WO2023128885A1 - A synthesis method of benzoxazole based optical brighteners - Google Patents

A synthesis method of benzoxazole based optical brighteners Download PDF

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Publication number
WO2023128885A1
WO2023128885A1 PCT/TR2021/051541 TR2021051541W WO2023128885A1 WO 2023128885 A1 WO2023128885 A1 WO 2023128885A1 TR 2021051541 W TR2021051541 W TR 2021051541W WO 2023128885 A1 WO2023128885 A1 WO 2023128885A1
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Prior art keywords
benzoxazole
mixture
based optical
optical brighteners
synthesis method
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French (fr)
Inventor
Mehmet Basalp
Gokay GUREL
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Akdeniz Chemson Kimya Sanayi Ve Ticaret AS
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Akdeniz Chemson Kimya Sanayi Ve Ticaret AS
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Priority to EP21970133.1A priority Critical patent/EP4457291A4/en
Priority to PCT/TR2021/051541 priority patent/WO2023128885A1/en
Priority to US18/717,185 priority patent/US20250034123A1/en
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D413/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms
    • C07D413/14—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms containing three or more hetero rings
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D263/00—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings
    • C07D263/52—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings condensed with carbocyclic rings or ring systems
    • C07D263/62—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings condensed with carbocyclic rings or ring systems having two or more ring systems containing condensed 1,3-oxazole rings
    • C07D263/64—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings condensed with carbocyclic rings or ring systems having two or more ring systems containing condensed 1,3-oxazole rings linked in positions 2 and 2' by chains containing six-membered aromatic rings or ring systems containing such rings
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent materials, e.g. electroluminescent or chemiluminescent
    • C09K11/06—Luminescent materials, e.g. electroluminescent or chemiluminescent containing organic luminescent materials

Definitions

  • the present invention relates to a synthesis method of benzoxazole based optical brighteners for polymer applications.
  • Optical brighteners also called as fluorescent whitening agents or optical whitening agents, are chemical compounds that absorb light in the ultraviolet and violet region of the electromagnetic spectrum, and re-emit light in the blue region by fluorescence.
  • the aforementioned optical brighteners have been used for many years to improve the colour of various polymers. They mask inherent yellowness in polymers and make polymers appear whiter.
  • the most commonly used optical brighteners are bis-benzoxazolyl-stilbene and bis-benzoxazolyl-thiophene.
  • the synthesis methods disclosed in mentioned documents possess solvents which have high boiling points or chlorinated solvents. In order to remove these solvents from the reaction mixture, the synthesis methods disclosed in the said documents have additional purification steps. Because of mentioned additional purification steps, the synthesis methods disclosed in the said patent documents take a long time and also the yield of optical brighteners obtained in the reaction is too low. Moreover, the synthesis methods disclosed in the said patent documents cause environmental problems.
  • the present invention provides a synthesis method of benzoxazole based optical brighteners.
  • the synthesis method of benzoxazole based optical brighteners comprises the steps of: placing in a reactor vessel at least one acid selected from thiophene-2, 5- dicarboxylic acid or stilbene-4,4’-dicarboxylic acid, at least one catalyst and at least one compound selected from liquid paraffin and/or xylene; obtaining a mixture by adding 2-amino-4-tert-butylphenol in the reactor vessel if the said at least one acid is selected as thiophene-2, 5-dicarboxylic acid or adding 2-aminophenol in the reactor vessel if the said at least one acid is selected as stilbene-4,4’-dicarboxylic acid; mixing the obtained mixture for a first time period under nitrogen atmosphere to carry out the synthesis reaction of benzoxazole based optical brighteners; during mixing the obtained mixture, increasing the temperature of the said mixture gradually to a first temperature; after mixing obtained mixture for the first time
  • the synthesis method provided by the present invention highly efficient benzoxazole based optical brighteners are obtained. Since the said synthesis method provided by the present invention does not have additional purification steps, the said method is environmental friendly and low-cost. Moreover, due the addition of liquid paraffin in the said synthesis method, the synthesis reaction of benzoxazole based optical brighteners takes place in short time period.
  • An object of the present invention is to provide a synthesis method of benzoxazole based optical brighteners.
  • Another object of the present invention is to provide a synthesis method of benzoxazole based optical brighteners for polymer applications.
  • Another object of the present invention is to provide a low-cost and environmental friendly synthesis method of benzoxazole based optical brighteners.
  • Another object of the present invention is to provide a highly efficient synthesis method of benzoxazole based optical brighteners.
  • Optical brighteners also known as fluorescent whitening agents or optical whitening agents, absorb light in the ultraviolet and violet region and emit visible blue lights.
  • the mentioned optical brighteners are chemical compounds that have a system of conjugated double bonds and electron-donating groups to show the high fluorescence activity.
  • the aforementioned optical brighteners are often used to enhance the colour of various polymers.
  • Optical brighteners make polymers appear whiter by masking inherent yellowness in polymers.
  • Bis-benzoxazolyl-stilbene and bis-benzoxazolyl-thiophene are most commonly used as optical brighteners.
  • various processes for the preparation of these optical brighteners are improved.
  • the aforementioned synthesis methods possess solvents which have high boiling points or chlorinated solvents.
  • the synthesis methods have additional purification steps. Due to the said additional steps, the synthesis methods take too much time and also have low yield of optical brighteners. Furthermore, the mentioned additional purification steps in the synthesis methods cause environmental problems. Therefore, in the present invention, a synthesis method of benzoxazole based optical brighteners for solving the above mentioned-problems is provided.
  • the synthesis method of benzoxazole based optical brighteners comprises the steps of: placing in a reactor vessel at least one acid selected from thiophene-2, 5- dicarboxylic acid or stilbene-4,4’-dicarboxylic acid, at least one catalyst and at least one compound selected from liquid paraffin and/or xylene; obtaining a mixture by adding 2-amino-4-tert-butylphenol in the reactor vessel if the said at least one acid is selected as thiophene-2, 5-dicarboxylic acid or adding 2-aminophenol in the reactor vessel if the said at least one acid is selected as stilbene-4,4’-dicarboxylic acid; mixing the obtained mixture for a first time period under nitrogen atmosphere to carry out the synthesis reaction of benzoxazole based optical brighteners; during mixing the obtained mixture, increasing the temperature of the said mixture gradually to a first temperature; after mixing obtained mixture for the first time period, filtering the mixture; after filtering the mixture, obtaining a first be
  • the said at least one acid is selected as thiophene-2, 5-dicarboxylic acid, 2-amino-4-tert-butylphenol is added into a reactor vessel in order to obtain a mixture.
  • thiophene-2, 5-dicarboxylic acid, 2-amino-4-tert-butylphenol, at least one catalyst (selected from metal based catalysts, Lewis acids and/or boric acid) and at least one compound selected from liquid paraffin and/or xylene are mixed preferably in a mechanical mixer, for a first time period (preferably 2-6 hours) under nitrogen atmosphere.
  • the temperature of the obtained mixture is gradually increased to a first temperature (preferably 220-270°C).
  • a first temperature preferably 220-270°C.
  • the obtained mixture is filtered and a first benzoxazole based optical brightener is obtained.
  • the said first benzoxazole based optical brightener is 2,5-thiophenediylbis(5- tert-butyl- 1 ,3-benzoxazole).
  • the said at least one acid is selected as stilbene-4,4’-dicarboxylic acid
  • 2-aminophenol is added into a reactor vessel in order to obtain a mixture.
  • stilbene-4,4’- dicarboxylic acid, 2-aminophenol, at least one catalyst (selected from metal based catalysts, Lewis acids and/or boric acid) and at least one compound selected from liquid paraffin and/or xylene are mixed preferably in a mechanical mixer, for a first time period (preferably 2-6 hours) under nitrogen atmosphere.
  • a first time period preferably 2-6 hours
  • the obtained mixture After mixing obtained mixture for the first time period, the obtained mixture is filtered and a second benzoxazole based optical brightener is obtained.
  • the said second benzoxazole based optical brightener is 4,4'-Bis(2-benzoxazolyl)stilbene.
  • the said liquid paraffin is utilized as nonpolar disintegrant. Due to its nonpolar feature, it can be easily removed from the first or second benzoxazole based optical brightener during the filtration of the mixture. In addition, after removing liquid paraffin from the first or second benzoxazole based optical brightener, liquid paraffin can be used again as disintegrant. Moreover, thanks to liquid paraffin being able to reach high temperatures, the benzoxazole based optical brighteners can be obtained in short time period (preferably 2-6 hours).
  • the said first or second benzoxazole based optical brighteners obtained by present invention are used for polymer applications.
  • the mentioned benzoxazole based optical brighteners cover the yellowness of the polymers and make them appear whiter.
  • the synthesis method provided by the present invention highly efficient benzoxazole based optical brighteners are obtained. Since the said synthesis method provided by the present invention does not have additional purification steps, the said method is environmental friendly and low-cost. Additionally, thanks to the addition of liquid paraffin utilized as nonpolar disintegrant in the said synthesis method, the temperature of the obtained mixture reaches the high temperatures and the synthesis reaction takes place in short time period.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Heterocyclic Carbon Compounds Containing A Hetero Ring Having Nitrogen And Oxygen As The Only Ring Hetero Atoms (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Abstract

The present invention is a synthesis method for benzoxazole based optical brighteners characterized by comprising the steps of; placing in a reactor vessel at least one acid selected from thiophene-2,5-dicarboxylic acid or stilbene-4,4'-dicarboxylic acid, at least one catalyst and at least one compound selected from liquid paraffin and/or xylene; obtaining a mixture by adding 2-amino-4-tert-butylphenol in the reactor vessel if the said at least one acid is selected as thiophene-2,5-dicarboxylic acid or adding 2-aminophenol in the reactor vessel if the said at least one acid is selected as stilbene-4,4'-dicarboxylic acid;; mixing the obtained mixture for a first time period under nitrogen atmosphere to carry out the synthesis reaction of benzoxazole based optical brighteners; during mixing the obtained mixture, increasing the temperature of the said mixture gradually to a first temperature; after mixing obtained mixture for the first time period, filtering the mixture;after filtering the mixture, obtaining a first benzoxazole based optical brightener or a second benzoxazole based optical brightener.

Description

A SYNTHESIS METHOD OF BENZOXAZOLE BASED OPTICAL BRIGHTENERS
Technical Field
The present invention relates to a synthesis method of benzoxazole based optical brighteners for polymer applications.
Background of the Invention
Optical brighteners, also called as fluorescent whitening agents or optical whitening agents, are chemical compounds that absorb light in the ultraviolet and violet region of the electromagnetic spectrum, and re-emit light in the blue region by fluorescence. The aforementioned optical brighteners have been used for many years to improve the colour of various polymers. They mask inherent yellowness in polymers and make polymers appear whiter. The most commonly used optical brighteners are bis-benzoxazolyl-stilbene and bis-benzoxazolyl-thiophene.
Within the known state of art, an example which is related to the process for the preparation of bis-benzazolyl compounds used as optical whitening agents is disclosed in EP1326850B1. In the said patent document, the synthesis reaction of the optical whitening agents takes place in the presence of an acidic catalyst and optionally in the presence of a secondary solvent capable of removing water from the reaction mixture. At the end of the synthesis reaction, the mentioned optical whitening agents are dissolved in the solvents. However, these agents have to be removed from the solvents and they have to be purified.
Another patent application No. US3407196A discloses a reaction between dicarboxylic acid chloride and ortho-aminophenol in the presence of solvents such as dichlorobenzene.
In addition, in the patent application No. CH439292A, a process for the preparation of new derivatives of thiophene is disclosed. In the mentioned process, the reaction occurs by melting dicarboxylic acid and orthoaminophenols. However, during said process, the temperature of reaction has to be risen to uncontrolled high temperatures.
On the other hand, the synthesis methods disclosed in mentioned documents possess solvents which have high boiling points or chlorinated solvents. In order to remove these solvents from the reaction mixture, the synthesis methods disclosed in the said documents have additional purification steps. Because of mentioned additional purification steps, the synthesis methods disclosed in the said patent documents take a long time and also the yield of optical brighteners obtained in the reaction is too low. Moreover, the synthesis methods disclosed in the said patent documents cause environmental problems.
Brief Description of the Invention
The present invention provides a synthesis method of benzoxazole based optical brighteners. The synthesis method of benzoxazole based optical brighteners comprises the steps of: placing in a reactor vessel at least one acid selected from thiophene-2, 5- dicarboxylic acid or stilbene-4,4’-dicarboxylic acid, at least one catalyst and at least one compound selected from liquid paraffin and/or xylene; obtaining a mixture by adding 2-amino-4-tert-butylphenol in the reactor vessel if the said at least one acid is selected as thiophene-2, 5-dicarboxylic acid or adding 2-aminophenol in the reactor vessel if the said at least one acid is selected as stilbene-4,4’-dicarboxylic acid; mixing the obtained mixture for a first time period under nitrogen atmosphere to carry out the synthesis reaction of benzoxazole based optical brighteners; during mixing the obtained mixture, increasing the temperature of the said mixture gradually to a first temperature; after mixing obtained mixture for the first time period, filtering the mixture; after filtering the mixture, obtaining a first benzoxazole based optical brightener or a second benzoxazole based optical brightener. Thanks to the synthesis method provided by the present invention, highly efficient benzoxazole based optical brighteners are obtained. Since the said synthesis method provided by the present invention does not have additional purification steps, the said method is environmental friendly and low-cost. Moreover, due the addition of liquid paraffin in the said synthesis method, the synthesis reaction of benzoxazole based optical brighteners takes place in short time period.
Object of the Invention
An object of the present invention is to provide a synthesis method of benzoxazole based optical brighteners.
Another object of the present invention is to provide a synthesis method of benzoxazole based optical brighteners for polymer applications.
Another object of the present invention is to provide a low-cost and environmental friendly synthesis method of benzoxazole based optical brighteners.
Another object of the present invention is to provide a highly efficient synthesis method of benzoxazole based optical brighteners.
Figure imgf000004_0001
of the Invention
Optical brighteners, also known as fluorescent whitening agents or optical whitening agents, absorb light in the ultraviolet and violet region and emit visible blue lights. The mentioned optical brighteners are chemical compounds that have a system of conjugated double bonds and electron-donating groups to show the high fluorescence activity. The aforementioned optical brighteners are often used to enhance the colour of various polymers. Optical brighteners make polymers appear whiter by masking inherent yellowness in polymers. Bis-benzoxazolyl-stilbene and bis-benzoxazolyl-thiophene are most commonly used as optical brighteners. In the state of art, various processes for the preparation of these optical brighteners are improved. However, the aforementioned synthesis methods possess solvents which have high boiling points or chlorinated solvents. To remove these solvents from the reaction mixture in the synthesis methods known in the art, the synthesis methods have additional purification steps. Due to the said additional steps, the synthesis methods take too much time and also have low yield of optical brighteners. Furthermore, the mentioned additional purification steps in the synthesis methods cause environmental problems. Therefore, in the present invention, a synthesis method of benzoxazole based optical brighteners for solving the above mentioned-problems is provided.
According to the present invention, the synthesis method of benzoxazole based optical brighteners comprises the steps of: placing in a reactor vessel at least one acid selected from thiophene-2, 5- dicarboxylic acid or stilbene-4,4’-dicarboxylic acid, at least one catalyst and at least one compound selected from liquid paraffin and/or xylene; obtaining a mixture by adding 2-amino-4-tert-butylphenol in the reactor vessel if the said at least one acid is selected as thiophene-2, 5-dicarboxylic acid or adding 2-aminophenol in the reactor vessel if the said at least one acid is selected as stilbene-4,4’-dicarboxylic acid; mixing the obtained mixture for a first time period under nitrogen atmosphere to carry out the synthesis reaction of benzoxazole based optical brighteners; during mixing the obtained mixture, increasing the temperature of the said mixture gradually to a first temperature; after mixing obtained mixture for the first time period, filtering the mixture; after filtering the mixture, obtaining a first benzoxazole based optical brightener or a second benzoxazole based optical brightener.
In an exemplary embodiment of the invention, if the said at least one acid is selected as thiophene-2, 5-dicarboxylic acid, 2-amino-4-tert-butylphenol is added into a reactor vessel in order to obtain a mixture. In the synthesis method provided by present invention, thiophene-2, 5-dicarboxylic acid, 2-amino-4-tert-butylphenol, at least one catalyst (selected from metal based catalysts, Lewis acids and/or boric acid) and at least one compound selected from liquid paraffin and/or xylene are mixed preferably in a mechanical mixer, for a first time period (preferably 2-6 hours) under nitrogen atmosphere. During mixing the obtained mixture, the temperature of the obtained mixture is gradually increased to a first temperature (preferably 220-270°C). After mixing obtained mixture for the first time period, the obtained mixture is filtered and a first benzoxazole based optical brightener is obtained. The said first benzoxazole based optical brightener is 2,5-thiophenediylbis(5- tert-butyl- 1 ,3-benzoxazole).
The synthesis reaction mechanism of first benzoxazole based optical brightener is given as below:
Figure imgf000006_0001
In an preferred embodiment of the invention, if the said at least one acid is selected as stilbene-4,4’-dicarboxylic acid, 2-aminophenol is added into a reactor vessel in order to obtain a mixture. In the synthesis method provided by present invention, stilbene-4,4’- dicarboxylic acid, 2-aminophenol, at least one catalyst (selected from metal based catalysts, Lewis acids and/or boric acid) and at least one compound selected from liquid paraffin and/or xylene are mixed preferably in a mechanical mixer, for a first time period (preferably 2-6 hours) under nitrogen atmosphere. During mixing the obtained mixture, the temperature of the obtained mixture is gradually increased to a first temperature (preferably 220-270°C). After mixing obtained mixture for the first time period, the obtained mixture is filtered and a second benzoxazole based optical brightener is obtained. The said second benzoxazole based optical brightener is 4,4'-Bis(2-benzoxazolyl)stilbene.
The reaction mechanism of synthesis of second benzoxazole based optical brightener is given as below:
Figure imgf000006_0002
In an exemplary embodiment of the invention, the said liquid paraffin is utilized as nonpolar disintegrant. Due to its nonpolar feature, it can be easily removed from the first or second benzoxazole based optical brightener during the filtration of the mixture. In addition, after removing liquid paraffin from the first or second benzoxazole based optical brightener, liquid paraffin can be used again as disintegrant. Moreover, thanks to liquid paraffin being able to reach high temperatures, the benzoxazole based optical brighteners can be obtained in short time period (preferably 2-6 hours).
In a preferred embodiment of the invention, the said first or second benzoxazole based optical brighteners obtained by present invention are used for polymer applications. The mentioned benzoxazole based optical brighteners cover the yellowness of the polymers and make them appear whiter.
Thanks to the synthesis method provided by the present invention, highly efficient benzoxazole based optical brighteners are obtained. Since the said synthesis method provided by the present invention does not have additional purification steps, the said method is environmental friendly and low-cost. Additionally, thanks to the addition of liquid paraffin utilized as nonpolar disintegrant in the said synthesis method, the temperature of the obtained mixture reaches the high temperatures and the synthesis reaction takes place in short time period.

Claims

1. A synthesis method for benzoxazole based optical brighteners characterized by comprising the steps of: placing in a reactor vessel at least one acid selected from thiophene-2, 5- dicarboxylic acid or stilbene-4,4’-dicarboxylic acid, at least one catalyst and at least one compound selected from liquid paraffin and/or xylene; obtaining a mixture by adding 2-amino-4-tert-butylphenol in the reactor vessel if the said at least one acid is selected as thiophene-2, 5-dicarboxylic acid or adding 2-aminophenol in the reactor vessel if the said at least one acid is selected as stilbene-4,4’-dicarboxylic acid; mixing the obtained mixture for a first time period under nitrogen atmosphere to carry out the synthesis reaction of benzoxazole based optical brighteners; during mixing the obtained mixture, increasing the temperature of the said mixture gradually to a first temperature; after mixing obtained mixture for the first time period, filtering the mixture; after filtering the mixture, obtaining a first benzoxazole based optical brightener or a second benzoxazole based optical brightener.
2. The synthesis method for benzoxazole optical brighteners according to any one of the preceding claims, characterized in that the first time period is within the range of 2-6 hours.
3. The synthesis method for benzoxazole optical brighteners according to any one of the preceding claims, characterized in that the first temperature is between 220 to 270°C.
4. The synthesis method for benzoxazole optical brighteners according to any one of the preceding claims, characterized in that the first benzoxazole based optical brightener is 2,5-thiophenediylbis(5-tert-butyl-1 ,3-benzoxazole).
7
5. The synthesis method for benzoxazole optical brighteners according to any one of the preceding claims, characterized in that the second benzoxazole based optical brightener is 4,4'-Bis(2-benzoxazolyl)stilbene.
6. The synthesis method for benzoxazole optical brighteners according to any one of the preceding claims, characterized in that said at least one catalyst is selected from metal based catalysts, Lewis acids and/or boric acid.
8
PCT/TR2021/051541 2021-12-28 2021-12-28 A synthesis method of benzoxazole based optical brighteners Ceased WO2023128885A1 (en)

Priority Applications (3)

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EP21970133.1A EP4457291A4 (en) 2021-12-28 2021-12-28 Process for the preparation of optical brighteners based on benzoxazole
PCT/TR2021/051541 WO2023128885A1 (en) 2021-12-28 2021-12-28 A synthesis method of benzoxazole based optical brighteners
US18/717,185 US20250034123A1 (en) 2021-12-28 2021-12-28 A synthesis method of benzoxazole based optical brighteners

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5332828A (en) * 1993-02-22 1994-07-26 Eastman Kodak Company Process for the preparation of bis (2-benzoxazolyl) stilbenes
WO2002032886A1 (en) * 2000-10-18 2002-04-25 Ciba Specialty Chemicals Holding Inc. A process for the preparation of bis-benzazolyl compounds
US20100076040A1 (en) * 2006-10-09 2010-03-25 Clariant Finance Wickhams Cay Method For Producing Bisbenzoxazoles

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5332828A (en) * 1993-02-22 1994-07-26 Eastman Kodak Company Process for the preparation of bis (2-benzoxazolyl) stilbenes
WO2002032886A1 (en) * 2000-10-18 2002-04-25 Ciba Specialty Chemicals Holding Inc. A process for the preparation of bis-benzazolyl compounds
US20100076040A1 (en) * 2006-10-09 2010-03-25 Clariant Finance Wickhams Cay Method For Producing Bisbenzoxazoles

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4457291A4 *

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