Novel dihydroxy compound
BACKGROUND OF THE INVENTION 
     This invention relates to a novel dihydroxy compound and a process for preparing the same. 
     Dihydroxy compounds have been widely used as a starting material for preparing various synthetic resins, such as polyarylate resin, polycarbonate resin, epoxy resin, polyester resin, etc. However, the resins obtained by using conventional dihydroxy compounds are not satisfactory in thermal and/or mechanical properties, and therefore it is desired to provide a dihydroxy compound capable of giving resins improved in these properties. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a novel dihydroxy compound useful as a starting material for preparing various resins and a process for preparing the compound. 
     A further object of the invention is to provide a novel dihydroxy compound capable of producing resins having improved thermal and/or mechanical properties and a process for preparing the compound. 
     These and other objects of the invention will become apparent from the following description. 
     The dihydroxy compound of the invention is 2,2-bis[4-(4&#39;-hydroxybenzoyloxy)cyclohexyl]propane represented by the formula (I): ##STR2## 
     DETAILED DESCRIPTION OF THE INVENTION 
     The dihydroxy compound of the invention having the formula (I) is useful as a starting material for preparing various synthetic resins such as polyarylate resin, polycarbonate resin, epoxy resin, polyester resin, etc., and is capable of giving resins having improved thermal and/or mechanical properties. 
     The dihydroxy compound of the invention can be prepared preferably by subjecting to transesterification reaction hydrogenated bisphenol-A, i.e., 2,2-bis(4-hydroxycyclohexyl)propane represented by the formula (II) ##STR3## and alkyl 4-hydroxybenzoate in the presence of a transesterification catalyst. The dihydroxy compound of the invention can be prepared also by a direct esterification process in which the compound of the formula (II) is esterified directly with 4-hydroxybenzoic acid in the presence of an acid catalyst such as sulfuric acid, paratoluenesulfonic acid, phosphoric acid, hydrochloric acid or the like. Among these methods the transesterification reaction is preferable in view of reaction velocity, and therefore the following description is made in reference to the transesterification reaction. 
     In carrying out the transesterification reaction of the present invention, it is preferable to use a specific transesterification catalyst selected from various transesterification catalysts. Preferable catalyst is at least one of organic tin compounds and inorganic tin compounds, which themselves are known as transesterification catalyst. Examples of organic tin compounds are tin oxalate, dibutyltin oxide, dibutyltin maleate, dibutyltin dichloride, tributyltin acetate, tributyltin chloride, trimethyltin chloride, etc. Examples of inorganic tin compounds are stannous oxide, stannic oxide, stannous chloride, etc. These catalysts can be used singly or in admixture with one another. 
     The amount of the catalyst to be used varies depending on the reaction temperature, but may usually be in the range of about 0.01 to about 10 mole %, preferably about 0.1 to about 5 mole %, based on the mole of 4- hydroxybenzoic acid ester. 
     Preferably exemplified as 4-hydroxybenzoic acid esters are lower alkyl 4-hydroxybenzoates, more preferably primary lower alkyl 4-hydroxybenzoates, such as methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, n-propyl 4-hydrobenzoate, isopropyl 4-hydroxybenzoate, n-butyl 4-hydroxybenzoate, isobutyl 4-hydroxybenzoate, etc. Secondary and tertiary alkyl esters having larger steric hindrance, although usable, are liable to retard the reaction. 
     The esters of 4-hydroxybinzoate can be used in an amount of about 2 to about 4 moles, preferably about 2 to about 2.5 moles, per mole of the 2,2-bis(4-hydroxycyclohexyl)propane. With less than 2 moles of alkyl 4-hydroxybenzoate, a reduced yield of the desired compound results, whereas more than 4 moles of alkyl 4-hydroxybenzoate used increases the amount of the compound remaining unreacted, not only making the purification procedure complicated but rendering the process uneconomical. 
     The reaction can be carried out at a temperature of usually about 80° to 240° C., preferably at about 150° to 220° C. The reaction tends to be retarded at a temperature of lower than about 80° C., whereas the reaction temperature of higher than about 240° C is likely to cause undesired decomposition of the contemplated compound. The reaction time is usually about 2 to 48 hours, although suitably determinable in consideration of the reaction temperature and the amount of transesterification catalyst. The reaction is preferably carried out in the presence of an inert solvent such as benzene, toluene, xylene, cyclohexane, tetralin or the like. 
     The 2,2-bis[4-(4&#39;-hydroxybenzoyloxy)cyclohexyl]propane thus obtained can be used as it is or as purified by conventional method such as recrystallization or the like, depending on the application utility, of the compound. 
    
    
     EXAMPLES 
     The present invention will be described in more detail with reference to the following examples. 
     EXAMPLE 1 
     In a reactor equipped with a stirrer, nitrogen-introducing tube, thermometer, separator and cooling tube were placed 480.8 g (2 moles) of 2,2-bis(4-hydroxy-cyclohexyl)propane, 699.9 g (4.6 moles) of methyl 4-hydroxybenzoate, 19.84 g (0.08 mole) of dibutyltin oxide and 100 ml of xylene. The mixture was heated to 200° C. while distilling off the xylene and kept with stirring at that temperature for 18 hours, giving 1,022 g of pale yellow semi-crystalline product. The crude product thus obtained was recrystallized from methylethyl ketone, giving 583 g of white crystal having a melting point of 288°-290° C. Yield was 60.7%. 
     The crystal was identified as 2,2-bis[4-(4&#39;-hydroxybenzoyloxy)cyclohexyl]propane by elementary analysis, IR absorption spectrum,  1  H--NMR spectrum and  13  C-NMR spectrum. 
     
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Elementary analysis                                                       
              C     H                                                     
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Calcd.:         72.47%  7.55%                                             
Found:          72.51%  7.62%                                             
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     IR 
     ν max  (KBr): 3340, 1680cm -1   
       1  H--NMR (DMSO-d 6 ) 
     δppm: 0.74 (6H, s), 1.14 (4H, m), 1.38 (6H, m), 1.74 (4H, d, J=12 Hz), 2.06 (4H, d, J=12 Hz), 4.72 (2H, m), 6.82 (4H, d, J=9 Hz), 7.78 (4H, d, J=9 Hz), 10.29 (2H, s). 
       13  C--NMR (DMSO-d 6 ) 
     δppm: 20.92 (q), 24.89 (t), 32.33 (t), 36.74 (s), 42.87 (d), 73.66 (d), 115.66 (d), 121.25 (s), 131.75 (d), 162.26 (s), 165.44 (s). 
     EXAMPLE 2 
     A 552 g quantity of white crystals was produced by following the same procedure as in Example 1 except that 10.78 g (0.08 mole) of stannous oxide was used in place of 19.84 g of dibutyltin oxide. Yield was 57.4%. 
     The obtained crystals were identical in melting point, IR spectra,  1  H--NMR spectra and  13  C--NMR spectra with the 2,2-bis[4-(4&#39;-hydroxybenzoyloxy)cyclohexyl]propane obtained in Example 1. 
     EXAMPLE 3 
     A 507 g quantity of white crystals was produced by following the same procedure as in Example 1 except that 26.62 g (0.08 mole) of tributyltin acetate was used in place of 19.84 g of dibutyltin oxide. Yield was 52.7%. 
     The obtained crystals were identical in melting point, IR spectra, 1H--NMR, 13C-NMR spectra with the 2,2-bis[4-(4&#39;-hydroxybenzoyloxy)cyclohexyl]propane obtained in Example 1. 
     EXAMPLE 4 
     A 498 g quantity of white crystals was produced by following the same procedure as in Example 1 except that 15.16 g (0.08 mole) of stannous chloride was used in place of 19.84 g of dibutyltin oxide. Yield was 51.6%. 
     The obtained crystals were identical in melting point, IR spectra, 1H--NMR, 13C-NMR spectra with the 2,2-bis[4-(4&#39;-hydroxybenzoyloxy)cyclohexyl]propane obtained in Example 1. 
     EXAMPLE 5 
     A 558 g quantity of white crystals was produced by following the same procedure as in Example 1 except that 893.2 g (4.6 moles) of butyl 4-hydroxybenzoate was used in place of 699.6 g of methyl 4-hydroxybenzoate. Yield was 58.0%. 
     The obtained crystals were identical in melting point, IR spectra, 1H-NMR, 13C-NMR spectra with the 2,2-bis[4-(4&#39;-hydroxybenzoyloxy)cyclohexyl]propane obtained in Example 1. 
     EXAMPLE 6 
     A 529 g quantity of white crystals was produced by following the same procedure as in Example 1 except that 828 g (4.6 moles) of isopropyl 4-hydroxybenzoate was used in place of 699.6 g of methyl 4-hydroxybenzoate. Yield was 55.0%. 
     The obtained crystals were identical in melting point, IR spectra, 1H-NMR, 13C-NMR spectra with the 2,2-bis[4-(4&#39;-hydroxybenzoyloxy)cyclohexyl]propane obtained in Example 1.