Abstract:
A series of novel phosphorus-containing compounds having the formula: 
                                 
is provided in which R 1 -R 4 , A, Q and m are as defined in the specification. A process for the preparation of the compound of formula (I) is also provided. A polymer of formula (PA), and preparation process and use thereof, as well as a polymer of formula (PI), and preparation process and use thereof are also provided.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of U.S. application Ser. No. 13/615,879 filed Sep. 14, 2012 now U.S. Pat. No. 8,791,229. Priority is claimed based on U.S. application Ser. No. 12/458,186 filed Jul. 2, 2009 now U.S. Pat. No. 8,293,865, which claims the priority date of Taiwanese Patent application 097124888 filed on Jul. 2, 2008, the content of which is hereby incorporated by reference into this application. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to phosphorus-containing compounds and preparation process and use thereof, and particularly to compounds deriving from phosphorus-containing diphenol (HPP) and preparation process thereof. The derivatives thereof can be further used for synthesis of polymer materials such as polyamides and polyimides. 
     DESCRIPTION OF THE PRIOR ART 
     Traditionally used flame resistant compositions generally contain flame resistant materials such as halogen containing compounds or oxidants containing antimony or vanadium as components to form a high thermal resistant composition, and use of these materials often causes severe environmental contamination problems. For example, bromine containing epoxy resins are particularly useful in flame resistant electronic materials, but release corrosive and toxic substances such as hydrogen bromide, dibenzo-p-dioxin and dibenzo-furan in combustion. In addition to the halogen containing compounds, another flame retardant approach is coating an additional non-flammable layer outside the plastics, with phosphorus-containing compounds being most preferred with respect to efficiency. For example, phosphorus-containing compound 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) has active hydrogen atoms capable of reacting with electron deficient compounds such as benzoquinone [1], oxirane [2], maleic acid [3], bismaleimide [4], diaminobenzophenone [5-6], and terephthaldicarboxaldehyde [7], and derivatives thereof have gained extensive attention from academic and industrial circles. Derivatives of DOPO can be used as raw materials for polymer materials such as epoxy resins, polyamides or polyimides. 
     Taiwan Patent No. 498084 discloses a method for synthesizing phosphorus-containing diphenol (HPP), in which the more expensive non-halogen phosphorus-containing flame resistant agent (DOPOBQ), which is synthesized from DOPO and benzoquinone [1], is successfully replaced by cheaper HPP. This invention further discloses a method for synthesizing HPP derivatives which can be used as raw materials for polymer materials such as epoxy resins, polyamides or polyimides. The HPP and DOPOBQ have the following structures: 
     
       
                 
         
             
             
         
      
     
     Common aromatic polyimide films with high molecular weight generally have advantages such as tenacity, flexibility, solvent resistance, a high glass transition temperature (Tg) and better thermal stability. However, polyimide films generally have a color between yellow and amber, and thus have high light absorption. Some research indicates that the formation of charge-transfer complex (CTC) will cause the color of polyimide films to be deepened. Use of aromatic diamine having bulky group can effectively lower the formation of CTC, thereby causing the color of polyimide films to become pale. 
     Varma et al. synthesized a polyimide having a structure of polyphenyleneoxide (PPO) [8]. However, the formation of CTC could not be effectively inhibited because the incorporated PPO group was not bulky enough; therefore, the polyimide containing PPO still had too dark a color. In 2001, Connell et al. developed a novel diamine having PPO group [9], and used the diamine as a raw material and a series of dianhydrides to synthesize polyimides containing phosphorus in the backbone. However, the polyimide films thus prepared had somewhat higher crispness and poor mechanical properties. 
     In 2002, Connell et al. synthesized another novel diamine containing phosphorus in the side chain [10], and used the diamine and a series of dianhydrides to synthesize polyimides containing phosphorus in the side chain. Because the incorporation of the bulky phosphorus group in the side chain obviously inhibited the formation of CTC, the polyimides had a paler color; with respect to mechanical properties, all the polyimides formed with anhydride other than pyromellitic dianhydride (PMDA) had tenacity, better mechanical properties, and a glass transition temperature (Tg) ranging from 212 to 251° C. Therefore, the polyimides containing phosphorus in the side chain can lower the color of the film. 
     The present invention synthesizes a novel diamine containing phosphorus in the side chain, and used the diamine and a series of dianhydrides or diacids to prepare polyamides or polyimides having better transparency and containing phosphorus in the side chain. The resulting phosphorus-containing polymers can be used as flexible printed circuit board materials. 
     REFERENCES 
     
         
         [1] Wang, C. S.; Lin, C. H. Polymer 1999; 40; 747. 
         [2] Lin, C. H.; Wang, C. S. Polymer 2001, 42, 1869. 
         [3] Wang, C. S.; Lin, C. H.; Wu, C. Y. J. Appl. Polym. Sci. 2000, 78, 228. 
         [4] Lin, C. H.; Wang, C. S. J. Polym. Sci. Part A: Polym. Chem. 2000, 38, 2260. 
         [5] Liu, Y. L.; Tsai, S. H. Polymer 2002, 43, 5757. 
         [6] Wu, C. S.; Liu, Y. L.; Chiu, Y. S. Polymer 2002, 43, 1773. 
         [7] Liu, Y. L.; Wu, C. S.; Hsu, K. Y.; Chang, T. C. J. Polym. Sci. Part A: Polym Chem. 2002, 40, 2329. 
         [8] Varma, K.; Rao, B. S. J Appl Polym Sci 1983, 28, 2805. 
         [9] Connell, J. W.; Watson, K. A. High Perform Polym 2001, 13, 23. 
         [10] Watson, K. A.; Palmeri, F. L.; Connell, J. W. Macromolecules 2002, 35, 4968. 
       
    
     SUMMARY OF THE INVENTION 
     The present invention provides phosphorus-containing compounds having the following chemical formula: 
     
       
                 
         
             
             
         
      
         
         
           
             in which: 
             R 1 -R 4  are each selected from the group consisting of hydrogen atom, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, C 1 -C 6 haloalkyl, C 3 -C 7 cycloalkyl, —CF 3 , —OCF 3 , and halogen atom; 
             A is —O— or 
           
         
       
    
     
       
                 
         
             
             
         
      
         
         
           
             Q is selected from the group consisting of —NO 2 , —NH 2 . 
           
         
       
    
                                
and
         m is an integer of 1-4.       

     The present invention also provides a process of preparing the compound of formula (I), which includes reacting an organophosphorous compound of formula (II) with a compound of formula (III) in a solvent in the presence of a catalyst to form the compound of formula (I); 
     
       
                 
         
             
             
         
      
     
     in which B is halogen or 
                                
X is halogen, and Q is defined as above.
 
     The present invention also provides a compound of formula (PA) and a process for preparing the same. The present invention further provides a compound of formula (PI) and a process for preparing the same. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a  1 H NMR spectrum of compound HPP-A; 
         FIGS. 2A and 2B  show  13 C NMR spectra of compound HPP-A; 
         FIG. 3  is a  1 H NMR spectrum of compound HPP-B; 
         FIGS. 4A and 4B  show  13 C NMR spectra of compound HPP-B; and 
         FIG. 5  shows a DSC analytic diagram of polymer HPP-PI. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to a series of novel phosphorus-containing compounds which can be used as raw materials for polymer materials such as epoxy resins, polyamides and polyimides, and further used in flame resistant materials. 
     The present invention provides phosphorus-containing compounds having the following chemical formula: 
     
       
                 
         
             
             
         
      
         
         
           
             in which: 
             R 1 -R 4  are each selected from the group consisting of hydrogen atom, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, C 1 -C 6 haloalkyl, C 3 -C 7 cycloalkyl, —CF 3 , —OCF 3 , and halogen atom; 
             A is —O— or 
           
         
       
    
     
       
                 
         
             
             
         
      
         
         
           
             Q is selected from the group consisting of —NO 2 , —NH 2 , 
           
         
       
    
                                
and
         m is an integer of 1-4.       

     When R 1 -R 4  are hydrogen atoms, A is —O—, and Q is —NO 2 , one embodiment of the compound of formula (I) can have a structural formula of 
     
       
                 
         
             
             
         
      
     
     When R 1 -R 4  are hydrogen atoms, A is —O—, and Q is —NH 2 , one embodiment of the compound of formula (I) can have a structural formula of 
     
       
                 
         
             
             
         
      
     
     When R 1 -R 4  are hydrogen atoms, A is 
                                
and Q is —NO 2 , one embodiment of the compound of formula (I) can have a structural formula of
 
     
       
                 
         
             
             
         
      
     
     When R 1 -R 4  are hydrogen atoms, A is 
                                
and Q is —NH 2 , one embodiment of the compound of formula (I) can have a structural formula of
 
     
       
                 
         
             
             
         
      
     
     When R 1 -R 4  are hydrogen atoms, A is —O—, and Q is 
                                
one embodiment of the compound of formula (I) can have a structural formula of
 
     
       
                 
         
             
             
         
      
     
     When R 1 -R 4  are hydrogen atoms, A is —O—, and Q is 
                                
one embodiment of the compound of formula (I) can have a structural formula of
 
     
       
                 
         
             
             
         
      
     
     When R 1 -R 4  are hydrogen atoms, A is 
                                
and Q is
 
                                
one embodiment of the compound of formula (I) can have a structural formula of
 
     
       
                 
         
             
             
         
      
     
     When R 1 -R 4  are hydrogen atoms, A is 
                                
and Q is
 
                                
one embodiment of the compound of formula (I) can have a structural formula of
 
     
       
                 
         
             
             
         
      
     
     The present invention also provides a process of preparing the compound of formula (I), which includes reacting an organophosphorous compound of formula (II) with a compound of formula (III) in a solvent in the presence of a catalyst to form the compound of formula (I); 
     
       
                 
         
             
             
         
      
     
     in which B is halogen or 
                                
X is halogen, and Q is defined as above.
 
     When R 1 -R 4  are hydrogen atoms, the process above includes: 
     (a) reacting an organophosphorous compound of formula (II) with a compound of formula (III) where B is a halogen in a solvent in the presence of a catalyst to form the compound of formula (HPP-A) in which A is —O— and Q is —NO 2 ; or 
     (b) repeating step (a) to produce the compound of formula (HPP-A) first, followed by hydrogenation in a solvent to form the product, i.e. compound of formula (HPP-B) in which A is —O— and Q is —NH 2 ; or 
     (c) reacting an organophosphorous compound of formula (II) with a compound of formula (III) where B is 
                                
in a solvent to form the compound of formula (HPP-C) in which A is
 
                                
and Q is —NO 2 ; or
 
     (d) repeating step (c) to produce the compound of formula (HPP-C) first, followed by hydrogenation in a solvent to form the product, i.e. compound of formula (HPP-D) in which A is 
                                
and Q is —NH 2 .
 
     The process according to the present invention can further include: 
     (e) after step (b), reacting the compound of formula (HPP-B) with maleic anhydride in a solvent to form the product, i.e. compound of formula (HPP-E) in which A is —O— and Q is 
                                
or
 
     (f) after step (b), reacting the compound of formula (HPP-B) with epichlorohydrin in a solvent to form the product, i.e. compound of formula (HPP-F) in which A is —O— and Q is 
     
       
                 
         
             
             
         
      
     
     (g) after step (d), reacting the compound of formula (HPP-D) with maleic anhydride in a solvent to form the product, i.e. compound of formula (HPP-G) in which A is 
                                
and Q is
 
                                
or
 
     (h) after step (d), reacting the compound of formula (HPP-D) with epichlorohydrin in a solvent to form the product, i.e. compound of formula (HPP-H) in which A is 
                                
and Q is
 
     
       
                 
         
             
             
         
      
     
     In the process of the present invention, for example, the compound of formula (III) in step (a) is 1-fluoro-4-nitrobenzene, and the compound of formula (III) in step (c) is 4-nitrobenzoyl chloride. 
     In the process of the present invention, the catalyst in step (a) is selected from the group consisting of compounds formed with elements of groups IA to VII A, with an inorganic base and halide being preferred. For example, the catalyst is selected from the group consisting of cesium fluoride (CsF), potassium fluoride (KF), cesium chloride (CsCl), potassium chloride (KCl), potassium carbonate (K 2 CO 3 ), sodium carbonate (Na 2 CO 3 ), potassium hydroxide (KOH) and sodium hydroxide (NaOH). 
     In the process of the present invention, the solvents used in each step are conventionally known in the art. For example, the solvent used in step (a) is N—N-dimethylacetamide (DMAc), the solvent used in steps (b) and (d) is dimethylformamide (DMF), and the solvent used in step (c) is tetrahydrofuran (THF). 
     In another aspect, the present invention provides phosphorus-containing polyamides having the following chemical formula: 
     
       
                 
         
             
             
         
      
     
     in which, A, R 1 -R 4  and m are defined as above, Ar′ is selected from the group consisting of 
                                
and n is an integer of 30-300.
 
     The phosphorus-containing polyamide of formula (PA) can be used as a flexible printed circuit board material. 
     When A is —O—, R 1 -R 4  are hydrogen atoms, and Ar′ is phenyl, one embodiment of the polyamide of formula (PA) above can have a structural formula of 
     
       
                 
         
             
             
         
      
     
     The present invention provides a process of preparing the phosphorus-containing polyamide of formula (PA) as described above, which includes reacting the compound of formula (I) with a diacid compound of formula (IV) in a solvent to produce the phosphorus-containing polyamide of formula (PA),
 
HOOC—Ar′.COOH  (IV)
 
in which Ar′ is selected from the group consisting of
 
     
       
                 
         
             
             
         
      
     
     The solvent used in the process above is conventionally known in the art, and is, for example, N-methyl-pyrrolidone (NMP). 
     In the above process according to the present invention, calcium chloride or triphenyl phosphite (TPP) can be used to accelerate the polymerization. Furthermore, pyridine can also be used in the process above to facilitate the dehydration. 
     The present invention further provides phosphorus-containing polyimides having the following chemical formula: 
     
       
                 
         
             
             
         
      
     
     in which A, R 1 -R 4  and m are defined as above, Ar″ is selected from the group consisting of 
     
       
                 
         
             
             
         
      
     
     and n is an integer of 30-300. 
     The phosphorus-containing polyimide of formula (PI) can be used as a flexible printed circuit board material. 
     When A is —O—, R 1 -R 4  are hydrogen atoms, and Ar″ is 
                                
one embodiment of the polyimide of formula (PI) above can have a structural formula of
 
     
       
                 
         
             
             
         
      
     
     The present invention also provides a process of preparing the phosphorus-containing polyimide of formula (PI) as described above, which includes reacting the compound of formula (I) above with a dianhydride compound of formula (V) in a solvent to produce the phosphorus-containing polyimide of formula (PI), 
                                
in which, Ar″ is selected from the group consisting of
 
     
       
                 
         
             
             
         
      
     
     The solvent used in the process above is conventionally known in the art, and is, for example, m-cresol. 
     The following embodiments are used to further illustrate the present invention, but are not intended to limit the scope of the present invention. Any modifications and changes achieved by those skilled in the art without departing from the spirit of the present invention will fall within the scope of the present invention. 
     Specific embodiments of the implementation of the present invention described above can be represented by Scheme 1 below. 
     
       
                 
         
             
             
         
      
     
     Example 1 
     Synthesis of Compound HPP-A 
     Monomer phosphorus-containing dinitrobenzene HPP-A was synthesized from starting material phosphorus-containing diphenol (HPP) and 1-fluoro-4-nitrobenzene in a solvent and in the presence of a catalyst, via the following steps. 
     8.2880 g (0.02 mol) of phosphorus-containing diphenol (HPP), 6.2085 g (0.044 mol) of 1-fluoro-4-nitrobenzene, 2.9025 g (0.021 mol) of potassium carbonate (K 2 CO 3 ) and 80 g of N—N-dimethylacetamide (DMAc) were added to a 250 ml reactor. 
     Next, the reaction temperature was raised to 80° C., and the reaction was continued for 24 h with stirring. The reactor was then cooled to room temperature, and the reactants were added dropwise to 1000 ml saturated saline and stirred to precipitate a light yellow solid, i.e. compound HPP-A. Afterwards, the synthesized compound HPP-A was filtered, washed with quantities of deionized water, and dried at 80° C. in a vacuum oven, to give 12.04 g of product HPP-A with a yield of 92%, which was then recrystallized with acetic anhydride to give 10.46 g of a light yellow product with a higher purity. The yield is 80%, and M.P. is 253° C.  1 H NMR and  13 C NMR spectra of the compound HPP-A are shown in  FIGS. 1 and 2A  and  2 B respectively. 
     Example 2 
     Synthesis of Compound HPP-B 
     Monomer HPP-B was synthesized from starting material HPP-A and hydrogen in solvent DMF and in the presence of catalyst Pd/C, via the following steps. 
     6 g of HPP-A, 0.10 g of Pd/C and 50 g of dimethylformamide (DMF) were first added to a 50 ml glass reactor and stirred. Purging and emptying were repeated three times with nitrogen and three times with hydrogen, and the reaction was continued for 12 h under a controlled pressure of 3.5 kg/cm 2 . After reaction, Pd/C was filtered off, and the filtrate was added dropwise to 500 ml saturated saline to precipitate compound HPP-B, which was then washed with quantities of deionized water. After filtration, it was dried at 60° C., and weighed 5.07 g with a yield of 93%. Afterwards, it was dissolved into methanol with heating, filtered while hot, and then poured into deionized water to precipitate out, giving 3.75 g of a white product with a higher purity. The yield is 74%, and M.P. is 104° C.  1 H NMR and  13 C NMR spectra of HPP-B are shown in  FIGS. 3 and 4A  and  4 B respectively. 
     Example 3 
     Synthesis of Compound HPP-C 
     Compound HPP-C was synthesized via the following steps. 
     41.00 g (0.10 mol) of HPP and 200 ml of THF were added to a 500 ml reactor and stirred until dissolved. 22.00 g (0.22 mol) of triethylamine were added and the reactor was cooled to 10° C., then 41.00 g (0.22 mol) of 4-nitrobenzoyl chloride were dissolved into 80 ml of THF, poured into a feeding funnel, and slowly added dropwise to the reactor in 2 h. The reaction was continued at a controlled temperature of 20° C. for 2 h, and then the product was filtered and recrystallized with glacial acetic acid to give a yellow DOPO derivative, HPP-C. 
     Example 4 
     Synthesis of Compound HPP-D 
     Monomer HPP-D was synthesized from starting material HPP-C and hydrogen in solvent DMF and in the presence of catalyst Pd/C, via the following steps. 
     6 g of HPP-C, 0.10 g of Pd/C and 50 g of DMF were first added to a 50 ml glass reactor and stirred. Purging and emptying were repeated three times with nitrogen and three times with hydrogen, and the reaction was continued for 8 h under a controlled pressure of 7 kg/cm 2 . After reaction, Pd/C was filtered off, and the filtrate was added dropwise to 500 ml deionized water to precipitate compound HPP-D, which was then filtered and dried at 100° C., to give a pure white product HPP-D. 
     Example 5 
     Synthesis of Compound HPP-E 
     Compound HPP-E was synthesized via the following steps. 
     29.83 g (0.05 mol) of HPP-B, 9.81 g (0.1 mol) of maleic anhydride and 200 ml of acetone were added to a 500 ml reactor, and reacted for 4 h in an ice bath. Next, 50 ml of acetic anhydride and 8.50 g of sodium acetate were added, warmed to 60° C. and reacted for 4 h, followed by solvent removal by distillation under reduced pressure, precipitation with ethanol, and then recrystallization with ethanol, to give a pure compound HPP-E. 
     Example 6 
     Synthesis of Compound HPP-F 
     Compound HPP-F was synthesized via the following steps. 
     300 g of HPP-B and 1000 g of epichlorohydrin were added to a 3 L reactor, and stirred under normal pressure until a homogeneously mixed solution was formed. The reaction temperature was raised to 70° C. under an absolute pressure of 190 mmHg, and 80.20 g of a 49% sodium hydroxide solution was added portionwise in 4 h while water in the reactor was removed by azeotropic distillation. After reaction, epichlorohydrin and solvent were distilled out by distillation under reduced pressure, the product was dissolved into methyl ethyl ketone and deionized water, sodium chloride in the resin was washed off with water, and then the solvent was distilled out by distillation under reduced pressure, to give a light yellow epoxy-containing DOPO derivative HPP-F with an epoxy equivalent of 217 g/eq. 
     Example 7 
     Synthesis of Polymer HPP-PA 
     Phosphorus-containing polyamide HPP-PA was synthesized with diamine based monomer (HPP-B) via the following steps. 
     0.7458 g (1.25 mmol) of diamine monomer HPP-B, 0.2079 g (1.25 mmol) of terephthalamic acid, 0.3 g of calcium chloride (CaCl 2 ), 0.9 ml of triphenyl phosphite (TPP), 1.2 ml of pyridine, and 5 ml of N-methyl-pyrrolidone (NMP) were added to a 100 ml three-necked flask purged with nitrogen for 30 min, and stirred. After reaction for 4 h at an elevated temperature of 100° C., the reaction was cooled to room temperature, and the resulting polymer solution was slowly added dropwise into 300 ml of methanol to precipitate out. The fibrous precipitate produced was filtered, washed with methanol and hot water, collected and dried at 150° C., to give 0.8973 g a product. Next, the synthesized polyetheramide polymer was dissolved into DMAc or NMP to a solid content of about 20%, and then the polyamide solution was coated onto a glass substrate with a coater, to form a film of about 45 μm in thickness. It was heated and treated for 12 h at 80° C. in a hot air circulating oven to remove most of the solvent, and then further treated for 2 h at an elevated temperature of 200° C. Finally, it was soaked in water to separate the HPP-PA film from the glass substrate. The glass transition temperature was determined to be 246° C. by DSC. 
     Example 8 
     Synthesis of Polymer HPP-PI 
     Phosphorus-containing polyimide HPP-PI was synthesized with monomer HPP-B via the following steps. 
     0.8949 g (1.5 mmol) of diamine monomer HPP-B, 0.4653 g (1.5 mmol) of 4,4′-oxydiphthalic anhydride (ODPA) and 7.8 g of m-cresol was stirred in a 100 ml three-necked flask, then the reaction temperature was raised to 200° C., and the reaction was continued for 2 h. Next the reactants were poured into methanol to precipitate out, and after being filtered, the product was washed for 24 h with hot methanol, filtered and dried at 100° C. to give 1.2310 g of a product. The dried product was dissolved into DMF to a solid content of about 20%, and then the polyimide solution was coated onto a glass substrate with a coater, to form a film of about 20 μm in thickness. It was heated and treated for 12 h at 80° C. in a hot air circulating oven to remove most of the solvent, and then further treated for 2 h at an elevated temperature of 200° C., to give a pale colored polyimide. The glass transition temperature was determined to be 259° C. by DSC.  FIG. 5  shows a DSC analytic diagram of the polymer HPP-PI. 
     The following claims are used to define the reasonable scope of the present invention. It should be appreciated that any obvious modifications achieved by those skilled in the art on the basis of the disclosure of the present invention should also fall within the reasonable scope of the present invention.