WO1992007880A1

WO1992007880A1 - Process for producing maleic acid copolymers with side perester groups and their use in the production of dispersant-free aqueous polymer dispersions

Info

Publication number: WO1992007880A1
Application number: PCT/EP1991/002031
Authority: WO
Inventors: Volker Steinert; Manfred Rätzsch; Karin Wendler; Steffi Reinhardt
Original assignee: Hoechst Aktiengesellschaft
Priority date: 1990-10-29
Filing date: 1991-10-28
Publication date: 1992-05-14

Abstract

A process for producing maleic acid copolymers with side perester groups in that a maleic acid anhydride copolymer in ketonic solution is reacted with triethyl amine is reacted, the addition product is then reacted with a hydro-peroxide and the reaction product is treated with aqueous alkaline hydroxide to hydrolyse the remaining copolymeric maleic acid anhydride groups. Use of the resulting and by-produced perester-group-containing maleic acid copolymers as initiators for the radical heterophase polymerisation of ethylenically unsaturated monomers for the production of emulsifier and dispersant-free aqueous polymer dispersions. The resultant emulsifier-free aqueous polymer dispersions have a narrow particle size distribution and are useful for many known applications for plastic dispersions.

Description

Process for the preparation of maleic acid copolymers with pendant perester groups and their use for the production of dispersant-free aqueous polymer dispersions

The invention relates to a process for the preparation of maleic acid copolymers with pendant ester groups. The compounds are suitable as polymer initiators for the radical polymerization of ethylenically unsaturated monomers, in particular for the preparation of emulsifier-free and dispersant-free polymer dispersions.

The invention further relates to a process for the production of emulsifier-free and dispersant-free aqueous polymer dispersions by heterophase polymerization, in which a polymeric initiator according to the invention of the aqueous monomeric reaction mixture as a group containing the radical monomer polymerization

Substance is added, in the result of which an emulsifier-free and dispersant-free aqueous polymer dispersion with a narrow particle size distribution is obtained which can be used without restriction for known uses.

From the patent literature a reference to the production of maleic anhydride copolymers with pendant perester groups is known, according to which it is recommended according to patent specification DD-PS 252 833, according to a Procedure for the synthesis of succinic acid mono-tert-butyl perester to proceed. It is also known to mix 3.4 to 6.5% maleic anhydride copolymer solutions in dry acetone with pyridine and tert-butyl hydroperoxide (molar ratio of the latter addition = 1: 1).

(Makromol. Former 190, 2325-2328 (1989)). The reaction time is very long and is given as 7 days. The polymer can be isolated by precipitation in 0.1 HCl. The space-time yields achievable according to this regulation do not permit economical production of the polymers mentioned and modified in the form given.

The aim of the invention is to develop a process for the production of maleic acid copolymers with pendant perester groups, which allows economical production. Another object of the invention is to develop a method whereby a polymer dispersion can be obtained using these side polymers containing perester groups, the carrier phase of which is free from emulsifiers and other stabilizing additives.

The invention was therefore based on the object of obtaining a maleic acid copolymer with pendant perester groups in a novel manner.

According to the invention, the object is achieved in that an addition product of triethylamine with a Maleic anhydride copolymer formed, this addition product is reacted with a hydroperoxide and the remaining maleic anhydride groups are hydrolyzed. A vacuum distillation is then carried out to remove the unreacted low molecular weight reactants. The starting copolymer is dissolved in an eton, acetone being particularly favorable. The polymer concentration should be as high as possible, the upper limit is determined by the installed Ruhr power in the reaction vessel. For propene-maleic anhydride (Manh.) Copolymers with a number-average molecular weight of 10 ⁵ , 40% solutions can be prepared, with molecular weights less than 10 ⁴ , up to 50% solutions can be prepared. The triethylamine must be added in such a way that no separate phase forms. A deep red-brown color appears, accompanied by an increase in the viscosity of the solution. Irreversible precipitation occurs if, contrary to the regulation, polymers containing acid groups are used. The hydroperoxide can be added when there are no more color changes in the reaction mixture. This is the case after a maximum of 15 minutes after the amine addition has ended.

After a reaction time of 3 to 4 hours in the ketone solution, the remaining copolymeric maleic anhydride groups are hydrolysed by adding In aqueous alkali metal hydroxide solution. The addition of lye is to be such that the pH of the reaction mixture which has become heterogeneous as a result of the aqueous addition of lye is greater than 10. After vacuum distillation at bottom temperatures below 40 ° C., a free aqueous solution of a maleic acid copolymer containing pendant perester groups is obtained if the pH in the bottom of the column is kept greater than or equal to 10 and

Water content in the solution is at the required level.

The solutions thus obtained can be used directly as initiator stock solutions for the preparation of emulsifier-free dispersions by radical heterophase polymerization.

The storage stability of these initiator solutions is limited, but is sufficient for practical purposes, such as that obtained according to a standard formulation according to Example 5, with the modification that the perester content of the initiator is 20.5% instead of 10.8%, monomer conversions obtained in the heterophase polymerization after a reaction time of 45 minutes show:

Service life (hours) of

Initiator solution (pH 10) before use 0 24 48 72 168

Sales in% (based on the

Starting monomer quantity) 96.1 95.9 95.3 95.1 79.0

The resulting polymers can be isolated without problems by known processes. Technically, the processes of suspension and emulsion polymerization are used to produce conventional polymer dispersions with solids contents of up to 50%; water is usually used as the dispersion medium. The ethylenically unsaturated monomers that can be used are only slightly soluble in water, so that in both processes the starting mixture is a 2-phase system; in the course of the emulsion polymerization, a third phase, the latex phase, is formed in the course of the reaction.

In both processes, it is necessary to stabilize the monomer and latex phases by adding auxiliaries and / or emulsifiers. Water-soluble natural and synthetic polymers such as gelatin, tall resin acids, cellulose derivatives, copolymers of maleic acid, acrylic and methacrylic acid, alkylaryl and alkylsulfonates, etc. are used as emulsifiers. Inorganic stabilizers which are insoluble in water and have a high degree of dispersity, such as carbonates, sulfates, phosphates, metal hydroxides, silicates and kaolin and the like, can also be used in some cases. Depending on the effectiveness, stabilizer additives in the range of 0.1 to 2% are common.

A major disadvantage of both methods is that the emulsifiers used can negatively influence the product quality. Is the polymer iso- by evaporation of the carrier phase (eg spray drying) giert, the entire emulsifier remains in the polymer. In the case of filtration processes, the emulsifier content (especially in the case of suspension polymers) in the polymer can be considerably reduced by washing processes, but the resulting filtrates require disposal. These disadvantages are well known and a number of methods for their elimination have been proposed. An essential principle is that a substance with stabilizing properties is added which either contains groups capable of copolymerization (for example vinylpyridine derivatives) or is capable of forming a chemical bond with the resulting polymer. These processes significantly reduce the organic load on the carrier phase. However, there are high demands on the selectivity and reactivity of these

Provided auxiliaries that conflict with the universal applicability of these compounds. Economic aspects also have a limiting effect on the technical use of such processes.

The invention was therefore also based on the object of producing polymer dispersions in water bypassing the use of surfactants or other low molecular weight auxiliaries.

According to the invention, the object is achieved in that a monomer is dispersed in water and polymerized in the presence of an initiator based on a maleic acid copolymer containing pendant perester groups is, the polymeric initiator units from succinic acid derivatives of structure I,

- HC CH - wherein = H, Me ⁺ , NH ₄ ⁺ and R ² = alkyl C, -C

0 = CC = 0 (I) phenylalkyl C ₈ -C _ιg , cycloalkyl C ₅ -C ₁₂

OR ^J OOR '' means

and the monoanion of structure II and the dianion of structure III

Alkali metal ions (Me ⁺ ), in particular Na ⁺ , are preferably suitable as cations R ¹ for charge balancing. The degree of polymerization of the polymers used for initiator production must be less than 500, in each case based on the number of man units in the copolymer molecules, otherwise no dispersions are obtained when the polymeric initiator is used in the heterophase polymerization, but phase separation occurs and the polymerization proceeds in the closed phase. The pH of the starting reaction mixture for the aqueous heterophase polymerization should be between 5 and 12, and pH values around 10 are particularly favorable proven, inter alia, to ensure the water solubility of the polymeric initiator.

Alternating copolymers are particularly suitable for initiator production, but copolymers with man contents of less than 50 mol% can also be used. Some of the available maleic anhydride groups can be modified by known reactions, e.g. for stabilization, coloring, etc., provided this does not negatively affect the water solubility of the polymer in the specified pH range The initiator disintegration is thermally induced, favorable working temperatures are between 65 and 85 ° C., but other usual methods of initiator decomposition can also be used.

The molar ratio monomer: initiator is usually 100 to 1000, higher and lower values are possible.

Surprisingly, the polymerization rates when using the polymeric initiators according to the invention are extremely high and, in comparison with the technically similar emulsion polymerization, remain constant up to substantially higher conversions. While in the emulsion polymerization of styrene with sales around 65% with the disappearance of the monomer phase the

If the reaction rate decreases, it remains constant in the heterophase polymerization process according to the invention up to conversions of more than 8G%. The particle size distributions obtained are also unusually narrow. The standard deviation for the mean particle volume is on average between 5 and 15%. In contrast, according to the known state of the art, with variation of all possible formulation parameters (liquor ratio, emulsifier, initiator, temperature), the corresponding standard deviations are between 26.5 and 58.2%, on average around 40% (cf. progress in high polymer research 1 (1959), 275-282).

A narrow particle size distribution is only achieved if the polymeric initiator used is not sufficiently dispersive to generate a stable emulsion of the monomer in water at room temperature by mechanical energy input, which can be seen from the fact that after the stirrer has been switched off, a closed monomer phase is formed trains. With regard to the monomers that can be used, the heterophasic polymerisation process according to the invention can be applied to all monomers and their mixtures, which can also be converted into polymers by the process of emulsion polymerisation with the main constituent water as carrier phase and radical initiation.

The polymers obtained according to the invention are not all completely soluble in the solvents which are otherwise typical for them. The insoluble fraction can preferably be between 15 and 70%, depending on the type of initiator and reaction conditions. Substantially higher degrees of crosslinking can be achieved in the usual way by adding at least bifunctional monomers can be obtained. For example, the proportion that can be extracted by benzene in polystyrene, which was produced using 2% divinylbenzene, is 1.6%. According to the invention, soluble polymers can preferably be obtained when polymerization is carried out in the presence of molecular weight regulators and preferably without the use of polyfunctional monomers.

The invention is explained in more detail by the following examples.

Examples 1 to 4

Production of maleic acid copolymers with pendant perester groups

example 1

In an Erlenmeyer flask with a magnetic stirrer, 21 g (= 0.15 mol Mann.) Propene-maleic anhydride (Manh.) - copolymer (propene: Manh. = 1: 1 molar ratio), molar mass 11000, in 31.5 g dry acetone dissolved, 0.037 mol of triethylamine and then 0.037 mol of tert-butyl hydroperoxide (70% purity, main impurity ditert-butyl peroxide) are then added via a dropping funnel. After a reaction time of 4 hours, 220 ml of NaOH are added over the course of 30 minutes, the temperature rising to 37 ^° C. The pH of the final solution is 12.9. In a rotary evaporator at a pressure of about 20 torr acetone and triethylamine like the main amount of di-butyl peroxide and unreacted hydroperoxide driven off with water. A further 20 ml of NaOH are added in the course of the distillation. The pH of the final solution is 11.2. After dilution to 300 ml, it is precipitated in HCl in 290 ml, the supernatant solution is decanted off and the polymer is isolated by freeze-drying.

Yield: 24 g = 92.8% (based on the starting components), perester content 19.9% (based on the man.

Amount in the starting copolymer), peroxide conversion 79.6% (based on the tert-butyl hydroperoxide used).

Example 2

The procedure is as in Example 1, except that an α-methylstyrene-mixed polymer with a molecular weight of 30,000 is used instead of the propene-mixed polymer. Yield: 94.6%, perester content 15.1%, peroxide conversion 60.4%.

Example 3

The procedure is as in Example 1, except that instead of the propene-Manh copolymers, an ethene-Manh copolymers, molecular weight 6000, in which 5% of the Manh groups are replaced by n-heptadecylsuccinimide units, is used. Yield: 98.4%, perester content 21%, peroxide conversion 84%.

Example 4

The procedure according to Example 1 is followed with the modification that the molar ratio of the mole numbers of Manh. (in propene-manh copolymer): amine: hydroperoxide = 1: 0.5: 0.5. Yield: 93.5%, perester content 32.6%, peroxide conversion 64.4%.

Examples 5 to 9 Preparation of Dispersant-Free Aqueous Polymer Dispersions

Variant A In a cylindrical reaction vessel, V = 500 ml, with a 4-bladed blade stirrer, inert gas feed and immersion (10 mm water), a mixture of monomer and water is heated to the reaction temperature after flushing with argon. The aqueous initiator solution, V = 30 ml, pH = 10.0, is then added. The determination of the

Conversion (% by weight of polymer, based on the amount of starting monomer) takes place gravimetrically. Variant B

A 1 l steel autoclave with a two-bladed blade stirrer (500 rpm) is charged with the liquid reactants, flushed 3 times with 10 atu nitrogen, then, if necessary, charged with gaseous monomer and, if appropriate, under excess pressure brought to reaction temperature. The sales are determined gravimetrisc.

Lateral perester groups containing propene-maleic acid copolymer, degree of polymerization 140 (= number of man-units in the copolymer molecule), perester content 10.8%

Reaction temperature 75 ° C

Standard deviation: 6.6 Soluble fraction: 75%. Example 6

option A

Recipe: styrene 54.4 g

Water 240 g of initiator 1.45 g of α-methylstyrene-maleic acid copolymer containing perester groups,

Degree of polymerization 270, perester content 15.1%

Reaction temperature 75 ° C

Water 240 g

Initiator 1.39 g ethene-maleic acid copolymer containing perester groups on the side, degree of polymerization 95, perester content 15.3%

Reaction temperature 75 ° C

Polymerization time (min): 25 45 110 conversion (%): 27.3 72.7 89.3

Polymer particle size: 0.0853 μm standard deviation: 10.8% - soluble fraction: 37.6% Example 8

Variant B

Recipe: styrene 150 g

Water 600 g of initiator 3.72 g of propene-maleic acid copolymer containing perester groups on the side, degree of polymerization 120, perester content 20.3% molecular weight regulator 0.52 g of dodecyl mercaptan

Reaction temperature 75 ° C

Conversion after 45 min polymerization 90.6%, after 3 hours 99.4%. Soluble fraction in the polymer 100%, evaporation residue in the aqueous carrier phase 0.32%, based on the carrier phase.

Example 9 Variant B

Recipe: Styro1

Butadiene

water

Initiator reaction temperature

Polymerization time (min): 15

Pressure (atu): 8.80

Reaction product: Stable latex, not coagulable in methanol.

Claims

1. A process for the preparation of Maleinsäuremischpoly¬ merisaten with pendant perester groups, characterized in that an addition product of triethylamine with a maleic anhydride copolymer, dissolved in a ketone, formed, the addition product reacted with a hydroperoxide and the remaining in the copolymer with maleic anhydride groups Alkali hydroxide are hydrolyzed.

2. The method according to claim 1, characterized in that the number of moles of triethylamine is 0.2 to 1 times the number of moles of the hydroperoxide.

3. The method according to claim 1 or 2, characterized gekenn¬ characterized in that the reaction mixture after the reaction with the hydroperoxide with aqueous alkali to a pH greater than 10, preferably 11.5, is adjusted.

4. The method according to one or more of claims 1 to 3, characterized in that the reaction mixture at bottom temperatures up to a maximum of 40 ° C is subjected to a vacuum distillation to the boiling point of the water at a correspondingly reduced pressure.

5. The method according to one or more of claims 1 to 4, characterized in that the copolymer concentration of the starting solution in the ketone is 20 to 60%, preferably 40%, based on the solution.

6. A process for the preparation of dispersant-free aqueous polymer dispersions from ethylenically unsaturated and free-radically polymerizable or copoly erizable monomers by heterophase polymerization, the aqueous monomer reaction mixture being added to a radical-triggering group-containing substance, characterized in that the aqueous monomer dispersion as radical initiator contains a maleic acid copolymer containing side-chain perester groups, prepared according to one or more of claims 1 to 5, the copolymeric initiator molecules comprising units of succinic acid derivatives of structure I,

where R ¹ = H, Me ⁺ , NH ₄ ⁺ and R ² = alkyl C ₃ to C ₁₀ , phenylalkyl C ₉ to C ₁₈ , cycloalkyl C ₅ to C ₁₂ ,

as well as units of structures II and III

contain and have an average degree of polymerization between 10 and 500, based on the sum of structures I to III, is added, the addition preferably taking place as an aqueous solution.

7. The method according to claim 6, characterized in that in the copolymeric initiator molecules the proportion of the structural element I is less than or equal to the sum of the structural elements II and III.

8. The method according to claim 6 or 1, characterized gekenn¬ characterized in that the copolymeric initiator is molecularly soluble in water at pH values greater than 4.0.