CZ220189A3 - process for preparing aminoplasts exhibiting small stress - Google Patents

Abstract

A method for producing aminoplasts with low surface tension treatment of chipboard, fibreboard, claw and similar plates by lamination in tray presses or short-time presses is that the urea is formaldehyde and melamine-formaldehyde the precondensates are modified by alkylamines the group C alkyl is less than or equal to 3, or melamine urea formaldehyde precondensates, or alkyl-amino alcohols, or ammonia, while reducing strongly nucleophilic carbonyl group as an undesirable carrier properties of solidified high-tension films and fragility.

Description

(57) The method for producing low-stress aminoplasts for surface treatment of particle board, fibreboard, shovel and similar boards by laminating in multi-stage presses or short-cycle presses is that urea-formaldehyde and melamine-formaldehyde precondensates are modified with alkyl amines or less than C is equal to 3, or melamine (urea-formaldehyde precondensates), or alkyl-amino-alcohols, or ammonia, reducing the strongly nucleophilic carbonyl group as a carrier of undesirable properties of the solidified high-tension films and brittleness.

In the surface treatment of chipboard, shovel and similar boards by lamination on short-stroke (KT) discontinuous presses of the latest design (10), the net pressing time has been reduced from the previous 60 to 70 seconds to a possible 20 to 30 seconds per 1 press cycle by automating file folding and file loading operation. The performance of such a peak device, which is equal to that of continuous presses, requires highly reactive and stable melamine-formaldehyde and urea-formaldehyde resins.

The resins that have been developed (7) for the first and second generation KT presses no longer meet the short pressing time of 20 to 30 seconds at a press plate temperature of 19 ° C. These resins are unsuitable because they give brittle solidified films under these conditions, on which microcracks form. 10092002, 04:21:31 Another feature of unsatisfactory resin quality is the peeling of the stiffened film from the backing layer - e.g. chipboard thatch.

The fragility of the drawn films and the formation of microcracks is attributed to (6) the asymmetry of the films, the thickness of the films - the deposition of resins.

In order to overcome these shortcomings, various film compositions, coating height and impregnation technique (6) are proposed. Fragility of films is solved eg. (8) by reducing the pressing temperature and extending the pressing time for laminating chipboard. The disadvantage of this method is that the production capacity of the device is reduced.

In the outdated processes for the production of urea-formaldehyde resins for decoratively laminates, the precondensation is about 5 to 10 minutes shortly before the precondensation is discontinued. adds urea to the reaction medium to bind unreacted or released formaldehyde. This procedure is used e.g. also in the production of particle board with reduced content of free formaldehyde, class E-1 ·. It is generally known that the bending strength has so far decreased, but there has not been any explanation in the literature to date of the nature of this phenomenon - chemism. In other processes (7), it is added to the reaction medium during heating

-? Batching together with melamine as a cyclic lactam modifying component to bind free or liberated formaldehyde and modify the precursors of melamine with formaldehyde - methylolmelamines.

The brittleness of the films and the solidified films is also caused by unsuitable catalysts with strong nucleophilic particles, which are used for the base films and in part for the first stage of impregnation of the decorative films (8).

The disadvantage of these processes is that substances containing a reactive carbonyl group capable of further oxidation are introduced into the reaction medium. The carbonyl group carries undesirable properties of the stiffened films - brittleness (microcracks formation). In addition, the cyclic lactams interact competitively with melamine in interaction with formaldehyde. Catalysts with a strong nucleophilic particle, e.g. NH4 Cl causes strong oxidation according to the scheme:

(Network (-) / · (+)

HC = 0 + 1 NH 2 3 OH ₊ ) ( ₊ ) r

NH ₉ l ^Z H h ₂ c

NH, + CH _O Ϊ0 / -7 *

HO - CH ₂

NH ₂ - CK ₂ - OH +

Cl ¹ + HOH — HCl + OH. (-) Γ (-)

H, C 4 O + OH - * H

L.

//

O) + H

OH

ho-ch ₂

- (R / 1H-CH3OH)

I,

H ( ⁺ )

H-O-10-CIX-NH-CH

W (-)

NH - CH - + H -> HO - CH - NH

i. -

ω ο, <4 ·

C-FRH

CA rho-ch ₉ -nw-ch '+ k £ ο «*? ζ ¹ · α-ι ₂ ί μη-ch ₃ ;

ω Ζ ^

CH ₉ —- ΝΗ - CH 2, y 2 - iu:

.0 /

CH

Í2J ¼ _CH-O - NH - CH "+

CH _q - NH - CH 2 + HCl 2 - C 4 - U - NH - CH 3 HCl 3 by warm

However, the HCl-stabilized dialkylamine decomposes at high temperature, releasing strong nucleophilic chloride ions which still oxidize the carbonyl groups of the free and liberated formaldehyde and the carbonyl groups of the methylolurea condensates. The bonds of already crosslinked polymers are cleaved according to the scheme:

Cl ⁷ + HOH - * HCl + OH (')

R.

\ C-)

C == O + OH

R

□ ¹

The cleavage fragments R @ 1 - and R @ ₉ - are bound by weak hydrogen bonds, which are manifested by the formation of micro-cracks. These hydrolytic cleavage reactions, in which formaldehyde is also incorporated, are common at high temperatures in the compression of films made from resins with a high content of free formaldehyde.

From the point of view of the chemical composition of the resins, the following factors cause the fragility of the films:

High content of carbonyl groups given by:

1. a high excess of formaldehyde relative to melamine or urea;

2. the presence of strong nucleophilic particles of acid-base catalysts in prescribed impregnating solutions,

3. the presence of unsuitable modifying agents which modify the rheology of the impregnating resin solutions and their melts during condensation in the press.

The available literature does not describe the chemism that causes polycondensate degradation, subsequent shrinkage and cracking on decorative films consisting of a cellulosic carrier (decorative paper, optionally barrier paper) and urea-formaldehyde, respectively. urea-melamine-formaldehyde, respectively. of the melamine-formaldehyde resin in the condensed-as-thermoset state.

These drawbacks are overcome by the process according to the invention, characterized in that the carbonyl groups of the free and liberated formaldehyde, the carbonyl groups of the methylol urea condensation fragments, are bonded with amino groups of C 3 or C 3 alkyloamines or cycloalkylamines or melamine or alkyl amino alcohols. or ammonia. Substances are added to the reaction medium as stabilizing modifiers at the interruption / termination / precondensation of the resins at the end of the batch, either substance being uniform in either or in combination.

.......... P rocedure ^- Stage ^- -induced invention-is-of-Ac-U is th-m -, - f-e -s -vyluč UJ-ú_ka cocatalyst having strong nucleophilic atom, e.g. NH "C1.

The acid-base catalysts used are substances whose basic component is either n-alkylamine having a carbon number of C = 3, or a cycloalkylamine, or an alkylamino alcohol, or preferably ammonium.

The corresponding araine can be used singly or in combination with ammonia. The acid component of the acid-base catalyst is formic acid (acidum forroicum). The essence of catalysis and bonding of carbonyl groups (hot and pressure) in polycondensation to a thermosetting film is that the specific property of formic acid - its reducing ability - is able to oxidize to carbon dioxide according to the Leuckart-Wallach reaction:

· -X = 0 + HpBI

-NH-R + H / + /

Rh ₂ o—>

R

R

CH-NH-R + CO ₂ Y

Where R 1, R 1, R 2 is alkyl.

The basic component of an acid-base oxidant catalyst.

Similarly, a catalyst is added to the structure of the polycondensate, the basic component of which is an alkyl amino alcohol.

R

R

N - _CH2 - _CH2 - OH + H + ⁺⁾ - H _o -Z 0 - CH, - CH, ^) 'Λ ^R i. (<<-n <*

R, χ '> * (-) * (+) ₂

C 1 ^ O * ^CH 2 ^CH 2 ^N \

Ro o

1. (+) XL cZo.

, CH ₂ - ch ₂

R, '4 R,

R

CH ₂ - CH ₂

CH O ”)

R, '¢ - 0 0 / r;

R

- 0 - CH 2 - CH 2: Z coZ

R

Ammonium formate, which is added to the resin solutions as an acid-base catalyst, reacts with carbonyl groups at high pressing temperatures to form primary amines which act as stabilizing antioxidants:

^ 4

H 0

C = NH \ (-)

nh ₂

n * « ^x 9

MU

The invention relates mainly to urea-formaldehyde resins, combined urea-melamine-formaldehyde resins produced by a two-stage precondensation;

a) In the alkaline range at pH 9 to 9.8, depending on the molar ratio of urea to formaldehyde from 1: 1.9 to 1: 2.

b / In the acid range at pH 4.2 to 5 depending on the excess of formaldehyde to urea from 2 to 1: 1.9: 1. The condensation is catalyzed by a 3M formic acid solution.

The invention particularly relates to urea-formaldehyde resins because they are predominantly carbonyl groups as compared to melamine-formaldehyde resins in which the source of carbonyl groups is free formaldehyde and an unsuitable modifying additive, e.g. cyclic lactam added together with melamine to the reactor to prepare the resin (7.8). This also implies a difference in the tension of the urea-formaldehyde and melamine-non-formaldehyde resins.

Carbonyl groups carry the undesirable properties of solid films (shrinkage, cracks, micro-cracks, peeling of solid films from the substrate). This phenomenon has been confirmed in the operational range (8) by the use of barrier foils (under foil decor) consisting of 100 g / m 2 paper impregnated with urea-formaldehyde resin (9 parts) and melamine-formaldehyde resin (1). %, with a total resin load of 42 to 44% by weight. originated on the flat laminate microcracks, ^J encountered in the processing of laminated chipboard in furniture plant. No micro-cracks were formed after the barrier foil was removed.

in

The invention further relates to melarin-formaldehyde resins pre-condensed in one step in alkaline medium at pH

8.9 to 9 at a molar ratio of melamine to formaldehyde of 1: 2, or at a pH of < 8.9 to a primary molar ratio of 1; 1.85 to 1.9, preferably 1: 1.9.

The object of the invention is a process for producing and modifying melamine-formaldehyde resins and adjusting impregnating solutions with an acid-base catalyst similar to urea-formaldehyde resins.

The procedure consists of two parts:

1, from the preparation of resins and their modification,

2. adjustment of the impregnating solutions with an acid-base catalyst.

1. The melamine-formaldehyde resin is prepared according to the flood procedures (7) for KT pressing, except that the cyclic lactam is not fed into the reactor together with the melamine, but the resin is modified after the batch is cyclohexylamine or diethylaminoethanol. DAE /.

1.1. The melamine-formaldehyde resin is prepared with a reduced molar ratio, melamine-formaldehyde 1: 1.8 to 1: 2, preferably 1: 1.9, at a pH of the reaction medium of 8.5 to 8.9, preferably 8.8.

Upon completion of the precondensation, the resin is modified with cyclohexylamine, or dicyclohexylamine, or diethylamino-ethanol.

1.2. The urea-formaldehyde resin is prepared according to the flooding procedures (7) for KT pressing, except that urea is excluded from the batch process as a modification additive added to the reactor before the batch is terminated. Either melamine or cyclohexylamine, or dicyclohexylamine, or diethylaminoethanol (DAE), or ammonia alone, or in combination with the amines mentioned, is used as modifying agent. The modification additive, except melamine, is added after cooling the reactor contents to 30 ° C.

1.3 '. The urea-formaldehyde resin is prepared with a reduced molar ratio of urea-fornaldehyde in the ratio of 1: 1.8 to: 2, preferably 1: 1.9, with the pM reaction medium maintained at alkaline condensation in the range of 3: 8 to 3/2 preferably 2 and in the precondensation in the acid range at a pH in the range of 4/3 to 5/2 preferably 5.

Upon completion of the precondensation (after the end of the batch), the urea-formaldehyde resin is modified with melamine after the temperature of the reaction medium has been reduced to 70 ° C. Using the other modifiers mentioned, the temperature of the reactor contents is lowered to 30 ° C before the appropriate modifying additive is added to the reactor.

The modification of the melamine-formaldehyde resins according to the invention with strong amine-bases is based on the interaction of the basic amino group of the modifier as a proton acceptor from the acidic end-group of the methylolmelamine side chain. The methylolmelamine conjugate base is then coupled with the conjugated acid of the corresponding alkylamine according to the scheme:

-C ^ ŇH

IN N

CH,

N,

-C * 'CV if

ŇH - CH ₂ - θίϊ

- + - (+) ALK - NH '+ H -> ALK - NH'

- ( ^- ) - (-)

ALK - NH ₃ + | O - CH ₂ - NH

-Ns.

C ^ ALK-NH - OBJECTIVE II

M

NH

4- H ₂ 0

Alkyl amines as the nucleophilic strong ^one substance influence the proteolytic reaction of terminal groups of the side chain-metylolmelan iínu, the amino side chains are maintained.

A suitable modifier of melamine-formaldehyde resins are also alkylamino alcohols, e.g. diethylaminoethanol (DAE). The modification process is characterized in that different polarization of the terminal hydroxyl groups of methylolmelamine and DAE is utilized. Due to this polarization, the condensation of methylolmelamine with DAE is more realistic than the expected condensation of methylolmelamine with each other.

The ease of similar condensation was verified in the catalytic treatment of a mixture of two types of resins for the first impregnation stage - urea-formaldehyde resin and melamine-formaldehyde resin. Condensation of this mixture proceeds faster with the same amount of catalysts than with pure melamine-formaldehyde resin or pure urea-formaldehyde resin, ·

Modification of urea-formaldehyde resins with melamine or alkyl amine according to the method for producing low-stress aminoplasts is characterized in that partial aminolysis of the terminal methylol groups, methylolureas, is carried out with a basic amino group. Amino derivatives are formed which are more reactive for 3 more condensation with methylolurea than methylolurea itself. The amino group of the modifying agent acts first as a proton acceptor for the methylolurea end group and then as a conjugated acid as a proton donor for the methylolurea carbonyl group. Modification of end groups and carbonyl groups proceeds as a protolytic reaction:

HO-CH ₂ -NH-CO-NH-CH ₂ -OH + H ₂ N-ALK (+) - ALK- * HO-CH ₉ -NH-C-NH-1

OH

HO-ch ₂ -NH-CO-IMH-ch ₉ y-1 ")" CH ₂ <01 * H ₂ N - ALK <0j ·, +

A method of modifying urea-formaldehyde resins for low-stress aminoplasts is characterized in that NH +, as conjugated ammonium hydroxide, participates as a proton donor to the carbonyl group, where the nitrogen residue fills the four-stage carbon gap.

NH - _CH2 - OH

CH

Ooh

- OH HO - _CH2 - NH - C

Ooh

NH - _CH2 - OH +

+. H (+) (-)

OH H ₉ O

The method of binding free, unreacted or protolytic reactions of formaldehyde liberated resins is characterized in that ammonia or alkylamine in the form of conjugated acids release a proton to the carbonyl group of formaldehyde while simultaneously filling the electron gap on carbon. Proton donors for amines are formic acid and methanol, which are the result of the Cannizzar reaction of formaldehyde in an alkaline medium. The reduction of formaldehyde results in hexamethylenetetramine (in ammonia reduction) or 1, 3, 5 trialkyl * hexahydro 1,3,5 triazine (in primary alkylamine reduction).

In the presence of the conjugated base H-COO acid. some form of secondary amine is also formed.

2.0. The impregnation of the impregnating solutions with the acid-base catalyst according to the method of producing low-stress aminoplasts consists in preparing the acid-base catalyst by mixing 38 parts of a 3 molar formic acid solution with 10 parts of a 25% aqueous ammonia solution under intense cooling,

This results in ammonium formate which is adjusted to a pH of 7.0 to 7.0

7.3, preferably 7.2. The ammonium formate solution is further diluted with water in a ratio of 1: 1 and used in such a concentration to lubricate the gelatinization of the resins according to the procedure described in the Example.

Example 1.

2520 L of 37% by weight of 1115 kg of formaldehyde, stabilized with melamine, are metered into the reactor. 800 l of treated / softened water and 2300 kg of melamine are then metered in. The reaction mixture was adjusted to pH 8/5 with 3 molar NaOH solution. The contents of the reactor are heated to 40 ° C and the addition is allowed to proceed for 10 min at this temperature. The pH is then adjusted to 9 and the reaction mixture is heated to 85-87 ° C. The exothermic reaction raises the condensation temperature to 90 ° C. The reaction is maintained at this temperature until the first turbidity of the precondensate with water is formed. When od-. condensation is allowed to proceed to the water miscibility with 1: 4 / then the cooling rate of the reactor is controlled so that the final water miscibility with the resin is 1: 1.3.

After the reactor contents have cooled to 25-30 ° C, 50 liters of cyclohexylaroin are added to the reactor, and the entire contents are stirred vigorously for 10 minutes. After homogenization, the resin is pumped into storage tanks.

Example 2.

The resin as in Example 1 was prepared except that instead of cyclohexylamine, 50 L of diethylaminoethanol was added to the reactor, which was mixed with the resin for 10 min. After homogenization, the resin is pumped into storage tanks.

Example 3 ·

A type M1 melamine-formaldehyde resin is prepared according to the procedure of G -old sc hm id (7) with the fact that it is an ae-nee-haga. -with dy- -. cyclic lactate and MEG as modifying additives. Upon completion of the reaction, the resin is cooled to 25-30 ° C and modified with 75 L of cyclohexylamine with vigorous stirring for 10 ', then pumped into a storage tank.

Example 4.

Is prepared urea resin formaldebydová DH 33 following the procedure of the firm Goldschmidt / 7 / except that the discharged dose of urea as a modifier of the second stage of condensation, the place of urea melamine was added as a modifier in an amount of 3% _{of the} balance converted to formaldehyde .

Example 5.

2300 kg of formaldehyde having a specific gravity of φ - 1115 kg.m, a concentration of 37% by weight, stabilized with melamine, are fed into the reactor. The pH is adjusted to 9.8 with 3 molar sodium hydroxide solution and then with 3M formic acid solution.

9.3. 850 kg of urea is added to the formaldehyde and the batch is heated slowly to a temperature of 40 ° C. After a 15 min partial addition, the pH of the reaction medium was adjusted to 9.7-9.8 with 3 molar sodium hydroxide solution. The reaction mixture is maintained at 92-94 ° C and at this temperature the first precondensation stage is run for 20 minutes. The temperature is then reduced by 5 to 7 ° C, the pH is adjusted to 5 with 3 molar formic acid solution and the second condensation stage is run at 94 to 95 ° C for 10 to 15 min. until 1 * turbidity; The turbidity is rapidly adjusted to pH 8.5 with 3 molar sodium hydroxide solution, the temperature is lowered to S8 ° C and 30 kg of melamine are added. The precondensation is allowed to continue until the resin is mixed with water at a ratio of 1: 4, whereby the resin is rapidly cooled to 30 ° C.

Example G.

A urea-formaldehyde resin is prepared according to the procedure of Example 5, except that after the second stage of acidic condensation after the temperature has been reduced to S3 ° C, melamine is not added but the pH is adjusted to 3 with sodium hydroxide solution. 3.5 and the condensation to a water miscibility value of 1 is terminated; 4, when cooling begins. During cooling the resin miscibility ratio with water drops to 1: 1.3.

After the resin has cooled to 30 ° C, 100 liters of 25% aqueous ammonia solution are added to the reactor and mixed thoroughly for 10-15 minutes. The finished resin is pumped into a container.

Example 7.

A resin as in Example 6 was prepared except that instead of a 25% aqueous ammonia solution, cyclohexylamine or diethylaminoethanol was used as a modifying agent in an amount of 75 L.

* <·} / '* Ζ

Example 8.

190 liters of a 3 molar formic acid solution are pumped into a tank equipped with a cooling coil and 50 liters of a 25% aqueous ammonia solution are gradually added thereto with vigorous cooling and stirring. After cooling the solution to 25 ° C, adjust the pH to 7.2 as necessary. The ammonium formate solution is diluted 1: 1 with treated water and used to adjust the impregnation solutions.

Example 9.

'' I · t «

900 L of resin produced according to the procedure described in the example

5. or 4. is mixed with 100 liters of the resin produced according to the procedure of Example 1. or Example 2. or Example 3. After complete mixing, the solution brought to 20 DEG C. is adjusted with 20 liters of the of Example 3 to a gelatinization value at 100 ° C of 5 to 7 minutes. The solution is used to impregnate the barrier paper.

'Ρτ'ίΊΠοΒ-ΓΟ'Τ'' ^r

The QQQ 1 of the resin prepared according to the procedure described in Examples 5 or 4 is mixed with 400 L of the resin produced according to the procedure of Example 1, or 2, or 3. After thorough mixing and warming to 20 ° C, the solution is adjusted to the gelatinization value at 100 ° C for 5-7 min. by adding 10 liters of the solution described in Example 8. The solution was used for the first step of impregnating decorative paper for KT films.

i Example 11.

okay, _________ _ '

·? * *, * 800 L of a resin prepared according to the procedure described in Example 5 or 4 are mixed with 200 L of a resin produced according to the procedure in Example 1. _# or., or 3. After thoroughly mixing and warming to 20 ° C, the solution is adjusted to the gelatinization value at 100 ° C for 5 to 7 minutes by adding 14 to 16 liters of the solution prepared as described in Example 8. The solution is used for 1st degree of impregnation of decorative paper with foil for floor pressing.

Example 12. ·. '

1000 liters of resin prepared according to the procedure described in Example 1, or 2, or 3 are set at 20 ° C with a solution prepared according to the procedure described in Example 8 for a gelation value of 100 ° C for 3 to 5 min. 17 l of the solution of Example 8 are used.

The solution is used for the 'second stage impregnation of decorative foils for KT pressing' or tray pressing. *

Claims (3)

PATENT CLAIMS 1. A process for the production of aminoplasts 5 by low stress for surface treatment of particle board, shovel, fibreboard and similar boards by lamination on KT presses, characterized in that the carbonyl groups of methylolurea precondensates and / or carbonyl groups of free and released formaldehyde are urea | the non-formaldehyde and / or melamine-formaldehyde pre-condensates are degraded by modification with alkylamines of> carbon atoms of an alkyl group of 0-3, or melamine (urea-formaldehyde precondensates), or an alkyl amino alcohol, or ammonia. 2. A process for the production of low-stress aminoplasts for a period of time characterized in that the impregnating solutions of the amino resins are adjusted with an acid-base catalyst, which is ammonium formate, for the desired gelatinization time for the first and second impregnating tub separately. The specific feature of the catalyst is that it degrades the carbonyl group, which carries the undesirable stress - film brittleness, according to the Leukart reaction to give the corresponding precursor condensate amino derivative which is capable of further condensation with the methylolurea and / or methylolmelamyl hydroxyl groups. . 3. A process for the production of low-stress aminoplasts according to items 1 and 2, which are suitable for processing by lamination by short-stroke pressing at a temperature of 190-200 ° C, a pressure of 0.26 MPa ° at a net pressing time of 30. * Corresponding stability without microcracks on flat laminate. $