DE1142856B - Process to increase the reactivity of paraformaldehyde - Google Patents

Description

Process for increasing the reactivity of paraformaldehyde It is known that the reactivity of paraformaldehyde with prolonged storage, especially at higher temperatures, as a result of aging. At all Reactions in which a good reactivity of the paraformaldehyde is desired This phenomenon creates considerable difficulties. Especially the one The influence of elevated temperatures can greatly reduce the reactivity, so that this phenomenon occurs, for example, during transport at summer temperatures can occur. So far, it has only been able to do this by immediately cooling the paraformaldehyde immediately after manufacture and delayed by storage in the cold will.

It was already known from> the chemistry and technology of artificial Harze «, 1943, p.469 that basic substances cause the condensation of paraformaldehyde with Accelerate phenols, e.g. B. ammonia, alkalis, organic amines, etc. Also are in German patent 537 452 strongly basic isocyclic hydroaromatic Compounds or their derivatives as condensing agents in phenolic resin production used, the strongly basic properties of the compounds being a fast Should cause condensation even when using small amounts. Upon recognition of this reference was expected to result in an increase in reactivity would only be caused by the alkalinity of the amines. Surprisingly However, it was found that it is precisely such amines that improve the reactivity cause which have a lower basicity. Again among these amines are those most suitable according to the present invention, their second substituent is a small aliphatic radical on the nitrogen atom. This is also possible from a comparative basis Resorcin tests show that, since they are carried out in the presence of caustic soda with more or less strongly basic amines, must not show any difference.

It has now been found that the reactivity of paraformaldehyde can be greatly increased if at least 0.50% of a primary and / or secondary aromatic mono- or diamine or one of its salts is added to the paraformaldehyde before it is reacted.

In particular, there is an increase in the reactivity of paraformaldehyde takes place in reactions that take place at a pH of more than 8.5. Preferably this will increase the reactivity in the manufacture of phenolic resins applied in an alkaline medium.

These amines can also be replaced in their aromatic radical by other groups, such as lower alkyl radicals, hydroxyl or alkoxy groups, may be substituted.

The salts of these amines are understood to mean those that are produced by reaction with mineral acids such as hydrochloric acid, sulfuric acid and acetic acid are.

According to the method of the invention, the reactivity of all Paraformaldehydes can be increased regardless of their production method. The paraformaldehydes can for example be prepared by acid or alkali polymerization.

The inventive method it is possible on the one hand to Reactivity of fresh formaldehyde, especially those given above Responses to increase even further, on the other hand, it is possible to increase the responsiveness of an aged paraformaldehyde so that it improves its reactivity of a fresh paraformaldehyde. After all, it is possible to be strong too to improve annealed paraformaldehydes in their reactivity significantly. It is possible in each case by the type of amine used and by the Size of the added amount to adjust the reactivity to a certain value.

The selection of the amine to be added is expediently made in this way meet that the reaction by the small amount of amine is not negative, for example in the sense of side reactions, is influenced.

The use of salts of the amines is particularly beneficial because these are always crystalline bodies that are easy to handle. In addition, the salts are generally more resistant to the effects of oxidation. It it was also found that among the secondary aromatic mono- or diamines or their salts are those particularly effective whose second substituent on Nitrogen atom is a low molecular weight alkyl radical, such as a methyl or ethyl radical, is. P-Toluidine shows the best effectiveness.

The amines are used in amounts of at least 0.5 weight percent, preferably 1 to 2 percent by weight, added. Because in this area the increase in responsiveness depends almost linearly on the amount of amine added, it is, as already stated, possible, by varying the amounts added, a certain reactivity adjust the paraformaldehyde.

To determine the reactivity of the paraformaldehydes, the customary resorcinol test known from US Patents 2,481,981 and 2,519,550 was used in all cases, with the modification that when the tests are returned, the test is not stirred but shaken. The results are summarized in the tables below. Table 1 Paraformaldehyde type Percent resorcinol (Grain fraction 60 Ec) added amine test Minutes 0 6.5 1% aniline 2.5 10/0 aniline hydro 2.7 chloride 10/0 β-naphthylamine 3.9 hydrochloride 10/0 monomethyl 1.7 N-paraformaldehyde, aniline made under 1% p-monomethyl-1,6 Use of aminophenol Formic acid as sulfate Catalyst 10/0 p-toluidine 2.2 1% p-phenylene-2.7 diamine 1% β-naphthylamine 2.7 1% p-anisidine 2.8 1% p-aminophenol 3.0 10/0 benzidine 3.3 10/0 o-aminophenol 3.4 Table 2 shows how the reactivity of a paraformaldehyde is influenced by increasing amounts of a p-toluidine additive. Table 2 Percent resorcinol Paraformaldehyde corte added substance test Minutes N-paraformaldehyde, 0 11.5 made under 0 # 1% p-toluidine 9.9 Use of 0 # 2p / o p-toluidine 8.6 Formic acid as 1 0.5 / 0 p-toluidine 5.8 Catalyst 1.0% p-toluidine 4.0 Grain fraction <60i, 2> 0ö / 0 p-toluidine 3.2 3.0 / 0 p-toluidine 3.1 Table 3 shows the action of p-toluidine on various types of paraformaldehyde. Table 3 Percent resorcinol Paraformaldehyde type added substance test Minutes Paraformaldehyde A, manufactured under 0 13.7 Use of 1% p-toluidine 5.4 Alkali as a catalyst Grain fraction <60 @. Paraformaldehyde OS, made under Use of 0 8.7 Oxalic acid as 1% p-toluidine 4.1 catalyst Grain fraction <60 #t Paraformaldehyde 1 OS / LT under use of oxalic acid as 0 9.0 Catalyst. Post-10/0 p-toluidine 3.3 tolerable thermal Treatment. Normal grind For the experiments shown in Table 4, a paraformaldehyde was used which had been stored at -2'C for 20 days. After this time, the paraformaldehyde still showed the behavior of a fresh product. The reactivity could be increased further by adding an amine according to the invention. Table 4 Resorcinol Paraformaldehyde type Added substance test Minutes N-paraformaldehyde, 1 manufactured below 0 0; 2.6 Use of 0 # 5 @o p-amino-2,2 Formic acid as 1 phenol catalyst 1.0% p-amino-1.7 60g. phenol For the experiments shown in Table 5, a paraformaldehyde was used which was tempered at 80 ° C. for 32 days. It was then stored at room temperature for a further 234 days. Table 5 Resorcinol Paraformaldehyde type Added substance test Minutes N-paraformaldehyde J 0 29.0 Grain fraction 60 #t 1 1% p-aminophenol 10.6

Claims (4)

CLAIMS: 1. A method for increasing the reactivity of paraformaldehyde, marked thereby characterized, that the paraformaldehyde prior to its implementation at least 0.5 ° / o primary and / or secondary aromatic mono- or diamines in the aromatic radical by lower alkyl, Hydroxyl or alkoxy groups can be substituted, or their salts can be added. 2. Method according to claim 1, characterized by the use of a secondary, aromatic mono- or diamine or its salt, whose second substituent on Nitrogen atom is a lower alkyl radical. 3. The method according to claim 1, characterized through the use of p-toluidine. 4. The method according to claims 1 to 3, characterized characterized in that the amines in amounts of 0.5 to 2 percent by weight, preferably from 1 to 2 percent by weight, can be added. Considered publications: German Patent No. 537,452; J. S c h e i b e r, Chemistry and Technology of artificial resins, 1943, p. 469.