FR2576026A2 - Process for the manufacture of aminoplastic resins - Google Patents

Abstract

Process for the manufacture of aminoplastic binders containing urea, formaldehyde, phenol and melamine. Process of manufacture from aqueous formaldehyde solutions. Use of these binders as adhesives in the wood industry.

Description

 The present invention relates to an improvement of the process for producing aminoplast resins according to French patent application 84 01188 filed January 26, 1984.

 This patent application relates to a process for producing aminoplast binders containing, for one mole of urea, 0.2 to 0.8 moles of melamine 2 to 5 moles of formaldehyde, 0.05 to 0.5 moles of phenol, characterized in that the phenol is condensed in a first step with a precondensate of urea and formaldehyde of molar ratio F 'U of between 3 and 6, in the presence of urea, so that the proportion of urea present at this step is between 33 and 100% relative to the final total urea contained in the finished resin, the condensation being carried out at a temperature of between 40 and 1000 ° C., first at neutral pH, then at acidic pH at more than 5.5 for at least 30 minutes and in a second step, after addition of all the melamine and, if necessary, a new quantity of urea, so that the proportion of urea present not more than 100% of the total urea content in the finished resin, the condensation being carried out at basic pH, at least equal to 8, at a temperature of between 40 and 100 ° C., until the viscosity of the reaction mixture is between 200 and 1500 mPa.s at 200C for a solids content of 60% and in a third step, if necessary, the remainder of the urea after cooling to a temperature between 40 and 800 C.

 This process for producing aminoplast binders containing urea, formalin, melamine and phenol is therefore a process which comprises two steps, optionally three steps.

 In the first step, all the phenol is condensed with a precondensate of urea and of formaldehyde in the presence of urea, in the second stage melamine and, if appropriate, a new quantity of urea are added and, if appropriate, in the third step, the remainder of the urea is added, these steps being carried out according to particular operating conditions.

 According to the present application it has been found that it is possible to carry out the process of making aminoplast resins starting in the first step of aqueous formalin solutions, instead of urea-formaldehyde precondensate.

 The present invention relates to an improved process for producing aminoplast binders containing, for one mole of urea, 0.2 to 0.8 moles of melanine, 2 to 5 moles of formaldehyde, 0.05 to 0.5 moles of phenol characterized by in a first step all the phenol is condensed with all the formalin added in the form of an aqueous solution in the presence of urea so that the proportion of urea present at this stage is between 33 and 100% relative to the final total urea contained in the finished resin, the condensation being carried out at a temperature between 40 and 1000C, first at neutral pH, then at an acid pH of at most 5.5 for at least 30 minutes and that in a second step, all the melamine and, where appropriate, a new quantity of urea are added after neutralization, so that the proportion of urea present at this stage is at most equal to 100%, relative to total urea contained in the resin finite, the condensation being conducted at basic pH, at least 8, at a temperature between 40 and 1000C, until the viscosity of the reaction mixture is between 200 and 1500 mPa.s at 200C for an extract 60% dry and in a third step, if necessary, the remainder of the urea after cooling to a temperature between 40 and 800C.

 According to the present application, the formalin is completely added in the first step in the form of an aqueous solution.

Commercial solutions containing between 35 and 50% by weight of formaldehyde are preferably used. The improved process for producing aminoplast resins is then carried out under the same conditions of the main patent application 84 01188.

 As a result of using formalin in solution it may be necessary to concentrate the resin obtained to obtain a resin having a desired solids content: this operation is carried out in a known manner, for example by distillation under reduced pressure.

 The following example illustrates the present invention.

-EXAMPLE
We condense in a reactor
- 1331.78 parts aqueous formalin grading 42.80% formalin
- - 557 parts of urea
92.1 parts of 95% phenol.

 The reaction medium is heated so that its temperature reaches 1000C. Condense for 30 minutes. 5 parts of a 24% sodium hydroxide solution are then added so as to raise the pH to 8.3 and then 550 parts of melanine are added.

 The reaction mixture is maintained at 90-950 ° C. and at a pH in the region of 9 by a further addition of 2.5 parts of sodium hydroxide solution until the viscosity of the reaction medium is 550 mPa.s at 20 ° C. what requires a duration of 45 minutes.

After cooling, a resin is obtained which has the following characteristics
- Dry extract: 61.41%
- pH: 8.5
Viscosity at 200 ° C: 595 mPa.s
- Reactivity determined: 2 minutes 29 seconds
according to the method
Beaker (described in
the main request)
- Free Formol: 0.24%
- Free Phenol: 0.96 X.

 The resin obtained is used for the manufacture of panels. The manufacturing conditions are the same as those used in the main application. The mechanical properties of the panel are also determined according to the standards indicated in the main application. The attached table shows the properties of the panel obtained.

BOARD

<tb> - <SEP> Perforator
<tb><SEP> Content <SEP> in <SEP> formol <SEP> (mg / hg) <SEP> 16.1
<tb> - <SEP> Thickness <SEP> (mm) <SEP> 18.66
<tb> - <SEP> Mass <SEP> volume <SEP> (kg / m3) <SEP> 705
<tb> - <SEP> Transverse <SEP> Transaction <SEP> V <SEP> 100 <SEP> 0.34
<tb><SEP> (MPa)
<tb> - <SEP> Swelling <SEP> (%)
<tb><SEP> 2 <SEP> hours <SEP> 4.1
<tb><SEP> 24 <SEP> hours <SEP> 8.7
<tb> - <SEP> Humidity <SEP> / sec <SEP> (%) <SEP> 8.2
<Tb>

Claims (1)

 CLAIM  An improved process for producing aminoplast binders containing, for one mole of urea, 0.2 to 0.8 moles of melamine, 2 to 5 moles of formalin, 0.05 to 0.5 moles of phenol according to claim 1 of the main patent characterized in that all the formalin is added in the first step in the form of aqueous solutions.