KR20010032225A - Method for producing graft polymers - Google Patents

Abstract

The present invention

a11) 50 to 100% by weight of diene having a conjugated double bond,

a12) comprising, as a main component, a1) consisting of 0-50% by weight of one or more additional monoethylenically unsaturated monomers, or

a11 *) 50 to 100% by weight of C ₁ -C ₁₀ alkyl ester of acrylic acid,

a12 *) 0 to 10 wt% of the crosslinkable monomer of the multifunctional group,

a13 *) 30 to 95% by weight of a1) a rubbery elastomeric basic step material comprising a1) consisting essentially of 0 to 40% by weight of one or more additional monoethylenically unsaturated monomers;

a21) general formula 1

Phosphorus styrol compound 50-100 wt%, wherein R ¹ and R ² are hydrogen or C ₁ -C ₂ alkyl,

a22) 0-40% by weight of acrylonitrile or methacrylonitrile or mixtures thereof and

a23) a graft polymer A comprising as a main component a2) a graft step of 5 to 70% by weight of a2) a main component comprising a2) consisting of 0 to 40% by weight of at least one additional monoethylenically unsaturated monomer in an aqueous phase It relates to a manufacturing method. The present invention first completes the polymerization of the base stage material a1) and then at least one free radical N-oxyl compound of sec-amine which does not have hydrogen in the α carbon before and / or during the polymerization of the graft stage material a2). It is characterized by the addition.

Description

Graft polymer production method {METHOD FOR PRODUCING GRAFT POLYMERS}

During the polymerization, in particular the graft polymerization for producing core-shell graft particles, it is common for example for polymer deposits to appear on the reactor walls. These polymer deposits usually make the process difficult and cost significant, since they must be removed at regular intervals after each polymerization.

Furthermore, deposits, for example, which are generally composed of polymers that are irregular in terms of their molecular weight distribution, may in some cases be separated, thus causing non-uniformity of the polymer or contamination of the polymer. Wall deposits reduce yield over time and cause loss of heat from the reactor, which causes local overheating and, in extreme cases, explosion of the reactor (with uncontrollable temperature rise).

Various methods have been developed to cure the formation of deposits. Since the level of deposits formed is highly dependent on the surface structure of the reactor walls, for example their roughness, this method is primarily aimed at smoothing the surface. In addition to mechanical methods, attempts have been made to maintain the quality of the surface by adding corrosion inhibitors to the polymerization (eg GW Becker, D. Braun (eds.), Kunststoff Handbuch, Hauser Verlag, Munich, Vienna 1986, See Volume 2/1, p. 153). However, this method generally cannot adequately prevent the formation of deposits.

It is known that the addition of aromatic condensation products to the reaction mixture can reduce the formation of wall deposits; See, for example, Japanese Patent A 08245704, Japanese Patent A 07025912, and European Patent A 632 058. However, this reduction is not satisfactory in all cases.

German Patent A 196 09312 describes a method for preventing premature polymerization of any vinyl containing monomer by adding N-oxyl compounds of secondary amines, for example, during processes such as distillation, purification, storage and transport. In addition, N-oxyl compounds have been described for use to stabilize styrene and other vinyl aromatic compounds during the distillation process (US Pat. No. 5,254,760). However, it is also known that even small amounts of such nitroxyl compounds can disrupt subsequent polymerization processes, and they can delay polymerisation and cause chain termination to be uncontrolled, resulting in polymers that lack regeneration and shorten chain lengths. have. This detrimental effect is reported by Mardare et al. Polym. Pre. (Am. Chem. Soc., Div. Polym. Sci.) 35 (1), (1994) 778.

Alternatively, steric hindrance N-oxyl radicals can be used as initiators in combination with active free radical polymerization with the open initiator.

In active free radical polymerization, the molecular weight of the polymer increases approximately linearly with the conversion, and the polydispersity is low (polydispersity index PDI = _w / _n , _{where w} = average weight and _n = number average molecular weight), which is why in US Patent A 5,401,804 and US Patent A 5,322,912 the ratio of N-oxyl radical / initiator is limited to 0.5-2.5 and in WO 96/24620 is 1.2-1.6 to be. Since the rate of the reaction is relatively low at the selected initiator ratio, the polymerization needs to be carried out at a relatively high temperature, usually 100 ° C. or higher.

On the other hand, in the case of conventional (traditional) free radical polymerization (in other words without N-oxyl radicals), a high molecular weight is obtained at the start of the polymerization and the PDI is greater than two. Moreover, traditional free radical polymerization has a relatively high reaction rate even at temperatures below 100 ° C.

Previously filed in 19648811.7 (not first published) in Germany, the addition of an N-oxyl compound to prevent wall deposition followed by the polymerization of vinyl monomers, in particular vinyl chloride, in the aqueous phase The process is described in general terms.

The present invention

a11) 50 to 100% by weight of diene having a conjugated double bond,

a12) 0-50% by weight of one or more additional monoethylenically unsaturated monomers,

As the main ingredient,

a11 *) 50 to 100% by weight of C ₁ -C ₁₀ alkyl ester of acrylic acid,

a12 *) 0 to 10 wt% of the crosslinkable monomer of the multifunctional group,

a13 *) 30 to 95 weight percent of a1) elastomeric base stage material, based on 0 to 40 weight percent of one or more additional monoethylenically unsaturated monomers;

a21) chemical formula

50 to 100% by weight phosphorus styrene compound, wherein R ¹ and R ² are hydrogen or C ₁ -C ₈ alkyl,

a22) 0-40% by weight of acrylonitrile or methacrylonitrile or mixtures thereof and

a23) Process for preparing a graft polymer A based in aqueous phase, consisting of A) consisting of 5 to 70% by weight of a substance in a graft step comprising a2) consisting of 0 to 40% by weight of at least one additional monoethylenically unsaturated monomer It is about.

The present invention also relates to the use of free radical N-oxyl compounds to prevent deposition on the surface of the reactor in graft polymerization in the aqueous phase and graft polymers produced by the process.

It is an object of the present invention to avoid the disadvantages set out above, in particular to reduce or completely inhibit the deposition of polymers on the reactor walls, for example without producing a significant effect on the polymerization process in terms of their speed, and in particular in the preparation of graft polymers in aqueous phase. to be.

First all the polymerization of the basic stage material a1) is completed, and then at least one free radical N-oxyl compound of a secondary amine having no hydrogen on the α carbon is added before and / or during the polymerization of the graft stage material a2). When found, this objective was found to be achieved by an initially defined method.

The present invention also provides the graft polymer A produced by the process and the use of free radical N-oxyl compounds to prevent deposition on the reactor surface during graft polymerization in the aqueous phase.

Graft polymer A)

a11) 50 to 100% by weight, preferably 60 to 100% by weight, particularly preferably 65 to 100% by weight of dienes having conjugated double bonds

a12) from 0 to 50% by weight, preferably from 0 to 40% by weight, particularly preferably from 0 to 35% by weight of at least one monoethylenically unsaturated monomer,

or

a11 *) 50 to 100% by weight, preferably 60 to 100% by weight, particularly preferably 70 to 100% by weight, C ₁ -C ₁₀ alkyl ester of acrylic acid,

a12 *) 0 to 10% by weight, preferably 0 to 5% by weight, particularly preferably 0 to 2% by weight, of the crosslinkable monomer of the multifunctional group,

a13 *) a1) elastomer based step material 30-95, consisting mainly of 0-40% by weight, preferably 0-30% by weight, particularly preferably 0-20% by weight of one or more additional monoethylenically unsaturated monomers Weight percent, preferably 40-90 weight percent, particularly preferably 40-85 weight percent,

a21) chemical formula

Phosphorus styrene compound 50-100% by weight, preferably 60-100% by weight, particularly preferably 65-100% by weight, wherein R ¹ and R ² are hydrogen or C ₁ -C ₈ alkyl,

a22) 0-40% by weight of acrylonitrile or methacrylonitrile or mixtures thereof, preferably 0-38% by weight, particularly preferably 0-35% by weight, and

a23) from 5 to 70% by weight of a2) graft step material, based on 0 to 40% by weight, preferably 0 to 30% by weight, particularly preferably 0 to 20% by weight of one or more additional monoethylenically unsaturated monomers, It preferably comprises A) consisting of 10 to 60% by weight, particularly preferably 15 to 60% by weight, as a main component.

Regarding the basic step substance a1) is as follows.

Suitable dienes a11) with conjugated double bonds are in particular derivatives substituted with their halogens such as butadiene, isoprene, norbornene and chloroprene. Butadiene and isoprene are preferred, butadiene is particularly preferred.

Examples of further monoethylenically unsaturated monomers a12) wherein graft cores a1) may be present in place of monomers a11)

Vinyl aromatic monomers, such as styrene, styrene derivatives,

Wherein R ¹ and R ² are hydrogen or C ₁ -C ₈ alkyl;

Acrylonitrile, methacrylonitrile;

C ₁ -C ₄ alkylesters of methacrylic acid, such as methacrylates, as well as glycidyl esters, glycidyl acrylate and glycyryl methacrylate;

N-substituted maleimides such as N-methyl maleimide, N-phenyl maleimide, N-cyclohexyl maleimide;

Dicarboxylic acids such as acrylic acid, methacrylic acid, 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 aliphatic esters of acrylic acid and methacrylic acid such as phenyl acrylate, phenyl methacrylate, benzyl acrylate, benzyl methacrylate, 2-phenoxyethyl acrylate and 2-phenoxyethyl methacrylate;

Unsaturated ethers such as vinyl methyl ether;

And mixtures of these monomers.

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

Instead of the base step monomers a11) and a12), the base step material may consist of monomers a11 *) to a13 *).

Suitable C ₁ -C ₁₀ alkyl ester components a11 *) of acrylic acid are mainly ethyl acrylate, 2-ethylhexyl acrylate and n-butylacrylate. 2-ethylhexyl acrylate and n-butyl acrylate are preferred, and n-butyl acrylate is particularly preferred. Mixtures of different alkyl acrylates with different alkyls thereof may also be used.

The crosslinkable monomers a12 *) are two or more di-esters of difunctional esters such as divinyl esters of dicarboxylic acids such as olefinic double bonds such as butadiene and isoprene, succinic acid and adipic acid, ethylene glycol and 1,4-butanediol Allyl ethers and divinyl ethers, diesters of the difunctional alcohols with acrylic acid and methacrylic acid, bifunctional or polyfunctional comonomers having 1,4, -divinylbenzene and triallyl cyanurate. Particular preference is given to the acrylic esters of tricyclodecenyl alcohols (see German Patent A 12 60 135), known under the name dihydrodicyclopentadienyl acrylate, of allyl esters of acrylic acid and methacrylic acid.

Depending on the properties of the molding compound to be prepared, in particular the properties required, it may or may not comprise a crosslinkable monomer a12 *). If included, the amount is 0.01 to 10% by weight, preferably 0.2 to 10% by weight, particularly preferably 1 to 5% by weight, based on a1).

As further monoethylenically unsaturated monomers a13 *), the same monomers already specified in monomer a12) can be used.

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

The graft core a1) may also consist of a mixture of monomers a11) and a12) and a11 *) to a13 *).

In the case where the graft core comprises monomers a11) and a12), mixing the plastic polymer (SAN) of styrene with acrylonitrile produces a molding compound in the form of ABS (acrylonitrile butadiene styrene). When the graft core comprises monomers a11 *) to a13 *), mixing the plastic polymer (SAN) of styrene with acrylonitrile produces a molding compound in the form of ASA (acrylonitrile styrene alkyl acrylate).

Thus, the graft polymer A) is an ABS or ASA graft polymer or mixtures thereof.

Regarding the graft step material a2) is as follows.

As the styrene compound of the formula (component a21), it is preferable to use styrene, α-methylstyrene and styrene ring alkylated with C ₁ -C ₈ alkyl such as p-methylstyrene or t-butylstyrene. Styrene itself is particularly preferred. Mixtures of these styrenes, in particular styrene and α-methylstyrene, may also be used.

Instead of monomers a21) and a22), a2) may further comprise at least one monoethylenically unsaturated monomer a23).

Preferred examples of the graft step material a2) are copolymers of polystyrene and styrene and / or at least one other monomer specified in a22) and a23) of α-methylstyrene. Of these, methyl methacrylate, N-phenylmaleimide, maleic anhydride and acrylonitrile are preferred, and methyl methacrylate and acrylonitrile are particularly preferred.

Possible examples of preferred graft step materials a2) are

a2-1: polystyrene

a2-2: styrene acrylonitrile copolymer

a2-3: α-methylstyrene acrylonitrile copolymer

a2-4: styrene methyl methacrylate copolymer.

The ratio of styrene or α-methylstyrene, or the ratio of styrene and α-methylstyrene in total is preferably 40% by weight or more based on a2).

The process of the invention relates to graft polymerization in an aqueous phase. The term aqueous phase includes solutions, emulsions and suspensions of the corresponding monomers or polymers in a solvent mixture comprising a large amount of water and water, in other words at least 20% by weight.

Graft polymerization is generally carried out in a customary manner by emulsion, miniemulsion, suspension or microsuspension polymerization processes.

In a preferred embodiment, the polymerization is carried out in an emulsion process and when the monomers are polymerized in an aqueous emulsion at 20 to 100 ° C., preferably 50 to 80 ° C., all the components of the batch (batch technique) are combined or monomers only Or gradually adding an emulsion containing a monomer, water and an emulsifier to another component (semi batch technique).

Examples of suitable emulsifiers are alkali metal salts of alkyl or alkylarylsulfonic acids, alkyl sulfates, fatty alcohol sulfates, salts of high fatty acids having 10 to 30 carbon atoms, sulfosuccinates, ether sulfonates or resin soaps. It is preferable to select an alkyl sulfonate or an alkali metal salt of a fatty acid having 10 to 18 carbon atoms. Generally the amount of emulsifier is from 0.5 to 5% by weight, based on the core monomer a1).

In order to prepare the dispersion, it is preferred to use sufficient water so that the final dispersion has 20 to 50% by weight solids.

Free radical initiators suitable for starting the polymerization reaction are all those which are separated at the selected reaction temperature and thus include both those that are purely pyrolyzed and those that are degraded in a redox system. Examples of preferred free radical polymerization initiators are preferably azo compounds such as azodiisobutyronitrile and peroxides such as peroxosulfate (for example sodium or potassium persulfate). However, redox systems, in particular hydroperoxides such as cumene hydroperoxides, may also be used.

Generally the polymerization initiator is used in an amount of 0.1 to 2% by weight, based on the graft base monomer a1).

Free radical initiators and emulsifiers are added to the reaction batch, for example, in discrete amounts in the form of discontinuities at the start of the reaction, or separated into two or more parts continuously at the start and at one or more subsequent time points or over a period of time. To the reaction batch. For example, it can be added continuously along a gradient, which can be a rising or falling linear or exponential function or other stepping (step function).

Molecular weight modifiers such as ethylhexyl thioglycolate, n-dodecyl mercaptan or t-dodecyl mercaptan or other mercaptans, terpinol and dimeric methylstyrene, or other compounds suitable for controlling the molecular weight can be used. The modulator may be added discontinuously or continuously to the reaction batch as described above for the free radical initiator and the emulsifier.

Preferably, in order to maintain a constant pH of 6 to 9, a buffering material such as Na ₂ HPO ₄ / NaH ₂ PO ₄ , sodium pyrophosphate, sodium hydrogen carbonate or citric acid / citrate can be added. . Regulators and buffering materials are used in conventional amounts, and thus no further details are needed.

In one specific embodiment, the grafting base material a1) can be prepared by polymerizing monomer a1) in the presence of finely divided seed latex. This latex is included in the initial filler into the polymerization reactor and may consist of monomers forming the elastomer or other monomers already mentioned. Suitable seed latexes consist for example of polybutadiene or polystyrene.

In another embodiment, the grafting base material a1) can be prepared by what is known in the feeding art. In the case of this technique, any proportion of monomer a1) is included in the initial filler and then the polymerization is started, after which the residue (feed component) a1) of the monomer is added as feed stream during the polymerization. Feed parameters (tilt type, quantity, duration, etc.) depend on other polymerization conditions. The descriptions relating to the mode of addition of free radical initiators and / or emulsifiers also apply here. In the case of the feeding technique, the proportion of monomer a1) contained in the initial filler is preferably 5 to 50% by weight, particularly preferably 8 to 40% by weight, based on a1). It is preferred to feed the feed component a1) over 1-18 hours, especially 2-16 hours, particularly preferably 4-12 hours.

Also suitable in structural forms such as a1) -a2) -a1) -a2), or a2) -a1) -a2), are graft polymers having two or more soft and hard shells, especially for relatively large particles.

Detailed information on the preparation of rubber latex in emulsions is described in German patent A 24 27 960 and European patent A 62 901.

The exact polymerization conditions, in particular the nature, quantity and addition of emulsifiers and other polymerization aids, can be attributed to the fact that the resulting latex of graft polymer A has a median particle size of generally 30 to 1000 nm, preferably 50 to 800 nm and particularly preferably 50 to 400 nm. Preferably defined as the d ₅₀ value of the particle size distribution.

If a bimodal particle size distribution is required, this can be obtained by (partial) agglomeration of the polymer particles. Possible method examples for this are as follows: The monomer a1) forming the core is generally polymerized with a conversion of at least 90%, preferably at least 95%, based on the monomers used. The rubber latex product preferably has a median particle size d ₅₀ of 200 nm or less and a narrow particle size distribution (near single dispersion system).

The rubber latex is continuously aggregated by addition, for example by dispersion of the acrylic ester polymer. 0.1 to 10% by weight of a monomer forming a polar polymer such as, for example, acrylic acid, methacrylic acid, acrylamide or methacrylamide, N-methylolmethacrylamide or N-vinylpyrrolidone, and acrylic acid, preferably ethylacryl Preference is given to using dispersions of copolymers of C ₁ -C ₄ alkyl esters of rates. Particular preference is given to copolymers of 96% ethylacrylate and 4% methacrylate.

The concentration of acrylic ester polymer in the dispersion used for flocculation should generally be from 3 to 40% by weight. In the flocculation step, 0.2 to 20 parts by weight, preferably 1 to 5 parts by weight of the flocculation dispersion per 100 parts by weight of rubber latex is used, in each case calculated as solids. Agglomeration is performed by adding agglomerates in the dispersion to the rubber.

If no acrylic ester polymer dispersion is used, the rubber latex may be aggregated by other flocculants such as acetic anhydride, for example. Coagulation by pressure and freezing (pressure coagulation or freeze coagulation respectively) is also possible. This method is known to those skilled in the art.

Under the conditions mentioned, only some of the polymer particles aggregate to show a bimodal distribution. In this case, depending on the aggregation, generally at least 50%, preferably 75 to 95% (many distributions) of the particles are in the non-aggregated state. The resulting partially agglomerated rubber latex is relatively stable and is therefore easily stored and transported without condensation.

To obtain the bimodal particle size distribution of the graft polymer A), two different grafts A ') and A' '), which may be prepared generally, are separated from one another and then A') in the required proportions. And A '') can be prepared by blending the graft polymer.

When the polymerization of the base stage material a1) is completed, the present invention involves adding a free radical N-oxyl compound to the base stage material before and / or during the polymerization of the graft stage material a2). N-oxyl compounds and further details are described below.

If the coagulation of the basic stage material a1) is carried out prior to the polymerization of the graft stage material a2), the N-oxyl compound can be added before, during or after the coagulation. It is preferred to add it before flocculation.

In one or more process steps, the graft step material a2) can be prepared in an emulsion under the same conditions as the base step material a1). At this time, the monomers a21), a22) and a23) may be added individually or in a mixture with each other. The monomer ratio of the mixture may be constant or have a gradient over time. Combinations of these methods are also possible.

For example, the styrene can be polymerized on its own first, and then the mixture of styrene and acrylonitrile can be polymerized with the base stage material a1).

The graft stage material a2) acts as a compatibilizer between the matrix polymer in which the graft polymer A) is inserted and the rubber base stage material a1). Thus, monomer a2) preferably corresponds to the monomer of the matrix. Where the matrix constitutes all or most of the styrene acrylonitrile copolymer (SAN), as in the case of the ABS and ASA molding compounds mentioned above, the graft shell is generally styrene and / or α-methylstyrene and acryl. It constitutes all or most of the nitrile. However, other monomers a2) such as methyl methacrylate can also be used.

The process of the invention may also be carried out with miniemulsion polymerization, the main difference between this and the general emulsion polymerization described above is that the particle size is generally between 50 and 500 nm, and generally for coalescence by the combination of ionic emulsifiers and covalent agents It is stabilized. Miniemulsions are generally less stable than their usual counterparts. Covalent agents used commercially are generally long chain alkanes such as hexadecane and long chain alcohols such as hexadecanol.

In the case of miniemulsion polymerization, a high shear force is applied to the mixture of monomers, water, emulsifiers, co-emulsifiers, and as a result the components are sufficiently mixed. Subsequently, polymerization is carried out. This high shear force can be produced, for example, by ultrasonic or microfluidizers or by the homogenizers mentioned below which describe the microsuspension polymerization. One skilled in the art will appreciate, for example, P. Covell, M. El-Aasser, Emulsion Polymerization and Emulsion Polymers, John Wiley, New York, 1997, pages 699 to 722 can be found a detailed description of the miniemulsion polymerization.

Possible methods of shearing (eg, continuous, batchwise, etc.) are described in more detail below for microsuspension polymerization.

Miniemulsion polymerization, on the other hand, depends on the description with respect to general emulsion polymerization.

The process of the invention can be carried out by suspension polymerization. This initiator is essentially different from emulsion polymerization in that the initiator does not dissolve at all or hardly dissolve in the aqueous phase, but instead dissolves in the monomer and a protective colloid is used rather than an emulsifier. In the case of suspension polymerization, the monomers are dispersed into droplets by stirring in the aqueous phase, and the protective colloid prevents the droplets from coalescing. The particles formed in the case of suspension polymerization are generally larger than the particles produced in the emulsion. Detailed descriptions of suspension polymerization are described below in connection with the description of microsuspension polymers, especially in terms of initiators and protective colloids, and described in Encyclopedia of Polymer Science and Engineering, Vol. 16, 2nd edition, John Wiley, New York, 1989, pp. It is also described in 443-472.

Apart from these differences, the suspension polymerization is fully explained by the description with respect to emulsion polymerization.

Alternatively, the process of the invention can be carried out by microsuspension polymerization. The difference between this and ordinary suspensions is that the aqueous suspensions of the monomers are mainly treated with substantially higher agitation (the action of significantly higher shear forces). This method is described in more detail in the following specification.

In the case of the microsuspension method, the monomer (or monomer mixture M corresponding to the required polymer A) is dispersed in water using a protective colloidal PC so that monomer droplets in water, generally having a medium droplet diameter d ₅₀ of 700 nm to 100 μm, Generate dispersion. The droplets are then polymerized using the free radical polymerization initiator RI.

The amount of monomer M and protective colloid PC dispersed in water is generally 25 to 95% by weight, preferably 40 to 85% by weight, particularly preferably 45 to 75% by weight, based on the sum of monomers, water and protective colloid. %to be. Protective colloidal PCs that stabilize dispersions are water soluble polymers that protect them from coalescence by surrounding monomer droplets and polymer particles formed therefrom.

Protective colloid PCs suitable for stabilizing dispersions include cellulose derivatives such as carboxymethylcellulose and hydromethylcellulose, poly-N-vinylpyrrolidone, polyvinyl alcohol and polyethylene oxides, anionic polymers such as polyacrylic acid and copolymers thereof, poly- Cationic polymers such as N-vinylimidazole. The content of this protective colloid is preferably 0.1 to 10% by weight based on the total mass of the emulsion.

Protective colloids and methods of making them are known per se, for example, in Encyclopedia fo Polymer Science and Engineering, Vol. 16, P. 448, John Wiley, 1989.

As the protective colloid, preference is given to using at least one polyvinyl alcohol having a degree of hydrolysis in particular of not more than 96 mol%, preferably of from 60 to 94 mol%, particularly preferably of from 65 to 92 mol%. Preferred polyvinyl alcohols have a viscosity of 2 to 100 mPa / s, in particular 4 to 60 mPa / s, as measured by 4% rigid solution in water at 20 ° C. according to DIN 53015.

In addition to the protective colloid, it is also possible to use colloidal silica, which generally has a concentration of 0.2 to 5% by weight, based on the amount of dispersion. A detailed description of this process which works particularly well on water-soluble polymers of adipic acid and diethanolamine as protective colloids is described in US Pat. No. 3,615,972.

In order to suppress the simultaneous emulsion polymerization process that is smaller and thus form unwanted particles, a water soluble inhibitor that inhibits emulsion polymerization during microsuspension polymerization can be used. Effective compounds of this form are, for example, chromium (+6) compounds such as potassium dichromate.

By applying high shear forces to the monomers M, water and protective colloid PC, emulsions are prepared using homogenizers known to those skilled in the art, examples of homogenizers are as follows.

-Laboratory dissolver Dispermat sold by VMA-Getzmann in Reichshof, Germany,

Ultra-Turrax sold by Janke and Kunkel in Staufen, Germany,

Pressurized homogenizer sold by Gaulin in Lubeck, Germany

Dispax, marketed by Janke and Kunkel, Staufen, Germany; v. Sprochhovel, Germany. Equipment equipped with a rotor-stator system such as the Cavitron homogenizer sold by Hagen & Funke, the homogenizer sold by Kotthoff, Essen, Germany, and the homogenizer sold by Dorr Oliver, Grevenbroich, Germany. ,

The apparatus is generally operated at a rotational speed of 1000 to 25,000 min ⁻¹ , preferably 2000 to 15,000 min ⁻¹ .

-The action of ultrasound

Passing a mixture of monomers, water and protective colloids through a nozzle with a narrow gap or small diameter under high pressure

Colloid mill

Or a high shear force can be generated by a suitable homogenizer.

Dispersions are generally prepared at room temperature, but higher or lower temperatures may be appropriate, depending on the nature of the monomer and protective colloid.

Dispersions can be prepared discontinuously (batch process) or continuously. In the case of discontinuous preparation, the monomers, water and protective colloid can be filled into a container and mixed into a microsuspension (dispersion) using a homogenizer.

The homogenizer may be arranged parallel to the vessel and the components may pass through the circuit through the homogenizer.

The duration of homogenization can be from 0.1 second to several hours, for example depending on the required diameter of the monomer droplets, the desired size distribution, the miscibility of the monomers and water, the relative ratio of monomers, water and protective colloids, in particular the protective colloids used. .

After filling the container with all monomers and all water, the protective colloid may be added when the homogenizer starts to operate.

In one preferred embodiment, in the case of the continuous preparation of the dispersion, monomer, water and protective colloid can be fed to the homogenizer and the resulting dispersion can be fed directly to the reactor in which the polymerization is carried out.

In another preferred embodiment of continuous dispersion preparation, monomer, water and protective colloid are passed through the homogenizer into the circuit and only a portion of the circulated mixture is redirected and fed to the polymerization reactor. After one pass through the homogenizer, when the degree of dispersion of the monomer is still inadequate; This circulation process is particularly preferred when the particle size is too large and / or the size of the distribution is too wide, for example.

In another embodiment, the dispersion can be prepared discontinuously in the first step and continuously in the second step: dispersing the components in batches as described above, followed by a second continuous dispersion action in the resulting dispersion. Add. This produces a final dispersion that is fed continuously to the reactor.

Microsuspension polymerization is initiated with the free radical polymerization initiator RI. Such compounds are known to those skilled in the art, preferably have a half life of 1 hour at 60 to 110 ° C. and have a significant solubility in monomers. Particular initiators RI used include organic peroxides, azo compounds and / or compounds with a single C-C bond. Likewise used as free radical polymerization initiators are monomers which spontaneously polymerize at elevated temperatures. Mixtures of the above initiators RI may also be used.

With regard to peroxides, preference is given to those having hydrophobicity, in particular molecules having a carbon: oxygen ratio of at least 3: 1. Dilauryl peroxide and dibenzoyl peroxide are particularly preferred, and dilauryl peroxide is more preferred.

Preferred azo compounds are 2,2'-azobis (2-methylbutyronitrile) and 2,2'-azobis (isobutyronitrile). The compound having an unstable C-C bond to be used is preferably 3,4-dimethyl-3,4-diphenylhexane and 2,3-dimethyl-2,3-diphenylbutane.

Preferred monomers for spontaneous polymerization at elevated temperatures are styrene and its derivatives such as vinyltoluene, with styrene being particularly preferred.

The amount of initiator RI is generally from 0.05 to 4% by weight, preferably from 0.1 to 2% by weight and particularly preferably from 0.3 to 1% by weight, based on the amount of monomer M. If the monomer is an initiator, for example in the case of styrene, this content of course does not apply.

Depending on the aggregation state of the initiator and its solubility behavior, it may be added in its original state, but is preferably added in the form of a solution, a dispersion (liquid in liquid) or a suspension (solid in liquid), and therefore, particularly a small amount of initiator Can be added correctly.

Compounds suitable as solvent or liquid phase of the initiator are, for example, organic solvents such as benzene, toluene, ethylbenzene and cyclohexane, in particular cyclohexane, or other monomers themselves. When the monomers themselves are used as solvents or liquid phases for the initiators, the initiators are dissolved or emulsified / suspended in the total monomers, preferably in a relatively small fraction of monomers, which fraction is added to the residual components.

The initiator may be dissolved in a solvent or in a monomer, and the resulting solution may be dispersed in water.

The initiator or initiator RI can be added only before or after the preparation of the dispersion or just before the start of the polymerization, else it can be measured continuously during the polymerization.

Particularly in the case of monomers which tend to be uncontrolled polymerization or which already polymerize at the temperature at which the dispersion is prepared, it is preferred not to add the initiator RI until after emulsification, and in some circumstances it is only preferred to add it immediately after polymerization.

Especially in the case of long term polymerization, it may be advantageous to add the initiator as a continuous feed stream or during the splitting during the polymerization. In this case, the initiator supply period may be the same as or different from the polymerization period.

Additional additives such as buffer substances and molecular weight modifiers may be added continuously or discontinuously at the start of the preparation of the dispersion and / or during the preparation and / or during the polymerization.

The polymerization is carried out in a general manner, for example by heating the material of the reactor to start the polymerization reaction. In addition, if necessary, the initiator RI can be added only at this point, in other words to the heated dispersion. The polymerization temperature depends in particular on the monomers and the initiator and on the degree of crosslinking of the resulting polymer A). It is also possible to establish different temperatures continuously or to establish a temperature gradient, but in general the polymerization is carried out at 30 to 120 ° C.

In general, the polymerization is carried out slowly or with gentle stirring in a process where the droplets no longer collapse further (unlike prior emulsification involving high shear forces).

Therefore, in the case of microsuspension polymerization, the particle size can be mainly controlled by appropriately selecting and controlling conditions in the preparation of the dispersion (eg homogenizer, homogenization period, monomer, water, relative proportion of protective colloid, dispersion mode). (Single, multiple, batch or continuous, cyclic), rotation speed of the homogenizer).

The general rule, irrespective of the chosen homogenization technique, is that the polymerization of the graft stage material a2) is carried out by the same technique as in the basic stage material a1). Thus, if the base stage material is polymerized, for example in an emulsion, the graft stage material is also generally polymerized in the emulsion.

When the graft step material a2) is polymerized in an emulsion, it is generally carried out at 20 to 100 ° C, with 50 to 80 ° C being preferred.

As the polymerization initiator for the graft step, the same water-soluble compound as used for polymerizing the base step material can be used. Oil soluble and / or monomer soluble initiators such as dialkyl peroxides such as dilauryl peroxide and dibenzyl peroxide, peresters such as t-butyl perpivalate and t-butyl peroxyneodecanoate and also Diperoxyketals, peroxycarbonates and azo compounds such as azodiisobutyronitrile (AIBN) and azodiisovaleronitrile (ADVN) can be used.

A detailed description of carrying out the graft reaction in the emulsion can be found, for example, in German patent A 24 27 960 and European patent A 62 901.

The overall composition of the graft polymer A remains unaffected by the embodiment of the method described above.

Graft polymers having a structure such as, for example, a1) -a2) -a1) -a2) or a2) -a1) -a2) are suitable, especially for relatively large particles. Suitable.

When producing an grafted polymer from monomer a2), this fraction, which generally produces less than 10% by weight of a2), is designated the mass of component A.

Regarding the addition of the free radical N-oxyl compound to the reaction mixture is as follows.

The process of the present invention uses one or more free radical N-oxyl compounds of sec-amines having no hydrogen in the α carbon. These compounds may exist in the form of free compounds or salts thereof.

For example, a suitable N-oxyl of an amine is of the structure

R is the same or different alkyl, cycloalkyl, aralkyl, or aryl, which may be joined in pairs to form a ring system, and Y is a group necessary to complete a 5- or 6-membered ring.

For example, R is C ₁ -C ₂₀ -alkyl, in particular C ₁ -C ₈ -alkyl, C ₅ -or C ₆ -cycloalkyl, benzyl or phenyl, Y is for example alkylene- (CH ₂ ) ₂ -or-(CH ₂ ) _3- .

Also suitable are N-oxyl compounds with the following structures.

At this time, each aromatic ring may also carry 1 to 3 inert substituents such as, for example, C ₁ -C ₄ -alkyl, C ₁ -C ₄ -alkoxy or cyano.

It is preferred to use sterically interrupted amine derivatives of cyclic amines such as piperidine or pyrrolidine compounds, which additionally contain heteroatoms such as nitrogen, oxygen or sulfur in the ring, the heteroatoms being steric It is not adjacent to the amine nitrogen which is impeded.

The steric hindrance is provided by substituents at both adjacent positions of the amine nitrogen, with suitable substituents being hydrocarbon radicals that replace all four hydrogens with the α-CH ₂ group. Examples of substituents are phenyl, C ₃ -C ₆ -cycloalkyl, benzyl, and in particular C ₃ -C ₆ -alkyl, in which alkyl bound to the same α carbon forms a 5- or 6-membered ring. Can be combined with one another. Particularly preferred radicals are listed under R ⁵ , R ⁶ . Preferred N-oxyl of the steric hindrance amine used is a derivative of 2,2,6,6-tetraalkylpiperidine.

Preferred N-oxyl compound in the composition of the present invention is the same as

Where

R ¹ and R ² are each independently of each other C ₁ -C ₄ -alkyl or phenyl, or together with the carbon to which they are attached, a 5- or 6-membered saturated hydrocarbon ring,

R ³ is hydrogen or hydroxy, amino, SO ₃ H, SO ₃ M, PO ₃ H ₂ , PO ₃ HM, PO ₃ M ₂ , organosilicon radicals or m-atoms which are bonded via oxygen or nitrogen Together with the silicon radical, or R ₄ , is a ring structure defined by oxygen or R ₄ , wherein M is an alkali metal,

R ^{4 together} with hydrogen, C ₁ -C ₁₂ -alkyl, C ₁ -C ₁₂ -alkoxy or R ³ , together with oxygen or R ³ and the carbon to which they are attached,

or

Wherein, when R ³ together with R ⁴ form a radical, m is 1,

R ⁵ is hydrogen, C ₁ -C ₁₂ -alkyl or-(CH ₂ ) _Z -COOR ⁶ ,

R ⁶ is the same as or different from C ₁ -C ₁₈ -alkyl,

k is 0 or 1,

z and p are each independently 1 to 12,

m is from 1 to 100.

R ¹ and R ² may be C ₁ -C ₄ -alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or t-butyl, together with tetra or pentamethylene groups Can be formed. R ¹ and R ² are preferably methyl.

R ⁴ is for example hydrogen, C ₁ -C ₄ -alkyl and pentyl described above, sec-pentyl, t-pentyl, neopentyl, 2,3-dimethylbut-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, Isooundesyl, dodecyl and isododecyl (isooctyl, isononyl, and isodecyl are common names derived from carbonyl compounds obtained by oxo synthesis, Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, Vol. Pages 290-293, and Vol. A10, pages 284 and 285), alkoxy radicals derived therefrom are also suitable.

As for p, 6-12 are preferable and 9 is especially preferable.

1-4 are preferable and z is especially preferable.

In addition to hydrogen, R ⁵ is suitable, for example, C ₁ -C ₁₂ -alkyl described above. R ⁵ is hydrogen, C ₁ -C ₄ -alkyl or (CH ₂ ) _Z -COO (C ₁ -C ₆ -alkyl), particularly preferably the radical -CH ₂ -CH ₂ -COO (CH ₂ ) ₁₁ -CH ₃ and -CH ₂ -CH ₂ -COO (CH ₂ ) ₁₃ -CH ₃ .

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

Preferred monovalent radicals R ³ are hydrogen, C ₁ -C ₄ -alkyl as described above, and organosilicon radicals of the formula

In this case, the T groups may be the same as or different from each other, and are C ₁ -C ₁₂ -alkyl or phenyl.

Examples of such organosilicon radicals

Si (CH ₃ ) ₃ , Si (C ₂ H ₅ ) _3,

And -Si (C ₆ H ₅ ) ₃ .

As the alkali metal M in the -SO ₃ M -PO ₃ HM -PO ₃ M ₂ group, it is preferable to use Li, Na and K.

Preferred monovalent R ³ groups bonded through oxygen are for example C ₁ -C ₄ -alkoxy such as hydroxyl and methoxy, ethoxy, propoxy and t-butoxy, but siloxanes derived from the organosilicon radicals It is also a radical.

Examples of preferred m-valent radicals R ³ are the following radicals.

Where

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 is C ₁ -C ₁₈ -alkyl, vinyl or isopropenyl,

R ¹⁰ is C ₈ -C ₂₂ -alkyl,

R ¹¹ is an organic radical such as is usually formed in free radical polymerization of hydrogen or starting materials,

k is 0 or 1,

x is 1 to 12,

n is even m.

R³When is one of these radicals,⁴Is preferably hydrogen. In this case the variable m can be from 1 to 100. m is preferably one of 1,2,3,4 or 10 to 50, and the mixture is generally an oligomer Or polymer radical R³Especially used in the case.

Suitable radicals R ⁷ are the same as those specified for R ⁹ . R ⁷ is preferably C ₁ -C ₄ -alkyl.

Besides hydrogen, suitable radicals R ⁸ are the same as those specified for R ⁶ . R ⁸ is preferably hydrogen.

R ⁹ is especially suitable for vinyl, isopropenyl, methyl, ethyl, propyl, isopropyl, t-butyl or C ₁₅ -C ₁₇ -alkyl.

Examples of suitable radicals R ¹⁰ are the C ₁ -C ₁₈ -alkyls described above, and also nonadecyl, eicosyl, unicosil and doeicosyl. In this case, mixtures of other radicals R ¹⁰ with different carbon chain lengths are preferred.

The radical R ¹¹ is an organic radical formed in the free radical polymerization of hydrogen or a starting compound; In other words, it is for example a radical formed from a polymerization initiator or from free radical generation as an intermediate, or another such radical familiar to those skilled in the art.

If the starting compound used is styrene, for example, such radicals R ¹¹

Etc.,

Where R 'is any primary radical which initiates the polymerization of styrene or compound (A) in general.

Nitroxyl compounds of formula 2 'may also be used.

Where

R ¹² and R ¹³ are each independently a 5- or 6-membered unsaturated hydrocarbon ring, together with C ₁ -C ₄ -alkyl or phenyl or the carbon to which they are attached,

R ¹⁴ is an m′-atom radical which is bonded via carbon, oxygen or nitrogen,

R ^{15, together} with hydrogen, C ₁ -C ₁₂ -alkyl or C ₁ -C ₁₂ -alkoxy, or R ¹⁴ , is m′- which is bonded via carbon, oxygen by means of a chemical double bond to the carbon carrying these groups. An atom is a radical or is a carbon atom carrying these groups together with R ^{14 a} saturated isocyclic or heterocyclic, 3- to 7-membered ring,

m 'is 1,2 or 3;

R ¹⁴ and R ¹⁵ together are chemical double bonds m 'valence radicals bonded through carbon and oxygen, and the values of 1,2 and 3 for the variable m' are of the piperidinyl ring represented by the formula (2 '). 1, 2, or 3 are intended to imply that m 'atoms are each bonded to a radical by a double bond.

The selection of the radicals R ¹² and R ¹³ is consistent with the radicals of R ¹ and R ⁷ described above and should also be usable here. In other words, it is preferable that the methyl group is used as the substituents R ¹² and R ¹³ .

And phenyl substituted by alkyl, C ₁ -C ₄ - - proper m 'atom is a radical R ¹⁴ is C ₁ -C ₄ - alkyl, unsubstituted phenyl, and one to three C ₁ -C ₄ alkyl is for example already It is described above. These radicals can be bonded to the piperidine ring via an oxygen, NH group or N (C ₁ -C ₄ -alkyl) group. In case of bonding via a carbon atom, this atom should already be considered to belong to the radical R ¹⁴ .

Examples of possible radicals R ^{14, where} the lines mean free valence, are as follows.

-N = C = N- and

Possible representative examples of the radical R ¹⁵ are C ₁ -C ₁₂ -alkyl or C ₁ -C ₁₂ -alkoxy groups which have already been described in the above illustrative manner for the radical R ⁴ . The radicals R ¹⁴ and R ¹⁵ may also form together groups which are bonded by chemical double bonds via carbon or nitrogen to the carbon carrying the groups (carbon at position 4 of the piperidine ring). Examples of such m 'valences (where the lines mean free valences) are as follows:

It is also possible to form three to seven membered isocyclic or heterocyclic rings with carbons carrying these groups for the radicals R ¹⁴ and R ¹⁵ .

Examples of such rings are as follows:

R ¹⁶ herein is hydrogen, C ₁ -C ₁₂ -alkyl or unsubstituted phenyl or mono to tetra-C ₁ -C ₄ -alkyl substituted phenyl. Examples of corresponding C ₁ -C ₁₂ -alkyl and C ₁ -C ₄ -alkyl as possible substituents on the phenyl ring have already been described above. The variable k 'may have a value of 0, 1 or 2.

Another suitable N-oxyl includes oligomers or polymeric compounds in which the polymer backbone is polysiloxane and the subchain is substituted with N-oxyl groups derived from 2,2,6,6-tetraalkylpiperidine. Preferred such N-oxyl groups for use are 2,2,6,6-tetramethylpiperidine-N-oxyl radicals. Examples of such N-oxyl that can likewise be used according to the invention are described in WO 69/17002, which also describes examples of the synthesis of amino compounds based on N-oxyl.

In addition, preferred free radical N-oxyl compounds are as follows:

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-t-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) hexahydroterephthalate,

N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipamide,

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-tri [N-butyl-N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -s-triazine,

N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -N, N'-bispotyl-1,6-diaminohexane,

4,4'-ethylenebis (1-oxyl-2,2,6,6-tetramethylpiperazin-3-one) and

Tris (2,2,6,6-tetramethyl-1-oxypiperidin-4-yl) phosphite.

Free radical N-oxyl compounds can be prepared from the corresponding amino compounds or piperidine compounds, for example by oxidation with hydrogen peroxide. A detailed description of this oxidation is for example described in German patent A 195 101 84. Secondary amines that do not have hydrogen on the α carbon like piperidine and their preparation are common sense. Since the oxidation reaction is not always complete, the N-oxyl containing composition may also include amino or piperidine starting compounds, and may include partially oxidized intermediates such as amine hydroxides.

According to the invention, the N-oxyl compound is added after the polymerization of the basic stage material a1), during and / or prior to the polymerization of the graft stage material a2).

If the polymer of the basic stage material a1) is partially or fully aggregated prior to the polymerization of the graft stage material a2) (see the description relating to emulsion polymerization), the N-oxyl compound may be added before, during or after aggregation. And transition aggregation is preferred.

In this specification, these N-oxyl compounds can be applied in various ways.

It has been proved advantageous to add N-oxyl compounds to the polymerization mixture comprising the fully polymerized base stage material a1) and the graft stage monomers a21) to a23). N-oxyl compounds may be present in the graft monomers a21) to a23) to protect them against premature polymerization.

The concentration of N-oxyl compound in the polymerization mixture should be such that it hardly affects the rate of polymerization. The sensitivity of the polymerization with respect to the amount of N-oxyl compound depends on various parameters, in particular the properties of the monomers, the structure of the N-oxyl compound, the temperature and the initiator of the free radical scavenger and other free radicals that may be present in the reaction mixture. do. However, the optimal concentration can be determined in a few preliminary experiments with other process parameters that remain constant.

Concentration ranges in which advantages for the N-oxyl compound (s) in the polymerization mixture have been found are from 3 to 200 ppm, in particular from 5 to 150 ppm, particularly preferably from 10 to 130 ppm (1 ppm = basic phase material a1) (solid). And 10 ^-6 parts by weight of the N-oxyl compound based on the total weight of the graft monomers a21) to a23). At these concentrations, the formation of deposits is generally completely prevented without any significant effect on the kinetics of the reaction.

In addition to adding the N-oxy compound to the polymerization mixture, a process change that has proven particularly appropriate is that the reactor surface is wetted with a solution of the N-oxy compound prior to the polymerization of the graft step material a2).

If the polymerization of the basic stage material a1) and the graft stage material a2) is carried out in a different reactor, it is therefore the surface of the graft stage reactor that is wetted. If the base stage material and the graft stage material are polymerized in the same reactor, a common process is to empty the reactor, wet the surface and then refill it with the previously drained mixture.

Other components in the reactor, such as reactor walls and stirrers, and heating or cooling components, can be sprayed with N-oxyl compound solutions to wet simply and effectively. In many cases, N-oxyl compounds show poor solubility in water, but are most soluble in organic solvents such as methanol, ethanol, propanol, acetone, ethyl acetate, dimethylformamide. A particularly suitable solvent for many N-oxyl compounds is methanol. The concentration of the N-oxyl compound in the spray solution is not critical and is advantageously set to 0.01 to 1% by weight based on the total mass of the spray solution.

Another way to wet the surface of the reactor is to charge it with a solution similar to the spray solution and then drain the solution.

Application Combinations of the two forms are also advantageous, in which case very small amounts are sufficient to add directly to the polymerization solution.

The resulting aqueous dispersion of graft polymer A) reaches a particulate graft polymer A) by separating a certain amount or the entire aqueous medium. For this purpose, if necessary, polymer A) of the fine particles of the dispersion is first precipitated in an aqueous medium by adding a coagulant precipitating agent such as CaCl ₂ , MgSO ₄ , acetic acid, sulfuric acid and the like. The aqueous phase is separated, for example, by sieving, pressing, filtration, decanting, centrifugation or by other solid / liquid separation techniques. The resulting moist polymer A) may be processed more directly, and residual moisture may be removed, for example, by thermal drying with a hot gas in a gas dryer. Aqueous dispersions can also be made by the method of spray drying.

Another possibility is to further treat the resulting aqueous polymer dispersion in that state. For example, the dispersion can be mixed with other polymers in a mixing device while simultaneously removing the aqueous phase.

Graft polymer A obtainable by the process of the present invention can be used as a constituent of a plastic molding compound.

Suitable plastic matrix polymers present in the molding compound are all plastic polymers having a glass transition temperature of T _g > Numerous such polymers are described by way of example below.

In a preferred embodiment, the matrix polymer is a styrene compound of the formula as described above for a21) or a C ₁ -C ₈ -alkyl ester of acrylic acid or methacrylic acid, or a styrene compound with acrylic acid or methacrylic acid. 50 to 100% by weight, preferably 60 to 95% by weight, particularly preferably 60 to 90% by weight, and also 0 to acrylonitrile or methacrylonitrile or mixtures thereof, of mixtures of C ₁ -C ₈ -alkyl esters. 0 to 40 weight percent, preferably 0 to 40 weight percent, preferably 5 to 38 weight percent, and at least one additional monoethylenically unsaturated monomer already specified for a12), a13 *), and a23) 30 weight percent.

The matrix polymer preferably has a glass transition temperature T _g of at least 50 ° C. The matrix is thus a hard polymer. Regarding the matrix polymer is as follows:

Preferred styrene compounds of the formulas described are styrenes such as p-methylstyrene or t-butylstyrene, α-methylstyrene, or other ring-C ₁ -C ₈ -alkylated styrenes. Styrene and α-methylstyrene are particularly preferred.

As or instead of or in admixture with styrene compounds, C ₁ -C ₈ -alkyl esters of acrylic acid and / or methacrylic acid, in particular methanol, ethanol, n-propanol, and isopropanol, sec-butanol, t-butanol Preference is given to using esters derived from isobutanol, pentanol, hexanol, heptanol, octanol, 2-ethylhexanol and n-butanol. Methyl methacrylate is particularly preferred.

Examples of preferred matrix polymers are as follows:

M / 1: polymethyl methacrylate (PMMA)-in this case A) can be obtained by polymerization of 100% by weight of methyl methacrylate (component m1),

M / 2: further with 0 to 30% by weight of monoethylenically unsaturated monomer, preferably with 0 to 20% by weight, with 10 to 60% by weight of acrylonitrile, preferably with 20 to 40% by weight A polymer obtainable by copolymerization from 40 to 90% by weight, preferably 50 to 80% by weight of the styrene compound and / or α-methylstyrene.

If the matrix polymer preferably comprises styrene and acrylonitrile, the product is known commercially as a SAN copolymer. It generally has a viscosity number VN of 40 to 160 ml / g (25 ° C., determined according to DIN 53 726 at 0.5% by weight in dimethylformamide) and corresponds to a mass-average molecular mass of about 40,000 to 250,000.

The matrix polymer can be obtained in a known manner per se, for example by bulk, solution, suspension, precipitate or emulsion polymerization. Details of these processes are described in Kunststoffhandbuch, Vieweg and Daumiller (eds.), Carl-Hanser-Verlag, Munich, Vol. 1 (1973), pages 37-42 and Vol. 5 (1969), pp. 118 to 130, Ullmanns Encyklopadia der technischen Chemie, 4th edition, Verlag Chemie Weinheim, Vol. 19, pp. 107-158 are described in ″ Polymerisationstechnik ″.

In another preferred embodiment, the matrix is polyvinyl chloride (PVC). Suitable polyvinyl chloride is known per se.

As a monomer for PVC, vinyl chloride may be used alone or as a mixture (comonomer) of vinyl chloride and other monomers, and contains 40% by weight or more of vinyl chloride based on the total monomer mass. Particularly suitable comonomers for vinyl chloride include vinyl esters such as vinyl acetate, vinyl propionate and the like, vinyl ethers such as vinyl methyl, ethyl and isobutyl ether, vinylidene chloride, butyl acrylate and 2-ethylhexyl acrylate; C ₁ -C ₁₈ -alkyl esters of acrylic acid, dialkyl maleates such as dibutyl maleate, olefins such as ethene, propene, isobutene and longer chain C ₆ -C ₁₅ -olefins, dienes such as butadiene, Vinylaromatic compounds such as styrene.

The vinyl chloride is polymerized in a manner known per se, for example in the form of emulsions, suspensions, or bulk polymerizations, preferably in suspension polymerization. The polymerization temperature depends on the required molecular weight and / or K value of the PVC product and is 20 to 100 ° C., preferably 35 to 80 ° C. and 45 to 70 ° C. for most of the product. The polymerization is usually terminated at a conversion of 60 to 95%, preferably 70 to 90%.

In another preferred embodiment, the matrix is polycarbonate or polyester.

Suitable polycarbonates are known per se. For example, they can be obtained by interfacial polymer condensation according to the method of German patent B 1 300 266 or by reacting bisphenol and biphenyl carbonate according to German patent A 14 95 730. Preferred bisphenols are 2,2-di (4-hydroxyphenyl) propane, generally referred to as bisphenol A below.

Instead of bisphenol A, other aromatic dihydroxy compounds, in particular 2,2-di (4-hydroxyphenyl) pentane, 2,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl sulfone, 4, 4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfite, 4,4'-dihydroxydiphenyl methane, 1,1-di (4-hydroxyphenyl) ethane or 4 It is possible to use, 4'-dihydroxybiphenyl, and mixtures of these dihydroxy compounds.

Particularly preferred polycarbonates are those having bisphenol A as the main component together with bisphenol A or 30 mol% or less of the aromatic dihydroxy compound described above.

The relative viscosity of these polycarbonates is generally in the range from 1.1 to 1.5, in particular from 1.28 to 1.4 (measured at 25 ° C. with a 0.5% by weight concentration solution in dichloromethane).

Suitable polyesters are likewise known per se and are described in the literature. They contain aromatic rings in the main chain and are derived from aromatic dicarboxylic acids. Aromatic rings are for example in halogen, methyl, ethyl, i-propyl, and / or n-propyl and C ₁ -C ₄ -alkyl, such as n-, i-, and / or t-butyl, such as chloro or bromo. It may be a ring substituted by. Polyesters can be prepared by reacting aromatic dicarboxylic acids, their esters or their other ester forming derivatives with aliphatic dihydroxy compounds in a manner known per se.

Preferred dicarboxylic acids are naphthalenedicarboxylic acid, terephthalic acid and isophthalic acid or mixtures thereof. Up to 10 mol% of the aromatic dicarboxylic acids can be replaced with aliphatic or cycloaliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acid and cyclohexanedicarboxylic acid.

Among the aliphatic dihydroxy compounds, diols having 2 to 6 carbons, in particular 1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-hexanediol, 1,4-cyclohexanediol , And neopentyl glycol or mixtures thereof are preferred.

Particularly preferred polyesters are polyethylene terephthalates derived from C ₂ -C ₆ -alkenediols. Of course, particularly preferred are polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. The viscosity number of the polyester is generally in the range of 60 to 200 ml / g (measured in a 0.5 wt% concentration solution in a phenol / o-dichlorobenzene mixture (weight ratio 1: 1 at 25 ° C.)).

Plastic molding compounds may include customary additives such as lubricants or mold release agents, pigments, dyes, fire retardants, antioxidants, light stabilizers, fibrous and powder fillers or reinforcing agents, or antistatic agents and also other additives, or mixtures thereof. Can be.

Suitable lubricants and shaped release agents are stearic acid, stearyl alcohol, stearic acid esters or stearamides, and silicone oils, montan waxes and waxes based on polyethylene and polypropylene.

Dyes are for example titanium dioxide, phthalocyanine, ultramarine blue, iron oxide or carbon black, and organic pigments.

Suitable dyes include all dyes that can be used for transparent, translucent or opaque coloring of the polymer, in particular those suitable for coloring of styrene copolymers. Such suitable dyes are known to those skilled in the art.

As fire retardants, for example, halogen-, phosphorus-containing compounds, magnesium hydroxide, and other common compounds or mixtures thereof known to those skilled in the art can be used.

Suitable antioxidants (heat stabilizers) are, for example, sterically hindered phenols, hydroquinones, representatives of the variously substituted groups, and mixtures thereof. Commercially available, it is marketed, for example, under the trademarks Topanol or Irganox.

Suitable light stabilizers are, for example, variously substituted resorcinols, salicylates, benzotriazoles, benzophenones, which are for example HALS (sterically hindered light stabilizers) such as those sold under the trademark Tinuvin.

Examples of fibrous and powdery fillers that may be mentioned are glass fibers in the form of carbon fibers or glass fabrics, glass mats, or glass silk rovings, cut glass, glass beads and wollastonite, preferably Is glass fiber. If glass fibers are used, they can be treated with size and adhesion promoters to make them more compatible with the mixed components. The glass fibers can be incorporated in the form of cut glass fibers or in the form of continuous strands (roving).

Suitable particulate fillers are carbon black, amorphous silica, magnesium carbonate (choke), powdered quartz, mica, bentonite, talc, feldspar or especially calcium silicates such as wollastonite or kaolin.

Examples of suitable antistatic agents include amine derivatives such as N, N-bis (hydroxyalkyl) alkylamines or -alkyleneamines, copolymers such as polyethylene glycol esters, glycerol mono- and distearates, ethylene oxide and polypropylene oxide , Polypropylene glycol, N, N-bis (hydroxyalkyl) -Nn-octyl-N-methyl ammonium p-toluenesulfonate, and mixtures thereof.

Each additive is used in each case in conventional amounts and no further explanation of these amounts is necessary.

Plastic molding compounds are prepared by mixing the matrix polymer and graft polymer A and any additives with a suitable mixer and processing the mixture at a suitable temperature to produce the molding compound. Molding compounds can be prepared by melting in known mixing techniques such as extruders, Banbury mixers, kneaders, roll mills or calenders. Alternatively, these ingredients can be used ″ cold ″, the mixture of powders or granules melted and homogenized only in the processing step. It is generally mixed at 130 to 350 ° C.

If the particulate polymer A still contains residual moisture, there is an advantage in that the molding composition can be produced on an extruder by removing residual moisture in the liquid phase through the drain hole and / or by steam through the exhaust hole.

It is possible to produce all kinds of moldings, including films, from particulate polymer A and in particular molding compounds.

The process of the present invention can produce graft polymers in the aqueous phase by any conventional polymerization technique where the formation of wall deposits on the reactor surface has been significantly reduced or completely gone. At the same time, there is no adverse effect in the polymerization process and in particular does not delay the polymerization process. Surprisingly, molding compounds comprising the matrix polymer and the graft polymer A) made according to the invention enhance the mechanical properties, in particular having a higher recorded impact strength.

If the weight-average particle size d ₅₀ of compound B) is described, it is described by W. Scholtan and H. Lange, Kolloid-Z. and Z.-Polymere 250 (1972) median gravimetric particle size as determined by an analytical ultracentrifuge by the method of pages 782 to 796. The ultracentrifuge measurement gives the overall mass distribution of the particle diameter of the sample. From this it can be deduced what is the weight percent of particles having a diameter equal to or less than a particular size.

By weight measurable median particle size d ₅₀ means a particle size above 50% by weight of all particles and below 50% by weight.

Examples 1 and 2

a) preparation of a basic stage material comprising polybutadiene

Butadiene was polymerized in an aqueous emulsion. This particular procedure is described in German patent A 31 49 046, page 15, line 5 to line 34. The resulting polybutadiene latex has a solids content of 40% by weight and a median particle size d ₅₀ of 80 nm.

b) flocculation of polybutadiene base material and grafting with styrene acrylonitrile

50 kg of polybutadiene latex prepared under a) was charged to a reactor equipped with a stirrer and a thermometer while stirring, and N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl The amounts indicated in the table of N-oxyl compounds named) -N, N'-bisfoyl-1,6-diaminohexane were added. After heating to 75 ° C., 1 kg (10 wt% solids) of flocculated latex comprising 96 wt% ethyl acrylate and 4 wt% of methacrylate was added. The product was (partly) aggregated polybutadiene latex with a bimodal particle size distribution and a median particle size d ₅₀ of 220 nm.

At 75 ° C., 0.2 kg of potassium stearate and 0.025 kg of potassium persulfate were added to the aggregated latex. After addition of 1.47 kg of styrene and 0.63 kg of acrylonitrile, the mixture was polymerized for 15 minutes and then a mixture of 1.47 kg of styrene and 3.15 kg of acrylonitrile was added for an additional 3 hours. Then 0.025 kg of potassium persulfate was added and stirred at 75 ° C. for 1.5 h.

c) testing for wall deposits

Graft latex was obtained with cooling under b) and withdrawn from the reactor, and the reactor wall surface was first evaluated by visual observation of the deposit. In the table,

++ means no wall deposits,

+ Means that there are some wall deposits about 1 mm thick,

-There is a significant wall deposit of about 2-3 mm in thickness.

Deposits on the reactor surface, stirrer and thermometer are separated mechanically and weighed.

d) preparation of matrix polymers from styrene and acrylonitrile

Copolymers of 65% styrene and 35% acrylonitrile by Kunststoff-handbuch, R.Vieweg and G.Daumiller (eds.), Vol.V ″ Polystyrol ″, Carl-Hanser-Verlag, Munich 1969, pages 122 to Prepared by the method of continuous solution polymerization as described in 124. The viscosity number VN (determined according to DIN 53 726 at 25 ° C., 0.5% by weight in dimethylformamide) was 80 ml / g.

e) production and forming test

The graft polymer A) discharged under c) is coagulated by adding magnesium sulfate solution, the precipitated graft polymer is separated, washed with water and dried with hot air.

46 parts by weight of this graft polymer (polybutadiene grafted with SAN) was thoroughly mixed with 54 parts by weight of the SAN matrix polymer from d) on a ZSK extruder from Warner + Pfleiderer to produce an ABS molding compound, which was discharged to granules. Make it angry.

The resulting ABS granules were injection molded at a melt temperature of 220 ° C. and a molding temperature of 60 ° C. to produce standard small bars (see DIN 53 435). The notch impact strength a _K of this bar was determined by flexural impact test according to ISO 179-211 eA (S).

Example 3 (Comparative Example)

The methods described in a) to e) of Examples 1 and 2 are repeated, but there is no addition of the N-oxyl compound in b).

Example number N-oxyl compound amount [ppm] *) Visual evaluation Deposit amount **) [kg] a _K [kJ / m ² ] One 20 ++ 0.25 41 2 35 + 0.11 48 3c 0 - 0.92 31

C: for comparison

*) Based on total weight of polybutadiene (solid) and styrene + acrylonitrile

**) Sum of deposits on walls, stirrers and thermometers

This experiment shows that adding only 20 ppm of N-oxyl compound significantly reduces the formation of wall deposits. When 35 ppm of N-oxyl compound is added, deposit formation on the reactor wall is completely suppressed, so there is only a small amount of deposit on the stirrer and thermometer.

At the same time, when the N-oxyl compound was included, the notch impact strength of the molding compound increased significantly, with the a _K value increasing by 31% at 20 ppm of N-oxyl compound and 55% at 35 ppm, respectively. The case was based on the examples used for comparison.

Claims (9)

a11) 50 to 100% by weight of diene having a conjugated double bond, a12) comprises as a main component a1) consisting of 0 to 50% by weight of one or more additional monoethylenically unsaturated monomers, or a11 *) 50 to 100% by weight of C ₁ -C ₁₀ alkyl ester of acrylic acid, a12 *) 0 to 10 wt% of the crosslinkable monomer of the multifunctional group, a13 *) 30 to 95 weight percent of a1) an elastomeric basic step material comprising a1) consisting primarily of a1) consisting of 0 to 40 weight percent of one or more additional monoethylenically unsaturated monomers; a21) chemical formula 50 to 100% by weight phosphorus styrene compound, wherein R ¹ and R ² are hydrogen or C ₁ -C ₈ alkyl, a22) 0-40% by weight of acrylonitrile or methacrylonitrile or mixtures thereof and a23) a graft polymer A comprising as a main component a2) a graft step of 5 to 70% by weight of a2) a main component comprising a2) consisting of 0 to 40% by weight of at least one additional monoethylenically unsaturated monomer in an aqueous phase A process for the preparation comprising: one free radical N-oxyl compound of sec-amine which does not have hydrogen in α carbon before the polymerization of the basic stage material a1) is completed and then before and / or during the polymerization of the graft stage material a2) The method including adding the above. The method of claim 1, The N-oxyl compound is added at a concentration of 3 to 200 ppm based on the total weight of the base step materials a1) (solid) and the graft monomers a21) to a23). The method according to claim 1 or 2, Wherein the N-oxyl compound used is a compound of Formula 1 or Formula 2: (Formula 1) (Formula 2) Wherein R is the same or different, straight or branched, unsubstituted or substituted alkyl, cycloalkyl, aralkyl or aryl, R may be combined in pairs to form a ring system, Y is the group necessary to complete a 5- or 6-membered ring or A compound of Formula 3, 4, or 5, (Formula 3) (Formula 4) (Formula 5) In this case, R is defined as above, and the aromatic ring may carry 1 to 3 inert substituents, respectively. The method according to any one of claims 1 to 3, Wherein the N-oxyl compound used is a compound of formula 6: (Formula 6) Where R ¹ and R ² are each independently of each other C ₁ -C ₄ -alkyl or phenyl, or together with the carbon to which they are attached, a 5- or 6-membered saturated hydrocarbon ring, R ³ is hydrogen or hydroxy, amino, SO ₃ H, SO ₃ M, PO ₃ H ₂ , PO ₃ HM, PO ₃ M ₂ , organosilicon radicals or m-atoms which are bonded via oxygen or nitrogen Together with the silicon radical, or R ₄ , is a ring structure defined under oxygen or R ₄ , wherein M is an alkali metal, R ^{4 together} with hydrogen, C ₁ -C ₁₂ -alkyl, C ₁ -C ₁₂ -alkoxy or R ³ , together with oxygen or R ³ and the carbon to which they are attached, ring structure or Wherein, when R ³ together with R ⁴ form a radical, m is 1, R ⁵ is hydrogen, C ₁ -C ₁₂ -alkyl or-(CH ₂ ) _Z -COOR ⁶ , R ⁶ is the same as or different from C ₁ -C ₁₈ -alkyl, k is 0 or 1, z and p are each independently 1 to 12, m is 1-100. The method of claim 4, wherein The method is derived from the group of the radical R ³ is of formula (VI): Hydrogen, C ₁ -C ₄ -alkyl, Wherein T is, independently, C ₁ -C ₁₂ -alkyl or phenyl, Where 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 is C ₁ -C ₁₈ -alkyl, vinyl or isopropenyl, R ¹⁰ is C ₈ -C ₂₂ -alkyl, R ¹¹ is an organic radical such as generally formed in free radical polymerization of hydrogen or starting materials, k is 0 or 1, x is 1 to 12, n is even m. The method according to any one of claims 1 to 5, The N-oxyl compound used is N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -N, N'-bis-formyl-1,6- Diaminohexane. The method according to any one of claims 1 to 6, Before polymerizing the graft step material a2), partially or completely agglomerates the polymerized base step material a1) and adds an N-oxyl compound prior to the agglomeration. A graft polymer prepared by the method of any one of claims 1 to 7. Use of sec-amine free radical N-oxyl compound without hydrogen on α carbon in preventing deposition on the reactor surface during graft polymerization in aqueous phase.