HK1116808B - METHOD FOR PRODUCTION OF BEAD POLYMERS WITH AN AVERAGE PARTICLE SIZE IN THE RANGE OF 1μM TO 40μM AND MOULDED MASSES AND MOULDED BODIES COMPRISING BEAD POLYMERS - Google Patents

Description

Method for producing bead polymers having an average particle size of 1 μm to 40 μm, and molding compositions and moldings comprising bead polymers

Technical Field

The invention relates to a method for producing bead polymers having an average particle size of 1 μm to 40 μm, wherein a polymerizable composition is dispersed and polymerized in an aqueous phase. The invention also relates to moulding compositions and mouldings comprising the bead polymers prepared according to the invention.

Background

Bead polymers having particle sizes on the order of 1 μm to 40 μm and having a relatively narrow particle size distribution are desired for different applications. These beads can be used, inter alia, as additives for PMMA moulding compositions.

Light-scattering molding compositions are particularly regarded as fields of application. Here, standard molding compositions are mixed with so-called scattering beads which are crosslinked and whose refractive index differs from that of the matrix. PMMA-based scattering particles, whose particle size is much greater than 40 μm, are currently used in these molding compositions. The advantage of these scattering particles is that the moldings have a high degree of forward scattering once the scattering particles have been incorporated into the molding composition. With conventional opacifying agents (Tru bungsmitetln), e.g. BaSO₄Or TiO₂In contrast, a significantly higher light efficiency at high scattering is achieved because the losses due to back scattering are smaller. Preferred forward scattering can be determined by measuring the light transmittance of the molded articles comprising the scattering beads in combination with the energy half-value angle or intensity half-value angle.

The smaller the particle size of the scattering beads, the higher the scattering effect for the same proportion by weight in the molding composition. Thus, their use can be reduced by using smaller beads. This saves costs and resources. Furthermore, the molding compositions charged with the smaller bead polymers exhibit excellent mechanical properties, since the influence of reduced amounts of scattering beads on these properties is significantly reduced. If scattering beads having a diameter of less than 5 μm are used, the yellow impression of the molding compositions prepared is markedly increased.

Furthermore, the beads as described above can also be used in matt moulding compositions and polyalkyl (meth) acrylate (PAMA) plastisols. However, these areas of application are not important in the present invention.

Polymer particles having a particle size of the order of 1 to 10 μm can be efficiently realized by a precipitation polymerization using a large amount of an organic solvent. However, the solvents used are not easy to handle in terms of safety and waste technology. There are also problems arising in the post-treatment aspect. The beads obtained in this way are therefore expensive and, for reasons of cost, have not been used in the fields of application described above.

The polymer beads can be obtained at low cost by conventional suspension polymerization. However, the particles thus obtained are generally larger than 40 μm and have a broad distribution.

For example, european patent application EP 0443609 a2 discloses a suspension process for preparing bead polymers, wherein two separately introduced phases (monomer and continuous) are combined in a mixing unit with high shear energy and the monomer is then polymerized in a conventional reaction vessel. To stabilize the dispersion, various auxiliaries are mentioned. These include, inter alia, inorganic substances, such as calcium phosphate, and organic compounds, such as cellulose derivatives or polyvinyl alcohol. EP 0443609 a2 does not describe the use of aluminium compounds.

Monomers used in EP 0443609 a2 are, in particular, styrene and (meth) acrylates. The examples show the polymerization of a monomer mixture comprising 80% by weight of styrene and 20% by weight of butyl acrylate. The polymer particles formed here have a particle size of from 5 μm to 10 μm. EP 0443609 a2 does not mention the use of a cross-linking agent.

According to EP 0443609 a2, the polymer particles can be used in particular in the powder production industry. However, they are not suitable for light-scattering molding compositions since the non-crosslinked polymer particles will dissolve in the molding composition to be prepared and are therefore not effective as light-scattering particles.

The publication DE 10065501A 1 discloses a process for preparing bead polymers having an average particle size of from 1 μm to 40 μm, in which a polymerizable composition comprising at least 50% by weight of (meth) acrylate is dispersed and polymerized in an aqueous phase. At not less than 10³s^-1At a shear rate of (a) to prepare a dispersion stabilized with an aluminum compound.

The bead polymers formed can be used in particular for producing moldings having a matt surface, the moldings shown in the examples having a light transmission according to DIN5036 of from 76.3 to 91.1, a yellowing index according to DIN 6167 of from 2.9 to 9.4 and an energy half-value angle of from 18.5 to 22.5. However, for many applications, higher scattering effects are desirable.

Disclosure of Invention

In view of the prior art described and discussed here, it is therefore an object of the present invention to provide moldings which scatter light more strongly, while having as high a transparency as possible and as low a yellowness index as possible. The intention here is to achieve an improved scattering action in a manner which is as inexpensive as possible.

These objects, as well as others which, although not explicitly mentioned, may be deduced in an obvious manner from the context discussed herein, or which must be derived therefrom, are achieved by a moulding obtainable from a bead polymer obtainable by a process according to claim 1. The invention therefore protects a process for preparing the bead polymer, a molding composition comprising the bead polymer and a molded article obtainable from the molding composition. The respective dependent claims describe particularly advantageous developments of the process, of the bead polymer, of the molding composition and of the molded article.

Surprisingly, a process for the preparation of high specification bead polymers having an average particle size of from 1 μm to 40 μm was successfully provided by the following means, without the substantial use of any organic solvent which has to be separated off after the polymerization: dispersing and polymerizing in an aqueous phase a polymerizable composition of the composition as given in claim 1, wherein the composition is at ≥ 10³s^-1At a shear rate of (a) to prepare a dispersion stabilized with an aluminum compound.

The following advantages are achieved in particular by the solution according to the invention:

the process of the invention allows the filtration of the bead polymer obtained.

The polymerization process of the present invention can be carried out using commercially available equipment.

According to the present invention, since the amount of organic solvent used is zero or only minimal, bead polymers can be obtained without major safety risks. This makes it possible in particular to avoid the release or disposal of substances which are harmful to the environment.

The bead polymer is extremely inexpensive.

The bead polymers prepared according to the invention exhibit a very high scattering effect when incorporated into molding compositions and shaped to give moldings. They are further distinguished by a low yellowness index, a high light transmission and a large intensity half-value angle.

The bead polymers to be prepared within the scope of the invention have an average particle size of from 1 μm to 40 μm, preferably from 5 μm to 35 μm. The particle size is based on the particle size. This value can be determined, for example, by a laser extinction method. For this purpose, a CIS particle analyzer from the company l.o.t.gmbh can be used, wherein the measurement method for determining the particle size is present in the user manual. This method is preferred. Particle size can also be determined by measuring and counting particles on a suitable scanning electron micrograph.

Particular embodiments of the bead polymers prepared according to the invention exhibit a narrow particle size distribution. The standard deviation of the mean particle diameter is particularly preferably ≦ 30 μm, more particularly preferably ≦ 20 μm and especially ≦ 10 μm.

In a particular embodiment of the process according to the invention, spherical or globular bead polymers are prepared which do not agglomerate, aggregate or agglomerate, or only very slightly (zusammenlagern).

According to the invention, bead polymers are prepared by polymerization of a composition comprising, in each case based on its total weight:

■ of more than 50.0% by weight, preferably more than 50.0% by weight to 99.0% by weight, advantageously 60.0% by weight to 98.5% by weight, particularly preferably 70.0% by weight to 94.3% by weight, in particular 80.0% by weight to 90.0% by weight, of at least one compound of the formula (I),

■ 0.1 wt.% to 10.0 wt.%, preferably 0.1 wt.% to 5.0 wt.%, advantageously 0.5 wt.% to 4.0 wt.%, particularly preferably 0.7 wt.% to 3.5 wt.%, in particular 1.0 wt.% to 3.0 wt.%, of at least one crosslinking agent and

■ less than 49.9% by weight, preferably from 0.9% by weight to less than 49.9% by weight, advantageously from 1.0% by weight to 40.0% by weight 40.0w t%, particularly preferably from 5.0% by weight to 30.0% by weight, in particular from 9.0% by weight to 19.0% by weight, of at least one compound of the formula (II)

Radical (I)¹R is hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms,hydrogen, methyl or ethyl, especially hydrogen, is preferred.

²R～⁶The R radicals are each, independently of one another, hydrogen, linear or branched alkyl having from 1 to 6 carbon atoms or halogen. Particularly preferred alkyl groups have 1 to 4 carbon atoms, advantageously 1 or 2 carbon atoms, in particular 1 carbon atom, and include in particular methyl, ethyl and isopropyl. Particularly preferred halogens are chlorine and bromine. In a very particularly advantageous embodiment, all²R to⁶The R group is hydrogen.

The radical R is hydrogen or methyl.

Radical (I)⁷R is a linear or branched alkyl group or an optionally alkylated cycloalkyl group having from 1 to 40, preferably from 1 to 24, advantageously from 1 to 12, particularly preferably from 1 to 6, in particular from 1 to 4, carbon atoms.

Radical (I)⁸R and⁹r is each, independently of one another, hydrogen or a radical of the formula-COOR ', where R' is hydrogen or an alkyl radical having 1 to 40, preferably 1 to 24, advantageously 1 to 12, particularly preferably 1 to 6, in particular 1 to 4, carbon atoms.

For the purposes of the present invention, particularly advantageous compounds of the formula (I) include in particular styrene, substituted styrenes having alkyl substituents in the side chains, such as α -methylstyrene and α -ethylstyrene, substituted styrenes having alkyl substituents in the ring, such as vinyltoluene and p-methylstyrene, halogenated styrenes, such as monochlorostyrene, dichlorostyrene, tribromostyrene and tetrabromostyrene.

Among the particularly preferred compounds of the formula (II), mention may in particular be made of (meth) acrylates, fumarates and maleates derived from saturated alcohols, such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, 2-tert-butyl heptyl (meth) acrylate, octyl (meth) acrylate, 3-isopropyl heptyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, 5-methylundecyl (meth) acrylate, dodecyl (, 2-methyldodecyl (meth) acrylate, tridecyl (meth) acrylate, 5-methyltrodecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, 2-methylhexadecyl (meth) acrylate, heptadecyl (meth) acrylate, 5-isopropylheptadecyl (meth) acrylate, 4-tert-butyloctadecyl (meth) acrylate, 5-ethyloctadecyl (meth) acrylate, 3-isopropyloctadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, hexadecyleicosyl (meth) acrylate, and mixtures thereof, Stearyl eicosyl (meth) acrylate, behenyl (meth) acrylate, and/or eicosyltrietetradecyl (meth) acrylate;

cycloalkyl (meth) acrylates, such as cyclopentyl (meth) acrylate, 2, 3, 4, 5-tetra-tert-butylcyclohexyl (meth) acrylate, cyclohexyl (meth) acrylate, bornyl (meth) acrylate;

and the corresponding fumarates and maleates.

Ester compounds having a long-chain alcohol residue, in particular alcohol residues having 6 and more carbon atoms, can be obtained, for example, by reaction of (meth) acrylates, fumarates, maleates and/or the corresponding acids with long-chain fatty alcohols, wherein generally a mixture of esters is formed, for example a mixture of (meth) acrylates having different long-chain alcohol residues. Among these fatty alcohols, particularly included are Oxo Alcohol7911、Oxo Alcohol7900、OxoAlcohol1100、Alfol610、Alfol810、Lial125 and NafolType (Sasol Olefins)& Surfactants GmbH)；Alphanol79(ICI)；Epal610 and Epal810(Ethyl Corporation)；Linevol79、Linevol911 and Neodol25E(Shell AG)；Dehydad，HydrenolAnd LorolType (Cognis); acropol35 and Exxal10(ExxonChemicals GmbH)；Kalcol 2465(Kao Chemicals)。

Among the compounds of the formula (II), (meth) acrylates are particularly preferred over maleates and fumarates, i.e. R is in a particularly preferred embodiment⁸And R⁹Is hydrogen. Methacrylates are generally preferred over acrylates.

Within the scope of the present invention, the term "(meth) acrylate" includes methacrylate, acrylate and mixtures of both.

According to the present invention, the kind of the crosslinking agent is not particularly limited. Instead, any compound known per se for crosslinking in the context of free-radical polymerization and which can be copolymerized with compounds of the general formulae (I) and (II) can be used. Wherein especially comprises

(a) Difunctional (meth) acrylates, preferably compounds of the formula:

wherein R is hydrogen or methyl, n is a positive integer greater than or equal to 2, preferably from 3 to 20, in particular di (meth) acrylates of propylene glycol, butylene glycol, hexylene glycol, octylene glycol, nonylene glycol, decylene glycol and eicosylene glycol.

A compound of the formula:

where R is hydrogen or methyl and n is a positive integer from 1 to 14, in particular the di (meth) acrylates of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dodecaethylene glycol, tetradecanethylene glycol, propylene glycol, dipropylene glycol (Dipropylglycol) and tetradecanethylene glycol.

Glycerol di (meth) acrylate, 2 '-bis [ p- (gamma-methacryloxy-beta-hydroxypropoxy) -phenyl propane or bis GMA, bisphenol A dimethacrylate, neopentyl glycol di (meth) acrylate, 2' -bis (4-methacryloxypolyethoxyphenyl) propane having 2 to 10 ethoxy groups per molecule, and 1, 2-bis (3-methacryloxy-2-hydroxypropoxy) butane.

(b) Tri-or polyfunctional (meth) acrylates, in particular trimethylolpropane tri (meth) acrylate and pentaerythritol tetra (meth) acrylate.

(c) Graft crosslinkers having at least two differently reactive carbon-carbon double bonds, in particular allyl methacrylate and allyl acrylate;

(d) aromatic crosslinking agents, in particular 1, 2-divinylbenzene, 1, 3-divinylbenzene and 1, 4-divinylbenzene.

For the purposes of the present invention, the following compounds have proven particularly suitable:

(meth) acrylic esters derived from unsaturated alcohols, such as oleyl (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, 2, 4, 5-tri-tert-butyl-3-vinylcyclohexyl (meth) acrylate, 3-vinylcyclohexyl (meth) acrylate;

methacrylates of unsaturated ether alcohols, such as vinyloxyethoxyethyl methacrylate, 1-methyl- (2-vinyloxy) ethyl methacrylate, allyloxymethyl methacrylate;

poly (meth) acrylates such as trimethylol (methyl) propane tri (meth) acrylate, diol di (meth) acrylate, bis ((meth) acryloyloxyethyl) sulfide; and dienes such as divinylbenzene.

Particular preference is given to using diol di (meth) acrylates.

Preferred mixtures for preparing the preferred bead polymers may additionally comprise, in particular, ethylenically unsaturated monomers which can be copolymerized with compounds of the general formulae (I) and/or (II). The proportion of comonomers is preferably from 0.01 to 25.0% by weight, particularly preferably from 0.01 to 10.0% by weight, particularly preferably from 0.01 to 5.0% by weight, in particular from 0.01 to 1.0% by weight, based on the total weight of the monomer composition.

Comonomers which are particularly suitable for the polymerization according to the invention here correspond to the following general formula:

wherein R is^1*And R^2*Independently selected from hydrogen, halogen, CN, linear or branched alkyl having 1 to 20, preferably 1 to 6, particularly preferably 1 to 4 carbon atoms, which may be substituted by 1 to (2n +1) halogen atoms, where n is the number of carbon atoms in the alkyl group (e.g. CF)₃) Cycloalkyl having 3 to 8 carbon atoms, which may be substituted with 1 to (2n-1) halogen atoms, preferably chlorine, wherein n is the number of carbon atoms of the cycloalkyl; an aryl group having 6 to 24 carbon atoms, which may be substituted with 1 to (2n-1) halogen atoms, preferably chlorine, and/or an alkyl group having 1 to 6 carbon atoms, wherein n is the number of carbon atoms of the aryl group; c (═ Y)^*)R^5*、C(＝Y^*)NR^6*R^2*、Y^* C(＝Y^*) R^5*、SOR^5*、SO₂R^5*、OSO₂R^5*、NR^8*、SO₂R^5*、PR^5* ₂、P(＝Y^*)R^5* ₂、Y^*PR^5* ₂、Y^*P(＝Y^*)R^5* ₂，NR^8* ₂It may be substituted by another R^8*Aryl or heterocyclyl quaternization, wherein Y^*Can be used forIs NR^8*S or O, preferably O; r^5*Is alkyl having 1 to 20 carbon atoms, alkylthio having 1 to 20 carbon atoms, OR¹⁵(R¹⁵Is hydrogen or an alkali metal), an alkoxy group, aryloxy group or heterocyclyloxy group having 1 to 20 carbon atoms; r^6*And R^7*Independently hydrogen or an alkyl group having 1 to 20 carbon atoms, R^8*Is hydrogen or a linear or branched alkyl or aryl group having 1 to 20 carbon atoms;

R^3*and R^4*Independently selected from hydrogen, halogen (preferably fluorine or chlorine), alkyl having 1 to 6 carbon atoms, and COOR^9*Wherein R is^9*Is hydrogen, an alkali metal or an alkyl group having 1 to 40 carbon atoms, or R^3*And R^4*May together form formula (CH)₂)_n’Which may be substituted by 1 to 2 n' halogen atoms or C₁-C₄Alkyl substitution, or formation of formula C (═ O) -Y^*-C (═ O) where n' is 2 to 6, preferably 3 or 4, Y^*As defined above; and wherein the radical R^1*、R^2*、R^3*And R^4*At least two of the groups in (a) are hydrogen or halogen.

Among the preferred comonomers, vinyl halides, such as vinyl chloride, vinyl fluoride, vinylidene chloride and vinylidene fluoride;

vinyl esters, such as vinyl acetate;

heterocyclic vinyl compounds, e.g. 2-vinylpyridine, 3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine, 2, 3-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine, 9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole, 1-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone, 2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine, N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane (Vinyloxolan), vinylfuran, vinylmethylfuranAzole and hydrogenated vinylAzole;

vinyl and isoprenyl ethers;

maleic acid and maleic acid derivatives such as maleic anhydride, methylmaleic anhydride, maleimide, methylmaleimide;

fumaric acid and fumaric acid derivatives;

acrylic acid and methacrylic acid;

aryl (meth) acrylates, such as benzyl methacrylate or phenyl methacrylate, where the aryl radicals can each be unsubstituted or substituted up to four times.

Methacrylic esters of halogenated alcohols, such as 2, 3-dibromopropyl methacrylate, 4-bromophenyl methacrylate, 1, 3-dichloro-2-propyl methacrylate, 2-bromoethyl methacrylate, 2-iodoethyl methacrylate, chloromethyl methacrylate;

hydroxyalkyl (meth) acrylates, such as 3-hydroxypropyl methacrylate, 3, 4-dihydroxybutyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2, 5-dimethyl-1, 6-hexanediol (meth) acrylate, 1, 10-decanediol (meth) acrylate;

carbonyl-containing methacrylates, e.g. 2-carboxyethyl methacrylate, carboxymethyl methacrylate, methacrylic acidOxazolidylethyl ester, N- (methacryloyloxy) formamide, acetonyl methacrylate, N-methacryloylmorpholine, N-methacryloyl-2-pyrrolidone, N- (2-methacryloyloxyethyl) -2-pyrrolidone, N- (3-methacryloyloxypropyl) -2-pyrrolidone, N- (2-methacryloyloxypentadecyl) -2-pyrrolidone, N- (N-methacryloyloxymethyl) methyl-2-pyrrolidone, N- (2-methacryloyloxypentadecyl) methyl-2-pyrrolidone, N- (2-methacryloyloxypentad,N- (3-methacryloyloxyheptadecyl) -2-pyrrolidone;

diol methacrylates, such as 1, 2-butanediol methacrylate, 2-butoxyethyl methacrylate, 2-ethoxyethoxymethyl methacrylate, 2-ethoxyethyl methacrylate;

methacrylates of ether alcohols, for example tetrahydrofurfuryl methacrylate, methoxyethoxyethyl methacrylate, 1-butoxypropyl methacrylate, cyclohexyloxymethyl methacrylate, methoxymethoxyethyl methacrylate, benzyloxymethyl methacrylate, furfuryl methacrylate, 2-butoxyethyl methacrylate, 2-ethoxyethoxyethoxymethyl methacrylate, 2-ethoxyethyl methacrylate, 1-ethoxybutyl methacrylate, methoxymethyl methacrylate, 1-ethoxyethyl methacrylate,

ethoxymethyl methacrylate, and ethoxylated (meth) acrylates, preferably having 1 to 20, especially 2 to 8 ethoxy groups;

aminoalkyl (meth) acrylates and aminoalkyl (meth) acrylamides, e.g. N- (3-dimethylaminopropyl) methacrylamide, dimethylaminopropyl methacrylate, aminopropyl methacrylate,

3-diethylaminopentyl methacrylate, 3-dibutylaminohexadecyl (meth) acrylate;

nitriles of (meth) acrylic acid and other nitrogen-containing methacrylates, such as N- (methacryloyloxyethyl) diisobutyl ketimine, N- (methacryloyloxyethyl) dihexadecyl ketimine, methacrylamidoacetonitrile, 2-methacryloyloxyethyl methyl cyanamide, cyanomethyl methacrylate;

heterocyclic (meth) acrylates such as 2- (1-imidazolyl) ethyl (meth) acrylate, 2- (4-morpholinyl) ethyl (meth) acrylate, and 1- (2-methacryloyloxyethyl) -2-pyrrolidone;

epoxy alkyl methacrylates, such as 2, 3-epoxybutyl methacrylate, 3, 4-epoxybutyl methacrylate, 10, 11-epoxyundecyl methacrylate, 2, 3-epoxycyclohexyl methacrylate, 10, 11-epoxyhexadecyl methacrylate;

glycidyl methacrylate.

These monomers may be used alone or in a mixture.

The polymerization is generally initiated using known free-radical initiators. Among the preferred initiators, mention may in particular be made of the azo initiators known in the art, such as AIBN and 1, 1-azobiscyclohexanecarbonitrile, and also peroxy compounds, such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl peroxide, tert-butyl per 2-ethylhexanoate, ketone peroxide, methyl isobutyl ketone peroxide, cyclohexanone peroxide, dibenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyisopropylcarbonate, 2, 5-bis (2-ethylhexanoylperoxy) -2, 5-dimethylhexane, tert-butyl peroxy 2-ethylhexanoate, tert-butyl peroxy 3, 5, 5-trimethylhexanoate, dicumyl peroxide, 1-bis (tert-butylperoxy) cyclohexane, 1-bis (tert-butylperoxy) -3, 3, 5-trimethylcyclohexane, cumyl hydroperoxide, tert-butyl hydroperoxide, bis (4-tert-butylcyclohexyl) peroxydicarbonate, mixtures of two or more of the abovementioned compounds with one another, and also mixtures of the abovementioned compounds with compounds not mentioned which likewise form free radicals.

These compounds are generally used in an amount of 0.1 to 10.0% by weight, preferably 0.5 to 3.0% by weight, based on the total weight of the monomers.

The ratio of water to monomer is usually 0.4: 1 to 20: 1, preferably 2: 1 to 8: 1, based on the weight of the components.

In order to stabilize the dispersion, aluminum compounds which are poorly soluble in water must be used. Among them, aluminum oxide Al is particularly included₂O₃And aluminum hydroxide Al (OH)₃Preference is given here to Al (OH)₃. Particularly suitable are aluminum hydroxides prepared by precipitation, wherein the precipitation should be carried out as close as possible to the time before the dispersion is formed. In a particular embodiment of the process according to the invention, the precipitation is carried out within 2 hours, preferably within 1 hour, particularly preferably within 30 minutes, before the formation of the dispersion.

For example, Al may be added₂(SO₄)₃Dissolving in water. Then, a sodium carbonate solution can be blended into the solution until the pH value is 5-5.5. A colloidal dispersion of the aluminium compound in water results from this procedure, which is particularly preferred.

The aluminum compounds are preferably used in amounts of from 0.5 to 200.0% by weight, particularly preferably from 3.0 to 100.0% by weight, very particularly preferably from 4.0 to 20.0% by weight, based on the total weight of the monomers used. If the amount is smaller, there is a risk that only an unstable dispersion is obtained, and phase separation occurs, at least relatively large aggregates are formed. If the amount is larger, there is a risk that a uniform dispersion cannot be obtained.

Other methods which are particularly suitable are those in which, for stabilization, other auxiliaries are used in addition to the aluminum compound. Among these, surfactants such as anionic, cationic and neutral emulsifiers are specifically included.

Examples of anionic emulsifiers are alkali metal salts of higher fatty acids having 8 to 30 carbon atoms, such as palmitic acid, stearic acid and oleic acid, alkali metal salts of sulfonic acids having, for example, 8 to 30 carbon atoms, in particular the sodium salts of alkyl or arylalkyl sulfonic acids, alkali metal salts of half esters of phthalic acid and alkali metal salts of resin acids, such as abietic acid.

The cationic emulsifiers include in particular salts of long-chain amines, in particular unsaturated amines having from 10 to 20 carbon atoms, or quaternary ammonium compounds having relatively long-chain olefin or paraffin radicals.

Examples of neutral emulsifiers are ethoxylated fatty alcohols, ethoxylated fatty acids and ethoxylated phenols, and fatty acid esters of polyhydric alcohols, such as pentaerythritol or sorbitol.

The amount of the above-mentioned emulsifier is preferably 0.0 to 5.0 wt%, particularly preferably 0.3 to 3.0 wt%, based on the weight of the aluminum compound.

Conventional additives and auxiliaries may additionally be added to the mixture before, during or after the formation of the dispersion. These include in particular substances which impart specific properties to the particles, such as polymers, dyes and pigments, which, if appropriate, are ferromagnetic. Complexing agents such as EDTA or Trilon A, and compounds that inhibit formation of the deposit layer on the container, such as polyethylene glycol, may additionally be used.

For the purposes of the present invention, the shear rate is ≥ 10³s^-1The dispersion was carried out. The shear rate is preferably 10⁴s^-1～10⁵s^-1. At < 10³s^-1The particle size of the bead polymer formed is greater than 40 μm at shear rate(s). The shear rate can be defined as the value obtained by dividing the absolute value of the difference in velocity of two planes, between which the mixture to be dispersed is located in the space, by the distance between the planes, which have a small separation of at most 6 mm.

The dispersion may be prepared by any method suitable for the purpose. For this purpose, dispersers known to the person skilled in the art are generally used. Including, inter alia, Dispermat, available from VMA-Getzmann, reichhof; Ultra-Turrax from Jankeund Kunkel, Staufen, and pressure homogenizer from Gaulin, Lubeck. Devices using rotor-stator systems are also known, such as Dispax, available from Janke undKunkel corporation, Staufen; cavitron homogenizer from V.Hagen&Funke Sprochhvel; homogenizers from Kotthoff, Essen, and homogenizers from DoeeOliver, Grevenbroich. This is achieved byThese devices are usually 1000 to 25000min^-1Preferably 2000 to 25000min^-1Is operated at the rotational speed of (1). In addition, the high shear forces required for the formation of the dispersion can likewise be achieved by exposure to ultrasound, by pressing the mixture to be dispersed under high pressure through a narrow gap or through a small-diameter nozzle, and by means of a colloid mill.

The dispersion of the monomers and other components in the reaction mixture is generally carried out at a temperature of 0 to 100 ℃, preferably 20 to 60 ℃, but not limited thereto.

The dispersion time can be within wide limits, depending on the desired diameter of the monomer droplets, the size distribution to be adjusted and the quantitative proportions of the mixture constituents. The dispersion can generally be prepared within a few hours.

The dispersion is generally carried out before the polymerization starts. However, in order to avoid any possibility of forming relatively large aggregates, in particular at the beginning of the polymerization reaction, high shear forces may be applied to the dispersion. On the other hand, the polymerization should be carried out shortly after the dispersion is formed. Surprisingly, however, it has been found that dispersions stabilized by means of aluminum compounds can be stored for relatively long times. This property makes it easy to use conventional polymerization equipment, since, unlike many conventional processes, exposure to shear forces is not necessary at the start of the polymerization reaction.

The polymerization reaction may be carried out at atmospheric pressure, subatmospheric pressure or superatmospheric pressure. The temperature of the polymerization reaction is also not critical. However, depending on the initiator system used, it is generally in the range from 0 ℃ to 200 ℃, preferably from 40 ℃ to 130 ℃, particularly preferably from 60 ℃ to 120 ℃, without this being intended to be limiting.

Once the polymerization has ended, the aluminum compound can be converted into a water-soluble form, for example by addition of sulfuric acid or hydrochloric acid. The bead polymer can be isolated without problems by filtration under water pressure. If known organic compounds are used to stabilize the dispersion, rather than the aluminum compounds essential to the invention, such filtration is not possible due to the rheological properties of the mixture.

The bead polymers obtained according to the process described above are used in particular in moulding compositions, which are likewise provided by the present invention. Suitable matrix polymers are any thermoplastically processable polymers known for this purpose. These include, in particular, polyalkyl (meth) acrylates, such as polymethyl methacrylate (PMMA), polyacrylonitrile, polystyrene, polyethers, polyesters, polycarbonates, polyvinyl chloride. Among them, preferred is a polyalkyl (meth) acrylate. These polymers may be used alone or in a mixture. These polymers may also be present in the form of copolymers.

The refractive indices of the matrix polymer and bead polymer are advantageously different from each other, and their difference is preferably at least 0.02.

The content of bead polymer is advantageously from 0.1% by weight to 20.0% by weight, preferably from 1.0% by weight to 15.0% by weight, advantageously from 3.0% by weight to 10.0% by weight, in particular from 4.0 to 8.0% by weight, based on the total weight of the molding composition.

The molding composition may comprise any type of conventional additives. Among these, in particular antistatic agents, antioxidants, mold release agents, flame retardants, lubricants, dyes, flow improvers, fillers, light stabilizers and organophosphorus compounds, such as phosphites or phosphonates, pigments, weathering stabilizers and plasticizers.

Moldings having light-scattering properties can be obtained from the molding compositions described above by known processes, such as extrusion. These moldings advantageously have a light transmission to DIN5036 of more than 40.0%, preferably more than 45.0%, in particular more than 50.0%. The strength half-value angle (. beta.) of the molded article is preferably 35.0 to less than 90.0 °, preferably 50.0 to less than 90.0 °, particularly 72.0 to less than 90.0 °. The moldings are further distinguished by a yellowness index to DIN 6167 of advantageously less than 10.0%, preferably less than 9.5%, in particular less than 9.0%.

If there is no difference in refractive index between the matrix and the scattering beads, a molding having a matt surface is obtained.

Detailed Description

The present invention is illustrated in more detail by the following examples and comparative examples, but the present invention is not intended to be limited to these examples.

Scattering beads A and C-F

For the preparation of the suspension polymers, aluminium hydroxide Pickering stabilizers were used, which were prepared by precipitation of aluminium sulphate and soda solutions immediately before the start of the actual polymerization reaction. For this purpose, first 16g of Al are added₂(SO₄)₃0.032g of complexing agent (Trilon A) and 0.16g of emulsifier (K30 emulsifier, available from Bayer AG; C)₁₅Sodium salt of paraffin sulphonic acid) in 0.8 litre of distilled water. The 1N sodium carbonate solution is then added to the water-soluble aluminium sulphate at a temperature of about 40 ℃ with stirring, the pH value then being 5 to 5.5. This procedure achieves a colloidal distribution of the stabilizer in water. In order to prevent the container wall from depositing layers, polyethylene glycol (with the molecular weight of 5000-6000 g/mol) is added after the dispersant precipitation step.

Once the stabilizer had precipitated, the aqueous phase was transferred to a glass beaker. To this was added 200g of a monomer mixture having the composition listed in Table 1, as well as 4g of dilauryl peroxide, 0.4g of tert-butyl per 2-ethylhexanoate and 1.6g of ammonium peroxodisulfate. This mixture was dispersed with a disperser (Ultra-Turrax S50N-G45MF from Janke undKunkel, Staufen) at 7000rpm for 15 minutes.

After the shearing step, the reaction mixture was charged into a reactor, which was preheated to a suitable reaction temperature of 90 ℃ and polymerized under stirring (600rpm) at about 90 ℃ (polymerization temperature) for 45 minutes (polymerization duration). This was followed by a post-reaction phase at an internal temperature of about 85 ℃ for 1 hour. After cooling to 45 ℃, the stabilizer is converted into water-soluble aluminum sulfate by adding 50% strength sulfuric acid. For the bead work-up, the suspension obtained was filtered with a commercially available filter cloth and the product was dried in a heated oven at 50 ℃ for 24 hours.

From the mean size V by means of laser extinction₅₀And the associated standard deviation. The results are shown in Table 1. The beads had a spherical shape, where no fibers could be found. No agglomeration occurred.

Scattering beads G and H

The preparation procedure followed the polymerization protocol for the scattering beads a and C-F, except that the monomer mixtures listed in table 1 were used and no Pickering stabilizer was added.

The size distribution of the bead polymer obtained is likewise shown in Table 1.

Scattering beads B

The preparation process corresponds essentially to the polymerization protocol for the scattering beads A and C to F, however, in each case 200 times the amount of components are used here. Whereby some technically induced changes have to be taken. The precipitated Pickering stabilizer, together with monomers, initiator and additives, was charged into a reactor as initial charge and then dispersed by means of a through-flow disperser (Dispax-Reaktor, Jankeund Kunkel) at a temperature of 40 ℃. For this purpose, the mixture is circulated through the disperser for 30 minutes, where the dispersion is stirred inside the reactor with a conventional stirrer at 150 rpm.

After 30 minutes, the dispersion was heated to 80 ℃. The polymerization and post-treatment followed the polymerization protocol for the scattering beads A, C-F.

The size distribution of the bead polymer obtained is likewise shown in Table 1.

TABLE 1

Scattering beads	Methyl methacrylate [ wt.%]	Styrene [ wt.%]	Diol dimethacrylate [ wt.%]	V50[μm]	σ[μm]
						A	13.0	85.0	2.0	30	25
B	13.0	85.0	2.0	30	45

C	28.0	70.0	2.0	32	24
						D	35.5	62.5	2.0	30	25
E	48.0	50.0	2.0	25	26
						F	0.0	98.0	2.0	22	24
G	13.0	85.0	2.0	53	42
						H	69.0	30.0	1.0	74	77

Light scattering test piece

For further investigation, standard PMMA moulding compositions (from R) were modified with the amounts of scattering beads A to H listed in Table 2hm PLEXIGLAS obtained from GmbH7N). Test specimens having dimensions of 60mm × 45mm × 3mm were prepared from these molding compositions by injection molding, and were measured for light transmittance (T) according to DIN5036, yellowness index (G) according to DIN 6167, and half-value angle of strength (. beta.) according to DIN5036 using a measuring apparatus LMT-goniometer measuring station GO-T-1500 from the company LMT.

The data obtained are shown in table 2.

TABLE 2

	Scattering beads	Content of scattering beads [ wt.%]	T[％]	G[％]	β[°]
						Example 1	A	4	57.19	8.84	71.42
Example 2	A	6	52.19	8.26	77.60
						Example 3	A	9	48.31	9.48	78.15
Example 4	A	12	44.79	11.97	80.25
						Example 5	B	4	61.28	10.27	47.50
Example 6	B	6	53.32	9.62	77.25
						Example 7	B	9	48.15	11.96	79.41
Example 8	B	12	45.88	14.30	79.23
						Example 9	C	3	64.06	9.86	45.02
Example 10	C	6	52.79	8.21	78.86
						Example 11	C	9	51.07	9.03	79.77

Example 12	C	12	49.19	10.81	79.37
						Example 13	D	6	63.00	8.90	54.33
Example 14	E	6	69.00	9.43	39.13
						Example 15	F	2	60.85	9.73	50.53
Example 16	F	4	50.41	8.78	77.93
						Example 17	F	6	50.41	9.69	78.25
Comparative example 1	G	6	55.81	9.68	71.32
						Comparative example 2	H	6	92.04	1.27	10.98

The test results in Table 2 show that the scattering beads compounded into the molding compositions and prepared according to the process of the invention (examples 1 to 17) scatter light very efficiently without large energy losses. Here, the scattering beads having a styrene content of 85% by weight have the highest degree of scattering. Although scattering beads with lower or higher styrene content also achieve high intensity half-value angles, this decreases more rapidly with decreasing concentration of scattering beads in the molding composition.

Claims (23)

1. Process for the preparation of bead polymers having an average particle size of 1 to 40 μm, in which a polymerizable composition is dispersed and polymerized in an aqueous phase, where the average particle size is 10 or more³s^-1At a shear rate of (a), characterized in that the polymerizable composition used comprises, based in each case on its total weight:

a) more than 50.0 wt% of at least one compound of formula (I)

Wherein¹R is hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms,²R～⁶the R radicals are each, independently of one another, hydrogen, linear or branched alkyl having from 1 to 6 carbon atoms or halogen,

b)0.1 to 10.0 wt.% of at least one crosslinking agent and

c) less than 49.9 wt.% of at least one compound of the formula (II)

Wherein R is hydrogen or a methyl group,⁷r is a linear or branched alkyl group having 1 to 40 carbon atoms or an optionally alkylated cycloalkyl group,⁸r and⁹the R radicals are each, independently of one another, hydrogen or a radical of the formula-COOR ', where R' is hydrogen or an alkyl radical having 1 to 40 carbon atoms.

2. The process according to claim 1, characterized in that the polymerizable composition used comprises, based in each case on its total weight:

more than 50.0 wt.% to 99.0 wt.% of at least one compound of the general formula (I),

0.1 to 5.0 wt.% of at least one crosslinking agent and

0.9 to less than 49.9% by weight of at least one compound of the formula (II),

the sum of the contents of all the components is 100 percent.

3. The process according to claim 2, characterized in that the polymerizable composition used comprises, based in each case on its total weight:

60.0 to 98.5 weight percent of at least one compound of the general formula (I),

0.5 to 4.0 wt.% of at least one crosslinking agent and

1.0 to 40.0 wt.% of at least one compound of the general formula (II),

the sum of the contents of all the components is 100 percent.

4. The process according to claim 3, characterized in that the polymerizable composition used comprises, based in each case on its total weight:

70.0 to 94.3 wt.% of at least one compound of the general formula (I),

0.7 to 3.5 wt.% of at least one crosslinking agent and

5.0 to 30.0 wt.% of at least one compound of the general formula (II),

the sum of the contents of all the components is 100 percent.

5. The process according to claim 4, characterized in that the polymerizable composition used comprises, based in each case on its total weight:

80.0 to 90.0 wt.% of at least one compound of the general formula (I),

1.0 to 3.0 wt.% of at least one crosslinking agent and

9.0 to 19.0 wt.% of at least one compound of the general formula (II).

6. Process according to any one of claims 1 to 5, characterized in that Al (OH) is used₃And (4) stabilizing.

7. Process according to claim 6, characterized in that Al (OH) is prepared by precipitation₃。

8. The process according to any one of claims 1 to 5, characterized in that the concentration of the aluminum compound is from 0.5% to 200.0% by weight, based on the weight of the polymerizable composition.

9. The process according to claim 8, characterized in that the concentration of the aluminum compound is from 3.0% to 100.0% by weight, based on the weight of the polymerizable composition.

10. The process according to claim 9, characterized in that the concentration of the aluminum compound is from 4.0% to 20.0% by weight, based on the weight of the polymerizable composition.

11. A process according to any one of claims 1 to 5, characterised in that the particle size is from 5 μm to 35 μm.

12. A process according to any one of claims 1 to 5, characterized in that an emulsifier is additionally used.

13. The process according to claim 12, characterized in that the concentration of the emulsifier is from 0.0% to 5.0% by weight, based on the weight of the aluminum compound.

14. The process according to claim 13, characterized in that the concentration of the emulsifier is between 0.3% and 3.0% by weight, based on the weight of the aluminum compound.

15. Process according to any one of claims 1 to 5, characterized in that the dispersion obtained after the polymerization is subjected to filtration.

16. Bead polymer prepared according to the process of claim 1, wherein the polymerizable composition used comprises b)0.5 to 10.0% by weight of at least one crosslinking agent, c)0.9 to less than 49.9% by weight of at least one compound of the general formula (II) as defined in claim 1, based in each case on its total weight.

17. Bead polymer prepared according to the process of claim 2, wherein the polymerizable composition used comprises b) from 0.5% to 5.0% by weight of at least one crosslinking agent, based in each case on its total weight.

18. A bead polymer prepared according to the process of any one of claims 3-5.

19. A molding composition comprising at least one bead polymer according to any of claims 16 to 18.

20. Molded article having light-scattering properties, comprising at least one bead polymer according to any of claims 16 to 18.

21. The molding according to claim 20, characterized in that it has a light transmission according to DIN5036 of more than 40.0%.

22. The molding according to claim 20 or 21, characterized in that it has a strength half-value angle β according to DIN5036 of 35.0 ° to less than 90.0 °.

23. The molding according to claim 20 or 21, characterized in that it has a yellowness index according to DIN 6167 of less than 10.0%.