Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K21/00—Fireproofing materials
  • C09K21/02—Inorganic materials

Definitions

• the invention relates to the use of at least one aluminosilicate polymer imogolite type or allophane type as flame retardant. It also relates to a flame retardant composition and a polymeric material comprising at least one aluminosilicate polymer imogolite type or allophane type.
• Organic additives used as fire retardants are often currently brominated or fluorinated molecules. Their use is therefore limited to certain uses because of the toxicity of combustion by-products. A by-product of combustion is particularly dangerous, it is hydrofluoric acid, HF.
• the inorganic additives used up to now are hydroxides or oxohydroxides of transition metals, or metals of groups III and IV of the Periodic Table of the elements, or even carbonates of these transition metals or groups III and IV. But these latter types of inorganic additives decompose by releasing CO 2 .
• the use of inorganic additives of the hydroxide type is based primarily on the oxidation mechanism: 2M-OH ⁇ MO + H 2 O.
• the formulator will therefore have to "load" his polymeric material in such a way that the composite obtained has the properties desired by the use, in particular in terms of surface appearance, mechanical strength, etc., as well as in terms of resistance. fire corresponding to the standards of the field of use.
• flame retardants are antimony or tin hydroxides.
• the formulator must also consider chemical incompatibilities that do not allow to mix any filler with any polymer. And because for the crystallized nanofillers the energy of the hydroxyls of surfaces is not at all homogeneous, for some surface hydroxyls, the oxidation will take place only at very high temperature, which limits its interest. for many uses, the damage having already taken place.
• the formulator must also consider the future recycling of the polymer-flame retardant composite and eliminate the environmentally toxic products.
• the antimony and tin currently used are toxic products.
• the invention responds to this need by proposing the use of at least one aluminosilicate polymer of the imogolite type or allophane type, as flame retardant.
• Aluminosilicate polymers are known in various forms.
• aluminosilicate polymers in fibrous form such as imogolite
• Imogolite is a filamentous, tubular aluminosilicate found naturally in volcanic ash and some soils.
• Natural imogolite is impure and is mixed with other aluminosilicates such as allophanes and / or boehmite. Natural imogolite can not be used in this impure form, particularly for the formulation of high-tech polymers.
• Farmer US Patents 4,152,404 and 4,252,779 describe a process for preparing an inorganic material similar to natural imogolite.
• the imogolite obtained is freed from the fillers, such as dialysis salts.
• this technique does not eliminate allophanes that do not carry charges.
• WADA et al. In Journal of Science, 1979,
• European Patent No. 0 741668 discloses a long and accurate process for obtaining imogolite having a high degree of purity. In particular, it is absolutely necessary, during the step of digestion or growth of the filaments, to maintain the pH and the concentration of Al + Si in precise ranges of values. In case of uncontrolled synthesis, the formation of silica gels, boehmite or allophanes is observed. Boehmite has a non-fibrous structure, with a molar ratio AI: Si greater than 4.
• the imogolite obtained is not sufficiently pure for applications as filler in polymeric materials.
• French Patent Application 2,817,488 describes a process for obtaining a high purity imogolite aluminosilicate polymer that can be used in the formulation of polymeric materials by purifying an aqueous dispersion of a mixture of colloidal aluminosilicate particles. obtained according to the process described in European Patent 0 741 668.
• the mixture of colloidal particles is purified by ultrafiltration in order to obtain in the retentate a fibrous polymeric aluminosilicate, of the imogolite type, having a molar ratio Al / Si of between 1.8 and 2.5.
• the ultrafiltration is a tangential ultrafiltration, also preferably using a polyethersulfone-based membrane.
• the retentate laminar flow is substantially equal to 1 l / min for a membrane area of 1 m 2 . It is also possible to pre-filter the mixture of particles before carrying out the ultrafiltration step.
• French Patent Application 2,802,912 describes a process for preparing a high purity imogolite aluminosilicate polymer. This process comprises the following steps: a) treating a mixed alkoxide of silicon and aluminum, or a precursor of a mixed compound of aliminium and silicon, with an alkali at a pH between 4.5 and 6.5 inclusive by maintaining the molar concentration of aluminum between 5 1 (T * and 10 -2 M inclusive and the molar ratio Ai / Si between 1 and 3 inclusive, in the presence of silanol, b) a maturation step is carried out at room temperature, preferably for a period of between 5 and 15 days inclusive, most preferably for a period of between 8 and 10 days inclusive, c) the mixture obtained is heated at room temperature. step a) at a temperature below 100 ° C., preferably at a temperature of 96-98 ° C. for 24 hours, d) the residual ions of the mixture obtained in step c) are removed, for example by ultrafiltration.
• iminosate-type aminosilicate polymer (s) refers to the aluminosilicate polymers obtained by the processes described in French Patent Application No. 2,817,488 and French Patent Application No. 2,802,912, and are those used in the invention. .
• Aluminosilicate polymers in the form of spherical particles, such as allophanes, are also known.
• US-A-6,254,845 discloses a process for preparing hollow spheres of aluminosilicate polymers of the allophane type.
• the resulting aluminosilicate polymer contains, because of the manufacturing process used, a high proportion of the salt used to form it.
• French Patent Application 2,842,514 describes a process for preparing an aluminosilicate polymer of the imogolite type or of the type Allophane, very pure, can be used for the formulation of many polymeric materials.
• This process consists in: a) treating a mixed alkoxide of aluminum and silicon having only hydrolysable functions (that is to say containing only substituents removed by hydrolysis during the process, and in particular to the occasion of the treatment with an aqueous alkali), or a mixed precursor of aluminum and silicon obtained by hydrolysis of a mixture of aluminum compounds and silicon compounds comprising only hydrolysable functions, with an aqueous alkali, in the presence of silanol groups, the aluminum concentration being kept below 0.3 mol / l, the molar ratio Al / Si being maintained between 1 and 3.6 and the molar ratio alkali / Al being maintained between 2.3 and 3, b ) stirring the resulting mixture at room temperature in the presence of silanol groups for a time sufficient to form the aluminosicate polymer, and finally c) removing from the reaction medium by-products formed in the previous steps.
• By-product removal can be carried out by various methods known per se, such as washing or diafiltration or
• the aluminosilicate polymer of the imogolite type or of the allophane type obtained is characterized by a Raman spectrum comprising, in the spectral zone 200-600 cm -1 , a broad band located at 250 + 5 cm -1 , a wide and intense band located at 359 + 4 cm -1 , a shoulder at 407 + 7 cm -1 , and a band at 501 + 2 cm -1 , the Raman spectrum being made on the material obtained just before the elimination step of the medium. reaction of by-products formed during steps a) and b).
• FIGS. 1 to 3 represent the Raman spectra of three aluminosilicate polymers used in the invention. It can be seen from these figures that the Raman spectrum of the aluminosilicate polymers used in the invention is well characterized as previously described.
• aluminosilicate polymer (s) imogolite type or allophane type refer to the preceding and following text aluminosilicate polymers obtained by the process described in the French patent application 2 802 912 or by the process described in French patent application 2,817,488, or by the process described in French patent application 2,842,514.
• the aluminosilicate polymers of the imogolite type used in the invention are hollow nanotubes 2nm in diameter and several microns in length. They are, as already mentioned, obtained by controlled co-hydrolysis of aluminum salts and silicon alkoxides. This hydrolysis is followed by a heat treatment which will allow the growth of the filaments. These filaments will then be washed and concentrated by ultrafiltration.
• the structure of these aluminosilicate polymers imogolite type is very particular: the outside of the tube is covered with Al-OH, while the inside of the tube is covered with Si-OH. Thus, the water remains trapped indefinitely inside the tube.
• the aluminosilicate polymers of the allophane type type used in the invention are hollow nanospheres of 5 nm in diameter also obtained by controlled co-hydrolysis of aluminum and silicon salts. But here the hydrolysis is not followed by a heat treatment, the main parameter to obtain either imogolite or allophane being the concentration of aluminum salts.
• This aluminosilicate polymer of the allophane type like the aluminosilicate polymer of the imogolite type, is also covered with Al-OH on the outside and Si-OH on the inside. Also, in this allophane type aluminosilicate polymer, the core of the particle is filled with water.
• aluminosilicate polymers of the imogolite type and those of the allophane type type are both amorphous. They are stable up to 300 0 C then abruptly decompose in H 2 O, Al 2 O 3 and SiO 2 .
• aluminosilicate polymers are particularly suitable as flame retardants because, inside and outside, they are coated with reactive hydroxyl groups, that is to say oxolisables at low temperature. In addition, water trapped within their structure will participate in cooling during evaporation.
• the invention relates to the use of these aluminosilicate polymers imogolite type or allophane type as flame retardant. It also relates to a flame retardant composition comprising these aluminosilicate polymers imogolite type or allophane type. Finally, it also relates to a polymeric material comprising at least one aluminosilicate polymer of the imogolite or allophane type, preferably having a Raman spectrum as shown in FIGS. 1 to 3.
• AI (OH) 3 leads to AI 2 O 3 when it is heated to
• the samples are dried beforehand for 48 hours under a pressure of 10 3 mm of mercury at 20 ° C. (room temperature) so as to remove the water that could be adsorbed on the surface of the particles. They are then kept under dry argon. One gram of each sample is taken and put in the oven. The temperature ramp is arbitrarily chosen at 10 ° C / minute. At 300 ° C., the sample is kept at this temperature for one hour and then cooled to room temperature (20 ° C.) under dry argon, and then weighed on a precise Mettler scale to the thousandth.
• the powders treated after being weighed under argon are left in the air for one hour then are re-weighed so as to evaluate a possible water uptake.
• particulate aluminosilicate polymer according to the invention (lyophilized powder).
• Boehmite nanofilaments from J. F. Hochepied, P. Nortier, Powder technology 128, (2002), 268-275, diameter 3 -5 nm, length 100 nm.
• the aluminosilicate polymers of the imogolite or allophane type according to the invention lose on average 45% of their mass during heat treatment at 300 ° C. This is due to the internal water reservoir which is collapsed during the heat treatment at 300 0 C but also to the water generated by the oxidation of the surfaces aluminols and silanols.
• the nanometric size of these aluminosilicate polymers of the imogolite or allophane type optimizes the oxidation mechanisms.
• the aluminosilicate polymers of the imogolite or allophane type of the invention release twice as much water as dried gibbsites (SH 500 and SH 950 samples), and almost three times as much water. water than nanometric boehmites
• PVC suspensions / flame retardants in 2-butanone are prepared and coated on microscope slides. These suspensions being very film-forming, it is not necessary to add surfactant to the formulation.
• the layers obtained are exposed to the air and dried at least 24 hours to remove all traces of 2-Butanone. In the same way polymer layers containing only PVC were made for use as a reference. The thickness of the layers obtained after drying is 300 .mu.m. In order to ensure that the layers will be subjected to an identical thermal treatment, the following protocol has been implemented.
• An iron straw filament is connected by crocodile clips to the terminals of a generator, as soon as the circuit is closed, the heated square section filament switches to red (hot red: 500-800 ° C) then to white (hot white: 1300-1500 ° C) before breaking.
• the filament is maintained at 0.5 mm from the surface of the layers to be evaluated, it is maintained in mechanical tension (stretching) so that it does not come into contact with the surface of the layer during the rupture. At constant voltage (4.5V), the iron straw filament breaks in 2 minutes.
• PVC suspensions / flame retardants were prepared in the following manner.
• the reference sample was repeated three times, the other two times.
• the duration of the exposure is each time of 2 minutes.
• the aluminosilicate polymers of the imogolite type or of the allophane type synthesized according to the processes described in the French patent applications 2,817,488, 2,802,912 and 2,842,514 can be used as an effective flame retardant, in particular to obtain effective flame retardant compositions that can be blended with polymer-based materials having flame-retardant properties.
• aluminosilicate polymers of the allophane type but also one or more aluminosilicate polymers of imogolite type can be used, but also a mixture of one or more more aluminosilicate polymers of the allophane type and one or more aluminosilicate polymers of the imogolite type.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Silicates, Zeolites, And Molecular Sieves (AREA)
• Fireproofing Substances (AREA)

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• 2008
  • 2008-02-21 FR FR0800937A patent/FR2927905B1/fr not_active Expired - Fee Related
• 2009
  • 2009-02-09 JP JP2010547215A patent/JP2011512452A/ja active Pending
  • 2009-02-09 WO PCT/FR2009/000142 patent/WO2009112712A2/fr active Application Filing
  • 2009-02-09 EP EP09719104A patent/EP2254966A2/de not_active Withdrawn
  • 2009-02-09 US US12/918,490 patent/US8287779B2/en not_active Expired - Fee Related

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