WO2010139564A2

WO2010139564A2 - Wall form units and systems

Info

Publication number: WO2010139564A2
Application number: PCT/EP2010/057000
Authority: WO
Inventors: Ian Stuart Biggin; Martin Peter Butters
Original assignee: Basf Se
Priority date: 2009-06-01
Filing date: 2010-05-20
Publication date: 2010-12-09
Also published as: EP2438247A2; US20120073226A1; GB0909280D0; CN102844503A; WO2010139564A3

Abstract

A wall form unit for containing a pourable, curable construction material for forming a wall section integrating said wall form unit and said construction material, comprising a first panel and a second panels spaced apart in predetermined relation thereby forming a hollow between first and second panels for defining said wall section and at least one tie assembly having a spacer member for maintaining said first and second panel in predetermined relation, in which both the first panel and second panels are rigid and adapted to retain said construction material, wherein the first panel is constructed of a thermally insulating material and the second panel is constructed of a thermally conducting material. A wall form system for forming a section of wall and wall section and method for constructing same are also defined. The invention also relates to a panel for use in forming a wall form unit and also claims a kit for constructing a wall form unit.

Description

Wall Form Units and Systems

This invention relates to wall form units and systems used to construct structural components such as walls. More particularly, the present invention relates to thermally conducting panels for use in wall form units and systems for constructing walls formed from pourable, curable construction material in which the form system remains in situ.

Construction components, such as walls and columns, are often made from curable construction materials such as concrete. It is well known to make a specifically shaped component from such materials in order to build or erect civil engineering structures. Previously such forms would have been typically made from materials such as wood. To make the construction component, the form is erected to create a cavity capable of holding the curable construction material, for instance concrete, in a liquid form. The concrete or other curable construction material is then poured or otherwise introduced into the cavity created by the form and then allowed to set. Once the material has hardened into a structural component, the form is removed.

Alternatively, the form can be built from several form units, each form unit having a pair of spaced panels. The form units are placed adjacent to each other, both horizontally and vertically, to build a complete form. Enhanced efficiency in the construction of a form may be achieved in such a system. This is particularly the case where the form units are designed to remain permanently in situ, once placed, and do not have to be removed once the concrete, or other curable construction material, has been poured and allowed to set. One such system has side panels for each form unit made of an insulated material. These side panels perform the dual purpose of functioning as side units for the cavity, and then after the concrete has set, as an insulating layer on each side of the concrete. These wall form units and wall form systems are frequently referred to as Insulating Concrete Forms (ICFs). The use of Insulating Concrete Forms or more generally wall form units or systems is well accepted as very effective building construction technology.

Typically an ICF or other wall form units or systems comprise an expanded plastic (foamed plastic), usually expanded polystyrene or polyurethane foam, form comprising two spaced apart panels or hollow blocks.

ICFs comprising two spaced apart panels will be generally supplied as a self assembly "flatpack" system comprising the two panels of foamed plastic and ties or other connecting components used for assembling the forms, hereinafter referred to as ties. ICFs are generally locked together by a suitable connecting means, for instance by use of tongue and groove joints around the edges of the ICFs, as they are stacked to form walls. Steel rebars or reinforcing steel mesh can be used in the space between the panels, into which concrete or other curable construction material is added, to provide added strength. When steel rebars are used then these can be in both horizontal and vertical orientation. The forms are assembled into a hollow vertical wall into which concrete or other curable construction material is poured thereby creating a solid wall. The ICF or wall form units remain in place and become a permanent part of the building and provide insulation. It has been generally accepted that employing ICFs as a permanent part of the building provides energy efficiency, contributing to environmentally responsible practices. As an alternative to delivering the ICFs to the construction site as a self-assembly "flatpack" the ICFs may also be delivered as preassembled units. As a further alternative wall sections may be built from the ICFs off site and these wall sections may be delivered to the construction site where the building is to be erected.

Typical insulating concrete forms are described in Canadian patents 1244668, 2551250, US patents 4703602, 4731968, 4949515, 5704180, 5724782, 5809728, 5896714, US published patent applications 20040040240, 20040045237, 20080022619, International applications WO9525207, WO9901626, WO2008009103 and WO2008136819.

French patent 2598447 describes a structure comprising a light weight loadbearing framework. The framework includes cavities which are closed in on the sites by panels. A material is poured into the cavity in which the material with high heat storage capacity and quick setting time in order to form a heat accumulator. An insulating layer is inserted between the external facing and the internal panel. Such a complex structure employs several panels and limited capacity for the construction material without making the framework excessively deep and intrusive.

European patent application 1959212 describes a wall element formed from glass plates with a core material consisting of microcapsules of phase change material filling the space. However, such a wall element would be completely unsuitable for retaining a curable construction material. The filling material incorporated in this wall element would not be curable.

PFSolutions describe cement bonded particle board used as a permanent formwork which is left in place after casting of concrete on-site on their website www.pfsolutions.ie. The cement bonded particle board apparently has a thermal conductivity of 0.26 W/m.K. Nevertheless the system is devoid of any thermally insulating panel in direct contact with the concrete core.

Although ICFs generally provide a multiple layer of insulation to walls, buildings constructed from ICF walls tend to suffer the disadvantage of inadequate temperature regulation to rooms within the building. The objective of the present invention is to provide wall form units and systems which overcome this problem. In particular it would be desirable to provide such wall form units and systems that are easily transportable and can be installed easily on-site where the building or other construction can be erected.

According to the present invention we provide a wall form unit for containing a pourable, curable construction material for forming a wall section integrating said wall form unit and said construction material, comprising a first panel and a second panel spaced apart in predetermined relation thereby forming a hollow between the first and second panels for defining said wall section and at least one tie assembly having a spacer member for maintaining said first and second panels in predetermined relation, in which both the first panel and second panels are rigid and adapted to retain said construction material, wherein the first panel is constructed of a thermally insulating material and the second panel is constructed of a thermally conducting material.

The invention also provides a wall form system for forming a wall section having a core of pourable, curable construction material sheathed by a plurality of panels comprising at least two wall form units, each said wall form unit having means for interlocking said wall form units to define said wall section, a first panel and a second panels spaced apart in predetermined relation thereby forming a hollow between the first and second panels for receiving said construction material, and a least one tie assembly, said tie assembly comprising a spacer member for maintaining said first panel and said second panels in said predetermined relation, in which both the first panel and second panels are rigid and adapted to retain said construction material, wherein the first panel is constructed of a thermally insulating material and the second panel is constructed of a thermally conducting material.

In accordance with a further aspect of the invention we provide a kit for constructing a wall form unit in accordance with the previously stated aspects of the invention. The invention also relates to a wall section comprising at least two wall form units or a wall form system as defined herein containing a cured construction material between the first and second panel, which cured construction material has been formed from a pourable, curable construction material that has been poured into the hollow between the first and second panels.

The wall section may often be formed on site where the building is to be erected. Alternatively the wall section may be formed at the manufacturer site and shipped to the location where the building is to be constructed.

The invention also concerns a novel panel suitable for constructing a wall form unit according to the aforementioned aspects of the invention in which said panel is constructed of a thermally conducting material.

The present invention also relates to a process of erecting a building structure which comprises a wall section formed from a plurality of ICF units comprising the steps, i) arranging the first and second panels of the plurality of ICF units in predetermined relation for defining said wall section such that a hollow is formed between the first and second panels by spacing apart the first and second panels in predetermined relation, ii) connecting at least one tie assembly having a spacer member for maintaining for spacing apart said first and second panels in predetermined relation, iii) introducing a pourable, curable construction material into the hollow, iv) allowing the pourable, curable construction material to cure, in which both the first panel and second panel are rigid and adapted to retain said construction material, wherein the first panel is constructed of a thermally insulating material and the second panel is constructed of a thermally conducting material. In constructing the wall form unit the second panels should be placed so that they form the side of the wall that will face the interior of the building and the first panels should be placed so that they form the side of the wall that will face the exterior of the building. The first panels and second panels should be maintained at a predetermined distance using ties. Into the hollow created between the first and second panels the pourable, curable construction material e.g. concrete should be introduced and allowed to set to form a wall section.

The pourable, curable construction material once introduced into the hollow should be in direct contact with the first and second panels. Once cured the pourable, curable construction material should form a solid core which is in direct contact with the first and second panels.

The inventors believe that by employing panels formed from a thermally conducting material and a thermally insulating material respectively each in direct contact with the cured construction material, for instance concrete, the thermal mass of the cured construction material can be utilised and this provides for improved temperature regulation within rooms of buildings whilst maintaining adequate insulation. The inventors believe that the reason that the buildings constructed from the prior art ICF walls tend to suffer the disadvantage of inadequate temperature regulation to rooms within the building is because of their lack of accessible thermal mass.

The pourable, curable construction material which sets to form the internal core of cured construction material, typically concrete, exhibits high thermal mass. Generally the thermal mass, expressed in terms of specific heat capacity, will be at least 700 J/kg.K and usually at least 800 J/kg.K or, more preferably, at least 900 J/kg.K for instance as much as 1000 J/kg.K or 1100 J/kg.K or more. The density of the concrete will have a bearing on the heat capacity in volume terms. The higher the density, the greater is the volumetric heat capacity. It is therefore preferable to use cured construction materials, typically concrete based on Portland cement, which have a high density. The density is generally always >0.5 kg/litre, preferably >1.0 and most preferably >2.0. The pourable, curable construction material once cured and solidified may desirably have an admittance value of between 1 and 6 W/m².K. Any concrete normally used for construction purposes may be used in accordance with the present invention but concrete designed specifically for ICF applications, such as Rheo Cell (Trade Mark) ICF concrete from BASF or U Crete (Trade Mark) from Bardon Concrete are preferable. Waterproof concrete may also be used especially for basement construction. It may also be desirable to include phase change material (PCM) to provide additional temperature regulation within the building. Suitable phase change materials are described herein in regard to the second panel.

The dimensions of the first and second panels may be typical of ICF dimensions commonly used. Suitably the panels may be between 1000 mm and 1500 mm in length, preferably between 1200 and 1300 mm, for instance around 1220 mm. The height of the first panel and second panel may be between 350 and 500 mm, preferably between 390 and 450 mm, for instance around 400 to 410 mm. However, in some situations it may be desirable to use larger dimensions. For instance, it may be desirable for the panels to be as much as 3000 mm or 4000 mm in length and/or width or larger. Even larger dimensions could be used if it is found to be practicable. Even larger dimensions may for instance be up to 10,000 mm in height and up to 20,000 mm in length.

The use of large dimensions include ICF structures, which could be preconstructed in a factory. Typical larger dimension IFC structures would be analogous the dimensions employed in HercuWall™, made by HercuWall lnc (USA).

Generally the first and second panels should be strong and sufficiently hard wearing to avoid being easily damaged during transportation or especially on the construction site. This would include during handling, assembly, pouring of concrete, during curing of the concrete, mechanical and electrical fixing and subsequent finishing, decoration etc.

The edges of the first and second panels may be formed to allow the wall form units (ICFs) to be stacked such that both horizontal and vertical edges lock into the neighbouring units. The locking system may be based on tongues and grooves. This may be achieved by for instance providing the upper edge and left side with a tongue and the lower edge and right side with a groove such that each panel may interlock with this neighbouring panel. These locking systems may be added, cast or cut into the panels during manufacture or alternatively may be formed by fixing several thinner panels together to form the tongues and grooves.

The first and second panels may be further adapted in order to facilitate better adhesion to the concrete. For instance this may be achieved by applying grooves or other surface formations on the sides of the panels intended to face the concrete or other curable/cured construction material. These grooves, on the second panels, should also facilitate improved thermal contact between the panel and the concrete.

The surface of the second panel facing the interior of the building, i.e. the opposite side to that in contact with the concrete or other curable/cured construction material, may also be adapted for a particular purpose required for the interior of the building. For instance the interior facing surface of the second panels may be smooth in order to accept paint or wallpaper or alternatively it may be brushed or roughened in order to accept tiles or any other covering where a surface key is desirable. The second panel may also be faced with suitable scrim e.g. of glass fibre to improve surface finish, strength or fire resistance properties. The first panel of the wall form units or systems may be any conventional panel used for forming ICFs. Typically the first panel may be constructed from a composite material, a polymer or a polymer-based compound. Suitably the first panel is formed from a foamed plastic, preferably an expanded polystyrene (for example Styropor (Trade Mark) from BASF) or polyurethane foam. The first panel may contain other insulating components with the foamed plastic, for instance Aerogel (Trade Mark) or vacuum panel insulation. Additives may be incorporated into the foamed plastic of the first panel to improve performance such as strength or insulation characteristics. Suitable additives for foamed plastic include graphite, for instance Neopor (Trade Mark), which is a graphite- containing expanded polystyrene maufactured by BASF. The first panel may contain two or more layers of foamed plastic thereby forming a composite form. The thickness of the first panel will be determined by the particular insulation value which is required for the particular building being constructed. Suitably the first panel may have a thermal conductivity below 0.045 W/m.K. Generally the thermal conductivity can be any value below this and may be as low can be measured. It is possible that the thermal conductivity may be as low as 0.005 W/m.K. Typically the thermal conductivity of the first panel may be in the range of 0.010 and 0.040 W/m.K often within the range 0.020 and 0.040 W/m.K.

The second panel may be constructed from any material that provides the right characteristics for use in the wall form units and system. It should be rigid and adapted to retain the construction material such as concrete. Furthermore, it should desirably possess a thermal conductivity of least 0.1 W/m.K (Watts per metre Kelvin) at least in the direction of the thickness of the panel, and preferably at least 0.2 W/m.K. In some cases the thermal conductivity of the second panel may be at least 0.25 W/m.K, at least 0.3 W/m.K, at least 0.4 W/m.K and preferably at least 0.5 W/m.K and more preferably at least 1.0 W/m.K. There is no upper limit to the thermal conductivity provided that the other properties such as rigidity and strength are not compromised. The thermal conductivity may be up to 100 W/m.K. The second panel may be constructed from any suitable metal in the form of a metal sheet for instance. Typically this may be aluminium or copper having thermal conductivities of 200 W/m.K and 380 W/m.K respectively. However, it is preferred that the second panel is constructed from suitable building materials which have been adapted to improve the thermal conductivity.

Second panels potentially include concrete panels or blocks, stone or marble panels or boards comprising cement, such as Portland cement or magnesia cement e.g. fibre board or particle board. Plasterboard may be used if it is made sufficiently durable such that it is not damaged during the construction process. Standard plasterboards are generally not suitable for this application.

Preferably the second panel comprises a combination of at least two components comprising a first component which is selected from inorganic binders, a polymer and a polymer-based compound and a second component selected from thermally conducting particles, filaments or mesh which are distributed throughout the first component.

Preferred first components of the second panel include inorganic hydraulic binders such as are found in cement-based boards, for instance Portland cement, particularly magnesia cement boards such as those based on magnesium oxysulphate, magnesium oxychlohde and magnesium phosphate. Hydraulic inorganic binders are for instance inorganic materials that react with water to form solid matrices. Other examples include magnesium oxide, calcium oxide, calcium hydroxide/pozzolana mixtures, calcium aluminate cements, gypsum plaster etc. Non-hydraulic inorganic binders may also be used as the first component of the second panel. Such binders harden by completely or partially drying out, and include calcium hydroxide, calcium carbonate, clay, magnesium hydroxide etc. Blends may also be used and it is preferred that an inorganic binder contains at least one hydraulic binder. The second component of the second panel will include materials that have high thermal conductivity. In order to provide the second panel with sufficient thermal conductivity the second component materials will desirably have thermal conductivities of at least 0.1 W/m.K and preferably at least 0.2 W/m.K. It is particularly preferred that the second component materials possess thermal conductivities in excess of 1.0 W/m.K and especially in excess of 2.0 W/m.K. there is no maximum limit of the thermal conductivity of the second component and this may be as high 200 or even 500 W/m.K.

Preferably, the second component of the second panel can be any of the material is selected from the group consisting of graphite, alumina particles, silica sand, fine gravel or stone particles, metallic fibres, metallic mesh and metallic particles. Suitable metals include iron, copper, aluminium or metal alloys such as steel or brass. Other metals or metal alloys may be used such as lead, tin, bronze, silver etc.

The second component of the second panel may be in the form of particles, fibres or other structure, such as mesh. Typically the particles may be relatively fine having weight average particle size diameters of below 1 mm, especially below 0.1 mm and for instance as low as 0.01 mm or below. Alternatively the particles may be relatively coarse having weight average particle size diameters of at least 1 mm and even at least 2 mm, for instance up to 5 mm or even up to 10 mm or 20 mm or more. The fibres may have cross-sectional diameters of between 0.01 mm and 1 mm or higher. The lengths of the fibres may be relatively short, for instance less than 5 mm or sometimes may be as much as 10 mm or 20 mm and considerably longer if in the form of a wool, for instance steel wool or steel mesh.

The second panel may comprise the first component in an amount between 5 and 100% by weight of the two components (not including any fillers or lining materials such as paper or scrim) and the second component in the amount of between 0 and 95% by weight of the panel. Typically the second component may be present in the panel in an amount between 5 and 95 % by weight whilst the first component may be present in an amount of between 5 and 95% by weight. In many systems the second component can be the major component, for instance between 65 and 95% by weight, preferably between 75 and 85% by weight and the first component can be between 5 and 35 % by weight, preferably between 15 and 25% by weight. Preferably the first component will form a matrix within the panel throughout which the second component is distributed. Should the second panel have high thermal conductivity, say >0.1 W/m.K, then a second component may not be necessary.

The second panel may be constructed from a material which contains partial aeration, for instance pumice, provided that the aeration does not compromise the thermal conductivity and ability to contain the pourable, curable construction material. Generally the material used to form the second panel desirably should not contain significant amounts of air voids, for instance by aeration as this may tend to yield lower thermal conductivity. Desirably the second panel should be as dense as it is practicable within the normal constraints of panel manufacturing, construction of the building and use of the building. Desirably the second panel has a density of at least 100 kg/m³ and preferably at least 300 kg/m³ and more preferably at least 700 kg/m³. Especially preferred materials tend to have densities of at least 1000 kg/m³ and often as much as 1500 kg/m³. Nevertheless, the density may be significantly higher, for instance up to 1750 kg/m³ or even up to 2400 kg/m³ or more.

An example of a second panel is one formed from Portland cement or magnesia cement as the first component comprising particles of sand or fine aggregate as the second component which is distributed throughout the Portland cement or magnesia cement. Suitably the sand or fine aggregate will form between 65 and 95 % of the total weight of the second panel the remainder being the magnesia cement. Preferably the sand or fine aggregate will form between 75 and 85 % of the total weight of the second panel and the magnesia cement will form between 15 and 25 % by total weight.

The second panel may also contain other components such as fillers or strengthening fibres. Such fillers may for instance be included where the second panel is based on a hydraulic inorganic binder such as magnesia cement. Typically this may include wood particles or fibres, synthetic fibres glass, basalt or carbon fibres or carbon particles. However, the aim must be to maximise the overall thermal conductivity of the second panel, and the addition of fillers, fibres etc must be considered carefully with this aim in mind. A balance must be found between achieving a suitably high thermal conductivity and achieving requirements such as strength, appearance, cost etc.

In a preferred form of the invention the second panel may contain phase change material (PCM). This feature will allow further temperature regulation of rooms within the building.

Suitable phase change materials may be organic, water insoluble materials that undergo solid-liquid/liquid-solid phase changes at useful temperatures (typically between 0 and 8O⁰C). Generally the enthalpy of phase change (latent heat of fusion and crystallization) is high. Suitable organic phase change materials exhibit a high enthalpy of phase change, typically >50 kJ/kg, preferably >100 kJ/kg and most preferably >150 kJ/kg when determined by Differential Scanning Calohmetry (DSC).

Suitable organic phase change materials include (but are not limited to) substantially water insoluble fatty alcohols, glycols, ethers, fatty acids, amides, fatty acid esters, linear hydrocarbons, branched hydrocarbons, cyclic hydrocarbons, halogenated hydrocarbons and mixtures of these materials. Alkanes (often referred to as paraffins), esters and alcohols are particularly preferred. Alkanes are preferably substantially n-alkanes that are most often commercially available as mixtures of substances of different chain lengths, with the major component, which can be determined by gas chromatography, between do and C₅o, usually between Ci₂ and C₃₂- Examples of the major component of an alkane organic phase change materials include n-octacosane, n-docosane, n-eicosane, n-octadecane, n-heptadecane, n-hexadecane, n- pentadecane and n-tetradecane. Suitable ester organic phase change materials comprise of one or more Ci - do alkyl esters of do - C₂₄ fatty acids, particularly methyl esters where the major component is methyl behenate, methyl arachidate, methyl stearate, methyl palmitate, methyl myristate or methyl laurate. Suitable alcohol organic phase change materials include one or more alcohols where the major component is, for example, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, and n-octadecanol.

It is also possible to include a halogenated hydrocarbon along with the main organic phase change material to act as a fire retardant.

Organic phase change materials are substantially water insoluble, as this is necessary for preparing particulate forms of the organic phase change material, for instance in emulsion form or encapsulated form.

Organic phase change materials are utilized in the invention in a particulate form, by which is meant either in emulsified or encapsulated form. For reasons discussed in more detail below, the particle size of phase change material particles should not be too large. Typically the phase change material particles are as small as possible within certain limitations. This is discussed in more detail below when considering the phase change material form, for instance in emulsion or encapsulated form.

In order to provide the composition of the invention where the organic phase change material is not encapsulated it is generally desirable to provide the organic phase change material in the form of an emulsion. Suitable emulsions comprise of a disperse phase of organic phase change material stabilized in an aqueous continuous phase, hence it is a type of oil-in-water or O/W emulsion. The term "emulsion" is often applied to liquid-in-liquid two phase systems. In this invention we allow the term "emulsion" to embrace both the liquid-in-liquid and solid-in-liquid systems depending on whether the particles of phase change material are liquid (molten) or solid (crystallized). Hence the term "particles", when referring to the organic phase change material, also embraces both the liquid and solid form. In a suitable emulsion, monomeric and/or polymeric surfactant(s) is/are used to facilitate emulsification of the organic phase change material and stabilize the particles in the aqueous continuous phase.

The particle size of an emulsion is generally limited to a fairly narrow range. Large oversized particles, especially very coarse particles, should be avoided since they tend to be more unstable and more prone to coalescence and hence phase separation. Thus, for practical reasons, the particle size of the organic phase change material in an emulsion form is typically between 0.05μm and 50μm, often between 0.1 μm and 20μm and more often between 0.5μm and 10μm (expressed as volume mean diameter as determined, for example, by a Sympatec particle-size analyzer). Therefore this definition includes emulsions described as microemulsions and nanoemulsions.

Preferably the emulsions will contain at least 20% w/w particles of organic phase change material and more preferably this will be at least 40% w/w. The emulsion may contain up to 75 or 80% w/w, although usually not more than 60 or 65% w/w.

Normally the emulsions should be suitably stable in that they should not phase separate after several hours in static storage; preferably they will be stable for at least 7 days and most preferably for at least 30 days. Often the emulsions are stable for several weeks or months and even up to one year or more. Although there may be a tendency for particles to migrate towards the surface of the storage container (an effect known as "creaming"), a good emulsion will not destabilize to form a substantial layer of coalesced phase change material and stirring will substantially rehomogenize the creamed particles.

Suitable emulsions may be prepared by conventional methods such as those described in the book "Emulsion Science" by Philip Sherman. A useful guide to monomehc surfactant (emulsifier) selection is given in a publication by ICI entitled "The HLB System". Numerous other literature articles describe the preparation of stable emulsions, including the selection and amount of monomehc and/or polymeric surfactant(s) to be used.

Note that it is generally preferred to prepare the emulsion using the liquid form of the organic phase change material i.e. in a molten state. Organic phase change materials that contain an additive such as a halogenated paraffin, organic nucleating agent, oil soluble surfactant etc should also be in a fully liquid state, ideally. It is preferable to maintain the organic phase change material (including optional additives) in a liquid state during the formation of the emulsion, which usually involves maintaining the temperature of the organic phase change material (including optional additives) above the temperature where wax crystals may form. The formation of an emulsion involves the combination of a disperse phase comprising the organic phase change material to an aqueous phase and it is sometimes necessary to control the temperature of the aqueous phase prior to and/or during the addition of the organic phase change material. This is to avoid cooling the disperse phase to a point where problematical crystallization can occur.

Typically encapsulated organic phase change materials comprise the organic phase change material and optional additives such as a halogenated paraffin or a nucleating agent which is surrounded by a shell that is impermeable to the phase change material. Unlike free (unconstrained) particles of organic phase change material, capsule particles remain as solid particles even when the organic phase change material in the core of the capsules is in its higher energy molten state. In capsule form the organic phase change material is completely surrounded and entrapped by the shell and is protected against contamination. When the shell is robust, the organic phase change material is more securely contained and less likely to escape from the capsules and compositions comprising capsules. For this reason it is preferred to use capsules in this invention, particularly capsules that are robust. Details of the robust character of the capsules are provided below.

Since encapsulated organic phase change materials tend to be stable, solid entities, they can be provided in a broader range of particle sizes than would be possible for the aforementioned emulsified organic phase change materials. It is possible to use capsules in this invention with mean primary particle size of between 0.1 μm and 1 mm. Generally, it is preferred to use smaller capsule particle sizes in this invention for a number of reasons. Smaller primary capsules tend to be more durable leading to inventive compositions which do not readily release organic phase change material. Due to their greater surface/volume ratio, smaller particle sizes are expected to give inventive compositions which more readily transfer heat to/from the particles of organic phase change material. It is generally possible for smaller capsules to be more uniformly distributed throughout the second panel.

Capsules may conveniently be used in the form of an aqueous dispersion or dry powder.

Suitable aqueous dispersions typically comprise 30 to 60% w/w, most preferably 40 to 50% w/w microcapsules. When provided as an aqueous dispersion, the particle size of capsules of organic phase change material should be carefully considered. In addition to the benefits of smaller capsules discussed earlier, dispersions of smaller capsules tend to exhibit the favourable property of better stability (reduced capsule creaming or settling) and the unfavourable property of increased viscosity compared to a dispersion of larger sized capsules at an equivalent concentration. It is also generally more difficult to prepare suitable capsules with very small particle sizes and/or the process required is more costly due to the extra processing that is required and/or the use of more specialized equipment. A balance must be found between these advantages and disadvantages and a volume mean diameter (VMD) of capsules (when in the form of an aqueous dispersion) of between 0.2μm and 20μm is usually chosen. Preferably the VMD of the capsules in an aqueous dispersion is between 0.7μm and 10μm and more preferably between 1μm and 5μm. VMD is determined by a Sympatec Helos particle size analyzer or another technique found to give results for microcapsules that are in very good agreement with the results from a Sympatec Helos analyzer.

Capsules in a dry form may also be used in this invention. Such capsules may be obtained when an aqueous dispersion or suspension of capsules is subjected to a water removal step, which may include spray-drying, air-drying, filtration or centhfugation. It is also possible to partially remove the water to produce a paste or cake form of the capsules. Spray-drying is particularly preferred when producing essentially dry products from a dispersion of microcapsules up to 10μm in VMD. Preferably the particle-size of the capsules to be spray-dried is 1μm to 5μm. Spray-dried particles of organic phase change material comprise of 1 or more primary particles (microcapsules), and often several primary particles in an agglomerated form. The VMD of the spray-dried particles is generally 5μm to 200μm, preferably 10μm to 100μm and more preferably 20μm to 80μm. This range balances the advantages of small particle sizes with the need to avoid dust and associated respiratory hazards.

It is preferable to use the aqueous dispersion form of capsules in this invention as this usually provides the preferred smaller capsule particle sizes and, as the water removal step needed for the dry product is avoided, at a lower cost. It is noted that typical microencapsulation processes provide an aqueous capsule dispersion as a product of the process. The encapsulation process results in capsules with a substantially core-shell configuration. The core comprises of organic phase change material and the shell comprises of encapsulating polymeric material. Usually the capsules are substantially spherical. Preferably the shell is durable such that the organic phase change material is protected from contamination and cannot easily escape from the capsules. Thermogravimetric analysis (TGA) provides an indication of the robustness of the capsules. "Half Height" is the temperature at which 50% of the total mass of dry (water-free) capsules is lost as a fixed mass of dry capsules is heated at a constant rate. In this analysis method mass may be lost due to organic phase change material escaping as vapour permeating through the shell and/or due to rupturing of the shell. Particularly suitable microcapsules of organic phase change material (in the 1μm to 5μm mean particle size range) have a Half Height value greater than 200⁰C or 25O⁰C, preferably greater than 300⁰C and more preferably greater than 35O⁰C, when TGA is carried out under a nitogen atmosphere using a Perkin-Elmer Pyris 1 at a rate of 2O⁰C per minute using typically 5 to 50 mg of dry sample. The dry sample is obtained by adding a quantity of the dispersion product (usually at 45% w/w solids content) to the sample pan of the analyzer and then holding the temperature at 11O⁰C to remove the water (the dry state has been reached when stable readings are obtained at 11O⁰C). The analysis then proceeds by increasing the temperature at a rate of 20°C/minute.

Microcapsule products in powder form, obtained from a spray-drying process as described earlier, for example, may be analyzed in the same way. In this case the drying step is usually very short as the powder is essentially dry.

Capsules may be formed by any convenient encapsulation process suitable for preparing capsules of the correct configuration and size. Various methods for making capsules have been proposed in the literature. Processes involving the entrapment of active ingredients in a matrix are described in general for instance in EP-A-356,240, EP-A-356,239, US 5,744,152 and WO 97/24178. Typical techniques for forming a polymer shell around a core are described in, for instance, GB 1 ,275,712, 1 ,475,229 and 1 ,507,739, DE 3,545,803 and US 3,591 ,090.

The phase change material may be applied to one or more surfaces of the formed second panel, preferably to the surface facing the interior of the building. More preferably, however, the phase change material is incorporated into the matrix of the second panel during its manufacture. In fact the major component, e.g. first component, of the second panel, preferably magnesia cement, will desirably form a matrix in which the phase change material is surrounded. More preferably both first component, preferably magnesia cement, and the second component, preferably sand or fine aggregate, will surround the phase change material. In particular the phase change material may be uniformly distributed throughout both the first component, e.g. magnesia cement, and second component, e.g. sand or fine aggregate of the second panel.

The phase change material may be incorporated during the production of the second panel or applied to the surface of the formed second panel in which the phase change material may be in the form of a dispersion or slurry in a continuous phase liquid. Typically this may be a dispersion or slurry in water or for instance in the form of an aqueous emulsion. Preferably the phase change material is microencapsulated and is applied as an aqueous dispersion. Alternatively the phase change material may be applied in the form of dried microcapsules.

The second panel may contain flame retardant additives and this may include inorganic salts or other inorganic compounds such as magnesium hydroxide, aluminium hydroxide or borates. The thickness of the second panel may be between 5 and 50 mm, preferably between 5 and 30 mm, more preferably between 10 and 20 mm.

The first and second panels may be fitted with suitable anchor points for the internal ties. The tie anchors may be cast into the foamed plastic during manufacture. Where the first panel is constructed from some other material other means for securing the anchor points may be more appropriate, for instance screws or other standard fixing means.

The ties may be any conventional ties used in ICFs or other wall form units are described in the prior art, for instance as referred to herein. Typically the ties can be constructed from metal or plastic. Where the ICFs are not based on the "flat pack" system but form an integrated block, the ties may be constructed of foamed plastic. The ties should desirably incorporate a spacer member which maintains the predetermined distance of the first and second panels. Typically the ties and spacer member will form an integrated entity and desirably will be constructed from metal or plastic, or foamed plastic as given above. It may be desirable to integrate the ties with the first and second panels to form an integrated block. Tie anchors may be cast into the panels, particularly the first panel. The first and/or second panel may contain slots where the ends of the ties are inserted and secured. In this case the ties may be permanently connected to one panel and connected to the other panel by inserting the free end of the ties into slots in the other panel. Alternatively the ties may be fitted into slots in both panels. Two or more types of ties may be used.

According to one aspect of the present invention the wall form unit (e.g. ICF) is assembled by interconnecting a multiplicity of first panels together and a multiplicity of second panels together, thus formed assembly of first panels and thus formed assembly of second panels being maintained in a predetermined distance by a suitable tie assembly. The hollow section formed between the assembly of first panels and the assembly of second panels, hereafter referred to as the cavity, may be between 50 and 500 mm in spatial distance between the two assemblies. Preferably the cavity may have an interspatial distance of between 100 and 220 mm. Typical cavity interspatial distances can for instance be 102 mm, 158 mm, and 203 mm depending upon the building structure required. Other pre-formed sections, such as corners, may also be made according to this invention.

The above described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be affected there to, by those skilled in the art, without departing from the scope of the invention which is specified in the claims.

Figure 1 shows a wall section according to the present invention having a first panel (1 ) of a thermally insulating material on the exterior side of the wall section; a metal rebar (2) for wall supporting strength; a tie (3) for maintaining the first and second panels spaced apart in predetermined relation; a corner post (4); a second panel (5) of thermally conducting material located on the interior side of the wall section; and concrete (6) as a pourable, curable construction material.

Claims

1. A wall form unit for containing a pourable, curable construction material for forming a wall section integrating said wall form unit and said construction material, comprising a first panel and a second panel in predetermined relation thereby forming a hollow between said first and second panels for defining said wall section and at least one tie assembly having a spacer member for maintaining said first and second panels spaced apart in predetermined relation, in which both the first panel and second panels are rigid and adapted to retain said construction material, wherein the first panel is constructed of a thermally insulating material and the second panel is constructed of a thermally conducting material.

2. A wall form unit according to claim 1 in which the first panel comprises a composite material, a polymer or a polymer-based compound, preferably an expanded polystyrene or polyurethane foam.

3. A wall form unit according to claim 1 or claim 2 in which the second panel comprises a first component which is selected from an inorganic binder, a polymer and a polymer-based compound and, optionally, a second component selected from thermally conducting particles, filaments or mesh that are distributed throughout the first component.

4. A wall form unit according to any preceding claim in which the second panel comprises a first component which is selected from an inorganic binder, a polymer and a polymer-based compound and a second component selected from graphite, alumina particles, silica sand, fine gravel or stone particles, metallic fibres, metallic mesh and metallic particles.

5. A wall form unit according to any preceding claim in which the second panel is formed from a hydraulic inorganic binder.

6. A wall form unit according to any preceding claim in which the second panel is formed from magnesia cement.

7. A wall form unit according to any preceding claim in which the second panel is formed from magnesia cement comprising particles of sand, or other additive of high thermal conductivity, which is distributed throughout the magnesia cement.

8. A wall form unit according to any preceding claim in which the second panel contains phase change material (PCM).

9. A wall form unit according to any preceding claim in which the second panel contains phase change material (PCM) and magnesia or magnesia cement.

10. A wall form unit according to claims 8 or claim 9 in which the phase change material (PCM) is microencapsulated.

11. A wall form system for forming a wall section having a core of pourable, curable construction material sheathed by a plurality of panels comprising at least two wall form units, each said wall form unit having means for interlocking set wall form units to define said wall section, a first panel and a second panel in predetermined relation thereby forming a hollow between the first and second panels for receiving said construction material, and a least one tie assembly, said tie assembly comprising a spacer member for maintaining said first panel and said second panels spaced apart in said predetermined relation, in which both the first panel and second panels are rigid and adapted to retain said construction material, wherein the first panel is constructed of a thermally insulating material and the second panel is constructed of a thermally conducting material.

12. A kit for constructing a wall form unit according to claim 1.

13. A wall section comprising at least two wall form units according to claim 1 or a wall form system according to claim 11 containing a cured construction material between the first and second panel, which cured construction material has been formed from a pourable, curable construction material that has been poured into the hollow between the first and second panels.

14. A process of erecting a building structure which comprises a wall section formed from a plurality of ICF units comprising the steps, i) arranging the first and second panels of the plurality of ICF units in predetermined relation for defining said wall section such that a hollow is formed between the first and second panels by spacing apart the first and second panels in predetermined relation, ii) connecting at least one tie assembly having a spacer member for maintaining said first and second panels spaced apart in predetermined relation, iii) introducing a pourable, curable construction material into the hollow, iv) allowing the pourable, curable construction material to cure, in which both the first panel and second panel are rigid and adapted to retain said construction material, wherein the first panel is constructed of a thermally insulating material and the second panel is constructed of a thermally conducting material.