FI121190B - Method for producing a coating product for a structural plate and a coating product - Google Patents

Description

Method for producing a coating product for a structural plate and a coating product

The invention relates to a method for treating sheet-like basic natural or synthetic fiber basic material and to sheet-like basic material to be used e.g. as a coating for building boards, in particular gypsum boards.

In this application, sheet-like basic material refers to a material that is planar, i.e., has a very small thickness compared to its width and length. Cardboard is an example of sheet-like basic material. The sheet-like basic material may be in sheet form or in web form during manufacture.

Structural panels often use a coating that can serve many separate or 15 simultaneous purposes. For the purposes of this invention, a structural panel refers to a gypsum, wood fiber, concrete or cement board or similar board which, due to some of its properties or method of manufacture, is desirable to be coated. Generally, the coating is paper-based or made of other fibers, according to the invention, the coating is intended for both indoor and outdoor use.

20

US 6,638,356 relates to a gypsum board which is protected against the development of hydrogen sulfide in the presence of sulfate reducing bacteria. The solution uses anthraquinone or its derivatives at about 100 ppm by weight of gypsum. US 6,680,127 (Temple - Inland Forest Products), in turn, discloses gypsum boards for protection against mold fungi with cetylpyridine chloride. Said substance may be free or encapsulated to release its chemical action over a longer period. Anthraquinone is a typical known oxidation-reduction catalyst.

Further, US 6,773,822 (Temple-Inland Forest Products) mentions how a mold release agent is a controlled release agent and is mainly encapsulated in gypsum itself. Approximately 200 compounds have been mentioned as flame retardants, including substances harmful to living beings. U.S. Patent No. 6,770,354 to G-P Gypsum Corporation discloses the preparation of a moisture resistant 35 gypsum panel or board. Here, the panel is coated with a glass fiber containing coating containing pigments and a mineral binder and a polymer latex binder. Further, the publication states that the coating must allow water to evaporate from the gypsum during drying. This is accomplished by bonding the coating and its fibers with a binder that apparently has sufficient inorganic binder, such as cement, and little polymeric binder, and that binder binds the fibers of the coating so that substantially all the fibers are covered.

US 6,833,137 relates to the treatment of gypsum board coating board with Cl-F-aminosulfinylpyrazoles against termites and other insects. Substances of this kind are harmful to humans.

10

US 6,800,361, in turn, deals with gypsum board coated with nonwoven fabrics of a certain strength. The idea is that nonwovens are polymeric and cannot serve as a nutrient medium for molds like paper fibers.

15

US 6,893,752 discloses a mold growth inhibiting solution using pyrithine as a treatment agent, which is mixed with gypsum mass and forms calcium salts therein at a concentration of at least 100 ppm.

The same problem, that is, mold inhibition, is dealt with in Publication 6,767,647, in which gypsum board is coated with a nonwoven and at least two different treatment agents have been added to the gypsum. These substances are, for example, propiconazole and sodium pyrithine, used in coating at 50-1200 ppm or in the gypsum core at 80-1200 ppm.

25

From the above it can be seen that e.g. mold control is perceived to be important in gypsum board products.

In the past, routinely e.g. gypsum boards covered with cardboard with a basis weight of 180 to 210 g / m2. In this solution of cardboard alone, the porosity has been so high that during drying, water vapor is removed from the gypsum without any problem. As previously stated in U.S. Patent No. 6,770,354, it is stated that '' said coating is so porous that it allows water vapor to evaporate from the panel during drying, 'but without substantiation. Thus, the problem with these 35 products, as we see in the peer-reviewed publications, is at least mold protection and sufficient porosity of the coating.

3

Of course, there are other ways to prevent mold than substances that are harmful to humans, and these other means are discussed in this invention. One of the important points is the water repellency of the sheet coating. At the same time, however, the sheet should be breathable, not only during the manufacturing stage, but preferably at other times as well. The board and / or its coating must be anti-mold but not hazardous to humans.

It is our understanding that buildings should not contain any volatile hazardous substances emitted from structures, as this can always be carried in contact with humans.

The solution according to the invention is such that no changes are needed to the normal gypsum board line, but still a water-repellent, breathable and long-lasting mold protected coating is achieved.

15 The coating gives the boards, among other things. protects, increases their bending resistance, prevents dusting, acts as a painting substrate or printing substrate, and protects sheet material from bumps. Of particular importance is such a coating for gypsum boards. Suitable surface friction properties are also required when the boards are stacked in the factory, transported and transported to the installation site. Further, the boards must be at least surface mold protected and preferably the coating must in many cases be permeable to water vapor so that excess water can be evaporated from the material behind the coating, as is the case with gypsum boards and cement boards. In gypsum boards, the hydration heat already increases the temperature of the board to at least + 66 ° C and during drying the temperature still rises above 100 ° C, so that, for example, home contamination always comes from outside.

Further, it is advantageous for the product to have a suitable coefficient of friction between the surfaces of the plates and to allow air to escape from the plates 30 in the plate-to-plate contact such that different slip damage is avoided. The friction must be suitable for holding the plate stack in transit and, on the other hand, so low that it is easy to move the plates out of the stack at the installation site. Preventing water infiltration reduces mold damage and prevents leachate from leaching out of the plate, even if the antifungal agent is not encapsulated in the product.

4

Our invention, which mainly applies to gypsum boards and cement boards, but can apply to any board made by casting, which is cast on top of the coating and needs to be drained of excess water, has solved e.g. these puzzles in an inexpensive and non-human manner. Further, the coating according to the invention can be used as a coating for various fiber boards. The sheet coating of the invention also allows the application of various moisture barrier layers on the surface of the coating, especially those which are aqueous emulsions of the polymeric binder. These are used in wet rooms under tiling.

10

According to the invention, a typical base material made from wood or cellulosic fibers or mixtures thereof having a thickness of 250-350 μητη, preferably about 300 μητη, is treated with a microorganism growth inhibitor, for example sodium benzoate, a sodium salt of benzoic acid. Em. In addition to wood or cellulose fibers, the base material may also contain synthetic fibers, such as viscose.

Benzoic acid, as is generally known, is e.g. a natural preservative in lingonberries and cranberries that prevents mold growth. Benzoic acid (E210) and its salts (E211, E213) are widely used in food as preservatives. Na-benzoate in the pulp or wood fiber structure causes more rapid water absorption and swelling of the fibers than water alone. According to the invention, a growth inhibitor of microorganisms such as benzoate is added with a binder, for example an acrylic polymer emulsion binder, and is typically used at 2-4 g / m 2. In the antifouling experiments 25, it was found that the salts of benzoic acid act best as an antifouling agent when the pH of the surface layer of the paper is first dropped to 3 to 6.5, for example, with sulfuric, boric, alum, most preferably with dilute sulfuric acid at a concentration of <1% by weight, with an aqueous solution of alu-30 nanoparticles or 1-3% by weight of boric acid. More preferably, the acidification treatment is performed prior to treatment with the growth inhibitory agent of the microorganisms and the binder. It is also possible that the acidification treatment is not carried out at all since the product is also found to be functional without acidification treatment.

It will be appreciated that the polymeric binder may be any other water-emulsifiable binder such as polyvinyl acetate. The polymeric binder may be mixed with a dye and antifungal agent (s). For them to function as desired, their HLB (Hydrophilic-Lipophilic Balance) must be within certain limits. Depending on the manufacturer, the polymer binder may have different HLB values generally in the range of 8-12, in a number range of 1-20, derived from the percentage of polyethylene oxide required for emulsification or dissolution. According to the invention, the HLB of the polymer binder and the dye mixture is at best 8 to 11 (equivalent to 28 to 32 g / m 2, preferably about 30 g / m 2 obtained by the Cobb 60 method. In this case the dye is insoluble in water and another water can be applied. repellent layer.

10

After the previous operation, a new layer is applied to the surface, typically 1/3 to 1 / 5th of a so-called. microcrystalline wax. Microcrystalline wax is a predominantly branched hydrocarbon wax with molecular structure. The microcrystalline wax typically has a melting point of 60-100 ° C. In addition to the microcrystalline wax, the layer-15 may contain linear wax and / or a mixture of these and typical polymeric binders. This is hereinafter referred to as the wax layer. The linear wax may be, for example, paraffin wax.

The purpose of the wax layer is to provide UV-light and ozone-resistant nozzles on the surface as well as suitable water repellency. After finishing, immediately scrape off any excess material of the wax layer with a sharp scraper and re-impregnate the wax layer using the same method as the previous acrylate + benzoate + paint layer, preferably with a drying cylinder surface temperature of 125-130 ° C. The above definition of "" suitable water repellency "means that it is not so repellent that it cannot be brushed or rolled with the moisture barrier layer of an aqueous emulsion required in wet rooms under tiling.

The wax layer penetrates to a depth of 90-150pm and is applied or tapped at about 12 g / m 2. The wax-containing layer is typically formulated at 125-130 ° C. A new layer is still formed which is well permeable to air and water vapor. After scraping, the free '' wax '' is not a uniform layer on the surface. According to the invention, the HLB value of the wax layer is correct if it is between 10 and 12. (see Figure 1 for loose fibers). The infiltration of the Va-35 chip to one side can be stopped by cooling the web so that its temperature preferably drops below 30 ° C. Cooling can be accomplished by using at least one cooling cylinder.

6

The water vapor permeability of the finished product was almost the same as that of the original cardboard, i.e., ~ 300 g / m2, 23 C, RH 50% = sd <0.1 m (ISO 2428: 1995). Surface strength (Dennison / KCL 129: 65) is improved by about 15%.

5

When the typical paper product from which the product according to the invention is made has a water properties of 20-25 g / m 2 according to the Cobb 60 method (ISO 535: 1991), it typically rises to 50-60 in acrylate + benzoate treatment and approximately 12-14 ' after.

10

The paper or paperboard air permeability of the Guerley apparatus (ISO 5636-5: 1986) is about 60-70 µ / s for base paper and about 200 µ / Pa after benzoate acrylic treatment. The benzoate attaches to the acrylic polymer in said treatment. Na-benzoate penetrates 50-60 µm into the fiber product under typical 15 conditions. Said typical conditions of the invention are created after the acrylic + benzoate surfactant is immediately dried by direct contact of the fiber product with the surface of the drying cylinder so that the coated surface is against the hot surface of the drying cylinder. In this case, the rapid vapor formation (30% acrylate and benzoate + ~ 70% water) renders the surface porous.

20

Preferred conditions are formed, for example, from 2 to 4 g / m 2, preferably 3 g / m 2 of Na-benzoate and from 7 to 9% of the weight of the surface layer in the surface layer. A completely surprising finding in itself has been that an identical identical and manufactured and coated sheet without Na-benzoate gave a significantly lower friction coefficient so that the products remained poorly stacked and difficult to transport. When Na benzoate was added, the friction increased to the desired value.

This is explained by the fact that the Na benzoate helped water penetrate the fibers better and the fibers swelled and the surface roughened. This can of course be accomplished by other known fiber-swelling chemicals, preferably such that it is at the same time anti-mold.

Although the paperboard was calendered, the surface kar-35 was more absorbed by the benzoate treatment than the water alone treatment. It is obvious that similar roughening can be achieved by other surface tension reducing agents only. The base board had a rest coefficient of 0.36, '' waxed '', without 7

Na-benzoate treatment 0.28, '' waxed '' and Na-benzoate treated (3 g / m 2) 0.36 (friction values measured with Instron 4665 according to the Applicant's Quality Manual).

The foregoing descriptions were good practical indicators, but one skilled in the art will appreciate that they may not be optimal and that many variations of these may be accomplished. These variations include e.g. Replacement of Na benzoate with its derivative parabens and their Na, K, Ca salts or esters of parabens known per se. Parabens are para-hydroxy-10 benzoic acids (E214-E219 in the positive list of food additives). Examples of suitable materials include ethyl p-hydroxybenzoate, Na, K, or Ca salt of ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, Na, K, or Ca salt of propyl p-hydroxybenzoate, methyl p-hydroxybenzoate; and the Na, K, or Ca salt of methyl p-hydroxybenzoate. Further suitable agents for use as growth inhibitors of microorganisms include hexamethylenetetramine, orthophenylphenol, orthophenylphenol salts such as Na, K or Ca salts, and thiabendazole. Mixtures of the above-mentioned agents may also be used as growth inhibitors of microorganisms.

20

The invention consists of many distinct elements which will be apparent from the foregoing text. However, essential elements of the invention, such as the use of benzoic acid salts or derivatives or other agents mentioned in this application as a mildew blocking agent and hot treatment of a binder such as an acrylate polymer and a wax layer such that the coated surface is directly against the hot cylinder surface.

We have talked about acrylic polymers in the text, but all water-emulsifiable polymers do essentially the same thing. These may include polyvinyl acetate and the ammonia form of polyethylene terephthalenesulfone (for example, EvCote, Asia Pacific Specialty Chemicals, USA). When many polymers can be used, additives having a favorable HLB value, hundreds of which have been listed in the literature, must be used.

35 The finished board is bonded to the gypsum board with gypsum slurry and the finished board is dried. In this process, the water vapor permeability of the paperboard is further improved and the friction is increased. Further, it has been found that the wax penetrates deeper during the drying of the gypsum boards, whereby a better water resistance is achieved for the board-gypsum boundary layer. This is a significant advantage in practice, since the wax cannot be placed on the surface where the gypsum board is to be fastened before the gypsum board is fixed, since in this case the adhesion of the gypsum board and the board would become poor.

The following are pictures showing

Figure 1 shows the surface 10 of a product manufactured by the process of the invention, and

Figure 2 shows the hydrophobicity of the product prepared by the process of the invention.

Figure 1 shows the surface of the product which is noteworthy that it has a plurality of upright fibers free. Figure 2 is a photograph of a drop of water dripping onto a plasterboard. Although there are free fibers on the surface, the contact angle of the water is> 90 °. Remarkably, these samples were about a year old in the laboratory, stored in the light. Oxidation of waxes and oils typically occurs and wetting angles rapidly decrease. In this example of the invention, this issue has been corrected by branched microwaves, which are known to be radical scavengers and protect the surface from ozone and UV light. It will be apparent to one skilled in the art that other radical scavengers, such as acrylated bis-phenols and lactones, may be used.

25

It was mentioned in the text that Na benzoate migrates to the surface layer during drying. Benzoic acid derivatives and other salts behave similarly. Based on our experiments, water is unable to rinse benzoic acid or its derivatives off the surface if the water has a temperature below ~ 60 ° C and HLB values as described above.

The mention of acidification of the paper product means that the pH is lowered to <7, but not to <3, since the fungicidal effect of the Na-benzoate and its derivatives is negligible on the acidic side. The aqueous solution of Na-benzoate is naturally slightly alkaline. At a pH below 3, the paper begins to hydrolyze too quickly into sugars and otherwise brittle. All acids that do not evaporate or decompose can be used, but 9 sulfuric acid is the cheapest and boric acid also significantly improves fire protection and serves as a particularly good antimicrobial agent. Advantageously, harmless substances such as melamine sulfate and zinc borate can also be used to improve fire protection.

5

According to the invention, making the surface water-repellent with wax means that the mold-blocking agents adhered to the polymer binder are not so easily washed away as otherwise. Further, the surface lipophilicity balance and the sub-surface layer libophilicity balance are emphasized, for example, by an acrylic binder 10, which in turn also reduces the leaching of mold inhibitors. The methods described in the art and the basis weights and penetration depths given in the examples are important parameters, because then the surface of the board, e.g., gypsum board side, remains completely in its original, gypsum binding form. In the first stage of product manufacture, where the board is, for example, slightly acidified, zinc borate or melamine sulfate may be advantageously added as flame retardants.

The coating according to the invention achieves a calorimetric calorific value of the coating of <4 MJ / m2, taking into account all additives, when the machine direction-20 nanolithic base board has a tensile strength of at least 12-13 kN / m, the board typically having a weight of 190 g / m2.

The term "" wax "is intended to mean a mixture of waxes and / or polymers having the above-mentioned HLB equilibrium and containing substances that enhance UV light and ozone resistance, i.e. radical scavengers. These may be other than e.g. the branched micro wax mentioned. Further, the common layer HLB value of the polymer layer and the dye and antifouling agent therein must be suitable, as mentioned above, so that the subsequent applied wax layer 30 penetrates, i.e. is absorbed, in the desired manner. Said polymer layer with excipients can be advantageously applied by known methods, such as raster roll coating, offset raster roll coating, rod coating, air brush coating, surface sizing press, curtain coating, or superficial blasting.

10

The production of the coating according to the invention can be carried out on the same production line as the base material. In other words, the treatment of the base material can be carried out, for example, on a paper or board machine. A liquid agent comprising a microorganism growth inhibitor and a binder may be applied to the surface of the base material, for example, by means of a surface sizing press. The wax-containing layer can be applied at elevated temperature and, after application, the excess material is removed by some molding method, for example, a blade scraper.

10 For example, logos can be printed on the finished surface using a common printing technique, as long as the ink has an HLB value of about 10.

The finished coating is fixed to the surface of the building board. In the case of gypsum board, fixing is done with gypsum board slurry. The coating is usually affixed on both sides of the building board.

Claims (18)

A method for treating a sheet-like, basic organic or synthetic fiber base material, wherein the first material having a first and a second side is treated, in a first treatment, with a first liquid treatment agent comprising a microorganism growth inhibitor and a binder, characterized in that in addition, 10 - drying the base material, - forming a wax-containing layer on the first side of the basic material after the first treatment, and - impregnating the wax-containing layer on the base material at a temperature of 100-145 ° C. 15 Process according to Claim 1, characterized in that the antimicrobial agent is a benzoic acid salt, a benzoic acid, a paraben, a parabenic salt, a parabenic ester, hexamethylenetetramine, orthophenylphenol, orthophenylphenol salt, thiabendazole, or a mixture thereof. 20 Process according to Claim 2, characterized in that the salt of benzoic acid or the salt of orthophenylphenol is a sodium, potassium or calcium salt. A process according to any one of the preceding claims, characterized in that the binder comprises an acrylic acid derivative such as acrylate, an ammoniacal form of polyethylene terephthalic sulfone, or polyvinyl acetate. Method according to one of the preceding claims, characterized in that the base material is dried so that its first surface is in contact with the surface of the drying cylinder. Method according to one of the preceding claims, characterized in that the wax-containing layer comprises linear wax and microcrystalline wax. Process according to Claim 6, characterized in that the linear wax is a paraffin wax. Process according to Claim 6, characterized in that the wax-containing layer contains at least 20% by weight of microcrystalline wax. Process according to any one of the preceding claims, characterized in that the wax-containing layer contains acrylated bis-phenols or lactones. The process according to any one of the preceding claims, characterized in that the pH of the base material is adjusted to a range of 3 to 6.5 before the first treatment. 10 Process according to Claim 10, characterized in that sulfuric acid, boric acid, alum or phosphoric acid are used to adjust the pH. Method according to Claim 10 or 11, characterized in that, when the pH is adjusted, a flame retardant is impregnated into the paperboard. Process according to Claim 12, characterized in that the flame retardant is melamine sulphate and / or zinc borate. Method according to one of the preceding claims, characterized in that the base material is cardboard. Method according to claim 14, characterized in that the cardboard has a basis weight of 180 to 210 g / m2. 25 Method according to Claim 14, characterized in that the carton is processed on the same production line as it is made. Base material treated by the method of any one of claims 1 to 16, characterized in that the base material comprises a potassium benzoate, sodium benzoate, benzoic acid, paraben, paraben Na, K, or Ca- as a microorganism growth inhibitor. salt, paraben ester, hexamethylenetetramine, orthophenylphenol, Na, K or Ca salt of orthophenylphenol, thiabendazole, or a mixture thereof. 35 Use of a base material according to claim 17 as a coating of a gypsum board.