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

Abstract

The invention relates to a method for producing an alkyl (meth) acrylate-polyester copolymer by means of suspension polymerization, and to an alkyl (meth) acrylate-polyester copolymer produced thereby. The process according to the invention particularly avoids the use of styrene in the preparation. The alkyl (meth) acrylate-polyester copolymers produced according to the invention are particularly useful as binders in printing inks.

Description

Technical Field

[0001] The present invention relates to a process for preparing alkyl (meth)acrylate-polyester copolymers by suspension polymerization and to the alkyl (meth)acrylate-polyester copolymers prepared thereby. The process according to the invention particularly avoids the use of styrene in the preparation. The alkyl (meth)acrylate-polyester copolymers prepared according to the invention can be used in particular as binders in printing inks. Background Art

[0002] WO 2007 / 098819 A1 describes compositions comprising copolyesters, (meth)acrylate homopolymers or copolymers and graft copolymers of the two. The preparation is carried out as a solution polymerization or bulk polymerization in the absence of styrene.

[0003] The composition described in WO 2007 / 098819 A1 already has good properties as a compatibilizer and can therefore be used as a binder for printing inks. However, its preparation is laborious and cost-intensive. In addition, the composition described in WO 2007 / 098819 A1 is obtained in the form of a dissolved composition in the preparation in the form of a solution polymerization, so that the solvent in the subsequent use of the composition is determined by the solvent used in the solution polymerization, in particular propyl acetate. The user is therefore unable to freely select the solvent in the subsequent use of the composition.

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

[0005] JP 09241490 describes the suspension polymerization of a monomer mixture comprising polyethylene terephthalate, a vinyl monomer and an unsaturated carboxylic acid amide in the presence of a germanium catalyst. The resulting polymers are particularly useful for producing films and molded articles.

[0006] EP 0 462 785 describes a resin composition for toners, which comprises a suspension polymerization product formed from a polyester, a vinyl monomer and a divinyl monomer. The polyester is a polycondensate of terephthalic acid, isophthalic acid, hydroxyphenylpropane and various diols.

[0007] The copolymers of vinyl monomers and polyesters described in the prior art do not have sufficiently good properties for use as compatibilizers and binders in printing inks in some cases. In addition, some of them contain styrene. However, aromatic monomers such as styrene are undesirable, even if not prohibited, in various applications, for example in areas of contact with food or in articles that come into direct contact with children. In addition, aromatic monomers often cause an odor load in the subsequent use of the copolymers. Summary of the invention

[0008] Purpose

[0009] Therefore, there is a need for a process for preparing polymer mixtures comprising alkyl (meth)acrylate-polyester copolymers in which the disadvantages of the processes described in the prior art are present to a reduced extent or are completely absent. In addition, polymer mixtures comprising alkyl (meth)acrylate-polyester copolymers should be particularly suitable as binders in printing inks.

[0010] Achievement of purpose

[0011] The object is achieved by a process for preparing a polymer mixture comprising an alkyl (meth)acrylate-polyester copolymer, the process comprising the steps of:

[0012] 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,

[0013] b) providing a second liquid phase comprising water and at least one suspending aid dispersed therein,

[0014] c) dispersing the first liquid phase in the second liquid phase, wherein droplets of the first liquid phase are formed in the second liquid phase,

[0015] d) polymerizing the at least one alkyl (meth)acrylate monomer and the at least one polyester present in the first liquid phase to obtain a polymer mixture comprising an alkyl (meth)acrylate-polyester copolymer,

[0016] wherein the polymerization in step d) is initiated by at least one initiator provided 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, and wherein the at least one polyester comprises polycarboxylic acid units having C-C double bonds in the range of 0.1 to 10 mol %, based on the total molar amount of polycarboxylic acid units.

[0017] Surprisingly, it has been found that the process according to the invention can be used to prepare polymer mixtures which are suitable as binders for printing inks and which have very good adhesion, in particular 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.

[0018] The method of the present invention also enables the rapid and solvent-free preparation of polymer mixtures. Through the method of the present invention, a polymer mixture in solid form can be obtained without the need for laborious removal of solvents. Therefore, in the application of the polymer mixture prepared according to the present invention, it is not limited to a specific solvent. When the polymer mixture prepared according to the present invention is used, for example, as a binder in a printing ink, this is particularly advantageous because, for example, solvents common in printing inks such as ethyl acetate can also be used.

[0019] Since the polymer mixture is obtained as a substantially solvent-free solid, subsequent applications are not restricted to specific solvent systems as, for example, in the case of preparation by solution polymerization.Since the resulting polymer mixtures are solvent-free, their transportation and storage costs are significantly reduced.

[0020] The process according to the invention also enables very good space-time yields to be achieved and known apparatuses can be used. At the same time, gelling of the alkyl (meth)acrylate-polyester copolymers present in the polymer mixture is avoided by the process according to the invention.

[0021] It has also been surprisingly found that the polymer mixtures prepared according to the invention have comparable properties to the copolymers described in the prior art, although in a preferred embodiment of the process according to the invention they contain less polyester. The lower polyester proportion also has a favorable effect on the overall costs of the process according to the invention.

[0022] The method of the present invention is explained in more detail below.

[0023] In step a) of the process according to the invention, a first liquid phase is provided which comprises at least one alkyl (meth)acrylate monomer and at least one polyester dissolved in the alkyl (meth)acrylate monomer.

[0024] In order to provide a first liquid phase, the at least one polyester is dissolved in the at least one alkyl (meth)acrylate monomer. The dissolution of the at least one polyester can be carried out by all methods known to those skilled in the art. In order to dissolve the at least one polyester, the at least one alkyl (meth)acrylate monomer is preferably brought to a temperature in the range of 20° C. to 45° C.

[0025] The at least one polyester is preferably dissolved in the alkyl (meth)acrylate while stirring.

[0026] The at least one alkyl (meth)acrylate monomer and the at least one polyester are present in the first liquid phase in a uniformly distributed form.

[0027] The first liquid phase contains, for example, the at least one polyester in the range of 0.1 to 15 wt%, preferably in the range of 0.5 to 5 wt%, more preferably in the range of 2.5 to 3.5 wt%, based on the total weight of the first liquid phase.

[0028] Preference is therefore also given to processes in which the first liquid phase contains in the range from 0.1% to 15% by weight, based on the total weight of the first liquid phase, of at least one polyester.

[0029] Therefore, the first liquid phase contains, for example, 85 wt % to 99.9 wt % of the alkyl (meth)acrylate monomer, preferably 95 wt % to 99.5 wt %, more preferably 96.5 wt % to 97.5 wt %, based on the total weight of the first liquid phase.

[0030] Preferably, the weight percentages of the polyester, the alkyl (meth)acrylate monomer, at least one initiator further described below and other comonomers optionally provided in the first liquid phase add up to 100 weight percent.

[0031] Preferably, the first liquid phase contains no other solvents besides the alkyl (meth)acrylate monomer.

[0032] Preferably, the first liquid phase consists of alkyl (meth)acrylate monomers, polyester and optionally initiator and other comonomers.

[0033] The weight percentages of polyester, alkyl (meth)acrylate monomer, and optional initiator and other comonomers refer to the weight percentages before the polyester, alkyl (meth)acrylate monomer, initiator and other comonomers have reacted with each other.

[0034] In the present invention, "alkyl (meth)acrylate monomer" is understood to mean both alkyl methacrylate monomer and alkyl acrylate monomer. 12 -alkyl ester monomer. "(Meth)acrylic acid C1-C 12 "-Alkyl ester monomers" are understood to mean alkyl esters of (meth)acrylic acid having 1 to 12 carbon atoms in the alkyl group. The alkyl group may be linear, cyclic and / or branched. In addition, it may also contain aromatic groups.

[0035] The term "(meth)acrylic acid" in the present invention includes both acrylic acid and methacrylic acid.

[0036] For example, the alkyl (meth)acrylate monomer of the present invention is selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isopentyl (meth)acrylate, octadecyl (meth)acrylate, benzyl (meth)acrylate or dodecyl (meth)acrylate.

[0037] Preferred alkyl (meth)acrylate monomers are methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methyl acrylate, n-butyl acrylate, isoamyl methacrylate, and mixtures thereof.

[0038] Also preferred according to the invention are therefore processes in which 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, isoamyl methacrylate, methyl acrylate, n-butyl acrylate and mixtures thereof.

[0039] The at least one polyester is prepared by polycondensation of a polycarboxylic acid with a polyol. Those skilled in the art will recognize that derivatives of the polycarboxylic acids, such as their lower alkyl esters and / or their anhydrides, can also be used in the polycondensation.

[0040] "Polycarboxylic acids" are understood in the context of the present invention 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 in this case also referred to as dicarboxylic acids.

[0041] Suitable polycarboxylic acids are those known to the person skilled in the art, for example aliphatic polycarboxylic acids, cycloaliphatic polycarboxylic acids and / or aromatic polycarboxylic acids.

[0042] Suitable polycarboxylic acids are selected, for example, from succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, octadecanedioic acid, cyclohexanedicarboxylic acid and its isomers, phthalic acid and its isomers and trimellitic acid.

[0043] The at least one polyester comprises polycarboxylic acid units having CC double bonds in an amount ranging from 0.1 to 10 mol %, preferably in an amount ranging from 0.2 to 5 mol %, more preferably in an amount ranging from 0.5 to 1.5 mol %, based on the total molar amount of polycarboxylic acid units.

[0044] The polyester is therefore usually prepared using a mixture of the polycarboxylic acids and unsaturated polycarboxylic acids mentioned above. An unsaturated polycarboxylic acid is understood to mean a polycarboxylic acid containing at least one C-C double bond. The C-C double bonds can, for example, be arranged in the main chain of the polycarboxylic acid. Examples of such polycarboxylic acids are fumaric acid, maleic acid and mesaconic acid.

[0045] Furthermore, the CC double bonds can be arranged as pendant groups in the polycarboxylic acids. An example of such a polycarboxylic acid is itaconic acid.

[0046] In the context of the present invention, a CC double bond which is arranged as a side group in a polycarboxylic acid and comprises a H2C=C unit is also referred to as a vinyl group.

[0047] The CC double bond is preferably a vinyl group.

[0048] Preference is therefore also given according to the invention to a process in which the CC double bonds present in the at least one polyester are vinyl.

[0049] It is further preferred according to the invention that the vinyl group is present in the itaconic acid unit. It is therefore preferred that the polycarboxylic acid unit having a CC double bond is an itaconic acid unit.

[0050] It is therefore preferred according to the invention that the at least one polyester is prepared / obtainable by polycondensation of polycarboxylic acids and polyols, wherein itaconic acid is used in an amount in the range of 0.1 to 10 mol %, preferably in the range of 0.2 to 5 mol %, particularly preferably in the range of 0.5 to 1.5 mol %, based on the total molar amount of the polycarboxylic acid.

[0051] Polyols are understood in the present invention to mean compounds containing at least two hydroxyl groups. The polyols used in the polycondensation preferably contain exactly two hydroxyl groups. Polyols are also referred to in this context as diols.

[0052] Suitable polyols are those known to the person skilled in the art, for example aliphatic polyols, aromatic polyols and / or ether diols. Aliphatic polyols are preferred.

[0053] Suitable polyols are selected, for example, from ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,12-dodecanediol, neopentyl glycol, 1,3-butylethylpropylene glycol, 1,3-methylpropylene glycol, methylpentanediol, cyclohexanedimethanol, trimethylolpropane, pentaerythritol, hydroquinone, bisphenol A, bisphenol F, dihydroxynaphthalene, the aforementioned ether diols and mixtures thereof.

[0054] The processes for preparing polyesters are known per se. For example, they can be obtained by polycondensation of polyols with polycarboxylic acids or their esters, anhydrides and / or acid chlorides in an inert gas atmosphere at temperatures of 100° C. to 260° C., preferably 130° C. to 240° C., in the melt or in azeotropic operation mode, as described, for example, in Methoden der organischen Chemie [Methods of Organic Chemistry] (Houben-Weyl), Vol. 14 / 2, 1-5, 21-23, 40-22, Georg Thieme Verlag, Stuttgart, 1963, CR Martens, Alkyl Resins, 51-59, Reinhold Plastics Appl., Series, Reinhold Publishing Comp., New York, 1961, or DE 27 35 497.

[0055] According to the invention, the at least one polyester comprises polycarboxylic acid units and polyol units.

[0056] In the present invention, polycarboxylic acid units are understood to refer to units derived from polycarboxylic acids in polyesters. In the present invention, polyol units are understood to refer to units derived from polyols in polyesters. The condensation of polyols with polycarboxylic acids results in the formation of polyester blocks. Blocks derived from polycarboxylic acids are referred to as polycarboxylic acid units in the present invention. Blocks derived from polyols are referred to as polyol units in the present invention.

[0057] The polycarboxylic acid units are preferably dicarboxylic acid units formed by the condensation of dicarboxylic acids and polyols. The polyol units are preferably diol units formed by the condensation of diols and polycarboxylic acids. Particularly preferably, the polycarboxylic acid units are dicarboxylic acid units, and the polyol units are diol units. They are formed by the condensation of dicarboxylic acids and diols.

[0058] For example, the at least one polyester has an OH value (hydroxyl value) in the range of 5 mg(KOH) / g to 150 mg(KOH) / g, preferably in the range of 10 mg(KOH) / g to 50 mg(KOH) / g.

[0059] The at least one polyester has an acid value of, for example, less than 10 mg(KOH) / g, preferably less than 5 mg(KOH) / g, more preferably less than 2 mg(KOH) / g.

[0060] 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 2000 to 12 000 g / mol, determined by GPC or HPLC, in each case using PMMA as standard.

[0061] Furthermore, at least one initiator may 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 in step b) described further below.

[0062] In the present invention, "provided in the first liquid phase in step a) or in the second liquid phase in step b)" therefore means that, preferably, the at least one initiator is provided only in the first liquid phase in step a) and not in the second liquid phase in step b), or the at least one initiator is provided only in the second liquid phase in step b) and not in the first liquid phase in step a).

[0063] It goes without saying that, although the at least one initiator is preferably provided only in the first liquid phase or only in the second liquid phase, the at least one initiator is capable of diffusing from the first liquid phase to the second liquid phase and vice versa during the process according to the invention, in particular during at least one of steps c) and d).

[0064] If the at least one initiator is provided in the first liquid phase in step a), it is generally likewise dissolved in the at least one alkyl (meth)acrylate monomer and is therefore present in the form of an initiator dissolved in the at least one alkyl (meth)acrylate monomer.

[0065] For example, the at least one initiator is provided in the first liquid phase in step a) in an amount ranging from 0.1 to 20 wt %, preferably from 0.5 to 5 wt %, based on the total weight of the first liquid phase.

[0066] The at least one initiator is preferably provided in the second liquid phase in step b). It is therefore preferred that an initiator-free first liquid phase is provided.

[0067] In an alternative preferred embodiment, the at least one initiator is provided in the first liquid phase in step a). In this case, it is preferred that an initiator-free second liquid phase is provided.

[0068] Suitable initiators are all compounds known to those skilled in the art that are capable of initiating free radical polymerization. For example, the at least one initiator is selected from peroxides, azo compounds, persulfates and mixtures thereof. The initiator is preferably selected from peroxides, azo compounds and mixtures thereof.

[0069] Preference is therefore also given to a process in which the at least one initiator is selected from peroxides, azo compounds and mixtures thereof.

[0070] Suitable peroxides are, for example, selected from hydrogen peroxide, dibenzoyl peroxide, dicyclohexyl peroxydicarbonate, dilauroyl 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, diisopropyl peroxydicarbonate and bis(4-tert-butylcyclohexyl) peroxydicarbonate.

[0071] Suitable azo compounds are selected, for example, from 2,2-azobisiso-2,4-dimethylvaleronitrile, 2,2-azobisisobutyronitrile, 2,2′-azobis(2-amidinopropane) dihydrochloride, 2-(carbamoylazo)isobutyronitrile and 4,4′-azobis(cyanovaleric acid).

[0072] Suitable persulfates are, for example, selected from lithium peroxodisulphate, sodium peroxodisulphate, potassium peroxodisulphate and ammonium peroxodisulphate.

[0073] Furthermore, the first liquid phase may additionally contain additional comonomers. "Additional comonomers" are understood in the present invention to mean monomers copolymerizable with the at least one alkyl (meth)acrylate monomer. It goes without saying that the additional comonomer is different from the at least one alkyl (meth)acrylate monomer. "Additional comonomers" in the present invention mean exactly one additional comonomer or a mixture of two or more comonomers.

[0074] Such additional comonomers are known per se to the person skilled in the art, examples being (meth)acrylic acid, hydroxyethyl methacrylate and / or hydroxypropyl methacrylate.

[0075] For example, the first liquid phase contains the additional comonomer in the range of 0 wt% to 20 wt%, preferably in the range of 0 wt% to 10 wt%, based on the total weight of the first liquid phase.

[0076] In one embodiment of the present invention, the first liquid phase contains no additional comonomer.

[0077] It is particularly preferred that the first liquid phase contains no styrene.

[0078] In step b), a second liquid phase is provided which comprises water and at least one suspension aid dispersed therein.

[0079] For example, the second liquid phase may be provided by dispersing a suspending aid in water while stirring.

[0080] The second liquid phase in step b) may be provided at any temperature, preferably at a temperature in the range of 25°C to 80°C, preferably in the range of 37°C to 65°C.

[0081] In the second liquid phase, water usually forms a continuous phase and the suspension aid forms a dispersed phase. The second liquid phase usually exists in the form of a suspension. The suspension aid exists in water as solid particles.

[0082] Suitable suspension aids are all suspension aids known to the person skilled in the art, for example polyacrylic acid, salts of polyacrylic acid and / or Pickering systems. Examples of suitable Pickering systems are colloidal silicon dioxide and / or aluminum hydroxide. The Pickering system formed by aluminum hydroxide is preferably made of aluminum sulfate and sodium carbonate (soda).

[0083] The suspension aid is preferably selected from polyacrylic acid, salts of polyacrylic acid and the Pickering system formed from aluminum hydroxide.

[0084] Preference is therefore given to a process in which the at least one suspension aid present in the second liquid phase is selected from polyacrylic acid, salts of polyacrylic acid and a Pickering system formed from aluminium hydroxide.

[0085] For example, the second liquid phase contains the suspension aid in the range of 0.01 wt % to 10 wt %, preferably in the range of 0.02 wt % to 5 wt %, based on the total weight of the second liquid phase.

[0086] Therefore, the second liquid phase contains water, for example, in the range of 90 wt % to 99.99 wt %, preferably in the range of 95 wt % to 99.98 wt %, based on the total weight of the second liquid phase.

[0087] The at least one initiator may 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 embodiments and preferences apply as above for the initiator provided in the first liquid phase in step a).

[0088] For example, the initiator is provided in the second liquid phase in step b) in an amount in the range of 0.1 to 20 wt %, preferably in the range of 0.2 to 10 wt %, based on the total weight of the second liquid phase.

[0089] In step c), the first liquid phase is dispersed in the second liquid phase, wherein droplets of the first liquid phase are formed in the second liquid phase.

[0090] The first liquid phase is typically substantially insoluble in the second liquid phase.

[0091] The dispersion in step c) is usually carried out under stirring. Droplets of the first liquid phase are formed in the second liquid phase. The droplets contain the (meth) acrylate monomer and the polyester dissolved therein, and optionally additional comonomers. The droplets also contain the at least one initiator, either by already providing the initiator in the first liquid phase or by diffusion of the initiator from the second liquid phase into the first liquid phase.

[0092] The suspension aid present in the second liquid phase generally surrounds the droplets of the first liquid phase and thus forms a boundary layer between the first and second liquid phases. The suspension aid thus stabilizes the droplets of the first liquid phase in the second liquid phase.

[0093] The first liquid phase and the second liquid phase generally form an emulsion in which the first liquid phase forms a dispersed phase and the second liquid phase forms a continuous phase.

[0094] The droplets of the first liquid phase in the second liquid phase obtained in step c) have a median diameter d according to the Coulter method, for example, in the range of 0.01 mm to 5 mm, preferably in the range of 0.05 mm to 0.40 mm. 50 .

[0095] It is therefore also preferred that the droplets of the first liquid phase obtained in step c) have a median diameter d according to the Coulter method in the range from 0.01 mm to 5 mm. 50 method.

[0096] The weight ratio of the first liquid phase to the second liquid phase in step c) is, for example, in the range of 1:2 to 2:1, preferably about 1:1.

[0097] Preference is therefore also given to a process in which the weight ratio of the first liquid phase to the second liquid phase during the dispersion in step c) is in the range from 1:2 to 2:1.

[0098] The dispersion in step c) is generally carried out at a temperature below the temperature at which the polymerization of the alkyl (meth)acrylate monomers and / or polyester present in the first liquid phase takes place. For example, the dispersion in step c) is carried out at a temperature in the range of 20°C to <50°C, preferably in the range of 35°C to 45°C.

[0099] In step d), the alkyl (meth)acrylate monomer and the polyester and optionally additional comonomers present in the first liquid phase are polymerized to obtain a polymer mixture comprising an alkyl (meth)acrylate-polyester copolymer.

[0100] The polymerization is usually carried out while stirring.

[0101] The polymerization in step d) is usually initiated by an initiator. For example, the initiator forms free radicals by photoactivation and / or by activation at elevated temperature, for example in the range of 50° C. to 100° C., preferably in the range of 65° C. to 85° C. These free radicals initiate free radical formation at the CC double bonds of the (meth) alkyl acrylate monomers and / or at the CC double bonds of the polyester. These reactions are known per se.

[0102] The polymerization in step d) is carried out, for example, at a temperature in the range of 50 to 100°C, preferably in the range of 65 to 85°C.

[0103] Preference is therefore also given to a process in which the polymerization in step d) is carried out at a temperature in the range from 50 to 100°C.

[0104] The polymer mixture is generally obtained in step d) in the form of a solid dispersed in the second liquid phase. The polymer mixture obtained in step d) is generally substantially insoluble in the second liquid phase.

[0105] The second liquid phase in this case forms a suspension together with the polymer mixture. The second liquid phase forms the continuous phase, while the polymer mixture forms the dispersed phase.

[0106] In step d), a polymer mixture comprising an alkyl (meth)acrylate-polyester copolymer is obtained.

[0107] In the polymerization in step d), the at least one alkyl (meth)acrylate monomer is polymerized with the polyester. In this reaction, an alkyl (meth)acrylate-polyester copolymer is usually formed. In this polymerization, free radicals are formed by the initiator at the CC double bonds of the polycarboxylic acid units of the polyester and / or at the CC double bonds of the alkyl (meth)acrylate monomers. These can react with each other and / or initiate further free radical formation, so that polymerization occurs. Such reactions are known per se.

[0108] This can, for example, lead to the formation of graft copolymers containing alkyl (meth)acrylate monomers or polymers thereof, optionally grafted with additional comonomers onto polyesters or copolymers thereof. A polyester backbone and polyalkyl (meth)acrylate side chains are then formed. In the present invention, the term "alkyl (meth)acrylate-polyester copolymers" therefore also encompasses such graft copolymers.

[0109] Alternatively or additionally, it is possible to form block copolymers containing blocks consisting of alkyl (meth)acrylate polymers (optionally with additional comonomers) and blocks consisting of polyesters or their copolymers. In the present invention, the term "alkyl (meth)acrylate-polyester copolymers" also encompasses such block copolymers.

[0110] The polymer mixture contains, for example, 5 to 95 wt %, preferably 10 to 50 wt %, more preferably 20 to 30 wt % of the alkyl (meth)acrylate-polyester copolymer, based on the total weight of the polymer mixture.

[0111] In the polymerization in step d), the polyester is also usually polymerized with itself to obtain at least one copolyester. Likewise, the at least one alkyl (meth)acrylate monomer may be polymerized with itself and with optional additional comonomers to obtain at least one alkyl (meth)acrylate polymer.

[0112] The polymer mixture obtained in step d) therefore generally contains, in addition to the alkyl (meth)acrylate-polyester copolymer, further polymers, in particular it generally also contains at least one copolyester and / or at least one alkyl (meth)acrylate polymer.

[0113] Furthermore, it is possible that a portion of the polyester and / or a portion of the alkyl (meth)acrylate monomers are unreacted and are present in the polymer mixture.

[0114] The alkyl (meth)acrylate monomers and optional additional comonomers can generally be substantially removed from the polymer mixture by drying.

[0115] Preference is therefore also given to processes in which the polymer mixture additionally contains the at least one polyester, at least one copolyester and / or at least one alkyl (meth)acrylate polymer. Preferably, it additionally contains at least one polyester, at least one copolyester and at least one alkyl (meth)acrylate polymer.

[0116] The total amount of polyesters and copolyesters in the polymer mixture is, for example, in the range from 0.01% to 15% by weight, preferably in the range from 0.01% to 5% by weight, more preferably in the range from 0.01% to 2% by weight, based in each case on the total weight of the polymer mixture.

[0117] The polymer mixture contains, for example, in the range from 5 to 95% by weight, preferably in the range from 50 to 90% by weight, more preferably in the range from 70 to 80% by weight, of at least one alkyl (meth)acrylate polymer, based in each case on the total weight of the polymer mixture.

[0118] After step d), the polymer mixture is usually separated from the second liquid phase. The separation can be carried out by any method known to those skilled in the art, for example by filtering and subsequent drying. In this case, the filtering can be carried out by a continuously operated decanter and centrifuge, and the drying can be carried out by a continuously operated fluidized bed or fluidized bed dryer.

[0119] Preference is therefore also given to a process in which the polymer mixture obtained in step d) is dried after step d).

[0120] After drying, the resulting polymer mixture is typically substantially free of water. For example, the polymer mixture contains up to 5 wt. %, preferably up to 1 wt. % water, based on the total weight of the polymer mixture.

[0121] The polymer mixture is generally obtained in step d) in the form of polymer beads. These preferably have a median diameter d determined by the Coulter method in the range from 0.01 to 0.6 mm. 50 .

[0122] The polymer mixture has, for example, a glass transition temperature Tg in the range from 50° C. to 70° C., determined by differential scanning calorimetry (DSC) in accordance with DIN EN ISO 11357-4.

[0123] According to the invention it is preferred that the process according to the invention is carried out in the absence of styrene. It is particularly preferred that no styrene is used in any of steps a) to d).

[0124] Steps a) to d) of the method of the present invention can be performed in the specified order. In addition, different orders are possible. The 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. In addition, additional steps can be performed.

[0125] The invention also provides a polymer mixture obtainable by the process according to the invention.

[0126] The above-described embodiments and preferences apply to the polymer mixture.

[0127] The polymer mixtures according to the invention are particularly suitable as binders in printing inks. In addition, the polymer mixtures according to the invention are suitable as heat-sealing lacquers. In general, the polymer mixtures according to the invention can be used as compatibilizers in all applications in which the poly(meth)acrylate-polyester mixture is to be dissolved in a solvent.

[0128] The present invention therefore also provides for the use of the polymer mixtures according to the invention as binders in printing inks.

[0129] The present invention is explained in detail below with reference to examples, but the present invention is not limited thereto. DETAILED DESCRIPTION

[0130] Example

[0131] Preparation of polymer mixtures by suspension polymerization

[0132] The suspension polymerization was carried out in a 5 L (liter) jacketed HWS glass reactor equipped with a reflux condenser under a nitrogen atmosphere. The reactor was equipped with an Inter-MIG stirrer with 4 stirring blades (blade width: 115 mm or 95 mm, blade spacing: 110 mm, stirrer speed 300 rpm). The reactor also contained four baffles.

[0133] The polymerization is then carried out according to the following steps a) to e).

[0134] a) Providing a first liquid phase

[0135] A first liquid phase having the composition specified in Table 1 was provided and homogenized under stirring for 3 to 5 minutes.

[0136] b) Providing a second liquid phase

[0137] A second liquid phase having the components specified in Table 1 without initiator was provided and homogenized under stirring for 3 to 5 minutes.

[0138] The initiator is weighed out separately and transferred to the reactor. The second liquid phase is then added and the mixture is heated to a predetermined jacket temperature. The second liquid phase is degassed at 400 mbar for 10 minutes.

[0139] c) dispersing the first liquid phase in the second liquid phase

[0140] At a temperature of about 40° C., the second liquid phase was introduced under stirring over a period of 20 minutes at about 800 mbar into the reactor containing the first liquid phase.

[0141] c1) Degassing and heating

[0142] The resulting dispersion was degassed at approximately 400 mbar for 20 minutes and heated to the polymerization temperature.

[0143] d) Aggregation

[0144] The components present in the first liquid phase were polymerized at the temperature specified in Table 1. The end of the polymerization can be seen from the significant rise in heat dissipation (Tmax). A conversion of >90% was achieved. The polymerization time is the time from reaching the polymerization temperature until the maximum temperature is reached.

[0145] The mixture was then heated further according to the time and temperature values ​​given in Table 1. After the further heating phase, the mixture was cooled.

[0146] e) Separation

[0147] After the obtained bead suspension was cooled to an internal temperature of about 30° C., the mother liquor was separated from the polymer beads by filtration and then dried. The obtained polymer beads were sieved with a sieve having a mesh size of 1000 μm.

[0148] The process of the invention enables the preparation of polymer mixtures by suspension polymerization in high yields. A ratio of first phase to second phase of 1:2 or 1:1 is particularly advantageous, whereby very good space-time yields are achieved.

[0149] Evaluate

[0150] 1. Determination of Agglomeration

[0151] The lumps loosely adhering to the stirrer and the baffle were washed off with water and their amount (weight) was measured.

[0152] 2. Visual Assessment of Beads

[0153] Beads were visually assessed using a microscope.

[0154] 3. Evaluation of mother liquor

[0155] The pH value of the mother liquor obtained by filtration was measured with a pH meter.

[0156] 4. Analysis

[0157] The following analytical tests were performed:

[0158] a) Particle size distribution measured by the Coulter method.

[0159] b) Residual content of monomers (comparison with HPLC)

[0160] c) Residual content of chain transfer agent (comparison with HPLC)

[0161] d) Residual content of initiator (comparison with HPLC)

[0162] e) Viscosity value measured using a 4-legged Ubbelohde capillary viscometer type 0c according to ISO / DIN 3105, DIN 51562, VZ (reduced viscosity)

[0163] f) Weight average molecular weight M W , GPC, relative to PMMA as standard

[0164] The evaluation results are shown in Table 1.

[0165] Table 1:

[0166]

[0167]

[0168] The polymer beads obtained in Examples 1 and 2 and the polymer according to Comparative Example 3 ( 1040L (from GmbH; copolymers of polyester and (meth)acrylate, 50% strength in n-propyl acetate)) were subjected to various tests. The following steps were performed:

[0169] 1. The polymer beads obtained in Examples 1 and 2 or DEGALAN 1040L were diluted with ethyl acetate to a solids content of 30% by weight. The resulting solution was evaluated visually.

[0170] 2. Preparation of CAP varnish: 14 wt% of cellulose acetate propionate (CAP 504.02, from Eastman) was mixed with 28 wt% of ethyl acetate and 53 wt% of ethanol and dissolved on a roller table (Rollbank). 52 wt% of this solution was dispersed with 4 wt% of bis(phenoxyethyl)formal (Desavin, Covestro), 15.5 wt% of ethanol, 8.5 wt% of ethyl acetate and 20 wt% of Monolite Blau 515303 (Heubach / Heucotech, Ltd.).

[0171] 3. Mix 5 g of polymer beads or DEGALAN 1040L with 15 g of the CAP lacquer prepared in 2.

[0172] 4. Use RheoStress viscometer (100s -1 ,PP35,100sec,23℃) to measure the viscosity of the paint obtained in 3.

[0173] 5. Apply the CAP solution onto the PET film using a No. 1 spiral doctor blade (6 μm wet layer thickness) and dry with a hair dryer.

[0174] 6. Apply Scapa 1112 tape over the entire length of the printed ink and then remove it by pulling sharply at an angle of 45°.

[0175] Table 2

[0176]

[0177] As can be seen from Table 2, the polymer mixtures prepared according to the invention (Examples 1 and 2) have comparable properties to the polymer mixtures prepared according to known methods (Comparative Example 3). The slight turbidity in Example 1 can be eliminated by simple filtration. The viscosity and the adhesion to PET film are likewise comparable. Solutions can also be easily prepared with the polymer mixtures according to the invention.

Claims

1. A method for preparing a polymer mixture comprising an alkyl (meth)acrylate-polyester copolymer, comprising the following steps: 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 suspending aid dispersed therein, c) dispersing the first liquid phase in the second liquid phase, wherein droplets of the first liquid phase are formed in the second liquid phase, d) polymerizing the at least one alkyl (meth)acrylate monomer and the at least one polyester present in the first liquid phase to obtain a polymer mixture comprising an alkyl (meth)acrylate-polyester copolymer, wherein the polymerization in step d) is initiated by at least one initiator provided 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 a polycarboxylic acid unit and a polyol unit, wherein the at least one polyester includes the polycarboxylic acid unit having a CC double bond in an amount ranging from 0.1 to 10 mol %, based on the total amount of the polycarboxylic acid unit.

2. The method according to claim 1, characterized in that The first liquid phase contains the at least one polyester in an amount in the range of 0.1 wt % to 15 wt %, based on the total weight of the first liquid phase.

3. The method according to claim 1 or 2, characterized in that The CC double bonds present in the at least one polyester are vinyl groups.

4. The method according to any one of claims 1 to 3, characterized in that The at least one alkyl (meth)acrylate monomer is also selected from methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isoamyl methacrylate, methyl acrylate, n-butyl acrylate, and mixtures thereof.

5. The method according to any one 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. The method according to any one of claims 1 to 5, characterized in that The at least one suspension aid present in the second liquid phase is chosen from polyacrylic acid, salts of polyacrylic acid and a Pickering system formed from aluminium hydroxide.

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

1.

8. The method according to any one 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 of 0.01 mm to 5 mm.

9. The method according to any one of claims 1 to 8, characterized in that The polymerization in step d) is carried out at a temperature in the range of 50°C to 100°C.

10. The method according to any one of claims 1 to 9, characterized in that The polymer mixture obtained in step d) is dried after step d).

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

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

Images