NO121765B - - Google Patents

Description

Process for the production of fire-retardant barrier or core film.

The invention relates to a method for producing a paper impregnated with curable phenol-formaldehyde resins which can be used as a core film for fire-retardant laminated materials or as a fire-retardant coating film (barrier film) for combustible wood materials, and as the phenol-formaldehyde resin contains fire-retardant nitrogen-phosphorus compounds.

Layer press materials are very often required to be highly flammable or have. flame retardant properties. These requirements are particularly encountered when such materials are used in shipbuilding in the manufacture of prefabricated houses and the like.

In the past, attempts have primarily been made to achieve these properties by preparing the carrier webs of which these layered press fabrics are built up with essentially inorganic fillers. Thus, one has e.g. paper webs containing larger amounts of antimony oxide are used as carrier webs. The fire-retardant effect of antimony oxide can also be increased by additionally adding chlorine-hydrogen-releasing compounds to the heat.

The finished paper has also been treated with salt solutions. Thereby, one uses primarily ammonium salts such as e.g. of ammonium phosphate and ammonium bromide. Also alkali borates have already been used for this purpose.

Ammonium salts, especially ammonium phosphates, can also be added to the resin solutions. However, limits have been set for such additives in that above a certain amount the added ammonium phosphate has a salinizing effect and the aqueous phenolic resin solution separates into two layers, one of which essentially contains the phenolic resin and the other essentially the ammonium phosphate. These difficulties can be partially countered by adhering to narrowly limited concentrations or uses auxiliary solvent. However, it also remains a disadvantage in these cases that the cured film is relatively water sensitive due to the presence of water-soluble ammonium phosphate and therefore has unfavorable application properties.

Surprisingly, it has now been found that the disadvantages mentioned above can be overcome in a simple way by adding certain amounts of formaldehyde to the aqueous solution of a phenol formaldehyde resin next to phosphoric acid and ammonia.

The method according to the invention is consequently characterized by adding 0.05 to 0.15 mol of phosphoric acid per mol to a solution of phenol formaldehyde resin. mol of phenol and at least 3 mol of ammonia per mol of phosphoric acid and so much formaldehyde that at least 1 mol of formaldehyde per moles of ammonia is present in a form not bound to phenol, after which the paper is impregnated with said solution in a known manner.

It is of course also possible to use reaction products of these compounds instead of the individual components, phosphoric acid, ammonia and formaldehyde. Thus, for example, instead of phosphoric acid and ammonia, you can add tertiary ammonium phosphate or primary resp. secondary ammonium phosphate and corresponding amounts of ammonia to the aqueous phenol formaldehyde resin solution. You can also first let ammonium phosphate react with formaldehyde and add a reaction product to the solution, which is obtained, for example, by reacting with 1 mol of phosphoric acid, 3 mol of ammonia and 3 mol of formaldehyde. The stated minimum amounts of ammonia and formaldehyde can be exceeded, as an excess of these compounds does not influence the performance of the process products. The amount of phosphoric acid, namely 0.05 to 0.15 mol per moles of phenol, indicates the quantity that is appropriately used in an economical way of working. You can also increase the amount of phosphoric acid, however, the fire resistance is not significantly improved by further additions, but the water resistance becomes progressively worse.

Appropriately, in the method according to the invention, formaldehyde is added in the form of its aqueous solution. It is of course also possible instead of free formaldehyde to use such compounds which release formaldehyde, such as e.g. paraformaldehyde.

The method according to the invention will be explained with the help of the following examples.

The phenol resin used for the experiments is condensed in the usual way from 1 mol of phenol, 1.25 mol of paraformaldehyde, 0.25 mol of formalin, 30$-ig, and 0.025 mol of sodium hydroxide at temperatures of approx. 70°c under reflux cooling. The reaction temperature is increased after the end of the exothermic reaction to 85 to 90°C, until a viscosity has been obtained which gives an outflow time of 80 to 120 seconds in a DIN beaker with a 4 mm nozzle at a temperature of 20°C. The finished resin solution has a concentration of 89%. Examples.

A) Production of the resin according to the invention.

Al) 1565 g of phenol formaldehyde resin, which is produced in the manner mentioned above, is mixed with 90 g of water, 750 g of 30% formalin, 172 g of 25% ammonia solution and 163.2 g of secondary ammonium phosphate. The resin solution thus formed is clear and has a pH value of approx. 4.5. The resin solution is 63.6%.

However, if the above-mentioned ingredients are mixed together in the indicated amounts without the addition of formalin, no clear resin solution is obtained. The ammonium phosphate also crystallizes when more water or methanol is added.

A 2) 225 g of paraformaldehyde, dissolved in 302.8 g of water, is added to 1565 g of the phenolic resin prepared as stated above.

Warming at 80°C favors dissolution. 162j2 g of methanol, 172 g of 25% ammonia solution and 163.2 g of secondary ammonium phosphate are then added. A clear resin solution with a pH value of approx. H, 5, which contains 70.5% solids. B) Production of the film according to the invention.

With the resin solutions prepared according to example A 1 or A 2 according to the invention, an absorbent, unglued soda paper of 150 g/m<2> containing 20 percent by weight of kaolin is moistened and dried at 130°C. After impregnation and drying, the formed film has a basis weight of 250 g/m 2 and a content of volatile constituents of 7.5 to -9.0%. The film can be wound on rolls without sticking together or breaking.

C) Processing of the film according to the invention.

C 1) Production of a layer press fabric.

Of 8 layers of the film produced according to example B and

a decorative film impregnated with melamine resin of 200 g/m 2 as a surface film is produced by curing in a heat press a layer material, the press side being 11 minutes, the press temperature 145°C and the pressure pressure 30 kg/cm p. The thickness of the formed layer material is 1 .5 mm.

This laminate board's water absorption is determined according to

DIN 53-799. To this end, the sample in format 50 x 50 mm, whose cut edges are carefully ground smooth, is weighed on an analytical balance and the layer material thickness is measured on all four sides with a micrometer screw.

The samples are placed in boiling water for 2 hours, then 5 min.

in cold water and weighed, and the edge thicknesses are also determined again.

The differences of both measurements give

a) of the weight change, a water intake of 1.7$)

b) of the thickness measurement, an edge swelling of 1.2%.

The laminate also does not delaminate after boiling and

shows no blistering.

C 2) Chipboard coating with the film according to the invention as a barrier film.

A melamine resin decorative film of 200 g/m , 8 layers of

the film of the invention and a phenolic resin film; of 180 g/m is pressed together on a 10 mm thick normal chipboard. The pressing time is 11 minutes, the pressing temperature 145°C and the pressing pressure 20 kg/cm<2>. Under these pressure conditions, the individual film layers adhere very well to each other and do not allow themselves to separate from each other after longer storage in water. D) Fire testing of the plates produced with the film according to the invention.

The fire tests were carried out according to the very strict methods according to the Statens Provningsanstalt Stockholm (Box method). In this test, the plates are exposed to the influence of an adjusted propane gas flame. Using a thermocouple, the temperature of the exiting flue gases is measured and recorded using a temperature recorder. At the same time, using a lamp and a photocell, the density of the escaping smoke is measured and expressed as a percentage of absorbed light. The laminated board produced according to example C 1 was glued using a cold-hardening phenolic resin adhesive on a 10 mm chipboard and then conditioned in a normal climate. The coated chipboard produced according to example C 2 was only conditioned and then examined.

Result: In both samples, the flue gas temperature was only a maximum of 40°C above the zero curve, while the flue gas density gave a maximum light absorption of 5%. The plates have therefore passed the fire test very well.

In the case of a laminate made with a normal core film, on the other hand, the flue gas temperature rises approximately 200-100°C above the zero curve.

Claims (1)

Process for the production of a paper impregnated with curable phenol formaldehyde resin, which can be used as a core film for fire-retardant laminated materials or as a fire-retardant coating film (barrier film) for combustible wood materials and as the phenol-formaldehyde resin contains fire-retardant nitrogen-phosphorus compounds, characterized by adding 0.05 to 0.15 mol of phosphoric acid per mol of phenol and at least 3 mol of ammonia per mol of phosphoric acid and so much formaldehyde that at least 1 mol of formaldehyde per moles of ammonia is present in a form not bound to phenol, after which the paper is impregnated with said solution in a known manner.