SK93097A3 - More easily washable aqueous aminoplast resins for the production of timber materials - Google Patents

Abstract

Aqueous aminoplast resins with a solids content of 50 to 75 wt % and a viscosity, related to a solids content of 67 wt %, of 150 to 400 mPa.s (measured at 20 DEG C and a shear gradient of 500 s<-1>) containing per mol melamine (component a) 0.5 to 13 mol urea (component b), 2 to 20 mol formaldehyde (component c), 0 to 1 mol phenol and/or a condensable phenol derivative (component d), 0 to 1 mol of an alkaline sulphite and/or alkaline hydrogen sulphite (component e) and 0 to 1 mol of a further condensable compound (component f), in which the ratio of the sum of the mol quantities of the (-NH2) groups originally present in components (a) and (c) to that of component (c) is 0.5:1 to 2:1.

Description

Aqueous aminoplast resin, process for its production and use

Technical field

The invention relates to an aqueous aminoplast resin. improved washability for the production of wood materials, a process for the production of such a resin, its use as a binder for the manufacture of wood materials and wood materials obtainable by the use of this aminoplast resin.

BACKGROUND OF THE INVENTION

Aqueous aminoplast resins consisting of melamine, urea and phenol are generally known (Ullmann: Encyclopädie der technischen Chemie, 4th edition, Volume 7, pages 403 to 422) and are mainly used for the production of high-quality, weather-resistant plywood.

Generally, plywood is produced by gluing pre-dried wood chips with an aqueous amino resin and compressing the wood chips at 130 to 250 ° C to plywood while curing the aminoplast resin.

In order to produce plywood economically, the aqueous aminoplast resins should have the highest solids content, so that relatively short pressing times are sufficient to remove excess water introduced by the glued chips, and that the wood chips can, if possible, be little pre-dried.

In addition, aqueous amine resins should have a sufficiently low viscosity at a relatively high solids content to ensure uniform gluing of the wood chips without technical difficulties.

Furthermore, the aqueous aminoplast resins should have a good washability both immediately after manufacture and after prolonged storage, which means that they should be allowed to dilute indefinitely with water and pass into a solution or dispersion which is largely free of sticky coagulate.

This feature greatly facilitates the cleaning of objects that come into contact with the aminoplast resins during transport and processing.

DE-Aq 31 25 874 discloses aminoplast resins of defined proportions of formaldehyde, urea, melamine and phenol, which are obtained when the precondensate is made from phenol, formaldehyde and alkali bisulfite and the precondensate from formaldehyde and urea and both of these precondensates. are condensed together with melamine and formaldehyde, and urea is added to the condensation product thus obtained after cooling. According to the description, these aminoplast resins have a viscosity of 100 to 1000 mPa · s at a solids content of 50 to 75% and preferably a viscosity of 200 to 800 mPa · s at a solids content of 60 to 70%.

Washability needs to be improved. Subsequent processing of the examples showed that although the aminoplast resins still showed satisfactory washability immediately and shortly after manufacture, the washability after several weeks of storage was no longer satisfactory. In addition, the specifically mentioned aminoplast resins with a solids content of 60% and a viscosity of 200 mPa.s have a viscosity of more than 400 mPa.s when their solids content is increased to 67% by distilling off water at room temperature.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide aqueous aminoplast resins suitable for the economical production of high-quality, weather-resistant plywood, which still exhibit good washability, especially after several weeks of storage. The invention fulfills this object.

SUMMARY OF THE INVENTION

The aqueous aminoplast resin having a solids content of 50 to 75% by weight and a viscosity of 150 to 400 mPa.s, based on a solids content of 67% by weight (measured at a temperature of 20 ° C and a shear gradient of 500 / s). that contains per mole of melamine as component (a)

b) 0.5 to 13 mol, preferably 1 to 6 mol of urea,

c) 2.0 to 20 mol, preferably 3 to 10 mol, of formaldehyde,

d) 0 to 1 mol, preferably 0 to 0.2 mol of phenol and / or condensable phenol derivative, up to 1 mol, preferably 0 to 0.2 mol of alkali sulfite

f) 0 to 1 mol, preferably 0 to 0.2 mol, of another condensable compound, wherein the ratio of the sum of the molar amounts of the groups (-NH ₂ ) existing initially in components (a) and (b) to the molar amount of component (c) is 0 5: 1 to 3.5: 1, preferably 0.75: 1.

The aminoplast resins according to the invention have a solids content of 50 to 75%, more preferably 60 to 75% and particularly preferably of 67 to 72% and a viscosity of 150 to 400 mPa.s, based on a solids content of 67%.

The solids data refers to a measurement where 1 g of aqueous aminoplast resin is poured onto a flat flask and kept in a forced air oven at 120 ° C for 2 hours and reweighed after cooling to room temperature.

Viscosities are measured according to DIN 53 018 in a rotary viscometer at 20 ° C and a shear gradient of 500 / s.

By designating the molar amounts of the groups (-NH ₂ ) existing initially in components (a) and (b) is meant the molar amount which was contained in the monomer components (b) and (c) prior to their reaction.

Components (a) to (f) that are contained in aminoplast resins are meant to include both monomers and units derived therefrom, as are usually in formaldehyde adducts and precondensates (Kundstoff Handbuch, 2nd edition, vol. 10, p. 6, 69 (1988)).

For the production of aqueous aminoplast resins, it is possible to employ components (a) to (f) both in monomeric form and in the form of reaction products containing both units derived from monomeric formaldehyde (component c) and monomer component (a) , (b), (d), (e) or (f), i.e. in the form of formaldehyde adducts and precondensates.

Components (a) and (b) (melamine and urea) can be used in solid form.

Preferably, component (b) is used in the form of a concentrated aqueous solution of urea and formaldehyde (component c), which are known from DE-A 24 51 990 and EP-A 0 083 427. 0, preferably 3.5 to 4.5, 5 moles of formaldehyde per mole of urea preferably have a solids content according to DIN 12 605 of 50 to 85% by weight, preferably 60 to 80%. They contain urea and formaldehyde partly in free monomeric form, partly in the form of reaction products such as methylolureas or low molecular weight condensation products.

These solutions are preferably adjusted to have a total formaldehyde content of 40 to 60, preferably 40 to 55% and a total urea content of 15 to 40, preferably 20 to 40%. They preferably contain, in addition to free formaldehyde and monomethylolurea or polymethylolurea products, which contain only one urea-derived unit, preferably less than 10% by weight of urea-formaldehyde condensation products, which contain more than one urea-derived unit.

In addition, it may in many cases be advantageous to employ at least one part of formaldehyde (component c), preferably as a 30 to 50% by weight aqueous solution, such as paraformaldehyde or in the form of its reaction products with components (a), (d), (e) and or (f).

In addition to phenol, condensable phenol derivatives are also suitable as component (d). Preferred phenol derivatives are, for example, phenol homologues, for example alkylphenols having 1 to 6 carbon atoms in the alkyl moiety, such as cresols, xylenols, naphthols, 2,2-bis (4-hydroxyphenyl) propane ( ^R Bisphenol A), 2,2'-methylenediphenol (Bisphenol F), 1,1-bis- (4-hydroxyphenyl) ethane or 1,1-bis (4-hydroxyphenyl) isobutane, hydroquinone and resorcinol.

A reaction product containing a phenol and / or a phenol-formaldehyde derivative may also be used in place of or in addition to the phenol or derivatives thereof. These reaction products are also generally known (Ullmann Encyclopedia of Industrial Chemistry, 5th Edition, Vol. A 19, pp. 371-384). Particularly suitable are aqueous solutions of resols having a solids content of 30 to 80, preferably 50 to 70% and a viscosity according to DIN 53 018 of 10 to 5000, preferably 50 to 500 mPa.s.

Resols usually contain phenol and / or a phenol derivative and formaldehyde in a ratio of 0.1: 1 to 3: 1 and preferably 0.3: 1 to 1: 1.

Component (e), the alkali sulfite or alkali sulfite may be used in solid form or as an aqueous solution.

Particularly preferably, component (e) is used in the form of a reaction product with a formaldehyde, such as hydroxymethanesulfic acid, or as a reaction product with a phenol or a phenol derivative and a formaldehyde, for example resol.

Particularly suitable are resols in which 0.35 to 0.02 mol per mol of phenol of alkali metal bisulfite and / or alkali metal sulfite are used. Such resins and their preparation are described in DE-A 31 25 874.

Suitable other condensable compounds (component f) are urea derivatives, for example ethylene urea, acetylenedimurea, dipropylene triisourea and guanamines, for example benzoguanamine, amides, for example epsilon-caprolactam, alcohols, for example ethylene glycol.

The aqueous aminoplast resins according to the invention can be obtained by condensing in step I in aqueous solution to 1 mole of melamine as component a)

- 0, 5 to 13 mol, preferably 1 until 6 mol, components (b) - 2 until 20 mol, preferably 3 until 10 mol, components (c) - 0 until 1 mol, preferably 0 until 0,2 mol, components (d) - 0 until 1 mol, preferably 0 until 0.2 mol, component (e) - 0 until 1 M preferably 0 until 0.2 mol, component (f). Appropriately condensation is carried out at a temperature of 60 to 100 ° c, · preferably at 75 to 95 "C and at a pH of 7.5 to 10,

preferably 8.2 to 9, then the solution is allowed to cool to 10 to 80 ° C, preferably to 40 to 75 ° C. >

The mole ratio of the sum of the molar amount of amino groups initially present in components (a) and (b) to the molar amount of component (c) is generally 0.5: 1 to 3.5: 1, preferably 0.7: 1 to 2: 1 and particularly preferably 0.8: 1 to 1.5: 1.

The condensation is otherwise carried out in a manner known per se. For more information, see, for example, Ullmanns Encyklopädie der technischen Chemie, 4th edition, Vol. 7, p. 403 to 415 and DE-A 34 42 454.

The condensate thus obtained is then mixed in step II with 0 to 0.8 moles, preferably 0.5 to 0.8 moles of urea per mole of the total amount of urea used in step Ia II, which amounts to a maximum of 13 moles per mole of melamine.

If the total amount of urea (component (b)) contained in the aqueous amino resin is already used in step I, components (a) to (f) will of course be condensed only until a viscosity of 150 to 400 mPa.s relative to a total solids content of 67% by weight. However, when one part of urea is added in stage II, it is generally necessary to condense components (a) to (f) until a viscosity of more than 150 mPa.s is reached, preferably 200 to 1500 mPa.s, based on the total solids by weight 67%, since the addition of the remaining urea reduces the viscosity. The amount of urea required to reduce the viscosity can be determined by simple preliminary tests.

The urea added in step II is preferably added in the form of a solid or in the form of a 40 to 80% by weight, preferably 60 to 70%, aqueous solution.

The mixing method is not critical and is practically carried out by mixing the urea into the condensate.

The solids content according to the definition of the aminoplast resins according to the invention can be achieved simply by adding the appropriate amount of water already in the reaction of components (a) to (f). However, it is also possible to adjust the solids content of aqueous amino resins additionally when higher or lower solids are selected in the reaction of components (a) to (f) and optionally in the mixing of urea condensates and water is added additionally, or water is preferably removed by distillation 15 to 30 ° C under reduced pressure.

The aqueous aminoplast resins are preferably adjusted to a pH of from 8 to 10, preferably from 8.5 to 9.5. In general, customary bases such as alkali and alkaline earth metal hydroxides, preferably in the form of aqueous solutions, tertiary amines such as C1-C6 trialkylamines such as tributylamine and triethylamine, and tertiary alkanolamines can be used to adjust the pH. having 1 to 6 carbon atoms, for example triethanolamine, methyldiethanolamine.

The aminoplast resins may also be mixed with other conventional excipients and additives.

In order to stabilize and to improve the mechanical properties of the wood products with aminoplast resins, it is possible to add to the aminoplast resins; polyalcohols, sugar and water-soluble polymers formed from monomers such as acrylamide, ethylene oxide, N-vinylpyrrolidone, vinyl acetate or copolymerized mixtures of these monomers.

The curing reactivity of the aminoplast resins can be increased by adding a curing agent in an amount of 0.1 to 2% by weight, based on the solids content of the binder. Suitable curing agents are ammonium salts such as ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium phosphates, strong carboxylic acids such as formic and oxalic acids, mineral acids such as sulfuric acid and toluenesulfonic acid.

It is furthermore possible to add to the aminoplast resins; means for controlling pests, for example conventional insecticides or fungicides. '

Aminoplast resins are particularly useful; as binders for the manufacture of wood-based materials such as plywood plywood, made-up wood beams and table tops, and in particular crushed fiber boards and particle board (Ullmanns Encyklopädie der technischen Chemie, 4th edition, vol. 12, pp. 709-727), 1976).

The production of wood materials is carried out by methods known in the art (Ullmanns Encyclopädie der technischen Chemie, 4th edition, vol. 12, pp. 709-726 (1976)). The sizing is suitably carried out by compressing the comminuted wood, provided with an aminoplast resin, at a temperature of 120 to 250 ° C. Under these conditions, the aminoplast resin cures rapidly and wood materials with good mechanical properties are obtained which are largely resistant to moisture.

The aminoplast resins according to the invention are particularly distinguished in that they are well washable even after prolonged storage. This facilitates the cleaning of shipping containers and lining parts treated with aqueous aminoplast resins.

The invention is illustrated, but not limited, by the following examples. Percentages and parts are by weight unless otherwise indicated.

DETAILED DESCRIPTION OF THE INVENTION

Explanation on the starting materials used in the production of aminoplast resins:

Phenol formaldehyde sulphite condensate (PFS condensate)

43.1 kg of a 40% aqueous formaldehyde solution (575 mol), 27.0 kg of phenol (287 mol) and 4.49 kg of sodium sulfite (35.6 mol) were mixed and the reaction mixture was heated to 60 ° C with stirring. . As a result of the exothermic reaction, the temperature was raised to 1.04 ° C and sodium sulfite dissolved. The temperature is maintained at 90 ° C until a viscosity of about 600 mPa · s (20 ° C) is obtained (10 minutes). The mixture was then allowed to cool to room temperature.

Formol 50

Mixtures consisting by weight of 50% formaldehyde, 25% urea and 25% water (EP-A 0 083 427).

Example 1

Mix 85 g of PFS condensate (corresponding to 0.65 mol of formaldehyde, 0.32 mol of phenol and 0.05 sodium sulfite), 581 g of Formol 50 (corresponding to 9.68 mol of formaldehyde and 2.42 mol of urea), 322 g (2 60 mol) of melamine and condensed at 95 ° C until the mixture has a viscosity of 650 mPa.s. After cooling to 62 ° C, 183 g (3.05 mol) of urea are added and the mixture is then cooled to room temperature.

Example IV (for comparison)

The procedure is as in Example 1, except that 170 g of water are added and cooling begins when a viscosity of 550 mPa.s is reached.

Example 2

66 kg of PFS condensate (corresponding to 502 mol of formaldehyde, 249 mol of phenol and 40.5 mol of sodium sulfite), 451 kg of Formol 50 (corresponding to 7517 mol of formaldehyde and 1879 mol of urea) are heated from room temperature to 95 DEG C. for 31 minutes, 250 kg of melamine (1984 mol) and 78 kg of water are condensed for 24 minutes at this temperature. The mixture is then cooled to 85 ° C over 10 minutes and condensed at this temperature for 10 minutes, the reaction mixture reaching a viscosity of 560 mPa.s. The mixture was then cooled to 60 ° C over 30 minutes, 142 kg (2367 mol) of urea was added and cooled to room temperature.

Example 3V (for comparison)

Example 1 of DE-A 31 45 328 is used.

Test of properties of aminoplast resins

Water dilutability

Place 10 g of glue in a beaker. While stirring, water is added until clumps begin to form. Water-dilutability is the ratio of the amount of glue to the amount of water added.

Zmývateľnosť

The stirrer equipped with a 1 mm mesh mesh was immersed in the aqueous aminoplast resin for 1 minute and then dripped for 1 minute. Then, a portion of the aminoplast resin is centrifuged from the agitator while the agitator is allowed to rotate. 1 minute at 650 rpm in air and weigh the amount of (E) aminoplast resin that remains on the stirrer. The stirrer is then allowed to rotate, initially at 650 rpm in water and, after dripping for 1 minute, again in air, and the residue (R) deposited on the stirrer is weighed.

Evaluation: (R x 100) / E = wet residue [%]

Wet residues less than 25% mean good washability. Wet residues greater than 25% mean poor washability.

Solids content

On a weighing plate (35 mm diameter, flat bottom) a heated amount of sizing resin (approximately 1 g) in a forced-air oven is maintained by heating at 120 ° C for 2 hours. After cooling to room temperature, the solids content is determined by weighing and weighing.

viscosity

The viscosity is measured according to DIN 53 018 at a temperature of 20 ° C and a shear gradient of 500 / s.

The test results are summarized in the table

table

Example 1 IV 2 3V Solids content 69.9 63.3 67.6 62.6 viscosity 400 410 560 410 Water dilutability on the day of preparation any 1: 0.9 any any after 3 weeks 1: 2 1: 0.5 any no Wet residue [%] on the day of preparation 19 71 17 33 after 2 weeks 28 67 after 3 weeks 18 87 after 6 weeks 19

- 12 Industrial Applicability

Aqueous aminoplast resins suitable for the economical production of high-quality, weather-resistant plywood, which still exhibit good washability, especially after several weeks of storage.

Claims (8)

PATENT CLAIMS Aqueous aminoplast resin having a solids content of 50 to 75% by weight and a viscosity of 150 to 400 mPa · s, based on a solids content of 67% by weight, measured at 20 ° C and a shear gradient of 500 / s, characterized in that contains per mol of melamine as component (a) b) 0.5 to 13 mol, urea, c) 2.0 to 20 moles of formaldehyde; d) 0 to 1 mol, phenol and / or condensable phenol derivative, e) 0 to 1 mol, alkali sulfite; f) 0 to 1 mol of another condensable compound, wherein the ratio of the sum of the molar amounts of (-NH ₂ ) groups initially present in components (a) and (b) to the molar amount of component (c) is 0.5: 1 to 3.5: first Aqueous aminoplast resin according to claim 1, characterized in that it can be prepared by being I) condenses component a) in aqueous solution per mole of melamine as 0 5 to 13 mol of component (b) 2 up to 20 mol of component (c) 0 up to 1 mol of component (d) 0 up to 1 mol of component (e) 0 up to 1 mol of component (f) until up to a viscosity of 150 to 1500 mPa.s, content-related 67% by weight, the ratio of the sum of the molar amounts of the -NH ₂ groups existing initially in components (a) and (b) to the molar amount of component (c) is 0.5: 1 to 3.5: 1 and components (a) to (f) can be used in free form and / or in the form of reaction products containing both formaldehyde as component c) and component (a), (b), (d), ( (e) or (f), and (II) the condensate obtained in stage I with 0 to 0.8 moles of urea per mole of the total amount of urea used in stages I and II (components (b)) containing not more than 13 moles of melamine is removed and optionally removing or adding water to adjust the solids content to 50-75% by weight. 4th 5th Aqueous dehyd Aqueous aminoplast and, as component (c) of the resin according to claim 2, characterized in that the reaction products comprise a formal component of (d). aminoplastic surfactants contain (formaldehyde (e). resin according to, with and as component (c) of claim 2 or 3, the reaction that the products of component (d) and component Aqueous aminoplasts initially in kole molar amounts of amino groups 2: 1. the resin component of at characterized in that (a) the quantity of the ingredient to 4, Claim 1 mole ratio of the sum (b) contained (c) is 0.75: 1 to ^'1 »' registration of the aqueous amino resins of claim 1 in that with a solution per 1 mol of melamine as process 6th until 5 n and no u j ú c and I) condenses vc > water component a) 0,5 to 13 M ingredients (B) 2 to 20 M ingredients (C) * 0 to 1 M ingredients (D) • 0 to 1 M ingredients (E) 9 0 to 1 M ingredients (F) until viscosity up to 1500 mPa.s, based on a solids content of 67% by weight, the ratio of the sum of the molar amounts of -NH ₂ groups existing initially in components (a) and (b), and the molar amount of component (d) to the molar amount of component ( (c) is 0.5: 1 to 3.5: 1 and components (a) to (f) may be wholly and / or partially replaced by a corresponding amount of formaldehyde reaction products as component (c) with component (a), (b) , (d), (e) and / or (f), II) the condensate obtained in stage I with 0 to 0.8 moles of urea per mole of the total amount of urea used in stages I and II (component (b)) containing not more than 13 moles of melamine is drained and, if necessary, removed by adding or adding water % solids to 50 to 75% by weight. Use of the aqueous aminoplast resin according to claims 1 to 5 as a binder for the production of wood materials. Wood materials obtainable using the aqueous aminoplast resins according to claims 1 to 6.