CS248596B1 - A method of producing niacotoxic three-packed polycondensates of formaldehyde, urea and melamine - Google Patents

Abstract

Method for the production of low-toxic three-component polycondensates of formaldehyde, urea and melamine, which releases a small amount of formaldehyde when applied in the woodworking and furniture industry, characterized by the initial molar ratio of urea and formaldehyde being 1:1 to 1:2.5, preferably 1:1.75, melamine content 0.5 - 20% by weight, preferably 5% by weight. The final molar ratio of urea and formaldehyde is 1:1.10 to 1:1.50* The process can be carried out discontinuously and/or continuously at temperatures of 90-130 C, pH 3.5 to 9.5, preferably 5.8 to 6.2. The finished product complies with emission class Ξ-1 according to DIN EN 120/79*

Description

The invention relates to a process for the production of low-toxic polycondensates of the form of ldehyde, urea and melamine which they release upon application. small amount of ldehyde form.

For the application of the currently known 8 urea-formaldehyde (UP) polycondensates as well as some mixed, multicomponent polycondensates of urea, formaldehyde and melamine mainly in the manufacture of particle board ε subsequent products thereof (furniture, wooden structures and the like) occur due to air humidity and presence acidic substances from the hardener to cleave polycondensates to form formsldehyde.

This formaldehyde has the following side effects, detrimental to the environment in the production of agglomerated materials and limits the use of a whole range of products based on this.

The currently used adhesives produced according to AO 206 094, 226 922, respectively. 235 3Q6 make it possible to produce chipboard that is classified according to the knitting methodology EESIP / DIN EN 120 (1979), respectively. Gasanalyze-Methode (WKI-Bericht Nr.13 Prsunhofer-Ihstitut fur Holzforschung, Germany) to the emission class E-2. The methodology is based on perforation of bodies and toluene manipulated from the test DTD in a prescribed device, which is described in detail in the cited DIN standard, resp. according to the WKI methodology, air is passed through the absorbed equipment. The formldehyde released from DTD is measured.

In both cases, the released formldehyde is determined by iodometric titration, respectively. Photocolorimetric.

The adhesives produced according to the above AQ release from 15 to 30 mg Fd / 100 g absolute dry DTD (class E-2).

The current hygiene standards for world-class products prescribe values of formeldehyde released below 10 mg Pd / 100 g DTD (B-class E-1).

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Formldehyde reduction is a global problem · In the case of the production of agglomerated materials using standard UF adhesives, the leakage of formldehyde by their surface treatment is reduced, notably by veneer or plate coating, or by staying DTD in an ammonia atmosphere · However, these modifications do not ensure the required requirements for , furniture and similar materials to emission class E * l, ie max. leakage of formsldehyde below 10 mg Fd / / 100 g absolute dry DTD.

Production processes according to AO 197 514, AO 189 229, USP 3,816,376,

USP 3,830,782, USP 3,842,039, FRG Pat 2,207,921, USSR pst.496 191,

BP 1 376 365 protects the production of binders with reduced formaldehyde leakage *, and · modification of binder production at customers, resp. modification of finished DTDs, which do not reliably ensure the achievement of emission class E * l, or the physical * mechanical properties of DTD are deteriorated.

Similar processes for the production of the adhesive according to AO 185 020, or for the preparation of the adhesive mixture, respectively. additive additives according to AO 195 490, AO 225 416, AO 229 417 ensure production of DTD, resp. its adjustment for the mechanical properties of the DTD, or the preparations are not available to the extent necessary on an industrial scale, or the economics of the process is questionable.

The present invention provides a process for the production of low-toxic polycondensates of formsldehyde, urea and melsmin by co-condensation in a discontinuous 1 / or continuous process, wherein the molar ratio of urea to formldehyde. at the end of the session is 1: 1.3 to 1: 2.5, preferably 1: 1.75 at the beginning of the session, adjusts the ss to a final molar ratio of 1: 1.1 to 1: 1.50, preferably 1: 1.16 . The molar ratio of melamine to dye-aldehyde is 1: 1.15 to 1:10, preferably 1: 3%. The content of melsmin in the mixture is from 0.5 to 20% by weight, preferably 5% by weight.

The urea-formaldehyde precondensate containing melamine is prepared in a pre-mixed apparatus by adding formaldehyde n with urea and melsmin at a temperature of 10 to 50 ° C and a pH in the range of

4.5 to 10, preferably 8.0 .mu.H aqueous solution of formsldehyde must be treated with the addition of alkali to prevent the formation of ammonium form from the present carboxylic acid (concomitant impurity for * msldehyde) and ammonia (present in free form in urea), · The amount of formldehyde in the form of an aqueous solution is dosed in such a way as to ensure the above mentioned molar ratio of urea to formldehyde and after 1 min to 5 * 3

248 588, preferably after 30 min, melamine is added. The pH of the reskone mixture is opSt? check 8 as needed abbot? denies the addition of alkali ns before * written value *

This mixture is pumped into a discontinuous and / or continuous single or multi-stage reactor where the condensation of formaldehyde, urea and melamine takes place at a temperature of 85-130 ° C with the three-component condensate poles.

The condensation step is monitored by titrating 8 with a non-aqueous solvent, e.g. acetone, or by measuring viscosity increase.

In the second resp. in the third regcon stage, further condensation takes place by adding so-called " modified urea, which is dosed in the form of an aqueous solution at normal or from a reduced pressure of 2 * 100 kPa, at a temperature of 20-90 ° 0, a pH of 5-9, preferably 8.2.

The dosage of urea is such that the resulting molar ratio of urea to formaldehyde is 1: 1.1 to 1: 1.50, preferably 1: 1.16. Is the amount of urea dosed necessary to be divided? twice.

According to the present invention, a simple resin technology suitable as an adhesive for the woodworking and furniture industry is obtained which has reduced formaldehyde leakage and complies with emission class B-1 (formaldehyde leakage below 10 mg Pd / 100 g DTD). The timber parameters of the glued joint will be maintained.

An essential advantage of the invention in addition to the aforementioned can be considered to be: deficient and expensive melamine content compared to previous production processes claimed for protection.

Example 1

6 350 l of a 37% by weight aqueous formaldehyde solution are metered into a 10 m < 2 > with content

1.4 wt. Stebilizing methanol, the temperature is adjusted to 25 ° C and the pH is adjusted to 4.2 with 1.5 l of 10% sodium hydroxide and 2675 hg of solid urea are added. The mixture was 10 min. the pH is checked and, if necessary, adjusted to 7.5-8 by the addition of the aforesaid NeOH. 645 kg of solid melin 8 are added to the mixture for a further 10 min. The apparatus is then pumped into a reaction system where, at 95-102 ° C, condensation takes place to the desired condensation degree as determined by titration with a nonaqueous solvent (15 * 20 ml acetone at a dilution of 1: 100), or by measuring viscosity rise to 30 * 60 mPa. .s / 20 ° C,

During the reaction by heating the pH spontaneously drops to a value of 5.8 - 6.2 β, the reaction of DC is stopped by adding 10% sodium hydroxide with a value of 6.8 - 7.5 and cooling.

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The condensate thus prepared is charged with 19% urea in the form of a 50% aqueous solution, cooled and further discontinuously evaporated to a dry matter content of at least 65% by weight, cooled to 20 ° C.

The produced three-component adhesive had an obssh dry matter analysis

65.5 wt. (3g / 120 ° C), pH 7.8 viscosity 200 mPa.s, reactivity at 100 ° G with ammonium chloride / 15% aqueous solution l »10/85 s · Formaldehyde emission from pressed DTD according to DIN BN 120 methodology / / 1979 was 8.2 mg / 100g absolute dry DTD · Thatched bending strength 18.5 MPa, Tensile strength perpendicular to thatched plane 0.50 MPa * nComfort after 2 h 4.5% ·

Example 2

Into a stainless steel tank containing 10 nP, equipped with a stirrer with a gearbox and the possibility of cooling or heating 88, is dosed 6,600 l of an aqueous solution of formaldehyde with a concentration of 37.1% by weight. containing 2% by weight of methanol, the temperature of the formalin is adjusted to 25 ° C, its pH is adjusted to 4.0 with 2 l of 10% sodium hydroxide and 2600 kg of solid urea are added, the mixture is stirred for 25 minutes, checked The pH is adjusted to 7.8-8.2 with NaOH by addition of NaOH as required. 500 kg of solid melemine are added to the mixture and mixed for 5 minutes.

The contents of the apparatus containing the formaldehyde-urea-melamine precondensate are pumped into the boilers, where at 90 ° -10 ° C the condensation to the desired condensation stage is gold-plated as described in Example 1.

The pH is controlled during the reaction, which is maintained at 5.6-6.3. The reaction is automatically stopped by adding 10% sodium hydroxide to 6.7-7.8 and cooling.

The condensate thus prepared is pumped through an intermediate tank into a separation system, where it is simultaneously metered together with a 60% aqueous urea solution and continuously evaporates ζβ vacuum at 60 ° C.

The amount of the urea condensate dosed is in the ratio 1 »0.30 - 0.45 / optimum of 19% by weight. urea solids as a modifier / · The vaporized glue is melted to 18-25 ° C. The product after 24 h stabilization is analyzed according to ISN 66 8629 · Reactivity 80 s / / 100 ° C with NH ₄ 01, viscosity 22O mPa.s, pH 8.2, Pd leak from pressed DTD 8.5 mg / 100 g absolute dry DTD * «* S—

Example ^3,248,596

The procedure for the preparation of the condensate is the same as that described in Example 1. The modification (additional addition of urea) in the amount of 19% solid urea is differentiated with two times that of 12% solid urea in the form of an aqueous solution of 60% by weight. whose pH has been adjusted to 6.5 · an additional 7% solid urea opaque in the form of a 60% aqueous solution is already added to the evaporated product, pH adjusted to 7.9 - 8.3. The product analysis was carried out according to the cited ČSN, Reactivity 75s / 100 ° C with NH 4 Cl, viscosity 190 mPa.s, pH 8.2 Pd leak from pressed DTD

7.5 mg Pd / 100 g absolutely dry DTD.

Example 4

In a stirred tank equipped with a cooling capsule, a 9.23% by weight aqueous solution of formaldehyde at a concentration of 37.2% by weight containing 0.45% by weight of methanol is not metered in, and its pH is adjusted by adding 6 L of 10% sodium hydroxide, cool to 25 ° C β add 3 000 kg of solid urea, after 20 min, add 1260 kg of melamine, adjust the pH of the solution to 6.5 * 7.2, Bto prepare the precondensate into the first reaction stage in an amount of 6 m ^ / h, where a condensation reaction takes place at a pressure of 2 bar and a temperature of 110 ° C. The product of the first reaction step, having a viscosity of 75 mPa · s, is continuously withdrawn to the second reaction step, where further condensation is carried out by adding 1.65 m ^ / h of a 60% aqueous urea solution and adjusting the pH by adding 10% sodium hydroxide. This step is carried out at a temperature of 55-65 ° C and a pressure of 10.5 kPa,

From the second reaction step, a product having a viscosity of 200 mPe.s, a free formaldehyde content of 0.4% by weight, a reactivity of 65s / (100 ° C) with ammonium chloride (all according to CSN 66 8629) is removed and cooled to 20-25 ° C. After curing, the product releases 0.12 mg of Pd / 1 g of cured adhesive according to the cited CSN and 7.5 mg of Pd / 100 g of absolute dry DTD according to the PESYP methodology (pérofraction with toluene DIN EN 120)

Claims (3)

DESCRIPTION OF THE INVENTION A method for producing low-toxicity polycondensates of formylhydroxy, urea and melamine, which when applied in the timber and woodworking industry releases a small amount of formyldehyde characterized in that the co-condensation of the urea 8 with melamine with prepare a precondensate at an initial molar amount of urea and formeldehyde of 1: 1.3 to 1: 2.5 preferably 1: 1.75 to 8: 1 molar ratio of melamine: formaldehyde 1: 1.15 to 1:10, preferably 1: 3, at a pH of 3.5 to 9.5, preferably 5.8 to 6.2, which is treated by the addition of hydroxides, or elkic earth carbonates, or metal preferably sodium hydroxide, this precondensate is treated with at a condensation temperature of 80 to 135 ° C, a non-condensation step of, for example, a titration with a non-aqueous solvent, preferably acetone for consumption of 15 to 30 ml, preferably 18 ml, is not necessary after neutralization with alkali hydroxide; Further, by condensing the modifying urea with a discontinuous and / or continuous process, the resulting molar ratio of the power to formeldehyde is 1: 1.1 to 1: 50, preferably 1: 1 to 1: 50 is preferably further reduced by the addition of sodium hydroxide to a pH of 6.5 to 8.5. 1.16, concentrated at a pressure of 2 to 150 kPa, a temperature of 40 to 90 ° C on a continuous and / or continuous dilution, wherein the melamine content of the finished product ranges from 0.5 to 20% by weight, preferably 5% mass · 2. A process as claimed in claim 1, wherein the modifying additive of the ointment is divided into two, wherein 0.5 to 20% by weight of urea, preferably 12% by weight, is added in the first step. 8 in a second step of 0.005 to 15 wt. urea. Printed Moravian Printing Works, Center. 11,100, People's Militia 3, Olomouc Price: 2,40 Kčs