Foamed plastics laminates

Refractory foam laminate

This invention relates to laminated articles having improved fire resistance, in which the core is made of a rigid foamed plastic material.

Rigid foams are widely used in the construction industry due to their unusually good thermal release properties. Unfortunately, the disadvantage of most rigid foams is their flammability, which is mainly due to their organic chemical structure. In addition, the physical structure of these foams can contribute to the spread of fire.

Laminated products with a rigid foam inside can be made continuously or individually in a mold or frame. The continuous lamination process usually involves applying a foam-forming plastic composition to one or two topsheets and contacting the second sheet with the composition prior to curing and sometimes prior to foaming. Because of their low cost and ease of handling, the cover sheets are suitably often paper or aluminum foil that can be fed from a roll. However, there is an obvious disadvantage of these materials in a fire. The paper cover is flammable and the aluminum foil may melt and peel.

As building regulations become more demanding, there is a growing need for a better flame retardant rigid foam laminate.

Various ways to improve the fire resistance of these laminates have been tried and include the addition of flame retardants to the foam itself and the use of bubbling and charring layers as well as non-combustible topcoats during combustion. The non-combustible materials used include asbestos cement board, steel, tempered glass, gypsum board and perlite board. Although these materials provide a refractory coating, they lack flexibility and are thus unsuitable for many purposes and are difficult to use in the continuous manufacture of laminates.

FR patent 1 386 455 describes panels for the production of wall coverings which act as sound insulation. The known panels consist of two layers of expanded vermiculite and are separated by a layer of rigid polyurethane foam.

The layers of expanded vermiculite can be provided with cover plates, which can be bitumen-coated aluminum or anodized aluminum. The FR patent publication does not disclose the fire resistance properties of the panels.

The invention relates to a refractory laminated product comprising a rigid foam core which is at least partially covered by a composite layer consisting of vermiculite and a metal film. The invention is characterized in that the vermiculite layer consists of delaminated vermiculite lamellae.

Rigid foam materials that can be used to make the laminated articles of the invention can include all materials previously known in the art. Examples of these materials are polyurethane, polyisocyanurate, polyurea, polyolefin, polystyrene, phenol formaldehyde, epoxy and other polymer foams.

The term rigid foam is commonly used by foam manufacturers and its manufacturing methods from these various materials are well known.

Of particular interest to us are laminates made of rigid polyurethane and rigid polyisocyanurate foam, and especially those made continuously. In general, the density of these foams is in the range of 10-80 kg / m 2. However, foams with a higher density, for example up to 1000 kg / m, can also be protected with a vermiculite / metal film combination; these foams are usually made in a press or rigid mold, for example by reaction injection molding. If desired, the foams may contain conventional flame retardants such as tris (haloalkyl) phosphates, reinforcing fibers (e.g. glass fibers or filaments) and fillers (e.g. fly ash, expanded perlite) which may have swellable substances on their surface when charred.

In combustion, carbonizable and swellable materials can also be used as sheets and can be placed as intermediate layers in laminates or as part of the top layer of laminate. Other cover materials may also be used in part.

The term vermiculite as used herein refers to materials that are mineralogically and commercially known as vermiculite. By the term vermiculite lamella we mean particles of shale vermiculite which are plate-like and have a large aspect ratio (length or width divided by thickness). They can be obtained by chemically slicing vermiculite and preferably have a particle size of less than 50 micrometers. The thickness of these particles is less than 0.5 micrometers, usually less than 0.05 and preferably less than 0.005 micrometers. They have an aspect ratio of at least 100, preferably at least 1000, for example 10,000.

The formation of vermiculite sheets from swollen vermiculite after its dealmination to reduce the size of individual particles or lamellae to colloidal dimensions is disclosed, for example, in British Patent Publication Nos. 1,016,385, 1,076,786 and 1,119,305 and in particular in GB Patent Applications 39,510 / 76 and 51.

The method disclosed in these GB patent applications is directed to the manufacture of shaped articles, including sheets, papers and films, from vermiculite and comprises the following steps:

1. Swelling of the vermiculite by contacting it with an aqueous solution containing at least one salt of sodium, lithium or organosubstituted ammonium cation, followed by washing with water so that the ore swells at least twice, preferably four times, the original volume.

2. Delamination of the swollen vermiculite by applying an abrasive effect to the particles of the aqueous suspension obtained from step 1 until a suspension can be obtained in which the vermiculite particles have dimensions of less than 50 micrometers and have a flocculated viscosity of at least 100 centipoise.

3. Removal of all particles larger than 50 micrometers in diameter, preferably greater than 20 micrometers, from the suspension.

4. Forming a shaped article from the resulting suspension by removing water and shaping the article against a solid surface by applying vermiculite particles from the suspension.

The term flocculated viscosity means the highest viscosity of a suspension, after flocculation with dilute hydrochloric acid, containing not more than 7% by weight of vermiculite solids.

-1 at a cutting speed of 58 see

The thickness of the vermiculite sheets obtained in this method may range from 0.05 to 0.5 mm.

The present invention is based on the finding that vermiculite lamella particles applied as a suspension or slurry to a metal substrate, and especially if sorted by removing larger particles from the sheet, adhere firmly to metal surfaces and cover them well. No detachment occurs when bending. Surprisingly, these properties of vermiculite turn out to be quite unique among silicate layer minerals and are not possessed by, for example, talc, mica, kaolinite or montmorillonite.

Metal films suitable for use in the invention are preferably low-melting films, especially films made of aluminum and its alloys, although other films, for example of the iron type, may be used. Commonly used alloying agents with aluminum are copper, magnesium, manganese, silicon, zinc and nickel. Chromium, titanium, cadmium, niobium, cerium, tin, lead, bismuth, beryllium, boron, zirconium and vanadium can also be used in these alloy films.

By low temperature melting films we mean films that melt at or below the temperature generated by a fire in a building and can be between 800 and 900 ° C. Thus, films that melt below 1000 ° C are included.

The laminates according to the invention have significant advantages in the event of a fire if they are used for lining the walls or roofs of a building. For example, most aluminum alloy films melt at high fire temperatures if the surface temperature exceeds 650 ° C so that the surface layers made of these films do not effectively protect the foam interior of the laminate. Aluminum films coated with vermiculite lamellae form a flame retardant layer on the foam, even though the aluminum surface film melts locally in high temperature flames.

Iron films become very brittle in a high temperature flame so that its use as a surface material as such is limited. When coated with vermiculite and especially fiber-reinforced vermiculite, as shown below, its value as a refractory layer is improved.

The vermiculite layer can be reinforced with a fibrous material that prevents the formation of cracks in the combination and also improves its rigidity. The folds are removed during manufacture.

Fibrous materials that can be used to reinforce the vermiculite layer include inorganic fibers and organic fibers, both naturally occurring and synthetic. They may be short or long fibers, strands or yarns cut, woven in gauze, mat or mesh form.

Examples of inorganic fibers that can be used include glass fibers including fibers made of calcium aluminum borosilicate glass (E glass), other glasses such as commercially known A and C glasses, and specialty glasses such as R and S glasses, aluminum and zirconium fibers, rock fibers and asbestos.

Examples of naturally occurring organic fibers include cellulosic fibers such as cotton, jute, flax and hemp, kapok, sisal, and lignocellulosic fibers as well as regenerated cellulosic fibers including cellulose acetate and viscose composite silks.

Examples of synthetic organic fibers are polyester, polyamide, polyacrylonitrile, polyvinyl alcohol, 'Aramid ¹-ofibres made from aromatic polyamide, polypropylene, high density polyethylene, polyvinyl chloride and carbon fibers.

Of particular interest are fiberglass.

They can be used as staple fibers or continuous fibers with a diameter of, for example, 5 to 30 micrometers; as continuous or discontinuous yarns which may consist of 10 to 1000 strands; as pre-spinning yarns consisting of a plurality of strands twisted, twisted and laminated; or as support platforms formed therefrom. The support substrates may consist, for example, of regular woven mats and mats consisting of both short and long mixed fibers, mixed staple fibers and continuous mixed fibers. They are preferably dense, substantially non-compressible mats.

The reinforcement layer of the vermiculite may also contain other chemicals, for example, lubricants, adhesives or binders derived from fiber production and flame retardants (especially those that retard the spread of flames such as halogenated materials, antiomonitrile, alumina trihydrate, borates) and phosphates.

The fire resistance of the composite layer of reinforced vermiculite and metal film is improved if the vermiculite particles completely surround the exposed surfaces of the fibrous reinforcement and preferably each individual fiber.

When preformed, the composite layer of vermiculite flakes and metal foil is preferably used either by direct application to a preformed foam using a suitable adhesive, which may be a suspension of vermiculite, or by forming a foam core Preferably, the vermiculite side of the combination is joined to its foam interior. This gives the product a pleasant metal finish and protects the vermiculite layer from damage caused by water, for example. In this case, the composite layer can be formed in situ on the foam, for example, by applying delaminated vermiculite flakes from an aqueous suspension to the part of the foam to be coated with the composite layer and contacting the still moist vermiculite layer with the metal film. If it is desired to attach the metal film to the foam, the preformed metal-faced laminate may be coated with a layer of vermiculite flake to form a composite layer in situ.

If a preformed composite layer is used, the surfaces of a suitable mold are first lined with the composite layer and the foam-forming plastic mixture is then added to the mold.

If the laminated article is desired in the form of a slab, it can be made individually in a suitably shaped mold, as described above, or continuously in a laminating machine suitable for making a foam sheet. These machines are well known in the art and include conveying means for feeding a flexible or rigid plate material continuously, usually horizontally; a spray device or other dispensing device for evenly applying the foam mixture to the surface of the sheet material, the uniform spread being achieved either by using a spreader, a multi-nozzle syringe or by turning the spray device transversely back and forth over the sheet material; and, if desired, means for applying the second sheet material to the foam in contact before it cures or possibly before or during foaming. If foam is formed between two surface sheets, the laminate is usually conveyed and the foam is allowed to form between two parallel conveyors, the conveyors either being kept at a set distance from each other or designed to create a predetermined pressure in the foam. The foam mixture can even be applied to the upper of the two sheets and then inverted when the foam layer no longer flows by gravity but is still sticky and then brought into contact with the lower sheet. Either or both of the sheets may be composite layers of vermiculite flakes and a metal film. If only one sheet is of such a composite layer, the second sheet may be of some material that is flexible or rigid and may be a non-combustible material. The foam core itself may contain glass fibers or other reinforcements to improve the rigidity and fire resistance of the article.

The rigid surface materials are usually in the form of separate sheets which are fed into the laminating machine one after the other. More preferably, a flexible material is used which is a continuous or semi-continuous sheet and which is fed from rolls.

Suitable preformed composite layers of vermiculite flakes and metal foils are prepared by applying an aqueous slurry of delaminated vermiculite from which particles larger than 50 micrometers in diameter have been removed to the metal foil by any suitable method such as brushing, pressing, dipping, spraying, blade / roll coating. Calendering prior to drying may be advantageous to remove any entrained air, which would cause blisters to form in the fire and to improve the appearance of the combination.

Usually, the flakes are applied from a suspension in a carrier liquid, which may be, for example, water or another aqueous medium. Suitably, the suspension obtained from the chemical delamination process can be used directly. In one such method, a vermiculite slurry is prepared by stirring vermiculite ore in brine for half an hour at 80 ° C. The suspension is centrifuged and washed with deionized water and the moist cake is then mixed with a swelling agent, for example n-butylamine hydrochloride, for a further half hour at 80 ° C. This suspension is also centrifuged and the cake is washed with deionized water. The slurry is then ground and particles larger than 50 micrometers in diameter are removed using, for example, a dam-type centrifuge.

Slurries containing 2 to 40, more often 10 to 20 weight percent vermiculite are usually used. For slurry and blade roller applications, 18 to 20% slurries are suitably used, but dilute slurries are more suitable for spraying, for example 10 to 12% and for dipping, for example 4% vermiculite slurry. The dilution is preferably performed with deionized water.

How much the fire resistance of a laminated article improves depends on the thickness of the coating formed by the vermiculite flakes applied to the metal film, and is generally larger the thicker the coating. When the coated film is exposed to flames or high temperatures, a vermiculite coating, which is a poor conductor of heat, tends to keep the temperature of the film lower than the target temperature and apparently the thicker the coating, the better the thermal insulation provided by the coating. However, a valuable feature of the invention is that only very thin coatings are required, e.g. coatings with a thickness of less than 50 micrometers, for example 5-10 micrometers or less, and these coatings cause the valuable property of the coating to improve film fire resistance, even when the film is damaged or destroyed by flames. effect is most obvious. The number of vermiculite flakes applied to the film to obtain the desired coating thickness is usually in the range

2

- 200 g / m, preferably between 5 and 100 g / m.

The vermiculite layer can be reinforced with fibers in various ways. For example, the fibers can be pressed into a vermiculite slurry pre-applied to a metal film; the fibers may first be attached to the film with, for example, low density polyethylene and the vermiculite is then applied to the fibrous layer; or a preformed combined fibrous layer of vermiculite and fibers may be attached to the film by means of a vermiculite slurry or other suitable adhesive, preferably using a silicate adhesive solution. An aluminum film bonded with low density polyethylene to a fiberglass mat is commercially available and suitable for use. The vermiculite slurry can then be applied to the mat in approximately the same manner as described above for direct application to a metal foil. Preferably, a sufficient amount of slurry is applied to completely impregnate the fibrous mat or woven mat so that the vermiculite flakes completely cover the surfaces of the fibers. A preformed fibrous composite layer containing fibers and vermiculite flakes can be prepared by similarly applying a vermiculite slurry to the fibrous layer.

Usually, vermiculite / metal film combinations are flexible and are suitably wound on rolls for storage and handling. A particular advantage of the invention is that a light, refractory foam laminate can be made using surface sheets that can be fed from rolls in the same way as paper. An additional advantage is that if the laminated article is made in a mold whose walls are curved or otherwise shaped, the combination can often follow the shape of the mold as the foam expands.

The invention is illustrated by the following non-limiting examples in which parts and percentages are by weight.