EP2504140A1

EP2504140A1 - Coating composition for foam particles

Info

Publication number: EP2504140A1
Application number: EP10782276A
Authority: EP
Inventors: Benjamin Nehls; Tatiana Ulanova; Sabine Fuchs; Klaus Hahn; Bernhard Schmied
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2009-11-27
Filing date: 2010-11-24
Publication date: 2012-10-03
Also published as: KR20120102729A; RU2012126601A; AU2010323202A1; CN102712117A; WO2011064230A1; US20120270052A1

Abstract

The invention relates to a coating composition, to foam particles coated therewith, to a method for producing foam bodies, and to the use thereof.

Description

The invention relates to a coating composition, coated foam particles, methods for producing foam moldings and their use.

Particle foams are usually obtained by combining foam particles, for example prefoamed expandable polystyrene particles (EPS) or expanded polypropylene particles (EPP) in closed molds by means of steam.

Flame-retardant polystyrene foams are generally equipped with halogen-containing flame retardants, such as hexabromocyclododecane (HBCD). However, the approval as an insulating material in the construction sector is limited to certain applications. One of the reasons for this is the melting and dripping of the polymer matrix in case of fire. In addition, the halogen-containing flame retardants can not be used without restriction in terms of their toxicological properties.

WO 00/050500 A1 describes flameproofed foams of prefoamed polystyrene particles which are mixed together with an aqueous sodium silicate solution and a latex of a high molecular weight vinyl acetate copolymer, poured into a mold and dried in air while shaking. This results in only a loose bed of polystyrene particles that are glued together at a few points and therefore have only insufficient mechanical strength.

WO 2005/105404 A1 describes an energy-saving process for the production of foam moldings, in which the prefoamed foam particles are coated with a resin solution which has a lower softening temperature than the expandable polymer. The coated foam particles are then sealed in a mold using external pressure or by post-expansion of the foam particles with hot steam.

WO 2007/023089 A1 describes a process for producing foam moldings from prefoamed foam particles which have a polymer coating. The preferred polymer coating used is a mixture of a waterglass solution, waterglass powder and a polymer dispersion. If desired, hydraulic binders based on cement or metal salt hydrates, for example aluminum hydroxide, may be added to the polymer coating. A similar process is described in WO 2008/0437 A1, according to which the coated foam particles dried and then processed into a fire and heat resistant foam moldings.

WO 00/52104 A1 relates to a fire-proofing layer-forming fire protection coating based on foam-forming and carbon-forming substances in the event of fire, which contains melamine polyphosphate as the blowing agent. Information on water resistance is not included.

WO 2008/043700 A1 relates to a process for producing coated foam particles with a water-insoluble polymer film. WO 2009/0371 16 relates to a coating composition for foam particles containing a clay mineral, an alkali metal silicate and a film-forming polymer.

Hydraulic binders such as cement bind in an aqueous slurry with carbon dioxide even at room temperature. As a result, embrittlement of the foam plate occur. In addition, the foam panels produced according to the cited prior art do not withstand temperatures of over 800 ° C in case of fire and collapse in case of fire. The known coating compositions are in need of improvement in view of the simultaneous improvement of flame / heat resistance and their water resistance in water exposure or in increased humidity. Many known materials lose their original shape after a short time in the case of direct water exposure. In addition, if a standard fire test is performed, such materials often completely lose their structural integrity. As a rule, this leaves powdery mixtures which no longer meet the technical requirements.

WO / 2004/022505 describes the preparation of an agglomerate-free, ceramic nanoparticle dispersion which enables homogeneous and uniform distribution of the nanoparticles in material systems to be prepared or supplemented.

In EP1043094 A1 a Si0 ₂ dispersion is described as a binder. It is about processes for the production of castings and investment materials. DE 19534764 A1 describes thin, crack-free, preferably transparent and colorless SiO ₂ films, a process for their preparation according to the sol-gel process and their use, for. As membranes, filters, components of laminates or substrates with incorporated functional additives. US-A-3783020 describes anti-hygroscopic coating of electrodes with colloidal Si0 ₂ .

US-A-4045593, EP-A-1537940, EP-A-468778 describe colloidal silica containing binders for various fluxes.

It was an object of the present invention to provide coating compositions for foam particles, coated foam particles and foam moldings which have both sufficient flame / heat resistance and adequate water resistance with prolonged water exposure, in particular in the case of so-called durability tests, in which a building material 65 ° C and where accelerated aging is determined by storage of the samples under certain conditions such as increased temperature, humidity or repetitive freeze-thaw cycles, in particular on the basis of increased humidities (near 100%) and temperatures of the "European Recommendations for Sandwich Panels, Part 1, Design" published on October 23, 2000 by ECCS (European Convention for Constructional Steelwork).

The invention relates to a coating composition for coating foams containing a ceramic material a), optionally an alkali metal silicate b) and optionally a film-forming polymer c), characterized in that in addition nanosize Si0 ₂ particles d) are included.

The ceramic materials to be used according to the invention ceramize in case of fire, that is to say not yet during the preparation of the coating compositions according to the invention and foam particles. Preferred ceramic materials are clay minerals and calcium silicates, in particular the mineral wollastonite.

In a preferred embodiment are included: a) 20 to 70 parts by weight of a ceramic material

b) optionally 20 to 70 parts by weight of an alkali metal silicate

c) 1 to 30 parts by weight of a film-forming polymer

d) 1 to 60, in particular 20 to 40 parts by weight of nanoscale Si0 ₂ particles.

The coating composition is preferably used as an aqueous dispersion, wherein the water content including the water bound, for example, as water of crystallization is preferably in the range of 10 to 40, in particular 15 to 30 wt .-% based on the total aqueous dispersion. In a particularly preferred embodiment, furthermore, e) contains a hydrophobizing amount of a silicon-containing compound, in particular a silicone, in particular 0.2 to 5 parts by weight. In a particularly preferred embodiment, this is a silicone emulsion with silicone particles of different sizes. As a result, a particularly good penetration in porous materials can be achieved.

A preferred coating composition contains a) 30 to 50 parts by weight of a ceramic material

b) 30 to 50 parts by weight of an alkali silicate

c) 5 to 20 parts by weight of a film-forming polymer

d) 5 to 10 parts by weight of nanoscale Si0 ₂ particles

e) 0.5 to 3 parts by weight of a silicone

f) 5 to 40 parts by weight of an infrared absorbing pigment.

The amounts given above each refer to solids based on solids of the coating composition. The components a) to e) or a) to f) preferably add up to 100% by weight.

Preferably, the weight ratio of the ceramic material to alkali silicate in the coating composition is in the range of 1: 2 to 2: 1.

As a ceramic-forming clay minerals a) are particularly suitable allophane Al ₂ [Si0 _5] 0 ₃ ^■ n H ₂ 0, kaolinite Al ₄ [(OH) ₈ | Si ₄ Oio], halloysite Al ₄ [(OH) ₈ | Si ₄ Oi _0] ^■ 2 H ₂ 0, montmorillonite (smectite) (Al, Mg, Fe) ₂ [(OH ₂ | (Si, Al) ₄ Oi _0] ^■ Na _0, ₃ 3 (H ₂ O) _4, vermiculite Mg ₂ (Al, Fe, Mg) [(OH ₂ | (Si, Al) ₄ Oio] ^■ Mg ₀ , ₃ 5 (H ₂ O) ₄ -containing minerals or mixtures thereof Particular preference is given to using kaolin as a ceramic-forming calcium silicate in particular wollastonite is suitable.

The alkali silicate b) used is preferably a water-soluble alkali metal silicate having the composition M ₂ O (SiO ₂ ) _n with M = sodium or potassium and n = 1 to 4 or mixtures thereof. Typically, the coating composition contains as the filming polymer e) an uncrosslinked polymer having one or more glass transition temperatures in the range of -60 ° to + 100 ° C. The glass transition temperatures of the dried polymer film are preferably in the range from -30 ° to + 80 ° C., more preferably in the range from -10 ° to + 60 ° C. The glass transition temperature can be determined by differential scanning calorimetry (DSC, according to ISO 1 1357-2, heating rate 20 K / min) be determined. The molecular weight of the polymer film, determined by gel permeation chromatography (GPC), is preferably below 400,000 g / mol.

The coating composition preferably comprises as film-forming polymer an emulsion polymer of ethylenically unsaturated monomers such as vinylaromatic monomers, such as α-methylstyrene, p-methylstyrene, ethylstyrene, tert-butylstyrene, vinylstyrene, vinyltoluene, 1,2-diphenylethylene, 1,1-diphenylethylene, alkenes such as ethylene or propylene, dienes such as 1, 3-butadiene, 1, 3-pentadiene, 1, 3-hexadiene, 2,3-dimethyl butadiene, piperylene or isoprene, α, ß-unsaturated carboxylic acids such as acrylic acid and methacrylic acid , their esters, in particular alkyl esters, such as C1 -10-alkyl esters of acrylic acid, in particular the butyl esters, preferably n-butyl acrylate, and the C1 -10-alkyl esters of methacrylic acid, in particular methyl methacrylate (MMA), or carboxamides, for example acrylamide and methacrylamide , The polymers may optionally contain from 1 to 5% by weight of comonomers, such as (meth) acrylonitrile, (meth) acrylamide, ureido (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, Acrylamidepropanesulfonic acid, methylolacrylamide or the sodium salt of vinylsulfonic acid. The film-forming polymer is particularly preferably made up of one or more of the monomers styrene, butadiene, acrylic acid, methacrylic acid, C 1-4 -alkyl acrylates, C 1-4 -alkyl methacrylates, acrylamide, methacrylamide and methylolacrylamide. Suitable polymers c) are obtainable, for example, by free-radical emulsion polymerization of ethylenically unsaturated monomers, such as styrene, acrylates or methacrylates, as described in WO 00/50480.

The polymers c) are prepared in a manner known per se, for example by emulsion, suspension or dispersion polymerization, preferably in the aqueous phase. The polymer can also be prepared by solution or bulk polymerization, optionally divided and the polymer particles subsequently dispersed in water in the usual way. During the polymerization, the initiators, emulsifiers or suspension aids, regulators or other auxiliaries customary for the particular polymerization process are used with used; it is polymerized continuously or discontinuously at the usual temperatures and pressures for the respective process in conventional reactors.

The nanoscale Si0 ₂ particles d) to be used according to the invention are preferably aqueous, colloidal SiO ₂ particle dispersions. Preference is given to using an aqueous, colloidal SiO ₂ particle dispersion which is stabilized by onium ions, in particular ammonium ions, such as NH ₄ ⁺ as the counterion (alternatively also by alkali metal oxides of alkaline earth metal ions). The average particle diameter of the Si0 ₂ particles is in the range of 1 to 200 nm, preferably in the range of 10 to 50 nm. The specific surface of the Si0 ₂ particles is generally in the range of 10 to 3000 m ² / g, preferably in the range of 30 to 1000 m ² / g. The solids content of commercial Si0 ₂ particle dispersion depends on the particle size and is generally in the range of 10 to 60, preferably in the range of 30 to 50 wt .-%. Aqueous, colloidal Si0 ₂ particle dispersions can be obtained by neutralization of dilute sodium silicates with acids, ion exchange, hydrolysis of silicon compounds, dispersion of fumed silica or gel precipitation.

The nanoscale Si0 ₂ particles to be used according to the invention are known per se and can be present in different forms depending on the production process. Thus, suitable dispersions can be obtained, for example, based on silica sol, silica gel, pyrogenic silicas, precipitated silicas or mixtures thereof. As is known, silica sols are colloidal solutions of amorphous silica in water, also referred to as silica sols or silica sols. Generally, the silica is in the form of spherical and surface-hydroxylated particles.

The surface of the Si0 ₂ particles may have a charge which is balanced by corresponding counterions. Alkaline-stabilized silica sols generally have a pH of 7 to 1 1, 5 and may be alkalized, for example, with alkali or nitrogen bases. The silica sols may also be weakly acidic as colloidal solutions. Finally, the surface of the brine can be covered with aluminum compounds, for example. In the case of precipitated silicas and fumed silicas, the particles can be present both as so-called primary particles and in the form of secondary particles (agglomerates). The mean particle size specified here according to the invention means the mean particle size determined by means of ultracentrifugation and includes the size of primary particles and any agglomerates present therefrom.

In a preferred embodiment, silicon dioxide dispersions are used in which the Si0 ₂ particles are present as discrete, uncrosslinked primary particles.

The silicone e) to be used according to the invention is preferably an aqueous silicone emulsion. In a particularly preferred embodiment, at least one of the following constituents is contained in the silicone emulsion: silicic acid dietho- xyloctylsilyltrimethylsilyl ester or dimethylsiloxane with aminoethylaminopropylsilsesquioxane (hydroxy-limited) or triethoxyoctylsilane.

To reduce the thermal conductivity, preference is given to using an infrared-absorbing pigment (IR absorber), such as carbon black, coke, aluminum, graphite or titanium dioxide, in amounts of from 5 to 40% by weight, in particular in amounts of from 10 to 30% by weight, based on the solid of the coating used. The particle size of the IR-absorbing pigment is generally in the range of 0.1 to 100 μηη, in particular in the range of 0.5 and 10 μηι.

Carbon black with an average primary particle size in the range from 10 to 300 nm, in particular in the range from 30 to 200 nm, is preferably used. The BET surface area is preferably in the range of 10 to 120 m ² / g. The graphite used is preferably graphite having an average particle size in the range from 1 to 50 μm.

Furthermore, the coating composition flame retardants, such as expanded graphite, borates, in particular zinc borates, in particular ortho-boron phosphate, or intumescent compositions which inflate when exposed to higher temperatures, usually over 80 to 100 ° C, swell, or foam, and a insulating and heat-resistant foam, which protects the underlying insulating foam particles from the effects of fire and heat. When using flame retardants in the polymer coating, it is also possible to achieve adequate fire protection with foam particles containing no, especially no halogenated flame retardants, or to get by with smaller amounts of flame retardants, since the flame retardant concentrated in the polymer coating on the Surface of the foam particles is located and forms a solid scaffolding net when exposed to heat or fire.

The coating composition may, as additional additives, cleave intumescent compositions containing chemically bound water, or at temperatures above 40 ° C, such as metal hydroxides, metal salt hydrates, and metal oxide hydrates.

Suitable metal hydroxides are in particular those of groups 2 (alkaline earth metals) and 13 (boron group) of the Periodic Table. Preferred are magnesium hydroxide, calcium hydroxide, aluminum hydroxide and borax. Particularly preferred is aluminum hydroxide. Suitable metal salt hydrates are all metal salts in whose crystal structure water of crystallization is incorporated. Likewise suitable metal oxide hydrates are all metal oxides which contain water of crystallization incorporated into the crystal structure. The number of crystal water molecules per formula unit may be the maximum possible or below, z. As copper sulfate pentahydrate, trihydrate or monohydrate. In addition to the water of crystallization, the metal salt hydrates or metal oxide hydrates may also contain constitutional water. Preferred metal salt hydrates are the hydrates of metal halides (especially chlorides), sulfates, carbonates, phosphates, nitrates or borates. Suitable examples are magnesium sulfate decahydrate, sodium sulfate decahydrate, copper sulfate pentahydrate, nickel sulfate heptahydrate, cobalt (II) chloride hexahydrate, chromium (III) chloride hexahydrate, sodium carbonate decahydrate, magnesium chloride hexahydrate, and the tin borate hydrates. Magnesium sulfate decahydrate and tin borate hydrates are particularly preferred.

Also suitable as metal salt hydrates are double salts or alums, for example those of the general formula: M'M '^ SCU ^ ^■ 12 H ₂ O. As M ¹ , z. As potassium, sodium, rubidium, cesium, ammonium, thallium or aluminum ions occur. As M ¹ ", for example, aluminum, gallium, indium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, rhodium or iridium.

As metal oxide hydrates z. For example, alumina hydrate and preferably zinc oxide hydrate or boron trioxide hydrate.

In addition to the ceramic materials, the coating may additionally be supplemented with other minerals, for example cements, aluminum oxides, vermicullite or perlite. These may be incorporated into the coating composition in the form of aqueous slurries or dispersions. Cements can also be applied by "powdering" on the foam particles. The water necessary for setting the cement can then be supplied with steam during sintering. The coating composition is used in particular for coating foam particles. The invention therefore furthermore relates to a process for producing coated foam particles by applying the coating composition according to the invention, preferably in the form of an aqueous dispersion, to the foam particles and optionally drying. Expanded polyolefins, such as expanded polyethylene (EPE) or expanded polypropylene (EPP) or prefoamed particles of expandable styrene polymers, in particular expandable polystyrene (EPS), can be used as the foam particles. The foam particles generally have a mean particle diameter in the range of 2 to 10 mm. The bulk density of the foam particles is generally 5 to 100 kg / m ³ , preferably 5 to 40 kg / m ³ and in particular 8 to 16 kg / m ³ , determined according to DIN EN ISO 60.

The foamed particles based on styrene polymers can be obtained by prefetching EPS with hot air or steam in a prefoamer to the desired density. By prefoaming once or several times in a pressure or continuous prefoamer, final bulk densities of less than 10 g / l can be obtained. Preference is given to using prefoamed, expandable styrene polymers containing athermal solids, such as carbon black, aluminum, graphite or titanium dioxide, in particular graphite having an average particle size in the range from 1 to 50 μm particle diameter in amounts of 0.1 to produce insulation boards with high thermal insulation properties to 10 wt .-%, in particular 2 to 8 wt .-%, based on EPS, and are known for example from EP-B 981 574 and EP-B 981 575.

Furthermore, the foam particles may contain from 3 to 60% by weight, preferably from 5 to 20% by weight, based on the prefoamed foam particles, of a filler. Suitable fillers are organic and inorganic powders or fibrous materials, as well as mixtures thereof. As organic fillers z. As wood flour, starch, flax, hemp, ramie, jute, sisal, cotton, cellulose or aramid fibers are used. As inorganic fillers z. As carbonates, silicates, barite, glass beads, zeolites or metal oxides are used. Preference is given to powdery inorganic substances such as talc, chalk, kaolin (Al ₂ (Si ₂ 0 ₅ ) (OH) ₄ ), aluminum hydroxide, magnesium hydroxide, aluminum nitrate, aluminum silicate, barium sulfate, calcium carbonate, calcium sulfate, silica, quartz powder, Aerosil®, alumina or Spherical or fibrous inorganic materials such as glass beads, glass fibers or carbon fibers. The mean particle diameter or, in the case of fibrous fillers, the length should be in the range of the cell size or smaller. An average particle diameter in the range from 1 to 100 μm, preferably in the range from 2 to 50 μm, is preferred. Particular preference is given to inorganic fillers having a density in the range from 1.0 to 4.0 g / cm ³ , in particular in the range from 1.5 to 3.5 g / cm ³ . The whiteness / brightness (DIN / ISO) is preferably 50-100%, in particular 60-98%. The type and amount of fillers can affect the properties of the expandable thermoplastic polymers and the particle foam moldings obtainable therefrom. The use of adhesion promoters, such as maleic anhydride-modified styrene copolymers, epoxy-group-containing polymers, organosilanes or styrene copolymers with isocyanate or acid groups, can significantly improve the binding of the filler to the polymer matrix and thus the mechanical properties of the particle foam moldings.

In general, inorganic fillers reduce flammability. In particular, by adding inorganic powders, such as aluminum hydroxide, magnesium hydroxide or borax, the fire behavior can be further improved.

Such filler-containing foam particles can be obtained, for example, by foaming filler-containing, expandable thermoplastic granules. At high filler contents required for this expandable granules by extrusion blowing agent-containing thermoplastic melts and subsequent pressurized underwater granulation such. As described in WO 2005/056653.

The polymer foam particles can additionally be equipped with flame retardants. For example, they may contain from 1 to 6% by weight of an organic bromine compound, such as hexabromodylcododecane (HBCD) and optionally additionally from 0.1 to 0.5% by weight of dicumyl or a peroxide in the interior of the foam particles or the coating. However, preferably no halogen-containing flame retardants are used.

The coating composition according to the invention is preferably applied to the foam particles in the form of an aqueous polymer dispersion.

The water glass powder contained in the coating mixture leads to a better or faster filming and thus a faster curing of the foam molding. Optionally, additional hydraulic binders based on cement, lime cement or gypsum may be added in amounts at which no appreciable embrittlement of the foam occurs. Conventional methods, such as spraying, dipping or wetting the foam particles with an aqueous coating composition in conventional mixers, spray devices, dipping devices or drum apparatuses, can be used to coat the foam particles.

Furthermore, the foam particles coated according to the invention can additionally be coated with amphiphilic or hydrophobic organic compound. The coating with hydrophobing agent is expediently carried out before the application of the aqueous coating composition according to the invention. Un- ter the hydrophobic organic compounds are in particular C1 ₀ - C ₃₀ - paraffin waxes, reaction products of N-methylolamine and a fatty acid derivative, reaction products of a C ₉ Cn oxo alcohol with ethylene oxide, propylene oxide or butylene oxide or polyfluoroalkyl (meth) acrylates or mixtures thereof to name, which can be preferably used in the form of aqueous emulsions.

Preferred hydrophobizing agents are paraffin waxes having 10 to 30 carbon atoms in the carbon chain, which preferably have a melting point between 10 and 70 ° C, in particular between 25 and 60 ° C. Such paraffin waxes are contained, for example, in the BASF commercial products RAMASIT KGT, PERSISTOL E and PERSISTOL HP, as well as in AVERSIN HY-N from Henkel and CEROL ZN from Sandoz.

Another class of suitable hydrophobizing agents are resinous reaction products of an N-methylolamine with a fatty acid derivative, e.g. Example, a fatty acid amide, amine or alcohol, as z. For example, in US-A 2,927,090 or GB-A 475 170 are described. Their melting point is generally 50 to 90 ° C. Such resins are for. B. in BASF's commercial product PERSISTOL HP included.

Finally, polyfluoroalkyl (meth) acrylates are suitable, for example Polyperfluoroctylacrylat. This substance is contained in the BASF commercial product PERSISTOL O and in OLEOPHOBOL C from Pfersee.

Further suitable coating agents are antistatic agents, such as emulsifier K30 (mixture of secondary sodium alkanesulfonates) or glycerol stearates, such as glycerol monostearate GMS or glycerol tristearate. However, the method according to the invention is distinguished by the fact that the coating materials which are customary for the coating of expandable polystyrene, in particular stearates, can be used to a reduced extent or eliminated altogether, without negatively influencing the product quality. For the production of foam moldings, the foam particles provided with the coating according to the invention can be sintered in a mold. The coated foam particles can be used while still wet or after drying.

The drying of the coating composition applied to the foam particles can take place, for example, in a fluidized bed, paddle dryer or by passing air or nitrogen through a loose bed. In general, a drying time of 5 minutes to 24 hours, preferably 30 to 180 minutes at a temperature in the range of 0 to 80 ° C, preferably in the range of 30 to 60 ° C is sufficient for the formation of the water-insoluble polymer film.

The water content of the coated foam particles after drying is preferably in the range from 1 to 40 wt .-%, more preferably in the range of 2 to 30 wt .-%, most preferably in the range of 5 to 15 wt .-%. It can be determined, for example, by Karl Fischer titration of the coated foam particles. The weight ratio of foam particles / coating mixture after drying is preferably 2: 1 to 1:10, particularly preferably 1: 1 to 1: 5. The foam particles dried according to the invention can be sintered in conventional molds with hot air or steam to give foam moldings.

When sintering or gluing the foam particles, the pressure can be generated for example by reducing the volume of the mold by means of a movable punch. As a rule, a pressure in the range from 0.5 to 30 kg / cm ^{2 is} set here. For this purpose, the mixture of coated foam particles is filled into the opened mold. After closing the mold, the foam particles are pressed with the stamp, wherein the air between the foam particles escapes and the gusset volume is reduced. The foam particles are connected by the coating to the foam molding.

Preferably, a compression takes place about 10 to 90%, preferably 60 to 30%, in particular 50 to 30% of the initial volume. In a mold with a cross section of about 1 m ² , a pressure of 1 to 5 bar is usually sufficient for this purpose.

The mold is designed according to the desired geometry of the foam molding. The degree of filling depends, inter alia, on the desired thickness of the later molded part. For foam boards, a simple box-shaped form can be used. In particular, in the case of more complicated geometries, it may be necessary to densify and deposit the bed of the particles introduced into the mold this way to eliminate unwanted voids. The compression can z. B. by shaking the form, tumbling or other suitable measures. To accelerate setting, hot air or water vapor can be pressed into the mold or the mold heated. For tempering the mold, however, any heat transfer media, such as oil or steam can be used. The hot air or the mold is suitably tempered for this purpose to a temperature in the range of 20 to 120 ° C, preferably 30 to 90 ° C.

Alternatively or additionally, the sintering can be carried out continuously or discontinuously under the action of microwave energy. As a rule, microwaves in the frequency range between 0.85 and 100 GHz, preferably 0.9 to 10 GHz, and irradiation times between 0.1 and 15 minutes are used. It is also possible to produce foam boards with a thickness of more than 5 cm. When using hot air or steam at temperatures in the range of 80 to 150 ° C or by irradiation of microwave energy usually forms an overpressure of 0.1 to 1, 5 bar, so that the method is carried out without external pressure and without volume reduction of the mold can be. The internal pressure resulting from higher temperatures allows the foam particles to be easily further expanded, whereby they can also weld themselves by softening the foam particles themselves, in addition to bonding via the polymer coating. The gussets disappear between the foam particles. To accelerate setting, the shape can also be heated with a heat transfer medium as described above. When microwaves are irradiated, the inorganic coating constituents are generally heated, which then crosslink or condense more quickly as a result.

For the continuous production of the foam moldings are also double belt systems as they are used for the production of polyurethane foams. For example, the prefoamed and coated foam particles may be continuously applied to the lower of two metal bands, which may optionally have a perforation, and processed with or without compression by the converging metal bands into endless foam sheets. In one process embodiment, the volume between the two belts is progressively reduced, compressing the product between the belts and eliminating the gussets between the foam particles. After a curing zone, an endless plate is obtained. In another embodiment, the volume between the bands can be kept constant and pass through a zone with hot air or microwave irradiation, in which the foam particles re-foam. Again, the gussets and an endless plate disappear will be received. It is also possible to combine the two continuous process operations.

The thickness, length and width of the foam sheets can vary within wide limits and is limited by the size and closing force of the tool. The thickness of the foam sheets is usually 1 to 500 mm, preferably 10 to 300 mm. Further preferred sizes and order ranges are 10 to 200 mm, preferably 20 to 1 10 mm, particularly preferably 25 to 95 mm.

The density of the foam moldings according to DIN 53420 is generally 10 to 150 kg / m ³ , preferably 20 to 90 kg / m ³ . With the method it is possible to obtain foam moldings with uniform density over the entire cross section. The density of the edge layers corresponds approximately to the density of the inner regions of the foam molding.

The process can also be used crushed foam particles made of recycled foam moldings. To produce the foam moldings of the invention, the comminuted foam recycled to 100% or z. B. in proportions of 2 to 90 wt .-%, in particular 5 to 25 wt .-% are used together with virgin material, without significantly affecting the strength and mechanical properties.

The coating may also contain other additives which preferably or only slightly contribute to the combustibility and / or substances which in the non-fired state have a positive influence on the mechanical or thermal properties, for example vermiculites, in addition to the mechanical and hydraulic properties to modify

A preferred method comprises the steps: i) prefoaming of expandable styrene polymers into foam particles, ii) applying the coating composition according to the invention in the form of an aqueous dispersion to the foam particles,

iii) drying the dispersion on the foam particles to form a water-insoluble polymer film

iv) filling the polymeric film coated foam particles into a mold and combined.

A particularly preferred method involves the compression of the still water-moist foam particles according to the following method: i) prefoaming of expandable styrene polymers into foam particles, ii) applying the coating composition according to the invention in the form of an aqueous dispersion to the foam particles,

iii) filling the coated with the coating composition and still wet with water foam particles in a mold, pressing and curing by the action of temperature and / or microwave.

The coating compositions according to the invention are suitable for the production of simple or complex foam moldings, such as plates, blocks, tubes, rods, profiles, etc. Preference is given to producing sheets or blocks which can subsequently be sawn or cut into sheets. For example, panels and blocks can be used in building construction to insulate exterior walls. They are particularly preferably used as the core layer for the production of sandwich elements, for example so-called structural insulation panels (SIP), which are used for the construction of cold stores or warehouses.

Examples: Test methods

To test the quality of the samples, a series of tests were carried out: Test A

First, after the proper deposition time, the volume loss in case of fire (Test A) was determined. For this purpose, a cube with 5 cm edge length was sintered for 15 minutes at 1030 ° C, or 800 ° C in a muffle furnace. The cubic volume was then determined again and subtracted from the initial value.

Test B

Furthermore, the leaching of the cubes was determined (test B). For this purpose, a cube of 5 cm edge length was completely immersed in 50 ° C warm water and completely wetted with water for 24 hours. Afterwards, the cube was weighed again after drying and thus the proportion of leached coating was determined. The water in the container was evaporated and the residue was weighed to give a more accurate reading.

Test C

Subsequently, the cube was again completely dried and subjected to a fire test as described in Test A). This resulted in the loss of fire after water exposure (Test C). Preparation of the coating mixtures and the polystyrene foam particles

Commercially available polystyrene foam particles (10 g / L, Neopor ^® 2300) were indicated by the in Table2 coating in the specified weight ratio there EPS: coated mix homogeneously. The coated particles were then filled into an aluminum mold (20 x 20 cm) and pressed under pressure to 50% of the original volume. The examination of the samples obtained was carried out as described under "Test Methods".

The following substances are used in the following examples:

Table 1

From this, the specimens given in Table 2 are prepared, wherein the numbers under the substances a1) to d1) denote the parts by weight used:

Table 2

The column EPS / Mix means the weight ratio of the inorganic components to the foam.

Table 3 below shows the results of testing the samples given in Table 2:

Table 3 Sample (Comparison) Test C Test A Test B

1 20 8 not measurable, because

Sample had decayed

2 2 16 17

3 8 7 3

4 8 2 4

5 3 3 0.6

6 5 3 7

It can be seen from Table 3 that samples 2 to 6 according to the invention, which in contrast to comparative example 1 contain a silica sol, are markedly improved both in terms of leaching and fire behavior.

Claims

claims

1. coating composition for foams, comprising a ceramic material a), optionally an alkali metal silicate b) and optionally a film-forming polymer c), characterized in that additionally nanoscale

Si0 ₂ particles d) are included.

Coating composition according to claim 1, characterized in that the nanoscale Si0 ₂ particles are contained as an aqueous, colloidal dispersion.

Coating composition according to at least one of the preceding claims, characterized in that the mean particle diameter of the nanoscale Si0 ₂ particles is 10 to 50 nm.

Coating composition according to at least one of the preceding claims, characterized in that it contains a) 20 to 70 parts by weight of a ceramic material, in particular a clay mineral or wollastonite

b) ggf.20 to 70 parts by weight of an alkali metal silicate

c) 1 to 30 parts by weight of a film-forming polymer

d) 1 to 60 parts by weight of nanoscale Si0 ₂ particles d) and optionally

e) a hydrophobizing amount of a silicon-containing compound.

Coating composition according to at least one of the preceding claims, characterized in that the nanoscale Si0 ₂ particles d) have a BET surface area of 10 to 3000 m ² / g.

Coating composition according to at least one of the preceding claims, characterized in that the weight ratio of the ceramic material a) to alkali silicate b) in the range of 1: 2 to 2: 1.

Coating composition according to at least one of the preceding claims, characterized in that it contains as a ceramic material wollastonite or allophan Al ₂ [Si0 ₅ ] 0 ₃ xn H ₂ O, kaolinite Al ₄ [(OH) 8 / Si ₄ Oio], Halloysite Al ₄ [(OH) 8 / Si ₄ 0io] x 2 H ₂ O, montmorillonite (smectite) (Al, Mg, Fe) ₂ [(OH ₂ / (Si, Al) ₄ Oio] x Na ₀ , ₃ 3 (H ₂ O) ₄ , vermiculite Mg ₂ (Al, Fe, Mg) [(OH ₂ / (Si, Al) ₄ Oi ₀ ] x Mg ₀ , 35 (H ₂ O), or mixtures thereof. Coating composition according to at least one of the preceding claims, characterized in that it contains as alkali silicate b) a water-soluble alkali metal silicate with the composition M ₂ 0 (Si0 ₂ ) _n with M = sodium or potassium and n = 1 to 4 or mixtures thereof.

Coating composition according to at least one of the preceding claims, characterized in that it contains, as the film-forming polymer, an emulsion polymer of ethylenically unsaturated monomers which has a glass transition temperature in the range from -30 ° to + 80 ° C.

Foamed particles with a coating according to at least one of the claims.

Foamed particles according to claim 10, characterized in that the foam particles are selected from expanded polyolefin particles or from possibly prefoamed particles of expandable styrene polymers.

Process for producing foam moldings, characterized in that foam particles according to claim 10 or 11 are sintered in a mold.

13. The method according to claim 12, characterized in that it is the stages

Prefoaming of expandable styrene polymers into foam particles,

Applying the coating composition according to the invention in the form of an aqueous dispersion to the foam particles, drying the dispersion on the foam particles to form a water-insoluble polymer film and

Filling the polymer film coated foam particles into a mold and sintering.

Method according to claim 12, characterized in that it comprises the steps

Prefoaming of expandable styrene polymers into foam particles,

Applying the coating composition according to the invention in the form of an aqueous dispersion to the foam particles) iii) filling the coated with the coating composition and still wet with water foam particles in a mold, pressing and curing by the action of temperature and / or microwave. includes.

15. Use of the foam molding produced according to at least one of the preceding methods for the production of plates, blocks, tubes, rods, profiles and as a core layer for the production of sandwich elements.