US2994620A

US2994620A - Method for fireproofing cellulosic materials

Info

Publication number: US2994620A
Application number: US694706A
Authority: US
Inventors: Franck Jean-Jacques; Sandor Basile
Original assignee: Ignicel SA
Current assignee: Ignicel SA
Priority date: 1956-11-06
Filing date: 1957-11-06
Publication date: 1961-08-01
Anticipated expiration: 1978-08-01
Also published as: BE562135A

Description

United States Patent i 2,994,620 METHOD FOR FIREPROOFING CELLULOSIC MATERIALS Jean-Jacques Franck, Neuilly-sur-Seine, and Basile Sandor, Paris, France, assignors to Ignicel Societe Anonyme, Paris, France, a corporation 'of France No Drawing. Filed Nov. 6, 1957, Ser. No. 694,706 Claims priority, application France Nov. 6, 1956 11 Claims. (Cl. 117137) The present invention relates to a method for the fireproofing of cellulosic materials.

The materials which may be treated according to the invention include timber, wood for making furniture, plywood, ligno-cellulosic fibers or particles, or agglomerates thereof such as heat and sound-insulating panels.

It is known that certain ammonium salts and more particularly ammonium phosphates can be used for modifying the inflammability of cellulosic materials impregnated therewith. The materials thus treated, when submitted to the action of a high temperature, undergo a fiameless carbonization and produce a carbonaceous mass without ignition of the evolved gases, thus avoiding the origination or propagation of a fire.

However, it has not been possible to generalize the use of such salts, and particularly the use of ammonium phosphates, as would have been desirable. The impregnation treatments as presently used are difficult to apply because they require either an expensive apparatus for carrying out the impregnation under pressure, or an impregnation by prolonged immersion, with a very low efiiciency in use of equipment. Moreover, the ammonium phosphates constitute a nutrient medium for the microorganisms which attack the wood and this may have an unfavorable influence on metal parts which come into contact with the treated materials.

On the other hand, it has been found that certain waterproofed ligno-cellulosic agglomerates may, when submitted to a fireproofing treatment, become non-inflammable but that, if no particular precautions are taken, the said treatment modifies certain of the characteristic features of the said agglomerates and, more particularly, their sensitiveness to humidity, which is substantially increased.

In order to take advantage of the fireproofing properties of ammonium phosphates, a commercial fireproofing method for cellulosic or ligno-cellulosic materials, must therefore, in any case:

(a) Cause a quantity of ammonium phosphate which is sufiicient to obtain the fireproofing to penetrate the material in a reasonable time;

(b) Avoid conferring to the treated materials an attacking action on metallic parts driven therein or brought into contact therewith;

(c) Protect the materials from the micro-organisms promoted by the presence of ammonium phosphates, such a protection being eventually obtained by conferring to said materials particular properties in addition to fireproofing and/or waterproofing;

(d) Cause no modification of the mechanical and surface properties of the treated materials;

(e) Avoid influencing unfavorably the prior or subsequent waterproofing of the treated materials.

It has been found that the above conditions could be satisfied by forming the waterproofing salts in situ in such a manner that for a given period of soaking or other treatment, the quantity of salt retained in the treated cellulosic or ligno-cellulosic material, is considerably increased.

It has furthermore been found that the said formation in situ of the waterproofing salts may, in certain cases,

e still further increased when the material which is to be Patented Aug. 1, 1961 fireproofed has a sufiieient degree of humidity and, more particularly, when the said material is submitted to a prior treatment causing a dilatation of the fibers. In the latter case, it has been found that the best results were obtained When the said treatment is such that it cooperates in the formation of the waterproofing salt.

A simplified flow diagram of an illustrative manner of practicing the invention when fireproofing insulating boards is as follows:

The fireproofing method according to the invention consists in incorporating in the material at least one fireproofing salt such as an ammonium hydrogen phosphate i.e. monoor diammonium phosphates or compounds capable of forming such a salt while simultaneously causing ammonium phosphates to be formed and retained in situ in sufiicient quantity without altering the mechanical and surface properties of the treated material.

The introduction of the waterproofing salts or components thereof may be carried out by immersion, sprinkling, atomizing, aspiration in vacuum vats or the like.

Prior to the introduction of the waterproofing compounds, it may be advantageous, more particularly for cellulosic materials, to cause the channels and cells in the said material to expand, such an expansion being obtained without alteration of the fibers by soaking the material in a solution of ammonia having a concentration comprised between about 3% and 10% according to the nature of the material. The immersion time of the material in the said solution as well as the concentration thereof, is determined in such a manner as to avoid an alteration of the fibers while expanding the channels, then the cells of the mass, to cause a penetration of ammonia therein, which makes possible thereafter a rapid penetration of a suflicient quantity of P0 ions which, by combination with the ammonia from the expanding solution will form in situ the waterproofing ammonium phosphates. When the material is first expanded the second bath furnishing P0 ions preferably consists of an aqueous solution of ammonium hydrogen phosphate PO (NH H wherein m and n are l-Z and m+n=3, having a concentration comprised between about 10 and 30% and pH comprised between 3 and 7 preferably between 3.9 and 6.2 according to the nature of the treated material. The pH of the phosphate solution determines that of the fireproofed material after treatment and consequently the activity or neutrality i.e. the degree of attack of the material on metal parts which will thereafter come into contact therewith. The above mentioned pH limits 3.9 and 6.2 for the phosphate solution correspond for wood fireproofed according to the invention, to pH values comprised between 6.3 and 7.4. The wood will have no attacking action on metal parts if the pH of said wood is at least equal to that at which ion phosphate precipitates, but too high a pH leads to a dissociation of the ammonium phosphate.

When it is desired to fireproof a ligno-cellulosic mate rial such as agglomerates or particles of fibers for the formation of agglomerates, which have already been waterproofed or are intended to be wateiproofed, the fireproofing solutions or components thereof should be adapted to the compatible waterproofing agent.

As fireproofing agents, one preferably uses mixture of ammonium phosphates or compounds capable of forming the same.

As waterproofing agents, one may use solutions or emulsions of substances such as micro-cristalline waxes which are precipitated and attached to the agglomerates or the constituting element thereof by causing the pH of the said emulsions or solutions to be modified in such a manner as to give rise to a flocculation of the said emulsion or to the precipitation of the compounds contained in the solution. This modification of the pH may be caused by the fireproofing salts themselves or by at least one of the compounds which are intended to form the said salts in situ.

The concentrations of the fireproofing salts or components thereof should be such that they lead to the presence in situ of quantities of H PO comprised between about 5 and 15% by weight of the dry material which is to be fireproofed. The concentration of the waterproofing solutions or emulsions should be such that the quantity of dry waterproofing agent, fixed on the treated material is comprised between about 0.5 and 5% by weight of dry material.

In certain cases, it may be advantageous to use solutions and/or emulsions containing an excess of the products which are to be finally fixed on the agglomerates. The said solutions or emulsions are forced to pass through the vessel of the material which is to be treated, e.g. by aspiration in vacuum vats, by atomizing or otherwise. Thereafter the unretained excess of product is recovered for future use, after a possible adjustment of the contents thereof in active material. The operation may be carried out in one or more successive steps and materials in a crude state or during the transformation or shaping thereof or on finished agglomerates. The application of the various ingredient solutions and/or emulsions, may be operated simultaneously or successively. The said ingredient solutions and/or emulsions, may have added to them salts or other agents for giving to the various treated materials special supplementary properties or features, e.g. fungicides, insecticides and the like. Whatever the process which is used and the order which is adopted for the various operations it is essential that the various ingredients, solutions or emulsions, as Well as the added substances, conform to the established conditions of compatibility. The method according to the invention therefore makes it possible if desired to apply the solution or emulsion in closed circuit. There is thus no loss of active substances, the quantities of which formed and fixed on the treated materials are determined, as concerns their homogeneous content and control distribution by the concentration of the circulating solutions or emulsions and by the number of cycles thereof. Furthermore a lesser quantity of active solution or emulsion may be used.

-- According to the invention, it istherefore possible:

(1) In the case of panels made of fibers and more particularly insulating panels:

(a) Either to operate a prior waterproofing of the fibers before the shaping into panels then, after the said shaping to operate the fireproofing by incorporating waterproofing solution throughout the total thickness of the panels;

(b) Or to first form the panels, then to waterproof and fireproof the same, the said two operations being carried out independently in the required conditions of compatibility and fixation by incorporating throughout the thickness of the panels the fireproofing and waterproofing solutions and/or emulsions.

(0) Or to form the panels and then simultaneously waterproofing and fireproofing the same in the required conditions of compatibility and fixation by incorporating in the panels fireproofing and waterproofing solution or emulsion.

(d) Or to operate the fireproofing on a finished panel, that is to say on a panel which has been shaped and dried, the said panel having been waterproofed beforehand or not.

If the panels which is submitted to the fireproofing treatment has not been previously waterproofed, it is possible to incorporate the waterproofing emulsion simul taneously with or independently of the fireproofing solution while conforming to the conditions of fixation. The panels are then finally subjected to a drying process.

(2) In the case of the treatment of particles, which are intended to form panels, to impregnate the said particles with the fireproofing solution, before they are dried and waterproofing the same by adding waterproofing .agent in the binding agent for the particles or to impregnate simultaneously or successively the particles before they are dried, with a fireproofing solution and a waterproofing emulsion in the required conditions of compatibility and fixation. Thequality of the waterproofing material must be such that the further binding of the particles by synthetic resins, more particularly urea-formaldehyde resins, is not disturbed.

In the said two cases for multiple layer panels, the particles in each layer should preferably be fireproofed and waterproofed in order to obtain a good result but diiferent proportions of the fireproofing and waterproofing agents may be used in the different layers. It is even possible not to use the said product in certain layers.

Various embodiments of the method according to the invention are described moreover by way of examples:

Example 1 Deal boards of 0.3 x 2.5 x 0.01 m. were immersed for 24 hours in 5% ammonia solution. After a quick draining, the said boards were immersed in 20% ammonium phosphate solution having a pH of 3.95. After drying, the said boards containing 10% by weight, of ammonium phosphates were subjected to infiammability tests and proved to be fireproof.

Example 2 Oak floor boards of 0.4 x 0.7 x 0.05 m. were immersed for 12 hours at room temperature in a 5% ammonia solution. After having been quickly drained, the said boards were immersed during 12 hours in a 22% aqueous bath of ammonium phosphates having a pH value of 3.9, at a temperature of 65 C. After drying, the said boards containing 9.5% by weight of fireproofing salt were submitted to the standard tests and proved to be fireproof.

Example 3 Deal boards of 0.3 x 2.5 x 0.02 m. were immersed in water for 24 hours, the said boards were then immersed for 12 hours in a 5% aqueous ammonia solution at 15 C. After draining, the boards were .immersed for 6 hours in a 20% solution of ammonium phosphate having apI-I .valueof 5.95, the temperature being maintained at 80 C. Aftert drying, the average of fireproofing salt contents of the boards was of 8% by weight.

When subjected to inflammability tests, the boards proved to be ditficult to burn.

Example 4 Beech plies of 2.1 mm. thick were immersed for 5 minutes in a 5% ammonia solution, then, after draining, were immersed for the same time in an ammonium phosphate solution having a specific gravity of 1.13 and a pH value of 3.9, the said solution beingmaintained at a temperature of 35 C.

After drying in air at room temperature, the treated plies had absorbed 11.1% by weight of fireproofing salts and proved to be non-inflammable.

Example 5 After being immersed for 15 minutes in a 5% aqueous ammonia solution, beech plies of 2.1 mm. thick were immersed for the same time in the same ammonium phosphate solution as in Example 4 but the temperature was maintained at 70 during the whole operation. After drying at room temperature, it was found that the wood had absorbed 10.3% by weight of fireproofing salts.

Example 6 The Example 4 was repeated with the difference that ammonium fluoride was added to the phosphate solution, in a proportion of 45 g./l. solution.

Bacteriological tests showed that no micro-organisms developed on the treated plies which had the same degree of fireproofing.

Example 7 1 mm. thick plies of Aucoumea klayneiana were immersed in water until they had absorbed 80% by weight or" water. The plies were then immediately subjected to a first immersion for minutes in a 5% ammonia solution, then after a quick draining, to a second immersion for the same time in a solution of an ammonium phosphate having a pH value of 3.9 and a P0,; ions content of 18%, the temperature of which was maintained at 65 C. The plies were then dried in a drying apparatus in which air was admitted at a temperature comprised between 130 and 150 C. After minutes in the drying apparatus, the wood contained 10% water by weight. The shape of the plies was not modified and the surface thereof had retained its initial aspect. They contained 12.2% of fireproofing salts and their pH value was 6.6.

Three-ply wood panels obtained with the above mentioned plies were submitted to standard inflammability test and proved completely fireproof.

Example 8 Example 7 was repeated with the only difference that 0.5% by weight of pentachlorophenol was added to the ammonia solution.

The fireproofed plies were submitted to bacteriological tests which showed that no micro-organisms developed therein.

Example 9 8 kg. of a 50% aqueous emulsion of an inorganic micro-crystalline wax were added to 10 m? of lignocellulosic fiber paste containing g./l. of dry material and the pH of which was brought between 8.5 and 9 by careful addition of an expanding ammonia solution and the wax was precipitated on the fibers by adding a strong mineral acid until the pH value of the mixture reached 5.5. The paste was then formed into panels and the said panels were placed on the band of a suction filter and sprinkled with a solution of ammonium phosphate containing 55 kg./m. of phosphoric acid and having a pH value comprised between 5.5 and 6.

When the volume of phosphate solution having passed through the filter, reached the panels, the sprinkling was stopped and the panels were quickly drained. The phosphate solution which had passed through the panels was recovered and used for a further impregnation after adding phosphoric acid and adjusting the pH thereof at the above indicated values. Samples taken from the panels showed that the absorption of fireproofing salts was acceptable. The panels proved to be fireproof.

Example 10 Fiber panels were prepared according to conventional methods and dried in a drying apparatus.

The said panels were then placed on a vacuum vat and uniformly impregnated with a solution of ammonium phosphate having a pH value of 6 and titrating g./l. of phosphoric acid to which had been incorporated 5 kg./m. of non-ionic micro-crystalline wax emulsified in water. The excess solution having passed through the panels was recovered and used for a further impregnation operation after readjusting the contents of the various ingredients. After drying the panels during which wax particles were fixed on the fibers, the panels contained 10% by weight of phosphoric acid in the form of ammonium phosphate.

Samples taken from the panels showed that the absorption was acceptable and the panels were fireproof.

Example 11 100 kg. of cut flax stalks were placed in a rotating cylinder in which they were successively impregnated by spraying:

(1) 65 l. of an expanding ammonia solution containing 15 g./l. of NH (2) 65 l. of orthophosphoric acid solution containing 102 g./l. of H PO The cut stalks were then dried and made into a pulp with a synthetic resin containing 2% based on weight of the stalks, of the micro-crystalline wax.

The pulped material was shaped into panels by the conventional method. The said panels contained 10% by weight of H PO in the form of ammonium phosphate. The standard tests showed that the said panels were fireproof.

Instead of operating discontinuously in the rotating cylinder, it is also possible to operate continuously by using a continuous pulping machine of known type in which the first sprayers are fed with the ammonia solution and the following sprayers are fed with the phosphoric solution, the rate of feed being adjusted in order to correspond to the quantity of solution specified in Example 11.

What we claim is:

1. A rapid process for fireproofing cellulose and lignocellulose material, which comprises impregnating said material with an aqueous solution of ammonia ina concentration and for a period of time suflicient to expand the channels and cells in the material and to permit the penetration into said material of a desired quantity of ammonium ions but insuificient to alter the fibers thereof; and thereafter causing phosphoric ions to penetrate into said material by contacting said material with an aqueous solution containing orthophosphoric acid ions in a concentration and for a period of time sufiicient for the phosphoric ions to combine with said ammonium ions present in said material to form in situ at the time of drying an ammonium phosphate uniformly distributed throughout said material while giving said material a. pH value that does not alter its initial mechanical and surface properties.

2. A process as defined in claim 1, in which said solution containing said orthophosphoric ions also contains ammonium ions in a quantity fixed by the ratio of the quantity of ammonium ions already contained in said cellulose or lignocellulose material to the quantity of orthophosphoric ions carried into said material in said solution.

3. A process for fireproofing cellulose and lignocellulose material, which comprises impregnating said material with an aqueoussolution of ammonia in a concentration and for a period of time sufficient to expand the channels and cells in the material but insufficient to alter the fibers thereof and thereafter impregnating the material with an aqueous solution of an ammonium hydrogen phosphate in a concentration and for a period of time suflicient to react with said ammonia and thereby form an ammonium phosphate in situ throughout the material and provide a pH between 6.3 and 7.4.

4. A process for fireproofing cellulose and lignocellulose material, which comprises impregnating said material with an aqueous solution of ammonia in a "concentration and for a period of time suflicient to expand the channels and cells in the material but insufiicient to alter the fibers thereof and thereafter impregnating the material with an excess of an aqueous solution of an ammonium hydrogen phosphate in a concentration and for a period of time 'sufiicient to react with said ammoniaand form in situ at the time of drying an ammonium phosphate uniformly distributed throughout said materialwhile giving said material a pH value that does not alter its initial mechanical and surface properties, and removing the excess of said ammonium phosphate solution after said in situ reaction has taken place.

5. A process for fireproofing cellulose and ligncellulose material, which comprises impregnating said material with a 3-10% aqueous solution of ammonia fora period of time sufiicient to expand the channels and cells in the material but insuflicient to alter the fibers thereof and thereafter impregnating the material with a --30% aqueous solution of an ammonium hydrogen phosphate for a period of time sufiicient to react with said ammonia and form in situ at the time of drying am ammonium phosphate uniformly distributed throughout said material while giving said material a pH value that does not alter its initial mechanical and surface properties.

6. A process for fireproofing cellulose and lignocellulose material, which comprises impregnating said material with an aqueous solution of ammonia in a concentration and for a period of time suflicient to expand-the channels and cells in the material but insuflicient to alter the fibers thereof and thereafter impregnating the material with an aqueous solution of an ammonium hydrogen'phosphate having a pH between 3 and 7 in -aconcentration and for a period of time sufficient to react with said ammonia and form in situ at the time ofdrying an ammonium phosphate uniformly distributed throughout said material while giving said material -a pH value that does not alter its initial mechanical and surface properties.

7. A process for fireproofing cellulose and lignocellulose material, which comprises impregnating said material with an aqueous solution of ammonia in a concentration and for a period of time sufiicient to expand the channels and cells in the material but insufiicient to alter the fibers thereof and thereafter impregnating the material with an aqueous solution of an ammonium hydrogen phosphate in a concentration and for a period of time sufficient to react with said ammonia and form in situ at the time of drying an ammonium phosphate uniformly distributed throughout said material while giving said material a pH value that does not. alter its initial mechanical and surface properties, and continuing said reaction until the amount of ammonium phosphate fixed on said material is equivalent to 5 to of phosphoric acid based on the dry weight of the material. I

8. A process for fireproofing and waterproofing cellulose and lignocellulose material, which comprises impregnating said material with an aqueous solution of ammonia in a concentration and for a period of time sufficient to expand the channels and cells in the material but insuflicient to alter the fibers thereof and thereafter impregnating the material with an aqueous solution containing phosphoric acid ions in a concentration and for a period of time suflicient to react with said ammonia and form in situ at the time of drying an ammonium phosphate uniformly distributed throughout said material while giving said material a pH value that does not alter its initial mechanical and surface properties, and providing together with one of said aqueous solutions an aqueous dispersion of a waterproofing agent dispersible therein under its pH conditions.

9. The process of claim 8 in which both the ammonium phosphate solution and the aqueous dispersion of the waterproofing agent are used in excess and in which said excess thereof are removed after said in situ reaction has taken place.

10. A process for fireproofing and waterproofing cellulose and lignocellulose material, which comprises impregnating said material with an aqueous solution of ammonia in a concentration and for a period of time sufficient to expand the channels and cells in the material but insufiicient to alter the fibers thereof and thereafter impregnating'the material with an aqueous solution containing phosphoric acid ions in a concentration and for a period of time sufiicientto react with said ammonia and form in situ at the time of drying an ammonium phosphate uniformly distributed throughout said material while giving said material a pH value that does not alter its initial mechanical and surface properties, and providing with one of said aqueous solutions an aqueous emulsion of a microcrystalline Wax stable in said solution under its pH conditions.

11. A process for fireproofing and waterproofing cellulose and lignocellulose material, which comprises impregnating said material with an aqueous solution of ammonia in a concentration and for a period of time sufficient to expand the channels and cells in the material but insufficient to alter the fibers thereof and thereafter impregnating the material with an aqueous solution containing phosphoric acid ions in a concentration and for a period of time sufiicient to react with said ammonia and form in situ at the time of drying an ammonium phosphate uniformly distributed throughout said material While giving said material a pH value that does not alter its initial mechanical and surface properties, and providing together with one of said aqueous solutions an aqueous dispersion of a waterproofing agent dispersible therein under its pH conditions and in a concentration sufi'icient to impregnate said material with 0.5 to 5% of its dry weight of waterproofing agent.

References Cited in the file of this patent UNITED STATES PATENTS 761,870 Baxter June 7, 1904 1,422,242 Valls July 11, 1922 1,942,977 Payne Jan. 9, 1934 1,945,714 Winogradow Feb. 6, 1934 2,698,816 Dosmann et al. Jan. 4, 1955 2,766,139 Green et a1. Oct. 9, 1956 2,868,673 Depew et al. Jan. 13, 1959 2,930,106 Wrotnowski Mar. 29, 1960 FOREIGN PATENTS 440,026 Great Britain Dec. 16, 1935

Claims

1. A RAPID PROCESS FOR FIREPROOFING CELLULOSE AND LIGNOCELLULOSE MATERIAL, WHICH COMPRISES IMPREGNATING SAID MATERIAL WITH AN AQUEOUS SOLUTION OF AMMONIA IN A CONCENTRATION AND FOR A PERIOD OF TIME SUFFICIENT TO EXPAND THE CHANNELS AND CELLS IN THE MATERIAL AND TO PERMIT THE PENETRATION INTO SAID MATERIAL OF A DESIRED QUANTITY OF AMMONIUM IONS BUT INSUFFICIENT TO ALTER THE FIBERS THEREOF: AND THEREAFTER CAUSING PHOSPHORIC IONS TO PENETRATE INTO SAID MATERIAL BY CONTACTING SAID MATERIAL WITH AN AQUEOUS SOLUTION CONTAINING ORTHOPHOSPHORIC ACID IONS IN A CONCENTRATION AND FOR A PERIOD OF TIME SUFFICIENT FOR THE PHOSPHORIC IONS TO COMBINE WITH SAID AMMONIUM IONS PRESENT IN SAID MATERIAL TO FORM IN SITU AT THE TIME OF DRYING AN AMMONIUM PHOSPHATE UNIFORMLY DISTRIBUTED THROUGHOUT SAID MATERIAL WHILE GIVING SAID MATERIAL A PH VALUE THAT DOES NOT ALTER ITS INITIAL MECHANICAL AND SURFACE PROPERTIES.