Production of alkyl(meth)acrylate polyester copolymers by means of suspension polymerization

Description

Field of the invention

[0001] The present invention relates to a process for producing alkyl (meth)acrylate-polyester copolymers by suspension polymerization, as well as to the alkyl (meth)acrylate-polyester copolymers thus produced. The process according to the invention, in particular, avoids the use of styrene in the production process. The alkyl (meth)acrylate-polyester copolymers produced according to the invention can be used, in particular, as binders in printing inks. State of the art

[0002] WO 2007 / 098819 A1 describes a composition containing a copolyester, a (meth)acrylate homo- or copolymer, and a graft copolymer of these two. Production takes place in the absence of styrene by solution or bulk polymerization.

[0003] The composition described in WO 2007 / 098819 A1 already possesses good properties as a compatibilizer and can therefore be used as a binder for printing inks. However, its production is complex and cost-intensive. Furthermore, the composition described in WO 2007 / 098819 A1 is obtained as a dissolved composition during solution polymerization, so that the solvent in the subsequent application of the composition is determined by the solvent used in the solution polymerization, in particular propyl acetate. This deprives the user of the freedom to choose the solvent in the subsequent application of the composition.

[0004] JP 11158204 describes the suspension polymerization of a monomer mixture containing styrene and an ethylenically unsaturated polyester, using polyvinyl alcohol as an emulsifier. The described process produces uniformly sized polymer particles.

[0005] JP 09241490 describes the suspension polymerization of a monomer mixture containing a polyethylene terephthalate, a vinyl monomer, and an unsaturated carboxylic acid amide in the presence of a germanium catalyst. The resulting polymer can be used, among other things, for the production of films and moldings.

[0006] EP 0 462 785 describes a resin composition for toners comprising a suspension polymer of a polyester, a vinyl monomer, and a divinyl monomer. The polyester is a polycondensate of terephthalic acid, isophthalic acid, a hydroxyphenylpropane, and various glycols.

[0007] Some of the copolymers of vinyl monomers and polyesters described in the prior art do not have sufficiently good properties for use as phase compatibilizers and binders in printing inks. Furthermore, some of them contain styrene. However, in various applications, such as areas with food contact or in items with which children come into direct contact, aromatic monomers such as styrene are undesirable, if not prohibited. Furthermore, aromatic monomers often cause unpleasant odors during subsequent use of the copolymers. Task

[0008] There was therefore a need for a process for producing polymer mixtures containing alkyl (meth)acrylate-polyester copolymers that does not have, or only to a reduced extent, the disadvantages of the processes described in the prior art. Furthermore, the polymer mixture containing the alkyl (meth)acrylate-polyester copolymer should be particularly suitable as a binder in printing inks. Solution

[0009] This object was achieved by a process for producing a polymer mixture containing an alkyl (meth)acrylate-polyester copolymer, comprising the steps: a) Providing a first liquid phase containing at least one alkyl (meth)acrylate monomer and at least one polyester dissolved in the alkyl (meth)acrylate monomer, b) Providing a second liquid phase containing water and at least one suspension aid dispersed therein, c) Dispersing the first liquid phase in the second liquid phase, whereby droplets of the first liquid phase form in the second liquid phase, d) Polymerizing the at least one alkyl (meth)acrylate monomer and the at least one polyester contained in the first liquid phase to obtain the polymer mixture containing the alkyl (meth)acrylate-polyester copolymer, wherein the polymerization in step d) is initiated by at least one initiator which is provided either in the first liquid phase in step a) or in the second liquid phase in step b), wherein the at least one polyester comprises polycarboxylic acid units and polyol units, wherein the at least one polyester comprises in the range of 0.1 to 10 mol% polycarboxylic acid units having a CC double bond, based on the total molar amount of polycarboxylic acid units.

[0010] It has surprisingly been found that the process according to the invention can be used to produce polymer mixtures that are suitable as binders for printing inks and that exhibit very good adhesion, particularly to polyethylene terephthalate (PET), polyvinyl chloride (PVC), polypropylene (PP), polybutylene terephthalate (PBT), and polystyrene (PS). At the same time, the use of styrene can be dispensed with in the process according to the invention.

[0011] The process according to the invention also allows for the rapid, solvent-free production of polymer mixtures. The process according to the invention allows the polymer mixtures to be obtained as solids, eliminating the need for laborious solvent removal. Thus, the polymer mixture produced according to the invention is not limited to a specific solvent. This is particularly advantageous when the polymer mixtures produced according to the invention are used, for example, as binders in printing inks, since common solvents such as ethyl acetate can also be used for printing inks.

[0012] Since the polymer blends are obtained as solids that are essentially free of solvent, there is no dependence on a specific solvent system in subsequent applications, as is the case, for example, with production by solution polymerization. Since the resulting polymer blends contain no solvent, their transport and storage costs are significantly reduced.

[0013] The process according to the invention also allows for very good space-time yields, and known equipment can be used. At the same time, gelation of the alkyl (meth)acrylate-polyester copolymer contained in the polymer mixture is avoided by the process according to the invention.

[0014] Surprisingly, it was also found that the polymer blends produced according to the invention have properties comparable to those of copolymers described in the prior art, even though they contain less polyester in a preferred embodiment of the process according to the invention. The lower polyester content also has a beneficial effect on the overall costs of the process according to the invention.

[0015] The method according to the invention is described in more detail below.

[0016] In step a) of the process according to the invention, a first liquid phase containing at least one alkyl (meth)acrylate monomer and at least one polyester dissolved in the alkyl (meth)acrylate monomer is provided.

[0017] To prepare the first liquid phase, the at least one polyester is dissolved in the at least one alkyl (meth)acrylate monomer. The at least one polyester can be dissolved by any method known to the person skilled in the art. Preferably, the at least one alkyl (meth)acrylate monomer is brought to a temperature in the range of 20°C to 45°C to dissolve the at least one polyester.

[0018] Preferably, the at least one polyester is dissolved in the alkyl (meth)acrylate while stirring.

[0019] In the first liquid phase, the at least one alkyl (meth)acrylate monomer and the at least one polyester are homogeneously distributed.

[0020] The first liquid phase contains, for example, in the range of 0.1 to 15 wt.% of the at least one polyester, preferably in the range of 0.5 to 5 wt.%, particularly preferably in the range of 2.5 to 3.5 wt.%, based on the total weight of the first liquid phase.

[0021] Therefore, a process is also preferred in which the first liquid phase contains in the range of 0.1 to 15 wt.% of the at least one polyester, based on the total weight of the first liquid phase.

[0022] Accordingly, the first liquid phase contains, for example, in the range of 85 to 99.9 wt.% of alkyl (meth)acrylate monomer, preferably in the range of 95 to 99.5 wt.%, particularly preferably in the range of 96.5 to 97.5 wt.%, based on the total weight of the first liquid phase.

[0023] Preferably, the wt.% of the polyester, the alkyl (meth)acrylate monomer and the at least one initiator and the further comonomer described below, optionally provided in the first liquid phase, add up to 100 wt.% in the first liquid phase.

[0024] It is preferred that the first liquid phase does not contain any further solvent apart from the alkyl (meth)acrylate monomer.

[0025] The first liquid phase preferably consists of the alkyl (meth)acrylate monomer, the polyester and optionally the initiator and the further comonomer.

[0026] The wt.% of the polyester, the alkyl (meth)acrylate monomer and optionally the initiator and the further comonomer refer to the wt.% before the polyester, the alkyl (meth)acrylate monomer, the initiator and the further comonomer have reacted with each other.

[0027] For the purposes of the present invention, "alkyl (meth)acrylate monomers" refers to both alkyl methacrylate monomers and alkyl acrylate monomers. C 1 -C 12 alkyl (meth)acrylate monomers are preferred. C 1 -C 12 alkyl (meth)acrylate monomers are understood to be alkyl esters of (meth)acrylic acid containing 1 to 12 carbon atoms in the alkyl radical. The alkyl radical can be linear, cyclic, and / or branched. Furthermore, it can also contain aromatic radicals.

[0028] The term "(meth)acrylic acid" in the context of the present invention includes both acrylic acid and methacrylic acid.

[0029] For example, alkyl (meth)acrylate monomers according to the invention are selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isopentyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate or lauryl (meth)acrylate.

[0030] Preferred alkyl (meth)acrylate monomers are methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methyl acrylate, n-butyl acrylate, isopentyl methacrylate and mixtures thereof.

[0031] According to the invention, therefore, a process is also preferred in which the at least one alkyl (meth)acrylate monomer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isopentyl methacrylate, methyl acrylate, n-butyl acrylate and mixtures thereof.

[0032] The at least one polyester is produced by polycondensation of polycarboxylic acids with polyols. It is known to those skilled in the art that derivatives of the polycarboxylic acids, such as their lower alkyl esters and / or their anhydrides, can also be used in the polycondensation.

[0033] For the purposes of the present invention, "polycarboxylic acids" are understood to mean compounds containing at least two carboxyl groups. The polycarboxylic acids used in the polycondensation preferably contain exactly two carboxyl groups. The polycarboxylic acids are then also referred to as dicarboxylic acids.

[0034] Suitable polycarboxylic acids are polycarboxylic acids known to the person skilled in the art, such as, for example, aliphatic polycarboxylic acids, cycloaliphatic polycarboxylic acids and / or aromatic polycarboxylic acids.

[0035] Suitable polycarboxylic acids are, for example, selected from the group consisting of succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, octadecanedioic acid, cyclohexanedicarboxylic acid and its isomers, benzenedicarboxylic acid and its isomers and trimellitic acid.

[0036] The at least one polyester comprises in the range of 0.1 to 10 mol%, preferably in the range of 0.2 to 5 mol% and particularly preferably in the range of 0.5 to 1.5 mol% of polycarboxylic acid units with a CC double bond, based on the total amount of polycarboxylic acid units.

[0037] To produce the polyester, a mixture of the aforementioned polycarboxylic acids and an unsaturated polycarboxylic acid is typically used. An unsaturated polycarboxylic acid is defined as a polycarboxylic acid containing at least one carbon-carbon double bond. The carbon-carbon double bond can, for example, be located in the backbone of the polycarboxylic acid. Examples of such polycarboxylic acids include fumaric acid, maleic acid, and mesaconic acid.

[0038] Furthermore, the CC double bond can be arranged as a side group in the polycarboxylic acid. One such polycarboxylic acid is itaconic acid.

[0039] In the context of the present invention, a CC double bond which is arranged as a side group in the polycarboxylic acid and comprises an H 2 C=C unit is also referred to as a vinyl group.

[0040] The CC double bond is preferably a vinyl group.

[0041] According to the invention, therefore, a process is also preferred in which the CC double bond contained in the at least one polyester is a vinyl group.

[0042] Furthermore, according to the invention, it is preferred that the vinyl group is present in an itaconic acid unit. It is therefore preferred that the polycarboxylic acid units with a carbon-carbon double bond are itaconic acid units.

[0043] It is therefore preferred according to the invention that the at least one polyester is produced / obtainable by polycondensation of polycarboxylic acids and polyols, wherein itaconic acid is used in an amount of 0.1 to 10 mol%, preferably in the range of 0.2 to 5 mol% and particularly preferably in the range of 0.5 to 1.5 mol%, based on the total amount of polycarboxylic acids.

[0044] For the purposes of the present invention, polyols are understood to be compounds containing at least two hydroxyl groups. The polyols used in the polycondensation preferably contain exactly two hydroxyl groups. The polyols are then also referred to as diols.

[0045] Suitable polyols are those known to those skilled in the art, such as aliphatic polyols, aromatic polyols, and / or ether diols. Aliphatic polyols are preferred.

[0046] Suitable polyols are, for example, selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,12-dodecanediol, neopentyl glycol, 1,3-butylethylpropanediol, 1,3-methylpropanediol, methylpentanediol, cyclohexanedimethanol, trimethylolpropane, pentaerythritol, hydroquinone, bisphenol A, bisphenol F, dihydroxynaphthalene, ether diols of the above-mentioned and mixtures thereof.

[0047] Processes for producing polyesters are known per se. For example, they can be obtained by polycondensation of the polyols with the polycarboxylic acids or their esters, anhydrides, and / or acid chlorides in an inert gas atmosphere at temperatures from 100°C to 260°C, preferably from 130°C to 240°C, in the melt or by an azeotropic process, as described, for example, in Methoden der organischen Chemie (Houben-Weyl), Vol. 14 / 2, 1-5, 21-23, 40-22, Georg Thieme Verlag, Stuttgart, 1963; in CR Martens, Alkyl Resins, 51-59, Reinhold Plastics Appl., Series, Reinhold Publishing Comp., New York, 1961; or in DE 27 35 497.

[0048] According to the invention, the at least one polyester comprises polycarboxylic acid units and polyol units.

[0049] For the purposes of the present invention, polycarboxylic acid units are understood to be units in the polyester derived from the polycarboxylic acid. For the purposes of the present invention, polyol units are understood to be units in the polyester derived from the polyol. Polyester blocks are formed by condensation of the polyol with the polycarboxylic acid. The block derived from the polycarboxylic acid therein is referred to as the polycarboxylic acid unit for the purposes of the present invention. The block derived from the polyol therein is referred to as the polyol unit for the purposes of the present invention.

[0050] The polycarboxylic acid units are preferably dicarboxylic acid units formed by the condensation of a dicarboxylic acid with a polyol. The polyol units are preferably diol units formed by the condensation of a diol with the polycarboxylic acid. Particularly preferred are the polycarboxylic acid units dicarboxylic acid units, and the polyol units diol units. They are formed by the condensation of a dicarboxylic acid with a diol.

[0051] For example, the at least one polyester has an OH number (hydroxyl number) in the range from 5 mg(KOH) / g to 150 mg(KOH) / g, preferably in the range from 10 mg(KOH) / g to 50 mg(KOH) / g.

[0052] The at least one polyester has, for example, an acid number of less than 10 mg(KOH) / g, preferably less than 5 mg(KOH) / g and particularly preferably less than 2 mg(KOH) / g.

[0053] The at least one polyester has, for example, a number-average molecular weight (Mn) in the range from 700 to 25,000 g / mol, preferably in the range from 2,000 to 12,000 g / mol, determined by GPC or HPLC, each with PMMA as standard.

[0054] At least one initiator can also be provided in the first liquid phase. If the at least one initiator is provided in the first liquid phase in step a), preferably no initiator is provided in the second liquid phase described below in step b).

[0055] In the context of the present invention, "provided either in the first liquid phase in step a) or in the second liquid phase in step b)" means that preferably the at least one initiator is either provided only in the first liquid phase in step a), but not in the second liquid phase in step b), or that the at least one initiator is provided only in the second liquid phase in step b), but not in the first liquid phase in step a).

[0056] It goes without saying that the at least one initiator is preferably provided only in the first liquid phase or only in the second liquid phase, but that the at least one initiator can diffuse from the first liquid phase into the second liquid phase or vice versa during the process according to the invention, in particular during at least one of steps c) and d).

[0057] If the at least one initiator is provided in the first liquid phase in step a), it is usually also dissolved in the at least one alkyl (meth)acrylate monomer and is thus present as an initiator dissolved in the at least one alkyl (meth)acrylate monomer.

[0058] For example, in the range of 0.1 to 20 wt.%, preferably 0.5 to 5 wt.% of the at least one initiator is provided in the first liquid phase in step a), based on the total weight of the first liquid phase.

[0059] Preferably, the at least one initiator is provided in the second liquid phase in step b). It is therefore preferred that the first liquid phase be provided without an initiator.

[0060] In an alternative preferred embodiment, the at least one initiator is provided in the first liquid phase in step a). It is then preferred that the second liquid phase be provided without an initiator.

[0061] Suitable initiators include all compounds known to those skilled in the art that can initiate radical polymerization. For example, the at least one initiator is selected from the group consisting of peroxides, azo compounds, persulfates, and mixtures thereof. Preferably, the initiator is selected from the group consisting of peroxides, azo compounds, and mixtures thereof.

[0062] Therefore, a process is also preferred in which the at least one initiator is selected from the group consisting of peroxides, azo compounds and mixtures thereof.

[0063] Suitable peroxides are, for example, selected from the group consisting of hydrogen peroxide, dibenzoyl peroxide, dicyclohexyl peroxodicarbonate, dilauryl peroxide, methyl ethyl ketone peroxide, acetylacetone peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, tert-butyl peroctanoate, tert-butyl per-2-ethylhexanoate, tert-butyl perneodecanoate, tert-amyl perpivalate, tert-butyl perpivalate, tert-butyl perbenzoate, di(tert-amyl) peroxide (DTAP), tert-butyl peroxy-(2-ethylhexyl)carbonate (TBPEHC), tert-butyl per-2-ethylhexanoate, dicumyl peroxide, diisopropyl peroxydicarbonate and bis(4-t-butylcyclohexyl)peroxydicarbonate.

[0064] Suitable azo compounds are, for example, selected from the group consisting of 2,2-azobisiso-2,4-dimethylvaleronitrile, 2,2-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2-(carbamoylazo)isobutyronitrile and 4,4'-azobis(cyanovaleric acid).

[0065] Suitable persulfates are, for example, selected from the group consisting of lithium peroxodisulfate, sodium peroxodisulfate, potassium peroxodisulfate and ammonium peroxodisulfate.

[0066] Furthermore, the first liquid phase may additionally contain a further comonomer. In the context of the present invention, a "further comonomer" is understood to mean a monomer that is copolymerizable with the at least one alkyl (meth)acrylate monomer. It goes without saying that the further comonomer is different from the at least one alkyl (meth)acrylate monomer. In the context of the present invention, "a further comonomer" means both precisely one further comonomer and a mixture of two or more comonomers.

[0067] Such further comonomers are known to the person skilled in the art and are, for example, (meth)acrylic acid, hydroxyethyl methacrylate and / or hydroxypropyl methacrylate.

[0068] For example, the first liquid phase contains in the range of 0 to 20 wt.%, preferably in the range of 0 to 10 wt.% of the further comonomer, based on the total weight of the first liquid phase.

[0069] In one embodiment of the invention, the first liquid phase contains no further comonomer.

[0070] It is particularly preferred that the first liquid phase does not contain styrene.

[0071] In step b), a second liquid phase containing water and at least one suspension aid dispersed therein is provided.

[0072] For example, the second liquid phase can be provided by dispersing the suspension aid in water while stirring.

[0073] The second liquid phase in step b) can be provided at any temperature, preferably it is provided at a temperature in the range of 25 °C to 80 °C, more preferably in the range of 37 °C to 65 °C.

[0074] In the second liquid phase, water typically forms the continuous phase; the suspending agent forms the dispersed phase. The second liquid phase is usually present as a suspension. The suspending agent is present as solid particles in the water.

[0075] Suitable suspension aids include all suspension aids known to the person skilled in the art, such as polyacrylic acids, salts of polyacrylic acids, and / or Pickering systems. Suitable Pickering systems include, for example, colloidal silicon dioxide and / or aluminum hydroxide. A Pickering system made of aluminum hydroxide is preferably made from aluminum sulfate and sodium carbonate (soda).

[0076] Preferably, the suspension aid is selected from the group consisting of polyacrylic acids, salts of polyacrylic acids and Pickering systems of aluminum hydroxide.

[0077] A preferred process is therefore one in which the at least one suspension aid contained in the second liquid phase is selected from the group consisting of polyacrylic acids, salts of polyacrylic acids, and Pickering systems of aluminum hydroxide. For example, the second liquid phase contains in the range of 0.01 to 10 wt. %, preferably in the range of 0.02 to 5 wt. %, of suspension aid, based on the total weight of the second liquid phase.

[0078] Accordingly, the second liquid phase contains, for example, in the range of 90 to 99.99 wt.%, preferably in the range of 95 to 99.98 wt.% of water, based on the total weight of the second liquid phase.

[0079] The at least one initiator can be provided in the second liquid phase in step b). If the initiator is provided in the second liquid phase in step b), the same statements and preferences apply to it as above for the initiator provided in the first liquid phase in step a).

[0080] For example, in the range of 0.1 to 20 wt.%, preferably in the range of 0.2 to 10 wt.% of initiator is provided in the second liquid phase in step b), based on the total weight of the second liquid phase.

[0081] In step c), the first liquid phase is dispersed in the second liquid phase, whereby drops of the first liquid phase are formed in the second liquid phase.

[0082] The first liquid phase is usually essentially insoluble in the second liquid phase.

[0083] Dispersing in step c) is typically carried out with stirring. Droplets of the first liquid phase form in the second liquid phase. The droplets contain the alkyl (meth)acrylate monomer and the polyester dissolved therein, as well as, if appropriate, the other comonomer. The droplets also contain at least one initiator, either by providing the initiator in the first liquid phase or by diffusion of the initiator from the second liquid phase into the first liquid phase.

[0084] The suspension agent contained in the second liquid phase typically surrounds the droplets of the first liquid phase, forming a boundary layer between the first liquid phase and the second liquid phase. The suspension agent thereby stabilizes the droplets of the first liquid phase in the second liquid phase.

[0085] Typically, the first liquid phase and the second liquid phase form an emulsion. The first liquid phase forms the dispersed phase, while the second liquid phase forms the continuous phase.

[0086] The drops of the first liquid phase in the second liquid phase obtained in step c) have, for example, an average diameter d 50 according to Coulter in the range from 0.01 mm to 5 mm, preferably in the range from 0.05 mm to 0.40 mm.

[0087] Therefore, a process is also preferred in which the drops of the first liquid phase obtained in step c) have an average diameter d 50 according to Coulter in the range from 0.01 mm to 5 mm.

[0088] The weight ratio of the first liquid phase to the second liquid phase in step c) is, for example, in the range from 1:2 to 2:1, preferably about 1:1.

[0089] Therefore, a process is also preferred in which the weight ratio of the first liquid phase to the second liquid phase during dispersion in step c) is in the range from 1:2 to 2:1.

[0090] Dispersing in step c) typically takes place at a temperature below the temperature at which the alkyl (meth)acrylate monomer and / or the polyester present in the first liquid phase polymerize. For example, dispersion in step c) takes place at a temperature in the range of 20 °C to <50 °C, preferably in the range of 35 °C to 45 °C.

[0091] In step d), the alkyl (meth)acrylate monomer and the polyester contained in the first liquid phase, as well as optionally the further comonomer, are polymerized to obtain the polymer mixture containing the alkyl (meth)acrylate-polyester copolymer.

[0092] Polymerization usually takes place with stirring.

[0093] The polymerization in step d) is usually initiated by the initiator. For example, the initiator forms radicals upon activation by light and / or at elevated temperatures, for example, in the range of 50 °C to 100 °C, preferably in the range of 65 °C to 85 °C. These radicals initiate radical formation at the CC double bond of the alkyl (meth)acrylate monomer and / or at the CC double bond of the polyester. These reactions are known as such.

[0094] The polymerization in step d) takes place, for example, at a temperature in the range from 50 °C to 100 °C, preferably in the range from 65 °C to 85 °C.

[0095] Therefore, a process is also preferred in which the polymerization in step d) takes place at a temperature in the range from 50 °C to 100 °C.

[0096] In step d), the polymer mixture is typically obtained as a solid dispersed in the second liquid phase. The polymer mixture obtained in step d) is typically essentially insoluble in the second liquid phase.

[0097] The second liquid phase then forms a suspension with the polymer mixture. The second liquid phase forms the continuous phase, while the polymer mixture forms the dispersed phase.

[0098] In step d), the polymer mixture containing the alkyl (meth)acrylate-polyester copolymer is obtained.

[0099] During the polymerization in step d), the at least one alkyl (meth)acrylate monomer polymerizes with the polyester. This reaction typically forms the alkyl (meth)acrylate-polyester copolymer. During the polymerization, the initiator forms radicals at the CC double bond of the polycarboxylic acid units of the polyester and / or at the CC double bond of the alkyl (meth)acrylate monomers. These radicals can react with each other and / or initiate the formation of further radicals, thereby leading to polymerization. This reaction is known as such.

[0100] This can, for example, result in the formation of a graft copolymer containing the alkyl (meth)acrylate monomer or its polymers, optionally with the additional comonomer, grafted onto the polyester or its copolymers. Polyester main chains and polyalkyl (meth)acrylate side chains are then formed. Within the scope of the present invention, the term "alkyl (meth)acrylate-polyester copolymer" therefore also encompasses such graft copolymers.

[0101] Alternatively or additionally, it is possible to form block copolymers containing a block of alkyl (meth)acrylate polymers, optionally with other comonomers, and a block of the polyester or its copolymers. Within the scope of the present invention, the term "alkyl (meth)acrylate-polyester copolymer" therefore also encompasses such block copolymers.

[0102] The polymer mixture contains, for example, in the range of 5 to 95 wt.%, preferably in the range of 10 to 50 wt.% and particularly preferably in the range of 20 to 30 wt.% of the alkyl (meth)acrylate-polyester copolymer, based on the total weight of the polymer mixture.

[0103] During the polymerization in step d), the polyester also typically polymerizes with itself to yield at least one copolyester. Likewise, the at least one alkyl (meth)acrylate monomer can polymerize with itself and optionally with the further comonomer to yield at least one alkyl (meth)acrylate polymer.

[0104] Therefore, the polymer mixture obtained in step d) usually contains, in addition to the alkyl (meth)acrylate-polyester copolymer, further polymers, in particular it usually contains at least one copolyester and / or at least one alkyl (meth)acrylate polymer.

[0105] In addition, it is possible that parts of the polyester and / or parts of the alkyl (meth)acrylate monomers do not react and are contained in the polymer mixture.

[0106] Alkyl (meth)acrylate monomers, as well as any other comonomers, can usually be largely removed from the polymer mixture by drying.

[0107] Therefore, a process in which the polymer mixture additionally contains at least one polyester, at least one copolyester, and / or at least one alkyl (meth)acrylate polymer is also preferred. Preferably, it additionally contains at least one polyester, at least one copolyester, and at least one alkyl (meth)acrylate polymer.

[0108] The total amount of polyester and copolyester in the polymer mixture is, for example, in the range from 0.01 to 15 wt.%, preferably in the range from 0.01 to 5 wt.% and particularly preferably in the range from 0.01 to 2 wt.%, in each case based on the total weight of the polymer mixture.

[0109] The polymer mixture contains, for example, in the range from 5 to 95 wt.%, preferably in the range from 50 to 90 wt.% and particularly preferably in the range from 70 to 80 wt.% of at least one alkyl (meth)acrylate polymer, in each case based on the total weight of the polymer mixture.

[0110] Following step d), the polymer mixture is typically separated from the second liquid phase. Separation can be carried out by any method known to those skilled in the art, for example, by filtration followed by drying. Filtration can be carried out using continuously operated decanters and centrifuges, and drying can be carried out using continuously operated fluidized bed dryers.

[0111] Therefore, a process is also preferred in which the polymer mixture obtained in step d) is dried after step d).

[0112] After drying, the resulting polymer mixture is typically substantially free of water. For example, the polymer mixture contains at most 5% by weight, preferably at most 1% by weight, of water, based on the total weight of the polymer mixture.

[0113] The polymer mixture is typically obtained in step d) in the form of polymer beads. These preferably have an average diameter d50, determined according to the Coulter method, in the range of 0.01 to 0.6 mm.

[0114] For example, the polymer mixture has a glass transition temperature Tg in the range of 50 °C to 70 °C, determined by differential scanning calorimetry (DSC) according to DIN EN ISO 11357-4.

[0115] According to the invention, the process according to the invention preferably takes place in the absence of styrene. In particular, it is preferred that styrene is not used in any of steps a) to d).

[0116] Steps a) to d) of the method according to the invention can be performed in the specified order. A different order is also possible. Steps can also be performed simultaneously. For example, the order of steps a) and b) can be reversed and / or steps a) and b) can be performed simultaneously. Furthermore, additional steps can be performed.

[0117] The present invention also relates to a polymer mixture obtainable by the process according to the invention.

[0118] The previously described specifications and preferences apply to the polymer mixture.

[0119] The polymer mixture according to the invention is particularly suitable as a binder in printing inks. Furthermore, the polymer mixture according to the invention is suitable as a heat-sealing lacquer. In general, the polymer mixture according to the invention can be used as a compatibilizer in all applications in which poly(meth)acrylate-polyester mixtures are to be dissolved in a solvent.

[0120] The present invention therefore also relates to the use of the polymer mixture according to the invention as a binder in printing inks.

[0121] The invention is explained in more detail below using examples. Examples Production of a polymer mixture by suspension polymerization

[0122] The suspension polymerization was carried out in a 5-liter (liter) jacketed HWS glass reactor equipped with a reflux condenser under a nitrogen atmosphere. The reactor was equipped with an Inter-MIG stirrer with four impellers (blade width: 115 mm or 95 mm, spacing between blades: 110 mm, stirrer speed: 300 rpm). The reactor also included four baffles.

[0123] The polymerization was then carried out according to the following steps a) to e). a) Providing a first liquid phase

[0124] The first liquid phase was prepared with the components listed in Table 1 and homogenized with stirring for three to five minutes. b) Providing a second liquid phase

[0125] The second liquid phase was prepared with the components listed in Table 1 without the initiator and homogenized with stirring for three to five minutes.

[0126] The initiator was weighed separately and transferred to the reactor. The second liquid phase was then added and heated to the specified jacket temperature. The second liquid phase was degassed at 400 mbar for 10 minutes. c) Dispersing the first liquid phase in the second liquid phase

[0127] At a temperature of about 40 °C, the second liquid phase was introduced into the reactor containing the first liquid phase at about 800 mbar within 20 min while stirring. c1) Degassing and heating

[0128] The resulting dispersion was degassed at approximately 400 mbar for 20 min and heated to polymerization temperature. d) Polymerization

[0129] The components contained in the first liquid phase were polymerized at the temperature specified in Table 1. The end of polymerization is indicated by the significantly increased heat dissipation (Tmax). A conversion of > 90% was achieved. The polymerization time is the time from reaching the polymerization temperature to reaching the temperature maximum.

[0130] The mixture was then reheated according to the time and temperature values ​​given in Table 1. After the reheating phase, the mixture was cooled. e) Separation

[0131] After cooling the resulting bead suspension to an internal temperature of approximately 30 °C, the mother liquor was separated from the polymer beads by filtration and then dried. The resulting polymer beads were sieved through a 1000 µm mesh sieve. The process according to the invention allows polymer mixtures to be produced by suspension polymerization with high yields. The ratio of the first phase to the second phase of 1:2 or 1:1 is particularly advantageous, resulting in very good space-time yields. Evaluation 1. Determination of caking

[0132] The loose deposits adhering to the stirrer and baffle were rinsed off with water and their quantity (weight) was determined. 2. Visual assessment of the pearls

[0133] The beads were visually assessed using a microscope. 3. Assessment of the mother liquor

[0134] The pH value of the mother liquor obtained during filtration was determined using a pH meter. 4. Analytics

[0135] The following analytical tests were carried out: a) Particle size distribution measured using the Coulter method. b) Residual monomer content (comparative HPLC). c) Residual regulator content (comparative HPLC). d) Residual initiator content (comparative HPLC). e) Viscosity number, VN (reduced viscosity) measured using an Ubbelohde capillary viscometer type 0c according to ISO / DIN 3105. DIN 51562, 4-leg. f) Weight-average molecular weight, Mw, GPC against PMMA as standard.

[0136] The results of the evaluations can be found in Table 1. Table 1: Description component Example 1 Example 2 Ratio of first liquid phase : second liquid phase Monomer-water ratio 1 : 2 1 : 1 first liquid phase Total amount of alkyl (meth)acrylate monomer and polyester [g] Total monomer amount 1600 2400 Alkyl (meth)acrylate monomer [% of total] MMA 59,0 59,0 Alkyl (meth)acrylate monomer [% of total] n-BuMA 38,0 38,0 Polyester [% of total] polyester 3 3 Molecular weight regulator [% based on total amount of alkyl (meth)acrylate and polyester] Ethylhexyl thioglycolate (TGEH) 1,4 1 Initiator [% based on total amount of alkyl (meth)acrylate and polyester] Dilauroyl peroxide (LPO) 0,5 1 second liquid phase [g] 3271 2401 Water [g] Water 3162 2340 Suspension aid [g] Polyacrylic acid 13% in water 99,11 60,52 Additive [g] Potassium hydrogen sulfate 0,63 0,47 Additive [g] Mowiol 10 15 PH value 2,85 2,92 Degassing after monodosing time in minutes / mbar 20 / 370 20 / 350 Dosing time first liquid phase [min] 25 22 Temperature when adding the first liquid phase [°C] 37 - 40 37 - 40 Polymerization temperature [°C] 76 76 Heating time to polymerization temperature [min] 40 35 Time to maximum temperature [min] 102 105 Reheating temperature [°C] 87 87 Reheating time [min] 60 60 Tmax in reactor [°C] 76,2 77,6 Tmax in mantle [°C] 71,8 67,6 Caking. Stirrer + Current [g] 25,7 24,1 Alkyl (meth)acrylate-polyester copolymer [g] 1544 2370 sieved coarse material [g] 11,8 6,8 Rest of monomers MMA / n-BuMA [%] 0,15 / 0,05 0,11 / 0,04 Residual initiator [ppm] 100 110 d50' Coulter [µm] 250 230 pH - mother liquor 3,1 3,2 Viscosity number [ml / g] 16 22 SEC (Mw / D) [g / mol] 26450 / 4,03 36600 / 2,30 Degree of grafting (grafted / ungrafted) [%] 27 / 73 29 / 70

[0137] The polymer beads obtained in Examples 1 and 2, as well as the polymer according to Comparative Example 3 (DEGALAN ®< 1040 L (Röhm GmbH; copolymer of polyester and (meth)acrylate 50% in n-propyl acetate)) were subjected to various tests. The following steps were carried out: 1 The polymer beads or DEGALAN 1040 L obtained in Examples 1 and 2 were diluted with ethyl acetate to 30 wt.% solids. The resulting solution was visually assessed. 2. CAP varnish formulation: 14 wt.% cellulose acetate propionate (CAP 504.02, Eastman) was mixed with 28 wt.% ethyl acetate and 53 wt.% ethanol and dissolved on a roller bench. 52 wt.% of this solution was dispersed with 4 wt.% di(phenoxyethyl)formal (Desavin, Covestro), 15.5 wt.% ethanol, 8.5 wt.% ethyl acetate, and 20 wt.% Monolite Blue 515303 (Heubach / Heucotech, Ltd.). 3. 5 g of polymer beads or DEGALAN 1040 L were mixed with 15 g of the CAP varnish prepared under 2. 4. To determine the viscosity of the coating obtained under 3., a rheostress viscometer (100 s -1< , PP35, 100 sec, 23 °C) was used. 5. The CAP solution was applied to a PET film with a No. 1 spiral doctor blade (6 µm wet film thickness) and dried with a hairdryer. 6.The Scapa 1112 adhesive tape was applied across the length of the printing ink and then peeled off abruptly at a 45° angle. Table 2 Step Example 1 Example 2 Comparison example 3 1. Visual assessment of the solution 0 to 5, 1-5 / 5 cloudy, 1 / 5 clear, 0 / 5 clear, 0 / 5 0 = clear, 5 = opaque 4. Viscosity [mPas] 65 60 60 6. Tape test [detachment in %] 2 1 1

[0138] As can be seen from Table 2, the polymer blends produced according to the invention (Examples 1 and 2) exhibit comparable properties to polymer blends produced by known processes (Comparative Example 3). The slight turbidity in Example 1 can be eliminated by simple filtration. The viscosities are comparable, as is the adhesion to PET film. Solutions can also be readily prepared using the polymer blends according to the invention.

Claims

1. Process for producing a polymer mixture that comprises an alkyl (meth)acrylate-polyester copolymer, comprising the steps of: a) providing a first liquid phase comprising at least one alkyl (meth)acrylate monomer and at least one polyester dissolved in the alkyl (meth)acrylate monomer, b) providing a second liquid phase comprising water and at least one suspension aid dispersed therein, c) dispersing the first liquid phase in the second liquid phase, wherein droplets of the first liquid phase form in the second liquid phase, d) polymerizing the at least one alkyl (meth)acrylate monomer present in the first liquid phase and the at least one polyester to obtain the polymer mixture comprising the alkyl (meth)acrylate-polyester copolymer, wherein the polymerization in step d) is initiated by at least one initiator that is provided either in the first liquid phase in step a) or in the second liquid phase in step b), characterized in that the at least one polyester includes polycarboxylic acid units and polyol units, wherein the at least one polyester includes in the range from 0.1 to 10 mol% of polycarboxylic acid units having a C-C double bond, based on the total amount of polycarboxylic acid units.

2. Process according to Claim 1, characterized in that the first liquid phase comprises in the range from 0.1% to 15% by weight of the at least one polyester, based on the total weight of the first liquid phase.

3. Process according to Claim 1 or 2, characterized in that the C-C double bond present in the at least one polyester is a vinyl group.

4. Process according to any of Claims 1 to 3, characterized in that the at least one alkyl (meth)acrylate monomer is also selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isopentyl methacrylate, methyl acrylate, n-butyl acrylate, and mixtures thereof.

5. Process according to any of Claims 1 to 4, characterized in that the at least one initiator is selected from the group consisting of peroxides, azo compounds, and mixtures thereof.

6. Process according to any of Claims 1 to 5, characterized in that the at least one suspension aid present in the second liquid phase is selected from the group consisting of polyacrylic acids, salts of polyacrylic acids, and aluminum hydroxide Pickering systems.

7. Process according to any of Claims 1 to 6, characterized in that the weight ratio of the first liquid phase to the second liquid phase during dispersion in step c) is in the range from 1:2 to 2:1.

8. Process according to any of Claims 1 to 7, characterized in that the droplets of the first liquid phase obtained in step c) have a diameter in the range from 0.01 mm to 5 mm.

9. Process according to any of Claims 1 to 8, characterized in that the polymerization in step d) takes place at a temperature in the range from 50°C to 100°C.

10. Process according to any of Claims 1 to 9, characterized in that the polymer mixture obtained in step d) is dried following step d).

11. Polymer mixture obtainable by a process according to any of Claims 1 to 10.

12. Use of a polymer mixture according to Claim 11 as a binder in printing inks.