DE4011159A1 - Prepn. of novel aq. melamine-modified amino resins - by heating mixt. of aq. UF precondensate and aq. melamine-UF precondensate, with opt. addn. of urea] - Google Patents

Abstract

Aq. amino resins (I) contg. 60-75 wt.% solids are claimed; (I) are obtd. by heating a mixt. of (A) 60-98 wt.% aq. UF precondensate and (B) 2-40 wt.% M/UF precondensate for 10-45 mins. at 70-100 deg.C and pH 7.5-9; (A) is derived from (a1) 30-50 mol.% urea, (a2) 50-70 mol.% formaldehyde (F) and (a3) 0-2 mol.% other condensable components, and (B) is derived from (b1) 15-35 wt.% melamine, (b2) 10-15 mol.% urea, (b3) 55-70 mol.% (F) and (b4) 0-2 mol.% other condensable components; the theoretical mol. ratio (F):(amino gps. in I) is (0.45-0.6):1, and this condition is fulfilled if necessary by addn. of urea after heating (A) and (B). - 2. The above process is claimed as such.

Description

The present invention relates to aqueous amino resins with a solids content from 60-75% by weight, obtainable by heating a mixture of

• A) 60-98% by weight of an aqueous urea-formaldehyde precondensate
  • a₁) 30-50 mol% urea,
  • a₂) 50-70 mol% formaldehyde and
  • a₃) 0-2 mol% of other condensable components,
• wherein the sum of a₁, a₂ and a₃ corresponds to 100 mol%, and
• B) 2-40% by weight of an aqueous melamine-urea-formaldehyde precondensate
  • b₁) 15-35 mol% melamine,
  • b₂) 10-15 mol% urea,
  • b₃) 55-70 mol% formaldehyde and
  • b₄) 0-2 mol% of further condensable component,
• where the sum of b₁, b₂, b₃ and b₄ corresponds to 100 mol%,

to 70 to 100 ° C at pH 7.5 to 9 for a period of 10 to 45 min, with the proviso that the calculated molar ratio of formaldehyde to NH₂ groups of the finished resin is 0.45 to 0.6: 1, which Condition if necessary by adding urea after heating the precondensates A and B must be met.

It is generally known to chipboard by pressing wood chips with binders under increased pressure and at elevated temperature Manufacture base of urea and formaldehyde. Because these chipboard often the disadvantage of highly undesirable formaldehyde emissions have, the molar ratio of formaldehyde to amino groups in the Binder as low as possible. However, this leads to unfavorable Strength and swelling properties.

To remedy this deficiency, melamine is used as a cross-linking component to what, however, the reactivity of the resin and thus the processing speed reduced.  

EP-A 25 245 describes a process for the production of chipboard known in which a mixture of an aminoplast resin and a polyisocyanate is used, the aminoplast resin with melamine is modified. Such modified aminoplast resins can be described by mixing urea-formaldehyde resins with melamine Urea-formaldehyde resins or by mixing melamine-formaldehyde resins obtained with (melamine) urea-formaldehyde resins.

DE-A 24 55 420 describes a process for the production of melamine Urea-formaldehyde condensation by condensation of urea Formaldehyde precondensates with melamine are described.

EP-B 54 755 describes a process for the production of melamine Formaldehyde resins are known, the melamine-formaldehyde resins according to Condensation can be mixed with a urea solution.

According to the teaching of EP-A 62 389, chipboard is made with the help of a melamine-containing urea-formaldehyde resin as a binder, wherein the binder by condensing melamine into one Urea-formaldehyde resin or by mixing a urea-formaldehyde Resin obtained with a melamine-urea-formaldehyde resin.

All known resins, however, leave useless as binders Too much left as far as they explained the above Requirements for low formaldehyde emissions, strength and high Processing speed only correspond to a limited extent.

The object of the present invention was to provide aqueous amino resins with better Properties, especially with regard to the gel time and thus the ver working speed, to find.

Accordingly, the aqueous amino resins defined at the outset have been found.

Further embodiments of the invention are set out in the subclaims remove.

The aqueous urea-formaldehyde pre-concentrate (component A) can according to known processes by condensation of 40-54 mol% urea with 46-60 mol formaldehyde and 0-2 mol% more condensable Components are made, the molar ratio of Formaldehyde to urea 1: 1-1.2: 1, preferably 1: 1-1: 1.1: 1, can be.  

The urea can be in solid form as well as in form 60 to 75 wt .-% aqueous solution can be used.

Formaldehyde can also be in the form of an aqueous solution with a formaldehyde proportion of 30-60 wt .-% can be used.

It is also possible to use a commercially available solution instead of an aqueous formaldehyde solution formaldehyde-rich formaldehyde urea precondensate with one Molar ratio of formaldehyde to urea of approx. 3-5: 1 with a to condense such an amount of urea that a mole ratio of 0.85-1.2: 1 is reached.

In addition, other condensable components such as Ammonia or substituted ureas are condensed.

The pre-condensates can also continue to be known Process with mono- or higher functional alcohols such as methanol or preferably ethylene glycol, are etherified.

The condensation can be carried out at 50-120 ° C and pressures of 1-4 bar will. Usually one works at pH values in the range of 3.5-5.5, the pH being, for example, with 25% strength by weight aqueous sodium hydroxide solution or 10 wt .-% aqueous formic acid in the desired manner can be adjusted.

The end point of the condensation can be determined via the cloud temperature (so-called Cloud point) can be determined, the temperature being determined in which a solution of 1 g of resin in 5 g of water becomes cloudy. in the generally condensed so long that the cloud temperature in Range is 30-50 ° C. The precondensates (A) thus obtained can Solids contents (drying residue at 120 ° C after 2 h) 40-60, preferably have 40-50% by weight and viscosities of 200-600 mPa · s (20 ° C) exhibit.

The preparation of (A) can be carried out batchwise or continuously, for example in a cascade of stirred tanks.

The melamine-urea-formaldehyde precondensate (component B) can also be used in be prepared in a conventional manner by 15-35 mol% Melamine, 10-15 mol% urea, 55-75 mol% formaldehyde and 0-2 mol% reacting further condensable components with one another, the molar ratio of formaldehyde to amino groups being 0.54-0.80: 1 can be.  

Melamine can be in solid form, urea both as a solid or in form 60-75 wt .-% aqueous solutions and formaldehyde also in 30-60 wt .-% aqueous solution can be used.

It is also possible to use melamine with a urea-formaldehyde precondensate to implement.

Furthermore, 0-2% by weight of further condensable components such as diethanolamine or ammonia.

As already described for component (A), the pre condensates (B) are etherified.

The condensation can occur in an alkaline environment at pH values from 8.5 to 10.5 be carried out, the pH being, for example, 25% by weight can adjust aqueous sodium hydroxide solution. In addition, for such Reactions conventional catalysts such as organic amines or ammonia, preferably diethylethanolamine can be added.

In general, temperatures from 80 to 120, preferably 92 up to 96 ° C and at pressures from 1 to 4 bar. The end point determination can be like described for component A, wherein in general condensed so long that the cloud temperatures in the range of 40 to 50 ° C.

The viscosity of the precondensates B thus obtained can be 500-1200 mPa · s (at 20 ° C). The solids content can range from 60-70 wt .-% lie.

The production of (B) can be carried out batchwise or continuously respectively.

To produce the aqueous amino resins according to the invention, the Components A and B mixed in such amounts that the final resin Melamine content of 1 to 15 wt .-%, based on the solids content and a Molar ratio of formaldehyde to amino groups of 0.45-0.65: 1, where usually 60-98 wt .-% of the precondensate (A) and 2-40 wt .-% of the precondensate (B) is used.

The mixture of (A) and (B) is preferred at pH 7.5-9.5 8.8-9.2, the pH being, for example, 25% by weight aqueous sodium hydroxide solution can be adjusted, and at temperatures of 70 heated to 100, preferably from 80 to 90 ° C.  

The time period for the implementation is 10-45 min. Do you work in lower temperature range, one will choose longer implementation times and heat correspondingly shorter at higher reaction temperatures.

The final resins can also, like the precondensates (A) and (B), also mono- or polyfunctional alcohols such as methanol or preferably Ethylene glycol can be etherified by known processes.

Usually one works at normal pressure. Both discontinuous as well as a continuous driving style is possible.

The aqueous amino resins thus obtained usually have a solids content of 60-75 wt .-% viscosities in the range of 300-700 ° C, mPa · s at 20 ° C.

In the event that the calculated molar ratio of formaldehyde to Amino groups of the end resin after heating is not yet 0.45-0.65, the resin solution becomes solid urea the 60-75 wt .-% aqueous urea solution admitted. If you use aqueous urea solution, you can the solids content is then adjusted by evaporation in vacuo will.

These amino resins are ideal as binders for the production Lignocellulose-containing molded article. Such molded articles can be, for example produce by using 8-20 wt .-% binder with 90-92 wt .-% wood chips at temperatures from 120 to 200 ° C under pressure pressed. In addition, hardeners such as acids, their ammonium salts, Aluminum sulfate, magnesium sulfate or mixtures thereof will.

Due to the relatively short gelation times, the moldings obtained exhibit good mechanical strength.

The gel time is with a glue bath of 1 g resin solution and 0.1 g a 15 wt .-% aqueous ammonium chloride solution determined at 100 ° C.  

Example 1

• 1.1 Production of the urea-formaldehyde resin A mixture of 4000 g of a 40 wt .-% formaldehyde solution (53.5 mol), 2240 g of a 68% by weight aqueous urea solution (25.4 mol) and 75 g (1.2 mol) ethanediol was with 25 wt .-% aqueous sodium hydroxide solution adjusted to a pH of 6.5 and 15 min heated at 80 ° C for a long time. Then the pH became 10% by weight aqueous formic acid adjusted to pH 4.7 and the reaction mixture heated at about 95 ° C until a mixture of 5 g of water and 1 g Reaction mixture had a cloud point of 18 ° C.
• 1.2 Production of the melamine-urea-formaldehyde resin A mixture of 6475 g of a 40 wt .-% formaldehyde solution (86.3 mol), 1406 g of a 68% by weight aqueous urea solution (15.9 mol), 4500 g (35.7 mol) melamine and 16 g (0.14 mol) diethyl ethanolamine was brought to pH with 50% by weight sodium hydroxide solution set from 9.8. The reaction mixture was then raised to 95.degree heated and stirred for 20 min until the cloud temperature was 45 ° C.
• 1.3 Preparation of the final resin 6314 g of the resin solution obtained according to 1.1 were mixed with 627 g of a resin solution obtained according to 1.2 and heated at 75 ° C. at a pH of 8.5 for 20 minutes. Then 2000 g of a 68% by weight aqueous urea solution were added. The mixture was then concentrated at 48 ° C. and 90 mbar until the solids content was 66.5% by weight.
  The characteristics of the resin solution thus obtained are shown in Table I.

Example 2 (for comparison)

• 2.1 Preparation of the urea-formaldehyde resin A mixture of 4000 g of a 40% by weight formaldehyde solution (53.5 mol), 2240 g of a 68% by weight aqueous urea solution (25.4 mol) and 74 g (1 , 2 mol) of ethanediol was adjusted to a pH of 6.5 with 25% strength by weight aqueous sodium hydroxide solution and heated at 80 ° C. for 15 minutes. Then the pH was adjusted to pH 4.7 with 10% strength by weight aqueous formic acid and the reaction mixture was heated at about 95 ° C. until a mixture of 5 g of water and 1 g of reaction mixture had a cloud point of 18 ° C. exhibited.
  The pH of the mixture was then adjusted to 9.0 using 25% strength by weight aqueous sodium hydroxide solution and 2000 g of a 68% strength by weight aqueous urea solution were added. The mixture was then concentrated at 48 ° C. and 90 mbar until the solids content was 66.5% by weight.
• 2.2 Production of the melamine-urea-formaldehyde resin The production was carried out analogously to 1.2
• 2.3 5740 g of the urea-formaldehyde solution obtained according to 2.1 were mixed with 627 g of the melamine-urea-formaldehyde solution.
  The characteristics of the resin thus obtained are listed in Table I.

Example 3

• 3.1 Production of the urea-formaldehyde resin A mixture of 4000 g of a 40 wt .-% formaldehyde solution (53.5 mol), 2240 g of a 68% by weight aqueous urea solution (25.4 mol) and 74 g (1.2 mol) of ethanediol were with 25 wt .-% aqueous sodium hydroxide solution adjusted to a pH of 6.5 and 15 min heated at 80 ° C for a long time. Then the pH became 10% by weight aqueous formic acid adjusted to pH 4.7 and the reaction mixture heated at about 95 ° C until a mixture of 5 g of water and 1 g Reaction mixture had a cloud point of 18 ° C.
• 3.2 Production of the melamine-urea-formaldehyde resin A mixture of 6475 g of a 40 wt .-% formaldehyde solution (86.3 mol), 1406 g of a 68% by weight aqueous urea solution (15.9 mol), 4500 g (35.7 mol) melamine and 16 g (0.14 mol) diethyl ethanolamine was brought to pH with 50% by weight sodium hydroxide solution set from 9.8. The reaction mixture was then raised to 95.degree heated and stirred for 20 min until the cloud temperature was 45 ° C.
• 3.3 Preparation of the final resin 6314 g of the resin solution obtained according to 1.1 were mixed with 1254 g of a resin solution obtained according to 1.2 and heated at 85 ° C. for 20 min at a pH of 8.5. Then 2000 g of a 68% by weight aqueous urea solution were added. The mixture was then concentrated at 48 ° C. and 90 mbar until the solids content was 66.5% by weight.
  The characteristics of the resin solution thus obtained are shown in Table I.

Example 4 (for comparison)

• 4.1 Preparation of the urea-formaldehyde resin A mixture of 4000 g of a 40% by weight formaldehyde solution (53.5 mol), 2240 g of a 68% by weight aqueous urea solution (25.4 mol) and 74 g (0 , 14 mol) ethanediol was adjusted to a pH of 6.5 with 25% strength by weight aqueous sodium hydroxide solution and heated at 80 ° C. for 15 minutes. Then the pH was adjusted to pH 4.7 with 10% strength by weight aqueous formic acid and the reaction mixture was heated at about 95 ° C. until a mixture of 5 g of water and 1 g of reaction mixture had a cloud point of 18 ° C. exhibited.
  The pH of the mixture was then adjusted to 9.0 using 25% strength by weight aqueous sodium hydroxide solution and 2000 g of a 68% strength by weight aqueous urea solution were added. The mixture was then concentrated at 48 ° C. and 90 mbar until the solids content was 66.5% by weight.
• 4.2 Production of the melamine-urea-formaldehyde resin The production was carried out analogously to 3.2
• 4.3 5740 g of the urea-formaldehyde solution obtained according to 2.1 were mixed with 1254 g of the melamine-urea-formaldehyde solution.
  The characteristics of the resin thus obtained are listed in Table I.

Table I

Claims (7)

1. Aqueous amino resins with a solids content of 60-75% by weight, obtainable by heating a mixture of

• A) 60-98% by weight of an aqueous urea-formaldehyde precondensate
  • a₁) 30-50 mol% urea,
  • a₂) 50-70 mol% formaldehyde and
  • a₃) 0-2 mol% of other condensable components,
• wherein the sum of a₁, a₂ and a₃ corresponds to 100 mol%, and
• B) 2-40% by weight of an aqueous melamine-urea-formaldehyde precondensate
  • b₁) 15-35 mol% melamine,
  • b₂) 10-15 mol% urea,
  • b₃) 55-70 mol% formaldehyde and
  • b₄) 0-2 mol% of further condensable component,
• where the sum of b₁, b₂, b₃ and b₄ corresponds to 100 mol%,

to 70 to 100 ° C at pH 7.5 to 9 for a period of 10 to 45 min, with the proviso that the calculated molar ratio of Formaldehyde to the NH₂ groups of the finished resin 0.45 to 0.6: 1 , this condition if necessary by adding Urea must be fulfilled after heating precondensates A and B. 2. A process for the preparation of aqueous amino resins according to claim 1, characterized in that a mixture of

• A) an aqueous urea-formaldehyde precondensate and
• B) a melamine-urea-formaldehyde precondensate

at pH 7.5 to 9 and a temperature of 70 to 100 ° C for 10 to Heated for 45 min.   3. Process for the production of lignocellulose-containing molded articles, thereby characterized in that as a binder aqueous amino resins according to Claim 1 or 2 used. 4. Process for the production of lignocellulose-containing moldings Claim 3, characterized in that the aqueous amino resin Binder with a proportion of 8-20 wt .-%, based on the Total weight of the molded body used. 5. Lignocellulose-containing molded article containing the as a binder aqueous amino resins according to one of claims 1 to 3.