DE19710212A1 - Production of finely-divided polymers derived from N-vinyl- formamide - Google Patents

Abstract

A process for the production of finely-divided polymers of N-vinylformamide (NVF) and polymers which may contain vinylamine units (I), by radical polymerisation of NVF and 0-80 wt.% comonomers (based on total monomer) in aqueous solutions or mixtures at 20-150 deg C, optionally followed by acid or basic hydrolysis of NVF units to vinylamine units. The monomers are polymerised in a reactor fitted with at least two parallel rotating stirrer shafts with stirrer organs, and the resulting water-containing gel polymer is pulverised with the rotating stirrers and then discharged from the reactor.

Description

The invention relates to processes for preferably continuous Lichen production of finely divided polymers N-Vinylformamids and possibly containing vinylamine units Polymers by radical homo- or Copolymerization of N-vinylformamide at 20 to 150 ° C in special reaction vessels and possibly subsequent acidic ones or basic hydrolysis of the fine particles produced Polymers.

The production of N-vinylformamide homo- and copolymers and hydrolysis to vinylamine units Tending polymer is known per se. So describes the DE-C 37 15 824 a process for the production of water-soluble polymers containing vinylamine units, in which man N-vinylformamide in the form of a 20 to 60% solution polymerized, the gel polymer obtained granulated, the formed gel particles dispersed in methanol and the right resulting polymer dispersion for hydrolysis of the N-vinyl formamide units in the polymer with an aqueous Ammonium salt solution of a monohydric acid in contact brings. From US-A 4 769 427 a method for Production of crosslinked gel-like polymers by Polymerization of monomer mixtures in single-wave Mi known. There are monomers containing crosslinkers mixtures such as partially neutralized acrylic acid, methacrylic acid, Acrylamide, methacrylamide or N-vinyl pyrrolidone in 20 to 65% aqueous solution with initiators at 45 to 95 ° C polymerized, with part of the water during the poly merization under reduced pressure from the reaction medium is removed so that a crumbly gel is discharged becomes. The resulting cross-linked polymer is insoluble in water  Lich, but adsorbs significant amounts after drying of water. According to the procedure of DE-A 40 07 312 N-vinylformamide, possibly together with comonomers, in conc polymeric aqueous solutions in kneaders so far siert that the resulting water-containing poly marl breaks down into particles, which then become vinylamine poly mer be hydrolyzed.

The present invention is based on the object known process for the preparation of N-vinylformamide to polymerize and vinylamine polymers therefrom that the polymerization process is continuous, quickly and with particularly good mixing and warmth control can be carried out and polymers in high Yield result which is a uniformly good quality and each have uniform particle sizes.

It has now been found that the task can be solved if you polymerize in a stirred kettle with at least at least 2 parallel, rotating stirrer shafts with stirrers is equipped, the resulting water Crushed the gel polymer using the rotating stirrer and then the finely divided water-containing gel polymer your reaction kettle discharges.

The invention thus relates to a method for Production of finely divided polymers of N-Vinylformamids and possibly containing vinylamine units Polymers by radical polymerization of N-vinylformamide and 0 to 80 wt .-% of the total amount of monomers on copolymerizable olefinically unsaturated comonomers in aqueous solution or mixture at 30 to 150 ° C in egg reaction vessel (reaction vessel) and possibly subsequent acidic or basic hydrolysis of the obtained N-vinylformamide polymers to vinylamine units  containing polymers, in which the preparation of the N-vinylformamide polymers the monomer solution or -mixture with the addition of a polymerization initiator polymerized in a reaction kettle, which with at least 2 parallel, rotating stirrer shafts with stirring elements is equipped, the resulting water-containing gel polymer crushed with the help of rotating stirrers and that crushed water-containing gel polymer from the reak discharge boiler.

Preferred reaction kettles contain in addition to specified stirrers still at least one conveyor for the discharge of the water-containing gel polymers.

The method according to the invention allows a continuous che preparation of the N-vinylformamide polymers, the Expression "continuously" when discharging the polymer a pulsating and briefly interrupted process wise, in which the Amount of water-containing gel polymer within the reak tion boiler is retained. The process achieved at continuous driving a very high polymer loot and no longer requires manual labor when the Polymerization reaction once its constant speed achieved. Compared to the known corresponding The method is a with the inventive method particularly effective mixing of the reaction mass aims. In the continuous process is the generation the heat of polymerization during the entire reaction time uniform because the finely divided water-containing gel poly mere, retained in the reaction kettle, and the fresh supplied aqueous monomer solution mixed uniformly be and the polymerization of the monomers on the upper Surface of the polymer gel takes place. The removal of the polyme heat of risk and the maintenance of the polymer  tion temperature at a constant level is very simple. As a result, the rate of polymerization can in turn efficiency, and thus productivity, and an increase maintaining product quality on a specified basis high level can be easily achieved. The continuous The method according to the invention also allows production of water-containing gel polymer particles with very uniform chem particle diameter in a shape that is easy to is drying. Although the particle diameter of the herge posed polymers are variable and of the applied Reaction conditions depend, with the fiction according to the continuous process of obtaining polymer particles th, the diameter of which is generally not 3 cm exceeds and preferably in the range of 0.05 to 1 cm lies.

In the process according to the invention, the reaction or Polymerization boiler play an essential role. The reak tion boiler is with several, d. H. with at least 2 parallel rotating stirrer shafts equipped Stirring devices, such as stirring blades, have. The agitator shafts can rotate in the same direction or in opposite directions. With help the rotating stirrer can be removed from the Monomer solution formed by polymerization Break water-containing gel polymers into small particles.

Examples of suitable reactors and associated apparatus parts for the process according to the invention are shown schematically in FIGS. 1 to 7.

Fig. 1 shows a typical reaction apparatus used for the method according to the invention in section.

FIG. 2 is a front view of the stirrer blades used in the reaction apparatus of FIG. 1.

Fig. 3 is a side view of a typical arrangement of the discharge sheets of the discharge device used for discharging the reaction apparatus of Fig. 1st

Fig. 4 shows schematically in section another typical reaction vessel's rule for the inventive method.

Fig. 5 shows in section a typical combination of the re action kettle of Fig. 4 with a conveyor and a dryer.

Fig. 6 is a perspective view of the agitator blades of the reaction apparatuses of Figs. 4 and 5.

Fig. 7 shows in section the diagram of a further suitable for the novel process reaction apparatus.

Generally are particular to the method of the invention Kneaders, especially two-arm kneaders and three-shaft kneaders, suitable. With two-arm kneaders, the 2 stirring shafts can be opposite directions with the same or rotate at different speeds. If the 2nd Stirrer shafts can be operated at the same speed the radii of rotation of the two stirrers also partially overlap. The rotating stirrers used can have different shapes, of which as very suitable stirrers of the Sigma type, S type, Banbury type and Fishtail type are mentioned.

According to the process of the invention, the polymer tion carried out in a reaction vessel in its middle or lower area several stirrers or kneaders has the stirrer shafts arranged parallel to one another to have. The reaction vessel with a lid is advantageous provided to the polymerization reaction under a To be able to carry out an inert gas atmosphere. Advantageous is the reaction vessel in the upper part with a back flow cooler provided to due to the heat of polymerization evaporated water condense and dissipate heat can. However, it is also possible to create water vapor through an inert gas introduced into the reaction vessel  to drive electricity out of the boiler. Preferred response boilers are provided with a casing through which a Heat exchange medium flows, causing heating or cooling development of the reaction mixture allowed. Very suitable reak tion boilers not only contain a discharge opening for the product exit, but have close to the product step opening a conveyor for discharging the Product such as a discharge screw or a double paddle sponsor. It has proven to be advantageous after a device, e.g. B. a tub, to provide in which at a higher temperature another Post-polymerization to complete the polymerization can be carried out. Overall, the equipment is there to be set up so that a continuous implementation of the Polymerization reaction is possible.

A polymerisation apparatus proven for the process according to the invention is shown in section in FIG. 1. It has 2 stirrers in a reaction vessel 5 , which is also provided with a thermometer 1 , a raw material feed pipe 2 , an inert gas inlet 3 , a cover 4 and with a jacket 7 . The agitator shafts 6 have sigma-shaped Rührblät ter, as shown in FIG. 2. The reactor opening for the product outlet 8 has arranged in its vicinity a conveying device 9 for the discharge of the product, which here are pad-shaped blades 9 as discharge blades on a horizontal shaft, as shown in FIG. 3 in a side view. The product outlet 8 is connected for post-polymerization with a tub 10 on a water bath 12 through a shaft 11 , which may consist of plastic such as polyethylene or poly vinyl chloride.

A further reaction apparatus suitable for the process according to the invention is shown in FIGS. 4 and 5. FIG. 4 schematically shows a section of a reaction vessel 25 with cover 24 and casing 27 , which in the lower area has 2 rotating stirring shafts 26 arranged in parallel with Banbury stirring blades, such as As shown in Fig. 5, as well as tet ausgerüs with an underlying discharge screw 29th Fig. 5 shows the combination of the reaction vessel 25 with the discharge screw 29 , the discharge opening 28 , egg nem provided with a jacket 31 double paddle conveyor 30 as conveyor, a conveyor belt 34 and a dryer 35th In the reaction vessel 25 , the stirrer blades can have different shapes, for which FIGS. 6 (A) to 6 (D) show advantageous shapes.

A further reaction apparatus suitable for the process according to the invention is shown in FIG. 7. It is similar to FIG. 1, but the vessel wall facing the discharge opening 48 is of a low height in order to allow the water-containing gel polymer produced to emerge by overflowing this never-ending wall. It is advantageous to design this wall as an overflow weir with adjustable wall height in order to be able to control the discharge quantity.

It has been found for the process of the invention the reaction vessels used have proven to be very advantageous, their inner surface with a coating of fluorhalti to provide resin to adhere the gel gel formed to prevent lymeren on the inner surface. For that ge Suitable fluorine-containing resins are e.g. B. Tetrafluoroethylene Po polymers, tetrafluoroethylene-perfluoropropyl vinyl ether copoly mers, tetrafluoroethylene-ethylene copolymers or trifluoro monochlorethylene polymers.

For the polymerization, the aqueous monomer solution is so like the polymerization initiator in the reaction vessel introduced. The air is expelled by introducing inert gas displaced the system and the poly  merization temperature set. As it progresses Polymerization is a water-containing gel polymer forms, which is crushed by the rotating stirrer, without interrupting the polymerization. By ongoing further addition of monomers and initiator is a con achieved continuous polymerization, whereby by discharge of the crushed water-containing gel polymer about constant amount of gel polymer in the reaction vessel is enough. It is often advantageous to do what is carried out gel-containing polymers still in a conveyor or heat in a water bath for post-polymerization and complete the polymerization reaction len. The resulting finely divided N-vinylformamide polymer risat is then dried or used to make vinyl amine polymers directly hydrolyzed.

According to the process of the invention, N-vinylformamide polymerized alone or in a mixture with comonomers. Comonomers which are present in amounts of 0 to 80% by weight of the total mo Amount of nomers that can be used are primarily copo Lymerizable olefinically unsaturated monomers, at least least after hydrolysis of the copolymers to vinylamine polymers ren water-soluble or water-dispersible copolymers give. Suitable monomers are, for. B. called acrylamide, Methacrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, Acrylic acid, methacrylic acid, methyl acrylate, 2-hydroxyethyl acrylate and methacrylate, vinyl acetate and N, N-dimethylami noethyl acrylate. The use of N-vinyl is preferred formamide as the sole monomer. The aqueous monomers Solution or mixture contains the monomers in a con concentration of 10 to 80 wt .-% and is preferably continuous or the polymerization or reaction kettle ben. The pH of the monomer solution or mixture is 5 to 8 and preferably 6 to 7. To maintain the pH during the It is important to keep polymerization as constant as possible  Advantage, in the presence of buffer systems such as sodium hy drug phosphate to work. The polymerization takes place at 20 to 150 and preferably at 40 to 100 ° C. The polymer is generally 0.5 to 4 hours.

As polymerization initiators, which are generally described in Men gene from 0.01 to 5 wt .-%, based on the total monomers Amount to be used are those that come under form radicals under the polymerization conditions. Prefers are water-soluble initiators. Examples of suitable poly Merger initiators are hydrogen peroxide, hydroper oxides, peroxides, redox initiators, and especially not oxidizing initiators such as azo compounds. From the Azo Compounds are 2,2'-azo-bis (2-amidinopropane) dihydro chloride, 2,2'-azobis (N, N'-dimethylene-isobutyramidine) - dihydrochloride, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azo-bis [2-methyl-N- (2-hydroxyethyl) propionamide] or 2,2'-Azobisisobutyronitrile mentioned as very suitable.

If polymers with low molecular weights he are desired, the concentration of polymeri sationsinitiator significantly increase or the polymerization perform in the presence of known molecular weight regulators, which are generally in amounts of about 0.05 to 20% by weight, based on the total amount of monomers used. Examples of known regulators are mercapto compounds such as Dodecyl mercaptan, thioglycolic acid, thioacetic acid, mercap toethanol, mercaptopropanol or mercaptobutanols.

The N-vinylformamide polymers obtained have K values according to Fikentscher from 20 to 300 and in particular from 140 up to 300.

The N-vinylformamide polymers produced as described can be subjected to partial or complete hydrolysis to vinylamine polymers as water-containing polymer powders in a process step directly following the polymerization. The hydrolysis can e.g. B. be carried out in a reaction apparatus, as shown in Fig. 5. The uniform properties of the finely divided or powdery N-vinylformamide polymers decisively and advantageously determine the properties of the resulting vinylamine polymers.

For hydrolysis, an acid or base is added to the mixture provided polymers. Depending on the hydroly conditions, d. H. the amount of acid or Base, based on the polymer to be hydrolyzed, the Amount of water and the reaction temperature, which in general is at 20 to 100 ° C, you get a partial or complete hydrolysis of the N-vinylformamide units in the Polymer to vinylamine units. For hydrolysis ge suitable acids are e.g. B. mineral acids, such as aqueous solutions genes of hydrogen halide, sulfuric acid, nitric acid or phosphoric acid, or organic acids such as carboxylic acids with 1 to 5 carbon atoms, e.g. B. formic acid, acetic acid or Propionic acid, or aliphatic or aromatic sulfone acids, e.g. B. methanesulfonic acid, benzenesulfonic acid or Toluenesulfonic acid. Suitable for hydrolysis with bases aqueous solutions of hydroxides of the metals of the first and second main group of the periodic table, such as lithium hydro xide, potassium hydroxide, sodium hydroxide, calcium hydroxide or Barium hydroxide. It is often beneficial to use ammonia or Amines such as aliphatic amines to be used for hydrolysis. For each formyl group equivalent in the polymer Hydrolysis generally 0.5 to 1.5 equivalents of acid or base and water needed.  

Following the hydrolysis, the finely divided polymers containing vinylamine units can be transported in an apparatus, as shown in FIG. 5, with a discharge screw 29 through the discharge opening 28 , brought from the double paddle conveyor 30 onto the conveyor belt 34 and dried in the dryer 35 . If necessary, the vinylamine polymer can be neutralized by adding alkali after acid hydrolysis or acid after alkali hydrolysis, e.g. B. in the double paddle conveyor 30 in Fig. 5 Darge presented reaction apparatus.

The water-soluble fine or powdery obtained Vinylamine polymers with very uniform properties can particularly advantageous for the known uses of these Polymers are used. It is suitable as drainage Retention, retention or flocculants in the paper industry position, for fixing agents in the manufacture of paper from paper containing interfering substances and as a means of Increase the strength of paper. You can also use Flocculant for waste water in sewage sludge dewatering tion, as a flocculant in ore processing and tertiary oil production find use.

The following examples are intended to be those of the invention In addition, explain the procedure, but do not restrict it. Unless otherwise stated, parts and Percentages by weight. The specified K values were determined according to H. Fikentscher, Cellulosechemie 13, 58 (1932) in 1% by weight aqueous polymer solutions.

example 1 a) Preparation of N-vinylformamide polymer

A mixture of 400 g of N-vinylformamide, 600 g of water and 4 g of sodium dihydrogen sulfate, which has a pH of 6.5, was filled in a 2 liter reaction vessel corresponding to FIG. 1. Thereafter, nitrogen was passed through the inert gas inlet 3 through the reactor to remove oxygen. The stirrer shafts rotated at 70 revolutions per minute, and 50 ° C warm water was passed through the reactor jacket. A solution of 0.5 g of 2,2'-azobis (N, N'-dimethyleneisobutyramidine) hydrochloride and 0.25 g of 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide ] in 10 ml of water was added to the reaction mixture. The polymerization started 15 minutes after the addition of the polymerization initiator. The internal temperature of the reaction vessel had risen to 76 ° C. after about 30 minutes. As the polymerization progressed, the aqueous monomer solution changed into a water-containing gel polymer, which gradually disintegrated under the influence of the rotating stirrers with stirrer shafts arranged in parallel. The reaction mixture was transferred through the paddle-shaped stirrer 9 into the tub 10 . The water temperature of the heating bath 12 was 85 ° C. After 3 hours the polymer was removed and had a solids content of 40% by weight and a K value of 180.

b) hydrolysis to vinylamine polymers

In a second stage of the process, the hydrolysis of the N-vinylformamide polymer was carried out by adding 451 g of a 50% strength aqueous sodium hydroxide solution to the finely divided polymer which had been introduced into a reaction kettle as shown in FIG. 1 with stirring at 75.degree . The mixture was left to react for a further 2 hours at this temperature and then 67 g of concentrated hydrochloric acid were slowly added. After cooling, a crumbly product was removed from the reactor. The degree of hydrolysis, ie the percentage of the N-vinylformamide units hydrolyzed in the polymer, determined by polymer titration and enzymatic determination of formic acid, was 99.1%.

Examples 2 to 4 a) Preparation of N-vinylformamide polymer

N-vinylformamide polymers were prepared by the procedure given in Example 1, but the reaction conditions and results corresponded in detail to the values given in Table 1. The following polymerization initiators were used:
Initiator 1: 2,2'-azobis (N, N'-dimethyleneisobutyramidine) dihydrochloride
Initiator 2: 2,2'-azo-bis [2-methyl-N- (2-hydroxyethyl) propionamide]

b) hydrolysis to vinylamine polymers

The procedure was as in Example 1, but corresponded to Reaction conditions and results in detail the in Table 2 given values. The specified degree of hydrolysis corresponds to the percentage of hydrolysed in the polymer ten N-vinylformamide units.  

Table 1

Table 2

Example 5 a) Preparation of the N-vinylformamide polymer

A coated two-arm kneader made of stainless steel according to FIG. 1 with an internal volume of the reactor of 2 liters, a cross section of 160 mm × 150 mm and a depth of 135 mm, was with 2 sigma-shaped stirrer blades with a rotation diameter of 70 min, a lid and one Discharge equipment equipped. The inner surface coming into contact with the reactants and the reaction products was provided with a coating of a tetrafluoroethylene-per fluoropropyl vinyl ether copolymer. A solution of 476 g of N-vinylformamide, 4.76 g of sodium dihydrogen sulfate in 480 g of water with a pH of 6.5 was introduced into the reaction kettle. Nitrogen was bubbled through the device for 30 minutes to remove oxygen. The 2 sigma-shaped stirrer blades had a speed of 67 and 56 revolutions per minute, and the jacket was flowed through by 50 ° C. warm water. A solution of 1 g of 2,2'-azobis (2-amidinopropane) dihydrochloride in 10 g of water was added to the reaction kettle as a polymerization initiator. As the polymerization time progressed, a water-containing polymer gel developed from the initial polymer solution, which was finely divided by the rotating stirrer. The internal reactor temperature reached 80 ° C and the temperature of the water for the jacket was raised to 90 ° C. An aqueous solution of 17.14 kg of N-vinylformamide and 0.17 kg of sodium dihydrogen sulfate in 17.28 kg of water was then prepared and dissolved oxygen was removed by passing nitrogen through it. The solution and an initiator solution of 8.2 g of 2,2'-azobis (2-amidinopropane) di hydrochloride in 82 ml of water are pumped separately at a constant rate into a mixing tank and from there continuously fed into the reaction kettle for 24 hours. At a polymerization temperature of 90 ° C, a finely divided, water-containing gel polymer was formed from the solutions, which was discharged from the reaction vessel with the aid of a paddle-shaped wing ( 9 ) and kept under a nitrogen atmosphere for a further 20 minutes to complete the polymerization. The resulting water-containing gel polymer was in the form of finely divided particles with a diameter of 2 to 7 mm. The solids content was 49.8% by weight. The polymer had a K value of 198.

b) hydrolysis to vinylamine polymers

5 kg of the N-vinylformamide polymer prepared were filled into a three-shaft knank corresponding to FIGS . 4 and 5. The kneader had an internal volume of 10 liters, a cross section of 240 mm × 220 min, a depth of 260 mm and was equipped with 2 Banbury stirrer blades with a rotation diameter of 110 mm. The Banbury agitator blades rotated at a speed of 30 revolutions per minute. Hot water at 70 ° C. was passed through the reactor jacket. After adding 2.8 kg of a 50% strength aqueous sodium hydroxide solution, the mixture was hydrolyzed for 2 hours. The hydrolyzed gel polymer was then transported to a double paddle conveyor with the rotating discharge screw, in which the pH of the gel polymer was adjusted to 7 by adding 3.9 kg of a 32% strength aqueous hydrochloric acid solution. In the resulting polymer, 96% of the N-vinylformamide units had been hydrolyzed to vinylamine units.

Reference list List of designations in FIGS. 1 to 7

Fig.

1 to 3:

1

thermometer

2nd

Raw material feed pipe

3rd

Inert gas inlet

4th

cover

5

Reaction kettle

6

Stirrer shafts

7

Sheathing

8th

Product leakage

9

paddle-shaped stirrer

10th

Tub

11

Synthetic shaft. resin

12th

Heating bath

13

Gel polymer

FIGS. 4 and 5:
21 thermometers
22 raw material feed pipe
23 Inert gas inlet
24 lids
25 reaction vessels
26 stirrer shafts
27 sheathing
28 Product leakage
29 discharge screw
30 double paddle conveyors
31 sheathing
32 discharge opening
33 gel polymer
34 transport device
35 dryers

Fig. 7:
41 thermometers
42 raw material feed pipe
43 Inert gas inlet
44 cover
45 reaction kettles
46 stirrer shafts
47 sheathing
48 Product leakage
50 tub
52 heating bath
53 gel polymer

Claims (7)

1. Process for the preparation of finely divided polymers of N-vinylformamide and, if appropriate, polymers containing vinylamine units by radical polymerization of N-vinylformamide and 0 to 80% by weight of the total amount of monomers of copolymerizable comonomers in aqueous solution or mixture at 20 to 150 ° C in a reaction kettle and, if appropriate, subsequent acidic or basic hydrolysis of the N-vinylforinamide polymers obtained to give polymers containing vinylamine units, characterized in that the monomers are polymerized in a reaction vessel which is equipped with at least two parallel, rotating stirrer shafts with stirring elements is, the resulting water-containing gel polymer is crushed using the rotating stirrer and discharged from the reaction kettle. 2. The method according to claim 1, characterized in that that one discharged from the reaction vessel hydrous gel polymer to complete the Polymerization reaction heated in a water bath. 3. The method according to claim 1 or 2, characterized characterized in that for the polymerization reaction kettle used at least 2 to each other stirrer shafts arranged in parallel with stirring blades for Breaking down the resulting from the polymerization Gel polymer and one below the stirrer arranged discharge screw contains.   4. The method according to any one of claims 1 to 3, characterized characterized in that the reaction vessel a Discharge opening and a conveyor for the Discharge of the crushed hydrated Gel polymer has. 5. The method according to claim 4, characterized in that the conveyor is a double paddle conveyor is. 6. The method according to claim 4, characterized in that the conveyor is a discharge screw. 7. The method according to any one of claims 1 to 6, characterized characterized in that from the reaction vessel worn crushed water-containing gel polymer dried a downstream conveyor belt becomes.