NO144352B - FIRE PROTECTED BUILDING ELEMENTS. - Google Patents

Description

The present invention relates to fire-protected building elements made of metal or wood.

It is known to shield fire-prone building elements with single- or multi-layer paint systems against burn damage in the event of a fire, at least for a certain period of time. In multi-layer fire protection paint systems, each of the layers has a completely specific and absolutely necessary function, and these

-ensures together the system's protective effect.

Thus, it has already been proposed to use three-layer paint systems whereby the bottom layer is a corrosion-inhibiting layer, the intermediate layer the actual effective layer which in the event of a fire provides protection by foaming, and the cover layer is a top coat that will protect the active layers. The period of time that can thus be achieved with fire protection must serve to be able to take other precautions that either prevent the occurrence of major fire damage or at least significantly reduce these.

Such a foam layer-forming flame protection system is, for example, a combination of dicyandiamide with a higher solid alcohol and an ammonium phosphate, whereby a homopolymer polyvinyl acetate dispersion containing trichloroethyl phosphate serves as a binder.

This fire protection paint must itself be applied in several layers to achieve the required layer thickness without dripping. However, this means a relatively high amount of work.

These known systems for building elements are not entirely satisfactory with regard to their fire protection effect.

From US patent no. 3-57^,644 it is further known that plastics such as polyester, epoxies or polyolefins can be made more flame-resistant by adding blisterable graphite. If this addition is made to ordinary paints or coating compounds, then these can be used for coating combustible materials such as wood, or also non-combustible building elements, e.g. metal, for insulation purposes.

For this purpose, the paint is applied and heated for a short time so that a relatively thick, insulating protective layer is achieved when the graphite expands.

This form of protection has the disadvantage that the coating on the one hand requires a relatively large amount of space and on the other hand, however, has a relatively low mechanical strength, so that damage to the coating must be feared even at low stresses.

The object of the present invention is to produce building elements which, in the event of fire, are protected by a paint system based on blister graphite and which, in the same way as the known systems, first develop their insulating effect by swelling in the event of fire, but which also then have such mechanical strength that the paint does not peel off under the influence of the flame suction or other mechanical loads and thus no longer protects the building element. According to the present invention, this can be achieved by adding a special binder system of two components whereby one provides a sticky bond and the other in the event of a fire and due to temperature-dependent decomposition, forms a coke skeleton that provides attachment for the blistered graphite.

The object of the present invention is, according to this, fire-protected building elements, in particular of metal or wood, which, as fire protection, have been applied with a 3-layer coating comprising:

a) a corrosion- or rot-preventing base layer,

b) an intermediate layer containing such amount of swellable

substance that in the event of a fire it will swell up to 10-40 times its original thickness, and

c) a thin covering layer, and the invention is characterized by the fact that the binder in the intermediate layer consists of a mixture of

bl) a sticky polychloroprene partially broken down by mechanical impact, a chlorinated rubber and/or a chlorinated polyolefin. and. b2) one or more phenolic resins of the type that remain thermoplastic up to at least 200°C,

as this middle layer as a swellable material contains swellable

graphite, which in and of itself is a known component in fire protection paints,

as the quantity ratios are such that per 100 parts by weight of graphite there are 10-50 parts by weight of each of the components b.l) and b2), and that the cover layer c) is a water-resistant silicate layer, formed from an organic polysilicate or water glass, with added relative metal powder, metal oxide and/or hydroxide and/or basic metal carbonate, borate and/or phosphate.

The base layer on the building element to be coated is indispensable and, as far as steel building parts are concerned, consists of known passivating and rust-protecting agents. What is important about this base layer is that it does not contain water-sensitive components, that it adheres well to the foundation and that it is well compatible with the fire-protective active layer that is to be applied above, i.e. that it provides a good attachment for this even in the event of a fire.

The intermediate layer constitutes the actual fire-protective active layer. The blisterable graphite present therein (component a) blisters strongly when heated during the release of some water vapor and traces of nitrous gases. The normal volume enlargement thereby amounts to 10-40 times, preferably 15-20 times, the original volume.

The swelling already begins at about 150°C or barely below this temperature, proceeds almost violently at first and then more slowly, and is finished at a temperature of 600°C at the latest. What remains is a loose, moss-like layer of sausage-like, swollen graphite lamellae, which exhibits an excellent insulating effect against heat transfer.

With regard to "inflatable graphite", the production of this and its properties, reference should be made to the following literature:

1. Hofmann & Prenzel: ibid. 63 (1930), p. 1249

2. Thiele: Zeitschr. f.anorg.u.allgem. Chemie 67 (1932), p. 340 3. US-PS 3,333-941.

In the technique, this blister-forming graphite is produced practically exclusively by short-term exposure of highly concentrated nitric acid to coarse-grained natural graphite. The whole thing is then washed neutrally and dried carefully at a low temperature (= 80°C).

To measure the growth in volume during the inflation of

The following laboratory methods are used for graphite:

5 - 10 g of graphite is accurately weighed into a nickel dish with a volume of 450 - 500 ml. The sample is placed in an annealing oven at 500°C for 30 minutes. This annealed sample is filled into a measuring cylinder and the cylinder with the sample is bumped against a solid surface for so long that no change in volume occurs. This same volume measurement is carried out with the graphite before heating.

Volume increase = ml/g shaken volume of inflated graphite

ml/g shaken volume not inflated graphite

As component b) which should give a sticky elastic bond, the following is used: 1. polychloroprene (so far degraded by mastication that the stickiness occurs and the viscosity in non-aqueous solutions is not too great)

2. chlorinated rubber or

3. chlorinated polyolefin plastics such as e.g. chlorinated polyethylene or polypropylene, whereby mixtures of these substances can also be used.

However, these components leave no coke in the event of a fire.'

This task is fulfilled by the phenolic resin used as component c), whereby the following phenolic resins are particularly suitable:

•1. natural resin-modified phenolic resins,

2. hydrocarbon-modified phenolic resins, e.g.

a) phenol terpene resins

b) phenol-acetylene condensates

c) phenolic condensates with hydrocarbon-formaldehyde resins,

3. phenolic resins modified with linseed oil or wood oil by boiling, 4. novolak-like products as they appear from the alkaline catalyzed reaction between furfural and phenols (preferably higher alkylphenols),

5. phenyl-allyl ether resoles,

6. condensates of phenols with benzyl chloride.

All these phenolic resins have in common that at temperatures up to 200°C they behave purely thermoplastic, i.e. that they cannot prevent swelling of the bladder graphite. At higher temperatures, the aforementioned resins either turn into coke without prior curing or they go through a partial curing which, however, does not in any way lead to rigid and highly cross-linked duroplasts, as these occur with phenol-formaldehyde resols. This also applies to each of the above-mentioned resin types which exhibit a purely formal resol character.

The structure of the binder according to the invention

for the blisterable graphite is preferably carried out as follows: 25 to 75 parts by weight of at least one of the aforementioned elastomer-like and halogen-containing polymers and 75 to 25 parts by weight of at least one of the mentioned phenolic resins are dissolved in suitable solvents or solvent mixtures. As such, hydrocarbons (e.g. toluene, solvent naphtha, test petrol) or ketones and esters respectively come into consideration. Naturally, one will try to dissolve as much as possible in this mixture, however, limits are set here due to the solubility of the substances as well as due to the viscosity of the obtained solution. With regard to optimum viscosity for the binder solution, it is recommended to have an outlet time for this between 30 and 60 seconds, measured using a Ford beaker with nozzle No. 8 at 22°C. According to this, the solids concentration in the solution will usually be between 20 and 30%.

For the production of the fire protection mass for building elements, a production that is preferably carried out shortly before use, one stirs up blisterable but not yet inflated graphite with so much binder solution that per 100 parts by weight contain 10 - 50 parts by weight of binder (calculated as a solvent-free solid). A paste-like mass is obtained that can be applied to building elements that are to be protected and that are already equipped with a base layer by sandblasting or preferably with the help of special spray guns. With this application, it is also easily possible on vertical surfaces, as the paste-like consistency of the mass which, in addition, on

due to the coarse lamellar graphite present in the mass, it is very thixotropic and prevents creep. For this reason, the desired layer thickness can also be achieved immediately, i.e. you do not need to carry out several applications with intermediate drying breaks. The optimal layer thickness for the fire protection system is preferably 2 + 1 mm (in a dried state).

The topcoat layer, which must only be applied to previously completely dried foam-forming application compound, has the following two purposes: a) protection of the underlying layer against the influence of water (e.g. rain) and other atmospheric deposits and, in addition, possibly against the corrosive influence of any any type. b) The most extensive protection against damage due to mechanical stresses. c) Foundation. for any desired decorative purposes when the fire protection compound is applied. visible surfaces, and more

end

d) in the event of a fire, the formation of an attached rigid cover layer which must be microporous to allow the passage of

pyrolysis gases and vapors escaping from the underlying layers of the fire protection application system. Crust formation is absolutely necessary, so that the loose heat-insulating, blister: graphite layer is not blown away by drafts from the combustion gases (stove draft).

In order to fulfill the above-mentioned requirements to the greatest extent possible, weakly reactive (self-hardening) inorganic or organic-silicate bound lacquer systems are preferably chosen, which are admittedly essentially already known in and of themselves, but which for the present special application offer advantages by a new modification.

Topcoats based on water glass are considered completely weathering-resistant after setting and are sufficient in most cases even if they contain small amounts of alkali carbonate. As a basis for such paints, commercially available highly concentrated solutions (approx. 25 - 30% solids content) of alkali silicates (water glass) serve. Thereby, priority is given to the use of potassium water glasses. As the resulting alkali carbonates are soluble in water, one therefore prefers low-alkali water glasses as much as possible, above all those with a ratio of SiO2 : K20 = 3.5 to 4.0. If, however, a complete freedom from alkali is required in special cases, esters of polysilicic acids must be chosen as the basis for the coverage measurement.

Most recommendable are methyl or ethyl polysilicates, which can be obtained by selective partial saponification of

tetraalkyl-ortho-silicic acid esters.

Reactive metal powders, oxides or hydroxides, (basic) carbonates, borates and possibly phosphates are added to the cover paint (whether it is based on water glass or silicic acid ester), which after a not too long "setting time" (approximately 1-6 hours) form water-insensitive silicate layer which, in the event of a fire, sinters together into a firm but microporous (and therefore gas permeable) crust.

As reactive additives to silicate binders, above all, the following should be mentioned: finely divided zinc dust (color zinc dust), zinc oxide, zinc borate, magnesium oxide, magnesium hydroxide, basic magnesium carbonate, aluminum hydroxide, lead oxide (so-called lead sheen and also fringe), lead white (= basic carbonate) and others.

Furthermore, in the event that a colour-rich, decorative covering layer is desired, medium-resistant, preferably inorganic pigments can be used. Examples of these include soot, ultramarine, chrome yellow, chrome oxide green, ochre, iron oxide pigments of various shades of colour, etc.

Furthermore, it is very advantageous to add "pore formers" to the cover layer according to the invention next to the aforementioned "reactive" additives. These have the task of releasing a large number of micropores in the silicate cover layer already at temperatures from 100 - 150°C (i.e. below the temperature range in which there is an exit of gases and vapors from the graphite layer which starts to form blisters). These should allow sufficient gas to escape and thus prevent tearing and/or peeling of the cover layer from the blister graphite thermal insulation layer. Finely powdered substances (grain sizes below 250 u5 preferably below 100 y) are suitable as "pore formers", which cannot react with the binder of the cover layer (water glass or polysilicic acid ester) and which cannot dissolve in them. Furthermore, the pore formers must either melt out at temperatures from 100 - 150°C, preferably around 120°C, or form a corresponding micropore system in the cover layer due to shrinkage or splitting. Examples of suitable pore formers include polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymers, novolak-type phenol-formaldehyde condensates, natural resins, short-fibre asbestos (maximum fiber length 2 mm), etc.

Also regular propellants, such as e.g. benzenesulfonic acid hydrazide may find application. However, one must dose very carefully in these cases and use particularly finely divided preparations as these and similar "propellants" due to a rapid decomposition within a narrow temperature range form a significant volume of gas, which can have a bursting and very undesirable effect on the tire layer.

Testing of such fire protection systems on steel building parts takes place according to DIN 410 2, sheet 2, section 5, whereby in order to obtain an official confirmation of a specific flame resistance class during fire tests, conditions such as in the aforementioned standard, sheet 2, section 3, 1, 1 must be met , 2.

The structure and the practical use of a fire protection system according to the invention can be seen from the following illustrative examples.

Example 1

A steel plate with a size of 500 x 500 mm and a thickness of 4 mm is carefully cleaned of adhering rust and other contaminants and then roughened on the surface using sand in a manner known per se. In most cases, a cleaning of the surface will be superfluous due to the always necessary treatment with sand. The plate is then immediately treated with corrosion-protective primer paint.

After 12 hours and after the base layer has thoroughly dried, the fire protection layer is applied, which consists of equal parts by weight of blisterable graphite and varnish binder. Regarding the individual components of this mass, the following should be noted: 1. The blisterable graphite must be completely neutral and dry. The particle size for the graphite lamellae was predominantly in the range of 1.5 to 3 mm. The graphite used had an absorption capacity of 18 times the initial volume.

2. The binder was prepared as follows:

a) first, non-vulcanized polychlorobutadiene ("Neoprene") was so far reduced by mastication to a 25% solution

in toluene exhibited a viscosity corresponding to an outflow time of 45 + 5 seconds from a Pord beaker with nozzle No. 8 at

22°C. 10 parts by weight of this decomposed polychlorobutadiene are stirred together with 5 parts by weight of a b) thermoplastic phenol-terpene condensation resin in 40 parts by weight of toluene with good stirring. The aforementioned phenol-terpene resin can be selected from commercially available products, e.g. known under the names "Durez", "Alresen" and others. c) Finally, 5 parts by weight of a novolak-like condensate of 2 mol isononyl-phenol and 1 mol furfural, which was prepared under the influence of alkaline catalysts, are dissolved (see Houben-Weyl: "Methoden der organischen Chemie", volume 14/2 (Macromolecular Substances II) on page 281, example 28), in 10 parts by weight of butyl acetate in a warm state and dilute with 10 parts by weight of toluene. ■ d) The solution consisting of the components described above under a) and b) is then combined with dissolve- • •

ning according to c) and dilutes with 2.0 parts by weight of petrol

boiling point 80 - 120°C. The petrol must be mixed in slowly with good stirring to achieve a homogeneous, stable solution.

Together, the binder produced in this way consists of:

The viscosity of this binder corresponds to a run-off time of 41 seconds, measured using a No. 8 Ford beaker at 22°C.

3. The fire protection layer

Shortly before use, equal parts by weight of blisterable graphite and binder are thoroughly mixed together. A pasty thixotropic mass is created which is applied to the well-dried primer. Using a spray gun with a 3 mm nozzle opening, the layer was applied in one work step and to achieve a homogenization of the layer thickness, it was then smoothed using a roller. After drying, the layer thickness averaged 2.0 mm.

4. The tire paint

The following components are mixed:

a) 60 parts by weight potash water glass (molar ratio Si02 : K20 = 3.8, concentration approx. 25% solids) with 5 parts by weight

fine sanding dust from wood (pore former) as homogeneous as possible.

b) 5 parts by weight of zinc oxide are mixed with 10 parts by weight of aluminum hydroxide, 20 parts by weight of finely powdered chalk and some

water, very thoroughly to a homogeneous paste.

The two components a) and b) are mixed immediately before use in equal parts by weight. Application of this tire protection varnish is also done with a spray gun.

Testing of the coated plate according to DIN 4102, sheet 2 "small fire test". The mean value of 9 temperature measuring points on the side facing away from the flame must not exceed 400°C, respectively no individual value must exceed 500°C. Depending on the time it takes to achieve this limit value, the flame resistance class is given. In two parallel trials, the limit value was reached once after . 90 minutes and once after 100 minutes.

Example 2

A steel building part as described in example 1 was primed with zinc chromate as corrosion protection and then applied a fire protection layer with the following composition:

40 parts by weight of blisterable graphite (as in example 1)

60 parts by weight of a commercially available synthetic resin mixture consisting of polychlorophene, phenol resin, terpene phenol resin dissolved in toluene-petrol-ethyl acetate.

After 36 hours, the fire protection layer was thoroughly dried, after which the topcoat layer was applied. This was produced by:

Component A

60 parts by weight ethyl polysilicate "DYNASIL A 40" 30 parts by weight crystalline aqueous zinc borate (zinc borate 2335)

10 parts by weight aluminum hydroxide

1 part by weight of polyvinyl chloride powder,

Component B

30 parts by weight 90 58ig technical alcohol in which it was dissolved

1 part by weight of anhydrous zinc chloride and

1 part by weight of mannitol.

The two components A and B were mixed together before use and applied with a spray gun.

Claims (4)

1. Fire-protected building elements, especially made of metal or wood, which, as fire protection, have been applied with a 3-layer coating comprising: a) a corrosion- or rot-preventing base layer, b) an intermediate layer containing such an amount of swellable material that in the event of fire will swell up to 10-40 times the original thickness, and c) a thin covering layer, characterized in that the intermediate layer's binder consists of a mixture of bl) a sticky polychloroprene partially degraded by mechanical action, a chlorinated rubber and/or a chlorinated polyolefin, and b2) one or more phenolic resins of the type that remain thermoplastic up to at least 200°C, as this intermediate layer as a swellable substance contains swellable graphite, which in and of itself is a known component in fire protection paints, as the quantity ratios are such that per 100 parts by weight of graphite there are 10-50 parts by weight of each of the components bl) and b2), and that the cover layer c) is a water-resistant silicate layer, formed from an organic polysilicate or water glass, with added reactive metal powder, metal oxide and/or hydroxide and/or basic metal carbonate, borate and/or phosphate. 2. Fire-protected building elements according to claim 1, characterized in that the thickness of the intermediate layer is 1-3 mm. 3. Fire-protected building elements according to claims 1 and 2, characterized in that the alkali silicate in the cover layer is potassium water glass with a SiC^K^O ratio of 3.5:4.0. 4. Fire-protected building elements according to claim 3, characterized in that the cover layer contains a pore former with a grain size below 0.25 mm, consisting of a thermoplastic melting below 150°C, a phenolic resin of the novolac type, a natural resin or wood sanding dust.