DE2351799B2 - PROCESS FOR THE PRODUCTION OF POWDERED METHYLOL COMPOUNDS OF UREA - Google Patents

Description

/ \
HN NH

H ₂ C CH ₂
N
R.

(D

where R is a methyl, ethyl, propyl, butyl, hydroxyaryl, hydroxypropyl, hydroxybutyl radical or a residue of the formula

(CHR ¹ ) (CHR ² I ₁₁ -CH ₂ -N

CH, -NH

CH, - NH

CO

where η = 0 to 4, R ¹ denotes a hydrogen atom or the methyl resl and R ² independently denotes a hydrogen atom, the methyl or OH radical, with the restriction that the OH and methyl radicals are contained in the radical R a maximum of twice , or their methylol compounds are added.

2. The method according to claim 1, characterized in that the triazones or their Methylol compounds are added before methylolation.

1 method according to claims 1 and 2, characterized in that the nichtmethylolierlen Triazone can be added.

4. The method according to claim 3, characterized in that ethyl triazone, hydroxyethyl triazone and / or Äthylenbistriazon can be added.

5. The method according to claims 1 to 4, characterized in that 0.5-5 percent by weight Triüzonverbindungen, based on the amount of urea used, are added.

6. The method according to claims 1 to 5, characterized in that the triazone compound in reactions of 1 mole of urea and 1.8 to 2.0 moles of formaldehyde is added.

7. The method according to claims 1 to 6, characterized in that the pH value with medium-strength organic bases, soda or barium hydroxide.

Methylol compounds of urea are in the form of aqueous solutions for textile finishing, in particular for wrinkle-free and shrink-free finishing of cellulosic textile materials, known for a long time. she mostly in the form of powdered, largely anhydrous products on the market that get through Reaction of urea with aqueous formaldehyde at pH values of 6.8 to 8.8 during some Days and drying, especially drying through

ι ο spraying, the pastes obtained are accessible.

It is also known the storage stability of the pulverulent Methylo'.verbindungen of urea to improve, in which even before the implementation small amounts of inter alia. cyclic alkylene urea compound

gene or their methylol derivatives are added.

The actual powdery products are made by spraying the after methylolation of the Urea obtained crystal mash obtained. In the case of the spray process, however, occurs after the state of the Technique causes considerable elimination of formaldehyde, especially when 1.8 and more moles Formaldehyde are converted per mole of urea. This elimination of formaldehyde increases the yield reduced in powdery products. aside from that

this elimination of formaldehyde brings about a considerable

Contamination of the atmosphere with it, so that great industrial expenditures are necessary for this Eliminate contamination as much as possible.

There has now been a method of making

yo powdery methylol compounds of urea from 1 mole of urea and 1.6-2.1 moles of formaldehyde, adjusting the pH value to about 6.8 to 8.0, reacting in known manner at 0-45 ⁰ C, short-term storage and drying found by spraying where

js, surprisingly, a substantial reduction of formaldehyde emission occurs during spraying, which is characterized in that before spraying 0.3 to ¹ O weight percent, based on the amount of urea used to triazones of the general formula

40

-15

so

Il c

/ ■ \

HN NH

H ₂ C

CH ₂

where R is a methyl, ethyl, propyl, butyl, hydroxyethyl, hydroxypropyl, hydroxybutyl radical or a radical ^s - ^{s of} the formula

- (CHR ¹ ) (CHR ² I ₁ , - CH, - N

CH ₂ -NH

CH ₂ -NH

is, where H = O to 4, R ^{1 is} a hydrogen atom or the methyl radical and R ^{2 is} independently a hydrogen atom, the methyl or OH radical, with the restriction that the OH and methyl radicals are contained in the radical R a maximum of twice , or their methylol compounds are added.

The compounds of the formula (1) are known, the following may be mentioned:

Methyl, ethyl and / or Propyltriazon, Isobutyltriazon hydroxyaryl and / or ß-or y-Hydroxypropyltriazon, as well as ethylene, hydroxypropylene, propylene and / or Hexylenbistriazon. Hydroxyethyl, ethyl and / or ethylenebistriazone are particularly suitable for the process according to the invention, since these compounds are particularly easily accessible. In addition to the triazones of the formula (I), the methylol compounds thereof can also be used. The use of the non-methylolated triazones is preferred, however, since the methylolation stage can be saved when these compounds are used. Both the triazones and their methylol compounds are prepared in a known manner, ie the triazone compounds (= triazones of the formula (I) and the methylated triazones) are used in technical quality.

The triazone compounds mentioned are particularly preferred from the outset, that is, even before the Methylolation added to the present mixtures of urea and formaldehyde, surprisingly even in extremely small amounts the formaldehyde elimination during spraying is quite considerable reduce. Even with amounts of 0.3% by weight, based on the amount of urea used, achieved good results. The upper limit is 10% by weight of triazone compound, based on the amount of urea, called. Of course, larger amounts can also be used to achieve the desired Effect can be used, but for economic reasons only 0.3-10 wt .-%, in particular 0.5-5% by weight of the triazone compounds, based on the urea used, are added.

In principle, it is also possible to add the triazone compounds to the finished paste shortly before drying add, but then a larger amount of formaldehyde is split off again, d. h "the reduction the elimination of formaldehyde is less pronounced, so that this procedure is less useful in practice suitable is.

To produce the methylolurea pastes, both the urea and the formaldehyde are in technical quality used, d. This means that the formaldehyde is generally in the form of 30-40% aqueous solutions is used.

The amounts of formaldehyde used are 1.6-2.1 moles per mole of urea, in particular will pulverulent methylolureas prepared by the process according to the invention, in which per mole Urea 1.8-2MoI formaldehyde have been converted.

The methylol compounds are prepared in a known manner. The urea is added to the formaldehyde solution provided, the pH of which has been adjusted to a value of 6.8-8.0, in particular 7.0-7.5 (measured with pH paper) using alkaline substances stirred in. However, it is also possible to pump the formaldehyde solution onto the urea initially introduced and thus to adjust the pH only after the urea has been added. The triazone compounds, in particular non-methylolated triazones, are preferably added after the urea has been added and the mixture is then stirred for about 1 hour at below 20 ° C., after which the temperature rises to 25-45 ° C. due to the exothermic methylolation reaction The mixture is kept for 2-4 days at 25-35 ° C. In this way, a thin to thick paste-like crystal slurry is obtained, which is dried by spraying Avoiding premature polycondensation phenomena, cooling it to below about 20 ^° C. As already stated, it is also possible - but far less suitable - to add the triazone compounds to the finished paste.

ίο The pH value is set in the usual way Way using basic reacting substances. As particularly suitable for the inventive Processes have medium-strength organic bases such as triethanolamine, diethanolamine and N-dimethylethanolamine, as well as soda and barium hydroxide have been shown to cause formaldehyde to be split off through these compounds on drying and storage stability is not adversely affected. But also can other known neutralization agents) such as alkali hydroxides, Sodium bicarbonate and sodium sulfite can be used to adjust the pH.

The pH value is adjusted to a value of about 6.8-8.0 with the compounds mentioned. As special A pH range of 7.0-7.5 has proven to be favorable, since the product stability when working in this range good and the elimination of formaldehyde during the final drying process is even lower.

In the process according to the invention, as is customary in the prior art, it is expedient not to spray immediately the methylolurea pastes which precipitate in crystalline form after about a day, but rather to store them before drying. A reaction and storage time (= residence time) of 2-4 days at a temperature of approx. 25-35 ° C has proven to be particularly advantageous. For obvious known reasons, it is sufficient at a temperature of z. B. 35 ° C a time of about 2 days, while at 25-30 ⁰ C a time of 3-4 days is usual or appropriate. If the paste obtained is dried after a short period of time, the formaldehyde elimination is noticeably higher and the spraying performance is poorer, while drying after a residence time of more than 4 days clearly worsens the solubility of the powder obtained, unless the paste is cooled after 2-4 days to below 20 ° C, whereby the residence time can be extended up to approx. 14 days, which is, however, uneconomical.

The methylolurea pastes obtained are dried in a known manner in nozzle or disk atomization dryers. The pastes are thereby dried at an inlet air temperature of 140 to about 180 ° C and at a starting temperature of about 50 to about 8O ⁰ C.

The most important advantage of the process according to the invention is that the formaldehyde is split off when spraying the methylolurea pastes up to half, sometimes even up to 60% compared to the state technology is reduced. Decreased by this

(10 elimination of formaldehyde is the purification of the exhaust air considerably facilitated and at the same time the yield of powdered methylolureas corresponding to the reduced formaldehyde release. It should also be emphasized that according to the invention Method a specifically more difficult, d. H. more free-flowing product is obtained, reducing the gluing of the spray devices is reduced, the separation in the cyclones is improved and the filling of the powder is improved

<f

is made much easier. The throughput speed increased noticeably during drying.

It was not foreseeable that the addition of small amounts of triazone compounds would result in the elimination of formaldehyde is reduced to such a considerable extent on drying. Other connections such as cyclic alkylene ureas, Caprolac fern or methylolmelamines do not reduce the Elimination of formaldehyde during the drying of the pastes. It is therefore a question of one for the methylolated resp. unmethylolated Triazone specific effect that was in no way predictable.

Example 1 ' ⁵

300 g of urea are stirred into soie 'a 37% aqueous formaldehyde solution that the molar ratio of urea to formaldehyde 1: 2.0 amount :. The pH of the formaldehyde solution was previously adjusted to 7.0 (measured with special indicator paper) with triethanolamine. Then will the resulting solution divided into three parts.

Part A:

This part is processed further without additives

(State of the art).
Part B:

According to the state of the art, 3 g of dihydroxyethylene urea are added to this part.

ben.
Part C:

5 g of hydroxyethyl triazon (60%) are added to this part of the solution.

.15

All three batches are then ^{stirred at 15 °} C. for 1 hour, then kept with stirring for about 1 day at 30 ^° C. and finally the crystalline pastes obtained are allowed to cool slowly with stirring (reaction time plus storage time equal to 3 days).

To determine the elimination of formaldehyde during drying, after a residence time of 3 days 5 g each of the approx. 54% paste obtained are dried with hot air at about 115 ° C., the exhaust air in cascading washing bottles washed out and the absorbed formaldehyde in known Way determined titrimetrically. The result is shown in the following table:

attempt

Elimination of formaldehyde in% (based on uie obtained
Powder quantity)

A (as of 3.5

B technique) 3.7

C (according to the invention) 1.5

Example 2

60 g of urea are stirred into so much 30% strength aqueous formaldehyde that a molar ratio from urea to formaldehyde of 1: 1.8 is obtained. The pH of the formaldehyde was with barium hydroxide solution has been set to 7.2. 0.8 g Äthylenbist riazon (60%) are added to this solution. the Methylolharriiitoffpastc is, as described in Example 1, manufactured. When drying this paste, as stated in Example 1 (but residence time only 2 days), only 1.95% of formaldehyde is split off, based on the amount of powder obtained.

There is only an insignificant increase in the elimination of formaldehyde when only 0.45 g of des mentioned triazons are used.

Example 3

In the manner indicated in Example 1, 300 g of urea and 850 g of 30% aqueous formaldehyde solution are used implemented, the pH of the HCHO solution before the addition of the urea with soda to a value of 7.4 was set and the triazone compound 27 g of ethyl triazon, also before the addition of the Urea, were added. The elimination of formaldehyde during the subsequent drying (see Example 1) can be reduced by 50% compared to a similar procedure without the addition of ethyl triazon will.

If the ethyl triazone is only added to the finished paste, with otherwise the same procedure, the HCHO split only reduced by 24%.

The n-propyl or methyl triazone can also be used with similar success instead of the ethyltriazone will.

Example 4

The example! 3 is repeated with the difference that the same amount of dimethylolethyltriazone is used as the triazone compound is used. In this case, too, there is a considerable reduction in formaldehyde elimination reached during drying.

Example 5

2 million! Urea are dissolved in 4 mol of formaldehyde in the form of an aqueous 37% solution and the pH of this solution with N-dimethylethanolamine set to 7.6. 6 g of jS-hydroxypropyltriazone are added to this solution. The received Mixture is, as described in Example 1, reacted and the paste obtained after a dwell time of 4 days, as indicated in Example 1, dried. The elimination of formaldehyde is compared to the same Approach (but without the addition of triazones) was considerably reduced.

Instead of the / 3-Hydroxypropyltriazons can also y-hydroxypropyltriazone can be used. In the same way you can also use hydroxypropylenebistriazone to be worked.

Example 6

2500 kg of a 37 percent strength by weight aqueous formaldehyde solution are placed in an open 4000 liter VA steel stirred tank, which is adjusted to a pH of 7.1 with triethanolamine (special indicator paper, range 6.4 - 8.0) ( required amount approx. 3 kg). Then 930 kg of urea are dissolved in it (thereby cooling to approx. 5 ° C.) and 35 kg of an approx. 50% solution of hydroxyethyl triazone prepared as described below are stirred in. After a slight warming to +12 ⁰ C, the Ansai /. held for 3 days with slow stirring, during which time it warms up to 32 ° C. after approx. 12 hours due to the exothermic methylolation. The remaining 2 1/2 days this temperature is maintained by gentle cooling. After this

Time is a very finely crystalline, flowing, white paste that is spray-dried in an atomization dryer will.

An atomization-drying system equipped with a rotating disk and cyclones is used for powder separation. The inlet temperature of the hot air (heating via steam-heated radiators) was approx. 175 ° C, the exhaust air approx. 70 ° C. The spray dryer is designed for water evaporation of approx. 700 kg / hour. ι ο

The paste prepared as described is in a known manner by means of a forced pump on the Rotary disk dosed in the spray tower. Only Required 2 hours, with a yield of 1640 kg of an almost anhydrous powder, consisting largely of Dimethylolurea.

In comparison, a methylolurea paste is produced and applied in exactly the same way and in the same amount spray-dried in the same plant under the same conditions, with the only difference that no triazone addition takes place. After a spraying time of 2 hours and 10 minutes, a yield is achieved of 1520 kg obtained.

In addition to the higher yield in the approach according to the invention, also due to better separation in the cyclones, the main advantage is a lower level of formaldehyde elimination in the exhaust air during the Spraying detectable. The measurement was carried out with a certain amount of exhaust air being sucked through Wash bottles filled with sodium sulfite solution and titration in a known manner.

The entire advantages of the method according to the invention are summarized in the following table:

Elimination of formaldehyde (pro
kg dry product)

yield

Drying time

Approach according to the invention, comparison test 12.6 g

18.1g

1640 kg 120 min.

1520 kg 130 min.

In addition, there is another technical advantage It should be emphasized that the powder produced by the process according to the invention has a higher bulk density having.

Finishing tests with the two products on cotton and cellulose fabrics showed that the Product according to the invention produces at least equivalent results, with minor advantages come to light in the abrasion and tear resistance as well as in the handle.

The Hydroxyäthyltriazonlösung is prepared in a known manner as follows:

66 liters of water are placed in a 250-liter kettle equipped with a stirrer, thermometer and reflux condenser, 72 kg of dimethylolurea powder are stirred into it, heated to 30 ° C. and 36 kg of monoethanolamine are added in portions over the course of 40 minutes, a temperature of 60 ° due to an exothermic reaction Reaches C and the product becomes clear. Then a further 1 hour at about 9O ⁰ C, cooled to about 30 ⁰ C, mixed with a further 30 liters of water and freed of any impurities by filtration.

«9539/448

Claims (1)

Patent claims: 1. A process for the preparation of pulverulent methylol compounds of urea from 1 mole of urea and 1.6 to 2.1 moles of formaldehyde, adjusting the pH value to about 6.8 to 8.0, reacting in known manner at 0-45 ⁰ C. , short-term storage and drying by spraying, characterized in that, prior to spraying, 0.3 to 10 percent by weight, based on the amount of urea used, of triazones of the general formula