DE3047688A1 - Amphoteric copolymers esp. used as emulsifiers for polymerisation - are of styrene!, methacrylate(s)! or acrylonitrile! with (meth)acrylic! acid or maleic anhydride and aminoalkyl (meth)acrylate(s) - Google Patents

Abstract

Amphoteric copolymers (I) with a mol. wt. of 500-5000 are prepd. by continuous bulk polymerisation of 1 mol. N-contg. monomer (I) with an amino and/or quaternary amino gp., 1.5-10 mol. (w.r.t. 1 mol. (I) nonionic, hydrophobic, ethylenically unsatd. monomer (II) and 0.5-1.5 mol. (w.r.t. to 1 mol. (I) ethylenically unsatd. carboxylic acid (III) at 180-400 deg.C and above 1 bar in the absence of regulators. (I) is pref. of formula CH2:CR3C(O)A-B-NR1R2 (where A is O or NH; B is CnH2n; n is 1-8; R1 and R2 are CmH2m+1, m is 1-4 and R3 is H or Me). (II) is (alpha-methyl) styrene, methacrylates of 1-8C alcohols and/or acrylonitrile. (III) is (meth)acrylic acid and/or maleic anhydride. (I) are emulsifiers and can be used in the prepn. of aq. polymer dispersions and esp. (surface) sizes for paper.

Description

Process for the production of amphoteric copolymers and

their use as an emulsifier GB-PS 1 185 283 is amphoteric Copolymers known by polymerizing monomer mixtures from a basic monomers, e.g. dialkylaminoalkyl acrylates or acrylamides, at least an ethylenically unsaturated carboxylic acid and at least one water-insoluble neutral copolymerizable monomers in solution or preferably in aqueous Emulsion can be produced. These known amphoteric copolymers have a relatively high molecular weight. They are used, for example, for coating surfaces, in particular as antithrombogenic coating compounds in medical technology as well as used as a surface sizing agent for paper. The well-known amphoteric However, copolymers are only insufficiently effective when used as a sizing agent for paper and also as an emulsifier.

From DE-AS 25 02 172 anionic paper sizing agents are known, by copolymerizing monomer mixtures from a) 30 to 80% by weight C2 bis C12 olefins with terminal double bonds and / or vinyl ethers, b) 2 to 35% by weight Acrylic acid and / or methacrylic acid and c) 5 to 35% by weight maleic anhydride, maleic acid, Fumaric acid, itaconic acid, vinyl phosphonic acid and vinyl lactic acid at temperatures between 130 and 320 0C and pressures above 1 bar can be produced.

DE-OS 2 519 581 relates to paper sizes produced by continuous Copolymerization of monomer mixtures from 30 to 85% by weight of 02 to C12 olefins with a terminal double bond and / or vinyl ethers and 15 to 70 % By weight of basic acrylic and / or methacrylic compounds,? .B. I <yluninoac.ryl esters or amides, at temperatures between 130 and 3200C. The anionic or the paper sizing agents containing basic monomers as polymerized units it also has emulsifying properties, but these are not for most purposes sufficient.

The object of the invention is to provide low molecular weight copolymers To make available that are suitable as an emulsifier.

The object is achieved according to the invention by amphoteric copolymers, produced by continuous copolymerization of a monomer mixture from a) 1.5 to 10 moles of at least one nonionic, hydrophobic, ethylenically unsaturated Monomers, b) 1 mole of at least one nitrogen-containing monomer which has an amino and / or carries a quaternary amino group and c) 0.5 to 1.5 mol of at least one ethylenically unsaturated carboxylic acid, the amounts given for the monomers a) and c) each based on 1 mole of the monomers b), in bulk at temperatures from 180 to 4000C and pressures above 1 bar in the absence of regulators.

The monomers of group a) for the preparation of the amphoteric copolymer are nonionic, hydrophobic, ethylenically unsaturated compounds. It deals These are monomers that are not noticeably soluble in water and - polymerized alone - form hydrophobic polymers. Such monomers are, for example vinyl aromatic monomers such as styrene and substituted styrenes such as methyl styrene or ethyl styrene, carboxylic acid ester of ethylenically unsaturated C3 to C6 mono- and dicarboxylic acids and monohydric alcohols with 1 to 8 carbon atoms, the nitriles of the carboxylic acids mentioned and vinyl esters of 1 to 12 carbon atoms containing aliphatic carboxylic acids, alkenes with 2 to 10 carbon atoms, preferably with a terminal double bond, such as ethylene or diolefins, in particular Butadiene and isoprene. From this group of monomers, styrene is preferably used, Acrylic acid esters, methacrylic acid esters, vinyl acetate and vinyl propionate. From the acrylic acid esters be in particular methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate and ethylhexyl acrylate highlighted.

It is of course also possible to use mixtures of the monomers mentioned to use, e.g. mixtures of styrene and ethylhexyl acrylate, styrene and n- or i-butyl acrylate> styrene, i-butyl acrylate and acrylonitrile or vinyl isobutyl ether. The monomers of group a) are in the monomer mixture, based on 1 mole of Monomers of group b) contain 1.5 to 10, preferably 3 to 8 mol.

The monomer mixture used in the copolymerization contains, as component b), at least one nitrogen-containing monomer which carries an amino and / or quaternary amino group. Compounds of this type have the general formula in which A = O, NH, B = CnH2n, n = 1 to 8, R¹, R² = CmH2m + 1, m = 1 to 4 and R³ = H, CH3.

The quaternized compounds can be expressed using the following formula X- = OH-, Cl-, Br-, CH-OSO3H-R4 = CmH2m + 1, m = 1 to 4 can be characterized. The other substituents have the meanings given above.

The compounds of formula II are usually called cationic Monomers referred to in the formula I as basic monomers. Basic, Ethylenic unsaturated monomers are, for example, acrylic acid and methacrylic acid esters of Amino alcohols, e.g. diethylamino diethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylate, Dimethylaminopropyl methacrylate, dibutylaminopropyl acrylate, dibutylaminopropyl metharylate, Dimethylaminoneopentyl acrylate, derivatives of acrylamide containing amino groups or methacrylamides such as acrylamidodimethylpropylamine, methacrylamidodimethylpropylamine and methacrylamidodimethylpropylamine.

The quaternary compounds of formula II are obtained by the basic monomers of formula I with known quaternizing agents reacts, e.g. with benzyl chloride, ethyl chloride, butyl bromide, dimethyl sulfate and diethyl sulfate. These monomers lose their basic character in the quaternized form.

The monomers of group c) are ethylenically unsaturated carboxylic acids used. This group of monomers is essentially ethylenic unsaturated C3 to C6 mono- and dicarboxylic acids, e.g. acrylic acid, methacrylic acid, Itaconic acid, maleic acid, maleic anhydride, styrene carboxylic acids and half esters of maleic acid with monohydric alcohols with 1 to 8 carbon atoms. Preferably acrylic acid, methacrylic acid and maleic anhydride are used. The one for the copolymerization The monomer mixture to be used contains the monomers of group c), based on 1 mol of the monomers b) in an amount of 0.5 to 1.5 mol. The polymers contain Units of the monomers in the amounts in which they are used for the polymerization There are monomer mixtures.

The molar ratios of the monomers a: b: c are between the values 20: 1: 3 and 3: 2: 1. Within these limits, copolymers are obtained which are water-soluble are.

The molecular weight of the copolymers is 500 to 5000, preferably 1000 to 3500.

The properties of the amphoteric copolymers can be modified by copolymerization be modified by monomers of group d). Belong to this group of monomers Acrylonitrile and methacrylonitrile as well as the amides of ethylenically unsaturated mono- and dicarboxylic acids with 3 to 6 carbon atoms, preferably acrylamide and methacrylamide. The monomers of group d) are from 0 to 1, based on 1 mole of monomers b) Moles contained in the monomer mixture.

The amphoteric copolymers can also be copolymerized the monomer mixture a) to c) and optionally d) in the presence of monomers of group e) can be modified. These monomers are nonionic, hydrophilic, ethylenically unsaturated compounds that have at least two reactive Centers, e.g. N-methylolacrylamide, N-methylol methacrylamide, as well as those with monohydric C1 to C6 alcohols etherified N-methylolacrylamides and N-methylolmethacrylamides. Di-, tri- and tetraallyl ethers of pentaerythritol and sorbitol, triallyl cyanurate, butanediol diacrylate and divinyldioxane.

The monomers of group e) are, based on 1 mol of the monomers of group 1), to 0 to 0.5, preferably 0 to 0.3 mol in the monomer mixture contain.

The amphoteric copolymers are produced by adding the monomers of groups a) to c) and optionally d) and e) continuously at temperatures copolymerized from 180 to 400, preferably from 250 to 3500.degree. The copolymerization is carried out in the absence of regulators at pressures above 1 bar. The pressures are generally between 3 and 50 bar. However, you can also press to Polymerize 100 bar or even above, but then requires appropriately designed Apparatus.

A pressure vessel, a pressure vessel cascade, a pressure tube or a pressure vessel with a downstream reaction tube, equipped with a static mixer can be used.

The monomers are preferably polymerized in at least two in succession switched polymerization zones. One of the reaction zones can be pressure-tight Kettle, the other from a pressure-tight reaction tube, preferably a heatable one static mixer. If you do the polymerization in two consecutive ways switched Carries out zones, conversions are obtained which are above 99%. During the It is useful for polymerization to ensure thorough mixing of the components ensure, for example, that the polymerization in a pressure-tight Makes kettle equipped with a stirrer or polymerization tubes used with static mixers. About sticking the polymer to the inner walls To prevent the polymerization apparatus, one can reduce the pressure in the polymerization zone lower periodically. The easiest way to do this is to end the A pressure relief valve is built into the polymerization zone to control the pressure in the polymerization apparatus periodically changes. The frequency of the pressure changes can be between 1 and 100 / min the amplitude is between 10 and 100 atm.

The known radical formers can be used in the copolymerization are, for example azo compounds, organic peroxides such as benzoyl peroxide and lauroyl peroxide or hydroperoxides such as tert-butyl hydroperoxide. One can also Use oligomers of p- or m-diisopropylbenzene or other compounds, their C-C bond can easily be thermally split. Based on the monomer mixture 0.01 to 0.1% by weight of a polymerization initiator is used. Styrene and its Derivatives can also be used in the absence of polymerization initiators with other monomers of group a) and the monomers of groups b) to d) are copolymerized.

The copolymerization of the above-mentioned monomer groups is continuous carried out, the residence times of the monomers in the polymerization zone about 2 to 60, preferably 5 to 30 minutes. The copolymerization is in the absence made by controllers in bulk. However, small amounts of a non-regulating the Solvents such as dioxane, toluene, dimethylformamide, tetrahydrofuran, benzene, xylene and acetic acid can be used. f) the amount of such solvents is based on the monomer mixture, 2 to 20% by weight. The solvents are from the reaction mixture, leaving the reactor with the aid of a separate degassing unit, e.g. Falling film evaporator, removed. This energy-intensive process step is unnecessary However, if the polymerization according to the preferred embodiment of Invention is carried out in the absence of solvents. According to the invention The amphoteric copolymers are obtained in a particularly high space-time yield (1 to 50 kg / l. H).

The polymer melt coming from the reactor can be in water or dilute aqueous acids or bases can be dissolved. The amphoteric ones are preferably dissolved Copolymers in water.

The amphoteric copolymers are used as emulsifiers, e.g. in the preparation of aqueous polymer dispersions or for emulsification of pulp and surface sizing agents for paper. If you use these copolymers As an emulsifier, they shape the properties of the aqueous products produced with them Polymer dispersions or the mass and surface sizing agents.

These products are then also amphoteric. For example, to amphoteric To produce polymer dispersions, the usual emulsion polymerization process is used, However, this is modified to the effect that instead of the usual emulsifiers and wetting agents, the amphoteric copolymers described above are used as emulsifiers. The amphoteric copolymers are dissolved in water, which is preferably acidified is.

The concentration of the amphoteric copolymer in the aqueous Solution is in the range of about 2 to 25 wt%. This aqueous solution is the Emulsifier for emulsion polymerization and is also used as a template for uses emulsion polymerization.

After the process of emulsion polymerization, nonionic polymerizes monoethylenically unsaturated monomers. These include, for example Alkenes with 2 to 12 carbon atoms, preferably those with a terminal double bond, such as ethylene or diolefins, especially butadiene and isoprene and vinyl aromatic Monomers such as styrene and substituted styrenes such as t-methyl styrene and ethyl styrene. Suitable monomers of this group are also carboxylic acid esters from ethylenic unsaturated C3 to C6 mono- and dicarboxylic acids and monohydric alcohols with 1 to 18, preferably 4 to 12 carbon atoms, the nitriles of the carboxylic acids mentioned, and vinyl esters of aliphatic carboxylic acids containing 1 to 12 carbon atoms. From this monomer group, preference is given to using styrene, n-butyl acrylate, i-butyl acrylate, Ethylhexyl acrylate, lauryl acrylate, acrylonitrile, methacrylonitrile, vinyl acetate and Vinyl propionate.

The emulsion polymerization takes place in the temperature range of 40 to 150, preferably 60 to 100 ° C using conventional amounts of water-soluble Polymerization initiators. The upper limit for the polymerization initiators is 4% by weight, based on the monomers to be polymerized. Suitable polymerization initiators for emulsion polymerization, for example, peroxides, hydroperoxides, hydrogen peroxide and inorganic peroxides, e.g. hydrogen peroxide, potassium peroxodisulfate or else Redox systems such as potassium peroxodisulfate / addition products of bisulfites with aldehydes and tert-butyl hydroperoxide / ascorbic acid.

The emulsion polymerization is carried out in the presence of the amphoteric copolymers carried out as an emulsifier. The amounts of amphoteric copolymer used as an emulsifier is used in emulsion polymerization is per 1 part by weight of to polymerizing monomers, 0.01 to 0.4 parts by weight (based on solid amphoteric Copolymer).

Although the emulsion polymerization is preferably carried out in the absence of otherwise customary emulsifiers are carried out, but also known Emulsifiers in an amount of up to 3 percent by weight, based on the emulsion polymer, can also be used. Suitable emulsifiers are, for example, nonionic emulsifiers, those by ethoxylation of phenol or phenol derivatives, e.g. octylphenol or nonylphenol can be obtained. Such emulsifiers contain 4 to 30 moles of ethylene oxide / mole of phenol. Cationic emulsifiers are also suitable, for example dimethyl-C12-Fettalkylbenzylammoniumchlorid, Laurylamidotrimethylammonium sulfate, dimethyl dodecylammonium sulfate or sacchanuate.

It is of course also possible, apart from the amphoteric copolymers also mixtures of nonionic and cationic emulsifiers in emulsion polymerization to use. However, the previously used emulsifiers can also be used after Preparation of the emulsion polymer to be added to the dispersion in order to stabilize.

The amphoteric copolymers can also be used as an emulsifier for the Manufacture of engine sizes for paper can be used. You are suitable for example for emulsifying fatty alkyldiketene (e.g. stearyldiketene) or substituted succinic anhydrides (conversion products from Oligomers of isobutene, butene, butadiene or propylene with maleic anhydride).

Aqueous solutions of the amphoteric copolymers also serve as Emulsifier in the production of aqueous polymer dispersions, which are used as surface sizing agents can be used for paper. These are essentially the ones above emulsion polymers described.

The parts given in the examples are parts by weight and the percentages refer to the weight of the fabrics. Those in the description and in the examples specified molecular weights were vapor pressure osmometry in chloroform at a Concentration of 0.1% by weight and a temperature of 370C determined (Mechrolab osmometer). The degree of sizing of the papers was determined using the Cobb value according to DIN 53132 and the ink swimming time in minutes up to 50 percent bleed-through with a standard ink determined according to DIN 53126.

Example 1 In a polymerization apparatus consisting of one 0.7 1 pressure vessel and a downstream one with static mixers equipped pressure tube of 1.5 l capacity, a mixture of 56 parts per hour 2.6 mol of styrene, 14 parts (1 mol) of acrylic acid and 30 parts (0.9 mol) of methacrylic acid dimethylaminopropylamide continuously fed in, each monomer being conveyed with the aid of a pump and was pressed into the reactor after mixing the monomer streams. The middle The residence time of the monomers in the polymerization zone was 15 minutes and the space-time yield 5 kg / l.h. The polymerization was carried out at a temperature of 270C and a pressure from 28 bar carried out. The conversion was greater than 99.5%. the Polymer melt was continuously discharged. The copolymer had a molecular weight 3000.

Example 2 A mixture of 44 parts of isobutyl acrylate, 26 parts Styrene, 10 parts of methacrylic acid and 20 parts of acrylic acid diethylaminopropylamide was in the apparatus described in Example 1 at a temperature of 2400C copolymerized continuously under a pressure of 30 bar. The mean residence time of the monomers in the reaction zone was 10 minutes and the conversion was 99.6%. The copolymer had a molecular weight of 3400. The space-time yield was 10 kg / l.h.

Example 3 A mixture of 35 parts of styrene, 15 parts of acetic acid, 9 parts of acrylic acid and 21 parts of methacrylic acid dimethylaminopropylamide was in the apparatus described in Example 1 continuously at a temperature of Polymerized at 2200 C. The mean residence time of the monomers in the reaction zone was 8 minutes, the pressure 36 bar. The conversion was above 99.5%. As Solvent used acetic acid and the unreacted monomers were out the polymer melt at a pressure of 10 to 15 mbar and temperatures of 120 to 1800C away. A copolymer with a molecular weight was obtained of 2800, with a space-time yield of 2 kg / l.h.

Example 4 A mixture of 56 parts of styrene, 14 parts of acrylic acid and 30 parts of methacrylic acid dimethylaminopropylamide in present of 0.1 part of azobisisobutyronitrile in the apparatus specified in Example 1 continuously at a temperature of 2400C and a residence time of 12 minutes polymerized. The pressure in the polymerization zone was 33 bar. One received a amphoteric copolymer which had a molecular weight of 3400. The space-time yield was 12 kg / l.h.

Example 5 A mixture of 50 parts of styrene, 16 parts of acrylic acid and 32 parts of methacrylic acid dimethylaminobutylamide was given in Example 1 Apparatus continuously at a temperature of 300 ° C. and a pressure of 56 bar polymerized. The conversion was 99.7% and the mean residence time of the monomers in the reaction zone for 10 minutes.

An amphoteric copolymer with a molecular weight was obtained of 1600. The space-time yield was 21 kg / l.h.

Comparative Example 1 According to GB-PS 1 185 283, Example 7, was a mixture of 56 parts of styrene, 14 parts of acrylic acid and 30 parts of methacrylic acid dimethylaminopropylamide, 5 parts of laurylamidotrimethylammonium methosulfate and 185 parts of water by vigorous Emulsified stirring. The emulsion was divided, half of it in a stir flask given with an internal temperature of 600C and a solution of 0.2 parts of sodium hydrogen sulfite in 2 parts of water and 0.4 parts of potassium peroxydisulfate in 12 parts of water were added dropwise.

After the temperature of the contents of the flask had risen to 680C, gave the remaining monomer emulsion is added within 25 minutes. In the same In addition, 0> 4 parts of potassium peroxodisulfate in 12 parts of water were added dropwise over a period of time. To Addition of the monomer emulsion was the mixture at one temperature for a further 6 hours heated from 65 to 70 0C. A copolymer was obtained which had a molecular weight of more than 30,000.

Application Examples Preparation of the dispersions 1 to 5 The in the Examples 1 to 5 obtained amphoteric copolymers and that according to the comparative example 1 produced copolymers were each used as an emulsifier in the production of a Emulsion copolymers used according to the following general procedure: 105 Parts by weight of the amphoteric copolymers according to Examples 1 to 5 or according to Comparative Example 1 were in a mixture of 60 parts of glacial acetic acid, 545 parts Water and 0.04 part by weight FeS04.7H20 dissolved at 850C.

Then 4 parts of a 30% hydrogen peroxide solution were added. Then it was added within 2 hours at the same temperature as the reaction mixture from 850C a mixture of 126 parts of isobutyl acrylate and 66 parts by weight of styrene and separately therefrom 80 parts by weight of a 6% strength hydrogen peroxide solution. Thereafter was post-polymerized for a further hour at a temperature of 850C. One received Dispersions with the characteristics given in Table 1.

Table 1 Sizing agent copolymer according to solids LD value used Emulsifier content% by weight Example Dispersion 1 1 28.7 93 Dispersion 2 2 30.7 97 Dispersion 3 3 31.4 99 dispersion 4 4 31.8 99 dispersion 5 5 30.4 98 comparative dis- compar 1 29.7 62 persion 1 The LT value is a measure of the particle size of the dispersion. To determine the LD value (light transmission), the dispersion is in 0.01 % aqueous solution in a cuvette with an edge length of 2.5 cm with light of the wavelength 546 nm measured. With the help of the Mie theory, the particle diameter can be derived from this calculate (see B. Verner, M. Barta, B. Sedlacek, Tables of Scattering Functions for Spherical Particles, Prague 1976, Edice Marco, Rada D-DATA, SVAZEK D-1.

Use of dispersions 1 to 5 and comparative dispersion 1 as a sizing agent for paper A. Surface sizing Procedure and test methods: A test paper with the following characteristics was used: wood-free offset, 14% ash (Clay), 250 SR; 1% alum; Unsized in the mass. Then there were aqueous preparation solutions produced, which in each case 0> 45% of one of the sizing agents mentioned in Table 2 (fixed) and each Contained 6.0% potato starch. The sizing values obtained with the respective preparations are in Table 2 compiled.

Table 2 Sizing agent Cobb value 50% ink penetration (1 min) (min) Dispersion 1 21 20 Dispersion 2 20 38 Dispersion 3 19 36 I) Isperutorl 4 18 47 Comparative dis- 24 18 persion 1 B. Inlay sizing Procedure: A pulp suspension (100% bleached spruce sulphite pulp with a freeness of 35 0SR with an addition of 20% china clay and 2% alum) were each with a consistency of 0.5% under Stirring 1.25% (based on solids) of the sizing agents mentioned below were added. The pH of the pulp suspension and of the dilution water was adjusted to 5.5. As a retention aid, 0.3% of a modified polyethyleneimine was used shortly before added to sheet formation on a Rapid Kóthen sheet former. The degree of sizing the standard sheets obtained in this way were dried and air-conditioned (24h, 60 % rel. Humidity, 200C). The results are shown in Table 3.

Table 3 Sizing agent Cobb value 50% ink (1 min) (min) dispersion 1 30 13 dispersion 2 26 14 dispersion 3 30 11 dispersion 4 28 18 comparison dispersion 1 33 9 In a further series of experiments, deflaking was used as a fabric model Corrugated board waste and newspapers (50:50).

The sizing was carried out without the addition of alum in a neutral medium with 1.25% (solid) carried out the dispersions given below. The leaves were without Retention aids formed.

The following results were obtained: Table 4 Sizing agent Cobb value 50% ink penetration (1 min) strike (min) Dispersion 1 36 35 Dispersion 2 31 46 Dispersion 3 30 55 dispersion 4 27 60 comparison dispersion 1 40 20

Claims (5)

Claims 1. Process for the production of amphoteric copolymers a molecular weight of 500 to 5000, characterized in that a monomer mixture from a) 1.5 to 10 mol of at least one nonionic, hydrophobic, ethylenic unsaturated monomers, b) 1 mole of at least one nitrogen-containing monomer, which carries an amino and / or a quaternary amino group, and c) 0.5 to 1.5 mol at least one ethylenically unsaturated carboxylic acid, the amounts being For the monomers a) and c) each based on 1 mole of the monomers b), continuously at temperatures from 180 to 4000C and pressures above 1 bar in the absence of Regulators polymerized in bulk. 2. The method according to claim 1, characterized in that a monomer mixture of a) styrene, methylstyrene, acrylic and methacrylic esters of monohydric Cl - to C8 alcohols and acrylonitrile b) a compound of the formula 539/80 Ks / Ys December 17th, 1980 in which A = O, NH, B = CnH2n, n = 1 to 8, R¹, R² = CmH2m + 1, m = 1 to 4 and R3 = H, CH3 means, c) Acrylic acid, methacrylic acid and / or maleic anhydride polymerized. 3. Amphoteric copolymers produced by continuous polymerization a monomer mixture of a) 1.5 to 10 mol of at least one nonionic, hydrophobic, ethylenically unsaturated monomers, b) 1 mole of at least one nitrogen-containing Monomers which carries an amino and / or quaternary amino group, and c) 0.5 to 1.5 mol of at least one ethylenically unsaturated carboxylic acid, the amounts being for the monomers a) and c) each based on 1 mol of the monomers b), in mass at temperatures from 180 to 4000C and pressures above 1 bar in the absence of Regulators. 4. Use of the amphoteric copolymers according to Claims 1 up to 3 as an emulsifier. 5. Use of the amphoteric copolymers according to Claims 1 to 3 for emulsifying mass and surface sizing agents for paper.