DE2025725B2 - ACRYLIC COOPOLYMER BASED FLOCCULATING AGENTS - Google Patents

Description

2. Flocculant according to claim I. characterized in that the carboxyl groups of Acrylic acid to 30 to 80%, preferably 55 to 70%. by an alkali or alkaline earth metal are paid off.

3. Flocculant according to claims 1 or 2, characterized in that the terpolymer has the following composition (based on 100 parts by weight of the polymer) has:

70 to 95% acrylamide,
5 to 20% acrylic acid neutralized to 55 to 70%,

3 to 15% acrylonitrile.

4. flocculant according to claim 1 to 3, characterized in that the terpolymer by known polymerization methods, in particular by polymerization in water-acetone solution or in reverse emulsion.

The invention relates to a new class of flocculants based on special acrylic copolymers, which serve to flocculate solid particles from aqueous media.

The use of acrylic polymers has been suggested for many years to reduce the Separation of solid substances from aqueous media in which they are suspended, by coagulation or To facilitate flocculation. Such solid materials in suspension are, for example, in industrial ones and household sewage, pulp from mineral extraction, and the like. To this Purpose the following polymers were described and found technical application: Homopolymers of Acrylamide, acrylic acid and / or alkali metal acrylates, binary copolymers of acrylamide and salts acrylic acid, acrylamide or acrylic acid with copolymerizable monomers such as styrene, vinyl acetate, Vinyl pyridine and the like

A new group of flocculants has now been found, consisting of certain water-soluble Acrylic terpolymers are made. The behavior of these flocculants, especially their adsorption capacity Due to the colloidal substances to be precipitated, those of the door already have this purpose superior to known, commercially available products.

The new polymers according to the invention are ternary copolymers of acrylamide, partially neutralized Acrylic acid and acrylonitrile having a molecular weight (determined from the intrinsic viscosity) of more than 500,000.

The proportions of the three comonomers must be kept within certain limits, which were determined with the help of a ternary diagram. Based on 100 parts by weight of the terpolymer the proportions of the monomers can be varied within the following limits:

Acrylamide 35 to 97%

Partially neutralized acrylic acid 2 to 55%
Acrylonitrile 1 to 20%

In order to achieve the excellent results described below with the aid of the agents according to the invention To achieve this, the acrylic acid must be neutralized so far with an alkali or alkaline earth metal. that the pH of the mixture of the three comonomers is between 5 and X. preferably between 5.5 and 7 lies. In practice, this degree of neutralization can vary between 30 and ΧΟ'Ό and is generally held between 55 and 70%

As already stated, the molecular weight of the terpolymer be at least 500,000. Is

is generally between 1 and 8 · 10 ⁶ .

The preparation of the flocculants according to the invention can be done according to procedure. Jie for the production of acrylic polymers are already known According to a particularly advantageous one of these processes: -.

the various monomers are dispersed in the form of an aqueous solution in the presence of a suitable surface-active agent with stirring in an organophilic phase. The organophilic phase can consist of an organic hydrocarbon, for example toluene or xylene. The polymerization initiated by a classic redox catalyst allows a water-soluble copolymer with a molecular weight to be produced within a very short time of the order of 10 to 20 minutes and with practically quantitative yield of at least 1 · 10 ⁶ in the form of a powder. According to another method, the comonomers can be polymerized in an aqueous-organic medium, for example in water and acetone at room temperature and in the presence of Hassische catalysts.

The new, water-soluble acrylic poly! icren show greatly improved properties compared to their already known homologues and result in significant technical progress in the field of acrylic-based polyelectrolytes. If they are used in the same concentrations as the previously proposed flocculants, they lead to a much higher sedimentation rate of turbidity. In addition, the degree of their adsorption to precipitated colloidal substances is around 100%. These properties have the consequence that their use for flocculation of industrial sewage, mine washing water, runoff water, and raw water that has been cleaned in the usual way by metal oxides such as Al ₂ O ₃ or Fe ₂ O ₃ , optionally in conjunction with a flocculating polyelectrolyte, in particular is recommended.

The following examples illustrate the properties of several of the invention Acrylic terpolymers and compare their coagulation and flocculation properties with a

represented a number of acrylic polymers recognized as the best agents to date in this field of application were considered.

Examples

1. Production of the polymers

For the production of the copolymers according to the invention and of known homopolymers and copolymers, which were used for comparison purposes in flocculation tests, several classic processes were used.

In a first process, pure acrylamide was polymerized in demineralized water that had previously been deoxygenated under conventional conditions (room temperature, redox catalyst).

According to another procedure, copolymers of acrylamide and partially neutralized acrylic acid and various ternary acrylamide-acrylic acid-acrylonitrile copolymers according to the invention were prepared by adding the monomers or comonomers in a water-acetone mixture at a temperature of 10 to 30 ° C were polymerized in the presence of a redox catalyst, the polymers being obtained directly in the form of small Forlen.

Terpolymers according to the invention were finally also produced by the so-called "reverse emulsion" method, with the comonomers in a mixture of water (dispersed phase) and hydrocarbon (continuous phase) in the presence of an emulsifier and classic initiators at a temperature of 20 to ^50.degree have been polymerized.

The polymers produced in this way and their most important properties are shown below Table 1 summarized.

Tabel

i'ohinere ·. 100/0/0 Ι.τ> ·.: ΠιιιΙ alic acid acrvlnitrile
(weight pro / enl of the monomers) Polvmt ivitiorisHp A. 955 0 aqueous solution B. 90/6/4 Acrylic acid to 60% by NaOH
re'-alized Water acetone
solution C. 90 6/4 100% acrylic acid through NaOH
neutralized the same D. 75/18/7 Acrylic acid to 60% by NaOH
neutralized the same E. 90/6/4 Acrylic acid to 60% by NaOH
neutralized the same F. 50/35 15 Acrylic acid to 60% by NaOH
neutralized reverse
emulsion Ω Acrylic acid to 60% by NaOH
neutralized the same

Ciren / viscosity
(', I Molecular
weight χ Kl " 4.6 1.2 13.7 4.7 12.4 4.1 22.5 8.7 ¹ 5.8 5.6 19th 7th 14.5 5

2. Use of the polymers as flocculants

a) As it is known that untreated water is often used with the help of coagulants. like in particular Al ₂ O ₁ . is cleaned, a series of comparative tests were first carried out to determine the flocculant properties of the various specified polymers on the precipitates or "flakes" of aluminum oxide hydrate at a pH of 7.1 and in various concentrations. These precipitates were obtained by adding aluminum sulfate and sodium aluminate to the crude water. The resulting aluminum oxide hydrate was expressed as the proportion of Al ₂ O ₃ in mg / l. For this purpose, the optimal amount of flocculant for a given amount of Al ₂ O _{3 was} determined in a series of preliminary tests. This optimal amount corresponded to the highest sedimentation rate, which was measured in a 2-1 measuring cylinder 42 cm high, in which fillings of aluminum oxide hydrate were produced.

The strength of the "flakes" obtained was then measured for each of the specified polymers and at various concentrations of Al ₂ O ₃ by subjecting them to vigorous mechanical stirring (stirring speed 50 revolutions / min.), And the quality of the sedimentation observed was determined with ratings between 1 (poor sedimentation) and 5 (excellent sedimentation).
The results obtained in this way are shown in Table 2 below.

Ar! of
Polymers

Table 2 Firmness of the flakes quality
the sedi
mentation '! lot
at
(mg / 1) Weight
pruient des
Polymers,
related to
Al ₂ O ₃ moderate 3.5 50
150 19th
10.75 moderate 3 50
150 16.5
5.5 moderate 3.5 50
150 21
9.5

A.
B.
C.

') The ratings listed in this column are the mean of two values measured _{at 50 and 150 mg / 1 Al 2} O _3.

lot
3Π 5 Firmness of the skirt 2 025 15th 725 Λ. Sedimentation AUO ₁ continuation Amount of polymer speed
in 10 * ^J cm / sec. Type of (mg U Weight
percent of very good quality Type of
Polymers (in pieces
per I million parts) Poly 50 Polymers, the Sedi- 5 35
70 meren 150 Dezogen on
Ai ₂ O ₃ very good mentation ¹ ) B. 10
20th 190 D. 50 8th 4.5 40 70 150 5.5 excellent F. 10 208 E. 50 11th 4.5 10 20th 310 150 7.3 excellent 40 62 F. 50 4.9 5 G 10 195 150 4.25 20th 320 G 7.5 4.5 40 6th

The evaluations listed in this column are the mean of values. which were measured at 50 b / u 150 mg 1 Al ₂ O ₃

The data in this table results, conclusions can be drawn, whose ^v ain to be hereinafter referred to as:

By means of the terpolymers according to the invention (products D to Cj), compared to the known Acrylic-based flocculants (polyacrylamide A or binary copolymers * B) reduce mechanical fragility of the sediments are significantly reduced and the quality of the sedimentation is considerably improved.

The optimal amounts of terpolymers. which are to be used in the range from 50 to 150 mg I Al, O, are on the one hand _{in the same order of magnitude for both proportions of Al 2} O ₃ and on the other hand are twice less than those of the acrylic polymers A and B of the known type.

Comparing the results obtained rr.ii product C. with the results obtained by the products D until Cj 'r / were held, clarifies the requirement that not to neutralize the acrylic acid comonomer used as starting material to K) O "ο.

Even if those for products D, E. F and G The results listed are very good and similar to one another, but seems to be essential for Terpolymer mil to lead the method of emulsion polymerization to products with a similar molecular weight, which have optimal flocculation properties.

b) To the effectiveness of various inventive i'erpolymereri to investigate the flocculation of clay beet in certain mining areas A major problem is, different proportions of polyelectrolytes A through G were too given clay water containing a montmorillonil-type clay in an amount of 50 g 1 and then the rate of sedimentation as a function of the amount of acrylic polymer added measured.

The results obtained are listed in Table 3 below (the sedimentation rate measured on an untreated comparative sample was 16 χ ΙΟ " ³ cm / sec.).

Table 3 Sedimentation
speed wedge
in 10 ~ ^J cm / sec. At the
Polymers Amount of polymer
■ in parts
per I million parts) 29
45
140 A. 10
20th
40

From this table it can be seen that, with the same proportions, the polymers 1 and G according to the invention to a 1.5- to 2.3ma. faster sedimentation of clay turnips lead as an acrylamide homopolymer or a copolymer * of acrylamide and acrylic acid.

c) Finally, the degree of adsorption of the polyelectrolytes according to the invention on the to be precipitated measured colloidal substances. Indeed, the ideal degree of adsorption (100%) gives the possibility of recirculated the raw water to be treated without running the risk that part of the Low molecular weight flocculants stabilize the suspensions and thus prevent later Makes flocculation impossible.

For this purpose measurements of the chemical oxygen consumption, i. H. the DCO value, carried out on filtrates of montmorillonite in the following way: 200 g of montmorillonite (No. 205 of Compagnie Commerciale des ivline.ais et Matieres premieres) were suspended in distilled water and then the suspension is precipitated by stirring the various flocculants for 6 minutes A, B and F according to Table 1 were added in proportions of 25. 50 and 75 parts per million parts, respectively became. Thereafter, the value DCO according to the provisions of the French standard AFNOR T. 9O.iO! (May 1968) determined The in Table 4 summarized results obtained.

Table 4 P'ilwiieres

A.
B.

IXO In,

O, Il

for 25 parts per

I million parts

of the sound

97.2
95.3
88.7

j door 50 files per

I million parts

of the sound

103.5 92.8 91.3

for 75 parts per

I million parts

of the sound

92.7 92.9 82.3

Since the value measured on reference clay (without the addition of the flocculant) DCO 92.5 mg / 1 the change in the DCO value could be derived from this in a simple manner:

Table 5

Polymer Change of DCO
compared to the comparative 50 parts per
1 MiIHfM, ieile 75 parts per
1 million parts 25 parts per
1 million parts + 11 + 0.2 A. + 4.7 + 0.3 + 0.4 B. + 2.8 - 1.2 - 10.2 F. -3.8

IO

It can be seen that only the terpolymer F according to the invention gave negative results in all respects leads.

On the basis of these results it can be said that this flocculant not only does not have any additional. Proportion of the value DCO imports when it is used as a flocculant for clay, but that it also has the ability to meet part of the chemical oxygen demand to hold back this tone.

Analogous results were obtained when using alumina hydrate instead of clay. In this way it could be shown that the acrylic terpolymers according to the invention were 100% adsorbed _{on flakes of Al 2} O ₃ , nH _{2 O.}

309 582/31

Claims (2)

Patent claims: 1. Flocculants for undocking solid particles. aqueous media based on acrylic polymers, characterized in that it consists of water-soluble terpolymers of Acrylamide, partially neutralized acrylic acid and acrylonitrile with and a molecular weight of more than 400,000 and the following proportion of the monomer units (based on to 100 parts by weight of the terpolymer) consist of: 35 to 97% acrylamide, 2 to 55% partially neutralized acrylic acid, 1 to 20% acrylonitrile.