DE1720268C3 - Process for the production of impregnating resins for paper and / or fabric-containing substrates - Google Patents

Description

Condensation products from melamine and formaldehyde are in large quantities in the form of their aqueous or alcoholic-aqueous solutions / um Soaking of carrier materials, /. B. of paper webs, are used, which are then dried and / or processed or for surface coating be pressed onto wooden materials such as hardboard or chipboard. Surface finishes of the type mentioned are characterized by great hardness and scratch resistance as well as high water levels Chemical resistant wedge. They also have outstanding brilliance and color clarity.

Aqueous solutions of melamine-formaldehyde-I condensates however, they have the disadvantage that they only last a relatively short time, e.g. B. a few days at room temperature can be stored, since under these conditions the condensation continues, so that water-insoluble condensate form. Aqueous components containing such insoluble components However, condensates are unsuitable for further processing.

It has now been found that impregnating resin solutions can be used for impregnating carrier materials Paper and / or fabric by condensation of melamine with formaldehyde in an aqueous medium with can produce particularly advantageous properties when in the presence of 3 to 15 percent by weight N-methylpyrrolidone, based on the mixture of melamine and formaldehyde, condensed.

The condensation of melamine with formaldehyde in an aqueous medium in the presence of N-methylpyrrolidone is used in the manufacture of melamine-formaldehyde condensates Working methods made. Such working methods are z. B. in Ullmann's Encyclopedia of technical Chemie, Volume 3, 3rd Edition, on pages 485 to 492 described. So you can, for example Condense melamine and formaldehyde in a molar ratio of 1: 1.4 to 1: 3. The reaction medium can besides melamine, formaldehyde and N-methylpyrrolidone 0 to 20% others, e.g. B. substances capable of forming aminoplasts, such as Urea and urea derivatives, acid amides, toluenesulfonamides and other reactive compounds, such as alcohols, glycols, amines.

Based on the mixture of melamine and formaldehyde at the start of the polycondensation reaction the reaction medium should be 3 to 15 percent by weight, preferably 5 to 10 percent by weight, of N-methylpyrrolidone contain.

The reaction components such as melamine, formaldehyde and N-methylpyrrolidone and, if necessary, other additives are used in amounts such that 3 to 70, preferably 50 to 60, aqueous impregnating solutions containing 1 to 10, preferably 3 to 6 ° and N-Mcthyipyrrolidon contain suitable solutions the Tränkhar / to / by impregnating paper reverberant and gewebehaltigcn Trägcistoffen as for the manufacture of d <-korativeil laminates or for the ^top. ^ enbcschichtung of wood and wood-based material, are ^used? Suitable carriers are, for example, absorbent papers as well as other nonwovens and textile fabrics.

It has been shown that the first storage stability of the invention The impregnation solution / solutions produced is significantly higher than the storage instability of the impregnation solution / solutions, as obtained by known methods. Furthermore, the wetting ability

ίο the Har / Lösungen produced according to the invention as well as whose penetration speed in the carrier materials is increased, so that the usual addition of which / u leads to unpleasant foam bubbles, can be reduced.

Another advantage is that the machine drying with the inventive The water / solutions produced impregnated papers in the hot air stream with an undiminished drying speed more evenly and with a reduced drying speed Bubble and crater formation occurs. This makes the surfaces of the coatings or decorative Laminated panels are particularly well closed, they are pore-free and have good strength.

The papers impregnated with the resin / solutions produced according to the invention can also be used Press with a higher content of so-called "volatile components" without adverse properties occur. The flowability of the resins is compared to other resins significantly increased.

The curing rate of the resin solutions prepared according to the invention is increased by the addition not changed by N-methylpyrrolidone and can also in a known manner, for example by

♦ 5 latent hardeners adjusted to the processing conditions will.

Also in the other properties, especially transparency and clarity of the surfaces as well The condensates produced according to the invention show no difference in their heat resistance such condensates, which consist solely of melamine formaldehyde and optionally known modifiers.

The parts mentioned in the examples are parts by weight.

example 1

A suspension containing 120 parts of melamine, 162 parts of 37% formaldehyde solution, 20 parts of N-methylpyrrolidone and 40 parts of water is heated to 85.degree. C., whereby it is brought to a pH of about 8 by adding aqueous alkali. 5 is set. The reaction mixture is ^{stirred for 6} S at the specified temperature and kept at a constant pH value by continuously adding base until a sample taken from the reaction mixture is at 20 ° C by adding

/ en the 1'Machen amount of water resin can be precipitated. Thereafter, 12.6 parts of melamine are added to the reaction mixture and the reaction mixture is kept at the temperature of AS C until resin can be precipitated from a sample taken from the reaction mixture at 20 ° C. by adding an equal amount of water. A water-clear, slightly opalescent impregnating resin solution which has a viscosity of 37 to 40 cP at 20 ° C. is obtained.

The impregnating resin solution obtained in this way can still be processed after storage for five days at room temperature The solution then has the same transparency as after its production and only slightly increased Viscosity. .

If, as indicated above, Mel? Min is condensed with formaldehyde in an aqueous solution in the absence of N-methylpyrrolidone, an impregnating resin solution is obtained received, which can only be stored for 6 days. After this period they will settle in the solution insoluble resin fractions.

If the impregnating resin solution, obtained only from melamine and formaldehyde, is used after completion the condensation of N-methylpyrrolidone, the storage stability is improved only insignificantly.

Example 2

If 126 parts of melamine and 162 parts of a 37% strength formaldehyde solution are condensed in 50 parts of water and H) parts of N-methylpyrrolidone under the conditions given in Example 1, an impregnating solution is obtained which is stable on storage for 30 days.
Example 3

As described in Example 1, melamine, formaldehyde and toluenesulfonamide are used in the presence of N-methylpyrrolidone under the conditions specified there, the reaction solution being 126 parts is melamine, 142 parts of a 37% formaldehyde solution, Man contains 6 parts of toluenesulfonamide, 10 parts of N-methylpyrrolidone and 62 parts of water receives a soaking solution that has a shelf life of 50 days

is.

ao If the solution is condensed under the same conditions, but with the addition of 16 g of toluenesulfonamide, a further 8 g of water and the absence of N-Meshylpyrrolidon, so you get an impregnating resin solution, which only takes about 20 to 30 days without damage

* S can be stored.

Claims (1)

Claim: Process for the production of Trünkhar / Uisungen for paper and / and fabric-containing substrates by condensation of melamine with Formaldehyde in an aqueous medium, thereby characterized in that the condensation in the presence of 3 to 15 percent by weight N-methylpyrrolidoin, based on the mixture made of melamine and formaldehyde.