Description

Field of the Invention

The present invention relates to an aqueous binder composition for use in the production of man-made vitreous fibres (MMVF), and a compacted body, in particular a briquette, suitable for use as a mineral charge in the production of man-made vitreous fibres (MMVF) comprising mineral wool material which comprises MMVF fibres in contact with said binder.

Background of the Invention

Man-made vitreous fibres (MMVF) such as, e.g., basalt fibres, slag fibres, glass fibres and stone fibres may be made by melting a mineral charge in a furnace and fiberizing the melt. The MMV fibres produced may form wool products such as stone wool.

In some of the furnaces used for MMVF production, there is a large pool of melt and the mineral charge is melted into this pool. Examples are tank and electric furnaces, which can be used for stone fibre production but mostly for glass fibre production. Another type of furnace which is used for forming the melt for MMVF production, especially of fibres of the types that are referred to as stone, slag and basalt fibres, is a shaft furnace or cupola furnace which contains a self-supporting column of solid coarse mineral and combustion material, and combustion gases permeate through this column so as to heat it and cause melting. The melt drains to the bottom of the column, where a pool of melt is usually formed, and the melt is removed from the base of the furnace. Since the column has to be both self- supporting and permeable it is necessary that the raw material should be relatively coarse and should have considerable strength, despite the high temperatures in the column which may exceed 1000°C.

The raw material can be formed of coarsely crushed, naturally occurring rock and slag or any other type of suitable coarse material, provided this will withstand the pressures and temperatures in the self-supporting column in the shaft furnace. When applying more fine grained raw materials it is known to convert the finer particulate materials such as sands into bonded briquettes for addition to the furnace. These should have sufficient strength and temperature resistance to withstand the conditions in the self-supporting column in the shaft furnace in order that they melt prior to collapsing.

It is necessary for the total charge in the furnace (i. e., lump mineral alone or lump mineral plus briquettes) to provide the composition which is desired for the MMV fibres which are to be made. However, in shaft furnaces the residence time of material in the small melt pool at the base of the furnace is short, and the raw materials must be incorporated sufficiently rapidly in this pool of melt if a melt is to be obtained which is suitable for provision of final product having specified properties.

In the manufacture of mineral wool products, the fibres obtained in the spinning process are blown into a collection chamber and, while airborne and while still hot, are sprayed with a binder solution and randomly deposited as a mat or web onto a travelling conveyor. The fibre web or mat is then transferred to a curing oven where heated air is blown through the mat to cure the binder. The cured mat or slab is trimmed at the sides and cut up into certain dimensions. Both during spinning and during trimming, cutting up into final dimension and subsequent final inspection and check for defects, waste products are arising which are either dumped or, preferably, recycled to the VF production process.

To that end, the waste products are broken up into smaller, fine-grained pieces by milling in a rod mill or any appropriate device/equipment and/or unravelled and then compacted to form briquettes. Briquettes from MMVF waste are normally produced by moulding a mix of the MMVF waste, optionally together with other fine-grained components in finely divided form, and an appropriate binder into the desired briquette shape and curing the binder. Preferably, a cement binder is used to produce cement briquettes.

The briquettes, possibly after interim storage, may be combined with virgin raw material and/or other lump raw material such as slag for MMVF production and returned via the melting furnace into the MMVF production process. Briquettes are particularly useful for forming part, often most of the charge in a shaft or cupola furnace. The amount of briquettes may be up to 100%, such as up to 80% or 50%, of the total charge. They may also be used as part of the charge in an electric furnace.

When using MMVF waste for briquette production, the waste products may contain cured and/or uncured mineral wool binder, depending on the point in the production line where the waste products are formed.

A group of formaldehyde-free mineral wool binders are those which contain carbohydrates, for instance, starch or sugar, as additives, extenders or as reactive components of the binder system; see, e.g. WO 2007/014236 .

Such carbohydrate-containing mineral wool binders are very advantageous both from the economical and ecological point of view, because carbohydrates are an inexpensive component and at the same time are non-toxic and renewable. Accordingly, in particular mineral wool binders which contain carbohydrates as a major component have been increasingly used in the field.

It has however been found that the presence of non-cured or partly cured carbohydrate-containing mineral wool binder in the MVF waste results in prolonged curing times of cement-containing briquettes, the reason being that carbohydrates are retarders for cement. The term carbohydrate, as used herein, refers to monosaccharides, disaccharides, polysaccharides and mixtures thereof.

Accordingly, the very advantageous properties of carbohydrate-containing mineral wool binders are somewhat impaired by the fact that they render the recycling of waste material from the mineral wool production more difficult. Consequently, there exists a need to overcome this disadvantage of carbohydrate containing mineral wool binders.

Summary of the Invention

Accordingly, it was an object of the present invention to provide an aqueous binder composition for use in the production of man-made vitreous fibres (MMVF) comprising a carbohydrate component, which aqueous binder composition has improved recycling properties. It was in particular an object of the present invention to provide the aqueous binder composition for use in the production of man-made vitreous fibres (MMVF) comprising a binder with a carbohydrate component which allows the production of a mineral wool product with improved recycling properties.

It was a further object of the present invention to provide a mineral wool material, comprising mineral fibres in contact with an uncured and/or cured binder composition comprising a carbohydrate component, and having improved recycling properties.

It was a further object of the present invention to provide a method for reducing the carbohydrate content of a mineral wool product prepared with said binder. It was a further object of the present invention to provide a product prepared by said method, and having improved recycling properties.

It was a further object of the present invention to provide a compacted body, in particular a briquette, suitable for use as a mineral charge in the production of man-made vitreous fibres (MMVF) comprising such a product, which is improved in strength.

In accordance with a first aspect of the present invention, there is provided an aqueous binder composition for use in the production of man-made vitreous fibres (MMVF) comprising a carbohydrate component and one or more microorganisms capable of metabolizing the carbohydrate component and/or an extract derived from one or more microorganisms capable of metabolizing the carbohydrate component.

In accordance with a second aspect of the present invention, there is provided a mineral wool material, comprising mineral fibres in contact with the uncured and/or cured binder composition.

In accordance with a third aspect of the present invention, there is provided a method for reducing the carbohydrate content in such a mineral wool material by subjecting the mineral wool material to a fermentation process.

In accordance with a fourth aspect of the present invention, there is provided a product, obtained by treating a mineral wool material with said process.

In accordance with a fifth aspect of the present invention, there is provided a compacted body, in particular a briquette, suitable for use as mineral charge in the production of man-made vitreous fibres (MMVF) said compacted body comprising : (i) such a product and (ii) a cement binder.

The present inventors have surprisingly found that it is possible to compensate for the disadvantages in the recyclability of mineral wool binders comprising a carbohydrate component by additionally including one or more microorganisms capable of metabolizing the carbohydrate component or an extract derived from one or more microorganisms capable of metabolizing the carbohydrate component. It is highly surprising that despite the quite extreme temperature conditions, under which the aqueous binder composition are applied to the newly airborne and still hot fibres during the manufacture of a mineral wool product, still the mineral wool product produced has improved recycling properties in that it is possible to reduce the carbohydrate content in the mineral wool product to a significant degree by a fermentation process performed on the mineral wool product which uses the microorganisms and/or extract of microorganism in order to reduce the carbohydrate content. At the same time, the present inventors have found that the cured end product produced by such a binder is as stable as a cured end product produced with a conventional carbohydrate-containing binder. Accordingly, the aqueous binder composition according to the present invention allows the production of a mineral wool material having improved recycling properties. Such mineral wool materials, in particular in form of waste materials from the production process of a mineral wool material and containing uncured and/or cured binder can be subjected to a fermentation process, which makes use of the microorganisms or extract of microorganisms in the binder, and which allows to significantly reduce the carbohydrate content in an easy and inexpensive way. No special equipment or expensive chemicals are needed for such a fermentation process. The product of such a fermentation process can be used for the production of a compacted body which is improved in strength.

Description of the preferred embodiments

The aqueous binder composition according to the present invention is an aqueous binder composition for use in the production of man-made vitreous fibres (MMVF) comprising a carbohydrate component and one or more microorganisms capable of metabolizing the carbohydrate component and/or an extract derived from one or more microorganisms capable of metabolizing the carbohydrate component.

Microorganisms or extract of microorganisms In a preferred embodiment, the microorganisms are selected from the group consisting of fungi, yeasts, and/or bacteria in particular of the genera lactobacillus, leuconostoc, pediococcus, and/or bifidobacterium. However, the method according to the present invention is not limited to those microorganisms. In principle, any microorganism which is capable of reducing the carbohydrate content in the binder can be used, be it in form of the microorganism itself or in form of an extract derived from the microorganism. In particular preferred embodiment, the one or more microorganisms is a yeast comprising saccharomyces cerevisiae.

In an especially preferred embodiment, the microorganism is in form of saccharomyces cerevisiae.

Preferably, the aqueous binder composition according to the present invention comprises one or more microorganisms capable of metabolizing the carbohydrate component in an amount of 0.1 x 10 ⁹ - 20 x 10 ⁹ microorganisms/g, preferably 1 x 10 ⁹ - 10 x 10 ⁹ microorganisms/g, based on the combined weight of the binder solids and the weight of the microorganism and/or extract of the microorganism.

In an alternative preferred embodiment, the aqueous binder composition according to the present invention comprises an extract of microorganisms. Preferably, the aqueous binder composition comprises an extract derived from a microorganism capable of metabolizing the carbohydrate component in an amount of 0.5 weight-% - 15 weight-%, preferably 2 weight-% - 12 weight-%, of dry extract, based on the combined weight of the binder solids and the weight of the microorganism and/or extract of the microorganism.

In a particular preferred embodiment, the extract of one or more microorganisms is an extract from one or more microorganisms in form of a yeast comprising- saccharomyces cerevisiae.

In an especially preferred embodiment, the extract is an extract of saccharomyces cerevisiae. These embodiments can also be combined, i.e. the aqueous binder composition according to the present invention can comprise one or more microorganisms capable of metabolizing the carbohydrate component and/or an extract of one or more microorganism capable of metabolizing.

Fermentation enhancer

The present inventors have found that the recycling properties of the aqueous binder composition according to the present invention can be further improved when the binder composition also comprises a fermentation enhancer.

Typically, this fermentation enhancer is a component that stabilizes the pH value and/or servers as a nutrient for the microorganisms, when a mineral wool product prepared by use of said binder is subjected to a fermentation process.

In a preferred embodiment the fermentation enhancer is one or more of the group of phosphoric acids and/or phosphates, acetic acid and/or any salts thereof.

In the context of the present invention, the term phosphoric acids is meant to cover all types of phosphor-containing mineral acids and the term phosphates is meant to cover the salts of all types of phosphor-containing mineral acids.

Alternatively, an extract of microorganisms can also serve as a fermentation enhancer.

While the amount of fermentation enhancer used is not generally limited, it is preferred that the binder composition comprises the fermentation enhancer in an amount of 0.5 to 15 wt.-%, preferably 2 to 10 wt.-%, based on the combined weight of the binder solids and the weight of the microorganism and/or the extract of microorganism.

Binder composition The aqueous binder composition according to the present invention can be based on any carbohydrate-containing binder composition, whereby one or more microorganisms capable of metabolizing the carbohydrate component and/or an extract derived from one or more microorganisms capable of metabolizing the carbohydrate component is added.

In a preferred embodiment, the binder according to the present invention comprises a phenol-formaldehyde-based resol and the carbohydrate component is selected from a sugar, such as dextrose.

In a further preferred embodiment, the binder according to the present invention comprises

(a) a polycarboxylic acid component or any salt thereof and/or an inorganic acid or any salt thereof

(b) a component selected from the group consisting of amine compounds, ammonia; and optionally,

(c) a reaction product of a polycarboxylic acid component or anhydride thereof and an alkanolamine component.

In a further preferred embodiment, the binder according to the present invention comprises a carbohydrate component selected from hexose, such as dextrose, fructose, pentose such as xylose and/or sucrose, glucose syrup.

Mineral wool material

The present invention is also directed to a mineral wool material comprising mineral fibres in contact with the uncured and/or cured binder composition as described above. For the purpose of the present invention, the term mineral wool material means any material where mineral wool is in contact with uncured and/or cured binder. In particular, the term mineral wool material refers to a waste material from the production process for a MMVF production.

In the following, the term "material" is used to describe the "mineral wool material".

The material can be prepared by a process that comprises the step of contacting mineral fibres with the aqueous binder composition described above. Such a material has improved recycling properties because it is possible to reduce the carbohydrate content in the material in an easy way by a fermentation process that makes use of the one or more microorganisms and/or extract of one or more microorganisms present in the material.

Method of reducing the carbohydrate content in a mineral wool material

The present invention is also directed to a method for reducing the carbohydrate content in a mineral wool material as described above by subjecting the mineral wool material to a fermentation process.

For the purpose of the present invention, the term fermentation is defined to encompass every process in which organic compounds are converted into other organic or inorganic compounds, including for example ethanol and carbon dioxide, by an enzymatic reaction, be it that the enzymes are part of a cell or of a cell extract.

Typically, such a fermentation process can easily be started by bringing the mineral wool material in contact with an appropriate amount of water so that the fermentation process can start.

For the purpose of the present invention, the term substrate means a composition comprising the mineral wool material and everything that is added to this material prior to the step of fermentation, in particular water. In a preferred embodiment, the method is carried out on a substrate which comprises water in an amount of 10-40 wt.-%, preferably 20-40 wt.-%, based on the total weight of the substrate. Preferably, the mineral wool material is comminuted, in particular by use of a rod mill, before the fermentation process is started.

In an alternative preferred embodiment, the method is carried out on a substrate which comprises water in an amount of more than 40 to 90 wt.-% (i.e. > 40 to 90 wt.-%), preferably 50 to 76 wt.-%, based on the total weight of the substrate. In this embodiment, the substrate typically is in form of a slurry.

While the fermentation process is not limited to a certain temperature range, in a preferred embodiment, the method involves the step of treating the substrate at a temperature of 10-50° C, preferably 15-45° C. This usually means that the fermentation takes place without any need of external heating or cooling and therefore without the need for any additional equipment.

While the fermentation is not restricted to any time regime, in a preferred embodiment, the method involves the step of fermenting the material over a time of three hours to thirty days, preferably one to three days.

Product obtained by the fermentation of the mineral wool material

The present invention is also directed to a product obtained by treating the mineral wool material with a fermentation method.

This product is significantly reduced in carbohydrate content when compared to the mineral wool starting product and has therefore improved recycling properties when used for the production of a compacted body, in particular a briquette.

Compacted body

The present invention is also directed to a compacted body, in particular a briquette, suitable for use as mineral charge in the production of man-made vitreous fibres (MMVF) said compacted body comprising :

(i) a product described above and

(ii) a cement binder.

In a preferred embodiment, the compacted body according to the present invention is produced from a product originating from stone wool fabrication. In particular, the compacted body according to the present invention is produced from a product obtained by fermenting a mineral wool material, in particular a waste material obtained from a stone wool production process.

The compacted body, in particular in form of a briquette, is in particular useful as a charge in a cupola oven

In view of the reduced carbohydrate component of the product obtained by fermenting a mineral wool material as described above, such compacted bodies according to the present invention have an improved strength when compared to previously known compacted bodies prepared from a mineral wool material produced by the use of a binder composition containing a carbohydrate component.

In view of the retarding effect of carbohydrates, in particular sugar, on the cement binding, the compacted bodies according to the present invention are also easier to produce, because the decreased retarding effect of the carbohydrate reduces the time necessary for producing the compacted bodies.

In a preferred embodiment, the compacted body according to the present invention comprises 1 to 30 percent by weight, preferably 5 to 15 percent by weight, of cement, based on the total weight (dry matter) of the compacted body. In a further preferred embodiment, the compacted body according to the present invention comprises 10 to 80, preferably 15 to 60, percent weight of said product, based on dry matter.

In a particular preferred embodiment, the compacted body according to the present invention is in form of a briquette.

EXAM PLES

The following examples are intended to further illustrate the invention without limiting its scope.

The following properties were determined for the binders according to the present invention and the binders according to the prior art, respectively:

Binder component solids content

The content of each of the components in a given binder solution before curing is based on the anhydrous mass of the components.

Fresh, compressed Baker's yeast, active cells of Saccharomyces cerevisiae, approx. 30% dry matter (>31% dry matter), was obtained from De Danske Gaerfabrikker. Instaferm® RED Instant Dry Baker's Yeast, Saccharomyces cerevisiae, approx. 95% dry matter (<6% moisture), approx. 20 billion live cells per gram, was obtained from Lallemand. Fresh and dry Baker's yeast were calculated as anhydrous for simplicity. 28% aq. ammonia was supplied by Sigma Aldrich. 75.1 % aq. glucose syrup with a DE-value of 95 to less than 100 (C*sweet D 02767 ex Cargill) was supplied by Cargill. Silane (Momentive VS- 142) was supplied by Momentive and was calculated as 100% for simplicity. All other components were supplied in high purity by Sigma-Aldrich and were assumed anhydrous for simplicity.

Binder solids The content of binder after curing is termed "binder solids".

Disc-shaped stone wool samples (diameter: 5 cm; height 1 cm) were cut out of stone wool and heat-treated at 580 °C for at least 30 minutes to remove all organics. The solids of the binder mixture were measured by distributing a sample of the binder mixture (approx. 2 g) onto a heat treated stone wool disc in a tin foil container. The weight of the tin foil container containing the stone wool disc was weighed before and directly after addition of the binder mixture. Two such binder mixture loaded stone wool discs in tin foil containers were produced and they were then heated at 200 °C for 1 hour. After cooling and storing at room temperature for 10 minutes, the samples were weighed and the binder solids was calculated as an average of the two results.

A binder with the desired binder solids could then be produced by diluting with the required amount of water and 10% aq. silane (Momentive VS-142).

Reaction loss

The reaction loss is defined as the difference between the binder component solids content and the binder solids.

Curing characteristics - DMA (dynamic mechanical analysis ^' ) measurements

A 15% binder solids binder solution was obtained as described above. Cut and weighed glass Whatman™ glass microfiber filters (GF/B, 150 mm 0, cat. no. 1821 150) (2.5x 1 cm) were submerged into the 15% binder solution for 10 seconds. The resulting binder-soaked filter was then dried in a "sandwich" consisting of (1) a 0.60 kg 8x8x 1 cm metal plate, (2) four layers of standard filter papers, (3) the binder soaked glass microfiber filter, (4) four layers of standard filter papers, and (5) a 0.60 kg 8x8x 1 cm metal plate for approximately 2x2 minutes by applying a weight of 3.21 kg on top of the "sandwich". In a typical experiment, the cut Whatman™ glass microfiber filter would weigh 0.035 g before application of the binder and 0.125 g after application and drying which corresponds to a binder solution loading of 72%. All DMA measurements were performed with 72± 1% binder solution loadings. The DMA measurements were acquired on a Mettler Toledo DMA 1 calibrated against a certified thermometer at ambient temperature and the melting points of certified indium and tin. The apparatus was operated in single cantilever bending mode; titanium clamps; clamp distance 1.0 cm; temperature segment type; temperature range 40-280 °C; heating rate 3 °C / min; displacement 20 μιτι; frequency 1 Hz; single frequency oscillation mode. Curing onset and endset were evaluated using STARe software Version 12.00.

Mechanical strength studies

The mechanical strength of the binders was tested in a tablet test. For each binder, six tablets were manufactured from a mixture of the binder and stone wool shots from the stone wool spinning production. The shots are particles which have the same melt composition as the stone wool fibers, and the shots are normally considered a waste product from the spinning process. The shots used for the tablet composition have a size of 0.25-0.50 mm.

A 15% binder solids binder solution containing 0.5% silane (Momentive VS-142) of binder solids was obtained as described above. A sample of this binder solution (4.0 g) was mixed well with shots (20.0 g). The resulting mixture was then transferred into a round aluminum foil container (bottom 0 = 4.5 cm, top 0 = 7.5 cm, height = 1.5 cm). The mixture was then pressed hard with a suitably sized flat bottom glass or plastic beaker to generate an even tablet surface. Six tablets from each binder were made in this fashion. The resulting tablets were then cured at 250 °C for 1 h. After cooling to room temperature, the tablets were carefully taken out of the containers. Three of the tablets were aged in a water bath at 80 °C for 3 h.

After drying for 1-2 days, all tablets were then broken in a 3 point bending test (test speed : 10.0 mm/min; rupture level : 50%; nominal strength : 30N/mm2; support distance: 40 mm; max deflection 20 mm; nominal e-module 10000 N/mm2) on a Bent Tram machine to investigate their mechanical strengths. The tablets were placed with the "bottom face" up (i.e. the face with 0 = 4.5 cm) in the machine.

Binder example, reference binder

A mixture of 75.1% aq. glucose syrup (53.3 g; thus efficiently 40.0 g glucose syrup), ammonium sulfamate (2.00 g, 17.5 mmol) and urea (2.00 g) in water (80.0 g) was stirred at room temperature until a clear solution was obtained. 28% aq. ammonia (0.12 g; thus efficiently 0.03 g, 1.97 mmol ammonia) was then added dropwise until pH = 8.2. The binder solids were then measured (23.3%). For DMA and mechanical strength studies (15% binder solids solution, 0.5% silane of binder solids), the binder mixture was diluted with water (0.542 g / g binder mixture) and 10% aq. silane (0.012 g / g binder mixture, Momentive VS- 142). The final binder mixture for mechanical strength studies had pH = 8.2.

Binder compositions according to the present invention

In the following, the entry numbers of the binder example correspond to the entry numbers used in Table 1.

Binder example, entry 3

A mixture of 75.1% aq. glucose syrup (53.3 g; thus efficiently 40.0 g glucose syrup), ammonium sulfamate (2.00 g, 17.5 mmol) and urea (2.00 g) in water (80.0 g) was stirred at room temperature until a clear solution was obtained. 28% aq. ammonia (0.04 g; thus efficiently 0.01 g, 0.66 mmol ammonia) was then added dropwise until pH = 7.7. The binder solids were then measured (23.0%). For DMA and mechanical strength studies (15% binder solids solution, 0.5% silane of binder solids), the binder mixture was diluted with water (0.522 g / g binder mixture) and 10% aq. silane (0.012 g / g binder mixture, Momentive VS- 142) and fresh Baker's yeast was added (0.023 g / g binder mixture). The final binder mixture for mechanical strength studies had pH = 7.6. Table 1

Example 1 ,ί 2 3

Binder composition

Carbohydrate (%-wt.)

Glucose syrup 100 100 100

Additive (%-wt.) ^[a]

Urea 5 5 5

Ammonium sulfamate 5 5 5

Amine (equiv.) ^[bI

Ammonia (added) 0,06 0,02 0,02

Silane (% of binder solids) 0,5 0,5 0,5

Microorganism (%-wt.) ^[CI

Fresh Baker's yeast 5 10

Binder properties

Curing onset (° C) 170 169 171

Curing endset (° C) 191 189 190

Reaction loss (%) 27% - - pH of 15% soln. 8,2 7,6 6,3

Mechanical strength, unaged (kN) 0, 17 0, 14 0, 15

Mechanical strength, aged (kN) 0,08 0,07 0,07

^[a] Of carbohydrate. ^[b] Molar equivalents added relative to inorganic acids. ^[c] binder solids.

The inclusion of 5-10% Fresh Baker's yeast (based on binder solids) into the shown binder system resulted in only minor changes in the curing on- and endsets and in unaged and aged mechanical strengths when compared to the reference example without addition of Baker's yeast (ex. 2-3 vs. 1).