IE48993B1 - Insulating-slabs and their use - Google Patents

Abstract

1. Method for producing insulated plaster facades by applying glass fibre fabric (3) and plaster to the grooved surface of rigid polystyrene foam slabs (1), wherein the latter have a defined after-shrinkage of at least 1 mm/m, characterized in that strip-foamed rigid polystyrene slabs with a compacted surface are used and that first of all the glass fibre fabric (3) is applied with the aid of a fixing agent (2) distributed above the slab (1) to the said slab at a distance of preferably 1 to 2 mm from the slab surface, following which a plaster containing 0 to 1% of plastics material is applied to the thus pretreated slab.

Description

Insulating-slab elements are used in the construction of, e.g,, insulated plaster facades for buildings.

With increasing frequency insulating layers are applied to outside walls, and such layers are subsequently spackled or plastered. The layers are formed from, e.g., sheets, plates or blocks (hereafter: slabs), generally from 20 to 30 millimeters (mm) in thickness, of a plastic material, such as polystyrene hard foam or polyurethane hard foam.

Because of the very high thermal-expansion coefficient of polyurethane hard foam and the attendant movements brought about by temperature changes, plaster coatings are frequently cracked or torn open at points or areas of contact between the plaster and such hard-foam insulation. Uhen, e.g., polystyrene hard-foam slabs are used, as is the case in many buildings, cracks readily form in the plaster coating over the contact surface and particularly at the juncture between insulating slabs, especially at those places where thicker insulating layers or fresh polystyrene hard-foam slabs are used. - 2 48993 Due to the increasing cost of heat energy, insulating-material thicknesses of at least about 30 mm are required. To-day, an insulating-material thickness of about 70 mm is generally considered to be optimum. For electrically-heated buildings, the optimum figure may even be as high as 180 mm. For such thick insulating layers polystyrene hard-foam slabs, which are smooth on both sides, are unsuitable because forces developed at the interface between the slabs and plaster coating thereon become so great that they exceed the physical limits of the plaster. The insulating slabs are subjected to inherent movement due to shrinkage, as well as to expansion and contraction with increasing and decreasing temperatures. That leads to excessive stress on the plaster coating, particularly that which is over joints between slabs.

The use of grooved hard-foam slabs provides a larger contact surface and results in stronger adherence between it and mortar applied thereto. The adherence is enhanced by the mortar which enters the grooves and thus forms a further interlock with the slabs. Unfortunately, the adverse effects of shrinkage are retained. Such shrinkage is reduced by storing the slabs for an extended period of time prior to use. Such extended storage tends to minimize residual follow-up shrinkage. When the preliminary storage time is insufficiently-long, damage from such shrinkage cannot be avoided and is merely postponed. Storage times of about six months are now customary.

According to the present invention there is provided a method for producing insulated plaster facades by applying glass fibre fabric and plaster to the grooved surface of rigid polystyrene foam slabs, wherein the latter have a defined after-shrinkage of at least 1 mm/m and wherein strip-foamed rigid polystyrene slabs with a compacted surface are used and first of all the glass fibre fabric is applied with the aid of a fixing agent distributed above the - 3 4 8 9 9 3 slab to the said slabs at a distance of preferably 1 to 2 mn from the slab surface, following which a plaster containing 0 to 1% of plastics material is applied to the thus pretreated slab.

The invention also provides an insulated slab of rigid polystyrene foam with an after-shrinkage of at least 1 mm/m and a surface having swallowtail-like milled grooves, for carrying out the method of the invention, wherein a glass fibre fabric is mounted on one side by means of fixing agents at a distance of 1 to 2 mm from the surface of the slab, and the slab consists of stripfoamed material having a compacted surface.

A wall is covered with such reinforcement-covered slabs, and plaster or mortar having only a small amount of or no synthetic plastic components is applied to the slab and web surfaces. After the plaster or mortar sets and provides a firm and integral structure with the plastic slabs and reinforcing web, the surface is optionally plastered or painted to produce a finished product.

Fig. 1 is a plan view of a slab and reinforcing web.

Fig. 2 is an end view of the slab of Fig. 1 covered with plaster and having a finish coating.

Throughout the specification a number of terms are repeatedly used. Unless otherwise indicated, the following terms are employed as defined. slab - a sheet, plate or block of hard-foam plastic, e.g. polystyrene, polymethane or even thermoset phenol/formaldehyde polymer, which has two major surfaces and, ordinarily, four sides or edges (ends). One of the major surfaces is substantially planar (it may have grooves, as indicated in Figure 2, but is referred to herein as planar); the other has plural grooves and lands between adjacent grooves. - 4 48993 The grooves are preferably milled or otherwise cut into the other surface; they are advantageously undercut in dove-tail fashion. The slab is, e.g., band-foamed or moulded to a density of, e.g., from 1 to 3 pounds per cubic foot. It has a follow-up shrinkage which is suitably at least 1 mm/m and preferably the maximum possible. The ends are optionally rabbetted for firm placement in juxtaposition. The slabs are preferably square, having edges from 50 to 250 centimeters in length, and are usually from 1 to 30 centimeters in thickness. fastening elements - pins, spacers, dots or slugs having a base and a head end. The base is secured to the other surface of the slab, and the head end is secured to a reinforcing web. The fastening elements maintain the web at a substantially uniform distance from the other surface of the slab. They are composed of adhesive, noncorroding metal or plastic. reinforcing web - a fabric of, e.g., glass fibre animal hair, sisel and/or synthetic fibres to reinforce the vapour-pervious layer of plaster or mortar applied directly to the other surface of the slab. plaster or mortar - alternative terms for the same compositions, ordinarily containing from 5 to 20 percent by weight of cement, from 70 to 90 percent by weight of sand, from 0 to 20 percent by weight of plastic and substantially the rest of water. synthetic-plastic-component-poor plaster or mortar - material applied to the emitter surface of the slab and which (after setting) permits passage of water vapour therethrough. When set, it preferably has a water-vapour-diffusionresistance factor (μ) within the range of from about 15 to about 25. The composition contains from 0 to 2.5 or 3.0, preferably from 0.5 to 1.5, percent by weight of plastic components. A suitable plaster composition contains from to 20, e.g. 12 percent of cement, from 70 to 90 e.g. 73, percent of sand, oio j-0 from owe, e.g. 0.7, percent of chalk, from 0 to 2, e.g. 0 to 0.2, percent of - 5 4 8 9 9 3 methylcellulose, from 0 to 3, e.g. 0 to 2.2, percent of polyvinylpropionate and water to 100 percent, all percentages being by weight. The surface of the set and dried material is optionally dyed. outer coat - any suitable coating material, e.g. mineral paint, syntheticplastic-component-containing dispersion paint or hydraulically-setting plaster with or without synthetic-plastic components. synthetic plastic - any suitable polymer with adhesive properties, e.g. methylcellulose, a homopolymer or copolymer of acrylic acid or methacrylic acid, e.g. polystyrolacrylate, or polyvinylacetate, preferably a polymer in water-dispersible form.

When hard-foam plastic insulating slabs are coated with plaster having a high content of synthetic plastic components, the resulting plaster mass softens under the influence of heat. Even when minor amounts of cement are added to the plaster, it yields, particularly in areas adjacent to joints between slabs.

With increasing and decreasing temperatures material fatigue develops in the plaster near joints. Reinforcing glass-fiber fabric, embedded in the plaster coating mass, becomes brittle from the alternating tension and compression to which it is subjected; it consequently loses its resistance.

The thicker the insulating layer of hard-foam slabs, the greater the shrinkage, the greater the expansion and contraction forces, and the greater the heat build-up in the plaster coating (in view of the increased insulating effect of the hard-foam slab). The totality of the previously-noted effects results in an increased formation of cracks in the plaster coating in the area in which the plaster contacts the hard-foam slab. There is also expected separation between the surface of the hard-foam slab and the plaster mass which contacts it. Bars of plaster coating which form in slab grooves also tend to shear off. - 6 4-8993 When insulated-plaster facades are preserved by placing glass-fiber fabric on, e.g., polystyrene hard-foam slabs and applying the plaster to them, a relatively large percentage (5 percent or more) of synthetic-plastic components are incorporated in the plaster to impart a sufficient adhesion force to it.

Unfortunately, the synthetic-plastic components severely restrict the passage of water vapour through the plaster coating. Water condensed from moist air inevitably penetrates into the interface or boundary area between the hard-foam slab and the plaster. When the plaster contains a relatively large proportion of synthetic-plastic components, the resulting plaster has a blocking effect, precluding the passage of water through it. Such plaster is thus forced away from the slab. Subsequent frost damages the insulated plaster facade.

By using such synthetic-plastic components as poly(butadiene/styrene), the synthetic-plastic components of the plaster or mortar were reduced to 2.5 percent by weight. Since such plastic components, however, impart a considerably15 higher water-vapour blocking value to plaster or mortar compositions than traditional synthetic-plastic substances, their use does not lead to satisfactory results. It is thus necessary either to reduce the synthetic-plastic components of the mortar or plaster even further or to eliminate such component altogether.

The present invention is based on a novel slab secured to a reinforcing web, the use of such a slab in preparing insulated plaster facades and the resulting facades. With reference to the drawings, a hard-foam slab (sheet, plate or block prepared from a synthetic plastic, such as polystyrene or polyurethane) 1 is provided with grooves 4 (preferably by milling) in one surface. In practice both major surfaces can actually be similarly grooved. Fastening elements 2 are placed on lands 6 between grooves 4. The fastening elements 2 act as spacers to maintain a reinforcing web 3 of, e.g., glass-fiber fabric at a substantially-fixed distance from lands 6. The respective opposite ends of each slab are rabbetted so that such ends will overlap or underlay corresponding - 7 993 portions of adjacent slabs, as indicated at 5, 5'.

A plaster or mortar composition 7 is applied to the slab face, incorporating the reinforcing web 3, as seen in Fig. 2. When this layer has set, a further finish plaster and/or paint is optionally applied thereto.

To insulate a wall, whether of wood, stone, brick or other material, the wall is faced with the hard-foam slabs 1 placed in juxtaposition over, e.g., substantially are the entire surface. The slabs/affixed to a wall with adhesive mortar, and/or rails or other fasteners. A coating of plaster which permits water vapour to pass therethrough is placed over the entire outer grooved surface thus formed. After the plaster sets, mortar and/or paint is optionally applied thereto to form a finish coat.

To prepare the individual slabs, grooves 4 are preferably milled (rather than moulded) into one surface. These grooves are advantageously in dove-tail form. On lands 5 between adjacent grooves, spacers (fastening elements) 2 are placed to secure a reinforcing web 3 to the hard-foam slab 1 and to maintain such web at a substantially fixed distance from the face of the slab 1.

Fastening elements 2 are preferably distributed in a substantially uniform fashion over the surface of the hard-foam plate to support the web, e.g. glass-fiber fabric, at a distance of from about 1 to about 2 mm from the slab surface. The plaster 7, which is applied to the slab surface after the reinforcing web is attached, contains little or no synthetic-plastic components so that the resulting insulated facade wil1 present a minimum barrier to the passage of water vapour therethrough.

A novel feature of this invention is the resulting insulated facade with optimum water-vapour-passage values. - 8 48993 The plaster or mortar applied to the hard-foam surface advantageously contains from 0 to 1.5 percent by weight of synthetic-plastic components. By maintaining such a small proportion of such components, water vapour has virtually no negative effect on the resulting insulated facade. The syntheticplastic ingredients (limited to at most about 1.5 percent of the compositions of the plaster applied to the hard-foam surface) are incorporated into the plaster to make it easier to process and apply in a relatively-thin plaster coating; the synthetic-plastic components are not included in the plaster composition to impart adhesion (after setting) properties thereto.

According to one embodiment dots or slugs of mortar (containing a large proportion of synthetic-plastic components) are distributed over the surface of the slabs, as indicated by 2. These dots or slugs act, when set, to secure an insulating web to the face of the hard-foam slab and at a substantially fixed distance therefrom. By using a high proportion of synthetic-plastic components in this mortar, good adhesion is obtained and the hardened or set slugs of such mortar act as spacers and retain the reinforcing web in a fixed position. The high-plastic-component mortar is thus limited to small zones distributed over the entire surface of each slab, and the main plaster coating is substantially free from synthetic components.

The adhesive slugs or dots of synthetic-plastic-component-containing mortar have effective adhesion surfaces in the order of magnitude of between 20 and 2,000 mm2 prior to setting. The reinforcing web, e.g. of glass-fiber fabric, is placed in contact with such dots or slugs immediately after they are applied to the hard-foam surface and before they set.

Appropriate synthetic-plastic-rich mortar (from which the dots or slugs are prepared) suitably has a composition: 10 to 80 (preferably 40 to 60) percent by weight of cement, 0 to 80 (preferably 30 to 50) percent by weight of sand, - 9 48983 quartz sand or other mineral filler, and from 2 to 50 (preferably from 5 to 25) percent by weight of synthetic-plastic components. Whenever synthetic-plastic components are referred to, they include any one or a combination of, e.g., methyl cellulose, polyacrylate, polymethacrylate, copolymers of acrylate or methacrylate, such as polystyrol acrylates, polyvinyl acetates and their copolymerizates. Adhesives based on each of these components are known and, per se, do not comprise the invention to which this application is directed. Virtually all known adhesives of any one or combination of these components are suitably incorporated as the synthetic-plastic component of plaster or mortar referred to in this disclosure.

The slugs or dots of synthetic-plastic-containing mortar are permitted to set after the reinforcing web IS placed in contact therewith. Only thereafter is the plaster (substantially free of synthetic-plastic components) applied to the slab surface. Quite surprisingly, the applied synthetic-plastic-poor plaster (which has virtually no adhesive effect) is sufficiently held in place by the reinforcing web, e.g., of glass-fiber fabric. The plaster is applied to slabs placed in juxtaposition over the surface of a wall and thus in a perpendicular arrangement. The slabs are suitably preliminarily attached to the wal1 surface to be insulated.

The best interconnection (after applied plaster has set) between the grooved slabs and plaster applied directly thereto is achieved when hard-foam slabs having a maximum follow-up shrinkage are used. It is thus advantageous to use slabs which are freshly prepared and thus contain a high proportion of propellant or solvent in their composition. According to what was previously recognized standard procedure, such slabs must be stored for at least three months to reduce such follow-up shrinkage as much as possible prior to use. The present invention thus has a further advantage of eliminating such storage time. - 10 48993 Another advantage is that the individual slabs with attached reinforcing web are readily prepared at a manufacturing plant. This was not possible with previous counterparts for which the reinforcing web had to be applied to insulating hard-foam slabs which had already been attached to a masonry wall which was being insulated. In such previous counterparts it was essential that, e.g., glass-fiber fabric did not contact slab surfaces along their edges, since such would inevitably lead to the formation of cracks along such edges within a short period of time. Such does not present any problem with the presentlydisclosed method, wherein contact surfaces of the reinforcing web can coincide with contact-surface edges of the hard-foam slabs without any crack formation. This is extremely surprising in view of the fact that slabs, having a high degree of follow-up shrinkage, are employed and there was thus every expectation of having an increased incidence of cracking brought about in this manner.

The present hard-foam slabs are thus readily manufactured with reinforcing webs having an identical surface or one which protrudes over the edges only to a minor extent. The slabs are readily attached to a wall because there is no need for any major overlap of the reinforcing web and such overlap can even be entirely omitted.

To assist in the retention of wet plaster to slab contact surfaces, fastening elements, such as slugs or dots 2, are arranged close to preferably from 1 to 10 centimeters from the edges of each slab.

If necessary or desirable under particular conditions, it is also possible to attach the reinforcing web to the hard-foam slabs at a construction site.

Under such circumstances, the web need not be separately attached to each individual plate as previously indicated; a larger reinforcing web is optionally attached to a more extensive portion of the wall to which numerous hard-foam slabs have previously been applied. Under such circumstances, the adhesive mortar dots or slugs are advantageously replaced by alternative fastening - 11 4899 3 elements, which are fixed in stud fashion to the hard-foam slabs and consist of noncorroding metal or plastic. Such fastening elements are affixed to the slab surface and to the reinforcing web in any suitable conventional manner. They are, e.g., merely pressed into the hard-foam slab or adhered thereto in any other convenient manner. They optionally have hooks of some sort on one end to engage the reinforcing web. The specific configuration of such fastening elements is not, per se, critical to this invention.

As previously noted, it is advantageous to mill the grooves into the surface of the slabs after the slabs are made rather than moulding the grooves on the surface of the slabs while the latter is being prepared. Needless to say, the two types of resulting slabs are not the same since the surface produced by milling a hard-foam structure has a far different surface make-up than a moulded surface. A moulded surface generally has a smooth skin which is destroyed by milling grooves therethrough.

When the hard-foam slabs are prepared by moulding, they have a compacted surface which was previously referred to as a skin. When moulding is effected without using a mould-release agent or other mould-separating means, the resulting moulded slabs more-readily adhere to plaster applied to their surfaces. The adhesion of synthetic-plastic-poor plaster or mortar to the hard-foam-slab surface is materially reduced by the use of mould-separation means during the preparation of the hard-foam slabs.

When the slabs are prepared by foaming plastic in the form of a band (formed continuously in an extension type mould), the resulting material has greater density and thus improved strength properties over the surface areas, i.e. the area in which the grooves are made. As such slabs have a lower density in their inner portions, they result in having a better balance of tensions, which are shifted into the center of such slabs. - 12 48993 Even an extremely small proportion of synthetic-plastic components in the composition of the plaster or mortar applied to the slab surface provides a coating on the hard foam which, after setting, presents a particularly good foundation for additional (outer) coats of plaster or paint based purely on a mineral composition. When a finish coat is placed over the reinforced plaster coating, adhesion between the two coats is very good in view of the porosity of the synthetic-plastic-poor plaster and the similarity between the compositions of the two coating masses.

The proportion of synthetic plastic components in cement-mortar mixtures has virtually no influence on the thermal (heat-expansion) coefficient of the resulting set product.

After plaster or mortar (with little or no synthetic-plastic components) has been applied to the slab surface and a coating (including the reinforcing web) has been formed thereon and permitted to set, a synthetic-plastic-modified mineral outside plaster, a synthetic-plastic component dispersion plaster and/or coats of paint are optionally applied to the outer surface. Any difference in heatexpansion coefficient between the initial reinforced-plaster coating (applied directly to the slab surface) and the synthetic-plastic-component-containing dispersion or other plaster and/or paint does not have a significant disadvantageous effect because the higher expansion coefficient brought about by the presence of synthetic-plastic components is balanced out by the elastic character of the resulting plaster coating.

As compared with the use of a synthetic-plastic-component dispersion plaster or synthetic-plastic-component-containing facade paint as an outer coating, mineralbased plaster or coats of paint are advantageously employed since they readily permit passage of water vapour and do not change in colour and other properties over extended periods of time. Synthetic-plastic-component-containing dispersion paints become dirty from increased electrostatic charging; with the passage of - 13 time they become brittle from decomposition resulting from ultraviolet radiation and separate from their base because of their increased resistance from water vapour diffusion. Moreover, they are softened by direct sun radiation.

Such softening is known to lead to the formation of vapour bubbles which disappear at night on subsequent cooling; the repeated formation and disappearance eventually results in a porous and cracked structure. The water-vapourdiffusion-resistance factors of commercially-available outside coatings are as follows: Outside plaster with only mineral components Synthetic-plastic-component-modified mineral outside plaster Synthetic-plastic-component-containing dispersion plaster Synthetic-plastic-component-containing dispersion paint p = 10 to 20 p = 15 to 25 μ = 100 to 500 p = 500 to 1000 After the insulating slabs have been glued on or otherwise affixed to a wall which is to be insulated, the synthetic-plastic-component-modified plaster or cement-mortar is applied and smoothed by hand or by a mortar spray machine. This coating is optionally dyed, left in this state, coated with customary plaster or painted.

This invention makes it possible to insulate, e.g., masonry or wood walls in a manner which minimizes on-site operations and maximizes the sturdiness and lasting qualities of the provided insulation. Advantage is taken of the shrinkage properties of freshly-prepared hard-foam plastic in producing an integral reinforced insulation.

The invention and its advantages are readily understood from the preceding description. The several components, the process and the obtained product are subject to various changes without departing from the spirit and scope of the - 14 4-89 9 3 invention or sacrificing its material advantages. The components, the process and the products described herein are merely illustrative of preferred embodiments of the invention.

Claims (10)

1. Method for producing insulated plaster facades by applying glass fibre fabric and plaster to the grooved surface of rigid polystyrene foam slabs, wherein the latter have a defined after-shrinkage of at least 1 mm/m, wherein strip-foamed rigid polystyrene slabs with a compacted surface are used and first of all the glass fibre fabric is applied with the aid of a fixing agent distributed above the slab to the said slab at a distance of preferably 1 to 2 mm from the slab surface, following which a plaster containing 0 to 1½ of plastics material is applied to the thus pretreated slab.

2. Method according to Claim 1 wherein that an adhesive mortar known per se and having the following composition is used as fixing agent: Cement 10-80 preferably 40 - 60% by wt. Sand, Quartz Sand or other Mineral filler 0-80 preferably 30 - 50% by wt. Plastics material 2-50 preferably 10 - 20% by wt.

3. Method according to Claim 1 or 2, wherein the slabs are provided with the glass fibre fabric before being applied to the wall to be insulated.

4. Method according to Claims 1 to 3, wherein the glass fibre fabric is fixed to the slabs preferably in the edge region of the slabs, with the aid of the fixing agent.

5. Method according to Claim 1, wherein the glass fibre fabric is fixed to the slabs with the aid of fastening elements that can be inserted into the rigid foam slabs and splay out like a dowel. - 15 4 8 9 9 3

6. Method according to Claims 1 to 5, wherein a plaster mortar consisting of cement and sand, optionally with the addition of lime, is applied to the glass fibre fabric, to which is then added in known manner methyl cellulose, acrylates, methacrylates and their copolymers e.g. styrene acrylates and 5 in addition preferably vinyl acetates and their copolymers, as plastics material

7. Insulated slab of rigid polystyrene foam with an after-shrinkage of at least 1 mm/m and a surface having swallowtail-like milled grooves, for carrying out the method according to Claims 1 to 6, wherein a glass fibre fabric is mounted on one side by means of fixing agents at a distance of 1 to 2 mm 10 from the surface of the slab, and the slab consists of strip-foamed material having a compacted surface. the

8. Insulated slab according to Claim 7, wherein/adhesive mortar serving as fixing agent has the following composition: Cement 10 - 80 preferably 40 - 60% by wt. 15 Sand, Quartz Sand or other Mineral filler 10 - 80 preferably 30 - 50% by wt. Plastics material 2-50 preferably 10 - 20% by wt.

9. An insulated slab of rigid polystyrene foam substantially as described herein with reference to the accompanying drawings.

10. A method for producing insulated plaster facades substantially as described herein with reference to the accompanying drawings.