Patent Application
20160053121
The present invention relates to facing papers for plasterboards having a high porosity, as well as the plasterboards comprising these facing papers and the coating slip for manufacturing these facing papers.
Plaster boards or panels are well known and are made conventionally from a body or core of gypsum-based plaster which is deposited, generally by casting, between two supports of paperboard providing both the mechanical support or reinforcement of the plaster and its external facing on its outer faces.
The manufacture of plaster panels of this type is described in document EP 0521804. It is also known, from the mentioned document, that depositing a coating slip on the external face of the facing paper with the objective of providing a good aesthetic appearance of the outer layer of said facing paper, preventing its yellowing and providing it with good uniformity of white colour is possible without having a negative influence on manufacture of said paper, on its durability over time and on its qualities of resistance, in particular of the mechanical strength.
Document WO 2006/010853 proposes an improved coating slip, containing plastic pigments as whitening agent. This coating slip makes it possible to obtain a particularly uniform visual appearance of the plasterboard.
However, it was found that the facing papers used in the prior art, in particular those having a satisfactory visual appearance, also have a reduced porosity. This leads to a relatively long drying time of the plasterboards.
It is therefore, desirable to develop facings for plasterboards having high porosity, yet also having satisfactory properties, in particular in terms of visual appearance.
The invention relates firstly to a plasterboard comprising a layer of plaster and at least one facing arranged on the latter, the facing being coated with a coating slip comprising a microporous material, said microporous material comprising agglomerates of precipitated silica.
According to one embodiment, the microporous material is present in an amount in the range from 0.1 to 10% in the coating slip, preferably in the range from 0.5 to 5%, and more preferably in the range from 2 to 4% of dry matter.
According to one embodiment, the coating slip is present on the facing in an amount of between 2 to 50 g/m2, preferably of between 5 to 35 g/m2, more preferably of between 10 to 20 g/m2 of dry matter.
According to one embodiment, the silica agglomerates have a size Dv50 of between 0.5 to 500 μm, preferably of between 5 to 200 μm, and more preferably of between 10 to 200 μm.
According to one embodiment, the agglomerates of precipitated silica correspond to the formula MeOx.mSiO2,
Wherein,
Me represents at least two metals selected from Ca, Mg, Cu, Zn, Mn, Cd, Pb, Ni, Fe, Cr, Ag, Al, Ti, V, Co, Mo, Sn, Sb, Sr, Ba and/or W;
x represents the molar ratio of oxygen to metallic constituents; and
m represents the molar ratio of SiO2 relative to the metallic constituents, and
wherein Me preferably represents Mg and Ca.
According to one embodiment, the molar ratio m is in the range from 1 to 4, preferably in the range from 2 to 3.5, more preferably in the range from 2.5 to 3.
According to one embodiment, the microporous material can be obtained by a method of manufacture comprising the following steps:
According to one embodiment, in the method of manufacture:
According to one embodiment, the coating slip further comprises plastic pigments, preferably in an amount in the range from 0.1 to 10%, more preferably in the range from 0.5 to 3% of dry matter.
According to one embodiment, the coating slip further comprises:
The invention also relates to a facing for plasterboard, the facing being coated with a coating slip comprising a microporous material, said microporous material comprising agglomerates of precipitated silica.
According to one embodiment, the coating slip is as described above.
The invention also relates to a composition for coating plasterboard, comprising a microporous material, said microporous material comprising agglomerates of precipitated silica.
According to one embodiment, this composition is a coating slip for facing plasterboard, said coating slip preferably being as described above.
According to an alternative embodiment, this composition is a paint for a wall made from plasterboard, in which preferably the microporous material is as described above.
According to one embodiment, this composition comprises:
The invention also relates to a method of manufacturing a facing as described above, comprising providing a facing paper, and applying the aforementioned coating slip on the facing paper.
The invention also relates to a method of manufacturing a plasterboard as described above, comprising:
According to one embodiment:
The invention also relates to the use of a microporous material comprising agglomerates of precipitated silica, in order to increase the porosity of a plasterboard surface.
According to one embodiment, the microporous material is as described above.
According to one embodiment, this use is for the purpose of increasing the porosity of a plasterboard facing.
According to one embodiment, the microporous material is incorporated in the form of a gel in a coating slip for plasterboard facing or in a paint for a wall made from plasterboards, said gel preferably having a water content in a range from 40 to 95%, more preferably in a range from 60 to 92%, and even more preferably in a range from 80 to 90%.
The present invention is able to overcome the drawbacks of the prior art. More particularly it provides plasterboards having both a satisfactory visual appearance, namely without yellowing, and with good uniformity of white colour, and an improved porosity.
This is achieved by incorporating a microporous material comprising agglomerates of precipitated silica in the coating slip. It was found that this incorporation leads to the appearance of microcracks on the surface of the facing, increasing the Gurley porosity of the facing; and that moreover the other properties of the coating slip and of the coated facing (viscosity, gloss, whiteness etc.) are essentially unchanged, or possibly are altered minimally, and any such change can easily be compensated by adjusting the other components of the coating slip.
In general, the invention proves to be useful in all applications of coating of surfaces, in which water or water vapour must be able to pass through or be transported through the coating.
Moreover, the capacity of the microporous material for creating microcracks can also be utilized in the formulation of a paint intended to be applied on any substrate, and in particular on plasterboards whether individual or assembled in the form of a wall (wall, ceiling, partition, false ceiling, etc.). Such a paint can notably allow improved properties of sound absorption to be obtained. The paint can be applied directly on the facing of the plasterboards, or on a coating layer deposited on the latter.
A more detailed, non-limiting description of the invention is given below.
Unless stated otherwise, any proportions stated are proportions by weight.
The microporous material used in the context of the invention is described in detail in document WO 2006/071183. It is a material of the aerogel type.
The microporous material can be manufactured by a reaction of precipitation where a solution of alkali metal silicate is brought in contact with a saline solution containing divalent or polyvalent metal cations.
On mixing a soluble silicate with salt solutions containing metals other than those of the alkali metal group, insoluble amorphous metal silicates are obtained by precipitation. This method is called the coagulation process; the particles form relatively compact aggregates, in which the silica is more concentrated than in the original solution, so that the coagulant sediments in the form of a relatively dense precipitate.
The precipitated coagulant thus obtained is then rinsed with water until the residual reaction products and excess reactants are removed. Some of the water of the suspension is then removed for example by vacuum filtration or by centrifugation, until a relatively viscous paste is obtained, for example with about 15% dry matter.
The material can be impregnated with impregnating agents, for example by adding these agents at a suitable concentration in a final step of rinsing of the coagulant. Alternatively, these agents can be added to the paste after rinsing and removal of some of the water from the suspension.
The document WO 2006/071183 describes forming of the material into granules or other forms, and drying of the material to a dry matter content above 75%, or 90%, or 95%, or 97%. Drying is typically carried out at a temperature from 50 to 250° C., for example of 105° C.
Although it is possible to use the microporous material in this dried form, it is preferred in the context of the invention to omit drying, or else carry out more limited drying, and consequently use the material in the form of a gel or a paste for making the coating slips. The water content is thus advantageously in a range from 40 to 95%, more preferably in a range from 60 to 92%, and even more preferably in a range from 80 to 90%, at the time of use of the material.
The alkali metal silicates usable for manufacture of the material can be based on sodium or potassium, or even lithium. It is also possible to use a silicate composed of SiO2 and Na2O. The commercially available alkali metal silicates generally have molar ratios of silicate fraction to alkali fraction in a range from 1.6 to 3.9.
To obtain the coagulation reaction, the dilute solution of alkali metal silicate, typically at a concentration of 1.5 M with respect to SiO2, is mixed with a concentrated or even saturated solution of salts containing magnesium and/or calcium, for example MgCl2 and CaCl2. However, any readily soluble salt such as a nitrate or an acetate can also be used. Moreover, other divalent or polyvalent cations can be used instead of Mg and Ca, such as Cu, Zn, Mn, Cd, Pb, Ni, Fe, Cr, Ag, Al, Ti, V, Co, Mo, Sn, Sb, Sr, Ba and/or W.
When the dilute solution of sodium silicate is mixed with magnesium chloride and/or calcium chloride with vigorous stirring, the mixture coagulates immediately, according to the following reaction:
Na2O.nSiO2 (l)+1/2Mg2++1/2Ca2+→(Mg, Ca)O.nSiO2 (s)+2Na+
where
The silica particles enriched with Mg and/or Ca are coagulated in the form of aggregates dispersed in the aqueous medium, then they are recovered on a filter, rinsed, and optionally formed and dried.
Thus, the microporous material used in the invention has the formula MeOx.mSiO2, in which
Me represents at least two metals selected from Ca, Mg, Cu, Zn, Mn, Cd, Pb, Ni, Fe, Cr, Ag, Al, Ti, V, Co, Mo, Sn, Sb, Sr, Ba and/or W;
x represents the molar ratio of oxygen to the metallic constituents; and
m represents the molar ratio of SiO2 to the metallic constituents.
The silica agglomerates preferably have a size Dv50 in a range from 0.5 to 500 μm, preferably in a range from 5 to 200 μm, and more preferably in a range from 10 to 200 μm.
Preferably, the molar ratio m=Si/Me is in a range from 1 to 4, preferably in a range from 2 to 3.5, more preferably in a range from 2.5 to 3.
The impregnating agents are for example impregnated in an amount in a range from 5 to 20%, and preferably in a range from 10 to 20%.
The material according to the invention preferably has a porosity in a range from 0.5 to 1.2 cm3/g, and/or a BET surface area in a range from 300 to 800 m2/g.
The material according to the invention is incorporated in a coating slip for plasterboard facing, preferably in the form of the gel described above, in an amount in a range from 1 to 30%, preferably in a range from 2 to 20%, and more preferably in a range from 5 to 15% of dry matter.
The coating slip is preferably based on water. It preferably comprises advantageously plastic pigments as whitening agent, as is described in detail in document WO 2006/010853.
The plastic pigments, also called organic pigments in contrast to the inorganic pigments such as clay, talc or calcium carbonate for example, are synthetic polymer latices whose glass transition temperature is high enough to give these latices a non-film-forming property or properties enabling the particles making up this type of latex to remain separate.
The plastic pigments or organic pigments usable in the coating slip according to the invention can be selected from the plastic pigments available on the market, and in particular from the plastic pigments with solid particles or with hollow particles. Preferably, the plastic pigments are formed from hollow particles, i.e. comprising a free internal space.
As a non-limiting example, the plastic pigments used in the slip can be plastic pigments sold under the reference Ropaque® by the company Dow.
In addition to the plastic pigments, the coating slip preferably also comprises a mineral filler. As mineral filler, it is possible to use calcium carbonate, or potassium carbonate, or any equivalent filler, for example calcium sulphate dihydrate. Combinations of these compounds can also be used.
The coating slip preferably also comprises a binder, in particular a synthetic binder, and preferably a synthetic latex. As an example, it is possible to use a styrene-butadiene or styrene acrylic binder, or several other synthetic polymer materials such as polyvinyl acetates and polymers based on acrylic monomers, as well as polymer materials of natural origin, such as, non-exhaustively, modified or unmodified amylaceous polymers, proteins of the casein type or a mixture of synthetic polymer materials with polymer materials of natural origin.
A relatively high content of binder improves the abrasion resistance of the coated paper, and therefore of the plasterboard.
In addition to the components stated above, the coating slip can optionally comprise additives or secondary compounds and preferably titanium dioxide (as additional filler), a pH regulator (for example sodium hydroxide), a thickener, an antifoaming agent, a biocide, a colorant and/or a dispersant.
According to one embodiment, the coating slip comprises an amount of water in a range from 10 to 50%, preferably in a range from 20 to 30%, and further comprises:
The coating slip is applied on a facing, or facing paper, either before manufacture of the plasterboard, optionally with intermediate steps of drying, cutting, conditioning of the coated facing; or during manufacture of the plasterboard, after applying the plaster paste on the facing.
In general, the plasterboard comprises two facings, between which the plaster body or core is cast or applied or formed. The two facings can comprise the coating slip, on their faces opposite to the plaster core, or preferably just one of these facings (the one that is intended to be exposed to view) comprises this coating slip on its face opposite to the plaster core.
The facings comprises or consists of sheets of paper or of paperboard.
The boards can preferably be manufactured by pouring the plaster on one of the facing papers, then placing the second facing paper, then drying of the board leading to considerable evaporation of water and production of the definitive building board after hardening. Reference is made to document EP 0521804 for more details.
The facing paper used is preferably a multilayer paper that can for example be formed by a stack of two or more layers, and in particular of two to nine layers, without the number of layers being limiting.
Particularly advantageously, the facing paper is formed by a succession of two layers, it being understood that it can also be made using a stack of three or five layers.
The characteristics of the paper, given below but not in any way limiting, for example its weight (standard NF Q 03-019), or its thickness (standard NF Q 03-016), its properties of water absorption, that is its properties of absorption of water on the face in contact with the sheet of plaster or Cobb three minutes (standard NF Q 03-014), its permeability to air (Gurley porosity—standard NF ISO 5636-5), its breaking strength (standard NF Q 03-004), its inter-ply strength, its elongation under water measured at one minute at 23° C. in the transverse direction (standard NF Q 03-063), etc. are suitable for withstanding the presence and the evaporation of water as well as the various manufacturing operations.
As non-limiting examples, the paper basis weight can be from 100 to 250 g/m2, and preferably from 160 to 200 g/m2, and even more preferably from 180 to 200 g/m2.
In general, production of a plasterboard at reduced cost, compared with the conventional boards, can be based on the use of a less expensive facing paper, which correlatively involves having recourse to fibres of less good quality leading finally to a paper generally of a darker colour and for example of the order of 50 to 70 ISO (ISO 2469/2470), and for example of the order of 60.
Advantageously, the top layer of the facing paper intended to form the exterior of the plasterboard, and which therefore constitutes the visible face of the board, is made starting from a mixture of bleached or semi-bleached recycled fibres such as white offcuts or out-of-date office papers. The references and nomenclatures of papers mentioned in document EP 0521804 are fully applicable here (group C and preferably C7 to C9 and C11, C12, C14 to C19).
The top layer can also be made from recycled unprinted office paper or from newspaper. For information, other fibres or pulps that can be used are bleached or semi-bleached virgin cellulose fibres such as chemical-mechanical fibres, thermo-mechanical fibres or thermo-mechanical chemical fibres.
The basis weight of the top layer can be for example in a range from 20 to 90 g/m2, and preferably in a range from 30 to 50 g/m2. The weight of the top layer of the facing paper plays an important role in obtaining the final whiteness of the paper and a person skilled in the art will adapt the weight of the top layer in relation to the weight and properties of the other layers, as well as in relation to the properties of the coating slip.
Non-exhaustively, the whiteness of the top layer can be of in a range from 65 to 68 ISO. The layer of the paper that is in contact with the plaster (gypsum) is advantageously made from old embossed cardboard, or else from recycled raw materials from domestic use and including for example packaging for liquids, or similar types of fibres, or a mixture of these fibres that can give these layers the necessary solidity and porosity.
The top face of the facing or top ply of the paper, which constitutes the visible face of the plasterboard, is intended to receive a coating slip to endow this surface with superior aesthetic qualities and preferably one or more qualities selected from:
The coating slip is able to meet the objectives stated above without altering the qualities and functions of the paper with respect to its role of reinforcement and removal of water during drying of the plaster.
The coating slip is applied on the facing in an amount of in a range from 2 to 50 g/m2, preferably in a range from 5 to 35 g/m2, more preferably in a range from 10 to 20 g/m2 of dry matter.
The provision of coating slip depends on the initial degree of whiteness of the paper: the whiter the base paper, the more the provision of the coating slip can be reduced. The degree of whiteness of the coated paper, i.e. coated with the coating slip is advantageously ISO gloss index of 75 and 85 and preferably from 78 to 80.
The coating slip is applied by the usual techniques used in this field such as by air knife or by roller or by doctor blade or by spraying or some other technique, or else by a combination of several of these techniques that are well known by a person skilled in the art and referenced for example in document EP 0521804.
Preferably, the Gurley porosity of the facing paper is less than or equal to 280 s/mL air, and according to certain embodiments less than or equal to 270, or 260, or 250 or 240, or 230, or 220, or 210, or 200 or 190, or 180, or 170, or 160, or 150, or 140, or 130, or 120, or 110, or 100, in seconds per 100 mL of air. This porosity notably allows rapid and effective drying of the plasterboards during manufacture.
The plasterboards according to the invention are used conventionally as building materials and serve for forming partitions or ceilings, or else to form double walls in particular for insulation.
A coating slip is prepared from the following basic formulation:
In certain variants, the styrene-butadiene copolymer is replaced with an acrylic polymer or a vinyl acetate polymer at equivalent amount of dry matter.
Depending on the experiment, a variable amount of gel of microporous material according to the invention (gel comprising 15% dry matter), supplied by the company Svenska Aerogel AB, is added to this basic formulation. More precisely, 5, 10, 15, 20 or 25 parts of gel of microporous material are added to 100 parts of coating slip.
The coating slip is prepared using a Heidolph® RZR2021 disperser equipped with a dispersing disc with a diameter of 70 mm. Firstly, one third of the water, the calcium carbonate, titanium dioxide, antifoaming agent and dispersant are mixed for 15 minutes. Then the rest of the water is added, as well as the thickener, plastic pigment, binder and crosslinking agent. The mixture is stirred for 10 minutes. The biocide and the yellow colorant are added and the mixture is homogenized for 3 minutes. Finally the gel of microporous material is added and the mixture is stirred until the gel of microporous material has dispersed (from 3 to 5 minutes).
The coating slip is then applied manually on sheets of paperboard of A4 format using bar applicators. Thicknesses of 16 and 26 μm are used. The weight obtained is about 15 g/m2. The sheets thus coated are left to dry in a stove at 105° C. for a few minutes. Next, the Gurley porosity of the sheets is tested according to standard NF ISO 5636-5. The results are presented in Table 1 below:
Furthermore, the gloss at 85° is tested according to standard ISO 2813 for the sheets prepared with the coating slip comprising the styrene-butadiene binder. The results are presented in Table 2 below:
It can therefore be seen that the invention allows significant improvement of the porosity to air of a facing paper, without degrading the gloss excessively. It should also be noted that the relative degradation of gloss observed can be compensated by adjusting the formulation of the coating slip (notably via the amounts of filler, of titanium dioxide, and of plastic pigment).
The coating slip from example 1, with styrene-butadiene binder, is used for making paper for plasterboards in a pilot plant.
Three coating slips were tested, the coating slip from example 1 without gel of microporous material, a coating slip in which 5 parts of gel of microporous material were dispersed and a coating slip in which 15 parts of gel of microporous material were dispersed.
In this example, the coating is applied by bath. The amount of coating slip applied is controlled by air knife. The paper is then dried in a hot air tunnel. The properties of the paper are summarized in Table 3 below:
The Cobb test is carried out according to standard ISO 535, the Dennison test is carried out according to standard TAPPI 459, the measurements of colour are carried out according to standard T527 OM94 (TAPPI), the colour system being expressed according to the CIE system L*, a*, b*.
It can be seen that the only significant effect on the coated paper from using the microporous material according to the invention is to increase its porosity.
The papers made on the pilot line were used for making plasterboards in the laboratory.
The properties of the boards prepared with the papers obtained in the pilot test are summarized in Table 4 below:
It can be seen that the plasterboards manufactured with the papers whose coating contains microporous material have properties equivalent to those of a plasterboard prepared with a paper not containing gel of microporous material and are also equivalent to those of a reference factory-made board, also without microporous material.
A paint is prepared from the following basic formulation:
The paint is applied by roller on a ceiling partition made from plasterboards. Observation of the surface after application reveals microcracks. The alpha w sound absorption after coating with paint is 0.45, whereas it was below 0.1 with a paint without gel of microporous material and 0.8 before coating.
The measurements were performed according to standard EN ISO 10534-2 (“Acoustics—Determination of sound absorption coefficient and impedance in impedance tubes—Transfer-function method”). Then the absorption coefficients were determined according to the calculation proposed by Albert Londin in “The determination of reverberant sound absorption coefficient from acoustic impedance measurements” (JASA Vol. 22, No. 2, March 1950). The single alpha w value was calculated with the absorption coefficients determined according to Londin's calculation and based on standard EN ISO 11654 (“acoustic sound absorber for use in building: rating of sound absorption”).
| Number | Date | Country | Kind |
|---|---|---|---|
| 1352946 | Mar 2013 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/055778 | 3/23/2014 | WO | 00 |
