CS247319B1 - Production method of formaldehyde condensates or polycondensates with urea and melamine - Google Patents

Abstract

A method for producing condensates and / or polycondensates formaldehyde with urea and melamine with reduced formaldehyde leakage two-stage urea condensation and melamine with formaldehyde. These condensates are used as binders in woodworking and the furniture industry. The advantage of the solution is that the resin releases when applied in the production of DTD, respectively. furniture less than 10 mg fd / 100 g absolutely dry DTD according to DIN EN 120/79, which suits emission class E-1 according to that standard while maintaining good adhesive properties and low swelling of the finished DTD. The essence of the solution is co-condensation of said raw materials from the precursor urea-melamine-formaldehyde, with the molar ratio of urea to formaldehyde is 1: 1.5 to 1: 2.2, preferably 1: 1.90 and a ratio of melamine to formaldehyde of 1: 1.5 up to 1: 10 preferably 1: 3. The resulting molar ratio of urea to formaldehyde is 1: 1.1 to 1: 1.40 preferably 1: : 1.18.

Description

The invention relates to a continuous, pressurized process for the production of condensates and / or polycondensates of formaldehyde with urea and melamine with reduced formaldehyde leakage by a two-stage condensation of urea and melamine with formaldehyde.

In the application of urea-iormaldehyde (UF) adhesives in the gluing process and especially in the further use of agglomerated materials mainly in the manufacture of furniture and wooden constructions, due to air humidity and the presence of acidic substances from the hardener UF condensates, they cleave to form formaldehyde. This formaldehyde has undesirable side effects, harms the environment and limits the use of a range of products based on agglomerated materials.

The currently used adhesives produced in a continuous process at elevated pressure according to AO 20S 094, 209 101, respectively. 226 922 enable the production of wood-based thatch (DTD), which is classified according to the internationally valid PESYP methodology (DIN EN 120/1979) in emission class E-2. The methodology is based on the perforation of the bodies manipulated from the DTD test with toluene in a prescribed device, in a manner known to the woodworking industry. Formaldehyde is determined after perforation in a T-shirt house, res p. at low values photocolourimetrically after previous staining with chromotropic acid. Adhesives produced according to the above AO release from 10 to 30 mg fd / 100 g of absolutely dry DTD (class E-2), which in the air of wooden buildings continues the value of the respective MS. 0.035 mg fd / m ^{3 of} air (fd = formaldehyde).

Reducing formaldehyde leakage is a global problem. In the case of the production of agglomerated materials using standard UF adhesives, formaldehyde leakage by their surface treatment is reduced, in particular by veneering or by coating boards or plates. by staying DNT in an ammonia atmosphere. However, these modifications do not ensure that the prescribed requirement for the inclusion of boards, furniture, etc. is achieved. materials in emission class E-1, ie. j. formaldehyde leakage below 10 mg / dd / 100 g of absolutely dry DTD.

Stage production processes AO 197 514, AO 189 229, USP 3,816,376, USP 3,830,782, USP 3,842,039, Germany Pat. 2,207,921, USSR Pat. 496 191, BP 1 576 365 protect the production of binder with reduced formaldehyde leakage, modification of binder production at the customer, or treatment of finished DTD, but do not reliably ensure the achievement of emission class E-1, or deteriorate the physico-mechanical properties of DTD.

Similar processes for the production of the adhesive according to AO 185 020, or the modification of the adhesive mixture, respectively. addition of additives according to no. AO 195 490, AO 225 416, AO 229 417 ensure the production of DTD, respectively. its adjustment at the cost of deteriorating the physico-mechanical properties produced

DTDs or products are not available on an industrial scale to the extent necessary, or their economy is questionable.

In practice, using AO 235 386, it has been confused that there is a decrease in formaldehyde leakage from the pressed] DTD detected by the FESYP perforation method from 18 to 20 mg fd / 100 g of absolute dry that averaged (AO 206 094) to 15 to 17 mg fd / 100 g of absolute dry thatch.

SUMMARY OF THE INVENTION The present invention provides a process for the continuous production of urea-formaldehyde formaldehyde resin with reduced formaldehyde leakage by two-stage condensation of urea and melamine at 102-130 ° C and a pressure of 0.001 to 0.5 MPa in a continuous flow device. : 1.5 to 1: 2.2, preferably: 1.90, molar ratio of melamine: formaldehyde 1: 1.5 to 1: 10, preferably 1: 3, the melamine content of the finished product is 0.005 to 20% by weight %, preferably 10% by weight. The urea-melamine-formaldehyde precondensate is prepared beforehand in a separate mixing apparatus by addition of the basic ingredients at a temperature of 10 to 60 ^° C and a pH in the range of 7 to 10, preferably 8.5, so as to maintain the above mole ratio of feedstocks. The pH is adjusted by addition of an alkaline hydroxide. The prepared precondensate is injected into a pressure reactor where the first stage of condensation of the feedstocks takes place.

The preparation of the two precondensates in the proportions mentioned above does not preclude separate mixing and mixing them just prior to the feed to the pressure stage of the reaction.

In the second, respectively. in the third reaction stage, further condensation of the so-called " of modifying urea which is metered in the form of an aqueous solution at a pressure of up to 20 KPa and a temperature of 20 to 90 ° C, a pH of 5 to 9, preferably 8.2. The components are dosed continuously to the second stage, the pH being adjusted by the addition of alkali metal hydroxides in the form of dilute solutions, most often at a 10% concentration. The amount of urea dosed is such that the resulting molar ratio of urea to formaldehyde is in the range of 1: 1.1 to 1: 1.40, preferably 1: 1.18. This dose of urea can be divided into two. The melamine content of the mixture is from 0.005 to 20% by weight, preferably 10% by weight.

According to the invention, a simple resin technology suitable as an adhesive for the wood and furniture industry is obtained which has reduced formaldehyde leakage and complies with emission class E-1 (formaldehyde leakage below 10 mg fd / 100 g DTD).

Wood parameters of the glued joint are compared to the original AO 206 094, 209 101, resp.

226 922 do not worsen and improve compared to AO 235 386.

Example 1

The mixed container provided with the jacket with the possibility of cooling is dosed

2.15 m ³ of a 37% by weight aqueous solution of formaldehyde, containing 0.45% by weight of methanol, adjusted to pH 8.5 by addition of 5 l of 10% sodium hydroxide solution and adding 1 260 kg of solid melamine . After stirring for 30 minutes, 7.18 m ^{3 of} an aqueous formaldehyde solution of the same concentration as above was added, and 3,000 kg of solid urea were added, the pH of the solution being 6 to 6.1. The precondensate thus prepared is metered in at a rate of 7 m ³ / h to the first reaction stage, where a condensation reaction takes place at a pressure of 0.3 MP and a temperature of 120 ^° C. The product of the first reaction step having a viscosity of 80 mPa. s is continuously taken to the second reaction stage, where further condensation takes place by the addition of 1.75 m ³ / h of a 50% aqueous urea solution and the pH is adjusted by adding 10 l / h of 10% sodium hydroxide. This step takes place at a temperature of 55 ° C and a pressure of 10.5 kPa. A product having a viscosity of 350 mPa is taken from the second reaction stage. with a free formaldehyde content of 0.4% by weight, a reactivity of 65 s / 100 ^C with ammonium chloride (all according to CSN 66 86 29) and cooled to 20-25 ° C. After curing, the product releases 0.15 mg fd / 1 g of cured adhesive according to the cited CSN and below 8.5 mg fd / 100 g of absolutely dry DTD according to the FESYP method of toluene perforation - DIN EN 120/1979.

The waste water from the plant contains 0.45% by weight of methanol and 1.65% by weight of formaldehyde.

Example 2

In the apparatus described in Example 1, 13 430 L of 37 wt% formalin is metered in a similar manner, adjusted to pH 4.5 by addition of 10 L of 10% sodium hydroxide, and 5,100 kg of solid urea are added. The mixture is stirred at 20 ^DEG C. for approximately 1 hour and then 4,000 l of formalin are added, checked and checked. adjust the pH to 8.5 and add 2000 kg of melamine. Spraying 10 m ³ / h.

The temperature in the first reactor was 110 ° C, condensing to 150 mPa. with viscosity mixtures. In the second step, a second portion of urea is added at a rate of 2.5 m ³ / h in the form of a 60% solution, temperature 60 ° C, pressure 11 kPa. The resulting product collected after reaching a refractive index of 1.482 has a dry matter content of 66.1% by weight, a viscosity of 400 mPa. s, free formaldehyde content 0.45%. Released fd according to FESYP 6 mg.

Example 3

17 430 L of 37% formalin is metered into the apparatus described in Example 1 in a similar manner, its pH is adjusted to 4.3 by adding 18 L of 10% sodium hydroxide, and 5,100 kg of solid urea are added. The mixture is stirred at 18-20 ° C for 1 hour, then the pH is checked and adjusted to 8.2-8.5 by addition of sodium hydroxide if necessary and 1,800 kg of solid melamine are added.

After 10 min. of the first reactor at a rate of 10 m ³ / h.

The next procedure is as in Example 1.

The resulting product collected after reaching a refractive index of 1.480 has a dry matter content

65.7 wt.%, Viscosity 190 mPa. %, the free formaldehyde content is 0.30% by weight. Released fd from test DTD according to FESYP 8.2 mg / 100 g absolute dry DTD.

Claims (3)

Example 1 Into a stirred tank equipped with a cooling jacket, 2.15 m 3 of an aqueous solution of formaldehyde is concentrated at 37% by weight with a content of 0.45% by weight of methanol, the pH of which is adjusted by the addition of 5 µl / cm 3 of sodium hydroxide to 8.5 and 1,260 kg of solid melamine are added. After stirring for 30 minutes, 7.18 m @ 3 of an aqueous solution of E-maldehyde of the same concentration as above was added and 3000 kg of urea were added, the pH of the solution was 6 to 6.1. The ready-to-use precondensate is fed at a rate of 7 m 3 / h to the first reaction stage where a condensation reaction takes place at a pressure of 0.3 MP and a temperature of 120 ° C. The product of the first reaction stage with a viscosity of 80mPa. s is continuously withdrawn to a second reaction stage where further condensation takes place by the addition of 1.75 m 3 / h of 50% non-aqueous urea solution and the pH is adjusted by the addition of 10 1/10% sodium hydroxide. This step is carried out at a temperature of 55 ° C and a pressure of 10.5 kPa. A product with a viscosity of 350mPa is taken from the second reaction step. with a free formaldehyde content of 0.4% by weight, a reactivity of 65 s / 100 CC with ammonium chloride (all according to CSN.66 86 29) and cooled to 20-25 ° C. After curing, the product releases 0.15 mg fd / l of the cured adhesive according to the cited CSNa below 8.5 mg fd / 100 g of absolutely dry DTD according to the FESYP perforation method with toluene - DIN EN 120/1979. Wastewater from the factory contains 0.45 percent by weight of methanol and 1.65 percent by weight of formaldehyde. Example In a similar manner to the apparatus described in Example 1, 13,430 of 1% formalin having a concentration of 37% by weight were added, the pH was adjusted to 4.5 by the addition of 10% of 10% sodium hydroxide and 5,100 kg of solid urea were added. The mixture was sealed with 20 cc of agitation for about 1 hour and then 4,000 liters of formalin was added, the pH adjusted to 8.5, and 2000kiograms of melamine added. Spray 10 m3 / h. The temperature in the first reactor was 110 ° C, and was condensed until 150 mPa. with viscosity mixtures. In a second step, a second portion of urea is added in an amount of 2.5 m3 / h in the form of a 60% solution, a temperature of 60 ° C, a pressure of 11 kPa. The resulting product collected at a refractive index of 1.482 has a dry matter content of 66.1%, a viscosity of 400 mPa. s, free formaldehyde content 0.45%. FESYP 6 mg released. Example 3 In a similar manner to the apparatus described in Example 1, 17,430 137% formalin is metered in, its pH is adjusted to 4.3 by the addition of 18 L of 10% sodium hydroxide and 5,100 kg of solid urea are added. The mixture is stirred for 1 hour at 18-20 ° C, then the pH is checked and if necessary, the sodium hydroxide addition is adjusted to 8.2-8.5a and 1800 kg of solid melamine are added. The mixture was stirred for 10 min. stirring the first reactor at 10 m 3 / h. The next procedure is as in Example 1. The resulting product collected after the refractive index of 1.480 has a dry matter content of 65.7 wt%, a viscosity of 190 mPa. % of formaldehyde is 0.30% by weight. The released fd from the DTD test according to the FESYP method of 8.2 mg / 100 g of absolutely dry DTD. SUBJECT MATERIALS A process for the production of formaldehyde condensates and / or urea with urea by amine amine with reduced formaldehyde leakage by two-stage condensation of urea and melamine with formaldehyde characterized in that the condensate is condensed at 80 to 130 ° C in the first stage. with a temperature of 120 ° C and a pressure of 0.001 to 0.5 MPa in a continuous continuous plant, the basic molar ratio of the feedstock urea and formaldehyde being 1: 1.5 to 1: 2.2, preferably 1: 1.9, the melamine content of the product is preferably 0.005 to 20% by weight, preferably 10% by weight, at pH 4.5 to 8.5, preferably 6.2, which is treated with alkali metal hydroxide, preferably sodium hydroxide, and the mixture is further condensed in a second stage and concentrating at a pressure of 2 to 20 kPa, a temperature of 20 to 90 ° C, preferably 55 ° C to a dry matter content of 50 to 70% by weight with continuous addition of urea so that the final molar ratio of urea to formaldehyde is 1: 1.1 to 1: 1.40, preferably 1: 1.18 with the addition of alkali metal hydroxide, preferably sodium hydroxide at pH 6 to 9.5, preferably 8.5.