FR2483322A1 - Light high strength, incombustible rigid articles - with low resin content, formed by coating liq. resin on fly ash, shaping and setting - Google Patents

Abstract

Mfr. of shaped, rigid articles comprises forming a thin coating of liq. resin of viscosity 10 Stokes on a thermally stable particulate material (I), where msot or all of (I) comprises fly ash spheres. The mixt. is then formed into a pre-selected shape with the resin bonding (I) together. The product contains 15 wt.% resin, adn pref. has a cold tensile strength of >=125 psi. In one method, liq. resin is dried to form coatings on individual particles of (I) prior to forming into required shape, and the resin is heated to soften or melt it. On resolidifying, the resin bonds (I) together. A pref. method is when (I) and liq. resin produce a doughy mixt. which is formed into require shape and set. The articles are esp. useful as building panels, fire doors, in furniture, etc.. High tensile strength and light wt. products are obtd. using little resin.

Description

 The present invention relates as a whole to rigid articles formed of a particulate material and of a binder of the resin type, and it relates in particular to articles of this kind in which a dominant proportion of the particulate material is in the form of fly ash spheres.

 One of the main aims of the present invention is to find an economical process for the production of rigid articles comprising fly ash spheres and a binder of the resin type and having a relatively high tensile strength, in particular in relation to to the amount of resin used.

 Another object of the present invention is to produce rigid articles comprising fly ash spheres and a binder of the resin type, and having a relatively high tensile strength for any given resin content.

 Another object of the present invention is to produce articles of this kind which also have other advantageous properties such as incombustibility, good structural integrity and correct acoustic properties.

 The invention also aims to produce articles of extremely light weight.

 Other characteristics and advantages of the present invention will emerge from the detailed description which follows and from the examples which illustrate it.

 The present invention provides a method for producing rigid articles of predetermined shapes, which method consists in preparing a mixture of a thermally stable particulate material and a liquid resin of viscosity less than about 10 3 m2 / s to form a thin coating of resin on the particles, at least a dominant proportion of the particulate material being formed of fly ash spheres, and to give the resulting mixture a preselected shape, the resin binding the particles together to form a rigid article having the shape predetermined and containing less than about 15% by weight of resin. The resulting article formed in accordance with the invention preferably has a cold tensile strength of at least about 1.05 MPa.

 The invention is based on the discovery that coating fly ash spheres with only small amounts of a resin in the form of a low viscosity liquid produces a product with extremely high tensile strength after the resin has solidified. Instead of decreasing in proportion to the reductions in resin content, the tensile strength remains relatively high for resin contents of less than 15% and even less than 10%, relative to the weight of the final product. found that the tensile strength per unit weight of the resin actually increases for resin levels of less than 15% by weight, in particular less than 10% by weight, and / or for viscosities of less than 10 3 m2 / s , notably less than 5.10 4m2 / s. Consequently, such products can be formed at a relatively low cost price due to the low resin content which is normally the most expensive ingredient in compositions of this type. However, the mechanical resistance of the product is high enough to allow its use in many applications which require appreciable structural resistance.

 Although it is not desired to limit the invention to any particular theory, it is believed that the low viscosity liquid resin forms an extremely thin coating on the fly ash spheres, and that these coated spheres agglomerate tightly so that the thin Resin coatings on adjacent spheres can come together and form a strong inter-particle bond. As a result, the final product has a relatively high tensile strength even when the resin is used only in small amounts.

The fly ash particles which are used according to the invention are not only spherical but also hollow and, therefore, their density is low. These spheres represent a common constituent of fly ash from most sources, and are separated from the denser solid constituents by methods well known and practiced in the industry, using selective flotation. For example, the fly ash spheres of the firm Fillite
USA Inc. of Huntington, West Virginia, which we find under the name of "Fillite", have a density less than 0.7 and their particles have a diameter of 5 to 300 pm Similar spheres of fly ash are proposed by PAIndustries Inc. of Chatanooga, Tennessee, under the designation "Extendospheres". As is well known, fly ash is mainly formed from silica and alumina with a small amount of iron oxide and alkali metal oxides, and they have a high melting point, for example 12000C.

 If necessary, other particulate and / or fiber materials can be mixed with the fly ash spheres, provided that the latter constitute at least about 50% of the non-resin content of the final product. Examples of other suitable particulate or fiber materials which can be added to fly ash to vary the properties of the final product are vermiculite, perlite, refractory material, calcined rice husk, graphite, wool mineral, asbestos, fiberglass, glass or plastic microspheres, etc.

 The resin which is used as a binder in the present invention must be available in liquid form and must have a viscosity of less than about 10 3 m2 / s.

It is preferable that the liquid resin is stable at room temperature, so that the fly ash and the resin can be mixed without the use of heaters, and also to allow the storage of the liquid resin at room temperature . Liquid resin can be formed by dissolving solid resin in a solvent, by dispersing extremely fine particles of solid resin in a liquid vehicle, or by using a resin that is normally in the liquid state before it solidifies.

 Several different resins which can be advantageously used in the present invention will be described below by way of examples, but it should be noted that the invention is applicable to most resins which are available in the form of liquids with the correct viscosity and which form a substantially continuous coating on each individual particle of fly ash when intimately mixed with them. The curing of the resin is preferably carried out by means of hot air which expels the solvent or the liquid vehicle and / or raises the temperature of the resin to its point of solidification, or at least accelerates the latter.

In the case of certain resins, a catalyst is mixed with the resin in its liquid form to activate its hardening, and this is the case for certain resins described by way of examples in the following.

 To facilitate the operation by which the desired shape is given to the mixture of fly ash and resin, the latter in the liquid state and the fly ash are preferably mixed in proportions capable of producing a paste-like mass which can further to be molded, but which no longer flows. This paste is then shaped to the desired shape, normally by molding, and finally the resin is hardened and dried so as to form the desired rigid article. For certain resins, such as a phenol-formaldehyde resin dissolved in alcohol, the resin-coated fly ash can be dried in the manner of a particulate material, for example by an operation in which the fly ash is subjected to the action of air heated to a certain temperature or by sustained mixture at room temperature, before transformation into an object of desired shape. The coated fly ash is then placed in a mold or in a pattern having the desired shape and is heated to a temperature in the range of 204 to 2600C so as to soften and ripen the resin and thereby bind the fly ash according to the desired shape. Again, examples.

particular of these mixing and forming operations will be described in detail in the following.

Examples of liquid resins which can advantageously be used in the present invention include a phenol-formaldehyde resin dissolved in ethyl alcohol and mixed with hexamethylenetetramine as catalyst (for example the resin "Plenco 212" from the firm Plastic Engineering Company); solutions of alkyd type resins (for example "Linocure", resin of the firm
Ashland Chemical Co. of Columbus, Ohio); solutions of phenolic urethane resins (for example the resin "6100/6300" from the company Ashland Chemical Co.); and furan resins which are normally in the liquid state at room temperature and which therefore do not require a solvent (for example the resin "Chem Rez 290" from the company
Ashland Chemical Co.).

 The rigid shaped articles of the present invention are particularly useful in applications which require noncombustible rigid cores of low weight, such as panels used in building, coated with thin sheets of metal, wood or plastic; basic supports for furniture; fire resistant doors, etc.

The invention is illustrated by the following examples, given without limitation. The tests to which reference is made in the examples were carried out substantially according to the procedures indicated below.
Cold tensile strength
An arc-type mechanical strength determination device, driven by a Dietert NO 400-1 motor (firm Harry W. Dietert Co.; Detroit, Michigan), equipped with an accessory for measuring the tensile strength at cold Dietert N0 610-N, is used to break up samples called "cookies". The cold tensile strength, in MPa, is read directly from the shear scale provided on the device.

Fire loss
Two grams of the test material are placed in a previously weighed basket with a cover, and the basket and the material are then placed in a muffle furnace maintained at 9270C, and they are heated for 45 minutes. The basket and material are then removed from the oven, allowed to cool to room temperature and weighed again. The final weight of the basket and the material is subtracted from the initial weight of the basket containing the material, and the difference obtained is divided by 2, then multiplied by 100 to give the percentage loss on ignition.

Compressive strength
An arc-type resistance measurement device is used, driven by a Dietert NO 400-1 motor (from the firm Harry W. Dietert Co., Detroit, Michigan) equipped with a Dietert NO 410 accessory for the measurement. strong mechanical strength when dry. The samples are cylinders 5.08 cm high and 5.08 cm in diameter.

Examples NO 1 to 4
90.72 kg of fly ash and the indicated amounts of a normal mixture of hexamethylene tetramine and calcium stearate are mixed in a standard Fordath mixer at room temperature. After stirring for 30 seconds, the indicated amounts of a solution of phenol-formaldehyde resin in ethanol are added (content of -4 solid resin of 50% by weight, viscosity of 1 to 2.10 m / s). Stirring is continued for 1 minute, then air heated to 2320C is introduced into the mixer to evaporate the solvents. Mixing is continued for another 7 to 9 minutes to form a mixture in which the agglomerated masses begin to fragment. This mixture is then discharged from the mixer, sieved and dried. Test "biscuits" for the tests are formed in a pattern at 2320C, matured for 1 minute, cooled to room temperature, then subjected to the tests for determining resistance to cold traction ("TF") and loss on ignition ("PF"), which gives the following results
Hexa resin / SCPF TF, TF / resin
liquid MPa NO 1 10.69 1.02 7.1% 0.59 0.083 NO 2 19.8 1.9 11.6% 0.97 0.084
N 3 28.9 2.8 17.5% 1.34 0.077
N 4 38.1 3.6 20.0% 1.57 0.079
Examples 5-6
For comparison purposes with Examples 1-4, the same procedure was repeated using the same resin, but in a solution containing 70% solid resin (viscosity 50.10 4 m2 / s), which gave the results following
Hexa resin / SCPFTF, TF / resin
liquid MPa
N 5 7.6 1.0 6.2% 0.37 0.060
N 6 20.7 2.8 16.0% 1.18 0.074
Examples 7-8
600 g of fly ash are mixed in a Hobart mixer with the indicated quantities of an alkyd-type liquid resin ("Linocure" from the company Ashland
Chemical Co.) containing 80% by weight of solid resin in a solvent and having a viscosity of 4.38 × 10 4 m2 / s. Stirring is continued until the fly ash is completely wet (approximately 4 minutes), by forming a pasty mass which is then transformed into "test cookies in a pattern at room temperature, which is left to mature for 24 hours at room temperature, then subjected to resistance tests to cold traction (TF), which gives the following results h
Resin Resin,% TF, TF / resin
liquid MPa
N 7 150 g 20% 3.91 0.195
N 8 60 g 8% 2.90 0.362
Examples 9 to 14
The procedure of Examples 7 and 8 is repeated using 600 g of fly ash and the indicated amounts of a phenolic urethane liquid resin (resin "6100/6300" from the company Ashland Chemical Co.) containing 70% by weight of resin solid, in a solvent, and having a viscosity of 0.5.10-4 m2 / s. It is a three-part resin, part A (30 g) of which is added first at the same time as the catalyst, stirred for approximately 2 minutes, then part B (30 g) is added and the whole is stirred for another 2 minutes. The resulting pasty mass is transformed into "cookies" test pieces in a pattern at room temperature, matured for 24 hours at room temperature, then subjected to cold tensile strength tests. ("TF") and compressive strength ("Comp.") Giving the following results
Resin Resin,% TF, TF / resin Comp.

liquid MPa MPa NO 9 36 g 4.2% 1.12 0.267 3.85 NO 10 48 g 5.6% 1.57 0.280 4.79 NO 11 60 g 7.0% 1.69 0.241 5.63 NO 12 72 g 8.4% 2.00 0.238 5.82 NO 13 90 g 10.5% 2.04 0.194 5.77 NO 14 120 g 14.0% 2.07 0.148 6.78
Examples 15-17
The procedure of Examples 7-8 is repeated using the indicated quantities of a liquid furan resin ("Chem Rez 290" from the company Ashland Chemical Co.) comprising 100% of resin having a viscosity of 0.75.

îo 4 m2 / s. The resulting pasty mass is transformed into
"biscuits" test tubes in a pattern at room temperature, matured for 24 hours at room temperature, then subjected to. cold tensile strength tests, which gave the following results
Resin Resin,% TF, TF / resin
liquid MPa
N 15 60 g 10% 2.88 0.288
N 16 45 g 7.5% 1.54 0.205
N 17 30 g 5% 1.12 0.224
As the preceding examples show, for any given resin, the tensile strength obtained per unit weight of resin generally increases sharply as the resin content drops below about 15% by weight and / or as the viscosity of the liquid resin decreases. This trend is particularly noticeable for resin contents of less than 10% by weight and for viscosities less than 5.10 4 m2 / s. For example, if we compare examples 1 to 4 with examples 5 and 6, we can see that the tensile strength per unit weight of resin decreases significantly when the 70% resin solution (50.10-4 m2 / s) is used instead of the 50% resin solution (1-2.

10-4 m / s). Examples 7-8 show an even greater variation in tensile strength per unit weight of resin at resin levels of 8 and 20% by weight.

 It goes without saying that the present invention has only been described for explanatory purposes, but in no way limiting, and that numerous modifications can be made thereto without departing from its scope.

Claims (7)

 1. Process for the production of rigid shaped articles, characterized in that it consists  preparing a mixture of thermally stable particulate matter and a liquid resin having a viscosity of less than about 10 3 m2 / s to form a thin coating of resin on the particles, the particulate matter being formed at least in a dominant proportion of fly ash spheres, and  causing the resulting mixture to take a predetermined shape by bonding the particles together by the resin to form a rigid article having said predetermined shape and containing less than about 15% by weight of resin.  2. Method for producing rigid articles according to claim 1, characterized in that the rigid article obtained has a cold tensile strength of at least about 0.875 MPa.  3. A method of producing rigid shaped articles according to claim 1, characterized in that the mixture of particulate matter and liquid resin is dried to form a solid coating of said resin on the individual spheres of fly ash and on all other particulate matter contained in the mixture, before the latter takes a predetermined shape, and the resin is melted and resolidified during the forming step to bond the particles together.  4. Method for producing rigid shaped articles according to claim 3, characterized in that the liquid resin is initially dried on - the fly ash particles to form a resin-coated particulate material, then the material thus coated is caused to take said predetermined shape, it is heated to soften the resin and the resin is cured to bond the particulate material into a rigid article having said predetermined shape.  5. Method for producing rigid articles of shapes according to claim 1, characterized in that the proportions of particulate matter and liquid resin in the mixture are chosen so as to produce a pasty mass which can be brought to take said shape predetermined.  6. A rigid shaped article comprising a mixture of a thermally stable particulate material and less than about 15% by weight of resin, said resin forming a coating on each individual particle and binding the particles together, at least a proportion dominant of said particulate material being formed of fly ash spheres and the resin coating being formed of a liquid resin having a viscosity of less than about 10 3 m3 / s.  7. rigid article of form according to claim 6, characterized in that its resistance to cold traction is at least equal to 0.875 MPa.