Caking-resistant neopentyl glycol press-processed product and method for producing the caking-resistant neopentyl glycol press-processed product

Abstract

The present invention relates to a method for producing a neopentyl glycol pressed product, the method comprising at least the following process steps: a) providing bulk material of NPG flakes; b) compressing the bulk material in a mold to form a pressed part, the compression being performed at a pressure of 0.5 MPa or more and 7.5 MPa or less; The present invention further relates to an NPG pressed product.

Description

[Technical field]

[0001] The present invention relates to a method for producing a neopentyl glycol pressed product, the method comprising at least the following process steps: a) providing bulk material of NPG flakes; b) compressing the bulk material in a mold to form a pressed part, the compression being performed at a pressure of 0.5 MPa or more and 7.5 MPa or less; The present invention further relates to an NPG pressed product. [Background technology]

[0002] Neopentyl glycol (NPG, 2,2-dimethylpropane-1,3-diol) is an important diol used in large quantities, for example, for the production of polyesters and polyurethanes. The industrial production of NPG usually starts from isobutyraldehyde, which is reacted with formaldehyde and then the reaction product is catalytically hydrogenated. NPG is a hygroscopic, crystalline compound with a melting point of about 129°C. For reasons of cost and feasibility, the diol is provided in the form of relatively small flakes, which are produced by solidifying the NPG melt using a crystallization or cooling belt and then crushing into individual, more or less irregular platelets. The NPG flakes are then prepared and shipped in big bags of 250 kg or more or as individual bags of 25 kg or more. Due to the hygroscopic nature and complex thermodynamic phase properties of NPG, the flakes may solidify over time into larger aggregates, depending on the specific storage and transport conditions present. Irregular agglomerations may lead to the formation of very large and compact NPG agglomerates, which may reduce the free-flowing properties of the product to the point of complete loss. This effect extends to the point where the entire contents of the sack are caked up in volumetric quantities, so that it is no longer possible to efficiently empty the sack for further processing. In order to use the product in standard manufacturing processes, a laborious and costly manual crushing is required before further processing to make the product free-flowing again. This unfavorable situation leads to major bottlenecks in the production process and is generally a source of complaints to the manufacturers.

[0003] Various approaches for tailoring and for improving the caking or packaging problems of NPGs can also be found in the patent literature.

[0004] For example, US 4,435,603A (Patent Document 1) teaches the addition of tertiary amines as caking inhibitors at a concentration of 0.25 to 0.5% by weight in the production of polyol flakes, particularly neopentyl glycol flakes. However, experience has shown that the addition of such caking inhibitors does not reliably prevent the occurrence of material caking, coarse lumps or agglomerates, and large-volume product caking, especially during storage of palletized bags or large bags.

[0005] For example, DE 3522359 A1 describes a process for preparing crystalline organic materials under standard conditions, in which the materials are processed in the powder and / or molten state in a self-cleaning twin-screw machine with screw shafts rotating in the same direction, forced through at least one narrow passage, discharged into a low pressure area, cooled and crushed into particles, characterized in that the materials are heated as they are discharged through the narrow passage to form a molten film.

[0006] Furthermore, EP0829298A2 (Patent Document 3) discloses a method for producing hydroxypivalic acid neopentyl glycol ester granules by applying a hydroxypivalic acid neopentyl glycol ester melt onto a cooling surface and solidifying the melt on the cooling surface, characterized in that the melt contains at least 3% by weight of hydroxypivalic acid neopentyl glycol ester crystals based on the total amount of hydroxypivalic acid neopentyl glycol ester.

[0007] EP1268378B1 also discloses a method for tailoring neopentyl glycol by cooling, crystallizing and grinding the neopentyl glycol melt and then packaging the neopentyl glycol particles thus obtained in a storage or transport container, in which at the start of cooling the melt is cooled for at least 1 / 10 minutes at a temperature ranging from 50 to 120°C without or with a coolant and packaged at a temperature below 30°C.

[0008] Such solutions known from the prior art may offer the possibility of further improvement, in particular with regard to the purest possible NPG shaped bodies which have a low tendency to caking even under unfavourable storage conditions. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US4,435,603A [Patent Document 2] DE3522359A1 [Patent Document 3] EP0829298A2 [Patent Document 4] EP1268378B1 Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present invention to provide an improved process for obtaining caking-resistant NPG shaped bodies in the form of pressed articles, as well as an improved dosage form of NPG which has a reduced tendency to agglomerate during storage. [Means for solving the problem]

[0011] The solution to this problem is achieved by the features of the independent claims, which relate to the method according to the invention and to the pressed product according to the invention. Preferred embodiments of the invention are recited in the dependent claims, the description and the drawings, whereby further features recited or implied in the dependent claims, the description or the drawings may, individually or in any combination, constitute the subject matter of the invention, unless the context clearly indicates otherwise.

[0012] According to the invention, the problem is solved by a method for producing neopentyl glycol pressed products, which comprises at least the following process steps: a) providing a bulk material of NPG flakes; and b) compressing said bulk material in a mould to form pressed products, said compressing being carried out at a pressure of 0.5 MPa or more and 7.5 MPa or less. Surprisingly, it has been found that the method according to the invention makes it possible to obtain a large number of different mechanically stable NPG pressed products which, compared to NPG flakes, have a significantly reduced tendency to form relatively large agglomerates during storage or transport. Besides a relatively low caking formation under various environmental conditions, pressed products which can be produced using the method furthermore have a relatively low tendency to sublimation and, particularly surprisingly, only slightly limited disintegrability in various solvents in large-scale processing. Without being bound by theory, the use of NPG flakes in mechanical pressing processes using relatively low pressures results in synergistic advantages from high mechanical strength, low sublimation tendency, relatively low caking tendency with relatively good disintegration ability, resulting in moldings that are mechanically very stable, but still can be easily disintegrated by solvents into their constituent parts. Due to the size distribution of the flakes and their irregular shape, the use of flakes seems to trap a probably correct amount of voids in the pressed product during pressing within a defined pressure range, which has only a slight effect on the mechanical strength of the pressed product, whereas it has a very favorable effect on the disintegration rate. A higher pressure range during pressing significantly reduces the disintegration rate in the solvent, while only slightly increasing the mechanical strength. The latter is probably due to an excessive increase in the density of the pressed product, which makes it difficult for the solvent to penetrate into the pressed product. Lower pressing pressures may make the mechanical strength of the pressed product insufficient for normal storage and transportation conditions. In addition, the pressing process proposed according to the invention does not change or restrict the desired NPG crystal structure, so that no or only very little thermal changes occur during the pressing process and the subsequent storage process, which is even more surprising as it does not change the basic properties of the pressed product.This offers a clear advantage over other solutions proposed in the prior art, since the temperature control of the pressing process can be more easily maintained. Finally, it is particularly advantageous that these property improvements can be achieved without adding further substances to the NPG pressed product. The latter solution is particularly disadvantageous, since these further substances either have to be removed laboriously in further steps of the process, or their properties have to be taken into account within the framework of the formulation of the further secondary products, or may have a detrimental effect on the quality of the secondary products produced therefrom.

[0013] The method according to the invention is a method for producing a neopentyl glycol pressed product, the pressed product being a shaped product obtained by compressing a material in a press mold, the pressed product being characterized by a regular shape resulting from the geometry of the press mold used. For example, spheres, cuboids or briquettes can be produced in various designs and sizes by the selection of the press mold. The pressed products are formed into essentially the same shape, so that, for example, different pressed products differ in their weight by less than 25% by weight, preferably less than 15% by weight, more preferably less than 10% by weight. The pressed product is a neopentyl glycol pressed product when it is composed of more than 90% by weight, even more preferably more than 95% by weight and more preferably more than 97% by weight of NPG. The method can be carried out using a conventional press in the form of an extruder press or roller press or in a press chamber method.

[0014] The method comprises a process step a) in which a bulk material of NPG flakes is provided. The NPG pressed product is produced from the bulk material of NPG flakes. The bulk material is a statistical distribution of randomly crushed NPG particles. The NPG flakes have a thickness and a size distribution that depends on the production method. Besides macroscopic flakes, NPG particles in the form of granules or NPG dust can also be present in the bulk material. The proportion of dust in the NPG bulk material also depends on the production method. Quantitatively, flakes in the form of flat platelets with randomly crushed edges are mainly present in the bulk material. The size distribution of the NPG flakes can be determined via mechanical action on the solidified NPG on the cooling belt. The composition of the NPG flakes can be freely selected in a certain proportion. Preferably, the NPG bulk material can consist of pure NPG. However, the bulk material can also comprise other substances as further constituents. Preferably, the weight percentage of NPG in the bulk material is 80% or more, more preferably 90% or more, and even more preferably 95% or more.

[0015] The method comprises a process step b) of compressing the bulk material in a mould to form a pressed product. In the present invention, said compression is carried out at a pressure of 0.5 MPa or more and 7.5 MPa or less. The bulk material of NPG flakes, filled in one or more press moulds, is subjected to the above pressure range by bringing both halves of the press mould into contact. This step can be carried out, for example, by manual pressing or continuously by a rotary press tool. The pressing step can optionally be carried out in a conditioned environment. However, it is not necessary to precondition the ambient air or temperature accordingly. Advantageously, the pressing step can be carried out at room temperature. However, it is also possible, for example, to precondition the press tool to a defined temperature range, for example between 10° C. and 40° C. or less. The duration for pressing the individual moulds can be different. For example, the bulk material of NPG flakes can be held in the press tool for 1 second or more, more preferably 2 seconds or more, more preferably 5 seconds or more. In this case, the application of a pressing pressure for a longer period is not necessary. In addition to the individual pressed parts, links between the individual pressed parts can also be formed in the press, which are formed by depositing material from the bulk material between the individual pressed parts. Such additional material does not constitute a pressed part in the sense of the present invention and can be sheared or sieved, for example, by slight mechanical pressure, before the pressed part is further processed.

[0016] In one preferred embodiment of the method, the NPG flakes have a density of 0.5 g / cm 3 That's 0.6g / cm 3It can have a bulk density of 0.1 to 0.5 MPa. In order to form a particularly mechanically stable and particularly well-disintegrable pressed part, it has been found to be particularly advantageous for the bulk density of the NPG bulk material to be in the above range. Without being bound by theory, it appears that in particular the bulk density is also decisive for a favorable porosity of the pressed part. Smaller bulk densities can be disadvantageous in these cases, since the mechanical strength of the pressed part may be insufficient. On the other hand, larger bulk densities can be disadvantageous in these cases, since the disintegration rate of the pressed part is excessively reduced. The measurement of the bulk density can be carried out, for example, according to DIN ISO 697 or DIN ISO 60.

[0017] In yet another preferred embodiment of the method, the NPG flakes can have a fine fraction of 6 mm or less, determined by sieving, of 80% by weight or more and 90% by weight or less. In addition, it has been found to be advantageous for the mechanical properties of the pressed product if the NPG flakes of the NPG bulk material used meet a defined size distribution. In particular, a larger proportion of small flakes, here designated as a fine fraction with a size of less than 6 mm, allows both the mechanical strength and the disintegration force of the pressed product to be improved.

[0018] In yet another preferred aspect of the method, the NPG flakes may have a thickness of 0.75 mm or more and 5 mm or less. In addition to the lateral dimensions of the NPG flakes, their thickness also has an influence on the achievable strength and achievable disintegration rate of the NPG pressed product. In this case, the thickness of the flakes may be advantageously determined by the height of the NPG melt on the cooling belt used in the production. Smaller thicknesses of the NPG flakes may be disadvantageous, since in these cases the mechanical strength of the resulting pressed product may be reduced. Larger thicknesses may be disadvantageous, since in these cases as well, adverse mechanical properties of the pressed product may be obtained. Without being bound by theory, this relationship may possibly be due to the fact that the individual flakes are more able to resist deformation in the press, and therefore a reduced interaction between the individual flakes is induced by the pressing process. The thickness of the NPG flakes may be determined, for example, by a vernier caliper. To obtain statistically reliable values ​​for bulk material, for example, 50 selected flakes can be measured. Furthermore, the thickness of the flakes can advantageously be ≧1 mm and ≦4 mm, more preferably ≧1.5 mm and ≦3 mm.

[0019] According to one of the preferred features of the method, the NPG flakes can have a D50 quantile of 2 mm or more and 8 mm or less, as determined by sieving. It has been found that NPG flakes with said quantiles are particularly suitable for producing pressed products that are particularly mechanically stable and disintegrate quickly. This size range of NPG flakes, which contains a high proportion of significantly smaller particles, together with relatively low pressing pressures and relatively short pressing times, can result in a particularly suitable interaction between the individual pressed particles. A very uniform pressed product is formed, which disintegrates well in a relatively short time when contacted with a solvent.

[0020] In yet another preferred embodiment of the method, the NPG flakes can have a D95 quantile, determined by sieving, of 7.5 mm or more and 10 mm or less. The use of NPG flakes with a relatively small proportion of flakes above 10 mm also allows for particularly uniform pressed products to be obtained, characterized by a low proportion of broken pieces even under relatively strong mechanical loads.

[0021] In yet another preferred embodiment of the method, the compression can be carried out at a pressure of ≧1.0 MPa and ≦4 MPa. It has been found that the above pressures are particularly suitable for obtaining a pressed part that is as homogeneous and mechanically stable as possible. In particular, in the range of relatively low pressures, sufficient stability and very rapid collapse behavior of the pressed part can be achieved.

[0022] In a further variant of the method, process step b) can be carried out in a temperature range from 5° C. to 40° C. The above-mentioned temperature range has been found to be particularly suitable for obtaining particularly uniform pressed products and for preventing caking in the press mould. Higher temperatures can be disadvantageous, since in these ranges undesirable thermodynamic phase transitions of NPG can be induced. Furthermore, higher temperatures in the method can lead to unintentional adhesion of the production material to the walls of the press during continuous production, which is not removed by itself from the mould during the pressing process. Lower temperatures in the press can be disadvantageous, since in these cases, due to the lower pressing pressure, the individual particles are only insufficiently pressed against each other.

[0023] In yet another preferred embodiment of the method, the NPG flakes can have a moisture content of 0.05% by weight or more and 3% by weight or less. It has been found to be particularly advantageous for the NPG flakes to have a defined moisture content in order to produce particularly uniform pressed products. Besides the influence on the mechanical properties, the moisture content of the bulk material can also affect the productivity of the pressed products. For example, mechanical pressing moulds may have to be cleaned more frequently, especially if the moisture content is too high. The moisture content of the NPG flakes can be determined by known methods, for example by the Karl Fischer method.

[0024] Furthermore, in the present invention, one of the NPG pressed products has a hardness of 0.9 g / cm 3 That's 1.02g / cm 3 The density of the pressed product is as follows: 0.05 to 0.05 mm. By using the method of the present invention, starting from the NPG used and starting from the use of NPG as flakes, pressed products with a very narrow range of specific densities can be obtained. Within this very narrow NPG density range, mechanically very stable pressed products are produced, which have a very low tendency to caking even under adverse storage conditions. In addition to the improved mechanical properties and low tendency to sublimation of the pressed product itself, the pressed product still shows good solubility in usual solvents for NPG, such as water. This good solubility compared to NPG flakes is surprising, since the pressed product has a significantly smaller surface area compared to NPG flakes. In this regard, based on the difference in surface area, the skilled person would expect the disintegration rate of the NPG pressed product to be significantly reduced. The density of the pressed product can be determined by methods known to the skilled person, for example by measuring the volume and weight of the pressed product.

[0025] In one preferred feature of the NPG pressing, the pressing is 2.5 cm 3 More than 15cm 3The pressings can have the following volumes: 1000 x 1000 x 1000 mm; ...

[0026] In yet another preferred embodiment of the NPG pressed product, the pressed product has a hardness of 0.95 g / cm 3 That's 1.05g / cm 3 The density of the resulting NPG pressed product can be determined by the bulk density of the NPG flakes and the pressing pressure applied during production. These parameters make it possible to obtain pressed products having densities in the above-mentioned ranges in particular. This very narrow range of material densities for the NPG pressed products makes it possible in particular to obtain mechanically very stable pressed products, which show particularly rapid disintegration in suitable solvents. In addition, this density range makes it possible to obtain the final mechanical strength of the pressed product already after a relatively short time.

[0027] In one preferred aspect of the NPG pressed product, the pressed product is 0.4 mm 2 / kg or more: 0.6m 2 The surface area: mass ratio can be less than 0.015 g / kg. It has been found that the use of press moulds with basic geometries with the above surface area: mass ratios is particularly suitable for NPG pressed products. These geometries have only a small degree of mass loss (sublimation) during storage, only a small degree of wear of the individual pressed products even under strong mechanical loads, and these geometries can also be processed with standard equipment in an industrial environment. The surface area: mass ratio can be determined by weighing and determining the size of the pressed products, for example with a vernier caliper.

[0028] In yet another preferred embodiment of the NPG pressed product, the pressed product can have an NPG content of 98% by weight or more. Surprisingly, it has been shown that mechanically stable shaped bodies can be obtained that have a very low tendency to caking during storage or transportation without the addition of further substances, for example in the form of disintegrants or anti-caking agents. In this regard, it is particularly noteworthy that the further processing of the NPG can be carried out without taking into account the presence of further substances. In particular, the pressed product according to the invention is almost free of further substances. For example, the proportion of NPG in the pressed product can be 98.5% by weight or more, more preferably 99.5% by weight or more, more preferably 99.9% by weight or more. Particularly preferably, the pressed product can be composed of 100% NPG. The proportion by weight of NPG in the pressed product can be quantitatively determined, for example, by HPLC analysis, ignoring the water content.

[0029] In yet another embodiment of the NPG pressed product, the pressed product can have a compression strength of 80 N or more and 400 N or less. The pressed product according to the invention is characterized by a relatively high breaking strength, which can be obtained, surprisingly, only by using a relatively low pressing pressure during production. In order to obtain consistent values, the breaking strength of the individual pressed products is determined after 24 hours of production and storage at room temperature. During this period, the pressed products themselves can further post-harden and develop a higher breaking strength. The compression strength is determined using an Ericson compression strength tester (model 469E4). The upper and lower plates each have a diameter of 80 mm. The diameter of the measuring body is 10 mm (horizontal) and the speed of the measuring body is 8 mm / min.

[0030] In yet another preferred embodiment of the NPG pressed product, the NPG pressed product can have a rectangular geometry. It has been found that for handling in industrial packaging and transport processes, it is particularly suitable for the pressed product to have a rectangular geometry. This geometry can contribute to a particularly low tendency to caking and a particularly low amount of wear, even under strong mechanical loads during transport. In this case, the pressed product can have a precise rectangular geometry or can also have a geometry that resembles a rectangular geometry. In the context of this definition, briquettes in the usual sense are understood as well as egg-shaped lump coal or egg-shaped briquettes having a rectangular basic geometry with rounded edges. The rectangular geometry can also be a cube. In addition to the basic geometry, the pressed product can also have (for example surrounding) press seams and other features, such as logos or similar on the surface.

[0031] In yet another preferred aspect of the NPG pressed product, the average ratio of the length and width of the rectangular pressed product to the height, calculated by dividing the length + width) / 2 by the height, can be 1.25 or more and 3.5 or less. This height and width ratio of the rectangular pressed product has been found to be particularly suitable, based on the fact that the pressed products are not stacked in an orderly manner in industrial production, but are provided as random bulk materials in sachets or bags. This aspect ratio of the pressed product can result in only a small amount of fracture occurring in the bulk pressed product even under adverse storage conditions and high mechanical loads. In addition, due to the above-mentioned asymmetry of the rectangular pressed product, a suitable disintegration rate of the pressed product in common solvents can also be achieved.

[0032] Furthermore, in the present invention, one of the bulk materials made of caking-resistant neopentyl glycol pressed products is one in which the proportion of fine particles smaller than 1 mm in the bulk material is less than 10%. These bulk materials can be characterized by an exceptionally low proportion of caking even under adverse storage and transportation conditions. EXAMPLES

[0033] To produce the NPG pressed products, bulk material consisting of NPG flakes is compressed in a roller press into various sizes of pressed products in the form of NPG briquettes. These NPG flakes consist of 100% NPG (neglecting the moisture content). No additional anti-caking, binding or disintegrating agents are added to the NPG flakes or to the NPG itself. The flakes were examined by sieve analysis using the following size classes (expressed in mm): >20, 20-10; 10-8; 8-6.3; 6.3-5; 5-4; 4-3.15; 3.15-2; 2-1; 1-0.5; 0.5-0.25; 0.25-0.125 and 0.125-0 mm. A D50 quantile of 3.45 mm and a D95 quantile of 8.7 mm result. The density of the NPG bulk material is 0.525 g / cm 3 It is.

[0034] Two different briquette sizes are produced, where the basic geometry of the press mould corresponds to the basic shape of the egg-shaped lump charcoal briquette. The dimensions of the briquettes are as follows:

[0035] [Table 1] The pressing is carried out at a pressing pressure of 1 MPa for both sizes respectively. The briquettes are then sieved for the separation of the fine fraction (particles smaller than 6.3 mm). The yield of the pressing process without the fine fraction is more than 90%. The briquettes are stored for 24 hours at room temperature and a relative air humidity of 85%. Under these storage conditions, no change in the briquette mass due to moisture absorption behavior was observed. The compressive strength of the pressed products improves significantly after 24 hours of storage. Immediately after pressing, as determined by compressive strength measurements, the compressive strength (measured with a machine type 469 ERICHSEN, "Compression Strength of Briquettes") is >100 N. After 24 hours of storage under the above conditions, the compressive strength can be improved once more. Typical compressive strength values ​​after storage are 109 N for the smaller briquettes and 155 N for the larger briquettes. The briquettes also pass a drop test from a height of 2 m. After two tests of unstored briquettes, approximately 90% intact briquettes were observed for both briquette sizes. These drop test results also improved after 24 hours of storage of freshly produced pressings.

[0036] For the determination of the mass loss of the pressed products due to sublimation during storage, the briquettes are placed in a fume hood and the mass loss is followed over a period of 49 days. These briquettes show a linear sublimation behavior, where the mass loss after 49 days is approximately 10 cm 3 For pressed products, the figure is about 10%, and for 5cm 3 In comparison, the mass loss of the NPG flakes is about 18% under the above conditions.

[0037] Furthermore, the pressed parts are tested for moisture absorption in a desiccator at defined air humidity. For this, the briquettes are placed in open petri dishes in desiccators containing various saturated salt solutions. A saturated NaCl solution provides a relative humidity of 74%, while a relatively low air humidity of 11% is achieved by using a saturated LiCl solution. The weight and moisture content of the pressed parts are recorded after two weeks. No significant increase in the moisture content or mass loss of the pressed parts can be observed upon storage at a relative air humidity of 11%. When stored at 74% air humidity, a moisture content of 1.3% (10 cm 3 briquettes) or 1.6% moisture content (5cm 3 The pressed products therefore show a significantly lower moisture absorption compared to the NPG flakes.

[0038] In addition, storage tests were performed on the pressed products under pressure. For this, glass cylinders (15.3 cm diameter) were used with an autoclave insert as a weight (14.3 kg) with the appropriate Teflon disk between them. This setup had a total of 78 g / cm 2 , which corresponds approximately to the pressure prevailing in the bottom bag of a stack or in the lower area of ​​a large bag. The test is carried out at room temperature with a bulk height of 10 cm, respectively. A clear difference in the storage behavior of the pressed products compared to the NPG flakes can be observed. In the case of the pressed products, only a very small part of the material on the surface caking occurs after one week of storage. The NPG flakes show a clearly higher proportion of caking and agglomeration under these conditions. The adhered briquettes can be separated from each other again very easily using a small force. After 4 weeks of storage, a similar picture results for the pressed products compared to the NPG flakes. The degree of adhesion increases for both the NPG flakes and the pressed products, but the proportion of caked material is still more evident in the case of the flakes. In addition, the adhered pressed products can be easily peeled off from each other with only a small force. The adhered NPG flakes cannot be completely peeled off from each other even with a stronger force.

[0039] For the comparison of the disintegration behavior between NPG flakes and NPG pressed products, a 25% by weight solution of NPG in water, respectively, is prepared under stirring. The disintegration behavior of the briquettes is surprisingly practically independent of the size of the pressed product used. The disintegration rate of the pressed products is 5 cm 3 For pressed products, it takes about 12:20 minutes or 10 cm 3 The NPG flakes disintegrate in about 2:53 minutes under the same test conditions. Considering the difference in surface area available for disintegration of the flakes and the pressed product, the surface area of ​​the flakes can be estimated to be at least 10 times greater than that of the pressed product. The surface area of ​​the flakes can be approximated by assuming a cylindrical particle with the height of the flake used and a diameter corresponding to the D50 quantile of the flakes. This approach does not take into account a significant proportion of very small fragments in the flakes and results in a very conservative estimate of the surface area of ​​the flakes. The pressed product is 4 to 5 times less soluble than the flakes, with the difference in the factor of available surface area being in both cases higher than 10. Therefore, the pressed product can dissolve much better than expected. Without being bound by theory, this is due to the specific density of the pressed product, which indicates that there are no compacted NPG pressed products. The pressed product also contains a significant proportion of pores and air in the pressed product due to the use of NPG flakes and the application of only low press pressure, which appears to facilitate solvent infiltration and diffusion and thus disintegration.

[0040] Some typical parameters of the pressings according to the invention that can be obtained by the method of the invention are:

[0041] [Table 2]

Claims

1. A method for producing a neopentyl glycol pressed product comprising at least the following process steps: a) providing bulk material of NPG flakes; b) compressing the bulk material in a mold to form a pressed product, the compression being performed at a pressure of at least 0.5 MPa and at most 7.5 MPa; A method comprising:

2. The NPG flakes have a density of 0.5 g / cm ３ Above 0.6 g / cm ３ 2. The method of claim 1 having a bulk density of:

3. 3. The method of claim 1 or 2, wherein the NPG flakes have a fine fraction of 6 mm or less, equal to or greater than 80% and equal to or less than 90% by weight, as measured by sieving.

4. The method according to any one of claims 1 to 3, wherein the NPG flakes have a thickness of 0.75 mm or more and 5 mm or less.

5. The method according to any one of claims 1 to 4, wherein the NPG flakes have a D50 quantile of 2 mm or more and 8 mm or less, as measured by sieving.

6. The method according to any one of claims 1 to 5, wherein the NPG flakes have a D95 quantile of 7.5 mm or more and 10 mm or less, as measured by sieving.

7. The method according to any one of claims 1 to 6, wherein the compression is carried out at a pressure of at least 1.0 MPa and at most 4 MPa.

8. The method according to any one of claims 1 to 7, wherein process step b) is carried out at a temperature range of ≧5°C and ≦40°C.

9. The method according to any one of claims 1 to 8, wherein the NPG flakes have a moisture content of 0.05% by weight or more and 3% by weight or less.

10. 0.9 g / cm ３ Above 1.02 g / cm ３ An NPG pressed product characterized by having the following density:

11. 2.5cm ３ That's it, 15cm ３ 11. The NPG pressed product of claim 10 having a volume:

12. 0.95 g / cm ３ Above 1.05 g / cm ３ 12. The NPG pressed product of claim 10 or 11, having a density of:

13. 0.4m ２ / kg or more, 0.6m ２ 13. The NPG pressed product according to any one of claims 10 to 12, having a surface area:mass ratio of 0.1 to 0.1 kg / kg or less.

14. The NPG pressed product according to any one of claims 10 to 13, having an NPG content of 98% by weight or more.

15. The NPG pressed product according to any one of claims 10 to 14, having a compressive strength of 80N or more and 400N or less.

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