DK143709B - PROCEDURE FOR THE PREPARATION OF COPOLY CONDENSATES FROM PHENOLES, FORMAL HYDERS, FURANDER DERIVATIVES AND URINE - Google Patents

Description

143709

The present invention relates to a process for preparing copolymer condensates from phenols, formaldehyde, furan derivatives and urea by condensation in part in the presence of alkaline catalysts.

5 For numerous applications, duroplastic resins such as e.g. phenol-formaldehyde resins of the resole type, urea-formaldehyde resins or furfuryl alcohol-based resins. Each of these resin types is distinguished by special properties in terms of gelatinization time, cure rate, bond strength, especially the bond strength after moist storage. To provide the desired end products with specially matched properties which cannot be achieved using pure resin components, it is known to modify some of the duroplastic resins by blending with a different resin type.

However, this method of modifying such resins is technically very costly as it is necessary to first prepare the individual resin components separately and then mix them with one another in a further process step. In addition, there is a frequent danger of precipitation of one of the components in the mixture.

It is simpler to produce resins by copolymer condensation, and from the specification to British Patent No. 905,393, it is known to prepare copolymer condensates by a two-step process, in which, in the first step, condensation of the entire phenolic and all formaldehyde amounts in alkaline medium to which the urea component is added and condensation is continued. This known process has the disadvantage that precipitation of one of the reactants often occurs upon cooling of the solution formed. From the disclosure of Swiss Patent No. 415,050, a process is known for producing stable urea-substance resin solutions which, however, have the disadvantage that they can only be cured at elevated temperature. Further, from the specification of Swiss Patent No. 423,252 2,143,709, a process for the preparation of phenol-formaldehyde urea condensation products is known. so called 2nd stage, where only urea is added. The resin solutions prepared by this process have insufficient storage stability, especially when stored in a humid atmosphere. In addition, from German Publication No. 1,061,070, a one-step process is known for preparing aqueous phenol-urea-formaldehyde resin solutions in which the condensation is carried out exclusively in alkaline medium. This known process requires the addition of butanol and the resin produced has limited storage stability in moist air.

It has now been found that copolymer condensates can be prepared from phenols, formaldehyde, furan derivatives, and urea in a specific molar ratio by a two-step condensation process using an alkaline catalyst in the second step and the process of the invention 20 is characterized by , that in a first step condensate approx. 30 weight of the phenols, approx. 60% by weight of the formaldehyde and the entire amount of urea without catalyst and condensing the obtained product in a second step with the residual amounts of phenols and the formaldehyde as well as the total amount of furan derivatives with the addition of a base as catalyst using the following relative moles: phenols 1.0 formaldehyde 2.0 to 4.0 furan derivatives 0.1 to 1.0 urea 0.3 to 1.0 and using furfural or furfuryl alcohol as furan derivative.

The resins prepared by the process according to the invention are substantially more moisture resistant than the resins produced by the known processes based on urea, formaldehyde and furfuryl alcohol. This moisture resistance is manifested by the fact that the resins made by the process according to the invention or uncured casting sand, even at elevated humidity, can be stored for a long time without occurring crystallization phenomena which would adversely affect the properties. Furthermore, it is possible to cure the resins produced by the process according to the invention cold, whereas e.g. those from the above description to Swiss patent no.

10 415,050 known resins must be cured at elevated temperature.

For the preparation of the copolycondensates by the process of the invention, phenols which can react with formaldehyde and which in this reaction are polyfunctional can be used as phenolic components. These are generally phenols which are useful in the preparation of the known phenol-formaldehyde resins such as phenol itself, substituted monovalent phenols such as cresols, xylenols, polyhydric phenols such as resorcinol, and alkylene bis-20 phenols. Of course, suitable mixtures of different phenols can also be used.

The second step of the copolymer condensation is carried out in the presence of alkaline catalysts such as preferably alkali or alkaline earth metal oxides and hydroxides. The condensation in the first step can take place in acidic environment. Furthermore, condensation time and temperature may be the same or different in the individual steps.

By the process of the invention, copolymer condensates are obtained which can be cured by means of curing catalysts for cross-linked products, with or without the application of external heat. Particularly used as curing catalysts are used inorganic acids and organic acids or such compounds which form these acids under the influence of heat.

The process of the invention is illustrated by the following examples.

Example 1.

In a glass flask with stirrer and reflux, 0.66 kg of phenol (90 $ s) and 3.1 kg of formalin (37 $ 's) together with 0.74 kg of urea are heated to 100 ° C for 20 minutes. Then 1.54 kg of phenol (90 $), 2.07 kg of formalin (37 $) and 0.15 kg of technical furfuryl alcohol are added in the order in which the flask content is again heated to 100 ° C. Ten drops of 0.0127 kg of NaOH (100 $ 's) are then added dropwise, preferably in the form of a 30-40 $ aqueous solution. The temperature is kept at 100 ° C for 55 minutes. Then, in vacuo, distill in so much water that a viscosity of approx. 3000 cp.

Example 2.

15 330 g of phenol (90 $), 1550 g of formalin (37 $) and 367 g of urine are kept for 20 minutes at 100 ° C in a flask equipped with reflux and stirrer. After the addition of an additional 550 g of phenol (90 $), 259 g of 3,5-xylenol, 1036 g of formalin (37 $'s) and 75 g of furfural (technical), condense 20 more for 55 minutes at 100 ° C. dropwise addition of 18.8 g of a 34 $ aqueous NaOH solution. The dewatering of the resin obtained is carried out until a viscosity (after Hoppier) of 2500-3000 cp is obtained.

Example 3

In a reaction boiler with reflux and stirrer, 330 kg of phenol (90 $) are mixed with 1550 kg of formalin (37 $) and 367 kg of urea. This mixture is heated to 100 ° C for 20 minutes. After adding an additional 770 kg of phenol (90 $), 1036 kg of formalin (37 $ * s), 125 kg of furfural, the boiler content is again heated to 100 ° C. When this temperature is reached, 18.8 kg of NaOH are added in the form of an aqueous solution (34 $) and the temperature is maintained at 100 ° 0 for another 50 minutes. Then, with vacuum distillation, so much water is removed that the liquid resin has a solids content of between 40 and 80 $ (determined by drying for 90 minutes at 150 ° C},

Testing of the curing speed and bonding speed of the resins or mechanical strength is done by using a defined sand as filler (Halterner quartz sand H 32) to produce test bars to measure the bending strength at various curing times. The binder content was $ 1.57 based on the solid resins. As a hardener, an aqueous solution containing 25 wt.% Ammonium nitrate and 40 wt.% Urea was used. Sand, resin and hardener were thoroughly mixed with each other; the mixture was filled into a + GF + test bar form at 225 ° C, compressed and held for 225 seconds at 225 ° 0. After cooling the sample bars 15, the bending strength measurement is performed with the + GF + test apparatus. The bending strength was determined on test bars of the same kind immediately after the 120-second curing time (curing temperature 225 ° C). The results are summarized in the following table.

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