CH633974A5 - Granular material and process for preparing it - Google Patents

Description

The invention relates to a granulate and a method for its production.

These granules are suitable as a material for absorbing liquids, e.g. Water and aqueous liquids, oil and oily liquids, and odors. You can e.g. as spreading material on floors of operating rooms, e.g. Garages, workshops and factories are used to absorb leaking liquids, but also as filler for cat troughs to absorb the liquid part of the excrement. They are also suitable as carriers for pesticides, e.g. Insecticides, herbicides, fungicides etc., for use in houses and business premises, in agriculture and horticulture and the like.

So far, mainly granules from natural types of clay have been used for such purposes, e.g. Walker earth that has a low density. These granules are obtained by allowing the clay to air dry, crushing, further drying or calcining and sieving the product. Both the dried and the calcined product are more or less suitable for absorbing liquids. By drying or calcining, free and / or bound water is expelled and a porous material is obtained which, in the form of granules, has a grain size of 0.3 to 7 mm, a density of approximately 550 g / dm3 and a water absorption of approximately 80 % By weight. Because clay is a natural material, the properties vary depending on the origin and batch to batch, making it difficult to produce a consistent and uniform product.

A granulate was found which does not have the disadvantages of the known granulate. The granulate according to the invention is characterized in that it consists of cement, an inorganic water-binding swelling agent, sand or ground stone and optionally dyes and /

or odoriferous substances. Small amounts of bound water may also be present.

The process for producing such a granulate is characterized in that cement, an inorganic water-binding swelling agent, sand or ground stone, excess water and, if appropriate, colorants and / or fragrances and / or other additives are mixed to give a paste, which allows the paste to harden, the hardened material dries and forms into granules before or after hardening and / or drying, and free water is removed by drying after hardening.

A water-binding swelling agent is a substance that can absorb water and swell in the process. In general, these swelling agents can absorb 10 to 40 times their weight in water.

The cement that hardens with the water serves as a scaffold and gives the granulate such a hardness that it does not easily break and / or break down into powder when it is exposed to mechanical pressure during storage and / or transportation.

The sand or the ground stone serves as an inert blending agent in order to lower the cost price of the granulate.

25 Cement only needs a few percent by weight of its own weight of water to harden. In the absence of other substances, it can be mixed to a pulp with a maximum of 35% by weight of water. If more than 35% by weight of water is added to the cement, the excess 30 water is not retained by the mass. If you only use cement made with water to form granules with a grain size of 0.3 to 7 mm, the granules in an absolutely dry state have a density of about 800-900 g / dm3 and a water absorption of about 5-40% by weight. %. 35 The lowest value of density and the highest value of water absorption are achieved with Portland cement class C. However, these values are generally not sufficient for the purpose intended according to the invention. In order to have sufficient absorption capacity, granules with a grain size of 0.3 to 7 mm in an absolutely dry state should have a density of at most 700 g / dm3 and a water absorption of at least 45% by weight.

This value, which is favorable for the intended purpose, is achieved according to the invention in that the granulate 45 contains a water-binding swelling agent in addition to the cement as a scaffold-forming substance. The absorption capacity for liquids and the density of the granulate are related to the volume of the capillary-active pores. The larger the pore volume of the hardened granulate, the more liquid can be absorbed and the lower the density.

Examples of inorganic swelling agents are many types of clay are considered, such as sepiolite, montmorillonite, kaolins, calcinable types of clay. Diatomaceous earth can also be used. The 55 best results are obtained with bentonite in the sodium form. This is found to a limited extent in nature, but it can also be produced by a complicated but known activation process from the bentonite in the calcium-6o form, which is widespread in nature. When bentonite is mentioned in this description, bentonite is meant in the sodium form.

All commercially available types can be used as cement. Because of the short hardening time, the 65 fast hardening cement types are preferred. These give the granulate made from it together with water also the lowest densities and the greatest water absorptions.

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As an extender to reduce the cost of the granulate, sand of any origin, e.g. B. dune sand, river sand and silver sand, or ground stone of natural or artificial origin used. The use of silver sand is preferred because it contains less impurities than other types and because the distribution of grain size is relatively constant regardless of the place of origin and the batches.

When preparing the slurry, the weight ratio of cement and extender is about 55:45 to about 65:35, preferably 60:40. The water content in the slurry, which determines the pore volume and therefore also the liquid absorption and the pore volume after curing and drying, varies within relatively narrow limits, namely from 60 to 120% by weight, calculated on the total dry substance.

The water-binding swelling agent content depends on the nature of the swelling agent. Generally, a mixture of swelling agent and water is added to a mixture of cement and extender. The most suitable is a mixture of water-binding swelling agent and water, which has a viscosity of 15 to 25 centipoises at 20 ° C. This applies e.g. for a mixture of sodium bentonite and water, which contains 3-8 wt .-% sodium bentonite.

By adding the water with the water-binding swelling agent, the amount of water required for the porridge can be precisely metered and taken up in the porridge.

The amount of water processed in the slurry must be such that, after the mixture has hardened and dried, the end product has the desired liquid-absorbing capacity, the desired density and the desired hardness. The more the cement is used, the harder the hardened product. The more water is added to the mixture, the greater the pore volume and the absorbency of the end product, the lower the hardness.

The amount of extender, the amount of water-binding swelling agent and the plasticity of the not yet hardened mixture of cement, sand, swelling agent and water should be such that the mixture can be spread out into a coherent layer and / or pressed into particles.

Although the cement and the swelling agent as well as sand and ground stone are the essential components of the granules, they can also contain other components. For example, the granules can be given a specific color by adding a dye to the mixture to be granulated, e.g. an inorganic or organic pigment. Thus, by adding 0.3-5% by weight of Fe203, calculated on dry matter in the slurry, to a slurry of cement, bentonite, sand and water, a light cream or red colored granulate can be obtained. The addition of Fe203 slightly increases the density of the granules and slightly reduces the water absorption. Fragrance substances can also be absorbed into the granules. However, this is expediently done after the mixture has dried in order to prevent the fragrances from evaporating during the drying. The dried material, preferably the finished granulate, is impregnated with the fragrance, which is expediently dissolved or dispersed in a liquid.

The procedure for producing the granules is expediently as follows. The amount of water, swelling agent, cement, extender and, if appropriate, additives required for a certain batch are introduced into a mixing device in succession. The mass is mixed continuously during the addition. After all components have been added and mixed well, the mixture is left for some time, e.g. B. 1 to 3 hours, at room temperature to give the water-binding swelling agent and the cement the opportunity to absorb water. This is particularly important in the embodiment to be discussed below, where the mixture is formed into particles prior to curing. This causes the mixture to stiffen, which is desirable when granules have to be produced. The porridge becomes drier by standing, which means that it does not or hardly sticks to the processing device during further processing.

The mixture thus obtained can now be processed in various ways.

First, the mixture can be shaped or rolled into skins, tapes, or tablets. These moldings are allowed to harden, in order to subsequently break them into granules and to dry and sieve them. You can also dry first after hardening and then break it into granules and sieve them, or after hardening you can first break them into granules and sieve and dry them.

The hardening takes place in that the cement absorbs water, whereby it fulfills its framework-forming function. This hardening can be accelerated by passing steam through or over the material from the moment when the framework formed by the cement is no longer washed out or leached out by the condensed water of the steam. Steam can be used about 4 to 10 hours after the mixture is made. If a mixture of cement, bentonite, sand and water is heated to about 80 ° C with steam, the hardening time can be reduced by about 30%.

The curing process can also be accelerated by adding calcium chloride to the mixture. With 2.5% by weight calcium chloride, calculated on cement, the hardening time is shortened by about 30%.

After the material has hardened, it is dried, if necessary after breaking it beforehand.

Drying can be done in air or in a cold air stream, but it is faster in heated air.

To do this, the material can be heated in still air, but preferably it is dried in a heated air stream. The temperature of the air should be at least 220 ° C. The hardened material can be heated up to about 350 ° C.

If fine greens or dust is formed during drying, this can be returned to the mixing stage.

The material is finally broken, e.g. in a jaw crusher and / or a roller crusher, and the fractions of the desired particle size are isolated by sorting on sieves. The too coarse fractions are returned to the breaking device, the too fine fractions to the mixing device.

Instead of spreading the somewhat stiffened mixture into tablets, skins or tapes, it can be done, even in the desired grain size and shape, by pressing, rolling, extruding or agglomerating by means of rollers and the like. Ä. Shaped into balls, chopsticks, blocks, etc. The particles shaped in this way can then be cured in the manner described above. After the cement framework has hardened sufficiently, steam can be conducted for the particles. After curing, the particles are dried and broken and sieved if necessary. Instead of after drying, the particles can also be broken, dried and sieved after hardening. In this embodiment too, too coarse material is returned to the breaking device and too fine material is returned to the mixing device. If the material is dried in the form of particles, this can take place in a fluidized bed.

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When processing the somewhat stiffened mixture of cement, water-binding swelling agent, extender and water, the use of bentonite as swelling agent also has the advantage that the so-called "green strength" of the mixture, i.e. the strength in the moist, non-hardened state is improved, which makes the mixture easier to handle because of the better connection.

The granules according to the invention have a density of about 400 to 800 g / dm 3 and a water absorption of about 40 to 115% by weight, calculated on absolutely dry granules, with a particle size of 0.3 to 7 mm. The absorbency for liquids is determined by saturating a weighed amount of granules, the moisture content of which is known, with the liquid to be absorbed and weighing the granules again. The absorbency is defined as the weight percent of the absorbed liquid, calculated on granulate.

The granules obtained are excellently suitable for the purposes mentioned at the beginning of this description and for thermal and acoustic insulation.

For use as a carrier for pesticides, the granules can be impregnated with a pesticide in liquid, dissolved or dispersed form.

Only a few comparative examples now follow, according to which granules of cement and water were produced without a water-binding swelling agent.

Comparative Example A

3 kg of blast furnace cement class A were mixed with 660 ml of water to form a slurry. This slurry was spread into tablets with a thickness of 1 cm, which were allowed to harden at room temperature. After curing, the tablets were broken into granules with the aid of a roller crusher, of which the fraction with a particle size of 0.3-7.0 mm was sieved out and dried in a drying cabinet at 210 ° C.

This experiment was repeated using class B blast furnace cement instead of class A. The results of the tests were as follows:

Class A Class B

Hardening time, hours 70 70

Density, g / dm3 894 875

Water absorption, wt% 12 14

Comparative Example B Comparative Example A was repeated, but using 1055 ml instead of 660 ml of water. The results were as follows:

Class A Class B

Hardening time, hours 100 100

Density, g / dm3 846 839

Water absorption, wt% 21 26

Comparative Example C Comparative Example A was repeated, but using Portland cement classes A, B and C instead of blast furnace cement.

The results were as follows:

Class A Class B Class C

Hardening time, hours 70 48 24

Density, g / dm3 877 862 853

Water absorption,% by weight 13 16 18

Comparative Example D Comparative Example B was repeated, but using Portland cement classes A, B and C instead of blast furnace cement.

The results were as follows:

Class A Class B Class C

Hardening time, hours 70 48 24

Density, g / dm3 841 829 806

Water absorption, wt% 26 33 39

The following examples were carried out to show the influence of a swelling agent (bentonite) on the properties of the granules. In the examples, "gel" is a mixture of 15% by weight of tin. Bentonite and 85 wt .-% Tin water meant.

Comparative Example E

3 kg blast furnace cement class A was mixed with 1.4 kg gel. The procedure was as in Comparative Example A.

This experiment was repeated using class B blast furnace cement instead of class A.

The results were as follows:

Class A Class B

Hardening time, hours 76 72

Density, g / dm3 798 771

Water absorption, wt% 34 41

Comparative Example F Comparative Example E was repeated, but using 2 kg instead of 1.4 kg of gel on 3 lcg of blast furnace cement.

The results were as follows:

Class A Class B

Hardening time, hours 84 80

Density, g / dm3 631 614

Water absorption, wt% 58 59

Comparative Example G Comparative Example F was repeated, but using 2 kg of blast furnace cement of 3 kg on 2 kg of gel. The results were as follows:

Class A Class B

Hardening time, hours 100 100

Density, g / dm3 608 611

Water absorption, wt% 67 62

Comparative Example H Comparative Example F was repeated, but using 3 kg of Portland cement classes A, B and C instead of blast furnace cement on 2 kg of gel.

The results were as follows:

Class A Class B Class C

Hardening time, hours 90 53 27

Density, g / dm3 626 602 584

Water absorption, wt% 55 61 68

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Comparative Example J Comparative Example G was repeated, but using 2 kg of Portland cement classes A, B and C instead of 2 kg of blast furnace cement on 2 kg of gel.

The results were as follows:

Class A Class B Class C

Hardening time, hours 96 54 27

Density, g / dm3 613 581 536

Water absorption,% by weight 62 69 76

Comparative Example K Comparative Example J was repeated with Portland cement classes B and C, but using 2.4 kg of gel instead of 2 kg per 2 kg of Portland cement. Because of the sufficient hardness of the granulate obtained with Portland cement class A, this quality cement was no longer used.

The results were as follows:

Class B Class C

Hardening time, hours 54 27

Density, g / dm3 570 522

Water absorption, wt% 73 88

Comparative Example L Comparative Example K was repeated, but using 2.8 kg of gel instead of 2.4 kg on 2 kg of Portland cement.

The results were as follows:

Class B Class C

Hardening time, hours 60 28

Density, g / dm3 549 506

Water absorption, wt% 79 102

Now follows a number of examples to illustrate the method according to the invention. “Sand” means silver sand.

Example I

1 kg of blast furnace cement class B and 1 kg of sand were mixed with 1 kg of gel. The procedure was as in Comparative Example A. Because of the long hardening time, blast furnace cement class A was not examined.

The results were as follows:

Hardening time, hours 92

Density, g / dm3 627

Water absorption, wt% 55

Example II

Example I was repeated using 1.1 kg blast furnace cement class B, 0.9 kg sand and 2 kg gel.

The results were as follows:

Hardening time, hours 92

Density, g / dm3 626

Water absorption, wt% 57

Example III

Example II was repeated, except that 2.5 kg of gel was used instead of 2 kg of gel on 1.1 kg of class B blast furnace cement and 0.9 kg of sand.

The results were as follows:

Hardening time, 100 hours

Density, g / dm3 609

Water absorption,% by weight 62

Example IV

Example II was repeated, but using 0.9 kg of class B and C Portland cement instead of blast furnace cement on 0.9 kg of sand and 2 kg of gel.

The results were as follows:

Class B Class C

Hardening time, hours 60 26

Density, g / dm3 610 543

Water absorption, wt% 63 75

Example V

Example III was repeated, except that 0.9 kg of class B and C Portland cement were used instead of 1.1 kg of class B blast furnace cement and 1.1 kg instead of 0.9 kg of sand on 2.5 kg of gel.

The results were almost the same as in Example IV, with the difference that the granules with class B are brittle, whereas the granules with class C have sufficient hardness.

Example VI

Example IV was repeated, but using 1.1 kg of Portland cement and 0.9 kg of sand 2 kg of gel instead of 2 kg of gel.

The results were as follows:

Class B Class C

Hardening time, hours 66 27

Density, g / dm3 581 514

Water absorption, wt% 71 97

Example VII

Example V was repeated, but using 0.9 kg of Portland cement and 1.1 kg of sand 3 kg of gel instead of 2.5 kg of gel.

The results were almost the same as in Example IV, but the granules were quite brittle.

A number of examples of the use of the granules produced according to the invention are then given.

Example of use 1

Surfaces of 1 m2 were contaminated with 300 ml of motor oil type 10W30 on various concrete floors (tiles, stelkonplatten, cast concrete). 400 g of granules obtained according to Example IV with Portland cement class B were sprinkled on the oil-coated areas. After 4 hours the granules were removed. It turned out that the oil had been almost completely absorbed by the granulate. In order to remove the last residues of oil, 50 g of the same granulate were sprinkled on the parts contaminated with oil. After walking and driving over these parts of the floor for a few hours, the granules were removed. It turned out that the oil was now completely absorbed.

When the same experiment was carried out with heating oil, it was found that the oil was completely absorbed after 45 minutes.

If the same test was carried out with used motor oil, it was found that this oil was completely absorbed after about 24 hours.

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Example of use 2

A cat trough, the bottom of which was covered with a 7 cm thick

Layer of peat garbage, sand, shredded paper or sawn granules according to one of Examples I to VII was used, chips were covered, started when used by a cat, so this filling could be used for 6 to 7 days before one day an unpleasant smell to 5 an unpleasant smell was noticeable.

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Claims (8)

633 974 1. Porous, liquid-absorbent and odor-binding granules, characterized in that it consists of a hardened mixture which contains cement, an inorganic water-binding swelling agent and sand or ground stone. 2. Granules according to claim 1, characterized in that it additionally contains dye. 2nd PATENT CLAIMS 3. Granules according to claim 1, characterized in that it additionally contains fragrance. 4. Granules according to claim 1, characterized in that it additionally contains dye and fragrance. 5. A process for the preparation of the granules according to claim 1, characterized in that cement, an inorganic water-binding swelling agent, sand or ground stone and excess water are mixed to form a slurry, the slurry is allowed to harden, the mixture during or after hardening to a granulate forms and after hardening free water is removed by drying. 6. The method according to claim 5, characterized in that a natural clay, in particular concrete, is used as the inorganic water-binding swelling agent. 7. The method according to claim 5 or 6, characterized in that one produces granules with a particle size of 0.3 to 7 mm. 8. The method according to any one of claims 5 to 7, characterized in that one produces a granulate with a volume weight of at most 700 g / dm3 and a water absorption of at least 45 weight percent.