CS195490B1 - Process for preparing condensates and/or polycondensates of formaldehyde with urea - Google Patents

Description

The invention solves the reduction of the content of the general ' s formaldehyde in the urea formulations, in which the melamine formaldehyde condensates and / or polycondensates used, as a rule, as binders and adhesives, e.g. vos to work, in paper hatch.yí; le "and so on," in a way appropriate. "

The increased content of free formaldehyde makes it much more difficult. operating conditions in the process industry for the application of formatdehyde condensates and polycondensates. formaldehyde fluids not only irritate the respiratory tract by a worker in contact with vapors of fdald3b.vdu, but. it also affects the conjunctival conjunctiva and can cause disturbances and incapacitation at high ejections.

In addition, finished products are also marked by the presence of formaldehyde released, which causes difficulties for the manufacturer, i. the consumer-user for more weeks, even months,

While manufacturers can eliminate the odor of formaldehyde from the working environment, they can be removed from the working environment, even from the air, the consumer is helpless to the odor. It is therefore an effort to reduce the free formaldehyde content immediately by the manufacturer of condensates and / or polycondensates.

Reduction of the free formaldehyde content is achieved by adjusting the technology, by working at natural pHs, or by various feedstock dosing methods, by adjusting the reaction temperature and the reaction time / German Pat. 2 207 921

243,857 /.

Various processes for the use of fine chemical reagents capable of reacting with formaldehyde can be used to form a low-volatile to non-volatile bile.

Urea is used as an additive when the adhesive contains less than 1.8% by weight of the free form] dehyde at temperatures above 60 ^° C. use additions of 10 to 70% by weight (Japanese Patent 74-18 925 and 74-18 926).

Other free formaldehyde depressants are peroxides of KunKun-San-Tai, Taiwan Sugar No. 3, No. 2. 2, 9 (1965), 3 " aldehydes / NSR Pat. 18), phenols (NSR patent)

154 570), sulphate substances are discarded (PLR Pat. 74,060 /, ketones / Jap, pat. 74-38 511 /, rantine oils / Jap. pat. 70-1 6 592 / a others Although these procedures destroy the content of free formaldehyde and in some cases almost complete, the adhesives have usually a low lifetime and therefore need to be applied during several hours. Moreover, even if the content of free formaldehyde is low, the content of formaldehyde released from the finished products is in many cases still considerable.

In many cases, the binder inherits reactivity in such a way that it cannot be cured in the usual manner. In other cases, according to the above procedures, the binder loses the adhesive property after curing, eventually the strength of the glued joints decreases, or the results are simply not reproducible with them,

In investigating the causes of these adverse consequences, a method has now been found that maintaining good adhesive properties of the condensates also results in good reproducibility of the results and in addition a low content of free and released formaldehyde.

It is an object of the present invention to provide a method of

Claims (4)

the condensates and / or polycondensates of formaldehyde with urea and / or melamine, optionally with the addition of further comonomers, carried out in at least two stages, the first stage being carried out with a molar ratio of formaldehyde to urea and / or melamine molar ratio of 1.3 to 10, preferably from 1.8 to 3.0, in which a single or successive urea and / or a formaldehyde reactant is added to the second step and / or the subsequent steps up to the final treatment, in an amount calculated on the basis of 1 to 3 steps. to achieve a final formaldehyde to urea ratio of 1 _? As a rule, with simultaneous and / or subsequent addition or additions to at least one of the compounds of elements L and II. groups of the periodic system and / or polymers in an amount of up to 5% by weight. The urea-formaldehyde condensate can be prepared in both acidic and alkaline environments, possibly in the presence of other substances - caffeine surfactants, such as phenol, alkylphenols, melamine or furfural, which increase the product's resistance to water and moisture. As a rule, the formaldehyde: urea molar ratio of 1.5 to 3 is employed in the first stage, with the condensation interrupted after the desired condensation stage has been reached. Achievement. of the desired condensation step. The condensation is interrupted by neutralizing the solution to a pK of 6.0 to 8.0. Since formaldehyde is most often used in the form of an aqueous solution having a concentration of 30 to 36% by weight, it is necessary to remove some of the water from the solution by distillation so that the final bitumen, respectively. The adhesive (adhesive) contained 65 to 75% by weight of dry matter. After part of the water has been distilled off, the final treatment of the adhesive is carried out by adding urea to the concentrated condensate and, if necessary, other amines and amides reacting with formaldehyde. The additions may be added either in a single or sequential manner, generally at a temperature of less than 100 ° C, preferably at 40 to 60 ^° C. Claims for temperature are reported because by not condensing free formaldehyde at a higher temperature, e.g. 2 h. at a temperature of 80 ° C, in addition to the condensate with a low content of free and liberated formaldehyde, but the condensate has only a short period of use or lifetime, as the gelling becomes blocked during the next hours to several days. Even at a temperature of 50 [deg.] C., a sufficient reaction time of 2 ft and sufficient condensate is sufficient. already has all the prerequisites for a successful application. Due to its low formaldehyde content and the good physical-chemical and mechanical properties of the polycondensates, i.e. the finished bond, the optimum molar ratio of formaldehyde to urea, if any, is to another comonomer. In accordance with the invention, it has been determined that for a condensate having all of the desired properties, the rotational result is a resulting inolar ratio of 1.12 to 0.118 mol of formaldehyde per mole urea or equivalent of another comonomer before application of the condensate. ., ie before the final after i. ycondensation, re> p. communication media. while a lower molar ratio deteriorates the mechanical properties of the product, a higher molar ratio has either a higher freeformaldehyde content or a lower condensate life. If the aa times formaldehyde binds with the addition of other agents, e.g. melamine, amine, or diamine, phenols, and the like, the molar ratio of formaldehyde applies according to the reaction possibilities of the particular comonomer, according to their reaction capabilities (mol equivalents). So eg. when formaldehyde reacts, one mole of urea binds 1 mol of formaldehyde, mole of melamine 1.5 moles of formaldehyde, any diamine 2 moles of formaldehyde and tri-