CS252958B1 - A method of producing condensates and / or polycondensates with urea and ammonia - Google Patents

Abstract

Method for producing condensates and/or polycondensates of formaldehyde with urea and ammonia or its compounds, used mainly in the woodworking industry as an adhesive or binder for the production of agglomerated materials with reduced formaldehyde emission. This effect is achieved by using suitable reaction conditions, in particular the input molar ratio of formaldehyde to ammonium ion, the input molar ratio of formaldehyde to urea and the resulting molar ratio of formaldehyde to urea. The adhesive can be produced by modified processes, most preferably by separate preparation of precondensates, their mutual condensation and modification of the resulting semi-product with urea and concentration to the desired dry matter content.

Description

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SUMMARY OF THE INVENTION The present invention provides a process for the preparation of condensate or polycondensates of formaldehyde by ammonium and ammonia and / or its compounds used in particular in the wood-processing industry as adhesives and binders for the production of agglomerated particulate particularly particle boards.

Despite the advantageous processing properties, low flavor and availability, the urea-formaldehyde adhesives, mainly due to the ecological ability of the cured adhesive, hydrolyze at elevated temperature and humidity, with the removal of formaldehyde and its subsequent and long-term release from the chipboard.

Increased formaldehyde concentration in the working air of DTD production, in most cases of reduced airflow, deteriorates working conditions. Formaldehyde already in low concentrations in the air irritates the respiratory tract and conjunctiva to the operators of DTD production technology. Likewise, if the finished products are used in an inorganic environment, the content of formaldehyde in the air often exceeds the prescribed concentration by hygiene.

Therefore, the worldwide trend in the development of urea-formaldehyde adhesives is the desire of their manufacturers to reduce the free formaldehyde content of the adhesives prior to their use in the manufacture of agglomerated materials, as well as the condensate and / or polycondensate produced therein or with the manufacturer DTD guaranteed the production of DTD with the desired value of formaldehyde released. Of the several reaction parameters and parameters of the quality of the formaldehyde cleavage from the cured adhesive, the molar ratio of urea to formaldehyde (resulting) is most significant, with the amount of cleaved form aldehyde decreasing with decreasing. As a result of the reduction in the molar ratio of said reactants by a process called urea modification, it is undesirable to reduce the reactivity of the adhesive, and when it reaches a certain value, there is an undesirable deterioration in the solubility, the stability of the adhesive and, in particular, the strength properties of the bonded materials.

Reducing the free and thus released formaldehyde content is most often achieved by adjusting the reaction conditions, e.g., pH, reaction temperature, and reaction time, respectively. in various ways of dispensing raw materials (NS Patent 2,207,921 and 2,243,857), but notably using different modifying agents capable of reacting with formaldehyde to form more stable compounds. The cost of these modifying reactants and the stability therefrom and the formaldehyde formed by the compounds are then an imitating factor in their application.

It is known that the use of urea as an additive for the condensation reaction of 1 free formaldehyde is less than or equal to 1.8. %, while at temperatures above 60 ° C, the so-called semi-product adds 10 to 70 wt. ureas (Jap. pat. 74-18925 and 74--18926). Other effective additives for reducing the free and amount of hardened chloride peroxide-cleaved formaldehyde are ethylene dimethylamine (Jap. Pat. 71-2874), peroxides (Kun-San-Tai, Taiwan Sugar 12, No. 2, No. 9 // 1965), aldehydes ( NSR Pat., 1810,925); lignosulfonates (PLR pat. 74,086, US Pat. No. 3,658,683), phenols (NSR Pat. No. 2154 570) phenylenediamine, caprolactam and resorcinol (PER pat. 74,060). Said additives are added to the adhesives predominantly by agglomerated materials manufacturers prior to their manufacture.

While the aforementioned modifiers with lepidaditives have reduced the free formaldehyde content, the adhesives have a shorter lifetime than those with the higher free formaldehyde content; In the case of the application of several additives, the formaldehyde leakage from the particleboard is considerable in the presence of free formaldehyde in the resin. The greater addition of the above-mentioned additives to the urea-formaldehyde condensate causes a decrease in the reactivity and viscosity of the binder entering the chipboard and consequently reduces the mechanical-physical properties of the chip dock. In some cases, the decrease in reactivity is so pronounced that the adhesive cannot be cured in a conventional manner.

The process of producing odorless syrup-like products, suitable for use as a glue, utilizes a condensation rate of 1 to 2.44: 1.0 formaldehyde to urea in the presence of 1-3.75 moles of ammonia. During the condensation, the excess ammonia is removed by distillation (U.S. Pat. No. 2,397,194). '

A disadvantage of the process is the long-term thermal exposure of the product at its yield, which affects the reactivity and curing properties of the adhesive during its assembly. Also protected by the preparation of a liquid by the addition of molar polyformaldehyde to 1.8-1.5% by the presence of ammonia in the mono corresponding to the colloidal fraction of ammonia to 1: 0.2 and 0.2. The modification of the present invention is the production of low-formaldehyde resins with low content of formaldehyde from DTD by condensation at a molar ratio of formaldehyde of 1.4 to 2.8: 1 in the presence of 0.1 mol of hexamethylentetramine per mole of urea. % followed by modification to a formaldehyde concentration of 0.01 to 0.8% by weight. and viscosities of 10 to 50 mPas (AO195 572). However, this procedure does not guarantee the achievement of emission reductions below 10 mg of aldehyde from 100 g of absolute DTD (DIN EN 120/79).

From the methods of making adhesives, the processing of which results in a reduction in the formaldehyde value of the DTD (values below 10 mg formaldehyde / 100 gDTD) are reported by MS. PV uses an input molar ratio of amino groups to aldehyde groups of 1.6 to 1.8: 1 followed by modification with an amino compound to a molar ratio of 1.8 to 2.5: 1. -vine, dicyandiamide and melamine. The process of producing condensates and / or polycondensate formaldehyde with urea and / or melamine podium MS. AO 195 490 is performed in two stages. The first step is the condensation of formaldehyde with urea and / or melamine at a molar ratio of 1.3 to 10: 1, preferably 1.88 to 3: 1, the second stage being the modification of the intermediate with urea or formeldehyde reactive molar ratio of formaldehyde to urea or molar equivalents of formaldehyde reactants 1.15 + 0.14, generally with the simultaneous or subsequent addition of at least one salt of elements I and II. groups of periodic system and / or polymers (PVC, PVAC, PVAL). '

By modifying the adhesive with additives as well as by technological modifications, the most common effect of the resulting molar ratio of form-aldehyde to urea is perhaps to make an adhesive by which DTDs can be produced by emission below 10 mg of formaldehyde (100 gabsoluble dry DTD). The problem, however, remains the durability of the adhesive and the deterioration of the physicochemical properties, especially strength. The first drawback is that the adhesive is added directly to the DTD product prior to processing. However, even in the case of the treatment of adhesives by DTD manufacturers, it remains a problem to maintain the required strengths.

In the study of the possibility of preparing formaldehyde and urea-free adhesives and without the presence of melamine, which would guarantee the production of DTD under 10 mg of formaldehyde, we have found that a similar effect to melamine can be achieved under certain conditions and as a third feedstock. ammonia, its aqueous solution or ammonia releasing compounds. The use of a molar ratio of form-aldehyde to ammonia for the formation of hexamethyloentetramine and its intermediates is utilized.

SUMMARY OF THE INVENTION The present invention provides a process for the production of condensates and / or polycondensate formaldehyde with urea and ammonia and / or its compounds, which is carried out in three steps. Ammonia is added to the aqueous formaldehyde solution in the first step, in order to obtain a molar ratio of formaldehyde to α-monoic ion of 1.6: 1 to 10: 1. In view of the desired formation of hexamethylenetetramine intermediates and the desired 8 properties of the addition condensation product, it is preferred to prepare the first stage product at a molar ratio of formaldehyde to ammonium ion 1, 9 to 2.5: 1 at a temperature of 10 to 60 ° C and a pH of 7 to 13.

The addition of urea to the formaldehyde solution at a mole ratio of formaldehyde to urea of 1.3 to 5: 1 at a temperature of 10 to 50 ° C and a pH of the solution of 5.5 to 9 provides the addition product of formaldehyde and urea. In view of the desired quality of the finished product, the addition of formaldehyde to urea is preferably carried out with a molar ratio of 1.6 to 2.1: 1 and 6%.

Thus separately prepared addon-conjugate, resp. the addition products are mixed at a second weight ratio of 4 to 99 parts of the urea-formaldehyde addition and / or addition-condensation product to 1 part of the formaldehyde addition-condensation product and ammonia and contacted! at a temperature of 60 to 130 ° C at a pH of 4 to 13 per condensation product having a viscosity of 20 to 300 mPas. It is advantageous from the aspect of the required technical-economic parameters of the adhesive and the process of manufacturing the condensation of the separately prepared products to give a temperature of 75 to 100 ° C, to a viscosity of 40 to 60 mPas.

The resultant condensation product, which contains even more than 1% by weight of water. In the third stage, the so-called free-formaldehyde is modified by urea with a solid or an aqueous solution to give a final mole ratio of formaldehyde to urea of 1 to 1.4: 1, most preferably a molar ratio of 1.1 to 1.21: 1, with simultaneous or subsequent water to a dry matter content of 50 to 80 wt. most often 64-66% by weight.

The desired product can also be produced by alternative processes. The formaldehyde / urea / ammonia mixed condensate (or polycondensate) is prepared by a process in which a formaldehyde / urea addition product of 1.3 to 1.0 is prepared in the first stage under the same temperature and pH conditions as in the separate preparation of the precondensates. 5.0: 1, with respect to the physical-chemical and mechanical properties of the adhesive most preferably at a molar ratio of 1.6 to 2.1: 1. Ammonia or an aqueous solution thereof, or ammonium salts, is subsequently added to the intermediate product. for example, ammonium carbonate in an amount such that the molar ratio of formaldehyde unreacted with urea to ammonium ion is greater than 1.6: 1, most preferably 2: 1. The mixed product obtained is at a temperature of 60-130 ° C and a pH of 4-13. it is allowed to react to a condensation degree of 20 to 600 mPas, most often to a viscosity of 40 to 60 mPas. Upon reaching said product viscosity, the rate of condensation reaction by adjusting the pH of 252958 8 and lowering the temperature of the substantial spomall and the so-called semi-product is added by adding urea to a final molar ratio of urea formaldehyde of 1 to 1.4: 1 most preferably 1.1 to 1, 2: 1. with additive addition of the product with urea or thickening of the semi-product.

It is also possible to produce the desired properties by a process in which a formaldehyde / ammonia product is first prepared in a molar ratio of formaldehyde to ammonium ion of greater than 1.6: 1, most preferably 3.2 to 19.2: 1. the urea is added in excess of 0.77 moles per mole of unreacted formaldehyde. The resulting semi-product is first condensed to the aforementioned condensation step, followed by the addition of a resulting mole ratio of formaldehyde to urea of 1 to 1.4: 1. wt.

Advantageously compared to the hitherto known processes for the production of urea-formaldehyde, melamine-urea-formaldehyde or additive-urea-formaldehyde resins, advantages are obtained by the process of the present invention: more amine and readily available ammonia or its compounds, which greatly improves the economics of the production of the adhesive itself, but also of particular chipboard.

The invention is illustrated by the following examples. Example 1 In a mixing apparatus B, a temperature of 50 ° C of 67.63 g of formaldehyde having a concentration of 37.2% by weight is mixed. with 50.36 g ammonia of 26% by weight. The apatite content is stirred for about 15 minutes. and then cooling to 20 ° C, pH 11.75. In the mixing apparatus A, a mono-urea formaldehyde precondensate addition product is prepared by introducing to the apparatus 1118 g of 37.2% formaldehyde. and pH 9.19 at 15 ° C is added 450 g of urea. The mixture is maintained at this temperature for 30-45 min. The formaldehyde / ammonia condensation product is then transferred to apparatus A from the Bquantitative apparatus. The mixture in apparatus A is heated to 95 ° C and condensed to the desired condensation stage. The reaction product is then cooled and adjusted to pH 7-8. In the third stage, 316 g of urea is added to the condensation product and the desired dry weight of 65% by weight is evaporated in a vacuum. Example 2

67.6 g of 37 wt% formalin are introduced into the mixing apparatus B, followed by the addition of 7.57 g of gaseous ammonia so that the temperature does not exceed 60 ° C. After dispensing the gaseous ammonia, the reaction mixture is cooled to 20 ° C. In the mixing apparatus A, the urea-formaldehyde precondensation product is prepared by introducing 1118 g of formaldehyde having a concentration of 37% by weight into the apparatus. and pH 4.2, 450 g of urea are added at 20 ° C.

In the second stage, the mixture is mixed with the reaction product from apparatus B and passed to a desired condensation stage, i.e. 50 mPas, at 100 ° C. The condensate is cooled to room temperature and the pH is adjusted to 8. In a third step, 316 g of calcium are added to the conditioned and cooled condensation product and the desired solids are evaporated to a vacuum of 65% by weight. : 'Example 3

Add 1,200 g of 37% non-formaldehyde to the mixing apparatus provided with a cooling and heating coil and a coolant, adjust the pH to 4.10% with NaOH and add 50 g of ammonia to a temperature not exceeding 60 ° C. Cool to 25 ° C and add 450 g of urea, the reaction mixture is stirred at this temperature for 30 to 45 min.

Then heat to 85 ° C and condense to the desired degree, i.e. 45 mPas In this step, cool and adjust the pH to 8 and add 592 g of a 5% urea solution.

Finally, the raw glue is vacuum-dried to 65% by weight. Example 4

Into the mixing apparatus we present 1185 g of formaldehyde at a concentration of 37% by weight. Adjust the pH to 4.2 with 10% NaOH solution and add 450 g of urea not added at 25 ° C for 30 min. Then add 50 g of ammonia water with a concentration of 26% by weight. Heat to 95 ° C and condense to this temperature up to the desired condensation stage, i.e. 60 ° Pas. Then cool, adjust the pH to 7.5 and add modifying urea V to a different 297 g.

Claims (2)

2 S 2 9 5 8 10 Overview of some mechanical properties and amount of formaldehyde released zDTD Example Flaking MPa Swelling in% Bending MPa Looseformald. z DTDv mg / 100 gDTD 2 h 24 h 1 0.4 6.5 15.5 18.01 7.5 2 0.41 5.86 14.8 17.85 7.4 3 0.38 5.9 15 , 1 18.3 7.1 4 0.385 5.95 14.8 17.9 8.2 SUBJECT MATTER A process for the production of formaldehyde condensates and / or polycondensates with urea and ammonia by a continuous and / or discontinuous process, characterized in that it is carried out in three stages, wherein formaldehyde and ammonia and ammonia addition and / or addition condensation products are separately prepared in the first stage. or an aqueous solution thereof, in a molar ratio of formaldehyde to ammonium ion of 1.6: 1 to 10: 1, preferably 1.9 to 2.5: 1, at a temperature of 10 to 60 degrees Celsius and a pH of 7 to 13 and formaldehyde and urea at an input molar ratio of 1.3 to 5: 1, preferably 1.6 to 2.1: 1, at a temperature of 10 to 50 ° C, preferably 20 to 21 degrees Celsius and a pH of 5.5 to 9, preferably 6, in the second stage the separately prepared products are contacted together at a temperature of 60 to 130 ° C, preferably at a temperature of 75 to 100 ° C at a pH of 4 to 13 in a weight ratio of 4 to 99 relative to each other. parts of urea-formaldehyde product per part of the reaction product of formaldehyde and ammonia or an aqueous solution thereof for a condensation step of 20 to 300 mPas, preferably 40 to 60 mPas, in the third stage the condensation product is modified with solid urea or an aqueous solution thereof to a final molar ratio of formaldehyde to urea of 1 to 1.4: 1 with simultaneous or subsequent stripping to a dry matter content of 50 to 80% by weight, preferably to 65% by weight. 2. A method according to claim 1, characterized in that it is carried out in three steps without separation of the individual stages in a single apparatus.