Bulk material comprising a solid diisocyanate and a prepolymer containing urethane groups obtained therefrom.

Abstract

To provide a bulk material, a process for production thereof, a process for preparing isocyanate prepolymers using the bulk material, the isocyanate prepolymers themselves, and the use thereof for preparation of polyurethane elastomers, especially cast polyurethane elastomers, for preparing prepolymers from solid diisocyanates in a simple and inexpensive manner with low by-product formation.SOLUTION: A bulk material contains a solid diisocyanate at room temperature (25°C). In a sieve analysis of the bulk material with a twin-sieve arrangement having mesh sizes 0.1 mm and 4 mm, at least 90 wt.% of the bulk material is obtained in a fraction between 0.1 mm and 4 mm.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to bulk materials containing solid diisocyanates, in particular naphthalene 1,5 - diisocyanate or p - phenylene diisocyanate, to a process for their production, and to a process for the production of isocyanate prepolymers using the bulk materials of the present invention, to the isocyanate prepolymers themselves, and to their use for the production of polyurethane elastomers, in particular cast polyurethane elastomers.

Background Art

[0002] Cast polyurethane elastomers are typically used for the production of foams or solid molded articles. They are typically prepared by the reaction of an isocyanate component with a component having a hydrogen atom reactive towards isocyanate groups. The latter component usually contains polyfunctional alcohols, amines and / or water.

[0003] In principle, there are two possible processes for the production of cast polyurethane elastomers, which differ by the order of addition of the co - reactants. In the so - called one - shot process, the components are weighed or measured by volume and then all mixed together and reacted while being shaped. The drawback here is that the intermediate formed from the short - chain polyol (chain extender) and the isocyanate precipitates partially from the reaction melt and is thus removed from further reaction, which disrupts the further orderly increase in molecular weight, so that only inferior elastomers are obtained, especially when high - melting - point isocyanates are used. A further drawback of the one - shot process is the rapid release of the high heat of reaction, which can often only be removed inadequately. The resulting high temperatures promote side reactions such as isocyanurate formation or carbodiimidization, which further impair the elastomer properties.

[0004] For these reasons, the prepolymerization method is primarily established for the production of cast elastomers, where a long-chain diol component is first reacted with an excess diisocyanate to obtain a liquid NCO prepolymer, which is then reacted with a short-chain diol (e.g., butane-1,4-diol) or an amine (e.g., methylenebis(o-chloroaniline) (MOCA) or diethyltoluenediamine (DETDA) and / or water). This has the advantage that some of the reaction heat is released and removed in advance during prepolymerization, making the reaction in actual polymer formation easier to control. This promotes a more regular increase in molar mass, allowing for longer casting times, which facilitates blister-free filling even with complex shapes.

[0005] The long-chain diol components used are polyether polyols, polycarbonate polyols, preferably polyester polyols, and more preferably polyε-caprolactone polyols. The isocyanate components used in particularly high-quality cast elastomers are high-melting-point diisocyanates such as p-phenylenediisocyanate (PPDI), 3,3-dimethyl-4,4'-biphenyl diisocyanate (TODI), and especially naphthalene 1,5-diisocyanate (NDI).

[0006] In the case of these high-quality cast elastomers, the prepolymer with a suitable NCO content prepared first still contains a certain amount of free, i.e., monomer diisocyanates, which tend to crystallize at low storage temperatures, so the use of the prepolymer method is not problematic, while storage at high temperatures leads to undesirable reactions and associated viscosity increases.

[0007] EP1918315A1 describes a method for producing an NDI prepolymer by mixing a polyol with solid NDI at a temperature of 80–240°C. Here, the temperature is selected so that the solid isocyanate melts during the exothermic reaction. After obtaining a clear, homogeneous molten material, the resulting prepolymer is rapidly cooled.

[0008] WO02081537A1 describes a method for preparing an NDI prepolymer, in which a polyol is first added at 140°C, and then miscible with solid NDI under vigorous stirring.

[0009] DE10060473A1 describes the preparation of prepolymers based on naphthalene 1,4-diisocyanate or, for comparison, naphthalene 1,5-diisocyanate. The polyol is first packed and dehydrated at 120°C and 20 mbar before adding the corresponding diisocyanate with stirring. The reaction mixture is then stirred at 20 mbar and 125-130°C for 15 minutes.

[0010] WO2015185659A1 describes a continuous preparation method for NDI prepolymers, in which a molten diisocyanate and polyol are reacted in a tubular reactor at 80-175°C. This application, like EP1918315A1, also discusses the chemical engineering problems in the dosing of diisocyanate. Therefore, for a controlled reaction with a uniform increase in molecular weight, initial heating is required to allow for rapid melting of the NDI, followed by rapid cooling after reaching the clearing point, to prevent the reaction temperature from clearly exceeding 127°C during the exothermic reaction. While continuous methods can avoid some of the problems associated with batch methods, they remain unestablished to this day due to their inherent lack of flexibility and high chemical engineering complexity.

[0011] In the described batch-style reverse prepolymerization method, i.e., in which the polyol component is first packed and then the isocyanate is added, each reactor having a batch undergoes a change from OH- to NCO- functional content. This results in a more pronounced tendency of the method to variability compared to conventional prepolymerization methods in which this change does not occur. In such a regular prepolymerization method, for example, by gradually metering in the deficient reactant, the latter is always supplied with an excess of reactant, thereby ensuring a very homogeneous reaction. This option of reaction control does not exist in reverse prepolymerization methods in which various excesses are inevitably present. To minimize problems, the change from an OH-dominant regime to an NCO-dominant regime must be carried out as quickly as possible, which means that the excess component, i.e., isocyanate in this case, must be supplied to the reaction very quickly. Nevertheless, as is evident from the prior art, reverse prepolymerization methods have been established as an intermediate step in the production of high-quality cast elastomers. This is particularly due to the use of solid isocyanates. When using conventional prepolymerization methods, these materials must be charged first and melted at high temperatures, and undesirable side reactions of the isocyanate are already underway.

[0012] A simple measure that can be used to assess the extent to which side reactions have occurred in prepolymer formation is the NCO content of the prepolymer, i.e., the mass of isocyanate groups based on the total mass of the prepolymer as a percentage. The stoichiometry of the main reactions of the two components can be used to confirm a theoretical value for the NCO content of the prepolymer, assuming that the reactive component is completely converted to NCO groups present in the deficient state. The further the NCO content of the prepolymer deviates from this theoretical value, i.e., the lower it is, the more frequently the NCO groups are involved in other reactions, such as reactions with urethane groups that give allophanates, uretdiones, isocyanurates, or other isocyanate groups that form 1-nylon, or reactions with urea groups that form biuret. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] EP1918315A1 [Patent Document 2] WO02081537A1 [Patent Document 3] DE10060473A1 [Patent Document 4] WO2015185659A1 [Overview of the project] [Problems that the invention aims to solve]

[0014] The problem addressed by this invention was to produce a prepolymer from solid diisocyanate in a simple and inexpensive manner, while minimizing the generation of by-products. [Means for solving the problem]

[0015] Surprisingly, it was found that NCO prepolymers based on solid diisocyanates can be prepared in a simple and inexpensive manner, with good quality and low levels of by-products, by using a bulk material essentially consisting of solid diisocyanate particles having a particle size between 0.1 mm and 4 mm as the diisocyanate component.

[0016] The present invention provides a bulk material containing or comprising a diisocyanate solid at room temperature (25°C), characterized in that, in sieve analysis of the bulk material in a known style using a twin sieve array having mesh sizes of 0.1 mm and 4 mm, at least 90% by weight, preferably at least 95% by weight, of the bulk material is obtained in fractions of 0.1 mm to 4 mm.

[0017] Sieve analysis is performed according to ASTM 1921-89, with the sieving time reduced to 5 minutes compared to the standard.

[0018] The particles from this sieve fraction are particularly suitable for the preparation of prepolymers by the industrially established reverse batch method. As described above, the equivalence point crosses in the reverse batch method, and it is known that this must be crossed very quickly to avoid the formation of long polymer chains and the resulting increase in viscosity until gelation. However, rapid addition of isocyanate alone is insufficient for this purpose. Instead, it is also necessary to ensure that the isocyanate groups are truly available in the co-reactants by melting, dissolving, and mixing operations. In larger particles, there is already a possibility that isocyanate groups will side-react with each other as the temperature rises in the absence of the desired co-reactants. In contrast, the upper limit of particle size in the bulk material of the present invention results in rapid melting and mixing of the isocyanate in the reaction mixture, and therefore results in rapid achievement of the clearing point and a uniform increase in molecular weight. The lower limit of size is undesirable, firstly for occupational health reasons, and secondly, helps to greatly avoid dust that causes technical problems. The large surface area of ​​dust particles promotes side reactions. For example, a reaction can occur between normally hygroscopic isocyanates and moisture, forming sparingly soluble urea. Complete elimination of air, and therefore air humidity, is practically impossible on an industrial scale and from the standpoint of handling solids. In particular, dust fractions are sometimes difficult to disperse completely in the reaction mixture and are more likely to adhere to surfaces or remain as suspended matter in the gaseous space above the liquid surface for a period of time. This affects the stoichiometry of the reaction and also promotes undesirable side reactions.

[0019] The bulk material is preferably of free-flowing nature. This is understood to mean a bulk material having an angle of repose of ≦55°, preferably ≦50°, measured with Granu Heap (manufactured by Granutools). The reason for the high fluidity of the bulk material of the present invention is essentially the claimed particle size or particle size distribution. Preferably, the bulk material contains 5% by weight or less, preferably 3% by weight or less, more preferably 2% by weight or less of particles obtained in the <0.1 mm fraction in sieve analysis. Such bulk material enables optimal emptying of the transport container and simple pneumatic transport of the bulk material due to its good fluidity.

[0020] Preferably, the bulk material of the present invention is a bulk material containing or consisting of diisocyanate solids at room temperature, and in a sieve analysis of the bulk material in a known manner using a twin-sieve arrangement having mesh sizes of 0.2 mm and 3 mm, at least 90% by weight, preferably at least 95% by weight of the bulk material is obtained in the fraction between 0.2 mm and 3 mm. The term "undersize" is understood to mean particles smaller than that specified by the lower limit of the corresponding fraction. In sieve analysis, it is in a shape that can fall through or be capable of falling through a finer sieve. Correspondingly, the term "oversize" refers to particles larger than that specified by the upper limit of the corresponding fraction. Thus, they remain on the coarser, upper sieve in sieve analysis.

[0021] In the case of an analysis having a mesh size of 0.1 - 4 mm, when 90% by weight of the bulk material is obtained in the 0.1 - 4 mm fraction, or in the case of an analysis having a mesh size of 0.2 - 3 mm, when obtained in the 0.2 - 3 mm fraction, the bulk material preferably contains 5% by weight or less of oversize and 5% by weight or less of undersize.

[0022] [[ID=!1]] In a further preferred embodiment, the bulk material contains ≧98% by weight, preferably ≧99% by weight, more preferably ≧99.5% by weight of solid diisocyanate, based on the total mass of the bulk material. Further components can be, for example, by-products from the production of the diisocyanate, in particular monoisocyanates, solvent residues or chlorinated by-products.

[0023] Suitable solid diisocyanates are diisocyanates which are solid at room temperature, i.e. have a melting point above 25°C. These are, for example, methylene 2,2-diisocyanate, methylene 2,4-diisocyanate, methylene 4,4-diisocyanate, naphthalene 1,4-diisocyanate, naphthalene 1,5-diisocyanate, naphthalene 1,8-diisocyanate, phenylene 1,3-diisocyanate, phenylene 1,4-diisocyanate, isomers of tetralin 2,3-diisocyanate, tetralin 2,4-diisocyanate, tetralin 2,5-diisocyanate, tetralin 3,4-diisocyanate, o-toluidine diisocyanate, durene diisocyanate, benzidine diisocyanate and / or anthrylene 1,4-diisocyanate. Diisocyanates having a melting point of 80°C or higher are particularly preferred. Naphthalene 1,5-diisocyanate or phenylene 1,4-diisocyanate are very particularly preferred.

[0024] The present invention further provides a method for producing bulk materials according to the present invention. For this purpose, diisocyanates are first prepared in known ways by phosgenating the corresponding amine. Phosgene-free methods, such as thermal urethane cleavage, are also possible, but these have not been established on an industrial scale for various reasons for the preparation of solid diisocyanates. One option for high-melting-point diisocyanates, e.g., naphthalene 1,5-diisocyanate or phenylene 1,4-diisocyanate, is suspension phosgenation, as described in WO2014044699. Methods available for separating diisocyanates from solvents and for further purification include methods known to those skilled in the art, e.g., crystallization, sublimation, or distillation, which may optionally involve the addition of seed crystals or azeotropes. In this context, the term "crystallization" is also understood to mean a simple solidification operation. Thus, obtaining a crystalline material is not absolutely necessary; even a precipitate of an amorphous solid, for example, may satisfy the requirements.

[0025] In the first embodiment, a method for producing the bulk material of the present invention comprises a crystallization operation (i) and at least one step (ii) selected from the group consisting of classification, agglomeration, and grinding. Preferably, step (ii) is agglomeration and / or grinding, and more preferably, step (ii) is grinding.

[0026] In a preferred embodiment of this method, the crystallization operation (i) is carried out by crystallizing a molten solid diisocyanate on a cooled surface, preferably on a cooling belt or a rotating drum flaker, more preferably on a rotating drum flaker cooled from the inside, and then scraping it off after solidification.

[0027] The thickness of the crystallized solid diisocyanate layer on the cooled surface can be adjusted here by operating parameters during the crystallization operation, particularly the temperature of the molten material and the cooled surface, as well as the advance rate of the cooled surface. Preferably, the layer thickness is in the range of ≥0.1 mm and ≤4.0 mm, more preferably in the range of ≥0.2 mm and ≤3.0 mm, and most preferably in the range of ≥0.5 mm and ≤2.5 mm. In this way, particles that already have an advantageous degree in one dimension are obtained in later stages, which has a positive effect on the melting properties of the finished bulk material, firstly, and secondly, simplifies further processing to give the bulk material according to the present invention.

[0028] Preferably, the crystallized diisocyanate is removed from the cooled surface using a scraper blade. Here again, it is already possible to influence the particle shape through the positioning and shape of the blade.

[0029] In the crystallization operation (i), only a portion of the particles with the shape and size required for the bulk material according to the present invention are already obtained. Therefore, the method according to the present invention requires at least one further step selected from the group consisting of classification, agglomeration, and grinding.

[0030] In embodiments of the present method in which classification is selected as step (ii), this is preferably carried out by a dry method, i.e., by sieving or by wind sieving, using a gas, preferably nitrogen or air, more preferably nitrogen, as the separation medium. Classification by sieving is preferred. The particles are separated here into various fractions by sieving in a manner known in itself, thereby allowing one or more fractions to be subsequently selected to yield the bulk material according to the present invention. In the sieving process, it is impossible to exclude the fact that some proportion of the particles have a high aspect ratio and are therefore larger by at least one dimension than the mesh size of the sieve used in each case. This is not important for the bulk material of the present invention, since such particles impair the melting and mixing properties in the reverse prepolymerization method only slightly. Excessively large or excessively small particles, i.e., particles not obtained in the sieved fraction according to claim 1, can be recycled back into the method and recrystallized. Alternatively or in addition to this, excessively large particles can be ground in a grinding apparatus.

[0031] In embodiments of the method according to the present invention, where agglomeration is selected as step (ii), this is preferably carried out in a dry form by sintering or molding press. This embodiment is particularly advantageous when a high proportion of primary particles, i.e., particles obtained after the crystallization operation, have a particle size that is too small for use in the bulk material according to the present invention. Alternatively, this embodiment is also advantageous in combination with a sieving or grinding step in which small particles are obtained in a controlled manner and then agglomerated back to a desired size. In this way, it is possible to produce a very limited bulk material. Compression molding, e.g., pelletization or tableting, is preferred, which results in very uniform particles and good fluidity of the bulk material therefrom.

[0032] In a preferred embodiment of the method according to the present invention, in which grinding is selected as step (ii), this is carried out in a grinding apparatus. Preferably, a conventional grinding apparatus designed for dry operation is suitable for this purpose. For example, it is possible to use a grinding apparatus consisting of two or more rotating rolls that together form a roll gap in which the applied particles are ground. It is also possible to use a so-called screw-roll grinder in which the particles are ground by means of a counter-rotating screw. The discharged ground bulk material can be, if necessary, at least partially returned to a grinding apparatus having a smaller grinding gap as necessary to achieve the desired particle size.

[0033] Preferred grinding devices are hammer mills or knife mills. A standard knife mill typically has a cylindrical grinding chamber. Stator blades protrude into this chamber from the outside, while a rotary drum with outward-facing cutting blades rotates within it. A sieve, preferably a perforated screen, is placed around the grinding chamber so that the ground particles leave the chamber, while excessively large particles are retained and further ground. The material to be ground can be introduced into the grinding chamber axially or radially. It is particularly preferable to use a hammer mill as the grinding device. A rotor rotates in the grinding chamber here, and the rotor is equipped with a movable or fixed hammer. The impact of the hammer on the material pieces grinds them, causing them to collide with the grinding wall, where further grinding occurs. As already described for knife mills, here again a sieve, preferably a perforated screen, is placed around the grinding chamber so that particles smaller than the maximum particle size can pass through it and leave the grinding chamber. Since this grinding process only involves the upper particle limit, a dust removal operation by air sieving or sieving of the bulk material is performed thereafter, if necessary.

[0034] In a further preferred embodiment of the present method, any oversized or undersized particles present are at least partially removed in step (iii) by classification from the bulk material obtained in step (iii), the classification being preferably by sieving or air sieving, more preferably by sieving, and the excessively large and / or excessively small particles are at least partially recycled back into the method, i.e., melted or dissolved and subjected again to crystallization operation (i). If step (ii) includes grinding, the excessively large particles may instead be recycled back into a grinding device.

[0035] The present invention further provides the use of the bulk material described above in the preparation of NCO-terminated prepolymers.

[0036] The present invention further provides a method for preparing an NCO-terminated prepolymer comprising the reaction of at least one component (A) containing or consisting of an isocyanate solid at room temperature with at least one isocyanate-reactive component (B), wherein component (A) corresponds to the bulk material described above.

[0037] The isocyanate-reactive component (B) preferably includes a polyol.

[0038] Suitable polyols for the production of prepolymers include, for example, polyols with a number-average molecular weight M of 400 to 8000 g / mol, preferably 600 to 6000 g / mol, and more preferably 1000 to 3000 g / mol. n They have the following properties. Their hydroxyl values ​​are 22-400 mgKOH / g, preferably 30-300 mgKOH / g, more preferably 40-250 mgKOH / g, and they have an OH functional value of 1.5-6, preferably 1.7-3, more preferably 1.9-2.2.

[0039] The polyols for producing the prepolymer are organic polyhydroxyl compounds known in polyurethane technology, such as standard polyester polyols, polyacrylate polyols, polyurethane polyols, polycarbonate polyols, polyether polyols, polyester polyacrylate polyols and polyurethane polyacrylate polyols, polyurethane polyester polyols, polyurethane polyether polyols, polyurethane polycarbonate polyols, polyester polycarbonate polyols, phenol / formaldehyde resins, or these alone or in mixtures. Polyester polyols, polyether polyols, polyacrylate polyols or polycarbonate polyols are preferred, and polyether polyols, polyester polyols and polycarbonate polyols are particularly preferred. The most preferred is polyester polyol.

[0040] Polyether polyols include, for example, polyether polyols obtained by the condensation of polyhydric alcohols or mixtures thereof, and polyether polyols obtained by the alkoxylation of polyhydric alcohols, amines, and amino alcohols. Suitable hydroxy-functional polyethers have an OH functional value of 1.5 to 6.0, preferably 1.7 to 3.0, more preferably 1.9 to 2.2, an OH value of 22 to 400, preferably 30 to 300, more preferably 40 to 250 mg KOH / g, and a molecular weight M of 400 to 8000, preferably 600 to 6000, more preferably 1000 to 3000 g / mol. nThese include, for example, alkoxylation products of hydroxy-functional starting molecules, such as ethylene glycol, propylene glycol, butanediol, hexanediol, trimethylolpropane, glycerol, pentaerythritol, sorbitol, or mixtures thereof, and also mixtures of other hydroxy-functional compounds with ethylene oxide, propylene oxide, or butylene oxide.

[0041] Examples of polyester polyols with good compatibility are known polycondensates of di- and optionally tri- and tetraols, as well as di- and optionally tri- and tetracarboxylic acids or hydroxycarboxylic acids or lactones. Instead of free polycarboxylic acids, it is also possible to use the polycarboxylic acid ester of the corresponding polycarboxylic acid anhydride or the corresponding lower alcohol to prepare the polyester. Examples of suitable diols are ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol, e.g., polyethylene glycol, and propane-1,2-diol, propane-1,3-diol, butane-1,3-diol, butane-1,4-diol, hexane-1,6-diol and its isomers, neopentyl glycol or neopentyl glycol hydroxypivalate, with the latter three compounds being preferred. To achieve a functional value > 2, polyols with a functional value of 3 in proportion may be used, e.g., trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene or trishydroxyethyl isocyanurate. Useful dicarboxylic acids include, for example, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, 2-methylsuccinic acid, 3,3-diethylglutaric acid, and 2,2-dimethylsuccinic acid. The anhydrides of these acids can also be used if they are present. Therefore, for the purposes of this invention, anhydrides are covered by the expression "acid". Monocarboxylic acids such as benzoic acid and hexanecarboxylic acid can also be used if the average functional value of the polyol is ≥ 2. Saturated aliphatic or aromatic acids such as adipic acid or isophthalic acid are preferred. Herein, an example of a polycarboxylic acid for optional additional use in smaller amounts is trimellitic acid.Examples of hydroxycarboxylic acids that can be used as co-reactants in the production of polyester polyols having terminal hydroxyl groups include hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid, and hydroxystearic acid. Usable lactones include ε-caprolactone, butyrolactone, and its congeners. Polyester polyols based on butanediol and / or neopentyl glycol and / or hexanediol and / or ethylene glycol and / or diethylene glycol and adipic acid and / or phthalic acid and / or isophthalic acid are preferred. Polyester polyols based on butanediol and / or neopentyl glycol and / or hexanediol and adipic acid and / or phthalic acid are particularly preferred. Linear polyester diols based on ε-caprolactone are also particularly preferred.

[0042] Useful polycarbonate polyols can be obtained by the reaction of diols with carbonate derivatives, such as diphenyl carbonate, dimethyl carbonate, or phosgene. Examples of useful diols of this type include ethylene glycol, propane-1,2- and 1,3-diols, butane-1,3- and 1,4-diols, hexane-1,6-diol, octane-1,8-diol, neopentyl glycol, 1,4-bishydroxymethylcyclohexane, 2-methylpropane-1,3-diol, 2,2,4-trimethylpentane-1,3-diol, dipropylene glycol, polypropylene glycol, dibutylene glycol, polybutylene glycol, bisphenol A, tetrabromobisphenol A, and lactone-modified diols. Preferably, the diol component contains 40% to 100% by weight of hexane-1,6-diol and / or hexanediol derivatives, preferably those having not only terminal OH groups but also ether or ester groups, for example, a product obtained by the reaction of 1 mole of hexanediol with at least 1 mole, preferably 1 to 2 moles, of ε-caprolactone, or a product obtained by the etherification of hexanediol with itself to give a di or trihexylene glycol. Polyether polycarbonate polyols can also be used. Dimethyl carbonate and hexanediol and / or butanediol and / or ε-caprolactone-based polycarbonate polyols are preferred. Dimethyl carbonate and hexanediol and / or ε-caprolactone-based polycarbonate polyols are particularly preferred.

[0043] Suitable polyacrylate polyols can be obtained, for example, by free radical polymerization of olefinic unsaturated monomers having a hydroxyl group, or by free radical copolymerization of olefinic unsaturated monomers having a hydroxyl group with optionally different olefinic unsaturated monomers, such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, styrene, acrylic acid, acrylonitrile, and / or methacrylonitrile. Suitable olefinic unsaturated monomers having a hydroxyl group are particularly 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, a mixture of hydroxypropyl acrylate isomers that can be obtained by the addition of propylene oxide to acrylic acid, and a mixture of hydroxypropyl methacrylate isomers that can be obtained by the addition of propylene oxide to methacrylic acid. Suitable free radical initiators are azo compounds, such as azobis(isobutyronitrile), or peroxides, such as di-tert-butyl peroxides.

[0044] The polyols described can be used individually or in mixtures.

[0045] The isocyanate-reactive compound of component (B) is reacted with one or more isocyanates of component (A) to obtain an NCO-terminated prepolymer containing urethane groups using an excess of isocyanate groups compared to the isocyanate-reactive groups. The quantitative ratio here is such that the isocyanate component is in excess, with the calculated (theoretical) NCO content being preferably in the range of 2.5% to 6.0%, and more preferably 3.0% to 5.0%.

[0046] Additives may be used further in the preparation of the prepolymer. Suitable additives include catalysts, emulsifiers, UV and hydrolysis stabilizers, and preferably stabilizers commonly used in polyurethane chemistry. An overview can be found, for example, in "Kunststoff Handbuch [Plastics Handbook] vol.7, ed. G. Oertel, 1983, Carl Hanser Verlag, Munich, Vienna".

[0047] Examples of catalysts include trialkylamines, diazabicyclooctane, dibutyltin dilaurate, N-alkylmorpholine, lead octanoate, zinc octanoate, calcium octanoate and magnesium octanoate, as well as their corresponding naphthenates and p-nitrophenoxides.

[0048] Suitable UV and hydrolysis stabilizers include 2,6-di-tert-butyl-4-methylphenol and carbodiimide.

[0049] Examples of suitable stabilizers include Brønsted acids and Lewis acids, such as hydrochloric acid, benzoyl chloride, dibutyl phosphate, adipic acid, malic acid, succinic acid, pyruvic acid, and citric acid, as well as alkyl- and aryl sulfonic acids, such as p-toluenesulfonic acid, and preferably dodecylbenzenesulfonic acid.

[0050] This method is preferably a reverse prepolymerization method in which the isocyanate reactive component (B) is first filled and the isocyanate component (A) is metered and supplied, as already described above. The isocyanate reactive component (B) is first filled in liquid form, i.e., a solution or melt, while component (B) is added to and mixed with the polyol component in bulk material form, i.e., solid form, preferably with stirring. This causes the bulk material to melt and react with the polyol component. The reaction temperature here is preferably in the range of 80 to 160°C, more preferably in the range of 100 to 150°C.

[0051] More preferably, the NCO-terminated prepolymer is prepared in a batch manner using a reverse prepolymerization method.

[0052] The NCO prepolymer prepared by the method of the present invention has an NCO content of 2.5% to 6.0%, preferably 3.0% to 5.0%, and a viscosity of 1000 to 12000 mPas / 70°C, preferably 2000 to 10000 mPas / 70°C, relative to DIN EN ISO 3219, and can be advantageously used in the production of solid or cellular elastomers. [Examples]

[0053] Examples raw materials: CAPA TM 2161A: A polyε-caprolactone diol from PERSTORP having a molecular weight of 1600 Da and an OH functional value of 2 (OH value of 70 mg KOH / g).

[0054] The theoretical NCO content of each prepolymer listed below was 4.07%.

[0055] Example 1 (Non-inventive, particles are too small): First, a representative sample of bulk material containing 99.7% by weight of naphthalene 1,5-diisocyanate was classified using a twin-sieve array (mesh diameter 4 mm, 0.1 mm square mesh), and the resulting fraction was divided into three parts, with their weight ratios determined. The fraction between 0.1 mm and 4 mm accounted for 88% by weight of the total mass of the bulk material, the fraction greater than 4 mm accounted for 1% by weight, and the fraction less than 0.1 mm accounted for 11% by weight.

[0056] First, put 100g of CAPA into a glass flask. TM2161A was charged under a nitrogen atmosphere and heated to 125°C by oil bath. Next, 25.94 g of bulk material, which had been previously analyzed by sieving, was added while stirring. The reaction mixture reached a maximum temperature of 135°C during the exothermic reaction. After 30 minutes, the still cloudy mixture was rapidly cooled. The NCO content of the obtained prepolymer was 3.82%.

[0057] Example 2 (Invention): First, a representative sample of bulk material containing 99.7% by weight of naphthalene 1,5-diisocyanate was classified using a twin-sieve array (mesh diameter 4 mm, 0.1 mm square mesh), and the resulting fraction was divided into three parts. The fraction between 0.1 mm and 4 mm accounted for 96.6% by weight of the total mass of the bulk material, the fraction greater than 4 mm accounted for 1% by weight, and the fraction less than 0.1 mm accounted for 2.4% by weight.

[0058] First, put 100g of CAPA into a glass flask. TM 2161A was charged under a nitrogen atmosphere and heated to 125°C by oil bath. Next, 25.94 g of bulk material, which had been previously analyzed by sieving, was added while stirring. The reaction mixture reached a maximum temperature of 134°C during the exothermic reaction, and the reaction mixture became completely clear. After 30 minutes, the solution was rapidly cooled. The NCO content of the obtained prepolymer was 3.90%.

[0059] Example 3 (Non-inventive, 10% oversized particles): First, a representative sample of bulk material containing 99.7% by weight of naphthalene 1,5-diisocyanate was classified using a twin-sieve array (mesh diameter 4 mm, 0.1 mm square mesh), and the resulting fraction was divided into three parts. The fraction between 0.1 mm and 4 mm accounted for 88% by weight of the total mass of the bulk material, the fraction greater than 4 mm accounted for 10% by weight, and the fraction less than 0.1 mm accounted for 2% by weight.

[0060] First, put 100g of CAPA into a glass flask. TM2161A was charged under a nitrogen atmosphere and heated to 125°C by oil bath. Next, 25.94 g of bulk material, previously analyzed by sieving, was added while stirring. The reaction mixture reached a maximum temperature of 134°C during the exothermic reaction. After 30 minutes, the reaction mixture still contained solid flakes and was rapidly cooled. The NCO content of the prepolymer was 3.79%.

[0061] Example 4 (Invention): The fractions ranging from 0.2 mm to 3 mm were isolated from a bulk material containing 99.7% by weight of naphthalene 1,5-diisocyanate by classification using a twin-sieve array (square mesh with mesh diameters of 3 mm and 0.2 mm), yielding a bulk material in which over 99% of the particles belonged to this fraction. Using this, a prepolymer was prepared as in Example 2. The NCO content of the obtained prepolymer was 3.91%.

Claims

1. A method for producing a bulk material comprising a crystallization operation (i) and at least one step (ii) selected from the group consisting of classification, agglomeration, and grinding, wherein step (ii) is characterized in that the crystallized diisocyanate is ground in a grinding apparatus, the bulk material contains diisocyanate which is solid at room temperature (25°C), and in sieve analysis of the bulk material using a twin sieve configuration having mesh sizes of 0.1 mm and 4 mm, at least 90% by weight of the bulk material is obtained in fractions between 0.1 mm and 4 mm, and the sieve analysis is performed in accordance with ASTM 1921-89.

2. The method according to claim 1, characterized in that, in the crystallization operation (i), the molten diisocyanate, which is a solid, is crystallized on a low-temperature surface and scraped off after solidification.

3. The method according to claim 1 or 2, characterized in that oversized and undersized particles are at least partially separated from the bulk material obtained in step (ii) by classification in step (iii), the classification being performed by sieving or air sieving, and excessively large and / or excessively small particles are at least partially recycled back into the method.