The present invention refers to a waterborne homo or copolymer dispersion obtained by homo or copolymerisation in an aqueous medium of at least one alkyl crotonate and/or at least one crotonic acid.

The most important industrial method for the manufacture of aqueous dispersion polymers is emulsion polymerisation. Emulsion polymerisation is well known in the art and frequently disclosed and discussed in the patent literature, in handbooks and encyclopaedias. Emulsion polymerisation is typically performed in an aqueous medium in the presence of a surfactant and a water-soluble initiator and is usually rapidly giving high molecular weight homo or copolymers at high solids content, typically 30-60%, and low dispersion viscosity. Traditional applications for these aqueous dispersions are mainly adhesives, binders for fibres, protective and decorative coatings, foam, paper coatings and thread and textile modifiers.

It has now quite unexpectedly been found that alkyl crotonates and/or crotonic acids can, despite previous assumptions and disclosures negating the possibility, yield excellent waterborne homo and copolymer dispersions for use as disclosed above. The present invention accordingly refers to a novel waterborne homo or preferably copolymer dispersion obtained by homo or preferably copolymerisation in an aqueous medium of at least one alkyl crotonate or isocrotonate, preferably a Ci-Cis alkyl crotonate or isocrotonate, such as methyl crotonate, ethyl crotonate, n-butyl crotonate, isobutyl crotonate, t-butyl crotonate, 2-ethylhexyl crotonate, 2-propylheptyl crotonate, neopentyl crotonate, glycidyl crotonate, vinyl crotonate, methyl isocrotonate, ethyl isocrotonate, n-butyl isocrotonate, isobutyl isocrotonate, t-butyl isocrotonate, 2-ethylhexyl isocrotonate, 2-propylheptyl isocrotonate, neopentyl isocrotonate, glycidyl isocrotonate, vinyl isocrotonate and/or at least one crotonic acid, such as crotonic acid and/or isocrotonic acid.

Further suitable alkyl crotonates include alkyl dicrotonates and alkyl diisocrotonates of diols, such as ethylene glycol, 1 ,2-propanediol, 1,3-propanediol, butylene glycols, and 2-alkyl-l ,3-propanediols, 2,2-dialkyl-l,3-propanediols, such as neopentyl glycol and 2-ethyl-2-butyl- 1 ,3-propanediol. Of course, also mono(iso)crotonates of diols, mono, di and tri(iso)crotonates of triols and mono di, tri and higher (iso)crotonates of polyols can be included, such as trimethylolpropane mono, di or tricrotonate or isocrotonate.

Further suitable monomers in a copolymerisation include, but are not limited to alkyl acrylates and/or alkyl methacrylates, preferably Ci-C ₁₈ alkyl acrylates or methacrylates, such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and/or acrylic acid and/or methacrylic acid, and/or polymerisable allyl, vinyl, maleic and/or diene monomers, such as, but not limited to, itaconic acid, cinnamic acid, maleic anhydride, fumaric acid, glycidyl acrylates, glycidyl methacrylates, acrylamides, methacrylamides, ethyl imidazolidon methacrylates, ethylene, propylene, styrene, divinylstyrene, vinylacetate, vinyl propionates, vinyl versatates, dibutyl maleate and/or butadiene or isoprene.

The homo or copolymer dispersion of the present invention is yielded in either a one stage or a multistage emulsion homo or copolymerisation. Said emulsion polymerisation may for instance yield latex particles having a heterogeneous morphology, such as a core-shell morphology. When monomers of different solubility or hydrophobicity are used or when staged polymerisations are carried out, core-shell morphologies are possible. In staged polymerisations, spherical core-shell particles are made when a polymer made from a first monomer is more hydrophobic than a polymer made from a second monomer.

Further embodiments of the dispersion according to the present invention include species comprising at least one polymerisable surfactant, such as a surfactant comprising at least one alkenyl group, and/or a conventional surfactant.

A copolymer according to the present invention is such that the crotonate based content of the total content, with water and/or other solvents excluded, is 0.1-99.9%, such as 5-60%, 5-30% or 10-25%), by weight. Storage stability, glass transition temperature and particle size distribution are important parameters whose optima are to be found within the monomer content levels given above.

Furthermore, crotonic acid and crotonic acid derivatives can be used together with mercaptans in the so called thiol-ene reaction to produce a crosslinked system. Thiol-enes can be part of hybrid systems that involve both thiol-enes and other types of systems, such as radical polymerised unsaturations. By this, the property range of the coatings can be expanded. Thiol-ene networks, due to their almost perfect network structure that is much more uniform than even epoxy networks, can be fabricated to exhibit a wide range of benchmark properties including rubber-like materials with resiliencies of greater than 95%o, glassy materials with properties resembling traditional rubbery materials (i.e. glasses that bounce better than conventional crosslinked super balls), and high energy absorbing materials for personal protection. These properties can be advantageous also for coating applications. Yet furthermore, cellulose can be modified, preferably covalently bonded, with crotonic acid and crotonic acid derivatives to obtain increased stability and/or a crosslinked structure.

In a further aspect, the present invention refers to the use of said novel waterborne homo or copolymer dispersion, as disclosed above, in binders for coatings, such as decorative and/or protective paints and lacquers, adhesives and glues. The following specific embodiments, Examples 1 -5, relating to preparations of polymers according to the present invention, are to be construed as merely illustrative and not limitative in any way whatsoever.

Example 1

Mixtures a), b) and c) were prepared according to the following:

a) Water, emulsifier Disponil ^® AES 72 (alkylaryl polyglycol ether sulphate, sodium salt, Cognis) and sodium acetate as buffer (calculated on 35% by weight on ammonium persulphate), heated to 80°C.

b) Monomer mixture: Ethyl crotonate, styrene and acrylic acid, room temperature.

c) Initiator solution: 25% by weight of ammonium persulphate in water, room temperature.

Procedure: a) was heated to 80°C and 10% of b) and c) were charged. Portions of b) and c) were every 20 minutes (during 4 hrs.) added. After completed addition, stirring at 80°C was carried out for one hour. Equipment: Teflon stirrer 100-150 rpm, oil bath and reaction vessel equipped with cooler and nitrogen inlet.

Following properties on yielded product were determined: Molecular weight (Mn) and molecular weight (Mw) by GPC (General Purpose Chromatography), polydispersity and glass transition temperature (Tg) by DSC (Differential Scanning Calorimetry).

Material Parts by weig

Water 477

Disponir AES 72 54

Sodium acetate 2 x 0.35

Ethyl crotonate 220

Styrene 220

Acrylic acid 25

Ammonium persulphate 2

Yielded product exibited following properties:

Mn, g/mol: 5800

Mw, g/mol: 17000

Polydispersity: 2.9

Tg, °C: 33 Example 2

Performed as Example 1 with the difference that the monomer mixture consisted of ethyl crotonate, methyl methacrylate and acrylic acid.

Material Parts by weig

Water 477

Disponil ^® AES 72 54

Sodium acetate 2 x 0.35

Ethyl crotonate 220

Methyl methacrylate 220

Acrylic acid 25

Ammonium persulphate 2

Yielded product exibited following properties:

Mn g/mol (GPC): 8500

Mw g/mol (GPC): 22000

Polydispersity: 2.6

Tg °C, (DSC): -2.6

Example 3

Performed as Example 1 with the difference that the monomer mixture consisted of ethyl crotonate, methyl methacrylate, butyl acrylate and acrylic acid.

Material Parts by weight

Water 477

Disponil ^® AES 72 54

Sodium acetate 2 x 0.35

Ethyl crotonate 86

Methyl methacrylate 225

Butyl acrylate 139

Acrylic acid 14

Ammonium persulphate 2 Yielded product exibited following properties:

Mn g/mol (GPC): 4300

Mw g/mol (GPC): 48000

Polydispersity: 1 1

Tg °C, (DSC): 4

Example 4

Performed as Example 1 with the difference that the monomer mixture consisted of ethyl crotonate, methyl methacrylate and acrylic acid.

Material Parts by weight

Water 477

Disponil ^® AES 72 54

Sodium acetate 2 x 0.35

Ethyl crotonate 86

methyl methacrylate 225

Butyl acrylate 139

Acrylic acid 14

Ammonium persulphate 2

Yielded product exibited following properties:

Mn g/mol (GPC): 1100

Mw g/mol (GPC): 158000

Polydispersity: 14.5

Tg °C, (DSC): 15

Example 5

Performed as Example 1 with the difference that the monomer mixture consisted of ethyl crotonate, methyl methacrylate and acrylic acid. Material Parts by weig

Water 477

Disponil ^® AES 72 54 Sodium acetate 2 x 0.35 Ethyl crotonate 102 Vinyl acetate 348 Acrylic acid 14

Ammonium persulphate 2

Yielded product exibited following properties:

Mn g/mol (GPC): 900

Mw g/mol (GPC): 5400

Polydispersity: 6.3

Tg °C, (DSC): 10