JPS6142068B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to waterproof expandable particles consisting of a core particle of hydrated soluble silicate glass and a surrounding protective waterproof coating. Bayil, J. Vail, JG, Soluble Silicates (1952, Reinhold Publishing
US Pat. U.S. Pat. Soluble silicates (e.g. sodium or potassium silicate) are taught. Patent literature discusses methods for insolubilizing soluble silicate glasses from very early on. Gesner published in 1890. US Pat. No. 4,196,577 discloses that spongy silicate glasses are treated with chemical agents (e.g. calcium chloride, acids such as sulfuric acid or hydrochloric acid; oxides such as barium hydroxide or strontium hydroxide; and calcium nitrate or barium nitrate). Kessner also teaches treating spongy material with soluble oxides or salts of metals other than alkali metals (including soluble salts). metal soap,
Alternatively, it is taught that it can be made impermeable to water by coating it with a solution of oleate or stearate and a rubber or resin. U.S. Pat. No. 3,365,322 to Hinds (1968) discloses coating expandable coated particles in asphalt emulsion, oil, silicone or latex. It is suggested that coating with emulsion can prevent the grains from absorbing water. Another example of prior art regarding the use of expandable silicate materials to make them flame retardant is
Vail (page 483) reports that wood can be coated with a thick silicate solution to reduce the risk of fire. For a different kind of teaching, see Cohen
US Patent No. 917,543 to U.S. Pat.
However, there has been no proposal to make sodium silicate granular or expandable as in the present invention. To the best of our knowledge, in the known prior art:
There is no teaching of a granular silicate glass that is not expanded but is expandable and that has a coating that protects and enhances its expansion capacity during the expansion process and also simplifies its manufacture. The expandable particles of the present invention differ from prior art silicate particles in that they contain a hydrated soluble silicate as a core rather than as a peripheral coating like prior art coated mineral particles. be. Despite past industrial research on hydrated soluble silicates, to the best of our knowledge, no particulate hydrated soluble silicates such as those of the present invention are commercially available, and such particulate hydrated silicates are not commercially available. Nor have soluble silicates been proposed as expandable fire retardant additives.
We have been successful in providing a commercially viable method of manufacturing such particles (described below) and have found that the use of these particles as a layer in roofing materials is superior to that provided by any conventional inflatable roofing material. It has also been found that a far superior fire protection property can be provided. The present invention allows for even more effective waterproofing due to novel hydrated soluble silicate particles with a unique protective coating. This protective coating contains components that ionize in the presence of water to provide metal cations that can react with the silicate ions in the core particles. This reaction between the metal ions and the silicate ions produces a reaction product that is less soluble in water than the core particles, thus forming a protective layer around the particles. This protective coating can be said to have a self-repairing effect. That is, any cleavages that occur in the protective layer tend to become sealed, thereby limiting the action of water on the core particles and preserving the expandability of the particles. Protective coatings also provide the key to conveniently manufacturing expandable particles. Prior to the present invention, two methods were generally considered in the industry for producing hydrated soluble silicate particles. One method involves drying a commercially available soluble silicate solution to a solid having the desired water content, and the other method involves hydrating a commercially available anhydrous soluble silicate material. Both of these methods have their drawbacks. The drying step of the first method creates a film that retards evaporation, significantly increasing operating time. In addition, the hydration step of the second method tends to produce aggregated glass-like substances that are difficult to break into desired sizes. Such difficulties can now be overcome by coating the anhydrous soluble silicate material, crushed to the desired particle size, with the protective coating described above, then hydrated in an autoclave under heat and pressure to the desired moisture content, and ready for use. This was overcome by the discovery that non-agglomerated particles could be obtained. In the remaining manufacturing method, anhydrous soluble silicate microparticles are agglomerated with liquid silicate to a desired particle size, coated with the above-mentioned protective coating, and heated to form an expandable hydrated soluble silicate. forming particles (the heating operation is believed to distribute the water present in the liquid silicate throughout the particles, making them expandable); Particles formed from agglomerated microparticles have the advantage that they tend to form multicellular products (higher crushing strength) during expansion. Another method of manufacturing the particles of the invention (less preferred) is to hydrate uncoated anhydrous soluble silicate particles in a bed of inert particles (eg clay). The protective coating of the present invention can be applied to particles that are already hydrated as well as to anhydrous particles. Although sodium silicate is preferred as the soluble silicate glass for the expandable particles of the present invention because of its low cost, other alkali metal formed silicates (including, for example, potassium and lithium formed silicates) may also be used. The ratio of silica to alkali metal oxide in the silicate used may vary, but silicates with the above ratio of about 2 to 1 or more are preferred because they are less soluble in water than those with lower ratios. . As shown in Table 1, a wide range of expandable particle sizes can be used, and the expanded volume varies with particle size.

[Table] The particle sizes listed in the table above increase above the minimum value,
In addition, the expanded volume has also increased significantly. From the table, particles with an average particle size of about 25 μm expand more than 10 times, and particles with an average particle size of about 100 μm expand more than 40 times. The particles of the present invention should be expanded by at least 4 times, preferably at least 40 times, for most applications as flame retardant additives. It is preferable to use particles with a particle size greater than about 300 μm to obtain the highest volume percent expansion (when giving maximum and minimum values for particle size, the above values apply only to 90 volume percent of the particles) (This is because after sieving, some of the remaining particles fall outside the sieve). For most satisfactory use in roofing, the average particle size should be less than 2 mm, preferably less than 1 mm. However, for special applications, particles up to several centimeters in diameter can be used. The amount of expansion of the particles varies depending on the amount of water present. Curve 1 of Figure 3 is a graph showing the expansion with varying water content of coated sodium silicate particles, generally of the type described in Example 1 below, at typical operating temperatures (i.e. about 200-300°C). and curve 2 is a similar graph for uncoated particles. (These curves represent the expanded volume of a 2 ml sample in ml)
). In Figure 3, the vertical axis represents the volume (ml) reached by expansion of 2 ml of sample particles of the present invention when heated to a temperature range of 200 to 300°C, and the horizontal axis represents the percentage of water present in these particles. represents. Curve 1 in the figure is cut off in the middle, and the water content is approximately
The line where the expansion volume increases until it reaches 13%, and the line where the expansion volume increases until it reaches 13%.
It consists of a downward curve starting from % moisture content. Curve 2 shows the variation in expanded volume obtained with particles similar to the particles of the invention, but not coated like the particles of the invention. To obtain a useful amount of expansion, the soluble silicate should generally contain at least 3% water (preferably at least 10%). The maximum expansion of the exemplified sodium silicate was obtained with a water content of approximately 15%. As the water content increases beyond 15%, the expansion decreases. However, expansion occurs up to (and in fact even beyond) the point at which the soluble silicate dissolves in water (approximately 30%). Containing more than 20% water typically does not provide any significant benefit. Whereas the core particles of the coated particles of the invention are highly soluble in water, the protective coating consists of less soluble components (preferably those having a solubility in water at room temperature of less than 0.2 g/cm ³ ). However, even at this low solubility, sufficient dissociation occurs to provide metal cations that undergo self-healing reactions with the silicate ions of the core particles. The preferred protective coating, which lasts the longest and provides the most complete protection against moisture, consists of metal salts of long chain fatty acids. Stearic acid is preferred as the long chain fatty acid, but other acids such as oleic acid or palmitic acid can also be used. Similarly, the metal is preferably calcium, but the alkaline earth metal barium and other metals such as magnesium, aluminum and zinc can also be used. In the case of the preferred coating just described, when the coating contains the metal as an ionizable compound in excess of the amount required for stoichiometric binding with the anion of the long-chain fatty acid, Maximum stability is achieved. The excess metal in such a metal cation-rich coating can be provided, for example, as a metal hydroxide, carbonate, chloride or fluoride. An ionizable compound that provides a typical excess amount of metal (which accounts for at least 1/2 of the protective coating)
(preferably present in an amount of 2% by volume) is
More soluble than metal salts of long-chain fatty acids. The protective coating of the present invention can also contain other water-insoluble components as adjuncts or substitutes for the metal salts of long-chain fatty acids. For example, polyethylene,
Films of organic polymers such as polypropylene, wax, epoxy resin or urethane resin may also be used. Ionizable components that provide metal cations to react with the silicate ions of the core particles should be included in such coatings to obtain the best stability to water. Yet another component preferably included in the protective coating of the particles of the present invention is a silicone water repellent.
A number of such water repellents are known to repel moisture from surfaces to which they are applied. It has been found that the use of such a water-repellent coating significantly increases the waterproof properties of the protective coating. The long-term stability of the coated particles of the present invention was confirmed by both long-term aging tests on test decks and forced laboratory tests (where the particles are completely immersed in water and their swelling properties are measured at various time intervals). It has been clarified by In the latter type of test, particles of sodium silicate, such as those described in Example 1 below, exhibit useful expansion upon heating even after being soaked in water for 40 days. When the same sodium silicate particles as in Example 1, or without a protective coating, are subjected to a similar test, they do not swell at all after being exposed to water for 1-3 days. Furthermore, when the same sodium silicate particles as in Example 1, but coated with calcium stearate in which calcium and stearate ions are in a stoichiometric ratio, were subjected to a similar test, the expansion of these particles was After 6 to 9 days it drops to the level of the particles of Example 1 after 40 days. The protective coating of the coated particles can be applied by known coating methods. For example, a core particle and a coating material,
For example, they can be mixed while being melted or dissolved in a liquid state. The coating is then cured, such as by cooling, drying, or by reaction, into a substantially continuous film. One of the useful coating methods is
The core particles are first coated with the liquefiable component of the coating (eg, molten stearic acid; oleic acid that is liquid at room temperature; molten polymer such as polyethylene; or liquid uncured epoxy resin cured composition). Then, before the coating cools or hardens, other ingredients, such as metal cation-providing ingredients, are added by mixing the powdered form of the ingredients with the coated core particles. For example, it is convenient to first mix core particles coated with molten stearic acid with powdered calcium hydroxide. After such mixing, the calcium hydroxide is partially embedded in the stearic acid coating, and the calcium and stearic acid react to form nearly insoluble calcium stearate, with unreacted calcium hydroxide remaining in the layer. to provide excess calcium cations for self-healing action. Alternatively to the above method, a metal cation-providing component such as calcium hydroxide can be incorporated into the other components of the protective coating, such as stearic acid, prior to coating the core particles. When using calcium hydroxide and stearic acid, calcium stearate is formed during such a premixing step and must be melted before coating the core particles. The waterproof expandable particles of the present invention have great utility as a component in roofing materials. Despite years of effort, there is no fire-rated asphalt roofing material that can be used as widely as standard non-fire-rated roofing materials. Previous research has taken several directions, namely: using mineral fibers as fillers in asphalt layers or as substitutes for fibers in roofing felt to reduce combustible materials and to reduce fire extinguishment of asphalt. (Fasold
et al., U.S. Pat. No. 2,555,401, Tomlinson et al., U.S. Pat. No. 3,332,830 and Schuetz, U.S. Pat.
3,369,956); containing chemical fire retardants in the roofing material (Tomlinson and Bierly, U.S. Pat. No. 3,369,956);
No. 2,667,425); and/or using an extra or heavier layer of roofing particles. By conducting research in this direction, Underwriter's Laboratories, Inc.
Laboratories Inc.: an independent, not―
for profit organization testing for public
In some cases, commercial roofing materials have been manufactured that are rated as A-class fire protection (by comparison, standard asphalt roofing is rated C-class). However, even this method is not the answer the industry is looking for because it significantly increases the cost of the roofing material, requires special manufacturing equipment and processes, or has limited fire protection. do not have. As an example of the latter drawback, commercially available roofing materials using fiberglass felt pass underwriter laboratories' flammability tests on 3/4-inch (2 cm) thick shingles; It will not pass the test for 3/8 inch (1 cm thick) roof shingles (currently approved for use in construction). Another method attempted by some prior art is to incorporate expandable particles into roofing materials and allow them to expand in the presence of fire, as described in Donegan, US Pat. No. 2,782,129. , to form a ``fire-retardant carrier or stiff sponge that absorbs the asphalt, prevents its runoff, and provides effective fire protection for the roof below.'' Donegan proposed using unexpanded vermiculite as the expandable material, placed as a separate layer between two layers of asbestos-filled asphalt. Bick et al., in U.S. Pat. No. 3,216,883, also proposed the use of vermiculite in an unexpanded or partially expanded state for "builtup" roofs. ing. Hinds, in U.S. Pat. No. 3,365,322 (1968), describes the disadvantages of using vermiculite (it is expensive and lightweight, making it difficult to incorporate a uniform amount into roofing materials), It is proposed to use mineral particles with an expandable coating of sodium acid and borax. None of these studies on inflatable roofing materials were as effective as the other methods mentioned above. Hinds' roofing material was on the market for some time, but without much success. The coated particles hardly expanded, and the fire protection was thought to be due to the asbestos fibers used as filler in the asphalt. Additionally, such filled asphalts are difficult to apply using standard coating equipment;
It was expensive, toxic, and had other drawbacks. Moreover, their coated mineral particles range from 100 to 100 per area of 10 × 10 m ² of applied roofing material.
Flat on the roofing material with a weight of 125Kg. The roof was flood-coated, which added to the cost and weight of the roofing material. Also, the particle coating was soluble in water, and the nearly continuous flat coated layer was particularly susceptible to leaching, resulting in reduced swellability. The vermiculite proposed by Donegan and Bitzke also provides a low volumetric expansion. Also, vermiculite will not expand unless the fire progresses sufficiently to reach a high temperature. In short, there is nothing in the known prior art regarding inflatable roofing materials to suggest that an effective and economical fireproof asphalt roof could be based on inflatables. Also, to the best of our knowledge, the prior art does not teach asphalt-impregnated felt-based roofing materials containing a layer of hydrated soluble silicate particles to impart flame retardancy. New roofing materials can be created by using the waterproof inflatable particles of the present invention. Although this roofing material is of the inflatable type, it has economical and effective fire protection properties that allow for widespread use as roofing materials. In basic construction, this new waterproof inflatable particle roofing material is similar to previous inflatable roofing materials. That is, it generally comprises a roofing felt, at least one asphalt coating on the felt, a layer of roofing particles partially embedded in the topmost asphalt coating of said roofing felt, and a roofing material comprising: Consists of a layer of expandable particles arranged in the roofing material so that it expands when exposed to fire. Also, the expandable material in this new roofing material is a hydrated soluble silicate, which, as mentioned above, is already used in fire-resistant roofing materials as a coating on mineral particles. Despite these similarities, the fire retardant inflatable particle roofing of the present invention is effective where prior art inflatable roofing has not been. One reason that the waterproof inflatable particle roofing materials of the present invention have excellent inflatability is that the hydrated soluble silicate glass particles are protected from erosion by moisture. Moisture leaches alkali metal oxides from the soluble silicate particles, robbing them of their expansive power. Protection against such erosion can be achieved by a particularly thick layer of asphalt, by a particularly high concentration of expandable particles, or by arranging these particles between impermeable films. The effectiveness of these methods is facilitated by the dense nature of the expandable particles used in the present invention. That is, because each expandable particle of the present invention expands to a large volume, fewer particles are required and the particles can be better surrounded and insulated by the waterproof structure. Because the coated particles of the present invention are small in size, highly inflatable, and waterproof, they can be easily and economically incorporated into asphalt roofing materials without significantly changing standard manufacturing methods. I can do things. Relatively small amounts of particles can be used per unit area of roofing material, and particles can be cascaded directly onto standard asphalt roofing materials or partially incorporated into asphalt coatings already incorporated into this roofing material. It can be embedded in. The inflatability exhibited by roofing materials using the waterproof inflatable particles of the present invention can be adjusted by selecting the amount of inflatable particles. Even with relatively small amounts of particles,
To obtain a roofing material having a large expansion volume and a high degree of fire protection. The roofing material containing the expandable particles of the present invention is
2cm thick by Underwriters Laboratories Inc.
Or pass the "standard burnup test" with a 1cm plate. In this test method, the test sample is dried at 40.5 to 49°C for 24 hours, and then placed 5.8cm above a gas burner (flame temperature 888±10°C) in a specified combustion device to be burned. In fact, this roofing material has been subjected to more rigorous experimental tests, namely a 15 x 15 cm ² sample of the roofing material used.
It also passes a test in which it is placed over a Bunsen burner for 30 minutes continuously. The test samples did not survive the fire in either test. When roofing materials using the waterproof inflatable particles of the present invention are subjected to further long-term testing (forced aging tests at restricted test points), the above fire protection properties are maintained over the useful life of the roofing material. There was found. Taken together, these various properties represent a major advance in roofing technology and, for the first time, offer the possibility of producing asphalt-saturated, felt-based roofing in a highly fire-resistant and economical manner. . In addition to being used in roofing materials, the coated particles according to the invention can be incorporated into a wide variety of materials, from solid foams to liquid coating compositions. These particles can be used simply and effectively at a reasonable price due to their waterproof properties and high degree of expansibility. FIG. 1 is a cross-sectional view of a representative roofing material 10 using waterproof expandable particles of the present invention. Roofing material 10
can be manufactured as follows. Roofing felt paper 11 is saturated with an asphaltic composition and its upper surface is coated with the asphaltic composition to form layer 12. Expandable soluble silicate particles 13 are sprinkled onto the coated felt to partially embed the particles in layer 12. A layer 14 of an asphaltic composition is then applied over the particles of the invention and sprinkled over the roofing particles 15 and this layer 14 to partially embed it. Bag coating 16 of asphaltic composition is coated with felt.
A dust coating 17 of mica or the like is applied to the bottom of the paper 11 to make the back side of the roofing material non-adhesive. FIG. 2 is a cross-sectional view of a typical expandable particle 19 of the present invention, which consists of a core particle 20 and a protective coating 21 surrounding it. FIG. 3 is a graph depicting swelling versus water content for coated particles of the present invention and otherwise similar particles without a coating. As shown in FIG. 1, when the expandable particles of the present invention are incorporated into a roofing material, they do not need to be tightly packed. This is because upon expansion, these particles occupy a much larger volume. The coating particles of the present invention may be present in an amount usually not more than about 50 Kg, more usually not more than 25 Kg ^{per 2} 10 x 10 m squares of roofing material to which it is applied. At least 5 Kg, preferably at least 10 Kg of particles per 10 x 10 m ^square are generally used. This layer of particles is typically embedded within the asphalt coating on the roofing felt, but may also be located elsewhere within the roofing material, such as within the felt itself. In addition to being used in roofing materials, the coated particles of the present invention can be used in a variety of polymeric products, including rigid or flexible foams, molded or sheet products, extruded or cast films, elastomeric products, etc. Also useful as a flame retardant additive. Such products may be made from polyurethane, epoxy resin, polyester, and the like. The particles can also be incorporated into various coating materials to form flame retardant coatings. Such coating materials generally consist of a liquid medium that upon exposure hardens to a solid coating to provide a thin coating in a predetermined environment. These particles can also be added in a loose mixture with other powdered materials to provide flame retardancy.
In addition to protecting the substrate from fire, the particles of the invention also serve as a heat barrier. For example, a coating containing a layer of particles of the present invention can be used to prevent steel from reaching temperatures that would damage and warp the steel during a fire. Additionally, the particles of the present invention can be expanded and used for various purposes. For example, the particles can be expanded at the construction site of a building and introduced into walls and other structural parts of the building as insulation. The invention is further illustrated by the following examples. In addition, in the following examples, parts mean parts by weight. Example 1 100 parts of anhydrous sodium silicate glass particles with a SiO ₂ :Na ₂ O ratio of 3.22 and a particle size ranging from 300 to 840 μm are heated in an oven to 250 μm (120° C.). After reaching this temperature, the particles are
Drop into a mixer and add 2 parts of stearic acid powder, the stearic acid will melt and coat onto the particles. Continue mixing for approximately 10 minutes, then add 2 parts of calcium hydroxide and continue mixing for an additional 10 minutes.
Then add 1 part silicone water repellent (DC-772 Sodium Siliconate from Dow Corning) and
Mix for a minute. Pour the coated particles into a tray to form a bed approximately 5 cm thick. Put a loose lid on this tray with aluminum foil and place it in an autoclave.
Hydrate for 2 hours at a steam temperature of 285〓 (140℃).
After removal from the autoclave, the particles are fluid, contain 10% water by weight, and when heated
Expands 65 times. For expansion, a 2 ml sample was gradually poured into an aluminum pot heated to a temperature higher than 400°C (205°C) using a hot plate.
The particles were immediately expanded, then the expanded particles were collected and their volume was measured using a graduated cylinder. The particles of this example were incorporated into a standard roofing material as shown in FIG. The weight of each layer is as follows. 12 layers per ² sections of 10 x 10 m of roofing material each used
is 100Kg, layer 13 is 15Kg, and layer 14 is 300Kg.
The roofing material obtained in this way has a "burning degree"
The test samples were impervious to heat when tested using the more stringent laboratory tests described above. A sample of the roofing material described above was placed on a roof deck within a fixed test point for 5 years and removed from the deck without any visible change, again passing the "burn-up" and more stringent laboratory tests described above. did. Example 2 Example 1 was repeated on a larger batch scale using a rotating autoclave. Calcium hydroxide is 2
I used 20 copies instead of 1. Higher amounts formed a thicker coating on the particles and made them more free-flowing without compromising expansion. Example 3 Example 1 was repeated except that no silicone water repellent was used. The resulting particles were tested in the forced aging test described above and showed useful expansion even after 20 days of exposure to water. Examples 4 and 5 Example 3 was repeated except that stearic acid was replaced with oleic acid (Example 4) or palmitic acid (Example 5). In forced aging tests, particles treated with calcium oleate had a useful life of 6 days in water, and particles treated with calcium palmitate had a useful life of 7 days. Examples 6-8 Example 3 is repeated using sodium silicate particles, except that the calcium hydroxide is replaced with aluminum hydroxide (Example 6), magnesium hydroxide (Example 7), or barium hydroxide (Example 8). Ta. In forced aging tests, particles treated with aluminum stearate had a lifetime of 6 days and particles treated with barium stearate had a lifetime of 9 days. Examples 9 and 10 Sodium silicate was replaced by lithium silicate (SiO ₂ :K ₂ O ratio 2.50) in Example 9 and potassium silicate (SiO ₂ :K ₂ O ratio 2.50) in Example 10 Example 3 was repeated with the following exceptions. When heated to about 200 degrees Celsius, the particles expanded many times. Example 11 Example 3 was repeated except that 2 parts of low density polyethylene powder was used in place of stearic acid. 2
of calcium hydroxide was used. In forced aging tests, the coated particles had a lifespan of 6 days. Reference Example 1 60 parts of the particles of Example 3 were added to precursor Part A.
and 100 parts of a mixture of B (Freeman Chemical
Corporation, Port Washington, Wisconsin). The precursors are cast to form a hard urethane foam having a density of about 0.032 g/cm ³ . This mixture was poured into dishes and allowed to harden. After removal from the pan, the cured sample was tested as described above regarding the flammability of plastics.
After being subjected to a drying process performed by Underwriters Laboratories Inc. prior to the fire test, horizontal fire tests (94HBF) and vertical fire tests (94VE-
O) was carried out. Those equivalent to the "94HBF class" are: A. Those that do not have a burning rate of more than 1.5 inches (38.1 mm) per minute over a 40 inch (101.6 mm) width, or B. Standard value with a flame of 5.0 inches (127 mm). The combustion stops before reaching . In addition, those belonging to the "94VE-O class" are: A. Those that do not burn for 10 seconds or more after the test flame is applied, B. Those that do not burn for a total of 50 seconds when a flame is applied to a set of 5 samples for 10 seconds. , C. does not produce falling combustion particles that scorch a dry absorbent surgical cotton cloth placed 12 inches (305 mm) below the test specimen, and D. combustion growth that remains for more than 30 seconds after the second removal of the test flame. Those that do not show . This sample passed both tests. Reference Example 2 10 parts of the particles of Example 3 were combined with a mixture of 100 parts polyol (TP740, commercially available from Wyandotte Chemical Corporation) and 55 parts polyisocyanate (Mondour MRS, commercially available from Mobay). Then 0.3 part of lead octoate was added to this mixture as a catalyst. After the samples were cured, the horizontal and vertical burn tests of Reference Example 1 were conducted. This sample passed both tests. Example 12 160 parts of anhydrous sodium silicate fine particles (SiO ₂ :
Na ₂ O ratio is 3.22 and particle size is less than about 300 μm) with 40 parts of liquid sodium silicate (silica to soda ratio is 3.22 and water content is about 62%) in a Hobart mixer. Mixed. Agglomerated particles are formed, which are sieved and 300~
Particles with a particle size in the range of 840 μm remained. The particles were coated with 2 parts stearic acid and 5 parts calcium hydroxide in the manner described in Example 1 and then heated in an oven for about 4 hours. The obtained particles are 300
When heated to ℃, it expanded approximately 50 times. Alternatively, particles can be made by coating the core particles with only calcium hydroxide without stearic acid, but these particles are not free-flowing during the hydration process.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an exemplary roofing material incorporating waterproof expandable particles of the present invention, FIG. 2 is a cross-sectional view of representative expandable particles 19 of the present invention, and FIG. 1 is a graph showing the amount of expansion and moisture content of coated particles and particles that are the same but not coated.

Claims (1)

[Scope of Claims] 1. A waterproof expandable particle consisting of a core particle of hydrated soluble silicate glass having a diameter of at least 25 μm and a protective waterproof coating surrounding the core particle, wherein the protective waterproof coating The coating includes a metal-containing component such as calcium stearate that ionizes in the presence of water, said ionization providing metal cations capable of reacting with the silicate ions of the core particles, and the reaction of the metal cations with the silicate ions. Waterproof expandable particles, wherein the product is less water soluble than the silicate glass of the particles, thereby limiting the action of water on the core particles. 2. The particle according to item 1 above, wherein the protective coating comprises a metal salt of a long-chain fatty acid and an amount of metal ions in excess of that required for stoichiometric bonding with the anion of the salt. 3. Particles according to paragraph 1 or 2 above, consisting of relatively small soluble silicate particles with core particles bound together. 4. The particles according to item 1, 2 or 3, wherein the core particles are made of sodium silicate with a silica to soda ratio of greater than 2:1.