NO152746B - SYNTHETIC CRYSTALLINIC ALUMINUM SILICATE AND USE THEREOF IN DETERGENT MIXTURES - Google Patents

Abstract

SYNTHETIC CRYSTALINIC ALUMINUM SILICATE AND ITS USE IN DETERGENT MIXTURES.

Description

The present invention relates to a synthetic crystal

English aluminum silicate obtained by adding an alkali silicate solution to an alkali aluminate solution, mod-

at elevated temperature and subsequent separation of the obtained aluminosilicate crystals, and the special

peculiar to the synthetic crystalline aluminum silicate according to the invention is that the crystalline aluminum silicate is obtained by mixing a sodium aluminate solution cooled to a temperature between -10 and +10°C with a sodium silicate solution at ambient temperature, subjecting the homogeneous mixture for a gel formation at a temperature between 60 and 100°C and maintaining this temperature until the conversion to the crystalline phase is complete, the concentration of the solution of the two reaction participants being adapted so that at the end of the maturation the liquid phase exhibits a content of at least 70 g/l of and at least 10 g/l of A^O^ in equilibrium with at least 200 g/l molecular sieve.

Advantageously, the crystalline aluminum silicate is used

as an additive in detergent mixtures.

These features of the invention appear from the patent claims.

The invention thus relates to a new synthetic crystalline aluminum silicate, in fine distribution suitable for use in detergents.

The usual production method for synthetic zeolites

has been known for a long time (Kurnakow. Journal de 1'Académie des Sciences d'USSR, 1381 (1937)). In this production method, a solution of silicate and aluminate is brought into contact with each other to obtain a gel which is subjected to crystallization.

The formation of such aluminosilicates depends on a wide range of factors, such as the concentration of the reaction components, the temperature when the components are brought into contact with each other, the temperature during the ripening phase, the duration of the ripening and the homogeneity of the environment. Methods such as e.g. grafting to obtain aluminosilicates with specific properties, e.g. production of faujasite in an environment already containing a zeolite of type 4 A, see French patent application No. 2,281,315.

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The influence of certain factors and especially the presence of sodium hydroxide and the alkalinity of the reaction mixture has already been demonstrated by Kurnakow.

In French patent document no. 1,404,467 it is demonstrated that the concentration of NaOH in the liquid environment in which the precipitate of aluminum silicate is formed has a decisive effect on the regularity and purity of the obtained crystals of zeolite 4 A, and that the more this concentration is kept constant the the greater the purity and homogeneity of the zeolite.

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Until relatively new! date have the proposed methods

been of a discontinuous type and this relationship is explained on the basis of the complex structure of the crystals which usually require a relatively long time for their formation from poorly oriented compounds and coincidences at the transition between the liquid and solid phases in the reaction mixture.

It has therefore been proposed in US Patent No. 3,071,434 to improve kinetics 1 in the formation of zeolites of type 4 A by inoculating the mixture with a recycled dispersion taken from a point after the reaction zone.

However, this method has been criticized due to the difficulties in carrying it out, and it is then proposed in US patent no. 3,425,800 to use a crystallizer with three layers, the suspension of the gel precipitated in a cold state being heated to 100°C and then introduced in a crystallizer where the formation of the crystalline aluminum silicate is carried out. In this process, crystalline aluminum silicate is obtained by decantation.

From US-PS 3535075 and 3674426 are. a method for the production of crystalline zeolite A is known, whereby the resulting gel is broken up and treated at 50 to 60°C, the temperature is then raised and the mixture is thus kept for a certain time. With this method, there is no homogeneous environment and additional compounds such as dichromate, permanganate or vanadate are added, which makes the method cumbersome. From US-PS 3516786, a preparation of zeolites of the faujasite type is known with a particle size between 10 and 100 m^u. Furthermore, from US-PS 3310373 a preparation of a crystalline aluminum silicate is known, where the reduction of the size of the formed crystals is achieved by mechanical impact during the crystallization. Finally, a method for the production of crystalline zeolitic molecular sieves is known from DE-AS 1038017 which, however, exhibits an extremely broad particle size spectrum from 0.01 to 100 .

In the French patent document 2,096,360, a simplification of the method is proposed in several steps by preheating the aqueous solution of sodium silicate approximately to the precipitation temperature and adding it hot to the solution of aluminate which is likewise kept at the precipitation temperature.

The products obtained on. this way has been valued because of their very high absorbency which acts selectively on the molecules, on the basis of their size and shape, so that the products are often called "molesiles".

Because of their properties, the products have also been able to be used for other purposes, especially as cation exchangers, and one of the more common uses in this area is that the compounds are used in detergents.

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For a very long time, aluminum silicate-based derivatives have been mixed into detergents, and this possibility has received renewed interest partly due to the fact that sodium tripolyphosphate (STPP) as an additive in detergents is no longer so relevant due to its polluting effect and on the other hand has it been possible to find practical and reproducible methods for the production of aluminum silicates.

Additives for Detergents such as e.g. STPP works

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in several ways and especially as cation exchangers. Aluminum silicates have this property and it is therefore natural to think about using them as there should be no ecological concerns on this level.

In recent times, several types of aluminum silicates have been proposed which are mostly crystalline and which are distinguished by an increased capacity for cation exchange and/or an increased exchange rate.

Unfortunately, these aluminosilicates present a double disadvantage in that they first .and; primarily cannot completely replace STPP, as they only act as cation exchangers in the washing environment, while the effect of STPP is more diverse and especially in the dispersing and complexing direction. Furthermore, the aluminum silicates are insoluble, and this leads to a condition called "crusting" or mineralization and which leads to the deposition of particles of the aforementioned aluminum silicate on the textiles, and especially on cotton.

It has been thought that the relationship with "crust formation" could

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can be remedied with a fine grain size, but the impact of the grain size on the washability and especially on the relationship with "crust formation" is poorly understood.

It has been easily established that the particles should be well individualized. With more particular regard to the replacement of sodium tripolyphosphate with an alkali aluminum silicate, it has been observed in this connection that the working conditions are increasingly critical as the relative amount of tripolyphosphate in relation to the aluminum silicate is reduced.

The aluminum silicates according to the invention have a lot

specific grain size within otherwise wide limits of average grain size values, which makes them suitable for use in such diverse ways as in detergents, dehumidifiers in association with a binder, and separation processes.

In the case of detergents, there is interest in

aluminum silicates according to the invention with a small grain size of 0.2 to 3 µm, with a high surface area between 1 and 10 m^/g and with cation exchange capacity and a high exchange rate.

Such an aluminum silicate is particularly well suited for

use in detergents where it has properties that stand up to comparison with the best known aluminum silicon

cater, and in addition offers the advantage of a much lower tendency to "crust formation".

The new aluminum silicate can be produced by a discount

current procedure, but practically carried out

the gait advantageously continuous. It is essential that the gelling step takes place in a concentrated and homogeneous environment, by proceeding in the following way:

a solution of sodium aluminate is first formed,

this solution is then cooled to a temperature

lower than the ambient temperature,

while stirring, a solution of sodium

silicate so that the<1>homogeneous environment is maintained,

the mixture is brought to a temperature of between 60 and

100°C which allows gelation of the mixture,

this temperature is maintained for between 0.2 and 5 hours in

to complete redispersion of the aluminum silicate formed in suspended state (complete conversion to crystalline phase).

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Advantageously, the starting mixture is prepared by mixing a solution of sodium aluminate cooled to between -10°C and +10°C and

a solution of sodium silicate at ambient temperature

temperature, practically above 10°C.

The mixture is carried out while stirring with the help of which

preferably suitable devices which allow homogenization of the mixture, within a shorter time than the time for gelation of the mixture at the equalization temperature for this mixture

Eng. This time is advantageously shorter than 15 min.

The concentrations of the two reaction components are chosen

so that a liquid phase of at least 70 is finally achieved

g/l and at least 10 g/l A^O^ in equilibrium with* at least 200 g/l molecular sieve.

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When you want to achieve a small grain size of 0.2 to 3

^um, the concentrations of the reaction components are chosen so that a liquid phase containing at least 100 g/l Na^O and at least 30 g/l A^O^ is finally obtained, in equal

weight with at least 200 g/l molecular sieve, while when

is a larger grain size, a liquid phase is preferably chosen with less than 100 g/l, preferably 70 to 100 g/l Na 20 g less than 30 g, preferably 10 to 30 g/l

<A1>2<0>3.

With continuous implementation, practical progress is made

in the following way:

a mixture of the cooled is first carried out solution of sodium aluminate cooled to the previously indicated temperature range and a solution of sodium silicate which is at a temperature close to ambient temperature,

before gelling, the mixture is finely ground in a first zone with

a lower density than the density of the aqueous mixture and which is heated to such a temperature that, after the components have been brought into contact with each other, the aqueous mixture is brought to the selected reaction temperature, the aforementioned first zone consisting of a heat-transferring agent which is not miscible with water, such as e.g. a bath of oil or petroleum,

this temperature is maintained in the bath, in another subsequent zone, until the conversion to the crystalline phase is complete, as a piston flow is ensured in this subsequent zone,

the reaction mixture is recovered in a suspended state containing crystals of aluminum silicate.

- the crystals are separated from the suspension by any known means such as filtration or centrifugation, washed and collected. The first zone is advantageously a pass-through zone where the mixture is subjected to a conversion in the lab for a very short residence time of 1 to 2 seconds, while the second zone is advantageously a zone with piston pressure and corresponds to a much longer residence time.

As mentioned earlier, the products obtained are particularly suitable for use in detergents.

The invention shall be explained with the help of the following examples of preferred forms of travel, and with reference to the attached figures, and with the help of comparison tests with known products where the following conditions are determined:

- Granulometric distribution:

This is determined using a Coulter counter where

the electrolyte chosen is a solution with the following composition by weight:

Dispersion time 2 min. (ultrasound) - 40,000 Herz - 100 watts.

- Washing effect:

The washing effect is determined by a washing test at 90°C on cotton rags soiled with a soil mixture normalized and produced by

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Wåschereiforschungsinstitut Krefeld.

The tests are carried out using an apparatus "LINITEST"

(manufactured by original Hanau). Two contaminated test pieces (4.2 g) and two non-contaminated test pieces (4.2 g) are introduced into each container and then a 100 ml washing solution with a composition as stated below. Washing is followed by four subsequent rinses for 30 seconds.

Water with a hardness of 28.5° is used and the detergent composition used in an amount of 9 g/l is as follows:

The light reflection from the test pieces is measured before and after washing using a photoelectric photometer "Elrépho" from the company ZEISS with filter 6.

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- Crust formation effect

The following composition is used:

The washing is carried out in the aforementioned device "Lini Test". Sample pieces of cotton (the cotton used is manufactured by TEST FABRICS INC. and is called "Bleached Cotton Sheeting</>in Style 405) of 10 x 12 cm are applied every 450 cm^ of the solution described above. The hardness of the water is 30° (NFT 90 003).

The washing itself is carried out at 60°C for 35 minutes. (25 min. to come up to temperature, +10 min. at 60°C).

Two rinses are then carried out, one quickly for about 1 min in 350 cm^ of water and the other carefully for 5 min in 450 cm^ of tap water (hardness 30°).

The pieces of soap are dewatered and used.

The cotton samples are then burned at 900°C for 2 hours and the ash content is weighed.

In addition to these tests, provisions are made on the product itself with:

surface BET

- exchange rate.

EXAMPLE 1

1 1 of a solution of sodium aluminate containing 200 g/l calculated as Na,,0 and 200 g/l calculated as Al-^o^ is cooled in a flask to 4°C.

Under vigorous stirring so that a homogeneous environment is constantly maintained, 0.4 1 of a solution of sodium silicate is added at a temperature of 20°C and containing 25.4% Sio2 and 7.42% Na,,0 on a weight basis. At the end of the addition, the temperature rises to 15°C and the mixture becomes slightly fluid again. The stirring is terminated and the temperature is allowed to rise to close to the ambient temperature, which causes the mixture to gel. The flask is then kept in a thermostat with water set at 83°C for 2 hours. At this point, the original solid gel mass is converted into a suspension of microcrystals which are suctioned onto a filter and washed continuously on a filter funnel with medium openings l^um. The concentration of crystalline aluminum silicate in the suspension of microcrystals is approximately 320 g/l. The washed mass is then dried to constant weight in a drying cabinet at 100°C before analysis.

The zeolite after drying and analysis has an approximate formula: 1.85 SiO 2 , 1 Al 2 O 3 , 1 Na 2 O, 3 H 2 O.

It produces the structure of molsil-er 4 by X-ray analysis

A.

Under the electron microscope, very small individual cubes with a homogeneous grain size of the order of ^um, well distributed as shown in fig. 1, with a magnification of 4,500.

Specific surface area is 7 m^/g.

For comparison, the following test 2 (blind test) is carried out: 1 1 solution of sodium aluminate with a content of 74 g/l calculated as Al^O^ and 127!g/l calculated as Na2O is brought to 83°C with good stirring in a flask.

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0.271 1 of a solution of silicate obtained by diluting 50 ml of a commercial

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solution of sodium silicate containing 477 g/l calculated as SiO2 and 239 g/l calculated as Na20. The temperature is then brought back to 83°C and held

this level for 2 hours, stirring all the time. The suspension of crystals is then dewatered and washed on the filter without special precautions. The washed pulp is then dried and analyzed as in the previous example.

The dried zeolite corresponds to the formula:

1.85 SiO 2 , 1 Al 2 O 3 , 1 Na 2 O, 3.8 H 2 O.

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It shows, by X-ray analysis, the structure of molsilar 4 A and the appearance given in fig. 2 (magnification 4,500).

Electron microscopic examination shows that the small cubes are well individualized but have a wider grain size distribution; (1 to 5yum). The specific surface area BET is 1 >.2 m^/g.

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With the powders from experiments 1 and 2, a test is carried out with an exchange rate of Na-(Ca in the following way: 1 g of powder dried at 100°C where the loss on ignition at 1,000°C is approximately 19%,' is placed in a liter of solution containing 594 mg of CaC] _2 within 1 min using an ultra-fast turbine stirrer with rotary

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figure 9000 rpm. and equipped with a stirring device designated "Ultraturax T 45 K". After dispersion has been achieved, the suspension is maintained under magnetic stirring for 1 min., 4 min. and 14 min. before quickly using vacuum filtration (20 sec.) on fine-porous filter "RAWP 047" to separate a volume of clear liquid sufficient for analysis of the ions Ca^<+> which are back in the solution.

The subsequently obtained results show an advantage of the exchange kinetics for the very fine aluminum silicate according to the invention:

Theoretical capacity for the mole sieve is 5.8,

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Washing effect

You can see that the washing effect is largely the same.

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Crust formation effect

You can see a pretty big difference here.

EXAMPLE 2

An aluminum silicate of type 4 A is produced, with properties identical to those described in example 1, by proceeding with a continuous process which allows industrial implementation of the invention (see fig. 4).

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A sodium aluminate solution with 200 g/l calculated as Na20 and

200 g/l calculated as A1203 is cooled to -4°C in a tube heat exchanger 1 in a quantity of 10 l/hour. The cooled stream is continuously mixed with a stream 3 of 4 l/hour of a sodium silicate solution at 20°C and containing 25.4%

Sic>2 and 7.42% Na2O by weight, in a stirred reactor 2.

The homogeneous mixture, where the temperature has settled to approximately 15°C, is supplied by means of a peristaltic pump 4

an injector 5 with capillaries of 0.5 mm diameter which continuously forms droplets which fall into the upper part of a reactor 6 filled with petroleum kept at 85°C by means of a circulation circuit 7 with heated brine.

The density in the bath is set so that the average fall time

for the drops formed from the -capillaries is 3 sec-. At the end of this period, the spherical particles have gelled and are collected on a grid 8 arranged at the bottom of the reactor and eventually converted into a liquid suspension of aluminum silicate which is collected in the conical part 9 of the reactor 6. This suspension is extracted continuously with the help of a trachea 10

in an amount of 14 l/hour, after one hour of continuous supply of the reaction components to achieve an average residence time of the reaction components in the reactor of 1 hour.

Removed suspension is then dewatered and washed in a known manner

manner.

EXAMPLE 3

Proceed as in example 1 with the exception that 0.6 1 of the silicate solution is added instead of 0.4 1.

A concentration in the suspension of aluminum silicate of approximately 450 g/l is then achieved.

It is observed that the average grain size of the aluminum silicate

is higher as shown|in fig. 3, with magnification 4500.

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EXAMPLE 4

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Aluminosilicate of type 4 A is produced according to the invention, by proceeding with the continuous process which allows the industrial implementation of the invention as shown in fig. 4.

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A solution of sodium aluminate with a content of 110 g/l calculated as Na20 and 150! g/l calculated as Al-jO^ cool-

es to 0°C in a tube heat exchanger 1 in a quantity of 10 l/hour. The cooled stream is continuously mixed with a stream 3 of 4 l/hour of a solution of sodium silicate at 20°C containing 25% SiO2 and 11.6% Na2<D by weight, in a stirred reactor 2.

The homogeneous mixture, the temperature of which is set at approximately 12°C, is supplied by means of a peristaltic pump 4 to an injector 5 with capillaries of 0.5 mm diameter which continuously form drops which fall into the upper parts of the reactor 6 filled with petroleum held at 85 °C

by means of a circulation circuit 7 with heated brine.

The density of the bath is set so that the average fall time for the formed drops from the capillaries is 3 sec. At the end of this period, the spherical particles have gelled and are collected over a grid 8 arranged at the bottom of the reactor and eventually converted into a liquid suspension of aluminum silicate which is collected in the conical part 9 of the reactor 6. This suspension is continuously drawn out using one! air pipe 10 in a quantity of 14 l/hour after 2 hours of continuous supply of the reaction components to establish an average residence time for the reaction components in the reactor of 2 hours.

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In this example, the concentration of crystalline sodium aluminum silicate in the suspension of small crystals is about 340 g/l, the liquid phase is practically free of SiC^ and contains 76 g/l Na 2 O and 12 g/l Al 2 O 3 . The suspension of small crystals obtained is dewatered and washed on a filter with an average pore size of 1 µm. The washed mass is then dried to constant weight in a drying cabinet at 100°C before analysis.

The product obtained is of type 4 A with a homogeneous average grain size of 3 to 4 µm with well distributed particles as shown in fig. 5 (magnification 4500).

The product has a surface BET of 1 m<2>/g.

The subsequent table III shows the grain size measured according to Coulter after drying for respectively the blank sample, the product according to example 2 and example 4. It is noted that on the one hand grain sizes that are very fine can be obtained and on the on the other hand, the grain size distribution is different for identical mean grain sizes.

The degree of "crust formation" or so-called "mineralization" is given in the following table IV

Claims (2)

1. Synthetic crystalline aluminum silicate obtained by adding an alkali-silicate solution to an alkali-aluminate solution, maturing at an elevated temperature and subsequent separation of the resulting aluminum silicate crystals, characterized in that the crystalline aluminum silicate is obtained by mixing a sodium aluminate solution cooled to a temperature between -10 and +10°C with a sodium silicate solution at ambient temperature, subjecting the homogeneous mixture to gel formation at a temperature between 60 and 100 °C and maintaining this temperature until the conversion to the crystalline phase is complete, the concentration of the solution of the two reaction participants being adapted so that at the end of maturation the liquid phase exhibits a content of at least 70 g/l of Ha^O and at least 10 g/l of M^ O^ in equilibrium with at least 200 g/l molecular sieve. 2. Use of the crystalline aluminum silicate specified in claim 1 as an additive in detergent mixtures.