CS205953B1 - Method of preparation of the reactoplastic fenolaminoformaldehyde resin - Google Patents

Description

The present invention relates to a process for preparing a thermosetting phenolamine formaldehyde resin by multi-stage condensation of phenols and amino compounds with formdehyde. These resins are suitable for impregnating papixirs used in the manufacture of laminated agglomerated boards or generally laminates.

Unsaturated phenol-formaldehyde resols are most commonly used as binder papers of kraft or sulphite cellulose for the inner tie layers, backing, barrier or leveling layers.

Their typical disadvantage is the high content of unreacted phenol, usually in the range of up to 10% at a commonly used condensation ratio of phenol and fosmaldehyde of 1: 1 to 2. Due to the good impregnation ability, low molecular weight resols are most commonly used. Both reactants »High molecular weight resols often lose their solubility in water and it is necessary to use a larger amount of solvents (methanol, ethanol, acetone, which worsens ecological processing conditions). In addition, in order to achieve the same viscosity, the amount of water as solvent must be significantly increased, thereby reducing the evaporation rate when impregnated with these solutions.

It is known to prepare a phenol urea-formaldehyde resin where a significant reduced content of only formaldehyde is achieved, whereas the free phenol contains more than

2 5 5,953

203 833% and, furthermore, because of the prevailing urea content against phenol, they are not suitable for impregnating papers for increased wettability. Another disadvantage of another method of preparation of phenol-formaldehyde resols with low content of free phenol and formaldehyde is the necessity to use multi-stage time-consuming condensation of both components. The achieved free phenol content is 2% even if the viscosity is unsuitable for impregnation and, in addition, the high alkali catalyst content results in a reddish-brown coloration, the intensity of which is further increased by further heat treatment.

While the preparation of phenol-aldehyde resols with a higher content of a basic catalyst such as NH 3 or its aqueous solutions is suitable for electrotechnical purposes, the resins show very poor miscibility with water, thus necessitating the use of organic solvents and very low reactivity at high free phenol content.

The above-mentioned disadvantages are overcome by the process for the preparation of the phenolanine-formaldehyde resin according to the invention, which consists in condensing in the first stage phenol with formaldehyde at a molar ratio of 1 to 2.0 to 3.3, the phenolic component being phenol, cresol or a mixture thereof. in the second step, the reaction mixture is treated with 0.2 to 1 mole of urea, melamine or mixtures thereof, and the preparation is terminated by treatment with 0.05 to 0.5 mole of ammonia in the form of its aqueous solution or allcananolamine.

In this way, the optimum molar ratios of, for example, phenol, urea, formaldehyde, alkali catalyst and ammonia resin are prepared and high reactivity even at temperatures below 150 ° C, low unreacted and cured components and very miscible with water. These resins have a high drying rate even at

In low solids solution and are well workable at low pressures. The first condensation stage takes place at a temperature of 60 to 100 ° C, preferably at 70 ° C between the phenol and formaldehyde with a molar ratio. 1: 2.2 to 3.3 in the presence of 2 to 10% by weight of an alkali catalyst such as an alkali metal or alkali metal hydroxide; earths to form mostly mononuclear phenol derivatives. The reaction is continued at an elevated temperature in the range of 80 to 100 ° C to partially form the polynuclear compounds and reduce the free phenol content.

Higher temperatures, in the range of 80 to 100 ° C, can be used at a reduced time from the start, resulting in a partial increase in the viscosity of the solution, a decrease in miscibility with water, and an increase in the proportion of polynuclear compounds. In the next step, the condensation of both unreacted fomnaldehyde and phenol-formaldehyde oligomers with urea in an alkaline medium at pH 7.5 to 10 and a temperature of 50 to 9 ° C is introduced, thereby increasing the dry matter content but decreasing the viscosity. Finally, ammonia or an aqueous solution or an amine containing at least 1 hydrogen on nitrogen is added at a temperature of 20 to 90 ° C. A gradual reaction takes place not only with the free foaldehyde to form hexamethylenetetramine or other amino compounds, but also with resin end groups such as methylols to form nitrous, for example dimethylene and trimethylene amine bridges, involved in the chemical structure of the resulting resin.

The synergistic effect of all substances in suitable molar ratios is higher than can be achieved by preparing partial resins with individual substances. If, for example, only urea is used to modify the phenol-formaldehyde resin after the first step, it is necessary to apply it

209 993 an increased amount to achieve the same free phenol and formaldehyde content, which causes deterioration of the wettability, water absorption and reduced resin reactivity. Conversely, completing the reaction of the phenol-monoaldehyde condensate with only ammonia or anine alone necessitates the use of an increased amount and additional dilution with water or solvents to achieve the same viscosity as can be achieved with the present invention.

Ammonia can also be used in the form of its salts with inorganic or organic acids or as a mixture, but it can also be used to adjust the pH of an additional amount of acids / inorganic or organic, while providing a slight reduction in reactivity. useful for some applications.

The resin can be treated by additionally adding water or solvents such as alcohols, especially aliphatic alcohols, but also by adding other auxiliaries such as surfactants, stabilizers or catalysts. If a resin with a higher dry matter content is required, vacuum distillation can be carried out, resulting in waste phenol waters having half to one fifth of the free phenol content and at the same time a low content of free formaldehyde.

The high reactivity of the prepared resin allows a shortening of the pressing time or lower temperatures. The very low content of free, unreacted substances and the nature of this multi-component phenolamine formaldehyde resol allow an increase in resin dry yield and a reduction in evaporation losses of the solutions. The quantity and harmfulness of the exhaled substances, as well as clogging of the equipment during drying, have a very favorable effect.

The following non-limiting examples illustrate the invention. Parts and percentages are by weight.

Example 1

A mixture of 100 parts of phenol, 230 parts of 36.5% formaldehyde and 5 parts of NaOH in 6 parts of H 2 O is heated to 90 ° C for 45 minutes, cooled to 70 ° C, add 30 parts urea and condense at 70 ° C for an additional 30 minutes. After this time, 10 parts of 25% aqueous ammonia were added and the reaction mixture was cooled to 30 ° C. 381 parts / resin solution are obtained with a dry matter content of 41 with a free phenol content of 0.6% and a reactivity of 36 measured as B-time at 150 ° C.

Example 2

A mixture of 100 parts of phenol, 230 parts of 36.5% formaldehyde and 5 parts of NaON in 6 parts of HgO was heated at 70 ° C for 50 minutes. After this time, the temperature is raised to 90 ° C and further condensed until the first turbidity with water at dilution 1 is reached; 15. Add 30 parts urea with cooling. After reaching a temperature of 45 ° C, 39 parts of an aqueous solution of 25% ammonia were added and further cooled to 30 ° C. 410 parts of a resin solution having a dry matter content of 38 containing a free phenol 1 content of 0.5% formaldehyde, a reactivity of 40 measured as B - time at 150 ° C and a reactivity at 100 ° 0 of 35 minutes are obtained. gel d) with a flow time of 12 s measured on a Ford cup with an opening of 4 mm.

205 953

Example 3

A mixture of 122 parts of phenol, 230 parts of formaldehyde 36.5% and 14 parts of 45% aqueous NaOH solution is maintained at 80 ° C for 50 minutes, then 36 parts of urea are added and condensed at 70 ° C for a further 30 minutes. After this time, 6 parts of 25% aqueous ammonia were added and the reaction mixture was cooled to 30 ° C. A resin solution is obtained with a dry matter content of 48%, a free phenol content of 1.85 fe and a reactivity of 70 s, measured as B-time at 150 ° C and a discharge time of 13.3 s, measured on a Ford cup with a 4 mm hole.

Example 4

The composition was the same as in Example 3 except that a 1: 1 mixture of phenol and cresol (containing 40% methomer) was used instead of phenol. The resulting solution had a dry matter of 47.5%, a free phenol content of 2.7 % and a reactivity of 75 s, measured as B-time at 150 ° C. · I:

Example 5

Composition as in Example 3 except that the same amount of melamine was used in place of urea and 5 parts of 100% monoethanolamine were added in place of aqueous ammonia.

To the finished solution was added 5% ethanol and 0.05% nonionic surfactant. The obtained resin solution had a dry matter content of 48.2%, a free phenol content of 1.91%, a reactivity of 68 sec, measured as a B-time at 150 ° C and a discharge time of 12.5 sec, measured on a Ford cup with a 4 mm hole. Example 6

The resin prepared according to Example 3 was adjusted to pH 6.5 by addition of H 2 PO 4 and concentrated by evacuation to a dry matter content of 55%. A light resin solution was obtained with 1.8% free phenol and a 90 sec reactivity, measured as B-time at 150 ° C.

Claims (1)

OBJECT OF NOW / CLIMB A process for the preparation of a thermosetting phenolamine formaldehyde resin by a multi-stage condensation of phenols, amino compounds and formaldehyde, wherein the condensation is catalyzed by an alkali catalyst, characterized in that in the first stage phenol and phonnaldehyde are condensed in a molar ratio of 1: 2.0 to 3.3. phenol, cresol or a mixture thereof, in the second step, the reaction mixture is treated with 0.2 to 1 mol of urea, melamine or a mixture thereof, and the preparation is terminated with 0.05 to 0.5 mol of ammonia in the form of an aqueous solution or alkanolamine.