DE1205072B - Stabilization of aqueous or aqueous-methanolic formaldehyde solutions - Google Patents

Description

Stabilization of aqueous or aqueous-methanolic formaldehyde solutions Formaldehyde solutions in water are less stable during storage, the higher the Concentration of formaldehyde and the lower the storage temperature. So are for example 300% solutions stable above 70 ° C, 370% above 350 ° C and 400% above 420 C. If this specified temperature is not reached, it is separated solid paraformaltdehyde from the solution, the faster the deeper the Temperature is selected.

To stabilize formaldehyde solutions of higher concentrations mostly methyl alcohol is used. To a 37 weight percent formaldehyde solution To stabilize so far that no paraformaldehyde deposits occur, is z. B. when stored in summer a methanol content of 7 to 10o / o, in winter even up to 130/0 necessary. In the case of more concentrated solutions, the paraformaldehyde deposits are prevented mostly by cooling below the shelf life limit temperature avoids, d. In other words, the formaldehyde solutions must be stored in heatable tanks and be transported.

It is already known to use melamine to stabilize formaldehyde solutions to use.

In order to achieve a satisfactory effect, however, additional amounts are required from 1 to 10 0 / o is necessary, which is particularly uneconomical when the formaldehyde to be used for the production of cheap urea and phenolic resins. It it has also been suggested to use certain colloids, e.g. B.

Cellulose ether in relatively small amounts of aqueous formaldehyde solutions add to achieve a certain stabilization, however, these additives the formaldehyde solutions cannot be prevented from gelling or pasty in the cold will.

The invention relates to the stabilization of aqueous or aqueous-methanolic Formaldehyde solutions against deposition of solid paraformaldehyde and is thereby characterized in that the formaldehyde solution is about 0.02 to 1.50 / o benzoguanamine or adding methylolbenzoguanamine.

Benzoguanamine can be added in solid form or advantageously also as a solution of methylol benzoguanamines, as they are when dissolving benzoguanamine arise in formalin.

It is particularly surprising that with these small additions Sufficient stabilization can be achieved even at temperatures below 50 C. With the discovery of this stabilizer, it has become possible to normal To use storage and transport tanks for formaldehyde solutions and on their special To do without insulation or even heating jacket cladding.

Example 1 In a 40 percent strength by weight aqueous formaldehyde solution, which does not contain methanol, 0.261o finely ground benzoguanamine is dissolved at about 600 ° C. on. After cooling to 200 ° C., the clear solution remains stable for 12 weeks.

Even after cooling the solution to 50 ° C., it separates during this No paraformaldehyde is released during the period.

When such a solution is cooled to 100 ° C., one observes Several weeks of storage a very slight cloudiness, which again when heated to 0 ° C disappears.

In the case of a comparative sample without a stabilizer, however, it was A large part of the formaldehyde is in the form after just 24 hours at room temperature deposited from paraformaldehyde.

Example 2 187 parts of benzoguanamine are dissolved in 400 parts by weight of 300% formaldehyde at 800 C and pH 7.0.

The product obtained in this way is chromatographically inconsistent. To Warming for 10 minutes at 800 ° C. is used to set the obtained, otherwise also durable Solution in an amount of 0.50 / 0 of a 40 weight percent aqueous formaldehyde solution, which does not contain methanol, at about 600 C.

After cooling to 200 ° C., the solution now remains clear for 12 weeks.

Even after cooling the solution to 50 ° C. it separates Don't time out paraformaldehyde.

A 40 weight percent stabilized comparatively with 0.50 / 0 melamine Formaldehyde solution already has considerable quantities after 14 days of storage at 200 C. Paraformaldehyde deposited.

Example 3 In a 37 percent strength by weight aqueous formaldehyde solution, which does not contain methanol, dissolve at about 600 ° C. 0.10 / o finely ground benzoguanamine on. After several weeks of storage at 100 ° C. there is only a very slight cloudiness can be seen, which disappears when the solution is warmed to 0 ° C.

If the above formaldehyde solution is stabilized, one additive is sufficient of 0.05u / 0 benzoguanamine in order to keep the solution completely clear at - 100 ° C.

Example 4 In a 40 percent strength by weight aqueous formaldehyde solution, which contains 50/0 methanol will be 0.10 / o benzoguanamine dissolved at about 400.degree. the Solution is completely stable at 200 C and can withstand weeks of storage both at 50 C as well as -100C.

A comparison sample without the addition of benzoguanamine, on the other hand, is already different considerable amounts of paraformaldehyde are removed after storage for 5 days at 200 ° C.

Claims (1)

Claim: Stabilization of aqueous or aqueous-methanolic Formaldehyde solutions against deposition of solid paraformaldehyde, d u r c h characterized in that the formaldehyde solution is about 0.02 to 1.50 / o benzoguanamine or adding methylolbenzoguanamine. Publications considered: Swiss patent specification No. 240,988; French patent specification No. 1228672.