SE460421B - Amino-resin compsn. comprising urea-phenol resin and melamine resin - Google Patents

Abstract

A method for the prodn. of a resin which is used for mfg. an adhesive for cellulose based prods., comprises mixing (i) 30-70 wt.% of a urea phenol resin (I); with (ii) 70-30 wt.% of a melamine resin (II). (I) is obtd. either by (1) adding to a precondensate of formaldehyde, urea and opt. melamine, a crosslinking agent contg. a co-condensate of phenol, formaldehyde and urea, or contg. also a co-condensate of phenol and formaldehyde as urea; condensing under acid conditions; stopping the reaction by alkalisation; and adding additional urea to adjust the final molar ratio to 1.4-0.6 moles of urea, 0.006-0.3 moles of phenol and 0-0.04 moles of melamine/mole of formaldehyde; or by (2) adding to an evaporated condensate of formaldehyde, urea and opt. melamine, a crosslinking agent as specified above, so that the final molar ratio is as specified previously in (1). (II) is obtd. by condensing melamine and formaldehyde in a molar ratio of formaldehyde to melamine of 1.7-2.4.

Description

460 42- “1 '10. 15. 20. 25. 30. 35. 2 buckles and often requires increased adhesive dosage.

A major reason for these disadvantages at low molar ratios is a reduced degree of crosslinking. Resins at low molar ratios are to some extent becoming more or less linear in their structure, compare novolaks in phenolic resins.

It is known to use melamine to crosslink such resins. By increasing the degree of crosslinking of the resin, the swelling of boards bonded with such resins will decrease and the strength will increase. In addition, the urea resin is mixed with a melamine resin in order to obtain satisfactory moisture resistance of the glued material.

Many resins are based on the addition of phenol to urea-formaldehyde. The additives are often large and are usually made together with resin to achieve property improvements. with a large proportion of melamine. These resins mainly consist of a mixture of a urea-formaldehyde resin and a phenol-formaldehyde resin, despite the fact that phenol is charged during the reaction process. This is because urea and phenol only react with significant yields if certain conditions are met. Only when methylolphenol is reacted with excess urea at acidic pH is a co-condensation of phenol, formaldehyde and urea obtained. If a mixture of urea and phenol is reacted with formaldehyde, no significant yield of co-condensate is obtained either at acidic or basic pH. When methylol urea is reacted with an excess of phenol at different pH, no co-condensation occurs either. At basic pH, the methylol group dissociates from the methylolurea. The resulting formaldehyde is added to the phenol which then condenses with itself. At acidic pH, self-condensation is nos urea The reaction between urea and methylolphenol has been confirmed by 13 C-nmr. the dominant reaction.

It has now been found that this so-called phenol / urea co-condensate with its free amide and methylol groups, more easily and better enables a reaction of phenol in derivative form in a precondensate consisting mainly of formaldehyde and urea and possibly a smaller amount of melamine. * few. m; The present invention thus relates to a process for producing a resin having a low molar ratio of formaldehyde to urea, and which in the production of adhesives and glued wood products gives low formaldehyde emission and good moisture resistance of the wood products.

The process for producing the resin is set out in the claims.

One component of the resin is a condensation product of formaldehyde, urea and phenol. It is prepared from a precondensate of formaldehyde and urea. To the precondensate is added a crosslinking reagent which contains a phenol-urea co-condensate or methylolphenol and urea. By adding this reagent, an increased degree of crosslinking is obtained despite a low molar ratio (F / U). The strength properties of the wood products increase compared to a resin without crosslinking reagent with the same molar ratio (F / U). Other, above-mentioned, disadvantages are also minimized. To further reduce the swelling of finished boards, smaller amounts of melamine may be included in the resin, which increases its crosslinking.

The addition of the phenol / urea crosslinking reagent is done in the process step where the resin is to be condensed, i.e. at acidic pH. Thus, said crosslinker can also be reacted.

The process can be described according to the following scheme:, Urea / formalin (MeLamin) _ Phenol / urea co-condensate LMetyLol step É crosslinking reagent I _ ".; ___........_._ Condensation h 1 Post-methylolization Evaporation. ... __ t. ...___: f_- ....., _-., ._...__. 460 421 'Even when the crosslinking reagent is charged in the form of me ~ 4 tyLoLphenol and the corresponding amount of urea as in phenol / urea The co-condensate above, this charge is made in the process step where the resin is to be condensed, i.e. at acidic pH. can be described according to the following scheme: 10.

Urea / formalin (Me [amine) MethylLoLphenoL MethylLoL step 15. - "- ~ - Condensation-1« - «--- Urea« = - Urea W After- 20. methylotization ___--- II l __- ... l Evaporation I 25.

Resins made in the manner described above and with this crosslinking reagent obtain improved properties.

YELLOW: The gel is shortened and the gel process becomes more distinct (quickly hardened). To this resin was added a methamine 30, formaldehyde resin, whereby a resin ignition was obtained. for the manufacture of adhesives for the manufacture of moisture-resistant wood products. Discs made with this resin ignition have lower sweating and increased strength, performed with good wet strength and good dimensional stability, compared with resin without a binder. The formal emission emission is as low as that of the corresponding low-resin resins, ie it meets the German E1 requirement $ ïï mg CHZ0 / 100 g chipboard.

In the preparation of the ureaphenol resin, a precondensate of urea u is first prepared. V) m fl about 10. 15. 20. 30. 35. 3 '5 469 421 and formaldehyde and possibly a minor amount of melamine by a methylolization step. Methylolization steps melamine and the molar ratio refer to the addition of formaldehyde to urea, phenol for the formation of urea / formaldehyde 0.15 0.25 - 0.75 methylol monomers. to 1 urea / mol formaldehyde, preferably 0.3 to 0.4. Molfor ~ 0 - 0.04 0.006 formaldehyde. to 90 ° C and at pH 8.0 - 8.6 mol is suitably kept at 0.027 at a temperature melamine / formaldehyde is suitably mol melamine / mol The reaction takes place from 75 8.4.

The crosslinking reagent in preferably 8.2 - co-in the form of a phenol / urea methylolization of phenol 8.7 - 8.9 is charged and condensate is made pH 8.5 - 9.0 of SO - 70 ° C - to 70 - 90 ° C and the reaction gradually gets 4.7 - 4.9. The molar ratio of 3.3 0.1 is preferably 0.3 ~ 0.7 moles of phenol / mol of formaldehyde, and the molar ratio of urea / phenol is 1 to 10 preferably 3.5 through preferably and a temperature the temperature is raised at pH 4 ~ 6 pre-phenol / formaldehyde Then urea is 6.5 mol urea / mol phenol. to the precondensate and the pH is adjusted to 4 - 7 preferably 4.5 - 5.5 preferably 4.5 - This crosslinking reagent is charged 5.0 and the condensation takes place at 75 - 85 ° C to the appropriate on the formaldehyde and desired viscosity viscosity. The viscosity varies depending on the concentration of the resin user. Usually the viscosity is in a range of 200 - 1500 at 20 ° C. A 50 Zig formaldehyde can 200 - 250 mPa.s. the pH is adjusted to 7.5 8.0. post-methylolization mPa.s suitable viscosity of product The reaction is then charged with 1.4 - 0.6 mol by raising further for known method.

The molar ratio of the Ufea resin is formaldehyde 1.05 - 0.9 0.04 moles of melamine / moles of formaldehyde preferably the final urea / moles preferably preferably 0.97 - 0.93, 0 - 0.006 - 0.027, 0.006 - 0.3 moles of ligen 0.02 - 0.2, preferably 0.041 - 0.2.

Alternatively, to the precondensate, phenol / mol of formaldehyde, a suitable crosslinker in the form of methylolienol (prepared with a molar ratio of 3.3 to 0.1, preferably 0.3 to 0.7 mol of phenol / mol of formaldehyde) and separately 1 to 10 preferably 3.5 ~ 6.5 moles of urea (calculated per mole of phenols). The reaction takes place as 460 # 21 2 6 10. 15. 20. 25. 30. 35. above, and the resin obtained has the same molar ratio as above. The melamine formaldehyde resin mixed with the ureaphenol resin is manufactured in a conventional manner with a molar ratio of formaldehyde: melamine of 1.7 ~ 2.4, preferably 1.8 - 2.1. 30-70% by weight of the melamine resin is mixed with 70 -30 wt-Z of ureaphenol resin.

In the production of particle boards using the present resins, conventional methods are used.

The initially very moist chips are dried to such a dry content that the total moisture content after the binder addition does not exceed the limit critical for steam blasting. To reduce moisture sensitivity, a hydrophobing agent such as a mineral wax or a natural or synthetic paraffin wax is added. If desired, known formalin-binding substances, eg urea, can be added together with the hydrophobing agent. After the dry chips have been glued, the chips are pressed at press temperatures of approximately 185 - 220 ° C.

The amount of glue added is normally between 7 and 12 percent dry resin based on the weight of the dry span. The hardener consists of conventional hardeners such as ammonium chloride, ammonium sulphate, suitable inorganic and organic acids. Press times used are in the range 8 - 12 s / mm chipboard. The following examples illustrate the present invention: EXAMPLE 1.

Preparation of ureaphenol resin Methylolstegz A reaction mixture of 4386 g of 50% is reacted with 1462 g of urea and 113 g of melamine. When the formalin is charged, the temperature is about S0 ° C. The temperature of the reaction mixture is raised to 80 ° C, the pH is adjusted to 8.2 - 8.4.

The reaction is allowed to proceed for 20 minutes. Then the molar ratio is lowered by adding 390 g of urea. The reaction is allowed to proceed for an additional 15 minutes.

Condenserino: A previously produced phenol / urea co-condensate is charged as a crosslinking reagent to the above reaction mixture (after 55 minutes) and the pH is adjusted to 4.8 - 5.0.

The reaction mixture is allowed to condense at 78 ° C - until 230 - 250 mPas is obtained in a viscosity C25'C). The reaction 10. iff 10. 15. 20. 25. 30. 35. w 460 421 and further to 7 (pH = 7.5 - evaporated is broken down with sodium hydroxide 8.0) 1836 g of urea are charged. The resin and cooled to room temperature.

The mentioned phenol / urea co-condensate is manufactured as follows: 120 parts of 50% formalin, 94 g of phenol and 100 g of water are charged into a flask. The pH is adjusted to 8 ,? - 8.9 and the temperature is maintained at 60 ° C for 60 minutes. 300 g of urea and 150 g of water are then charged to the methylol phenol. The temperature is raised to 80 ° C and the reaction time is 60 minutes at pH 4.7 - 4.9.

Preparation of melamine resin 5698 g of 39% formaldehyde are charged at 25 ° C and the pH 7.8 is rapidly raised to 90-92 ° C and the pH is maintained at 8.8-9.1. the ion mixture is reached at 1: 1.2 at 25 ° C. adjusted to 9.4 - 9.7. 57% melamine resin - 8.6. 4286 g of melamine are then charged, whereupon the temperature Reak water tolerance DH condenses a The solution is cooled rapidly and of this is mixed with 43% of the phenol urea resin, whereby a resin suitable for the production of moisture-resistant exterior clamping discs is obtained.

EXAMPLE 2.

Preparation of ureaenol resin Metxlolstegz A reaction mixture of 10,750 g of 502 g of formalin is reacted with 3597 g of urea. When charged, the temperature is about 50 ° C. The temperature of the reaction mixture is raised to 80 ° C, the pH is adjusted to 8.2 - 8.4.

The reaction is allowed to proceed for 20 minutes. Then the molar ratio is lowered by adding 960 g of urea. The reaction is allowed to proceed for an additional 15 minutes.

Condensation: 2370 g of methylolphenol produced are charged previously with 735 g of urea as a crosslinking reagent to the above reaction mixture (after 35 minutes) and the pH is adjusted to 4.8 5.0.

The reaction mixture is allowed to condense at 78 ° C until 230-P50 mPas is obtained in viscosity (25 ° C). The reaction is quenched with sodium hydroxide (pH = 7.5 - 8.0) and an additional 4508 g of 460 42-1 a urea is charged. The resin is evaporated and cooled to room temperature.

The mentioned methylolphenol is manufactured as follows: 120 parts of SO 2 -g formalin, 94 parts of phenol and 100 parts of water are charged to a flask. The pH is adjusted to 8.7 - 8.9 and the temperature is maintained at 60 ° C for 60 minutes. 452 of the melamine resin from Example 1 is mixed with 55% of this phenol urea resin to obtain a resin suitable for the production of moisture-resistant exterior chipboards. and g:

Claims (3)

460 4-21 in Patent Claims A process for the preparation of resins used in the manufacture of adhesives for cellulose-based products is characterized in that 30-70% by weight of a) a ureaphenol resin which is prepared by adding to a precondensate of formaldehyde, urea and optionally melamine a crosslinking reagent containing a co-condensate of phenol fl formaldehyde and urea, after which the mixture is condensed in an acidic environment and the reaction is broken down by alkalization, after which additional urea is added to adjust the final molar ratio of the resin to 1.4-0.6 moles of urea, 0.006 0.3 moles of phenol and 0 to 0.04 moles of melamine per mole of formaldehyde, are mixed with 70-30% by weight of o) a melamine resin prepared by condensation of melamine and formaldehyde with a molar ratio of formaldehyde: melamine of 1 , 7 ~ 2.4. Process according to Claim 1, characterized in that the crosslinking reagent is prepared with a molar ratio of 3.3-0.1 moles of phenol / moles of formaldehyde and 1-10 moles of urea / moles of phenol at a pH of 4-6 and a temperature of 70 ~ 90 ° C. 3. A process according to claim 2, characterized in that the crosslinking reagent is prepared at a pH of 4.7-4.9.