EP1343853A1

EP1343853A1 - Particulate binding agent compositions with a low tendency towards pulverulence, production and use thereof

Info

Publication number: EP1343853A1
Application number: EP01995675A
Authority: EP
Inventors: Paul Birnbrich; Sandra Hoffmann; Thomas Huver; Bernhard SCHÖTTMER; Rolf Tenhaef
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 2000-12-07
Filing date: 2001-11-28
Publication date: 2003-09-17
Also published as: DE10157485A1; WO2002046324A1

Abstract

The invention relates to a particulate binding agent composition comprising at least one natural or synthetic polysaccharide and at least one synthetic water dispersible polymer. The amount of particles having a diameter of less than 30 mu m is less than 1 wt. % and the free fibre content in 5mg of the binding agent composition is at least 40. The invention also relates to a method for the production and the use thereof.

Description

Particulate binder compositions with a low tendency to dust, the

Manufacture and use

The present invention relates to a particulate composition of a composition comprising at least one natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer, the proportion of particles with a particle diameter of less than 30 μm being less than 1% by weight and the content of free fibers in 5 mg of the binder composition is at least 40, processes for the preparation of such binder compositions and their use.

Binder compositions which contain a natural or synthetic polysaccharide and a synthetic polymer are essentially known. Such binder compositions are used for gluing, solidifying or sealing. Specific examples of such applications are, for example, paste, dispersion adhesives, primers for mineral substrates and the like. The abovementioned binder compositions known from the prior art, in particular their pulverulent preparations, are used in particular for the production of the products mentioned if the products can be prepared at the point of use by simple mixing with water and in particular can be carried out and desired by the user. The use of such binders in the production of adhesives is particularly preferred when the type of use of the adhesives permits the use of adhesives prepared by the user himself.

The use of such binder compositions generally saves transportation costs because the weight of the water is eliminated. Binder compositions of this type are frequently used for coating a surface with paper or other coverings. A particularly common use of such binders is wallpaper paste, which is used for the decorative coating of walls or ceilings indoors. If such binder compositions are to be brought into a form suitable for use by the user themselves, it is necessary that they meet a number of requirements which, on the one hand, ensure the handling of the binders and, on the other hand, as constant a product quality as possible, both with regard to the binder compositions themselves and relate to the products that can be produced from such binder compositions. Such requirements include in particular the portionability with constant product quality within the individual portions, the absence of dust when used, for example when portioning the binder compositions, and the dissolution behavior of the binder compositions. Such binder compositions frequently tend to clump when stirred into water, which either means that unacceptably long periods of time are required to remove the lumps, or else the lumps do not dissolve at all. When using a product containing such lumps, however, there are disadvantages with regard to optical or technical faults. If, for example, a wallpaper paste has such lumps, disturbances in the surface structure can occur, in particular when gluing smooth, unstructured wallpapers.

Furthermore, the fastest possible use of a product obtained with the aid of the named binders is required. Here, particular importance is attached to the quickest possible solubility or dispersibility combined with the fastest possible viscosity build-up of the product, and despite the fastest possible build-up of viscosity, a lump-free dissolution or dispersion of the binder should still take place.

In addition, such binder compositions generally have a high proportion of dust-forming constituents, which the user perceives as being disruptive in the production of the end product. Furthermore, such constituents already lead to a high level of dust development when the binder compositions are filled into packaging, which either require complex measures to avoid dust or lead to an increased dust load on the persons involved in the filling of the binders. Various measures have been proposed in the past to avoid the above problems.

For example, EP-B 0 541 526 describes free-flowing, rapidly disintegrating dry powders with adhesive character, a process for their production and their use. The publication describes that so-called special pastes have a mixture of binders which, due to different particle size and density, tend to separate and develop dust when stirred into water. In order to avoid this effect, dry powders are proposed in the publication which have a grain structure in which the at least predominant proportion of the granular dry material has closed cores of a nonionic cellulose ether which are encased in a shell of a redispersion polymer and are firmly bonded to it. Dry powders of this type are prepared by intimately mixing nonionic cellulose ethers as a powder or aqueous powder slurry with an aqueous polymer dispersion, the aqueous phase being kept at a temperature above the cloud point of the nonionic cellulose ethers used and the aqueous mixture obtained in this way while maintaining certain temperature conditions Spray drying is subjected. The products obtained in this way have average particle diameters in the range from about 50 to about 500 μm. The spray drying process described, however, requires a high level of equipment and energy.

WO 97/27258 relates to a porous molded part for producing an aqueous binder system. The porous molded part described preferably has a cylindrical shape with porous edges. On the one hand, however, the production of the molded parts is very complex owing to the use of microwave technology; However, the use of larger molded parts, in particular the tablets described in the publication, meets with reservations from some consumers. DE-C 31 03 338 relates to a process for the production of rapidly soluble paste based on cellulose ethers, in which pulverulent, optionally partially crosslinked cellulose ethers are converted into rapidly dissolving granules in a granulating device with the addition of water. The problem with the pastes described, however, is that the yields of good grain leave something to be desired. Furthermore, the removal of the water introduced during the granulation is lengthy and energy-intensive due to the swelling of the cellulose ethers contained in the paste.

EP-A 0 416 405 relates to cellulose ether compositions for aqueous media which, in addition to pulverulent cellulose ethers and, if appropriate, further auxiliaries and additives, also contain swelling and absorbent superabsorbents. For example, mixtures of methyl cellulose and a superabsorbent made of sodium polyacrylate are described, which leads to rapidly dissolving binder mixtures. The sodium polyacrylate used as a superabsorbent is not water-soluble. A disadvantage of the binder compositions described, however, is that no reduction in dust formation is discernible. In addition, the superabsorbents contained in the cellulose ether compositions give off water only very poorly, so that, on the one hand, a comparatively granular paste is formed and, on the other hand, an adhesive bond made with such a paste remains wet for a long time.

There was therefore a need for binder compositions which can be used in particular in the production of aqueous binder preparations which have a reduced tendency to dust and nevertheless have excellent dissolving behavior. There was also a need for a process for the preparation of such compounds in which the highest possible yield of good grain can be achieved. There was also a need for a method for producing such compounds which has the lowest possible energy consumption in comparison with known methods.

The present invention was therefore based on the object of providing binder compositions and processes for their preparation which satisfy the above-mentioned needs. The objects of the invention are achieved by means of binder compositions and processes for their preparation, as described in the context of the present text.

The present invention therefore relates to a particulate binder composition, at least comprising a natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer, the proportion of particles with a particle diameter of less than 30 μm being less than 1% by weight and the content of free fibers in 5 mg of the binder composition is at least 40.

The binder compositions according to the invention contain substances which are suitable for the production of aqueous binder systems. An aqueous binder system is to be understood as meaning solutions or dispersions which are suitable for adhesive bonding, sealing, solidifying or in general for surface treatment. Specific examples of such solutions or dispersions are paste, dispersion adhesives, primers for mineral substrates and the like.

In order to obtain a ready-to-use product, for example a paste, a dispersion adhesive, a sealant or a primer for mineral substrates, the particulate binder compositions according to the invention must first be mixed by the user with a suitable amount of water, that is to say they must be dissolved or dispersed therein.

At least about 80% by weight of the particles present in the particulate binder compositions according to the invention preferably have a size of at least about 0.01 and at most about 1 mm in the context of the present invention. In the context of a preferred embodiment of the present invention, the binder particles have a particle size of approximately 0.05 to approximately 0.95 or approximately 0.1 to approximately 0.8 mm. The proportion is preferably at least about 90% by weight or more, for example at least about 95, 96, 97, 98 or 99% by weight. The term "particle size" is used in the context of the present invention to refer to the actual size of the particles contained in the binder composition, both binder agglomerate particles and non-agglomerated particles. The actual particle size can be determined using suitable measuring methods such as light - or electron microscopy, light scattering or using a screening method.

The particulate binder agglomerates according to the invention contain at least one natural or synthetic polysaccharide. Suitable natural or synthetic polysaccharides are, for example, starch or cellulose and their derivatives obtainable by suitable processes and substituted on one or more OH groups.

All types of starch such as potato starch, corn starch, wheat starch, rice starch, milo starch, tapioca starch or mixtures of two or more of the starches mentioned and the like are suitable as starch or as the basis of the starch derivatives. In a preferred embodiment of the present invention, starch or starch derivatives based on potato or corn starch or mixtures thereof are used.

The starch should be water-soluble, possibly at least water-swellable. Modified starch is particularly suitable in the context of the present invention, a corresponding modification being brought about by physical or slight chemical action. Specific examples of such starch derivatives are partially degraded starch and swelling starch.

The starch derivatives should in particular be water-soluble or at least water-swellable. In this connection, starch esters or starch ethers are particularly suitable, especially carboxylated or alkoxylated starches. Suitable carboxylated or alkoxylated starches are all appropriately modified natural starch types already mentioned above. Useful starch derivatives have a degree of carboxylation from about 0.1 to about 2.0 or an alkoxylation degree from about 0.05 to about 1.5. Suitable starch derivatives can also be crosslinked with difunctional compounds, as are known, for example, from EP-B 0311 873 (page 3, line 49 to page 4, line 5). In addition to natural cellulose, cellulose ethers are particularly suitable as cellulose compounds. Carboxymethyl cellulose (CMC), carboxymethyl methyl cellulose (CMMC), ethyl cellulose (EC), hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), hydroxybutyl cellulose (HBC), hydroxybutyl methyl cellulose (HBMC), hydroxyethyl cellulose (HEC) are suitable, for example.

Hydroxyethylcarboxymethylcellulose (HECMC), Hydroxyethylethylcellulose (HEEC), Hydroxypropylcellulose (HPC), Hydropropylcarboxymethylcellulose (HPCMC), Hydroxypropyhnefhylcellulose (HPMC), Hydroxyethylmethylcellulose (HEMC), Mefhylhydroxyefhylcellulose (MHECp) cellulose (MHethyl) cellulose (MHethyl) cellulose (MHethyl) cellulose (MHethyl) cellulose (MHP) cellulose, methyl hydroxyl cellulose (MHEC) cellulose (Methylpropyl cellulose) () wherein carboxymethyl cellulose, methyl cellulose, methyl hydroxy cellulose and methyl hydroxypropyl cellulose and mixtures of two or more thereof and the alkali metal salts of CMC and the slightly ethoxylated MC or mixtures of two or more of the compounds mentioned.

The cellulose derivatives mentioned can be slightly crosslinked so that they are soluble at a pH of more than 8 and the solution in water is delayed. Crosslinking can take place, for example, in a known manner by adding glyoxal.

In addition to the polysaccharides and their derivatives described, a binder agglomerate according to the invention also contains at least one synthetic polymer.

Such synthetic polymers are to be ensured, for example, to increase the adhesive strength or to improve the water resistance of an end product obtained using a product obtainable from a binder agglomerate according to the invention. Suitable synthetic polymers in the context of the present invention are, in particular, redispersible dispersion powders of fully synthetic polymers (base polymers). Basically, these are homopolymers and copolymers of vinyl esters, styrene, acrylic acid esters and vinyl chloride.

Vinyl ester polymers suitable as the base polymer are, for example, vinyl acetate homopolymers, copolymers of vinyl acetate with ethylene and / or vinyl chloride and / or other vinyl esters such as vinyl laurate, vinyl versatic acid, vinyl pivalate or Esters of maleic acid or fumaric acid or copolymers of two or more of the monomers mentioned or homopolymers of vinyl esters of saturated C ₃ . ₈ - alkyl carboxylic acids or their copolymers with ethylene, vinyl chloride or other vinyl esters.

The above-mentioned acrylic acid esters, methacrylic acid esters or styrene polymers are derived from the polymerization of styrene or esters of acrylic acid or methacrylic acid. Esters of acrylic acid or methacrylic acid are preferably esters with straight-chain or branched or cyclic aliphatic alcohols with 1 to 20 carbon atoms. Other styrenic polymers can be, for example, copolymers of styrene with one or more other monomers. For example, styrene-butadiene copolymers are suitable. Vinyl chloride / ethylene copolymers are suitable as vinyl chloride polymers.

In the context of the present invention, preference is given to vinyl acetate homopolymers, vinyl acetate-ethylene copolymers or copolymers of vinyl esters of saturated alkylcarboxylic acids and ethylene with an ethylene content of 1 to about 40% by weight of ethylene and 0 to about 40% by weight of further redispersion powder Vinyl ester from the group of vinyl esters of saturated C ₃ . _8- alkyl carboxylic acids or vinyl chloride or mixtures of two or more thereof, styrene acrylates such as styrene-butyl acrylate or styrene-ethylhexyl acrylate with a styrene content of 1 to about 70% by weight. These redispersing polymers are usually produced by spray drying polymer dispersions in spray towers.

Particularly suitable are, for example, vinyl ester homopolymers or copolymers, for example with ethylene, whose monomeric basic unit is a vinyl ester of a linear or branched carboxylic acid having from about 2 to about 44, for example from about 3 to about 15, carbon atoms. Monomers for these homo- or polymeric polyvinyl esters are vinyl formate, vinyl acetate, vinyl propionate, vinyl isobutyrate, vinyl pivalate, vinyl 2-ethylhexanoate, vinyl esters of saturated branched monocarboxylic acids with 9 to about 15 carbon atoms in the acid residue, vinyl esters of longer-chain saturated or unsaturated fatty acids Vinyl laurate, vinyl stearate or vinyl ester of benzoic acid and substituted derivatives of benzoic acid such as vinyl p-tert-butylbenzoate in question. The above Vinyl esters can each be present individually or as mixtures of two or more of the vinyl esters mentioned in the vinyl ester polymers.

It may be expedient if, in the context of the present invention, the binder agglomerates according to the invention contain two or more of the synthetic polymers mentioned.

In a further preferred embodiment of the present invention, mixtures of a homopolymer and a copolymer are used as polymer particles. Suitable homopolymers are the homopolymers already mentioned, but in particular homopolymers of vinyl esters, preferably polyvinyl acetate. The copolymers mentioned above are also suitable as copolymers. In a preferred embodiment, however, copolymers of ethylene and vinyl acetate, vinyl acetate and vinyl versatate or terpolymers, in particular ethylene-vinyl acetate-acrylate terpolymers, are used in the mixtures of two or more polymer particles mentioned.

The proportion of homopolymers in such mixtures of polymer particles is preferably at least about 20% by weight, but preferably 40% by weight or more, for example at least about 50% by weight. Suitable mixing ratios of homopolymers and copolymers are, for example, about 75:25 or about 80:20.

In addition to the ingredients mentioned, namely at least one natural or synthetic polysaccharide and at least one synthetic polymer, the binder agglomerates according to the invention can also contain further additives.

Suitable additives are, for example, compounds which bring about an alkalization of the adhesive which can be prepared by dissolving the water-soluble preparations according to the invention. These include, for example, ammonium, alkali and / or alkaline earth metal hydroxides, the water-soluble, preferably powdered alkali metal silicates (water glass), in particular sodium or potassium water glass, and ammonia and amines or basic salts and neutral salts, which are derived from strong and weak acids. These include, for example, the alkali salts of carbonic acid or the carboxylic acids or the tertiary phosphates. The compounds mentioned can be used alone or as a mixture of two or more thereof.

If an alkalization is to take place in the course of dissolving the water-soluble preparations according to the invention, the proportion of the abovementioned additives in the total water-soluble preparation according to the invention is generally about 0.1 to about 2% by weight.

Auxiliaries or fillers, wetting agents and preservatives, consistency formers and additional components with adhesive properties such as dextrins or ionogenic cellulose ethers are also suitable as additives.

In the context of a further embodiment of the present invention, the water-soluble preparation contains auxiliaries or fillers. Suitable auxiliaries or fillers are, for example, carbonates (in particular calcium carbonate), silicates (for example talc, clay, mica), silica, sulfates such as calcium or barium sulfate, aluminum hydroxide and glass fibers or glass balls. Such auxiliaries or fillers can be contained in the water-soluble composition according to the invention for example in an amount of up to about 30, preferably from about 0.1 to about 20% by weight, based on the total water-soluble preparation.

Furthermore, a binder agglomerate according to the invention may also contain additives. Particularly suitable additives are water-soluble ionic or nonionic polymers from the group of the polyvinylpyrrolidones, methylpyrrolidone / methyl ester copolymers, water-soluble amphoteric polymers from the group of alkyl acrylamide / acrylic acid copolymers, alkyl acrylamide / methacrylic acid copolymers, alkyl acrylamide / acrylic acid / acrylic acid / methyl methacrylate acid - Noalkyl (meth) acrylic acid copolymers, A ^ lacrylarmd / Memacrylsäiire / Alkylarnmoalkyl- (meth) acrylic acid copolymers, Alkylacrylann ^' d ethyl methacrylic acid / All-ylammoalJ yl- (meth) acrylic acid copolymers, Alkylacrylarrn AlkylmemacrylaV acrylate, alkyl methacrylate copolymers from unsaturated carboxylic acids, cationically derivatized unsaturated carboxylic acids, optionally further ionic or nonionic monomers, water-soluble zwitterionic polymers from the group the Acrylamidoalkyltrialkylammoniumclüorid / acrylic acid copolymers and their alkali and ammonium salts, Acrylamidoal ltrialkylarrimoniu ^ copolymers and their alkali and ammonium salts, methacroylethylbetaine / Mefhacrylat-copolymers, water-soluble anionic polymers from the group of Ninylacyrolololonolonololonololonolonolonolonolonolonolonolonotolononolonololonolonate, Cry Acrylic acid / Ε ylacrylate / Ν-tert.Butylacrylamid Te olymers, graft polymers of vinyl esters, esters of acrylic acid or methacrylic acid alone or in a mixture, copolymerized with crotonic acid, acrylic acid or methacrylic acid with polyalkylene oxides and / or polyalkylene glycols, grafted and crosslinked copolymers from Copolymerization of at least one non-ionic type monomer, at least one ionic type monomer, polyethylene glycol and a crosslinker by copolymerizing at least one monomer of each of the following three groups, copolymers, esters of unsaturated alcohols and the like Short-chain saturated carboxylic acids and / or esters of short-chain saturated alcohols and unsaturated carboxylic acids, unsaturated carboxylic acids, esters of long-chain carboxylic acids and unsaturated alcohols and / or esters from the carboxylic acids of the group with saturated or unsaturated, straight-chain or branched C ₈ . ₁₈ - Alcohols, terpolymers from crotonic acid, vinyl acetate and an allyl or mefhallyl ester, tetra- and pentapolymers from crotonic acid or allyloxyacetic acid, vinyl acetate or vinyl propionate, branched allyl or methallyl esters, vinyl ethers, vinyl esters or straight-chain copolymers with a allyl, or methallyl acid or more monomers from the group consisting of ethylene, vinylbenzene, vinyl methyl ether, acrylamide and their water-soluble salts, terpolymers made from vinyl acetate, crotonic acid and vinyl esters of a saturated aliphatic monocarboxylic acid branched in the α-, β- or γ-position, water-soluble cationic polymers from the group of the quaternized cellulose Derivatives, polysiloxanes with quaternary groups, cationic guar derivatives, polymeric dimethyldiallylammonium salts and their copolymers with esters and amides of acrylic acid and methacrylic acid, copolymers of vinylpyrrolidone with quaternized derivatives of dialkylaminoacrylate and methacrylate, Vi nylpyrrolidone-methoimidazolinium chloride copolymers, quaternized polyvinyl alcohol, under the IΝCI names Polyquaternium 2, Polyquaternium 17, Polyquaternium 18 and Polyquaternium 27 specified polymers. Water-soluble polymers such as those obtainable by graft copolymerization are particularly suitable as additives. Suitable graft bases are, for example, polyalkylene glycols, in particular polyethylene glycol, with a molecular weight of approximately 100 to approximately 50,000, in particular approximately 1000 to approximately 10,000. to produce the graft branches it is in principle possible to use all compounds which can be grafted onto polyalkylene glycols and have at least one olefinically unsaturated double bond. However, esters of vinyl alcohol with linear or branched, saturated monocarboxylic acids having 2 to 24 carbon atoms, in particular 2 to about 18 carbon atoms, are preferably used to prepare the graft branches. Such vinyl esters have already been described above in the context of the present text. For example, graft copolymers can be used which have a graft base content of about 10 to about 90% by weight and a graft base content of about 90 to about 10% by weight. The ratio of graft base to graft branches is preferably chosen so that the graft copolymers are water-soluble, the water solubility at 20 ° C. should be at least about 1 g / 1, but preferably more, for example about 2, 5 or 10 g / 1.

In the context of a preferred embodiment of the present invention, a graft copolymer is used as the additive, which carries about 40% by weight of a polyethylene glycol (PEG) with a molecular weight (M _w ) of about 6000 as the graft base and about 60% by weight of polyvinyl acetate as the graft branches ,

The additives mentioned can be present in the binder compositions according to the invention in an amount of about 1 to about 10% by weight, for example about 3 to about 7% by weight.

The present invention further relates to an aqueous solution or dispersion of a binder composition according to claims 1 to 4 or 10 or a binder composition prepared according to claims 5 to 9.

The particulate composition of the invention has a proportion of particles with a particle diameter of less than 30 μm or less than about 35 μm or less than about 40 μm, which is less than 1% by weight. in the In the context of a preferred embodiment, the proportion of such particles is less than 0.8% by weight, for example less than 0.5% by weight.

A particulate binder composition according to the invention has a free fiber content in 5 mg of the binder composition of at least 40. The number 40 refers to the actual number of free fibers found in 5 mg of the binder composition.

In the context of the present invention, free fibers are understood to mean polysaccharide fibers which do not show any adherence of agglomerates, but can be recognized as free fibers in a suitable enlargement. In the context of the present invention, fibers are referred to as elongated spatial structures in which the ratio of the expansion of two spatial axes in the ideally elongated state is at least approximately 10.

The structures referred to as "free fibers" in the context of the present text are clearly recognizable as such within the scope of a microscopic examination of corresponding particulate binder compositions. According to the present invention, a free fiber has no adhesions which have an expansion of more than 50%, preferably more than 30% and particularly preferably more than 10% of the longest spatial axis of the free fiber. In the context of a particularly preferred embodiment of the present invention, a free fiber has no recognizable adhesions.

The constituents of a composition of the invention according to the invention which are referred to as free fibers in the context of the present invention preferably have a length of at least approximately 30, for example at least approximately 35, 40, 45 or 50 μm, but preferably at least approximately 60, 70 or 80 μm.

In the context of the present invention, adhesions are understood to mean any structures connected to the fiber by adhesion. Such adhesions are usually polymer particles. The content of free fibers is determined by distributing a sample of 5 mg of the binder composition to be examined on a slide as evenly as possible. An area of about 3 to about 4 cm is usually sufficient for such a distribution. The free fibers as defined above are counted at a 25-fold magnification under a stereomicroscope. The arithmetic mean is calculated from a double determination and the proportion of fibers in free fibers / 5 mg is given.

In the context of a preferred embodiment of the present invention, the lower limit for the content of free fibers in the binder composition according to the invention is approximately 41, 42, 45, 50, 55, 60, 70, 80, 90 or approximately 100 fibers / 5 mg. The upper limit is approximately 250 or fewer fibers / 5 mg, for example approximately 240, 230, 220, 200 or 150 fibers.

In a preferred embodiment, the number of fibers in a binder composition according to the invention is approximately 50 to 250, in particular approximately 70 to approximately 230 fibers / 5 mg.

The binder compositions according to the invention have excellent portioning and pouring behavior. In a preferred embodiment of the present invention, the bulk volume is more than about 88 ml / 50 g of binder composition, preferably more than about 95 or more than about 100 ml of 50 g of binder composition. The upper limit for the bulk volume of the binder compositions according to the invention is about 150 ml / 50 g of binder composition, preferably about 130 ml / 50 g of binder composition.

The binder compositions according to the invention also show excellent storage behavior. Even storage of the binder compositions according to the invention, packaged in polyethylene bags, at a temperature of more than 35 ° C. and a load of about 1 kg / 50 cm ² over a period of 24 hours does not lead to caking of the powders according to the invention. The compositions according to the invention have an extremely low tendency to dust. The amount of dust was determined optically by observing the development of dust, a detailed representation of the dust content can be found in the example section.

In the context of a preferred embodiment, the binder compositions according to the invention contain about 30 to about 75% by weight of a natural or synthetic polysaccharide or polysaccharide derivative, about 20 to about 40% by weight of a synthetic polymer, about 0 to about 20% by weight of fillers and about 0 to about 10% by weight additives.

In the context of a further preferred embodiment, a binder composition according to the invention receives approximately 40 to approximately 60% by weight of a natural or synthetic polysaccharide or polysaccharide derivative, in particular

Methylhydroxyethyl cellulose, about 25 to about 35% by weight of a synthetic polymer, in particular polyvinyl acetate or poly (vinyl alcohol-co-vinyl acetate), about 5 to about 20% by weight of auxiliaries, for example calcium carbonate and about 2 to about 7% by weight additives.

The binder compositions according to the invention are used to prepare aqueous, ready-to-use solutions or dispersions. For this purpose, the binder compositions according to the invention are introduced into water by the user, the ready-to-use preparation being available after a short time. The dissolution process can optionally be supported by stirring. Suitable application concentrations for the binder compositions according to the invention are, for example, 0.5 to 20% by weight in water, in particular approximately 1 to 5% by weight.

The binders according to the invention are produced by contacting a particulate mixture of at least one natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer with a solvent which may contain an additive or a mixture of two or more additives. The present invention therefore also relates to a process for producing a low-dust particulate binder composition, in which a particulate mixture of at least one natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer is contacted with a solvent, the solvent being chosen such that swelling or Solution of the synthetic polymer takes place within 3 h at 20 ° C.

In the context of the present method, the term “solvent” relates both to compounds which cause the polymer to swell and to compounds which partially or completely dissolve the polymer.

The process according to the invention can be carried out, for example, with solvents which exclusively cause the synthetic, water-dispersible polymer to swell. The swelling can take place, for example, on the surface, but complete swelling of the polymer can also take place.

Furthermore, solvents can be used in the process according to the invention, which basically dissolve the polymer completely or at least partially.

In the context of a preferred embodiment of the present invention, the amount of solvent used is such that, after the solvent has been added completely, any observed lumping of the mixture of natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer used is reversible, i.e. after the removal of the Solvent disappears either without external influence or with little effort, for example by stirring or shaking.

omitted. Preferably, there should be essentially no adhesion of the particles of the mixture of natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer mixed with the solvent or solvent mixture to the walls of an aggregate used for the mixing. The amount of solvent used in the present process can in principle be within any range. However, the amount of solvent should preferably not be greater than the total amount of mixture of natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer, based on the weight of the compounds used in the process.

If, for example, solvents are used which only cause the polymer to swell, the amount of solvent used can be, for example, about 10 to about 90% by weight or about 20 to about 80% by weight, based on the weight of the mixture of natural or synthetic Polysaccharide and at least one synthetic water-dispersible polymer. In this case, the proportion of solvent used preferably remains below a value of approximately 100% by weight, based on the weight of the polymer present in the mixture of natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer, for example within a range of approximately 5 to about 95 or about 25 to about 85 weight percent.

If solvents which dissolve the polymer are used in the context of the present process, the amount of solvent used can be, for example, about 10 to about 70% by weight or about 20 to about 80% by weight, based on the weight of the mixture of natural or synthetic Polysaccharide and at least one synthetic water-dispersible polymer. In this case, however, the proportion of solvent used preferably remains below a value of approximately 100% by weight, based on the weight of the polymer present in the mixture of natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer, for example within a range of approximately 10 to about 85 or about 50 to about 80% by weight.

In a preferred embodiment, the solvent used is a solvent which contains at least one linear or branched, saturated or unsaturated alcohol having 1 to about 10 carbon atoms. Alcohols with 1 to about 10 carbon atoms are particularly suitable alcohols with 1 or 2 OH groups, in particular monoalcohol. Suitable alcohols are, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, the isomeric pentanols, hexanols, heptanols, octanols and decanols, AUyl alcohol, 3-pentanol, or aromatic alcohols such as benzyl alcohol. Glycols such as ethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol or heptanediol are also suitable, the alcohols mentioned being able to carry the OH groups at the end or at any point within the carbon chain. The partial or full ethers of the alcohols and glycols mentioned are also suitable.

Also suitable as solvents in the context of the present invention are mixtures of two or more of the alcohols or ethers mentioned, if appropriate in a mixture with water. If the alcohols mentioned are used together with water as the solvent, the alcohol content in the solvent should be at least about 20% by weight, but preferably more, for example at least about 50 or at least about 80% by weight.

In addition, suitable solvents are, for example, cyclic ethers or aromatic solvents such as toluene, THF or dioxane.

In the context of a further preferred embodiment of the present invention, the method according to the invention is carried out with a solvent which contains an additive. Suitable additives are the ionic or nonionic, water-soluble polymers already mentioned above in the context of the present text.

If an additive-containing solvent is used, the solvent in a preferred embodiment contains about 5 to about 50% by weight, for example about 10 to about 30% by weight, in particular about 15 to about 25% by weight of additive.

In the context of a preferred embodiment of the present invention, the method according to the invention is carried out with a mixture of ethanol as solvent and polyethylene glycol with a molecular weight of approximately 200 to approximately 5000, in particular approximately 400 to approximately 2000, polyvinylpyrrolidone or a poly (ethylene glycol graft vinyl acetate). To carry out the process according to the invention, the above-mentioned particulate mixture of at least one natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer with a solvent or a mixture of two or more solvents or a mixture of one or more solvents and an additive or a mixture of two or more additives contacted. The contacting takes place by means of commonly used mixing methods, in particular in a stirred tank using a ploughshare mixer. Other devices suitable for carrying out the method according to the invention are, for example, Lödige mixers or rotary tube mixers

The contacting of the particulate mixture with the solvent or the additive-containing solvent is usually carried out by dropping solvent or additive-containing solvent into the particulate mixture while the particulate mixture is kept in motion. The rate of addition is selected so that both wall wetting of the mixing vessel and the stirring device and clumping of the particles with one another essentially do not occur, but at least in such a way that any clumping or adherence that may be observed essentially disappears completely after removal of the solvent. The addition can be carried out, for example, by dropping at one or more points on the stirred vessel or by spraying the agitated mixture.

In the process according to the invention, the mixing can be ended immediately after the addition of the solvent or the additive-containing solvent has ended. In a preferred embodiment, however, the movement of the mixture is maintained for at least about 5 minutes after the end of the addition of the solvent or solvent containing additive.

The solvent added to the particulate mixture is preferably removed from the mixture after the mixture has been mixed with the solvent after a sufficient contact time. This is preferably done by heating the mixture to a temperature at which the solvent evaporates from the mixture. in the In the context of a preferred embodiment of the present invention, this process is supported by reducing the pressure.

In a preferred embodiment, the temperature of the mixture when removing the solvent should not exceed a temperature of about 60 ° C., in particular about 50 or about 40 ° C. In the context of a further preferred embodiment, the pressure is reduced to about 10 mbar or less, for example less than about 5 mbar.

The present invention furthermore relates to a binder composition which can be prepared by a process according to the invention.

The binder compositions according to the invention are suitable for the preparation of aqueous solutions or dispersions. The present invention therefore also relates to an aqueous solution or dispersion of a binder composition according to the invention or of a binder composition produced by a method according to the invention.

Another object of the invention is the use of a binder composition according to the invention or a binder composition produced by a method according to the invention for the production of aqueous preparations. Corresponding aqueous preparations have already been described in the context of this text.

The present invention is illustrated by the figures.

Fig. 1 shows three electron micrographs of a commercial wallpaper paste in different magnifications and different image sections. The wallpaper paste examined contains methylhydroxyethyl cellulose, poly (vinyl alcohol-co-vinyl acetate), calcium carbonate and polyvinyl pyrrolidone. As can be seen in Figure 1.1, such a commercially available mixture for the production of wallpaper paste has a high proportion of components of a size of less than approximately 50 μm. Figures 1.2 and 1.3 show a proportion of free fibers in addition to other components, the particle diameter of which is sometimes less than 10 μm.

2 shows separated fibers of a binder mixture obtained by spray drying. The separated fibers shown in Figures 2.1, 2.2 and 2.3 are clearly surrounded by adhering agglomerated binder components.

3 shows images of a binder mixture according to the invention. Figure 3.1 shows both agglomerates with a diameter of significantly more than 200 μm and individual free fibers. No proportion of components with a diameter of less than about 100 μm can be seen. Figures 3.2 and 3.3. each show detailed enlargements of fiber components of the binder composition according to the invention, which are clearly surrounded by agglomerates.

4 shows further illustrations of a binder composition according to the invention. Figures 4.1, 4.2 and 4.3 show free fibers as components of the binder composition.

5 also shows detailed images of free fibers in the binder composition according to the invention. Figures 5.1, 5.2 and 5.3 show detailed images of free fibers.

The invention is explained in more detail below by examples.

Examples

example 1

100 g of a mixture consisting of 53 g of methylhydroxyethyl cellulose, 32 g of poly (vinyl alcohol-co-vinyl acetate) and 15 g of calcium carbonate with vigorous stirring (200 rpm) with 25 g of a solvent or an additive dissolved in a solvent were placed in an 11 flat-bottomed flask with anchor stirrer , as explained in Table 1. The solution was added dropwise so slowly that there was no wall wetting or lump formation (Duration approx. 5 to 7 minutes). The mixture obtained was stirred for a further 5 minutes after the addition was complete. The flat-bottomed flask was then immersed in a 50 ° C. water bath and the solvent was removed in vacuo (<5 mbar) while stirring further. The temperature of the mixture was about 30 ° C.

The tendency to dust of the binder agglomerates thus obtained was then determined. 100 g of binder composition were emptied suddenly by inverting a pouring vessel (250 ml beaker) into a 2 l beaker placed against a black background. After the inversion, the time t was determined, which elapsed from the inversion until the dust cloud formed after the inversion fell below the upper edge of the 2 1 beaker. The dustiness was classified as follows:

extremely dusty t> 30 s heavily dusted t> 6 s - 30 s hardly dusted t = 3 - 6 s does not dust t <3 s.

Properties of the binder compositions obtained by various additives according to the above preparation instructions:

Table 1

PEG = polyethylene glycol PVP = polyvinyl pyrrolidone

Comparative investigation of binder compositions according to the prior art and a binder composition according to the invention

In order to investigate the different characteristics of the binder compositions known from the prior art and the binder composition according to the invention, various samples of binder compositions known from the prior art and a binder composition according to the invention were subjected to a microscopic examination. As a comparative example 1, a commercially available product for the production of wallpaper strips, as used for the production of the binder compositions according to the invention, was investigated. As a comparative example 2, a product obtained by spray drying was examined. The results are summarized in Table 2. Table 2

Claims

claims

1. Particulate binder composition, at least containing a natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer, the proportion of particles with a particle diameter of less than 30 microns less than 1 wt .-% and the content of free fibers in 5 mg of the binder composition is at least 40.

2. Binder composition according to claim 1, characterized in that the content of particles with a particle diameter of more than 10 mm is less than 1 wt .-%.

3. Binder composition according to claim 1 or 2, characterized in that it contains an additive from the group of water-soluble ionic or nonionic polymers.

4. Binder composition according to one of claims 1 to 3, characterized in that the bulk volume is more than 88 ml per 50 g of binder composition.

5. A process for producing a low-dust particulate binder composition in which a particulate mixture of at least one natural or synthetic polysaccharide and at least one synthetic water-dispersible polymer is contacted with a solvent, the solvent being chosen such that swelling or solution of the synthetic polymer is carried out within 3 h at 20 ° C.

6. The method according to claim 5, characterized in that the solvent contains at least one linear or branched, saturated or unsaturated alcohol having 1 to 10 carbon atoms.

7. The method according to claim 5 or 6, characterized in that the solvent contains an additive.

8. The method according to any one of claims 5 to 7, characterized in that the solvent contains as an additive a water-soluble ionic or nonionic polymer.

9. The method according to any one of claims 5 to 8, characterized in that the particulate mixture is contacted with the solvent or the mixture of solvent and additive and the solvent is removed after a sufficient contact time.

10. Binder composition, producible according to one of claims 5 to 9.

11. An aqueous solution or dispersion of a binder composition according to claims 1 to 4 or 10 or a binder composition prepared according to claims 5 to 9.

12. Use of a binder composition according to claim 1 to 4 or 10 or a binder composition prepared according to claim 5 to 9 for the preparation of aqueous preparations.