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

Abstract

To provide an improved process for the solidification of DHHB.SOLUTION: The present invention relates to a process for the solidification of hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate (INCI diethylamino hydroxybenzoyl hexyl benzoate, DHHB), where the process comprises a step (a) of applying a shear rate of at least 400 s-1 to liquid hexyl 2-[4-5 (diethylamino)-2-hydroxybenzoyl]benzoate.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for solidifying 2-[4-(diethylamino)-2-hydroxybenzoyl] benzoic acid hexyl (INCI diethylamino hydroxybenzoyl benzoic acid hexyl, DHHB), which comprises applying a shear rate of at least 400 s to liquid 2-[4-(diethylamino)-2-hydroxybenzoyl] benzoic acid hexyl in step (a). -1 and relates to a method comprising the step (a).

Background Art

[0002] 2-[4-(Diethylamino)-2-hydroxybenzoyl] benzoic acid hexyl (INCI diethylamino hydroxybenzoyl benzoic acid hexyl), also referred to as DHHB, is a UV-A filter belonging to the group of benzophenone derivatives. It is sold by BASF under the trade name Uvinul A Plus. It has a melting point of about 54°C.

[0003] It is known in the art that a solvent-free DHHB melt is difficult to crystallize. The supercooled melt can maintain a metastable liquid state for several weeks until it finally crystallizes. For such a very slowly crystallizing product, economic solidification methods such as flaking or pastillation on a cooling belt are not possible. Only methods such as crystallizing DHHB in tabs or drums and then crushing it are applicable. However, these methods have a low space-time yield and lead to non-uniform particle shapes and sizes, which can lead to disadvantages, for example, regarding its caking properties.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Accordingly, an object of the present invention was to provide an improved method for solidifying DHHB. In particular, an object of the present invention was to provide a method having economic advantages compared to the methods of the prior art. Further, the object was to provide solidified DHHB having a uniform particle shape and size and preferably exhibiting good flowability.

Means for Solving the Problems

[0005] Surprisingly, it has been found that at least one of the aforementioned objects can be achieved by the method of the present invention. In particular, the present invention relates to a method for solidifying 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl (INCI diethylamino hydroxybenzoyl hexyl benzoate, DHHB), comprising applying a shear rate of at least 400 s -1 to liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl in step (a).

[0006] Surprisingly, it has been found by the inventors of the present invention that applying a shear rate to a DHHB melt or a subcooled melt can induce crystallization of DHHB and thus strongly accelerate crystallization.

[0007] In a preferred embodiment, the melt has a temperature above 54 °C to 70 °C, preferably above 54 °C to 65 °C, or the subcooled melt has a temperature of 15 to 54 °C, preferably 20 to 35 °C.

[0008] In a preferred embodiment, the applied shear rate is at least 500 s -1 preferably at least 1000 s -1 or at least 2000 s -1 . An apparatus for generating a very high shear rate is an extruder.

[0009] Accordingly, in a preferred embodiment, the method of the present invention is carried out in an extruder, a surface scraping heat exchanger, a cooling disc crystallizer, or a stirred tank equipped with a scraping mixer.

[0010] According to a preferred embodiment, step (a) is carried out in an extruder, In a preferred embodiment, the method of the present invention (a1) heating 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl until a liquid melt is obtained, (a2) supplying liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl to an extruder, (a3) extruding the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl is included.

[0011] In another preferred embodiment, step (a) is carried out in a surface scraping heat exchanger, a cooling disc crystallizer, or a stirred tank equipped with a scraping mixer, and the method of the present invention comprises (a1r) heating 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl until a liquid melt is obtained, (a2r) cooling the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl to obtain a subcooled melt of 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl, (a3r) supplying the subcooled melt of 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl to a device, preferably a surface scraping heat exchanger, a cooling disc crystallizer, or a stirred tank equipped with a scraping mixer, and (a4r) applying shear to the subcooled melt of 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl is included.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] The following presents preferred embodiments of the method of the present invention. It should be understood that the above-described preferred embodiments and the preferred embodiments exemplified below are preferred either alone or in combination with each other.

[0013] As shown above, the method of the present invention includes step (a) of applying a shear rate of at least 400 s to liquid hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate to induce crystallization. -1 of.

[0014] In a preferred embodiment, the liquid hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate is provided as a melt or a subcooled melt. Depending on the apparatus used, it should be understood that the liquid hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate is provided as a melt or a subcooled melt.

[0015] In a preferred embodiment, the melt has a temperature above 54 °C to 70 °C, preferably above 54 °C to 65 °C, or the subcooled melt has a temperature of 15 to 54 °C, preferably 20 to 35 °C.

[0016] The application of the shear rate determines the period until nucleation starts and causes solidification. Preferably, the shear rate is adapted such that nucleation starts in less than 2 hours, more preferably in less than 1 hour. In a preferred embodiment, the applied shear rate is at least 500 s -1 , preferably at least 1000 s -1 or at least 2000 s -1 . In a more preferred embodiment, the applied shear rate is at least 5000 s -1 . The preferred shear rate is in the range of 1000 to 100000, preferably 2000 to 50000, more preferably 8000 to 30000. Such a high shear rate further reduces the period until nucleation starts, thereby increasing the efficiency of the solidification process.

[0017] As used herein, the term "shear rate" refers to the rate at which a progressive shear deformation is applied to the liquid DHHB. Generally, the shear rate for a fluid flowing between two parallel plates, one moving at a constant speed and the other stationary, is given by the following equation: γ = v / h (where "γ" is the shear rate measured in reciprocal seconds (per second), "v" is the speed of the moving plate measured in meters per second, and "h" is the distance between the two parallel plates measured in meters) and can be determined based thereon. Based on this principle, the rotational speed and dimensions of the apparatus used for the application of the shear rate predetermine the shear rate.

[0018] The solidification of DHHB can be further enhanced by applying a temperature below the melting point, i.e., a temperature below 54°C. In a preferred embodiment, step (a) of the method of the present invention is carried out in an apparatus cooled to a temperature below 54°C, preferably below 40°C. A temperature in the range of 20°C to 35°C, for example about 30°C, is particularly preferred.

[0019] A suitable apparatus for the method of the present invention is an extruder. Thus, in a preferred embodiment, the method of the present invention is carried out in an extruder. The extruder can be used for partial or complete solidification. Complete solidification can occur within a few minutes, preferably within 30 minutes, more preferably within 20 minutes. Suitable extruders include single-screw and twin-screw extruders. A twin-screw extruder with co-rotating or counter-rotating screws is preferred. The extruder may optionally be equipped with heating means and cooling means. To apply the required shear rate, the screw speed of the extruder, i.e., the rotational speed (screw speed measured in rpm), is adapted. It is known to those skilled in the art that the shear rate is also determined, inter alia, by the screw diameter and the distance between the screw and the wall. In particular, a high screw speed, a large screw diameter and a short distance between the screw and the wall result in a high shear rate, and vice versa.

[0020] As described above, step (a) of the method is preferably carried out in an apparatus cooled to a temperature of less than 54°C, preferably less than 40°C. Therefore, the barrel temperature of the extruder is preferably less than 54°C, preferably less than 40°C. For this purpose, a cryostat can be used.

[0021] DHHB is preferably introduced into the extruder in liquid form. Therefore, it is preferable that DHHB is heated before the step of supplying it to the extruder. Thus, in a preferred embodiment, the method of the present invention comprises (a1) heating hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate until a liquid melt is obtained, (a2) supplying liquid hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate to an extruder, (a3) extruding liquid hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate and includes.

[0022] In a preferred embodiment, in step (a1), a temperature above 54 °C is applied. Preferably, the liquid melt in step (a1) is obtained at a temperature above 54 °C to 80 °C, more preferably 60 to 75 °C. In another preferred embodiment, step (a2) is carried out while heating the feed to a temperature above 54 °C. Preferably, the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in step (a2) is fed at a temperature above 54 °C to 75 °C, more preferably above 54 °C to 70 °C, even more preferably 54 to 65 °C. In yet another preferred embodiment, step (a3) is carried out at a barrel temperature below 54 °C, preferably below 40 °C. Preferably, the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in step (a3) is extruded at a temperature of 10 to 54 °C, more preferably 11 to 50 °C. In another preferred embodiment, in step (a3), the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate has a temperature of 10 to 30 °C, more preferably 12 to 25 °C, even more preferably 14 to 22 °C, particularly 15 to 21 °C.

[0023] In another preferred embodiment, step (a3) is carried out at least under atmospheric pressure, preferably at a pressure higher than atmospheric pressure, to ensure efficient extrusion from the extrusion head.

[0024] The extrusion step (a3) can provide DHHB in various forms.

[0025] In a preferred embodiment, the extrusion step (a3) provides 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a solidified strand.

[0026] In another preferred embodiment, the extrusion step (a3) provides 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a suspension, which is (a4i) A further step of cooling the suspension with a cooling belt or drum flaker at a temperature below 54 °C, preferably below 40 °C, to obtain a solidified melt to solidify it.

[0027] More preferably, in step (a4i), the suspension is cooled at a temperature within the range of 20 - 30 °C, particularly at room temperature. Then, in a further step following step (a4i), the obtained solidified melt can be broken into flakes or particles. Thus, in a preferred embodiment, the method (a5i) A step of breaking the solidified melt into flakes or particles is further included.

[0028] In another preferred embodiment, the extrusion step (a3) provides 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl in the form of a suspension, which is (a4ii) A further step of forming droplets of the suspension and cooling them with a cooling belt at a temperature of 25 °C or below to obtain solidified pastilles to solidify it.

[0029] In a preferred embodiment, the extruder is a single-screw extruder or a twin-screw extruder, preferably a twin-screw extruder.

[0030] In a further preferred embodiment, the method of the present invention is carried out as a continuous process in which liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl is continuously supplied to the extruder and 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid hexyl is continuously collected from the extruder in the form of a solidified strand or in the form of a suspension.

[0031] Any device that provides a sufficient shear rate, such as a rheometer, a surface scraping heat exchanger, a cooling disk crystallizer, or a stirred tank equipped with a scraping mixer, is suitable. Thus, in a preferred embodiment, the method of the present invention is carried out in a stirred tank equipped with a rheometer, a surface scraping heat exchanger, a cooling disk crystallizer, or a scraping mixer, more preferably in a stirred tank equipped with a surface scraping heat exchanger, a cooling disk crystallizer, or a scraping mixer.

[0032] In this regard, the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl] benzoic acid hexyl in step (a) of the method is preferably provided as a subcooled melt.

[0033] The subcooled melt preferably has a temperature of 15 to 54 °C, more preferably 15 to 40 °C, even more preferably 20 to 35 °C, particularly 20 to 30 °C.

[0034] The device preferably has a temperature of 15 to 54 °C, more preferably 15 to 40 °C, even more preferably 20 to 35 °C, particularly 20 to 30 °C.

[0035] The subcooled melt can be provided according to any known method.

[0036] When a stirred tank equipped with a surface scraping heat exchanger, a cooling disk crystallizer, or a scraping mixer is used, DHHB is preferably introduced into the stirred tank equipped with a surface scraping heat exchanger, a cooling disk crystallizer, or a scraping mixer as a subcooled melt. Thus, it is preferable that DHHB is first heated and then cooled before the step of supplying it to a suitable device, such as a stirred tank equipped with a surface scraping heat exchanger, a cooling disk crystallizer, or a scraping mixer.

[0037] In a preferred embodiment, the method of the present invention is Heating hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate until a liquid melt is obtained; (a2r) Cooling liquid hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate to obtain a subcooled melt of hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate; (a3r) Feeding the subcooled melt of hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate to a device, preferably a surface scraping heat exchanger, a cooling disk crystallizer, or a stirred tank equipped with a scraping agitator; and (a4r) Applying shear to the subcooled melt of hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate comprising.

[0038] In a preferred embodiment, in step (a1r), a temperature above 54 °C is applied. Preferably, the liquid melt in step (a1r) is obtained at a temperature above 54 °C to 80 °C, more preferably 60 - 75 °C. In another preferred embodiment, in step (a2r), the subcooled melt preferably has a temperature of 15 - 54 °C, more preferably 15 - 40 °C, even more preferably 20 - 35 °C, particularly 20 - 30 °C. In another preferred embodiment, step (a4r) is carried out at a temperature below 54 °C, preferably below 40 °C, more preferably below 35 °C, particularly below 30 °C. In yet another preferred embodiment, step (a4r) is carried out at a temperature of 15 - 54 °C, more preferably 15 - 40 °C, more preferably 20 - 35 °C, particularly 20 - 30 °C.

[0039] In another preferred embodiment, step (a4r) is carried out at least under atmospheric pressure.

[0040] The shear step (a4r) can provide DHHB in various solidified forms.

[0041] The present invention is further illustrated by the following examples.

Example

[0042] [Comparative Example] The solidification of DHHB was tested under the following conditions.

[0043]

Table 1

[0044] These results indicate that the solidification reaction rate of DHHB is very slow.

[0045] [Example 1] Solidification of DHHB in a rheometer Shearing was applied to a subcooled melt of DHHB having a temperature of 25 °C by a rotating cone.

[0046] The onset of nucleation was determined by observing the shear rate and viscosity. Nucleation begins when the shear rate decreases and the viscosity increases.

[0047] It was observed that as the shear rate increased, the period until nucleation began was shortened. Nucleation then causes the solidification of DHHB. The results for different shear rates are summarized in Table 2.

[0048]

Table 2

[0049] [Example 2] Solidification of DHHB in an extruder An extruder without a die head was used. For melting DHHB, a heating cabinet at a temperature of 70 °C was used. The supply unit was heated at a temperature of 60 °C. The extruder was cooled using a cryostat. The rotational speed of the screw was adjusted as shown in Table 3. The throughput of the extruder and the temperature of the extruded mass were adjusted as shown in Table 3. The results for the solidification time are presented in Table 3.

[0050]

Table 3

Claims

1. A method for solidifying 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate (INCI diethylamino hydroxybenzoyl hexyl benzoate, DHHB), comprising: subjecting liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate to at least 400 s -1 (a) applying a shear rate of

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

3. the melt has a temperature of from above 54°C to 70°C, preferably from above 54°C to 65°C; or 3. The process according to claim 2, wherein the subcooled melt has a temperature of 15 to 54°C, preferably 20 to 35°C.

4. The applied shear rate must be at least 500 s -1 , preferably at least 1000 s -1 Or at least 2000s -1 The method according to any one of claims 1 to 3, wherein

5. 5. The method according to any one of claims 1 to 4, wherein step (a) is carried out in an apparatus cooled to a temperature below 54°C, preferably below 40°C.

6. 6. The process of any one of claims 1 to 5, wherein step (a) is carried out in an extruder, a scraped surface heat exchanger, a cooled disk crystallizer, or a stirred tank equipped with a scraped agitator.

7. Step (a) is carried out in an extruder and the process comprises: (a1) heating hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate until a liquid melt is obtained; (a2) feeding liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate into an extruder; (a3) extruding the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate 7. The method of claim 1 , comprising:

8. In step (a1), a temperature of above 54° C. is applied, and / or 8. The method of claim 7, wherein step (a2) is carried out while heating the feed to a temperature above 54°C.

9. 9. The method of claim 7 or 8, wherein the extrusion step (a3) ​​provides the 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of solidified strands.

10. The extrusion step (a3) ​​provides 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a suspension, which is (a4i) a further step of cooling the suspension on a cooling belt or drum flaker at a temperature below 54° C., preferably below 40° C., to obtain a solidified melt. The method according to claim 7 or 8, wherein solidification is carried out by

11. (a5i) The further step of breaking the solidified melt into flakes or particles. The method of claim 10, comprising:

12. The extrusion step (a3) ​​provides 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate in the form of a suspension, which is (a4ii) a further step of forming droplets of the suspension and cooling them on a cooling belt at a temperature below 54° C., preferably below 40° C., to obtain solidified pastilles. The method according to claim 7 or 8, wherein solidification is carried out by

13. 13. The process according to any one of claims 7 to 12, wherein the extruder is a single screw extruder or a twin screw extruder, preferably a twin screw extruder.

14. 14. The method according to any one of claims 7 to 13, which is carried out as a continuous process, in which liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexylbenzoate is continuously fed to an extruder and 2-[4-(diethylamino)-2-hydroxybenzoyl]hexylbenzoate is continuously collected from the extruder in the form of solidified strands or in the form of a suspension.

15. [0023] Step (a) is carried out in a scraped surface heat exchanger, a cooled disk crystallizer, or a stirred tank equipped with a scraped surface agitator, and the process comprises: (a1r) heating hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate until a liquid melt is obtained; (a2r) cooling the liquid 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate to obtain a subcooled molten 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate; (a3r) feeding the subcooled melt of 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate to an apparatus, preferably a scraped surface heat exchanger, a cooled disk crystallizer, or a stirred tank equipped with a scraped agitator; and (a4r) applying shear to the subcooled melt of 2-[4-(diethylamino)-2-hydroxybenzoyl]hexyl benzoate 7. The method of claim 1 , comprising:

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