Abstract:
Disclosed is a polyester-imide prepared from a condensation polymerization of aromatic diacid, diimide diacid, and diol, having a carboxy to hydroxy equivalent molar ratio of 0.9:1 to 1.1:1. The disclosed polyester-imide has outstanding heat-resistance, remarkable filming ability, and high solubility in both phenol series and amide series solvents.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a novel polyesterimide which is soluble in both phenol series and amide series solvent, and the preparation of the same. 
     Polyimide is a known polymer with outstanding heat stability and mechanical property. But it is not available for application in solution processing because it is insoluble in general organic solvents. Conventional preparation of polyimide utilizes the precursor polyamic acid for processing, followed by cyclization. However, due to difficulties in storage and the strong corrosive property of polyamic acid, handling and processing are problematic. 
     In order to improve the processing ability but retain the heat stability of polyimide, polyester-imides are prepared by introducing an ester group into the main chain of the polymer. However, it is necessary to use the phenol series, such as m-cresol and cresylic acid, as the solvent of conventional polyester-imide. As to the solvent of amide series, e.g., N-methyl-2-pyrrolidone (NMP), N,N&#39;-dimethylformamide (DMF), and N,N&#39;-dimethylacetamide (DMAC), the solubility of polyester-imide is poor. Additionally, the strong odor and the corrosive damage to skin make a phenol series solvent inappropriate for polyester-imide processing. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a polyester-imide having good heat stability, filming ability, and high solubility in both the phenol series and amide series solvents. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The above object can be attained by providing a polyester-imide of the present invention which has been made with the following three ingredients: 
     (a) An aromatic diacid mixture of terephthalic acid (TPA) and isophthalic acid (IPA) having a mixing ratio of 1:0 to 0:1 and comprising 0-49 molar percent of the total ingredients, 
     (b) Diimide diacid(DID) having the formula shown as following: ##STR1## wherein X=O, S, SO 2 , CO, or CH 2  ; ##STR2##  and comprising 1-50 molar percent of the total ingredients, 
     (c) Aryl diol c 1  or c 2 , comprising 50 molar percent of the total ingredients, wherein C 1  has the formula shown as below: ##STR3## wherein Y=C(CH 3 ) 2 , SO 2 , or S; and c 2  is a mixture of hydroquinone (HQ) and resorcinol (RC) with a mixing ratio of 1:0 to 1:1. 
     According to the present invention, the molar ratio between diacids ((a) &amp; (b)) and diol (c 1  or c 2 ) is 0.9:1 to 1.1:1. 
     The polymerization method of the polyester-imide of the present invention can be direct condensation, solution, and hot melt polymerization, which are all familiar to those skilled in this art. 
     When direct condensation polymerization is used in the present invention, the condensing agent can be diphenyl chlorophosphate, thionyl chloride(SOCl 2 ), or tosyl chloride, the solvent can be pyridine or DMF, and lithium chloride or calcium chloride is added as condensing coagent. 
     When solution polymerization is used in the present invention, diols are added to acid chloride, which is the chlorination product of the diacids, and pyridine or triethyl amine is used as a deacidizing agent. 
     When hot melt polymerization is used, the derivatives of esterification of diols are mixed with diacids as the reactants, or alternatively a mixture of diols, diacids, and acetic anhydride is used as reactant. Both will result in same polymer product of the present invention. In this polymerization, tetrabutyl titanate, isopropyl titanate, or zinc acetate are added as a catalyst. 
    
    
     This invention will be more clearly understood by referring to the following illustrative examples. 
     EXAMPLE 1 
     Trimellitic anhydride (TMA) of 57.6 g, p-aminobenzoic acid of 41.1 g, and DMF of 400 ml were mixed and mechanically stirred at 120° C. for 2 hours. After cooling, 0.4 mole of acetic anhydride was added. The mixture was reheated to 120° C. for 2 hours, then poured into ice water, filtered. N-(p-carboxyphenyl)trimellitimide (DID M 1 ) was obtained after and drying under vacuum at 80° C. overnight. 
     EXAMPLE 2 
     The same procedure as described in Example 1 was employed, except TMA of 80.7 g, m-aminobenzoic acid of 57.6 g, and 0.42 mole of acetic anhydride were used in place of the corresponding reagent, respectively. N-(m-carboxyphenyl)trimellitimide (DID M 2 ) was obtained. 
     EXAMPLE 3 
     0.2 mole of TMA, 0.1 mole of 4,4&#39;-diaminodiphenyl ether, and 400 ml of DMF were mixed and circulated for 4 hrs. After cooling, methanol was poured into the solution for precipitation, followed by filtration and drying under vacuum at 80° C. overnight. Oxy-bis(N-(4-phenylene)-4&#39;-(carboxylic acid)-phthalimide) (DID M 3 ) was obtained. 
     EXAMPLE 4 
     A solution was prepared by mixing 3.4923 g (13 mmol) of diphenyl chlorophosphate, 10 ml of pyridine, 2.5 mmol of DID M 2 , and 2.5 mmol of IPA, at room temperature, under nitrogen, and this solution was stirred for 20 minutes. Subsequently, this solution was poured into a mixed solution of 0.4239 g of lithium chloride dissolved in 10 ml of pyridine, and was stirred for 30 min. The resulting solution was heated to 120° C., followed by further stirring for 20 minutes to finish the dissolution. Another solution prepared from 5 mmol of bisphenol (5 mmol) and 10 ml of pyridine was added dropwise to the reactant solution during a period of 25 minutes. The reaction was carried out at 120° C. for 3 hrs. After pouring the reaction solution into a glass of water under stirring, followed by washing with boiling methanol for 1 hour and dried in a vacuum oven at 80° C., the polyester-imide of the present invention was obtained. 
     The polyester-imide thus produced was made into samples and tested. The testing method, testing instruments, and conditions for each sample are as follows: 
     T g  : Detector, Du Pont TMA 2940, under N 2  gas, temperature increase rate of 20° C./min; 
     T d  : Detector, Du Pont TGA 951, under N 2  gas, temperature increase rate of 10° C./min(T d  is defined as a characteristic temperature at which 5% of weight loss is detected); 
     Mechanical property: ASTM D638. 
     These tests show that the polyester-imide prepared has a T g  of 192° C., a T d  of 449° C., a stress strength of 7.70 kg/mm 2 , and a strain of 8.97%. 
     EXAMPLES 5-22 
     The same procedure and test methods as described in Example 4 were employed except that different DID, Diacid and Diol and different molar ratio as indicated in Table 1 were used. The physical properties of the tested polyester-imide are shown in Table 1 and their solubility in NMP, DMF, DMSO, DMAC and m-cresol are shown in Table 2. 
     COMPARATIVE EXAMPLE 23 
     Samples made from ISOMID (Trademark, Nippon Shokubai Co. Ltd., a known commercial polyester-imide) were tested by the same methods as described in Example 4 and found that ISOMID has a T g  of 182° C., a T d  of 427° C., fair filming ability, and poor mechanical strength. The dry isomid film has poor solubility in NMP, DMAC, DMF, and m-cresol. The test results of this commercial available ISOMID are also shown in Table 1 and Table 2. 
     
                                           TABLE 1__________________________________________________________________________Monomer Compositions and Physical Properties of Polyester-imideDID Diacid Diol @ExampleMolar ratio among            η.sub.inh                Property                     T.sub.g                          T.sub.d                             Strees                                   StrainNo.  (diacids and diol )            (dl/g)                of film                     (°C.)                          (°C.)                             (6 kg/mm.sup.2)                                   (%)__________________________________________________________________________ 4   M.sub.2  IPA BPA            0.40                flexible                     192(195*)                          449                             7.70  8.97(5:5:10) 5   M.sub.1  -- BPA            0.39                flexible                     --   418(5:10) 6   M.sub.1  IPA BPA            0.30                flexible                     198  --(5:5:10) 7   M.sub.2  -- BPA            0.42                fIexible                     217  465(5:10) 8   M.sub.2  IPA BPA            0.41                flexible                     193(210*)                          441                             7.16  9.35(7:3:10) 9   M.sub.3  IPA BPA            0.55                flexible                     213(200*)                          474(5:5:10)10   M.sub.3  -- BPA            0.40     --   441(5:10)11   M.sub.3  IPA BPA            0.47                flexible                     223  429                             6.35  8.60(7:3:10)12   M.sub.2  TPA BPA            0.58                flexible                     211  --(5:5:10)13   M.sub.2  IPA HQ/RC            0.45                flexible                     177  422(5:5:5:5)14   M.sub.2  IPA HQ/RC            0.39                flexible  420(7:3:5:5)15   M.sub.2  -- HQ/RC            0.41     --   --(5:5:5)16   M.sub.1  IPA HQ/RC            --       --   --(5:5:5:5)17   M.sub.1  IPA HQ/RC            --       --   --(7:3:5:5)18   M.sub.3  IPA HQ/RC            --       --   --(7:3:5:5)19   M.sub.3  IPA HQ/RC            --       --   --(5:5:5:5)20   M.sub.2  IPA HQ            --  flexible                     200  --(5:5:10)21   M.sub.3   TPA BPA            0.58                flexible                     206  462(5:5:10)22   M.sub.3  TPA BPA            0.50                flexible                     215(214*)                          466(7:3:10)23   (ISOMID)        brittle                     182* 427                             **__________________________________________________________________________ @ Bisphenol A(BPA) or hydroquinone(HQ)/resorcinol(RC) mixture is employed *Under DSC testing: N.sub.2 gas, heating rate = 20° C./min. **Poor filming ability, can not be tested under stress. 
    
     
                       TABLE 2______________________________________Solubility of Polyester-imideExample No.    NMP      DMF     DMSO  DMAC   m-Cresol______________________________________ 4       ++       ++      ++    ++     ++ 5       ++       ++      ++    ++     ++ 6       ++       ++      ++    ++     ++ 7       ++       ++      ++    ++     ++ 8       ++       ++      ++    ++     ++ 9       ++       ++      ++    ++     ++10       ++       ++      -     ±   ++11       ++       ++      ++    ++     ++12       ++       ++            ++     ++13       ++       ++      -     ++     ++14       ++       ++      ±  ++     ++15       +                ±         ++16       ±             -     ±   ++17       ±     ±    -     +      ++18       ±     -       -     +      ++19       ±     -       -20       ±     -       -     -21       ++       ++      -     ++     ++22       ++       ++            ++     ++23 (ISOMID)    -        -       -     -      -______________________________________ ++: soluble at room temperature. +: soluble during heating. ±: partially soluble during heating. -: insoluble during heating. 
    
     In view of the above results, it is apparent that the polyester-imide of the present invention has good heat stability (T d  &gt;420° C.), high T g  (most of them&gt;200° C.), good filming ability, flexibility, strong mechanical strength, and good solubility in NMP, DMF, DMAC, DMSO, and m-cresol.