HK1144099B - Process for the synthesis of improved binders having a defined particle size distribution - Google Patents

Description

Improved binder synthesis with particle size distribution

Technical Field

The invention relates to a method for producing polymers for paint applications by polymerizing esters of acrylic or methacrylic acid or vinylaromatic or other free-radically polymerizable vinyl compounds or monomer mixtures consisting essentially of these monomers by means of a continuous polymerization process. The invention relates in particular to a solvent-free, continuous polymer production process by means of which binders for lacquer applications can be produced with adjustable particle size. The polymer pellets produced according to the invention are characterized by improved processability without fine fractions.

Background

The preparation of (meth) acrylate binders or vinylaromatic binders for lacquer applications is generally carried out according to the prior art by means of suspension polymerization or solution polymerization. (meth) acrylates refer both to acrylic acid and its derivatives, such as esters, and also to methacrylic acid and its derivatives, such as esters, and to mixtures of the above-mentioned components.

In contrast, the present invention describes a continuous bulk polymerization process. The process can be carried out without interfering solvents. The solvent may cause side reactions during the polymerization of e.g. the (meth) acrylates, such as chain transfer reactions, undesired termination reactions or even polymer analogous transformations (polymeraloge) reactions. Furthermore, handling the solvent under the manufacturing conditions poses a safety risk. Furthermore, the choice of solvent may also be limited by the preparation process, e.g. the desired reaction temperature. This in turn can impair the subsequent formulation and use forms, for example in view of excessively long drying times caused by solvents having an excessively high boiling point.

The alternative removal of the solvent used for the preparation necessitates an additional, undesired preparation step and additionally places a burden on the environment since two different solvents are used for the preparation and the application. Furthermore, solvent residues in the product create disturbances in the granulation, extrusion, formulation and processing of the binder. Moreover, these additional solvent components can also impair the quality of the coating in paint applications, for example in terms of gloss, coloration or weather stability.

The suspension polymerization of esters of acrylic or methacrylic acid or vinylaromatic compounds or monomer mixtures composed predominantly of these monomers is known in principle. The process is also carried out in the absence of a solvent. However, there is a great disadvantage over bulk polymerization in that a large amount of water is used in the process. This necessitates additional process steps such as filtration and subsequent drying. The drying is mostly carried out only incompletely. However, even small residual water contents can lead to a marked impairment of the appearance properties, such as gloss or pigment dispersion, in paint applications.

Also, the suspension polymerization may not be carried out continuously, but only in a batch-wise manner. Such processes are less flexible and less efficient to perform relative to continuous polymerization.

Another disadvantage of suspension polymerization, relative to other polymerization processes, is the large number of auxiliaries, such as dispersants, emulsifiers, defoamers or other auxiliaries, which have to be used and are still contained in the final product even after work-up. As impurities, these auxiliaries can lead, for example, to reduced gloss values, to deteriorated pigment dispersion in the lacquer, or to specks as a result of insufficiently washed-off dispersants which are not soluble in organic solvents. Also disadvantageous is the only very limited copolymerizability of polar comonomers, such as (meth) acrylic acid, amino-functional or hydroxy-functional (meth) acrylates. The proportion of these monomers in the respective monomer mixture must be greatly limited by their water solubility.

Another great disadvantage of suspension polymerization is the required reaction temperature. Such processes can only be carried out in a very low temperature range. Temperatures above 100 ℃ can in principle only be adjusted poorly because of the water used. In principle, the practice under pressure and at temperatures above 100 ℃ is not advisable, since under such conditions the solubility of the monomers in the aqueous phase is additionally improved. In contrast, at too low temperatures, suspension polymerization proceeds only very slowly or incompletely and it is extremely difficult to adjust the process-compatible particle size. An example of the preparation of suspension polymers as binders for lacquer applications is found in EP 0190433.

Another disadvantage of suspension polymerization relative to the present invention is the particle size of the product. Known to those skilled in the art: the suspension polymers are produced in a particle size range of a few micrometers up to a maximum of 1 cm. However, even large polymer beads additionally have a large fine fraction. This fine fraction causes some disadvantages of such materials. On the one hand, these product fractions can cause problems in the cleaning, drying and packaging of the material, up to the risk of explosion of the fine dust. On the other hand, products containing the relevant fine fraction cannot be used in extrusion processes either. Most extruders require a minimum particle size that is optimal for this in order to take in the raw material. A further disadvantage is the often non-uniformity of the particles, which leads to very different dissolution times, for example, during the dissolution process.

Another disadvantage of suspension polymerization over bulk polymerization is the energy balance: the heating of about 50% of the aqueous phase and the cooling of this aqueous phase required after the polymerization is energy-consuming and time-consuming.

Discontinuous bulk polymerization in stirred tanks or tanks leads in principle only to incomplete reaction of the monomers and thus to high residual monomer contents, which in turn interfere with the lacquer properties or have to be removed at high expense before formulation. Furthermore, the granulation of the product must be carried out in a separate process step and cannot be integrated into the production process.

A large number of different continuous bulk polymerization processes for the preparation of poly (meth) acrylates are known to the person skilled in the art. For example, EP 0096901 describes a process in which a monomer mixture consisting of styrene, α -methylstyrene and acrylic acid is charged continuously into a stirred tank and the polymer is removed at the same time. The range from 170 ℃ to 300 ℃ is described as the reaction temperature. It is obvious to the person skilled in the art that in continuously operated stirred tanks the polymerization reaction proceeds only incompletely and necessarily leads to products having a high residual monomer content. EP 0096901 furthermore does not describe a method step for the working up of the product or for the granulation thereof.

During this time, the tubular reactor is of great importance for carrying out continuous bulk polymerization. WO 98/04593 describes a process for the continuous preparation of acrylate resins or copolymers of styrene, alpha-methylstyrene and acrylic acid. The polymerization is carried out at a temperature between 180 ℃ and 260 ℃. In US 6,476,170 it is disclosed to prepare polymers of similar composition for dispersion applications or for emulsifier applications in a temperature range between 210 ℃ and 246 ℃. WO 99/23119 claims a process for preparing adhesive resins in a tubular reactor at polymerization temperatures between 100 ℃ and 300 ℃ -WO2005/066216 claims a process for preparing hot melt adhesives at temperatures below 130 ℃. In the process described, all the products listed here are not granulated or subjected to similar work-up. This corresponds to the conventional practice of products which are usually present in a waxy or liquid state in adhesive or hot melt adhesive applications. Coatings in the form of clear coats (rock) or pigmented coats (Farbe) are also not mentioned as fields of application.

The same applies to the polymerization process described in WO 98/12229. This relates to a variant of the tubular reactor: the reactor was circulated. The object of the claimed process is to produce polymethacrylates for producing shaped bodies. Granulation of the product or use in coatings is not described. Likewise, the change of formulation in a continuously operating kneader, for example, is significantly less expensive than in such a tubular reactor. The reaction path is also significantly shorter or thorough mixing is more efficient and thus the residence time within the reaction chamber is shorter. This in turn can potentially lead to a greater heat load on the product in such a tubular reactor.

A new generation of reactors for the continuous bulk polymerization of (meth) acrylates is the so-called Taylor (Taylor) reactor. The reactor can also be used over a wide temperature range. A corresponding process for preparing binders for coatings or adhesives or sealants is described in detail in WO 03/031056. However, these reactors also suffer from poor thorough mixing and long residence times.

Although coatings are mentioned in WO 03/031056 as potential applications for the process according to the invention. However, no mention is made of processing after polymerization, in particular pelletization. An alternative to continuously feeding the reactor is reactive extrusion. WO 2007/087465 describes a process for the continuous preparation of binding poly (meth) acrylates. However, no targeted adjustment of the microstructure of the product has been described so far.

Reactive extrusion is in principle very similar to the kneader technique. WO2006/034875 describes a continuous bulk polymerization process, in particular a process for the homo-or copolymerization of thermoplastics and elastomers, in a back-mixed kneader reactor at temperatures above the glass transition temperature. Here, monomers, catalysts, initiators, etc. are continuously introduced into the reactor and back-mixed with the already reacted products. While the reaction product is continuously removed from the mixing kneader. The process can be applied, for example, to the continuous bulk polymerization of MMA. Unreacted monomers are separated off by means of an exhauster and can be reintroduced into the reactor. The use of kneader technology enables significantly higher conversions to be achieved with comparable throughput times compared with unfavourable reactive extrusion. In order to achieve comparable conversions by means of reactive extrusion, significantly longer residence times in the extrusion section or significantly longer extrusion chambers have to be taken into account. However, this leads to a high thermal load on the material and may lead to disadvantages, such as discoloration of the product or an inhomogeneous molecular weight distribution.

WO2007/112901 describes a process for treating viscous products, in particular for carrying out homo-or copolymerization of thermoplastics and elastomers, with conversions of 90 to 98% being achieved. One or more monomers, catalysts and/or initiators and/or chain regulators (Kettenregler) are continuously fed into a back-mixed mixing kneader or kneader reactor and back-mixed with the already reacted product, and the reacted product is discharged from the mixing kneader. Here, the product in the kneader is heated to the boiling temperature, part of the starting material (Edikte) is evaporated, and the exothermic heat of the product is absorbed by evaporative cooling. The process can be carried out without solvent or with only small amounts of solvent. The optimum boiling temperature is adjusted by varying the pressure. Back mixing is performed until a predetermined viscosity of the product is reached. The viscosity is maintained by continuous addition of the raw materials. The integrated product work-up or the process of minimizing the fine particle fraction in the product in combination with continuous bulk polymerization in the preparation of binders, for example for coatings, is not described in the above-mentioned documents and is not prior art.

Disclosure of Invention

Purpose(s) to

The object of the present invention is to provide an improved binder for paint formulations based on acrylate or methacrylate (hereinafter referred to as (meth) acrylate).

It is an object of the present invention, inter alia, to provide (meth) acrylate binders having improved processing properties relative to the prior art. For this purpose, the binder should be present in the form of granules after production and have a fine-particle fraction or dust fraction of less than 0.5% by weight, i.e. particles of less than 250 μm. The binder should also not contain coarse components, i.e. particles larger than 3 mm.

The invention also relates to the production of said binding agents by means of a continuous production method. Continuous production processes are understood to mean processes which can be carried out continuously and without interruption and which consist in particular of the process steps of monomer metering, polymerization, degassing and granulation.

It is a further object of the present invention to provide an environmentally friendly process which can either be carried out solvent-free or with a solvent proportion of up to 10% by weight and which can be carried out at high conversions or with only very low residual monomer proportions.

Furthermore, the binder should have a high thermal stability, for example at a temperature of about 214 ℃. This should be ensured by a particularly low proportion of head-to-head linkages in the polymer chain.

A further object is to be able to meet the requirements made of the high-gloss properties of the binder in such a way that the process can be carried out without the addition of auxiliaries, such as emulsifiers, stabilizers or defoamers.

Solution scheme

The object is achieved by the improved use of a continuous bulk polymerization process by means of which (meth) acrylates can be polymerized without solvent with high conversions. The advantage of the bulk polymerization process over suspension polymerization is a high purity product which can be prepared without the addition of auxiliaries, such as emulsifiers, stabilizers, defoamers or other suspension auxiliaries. Another advantage is that the product is water-free. Binders prepared by means of suspension polymerization often exhibit reduced gloss properties in paints and sometimes also reduced dispersibility in paints. This effect is not only due to the polymer microstructure but also to the process-induced residual moisture of the polymer.

Another advantage of bulk polymerization over suspension polymerization is the use of any amount of hydrophilic comonomers, such as (meth) acrylic acid, amino-functional or hydroxy-functional (meth) acrylates.

The advantage over solution polymerization is that there is no or only a very low proportion of volatile constituents in the polymerization process or in the primary product.

The advantage of the process of the invention over bulk polymerization in batch mode of operation is the significantly higher achievable conversion and thus the lower residual monomer proportion in the end product. In addition, the preparation speed is higher, and the possibility of process parameter variation is wider.

A particular advantage of the process of the invention for preparing binders for paints or coatings is the form in which the product is present at the end of the preparation process without further processing. By combining a continuously operating kneader for the polymerization, a degassing stage (for example a Flash-Entgaser or a degassing kneader for removing volatile constituents or thermally post-treating the polymer) and a granulator, products are obtained which are first free of solvent, second have a water content of less than 1% by weight and third consist only of constituents which are based on the monomers used, chain transfer agents and initiators and have an adjustable particle size.

The granules prepared according to the invention contain less than 0.5% by weight of a fine particle fraction or dust fraction, i.e. particles smaller than 250 μm. The dust fraction can be problematic in many respects in subsequent processing. Particles of this size may adhere to various surfaces due to electrostatic charging and this leads to, for example, nozzle clogging. Dust clouds can also form, for example, during pouring, which not only result in product losses and require special respiratory precautions, but also risk the potential occurrence of dust explosions.

The binders prepared according to the invention are furthermore also free of coarse-grained constituents, i.e. particles larger than 3 mm. Larger particles may not only cause clogging of, for example, the nozzle, but also reduce the bulk density. A particular disadvantage of such coarse-grained materials is, in particular, the reduced dissolution rate in organic solvents, plasticizers or water. This is clearly derived from the more unfavorable surface-to-mass ratio relative to the smaller particles.

The preferred process for achieving the object of the invention is the continuously operating kneader technology. A description of such back-mixed kneading reactors for continuous bulk polymerization from List is given in WO2006/034875 or WO 2007/112901. The polymerization is carried out at a temperature above the glass transition temperature of the polymer. Here, the monomers, catalysts, initiators, etc. are continuously conducted into the reactor and back-mixed with the already reacted products. While the reacted product is continuously removed from the mixing kneader. Unreacted monomers are separated off by means of a residual degassing vessel and are then reintroduced into the reactor. While the thermal after-treatment of the polymer takes place in the residue gas discharge vessel.

A special aspect of the inventive solution is that: the polymerization temperature can be selected individually according to the requirements of the respective product or the respective application. The properties of the binders to be prepared with respect to gloss, thermal stability, dispersing or wetting properties of the pigments and processing properties of the binder or lacquer formulation are surprisingly dependent not only on the composition, molecular weight distribution, functional groups and end groups, but also in particular on the microstructure of the polymer chains. Microstructure in this case refers to the tacticity and the proportion of head-to-head linkages in the polymer chain. Known to those skilled in the art: poly (meth) acrylates prepared by free-radical means are, depending on the monomer composition, copolymers between syndiotactic and random segments (triads) — having only a low proportion of isotactic triads. Polymethacrylates with particularly large syndiotactic proportions can only be prepared by technically expensive methods, for example anionic polymerization at particularly low temperatures or metal-initiated Group Transfer Polymerization (GTP) using stereoselectively acting catalysts. Whereas highly isotactic polymers can be achieved almost exclusively by the latter process. A third possibility for effecting the stereoselective influence on the polymerization consists in adding the complexing agent in the form of an optically active reactant to the polymerization solution. See, for example, EP 1611162 for a related description. However, this mode of operation also has various disadvantages: on the one hand, they are only effective for solution polymerization, and on the other hand, the auxiliary is another polymeric component which either has to be removed at high expense or affects the optical properties of the end product.

Another aspect of paint quality is gloss. It has been shown that gloss is greatly affected by the water or solvent content of the coating matrix. The continuously operated bulk polymerization in the kneader according to the invention has the great advantage over conventional processes such as solution, suspension or emulsion polymerization that it can be carried out without addition of solvents, water or whatever process auxiliaries, such as emulsifiers, defoamers, stabilizers or dispersants. However, these ingredients have a negative impact on gloss performance in applications.

Surprisingly, however, it has additionally been found that the microstructure can also cause a measurable, large influence on the gloss change value of the lacquer. Depending on the polymer composition, it is possible to show that polymers with a less syndiotactic proportion exhibit improved gloss values compared to suspension polymers prepared at 80 ℃ which are regarded as standard.

A further aspect of the invention is the production of (meth) acrylate-based adhesives which have a thermal stability of up to 214 ℃, preferably up to 230 ℃, particularly preferably up to 250 ℃. Thermal stability at a given temperature means that the mass loss is less than 1% by weight when subjected to thermogravimetric analysis (TGA) according to DIN EN ISO 11358. Polymerization at higher temperatures is particularly advantageous for forming so-called head-to-head connections. These bonds in the polymer chain, in which two quaternary carbon atoms are linked to each other in the case of poly (meth) acrylates, exhibit thermal instability at temperatures above 150 ℃ and may initiate depolymerization of the chain upon cleavage. This results in a decrease in product yield and an increase in the residual monomer content in the polymer. Furthermore, such products may show reduced storage stability or weather stability due to unstable bonds.

At higher polymerization temperatures, the formation of head-to-head bonds in poly (meth) acrylates is not only a phenomenon which is observed during bulk polymerization, but also occurs in solution polymers prepared at the corresponding temperatures. The problem of head-to-head connection and the resulting reduction in thermal stability in the present invention is solved by subjecting the product to a thermal after-treatment after the completed polymerization. At temperatures above 120 ℃, preferably above 160 ℃ and particularly preferably above 180 ℃, it is possible not only to remove volatile constituents contained in the product, such as residual monomers or optionally used solvents, but also to open head-to-head bonds and thus to stabilize or depolymerize the relevant polymer chains and to remove the low molecular compounds produced. Optionally, the monomers thus recovered can even be returned to the polymerization process. Such a mode of operation can be achieved without problems in the kneader technology by subsequent process steps, such as rapid degassing, degassing kneaders or degassing extruders.

In one variant of the method, the thermal decomposition of the head-to-head connection and the degassing are carried out separately from one another. The polymer is first conveyed through a melt pipe or heat exchanger. Where a thermal after-treatment is carried out. Volatile constituents, such as residual monomers, solvents and volatile constituents formed during the thermal aftertreatment, are subsequently removed as described above by means of a degassing -machine, a degassing extruder or a rapid degassing machine, and the melt is conducted further to the granulation process.

The monomers to be polymerized are selected from: (meth) acrylic acid esters, for example alkyl (meth) acrylates of linear, branched or cycloaliphatic alcohols having from 1 to 40 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octadecyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate; aryl (meth) acrylates, such as benzyl (meth) acrylate or phenyl (meth) acrylate, each having an unsubstituted or 1 to 4-substituted aryl group; other aromatic substituted (meth) acrylates, such as naphthyl (meth) acrylate; mono (meth) acrylates of ethers, polyethylene glycol, polypropylene glycol or mixtures thereof having 5 to 80 carbon atoms, such as tetrahydrofurfuryl methacrylate, methoxy (meth) ethoxyethyl methacrylate, 1-butoxypropyl methacrylate, cyclohexyloxymethyl methacrylate, benzyloxymethyl methacrylate, furfuryl methacrylate, 2-butoxyethyl methacrylate, 2-ethoxyethyl methacrylate, allyloxymethyl methacrylate, 1-ethoxybutyl methacrylate, 1-ethoxyethyl methacrylate, ethoxymethyl methacrylate, poly (ethylene glycol) methyl ether (meth) acrylate, and poly (propylene glycol) methyl ether (meth) acrylate. The choice of monomers may also include the respective hydroxy-and/or amino-and/or mercapto-and/or olefinic-and/or carboxy-functional acrylates or methacrylates, for example allyl methacrylate or hydroxyethyl methacrylate.

In addition to the abovementioned (meth) acrylates, the compositions to be polymerized may also have other unsaturated monomers which can be copolymerized with the abovementioned (meth) acrylates or can be homopolymerized. Of this class are, in particular, 1-olefins, such as 1-hexene, 1-heptene, branched olefins, such as vinylcyclohexane, 3, 3-dimethyl-1-propene, 3-methyl-1-diisobutylene, 4-methyl-1-pentene, acrylonitrile, vinyl esters, such as vinyl acetate, styrene, substituted styrenes having an alkyl substituent on the vinyl group, such as α -methylstyrene and α -ethylstyrene, substituted styrenes having one or more alkyl substituents on the ring, such as vinyltoluene and p-methylstyrene, halogenated styrenes, such as monochlorostyrene, dichlorostyrene, tribromostyrene and tetrabromostyrene; heterocyclic compounds, such as 2-vinylpyridine, 3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine, 2, 3-dimethyl-5-vinylpyridine, vinylpyrimidine, 9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole, 2-methyl-1-vinylimidazole, vinyloxolane (Vinyloxolan), vinylfuran, vinylthiophene, vinylthiolane (Vinylthiolan), vinylthiazole, vinyloxazole and isoprenyl ethers; maleic acid derivatives, such as maleic anhydride, maleimide, methylmaleimide, cyclohexylmaleimide, and dienes, such as divinylbenzene, and also the respective hydroxy-and/or amino-and/or mercapto-and/or olefinic-functionalized compounds. Furthermore, these copolymers can also be prepared in such a way that they have hydroxyl functions and/or amino functions and/or mercapto functions and/or olefinic functions in the substituents. Examples of these monomers are vinylpiperidine, 1-vinylimidazole, N-vinylpyrrolidone, 2-vinylpyrrolidone, N-vinylpyrrolidone, 3-vinylpyrrolidone, N-vinylcaprolactam, N-vinylbutyrolactam, hydrogenated vinylthiazoles and hydrogenated vinyloxazoles.

The free-radical initiators usually used, in particular peroxides and azo compounds, can be used as polymerization initiators which are usually added to the monomer phase. In some cases, it may be advantageous to use mixtures of various initiators. The amount is generally between 0.1 and 5% by weight, based on the monomer phase. Preference is given to using azo compounds as free-radical initiators, such as azobisisobutyronitrile, 1, 1' -azobis (cyclohexanecarbonitrile) ((R))V40), 2- (carbamoylazo) -isobutyronitrile (N), (N-acetyl-N-V30) or peresters such as t-butyl peroctoate, di (t-butyl) peroxide (DTBP), di (t-amyl) peroxide (DTAP), t-butyl peroxy- (2-ethylhexyl) carbonate (TBPEHC) and other peroxides which decompose at high temperatures. Examples of other suitable initiators are octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, monochlorobenzoyl peroxide, dichlorobenzoyl peroxide, p-ethylbenzoyl peroxide, tert-butyl perbenzoate or azobis- (2, 4-dimethyl) -valeronitrile.

In order to adjust the molecular weight of the polymers formed, up to 8% by weight of one or more chain regulators known per se can also be added to the monomer phase in a conventional manner. Mention may be made, for example, of: mercaptans, such as n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan or mercaptoethanol; thioglycolic acid or esters such as isooctyl thioglycolate or lauryl thioglycolate; an aliphatic chlorine-containing compound; enol ethers or dimeric alpha-methylstyrene. If a branched polymer is to be prepared, the monomer phase may also contain up to about 1% by weight of polyfunctional monomers, such as ethylene glycol di (meth) acrylate, butanediol di (meth) acrylate or divinylbenzene.

In order to be able to optimally adjust the viscosity in a continuously operating reactor, up to 10% by weight of solvents or plasticizers can optionally be added to the system. Such additions may be necessary at particularly high melt viscosities in order to ensure optimum thorough mixing of the reaction solution. Preferably, up to 5% by weight is added to the monomer mixture. It is particularly preferred to carry out the polymerization without adding a solvent or a plasticizer. There is no limitation in terms of the additive substances that can be used. The additive substances may be, for example, acetates, aliphatic compounds, aromatic compounds, or also polyethers or phthalates.

There is a wide range of applications for the products prepared according to the invention. The (meth) acrylate-based bulk polymers are preferably applied in coatings, for example, on metal surfaces, plastic surfaces, ceramic surfaces or wood surfaces. An example of a coating is the use of the polymers according to the invention as binders in building paints, ship paints or container paints. The polymers can likewise be used for road markings, floor coatings, printing inks, heat-sealing lacquers, reactive hot-melt adhesives, adhesive materials or sealing materials.

The examples given below are provided to better illustrate the invention but are not intended to limit the invention to the features disclosed herein.

Detailed Description

Examples

Particle size

Hereinafter referred to as d₅₀-value ofThe particle sizes and particle size distributions indicated are determined according to ISO 13320-1 with a Coulter LS 13320 in the measurement range between 0.04 μm and 2000. mu.m.

Furthermore, particle sizes of greater than 2000 μm are in accordance with ISO/FDISm 13322-2.2: 2006(E) was measured with a Camsizer from Retsch technology.

Measurement of glass transition temperature

The glass transition temperature is measured by means of dynamic differential thermal analysis (DSC) in accordance with DIN EN ISO 11357-1.

Measurement of dissolution time

The unaltered products synthesized in the examples or comparative examples were subjected to temperature-adjusting treatment at 23 ℃ for 24 hours in an air-conditioning room. A4 cm diameter dissolver disk was mounted on the dissolver (Getzmann VMA type) and the apparatus thermostat was set to 23 ℃. 90mL of solvent were pre-charged to a 250mL double-walled vessel and tempered with gentle stirring over a period of 5 minutes. Then a 60g sample of the polymer was added, the lid immediately closed and the stirrer adjusted to 1200 rpm. At 1 minute intervals, the lid was opened and the sample was aspirated by means of a glass pipette for visual assessment. And then replaced into the container. After 20 minutes, the measurement interval was extended to 5 minutes.

Once no more solids or suspended matter could be found at the visual evaluation, the stirrer was removed, the time was noted, and the entire sample was visually evaluated for control. For the case where suspended matter can still be found, the entire measurement process is repeated.

All measurements were performed five times in total and are given as measurement ranges in the corresponding tables.

Example B1, composition 1

Continuous bulk polymerization

A mixture consisting of 20% by weight of methyl methacrylate, 80% by weight of n-butyl methacrylate, 0.4% by weight of TBPEHC from Degussa Initiators and 0.4% by weight of ethylhexyl Thioglycolate (TGEH) is continuously fed to a back-mix kneading reactor from List, as described for example in WO2006/034875, while the reacted polymer is continuously withdrawn from the reactor. The internal temperature in the reactor was 140 ℃. The average residence time was about 30 minutes. The polymer melt was transferred directly after the reactor into a degassing kneader of List, through melt pipes, in which the thermally unstable head-to-head connection was broken at 190 ℃, and in which the residual unreacted monomers were removed from the polymer at a temperature of 180 ℃. There is a possibility to take out samples for TGA measurement between the reactor and the vented kneader. After the degassing, the polymer melt was directly conducted further to a Compact 120 underwater pelletizer of the company BKG GmbH equipped with a 0.8mm orifice plate. Subsequently, the granules were dried in a Master300 dryer, the pellets were collected in an appropriate container, and the particle size was determined as described above.

Comparative example R1, composition 1 (suspension polymerization)

3200ml of VE water were initially introduced into a 5LHWS glass reactor equipped with an Inter-MIG stirrer and a reflux condenser, the stirrer was set to a rotation of 300 revolutions per minute and heated to an external temperature of 40 ℃. 200g of polyacrylic acid and 0.5g of potassium hydrogensulfate were added and dispersed by stirring. 1280g (80%) n-butyl methacrylate, 320g (20%) methyl methacrylate, 7.5g Peroxan LP and 4g TGEH were mixed in a beaker and homogenized by stirring half. The raw monomer solution was pumped into the reactor. The internal temperature was adjusted to 85 ℃. When the exotherm subsided, the polymerization reaction ended. The batch was cooled. The mother liquor was separated from the polymer beads by means of a suction filter. The particle size was determined as described above.

Example B2, composition 2

As in example 1, but the mixture fed to the reactor consisted of 65% n-butyl methacrylate, 34% methyl methacrylate, 1% methacrylic acid, 0.8% Dr.Spiess Chemische Fabrik GmbH lauryl mercaptan. After degassing in the degassing kneader, the polymer melt was passed directly further to a minigranulator from the company BKG GmbH equipped with a 0.6mm perforated plate. Subsequently, the granules were dried, collected and the particle size was determined in analogy to example B1.

Example B3, breakdown to 2

As in example 2, the preliminary setting of the aperture size of the micro-granulator was changed by using a 1.5mm aperture plate in order to obtain relatively coarse particles.

Comparative example R2, composition 2 (suspension polymerization)

As comparative example 1, but using 510g of methyl methacrylate, 975g of n-butyl methacrylate, 15g of methacrylic acid, 7.5g of Peroxan LP and 12g of lauryl mercaptan from Dr.

Comparative example R3, composition 2 (bulk polymerization)

10g of methacrylic acid, 340g of methyl methacrylate, 650g of n-butyl methacrylate, 2.5g of TRIGONOX 21S (Akzo Nobel) and 3.5g of lauryl mercaptan from Dr. Spiess Chemische Fabrik GmbH were pre-charged between two glass plates sealed at their edges with a sealing strip (Keder), the spacing between the two glass plates being 10 mm. The entire mold was placed in a water bath at 40 ℃ for 24 hours. The temperature was subsequently adjusted at 100 ℃ for a further 8 hours. After cooling, the product is removed from the mold and broken up with the aid of a mill.

Two comparative examples prepared by means of suspension polymerization show a fraction of fine-grained material associated with 7.3 wt.% or 31.6 wt.% of material having a particle size of less than 250 μm. In contrast, the polymers prepared according to the invention are free of fine-grained materials of this size. At the same time, polymer powders which, like the suspension polymers R1 or R2, contain no coarse particles can be prepared by the process of the invention. These constituents adversely impair the dissolution rate and the workability of the lacquer.

Dissolution time

MEK: methyl ethyl ketone

Comparative example R4 is the sieve fraction from example B2 with a particle size of less than 710 μm. Comparison with comparative example R2 shows that a large particle size-independent effect in terms of dissolution time is not to be expected. Also shown is: example B2 was compared with control R2 or B1 was compared with R1, although D₅₀Values of about two or more than three times, but dissolution times of only 20% to 37% more, or about 130%. In contrast, the great advantage is that the product has no fine fractions as in the suspension polymer, so that, as already mentioned, a significantly better processability is ensured.

By selecting a suitable perforated plate, it can also be shown from example B2 that the process according to the invention can be optimized with minor modifications also in terms of product dissolution time — further avoiding the formation of coarse or fine fractions.

The advantages over discontinuously prepared, ground bulk polymerization according to the prior art (comparative example R3) are evident from a three to four times dissolution time. Even the inventive example (B3) granulated particularly coarsely shows a significantly faster solubility.

Claims (14)

1. A bulk polymerization process for preparing (meth) acrylate-based binders for lacquer formulations by continuous bulk polymerization,

it is characterized in that the preparation method is characterized in that,

a) the process is carried out in a kneader at a reaction temperature of from 20 ℃ to 250 ℃,

b.) the monomers are metered continuously in a kneader,

c.) the thermal aftertreatment of the binder in the melt line or in a heat exchanger in a continuous process step immediately following the polymerization,

d) the binder is subsequently freed of volatile constituents by means of a degassing kneader, degassing extruder or rapid degassing machine at temperatures above 160 ℃,

e.) granulating the binder in the immediately subsequent continuous process step,

and the granulated binder has a particle size with a particle content of less than 250 μm of at most 0.5% by weight;

wherein the binder has a thermal stability of up to 214 ℃ by carrying out the thermal after-treatment at a temperature of more than 160 ℃ in a device connected downstream of the reactor, and volatile constituents are removed from the binder in a further continuously operating process step immediately following the thermal after-treatment.

2. A bulk polymerization process according to claim 1,

a.) the binder is made from a monomer mixture consisting only of monomers and initiators and optionally chain transfer agents and up to 10% by weight of a solvent,

b.) the process is carried out without addition of auxiliaries,

and c) imparting thermal stability to the polymer up to at least 214 ℃ by thermal post-treatment in the process.

3. A bulk polymerisation process according to claim 2 characterised in, that said auxiliary agent is an emulsifier, a stabiliser or an antifoaming agent.

4. A bulk polymerization process according to claim 1,

the binder is obtained by granulation without sieving, the binder

a.) does not contain ingredients greater than 3mm and

b.) contains at most 0.5% by weight of constituents smaller than 250 μm.

5. A bulk polymerization process according to claim 1,

the reaction temperature is higher than 100 ℃ and the glass transition temperature is 2 ℃ lower than that of the same fine polymer prepared by means of suspension polymerization at 80 ℃.

6. A (meth) acrylate-based binder for coatings preparable according to the bulk polymerization process of claim 1.

7. The (meth) acrylate-based binder for coatings according to claim 6, which additionally contains styrene and/or other free-radically polymerizable vinyl compounds.

8. Use of the binder of claim 6 in paint formulations for coating metal surfaces, plastic surfaces, ceramic surfaces or wood surfaces.

9. Use of the binder of claim 6 in marine or container paints.

10. Use of the binder of claim 6 in architectural paints.

11. Use of the binder of claim 6 in road markings or floor coatings.

12. Use of the binder of claim 6 in printing inks.

13. Use of the binder according to claim 6 in reactive hot melt adhesives or heat seal paints.

14. Use of the binder according to claim 6 in adhesive or sealant materials.