DE102008022007A1 - Dicyandiamide granules with high dissolution rate and good flowability and process for its preparation - Google Patents

Abstract

It describes a dicyandiamide granules with high abrasion resistance and good flowability, which a) has an average primary crystal size of 0.01 to 1 mm and b) an average agglomerate size of 0.2 to 20 mm. Surprisingly, the dicyandiamide granules according to the invention, in which small dicyandiamide crystallites are combined to form larger agglomerates during the granulation process, have very good performance properties, e.g. good flowability and high dissolution rate.

Description

object The present invention is a dicyandiamide granules with high Dissolution rate and good flowability and a method for its production.

dicyandiamide (Cyanoguanidine) is a large-scale product with broad Application area, such. In textile and leather equipment, in wastewater treatment, in the curing of epoxy resins, in aminoplast resins and flame retardant (Ullmann, 7th edition, online release 2008, chapter "Cyanamides").

For most purposes dicyandiamide is required in dissolved form. Therefore, a small grain size and consequent high dissolution rate are desirable. Fine crystalline dicyandiamide can be obtained by rapidly cooling the dicyandiamide-containing process solutions. Such fine crystalline dicyandiamide is difficult to filter ( Gmelin, Vol. C, D1, p. 281 (1971) ) and shows a strong tendency to cake. The lack of flowability leads to increased handling costs, since only bags come as packaging in question, larger containers (intermediate bulk containers, silos) can not be emptied.

Fine-grained dicyandiamide can be rendered free-flowing by the addition of anti-caking agents, preferably from the group of the silica derivatives ( DE 33 40 788 ). On the other hand, the addition of insoluble anti-caking agent prevents the clear solubility, so that thus treated dicyandiamide is unsuitable for many applications.

By special crystallization processes with the addition of Kristalltracht modifying polymeric additives (see. JP 05279317 ) dicyandiamide can be obtained in the form of coarse crystals. These show a very low tendency to cake and are generally free-flowing. The disadvantage, however, that such coarse crystals have only a very low dissolution rate, so that the handling advantage is consumed in the subsequent reaction of dicyandiamide again.

Of the The present invention was therefore based on the object, a dicyandiamide granules produce, which at the same time a good flowability and has a high dissolution rate.

• a) eine durchschnittliche Primärkristallgröße von 0,01 bis 1 mm und
• b) eine durchschnittliche Agglomeratgröße von 0,2 bis 20 mm

aufweist.This object is achieved in that the dicyandiamide granules

• a) an average primary crystal size of 0.01 to 1 mm and
• b) an average agglomerate size of 0.2 to 20 mm

having.

Surprisingly shows the dicyandiamide granules in which small dicyandiamide crystallites during the granulation process to larger agglomerates very good performance characteristics, such as B. good flowability and high dissolution rate.

• a) die durchschnittliche Primärkristallgröße von 0,01 bis 1 mm, vorzugsweise 0,05 bis 0,5 mm, sowie durch
• b) eine durchschnittliche Agglomeratgröße von 0,2 bis 20 mm, insbesondere 0,5 bis 5 mm.

The dicyandiamide granules according to the present invention are defined by

• a) the average primary crystal size of 0.01 to 1 mm, preferably 0.05 to 0.5 mm, and by
• b) an average agglomerate size of 0.2 to 20 mm, in particular 0.5 to 5 mm.

The relatively coarse-grained dicyandiamide granules are distinguished preferably characterized in that less than 10 wt .-%, in particular less than 5% by weight, the particle is an agglomerate size of <0.1 mm.

The dicyandiamide granules according to the invention Furthermore, characterized in that the dicyandiamide content is relatively is high. Depending on the manufacturing process, the inventive Granules have a dicyandiamide content of preferably> 95%, in particular> 99%.

One Another object of the present invention is a method for the preparation of the corresponding dicyandiamide granules, wherein dicyandiamide in the presence of water and optionally a binder granulated and the granules with an average agglomerate size from 0.2 to 20 mm.

The starting material for the claimed dicyandiamide granules is fine-grained dicyandiamide, as it usually results from the synthesis and crystallization. The average grain size of the primary crystals is 0.01 to 1 mm, preferably 0.05 to 0.5 mm. According to a preferred embodiment have at least 95 wt .-% of the particles have a particle size of less than 2 mm, preferably less than 0.5 mm. The water content of the starting material is preferably 1 to 25 wt .-%, particularly preferably 10 to 15 wt .-%. The water content preferably results from the residual moisture of the upstream filtration ago. However, a starting material with a lower water content can also be adjusted to the desired content by adding water.

In In a preferred embodiment, the granulation process takes place without addition of further auxiliaries, d. H. exclusively with dicyandiamide and water.

In Another preferred embodiment is cyanamide or a cyanamide-containing aqueous solution (preferably with cyanamide in the concentration range from 10 to 60% by weight) as a binder. The added amount of cyanamide is preferably 1 to 10 wt .-%, based on dicyandiamide, wherein the Proportion of water plus cyanamide preferably 2 to 20% by weight, especially preferably 8 to 16 wt .-%, is.

Finally, in the context of the present invention, it is also possible to use a binder from the group of cellulose derivatives, starch or starch derivatives, polyvinyl alcohol, polyvinylpyrrolidone, gelatin, xanthan or copolymers of vinyl compounds selected from the group vinyl alcohol, vinyl acetate, vinyl propionate, acrylic acid, acrylamide or vinylpyrrolidone , or mixtures thereof. Examples of such binders are:
Methyl cellulose, ethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, carboxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, starch, modified starch, amylose, dextrin, hydroxyethyl starch, hydroxypropyl starch, carboxymethyl starch, gelatin, polyvinyl alcohol, polyvinyl acetate, polyvinyl propionate, polyvinyl butyrate, polyvinyl pyrrolidone, chitosan, xanthan, gum arabic, and mixtures thereof. The binder is added in an amount of 0.01 to 4% by weight, preferably 0.2 to 1% by weight.

The thus prepared starting material is in a for granulation treated technical apparatus. Preferred apparatus are z. B. Intensive mixers, vertical granulators, spray granulators, fluidized bed granulators, Ring-layer granulators or plowshare mixers. Depending on the type, size and capacity of the apparatus have rotational speeds from 300 to 2500 per minute proved suitable. The granulation times are 1 to 90 minutes, with 3 to 30 minutes being preferred. The granulation can take place at temperatures from 20 to 100 ° C be performed. The described method provides Granules of 0.2 to 20 mm average diameter, preferably 0.5 up to 5 mm.

The Granules obtained are then to a residual moisture less than 2 wt .-%, preferably less than 0.5 wt .-%, dried. Therefor are common technical equipment, such. B. fluid bed dryer, Fluidized bed dryer, conical dryer or drum dryer used. In a particular embodiment, the for the granulation used apparatus (eg a plowshare mixer) also be used for drying, so that the overall process is simplified. Drying takes place at temperatures of 30 to 160 ° C, preferably 60 to 140 ° C, wherein the outer Pressure is in the range between 20 and 1050 mbar.

The if necessary, the dry granules obtained can still be sieved off, to separate dust or fine particles. The separated shares can easily be attributed to the granulation process become.

On This is a free-flowing dicyandiamide granules with low fines content and high dissolution rate receive.

The The following examples are intended to explain the invention in more detail.

Examples

Example 1:

Preparation of dicyandiamide granules

1.2 kg of fine-grained dicyandiamide (mean particle size 96 μm) were mixed with 0.192 kg of water in an Eirich countercurrent star vortexer R 02 E. The mixture was granulated for 4 minutes at 3800 rpm. The wet granules were dried in a vacuum laboratory drying cabinet. The granules obtained had the following sieve analysis: 1.4% <200 μm, 0.7% 200-315 μm, 2.1% 315-500 μm, 95.1% 500-850 μm, 0.7%> 850 μm.

Example 2:

Technical preparation of dicyandiamide granules

250 kg centrifuge-moist dicyandiamide with an average grain size of 86 microns and a water content of 12.6% were in a Eirich Granuliermischer type RV12 submitted at 20 ° C. The Material was for 6 minutes at 950 rpm Granulated, with a uniform granules with nearly spherical particles. The moist granules was dried in a fluidized bed dryer at 75 ° C. Granules were obtained with the following properties: water content 0.2%, sieve analysis: 1.0% <200 mm, 1.6% 200-315 μm, 3.4% 315-500 μm, 87.7% 500-850 μm, 5.8% 850-1500 μm, 0.5%> 1500 μm.

Example 3:

Checking the flowability

• the following samples were examined:
  • a) a fine-grained, technical Dicyandiamid with an average particle size of 96 microns. 95.2% of the particles had a particle size <200 microns. The residual moisture was 0.1%.
  • b) fine-grained dicyandiamide as in a) treated with 1.5 wt .-% of a fumed silica (Aerosil 200) as anti-caking agent.
  • c) a coarsely crystalline dicyandiamide having an average particle size of 352 microns. 96.3% of the particles had a particle size <1 mm. The residual moisture was 0.2%.
  • d) the granules from Example 1.
  • e) the granules from Example 2.

100 g of the respective product were filled into a test funnel with a sealed outlet opening of 8 mm diameter. Then the opening was released and the run-out behavior was observed. sample Stopping behavior 3a) does not flow. By shaking portions of a few grams flow, the spout then stops again. 3b) flows completely freely, dusting heavily 3c) flows freely, only short stoppages 3d) flows completely free 3e) flows completely free

Example 4:

Testing for solubility in methyl glycol

90 g methylglycol (2-methoxyethanol) were at 20 ° C in a Poured and stirred at 500 revolutions per minute. Then, at once, 10 g of the respective dicyandiamide sample added. The solution behavior was observed.

The samples correspond to those from Example 3. sample Solution behavior in methyl glycol 3a) Clearly solved within 85 seconds 3b) does not clear, anti-caking agent remains unresolved 3c) clearly resolved within 350 seconds 3d) clearly resolved within 90 seconds 3e) Clearly solved within 95 seconds

Example 5:

Testing for solubility in formaldehyde solution

125 g of 30% formaldehyde solution was added with sodium hydroxide to a pH 8.7, heated to 80 ° C and 500 Stirred revolutions per minute. Then at once 50 g of the respective dicyandiamide sample added. The solution behavior was observed.

The samples correspond to those from Example 3. sample Solution behavior in formaldehyde solution 3a) clearly resolved within 125 seconds 3b) does not clear, anti-caking agent remains unresolved 3c) clearly resolved within 570 seconds 3d) clearly resolved within 125 seconds 3e) clearly resolved within 140 seconds

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3340788 [0004]
• - JP 05279317 [0005]

Cited non-patent literature

• Gmelin, Vol. C, D1, p. 281 (1971) [0003]

Claims (18)

Dicyandiamide granules having high abrasion resistance and good flowability, characterized in that it comprises a) an average primary crystal size of 0.01 to 1 mm, and b) has an average agglomerate size of 0.2 to 20 mm. Dicyandiamide granules according to claim 1, characterized in that that it has an average primary crystal size from 0.05 to 0.5 mm. Dicyandiamide granules according to claim 1 or 2, characterized characterized in that the average agglomerate size 0.5 to 5 mm. Dicyandiamide granules according to any one of claims 1 to 3, characterized in that less than 10 wt .-%, preferably less than 5 wt .-%, the particles have an agglomerate size <0.1 mm. Dicyandiamide granules according to any one of claims 1 to 4, characterized in that the dicyandiamide content is> 95%, in particular> 99%. Process for the preparation of dicyandiamide granules according to one of claims 1 to 5, characterized that is dicyandiamide having an average primary crystal size from 0.01 to 1 mm in the presence of water and optionally a binder granulated and the granules with an average agglomerate size from 0.2 to 20 mm. Method according to Claim 6, characterized that is dicyandiamide having an average primary crystal size from 0.05 to 0.5 mm. Method according to one of claims 1 to 7, characterized in that the water content during the Granulation 1 to 25 wt .-%, preferably 10 to 15 wt .-%, is. Method according to one of claims 1 to 8, characterized in that the granulation in the presence a binder is carried out. Method according to one of claims 6 to 9, characterized in that as a binder cyanamide or a aqueous cyanamide solution with a cyanamide concentration from 10 to 60 wt .-% is used. Method according to claim 10, characterized in that that the cyanamide in an amount of 1 to 10 wt .-%, based on the dicyandiamide, admits. Method according to claim 10 or 11, characterized the proportion of water and cyanamide is 2 to 20% by weight, in particular 8 to 16 wt .-%, based on the dicyandiamide. Method according to one of claims 6 to 9, characterized in that as binder cellulose derivatives, Starch or starch derivatives, polyvinyl alcohol, Polyvinylpyrrolidone, gelatin, xanthan gum or copolymers of vinyl compounds, selected from the group of vinyl alcohol, vinyl acetate, vinyl propionate, Acrylic acid, acrylamide or vinylpyrrolidone, or mixtures of these compounds in an amount of 0.01 to 4 wt .-%, preferably 0.1 to 1% by weight. Method according to one of claims 6 to 13, characterized in that the granulation with the aid of Intensive mixers, vertical granulators, spray granulators, Fluidized bed granulators, annular layer granulators or plowshare mixers performs. Method according to one of claims 6 to 14, characterized in that the dicyandiamide granules a average agglomerate size from 0.5 to 5 mm. Method according to one of claims 6 to 15, characterized in that less than 10 wt .-%, in particular less than 5% by weight, the particle is an agglomerate size of <0.1 mm. Method according to one of claims 6 to 16, characterized in that the drying of the dicyandiamide granules at temperatures of 30 to 160 ° C, preferably 60 to 140 ° C, and carried out at a pressure of 20 to 1050 bar. Method according to one of claims 6 to 17, characterized in that the dicyandiamide granules after the drying has a residual moisture content of <2 wt .-%, in particular <0.5 wt .-%, having.