CS256327B1 - Method of aminoplastics production - Google Patents

Abstract

Method of production of aminoplasts in suspension, modified and unmodified melamine-formaldehyde, melamine or urea, intended for processing all known technologies, especially pressing. Primary polycondensation raw materials such as melamine, 6-caprolactam, urea, formaldehyde, mineral additives and acids or the bases are first condensed at 60-110 ° C, then under reduced pressure 1 to 95 KPa removes free water and methanol whereupon at 70 to 150 ° C, under pressure 0.1 MPa performs its own polycondensation. Porraaldehyde is fed to the reaction mixture in one or more parts, towing, loose water following each dosing. The bases are added in an amount of 5 to 200 molar, based on the amount of acid.

Description

The present invention relates to a process for the production of buoyant aminoplasts, both modified and unmodified melamine-formaldehyde, melamine or urea, produced from primary polycondensation

6-caprolactam, urea, cellulose, carbon and mineral fibers, formaldehyde and acid; or bases. Aminoplasts of this kind can be processed by all known technological processes, in particular by pressing. They are characterized by high flowability, aging resistance and excellent electrical and physico-mechanical properties.

raw materials such as melamine calcium tann, mica

Aminoplasts are thermosetting thermosetting plastics, which are mainly used for demanding technical moldings. Prior art processes used worldwide, for example according to US-PS 3,376,239, work with resin prepared by polycondensation in solution predominantly at normal pressure, which is then impregnated with cellulose and other components in a batch or continuous kneader and dried to obtain the final product. No. 129,445 or U.S. Pat. AO 212 873, the pressing aminoplasts are produced by a progressive fluid process in which polycondensation of all reactants is carried out under normal pressure in the presence of all primary components, and after reaching the optimum polycondensation degree the granular molding compound is dried to the final state under maximum vacuum.

Since the condensation and polycondensation reactions are always equilibrium reactions, the condensation water shifts the equilibrium to the detriment of increasing the polycondensation degree of the resulting aminoplast.

The above-mentioned disadvantages are eliminated by the method of production of the floated aminoplasts, both modified and unmodified melamine-formaldehyde

256 327 melamine or urea produced from primary polycondensation raw materials such as melamine, 6-caprolactam, urea, cellulose, calcium carbonate, mica, glass or mineral fibers, formaldehyde and acid or base, at temperatures of 60-150 ° C. The essence of the process is that it is first carried out at a temperature of 60 to 110 ° C for 0.5 to 10 minutes. condensation of the primary raw materials, then free water and methanol are removed under reduced pressure of 1 to 95 kPa and then at 70 to 150 ° C for 2 to 15 min. it performs its own polycondensation at a pressure of 0.1 MPa or at a slightly reduced pressure of 0.02 to 0.09 MPa. According to further features, formaldehyde is metered in one, two or more portions, and after each metering after methylation of the reaction groups and incorporation of 6-caprolactam in the case of modified aminoplasts, the free water and methanol are withdrawn. During the polycondensation and / or after the polycondensation, the bases are added in an amount of 5 to 200 mol%, based on the amount of acid used.

Removing the water contained in the feedstock and the water formed during the reaction shifts the equilibrium towards higher polymerization stages and increases the polyreaction rate. This results in the creation of a maximum spatially symmetrical network, which, of course, results in an improvement in physico-mechanical properties. At the same time, the production time for the finished aminoplast is substantially reduced.

Removal of the methanol contained in the aqueous formaldehyde solution from the reaction mixtures due to reduced pressure has a significant effect on shortening the production time and improving the properties of the resulting aminoplasts. Methanol, as a formaldehyde stabilizer, is present in relatively large amounts in the range of 6 to 12% by weight. In the processes used to date, it binds to the resulting methylol groups of the aminoplasts to form the ether group -CPCP-O-CH ^, thereby reducing the curing capacity of the thermosetting plastics and reducing the resulting polymerization degree. At the same time, after opening the lactam ring of the modified aminoplasts, it forms methyl esters of .alpha.-aminocarboxylic acids, thereby blocking one of the two reaction groups and disproportionately increasing the proportion of oligomeric moieties in the resulting thermosetting plastics. Therefore, the processes used hitherto require a longer manufacturing, i.e. essentially reaction time, to suppress these side reactions. In addition, the increased content of low molecular weight constituents in the mass causes it to stick in the mold and deteriorates the appearance properties of the cured product. The methanol content also reduces the curing enthalpy of the aminoplasts, resulting in a deterioration in the physico-mechanical and processing properties.

256 327

By heating the reaction mixture in a fluid mixture with vigorous stirring at 60 to 110 ° C for 0.5 to 10 minutes, the reaction groups are methylated with formaldehyde, incorporating 6-caprblactam in the case of modified aminoplasts, then methanol and a substantial portion of the free water from the reaction system are evacuated. The temperature of the reaction mixture thus decreases by 10 to 40 ° C, slowing down or decreasing the temperature. another chemical reaction stops during the evacuation. After methanol and water evacuation. and after depressurizing the vacuum, the reaction direction is rapidly heated to a polycondensation temperature of 70 to 150 ° C, and within this temperature range the polycondensation is carried out for 2 to 15 minutes. By largely removing liquid components prior to the polycondensation, the granule size does not increase in accordance with the increase in the polycondensation degree, as is the case. eg when proceeding according to Cs. A0 212 873. Since the size of the granules is stabilized to the required size before the polycondensation takes place, there can be no significant increase in the resistance to the agitator, and therefore no significant increase in the load or load. increase of electric motor input. If the liquid components remain in the system during polycondensation, the load on the main agitator will increase by at least 100% during evacuation, and this load limits the weight of the batch with respect to operational safety. The increase in resistance to the agitator is even more significantly suppressed when the formaldehyde is dosed in two or more portions. and after each metering and methylation of the reaction groups, water and methanol are withdrawn from the reaction space. This can significantly increase the weight of the batch. This method also makes it possible to use a significantly higher molar ratio of formaldehyde to melamine without agglomerating the granules or increasing the load. At the same time, it has been found that the absence of blocking methanol from the onset of polycondensation makes it possible to conduct the polycondensation process to twice as high as the polycondensation step, reacting up to 70% of the methylols compared to the previously described methods.

In the process of the present invention, polycondensation is primarily in the form of linear chains, thereby reducing the viscosity of the resulting aminoplast, so that shear stresses of up to 0.05 MPa in the plasmatic state at 120 ° C can be achieved with aminoplasts modified with 6-caprolactam.

The high polycondensation degree determines a high curing enthalpy value of up to 250 3 / g, which also ensures high values of all the physico-mechanical properties of the aminoplasts, so that they are equal to polyester and epoxy molding compositions. According to the present invention, the production times in the polycondensation and drying stages of thermosetting plastics are reduced to a maximum, even in the case of highly condensed polymer. In addition, this procedure allows optimal control of the length of the viscous-liquid state of the melt, the overall reaction time and the injection-safe time.

The following examples illustrate the process for producing the aminoplasts according to the invention.

Example 1

In a fluidized bed reactor heated to 100 ° C under intense conditions The following ingredients will introduce the mixing: melamine 50 kg 6-caprolactam 10 kg cellulose aspen 20 May kg calcium carbonate 40 kg zinc stearate 1 kg triethanolamine 1 kg formaldehyde (35.5% aqueous solution) 50 kg orthophosphoric acid (85%) 0.5 kg The condensation takes place in the float at system temperature up to 80 ° C Mon

water and methanol are removed under reduced pressure (40 kPa). Then under normal pressure at a reaction temperature of 110 ° C for 10 min. polycondensation is carried out, the granular product is dried at 20 kPa for 5 minutes. The loading of the agitator unit increases by max. 50%; after reaching a temperature of 110 ° C, the product is drained, cooled, and usable for final processing. The resulting thermosetting resin is characterized by a curing enthalpy of 180 J / g, a shear stress at 120 ° C of 0.1 MPa, an electrical strength of 17 kV / mm and a shrinkage of 0.1%

Example 2

The following components are introduced into a fluidized bed reactor heated to 100 ° C with vigorous stirring:

melamine 6-caprolactam beech cellulose 1itopon

50 kg 25 kg 30 kg 50 kg

256 327

zinc stearate 2 kg triethanolamine 0.5 kg formaldehyde (36.5% aqueous solution) 40 kg orthophosphoric acid (85%) 1 kg The condensation takes place in the air at the reaction temperature mixtures

for 5 min, after which the pressure was reduced to 20 kPa, water and methanol were removed while the temperature of the reaction mixture dropped to 60 ° C. A second portion of formaldehyde as a 36.5% aqueous solution (40 kg) was metered in at normal pressure, condensed at 90 ° C for 3 min, reduced to 20 kPa, water and methanol removed . After the evacuation of methanol and most of the water, the reaction mixture is heated to 100 ° C and polycondensation is effected within 7 min so that 70% of the methylol bonds react. The granulated product is dried at 30 kPa for 7 min, drained, cooled and ground.

Max. the aggregate load in this procedure increases by 40%. The resulting 2 thermosetting plastics are characterized by an impact strength of 1.2 3 / cm, a curing enthalpy of 250 J / g, a shear stress of 0.05 MPa at 120 ° C, a specific surface resistivity ΙΟ ^^ Ώ- shrinkage of 0.1%, a water absorption of 0.1 % and is resistant to reduced climatic conditions.

Example 3

The following components are introduced into a fluidized bed reactor heated to 110 ° C:

melamine 100 kg cellulose aspen 100 kg zinc stearate 2 kg titanium white 5 kg triethanolamine 2 kg orthophosphoric acid (85%) 0.2 kg formaldehyde (35.5% aqueous solution) 200 kg The condensation takes place in the float at temperature of the reaction mixture

The methanol and a substantial portion of the free water were removed under reduced pressure (20 kPa). Polycondensation is then carried out under normal pressure at the reaction mixture temperature of 95 ° C for 5 min. The load of the agitator is increased to 80% and when the temperature reaches 105 ° C the material is drained, cooled and usable for final processing. The resulting thermoset is characterized by an impact strength of 10 / cm

AND

256 327 with a curing enthalpy of 150 J / g, an electrical strength of 18 kV / mm, is resistant to creep currents at 500 V and has a water absorption of less than 0.1%.

Example 4

In a fluidized bed reactor heated to 100 ° C under intense conditions

mixing the following components: urea 50 kg cellulose aspen 50 kg stearin 1 kg hexamethylenetetramine 5 kg titanium white 5 kg formaldehyde (35.5% aqueous solution) 120 kg calcium carbonate 10 kg The condensation takes place in the float at the reaction temperature 80 ° C

min and then methanol and free water were removed under reduced pressure (10 kPa). Polycondensation is carried out at 90 ° C under normal pressure for 7 min, 5 kg of 50% aqueous ammonium oxalate solution are added to the system, the fine granulated product is dried at 10 kPa for 5 min, discharged from the reactor, cooled and cooled. usable for further processing. The loading of the mixing unit rises by max. 30%. The resulting urea reactor is characterized by an impact strength of 10 / cm, a curing enthalpy of 200 J / g and a shear stress of 0.2 MPa at 20 ° C.

Example 5

The following components are introduced into a fluidized bed reactor heated to 120 ° C with vigorous stirring:

melamine 50 kg cellulose aspen 20 May kg 6-caprolactam 10 kg ground mica 40 kg zinc stearate 1 kg triethanol'amine 1 kg formaldehyde (35.5% aqueous solution) 55 kg Formic acid (85%) 1 kg The condensation takes place in the float at system temperature 110

bu 0.5 min, then water and methanol are removed under reduced pressure of 30 kPa, then the reaction is carried out at 130 g for 0.5 min at normal pressure,

25B 327, 1.2 kg of a 25% aqueous ammonium hydroxide solution is added, and polycondensation occurs within 2 min, and the granular product is dried at 20 kPa pressure for 5 min. The resulting modified thermosetting resin is characterized by a curing enthalpy of 145 J / g, a shear stress of 0.05 MPa at 120 ° C, a viscous-liquid residence time at 120 ° C of 750 s, a total reaction time of 60 min, an injection safety time of 42 min. , a shrinkage of 0.15% and an electrical strength of 17.8 kV / mm

Claims (3)

A process for the manufacture of buoyant aminoplasts, both modified and unmodified melamine-formaldehyde, melamine or urea, produced from primary polycondensation raw materials such as melamine, 6-caprolactam, urea, cellulose, calcium carbonate, mica, glass and mineral fibers, formaldehyde and acid; at 60 to 150 ° C, characterized in that the primary raw materials are first condensed at 60 to 110 ° C for 0.5 to 10 minutes, after which free water and methanol are removed under reduced pressure of 1 to 95 kPa and then the polycondensation is carried out at 70 to 150 [deg.] C. for 2 to 15 minutes at a pressure of 1 bar or at a slightly reduced pressure of 0.02 to 0.09 bar. 2. A process according to claim 1, wherein the formaldehyde is metered in one, two or more portions, and after each metering, methylation of the reaction groups and incorporation of 6-caprolactam in the case of modified aminoplasts is followed by withdrawal of water and methanol. 3. Process according to claim 1, characterized in that, during or after the polycondensation, bases are added in an amount of 5 to 200 mol%, based on the amount of acid used.