CS251734B1 - A method for producing fluidized aminoplasts - Google Patents

Abstract

Method for producing aminoplasts in suspension from polycondensation raw materials, such as melamine, 6-caprolactam, urea, formaldehyde, in the presence of an initiation system and fillers at temperatures of 60 to 160 °C within 10 to JO min. The deactoplast reacted in the reactor to 90% of the optimal degree of polycondensation is transferred to a fluidized bed dryer, where it is further condensed and dried within 1 to JO min. under reduced pressure of 1 to 95 kPa.

Description

The invention relates to a method for producing aminoplasts in suspension, namely modified and unmodified melamine-formaldehyde or urea aminoplasts, produced by condensation of raw materials such as melamine, 6-caprolactam, urea, formaldehyde, in the presence of an initiation system and fillers. Materials of this type can be processed by all known technological processes and are characterized by high flowability, resistance to difficult climatic conditions and excellent electrical and physical-mechanical properties.

Aminoplasts are heat-curable thermosetting resins, which are used mainly for demanding technical moldings and for moldings that require hygienic safety in contact with food. Current production methods used in the world work with resin prepared by polycondensation in solution mainly under normal pressure (e.g. US-PS 3,376,239), which is then impregnated with filler and other components, and the final product is obtained by drying. According to Czechoslovak patent 129,445 or Czechoslovak AO 212,873, the molding aminoplast is produced by a progressive fluid process, in which polycondensation of all reaction components takes place in the presence of all other components of the thermosetting resin, such as fillers, lubricants, etc., after which, after reaching the optimal polycondensation degree, the molding material in the form of granules is dried in a reactor under maximum vacuum to the final state. However, this significantly reduces the capacity of the fluid reactor.

The above-mentioned disadvantage is eliminated by the method of producing aminoplasts in suspension from polycondensation raw materials, such as melamine, 6-caprolactam, urea, formaldehyde and an initiation system with the addition of fillers, such as cellulose, calcium carbonate, mica, silicon dioxide, at temperatures of 60 to 160 °C for 10 to 30 min.

251,734

The essence of the production method is that the resulting thermoset, reacted to 90% of the optimal degree of polycondensation, is transferred to a fluidized bed dryer, where it is further condensed and dried within 1 to 30 minutes under reduced pressure of 1 to 95 kPa.

Since the polycondensate in the reactor is not condensed to the optimum degree, by which we mean the degree of condensation at which the mass is still processable, but only to 90% of this optimum degree, which can be characterized by a methylol group content of 19 to 25%, it does not harden during drying, but its polycondensation is completed during drying in a time of 10 to 30 minutes. This prevents a decrease in the reaction enthalpy of the resulting aminoplast, and thus a decrease in the required physical and mechanical properties, higher resistance to difficult climatic conditions is achieved and the distribution of the resulting granulate, which no longer needs to be further ground and additionally granulated, is improved. The above-mentioned production method increases the capacity of the fluidized bed reactor more than twice. '

The advantage of this solution will be even more evident from a comparison of the hourly capacity of the fluidized bed reactor. If we consider the hourly capacity of the fluidized bed reactor in the process according to Czech patent 129 445 equal to 100%, this capacity in the process according to Czech patent 224 435 is 200%, and in the production process according to the invention it reaches 400%♦

The method for producing molding aminoplasts according to this invention is explained in more detail in the following examples.

Example 1

Raw materials are added to an intensively stirred reactor heated to 90 °C in the following quantities:

melamine 100 kg beech cellulose 60 kg 6Jcaprolactam 70 kg ground calcium carbonate 120 kg zinc stearate 4 kg titanium white 5 kg

The raw materials are heated to 120 °C, after which liquid raw materials are added:

- 3 formaldehyde (36% aqueous solution) 165 kg triethanolamine 4 kg formic acid (85%) 1 kg

Condensation takes place within 10 min. at a flow rate of up to 90% (methylol content 21%), after which the reaction mixture is transferred to a fluidized bed dryer, where the material is dried at a pressure of 1 kPa and a temperature of 90 °C, completing the polycondensation reaction. The resulting modified melamine formaldehyde mass is characterized by a content of free methylol groups of 18.5% and a curing enthalpy of 120 J/g before curing. The cured aminoplast has a notch toughness of 0.25 J/cm ² .

Example 2

Into a fluidized bed reactor heated to 80 °C be behind intensive the following ingredients are added to the mixture: urea 100 kg aspen cellulose 100 kg stearin 2 kg capital yellow oh, .7 kg hexamethylenetetramine 10 kg titanium white 10 kg formaldehyde (36% aqueous solution) 230 kg ground mica 30 kg

Condensation to 90% takes place within 30 min., after which the polycondensate is transferred to a fluidized bed dryer, where it is dried at a pressure of 95 kPa at a temperature of 80 °C for 30 min. and the resulting urea granulate is ready for further use. The molding compound is characterized by a curing enthalpy of 170 J/g and a shear stress of 0.19 MPa at 120 °C. The cured compound has a notch toughness of 0.35 J/cm and a bending strength of 115 MPa.

Claims (1)

SUBJECT OF VYSXIEZ 251 734 Process for producing aminoplasts in fluidized form from polycondensation raw materials such as melamine, 6-caprolactam, urea, formaldehyde, and an initiator system with the addition of fillers such as cellulose, calcium carbonate, mica, silica at temperatures of 60-160 ° C for 10-30 min Characterized in that the resulting thermosetting material reacted to 90% of the optimum degree of polycondensation is transferred to a fluidized bed dryer, where it is carried out within 1 to 30 min.