DE2451393A1 - METHOD OF MANUFACTURING A LOW DENSITY AGGREGATE BONDED WITH POLYURETHANE FOAM - Google Patents

Description

PATENT LAWYERS

DR-ING, H. FINCKE DIPL-ING. H. BOHR DIPL.-ING. S. STAEGER

Palentanwälte Dr. Back. Bohr · Staeger ■ 8 Munich 5 ■ MOIIerstraBe

β Munich β, 29. October 1974

MOIIarslraße 31 Telephone: {089) · 2ί6OiO Telegrams ι Claims MOnditn X * ♦ 5 I 3 9 Telex 523903 claim d

FolderNo. 23636 - Dr.K / Hö

Please indicate in the answer

IMPERIAL CHEMICAL INDUSTRIES LIMITED, London - Great Britain

"Process for producing a low-density aggregate bonded with polyurethane foam"

PRIORITY: October 29, 1973 - Great Britain

The invention relates to a composite material and more particularly to a low density aggregate bonded with polyurethane foam.

In U.S. Patent No. 3,243,388, a plastic bonded one is used Concrete described in which the spaces between

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the pieces of a mineral aggregate contain expanded plastic, which has closed pores. The mineral aggregate is highly porous. A preferred material is expanded concrete or clay, The expanded Plastic can be a polyurethane foam. For the production of these materials an expandable liquid is used Plastic capable of setting mixed with the pieces of the highly porous mineral aggregate, whereupon the mixture obtained in this way is caused to expand and set, possibly at the same time a Forming the mixture is made.

It has now been found that in the case of polyurethane bonded materials, an improved product is obtained when the pieces of aggregate or filler are moistened with water before being coated with a foamable polyurethane prepolymer be mixed.

The invention therefore relates to a method for producing an aggregate bonded with polyurethane / polyurea Density, being pieces of an inorganic low density filler with a polyurethane prepolymer composition and then causing the composition to foam and set with the label therein is that "the filler is prior to mixing with the polyurethane prepolymer is moistened with water.

It can be considered a number of materials in granular form Filler such as expanded clay, expanded vermiculite, pumice stone, crushed foamed concrete and hollow glass spheres. A preferred material consists of expanded clay balls that are im Are commercially available and can have a wide variety of particle diameters. It is also possible to have a small amount

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a crushed hard polyurethane or isocyanurate foam waste to incorporate. By the term "low density filler" is a filler with a bulk density not over 700 kg / no. Meant.

The amount of water used to moisten the filler should be sufficient, essentially all of its surface area to cover. The water can be prepared by dissolving a thickener such as sodium alginate, sodium carboxymethyl cellulose or sodium silicate, to decrease the rate of water absorption on the porous filler. It can be advantageous to add a water-soluble dye or a pigment dispersion to the water dye so that you can better overlook whether the grains of the filler are sufficiently covered with water.

Wetting the pieces of filler in this manner also reduces the penetration of the polyurethane prepolymer composition into the pieces, thereby reducing the amount of composition required to bind the filler together. The adhesion of the composition to the filler is improved since free isocyanate groups in the composition react with the surface moisture on the filler, with polyurea formation and simultaneous formation of carbon dioxide, which causes foaming, taking place. In this way, a better binding of the filler is obtained than is the case if the filler is subsequently coated with the polyurethane prepolymer composition. ^s

It is of course well known that the mass of the filler by injecting an amount of a conventional Foam mixture for hard urethane can be consolidated,

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but the resistance of the foam to it Expansion through the free space between the pieces gives poor flow and remarkable Tendency to separate the individual pieces, whereby the composition must be held tightly together the dimensions are preserved.

It is therefore preferred that the volume of the polyurethane / polyurea foam is slightly smaller than the volume of the spaces between the filler pieces.

The manufacture of polyurethane prepolymers is in the Literature described in detail. The prepolymers used in the process according to the invention are obtained by that an organic polyol having a molecular weight of at least 300 with an excess, i.e. with 2 to 5 equivalents, of an organic polyisocyanate (both reactants being liquid at the working temperature), so that the product is free isocyanate contains groups. The most favorable excess of polyisocyanate for a given polyol can be found by experiment. For a hard foam, however, the use of approximately 3 to 4 equivalents of polyisocyanate has proven suitable proven.

Any of a wide variety of organic polyisocyanates described in the literature can be used in the preparation of the prepolymers, but the most convenient polyisocyanates for this purpose are, of course, those which are commercially available in large quantities.

It is preferred to use diphenylmethanedilsocyanate,

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which as essentially pure diphenylmethane-4,4'-diisocyanate is available. Of particular importance, however, are the crude MDI compositions, in particular those that are $ 30 to 90, preferably $ 40 to 80, of that 4,4'-isomer, with the remainder from other isomers and poly (pheny! isocyanates) containing methylene bridges with a functionality greater than 2. Such compositions are obtained by phosgenating the crude diaminodiphenylmethane; obtained by condensation of aniline with formaldehyde under acidic conditions as it is described in more detail in the literature. Crude MDI is the preferred polyisocyanate for use in the manufacture of those used according to the invention Prepolymer compositions.

The organic polyols that can be used to implement An excess of an organic polyisocyanate in the preparation of the polyurethane prepolymers are any those polyols which have already been used in the art for this purpose. In particular, polyethers can be used and preferably those having molecular weights of 300 to 8000 and by reaction or more alkylene oxides are prepared with compounds having a plurality of reactive hydrogens, wherein if appropriate, the work is carried out in the presence of a basic or acidic catalyst, as detailed in the literature is described.

Other suitable polyols are the polyesters, which preferably have molecular weights from 300 to 6000, and which can be obtained from polycarboxylic acids and polyhydric alcohols. This is also described in detail in the literature. By

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the incorporation of a portion of a diamine or a Amino alcohol to the polyhydric alcohol in the polyester formation reaction mixture a polyester amide is obtained.

The viscosity of the prepolymer depends on the composition of the starting materials and on the excess polyisocyanate used away. It can be varied accordingly. In general, the use of a polyol yields with a high functionality and a high hydroxyl number Prepolymers with a high viscosity, while the use of a large excess of polyisocyanates tends to be the viscosity decreases.

The prepolymer which is preferred for this application is one based on crude diphenylmethane di-cyanate, which is reacted with a polyether or with a polyester in such an amount that a viscous but still liquid composition is obtained. Prepolymers with a viscosity of 2 to 20,000 poise, preferably 20-2000 poise at 25O ⁰ C, are suitable.

The polyurethane prepolymers used according to the invention can also contain other additives, such as catalysts, surface active agents, flame retardants and low boiling point blowing agents. Suitable catalysts are tertiary Amines or organometallic compounds. They accelerate the reaction between isocyanate and hydroxyl groups. Suitable Surfactants are e.g. organosilicon polymers which stabilize the foam until hardening has taken place Has. The other flame retardants are tris (chloroethyl) phosphate and tris (chloropropyl) phosphate.

The propellant used in the process of the invention Is opposite to the other constituents

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of the system inert. It has a sufficiently low boiling point that it can rapidly evaporate due to the heat from the polyurethane formation reaction. Suitable inert blowing agents are those which have already been used in the past for the production of polyurethane foams. It should, for example, halogenated hydrocarbons having boiling points not mentioned about 5O ⁰ C at atmospheric pressure and in particular fluorinated hydrocarbons. Dichlorodifluoromethane and trichlorofluoromethane are particularly suitable propellants for the compositions used according to the invention. The amount of blowing agent in the prepolymer can be varied depending on the foam density desired. It can be from 10 to 100 weight. -% or more, based on the polymer, are sufficient.

The propellant also serves as a reduction solvent the viscosity of the mixture.

Water can also be used as a blowing agent. The water used to dampen the filler also works that way. When water reacts with isocyanate groups, carbon dioxide is set free and one Urea bond formed. The carbon dioxide released causes the mixture to foam. There is presence of free isocyanate groups required. A prepolymer, which Contains free isocyanate groups, so foams on contact with water.

It should be noted that because of the presence of

the polymer formed. Water in the process according to the invention / in addition to urethane grouting also contains urea groupings. The expression "Polyurethane" as used in this specification also includes polymers that are both urea and Contain urethane groupings.

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The method according to the invention is carried out by that first the aggregate or the filler with water as described above, moistened, then the moistened filler is coated with the polyurethane foam raw material, using a suitable drum device, such as an ordinary concrete mixer is used. That The entire mixture is then transferred into a cavity formed by a mold in which the foaming and Curing of the polyurethane takes place. The amount of the polyurethane foam raw material is preferably such that the resulting foam occupies slightly less volume than the volume required to fill all of the free Space between the particles of the filler is necessary. It should be noted, however, that the amount of hardened Foam must be sufficient to achieve a firm bond between the aggregate particles. The minimum amount, which can be used is approximately $ 90 of the free space between the particles. The amount of polyurethane foam raw material must therefore be sufficient to produce at least this amount of cured foam.

The use of the preferred MDI-based polymer compositions in the process of the present invention provides one simple technique, since the only component is packaged and, as required, using a concrete mixer Moistened aggregate can be applied, whereby none of the usual foam measuring devices is required.

Because the entire space between the aggregate particles is not filled, only little pressure is developed, therefore light forms can be used, such as those used for pouring concrete. Because the aggregate particles largely in physical contact with each other

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remain, an optimal compressive strength is ensured in the hardened material. Furthermore, the presence of small residual pores and interconnected spaces of value insofar as when exposed from heat or fire caused by pyrolysis of the polyurethane foam formed gases can escape internally and thus possibly not existing surface coverings be pushed away by a pressure development of these gases.

The filler / prepolymer composition can be sandwiched between panels a top layer material can be caused to foam, for example between gypsum boards, with lightweight building boards can be obtained. In this case, the same polyurethane prepolymer composition can be used can be used for bonding between the surface material and the foam when the surface mate rial is precoated.

There is a tendency for more free space to develop at the foam / surfacing material interface and therefore some more prepolymer blend can be used to make this Counteract appearance. But it is also possible to pre-coat the surface layers with the prepolymer mixture, by spraying this on by any suitable device.

The adhesion properties of the foamed material obtained according to the invention are extremely good. The procedure is effective even on damp surface layers. If no surface layers are required, then extraction can take place of the product from the mold can be facilitated by using a polyethylene film or one coated with silicone Insert paper into the form. The inventive method can generally be used in a similar manner for pouring lightweight concrete. When removing from the mold

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The rough surfaces that are held provide a good anchorage for mortar or approaches, as is customary in building practice. By appropriately setting the amount of catalyst used, either rapidly curing systems can be obtained, which are particularly suitable for the production of building panels in the factory. But slow-reacting systems can also be used can be obtained that are used on the spot when the coated aggregate is driven a distance must before it is shed.

The invention will now be explained in more detail by the following examples, in which all parts and percentages are by weight are expressed unless otherwise specified. The ratio between parts by weight and parts by volume is that of kg: l.

example 1

8000 parts of dry unscreened expanded clay balls "Leca" 4-30 mm in diameter were placed in a concrete mixer and then tumbled with 150 parts of water. That Water contained IJS sodium carboxymethyl cellulose as a thickener. Mixing was continued for 2 minutes to distribute the water. Then 1000 parts of an MDI-based prepolymer ( as described below) and tumbling continued for an additional 2 minutes. The coated Balls were then placed in a yoked plate-made mold, that is, sandwiched between a Metal plate and a plasterboard was placed, with the form at the base and on the side edges was framed.

The mass of the balls and the foam-forming composition

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was then vibrated to consolidate the mixture. To a few minutes the prepolymer composition began to foam, largely removing the voids between the Balls and also between the surface layers filled up. The foaming was over in 15 minutes. It was cured after 30 minutes so advanced that the yoke could be removed from the surface plates.

The prepolymer used in this example was prepared by mixing 60 parts of an oxypropylated glycerol with a molecular weight of 600, 50 parts of tris (chloropropyl phosphate, 2 parts of silicone 1.53 ² JO and 1 part of N, N-dimethylhexadecylamine, and the mixture The reaction proceeded with generation of heat and an increase in the viscosity of the mixture. After 15 minutes the stirring was discontinued and the mixture was allowed to cool to below 23 ° C, whereupon 60 parts of trichlorofluoromethane were added and under Stirring were incorporated, so that a storage-stable, viscous but pourable liquid was obtained ..

In the finished composite product, these are the gaps between the expanded clay balls mostly but not completely filled with foam. The surface plates are well connected, but with some interconnected voids at the interface, which allow pyrolysis gases to escape, if For example, the steel surface is heated above the decomposition temperature of the foam. This avoids that the surface layer due to the pressure in the gas pockets, which, if the cavity is completely filled with foam,

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standing, being pushed away.
Example 2

The procedure of Example 1 was repeated except that only 700 parts of MDI-based prepolymer were used and the inner surfaces of the topsheet panels were coated with JOO parts of the same mixture as that was diluted with a further 300 parts of trichlorofluoromethane to obtain a prepolymer viscosity suitable for spraying to achieve.

In this way those related to each other became Relocated cavities in the central area of the unit, which also improves the bonding of the surface layers so that the entire structure had increased strength.

PATENT CLAIMS

PATCNT LAWYER'S MUM. H. FiNCXE, DIPL-INO. H.

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Claims (9)

PATENT CLAIMS / l / Method of manufacturing with polyurethane / polyurea bonded low density aggregates in which pieces of an inorganic low density filler mixed with a polyurethane prepolymer composition and the composition for foaming and setting is caused, characterized in that the filler prior to mixing with the polyurethane prepolymer is moistened with water. 2. The method according to claim 1, characterized in that expanded clay balls are used as filler. 3. The method according to claim 1 or 2, characterized in that the amount of water used to moisten the filler is sufficient to coat substantially the entire surface of the filler. ^. Method according to one of Claims 1 to 3 »thereby characterized in that that for wetting the filler water used contains a thickener. 5. The method according to claim k _t, characterized in that sodium alginate, sodium carboxymethyl cellulose or sodium silicate is used as the thickening agent. 6. The method according to any one of claims 1 to 5> characterized in that the volume of the polyurethane / polyurea foam makes up at least 90% but less than $ 100 of the space that is present between the filler pieces. 509819/1016 7. The method according to any one of claims 1 to 6, characterized characterized in that the filler / prepolymer composition between panels of a surface material is caused to foam in order to produce lightweight construction panels to manufacture. 8. The method according to claim 7, characterized in that that the surface material consists of plasterboard. 9. The method according to claim 7 or 8, characterized in that the surface material with the polyurethane prepolymer is precoated. 509819/1016