DE1200270B - Process for the production of fibrous aluminum oxide monohydrate with the boehmite crystal lattice - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY GERMAN JfflUTWt PATENT OFFICE

Int. σ .:

COIf

EDITORIAL

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German class: 12 m -7/02

1200270
P 22279IV a / 12 m February 24, 1959 September 9, 1965

Process for the production of fibrous Aluminum oxide monohydrate with the boehmite crystal lattice

The invention relates to a method for producing a new aluminum oxide monohydrate with the boehmite crystal lattice, its particles fibrous shape and in at least one direction have colloidal dimensions and are suitable for a wide variety of commercial uses. When an aqueous dispersion of the boehmite fibrous particles e.g. B. spread on a pad and is dried, a cohesive surface film is created.

According to a known method, hydrargillite is converted into a by heating in an autoclave to 205 ° C crystalline product with a water content of 17.8% transferred, which although the X-ray diagram of boehmite, but is not identical to the new fibrous boehmite.

It is known that activated with mercury
Aluminum in humid air with fiber-like, very
voluminous outgrowths of aluminum hydroxide
covered, which are referred to as "fiber clay". 20th
However, this product does not appear fibrous under the microscope, shows in the X-ray diagram
not the crystal lattice of boehmite and can
when spreading into aqueous suspension and drying
do not process into contiguous films. 25th

It is also known from sodium aluminate solution

with acid a very finely crystalline aluminum oxide 2

hydrate precipitate after washing and

Drying has a water content of 21 Vo. Boehmite crystal lattice to the desired extent However, this product is neither pure boehmite nor 30 has been made. fibrous still persistent. Rather, it can be shown at In the drawings

the inventive method as starting material Fig. 1 is a photomicrograph of the

for the production of the new fibrous boehmite new boehmite fibers, which are used from parallel to the fiber length will. axially arranged fibrils are built up

The inventive method for producing 35 25,000 times linear magnification, the Darvon fibrous aluminum oxide monohydrate with a position at the top right due to the microdem Boehmite crystal lattice shows ink drawing made by heating water absorption, rigen aluminum oxide dispersions at temperatures Fig. 2 in a similar representation a product in

above the atmospheric boiling point at which the fibrils do not aggregate Water consists in being an alumina, 40 and not oriented,

- - ■ Fig. 3 in a similar representation at 50,000 times

linear magnification a product in which the fibrils are in a more aggregated, more oriented State than in the case of the product according to FIG. 2

more than 3 molar aqueous dispersion, which is also present, the black, circular dots denoting the remainder of a monobasic acid with a dissociation constant of more than 25 ° C., measured here and in the following photomicrographs
than 0.1 in a concentration of at least 0.05

Applicant:

E. I. du Pont de Nemours and Company, Wilmington, Del. (V. St. A.)

Representative:

Dr.-Ing. W. Abitz, patent attorney, Munich 27, Pienzenauer Str. 28

Named as inventor:

Edward C. Broge, Wilmington, Del. (V. St. A.); Erick Wilkinson Bruce, London; John Bugosh, Wilmington, Del .; Emmette Fair Izard, Kenmore, N.Y .;

James Albert Mitchell, Richmond, Va .;

Randall N. Pratt, Claymont, DeL; Rudolph Schlatter, Wilmington, Del. (V. St. A.)

half of which can be dissolved in concentrated hydrochloric acid at 98 ° C in less than 10 minutes, in the form of an "aluminum oxide", calculated as Al ₂ Oj, at least 0.05 molar, but not

with a diameter of

up to about 4.2 mol / l, as long as a temperature

styrene latex particles

represent ΐημ,

Fig. 4 at 1800 times linear magnification

temperature in the range from above 120 to 250 ° C, 50 a modified product that by azeotropic Entbis the conversion of aluminum oxide in fiber removal of water from a product of the in Fi g. 2 shaped aluminum oxide monohydrate is obtained with the type shown,

509 660/423

3 4

5 shows the ultrared spectrum of the basic produced according to the invention in German patent specification 444517 manufactured product, aluminum chloride or nitrate solutions. Nitrates

F i g. 6 to 10 curves, which in consecutive curves have the advantage over chlorides that they are not required in cor-steps to have the effect of erasing the time {Θ, abscissa.

values) necessary for the depolymerization of the 5 A suitable basic ammonium nitrate can be obtained in half of a given amount of aluminum oxide by heating aluminum acid, nitrate nonahydrate to 150 ° C according to the USA patent fig . 11 a photomicrograph of the font 2127 504 initially _{produces Al (OH) 2} NO ₃ and produces the product according to example 11 at 26,000 times this by further heating in a basic magnification, io aluminum nitrate with a higher ratio. FIG. 12 shows the product in a similar representation converted to Al ₂ O ₃ : NO ₃ from 1: 1 to 4: 1; a specific example 12 at 18,000 magnifications which is the preferred range of this ratio

F i g. 13 shows the product according to 1.2: 1 to 2.0: 1 in a similar representation.

Example 13 at 18,000 times magnification and aluminum oxide dispersions can also be produced

Fig. 14 in a similar representation, the product after 15 can be prepared by adding freshly precipitated, salt-free

Example 14 at 35,000 times magnification. washed aluminum hydroxide mechanically in

Depending on the process, water is dispersed and a strong acid is added, conditions takes the resulting brine of amorphous aluminum oxide, which the

fibrous aluminum oxide in the form of fibrils may contain the desired amount of nitrate residues which have one or more dimensions lying in the colloidal region 20, also by electrodialysis of aluminum nitrate. Such fibrils can be dissolved or by ion exchange of aluminum Form aggregates of large fibers, which are produced from salts on ion exchangers, unions or groups of fibrils built up The aqueous dispersion or the sol should be present, which in turn have no connections other than AIuder parallel to the longitudinal axis Fibers extend. 25 minium oxide and the desired acid residue

As a result of their colloidal nature, the new ten form. Many commercial brines, gels and salt solutions Boehmite fibers in water or organic liquid contain soluble salts, such as sodium chloride or stable brine, the colloid particles of which are similar to sodium nitrate. Preferably the concentration Allow to re-disperse easily after drying. such inactive substances or impurities possible

30 borrowed low. It is especially important that

The starting material compounds of silicon, boron and molybdenum

are only present in small quantities, there

The method according to the invention is based on aluminum - they suppress fiber formation. Boron compounds miniumoxide in the form of an aqueous dispersion. are particularly harmful. To focus on The aluminum oxide must keep such a molecular level as low as possible, recommends structure, such a degree of hydration and a need, especially when working at high temperatures Grain size have that the time (Θ) to use the temperature over 250 ° C devices, Depolymerization of half of a sample in areas that are not lined with glass. Other soluble If there is an excess of hydrochloric acid at 98 ° C to form aluminum salts, the dispersibility of the dry prominium ions can be reduced is required, less than 10 minutes to promote 40 ducts or for other reasons in the and is preferably less than 1 minute. Product to be desired and in the starting materials

This variable Θ is at the same time a means of marking the process products or being added to them.

Basic aluminum chloride, basic aluminum nitrate, aluminum hydroxide, aluminum oxide can be used to prepare the aqueous aluminum oxide dispersions to be used as starting material. The aqueous, acidic aluminum oxide dispersion is heated to gel or colloidal aluminum oxide solutions until the fibrous boehmite has formed. turn around. In all of these substances, the aluminum oxide used as the starting material has a high degree of polymerization in the aqueous system in a dispersed oxide, can state. In the process according to the invention, during the conversion to a depolymerization first, the aluminum is also associated with an acid radical, lower molecular weight units and then with one such as chlorine. Rückpolymerisation to fibrous boehmite SUC-AIs "alumina content" of Ausgangsdisper- gene. The formation of the fibrous boehmite can sion or solutions but here the one Al ₂ O ₃ content 55 denotes the result of a local rearrangement of the drying of the dispersion or of the already polymerized good. Solution and glow of the residue is determined. As a starting material, for. B. an aluminum oxide sol Specifying a di- can be used in an aqueous system. If an aluminum-dispersed aluminum oxide is used, solutions oxide which dissolves in water at the pH of the reaction of e.g. B. basic aluminum chloride, colloidal 60 Hch, this is simply dissolved in water, dispersions or solutions, such as aluminum, which contains the acid to be used in the process, hydroxydsole, or suspensions of strongly hydrati-.

ized aluminum oxide, such as precipitated aluminum If the aluminum oxide is to be used in the

hydroxide. Acid solution is not easily soluble, it can be

Suspend as the starting material in the 65 times according to the invention by stirring. Generally supposed Typical substances which can be used for the process and have a high-polymerized AIu-0 value of less than 10 are e.g. according to the USA - miniumoxyds the particle size is less than 150 μ, Patents 2196 016 and 2127 504 or which is preferably less than 45 μ.

The type of product obtained is mainly of. influences the following process conditions:

1. the acids used,

2. the Al ₂ O ₃ concentration,

3. the acid concentration,

4. the ratio of Al ₂ O ₃ to acid,

5. the working temperature and

6. the temperature-time relationship.

The conditions given below mainly relate to strong monobasic Acids. When using acetic acid, formic acid and other weak acids, the Conditions changed approximately.

1. Acids

In the initial dispersions there is an acid residue in solution that can be titrated with NaOH. ao As a result, for example, the chlorine ion in salts, such as sodium chloride, and similar acid residues in other neutral salts that may be contained in the dispersion are excluded. The acid residues can, however, be present, for example, in solutions of basic aluminum chloride; because the chlorine ions in such solutions can be titrated with alkali. So the acid residue concentration is as that Amount of anion in the aqueous dispersion defines which is the stoichiometric amount to be formed of normal salts with all cations except aluminum exceeds the required amount.

The acid residues used in aqueous dispersions according to the invention are more strongly monobasic Acids, e.g. B. of acids with a dissociation constant of more than 0.1 at 25 ° C. Typical examples such acids are hydrochloric, nitric, perchloric, iodic, hydrobromic and trichloroacetic acids. As shown later, other acids such as acetic acid and formic acid can also be used Find.

2. Al ₂ O ₃ concentration

The concentration of aluminum oxide as Al ₂ O ₃ can be changed within wide limits without the type of products produced changing significantly. The upper limit of the aluminum oxide concentration is determined by the excessive, irreversible aggregation of the product. If more than about 1.6 molar Al ₂ O ₃ concentration is used at temperatures below about 250 ° C., the products obtained are so poorly and irreversibly aggregated that they no longer count among the products obtained according to the invention. The tendency to aggregate depends on the reaction temperature and the aluminum oxide concentration. In general, when working at temperatures considerably above 250 ° C., preferred products according to the invention can also be obtained at high aluminum oxide concentrations of 3 molar.

Fibrous boehmite does not form below an Al ₂ O ₃ concentration of about 0.05 mol / l. The aluminum oxide concentration is preferably between 0.05 and 1.6 mol / l when working at temperatures below 250.degree. If temperatures above 250 ° C. are used, the concentrations can be between 1.6 and 3.0 mol / l. Temperatures below 250 ° C are preferred.

3. Acid concentration

The anion concentration should not greatly exceed 4.2 mol / l.

If the residual acid concentration falls below about 0.05 molar, the efficiency of the process will increase restricted. The hydrogen ion is likely to act in the formation of fibrous boehmite as a catalyst, and possibly at a concentration less than 0.05 molar is the amount of acid too little for this catalytic effect.

4. Al ₂ O ₃ acid ratio

The ratio of alumina to acid residue can be varied considerably. An aqueous dispersion is preferably used whose _{residual acid concentration is between about a quarter of the Al 2} O ₃ molarity and the sum of this molarity and 0.2.

A molarity of the acid radical of 0.5 (Al ₂ O ₃ ) to (Al ₂ O ₃ ) + 0.2 is particularly preferred.

These conditions are preferred for the strong acids, but it is also possible, as described later, to work with much larger amounts of weak acids, such as acetic and formic acids. Such weak acids do not undergo complete ionization and an excess of them does not disturb the reaction. The molar concentration of the remainder of weak acids can be up to 4 (Al ₂ O ₃ ) or even 6 (Al ₂ O ₃ ) or even more.

5. Working temperatures

This aluminum oxide dispersion is heated in the autoclave, usually with stirring, until which has formed fibrous boehmite.

In general, the lowest temperature at which the process can be carried out is without unduly long treatment times can be carried out, 120 ° C. Assuming a rapidly depolymerizable aluminum oxide off, so you can heat it at such low temperatures for a long time in order to allow the growth of the To effect aluminum oxide fibers.

Temperatures above 250 ° C are not preferred. The boehmite form is not above 400 ° C completely stable, and other, more stable crystalline forms begin to appear. The inventive The process is preferably carried out at a temperature between about 150 and 220 ° C.

The temperature does not need to be constant during the entire process. The temperature of the Autoclave can be slowly increased from room temperature to the desired value and the autoclave load be cooled before discharge. The reaction can also be carried out in this way that the period of time for heating up and cooling down is short. The temperatures given above are the maximum temperatures, and usually the feed will be held at these temperatures for the majority of the heating period.

6. Temperature-time relationship

At low temperatures of e.g. B. 120 ° C very long heating times are required. aside from that At low temperatures, large particles of other alumina modifications, such as

Gibbsite prisms. The higher the heating temperature, the shorter the time required for the boehmite fibers to form. In general, a heating time of a few minutes to an hour ^{at 220 ° C. is sufficient.} At 160 ° C, fibrils of increasing length are obtained when z. B. ^l h hour to about 1 day heated. Advantageous results have been obtained by heating brines at 160 ° C for 50 to 100 hours.

At temperatures above 250 ° C, heating times of a few minutes are sufficient during Heating times of more than about one-half hour lead to the formation of fibers that are too thick.

When choosing the heating times and temperatures, it should be noted that in general the production of fibrils that have at least two dimensions falling within the colloidal range is desired.

In practice it is easy to determine the heating time required at a given temperature, by taking samples from time to time or otherwise determining the amount of aluminum oxide, which has been converted into the fibrous form.

treatment
of unreacted aluminum oxide and acid

The acid residue remaining in an aqueous dispersion after heating can be caused by gelling of the aqueous sol are removed, including the pH is increased rapidly to 8-10. Gelation can take place at temperatures above 60 ° C. by adding the aqueous sol to a base. The salt formed during the neutralization of the acid residue is removed by filtration and washing.

Another procedure is to gel at a higher pH, e.g. B. above 11, where the unpolymerized aluminum is converted into soluble aluminate and washed out with the salts can be.

The anion-free gels produced in this way can be converted into a sol again in distilled water which is essentially neutral (pH 7 to 8.5). The gels can also be used in an acid, including weak acids such as those with a dissociation constant of less than 0.1 at 25 ° C, such as acetic and formic acid, are dispersed. The sol obtained in this way can have a pH of 10 to own 1.

If the sols are to be dispersed in basic solutions, care must be taken that no forms of aluminum oxide other than fibrous aluminum oxide and aluminum ions in the form of [Al (H ₂ O) ₆ ***] are present. Partially polymerized "aluminum oxide forms, such as basic aluminum ions, have a disruptive effect when an anion-free gel is dispersed at pH values above 8.5.

The absence of interfering aluminum oxide forms can be ensured by heating what continues until complete conversion to aluminum oxide monohydrate and aluminum ions can be determined by titration.

Sodium, potassium, Lithium, ammonium hydroxide, organic amines, such as triethylamm, tetrasubstituted ammonium bases, such as tetramethylammonium hydroxide, and other bases can be used.

Treatment of unreacted aluminum oxide When the process is carried out, the binds Rest of the strong acid part of the aluminum and prevents its conversion into crystalline Boehmite. Even if the reaction is practically complete, the resulting dispersion contains hence a less basic salt of aluminum with the rest of the strong acid. When the reaction does not run completely, something can also not

ίο converted starting material or basic salt are present.

This remaining aluminum salt can, for. B. be treated with an anion exchanger so that that part of the strong acid residue is removed.

If the dispersion is then heated, the unpolymerized aluminum oxide also turns into boehmite converted. A large part of the aluminum oxide appears to be deposited as a coating on the boehmite fibers, which are already in the dispersion,

ao although a part can also form new nuclei.

If the alumina has not yet polymerized, the process can be repeated. Man can in turn remove acid residue and reheat it. This treatment can be repeated until the anion content has reached the desired low level.

The unpolymerized aluminum oxide, which is present in different, according to the invention dispersions as aluminum salt is a minor proportion of the aluminum total amount present in the system. Thus, the aluminum salt amount can be about 30%, calculated as Al ₂ O _3, located on the total weight of the dispersion Aluminum oxides; in general, however, it is no more than about 20%. There is no lower limit, since the amount of unpolymerized aluminum becomes smaller and smaller as the process is repeated.

Increase in basicity

The removal of the remainder of the strong acid can except with the help of an anion exchanger or by gelling and washing also by dialysis or by chemical precipitation in the form of an insoluble one Salt of a metal take place, which is added in the form of the base or the bicarbonate. So For example, the chlorine ion can be removed with silver oxide. Preferably the rest of the strong Removes acid using the bicarbonate form of a strongly basic anion exchanger which contains quaternary ammonium groups (see US Pat. No. 2,733,205).

Heating time and temperature when removing unreacted aluminum oxide in

Presence of fibrous boehmite

After removing the remainder of the strong acid, the dispersion of the fibrous boehmite is heated. This causes the non-polymerized aluminum oxide converted into boehmite. In the sols prepared in the manner described above, the contain fibrous boehmite, this conversion takes place at lower temperatures than in aqueous aluminum oxide dispersions which contain little or no fibrous boehmite. Usually the dispersion should be heated to at least 80 ° C. A temperature of 100 ° C is satisfactory. Higher temperatures up to two

9 10

375 ° C, for example, can be used, but in general the products have the form of small fibrils, which in general are preferably colloidal at temperatures of at least two dimensions (Fig. 2), do not exceed 280 ° C or from Aggregates or bundles according to Fig. 1. The heating time depends on the amount. The products according to Fig. 1 are formed because part of the unreacted aluminum oxide. At a 5 chen have such a charge that a certain sol, which contains 12% unreacted aluminum oxide and agglomeration and aggregation of the fibrils under Al ₂ O ₃ and Cl in the ratio of 120: 1, is enabled to form fibers in which which required about 3 hours at 100 ° C. Particles are oriented parallel to the longitudinal axis of the fiber. The boehmite dispersions obtained in this way contain FIG. 2 shows the many small fibrils which, in only small amounts, of other aluminum ions and acid residues are oxidized by the process according to the invention. Through repeated aqueous dispersion under the electron-anion exchange and heating treatments, the products of acid residues and other aluminum can be seen under the microscope at about 25,000 times the linear magnification. The fibrils can appear in beminium oxide forms as boehmite, essentially in any arrangement; however, they are released. 15 usually not in the form of individual fibrils, but the dispersions obtained by the above process in groups of two, three or even significant dispersions are more stable than more fibrils at a higher pH. Such groups form colloidal dispersions, which are unpolymerized aluminum fibers.

contain salt. They also have a greater consistency. The products obtained differ in their compatibility with organic solvents and 20 rods in that their aspect ratio, ie the resin dispersions. These properties expand the ratio of fiber length to fiber width, from the scope of the products. Electron micrograph determined or by stick- The fibrous boehmite can also be determined using substance absorption, generally using at least weak organic acids produced is about 20: 1. The determined width of the fibrils will be. Preferably, a mixture of a weak monobasic organic acid determined by nitrogen absorption, such as vinegar knives are about the same for some products, acid or formic acid, and one with carbon, but most are shaped like a slat, so that the acid treated hydrated alumina gel two smallest dimensions are different,
heated, the fibrils seem to have a rectangular "... ,,, .... _,. 30 cross-section are considered here as

1. a molar ratio of carbonate ions to aluminum _{as if their cross-section were} circular,
minium of about 1.50 b _1S 1.90, in particular preferably the axis ratio is min-

"V? I 7 ^υ:> ! ..,. "". ,. . at least about 20: 1, in particular about 50: 1 to 150: 1.

2. a molar ratio of sulfate clays to aluminum. _The aspect ratio can even be 300: 1; of less than about 0.01: 1, preferably _{in the case of the preferred} products it is between less than about 0.005: _{1.6Q: 1 and 80} . _L ⁶

3. em Molverhaltms of cations to aluminum _The term "fibril" herein in its less than about 0.04: 1 is used and which, in contrast: less than about 0.03 1, preferably _üb i _icnen sense to identify products to formations made from

4. Has such an activity that the time it takes for the ₄₀ aggregates of a number of separate limbs to build up for the depolymerization of half of a sample _; A gel with an Al ₂ O weight _equivalent appears _{uniformly under the electron microscope.} Under "fiber" are both ^VOn ° 'ί? 'Ι ™ ^{111 Ov} f ^{shot of} 0.5U-acetic _{fibrils and} fibril aggregates to understand ^ n ¹ L- required is less than _the relatively long yarn-like formation is-300 minutes, preferably less than 150 micro _{45 illustrate the} The expression "fibrous" thus includes grooves. _{also products; in which the} fibrils are single particles

Acid and gel are in the mixture in the form and are not aggregated,
parts used to achieve a molar ratio in the products according to F i g. 2 have widths from aluminum to acid anion of about and thickness of the fibrils usually the same 0.5: 1 to 4.0: 1, especially 0.75: 1 to 1.5: 1.5 degrees and are usually less necessary is. The mixture is first heated to about 15, but not much less than about 3 ΐημ. a temperature which the reflux temperature preferably does not exceed a value of 3 to 10 πΐµ in order to cause carbon dioxide evolution, especially a considerably small one, and presupposes the heating after cessation ren diameter of about 4 to 7 πΐµ.
the evolution of gas takes about 10 minutes to 7 hours 55 The diameter range relates to the autogenous pressure at around 140 to 180 ° C. Particle diameter in various products.

It was noted that associations of one of the characteristics of the inventively manufactured

Fibrils in the form shown in FIG. 1 shown under BiI- th products is that the diameter of the

formation of fibers, which form a super- particle of a given product of particles

have colloidal size and are very advantageous 60 particles surprisingly constant and that the

have proven. The shape of the particles in Aqasolen diameter of each particle on its entire

can be determined by being substantially uniform with length, while the

Water can vary greatly to an Al ₂ O ₃ content of about 0.1% or particle length. It is 100

preferably diluted to a lower concentration, up to 1500 ηΐμ; preferred products have a

dries and the dried material with the elec- 65 fibril length of about 100 to 700 ιημ.

electron microscope examined. The redispersible powdery pro-

Depending on the heating time and temperature and products that are obtained from aqueous systems by drying

the ratio of alumina to acid residue obtained have shorter fibrils and one

11 12

slightly smaller surface than in the brines, from The resistance of the products to the acid

which they were received. So such pro-attack is higher than that of the starting materials and

ducts have a fibril length of 25 to 1500 πΐμ than that of, in a known manner, below the

point. Preferred powdery products have the boiling point of precipitated aluminum oxide hydrate,

a fiber length of 50 to 700 ηΐμ. The surface 5 Depending on the temperature and time

and other peculiarities of such powdery test conditions in the autoclave treatment

products fall within the limits specified here. the sols produced according to the invention are different

Such products have three different types for a specific amount of aluminum oxide

Surface area of 200 m ² / g a diameter of degrees of polymerization, namely something not polymeric

6.65 ηΐμ and with a length of 25 ΐημ an axially-ionized aluminum oxide, some partially polymeric

ratio of 3.76: 1. In the case of a specific “cores” and the completely polymerized

area of 400 m ² / g is the aspect ratio product. As a result, the solution curve has the

7.5: 1 if the product has a fiber length of 25 ηΐμ F i g. 6, in which the percentage of the non-polymer

having. alumina, expressed as Al

The specification of the particle size and shape relates to 15 of the ordinate against time (abscissa values)

refer to the average fibril particle, e.g. B. is worn, the following features: The

the average width of all particles, etc. The intersection point X at time zero with the ordinate is

however, the individual fibrils in the products are non-zero and the curve is not complete

Because of its surprising evenness to the straight, it consists of the steeper, straight

for the most part about the same dimensions. 20 running part XY for the time up to the beginning

The products made according to the invention have the depolymerization reaction and the less

generally a specific surface area between roughly steep curve parts YZ for the time after the start

200 and 400 m ² / g; Products with a specific of depolymerization.

Surface areas between about 250 and 350 m ² / g are usually preferred at the end of the autoclave treatment. 25 Highly non-polymerized aluminum oxide

How far the purified solution of the colloidal has remained, is the percentage of dissolved aluminum-aluminum oxide that can be reduced without adding minium oxide to time zero not equal to zero; because becoming viscous depends on the specific surface area of the colloidal particles present at the beginning of the titration. Thus a merized aluminum oxide appears immediately as such in a purified sol of colloidal aluminum oxide. If this amount of aluminum oxide is monohydrate, from which subtracts most of the free from that which has been removed at all other time ions and in which the particle points is obtained, one of two obtains a specific surface area of 200 m ² / g have clearly defined parts consisting of the curve leading to a stable flowable sol with an Al ₂ O ₃ zero point (cf. FIG. 8).
Reduce the content by 15 ° / o. If the boehmite fibers 35 The steeper part XY near the start of the reaction a specific surface area of about 400 m ² / g should have been smaller from the depolymerization, the sol can result after the removal of the large cores. The less steep rectilinear part of the anions to about 10% Al ₂ O ₃ con- Part YZ illustrates the depolymerization of the fibrous boehmite formed according to the invention without its flowability. loses. 40 If one uses this YZ part of the curve to

The fibrous boehmite particles are not able to depolymerize the products

neatly stable. Unlike previously known aluminum, the steep initial part XZ can be related to

minium oxide sols and particles they can be rectified into what- on the aluminum oxide that is made out

These are heated to 100 ° C for a long time, the depolymerization of the fibrous boehmite

without deriving their spatial or crystalline form 45 during this part of the reaction. if

changes. this amount is then derived from the total amount of the

The suspension of the fibrous boehmite white aluminum oxide is drawn off, following a curve

sen flow birefringence. F i g. 9 obtained, the depolymerization

The fibrous speed of the fibrous alumina-alumina monohydrate products produced according to the invention have illustrated the 5 ° monohydrate cores,
characteristic X-ray diagram of boehmite. The amount of these cores is determined from the cut - they do not tend to merge into other crystalline forms at the point of the product depolymerization line, as determined by the ordinate (point Y ' in FIG. 8), as previously known,
synthetic boehmite particles, e.g. B. determined from The curve of FIG. 10 is obtained by adding aluminum salt mixtures to precipitated gels, which is 55 the increase for the depolymerization of the cores case. corrected, and is for the inventively obtained

The electron diffraction spectrum of the fibrous product is characteristic. From curves of the

In the case of aluminum oxide monohydrate, which is derived from a species of FIG. 10, the 0 values of the products

thin dispersion obtained on the electron diffraction.

60 The value of Θ determined in this way is higher than that borrowed from that of an arbitrarily aggregated preferred starting material, it is accustomed boehmite. borrowed more than 10 and preferably more than 50. He

However, the fibrous produced according to the present invention usually exceeds about 400 minutes

Boehmite still shows a considerable resistance - not.

ability against attack by acid. It is suitable 65 The obtained with the method according to the invention

therefore for use under conditions under ten aqueous suspensions can before or after

those known aluminum oxide forms unsuitable for concentration in organic liquids, e.g. Am

are. aliphatic alcohols, methyl ethyl ketone, acetone,

13 14

Acetonitrile or butyl acetate, which are at least partially 241.4 g of aluminum chloride hexahydrate in are miscible with water, are dispersed. Often 1000 g of water dissolved. Then you put the Aluist It is advantageous to carefully adjust the pH of the aqueous minium chloride solution beforehand to 27 g of aluminum-aluminum oxide dispersions z. B. by adding powder to. At the beginning of the aluminum addition, ammonium hydroxide or other bases or with 5 the solution is heated to 65 ° C to aid the reaction of anion exchange resins to about 5 or, whereupon, with vigorous stirring, the rest of the to increase about it. Aluminum is added. The reaction proceeds

The products can also be in any then exothermic with evolution of hydrogen,

other organic solvent or a solution of the basic aluminum

Any other organic liquid dispersed in io chlorides contains 8.00% Al ₂ O ₃ and 8.43% Cl, what

will. an alumina concentration calculated as

The drying then takes place, for. B. by azeotropic Al ₂ O ₃ , of 0.90 mol / l. The solution owns

Distillation, being a very fluffy dry - a specific gravity of 1.1388 at 25 ° C

product remains. For products with a high specific pH of 2.96 and a specific conductivity of

fischer surface, the organic liquid is 15 96 600 microsiemens / cm; Θ is less than a minute,

preferably separated by dissolving this solution over their critical parts by volume with water

heated at the table and then the vapors are removed. filled up to 100 parts of the room. The aluminum content

The azeotropic distillation of the brine of the fibrous dilute solution, _{calculated as Al 2} O ₃ , amounts to boehmite in addition to purification 0.09 mol / l and the acid residue concentration (chloride) by adding the after the azeotropic 20 0.271 Minor. The solution has a pH of 4.01 and the residual water is distilled off.

Flash evaporation is separated. This will put the solution in a sealed jar the product is not only heated to 160 ° C for 16 hours in the form of a dry container; here falls fluffy powder isolated, but surprisingly - 35 from the initially water-clear solution in the form of fibers also freed from the acid residue. ger boehmite, which by gently shaking it easily

The cleaning efficiency in terms of which is dispersible. The suspension has a pH

Acid residue depends on the specific surface area of 1.78 and a specific conductivity of

fibrous boehmite. At a specific 27100 microsiemens / cm.

Surface up to 200 m ² / g results in a very effective 30 An examination of the boehmite under the elec-

Cleaning, whereby e.g. when venting, about 99% electron microscope with 25,000 times linear disintegration

the chlorine ion content can be removed. The enlargement shows that the fibrils are for the most part

The degree of efficiency drops if, according to this method, axis ratios of at least 50: 300 and

Products with a higher specific surface treated have a diameter of 5 to 10 ηΐμ. The fibril

delt. So z. B. in the treatment of a profile 35 show a certain parallel alignment under images

ducts with a specific surface area of aggregate bundles. This product has that

400 m ² / g only 90% of that originally present in FIG. 2 appearance shown.

Chlorine ions removed. ".

The products of this treatment are characterized by B e 1 s ρ 1 e 1 Z
especially with specific surface areas of less than 4 ° Basic aluminum chloride with a molar 250 m ² / g due to its easy dispersibility in Al ₂ O ₃ : Cl ratio of 2: 3, aqueous and nonaqueous liquids are selected according to Example 1. In the case of 241.1 g of aqueous aluminum chloride liquids, they are dissolved in acidic and alkali crystals in 1000 g of water and are dispersible in this solution. evenly and slowly 81.0 g of aluminum powder

Similar readily dispersible dry products 45 add until the metal has dissolved and none

can also be done by spray drying of aqueous hydrogen evolution more. The solution

Sols or organosols, which are described in the above- is initially preheated to 50 to 60 ° C, whereupon the

n manner are produced, by azeotropic distillation further reaction exothermic at 80 to 90 ° C

lation or by freeze-drying such brine,

will hold. 5 ° The reaction product is clear as water and somewhat

For the fibrously viscous solution produced according to the invention, which is more viscous than the solution according to Example 1. The boehmite solution is extremely large and contains 15.4 percent by weight Al ₂ O ₃ and 8.05 Ge applications. So the product can weight percent Cl, which corresponds to a molar ratio Al ₂ O ₃ : Cl z. B. as a thickener for oils for the production of 0.67: 1.00 and an Al concentration of greases, as a treatment agent of 55 corresponds to 1.86 mol / l. The solution has a density of gastric ulcers, as a thickening additive to near- of 1.2244 g / cm ³ at 25 ° C, a pH of 3.11, and as an additive to natural and synthetic a specific conductivity of 77,600 micro-rubbers to improve strength and siemens / cm; Θ is less than a minute.
To impart abrasion resistance as a filler for plastics, and in space is filled 5 parts of this solution with destilbesondere after previous staining of the boehmite, ⁶ ° of water required to 100 parts by volume and shaken around the plastics certain colors, the mixture. In this solution, the aluminum alumina is used as a filler for cigarette tobacco and for many other oxyd in a concentration (as Al ₂ O ₃ ) of purposes. 0.093 mol / l, the chlorine in a concentration of _K. -I ₁ contain 0.140 mol / l. The water-clear solution has an example! 65 has a pH of 4.08. She will be locked in a

A solution of basic aluminum chloride glass container in an autoclave at 160 ° C for 5 hours according to US Pat. No. 2,196,016. After cooling down it has become white produced in the same way: precipitate formed. Under the electron micro-

15 16

The scopes and radiographs are used to relax the hair for a very long time, to remove the alcohol and acid residue

like boehmite fibrils were found. Virtually all of them can be removed. The product is then used for removal

these boehmite fibrils have, through an alignment, dried residual butanol in a vacuum,

in which they are parallel to each other on each side,. .

"Tactoids" formed; these little tactoids are S example 4

even again in the manner shown in Fig. 1 end. According to U.S. Patent No. 2,763,620

at the end with the formation of very long fiber bundles from an ln solution of a commercially available sodium

Bohtnite aligned. aluminats made in water, their molar ratio

The fine hair-like end fibers or fibrils Al ₂ O ₃ : Na ₂ O is 0.966: 1. 1000 parts of the room

made of aluminum oxide are about 3 to 10 πΐμ wide and io ser solution together with 1440 parts of space

about 0.5 to 1.0 μ long and gradually lower at 25,000 times the linear 0.5 normal aqueous hydrochloric acid

Clearly visible magnification; the individual tactoids stirring in the course of one hour in a reaction

are about 0.25 to 0.5 μ wide and up to 5 to 10 μ vessel, which is 300 parts by volume with hydrochloric acid to pH 4.25

long. The sample does not contain any other crystalline acidified distilled water at 95 ° C

Determine forms. 15 entered at such a speed that the

The suspension of this easily dispersible low pH value is kept at 4.25,
the shock has a pH of 2.03. The suspension The result is an opalescent, stable aluminum that easily runs through filter miniumoxide sol, the 0.867 percent by weight of Al ₂ O ₃ paper, during vacuum filtration. When dry, it forms a contains, a pH of 4.20 and a specific guide thin film, which when removed from the base 20 has a capacity of 24,000 microsiemens / cm; Θ remains coherent and translucent. is less than a minute.

. This aqueous aluminum oxide dispersion is in

Example 3 a sealed glass jar 16 hours at 150

2442 g of aluminum chloride hexahydrate are dissolved at temperatures of up to 160 ° C., a very viscous, cloudy 1000 g of water being obtained when this solution is heated to about 50 to 25 bes, weakly thixotropic, stable boehmite sol. 60 ° C and then sets slowly and evenly under The sol has a pH of 2.0 and a specific good stirring to 135 g of aluminum dust. After an- conductivity of 31500 microsiemens / cm. It shows extensive warming, the reaction proceeds exothermically when stirring between crossed polarizations with evolution of hydrogen; the temperature remains flat flow birefringence,
to about 80 to 90 ° C. 30 In the electron microscope the aluminum appears

The solution is almost as clear as water, but noticeably fibrous visminium oxide; in the micrograph kos. Analysis of the solution reveals that there are also large cubic sodium chloride crystals containing 22.73% Al ₂ O ₃ and 7.58% Cl, which is a mole detection. The aluminum oxide fibrils have an Al ₂ O ₃ : Cl ratio of 1.04: 1. The diameter of about 5 to 7 ιημ and axis solution has a density of 1.322 g / cm ³ at 25 ° C, 35 ratios of about 100: 1. They are not aggregated to the largest pH of 3.81 and a specific conductivity th part, but are easily directed from 53,400 microsiemens / cm. 10 parts by volume of this sideways with formation of tactoids, if solution are made up with distilled water to get the pH-value of the sol with sodium hydroxide 100 parts by volume. The clear solution has increased to 4.50. The product has something like that in FIG. Fig. 3 shows an alumina concentration of 0.295 mol / l, 40.

a chloride content of 0.283 mol / l and a pH of The sol of the fibrous boehmite is used to develop

4.51 on; Θ is less than a minute. removal of excess sodium chloride

3.3 parts by volume of the concentrated product obtained in this way is purified by making it up to 100 parts by volume using Zeil solution of the basic aluminum chloride with glass foils for 66 hours of static dialysis against distilled water. 45 distilled water subjects. The dialyzed sol This solution contains aluminum oxide in a con-has a pH of 4.0 and a specific reference concentration of 0.097 mol / l and chlorine ions with a capacity of 255 microsiemens / cm; it contains 0.0934 mol / l; it has a pH of 5.20 and a specific value of 0.890% Al ₂ O ₃ and 0.01% Cl. The sol is now fish conductivity of 6190 microsiemens / cm; Θ opalescent; practically its entire on thixotrol is less than a minute. 50 pie based viscosity has disappeared. It shows

Part of the dilute solution becomes a strong flow birefringence and further

closed glass container for 16 hours at 160 ° C when swirling in a bottle streak effects,

heated. Examination of the particles of the dialyzed

The product obtained on heating is a stabi- sol under the electron microscope shows Boehmitles, sediment-free, opalescent, film-forming, 55 fibrils that are not parallel to aggregates zuuthixotropes Aluminum oxide sol, in which the aluminum is stored. All cubic sodium chloride minium oxide in the form of fibrous boehmite crystals have disappeared. This product has that is present. The product has a pH of 2.51 and in FIG. 2 appearance shown.

a specific conductivity of 10 650 micro- If you put the dialyzed sol on a glass or

siemens / cm. It has a 50,000-fold linear displacement of ⁶ Q mercury surface, it dries easily

enlargement that in Fig. 3, but is of a smooth, transparent, uninterrupted, too-

a little wider. coherent, solid boehmite foil. The slide is

A portion of a prepared in the above manner, in this form obtained during casting water-

but fibrous boehmite particles with a diameter of 7 ηΐμ, but becomes insensitive to water

knife and from V2 to 1 μ length containing Sols 65 foil that of strong acids, such as hydrochloric acid, not

is attacked by azeotropic distillation at constant, transferred after a few hours

Volume dispersed in n-butanol. The solution is heated to between 600 and 1000 ° C. Hydrophobic, self-

heated in the autoclave to 300 ° C, whereupon the pressure-bearing, coherent foils made of the fiber

17 18

shaped boehmite are readily available if one uses Al ₂ O ₃ and 7.15 percent by weight NO ₃ ; Θ is under

the dialyzed sol of this example in one minute with silicone.

Pour oil-coated glass dish and then the sol 6.66 parts by volume of the freshly prepared solution let dry up. The resulting foils can be diluted to 100 parts with distilled water

from the base in the form of flat structures diluted by at 5; the diluted solution has a pH of

for example 75 to 125 μ thickness can be deducted. 4.77 and a specific conductivity of 6310

_. . ₁ microsiemens / cm.

Example Λ By heating the diluted in a glass reaction vessel for 16 hours, the inlet and outlet pipes connected to a thermo-solution in a closed glass vessel, reflux condenser, heating element and a stable, apalescing, sediment circulation pump are free Receiving boehmite sol, which is provided with a double flow, shows 100 parts of volume to pH 5.0 collapse. The boehmite is fibrous, and placed in distilled water. End fibrils have a width in the colloidal range. The turbulent circulating flow will have axial ratios of about 50: 1. The product 80 ° C simultaneously within 6 hours has a 0.250-15 that in FIG. Appearance shown in 2, but is broader, molar aqueous solution of AlCl ₃ · 6 H ₂ O and a. 0.758 molar aqueous NH ₄ OH solution was added at rates such that the pH in Example 7 was maintained in a concentrated colloidal range of 4.0 to 5.0. The resulting translucent, opalescent sol as in Example 5 with particles with an aluminum oxide sol with a pH of 4.34 has a specific surface area of 200 m ² / g. Aluminum oxide concentration, calculated as Al ₂ O _3. This sol is stirred vigorously by means of a high-speed stirrer at 0.129 mol / l and a chloride concentration; using the bicarbonate form of a (an excess over the stoichiometric amount of the an ion exchanger, the chlorine ions are _{equivalent to the amount of chloride equivalent to the NH 4} + ion) of 25, a pH of 5.2 and a chlorine of 0.0621 mol / l on; Θ is less than a minute. The ion concentration of 0.01% removed. The Al ₂ O ₃ examination under the electron microscope shows the concentration at this point is 1.0%. This no anisotropic crystalline alumina; The purified sol is evaporation in a vacuum umpteen crystals consist of ammonium chloride and collapse into a flowable, film-forming, stable colder under the bombardment of electrons. This organic dispersion of fibrous boehmite with gangue sol does not produce any coherent _{transparent films on glass with an Al 2} O ₃ content of 15 percent by weight. narrowed. In another, similar preparation, the aluminum oxide sol is in the autoclave for 1 hour, a sol with an Al ₂ O ₃ content of 18.5% is heated to 150 to 160 ° C, which is very viscous, which is also stable , flowable product passes through a loose, translucent boehmite sol, which represents 35.
Flow birefringence shows. The exam under. . the electron microscope shows that the aluminum example 8 is in the form of minium oxide fibers. The boehmite sol has a solution of basic aluminum chloride with a pH of 2.72 and a specific conductivity, an Al ₂ O ₃ content of 24% and a molar value of 43,200 microsiemens / cm. 40 Al ₂ O ₃ : Cl ratio of 1: 1 is converted to an Al ₂ O ₃ -Ge-If this sol is diluted for 15 days at room temperature of 3%. 3000 parts by weight of the wastur through cell glass against distilled water dialyzed solution are siert in an autoclave, the pH is 5.80 and the specific conductive Pyrex glass, which with a spiral, capacity 13.5 microsiemens / cm. The dialyzed vented capillary head is fitted. The autoclave Böhmitsol is less cloudy than the original 45 is surrounded with water and in 4 hours on Böhmitsol, but still quite viscous and shows heated at 160 ° C and 3 ³ A hours on this temple of easy movement still flow birefringence. temperature kept. The autoclave and its contents are then cooled to 58 ° C. under the electron microscope.

shows that the dialyzed sol is now a solid. After heating, the product has a half-

contains only fibrous boehmite, while the am- 5 ° represents a stiff gelatinous mass, which when moved easily

monium chloride crystals have disappeared. That becomes liquid and pourable. The sol shows between

Boehmite fibrils have a diameter of roughly crossed polarizer disks.

3 ΐημ and axial ratios of more than 100: 1. refraction. The product has at 50,000 times the line-

The product has the one shown in FIG. Appearance shown in FIG. 2, the enlargement in FIG. 2 appearance shown,

however, it is shorter and thinner. The sol forms when 55 An electron diffraction pattern of the dried sol

it is dried on a glass support, easily shows that the aluminum oxide is present as boehmite,

transparent foils. Radiographically, an aluminum oxide mono-

. . hydrate of small particle size with the boehmite

For example ο determining the crystal lattice, which is a special line

A solution of 60 2.73 Å preheated to 80 to 90 ° C shows. When titrating for unpolymerized

g A1 (NO ₃ ) ₃ 9 H ₂ O in 1000 g distilled water-aluminum oxide gives a value of 19.2%,

54 g of aluminum powder are gradually added to this. while the pH is 3.18.

An exothermic reaction takes place with abundant The turbidity of a _{0.1% Al 2} O ₃ sol is

Development of reddish-brown fumes from oxides measured with an electrophotometer Nitrogen. 65 Fisher using a blue filter on the

A water-clear solution with a pH permeability scale of 70.4% is obtained. The analysis of the original

of 4.06, a specific conductivity of initial sols, gives a silica content

500 microsiemens / cm, 9.57 weight percent from just 53 ppm.

For measurements of the flow birefringence of this sol to obtain a common particle length L _f of 1200mn, a polydispersity of 1.7 P ηΐμ ² and an average Teilcheneigenanisotropie ~ Ä to 5.8 x 10 ~ ² only. Long by 30 minutes krätiges stirring of the sol is the apparent length of the particles to 670 mn with a polydispersity of 1.5 and an average ηΐμ ² Teilchenanisotropie of 5.5-10 ~ ² reduced. When depolymerizing with acid, the percentage of cores is 9.1 and thus a corrected depolymerization half-time Θ of 160 minutes.

If this sol is air-dried on a glass plate at a _{thickness corresponding to about 5 mg Al 2} O ₃ / cm ² , a coherent film is obtained.

Part of the sol is freed from anions by gelling it to pH 10 with ammonium hydroxide, then washing with hot distilled water and adjusting to pH 10 with ammonia until the filtrate is chloride-free. After washing, the filter cake contains 15.7% Al ₂ O ₃ and 0.005% Cl, which corresponds to an Al ₂ O ₃ : Cl ratio of 350: 1.

The filter cake is made into a paste with water to form a 5% dispersion of aluminum oxide in water. This 5% sol is quick frozen in a bath of dry ice and acetone by rapidly rotating a freeze drying flask containing the dispersion to obtain a thin frozen film of the alumina dispersion on the flask walls. Freeze-drying overnight gives a very light, white, fluffy or flaky powder as the dried product which has a specific surface area, determined by nitrogen adsorption, of 251 m ² / g, contains 74.3% Al ₂ O ₃ and at a Pressure of 0.21 atm has a bulk density of 0.250 g / cm ³ .

The analysis of the freeze-dried material in a high-temperature X-ray camera shows that at 25 and boehmite is present at 200 ° C, but at 400 ° C a new phase begins to appear, the broad one on which Has bands indicative of the presence of kappa aluminum oxide. This new phase stays at 600 and 900 ° C.

Further analysis of the X-ray diffractometer curve of this sample at room temperature shows the following:

The exact "^" distance, which corresponds to the 020 plane of this sample, is 6.231. The line half-widths and the intensities of the thicker lines are given in the following table.

»Λ-spacing Half width of
Inflection line Intensity 1/1 $ Ä in degree 2 Θ 6.23 2.24 100 3.17 2.80 20th 2.35 1.68 34 1.86 1.40 41 1.85 1.44 41 1.435 1.44 15th 1.38 1.68 9

The intensity of the most intense line of this spectrum, at 6.23 Å, is related to that of the same line of a low surface area, well crystallized boehmite as 23: 100. The half-widths in degrees 2Θ for some lines of a 5-20-ii fraction of α-quartz are, determined with the same device:

4.27A = 0.20; 3.48 A = 0.20; 2.46 A = 0.25; 1.82A = 0.20; 1.54A = 0.30.

The infrared spectrum of this sample is shown in FIG. 5 shown.

A dispersion of this freeze-dried material with an Al ₂ O ₃ concentration of 0.05% and a

ίο pH of 2 results in a most common particle length L _} of 1400 ηΐμ, a polydispersity P of 7.8 ΐημ ² and an average pond intrinsic anisotropy Ά of 8.8 · 10 ~ ² .

Part of the deionized cake is passed through a coarse sieve with holes about 4.8 mm in diameter.

Knives are pressed into “noodles”, which are air-dried for 18 hours at 50 ° C. The dried white material consists of quite hard and mechanically stable pellets with a specific surface area of 253 m ² / g and an Al ₂ O ₃ content of 75.25%,

with a loss of 1.7% on drying at 110 ° C.

The quantitative determinations of the flow birefringence result in a dispersion produced from this material with an Al ₂ O _{3 concentration}

tration of 0.05% and a pH of 2 a most common particle length of 750 πΐμ, a polydispersity of 2.0 ΐημ ² and a mean particle intrinsic anisotropy of 6.8-10 ~ ² .
Another portion of the deionized filter cake described above is azeotropically distilled with n-butanol to remove the water. The butanol-aluminum oxide dispersion is dried in vacuo at 83 ° C. for 24 hours. The dry, white, very friable powder has a specific surface

of 280 m ² / g and contains 71.7% Al ₂ O ₃ and 0.069% chlorine ions, which corresponds to an Al ₂ O ₃ : Cl ratio of 361: 1. Weight loss at 110 ° C = 0%; C = 2.97%, SiO ₂ = 0.021%. The number of butoxy groups per ΐημ ² surface is 1.3. Under the

With an electron microscope, this powder has roughly the same appearance as the original material. After micropulverization using a sieve with 0.51 mm openings, the product has a bulk density of 0.21 at 0.271 g / cm ^s and a specific upper

area of 270 m ² / g. It can be easily dispersed in n-butanol and in water and shows flow birefringence.

Examination of a dispersion of this powder in water which contains 0.05% Al ₂ O ₃ gives: pH = 2;

most frequent particle _{length L f} = 1030 πΐμ; Polydispersity P = 4 ηΐμ ² ; mean inherent anisotropy]! = 5.8 · 10 ~ ² . An aqueous dispersion of the finely ground product gives: most frequent particle length = 790 μm; Polydispersity = l, 7; mittlereEigenanisotropie = 6,5-10-. ²

Example 9

In the manner described earlier, a solution of basic aluminum chloride is prepared by adding 5 mol of aluminum dust extracted with ether to an 1 molar aluminum chloride solution. The solution contains about 22% Al ₂ O ₃ ; the Al ₂ : Cl molar ratio is 1: 1.
This solution is diluted with distilled water to an Al ₂ O ₃ gel content of 2% and heated in an autoclave in a container made of difficult-to-melt glass to 160 ° C. for 1 hour and kept at this temperature for 4 hours. The product is a

Translucent, thixotropic gel which can be seen in the electron microscope as fibrous particles lets and that in F i g. 2 has the appearance shown. The viscosity is increased by vigorous stirring for several minutes decreased.

A quaternary ammonium ion exchange resin is made from the chloride in with 10% sodium hydroxide solution converted the hydroxide form, washed with water, then converted into the bicarbonate form, filtered and drained.

A portion of the boehmite sol is deionized by slowly adding the ion exchange resin while stirring and passing nitrogen through until a pH value of 5.0 to 5.5 is reached. Between crossed polarizers, the sol shows different colors even without shaking. If a bottle with the sol is left to stand overnight, the sol separates into two distinctly different layers, between which there is a very sharp dividing line. The top layer shows only flow birefringence and is therefore dark with no movement between crossed polarizers, but the bottom layer shows constant birefringence between crossed polarizers. Who relaxes in this floor. The white fluffy powder is dried in vacuo at 80 ° C. for 16 hours. It contains 77.81 _{% Al 2} O ₃ , 0.61% chlorine ions and 2.43% carbon. The Al ₂ O ₃ : CI ratio is 64: 1 and the specific surface is 198 m ² / g, which corresponds to 1.5 butoxy groups per πΐμ ² surface.

This powder can be dispersed in water as well as in n-butanol or other polar organic solvents. The determination of the flow _{birefringence results in an Al 2} O ₃ content of 0.05% in water! -, = 13651 ^. Ρ = Γ7,3πΐμ ² and Z = 3 -lO-A

c) Deionized sol

Part of the non-deionized sol is gelled with aqueous ammonia at pH 10; the gel is filtered and washed free of chlorine ions at 80 ° C. with distilled water which has been adjusted to pH 10 with ammonium hydroxide. The product is washed with distilled water. The deionized cake contains 20.13% Al ₂ O ₃ and 0.02% chlorine ions, which corresponds to an Al ₂ O ₃ : Cl ratio of 350: 1. Obtained by reposing in water

The boehmite contained in the layer is here, in analogy to
crystalline ”.

will

The oriented soil layer is disoriented by adding a small urea crystal. if If the upper layer is concentrated to a concentration above about 2%, more will form from it Amounts of the soil layer. If this sol is further narrowed, the whole sol goes into the paracrystalline Condition over.

d) Butanol drying of the deionized sol

Example 10

a) Non-deionized sol

383 parts by weight of a solution of aluminum chloride (23.5%

Al ₂ O ₃ ;

of basic Al ₂ O ₃ : Cl = 1.1) 00 Part of the deionized cake is freed from water by azeotropic distillation with n-butanol and heated to 300 ° C. in the autoclave, whereupon the pressure is released. The white fluffy powder is dried in a vacuum oven at 84 ° C. for 24 hours. The analysis gives: Al ₂ O ₃ = 77.70%, Cl = 0.072% (molar ratio Al ₂ O ₃ : Cl = 375: 1); Weight loss on drying at 110 ° C. = 2.1%; C = 2.21%, which corresponds to 1.3 butoxy groups per ηΐμ ² surface. The bulk density at 0.21 kg / cm ² is 0.125.

_{23 23}

are diluted to 3000 parts by weight with distilled water. This water-clear solution contains 3% Al ₂ O ₃ ; θ is less than 1 minute. i

40

e) drying the deionized product from butanol

The solution is treated at 160 ° C. for 16 hours. The product is an opaque, white, semi-rigid, 45 cake, gelatinous mass that liquefies slightly when moved. The titration gives 17.0% unpolymerized aluminum oxide. The haze (percentage of light transmission) is _{44.0% at an Al 2} O ₃ concentration of 0.1%.

This sol is at 50,000 times linear magnification the one shown in FIG. 3 shown quite similar.

The X-ray examination of a sample dried at room temperature shows boehmite crystals

A portion of the deionized material obtained by azeotropic distillation with n-butanol is used as the starting material. This organosol is dried in a dish in a vacuum oven at 80 ° C. for 24 hours. Analysis of the white powder shows: specific surface area = 197 m ² / g; Al ₀ O ₃ = 75.81%, Cl = 0.12% (molar ratio Al ₂ O ₃ : Cl of 220: 1); Weight loss on drying at 110 ° C = 0.0%; C = 2.62%, which corresponds to 1.7 butoxy groups per πιμ ² surface.

When redispersing in water in an Al ₂ O ₃ -

and additionally two special diffraction lines 55 concentration of 0.05% one obtains a sol, its at 2.75 and 3.88 Å. Light transmission at pH 3.5 is 42%. One

Determinations of the flow birefringence of the dispersion of the non-finely ground powder in _{sols diluted to an Al 2} O ₃ content of 0.05% and water in an Al ₂ O ₃ concentration of 0.05% with sols adjusted to pH 2.0 give L ₁ = 1670 ηΐμ, pH 2 results in L, = 1520 ηΐμ; F = 9.70 πιμ ² . At P = 19.2 ηΐμ ² . After 30 minutes of vigorous rest 60 redispersion of the finely ground material, L, = 900 ΐημ, P = 0.4 ηΐμ ² and Z = 5.5 · 10 " ^2. one holds L, = 1254 πΐμ; P = 5, 4th

The depolymerization half-time Θ is 280 minutes.

b) Butanol drying of the non-deionized sol

After the azeotropic distillation of the water from the above boehmite sol with n-butanol, the material is heated to 300 ° C. in the autoclave and the pressure is applied. Part of this powder is finely ground using a sieve with 0.51 mm openings. The bulk density is then at a pressure of 0.21 at 0.040 g / cm », the specific surface area is 200 m ² / g. In the electron microscope, no change compared to the state before the finest grinding can be seen.

f) drying the deionized product

of water

Part of the deionized cake is pressed through a coarse sieve to form "noodles" 6.4 mm in diameter. The noodles are dried in a convection oven at 50 ° C and broken into pieces, which are mechanically very strong and can be used as catalysts in the dehydrogenation of alcohols in the vapor phase. Specific surface area = 196 m ² / g; Al ₂ O ₃ = 76.32%; Weight loss on drying at 110 ° C = 0.0%.

Despite their high hardness, the pieces can be easily dispersed in acidified water. The quantitative determination of the flow _{birefringence at an Al 2} O ₃ content of 0.05% gives: L, = 1135 πιμ; P = 4, l πΐμ ² ; Ζ = 6.6 x 10- ^second

g) freeze drying the deionized sol

37.3 parts by weight of the deionized cake are made up by filling with distilled water

150 parts by weight processed into a dispersion with an Al _a O ₃ content of 5%. Since this dispersion is still somewhat viscous, the aluminum oxide content is brought to 3% by adding a further 100 parts by weight of water.

This dispersion is quick frozen in an acetone and dry ice bath by adding the Dispersion containing piston to produce a thin film of the frozen material on the

ίο piston walls rotates quickly. The fluffy powder obtained after freeze-drying this sample using a high vacuum pump has a surface area of 193 m ² / g, a bulk density at 0.21 at of 0.303 g / cm ³ and an aluminum oxide

content of 79.01%. The ultra-red spectrum of this powder is shown in FIG. 5 shown. Redispersing in water at an Al ₂ O ₃ concentration of 0.05% gives: L, = 1408 ΐημ; Ρ = 7.8 ΐημ ² .

The X-ray diffraction analyzes of this sample and of the products according to Examples 8 and 9 are shown in FIG summarized in the following table.

ASTM test standard "D"
A. Uh Example 9, I / h Example 10, g), »Rf«
Ä I / h Half width
Degree Example 8 "D"
A. I / h Half width
Degree 2-0129 6.20 100 paracrystalline 100 freeze dried 6.19 100 1.16 6.21 100 2.24 3.17 100 "D"
A. 100 3.17 33 1.28 freeze dried 3.09 20th 2.80 2.34 100 6.18 100 2.35 26th 0.960 2.34 34 1.68 1.98 60 3.173 50 - - - - - - 1.86 100 2,347 50 1.86 33 1.28 1.87 41 1.40 - - 1.987 80 - - - 1.85 41 1.44 1.77 60 1.87 50 1.78 4th 1.44 1.66 70 1.85 50 1.66 7th 1.20 -. -. - 1.53 60 1,769 40 1.53 5 1.36 - - - 1.45 60 1.661 60 1.45 6th 1.16 - - - 1.43 60 1.530 60 1.44 7th 1.12 1.435 15th 1.44 1.453 50 1.38 70 1.435 50 1.38 10 1.20 1.38 9 1.68 1.31 80 1.396 80 1.22 20th 1,382 20th 1.21 40 1,310 40 1.18 60 1,226 40 1.16 60 1.206 40 1.13 70 1.179 60 1.11 60 1.160 40 1.09 30th 1,135 20th 1.05 60 1.114 40 1.03 50 1,089 40 1.02 40 1.046 - 0.988 20th 1.027 - 0.980 ' 40 - 0.949 ' 60 - 60 0.929 50 60 0.923 I. 60 0.9521 60 0.913 30th 0.9329 60 0.910 60 0.9248 - i 0.901 60 0.9133 60 - 60 0.9024 60 0.8908 60 0.8319 60 0.8276 40 0.8023 0.7768 I.
I. I.

Example 11

Aluminum nitrate [A1 (NO ₃ ) ₃ · 9 H ₂ O] is heated to 275 ° C. for 8 hours. The white product is ground to a fine white powder. This intermediate product contains Al ₂ O ₃ and NO ₃ in a ratio of 1.6: 1; 0 = 1 minute. An aqueous slurry of the powder with an Al ₂ O ₃ content of 8.7% is treated in an autoclave at 160 ° C. for 3 hours.

An opalescent sol with strong flow birefringence, 8.7% aluminum oxide, 3.4% NO ₃ (Al ₂ O ₃ : NO ₃ ratio 1.55: 1), 15% unpolymerized aluminum oxide and a pH of 2 is obtained , 9; an electron micrograph shows a fiber length of 500 πΐμ and an aspect ratio of about 110: 1. The product has the appearance shown in FIG. In this figure, as in some earlier figures and in the three following figures, an inserted line drawing shows approximately the image of the original plate on the basis of which the remaining part of the figure was obtained. As in FIG. 1, a few individual fibers can be seen, but most of the fibers are arranged side by side to form fiber-like bundles 2.

Part of this sol is deionized with the aid of ion exchange resin. By sieving off the resin, an opalescent sol is obtained which has the following parameters: pH = 6.5; specific resistance 3600 ohm / cm; Θ = 178 minutes; unpolymerized alumina 6.8%; specific surface area 278m ² / g; L, = 562n ^.

Part of the sol is gelled with dilute ammonium hydroxide at pH 8.3 and 12 hours at 180 ° C dried, giving a lumpy, solid mass that can easily be finely ground. That white, free flowing, dry powder is easily dissolved in water to a sol with an alumina content dispersible of 2.1% and a nitrate content of 0.15%. When drying the sol on a A hard, cohesive, abrasion-resistant film is obtained on the glass plate.

Example 12

The mixture is heated 1171 parts by weight of aluminum nitrate [Al (NO ₃ V 9 ^H 2 °] ¹² hours 280 ° C and subjecting the lumpy product of the pulverizing The analysis gives: Molverhätlnis Al ₂ O _3: NO ₃ = 2.8:. 1; Θ = 2 minutes The product is _{slurried in water at an Al 2} O ₃ concentration of 8.4% and treated in an autoclave at 160 ° C. for 3 hours.

An opalescent, thixotropic sol is obtained with the following parameters: pH = 3.4; 8.4% Al ₂ O ₃ , 1.9% NO ₃ ; Al ₂ NO ₃ : NO ₃ ratio 2.7: 1; unpolymerized alumina 5.8%; strong flow birefringence; Fiber length about 600 πιμ; Axis ratio 25: 1; L, = 610 πΐμ.

This sol is deionized with the aid of ion exchange resin. The resin is sieved off, giving an opalescent sol with the following parameters: pH = 4.1; specific resistance 500 ohm / cm; 5.46% Al ₂ O ₃ , 0.024% nitrate, unpolymerized alumina 2.79%; Θ - 105 minutes. When dried on a glass plate, this deionized sol provides a clear, cohesive film.

This product is shown in Figure 12; there are As with 1, a few individual fibrils can be seen, but most of the fibrils are in fiber-like bundles 2 stored together.

Example 13

A sample of aluminum nitrate [A1 (NO ₃ ) ₃ · 9 H ₂ O] is heated to 275 ° C. for 6 hours and then ground, resulting in a white powder with an Al ₂ O ₃ : NO ₃ molar ratio of 1.26 and a value of Θ of a minute received. This powder is slurried in water at an Al ₂ O ₃ concentration of 5.4% and treated in an autoclave at 160 ° C. for 3 hours. A product is obtained with the following

ίο key figures: 5.4% Al ₂ O ₃ , 2.6% NO ₃ , non-polymerized aluminum oxide 13%; pH = 3.2; L ₁ = 1085 and θ = 151 minutes. The fibrous aluminum oxide monohydrate shows strong flow birefringence and, as electron micrographs show, has a fiber length of about 1000 ηΐμ and an aspect ratio of about 280: 1. The product of this example is shown in Figure 13; it contains a number of individual fibrils 1, but like 3 it also has a certain agglomeration of fibrils

so there are bundles of two, three or more fibrils.

Example 14

A sample of aluminum nitrate [A1 (NO ₃ ) ₃ · 9 H ₂ O]

is heated to 275 ° C for 7 hours and then ground, giving a white powder with a molar ratio of Al ₂ O ₃ : NO ₃ of 1.45 and a Θ of one minute. This powder is slurried in water at an Al ₂ O ₃ concentration of 2.4%

and treated for 4 hours at 160 ° C in the autoclave.

A product is obtained with 2.4% Al ₂ O ₃ , 1.2% NO ₃ , 15.8% unpolymerized aluminum oxide, a pH of 1.8 and Θ = 182 minutes. The fibrous boehmite shows strong flow birefringence and has a fiber length of about 500 ΐημ and an aspect ratio of 30. The product is shown in FIG. 14; the aluminum oxide fibrils 1 are only very weakly bound together.

Example 15

A completely deionized sol prepared according to Example 3 forms a solid within one day Gel when the pH of the deionized sol is between 5.5 and 6.5. However, if you get through Addition of acetic acid reduces the pH to 4.5, a sol can be obtained that over time is stable for 6 months or more. In the same way you can stabilize this deionized brine Use formic, propionic, hydroiodic, hydrobromic, nitric and perchloric acids. These Acids are added in small amounts, which only need to be sufficient to bring the pH to around 4.5 to bring.

Example 16

A solution of 1 part A1 ₂ (SO ₄ ) ₃ · 18 H ₂ O in 2 parts of distilled water and a solution of 1 part of Na ₂ CO ₃ in 4 parts of distilled water are allowed to flow simultaneously with stirring into a reaction mass in an open container . The molar reactant ratio, CO ₂ : Al, is kept at 1.67 ± 0.02. After the precipitation, the gel slurry is filtered on a suction filter. The filter cake is washed nine times on the suction filter with distilled water at 70 ° C., in each case with the amount of space corresponding approximately to its volume. 38 parts of washed cake are transferred to a stirred kettle and

509 660/423

Claims (1)

27 28 mixed with 10.2 parts of distilled water. In the sol and in the end product, the aluminum mixture is homogenized in that it is four times nium oxide in the form of a fibrous boehmite.
pumps through a centrifugal pump. The homogenized slurry gives analytically 7.94% Al ₂ O ₃ , claims
0.010 ° / Na, 0.054 ⁰ Zo SO ₄ and a ratio Na: Al 5 of 0.0028 and SO ₄ : Al of 0.0036. 2200 parts of the 1st method of making fibrous The suspension is mixed with the boehmite for 24 hours at 25 ° C. ages and then with 1218 parts of distilled water crystal lattice by heating aqueous AIu- and 82.4 parts of glacial acetic acid mixed. The mixture is miniumoxide dispersions at temperatures above in a paddle mixer equipped with half of the atmospheric boiling point of the water ben heated to boiling and 5 minutes under reflux sers, characterized in that one held to drive off carbon dioxide. The reac- an aluminum oxide, which is concentrated in tion mixture is made from rust hydrochloric acid in a stirred autoclave at 98 ° C in less than 10 minutes Free steel heated to 160 ° C within 24 minutes can be brought to half the solution, in the form of a and kept at this temperature for 1 hour. The 15 in "aluminum oxide", calculated as Al ₂ O ₃ , min- Batch is cooled to 70 ° C in 10 minutes and at least 0.05 molar, but not more than discharged from the autoclave. The obtained through 3 molar aqueous dispersion, which also has the Apparent, flowable sol gives analytically 4.96% remainder of a monobasic acid with one at 25 ° C Al ₂ O ₃ and 2.40% CH ₃ COOH. The fibers have a measured dissociation constant greater than specific surface area of 301 m ² / g; L _f = 279 ΐημ. 2o 0.1 in a concentration of at least 0.05 In the same way and using equi- to about 4.2 mol / l, as long as one temperature Equivalent molar amounts can be brine of a similar temperature in the range from above 120 to 250 ° C Kind of heated with iodic acid, trichloroacetic acid, perchloric acid until the conversion of aluminum oxide and hydrobromic acid residues in place of the chlorine in fibrous aluminum oxide monohydrate with make hydrofluoric acid. 25 the boehmite crystal lattice to the desired . . Extent is done. Example 17 ₂ Method according to claim 1, characterized in that From Aquasolen, which is produced according to Example 16, indicates that it is a starting dispersion, dry, free powder is used by spray-drying, the concentration of which is made of aluminum-flowing, redispersible powders. 30 oxide, calculated as Al ₂ O ₃ , not more than The spray drying is a translucent sol is 1.5 mol / l and is subjected to the acid residue concentration, which has the following key figures: tion between about a quarter of the Al ₂ O ₃ -Mo- _{0 /} αϊ r »ς ης larity and the sum of this molarity and «/ 0 CHXOOH 2.37 'VvfS,, _A -u λ λ -, α λ u I _{1 m} 287 ³⁵ Method according to claim 1 or 2, characterized Specific surface ', "mV / g"'.'//.'. [ 307 indicates that the dispersion is after Average fibril ^length (be f ™ _{heating T} ^{treated in such a} way that the basicity of the agrees after the spray mist aluminum salt is increased, whereupon the • tv _m ο on dispersion to a temperature in the range of mk), mu Ιου _o "f. _o - _o , -, ■. · .. '* 40 80 to 375 ° C heated. The powdery dry product is free flowing 4. The method according to claim 1 to 3, characterized ßend and 100% dispersible in water; it has characterized that one follows the basicity of aluminum Key figures: by increasing the minimum salt in the dispersion % Al ₀ O ₃ 72.2 the dispersion with an anion exchange ° / o CH ₃ COOH 8.0 45 shear treated in bicarbonate form. L _f , τημ 277 Specific surface, m ² / g 281 Considered publications: <9, in minutes 80 Gmelin's Handbook of Inorganic Chemistry, 9, Average fibril length (loading system no. 35, part B, p. 100; according to the spray mist technology 50 Angewandte Chemie, 65th year (1953), No. 22, nik), ma 110 p. 549. For this purpose 2 sheets of drawings 5OS 660.423 8.65 © Bundesdruckerei Berlin