CS209101B1 - Manufacturing method of urea formaldehyde condensates - Google Patents

Description

5 CZECHOSLOVAK SOCIALISTS

(19)

DESCRIPTION OF THE INVENTION

TO THE COPYRIGHT CERTIFICATE (11) (B1)

(61) (23) Show Priority (22) Enrolled 28 09 79 (21) PV 6562-79 (51) Int. Cl? C 08 G 3.2 /

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& DISCOVERY (40) Published 31 12 60 (45) Published 30 π gi (75) KELLKER MICHAL ing., HUMENNÉ

The inventor

AMBROŽ EROTlSEK ing., MICHALOVCEHOST MIROSLAV ing.,. STRÁŽSKELIPKA RADÍSLAV, MICHALOVCE (54) Method of production of urea-formaldehyde condensates in 1

The invention solves the process of producing reactive mono-formaldehyde resins suitable for adhesives for agglomerated materials, such as high reactivity adhesives in the veneer furniture industry, and can also be used in furniture manufacturing as a le-pile assembly which has good adhesive properties even when cold.

BACKGROUND OF THE INVENTION The art has been used to produce urea-formaldehyde adhesives in the presence of organic or inorganic acids and the basic urea-formaldehyde ratio is 1.0: 1.8 - 1.0: 2.2. By adding more urea, the salt product is adjusted to a urea: formaldehyde molar ratio of 1.0: 1.3 - 1.0, 1.8 (NSR Pat. 2,207,921, 2,443,857). As a rule, the condensation in the first stage is carried out in an acidic environment at a pH below 5, possibly according to German Pat. 2,207,921 at pH below 3. In Germany, patent pending. 2,109,754 is operated continuously in stirred cascade reactors in the presence of amino acids at varying pHs of 4.2 - 8.0 at normal pressure.

However, for practical use, it is important that the resulting resin used in the wood and furniture industry has specific properties, particularly high reactivity, optimal formaldehyde content, and provides joints characterized by good mechanical-mechanical properties.

So far, the urea-formaldehyde resins produced have been predominantly discontinuous and specific application properties in the wood and furniture industry have been achieved by the demanding metering unit of the basic urea and foraldehyde feedstocks, or by blending the finished low-formaldehyde content (below 0.5% by weight). a high reactivity (formaldehyde content of about 5% w / w) in a suitable ratio. The quality of the product thus prepared was not always optimal.

SUMMARY OF THE INVENTION The subject of the present invention is a method for the continuous production of urea-formaldehyde resins at a temperature of 102-150 ° C and a pressure of 0.002-0.5 MPa in a continuous continuous plant, wherein the basic molar ratio of urea-formaldehyde feedstock is 1: 1.5-1: 2.2 s preferably 1, 1.95. The urea-formaldehyde precondensate is prepared predominantly by a separate mixing apparatus and, after adjusting the pH to 5-8 with an organic or inorganic acid, is fed to a pressurized reactor where the first condensation takes place. In the second step, more condensation of the added urea, which is added in solid form, or in the form of an aqueous solution at 2-20 kPa and a temperature of 30-90 ° C, pH 7-9, preferably 8.2, takes place. The components are fed batchwise to the second stage, the pH being adjusted by the addition of alkali metal hydroxides or alkali earths, e.g. sodium hydroxide. The amount of urea metered in is such that the final molar ratio of urea to formaldehyde is between 1: 1.3 and 1 with 1.85.

According to the invention, a resin with a viscosity of 500 - 2,000. suitable as a glue .product industry which has a high reactivity when using ammonium chloride as a hardener. Example 3 glue can be used as a mounting adhesive for cold glueing in the furniture industry.

In the production of the urea-formaldehyde condensate of the present invention, an exothermic reaction of urea and formaldehyde is utilized, the less production being. energy-intensive and known in the art, solid urea is being fed to a single formaldehyde solution, thus saving the energy needed to evaporate the water, representing viao as a 20% of total energy consumption. A minimum amount of catalysts of 0.001-0.495% w / w is used in the manufacturing process, and the process takes place at pH 5-8 preferably at 5.5-7%, which has a significant effect on reactivity. So far known processes use a catalyst amount above 0.5% by weight, which, for example, when using formic acid, deteriorates the reactivity of the product due to the formation of sodium formate, which is a practical problem.

The manufacturing process of the present invention guarantees a uniform product quality, guaranteeing a 5-10% strength increase in bond strength, which is of great importance for practical use of the condensates. The results of the analysis of the product thus prepared on the gel chromatograph show a narrowing of the distribution curve, which is advantageous for application in woodworking and furniture industry, thereby confirming the high quality and uniformity of the product, which cannot be achieved in the prior art cited procedures.

The manufacturing process of the present invention is, by virtue of the lesser handling and individual types of adhesives, also about 10% more homogeneous in this respect and contributes to the energy savings of the adhesive manufacturers. Example 1

Add 20.08 ml of 37% w / w aqueous formaldehyde solution to a stirred tank equipped with a cooling mixer, add 15 l of a 5% calcium hydroxide suspension to adjust the pH, which, after treatment, is between 7 and 8, 5 and 8,400 kg of solid urea are added. After dissolution, 10% formic acid is added in such a quantity that the pH is in the range of 5 - 7.9%. The pre-condensate thus prepared (1: 1, 95 urea / formaldehyde ratio) is metered at 6 nP / h into the first reaction mixture. The reaction product from the first reaction stage with a viscosity of 30-70 mPas is continuously withdrawn into a second reaction stage, where condensation is effected by the addition of 1.34 m 2 / h 50. % urea solution and 12 L of 5% calcium hydroxide slurry at 55 ° C and 10 mbar. From the second reaction step, the product is continuously collected with a solids content of 67% by weight, a viscosity of 500 mPas, a free formaldehyde content of 0.6% by weight, a reactivity of 52 seconds (measured at 100 ° C with ammonium chloride) and cooled to 20 ° C. Example 2

Add 20.08 ml of 37% aqueous formaldehyde solution to a container fitted with a stirrer and jacket cooling, add 15 l of 10% sodium hydroxide to adjust the pH, which, after treatment, is between 7.0 and 8.5 and adds sa8 400 kg of solid urea. After dissolution, 10% formic acid is added to pH 5.0 - 8.0. The pre-condensate thus prepared (molar ratio of urea: formaldehyde 1: 1.95) is metered in at a rate of 8 m / h to the first reaction stage, where a condensation reaction takes place at a temperature of 125 ° C and a pressure of 0.3 MPa. The product of the first reaction stage with a viscosity of 40-80 mPas is continuously fed to the second reaction

A step where additional condensation takes place by adding 0.38 µm / h of a 50% urea solution and 7 µl of 10% sodium hydroxide at 55 ° C and 10.2 kPa. From the second stage, the product is continuously collected at a dry weight of 66.7% by weight, viscosity 1400 mPas, free formaldehyde content 4.3% by weight and cooled to 20 ° C. Example 3

Add 20.08 ml of 37% aqueous formaldehyde solution to a container fitted with a stirrer and jacket cooling, add 15 l of 10% sodium hydroxide to adjust the pH, which, after treatment, is between 7.0 and 8.5 and adds sa8 400 kg of solid urea. After dissolution, 10% formic acid is added to make the pH 5.0 to 7.9. The precondensate thus prepared (molar ratio of urea to

Claims (1)

4 dehyd 1: 1.95) is metered in at 8 rpm to the first reaction stage, where a condensation reaction takes place at a temperature of 120 ° C and a pressure of 0.3 MPa. The first stage product with a viscosity of 40-80 mPas is continuously withdrawn into a second reaction stage where a second stage condensation is carried out by the addition of 0.89 nr / h of a 50% urea solution and 10 of 110% sodium hydroxide at 55 ° C and a pressure of 10.2 kPa. From the second reaction step, the product is continuously collected with a solids content of 67% by weight, a viscosity of 1200mPas, a free formaldehyde content of 2.3% by weight, a reactivity of 42 seconds (at 100 ° C with ammonium chloride as a hardener) and cooled to 20 ° C. Table of physico-chemochemical properties of urea-formaldehyde condensate prepared according to Example 1-3. Parameter Example 1 Example 2 Example 3 - Dry matter content% by weight 67 66.7 67 pH 7.8 7.6 7.7 Printability mPas / 20 ° C 500 1,400 1,200 Reactivity (Pigment time) with ammonium chloride at 100 ° C ( s) 52 42 39 at 20 ° C (min) Ί 360 40 20 molar ratio of urea to formaldehyde 1: 1.4 1: 1.8 1 · 1.6 Bond strength of glued plywood after IP- 20 (MPa) according to the methodology of the State Testing Laboratory. 216 at the SDV 2,2 2,4 2,3 PRINCIPLE OF PRESENTATION Process for the production of urea-formaldehyde condensates suitable as adhesives in the wood and furniture industry for the production of chipboard, plywood, agglomerated materials and furniture, which are produced from an urea-formaldehyde aqueous solution characterized by Thus, the polycondensate is carried out in a two-stage, first stage, at a temperature of 102 to 150 ° C, at a pressure of 0.002 and 0.5 MPa in a continuous flow device with a starting molar ratio of feedstock of 1: 1.5 to 1. with 2.25 preferably 1: 1.95 in the presence of 0.001 to 0.495% by weight, preferably 0.005% by weight of organic or inorganic acid, preferably formic acid, and in a second stage condensate at a pressure of 2 to 20 kPa, at a temperature of 30 to 90 ° of continuous addition of an aqueous urea solution having a concentration of 20 to 80% by weight, preferably 50% by weight, in an amount such that the resulting molar ratio of urea and formaldehyde was 1 s 1.3 to 11.85 with continuous dosing of the alkali metal and alkaline earth hydroxide solution.