MICROINCAPSULATED FLAME RETARDERS

Abstract: Microincapsulated flame retarders, such as decabromodiphenyloxide, octabromodiphenyloxide, tetrabromoparaxylene, hexabromocyclododecane, chlorophosphorated esters in general, tris-(2,3-dibromopropyl)phosphate, trichloroethylphosphate, tetrabromophthalic anhydride, tetrabromobisphenol, red phosphorus, ammonium polyphosphate, dibromopropanol and the like and microincapsulated mixtures thereof. Said flame retarders have an inert and impermeable membrane which isolate each single crystal or liquid drop from the surrounding environment, thus preventing undesired chemico-physical reactions, and eliminating the toxicity of the flame retarders themselves.

Description: MICROINCAPSULATED FLAME RETARDERS The present invention relates to flame retarders for rigid and flexible synthetic foams, binding resins and plastics in general. Flame retarding agents are known to be substantial- ly limited in their possible applications, due to the following drawbacks : - most flame retarders are more or less toxic and/or cor¬ rosive, therefore involving unnegligible problems and difficulties in use and handling. This is the case of tris(2, 3-dibromopropyl)phosphate which, in spite of its excellent antiflame properties, at present is not used, due to its high toxicity; - some flame retarders have stability problems. This is the case of red phosphorus which, in addition to a re- markable toxicity, shows a considerable tendency to spontaneous ignition; - flame retarders frequently react with the material to be made resistant to fire (for example a polyurethan foam) and said reaction may negatively affect the quality of the manufactured product; - most of the common flame retar-ders decompose at a tempe¬ rature lower than fire decomposition temperature of the treated material, so that, when the material is burning and the flame retarding effect is required, a part of the retarder has been already removed; - most of usual flame retarders have a limited duration, due to decomposition caused by oxidation and/or photo¬ chemical reactions, so that, after some time, the fire resistance of the treated material decreases. According to the present invention, in order to overcome the above drawbacks, the various flame retarders are microincapsulated, that is, the particles of said retarders, at the level of each single crystal or micro¬ scopic drop, are completely enveloped by an inert and atoxic stable microscopic film, according to various mi- croincapsulation processes, so attaining the following advantages: - transformation of any flame retarder, independently on the nature and characteristics thereof, into a simple inert additive till the moment when temperature exerted by fire causes the microcapsules to open, so releasing the flame retarder contained therein, which only from that moment carries on its action; - possibility to increase flame retarder effectiveness, by incapsulating in one single capsule various compounds having a synergetic action, or using mixtures of micro¬ incapsulated flame retarders, which are not compatible under the usual conditions; - obtaining of a product which is inert at room temperatu¬ re, but active at the beginning of fire; - attainment of a product which is safe from risks in handling, being externally non " toxic; - stability during the time of the retarder characteri¬ stics, since the retarder is protected by the membrane from any degradation process. All of the known flame retarders' may be microincap¬ sulated according to the present invention, particularly all the known organic and inorganic halogenated and/or phosphorated derivatives (used to this scope), such as decabromodiphenyloxide, octabro odiphenyloxide, tetrabro- moparaxylene, hexabromocyclododecane, chlorophosphorated esters in general, tris-(2, 3-dibromopropyl)phosphate, trichloroethylphosphate, tetrabromophthalic anhydride, tetrabromobisphenol, red phosphorus, ammonium polyphospha¬ te, dibromopropanol and mixtures thereof. Microincapsulation of • said flame retarders may be carried out according to various techniques, such as the method based on gelatins having different viscosities, the one based on gelatins and gum arabic, those based on cel¬ lulose derivatives and the like. The following examples illustrate some of these techniques, without limiting the scope of the invention. EXAMPLE 1 100 Ml of a 10% gelatin solution, 100 g of tetra- bromoparaxylene having a particle size of 150 to 300 mi¬ cron, 100 ml of gum arabic in solution and 300 ml of water were mixed in a vessel and stirred at a temperature from 45 to 50°C. The pH of the solution was adjusted to 4.2 and, during stirring, temperature was slowly lowered to 25°, at which temperature a membrane formed around the particles; thereafter the vessel was quickly cooled and stirring was continued during one hour, in order to make the membrane more rigid. 15 Ml of a 25% concentrate of glutaraldehyde was added to harden the membrane " and stirring was continued for some hours. The stirring time may be reduced by heat¬ ing the mass to about 25°C. A dehydrating agent was subsequently added in a rate equal to 3% by weight of the incapsulated compound, e.g. a compound commercially available under the mark Syloid, said compound being added in order to ease drying, while continuing stirring for about 30 minutes. Water was subsequently separated by filtration or other separation techniques, before drying the microcapsu- les. The obtained microcapsules have a weight ratio of 5:1 with respect to the product, i.e. 20 g of material making up the membrane for 100 g of incapsulated tetrabro- moparaxylene. The above cited Example may be carried out varying the compound/membrane ratio in the following percentages: 10:1; 20:1; 40:1. The same Example may carried out, for all the above cited compound/membrane ratios, using particles of 10 to 1000 microns size. Particularly, when tetrabromoparaxylene is used as flame retarding agent in flexible polyurethan foams, the maximum effectiveness was found for crystal sizes from 50 to 250 microns. EXAMPLE 2 100 Ml of a 10% gelatin solution was placed in a vessel, at a temperature from 45 to 50°C, under stirring, then 100 g of water, 15 ml of a 5% sodium hexametaphospha- te solution and 100 g of decabromodiphenyloxide having particle size of 150 to 300 microns were added, under stirring. pH was adjusted to about 4 and the temperature of the solution was first slowly lowered to 25°C, then quickly lowered to 10°, stirring for one hour at this temperature in order to make more rigid the membrane. As in Example 1, microcapsule membranes were hard¬ ened by addition of glutaraldehyde. Water separation and microcapsule drying were car¬ ried out as described in Example 1. The resulting microcapsules have a membrane/compo¬ und weight ratio of 1:10. As for Example 1, membrane/compound weight ratio as well as microcapsule size may be varied. EXAMPLE 3 250 Ml of cyclohexane, 4 g of ethylcellulose and 4 g of carboxylated wax were placed in a vessel. Temperature was raised to 70°C, under strong stirring, to complete dissolution. Then 30 g of ammonium polyphosphate was ad¬ ded, and temperature was lowered to 20°C, continuing stir- ring. The reaction mixture was filtered, the filtrate was repeatedly washed with pure cyclohexane. Microincapsulated ammonium polyphosphate was then dried in oven, at a tempe¬ rature not higher than 40°C. As in the above Examples, membrane/compound ratio as well as microcapsule sizes may be varied. EXAMPLE 4 100 Grams of red phosphorus is added to 300 g of H O, 2 g of urea, 5 g of resorcine and 40 ml of 40% for¬ maldehyde. The pH is slowly brought down to 1.5 to obtain a polymerization yielding an urea-formaldehyde membrane including red phosphorus. The water is then separated from the obtained microcapsules which are dried.

Claims: CLAIMS 1. Microincapsulated flame retarders. 2. Microincapsulated flame retarders as claimed in claim 1, said microincapsulated flame retarders consisting of any organic or inorganic halogenated and/or phosphorat¬ ed derivative utilizable as flame retarder, or of red phosphorus or mixtures thereof. 3. Microincapsulated flame retarders as claimed in claims 1-2, said microincapsulated flame retarders consi¬ sting of decabromodiphenyloxide, octabromodiphenyloxide, tetrabromoparaxylene, hexabromocyclododecane, chloropho- sphorated esters in general, tris-(2, 3-dibromopropyl)pho¬ sphate, trichloroethylphosphate, tetrabromophthalic anhy- dride, tetrabromobisphenol, red phosphorus, ammonium poly¬ phosphate, dibromopropanol or mixtures thereof. 4. Microincapsulated flame retarders as claimed in claims 1-3, wherein the coating membrane is one of the usual coating membranes suited for microincapsulation. 5. Microincapsulated flame retarders as claimed in claim 4, wherein the coating membrane consists of gelatins and derivatives thereof, natural resins and derivatives thereof, synthetic resins and derivatives thereof, 'cellu¬ lose derivatives, and mixtures thereof. * 6. Microincapsulated flame retarders as claimed in any one of claims 1 to 5, wherein the membrane is a urea-for¬ maldehyde membrane. 7. Microincapsulated flame retarders as claimed in claim 6, wherein the flame retarder is red phosphorus.

Inventors: CICUTO DANILO, CICUTO, DANILO
Applicants: CAPSALARM SARL, CAPSALARM S.A.R.L.
Application year: 1986
Main classification: C08K9
IPC codes: C08K9