FI66627B - FRAMSTAELLNINGSFOERFARANDE FOER BLADKONDENSATER OCH DERAS ANVAENDNING I LIMBLANDNINGAR - Google Patents

Abstract

1. A process for the production of co-condensates of phenol and melamine with formaldehyde in aqueous solution, wherein a) formaldehyde and phenol are condensed in a molar ratio of 4:1 to 10:1 in a conventional manner in aqueous solution at an initial pH of at least 7.5 until the condensate just exhibits unlimited dilutability with water (or limited dilutability with 5 % strength magnesium sulfate solution), and b) the aqueous condensate thus obtained is condensed with at least 0.3 mole of melamine per mole of formaldehyde at a pH of 7.5 to 10 until it exhibits limited dilutability with water, with the proviso that the amount of formaldehyde, based on the sum of the molar amounts of melamine and phenol, is at least 1.5.

Description

1 66627

Method of preparation of mixed condensates and their use in adhesive mixtures

German patent publication DE 20 20 481 5 discloses mixed condensates formed by melamine, urea and phenol with formaldehyde and which, as aqueous solutions, are suitable as binders (sizing agents) for wood gluing and withstand weather conditions better than previously known urine resins.

10 Such mixed condensates can be used, for example, to produce chipboards that can withstand the effects of long-term outdoor air.

In order to simplify the preparation and improve the properties of such resins, DE 23 05 983 proposes a relatively complicated mixed condensation of phenol, urea, melamine and formaldehyde with only a partial amount of an aminoplastic former and the mixing of the thus obtained mixed condensate with an ordinary amino resin. The weathering of the resins obtained in this way is not as good as would be desired and in addition 4 different substances, namely melamine, urea, phenol and formaldehyde, have to be condensed with each other, albeit to a lesser extent, with constant lifting and monitoring problems on a technical scale. .

Other proposals for the preparation of mixed condensates from phenols and amino resins are included, for example, in DE 891 023, DE 17 20 416, CH 445 859 and US 3 321 551, but all of these focus on aspects other than the present invention and the objects are to be achieved by other means. , in terms of reaction mode, reaction order and amounts of reactants.

It is an object of the present invention to make mixed condensates or condensate mixtures between formaldehyde and phenol, melamine and urea more simply and thus to provide resins which 2 66627 release less formaldehyde in wood adhesives than has hitherto been possible.

The invention relates to a process for the preparation of mixed condensates of phenol and melamine with formeldehyde in aqueous solution, such that a) formaldehyde is condensed with phenol in a molar ratio of 4: 1 to 10: 1 in a known manner in aqueous solution with an initial pH of at least 7.5 and (b) the aqueous condensate solution thus obtained is condensed using 0.3 moles of melamine per mole of formaldehyde in the pH range of 7.5 to 10 to the limit of mixing with water to the limit of mixing with water to a limit of 5% by weight in a 5% by weight magnesium-10 sulphate solution. provided that the amount of formaldehyde used, calculated on the basis of the molar sum of melamine and phenol, is not less than 1.5.

The mixed condensate thus obtained is mixed in all proportions with ordinary urea resin solutions.

As such, it can be used for weatherproof gluing purposes.

20 However, for economic reasons, it is possible to use mixed condensates in adhesive mixtures containing not more than 70% urea (calculated on the solids content of the resin) without losing the weather-resistance properties.

When the phenol is first condensed with excess formaldehyde and then the melamine is condensed under basic conditions, mixed condensates of phenol, melamine and formaldehyde are obtained in one step, which can be mixed with common commercial urea resins on the market and are preferred weather-resistant wood adhesives or wood adhesives. mixed with resins.

In the condensate of phenol, melamine and formaldehyde, the molar ratio of formaldehyde to the other condensation components should be about 1.5-2.2: 1, with the result that the proportion of melamine, based on the molar sum of phenol and melamine, is about 0.4-0.9.

In this case, it is advantageous in the finished mixture to achieve a situation in which the total molar ratio is 1.1 to 2.5, preferably 1.1 to 1.7 moles of formaldehyde, based on the molar sum of melamine, urea and phenol, and the phenol 5 is 0. , 05-0.5 moles per 0.1-0.9 moles of melamine or urea (melamine and urea each time supplemented to Chapter 1).

It will be appreciated that the use of lower amounts of urea in the preparation step of phenolic resin components is not advisable, although it will not interfere with the preparation if the condensation steps are carried out in the order of the invention, i.e. the phenol is first reacted with formaldehyde.

The detailed implementation of the method is as follows:

First, the phenol is reacted - batchwise or continuously - with an aqueous solution of formaldehyde in excess of formaldehyde under heating and so much alkali is added that the pH remains at or above 8.5. If necessary, an alkali base is added up to pH 9 and the condensation is monitored with 5% magnesium sulfate solution.

Cool and add enough melamine such that the total molar ratio of formaldehyde to the molar sum of phenol and melamine is about 1.75 (e.g., 1.5-2.2).

The melamine, mixed and dissolved, is allowed to adjust to the condensed pH (base is added) up to the water mixing limit. At a technically standard resin concentration of 55-65%, the viscosity of the resin solution is about 200-600 mPas. (20 ° C).

The above-mentioned mixed condensates can be mixed with ordinary urea-formaldehyde condensate-based (UF) wood sizing agents. Preferred UF condensates are those having the same formaldehyde content as the UF adhesive currently used as such, e.g. a molar ratio of 1: 1 to 1.8: 1.

4,66627

Example 1 To 4,005 kg of a 40% aqueous solution of formaldehyde is added 687 kg of phenol and 40 kg of a 50% aqueous solution of sodium hydroxide / mixture is heated to 90 ° C with stirring and condensed at this temperature for about 30 minutes. The resulting solution is cooled to 25 ° C and 2400 kg of melamine are added with stirring. The reaction mixture is heated to 90 ° C and allowed to react at 90-95 ° C for about 50 minutes to reach a viscosity of 300 mPas (20 ° C). An additional 6 kg of 50% aqueous sodium hydroxide solution is required to maintain a constant pH of 10.

The resin solution thus obtained is cooled to 25 ° C and added to 5,952 kg of a standard commercial urea-formaldehyde sizing resin having a molar ratio of form-15 to maldehyde to urea of 1.8: 1 and a solids content of 65. %.

The sizing compound has the following properties:

Viscosity 550 mPas (20 ° C) pH at 20 ° C: 8.9 20 Specific gravity at 20 ° C: 1.278

Solids content: 63.5%

Gelling time at 50 ° C: 35 min (after addition of 10% 15% NH 4 Cl solution) 25 Shelf life at 20 ° C for at least 4 weeks.

Example 2 To 5.666 kg of a 40% aqueous solution of formaldehyde are added 850 kg of phenol and 51 kg of 50% sodium hydroxide solution, the mixture 30 is heated to 90 ° C with stirring and precondensed for 30 minutes at this temperature. The solution obtained is cooled to 25 [deg.] C. and 3400 kg of melamine are added with stirring. The reaction mixture is heated to 90 ° C and allowed to react at this temperature for 60 minutes to give a viscosity of 350 mPas (20 ° C). In order to keep the pH constant at 8.9, an additional 8 kg of 50% sodium hydroxide solution must be added. The mixture is cooled to 25 ° C and 7,040 kg of urea-formaldehyde sizing resin obtained as follows are added: 10,000 kg of an aqueous precondensation product containing 4850 kg of formaldehyde in a molar ratio of 4: 1 bound to urea are added, 3230 kg of urine are added. solution (68%, at 70 ° C) and 1310 kg of methanol, the pH is adjusted to 7.3 with 25% sodium hydroxide solution and heated to 90 ° C with stirring. The reaction mixture is kept at this temperature for 10 minutes, at which point the pH decreases. The pH is then adjusted to 4.5 with 20% formic acid and condensed at 90-98 ° C to cloud point (25 ° C) (1 part of the reaction mixture is diluted with 5 parts of hot water). Condensation takes about 50 minutes to 15 minutes.

When the cloud point is reached, the reaction is stopped by adding 25% sodium hydroxide solution to a pH of 7.5, and then 3120 kg of hot urea solution are added. The mixture is cooled to 50 [deg.] C., 3700 kg of water are distilled off under reduced pressure and then a further 3120 kg of urea solution are added. The resulting resin solution is rapidly cooled to below 20 ° C.

It has the following features:

Water miscibility: 1: 3.5 Viscosity: 662 mPas pH: 8.6 8.6

Shelf life: at least 3 months 3

Specific gravity: 1.2775 g / cm

Gelling time (at 50 ° C): 113 min 30 (after addition of 10% 15% NH 4 Cl solution)

The condensate mixture has the following properties: Viscosity: 484 mPas (20 ° C)

Specific gravity (20 ° C): 1.272 g / cm 2 pH value (20 ° C): 8.9

Solids content: 62.8% 6,66627

Gelling time (50 ° C) 67 minutes (after addition of 10% 15% NH.Cl solution) 4

Shelf life (20 ° C): at least 4 weeks Example 3 250 kg of phenol and 13 kg of 50% sodium hydroxide solution are mixed with 1,548 kg of a 40% aqueous formaldehyde solution, the mixture is heated to 90 ° C and kept at this temperature until drops of this solution in 5% magnesium sulphate solution show turbidity. The mixture is cooled to 25 ° C and 1000 kg of melamine are added with stirring. The mixture is heated to 90 ° C, at which point the viscosity at this temperature rises to 400 mPas (20 ° C) within 60 minutes, and the pH is maintained at 8.9 at all times by adding a total of 3 kg of 50% sodium hydroxide solution.

The resulting resin solution is cooled to 25 ° C and mixed with 2190 kg of sizing resin having a molar ratio of formaldehyde to urea of 1.1: 1 and a solids content of 66%.

The mixture has the following properties:

Viscosity: 356 mPas (20 ° C) pH-value (20 ° C): 9.0

Specific gravity (20 ° C) 1.283 g / cm 2 Solid content: 63.7%

Gelling time at 50 ° C: 70 minutes (after addition of 10% 15% NH 4 -Cl solution)

Storage stability at 20 ° C; at least 30 6 weeks

Example 4 500 g of phenol and 25 g of 50% sodium hydroxide solution are mixed with 2620 g of a 40% aqueous formaldehyde solution, the mixture is heated to 90 ° C and condensed at this temperature for 30 minutes, at which point a drop of the precondensate thus obtained shows a cloudiness of 5%. in magnesium 7 66627 sodium sulphate solution. The precondensate obtained is cooled to 25 [deg.] C. and 2200 g of melamine are added with stirring. When the reaction mixture is heated to 107 ° C in a closed reaction vessel, the pressure rises to 1.3 bar.

The condenser is then condensed for 20-30 minutes at a constant pH of 8.8 until the viscosity is 400 mPas (20 ° C). The resulting resin solution is cooled to 25 ° C and mixed with 4655 g of the same urea-formaldehyde sizing resin as used in Example 2.

10 The mixture has the following properties:

Viscosity: 500 mPas.s (20 ° C)

Specific gravity (20 ° C): 1.284 g / cm 2 pH (20 ° C): 8.9

Solids content (50 °): 64% 15 Gelling time at 50 ° C 105 minutes (after addition of 10% 15% NH4Cl solution) Storage shelf life at 20 ° C: at least 6 weeks.

Claims (2)

8 66627 A process for the preparation of mixed condensates of phenol and melamine with formaldehyde in aqueous solutions, characterized in that (a) formaldehyde is condensed with phenol in a molar ratio of 4: 1 to 10: 1 in a manner known per se in aqueous solution at an initial pH of up to a limit of at least 7.5 for unrestricted mixing with water (or a limit of 10 for mixing with water in a 5% magnesium sulphate solution) and (b) condensing the aqueous condensate solution thus obtained using 0.3 moles of melamine per mole of formaldehyde at pH 7.5 -10 up to the limit of mixing with water, provided that the amount of formaldehyde used, calculated on the basis of the molar sum of melamine and phenol, is at least 1.5. Use of a mixed condensate prepared by the process according to claim 1 in adhesive mixtures having in aqueous solution at least 30% of the dry matter content of said mixed condensate and at most 70% of a conventional urea-formaldehyde condensate suitable as an adhesive resin, wherein the molar ratio of formaldehyde to urea is 1.1: 1 to 1.8: 1.