WO2024243729A1

WO2024243729A1 - Intumescent composition

Info

Publication number: WO2024243729A1
Application number: PCT/CN2023/096538
Authority: WO
Inventors: Yufeng Zhang; Qing Liu
Original assignee: Sika Technology AG
Current assignee: Sika Technology AG
Priority date: 2023-05-26
Filing date: 2023-05-26
Publication date: 2024-12-05
Anticipated expiration: 2025-11-26
Also published as: CN119019108A

Abstract

Intumescent composition, in particular for protecting a building substrate from fire damage, comprising: a) 10 − 50 wt. -%, in particular 20 − 40 wt. -%, especially 30 wt. -%, water glass, b) 1.0 − 6.0 wt. -%, in particular 2.0 − 5.0 wt. -%, especially 3.0 wt. -%, expandable microspheres, c) 10 − 50 wt. -%, in particular 20 − 45 wt. -%, especially 41.7 wt. -%, aluminium hydroxide and/or magnesium hydrate, d) 20 − 40 wt. -%, in particular 25 − 35 wt. -%, especially 30 wt. -%, water.

Description

INTUMESCENT COMPOSITION

Technical field

The invention relates to an intumescent composition, in particular for protecting a building substrate from fire damage. Another object of the invention is a substrate, in particular a building substrate, especially a steel based building substrate, coated with the intumescent composition. Furthermore, the invention concerns a method for providing a fireproof substrate, in particular a fireproof building substrate, especially a fireproof steel based building substrate, as well as the use of the intumescent composition for fire protection of a substrate, especially a building substrate, in particular a steel based building substrate.

Background Art

Fire can cause significant damage to the supporting structure of buildings. Especially buildings with steel based building substrates are prone to collapse in the event of a fire. Steel is not flammable but its load capacity decreases with increasing temperature. Under full-scale fire, temperatures of more than 500 ℃are reached after only a few minutes. At these temperatures, the strength of steel decreases strongly. Furthermore, steel beams tend to undergo a considerable length expansion at high temperatures, exerting immense forces on walls and ceilings. In the event of a fire, these influences can result in steel structures no longer fulfilling their structural functions.

Consequently, it is important to have systems in place to mitigate the impact of fire to substrates, in particular building substrates, especially steel based building substrates, and maintain the load capacity of these substrates as long as possible during a fire. This helps to win enough time to allow rescue workers to evacuate people and extinguish the fire.

Intumescent compositions offer a reliable and cost-effective solution by providing a passive fire protection system, e.g. as a coating. These compositions have the ability to expand and form a protective layer when exposed to high temperatures. The heat transfer from the flames to the building substrates is thereby greatly diminished and the time is prolonged until the load capacity of the building substrates is critically impaired. Common areas of application of such intumescent compositions include for example steel based building substrates in industrial and administrative buildings, event and sports centres, shopping malls, airports and/or train stations, such as hollow profiles, steel beams and steel pipes.

Fire protective intumescent compositions are described extensively in the patent literature. WO 2010/131037, for instance, describes an intumescent composition comprising a polymer, a plasticizer and an intumescent ingredient. The composition is thought to enhance, i. a., the setting time.

CN 112175436 describes an inorganic intumescent fire-retardant coating comprising, i. a., water glass, calcium carbonate, potassium alum, metakaolin, inorganic phosphate, aluminium hydroxide, aluminium powder and expanded graphite. The coating is supposed to, i. a., release less harmful substances and enhance expansion.

Furthermore, CN 106147416 is about a fireproof organic coating containing water glass, cornstarch, carboxymethylcellulose calcium, styrene-acrylate emulsion, organic curing agents and inorganic solidification agents. The coating is thought to, i. a., decrease the setting time and enhance fire resisting properties.

However, although the available compositions have a fireproofing effect and may improve certain properties of intumescent compositions, they may not always be suitable for specific applications.

There is thus a need to develop alternative intumescent compositions which overcome the aforementioned drawbacks.

Disclosure of the invention

It is an object of the present invention to provide an advantageous intumescent composition. In particular, the intumescent composition should show a high fire resistance. Furthermore, the intumescent composition should be suitable for indoor applications. Also, the intumescent composition should be environment-friendly. The intumescent composition should in particular have a good adhesion to different materials, especially to steel. As well, the intumescent composition should be easy and safe to produce.

Surprisingly, it has been found that these objects are achieved by the features of claims 1. Thus, a first aspect of the invention is an intumescent composition, in particular for protecting a building substrate from fire damage, comprising or consisting of:

a) 10 –50 wt. -%, in particular 20 –40 wt. -%, especially 30 wt. -%, water glass,

b) 1.0 –6.0 wt. -%, in particular 2.0 –5.0 wt. -%, especially 3.0 wt. -%, expandable microspheres,

c) 10 –50 wt. -%, in particular 20 –45 wt. -%, especially 41.7 wt. -%, aluminium hydroxide and/or magnesium hydrate,

d) 20 –40 wt. -%, in particular 25 –35 wt. -%, especially 30 wt. -%, water.

Such intumescent compositions can be used to better protect building substrates, especially steel based building substrates, when exposed to high temperatures, e.g. during a fire incident. Furthermore, the composition may provide an aesthetically appealing structure, making it suitable for indoor applications. Moreover, it is possible to improve the environmental impact because the intumescent compositions are mainly inorganic. Organic components tend to have a low heat resistance, are flammable and/or release potentially carcinogenic volatile organic compounds. As well, the intumescent composition may show an enhanced adhesion to the building substrates, especially to steel based building substrates.

Additional aspects of the invention are subject of the further independent claims 12, 13 and 15. Particularly preferred embodiments are outlined throughout the description and the dependent claims.

Ways of carrying out the invention

In the present context, an "intumescent composition" is a composition that is able to expand as a result of heat exposure, thus increasing in volume and decreasing in density.

The term "expandable microspheres" stands for sperically formed microscopic particles with a thermoplastic shell encapsulating at least one blowing agent. When the microspheres are heated, the thermoplastic shell softens and the blowing agent increases its pressure, resulting in an expansion of the spheres. The volume of the microspheres can thereby increase by 50 -100 times. Once cooled, the microsphere maintains its shape encapsulating the blowing agent.

A first aspect of the invention is an intumescent composition, in particular for protecting a building substrate from fire damage, comprising:

d) 20 –40 wt. -%, in particular 25 –35 wt. -%, especially 30 wt. -%, water.

In particular, all the amounts are with respect to the total weight of the intumescent composition.

It turns out that the inventive composition can be formulated as a Class A fire retardant based on known fire class ratings such as the fire class ratings according to the National Fire Protection Association Life Safety Code, NFPA No. 101. Fire class ratings are a way of classifying materials by their ability to support and propagate fire. A class A (or class 1) fire rating is the best fire rating of materials that can be achieved. Class A fire ratings indicate a flame spread rating between 0 and 25. This means that these materials do not burn well and are very unlikely to contribute fuel to a fire. The flame spread rating value is expressed as an arbitrary numerical value, where the asbestos-cement board has a rating of 0, and red oak has a value of 100.

Water glasses are defined as glassy, i.e. amorphous, water-soluble sodium silicates, potassium silicates and/or lithium silicates or their aqueous solutions solidified from a melt. Depending on whether sodium silicates, potassium silicates or lithium silicates are predominantly present, one speaks of sodium water glass, potassium water glass or lithium water glass. The inventive solution covers sodium water glass, potassium water glass and/or lithium water glass. The water glass component in the inventive composition provides a strong bond between the intumesecent composition and the building substrate, especially the steel based building substrate. Moreover, water glass can replace the polymer share in the composition. This contributes to a lower release of volatile organic compounds.

Sodium silicates, potassium silicates and/or lithium silicates have the formula M₂O ·nSiO₂, where M is an alkali metal oxide such as sodium, potassium and/or lithium and n is the molar ratio defining the number of moles of silicon dioxide (SiO₂) per mole of alkali metal oxide (M₂O) .

Preferably, the SiO₂: Na₂O weight ratio for sodium silicates is between 0.5 and 4, especially between 1 and 3.5, most preferably between 1.5 and 3.

Preferably, the SiO₂: K₂O weight ratio for potassium silicates is between 0.5 and 5, especially between 1 and 4, most preferably between 1.5 and 3.

Preferably, the SiO₂: Li₂O weight ratio for lithium silicates is between 5 and 16, especially between 6 and 14, especially preferred between 7 and 12, most preferably between 7.5 and 8.5.

In particular, the expandable microspheres have the form of a fine powder on low temperatures. They can contribute to a smooth composition surface under low temperatures. The intumescent composition is therefore very suitable for visibly mounted building substrates. Especially, the intumescent composition is suitable for indoor applications, such as in buildings that are often crowded with people.

Preferably, the microspheres are of a bright color, especially white. This brings the advantage that the intumescent composition can be used on bright substrates, especially on bright building substrates. Interiors are brightened up as a result.

However, it is also possible that the microspheres have a dark color, e.g. black.

The microspheres only expand under increased temperatures. This can enhance the protection of the building substrate from heat damage. Their excellent compressibility, elasticity, expansion cabability and/or low density can make expandable microspheres an easy to handle and/or safe component.

It has further been surprisingly shown, that the inventive compositions may lower the setting time. This can help to speed up the processing time of substrates, especially building substrates. Also, the inventive solution may provide intumescent compositions that show a high hardness, a long durability and/or a high cost-performance.

In a preferred embodiment, the intumescent composition comprises 1 –20 wt. -%, in particular 10 –18 wt. -%, especially 15 wt. -%, titanium dioxide.

According to recent findings, titanium dioxide may improve fire protection, the thermal stability and/or the water resistance of the intumescent compositions. It is however also conceivable to use calcium aluminate sulphate, e.g. the calcium aluminate sulphate based white mineral instead of titanium dioxide.

In another preferred embodiment, the intumescent composition comprises

i) 0 –10 wt. -%, in particular 0.1 –8 wt. -%, especially 0.5 –6 wt. -%, mica powder,

ii) 0 –10 wt. -%, in particular 0.1 –8 wt. -%, especially 0.5 –6 wt. -%, kaolin,

iii) 0 –30 wt. -%, in particular 0.1 –25 wt. -%, especially 1 –20 wt. -%, calcium carbonate,

iv) 0 –2 wt. -%, in particular 0.01 –1 wt. -%, especially 0.1 wt. -%, defoamer,

v) 0 –2 wt. -%, in particular 0.01 –1 wt. -%, especially 0.1 wt. -%, dispersing agent,

vi) 0 –2 wt. -%, in particular 0.01 –1 wt. -%, especially 0.1 wt. -%, thickener and/or

vii) 0 –5 wt. -%, in particular 0.1 –4 wt. -%, especially 0.5 –3 wt. -%, other additives.

This may enhance the consistency, appareance and/or durability of the intumescent composition.

Especially, the expandable microspheres have a cavity volume of at least 30 %, in particular at least 50 %, especially at least 75 %, of the total volume of the expandable microsphere.

A cavity volume is defined as the total of hollow volumes in the expandable microsphere located within the shell of the expandable microsphere before expansion. Preferably, compounds contained in the cavity volume, such as blowing agents, cannot penetrate the shell of the expandable microsphere.

A cavity volume of at least 30 %may enhance the expansion behaviour of the microspheres. However, it would also be possible to use microspheres with a cavity volume of less than 30 %, depending on the desired expansion rate and/or expansion layer thickness.

Preferably, the expandable microspheres contain at least one blowing agent in the cavity volume.

Especially, the blowing agent is a physical blowing agent.

Physical blowing agents (PBAs) are volatile liquids that undergo a change of state during processing to form a cellular structure in plastics or composites. PBAs can also be in the form of compressed gases. Compared to other blowing agent classes, e.g. chemical blowing agents, PBAs are more economical, yield better cell morphology and generate larger volume expansion ratios. A volume expansion ratio of a substance is defined as the volume of a given amount of that substance in liquid form compared to the volume of the same amount of substance in gaseous form, at room temperature and normal atmospheric pressure.

Preferably, the at least one blowing agent is a gas, especially selected from air, carbon dioxide, oxygen, nitrogen, helium, neon, argon, xenon and/or organic compounds which are gaseous at room temperature, in particular hydrocarbons and/or halogenated hydrocarbons, especially methane, ethane, propane, butane and/or pentane, most preferably isobutane and/or isopentane.

The blowing agents used in this invention may provide various advantages such as inert, non-toxic and/or non-flammable properties and/or a very low thermal conductivity.

Preferably, the used halogenated hydrocarbons in the invention have low ozone depletion potential. Ozone depleting potential is a measure of how much damage a chemical can cause to the ozone layer.

However, it is also possible to use solid organic compounds and/or minerals as blowing agents, e.g. ammonium bicarbonate (decomposition temperature 60 ℃) and/or sodium bicarbonate (decomposition temperature between 100–140 ℃) .

In a special embodiment, the expandable microspheres, in particular a shell of the exapandable microspheres, comprise or consist of a thermoplastic material, in particular acrylic resin and/or polystyrene.

Thermoplastic materials have various advantageous properties such as a good adherence to metals, a high-quality aesthetic surface, a resistance to chemicals and/or cleaning agents, they are light-weight and/or exhibit high insulating properties. These properties may improve the intumescent composition with regard to the adherence to building substrates, especially to steel based building substrates, to aesthetics, to the handling, the longevity and/or the fire protection capability.

It is also conceivable that the shell of the microsphere comprises or consists of a mix of thermoplastic, duroplastic and/or elastoplastic material. Generally, it is possible that the shell of microsphere comprises or consists of plastic material.

Preferably, the expandable microspheres have an expansion starting temperature below 100 ℃, in particular between 35 –99 ℃, especially between 50 –99 ℃, preferably between 85 –99 ℃, most preferred between 90 –99 ℃.

This may ensure that a fireproof protective layer is activated in good time before serious heating damage affects the building substrate. However, it is also possible to have an expansion starting temperature that is higher than 100 ℃.

The "expansion starting temperature" is defined as the temperature at which the expansion of the expandable microspheres starts.

Especially, the expandable microspheres have an expansion maximum temperature between 130 -150 ℃, especially between 135 -145 ℃, most preferably between 136 –143 ℃.

This may ensure that the microspheres enfold their maximum volume in the beginning phase of the fire to maximize the fire protection of the building substrate. However, it is also possible to have an expansion maximum temperature that is lower than 130 ℃.

The "expansion maximum temperature" is defined as the temperature at which the expandable microspheres reach their maximum expansion.

In another preferred embodiment, the expandable microspheres have a particle size between 5 –20 μm, in particular between 8 –18 μm, preferably between 10 –16 μm.

The particle size of the expandable microsphere is determined by laser diffraction analysis. This method is advantageous because it provides quick measurement results, has a high sample throughput and no calibration is required.

The diameter of the expandable microsphere can contribute to a smooth surface of the intumescent composition. The intumescent composition is therefore easy applicable to the building substrate, e.g. by spray coating. The inventive particle size can further lead to an even and smooth surface of the intumescent composition when dried, adding to an aesthetically pleasing appearance. The latter is of great importance in regard to visibly installed building substrates, e.g. steel based building substrates installed indoors, such as in shopping malls.

In an especially preferred embodiment, the water glass is selected from the group of sodium silicates, especially sodium orthosilicate, sodium pyrosilicate and/or sodium metasilicate.

Sodium silicates have shown to be stable in neutral and alkaline solutions. Furthermore, sodium silicates seem to be resistant to high temperatures and water.

However, it is also possible to use potassium silicates and/or lithium silicates.

A second aspect of the invention concerns a substrate, especially a building substrate coated with the intumescent composition as described above.

A third aspect of the invention is a method for providing a fireproof substrate, in particular a fireproof building substrate, especially a fireproof steel based building substrate, comprising the steps of

1) Preparing an intumescent composition according to any of the preceeding claims by mixing the components.

2) Applying the intumescent composition to a substrate.

3) Allowing the intumesecent composition to cure.

In a preferred embodiment, step 1) of the method described above comprises the steps of

(i) Mixing the liquid components and stirring

(ii) Adding the solid components and stirring

(iii) Adding the microspheres and stirring

A fourth aspect of the invention concerns the use of the intumescent composition as defined above for fire protection of a substrate, in particular a building substrate, especially a steel based building substrate.

Exemplary embodiments

Preliminary remark

The following exemplary embodiments do not exclude other embodiments according to the invention.

1. Intumescent composition

Table 1 shows five inventive intumescent compositions IC1 –IC5. The intumescent compositions have been prepared by stirring all of the components as follows:

1) Weighing out water, adding sodium silicate (water glass) , defoamer and thickener. Stirring for 20 minutes.

2) Adding titanium dioxide and aluminium hydroxide. Stirring for 10 minutes.

3) Adding expandable microspheres. Stirring for 5 minutes.

The intumescent compositions IC1 –IC5 are present in liquid form.

Table 1:

2. Intumescent composition properties

The intumescent compositions IC1 –IC5 were tested according to the Chinese standard GB 14907–2018 and the standard ISO834. The values obtained by the test methods are summarized in Table 2.

Table 2:

As can be deduced from Table 2, compositions IC1 and IC2 show the highest drying times and are the only ones that show surface cracking. Compared to the remaining compositions IC3 –IC5, IC1 and IC2 contain amounts of aluminium hydroxide (61.7 and 56.7 wt. -%) that are off the proposed inventive solution (i.e. 10 –50 wt. -%) . A positive correlation trend can be presumed in regard to aluminium hydroxide and the surface dying time for all compositions IC1 –IC5, suggesting that higher amounts of aluminium hydroxide may lead to higher surface drying times. Furthermore, IC3 –IC5 were prepared with a higher share of sodium silicate (water glass) , compared to IC1 and IC2. However, for IC5 coat sheading and a higher surface drying time was observed. It is considered unlikely that the amount of sodium silicate (25 wt. -%) in IC5 caused the coat sheading, since IC3 and IC4 were prepared with an even higher amount of sodium silicate (30 and 35 wt. -%) but show no negative sheading effects. IC3 and IC4 exhibit the most favorable properties out of all compositions, while IC3 was prepared according to preferred embodiments according to the invention.

3. Test methods

Surface cracking was tested using a machine similar to a wind tunnel at a wind speed of 3 m/s. Surface cracking was determined by looking at the hardened intumescent composition. If cracks were detected by the naked eye, it was described that surface cracking had occurred.

Hardness was assessed by a pencil hardness test. For this purpose, graphite pencils of varying hardness were moved across the hardened intumescent composition's surface. Its hardness relative to the graphite pencils was determined by the softest pencil that left a scratch on the surface of the hardened intumescent composition, The hardness scale ranged from 9H (hardest) , 8H, 7H, 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B, 4B, 5B, 6B, 7B, 8B to 9B (softest) .

The Fire Resistance Test (FRT) was conducted according to the standard ISO834 using a muffle furnace simulating the effect of a fully developed fire. A steel plate of the size of 500 mm *500 mm *6 mm was coated with intumescent composition. The steel plate was then placed with the coated side facing the heating elements of the muffle furnace. Subsequently, the performance of the composition was determined against a standard temperature-time curve. A sensor was used to measure the back temperature. In this example, the FRT gave information about the time passed until the critical temperature was reached, i.e. the temperature, at which the steel plate failed.

The surface drying time is defined as the time between the application of the intumescent composition and the moment the composition has hardened. For the assessment of the drying time, the applied intumescent composition was touched with a finger. If the surface did not exhibit any stickiness, it was considered hardened.

Expansion ratio is defined as the ratio between the thickness of the intumescent composition after the FRT divided by the thickness of the applied intumescent composition before the FRT.

The bonding strength between the applied intumescent composition and a steel plate of an area of 40 mm *40 mm was measured with a tensile machine.

Claims

Intumescent composition, in particular for protecting a building substrate from fire damage, comprising:

a) 10 –50 wt. -%, in particular 20 –40 wt. -%, especially 30 wt. -%, water glass,

b) 1.0 –6.0 wt. -%, in particular 2.0 –5.0 wt. -%, especially 3.0 wt. -%, expandable microspheres,

c) 10 –50 wt. -%, in particular 20 –45 wt. -%, especially 41.7 wt. -%, aluminium hydroxide and/or magnesium hydrate,

d) 20 –40 wt. -%, in particular 25 –35 wt. -%, especially 30 wt. -%, water.
Intumescent composition according to claim 1 comprising 1 –20 wt. -%, in particular 10 –18 wt. -%, especially 15 wt. -%, titanium dioxide.
Intumescent composition according to any of the preceeding claims comprising:

(i) 0 –10 wt. -%, in particular 0.1 –8 wt. -%, especially 0.5 –6 wt. -%, mica powder,

(ii) 0 –10 wt. -%, in particular 0.1 –8 wt. -%, especially 0.5 –6 wt. -%, kaolin,

(iii) 0 –30 wt. -%, in particular 0.1 –25 wt. -%, especially 1 –20 wt. -%, calcium carbonate,

(iv) 0 –2 wt. -%, in particular 0.01 –1 wt. -%, especially 0.1 wt. -%, defoamer,

(v) 0 –2 wt. -%, in particular 0.01 –1 wt. -%, especially 0.1 wt. -%, dispersing agent,

(vi) 0 –2 wt. -%, in particular 0.01 –1 wt. -%, especially 0.1 wt. -%, thickener, and/or

(vii) 0 –5 wt. -%, in particular 0.1 –4 wt. -%, especially 0.5 –3 wt. -%, other additives.
Intumescent composition according to any of the preceeding claims, characterized in that the expandable microspheres have a cavity volume of at least 30 %, in particular at least 50 %, especially at least 75 %, of the total volume of the expandable microsphere.
Intumescent composition according to any of the preceeding claims, characterized in that the expandable microspheres contain at least one blowing agent in the cavity volume.
Intumescent composition according to any of the preceeding claims, characterized in that the at least one blowing agent is a gas, especially air, carbon dioxide, oxygen, nitrogen, helium, neon, argon, xenon and/or organic compounds which are gaseous at room temperature, in particular hydrocarbons and/or halogenated hydrocarbons, especially methane, ethane, propane, butane, most preferably isobutane, and/or propane, most preferably isopentane.
Intumescent composition according to any of the preceeding claims, characterized in that the expandable microspheres comprise a thermoplastic material, in particular acrylic resin and/or polystyrene.
Intumescent composition according to any of the preceeding claims, characterized in that the expandable microspheres have an expansion starting temperature below 100 ℃, in particular between 35 –99 ℃, especially between 50 –99 ℃, preferably between 85 –99 ℃, most preferred between 90 –99 ℃.
Intumescent composition according to any of the preceeding claims, characterized in that the expandable microspheres have an expansion maximum temperature between 130 -150 ℃, especially between 135 -145 ℃, most preferably between 136 –143 ℃.
Intumescent composition according to any of the preceeding claims, characterized in that the expandable microspheres have a particle size between 5 –20 μm, in particular between 8 –18 μm, preferably between 10 –16 μm.
Intumescent composition according to any of the preceeding claims, characterized in that the water glass is selected from the group of sodium silicates, especially sodium orthosilicates, sodium pyrosilicates and/or sodium metasilicates.
Substrate, in particular a building substrate, especially a steel based building substrate, coated with the intumescent composition according to any of the preceeding claims.
A method for providing a fireproof substrate, in particular a fireproof building substrate, especially a fireproof steel based building substrate, comprising the steps of

1) Preparing an intumescent composition according to any of the preceeding claims by mixing the components.

2) Applying the intumescent composition to a substrate.

3) Allowing the intumesecent composition to cure.
The method according to claim 13, whereas step 1) comprises the steps of

(i) Mixing the liquid components and stirring

(ii) Adding the solid components and stirring

(iii) Adding the microspheres and stirring
Use of the intumescent composition as defined in any of the preceeding claims for fire protection of a substrate, in particular a building substrate, especially a steel based building substrate.