%, particularly preferably 30 to 80 wt.% and most preferably 60 to 75 wt.% on monomers a2), based on the total weight of the monomers of stage a) or of the monomers a1), a2) and optionally a3).

[0037] The multi-stage copolymers are based preferably 1 to 95 wt.%, more preferably 5 to 85 wt.%, particularly preferably 30 to 80 wt.% and most preferably 60 to 75 wt.% on monomers a2), based on the total weight of the multi-stage copolymers.

[0038] The copolymers from the first step a) may optionally be based on one or more auxiliary monomers a3). Examples of auxiliary monomers a3) are ethylene-unsaturated carboxylic acid amides, preferably acrylamide; diesters of fumaric acid such as the diethyl and diisopropyl esters. Further examples are pre-crosslinking comonomers such as polyethylene-unsaturated comonomers, for example divinyl adipate, diallyl maleate, allyl methacrylate, or triallyl cyanurate, or post-crosslinking comonomers, for example methyl acrylamidoglycolic acid methyl ester (MAGME), N-methylolacrylamide (NMA), N-methylolmethacrylamide (NMMA), N-methylolallylcarbamate, alkyl ethers such as the isobutoxy ether or esters of N-methylolacrylamide, N-methylolmethacrylamide, and N-methylolallylcarbamate. Epoxy-functional comonomers such as glycidyl methacrylate and glycidyl acrylate are also suitable.Further examples include silicon-functional comonomers such as acryloxypropyltri(alkoxy)- and methacryloxypropyltri(alkoxy)-silanes, vinyltrialkoxysilanes, and vinylmethyldialkoxysilanes, where the alkoxy groups can be, for example, methoxy, ethoxy, and ethoxypropylene glycol ether residues. Monomers with hydroxy or CO groups should also be mentioned, such as methacrylic acid and acrylic acid hydroxyalkyl esters like hydroxyethyl, hydroxypropyl, or hydroxybutyl acrylate or methacrylate, as well as compounds like diacetone acrylamide and acetylacetoxyethyl acrylate or methacrylate. Vinyl ethers, such as methyl, ethyl, or isobutyl vinyl ethers, are another example.

[0039] The multi-stage copolymers are based preferably 0 to 20 wt.%, particularly preferably 0.5 to 10 wt.% on auxiliary monomers a3), based on the total weight of the monomers of stage a) or of the monomers a1), a2) and optionally a3).

[0040] The multi-stage copolymers are based preferably on 0 to 20 wt.%, particularly preferably on 0.5 to 10 wt.% auxiliary monomers a3), based on the total weight of the multi-stage copolymers.

[0041] The multi-stage copolymers are based preferably 85 to 99.5 wt.%, particularly preferably 90 to 99 wt.% and most preferably 92 to 97 wt.% on the monomers a1), a2) and optionally a3), based on the total weight of the multi-stage copolymers.

[0042] In step a), preferably no ethylene unsaturated acid monomers and / or preferably no ethylene unsaturated anhydrides are copolymerized, particularly preferably no monomers b1) are copolymerized.

[0043] The ethylene-unsaturated, acid-group-bearing monomers b1) can be, for example, ethylene-unsaturated carboxylic acids, ethylene-unsaturated anhydrides, ethylene-unsaturated phosphoric acids, ethylene-unsaturated sulfonic acids or ethylene-unsaturated sulfuric acids or their salts.

[0044] Examples of ethylene-unsaturated carboxylic acids are acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, and vinylacetic acid; or monoesters of maleic acid or fumaric acid, such as the monoethyl and monoisopropyl esters. Examples of ethylene-unsaturated anhydrides are maleic anhydride, methacrylic anhydride, and acrylic anhydride. Examples of ethylene-unsaturated phosphoric acids are vinylphosphonic acid, phosphoric acid 2-hydroxyethyl methacrylate ester, phosphoethyl methacrylate, and 2-(methacryloyloxy)ethylphosphonic acid. Examples of ethylenically unsaturated sulfonic acids are 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), vinylsulfonic acid, allylsulfonic acid, methylallylsulfonic acid, styrenesulfonic acid, vinylbenzenesulfonate, 2-sulfoethyl acrylate, 2-sulfoethyl methacrylate, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, 2-propene-1-sulfonic acid and acrylamidoglycolic acid.

[0045] Preferably as monomers b1) are ethylene-unsaturated sulfonic acids and in particular ethylene-unsaturated carboxylic acids.

[0046] Preferred ethylene-unsaturated carboxylic acids are acrylic acid, methacrylic acid, and fumaric acid. Preferred ethylene-unsaturated sulfonic acids are vinylsulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid.

[0047] The multi-stage copolymers are based preferably 0.5 to 15 wt.%, particularly preferably 1 to 10 wt.% and most preferably 3 to 8 wt.% on monomers b1), based on the total weight of the monomers of stage a) or of the monomers a1), a2) and optionally a3).

[0048] The multi-stage copolymers are based preferably 25 to 100 wt.%, particularly preferably 50 to 100 wt.% and most preferably 90 to 100 wt.% on monomers b1), based on the total weight of the monomers of stage b) or of the monomers b1) and b2).

[0049] The multi-stage copolymers are based preferably on monomers b1) to a wt.% of 0.5 to 15 wt.%, particularly preferably on 1 to 10 wt.% and most preferably on 3 to 8 wt.%, based on the total weight of the multi-stage copolymers.

[0050] Furthermore, in step b) one or more additional ethylene-unsaturated monomers b2) different from the monomers b1) can be copolymerized.

[0051] The monomers b2) may, for example, be the monomers a2) mentioned above and / or auxiliary monomers a3), with the preferences mentioned above.

[0052] The multi-stage copolymers are based preferably 0 to 75 wt.%, more preferably 0 to 50 wt.% and even more preferably 0 to 10 wt.% on monomers b2), based on the total weight of the monomers of stage b) or of the monomers b1) and b2).

[0053] Particularly preferred is the use of no monomers b2) in stage b).

[0054] In stage b), cyclic ketene acetal monomers a1) are particularly preferred.

[0055] In stage b), only monomers b1) are most preferably used.

[0056] Following step a) and before step b), further polymerization of additional ethylene-unsaturated monomers can take place. Alternatively, further ethylene-unsaturated monomers can be polymerized following step b). Preferably, step b) takes place immediately following step a) and / or preferably, no further polymerization takes place following step b).

[0057] The selection of monomers or the weight fractions of comonomers is carried out such that a glass transition temperature Tg of -65°C to +65°C, preferably -20°C to +20°C, is generally achieved. The glass transition temperature Tg of the polymers can be determined in a known manner using differential scanning calorimetry (DSC). Tg can also be approximately predicted using the Fox equation. According to Fox TG, Bull. Am. Physics Soc. 1, 3, page 123 (1956): 1 / Tg = x1 / Tg1 + x2 / Tg2 + ... + xn / Tgn, where xn represents the mass fraction (wt% / 100) of monomer n, and Tgn is the glass transition temperature in Kelvin of the homopolymer of monomer n. Tg values ​​for homopolymers are listed in Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975).

[0058] A further object of the invention is a process for producing the multi-stage copolymers, preferably in the form of solid resins, by means of multi-stage, radically initiated bulk or solution polymerization, characterized in that a) in a first step, one or more cyclic ketene acetal monomers a1) and one or more monomers a2) selected from the group comprising vinyl esters of carboxylic acids with 1 to 15 C atoms, methacrylic acid esters or acrylic acid esters of carboxylic acids with unbranched or branched alcohols with 1 to 15 C atoms, olefins, dienes, vinyl aromatics and vinyl halides are copolymerized, and b) in a further step, in the presence of the copolymer from the first step a), one or more ethylene-unsaturated, acid-group-bearing monomers b1) are polymerized.

[0059] In general, both stage a) and stage b) are polymerized using mass and / or solution polymerization processes.

[0060] The polymerization temperature is preferably 30°C to 120°C, particularly preferably 40°C to 100°C, and most preferably 50°C to 90°C. When copolymerizing gaseous comonomers, such as ethylene, polymerization is preferably carried out under pressure, generally between 5 bar and 100 bar.

[0061] The polymerization can be initiated using initiators commonly used in bulk or solution polymerization processes, such as peresters, perdicarbonates, and diacyl peroxides like di-tert-amyl peroxyoxalate, tert-amyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, tert-amyl peroxypivalate, tert-butyl peroxypivalate, and dicyclohexyl peroxydicarbonate. Optionally, these radical initiators can also be combined with reducing agents in a known manner. Suitable examples include formaldehyde sulfoxylate salts or ascorbic acid. In redox initiation, one or both redox catalyst components are preferably added during the polymerization. The amount of radical initiator used is preferably 0.005 to 1 mol%, based on the comonomer phase.

[0062] Commonly used regulating substances can be employed during polymerization to control the molecular weight. If regulators are used, they are typically added in amounts between 0.01 and 5.0 wt%, based on the monomers being polymerized. Regulators are preferably dosed separately or premixed with reaction components. Examples of regulators include n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptopropionic acid, methyl mercaptopropionic acid ester, and acetaldehyde.

[0063] The monomers in step a) can be supplied wholly or preferably partially, and any remaining amount of monomers can be added during polymerization.

[0064] After complete dosing of the monomers from step a), the monomers of step b) are generally dosed. The dosing of the monomers of step b) preferably begins after complete or largely complete polymerization of the monomers of step a), in particular after a conversion of the monomers of step a) of at least 85%, more preferably at least 90% and particularly preferably at least 95%.

[0065] Any emulsifiers and any protective colloids can be added in whole or, preferably, partially, and any remaining amounts of emulsifiers and / or protective colloids can be added during polymerization. Suitable emulsifiers and / or protective colloids are described in detail below. Preferably, the polymerization takes place in the absence of emulsifiers and / or protective colloids.

[0066] The multi-stage copolymers are preferably not emulsifier-stabilized and / or preferably not stabilized with protective colloids.

[0067] Bulk polymerization generally takes place without the addition of solvents or in the absence of solvents, i.e., in bulk.

[0068] Solution polymerization preferably takes place in one or more non-aqueous organic solvents, particularly preferably aprotic organic solvents such as esters, ethers, or ketones. Esters are especially preferred. The organic solvents preferably contain 1 to 12 carbon atoms and particularly preferably 1 to 8 carbon atoms. Examples of ethers are dioxane, tetrahydrofuran, diethyl ether, diisopropyl ether, and diethylene glycol dimethyl ether. Examples of esters are ethyl acetate, butyl acetate, propyl propionate, ethyl butyrate, and ethyl isobutyrate. Particularly preferred solvents are ethyl acetate and acetone. Preferably, no alcohol, in particular no methanol, ethanol, propanol, butanol, or benzyl alcohol, is used as a solvent.

[0069] After completion of the polymerization, residual monomers can be removed by post-polymerization using known methods, for example, by post-polymerization initiated with a redox catalyst. Volatile residual monomers can also be removed by distillation, preferably under reduced pressure, and optionally by passing or over inert carrier gases such as air, nitrogen, or steam.

[0070] The multi-stage copolymers of stages a) and / or b) of the process according to the invention are preferably in the form of melts, solid resins or in the form of solutions or dispersions.

[0071] The mixtures obtained by solution polymerization can be converted into solid resins using conventional methods, for example by precipitation, filtration and subsequent drying, or by decantation and subsequent drying. Drying can be carried out in a known manner, for example in a drum dryer, a flow tube, a fluidized bed, or a cyclone dryer.

[0072] Another object of the invention is a process for producing multi-stage copolymers in the form of aqueous dispersions, characterized in that one or more multi-stage copolymers according to the invention are dispersed in water.

[0073] For the production of multi-stage copolymers in the form of aqueous dispersions, multi-stage copolymers in the form of solid resins or mixtures obtained by solution polymerization can generally be used. Melts obtained by bulk polymerization can also be directly converted into aqueous dispersions.

[0074] The mixtures obtained by solution polymerization can, for example, be mixed with water or added to water, and the organic solvent then removed, preferably as completely as possible, for example by distillation, optionally under vacuum. Multi-stage copolymers in the form of melts, for example obtained by bulk polymerization or by melting solid resins, can be directly introduced into water and dispersed, for example by stirring with conventional agitators. Multi-stage copolymers in the form of solid resins can be dispersed directly in water, analogous to the process described above for melts. These methods are particularly efficient.

[0075] Alternatively, multi-stage copolymers in the form of solid resins or melts can first be dissolved with one or more organic solvents, preferably water-soluble solvents such as alcohols like methanol or ethanol, ethers like THF, or especially ketones like acetone, and then treated with water or added to water, after which the organic solvent is removed, preferably as completely as possible, for example by distillation, optionally under vacuum. The organic solvents typically have a lower boiling point than water, particularly under the conditions present during solvent exchange.

[0076] Mixing the multi-stage copolymers with water and / or dissolving the solid resins in organic solvent can generally be carried out at room temperature or elevated temperature, at ambient pressure or elevated pressure. Preferably, dissolution takes place below the boiling point of the organic solvent at the pressure applied in each individual case.

[0077] Conventional devices and common mixing units can be used to transfer the multi-stage copolymers into aqueous dispersions, for example high-weight stirring units such as Ultrathurrax stirrers.

[0078] The multi-stage copolymers are preferably treated with one or more bases. For example, the multi-stage copolymers can be treated with bases in the form of aqueous dispersions, or preferably in organic solvents. Inorganic or, preferably, organic bases can be used. Examples of inorganic bases are alkali or alkaline earth hydroxides or ammonia, in particular sodium or potassium hydroxide. Examples of organic bases are alkanolamines or alkyl or arylamines, in particular dialkyl or trialkylamines. Preferred alkanolamines are dimethylethanolamine, ethanolamine, diethanolamine, triethanolamine, 2-aminomethylpropanol, diethylethanolamine, methyldiethanolamine, dimethylisopropylamine, and dimethylisopropanolamine. Preferred alkyl or arylamines are trimethylamine, triethylamine, tributylamine, dibutylamine, dimethylaniline, diethylaniline, or triphenylamine.The amount of base is preferably based on the amount of ethylene-unsaturated, acid-group-bearing monomers (b1) incorporated into the polymerization. Preferably, 70 to 130 mol%, and particularly preferably 80 to 120 mol% of base are used, based on the molar amounts of monomer units (b1) incorporated into the multi-stage copolymers. Most preferably, equimolar amounts of base are used, based on the molar amounts of monomer units (b1) incorporated into the multi-stage copolymers. The incorporated molar amounts of monomer units (b1) can be determined, for example, by 1H NMR. These measures can, for example, further improve the stability of the aqueous dispersions of the multi-stage copolymers.

[0079] Preferred are multi-stage copolymers in the form of solid resins, aqueous dispersions or water-redispersible powders containing one or more bases.

[0080] Alternatively, the addition of base to the multi-stage copolymers can be omitted.

[0081] One or more emulsifiers and / or one or more protective colloids can be added to the multi-stage copolymers. This makes it possible, for example, to obtain more stable aqueous dispersions of multi-stage copolymers or multi-stage copolymers in the form of aqueous dispersions with higher solids contents.

[0082] Emulsifiers and / or protective colloids are preferably added to the multi-stage copolymers after their production by polymerization, particularly preferably to the mixtures obtained by solution polymerization or to the solutions of the multi-stage copolymers in organic solvents or to the aqueous dispersions of the multi-stage copolymers.

[0083] Preferred are multi-stage copolymers in the form of solid resins, aqueous dispersions or water-redispersible powders containing one or more emulsifiers and / or one or more protective colloids.

[0084] Examples of emulsifiers include, in particular, anionic and nonionic surfactants. Examples of anionic surfactants are alkyl sulfates with a chain length of 8 to 18 carbon atoms, alkyl and alkylaryl ether sulfates with 8 to 18 carbon atoms in the hydrophobic residue and up to 40 ethylene or propylene oxide units, alkyl or alkylaryl sulfonates with 8 to 18 carbon atoms, oleic acid sulfonates, and esters and semi-esters of sulfosuccinic acid with monohydric alcohols or alkylphenols. Suitable nonionic surfactants include, for example, alkyl polyglycol ethers or alkylaryl polyglycol ethers with 8 to 40 ethylene oxide units. The use of alkyl ether sulfates or dodecylbenzenesulfonates is preferred.

[0085] Preferably, up to 10 wt.%, particularly preferably 0.1 to 7 wt.% and most preferably 1 to 4 wt.% of one or more emulsifiers are used, based on the dry weight of the multi-stage copolymers.

[0086] Examples of protective colloids include polyvinyl alcohols; polyvinylpyrrolidones; polyvinyl acetals; polysaccharides; synthetic polymers such as poly(meth)acrylic acid, copolymers of (meth)acrylates with carboxyl-functional comonomer units, poly(meth)acrylamide, polyvinylsulfonic acids and their water-soluble copolymers; styrene maleic acid and vinylethermaleic acid copolymers. Preferred protective colloids are polyvinyl alcohols, in particular partially or fully saponified polyvinyl alcohols with a degree of hydrolysis of 80 to 100 mol%. Particularly preferred are partially saponified polyvinyl alcohols with a degree of hydrolysis of 80 to 95 mol%, and in particular with a Höppler viscosity of 1 to 30 mPas in a 4% aqueous solution (Höppler method at 20°C, DIN 53015). The aforementioned protective colloids are accessible by methods known to those skilled in the art.

[0087] Protective colloids are present in an amount of preferably 0.1 to 20 wt.%, more preferably 0.1 to 15 wt.% and particularly preferably 1 to 10 wt.%, based on the dry weight of the multi-stage copolymers.

[0088] To improve their application-related properties, one or more additives can be added to the multi-stage copolymers, preferably after their production by polymerization, particularly preferably to mixtures obtained by solution polymerization, to solutions of the multi-stage copolymers in organic solvents, or to aqueous dispersions of the multi-stage copolymers. Examples of additives include pigments, fillers, foam stabilizers, water repellents, or cement plasticizers.

[0089] The multi-stage copolymers in the form of aqueous dispersions have a solids content of preferably 5 to 75%, more preferably 10 to 70%, particularly preferably 20 to 60% and most preferably 30 to 50%.

[0090] The multi-stage copolymers in the form of protective colloid-free and emulsifier-free aqueous dispersions have a solids content of preferably 5 to 30%, particularly preferably 6 to 20% and most preferably 7 to 10%.

[0091] The multi-stage copolymers in the form of aqueous dispersions, which contain either protective colloids or emulsifiers, have a solids content of preferably >10 to 40%, particularly preferably 15 to 35% and most preferably 20 to 30%.

[0092] The multi-stage copolymers in the form of aqueous dispersions containing protective colloid and emulsifiers have a solids content of preferably 10 to 75%, particularly preferably 20 to 60% and most preferably 30 to 50%.

[0093] The multi-stage copolymers have number-average molecular weights of preferably 5,000 to 1,500,000 Daltons, particularly preferably 10,000 to 500,000 Daltons and most preferably 15,000 to 200,000 Daltons.

[0094] Multi-stage copolymers in the form of aqueous dispersions have viscosities of preferably 1 to 50,000 mPas, particularly preferably 2 to 10,000 mPas and most preferably 5 to 1,000 mPas.

[0095] The particle size of the multi-stage copolymers is preferably from 200 to 10,000 nm, more preferably 300 to 5,000 nm, particularly preferably 600 to 4,000 nm and most preferably 1,000 to 3,000 nm.

[0096] The methods for determining the solids content, molecular weight, viscosity and particle size are described below for the examples.

[0097] Another object of the invention is a process for producing multi-stage copolymers in the form of water-redispersible powders, characterized in that aqueous dispersions of the multi-stage copolymers according to the invention are dried.

[0098] To produce water-redispersible polymer powders, aqueous dispersions of multi-stage copolymers (polymer dispersions) are generally dried, optionally after the addition of protective colloids as drying aids, for example by fluidized bed drying, freeze-drying, or spray drying. Preferably, the dispersions are spray-dried. Spray drying can be carried out in conventional spray drying systems, with atomization achieved using single-, double-, or multi-component nozzles or a rotating disc. The outlet temperature is generally selected in the range of 45°C to 120°C, preferably 60°C to 90°C, depending on the system, the temperature of the copolymer, and the desired degree of dryness. Examples of drying aids are the protective colloids mentioned above, particularly polyvinyl alcohol. The drying aid (protective colloid) is typically added in a total amount of 3 to 30 wt.%, particularly 5 to 20 wt.%.-%, based on the polymeric components of the dispersion, is used.

[0099] In the atomization process for drying aqueous polymer dispersions, a content of up to 3 wt% antifoaming agent, based on the base polymer, has often proven advantageous. To increase shelf life by improving blocking stability, the resulting polymer powder can be equipped, for example, with an antiblocking agent (anti-caking agent), preferably up to 30 wt%, based on the total weight of polymeric components. Examples of antiblocking agents are calcium or magnesium carbonate, talc, gypsum, silica, kaolins, metakaolin, calcined kaolin, and silicates with particle sizes preferably in the range of 10 nm to 100 µm.

[0100] The viscosity of the mixture to be dried is adjusted via the solids content to achieve a value preferably < 1,500 mPas, particularly preferably < 500 mPas (viscosity at 20 revolutions and 25.0°C). The solids content of the mixture to be dried is preferably > 35%, particularly preferably > 40%.

[0101] To improve the application-related properties, further additives can be added during drying. Other components of dispersion powder compositions included in preferred embodiments are, for example, pigments, fillers, foam stabilizers, water repellents, or cement plasticizers.

[0102] The multi-stage copolymers, particularly in the form of aqueous dispersions, are generally suitable as binders for coating materials or, in particular, as adhesives, for example for paints, fibers, textiles, leather, paper, or carpets. The use of the multi-stage copolymers as binders for bonding fibrous materials is also preferred, especially for the production of textile fabrics such as nonwovens, knitted and woven fabrics, leather and furs, or carpets.

[0103] Furthermore, the multi-stage copolymers can also be used as additives for the production of molded parts, especially for composite components based on radically crosslinkable polymer compositions, such as unsaturated polyester resins (UP resins). In addition, the multi-stage copolymers can also be used as gum base in the production of chewing gum.

[0104] Multi-stage copolymers can also be used in construction chemicals. They can be used alone or in combination with conventional polymer dispersions or dispersion powders, optionally in conjunction with hydraulically setting binders such as cements (Portland, aluminate, trass, blast furnace, magnesia, phosphate cement), gypsum, and water glass, for example, for the production of self-leveling compounds, construction adhesives, plasters, fillers, joint mortars, waterproofing slurries, external thermal insulation composite systems (ETICS), or paints, such as powder paints. Among construction adhesives, tile adhesives and external thermal insulation composite system (ETICS) adhesives are preferred applications. Self-leveling compounds are also preferred, particularly self-leveling floor screeds and leveling compounds.

[0105] Advantageously, the multi-stage copolymers according to the invention are very readily and extensively biodegradable or degradable under natural conditions. The term biodegradable copolymers generally means that the copolymers are wholly or partially biodegradable, i.e., under the influence of microorganisms, or generally under natural conditions, particularly under the influence of alkaline media, and are particularly more biodegradable than corresponding polymers that, for example, contain monomer units a2) and b1) but no monomer units a1).

[0106] Particularly surprising was the fact that, using the processes according to the invention, cyclic ketene acetal monomers could be polymerized into the multi-stage copolymers with high yield, and that the problem of hydrolysis of the cyclic ketene acetal monomers during the production of polymer dispersions or during the polymerization of ethylene unsaturated acids could at least be reduced or even eliminated. Hydrolysis of the cyclic ketene acetal monomers can be quantified, for example, by gas chromatography. According to the inventive procedure, the incorporation of the cyclic ketene acetals a1) into the copolymers advantageously occurred selectively via ring opening, thereby forming the monomer units a1) of formula 2 according to the invention. Side reactions, such as vinyl polymerization or polymerization with the elimination of, for example, aldehydes or ketones, preferably did not occur to a significant extent.The polymer dispersions accessible according to the invention are surprisingly stable, even without emulsifiers or protective colloids as stabilizing agents. These objectives have been achieved even better with the preferred embodiments of the present invention.

[0107] Furthermore, the multi-stage copolymers exhibit surprisingly high tackiness and surprisingly high adhesion and cohesion after application.

[0108] The following examples serve to further illustrate the invention: Determination of the number-mean and mass-mean molecular weights Mn, Mw and the polydispersity by means of SEC (Size-Exclusion Chromatography): The measurement was carried out against polystyrene standard in THF at 35°C, a flow rate of 0.3 ml / min and detection with RID (refractive index detector) on an Agilent PLgel MiniMIX-C Guard column with an injection volume of 20 µl.

[0109] Determination of the glass transition temperature Tg by DSC (Differential Scanning Calorimetry / Dynamic Difference Thermal Analysis): The measurements were carried out on a DSC-1 instrument from Mettler Toledo in a temperature range of -150°C to +150°C in two runs with a heating or cooling rate of 10 K / min, whereby the second run was used to determine the glass transition temperature. Solid content of the dispersions:

[0110] The solids content was determined using a Sartorius hot balance. One gram of polymer sample was spread thinly on an aluminum measuring plate and dried at 130°C until a constant weight was achieved. Brookfield viscosity of the dispersions:

[0111] The measurement was performed on a Brookfield DV-II viscometer at 23°C. Measurements were taken using spindle 1 and spindle 4 at speeds of 20 rpm and 10 rpm, respectively.

[0112] Particle size distribution (Z-average) via dynamic light scattering (DLS) of the dispersions: The particle size distribution was determined using a Malvern ZetaSizer Nano S with software version 2.2. The dispersion was diluted with demineralized water and measured at 20°C; the Z-average (Dz) was calculated by the software. Detailed information on the calculation of Dz can be found in ISO 22412:2017 (Particle size analysis - Dynamic light scattering (DLS)). Example 1:

[0113] Acid-modified MDO-containing polyvinyl acetate solid resin: 241.3 g ethyl acetate, 30.5 g 2-methylene-1,3-dioxepane (MDO), 70.0 g vinyl acetate (VAM) and 0.7 g tert-butyl peroxypivalate (PPV, 75%) were placed in a reactor and heated to 77°C.

[0114] A mixture of 7.5 g ethyl acetate and 3.9 g PPV (75%) was administered over 300 min. 45 min after the start of the initiator dose, a mixture of 81.3 g MDO and 176.0 g VAM was started and administered over 220 min.

[0115] After the monomer dosage was complete, 18.6 g of acrylic acid was added over 20 minutes, followed by dilution with 125.1 g of ethyl acetate, which was added over 35 minutes. The mixture was refluxed for a further 60 minutes and then cooled to room temperature.

[0116] Residual monomer and solvent were removed by drying under vacuum.

[0117] The resulting multi-stage copolymer in the form of a solid resin had a glass transition temperature Tg of 2°C and a mean molecular weight Mw of 26 kDa. Example 2:

[0118] Secondary dispersion of the acid-modified MDO-containing solid resin from Example 1, without the addition of an emulsifier: 25.5 g of a 20% solution of the solid resin from Example 1 in acetone were mixed with 0.35 ml of dimethylethanolamine. 55 g of water were added to this polymer solution while stirring. The resulting dispersion was sheared for 15 min using an IKA Ultrathurrax at 14,000 rpm. The solvent was removed using a rotary evaporator, yielding a stable secondary dispersion of the polymer.

[0119] The resulting dispersion had a solids content of 8.5%, a Brookfield viscosity of 9 mPas, and an average particle size Dz of 1,003 nm. Example 3:

[0120] Secondary dispersion of the acid-modified MDO-containing solid resin from Example 1, with protective colloid addition: 75 g of a 20% solution of the solid resin from Example 1 in acetone were mixed with 1.04 ml of dimethylethanolamine.

[0121] To this polymer solution, a solution of 9.0 g of a 10% aqueous solution of polyvinyl alcohol (Mowiol 4-88) and 55 g of water was added while stirring.

[0122] The resulting dispersion was sheared for 15 minutes using an IKA Ultrathurrax at 14,000 rpm.

[0123] The solvent was removed using a rotary evaporator, resulting in a stable secondary dispersion of the polymer.

[0124] The resulting dispersion had a solids content of 20.3%, a Brookfield viscosity of 127 mPas, and an average particle size Dz of 2,382 nm. Example 4:

[0125] Secondary dispersion of the acid-modified MDO-containing solid resin from Example 1, with emulsifier addition: 75 g of a 20% solution of the solid resin from Example 1 in acetone were mixed with 1.04 ml of dimethylethanolamine.

[0126] A solution of 0.9 g sodium dodecyl sulfate (SDS) and 50 g water was added to this polymer solution while stirring.

[0127] The resulting dispersion was sheared for 15 minutes using an IKA Ultrathurrax at 10,000 rpm. The speed was reduced to minimize foaming.

[0128] The solvent was removed using a rotary evaporator, resulting in a stable secondary dispersion of the polymer.

[0129] The resulting dispersion had a solids content of 26.3%, a Brookfield viscosity of 451 mPas, and an average particle size Dz of 1,251 nm. Example 5:

[0130] Secondary dispersion of the acid-modified MDO-containing solid resin from Example 1, with emulsifier and protective colloid addition: 950 g of a 20% solution of the solid resin from Example 1 in acetone were mixed with 13.2 ml of dimethylethanolamine.

[0131] To this polymer solution, an emulsifier solution containing 7.6 g sodium dodecyl sulfate, 76 g of a 10% aqueous solution of polyvinyl alcohol (Mowiol 4-88), and 250 g water was added while stirring.

[0132] The resulting dispersion was sheared for 15 minutes using an IKA Ultrathurrax at 14,000 rpm. The solvent was removed using a rotary evaporator, yielding a stable secondary dispersion of the polymer.

[0133] The resulting dispersion had a solids content of 43.7%, a Brookfield viscosity of 151 mPas, and an average particle size Dz of 1924 nm. Comparative example 6:

[0134] Non-acid-modified MDO-containing polyvinyl acetate solid resin: 73.9 g ethyl acetate, 15.1 g 2-methylene-1,3-dioxepane (MDO), 35.1 g vinyl acetate (VAM), and 0.2 g tert-butyl peroxypivalate (PPV, 75%) were placed in a reactor and heated to 77°C. A mixture of 2.3 g ethyl acetate and 1.2 g PPV (75%) was added over 300 min.

[0135] 45 minutes after the start of the initiator dosage, the dosage of a mixture of 53.3 g MDO and 124.5 g VAM was started and administered over 240 minutes.

[0136] 15 minutes after the end of the monomer dosage, a dilution with 76.7 g of ethyl acetate was carried out, which was added over 45 minutes.

[0137] The solution was kept under reflux for a further 50 minutes and then cooled to room temperature.

[0138] Residual monomer and solvent were removed by drying under vacuum.

[0139] The polymer obtained had a glass transition temperature Tg of 0°C and a mean molecular weight Mw of 43 kDa. Comparative example 7:

[0140] Dispersion test of the non-acid-modified MDO-containing solid resin from comparative example 6, with emulsifier and protective colloid addition: To 75 g of a 20% solution of the solid resin from comparative example 6 in acetone, an emulsifier solution containing 0.6 g sodium dodecyl sulfate and 6 g of a 10% aqueous solution of polyvinyl alcohol (Mowiol 4-88) and 20 g water was added while stirring.

[0141] The resulting mixture was sheared for 15 minutes using an IKA Ultrathurrax at 14,000 rpm.

[0142] The solvent was removed using a rotary evaporator, with the polymer precipitating as sediment and no dispersion being obtained. Comparative example 8:

[0143] Dispersion experiment of the non-acid-modified MDO-containing solid resin from comparative example 6, with the addition of emulsifier and polyacrylic acid: To 50 g of a 20% solution of the solid resin from example 6 in acetone, an emulsifier solution containing 0.4 g sodium dodecyl sulfate, 4 g of a 10% aqueous solution of polyvinyl alcohol (Mowiol 4-88), 500 mg polyacrylic acid (Mw = 1800 g / mol), 0.69 ml dimethylethanolamine and 13 g water was added while stirring.

[0144] The resulting dispersion was sheared for 15 minutes using an IKA Ultrathurrax at 14,000 rpm.

[0145] The solvent was removed using a rotary evaporator, with the polymer precipitating as sediment and no dispersion being obtained. Comparative example 9:

[0146] Attempt at emulsion polymerization of MDO (replication of ACS Macro Lett. 2021, 10, 5, pages 591 to 597): 16.7 g of Disponil FES 32, 25 mg of FeSO₄·7 H₂O in 16 ml of water, 3.5 g of a 1% aqueous solution of EDTA, and 0.06 ml of 2M sodium hydroxide solution were added to 310 ml of water and adjusted to a pH of 8 by adding 25% aqueous ammonium hydroxide solution. The reaction vessel was heated to 40°C.

[0147] A mixture of 173.0 g vinyl acetate (VAM) and 43.9 g 2-methylene-1,3-dioxepane (MDO) was administered over a period of 60 minutes.

[0148] Simultaneously, a mixture of 46.4 g water, 1.4 g of a 50% aqueous solution of 2-acrylamido-2-methyl-propanesulfonic acid (AMPS), 1.6 g of a 70% aqueous solution of Tergitol, and 6.2 g Disponil FES 32 was dosed over 60 minutes.

[0149] Parallel to the monomer dosing, the initiator phase, consisting of 1.4 g ammonium peroxodisulfate, 0.64 g tert-butyl hydroperoxide (tBHP), and 38.6 g water, was dosed over 70 minutes, as was the reduction phase, consisting of 2.6 g FF6 in 37.6 g water. Polymerization took place at 40°C. A pH of 8 was maintained by the addition of a 25% aqueous ammonium hydroxide solution.

[0150] The resulting dispersion had an average particle size of 164 nm and a solids content of 30.7%.

[0151] In the crude <1H NMR of the dispersion in CDCl3, a triplet was found at 4.05 ppm, which is characteristic of the hydrolysis product of MDO, 4-hydroxybutyl acetate. This was also detected in the dispersion by gas chromatography.

[0152] Drying of the dispersion and re-examination of the resulting solid via 1H-NMR showed that the polymer consisted of only 1.9 mol-% polymerized MDO (triplet at 3.95 ppm in CDCl3) (theory: 16.1 mol-%). Comparative example 10:

[0153] Attempt to produce a crotonic acid-modified MDO-containing polyvinyl acetate solid resin with simultaneous dosing of acid monomer and MDO: 75.6 g ethyl acetate, 2.6 g 2-methylene-1,3-dioxepane (MDO), 48.8 g vinyl acetate (VAM), 1.6 g crotonic acid and 0.2 g tert-butyl peroxypivalate (PPV, 75%) were placed in a reactor and heated to 77°C.

[0154] A mixture of 2.4 g ethyl acetate and 1.23 g PPV (75%) was administered over 300 min.

[0155] 45 minutes after starting the initiator dose, a mixture of 9.1 g MDO, 10.8 g crotonic acid, and 172.9 g VAM was started and dosed over 240 minutes. After the dose was completed, the mixture was refluxed for a further 60 minutes and then cooled to room temperature.

[0156] Residual monomer and solvent were removed by drying under vacuum.

[0157] The resulting polymer had a glass transition temperature Tg of 42°C and a mean molecular weight Mw of 58 kDa. No incorporation of MDO could be detected by 1H NMR spectroscopy. Comparative example 11:

[0158] Attempt to prepare an acid-modified MDO-containing polyvinyl acetate solid resin in methanol: 112.7 g methanol, 14.2 g 2-methylene-1,3-dioxepane (MDO), 30.8 g vinyl acetate (VAM) and 0.3 g tert-butyl peroxypivalate (PPV, 75%) were placed in a reactor and heated to 77°C.

[0159] A mixture of 3.5 g ethyl acetate and 1.8 g PPV (75%) was administered over 300 min.

[0160] 45 minutes after the start of the initiator dosage, the dosage of a mixture of 37.9 g MDO and 82.2 g VAM was started and administered over 220 minutes.

[0161] After the monomer dosage was complete, 8.7 g of acrylic acid was added over 20 minutes, followed by dilution with 58.4 g of methanol, which was added over 35 minutes.

[0162] The solution was kept under reflux for a further 60 minutes and then cooled to room temperature.

[0163] Residual monomer and solvent were removed by drying under vacuum.

[0164] The resulting polymer had a glass transition temperature Tg of 41°C and a mean molecular weight Mw of 25 kDa. No incorporation of MDO could be detected by 1H NMR spectroscopy. Example 12:

[0165] Acid-modified MDO-containing polyvinyl acetate solid resin: 591 g ethyl acetate, 135 g 4-methylene-1,3-dioxepane (MDO), 187.0 g vinyl acetate (VAM), and 1.3 g tert-butyl peroxypivalate (PPV, 75%) were placed in a reactor and an equivalent of 147 g ethylene was injected. The mixture was then heated to 77°C.

[0166] A mixture of 31 g ethyl acetate and 16 g PPV (75%) was administered over 300 min.

[0167] 45 minutes after the start of the initiator dosage, the dosage of a mixture of 397 g MDO and 727 g VAM was started and administered over 220 minutes.

[0168] After the monomer dosage was complete, 93 g of acrylic acid was added over 20 minutes, followed by dilution with 713 g of ethyl acetate, which was added over 45 minutes. The mixture was refluxed for a further 50 minutes and then cooled to 30°C.

[0169] Residual monomer and solvent were removed by drying under vacuum.

[0170] The resulting multi-stage copolymer in the form of a solid resin had a glass transition temperature Tg of -15°C and a mean molecular weight Mw of 33 kDa. Example 13:

[0171] Secondary dispersion of the acid-modified MDO-containing polyvinyl acetate solid resin from Example 12, with emulsifier and protective colloid addition: 500 g of a 20% solution of the solid resin from Example 12 in acetone were mixed with 7.0 ml of dimethylethanolamine.

[0172] To this polymer solution, an emulsifier solution containing 4.0 g sodium dodecyl sulfate, 40 g of a 10% aqueous solution of polyvinyl alcohol (Mowiol 4-88), and 130 g water was added while stirring.

[0173] The resulting dispersion was sheared for 15 minutes using an IKA Ultrathurrax at 14,000 rpm. The solvent was removed using a rotary evaporator, yielding a stable secondary dispersion of the polymer.

[0174] The resulting dispersion had a solids content of 37.6%, a Brookfield viscosity of 26,340 mPas, and an average particle size Dz of 1,114 nm. Comparative example 14:

[0175] Attempt to synthesize an acrylic acid-modified, MDO-containing polyvinyl acetate solid resin with simultaneous dosing of acid monomer and MDO: 60.3 g ethyl acetate, 7.6 g 2-methylene-1,3-dioxepane (MDO), 16.5 g vinyl acetate (VAM), and 0.2 g tert-butyl peroxypivalate (PPV, 75%) were placed in a reactor and heated to 77°C. A mixture of 3.5 g ethyl acetate and 1.0 g PPV (75%) was added over 300 minutes.

[0176] 45 minutes after the start of the initiator dosage, the dosage of a mixture of 20.3 g MDO, 4.7 g acrylic acid and 44.0 g VAM was started and dosed over 240 minutes.

[0177] After the monomer dosage was complete, the mixture was diluted with 34.7 g of ethyl acetate, which was added over 45 minutes. The mixture was then refluxed for a further 60 minutes and subsequently cooled to room temperature.

[0178] Residual monomer and solvent were removed by drying under vacuum.

[0179] The resulting copolymer, in the form of a solid resin, had a glass transition temperature Tg of 17.9°C and a mean molecular weight Mw of 39 kDa. ¹H NMR spectroscopy revealed only a partial MDO incorporation of 7.9 mol% (theoretical: 24.2 mol%). Comparative example 15:

[0180] Attempt to synthesize an acrylic acid-modified, MDO-containing polyvinyl acetate solid resin by parallel dosing of acid monomer and MDO: 60.3 g ethyl acetate, 7.6 g 2-methylene-1,3-dioxepane (MDO), 16.5 g vinyl acetate (VAM), and 0.2 g tert-butyl peroxypivalate (PPV, 75%) were placed in a reactor and heated to 77°C. A mixture of 3.5 g ethyl acetate and 1.0 g PPV (75%) was added over 300 minutes.

[0181] 45 minutes after the start of the initiator dosing, the dosing of a mixture of 20.3 g MDO and 44.0 g VAM was started and continued over 240 minutes. Simultaneously, 4.7 g of acrylic acid was dosed over 240 minutes from a separate reservoir.

[0182] After the monomer dosage was complete, the mixture was diluted with 34.7 g of ethyl acetate, which was added over 45 minutes. The mixture was then refluxed for a further 60 minutes and subsequently cooled to room temperature.

[0183] Residual monomer and solvent were removed by drying under vacuum.

[0184] The resulting copolymer, in the form of a solid resin, had a glass transition temperature Tg of 16.4°C and a mean molecular weight Mw of 33 kDa. ¹H NMR spectroscopy revealed only a partial MDO incorporation of 8.8 mol% (theoretical: 24.2 mol%).

Claims

1. Multistage copolymers obtainable by means of multistage, free-radically initiated bulk or solution polymerization, characterized in that, a) in a first stage, one or more cyclic ketene acetal monomers a1) and one or more monomers a2) selected from the group comprising vinyl esters of carboxylic acids having 1 to 15 carbon atoms, methacrylic esters or acrylic esters of carboxylic acids with unbranched or branched alcohols having 1 to 15 carbon atoms, olefins, dienes, vinylaromatics and vinyl halides are copolymerized, and, b) in a further stage, one or more ethylenically unsaturated, acid group-bearing monomers b1) are polymerized in the presence of the copolymer from the first stage a).

2. The multistage copolymers as claimed in claim 1, characterized in that the multistage copolymers are in the form of solid resins, in the form of aqueous dispersions or in the form of water-redispersible powders.

3. The multistage copolymers as claimed in claim 1 or 2, characterized in that one or more cyclic ketene acetal monomers a1) are compounds of the general formula 1 in which n = 0, 1, 2 or 3; R is a hydrogen atom or a C1-C6 alkyl radical; R1 and R2 are each independently a hydrogen atom or a C1-C12 alkyl, phenyl, vinyl or halogen radical; or R1 and R2, together with the carbon atoms to which they are bonded, form a fused benzene ring or a fused C3-C7 cycloaliphatic ring; and R1' and R2' are each independently a hydrogen atom or a C1-C12 alkyl, phenyl, vinyl or halogen radical; or R1 and R1' and / or R2 and R2' form an exocyclic double bond; and R3 and R3' are each independently a hydrogen atom or a C1-C12 alkyl, phenyl, vinyl or halogen radical; or R3 and R3' form an exocyclic double bond or a spirocycloaliphatic group or a spiro-2-methylene-1,3-dioxepane group; or R3 and R3', with the carbon atoms to which they are bonded, form an internal double bond, a fused benzene ring or a fused C3-C7 cycloaliphatic ring; where optionally one or more -(CR3R3') groups are each replaced by an oxygen atom.

4. The multistage copolymers as claimed in claim 1 to 3, characterized in that one or more cyclic ketene acetal monomers a1) are selected from the group comprising 2-methylene-1,3-dioxolane, 2-methylene-4-methyl-1,3-dioxolane, 2-methylene-4,5-dimethyl-1,3-dioxolane, 8-methylene-7,9-dioxabicyclo[4.3.0]nonane, 2-methylene-1,3-dioxane, 2-methylene-5-methyl-1,3-dioxane, 2-methylene-5,5-dimethyl-1,3-dioxane, 2-methylene-1,3-dioxolane-5-spirocyclopentane, 2-methylene-1,3-dioxolane-5-spirocyclopentane, 2-methylene-1,3-dioxepane, 2-methylene-1,3-dioxocane, 2-methylene-4-phenyl-1,3-dioxolane, 4,7-dimethyl-2-methylene-1,3-dioxepane, 5,6-benzo-2-methylene-1,3-dioxepane, 2-methylene-1,3,6-trioxocane and 2-methylene-1,3,5-trioxane.

5. The multistage copolymers as claimed in claim 1 to 4, characterized in that the cyclic ketene acetal monomer a1) is 2-methylene-1,3-dioxepane.

6. The multistage copolymers as claimed in claim 1 to 5, characterized in that the multistage copolymers are based on cyclic ketene acetal monomers a1) to an extent of 20% to 70% by weight, based on the total weight of the monomers of stage a).

7. The multistage copolymers as claimed in claim 1 to 6, characterized in that the multistage copolymers are based on monomers a2) to an extent of 30% to 80% by weight, based on the total weight of the monomers of stage a).

8. The multistage copolymers as claimed in claim 1 to 7, characterized in that one or more ethylenically unsaturated, acid group-bearing monomers b1) are selected from the group comprising ethylenically unsaturated carboxylic acids, ethylenically unsaturated anhydrides, ethylenically unsaturated phosphoric acids, ethylenically unsaturated sulfonic acids, ethylenically unsaturated sulfuric acids, or salts thereof.

9. The multistage copolymers as claimed in claim 1 to 8, characterized in that the multistage copolymers are based on monomers b1) to an extent of 0.5% to 15% by weight, based on the total weight of the monomers of stage a).

10. The multistage copolymers as claimed in claim 1 to 9, characterized in that the multistage copolymers are based on monomers b1) to an extent of 25% to 100% by weight, based on the total weight of the monomers of stage b).

11. The multistage copolymers as claimed in claim 1 to 10, characterized in that exclusively monomers b1) are used as ethylenically unsaturated monomers in stage b).

12. A process for preparing the multistage copolymers from claim 1 to 11 by means of multistage, free-radically initiated bulk or solution polymerization, characterized in that, a) in a first stage, one or more cyclic ketene acetal monomers a1) and one or more monomers a2) selected from the group comprising vinyl esters of carboxylic acids having 1 to 15 carbon atoms, methacrylic esters or acrylic esters of carboxylic acids with unbranched or branched alcohols having 1 to 15 carbon atoms, olefins, dienes, vinylaromatics and vinyl halides are copolymerized and, b) in a further stage, one or more ethylenically unsaturated, acid group-bearing monomers b1) are polymerized in the presence of the copolymer from the first stage a).

13. The process for preparing the multistage copolymers as claimed in claim 12, characterized in that polymerization is effected in the absence of emulsifiers and / or protective colloids.

14. The process for preparing the multistage copolymers in the form of aqueous dispersions, characterized in that multistage copolymers are prepared as claimed in claim 12 or 13 and dispersed in water.

15. The process for preparing the multistage copolymers as claimed in claim 12 to 14, characterized in that the multistage copolymers are admixed with one or more organic or inorganic bases.

16. The process for preparing the multistage copolymers as claimed in claim 12 to 15, characterized in that one or more emulsifiers and / or one or more protective colloids are added to the multistage copolymers.

17. The use of the multistage copolymers from claim 1 to 11 as binders for coating compositions or adhesives, in particular for paints, textiles, paper or carpets, or in construction-chemical products.