FI61320B - RELEASE FOER IMPREGNERING AV CELLULOSAHALTIGT MATERIAL FOER ATT FOERBAETTRA DESS BRANDSAEKERHET OCH SAETT ATT FRAMSTAELLA DENSAMMA - Google Patents

Description

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FINLAND —FINLAND (21) PKmttlhtk «mw-Nt« M> MBknin · 772397 (22) HakwnltpUvi - AmMcnlngadag 09.08.77 * '(23) Alkupilvt —Glklfhatsdif 09.08.77 (41) Tullvt lulklMk ·! - Bllvlt offantllf 10.02.79 _. , (44) Nlhtlvlk »fp« noo | t date of issue. - __ Qo

Patent) · och regi * terityral * an 'Antitkin utlacd och utl. * Rtft «i puMkmd 31 · ° 3 · o2 (32) (33) (31) Pyydetty« tuolkeuj —Begird priorltet (71) Kemira Oy, Malminkatu 30, 00100 Helsinki 10, Finland-Finland (FI) (72) Niilo Einar Salle, Espoo, Finland-Finland (Fl) (7 ^) Berggren Oy At (5U) Aqueous solution for impregnating a cellulosic substance to improve its fire resistance and the way to prepare it -Vattenlösning This invention relates to an aqueous solution for improving the fire resistance of a cellulosic material such as paperboard, fibreboard, particle board, plywood and the like.

Although many flame retardants have been developed for wood panels, few have been qualified for use in commercial panel products. Of the inorganic salts that have perhaps been used most for wood fire protection, the most common are ammonium phosphates, alkali metal borates, and bromides. Of the organic substances, mixtures of dicyandiamide, urea, melamine and phosphoric acid have proved to be the most suitable for this purpose. However, these do not appear to be as effective flame retardants as the inorganic compounds mentioned above.

For effective fire protection, one salt is usually not enough, but a mixture of several salts and specifically one containing nitrogen and phosphorus is required. In addition, compounds containing boron and / or halogens are often required. In a fire, nitrogen dilutes the combustion gases and thus slows down the spread of the fire, while phosphorus 2,61320 promotes the dehydration of wood in the form of phosphoric acid and the formation of a heat-insulating carbon layer. Boron, in turn, forms esters with its vitreous heat-insulating layer and cellulose when its compounds melt, thereby preventing the formation of levoglucosane, which is vital for the wood to continue to burn. Halogens produce hydrogen halide, which acts as a good flame retardant. In addition, the water formed when the wood dehydrates and the crystal water released from the salts inhibits combustion.

It is therefore an object of the present invention to provide an impregnating aqueous solution which improves the fire resistance of a cellulosic material, which has even better properties and does not generate toxic gases when decomposed.

The main features of the invention appear from the appended claim 1.

It is known from FI patent application 3564/68 to protect a sheet of wood with ammonium hydrogen phosphate, boric acid and borates. U.S. Defensive Publication T 876005 discloses fire protection of jute mats with a mixture of sodium tetraborate, sodium phosphate, boric acid, and ammonium tetraborate, and U.S. Patent No. 2,658,000 discloses a fire retardant composition comprising borax, boric acid, and diammonium hydrogen. However, it is not apparent from these publications that tripolyphosphates have been used in such solutions. However, sodium tripolyphosphate is an essential ingredient in the aqueous solution of the present invention.

It is known from DE 674 633 to treat paper and textiles with sodium tripolyphosphate together with mono- and diammonium phosphates and borax has also been disclosed for use with these phosphates. However, the solution described in this publication does not contain boric acid, which is an essential ingredient in the present aqueous solution.

The present invention is thus directed to a novel aqueous solution having a synergistic effect, in which the combined effect of different elements in preventing ignition and combustion is quite essential, and it was therefore surprising that the aqueous solution 61320 according to the invention was as effective as it proved.

It is clear that the aqueous solution according to the invention can be prepared by dissolving said substances either separately or as a mixture in water. However, the solution is preferably prepared by first dissolving the sodium tripolyphosphate in water and only then adding the other ingredients. Dissolution of the ingredients is greatly facilitated if this order of addition is followed. Finally, the pH of the aqueous solution is adjusted, if necessary, by adding ammonia or phosphoric acid. In the prevention of ignition and combustion, this interaction (synergistic effect) of different elements is relevant when the material ratios are correct. An example of this is a 1: 5: 1 mixture of urea diammonium phosphate and boric acid, which gives a weight loss of 76% in thermal analysis with a flame retardant content of 36.2%, while a mixture of sodium tripolyphosphate at the same concentrations at the same concentration ratio of 61% by weight.

Ammonium borate can be replaced with ammonia, but in this case more boric acid must be used. A mixture of ammonium borates, boric acid and sodium tripolyphosphate is a very effective flame retardant. This has been found thermoanalytically by comparing 4,61320 weight loss curves (tg curves) obtained with different substances. To this end, a large number of samples of fire-retardant plywood made of birch veneers were fired in a Mettler TA thermal analyzer at a constant heating rate of 15 ° C / min. The runs were performed up to a temperature of 700 ° C. The developed fire retardant plywoods were compared with samples impregnated with fire retardants known to be effective and having almost the same fire retardant concentrations. Here are some examples of test results:

Impregnants Flame retardant content Heating weight% in wood JseiiS.

15 ° C / nun, weight loss at 700 ° C

Disodium hydrogen phosphate · 2H 2 O 23.2 68

Disodium hydrogen phosphate · 2H 2 O 19.2 80

Sodium tripolyphosphate 16.6 68

Sodium tetraborate · IOHjO 16.5 77

Diammonium (hydrogen) phosphate 19.5 74

Ammonium phosphate 20.2 73

Diammonium phosphate + boric acid (5: 1) 34.0 67

Monoammonium phosphate + boric acid (5: 1) 34.9 64

Urea + monoammonium phosphate (2: 1) 35.0 88 "Retroflame" approx. 30.0 77 "Delignite FRCW" "73

Sodium tripolyphosphate + boric acid + ammonia (according to the invention) 33.0 61 Sodium tripolyphosphate + boric acid + airmonia 47.0 58 Sodium tripolyphosphate + Aimonundecaborate + Ammonia 45.6 54

First, when comparing the weight losses of disodium hydrogen phosphate and diammonium hydrogen phosphate at 700 ° C, it is seen that nitrogen is a very important element for flame retardancy. However, based on thermal analysis, sodium tripolyphosphate is more effective in preventing combustion than ammonium phosphates and disodium hydrogen phosphate.

Combustion tests according to norms and standards confirm the results of thermoanalyses. 9-ply plywood well meets the requirements of British Standard 476, Part 6 (fire propagation test) class O, with performance indices I of 9.9 and 10.4 in two parallel tests with a requirement of 1 <12. On the other hand, the same board met Class 1 requirements of British Standard Part 7 (surface spread of flame). Thirdly, 12 mm plywood impregnated with ammonium borates, boric acid and sodium tripolyphosphate meets the requirements of fire test class 1 of the Nord test method NT Fire 004 so well that the combustion curve obtained for it follows the combustion curve of asbestos, which corresponds to the best possible combustion result. Plywood treated with these mixtures generates only 1/15 of the permitted amount of flue gases when smoked (smoke evolution <2). All boards impregnated with the mentioned flame retardant mixtures meet the requirements of Nordtest method NT Fire 004 flammability class 1 (ignition time> 20 min).

With the same system, fibreboard and chipboard are easily obtained in fire spreading class II.

To prepare a fire-retardant sheet with the mixture according to the invention, the procedure is as follows:

The finished board, plywood, chipboard or fibreboard is impregnated with a 25-34% solution of ammonia, boric acid and sodium tripolyphosphate, preferably under vacuum or vacuum pressure, with a vacuum time of 15-30 min, a pressure period of 15-90 min and possibly a post-vacuum length of 15-30 min. temperature depending on the quality of the plate being processed. The magnitude of the vacuum is then about 5-10 kPa and the pressure 400-1000 kPa. Veneers, either hardwood or softwood, can also be impregnated, either dried or wet, by one of the following methods: 1) They are immersed in an impregnation solution of 40-50 ° C for 1-4 d 2) They are first immersed in an impregnation solution of 70-90 ° C 10-240 minutes and then set at 100% relative humidity for 1 day 3) They are first immersed in a saturation solution of 70-90 ° C for 10-120 minutes and then in a solution of 20-30 ° C for 15-30 minutes.

The chips are impregnated either wet or dry by immersing them in a 5-25% solution of flame retardant for a specified time (1 s-1 d) or by spraying with it. Fire protection changes the color of the product, but not adversely. It should be noted that the elevated temperature accelerates the absorption of the flame retardant.

The use of certain fire retardant salts is hindered by their acidity. This applies in particular to zinc chloride and monoammonium phosphate, 61320, which have a hydrolysing effect on wood cellulose and also strongly corrosive to metals. The solution according to the invention is basic and not harmful in this respect.

The disadvantage of many flame retardants is their toxicity, either as such or only when they decompose in a fire. The new flame retardant according to the invention is free of first-class toxins.

The leaching of the flame retardant mixture from wood can be significantly reduced by zinc compounds such as zinc acetate, chloride and hydroxide without deteriorating the fire properties. This fact is rarely likely to be relevant, as the treated sheet is either used indoors or protected with a coating against wetting.

The invention is described in more detail below by means of examples.

Example 1

Preparation of flame retardant solution:

Weigh 60 kg of hot water into the dissolution vessel, start the stirring and add 11.4 kg of sodium tripolyphosphate. After about 15 minutes, 22.3 kg of boric acid and finally 6.3 kg of 25% ammonia are added. To facilitate dissolution, the temperature of the solution is raised to 40-60 ° C. After clarification, the pH of the solution is adjusted to 6.5-8.0 by adding concentrated phosphoric acid or ammonia, whichever is closer to the pH range. The final concentration of the solution is about 35% by weight.

5 pieces of mixed plywood and 5 pieces of birch plywood with a thickness of 12 mm and a size of 34 x 98 cm were placed in the above-mentioned impregnation solution after first diluting to 32% by weight. The plates were then treated in solution under vacuum, removed from the autoclave and dried. A solution of 538 kg / m 2 was absorbed into the mixed plywood, and about 600 kg / m 2 into the birch plywood. It had a final salinity of 190 kg / m · 3 and the plate met the requirements of fire spreading class 1 in the combustion box test.

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Example 2 6.4 kg of sodium tripolyphosphate are dissolved in 65 kg of water with stirring. 22.3 kg of boric acid and 6.3 kg of 25% ammonia are then added.

The solution is heated to about 40 ° C to facilitate dissolution.

Finally, the pH of the solution is adjusted to 6.5-8 by adding concentrated phosphoric acid or ammonia as needed. The final concentration of the solution is about 30% by weight.

25 pieces of wet birch veneer sheets with a dry thickness of 1.5 mm and an area of 3600 cm were immersed in the above solution for 3 d.

They were then dried and glued with melamine-urea glue to form a 9-ply 3 fire retardant plywood with an amount of fire retardant of 187 kg / m 2. The resulting plate met the requirements of fire spreading class I of the Nordtest method.

Example 3 50 pieces of dry birch veneer sheets, 34 x 100 cm in size, were immersed in the undiluted impregnation solution according to Example 1 and impregnation was performed under vacuum pressure. The impregnated veneers were dried and glued with phenolic resin impregnated paper to form a 9-ply fire retardant plywood, the fire properties of which were tested in England and Finland. In England it met the requirements corresponding to classes 0 and 1, in Finland in the fire distribution class I combustion box test.

3

The salinity of the plate then varied from 180 to 200 kg / m.

Example 4 25 wet birch veneer sheets, 1.5 mm thick and 60 x 60 cm thick, were immersed for 2 h in the 90 ° C impregnation solution used in connection with Example 2. The veneers were then placed at 100% relative humidity for 1 d to achieve diffusion equilibrium. Finally, the veneers were dried and glued with a phenolic resin film to 9-plyn 3 flame retardant plywood with a flame retardant content of 220 kg / m 2. Example 5

The board is passed rapidly through an aqueous solution containing ammonium decaborate, sodium tripolyphosphate, ammonia and a wetting agent. The concentration of the treatment solution was 23% by weight and the pH was> 7.5. It contained 141 g of ammonium decaborate, 82 g of sodium tripolyphosphate, 27 g of 25% ammonia and a little boric acid and 1.5% by weight of wetting agent based on the total weight of the solution. Finally, the board was dried.

8 61320

Example 6 33 x 98 cm center portions of dry birch veneers were treated with a solution of 7.5 kg of ammonium borate (acidic ammonium borate), 4.3 kg of boric acid; 5.6 kg of sodium tripolyphosphate, 2.4 kg of 25% by weight ammonia and 30.4 kg of water. The treatment took place under vacuum pressure in an autoclave. The veneers were then dried and glued to plywood.

Example 7

First, 72 kg of water was dissolved in 8.4 kg of sodium tripolyphosphate with vigorous stirring. 15.6 kg of boric acid and 4 kg of 25% ammonia were then added. The concentration of the solution was 25% by weight.

10 particle boards, 9 mm thick and the same amount of semi-hard fibreboards, 6.4 mm thick and both types of boards measuring 30 x 98 cm were impregnated with this solution under vacuum pressure at 40 ° C and dried after impregnation. The salt content of the plates was about 130 kg / m 2. They met the requirements of fire propagation class II and flammability class 1.

Example 8 4 kg of wet surface chips were placed in a drum which was rotated at a constant speed. During rotation, the solution of Example 7 was injected there. Thereafter, 6 kg of wet coarse middle chips were treated in the same manner with said solution. All chips were then dried, sprinkled and pressed into a 3-layer chipboard. It met the requirements of fire spread class II and flammability class 1.

Example 9

The impregnation solution was prepared as follows: 1.4 kg of sodium tripolyphosphate was dissolved in 94.3 kg of water. 3.4 kg of boric acid and 0.9 kg of 25% ammonia were then added. The concentration of the solution was 5% by weight of 1.2 kg of dry surface chips and 1.0 kg of dry medium chips were impregnated by spraying them with said solution. They were then dried and pressed into a particle board that met the requirements of fire spreading class II and flammability class 1.

Claims (4)

9 61 320 1. The production of impregnation of cellulosic material, paperboard, fibers, spinning and fan for the manufacture of branded products, the use of which is effective for the production of sulfur-free boron and ammonium borate and / or ammonium. Aqueous solution for impregnating a cellulosic material such as paperboard, fibreboard, particle board and plywood to improve their fire resistance, characterized in that it contains essentially boric acid and ammonium borates and / or ammonia and sodium tripolyphosphate as active ingredients. 2. Vattenlösning enligt patentkravet 1, converting the composition to ammonia, phosphate and borosyrene in an N: P: B-fold ratio of 1: 1.20 to 2.20: 1.50 to 3.30. Aqueous solution according to Claim 1, characterized in that it contains ammonia, phosphate and boric acid in an N: P: B weight ratio of 1: 1.20 to 2.20: 1.50 to 3.30. 3. The use of a patent according to claims 1 or 2, which comprises 5-35% by weight of effective effects. Aqueous solution according to Claim 1 or 2, characterized in that it contains 5 to 35% by weight of active ingredients. Process for preparing an aqueous solution according to Claim 1, characterized in that sodium tripolyphosphate is added to the water first and only then the remaining ingredients, after which the pH is adjusted, if necessary, by adding ammonia or phosphoric acid. 4. In addition to the addition of water to a patent, it can be used to adjust the pH of the sodium tripolyphosphate and the other components, the pH of which is adjusted by adjusting the genome to ammonia or phosphorus.