SE528216C2 - Primer for applying to building ventilation panels or boards, is prepared by mixing cement and sand component with styrene butadiene latex - Google Patents

Abstract

The primer is prepared by mixing a first component in the form of a dry curing agent comprising cement and sand with a second component comprising a styrene-butadiene latex which is incompatible with the cement in the curing agent. At least some of the latex coagulates when the two components are mixed together.

Description

528 216 l II rara:: -2: -; . .u .v v »~ o: ._ :; ',, I, 2: u: o- ø. so. : 0 °,. nu u n u _ _ _,,. u u n. - co coon c ~ I Ueno In order to increase the load-bearing capacity of such discs or mats made with projecting spacers, the upwardly open cavities must be filled with a load-bearing material.

However, it is not possible to fill only the cavities themselves, then when loading such a construction, as e.g. is coated with a soft mat or the like, the material bodies in the cavities would protrude above the part of the disc or mat otherwise pressed down by the load. It is thus necessary to provide a load-resistant layer also between the bodies in the cavities, which binds all the support bodies together into one unit.

When using air gap-forming sheets or mats of plastic material, such as HDPE, with a hydrophobic surface, difficulties arise in producing a putty which can adhere even in thin layers to such surfaces.

To date, in order to prevent the putty from coming loose from the surface and to obtain the required load-bearing capacity, layers of putty or concrete with thicknesses of at least 1.5-2 cm must be laid.

Prior art According to the prior art, different types of floor putty such as float putty or concrete putty have been used in the construction of inner floors on such air gap-binding boards.

Such known fillers have low adhesion to the hydrophobic surface of the HDPE plates. If the putty is applied in thinner layers, therefore movements in the floor and the air gap-forming tiles will cause the putty layer to crack, especially where the putty layer is thinnest, between the cavities in the tiles. Due to the poor adhesion of the putty to the HDPE substrate, such cracking can lead to smaller pieces or larger pieces of the putty coming loose from the substrate, 528 216 whereby the strength deteriorates considerably and irregularities in the indoor floor occur. Such putties also show a certain shrinkage when they solidify, which shrinkage in combination with the poor adhesion also leads to cracking with corresponding harmful consequences.

Therefore, in order to provide a stable substrate, it is necessary according to the prior art to apply the putty with thicknesses of at least 15-20 mm, measured from the upper level of the air gap-forming plates between the cavities. These layers have also had to be provided with reinforcement. Layer thicknesses of this order of magnitude mean that the construction height, i.e. floor thickness, increases very considerably, which in many situations makes the combination of air gap-forming carpet and load-absorbing layer impossible. The previously required thick layers have also entailed relatively high material costs.

US 5,188,389 discloses a mortar and a concrete product comprising cement, sand and a binder in the form of a latex with additives. In one embodiment, the binder comprises a styrene butadiene latex marketed by Dow Chemical Company 20 of Midland, USA, under the name Dow 460 Latex. The described mortar product is said to be able to be used as putty or putty and it is stated that the product shows better adhesion to other materials than other previously known latex-modified mortars. However, the document does not mention that the product U! is suitable for or even can be used as a primer, which can lg. J is applied to a surface to increase the adhesion to the surface of another product applied to the primer. The document also does not mention the product's adhesion to hydrophobic surfaces, such as HDPE surfaces. On the contrary, it is likely that ... šo ot 0 1 n the adhesion of the mortar product to hydrophobic surfaces is low.

Ivøo UII 'The polymer component of the styrene-butadiene latex used Dow 460: ~ Ü Latex is inherently hydrophobic and thus incompatible with water and 10 15 20 coon nu na coon 0 IIIOI 000 O ole 0000 0 9 ao o ßå U'I 528 216 000001 na 0 In a ua now 0 u oo I ouoo s aqueous solutions of cement. To enable the latex to be used together with cement, a mixture stabilizing component in the form of a dispersant has been added. This substance stabilizes the dispersion of polymer component in the water by adsorbing on the surface of the polymer particles and thereby preventing coagulation of the polymer particles into larger aggregates. The interaction of the dispersant with the polymer component reduces its hydrophobic properties and thus its ability to adhere to other hydrophobic surfaces, such as HDPE surfaces.

Since Dow 460 Latex is developed for mixing with cement products, the dispersant is added in such an amount that the polymer component is kept dispersed in the mixture even during and after mixing with a corresponding amount of cement. There is nothing in US 5,185,389 to suggest that the latex would be designed to break the dispersion and the styrene butadiene particles coagulate when the latex is mixed with the cement. Thus, in the mortar product described in US 5,185,389, even after the mixing of latex and cement, the dispersant will cooperate with the surface of the polymer particles. thereby greatly reducing the adhesion of the styrene butadiene and thus the cement mixture to hydrophobic surfaces.

Thus, according to the prior art described above, which is also completely natural, styrene-butadiene latexes which are compatible with cement are used to produce latex-modified cement products. By the term compatible is meant in this description that the composition of the latex is such that the polymer component is kept dispersed in the cement mixture even after the latex has been mixed with the cement and any other constituents included in the final product.

Brief Description of the Invention The present invention is based on the realization that, contrary to popular belief, it is possible to improve the properties of the latex-modified cement product of the latex-modified cement product. by using a latex that is incompatible with cement. By the expression "that the latex is incompatible with cement" is meant in this description that the composition of the latex is such that the dispersion is broken and the polymer particles coagulate when the latex is mixed with the proportion of cement which is intended to be included in the final product.

An object of the present invention is therefore to provide a primer which makes it possible to greatly reduce the thickness of the putty layer when building an inner floor or the like on a surface which exhibits hydrophobic properties.

Another object is to provide such a primer which shows good adhesion to both a hydrophobic surface and a putty layer applied on top of the primer.

Another object is to provide such a primer of the two-component type which is easy to mix and apply. Yet another object is to provide such a primer with which the properties of the primer such as the curing time can be adapted at the time of mixing.

These objects and other advantages are achieved with a primer of the type indicated in the first paragraph of this description, which primer is characterized in that it comprises two components for mixing with each other, that one of them is a dry hardener comprising cement and sand, that the second component is liquid and comprises a styrene-butadiene latex which is incompatible with the cement contained in the hardener, so that at least a part of the styrene-butadiene latex coagulates when the two components are mixed. The styrene-butadiene latex thus has such a composition that the styrene-butadiene particles are kept dispersed in the water contained in the latex as long as 10 15 20 ÛÛÛ: N: '(11 o to 0000 nnonc Ino o II IQ 000 - .. 3o 528 216 Cf \ ooocoø I 1 en. The styrene-butadiene latex contains a dispersant which interacts with the styrene-butadiene particles to keep them dispersed in the water. However, since the latex is incompatible with the cement, during this mixing, the cement will affect the interaction of that dispersant with the dispersed styrene-butadiene particles, so that they coagulate and the dispersion breaks.

The styrene-butadiene particles will thereby have more hydrophobic properties when the cement is mixed in, so that its adhesion to other hydrophobic surfaces, such as a substrate of HDPE, increases.

Since the styrene butadiene particles are initially kept dispersed in the latex during the mixing of the two components, the coagulated styrene butadiene particles will be evenly distributed in the finished mixture. In this way, the same good adhesion is obtained at hydrophobic surfaces along the entire surface when the ready-mixed primer is applied.

Thanks to the good adhesion of the primer to, for example, surfaces of HDPE, it is sufficient to apply only a very thin layer of primer. This thin primer layer remains at the substrate even if the substrate is moving. Once the primer has solidified, it in turn forms an excellent substrate for applying a filler on top of the primer. It is above all the constituents of the dry component in the primer, ie. cement and sand, which provides a rough surface to which the putty adheres very well. 10 15 20 Ince con oc: lova n .JU u '2 UI 528 216 The good adhesion between on the one hand the putty and the primer and on the other hand the primer and the hydrophobic substrate means that both the primer and the putty can be applied in very thin layers. In this way, it is thus possible to substantially reduce the total construction height when, for example, building an inner floor on a surface that is aerated with the aid of HDPE boards or mats.

The styrene butadiene latex suitably contains about 37% butatin, 13% styrene, 50% water and substantially smaller amounts of additives, such as a dispersant in the form of a surfactant.

Suitably, said styrene-butadiene latex serving as a binder in the liquid component is mixed with substantially the same amount of filler, e.g. magnesium or calcium carbonate, talc, chalk or dolomite.

The two main components are then conveniently composed from a practical point of view so that they can be mixed with each other in equal proportions to achieve an easily applicable mass with a suitable consistency.

To obtain the desired processing time, the hardener component may suitably contain 90-95, preferably 94% by weight of dried quartz sand and 10-5, preferably 6% by weight of standard cement. The larger the proportion of cement, the shorter the treatment time allowed, before the final product hardens. Other features of a primer according to the invention and a use thereof and a method of preparing the same appear from the appended claims. Detailed description of the invention In the following, the invention is described i.a. with reference to figure 1 which shows a schematic sketch of how the primer can be used in the construction of an aerated inner floor with a plastic mat.

In Fig. 1, 1 denotes a slab or mat, which is laid out on a concrete slab to allow air circulation between it and the mat. The air gap-forming mat is of known design and comprises pressed-down portions 2 serving as spacers, which constitute the only points of contact between the mat 1 and the substrate.

When the floor is to be covered with e.g. a plastic mat 3, the cavities 2 in the air gap-forming mat 1 must be filled out.

For this purpose, a thin layer 4 of a primer according to the invention is first applied to the carpet 1, so that the primer, when it has solidified, follows the contour of the carpet. The primer layer can, for example, have a thickness of only 0.5 mm. Then a thin layer 5 of a conventional floor putty, for example a float putty, is applied to the solidified primer 4, so that the putty fills the cavities 2 and forms a thin layer 5 on top of the primer 4. The thin putty layer 5 binds together the bodies formed in the cavities 2 of the putty. The putty layer 5 between the cavities 2 can, for example, have a thickness of only a few millimeters. Since the cavities 2 serving as spacers only need to have a depth of the order of 3 mm, a very small total construction height is obtained. When the putty layer S has solidified, the plastic mat 3 can be laid directly on top of this.

In some applications it is possible to replace the layer of conventional floor putty with a second layer of the primer according to the invention. In this case it is possible to vary the grain size in the dry component of the primer between the first and UI o I 0 :: = U1 Ia 0 00 41 0000 00 now 0 v 0 0 III 0 0 0 i I '0 0 ncnon non 0 06,0: onl 0 0 bo 0 o! 00 oc: CJ 528 216 second application to achieve the desired surface finish of the top layer.

If necessary, of course, any number of layers of either the primer according to the invention or conventional or other fillers can be applied on top of the lower primer layer 4 applied to the hydrophobic surface.

The primer layer 4 shown in the figure, which consists of a primer according to the invention, becomes hard and can withstand even large loads without reinforcement without cracking. One reason for this is that the constituent polymeric binder maintains a certain toughness and flexibility of the primer layer, which allows it to move to some extent together with the underlying mat without cracking. The good adhesion of the primer layer to the hydrophobic substrate and its surface structure further means that a putty layer applied on top of the primer layer can be kept very thin and still be held securely at the substrate without cracking or other damage occurring even if the substrate moves or the layers are exposed to large loads from above.

As a binder, a carboxylated styrene-butadiene copolymer latex can be used, which is mixed with fillers and certain other additives to form the liquid component. The binder may, for example, comprise 50% solids in the form of 37% butadiene units and 13% styrene units and the remainder water and additives, such as one or more dispersants in the form of surfactants, in relatively small but well-balanced amounts. One such binder is sold under the name Synthomer 47B40 by Synthomer Ltd, England.

To form the liquid component, this binder can be mixed with a filler, such as magnesium and / or calcium carbonate, talc, chalk or dolomite, and optionally certain additional substances and agents are added to achieve the desired properties with respect to e.g. a. viscosity, freezing point, color etc.

However, the main constituents of the liquid component are binders and fillers, the binder e.g. may constitute 46.8% and the filler 45.5% of the total weight. If desired to further increase the strength, a smaller amount, e.g. 0.05-0.2% by weight, short glass fibers are added. The fibers may have a length of the order of 2-4 mm, preferably about 3 mm. Otherwise, small amounts of defoamers, antifreeze, pigments and viscosity-affecting substances can be added up to 100% by weight. The choice of such additives can be made by the person skilled in the art depending on the desired effect.

The second, dry component containing cement and quartz sand, when mixed with the liquid component, has the function of hardener and causes the binder to first coagulate and then harden the mixed mass into load-resistant layers. The sand is suitably composed of dried quartz sand with a particle size of the order of 0.1-0.3 mm and standard cement is suitably used as cement. However, the particle size of the sand can be selected depending on the requirements of the finished surface.

Experiments have shown that if you mix equal parts of the liquid component with a composition as above and a dry, hardening component containing 8 parts of standard cement and 92 parts of quartz sand, you get a mixture with a suitable consistency, which allows a working time before curing of 5 -10 minutes. By reducing the cement mixture to 6 parts and adding 94 parts of quartz sand, the possible working time is increased to 20-30 minutes. Other proportions give other working hours oo us; on oo oloo 0 o c o I o oao too ola: n 0 o o oo lo o o 10 15 20 528 216 ll and the person skilled in the art can easily adapt these depending on current conditions. The resulting primer layer can be covered with a putty layer after about 60 minutes and becomes fully load-resistant after about 24 hours at room temperature.

The invention has been described above in connection with some embodiments. However, as will be appreciated by those skilled in the art, these can be varied in several respects within the scope of the claims.

Thus, other types of copolymeric latex binders can be used, which can be made to coagulate and harden with the help of cement. The proportions between fillers in the wet and dry component can also be varied depending on what is considered to be most practical from a handling and processing point of view.

It will be appreciated, however, that the choice of constituents and their proportions must be made with a view to achieving the desired incompatible property of the latex relative to the cement component of the final product.

A primer according to the invention can also find a number of other uses than those stated above due to its very good adhesion, e.g. against different types of plastic material with a hydrophobic surface, and its high strength and toughness even when applied in very thin layers.

Claims (14)

10 15 20 onto 0 0 I 0 oo coon -0 IO Q. a 0 I o 0 con ou: II: "'° un. coat-kn) II 00 co I 0 o u: ao I cool * nya 528 216 12 u ä-ï 2 å * ~ van nu Krav Primer (4) intended to be applied to a hydrophobic surface (1), such as a surface of HDPE, to improve the adhesion of a later applied putty product (5) to the surface, characterized in that it comprises two components intended for mixing with each other, that one of these is a dry hardener comprising cement and sand, that the other component is liquid and comprises a styrene-butadiene latex which is incompatible with the cement contained in the hardener, so that at least a part of the styrene-butadiene latex coagulates when mixing the two components . The primer of claim 1, wherein the liquid component comprises a dispersant in the form of a surfactant. A primer according to claim 1 or 2, wherein the styrene butadiene latex is carboxylated. The primer of any one of claims 1-3, wherein the styrene butadiene latex comprises about 37% butadiene, 13% styrene and 50% water. A primer according to any one of claims 1-4, wherein said binder-serving styrene butadiene latex in the liquid component is mixed with substantially the same amount of filler. A primer according to claim 5, wherein said filler comprises one or more of the substances magnesium g or calcium carbonate, dolomite, talc or chalk. A primer according to any one of claims 1 to 6, wherein the liquid component comprises short reinforcing fibers in an amount corresponding to 0.05-0.2% by weight. 10 15 20 oo Iooo oo lo o I o o o o o o nu; un: Ioo tool o o o 0 oo ooo 09% oo U1 528 216 non-oo c u n n oo nu 13 Primer according to claim 7, in which the fibers consist of glass fibers with an average length of the order of 2-4 mm, preferably about 3 mm. A primer according to any one of claims 1-8, wherein the hardener component contains 90-95% by weight of dried quartz sand and 10-5% by weight of standard cement, preferably 94% by weight of dried quartz sand and 6% by weight of standard cement. Primer according to claim 9, in which the particle size of the sand is of the order of 0.1-0.3 m. Use of a primer according to any one of claims 1-10, wherein the primer is applied to a hydrophobic surface and is allowed to solidify, after which a putty or another layer of a primer according to any one of claims 1-10 is applied to the solidified primer. Use according to claim 11, wherein the primer is applied to an air gap-forming sheet or carpet of HDPE. 13. A method of preparing a primer for floors and walls, especially for application to a hydrophobic surface, such as a surface of HDPE, to improve the adhesion of a later applied putty product to the surface, characterized by mixing a hardening component with a binder-containing component, that a dry hardener comprising cement and sand is used as a hardener in the first-mentioned component, that a liquid styrene-butadiene latex which is incompatible with the elements contained in the hardener is used as binder in the second component, and that the two components are mixed in such proportions so that at least a portion of the styrene-butadiene latex coagulates upon mixing of the two components. 528 216 14 The method of claim 13, wherein the two components are mixed with each other in substantially equal proportions.