Solidification of hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate

Abstract

This invention relates to a method for curing 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate (INCI diethylaminohydroxybenzoyl hexyl benzoate, DHHB), wherein the method comprises the following steps: (a) applying a shear rate of 800 s⁻¹ or greater to liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate and (b) adding seed crystals of 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate.

Description

Technical Field

[0001] This invention relates to a method for curing 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate (INCI diethylaminohydroxybenzoyl hexyl benzoate, DHHB), wherein the method comprises the following steps: (a) applying a shear rate of 800 s⁻¹ or greater to liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate and (b) adding seed crystals of 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate. Prior Technology

[0002] 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate (INCI diethylaminohydroxybenzoylhexyl benzoate), also known as DHHB, is a UV-A filter belonging to the benzophenone derivative group. It is marketed by BASF under the trademark Uvinul A Plus. It has a melting point of approximately 54°C.

[0003] It is known in this technology that solvent-free DHHB melts are difficult to crystallize. Supercooled melts can remain in a metastable liquid state for several weeks until they finally crystallize. To date, no economical solidification method is known, such as using this extremely slow-crystallizing product to shave flakes or form tablets on a cooling zone. Currently, methods such as crystallizing DHHB in basins or barrels and then crushing it are applicable. However, these methods have poor space-time yields and result in inhomogeneous particle shape and size, which can lead to disadvantages, for example, regarding its agglomeration properties. Summary of the Invention

[0004] Therefore, the object of this invention is to provide an improved method for curing DHHB. Specifically, the object of this invention is to provide a method that has economic advantages compared to prior art methods. In this regard, specifically, the object of this invention is to provide a method that provides improved space-time yield. Furthermore, the object is to provide cured DHHB with uniform particle shape and size, which preferably exhibits good flowability and / or good storage stability.

[0005] It has been unexpectedly discovered that at least one of the aforementioned objectives can be achieved by the method of the present invention. Specifically, the inventors of the present invention have unexpectedly discovered that applying a high shear rate to a DHHB melt or a supercooled melt in combination with a seeding agent can induce extremely accelerated crystallization of DHHB.

[0006] In the first state, the present invention relates to a method for curing 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate (INCI diethylaminohydroxybenzoyl hexyl benzoate, DHHB), wherein the method comprises the following steps: (a) applying a shear rate of 800 s⁻¹ or greater to liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate and (b) adding seed crystals of 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate while applying the shear rate of step (a).

[0007] The preferred embodiments of the first-state method are further described in detail below. It should be understood that each preferred embodiment is related to itself and to combinations with other preferred embodiments.

[0008] In the preferred embodiment A1 of the first state sample, the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is provided as a melt having a temperature greater than about 54 to about 70°C, more preferably greater than about 54 to about 65°C, or as a supercooled melt having a temperature of about 15 to about 54°C, more preferably about 20 to about 52°C.

[0009] In the preferred embodiment A2 of the first state sample, the applied shear rate is 900 s⁻¹ or greater, preferably 1000 s⁻¹ or greater, and / or wherein the shear rate is obtained by stirring the melt or supercooled melt at a stirring speed of 50 to 600 rpm, preferably 90 to 500 rpm, preferably 100 to 250 rpm.

[0010] In the preferred embodiment A3 of the first state sample, the temperature of the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate to be cured in step (b) is about 15 to about 54°C, preferably about 25 to about 52°C.

[0011] In the preferred embodiment A4 of the first state sample, in step (b), 0.0001 to 0.1 g, more preferably 0.0005 to 0.05 g, more preferably 0.001 to 0.03 g of seed crystals are added per 1 g of the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate melt to be cured, and / or the seed crystals have a particle size of less than 100,000 µm, more preferably 1 to 10,000 µm, more preferably 5 to 5,000 µm as determined by sieve analysis.

[0012] In the preferred embodiment A5 of the first state sample, step (a) is carried out in an apparatus preferably selected from the group consisting of an extruder, a scraper surface heat exchanger, a cooling plate crystallizer, or a stirred vessel (preferably a stirred vessel with a scraper agitator), which is cooled to a temperature of less than about 54°C, preferably about 40°C or lower.

[0013] In the preferred embodiment A6 of the first state sample, step (a) is performed in a scraped surface heat exchanger, and the method further includes the following steps: (i-1) Hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate is heated until a liquid melt is obtained and (i-2) The liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate obtained in step (i-1) is fed into a scraped surface heat exchanger. Next, in step (a), the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is stirred by the scraper.

[0014] In the preferred embodiment A7 of the first state sample, in step (i-1), a temperature greater than about 54°C is applied and / or This step (i-2) is performed while heating the feed to a temperature greater than approximately 54°C and / or The temperature in this scraper-type surface heat exchanger is less than approximately 54°C.

[0015] In the preferred embodiment A8 of the first state sample, step (b) yields the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in a cured strand form.

[0016] In the preferred embodiment A9 of the first state sample, step (b) yields the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a melt suspension, which is cured by the following additional steps: (c) Cool the melt suspension in a maturation zone, preferably a cooling zone, or on a drum shaving machine at a temperature less than about 54°C, preferably less than about 40°C, to obtain a solidified melt and (d) Break the solidified melt into flakes or particles, as appropriate.

[0017] In the preferred embodiment A10 of the first state sample, step (b) yields the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a melt suspension, which is cured by the following additional steps: (ci) forming droplets of the melt suspension and cooling them in a maturation zone, preferably a cooling zone, at a temperature of less than about 54°C, preferably less than about 40°C, to obtain a solidified ingot.

[0018] In the preferred embodiment A11 of the first state sample, a cooling strip is applied and the cooling strip includes at least one cooling zone, preferably, wherein the at least one cooling zone is in a temperature range of about 0 to about 40°C, more preferably about 10 to about 38°C, and specifically about 20 to about 35°C.

[0019] In the preferred embodiment A12 of the first state sample, the cooling strip includes at least two cooling zones. Preferably, the temperature of the first cooling zone is higher than the temperature of the second cooling zone. More preferably, the first cooling zone is in a temperature range of about 15 to about 40°C and the second cooling zone is in a temperature range of about 5 to about 30°C.

[0020] In the preferred embodiment A13 of the first state sample, the method is carried out in a continuous manner, wherein the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is continuously fed into the scraping heat exchanger and the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of solidified strands or melt suspension is continuously collected from the scraping heat exchanger.

[0021] In the second state sample, the present invention relates to cured 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the following form. Castable or flowable particles having a particle size of less than 30 mm, preferably greater than 5 to 30 mm. Tablets having a particle size of less than 30 mm, preferably greater than 5 to 30 mm, or Thin sheets having a particle size of less than 150 mm, preferably 1 to 100 mm. Implementation

[0022] Before describing in detail exemplary embodiments of the present invention, definitions important for understanding the present invention are provided.

[0023] As used in this specification and the accompanying claims, unless the context clearly specifies otherwise, the singular form "a / an" also includes the corresponding plural. In the context of this invention, the term "about" indicates a range of precision that, as those skilled in the art will understand, still ensures the technical effect of the features under discussion. This term typically indicates a deviation from a specified value of ±15%, preferably ±10%, more preferably ±5%, and specifically ±3%. It should be understood that the term "comprising" is not restrictive. For the purposes of this invention, the term "consisting of" is considered a preferred embodiment of the term "comprising." If a group is defined below as comprising at least a certain number of embodiments, this means that it also includes a group preferably consisting only of such embodiments. It should be understood that this invention is not limited to the specific methodologies, protocols, reagents, etc., described herein, as these can vary. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of the invention, which is limited only by the claims attached. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill.

[0024] As used herein, the term "castable or flowable particles" refers to any solid form that can be cast or granulated and is safe and easily processed by a processing machine (e.g., having reduced electrostatic properties compared to powder).

[0025] As used herein, the term "tablet" refers to a subtype of castable or flowable particles, preferably of a hemispherical structure. Tablets are preferably obtained from a liquid melt or melt suspension, which can be aliquoted into droplets and placed on a flat surface to form the tablets. After the melt or melt suspension has crystallized, the tablets can be removed and bottled.

[0026] As used herein, the term "flake" refers to a specific solid form that can be obtained by casting a still-liquid melt or melt suspension onto a flat surface, preferably wherein the obtained layer has a thickness of 0.1 to 10 mm, more preferably 0.2 to 8 mm, 0.2 to 5 mm, or 0.2 to 2 mm. After the melt or melt suspension has crystallized, the solid layer is conventionally removed from the flat surface and bottled, usually by crushing the layer to the desired flake size.

[0027] The production methods for castable or flowable particles, ingots and sheets can occur intermittently (batch methods) or continuously. In the continuous method, for the purposes of this invention, a continuous circulating steel strip can be used as a mold, for example.

[0028] The following describes preferred embodiments of the method according to the present invention. It should be understood that preferred embodiments of the present invention are preferred individually or in combination with each other.

[0029] As indicated above, in one embodiment, the present invention relates to a method for curing 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate (INCI diethylaminohydroxybenzoyl hexyl benzoate, DHHB), wherein the method comprises the following steps: (a) Applying a shear rate of 800 s⁻¹ or greater to liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate and (b) While applying the shear rate of step (a), add seed crystals of 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate.

[0030] In a preferred embodiment, the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is provided as a melt or a supercooled melt.

[0031] 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate has a melting point of about 54°C. The melting point can vary depending on potential impurities. Therefore, it should be understood that when referring to a temperature value according to the method of the present invention, it means ±2°C, preferably ±1°C. For example, if referring to a melting point of DHHB of about 54°C, it means a temperature range of 54°C ± 2°C, preferably ±1°C.

[0032] In a preferred embodiment, the melt has a temperature greater than about 54 to about 70°C, preferably greater than about 54 to about 65°C.

[0033] In a preferred embodiment, the supercooled melt has a temperature of about 15 to about 54°C, more preferably about 20 to about 52°C.

[0034] In a preferred embodiment, the applied shear rate is 900 s⁻¹ or greater, more preferably 1000 s⁻¹ or greater, more preferably 1500 s⁻¹ or greater, still more preferably 2000 s⁻¹ or greater, and specifically 5000 s⁻¹ or greater. A preferred shear rate is in the range of 800 to 100000 s⁻¹, more preferably 900 to 50000 s⁻¹, and more preferably 1000 to 30000 s⁻¹. In yet another preferred embodiment, the applied shear rate is in the range of 800 to 50000 s⁻¹, more preferably 900 to 30000 s⁻¹, and specifically 900 to 20000 s⁻¹.

[0035] This high shear rate further reduces the time until nucleation begins, thereby increasing the efficiency of the curing method.

[0036] As used herein, the term "shear rate" refers to the rate of progressive shear deformation applied to a fluid DHHB. Generally, the shear rate of a fluid flowing between two parallel plates (one moving at a constant velocity and the other stationary) can be determined based on the following equation: γ = v / h Where "γ" is the shear rate measured in countdown seconds, "v" is the velocity of the moving plate measured in meters per second, and "h" is the distance between the two parallel plates measured in meters. Based on this principle, the rotational speed and dimensions of the device used to apply the shear rate are predetermined to determine the shear rate.

[0037] In a preferred embodiment, the melt or supercooled melt system is stirred at a stirring speed greater than 50 rpm, more preferably greater than 80 rpm, and specifically greater than 100 rpm. It is also preferable that the melt or supercooled melt system is stirred at a stirring speed of 50 to 600 rpm, more preferably 80 to 500 rpm, and more preferably 100 to 250 rpm.

[0038] Preferably, a high shear rate is obtained by stirring the melt or supercooled melt at a stirring speed of 50 to 600 rpm, more preferably 80 to 500 rpm, and more preferably 100 to 250 rpm.

[0039] In a preferred embodiment, the seed crystals are added at a temperature of about 30 to about 60°C, more preferably about 35 to about 55°C, and still more preferably about 40 to less than about 54°C.

[0040] In a preferred embodiment, after adding the seed crystal, the temperature of the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate to be cured is maintained at about 15 to less than about 54°C, preferably in the range of about 25 to about 52°C.

[0041] In a preferred embodiment, in step (b), 0.0001 to 0.1 g, more preferably 0.0005 to 0.05 g, and more preferably 0.001 to 0.03 g of seed crystals are added to every 1 g of the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate to be cured.

[0042] In a preferred embodiment, the seed crystals have a particle size of less than 100,000 µm, more preferably 1 to 10,000 µm, and more preferably 5 to 5,000 µm, as determined by sieve analysis.

[0043] In this regard, particle size determination is preferably performed using two sieves, with the first sieve having a wider mesh than the second. Preferably, an amplitude of 1.5 mm is applied and both sieves are positioned in a Retsch sieve apparatus, with the sieve with the wider mesh positioned at the top. After the sample is applied to the top sieve, sieving is performed. The residue is weighed at intervals of 1 to 20 minutes to verify whether the residue of the three obtained fractions has changed. Generally, the distribution of the three fractions no longer changes after 5 to 10 minutes.

[0044] Preferably, particle size determination is performed using two sieves, the first with a 5 mm grid width and the second with a 0.1 mm grid width. Preferably, an amplitude of 1.5 mm is applied and the two sieves are positioned in a Retsch sieve apparatus, with the 5 mm grid width sieve positioned at the top. After applying the sample to the top sieve, sieving is performed. The residue is weighed at intervals of 1 to 20 minutes to verify whether the residues of the three obtained fractions have changed. Generally, the distribution of the three fractions no longer changes after 5 to 10 minutes. The first fraction contains particles with a size less than 0.1 mm, the second fraction contains particles with a size from 0.1 to 5 mm, and the third fraction contains particles with a size greater than 5 mm.

[0045] In a preferred embodiment, step (a) is performed in an apparatus preferably selected from the group consisting of an extruder, a scraper surface heat exchanger, a cooling plate crystallizer, or a stirred vessel (preferably a stirred vessel with a scraper agitator), which is cooled to a temperature of less than about 54°C, preferably about 40°C or lower.

[0046] In this regard, it should be understood that each device that can be cooled and enables stirring can be used.

[0047] In a preferred embodiment, the method is a continuous method.

[0048] Preferably, the continuous operation method includes the use of a scraper-type surface heat exchanger and a storage container, wherein the DHHB melt can be stored above its melting temperature. The scraper-type surface heat exchanger, which can feed DHHB melt from the storage container, is used to generate a melt suspension. In the scraper-type surface heat exchanger, liquid DHHB is cooled by means of a cooled inner surface (also called a scraper surface) and stirred by a scraper. According to the invention, seed crystals are added. After crystallization begins, crystals are generated on the cooled inner surface and scraped off by means of a scraper contained in the scraper-type surface heat exchanger. During the start-up phase, the generated melt suspension is fed back to the storage container until the desired solids content of the generated melt suspension is achieved. Once crystallization has clearly begun, an increase in the turbidity of the DHHB melt suspension can be observed (e.g., via a turbidity probe signal). Furthermore, when crystallization has clearly begun, a color change from brown to bright yellow can be observed.

[0049] Once the desired solids content is reached, the melt suspension can be continuously applied to the maturation zone, preferably the cooling zone (more preferably, with multiple temperature zones).

[0050] In a preferred embodiment, step (a) is performed in a scraped surface heat exchanger, and the method further includes the following steps: (i-1) Hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate is heated until a liquid melt is obtained and (i-2) The liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate obtained in step (i-1) is fed into a scraped surface heat exchanger. Next, in step (a), the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is stirred by the scraper.

[0051] Preferably, in step (i-1), a temperature greater than about 54°C is applied. More preferably, in step (i-1), a temperature greater than about 54°C to about 70°C is applied, and even more preferably, a temperature greater than about 54°C to about 65°C is applied.

[0052] Preferably, step (i-2) is performed by heating the feed to a temperature greater than about 54°C. More preferably, step (i-2) is performed by heating the feed to a temperature greater than about 54°C to about 70°C, and even more preferably, to a temperature greater than about 54°C to about 65°C.

[0053] Preferably, the temperature in the scraper-type surface heat exchanger is less than about 54°C, and more preferably less than about 52°C.

[0054] Preferably, the inner surface of the scraped surface heat exchanger has a temperature of less than about 50°C, more preferably less than about 40°C, still more preferably less than about 30°C, and specifically less than about 20°C. Also preferably, the inner surface of the scraped surface heat exchanger has a temperature of about 1 to about 50°C, more preferably about 2 to about 40°C, still more preferably about 3 to about 30°C, and specifically about 5 to about 20°C.

[0055] In this regard, it should be understood that the scraped surface heat exchanger is cooled via its inner surface. Therefore, when referring to the temperature within the scraped surface heat exchanger, it refers to the approximate temperature of the melt / melt suspension cooled via the cooled inner surface. When referring to the temperature of the inner surface, it refers to the temperature of the inner surface of the scraped surface heat exchanger.

[0056] In a preferred embodiment, in step (i-1), a temperature greater than about 54°C is applied, and step (i-2) is performed while the feed is heated to a temperature greater than about 54°C and the temperature in the scraper-type surface heat exchanger is less than about 54°C.

[0057] In a preferred embodiment, step (a) is performed in a stirring vessel and the method further includes the following steps: (ii-1) Hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate is heated until a liquid melt is obtained. (ii-2) The liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate obtained in step (ii-1) is cooled, preferably while being stirred, to obtain a supercooled melt of 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate. (ii-3) The supercooled melt of 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is fed into a stirred container. Next step (a).

[0058] Preferably, in step (ii-1), a temperature greater than about 54°C is applied. More preferably, in step (ii-1), a temperature greater than about 54°C to about 70°C is applied, and even more preferably, a temperature greater than about 54°C to about 65°C is applied.

[0059] Preferably, in step (ii-2), the supercooled melt has a temperature of less than about 54°C. Also preferably, in step (ii-2), the supercooled melt has a temperature in the range of about 15 to about 54°C, and more preferably about 20 to about 52°C.

[0060] In a preferred embodiment, in step (ii-1), a temperature greater than about 54°C is applied and in step (ii-2), the supercooled melt has a temperature less than about 54°C.

[0061] In a preferred embodiment, step (b) yields a melt suspension.

[0062] It should be understood that, according to the present invention, the term "melt suspension" refers to a melt containing solids. For example, a melt suspension of DHHB includes DHHB in both liquid (i.e., molten) and solid forms.

[0063] The melt suspension obtained by step (b) can be poured into any suitable container to allow the melt suspension to cool and solidify further.

[0064] In a preferred embodiment, step (b) yields 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in a cured strand form.

[0065] In a preferred embodiment, step (b) yields 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a melt suspension, which is cured by the following additional steps: (c) Cooling the melt suspension in a maturation zone, preferably a cooling zone, or on a drum shaving machine at a temperature less than about 54°C, preferably less than about 40°C, to obtain a solidified melt and (d) Break the solidified melt into flakes or particles, as appropriate.

[0066] In a preferred embodiment, step (b) yields 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a melt suspension, which is cured by the following additional steps: (ci) forming droplets of a melt suspension and cooling them in a maturation zone, preferably a cooling zone, at a temperature of less than about 54°C, preferably less than about 40°C, to obtain a solidified ingot.

[0067] In a preferred embodiment, a cooling strip is applied and the cooling strip includes at least one cooling zone. Preferably, the at least one cooling zone is within a temperature range of about 0 to about 40°C, more preferably about 10 to about 38°C, and specifically about 20 to about 35°C.

[0068] Preferably, the cooling zone comprises at least two cooling zones, and more preferably, the temperature of the first cooling zone is higher than the temperature of the second cooling zone. Preferably, the temperature of the first cooling zone is about 5°C higher than the temperature of the second cooling zone, more preferably about 10°C. Preferably, the first cooling zone is in a temperature range of about 15 to about 40°C, more preferably about 22 to about 38°C, and the second cooling zone is in a temperature range of about 5 to about 30°C, more preferably about 10 to about 20°C.

[0069] In a preferred embodiment, the method is carried out continuously, wherein the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is continuously fed into a scraped surface heat exchanger or an extruder and continuously collected from the scraped surface heat exchanger or extruder in the form of a solidified strand or a melt suspension.

[0070] If 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is not completely cured after the dwell time in the cooling zone, a ripening zone can be used after the cooling zone.

[0071] In the second state sample, the present invention relates to cured 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the following form. Castable or flowable particles having a particle size of less than 30 mm, preferably greater than 5 to 30 mm. Tablets having a particle size of less than 30 mm, preferably greater than 5 to 30 mm, or Thin sheets having a particle size of less than 150 mm, preferably 1 to 100 mm.

[0072] In a preferred embodiment, the castable or flowable particles have a particle size of 0.01 to 30 mm, more preferably 0.1 to 30 mm, still more preferably greater than 5 to 30 mm, and specifically 10 to 25 mm, as determined by sieve analysis.

[0073] It can be applied to any suitable method for determining the particle size of castable or flowable particles.

[0074] The particle size of castable or flowable particles can be determined by sieving analysis. Preferably, the particle size is determined using two sieves, the first and second of which have grid widths suitable for measurement, for example, 1 to 30 mm. Preferably, an amplitude of 1.5 mm is applied and the two sieves are positioned in a Retsch sieve apparatus, with the sieve with the wider grid width located at the top. After the sample is applied to the top sieve, sieving is performed for 1 to 20 minutes until no change in the distribution of the three fractions is detected.

[0075] The particle size of castable or flowable particles can also be determined using a diameter gauge. In this regard, it should be understood that the Feret's diameter, Feret max., is crucial for particle size determination.

[0076] The sieving is preferably used for castable or flowable particles with a particle size of less than 20 mm, more preferably less than 10 mm, and specifically 5 mm and smaller.

[0077] Image analysis or diameter measuring devices are preferably used for castable or flowable particles with a particle size greater than 5 mm, more preferably greater than 10 mm.

[0078] Preferably, the castable or flowable particles have a bulk density of 0.35 g / mL or greater, more preferably 0.35 to 0.5 g / mL.

[0079] In a preferred embodiment, the tablets have a particle size of 1 to 30 mm, more preferably 2 to 30 mm, still more preferably greater than 5 to 30 mm, and specifically 6 to 20 mm.

[0080] It can be applied to any suitable method for determining the particle size of tablets.

[0081] The particle size of the tablets can be determined using image analysis. Therefore, 100 tablets were randomly selected from the final product. The particle size was measured, and the average particle diameter was derived from it.

[0082] The particle size of tablets can also be determined using a diameter gauge. In this regard, it should be understood that the Feret max (Freret diameter) is crucial for particle size determination. Using a diameter gauge is preferable for tablets with a particle size greater than 5 mm.

[0083] Preferably, the tablets have a bulk density of 0.35 g / mL or greater, more preferably 0.35 to 0.5 g / mL.

[0084] In a preferred embodiment, the sheets have a particle size of 1 to 100 mm, more preferably 5 to 90 mm, even more preferably greater than 5 to 85 mm, still more preferably 7 to 80 mm, and specifically 10 to 80 mm.

[0085] It can be applied to any suitable method for determining the particle size of thin films.

[0086] The particle size of the flakes can be determined through image analysis. Therefore, 100 flakes were randomly selected from the final product. The particle size was measured, and the average particle diameter was derived from it.

[0087] The particle size of the flakes can also be determined using a diameter gauge. In this regard, it should be understood that the Feret max (Freret diameter) is crucial for particle size determination. The diameter gauge method is preferred for flakes with a particle size of 5 mm and larger.

[0088] Preferably, the thin films have a volume density of 0.35 g / mL or greater, more preferably 0.35 to 0.5 g / mL.

[0089] The invention is further illustrated by the following examples.

[0090] Example Comparative Example 1: Experiment using a cooling plate with low shear rate and no seed crystals To evaluate the solidification behavior of thin layers (1 to 3 mm) of DHHB melt, a cooling plate experiment was conducted at a constant cooling plate temperature of 20°C. In this experiment, a thin layer of DHHB melt was placed on the surface of a constant-temperature cooling plate (material: stainless steel). To apply a low shear rate of approximately 50 s⁻¹, the liquid DHHB melt was gently stirred with a spatula for several minutes. No crystallization was observed within 2 hours.

[0091] Comparative Example 2: High shear rate without seeding The following example is based on Example 6 of EP 2155660 B1: 5 kg DHHB was poured into a 5 L aluminum container. The melt was stirred using a PTFE propeller stirrer (60 mm diameter) powered by an electric motor. The melt was stirred at 25°C at a stirring speed of 250 rpm (approximately 1000 s⁻¹). After 11 hours of stirring, the melt viscosity increased significantly, making stirring impossible. Crystals were first observed after 5 hours of stirring. Complete solidification was achieved after 24 hours.

[0092] Comparative Example 3: No shear rate and under seeding conditions The following example is based on Example 10 of EP 2155660 B1: DHHB seed particles were added to 5 kg of DHHB melt. The melt temperature at the time of addition of the seed particles (< 100 µm) was approximately 40°C. The DHHB melt was then allowed to cool to room temperature. Crystals were first observed after 10 days. Complete solidification was achieved after 2 months. The melt was not stirred during this experiment.

[0093] Example 1 of the present invention: High shear rate (800 s⁻¹ or greater) and under seeding conditions A scraper-type surface heat exchanger covering approximately 90 L of melt volume was used for this experiment. The DHHB melt was fed from the storage tank to the scraper-type surface heat exchanger, where it was cooled to below its melting temperature (i.e., below approximately 54°C). The agitation speed of the scraper was maintained at 120 rpm throughout the experiment. Once the DHHB melt temperature was below 54°C, DHHB seed particles were added to the melt. DHHB powder of approximately <200 µm was used as the seed particles. After approximately 2 to 3 hours, crystallization was observed to begin clearly. To monitor the crystallization process, samples of the DHHB melt were taken from the scraper-type surface heat exchanger (every 30 minutes). The onset of crystallization could be observed visually (increased turbidity) and by increasing scraper torque. Similarly, a color change from brown to yellow was observed in the product. After achieving the desired (high) solids content in the DHHB melt suspension, the melt suspension was poured into the cooling zone. Depending on the tool used to apply the melt suspension onto the cooling zone, DHHB ingots or DHHB layers are produced on the cooling zone. This cooling zone comprises two distinct cooling zones. A first section of the cooling zone's length is maintained at 30°C, while a second section is maintained at 15°C. This temperature distribution was identified as causing a high curing process until the DHHB ingots or DHHB layers are scraped off at the end of the cooling zone. When the DHHB layer is applied to the cooling zone, DHHB flakes are produced (Example 1.1 of the present invention). Complete curing of the DHHB ingots (Example 1.2 of the present invention) and DHHB flakes (Example 1.1 of the present invention) is achieved after curing at room temperature for approximately 2 to 3 hours following scraping from the cooling zone. It should be noted that curing can also be carried out at room temperature on a separate curing zone. Other experimental parameters are summarized in Table 1.

[0094] The resulting tablets (Example 1.2 of the present invention) have an average height of 3.5 to 4.5 mm and an average diameter of 7 to 9.5 mm. Therefore, as understood according to the present invention, their particle size is 7 to 9.5 mm (i.e., Feret max.). Table 1: Process parameters used to produce DHHB flakes and tablets. [Manufacturing Process] [parameter] [parameter] [scope] Volume of scraper surface heat exchanger Approximately 90 L The amount of melt in a scraper-type surface heat exchanger Approximately 95 kg Shear rate Approximately 1000 s⁻¹ Crystallization temperature of UVA+ melt inside scraper-type surface heat exchanger < 54℃ Cooling surface temperature of scraper-type surface heat exchanger 13℃ Added seed quality* Approximately 0.001 g seed crystals / g melt Seed size < 200 µm Seeding temperature < 54℃ Melt temperature in storage container > 54℃ Cooling zone temperature 30℃ (first), 15℃ (second) The time from seeding to the start of crystallization Approximately 3 hours

[0095] When seed crystals are applied in combination with a high shear rate, complete solidification of the DHHB melt suspension can be achieved unexpectedly quickly.

Claims

1. A method for curing 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate (INCI diethylaminohydroxybenzoyl hexyl benzoate, DHHB), wherein the method comprises the steps of: (a) applying a shear rate of 800 s⁻¹ or greater to liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate and (b) adding seed crystals of 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate while applying the shear rate of step (a).

2. The method of claim 1, wherein the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is provided as a melt or as a supercooled melt.

3. The method of claim 2, wherein the melt has a temperature greater than about 54 to about 70°C, and the supercooled melt has a temperature of about 15 to about 54°C.

4. The method of claim 2, wherein the applied shear rate is 900 s⁻¹ or greater and / or wherein the shear rate is obtained by stirring the melt or supercooled melt at a stirring speed of 50 to 600 rpm.

5. The method of any one of claims 1 to 4, wherein the temperature at which the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate to be cured in step (b) is about 15 to about 54°C.

6. The method of any one of claims 1 to 4, wherein in step (b), 0.0001 to 0.1 g of seed crystals are added per 1 g of the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate to be cured, and / or wherein the seed crystals have a particle size of less than 100,000 µm as determined by sieve analysis.

7. The method of any one of claims 1 to 4, wherein step (a) is performed in an apparatus cooled to less than about 54°C.

8. The method of claim 7, wherein the apparatus is selected from the group consisting of an extruder, a scraper surface heat exchanger, a cooling plate crystallizer, and a stirring vessel.

9. The method of any one of claims 1 to 4, wherein step (a) is carried out in a scraper-type surface heat exchanger and wherein the method further comprises the following steps: (i-1) heating 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate until a liquid melt is obtained and (i-2) feeding the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate obtained in step (i-1) into the scraper-type surface heat exchanger, followed by step (a), wherein the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is stirred by the scraper.

10. The method of claim 9, wherein in step (i-1), a temperature greater than about 54°C is applied and / or wherein step (i-2) is performed while the feed is heated to a temperature greater than about 54°C and / or wherein the temperature in the scraper surface heat exchanger is less than about 54°C.

11. The method of any one of claims 1 to 4, wherein step (b) yields the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a cured strand.

12. The method of claim 1, wherein step (b) yields the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a melt suspension, which is cured by the following additional steps: (c) cooling the melt suspension in a curing zone or on a drum shaving machine at a temperature of less than about 54°C to obtain a cured melt, and (d) breaking the cured melt into flakes or particles as appropriate.

13. The method of claim 1, wherein step (b) yields the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a melt suspension, which is cured by the following additional steps: (ci) forming droplets of the melt suspension and cooling them on a maturation zone at a temperature less than about 54°C to obtain a cured ingot.

14. The method of claim 12 or 13, wherein the maturation belt is a cooling belt.

15. The method of claim 14, wherein a cooling strip is applied and the cooling strip includes at least one cooling zone, wherein the at least one cooling zone is at about 0 to about 40°C.

16. The method of claim 14, wherein the cooling strip comprises at least two cooling zones, wherein the temperature of the first cooling zone is higher than the temperature of the second cooling zone, wherein the first cooling zone is in a temperature range of about 15 to about 40°C and the second cooling zone is in a temperature range of about 5 to about 30°C.

17. The method of claim 9, wherein the method is carried out in a continuous manner, wherein the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate is continuously fed into the scraper cooler and the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a solidified strand or a melt suspension is continuously collected from the scraper cooler.

18. A cured 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate prepared by any one of claims 1 to 17, having castable or flowable particles with a particle size greater than 5 to 30 mm, in tablets with a particle size greater than 5 to 30 mm, or in flakes with a particle size less than 150 mm.