WO2019011780A1 - Thermal-insulation materials based on high-thickening silicas - Google Patents

Thermal-insulation materials based on high-thickening silicas Download PDF

Info

Publication number
WO2019011780A1
WO2019011780A1 PCT/EP2018/068255 EP2018068255W WO2019011780A1 WO 2019011780 A1 WO2019011780 A1 WO 2019011780A1 EP 2018068255 W EP2018068255 W EP 2018068255W WO 2019011780 A1 WO2019011780 A1 WO 2019011780A1
Authority
WO
WIPO (PCT)
Prior art keywords
thermal
hydrophilic
insulation
pulverulent
silica
Prior art date
Application number
PCT/EP2018/068255
Other languages
French (fr)
Inventor
Matthias Geisler
Claudia SEVERIN
Joachim Erz
Original Assignee
Evonik Degussa Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Evonik Degussa Gmbh filed Critical Evonik Degussa Gmbh
Publication of WO2019011780A1 publication Critical patent/WO2019011780A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B30/00—Compositions for artificial stone, not containing binders
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B30/00—Compositions for artificial stone, not containing binders
    • C04B30/02—Compositions for artificial stone, not containing binders containing fibrous materials
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C04B38/0067—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof characterised by the density of the end product
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/46—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with organic materials
    • C04B41/49—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes
    • C04B41/4905—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes containing silicon
    • C04B41/4922—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes containing silicon applied to the substrate as monomers, i.e. as organosilanes RnSiX4-n, e.g. alkyltrialkoxysilane, dialkyldialkoxysilane
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/60—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only artificial stone
    • C04B41/61—Coating or impregnation
    • C04B41/62—Coating or impregnation with organic materials
    • C04B41/64—Compounds having one or more carbon-to-metal of carbon-to-silicon linkages
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C04B2111/28—Fire resistance, i.e. materials resistant to accidental fires or high temperatures

Definitions

  • the invention relates to a thermal-insulation material containing a high-thickening silica, to a process for the production thereof and to the use thereof for producing a thermal-insulation sheet or thermal- insulation granules.
  • microporous thermal-insulation materials based on fumed silicas or silica aerogels are distinguished especially by a high thermal- insulation effect in the range from minus 200°C right up to 1000°C.
  • Microporous sheets based on fumed silicas or aerogels, opacifiers and reinforcing fibres have been considered to be state of the art for decades and are successfully used in numerous thermal-insulation applications.
  • thermo-insulation sheet containing a finely divided silica is thermally treated in an oven at temperatures of up to 1000°C and thereby cured.
  • WO2016/162261 discloses a process for producing a thermal-insulation sheet, which process involves treating a hydrophilic silica-comprising thermal-insulation sheet with ammonia by introducing the thermal-insulation sheet into a chamber and supplying gaseous ammonia until the pressure difference ⁇ is > 20 mbar. As a result, it is possible to improve the compressive strengths of thermal-insulation sheets even after compression.
  • WO201 1/150987 discloses a thermal-insulation powder mixture having a bulk density of 20-60 g/l, which mixture contains at least one silica having a BET surface area of 130-1200 m 2 /g and having a D50 value of less than 60 ⁇ and at least one fibrous material having a fibre diameter of 1-50 ⁇ .
  • the silica can be hydrophilic and hydrophobic silicas.
  • a thermal-insulation sheet obtained from the thermal-insulation powder mixture is disclosed. To this end, use is made of hydrophilic silicas and solid, hydrophobic materials such as PVDF or mixtures of hydrophilic and hydrophobic silica. Owing to the desired hydrophobicity, the thermal-insulation sheets thus obtained cannot be subsequently cured by temperature treatment, since they would lose their hydrophobic properties as a result.
  • WO201 1/069923 states that hydrophobic silicas cannot be compressed. Furthermore, it is stated that an after-treatment of the insulation material with organosilanes after compression is highly complicated, since the core material can only be penetrated very slowly and at high pressure. In addition, in this process, the structure of the core material is sometimes destroyed. Therefore, it is proposed to use non-volatile, functional organosilanes having boiling points of more than 130°C, preferably those which can be evaporated without decomposition. Such an organosilane is then added to a hydrophilic silica, the mixture compressed and then thermally treated. However, the sheet thus obtained exhibits a non-uniform hydrophobization.
  • Binder-free, hydrophilic-silica-containing thermal-insulation sheets have a mechanical sheet stability in need of improvement.
  • a chemical treatment for example with ammonia.
  • such a treatment is also associated with an undesired rise in thermal conductivity.
  • such a treatment means that an additional process step becomes necessary.
  • thermal-insulation material and a resultant thermal-insulation sheet or resultant thermal-insulation granules having primarily improved thermal conductivity.
  • mechanical properties of the thermal-insulation sheets known from the prior art be improved.
  • process which leads to said thermal-insulation material and thermal-insulation sheet without the need for a subsequent treatment step is provided.
  • the invention provides a hydrophilic, pulverulent thermal-insulation material containing from 5 to 30% by weight, based on the hydrophilic, pulverulent thermal-insulation material, of an IR opacifier and from 70 to 95% by weight, based on the hydrophilic, pulverulent thermal-insulation material, of aggregated particles of a hydrophilic silica having a BET surface area of 200-600 m 2 /g and a thickening of at least 5000 mPas, wherein the thickening is determined in a dispersion of the silica in an unsaturated polyester resin.
  • a hydrophilic, pulverulent thermal-insulation material is to be understood to mean a material in which the surface of the particles forming the powder behaves hydrophilically upon stirring into water, i.e. the surface is completely wetted by water and thus has a contact angle of less than 90° with respect to water.
  • Contact angle determination is, for example, described in EP-A-1433749.
  • a hydrophilic silica is to be understood as meaning a silica whose surface bears no organic groups, such as alkyl groups for example, that would impart a hydrophobic, water-repelling character to it.
  • the groups disposed at the surface shall consist completely or to the greatest possible extent of Si-OH and Si-O-Si groups.
  • the thermal-insulation material according to the invention comprises a hydrophilic silica having a silanol group density SiOH of 1.8 to 2.5 OH/nm 2 , determined in accordance with the LiAlhU method by J. Mathias and G. Wanneraum, Journal of Colloid and Interface Science 125 (1988).
  • a silica is referred to as a hydrophobic silica when the Si-OH and Si-O-Si groups disposed at the surface are at least partly reacted with an organic compound which imparts a hydrophobic, water- repelling character to the material.
  • the hydrophilic, pulverulent thermal-insulation material contains a fumed silica as hydrophilic silica.
  • a fumed silica as hydrophilic silica.
  • This has a specific structure. Primary particles of size from 5 to 50 nm accrete to give larger aggregates which in turn combine to give even larger structures, the agglomerates.
  • Fumed silica is produced via flame hydrolysis of volatile silicon compounds such as organic and inorganic chlorosilanes. This process comprises bringing a vaporized, hydrolysable silicon halide to reaction with a flame formed by combustion of hydrogen and an oxygenous gas. The combustion flame here provides water for the hydrolysis of the silicon halide, and sufficient heat for the hydrolysis reaction.
  • a non-halogenated silicon compound for example a siloxane
  • flame pyrolysis A silica produced by flame hydrolysis or flame pyrolysis is termed fumed silica.
  • fumed silica This process initially forms primary particles which are virtually free of interior pores. These primary particles then fuse during the process via so-called "sinter necks" to afford aggregates.
  • fumed silica is an ideal thermal-insulation material, since the aggregate structure provides adequate mechanical stability, minimizes heat transfer due to conductivity in the solid by way of the "sinter necks", and produces sufficiently high porosity.
  • the BET surface area of the silica is 200-600 m 2 /g, preferably 250-400 m 2 /g. It can be determined in accordance with DIN 66131. This range is most suitable with regard to thermal conductivity.
  • the thickening of the hydrophilic silica present in the thermal-insulation material according to the invention is at least 5000 mPas, preferably 5000-10 000 mPas, particularly preferably 7000-9000 mPas.
  • the thickening, in mPas, is determined in a dispersion of a silica in an unsaturated polyester resin.
  • Suitable unsaturated polyester resins encompass cocondensates of ortho- or meta-phthalic acid and maleic acid or fumaric acid, or the anhydrides thereof, and a low molecular weight diol, for example ethylene glycol, propane-1 ,2- or -1 ,3-diol, butane-1 ,2- or -1 ,3- or -1 ,4-diol or neopentyl glycol ((CH3)2C(CH20H)2), or polyols, such as pentaerythritol, preferably dissolved in an amount of 30% to 80% by weight, preferably 60% to 70% by weight, in an olefinic reactive diluent as solvent, for example monostyrene.
  • a low molecular weight diol for example ethylene glycol, propane-1 ,2- or -1 ,3-diol, butane-1 ,2- or -1 ,3- or -1 ,4-diol or n
  • the viscosity of the polyester resin is 900-1200 mPas at a temperature of 22°C.
  • a suitable unsaturated polyester resin is, for example, Palatal ® P6-01 (DSM; viscosity at 23°C: 900-1200 mPas).
  • the thickening is, inter alia, most suitable for describing the hydrophilic silica used in the hydrophilic pulverulent thermal-insulation material according to the invention.
  • the thickening value is customarily used for characterizing the rheological properties of diverse formulations containing silicas. Said value may be dependent on many material properties of the silicas used, such as their porosity, aggregate shape and aggregate size. It has now been found that, surprisingly, there is a direct link between this easy-to-measure parameter and the thermal conductivity of thermal-insulation materials containing silicas: a higher thickening of the silica leads to a lower thermal conductivity of thermal-insulation materials.
  • thermally insulating materials are customarily produced from the corresponding halogen-containing silanes by flame hydrolysis.
  • WO2016/020215A1 and DE102015206433A1 describe thermal-insulation materials based on
  • AEROSIL ® 300 a silica produced from silicon tetrachloride by flame hydrolysis and having a BET of 300 m 2 /g. From "Technical Bulletin Fine Particles: Basic Characteristics of AEROSIL ® Fumed Silica, Number 1 1 ", page 56, published in 2003, it is known that the thickening (viscosity) of all customary AEROSIL ® product types, including AEROSIL ® 300, measured in an unsaturated polyester resin
  • octamethylcyclotetrasiloxane (D4) are used in the flame hydrolysis under certain reaction conditions.
  • the use of such high-thickening silicas, especially in combination with IR opacifier, in thermal- insulation materials is not known from the prior art.
  • hydrophilic silica it has been found to be advantageous for the mechanical properties and the thermal conductivity of a thermal-insulation sheet when the hydrophilic, aggregated silica has a highest possible silanol group density.
  • the IR spectra are obtained on powder layers by means of a Bruker IFS 85 FT-IR spectrometer.
  • the sample to be determined is sprinkled onto an NaCI monocrystalline window.
  • the measurement is carried out with the following parameters: Resolution: 2 cm “1 ; measurement interval: 4500 cm “1 to 100 cm “1 ; apodization function: triangular; number of scans: 128.
  • the absorbance is determined as follows: To define the baseline, tangents to the baseline are drawn in the region between
  • hydrophilic, pulverulent thermal-insulation material according to the invention preferably have a tamped density of 30-70 g/l.
  • the hydrophilic, pulverulent thermal-insulation material also contains at least one IR opacifier.
  • This is preferably selected from the group consisting of titanium oxides, zirconium oxides, ilmenites, iron titanates, iron oxides, zirconium silicates, silicon carbide, manganese oxides, graphite, carbon blacks, or mixtures thereof. Particular preference is given to silicon carbide, titanium oxide, iron oxide or carbon black.
  • the particle size of the opacifiers is generally between 0.1 and 25 ⁇ . In the case of silicon carbide and titanium oxides, the average particle diameter dso is preferably 1 to 10 ⁇ , particularly preferably 2 to 8 ⁇ .
  • the proportion of IR opacifier, based on the hydrophilic, pulverulent thermal-insulation material, is 5 to 30% by weight.
  • the proportion of hydrophilic silica is preferably 70 to 95% by weight, based on the hydrophilic, pulverulent thermal-insulation material.
  • fibres can be added to the hydrophilic, pulverulent thermal-insulation material.
  • Said fibres can be of inorganic or organic origin and are generally 2 to 10% by weight, based on the sum total of silicas and opacifiers.
  • inorganic fibres which can be used are glass wool, stone wool, basalt fibres, slag wool and ceramic fibres, consisting of melts of aluminium oxide and/or silicon dioxide, and also of other inorganic metal oxides.
  • pure silicon dioxide fibres are silica fibres.
  • organic fibres which can be used are cellulose fibres, textile fibres and synthetic fibres.
  • the diameter of the fibres is preferably 1 to 30 ⁇ , more preferably 5 to 15 ⁇ , very preferably 6 to 9 ⁇ , and the length is preferably 1 to 25 mm, more preferably 3 to 12 mm.
  • the hydrophilic thermal-insulation material can contain inorganic additives.
  • Materials that can be used are arc silicas, SiC -containing fly ash produced via oxidation reactions of volatile silicon monoxide during electrochemical production of silicon or ferrosilicon. It is moreover possible to use naturally occurring SiC -containing compounds such as diatomaceous earths and kieselguhrs.
  • thermally expanded minerals such as perlites and vermiculites, and fine- particle metal oxides such as aluminium oxide, titanium dioxide, iron oxide.
  • the proportion of the inorganic additives can be up to 25% by weight, based on the hydrophilic thermal-insulation material.
  • the thermal-insulation material is free of said inorganic additives as far as possible.
  • the invention further provides a process for producing the hydrophilic pulverulent thermal-insulation material according to the invention, comprising the following steps:
  • step a) of the process according to the invention the hydrolysable and oxidizable siloxane that is used is combined with at least one fuel and oxygen for the flame hydrolysis or flame pyrolysis reaction, yielding a silica as product.
  • a possible fuel is, for example, hydrogen, methane, ethane, propane, butane and/or natural gas.
  • the oxygen source used is preferably air.
  • the siloxane is selected from the group consisting of octamethyltrisiloxane,
  • the index ⁇ (lambda) is the ratio of the amount of oxygen present in the reaction mixture divided by the amount of oxygen needed for the complete combustion of all combustible constituents of the reaction mixture, each in mol/h.
  • ⁇ greater than 4 is set; very particularly preferably, ⁇ of 5.5 to 12.5 is chosen.
  • the constituents of the thermal-insulation material can be mixed in step b) of the process according to the invention by means of, for example, planetary mixers, cyclone mixers, dissolvers, fluid mixers, fine- impact mills, air stream mills or classifier mills.
  • the invention further provides for the use of the hydrophilic pulverulent thermal-insulation material according to the invention for producing a hydrophilic or hydrophobic thermal-insulation sheet or hydrophilic or hydrophobic thermal-insulation granules.
  • the invention further provides a hydrophilic thermal-insulation sheet or hydrophilic thermal-insulation granules containing hydrophilic, pulverulent thermal-insulation material according to the invention.
  • the invention further provides a hydrophilic thermal-insulation sheet having a density of 130-200 g/l, containing 70-95% by weight of aggregated particles of a hydrophilic silica having a BET surface area of 300-400 m 2 /g and a thickening of at least 5000 mPas, wherein the thickening is determined in a dispersion of the silica in an unsaturated polyester resin, 4-30% by weight of IR opacifier, 1-10% by weight of fibres and 0-25% by weight of fine additives.
  • thermo conductivity TC at standard pressure of 18 ⁇ TC ⁇ 20 mW/(m ⁇ K) and a flexural strength of at least 40 kPa, preferably 50-75 kPa.
  • Its half-value pressure defined as the gas pressure at which the gas thermal conductivity is halved, i.e. approximately 13 mW/(m ⁇ K), is more than 800 hPa, preferably 830-880 hPa.
  • a half-value pressure of 600-800 mbar is determined for microporous materials.
  • the hydrophilic thermal- insulation sheet according to the invention is distinctly above this value.
  • the invention further provides a process for producing a thermal-insulation sheet or thermal-insulation granules, comprising compressing or compacting the hydrophilic, pulverulent thermal-insulation material according to the invention to obtain a hydrophilic thermal-insulation sheet or hydrophilic thermal-insulation granules.
  • the hydrophilic thermal-insulation material and the inorganic fibres can be compressed in either a batchwise or continuous manner according to known processes.
  • hydrophilic thermal-insulation sheets are continuously produced by means of a belt press. A thermal or chemical after-treatment of the hydrophilic thermal-insulation sheet in order to improve its mechanical properties is possible, though not necessary because of the thermal-insulation material according to the invention that is used.
  • hydrophilic thermal-insulation sheet or the hydrophilic thermal-insulation granules can additionally be hydrophobized with a hydrophobization agent.
  • the hydrophilic thermal-insulation sheet is hydrophobized by:
  • the temperature in the chamber is 20 to 300°C and c) from the time at which the organosilane is added, leaving the sheet for additionally 1 minute to 1 hour in the chamber.
  • the hydrophobic thermal-insulation sheet produced from the hydrophilic, pulverulent thermal- insulation material according to the invention can preferably have a density of 150-200 g/l, and can contain 70-95% by weight of aggregated particles of a hydrophobic silica having a BET surface area of 300-400 m 2 /g and 3-8% by weight of carbon, based on the hydrophobic silica, 4-30% by weight of IR opacifier, 1-10% by weight of fibres and 0-25% by weight of fine additives.
  • It has a thermal conductivity TC at standard pressure of 16 ⁇ TC ⁇ 18.5 mW/(m ⁇ K) and a flexural strength of at least 50 kPa, preferably 60-80 kPa.
  • the hydrophilic thermal-insulation granules producible from the hydrophilic, pulverulent thermal- insulation material according to the invention can be produced by compacting, generally by compaction, of the hydrophilic, pulverulent thermal-insulation material according to the invention.
  • the granules obtained after compacting can be cured in a treatment step, specifically by thermal treatment at a temperature of 200-1200°C or by treatment with gaseous ammonia.
  • the hydrophilic, thermally insulating granules with or without curing can be subjected to a further treatment step with a hydrophobization agent to form hydrophobic, thermally insulating granules.
  • hydrophobization agents are organosilanes selected from the group consisting of R n -Si-X4- n ,
  • Thickening 7.5 g of hydrophilic silica and 142.5 g of unsaturated polyester resin Palatal ® P6-01 (DSM; viscosity at 23°C: 900-1200 mPas) are dispersed using the dissolver Dispermat AE02-C1 , VMA- Getzmann (diameter of dissolver disc: 50 mm) for a period of 5 minutes at 3000 min -1 .
  • the dispersion obtained has a content of hydrophilic silica of 2.0% by weight. Air bubbles are removed by centrifugation. The dispersion is adjusted in temperature to 22°C and the viscosity thereof is determined using a Physica-Rheolab MC1 , Anton Paar.
  • Thermal-insulation sheets Thermal conductivity in accordance with DIN EN 12667:2001 at a mean temperature of 10°C and a contact pressure of 250 Pa.
  • Flexural strength in accordance with DIN EN 12089:2013 is determined according to test method B on sheets approximately 20 mm thick.
  • Half-value pressure defined as the gas pressure at which the gas thermal conductivity is halved, as per R.
  • Test method 1A The long-term water absorption upon partial immersion is determined by measuring the change in weight of a test specimen, the underside of which is immersed in water for a period of 28 days. Test method 1A (drip-off).
  • hydrophilic silicas are produced on the basis of EP-A-38900
  • Example 1 In an evaporator, 1.5 kg/h of octamethylcyclotetrasiloxane are evaporated, and mixed with 14.5 Nm 3 /h of air (primary air). The siloxane/air mixture is then introduced into a burner, where it is mixed and ignited with 0.80 Nm 3 /h of hydrogen (core hydrogen). In addition, a further 15 Nm 3 /h of air (secondary air) is supplied. To stabilize the flame, 0.35 Nm 3 /h of hydrogen (shell hydrogen) is additionally introduced through an annular gap surrounding the burner mouth.
  • the BET surface area of the hydrophilic silica obtained is 312 m 2 /g.
  • the thickening is 5220 mPas.
  • Examples 2-4 are produced analogously to Example 1. The starting materials are shown in Table 1.
  • Example 5 comparative example: corresponding to EP-A-1686093, Example 1.
  • hydrophilic silicas of Examples 1-5 are mixed with silicon carbide, SiC 1000, Keyvest and glass fibres, PSF 61 1/2,2, Asglawo in a batch mixer, Amixon, in a 82: 15:3 weight ratio.
  • the tamped densities of the hydrophilic pulverulent thermal-insulation material are shown in Table 3.
  • the hydrophilic pulverulent thermal-insulation material is compressed using a press to form a hydrophilic sheet of dimensions 20 mm x 330 mm x 330 mm.
  • the pressing force during the compression of the hydrophilic, pulverulent thermal-insulation material is shown in Table 3, and the density of the hydrophilic sheets is shown in Table 4.
  • Figure 1 shows the profile of the thermal conductivity (y-axis; in 10 3 Wnrr K ⁇ 1 ) of the hydrophilic thermal-insulation sheets according to the invention from Examples 1-3 as a function of the pressure (x-axis; in hPa).
  • HMDS hexamethyldisilazane
  • the density of the hydrophobic thermal-insulation sheet and also the thermal conductivity and the flexural strength of the hydrophilic and the hydrophobic thermal-insulation sheets are shown in Table 4.
  • the hydrophobic thermal-insulation sheets exhibit, in accordance with EN 12087:2013, a very low area-based water absorption in the region of 0.01 kg/m 2 .
  • PTamped Tamped density of the hydrophilic, pulverulent thermal-insulation material
  • Fp re ss Pressing force during the compression of the hydrophilic, pulverulent thermal-insulation material
  • Anrihydraphob Increase in mass of the hydrophilic thermal-insulation sheet during the hydrophobization

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Silicon Compounds (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

Hydrophilic, pulverulent thermal-insulation material containing from 5 to 30% by weight, based on the hydrophilic, pulverulent thermal-insulation material, of an IR opacifier and from 70 to 95% by weight, based on the hydrophilic, pulverulent thermal-insulation material, of aggregated particles of a hydrophilic silica having a BET surface area of 200-600 m2/g and a thickening of at least 5000 mPas, wherein the thickening is determined in a dispersion of the silica in an unsaturated polyester resin, process for the production thereof, and use for producing a thermal-insulation sheet or thermal- insulation granules.

Description

Thermal-insulation materials based on high-thickening silicas
The invention relates to a thermal-insulation material containing a high-thickening silica, to a process for the production thereof and to the use thereof for producing a thermal-insulation sheet or thermal- insulation granules.
Besides their non-combustibility and their physiological harmlessness, microporous thermal-insulation materials based on fumed silicas or silica aerogels are distinguished especially by a high thermal- insulation effect in the range from minus 200°C right up to 1000°C. Microporous sheets based on fumed silicas or aerogels, opacifiers and reinforcing fibres have been considered to be state of the art for decades and are successfully used in numerous thermal-insulation applications.
In EP-A-623567 or W098/175596, a thermal-insulation sheet containing a finely divided silica is thermally treated in an oven at temperatures of up to 1000°C and thereby cured.
WO2016/162261 discloses a process for producing a thermal-insulation sheet, which process involves treating a hydrophilic silica-comprising thermal-insulation sheet with ammonia by introducing the thermal-insulation sheet into a chamber and supplying gaseous ammonia until the pressure difference Δρ is > 20 mbar. As a result, it is possible to improve the compressive strengths of thermal-insulation sheets even after compression.
WO201 1/150987 discloses a thermal-insulation powder mixture having a bulk density of 20-60 g/l, which mixture contains at least one silica having a BET surface area of 130-1200 m2/g and having a D50 value of less than 60 μιτι and at least one fibrous material having a fibre diameter of 1-50 μιτι. The silica can be hydrophilic and hydrophobic silicas. Furthermore, a thermal-insulation sheet obtained from the thermal-insulation powder mixture is disclosed. To this end, use is made of hydrophilic silicas and solid, hydrophobic materials such as PVDF or mixtures of hydrophilic and hydrophobic silica. Owing to the desired hydrophobicity, the thermal-insulation sheets thus obtained cannot be subsequently cured by temperature treatment, since they would lose their hydrophobic properties as a result.
However, WO201 1/069923 states that hydrophobic silicas cannot be compressed. Furthermore, it is stated that an after-treatment of the insulation material with organosilanes after compression is highly complicated, since the core material can only be penetrated very slowly and at high pressure. In addition, in this process, the structure of the core material is sometimes destroyed. Therefore, it is proposed to use non-volatile, functional organosilanes having boiling points of more than 130°C, preferably those which can be evaporated without decomposition. Such an organosilane is then added to a hydrophilic silica, the mixture compressed and then thermally treated. However, the sheet thus obtained exhibits a non-uniform hydrophobization.
Binder-free, hydrophilic-silica-containing thermal-insulation sheets have a mechanical sheet stability in need of improvement. In principle, it is possible to increase the stability of hydrophilic thermal- insulation sheets by thermal treatment at temperatures of approximately 600-1000°C or by a chemical treatment, for example with ammonia. In general, such a treatment is also associated with an undesired rise in thermal conductivity. Moreover, such a treatment means that an additional process step becomes necessary.
In the case of sheets containing a hydrophobic silica, neither a thermal nor a chemical treatment is possible, since the sheets would lose their hydrophobic properties as a result.
It is therefore a technical object of the present invention to provide a thermal-insulation material and a resultant thermal-insulation sheet or resultant thermal-insulation granules having primarily improved thermal conductivity. In addition, it is intended that the mechanical properties of the thermal-insulation sheets known from the prior art be improved. It is a further technical object to provide a process which leads to said thermal-insulation material and thermal-insulation sheet without the need for a subsequent treatment step.
The invention provides a hydrophilic, pulverulent thermal-insulation material containing from 5 to 30% by weight, based on the hydrophilic, pulverulent thermal-insulation material, of an IR opacifier and from 70 to 95% by weight, based on the hydrophilic, pulverulent thermal-insulation material, of aggregated particles of a hydrophilic silica having a BET surface area of 200-600 m2/g and a thickening of at least 5000 mPas, wherein the thickening is determined in a dispersion of the silica in an unsaturated polyester resin.
A hydrophilic, pulverulent thermal-insulation material is to be understood to mean a material in which the surface of the particles forming the powder behaves hydrophilically upon stirring into water, i.e. the surface is completely wetted by water and thus has a contact angle of less than 90° with respect to water. Contact angle determination is, for example, described in EP-A-1433749.
In the context of the present invention a hydrophilic silica is to be understood as meaning a silica whose surface bears no organic groups, such as alkyl groups for example, that would impart a hydrophobic, water-repelling character to it. On the contrary, the groups disposed at the surface shall consist completely or to the greatest possible extent of Si-OH and Si-O-Si groups. Preferably, the thermal-insulation material according to the invention comprises a hydrophilic silica having a silanol group density SiOH of 1.8 to 2.5 OH/nm2, determined in accordance with the LiAlhU method by J. Mathias and G. Wannemacher, Journal of Colloid and Interface Science 125 (1988).
A silica is referred to as a hydrophobic silica when the Si-OH and Si-O-Si groups disposed at the surface are at least partly reacted with an organic compound which imparts a hydrophobic, water- repelling character to the material.
Preferably, the hydrophilic, pulverulent thermal-insulation material contains a fumed silica as hydrophilic silica. This has a specific structure. Primary particles of size from 5 to 50 nm accrete to give larger aggregates which in turn combine to give even larger structures, the agglomerates. Fumed silica is produced via flame hydrolysis of volatile silicon compounds such as organic and inorganic chlorosilanes. This process comprises bringing a vaporized, hydrolysable silicon halide to reaction with a flame formed by combustion of hydrogen and an oxygenous gas. The combustion flame here provides water for the hydrolysis of the silicon halide, and sufficient heat for the hydrolysis reaction. If a non-halogenated silicon compound, for example a siloxane, is employed as raw material, the corresponding thermal oxidative conversion thereof to form silica is called flame pyrolysis. A silica produced by flame hydrolysis or flame pyrolysis is termed fumed silica. This process initially forms primary particles which are virtually free of interior pores. These primary particles then fuse during the process via so-called "sinter necks" to afford aggregates. By virtue of this structure, fumed silica is an ideal thermal-insulation material, since the aggregate structure provides adequate mechanical stability, minimizes heat transfer due to conductivity in the solid by way of the "sinter necks", and produces sufficiently high porosity.
The BET surface area of the silica is 200-600 m2/g, preferably 250-400 m2/g. It can be determined in accordance with DIN 66131. This range is most suitable with regard to thermal conductivity.
The thickening of the hydrophilic silica present in the thermal-insulation material according to the invention is at least 5000 mPas, preferably 5000-10 000 mPas, particularly preferably 7000-9000 mPas. The thickening, in mPas, is determined in a dispersion of a silica in an unsaturated polyester resin. Suitable unsaturated polyester resins encompass cocondensates of ortho- or meta-phthalic acid and maleic acid or fumaric acid, or the anhydrides thereof, and a low molecular weight diol, for example ethylene glycol, propane-1 ,2- or -1 ,3-diol, butane-1 ,2- or -1 ,3- or -1 ,4-diol or neopentyl glycol ((CH3)2C(CH20H)2), or polyols, such as pentaerythritol, preferably dissolved in an amount of 30% to 80% by weight, preferably 60% to 70% by weight, in an olefinic reactive diluent as solvent, for example monostyrene. In general, the viscosity of the polyester resin is 900-1200 mPas at a temperature of 22°C. A suitable unsaturated polyester resin is, for example, Palatal® P6-01 (DSM; viscosity at 23°C: 900-1200 mPas).
It has been found that the thickening is, inter alia, most suitable for describing the hydrophilic silica used in the hydrophilic pulverulent thermal-insulation material according to the invention. The thickening value is customarily used for characterizing the rheological properties of diverse formulations containing silicas. Said value may be dependent on many material properties of the silicas used, such as their porosity, aggregate shape and aggregate size. It has now been found that, surprisingly, there is a direct link between this easy-to-measure parameter and the thermal conductivity of thermal-insulation materials containing silicas: a higher thickening of the silica leads to a lower thermal conductivity of thermal-insulation materials.
The silicas known from the prior art and used as thermally insulating materials are customarily produced from the corresponding halogen-containing silanes by flame hydrolysis. For instance, WO2016/020215A1 and DE102015206433A1 describe thermal-insulation materials based on
AEROSIL® 300, a silica produced from silicon tetrachloride by flame hydrolysis and having a BET of 300 m2/g. From "Technical Bulletin Fine Particles: Basic Characteristics of AEROSIL® Fumed Silica, Number 1 1 ", page 56, published in 2003, it is known that the thickening (viscosity) of all customary AEROSIL® product types, including AEROSIL® 300, measured in an unsaturated polyester resin
(Ludopal P6), is less than 3500 mPas. The same data in relation to the thickening (<3500 mPas) of fumed silicas having a BET of 130 to 380 m2/g in an unsaturated polyester resin are additionally reported in EP 0038900 A1 , on page 2. Hydrophilic, aggregated silicas having a BET surface area of 200-600 m2/g and a thickening of at least 5000 mPas are known in the prior art via EP 0038900 A1 . Said silicas can be obtained when siloxanes such as octamethyltrisiloxane, hexamethylcyclotrisiloxane (D3) or
octamethylcyclotetrasiloxane (D4) are used in the flame hydrolysis under certain reaction conditions. The use of such high-thickening silicas, especially in combination with IR opacifier, in thermal- insulation materials is not known from the prior art.
Moreover, it has been found to be advantageous for the mechanical properties and the thermal conductivity of a thermal-insulation sheet when the hydrophilic, aggregated silica has a highest possible silanol group density. For instance, preference is given to a hydrophilic silica to which 3≤ A3745/A1870≤ 5 and 3≤ A3660 A1870≤ 4 applies, where A3745, A3660 and Awo correspond to the absorbance of the IR vibration band at 3745 cm 1, 3660 cm"1 and 1870 cm 1, respectively.
The IR spectra are obtained on powder layers by means of a Bruker IFS 85 FT-IR spectrometer. The sample to be determined is sprinkled onto an NaCI monocrystalline window. The measurement is carried out with the following parameters: Resolution: 2 cm"1 ; measurement interval: 4500 cm"1 to 100 cm"1; apodization function: triangular; number of scans: 128. The absorbance is determined as follows: To define the baseline, tangents to the baseline are drawn in the region between
approximately 3800 cm"1 and approximately 2800 cm"1 and in the region between approximately 2100 cm"1 and 1750 cm"1. From the maximum of the relevant bands 3745, 3660 and 1870 cm 1 , the perpendicular is dropped to the baseline, and the respective heights from the maximum to the baseline are measured in mm. It is assumed that the basis of the vibration band at 3660 cm"1 is a bridged SiOH vibration and the basis of the vibration band at 3745 cm"1 is a free SiOH vibration. The absorbance of these bands is normalized by dividing by the absorbance of the band of the SiO combination vibration at 1870 cm"1.
Furthermore, it is intended that the hydrophilic, pulverulent thermal-insulation material according to the invention preferably have a tamped density of 30-70 g/l.
In addition to a silica, the hydrophilic, pulverulent thermal-insulation material also contains at least one IR opacifier. This is preferably selected from the group consisting of titanium oxides, zirconium oxides, ilmenites, iron titanates, iron oxides, zirconium silicates, silicon carbide, manganese oxides, graphite, carbon blacks, or mixtures thereof. Particular preference is given to silicon carbide, titanium oxide, iron oxide or carbon black. The particle size of the opacifiers is generally between 0.1 and 25 μιτι. In the case of silicon carbide and titanium oxides, the average particle diameter dso is preferably 1 to 10 μιτι, particularly preferably 2 to 8 μιτι.
The proportion of IR opacifier, based on the hydrophilic, pulverulent thermal-insulation material, is 5 to 30% by weight. The proportion of hydrophilic silica is preferably 70 to 95% by weight, based on the hydrophilic, pulverulent thermal-insulation material.
For mechanical reinforcement, fibres can be added to the hydrophilic, pulverulent thermal-insulation material. Said fibres can be of inorganic or organic origin and are generally 2 to 10% by weight, based on the sum total of silicas and opacifiers. Examples of inorganic fibres which can be used are glass wool, stone wool, basalt fibres, slag wool and ceramic fibres, consisting of melts of aluminium oxide and/or silicon dioxide, and also of other inorganic metal oxides. Examples of pure silicon dioxide fibres are silica fibres. Examples of organic fibres which can be used are cellulose fibres, textile fibres and synthetic fibres. The diameter of the fibres is preferably 1 to 30 μιτι, more preferably 5 to 15 μιτι, very preferably 6 to 9 μιτι, and the length is preferably 1 to 25 mm, more preferably 3 to 12 mm.
Furthermore, the hydrophilic thermal-insulation material can contain inorganic additives. Materials that can be used are arc silicas, SiC -containing fly ash produced via oxidation reactions of volatile silicon monoxide during electrochemical production of silicon or ferrosilicon. It is moreover possible to use naturally occurring SiC -containing compounds such as diatomaceous earths and kieselguhrs.
It is likewise possible to add thermally expanded minerals such as perlites and vermiculites, and fine- particle metal oxides such as aluminium oxide, titanium dioxide, iron oxide. The proportion of the inorganic additives can be up to 25% by weight, based on the hydrophilic thermal-insulation material. Preferably, the thermal-insulation material is free of said inorganic additives as far as possible.
The invention further provides a process for producing the hydrophilic pulverulent thermal-insulation material according to the invention, comprising the following steps:
a) producing a fumed silica from a siloxane by the flame hydrolysis or flame pyrolysis thereof;
b) mixing the fumed silica with an IR opacifier.
In step a) of the process according to the invention, the hydrolysable and oxidizable siloxane that is used is combined with at least one fuel and oxygen for the flame hydrolysis or flame pyrolysis reaction, yielding a silica as product. A possible fuel is, for example, hydrogen, methane, ethane, propane, butane and/or natural gas. The oxygen source used is preferably air.
Preferably, the siloxane is selected from the group consisting of octamethyltrisiloxane,
hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4) or mixtures thereof.
It is particularly advantageous when, in the process according to the invention, oxygen is present in excess compared to combustible constituents of the reaction mixture. The index λ (lambda) is the ratio of the amount of oxygen present in the reaction mixture divided by the amount of oxygen needed for the complete combustion of all combustible constituents of the reaction mixture, each in mol/h.
Preferably, λ greater than 4, particularly preferably greater than 5.5, is set; very particularly preferably, λ of 5.5 to 12.5 is chosen.
To produce the hydrophilic, pulverulent thermal-insulation material according to the invention, the constituents of the thermal-insulation material can be mixed in step b) of the process according to the invention by means of, for example, planetary mixers, cyclone mixers, dissolvers, fluid mixers, fine- impact mills, air stream mills or classifier mills. The invention further provides for the use of the hydrophilic pulverulent thermal-insulation material according to the invention for producing a hydrophilic or hydrophobic thermal-insulation sheet or hydrophilic or hydrophobic thermal-insulation granules.
The invention further provides a hydrophilic thermal-insulation sheet or hydrophilic thermal-insulation granules containing hydrophilic, pulverulent thermal-insulation material according to the invention.
The invention further provides a hydrophilic thermal-insulation sheet having a density of 130-200 g/l, containing 70-95% by weight of aggregated particles of a hydrophilic silica having a BET surface area of 300-400 m2/g and a thickening of at least 5000 mPas, wherein the thickening is determined in a dispersion of the silica in an unsaturated polyester resin, 4-30% by weight of IR opacifier, 1-10% by weight of fibres and 0-25% by weight of fine additives. It has a thermal conductivity TC at standard pressure of 18 < TC < 20 mW/(m · K) and a flexural strength of at least 40 kPa, preferably 50-75 kPa. Its half-value pressure, defined as the gas pressure at which the gas thermal conductivity is halved, i.e. approximately 13 mW/(m · K), is more than 800 hPa, preferably 830-880 hPa. In the literature, a half-value pressure of 600-800 mbar is determined for microporous materials. The hydrophilic thermal- insulation sheet according to the invention is distinctly above this value.
The invention further provides a process for producing a thermal-insulation sheet or thermal-insulation granules, comprising compressing or compacting the hydrophilic, pulverulent thermal-insulation material according to the invention to obtain a hydrophilic thermal-insulation sheet or hydrophilic thermal-insulation granules. To produce the hydrophilic thermal-insulation sheet, the hydrophilic thermal-insulation material and the inorganic fibres can be compressed in either a batchwise or continuous manner according to known processes. According to WO2005/028195, hydrophilic thermal-insulation sheets are continuously produced by means of a belt press. A thermal or chemical after-treatment of the hydrophilic thermal-insulation sheet in order to improve its mechanical properties is possible, though not necessary because of the thermal-insulation material according to the invention that is used.
A thus produced hydrophilic thermal-insulation sheet or the hydrophilic thermal-insulation granules can additionally be hydrophobized with a hydrophobization agent. Preferred hydrophobization agents are organosilanes selected from the group consisting of Rn-Si-X4-n, R3Si-Y-SiR3, RnSinOn, (CH3)3-Si-(0- Si(CH3)2)n-OH, HO-Si(CH3)2-(0-Si(CH3)2)n-OH, where n = 1-8; R = -H, -CH3, -C2H5; X= -CI, -Br; -OCH3, -OC2H5, -OC3H8, Y= N H , O.
Particularly preferably, the hydrophilic thermal-insulation sheet is hydrophobized by:
a) introducing the hydrophilic thermal-insulation sheet into a chamber and supplying to the chamber one or more hydrophobization agents that are vaporous under the reaction conditions, preferably organosilanes, until the pressure difference Δρ > is 20 mbar, where Δρ = p2 - p1 , where p1 = pressure in the chamber before introduction of the hydrophobization agent, where p1 is less than atmospheric pressure, and p2 = pressure in the chamber at which the introduction of the organosilane is stopped,
b) the temperature in the chamber is 20 to 300°C and c) from the time at which the organosilane is added, leaving the sheet for additionally 1 minute to 1 hour in the chamber.
The hydrophobic thermal-insulation sheet produced from the hydrophilic, pulverulent thermal- insulation material according to the invention can preferably have a density of 150-200 g/l, and can contain 70-95% by weight of aggregated particles of a hydrophobic silica having a BET surface area of 300-400 m2/g and 3-8% by weight of carbon, based on the hydrophobic silica, 4-30% by weight of IR opacifier, 1-10% by weight of fibres and 0-25% by weight of fine additives.
It has a thermal conductivity TC at standard pressure of 16 < TC≤ 18.5 mW/(m · K) and a flexural strength of at least 50 kPa, preferably 60-80 kPa.
The hydrophilic thermal-insulation granules producible from the hydrophilic, pulverulent thermal- insulation material according to the invention can be produced by compacting, generally by compaction, of the hydrophilic, pulverulent thermal-insulation material according to the invention. The granules obtained after compacting can be cured in a treatment step, specifically by thermal treatment at a temperature of 200-1200°C or by treatment with gaseous ammonia. The hydrophilic, thermally insulating granules with or without curing can be subjected to a further treatment step with a hydrophobization agent to form hydrophobic, thermally insulating granules. Preferred
hydrophobization agents are organosilanes selected from the group consisting of Rn-Si-X4-n,
R3Si-Y-SiR3, RnSinOn, (CH3)3-Si-(0-Si(CH3)2)n-OH, HO-Si(CH3)2-(0-Si(CH3)2)n-OH, where n = 1-8; R = -H, -CH3, -C2H5; X= -CI, -Br; -OCH3, -OC2H5, -OC3H8, Y= NH, O. Examples
Analytical methods
Hydrophilic silica
Thickening: 7.5 g of hydrophilic silica and 142.5 g of unsaturated polyester resin Palatal® P6-01 (DSM; viscosity at 23°C: 900-1200 mPas) are dispersed using the dissolver Dispermat AE02-C1 , VMA- Getzmann (diameter of dissolver disc: 50 mm) for a period of 5 minutes at 3000 min-1.
60 g of this dispersion are admixed with a further 63 g of Palatal® P6-01 and 27 g of a solution of monostyrene and paraffin having a congealing point of 46-48°C, monostyrene/paraffin weight ratio = 100/0.4, and dispersed for a period of 3 minutes at 1500 min"1.
The dispersion obtained has a content of hydrophilic silica of 2.0% by weight. Air bubbles are removed by centrifugation. The dispersion is adjusted in temperature to 22°C and the viscosity thereof is determined using a Physica-Rheolab MC1 , Anton Paar.
Hydrophilic, pulverulent thermal-insulation material:
Tamped density in accordance with ISO 787-1 1 : 1995
Thermal-insulation sheets Thermal conductivity in accordance with DIN EN 12667:2001 at a mean temperature of 10°C and a contact pressure of 250 Pa.
Density in accordance with DIN EN 1602:2013
Flexural strength in accordance with DIN EN 12089:2013. Here, the flexural strength is determined according to test method B on sheets approximately 20 mm thick.
Hydrophilic thermal-insulation sheet:
Half-value pressure, defined as the gas pressure at which the gas thermal conductivity is halved, as per R. Caps et al., Vacuum 82 (2008) 691-699.
Hydrophobic thermal-insulation sheet
Warmedammstoffe fiir das Bauwesen - Bestimmung der Wasseraufnahme bei langzeitigem
Eintauchen [Thermal insulating products for building applications - Determination of long-term water absorption by immersion]; German version EN 12087:2013
The long-term water absorption upon partial immersion is determined by measuring the change in weight of a test specimen, the underside of which is immersed in water for a period of 28 days. Test method 1A (drip-off).
Hydrophilic silica
The hydrophilic silicas are produced on the basis of EP-A-38900
Example 1 : In an evaporator, 1.5 kg/h of octamethylcyclotetrasiloxane are evaporated, and mixed with 14.5 Nm3/h of air (primary air). The siloxane/air mixture is then introduced into a burner, where it is mixed and ignited with 0.80 Nm3/h of hydrogen (core hydrogen). In addition, a further 15 Nm3/h of air (secondary air) is supplied. To stabilize the flame, 0.35 Nm3/h of hydrogen (shell hydrogen) is additionally introduced through an annular gap surrounding the burner mouth.
The BET surface area of the hydrophilic silica obtained is 312 m2/g. The thickening is 5220 mPas.
Examples 2-4 are produced analogously to Example 1. The starting materials are shown in Table 1. Example 5 (comparative example): corresponding to EP-A-1686093, Example 1.
The BET surface area, thickening and absorbances of the hydrophilic silicas are shown in Table 2.
Hydrophilic pulverulent thermal-insulation material
The hydrophilic silicas of Examples 1-5 are mixed with silicon carbide, SiC 1000, Keyvest and glass fibres, PSF 61 1/2,2, Asglawo in a batch mixer, Amixon, in a 82: 15:3 weight ratio.
The tamped densities of the hydrophilic pulverulent thermal-insulation material are shown in Table 3.
Hydrophilic thermal-insulation sheet
The hydrophilic pulverulent thermal-insulation material is compressed using a press to form a hydrophilic sheet of dimensions 20 mm x 330 mm x 330 mm. The pressing force during the compression of the hydrophilic, pulverulent thermal-insulation material is shown in Table 3, and the density of the hydrophilic sheets is shown in Table 4.
Figure 1 shows the profile of the thermal conductivity (y-axis; in 10 3 Wnrr K ~1) of the hydrophilic thermal-insulation sheets according to the invention from Examples 1-3 as a function of the pressure (x-axis; in hPa).
A= half the gas thermal conduction = 13 mW/(m*K); B = half-value pressure = 850 mbar.
Hydrophobic thermal-insulation sheet
Subsequently, the hydrophilic sheet is introduced into a chamber and heated to 165°C. Meanwhile, hexamethyldisilazane (HMDS) is evaporated in a separate vessel. The chamber is evacuated to a negative pressure and then the evaporated HMDS is conducted into the chamber. After a reaction time of one hour, a hydrophobic sheet can be removed.
The increase in mass of the hydrophilic thermal-insulation sheet during the hydrophobization is shown in Table 3.
The density of the hydrophobic thermal-insulation sheet and also the thermal conductivity and the flexural strength of the hydrophilic and the hydrophobic thermal-insulation sheets are shown in Table 4. The hydrophobic thermal-insulation sheets exhibit, in accordance with EN 12087:2013, a very low area-based water absorption in the region of 0.01 kg/m2.
Table 1 : Production of the hydrophilic silicas used
Figure imgf000011_0001
Table 2: Physical/chemical properties of the silicas used
Figure imgf000011_0002
BETs phii = BET surface area of the hydrophilic silica used; r\s Pm = Thickening of the hydrophilic silica used
Table 3: Starting materials, reaction conditions for hydrophilic thermal-insulation sheets
Figure imgf000012_0001
PTamped = Tamped density of the hydrophilic, pulverulent thermal-insulation material; Fpress = Pressing force during the compression of the hydrophilic, pulverulent thermal-insulation material; Anrihydraphob = Increase in mass of the hydrophilic thermal-insulation sheet during the hydrophobization
Table 4: Properties of the hydrophilic and hydrophobic thermal-insulation sheets
Figure imgf000012_0002
p = Density; TC = Thermal conductivity at standard pressure; FS = Flexural strength

Claims

Claims
1. Hydrophilic, pulverulent thermal-insulation material containing from 5 to 30% by weight, based on the hydrophilic, pulverulent thermal-insulation material, of an IR opacifier and from 70 to 95% by weight, based on the hydrophilic, pulverulent thermal-insulation material, of aggregated particles of a hydrophilic silica having a BET surface area of 200-600 m2/g and a thickening of at least 5000 mPas, wherein the thickening is determined in a dispersion of the silica in an unsaturated polyester resin.
2. Hydrophilic, pulverulent thermal-insulation material according to Claim 1 ,
characterized in that the hydrophilic silica is a fumed silica.
3. Hydrophilic, pulverulent thermal-insulation material according to Claim 1 or 2,
characterized in that 3 A374s Ai87o≤ 5 and 3≤ A366o/A o≤ 4 applies to the hydrophilic silica, where A3745, A3660 and Awo correspond to the absorbance of the IR vibration band at 3745 cm" , 3660 cm-1 and 1870 cm 1, respectively.
4. Hydrophilic, pulverulent thermal-insulation material according to Claims 1 to 3,
characterized in that it has a tamped density of 20-70 g/l.
5. Hydrophilic, pulverulent thermal-insulation material according to Claims 1 to 4,
characterized in that the IR opacifier is selected from the group consisting of titanium oxides, zirconium oxides, ilmenites, iron titanates, iron oxides, zirconium silicates, silicon carbide, manganese oxides, graphite, carbon blacks, or mixtures thereof.
6. Process for producing the hydrophilic pulverulent thermal-insulation material according to any of Claims 1 to 5, comprising the following steps:
a) producing a fumed silica from a siloxane by the flame hydrolysis or flame pyrolysis thereof; b) mixing the fumed silica with an IR opacifier.
7. Process according to Claim 6, characterized in that the siloxane is selected from the group consisting of octamethyltrisiloxane, hexamethylcyclotrisiloxane (D3),
octamethylcyclotetrasiloxane (D4) or mixtures thereof.
8. Process according to Claim 6 or 7, characterized in that a lambda value of greater than 5.5 is set in step a).
9. Use of the hydrophilic pulverulent thermal-insulation material according to any of Claims 1 to 5 for producing a hydrophilic or hydrophobic thermal-insulation sheet or hydrophilic or hydrophobic thermal-insulation granules.
10. Hydrophilic thermal-insulation sheet or hydrophilic thermal-insulation granules containing
hydrophilic, pulverulent thermal-insulation material according to any of Claims 1 to 5.
11. Hydrophilic thermal-insulation sheet according to Claim 10 having a density of 130-200 g/l, containing 70-95% by weight of aggregated particles of a hydrophilic silica having a BET surface area of 300-400 m2/g and a thickening of at least 5000 mPas, 4-30% by weight of IR opacifier, 1-10% by weight of fibres and 0-25% by weight of fine additives, wherein the thickening is determined in a dispersion of the silica in an unsaturated polyester resin.
12. Process for producing a thermal-insulation sheet or thermal-insulation granules, comprising compressing or compacting the hydrophilic, pulverulent thermal-insulation material according to any of Claims 1 to 5 to obtain a hydrophilic thermal-insulation sheet or hydrophilic thermal- insulation granules.
13. Process according to Claim 12, characterized in that the hydrophilic thermal-insulation sheet or the hydrophilic thermal-insulation granules is/are additionally hydrophobized with a hydrophobization agent.
14. Process according to Claim 13, characterized in that
a) the hydrophilic thermal-insulation sheet is introduced into a chamber and one or more organosilanes that are vaporous under the reaction conditions are supplied, as
hydrophobization agent(s), to the chamber until the pressure difference Δρ > is 20 mbar, where Δρ = p2 - p1 , where p1 = pressure in the chamber before introduction of the organosilane, where p1 is less than the atmospheric pressure, and p2 = pressure in the chamber at which the introduction of the organosilane is stopped,
b) the temperature in the chamber is 20 to 300°C and
c) from the time at which the organosilane is added, the sheet is left for additionally 1 minute to 1 hour in the chamber.
PCT/EP2018/068255 2017-07-14 2018-07-05 Thermal-insulation materials based on high-thickening silicas WO2019011780A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP17181408.0A EP3428135A1 (en) 2017-07-14 2017-07-14 Heat insulating materials based on high-density silicic acid
EP17181408.0 2017-07-14

Publications (1)

Publication Number Publication Date
WO2019011780A1 true WO2019011780A1 (en) 2019-01-17

Family

ID=59485131

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2018/068255 WO2019011780A1 (en) 2017-07-14 2018-07-05 Thermal-insulation materials based on high-thickening silicas

Country Status (2)

Country Link
EP (1) EP3428135A1 (en)
WO (1) WO2019011780A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021069351A1 (en) * 2019-10-07 2021-04-15 Evonik Operations Gmbh Silica-based thermal-insulation sheet coated with intumescent composition

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110256035B (en) * 2019-06-24 2022-06-21 广州晖能环保材料有限公司 Preparation method of high-strength nanometer thermal insulation board and high-strength nanometer thermal insulation board

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0038900A1 (en) 1980-04-25 1981-11-04 Degussa Aktiengesellschaft Process for the production of pyrogenic silica
EP0623567A1 (en) 1993-05-06 1994-11-09 Wacker-Chemie GmbH Process for preparing microporous bodies with thermal insulating properties
WO1998017596A1 (en) 1996-10-24 1998-04-30 Wacker-Chemie Gmbh Heat insulating moulded body and process for producing the same
EP1433749A1 (en) 2002-12-20 2004-06-30 Wacker-Chemie GmbH Wettable silylated metal oxides
WO2005028195A1 (en) 2003-08-28 2005-03-31 Wacker-Chemie Gmbh Continuous method for producing a thermal insulation board
EP1686093A2 (en) 2005-01-12 2006-08-02 Degussa AG Pyrogenically produced silicium dioxide
WO2011069923A1 (en) 2009-12-11 2011-06-16 Wacker Chemie Ag Hydrophobic thermal insulation
WO2011150987A1 (en) 2010-05-31 2011-12-08 Wacker Chemie Ag Insulation having a layered structure
WO2016020215A1 (en) 2014-08-08 2016-02-11 Evonik Degussa Gmbh Method for producing a hydrophobic heat-insulating molded body
WO2016162261A1 (en) 2015-04-10 2016-10-13 Evonik Degussa Gmbh Method for producing a molded heat-insulating element

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0038900A1 (en) 1980-04-25 1981-11-04 Degussa Aktiengesellschaft Process for the production of pyrogenic silica
EP0623567A1 (en) 1993-05-06 1994-11-09 Wacker-Chemie GmbH Process for preparing microporous bodies with thermal insulating properties
WO1998017596A1 (en) 1996-10-24 1998-04-30 Wacker-Chemie Gmbh Heat insulating moulded body and process for producing the same
EP1433749A1 (en) 2002-12-20 2004-06-30 Wacker-Chemie GmbH Wettable silylated metal oxides
WO2005028195A1 (en) 2003-08-28 2005-03-31 Wacker-Chemie Gmbh Continuous method for producing a thermal insulation board
EP1686093A2 (en) 2005-01-12 2006-08-02 Degussa AG Pyrogenically produced silicium dioxide
WO2011069923A1 (en) 2009-12-11 2011-06-16 Wacker Chemie Ag Hydrophobic thermal insulation
WO2011150987A1 (en) 2010-05-31 2011-12-08 Wacker Chemie Ag Insulation having a layered structure
WO2016020215A1 (en) 2014-08-08 2016-02-11 Evonik Degussa Gmbh Method for producing a hydrophobic heat-insulating molded body
WO2016162261A1 (en) 2015-04-10 2016-10-13 Evonik Degussa Gmbh Method for producing a molded heat-insulating element
DE102015206433A1 (en) 2015-04-10 2016-10-13 Evonik Degussa Gmbh Process for the preparation of a thermal insulation molding

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
IND. EVONIK: "Sicherheitsdatenblatt Aerosil 300", SICHERHEITSDATENBLATT (EC1907/2006) AEROSIL 300, 16 November 2015 (2015-11-16), pages 1 - 9, XP055429644, Retrieved from the Internet <URL:http://www.reininghaus.de/index.php/content/download/4902/52855/file/Aerosil-300-SDB-Evonik.pdf> [retrieved on 20171128] *
J. MATHIAS; G. WANNEMACHER, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 1988, pages 125
R. CAPS ET AL., VACUUM, vol. 82, 2008, pages 691 - 699

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021069351A1 (en) * 2019-10-07 2021-04-15 Evonik Operations Gmbh Silica-based thermal-insulation sheet coated with intumescent composition

Also Published As

Publication number Publication date
EP3428135A1 (en) 2019-01-16

Similar Documents

Publication Publication Date Title
US5708069A (en) Method for making hydrophobic silica gels under neutral conditions
RU2721110C2 (en) Method for making airgels and composite material based on airgel
KR102353289B1 (en) Method for producing a hydrophobic heat-insulating molded body
CN112424144B (en) Method for hydrophobicizing shaped insulating material bodies based on silicon dioxide at ambient pressure
KR101681439B1 (en) Method for producing a thermally insulating mixture
EP1276695A1 (en) Precipitated silicas, silica gels with and free of deposited carbon from caustic biomass ash solutions and processes
KR20120070948A (en) Manufacturing method of hydropobic silica aerogel powder with insulating performance
JP5732384B2 (en) Flexible silica-containing foam
KR20060082382A (en) Pyrogenically produced silicon dioxide powder
KR101470764B1 (en) Silicon dioxide powder having special surface properties and toner composition containing said powder
JP4263325B2 (en) Toner and / or toner mixture
US20190276358A1 (en) Method for producing hydrophobic heat insulation material
WO2019011780A1 (en) Thermal-insulation materials based on high-thickening silicas
JP2023511850A (en) Fumed silica with modified surface activity
JPH0116794B2 (en)
Heley et al. Fine low density silica powders prepared by supercritical drying of gels derived from silicon tetrachloride
CA1318481C (en) Method of making high purity dense silica of large particle size
JP4352355B2 (en) Ultrafine silicon dioxide and production method thereof
JP2023516146A (en) Silica-based heat insulating molding
CN112300445B (en) Ceramic refractory filler and preparation method and application thereof
KR102150978B1 (en) Method for producing hydrophobic silica molded article
CN115368113A (en) Method for recycling waste porcelain
JPH03199115A (en) Spherical monodispersion beta-sic particle and its production

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 18734594

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 18734594

Country of ref document: EP

Kind code of ref document: A1