DE19752394A1 - Graft copolymer production with minimal reactor coating - Google Patents

Abstract

Graft copolymers are obtained by an aqueous- phase process in which polymerization of the rubber-elastic base is taken to completion and an N-oxyl radical compound of a sec. amine with no hydrogens on the alpha -carbon atom is added before and/or during polymerization of the grafted shell. A process for the production, in the aqueous phase, of graft copolymers (A) of (a1) 30-95 wt% rubber-elastic graft base derived from (a11) 50-100 wt% conjugated diene and (a12) 0-50 wt% other monounsaturated monomer(s) or from (a11 asterisk ) 50-100 wt% 1-10C alkyl acrylate, (a12 asterisk ) 0-10 wt% polyfunctional crosslinking monomer and (a13 asterisk ) 0-40 wt% other monounsaturated monomer(s) and (a2) 5-70 wt% grafted shell derived from (a21) 50-100 wt% styrene compound of formula (S): R<1>, R<2> = H or 1-8 C alkyl (a22) 0-40 wt% (meth)acrylonitrile and (a23) 0-40 wt% other monounsaturated monomer(s). In this process, polymerization of the base stage (a1) is taken to completion and then at least one N-oxyl radical compound of a sec. amine with no hydrogen atoms on the alpha -carbon atom is added before and/or during polymerization stage (a2). An Independent claim is also included for graft copolymers obtained by this process.

Description

The invention relates to a process for the preparation of graft polymers A, based on A),

• a1) 30 to 95% by weight of a rubber-elastic basic stage, based on a1),
  • a11) 50 to 100% by weight of a diene with conjugated double bonds,
  • a12) 0 to 50% by weight of one or more further monoethylenically unsaturated monomers,
    or off, based on a1)
  • a11 *) 50 to 100% by weight of a (C ₁ -C ₁₀ alkyl) ester of acrylic acid,
  • a12 *) 0 to 10% by weight of a polyfunctional, crosslinking monomer,
  • a13 *) 0 to 40% by weight of one or more further monoethylenically unsaturated monomers,
• a2) 5 to 70% by weight of a graft stage, based on a2),
  • a21) 50 to 100 wt .-% of a styrene compound of the general formula
    in which R ¹ and R ^{2 represent} hydrogen or C ₁ -C ₈ alkyl,
  • a22) 0 to 40% by weight of acrylonitrile or methacrylonitrile or mixtures thereof and
  • a23) 0 to 40% by weight of one or more further monoethylenically unsaturated monomers,

in the aqueous phase. In addition, the invention relates to the after Process produced graft polymers, and their use the radical N-oxyl compounds to prevent fouling gene on reactor surfaces in graft polymerization in aq phase.

In the course of polymerization reactions, especially in the Graft polymerization for the production of e.g. B. Core-shell graft particles, polymer deposits often appear on the reactor walls. These polymer coatings lead to procedural difficulties ten since they are at regular intervals, usually after each polyme risk reaction, which must often be removed Chen effort means. In addition, rubbers that are in the Rule from atypical polymers z. B. regarding their Molecular weight distribution exist, partially detach and on this leads to inhomogeneities or contamination of the polymer lead sate. The wall covering reduces the space-time yield and affects heat removal from the reactor, leading to local Overheating and - in extreme cases - a "runaway" of the Re actuator (uncontrollable heating) can lead.

Various measures were taken to remedy the deposit formation developed. Because the deposit formation strongly depends on the surface structure depends on the reactor walls, e.g. B. from their roughness, aim the Measures mainly on the smoothing of the surfaces. In addition to me Chinese measures have also been attempted to improve the quality of the surface by adding anti-corrosion agents for the polymerization preserved (see e.g. G. W. Becker, D. Braun (ed.), plastic hand book, Hauser Verlag, Munich, Vienna 1986, Volume 2/1, p. 153). These As a rule, however, measures can only lead to the formation of deposits prevent enough.

It is known that the addition of aromatic condensation pro products to the reaction mixture reduce the formation of wall coverings can, see e.g. B. JP-A 08245704, JP-A 07025912, EP-A 632058. Each however, the extent of the reduction is not in all cases too peaceful.

DE-OS 196 09 312 describes a method for preventing the premature polymerization of certain vinyl groups Monomers, e.g. B. in distillation, cleaning, storage and during transport, by adding N-oxyl compounds se described customary amines. Also for the stabilization of Styrene and other vinyl aromatic compounds during the De Stillation describes the use of N-oxyl compounds (US-A-5 254 760). However, it is also known that traces already exist such nitroxyl compounds the following polymerization process  to disturb; they cause a delayed polymerization and uncon trolled chain terminations, resulting in poorer polymers Reproducibility and short chain length leads. This night Some effects are described by Mardare et al in Polym. Prep. (Am. Chem. Soc., Div. Polym. Sci.) 35 (1), 778 (1994).

On the other hand, sterically hindered N-oxyl radicals become together with a co-initiator as initiators in living radika Chemical polymerization used.

In the case of living radical polymerization, the molecular weight of the polymer increases approximately linearly with the conversion and the polydispersity is small (polydispersity index PDI = M _w / M _n , with M _w = weight-average and M _n = number-average molecular weight), for which purpose in the US - Writings 5 401 804 and 5 322 912 the ratio of N-oxyl radical / co-initiator is limited to 0.5 to 2.5 and in WO 96/24620 to 1.2 to 1.6. Since the reaction rate is comparatively slow at the selected initiator ratios, polymerization must be carried out at higher temperatures, usually above 100.degree.

In contrast, the usual ("classic") radical Polymerization (i.e. without N-oxyl radical) at the very beginning of the Polymerization reached high molecular weights and the PDI is larger than 2. In addition, the classic radical polymer already a comparatively high reaction rate at temperatures below 100 ° C.

The older, not prepublished application DE 196 48 811.7 be generally describes a process for the polymerization of vinylic monomers, especially vinyl chloride, in aqueous Phase in which an N-oxyl compound is used to prevent wall covering is added, and then the polymerization is started.

The task was to provide a method that does not have the disadvantages described. In particular, a Processes are found that manufacture specifically from Graft polymers made possible in the aqueous phase, the ent standing of polymer deposits on the reactor walls reduced or is completely prevented without feeling the polymerization process bar affect, for example in terms of its speed.

Accordingly, the process defined at the outset was found, where the polymerization of basic step a1) is first completed and then before and / or during the polymerization of the graft stage a2) at least one radical N-oxyl compound of a secondary  Amine which has no hydrogen atoms on the α-C atoms, admits.

In addition, the graft prepared by the process polymer A and the use of radical N-oxyl ver bindings to prevent deposits on reactor surfaces the graft polymerization found in the aqueous phase.

The graft polymers A) contain, based on A),

• a1) a1) 30 to 95, preferably 40 to 90 and particularly preferably 40 to 85% by weight of a rubber-elastic basic stage, based on a1)
  • a11) 50 to 100, preferably 60 to 100 and particularly preferably 65 to 100% by weight of a diene with conjugated double bonds,
  • a12) 0 to 50, preferably 0 to 40 and particularly preferably 0 to 35% by weight of one or more monoethylenically unsaturated monomers,
    or off, based on a1),
  • a11 *) 50 to 100, preferably 60 to 100 and particularly preferably 70 to 100% by weight of a (C ₁ -C ₁₀ alkyl) ester of acrylic acid,
  • a12 *) 0 to 10, preferably 0 to 5 and particularly preferably 0 to 2% by weight of a polyfunctional, crosslinking monomer,
  • a13 *) 0 to 40, preferably 0 to 30 and particularly preferably 0 to 20% by weight of one or more further monoethylenically unsaturated monomers,
• a2) 5 to 70, preferably 10 to 60 and particularly preferably 15 to 60% by weight of a graft stage, based on a2),
  • a21) 50 to 100, preferably 60 to 100 and particularly preferably 65 to 100% by weight of a styrene compound of the general formula
    in which R ¹ and R ^{2 represent} hydrogen or C ₁ -C ₈ alkyl,
  • a22) 0 to 40, preferably 0 to 38 and particularly preferably 0 to 35% by weight of acrylonitrile or methacrylonitrile or mixtures thereof,
  • a23) 0 to 40, preferably 0 to 30 and particularly preferably 0 to 20% by weight of one or more further monoethylenically unsaturated monomers.

The following can be said about basic level a1):
Butadiene, isoprene, norbornene and their halogen-substituted derivatives, such as chloroprene, are particularly suitable as dienes with conjugated double bonds, a11). Butadiene and isoprene, in particular butadiene, are preferred.

The other monoethylenically unsaturated monomers a12) which may be present in the graft core a1) at the expense of the monomers a11) are, for example:
vinyl aromatic monomers such as styrene, styrene derivatives of the general formula

in which R ¹ and R ^{2 are} hydrogen or C ₁ - to C ₈ -alkyl;
Acrylonitrile, methacrylonitrile;
C ₁ to C ₄ alkyl esters of methacrylic acid, such as methyl methacrylate, and also the glycidyl esters, glycidyl acrylate and methacrylate;
N-substituted maleimides such as N-methyl, N-phenyl and N-cyclo hexyl maleimide;
Acrylic acid, methacrylic acid, furthermore dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid and their anhydrides such as maleic anhydride;
Nitrogen-functional monomers such as dimethylaminoethyl acrylate, diethylaminoethyl acrylate, vinylimidazole, vinylpyrrolidone, vinyl caprolactam, vinylcarbazole, vinylaniline, acrylamide and methacrylamide;
aromatic and araliphatic esters of acrylic acid and methacrylic acid such as phenyl acrylate, phenyl methacrylate, benzyl acrylate, benzyl methacrylate, 2-phenylethyl acrylate, 2-phenylethyl methacrylate, 2-phenoxyethyl acrylate and 2-phenoxyethyl methacrylate;
unsaturated ethers such as vinyl methyl ether,
as well as mixtures of these monomers.

Preferred monomers a12) are styrene, acrylonitrile, methyl meth acrylate, glycidyl acrylate and methacrylate, acrylamide and meth acrylamide.

Instead of the basic monomers a11) and a12), the basic stage can also be built up from the monomers a11 *) to a13 *).

Suitable as (C ₁ -C ₁₀ alkyl) esters of acrylic acid, component a11 *), are especially ethyl acrylate, 2-ethylhexyl acrylate and n-butyl acrylate. Preferred are 2-ethylhexyl acrylate and n-butyl acrylate, n- Butyl acrylate. Mixtures of different alkyl acrylates which differ in their alkyl radical can also be used.

Crosslinking monomers a12 *) are bifunctional or polyfunctional comono mers with at least two olefinic double bonds, for example as butadiene and isoprene, divinyl esters of dicarboxylic acids such as succinic acid and adipic acid, diallyl and divinyl ether bi functional alcohols such as ethylene glycol and Butane-1,4-diols, diesters of acrylic acid and methacrylic acid with the bifunctional alcohols mentioned, 1,4-divinylbenzene and Triallyl cyanurate. The acrylic acid ester is particularly preferred of tricyclodecenyl alcohol (see DE-OS 12 60 135), the under the name dihydrodicyclopentadienyl acrylate is known, and the Allyl esters of acrylic acid and methacrylic acid.

Crosslinking monomers a12 *) can be used in the molding compounds depending on the type the molding compounds to be produced, in particular depending on the ge desired properties of the molding compositions, be included or  Not. If crosslinking monomers a12 *) are contained in the molding materials ten, the amounts are 0.01 to 10, preferably 0.2 to and particularly preferably 1 to 5% by weight, based on a1).

As further monoethylenically unsaturated monomers a13 *) the monomers are also used, as they are for the monomers a12) have already been mentioned.

Preferred monomers a13 *) are styrene, acrylonitrile, methyl meth acrylate, glycidyl acrylate and methacrylate, acrylamide and meth acrylamide.

The graft core a1) can also consist of a mixture of the monomers ren a11) and a12), and a11 *) to a13 *).

If the graft core contains the monomers a11) and a12), the result is after mixing with a thermoplastic polymer Styrene and acrylonitrile (SAN) molding compounds of the ABS type (acrylonitrile bu tadiene styrene). Does the graft core contain the monomers a11 *) to a13 *), this results after mixing with a thermoplastic Polymer made of styrene and acrylonitrile (SAN), so-called ASA molding compounds (acrylonitrile styrene alkyl acrylate).

The graft polymer A) is therefore ABS or A-A graft polymers, or their mixtures.

The following can be said about graft stage a2):
The styrene compound of the general formula (I) (component a21)) is preferably styrene, α-methyl styrene, and also with C ₁ -C ₈ alkyl ring-alkylated styrenes such as p-methyl styrene or tert-butylstyrene, a. Styrene is particularly preferred. Mixtures of the styrenes mentioned, in particular styrene and α-methylstyrene, can also be used.

Component a2) can also be used at the expense of monomers a21) and a22) one or more further, monoethylenically unsaturated Monomers a23) included. With regard to the monomers a23), see Reference was made to component a13).

Preferred grafting steps a2) are, for example, polystyrene and Copolymers of styrene and / or α-methylstyrene and one or more reren of the other monomers mentioned under a22) and a23). Before methyl methacrylate, N-phenylmaleinimide and malein are added acid anhydride and acrylonitrile, particularly preferably methyl meth acrylate and acrylonitrile.  

Examples of preferred grafting steps a2) are:

a2-1: polystyrene
a2-2: copolymer of styrene and acrylonitrile,
a2-3: copolymer of α-methylstyrene and acrylonitrile,
a2-4: copolymer of styrene and methyl methacrylate.

The proportion of styrene or α-methyl is particularly preferred styrene, or the proportion of the sum of styrene and α-methylstyrene, at least 40% by weight, based on a2).

The process according to the invention relates to graft polymerizations in aqueous phase. Under aqueous phase, both solutions, Emulsions and suspensions of the corresponding monomers or Po lymeren in water as well as in solvent mixtures, which too a large part, d. H. contain at least 20% by weight of water, be understood.

The graft polymerization is generally known per se Way according to the method of emulsion, mini emulsion, Suspension or microsuspension polymerization carried out.

In a preferred embodiment, the polymerization is carried out after the emulsion procedure carried out, in which the monomers in aqueous emulsion at 20 to 100 ° C, preferably at 50 to 80 ° C are polymerized, with all components of the batch together can be given (batch process), or the monomer alone or an emulsion of monomer, water and emulsifiers can be gradually added to the other components (semi-batch process). Also a continuous driving style of the Reaction is possible. The semi-batch process is preferred.

Suitable emulsifiers are, for example, alkali metal salts of Alkyl or alkylarylsulfonic acids, alkyl sulfates, fatty alcohol sulfonates, salts of higher fatty acids with 10 to 30 carbon atoms, sulfosuccinates, ether sulfonates or resin soaps. Preferential one takes the alkali metal salts of alkyl sulfonates or Fatty acids with 10 to 18 carbon atoms. Your amount is usually 0.5 to 5 wt .-%, based on the core monomers a1).

So much is preferably used to prepare the dispersion Water that the finished dispersion has a solids content of up to 50% by weight.  

All radical formers are used to start the polymerization reaction suitable, which disintegrate at the selected reaction temperature, So both those that decay thermally alone, as well as sol who do this in the presence of a redox system. As a polyme Risk initiators preferably come from radical formers for example peroxides such as preferably peroxosulfates (about sodium or Potassium persulfate) and azo compounds such as azo diisobutyro nitrile into consideration. However, redox systems can also be used especially those based on hydroperoxides such as cumene hydro peroxide.

As a rule, the polymerization initiators are used in an amount from 0.1 to 2% by weight, based on the graft base monomers a1), used.

The radical formers and also the emulsifiers become the reaction approach, for example, discontinuously as the total amount at the beginning the reaction, or divided into several portions Added at the beginning and at one or more later times, or continuously during a certain time interval adds. The continuous addition can also be along a gradient ten take place, the z. B. ascending or descending, linear or expon tiell, or also gradually (stair function).

Molecular weight regulators such as e.g. B. Ethylhexylthio glycolate, n- or t-dodecyl mercaptan or other mercaptans, Terpinols and dimeric α-methylstyrene or others, for regulation of the molecular weight suitable compounds. The Molecular weight regulators are discontinuous to the reaction mixture Lich or continuously added, as is the case for the radical former and emulsifiers have been described.

To maintain a constant pH, which is preferably 6 to 9, buffer substances such as Na ₂ HPO ₄ / NaH ₂ PO ₄ , sodium pyrrophosphate, sodium hydrogen carbonate or buffer based on citric acid / citrate can also be used. Regulators and buffer substances are used in the usual quantities, so that further details are not necessary.

One can the graft base a1) in a special execution form also by polymerization of the monomers a1) in the presence produce a finely divided latex (so-called "seed latex driving style" polymerization). This latex is presented and can be made rubber-elastic polymer-forming monomers, or from other monomers, as already mentioned, exist. Ge  suitable seed latices consist, for example, of polybutadiene or Polystyrene.

In another embodiment, the graft base a1) produce in the so-called feed process. With this procedure a certain proportion of the monomers a1) is presented and the Polymerization started, after which the rest of the monomers ("Zu running portion ") a1) as feed during the polymerization. The inflow parameters (shape of the gradient, amount, duration, etc.) depend on the other polymerization conditions. Analogous also apply here to the way of adding the radical start or Emulsifier made executions. Is preferred at the inlet proceed the submitted proportion of monomers a1) 5 to 50, be particularly preferably 8 to 40% by weight, based on a1). Prefers let the inflow portion of a1) within 1-18 hours, ins extra 2-16 hours, especially 4 to 12 hours to run.

Graft polymers with several are also suitable "soft" and "hard" shells, e.g. B. structure a1) -a2) -a1) -a2), or a2) -a1) -a2), especially in the case of larger particles.

Detailed information on the production of rubber latices in Emulsion can be found in DE-A 24 27 960 and EP-A 62901.

The exact polymerization conditions, in particular the type, amount and dosage of the emulsifier and the other polymerization auxiliaries are preferably chosen so that the latex of the graft polymer A obtained, an average particle size, defined by the d ₅₀ value of the particle size distribution, from usually to 1000, preferably 50 to 800 and particularly preferably 50 to 400 nm.

If a bimodal particle size distribution is desired, this can be achieved by a (partial) agglomeration of the polymer particles. This can be done, for example, as follows: The monomers a1) which build the core are polymerized up to a conversion of usually at least 90%, preferably greater than 95%, based on the monomers used. The rubber latex obtained preferably has an average particle size d ₅₀ of at most 200 nm and a narrow particle size distribution (almost monodisperse system).

Then the rubber latex is agglomerated, e.g. B. by adding a dispersion of an acrylic ester polymer. Preferably, who the dispersions of copolymers of (C ₁ -C ₄ alkyl) esters of acrylic acid, preferably of ethyl acrylate, with 0.1 to 10 wt .-% polar polymers forming monomers, such as. As acrylic acid, methacrylic acid, acrylamide or methacrylamide, N-methylol methacryl amide or N-vinyl pyrrolidone used. A copolymer of 96% ethyl acrylate and 4% methacrylamide is particularly preferred.

The concentration of the acrylic ester polymers in the agglomeration ration dispersion should generally be between 3 and 40% by weight. In agglomeration, 0.2 to 20, preferably 1 to 5 parts by weight of the agglomerating dispersion 100 parts of the rubber latex, each calculated on solids, used. The agglomeration is done by adding the agglomerate dispersion carried out to the rubber.

In addition to using an acrylic ester polymer dispersion, the Rubber latex also by other agglomerating agents such. B. Acetic anhydride, agglomerate. Also an agglomeration by pressure or freezing (pressure or freeze agglomeration) is possible. The methods mentioned are known to the person skilled in the art.

Under the conditions mentioned, only part of the rubber Particles agglomerate, so that a bimodal distribution arises. After agglomeration there are generally more than 50 preferably between 75 and 95% of the particles (number distribution lung) in the non-agglomerated state. The part received agglomerated rubber latex is relatively stable, so that it can be easily stored and transported without Coagulation occurs.

A bimodal particle size distribution of the graft polymer A) to achieve, it is also possible to use two different grafts polymers A ') and A' '), which are in their middle particles Differ size, separated from each other in the usual way deliver and the graft polymers A ') and A' ') in the desired Quantity ratio together.

After the polymerization of basic step a1) is completed, according to the invention before and / or during the polymerization of the Graft stage a2) to the basic stage a radical N-oxyl ver bond added. The N-oxyl compound and more details are described below.

If there is an agglomerate before the polymerization of graft stage a2) tion of the basic stage a1) is carried out, the N-oxyl Ver binding before the agglomeration, during or after the agglomera tion are added. The addition before agglomeration is preferred ration.  

The preparation of the graft stage a2) can be carried out under the same conditions conditions in emulsion like the preparation of basic level a1) er follow, whereby the graft stage a2) in one or more ver can produce driving steps. The monomers a21), a22) and a23) individually or in a mixture with one another the. The monomer ratio of the mixture can be constant over time or be a gradient. Combinations of this procedure are possible.

For example, you can first use styrene alone, and then one Mixture of styrene and acrylonitrile, to basic level a1) poly merize.

The graft stage a2) acts as a compatibility agent between the basic rubber stage a1) and the matrix polymer into which the Graft polymers A are embedded. Preferably correspond there forth the monomers a2) those of the matrix. Is the matrix whole? or predominantly from a styrene-acrylonitrile copolymer (SAN), as is the case with the ABS or ASA molding compositions mentioned, the graft cover usually also exists in whole or in part from styrene and / or α-methylstyrene and acrylonitrile. It can However, other monomers a2) can also be used, for example wise methyl methacrylate.

The process according to the invention can also be used as a miniemulsion polymer be carried out. The miniemulsion polymerization un differs from the normal emul just described sionpolymerisation mainly in that the particle size in is usually 50 to 500 nm and the particles usually through a combination of ionic emulsifiers and co-emulsifiers be stabilized against convergence. The stability a miniemulsion is usually less than that of a con conventional emulsion. Usually used as co-emulsifiers long chain alkanes such as hexadecane, or long chain alcohols such as Hexadecanol used.

In mini-emulsion polymerization, the mixture is made of monomers water, emulsifiers and co-emulsifiers with high shear forces exposed, whereby the components are mixed intimately. On finally polymerizing. The high shear forces can for example by ultrasound or a microfluidizer device generated, or by the description of the Micro suspension polymerization Homogenisa mentioned below goals. Details of the miniemulsion polymerization can be found in the Expert z. In P. Covell, M. El-Aasser, Emulsion Polymerization  and Emulsion Polymers, published by John Wiley, New York, 1997, Pp. 699-722.

Possible modes of shear control (e.g. continuous, batch, etc.) are further below in microsuspension polymerization described.

Otherwise apply to the miniemulsion polymerization to the nor paint emulsion polymerization made executions.

The process according to the invention can also be used as a suspension polymer be carried out. From emulsion polymerization un the suspension polymerization essentially differs in that the initiators are not or only slightly in the aqueous phase, but dissolve in the monomer, and that instead a protective colloid is also used in an emulsifier. In the Suspension polymerization is carried out by stirring in the monomer dispersed aqueous phase into droplets, the protective colloid Prevents the droplets from converging. The one at the suspension Particles resulting from polymerization are generally considerable larger than particles made in emulsion. Details on Suspension polymerization, especially with regard to initiation and protective colloids can be found below at Be description of microsuspension polymerization, and also in Encyclopedia of Polymer Science and Engineering, Vol. 16, 2nd edition, published by John Wiley, New York, 1989, pp. 443-472.

Apart from the differences mentioned, the same applies to the Suspension polymerization essentially that of the emulsion Polymerization made executions.

The method according to the invention can also be used as a microsuspension polymerization are carried out. The microsuspension poly merisation differs from the normal suspension polymer rization essentially in that the suspension of the monomers stirring in water much more intensely (action considerably higher shear forces). The procedure is closer below described.

In the microsuspension process, the monomers M (or the monomer mixture M), which correspond to the desired polymer A), are dispersed in water using at least one protective colloid SK, so that a dispersion of the monomer droplets in water with a volume-average droplet diameter d ₅₀ from usually 700 nm to 100 µm arises. The droplets are then polymerized using a radical polymerization initiator RI.

Usually the amount of water in which the monomials are ren M and the protective colloids SK are dispersed, 25 to 95% by weight, preferably 40 to 85% by weight and particularly preferably 45 up to 75 wt .-%, based on the sum of monomers, water and Protective colloids.

The protection suitable for stabilizing the dispersion colloidal SK are water-soluble polymers, which are the monomers droplets and envelop the polymer particles formed therefrom and protect against coagulation in this way.

Cellulose derivatives such as carboxy are suitable as protective colloids SK methyl cellulose and hydroxymethyl cellulose, poly-N-vinyl pyrrole don, polyvinyl alcohol and polyethylene oxide, anionic polymers such as polyacrylic acid and its copolymers and cationic such as poly-N-vin ylimidazole. The amount of these protective colloids is preferred as 0.1 to 10 wt .-%, based on the total mass of the emul sion.

Protective colloids and methods for producing protection colloids are known per se and for example in Encyclopedia of Polymer Science and Engineering, Vol. 16, p. 448, Verlag John Wiley, 1989.

One or more polyvinyl alcohols are preferred as protection colloid used, especially those with a degree of hydrolysis below 96 mol%, particularly preferably 60 to 94 and very particularly preferably 65 to 92 mol%. The preferred polyvinyl alcohols have a viscosity of 2 to 100 mPa.s, especially 4 to 60 mPa.s, measured as a 4% by weight solution in water at 20 ° C DIN 53 015.

One can use colloidal silica in addition to the protective colloids in a concentration of generally 0.2 to 5% by weight, based on the amount of dispersion. More about this Method that works particularly well with a water-soluble polymer from adipic acid and diethanolamine as a protective colloid from US-A 3 615 972.

To at the same time blue in the microsuspension polymerization Emulsion polymerization process, which is essential form smaller and therefore undesirable particles to suppress them, you can use a water-soluble inhibitor that  Emulsion polymerization suppressed. Effective connections of these Kind are z. B. Chromium (+6) compounds such as potassium dichromate.

The monomers M, water and the protective colloids SK become one Prepare emulsion by applying high shear forces. Homogenizers known to those skilled in the art are used for this are.

Examples include:

• - Laboratory dissolver Dispermat, VMA-Getzmann, Reichshof, DE,
• - Ultra-Turax, from Janke and Kunkel, Staufen, DE,
• - pressure homogenizer, Gaulin, Lübeck, DE,
• - Devices with a rotor-stator system, for example,
  • - Dispax, Fa. Janke and Kunkel, Staufen, DE,
  • - Cavitron homogenizers, from v. Hagen & Funke, Sprochhövel, DE,
  • - Homogenizers from Kotthoff, Essen, DE,
  • - Homogenizers from Dorr Oliver, Grevenbroich, DE.

These devices are usually operated at speeds of 1000 to 25,000 min ^-1 , preferably 2000 to 15,000 min ^-1 .

Furthermore, the high shear forces can also

• - exposure to ultrasound,
• - Pushing through the mixture of monomers, water and Protective colloids under high pressure through a narrow gap or through small diameter nozzles
• - colloid mills

or other suitable homogenizers are generated.

The dispersion is usually produced at room temperature temperature, however, depending on the type of monomers and protection colloidal higher or lower temperatures may also be useful.

The preparation of the dispersion can either be batchwise (Batch mode) or continuously. At the discount Monomeric production, water and protection colloids are placed in a container and by means of the Homogenisa tors mixed into a microsuspension (dispersion).

The homogenizer can also be arranged parallel to the container and the components are circulated through the homogenizer guided.  

The homogenization time can range from 0.1 sec to several hours depending on, for example, the desired Diameter of the monomer droplets and the sizes to be set distribution, of the mixing behavior of the monomers with water, of the proportions of monomer, water and protective colloid, and from the protective colloid used.

It is also possible to determine the total amount of monomers and the Submit the total amount of water and add the protective colloids, when the homogenizer is started.

In the continuous production of the dispersion, in a preferred embodiment, the monomers, water and Protective colloids are fed to the homogenizer and so prepared dispersion directly into the reactor in which the Polymerization is carried out.

In another preferred embodiment the continuous Dispersion production involves monomers, water and protection colloid in a circle through the homogenizer and only one Part of the mixture circulated is branched off and the Po lymerization reactor supplied. This circular approach recommends especially when the dispersion of the monomers after only one throughput through the homogenizer is still insufficient is appropriate if, for example, the droplet size is too large and / or the size distribution is too wide.

The preparation of the dispersion can in a further Aus in a first step discontinuous and in a second step: the components are dispersed as a batch as described, and the resulting Dispersion then a second continuously carried out Subjected to dispersion. This creates the finished dispersion, which is continuously fed to the reactor.

The microsuspension polymerization is carried out with a radical Polymerization initiator RI initiated. Such connections are known to the person skilled in the art. Compounds with a are preferred Half-life of one hour when the temperature is 60 to 110 ° C, and which are noticeably soluble in the monomers. Ins Organic peroxides, azo compounds and / or become special Compounds with C-C single bonds as initiators RI used. Likewise, as a radical polymerization initiation toren monomers used, which spontaneously po at elevated temperature lymerize. Mixtures of the initiators mentioned can also be used RI can be used.  

The peroxides are those with hydrophobic properties preferred, especially those molecules with an atomic ratio Carbon to oxygen greater than 3: 1. Especially before Dilauryl peroxide and dibenzoyl peroxide are particularly prevalent Dilauryl peroxide.

2,2'-Azobis (2-methylbutyronitrile) and 2,2'-Azobis (isobutyronitrile) is preferred. As connections with labile C-C bonds are preferred 3,4-dimethyl-3,4-diphenylhexane and 2,3-dimethyl-2,3-diphenyl butane.

As initiating monomers that spontaneously at elevated temperature polymerize, styrene and its derivatives such as Vinyl toluene used, particularly preferably styrene.

The amount of initiator RI is usually 0.05 to 4, preferably 0.1 to 2 and particularly preferably 0.3 to 1% by weight, based on the amount of the monomers M. These amounts apply naturally not in the event that the monomer is also an initiator is like styrene.

Depending on the physical state of the initiator and its solubility he can behave as such, but preferably as a solution, Dis persion (liquid in liquid) or suspension (solid in liquid) are added, which in particular small amounts of substance In Have the itiator metered more precisely.

Suitable as a solvent or liquid phase for the initiator organic solvents such as benzene, toluene, Ethylbenzene and cyclohexane, especially cyclohexane, or also the monomers themselves. When using the monomers themselves as Solvent or liquid phase for the initiator is the Initiator in the total amount of the monomers or preferably in a smaller proportion of the monomers dissolved or emulsified / sus oscillates, and this share then to the remaining components given.

It is also possible to use the initiator in the solvent or in mono dissolve and dissolve the resulting solution in water ren.

The initiator (s) RI can be used before or after production be added to the dispersion, or only immediately before the start the polymerization, or continuously in the course of Polymerization be metered.  

Especially with monomers that lead to uncontrolled polymer sation tend, or already at the temperature of the dispersion polymerize production, it is advisable to start the initiator RI first after emulsification, u. U. just before the polymer sation to admit.

Especially for polymerizations with a long polymer it can be advantageous to use the initiator as a continuous Liche inflow or in portions during the polymerization admit. The duration of the initiator inflow can vary from the duration the polymerization may be different or the same.

Other additives such as buffer substances and molecular weight regulators can be continuous or discontinuous at the beginning and / or during the preparation of the dispersion and / or during the polymerization.

The polymerization is carried out in the usual manner by for example, the reactor contents are heated, whereby the poly merization reaction is started. If necessary, the Initiator RI only then, i.e. to the heated dispersion, be added. The polymerization temperature depends u. a. of the monomers and initiators used and of the desired crosslinking degree of formation of the resulting polymers A). In general polymerized at 30 to 120 ° C, ver also in succession different temperatures or a temperature gradient can be.

The polymerization reaction is usually taken under Langsa before or moderate stirring, in which (in contrast to the emulsification due to high shear forces) the droplets more to be divided.

The particle size of the microsuspension poly Merisation control essentially by the fact that the loading conditions selected accordingly in the preparation of the dispersion and checked (e.g. choice of homogenizer, duration of the Homogenization, quantitative ratios of monomers: water: protective colloids, Dispersion mode (single, multiple, as a batch or continuous, circular mode), speed of the homogenizer Etc.).

Regardless of the chosen polymerization process, the following applies in Re gel that the polymerization of the graft a2) after the same The procedure is the same as basic level a1). So becomes the reason  stage polymerized in emulsion, for example, polymerized usually the graft stage in emulsion.

If the graft stage a2) is polymerized in emulsion, it works usually at 20 to 100 ° C, preferably 50 to 80 ° C.

As the polymerization initiator for the graft stage, the same Chen water-soluble compounds are used in the Polymerization of the basic level are used. You can also Oil-soluble or monomer-soluble initiators, for example Dialkyl peroxides such as dilauryl peroxide and dibenzyl peroxide, perester such as tert-butyl perpivalate and tert-butyl peroxyneodecanoate, white further di-peroxyketals, peroxycarbonates and azo compounds such as Azodiisobutyronitrile (AIBN) and Azodiisovaleronitrile (ADVN) be used.

Details of the execution of the grafting reaction in emulsion fin can be found, for example, in DE-A 24 27 960 and EP-A 62901.

The gross composition of graft polymers A remains the same mentioned developments of the method are not affected.

Graft polymers with several are also suitable "soft" and "hard" levels, e.g. B. structure a1) -a2) -a1) -a2) or a2) -a1) -a2), especially in the case of larger particles.

So far in the grafting not grafted polymers from the mono meren a2) arise, these quantities are usually below 10% by weight of a2) are assigned to the mass of component A.

The following can be said about the radical N-oxyl compounds and their addition to the reaction mixture:
The process according to the invention uses at least one radical N-oxyl compound of a secondary amine which does not have any hydrogen atoms on the α-C atoms. These compounds can exist as free compounds or in the form of their salts.

Suitable N-oxyls of amines are e.g. B. the following structures

where R is the same or different alkyl, cycloalkyl, aralkyl or aryl radicals, which can also be connected in pairs to form a ring system, and Y is a group which is required to complete a 5- or 6-membered ring. For example, R represents a C ₁ -C ₂₀ -, in particular C ₁ -C ₈ -alkyl radical, a C ₅ - or C ₆ -cycloalkyl radical, a benzyl radical or a phenyl radical. Y is, for example, an alkylene group - (CH ₂ ) ₂ - or - (CH ₂ ) ₃ -.

N-oxyl compounds such as the following structures are also suitable

wherein the aromatic rings can each carry 1 to 3 inert substituents, such as. B. C ₁ -C ₄ alkyl, C ₁ -C ₄ alkoxy or cyano.

Sterically hindered amine derivatives of cyclic amines are preferably used, for. B. of piperidine or pyrrolidinver bonds, which may contain a further heteroatom such as nitrogen, oxygen or sulfur in the ring, this hetero atom is not in the vicinity of the hindered amine nitrogen. The steric hindrance is given by substituents in both neighboring positions to the amine nitrogen, with hydrocarbon residues which replace all 4 hydrogen atoms of the α-CH ₂ groups being considered as substituents. Examples of phenyl, C ₃ -C ₆ cycloalkyl, benzyl and in particular C ₁ -C ₆ alkyl radicals may be mentioned as substituents, the alkyl radicals bonded to the same α-C atom also being linked to one another to form a 5- or 6-ring can. The radicals listed below under R ⁵ , R ⁶ are particularly preferred. Derivatives of 2,2,6,6-tetraalkylpiperidine are preferably used as N-oxyls of sterically hindered amines.

Preferred N-oxyl compounds in the substance mixtures according to the invention are those of the general formula (VI)

in which
R ¹ and R ² independently of one another are each C ₁ -C ₄ alkyl, phenyl or, together with the C atom to which they are attached, a 5- or 6-membered saturated hydrocarbon ring,
R ^{3 is} hydrogen, hydroxy, amino, SO ₃ H, SO ₃ M, PO ₃ H ₂ , PO ₃ HM, PO ₃ M ₂ , organosilicon radicals or a m-valent organic or organosilicon radical bonded via oxygen or nitrogen or together with R ⁴ oxygen or a ring structure defined under R ⁴ , where M stands for an alkali metal,
R ^{4 is} hydrogen, C ₁ -C ₁₂ alkyl, C ₁ -C ₁₂ alkoxy or together with R ³ oxygen or together with R ³ and the C atom to which they are attached, the following ring structures

where for the cases in which R ³ forms a common residue with R ⁴ , m = 1,
R ^{5 is} hydrogen, C ₁ -C ₁₂ alkyl or (CH ₂ ) _z -COOR ⁶ ,
R ^{6 is the} same or different C ₁ -C ₁₈ alkyl,
k 0 or 1,
z and p are independently 1 to 12 and
m 1 to 100
mean.

R ¹ and R ² can be C ₁ -C ₄ alkyl groups such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl or tert-butyl or they can together be a tetra - or pentamethylene group. R ¹ and R ² are preferably methyl groups.

As R ⁴ are, for example, hydrogen, the above-mentioned C ₁ -C ₄ -alkyl groups and pentyl, sec-pentyl, tert-pentyl, neopentyl, 2,3-dimethyl-but-2-yl, hexyl, 2-methylpentyl , Heptyl, 2-methylhexyl, 2-ethylhexyl, octyl, isooctyl, 2-ethylhexyl, nonyl, 2-methylnonyl, isononyl, 2-methyloctyl, decyl, isodecyl, 2-methylnonyl, undecyl, isoundecyl, dodecyl and isododecyl, (the designations Isooctyl, isononyl and isodecyl are trivial names and are derived from the carbonyl compounds obtained after oxo synthesis; see Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. Al. Pages 290-293, and Vol. A10, Pages 284 and 285) and the alkoxy radicals derived therefrom.

p is preferably 6 to 12, particularly preferably 9.

z is preferably 1 to 4, particularly preferably 2.  

As R ⁵ , in addition to hydrogen, for example, the C ₁ -C ₁₂ -alkyl groups given above come into consideration. R ⁵ preferably represents hydrogen, C ₁ -C ₄ -alkyl or (CH ₂ ) - _z -COO (C ₁ -C ₆ -alkyl), particularly preferably the radicals -CH ₂ -CH ₂ -COO (CH ₂ ) ₁₁ -CH ₃ and -CH ₂ -CH ₂ -COO (CH ₂ ) ₁₃ -CH ₃ .

R ⁶ can be, for example, one of the above-mentioned C ₁ -C ₁₂ alkyl groups or tridecyl, isotridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl or octadecyl. Dodecyl and hexadecyl are preferred.

Preferred monovalent radicals R ³ are hydrogen, the C ₁ -C ₄ -alkyl groups already mentioned above and organosilicon radicals of the formula

where the groups T may be identical or different from one another and denote C ₁ -C ₁₂ alkyl or phenyl.

Examples of such organosilicon radicals are

Li, Na and K are preferably used as alkali metals M in the groups -SO ₃ M, -PO ₃ HM and -PO ₃ M ₂ .

Preferred monovalent groups R ^{3 which} are linked via oxygen are hydroxyl and C ₁ -C ₄ -alkoxy groups such as, for example, methoxy, ethoxy, propoxy and t-butoxy, but also the siloxane radicals derived from the above organosilicon radicals.

Preferred m-valent radicals R ³ are, for example, the following radicals

in which
R ^{7 is} C ₁ -C ₁₂ alkyl or - (CH ₂ ) _z -COOR ⁶
R ^{8 is} hydrogen or C ₁ -C ₁₈ alkyl,
R ⁹ C ₁ -C ₁₈ alkyl, vinyl or isopropenyl,
R ¹⁰ C ₈ -C ₂₂ alkyl,
R ^{11 is} hydrogen or an organic radical, as is customarily formed in the radial polymerization of the starting compounds,
k 0 or 1,
x 1 to 12 and
n an even number m
mean.

If R ^{3 is} one of these radicals, R ^{4 is} preferably hydrogen. The variable m can mean 1 to 100. M is 1, 2, 3, 4 or a number from 10 to 50, preference being given to using mixtures, in particular in the case of the oligomeric or polymeric radicals R ³ .

The same radicals as R ⁷ are those which are mentioned for R ⁹ . R ⁷ is preferably C ₁ -C ₄ alkyl.

As R ⁸ , in addition to hydrogen, the same radicals come into consideration as have been mentioned for R ⁶ . R ⁸ is preferably hydrogen.

R ^{9 in} particular includes vinyl, isopropenyl, methyl, ethyl, propyl, i-propyl, t-butyl or C ₁₅ -C ₁₇ alkyl radicals.

R ¹⁰ includes, for example, the above-mentioned C ₈ -C ₁₈ -alkyl radicals and nonadecyl, eicosyl, uneicosyl and doeicosyl. Mixtures of different radicals R ¹⁰ , which differ in the length of the carbon chain, are preferred.

The radicals R ¹¹ are hydrogen or organic radicals as they arise during the radical polymerization of the starting compounds, that is, for. B. a residue that arises from the polymerization initiator or from an intermediate radical or another such residue, as is known to the person skilled in the art.

Such radicals R ¹¹ can, for example, be styrene in the case of the starting compound

where R 'for any, the polymerization of styrene - or in the general case of compounds (A) - starting Pri stands radical.

Nitroxyl compounds of the formula (II ') can also be used

where mean
R ¹² and R ¹³ independently of one another are each C ₁ -C ₄ -alkyl, phenyl or, together with the carbon atom to which they are attached, a 5- or 6-membered saturated hydrocarbon ring,
R ^{14 is} an m'valent radical bound via carbon, oxygen or nitrogen,
R ^{15 is} hydrogen, C ₁ -C ₁₂ -alkyl, C ₁ -C ₁₂ -alkoxy or together with R ¹⁴ a m'-valent radical bonded via carbon or nitrogen through a chemical double bond to the carbon atom bearing these groups or together with R ¹⁴ and the C atom carrying these groups a saturated isocyclic or heterocyclic 3- to 7-membered ring,
m '1, 2 or 3.

In the event that R ¹⁴ and R ¹⁵ together represent an m′-valent radical bonded via carbon or nitrogen through a chemical double bond, the values 1, 2 or 3 of the variables m ′ should imply that 1, 2 or 3 of the piperidinyl rings shown in formula (II ') are each bonded to the m'-valent radical via a double bond.

The selection for the radicals R ¹² and R ¹³ corresponds to that of the radicals R ¹ and R ⁷ already mentioned above and should also be used here. Again methyl groups are preferably used as substituents R ¹² and R ¹³ .

Possible m′-valent radicals R ¹⁴ are C ₁ -C ₄ -alkyl, and unsubstituted phenyl which is substituted by one to three C ₁ -C ₄ -alkyl radicals, examples of C ₁ -C ₄ -alkyl radicals already being known were listed above. These residues can be linked to the piperidine ring via oxygen, an NH or also an N (C ₁ -C ₄ alkyl) group. In the case of a connection via a C atom, this should already be counted as belonging to the radical R ¹⁴ .

Possible residues R ¹⁴ are, for example (the lines here indicate the free valences):

The C ₁ -C ₁₂ alkyl and C ₁ -C ₁₂ alkoxy groups which are possible representatives of the R ¹⁵ radicals have already been mentioned as examples above for the R ⁴ radicals. The radicals R ¹⁴ and R ¹⁵ can also together form a group, which is then bonded via a chemical double bond via carbon or nitrogen to the carbon atom bearing the groups (the carbon atom in position 4 of the piperidine ring). Such m'valent groups can be, for example (the dashes indicate the free valences):

The radicals R ¹⁴ and R ¹⁵ with which these groups carry the C atoms can form a 3- to 7-membered isocyclic or heterocyclic ring.

Examples of such rings are:

The groups R ¹⁶ here mean hydrogen, C ₁ -C ₁₂ -alkyl and unsubstituted or substituted with one to four C ₁ -C ₄ -alkyl groups phenyl. Examples of corresponding C ₁ -C ₁₂ alkyl groups and C ₁ -C ₄ alkyl groups which can occur as substituents on the phenyl ring have already been mentioned above. The variable k 'can have a value of 0, 1 or 2.

Other suitable N-oxyls are also oligomeric or polymeric Compounds which have a polysiloxane as the main polymer chain zen and substituted in the side chain with N-oxyl groups are, which are derived from 2,2,6,6-tetraalkylpiperidine. As the preferred N-oxyl grouping is 2,2,6,6-tetramethyl piperidine-N-oxyl residue used. Examples of such fiction N-oxyls, which are also to be used, can be found in the document WO 69/17002. There are also examples of Synthe in this document  sen of the amino compounds on which the N-oxylene is based leads.

Preferred radical N-oxyl compounds are also the following:

1-oxyl-2,2,6,6-tetramethylpiperidine,
1-oxyl-2,2,6,6-tetramethylpiperidin-4-ol,
1-oxyl-2,2,6,6-tetramethylpiperidin-4-one,
1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl acetate,
1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-2-ethylhexanoate,
1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl stearate,
1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl benzoate,
1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl- (4-tert-butyl) benzoate,
Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) succinate,
Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipate
Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate,
Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -n-butylmalonate,
Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) phthalate,
Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) isophthalate,
Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) terephthalate,
Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) hexyhydroterephthalate,
N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipinamide,
N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) caprolactam,
N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) dodecylsuccinimide,
2,4,6-tris- [N-butyl-N- (1-oxyl-2,2,6,6, -tetramethylpiperidine-4-yl] -s-triazine,
N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -N, N'-bis formyl-1,6-diaminohexane,
4,4'-ethylenebis (1-oxyl-2,2,6,6-tetramethylpiperazin-3-one) and
Tris (2,2,6,6-tetramethyl-1-oxyl-piperidin-4-yl) phosphite.

The radical N-oxyl compounds can be derived from the The corresponding amino or piperidine compounds by oxidation z. B. with hydrogen peroxide. Details on this oxidation are z. B. called in DE-OS 195 10 184. The secondary amines which have no hydrogen atoms on the α-C atoms, such as pipe ridine compounds, and their preparation are generally known. Since the oxidation reactions do not always take place completely, can also serve as the starting compounds amino or Piperidine compounds and partially oxidized intermediates such as hydroxylamines in the N-oxyl-containing mixtures be included.

According to the invention, the N-oxyl compound is added after Polymerization of basic step a1) before and / or during the Polymerization of the graft stage a2). If the polymers reason  stage a1) before the polymerization of the graft stage a2) a part wise or complete agglomeration (see the explanations for emulsion polymerization), the addition the N-oxyl compound before, during or after agglomeration take place, preferably before agglomeration.

The application of these N-oxyl compounds can ver in different ways.

The addition of the N-oxyl compound to the bottom has proven advantageous polymerization mixture for the end-polymerized reason stage a1) and the graft stage monomers a21) to a23) have been proven. The N-oxyl compound can also in the graft monomers a21) to a23) may be included to prevent them from premature polymerization protect.

The N-oxyl compound should be at a concentration in the polymer risk mix which includes the speed of the Polymerization is only slightly influenced. The sensitivity of the Polymerization depends on the amount of the N-oxyl compound on various parameters, in particular on the type of Mo nomeren, on the structure of the N-oxyl compound, on the Temperature and others possibly in the reaction mixture existing radical formers and radical scavengers. The optimal one Concentration can be given in a few preliminary tests Determine process parameters.

An advantageous concentration range for the N-oxyl compound (s) in the polymerization mixture is 3 to 200 ppm, particularly 5 to 150 ppm, very particularly 10 to 130 ppm (1 ppm = 10 ^-6 parts by weight of N-oxyl compound) on the total weight of basic stage a1) (as a solid) and graft monomers a21) to a23). At these concentrations, the formation of deposits is generally completely inhibited, without, however, appreciably influencing the kinetics of the reaction.

In addition to the addition to the polymerization mixture has been particularly proven a process variant in which the reactor top area before the polymerization of the graft stage a2) with a Solution of the N-oxyl compound wetted.

If the polymerization of basic stage a1) and graft stage a2) are carried out in different reactors Surface of the graft reactor wetted. If basic and Grafting polymerized in the same reactor, emptied you usually the reactor, wet its surface and be  then refills it with the previously drained one Mixture.

The wetting can be done simply and effectively by spraying the Reactor wall and other parts in the reactor, such as the Stirrer and heating or cooling elements, with a solution of N-oxyl connection can be achieved. The N-oxyl compounds are often only not very soluble in water, but mostly dissolve in organic solvents solvents such as methanol, ethanol, propanol, acetone, ethyl acetate, dimethylformamide, etc. A particularly suitable solution methanol is medium for many N-oxyl compounds. The concessions tration of the N-oxyl compound in the spray solution is not critical table, it is advantageously between 0.01 and 1 wt .-%, based on the total mass of the spray solution.

Alternatively, the wetting of the reactor surface can also be carried out by Fill with a solution similar to the spray solution and then draining.

The wetting of the reactor surface compared to the addition of N-oxyl compound to the polymerization mixture has the advantage that Influence on the rate of polymerization is extremely low and that the area above the liquid level, ins especially the area just above the liquid level, in which are often to be found, is protected from the formation of deposits becomes.

A combination of the two is also advantageous in some cases Application forms, whereby then for the direct addition to the poly solution, very small amounts are sufficient.

The aqueous dispersion of the graft polymers A) obtained is worked up to give the particulate graft polymers A), in which the aqueous medium is completely or partially separated off. For this purpose, the particulate polymer A) dispersed in the aqueous medium is first precipitated, if necessary, for example by adding a coagulating precipitant such as CaCl ₂ , MgSO ₄ , acetic acid, sulfuric acid, etc. Centrifuging or other solid-liquid separation processes separated. The moist polymer A) obtained can either be processed directly, or the residual moisture can be dried by thermal drying, e.g. B. can be removed by means of warm air in a current dryer. The aqueous dispersion can also be worked up by the spray drying method.

It is also possible to obtain the aqueous polymer dispersion obtained to be further processed as such. For example, the Disper sion with other polymers in a mixing device simultaneous removal of the aqueous phase can be mixed.

The graft obtainable by the process according to the invention polymers A can be used as a component in thermoplastic form masses are used.

As a thermoplastic matrix polymer in the molding compounds is included, all thermoplastic polymers with a Glass transition temperature Tg <25 ° C suitable. Be exemplary some such polymers are mentioned below.

In a preferred embodiment, the matrix polymer contains 50 to 100, preferably 60 to 95 and particularly preferably 60 to 90% by weight of a styrene compound of the general formula as already described above for a21), or one (C ₁ -C ₈ - Alkyl) esters of acrylic acid or methacrylic acid or mixtures of the styrene compound and (C ₁ -C ₈ alkyl) ester of acrylic acid or methacrylic acid, furthermore 0 to 40, preferably up to 38% by weight of acrylonitrile or methacrylonitrile or mixtures thereof, and 0 to 40, preferably 0 to 30% by weight of one or more further monoethylenically unsaturated monomers as have already been mentioned for a12), a13 *) and a23).

The matrix polymer preferably has a glass transition temperature Tg of 50 ° C. or above. The matrix is therefore a hard polymer. The following applies to the matrix polymer:
The styrene compound of the general formula described is preferably styrene, α-methylstyrene and, moreover, styrenes which are core-alkylated with C ₁ -C ₈ -alkyl, such as p-methylstyrene or tert-butylstyrene. Styrene and α-methylstyrene are particularly preferred.

Instead of the styrene compounds or in a mixture with them, C ₁ - to C ₈ -alkyl esters of acrylic acid and / or methacrylic acid can be considered, especially those which are derived from methanol, ethanol, n- and iso-propanol, sec.-, tert.- and iso-butanol, pentanol, hexanol, heptanol, octanol, 2-ethylhexanol and n-butanol. The preferred method is methyl methacrylate.

Preferred matrix polymers are, for example:

M / 1: polymethyl methacrylate (PMMA) - in this case A) can be obtained by polymerizing 100% by weight of methyl methacrylate (component ml)),
M / 2: polymers obtainable by copolymerization of 40 to 90, preferably 50 to 80% by weight of styrene and / or α-methylstyrene with 10 to 60, preferably 20 to 40% by weight of acrylonitrile, and optionally 0 to 30, preferably 0 to 20% by weight of further monoethylenically unsaturated monomers.

If the matrix polymer preferably contains styrene and acrylonitrile, see above the well-known commercially available SAN copolymers are created. they usually have a viscosity number VZ (determined from DIN 53 726 at 25 ° C, 0.5 wt .-% in dimethylformamide) from 40 to 160 ml / g, corresponding to an average molecular weight of about 40,000 up to 250000 (weight average).

The matrix polymers can be used in a manner known per se, e.g. B. by substance, solution, suspension, precipitation or emulsion receive polymerization. Details of these procedures are e.g. B. in the plastics handbook, ed. Vieweg and Daumiller, Carl-Hanser-Verlag Munich, Vol. 1 (1973), pp. 37 to 42 and Vol. 5 (1969), Pp. 118 to 130, as well as in Ullmann's encyclopedia of technical Chemistry, 4th edition, Verlag Chemie Weinheim, Vol. 19, pp. 107 to 158 "Polymerization technology" described.

In another preferred embodiment, the matrix is poly vinyl chloride PVC. Suitable polyvinyl chlorides are per se knows.

Either only vinyl chloride or mixtures of vinyl chloride and other monomers (comonomers) with at least 40% by weight of vinyl chloride, based on the total mass of the monomers, can be used as the monomer for PVC. As comonomers of vinyl chloride come in particular vinyl esters, e.g. B. vinyl acetate, vinyl propionate and others, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether and others, vinylidene chloride, C ₁ -C ₁₈ alkyl esters of acrylic acid such as butyl acrylate and 2-ethylhexyl acrylate, dialkyl maleates such as dibutyl maleate, olefins such as ethene, propene, isobutene and longer chain ₆ -C ₁₅ olefins, dienes such as butadiene and vinyl aromatic compounds such as styrene into consideration.

The polymerization of vinyl chloride is carried out in a manner known per se ter way, e.g. B. as an emulsion, suspension or mass polymerization, preferably as suspension polymerization, by.  

The polymerization temperature depends on the desired Molecular weight or K value of the PVC product and is between and 100 ° C, preferably between 35 and 80 ° C, for most Products between 45 and 70 ° C. The polymerization is generally mean with a turnover of 60 to 95%, preferably 70 to 90%, canceled.

In another preferred embodiment, the matrix is a Polycarbonate or a polyester.

Suitable polycarbonates are known per se. You are e.g. B. ent speaking the method of DE-B-13 00 266 by interfacial po lycondensation or according to the method of DE-A-14 95 730 Reaction of biphenyl carbonate with bisphenols available. Before added bisphenol is 2,2-di (4-hydroxyphenyl) propane, generally mean - as in the following - called bisphenol A.

Instead of bisphenol A, other aromatic Dihydroxy compounds are used, in particular 2,2-di (4-hydroxyphenyl) pentane, 2,6-dihydroxynapthalene, 4,4'-dihy hydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy diphenyl sulfite, 4,4, -dihydroxydiphenylmethane, 1,1-di- (4-hydroxy phenyl) ethane or 4,4-dihydroxydiphenyl and mixtures of the above called dihydroxy compounds.

Particularly preferred polycarbonates are those based on Bisphenol A or Bisphenol A together with up to 30 mol% of the aromatic dihydroxy compounds mentioned above.

The relative viscosity of these polycarbonates is in general in the range from 1.1 to 1.5, in particular 1.28 to 1.4 (measured at 25 ° C in a 0.5 wt .-% solution in dichloromethane).

Suitable polyesters are also known per se and are described in the literature. They contain an aromatic ring in the main chain, which stems from an aromatic dicarboxylic acid. The aromatic ring can also be substituted, e.g. B. by halogen such as chlorine and bromine or by C ₁ -C ₄ alkyl groups such as methyl, ethyl, i- or n-propyl and n-, i- or tert-butyl groups. The polyesters can be prepared in a manner known per se by reacting aromatic dicarboxylic acids, their esters or other ester-forming derivatives thereof with aliphatic dihydroxy compounds.

Preferred dicarboxylic acids are naphthalenedicarboxylic acid, Terephthalic acid and isophthalic acid or mixtures thereof nen. Up to 10 mol% of the aromatic dicarboxylic acids can  by aliphatic or cycloaliphatic dicarboxylic acids such as Adipic acid, azelaic acid, sebacic acid, dodecanedioic acids and Cyclohexanedicarboxylic acids are replaced.

Of the aliphatic dihydroxy compounds, diols with 2 up to 6 carbon atoms, in particular 1,2-ethanediol, 1,4-butane diol, 1,6-hexanediol, 1,4-hexanediol, 1,4-cyclohexanediol and neo Pentylglycol or mixtures thereof are preferred.

Polyalkylene terephthalates are particularly preferred polyesters, which are derived from alkane diols with 2 to 6 carbon atoms nen. Of these, especially polyethylene terephthalate, Polyethylene naphthalate and polybutylene terephthalate are preferred. The Viscosity number of the polyester is generally in the range of 60 to 200 ml / g (measured in a 0.5 wt .-% solution in one Phenol / o-dichlorobenzene mixture (weight ratio 1: 1 at 25 ° C)).

Furthermore, the thermoplastic molding compositions can be added conventionally fabrics such as B. lubricants or mold release agents, pigments, paints substances, flame retardants, antioxidants, stabilizers against Exposure to light, fibrous and powdery fill or reinforcement agents or antistatic agents, as well as other additives, or their mixtures.

Suitable lubricants and mold release agents are e.g. B. stearic acids, Stearyl alcohol, stearic acid esters or amides and silicone oils, Montan waxes and those based on polyethylene and poly propylene.

Pigments are for example titanium dioxide, phthalocyanines, ultra navy blue, iron oxides or soot, as well as the class of organic Pigments.

Dyes are all dyes to understand the transparent, semi-transparent or non-transparent on Coloring of polymers can be used, especially sol che, which are suitable for coloring styrene copolymers. The like dyes are known to those skilled in the art.

As flame retardants such. B. those known to those skilled in the art halogen-containing or phosphorus-containing compounds, magnesium hydroxide, as well as other common compounds, or their Mixtures are used.  

Suitable antioxidants (heat stabilizers) are roughly steric hindered phenols, hydroquinones, various substituted ver treads from this group, as well as their mixtures. They are about as Topanol® or Irganox® commercially available.

Suitable light stabilizers are e.g. B. ver various substituted resorcinols, salicylates, benzotriazoles, Benzophenone, HALS (Hindered Amine Light stabilizers) like them e.g. B. are commercially available as Tinuvin®.

As examples of fibrous or powdery fillers be carbon or glass fibers in the form of glass fabrics, Glass mats or glass silk rovings, cut glass, glass balls as well Called wollastonite, particularly preferably glass fibers. When ver Glass fibers can be used for better tolerance with the blend components with a size and a Haftver be medium equipped. The incorporation of the glass fibers can both in the form of short glass fibers and in the form of endless strands (rovings).

Carbon black and amorphous pebbles are suitable as particulate fillers acid, magnesium carbonate (chalk), powdered quartz, mica, Mica, bentonite, talc, feldspar or especially calcium silicates such as wollastonite and kaolin.

Suitable antistatic agents are, for example, amine derivatives such as N, N-bis (hydroxyalkyl) alkyl amines or alkylene amines, polyethylene glycol esters, glycerol mono- and distearates, copolymers Ethylene oxide and propylene oxide, polypropylene glycol, N, N-bis (2-hy hydroxyalkyl) -N-n-octyl-N-methyl-ammonium-p-toluenesulfonate, as well as their mixtures.

The individual additives are in the usual amounts used, so that further details are unnecessary.

The thermoplastic molding compositions are produced by the matrix polymers and the graft polymers A, and against if necessary, the additives, in a suitable mixing device mixed and ver at suitable temperatures to a molding compound is working. The production of the molding compositions can be known mixing processes take place, for example with melting zen in an extruder, Banbury mixer, kneader, roller mill or Calender. However, the components can also be used "cold" and the powdery or granular mixture is only melted and homogenized during processing.  

Mixing usually takes place at temperatures from 130 to 350 ° C.

If the particulate polymers A still ent moisture hold, the production of the molding compositions can be advantageous an extruder in which the residual moisture by Ent water openings as liquid water and / or by degassing openings as steam is removed.

From the particulate polymers A) and in particular from the molding compounds can be molded articles of all kinds, including foils, produce.

The method according to the invention enables the production of Graft polymers in aqueous phase according to all conventional polymers risk assessment procedure with a significantly reduced wall covering balance dung or without any formation of wall coverings on the reactor surfaces. The polymerization process is not affected, ins special not slowed down. Surprisingly, they have molding compounds from matrix polymer and those produced according to the invention Graft polymers A) better mechanical properties, ins especially a higher notched impact strength.

Examples

When specifying the weight-average particle size d ₅₀ of component B), it is the weight-average particle size, as determined by means of an analytical ultracentrifuge according to the method of W. Scholtan and H. Lange, Kolloid-Z. and Z.-Poly mere 250 (1972) pages 782 to 796. The ultra centrifuge measurement provides the integral mass distribution of the particle diameter of a sample. From this it can be seen what percentage by weight of the particles have a diameter equal to or smaller than a certain size.

The weight-average particle diameter d ₅₀ indicates that particle diameter in which 50% by weight of all particles have a larger and 50% by weight a smaller particle diameter.

Examples 1 and 2 a) Preparation of the basic stage from polybutadiene

Butadiene was polymerized in an aqueous emulsion. In detail, the procedure was as described in DE-OS 31 49 046, page 15, lines 5 to 34. The polybutadiene latex obtained had a solids content of 40% by weight and an average particle size d ₅₀ of 80 nm.

b) agglomeration of the polybutadiene basic stage and grafting with Styrene acrylonitrile

50 kg of the polybutadiene latex prepared under a) were initially introduced into a reactor with a stirrer and thermometer and the amount of N-oxyl compound, namely N, N'-bis (1-oxyl-2,2,6, 6-tetramethylpiperidin-4-yl) -N, N'-bis-formyl-1,6-diaminohexane added. After heating to 75 ° C., 1 kg of an agglomerating latex composed of 96% by weight of ethyl acrylate and 4% by weight of methacrylamide (solids content 10% by weight) was added. A (partially) agglomerated polybutadiene latex with a bi-modal particle size distribution and an average particle size d ₅₀ of 220 nm was obtained.

The agglomerated latex was at 75 ° C and 0.2 kg of potassium stearate 0.025 kg of potassium persulfate added. After adding 1.47 kg of styrene and 0.63 kg of acrylonitrile was polymerized for 15 min and then in within a further 3 hours a mixture of 7.35 kg styrene and 3.15 kg of acrylonitrile were added. Then 0.025 kg Potassium persulfate was added and the mixture was stirred at 75 ° C. for a further 1.5 hours.

c) Check for wall covering

After cooling, the graft latex obtained under b) was drained from the kettle and the wall covering of the reactor surface was first assessed visually. Mean in the table

++ no wall covering
+ some wall covering, thickness about 1 mm
- strong wall covering, thickness about 2-3 mm.

Then the coating on the reactor surface, on the stirrer and mechanically removed and balanced on the thermometer.

d) Preparation of a matrix polymer from styrene and acrylonitrile

A copolymer of 65% by weight styrene and 35% by weight Acrylonitrile using the process of continuous solution poly merisation, as in the plastic manual, Ed. R. Vieweg and G. Daumiller, Vol. V "Polystyrene", Carl-Hanser-Ver lay Munich 1969, pages 122 to 124, is described. The Viscosity number VZ (determined according to DIN 53 726 at 25 ° C, 0.5% by weight in dimethylformamide) was 80 ml / g.  

e) Production and testing of moldings

The latex of the graft polymer A) drained off under c) was by adding a magnesium sulfate solution and coagulated fallen graft polymer separated, washed with water and dried with warm air.

46 parts by weight of this graft polymer (grafted polybutadiene with SAN) were mixed with 54 parts by weight of the SAN matrix polymer from d) on an extruder ZSK 30 from Werner & Pfleiderer an ABS molding compound intimately mixed, discharged and granulated.

The ABS granules obtained were injected at 220 ° C. melt temperature and 60 ° C. mold temperature into standard small bars (see DIN 53 453). The notched impact strength a _K was determined on the standard small bars in the impact bending test according to ISO 179-211 eA (S).

Comparative Example 3

The procedure was as for Examples 1 and 2 under a) to e) described, but no N-oxyl compound was added to b) adds.

table

The experiments show that the addition of 20 ppm of N-oxyl compound significantly reduces the formation of wall coverings. Who added to the 35 ppm N-oxyl compound, the formation of Completely prevented deposits on the reactor surface, and on There are only a few deposits on the stirrer and thermometer.  

At the same time, the notched impact strength of the molding compositions increases considerably if the N-oxyl compound is also used: the a _K value increases by 31% at 20 ppm and by 55% at 35 ppm N-oxyl compound, in each case based on the comparative example .

Claims (9)

1. Process for the preparation of graft polymers A from
based on A),

• a1) 30 to 95% by weight of a rubber-elastic basic stage, based on a1),
  • a11) 50 to 100% by weight of a diene with conjugated double bonds,
    a12) 0 to 50% by weight of one or more further monoethylenically unsaturated monomers,
    or off, based on a1)
    a11 *) 50 to 100% by weight of a (C ₁ -C ₁₀ alkyl) ester of acrylic acid,
    a12 *) 0 to 10% by weight of a polyfunctional, crosslinking monomer,
    a13 *) 0 to 40% by weight of one or more further monoethylenically unsaturated monomers,
• a2) 5 to 70% by weight of a graft stage, based on a2),
  • a21) 50 to 100% by weight of a styrene compound of the general formula
    in which R ¹ and R ^{2 represent} hydrogen or C ₁ -C ₈ alkyl,
    a22) 0 to 40% by weight of acrylonitrile or methacrylonitrile or mixtures thereof and
    a23) 0 to 40% by weight of one or more further monoethylenically unsaturated monomers,

in the aqueous phase, characterized in that the polymerization of the basic stage a1) is first completed and then, before and / or during the polymerization of the graft stage a2), at least one radical N-oxyl compound of a secondary amine which has no hydrogen atoms on the α- C atoms carries, admits. 2. The method according to claim 1, characterized in that one the N-oxyl compound in a concentration of 3 to 200 ppm, based on the total weight of basic level a1) (as a solid) and graft monomers a21) to a23) are added. 3. Process according to claims 1 to 2, characterized in that a compound of the general formula (I) or (II) is used as the N-oxyl compound
in which
R = identical or different, straight or branched, optionally substituted alkyl, cycloalkyl, aralkyl or aryl radicals, where the radicals R can also be connected in pairs to form a ring system,
Y = a group required to complete a 5- or 6-membered ring,
or a compound of the general formulas (III), (IV) or (V),
where R has the meaning given above and the aromatic rings can each carry 1 to 3 inert substituents. 4. Process according to Claims 1 to 3, characterized in that a compound of the general formula (VI) is used as the N-oxyl compound
in which
R ¹ and R ² independently of one another are each C ₁ -C ₄ -alkyl, phenyl or, together with the carbon atom to which they are attached, a 5- or 6-membered saturated hydrocarbon ring,
R ^{3 is} hydrogen, hydroxy, amino, SO ₃ H, SO ₃ M, PO ₃ H ₂ , PO ₃ HM, PO ₃ M ₂ , organosilicon radicals or an m-valent organic or organosilicon radical bonded via oxygen or nitrogen or together with R ^{4 is} oxygen or a ring structure defined under R ⁴ , where M is an alkali metal,
R ^{4 is} hydrogen, C ₁ -C ₁₂ alkyl, C ₁ -C ₁₂ alkoxy or together with R ³ oxygen or together with R ³ and the C atom to which they are attached, the following ring structures
where for the cases in which R ³ forms a common residue with R ⁴ , m = 1,
R ^{5 is} hydrogen, C ₁ -C ₁₂ alkyl or - (CH ₂ ) _z -COOR ⁶ ,
R ^{6 is the} same or different C ₁ -C ₁₈ alkyl,
k 0 or 1,
z and p are independently 1 to 12 and
m 1 to 100
mean. 5. The method according to claim 4, characterized in that the radical R ³ from formula (VI) is a radical from the following group:
Hydrogen,
C ₁ -C ₄ alkyl,
with T = independently of one another C ₁ -C ₁₂ alkyl or phenyl
in which
R ^{7 is} C ₁ -C ₁₂ alkyl or - (CH ₂ ) _z -COOR ⁶ ,
R ^{8 is} hydrogen or C ₁ -C ₁₈ alkyl,
R ⁹ C ₁ -C ₁₈ alkyl, vinyl or isopropenyl,
R ¹⁰ C ₈ -C ₂₂ alkyl,
R ^{11 is} hydrogen or an organic radical, as is usually produced in the free-radical polymerization of the starting compounds,
k 0 or 1,
x 1 to 12 and
n an even number m
mean. 6. The method according to claims 1 to 5, characterized in net that as N-oxyl compound N, N'-bis (1-oxyl-2,2,6,6-tetra methylpiperidin-4-yl) -N, N'-bisformyl-1,6-diaminohexane is set. 7. The method according to claims 1 to 6, characterized in net that the polymerized basic stage a1) before Polymerization of the graft stage a2) of a partial or subject to complete agglomeration, and that one N-oxyl compound is added before this agglomeration. 8. Graft polymers prepared by the process according to Claims 1 to 7. 9. Use of radical N-oxyl compounds one sec där amine, which has no hydrogen atoms on the α-C atoms contributes to the prevention of deposits on reactor surfaces the graft polymerization in the aqueous phase.