SI9010954A - Foamed gypsum material having a porous structure, process of its preparation and its use - Google Patents

Abstract

The proposed invention refers to a foamed gypsum material having a porous structure and containing a polycarbamide which is characterized by having a specific weight within the range of 0,1 up to 0,4 g/cm3, an open cell structure and as a polycarbamide contains a product of condensation of diphenylmethane-4,4'-diisocianate and water, as well as to the process of its preparation. The proposed invention refers to the use of the foamed gypsum material as a sound and/or thermal insulating material as well.

Description

FRAUNHOFER-Gesellschaft zur Forderung der angewandten Forschung e. V.

Foamed gypsum material with porous structure, process for its preparation and use

The field of technology

The present invention is in the field of inorganic chemistry. It refers to a foamy gypsum material with a porous structure, a process for its preparation and its use.

A technical problem

It is an object of the present invention to provide materials for sound and thermal insulation and a process for their preparation.

These materials must be prepared without high energy consumption and without elevated temperatures. They should not have short fibers that can cause unpleasant reactions such as itching or difficulty breathing. The materials must be inexpensive and hygienically sound. In addition, these materials must be lightweight.

Sound and thermal insulation materials play an important role in the construction industry.

Thermal insulation materials reduce energy consumption for building heating and thus contribute to the protection of the human environment by reducing smoke emissions. Sound insulation materials are used for noise protection in building acoustics and room acoustics.

The state of the art

The materials used for thermal insulation are mats, sheets or profiles made of porous or non-porous materials. low-thermal conductivity fibrous organic and inorganic materials such as coconut, wood, glass and mineral fibers or cork, gaseous concrete, foamed plastic materials.

Sound absorbing building materials are predominantly mineral fiber absorbers or other open-pore gaseous materials which, for design reasons, may have a sound-permeable coating and are secured to the substrates between structural members or supporting structures as non-self-supporting structural elements. .

In order for such material to function in such a way that the damping sound (absorbing sound) must have a porous structure. This is the case for fibrous (eg glass or mineral wool) or foamed materials with open pores so that air can flow. Due to the porous structure, sound absorption is possible in the absorbent material, and due to local losses due to friction on the fibers or edges of the cells, the energy is converted into thermal energy.

Mineral fibers require considerable energy consumption when melting glass or basalt starting material. The drawn fibers are glued to the required densities and thicknesses, with the adhesive extending into the surrounding area for a longer time. The starting materials are available in sufficient quantities and at a good price. In the treatment of mats made of fibrous materials, short cuts of fibers are formed by cutting or grinding, which are introduced into the garment and cause itching. Respiratory disorders in humans also occur.

Even artificial foam materials are not ecologically perfect because many of them can be made only by treating foam with hydrofluorocarbons (FKOV), and these FKOVs significantly affect the degradation of the ozone layer.

Plaster is a well-known and widely used building material for interior construction, which is found on the one hand in nature and on the other hand is obtained in factories in flue gas (NOD) plants in such large quantities that only NOD is used - gypsum can cover the yearly need for gypsum in the Federal Republic of Germany. Continued efforts to maintain the cleanliness of the air increase the amount of NOD - gypsum, which will lead to serious problems with its removal. For this reason, there is a great need, in addition to the well-known uses of gypsum, such as the treatment of gypsum walls, the use of gypsum floor, wall and ceiling panels to market new multi-properties gypsum products; these include gypsum foam.

So far, ordinary market plasters with various additives have been used for the preparation of porous gypsum building elements, for example. with aluminum powder, magnesium powder, obtained by heating the mass to 300 to 800 ° C. This produces gypsum foams with closed pores, which are offered as thermal insulation material. These gypsum foams have the disadvantage that their preparation is expensive and they also contain physiologically hazardous materials and require a lot of extra energy to prepare them.

US-PS 4 330 589 describes a foamed gypsum product having many isolated cells, with cell walls having fine channels connecting the cells. This foamy gypsum object is obtained by foaming a mixture of gypsum containing carbon peroxide and a cobalt compound. The cobalt compound used is physiologically dangerous. Preparation requires an additional drying process at 45 ° C for more than 6 hours.

EP 0 263 975 describes an open-pore foam plaster containing hydrocarbon material and absorbing liquid materials. This material is intended to be a filter material but is not intended to be used for acoustic and thermal engineering applications.

DE 38 04 884 describes an artificial stone containing, inter alia, foam plaster. This stone is suitable as a thermal insulator. Among other things, it has the disadvantage that it requires cooking in an oven at elevated temperature.

DE 25 46 181 describes a process for preparing foam plaster and foam plaster elements. The resulting materials have a porous structure and, in contrast to normal, non-foamed gypsum products, improved thermal insulation. Their density ranges from 0.45 to 0.8 g / cm ³ . They have to use a variety of additional materials in this known process. The addition of plaster remover is detrimental. They use melamine resin, a modified sulfonic acid, which is relatively expensive, as a plaster remover. In the known methods, the mixture of gypsum and water used has a relatively low viscosity and is fluid. It has the disadvantage of flowing out of molds in cracks and openings.

Further, the mixture has an initial cure time of only 5 minutes. This time is relatively short in manual mode and is not sufficient for practical applications.

DE 29 40 785 describes a foam plaster prepared as the one in DE 25 46 181 which additionally contains polyvinyl alcohol and boric acid. This known gypsum has the disadvantage of containing boric acid, which is physiologically dangerous, and in its preparation produces the same defects as those described in DE 25 46 181.

DE-OS 22 50 611 relates to a process for the preparation of lightweight reinforced structural material with favorable pressure resistance, tensile strength and tensile strength for the construction of building boards. These materials must also have good sound absorption and thermal conductivity properties.

In Example 3, the stated K-factor cannot be attributed to the known thermal conductivities because the physical units are missing. In example 4, the size specified is unknown. Cannot compare. When the building boards are placed among the reinforced paper cover sheets, this has a significant adverse effect on the sound absorption properties.

DE 27 16 918 describes gypsum masses containing gypsum and hard foam powder. From these gypsum masses, a gypsum is prepared for application to the wall, gypsum plasterboards, seals, modeling masses and fill masses. The use of this material for acoustic and thermal engineering purposes is not intended.

The utility model application G 83 13 354.2 describes mining crack sealing bodies containing foamed gypsum anhydride with a porous cellular structure. These products are not suitable as materials for thermal insulation and sound absorption.

Description of the solution

It is an object of the present invention to provide sound insulation materials and thermal insulation materials that have good thermal insulation and sound absorption. In addition, we must provide a process for the preparation of insulating materials. They do not require elevated temperatures. They need to be prepared without much energy consumption. These insulating materials must be free of short fibers that can cause an unpleasant reaction, such as itching or respiratory distress. The material must be inexpensive and hygienically sound.

According to the invention, it is necessary to provide a process for the use of gypsum, in particular

NOD gypsum in which it is used as a raw material.

The object of the invention is a foamy gypsum material with a porous structure containing polycarbamide, characterized in that it has a specific mass of 0.1 to 0.4 g / cm ³ , to have open cells and as a polycarbamide contains the condensation product diphenylmethane-4,4 'diisocyanate of prepolymer and water.

The subject of the invention is also a process for the preparation of foamed gypsum material, characterized in that the plaster is moistened with water and diphenylmethane4,4′-diisocyanate prepolymer and crosslinker are added to the resulting slurry, the mixture is well mixed, placed in the desired mold and cured.

The present invention further relates to the use of foam plaster material as a material for sound and / or thermal insulation.

In the present invention, all the neutral and poorly acidic hydraulically binding calcium sulfate modifications in powder form with a conventional particle size can be used as a plaster.

Preferably, conventional grade-quality gypsum with a water-gypsum factor of 0.3 is used. It is particularly convenient to use an α-plaster or NOD plaster. The NOD plaster originates from a flue gas removal device. NODs are wet dihydrates, which, depending on the quantity, can also be delivered in the form of semihydrates.

According to the invention, the gypsum is mixed with diphenylmethane-4,4'-diisocyanate prepolymers. The diphenylmethane-4,4′-diisocyanate prepolymer has the particular advantage of being solvent-free, of having a NCO content that remains constant and of having a monomer content of less than 0.5%. It is advantageous to use a product having an NCO content in the range of from 12 to 20% by weight, preferably from 14 to 18% by weight, particularly preferably 16% by weight. Such products are commercially available. The products have a viscosity of 10,000 mPa / s ± 2,000 at 20 ° C.

The diisocyanate prepolymer reacts with the water required to make the plaster and the crystalline water of the plaster, in a known manner, to form a carbamide acid derivative which, upon cleavage of carbon dioxide, is converted into an amine. The primary amine reacts with isocyanate to give the carbamide deriv. ureid, which can react further if necessary. In this application, the term polycarbamide comprises the condensation products formed from diphenylmethane-4,4'6 diisocyanate prepolymer and water. The foam plaster material of the invention has a specific mass in the range from 0.1 to 0.4 g / cm ³ , preferably from 0.15 to 0.35 g / cm ³ , particularly preferably from 0.2 to 0.3 g / cm ³ . cm ³ . It has open cells and contains at least 80% of cells with a size of 0.3 to 2 mm. Advantageously, there are as many cells as possible in the foam gypsum material of the invention, with a maximum size of 0.8 to 1.2 mm. The specific mass is adjusted by the amount of diphenylmethane-4,4'-diisocyanate prepolymers used. The greater this amount, the smaller the specific mass, and the expert can determine, on the basis of simple preliminary experiments, what amount of diisocyanate prepolymer is required to prepare foam gypsum material with a specific mass.

The foam gypsum material of the invention comprises 55 to 90% by weight of gypsum and 45 to 10% by weight of polycarbamide and 0.1 to 2.0% by weight of crosslinker. The foamed gypsum material of the invention is not required to contain other additives, although it may optionally contain conventional additives in an amount of 0.1 to 2% by weight based on the weight of the dry gypsum, polycarbamide and the crosslinker. For the preparation of the foamed gypsum material of the invention, the gypsum, preferably the a-gypsum, is moistened with water, diphenylmethane-4,4′-diisocyanate prepolymer and crosslinker are added to the resulting slurry. Mix the mixture well. The mixture has an initial cure time of 10 to 15 minutes. Then, after mixing, place it in the desired mold and allow it to solidify. The solidification takes place at room temperature for 30 minutes to 2 hours. After curing, the material can be taken from the mold. Subsequent curing, which may take place inside or outside the mold, is generally completed within 8 to 12 hours.

According to the invention, 50 to 70% by weight, preferably 55 to 56% by weight of gypsum, 10 to 25% by weight, preferably 15 to 25% by weight of water and 10 to 30% by weight, preferably 15 to 25% by weight, are mixed diphenylmethane-4,4'-diisocyanate prepolymer and 0.1 to 2.0% by weight, preferably 0.1 to 1% by weight of the crosslinker. As the cross-linking agents of the invention, known cross-linking agents can be used, ie marketable products such as fatty alcohol sulfonates, quaternary ammonium compounds and other cationic, non-ionic and anionic agents. Specific examples of cross-linking agents are ethylene oxide / propylene oxide / polyglycol, beta-siloxane surfactant, low molecular weight acrylic copolymer and alkylphenoloxetilate. It is preferred. Crosslinking agents have the effect of completely solidifying and elastifying. They are used in amounts of 0.1 to 2.0% by weight, preferably in amounts of 0.5 to 1.0% by weight, especially preferably in amounts of 0.5% by weight. They are added to regulate the pore size. The greater the proportion of cross-linking agent, the smaller the pores. The foam gypsum material of the invention is used as sound insulation material and / or as thermal insulation material. In a preferred embodiment of the invention, the gypsum slurry is filled into special molds and foaming is carried out to obtain specially shaped building elements. It is particularly advantageous for the foam gypsum material of the invention to be used in the form of pre-fabricated systems for partitioning rooms or as acoustic ceilings or acoustic building elements (including under masking partition walls or wall coverings). We can also produce panels, tubes and elements of various geometric shapes. The foam plaster material can be inserted inserts, nails nailed and can be glued. Machining by cutting, sawing and milling and brushing is possible.

This is especially necessary when treating gypsum foam material as sound insulation material. Since the plaster foam has a closed crust after the foaming process, the surface needs to be peeled off to open the pores. This can be done with the above processing methods. Several of these post-machining processes can also be performed on one object. E.g. for panels we can make the surface rough with brushes and cut the sides.

Material that is lost in subsequent machining can be reused. When it falls into pieces, it can be crushed and then ground. The powdered material is then mixed with a starting mixture of diphenylmethane-4,4′-diisocyanate-prepolymer, gypsum, water and crosslinker. 5 to 15% by weight, preferably 8 to 12% by weight, particularly preferably 10% by weight of the waste powder relative to the mixture can be added to the starting mixture.

The material can also be used lined with foil or covered with foil. In this way we increase the mechanical loading capacity and can regulate the resistance to diffusion of water vapor (vapor barrier). Acoustic properties are not affected by the proper choice of film thickness; it can also be used in the form of sandwich plates. The process of the invention may be carried out discontinuously or continuously. In the discontinuous mode, pour the gypsum paste into molds, e.g. casting forms. To prepare sandwich panels, floor or cover panels can be placed in casting molds. In a continuous process, e.g. a plaster porridge is continuously added to the mold-shaped strip and the tape is then fitted with a cover plate. In this way, we get endless plates that can be cut or cut to the desired shapes and dimensions.

According to the invention, the prepared plaster has the following advantages:

(a) Foam plaster material of the invention has a very good sound absorption.

Sound absorption rate for orthogonal sound (measurement according to DIN 52

215) for a standard with a thickness of 38 mm is shown in Table 1 for different frequencies.

For the sake of comparison, the values for the standard of glass wool are of equal thickness.

TABLE 1

Sound absorption rate a

frequency gypsum foam glass wool 100 Hz 0.18 0.14 200 Hz 0.20 0.21 400 Hz 0.49 0.46 800 Hz 0.77 0.76 1600 Hz 0.57 0.91 3200 Hz 0.65 0.89

(b) It has excellent thermal insulation. Value Where 0.045 W / mK. Polystyrene foams and mineral wools have a thermal conductivity of λ = 0.035 W / mK to 0.05 W / mK. The material of the invention has extremely good values.

(c) In contrast to known building materials, it has a significantly lower specific mass. The known foam plaster has a specific mass of 0.6 to 0.7 g / cm ³ . The foamed gypsum material of the invention is easier to handle, especially easier to process and transport, which is very important for its practical use.

(d) Inserts and nails may be inserted into the foamed gypsum material of the invention or glued, and further machining is possible by cutting, sawing, milling and brushing.

The process of the invention has the following advantages:

(a) It is not necessary to use other additives in addition to gypsum, isocyanate and crosslinker; no metals are particularly required. This does not result in environmental pollution.

(b) In the process according to the invention, it is not necessary to add plaster dissolving agents. In this way, the higher viscosities of the gypsum-water slurry can be employed in the process of the invention, thereby avoiding leakage from cracks and molds.

(c) The initial setting time of the process of the invention is at least 10 minutes, mostly 15 minutes. This allows the processor to perform thorough mixing and to fill the mold into the mold without the risk of premature hardening.

(d) It is not necessary to use foaming accelerators. Foaming agents are known to be metal compounds which are physiologically hazardous, as explained above, in known methods.

(e) Contrary to known procedures, it is not necessary to preheat the plaster mix water. This means that even smaller companies and plants can work easily according to the process of the invention, without having to have complex devices in their systems.

(f) In the process of the invention, it is not necessary, as in the known process of DE 25 46 181, to use other foaming agents, such as e.g. hydrofluorocarbons. The use of hydrofluorocarbons is detrimental to the environment.

(g) Through the process of the invention, it is possible to make reasonable use of the excess NOD gypsum and use it to prepare useful building materials.

(h) The process of the invention is cost-effective, since expensive devices, not much energy or much labor are required.

The following examples illustrate the present invention.

EXAMPLE 1

66,5 wt. parts of plaster are moistened with 16.5 parts by weight of water. To the gypsum slurry was added 16.5 parts by weight of diphenylmethane-4,4'-diisocyanate-prepolymer, solvent-free, with a NCO content of 16% by weight and 0.5% by weight of nonionic alkylphenoloxetilate as a cross-linking agent.

The whole mixture is thoroughly mixed and put into the desired mold.

The reaction begins after approx. 10 to 12 minutes and is completed in approx. 1 hour. The resulting product is a board with good surface hardness.

EXAMPLE 2 parts by weight of α-gypsum were mixed with 21.5 parts by weight of water and 0.4 parts by weight of the cross-linking agent of commercial alkylphenol oxetilate and 13.1 parts by weight of diphenylmethane-4,4'-diisocyanate prepolymer, without solvent, with a NCO content of 16% by weight.

The whole mixture is thoroughly mixed and put into the desired mold.

The reaction begins after 10 to 12 minutes and is completed in approx. 1 hour. The resulting product is a board with good surface hardness.

EXAMPLE 3

We do as described in Example 1 and use the following components:

59.4% by weight of a-gypsum

15.0% by weight of water

16.0% by weight diphenylmethane-4,4′-diisocyanate prepolymer with NCO content 16% by weight 0.4% by weight of the cationically active amine salt of fatty acid as a cross-linking agent

9.0% by weight of unreacted residual gypsum.

After mixing, the whole mixture is put into molds. The reaction begins after approx. 10 minutes and completed in approx. 1 hour.

EXAMPLE 4 parts by weight of α-gypsum were mixed with 20 parts by weight. parts of water and with 0,5 wt. of a cross-linking agent of commercial alkylphenol oxetilate, containing by weight 16% diphenylmethane4,4′-diisocyanate prepolymer with a NCO content of 16% by weight and 4% by weight parts of unreacted foam gypsum material prepared according to Example 3 in powder form.

After mixing, the whole mixture is put into molds. The reaction begins after approx. 10 minutes and completed in 1 hour.

The panels prepared according to Examples 1, 2, 3 and 4 can be machined by cutting and sawing. Scratches formed on the surface during preparation can be removed by milling (grinding), thereby affecting the sound insulation property. Covers with different material qualities provide a special influence on the frequency-dependent absorption properties. Inserts can be inserted into the panels and nails inserted.

Claims (13)

PATENT APPLICATIONS A foamy gypsum material with a porous structure containing polycarbamide, characterized in that it has a specific mass in the range of 0.1 to 0.4 g / cm ³ , that it has open cells and that, as a polycarbamide, it contains the condensation product of diphenylmethane, 4,4'diisocyanate-prepolymer and water. Foamy gypsum material according to claim 1, characterized in that at least 80% of the cells have a size of 0.3 to 2 mm. Foamy gypsum material according to claim 1 or 2, characterized in that it contains 55 to 90 wt. % gypsum 45 to 10% by weight of polycarbamide, 0.1 to 2.0% by weight of the cross-linking agent, and optionally 0.1 to 2.0% by weight of other conventional additives relative to the dry weight of the plaster, polycarbamide and cross-linking agent. Process for the preparation of foamed gypsum material according to one of claims 1 to 3, characterized in that the plaster is moistened with water, diphenylmethane-4,4'-diisocyanate-prepolymer and crosslinker are added to the resulting slurry, the mixture is then thoroughly mixed, into the desired shape and harden. Method according to claim 4, characterized in that the surface of the resulting pore-opening product is exposed to, or is subjected to, several machining operations by cutting, sawing, milling or brushing. A process according to claim 4 or 5, characterized in that 50 to 70% by weight of plaster, 10 to 25% by weight of water, 10 to 30% by weight of diphenylmethane-4,4'-diisocyanate prepolymer and 0 are mixed. 1 to 2% by weight of the crosslinking agent, wherein the% by weight refers to the total mixture. Method according to at least one of Claims 4 to 6, characterized in that the cut, burned, cut or brushed material is optionally mixed with gypsum, water, diphenylmethane-4,4'-diisocyanate prepolymer after crushing and / or milling. crosslinking agents in an amount of from 5 to 15% by weight based on the weight of the mixture. Process according to at least one of claims 4 to 7, characterized in that diphenylmethane-4,4'-diisocyanate prepolymer with an NCO content in the range of 12 to 20% by weight is used. Method according to at least one of claims 4 to 8, characterized in that a-gypsum is used as plaster. A method according to at least one of claims 4 to 9, characterized in that the mixing is carried out at room temperature and at normal pressure. A process according to at least one of claims 4 to 10, characterized in that commercially available alkylphenoloxylate is used as the cross-linking agent. Use of foam plaster material according to at least one of claims 1 to 3 as sound insulation material and / or thermal insulation material. Use according to claim 12 in previously prepared room separation systems and in acoustic insulation ceilings.