NO130647B - - Google Patents

Description

Moisture resistant modified

urea resins, and method

for the production of these.

Duroplastic synthetic resins are used for numerous applications, such as e.g. phenol-formaldehyde resins of the resol type, urea-formaldehyde resins, as well as resins based on furfuryl alcohol. Each of these resin types is distinguished by its special properties regarding gelation time, curing speed, bond strength and particularly bond strength after moist storage. In order to give the desired end product properties which are in a particular way coordinated with each other, and which cannot be achieved by using pure resin components, it is known to modify some of the duroplastic resins by mixing them with another type of resin.

However, these methods for modifying such resins are technically very complicated, as it is necessary to first prepare the individual resin components separately, and then to mix them with each other in a further method step. In addition, there is often a risk that one of the components will precipitate during the mixing. It is easier to produce resins by co-polycondensation, since, according to the invention, optimal mechanical strength properties and optimal curing speed are achieved, if in the co-polycondensate a completely specific molar ratio is maintained between the reaction components, and the condensation is carried out on

a very specific way.

The invention therefore relates to moisture-resistant, modified urea resins with a good curing speed, the resin being characterized in that they comprise condensation products obtained in two stages by reacting phenols, urea, a furan derivative and an aliphatic aldehyde, in a molar ratio of 0.1 to 1.0:0, 3 to 1.0:

0. 1 to 1.0:2.0 to 4.0 in the 1st step urea is converted with 55-65

% by weight of the aldehyde and 25-35% by weight of phenolene in the absence of catalysts at 80° to 100°C, optionally with the addition of melamine, after which in the 2nd step the reaction mixture is further condensed with the furand.eriate and the remaining amount of phenol and aldehyde in alkaline environment at temperatures 60-100°C to the desired degree of condensation.

The invention further relates to a method for producing modified urea resins as mentioned above, the method being characterized by condensing phenols, urea, a furan derivative and an aliphatic aldehyde in a molar ratio of 0.1 to 1.0:0.3 to 1 in two stages ,0:0.1 to 1.0:2.0 to 4.0, whereby in the 1st step urea is reacted with 55-65% by weight of the aldehyde and 25-35% by weight of the phenol in the absence of catalysts at 80° to 100°C, optionally with the addition of melamine, after which, in the 2nd step, the furan derivative and the remaining amounts of phenol and aldehyde are added to the reaction mixture and further condensed in an alkaline environment at a temperature of 60-100°C to the desired degree of condensation.

The modified resins (hereinafter referred to as copolycondensates) are formed from four starting components. They are distinguished by the following properties: 1. They are resistant to moisture and can be stored in moist air 2. They can be cured without heating; this property appears due to the presence of the furan derivatives. 3. No crystallization of reaction compo-

the nents in the finished resin after its manufacture.

4. Mold sanders that are produced using the resin according to the invention show considerably higher bending strength than such mold sanders that are produced with resins without urea components (US patent no. 3,312,650), or urea resins (US patent no. 3,539,484). For the preparation of the co-polycondensates according to the invention, the phenolic component refers to all phenols which can react with aliphatic aldehydes and which behave polyfunctionally in this reaction. These phenols generally include all phenols that are suitable for the production of the known phenol-formaldehyde resins, such as phenol itself, substituted monovalent phenols such as cresols, xylenols, polyvalent phenols such as resorcinol, alkylene bisphenols, etc.. Ivan can also use suitable mixtures of different phenols. "Unsubstituted phenol and/or a xylenol is preferred.

Preferred furan derivatives are furfurol and furfuryl alkanol.

Aldehydes that can be used for the production of the copolycondensates include saturated and unsaturated aliphatic aldehydes, especially saturated and unsaturated lower aliphatic aldehydes, such as acetaldehyde, propionaldehyde, acrolein, crotonaldehyde, formaldehyde or mixtures of several of these aldehydes. Formaldehyde is preferred.

The 2nd step of the co-polycondensation is carried out in presence

- of alkaline catalysts, preferably of alkali or alkaline earth oxides and hydroxides. The condensation must be carried out step by step, with total or partial amounts of output components being introduced in the individual steps as specified in the requirements. The multi-stage condensation is also characterized by the fact that no catalyst is used in the first stage, since the Jton condensation in the first stage can also take place in an acidic medium. ..-Furthermore, the condensation time and temperature in the individual steps can be the same or different.

With the help of the method according to the invention, co-polycondensates are obtained which can be cured into net-formed products with or without the supply of external heat by means of curing catalysts. In particular, inorganic and inorganic acids are used as curing catalysts, or such compounds which form these acids under the influence of heat.

The co-polycondensates of the invention are distinguished, compared to phenolic resins, by a better curing speed,

and compared to urea resins at a higher bond strength, especially after moist storage. Compared to pure furan resins, the copolycondensates are more advantageous economically due to cheaper and more readily available starting materials.

The invention is illustrated by means of the following examples:

Example 1..

In a glass flask with a stirrer and reflux condenser, 0.66 lg phenol (90% strength) and 3.1 kg formalin (37% strength) are heated together with 0.74 kg urea for 20 minutes at 100°C. 1.54 kg of phenol (90% strength), 2.07 kg formalin (37% strength) and 0.15 kg technical furfuryl alcohol are then added in the aforementioned order. The contents of the flask are heated again to 100°C. Then preferably add dropwise in the form of a 30 - 40% aqueous solution 0.0127 kg of NaOH' (100%). The temperature of 100°C is maintained for 55 minutes. Then, enough water is distilled off in a vacuum to achieve a viscosity of approx. 3000 cP. Example 2.

330 g of phenol (90% strength), 1550 g of formalin (37% strength) and 367 g of urea are held for 20 minutes at 100°C in a flask equipped with a reflux condenser and a stirrer. After adding a further 550 g of phenol (90%-ig), 259 g of 3,5-xylenol, 1036 g of formalin (37%-ig)

and 75 g of furfurol (technical), is condensed while introducing dropwise 18.8 g of a 34% aqueous NaOH solution for a further 55 minutes at 100°C. The dewatering of the resin formed is carried out until a viscosity (according to Hoppler) of 2500 - 3000 cP is achieved.

Example 3»

In a suitable reaction boiler with reflux cooler and agitator, mix 330 kg of phenol (90%) with 1550 kg of formalin (37%) and 367 kg of urea. This mixture is heated for 20 minutes at 100°C. After adding a further 770 kg of phenol (90%),

1036 kg of formalin (37$-ig), 125 kg of furfurol, the boiler contents are heated again to 100°C. After this temperature has been reached, 18.8 kg of NaOH are added in the form of an aqueous solution (34%), and the temperature is maintained for a further 50 minutes at 100°C. So much water is then removed by vacuum distillation that the liquid resin has a solids content (determined by drying for 90 minutes at 150°C) between 40 and 80%.

Example 4.

A mixture of 396 g phenol (90% strength), 1860 g formalin

(37% strength) and 440.4 g of urea are heated in a flask fitted with a stirrer and a reflux condenser for 25 minutes at 100°C. After adding a further 925 g of phenol (96%), 1243.2 g of formalin (37%), 90 g of melamine and 90 g of furfurol, the mixture is heated again to 100°C. When this temperature is reached, a 30 - 40% aqueous solution containing 3.16 g of NaOH is added dropwise. The temperature of 100°C is maintained for 50 minutes.

It is then evaporated in a vacuum until a viscosity of 2800 - 4000 cP is achieved.

The examination of the resins for curing speed and binding ability, respectively mechanical strength, took place in the same way as when using a specific sand as filler (Halterner quartz sand H .

32) produced test rods for measuring the bending strength at different curing times. The binder content calculated on solid resin was 1.57%. An aqueous solution containing 25% by weight of ammonium nitrate and 40% by weight of urea was used as a curing agent. Sand, resin and hardener were thoroughly mixed together, the mixture filled into a +GP+ test rod mold of 225°C, densified, and allowed to stand for 15 seconds and 30 seconds respectively at 225°C. After the rods were cold, the bending strength was measured with the +GP+ test apparatus. The heat bending strength was determined with test rods of the same type immediately after completion of a 120-second curing time (curing temperature 225°C). The results are summarized in the following table:

Claims (5)

1. Moisture-resistant modified urea resins with a good curing speed, characterized in that they comprise condensation products obtained in two stages by reacting phenols, urea, a furan derivative and an aliphatic aldehyde, in a molar ratio of 0.1 to 1.0:0.3 to 1, 0:0.1 to 1.0:2.0 to 4.0 in the 1st step urea is reacted with 55-65% by weight of the aldehyde and 25-35% by weight of the phenol in the absence of catalysts at 80° to 100° C, optionally with the addition of melamine, after which in the 2nd step the reaction mixture is further condensed with the furan derivative and the remaining amount of phenol and aldehyde in an alkaline environment at temperatures 60-100°C to the desired degree of condensation. 2. Resin according to claim 1, characterized in that the furan derivative is furfurol or furfuryl alcohol. 3. Resin according to claim 1, characterized in that the aliphatic aldehyde is formaldehyde. 4. Resin according to claim 1, characterized in that the phenol is unsubstituted phenol and/or a xylenol. 5. Process for the production of modified urea resins according to claim 1, characterized in that phenols, urea, a furan derivative and an aliphatic aldehyde are condensed in two steps in a molar ratio of 0.1 to 1.0:0.3 to 1.0:0, 1 to 1.0:2.0 to 4.0, whereby in the 1st step urea is reacted with 55-65% by weight of the aldehyde and 25-35% by weight of the phenol in the absence of catalysts at 80° to 100°C, optionally while adding melamine, after which in the 2nd step the furan derivative and the remaining amounts of phenol and aldehyde are added to the reaction mixture and further condensed in an alkaline environment at a temperature of 60-100°C to the desired degree of condensation.