FI86073B - KOELDSTABIL VATTENHALTIG LIMHARTSLOESNING, SOM INNEHAOLLER KONDENSATIONSPRODUKTER AV FORMALDEHYD OCH EN KOMBINATION AV FENOL-, UREA- OCH MELAMINKOMPONENTER. - Google Patents

Abstract

A cold-stable, aqueous adhesive resin solution of products of the condensation of formaldehyde with a combination of phenol, urea and melamine components is obtainable by condensation of the phenol, urea and melamine components with formaldehyde in the presence of at least 0.5% by weight of epsilon -aminocaprolactam or epsilon -aminocaproic acid, based on the total weight of the adhesive resin solution.

Description

1 86073

The invention relates to a cold-stable aqueous adhesive resin solution comprising a combination of formaldehyde and a combination of phenol, urea and melamine components The use of ε-aminocaproic acid as a cold stabilizer for this solution.

It is known that phenolic-urea-melamine-formaldehyde adhesive resins exhibit cold instability. This is observed in that when the temperature is lowered below about 12 ° C for a long storage time, for example 15 weeks, the viscosity of the adhesive resin rises very strongly and even leads to a pasty or gelatinous state. The reason for this is not the dependence of viscosity on temperature. This phenomenon would recover as soon as the temperature was raised. The change in viscosity is such that during a rather long storage time at low temperatures, a change in the macrostructure takes place, so that the system becomes high viscosity and also thixotropic. An increase in viscosity can even lead to a pasty state. This space can only be broken up by •:: 25 heating vigorously for a long time at 60 - 70 ° C.

However, the solution is then preloaded and changes back to a pasty state even more rapidly if it is recooled. This phenomenon can only be explained by a change in the intermolecular structure of the liquid.

30 The onset of cold instability is detrimental.

It prevents transport, storage and transfer by pumps during the cold season, consumes a lot of energy V * when returning the product to a sensitive liquid: or requires manual removal of the thickened resin from 35 tanks, be it a tank train, barrel, tank, tank or tank truck . When the adhesive resin is in a pasty state, it is no longer possible to process it. Even when the increase in viscosity has not yet led to a paste-like structure, the processability of the resin is already substantially more difficult.

The problem of cold instability can be solved by storing the resin at a temperature above 12 ° C during storage or transport. This is achieved by good packaging insulation or heating, for example by storing barrels in heated spaces. Sometimes it is possible to use the resin so quickly that its temperature has not yet dropped sufficiently or that the time elapsed is not long enough to increase the viscosity caused by the low temperature.

Phenol-urea-melamine-formaldehyde adhesive resins are used in the manufacture of weather-resistant particle board and for weather-resistant solid wood gluing, i. for gluing boards to make layered board supports, for example beams. The cold stability of the resin is very important so that it can be transported long distances and stored on site. If the resin is in the form of a tah-20, it can no longer be pumped. When the resin is transported by ship, which takes a long time, or is stored in outer tank warehouses for long periods of time, cold-induced thickening is particularly problematic: because large amounts of adhesive resin in the tank do not -Y; 25 can no longer be heated at a technically acceptable cost.

DE-C-1 595 368 addresses another technical problem. It relates to aminoplast impregnation solutions which impregnate paper or fabric supports and which are obtained by condensing melamine with formaldehyde in an aqueous medium, possibly using other modifiers suitable for the production of amino plastics. These impregnating resin solutions have improved storage stability. Improved storage stability. ···. 35 is obtained by carrying out the condensation using 3-15% by weight of ε-aminocaprolactam.

3,86073

The improvement in storage stability according to DE-C-1 595 368 is a phenomenon which is important for adhesive and impregnating resins and which is in no way related to the phenomenon of cold stability.

5 The storage stability of formaldehyde condensation products is always limited because these oligomeric products continue to condense over time. This happens at high temperatures quickly and at low temperatures slowly. Further condensation is observed with 10 irreversible increases in viscosity. Viscosity itself is a temperature-dependent property, which is why it is measured at a certain temperature, most often at 20 ° C.

For resins stored at an initial viscosity of 200 to 1,200 mPa.s, depending on the type of resin 15, which is technically conventional, the viscosity may change over a relatively long period of storage at a relatively warm temperature, for example about 30 ° C, to as high as 5,000 mPa.s: and beyond. In this case, the resins 20 can no longer be pumped by simple pumps. In addition, irreversible formation of water-insoluble polymers may occur; these appear as turbidity and possibly precipitate. This phenomenon is detrimental, especially to impregnating resins, which are known to be required to remain water clear.

Cold instability, on the other hand, is a phenomenon that can be observed when resins become thixotropic and pasty under the influence of low temperature. However, these pastes can be re-liquefied when the resin 30 is heated to 60 ° C or above for some time.

The more sensitive state remains permanent for a longer period of time, although not for as long as in the case of an unloaded resin. These altered properties appear to be the result of a change in the macrostructure. 35 therefore, in the case of certain manifestations of thixotropy, it is also common to speak of structural viscosity.

4,86073

The problem of cold instability does not occur with most types of condensation products, nor with the condensation products according to DE-C-1 595 368. However, with phenolic urea-melamine-formaldehyde adhesive resins, it is an extremely difficult phenomenon for technical use.

FR-A-898 175 relates to amino resins which have been condensed to increase alkali solubility and acid precipitation in the presence of aminocarboxylic acids, for example in the presence of i-aminocaproic acid or έ-aminocaprolactam. The publication does not address the problem of cold stability of resin solutions, as this does not occur in phenol-free amino resins.

It is an object of the invention to provide a cold-stable aqueous adhesive resin solution containing condensation products of a combination of formaldehyde and phenolic, urea and melamine components and which does not suffer from the cold stability problem described above.

This object is solved by preparing a cold-20 ml aqueous adhesive resin solution containing condensation products of a combination of formaldehyde and phenolic, urea and melamine components and obtained by condensing the phenolic, urea and melamine components with form-) ·· aldehyde in the presence of at least 0.5 wt.%: 25% by weight of 6-aminocaprolactam or 6-aminocaproic acid, based on the total weight of the sizing resin solution, without the phenolic components, if used in the form of a precondensate of a phenolic compound and formaldehyde (novolak), reacting with ethylene oxide.

According to a preferred embodiment of the invention. . the sizing resin solution is prepared by performing condensation in the presence of 0.5 to 2% by weight, preferably 0.8 to · 1.3% by weight of ε-aminocaprolactam or ε-aminocaproic acid based on the total weight of the sizing resin solution.

The adhesive resin solution of the invention may contain modifiers for use in phenolic resins. Examples of modifiers are sodium sulphite, sodium hydrogen sulphite, methanol, ethylene glycol and other conventional modifiers, for example substances which are effective against termites and fungi or which prolong the durability of the wood product 5 treated with the adhesive resin solution.

The invention also relates to a process for preparing a cold-stable aqueous adhesive resin solution containing condensation products of a combination of formaldehyde and phenolic, urea and melamine components; this process is characterized in that the phenolic, urea and melamine components are condensed with formaldehyde in the presence of ε-aminocapronylactam or ε-aminocaproic acid in an amount of at least 0.5% by weight, preferably 0.5-2% by weight , in particular 0.8 to 1.3% by weight, based on the total weight of the adhesive-15 resin solution, without the phenolic components, if used in the form of a precondensate of a phenolic compound and formaldehyde (novolak), reacting with ethylene oxide.

i

The invention further relates to the use of ε-aminocaprolactam or 20 ε-aminocaproic acid as a cold stabilizer in aqueous adhesive resin solutions with condensation products of a combination of formaldehyde and phenol, urea and melamine components in the form of , react with ethylene oxide in an amount of at least 0.5% by weight, preferably 0.5-2% by weight, in particular 0.8 to 1.3% by weight, based on the total weight of the sizing resin solution, in which case a cold stabilizer is present in the formaldehyde and said during condensation of components.

It was surprisingly found that with the addition of β-aminocaprolactam or O-aminocaproic acid, the adhesive resin solutions are cold stable and remain stable up to -335 ° C for at least 4 weeks, i.e. flowing, when the untreated resins become paste in a number of cases · --- 'after a week. When ε-aminocaprolactam-6,86073 m or i-aminocaproic acid, respectively, is added less than 0.5% by weight, the cold stabilizing effect is very small. When β-aminocaprolactam or i-aminocaproic acid, respectively, is used in excess of 2% by weight, no additional advantages are obtained. However, more abundant use is not a disadvantage, but it leads to an unnecessary increase in the price of the resin.

The reason why ε-aminocaprolactam and ε-aminocaproic acid, respectively, act as cold stabilizers in the adhesive resins in question is not yet known.

Since storage instability and cold instability are based on completely different phenomena and also occur in different types of resins, no indication of the solution of the storage stability problem for phenol-free melamine resins 15 in DE-C-1 595 368 could be deduced from the technical basis of this invention. Interestingly, in order to improve the storage stability according to DE-C-1 595 368 20, relatively high concentrations of i-aminocaprolactam are required, namely 3-15% by weight based on the mixture of melamine and formaldehyde, while the cold stability of the adhesive resin solutions in question:. already improves with an addition of only 0.5% by weight based on the total weight of the Ύ: 25 adhesive resin solution.

According to the invention, unsubstituted phenol and substituted phenols can be preferably used as the phenol component. Suitable substituted phenols are cresols and xylenols. These should be unsubstituted at at least two carbon atoms ortho or para to the OH group.

As the phenol-urea-melamine-formaldehyde condensation products, conventional compositions can be selected, as described, for example, in DE-C-2 951 957. ···. 35 and EP-B-31 533. To prepare a typical sizing resin solution according to the invention, 1-10% by weight of phenol, 15 to 25% by weight of urea, 10 to 20% by weight of 7 80073 melamine, 20 to 45% by weight are used as ingredients. % by weight of formaldehyde, 0.1 to 0.2% by weight of sodium hydroxide and 0.5 to 2% by weight of S-aminocaprolactam or ε-aminocaproic acid. The difference to 100% by weight is water.

A typical sizing resin solution according to the invention is prepared using about 5% by weight of phenol, 21% by weight of urea, 13% by weight of melamine, 32% by weight of formaldehyde, 0.12% by weight of sodium hydroxide and 1% by weight of ε-aminocrolactam or ί-aminocaproic acid. The rest is water.

The sizing resin solutions according to the invention are prepared by methods known per se, such as those described in the above-mentioned patents, in which ε-aminocaprolactam or ε-aminocaproic acid, respectively, are condensed from the beginning of the condensation. However, other methods described in the literature can also be used.

If ε-aminocaprolactam is added after condensation of the ingredients, virtually no cold stabilizing effect is achieved.

The invention is further illustrated by the following examples.

Example 1 3,230 parts of a 40% aqueous formaldehyde solution and: Y: 25 4,887 parts of a commercial aqueous urea-formaldehyde sizing resin having a molar ratio of formaldehyde to urea of 1.8: 1 and a solids content of about 65% are weighed into a reaction vessel and 1,300 parts of melamine, 466 parts of phenol, 99 parts of ε-aminocaprolactam-30 and 23 parts of 50% aqueous sodium hydroxide solution are added with stirring.

The mixture is heated to 90 ° C and condensed at 90-95 ° C for two hours to a viscosity of 700 v mPa.s (20 ° C), keeping 4 parts of a 50% aqueous sodium hydroxide solution at a constant pH. as 8.9.

. ···. 35 The adhesive resin thus obtained is then cooled to 20 ° C and has the following properties: 8 86073 viscosity 750 mPa.s (20 ° C) pH at 20 ° C 9.1 density at 20 ° C 1.262 g / cm 3 dry matter content 61% 5 gel time 32 minutes (with the addition of 40% hardener at 34 ° C = 34% formic acid) storage stability at 25 ° C for 6 weeks (increase in viscosity 10 2,500 mPa.s to)) cold stability at 0 ° C for more than 3 months Using the corresponding amount of ε-aminocaproic acid instead of β-aminocaprolactam gives essentially the same results.

Comparative Experiment 1 3 230 parts of a 40% aqueous solution of formaldehyde and 4 887 parts of the commercial aqueous urea-formaldehyde lead-20 resin described in Example 1 are weighed into a reaction vessel and 1,300 parts of melamine, 466 parts of phenol and 23 parts of a 50% aqueous solution of sodium hydroxide.

The mixture is heated to 90 ° C and condensed at this temperature for two hours to a viscosity of 700 mPa.s (20 ° C) at a constant pH of 8.9.

The adhesive resin thus obtained is cooled to 20 ° C and has the following properties: viscosity 750 mPa.s (20 ° C) 30 pH at 20 ° C 9.0 density at 20 ° C 1.26 g / cm 3 dry content 59% gel time 30 minutes (with the addition of: at 40 ° C ty 3% hardener = 34-, ···. 35% acetic acid) 9 86073 storage stability at 25 ° C for 5 weeks (viscosity 2,500 mPa.s) cold stability at 50 ° C after 3 weeks

Thus, the adhesive resin that has become pasty can be returned to the fluid state by heat treatment at 60-10 ° C, but the cold stability further deteriorated and is only about 3 days thereafter.

Example 2 To 5,343 parts of a 40% aqueous formaldehyde solution are added 912 parts of phenol and 54 parts of a 50% aqueous sodium hydroxide solution, heated to 90 ° C with stirring and condensed at this temperature for 30 minutes. The solution obtained is cooled to 25 [deg.] C. and 3,200 parts of melamine and 174 parts of .beta.-aminocrolactam are added with stirring. The reaction mixture is heated to 90 ° C and allowed to react at 90-95 ° C for about 70 minutes to a viscosity of 400 mPA.s (20 ° C).

The resulting resin solution is cooled to 25 ° C and mixed with 7,940 parts of a commercial aqueous urea-formaldehyde adhesive resin as described in Example 1.

The adhesive resin mixture has the following properties: viscosity 606 mPa.s (20 ° C) pH at 20 ° C 9.1 density at 20 ° C 1.276 g / cm 3 dry matter content 62.8% gel time 32 minutes (after add- at 50 ° C i.e. 10% 15% NH 4 Cl solution) from storage-. 35 stability at 25 ° C for 6 weeks (viscosity increase to 2,500 mPa.s) 10,86073 cold stability at 0 ° C for 4 weeks Using an equivalent amount of ε-aminocaproic acid instead of ε-aminocaprolactam gives essentially the same results.

Comparative Experiment 2 To 5,343 parts of a 40% aqueous solution of formaldehyde are added 912 parts of phenol and 54 parts of a 50% aqueous solution of sodium 10 hydroxide, heated to 90 ° C with stirring and condensed at this temperature for 30 minutes. The resulting solution is cooled to 25 ° C and 200 parts of melamine are added with stirring. The reaction mixture is heated to 90 ° C and allowed to react at 90-95 ° C for about 70 ml to 15 minutes to a viscosity of 380 mPA.s (20 ° C).

The resin solution thus obtained is cooled to 25 ° C and mixed with 7,940 parts of a commercial aqueous urea-formaldehyde adhesive resin as described in Example 1.

20 The adhesive resin mixture has the following properties: viscosity 560 mPa.s (20 ° C) pH at 20 ° C 9.0 density at 20 ° C 1.275 g / cm3 dry matter content 63% - 25 gelling time 32 minutes (when added at 50 ° C i.e. 10% 15% NH 4 Cl solution) from storage. "·. stability at 25 ° C for 4 weeks (increase in viscosity to 2,500 mPa.s) cold stability at 0 ° C for 2 weeks

Claims (7)

11 86073 A cold-stable aqueous adhesive resin solution containing condensation products of a combination of formaldehyde and phenolic, urea and melamine components, characterized in that the adhesive resin solution is obtained by condensing the phenolic, urea and melamine components with formaldehyde in the presence of at least 0.5 % by weight of ε-aminocaprolactam or 6-aminocaproic acid, based on the total weight of the sizing resin solution, without the phenolic components, if used in the form of a precondensate of a phenolic compound and formaldehyde (Novo lacquer), reacting with ethylene oxide. Adhesive resin solution according to Claim 1, characterized in that it is obtained by carrying out the condensation in the presence of 0.5 to 2% by weight of ε-aminocaprolactam or ε-aminocaproic acid. Adhesive resin solution according to Claim 1, characterized in that it is obtained by carrying out the condensation in the presence of 0.8 to 1.3% by weight of ε-aminocaprolactam or ε-aminocaproic acid. Adhesive resin solution according to one of Claims 1 to 3, characterized in that it contains modifiers for use in phenolic plastics. Process for preparing a cold-stable aqueous adhesive resin solution according to one of Claims 1 to 4, characterized in that the phenolic, urea and melamine components are condensed with formaldehyde. with in the presence of β-aminocaprolactam or ε-aminocaproic acid in an amount by weight according to any one of claims 1 to 3, without the phenolic component being present. . if used in the form of a precondensate of a phenolic compound and formaldehyde (novolac), * react with ethylene oxide. • · i2 86073 6. Use of ε'-aminocaprolactan or 6-aminocaproic acid as a cold stabilizer in aqueous adhesive resin solutions containing condensation products of a combination of formaldehyde and phenol, urea and melamine components formaldehyde and without phenol components, in the form of a precondensate (novolac), react with ethylene oxide in an amount of at least 0.5% by weight based on the total weight of the sizing resin solution, 10 cold stabilizers being present during the condensation of formaldehyde and said components. Use according to claim 6, in an amount of 0.5 to 2% by weight, preferably 0.8 to 1.3% by weight. i3 86073