DE539473C - Process for the production of a pressable powder by condensation of carbonic acid amide and its derivatives and formaldehyde - Google Patents

Description

Process for the production of a pressable powder by condensation of carbonic acid amide and its derivatives and formaldehyde. The invention relates on the production of a pressable powder by the known condensation of urea or its derivatives with formaldehyde and processing this powder into artificial masses through the action of pressure and heat.

When urea condenses with formaldehyde, each is formed a more or less hydrophobic resin, depending on the type of condensation, which in can be poured when hot, and into a coherent jelly when cold stiffens.

For the production of fittings on your Gußwege the hot more or less highly viscous mass poured into molds, left to gelatinize and finally by adding heat. hardened. In order to obtain molding powder that to be pressed into molded pieces in the hot press under heat and pressure so far, the resin composition produced in any way has been gelatinized by cooling and mechanically crush the coherent jelly.

The extensive comminution necessary for the production of press powder the jelly is economically inefficient and offers considerable technical Difficulty as it does not pollute the rather delicate mass is feasible. All of these drawbacks are attached to another proposal, the then, through the action of acids, dimethylolurea becomes porcelain-like Produce condensation product, which then powdered, - dried and through Hot pressing is to be transferred into the artificial mass.

The surprising observation has now been made that a molding powder can be obtained directly from the condensation solution. Essentially, the procedure consists in that the resin from a condensation solution which is so diluted that no gelatinization can occur due to the addition of flocculants (e.g. electrolytes or protein precipitants) is precipitated as a flaky precipitate, which after drying results in a powder that can be compressed into homogeneous shaped pieces.

To give a guideline for the dilutions that are required in order to obtain a solution which tends to gelatinize instead of the solution which Is precipitated by electrolytes, it is stated that the solution is expediently so far thinned that in i ooo parts by volume of liquid about 150 Parts by weight of carbamide are included.

Acids and other compounds are used as flocculants, which split off hydrogen ions in the solution, such as acidic salts, acidic esters, etc. Like., Consider, also compounds that are in solution with substances, which are already in the solution are hydrogen ions, such. B. hydrogen peroxide, which reacts with the existing formaldehyde to formic acid. Work in the same way such compounds, which split off hydroxyl ions, such as bases, are basic reacting salts o. The like., a fact that with previous experience over the electrolyte precipitation of brines is in agreement. As the third group of All protein precipitants, such as tannins, can be used as flocculants of natural and synthetic origin, also phosphotungstic acid and the like, in Consideration. The effects of all of these flocculants can be achieved by lyotropic neutral salts can be increased. It can affect the effects of these various flocculants Groups also overlap, of course.

Is the diluted xloid solution with one of the aforementioned flocculants offset, flocculation occurs either immediately or after a while; it can also be accelerated by heating the solution. Here, the reaction mixture appropriately stirred. The onset of coagulation is noticeable by a cloudiness, whereupon a coarse, voluminous precipitate separates out after a short time. The start and time until complete flocculation is achieved also depend on the flocculation temperature and the intensity of stirring on the type and amount of Flocculant off.

Instead of starting from dilute solutions of the finished sol, one can also the appropriately diluted mixture of the starting products or the short one Heating this mixture primarily resulting condensation products after appropriate Add suitable amounts to dilution with flocculants, so that when heating continues the dehydrated, flaky precipitate is created in one go, i.e. the sol is flocculated to a certain extent in statu nascendi.

The further treatment of the precipitate precipitated by flocculation is the same in all cases.

The soft, easily crushable precipitate, the freshly coagulated Cheese material is similar, is made possible by the medium from which it was flocculated completely freed by washing with water. This washing continues for so long until all soluble admixtures, such as flocculants, unchanged initial or intermediate reaction products, are away. After a short wash, the precipitate loses its flaky texture and turns into an extremely light powder, the fineness of which is so. big is that the individual particles only become visible at threefold magnification. After a short time Storage in the air or after washing with fuel and ether gives the anhydrous one Condensation product as a fine, dazzling white, apparently amorphous powder.

This powder is in the cold in the common solvents, especially in water, insoluble. It dissolves easily in acids and can trigger these solutions are separated again by flocculation. In the heat, especially with simultaneous application of increased pressure, it dissolves both in formaldehyde as well as in most hydroxyl-containing solvents with a high boiling point such as in particular in glycerine, chlorohydrins, benzyl alcohol o. The like. On. The won Powder is easy to use, especially when mixed with small amounts of dispersing agent processed into crystal-clear pellets under heat and pressure. But it can also together with fibrous or powdery fillers of all kinds, organic or of inorganic origin, mixed and pressed. Mixing with the fillers is expediently done in such a way that the latter is in the aqueous colloid solution distributed and precipitates together with the urea-formaldehyde condensation product. But it can also be done in any other way that is customary for such mixtures - @ Terfahren. For example, you can have individual layers of paper, cellulose or Sprinkle a tissue with the powder and press together hot until a uniform Press body has arisen. In this way, materials of particularly high quality are created mechanical and electrical strength. The electrical insulation capacity of Pressed pieces, which are made using insulating fillers and fibers with cellulose, Asbestos, Chinaclay, etc. are produced, is also extremely large.

The coloring of the molding powder used can either be before or during the precipitation of the same or only within the mold by addition soluble dyes or pigment colors can be achieved.

Finely powdered or fibrous or in the serve as opacifiers Colloid insoluble liquid substances, e.g. B. Oxides can be used less frequently Earth, such as titanium oxide, zirconium oxide, oils and the like, are used. One can also use it To achieve special effects, add fluorescent paints, radioactive substances, etc. Also all other possible effects here, for example the production cloudy, grained, semi-cloudy, fluorescent or iridescent masses of course possible when using this procedure. There is no need to be attainable at all Effects in detail.

It is also understood that the fine powdery ones obtained Masses after their solution also for look or mixed with fillers or coloring agents of all kinds as paints, adhesives, binders or impregnants in the usual way can find. Reheating is not necessary here.

Embodiment i 3o parts by weight of pure, neutrally reacting urea are with 100 parts by weight of an acid-free or neutralized or weakly alkaline 30% aqueous formaldehyde solution is added and the mixture is brought to the boil on the reflux condenser heated. After a short boil, 5 parts by weight of boric acid, dissolved in a little water, added, whereupon the whole mixture is refluxed continues to cook. 5o parts by weight of the liquid intermediate produced in this way diluted with 50 parts by weight of water and mixed with 3 parts by weight of a 2N hydrochloric acid and kept at about 90 ° C. with stirring. After about half an hour it starts the separation of a flaky precipitate. After another half an hour 100 parts by weight of water are added. The resulting flaky precipitate is then separated from the mother liquor as carefully as possible from all soluble ones Admixtures cleaned and freed from adhering water with fuel. After short Drying the powder is ready for use.

Embodiment e instead of the one used according to embodiment i 2N hydrochloric acid can contain the same amount of 2N formic acid or the corresponding amount an acid salt, especially of alum, serve as a flocculant.

Embodiment 3 ioo Ge, v. Parts of the according to the embodiment example i diluted solution prepared with 1.6 parts by weight of solid sodium hydroxide added and left at 90 ° for 2 hours. After this time it is a coarse flake Precipitated, which exactly as described in Example i, treated further can be.

Embodiment 4 1 3r2 parts by weight of 40 ° 10% formaldehyde with 1888 parts by weight of water, 12 parts by weight of 10% sodium hydroxide solution and 48o parts by weight Carbamide added. After a short boil, 80 ccm of 2N hydrochloric acid are added, whereupon the mixture is allowed to reflux for several hours. Here As a result of the large amounts of water added at the beginning, a flocculent one forms Precipitate, which is worked up and dried in the manner described above can.

Embodiment 262 parts by weight of 40% formaldehyde solution with 698 parts by weight of water, 2 parts by weight of 10% sodium hydroxide solution and 96 parts by weight Carbamide added. After briefly boiling this mixture, 1 part by weight becomes more concentrated Formic acid and 32 parts by weight of thiourea were added and the entire mixture further heated. After one hour the boiling reaction mixture begins to opalesce. After one and a half hours, very strong flake formation has occurred, since the solution has already been was diluted so much at the beginning that no coherent jelly was formed can. After cooling, @ the precipitate, exactly as described in example i, washed and dried.

Embodiment 6 That produced according to the examples i to 5 Powder is produced with a specific pressure of goo kg / crn 'at a temperature of i2o to 13o ° C pressed. This creates crystal-clear, completely transparent pressed bodies, which in contrast to the products of the previously known processes for the production of synthetic compounds from urea and formaldehyde through and through absolute represent homogeneous masses.

From urea derivatives, in particular, thiourea comes for the process into consideration.

Claims (1)

PATENT CLAIMS: i. Process for the production of a pressable powder by condensation of carbonic acid amide and its derivatives with formaldehyde, thereby characterized in that the resin consists of a condensation solution which is diluted so far is that no gelatinization can occur, by adding flocculants (e.g. by electrolytes or by protein precipitants) as a flaky precipitate is precipitated, which after drying becomes a homogeneous moldings compressible Powder yields. a. Embodiment of the method according to claim r, characterized in that that you mix the aqueous resin solution with fillers and then only that Resin precipitates together with the fillers.